Subaru LEGACY 2002 Quick Reference Index page 469

Mid-range-speed operation (B – D range)
During mid-range speed operation, the pump increases its delivery rate. Since the pressure before
passing through the variable orifice increases, the control valve moves rightward, overcoming the
tension of the control valve spring. This movement of the control valve allows the pressure up-
stream of the variable orifice to be directed to chamber A after being adjusted to a necessary pres-
sure* by the port opening area created by the control valve. On the other hand, chamber B
receives the reservoir pressure (suction pressure). This means that the pressure in chamber A is
higher than that in chamber B. As a result, the cam ring moves rightward against the tension of
the cam spring. This causes the delivery rate per rotation of the pump to be reduced, so that the
flow rate of the fluid to the steering gear box decreases accordingly.
The above control is performed when the pump is operating at a speed in the B – D range.
* The "necessary pressure" for chamber A is a pressure required to move the cam ring to the po-
sition corresponding to each predetermined flow rate (pump delivery rate). The pressure is ob-
tained by changing the port opening area appropriately through displacement of the control valve.
The displacement of the control valve is determined by how much the pressure before the variable
orifice is different from that after the orifice.
(1) Control valve
(2) Reservoir tank fluid
(3) Control valve spring
(4) Gear box
(5) Cam ring spring
POWER STEERING SYSTEM
(1)
(10)
(7)
(9)
Power Assisted System (Power Steering)
(2)
(3)
(6) Variable orifice
(7) Pressure chamber A
(8) Pressure chamber B
(9) Cam ring
(10) Opening area
PS-29
(4)
(5)
(6)
(8)
B4H2480A