Motor vehicles – Steering by driving – Auxiliary steering motor
Reexamination Certificate
1999-09-29
2001-01-09
Johnson, Brian L. (Department: 3618)
Motor vehicles
Steering by driving
Auxiliary steering motor
C180S006700, C180S009440, C180S421000
Reexamination Certificate
active
06170584
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a tracked vehicle drive/steering system.
Known production tracked vehicles, such as the John Deere 8000T and 9000T series track tractors have a hydrostatic steering system which includes an engine-driven variable displacement steering pump which powers a hydraulic fixed displacement steering motor. The steering motor drives, via a cross shaft and a gear a left planetary drive. The steering motor also drives, via the cross shaft, a gear and a reverser gear, a right planetary drive. A steering control signal is provided by a transducer which detects rotation of a steering wheel. A pump displacement control controls the output of the pump as a function of the steering control signals. The speed and direction of rotation of the steering motor is normally proportional to the position of the steering wheel, and these parameters are sensed by a Hall effect motor speed and direction sensor. The output of the steering system is motor speed, which is measured using a Hall effect motor speed and direction sensor. It would be desirable to have a means of detecting and responding to pump malfunctions wherein the pump output flow exceeds the amount which corresponds to the steering control signal and that which is commanded by the pump displacement control.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to provide a system or method of detecting certain failures in a tracked vehicle drive/steering system.
A further object of the invention is to provide such a system which detects when the steering pump output flow exceeds the amount which corresponds to the steering control signal.
These and other objects are achieved by the present invention, wherein a control system is provided for a tracked vehicle drive/steering system having an engine driven hydraulic steering pump which drives a hydraulic steering motor. The pump output flow is measured in terms of the steering motor speed. The steering pump is responsive to steering control signals representing a status of an operator manipulated steering wheel. The steering motor provides an input to a differential track drive mechanism which responds to manipulation of the steering wheel and drives left and right tracks to turn the vehicle. The control system includes a control unit which receives signals from an engine speed sensor, a steering motor rotation speed and direction sensor, and the steering control signals. The control unit calculates a motor speed threshold value as a function of sensed engine speed and steering control signals, and generates a fault signal as a function of a relationship between the steering motor speed signal and the motor speed threshold value. The control unit generates an overspeed fault signal when the steering motor speed signal is greater than the motor speed threshold value, and generates a data conflict fault signal when the steering motor speed signal is less than a negative minimum motor speed threshold value. The control unit, when the vehicle is not being commanded to turn by the steering control signals, generates a minimum threshold value, and generates an overspeed fault signal when the motor speed signal is greater than the minimum threshold value or is less than a negative minimum threshold value.
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U.S. application No. 09/053,600.
Bergene Mark Allen
Hou Yifei
Mistry Sanjay Ishvarlal
Toppin Scott Allen
Deere & Company
Johnson Brian L.
Yeagley Daniel
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