U.S. patent application number 10/501540 was filed with the patent office on 2005-07-07 for expander.
Invention is credited to Makino, Hiroyuki, Uda, Makoto.
Application Number | 20050147507 10/501540 |
Document ID | / |
Family ID | 27678061 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050147507 |
Kind Code |
A1 |
Makino, Hiroyuki ; et
al. |
July 7, 2005 |
Expander
Abstract
An expander is provided in which a rotor (22) is rotated by
supplying high-temperature, high-pressure steam to an expansion
chamber (43) defined between a piston (42) and a cylinder sleeve
(41) so that the piston (42) pushes a swash plate (31), and sliding
surfaces of the piston (42) and the cylinder sleeve (41) are
lubricated with oil supplied via an oil hole (32c). The piston (42)
includes a top part (63) that is exposed to high-temperature,
high-pressure steam within the expansion chamber (43), an end part
(61) that abuts against the swash plate (31), and a middle part
(62) that is present between the end part (61) and the top part
(63) and is in sliding contact with the cylinder sleeve (41), the
top part (63) being formed from a heat-resistant and
corrosion-resistant material, the end part (61) being formed from a
material having high surface pressure resistance, and the middle
part (62) being formed from a material having high abrasion
resistance. This enables the durability of the piston (42) of an
axial piston cylinder type expander to be improved.
Inventors: |
Makino, Hiroyuki; (Wako-shi
Saitama, JP) ; Uda, Makoto; (Wako-shi Saitama,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
27678061 |
Appl. No.: |
10/501540 |
Filed: |
March 4, 2005 |
PCT Filed: |
January 21, 2003 |
PCT NO: |
PCT/JP03/00454 |
Current U.S.
Class: |
417/375 ;
417/269; 417/410.4; 417/437 |
Current CPC
Class: |
F01B 3/0088 20130101;
F01B 3/0085 20130101; F01B 3/002 20130101; F01B 3/0044
20130101 |
Class at
Publication: |
417/375 ;
417/269; 417/410.4; 417/437 |
International
Class: |
F04B 017/00; F04B
001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2002 |
JP |
2002-35614 |
Claims
1. An expander comprising: a casing (11); a rotor (22) rotatably
supported in the casing (11); and an axial piston cylinder group
(56) arranged annularly in the rotor (22) so as to surround an axis
(L) of the rotor; the rotor (22) being rotated by supplying
high-temperature, high-pressure steam to an expansion chamber (43)
defined between a piston (42) and a cylinder sleeve (41) of the
axial piston cylinder group (56), and sliding surfaces of the
piston (42) and the cylinder sleeve (41) being lubricated with oil;
characterized in that that piston (42) comprises a top part (63)
that is exposed to high-temperature, high-pressure steam within
expansion chamber (43), an end part (61) that abuts against a swash
plate (31), and a middle part (62) that is present between the end
part (61) and the top part (63) and is in sliding contact with the
cylinder sleeve (41), the top part (63) being formed from a
heat-resistant and corrosion-resistant material, the end part (61)
being formed from a material having high surface pressure
resistance, and the middle part (62) being formed from a material
having high abrasion resistance.
2. The expander according to claim 1, wherein a heat-insulating
space (65) is provided between the top part (63) and the middle
part (62).
3. The expander according to, claim 1 wherein a hollow space (62a)
is formed in the middle part (62), an oil ring channel (63b) formed
on an outer peripheral face of the top part (63) communicates with
the hollow space (62a) via a first oil hole (63c), and a small
diameter part (62b) formed on an outer peripheral face of the
middle part (62) communicates with the hollow space (62a) via a
second oil hole (62c).
4. The expander according to claim 2, wherein a hollow space (62a)
is formed in the middle part (62), an oil ring channel (63b) formed
on an outer peripheral face of the top part (63) communicates with
the hollow space (62a) via a first oil hole (63c), and a small
diameter part (62b) formed on an outer peripheral face of the
middle part (62) communicates with the hollow space (62a) via a
second oil hole (62c).
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an expander that includes a
casing, a rotor rotatably supported in the casing, and an axial
piston cylinder group arranged annularly in the rotor so as to
surround the axis of the rotor, the rotor being rotated by
supplying high-temperature, high-pressure steam to expansion
chambers defined between pistons and cylinder sleeves of the axial
piston cylinder group, and sliding surfaces of the piston and the
cylinder sleeve being lubricated with oil.
BACKGROUND ART
[0002] Such an expander has been proposed by the present applicant
in Japanese Patent Application No. 2001-61424. This expander is
used in a Rankine cycle system, and includes an axial piston
cylinder group arranged annularly in a rotor so as to surround the
axis of the rotor, and lubrication of a section where a piston and
a cylinder sleeve slide against each other is carried out by oil,
which is separate from the steam (water) that is the working medium
of the expander.
[0003] A top part of the piston of such an expander is exposed to
high-temperature, high-pressure steam supplied to an expansion
chamber of the cylinder sleeve, and is not only easily oxidized,
but also might be corroded by contact with water formed by
condensation of the steam. An end part of the piston might be
damaged by a large load due to abutment against a swash plate. A
middle part of the piston, which slides against the cylinder
sleeve, is lubricated with oil, but if steam that has leaked from
the expansion chamber of the cylinder sleeve condenses to become
water and adheres to the sliding surfaces, the oil will be
contaminated by the water, it becomes difficult to maintain an oil
film, and abnormal wear might occur.
[0004] However, in the above-mentioned conventional arrangement,
since the top part, the end part, and the middle part of the piston
are made integrally of identical materials, it is difficult to
completely satisfy the requirements of each part for heat
resistance, corrosion resistance, high surface pressure resistance,
abrasion resistance, etc.
DISCLOSURE OF INVENTION
[0005] The present invention has been achieved under the
above-mentioned circumstances, and it is an object thereof to
improve the durability of a piston of an axial piston cylinder type
expander.
[0006] In order to attain this object, in accordance with a first
aspect of the present invention, there is proposed an expander that
includes a casing, a rotor rotatably supported in the casing, and
an axial piston cylinder group arranged annularly in the rotor so
as to surround the axis of the rotor, the rotor being rotated by
supplying high-temperature, high-pressure steam to an expansion
chamber defined between a piston and a cylinder sleeve of the axial
piston cylinder group, and sliding surfaces of the piston and the
cylinder sleeve being lubricated with oil, characterized in that
the piston includes a top part that is exposed to high-temperature,
high-pressure steam within the expansion chamber, an end part that
abuts against a swash plate, and a middle part that is present
between the end part and the top part and is in sliding contact
with the cylinder sleeve, the top part being formed from a
heat-resistant and corrosion-resistant material, the end part being
formed from a material having high surface pressure resistance, and
the middle part being formed from a material having high abrasion
resistance.
[0007] In accordance with this arrangement, with regard to the
expander piston that includes the end part, the top part, and the
middle part, the top part, which is exposed to high-temperature,
high-pressure steam supplied to the expansion chamber, is formed
from the heat-resistant and corrosion-resistant material, and it is
therefore possible to prevent the top part from being oxidized due
to heat and from being corroded by contact with water from the
liquefaction of steam. Furthermore, since the end part of the
piston, which abuts against the swash plate, is formed from the
material having high surface pressure resistance, it is possible to
prevent the end part from being damaged by a strong surface
pressure applied by the swash plate. Moreover, since the middle
part of the piston, which is in sliding contact with the cylinder
sleeve, is formed from the material having high abrasion
resistance, even if water from the condensation of steam
contaminates the oil on the sliding surfaces and degrades the
lubrication performance, it is possible to prevent the occurrence
of abnormal wear.
[0008] Furthermore, in accordance with a second aspect of the
present invention, in addition to the first aspect, there is
proposed an expander wherein a heat-insulating space is provided
between the top part and the middle part.
[0009] In accordance with this arrangement, since the
heat-insulating space is provided between the top part and the
middle part of the piston, it is possible to suppress escape, from
the top part to the cylinder sleeve via the middle part, of the
heat of the high-temperature, high-pressure steam that has been
supplied to the expansion chamber, thereby enabling degradation of
the thermal efficiency of the expander to be minimized.
[0010] Moreover, in accordance with a third aspect of the present
invention, in addition to the first or second aspect, there is
proposed an expander wherein a hollow space is formed in the middle
part, an oil ring channel formed on an outer peripheral face of the
top part communicates with the hollow space via a first oil hole,
and a small diameter part formed on an outer peripheral face of the
middle part communicates with the hollow space via a second oil
hole.
[0011] In accordance with this arrangement, since the hollow space
is formed in the middle part of the piston, not only is it possible
to reduce the weight of the piston, but it is also possible to
suppress the escape of heat from the piston to the cylinder sleeve
due to the hollow space functioning as a heat-insulating layer,
thus minimizing degradation of the thermal efficiency of the
expander. Furthermore, since the hollow space of the piston
communicates with the bottom of the oil ring channel formed in the
top part via the first oil hole and with the small diameter part
formed in the middle part via the second oil hole, it is possible
to discharge, into the small diameter part of the piston via the
second oil hole, the oil recovered in the hollow space from the oil
ring channel via the first oil hole, and provide the oil for
lubrication of sliding surfaces of the piston and the cylinder
sleeve.
[0012] Oil holes 63c and 62c of an embodiment correspond to the
first oil hole and the second oil hole respectively of the present
invention.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 to FIG. 13 show one embodiment of the present
invention;
[0014] FIG. 1 is a vertical sectional view of an expander,
[0015] FIG. 2 is a sectional view along line 2-2 in FIG. 1,
[0016] FIG. 3 is a view from arrowed line 3-3 in FIG. 1,
[0017] FIG. 4 is an enlarged view of part 4 in FIG. 1,
[0018] FIG. 5 is an enlarged view of part 5 in FIG. 1,
[0019] FIG. 6 is an exploded perspective view of a rotor,
[0020] FIG. 7 is a sectional view along line 7-7 in FIG. 4,
[0021] FIG. 8 is a sectional view along 8-8 in FIG. 4,
[0022] FIG. 9 is an enlarged view of part 9 in FIG. 4,
[0023] FIG. 10 is a sectional view along line 10-10 in FIG. 5,
[0024] FIG. 11 is a sectional view along line 11-11 in FIG. 5,
[0025] FIG. 12 is a sectional view along line 12-12 in FIG. 5,
and
[0026] FIG. 13 is a sectional view along line 13-13 in FIG. 5.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] One embodiment of the present invention is explained below
with reference to the attached drawings.
[0028] As shown in FIG. 1 to FIG. 9, an expander M of this
embodiment is used in, for example, a Rankine cycle system, and
converts the thermal energy and the pressure energy of
high-temperature, high-pressure steam as a working medium into
mechanical energy and outputs it. A casing 11 of the expander M is
formed from a casing main body 12, a front cover 15 joined via a
seal 13 to a front opening of the casing main body 12 by a
plurality of bolts 14, a rear cover 18 joined via a seal 16 to a
rear opening of the casing main body 12 by a plurality of bolts 17,
and an oil pan 21 joined via a seal 19 to a lower opening of the
casing main body 12 by a plurality of bolts 20.
[0029] A rotor 22 disposed rotatably around an axis L extending in
the fore-and-aft direction in the center of the casing 11 has a
front part thereof supported by a ball bearing 23 provided in the
front cover 15 and a rear part thereof supported by a ball bearing
24 provided in the casing main body 12. A swash plate holder 28 is
fitted in a rear face of the front cover 15 via two seals 25 and 26
and a knock pin 27, and fixed thereto via a plurality of bolts 29,
and a swash plate 31 is rotatably supported by the swash plate
holder 28 via an angular ball bearing 30. The axis of the swash
plate 31 is inclined relative to the axis L of the rotor 22, and
the angle of inclination is fixed.
[0030] The rotor 22 includes an output shaft 32 supported by the
front cover 15 via the ball bearing 23, three sleeve support
flanges 33, 34, and 35 formed integrally with a rear part of the
output shaft 32 via cutouts 57 and 58 having predetermined widths
(see FIG. 4 and FIG. 9), a rotor head 38 that is joined by a
plurality of bolts 37 to the rear sleeve support flange 35 via a
metal gasket 36 and supported by the casing main body 12 via the
ball bearing 24, and a heat-insulating cover 40 that is fitted over
the three sleeve support flanges 33, 34, and 35 from the front and
joined to the front sleeve support flange 33 by a plurality of
bolts 39.
[0031] Sets of five sleeve support holes 33a, 34a, and 35a are
formed in the three sleeve support flanges 33, 34, and 35
respectively at intervals of 72.degree. around the axis L, and five
cylinder sleeves 41 are fitted into the sleeve support holes 33a,
34a, and 35a from the rear. A flange 41a is formed on the rear end
of each of the cylinder sleeves 41, and axial positioning is
carried out by abutting this flange 41a against the metal gasket 36
while fitting the flange 41a into a step 35b formed in the sleeve
support holes 35a of the rear sleeve support flange 35 (see FIG.
9). A piston 42 is slidably fitted within each of the cylinder
sleeves 41, the front end of the piston 42 abutting against a
dimple 31 a formed on the swash plate 31, and a steam expansion
chamber 43 is defined between the rear end of the piston 42 and the
rotor head 38.
[0032] An oil passage 32a is formed so as to extend on the axis L
within the output shaft 32, which is integral with the rotor 22,
and the front end of the oil passage 32a branches in a radial
direction and communicates with an annular channel 32b on the outer
periphery of the output shaft 32. An oil passage blocking member 45
is screwed into the inner periphery of the oil passage 32a via a
seal 44 at a radially inner position of the middle sleeve support
flange 34 of the rotor 22, and a plurality of oil holes 32c
extending radially outward from the oil passage 32a in the vicinity
of the oil passage blocking member 45 open on the outer periphery
of the output shaft 32.
[0033] A trochoidal oil pump 49 is disposed between a recess 15a
provided in a front face of the front cover 15 and a pump cover 48
fixed via a seal 46 to the front face of the front cover 15 by a
plurality of bolts 47, and includes an outer rotor 50 that is
rotatably fitted in the recess 15a, and an inner rotor 51 that is
fixed to the outer periphery of the output shaft 32 and meshes with
the outer rotor 50. An internal space of the oil pan 21
communicates with an intake port 53 of the oil pump 49 via an oil
pipe 52 and an oil passage 15b of the front cover 15, and a
discharge port 54 of the oil pump 49 communicates with the annular
channel 32b of the output shaft 32 via an oil passage 15c of the
front cover 15.
[0034] The piston 42, which is slidably fitted into the cylinder
sleeve 41, is formed from an end part 61, a middle part 62, and a
top part 63. The end part 61 is a member having a spherical part
61a that abuts against the dimple 31a of the swash plate 31, and is
joined by welding to the forward end of the middle part 62. The
middle part 62 is a cylindrical member having a large volume hollow
space 62a; an outer peripheral part of the middle part 62 close to
the top part 63 has a small diameter part 62b whose diameter is
slightly reduced, a plurality of oil holes 62c are formed so as to
run radially through the small diameter part 62b, and a plurality
of spiral oil channels 62d are formed in an outer peripheral part
that is present forward of the small diameter part 62b. The top
part 63 faces the expansion chamber 43 and is formed integrally
with the middle part 62, and a heat-insulating space 65 is formed
between a dividing wall 63a formed on an inner face of the top part
63 and a cover member 64 fitted into and welded to a rear end face
of the top part 63 (see FIG. 9). Two compression rings 66 and one
oil ring 67 are mounted on the outer periphery of the top part 63,
and an oil ring channel 63b into which the oil ring 67 is fitted
communicates with the hollow space 62a of the middle part 62 via a
plurality of oil holes 63c.
[0035] The end part 61 and the middle part 62 of the piston are
made of high-carbon steel, and the top part 63 is made of stainless
steel; among these, the end part 61 is subjected to induction
hardening, whereas the middle part 62 is subjected to hardening. As
a result, high surface pressure resistance can be imparted to the
end part 61, which abuts against the swash plate 31 at a high
surface pressure, abrasion resistance can be imparted to the middle
part 62, which is in sliding contact with the cylinder sleeve 41
under severe lubrication conditions, and heat resistance and
corrosion resistance can be imparted to the top part 63, which
faces the expansion chamber 43 and is exposed to high temperature
and high pressure.
[0036] An annular channel 41b is formed on the outer periphery of a
middle part of the cylinder sleeve 41 (see FIG. 6 and FIG. 9), and
a plurality of oil holes 41c are formed in the annular channel 41b.
Regardless of where rotationally the cylinder sleeve 41 is mounted,
the oil holes 32c formed in the output shaft 32 and oil holes 34b
formed in the middle sleeve support flange 34 of the rotor 22 (see
FIG. 4 and FIG. 6) communicate with the annular channel 41b. A
space 68 formed between the heat-insulating cover 40 and the front
and rear sleeve support flanges 33 and 35 of the rotor 22
communicates with the internal space of the casing 11 via oil holes
40a formed in the heat-insulating cover 40 (see FIG. 4 and FIG.
7).
[0037] An annular cover member 69 is welded to the front, or
expansion chamber 43 side, of the rotor head 38, which is joined to
the rear face of the front sleeve support flange 33 of the rotor 22
by the bolts 37, and an annular heat-insulating space 70 is defined
at the back, or rear face of the cover member 69 (see FIG. 9). The
rotor head 38 is positioned rotationally relative to the rear
sleeve support flange 35 by a knock pin 55.
[0038] The five cylinder sleeves 41 and the five pistons 42 form an
axial piston cylinder group 56 of the present invention.
[0039] The structure of a rotary valve 71 for the supply and
discharge of steam to and from the five expansion chambers 43 of
the rotor 22 is now explained with reference to FIG. 5, and FIG. 10
to FIG. 13.
[0040] As shown in FIG. 5, the rotary valve 71, which is disposed
along the axis L of the rotor 22, includes a valve main body 72, a
stationary valve plate 73, and a movable valve plate 74. The
movable valve plate 74 is fixed to a rear face of the rotor 22 by a
bolt 76 screwed into the oil passage blocking member 45 (see FIG.
4) while being positioned in the rotational direction by a knock
pin 75. The bolt 76 also has the function of fixing the rotor head
38 to the output shaft 32.
[0041] As is clear from FIG. 5, the stationary valve plate 73,
which abuts against the movable valve plate 74 via flat sliding
surfaces 77, is fixed to the center of a front face of the valve
main body 72 by one bolt 78, and also to an outer peripheral part
of the valve main body 72 by an annular fixing ring 79 and a
plurality of bolts 80. During this process, a step 79a formed on
the inner periphery of the fixing ring 79 is press-fitted around
the outer periphery of the stationary valve plate 73 so as to be
fitted in a socket-and-spigot type, and a step 79b formed on the
outer periphery of the fixing ring 79 is fitted in a
socket-and-spigot type around the outer periphery of the valve main
body 72, thereby ensuring that the stationary valve plate 73 is
coaxial with the valve main body 72. A knock pin 81 is disposed
between the valve main body 72 and the stationary valve plate 73,
and determines the position of the stationary valve plate 73 in the
rotational direction.
[0042] When the rotor 22 rotates, the movable valve plate 74 and
the stationary valve plate 73 therefore rotate relative to each
other on the sliding surfaces 77 in a state in which they are in
intimate contact with each other. The stationary valve plate 73 and
the movable valve plate 74 are made of a material having excellent
durability, such as carbon or a ceramic, and the durability can be
further improved by providing or coating the sliding surfaces 77
with a member having heat resistance, lubricating properties,
corrosion resistance, and abrasion resistance.
[0043] The valve main body 72, which is made of stainless steel, is
a stepped cylindrical member having a large diameter part 72a and a
small diameter part 72b; outer peripheral faces of the large
diameter part 72a and the small diameter part 72b are slidably
fitted in the axial L direction into circular cross-section support
faces 18a and 18b of the rear cover 18 via seals 82 and 83
respectively, and positioned in the rotational direction by fitting
a pin 84 implanted in an outer peripheral face of the valve main
body 72 into a cutout 18c formed in the axial L direction in the
rear cover 18. A plurality of preload springs 85 are supported in
the rear cover 18 so as to surround the axis L, and the valve main
body 72, which has a step 72c between the large diameter part 72a
and the small diameter part 72b pushed by these preload springs 85,
is biased forward so as to put the sliding surfaces 77 of the
stationary valve plate 73 and the movable valve plate 74 in
intimate contact.
[0044] A steam supply pipe 86 connected to a rear face of the valve
main body 72 communicates with the sliding surfaces 77 via a first
steam passage P1 formed in the interior of the valve main body 72
and a second steam passage P2 formed in the stationary valve plate
73. A steam discharge chamber 88 sealed by a seal 87 is formed
between the casing main body 12, the rear cover 18, and the rotor
22, and this steam discharge chamber 88 communicates with the
sliding surfaces 77 via sixth and seventh steam passages P6 and P7
formed in the interior of the valve main body 72 and a fifth steam
passage P5 formed in the stationary valve plate 73. Provided on
surfaces where the valve main body 72 and the stationary valve
plate 73 are joined are a seal 89 surrounding a part where the
first and second steam passages P1 and P2 are connected to each
other and a seal 90 surrounding a part where the fifth and sixth
steam passages P5 and P6 are connected to each other.
[0045] Five third steam passages P3 disposed at equal intervals so
as to surround the axis L run through the movable valve plate 74,
and opposite ends of five fourth steam passages P4 formed in the
rotor 22 so as to surround the axis L communicate with the third
steam passages P3 and the expansion chambers 43. The part of the
second steam passage P2 opening on the sliding surface 77 is
circular, whereas the part of the fifth steam passage P5 opening on
the sliding surface 77 has an arc shape with the axis L as its
center.
[0046] The operation of the expander M of this embodiment having
the above-mentioned arrangement is now explained.
[0047] High-temperature, high-pressure steam generated by heating
water in an evaporator reaches the sliding surfaces 77 of the
stationary valve plate 73 with the movable valve plate 74 from the
steam supply pipe 86 via the first steam passage P1 formed in the
valve main body 72 of the rotary valve 71 and the second steam
passage P2 formed in the stationary valve plate 73, which is
integral with the valve main body 72. The second steam passage P2
opening on the sliding surface 77 communicates momentarily during a
predetermined intake period with the corresponding third steam
passage P3 formed in the movable valve plate 74, which rotates
integrally with the rotor 22, and the high-temperature,
high-pressure steam is supplied, via the fourth steam passage P4
formed in the rotor 22, from the third steam passage P3 to the
expansion chamber 43 within the cylinder sleeve 41.
[0048] Even after the communication between the second steam
passage P2 and the third steam passage P3 has been blocked due to
rotation of the rotor 22, the high-temperature, high-pressure steam
expands within the expansion chamber 43 and causes the piston 42
fitted in the cylinder sleeve 41 to be pushed forward from top dead
center toward bottom dead center, and the end part 61 at the front
end of the piston 42 pushes against the dimple 31a of the swash
plate 31. As a result, the reaction force that the pistons 42
receive from the swash plate 31 gives a rotational torque to the
rotor 22. For each one fifth of a revolution of the rotor 22, the
high-temperature, high-pressure steam is supplied into a fresh
adjoining expansion chamber 43, thus continuously rotating the
rotor 22.
[0049] While the piston 42, having reached bottom dead center
accompanying rotation of the rotor 22, retreats toward top dead
center by being pushed by the swash plate 31, the low-temperature,
low-pressure steam pushed out of the expansion chamber 43 is
discharged into the steam discharge chamber 88 via the fourth steam
passage P4 of the rotor 22, the third steam passage P3 of the
movable valve plate 74, the sliding surfaces 77, the arc-shaped
fifth steam passage P5 of the stationary valve plate 73, and the
sixth and seventh steam passages P6 and P7 of the valve main body
72, and is supplied therefrom into a condenser.
[0050] The oil pump 49 provided on the output shaft 32 operates
accompanying rotation of the rotor 22, and oil is taken in from the
oil pan 21 via the oil pipe 52, the oil passage 15b of the front
cover 15, and the intake port 53, discharged from the discharge
port 54, and supplied to a space between the cylinder sleeve 41 and
the small diameter part 62b formed in the middle part 62 of the
piston 42 via the oil passage 15c of the front cover 15, the oil
passage 32a of the output shaft 32, the annular channel 32b of the
output shaft 32, the oil holes 32c of the output shaft 32, the
annular channel 41b of the cylinder sleeve 41, and the oil holes
41c of the cylinder sleeve 41. A portion of the oil retained by the
small diameter part 62b flows into the spiral oil channels 62d
formed in the middle part 62 of the piston 42 and lubricates the
surface that slides against the cylinder sleeve 41, and another
portion of the oil lubricates surfaces of the compression rings 66
and the oil ring 67 provided at the top part 63 of the piston 42
that slide against the cylinder sleeve 41.
[0051] Since water formed in the expansion chamber 43 by
condensation of a portion of the supplied high-temperature,
high-pressure steam inevitably enters between the sliding surfaces
of the cylinder sleeve 41 and the piston 42 and contaminates the
oil, the lubrication conditions of the sliding surfaces are severe,
but by supplying a necessary amount of oil directly to the sliding
surfaces of the cylinder sleeve 41 and the piston 42 from the oil
pump 49 via the interior of the output shaft 32, it is possible to
maintain a sufficient oil film, thereby ensuring the lubrication
performance and enabling the dimensions of the oil pump 49 to be
reduced.
[0052] Oil scraped off the surface of the cylinder sleeve 41 that
the piston 42 slides against by the oil ring 67 flows from the oil
holes 63c formed in the base of the oil ring channel 63b into the
hollow space 62a within the piston 42. The hollow space 62a
communicates with the interior of the cylinder sleeve 41 via the
plurality of oil holes 62c running through the middle part 62 of
the piston 42, and the interior of the cylinder sleeve 41
communicates with the annular channel 41b on the outer periphery of
the cylinder sleeve 41 via the plurality of oil holes 41 c.
Although the surroundings of the annular channel 41b are covered by
the middle sleeve support flange 34 of the rotor 22, since the oil
hole 34b is formed in the sleeve support flange 34, the oil within
the hollow space 62a of the piston 42 is biased radially outward
due to centrifugal force, discharged to the space 68 within the
heat-insulating cover 40 via the oil hole 34b of the sleeve support
flange 34, and returned therefrom to the oil pan 21 via the oil
holes 40a of the heat-insulating cover 40. During this process,
since the oil hole 34b is positioned toward the axis L relative to
the radially outer edge of the sleeve support flange 34, the oil
that is present radially outside the oil hole 34b is retained in
the hollow space 62a of the piston 42 by centrifugal force.
[0053] In this way, the oil retained in the hollow space 62a within
the piston 42 and the oil retained in the small diameter part 62b
on the outer periphery of the piston 42 are supplied from the small
diameter part 62b to the top part 63 side during an expansion
stroke in which the volume of the expansion chamber 43 increases,
and are supplied from the small diameter part 62b to the end part
61 side during a compression stroke in which the volume of the
expansion chamber 43 decreases, and it is therefore possible to
ensure reliable lubrication over the entire axial region of the
piston 42. Furthermore, as a result of the oil flowing within the
hollow space 62a of the piston 42, the heat of the top part 63,
which is exposed to high-temperature, high-pressure steam, is
transmitted to the end part 61, which has a low temperature, and it
is thus possible to avoid the temperature of the piston 42
increasing locally.
[0054] When high-temperature, high-pressure steam is supplied from
the fourth steam passage P4 to the expansion chamber 43, since the
heat-insulating space 65 is formed between the middle part 62 and
the top part 63 of the piston 42, which faces the expansion chamber
43, and the heat-insulating space 70 is formed in the rotor head
38, which faces the expansion chamber 43, it is possible to
minimize the escape of heat from the expansion chamber 43 to the
piston 42 and the rotor head 38, thereby contributing to an
improvement in the performance of the expander M. Furthermore,
since the large volume hollow space 62a is formed within the piston
42, not only is it possible to reduce the weight of the piston 42,
but also it is possible to reduce the heat capacity of the piston
42, thereby enabling the escape of heat from the expansion chamber
43 to be suppressed yet more effectively.
[0055] Since the expansion chamber 43 is sealed by interposing the
metal gasket 36 between the rear sleeve support flange 35 and the
rotor head 38, in comparison with a case in which the expansion
chamber 43 is sealed via a thick annular seal, unnecessary volume
around the seal can be reduced, thus ensuring that the expander M
has a large volume ratio (expansion ratio) and thereby improving
the thermal efficiency, which enables the output to be increased.
Moreover, since the cylinder sleeve 41 is formed separately from
the rotor 22, the material of the cylinder sleeve 41 can be
selected without being restricted by the material of the rotor 22,
while taking into consideration the thermal conductivity, heat
resistance, strength, abrasion resistance, etc., and, moreover, it
is possible to replace only a worn or damaged cylinder sleeve 41,
which is economical.
[0056] Furthermore, since the outer peripheral face of the cylinder
sleeve 41 is exposed through the two cutouts 57 and 58 formed
circumferentially in the outer peripheral face of the rotor 22, not
only is it possible to reduce the weight of the rotor 22, but it is
also possible to reduce the heat capacity of the rotor 22, thereby
improving the thermal efficiency and, moreover, the cutouts 57 and
58 function as a heat-insulating space, thus suppressing the escape
of heat from the cylinder sleeve 41. Furthermore, since the outer
peripheral part of the rotor 22 is covered by the heat-insulating
cover 40, it is possible to suppress the escape of heat from the
cylinder sleeve 41 yet more effectively.
[0057] Since the rotary valve 71 supplies and discharges steam to
and from the axial piston cylinder group 56 via the flat sliding
surfaces 77 between the stationary valve plate 73 and the movable
valve plate 74, it is possible to prevent the leakage of steam
effectively. This is because the flat sliding surfaces 77 can
easily be machined with high precision, and control of the
clearance is easy compared with cylindrical sliding surfaces.
Moreover, since a surface pressure is generated on the sliding
surfaces 77 of the stationary valve plate 73 and the movable valve
plate 74 by applying a preset load to the valve main body 72 by
means of the plurality of preload springs 85, it is possible to
suppress the leakage of steam past the sliding surfaces 77 yet more
effectively.
[0058] Furthermore, since the valve main body 72 of the rotary
valve 71 is made of stainless steel, which has a large coefficient
of thermal expansion, and the stationary valve plate 73 fixed to
the valve main body 72 is made of carbon or a ceramic, which has a
small coefficient of thermal expansion, there is the possibility
that the centering between the two might be displaced due to a
difference in the coefficients of thermal expansion, but since the
fixing ring 79 is fixed to the valve main body 72 by means of the
plurality of bolts 80 in a state in which the step 79a on the inner
periphery of the fixing ring 79 is press-fitted over the outer
periphery of the stationary valve plate 73 in a socket-and-spigot
type fitting and the step 79b on the outer periphery of the fixing
ring 79 is press-fitted over the outer periphery of the valve main
body 72 in a socket-and-spigot type fitting, it is possible to
carry out precise centering of the stationary valve plate 73
relative to the valve main body 72 by the aligning action of the
socket-and-spigot type fitting of the fixing ring 79 and prevent
the timing of supply and discharge of steam from deviating, thereby
preventing deterioration in the performance of the expander M.
Moreover, it is possible to make the abutting surfaces of the
stationary valve plate 73 and the valve main body 72 come into
intimate and uniform contact by virtue of the securing force of the
bolts 80, thereby suppressing the leakage of steam past the
abutting surfaces.
[0059] Moreover, since the rotary valve 71 can be attached to and
removed from the casing main body 12 merely by removing the rear
cover 18 from the casing main body 12, the ease of maintenance
operations such as repair, cleaning, and replacement can be greatly
improved. Furthermore, although the rotary valve 71 through which
the high-temperature, high-pressure steam passes reaches a high
temperature, since the swash plate 31 and the output shaft 32,
where lubrication by oil is required, are disposed on the opposite
side of the rotor 22 to the rotary valve 71, degradation of the
lubrication performance of the swash plate 31 and the output shaft
32 due to heating of the oil by the heat of the rotary valve 71,
which reaches a high temperature, can be prevented. Moreover, the
oil also exhibits the function of cooling the rotary valve 71, thus
preventing overheating.
[0060] Although an embodiment of the present invention is explained
above, the present invention can be modified in a variety of ways
without departing from the spirit and scope thereof.
[0061] For example, the expander M is illustrated for a Rankine
cycle system in the embodiment, but the expander M of the present
invention can be applied to any other purpose.
[0062] Furthermore, the materials and procedures for a thermal
treatment, surface treatment, etc. of the end part 61, the middle
part 62, and the top part 63 of the piston 42 are not limited by
the embodiment, and can be changed appropriately as long as desired
properties can be maintained.
INDUSTRIAL APPLICABILITY
[0063] The expander of the present invention is suitable for
application to a Rankine cycle system, but the present invention
can be applied to an expander for any purpose as long as the
thermal energy and the pressure energy of a high-temperature,
high-pressure working medium is converted into mechanical energy
and output.
* * * * *