Photosensitive drum cartridge and an image forming apparatus using the same

An image forming apparatus comprising an image forming apparatus main body, and a photosensitive drum cartridge which is to be mounted to the image forming apparatus main body, said photosensitive drum cartridge comprising:

• a photosensitive drum cartridge main body provided with a supporting member made of an elastic material for supporting a photosensitive drum, the supporting member comprising:
• a supporting shaft for rotatably supporting the photosensitive drum;
• and a base body means integrated with the supporting shaft for positioning the supporting shaft with respect to the photosensitive drum cartridge main body;
• said base body means including a flat plate having a shape identical to a front end portion of a sidewall of the cartridge main body, said base body means also having an engaging body integrally formed at the center of said flat plate, said engaging body having an oval projection protruding form said flat plate, and a pair of engaging pieces integrally formed at right and left sides of said projection and separated form said flat plate by a predetermined distance, said supporting shaft projecting from the center of said projection,
• wherein a positioning boss is formed on the photosensitive drum cartridge, said positioning boss comprising a half-cylinder shaped projection formed integrally on an outer face of said flat plate, a positioning piece having a half-disk shape protruding from an under portion of said half-cylinder shaped projection so as to be separated from the flat plate by a gap having a greater thickness than a frame of said printer main body, the image forming apparatus main body comprises an insertion portion into which the positioning boss is to be inserted, and the insertion portion comprises a positioning member for positioning the positioning boss in the vertical and horizontal directions through the rotation of the photosensitive drum cartridge.