Patent ID: 7450886

Claim:
A developer-driving device, comprising: a photosensitive drum-driving unit that rotates a photosensitive drum; and a developing roller-driving unit that rotates a developing roller; wherein each of the photosensitive drum-driving unit and the developing roller-driving unit includes a one-way power transmission unit and a reduction gear slidably installed on a rotational shaft to receive power from a driving motor; and the one-way power transmission unit idles when a developer is being mounted on a main body and transmits power to the photosensitive drum and the developing roller after the developer is mounted on the main body; wherein the one-way power transmission unit includes a first clutch fixed on the rotational shaft and provided with concave portions, and a second clutch installed between the first clutch and the reduction gear with projections inserted in the concave portions of the first clutch and having driven teeth of the second clutch facing the reduction gear.