Speed control for a utility vehicle
First Claim
1. A speed control system for a utility vehicle, comprising:
- a controller having an input for receiving a selectable set speed signal;
an input device responsive to an operator command to select a selectable set speed signal, said input device signal-connected to said input;
a variable displacement pump providing a pressurized hydraulic fluid, said pump having an angularly adjustable swashplate, pump displacement set by the angle of the swashplate;
a proportional pressure control valve operatively connected to said swashplate to change the angle of said swashplate, said control valve signal-connected to said controller;
a hydraulic motor receiving the pressurized hydraulic fluid from the pump to rotate the motor;
a part operatively connected for rotation by the hydraulic motor;
a rotation sensor arranged to sense rotational speed of said part, said sensor signal-connected to said controller to send a rotational speed signal to said controller;
said controller controlling said proportional control valve with a control signal to change the angular position of said swashplate in response to a difference calculated by said controller between said rotational speed signal and the set speed signal.
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Accused Products
Abstract
A cruise control system for a utility vehicle, which is speed-controlled by a hydrostatic transmission, includes a controller having an input for receiving a selectable set speed signal, and an output for sending a speed control signal to at least one proportional valve of a hydrostatic transmission servo control system. The vehicle ground speed is continuously monitored by a speed sensor operatively associated with a rotating gear in the vehicle drive train that rotates in proportion to vehicle ground speed, to create a ground speed signal. The selectable set speed signal can be input to controller memory by driving the vehicle at a desired ground speed and then activating a speed set switch. The speed control algorithm of the controller thereafter compares the set speed to the ground speed signal from the speed sensor and corrects the control signal to the proportional valve to correct hydrostatic transmission speed output.
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Citations
11 Claims
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1. A speed control system for a utility vehicle, comprising:
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a controller having an input for receiving a selectable set speed signal;
an input device responsive to an operator command to select a selectable set speed signal, said input device signal-connected to said input;
a variable displacement pump providing a pressurized hydraulic fluid, said pump having an angularly adjustable swashplate, pump displacement set by the angle of the swashplate;
a proportional pressure control valve operatively connected to said swashplate to change the angle of said swashplate, said control valve signal-connected to said controller;
a hydraulic motor receiving the pressurized hydraulic fluid from the pump to rotate the motor;
a part operatively connected for rotation by the hydraulic motor;
a rotation sensor arranged to sense rotational speed of said part, said sensor signal-connected to said controller to send a rotational speed signal to said controller;
said controller controlling said proportional control valve with a control signal to change the angular position of said swashplate in response to a difference calculated by said controller between said rotational speed signal and the set speed signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of controlling the speed of a utility vehicle, said vehicle having an engine driving a hydrostatic transmission, said hydrostatic transmission driving a drive train, said drive train including at least one gear and a driven wheel, comprising the steps of:
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continuously sensing the rotational speed of a rotating part in the drive train;
operating said vehicle at a desired vehicle speed;
at the desired vehicle speed, selecting the rotational speed as a set speed and savings said set speed in memory;
thereafter, if the rotational speed of the rotating part differs from the set speed, changing the hydrostatic transmission output to diminish the difference. - View Dependent Claims (9, 10, 11)
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Specification