Patent ID: 8316730

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 an 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 to execute shifting, the engaging means comprising: an engaging projection formed on an inner circumferential surface of each gear to project therefrom and have an engaging surface in a circumferential direction; a cam rod brought into axially movably slidable contact with a hollow inner circumferential surface of the gear shaft and formed with a plurality of cam grooves on a slidable contact surface at desired axial positions; a pin member insertably fitted into a through-hole radially passing through the gear shaft at a desired position and advancing and retracting while coming into alternate contact with the slidable contact surface and cam grooves of the axially moved cam rod; a swing claw member pivotally supported for swing by a spindle pin provided on the gear shaft, having a pin-receiving portion adapted to receive the pin member and an engaging claw portion coming into abutment against an engaging surface of the engaging projection, on respective sides opposite to each other with respect to the swing center, and swung by the advancement and retraction of the pin member to allow the engaging claw portion to establish engagement with and disengagement from the engaging projection; and biasing means for biasing the swing claw member in a swing direction of bringing the engaging claw portion into engagement with the engaging surface of the engaging projection, wherein the biasing means is a compression spring interposed between the inner surface of the engaging claw portion of the swing claw member and a surface of the gear shaft opposed thereto.