A first rotary body is configured to rotate by a drive force input from an external source and has a first outer peripheral surface. A second rotary body has a second outer peripheral surface and is configured to rotate by following a rotation of the first rotary body through a friction generated between the first outer peripheral surface and the second outer peripheral surface. A first gear is configured to rotate together with the first rotary body. A second gear is configured to rotate together with the second rotary body and is directory engaged with the first gear. The first gear has a first pitch circle and the second gear has a second pitch circle. A radius of the first pitch circle is smaller than a radius of the first rotary body, and a radius of the second pitch circle is larger than a radius of the second rotary body.