Patent ID: 7483655

Claim:
A developing unit, comprising: a developing roller configured to support developer on the surface thereof; a first agitation transport member configured to simultaneously agitate and transport the developer in the axial direction and supply the developer to the developing roller; a second agitation transport member arranged to be parallel to the first agitation transport member in an approximately horizontal direction and configured to circulate and transport the developer with the first agitation transport member and mix the developer with externally supplied developer, the developing roller being arranged above the first agitation transport member and the second agitation transport member; a bulkhead comprising a partition member arranged between the first agitation member and the second agitation member in the horizontal direction and configured to connect the first agitation transport member side and the second agitation transport member side at a region of the partition member in the axial direction, and a guide member integral with the partition member and configured to guide developer removed from the surface of the developing roller to the first agitation transport member, the bulkhead is configured such that the guide member is arranged above the partition member; and a housing assembly including an upper housing member on the upper side of the housing assembly and a lower housing member on the lower side of the housing assembly, the lower housing member being attachable to the upper housing member, the housing assembly being arranged to accommodate at least the first agitation transport member, the second agitation transport member, and the bulkhead, the bulkhead being arranged such that there are no gaps between first and second ends of the bulkhead and the housing assembly, and either a first end on the partition member side thereof or a second end on the guide member side thereof is formed to be integral with the housing assembly.