Information
-
Patent Grant
-
6632074
-
Patent Number
6,632,074
-
Date Filed
Monday, September 10, 200122 years ago
-
Date Issued
Tuesday, October 14, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 417 254
- 417 269
- 417 2221
- 417 271
-
International Classifications
-
Abstract
A multistage piston compressor includes a case and a suction chamber and a discharge chamber provided in the case. A rotary shaft is supported in the case. A valve plate provided in the case includes suction ports and discharge ports. A plurality of bores are provided at predetermined intervals about the axis of the shaft. Pistons are housed in the bores and compress refrigerant by reciprocating in accordance with the rotation of the shaft. An intermediate chamber connects a discharge port with a suction port. The refrigerant is compressed in stages by passing through a plurality of bores via the intermediate chamber. Compression chambers are defined between the pistons and the valve plate. A communication passage is provided for setting the pressures acting on the rear faces of the pistons to an intermediate pressure between the suction pressure and the discharge pressure.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a multistage piston compressor used in, e.g., a vehicular air-conditioning system.
Japanese Unexamined Patent Publication No. Hei 10-184539 discloses a conventional multistage piston compressor. This kind of compressor is provided with a rotary shaft, which is rotatably supported in a case. A valve plate is provided in the case. The valve plate has a plurality of discharge ports and suction ports. A plurality of bores are arranged at predetermined intervals on a circle, the center of which is on the axis of the rotary shaft. A reciprocating piston is housed in each bore. Each piston is connected with a swash plate by a pair of shoes. When the rotary shaft is rotated, the swash plate rotates. The rotation of the swash plate is converted into reciprocating motion of the pistons in the bores by the shoes. A connecting passage connects the discharge port of one bore with the suction port of another bore. A refrigerant passes through a plurality of cylinder bores successively via the connecting passage and is compressed in a multiple stages.
Between an end face of the pistons and the valve plate, compression chambers are defined in the bores. When the difference between the pressure in one of the compression chambers and the pressure in a crank chamber is large, the refrigerant is likely to leak through the gap between the bore and the piston. As a result, since a large amount of blow-by gas, or leakage loss occurs, the performance of the compressor falls.
When the difference between the pressure in the compression chamber and the pressure in the crank chamber is large, the difference between the pressure acting on the front face of the piston and the pressure acting on the rear face of the piston is large. In this case, the piston receives a large compressive reaction force. The compressive reaction force produces a large frictional force between the shoes and the swash plate and between the shoes and the piston. Furthermore, the reaction force acts also on the rotary shaft, to which the swash plate is fixed. Therefore, a mechanical loss is generated and the performance of the compressor falls.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a multistage piston compressor that decreases the leakage loss and the mechanical loss.
In order to achieve the above object, the present invention provides the following multistage piston compressor: The compressor includes a case, a suction chamber, which is provided in the case and the internal pressure of which is a suction pressure, and a discharge chamber, which is provided in the case and the internal pressure of which is a discharge pressure. A rotary shaft is rotatably supported in the case. A valve plate is provided in the case. The valve plate includes suction ports and discharge ports. A plurality of bores are provided at predetermined intervals about the axis of the rotary shaft. Pistons are housed in the bores and reciprocate therein in accordance with the rotation of the rotary shaft to compress a refrigerant. A connecting passage connects the discharge port of a specific bore with the suction port of another bore. The refrigerant passes through a plurality of bores via the connecting passage and is compressed in a multistage manner. A compression chamber is defined between an end face of each piston and the valve plate. Pressure setting means sets the pressure acting on the rear face of the piston to an intermediate pressure between the suction pressure and the discharge pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a sectional view of a multistage piston compressor according to an embodiment of the present invention; and
FIG. 2
is a sectional view along the line
2
—
2
in FIG.
1
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment in which the present invention is embodied in a multistage piston compressor using carbon dioxide as a refrigerant will be described with reference to
FIGS. 1 and 2
.
As shown in
FIG. 1
, a housing of a cylindrical compressor
10
includes a motor housing member
11
, a front housing member
12
, a cylinder block
13
and a rear housing member
14
.
Between the motor housing member
11
and the cylinder block
13
, a rotary shaft
20
is supported by bearings
18
,
21
. The rotary shaft
20
passes through a center hole
12
b
of a wall portion
12
a
formed in the front housing member
12
.
Between the motor housing member
11
and the front housing member
12
, a motor chamber
29
is defined. In the motor chamber
29
, an electric motor
17
is housed. The electric motor
17
is provided with a rotor
15
and a stator
16
.
The cylinder block
13
has a first bore
13
b
and a second bore
13
a
. The first bore
13
b
is larger in diameter than the second bore
13
a
. As shown in
FIG. 2
, the bores
13
a
,
13
b
are located at positions substantially opposed to each other with respect to the axis L of the rotary shaft
20
.
As shown in
FIG. 1
, a crank chamber
30
is defined between the front housing member
12
and the cylinder block
13
. In the crank chamber
30
, a disk-like swash plate
22
is fixed on the rotary shaft
20
. The swash plate
22
is supported in a thrust direction by a bearing
27
, which contacts the rear face of the wall
12
a
of the front housing member
12
. In the respective bores
13
a
,
13
b
, corresponding pistons
25
,
26
reciprocate.
The pistons
25
,
26
are provided with grooves
25
a
,
26
a
, respectively. In each groove
25
a
,
26
a,
a pair of semispherical shoes
23
,
24
is provided. The swash plate
22
is fitted between the shoes
23
and
24
. In this embodiment, a crank mechanism is formed by the swash plate
22
, the grooves
25
a,
26
a
and the shoes
23
,
24
.
A suction passage
42
and a discharge passage
40
are formed in the peripheral wall and end wall of the rear housing member
14
, respectively. Between the rear housing member
14
and the cylinder block
13
, a suction chamber
37
, an intermediate chamber
38
and a discharge chamber
39
are defined. As shown in
FIGS. 1 and 2
, the suction chamber
37
is connected with the suction passage
42
. The intermediate chamber
38
functions as a connecting passage for connecting the bores
13
a
and
13
b
. The discharge chamber
39
is connected with the discharge passage
40
. Between the rear housing member
14
and the cylinder block
13
, a first valve plate
31
and a second valve plate
32
are provided. The first valve plate
31
is provided with five ports
31
a
,
31
b
,
31
c
,
31
d
and
31
e.
The port
31
a
connects the suction chamber
37
to the first bore
13
b
. The port
31
b
connects the first bore
13
b
to the intermediate chamber
38
. The port
31
c
connects the second bore
13
a
to the intermediate chamber
38
. The port
31
d
connects the second bore
13
a
to the discharge chamber
39
. The port
31
e
connects a communication passage
45
, which will be described later, to the intermediate chamber
38
.
In the second valve plat
32
, suction valves
32
a
,
32
b
are formed at the positions corresponding to the ports
31
a
,
31
c
of the first valve plate
31
. The suction valves
32
a
,
32
b
open and close the respectively corresponding ports
31
a
,
31
c
. In the rear housing member
14
, discharge valves
34
,
36
are provided at positions respectively corresponding to the ports
31
b
,
31
d
. Retainers
33
,
35
are fixed to cylinder block
13
.
In the cylinder block
13
, a communication passage
45
is formed to serve as pressure setting means for connecting the crank chamber
30
to the intermediate chamber
38
. Therefore, the crank chamber
30
communicates with the intermediate chamber
38
through the communication passage
45
and further communicates with the motor chamber
29
through a gap in the bearing
27
and the center hole
12
b.
Next, the operation of the compressor of this embodiment will be described.
When the rotary shaft
20
is rotated by the electric motor
17
, the swash plate
22
rotates. The rotation of the swash plate
22
is converted into reciprocating motion of the pistons
25
,
26
through the shoes
23
,
24
. When the piston
26
moves from its top dead center position to its bottom dead center position, i.e., during the suction stroke, the refrigerant that enters through the suction passage
42
into the suction chamber
37
forces the suction valve
32
a
to open and then flows into the first bore
13
b
. By the rotation of the swash plate
22
, the piston
26
moves from its bottom dead center position toward its top dead center position to compress the refrigerant in the first bore
13
b
. This is the first stage of compression. Next, when the piston
26
has moved near its top dead center position as shown in
FIG. 1
, the discharge valve
34
is opened so that the compressed refrigerant in the first bore
13
b
flows into the intermediate chamber
38
.
Some of the refrigerant in the intermediate chamber
38
passes through the port
31
e
and the communication passage
45
into the crank chamber
30
. Further, the refrigerant is supplied from the crank chamber
30
to the motor chamber
29
through the bearing
27
and the hole
12
b
of the front housing member
12
.
On the other hand, when he piston
25
moves towards its bottom dead center position, the refrigerant in the intermediate chamber
38
forces the suction valve
32
b
to open, so that the refrigerant enters the second bore
13
a
. Next, when the piston
25
moves toward its top dead center position, it compresses the refrigerant in the second bore
13
a
. This is the second stage of compression. When the piston
25
has moved near its top dead center position, the discharge valve
36
is opened so that the compressed refrigerant is discharged into the discharge chamber
39
. The co pressed refrigerant is then supplied through the discharge passage
40
to another part, not shown, of the air-conditioning system, e.g., a condenser.
This embodiment has the effects described below.
Since the communication passage
45
connects the crank chamber
30
to the intermediate chamber
38
, the pressure in the crank chamber
30
becomes almost equal to the pressure in the intermediate chamber
38
. That is, the pressure in the crank chamber
30
, or the pressure acting on the rear face of the piston
25
, is set to an intermediate pressure that is higher than the suction pressure (the pressure in the suction chamber
37
) and lower than the discharge pressure (the pressure in the discharge chamber
39
). Therefore, the difference between the pressure in the crank chamber
30
and the pressure in the compression chamber of the first bore
13
b
is small. As a result, the refrigerant in the compression chamber scarcely leaks into the crank chamber
30
. Also, the difference between the pressure of the refrigerant compressed in the compression chamber of the second bore
13
a
and the pressure in the crank chamber
30
is also small. Therefore, the compressed refrigerant in the compression chamber of the second bore
13
a
hardly leaks into the crank chamber
30
. Thus, the gas leakage through the gaps between the pistons
25
,
26
and the first and second bores
13
b
,
13
a
is reduced. Also, since the differences in pressure between the crank chamber
30
and the compression chambers in both bores
13
a
,
13
b
is small, the compressive reaction forces due to reciprocation of the pistons
25
,
26
also become small, and mechanical losses are reduced.
With only the simple construction of providing the communication passage
45
between the crank chamber
30
and the intermediate chamber
38
, the pressure in the crank chamber
30
can be set to substantially the same pressure as the pressure in the intermediate chamber
38
.
Since the refrigerant, which contains lubricating oil, passes through the bearing
27
, a sufficient amount of lubricating oil is supplied between the bearing
27
and the rotary shaft
20
. In particular, since the bearing
27
receives the compressive reaction force, mechanical losses are reduced further.
This invention can also be embodied as follows.
Although this embodiment includes a fixed displacement single-headed swash plate type multistage piston compressor, the invention may be applied also to a variable displacement swash plate type multistage piston compressor or to a double-headed type multistage piston compressor. Of course, the invention is not limited to swash plate type compressor and it may be applied also to a wave cam type multistage piston compressor.
The present invention may be applied to a compressor that is connected with and driven by an external drive source such as a vehicular engine through a clutch mechanism such as an electromagnetic clutch.
The motor chamber
29
may not communicate with the crank chamber
30
. Further, a radial bearing may be provided between the swash plate
22
and the front housing member
12
.
Although the pressures acting on the rear faces of the pistons
25
,
26
are almost equal to the pressure of the refrigerant compressed in the first bore
13
b
here, the pressures acting on the rear faces of the pistons
25
,
26
may be any pressures higher than the suction pressure and lower than the discharge pressure. Of course, the present invention may be applied not only to such a two-stage compressor as in the above embodiment but also to a multistage compressor of three or more stages. Further, a plurality of pairs of bores may be provided.
As the refrigerant, in place of carbon dioxide, another refrigerant gas, e.g., ammonia or propane gas may be used.
Claims
- 1. A multistage piston compressor comprising:a housing; a suction chamber located in the housing, wherein the pressure in the suction chamber is a suction pressure; a discharge chamber located in the housing, wherein the pressure in the discharge chamber is a discharge pressure; a rotary shaft supported in the housing; a plurality of bores formed in the housing at predetermined angular intervals about the axis of the shaft; a valve plate located in the housing, wherein the valve plate includes a suction port and a discharge port corresponding to each bore; a piston housed in each bore, wherein each piston reciprocates and compresses a refrigerant when the shaft is rotated; compression chambers defined in each bore between a rear end of the associated piston and the valve ate, wherein the compression chambers include a first compression chamber and a second compression chamber; an intermediate chamber connecting the discharge port of the first compression chamber to the suction port of the second compression chamber, wherein the refrigerant is compressed in stages and flows from the first compression chamber to the second compression chamber through the intermediate chamber; a crank chamber formed within the housing, wherein each piston has a front end opposite to the rear end and exposed in the crank chamber, and a passage for connecting the intermediate chamber with the crank chamber such that the pressure of the intermediate chamber is applied to the crank chamber and acts on the front ends of the postions, herein the pressure of the intermediate chamber is between the suction pressure and the discharge pressure.
- 2. The multi-stage piston compressor of claim 1 comprising:a crank mechanism located in the crank chamber, wherein the crank mechanism converts rotation of the shaft to reciprocating motion for driving the pistons.
- 3. The multi-stage piston compressor of claim 2 comprising:a swash plate fixe to the shaft; and shoes coupled to each piston, wherein the shoes contact the swash plate and transmit force between the swash plate and the pistons.
- 4. The multi-stage piston compressor according to claim 2 comprising:a motor chamber; and electric motor for driving the shaft, wherein the motor is located in the motor chamber.
- 5. The multi-stage piston compressor according to claim 2 comprising:a motor chamber; an electric motor for driving the shaft, wherein the motor is located in the motor chamber; and a bearing for receiving thrust force transmitted from the swash plate, wherein the bearing is located in the crank chamber and is adjacent to the motor chamber.
- 6. The multi-stage piston compressor of claim 1 wherein the plurality of bores is first bore located upstream of the intermediate chamber and a second bore located downstream of the intermediate chamber.
- 7. A multistage piston compressor comprising:a housing; a suction chamber located in the housing, wherein the pressure in the suction chamber is a suction pressure; a discharge chamber located in the housing, wherein the pressure in the discharge chamber is a discharge pressure; a rotary shaft supported in the housing; a plurality of bores formed in the housing at predetermined angular intervals about the axis of the shaft; a valve plate located in he housing, wherein the valve plate includes a suction port and a discharge port corresponding to each bore; a piston housed in each bore, wherein each piston reciprocates and compresses a refrigerant when the shaft is rotated, wherein each piston has a rear end and a front end, the front end being opposite to the rear end; compression chambers defined in each bore between a rear end of the associated piston and the valve plate, wherein the compression chambers include a first compression chamber and a second compression chamber; an intermediate chamber connecting the discharge port of the first compression chamber to the suction port of he second compression chamber, wherein the refrigerant is compressed in stages and flows from the first compression chamber to the second compression chamber through the intermediate chamber and the pressure of the intermediate chamber is between the suction pressure and the discharge pressure; and a passage connected to the intermediate chamber for applying the pressure of the intermediate chamber to the front ends of the pistons.
- 8. The multi-stage piston compressor of claim 7 comprising:a crank chamber formed within the housing, wherein the pressure of the crank chamber is set approximately to he pressure of the intermediate chamber by the passage; and a crank mechanism located in the crank chamber, wherein the crank mechanism converts rotation of the shaft to reciprocating motion for driving the pistons.
- 9. The multi-stage piston compressor of claim 8 comprising:a swash plate fixe to the shaft; and shoes coupled to each piston, wherein the shoes contact the swash plate and transmit force between the swash plate and the pistons.
- 10. The multi-stage piston compressor according to claim 9 further comprising:a motor chamber; an electric motor for driving the shaft, wherein the motor is located in the motor chamber; and a bearing for receiving thrust force transmitted from the swash plate, wherein the bearing is located in the crank chamber and is adjacent to the motor chamber.
- 11. The multi-stage piston compressor of claim 7 wherein the plurality of bores is first bore located upstream of the intermediate chamber and a second bore located downstream of the intermediate chamber.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-002970 |
Jan 2000 |
JP |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/JP01/00054 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO01/51809 |
7/19/2001 |
WO |
A |
US Referenced Citations (6)
Number |
Name |
Date |
Kind |
4495855 |
Murakami et al. |
Jan 1985 |
A |
5921756 |
Matsuda et al. |
Jul 1999 |
A |
5931645 |
Goto et al. |
Aug 1999 |
A |
6079952 |
Harte et al. |
Jun 2000 |
A |
6183211 |
Wood |
Feb 2001 |
B1 |
6280151 |
Murakami et al. |
Aug 2001 |
B1 |
Foreign Referenced Citations (3)
Number |
Date |
Country |
63-10307 |
Mar 1988 |
JP |
10-176671 |
Jun 1998 |
JP |
10-184539 |
Jul 1998 |
JP |