Importance

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Abstract

An automotive control driving mechanism for a vehicle, such as a wheel loader or fork lift, comprising a plurality of wheels (18) supporting a vehicle frame, an engine (16) on the frame for driving the wheels (18), and a hydrostatic transmission having a variable displacement pump (12) operatively connected to the engine (16) and to at least one motor (14). The motor (14) is connected to at least one of the wheels (18) to propel the vehicle. The transmission generates a working system pressure in a pair of fluid conduits (32,34) between its pump (12) and motor (14). A microprocessor (40) is connected to a speed pickup (38) on the engine shaft (39) and conduits (32,34) of the hydrostatic transmission for controlling the displacement of the pump through swashplate (20), and thus the transmission ratio, based not only on the engine speed but also system pressure. The sensed system pressures values are embedded into microprocessor's (40) control algorithms for the transmission ratio. The transmission may also include variable displacement motors controlled in the same manner. When electronically proportional high pressure relief valves are associated with said conduits, improved braking and coasting are realized.

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First Claim