Hydraulically operated transmission

Claim 1

A hydraulically operated transmission comprising first- to fourth-speed gear trains established by corresponding first-speed to fourth-speed hydraulic clutches, a one-way clutch incorporated in the first-speed gear train for permitting overrotation of an output side, and a first-speed maintaining hydraulic clutch also incorporated in the first-speed gear train so as to be in parallel with the one-way clutch, said transmission further including a pair of first and second input shafts and an output shaft carried in parallel with one another within a transmission case, said first input shaft being connected to a fluid torque converter connected to a crankshaft of an engine, through that end wall of the transmission case which is closer to the engine and to which a valve block is assembled, said first and second input shafts being rotatably connected at an opposite end to the engine, through an idle gear on said output shaft in an interlocking manner, said first-speed to fourth-speed gear trains being divided into two sets, each set including two gear trains, the two gear trains of one of the sets being interposed in parallel between said first input shaft and said output shaft, the two hydraulic clutches for establishing, respectively, said two gear trains of said one set being disposed in a back-to-back relation on said first input shaft, said two gear trains of the other set being interposed in parallel between said second input shaft and said output shaft, the two hydraulic clutches for establishing, respectively, said two gear trains of said other set being disposed in a back-to-back relation on said second input shaft, and said first-speed maintaining hydraulic clutch being disposed on said output shaft so as to be axially overlapped with said valve block.