Motor Operating Principles - jcb JS300 Service Manual

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The following detailed description explains the operating

cycle of an individual piston.

High pressure hydraulic fluid P from the pump flows via

input port a and control valve A into cylinder B when it is

aligned with the input side A(a) of the control plate. The

force F against piston C generates a force F2 (shown

vectorially) which acts on piston shoe D. The piston shoe

moves against stationary swash plate E, causing cylinder

block F and hence drive shaft G to rotate. This situation

exists for 180° of rotation of the cylinder block i.e. until the

cylinder aligns with the output side A(b) of the control plate.

For the next 180° of rotation of the cylinder block the piston

Motor Operating Principles

expels low pressure hydraulic fluid T via the output side

A(b) of the control plate, port b and back to tank. Driving

force F2 varies according to the flow rate of the high

pressure hydraulic fluid input.

There are nine pistons equally spaced around the cylinder

block. As each one in turn goes through the cycle

described, a continuous even rotation of the output shaft is

By reversing the hydraulic fluid flow direction i.e. high

pressure feed into port b, the motor rotation is reversed.

Section E - Hydraulics

Motor Operating Principles

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