Komatsu ecot3 PC300LC-8 Shop Manual page 118

SEN01993-00
(2) When load on actuator is large and pump discharge pressure is high
Outline
q When the load is large and pump discharge
pressures (PP1) and (PP2) are high, the force
pushing spool (3) to the right becomes larger
and spool (3) will be moved to the position
shown in above figure.
q Part of the pressure to be conducted from port
(C) to LS valve flows from port (B) to port (C)
and (D) via LS valve. At the end this flow, level
of this pressure becomes approximately half of
the main pump pressure (PP2).
22
10 Structure, function and maintenance standard
Operation
q When port (E) and port (G) of the LS valve are
connected, this pressure from port (J) enters
the large diameter end of servo piston (9),
stopping servo piston (9).
q If main pump pressure (PP2) increases further
and spool (3) moves further to the right, main
pump pressure (PP1) flows to port (C) and acts
to make the pump delivery the minimum.
q When servo piston (9) moves to the right,
springs (4) and (6) are compressed and push
back spool (3).
When spool (3) moves to the left, the opening
q
of port (C) and port (D) becomes larger.
q As a result, the pressure on port (C) (= J) is
decreased and the rightward move servo pis-
ton (9) is stopped.
q The position in which servo piston (9) stops at
this time is further to the right than the position
when pump pressures (PP1) and (PP2) are
low.
PC300, 350-8