Patent ID: 7167667

Claim:
A developing apparatus comprising: a supply roller supplying a toner; an agitating mechanism portion which is supplied with the toner from the supply roller and includes a carrying member agitating to mix a developer and the toner while carrying the developer in an axial direction of the agitating mechanism portion; and a toner concentration sensor detecting a concentration of the toner in the developer, wherein the supply roller and the carrying member are arranged substantially in parallel with each other, and a flow of the developer includes a flow of passing the agitating mechanism portion and a flow which does not pass the agitating mechanism portion; and the developing apparatus satisfies the following equation: ( W ×( Tc/ 100)+ M )/( W+M )≦ T max/100 where W is an amount (g) of the developer carried by 1 pitch of the carrying member; M is an amount (g) of the toner supplied to the 1 pitch of the carrying member during a time period in which the developer carried by the 1 pitch passes a supply region by the supply roller; Tc is a concentration (%) of the toner in the developer detected by the toner concentration sensor; and Tmax is a mixing limit toner concentration (%).