A dual speed gearbox is provided that utilizes hydraulically actuated one way clutches and a planetary gear assembly to shift between a direct drive configuration and an overdrive configuration.

A method of controlling an automatic transmission is provided. The automatic transmission includes a piston having first and second surfaces opposite from each other, friction plates, engaging and disengaging hydraulic pressure chambers for supplying and discharging hydraulic pressure and directing the piston to push the friction plates to be engaged and disengaged, a hydraulic pressure control valve for supplying and discharging hydraulic pressure to and from the chambers, first and second oil paths communicating the valve with the chambers, and a pressure reducing valve disposed in the second oil path and for preventing hydraulic pressure of the disengaging hydraulic pressure chamber from exceeding a given set pressure. The second surface has a larger area for receiving hydraulic pressure than an area of the first surface for receiving hydraulic pressure. The method includes changing the given set pressure according to information regarding a state of the automatic transmission.

A method of controlling an automatic transmission is provided. The automatic transmission includes a piston having first and second surfaces opposite from each other, friction plates, engaging and disengaging hydraulic pressure chambers for supplying and discharging hydraulic pressure and directing the piston to push the friction plates to be engaged and disengaged, a hydraulic pressure control valve for supplying and discharging hydraulic pressure to and from the chambers, first and second oil paths communicating the valve with the chambers, and a pressure reducing valve disposed in the second oil path and for preventing hydraulic pressure of the disengaging hydraulic pressure chamber from exceeding a given set pressure. The second surface has a larger area for receiving hydraulic pressure than an area of the first surface for receiving hydraulic pressure. The method includes changing the given set pressure according to information regarding a state of the automatic transmission.

A vehicle drive device includes: rotary electric machine; rotor support member; friction engagement device disposed at position on inner side in radial direction with respect to a rotor and at which friction engagement device overlaps rotor as viewed in radial direction along radial direction; and a first and second bearing that rotatably support rotor support member. Friction engagement device has a first and second engagement device disposed side by side in axial direction. First piston portion of first engagement device and a second piston portion of second engagement device are disposed separately on both sides in axial direction across a first and a second friction member. First bearing is disposed at a position at which first bearing overlaps first piston portion as viewed in the radial direction. Second bearing is disposed at a position at which second bearing overlaps second piston portion as viewed in the radial direction.

A transmission device, wherein the compound planetary gear mechanism increases the speed of the power transmitted to the input element and transmits the resultant power to the first and the second output elements when the fixable element is non-rotatably held stationary by the first brake; and the first and the second clutches are disposed on a side closer in the axial direction to the compound planetary gear mechanism than the first and the second planetary gear mechanisms.

A dual clutch transmission comprises a housing formed therein with a gear chamber incorporating an odd-numbered speed gear train group and an even-numbered speed gear train group. An end of the input shaft is connected to an engine, and a cover is detachably attached to the housing opposite the end of the input shaft so as to define a clutch chamber divided from the gear chamber. A first clutch for the odd-numbered speed gear train group and a second clutch for the even-numbered speed gear train group are disposed in the clutch chamber. Fluid passages for supplying hydraulic fluid to the first and second clutches are formed in the cover.

A dual clutch transmission comprises a housing formed therein with a gear chamber incorporating an odd-numbered speed gear train group and an even-numbered speed gear train group. An end of the input shaft is connected to an engine, and a cover is detachably attached to the housing opposite the end of the input shaft so as to define a clutch chamber divided from the gear chamber. A first clutch for the odd-numbered speed gear train group and a second clutch for the even-numbered speed gear train group are disposed in the clutch chamber. Fluid passages for supplying hydraulic fluid to the first and second clutches are formed in the cover.

An electronic control device for controlling at least one rotatably arranged actuator includes electronic components, such as a device for the contact-free reception of electrical energy and the contact-free reception of signals, a device for generating magnetic fields, and a common housing that encloses the electronic components and assimilates them. The control device is rotatable and designed for attaching on or into a component rotating around a rotational axis.

An electronic control device for controlling at least one rotatably arranged actuator includes electronic components, such as a device for the contact-free reception of electrical energy and the contact-free reception of signals, a device for generating magnetic fields, and a common housing that encloses the electronic components and assimilates them. The control device is rotatable and designed for attaching on or into a component rotating around a rotational axis.

Provided is an automatic transmission including: an input section to which power generated by a drive source is input; an output section configured to output a drive force; and a gear shifting mechanism configured to change a gear ratio. The power is input to the input section without intervention of a hydraulic power transmission device. The gear shifting mechanism includes a predetermined frictional engagement element for achieving a starting gear ratio of a vehicle. The frictional engagement element includes: a plurality of friction plates arranged with clearances therebetween; a piston movable between a releasing position where the friction plates are brought into a released state, and an engaging position where the friction plates are brought into an engaged state by pressing the friction plates; and an urging mechanism configured to urge the piston so that the piston abuts against the friction plates and the clearances are reduced.