Patent ID: 8023879

Claim:
An image forming apparatus, comprising: a roller shaft; a paper-transporting roller which is coupled to the roller shaft and transports a document; a driving wheel which is coupled to the roller shaft and rotates along with the roller shaft; a main frame to support the roller shaft and the paper-transporting roller and the driving wheel; and one of a high speed driving module and a low speed driving module to supply a rotational driving force to the paper transporting roller and detachably coupled to the main frame, wherein the high speed driving module comprises a driving part to generate the rotational driving force and a clutch unit having a clutch shaft having an axial line deviated from an axial line of the roller shaft, a transmission wheel connected to the clutch shaft and which transmits the rotational driving force to the driving wheel, and a rotation connecting part to selectively transmit the rotational driving force to the transmission wheel, and wherein the low speed driving module comprises a driving part to generate the rotational driving force, a transmission gear to transmit the rotational driving force to the driving wheel and a one-way gear to selectively transmit the rotational driving force from the driving part to the transmission gear, wherein both the high and the low speed driving modules are compatibly coupled to the main frame such that one of the high and the low speed driving modules can be replaced with the other of the high and the low speed driving modules.