U.S. patent application number 10/996585 was filed with the patent office on 2005-05-26 for fluid compressor.
Invention is credited to Fujii, Toshiro, Kato, Hiroaki, Kawamura, Koji, Shiromaru, Katsutoshi.
Application Number | 20050112014 10/996585 |
Document ID | / |
Family ID | 34594001 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050112014 |
Kind Code |
A1 |
Shiromaru, Katsutoshi ; et
al. |
May 26, 2005 |
Fluid compressor
Abstract
A fluid compressor that ensures the discharge of water from a
discharge port when water is drawn into or condensed in a pump
chamber. The compressor includes a pump chamber for drawing in
fluid. The pump chamber includes a bottom part located in a lower
portion of the pump chamber. Two rotors arranged in the pump
chamber are rotated to compress the fluid in the pump chamber. A
discharge port located in the bottom part discharges the compressed
fluid out of the pump chamber. The bottom part defines a guide
surface formed continuously from the discharge port. The guide
surface is sloped downward so that water on the guide surface moves
downward to the discharge port due to gravitational force.
Inventors: |
Shiromaru, Katsutoshi;
(Kariya-shi, JP) ; Kawamura, Koji; (Kariya-shi,
JP) ; Kato, Hiroaki; (Kariya-shi, JP) ; Fujii,
Toshiro; (Kariya-shi, JP) |
Correspondence
Address: |
Morgan & Finnegan, L.L.P.
3 World Financial Center
New York
NY
10281-2101
US
|
Family ID: |
34594001 |
Appl. No.: |
10/996585 |
Filed: |
November 24, 2004 |
Current U.S.
Class: |
418/206.1 ;
418/206.4 |
Current CPC
Class: |
F04C 2210/24 20130101;
F04C 29/0092 20130101; F04C 2240/102 20130101 |
Class at
Publication: |
418/206.1 ;
418/206.4 |
International
Class: |
F01C 001/18; F04C
018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 2003 |
JP |
2003-394414 |
Nov 17, 2004 |
JP |
2004-333357 |
Claims
What is claimed is:
1. A compressor for compressing a fluid, the compressor comprising:
a pump chamber for drawing in fluid, the pump chamber including a
bottom part located in a lower portion of the pump chamber with
respect to the gravitational direction in a normal installation
state of the compressor; two parallel rotation shafts arranged in
the pump chamber; two rotors respectively fixed to the two rotary
shafts, the rotors being rotated to compress the fluid in the pump
chamber; and a discharge port for discharging the compressed fluid
out of the pump chamber, the discharge port located at a lowermost
position in the pump chamber when a plane including the axes of the
two rotary shafts is substantially lies along a horizontal plane or
is inclined by a predetermined angle relative to the horizontal
plane; wherein the bottom part partially or entirely defines a
guide surface formed continuously from the discharge port, the
guide surface being sloped downward so that water on the guide
surface moves downward to the discharge port due to gravitational
force when the discharge port is located at the lowermost portion
in the bottom part of the pump chamber.
2. The compressor according to claim 1, wherein the guide surface
is generally funnel-shaped so that the discharge port is located at
the bottom of the guide surface.
3. The compressor according to claim 1, wherein the rotors rotate
along a rotation path, and the guide surface is shaped differently
from the rotation path.
4. The compressor according to claim 1, wherein the guide surface
has a cross-section generally shaped in correspondence with part of
an ellipse, and the discharge port is located at a position where
the minor axis and circumference of the ellipse intersect or in the
vicinity of the position where the minor axis and circumference of
the ellipse intersect.
5. The compressor according to claim 1, wherein the guide surface
has a cross-section generally shaped in correspondence with part of
an ellipsoid, and the discharge port is located at a position along
the direction of the minor axis that extends from the center of the
ellipsoid or in the vicinity of the position along the direction of
the minor axis that extends from the center of the ellipsoid.
6. A compressor for compressing a fluid, the compressor comprising:
a pump chamber for drawing in fluid, the pump chamber including a
bottom part located in a lower portion of the pump chamber; a rotor
arranged in the pump chamber, the rotor being rotated to compress
the fluid in the pump chamber; and a discharge port, located in the
bottom part, for discharging the compressed fluid out of the pump
chamber; wherein the bottom part partially or entirely defines a
guide surface formed continuously from the discharge port, the
guide surface being sloped downward so that water on the guide
surface moves downward to the discharge port due to gravitational
force.
7. The compressor according to claim 6, wherein the guide surface
is generally funnel-shaped so that the discharge port is located at
the bottom of the guide surface.
8. The compressor according to claim 6, wherein the rotors rotate
along a rotation path, and the guide surface is shaped differently
from the rotation path.
9. The compressor according to claim 6, wherein the guide surface
has a cross-section generally shaped in correspondence with part of
an ellipse, and the discharge port is located at a position where
the minor axis and circumference of the ellipse intersect or in the
vicinity of the position where the minor axis and circumference of
the ellipse intersect.
10. The compressor according to claim 6, wherein the guide surface
has a cross-section generally shaped in correspondence with part of
an ellipsoid, and the discharge port is located at a position along
the direction of the minor axis that extends from the center of the
ellipsoid or in the vicinity of the position along the direction of
the minor axis that extends from the center of the ellipsoid.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a compressor, and more
particularly, to a compressor for compressing fluid drawn into a
pump chamber by rotating a rotor and discharging the fluid out of
the pump chamber through a discharge port.
[0002] A compressor that compresses fluid, or a fluid compressor,
may be used in, for example, a fuel cell system. A fuel cell uses
hydrogen gas and an oxidizer gas to generate electric power. The
fuel cell produces water when generating power. To discharge the
water out of the fuel cell, more hydrogen gas and oxidizer gas than
the amount of hydrogen gas and oxidizer gas consumed to generate
power must be supplied to the fuel cell. Further, the fuel cell
discharges hydrogen gas (i.e., hydrogen off gas), which includes
hydrogen gas that was not subject to reaction. The discharge of
such hydrogen gas lowers fuel efficiency. To improve fuel
efficiency, a typical compressor positively circulates the hydrogen
off gas and mixes the hydrogen off gas with fresh hydrogen gas to
return the hydrogen off gas to the fuel cell. FIG. 1 shows an
example of such a compressor.
[0003] As shown in FIG. 1, a fluid compressor 51 has a case 52,
which has the shape of a generally oval cylinder. A pump chamber 53
is defined in the case 52. Hydrogen off gas is drawn into the pump
chamber 53 to be compressed. Two parallel rotation shafts (drive
shaft 54 and driven shaft 55) are supported in the pump chamber 53.
Two rotors 56 and 57 are respectively fixed to the drive shaft 54
and the driven shaft 55. A driver, such as a motor, drives the
drive shaft 54 and the driven shaft 55 to rotate the rotors 56 and
57 with a predetermined interval (phase difference) therebetween.
As a result, hydrogen off gas is drawn into the pump chamber 53
through a suction port 58, which is located at the upper part of
the pump chamber, and discharged out of the pump chamber 53 through
a discharge port 59, which is located at the lower part of the pump
chamber 53. The wall of the pump chamber 53 is shaped to form two
hollow cylindrical portions connected to each other so that the
rotors 56 and 57 rotate along the wall. More specifically, the
lower middle part of the pump chamber 53 is projected upward as
viewed in FIG. 1. The discharge port 59 is formed in the upwardly
projecting, lower part of the pump chamber 53. A recess 60 is
formed in each side of the discharge port 59.
[0004] As described above, when a fuel cell generates electric
power, water is produced and discharged together with hydrogen off
gas. Accordingly, water is also drawn into the pump chamber 53 in
addition to hydrogen off gas. The hydrogen off gas may be supplied
to the fluid compressor 51 via a gas-liquid separator. In such a
case, however, the humidity of the hydrogen off gas would be high.
Thus, when the fluid compressor 51 is in a low temperature
atmosphere, the moisture in the hydrogen off gas condenses as the
dew point changes and produces water in the pump chamber 53. Such
water remains in the recess 60 of the pump chamber 53. If the fluid
compressor 51 is left in such a state under a low temperature for a
long period of time, the residual water in the fluid compressor 51
would freeze. Activation of the fuel cell when water is frozen in
such a manner would interfere with normal activation of the fuel
cell. For example, abnormal current may flow through a motor that
drives the fluid compressor 51.
[0005] The above describes only one example of such problem. This
problem may occur in any system in which liquid collects in a pump
chamber.
[0006] Japanese Laid-Open Patent Publication No. 8-109089 describes
a root pump (one type of a fluid compressor) that solves the above
problem. The root pump has a suction port formed in the upper part
of a case and a discharge port formed in the lower part of the
case. The vicinity of the discharge port in the lower part of the
case is flat. That is, recesses are not formed in the lower part of
the pump chamber. Accordingly, the root pump discharges from the
discharge port the water drawn into and the water condensed in the
pump chamber so that water does not remain in the pump chamber.
[0007] However, the root pump also has a shortcoming. A root pump
is used for various purposes, such as a movable pump or as a pump
for use in a vehicle. With regard to vehicle pumps, an automobile
is driven (or parked) along sloped roads in addition to level
roads. Thus, the pump would also be inclined depending on the
posture of the automobile. If the pump is inclined, water would
flow toward the lower position in the inclined state. Accordingly,
depending on the posture of the automobile, water may remain in the
pump chamber without being discharged through the discharge port.
As a result, in the root pump described in Japanese Laid-Open
Patent Publication No. 8-109888, the residual water would freeze
under a low temperature atmosphere and interfere with normal
activation of the pump.
SUMMARY OF THE INVENTION
[0008] The present invention provides a fluid compressor that
ensures that water drawn into the pump chamber or condensed in the
pump chamber is discharged out of the pump chamber through the
discharge port.
[0009] One aspect of the present invention is a compressor for
compressing a fluid. The compressor includes a pump chamber for
drawing in fluid. The pump chamber includes a bottom part at which
water in the pump chamber collects due to gravitational force when
the compressor is horizontal. Two rotatable and parallel rotation
shafts are arranged in the pump chamber. Two rotors are
respectively fixed to the two rotary shafts. The rotors are rotated
to compress the fluid in the pump chamber. A discharge port
discharges the compressed fluid out of the pump chamber. The
discharge port is located at a lowermost position in the bottom
part of the pump chamber when a plane lying along the axes of the
two rotary shafts is parallel to a horizontal plane or inclined by
a predetermined angle relative to the horizontal plane. The pump
chamber includes a guide surface for continuously connecting the
bottom part partially or entirely to the discharge port. The guide
surface is sloped downward so that water on the guide surface moves
downward to the discharge port due to gravitational force when the
discharge port is located at the lowermost portion in the bottom
part of the pump chamber.
[0010] A further aspect of the present invention is a compressor
for compressing a fluid. The compressor includes a pump chamber for
drawing in fluid. The pump chamber includes a bottom part at which
water in the pump chamber collects due to gravitational force. The
bottom part has a lowermost portion. A rotor is arranged in the
pump chamber. The rotor is rotated to compress the fluid in the
pump chamber. A discharge port located in the lowermost portion of
the bottom part discharges the compressed fluid out of the pump
chamber. The pump chamber includes a guide surface for continuously
connecting the bottom part partially or entirely to the discharge
port. The guide surface is sloped downward so that water on the
guide surface moves downward to the discharge port due to
gravitational force.
[0011] Other aspects and advantages of the present invention will
become apparent from the following description, taken in
conjunction with the accompanying drawings, illustrating by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0013] FIG. 1 is a cross-sectional view showing a pump chamber of a
fluid compressor in the prior art;
[0014] FIG. 2 is a cross-sectional plan view of a hydrogen
compressor according to a preferred embodiment of the present
invention;
[0015] FIG. 3 is a cross-sectional view taken along lone 3-3 in
FIG. 2; and
[0016] FIG. 4 is a partial cross-sectional view taken along line
4-4 in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] A hydrogen compressor 10 according to a preferred embodiment
of the present invention will now be described with reference to
FIGS. 2 to 4. The hydrogen compressor 10 is one type of fluid
compressor that is used in a fuel cell system.
[0018] Referring to FIG. 2, in the preferred embodiment, the
hydrogen compressor 10 includes a motor M and a root pump P. The
motor M includes a motor housing 11, which is cylindrical, and a
partition wall 12. The motor housing 11 has a closed first end
(left end as viewed in FIG. 2) and an open second end (right end as
viewed in FIG. 2). The partition wall 12 is coupled to the motor
housing 11 so as to close the open second end of the motor housing
11. A motor chamber 13 is defined by the inner surface of the motor
housing 11 and the inner surface of the partition wall 12. The pump
P includes a pump housing 14, which has the shape of a generally
oval cylinder with a closed end, and a bearing block 16. The pump
housing 14 has an open first end (left end as viewed in FIG. 2).
The bearing block 16 is fastened to the pump housing 14 by bolts 15
so as to close the open first end of the pump housing 14. A pump
chamber 17 is defined by the inner surface of the pump housing 14
and the inner surface of the bearing block 16.
[0019] In the pump P, a gear housing 18, which has the shape of a
generally oval cylinder and which is smaller than the pump housing
14, is coupled to the second end (right end as viewed in FIG. 2) of
the pump housing 14. A gear chamber 19 is defined by the outer
surface of the second end of the pump housing 14 and the inner
surface of the gear housing 18. A fastener, such as a bolt, fastens
the partition wall 12 to the bearing block 16. In other words, the
fastener integrally fastens the motor M and the pump P to each
other. O-rings 20 for ensuring hermetic seal are arranged in the
surface joining the motor housing 11 and the partition wall 12, the
surface joining the pump housing 14 and the bearing block 16, the
surface joining the pump housing 14 and the gear housing 18, and
the surface joining the partition wall 12 and the bearing block
16.
[0020] A bearing 22 is arranged facing towards the motor chamber 13
on the end face 21 of the motor housing 11 in a manner concentric
to the motor housing 11. The bearing 22 rotatably supports a first
end (left end as viewed in FIG. 2) of a drive shaft 23, which
functions as a rotation shaft. The drive shaft 23 extends through
the partition wall 12, the bearing block 16, and the end face 24 of
the pump housing 14 and into the gear chamber 19. A bearing 25 is
arranged on the end face 24 of the pump housing 14. The bearing 25
rotatably supports a second end of the drive shaft 23. A bearing 26
is arranged in the bearing block 16. The bearing 26 rotatably
supports a middle portion of the drive shaft 23. A motor rotor 27
is fixed to the drive shaft 23. A motor stator 28 is fixed to the
motor housing 11 around the motor rotor 27. The motor rotor 27 and
the motor stator 28 form an electric motor 29.
[0021] A driven shaft 30 (rotation shaft) extends parallel to the
drive shaft 23 in the pump chamber 17 of the pump P. The driven
shaft 30 has a first end that is rotatably supported by a bearing
32, which is arranged in the bearing block 16. A second end of the
driven shaft 30 is rotatably supported by a bearing 31, which is
arranged in the end face 24 of the pump housing 14. A drive rotor
33, which is formed by two lobes, is fixed to the drive shaft 23. A
driven rotor 34, which is formed by two lobes, is fixed to the
driven shaft 30. In the same manner as the drive shaft 23, the
driven shaft 30 extends through the end face 24 of the pump housing
14 and into the gear chamber 19. In the gear chamber 19, a drive
gear 35, which is fixed to the second end of the drive shaft 23, is
meshed with a driven gear 36, which is fixed to the second end of
the driven shaft 30. Seal rings 37 are arranged in the bearing
block 16 and the end face 24 of the pump housing 14 at locations
contacting the drive shaft 23 and the driven shaft 30.
[0022] The internal structure of the pump chamber 17 in the pump P
will now be described.
[0023] As viewed in FIG. 3, a suction port 38 extends through the
top of the pump housing 14 in the pump P. Hydrogen off gas
discharged from a fuel cell V is drawn into the pump chamber 17
through the suction port 38. Further, a discharge port 40 extends
through the middle of a bottom part 39 of the pump chamber 17. The
hydrogen off gas compressed in the pump chamber 17 by rotation of
the rotors 33 and 34 is discharged through the discharge port 40.
The rotors 33 and 34 are rotated so that their outermost portions
define rotation paths R shown in FIG. 3 with a phase difference (90
degrees) between the drive shaft 23 and the driven shaft 30. The
rotors 33 and 34 that are rotated in this manner cooperate with the
wall of the pump chamber 17 to compress the hydrogen off gas drawn
into the pump chamber 17. The wall of the pump chamber 17 includes
a cooperation surface formed along the rotation paths R of the
rotors 33 and 34 so that a slight clearance exists between the wall
of the pump chamber 17 and the rotors 33 and 34. An increase in the
area of the cooperation surface improves the efficiency of the
compressor. Thus, the cooperation surface at the upper part of the
pump chamber 17 in the vicinity of the suction port 38 is gradually
projected inward along the rotation paths R of the of the rotors 33
and 34.
[0024] The inner surface of the bottom part 39 in the pump chamber
17 is sloped downward toward the discharge port 40 in a generally
conical manner, or in a generally funnel-shaped manner. Like the
driven rotor 34 shown in FIG. 3, when each of the rotors 33 and 34
are arranged in a vertical state in the pump chamber 17, the rotors
33 and 34 become closest to the bottom part 39 of the pump chamber
17 at proximal positions r. A downwardly sloped conical guide
surface 41 is formed from the proximal positions r toward the edge
40a of the discharge port 40. The guide surface 41 is sloped from
the proximal positions r to the discharge port 40 from every
direction (radial direction about the discharge port 40) including
the axial directions of the rotors 33 and 34 (the directions that
the drive shaft 23 and the driven shaft 30 extend) and directions
perpendicular to the axial directions. Accordingly, the edge 40a of
the discharge port 40 at the center of the conical guide surface 41
is located at the lowermost portion (deepest portion) of the bottom
part 39. More specifically, the bottom part 39 of the pump chamber
17 includes the guide surface 41, which is sloped outward in the
pump housing 14. In the bottom part 39, the discharge port 40 is
formed at the lowermost portion of the guide surface 41.
[0025] In other words, the guide surface 41 has a cross-section
generally shaped in correspondence with part of an ellipse or part
of an ellipsoid. The discharge port 40 is located at a position
where the minor axis of the ellipse and the circumference of the
ellipse intersect or at a position located along the direction of
the minor axis that extends from the center of the ellipsoid.
[0026] The operation of the hydrogen compressor 10 (fluid
compressor) when water flows out of the pump chamber 17 from the
discharge port 40 will now be discussed.
[0027] First, the electric motor 29 is driven to rotate the drive
shaft 23. As a result, the meshing engagement of the drive gear 35
and the driven gear 36 rotates the driven shaft 30 with the
predetermined phase difference from the drive shaft 23.
Accordingly, the drive rotor 33 and the driven rotor 34 are
synchronously rotated in the pump chamber 17 in the directions
indicated by the arrows in FIG. 3. The synchronous rotation of the
two rotors 33 and 34 draws the hydrogen off gas discharged from the
fuel cell V into the pump chamber 17. Further, the hydrogen off gas
is compressed by the rotation of the rotors 33 and 34 and delivered
toward the bottom part 39 to be discharged out of the pump chamber
17 from the discharge port 40, which is located at the lowermost
portion of the bottom part 39.
[0028] As described above, the hydrogen off gas drawn into the pump
chamber 17 may include water that is produced in the fuel cell V.
Accordingly, the hydrogen compressor 10 may draw water into the
pump chamber 17 together with the hydrogen off gas. Further, the
humidity of the hydrogen off gas may high. In this case, changes in
the dew point may condense the water in the hydrogen off gas. When
the hydrogen compressor 10 is left in a low temperature atmosphere
in a state in which water (condensed water) remains in the pump
chamber 17, the residual water may freeze and hinder activation of
the hydrogen compressor 10. However, the first embodiment avoids
the occurrence of such a state in a preferable manner.
[0029] The water drawn into the pump chamber 17 collects at the
bottom part 39 of the pump chamber 17 due to gravitational force or
the rotation of the rotors 33 and 34. At the bottom part 39, the
water flows along the downwardly sloped guide surface 41 to the
discharge port 40. The discharge port 40 is located at the
lowermost portion of the bottom part 39 in the pump chamber 17.
Thus, the guide surface 41 guides the water collected on the bottom
part 39 to the edge 40a of the discharge port 40. Then, the water
that reaches the edge 40a of the discharge port 40 is discharged
out of the pump chamber 17 through the discharge port 40.
Accordingly, water does not remain in the pump chamber 17.
[0030] The hydrogen compressor 10 may be installed as a compressor
for a fuel cell system of an electric automobile. In such a case,
the hydrogen compressor 10 may be inclined when, for example, the
vehicle is parked on a sloped road. However, with the hydrogen
compressor 10, the downwardly sloped, conical guide surface 41
extending about the discharge port 40 guides the water collected on
the bottom part 39 of the pump chamber 17 to the discharge port 40.
This ensures that the water is discharged out of the pump chamber
17 from the discharge port 40. Accordingly, the hydrogen compressor
10 prevents water from remaining in the pump chamber 17.
[0031] As mentioned above, in the hydrogen compressor 10, the pump
chamber 17 into which the hydrogen off gas is drawn in. The pump
chamber 17 includes the bottom part 39 at which water in the pump
chamber 17 collects due to gravitational force. The rotors 33 and
34 arranged in the pump chamber 17 are rotated to compress the
hydrogen off gas in the pump chamber 17. The discharge port 40
located in the lowermost portion of the bottom part 39 discharges
the compressed hydrogen off gas out of the pump chamber 17. The
pump chamber 17 includes a guide surface 41 for continuously
connecting the bottom part 39 to the discharge port 40. The guide
surface 40 is sloped downward so that water on the guide surface 40
moves downward to the discharge port 40 due to gravitational force.
Thus, when the water in the pump chamber 17 collects at the bottom
part 39 due to gravitational force, the water is guided in the
downward sloping direction of the guide surface 41, which is
continuous with the discharge port 40, to the discharge port 40,
which is located at the lowermost portion of the bottom part 39.
This ensures that the water flows out of the pump chamber 17 from
the discharge port 40. Accordingly, there is no residual water in
the pump chamber 17.
[0032] The hydrogen compressor 10 of the preferred embodiment has
the advantages described below.
[0033] (1) In the hydrogen compressor 10, the water drawn into the
pump chamber 17 is guided along the downwardly sloped guide surface
41 toward the discharge port 40, which is formed at the lowermost
portion of the bottom part 39 in the pump chamber 17. The hydrogen
compressor 10 then discharges the water together with compressed
hydrogen off gas out of the pump chamber 17 through the discharge
port 40. Accordingly, in the hydrogen compressor 10, water does not
remain in the pump chamber 17. This prevents residual water from
freezing and hindering activation of the hydrogen compressor
10.
[0034] (2) The guide surface 41 is conical and downwardly sloped
toward the discharge port 40 about the discharge port 40 from every
direction about the discharge port 40. Thus, even if the hydrogen
compressor 10 is inclined, the guide surface 41 guides water to the
discharge port 40 from any direction. Accordingly, the hydrogen
compressor 10 discharges water out of the pump chamber 17 through
the discharge port 40 even if the hydrogen compressor 10 is
inclined when it is installed in a vehicle or when it is
movable.
[0035] (3) The discharge port 40 is formed in the middle of the
bottom part 39 of the pump chamber 17. Thus, the conical guide
surface 41 is easily formed.
[0036] (4) The guide surface 41 is downwardly sloped from the
proximal positions r toward the edge of the discharge port 40. That
is, the guide surface 41 is downwardly sloped and smoothly
connected to the discharge port 40 from the proximal positions r,
which are the lowermost positions of the arcuate surface of the
pump chamber 17 along the rotation path R of the rotors 33 and 34.
Accordingly, the guide surface 41 smoothly guides the water in the
pump chamber 17 to the discharge port 40. Further, the rotors 33
and 34 and the wall of the pump chamber 17 cooperate to start
enclosing hydrogen gas at a timing that is earlier than the timing
at which the rotors 33 and 34 become vertical in the pump chamber
17 (more specifically, at a timing in which the rotors 33 and 34
pass by the end of the suction port 38). Accordingly, the
compression efficiency remains the same.
[0037] It should be apparent to those skilled in the art that the
present invention may be embodied in many other specific forms
without departing from the spirit or scope of the invention.
Particularly, it should be understood that the present invention
may be embodied in the following forms.
[0038] The hydrogen compressor 10 may be configured as mentioned
below. The hydrogen compressor 10 (fluid compressor) includes the
pump chamber 17 into which hydrogen off gas (fluid) is drawn in.
The pump chamber 17 includes the bottom part 39 at which water in
the pump chamber 17 collects due to gravitational force when the
compressor 10 is horizontal. The two rotatable and parallel shafts
23 and 30 are arranged in the pump chamber 17. The two rotors 33
and 34 respectively fixed to the two shafts 23 and 30 are rotated
to compress the hydrogen off gas in the pump chamber 17. The
discharge port 40 discharges the compressed hydrogen off gas out of
the pump chamber 17. The discharge port 40 is located at a
lowermost position in the bottom part 39 of the pump chamber 17
when a plane lying along the axes of the two shafts 23 and 30 is
parallel to a horizontal plane or inclined by a predetermined angle
relative to the horizontal plane. The pump chamber 17 includes the
guide surface 41 for continuously connecting the bottom part 39 to
the discharge port 40. The guide surface 41 is sloped downward so
that water on the guide surface 41 moves downward to the discharge
port 40 due to gravitational force when the discharge port 40 is
located at the lowermost portion in the bottom part 39 of the pump
chamber 17.
[0039] The guide surface 41 may be downwardly sloped only in the
axial direction of the rotors 33 and 34 (the direction in which the
drive shaft 23 and driven shaft 30 extend). In such a case, for
example, the hydrogen compressor 10 is installed in an automobile
so that the rotation shaft (e.g., drive shaft 23) is parallel to
the longitudinal direction of the automobile. Thus, when the
automobile is driven or stopped (parked) on a sloped road, the
hydrogen compressor 10 discharges water out of the pump chamber 17
through the discharge port 40 in a satisfactory manner.
[0040] The guide surface 41 may be downwardly sloped only in the
direction perpendicular to the axial direction of the rotors 33 and
34 (the direction in which the drive shaft 23 and driven shaft 30
extend). In such a case, for example, the hydrogen compressor 10 is
installed in an automobile so that the rotation shaft (e.g., drive
shaft 23) is parallel to the longitudinal direction of the
automobile. Thus, when the automobile sways sideward when driven,
the hydrogen compressor 10 discharges water out of the pump chamber
17 through the discharge port 40 in a satisfactory manner.
[0041] The guide surface 41 may be downwardly sloped in the axial
direction of the rotors 33 and 34 (the direction in which the drive
shaft 23 and driven shaft 30 extend) and the direction
perpendicular to the axial direction (i.e., only in two
directions).
[0042] A groove having a bottom surface, which is downwardly sloped
to and connected to the discharge port 40, may be formed in the
bottom part 39 of the pump chamber 17. In this case, the bottom
surface of the groove functions as the guide surface. Further, more
than one groove may radially extend from the discharge port 40.
[0043] In the preferred embodiment, the guide surface 41 has a
cross-section generally shaped in correspondence with part of an
ellipse or part of an ellipsoid. Further, the discharge port 40 is
located at a position where the minor axis of the ellipse and the
circumference of the ellipse intersect or located at a position
along the direction of the minor axis that extends from the axis of
the ellipsoid. Instead, the discharge port 40 may be located in the
vicinity of where the minor axis of the ellipse and the
circumference of the ellipse intersect or in the vicinity of a
position located along the direction of the minor axis that extends
from the axis of the ellipsoid.
[0044] In the preferred embodiment, the compressor 10 includes the
two shafts 23 and 30 and two rotors 33 and 34. Alternatively, the
compressor may include more than two shafts and more than two
rotors.
[0045] In the preferred embodiment, the present invention is
embodied in a hydrogen compressor 10, which forcibly circulates
hydrogen off gas in a fuel cell system. Instead, the present
invention may be embodied in an air compressor. Alternatively, the
present invention may be embodied in a fluid compressor other than
one used for a fuel cell system.
[0046] The present examples and embodiments are to be considered as
illustrative and not restrictive, and the invention is not to be
limited to the details given herein, but may be modified within the
scope and equivalence of the appended claims.
* * * * *