Frictional drive transmission

A frictional drive transmission comprising:

• a transmission case including a first support member and a second support member;
• a drive roller unit including a plurality of drive rollers having different diameters, with the drive rollers being rotatably supported on the transmission case by the first support member;
• a driven roller unit including a plurality of driven rollers having different diameters, with the driven rollers being rotatably supported on the transmission case by the second support member and each of the driven rollers being associated with a corresponding one of the drive rollers to form a plurality of roller pairs;
• a gear shifting mechanism operatively coupled to one of the drive and driven roller units to selectively contact one of the roller pairs together to form a contacting roller pair,
• at least one of the first and second support members including
• a roller shaft support member supporting a shaft of one of the drive and driven roller units;
• a cam-shaped support structure having a cam slanted surface and a mounting surface with the cam slanted surface being slanted with respect to a contact direction of the contacting roller pair to contact the roller shaft support member such that a pushing force is developed in the contact direction between the contacting roller pair and the mounting surface being arranged at an angle smaller than forty-five degrees with respect to the cam slanted surface;
• and
• an elastic member arranged between the transmission case and the mounting surface to apply the pushing force in the contact direction of the contacting roller pair, with the elastic member biasing the mounting surface relative to the transmission case such that the mounting surface is movable in a direction parallel to the contact direction of the contacting roller pair relative to the transmission case.