A Hydromechanical Transmission is disclosed which consists of a multiple turbine converter, a planetary gear set, one input shaft and one output shaft. The converter and planetary gear set are so arranged that an impeller is fastened to the ring gear of the planetary gear set. At least one turbine, which is driven directly by the input shaft, is fastened to the planet carrier; and the remaining turbines and the sun gear are splined to the output shaft. During low output speed operation, the impeller is driven by the differential action of the planetary gear set and rotates with a speed higher than that of the input shaft. Regenerative torque multiplication is achieved by the special arrangement of this invention resulting in a high torque ratio. During operation, the transmission of torque is accomplished through split mechanical and hydrodynamic paths, thereby improving both the power transmission efficiency, and the responsiveness and smoothness of operation.

An automatic transmission using a torque converter as a starting apparatus comprises a stator hub, an one-way clutch both of which are offset on the pump impeller side respectively, a brake cylinder case provided in an inner diameter portion of the torque converter, a brake piston provided in the brake cylinder case, a part or the whole of a reverse brake and a part of or the whole of a planetary gear which are accommodated in the inner diameter portion of the torque converter, thereby the axial length of the automatic transmission can be reduced.

The invention provides a power transmission apparatus which includes a hydraulic torque converter and mechanical gears. The torque converter includes a circulatory turbine in addition to the usual output turbine. The mechanical gears include first, second and third gearings. The first gearing connects the circulatory turbine to the converter input shaft. The second gearing connects the first gearing to the converter output member through a unidirectional freewheel. The third gearing connects the second gearing to an output member of the apparatus.

Power transmission apparatus having a torque convertor with an input shaft, an impeller connected to the input shaft, an output turbine, a first uni-directional detent, a reactor connected to a fixed part on which to react by means of the first uni-directional detent which is arranged to prevent rotation of the reactor in a reverse direction, a circulatory turbine, a first gearing connecting the circulatory turbine to the input shaft, a second gearing connecting the first gearing to an output shaft, a second uni-directional detent, and a brake arranged to act between part of the second gearing and a stationary part. The apparatus also includes a ring gear and a holding device acting on the ring gear, both being included in the second gearing, so that when the ring gear is held stationary by the holding device, the output shaft is driven in reverse.