Patent ID: 7146121

Claim:
An image forming apparatus comprising: an image carrier that carries an electrostatic latent image thereon; an electrostatic latent image forming unit that forms an electrostatic latent image on a surface of the image carrier; a developing unit comprising: a developer casing having a pair of side plates that oppose with each other and receives developer therein; a developing roller that carries the developer and supplies the developer to an image carrier, the developing roller being rotatably supported by an axis thereof that is supported by the side plates; and at least two protrusions being protruded from the side plates, at least one of the two protrusions is provided on an extensional line that passes an abutting portion where the developing roller and the image carrier abut with each other, and a rotational axis of the axis that supports the developing roller; wherein the developing unit is provided with two protrusions of a first protrusion and a second protrusion; wherein the first protrusion is provided on the extensional line; and wherein a distance between the abutting portion and the second protrusion is configured to be larger than a distance between the abutting portion and the first protrusion, and a guide mechanism that supports the developing unit to be displaceable in a predetermined direction so as to bring the contact portion of the developing unit into contact with an upper portion of the image carrier due to a weight of the developing unit.