Patent ID: 7421227

Claim:
A developing device comprising: a predetermined housing structure; a developing sleeve provided in a housing for supplying toner particles to a latent image area on a peripheral surface of a photoconductive drum while rotating about an axis, the developing sleeve including a magnet therein; a pair of magnetic members provided so as to face opposite end portions of a peripheral surface of the developing sleeve at a spacing of a predetermined distance from the peripheral surface of the developing sleeve, the magnetic members each having an inner surface having the shape of an arc; and a blade provided so as to face a central portion of the peripheral surface of the developing sleeve at a spacing of a predetermined distance from the peripheral surface of the developing sleeve, the blade being adapted for adjusting the amount of toner particles to be supplied to the photoconductive drum; wherein the magnetic member and the developing sleeve are mounted to maintain a gap between the arc-shaped inner surface of the magnetic member and the peripheral surface of the developing sleeve that gradually increases from upstream to downstream in a rotational direction of the developing sleeve.