Dual input clutch transmission

Claim 1

A dual input clutch transmission in which a pair of input clutches (12 and 14) are selectively operable to connect a drive shaft (10) to respective ones of a pair of input shafts (16 and 18), a plurality of ratio gears (20, 22, 24, 40, 42 and 44) are drivingly connected to respective ones of the input shafts (16 and 18), a plurality of driven gears (28, 30, 32, 46, 48 and 50) are rotatably supported on an output shaft (34) and mesh with respective ones of the ratio gears (20, 22, 24, 40, 42 and 44) on the input shafts (16 and 18), and a plurality of mechanical clutch means (58, 60 and 62) are selectively engageable for drivingly connecting selected ones of the driven gears (28, 30, 32, 46, 48 and 50) to the output shaft (34), characterised in that the ratio gears (20, 22, 24, 40, 42 and 44) comprise first, second and third ratio gears (40, 42 and 44) drivingly connected to one (18) of the input shafts (16 and 18), and first, second and fourth ratio gears (20, 22 and 24) drivingly connected to the other (16) of the input shafts (16 and 18), with the said plurality of mechanical clutch means (58, 60 and 62) in operation co-operating with the input clutches (12 and 14) to selectively provide first, second, third and fourth ratios between the drive shaft (10) and the output shaft (34), whereby a shift from fourth ratio to second ratio can be accomplished by engagement of the appropriate one of the mechanical clutch means (58, 60 and 62) to establish second ratio between the said one input shaft (18) and the output shaft (34), with fourth ratio being established through the said other input shaft (16), followed by interchanging of the input clutches (12 and 14) such that fourth ratio is thereby disengaged from the drive shaft (10) and second ratio is engaged with the drive shaft (10).