Patent ID: 7577387

Claim:
A developing unit for use in an image forming apparatus including an image carrying member, the developing unit comprising: an agent carrying member configured to carry a two-component developing agent having a magnetic carrier and a toner thereon, and configured to rotate to supply the toner to a latent image formed on the image carrying member at a position where the agent carrying member faces the image carrying member, the agent carrying member including a plurality of magnets therein to generate a magnetic flux density over the agent carrying member; a supply compartment configured to transport the developing agent to be supplied to the agent carrying member; a supply screw, included in the supply compartment, configured to supply the developing agent to the agent carrying member while transporting the developing agent in a longitudinal direction of the supply compartment; a recovery compartment, provided under the agent carrying member, configured to recover the developing agent dropped from the agent carrying member after the toner is supplied to the image carrying member from the agent carrying member; a recovery screw, included in the recovery compartment, configured to transport the recovered developing agent in a longitudinal direction of the recovery compartment, wherein the recovery screw and supply screw transport the developing agent in a same direction; an agitation compartment configured to receive the developing agent from the supply compartment, which is not supplied to the agent carrying member for developing operation and transported to a most downstream portion of the supply compartment, and the recovered developing agent from the recovery compartment, which is transported to a most downstream portion of the recovery compartment; and an agitation screw, included in the agitation compartment, configured to agitatingly transport the developing agent in a longitudinal direction of the agitation compartment to supply agitated developing agent to the supply compartment, wherein the agitation screw and supply screw transport the developing agent in opposite directions to each other, wherein the recovery compartment, supply compartment, and agitation compartment are provided side-by-side in a substantially horizontal direction, and wherein the magnetic flux density on a surface of the agent carrying member in a normal line direction, extended from a center of the agent carrying member to a center of the recovery screw, is set to 10 mT or less.