US 5,857,532 AGranted

Differential steer system for a machine

AssigneeCaterpillar Inc.

InventorRonald L. Satzler

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Abstract

A differential steer is provided for use in a machine and includes a variable displacement motor operatively connected to a differential disposed between first and second output members. The variable displacement motor is an over-center type and the displacement thereof is varied from zero to maximum in both directions of movement. Pressurized fluid to drive the steer motor is received from the main system pump. A microprocessor senses the direction and rate of rotation of the steer motor output, the speed of the outputs from the differential, the magnitude of a steer input, and controls the output speed of the steer motor to the differential in response to the magnitude of the steer input. Consequently, the quantity of fluid taken from the main system pump is limited to only that necessary to rotate the steer motor at a rate necessary to satisfy the desired steer input. Since the steer motor is using only the flow necessary to rotate the steer motor output at a desired speed and the steer motor torque is generally proportional to the steer motor displacement, the overall operating efficiency is increased as compared to known differential steer systems.

Claims13

Dependent claims

A differential steer system adapted for use in a machine having an engine, a source of pressurized fluid connected to a work system, a differential disposed between first and second outputs, and a steer input mechanism, the differential steer system comprising:

a variable displacement steer motor having a displacement adjustment mechanism and being fluidity connected to the source of pressurized fluid, the steer motor has an output shaft connected to the differential and the displacement adjustment mechanism is movable in opposite directions from a zero displacement position towards a maximum displacement position;
a steer motor input control mechanism connected to the displacement adjustment mechanism of the steer motor and being operative in response to the steer input mechanism to control the displacement of the steer motor;
a first sensor associated with the steer input mechanism and operative to sense the direction and degree of rotation of the steer input mechanism;
a second sensor associated with the output shaft of the steer motor and operative to sense the direction of rotation and the speed of rotation of the steer motor output shaft;
and
a microprocessor operative to receive the sensed signals from the first and second sensors and deliver a control signal to the steer motor input control mechanism to change the displacement of the steer motor in response to the movement of the steer input mechanism.

3 more elements

Dependencies are inferred from the claim text.