Patent ID: 7991331

Claim:
A developing unit comprising: a developer carrying body accommodated in a developer-carrying-body accommodation chamber, the developer carrying body that holds a developer on a surface thereof to convey the developer to a developing zone where a latent image is developed into a visualized image; a circulation conveyance chamber comprising a first agitating conveyance chamber disposed to be adjacent to the developer-carrying-body accommodation chamber, the first agitating conveyance chamber that accommodates therein a two-component developer, and a second agitating conveyance chamber disposed to be adjacent to the first agitating conveyance chamber, the second agitating conveyance chamber that includes an inlet portion through which the developer flows in from the first agitating conveyance chamber, and an outlet portion through which the developer flows out to the first agitating conveyance chamber, in the circulation conveyance chamber, the developer being conveyed in a circulating fashion; a circulation conveyance member comprising a first developer conveyance member accommodated in the first agitating conveyance chamber, the first developer conveyance member that conveys the developer in the first agitating conveyance chamber in a first conveyance direction, and a second developer conveyance member accommodated in the second agitating conveyance chamber, the second developer conveyance member that conveys the developer in the second agitating conveyance chamber in a second conveyance direction opposite to the first conveyance direction, the circulation conveyance member that conveys the developer in the circulation conveyance chamber in a circulating fashion; and a developer supply portion provided in a developer supply position of the circulation conveyance chamber; at least a part of the circulation conveyance chamber is divided into a plurality of zones each having a predetermined range, a consumption calculator that calculates a consumption of the developer in each zone, and the developer supply portion supplies a developer based on the calculated consumption of each zone after developing, an accumulated consumption of developer in each zone is calculated while each zone is moving in the circulation conveyance chamber as the circulation conveyance member conveys the developer, and when each zone reaches the developer supply position, a developer that is equal to in amount to the accumulated consumption of developer in each zone is supplied to each zone.