Importance

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Abstract

A control system for a work vehicle transmission includes a sensor for detecting the output speed of the vehicle engine and an operator-movable command device for placing the transmission in a neutral condition. The transmission includes a plurality of intermeshing gears, and clutches associated with certain of the gears for selectively placing the transmission in various gear ratios for driving the vehicle. The clutches are engaged and disengaged by fluid valving in response to energization of solenoid coils driven by valve driver circuits. The sensor, the command device and the driver circuits are coupled to a control circuit, preferably including a microprocessor, for controlling engagement and disengagement of the transmission clutches. Upon startup, the control circuit disables the driver circuits to place the transmission in a neutral condition despite the position of the command device. The control circuit maintains the driver circuits disabled until the vehicle engine is running, as indicated by the speed sensor, and a neutral command signal is received. The neutral start routine serves as a redundant system with an analog neutral start circuit that normally disables the vehicle starter unless a neutral transmission condition is commanded upon startup. The system thus provides a neutral start feature in the event the neutral start circuit fails or is defeated, such as by jump starting the vehicle engine.

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First Claim