Komatsu PC500LC-10R Shop Manual page 250

COMPONENT PARTS OF HYDRAULIC SYSTEM
HI VALVE OF CONTROL VALVE
FUNCTION OF HI VALVE OF CONTROL VALVE
• By operating Lo valve and Hi valve simultaneously, the
opening of spool becomes double so that the pressure
loss is reduced and enough flow is secured.
• When the boom is raised, boom Hi valve operates simulta-
neously with boom Lo valve, and increases the flow to the
cylinder bottom side.
• When the arm is moved IN, arm Hi valve operates simulta-
neously with arm Lo valve, and increases the flow to the
cylinder bottom side.
• When the arm is moved OUT, arm Hi valve operates simul-
taneously with arm Lo valve, and decreases the flow from
the cylinder head side.
OPERATION OF HI VALVE OF CONTROL VALVE
Hi-valve looks as if it has only 1 spool, but it actually has divided 2 spools. The left side is the boom Hi-spool,
and the right side is the arm Hi-spool. The arm Hi-spool moves to both right and left, and the 2 spools are inde-
pendently controlled.
A
d
A: From boom Lo valve
10-156
1
E
5
c b
D
4
B: From arm Lo valve
10 STRUCTURE AND FUNCTION
Boon raise Arm digging
Arm dumpimg
Hi valve
Boon Hi Arm Hi
Bucket
R.H. Travel
Boom Lo
Swing
L.H. Travel
Arm Lo
2
B
C
3
A4P15732
a
A4P15733
PC500LC-10R