Komatsu PC200-8M0, Shop Manual, Page: 190 / 1254

SEN06120-00
10-402
48
PC200, 200LC, 220, 220LC-8M0
402 Hydraulic system, Part 2
Functions and operation by valve
Arm quick return valve
Function
q
Large amount of oil is returned from the cylinder bottom when arm OUT operation is performed.
q
The valve reduces this pressure loss.
Operation
In arm “OUT” operation
q
In arm “OUT” operation, the pilot pressure from the PPC valve pushes pilot piston (1).
q
The pressurized oil in chamber (b) inside the valve is drained through orifice (c).
q
The pressurized oil of the arm cylinder bottom side flows from orifice (c) to drain port (T) through orifice
(a) and chamber (b).
q
Chamber (b) and drain port (T) are interconnected, and the pressure of chamber (b) drops.
q
If the pressure in chamber (b) drops lower than that of port (A), the force exerted on the pressure receiv-
ing surface of [Area (S2) of
f
d2 (surface of seat diameter)] on the port (A) side exceeds the combined
force of the force exerted on the pressure receiving surface [Area (S1) of
f
d1] on the chamber (b) side
of valve (2) and the spring force.
q
The result is, (Force exerted on surface of
f
d2 > Force exerted on surface of
f
d1 + Force of spring).
q
Valve (2) is pressed to the right and pressurized oil flows from port (A) to port (B).
q
The pressurized oil of the arm cylinder bottom side is drained directly to the tank from port (B).