9-5 Sport Wagon (9600) L4-2.3L Turbo (B235) (2003)
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The pump element consists of a rotor containing a number of slots, a vane for each slot, a pump casing and two end plates with inlet and outlet ports
for the power steering fluid.
Due to the oval shape of the pump casing, the volume between the vanes increases and decreases twice during each revolution of the rotor. Inlet ports
lead to the areas in which the volume increases and outlet ports lead from those in which the volume decreases, thereby producing a pumping effect.
Apart from being forced outwards by centrifugal force, the vanes are also pressed outwards against the pump casing by the pressure of the fluid. The
fluid is directed into the slots inside the vanes.
Pressure and flow control
The purpose of the control valve is to regulate the flow from the pump so that it remains constant, regardless of engine pump rpm.
One side of the control valve is in direct contact with the delivery side of the pump (A). The outlet (B) from the pump incorporates a restriction from
which a connecting line (1) leads to the other side of the valve, which is fitted with a spring (2). When not actuated, the valve is pressed against the
outlet side.
Inside the control valve is an overflow valve (3) which, when the pressure exceeds a certain limit, is actuated by the pressure of the power steering
fluid on the spring-loaded side of the control valve.
For the control valve to operate, a certain amount of power steering fluid must circulate through it continuously at (A) and (C), although not when the
steering wheel is at full lock.
The pump delivers a maximum pressure of about 120 bar and a maximum flow of about 7.2 L per minute.
Steering and parking at low engine speed
