PROBLEM TO BE SOLVED: To compactly constitute a detent mechanism and an assist mechanism of a trunnion shaft, while avoiding complication of a structure.SOLUTION: A base part of a main shift lever 13 is provided with a cam 25 for rotating the trunnion shaft by integrally rotating with the main shift lever 13, and a cam arm 26 push-contacting with a cam surface of the cam 25. The cam surface of the cam 25 is provided with a neutral holding recessed part 25a for push-contacting in an engaging shape with the cam arm 26 when the trunnion shaft is a neutral position, an advance time push-contact surface 25b for push-contacting with the cam arm 26 when the trunnion shaft is an advance shift area, and a retreat time push-contact surface 25c for push-contacting with the cam arm 26 when the trunnion shaft is a retreat shift area. An inclination for making push-contact force of the cam arm 26 act so as to assist operation to the speed increase side of the trunnion shaft, is arranged on the advance time push-contact surface 25b and/or the retreat time push-contact surface 25c.COPYRIGHT: (C)2013,JPO&INPIT【課題】トラニオン軸のデテント機構及びアシスト機構を、構造の複雑化を回避しつつコンパクトに構成する。【解決手段】主変速レバー13の基部に、主変速レバー13と一体的に回動してトラニオン軸を回動させるカム25と、該カム25のカム面に押接するカムアーム26とを設けると共に、カム25のカム面に、トラニオン軸が中立位置のときにカムアーム26が係合状に押接する中立保持用凹部25aと、トラニオン軸が前進変速領域のときにカムアーム26が押接する前進時押接面25bと、トラニオン軸が後進変速領域のときにカムアーム26が押接する後進時押接面25cとを備え、前進時押接面25b及び/又は後進時押接面25cに、カムアーム26の押接力をトラニオン軸の増速側への操作を補助するように作用させる傾斜を設けた。【選択図】図7
