Variable displacement compressor

Details Variable displacement compressor Variable displacement compressor

1999-11-10

2001-06-05

Thorpe, Timothy S. (Department: 3746)

Pumps

Condition responsive control of drive transmission or pump...

Adjustable cam or linkage

C417S269000

Reexamination Certificate

active

06241483

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor for vehicle air-conditioning.
In a prior art variable displacement compressor shown in
FIG. 4
, a drive shaft
103
is rotatably supported in a housing
101
, which includes a crank chamber
102
. The front end (left end in
FIG. 4
) of the drive shaft
103
projects from the housing
101
and is coupled to an engine (not shown). A lip seal
104
is located between the housing
101
and the drive shaft
103
to prevent leakage of fluid along the surface of the drive shaft
103
.
A lug plate
117
is fixed to the drive shaft
103
in the crank chamber
102
. The lug plate
117
is coupled to a swash plate
105
via a hinge mechanism
116
. The swash plate
105
is supported by the drive shaft
103
to axially slide and incline with respect to the axis L of the drive shaft
103
. The hinge mechanism
116
causes the swash plate
105
to integrally rotate with the drive shaft
103
. A limit ring
106
is located on the drive shaft
103
. When the swash plate
105
abuts against the limit ring
106
, the swash plate
105
is at the minimum inclination position.
The housing
101
includes cylinder bores
107
, a suction chamber
108
, and a discharge chamber
109
. A piston
110
is accommodated in each cylinder bore
107
. Each piston
110
is coupled to the swash plate
105
. A valve plate
111
separates the cylinder bores
107
from the suction chamber
108
and the discharge chamber
109
.
When the drive shaft
103
is rotated by a vehicle engine, the swash plate
105
reciprocates the pistons
110
. This draws refrigerant gas from the suction chamber
108
to the corresponding cylinder bore
107
via a suction port
111
a
and a suction valve
111
b,
which are formed in the valve plate
111
. Refrigerant gas in the cylinder bore
107
is compressed to reach a predetermined pressure and is discharged to the discharge chamber
109
via a discharge port
111
c
and a discharge valve
111
d,
which are formed in the valve plate
111
.
An axial spring
112
is located between the housing
101
and the drive shaft
103
. The axial spring urges the drive shaft
103
in the frontward direction (leftward in
FIG. 4
) and prevents axial chattering of the drive shaft
103
.
A bleed passage
113
connects the crank chamber
102
to the suction chamber
108
. A pressurizing passage
114
connects the discharge chamber
109
to the crank chamber
102
. A displacement control valve
115
, which is an electromagnetic valve, adjusts the opening size of the pressurizing passage
114
.
The displacement control valve
115
adjusts the flow rate of refrigerant gas from the discharge chamber
109
to the crank chamber
102
, which varies the pressure in the crank chamber
102
. This varies the inclination of the swash plate
105
, the stroke of the pistons
110
, and the compressor displacement.
When there is a relatively great cooling demand on a refrigeration circuit that includes the compressor of
FIG. 4
, for example, when the temperature in a passenger compartment of a vehicle is much higher than a target temperature set in advance, the control valve
115
closes the pressurizing passage
114
and maximizes the compressor displacement.
In this state, when the cooling demand decreases, the control valve
115
quickly and fully opens the closed pressurizing passage
114
. Also, when the vehicle is suddenly accelerated while the compressor is operating at the maximum displacement, the control valve
115
quickly and fully opens the pressurizing passage
114
to minimize the displacement to reduce the load applied to the engine.
Accordingly, refrigerant gas in the discharge chamber
109
is quickly supplied to the crank chamber
102
, which rapidly increases the pressure in the crank chamber
102
to a high pressure level. Since the amount of refrigerant gas that flows to the suction chamber
108
through the bleed passage
113
is limited, the pressure in the crank chamber
102
quickly increases.
Therefore, the swash plate
105
(as shown by the broken line in
FIG. 4
) is pressed against the limit ring
106
by a relatively great force when at the minimum inclination position. The swash plate
105
consequently pulls the lug plate
117
in the rearward direction (rightward in
FIG. 4
) via the hinge mechanism
116
. As a result, the drive shaft
103
moves axially against the force of the axial spring
112
.
When the drive shaft
103
moves rearward, the pistons
110
, which are coupled to the drive shaft
103
via the swash plate
105
, also move rearward. Therefore, the top dead center positions of the pistons
110
move toward the valve plate
111
, which may cause the pistons
110
to repeatedly collide with the valve plate
111
. This generates noise and vibration.
When the drive shaft
103
moves rearward, the axial position of the drive shaft
103
relative to the lip seal
104
, which is retained in the housing
101
, changes. Normally, a predetermined annular area of the drive shaft
103
contacts the lip seal
104
. Foreign particles and sludge adhere to a surface of the drive shaft
103
that is axially adjacent to the predetermined annular area. Therefore, if the axial position of the drive shaft
103
relative to the lip seal
104
changes, sludge enters between the lip seal
104
and the drive shaft
103
. This lowers the effectiveness of the lip seal
104
and results in gas leakage from the crank chamber
102
.
An objective of the present invention is to provide a variable displacement compressor that prevents the pressure in the crank chamber from increasing to an excessive degree.
To achieve the above objective, the present invention provides a variable displacement compressor compressing gas supplied from an external circuit and returning the gas to the external circuit. The compressor comprises a housing, a cylinder bore formed in the housing, a crank chamber formed in the housing. A suction chamber is formed in the housing such that the suction chamber is connected with the external circuit. Gas is supplied from the external circuit to the suction chamber. A discharge chamber is formed in the housing. A valve plate separates the cylinder bore from the suction chamber and the discharge chamber. A piston is accommodated in the cylinder bore. The piston draws gas from the suction chamber to the cylinder bore via the valve plate. The piston discharges gas, which has been compressed in the cylinder bore, to the discharge chamber via the valve plate. A drive shaft is supported in the housing. A drive plate is coupled to the piston for converting rotation of the drive shaft to reciprocation of the piston. The drive plate is supported on the drive shaft. The drive plate moves between a maximum inclination position and a minimum inclination position in accordance with the pressure in the crank chamber. The inclination of the drive plate determines the piston stroke and the displacement of the compressor. A pressure control mechanism controls the pressure in the crank chamber to change the inclination of the drive plate. A discharge passage passes through the housing and the valve plate to connect the discharge chamber to the external circuit. Gas is sent from the discharge chamber to the external circuit through the discharge passage. A check valve is located on the valve plate to selectively open and close the discharge passage. The check valve is a reed valve. The check valve checks gas flow from the external circuit to the discharge chamber.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.


REFERENCES:
patent: 4011029 (1977-03-01), Shimizu
patent: 5129792 (1992-07-01), Abousabha
patent: 5871337 (1999-02-01), Fukanuma et al.
patent: 10-153175 (1998-06-01), None
patent: 10-205446 (1998-08-01), None

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