Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2001-06-28
2003-12-16
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S269000
Reexamination Certificate
active
06663355
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor having single-headed pistons, which is used, for example, in a vehicular air conditioning system.
A variable displacement swash plate clutch compressor shown in
FIG. 8
has a solenoid clutch
101
, which can interrupt power transmission from a vehicular engine Eg. The compressor also has a displacement control mechanism, which can reduce the displacement so that the solenoid clutch is not be turned on and off frequently when the cooling load is low.
The displacement control mechanism has a swash plate
103
connected to pistons
102
through shoes
102
a
. A rotary support
105
is fixed to a drive shaft
104
. The swash plate
103
is connected to the rotary support
105
through a hinge mechanism
106
. The swash plate
103
is housed in the crank chamber
107
. The differential pressure between the crank chamber
107
and the cylinder bores
18
varies to change the inclination angle of the swash plate
103
. As the inclination angle of the swash plate
103
is changed, the stroke of each piston
102
is changed to change the displacement.
For example, when the pressure of the crank chamber
107
is increased to increase the difference between the pressure of the pressures of the cylinder bore
108
, the inclination angle of the swash plate
103
is reduced, which reduces the compressor displacement. In
FIG. 8
, the swash plate
103
indicated by the broken double-dashed line is at the minimum inclination position, where it abuts against a regulating ring
109
attached to the drive shaft
104
. When the internal pressure of the crank chamber
107
is reduced to reduce the differential pressure the cylinder bores
108
, the inclination angle of the swash plate
103
is increased to increase the compressor displacement.
Generally, in the step of compressing a refrigerant gas, the piston
102
, the swash plate
103
, the hinge mechanism
106
, the rotary support
105
and the drive shaft
104
transmit force to the internal wall surface of a housing
110
(leftward in
FIG. 8
) through a thrust bearing
111
due to the compression load on the piston
102
.
The internal pressure of the crank chamber
107
remains high so that the compressor can be started from the minimum displacement state, at which the load torque is minimized, even if the solenoid clutch is turned on soon after it is turned off. Further, control of the compressor displacement is performed to minimize the displacement, regardless of the cooling load, to reduce load of the engine Eg during rapid acceleration of the vehicle.
When the internal pressure of the crank chamber
107
is increased rapidly to minimize the displacement, the swash plate
103
may be pressed against the regulating ring
109
with excessive force, or the rotary support
105
may be pulled strongly to the rear side of the compressor through the hinge mechanism
106
. Thus, the drive shaft
104
is caused to slide or shift backward (rightward in
FIG. 8
) along the axis L.
Upon such movement of the drive shaft
104
, the top dead center position of the piston
102
shifts toward the valve plate
112
. Therefore, the piston
102
may impinge upon the valve plate
112
when reaching the top dead center position. This impingement causes vibrations and noise and may damage the pistons
102
or the valve plate
112
.
Also, when such backward movement of the drive shaft
104
takes place when the solenoid clutch
101
is turned off, an armature
101
a
of the solenoid clutch
101
moves toward a rotor
101
b
to eliminate a clearance between the armature
101
a
and the rotor
101
b
or to bring the armature
101
a
into contact with the rotor
101
b
, which causes rattling or vibration and unnecessary power transmission.
To solve the above problems, a spring
113
is located between the housing
110
and the drive shaft
104
. The spring
113
urges the drive shaft
104
axially forward.
Japanese Unexamined Patent Publication No. Hei 11-62824 discloses a compressor having a restricting member for restricting axial shifting of the drive shaft. The restricting member is located in a hole in which the rear end of the drive shaft is fitted. The hole communicates with a suction chamber through a space. A sealing member, which prevents communication between a crank chamber and the space through the hole is applied around the rear end of the drive shaft.
To securely prevent backward axial shifting of the drive shaft
104
shown in
FIG. 8
, it is essential to use a very stiff spring
113
. As a result, the thrust bearing
111
receives a great load from the spring
113
, which reduces the life of the thrust bearing
111
and increases the power loss of the compressor at the thrust bearing
111
. The increased power loss adversely affects the fuel consumption rate of the engine Eg that drives the compressor.
In the compressor disclosed in Japanese Unexamined Patent Publication No. Hei 11-62824, a sealing member is located in the hole in which the rear end of a drive shaft is supported. The sealing member prevents entry of refrigerant into the hole. Therefore, lubricant cannot be supplied fully to the radial bearing, which shortens the life of the bearing.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a variable displacement compressor having a simple constitution and being capable of maintaining sufficient lubrication of the radial bearing.
To achieve the above objective, the present invention provides a variable displacement compressor. The compressor comprises a housing having a suction chamber and a discharge chamber. A crank chamber is defined in the housing. A drive shaft has a front end and a rear end. The shaft is supported in the housing so that the front end protrudes from the housing. A cylinder block forms part of the housing. Cylinder bores are defined in the cylinder block. A valve plate assembly includes a suction port, a suction valve, a discharge port and a discharge valve for each cylinder bore. Single-headed pistons are housed in the cylinder bores, respectively. A drive plate is housed in the crank chamber and is connected to the pistons to convert rotation of the drive shaft into reciprocating motion of the pistons. The drive plate rotates integrally with the drive shaft. A control mechanism controls inclination of the drive plate by controlling the pressure of the crank chamber to change the volume of a refrigerant discharged from each cylinder bore into the discharge chamber. A radial bearing supports the rear end of the drive shaft. The refrigerant flows through the radial bearing. A holding bore houses the rear end of the drive shaft and the radial bearing. The holding bore is connected to a holding space. The holding space is defined by the valve plate assembly. A passage connects the holding space and the suction chamber. A restricting member is located in the holding space. The restricting member restricts axial movement of the drive shaft and divides the holding space into a first region and a second region. The first region and the second region communicate with each other. A clearance is formed between the drive shaft and the restricting member or between the restricting member and the valve plate assembly in a normal compressing operation. The clearance disappears when the pressure of the crank chamber is increased rapidly by the control mechanism.
The present invention also provides a variable displacement compressor. The compressor comprises a housing having a suction chamber and a discharge chamber. A crank chamber is defined in the housing. A drive shaft has a front end and a rear end. The shaft is supported in the housing so that the front end protrudes from the housing. A cylinder block forms part of the housing. Cylinder bores are defined in the cylinder block. A valve plate assembly includes a suction port, a suction valve, a discharge port and a discharge valve for each cylinder bore. Single-headed pistons are housed in the cylinder bores, respectively. A drive plate is housed in
Fukanuma Tetsuhiko
Kubo Hiroshi
Murase Masakazu
Nakayama Osamu
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Patel Vinod D.
Walberg Teresa
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