Subaru SVX 1992 Manual page 945

AUTOMATIC AIR CONDITIONING SYSTEM
[nnaoo] 4-7
(1) Variable delivery mechanism
The piston delivery is changed when the hinge ball slides
on the drive shaft. As the hinge ball slides, the inclination
angle "a" of the wobble plate changes. That is, as the
wobble plate tilts down, the effective piston stroke
increases, and this results in increased piston delivery.
Contrary, as the wobble plate rises, the effective piston
stroke decreases, and this results in reduced piston
delivery .
Thrust bearing
~
i ~t Fi 07`j
1
~
u
.J
Tu
p
J
~,1 /
Liu
Drive shaft
_ fl
Thrust flange
Link
\ Hinge ball
Piston
e
m
St
L Wobble plate
C4-1013
Fig. 2
(2) Operating principle
The wobble plate inclination angle is determined by the
equilibrium of the force caused by the discharge and
suction pressure acting on the piston top and the force
caused by the wobble chamber pressure acting on the
underside of the piston .
The wobble chamber pressure is determined by the
opening of the solenoid valve in the cylinder (valve
stroke).
Valve
stroke -~ ry` P°'
Ps
u.
Pd - ~ '
C41014
Fig . 3
(3) Control of solenoid valve
Fig. 4
The valve opening force is created by the suction pres-
sure (Ps) while the valve closing force originates from the
spring and solenoid activating current. The spring set
force is constant . The pressure (Pw) in the wobble cham-
ber is varied by changing the amount of solenoid valve
input current.
As the solenoid valve input current is increased, the valve
opening decreases. As a result, the pressure (Pw) in the
wobble chamber increases, and the wobble plate tilt
angle decreases, which in turn decreases the compres-
sor delivery .
Contrary, if the solenoid valve input current is reduced,
the valve opening increases, and the wobble chamber
pressure (Pw) decreases. This results in a reduced wob-
ble plate tilt angle and increased compressor delivery .
The solenoid valve input current is continuously con-
trolled by the auto control unit .
Fig. 5
Pd : Discharge pressure
Ps : Suction pressure
Pw: Wobble chamber pressure (Blow by from discharge
pressure + pressure from orifice)
3