Subaru XT 1988 Service Manual page 542

3-2
AUTOMATIC TRANSMISSION AND DIFFERENTIAL
3) OPERATION OF EACH VALVE
(1) Pressure Regulator Valve
In the regulator valve, force "F L" generated by oil pump
pressure (line pressure) acts to the right, while force "FMF"
generated by the pressure modifier pressure, force "F
RIC"
and
spring force "Fs" act to the left.
If FL becomes larger than FM
F
+
F
R/C
+
Fs, the valve moves
toward the right, and passage
CD
communicates with passage
ell.
Hydraulic pressure is then applied to the control piston
of the oil pump, decreasing the oil pump discharge pressure.
As a result, oil pump pressure is adjusted to maintain an
equilibrium between FL and FMF
+
F
R/C
+
Fs.
With this valve, the discharge pressure of the oil pump is
adjusted to an optimum pressure (line pressure) corresponding
to the running conditions of the vehicle, so that oil pump
driving energy loss is reduced and gearshift shock is rei ieved.
Line pressure
x piston
Line pressure
F L (Force of line pressure)
pressure
Fs (Spring force)
FMF (Force of pressure modifier pressure)
FR/C (Force of reverse clutch pressure)
To oil pump To torque converter
control piston regulator valve
Fig. 43
28
L3·625