Speed control for a utility vehicle

• US 20030010152A1
• Filed: 07/13/2001
• Published: 01/16/2003
• Est. Priority Date: 07/13/2001
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Burgart, Joseph Gerard, Evans, Mark David
• Granted Patent: US 6,655,233 B2
• Time in Patent Office: Days
• US Class Current: 74/730.1
• CPC Class Codes: B60K 31/00 Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator fittings acting on two or more sub-units B60W30/14; speedometers G01P; systems or devices for controlling speed in general G05D13/00 ; in traffic anti-collision system for road vehicles G08G1/16
• CPC Class Codes: B60W 2720/10 Longitudinal speed
• CPC Class Codes: F16H 2061/0078 Linear control, e.g. PID, state feedback or Kalman
• CPC Class Codes: F16H 2061/0258 Proportional solenoid valve
• CPC Class Codes: F16H 59/40 Output shaft speed
• CPC Class Codes: F16H 59/44 dependent on machine speed of the machine, e.g. the vehicle
• CPC Class Codes: F16H 59/46 dependent on a comparison between speeds
• CPC Class Codes: F16H 61/46 Automatic regulation in accordance with output requirements
• CPC Class Codes: F16H 61/47 for achieving a target output speed
• CPC Class Codes: Y10T 74/19149 with fluid drive
• CPC Class Codes: Y10T 74/19153 Condition responsive control

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.

Claims

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.

2. The speed control system according to claim 1, further comprising an incremental speed switch signal-connected to said controller, each activation of said incremental speed switch causing said controller to increase the set speed by an amount proportional to the set speed.

3. The speed control system according to claim 1, further comprising an incremental speed switch signal-connected to said controller, each activation of said incremental speed switch causing said controller to decrease the set speed by an amount proportional to the set speed.

4. The speed control system according to claim 1, wherein said part comprises a gear and said sensor comprises a Hall effect pickup sensor arranged adjacent said gear to sense pulses of rotating teeth of said gear.

5. The speed control system according to claim 1, comprising forward and reverse proportional pressure control valves, and a servo valve mechanically connected to said swashplate, said forward and reverse proportional control valves operable to relatively pressurized one side of said servo pistron to move said servo piston and cause corresponding movement of said swashplate.

6. The speed control system according to claim 1, comprising a speed set switch and said controller includes a memory, said memory for instantaneously recording said rotational speed signal and said control signal upon switch actuation of said speed set switch.

7. The speed control system according to claim 1, wherein said input device comprises a switch and a circuit configured to import the rotational speed signal as a set speed when said switch is activated.

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:

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.

9. The method according to claim 8, wherein the hydrostatic transmission includes a variable displacement pump, said variable displacement pump including a swashplate which can be angularly adjusted to adjust hydrostatic transmission output, and a proportional pressure control valve signal-actuated to adjust swashplate angle, wherein the step of changing the hydrostatic transmission output is further defined by the step of changing a driving signal to the proportional control valve to change the angle of the swashplate in the variable displacement pump of the hydrostatic transmission.

10. The method according to claim 8, comprising the further step of:

providing a manual step of changing said set speed by incremental amounts, activating said manual step to change the set speed by a percentage of the set speed.

11. The method according to claim 8, comprising the step of:

at the desired vehicle speed, when said rotational speed is selected as the set speed, saving said driving signal to the proportional control valve as an initial driving signal, and thereafter, if the rotational speed of the rotating part differs from the set speed, changing the driving signal to diminish the difference between the rotational speed and the set speed.