A method of operating an automatic transmission of a motor vehicle, in which a hydraulic pump associated with a hydraulic system for the supply of pressure is driven by a drive motor. When the motor vehicle starts, a hydrodynamic starting element forms a driving connection between the drive motor and the automatic transmission. Hydraulic shifting elements (B1, B2, B3, C1, C2) are actuated for engaging gear steps. When the drive motor is started, a shifting element (B1, B2, B3, C1, C2) of the automatic transmission is engaged, and, during the engagement process of the shifting element (B1, B2, B3, C1, C2), a time of a rotational speed variation (n.sub.Ab, n.sub.Tu) of the automatic transmission is determined. With the help of the determined rotational speed variation (n.sub.ab, n.sub.Tu), a time point is determined at which a pressure present in the hydraulic system reaches or exceeds a target pressure level.

A method for operating a multispeed transmission in a motor vehicle, provided with planetary gearings which can be switched with four switching elements to different gear ratios, and which can be connected by input elements and output elements to a driven input shaft and to an output shaft. The reaction elements can be coupled or locked with a brake, wherein the four planetary gearings can be switched by two brakes and by three shifting clutches to eight forward gear ratios. In the higher gear ratios, at least one first shifting clutch is connected to produce a force flow in the transmission, and in the lower gear ratios, at least a second shifting clutch is connected to produce a force flow in the transmission.

A pressurized oil supply system for a transmission of an automotive vehicle having an engine cut off system is provided that includes an accumulator, a supply line connected with the accumulator, a check valve fluidly connecting the accumulator with the supply line, a solenoid controlled valve fluidly connected with the accumulator, and a discharge line connected with the transmission. A feed line supplying transmission pump pressurized oil is provided. A metering valve connects the feed line with the supply line to regulate the oil pressure delivered to the supply line.

A hydraulic control device includes an oil pump for generating a hydraulic pressure by being rotated by power of a driving force source, a driving force source stopping unit that stops rotation of the driving force source when a predetermined condition holds, and a cut-off unit that cuts off transmission of the power from the driving force source to the oil pump when the driving force source rotates in a reverse direction as the rotation of the driving force source is stopped by the driving force source stopping unit.

A hybrid vehicle is equipped with a drive unit, and an automatic transmission. The automatic transmission includes engagement elements that can transmit power between the drive unit and driving wheels. The drive unit includes an engine, a first motor generator, a second motor generator, and a planetary gear mechanism. The hybrid vehicle is further equipped with a mechanical oil pump and an electrical oil pump, and a controller. The controller continues operating the electrical oil pump while the internal combustion engine is not in operation after the internal combustion engine is stopped as a result of a system stop operation by a user while the vehicle is running at a vehicle speed equal to or higher than a predetermined value.

A hydraulic control system of an automatic transmission for a vehicle provided with an idle stop and go (ISG) system includes a mechanical hydraulic pump driven by a torque of an engine, the mechanical hydraulic pump pumping a fluid stored in an oil pan, a regulator valve, a manual valve, a linear solenoid valve for controlling the hydraulic pressure supplied from the manual valve through the second hydraulic line and for supplying the controlled hydraulic pressure to a third hydraulic line, a switch valve, and an electric hydraulic pump driven by electric energy for pumping the fluid stored in the oil pan through a fifth hydraulic line and for feeding the pumped fluid to a sixth hydraulic line connected to the fourth hydraulic line.

A hydraulic control system of an automatic transmission for a vehicle provided with an ISG system is disclosed. The hydraulic control system supplies hydraulic pressure to first and second friction members operated at a gear stage where starting control is performed. In particular, the hydraulic control system includes: a mechanical hydraulic pump; an electric hydraulic pump; first and second linear solenoid valves to control hydraulic pressure generated by the mechanical pump; first and second switch valves to selectively supply the controlled hydraulic pressure to the first and second friction members, respectively; and a third switch valve to selectively supply a portion of the hydraulic pressure of the first friction member to the second friction member.

A method and device for actuating a shift element of an automatic transmission having a start-stop function and a pressure medium pump driven by an internal combustion engine. The shifting elements are clutches or brakes that can be actuated by a piston which is actuated for engagement via pressure supplied to a pressure space. The pressure space is depressurized when the engine stops. To enhance start-stop operation, the shifting elements comprise an additional pressure space that acts, in opposition to the pressure space acting in the engaging direction, as a controllable restoring mechanism which can be rendered inactive, if desired. If the engine stops and the automatic start-stop function is activated, the additional pressure spaces, acting in the restoring direction, are depressurized before the pressure drop in the pressure spaces, acting in the engaging direction, of the pistons, but are otherwise permanently pressurized during driving operation.

A vehicle includes an engine, automatic transmission, and a controller. The engine is configured to auto-start and auto-stop. The automatic transmission has a shift-by-wire gear selector. The controller is programmed to, in response to shifting the gear selector to a neutral position while the engine is running, command the engine to auto-stop.

A power transmission device that includes a transmission including a plurality of engagement elements for transmitting power from a motor to axles; a case to accommodate the transmission; a hydraulic control device to control hydraulic pressure to the engagement elements; a hydraulic oil reservoir that stores hydraulic oil; and a first pump that is operated by the power from the motor and that suctions the hydraulic oil from the hydraulic oil reservoir through a strainer and supplies the hydraulic oil to the hydraulic control device.