To provide a structure of a device having good efficiency to be addi tionally difficult for generating a vibration when the device is driven to rotate.

Drive rollers 6a, 6a are driven to rotate, a driven disc 9a and an idler disc 11a are rotated, respectively by a pair of electric motors 19, 19. Of this operation, rotation of the driven disc 9a is transmitted to an output shaft 2a through a loading cam device 10a and a driven bracket 35. Applying of force in a circumferential direction of the driven disc 9a and the idler disc 11a to each of the drive rollers 6a, 6a is made difficult, to make its vibration difficult, so that the subject can be solved.