Abstract: A planetary gear set including a plurality of pinions meshing with a sun gear and a carrier C that shaft-supports the pinions. The carrier has an annular peripheral wall that extends entirely around outer peripheries of the plurality of pinions. Thin-wall portions receded at a radially inner side are formed in the annular peripheral wall, at circumferential-direction positions corresponding to the positions of the pinions.

Abstract: A planetary gear set comprises a plurality of pinions P1, P2 meshing with a sun gear, and a carrier C that shaft-supports the pinions. The carrier has an annular peripheral wall 12 that extends entirely around outer peripheries of the plurality of pinions. Thin-wall portions 12a receded at a radially inner side are formed in the annular peripheral wall, at circumferential-direction positions corresponding to the positions of the pinions. The circumferential continuity of the annular peripheral wall secures a carrier rigidity. The formation of the thin-wall portions avoids interference between each pinion and the annular peripheral wall without involving an increased diameter of the carrier. The pinions P1 have a smaller diameter than the pinions P2. A platy wall portion 32 of a bridge portion 3 extends in the direction of a circumference of the carrier, outwardly of the pinions P1.

Abstract: A rotational direction of a rotational element at a high speed gear stage is different from a operational direction of a reaction torque at a low speed gear stage. The rotation by the reaction torque at the low speed gear stage is stopped with a self-energizing operation of a band brake operated by a hydraulic servo. A waiting pressure, which is lower for a predetermined amount than a engagement pressure at the self-energizing operation, and with which a basis of a racing amount occurs after a synchronizing point, is applied to the hydraulic servo until the synchronization is determined. The waiting pressure increases to the engagement pressure after determining the synchronization so that the rotational element is stopped gradually as preventing a long shift time.

Abstract: A hydraulic servo unit for a vehicular power transmission system having a helical gear, including a clutch for connecting predetermined rotary elements to each other and a hydraulic servo for applying the clutch, the hydraulic servo including a cylinder, a piston fitted in the cylinder, a push member abutting against the piston through a bearing for transmitting the push force of the piston to the clutch, and a return spring for the piston, one of the rotary elements including a reaction member opposed to the push member for transmitting the push force of the piston to a case, and the cylinder is a stationary cylinder formed in the case. Further, the return spring is arranged between the push member and the reaction member and is loaded to apply a load higher than the thrust force of the helical gear, as acting upon the reaction member.

Abstract: A band brake drum supporting device for an automatic transmission having a band drum to be retained in a case by fastening a band brake which is joined to a rotary element of the automatic transmission and arranged in the case. The drum includes a band engaging portion and a cylindrical drum supporting portion extending radially inward from the band engaging portion while being offset axially with respect to the band engaging portion. The outer circumference of the drum supporting portion is supported through two axially juxtaposed bearings on a stationary support portion which extends radially outward of the drum supporting portion from the case. The stationary support portion includes a cylindrical boss portion disposed coaxially with the drum supporting portion and engaging at its inner circumference with the two bearings and a planar flange portion extending radially outward from the end portion of the boss portion which is located closer to the band brake.