Control means for vehicle automatic transmissions

Claim 1

A vehicle automatic transmission including a hydraulic torque converter having an input member connected with an engine output shaft and an output member connected with a multiple stage transmission gear mechanism which has a plurality of gear stages, gear stage selecting means including hydraulic actuator means for selecting a desired one of said gear stages, a hydraulic circuit including solenoid valve means for controlling supply of hydraulic pressure to said actuator means, speed detecting means for detecting a rotating speed of said output member of said torque converter and producing a speed signal, load detecting means for detecting engine load and producing a load signal, shift control means including shift control map means having a shift down control line which is determined by a line passing through points of maximum curvature on iso-engine-output-power lines based on the rotating speed of said output member of the torque converter and the engine load and at least one shift up control line which is shifted to a high speed side with respect to the shift down control line by an amount corresponding at least to a difference in gear ratio between two adjacent gear stages, said shift control means further including means for comparing the speed signal and the load signal with said shift control map to produce a shift control signal for energizing the solenoid valve means to perform a required gear shifting operation.