Patent ID: 8090272

Claim:
An image forming apparatus comprising: a main unit; and a developer cartridge detachably attached to the main unit, wherein the developing cartridge comprises: a rotation body having a rotational axis and rotatable in a rotation direction; and a first rotational arm and a second rotational arm which are rotatable around the rotational axis, and the main unit comprises: a driving unit configured to rotate the rotation body in the rotation direction; a detecting arm swingable from a neutral position toward a first swing direction and toward a second swing direction opposite to the first swing direction; an elastic member that urges the detecting arm toward the neutral position; a detecting unit configured to detect a swing of the detecting arm; and a controller configured to determine whether the developer cartridge is a new product according to the presence of a swing of the detecting arm detected by the detecting unit and determine a type of the developer cartridge according to a number of swings detected by the detecting unit, wherein, when the developer cartridge is attached to the main unit, the first rotational arm contacts with the detecting arm to swing in the first swing direction from the neutral position, wherein when the rotation body rotates by a predetermined rotation amount, the second rotational arm contacts with the detecting arm causing the detecting arm to swing in the second direction from the neutral position.