Abstract: A vehicle automatic transmission including a torque converter and a multiple stage transmission gear mechanism. The gear mechanism is controlled through a hydraulic system having solenoid valves. An electronic control unit is provided to control the hydraulic system under a shift control map having shift up and shift down control lines. The shift down control line is determined in terms of the torque converter turbine speed and the engine throttle valve position as a line in which the torque converter is operated with a torque ratio of substantially one.

Abstract: A steplessly variable vehicle transmission has a speed ratio control system including an electronic control unit which functions to calculate a required vehicle acceleration rate based on the position of an engine control foot pedal and the rate of change of the position of the foot pedal. The control unit further calculates an engine output power required for accomplishing the vehicle acceleration rate, as well as the engine speed under which the required engine output power can be obtained with the given position of the engine control foot pedal. Further, the control unit produces an output for controlling the speed ratio of the transmission so that the required engine speed is obtained.

Abstract: A vehicle automatic transmission including a torque converter and a multiple stage transmission gear mechanism. The gear mechanism is controlled through a hydraulic system having solenoid valves. An electronic control unit is provided to control the hydraulic system under a shift control map having shift up and shift down control lines. The shift down control line is determined in terms of the torque converter turbine speed and the engine throttle valve position as a line passing through points of maximum curvature on iso-engine-output-power lines as functions of the torque converter turbine speed and the engine load.

Abstract: A steplessly variable vehicle transmission of a belt-pulley type which is provided with an electronic control unit for controlling the speed ratio of the transmission in accordance with the engine operating condition, such as the engine load and the engine speed. The control unit has a shift control map which includes a shift-up zone, a shift-down zone and a speed ratio hold zone between the shift-up and shift-down zones so that the speed ratio of the transmission is maintained constant in acceleration and deceleration as long as the engine operating condition is in the hold zone.

Abstract: A clutch control system for automobiles comprising a clutch actuating member for actuating a clutch positioned between an engine output shaft and a transmission input shaft, and a suction pressure operated actuator for moving a clutch actuating member to a clutch releasing position. A detecting circuit is provided for detecting a negative differential coefficient of the engine speed and generating a corresponding output. A vacuum control valve is provided in a line to the clutch actuator to operate the clutch release. The line is also provided with a holding valve which is closed when the detecting circuit detects the negative differential coefficient of the engine speed to thereby stop the clutch engaging movement of the actuator momentarily so as to prevent the engine speed from falling off.