3-4
3
PISTON PUMP
FUNCTION
Relief valve and solenoid valve
If the oil pressure discharged from the pump P4 (2) be-
comes higher than the set value, the relief valve (1) releases
the oil into the tank circuit. In this way, the relief valve (1)
keeps the pressure in the pilot circuit constant.This pilot
pressure is turned of or off by the solenoid valve A, used
to switch the 2nd speed, and the solenoid valve B, used to
switch the lever lock.
Solenoid valve
When the solenoid valve is not energized
The oil in the port P is blocked by the spool (1).
Since the port A is connected with the port T, the pressure
in the downstream pilot circuit becomes equal to the tank
pressure.
When the solenoid valve is energized
A magnetic field is generated around the coil that causes
the plunger (2) to be pulled downward and the spool (1)
to be pushed down. In this way, the oil in the port A flows
to the port A, transferring the pressure to the downstream
pilot circuit.
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