Komatsu PC88MR-10 Shop Manual page 136

10 Structure and function
Main pump
When the servo piston is balanced
When balanced
The stop position (= pump discharged volume) of servo piston (6) is determined by the position where the
thrust caused by pressure (PAVE) applied to spool (4) is balanced with the force of spring (2).
When swing gear pump pressure increases and decreases
The pressing force of spool (4) changes, and the pump discharged volume changes similarly to the
changes when (PAVE) increases or decreases.
When the PC-EPC valve is operating
PC-EPC valve changes output pressure corresponding to the input current from the controller to change
the pressing force of spool (5). As a result, the pump discharged volume changes similarly to the changes
when (PAVE) increases or decreases.
10-58 PC88MR-10