Control system for a combined shift in which an accumulator is disconnected in an automatic transmission

摘要

A control system is provided for an automatic transmission which has primary and second shifting units connected together to provide multi-stage speed ranges. Upon performing a combined shift, a hydraulic control circuit disconnects a hydraulic servomotor and its corresponding accumulator and the pressure in the servomotor is controlled by an electrical signal. When a decision for a second shift is made in the course of the combined shift, the pressure in a hydraulic servomotor for a downshift frictional engagement element is controlled by an electrical signal to return the element to its position before the combined shift while monitoring the number of revolutions of a rotating member in the transmission. As a consequence, a particular speed stage is configured and a shift signal corresponding to the decision of the second shift is outputted to the circuit. Since the shift signal corresponding to the decision of the second shift is not outputted until the particular shift is configured, the servomotor and the accumulator remain disengaged.