Patent ID: 7991330

Claim:
A developing unit, comprising: a developer bearing member provided across from a latent image bearing member, configured to bear a developer on a surface of the developer bearing member and supply a toner to a latent image on a surface of the latent image bearing member while rotating; a developer transporter configured to convey the developer; a developer conveyance system configured to direct the developer, the developer conveyance system including: a supply path configured to direct the developer along an axial direction of the developer bearing member and supply the developer to the developer bearing member; a recovery path configured to direct the developer collected from the developer bearing member along the axial direction of the developer bearing member after passing an area opposite the latent image carrier and in substantially the same direction as a transporting direction of the supply path; an agitation path configured to: receive excess developer not used in development and transported to a vicinity of a downstream end of the supply path in a direction of developer transport and collected developer transported to a vicinity of a downstream end of the recovery path in the direction of developer transport; direct the excess developer and the collected developer along the axial direction of the developer bearing member and in a direction opposite that of the supply path while mixing the excess developer and the collected developer together; and supply the mixed developer to the supply path after mixing the excess developer and the collected developer together; a developer supply opening through which the developer is supplied to the developer conveyance system; a developer supply device configured to supply the developer from the developer supply opening to the developer conveyance system; a developer discharge device configured to discharge the developer outside the developing unit; a developer detector configured to detect an increase in a level of the developer between the downstream end of the recovery path facing the developer bearing member in the direction of developer transport and a portion of the agitation path where the agitation path receives the collected developer from the recovery path; and a controller configured to control the developer discharge device based on a detection result provided by the developer detector.