Image forming apparatus with detachable drum unit and developing unit

An image forming apparatus comprising:

• a drum unit provided in an apparatus main body and including a rotatably supported photoconductor drum;
• and
• a developing unit including a rotatably supported developing roller, a primary gear, and a secondary gear and configured to be attached to the drum unit, the primary gear receiving a rotational force from a drive portion provided in the apparatus main body, the secondary gear being integrally provided with a rotation shaft of the developing roller and receiving a rotational force from the primary gear;
• and
• a biasing mechanism that elastically biases the developing unit toward the photoconductor drum, wherein
• the developing unit includes:
• a first developing unit projection formed to project out from opposite sides of the developing unit along an extension line of a rotation shaft of the developing roller;
• and
• a second developing unit projection provided on an opposite side to the first developing unit projection with respect to the primary gear in a state where the developing unit has been attached to the drum unit, the second developing unit projection projecting out from the opposite sides in parallel to the first developing unit projection, and
• the drum unit includes:
• a first support surface that supports the first developing unit projection against a moment of a force that is applied from the primary gear to the developing unit via the secondary gear, the first support surface being parallel to a biasing direction of the biasing mechanism;
• and
• a second support surface that supports the second developing unit projection against the moment of the force, the second support surface being parallel to the biasing direction.

An image forming apparatus comprising:

• an apparatus main body having an opening that is closed by a cover portion;
• a drum unit including a rotatably supported photoconductor drum and attached through the opening to the apparatus main body in a detachable manner;
• and
• a developing unit including a rotatably supported developing roller and attached to the drum unit in a detachable manner, wherein
• the drum unit includes:
• an abutting member supported in such a way as to be displaced between a reference position and an action position that is further away from the photoconductor drum than the reference position, the abutting member abutting on the developing unit attached to the drum unit to be displaced from the reference position to the action position;
• and
• an elastic member that elastically biases the abutting member toward the photoconductor drum, and thereby biases the developing unit toward the photoconductor drum via the abutting member, and
• the apparatus main body includes a locking portion configured to lock the abutting member located at the action position, thereby restricting the drum unit from moving in a direction of being removed from the apparatus main body, wherein a locking of the abutting member by the locking portion is released, when the abutting member is displaced to the reference position by a biasing force of the elastic member.