Patent ID: 7596339

Claim:
An image forming apparatus comprising: an image forming subsystem including an image bearing member, an exposure unit, a charging unit, and a developing unit, the image forming subsystem being interchangeable; a sheet transport subsystem configured to transport a sheet medium in the image forming apparatus, the sheet transport subsystem being interchangeable; a mounting base configured to removably support the image forming subsystem and the sheet transport subsystem; a control unit configured to control operation of the image forming apparatus; a guiding mechanism configured to allow each of the image forming subsystem and the sheet transport subsystem to move on the mounting base; a positioning unit configured to determine the position of the subsystem relative to the mounting base when the subsystem is mounted on the mounting base; and a position detecting unit configured to detect a relative position between the image forming subsystem and the sheet transport subsystem in a condition that that the subsystems are mounted on the mounting base, wherein the mounting base is capable of mounting one of a plurality of the image forming subsystems having different performances and one of a plurality of the sheet transport subsystem having different specifications thereon, wherein the control unit is configured to control the operation of the image forming apparatus in accordance with a combination of the mounted image forming subsystem and the sheet transport subsystem, and wherein the image forming subsystem controls an image forming position based on the detected relative position.