JLG 600SC_660SJC Service Manual - Manual (Page 97)

SECTION 5 - CAT CHASSIS (S/N 0300128000 TO PRESENT)
3121157 – JLG Lift – 5-5
5.3 CONSTRUCTION AND FUNCTION
The drive motor consists of swash plate type axial piston
motor, shuttle valves, crossover relief valves, low pressure
relief valves, and reduction gear as one component.
Working Principle of Swash Plate Type Axial
Piston Motor
Nine piston sub assemblies are assembled in the cylinder
block. The end of the cylinder block is adjacent to the
valve plate with two half moon shaped ports, B and C
(high and low pressure ports). When supplying pressure
fluid (pressure P) to B port, the force of piston sub assem-
blies having F=PEA (A: Piston pressure area) pushes the
swash plate. The piston sub assemblies receive reaction
force from it, and reaction force (Ft) in rotating direction is
produced. The total force of high pressure side piston sub
assemblies in rotating direction produces a rotating force
in the cylinder block, and the force through a spline con-
veys the torque to the shaft, which causes the shaft to
rotate.
According to the above working principle, the output
torque and rotating speed of the piston motor are deter-
mined by supply pressure (P) and flow rate (Q), and are
calculated by the following formula.
Figure 5-1. Structure of Drive Motor
Figure 5-2. Structure of Swash Plate Type Axial Piston
Motor
Cylinder block
Shaft
Swash plate
Piston sub assembly
Valve plate