Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-10-28
2001-04-10
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
Reexamination Certificate
active
06213728
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor for vehicle air-conditioning.
FIG. 8
shows a prior art variable displacement compressor. A drive shaft is rotatably supported in the housing
101
, which encloses a crank chamber
102
. A lip seal
104
is located between the housing
101
and the drive shaft
103
to prevent leakage of fluid from the housing
101
.
An electromagnetic friction clutch
105
is located between the drive shaft
103
and the engine Eg, which serves as a power source. The clutch
105
includes a rotor
106
that is coupled to the engine Eg, an armature
107
that is fixed to the drive shaft
103
, and an electromagnetic coil
108
. When the coil
108
is excited, the armature
107
is attracted to and contacts the rotor
106
. In this state, power of the engine Eg is transmitted to the drive shaft
103
. When the coil
108
is de-excited, the armature
107
is separated from the rotor
106
, which disconnects the power transmission from the engine Eg to the drive shaft
103
.
A lug plate
109
is fixed to the drive shaft
103
in the crank chamber
102
. A thrust bearing
122
is located between the lug plate
109
and the housing
101
. A swash plate
110
is coupled to the lug plate
109
via a hinge mechanism
111
. The swash plate
110
is supported by the drive shaft
103
such that the swash plate
110
slides axially and inclines with respect to the axis L of the drive shaft
103
. The hinge mechanism
111
causes the swash plate
110
to integrally rotate with the drive shaft
103
. When the swash plate
110
contacts the limit ring
112
, the swash plate
110
is positioned at the minimum inclination position.
The housing
101
includes cylinder bores
113
, a suction chamber
114
, and a discharge chamber
115
. A piston
116
is accommodated in each cylinder bore
113
and is coupled to the swash plate
110
. A valve plate
117
partitions the cylinder bores
113
from a suction chamber
114
and a discharge chamber
115
.
When the drive shaft
103
rotates, the swash plate
110
reciprocates each piston
116
. Accompanying this, refrigerant gas in the suction chamber
114
flows into each cylinder bore
113
through the corresponding suction port
117
a
and suction valve
117
b,
which are formed in the valve plate
117
. Refrigerant gas in each cylinder bore
113
is compressed to reach a predetermined pressure and is discharged to the discharge chamber
115
through the corresponding discharge port
117
c
and discharge valve
117
d,
which are formed in the valve plate
117
.
An axial spring
118
is located between the housing
101
and the drive shaft
103
. The axial spring
118
urges the drive shaft
103
frontward (leftward in
FIG. 8
) along the axis L and limits axial chattering of the drive shaft
103
. A thrust bearing
123
is located between the axial spring
118
and an end surface of the drive shaft
103
. The thrust bearing
123
prevents transmission of rotation from the drive shaft
103
to the axial spring
118
.
A bleed passage
119
connects the crank chamber
102
to the suction chamber
114
. A pressurizing passage
120
connects the discharge chamber
115
to the crank chamber
102
. A displacement control valve, which is an electromagnetic valve, adjusts the opening size of the pressurizing passage
120
.
The control valve
121
adjusts the flow rate of refrigerant gas from the discharge chamber
115
to the crank chamber
102
by varying the opening size of the pressurizing passage
120
. This varies the inclination of the swash pate
110
, the stroke of each piston
116
, and the displacement.
When the clutch
105
is disengaged, or when the engine Eg is stopped, the control valve
121
maximizes the opening size of the pressurizing passage
120
. This increases the pressure in the crank chamber
102
and minimizes the inclination of the swash plate
110
. As a result, the compressor stops when the inclination of the swash plate
110
is minimized, or when the displacement is minimized. Accordingly, since the displacement is minimized, the compressor is started with a minimal torque load. This reduces torque shock when the compressor is started.
When the cooling load on a refrigeration circuit that includes the compressor is great, for example, when the temperature in a vehicle passenger compartment is much higher than a target temperature set in advance, the control valve
121
closes the pressurizing passage
120
and maximizes the displacement of the compressor.
Suppose that when the compressor is operating at maximized displacement, it is stopped by disengagement of the clutch
105
or by shutting off the engine Eg. In this case, the control valve
121
quickly maximizes the opening size of the closed pressurizing passage
120
to minimize the displacement. Also, when the vehicle is suddenly accelerated while the compressor is operating at maximum displacement, the control valve
121
quickly maximizes the opening size of the pressurizing passage
120
to minimize the displacement and to reduce the load applied to the engine Eg. Accordingly, refrigerant gas in the discharge chamber
115
is quickly supplied to the crank chamber
102
. Though some refrigerant gas flows to the suction chamber
114
through the bleed passage
119
, the pressure in the crank chamber
102
quickly increases.
Therefore, the swash plate
110
, when at a minimum displacement position (as shown by the broken line in
FIG. 8
) is pressed against a limit ring
112
. Also, the swash plate
110
pulls the lug plate
109
in a rearward direction (rightward in
FIG. 8
) through the hinge mechanism
111
. As a result, the drive shaft
103
moves axially rearward against the force of the axial spring
118
.
When the drive shaft
103
moves rearward, the axial position of the drive shaft
103
with respect to a lip seal
104
, which is held in the housing
101
, changes. Generally, a predetermined contact area of the drive shaft
103
contacts the lip seal
104
. Foreign particles such as sludge exist on the peripheral surface of the drive shaft
103
that is outside the predetermined contact area. Therefore, when the axial position of the drive shaft
103
with respect to the lip seal
104
changes, the sludge will be located between the lip seal
104
and the drive shaft
102
. This lowers the sealing performance of the lip seal
104
and may cause leakage of refrigerant gas from the crank chamber
102
.
When the operation of the compressor is stopped by the disengagement of the clutch
105
and the drive shaft
103
moves rearward, the armature
107
, which is fixed to the drive shaft
103
, moves toward the rotor
106
. The clearance between the rotor
106
and the armature
107
when the clutch
105
is disengaged is set to a small value, for example, 0.5 mm. Accordingly, when the drive shaft
103
moves rearward, the clearance between the rotor
106
and the armature
107
is eliminated, which causes the armature
107
to contact the rotating rotor
106
. This may cause noise and vibration or may transmit power from the engine Eg to the drive shaft
103
regardless of the disengagement of the clutch
105
.
When the drive shaft
103
moves rearward, each piston
116
, which is coupled to the drive shaft through the lug plate
109
and the swash plate
110
, also moves rearward. This moves the top dead center position of each piston
116
toward the valve plate
117
which may permit the pistons
116
to collide with the valve plate
117
. Since the control valve
121
maximizes the opening size of the pressurizing passage
120
during sudden accelerations of the vehicle while the compressor is operating, the rearward movement of the drive shaft
103
accompanying the control may cause the pistons
116
to repeatedly collide with the valve plate
117
. This generates noise and vibration.
To prevent the rearward movement of the drive shaft
103
, the force of the axial spring
118
can be increased. However, increasing the force of the axial spring
118
lowers the durability of the thrus
Adaniya Taku
Inaji Satoshi
Kato Keiichi
Kurakake Hirotaka
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho +
Morgan & Finnegan , LLP
Patel Vinod D
Walberg Teresa
LandOfFree
Variable displacement compressor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Variable displacement compressor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Variable displacement compressor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2468918