Coasting downshift control strategy for a multiple-ratio automatic transmission

摘要

A control strategy for a multiple-ratio transmission for an automotive vehicle comprising a shift valve system that responds to shift valve signals developed by a microprocessor controller, the controller being in communication with engine sensors indicating engine operating variables and transmission sensors indicating transmission operating variables, the shift valve system responding to shift signals developed by the microprocessor during coasting downshift of the vehicle from one gear ratio to a lower gear ratio with a closed engine throttle whereby torque reversals are avoided during coast-down, thereby eliminating inertia torque changes to improve the smoothness of coasting downshifts during cold engine operation.