Subaru 2002 Impreza Service Manual page 363

POWER STEERING SYSTEM
Power Assisted System (Power Steering)
0
During straight-ahead driving
The speed of the fluid pump increases and the fluid pressure becomes high. The metering ori-
fice does not allow whole fluid to pass through it any longer.
Since the amount of the fluid flowing toward the left end of the flow control valve is larger than
the amount of the fluid flowing toward the right end of the valve passing through the pressure
sensing holes, pressure
P1
becomes larger than pressure
P2.
As a result, pressure
P1
overcomes the force of the flow control valve spring and pushes the
valve rightward. This keeps the passage to the fluid pump suction port open, allowing part of
the fluid to return to the pump suction port and thus reducing flow of fluid to the steering gear
box.
The energy-saving valve mechanism reduces the fluid pump delivery pressure in this way when
steering power assistance is unnecessary, thus reducing load on the engine.
NF0302
I'
(A) From fluid pump delivery port
(B) To steering gear box
(C) To fluid pump suction port
(1) Metering orifice
(2)
Flow control valve
(3) Flow control valve spring
PS-19