Cushion Valve - Komatsu WA250-6 Shop Manual

300 Steering system

Cushion valve

Cushion valve

A: From steering cylinder left turning port
B: From steering cylinder right turning port
1. Valve seat
2. Valve body
3. Spring
4. Poppet
5. Orifice
6. Plug
7. Spring
8. Spool
9. Plug
10. Spring
11. Poppet
WA250, 250PZ-6
Outline
If sudden increase or bouncing occurs in oil
q
pressure of the steering cylinder circuit, this
valve mitigates the impacts by releasing the
highly pressurized oil to instantly to other line.
Function
As highly pressurized oil rushed into port (A), it
q
compresses spring (3) and opens poppet (4) of
port (A) side, then flows through the center
groove of spool (8) up to port (B) opening pop-
pet (11) of port (B) side.
At the same time, the highly pressurized oil
q
flows to the pressure chamber of plug (6)
through orifice (5) of port (A) side. Then over-
coming the port (B) side pressure and repul-
sive force of spring (7), it pushes spool (8) in
the right direction, cutting off the flow of oil from
port (A) to port (B).
Temporary flow of oil to the cushion valve
q
works as cushioning effects in mitigating the
steering impacts. After the operation of the
cushion valve is completed, the steering func-
tions as usual.
If the pressure change on the steering cylinder
q
circuit is gradual, spool (8) cuts off the circuit
before poppet (4) opens. Thus, the cushion
valve remains inactivated.
SEN03827-01
1
17
10-300