Operation Of Unload Valve And Ls Pressure - Komatsu PC500LC-10R Shop Manual

10 STRUCTURE AND FUNCTION

OPERATION OF UNLOAD VALVE AND LS PRESSURE

Operation of unload valve and LS pressure
• When lever is in NEUTRAL
When lever is in NEUTRAL, spool is closed and the oil in
pump circuit has no where to go, so it opens unload valve
(2) and drain to the tank (unload pressure). LS pressure
(PLS) transmitted to the spring chamber is drained to the
tank through LS bypass valve (3), and it become to 0 MPa.
Note) The pressure is for PC200-10
• When lever is operated (before relief)
When lever is operated, spool opens and cylinder is acti-
vated. LS pressure (PLS) is transmitted to the spring
chamber of unload valve (2), and it is closed by LS pres-
sure + set pressure {spring force (F)}.
PC500LC-10R
1
PP
3.9MPa
3.9MPa
PLS
13MPa
1
PP
15MPa
3.9MPa
CLSS
3
2
F PLS
+
0MPa
A4P15702
2
F PLS
+
13MPa
A4P15703
10-79