Komatsu PC88MR-10 Shop Manual page 129

3. Case
4. Rocker cam
5. Shoe
6. Piston
7. Cylinder block
8. Valve plate
9. Servo piston
10. Oil seal
This pump consists of a variable capacity swash plate piston pump, gear pump (for blade and swing
operations), and servo valve.
Structure
Cylinder block (7) is supported on shaft (1) through spline (a). Shaft (1) is supported on the front and rear
bearings.
The tip of piston (6) is shaped as a concave sphere and is crimped with shoe (5). Piston (6) and shoe (5)
constitute a spherical bearing.
Rocker cam (4) has flat surface (A) and shoe (5) is always pressed against this surface while sliding in a
circular pattern.
Rocker cam (4) is supported on flange (2) fixed to case (3) and ball (12).
Shoe (5) leads high-pressure oil to flat surface (A) of rocker cam (4) and form a static pressure bearing for
its sliding.
Piston (6) moves relatively in the axial direction in each cylinder chamber of cylinder block (7).
Cylinder block (7) rotates relatively to valve plate (8) while blocking the pressurized oil and the oil pressure
is balanced properly on this plane.
The pressurized oil can be sucked in and discharged from each cylinder chamber in cylinder block (7)
through valve plate (8).
Function
(PC88MR-C200-042-K-00-A)
This pump converts the rotation and torque of the engine transmitted to its shaft into hydraulic pressure
and discharges pressurized oil corresponding to the load.
PC88MR-10
10 Structure and function
Main pump
10-51