Shift control system and method for automatic transmission, including both a timer and an inertia phase start detector

摘要

A shift control system for an automatic transmission includes a first transmission assembly for changing gear ratios in accordance with the release or engagement of a first frictional engagement system and a second transmission assembly connected in series to the first transmission assembly for changing gear ratios in accordance with the engagement or release of a second frictional engagement system. An engagement start instruction generator instructs the start of the engagement of the second frictional engagement system, a timer outputs a signal after the lapse of a predetermined constant time from the instruction of the engagement start of the second frictional engagement system, a detector detects the start of an inertia phase of the second transmission assembly accompanying the engagement start of the frictional engagement system from the rotary state of a rotary member in either of the first or second transmission assemblies, to output a detection signal, and a release start instructing generator instructs the start of the release of the first frictional engagement system simultaneously with either the output of the signal from the timer or the output of the signal from the detector.