U.S. patent application number 09/262599 was filed with the patent office on 2001-09-06 for single-ended swash plate compressor.
This patent application is currently assigned to KABUSHIKI KAISHA TOYODA JIDOSHOKKI SEISAKUSHO. Invention is credited to FUJII, TOSHIRO, IMAI, TAKAYUKI, KOIDE, TATSUYA, MURAKAMI, KAZUO, YOKOMACHI, NAOYA.
Application Number | 20010019698 09/262599 |
Document ID | / |
Family ID | 26397994 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019698 |
Kind Code |
A1 |
MURAKAMI, KAZUO ; et
al. |
September 6, 2001 |
SINGLE-ENDED SWASH PLATE COMPRESSOR
Abstract
In a single-ended swash plate compressor, unbalanced thrust
loads in either axial direction are reduced so that thrust loads
acting on pistons in the direction of the front end are practically
balanced by those in the direction of the rear end, for example, by
connecting an intake chamber to a swash plate chamber by means of
an adjustment valve to adjust the pressure in the swash plate
chamber acting on the front end surfaces of the pistons to a
suitable intermediate pressure by the action of the adjustment
valve. In a single-ended swash plate compressor with pistons housed
in both ends of a cylinder assembly comprising one set of pistons
for guidance and another set for compression, discharge pressure is
introduced into some of the cylinder bores housing guide pistons
and intake pressure is introduced into the cylinder bores housing
guide pistons into which discharge pressure is not introduced.
Inventors: |
MURAKAMI, KAZUO; (AICHI-KEN,
JP) ; FUJII, TOSHIRO; (AICHI-KEN, JP) ;
YOKOMACHI, NAOYA; (AICHI-KEN, JP) ; IMAI,
TAKAYUKI; (AICHI-KEN, JP) ; KOIDE, TATSUYA;
(AICHI-KEN, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN L L P
345 PARK AVENUE
NEW YORK
NY
10154
|
Assignee: |
KABUSHIKI KAISHA TOYODA JIDOSHOKKI
SEISAKUSHO
|
Family ID: |
26397994 |
Appl. No.: |
09/262599 |
Filed: |
March 4, 1999 |
Current U.S.
Class: |
417/222.2 |
Current CPC
Class: |
F04B 27/1063 20130101;
F04B 27/1036 20130101; F04B 2027/1813 20130101 |
Class at
Publication: |
417/222.2 |
International
Class: |
F04B 001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 1998 |
JP |
10-058492 |
Mar 9, 1998 |
JP |
10-056987 |
Claims
What is claimed is:
1. A single-ended swash plate compressor comprising: a cylinder
assembly having a plurality of cylinder bores disposed parallel to
the axial center thereof; a cylinder cover joined to the rear end
of said cylinder assembly, having an intake chamber and a discharge
chamber therein; an outer shell formed by joining a front housing
to the front end of said cylinder assembly; a swash plate chamber
formed within said outer shell; a drive shaft disposed at the axial
center of said outer shell so as to pass from an axial center
portion of said cylinder assembly, through an axial center portion
of said front housing, and extend outwards; a swash plate secured
to said drive shaft so as to rotate together with said drive shaft
within said swash plate chamber; pistons housed in said cylinder
bores so as to be reciprocated in both axial directions by said
swash plate; and a means for practically balancing thrust loads
acting on said pistons in both axial directions by adjusting the
refrigerant pressure acting in the axial direction opposite to the
thrust load acting on said pistons due to the internal pressure of
said cylinder bores.
2. The single-ended swash plate compressor according to claim 1
wherein thrust bearings are disposed at both the front end and the
rear end of said swash plate.
3. A single-ended swash plate compressor comprising: a cylinder
block having a plurality of cylinder bores disposed parallel to the
axial center thereof; a cylinder cover joined to the rear end of
said cylinder block, having an intake chamber and a discharge
chamber therein; an outer shell formed by joining a front housing
to the front end of said cylinder block; a swash plate chamber
formed within said outer shell when said cylinder block and said
front housing are joined; a drive shaft disposed at the axial
center of said outer shell so as to pass from an axial center
portion of said cylinder block, through an axial center portion of
said front housing, and extend outwards; a swash plate secured to
said drive shaft so as to rotate together with said drive shaft
within said swash plate chamber; pistons formed on the rear end of
piston rods housed in said plurality of cylinder bores so as to be
reciprocated in both axial directions by said swash plate; and an
adjustment means for adjusting the internal pressure of said swash
plate chamber acting on the front end surfaces of said pistons to
an intermediate pressure between the intake pressure and the
discharge pressure; the thrust load directed towards said front end
due to the internal pressure of said cylinder bores acting on said
pistons and the thrust load directed towards said rear end due to
the internal pressure of said swash plate chamber acting on said
pistons being practically balanced by said adjustment means.
4. The single-ended swash plate compressor according to claim 3
wherein: an intake port for introducing intake gas from a
refrigerant circuit outside said compressor is disposed so as to be
connected to an intake chamber; said intake chamber and said swash
plate chamber are connected by means of an adjustment valve; and
said adjustment means is constructed such that said swash plate
chamber is maintained at a predetermined intermediate pressure by
the action thereof.
5. The single-ended swash plate compressor according to claim 3
wherein the relationship between said intake pressure Ps, said
discharge pressure Pd, and said intermediate pressure Pm is:
Pm.apprxeq.Ps*(1-x)+Pd*x, provided that x=0.25 to 0.4.
6. A single-ended swash plate compressor comprising: a cylinder
assembly having a swash plate chamber within formed with pairs of
cylinder bores in the front end and the rear end thereof,
respectively; a drive shaft disposed in a central portion of said
cylinder assembly; piston assemblies having pistons formed on both
ends of piston rods housed in said pairs of cylinder bores; a swash
plate housed in said swash plate chamber which rotates together
with said drive shaft and reciprocates said piston assemblies; and
housings disposed on both end surfaces of said cylinder assemblies
so as to cover said end surfaces, the cylinder bores in one end
being connected to a discharge chamber and an intake chamber by
means of a discharge valve and an intake valve, a compression
action being performed by the pistons housed within said cylinder
bores in said end, and a guide action being performed by the
pistons in said cylinder bores in the other end, whereby pressure
is introduced into said cylinder bores in said guide end to cancel
reactive forces due to compression acting on said pistons in said
compression end.
7. The single-ended swash plate compressor according to claim 6
wherein discharge pressure is introduced into at least some of said
cylinder bores in said guide end as said pressure to cancel said
reactive forces due to compression.
8. The single-ended swash plate compressor according to claim 7
wherein intake pressure is introduced into the cylinder bores in
said guide end into which discharge pressure is not introduced.
9. The single-ended swash plate compressor according to claim 7
wherein piston rings are mounted on the outer circumferential
sliding surfaces of said pistons housed in said cylinder bores in
said guide end into which said discharge pressure is
introduced.
10. The single-ended swash plate compressor according to claim 6
wherein: the diameters of said cylinder bores in said guide end are
made smaller than the diameters of said cylinder bores in said
compression end; and discharge pressure is introduced into said
cylinder bores in said guide end as said pressure to cancel said
reactive forces due to compression.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a single-ended swash plate
compressor for use in automotive vehicles and the like.
[0003] 2. Description of the Related Art
[0004] Swash plate compressors, in which a plurality of cylinder
bores are disposed parallel to a drive shaft in a peripheral
portion of a cylinder block, with piston assemblies housed in the
cylinder bores, the piston assemblies being reciprocated by a swash
plate which rotates together with the drive shaft so as to compress
a refrigerant gas, are in general use as compressors for
conventional automotive air-conditioners. Moreover, double-ended
swash plate compressors, which include double-headed piston
assemblies in which compression pistons are formed on both ends of
piston rods and a compression action is performed at both the front
end and the rear end of the piston bores, are often used. However,
when using carbon dioxide (CO2) as a refrigerant as an alternative
to chlorofluorocarbons, there are cases where single-ended swash
plate compressors are used.
[0005] Generally-known conventional single-ended swash plate
compressors include single-headed piston assemblies in which
compression pistons are formed on one end of the piston rods only
and the compression action is performed at one end of the piston
bores, for example, the rear end only.
[0006] The fixed-capacity single-ended swash plate compressor shown
in FIG. 13 is a known example of such a swash plate compressor.
[0007] In the figure, the outer shell 201 of the compressor is
formed by joining a front housing 201b to the front end of a
cylinder block 201a, forming a swash plate chamber 202 within. A
cylinder cover 203 functioning as a rear housing having a discharge
chamber 203a and an intake chamber 203b therein is joined to the
rear end of the cylinder block 201a by means of a valve plate 204.
An intake port 205 for receiving intake gas from an external
refrigerant circuit (not shown) is disposed in a side wall of the
cylinder cover 203 and is connected to the intake chamber 203b. A
drive shaft 206 is disposed in a central portion of the outer shell
201 of the compressor and is rotatably supported by radial bearings
207. A plurality of cylinder bores 208 are formed in the cylinder
block 201a parallel to the drive shaft 206 and equidistantly spaced
in a circle of fixed circumference centered on the drive shaft 206.
Consequently, a cylinder assembly is formed by the cylinder block
201a. Piston assemblies 209 each comprise a piston rod 209b and a
single-headed piston 209a formed on the rear end of the piston rod
209b. A single-headed piston 209a is housed within each of the
cylinder bores 208 so as to be free to slide and reciprocate.
[0008] A swash plate 210 is secured to the drive shaft 206 within
the swash plate chamber 202 so as to rotate together with the drive
shaft 206, the pistons 209a being engaged by the swash plate 210 by
means of shoes 211. Furthermore, a thrust bearing 214 is disposed
at the front end of a boss portion 210a of the swash plate 210,
that is to say, between the boss portion 210a and the front housing
201b, thrust loads acting on the swash plate 210 being supported by
the thrust bearing 214.
[0009] Discharge holes 204a connecting each of the cylinder bores
208 to the discharge chamber 203a and intake holes 204b connecting
each of the cylinder bores 208 to the intake chamber 203b are
disposed in the valve plate 204. An intake valve-forming plate 212
integrally formed with a plurality of intake valves 212a for
controlling the opening and closing of each of the intake holes
204b is interposed between the valve plate 204 and the cylinder
block 201a, and a discharge valve-forming plate 213 integrally
formed with a plurality of discharge valves 213a for controlling
the opening and closing of each of the discharge holes 204a is
interposed between the valve plate 204 and the cylinder cover
203.
[0010] Gas passages 215 are disposed in the cylinder block 201a in
the spaces between the plurality of cylinder bores 208, the swash
chamber 202 being connected to the intake chamber 203b by means of
the gas passages 215, so that blowback gas flowing into the swash
chamber 202 during the process of compression by the pistons 209a
is expelled to the intake chamber 203b.
[0011] Moreover, 216 is a retainer, 217 is a discharge port, and
218 is a bolt joining the cylinder block 201a, the front housing
201b, and the cylinder cover 203 together.
[0012] When a single-ended swash plate compressor constructed in
the above manner is activated, intake gas is directed from the
external refrigerant circuit through the intake port 205 into the
intake chamber 203b. Then, the refrigerant gas is taken from the
intake chamber 203b through the intake holes 204b and intake valves
212a into the cylinder bores 208 and is compressed by the pistons
209a. The compressed refrigerant gas is expelled through the
discharge holes 204a and the discharge valves 213a to the discharge
chamber 203a and is discharged through the discharge port 217 to
the external refrigerant circuit.
[0013] In a single-ended swash plate compressor constructed in the
above manner, the front ends of the pistons 209a (1eft side in
figure) are exposed to the swash chamber which is at intake
pressure, and at the same time the rear ends of the pistons 209a
are exposed to the cylinder bores 208 which are filled with
compressed refrigerant gas, Thus, the internal pressure (intake
pressure) of the swash chamber 202 acts on the front end surface of
each of the pistons 209a, and the internal pressure of the cylinder
bores 208 acts on the rear end surface of each of the pistons 209a.
FIG. 14 is a graph explaining the conditions in one piston and
shows the changes in the internal pressure Pc in the swash plate
chamber 202 and the changes in the internal pressure Pb in the
cylinder bore 208 relative to the rotational angle of the swash
plate 210 (in degrees). As shown in this diagram, the internal
pressure Pc in the swash plate chamber 202 always remains at a
practically constant low pressure, that is at the intake pressure,
but the internal pressure Pb in the cylinder bore 208 fluctuates
periodically between a low intake pressure and a high discharge
pressure depending on the rotational angle of the swash plate
210.
[0014] Now, thrust loads from the front end towards the rear end
act on the front end surfaces of the pistons 209a, and thrust loads
from the rear end towards the front end act on the rear end
surfaces of the pistons 209a. Thus, the thrust load acting on the
thrust bearing 214 is given by the sum of these loads acting on the
pistons 209a.
[0015] FIG. 15 is a graph explaining the axial load, and the
vertical axis shows the thrust load, the direction from the rear
end towards the front end being taken as positive. The number of
pistons 209a has been taken to be six and the loads acting on all
six pistons have been totalled. In FIG. 15, Ff indicates the thrust
load acting from the front end towards the rear end due to the
internal pressure in the swash chamber 202. Fr indicates the thrust
load acting from the rear end towards the front end due to the
internal pressure in the cylinder bores 208. Ft indicates the total
load resulting from Ff and Fr. Since Ft is the sum of all of the
loads acting on a plurality of pistons (in this case six), the
amplitudes and periods of the fluctuations are small compared to
those of the internal pressure in the single cylinder bore 208
shown in FIG. 14.
[0016] Now, as can be understood from FIGS. 14 and 15, because the
difference between the internal pressure Pb in the cylinder bores
208 and the internal pressure Pc in the swash plate chamber 202 is
great, the difference between the thrust load Ff acting from the
front end towards the rear end and the thrust load Fr acting from
the rear end towards the front end is great, making the overall
total thrust load Ft a large unbalanced load from the rear end
towards the front end. This unbalanced load is transmitted through
the shoes 211 to the swash plate 210 and is supported by the thrust
bearing 214 disposed at the front end of the boss portion 210a of
the swash plate 210 so as to support the thrust load from the swash
plate 210.
[0017] Thus, in a conventional fixed-capacity single-ended swash
plate compressor, because compression is performed on only one side
of the swash plate, the load acting on the thrust bearing 214
disposed at the front end of the boss portion 210a of the swash
plate 210 is great. In particular, the working pressure when carbon
dioxide is used as the refrigerant is greater than when
chlorofluorocarbons or the like are used, which tends to shorten
the working life of the thrust bearing 214 disposed at the front
end of the swash plate 210, and a thrust bearing 214 with a high
load rating is required to prevent this. However, the problem is
that by using a thrust bearing 214 with a high load rating, the
size of the thrust bearing 214 at the front end is increased, in
turn leading to increases in the size and weight of the
compressor.
SUMMARY OF THE INVENTION
[0018] The present invention aims to solve the above problems and
an object of the present invention is to provide a single-ended
swash plate compressor which reduces the load acting on the thrust
bearing, and suppresses shortening of the working life of the
thrust bearing and increases in the size of the thrust bearing.
[0019] In order to achieve the above object, according to claim 1
of the present invention, there is provided a single-ended swash
plate compressor having a means of substantially balancing the
thrust load acting on the pistons in both axial directions by
adjusting the pressure of the refrigerant acting in a direction
opposite to the thrust load directed towards the front end due to
internal pressure in the cylinder bores acting on the pistons.
According to claim 3 of the present invention, there is provided a
single-ended swash plate compressor having an adjustment means for
adjusting the internal pressure of the swash plate chamber acting
on the front end surface of the pistons to an intermediate pressure
between the intake pressure and the discharge pressure, whereby the
thrust load directed towards the front end due to internal pressure
in the cylinder bores acting on the pistons and the thrust load
directed towards the rear end due to the internal pressure of the
swash plate chamber are practically balanced.
[0020] These constructions eliminate imbalances in the loads acting
on the thrust bearing, reducing the overall size of the thrust
load.
[0021] In the present invention, the thrust load fluctuates in both
axial directions, but according to claim 2 of the present
invention, the thrust load fluctuating in both axial directions can
be supported by the provision of thrust bearings at both the front
end and the rear end of the swash plate.
[0022] According to claim 4 of the present invention, by providing
an adjustment means, such as disposing the intake port which
receives intake gas from the refrigerant circuit external to the
compressor in connection with the intake chamber, connecting the
intake chamber to the swash plate chamber by means of an adjustment
valve and maintaining the swash plate chamber at a predetermined
intermediate pressure by the action of the adjustment valve, the
internal pressure in the swash plate chamber can be set at any
desired intermediate pressure suitable to the working conditions,
such as the refrigerant used, the specifications of the compressor,
the operating environment, etc.
[0023] According to claim 5 of the present invention, by
establishing a relationship between the intake pressure, the
discharge pressure, and the intermediate pressure, it is possible
to use carbon dioxide which is a promising substitute for
chlorofluorocarbons as a refrigerant medium.
[0024] The single-ended swash plate compressor according to claim 6
of the present invention is constructed such that cylinder bores
are formed in both the front end and the rear end, and a
compression action is performed in the cylinder bores at one end by
pistons housed within the cylinder bores at that end, and a guide
action is performed in the cylinder bores at the other end by
pistons housed within the cylinder bores at that other end, whereby
pressure is introduced into the cylinder bores in the guide end to
cancel the reactive forces due to compression acting on the pistons
in the compression end.
[0025] By this construction, the thrust load acting from the rear
end to the front end due to pressure within the cylinder bores in
the compression end is cancelled by a thrust load from the front
end to the rear end, reducing unbalanced thrust loads in either
axial direction.
[0026] Furthermore, as means of introducing a pressure into the
cylinder bores in the guide end to cancel the reactive forces due
to compression acting on the pistons in the compression end, the
single-ended swash plate compressor according to claim 7 of the
present invention is constructed such that discharge pressure is
introduced into some of the cylinder bores in the guide end,
enabling the thrust loads in both axial directions to be balanced
by a simple construction.
[0027] According to claim 8 of the present invention, by
introducing intake pressure into the cylinder bores in the guide
end to which discharge pressure is not introduced, the internal
pressure in each of the cylinder bores in the guide end is
stabilized, thereby stabilizing the thrust load acting from the
front end to the rear end.
[0028] According to claim 9 of the present invention, piston rings
are mounted on the outer circumferential sliding surfaces of the
pistons housed in the cylinder bores in the guide end into which
discharge pressure is introduced, whereby the blowback of gas from
those cylinder bores to the swash plate chamber can be reduced.
[0029] According to claim 10 of the present invention, the diameter
of the cylinder bores in the guide end is made smaller than the
diameter of the cylinder bores in the compression end and discharge
pressure is introduced into each of these cylinders in the guide
end, whereby the thrust loads in both axial directions can be
balanced by the ratio between the area of the piston assemblies
subjected to the pressure of the cylinder bores in the guide end
and the area of the piston assemblies subjected to the pressure of
the cylinder bores in the compression end.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a longitudinal section of a single-ended swash
plate compressor according to Embodiment 1 of the present
invention;
[0031] FIG. 2 is a partial cross-section explaining the operation
of an adjustment valve in Embodiment 1 of the present
invention;
[0032] FIG. 3 is a graph explaining the balance of thrust loads in
Embodiment 1 of the present invention;
[0033] FIG. 4 is a longitudinal section of a single-ended swash
plate compressor according to a variation of Embodiment 1 of the
present invention;
[0034] FIG. 5 is a longitudinal section of a single-ended swash
plate compressor according to Embodiment 2 of the present invention
taken along line V-V in FIG. 6;
[0035] FIG. 6 is a cross-section taken along line VI-VI in FIG.
5;
[0036] FIG. 7 is a cross-section taken along line VII-VII in FIG.
5;
[0037] FIG. 8 is a graph explaining the balance of thrust loads in
Embodiment 2;
[0038] FIG. 9 is a longitudinal section of a single-ended swash
plate compressor according to Embodiment 3 of the present invention
taken along line IX-IX in FIG. 10;
[0039] FIG. 10 is a cross-section taken along line X-X in FIG.
9;
[0040] FIG. 11 is a graph explaining the balance of thrust loads in
Embodiment 3 in comparison to those of Embodiment 2 and a
conventional example;
[0041] FIG. 12 is a longitudinal section of a single-ended swash
plate compressor according to Embodiment 4 of the present
invention;
[0042] FIG. 13 is a longitudinal section of a conventional
single-ended swash plate compressor;
[0043] FIG. 14 is a graph explaining the usual changes in pressure
in a cylinder bore; and
[0044] FIG. 15 is a graph explaining the balance of thrust loads in
a conventional single-ended swash plate compressor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] The actual embodiments of swash plate compressors according
to the present invention will now be explained using FIGS. 1 to
12.
[0046] Embodiment 1
[0047] Firstly, Embodiment 1 will be explained with reference to
FIGS. 1 to 3. FIG. 1 is a cross-section similar to that of FIG. 13
for the conventional example above and shows a single-ended swash
plate compressor according to the present invention which uses
carbon dioxide as a refrigerant. In the figure, the outer shell 1
of the compressor is formed by joining a front housing 1b to the
front end of a cylinder block 1a. The joining thereof forms a swash
plate chamber 2 within the outer shell 1. A cylinder cover 3
functioning as a rear housing formed with a discharge chamber 3a in
a central region and an intake chamber 3b in a peripheral portion
is joined to the rear end of the cylinder block 1a by means of a
valve plate 4.
[0048] One end of a drive shaft 6 is inserted into an axial center
portion of the cylinder block 1a and the other end passes through
an axial center portion of the front housing 1b and extends
outside, the drive shaft 6 being rotatably supported by radial
bearings 7 disposed in the cylinder block 1a and the front housing
1b, respectively. A plurality of cylinder bores 8 are formed in the
cylinder block 1a parallel to the drive shaft 6 and equidistantly
spaced in a circle of fixed circumference centered on the drive
shaft 6, and a single-headed piston 9a is housed within each of
these cylinder bores 8 so as to be free to slide and reciprocate.
Moreover, 9 represents piston assemblies each comprising a piston
rod 9b and a piston 9a formed on the rear end of the piston rod 9b.
A cylinder assembly is constituted by the cylinder block 1a formed
in this manner.
[0049] A swash plate 10 is secured to the drive shaft 6 within the
swash plate chamber 2 so as to rotate together with the drive shaft
6. The pistons 9a are engaged by the swash plate 10 by means of
shoes 11. Furthermore, thrust bearings 14 are disposed at both the
front end and the rear end of a boss portion 10a of the swash plate
10, that is to say, between the boss portion 10a and the front
housing 1b and between the boss portion 10a and the cylinder block
1a, thrust loads acting on the swash plate 10 being supported by
the thrust bearings 14.
[0050] Discharge holes 4a connecting each of the cylinder bores 8
to the discharge chamber 3a and intake holes 4b connecting each of
the cylinder bores 8 to the intake chamber 3b are disposed in the
valve plate 4. An intake valve-forming plate 12 integrally formed
with a plurality of intake valves 12a for controlling the opening
and closing of each of the intake holes 4b is interposed between
the valve plate 4 and the cylinder block 1a, and a discharge
valve-forming plate 13 integrally formed with a plurality of
discharge valves 13a for controlling the opening and closing of
each of the discharge holes 4a is interposed between the valve
plate 4 and the cylinder cover 3.
[0051] 25 is an intake port and is disposed in the end wall of the
intake chamber 3b, that is to say, the end wall of the intake
chamber 3b portion of the cylinder cover. A retainer 16 for
controlling the opening angle of the discharge valves 13a is
disposed in a central portion of the discharge chamber 3a in
contact with the discharge valve-forming plate 13. In addition, a
discharge port 17 connected to the external refrigerant circuit is
disposed in the central portion of the cylinder cover 3 forming the
discharge chamber 3a. Moreover, 18 is a bolt joining the cylinder
block 1a, the front housing 1b, and the cylinder cover 3
together.
[0052] In Embodiment 1, the adjustment means for adjusting the
internal pressure of the swash plate chamber 2 to an intermediate
pressure between the intake pressure and the discharge pressure is
an adjustment valve 20 described below and is disposed and
constructed in the manner described below.
[0053] An adjustment valve accommodating hole 21 is formed in the
cylinder block 1a, and a control passage 22 connecting the
accommodating hole 21 to the intake chamber 3b is formed so as to
pass through the valve plate 4, the intake valve-forming plate 12,
and the discharge valve-forming plate 13. The adjustment valve 20
is accommodated within the accommodating hole 21 so as to be able
to open and close the connection between the swash plate chamber 2
and the intake chamber 3b. More specifically, the adjustment valve
20 comprises: a securing portion 20a screwed into the portion of
the accommodating hole 21 opening onto the swash plate chamber
side; a case 20b forming a pressure sensing chamber 20c within; a
bellows 20d functioning as a pressure sensing portion disposed
within the pressure sensing chamber 20c; and a valve body 20e which
opens and closes a port 20h by opening and closing a valve seat 20g
in response to the contraction and expansion of the bellows 20d. A
connecting passage 20f for introducing the pressure of the swash
plate chamber 2 into the pressure sensing chamber 20c is formed in
the securing portion 20a, the bellows 20d expanding and contracting
in response to changes in pressure in the swash plate chamber 2.
Moreover, 20i is an adjustor portion for modifying the set pressure
of the bellows 20d by adjusting the position thereof relative to
the securing portion 20a, the set pressure in Embodiment 1 being
adjusted to a suitable intermediate pressure between the intake
pressure and the discharge pressure.
[0054] When a single-ended swash plate compressor constructed in
the above manner is activated, intake gas is drawn from the
external refrigerant circuit through the intake port 25 into the
intake chamber 3b. Then, the intake gas is drawn through the intake
holes 4b and intake valves 12a into the cylinder bores 8 and is
compressed by the pistons 9a. The compressed refrigerant gas is
expelled through the discharge holes 4a and the discharge valves
13a to the discharge chamber 3a and is discharged from the
discharge port 17 to the external refrigerant circuit. During this
operation, the pressure in the swash plate chamber 2 is maintained
at a desired level by the action of the adjustment valve 20
described above. More specifically, because some of the refrigerant
gas in the cylinder bores 8 leaks through the clearances between
the pistons 9a and cylinder bores 8 into the swash plate chamber 2
as blowback gas, when the adjustment valve 20 is closed, the
internal pressure of the swash plate chamber 2 gradually increases.
The internal pressure of the swash plate chamber 2 is introduced
into the pressure sensing chamber 20c by means of the connecting
passage 20f, and when the internal pressure of the swash plate
chamber 2 rises above the predetermined intermediate pressure due
to blowback gas, the bellows 20d contracts in response thereto as
shown in FIG. 2. Consequently, the valve body 20e opens the port
20h, and pressure from the swash plate chamber 2 is released
through the port 20h and the control passage 22 to the intake
chamber 3b until the pressure decreases to the predetermined
intermediate pressure.
[0055] Consequently, the swash plate chamber 2 is maintained at the
predetermined intermediate pressure during operation, and the
intermediate pressure acts on the front end surfaces of the pistons
9a. The fluctuating internal pressure in the cylinder bores 8 acts
on the rear end surfaces of the pistons 9a. Carbon dioxide is used
as the refrigerant in this embodiment, and here, can be handled
under normal conditions with the thrust loads in both axial
directions in balance if the intermediate pressure in the swash
plate chamber 2 is adjusted by the adjustment valve 20 such
that:
Pm.apprxeq.Ps*(1-x)+Pd*x,
[0056] provided that x=0.25 to 0.4,
[0057] where Ps is the intake pressure, Pd is the discharge
pressure, and Pm is the intermediate pressure.
[0058] For example, FIG. 3 shows the thrust load when the
intermediate pressure is adjusted so that x is 0.33. This graph
shows a case where there are six pistons 9a, Ff1 representing the
thrust load acting from the front end towards the rear end, Fr1
representing the thrust load acting from the rear end towards the
front end, and Ft1 representing the sum of both thrust loads (total
load). As this graph shows, since Ff1 and Fr1 are practically
balanced, Ft1 fluctuates only slightly in either axial
direction.
[0059] Consequently, the thrust bearings 14 are not subjected to a
large load. Furthermore, because the thrust bearings 14 are
disposed at both the front end and the rear end of the swash plate
10, the total thrust load can be supported even if it fluctuates in
both axial directions. As a result, the durability of the thrust
bearings 14 is improved, and furthermore, because there is no need
to use large thrust bearings, a contribution can be made to
reducing the size of the compressor.
[0060] Moreover, the following modifications can be applied to
Embodiment 1 of the present invention:
[0061] (1) In Embodiment 1 above, the adjustment valve 20 is housed
in the cylinder block 1a, but the adjustment valve 20 may be
disposed in any other appropriate space, such as the exterior, etc.
Furthermore, the adjustment valve 20 is not limited to a bellows
type, as any other type may be used;
[0062] (2) The compressor according to the present invention is not
limited to use in a refrigerating cycle having carbon dioxide as a
refrigerant; as it may be used in the refrigerating cycles for
other refrigerants;
[0063] (3) In Embodiment 1 above, the increased pressure in the
swash plate chamber 2 is caused by blowback gas when refrigerant
inside the cylinder bores 8 leaks through the clearances between
the pistons 9a and the cylinder bores 8 into the swash plate
chamber 2, but suitable perforations may be disposed in the
cylinder block 1a to positively connect the discharge chamber 3a to
the swash plate chamber 2;
[0064] (4) The internal pressure of the swash plate chamber 2 may
be adjusted by a restriction passage instead of the adjustment
valve 20 of Embodiment 1 above; and
[0065] (5) In Embodiment 1 above, the pressure in the swash plate
chamber 2 is adjusted to an intermediate pressure by an adjustment
valve 20, but the swash plate chamber 2 may be isolated from the
discharge chamber 3a and the intake chamber 3b in a practically
sealed condition. In that case, the swash plate chamber 2 is
connected to compression chambers 8a, 8b (hereinafter simply
"bores" in this variation) by the clearance between the pistons 9a
and the cylinder bores 8.
[0066] Because the relationship between the pressure Pc in the
swash plate chamber 2 and the pressure Pb1 in the bores 8a in the
compression stage is Pb1.apprxeq.Pd>Pc, blowback gas flows from
the bores 8a into the swash plate chamber 2 due to the differences
in pressure and pressure increases in the swash plate chamber 2. On
the other hand, since the relationship between the pressure Pc in
the swash plate chamber 2 and the pressure Pb2 in the bores 8b in
the intake stage is Pb2.apprxeq.Ps<Pc, gas instead moves from
the swash plate chamber 2 into the bores 8b. Moreover, Ps is the
intake pressure and Pd is the discharge pressure. Thus, the amount
of gas moving from the bores 8a in the compression stage into the
swash plate chamber 2 is balanced by the amount of gas moving from
the swash plate chamber 2 into the bores 8b in the intake stage,
and consequently the pressure of the swash plate chamber 2 is
maintained at a predetermined intermediate pressure.
[0067] Embodiment 2
[0068] Next, Embodiment 2 embodying the swash plate compressor of
the present invention will be explained using FIGS. 5 to 8.
[0069] The single-ended swash plate compressor according to
Embodiment 2 has pistons in both the front end and the rear end,
the pistons in one end only performing the compression action and
the pistons in the other end performing only a guide action. FIG. 5
is a longitudinal section of this single-ended swash plate
compressor, and in this figure, the cylinder assembly 101 is formed
by joining a front cylinder block 101a and a rear cylinder block
101b. A space is formed in the center of the cylinder assembly 101
between the cylinder blocks 101a, 101b when the cylinder block 1a
is joined to the cylinder block 1b, and this space constitutes a
swash plate chamber 107. The swash plate chamber 107 connects to an
intake passage (not shown) which is connected to an inlet 121.
[0070] Drive shaft openings 103a, 103b are formed in the center of
the cylinder blocks 101a, 101b, respectively. A drive shaft 105 is
disposed in the center of the cylinder assembly 101 and is
rotatably supported by radial bearings 104, which are disposed in
the drive shaft openings 103a, 103b.
[0071] A swash plate 108 is disposed in the swash plate chamber 107
so as to be rotatable by the drive shaft 105, the boss portion of
the swash plate 108 being fitted over and secured to the center of
the drive shaft 105. Thrust bearings 112 are disposed between both
the front end and the rear end of the boss portion of the swash
plate 108 and the central inside end surfaces of the cylinder
blocks 101a, 101b to support the load in both axial directions of
the swash plate 108.
[0072] Six cylinder bores 109a, 109b are disposed equidistantly in
a circle of prescribed radius around the drive shaft 105 in each of
the cylinder blocks 101a, 101b. The cylinder bores 109a in the
front cylinder block 101a and the cylinder bores 109b in the rear
cylinder block 101b are disposed so as to form six pairs of
cylinder bores, each pair having the same axial center. The
cylinder bores 109a in the front end are used as guides, and the
cylinder bores 109b in the rear end are used for compression.
[0073] Piston assemblies 110 each comprise: a piston rod 110a; a
guide piston 110b formed on the front end of the piston rod 110a;
and a compression piston 110c formed on the rear end of the piston
rod 10a. The piston assemblies 110 are disposed such that each of
the guide pistons 110b is housed in a cylinder bore 109a in the
front end, and each of the compression pistons 110c is housed in a
cylinder bore 109b in the rear end. A swash plate engaging portion
110d with a portal-shaped cross-section in the axial direction is
formed in the center of each of the piston rods 110a and shoes 111
are engaged by these swash plate engaging portions 110d. The piston
assemblies 110 are constructed so as to be engaged by the surface
108a of the swash plate 108 by means of these shoes 111 and to be
reciprocated as the swash plate 108 rotates.
[0074] In this compressor, the front end surface of the cylinder
assembly 101 constructed as described above is covered by a front
housing 150 forming an outer shell. The rear end surface of the
cylinder assembly 101 is covered by a rear housing 115 functioning
as a cylinder cover by means of a valve plate assembly 116. These
housings 150, 115 are joined and secured to the cylinder assembly
101 by means of a plurality of bolts 138. Moreover, 138a are bolt
holes for leading the bolts 138 from the front housing 150 to the
valve plate assembly 116. The front housing 150 is joined to the
front end surface of the cylinder assembly 101 by means of a gasket
150a, two intake pressure chambers 151 and two discharge pressure
chambers 152 being formed therein as shown in FIG. 6.
[0075] As shown in FIG. 6, the intake pressure chambers 151 are
each formed in an oval shape so as to connect two cylinder bores
109a, and are disposed on the left and right in FIG. 6.
Furthermore, the intake pressure chambers 151 are connected to the
swash plate chamber 107 by connecting passages 156 which pass
through the length of the front end cylinder block 101a.
[0076] The discharge pressure chambers 152, on the other hand, are
positioned over the two cylinder bores 109a lying between the
intake pressure chambers 151, and form an approximately cylindrical
space with a diameter approximately equal to that of the two
cylinder bores 109a. Furthermore, the discharge pressure chambers
152 are each connected to one of the bolt holes 138a formed around
the bolts 138 by connecting grooves 153 cut into the end surface of
the cylinder assembly 101 of the front housing 150.
[0077] At the same time, the interior of the rear housing 115 is
divided into two concentric spaces by a partition. The inner of
these divided spaces is connected to the swash plate chamber 107 by
means of a plurality of connecting passages 127 formed in the
cylinder block 101b, forming an intake chamber 131. Furthermore,
the intake chamber 131 is connected to the rear cylinder bores 109b
by means of intake ports 133 and intake valves 132 described below.
The outer of the spaces within the rear housing 115 forms a
discharge chamber 134 connected to each of the cylinder bores 109b
by means of discharge ports 136 and discharge valves 135 described
below. Furthermore, the discharge chamber 134 is connected to a
discharge outlet 122 by means of a discharge passage 124.
[0078] The valve plate assembly 116 is formed by disposing an
intake valve-forming plate 116A, a valve plate 116B, a discharge
valve-forming plate 116C, and a retainer gasket 116D in order from
the cylinder assembly 101 side, and is held between the cylinder
assembly 101 and the cylinder cover 115.
[0079] The valve plate 116B is perforated by a plurality of intake
ports 133 connecting the intake chamber 131 to each of the cylinder
bores 109b, and a plurality of discharge ports 136 connecting the
discharge chamber 134 to each of the cylinder bores 109b. The
intake valve-forming plate 116A is integrally formed with a
plurality of intake valves 132 for individually controlling the
opening and closing of each of the intake ports 133. The discharge
valve-forming plate 116C is integrally formed with a plurality of
discharge valves 135 for individually controlling the opening and
closing of each of the discharge ports 136. The retainer gasket
116D is integrally formed with a plurality of retainers for
individually regulating the opening angle of each of the discharge
valves 135.
[0080] As can be seen from FIG. 5, by making the walls of the
discharge chamber 134 in the rear end surrounding the bottle holes
138a shorter, the valve plate assembly 116 ends of the bolt holes
138a are opened to the discharge chamber 134, whereby the bolt
holes 138a and the discharge chamber 134 are connected.
[0081] When a single-ended swash plate compressor constructed in
the above manner is driven, intake gas is drawn from the external
refrigerant circuit through the inlet 121 into the swash plate
chamber 107. Then, the intake gas flows through the connecting
passages 127 to the intake chamber 131. Next, this intake gas is
sucked through the intake ports 133 and the intake valves 132 into
the cylinder bores 109b and is compressed by the compression
pistons 110c. The compressed refrigerant gas is discharged through
the discharge ports 136 and the discharge valves 135 to the
discharge chamber 134. During this compression operation, because
the intake pressure chamber 151 in the front housing 150 is
connected to the swash plate chamber 107 by means of the connecting
passages 156, low pressure is constantly being introduced into the
intake pressure chamber 151. Consequently, the inside of the
cylinder bores 109a in the front end directly connected to the
intake pressure chamber 151 are constantly maintained at low
pressure. At the same time, because the discharge pressure chamber
152 in the front housing 150 is connected to the discharge chamber
134 by means of the bolt holes 138a, discharge pressure is
constantly being introduced into the discharge pressure chamber
152, and therefore the cylinder bores 109a directly connected
thereto are constantly maintained at discharge pressure.
[0082] Consequently, at the front end of the piston assemblies 110
during the compression operation, low pressure acts on the surfaces
of the four guide pistons 110b exposed to low pressure and
discharge pressure acts on the surfaces of the two guide pistons
110b exposed to discharge pressure. At the same time, at the rear
end of the piston assemblies 110, the internal pressure of the
cylinder bores 109b, which changes between intake pressure and
discharge pressure due to the compression action, acts on the
surface of each of the compression pistons 110c. FIG. 8 is a graph
showing the thrust loads acting on a six-piston assembly 110 due to
such pressure conditions, Ff2 representing the thrust load acting
from the front end towards the rear end, Fr2 representing the
thrust load acting from the rear end towards the front end, and Ft2
representing the total load being the sum of these thrust loads Ff2
and Fr2. As can be seen from this graph, the thrust load acting
from the front end towards the rear end Ff2 and the thrust load
acting from the rear end towards the front end Fr2 are practically
balanced and the sum of these two thrust loads (total load) Ft2
fluctuates only slightly in either axial direction, exhibiting no
great imbalances in load. Consequently, this total load Ft2 shows
the same magnitude and variance as the total thrust load Ft1 in
Embodiment 1above.
[0083] Moreover, if the cylinder bores other than the cylinder
bores into which discharge pressure of the front end cylinder bores
109a is introduced are constructed without purposely introducing
intake pressure and are not controlled, there is a possibility that
the internal pressure therein will rise due to the leaking of
refrigerant from the discharge pressure side to the low pressure
side and there is a risk that the balance of the thrust loads in
either axial direction will shift as operating time increases.
However, by purposely introducing intake gas as in Embodiment 2,
the internal pressure therein and the balance of thrust loads in
either axial direction are stabilized.
[0084] Furthermore, since in this case, the two cylinder bores 109a
in the front end whose internal pressure is discharge pressure and
the four cylinder bores 109a in the front end whose internal
pressure is intake pressure are disposed symmetrically about the
axial center of the drive shaft, the moments about the center of
the swash plate due to the thrust loads acting on each of the
pistons are in a mutually cancelling relationship, reducing
deformation of the drive shaft 105 and load on the radial bearings
104.
[0085] Furthermore, in the guide pistons 10b, if piston rings 110e
are mounted on the outer circumferential surfaces of the two
pistons in which the internal pressure of the cylinder bores 109a
is discharge pressure, blowback gas from these cylinder bores 109a
to the swash plate chambers 107 is reduced, improving compression
efficiency.
[0086] Embodiment 3
[0087] Next, Embodiment 3 will be explained on the basis of FIGS. 9
to 11. Moreover, since Embodiment 3 has many points in common with
Embodiment 2 above, identical structural elements will be given
identical reference numerals and explanations thereof will be
simplified.
[0088] As in the case of Embodiment 2, Embodiment 3 has six pairs
of cylinder bores 109a, 109b, the difference being that in
Embodiment 3discharge pressure is introduced into every second
cylinder bore 109a. Moreover, FIG. 9 is a cross-section similar to
that of FIG. 5 for Embodiment 2 above, but the section is taken
along a line passing through two cylinder bores positioned
symmetrically relative to the center of the drive shaft (line IX-IX
in FIG. 10). Furthermore, FIG. 10 is a cross-section of a front
housing 160 taken along line X-X in FIG. 9.
[0089] In FIG. 9, a front housing 160 is joined to the front end
surface of the cylinder assembly 101 by means of a plate 165 so as
to cover the cylinder assembly 101. Gaskets 160a, 160b are disposed
between the plate 165 and the front housing 160, and between the
plate 165 and the cylinder assembly 101, respectively, so as to
seal the joints. As can be seen from FIG. 10, the interior of the
front housing 160 is divided into two concentric chambers by a
partition 164 formed integrally with the front housing 160 so as to
protrude inwards from the end wall thereof, the inner chamber
forming an intake pressure chamber 161 and the outer chamber
forming a discharge pressure chamber 162.
[0090] As in Embodiment 2, the intake pressure chamber 161 is
connected to the swash plate chamber 107 by connecting passages 166
(see FIG. 10) running the length of the front end cylinder bores
109a. Furthermore, the intake pressure chamber 161 is constantly
connected to three alternately-positioned cylinder bores 109a by
intake gas passage holes 167 disposed in the plate 165.
Consequently, intake pressure is constantly introduced into these
cylinder bores 109a during operation.
[0091] Three connecting grooves 163 (see FIG. 10) connecting the
bolt holes 138a to the discharge pressure chamber 162 are cut into
the end surface of the front housing 160. As in the case of
Embodiment 2, these bolt holes 138a are connected to the discharge
chamber 134 within the cylinder cover 115. In addition, the
remaining cylinder bores 109a other than the cylinder bores
connected to the intake pressure chamber 161 are constantly
connected to the discharge pressure chamber 162 by discharge gas
passage holes 168 disposed in the plate 165. Consequently,
discharge pressure is constantly introduced into these cylinder
bores 109a during operation. Moreover, the intake gas passage holes
167 and the discharge gas passage holes 168 are formed sufficiently
large so that no compression action occurs within the guide end
cylinder bores 109a.
[0092] As a result of this construction, intake pressure and
discharge pressure act on the front end surfaces of alternate guide
pistons 110b respectively, the acting thrust loads being based on
this pressure.
[0093] FIG. 11 is a graph showing the total load Ft3 being the sum
of the thrust loads acting on a six-piston assembly 110 in both
axial directions, showing the total load Ft2 acting in the case of
Embodiment 2 and the thrust load Ft acting in the case of the
conventional example for comparison. For each of these curves,
carbon dioxide has been used as the refrigerant. Consequently, it
can be seen that when the refrigerant is carbon dioxide,
introduction of discharge gas into two of the cylinder bores 109a,
as in Embodiment 2, gives the best balance of thrust loads.
However, Embodiment 3 is still an improvement over the conventional
technique. Furthermore, the present embodiment may be preferable
depending on the type of refrigerant.
[0094] Concerning the moments about the center of the swash plate 7
mentioned in Embodiment 2, the present embodiment is preferable
because it is more evenly balanced in all directions.
[0095] Embodiment 4
[0096] Next, Embodiment 4 will be explained on the basis of FIG.
12. Moreover, since Embodiment 4 has many points in common with
Embodiments 2 and 3 above, structural elements identical to those
in Embodiments 2 and 3 will be given identical reference numerals
and explanations thereof will be simplified.
[0097] As in the case of Embodiments 2 and 3, Embodiment 4 has six
pairs of cylinder bores 109a, 109b, the difference being that in
Embodiment 4 the diameter of the front end cylinder bores 109a is
made smaller than the diameter of the rear end cylinder bores 109b,
and the cross-sectional area of the guide pistons is made smaller
than that of the compression pistons, and in addition, discharge
pressure is introduced into all of the front end cylinder bores
109a. Moreover, FIG. 12 is a cross-section similar to that of FIG.
5 for Embodiment 2 above.
[0098] As shown in FIG. 12, a front housing 170 is connected to the
front end surface of the cylinder assembly 101. The interior of the
front housing 170 is formed into a single chamber functioning as a
discharge pressure chamber 172. The construction for introducing
discharge gas to the discharge pressure chamber 172 is similar to
that in Embodiment 2 and is achieved by connecting the discharge
pressure chamber 172 to the bolt holes 138a by means of connecting
grooves 173 cut into the end surface of the front housing 170 and
connecting the bolt holes 138a to the discharge chamber 134 in the
cylinder cover 115. Furthermore, since there is no need to limit
the reciprocation of the guide pistons 110b to within the cylinder
bores 109a, when any of the compression pistons 110c is at bottom
dead center, the end of the corresponding guide piston 110b
projects into the discharge pressure chamber 172 as shown in FIG.
12, allowing the size of the compressor to be reduced.
[0099] In this construction, the balance of thrust loads can be
variously altered by changing the cross-sectional area of the guide
pistons 110b. Consequently, the acting thrust loads and the balance
of thrust loads in both axial directions may change depending on
the refrigerant, but the balance of thrust loads in both axial
directions can be adjusted by means of the designed cross-sectional
area of the pistons 110b, 110c.
[0100] Thus, by making the guide pistons 110b smaller, the force
required to drive the piston assemblies 110 is reduced, enabling
the efficiency of the compressor to be improved.
[0101] Moreover, the reduction of the size of the guide pistons
110b as in Embodiment 4 can also be applied to Embodiments 2 and 3
above.
* * * * *