Abstract: A safety control device for an actuator of a flap solenoid valve, such as for an automatic transmission. The device includes a current control device which is connected to a shunt resistor for measuring the current through the solenoid valve and the current control device. It also includes a control package which measures the time between the starting of the power to the solenoid valve and the moment when the current reaches a threshold intensity. The control package compares this time with a time range which indicates the proper operation of the solenoid valve so that if the time falls outside this time range, the control package instructs the current control device to cut power to the solenoid valve.

Abstract: Automatic transmission with stepped ratios for vehicle, characterized in that it comprises a system inhibiting untimely changes to the higher ratio, which system is arranged so that, on the one hand it generates a negative acceleration curve (3) located mainly below the up shift (1) and down shift (2) curves and an increasing throttle opening curve (4) located slightly above the negative acceleration curve and, on the other hand, it only enables the shift up to the higher ratio if the value of the opening (.alpha.c) settles down, i.e. stops varying for a minimum time and if the corresponding configuration point in the plane of the vehicle speeds and throttle openings lies either between the up shift curve (1) and the negative acceleration curve (3) if the opening varies in the decreasing direction, or between the increasing opening curve (4) and the up shift curve (1) if the opening varies in the increasing direction.

Abstract: An electronic system for controlling the drive ratio changes in an automatic transmission of a motor vehicle having solenoid valves for actuating the gear changes. A microcomputer selectively governs the solenoid valves through power amplifiers, in such a way that when the solenoid valves are not energized the highest drive ratio is engaged. The ratio of the power amplifiers to the corresponding output signals of the microcomputer is such that the solenoid valves are not energized when the supply voltage is zero or when the microcomputer voltage drops below the threshold value necessary for its proper operation.

Abstract: An electronic governor receiving two signals, one corresponding to the load on the motor and the other to the speed of the vehicle comprises two time-interval comparators controlled by two switches corresponding to the manual control imposing transmission ratios and by a retrocontact switch. The output signals of the governor supplying orders for speed changes feed a sequential commutation device which controls two electrically actuated valves controlling the gear box with time delays and for transitory changes.

Abstract: A device controlling a multi-stage automatic transmission for an engine-driven vehicle with three forward drive ratios and change-under torque, damped by a hydrokinetic torque converter, and one reverse drive, of the type consisting of an epicyclic gear train actuated by two clutches and two brakes hydraulically controlled. A hydraulic distribution unit is monitored by two electric valves in order to feed selectively the two clutches and the two brakes on the basis of data concerning the running of the vehicle. The two electric valves are controlled in response to three different states of the two electric valves for providing selective feeds corresponding respectively to each of the three forward drive ratios and for providing an additional control of the electric valves in response to a fourth transient state for the transmission between the third and second forward drive ratios.