Abstract: A developing method of the present invention is practicable with a developing unit of the type including a rotatable, nonmagnetic sleeve and a rigid metering member. A two ingredient type developer made up of magnetic carrier grains and toner grains is magnetically deposited on the sleeve. The metering member meters the amount of the developer deposited on the sleeve. The sleeve has surface roughness Rz ranging from 5 &mgr;m to 20 &mgr;m. The carrier grains each are covered with a coating layer containing at least binder resin and grains. The ratio of the diameter D of the individual grain contained in the coating layer to the thickness h of the binder resin layer lies in the range of 1<D/h<10. The carrier grains have a weight-mean grain size ranging from 20 &mgr;m to 60 &mgr;m.

Abstract: A developing device includes a developer including toner having a coloring agent dispersed in a binder resin, and carrier having a core material, and a coating layer covering the core material and containing a binder resin and a powder. A toner density detecting device detects a toner density of the developer by use of a bulk density sensor, and a control device controls the toner density based on a detection result of the toner density detecting device. The toner density is controlled such that ratio (D/h) of an average particle diameter (D) of the powder to a thickness of the coating layer is greater than 1 and less than 10.

Abstract: In accordance with the present invention, in an image forming apparatus of the type developing a latent image formed on an image carrier, which moves at a linear velocity of 400 mm/sec or above, with a developer containing toner grains having a volume mean grain size of 5 &mgr;m to 10 &mgr;m and 60 number percent to 80 number percent of which has a grain size of 5 &mgr;m or below, the developer contains carrier grains having a weight mean grain size of 65 &mgr;m or below. When use is made of toner with a small grain size, the apparatus successfully obviates background contamination, toner scattering and sleeve contamination without regard to operation speed or environmental conditions.

Abstract: A developing device incorporated in an image forming apparatus and having a developing roller facing an image carrier via an opening formed through a casing, and a pair of seal members attached to the casing and adjoining opposite side edges of the opening for preventing a developer from being scattered around. The seal members each has a side seal portion for sealing the associated side edge of the opening, and an under seal portion extending from the lower end of the side seal portion. The under seal portion extends from the side seal portion toward the center of the developing roller, providing the entire seal member with a form of a letter L.