Abstract: Control device of an automatic transmission having four forward speeds with shifting under torque together with a hydrokinetic torque converter with an integrated torsional damper, and one reverse speed, of the type comprising a planetary gear train controlled by three clutches and two brakes with hydraulic control. A hydraulic distributor controlled by four solenoid valves selectively feeds the clutches and brakes, depending on the running conditions of the vehicle. The control means of the solenoid valves are made to use two states of one of these solenoid valves to allow fast filling and progressiveness of the active receiver or receivers during shifting and two states of the other solenoid valves to assure the various sequences during shifting.

Abstract: Pressure control device comprising a manual valve (VM) associated with a pressure control valve (VRP), includes a first line pressure (P.sub.L), defined by two calibrated jets in series, which are placed on a duct set at zero pressure by the manual valve (VM) being in a first position R. At a second line pressure range (P.sub.L), a duct is fed at line pressure (P.sub.L), the manual valve (VM) is in a second position A. A variation of line pressure (P.sub.L) is assured by a modulating solenoid valve (EVM), which establishes a modulated pressure (P.sub.M) acting on a differential section (.SIGMA.) of said pressure control valve (VRP).

Abstract: Two-level pressure control device has a pressure control valve VLP 3 associated with a system of jets and in series to obtain a first reference pressure level P.sub.1 and a second reference pressure level P.sub.2.

Abstract: A pressure limiter-regulator for a hydraulic control circuit. In a single body, a single spring acts both on a central spindle, which provides the pressure regulating function, and on a ball which provides the limiting function. The invention is applicable to the hydraulic feeding of a hydrokinetic torque converter.

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.

Abstract: A multi-level pressure regulating valve for a hydraulic control circuit. It includes a three-level or four-level pressure regulating valve utilizing an intermediate chamber which is fed with fluid through two parallel ducts, each having its own throttling device.