When a third sun gear is fitted into a fitting hole of a clutch drum, external circumferential spline teeth and internal circumferential spline teeth that configure a spline-fitted part start meshing with each other before a tolerance ring comes into contact with the third sun gear and the clutch drum. Accordingly, the external circumferential spline teeth and the internal circumferential spline teeth mesh with each other, thereby centering the third sun gear and the clutch drum, thus accurately assembling the third sun gear and the clutch drum without causing eccentricity thereof

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 mounted on a vehicle having an automatic engine stop mechanism for automatically stopping and restarting an engine, is provided. The transmission includes a piston having first and second surfaces, friction plates, engaging and disengaging hydraulic pressure chambers, a hydraulic pressure control valve for supplying/discharging hydraulic pressure to/from the chambers, first and second oil paths communicating the control valve with the chambers, a pressure reducing valve for preventing pressure of the disengaging chamber from exceeding a given set pressure, a hydraulic pressure supply device for supplying pressure to the control valve in the automatic stop state, and a mechanical oil pump for supplying pressure to the control valve while the engine is driving, the second surface having a larger pressure receiving area than the first surface. The method includes adjusting the set pressure to be lower in the automatic stop state than while driving.

In a control apparatus for a vehicle, when it is not determined that a downshift to a second gear stage should be carried out and an accelerator depression amount change rate is equal to or smaller than a predetermined value when it is determined that a downshift to a first gear stage should be carried out, a single downshift command to the first gear stage is output. When it is not determined that the downshift to the second gear stage should be carried out and the accelerator depression amount change rate is larger than the predetermined value when it is determined that the downshift to the first gear stage should be carried out, a current gear stage is maintained. Therefore, a skip downshift to the second gear stage can be carried out when it is determined that the downshift to the second gear stage should be carried out.

A transmission (G) includes an input shaft (GW1), an output shaft (GW2), an electric machine (EM), a plurality of planetary gear sets (P1-P3; 2P1-2P5), and gear-implementing shift elements (S1-S6; 2S1-2S5). Via engagement of a first of the gear-implementing shift elements (S1, 2S1), which is a force-locking shift element having a variable torque transmission capacity, the input shaft (GW1) and an element (E1, 22E1) of one of the planetary gear sets (P3; 2P4) can be brought into a fixed rotational speed relationship with respect to each other. Another element (E2, 22E2a, 22E2b) of one of the planetary gear sets (P1, 2P3, 2P5) is permanently connected to a rotor (R) of the electric machine (EM). By engaging an auxiliary shift element (ZS, 2ZSa, 2ZSb), which is a form-locking shift element, the rotor (R) and the input shaft (GW1) can be brought into a fixed rotational speed relationship with respect to each other.

A family of transmission gearing arrangements provides between eight and ten forward speed ratios and a reverse speed ratio. Three planetary gear sets are located on the input axis and a fourth planetary gear set is located on an offset axis. Axis transfer gears convey power between the input axis and the offset axis. One axis transfer gear is supported by a front support while another is supported by a center support. The center support also supports a clutch module and supplies pressurized fluid to engage the clutches in the clutch module.

A planetary carrier where the second pinion gears are disposed so as to be at least partially located in the spaces between the adjacent bridge portions, an outer peripheral surface of each of the bridge portions is provided with a spline onto which a friction engagement plate constituting a friction engagement element is fitted, an inner peripheral surface of each of the bridge portions is provided with a pair of wall portions that extend in the axial direction along side edges on both sides of each of the bridge portions and protrude radially inward, and each of the bridge portions is provided with a plurality of oil holes through which an inside and an outside of each of the bridge portions communicate with each other.

An automatic transmission includes a first planetary gear set, a second planetary gear set, and a first brake. A first sun gear includes a first split sun gear on a drive source side, and a second split sun gear on a side opposite to the drive source. The first spilt sun gear is coupled to the first brake, and is fixed to a transmission case during engagement of the first brake. The second split sun gear is constantly coupled to a second sun gear. An input shaft is constantly coupled to a first carrier while passing through the first split sun gear, and between the first and second split sun gears. An output shaft is constantly coupled to a second carrier.

A dual clutch transmission for motor vehicles has first and second input shafts, two clutches configured to selectively couple the input shafts to an engine, two intermediate shafts arranged parallel to the input shafts, gearwheel pairs of which a fixed gearwheel is arranged on one of the input shafts and a freely rotating gearwheel is arranged on one of the intermediate shafts, freely rotating output gearwheels arranged on each of the two intermediate shafts and meshing with a differential wheel, and coupling devices configured to selectively couple the freely rotating gearwheels to the respective intermediate shaft, of which at least the coupling devices for the output gearwheels are of double acting design. A dual clutch transmission of this kind makes a large number of gears possible without significantly increasing the dimensions of the transmission or the weight thereof.

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.