Komatsu ecot3 PC300LC-8 Shop Manual page 176

SEN01994-01
Quick return valve
1. When arm OUT
Function
When arm OUT, large volume of oil returns
q
from the cylinder bottom.
q Reduces this pressure loss.
Operation
q When the arm OUT is operated, pilot spool (1)
is pushed under the pilot pressure from the
PPC valve.
q Pressurized oil in chamber (b) inside the valve
is drained via orifice (c).
q Pressurized oil of the arm bottom side flows to
o
orifice (a) chamber (b)
(T), and the pressure in chamber (b) lowers.
If the pressure of chamber (b) drops lower than
q
that of port (A), pressure receiving force of the
pressure receiving portion [
d ia m e t e r a r e a ) ] o n t h e s i d e o f p o r t ( A )
50
o o
orifice (c) drain
φ
d2 area (S2) (seat
10 Structure, function and maintenance standard
increases by the sum of the pressure receiving
force of pressure receiving portion[
(S1)] on the chamber (b) side of valve (2) and
the spring force.
φ
Or ( d2 pressure receiving force >
q
sure receiving force + spring force)
q Valve (2) is pressed to the left and pressurized
oil is led from port (A) to (B).
From port (B), pressurized oil is drained
q
directly to the tank.
φ
d1 area
φ
d1 pres-
PC300, 350-8