Komatsu PC200-8M0 Shop Manual page 126

SEN06119-00
2) Action for the direction of maximizing the pump discharge
When the difference between the main pump
q
pressure (PP) and LS pressure (PLS), in other
wo r ds , L S d iff er e nti a l p re s s ur e ( d P L S)
becomes smaller (for example, when the area
of opening of the control valve becomes larger
and pump pressure PP drops), spool (6) is
pushed to the left by the combined force of LS
pressure (PLS) and the force of spring (4).
q When spool (6) moves, port (D) and port (E)
are interconnected and connected to the PC
valve.
q The PC valve is connected to the drain port, so
the pressure across circuits (D) and (K)
becomes drain pressure (PT). (The operation
of the PC valve is explained later.)
q The pressure at the large diameter end of
servo piston (12) becomes drain pressure
(PT), and pump pressure (PP) enters port (J)
at the small diameter end, so servo piston (12)
is pushed to the left side. Therefore, the swash
plate is moved in the direction to make the dis-
charge amount larger.
14
10-401
401 Hydraulic system, Part 1
If the output pressure of the EPC valve for the
q
LS valve enters port (G), rightward force is
generated on piston (7).
If piston (7) is pushed to the right, setting force
q
of spring (4) is weakened, changing the LS dif-
ferential pressure (dPLS) [Difference between
oil pressures (PLS) and (PP)] when ports (D)
and (E) of spool (6) are connected.
PC200, 200LC, 220, 220LC-8M0
Hydraulic pump