Patent ID: 8611797

Claim:
A developing device that circulates developer including carrier and toner in a circulation passage having first and second conveyance passages by conveying the developer in a first conveyance direction in the first conveyance passage and conveying the developer in a second conveyance direction in the second conveyance passage, so that the developer is supplied to a developing roller provided along one of the first and second conveyance passages, the developing device comprising: a first conveyance member provided in the first conveyance passage and driven to rotate to convey the developer in the first conveyance direction; a communicating passage through which the developer flows from the first conveyance passage to the second conveyance passage; a second conveyance member provided in the second conveyance passage and driven to rotate to convey the developer that has flowed through the communicating passage in the second conveyance direction; a discharge passage extending from an end portion of the first conveyance passage located downstream in the first conveyance direction; a passing developer amount changing mechanism configured to change an amount of developer per unit time passing through the communicating passage, according to a pressure applied to the developer at a junction between the first conveyance passage and the discharge passage, wherein the passing developer amount changing mechanism comprises a detection unit configured to acquire information indicating fluctuations of the pressure applied to the developer at the junction; and a movement control unit to control a moving unit based on the acquired information to change a size of an opening of the communicating passage.