Anti-stall transmission control for utility vehicle
First Claim
1. An engine control system for a compact utility tractor having an engine coupled to a hydrostatic transmission, that is coupled to a driven wheel, comprising:
- a controller;
an engine speed sensor, signal-connected to said controller to send an actual engine speed signal to said controller;
a speed control actuator having at least a forward and a neutral position, said speed control actuator causing speed command signals from said controller to adjust said hydrostatic transmission speed output to said wheel;
said controller having circuitry that continuously monitors engine speed and the position of said control actuator;
said controller having circuitry that records said engine speed at the occurrence of said neutral position of said speed control actuator as an unloaded engine speed; and
when the engine speed signal decreases under load by a specified amount below said unloaded engine speed, said controller having circuitry that sends a control command to said hydrostatic transmission to reduce tractor speed proportional to the difference between said unloaded engine speed and said actual engine speed signal.
1 Assignment
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Accused Products
Abstract
A control system for a utility vehicle, particularly a compact utility tractor, that is speed-controlled by a hydrostatic transmission, prevents engine stalling by automatically reducing the stroke of a pump of the hydrostatic transmission, and thus reducing the vehicle speed, when the unloaded engine speed drops below a predetermined threshold. The apparatus includes a servo controlled hydrostatic transmission, an engine speed sensor, a throttle position sensor and a controller. The unloaded engine speed is determined by either an engine throttle lever position or by an engine speed capture algorithm that continuously monitors engine speed and records engine speed occurring when the transmission control pedals are positioned in neutral.
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Citations
11 Claims
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1. An engine control system for a compact utility tractor having an engine coupled to a hydrostatic transmission, that is coupled to a driven wheel, comprising:
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a controller;
an engine speed sensor, signal-connected to said controller to send an actual engine speed signal to said controller;
a speed control actuator having at least a forward and a neutral position, said speed control actuator causing speed command signals from said controller to adjust said hydrostatic transmission speed output to said wheel;
said controller having circuitry that continuously monitors engine speed and the position of said control actuator;
said controller having circuitry that records said engine speed at the occurrence of said neutral position of said speed control actuator as an unloaded engine speed; and
when the engine speed signal decreases under load by a specified amount below said unloaded engine speed, said controller having circuitry that sends a control command to said hydrostatic transmission to reduce tractor speed proportional to the difference between said unloaded engine speed and said actual engine speed signal. - View Dependent Claims (2, 3, 4, 5)
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6. A method of controlling an engine transmission system of a utility tractor, wherein the engine throttle remains substantially stationary in the transmission is controlled by a speed actuator to adjust speed, the speed actuator having at least a forward and a neutral position, comprising the steps of:
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continuously monitoring engine speed;
sensing for the neutral position of said speed actuator;
at the neutral position of said speed actuator, recording the engine speed as an unloaded engine speed;
during a forward drive of the vehicle, when the engine speed drops by a preselected amount below said unloaded engine speed, commence decreasing ground speed of said vehicle proportionally to amount of engine speed drop below unloaded engine speed, to increase engine speed. - View Dependent Claims (7, 8)
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9. 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 arranged to drive a driven wheel, comprising the steps of:
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continuously sensing the rotational speed of the engine;
operating said vehicle in forward and reverse;
sensing the rotational speed of the engine between forward and reverse as an unloaded set speed and saving said unloaded set speed in memory;
thereafter, if the rotational speed of the engine differs from the unloaded set speed, changing the hydrostatic transmission output to diminish the difference. - View Dependent Claims (10, 11)
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Specification