Patent ID: 8135315

Claim:
A developing unit, comprising: a developer bearing member to bear a two-component developer on a surface thereof, the two-component developer including magnetic carrier particles and toner particles, the developer bearing member including a magnetic field generator, and a nonmagnetic hollow body containing the magnetic field generator for bearing the two-component developer on an exterior perimeter surface thereof via a magnetic force generated via the magnetic field generator, a developer container disposed adjacent to and oriented vertically lower than the developer bearing member, the developer container including a developer storing chamber to store the two-component developer therein; an agitation/conveyance member disposed in the developer container to convey the two-component developer in an axial direction of the developer bearing member while agitating the two-component developer; and a developer regulating member disposed opposite the developer bearing member to regulate a thickness of a layer of the two-component developer held on the developer bearing member, wherein the two-component developer conveyed in the developer container is attracted by the magnetic force exerted by the magnetic field generator to the developer bearing member, the two-component developer being regulated by the developer regulating member and then passing through a development region of the developer bearing member facing an image bearing member and returning to the developer container, wherein the magnetic field generator includes first and second magnetic poles with an identical polarity disposed adjacent to each other and downstream from the development region in a direction of rotation of the developer bearing member, the first and second magnetic poles generating respective magnetic forces for removing the two-component developer from the developer bearing member after the two-component developer passes through the development region, wherein the second magnetic pole is disposed downstream from the first magnetic pole, in a direction of conveyance of the two-component developer by the developer bearing member, and proximate to the developer regulating member so as to generate a magnetic force to attract the two-component developer from the developer storing chamber in the developer container, thereby forming a magnetic brush of the two-component developer on the developer bearing member regulated by the developer regulating member, and wherein the developer regulating member includes a base member and a thin plate magnetic member projecting outwardly from the base member toward an exterior perimeter surface of the developer bearing member upstream from the base member in the direction of conveyance of the two-component developer by the developer bearing member, a planar surface of the magnetic member facing the second magnetic pole across an effective development region, and the magnetic member projecting in a direction transverse to a vertical direction between the developer container and the developer bearing member.