Importance

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Abstract

An interactive engine and automatic transmission control system is provided wherein spark and air control are used to control engine speed to maintain a small positive torque on the transmission before and after coast down shifts. More particularly, a transmission controller is electrically coupled to an engine controller in a motor vehicle such that information can be passed therebetween. Such information includes a start of shift signal, a phase of the shift signal (i.e., clutch release phase, speed change phase, or clutch application phase), and a shift complete signal. In addition, the transmission controller identifies the type of shift that is occurring (i.e., fourth gear to third, third to second, or second to first), transmission oil temperature and the acceleration (braking) rate of the vehicle to the engine controller. During the three phases of a coast down shift, air flow control is used to supply an appropriate amount of air to the engine so that closed loop spark control can be used to adjust the speed of the engine. By maintaining the engine speed slightly above the turbine speed just before and just after a coast down shift, very little torque is transmitted through the transmission during the shift. As such, the coast down shift is practically imperceivable to the driver.

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First Claim