Patent ID: 8474346

Claim:
A multi-stage transmission wherein a drive gear shaft and a driven gear shaft are disposed in parallel; a plurality of drive gears and a plurality of driven gears are supported on the drive gear shaft and the driven gear shaft, respectively, in a manner that the drive gears and the driven gears are constantly meshed with each other to constitute meshing gear combinations for different speeds; said plurality of drive gears are fixed to the drive gear shaft supporting the same, while the plurality of driven gears are supported on the driven gear shaft, said driven gear shaft is a hollow gear shaft; and the plurality of driven gears are supported on the hollow gear shaft individually in an engageable and disengageable manner through engaging means, which are operated by gear shift driving means for gear shift: said engaging means comprises: engaging parts provided on an inner peripheral surface of each of the plurality of driven gears at circumferentially spaced positions and having engaging surfaces in circumferential directions; a first engaging device provided in the hollow gear shaft to cause the engaging parts of a first driven gear and the hollow gear shaft to be engaged with each other in a rotational direction of the first driven gear; a second engaging device provided in the hollow gear shaft to cause the engaging parts of a second driven gear, one step lower in reduction ratio than the first driven gear, and the hollow gear shaft to be engaged with each other in the rotational direction of the second driven gear; a third engaging device provided in the hollow gear shaft to cause the engaging parts of the first driven gear and the hollow gear shaft to be engaged with each other in a counter-rotational direction of the first driven gear; a fourth engaging device provided in the hollow gear shaft to cause the engaging parts of the second driven gear and the hollow gear shaft to be engaged with each other in the counter-rotational direction of the second driven gear; first cam rods put in sliding contact with an inner peripheral surface of an internal hole of the hollow gear shaft so as to be movable in an axial direction, and provided in sliding contact surfaces thereof with a plurality of cam surfaces at axially spaced locations to operate the second engaging device and the third engaging device by movement thereof; and second cam rods put in sliding contact with the inner peripheral surface of the internal hole of the hollow gear shaft so as to be movable in the axial direction, and provided in sliding contact surfaces thereof with a plurality of cam surfaces at axially spaced locations to operate the first engaging device and the fourth engaging device by movement thereof; the first cam rods and the second cam rods being moved by the gear shift driving means so as to make a gear shift.