Patent ID: 8302501

Claim:
A multistage transmission in which a plurality of drive gears and driven gears are rotatably supported by respective parallel gear shafts in a constant-mesh state for each speed-change stage, one of the plurality of drive gears and driven gears is secured to a gear shaft and engaging means provided between the other of the plurality of drive gears and driven gears and the gear shaft to establish engagement therebetween is switchably driven by shift drive means to execute shifting, the engaging means comprising: normal rotation odd-numbered engaging members each adapted to bring an odd-numbered stage gear of an odd-numbered speed-change stage into engageable abutment against a gear shaft in a normal rotation direction of the gear to simultaneously rotate the odd-numbered stage gear and the gear shaft; normal rotation even-numbered engaging members each adapted to bring an even-numbered stage gear of an even-numbered speed-change stage into engageable abutment against the gear shaft in a normal rotation direction of the gear to simultaneously rotate the even-numbered stage gear and the gear shaft; a normal rotation odd-numbered cam rod adapted to come into axially movably slidable contact with a hollow inner circumferential surface of the gear shaft, formed with a plurality of odd-numbered stage cam grooves on a slidable contact surface at desired axial positions, and operating the normal rotation odd-numbered engaging members; and a normal rotation even-numbered stage cam rod adapted to come into axially movably slidable contact with the hollow inner circumferential surface of the gear shaft, formed with a plurality of even-numbered stage cam grooves on a slidable contact surface at desired axial positions, and operating the normal rotation even-numbered engaging members, wherein when the shift drive means executes upshift to a one-step-upper speed-change stage reduced in reduction ratio by one stage, the normal rotation odd-numbered stage cam rod and the normal rotation even-numbered stage cam rod alternately operate the normal rotation odd-numbered stage engaging members and the normal rotation even-numbered stage engaging members for shifting.