Komatsu Galeo PC800-8 Shop Manual page 138

Hydraulic excavator

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VC valve controls servo piston (4) position (pump

delivery) responding to the EPC valve output

pressure (controller command current).

Sleeve (2) moves to and stops at a position

where the EPC valve output pressure and the

force of spring (1) are balanced.

The large diameter end pressure is changed by

the changes of the opening area on the notches

(A) and (B) between sleeve (2) and spool (3) plus

by the switching of the connection port. As the re-

sult, servo piston (4) is moved.

Spool (3) is pressed against cam (8) by spring (7)

and feeds back the position of servo piston (4).

10 Structure, function and maintenance standard

Move of servo piston to the maximum side

As the EPC valve output pressure increases,

sleeve (2) compresses spring (1) to move up-

Port (A) of sleeve (2) and spool (3) is opened and

port (B) is closed.

Port (PS) on the large diameter side is connected

to the drain case.

Servo piston (4) is pressed toward the MAX side

by the pressure of port (PH) on the small diame-

Move of servo piston (4) toward the maximum

side is stopped at a position where it contacts

against the MAX adjustment screw (5).

PC800, 850-8

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