Subaru 2002 Impreza Service Manual page 364

POWER STEERING SYSTEM
Power Assisted System (Power Steering)
During a turn
When the steering wheel is turned, the power steering system starts the steering assist function
and the fluid pressure increases.
Although the pressure of the fluid entering chamber B through the pressure sensing holes in the
valve body increases, the pump delivery pressure is still higher than the chamber B pressure.
So, the flow control valve cannot move leftward.
The fluid in chamber B then enters chamber A at the right end of energy-saving valve piston and
increase the pressure of chamber A.
Since the pressure in chambers A and B is higher than the pressure (ambient pressure) in cham-
ber C at the left end of the energy-saving valve piston, the energy-saving valve piston moves
leftward, overcoming the force of the energy-saving valve spring.
Leftward movement of the energy-saving valve piston compresses the flow control valve spring.
The combination of the tension of the spring and the pressure in chamber B now causes the flow
control valve to move leftward, overcoming the fluid pump delivery pressure. As a result, the flow
control valve closes the passage to the fluid pump suction port and the passage in the metering
orifice opens wider. This enables the fluid delivered by the pump to be supplied to the steering
gear box at the same rate as in the system without an energy-saving valve mechanism.
(8)
NF0303
(A) From fluid pump delivery port (1 ) Metering orifice (7) Low-pressure hole in energy-sav-
(B) To steering gear box (2) Flow control valve (8) Low-pressure hole in valve body
(C) To fluid pump suction port (3) Energy-saving valve piston (9) ChamberC
(4) Energy-saving valve spring (10) Chamber
B
(5) Pressure sensing hole in piston
(11)
Pressure sensing holes in the
valve body
(6) ChamberA
-
ing valve
PS-20