Variable displacement compressor

Details Variable displacement compressor Variable displacement compressor

2000-03-14

2001-11-20

Walberg, Teresa (Department: 3742)

Pumps

Condition responsive control of drive transmission or pump...

Adjustable cam or linkage

Reexamination Certificate

active

06318971

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor for air-conditioning vehicles that compresses refrigerant gas and varies the displacement.
FIG. 8
shows an example of the variable displacement compressor (later simply called compressor). A crank chamber
102
is formed in a housing
101
, in which a drive shaft
103
is supported. A lip seal
104
is located between the housing
101
and the drive shaft
103
.
The drive shaft
103
is connected to a vehicle engine Eg through an electromagnetic clutch
105
. The clutch
105
includes a rotor
106
coupled to the engine Eg, an armature
107
fixed to the drive shaft
103
, and an electromagnetic coil
108
. The coil
108
, when excited, causes the armature
107
to be attracted to the rotor
106
, which engages the armature
107
with the rotor
106
. This transmits power from the engine Eg to the drive shaft
103
. At this time, the clutch
105
is engaged. When the coil
108
is de-excited, the armature
107
is separated from the rotor
106
, which disconnects power transmission from the engine Eg to the drive shaft
103
. At this time, the clutch
105
is disengaged.
A lug plate
109
is fixed to the drive shaft
103
in the crank chamber
102
. A swash plate
110
is coupled to the lug plate
109
through a hinge mechanism
111
and integrally rotates with the drive shaft
103
. The inclination angle of the swash plate
110
relative to the axis L of the drive shaft
103
is varied. A snap ring
112
is secured to the drive shaft
103
to abut against the swash plate
110
and to limit its minimum inclination angle.
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
to reciprocate. Each piston is coupled to the swash plate
110
. A valve plate
117
is located in the housing
101
. The valve plate
117
separates the adjacent cylinder bores
113
from the suction chamber
114
and from the discharge chamber
115
.
Rotation of the drive shaft
103
is converted into reciprocation of each piston
116
through the lug plate
109
, the hinge mechanism
111
, and the swash plate
110
. This draws refrigerant gas from the suction chamber
114
to the cylinder bores
113
through suction ports
117
a
and suction valves
117
b
of the valve plate
117
. Refrigerant gas is compressed in each cylinder bore
113
and discharged to the discharge chamber
115
through discharge ports
117
c
and discharge valves
117
d
of the valve plate
117
.
A spring
118
is located between the housing
101
and the drive shaft
103
. The spring
118
urges the drive shaft
103
toward the front (left in
FIG. 1
) of the compressor along the axis L and absorbs dimensional tolerance of parts, which prevents chattering.
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 control valve
121
includes a solenoid and varies the opening size of the pressurizing passage
120
. The control valve
121
operates depending on the passenger compartment temperature, a target temperature, disengagement of the clutch
105
, the state of the engine Eg, and the like.
The control valve
121
varies the size of a valve opening to control the flow rate of gas in the pressurizing passage
120
, which supplies high-pressure refrigerant gas to the crank chamber
102
. The pressure in the crank chamber is varied by the relationship between the supply of refrigerant gas to the crank chamber
102
and the release of refrigerant gas from the crank chamber
102
. This varies the difference between the pressure in the crank chamber
102
and the pressure in the cylinder bores
113
, which varies the inclination of the swash plate
110
. As a result, the stroke of the pistons
116
is varied, which adjusts the displacement.
When the clutch
105
is disengaged or when the engine Eg stops, the control valve
121
maximizes the size of the valve opening. This increases the pressure in the crank chamber
102
and the difference of the pressure in the crank chamber
102
and the pressures in the cylinder bores
113
, which reduces the inclination of the swash plate
110
. As a result, inclination of the swash plate
110
is minimized when the compressor is stopped. Therefore, the compressor is restarted with a minimum torque load, and less shock is produced.
However, in this prior art compressor, when the temperature in the passenger compartment is much higher than the target temperature, that is, when the cooling requirement is great, the control valve
121
closes the pressurizing passage
120
and maximizes the compressor displacement.
Suppose that the compressor operated is stopped by the disengagement of the clutch
105
or the shutting off of the engine Eg when operating at maximum development. Also, suppose that a controller minimizes the compressor displacement despite the cooling requirement to reduce the torque load on the engine Eg when the vehicle is suddenly accelerated.
In this case, the closed pressurizing passage
120
is suddenly opened to minimize the displacement. Accordingly, high-pressure refrigerant gas in the discharge chamber
115
is quickly supplied to the crank chamber
102
, and the bleed passage
119
does not release the extra gas sufficiently, which increases the pressure in the crank chamber
102
excessively. As a result, the difference between the pressure in the cylinder bores
113
and the pressure in the crank chamber
102
is excessive.
Therefore, the swash plate
110
(shown by the broken line in
FIG. 8
) is forcefully abutted against the snap ring
112
, which strongly draws the lug plate
109
rearward through the hinge mechanism
111
. As a result, a strong rearward force is applied to the drive shaft
103
, which moves the drive shaft
103
against the force of the spring
118
.
When the drive shaft
103
moves rearward, the contact area between the lip seal
104
and the drive shaft
103
may shift. There may be foreign particles like sludge on the surface of the drive shaft
103
at the new contact area. Therefore, the sludge may enter between the lip seal
104
and the drive shaft
103
, which degrades the performance of the lip seal
104
and causes gas leakage.
When the compressor is disengaged from the engine Eg 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 very small (0.5 mm, for example). The rearward movement of the drive shaft
103
eliminates the clearance between the rotor
106
and the armature
107
, which causes the armature
107
to contact the rotating rotor
106
. This causes noise and vibration and transmits power to the compressor.
The rearward movement of the drive shaft
103
during the acceleration of the vehicle moves the pistons
116
and the swash plate
110
rearward, which moves the top dead centers of the pistons
116
rearward. Accordingly, the pistons
116
collide against the valve plate
117
when the pistons
116
reach their top dead center positions. This causes noise, vibration, and damage to the pistons
116
and the valve plate
117
.
To prevent the rearward movement of the drive shaft
103
, it is possible to increase the force of the spring
118
. However, this decreases the life of a thrust bearing
122
, which receives the increased force, and increases power losses.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a variable displacement compressor that prevents sudden increase of the difference between the pressure in the crank chamber and the pressure in the cylinder bores.
To achieve the above objective, the present invention provides a variable displacement compressor that draws, compresses, and discharges refrigerant gas. The compressor is structured as follows. A housing includes a crank chamb

Affiliated with

Also associated with

Rating

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.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2571841