Control of clutch pressure and torque capacity during downshift of an automatic transmission

摘要

In power-on, high-vehicle-speed and high-torque conditions, a control unit sets a torque allotment ratio such that a main clutch (Tmc) bears all the torque. Thereby, the input shaft rotational speed is increased by controlling solely the main clutch releasing pressure (Pmc). In power-on and low-torque or low-vehicle-speed conditions, the control unit sets a torque allotment ratio of the main clutch torque and the sub-clutch torque to 1:1. Thereby, the controls of the main clutch releasing pressure (Pmc) and the sub-clutch engaging pressure (Psc) simultaneously proceed in parallel to cause a change in the input shaft rotational speed without a time lag. The hydraulic control apparatus thus conducts proper downshift control involving clutch engagement changeover, in all vehicle running conditions, without increasing control logic.