Komatsu ecot3 PC300LC-8 Shop Manual page 110

SEN01993-00
2) Action for the direction of maximizing the pump delivery
When the difference between the main pump
q
pressure (PP) and LS pressure (PLS), in other
words, LS differential pressure (EPLS)
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 Structure, function and maintenance standard
If the output pressure of the EPC valve for the
q
LS valve enters port (G), rightward force is
generated on piston (7).
q If piston (7) is pushed to the right, setting force
of spring (4) is weakened, changing the LS dif-
ferential pressure (EPLS) [Difference between
oil pressures (PLS) and (PP)] when ports (D)
and (E) of spool (6) are connected.
PC300, 350-8