Komatsu PC500LC-10R Shop Manual page 281

10 STRUCTURE AND FUNCTION
When engine is in operation (other than swing and travel operations)
1.
Pressurized oil (PR) output from self-pressure reducing
valve (1) flows to variable back pressure solenoid valve
(3).
2.
Since drive signal (IS3) to variable back pressure solenoid
valve (3) is turned "ON", pressurized oil (PR) from self-
pressure reducing valve (1) that is flowing into spring
chamber (C) of variable back pressure valve (4) is drained
through variable back pressure solenoid valve (3).
3.
Only the reaction force of spring (5) acts on valve (6), and
pushes valve (6) to the right.
4.
Pressure (PA) in drain circuit (A) of the control valve acts
on the right end surface (area of diameter "d1") of valve (6)
and pushes valve (6) to the left.
5.
Valve (6) keeps balance so that the back pressure be-
comes (PA) in the following equation. PA = Reaction force
of spring (5) ) / Area of diameter "d1"
6.
The oil flow from drain circuit (A) of the control valve to
port (T) is adjusted to the set pressure of variable back
pressure valve (4).
MAIN RELIEF VALVE OF CONTROL VALVE
STRUCTURE OF MAIN RELIEF VALVE OF CONTROL VALVE
Sectional view
1: Spring
PC500LC-10R
COMPONENT PARTS OF HYDRAULIC SYSTEM
2: Poppet
A EP2 16 1 5
10-187