U.S. patent application number 10/300508 was filed with the patent office on 2003-05-22 for swash plate type compressor.
Invention is credited to Inoue, Yoshinori, Mochizuki, Kenji, Shintoku, Noriyuki, Tarutani, Tomoji.
Application Number | 20030095876 10/300508 |
Document ID | / |
Family ID | 19168938 |
Filed Date | 2003-05-22 |
United States Patent
Application |
20030095876 |
Kind Code |
A1 |
Tarutani, Tomoji ; et
al. |
May 22, 2003 |
Swash plate type compressor
Abstract
A shaft and a rotary valve, which are formed integrally, are
made of an iron-based metal while a cylinder block is made of an
aluminum-based metal. A sleeve forms a slide surface between the
cylinder block and the rotary valve when the shaft and the rotary
valve rotate together. The sleeve has a coefficient of thermal
expansion closer to those of the shaft and the rotary valve than
that of the cylinder block. This structure prevents an increase in
the clearance between the housing and the rotary valve due to the
increased temperature at the time the shaft rotates at a high
speed, and prevents gas leakage and a reduction in sealability.
Inventors: |
Tarutani, Tomoji;
(Kariya-shi, JP) ; Shintoku, Noriyuki;
(Kariya-shi, JP) ; Mochizuki, Kenji; (Kariya-shi,
JP) ; Inoue, Yoshinori; (Kariya-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154
US
|
Family ID: |
19168938 |
Appl. No.: |
10/300508 |
Filed: |
November 20, 2002 |
Current U.S.
Class: |
417/269 ;
417/222.1; 417/222.2; 92/12.2 |
Current CPC
Class: |
F04B 27/1018
20130101 |
Class at
Publication: |
417/269 ;
417/222.1; 417/222.2; 92/12.2 |
International
Class: |
F04B 001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2001 |
JP |
2001-357630 |
Claims
What is claimed is:
1. A swash plate type compressor including a housing having a
cylinder block, the cylinder block having a plurality of cylinder
bores around a shaft, the shaft being rotatably supported in the
housing, an suction pressure area being formed in the housing,
wherein a plurality of pistons are respectively inserted into the
cylinder bores and reciprocate in the respective cylinder bores via
a swash plate in accordance with rotation of the shaft to thereby
perform a suction stroke for taking a refrigerant gas in the
suction pressure area into a compression chamber formed in each
cylinder bore, the swash plate type compressor comprising:
communication passages formed in the cylinder block in such a way
as to communicate with the cylinder bores, respectively; a rotary
valve formed integral with the shaft, wherein the rotary valve has
a suction passage for connecting the communication passage of each
cylinder bore in the suction stroke to the suction pressure area;
and a sleeve provided on the rotary valve in the cylinder block,
wherein the sleeve has a coefficient of thermal expansion closer to
that of the shaft than that of the cylinder block.
2. The swash plate type compressor according to claim 1, wherein
the sleeve forms a slide surface to the rotary valve.
3. The swash plate type compressor according to claim 1, wherein
the shaft and the rotary valve are made of an iron-based metal and
the cylinder block is made of an aluminum-based metal.
4. The swash plate type compressor according to claim 1, wherein
the sleeve is made of an iron-based metal.
5. The swash plate type compressor according to claim 4, wherein
the coefficient of thermal expansion of the sleeve ranges about 7
to 15.times.10.sup.-6/.degree. C.
6. The swash plate type compressor according to claim 1, wherein
the sleeve is made of a resin or ceramics.
7. The swash plate type compressor according to claim 1, wherein
the shaft, the rotary valve and the sleeve are made of an
iron-based metal.
8. The swash plate type compressor according to claim 7, wherein
the coefficient of thermal expansion of the sleeve ranges about 7
to 15.times.10.sup.-6/.degree. C.
9. The swash plate type compressor according to claim 1, wherein
the sleeve is cast or press-fitted in the cylinder block.
10. A swash plate type compressor including a housing having a
cylinder block, the cylinder block having a plurality of cylinder
bores around a shaft, the shaft is rotatably supported in the
housing having a suction chamber and a discharge chamber, and
wherein a plurality of pistons are respectively inserted into the
cylinder bores and reciprocate in the respective cylinder bores via
a swash plate in accordance with rotation of the shaft to thereby
perform a suction stroke for taking a refrigerant gas in the
suction chamber into a compression chamber formed in each cylinder
bore, a compression stroke for compressing the refrigerant gas and
a discharge stroke for discharging the refrigerant gas, sucked into
the compression chamber, into the discharge chamber, the swash
plate type compressor comprising: communication passages formed in
the cylinder block in such a way as to communicate with the
cylinder bores, respectively; a rotary valve formed integral with
the shaft, wherein the rotary valve has a suction passage for
connecting the communication passage of each cylinder bore in the
suction stroke to the suction chamber; and a sleeve provided on the
rotary valve in the cylinder block, wherein the sleeve has a
coefficient of thermal expansion closer to that of the shaft than
that of the cylinder block.
11. The swash plate type compressor according to claim 10, wherein
the sleeve forms a slide surface to the rotary valve.
12. The swash plate type compressor according to claim 10, wherein
the shaft and the rotary valve are made of an iron-based metal and
the cylinder block is made of an aluminum-based metal.
13. The swash plate type compressor according to claim 10, wherein
the sleeve is made of an iron-based metal.
14. The swash plate type compressor according to claim 13, wherein
the coefficient of thermal expansion of the sleeve ranges about 7
to 15.times.10.sup.-6/.degree. C.
15. The swash plate type compressor according to claim 10, wherein
the sleeve is made of a resin or ceramics.
16. The swash plate type compressor according to claim 10, wherein
the shaft, the rotary valve and the sleeve are made of an
iron-based metal.
17. The swash plate type compressor according to claim 16, wherein
the coefficient of thermal expansion of the sleeve ranges about 7
to 15.times.10.sup.-6/.degree. C.
18. The swash plate type compressor according to claim 10, wherein
the sleeve is cast or press-fitted in the cylinder block.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a bearing structure of a
rotary valve in a swash plate type compressor suitable for
air-conditioning of a vehicle.
[0002] A reciprocative compressor as disclosed in Japanese
Unexamined Patent Publication No. Hei 6-137265 is known. This
compressor has a cylinder block having a plurality of cylinder
bores around the axial center, a shaft inserted into an axial hole
of the cylinder block, a plurality of pistons which are coupled to
a swash plate in a crank chamber that operates together with the
shaft and reciprocate in the respective cylinder bores, and a
housing which has a suction chamber communicatable to the axial
hole of the cylinder block and a discharge chamber formed in an
outward area of the suction chamber and closes end faces of the
cylinder block. This type of compressor has communication passages
formed between the respective cylinder bores and the axial hole of
the cylinder block, and a rotary valve coupled to the shaft in such
a way as to be rotatable in synchronism with the shaft. The rotary
valve has a suction passage for sequentially connecting the
communication passages of the individual cylinder bores in a
suction stroke to the suction chamber. The shaft is made of an
iron-based metal, and the rotary valve of an aluminum-based metal.
An engage hole is bored in one end portion of the rotary valve.
Attached to the engage hole is a steel liner that has a base plate
portion, which abuts on one end of the shaft, and extruding pieces,
which are split from the base plate portion through selectively
bending and are fitted in the engage hole. The split opening
portion of the liner is fitted over an engage shaft protruding from
the shaft end.
[0003] Because the shaft and the rotary valve in such a compressor
are formed of different members, however, the compressor has a
larger number of components. To reduce the number of the
components, the shaft and the rotary valve may be formed
integrally. From the viewpoint of securing the strength, the shaft
is often made of an iron-based metal having rigidity. In a case
where the shaft and the rotary valve may be formed integrally,
therefore, the rotary valve is likely to be made of an iron-based
metal. Generally, the housing is made of an aluminum-based metal to
become lighter. As the shaft rotates at a high speed, therefore,
the temperature of the slide surface between the housing and rotary
valve, which are made of different metals, rises and the clearance
between the housing and the rotary valve increases due to the
difference between their coefficients of thermal expansion. The
increased clearance leads to gas leakage and a reduction in
sealability, which would lower the performance of the
compressor.
[0004] Accordingly, it is an object of the present invention to
provide a swash plate type compressor which prevents an increase in
the clearance between the housing and the rotary valve when the
shaft rotates at a high speed.
BRIEF SUMMARY OF THE INVENTION
[0005] A swash plate type compressor includes a housing having a
cylinder block. The cylinder block has a plurality of cylinder
bores around a shaft. The shaft is rotatably supported in the
housing. An suction pressure area is formed in the housing. A
plurality of pistons are respectively inserted into the cylinder
bores and reciprocate in the respective cylinder bores via a swash
plate in accordance with rotation of the shaft to thereby perform a
suction stroke for taking a refrigerant gas in the suction pressure
area into a compression chamber formed in each cylinder bore. The
swash plate type compressor comprises communication passages, a
rotary valve, and a sleeve. The communication passages is formed in
the cylinder block in such a way as to communicate with the
cylinder bores, respectively. The rotary valve is formed integral
with the shaft. The rotary valve has a suction passage for
connecting the communication passage of each cylinder bore in the
suction stroke to the suction pressure area. The sleeve is provided
on the rotary valve in the cylinder block. The sleeve has a
coefficient of thermal expansion closer to that of the shaft than
that of the cylinder block.
[0006] Other aspects and advantages of the 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 SEVERAL VIEWS OF THE DRAWINGS
[0007] 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:
[0008] FIG. 1 is a schematic cross-sectional view of a compressor
according to one embodiment of the invention taken along the line
B-B in FIG. 2;
[0009] FIG. 2 is a cross-sectional view of the compressor taken
along the line A-A in FIG. 1; and
[0010] FIG. 3 is a partly enlarged cross-sectional view showing the
details of the compressor in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] One embodiment of the present invention as embodied into a
swash plate type compressor which is used in a vehicular
air-conditioning system will be described below with reference to
FIGS. 1 to 3.
[0012] As shown in FIG. 1, a front housing 11 is connected to the
front end of a cylinder block 12. A rear housing 13 is connected to
the rear end of the cylinder block 12 via a valve plate assembly
14. The front housing 11, the cylinder block 12 and the rear
housing 13 are fastened by through bolts 11a (see FIG. 2) and
constitute the housing of the compressor. The front housing 11, the
cylinder block 12 and the rear housing 13 are made of an
aluminum-based metal. The coefficient of thermal expansion of
aluminum is about 19 to 23.times.10.sup.-6/.degree. C. Note that
the lefthand side in FIG. 1 shows the frontward of the compressor,
and the right-hand side shows the rearward thereof.
[0013] The valve plate assembly 14 includes a main plate 14a, a sub
plate 14b stacked over the rear surface of the main plate 14a and a
retainer plate 14c stacked over the rear surface of the sub plate
14b. The valve plate assembly 14 is connected to the cylinder block
12 at the front surface of the main plate 14a.
[0014] A crank chamber 15 is defined between the front housing 11
and the cylinder block 12. A shaft 16 is rotatably supported
between the front housing 11 and the cylinder block 12 in such a
way as to pass through the crank chamber 15. The front end portion
of the shaft 16 is supported on the front housing 11 via a radial
bearing 17. A retaining hole 18 is formed nearly in the center of
the cylinder block 12. The rear end portion of the shaft 16 is
supported on a radial bearing 19 which is provided in the retaining
hole 18. A shaft seal 20 is provided at the front end portion of
the shaft 16. The shaft 16 is made of an iron-based metal. The
coefficient of thermal expansion of iron is about 10 to
12.times.10.sup.-6/.degree. C.
[0015] A plurality of cylinder bores 12a (only two shown in FIG. 1)
are formed in the cylinder block 12 in such a way as to surround
the shaft 16 at equiangles and equal distances. One-headed pistons
21 are retained in a reciprocative manner in the respective
cylinder bores 12a. The front opening of each cylinder bore 12a is
closed by the front surface of the associated piston 21, and the
rear opening of that cylinder bore 12a is closed by the front
surface of the valve plate assembly 14. A compression chamber 22 is
defined in each cylinder bore 12a and its volume varies in
accordance with the reciprocation of the associated piston 21.
[0016] A lug plate 23 is fixed to the shaft 16 in the crank chamber
15 in such a way as to be rotatable together with the shaft 16. The
lug plate 23 is abuttable on an inner wall surface 11b of the front
housing 11 via a thrust bearing 24. The inner wall surface 11b
supports the axial weight originated from the compression repulsive
force of each piston 21 and restricts the forward slide movement of
the shaft 16.
[0017] A swash plate 25 is provided in the crank chamber 15 with
the shaft 16 put through a through hole formed in the swash plate
25. A hinge mechanism 26 is positioned between the lug plate 23 and
the swash plate 25. The hinge coupling with the lug plate 23 via
the hinge mechanism 26 and the support on the shaft 16 allow the
swash plate 25 to be rotatable in synchronism with the lug plate 23
and the shaft 16, be slidable in the axial direction of the shaft
16 and be tiltable with respect to the shaft 16. The lug plate 23
and the hinge mechanism 26 constitute a variable displacement
mechanism.
[0018] Each piston 21 is engaged with the peripheral portion of the
swash plate 25 via a shoe 27. The rotation of the shaft 16 is
converted into the reciprocating motion of the pistons 21 via the
swash plate 25 and the shoes 27.
[0019] The lug plate 23, the swash plate 25, the hinge mechanism 26
and the shoes 27 constitute a crank mechanism which converts the
rotational movement of the shaft 16 to a compression action to
compress the refrigerant gas in the compression chamber 22.
[0020] A restricting portion 28 is provided on the shaft 16 between
the swash plate 25 and the cylinder block 12. The restricting
portion 28 is a ring-like member secured to the outer surface of
the shaft 16. The minimum inclination angle of the swash plate 25
is defined by the abutment on the restricting portion 28, while the
maximum inclination angle of the swash plate 25 is defined by the
abutment on the lug plate 23.
[0021] As shown in FIG. 1, a suction chamber 29 and a discharge
chamber 30 are defined in the rear housing 13. Discharge ports 33
and discharge valves 34 which open and close the respective ports
33 are formed in the valve plate assembly 14 in association with
the respective cylinder bores 12a. Each cylinder bore 12a
communicates with the discharge chamber 30 via the respective
discharge port 33. The suction chamber 29 is connected to the
discharge chamber 30 via an external refrigeration circuit (not
show).
[0022] An supply passage 35 which connects the crank chamber 15 to
the discharge chamber 30 is formed in the cylinder block 12 and the
rear housing 13. Disposed in the supply passage 35 is a control
valve 36 which constitutes the variable displacement mechanism. The
control valve 36 is a known solenoid valve. The control valve 36
provides a valve chamber in the supply passage 35. The angle of
opening of the control valve 36 is adjustable by the amount of the
excitation current of the solenoid. The control valve 36 also
serves as a restrictor. Therefore, the supply passage 35 is closed
by the excitation of the solenoid and is released by the
deexcitation of the solenoid.
[0023] The rear end portion of the shaft 16 forms a rotary valve
37. The shaft 16 is integral with the rotary valve 37 so that as
the shaft 16 rotates, the rotary valve 37 rotates together with the
shaft 16. The shaft 16 and the rotary valve 37 are made of the same
iron-based metal. A circulation passage 38 is formed in the shaft
16 and the rotary valve 37. An oil separator 39, which separates
oil from the refrigerant gas, is provided at the rear end portion
of the circulation passage 38, i.e., nearly the center portion of
the rotary valve 37. Coating is applied to the surfaces of the
shaft 16 and the rotary valve 37.
[0024] An inlet 38a of the circulation passage 38 is formed in the
rearward of the radial bearing 17. The rear end portion of the
circulation passage 38 is widened by the oil separator 39 and forms
a communication chamber 41b. The rear end of the communication
chamber 41b is connected to the suction chamber 29 in such a way
that the refrigerant gas flows there. Accordingly, the circulation
passage 38 constitutes a bleed passage which connects the crank
chamber 15 to the suction chamber 29.
[0025] The inner surface of the oil separator 39 is inclined in
such a way that the inside diameter of the oil separator 39 becomes
larger toward the rear end, which is the downstream side to the
flow of the refrigerant gas from the crank chamber 15 to the
suction chamber 29, from the distal end which is the upstream side.
The diameter of the oil separator 39 is the largest at the rear
end.
[0026] A communication hole 41a which communicates with the
circulation passage 38 from the side is formed in the rotary valve
37, as shown in FIG. 1. As the rotary valve 37 rotates in the
direction of the arrow in FIG. 2 in accordance with the rotation of
the shaft 16, communication passages 42 of the cylinder bores 12a
communicate with the communication hole 41a. The communication hole
41a and the communication chamber 41b constitute a suction passage
41.
[0027] The suction passage 41 is provided on a rearer end side (the
downstream side or right-hand side in FIG. 1) to the shaft 16 than
the oil separator 39. One end of the communication passage 42
communicates with the associated cylinder bore 12a and the other
end of the passage 42 is located in a position corresponding to the
suction passage 41 (communication hole 41a). When the rotary valve
37 rotates, the communication passage 42 of the cylinder bore 12a
in a suction stroke communicates with the suction passage 41, while
the communication passage 42 of the cylinder bore 12a in a
discharge stroke does not communicate with the suction passage 41.
At this time, the slide surface (sealed portion) between the rotary
valve 37 and the cylinder block 12 is sealed in an air-tight
manner.
[0028] The slide surface between the rotary valve 37 and the
cylinder block 12 is formed by a sleeve 43. The sleeve 43 is fitted
in the cylinder block 12 by casting or press fitting. The sleeve 43
is made of an iron-based metal which has a coefficient of thermal
expansion closer to those of the shaft 16 and the rotary valve
37.
[0029] The action of the compressor with the above-described
structure will be discussed below.
[0030] As the shaft 16 rotates, the swash plate 25 rotates together
with the shaft 16 via the lug plate 23 and the hinge mechanism 26.
The rotational motion of the swash plate 25 is converted to the
reciprocating motion of the pistons 21 via the shoes 27. As this
driving continues, the suction, compression and discharge of the
refrigerant are repeated one after another in the compression
chamber 22. The refrigerant is supplied to the suction chamber 29
from the external refrigeration circuit, is fed into the
compression chamber 22 (suction stroke), is compressed by the
movement of the associated piston 21 (compression stroke) and is
discharged to the discharge chamber 30 via the associated discharge
port 33 (discharge stroke). The discharged refrigerant is fed out
to the external refrigeration circuit via a discharge passage.
[0031] Then, a control apparatus (not shown) adjusts the degree of
opening of the control valve 36 or the degree of opening of the
supply passage 35 in accordance with the refrigerant load, thereby
changing the state of communication of the discharge chamber 30
with the crank chamber 15.
[0032] When the refrigerant load is large, the degree of opening of
the supply passage 35 is reduced, thereby decreasing the flow rate
of the refrigerant gas to be supplied to the crank chamber 15 from
the discharge chamber 30. As the amount of the refrigerant gas to
be supplied to the crank chamber 15 is reduced, the pressure in the
crank chamber 15 gradually drops due to the escape of the
refrigerant gas to the suction chamber 29 via the circulation
passage 38 or the like. As a result, the difference between the
pressure in the crank chamber 15 and the pressure in each cylinder
bore 12a via the associated piston 21 becomes smaller, so that the
swash plate 25 is displaced in the direction of increasing the
inclination angle (leftward in FIG. 1). Therefore, the amount of
the stroke of the piston 21 increases, thus making the discharge
volume greater.
[0033] When the refrigerant load becomes smaller, on the other
hand, the degree of opening of the control valve 36 is increased,
thereby increasing the flow rate of the refrigerant gas to be
supplied to the crank chamber 15 from the discharge chamber 30.
When the amount of the refrigerant gas to be supplied to the crank
chamber 15 exceeds the escape amount of the refrigerant gas to the
suction chamber 29 via the circulation passage 38, the pressure in
the crank chamber 15 gradually rises. Consequently, the difference
between the pressure in the crank chamber 15 and the pressure in
each cylinder bore 12a via the associated piston 21 becomes larger,
so that the swash plate 25 is displaced in the direction of
decreasing the inclination angle (rightward in FIG. 1). The amount
of the stroke of the piston 21 therefore decreases, thus reducing
the discharge volume.
[0034] The refrigerant gas which is fed toward the suction chamber
29 via the circulation passage 38 is whirled in accordance with the
rotation of the oil separator 39. This causes the centrifugal
separation of the oil from the refrigerant gas. The separated oil
is discharged out of the oil separator 39 by the centrifugal force
or the like based on the rotation of the oil separator 39. The
discharged oil is supplied between the rotary valve 37 and the
cylinder block 12 and between the piston 21 and the associated
cylinder bore 12a via the suction passage 41 and the associated
communication passage 42.
[0035] Part of the refrigerant gas, from which the oil has been
separated in the oil separator 39, is supplied to the suction
chamber 29 via the communication chamber 41b. The refrigerant gas
supplied to the suction chamber 29 (this gas has a small amount of
oil mixed therein) is discharged to the external refrigeration
circuit via the associated compression chamber 22 and the discharge
chamber 30.
[0036] As the shaft 16 and the rotary valve 37 rotate together, the
refrigerant gas in the suction chamber 29 is sucked into each
cylinder bore 12a via the suction passage 41 of the shaft 16 and
the communication passage 42 of that bore 12a in the suction
stroke. Because the suction of the refrigerant gas continues in
each cylinder bore 12a smoothly and stably, a pressure loss becomes
extremely small.
[0037] The sleeve 43 serves as a rotary valve receiving portion of
the cylinder block 12. The sleeve 43 is formed by casting or press
fitting in the cylinder block 12. When the shaft 16 rotates at a
high speed, the rotary valve 37 slides with respect to the sleeve
43, raising the temperature of the slide surface therebetween.
Since the rotary valve 37 and the sleeve 43 are both made of an
iron-based metal and their coefficients of thermal expansion are
almost equal to each other, the clearance between the rotary valve
37 and the sleeve 43 can be prevented from increasing.
[0038] The above-mentioned embodiment have the following
advantages.
[0039] The rotary valve 37 and the shaft 16 are integrally formed
of an iron-based metal and the sleeve 43 is made of an iron-based
metal whose coefficient of thermal expansion is closer to that of
the shaft 16 (and the rotary valve 37). This can reduce the number
of components and prevents an increase in the clearance between the
slide surfaces of the rotary valve 37 and the sleeve 43, which
would be caused by a temperature rise at the time the shaft 16
rotates at a high speed. This prevents gas leakage from the
clearance and a reduction in the performance of the compressor. The
sleeve 43 maintains the sealability between the rotary valve 37 and
the cylinder block 12 over a long period of time. It is therefore
possible to smoothly rotate the rotary valve 37 and suppress
sliding noise of the rotary valve 37.
[0040] The rotary valve 37 and the sleeve 43 are made of an
iron-based metal, which is excellent in rigidity over an
aluminum-based metal. This can ensure a high strength.
[0041] Coating is applied to the surfaces of the shaft 16 and the
rotary valve 37. The coating can prevent burning of the shaft 16
and the rotary valve 37 when they rotate together.
[0042] The control valve 36 is provided in the supply passage 35.
The control valve 36 can control the pressure in the crank chamber
15 by using the high pressure in the discharge chamber 30. Thus,
discharge volume can be controlled with high accuracy.
[0043] The inner surface of the oil separator 39 is inclined in
such a way that the inside diameter of the oil separator 39 becomes
larger from the upstream side toward the downstream of the flow of
the refrigerant gas with respect to the flow of the refrigerant
gas. This facilitates the oil adhered to the inner surface of the
oil separator 39 to be discharged outside from the downstream of
the oil separator 39 by the centrifugal force at the time the shaft
16 rotates.
[0044] 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 invention may be
embodied in the following forms.
[0045] The iron-based metal for the sleeve can be any metal as long
as its coefficient of thermal expansion is close to that of the
iron-based metal for the shaft. For example, such iron-based metals
available include gray cast iron (11 to 12.times.10.sup.-6/.degree.
C.), ductile iron (11 to 12.times.10.sup.-6/.degree. C.) and
Niresist D-3 (8 to 9.times.10.sup.-6/.degree. C.). In this case,
similar advantages to those obtained when iron is used are also
obtained.
[0046] Since the coefficient of thermal expansion of aluminum is
approximately 19 to 23.times.10.sup.-6/.degree. C. and the
coefficient of thermal expansion of iron is approximately 10 to
12.times.10.sup.-6/.degr- ee. C., the coefficient of thermal
expansion of the iron-based metal for the sleeve can lie in a range
of approximately 7 to 15.times.10.sup.-6/.degree. C.
[0047] The sleeve may be made of any material other than a metal,
as long as its coefficient of thermal expansion is close to that of
the iron-based metal for the shaft. That is, a resin or ceramics
may be used in place of a metal. Of ceramics, alumina which has a
coefficient of thermal expansion of 6 to 8.times.10.sup.-6/.degree.
C. and zirconia which has a coefficient of thermal expansion of 9
to 11.times.10.sup.-6/.degree. C. can be used, for example. Those
of various kinds of engineering plastics whose coefficients of
thermal expansion are near 10 to 13.times.10.sup.-6/.degree. C. may
be used. In this case, advantages similar to those mentioned above
are also obtained.
[0048] The suction chamber 29, which is provided in the rear
housing 13, may be omitted. In this case, the refrigerant is led
directly into the communication chamber 41b, which constitutes an
suction pressure area.
[0049] The radial bearing 19 may be omitted. The shaft 16 may be
supported by the sleeve 43 only.
[0050] The compressor may be a wobble type variable displacement
compressor.
[0051] The compressor may be a double-headed piston type
compressor.
[0052] Therefore, 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.
* * * * *