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When valve is in fine control range
(when control lever is returned)
When disc (5) begins to return, spool (1) is pushed up by the force of centering spring (3) and the pressure
in port (P1).
Fine control hole (f) is connected to drain chamber (D), and the pressurized oil in port (P1) is released.
When the pressure in port (P1) decreases too much, spool (1) is pushed down by metering spring (2).
Fine control hole (f) is disconnected from drain chamber (D) and connected to pump pressure chamber
(PP) almost at the same time.
The pump pressure is supplied until the pressure in port (P1) recovers to the pressure corresponding to
the lever position.
When the spool of control valve returns, the pressurized oil in drain chamber (D) flows in through fine
control hole (f') in the valve on the side that is not operated. The oil passes through port (P2) and flows into
chamber (B) to replenish the port with pressurized oil.
PC88MR-10
10 Structure and function
Work equipment and swing PPC valve
10-135
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