Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1999-09-29
2001-05-29
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S050000, C180S006440
Reexamination Certificate
active
06240351
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, include 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. 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. Certain types of steering pump related failures, such as contamination in the control valve and malfunction of the feedback linkage between the steering pump swashplate and its second stage control valves could cause the pump swashplate to hydraulically lock (stick) at a certain non-zero position. This type of failure can lead to a continuous turning of the vehicle, even when the steering wheel is in a position commanding no turn. It would be desirable to provide a method of detecting such failures, and of preventing vehicle turning unless turning is actually commanded by the operator.
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 prevents vehicle turning unless turning is actually commanded by the operator.
These and other objects are achieved by the present invention, wherein a control system for a tracked vehicle drive/steering system includes a steering system control unit which receives signals from a pump speed (engine speed) sensor and from a steering motor speed sensor. The ratio of the motor speed to the pump speed represents the swashplate angle of the steering pump during steering action. For a normally functioning steering system, if the pump receives a control signal in a reverse steering direction, the pump swashplate angle will start do decrease. When the control unit sends out a reverse steering direction command above a certain magnitude, it also calculates and saves the ratio of the motor speed to the pump speed. The control unit recalculates the above ratio after a certain time duration, if the same reverse steering direction command is still present. The control unit generates a fault signal if the ratio is not decreasing.
REFERENCES:
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patent: 5535840 (1996-07-01), Ishino et al.
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patent: 5921335 (1999-07-01), Staetker
patent: 5948029 (1999-09-01), Straetker
patent: 6039132 (2000-03-01), Easton
U.S. Application No. 09/053,600.
Bergene Mark Allen
Hou Yifei
Mistry Sanjay Ishvarlal
Toppin Scott Allen
Cuchlinski Jr. William A.
Deere & Company
Donnelly Arthur D.
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