Image forming apparatus including developing device supporting structure having guide groove

An image forming apparatus comprising:

• a main casing having an opening;
• an opening-closing member configured to open and close the opening;
• a drum frame detachably attached to the main casing through the opening and including a photosensitive drum;
• a developing device detachably attached to the main casing through the opening and including a developing roller;
• and
• a developing device supporting structure including left and right side walls, each of the side walls having a guide groove, the guide groove extending from an upper end of each of the side walls in a direction away from the opening,
• wherein
• the developing device includes a developing device frame configured to support the developing roller, the developing device frame has left and right protrusions each of which protrudes and extends along an axis of the developing roller, and each of the protrusions is configured to fit into the guide groove at a position farthest from the opening,
• in a state where the developing device is positioned between the left and right side walls and each of the protrusions of the developing device are fitted into the guide groove of each of the left and right side walls, the left and right side walls is supported by the main casing so as to be movable between a first position, in which the developing roller is close to the photosensitive drum, and a second position, in which the developing roller is away from the photosensitive drum, and
• the developing device is interlocked with the opening-closing member such that the developing roller is separated from the photosensitive drum when the opening-closing member is opened, and the developing roller is close to the photosensitive drum and developable when the opening-closing member is closed.