Lesson 2/Learning Event 1
In the neutral position, there is no force required of the power steering
system to turn the wheels; therefore, the fluid under pressure must be
bypassed through the system. This usually is accomplished in the control
valve. When there is no steering force required by the driver, the spool in
the control valve is centered by springs or hydraulic pressure or both.
This allows the oil to flow through the valve and back to the reservoir and
allows the steering system to maintain position.
Left and right turns
As the driver starts to turn the steering wheel to make a left or right
turn, the power steering system is activated. The spool is moved off center
position and forced to the left or right end of the control valve. This
opens the proper passageways for the pressurized oil. The return port is
also opened, and the fluid being displaced by the piston in the cylinder
returns to the reservoir.
In the linkage configuration, the control valve and power cylinder may be
separate parts mounted on different parts of the linkage.
The integral system incorporates the control valve and power assist into the
steering gear as a unit.
The control valve on the semiintegral system is mounted to the steering
gear, and a separate hydraulic cylinder is mounted to the linkage.