Constant-mesh transmission

A constant-mesh transmission comprising:

• a first gear provided for a first rotary shaft so as to rotate integrally with the first rotary shaft;
• a second gear which meshes with the first gear and is rotatably provided for a second rotary shaft;
• and
• a synchronizing mechanism, said synchronizing mechanism having
• a shifter provided for said second rotary shaft so as to rotate integrally with said second rotary shaft and to be movable in the axial direction,
• a ring-shaped recess formed in said first gear, and
• a synchronizer ring disposed in the recess so as to be rotatable relative to said second gear and pressed by said shifter at the time of changing speed to move in said axial direction so as to come into frictional engagement with said first gear, thereby achieving synchronization between said shifter and said first gear,
• an index washer as a synchronization positioning member, and
• a synchronizer spring as an intermediate member for transmitting a press force in the axial direction of th second gear to the synchronizer ring,
• wherein a first connection spline formed in a circumferential wall face of said recess and a first synchronization spline formed in a circumferential face of said synchronizer ring occupy positions where the first connection spline, the first synchronization spline, and the synchronizer ring at least partly overlap with each other in said axial direction,
• a second connection spline and a second synchronization spline are formed in said shifter, the second connection spline meshes with said first connection spline, and the second synchronization spline presses said first synchronization spline in said axial direction to make said synchronizer ring and said first gear come into frictional engagement with each other and meshes with said first synchronization spline, and
• at the time of changing speed, said first and second synchronization splines mesh with each other and, after that, said first and second connection splines mesh with each other.