Komatsu PC500LC-10R Shop Manual page 279

10 STRUCTURE AND FUNCTION
5.
When pressure in chamber (b) becomes lower than that in port (A), the receiving pressure of pressure re-
ceiving portion "diameter d2 area (S2)(seat diameter area)" on the port (A) side becomes larger than the
total of receiving pressure of "diameter d1 area (S1)" of pressure receiving portion on the (b) chamber side
of the valve (2) and the reaction force of the spring.
6.
That is; (diameter d2 receiving pressure>diameter d1 receiving pressure + reaction force of the spring).
7.
Valve (2) moves to the left, and pressurized oil flows from port (A) to port (B).
8.
The pressurized oil on the arm cylinder bottom side is drained from port (B) directly to the tank.
When arm is in "NEUTRAL"
1.
When the Arm is returned from DUMP to NEUTRAL operation, the pilot pressure from the PPC valve is
shut off.
2.
The pressurized oil which is sent from the orifice (a) of the valve (2) and drained is hold by the pilot piston
(1).
3.
The holding pressure of the arm cylinder bottom side acts rightward on the left side of the area of the ring
formed by the difference between area (S2) of valve (2) and area (S1).
4.
The combined force of the force acting rightward on the area of the ring and the reaction force of spring (3)
moves valve (2) to the right, and port (A) and port (B) are disconnected.
PC500LC-10R
COMPONENT PARTS OF HYDRAULIC SYSTEM
AEP21612
10-185