Attachment structure for primary gear of engine

摘要

A primary drive gear 10 is configured so as to have its position changed, by mounting the primary drive gear 10 in an axial direction within a length range of a crankshaft so as to displace a toothed portion 12 of said primary drive gear 10 in the axial direction of said crankshaft in response to a boss portion 13 integrally provided on said toothed portion 12 of said primary drive gear 10 so that said primary drive gear 10 is registered with a position in the axial direction of the primary driven gear meshing with said primary drive gear 10.

主权项

1. An attachment structure for a primary gear of an engine, comprising:
a crankshaft accommodated in a crankcase; a main shaft disposed in parallel to said crankshaft; a primary drive gear mounted on said crankshaft; and a primary driven gear mounted on said main shaft and configured to mesh with said primary drive gear to transmit power to said main shaft through a clutch, wherein a position of said primary drive gear is configured to be changed and is mounted in an axial direction of said crankshaft within a length range of said crankshaft so as to displace a toothed portion of said primary drive gear in the axial direction of said crankshaft in response to a boss portion integrally provided on said toothed portion of said primary drive gear, wherein said primary drive gear is registered with a position in the axial direction of said primary driven gear meshing with said primary drive gear, wherein said primary drive gear is configured to be mounted in a first direction, and in a second direction reverse of the first direction, so as to accommodate one of a manual transmission or an automatic transmission, wherein the primary driven gear is disposed on an inner side of the engine in an axial direction of the main shaft, wherein said clutch comprises a twin clutch comprising a pair of clutch housings provided in a juxtaposed relationship with each other in an axial direction and configured to individually transmit power to said main shaft of an inner and outer dual structure with said primary driven gear interposed therebetween, and wherein the twin clutch comprises a first clutch and a second clutch provided in a back to back relationship with the primary driven gear sandwiched therebetween in the axial direction of the main shaft; and an extension to which said primary drive gear is mounted, wherein the extension is provided on the end portion side of said crankshaft within the length range of said crankshaft; and a projection projected in conformity with said extension is provided on said boss portion of said primary drive gear, and said boss portion is configured to be displaced on said extension of said crankshaft.