System for shiftable multi-speed hydraulically operated power transmission and electronic controller therein

Claim 1

In a control system for a power transmission including a power input shaft and a power output shaft and having a plurality of speed change gears, a plurality of selectively operable fluid-actuated clutches for operating said speed change gears to provide different transmission output speed ranges, a selectively movable range selector valve for distributing pressurized fluid to operate different clutches, and a lock-up clutch which is disengageable during shifting; first solenoid means for operating said lock-up clutch; means for sensing the rotational speeds of said power input and power output shafts and for providing electric speed signals indicative of the speeds of said shafts; second solenoid means for moving said movable range selector valve; selectively operable range selector switch means for providing an electric signal indicative of a selected shift range; position responsive switch means for providing an electric signal indicative of the position of said range selector valve, said position responsive switch means including first switch means for providing a signal indicative that said range selector valve is in readiness regardless for movement and second switch means for providing a signal indicative of the range selector valve position; and an electronic controller for receiving said signals and for providing output signals to operate said second solenoid means to effect movement of said range selector valve to effect shifting of said transmission selected to a speed range, provided said range selector valve is in a predetermined position, and provided said means for sensing the rotational speeds of said shaft indicates that there is rotation at predetermined speeds, and to operate said first solenoid means to disengage said lock-up clutch during shifting.