U.S. patent application number 11/630900 was filed with the patent office on 2009-07-02 for booster pump and low-temperature-fluid storage tank having the same.
Invention is credited to Yasuharu Chuman, Shuichi Kawasaki, Takashi Maemura, Kenji Nakamichi, Ichirou Takeno, Atsushi Yuge.
Application Number | 20090165640 11/630900 |
Document ID | / |
Family ID | 35782679 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090165640 |
Kind Code |
A1 |
Kawasaki; Shuichi ; et
al. |
July 2, 2009 |
Booster pump and low-temperature-fluid storage tank having the
same
Abstract
A low-temperature-fluid storage tank capable of efficiently
increasing the pressure of fluid without heating the fluid is
provided. There is provided a booster pump which includes a piston
having a piston head and a piston rod and a cylinder having a
compression chamber that accommodates the piston head so that a
fluid is compressed by one end surface of the piston head. The
piston head is provided with a bellows for separating a space
adjacent to the piston rod from a space adjacent to the cylinder in
the compression chamber.
Inventors: |
Kawasaki; Shuichi;
(Aichi-ken, JP) ; Nakamichi; Kenji; (Nagasaki-ken,
JP) ; Chuman; Yasuharu; (Nagasaki-ken, JP) ;
Yuge; Atsushi; (Nagasaki-ken, JP) ; Takeno;
Ichirou; (Nagasaki-ken, JP) ; Maemura; Takashi;
(Aichi-ken, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
35782679 |
Appl. No.: |
11/630900 |
Filed: |
June 28, 2005 |
PCT Filed: |
June 28, 2005 |
PCT NO: |
PCT/JP05/11783 |
371 Date: |
January 25, 2008 |
Current U.S.
Class: |
91/169 ;
91/245 |
Current CPC
Class: |
F04B 1/141 20130101;
F04B 45/02 20130101; F04B 53/02 20130101; F04B 15/06 20130101; F04B
15/08 20130101; F04B 23/02 20130101 |
Class at
Publication: |
91/169 ;
91/245 |
International
Class: |
F01B 7/20 20060101
F01B007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2004 |
JP |
2004-194641 |
Oct 15, 2004 |
JP |
2004-302048 |
Dec 27, 2004 |
JP |
2004-377938 |
Jan 11, 2005 |
JP |
2005-003993 |
Claims
1. A booster pump comprising: a piston having a piston head and a
piston rod; and a cylinder having a compression chamber that
accommodates the piston head so that a fluid is compressed by one
end surface of the piston head, wherein the piston head is provided
with a bellows for separating a space adjacent to the piston rod
from a space adjacent to the cylinder in the compression
chamber.
2. The booster pump according to claim 1, wherein a filler filling
a space between an outer surface of the bellows and an inner
circumferential surface of the cylinder is provided.
3. The booster pump according to claim 1, wherein a ring-shaped
sealing member is provided at one end portion, adjacent to the
piston head, of the bellows.
4. The booster pump according to claim 1, wherein the piston rod
has a heat-insulating vacuum structure that is hollow and
vacuumed.
5. A booster comprising at least two of the booster pumps according
to claim 1, wherein multistage compression is performed with the
booster pumps.
6. A low-temperature-fluid storage tank for storing a
low-temperature fluid in a low-temperature state, comprising: the
booster pump according to claim 1; a low-temperature-fluid
reservoir reserving the low-temperature fluid; and a
low-temperature container for accommodating the booster pump or the
booster and the low-temperature-fluid reservoir.
7. The low-temperature-fluid storage tank according to claim 6,
wherein the booster pump or the booster is disposed downstream of
the low-temperature-fluid reservoir and outside the
low-temperature-fluid reservoir.
8. The low-temperature-fluid storage tank according to claim 6,
wherein a low-temperature slush fluid in a solid/liquid two-phase
state is reserved in the low-temperature-fluid reservoir.
9. The low-temperature-fluid storage tank according to claim 8,
wherein a mesh is provided at an outlet of the
low-temperature-fluid reservoir.
10. The low-temperature-fluid storage tank according to claim 9,
wherein a heater is provided in the low-temperature-fluid
reservoir.
11. The low-temperature-fluid storage tank according to claim 6,
wherein a heat exchanger is disposed downstream of the booster pump
or the booster.
12. The low-temperature-fluid storage tank according to claim 6,
wherein a radiation shield plate is provided on an inner surface of
the low-temperature container.
13. A low-temperature-fluid boosting pump comprising a cylinder
block having therein a compression chamber; and a piston head that
is accommodated in the compression chamber and reciprocates in the
compression chamber so that a low-temperature fluid is compressed
by one end surface of the piston head, wherein a flexible partition
for separating a space adjacent to an inner circumferential side
from a space adjacent to an outer circumferential side of the
piston head is provided between the one end surface of the piston
head and an inner surface of the compression chamber which faces
the one end surface.
14. The low-temperature-fluid boosting pump according to claim 13,
wherein a pressure-boosted fluid resides on an outer side of the
partition.
15. The low-temperature-fluid boosting pump according to claim 13,
wherein an outer side of the partition is vacuumed.
16. A low-temperature-fluid boosting pump comprising: a piston rod
driven by a drive unit connected to a driving source; a piston head
that is connected to the piston rod and reciprocates with the
piston rod; and a cylinder having a compression chamber that
accommodates the piston head so that a low-temperature fluid is
compressed by one end surface of the piston head, wherein the drive
unit is disposed adjacent to the one end surface of the piston
head, and a shank of the piston rod is subjected to a tensile force
in a direction substantially equal to a direction in which the
shank extends when the low-temperature fluid is to be
compressed.
17. The low-temperature-fluid boosting pump according to claim 16,
wherein the piston head is divided into at least two concentric
subsections to achieve a multistage compression structure where the
low-temperature fluid is gradually increased to a desired pressure
by sequentially passing through the one end surface of the divided
piston head.
18. The low-temperature-fluid boosting pump according to claim 16,
wherein a flexible partition for separating a space adjacent to the
piston rod from a space adjacent to the cylinder in the compression
chamber is provided adjacent to the one end surface and adjacent to
the other end surface of the piston head.
19. The low-temperature-fluid boosting pump according to claim 16,
wherein a flexible partition for separating a space adjacent to the
piston rod from a space adjacent to the cylinder in the compression
chamber is provided adjacent to the other end surface of the piston
head.
20. The low-temperature-fluid boosting pump according to claim 16,
wherein a precooling layer is formed in the cylinder.
21. The low-temperature-fluid boosting pump according to claim 16,
wherein the drive unit is linked to the piston rod via a
heat-insulating connection section.
22. The low-temperature-fluid boosting pump according to claim 16,
wherein the piston head is linked to the piston rod via a heat
insulator.
23. The low-temperature-fluid boosting pump according to claim 16,
wherein a guiding member for guiding the shank of the piston rod is
provided between a cylinder block and the piston rod.
24. The low-temperature-fluid boosting pump according to claim 16,
wherein a space between a cylinder block and the shank of the
piston rod is a vacuum.
25. The low-temperature-fluid boosting pump according to claim 16,
wherein the cylinder is immersed in low-temperature fluid stored in
a low-temperature-fluid storage tank and is attachable to and
detachable from the low-temperature-fluid storage tank.
26. The low-temperature-fluid boosting pump according to claim 16,
wherein the drive unit and the cylinder are immersed in
low-temperature fluid stored in a low-temperature-fluid storage
tank and are attachable to and detachable from the
low-temperature-fluid storage tank.
27. A low-temperature-fluid feeder comprising: the
low-temperature-fluid boosting pump according to claim 16; a
chamber for reserving a low-temperature fluid whose pressure has
been increased by the low-temperature-fluid boosting pump; and a
fuel injector supplied with the low-temperature fluid from the
chamber.
28. The low-temperature-fluid feeder according to claim 27, wherein
a booster-fluid feeding unit for liquefying or vaporizing the
low-temperature fluid in the chamber and supplying the
low-temperature fluid into the cylinder disposed adjacent to the
other end surface of the piston head of the low-temperature-fluid
boosting pump is provided.
29. The low-temperature-fluid feeder according to claim 27, wherein
a heat exchanger for vaporizing liquid hydrogen is provided between
the chamber and the fuel injector, and a booster-fluid feeding unit
for adjusting the pressure of the vaporized hydrogen and supplying
the hydrogen into the cylinder disposed adjacent to the other end
surface of the piston head of the low-temperature-fluid boosting
pump is provided.
30. The low-temperature-fluid feeder according to claim 27, wherein
the chamber is provided with a relief valve.
31. A low-temperature-fluid boosting pump comprising a cylinder
block having therein a compression chamber; and a piston head that
is accommodated in the compression chamber and reciprocates in the
compression chamber so that a low-temperature fluid is compressed
by one end surface of the piston head, wherein a flexible partition
for separating a space adjacent to an inner circumferential side
from a space adjacent to an outer circumferential side in the
compression chamber is provided adjacent to the other end surface
of the piston head.
32. The low-temperature-fluid boosting pump according to claim 31,
wherein a pressure-boosted fluid resides on an inner side of the
partition.
33. The low-temperature-fluid boosting pump according to claim 31,
wherein an inner side of the partition is vacuumed.
34. The low-temperature-fluid boosting pump according to claim 16,
wherein a guiding member for guiding the piston head is provided
between the cylinder block and the piston head.
35. The low-temperature-fluid boosting pump according to claim 13,
wherein the cylinder block is immersed in low-temperature fluid
stored in a low-temperature-fluid storage tank and is attachable to
and detachable from the low-temperature-fluid storage tank.
36. The low-temperature-fluid boosting pump according to claim 31,
wherein a guiding member for guiding the piston head is provided
between the cylinder block and the piston head.
37. The low-temperature-fluid boosting pump according to claim 31,
wherein the cylinder block is immersed in low-temperature fluid
stored in a low-temperature-fluid storage tank and is attachable to
and detachable from the low-temperature-fluid storage tank.
38. The low-temperature-fluid boosting pump according to claim 34,
wherein the cylinder block is immersed in low-temperature fluid
stored in a low-temperature-fluid storage tank and is attachable to
and detachable from the low-temperature-fluid storage tank.
Description
TECHNICAL FIELD
[0001] The present invention relates to a booster pump for
compressing low-temperature fluids to increase the pressure and to
a low-temperature-fluid storage tank having the same.
BACKGROUND ART
[0002] Some known (low-temperature-fluid) booster pumps for
compressing low-temperature (e.g., -273.degree. C. to 0.degree. C.)
fluids (e.g., hydrogen, nitrogen, LNG) to increase the pressure
have piston rings on piston heads thereof (refer to, for example,
non-Patent Document 1).
[0003] Non-patent Document 1:
[0004] Takuya Endo et al., "Shin Enerugii Jidousha (New Energy
Automobile)," Sankaido, January 1995, p. 221-222
DISCLOSURE OF INVENTION
[0005] However, such a known (low-temperature-fluid) booster pump
has a problem in that a sliding motion occurs while the outer
circumferential surfaces of the piston rings are being pressed onto
the inner circumferential surface of a cylinder in order to
maintain hermeticity, and consequently, friction between these
piston rings and the cylinder generates heat, which warms up the
fluid. Another problem is that, particularly when high pressure is
to be achieved, a high-pressure fluid flowing towards the inner
circumferential surfaces of the piston rings even more forcibly
presses the outer circumferential surfaces of the piston rings onto
the inner circumferential surface of the cylinder, which produces
still more considerable friction between these piston rings and the
cylinder and consequently generates a larger amount of heat.
[0006] In addition, it is not possible to completely eliminate gaps
between the outer circumferential surfaces of the piston rings and
the inner circumferential surface of the cylinder, and therefore,
fluid leaks through these gaps, thus causing the compression
efficiency to decrease.
[0007] Furthermore, such a known (low-temperature-fluid) booster
pump requires a piston rod disposed between a piston head and a
drive mechanism to have a large diameter in order to prevent this
piston rod from buckling due to compressive force when a
low-temperature fluid is to be compressed. For this reason, heat
originating from the drive mechanism is transmitted to
low-temperature fluid via the piston rod and the piston head,
thereby warming up the low-temperature fluid so considerably as to
cause boil-off.
[0008] The present invention has been conceived in light of the
above-described circumstances, and an object of the present
invention is to provide a booster pump for increasing the pressure
of a fluid efficiently without heating the fluid and to provide a
low-temperature-fluid storage tank having such a booster pump.
[0009] To overcome the above-described problems, the present
invention employs the following solutions.
[0010] The present invention provides a booster pump which includes
a piston having a piston head and a piston rod and a cylinder
having a compression chamber that accommodates the piston head so
that a fluid is compressed by one end surface of the piston head,
wherein the piston head is provided with a bellows for separating a
space adjacent to the piston rod from a space adjacent to the
cylinder in the compression chamber.
[0011] According to the present invention, the bellows separates a
space adjacent to the piston rod from a space adjacent to the
cylinder in the compression chamber, and there is no component
(e.g., piston ring in the known art) that moves in contact with the
inner circumferential surface of the compression chamber. This
prevents heat from being generated in the compression chamber and
therefore prevents the fluid from being heated.
[0012] In addition, since the bellows completely separates a space
adjacent to the piston rod from a space adjacent to the cylinder in
the compression chamber, the fluid is prevented from leaking from
the cylinder side of the compression chamber to the piston rod side
of the compression chamber. This improves the pump efficiency.
[0013] In the above-described invention, it is preferable that a
filler filling a space between an outer surface of the bellows and
an inner circumferential surface of the cylinder be provided.
[0014] By doing so, the gap between the outer surface of the
bellows and the inner circumferential surface of the compression
chamber is filled, and the dead volume of the compression chamber
decreases. This improves the pump efficiency.
[0015] In the above-described invention, it is preferable that a
ring-shaped sealing member be provided at one end portion, adjacent
to the piston head, of the bellows.
[0016] By doing so, the sealing member can reduce leakage of the
fluid from one end surface towards the other end surface of the
piston head, which would reduce the pressure applied to the outer
circumferential surface of the bellows. This allows a low-pressure
bellows which does not need to meet strict robust design
requirements to be employed and therefore allows the piston to have
a large stroke. Consequently, the compression efficiency (pump
efficiency) can be improved.
[0017] This sealing member neither has tension, as has been
problematic, for example, with a piston ring in the known art, nor
generates heat, as with a piston ring, because the bellows
considerably restricts the stroke of the piston (the stroke is
small).
[0018] In the above-described invention, it is preferable that the
piston rod have a heat-insulating vacuum structure that is hollow
and vacuumed.
[0019] As a result of the piston rod having a hollow structure, the
weight of the piston rod can be reduced so that the piston can be
pushed up under a small load. In addition, by vacuuming the
interior of the piston rod, the piston rod can block heat to reduce
the amount of heat propagating from the piston rod into the
fluid.
[0020] The present invention provides a booster pump which includes
at least two of the above-described booster pumps, wherein
multistage compression is performed with these booster pumps.
[0021] According to the present invention, if, for example, two
booster pumps are provided, one booster pump can be used as a
low-pressure pump and the other can be used as a high-pressure
pump. By doing so, since the low-pressure pump can employ a
low-pressure bellows, the piston can have a large stroke to easily
increase the pressure of the fluid from a low pressure to an
intermediate pressure. Furthermore, since the high-pressure pump
can employ a high-pressure bellows, the intermediate pressure of
the fluid can easily be increased to a high pressure, even though
the piston cannot have a large stroke.
[0022] In other words, if the pressure of the fluid is to be
increased from low pressure to high pressure in one stroke using
only one booster pump, the high-pressure bellows needs to be
employed, which does not allow a large stroke. This makes it
difficult to increase the fluid to the desired pressure (high
pressure).
[0023] In contrast, as described above, the fluid can easily be
increased to the desired pressure by carrying out dual-stage
compression of the fluid using, for example, two pumps.
[0024] The present invention provides a low-temperature-fluid
storage tank for storing a low-temperature fluid in a
low-temperature state. The low-temperature-fluid storage tank
includes the above-described booster pump or the above-described
booster; a low-temperature-fluid reservoir reserving the
low-temperature fluid; and a low-temperature container for
accommodating the booster pump or the booster and the
low-temperature-fluid reservoir.
[0025] According to the present invention, since the booster pump
or the booster is disposed in the low-temperature container, the
booster pump or the booster is forcibly cooled and is not easily
heated up.
[0026] In the above-described invention, it is preferable that the
booster pump or the booster be disposed downstream of the
low-temperature-fluid reservoir and outside the
low-temperature-fluid reservoir.
[0027] Since the booster pump or the booster is disposed outside
the low-temperature-fluid reservoir (i.e., separately from the
low-temperature-fluid reservoir in the heat-insulated vacuum
chamber of the low-temperature container), heat generated in a
driving source of the booster pump or the booster is prevented from
being transmitted to the low-temperature fluid reserved in the
low-temperature-fluid reservoir, and therefore, temperature
increase and vaporization of the low-temperature fluid can be
prevented.
[0028] In the above-described invention, it is preferable that a
low-temperature slush fluid in a solid/liquid two-phase state be
reserved in the low-temperature-fluid reservoir.
[0029] The low-temperature-fluid storage layer contains the slushy
low-temperature fluid (mixture of solid low-temperature fluid and
liquid low-temperature fluid in a liquid/ice state) and experiences
vaporization less easily than tanks containing only liquid
low-temperature fluids. This improves the suction performance of
the booster pump or the booster and therefore increases the amount
of low-temperature fluid supplied.
[0030] In the above-described invention, it is preferable that a
mesh be provided at an outlet of the low-temperature-fluid
reservoir.
[0031] Solid low-temperature fluid of the slush fluid is captured
by the mesh, and therefore, only liquid low-temperature fluid is
supplied to the booster pump or the booster downstream of the
low-temperature-fluid reservoir. This prevents the booster pump or
the booster from clogging.
[0032] In the above-described invention, it is preferable that a
heater be provided in the low-temperature-fluid reservoir.
[0033] By doing so, the solid low-temperature fluid in the
low-temperature-fluid reservoir is heated by the heater into a
liquid low-temperature fluid, which then passes though the mesh up
to the booster pump or the booster.
[0034] In the above-described invention, it is preferable that a
heat exchanger be disposed downstream of the booster pump or the
booster.
[0035] By doing so, the low-temperature fluid that has passed
through the booster pump or the booster by the heat exchanger is
vaporized by the heat exchanger and is then supplied to, for
example, an engine disposed downstream for smooth consumption in
the engine.
[0036] In the above-described invention, it is preferable that a
radiation shield plate be provided on an inner surface of the
low-temperature container.
[0037] By doing so, the radiation shield plate prevents heat from
being transmitted from the outside to the inside of the
low-temperature container. This prevents an increase in the
temperature of the heat-insulating vacuum layer in the
low-temperature container.
[0038] The present invention provides a low-temperature-fluid
boosting pump which includes a cylinder block having therein a
compression chamber; and a piston head that is accommodated in the
compression chamber and reciprocates in the compression chamber so
that a low-temperature fluid is compressed by one end surface of
the piston head, wherein a flexible partition for separating a
space adjacent to an inner circumferential side from a space
adjacent to an outer circumferential side of the piston head is
provided between the one end surface of the piston head and an
inner surface of the compression chamber which faces the one end
surface.
[0039] According to the present invention, as a result of the
piston head moving in one direction, a low-temperature fluid is
drawn into (supplied to) the inner space (i.e., the space formed by
the one end surface of the piston head, the inner circumferential
surface of the partition, and the inner surface of the compression
chamber) of the partition. Then, as a result of the piston head
moving in the other direction, the low-temperature fluid is
compressed (pressure-boosted) to a predetermined pressure.
[0040] More specifically, there are no components (e.g., piston
rings in the known art) that move in contact with each other
between the piston head and the inner circumferential surface of
the compression chamber and between the partition and the inner
circumferential surface of the compression chamber. This prevents
heat from being generated in the compression chamber and therefore
prevents the low-temperature fluid from being heated.
[0041] In addition, the partition completely partitions the inner
circumferential side (inward position in the radial direction) from
the outer circumferential side (outward position in the radial
direction) of the compression chamber. Therefore, low-temperature
fluid can be prevented from leaking from the inner circumferential
side of the compression chamber to the outer circumferential side
of the compression chamber (or from the outer circumferential side
of the compression chamber to the inner circumferential side of the
compression chamber). This improves the compression efficiency of
the low-temperature-fluid boosting pump.
[0042] In the above-described invention, it is preferable that a
pressure-boosted fluid reside on an outer side of the
partition.
[0043] For example, a vaporized low-temperature fluid having a
predetermined pressure is provided (supplied) to an outer side of
the partition, and the pressure difference between the inner side
and the outer side of the partition becomes small (becomes
closer).
[0044] More specifically, for example, a low-temperature fluid that
has been vaporized as a result of being heated by the heat
exchanger and subjected to pressure adjustment by the pressure
regulator to a predetermined pressure (e.g., a pressure half the
pressure-boosting force of the present booster pump) exists on the
outer side (towards the outside in the radial direction) of the
partition. Because of this, deformation of the partition can be
prevented when the low-temperature fluid drawn into the inner space
of the partition is to be compressed, and therefore, the service
life of the partition can be extended. This improves the
reliability of the low-temperature-fluid boosting pump.
[0045] In the above-described invention, it is preferable that an
outer side of the partition be vacuumed.
[0046] In other words, the space between the partition and the
cylinder block is vacuumed so that the heat on an inner side of the
partition (i.e., heat of the low-temperature fluid compressed on
the inner side of the partition) is prevented from being
transmitted to the cylinder block.
[0047] By doing so, not only is an increase in the temperature of
the cylinder block suppressed, but also an increase in the
temperature of the low-temperature fluid flowing into the
compression chamber is suppressed.
[0048] The present invention provides a low-temperature-fluid
boosting pump which includes a piston rod driven by a drive unit
connected to a driving source; a piston head that is connected to
the piston rod and reciprocates with the piston rod; and a cylinder
having a compression chamber that accommodates the piston head so
that a low-temperature fluid is compressed by one end surface of
the piston head, wherein the drive unit is disposed adjacent to the
one end surface of the piston head, and a shank of the piston rod
is subjected to a tensile force in a direction substantially equal
to a direction in which the shank extends when the low-temperature
fluid is to be compressed.
[0049] According to the present invention, as a result of the
piston rod being pulled towards the drive unit, the low-temperature
fluid is compressed by one end surface of the piston head. In other
words, when the low-temperature fluid is to be compressed, no
compressive force is applied to the piston rod.
[0050] As a result, the diameter of the piston rod can be reduced
compared with a piston rod in the known art, which is subjected to
a compressive force. Therefore, not only can the amount of heat
entering from a driving source be reduced, but also the weight of
the piston rod can be reduced. Consequently, the weight of the
entire pump can also be reduced.
[0051] In addition, since the piston rod is not subjected to a
compressive force when the low-temperature fluid is to be
compressed, the diameter of the piston head can be increased. In
other words, for the known pump where a compressive force is
applied to the piston rod, the diameter of the piston head is
limited to, for example, 40 mm to prevent the piston rod from
buckling. For this reason, the known pump required, for example,
five cylinders to achieve a sufficient flow volume of
low-temperature fluid. For the pump according to the present
invention, however, the diameter of the piston head can be, for
example, 100 mm, and therefore, a sufficient flow volume can be
achieved with a single cylinder.
[0052] As a result, for the pump according to the present
invention, not only can the structure of the pump be simplified,
but also the entire pump can be made lightweight and compact.
[0053] In the above-described invention, it is preferable that the
piston head be divided into at least two concentric subsections to
achieve a multistage compression structure where the
low-temperature fluid is gradually increased to a desired pressure
by sequentially passing through the one end surface of the divided
piston head.
[0054] The piston head is divided into, for example, two
subsections, one subsection disposed towards the outside in the
radial direction and the other disposed towards the inside in the
radial direction, so that the first compression (first-stage
compression) is carried out with the subsection disposed towards
the outside in the radial direction and the second compression
(second-stage compression) is carried out with the subsection
disposed towards the inside in the radial direction. In other
words, instead of increasing the pressure from a low pressure to a
high pressure in one stroke, the low-temperature fluid is
temporarily increased to an intermediate pressure, which is then
increased to a desired pressure (high pressure).
[0055] By doing so, the stroke of the piston head can be made
small, and therefore, the size of the entire pump in the
longitudinal direction can be reduced. This contributes to compact
design of the pump.
[0056] In the above-described invention, it is preferable that a
flexible partition for separating a space adjacent to the piston
rod from a space adjacent to the cylinder in the compression
chamber be provided adjacent to the one end surface and adjacent to
the other end surface of the piston head.
[0057] The partition separates the space adjacent to the piston rod
from the space adjacent to the cylinder in the compression chamber,
and there is no component (e.g., piston ring in the known art) that
moves in contact with the inner circumferential surface of the
compression chamber. This prevents heat from being generated in the
compression chamber and therefore prevents the flow-temperature
fluid from being heated.
[0058] In addition, since the partition completely separates a
space adjacent to the piston rod from a space adjacent to the
cylinder in the compression chamber, the low-temperature fluid is
prevented from leaking from the cylinder side of the compression
chamber to the piston rod side of the compression chamber. This
improves the compression efficiency.
[0059] In the above-described invention, it is preferable that a
flexible partition for separating a space adjacent to the piston
rod from a space adjacent to the cylinder in the compression
chamber be provided adjacent to the other end surface of the piston
head.
[0060] By doing so, since all the flexible partitions are provided
on the side opposite to the one end surface (compressive surface)
of the piston head, the length of the pump in the height direction
(longitudinal direction) can be reduced, and therefore, the pump
can be made compact.
[0061] In addition, since the one end surface (compressive surface)
of the piston head can be utilized to the full extent for
compression of the low-temperature fluid, a larger amount of
low-temperature fluid can be compressed at a time. In short, the
efficiency (performance) of the pump can be improved.
[0062] In the above-described invention, it is preferable that a
precooling layer be formed in the cylinder.
[0063] By doing so, the entire pump can be cooled sufficiently
before the pump is started. This decreases vaporization (boil-off)
of the low-temperature fluid supplied to the pump.
[0064] Furthermore, since this precooling layer also serves as a
heat-insulating layer while the pump is being operated,
vaporization (boil-off) of the low-temperature fluid can be reduced
also while the pump is being operated.
[0065] In the above-described invention, it is preferable that the
drive unit be linked to the piston rod via a heat-insulating
connection section.
[0066] Since the drive unit is linked to the piston rod via, for
example, rolling elements (e.g., balls and rollers) in point or
line contact, heat can be significantly prevented from being
transmitted (entering) from the drive unit (i.e., driving source)
to the piston rod (i.e., piston head).
[0067] In the above-described invention, it is preferable that the
piston head be linked to the piston rod via a heat insulator.
[0068] Since the piston head is linked to the piston rod via the
heat insulator, even if heat is transmitted (enters) from the drive
unit to the piston rod, heat being transmitted (entering) from the
piston rod to the piston head is blocked by the heat insulator.
[0069] In the above-described invention, it is preferable that a
guiding member for guiding the shank of the piston rod be provided
between the cylinder and the piston rod.
[0070] The guiding member is provided to prevent the piston rod,
the piston head, etc., which are housed in the cylinder and
reciprocate in the cylinder, from interfering with the inner wall
surface (cylinder wall) of the cylinder.
[0071] By doing so, reciprocating members such as the piston rod
and the piston head perform reciprocal movement in the cylinder
without wobbling or vibrating. This can prevent such reciprocating
members from interfering with the inner wall surface of the
cylinder, and furthermore, allows the reciprocating members to be
driven smoothly with minimum driving force.
[0072] In the above-described invention, it is preferable that a
space between the cylinder and the shank of the piston rod be a
vacuum.
[0073] In other words, since the space between the cylinder and the
piston rod is vacuumed, heat from the piston rod (i.e., heat from
the driving source to the piston rod) is prevented from being
transmitted to the cylinder.
[0074] As a result, not only is an increase in the temperature of
the cylinder suppressed, but also an increase in the temperature of
the low-temperature fluid flowing into the compression chamber is
suppressed.
[0075] In the above-described invention, it is preferable that the
cylinder be immersed in low-temperature fluid stored in a
low-temperature-fluid storage tank and be attachable to and
detachable from the low-temperature-fluid storage tank.
[0076] By doing so, the exterior of a portion that accommodates
portions for compressing the low-temperature fluid therein, such as
the cylinder and the piston head, is immersed in the
low-temperature fluid and is always maintained in a low-temperature
state. Furthermore, the cylinder is mounted on a lower portion
(bottom portion) of the low-temperature-fluid storage tank such
that it is easily replaceable.
[0077] It is preferable that the drive unit and the cylinder be
immersed in low-temperature fluid stored in a low-temperature-fluid
storage tank and be attachable to and detachable from the
low-temperature-fluid storage tank. By doing so, the exterior of
the entire pump, including a portion that accommodates portions for
compressing the low-temperature fluid therein, such as the cylinder
and the piston head, is immersed in the low-temperature fluid and
is always maintained in a low-temperature state. Furthermore, the
low-temperature-fluid boosting pump is mounted on a lower portion
(bottom portion) of the low-temperature-fluid storage tank such
that it is easily replaceable.
[0078] The present invention provides a low-temperature-fluid
feeder which includes the above-described low-temperature-fluid
boosting pump; a chamber for reserving a low-temperature fluid
whose pressure has been increased by the above-described
low-temperature-fluid boosting pump; and a fuel injector supplied
with the low-temperature fluid from the chamber.
[0079] According to the present invention, the low-temperature
fluid whose pressure has been increased to a desired pressure by
the low-temperature-fluid boosting pump is temporarily reserved in
the chamber disposed downstream of the low-temperature-fluid
boosting pump and then passes through a fuel injector into, for
example, a combustion chamber, such as an engine.
[0080] In the above-described invention, it is preferable that a
booster-fluid feeding unit for liquefying or vaporizing the
low-temperature fluid in the chamber and supplying the
low-temperature fluid into the cylinder disposed adjacent to the
other end surface of the piston head of the low-temperature-fluid
boosting pump be provided.
[0081] By doing so, the low-temperature fluid in the chamber (or
the fluid generated by liquefying or vaporizing the low-temperature
fluid in the chamber and decreasing the pressure of the liquefied
or vaporized fluid using, for example, a pressure regulator) is
supplied into the cylinder disposed adjacent to the other end
surface of the piston head. This decreases the difference between
the pressure on the one end surface (compressive surface) side and
the pressure on the other end surface side of the piston head, thus
allowing a bellows with low pressure resistance to be employed.
[0082] In the above-described invention, it is preferable that a
booster-fluid feeding unit for vaporizing the low-temperature fluid
in the above-described chamber in a path to the fuel injector and
for supplying the low-temperature fluid to the cylinder disposed
adjacent to the other end surface of the piston head of the
low-temperature-fluid boosting pump be provided.
[0083] By doing so, the low-temperature fluid in the chamber (or
the fluid generated by or vaporizing the low-temperature fluid in
the chamber and decreasing the pressure of the vaporized fluid
using, for example, a pressure regulator) is supplied into the
cylinder disposed adjacent to the other end surface of the piston
head. This decreases the difference between the pressure on the one
end surface (compressive surface) side and the pressure on the
other end surface side of the piston head, thus allowing a bellows
with low pressure resistance to be employed.
[0084] In the above-described invention, it is preferable that the
chamber be provided with a relief valve.
[0085] By doing so, if the pressure of the chamber storing the
low-temperature fluid exceeds a predetermined pressure, the relief
valve operates to prevent the chamber from being damaged. The
low-temperature fluid discharged from the relief valve returns
through, for example, a return pipe to the suction side of the pump
(or a separate fuel battery, if any fuel battery is provided).
[0086] The present invention provides a low-temperature-fluid
boosting pump which includes a cylinder block having therein a
compression chamber; and a piston head that is accommodated in the
compression chamber and reciprocates in the compression chamber so
that a low-temperature fluid is compressed by one end surface of
the piston head, wherein a flexible partition for separating a
space adjacent to an inner circumferential side from a space
adjacent to an outer circumferential side in the compression
chamber is provided adjacent to the other end surface of the piston
head.
[0087] According to the present invention, as a result of the
piston head moving in one direction, a low-temperature fluid is
drawn into (supplied to) the compression chamber. Then, as a result
of the piston head moving in the other direction, the
low-temperature fluid is compressed (pressure-boosted) to a
predetermined pressure.
[0088] More specifically, there are no components (e.g., piston
rings in the known art) that move in contact with each other
between the piston head and the inner circumferential surface of
the compression chamber and between the partition and the inner
circumferential surface of the compression chamber. This prevents
heat from being generated in the compression chamber and therefore
prevents the low-temperature fluid from being heated.
[0089] In addition, the partition completely partitions the inner
circumferential side (inward position in the radial direction) from
the outer circumferential side (outward position in the radial
direction) of the compression chamber. Therefore, low-temperature
fluid can be prevented from leaking from the inner circumferential
side of the compression chamber to the outer circumferential side
of the compression chamber (or from the outer circumferential side
of the compression chamber to the inner circumferential side of the
compression chamber). This improves the compression efficiency of
the low-temperature-fluid boosting pump.
[0090] In the above-described invention, it is preferable that a
pressure-boosted fluid reside on an inner side of the
partition.
[0091] For example, a vaporized low-temperature fluid having a
predetermined pressure is provided at (supplied to) an inner side
of the partition, and the pressure difference between the inner
side and the outer side of the partition becomes small (becomes
closer).
[0092] More specifically, for example, a low-temperature fluid that
has been vaporized as a result of being heated by the heat
exchanger and subjected to pressure adjustment by the pressure
regulator to a predetermined pressure (e.g., a pressure half the
pressure-boosting force of the present booster pump) exists on the
inner side (towards the inside in the radial direction) of the
partition. Because of this, deformation of the partition can be
prevented when the low-temperature fluid drawn into the compression
chamber is to be compressed, and therefore, the service life of the
partition can be extended. This improves the reliability of the
low-temperature-fluid boosting pump.
[0093] In the above-described invention, it is preferable that an
inner side of the partition be vacuumed.
[0094] By doing so, even if, for example, a piston rod linked to
the piston head is provided on the inner side of the partition,
heat from this piston rod (e.g., heat being transmitted from the
driving source to the piston rod) is prevented from being
transmitted to the outer side of the partition.
[0095] As a result, not only is an increase in the temperature of
the cylinder block disposed on the outer side of the partition
suppressed, but also an increase in the temperature of the
low-temperature fluid flowing into the compression chamber is
suppressed.
[0096] In the above-described invention, it is preferable that a
guiding member for guiding the piston head be provided between the
cylinder block and the piston head.
[0097] The guiding member is provided to prevent the piston rod,
the piston head, etc., which are housed in the cylinder and
reciprocate in the cylinder, from interfering with the inner wall
surface (cylinder wall) of the cylinder.
[0098] By doing so, reciprocating members such as the piston rod
and the piston head perform reciprocal movement in the cylinder
without wobbling or vibrating. This can prevent such reciprocating
members from interfering with the inner wall surface of the
cylinder, and furthermore, allows the reciprocating members to be
driven smoothly with minimum driving force.
[0099] In the above-described invention, it is preferable that the
cylinder block be immersed in low-temperature fluid stored in a
low-temperature-fluid storage tank and be attachable to and
detachable from the low-temperature-fluid storage tank.
[0100] By doing so, the exterior of a portion that accommodates
portions for compressing the low-temperature fluid therein, such as
the cylinder block and the piston head, is immersed in the
low-temperature fluid and is always maintained in a low-temperature
state. Furthermore, the cylinder block is mounted on a lower
portion (bottom portion) of the low-temperature-fluid storage tank
such that it is easily replaceable.
[0101] The present invention affords an advantage in that the
pressure of fluid can be increased efficiently without heating the
fluid.
BRIEF DESCRIPTION OF DRAWINGS
[0102] FIG. 1 is a schematic longitudinal sectional view of a first
embodiment of a booster pump according to the present
invention.
[0103] FIG. 2 is a magnified and simplified cross-sectional view of
a main part shown in FIG. 1.
[0104] FIG. 3 is a magnified cross-sectional view of a main part of
a second embodiment of a booster pump according to the present
invention.
[0105] FIG. 4 is a magnified cross-sectional view of a main part of
a third embodiment of a booster pump according to the present
invention.
[0106] FIG. 5 is a magnified cross-sectional view of a main part of
a fourth embodiment of a booster pump according to the present
invention.
[0107] FIG. 6 is a magnified cross-sectional view of a main part of
a fifth embodiment of a booster pump according to the present
invention.
[0108] FIG. 7 is a schematic diagram of a main part of one
embodiment of a booster according to the present invention.
[0109] FIG. 8 is a graph illustrating dual-stage compression
achieved using the booster shown in FIG. 7.
[0110] FIG. 9 is a schematic diagram depicting one embodiment of a
low-temperature-fluid storage tank according to the present
invention.
[0111] FIG. 10 is a schematic diagram depicting another embodiment
of a low-temperature-fluid storage tank according to the present
invention.
[0112] FIG. 11 is a schematic longitudinal sectional view of a
sixth embodiment of a low-temperature-fluid boosting pump according
to the present invention.
[0113] FIG. 12 is a cross-sectional view taken along line XII-XII
of FIG. 11.
[0114] FIG. 13 is a schematic longitudinal sectional view of a
seventh embodiment of a low-temperature-fluid boosting pump
according to the present invention.
[0115] FIG. 14 is a schematic longitudinal sectional view of an
eighth embodiment of a low-temperature-fluid boosting pump
according to the present invention.
[0116] FIG. 15 is a cross-sectional view taken along line XV-XV of
FIG. 14.
[0117] FIG. 16 is a magnified longitudinal sectional view of a main
part of a ninth embodiment of a low-temperature-fluid boosting pump
according to the present invention.
[0118] FIG. 17 is a schematic longitudinal sectional view of a
tenth embodiment of a low-temperature-fluid boosting pump according
to the present invention.
[0119] FIG. 18 is a schematic longitudinal sectional view of an
eleventh embodiment of a low-temperature-fluid boosting pump
according to the present invention.
[0120] FIG. 19 is a schematic longitudinal sectional view of a
twelfth embodiment of a low-temperature-fluid boosting pump
according to the present invention.
[0121] FIG. 20 is a schematic longitudinal sectional view of a
thirteenth embodiment of a low-temperature-fluid boosting pump
according to the present invention.
[0122] FIG. 21 is a schematic longitudinal sectional view of a
fourteenth embodiment of a low-temperature-fluid boosting pump
according to the present invention.
[0123] FIG. 22 is a magnified longitudinal sectional view of
another embodiment of a bellows applied to a low-temperature-fluid
boosting pump according to the present invention.
[0124] FIG. 23 is a magnified longitudinal sectional view of
another embodiment of a heat-insulating connection section applied
to a low-temperature-fluid boosting pump according to the present
invention.
[0125] FIG. 24 is a schematic longitudinal sectional view
illustrating a fifteenth embodiment of a low-temperature-fluid
boosting pump according to the present invention.
[0126] FIG. 25 is across-sectional view taken along line XXV-XXV of
FIG. 24.
[0127] FIG. 26 is a schematic longitudinal sectional view of a
sixteenth embodiment of a low-temperature-fluid boosting pump
according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0128] A first embodiment of a (low-temperature-fluid) booster pump
according to the present invention will now be described with
reference to the drawings.
[0129] As shown in FIG. 1, a booster pump 1 according to this
embodiment is a so-called swash-plate (or swash) booster pump. The
booster pump 1 includes major components such as a plurality of
(e.g., seven) pistons 11; a cylinder block 12; a cylinder head 13;
a drive shaft 14; and a swash plate (also called a "yoke") 15.
[0130] Each piston 11 is a substantially rod-like member which has
a circular cross-section. Each piston 11 has a piston head 11a on
one end portion thereof and a piston shoe 11b on the other end
portion thereof. Each of the pistons 11 is reciprocably housed in a
cylinder 12a, which will be described later.
[0131] The piston head 11a is a so-called large-diameter portion
that has an outer diameter larger than the outer diameter of a
piston rod 11c that links this piston head 11a and the piston shoe
11b. A low-temperature fluid (e.g., liquid hydrogen, liquid
nitrogen, liquefied carbon dioxide, liquefied natural gas, or
liquefied propane gas) is compressed by one flat end surface (upper
end surface in FIG. 1) of this piston head 11a.
[0132] Like the piston head 11a, the piston shoe 11b is also a
so-called large-diameter portion that has an outer diameter larger
than the outer diameter of the piston rod 11c. The piston shoe 11b
is partially interposed, on an end-surface side thereof, between a
shoe plate 15a and a retainer ring 15b of the swash plate 15, which
will be described later. Furthermore, the end surface of the piston
shoe 11b slides along a tilt angle of the swash plate 15 (a sliding
surface P of a thrust roller bearing 16 disposed between the shoe
plate 15a and the retainer ring 15b).
[0133] The cylinder block 12 has therein the same number of
cylinders 12a as that of the pistons 11 and the cylinders 12a are
formed in a ring, extending along a longitudinal direction
(vertical direction in FIG. 1). Each cylinder 12a accommodates one
piston 11.
[0134] A compression chamber 12b having an inner diameter larger
than the outer diameter of the piston head 11a is provided on one
end of each cylinder 12a (upper side in FIG. 1) so that this
compression chamber 12b accommodates the piston head 11a.
[0135] As shown in FIG. 1 and FIG. 2, which is a magnified view of
the main part shown in FIG. 1, a bellows 17 is provided in the
compression chamber 12b.
[0136] This bellows 17 partitions (separates) an inner
circumferential side (piston 11 side) from an outer circumferential
side (cylinder block 12 side) of the compression chamber 12b, which
is disposed closer to the piston shoe 11b (lower side in FIG. 1)
than the piston head 11a. One end surface of the bellows 17 is
affixed to a surface opposite (other end surface) one end surface
of the piston head 11a, and the other end of the bellows 17 is
affixed to an inner wall surface of the cylinder block 12.
[0137] Furthermore, this bellows 17 is made of, for example,
stainless steel or Inconel, which exhibits elasticity at (super)
low temperatures.
[0138] The cylinder head 13 covers one end surface (upper end
surface in FIG. 1) of the cylinder block 12 to close the open ends
of the cylinders 12a formed in the cylinder block 12 (i.e., open
ends of the compression chambers 12b).
[0139] On one end surface (lower end surface in FIG. 1) of this
cylinder head 13, that is, on the surface which faces one end
surface of the cylinder block 12, a suction port 13a and a
discharge port 13b are provided for each compression chamber 12b.
Each of the suction port 13a and the discharge port 13b is provided
with a ball check valve 18 (a spring is not shown in the figure for
the sake of simplicity) to control suction and discharge of
low-temperature fluid. Furthermore, each suction port 13a
communicates with a fluid-suction channel 19 formed in the cylinder
head 13, whereas each discharge port 13b communicates with a
fluid-discharge channel 20 formed in the cylinder head 13 and the
cylinder block 12. Therefore, low-temperature fluid flowing from
the fluid-suction channel 19 through each suction port 13a to the
compression chamber 12b is subjected to a pressure increase as a
result of being compressed by one end surface of the piston head
11a and then goes out from the discharge port 13b through the
fluid-discharge channel 20.
[0140] The drive shaft 14 transmits a driving force from a driving
source (e.g., an electric motor or an engine), not shown in the
figure, to the swash plate 15. The drive shaft 14 is rotatably
supported at the other end portion of the cylinder block 12 by
bearings 21.
[0141] The swash plate 15 includes the shoe plate 15a and the
retainer ring 15b. The sliding surface P of the thrust roller
bearing 16 disposed between the shoe plate 15a and the retainer
ring 15b is defined at an angle of, for example, 1.43 degree
relative to an axis perpendicular to the longitudinal axis of the
cylinder block 12. Furthermore, the above-described piston shoe 11b
is partially interposed between the retainer ring 15b and the
thrust roller bearing 16.
[0142] On the other hand, a thrust roller bearing 22 is disposed
also between the shoe plate 15 and the cylinder block 12. This
thrust roller bearing 22 provides a thrust (load) in the axial
direction (longitudinal direction of the cylinder block 12).
[0143] The shoe plate 15a, retainer ring 15b, and thrust roller
bearings 16 and 22 rotate integrally with the drive shaft 14.
[0144] Therefore, when the drive shaft 14 is rotated (in one
direction) by the driving source, the piston shoes 11b slide along
the sliding surface P, and thereby the pistons 11 reciprocate in
the cylinder 12, thus causing low-temperature fluid flowing in the
compression chambers 12b to be compressed successively. In this
embodiment, the stroke of each piston 11 is set to 2 mm.
[0145] Reference numeral 23 in FIG. 1 denotes continuous holes that
allow the respective compression chambers 12b to communicate with
the outside of the booster pump 1. A pipe 24 is connected to each
of these continuous holes 23, and an on-off valve 25 is disposed at
an intermediate point in this pipe 24.
[0146] When low-temperature fluid is drawn into each compression
chamber 12b, the continuous hole 23, the pipe 24, and the on-off
valve 25 are used to cause low-temperature fluid residing adjacent
to the other end surface of the piston head 11a to flow out of the
compression chamber 12b to reduce the drive resistance of the
piston 11 or to cause low-temperature fluid built up in the
compression chamber 12b disposed adjacent to the other end surface
of the piston head 11a to flow out of the compression chamber
12b.
[0147] Therefore, the on-off valves 25 are closed (off) during a
compression stroke or if it is not necessary to expel
low-temperature fluids out of the compression chambers 12b.
[0148] The booster pump 1 according to this embodiment does not
include a component (e.g., piston ring in the known art) that moves
in contact with the inner circumferential surfaces of the
compression chambers 12b. This prevents heat from being generated
in the compression chambers 12b and therefore prevents the
low-temperature fluid from being heated.
[0149] Furthermore, the bellows 17 completely separates the inner
circumferential side from the outer circumferential side of each
compression chamber 12b disposed closer to the piston shoe 11b than
the piston head 11a. This can prevent the low-temperature fluid
from leaking from the outer circumferential side of the compression
chamber 12b into the inner circumferential side of the compression
chamber 12b. In other words, the low-temperature fluid can be
prevented from flowing out from the compression chamber 12b side
towards the piston shoe 11b side along the piston rods 11c. As a
result, the compression efficiency of the booster pump 1 can be
improved.
[0150] A second embodiment of a (low-temperature-fluid) booster
pump according to the present invention will now be described with
reference to FIG. 3.
[0151] A booster pump 2 in this embodiment differs from the booster
pump according to the above-described first embodiment in that
(thin) wires (fillers) 31 made of a material that can be used at
(super) low temperatures, such as Teflon.RTM., is wound around the
outer circumferential surface of the bellows 17. The other
components are the same as those described in the above-described
embodiment, and hence a description thereof will be omitted.
[0152] The same components as those in the above-described first
embodiment are denoted with the same reference numerals or
symbols.
[0153] As shown in FIG. 3, the wires 31 are wound around the outer
surface of the bellows 17 so as to minimize the gap between the
outer surface of the bellows 17 and the inner circumferential
surface of the compression chamber 12b.
[0154] Here, care should be exercised to prevent the outer surface
of the wires 31 wound around the outer surface of the bellows 17
from coming into contact with the inner circumferential surface of
the compression chamber 12b, particularly when the piston 11
retracts (goes down in FIG. 1) and the bellows 17 contracts.
[0155] According to the booster pump 2 of this embodiment, the gap
between the outer surface of the bellows 17 and the inner
circumferential surface of the compression chamber 12b is minimized
to reduce a dead volume of the compression chamber 12b. This
increases the compression efficiency.
[0156] The other effects and advantages are the same as those of
the above-described first embodiment, and hence a description
thereof will be omitted.
[0157] A third embodiment of a (low-temperature-fluid) booster pump
according to the present invention will now be described with
reference to FIG. 4.
[0158] A booster pump 3 in this embodiment differs from the booster
pump according to the above-described second embodiment in that
spacers (fillers) 41 made of a material that can be used at (super)
low temperatures, such as Teflon.RTM., are provided on the outer
circumferential surface of the bellows 17. The other components are
the same as those described in the above-described embodiment, and
hence a description thereof will be omitted.
[0159] The same components as those in the above-described
embodiment are denoted with the same reference numerals or
symbols.
[0160] As shown in FIG. 4, one spacer 41, which is substantially
ring-shaped in plan view, is disposed in each valley (portion
recessed towards the piston rod 11c, that is, portion further away
from the inner circumferential surface of the compression chamber
12b) of the bellows 17 so as to minimize the gap between the outer
surface of the bellows 17 and the inner circumferential surface of
the compression chamber 12b. This spacer 41 in each valley has a
cross section whose shape is substantially equal to the shape of
the cross section of each valley of the bellows 17 so as not to
prevent the bellows 17 from extending and contracting.
[0161] Here, care should be exercised, as described in the second
embodiment, to prevent the outer surface of the spacer 41 disposed
in each valley of the bellows 17 from coming into contact with the
inner circumferential surface of the compression chamber 12b,
particularly when the piston 11 retracts (goes down in FIG. 1) and
the bellows 17 contracts.
[0162] Also, according to the booster pump 3 of this embodiment,
the gap between the outer surface of the bellows 17 and the inner
circumferential surface of the compression chamber 12b is minimized
to reduce a dead volume of the compression chamber 12b. This
increases the compression efficiency.
[0163] The other effects and advantages are the same as those of
the above-described first embodiment, and hence a description
thereof will be omitted.
[0164] A fourth embodiment of a (low-temperature-fluid) booster
pump according to the present invention will now be described with
reference to FIG. 5.
[0165] A booster pump 4 in this embodiment differs from the booster
pumps according to the above-described second and third embodiments
in that particulate filler 51 made of a material that can be used
at (super) low temperatures, such as Teflon.RTM., is disposed on or
near the outer circumferential surface of the bellows 17. The other
components are the same as those described in the above-described
embodiments, and hence a description thereof will be omitted.
[0166] The same components as those in the above-described
embodiments are denoted with the same reference numerals or
symbols.
[0167] As shown in FIG. 5, the particulate filler 51 is disposed
between the outer surface of the bellows 17 and the inner
circumferential surface of the compression chamber 12b so as to
minimize the gap between the outer surface of the bellows 17 and
the inner circumferential surface of the compression chamber
12b.
[0168] Furthermore, an anti-flow ring 52 is provided at one end
portion of the bellows 17 to prevent the filler 51 from flowing
towards one end surface of the piston head 11a. This ring 52 is
formed so as to have an outer diameter that is smaller than the
inner diameter of the compression chamber 12b. This prevents the
outer circumferential surface of the ring 52 from sliding along the
inner circumferential surface of the compression chamber 12b.
[0169] Particles constituting the filler 51 are each formed so as
to have an outer diameter larger than the size of the gap between
the outer circumferential surface of the ring 52 and the inner
circumferential surface of the compression chamber 12b.
Furthermore, as much filler 51 as necessary is supplied so long as
it does not prevent the bellows 17 from extending and
contracting.
[0170] Also, according to the booster pump 4 of this embodiment,
the gap between the outer surface of the bellows 17 and the inner
circumferential surface of the compression chamber 12b is minimized
to reduce a dead volume of the compression chamber 12b. This
increases the compression efficiency.
[0171] The other effects and advantages are the same as those of
the above-described first embodiment, and hence a description
thereof will be omitted.
[0172] A fifth embodiment of a (low-temperature-fluid) booster pump
according to the present invention will now be described with
reference to FIG. 6.
[0173] A booster pump 5 in this embodiment differs from the booster
pump according to the above-described embodiment in that a sealing
member 61 made of a material that can be used at (super) low
temperatures, such as Teflon.RTM., is affixed at one end portion on
the outer circumferential surface of the bellows 17. The other
components are the same as those described in the above-described
embodiment, and hence a description thereof will be omitted.
[0174] The same components as those in the above-described
embodiment are denoted with the same reference numerals or
symbols.
[0175] As shown in FIG. 6, the sealing member 61 for reducing the
pressure applied by the low-temperature fluid to the outer
circumferential surface of the bellows 17 is disposed at one end
portion of the bellows 17. This sealing member 61 is formed so as
to have an outer diameter that is substantially equal to the inner
diameter of the compression chamber 12b so that the outer
circumferential surface of the ring 52 moves along in slight
contact with the inner circumferential surface of the compression
chamber 12b. This sealing member 61 neither has tension, as has
been problematic, for example, with a piston ring in the known art,
nor generates heat, as with a known piston ring, because the
bellows 17 considerably restricts the stroke of the piston 11 (the
stroke is small).
[0176] In addition, low-temperature fluid built up in the
compression chamber 12b disposed adjacent to the other end surface
of the piston head 11a are stored temporarily in a buffer
(chamber), not shown in the figure, through the above-described
continuous hole 23, pipe 24, and on-off valve 25 and are then
vaporized for use. Alternatively, this low-temperature fluid
returns through a pipe, not shown in the figure, to the
fluid-suction channel 19 of the booster pump 5 for the purpose of
recompression.
[0177] According to the booster pump 5 of this embodiment, the
sealing member 61 can reduce leakage of the low-temperature fluid
from one end surface towards the other end surface of the piston
head 11a, which would reduce the pressure applied to the outer
circumferential surface of the bellows 17. This allows a
low-pressure bellows which does not need to meet strict robust
design requirements to be employed and therefore allows the piston
11 to have a large stroke. Consequently, the compression efficiency
(pump efficiency) can be improved.
[0178] Furthermore, since the outer circumferential surface of the
sealing member 61 is designed to move along in slight contact with
the inner circumferential surface of the compression chamber 12b,
heat generation in the compression chamber 12b can be reduced
significantly. Consequently, heating of the low-temperature fluid
can also be moderated.
[0179] The other effects and advantages are the same as those of
the above-described first embodiment, and hence a description
thereof will be omitted.
[0180] A (low-temperature-fluid) booster 6 including one of the
above-described (low-temperature-fluid) booster pumps as a
low-pressure pump 6L and one of the above-described
(low-temperature-fluid) booster pumps as a high-pressure pump 6H
will be described below with reference to FIGS. 7 and 8.
[0181] The low-pressure pump 6L compresses low-pressure (low bulk
modulus) low-temperature fluid to an intermediate pressure. The
low-pressure pump 6L includes a low-pressure bellows 17a which does
not need to meet strict robust design requirements so long as it
can withstand intermediate pressure.
[0182] On the other hand, the high-pressure pump 6H compresses to
high pressure the intermediate-pressure (high bulk modulus)
low-temperature fluid compressed by the low-pressure pump 6L. The
high-pressure pump 6H includes a high-pressure bellows 17b which
meets strict robust design requirements so as to withstand high
pressure.
[0183] According to this booster 6, since the low-pressure pump 6L
employs the low-pressure bellows 17a, the piston 11 can have a
large stroke to easily increase the pressure of the low-temperature
fluid to an intermediate pressure. Furthermore, since the
high-pressure pump 6H employs the high-pressure bellows 17b, the
intermediate pressure of the low-temperature fluid can easily be
increased to a high pressure, even though the piston 11 cannot have
a large stroke in the high-pressure pump 6H.
[0184] In other words, if the pressure of low-temperature fluid is
to be increased from low pressure to high pressure in one stroke
using only one booster pump, the high-pressure bellows 17b needs to
be employed, which does not allow a large stroke. This makes it
difficult to increase the low-temperature fluid to the desired
pressure (high pressure).
[0185] In contrast, as described above, the low-temperature fluid
can be increased to the desired pressure more easily by carrying
out dual-stage compression of the low-temperature fluid using two
pumps.
[0186] One embodiment of a low-temperature-fluid storage tank
including a (low-temperature-fluid) booster pump or a
(low-temperature-fluid) booster will now be described with
reference to FIG. 9.
[0187] A low-temperature-fluid storage tank 7 in this embodiment
includes major components such as a (low-temperature-fluid) booster
pump 71 or a (low-temperature-fluid) booster 72; a low-temperature
container 73 having therein a heat-insulated vacuum chamber 73a; a
low-temperature-fluid reservoir 74; and a heat exchanger 75.
[0188] The booster pump 71 or the booster 72 increases
low-temperature fluid to a desired pressure. The booster pump 71
can be realized by, for example, one of the above-described
(low-temperature-fluid) booster pumps 1, 2, 3, 4, and 5. The
booster 72 can be realized by, for example, the above-described
(low-temperature-fluid) booster 6.
[0189] The low-temperature container 73 has a vacuum inside and has
a radiation shield plate 76, such as a copper plate, affixed to the
inner surface thereof. The above-described booster pump 71 or the
booster 72, the low-temperature-fluid reservoir 74, to be described
later, and the heat exchanger 75 are housed in the heat-insulated
vacuum chamber 73a of the low-temperature container 73.
[0190] The low-temperature-fluid storage layer 74 stores therein a
low-temperature (e.g., -253.degree. C.) fluid (e.g., liquid
hydrogen). This stored low-temperature fluid is guided to the
low-temperature-fluid boosting pump 71 or the low-temperature-fluid
booster 72 through a pipe 77.
[0191] One end of the heat exchanger 75 is in contact with the
inner surface of the low-temperature container 73 (i.e., inner
surface of the radiation shield plate 76). The heat exchanger 75
exchanges heat with the low-temperature container 73 to vaporize a
low-temperature fluid that has been subjected to a pressure
increase by the booster pump 71 or the booster 72 and guided
through a pipe 78. The low-temperature fluid (gas) vaporized by the
heat exchanger 75 is supplied to, for example, an engine through a
pipe 79. Furthermore, cool air collected by the heat exchanger 75
is used to cool the above-described radiation shield plate 76 or is
stored in a regenerating agent, not shown in the figure, provided
in the heat-insulated vacuum chamber 73.
[0192] According to this low-temperature-fluid storage tank 7, as
shown in FIG. 9, the booster pump 71 or the booster 72 is disposed
in the heat-insulated vacuum chamber 73a and outside the
low-temperature-fluid reservoir 74 (i.e., disposed separated from
the low-temperature-fluid reservoir 74 in the heat-insulated vacuum
chamber 73a). Therefore, the booster pump 71 or the booster 72 is
forcibly cooled and is not easily heated up, and furthermore, heat
generated from the driving source can be prevented from being
transmitted to the low-temperature fluid reserved in the
low-temperature-fluid reservoir 74. Consequently, an increase in
temperature of the low-temperature fluid can also be prevented.
[0193] It is preferable that the booster pump 71 or the booster 72
be cooled sufficiently before being operated.
[0194] Another embodiment of a low-temperature-fluid storage tank
provided with a (low-temperature-fluid) booster pump or a
(low-temperature-fluid) booster will be described below with
reference to FIG. 10.
[0195] A low-temperature-fluid storage tank 8 in this embodiment
includes major components such as a (low-temperature-fluid) booster
pump 81 or a (low-temperature-fluid) booster 82; a low-temperature
container 83 having therein a heat-insulated vacuum chamber 83a; a
low-temperature-fluid reservoir 84; and a heater 85.
[0196] The booster pump 81 or the booster 82 increases
low-temperature fluid to a desired pressure. The booster pump 81
can be realized by, for example, one of the above-described
(low-temperature-fluid) booster pumps 1, 2, 3, 4, and 5. The
(low-temperature-fluid) booster 82 can be realized by, for example,
the above-described (low-temperature-fluid) booster 6.
[0197] The low-temperature container 83 has a vacuum inside and has
a radiation shield plate 86, such as a copper plate, affixed to the
inner surface thereof. The above-described booster pump 81 or the
booster 82 and the low-temperature-fluid reservoir 84, to be
described later, are housed in the heat-insulated vacuum chamber
83a of the low-temperature container 83.
[0198] The low-temperature-fluid storage layer 84 stores therein a
low-temperature (e.g., -260.degree. C.) slushy fluid (e.g., slush
hydrogen: mixture of solid hydrogen and liquid hydrogen in a
liquid/ice state, with higher density and a higher coldness
capacity than liquid hydrogen). This stored low-temperature fluid
is guided to the low-temperature-fluid boosting pump 81 or the
low-temperature-fluid booster 82 through a pipe 87.
[0199] If slush hydrogen is stored in the low-temperature-fluid
storage layer 84, the slush hydrogen is produced by a slush
hydrogen producing apparatus, not shown in the figure, provided in
this low-temperature-fluid storage layer 84 or by a slush hydrogen
producing facility 88 separately provided outside the
low-temperature container 83.
[0200] A mesh (screen) 89 is provided in the pipe 86. This mesh 89
is formed so as to pass only liquid low-temperature fluid (e.g.,
liquid hydrogen) (i.e., so as to block solid hydrogen). By doing
so, the booster pump 81 or the booster 82 downstream is supplied
with only liquid low-temperature fluid to prevent clogging from
occurring in the booster pump 81 or the booster 82.
[0201] The heater 85 changes (melts) solid low-temperature fluid
(e.g., solid hydrogen) into liquid low-temperature fluid (e.g.,
liquid hydrogen).
[0202] Furthermore, it is more preferable that the above-described
heat exchanger 75 be disposed downstream of the booster pump 81 or
the booster 82 inside (or outside) the low-temperature container
83.
[0203] According to this low-temperature-fluid storage tank 8, the
low-temperature-fluid storage layer 84 contains a slushy
low-temperature fluid and experiences vaporization less easily than
tanks containing only liquid low-temperature fluids. This improves
the suction performance of the booster pump 81 or the booster 82
and therefore increases the amount of low-temperature fluid
supplied.
[0204] Although a dual-stage compression technique using two pumps
is employed in the embodiment described with reference to FIGS. 7
and 8, the present invention is not limited to this technique.
Three-stage compression using three pumps or multi-stage
compression using three or more pumps can also be employed.
[0205] Furthermore, such multi-stage compression does not always
require a plurality of pumps. Instead, multi-stage compression may
be achieved with a single pump.
[0206] In addition, the booster pump according to the present
invention can be used to increase the pressure of not only
low-temperature fluids but also fluids having various temperatures
ranging from normal to high temperatures.
[0207] Furthermore, the piston rods of the booster pump preferably
have a heat-insulating vacuum structure that is hollow and
vacuumed. As a result of the piston rods having a hollow structure
in this manner, the weight of the piston rods can be reduced so
that the pistons can be pushed up under a small load. In addition,
by vacuuming the interiors of the piston rods, the piston rods can
block heat to reduce the amount of heat propagating from the piston
rods into the fluids.
[0208] A sixth embodiment of a low-temperature-fluid boosting pump
according to the present invention will be described below with
reference to drawings.
[0209] As shown in FIG. 11, a low-temperature-fluid boosting pump
101 according to this embodiment includes major components such as
a drive unit 111 and a pump unit 112 driven by this drive unit
111.
[0210] The drive unit 111 includes a rod 115 and a power
transmission unit 116 for transmitting a driving force from a
driving source (e.g., an electric motor or an engine), not shown in
the figure, to the rod 115.
[0211] The rod 115 is a substantially rod-like member having a
circular cross section, extending downwards from the lower end
surface of the power transmission unit 116. The rod 115 has a
heat-insulating connection section 128 at a lower end portion
thereof.
[0212] The power transmission unit 116 causes the rod 115 to
reciprocate linearly in the vertical direction (in the direction
indicated by the arrow in FIG. 11) with a stroke of, for example, 2
mm by using a driving force from the driving source, not shown in
the figure.
[0213] The pump unit 112 includes a piston 121, a piston rod 122,
and a cylinder block 123.
[0214] The piston 121 includes one piston main body 124 and one or
more (four in this embodiment) piston heads 125, and is
reciprocably housed in a cylinder 126 formed in the cylinder block
123.
[0215] The piston main body 124 is a substantially disc-shaped
member. One end portion of the piston rod 122 is linked to a center
portion of the piston main body 124. In addition, four rods 127 for
linking the lower end surfaces of the respective piston heads 125
to the upper end surface of the piston main body 124 are provided
on the outer circumference of the piston main body 124.
[0216] The four piston heads 125 are arranged at regular intervals
(90.degree.) as shown in FIG. 12. Each of the piston heads 125 is a
substantially disc-shaped member and is constructed so as to
compress low-temperature fluids (e.g., liquid hydrogen, liquid
nitrogen, liquefied carbon dioxide, liquefied natural gas),
liquefied propane gases, etc. by means of one end surface thereof
(upper end surface in FIG. 11).
[0217] The piston rod 122 is a circular-cross-section,
substantially rod-like member and has one end portion thereof
linked to the upper end surface of the piston main body 124, as
described above, and the other end portion thereof connected to an
end portion (lower end portion in FIG. 11) of the rod 115 via the
heat-insulating connection section 128.
[0218] The heat-insulating connection section 128 includes an end
portion 128a of the rod 115 having a structure similar to the inner
race of a roller bearing; the other end portion 128b of the piston
rod 122 having a structure similar to the outer race of a roller
bearing; and a plurality of (four in this embodiment) rolling
elements (e.g., balls and rollers) 128c disposed between the end
portion 128a of the rod 115 and the other end portion 128b of the
piston rod 122.
[0219] By doing so, the end portion 128a of the rod 115 and the
other end portion 128b of the piston rod 122 are linked to each
other in point or line contact via the rolling elements 128c. This
significantly reduces the amount of heat transmitted (entering)
from the rod 115 to the piston rod 122.
[0220] In addition, since the piston rod 122 is designed to have
the maximum possible length, even if heat is transmitted (enters)
from the rod 115 to the piston rod 122, the amount of heat
transmitted (entering) from the piston rod 122 to the piston main
body 124 is minimized.
[0221] A through-hole 123a through which the rod 115 passes is
formed in the top center of the cylinder block 123. An inner space
129 communicating with the through-hole 123a is formed inside the
top portion of the cylinder block 123. The heat-insulating
connection section 128 is accommodated in this inner space 129.
[0222] Furthermore, in the cylinder block 123 below this inner
space 129, the cylinder 126 communicating with the inner space 129
via a through-hole 123b through which the piston rod 122 passes is
formed in the longitudinal direction (vertical direction in FIG.
11). One end (upper side in FIG. 11) of the cylinder 126
constitutes compression chambers 126a each having an inner diameter
larger than the outer diameter of the piston head 125. The piston
heads 125 are accommodated in these compression chambers 126a,
respectively.
[0223] As indicated by reference symbol 123c, the interiors of the
side wall, the bottom surface, and the top surface of the cylinder
block 123 are hollow and vacuumed to achieve a heat-insulating
vacuum structure.
[0224] On the other hand, a suction port 123d and a discharge port
123e communicating with a compression chamber 126a are provided at
a position which faces the center of one end surface of the
corresponding piston head 125 in the cylinder block 123, disposed
between the compression chamber 126a and the inner space 129. The
suction port 123d and the discharge port 123e are each provided
with a ball check valve 130 to control suction and discharge of
low-temperature fluids.
[0225] Each suction port 123d is provided so as to communicate with
a fluid-suction channel 131 formed in the cylinder block 123,
whereas each discharge port 123e is provided so as to communicate
with a fluid-discharge channel 132 formed in the cylinder block
123. Therefore, a low-temperature fluid guided from the
fluid-suction channel 131 via each suction port 123d into the
compression chamber 126a is compressed by one end surface of the
piston head 125 so that the pressure is increased to, for example,
30 MPa. Thereafter, the low-temperature fluid is guided out of the
cylinder block 123 from the discharge port 123e via the
fluid-discharge channel 132.
[0226] The low-temperature fluid that has been guided out of the
cylinder block 123 via the fluid-discharge channel 132 is
temporarily stored (reserved) in a chamber 134 via a pipe 133. The
low-temperature fluid reserved in the chamber 134 is guided into a
heat exchanger 136 through a pipe 135 and then vaporized. Most of
the low-temperature fluid is supplied to a fuel injector, not shown
in the figure, through a pipe 137, whereas part of the
low-temperature fluid is guided through a pipe 138 and a pressure
regulator (decompressor) 139 into the cylinder 126 (a space between
the lower surface at the other end portion of the piston main body
124, disposed adjacent to the other end side, i.e., the side
opposite to the compression chambers 126a, of the cylinder 126, and
the bottom surface of the cylinder 126).
[0227] Low-temperature fluid whose pressure has been increased to,
for example, 30 MPa is reserved in the chamber 134.
[0228] In addition, vaporized low-temperature fluid whose pressure
has been decreased to, for example, 15 MPa by the pressure
regulator 139 is supplied into the cylinder 126.
[0229] Each compression chamber 126a has a bellows (partition) 140
therein. This bellows 140 partitions (separates) an inner
circumferential side (inward position in the radial direction) from
an outer circumferential side. (outward position in the radial
direction) of the corresponding compression chamber 126a, which is
disposed above the piston head 125 (on the opposite side to the
piston main body 124). One end of the bellows 140 is affixed to an
outer circumferential end portion on one end surface of the piston
head 125, and the other end of the bellows 140 is affixed to the
inner wall surface of the cylinder block 123 located at an outward
position in the radial direction of the suction port 123d and the
discharge port 123e.
[0230] Furthermore, a bellows (partition) 141 is also provided at
an outward position in the radial direction at one end portion of
the piston rod 122. This bellows 141 partitions (separates) an
inner circumferential side (adjacent to the piston rod 122) from an
outer circumferential side (adjacent to the cylinder block 123) of
the piston rod 122 at one end portion thereof. One end of the
bellows 141 is affixed to the upper end surface of the piston main
body 124, and the other end of the bellows 141 is affixed to the
inner wall surface of the cylinder block 123.
[0231] Furthermore, these bellows 140 and 141 are made of, for
example, stainless steel or Inconel, which exhibits elasticity at
(super) low temperatures.
[0232] Reference numerals 142, 143, and 144 in FIG. 11 each denote
a (heat-insulating) sealing member which is ring-shaped in plan
view.
[0233] FIG. 12 is a cross-sectional view taken along line XII-XII
of FIG. 11.
[0234] With the above-described structure, when the rod 115 of the
drive unit 111 reciprocates linearly in the vertical direction, the
piston rod 122 linked to the rod 115 through the heat-insulating
connection section 128 reciprocates linearly in the vertical
direction together with the piston 121, low-temperature fluid
supplied from the suction ports 123d is compressed by one end
surface of each piston head 125 so that the pressure is increased,
and then the low-temperature fluid is expelled from the discharge
port 123e via the fluid-discharge channel 132 to the outside of the
cylinder block 123.
[0235] The low-temperature-fluid boosting pump 101 according to
this embodiment does not include a component (e.g., piston ring in
the known art) that moves in contact with the inner circumferential
surfaces of the compression chambers 126a. This prevents heat from
being generated in the compression chambers 126a and therefore
prevents the low-temperature fluid from being heated.
[0236] In addition, each bellows 140 completely partitions an inner
circumferential side (inward position in the radial direction) from
an outer circumferential side (outward position in the radial
direction) of the corresponding compression chamber 126a.
Therefore, low-temperature fluid can be prevented from leaking from
the inner circumferential side of the compression chamber 126a to
the outer circumferential side of the compression chamber 126a (or
from the outer circumferential side of the compression chamber 126a
to the inner circumferential side of the compression chamber 126a).
This improves the compression efficiency of the
low-temperature-fluid boosting pump 101.
[0237] Furthermore, since low-temperature fluid that is vaporized
by the heat exchanger 136 and subjected to pressure adjustment to a
predetermined pressure (e.g., 15 MPa) by the pressure regulator 139
exists outside each bellows 140 (outward position in the radial
direction), deformation of the bellows 140 can be reduced when
low-temperature fluid drawn into the bellows 140 is to be
compressed. This extends the service life of the bellows 140 and
increases the reliability of the low-temperature-fluid boosting
pump 101.
[0238] In addition, according to the low-temperature-fluid boosting
pump 101 of this embodiment, since low-temperature fluid is
compressed in the inner space of each bellows 140 (the space
defined by the inner circumferential surface of the bellows 140,
one end surface of the piston head 125, and the top surface of the
compression chamber 126a), the length of each rod 127 linking the
piston head 125 to the piston main body 124 can be reduced.
Consequently, not only can the length of the pump unit 112 in the
longitudinal direction (axial direction) be reduced, but also the
length of the entire pump in the longitudinal direction (axial
direction) can be reduced. This contributes to compact and
lightweight design of the pump.
[0239] Furthermore, as a result of the piston rod 122 being pulled
towards the drive unit 111 (upward in FIG. 11), low-temperature
fluid is compressed by one end surface of each piston head 125. In
other words, when low-temperature fluid is to be compressed, no
compressive force is applied to the piston rod 122.
[0240] As a result, the diameter of the piston rod 122 can be
reduced compared with a piston rod in the known art, which is
subjected to a compressive force. Therefore, not only can the
amount of heat entering from a driving source be reduced, but also
the weight of the piston rod 122 can be reduced. Consequently, the
weight of the entire pump can also be reduced.
[0241] In addition, the heat-insulating connection section 128
reduces the amount of heat entering from the rod 115 to the piston
rod 122, thereby further reducing the amount of heat entering from
the driving source.
[0242] Furthermore, because the piston main body 124 is provided
between the piston rod 122 and the piston heads 125, heat from the
piston rod 122 reaches the piston heads 125 through the piston main
body 124. This can further reduce the input amount of heat.
[0243] In addition, since the rod 115 connecting to the power
transmission unit 116 extends to the side where the suction ports
123d and the discharge ports 123e are disposed (upper side in FIG.
11), not only can the length of the pump unit 112 in the
longitudinal direction (axial direction) be reduced, but also the
length of the entire pump in the longitudinal direction (axial
direction) can be reduced. This contributes to compact and
lightweight design of the pump.
[0244] A seventh embodiment of a low-temperature-fluid boosting
pump according to the present invention will now be described with
reference to FIG. 13.
[0245] A low-temperature-fluid boosting pump 202 according to this
embodiment is a so-called swash plate (or swash) pump. The
low-temperature-fluid boosting pump 202 includes major components
such as a drive unit 261 and a pump unit 262 that is driven by this
drive unit 261.
[0246] The same components as those in the above-described sixth
embodiment are denoted with the same reference numerals or
symbols.
[0247] The drive unit 261 includes a rod 265 and a power
transmission unit 266 that transmits a driving force from a driving
source (e.g., an electric motor or an engine), not shown in the
figure, to the rod 265.
[0248] The rod 265 is a substantially rod-like member having a
circular cross section, extending downwards from the lower end
surface of the power transmission unit 266.
[0249] The power transmission unit 266 rotates the rod 265 in one
direction (direction indicated by the arrow in FIG. 13) using a
driving force from a driving source, not shown in the figure.
[0250] The pump unit 262 includes one or more (four in this
embodiment) pistons 271, a swash plate (also called a "yoke") 272,
and a cylinder block 273.
[0251] Each piston 271 is a circular-cross-section, substantially
rod-like member having a piston head 271a at one end portion
thereof and a piston shoe 271b at the other end portion thereof.
Each piston 271 is reciprocably housed in a cylinder 276.
[0252] The piston head 271a is a so-called large-diameter portion
that has an outer diameter larger than the outer diameter of a
piston rod 271c that links this piston head 271a and the piston
shoe 271b. Low-temperature fluid (e.g., liquid hydrogen, liquid
nitrogen, liquefied carbon dioxide, liquefied natural gas),
liquefied propane gas, etc. are compressed by one flat end surface
(upper end surface in FIG. 13) of this piston head 271a.
[0253] Like the piston head 271a, the piston shoe 271b is also a
so-called large-diameter portion that has an outer diameter larger
than the outer diameter of the piston rod 271c. One end surface
(lower surface in FIG. 13) of the piston shoe 271b slides along a
sliding surface P of the swash plate 272 having a tilt angle.
[0254] The cylinder block 273 has therein the same number of
compression chambers 126a as that of the pistons 271 and the
compression chambers 126a are formed along a longitudinal direction
(vertical direction in FIG. 13). Each compression chamber 126a
accommodates one piston head 271a.
[0255] As shown in FIG. 13, the piston shoes 271b and the swash
plate 272 are housed adjacent to the other end side (lower side in
FIG. 13) of the cylinder 276.
[0256] Furthermore, a through-hole 123a through which the rod 265
passes is formed in the center of the cylinder block 273.
Furthermore, the interiors of the side wall, the bottom surface,
and the top surface of the cylinder block 123 constitute a
heat-insulating vacuum structure that is hollow and vacuumed, as
shown by reference symbol 123c.
[0257] On the other hand, a suction port 123d and a discharge port
123e communicating with a compression chamber 126a are provided at
a position which faces the center of one end surface of the
corresponding piston head 271a, i.e., at a top portion in the
cylinder block 273. The suction port 123d and the discharge port
123e are each provided with a ball check valve 130 to control
suction and discharge of low-temperature fluid.
[0258] Each suction port 123d is provided so as to communicate with
a fluid-suction channel 131 formed in the cylinder block 123,
whereas each discharge port 123e is provided so as to communicate
with a fluid-discharge channel 132 formed in the cylinder block
123. Therefore, low-temperature fluid guided from the fluid-suction
channel 131 via each suction port 123d into the compression chamber
126a is compressed by one end surface of the piston head 271a so
that the pressure is increased to, for example, 30 MPa. Thereafter,
the low-temperature fluid is guided out of the cylinder block 273
from the discharge port 123e via the fluid-discharge channel
132.
[0259] The low-temperature fluid that has been guided out of the
cylinder block 273 via the fluid-discharge channel 132 is
temporarily stored (reserved) in a chamber 134 via a pipe 133. The
low-temperature fluid reserved in the chamber 134 is guided into a
heat exchanger 136 through a pipe 135 and then vaporized. Most of
the low-temperature fluid is supplied to a fuel injector, not shown
in the figure, through a pipe 137, whereas part of the
low-temperature fluid is guided through a pipe 138 and a pressure
regulator (decompressor) 139 into the compression chamber 126a
(i.e., a space adjacent to the other end surface of each piston
head 271a, located opposite to a bellows 140).
[0260] Low-temperature fluid whose pressure has been increased to,
for example, 30 MPa is reserved in the chamber 134.
[0261] In addition, vaporized low-temperature fluid whose pressure
has been decreased to, for example, 15 MPa by the pressure
regulator 139 is supplied into the compression chamber 126a.
[0262] Each compression chamber 126a has the bellows (partition)
140 therein. This bellows 140 partitions (separates) an inner
circumferential side (inward position in the radial direction) from
an outer circumferential side (outward position in the radial
direction) of the corresponding compression chamber 126a, which is
disposed above the piston head 271a (on the opposite side to the
piston rod 271c). One end of the bellows 140 is affixed to an outer
circumferential end portion on one end surface of the piston head
271a, and the other end of the bellows 140 is affixed to the inner
wall surface of the cylinder block 273 located at an outward
position in the radial direction of the suction port 123d and the
discharge port 123e.
[0263] Furthermore, a bellows (partition) 280 is also provided at
an outward position in the radial direction at one end portion of
the piston rod 271c. This bellows 280 partitions (separates) an
inner circumferential side (adjacent to the piston rod 271c) from
an outer circumferential side (adjacent to the cylinder block 273)
of the piston rod 271c at one end portion thereof. One end of the
bellows 280 is affixed to an outer circumferential end portion on
the other end surface (upper surface in FIG. 13) of the piston shoe
271b, and the other end of the bellows 280 is affixed to the inner
wall surface of the cylinder block 273.
[0264] These bellows 140 and 280 are made of, for example,
stainless steel or Inconel, which exhibits elasticity at (super)
low temperatures.
[0265] Reference numerals 142, 143, and 144 in FIG. 13 each denote
a (heat-insulating) sealing member which is ring-shaped in plan
view. Reference numerals 281 and 282 each denote a thrust roller
bearing.
[0266] With the above-described structure, when the rod 265 is
rotated by the driving source (in one direction), the piston shoes
271b slide along the sliding surface P by means of the thrust
bearings 281, and furthermore, the pistons 271 are caused to
reciprocate in the cylinder 276, thereby successively compressing
low-temperature fluid flowing into the compression chambers 126a.
In this embodiment, the strokes of the pistons 271 are set to, for
example, 2 mm.
[0267] The low-temperature-fluid boosting pump 202 according to
this embodiment does not include a component (e.g., piston ring in
the known art) that moves in contact with the inner circumferential
surfaces of the compression chambers 126a. This prevents heat from
being generated in the compression chambers 126a and therefore
prevents the low-temperature fluid from being heated.
[0268] In addition, each bellows 140 completely partitions
(separates) an inner circumferential side (inward position in the
radial direction) from an outer circumferential side (outward
position in the radial direction) of the corresponding compression
chamber 126a. Therefore, low-temperature fluid can be prevented
from leaking from the inner circumferential side of the compression
chamber 126a to the outer circumferential side of the compression
chamber 126a (or from the outer circumferential side of the
compression chamber 126a to the inner circumferential side of the
compression chamber 126a). This improves the compression efficiency
of the low-temperature-fluid boosting pump 202.
[0269] Furthermore, since low-temperature fluid that is vaporized
by the heat exchanger 136 and subjected to pressure adjustment to a
predetermined pressure (e.g., 15 MPa) by the pressure regulator 139
exists outside each bellows 140 (outward position in the radial
direction), deformation of the bellows 140 can be reduced when
low-temperature fluid drawn into the bellows 140 is to be
compressed. This extends the service life of the bellows 140 and
increases the reliability of the low-temperature-fluid boosting
pump 202.
[0270] In addition, according to the low-temperature-fluid boosting
pump 202 of this embodiment, since low-temperature fluid is
compressed in the inner space of each bellows 140 (the space
defined by the inner circumferential surface of the bellows 140,
one end surface of the piston head 271a, and the top surface of the
compression chamber 126a), the length of each piston rod 271c
linking the piston head 271a to the piston shoe 271b can be
reduced. Consequently, not only can the length of the pump unit 262
in the longitudinal direction (axial direction) be reduced, but
also the length of the entire pump in the longitudinal direction
(axial direction) can be reduced. This contributes to compact and
lightweight design of the pump.
[0271] Furthermore, as a result of the rod 265 being rotated in one
direction (as indicated by the arrow in FIG. 13), the
low-temperature fluid is compressed by one end surface of each
piston head 271a. In other words, when the low-temperature fluid is
to be compressed, no compressive force is applied to the rod
265.
[0272] As a result, the diameter of the rod 265 can be reduced
compared with the type of piston rod used in the known art, which
is subjected to a compressive force. Therefore, not only can the
amount of heat entering from a driving source be reduced, but also
the weight of the rod 265 can be reduced. Consequently, the weight
of the entire pump can also be reduced.
[0273] In addition, since the rod 265 connecting to the power
transmission unit 266 extends to the side where the suction ports
123d and the discharge ports 123e are disposed (upper side in FIG.
13), not only can the length of the pump unit 262 in the
longitudinal direction (axial direction) be reduced, but also the
length of the entire pump in the longitudinal direction (axial
direction) can be reduced. This contributes to compact and
lightweight design of the pump.
[0274] Although a four-cylinder structure provided with four
pistons and four cylinders has been described in the
above-described embodiment, the present invention is not limited to
this structure. For example, a single-cylinder, two-cylinder,
three-cylinder, or five-or-more-cylinder structure is also
acceptable.
[0275] Furthermore, the thrust roller bearing 282 described in the
seventh embodiment is not limited to the type of bearing that
supports the swash plate 272 at a single point in the center on the
bottom surface of the swash plate 272, as shown in FIG. 13.
Instead, the entire bottom surface of the swash plate 272 can be
supported with two or more thrust roller bearings disposed in the
circumferential direction.
[0276] In addition, it is preferable that the angle of this swash
plate 272 be variable using, for example, an actuator. In other
words, a variable-capacity structure is preferable. By doing so,
the amount of discharge by the pump can be changed simply by
changing the angle of the swash plate 272, i.e., without changing
the number of revolutions for driving the pump.
[0277] Furthermore, although each of the suction port 123d and the
discharge port 123e is provided with the ball check valve 130 in
the above-described embodiment, the present invention is not
limited to this structure. Instead, a forcible drive system as seen
with, for example, a DOHC of an internal-combustion engine is also
acceptable. Furthermore, a structure with a reed valve, a poppet
valve, etc. can also be used.
[0278] In addition, although low-temperature fluid vaporized by the
heat exchanger 136 is supplied to the outside of the bellows 140
and 280 in the above-described sixth embodiment or the seventh
embodiment, the present invention is not limited to this structure.
Instead, the space receiving vaporized low-temperature fluid can be
vacuumed.
[0279] More specifically, the spaces between the bellows 140 and
280 and the cylinder blocks 123 and 273 are vacuumed to prevent
heat in the bellows 140 and 280 (i.e., heat of low-temperature
fluid compressed at the inner sides of the bellows 140 and 280)
from being transmitted to the cylinder blocks 123 and 273.
[0280] By doing so, not only is an increase in the temperature of
the cylinder blocks 123 and 273 suppressed, but also an increase in
the temperature of the low-temperature fluid flowing into the
compression chambers is suppressed.
[0281] In this case, the pipe 138 and the pressure regulator 139
shown in FIGS. 11 and 13 are omitted.
[0282] Furthermore, in the above-described sixth embodiment, it is
more preferable that a guiding member be provided, for example,
between the piston rod 122 and the cylinder block 123 or between
the linkage member 124 and the cylinder 126 so that the piston main
body, the piston heads, etc. that are housed in the cylinder to
reciprocate in the cylinder do not interfere with the inner wall
surface of the cylinder (cylinder wall).
[0283] Examples of such a guiding member include a linear bearing
disposed between the piston rod 122 and the cylinder block 123 or
between the outer circumferential surface of the linkage member 124
and the inner wall surface of the cylinder 126, a member that
guides a cylindrical protrusion protruding downwards from the lower
end surface of the linkage member 124 into a cylindrical
indentation (dent) formed in the center of the bottom surface of
cylinder 126, and so forth.
[0284] By doing so, reciprocating members such as the piston main
body and the piston heads perform reciprocal movement in the
cylinder without wobbling or vibrating. This can prevent such
reciprocating members from interfering with the inner wall surface
of the cylinder, and furthermore, allows the reciprocating members
to be driven smoothly with minimum driving force.
[0285] In addition, in each of the above-described sixth and the
seventh embodiments, spaces receiving the low-temperature fluid
vaporized in these embodiments can be vacuumed.
[0286] By doing so, not only is an increase in the temperature of
the cylinder blocks suppressed, but also an increase in the
temperature of low-temperature fluid flowing into the compression
chambers is suppressed.
[0287] In this case, the pipe 138 and the pressure regulator 139
shown in FIGS. 11 and 13 are omitted.
[0288] Furthermore, in the above-described sixth embodiment, it is
more preferable that an vacuumed space be formed between the piston
rod 122 and the cylinder block 123.
[0289] For example, a bellows (same as the bellows 141) for
separating a space adjacent to the inner circumferential side from
a space adjacent to the outer circumferential side of the piston
rod 122 is provided between the lower surface of the other end
portion 128b of the piston rod 122 and the upper surface of the
bottom of the inner space 129 shown in FIG. 11.
[0290] More specifically, the space between the cylinder block 123
and the piston rod 122 is vacuumed to prevent heat from the piston
rod 122 (i.e., heat moving from the drive unit 111 side to the
piston rod 122 side) from being transmitted to the cylinder block
123.
[0291] By doing so, not only is an increase in the temperature of
the cylinder blocks 123 suppressed, but also an increase in the
temperature of low-temperature fluid flowing into the compression
chambers 126a is suppressed.
[0292] An eighth embodiment of a low-temperature-fluid boosting
pump according to the present invention will be described with
reference to the drawings.
[0293] As shown in FIG. 14, a low-temperature-fluid boosting pump
301 according to this embodiment includes major components such as
a drive unit 311 and a pump unit 312 driven by this drive unit
311.
[0294] The drive unit 311 includes a cam 313; a reciprocating
section 314; a linear bearing 315; an urging member 316; and a
casing 317 for accommodating these elements.
[0295] The cam 313 is a circular arc cam (convex cam) having a
maximum lift of, for example, 2 mm and is fixed on a drive shaft
318 of a driving source (e.g., an electric motor or an engine), not
shown in the figure. The cam 313 rotates in one direction along
with the drive shaft 318, which rotates as a result of the driving
source being driven.
[0296] The reciprocating section 314 is a substantially cylindrical
member having an inner space formed therein. The reciprocating
section 314 has a roller bearing 319 in the inner space thereof,
and furthermore, a substantially bar-like rod 320 having a circular
cross section extends downwards from the lower end surface of the
reciprocating section 314.
[0297] The roller bearing 319 includes an inner race (inner ring)
319a; an outer race (outer ring) 319b; and a plurality of rolling
elements (e.g., balls and rollers) 319c disposed between the inner
race 319a and the outer race 319b. The inner race 319a is affixed
to a shaft 314a protruding in the inner space of the reciprocating
section 314, whereas the outer race 319b rotates together with the
cam 313 as a result of the outer surface thereof being in line
contact with the outer surface of the rotating cam 313.
[0298] The linear bearing 315 guides the outer circumferential
surface, at a radially outward position, of the reciprocating
section 314 such that the reciprocating section 314 reciprocates
linearly in the vertical direction. The linear bearing 315 is
affixed to an inner surface of a side wall of the casing 317 at a
radially outward position of the reciprocating section 314. A
plurality of rolling elements (e.g., balls and rollers) 315a is
disposed in the linear bearing 315. By doing so, the reciprocating
section 314 can perform smooth linear reciprocation in the vertical
direction.
[0299] The linear bearing 315 can be made of, for example, resin,
titanium, or ceramic.
[0300] The urging member 316 is affixed to an inner wall surface at
the upper portion of the casing 317. The urging member 316 is, for
example, a compression spring that is disposed above the
reciprocating section 314 to urge the reciprocating section 314
downwards, that is, to urge the outer surface of the outer race
319b of the roller bearing 319 onto the outer surface of the cam
313.
[0301] The casing 317 is a substantially cylindrical member having
an inner space therein for accommodating the cam 313, the
reciprocating section 314, the linear bearing 315, and the urging
member 316. The casing 317 is disposed above the pump unit 312.
[0302] With the above-described structure, as the driving source is
driven to cause the cam 313 to rotate along with the drive shaft
318, the roller bearing 319, whose outer surface is pressed against
the outer surface of the cam 313, reciprocates linearly in the
vertical direction together with the reciprocating section 314.
Accordingly, the rod 320 also reciprocates in the vertical
direction.
[0303] The pump unit 312 includes a piston 321, a piston rod 322,
and a cylinder block 323.
[0304] The piston 321 includes a piston main body 324 and a piston
head 325 and is reciprocably housed in a cylinder 326 formed in the
cylinder block 323.
[0305] The piston main body 324 is a substantially cup-shaped
hollow member with a bottom. The piston main body 324 has the
piston head 325 formed at one end portion (upper end portion in
FIG. 14) thereof and has, in the center of the other end portion
(bottom) thereof, a through-hole 324a through which one end portion
of the piston rod 322 passes and one end portion of the piston rod
322 which is mounted via a heat insulator 327. In addition, as
indicated by reference symbol 324b, the interior of the side wall
of the piston main body 324 has a heat-insulating vacuum structure
that is hollow and vacuumed.
[0306] The piston head 325 is a member which is ring-shaped in plan
view (doughnut) and has in the center thereof a through-hole 325a
through which the piston rod 322 and a bulkhead 334, to be
described later, pass. A low-temperature fluid (e.g., liquid
hydrogen, liquid nitrogen, liquefied carbon dioxide, liquefied
natural gas, or liquefied propane gas) is compressed by one flat
end surface (upper end surface in FIG. 14) of the piston head
325.
[0307] The piston rod 322 is a circular-cross-section,
substantially rod-like member and has one end portion thereof
affixed to the center at the other end portion of the piston main
body 324 via the heat insulator 327, as described above, and the
other end portion thereof connected to an end portion (lower end
portion in FIG. 14) of the rod 320 via a heat-insulating connection
section 328.
[0308] The heat-insulating connection section 328 includes an end
portion 328a of the rod 320 having a structure similar to the inner
race of a roller bearing; the other end portion 328b of the piston
rod 322 having a structure similar to the outer race of a roller
bearing; and a plurality of (four in this embodiment) rolling
elements (e.g., balls and rollers) 328c disposed between the end
portion 328a of the rod 320 and the other end portion 328b of the
piston rod 322.
[0309] By doing so, the end portion 328a of the rod 320 and the
other end portion 328b of the piston rod 322 are linked to each
other in point or line contact via the rolling elements 328c. This
significantly reduces the amount of heat transmitted (entering)
from the rod 320 to the piston rod 322.
[0310] In addition, since one end portion of the piston rod 322 is
linked to the center of the other end portion of the piston main
body 324 via the heat insulator 327, even if heat is transmitted
(enters) from the rod 320 to the piston rod 322, heat transmitted
(entering) from the piston rod 322 to the piston main body 324 is
blocked by the heat insulator 327.
[0311] A through-hole 323a through which the rod 320 passes is
formed in the top center of the cylinder block 323. An inner space
329 communicating with the through-hole 323a is formed inside the
top portion of the cylinder block 323. The heat-insulating
connection section 328 is accommodated in this inner space 329.
[0312] Furthermore, in the cylinder block 323 disposed below this
inner space 329, the cylinder 326 communicating with the inner
space 329 via a through-hole 323b through which the piston rod 322
passes is formed in the longitudinal direction (vertical direction
in FIG. 14). One end (upper side in FIG. 14) of the cylinder 326
constitutes a compression chamber 126a having an inner diameter
larger than the outer diameter of the piston head 325. The piston
head 325 is accommodated in this compression chamber 326a.
[0313] As indicated by reference symbol 323c, the interiors of the
side wall, the bottom surface, and the top surface of the cylinder
block 323 are hollow and vacuumed to achieve a heat-insulating
vacuum structure.
[0314] On the other hand, a suction port 323d and a discharge port
323e communicating with the compression chamber 326a are provided
at a position which faces a circumferential portion on one end
surface of the piston head 325 between the compression chamber 326a
and the inner space 329 in the cylinder block 323. The suction port
323d and the discharge port 323e are each provided with a poppet
check valve (or a ball check valve, a reed valve, a forcibly driven
valve) 330 having a valve body 330a and a spring 330b to control
suction and discharge of low-temperature fluid.
[0315] The suction port 323d is provided so as to communicate with
a fluid-suction channel 331 formed in the cylinder block 323,
whereas the discharge port 323e is provided so as to communicate
with a fluid-discharge channel 332 formed in the cylinder block
323. Therefore, low-temperature fluid guided from the fluid-suction
channel 331 via the suction port 323d into the compression chamber
326a is compressed by one end surface of the piston head 325 so
that the pressure is increased to, for example, 30 MPa. Thereafter,
the low-temperature fluid is guided out of the cylinder block 323
from the discharge port 323e via the fluid-discharge channel
332.
[0316] The low-temperature fluid that has been guided out of the
cylinder block 323 via the fluid-discharge channel 332 is
temporarily stored (reserved) in a chamber C via a pipe 333.
Thereafter, the low-temperature fluid is supplied to a fuel
injector, not shown in the figure, via a pipe 335.
[0317] Low-temperature fluid whose pressure has been increased to,
for example, 30 MPa is reserved in the chamber C.
[0318] The bulkhead 334 enclosing the shank outer surface of the
piston rod 322 is disposed between the piston rod 322 and the
piston 321. As indicated by reference symbol 334a, this bulkhead
334 has a heat-insulating vacuum structure that is hollow and
vacuumed. Because of this, radiant heat from the piston rod 322 is
prevented from being transmitted to the piston 321.
[0319] The compression chamber 326a has a bellows (partition) 336
therein. This bellows 336 separates (partitions) an inner
circumferential side (piston 321 side) from an outer
circumferential side (cylinder block 323 side) of the compression
chamber 326a, which is disposed closer to the piston main body 324
(lower side in FIG. 14) than the piston head 325. One end of the
bellows 336 is affixed to a surface opposite (the other end
surface) one end surface of the piston head 325, and the other end
of the bellows 336 is affixed to the inner wall surface of the
cylinder block 323.
[0320] A bellows (partition) 337 is also provided at a radially
outward position of the bulkhead 334 and above one end surface of
the piston head 325. This bellows 337 separates (partitions) an
inner circumferential side (piston rod 322 side) from an outer
circumferential side (cylinder block 323 side) in the upper section
of the cylinder 326. One end of the bellows 337 is affixed to one
end surface of the piston head 325, whereas the other end of the
bellows 337 is affixed to the inner wall surface of the cylinder
block 323.
[0321] Furthermore, these bellows 336 and 337 are each made of, for
example, stainless steel or Inconel, which exhibits elasticity at
(super) low temperatures.
[0322] FIG. 15 is a cross-sectional view taken along line XV-XV of
FIG. 14. The imaginary line in FIG. 15 (two-dot chain line) denotes
the bellows 337.
[0323] Furthermore, reference numerals 338, 339, 340, and 341 in
FIG. 14 each denote a (heat-insulating) sealing member which is
ring-shaped in plan view.
[0324] With the above-described structure, when the rod 320 of the
drive unit 311 reciprocates linearly in the vertical direction, the
piston rod 322 linked to the rod 320 through the heat-insulating
connection section 328 reciprocates linearly in the vertical
direction together with the piston 321, low-temperature fluid
supplied from the suction port 323d is compressed by one end
surface of the piston head 325 so that the pressure is increased,
and then the low-temperature fluid is expelled from the discharge
port 323e via the fluid-discharge channel 332 to the outside of the
cylinder block 323.
[0325] According to the low-temperature-fluid boosting pump 301 of
this embodiment, as a result of the piston rod 322 being pulled
towards the drive unit 311 (upwards in FIG. 14), low-temperature
fluid is compressed by one end surface of the piston head 325. In
short, when low-temperature fluid is to be compressed, the piston
rod 322 is not subjected to a compressive force.
[0326] As a result, the diameter of the piston rod 322 can be
reduced compared with a piston rod in the known art, which is
subjected to a compressive force (if the piston rod 322 is made of,
for example, Inconel, the diameter of the piston rod 322 can be,
for example, 8 mm). Therefore, not only can the amount of heat
entering from the driving source be reduced, but also the weight of
the piston rod 322 can be reduced. Consequently, the weight of the
entire pump can also be reduced.
[0327] In addition, when low-temperature fluid is to be compressed,
the piston rod 322 is not subjected to a compressive force. For
this reason, the diameter of the piston head 325 can be increased
(e.g., diameter of 100 mm). In other words, for the known pump
where a compressive force is applied to the piston rod, the
diameter of the piston head is limited to, for example, 40 mm to
prevent the piston rod from buckling. For this reason, the known
pump required, for example, five cylinders to achieve a sufficient
flow volume of low-temperature fluid. For the pump according to the
present invention, however, the diameter of the piston head 325 can
be, for example, 100 mm, and therefore, a sufficient flow volume
can be achieved with a single cylinder.
[0328] As a result, for the pump according to the present
invention, not only can the structure of the pump be simplified,
but also the entire pump can be made lightweight and compact.
[0329] Furthermore, since the cam 313 is in line contact with the
roller bearing 319, the amount of heat entering from the driving
source can be further reduced.
[0330] In addition, since the heat-insulating connection section
328 reduces the amount of heat entering from the rod 320 into the
piston rod 322, the amount of heat entering from the driving source
can be further reduced.
[0331] Moreover, even if heat is transmitted (enters) from the rod
320 to the piston rod 322, heat can be prevented from being
transmitted (entering) from the piston rod 322 to the piston main
body 324 by the heat insulator 327.
[0332] Furthermore, since the piston main body 324 is provided
between the piston rod 322 and the piston head 325 so that heat
from the piston rod 322 reaches the piston head 325 via the piston
main body 324, the amount of heat input can be further reduced.
[0333] Also, since the piston main body 324 has a heat-insulating
vacuum structure that is hollow and vacuumed, the amount of heat
input can be further reduced.
[0334] Because of this, the amount of heat input to the piston head
325 can be reduced, and therefore, low-temperature fluid compressed
by one end surface of the piston head 325 can be prevented from
being vaporized (boiled off).
[0335] Furthermore, the low-temperature-fluid boosting pump 301
according to this embodiment does not include a component (e.g.,
piston ring in the known art) that moves in contact with the inner
circumferential surface of the compression chamber 326a. This
prevents heat from being generated in the compression chamber 326a
and therefore prevents the low-temperature fluid from being
heated.
[0336] A ninth embodiment of a low-temperature-fluid boosting pump
according to the present invention will now be described with
reference to FIG. 16.
[0337] A low-temperature-fluid boosting pump 402 according to this
embodiment differs from the pump in the above-described eighth
embodiment in that the piston head 325 is provided directly at one
end portion of the piston rod 322. The other components are the
same as those described in the above-described embodiment, and
hence a description thereof will be omitted.
[0338] The same components as those in the above-described eighth
embodiment are denoted with the same reference numerals or
symbols.
[0339] As shown in FIG. 16, in the low-temperature-fluid boosting
pump 402 according to this embodiment, the length of the piston rod
322 is about one-fourth of that in the eighth embodiment, and one
end portion of the piston rod 322 is affixed directly to a
through-hole 325b formed in the center of the piston head 325 via
the heat insulator 327. For this reason, in this embodiment, the
piston main body 324, the bulkhead 334, and the cylinder 326 that
is provided below the bellows 336 in the eighth embodiment are
omitted. Therefore, in this embodiment, the length of the entire
pump in the longitudinal direction (vertical direction in the
figure) is reduced by the length of the omitted components.
[0340] Omitting the piston main body 324 and the bulkhead 334 may
seem to cause a problem in that heat enters from the driving
source. In fact, however, as described above, the cam 313 is in
line contact with the roller bearing 319, and furthermore, the end
portion 328a of the rod 320 is linked to the other end portion 328b
of the piston rod 322 in point or line contact through the rolling
elements 328c of the heat-insulating connection section 328.
Therefore, there is substantially no problem of heat entering from
the driving source.
[0341] This embodiment affords an advantage in that the
longitudinal length of a pump unit 412 can be reduced considerably,
which allows the longitudinal length of the entire pump to be
reduced and therefore the pump to be made compact.
[0342] A tenth embodiment of a low-temperature-fluid boosting pump
according to the present invention will be described with reference
to FIG. 17.
[0343] A low-temperature-fluid boosting pump 503 according to this
embodiment differs from the pump in the above-described eighth
embodiment in that a first compression (first-stage compression) is
performed with the outer circumferential side of a piston head 525
and a second compression (second-stage compression) is performed
with the inner circumferential side of the piston head 525. The
other components are the same as those described in the
above-described embodiment, and hence a description thereof will be
omitted.
[0344] The same components as those in the above-described eighth
embodiment are denoted with the same reference numerals or
symbols.
[0345] As shown in FIG. 17, according to the low-temperature-fluid
boosting pump 503 of this embodiment, a first compression is
performed with the outer circumferential side of the piston head
525, a second compression is performed with the inner
circumferential side of the piston head 525, and a drive unit 311
and a low-pressure chamber 534 are provided in a cylinder block
523.
[0346] A piston 521 in this embodiment includes a piston main body
524 and the piston head 525, and is reciprocably housed in a
cylinder 326 formed in the cylinder block 523.
[0347] The piston head 525 is a member which is ring-shaped in plan
view (doughnut), and has a first compressive surface 525a on one
end surface (upper end surface in FIG. 17) adjacent to the outer
circumferential side thereof and a second compressive surface 525b
on one end surface adjacent to the inner circumferential side
thereof. A low-temperature fluid (e.g., liquid hydrogen, liquid
nitrogen, liquefied carbon dioxide, liquefied natural gas, or
liquefied propane gas) is compressed by these flat compressive
surfaces 525a and 525b.
[0348] Therefore, low-temperature fluid guided from a fluid-suction
channel 331 through a suction port P1 on the low-pressure side into
a compression chamber 326a is compressed by the first compressive
surface 525a of the piston head 525 for pressure increase to, for
example, 5 MPa. Thereafter, the low-temperature fluid flows from a
discharge port P2 on the low-pressure side through a first
communication channel (a flow channel for connecting between the
discharge port P2 on the low-pressure side and the low-pressure
chamber 534) R1 and is then temporarily reserved in the
low-pressure chamber 534.
[0349] The low-temperature fluid reserved in the low-pressure
chamber 534 is guided from the low-pressure chamber 534 through a
second communication channel (flow channel that connects between
the low-pressure chamber 534 and a suction port P3 on the
high-pressure side) into the suction port P3 on the high-pressure
side, and is then drawn into the compression chamber 326a. The
low-temperature fluid drawn into the compression chamber 326a is
compressed by the second compressive surface 525b of the piston
head 525 to increase the pressure to, for example, 30 MPa.
Thereafter, the low-temperature fluid is expelled out of the
cylinder block 523 from a discharge port P4 on the high-pressure
side via a fluid-discharge channel 332. The low-temperature fluid
that has been expelled out of the cylinder block 523 passes through
a pipe 333, is temporarily reserved in a chamber C, and is supplied
to a fuel injector, not shown in the figure, through a pipe
335.
[0350] According to the low-temperature-fluid boosting pump 503 of
this embodiment, low-temperature fluid is subjected to a pressure
increase to, for example, 5 MPa with the first compressive surface
525a of the piston head 525 and is then subjected to another
pressure increase with the second compressive surface 525b of the
piston head 525, up to a desired pressure (e.g., 30 MPa).
[0351] In short, this embodiment employs a dual-stage compression
technique where low-temperature fluid is temporarily increased to
an intermediate pressure and is then further increased to a desired
pressure (high pressure), instead of increasing the low-temperature
fluid from a low pressure to a high pressure in one stroke.
[0352] By doing so, since the stroke of the piston 521 (i.e., the
maximum lift of the cam 313) can be reduced, the longitudinal
length of a pump unit 512 can be further reduced, which can reduce
the longitudinal length of the entire pump. This contributes to
more compact design of the pump.
[0353] In addition, as a result of the stroke of the piston 521
being reduced, the expansion ratio of the bellows 336 and 337 can
be decreased (i.e., the bellows 336 and 337 can be expanded or
contracted within a smaller range). Therefore, the service life of
these bellows 336 and 337 can be extended, and accordingly, the
reliability of the pump can be improved.
[0354] The other effects and advantages are the same as those of
the above-described eighth embodiment, and hence a description
thereof will be omitted.
[0355] An eleventh embodiment of a low-temperature-fluid boosting
pump according to the present invention will now be described with
reference to FIG. 18.
[0356] A low-temperature-fluid boosting pump 604 according to this
embodiment differs from the pump in the above-described eighth
embodiment in that a precooling layer 630 is provided on an inner
side of a heat-insulating vacuum structure 323c of a cylinder block
623 which constitutes a pump unit 612. The other components are the
same as those described in the above-described embodiment, and
hence a description thereof will be omitted.
[0357] The same components as those in the above-described eighth
embodiment are denoted with the same reference numerals or
symbols.
[0358] As shown FIG. 18, the low-temperature-fluid boosting pump
604 according to this embodiment is provided with the precooling
layer 630 in the side wall, the bottom surface, and the top surface
of the cylinder block 623. A coolant inlet pipe 631 and a coolant
outlet pipe 632 are connected to this precooling layer 630 so that
a coolant (low-temperature fluid such as liquid hydrogen, liquid
nitrogen, liquefied carbon dioxide, liquefied natural gas, or
liquefied propane gas) supplied into the precooling layer 630 from
the coolant inlet pipe 631 is guided to the outside of the cylinder
block 623 via the coolant outlet pipe 632.
[0359] By providing this precooling layer 630, the entire pump can
be cooled sufficiently before the pump is started. This decreases
vaporization (boil-off) of low-temperature fluid supplied to the
low-temperature-fluid boosting pump 604.
[0360] Furthermore, since this precooling layer 630 also serves as
a heat-insulating layer while the pump is being operated,
vaporization (boil-off) of the low-temperature fluid can be reduced
also while the pump is being operated.
[0361] The other effects and advantages are the same as those of
the above-described eighth embodiment, and hence a description
thereof will be omitted.
[0362] A twelfth embodiment of a low-temperature-fluid boosting
pump according to the present invention will now be described with
reference to FIG. 19.
[0363] A low-temperature-fluid boosting pump 705 according to this
embodiment differs from the pump in the above-described eleventh
embodiment in that a bellows 737 is provided in place of the
bellows 337. The other components are the same as those described
in the above-described embodiment, and hence a description thereof
will be omitted.
[0364] The same components as those in the above-described eleventh
embodiment are denoted with the same reference numerals or
symbols.
[0365] As shown in FIG. 19, the bellows (partition) 737 of the
low-temperature-fluid boosting pump 705 according to this
embodiment is provided at a radially inward position of a bellows
336 and in a compression chamber 326a, which is disposed closer to
a piston main body 324 (lower side in FIG. 19) than a piston head
325. One end of the bellows 737 is affixed to a surface opposite
(the other end surface) the one end surface of the piston head 325,
and the other end of the bellows 737 is affixed to the top surface
of a tongue portion of a bulkhead 334.
[0366] Like the above-described bellows 336 and 337, the bellows
737 is made of, for example, stainless steel or Inconel, which
exhibits elasticity at (super) low temperatures.
[0367] In this manner, by providing the bellows 737 on the same
side as the bellows 336, that is, the side opposite to the one end
surface (compressive surface) of the piston head 325, the length of
the pump in the height direction (vertical direction in the figure)
can be reduced, and therefore, the entire pump can be made
compact.
[0368] In addition, since the compressive surface of the piston
head 325 can have a larger area than that in the eleventh
embodiment, a larger amount of low-temperature fluid can be
compressed at a time. In short, the efficiency (performance) of the
pump can be improved.
[0369] The other effects and advantages are the same as those of
the above-described eleventh embodiment, and hence a description
thereof will be omitted.
[0370] Reference numeral 712 in the figure denotes a pump unit.
[0371] A thirteenth embodiment of a low-temperature-fluid boosting
pump according to the present invention will be described with
reference to FIG. 20.
[0372] A low-temperature-fluid boosting pump 806 according to this
embodiment differs from the pump in the above-described twelfth
embodiment in that a bellows 837 is additionally provided. The
other components are the same as those described in the
above-described embodiment, and hence a description thereof will be
omitted.
[0373] The same components as those in the above-described twelfth
embodiment are denoted with the same reference numerals or
symbols.
[0374] As shown in FIG. 20, the low-temperature-fluid boosting pump
806 according to this embodiment is provided with another bellows
(partition) 837 adjacent to the other end side (lower side in the
figure) of the bellows 737. This bellows 837 has one end thereof
affixed to a lower surface of a tongue portion of a bulkhead 334
and has the other end thereof affixed to an upper surface of the
inner wall at the other end portion of a piston main body 324. This
bellows 837 separates (partitions) an inner circumferential side
(piston rod 322 side) from an outer circumferential side (cylinder
block 323 side) in the space between the lower surface of the
tongue portion of the bulkhead 334 and the upper surface of the
inner wall at the other end portion of the piston main body
324.
[0375] Like the above-described bellows 336, 337, and 737, the
bellows 837 is made of, for example, stainless steel or Inconel,
which exhibits elasticity at (super) low temperatures.
[0376] With the bellows 837 provided, the pressure in the space
defined by the bellows 837 and the above-described sealing member
341 adjacent to the piston rod 322 is maintained substantially at
atmospheric pressure. Therefore, the difference (pressure
difference) between the pressure on the inner circumferential side
and the pressure on the outer circumferential side of the bellows
336, 737, and 837 can be reduced. This allows the service life of
these bellows 336, 737, and 837 to be extended. Consequently, the
reliability of the pump can be improved.
[0377] The other effects and advantages are the same as those of
the above-described eleventh embodiment, and hence a description
thereof will be omitted.
[0378] Reference numeral 812 in the figure denotes a pump unit.
[0379] A fourteenth embodiment of a low-temperature-fluid boosting
pump according to the present invention will be described with
reference to FIG. 21.
[0380] A low-temperature-fluid boosting pump 907 according to this
embodiment differs from the pump in the above-described eighth
embodiment in that a booster-fluid feeding unit 930 is provided.
The other components are the same as those described in the
above-described embodiment, and hence a description thereof will be
omitted.
[0381] The same components as those in the above-described eighth
embodiment are denoted with the same reference numerals or
symbols.
[0382] As shown in FIG. 21, the low-temperature-fluid boosting pump
907 according to this embodiment is provided with the booster-fluid
feeding unit 930. This booster-fluid feeding unit 930 includes a
communicating tube 931 that connects the interior of a chamber C to
the interior of a cylinder 326 (a space between the lower surface
at the other end portion of a piston main body 324, disposed
adjacent to the other end side, i.e., the side opposite to a
compression chamber 326a, of the cylinder 326, and the bottom
surface of the cylinder 326) and a pressure regulator
(decompressor) 932 disposed at an intermediate point in this
communicating tube 931.
[0383] By providing this booster-fluid feeding unit 930,
low-temperature fluid whose pressure has been decreased by the
pressure regulator 932 to, for example, 15 MPa can be supplied to
the cylinder 326. Therefore, the difference between the pressure on
the one end surface (compressive surface) side and the pressure on
the other end surface side of a piston head 325 can be reduced, and
consequently, a bellows with low pressure resistance can be
employed.
[0384] The other effects and advantages are the same as those of
the above-described thirteenth embodiment, and hence a description
thereof will be omitted.
[0385] Reference numeral 912 in the figure denotes a pump unit.
[0386] The present invention is not limited to the above-described
embodiments. For example, the bellows 336, 337, 737, and 837 can be
realized by bellows having cross sections as indicated by solid
lines or two-dot chain lines in FIG. 22.
[0387] More specifically, convex bellows having one projection
towards the outside in the radial direction, as indicated by the
solid lines in FIG. 22, or concave bellows having one indentation
towards the inside in the radial direction, as indicated by the
two-dot chain lines in FIG. 22, can be employed.
[0388] Furthermore, the heat-insulating connection sections 128 and
328 are not limited to those described above. A heat-insulating
connection section as shown in, for example, FIG. 23 can also be
employed.
[0389] In a heat-insulating connection section 428 shown in FIG.
23, a heat insulator 428c is interposed between an end portion 428a
of a cross-sectionally T-shaped rod 320 and the other end portion
428b of a cross-sectionally T-shaped piston rod 322, and
furthermore, these elements are linked to each other with fasteners
J, such as bolts or nuts.
[0390] In addition, although a dual-stage compression technique for
compression using the outer circumferential side and the inner
circumferential side of the piston head 525 has been employed in
the embodiment described with reference to FIG. 17, the present
invention is not limited to this technique. Instead, one end
surface of the piston head may be further divided in a concentric
manner to achieve a three-or-more-stage compression technique.
[0391] Furthermore, it is more preferable that the above-described
chamber C and the low-pressure chamber 534 include a relief valve
so that low-temperature fluid discharged from this relief valve
returns through a return pipe to the suction side of the pump (or a
separate fuel battery, if any fuel battery is provided).
[0392] A fifteenth embodiment of a low-temperature-fluid boosting
pump according to the present invention will be described with
reference to FIG. 24.
[0393] As shown in FIG. 24, a low-temperature-fluid boosting pump
1008 according to this embodiment includes major components such as
a drive unit 1111 and a pump unit 1112 driven by this drive unit
1111.
[0394] The drive unit 1111 includes a rod 1115 and a power
transmission unit 1116 for transmitting a driving force from a
driving source (e.g., an electric motor or an engine), not shown in
the figure, to the rod 1115.
[0395] The rod 1115 is a circular-cross-section, substantially
rod-like member extending downwards from a lower end surface of the
power transmission unit 1116 and has a heat-insulating connection
section 328 at a lower end portion thereof.
[0396] The power transmission unit 1116 causes the rod 1115 to
reciprocate linearly in the vertical direction (as indicated by the
arrow in FIG. 24) with a stroke of, for example, 2 mm by using a
driving force from the driving source, not shown in the figure.
[0397] The pump unit 1112 includes a piston 1121, a piston rod
1122, and a cylinder block 1123.
[0398] The piston 1121 includes one linkage member 1124 and one or
more (four in this embodiment) piston heads 1125, and is
reciprocably housed in a cylinder 1126 formed in the cylinder block
1123.
[0399] The linkage member 1124 is a substantially disc-shaped
member. One end portion of the piston rod 1122 is linked to a
center portion of the linkage member 1124. In addition, four rods
1127 for linking the lower end surfaces of the respective piston
heads 1125 to the upper end surface of the linkage member 1124 are
provided on the outer circumference of the linkage member 1124.
These four rods 1127 are arranged at regular intervals (90.degree.)
as shown in FIG. 25.
[0400] Each of the piston heads 1125 is a substantially disc-shaped
member and is constructed so as to compress a low-temperature fluid
(e.g., liquid hydrogen, liquid nitrogen, liquefied carbon dioxide,
liquefied natural gas), liquefied propane gases, etc. by means of
one end surface thereof (upper end surface in FIG. 24).
[0401] The piston rod 1122 is a circular-cross-section,
substantially rod-like member and has one end portion thereof
linked to the upper end surface of the linkage member 1124, as
described above, and the other end portion thereof connected to an
end portion (lower end portion in FIG. 24) of the rod 1115 via the
heat-insulating connection section 328.
[0402] The heat-insulating connection section 328 includes an end
portion 328a of the rod 1115 having a structure similar to the
inner race of a roller bearing; the other end portion 328b of the
piston rod 1122 having a structure similar to the outer race of a
roller bearing; and a plurality of (four in this embodiment)
rolling elements (e.g., balls and rollers) 328c disposed between
the end portion 328a of the rod 1115 and the other end portion 328b
of the piston rod 1122.
[0403] By doing so, the end portion 328a of the rod 1115 and the
other end portion 328b of the piston rod 1122 are linked to each
other in point or line contact via the rolling elements 328c. This
significantly reduces the amount of heat being transmitted
(entering) from the rod 1115 to the piston rod 1122.
[0404] In addition, since the piston rod 1122 is designed to have a
maximum possible length, even if heat is transmitted (enters) from
the rod 1115 to the piston rod 1122, the amount of heat being
transmitted (entering) from the piston rod 1122 to the linkage
member 1124 is minimized.
[0405] A through-hole 323a through which the rod 1115 passes is
formed in the top center of the cylinder block 1123. An inner space
329 communicating with the through-hole 323a is formed inside the
top portion of the cylinder block 1123. The heat-insulating
connection section 328 is accommodated in this inner space 329.
[0406] Furthermore, in the cylinder block 1123 below this inner
space 329, the cylinder 1126 communicating with the inner space 329
via a through-hole 1123b through which the piston rod 1122 passes
is formed in the longitudinal direction (vertical direction in FIG.
24). One end (upper side in FIG. 24) of the cylinder 1126
constitutes compression chambers 1126a each having an inner
diameter larger than the outer diameter of the piston head 1125.
The piston heads 1125 are accommodated in these compression
chambers 1126a, respectively.
[0407] As indicated by reference symbol 1123c, the interiors of the
side wall, the bottom surface, and the top surface of the cylinder
block 1123 are hollow and vacuumed to achieve a heat-insulating
vacuum structure.
[0408] On the other hand, a suction port 1123d and a discharge port
1123e communicating with a compression chamber 1126a are provided
at a position that faces the center of one end surface of the
corresponding piston head 1125 in the cylinder block 1123, disposed
between the compression chamber 1126a and the inner space 329. The
suction port 1123d and the discharge port 1123e are each provided
with a ball check valve 1130 to control suction and discharge of
low-temperature fluid.
[0409] Each suction port 1123d is provided so as to communicate
with a fluid-suction channel 1131 formed in the cylinder block
1123, whereas each discharge port 1123e is provided so as to
communicate with a fluid-discharge channel 1132 formed in the
cylinder block 1123. Therefore, low-temperature fluid guided from
the fluid-suction channel 1131 via each suction port 1123d into the
compression chamber 1126a is compressed by one end surface of the
piston head 1125 so that the pressure is increased to, for example,
30 MPa. Thereafter, the low-temperature fluid is guided out of the
cylinder block 1123 from the discharge port 1123e via the
fluid-discharge channel 1132.
[0410] The low-temperature fluid that has been guided out of the
cylinder block 1123 via the fluid-discharge channel 1132 is
temporarily stored (reserved) in a chamber 1134 via a pipe 1133.
The low-temperature fluid reserved in the chamber 1134 is guided
into a heat exchanger 1136 through a pipe 1135 and then vaporized.
Most of the low-temperature fluid is supplied to a fuel injector,
not shown in the figure, through a pipe 1137, whereas part of the
low-temperature fluid is guided through a pipe 1138 and a pressure
regulator (decompressor) 1139 into the cylinder 1126 (a space
between the lower surface at the other end portion of the linkage
member 1124, disposed adjacent to the other end side, i.e., the
side opposite to the compression chambers 1126a, of the cylinder
1126, and the bottom surface of the cylinder 1126).
[0411] Low-temperature fluid whose pressure has been increased to,
for example, 30 MPa is reserved in the chamber 1134.
[0412] In addition, vaporized low-temperature fluid whose pressure
has been decreased to, for example, 15 MPa by the pressure
regulator 1139 is supplied into the cylinder 1126.
[0413] Each compression chamber 1126a has a bellows (partition)
1140 therein. This bellows 1140 partitions (separates) an inner
circumferential side (rod 1127 side) from an outer circumferential
side (cylinder block 1123 side) of the corresponding compression
chamber 1126a, which is disposed closer to the linkage member 1124
(lower side in FIG. 24) than the piston head 1125. One end of the
bellows 1140 is affixed to a surface opposite (the other end
surface) one end surface of the piston head 1125, and the other end
of the bellows 1140 is affixed to the inner wall surface of the
cylinder block 1123.
[0414] Furthermore, a bellows (partition) 1141 is also provided at
an outward position in the radial direction at one end portion of
the piston rod 1122. This bellows 1141 partitions (separates) an
inner circumferential side (adjacent to the piston rod 1122) from
an outer circumferential side (adjacent to the cylinder block 1123)
of the piston rod 1122 at one end portion thereof. One end of the
bellows 1141 is affixed to the upper end surface of the linkage
member 1124, and the other end of the bellows 1141 is affixed to
the inner wall surface of the cylinder block 1123.
[0415] These bellows 1140 and 1141 are made of, for example,
stainless steel or Inconel, which exhibits elasticity at (super)
low temperatures.
[0416] Reference numerals 1142, 1143, and 1144 in FIG. 24 each
denote a (heat-insulating) sealing member which is ring-shaped in
plan view.
[0417] FIG. 25 is a cross-sectional view taken along line XXV-XXV
of FIG. 24.
[0418] With the above-described structure, when the rod 1115 of the
drive unit 1111 reciprocates linearly in the vertical direction,
the piston rod 1122 linked to the rod 1115 through the
heat-insulating connection section 328 reciprocates linearly in the
vertical direction together with the piston 1121, the
low-temperature fluid supplied from the suction ports 1123d is
compressed by one end surface of each piston head 1125 so that the
pressure is increased, and then the low-temperature fluid is
expelled from the discharge port 1123e via the fluid-discharge
channel 1132 to the outside of the cylinder block 1123.
[0419] According to the low-temperature-fluid boosting pump 1008 of
this embodiment, as a result of the piston rod 1122 being pulled
towards the drive unit 1111 (upward in FIG. 24), low-temperature
fluid is compressed by one end surface of each piston head 1125. In
other words, when low-temperature fluid is to be compressed, no
compressive force is applied to the piston rod 1122.
[0420] As a result, the diameter of the piston rod 1122 can be
reduced compared with a piston rod in the known art, which is
subjected to a compressive force. Therefore, not only can the
amount of heat entering from a driving source be reduced, but also
the weight of the piston rod 1122 can be reduced. Consequently, the
weight of the entire pump can also be reduced.
[0421] Furthermore, since there is no component (e.g., piston ring
in the known art) that moves in contact with the inner
circumferential surfaces of the compression chambers 1126a, heat is
prevented from being generated in the compression chambers 1126a,
and therefore, low-temperature fluid is prevented from being
heated.
[0422] In addition, each bellows 1140 completely partitions
(separates) an inner circumferential side (inward position in the
radial direction) from an outer circumferential side (outward
position in the radial direction) of the corresponding compression
chamber 1126a. Therefore, low-temperature fluid can be prevented
from leaking from the inner circumferential side of the compression
chamber 1126a to the outer circumferential side of the compression
chamber 1126a (or from the outer circumferential side of the
compression chamber 1126a to the inner circumferential side of the
compression chamber 1126a). This improves the compression
efficiency of the low-temperature-fluid boosting pump 1008.
Furthermore, since low-temperature fluid that is vaporized by the
heat exchanger 1136 and subjected to pressure adjustment to a
predetermined pressure (e.g., 15 MPa) by the pressure regulator
1139 exists outside each bellows 1140 (outward position in the
radial direction), deformation of the bellows 1140 can be reduced
when low-temperature fluid drawn into the bellows 1140 is to be
compressed. This extends the service life of the bellows 1140 and
increases the reliability of the low-temperature-fluid boosting
pump 1008.
[0423] In addition, the heat-insulating connection section 328
reduces the amount of heat entering from the rod 1115 to the piston
rod 1122, thereby further reducing the amount of heat entering from
the driving source.
[0424] Furthermore, because the linkage member 1124 is provided
between the piston rod 1122 and the piston heads 1125, heat from
the piston rod 1122 reaches the piston heads 1125 through the
linkage member 1124. This can further reduce the amount of input
heat.
[0425] In addition, since the rod 1115 connecting to the power
transmission unit 1116 extends to the side where the suction ports
1123d and the discharge ports 1123e are disposed (upper side in
FIG. 24), not only can the length of the pump unit 1112 in the
longitudinal direction (axial direction) be reduced, but also the
length of the entire pump in the longitudinal direction (axial
direction) can be reduced. This contributes to compact and
lightweight design of the pump.
[0426] A sixteenth embodiment of a low-temperature-fluid boosting
pump according to the present invention will be described with
reference to FIG. 26.
[0427] A low-temperature-fluid boosting pump 2009 according to this
embodiment is a so-called swash plate (or swash) pump. The
low-temperature-fluid boosting pump 2009 includes major components
such as a drive unit 2161 and a pump unit 2162 that is driven by
this drive unit 2161.
[0428] The same components as those in the above-described
fifteenth embodiment are denoted with the same reference numerals
or symbols.
[0429] The drive unit 2161 includes a rod 2165 and a power
transmission unit 2166 that transmits a driving force from a
driving source (e.g., an electric motor or an engine), not shown in
the figure, to the rod 2165.
[0430] The rod 2165 is a substantially rod-like member having a
circular cross section, extending downwards from the lower end
surface of the power transmission unit 2166.
[0431] The power transmission unit 2166 rotates the rod 2165 in one
direction (direction indicated by the arrow in FIG. 26) using a
driving force from a driving source, not shown in the figure.
[0432] The pump unit 2162 includes one or more (four in this
embodiment) pistons 2171, a swash plate (also called a "yoke")
2172, and a cylinder block 2173.
[0433] Each piston 2171 is a circular-cross-section, substantially
rod-like member having a piston head 2171a at one end portion
thereof and a piston shoe 2171b at the other end portion thereof.
Each piston 2171 is reciprocably housed in the cylinder 2176.
[0434] The piston head 2171a is a so-called large-diameter portion
that has an outer diameter larger than the outer diameter of a
piston rod 2171c that links this piston head 2171a and the piston
shoe 2171b, and (for example, liquid hydrogen, liquid nitrogen,
liquefied carbon dioxide, liquefied natural gas), liquefied propane
gas, etc. is compressed by one flat end surface (upper end surface
in FIG. 26) of this piston head 2171a.
[0435] Like the piston head 2171a, the piston shoe 2171b is also a
so-called large-diameter portion that has an outer diameter larger
than the outer diameter of the piston rod 2171c. One end surface
(lower surface in FIG. 26) of the piston shoe 2171b slides along a
sliding surface P of the swash plate 2172 having a tilt angle.
[0436] The cylinder block 2173 contains the same number of
compression chambers 1126a as that of the pistons 2171, and the
compression chambers 1126a are formed along a longitudinal
direction (vertical direction in FIG. 26). Each compression chamber
1126a accommodates one piston head 2171a.
[0437] As shown in FIG. 26, the piston shoes 2171b and the swash
plate 2172 are housed adjacent to the other end side (lower side in
FIG. 26) of the cylinder 2176.
[0438] Furthermore, a through-hole 1123a through which the rod 2165
passes is formed in the center of the cylinder block 2173. In
addition, the interiors of the side wall, the bottom surface, and
the top surface of the cylinder block 2173 constitute a
heat-insulating vacuum structure that is hollow and vacuumed, as
shown by reference symbol 1123c.
[0439] On the other hand, a suction port 1123d and a discharge port
1123e communicating with a compression chamber 1126a are provided
at a position that faces the center of one end surface of the
corresponding piston head 2171a, i.e., at a top portion in the
cylinder block 2173. The suction port 1123d and the discharge port
1123e are each provided with a ball check valve 1130 to control
suction and discharge of low-temperature fluid.
[0440] Each suction port 1123d is provided so as to communicate
with a fluid-suction channel 1131 formed in the cylinder block
2173, whereas each discharge port 1123e is provided so as to
communicate with a fluid-discharge channel 1132 formed in the
cylinder block 2173. Therefore, a low-temperature fluid guided from
the fluid-suction channel 1131 via each suction port 1123d into the
compression chamber 1126a is compressed by one end surface of the
piston head 2171a so that the pressure is increased to, for
example, 30 MPa. Thereafter, the low-temperature fluid is guided
out of the cylinder block 2173 from the discharge port 1123e via
the fluid-discharge channel 1132.
[0441] The low-temperature fluid that has been guided out of the
cylinder block 2173 via the fluid-discharge channel 1132 is
temporarily stored (reserved) in a chamber 1134 via a pipe 1133.
The low-temperature fluid reserved in the chamber 1134 is guided
into a heat exchanger 1136 through a pipe 1135 and then vaporized.
Most of the low-temperature fluid is supplied to a fuel injector,
not shown in the figure, through a pipe 1137, whereas part of the
low-temperature fluid is guided through a pipe 1138 and a pressure
regulator (decompressor) 1139 into the compression chambers 1126a
(i.e., a space adjacent to the other end surface of each piston
head 2171a, located opposite to a bellows 1140).
[0442] Low-temperature fluid whose pressure has been increased to,
for example, 30 MPa is reserved in the chamber 1134.
[0443] In addition, vaporized low-temperature fluid whose pressure
has been decreased to, for example, 15 MPa by the pressure
regulator 1139 is supplied into the compression chambers 1126a.
[0444] Each compression chamber 1126a has the bellows (partition)
1140 therein. This bellows 1140 partitions (separates) an inner
circumferential side (piston rod 2171c side) from an outer
circumferential side (cylinder block 2173 side) of the
corresponding compression chamber 1126a, which is disposed closer
to the piston shoe 2171b (lower side in FIG. 26) than the piston
head 2171a. One end of the bellows 1140 is affixed to a surface
opposite (the other end surface) one end surface of the piston head
2171a, and the other end of the bellows 1140 is affixed to the
inner wall surface of the cylinder block 2173.
[0445] Furthermore, a bellows (partition) 2180 is also provided at
an outward position in the radial direction at one end portion of
each piston rod 2171c. This bellows 2180 partitions (separates) an
inner circumferential side (adjacent to the piston rod 2171c) from
an outer circumferential side (adjacent to the cylinder block 2173)
of the corresponding piston rod 2171c at one end portion thereof.
One end of the bellows 2180 is affixed to an outer circumferential
end portion on the other end surface (upper surface in FIG. 26) of
the piston shoe 2171b, and the other end of the bellows 2180 is
affixed to the inner wall surface of the cylinder block 2173.
[0446] These bellows 1140 and 2180 are made of, for example,
stainless steel or Inconel, which exhibits elasticity at (super)
low temperatures.
[0447] Reference numerals 1142, 1143, and 1144 in FIG. 26 each
denote a (heat-insulating) sealing member which is ring-shaped in
plan view. Reference numerals 2181 and 2182 each denote a thrust
roller bearing.
[0448] With the above-described structure, when the rod 2165 is
rotated by the driving source (in one direction), the piston shoes
2171b slide along the sliding surface P by means of the thrust
bearings 2181, and furthermore, the pistons 2171 are caused to
reciprocate in the cylinder 2176, thereby successively compressing
low-temperature fluid flowing into the compression chambers 1126a.
In this embodiment, the strokes of the pistons 2171 are set to, for
example, 2 mm.
[0449] According to the low-temperature-fluid boosting pump 2009 of
this embodiment, as a result of the rod 2165 being rotated in one
direction (as indicated by the arrow in FIG. 26), low-temperature
fluid is compressed by one end surface of each piston head 2171a.
In other words, when low-temperature fluid is to be compressed, no
compressive force is applied to the rod 2165.
[0450] As a result, the diameter of the rod 2165 can be reduced
compared with the type of piston rod used in the known art, which
is subjected to a compressive force. Therefore, not only can the
amount of heat entering from a driving source be reduced, but also
the weight of the rod 2165 can be reduced. Consequently, the weight
of the entire pump can also be reduced.
[0451] Furthermore, since there is no component (e.g., piston ring
in the known art) that moves in contact with the inner
circumferential surfaces of the compression chambers 1126a, heat is
prevented from being generated in the compression chambers 1126a,
and therefore, low-temperature fluid is prevented from being
heated.
[0452] In addition, each bellows 1140 completely partitions
(separates) an inner circumferential side (inward position in the
radial direction) from an outer circumferential side (outward
position in the radial direction) of the corresponding compression
chamber 1126a. Therefore, low-temperature fluid can be prevented
from leaking from the inner circumferential side of the compression
chamber 1126a to the outer circumferential side of the compression
chamber 1126a (or from the outer circumferential side of the
compression chamber 1126a to the inner circumferential side of the
compression chamber 1126a). This improves the compression
efficiency of the low-temperature-fluid boosting pump 2009.
Furthermore, since low-temperature fluid that is vaporized by the
heat exchanger 1136 and is subjected to pressure adjustment to a
predetermined pressure (e.g., 15 MPa) by the pressure regulator
1139 exists outside each bellows 140 (outward position in the
radial direction), deformation of the bellows 1140 can be reduced
when the low-temperature fluid drawn into the bellows 1140 is to be
compressed. This extends the service life of the bellows 1140 and
increases the reliability of the low-temperature-fluid boosting
pump 2009.
[0453] In addition, since the rod 2165 connecting to the power
transmission unit 2166 extends to the side where the suction ports
1123d and the discharge ports 1123e are disposed (upper side in
FIG. 26), not only can the length of the pump unit 2162 in the
longitudinal direction (axial direction) be reduced, but also the
length of the entire pump in the longitudinal direction (axial
direction) can be reduced. This contributes to compact and
lightweight design of the pump.
[0454] Although a four-cylinder structure provided with four
pistons and four cylinders has been described in the
above-described embodiment, the present invention is not limited to
this structure. For example, a single-cylinder, two-cylinder,
three-cylinder, or five-or-more-cylinder structure is also
acceptable.
[0455] Furthermore, the thrust roller bearing 2182 described in the
sixteenth embodiment is not limited to the type of bearing that
supports the swash plate 2172 at a single point in the center on
the bottom surface of the swash plate 2172, as shown in FIG. 26.
Instead, the entire bottom surface of the swash plate 2172 can be
supported with two or more thrust roller bearings disposed in the
circumferential direction.
[0456] In addition, it is preferable that the angle of this swash
plate 2172 be variable using, for example, an actuator. In other
words, a variable-capacity structure is preferable. By doing so,
the amount of discharge of the pump can be changed simply by
changing the angle of the swash plate 2172, i.e., without changing
the number of revolutions for driving the pump.
[0457] Furthermore, although each of the suction port 1123d and the
discharge port 1123e is provided with the ball check valve 1130 in
the above-described embodiment, the present invention is not
limited to this structure. Instead, a forcible drive system as seen
with, for example, a DOHC of an internal-combustion engine is also
acceptable. Furthermore, a structure with a reed valve, a poppet
valve, etc. can also be used.
[0458] In addition, the present invention is not limited to the
above-described embodiments. For example, the bellows 1140, 1141,
and 2180 can be realized by bellows having cross sections as
indicated by solid lines or two-dot chain lines in FIG. 22.
[0459] More specifically, convex bellows having one projection
towards the outside in the radial direction, as indicated by the
solid lines in FIG. 22, or concave bellows having one indentation
towards the inside in the radial direction, as indicated by the
two-dot chain lines in FIG. 22, can be employed.
[0460] Furthermore, the heat-insulating connection section 328
shown in FIG. 24 is not limited to that described above. A
heat-insulating connection section as shown in, for example, FIG.
23 can also be employed.
[0461] Furthermore, it is more preferable that the above-described
chamber 1134 include a relief valve so that low-temperature fluid
discharged from this relief valve returns through a return pipe to
the suction side of the pump (or a separate fuel battery, if any
fuel battery is provided).
[0462] Furthermore, the drive unit 311 according to the eighth to
fourteenth embodiments is not limited to a cam-driven drive unit as
shown in the figures. The drive unit 311 can be realized by, for
example, a crank-driven drive unit where the rod 320 is forcibly
driven.
[0463] In addition, it is more preferable that, in the fifteenth
and sixteenth embodiments, the piston rod 1122 be linked
(connected) to the linkage member 1124 and the rod 2165 be linked
(connected) to the swash plate 2172 through the heat insulator 327
described in the eighth to fourteenth embodiments.
[0464] Moreover, in each of the above-described eighth to fifteenth
embodiments, it is more preferable that a guiding member be
provided, for example, between the piston rods 322 and 1122 and the
cylinder blocks 323 and 1123, between the piston main bodies 324
and 524 and the cylinder 326, or between the linkage member 1124
and the cylinder 1126, so that the piston main bodies, the piston
heads, etc. that are housed in the cylinders and reciprocate in the
cylinders do not interfere with the inner wall surfaces of the
cylinders (cylinder walls).
[0465] Examples of such a guiding member include a linear bearing
disposed between the piston rods 322 and 1122 and cylinder blocks
323 and 1123, between the outer circumferential surfaces of the
piston main bodies 324 and 524 and the inner wall surface of the
cylinder 326, or between the outer circumferential surface of the
linkage member 1124 and the inner wall surface of the cylinder
1126, a member that guides a cylindrical protrusion protruding
downwards from the lower end surfaces of the piston main bodies 324
and 524 into a cylindrical indentation (dent) formed in the centers
of the bottom surfaces of the cylinders 326 and 1126, and so
forth.
[0466] By doing so, reciprocating members such as the piston main
bodies and the piston heads perform reciprocal movement in the
cylinders without wobbling or vibrating. This can prevent such
reciprocating members from interfering with the inner wall surfaces
of the cylinders, and furthermore, allows the reciprocating members
to be driven smoothly with minimum driving force.
[0467] In addition, in each of the above-described fourteenth to
sixteenth embodiments, spaces receiving vaporized low-temperature
fluid in these embodiments can be vacuumed.
[0468] By doing so, not only is an increase in the temperature of
the cylinder blocks suppressed, but also an increase in the
temperature of low-temperature fluid flowing into the compression
chambers is suppressed.
[0469] In this case, the pipes 931 and 1138 and the pressure
regulator 1139 shown in FIGS. 21, 24, and 26 are omitted.
[0470] Furthermore, in the above-described embodiments, it is more
preferable that an vacuumed space be formed between the piston rods
322 and 1122 and the cylinder blocks 323 and 1123.
[0471] For example, in the fifteenth embodiment shown in FIG. 24, a
bellows (same as the bellows 1141) for separating a space adjacent
to the inner circumferential side from a space adjacent to the
outer circumferential side of the piston rod 1122 is provided
between the lower surface of the other end portion 328b of the
piston rod 1122 and the upper surface of the bottom of the inner
space 329.
[0472] More specifically, the space between the cylinder block 1123
and the piston rod 1122 is vacuumed to prevent heat from the piston
rod 1122 (i.e., heat moving from the driving source 1111 side to
the piston rod 1122 side) from being transmitted to the cylinder
block 1123.
[0473] By doing so, not only is an increase in the temperature of
the cylinder block 1123 suppressed, but also an increase in the
temperature of low-temperature fluid flowing into the compression
chambers 1126a is suppressed.
[0474] In the current description, the term "low temperature"
designates temperatures of about -273.degree. C. to 0.degree. C.,
and the term "high pressure" designates pressures of about 0.2 MPa
to 200 MPa.
[0475] The word "fluid" used in the current description includes
"liquid," "gas," and "colloid."
* * * * *