Abstract: Under a higher speed gear position of the transmission, a control valve can drain a hydraulic pressure of a forward clutch to cause the forward clutch to take a disengaged condition. With this, undesired friction of a forward one-way clutch under such higher speed gear position is suppressed. A fail-safe system is employed for recovering an engaged condition of the forward clutch even when the control valve is stuck at such pressure draining position.

Abstract: An automobile automatic transmission shift control system, for causing a specific gear shift by unlocking a first frictional element with a simultaneously with locking a second frictional element, discharges locking pressure from the first frictional element in such a way that the locking pressure is throttled after it has dropped below a specified level of pressure.

Abstract: A multi-speed transmission has a hydraulic control system for establishing a plurality of forward drive ratios and a reverse drive ratio. Each drive ratio is established by the engagement of a fluid operated friction device, such as a clutch or brake. The engagement timing of each friction device is controlled in part by an accumulator. Each accumulator is disposed to accommodate friction devices, such that five forward speed and one reverse speeds require only a maximum of three accumulators.

Abstract: An automatic transmission has a hydraulic circuit which controls supply of engaging pressures to friction coupling elements. The hydraulic circuit has a first hydraulic passage having a hydraulic pressure control valve including an accumulator, a second hydraulic passage which is provided in parallel to the first hydraulic passage and is provided with an electrically controlled hydraulic pressure control valve, and a shift valve which selectively connects a predetermined friction coupling element to the first hydraulic passage or the second hydraulic passage.

Abstract: In an automatic selector device of an epicyclic change-speed gearbox, a frictional connection, i.e. a clutch or brake, participating in the selection of a forward gear is engaged by a pressure medium setting element and disengaged by a spring device. In a neutral selection condition, a partial quantity of the pressure medium filling of the selector setting element is accommodated in a pressure reservoir so that the friction surfaces are just unloaded and does not transmit torque.

Abstract: An accumulator fluid control system for a hydraulic servo in a vehicular automatic transmission includes an accumulator having a cylinder, a piston, a return spring, a chamber disposed in the cylinder, a first and second input ports connected to a first passage, an output port connected to a second passage, and a check valve for controlling the connection between the first and second passages through the second input port.

Abstract: An automatic power transmission includes a primary transmission unit having plurality of gear elements for establishing predetermined speed ratios and a subsidiary transmission unit having an under-drive gear element for establishing at least one and a direct drive. Each gear element is associated with a friction element which controls associated one of the gear element for establishing one of a plurality of predetermined speed ratios. The friction element is connected to a hydraulic circuit which controls position of the friction element between engaged position and released position for establishing the one of speed ratios.

Abstract: A hydraulic controller for an automatic transmission, having a band brake having a large stopping force based on a self-boosting effect against rotation in a self-binding direction and having a comparatively small stopping force against rotation in the unbinding direction, a modulator valve for producing a modulator pressure by reducing a line pressure, a band brake hydraulic servo having a brake engaging hydraulic chamber and a brake releasing hydraulic chamber. A line pressure is supplied to the band brake hydraulic servo to stop rotation in the self binding direction when a predetermined transmission speed is selected. The line pressure is also supplied the band brake hydraulic servo to stop rotation in the unbinding direction when another transmission speed is selected. A modulator pressure is supplied to the brake engaging hydraulic chamber to stop the rotation in the self-binding direction of the band brake and to allow the rotation in the unbinding direction when an intermediate speed is selected.

Abstract: An electrohydraulic control for an automatically shiftable transmission (G 1) has at least two solenoid valves (1a, 1b) which are connected via the control pressure lines (13, 14) with gear control valves (2, 3) and these with coupling valves (4, 5) and shock absorbers (6, 7) via system pressure lines (260, 261, 262) for the engagement of the couplings (C, C'). In order to shift into a gear, two couplings are engaged and the coupling valves have an additional connection for the supply of a load-dependent modulation pressure. Via a control pressure line (14), system pressure lines (330, 331, 332 and 530, 531) as well as a modulation pressure line (17), a gear-control valve (3) and a coupling valve (5) with a shock absorber (6 ) are connected in such a manner that one of the couplings (C') is closed with a delay. Due to this delay, a smoother shifting results, particularly when shifting with a zero load or in the lower load range.

Abstract: A method of reverse clutch operation prevents excessive wear of the reverse clutch in a four-speed automatic transmission by venting one clutch, filling the reverse clutch and applying it, and filling and reapplying the one clutch.

Abstract: A hydraulic control system for an automatic transmission comprises a one-way valve arranged between a hydraulic line leading to a second speed apply chamber of a band brake and a hydraulic line leading to a fourth speed apply chamber of the band brake in such a manner as to allow fluid communication between them when a pressure dfferential takes place. The pressure differential takes place when the transmission upshifts from the first speed ratio to fourth speed ratio. Thus, during the 1-4 shift, a pressure build-up in the fourth speed apply chamber takes place in the same manner as a pressure build-up taking place in the second speed apply chamber under the control of a 1-2 accumulator valve.