Patent ID: 8590410

Claim:
An automatic dual-clutch transmission comprising: a first input shaft and a second input shaft arranged coaxially, a first output shaft and a second output shaft arranged in parallel to the first input shaft, a dual clutch having a first clutch for transmitting a rotational drive power from a prime mover to the first input shaft and a second clutch for transmitting the rotational drive power to the second input shaft, a plurality of odd-number stage drive gears comprising gears for odd-number stages, fixedly provided on the first input shaft, a plurality of even-number stage drive gear comprising gears for even-number stages, fixedly provided on the second input shaft, a plurality of first driven gears provided on the first output shaft to be freely rotatable, including at least a lowest speed driven gear and meshing with some gears of the odd-number stage drive gears and the even-number stage drive gears, a plurality of second driven gears provided on the second output shaft to be freely rotatable, including at least a highest speed driven gear and meshing with remaining gears of the odd-number stage drive gears and the even-number stage drive gears, a reverse gear provided on the first output shaft to be freely rotatable and meshing with a 2nd speed driven gear of the plurality of second driven gears, a first output shaft side gearshift clutch for connecting a gear selected from the plurality of first driven gears and the reverse gear with the first output shaft not to be relatively rotatable, and a second output shaft side gearshift clutch for connecting a gear selected from the plurality of second driven gears with the second output shaft not to be relatively rotatable, wherein the 2nd speed driven gear comprises a large-diameter gear meshing with a 2nd speed drive gear of the even-number stage fixed gears, and a small-diameter gear provided bodily with the large-diameter gear, being fewer in tooth number and smaller in diameter than the large-diameter gear and meshing with the reverse gear, the 2nd speed drive gear is formed directly on an outer circumferential surface of the second input shaft, the second output shaft side gearshift clutch is provided between the large-diameter gear of the 2nd speed driven gear and the second driven gear provided to be adjacent to the 2nd speed driven gear on a side opposite to the dual clutch in the axial direction, the small-diameter gear is provided on the second output shaft on a dual clutch side in comparison with the large-diameter gear in the axial direction, a cutting portion is formed on the second input shaft, on the side opposite to the dual clutch side of the 2nd speed drive gear in the axial direction, at the same position in the axial direction where the output side gearshift clutch exists, and a groove portion is formed on the second input shaft, on the dual clutch side of the 2nd speed drive gear, at the same position in the axial direction where the small-diameter gear exists.