Komatsu Galeo PC138US-8 Shop Manual page 116

SEN02548-01
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 differ ential press ure ( P LS)
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 right by the combined force of
LS pressure (PLS) and the force of spring (4).
When spool (6) moves, port (D) and port (E)
q
are interconnected and connected to the PC
valve.
The PC valve is connected to the drain port, so
q
the pressure across circuits (D) and (K)
becomes drain pressure (PT). (The operation
of the PC valve is explained later.)
The pressure at the large diameter end of
q
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 right side. Therefore, the
swash plate is moved in the direction to make
the delivery larger.
16
10 Structure, function and maintenance standard
PC138US, USLC-8