S0709730K
Page 6
Power Steering Unit
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CUSHION VALVE OPERATION
Function
The cushion valve absorbs any excessive peak pressure that my be generated during initial movement of
the steering wheel or during a change in steering direction. The cushion valve also prevents excessive
high pressure and shock that can result from steering load inertia.
Working Principle
If a high pressure oil is fed back to the port R, it pushes the spring (3) and opens the poppet (2). And this
operation directs the high pressure oil to the port L through the center hole in the spool (12) and the check
valve poppet in the port L part. At the same time, oil reaches the pressure room of the plug through the
orifice (8). This operation closes the passage from the port R to the port L. This releases the pressure and
prevents machine shock by intercepting oil. If a low pressure oil flows, the cushion operation is not
necessary. It is due that the speed of the closing the spool (12) is faster than the speed of the opening the
poppet (2), therefore, the cushion valve does not work.
Figure 4
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