Information
-
Patent Grant
-
6544004
-
Patent Number
6,544,004
-
Date Filed
Thursday, April 26, 200123 years ago
-
Date Issued
Tuesday, April 8, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Freay; Charles G.
- Gray; Michael K.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 417 2222
- 417 269
- 092 71
- 277 385
-
International Classifications
-
Abstract
A compressor which has a housing defining therein a suction chamber, a discharge chamber and a crank chamber, a drive shaft rotatably supported in the housing, a first end of which penetrates through the suction chamber and protrudes from the housing, and a second end of which is disposed in the crank chamber, a single-headed piston accommodated in a cylinder formed in the housing, and a swash plate integrally rotatably mounted on the drive shaft and coupled with the piston. The cylinder is located between the crank chamber and the first end of the drive shaft so that pressure in the crank chamber acts on the drive shaft in an opposite direction of compressive reaction force acting on the drive shaft. A shaft seal is provided on the drive shaft between the suction chamber and the first end of the drive shaft in order to seal the suction chamber.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a swash plate type compressor having a single-headed piston for use in, for example, a vehicle air conditioner.
In a variable displacement swash plate type compressor shown in
FIG. 9
, in general, a compressor housing is formed such that a front housing
102
and a rear housing
103
are arranged to sandwich a cylinder block
101
. A crank chamber
104
is formed between the front housing
102
and the cylinder block
101
. A drive shaft
105
across the crank chamber
104
is rotatably supported by the housing. A first end of the drive shaft
105
penetrates through a through hole
106
of the front housing
102
, whereas a second end of the drive shaft
105
is in the crank chamber
104
. A shaft seal
107
is arranged to seal a gap between the drive shaft
105
and the front housing
102
, thereby preventing refrigerant in the crank chamber
104
from leaking out. A plurality of cylinder bores
108
are formed in the cylinder block
101
to surround the drive shaft
105
. A piston
109
is disposed in each of the cylinder bores
108
and reciprocates there. A suction chamber
110
and a discharge chamber
111
are formed in the rear housing
103
.
A swash plate
113
is mounted on the drive shaft
105
through a hinge mechanism
112
and rotates together with the drive shaft
105
. The swash plate
113
is capable of sliding in the axial direction of the drive shaft
105
and of inclining with respect to the drive shaft
105
. Each piston
109
is engaged with an outer peripheral portion of the swash plate
113
through a pair of shoes
114
so that the rotational movement of the drive shaft
105
is converted to the reciprocating movement of the piston
109
. Refrigerant in the suction chamber
110
is drawn into the cylinder bore
108
and compressed there by the reciprocating piston
109
. When pressure in the crank chamber
104
is adjusted, an inclination angle of the swash plate
113
changes. Therefore, the piston stroke changes. Accordingly, the discharge capacity of the compressor becomes variable. For example, the inclination angle of the swash plate
113
, the angle between a plane perpendicular to the drive shaft
105
and the swash plate
113
, decreases when the pressure in the crank chamber
104
increases. Reduction of the piston stroke decreases the discharge capacity of the compressor.
During operation of the compressor, compressive reaction force of each piston
109
acts on the drive shaft
105
through the swash plate
113
. On the other hand, pressure difference between the pressure Pc in the crank chamber
104
and the atmospheric pressure P
0
, which is multiplied by a cross-sectional area of the drive shaft
105
substantially at which the shaft seal
107
is provided, acts on the drive shaft
105
. Both the reaction force and the pressure difference intend to push the drive shaft
105
frontwards. The thrust load based on the reaction force and the pressure difference is supported by the front housing
102
through a thrust bearing
116
arranged between a rotor
115
or lug plate and the front housing
102
.
In recent years, a compressor has been proposed for use in a refrigerant circuit which employs a refrigerant gas such as carbon dioxide, instead of chloro-fluoro carbon. Such a circuit, after compression of the gas, cools down the gas in a super critical range that exceeds a critical temperature of the gas. For example, according to Japanese Patent Application Publication No. 11-223179 discloses a variable displacement type of compressor employing carbon dioxide as refrigerant. In this compressor, refrigerant in a discharge pressure region supplied into the crank chamber
104
is controlled by an electric displacement control valve
117
as shown conventionally in FIG.
9
. The amount of refrigerant passing through the refrigerant circuit is adjusted based on the external data such as a heat load.
When the circuit employs chloro-fluoro carbon as refrigerant, the pressure Pc in the crank chamber is relatively small, less than or equal to 9.8×10
5
Pa. However, when the refrigerant such as carbon dioxide is employed, the pressure Pc in the crank chamber rises greatly. For example, employment of carbon dioxide raises the pressure Pc higher than the pressure in employment of chloro-fluoro carbon by about several tens to a hundred ×10
4
Pa. As a result, the thrust load supported by the thrust bearing
116
increases greatly, and sealing function of the shaft seal
107
against the high pressure is required.
When the thrust load acting on the drive shaft
105
in the same direction as the compressive reaction force becomes higher, mechanical loss increases as well as the power consumption to drive the drive shaft
105
. The power consumption is typically apparent when the power of the drive source such as an engine is transmitted to the drive shaft
105
without using a clutch, for instance, in a clutchless variable displacement type of swash plate compressor. That is, when the compressor is driven in a minimum capacity state or off-drive state, the power consumption, which should be minimum, increases.
Further, when the shaft seal
107
is arranged in the crank chamber region, the lubrication of the shaft seal
107
is not satisfactorily performed because refrigerant in the crank chamber has not only high pressure but high temperature.
SUMMARY OF THE INVENTION
Accordingly, it is a first object of the present invention to provide a swash plate type compressor in which required power to drive the compressor is reduced by reducing a thrust load in the same direction as compressive reaction force acting on a drive shaft.
To achieve the above first object, a swash plate type compressor of the present invention has a housing including a suction chamber, a discharge chamber and a crank chamber, a drive shaft rotatably supported by the housing, the drive shaft having a first end protruding from the housing and a second end disposed in the crank chamber, a cylinder bore defined between the crank chamber and the first end of the drive shaft, a single-headed piston disposed in the cylinder bore to be reciprocated, and a cam plate rotatably mounted on the drive shaft in the crank chamber, the cam plate being operatively engaged with the piston, whereby rotational movement of the drive shaft is converted to reciprocating movement of the piston through the cam plate.
In the present invention, when refrigerant is compressed during operation of the compressor, the compressive reaction force of the piston acts on the drive shaft through the cam plate thereby pushing the drive shaft toward its second end. On the other hand, pressure in the crank chamber acts on the second end portion of the drive shaft against atmospheric pressure acting on the first end of the drive shaft so that pressure difference between them pushes the drive shaft in the opposite direction to the reaction force. Therefore, according to the present invention the power to drive the drive shaft of the compressor is reduced by reduction of thrust force acting on the drive shaft.
It is a second object of the present invention to provide a swash plate type compressor in which a shaft seal arranged to seal a gap between a drive shaft and a housing is improved.
To achieve the above second object according to the present invention, the suction chamber is in the housing defined adjacent to the first end of the drive shaft. The drive shaft is arranged in the housing such that the first end of the drive shaft penetrates the suction chamber and protrudes from the housing. A shaft seal is arranged between the suction chamber and the first end of the drive shaft, thereby sealing the suction chamber.
The foregoing shaft seal arrangement of the present invention simply requires resistance against pressure difference between atmospheric pressure and suction pressure which is lowest in the compressor. Accordingly, durability of the shaft seal is sufficiently extended, and sealing function thereof is improved. This is apparently effective when carbon dioxide and the like is employed as refrigerant instead of chloro-fluoro carbon, because carbon dioxide is used in its high pressure range, super critical range. The pressure in the crank chamber of the variable displacement compressor is to be higher than that of the fixed displacement compressor. Accordingly, the variable displacement compressor according to the present invention is more effective than the fixed displacement compressor according to the present invention because carbon dioxide is used in its high pressure range, super critical range.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. 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:
FIG. 1
is a cross-sectional view illustrating a variable displacement type of compressor according to a preferred embodiment of the present invention;
FIG.
2
(
a
) is an enlarged partial cross-sectional view illustrating a shaft seal of the compressor;
FIG.
2
(
b
) is a cross-sectional view as seen from line IIb—IIb in FIG.
2
(
a
), where a front housing is omitted;
FIG. 3
is a partial cross-sectional view illustrating a middle portion of the compressor according to the present invention;
FIG. 4
is a partial cross-sectional view illustrating a front portion of the compressor according to the present invention;
FIG. 5
is a cross-sectional view illustrating a control valve according to the present invention;
FIG. 6
is a partial cross-sectional view illustrating a rear portion of the compressor according to the present invention;
FIG. 7
is a partial cross-sectional view illustrating a rear portion of the compressor according to the present invention;
FIG. 8
is a cross-sectional view illustrating a fixed displacement compressor according to the present invention; and
FIG. 9
is a cross-sectional view illustrating a variable displacement compressor according to a prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is applied to a variable displacement compressor for a vehicle air conditioner. An embodiment according to the present invention will now be described with reference to
FIGS. 1 and 2
.
As shown in
FIG. 1
, a front housing
12
, a cylinder block
13
and a rear housing
14
constitute a housing
11
of a compressor
10
. These members are arranged from front to rear (left to right in FIG.
1
), and secured by a plurality of through bolts
15
(only one through blot is illustrated). A valve plate assembly
16
is arranged between the front housing
12
and the cylinder block
13
. A crank chamber
17
is defined between the cylinder block
13
and the rear housing
14
.
A drive shaft
18
is rotatably supported by the housing
11
. A first end of the drive shaft
18
protrudes from the front housing
12
, and a second end of the drive shaft
18
is disposed in the crank chamber
17
. In the front housing
12
a suction chamber
19
is formed around the drive shaft
18
, and an annular discharge chamber
20
is formed to surround the suction chamber
19
. A recess
21
is formed at a central inner wall of the front housing
12
adjacent the suction chamber
19
. An axial hole
22
is formed in the cylinder block
13
to communicate the crank chamber
17
with the suction chamber
19
. A recess
23
is formed in the rear housing
14
facing the crank chamber
17
. The recess
23
supports the second end of the drive shaft by means of a radial bearing
24
.
The drive shaft is further supported at its intermediate portion by the cylinder block
13
through a radial bearing
25
arranged in the axial hole
22
.
A shaft seal
26
is disposed in the recess
21
of the front housing
12
. As shown in FIG.
2
(
a
), the shaft seal
26
includes a ring
27
fitting in the recess
21
of the front housing
12
and a sliding ring
29
made of carbon. The sliding ring
29
is mounted on the drive shaft
18
through an O-ring
30
such that the sliding ring
29
rotates integrally with the drive shaft
18
and slides against the ring
27
. The ring
27
is loosely mounted around the drive shaft
18
, and the O-ring
28
is arranged between the ring
27
and the front housing
12
. The rings
27
and
29
each have a sliding contact surface perpendicular to the drive shaft
18
. The ring
29
is urged to the ring
27
by a spring
32
. The sliding contact of the rings
27
and
29
conducts the sealing function of the shaft seal. As shown in FIG.
2
(
b
), three grooves
29
a
are formed at an outer periphery of the sliding ring
29
. The shaft seal
26
has a support ring
31
which integrally rotates with the drive shaft
18
. The support ring
31
has three hooks
31
a
engaging with the respective grooves
29
a.
A spring
32
urging the sliding ring
29
toward the ring
27
is provided between the support ring
31
and the sliding ring
29
. The O-ring
30
, the sliding ring
29
, the ring
27
and the O-ring
28
together seal a gap or clearance between the drive shaft
18
and the housing
11
.
A plurality of cylinder bores
33
(only one cylinder bore is illustrated in
FIG. 1
) are formed in the cylinder block
13
around the drive shaft
18
so that the cylinder bores
33
are located at front side of the crank chamber, or between the crank chamber
17
and the first end of the drive shaft
18
. A single-headed piston
34
is disposed in each of the cylinder bores
33
and reciprocates there. A compression space or chamber
35
is defined in the cylinder bore
33
by the valve plate assembly
16
and the piston
34
. The compression chamber
35
changes its capacity in accordance with the reciprocating movement of the piston
34
, thereby defined the refrigerant is compressed.
A lug plate
36
as a rotor is mounted on and integrally rotatably with the drive shaft
18
in the crank chamber
17
. The lug plate
36
is supported by an inner wall surface
14
a
of the rear housing
14
through a first thrust bearing
37
. The axial load by the compressive reaction force is received by the inner wall surface
14
a
of the housing
11
so that the inner wall surface
14
a
functions as a regulating surface regulating the position of the drive shaft
18
in the axial direction.
A swash plate
38
as a cam plate arranged in the crank chamber
17
has a through hole
38
a
through which the drive shaft
18
penetrates. A hinge mechanism
39
is arranged between the lug plate
36
and the swash plate
38
. The hinge mechanism has a pair of support arms
40
(only one support arm is illustrated in
FIG. 1
) protruding from a front surface of the lug plate
36
, guide holes
41
each formed in the respective support arms
40
, and a pair of guide pins
42
(only one guide pin is illustrated) fixed to the swash plate
38
. Each guide pin
42
has at its distal end a spherical portion
42
a
engaged with the guide hole
41
. The swash plate
38
is supported by the drive shaft
18
through the hinge mechanism
39
, and is rotatable together with the lug plate
36
and the drive shaft
18
. The swash plate
38
is further inclinable with respect to the drive shaft
18
, and is slidable in the axial direction of the drive shaft
18
by means of the hinge mechanism
39
. A counter weight portion
38
b
is formed integrally with the swash plate
38
at the opposite side to the hinge mechanism
39
with respect to the drive shaft
18
.
A circular clip
43
is fixed to the drive shaft
18
, such that the clip
43
positions within a large diameter portion
22
a
of the axial hole
22
. A thrust bearing
44
is disposed in the large diameter portion
22
a
. A first coil spring
45
is arranged around the drive shaft
18
between the clip
43
and the thrust bearing
44
. The coil spring
45
urges the drive shaft
18
, thereby urging the lug plate
36
toward the inner wall surface
14
a
of the rear housing
14
.
A seal or a sealing ring
46
is arranged in the axial hole
22
to seal a gap between the outer peripheral surface of the drive shaft
18
and the cylindrical inner surface of the axial hole small diameter portion. The sealing ring
46
prevents gas in the crank chamber from leaking into the suction chamber through the axial hole
22
. The sealing ring
46
is made of rubber or fluoroprastic resin, and its cross-section is U-shape, lip-shape or the like.
A second coil spring
47
to reduce the inclination angle of the swash plate
38
is arranged around the drive shaft
18
between the lug plate
36
and the swash plate
38
. The coil spring
47
urges such that the swash plate
38
approaches the cylinder block
13
or reduces its inclination angle.
A third coil spring
48
as a return spring is arranged around the drive shaft
18
between the swash plate
38
and the clip
43
. When the swash plate
38
is in its large inclination angle state as shown with a solid line in
FIG. 1
, the third coil spring
48
does not urge the swash plate
38
because of natural length of the third coil spring
48
. On the other hand, when the swash plate
38
is in its small inclination angle state as shown with two dot chain line in
FIG. 1
, the third coil spring
48
is contracted between the swash plate
38
and the clip
43
. In this state the third coil spring
48
urges the swash plate
38
away from the cylinder block
13
and increases the inclination angle of the swash plate.
The piston
34
engages with the periphery of the swash plate
38
through a pair of shoes
49
so that the rotational movement of the swash plate
38
accompanied by the rotation of the drive shaft
18
is converted to the reciprocating movement of the piston
34
through the shoes
49
. The swash plate
38
and the shoes
49
are made of steel. Surface treatments such as thermally spraying or frictionally welding aluminum or aluminum alloy is performed on the sliding portion of the swash plate
38
, on which the shoes
49
slide, to prevent their seizure.
The drive shaft
18
is operatively connected to an engine
51
as a drive source through a power transmitting mechanism
50
. The power transmitting mechanism
50
may be a clutch mechanism such as magnetic clutch which selectively connects and disconnects the drive shaft
18
with the engine. The power transmitting mechanism
50
may be a clutchless mechanism such as a belt and a pulley which always connects the drive shaft to the engine
51
. In this embodiment a clutchless type of the power transmitting mechanism
50
is applied.
On the valve plate assembly
16
, a suction port
52
, a suction valve
53
which opens and closes the suction port
52
, a discharge port
54
, and a discharge valve
55
which opens and closes the discharge port
54
are formed corresponding to the respective cylinder bore
33
. The suction chamber
19
and the cylinder bore
33
are communicated with each other through the suction port
52
. The cylinder bore
33
and the discharge chamber
20
are communicated with each other through the discharge port
54
. The refrigerant gas in the suction chamber
19
is drawn into the cylinder bore
33
through the suction port
52
while opening the suction valve
53
by the movement of the piston
34
from its top dead center to bottom dead center. The refrigerant gas in the cylinder bore
33
is compressed to predetermined pressure, and discharged into the discharge chamber
20
through the discharge port
54
while opening the discharge valve
55
by the movement of the piston
34
from its bottom dead center to top dead center.
A muffler
56
having a chamber
56
a
is formed on an outer periphery of the housing
11
in such a manner that the muffler lies from the cylinder block
13
to the rear housing
14
. The muffler chamber
56
a
is communicated with the discharge chamber
20
through a discharge passage
57
formed in the cylinder block
13
. The muffler functions to expand gas in the muffler chamber
56
a
, and to reduce the pulsation of the gas discharged out of the discharge chamber
20
.
A supply passage
58
as a control passage is formed to communicate the muffler chamber
56
a
with the crank chamber
17
. A control valve
59
is arranged in the supply passage
58
. The opening degree of the supply passage
58
is adjusted by the control valve
59
. In this embodiment the muffler
56
is arranged downstream the discharge chamber
20
. An end of the supply passage
58
opens to the crank chamber where the radial bearing
24
is disposed. The bearing
24
is therefore lubricated by the gas which includes oil mist. The supply passage functions to add the discharge pressure to the second end of the drive shaft
18
. A bleeding passage
60
is formed in the cylinder block
13
and the valve plate assembly
16
to communicate the crank chamber
17
with the suction chamber
19
. An orifice
61
is arranged in the bleeding passage
60
.
The control valve
59
is a magnetic valve. The valve
59
includes a valve chamber
62
, a valve spherical body
63
disposed in the valve chamber
62
, a valve hole
64
opened to the valve chamber
62
and a solenoid
65
. The valve chamber
62
and the valve hole
64
constitute a part of the supply passage
58
.
The solenoid
65
includes a stator core
66
, a movable core
67
and a coil
68
and a rod
69
operatively connecting the movable core
67
and the valve body
63
. A spring
70
urges the movable core
67
and the rod
69
toward the valve body
63
so that the valve body
63
opens the valve hole
64
. The coil
68
is arranged to surround the stator core
66
and the movable core
67
. When the solenoid
65
is excited, a magnetic force is produced between the stator core
66
and the movable core
67
. The movable core
67
moves against the spring
70
, and the rod
69
and the valve body
63
are urged by another spring in the valve chamber
62
and close the valve hole
64
. When the solenoid
65
is de-excited, the movable core
67
and the rod moves toward the valve body
63
by the spring
70
, and the valve body
63
opens the valve hole
64
.
The suction chamber
19
and the muffler chamber
56
a
are communicated through an external refrigerant circuit
71
which includes a condenser
72
, an expansion valve
73
and an evaporator
74
. The external refrigerant circuit
71
and the above described variable displacement compressor constitute a refrigerant circuit for a vehicle air conditioner. In this embodiment carbon dioxide is applied as refrigerant gas.
Provided is a controller
75
which determines a current value to a drive circuit
79
for the solenoid
65
due to external signal such as actual temperature obtained by a temperature sensor
76
disposed in a vehicle compartment, pre-set temperature by a temperature setting device
77
disposed in the vehicle compartment, rotational speed of the engine
51
from a speed sensor
78
. The drive circuit
79
outputs the current value to the coil
68
of the control valve
59
.
The operation of the above described compressor will be described.
The swash plate
38
rotates integrally with the drive shaft
18
through lug plate
36
and the hinge mechanism
39
. The rotational movement of the swash plate
38
is converted to the reciprocating movement of the piston
34
through the respective shoes
49
. During the compressor operation, the refrigerant gas returns to the suction chamber
19
from the external refrigerant circuit
71
. The refrigerant is drawn through the port
52
, compressed in and discharged through the port
54
from the compression chamber
35
, continuously. The refrigerant discharged to the discharge chamber
20
is sent to the external refrigerant circuit
71
through the discharge passage
57
and the muffler chamber
56
a.
The control valve
59
adjusts the opening degree of the supply passage
58
in accordance with a cooling load. For example, when temperature detected by the temperature sensor
76
is higher than pre-set temperature set by a temperature setting device
77
, the controller
75
estimates cooling requirement large and determines a corresponding current value given to the solenoid
59
. The controller
75
operates the drive circuit
79
to drive the solenoid
65
of the control valve
59
. The drive circuit
79
supplies the current determined by the controller
75
to the coil
68
. According to the solenoid energized the valve body
63
moves against the spring
70
and closes the valve hole
64
. The opening degree of the supply passage
58
is therefore reduced.
When introduction of the discharge pressure to the crank chamber
17
is reduced, the pressure in the crank chamber
17
gradually becomes small because the refrigerant flows through the bleeding passage
60
to the suction chamber
19
. As a result, the pressure difference between the crank chamber pressure and the cylinder bore pressure or the suction pressure is reduced, and the inclination angle of the swash plate
38
increases. Accordingly, the piston stroke increases, and the discharge capacity also increases.
On the contrary, when temperature detected by the temperature sensor
76
comes close to the pre-set temperature of the temperature setting device
77
, the controller
75
estimates the cooling requirement small and directs the drive circuit
79
to de-energize the solenoid
65
of the control valve
59
. The drive circuit
79
then stops supplying the current to the coil
68
. Accordingly, the valve body
63
moves to open the valve hole
64
, and the opening degree of the supply passage
58
increases.
When introduction of the discharge pressure to the crank chamber
17
pressurizes there, the difference between the crank chamber pressure and the suction pressure increases, and the inclination angle of the swash plate
38
therefore decreases. Accordingly, the piston stroke decreases, and the discharge capacity also decreases.
When the piston
34
compresses the refrigerant gas, compressive reaction force F
1
by the piston
34
acts on the drive shaft
18
through the shoes
49
, the hinge mechanism
39
and the lug plate
36
. The reaction force is finally received by the receiving surface of the rear housing
14
. Crank chamber pressure Pc acts on the second end of the drive shaft
18
frontward, an opposite direction of the compressive reaction force. External pressure (atmospheric pressure P
0
) which is smaller than the pressure Pc in the crank chamber
17
acts on the first end of the drive shaft
18
in the same direction as the reaction force. When pressure difference Pc-P
0
multiplied by the cross-sectional area S of the drive shaft
18
at the position of which the sealing ring
46
is provided denotes force F
2
or F
2
=(Pc-P
0
)×S, the force F
2
acts on the drive shaft
18
against the reaction force F
1
. Conventionally, the reaction force F
1
and the pressure based force F
2
were in the same direction. However, in the present invention the force F
2
works in the opposite direction to the reaction force F
1
. Accordingly, some thrust load received by the bearing
37
is cancelled, and the power to drive the drive shaft
18
is reduced because of reduction of bearing friction.
When carbon dioxide is applied as refrigerant instead of chloro-fluoro carbon, the pressure Pc of carbon dioxide becomes higher than the pressure of chloro-fluoro carbon by about from several tens to a hundred×10
4
Pa. Therefore, in the conventional constitution a large thrust force might act on the drive shaft
18
if carbon dioxide is employed. However, in the present invention the drive force is sharply reduced because the force F
2
by the pressure in the crank chamber
17
contradicts the reaction force F
1
.
In the crutchless type of compressor, even while the air conditioner stops, the rotation of the engine
51
is transmitted to the drive shaft
18
, so called off-drive of the compressor. At this time, the inclination angle of the swash plate
38
is minimum, and the reaction force acts on the drive shaft
18
by the minimum movement of the piston
34
. However, as above described, the force F
2
due to the pressure deference Pc-P
0
acts on the drive shaft
18
to contradict the reaction force, the power consumption is reduced when the off-drive of the compressor is performed.
While the drive shaft
18
rotates, the compressive movement of the piston
34
is accompanied by the swash plate
38
. The reaction force urges the drive shaft
18
toward the rear housing
14
. The lug plate
36
, which contacts the thrust bearing
37
, is also urged toward the receiving surface (the inner wall surface
14
a
) regulating the drive shaft position in the axial direction. However, while the compressor stops and the reaction force of the piston
34
does not act on the drive shaft
18
, pressure in the crank chamber
17
urges the drive shaft
18
frontward because the pressure in the crank chamber is normally higher than the atmospheric pressure. When the compressor starts, the frontwardly urged drive shaft
18
may cause to generate noise due to collision between the thrust bearing and the lug plate. However, in this embodiment the first coil spring
45
always urges the drive shaft
18
to the rear housing
14
so that the lug plate
36
maintain its contact with the thrust bearing
37
while the compressor
10
stops. Accordingly, when the compressor starts again, noise is reduced because the lug plate
36
does not collide with the thrust bearing
37
. The urging force of the first coil spring
45
is so determined that the force overcomes the pressure difference Pc-P
0
and slightly urges the lug plate
36
to the thrust bearing
37
. Therefore, the urging force does not influence the drive force of the drive shaft
18
.
In this embodiment following effects may be obtained.
(1) Compared with the conventional compressor in which both the forces act in the same direction, the foregoing compressor sharply reduces the power to drive the drive shaft
18
since the force, which is proportional to the difference between the pressure in the crank chamber
17
and the atmospheric pressure, acts on the drive shaft
18
in the opposite direction to the reaction force of the piston. Furthermore, the crank chamber pressure against the reaction force reduces friction at the thrust bearing
37
. Therefore, the durability of the thrust bearing
37
is improved. When carbon dioxide is applied as refrigerant instead of chloro-fluoro carbon, the above effect is remarkably obtained.
(2) The first end of the drive shaft
18
penetrates through the suction chamber
19
and protrudes from the housing
11
. The shaft seal
26
requires only sealing force to endure the difference between the suction pressure which is the lowest in the compressor and the atmospheric pressure, whereas the shaft seal in the conventional compressor needs to endure the difference between the crank chamber pressure which may be the highest in the compressor and the atmospheric pressure. Accordingly, the shaft seal arrangement according to the present invention endures longer than the shaft seal arrangement of the conventional compressor. Compared to the conventional shaft seal, the shaft seal
26
is disposed in lower temperature region, the suction chamber. Therefore, the endurance of the shaft seal
26
is further improved. The mist oil in the refrigerant returning from the external circuit to the suction chamber
19
is smoothly supplied between the ring
27
and the sliding ring
29
, thereby improving the quality of the shaft seal.
(3) The sliding ring
29
is always urged by the spring
32
to the ring
27
through their respective sliding contact surfaces perpendicular to the drive shaft. Accordingly, even if the sliding contact surface is worn, the ring
27
and the sliding ring
29
maintain their contacts, therefore, maintain sufficient sealing function.
(4) The inner wall surface
14
a
of the rear housing receives the thrust load by the reaction force of the piston
34
and regulates the position of the drive shaft
18
in the axial direction. The lug plate
36
is urged toward the thrust bearing
37
by the first coil spring while the compressor
10
stops. Accordingly, vibrations or noise due to shaking of the drive shaft
18
is prevented when the drive shaft
18
starts again. Because the relative movement between the seal ring
46
and the drive shaft
18
is prevented, foreign substances are prevented from entering between the seal ring
46
and the drive shaft
18
. Therefore, the seal ring
46
is prevented from deteriorating at an early stage of its use, and the endurance of the compressor is improved.
(5) The swash plate
38
is rotatable integrally with drive shaft
18
through the lug plate
36
fixed to the drive shaft
18
and the hinge mechanism
39
, and is inclinable with respect to the drive shaft
18
. The inclination angle of the swash plate
38
is adjusted simply in accordance with the pressure in the crank chamber
17
. Accordingly, the compressor
10
runs at its proper discharge capacity by the inclination angle of the adjustment of the swash plate which is accompanied by the cooling load.
(6) The control passage to introduce the discharge pressure to the crank chamber
17
is formed. The opening degree of the control passage is adjusted by the control valve
59
arranged in the control passage, and the pressure in the crank chamber
17
is adjusted. Accordingly, the pressure in the crank chamber
17
is adjusted easily by the control valve
59
.
(7) Compared to the conventional so called inner control valve having pressure sensitive mechanism such as bellows or a diaphragm which moves by the suction pressure and which adjusts an opening degree of the supply passage, the magnetic valve as the control valve according to the present invention smoothly adjusts its opening degree by using the external electric signals, thereby adjusting the pressure Pc in the crank chamber
17
.
(8) The control valve
59
is arranged in the rear housing, and isolated from the discharge chamber
20
formed in the front housing. Accordingly, the control valve
59
is not influenced by high temperature of the discharge gas. Therefore, the solenoid
65
is prevented from raising its temperature, and the control valve operates accurately.
(9) Since the control valve
59
is arranged at the downstream of the muffler
56
, the refrigerant supplied to the control valve
59
has substantially no pulsation, therefore prevents the valve from hunting. Accordingly, the pressure Pc in the crank chamber
17
is improved in accuracy.
(10) Since the muffler
56
is arranged between the discharge chamber in the front housing and the control valve in the rear housing which is preferably away from the discharge chamber, manufacture of the housing
11
and machining of the control passage between the muffler
56
and the crank chamber
17
through the control valve are performed easily.
(11) The sealing ring
46
arranged in the axial hole
22
to seal between the drive shaft
18
and the cylinder block
13
prevents the refrigerant gas in the crank chamber
17
from leaking through the axial hole
22
. As a result, the refrigerant gas in the crank chamber
17
bleeds into the suction chamber
19
only through the bleeding passage
60
. Therefore, the pressure in the crank chamber
17
is adjusted in high accuracy when the discharge capacity is changed.
(12) The orifice
61
is useful to restrict the bleeding gas amount because it is hard to machine the entire bleeding passage
60
with a predetermined diameter which should be severely provided when the compressor employs carbon dioxide as refrigerant gas which causes higher pressure in the housing than chloro-fluoro carbon.
(13) The clutchless compressor according to this embodiment is always driven, regardless of need of its operation, whenever the engine runs. However, this compressor generates no vibration and noise caused by clutch ON and OFF. Moreover, the power consumption is small for the reason mentioned in the effect (1).
(14) Since the lubricating passage or the control passage opens to the crank chamber
17
where the radial bearing
24
is provided, the oil mist involved in the gas lubricates the radial bearing
24
whenever the gas flows into the crank chamber through the passage.
(15) The control passage is applied as the lubricating passage. Accordingly, separate fabrication of the lubricating passage for the radial bearing
24
is not necessary.
(16) The first coil spring
45
isolates from the third coil spring
48
. Accordingly, each spring force of the coil springs
45
and
48
according to the embodiment is adjusted more easily than each spring force of the coil springs
45
and
48
formed integrally.
The present invention may be modified as follows.
The first coil spring
45
urging the drive shaft
18
against the inner wall surface
14
a
and the third coil spring
48
urging the swash plate
38
rearward to increase the inclination angle with respect to the drive shaft
18
may be integrally formed as a single coil spring
80
arranged between the thrust bearing
44
and the swash plate
38
, as shown in FIG.
3
. In this case the number of assembled parts is reduced, and time and process of assembling is also reduced. When the swash plate
38
is nearly in the maximum inclination angle state, the contact between the coil spring
80
and the swash plate
38
is removed. That is, when the compressive reaction force is the maximum, the coil spring
80
does not urge the swash plate
38
in the same direction as the reaction force. Accordingly, the drive force is reduced. The coil spring
80
may, however, always urge the swash plate
38
if so desired.
While the compressor
10
is driven, the thrust load is received by the rear housing through the first thrust bearing
37
. The second thrust bearing
44
prevents the front end of the coil spring
45
or
80
from being worn due to its sliding contact with the cylinder block
13
. The drive shaft
18
and the coil spring
45
or
80
rotate integrally and smoothly by the second thrust bearing
44
. The thrust bearing
44
which the front end of the coil spring
45
or
80
contacts can, however, be omitted. The coil spring
45
or
80
may be directly supported by a step portion of the axial hole
22
.
The orifice
61
of the bleeding passage
60
can be omitted when the bleeding passage
60
is formed at a predetermined diameter by which the bleeding amount is controlled.
The radial bearing
25
may be applied as an orifice by eliminating the sealing ring
46
in the axial hole
22
and adjusting the diameter of the axial hole
22
. In this case, the bleeding passage
60
is not needed.
The drive shaft
18
does not necessarily penetrate the suction chamber
19
. As shown in
FIG. 4
, an annular suction chamber
19
may be formed in the front housing
12
, and the through hole
61
for the drive shaft
18
may be formed inside the suction chamber
19
.
In order to change pressure in the crank chamber
17
a control valve may be disposed in the bleeding passage instead of the supply passage. The bleeding passage in this case is a control passage. As shown in
FIG. 5
, the control valve
59
controls an opening degree of the bleeding passage communicating the crank chamber
17
with the suction chamber
19
. Ps denotes pressure in the suction chamber
19
.
In the constitution that the control valve is arranged in the bleeding passage, a sealing ring
82
may be arranged in the recess
23
of the rear housing
14
, and a passage
83
may be formed to supply discharge pressure into the recess
23
, as shown in FIG.
6
. The discharge pressure is added to the rear end of the drive shaft
18
by the passage
83
. While the compressor
10
is being driven, the discharge pressure always acts on the rear end of the drive shaft
18
. Accordingly, force against the compressive reaction force increases, and reduction of the drive force is achieved. The control of the pressure Pc adjusted by the control valve does not have a bad influence, because the sealing ring
82
seals between the pressure in the crank chamber
17
and the discharge pressure. The sealing ring
82
may be arranged to seal between the crank chamber
17
and the radial bearing
24
.
According to
FIG. 4
, the drive shaft
18
, which is isolated from the suction chamber
19
or the discharge chamber
20
, protrudes from the housing
11
through the through hole
81
. The discharge chamber
20
may be arranged inside the suction chamber
19
. When the control valve is arranged in the bleeding passage, the control valve is easy to arrange, and the position of the arrangement may be selected from wide range.
The control valve
59
is not limited to a magnetic control valve, and may be a so-called internal control valve including a diaphragm or bellows as disclosed in Japanese Unexamined Patent Publication No. 6-123281. The diaphragm detects the suction pressure. The control valve adjusts the opening degree of the control passage by the movement of the diaphragm. In the clutchless type of compressor, however, a magnetic valve which is controllable in the exterior of the compressor is preferable.
The control valve is not limited to one disposed in either the supply passage or bleeding passage, but may be disposed in both the passage, as disclosed in Japanese Unexamined Patent Publication No. 10-54349.
As shown in
FIG. 7
, the supply passage
58
may open to the crank chamber at the first thrust bearing
37
. Accordingly, the first thrust bearing
37
is lubricated satisfactorily.
The lubricating passage may be formed separately from the control passage in order to lubricate the radial bearing
24
or the thrust bearing
37
satisfactorily. The lubricating passage may be arranged to communicate with the radial bearing
25
.
The control valve
59
may be arranged in the front housing
12
or in the cylinder block
13
.
The muffler
56
may be arranged in the front housing
12
, or in the rear housing where the control valve is provided.
The inclination angle of the swash plate
38
may be changed directly by an actuator such as an electric cylinder.
In the hinge mechanism shown in
FIG. 1
, the guide pin
42
having the spherical portion
42
a
moves in the cylindrical guide hole
41
. The hinge mechanism, however, is not limited to this constitution. The hinge mechanism may include a support arm, a swing arm and a guide pin. The support arm protrudes from the lug plate
36
and has a guide hole thereon. The swing arm is formed on the swash plate
38
to face the lug plate. The guide pin is fixed to the swing arm and inserted in the guide hole. The swash plate
38
is slidable on the drive shaft
18
and inclinable with respect to the drive shaft
18
because the guide pin slidably moves in the guide hole. The guide pin may be a simple cylindrical shape. This simple guide pin can be manufactured more easily than the guide pin having a spherical portion.
The swash plate
38
does not always need to be supported directly by the drive shaft
18
inserted in the through hole
38
a
of the swash plate
38
. The swash plate may be supported by a sleeve slidably mounted on the drive shaft. The sleeve may have a support shaft or a spherical surface inclinably supporting the swash plate.
The present invention may be applied not only to a variable displacement compressor but to a fixed displacement compressor. As shown in
FIG. 8
, a swash plate
84
is integrally rotatably fixed to the drive shaft
18
, and the swash plate
84
is supported by a compressor housing through a pair of thrust bearings
85
contacting respective boss portions of the swash plate
84
. In this case force due to the difference between the pressure in the crank chamber
17
and the atmospheric pressure acts on the drive shaft
18
against the compressive reaction force. Accordingly, the power consumption is reduced. A sealing ring
82
and a passage
83
shown in
FIG. 6
may be applied to the compressor in FIG.
8
. In this case the power consumption is further reduced.
The swash plate
84
does not need to be rotated integrally with the drive shaft
18
as a fixed displacement compressor. For example, as disclosed in Japanese Unexamined Patent Publication No. 10-159723, the swash plate may be supported to be rotatable relatively with respect to the drive shaft through a radial bearing and to incline with respect to the drive shaft at a predetermined angle, and the swash plate may be oscillated without rotating integrally with the drive shaft.
Not only carbon dioxide but chloro-fluoro carbon and the like are applied as refrigerant.
A lip seal may be applied as a shaft seal so that a sliding seal surface is a cylindrical surface of the drive shaft
18
. In this case, a slot to introduce lubricating oil to the sliding seal surface is preferably applied.
The present invention may be applied to a wobble type of variable displacement compressor.
Instead of the engine
51
a motor may be applied as a drive source driving a compressor provided in an electric or hybrid car for example. The compressor driven by the motor, even a fixed displacement compressor may not need a clutch between the motor and the compressor. The discharge capacity may be changed by adjusting rotational speed of the motor. Accordingly, the fixed displacement compressor functions substantially as a variable displacement compressor.
As mentioned before, the thrust load acting on the drive shaft is reduced, and the required power to drive the compressor is reduced by the present invention. The shaft seal between the pressure inside the compressor and the atmospheric pressure is also improved its own durability.
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 of the appended claims.
Claims
- 1. A single-headed piston type compressor comprising:a housing including a suction chamber, a discharge chamber and a crank chamber therein; a drive shaft rotatably supported by said housing, wherein a first end of said drive shaft protrudes from said housing, and a second end of said drive shaft is disposed within said housing, and the suction chamber of said housing is defined adjacent to the first end of said drive shaft such that said drive shaft penetrates the suction chamber and protrudes from said housing; a cylinder bore formed in said housing, said cylinder bore being located between the crank chamber and the first end of said drive shaft; a single-headed piston disposed in said cylinder, said piston being reciprocally movable therein; a cam plate mounted on and integrally rotating with said drive shaft in the crank chamber, said cam plate being operatively engaged with said piston, whereby rotational movement of said drive shaft is converted to reciprocating movement of said piston through said cam plate; and a shaft seal arranged between the suction chamber and the first end of said drive shaft, thereby sealing the suction chamber.
- 2. A single-headed piston type compressor according to claim 1 further comprising:a regulating surface formed in said housing, said regulating surface receiving an axial load by compressive reaction force of said piston and regulating said drive shaft positioning in the axial direction of said drive shaft; and a spring for urging said drive shaft to said regulating surface at least while the compressor stops.
- 3. A single-headed piston type compressor according to claim 2 further comprising means for controlling an inclination angle of said cam plate which is inclinably supported by said drive shaft, whereby a stroke of said piston is changeable in accordance with the control of said cam plate inclination angle.
- 4. A single-headed piston type compressor according to claim 3 further comprising:a rotor mounted on and integrally rotating with said drive shaft; and a hinge mechanism arranged between said rotor and said cam plate.
- 5. A single-headed piston type compressor according to claim 4, wherein said drive shaft is inserted in an axial hole formed in said housing, the axial hole communicating the crank chamber with the suction chamber, and wherein said shaft seal is mounted in the axial hole to seal clearance between said drive shaft and said housing.
- 6. A single-headed piston type compressor according to claim 4, wherein said spring urges and inclines said cam plate in the direction of increasing said cam plate angle with respect to a plane perpendicular to an axis of said drive shaft, at least when the inclination angle of said cam plate is minimum.
- 7. A single-headed piston type compressor according to claim 6, wherein said spring is released from its contact with said cam plate when the inclination angle of said cam plate is substantially maximum.
- 8. A single-headed piston type compressor according to claim 6, wherein a first end of said spring contacts a thrust bearing arranged between said drive shaft and said housing.
- 9. A single-headed piston type compressor according to claim 1 further comprising a control passage which communicates the discharge chamber and/or the suction chamber with the crank chamber; and a control valve disposed in said control passage, said control valve adjusting an opening degree of said control passage to adjust the pressure in the crank chamber.
- 10. A single-headed piston type compressor according to claim 9, wherein said control passage communicates the discharge chamber with the crank chamber.
- 11. A single-headed piston type compressor according to claim 10 further comprising a muffler chamber arranged at a downstream of the discharge chamber, wherein said control passage communicates said muffler chamber with the crank chamber.
- 12. A single-headed piston type compressor according to claim 11, wherein the discharge chamber, said muffler chamber and said control valve are arranged from a first end to a second end of said housing in the axial direction in turn.
- 13. A single-headed piston type compressor according to claim 9, wherein said control passage is a lubricant passage.
- 14. A single-headed piston type compressor according to claim 3, wherein the first end of said drive shaft is always operatively connected to a drive source.
- 15. A single-headed piston type compressor according to claim 1 further comprising:a lubricant passage communicating the suction chamber and/or the discharge chamber with the crank chamber; and a bearing supporting said drive shaft, said bearing being located in said lubricant passage.
- 16. A single-headed piston type compressor according to claim 1 further comprising a passage for adding discharge pressure to the second end of said drive shaft so that force due to the discharge pressure against compressive reaction force of said piston acts on said drive shaft.
- 17. A single-headed piston type compressor according to claim 1, wherein carbon dioxide is applied as refrigerant gas.
- 18. A single-headed piston type compressor comprising:a housing including a front housing, a rear housing and a cylinder block provided between the front and rear housings, the front housing having a suction chamber and a discharge chamber therein, the cylinder block and the rear housing defining a crank chamber therebetween; a drive shaft rotatably supported by said housing, said drive shaft having a first end protruding from the front housing and a second end disposed within said housing so that said drive shaft is urged frontward by pressure in said housing, wherein the suction chamber of said housing is defined adjacent to the first end of said drive shaft such that said drive shaft penetrates the suction chamber and protrudes from said housing; a cylinder bore formed in the cylinder block, said cylinder bore connecting the crank chamber to the suction and discharge chambers of the front housing; a single-headed piston reciprocally disposed in said cylinder bore; a cam plate mounted on said drive shaft within said crank chamber, said cam plate being coupled with said piston and integrally rotating with said drive shaft so that rotational movement of said cam plate reciprocates said piston in said cylinder bore; whereby compressive reaction force due to the piston reciprocation acts on said drive shaft rearward against the pressure in said housing; and a shaft seal arranged between the suction chamber and the first end of said drive shaft, thereby sealing the suction chamber.
- 19. A single-headed piston type compressor according to claim 18 further comprising a shaft seal sealing a clearance between the front housing and said drive shaft, said shaft seal being disposed in the suction chamber of said front housing.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-129891 |
Apr 2000 |
JP |
|
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
5000666 |
Esaki |
Mar 1991 |
A |
6158974 |
Tarutani et al. |
Dec 2000 |
A |
6213727 |
Kawaguchi |
Apr 2001 |
B1 |
6241483 |
Kato et al. |
Jun 2001 |
B1 |
6290470 |
Okuno et al. |
Sep 2001 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
2-153272 |
Dec 1990 |
JP |