Komatsu PC88MR-10 Shop Manual page 131

Control of discharged volume
When the swash plate angle (a) increases, the difference between volumes (E) and (F) increases and also
pump discharged volume (Q) increases.
Swash plate angle (a) is changed by servo piston (11).
Servo piston (11) moves in a linear reciprocating motion corresponding to the signal pressure from the PC
valve and LS valve.
This linear motion is transmitted to rocker cam (4).
Rocker cam (4) which is supported by ball (12) in flange (2) rotates.
PC88MR-10
10 Structure and function
Main pump
10-53