Vehicle automatic transmission control system

摘要

In a system for controlling a gear ratio of a multi-step geared or continuously variable automatic transmission of a vehicle, the gear ratio is determined through fuzzy production rules each having one of an ATF temperature, a steering or an engine coolant temperature. For example, the rule regarding the ATF temperature defines such that the gear position should be shifted down if the ATF temperature is high. With the arrangement, when the ATF temperature is high, the gear position is determined in the downshifting direction so that the amount of torque converter slippage can be reduced, whereby avoiding temperature rise in the transmission. And since the engine speed is relatively high at that situation, motive force could be sufficient even climbing a hill.