Patent ID: 8903270

Claim:
A developing device, comprising: a cylindrical and rotatable developer bearing member comprising a magnetic field generator having multiple magnetic poles, the developer bearing member being disposed facing an electrostatic latent image bearing member to form a developing area therebetween; and a developer chamber comprising a two-component developer comprising magnetic carrier particles having a saturated magnetization of 58 to 70 emu/g in a magnetic field of 1KOe and toner particles, the developer comprising chamber having a divider to define an upper supply chamber and a lower collection chamber, the supply chamber disposed on a substantially upper side of the developer bearing member, the supply chamber comprising a supply conveyer to supply the two-component developer to the developer bearing member at an upstream side from the developing area while conveying the two-component developer in an axial direction of the developer bearing member within the supply chamber, the collection chamber disposed on a substantially lower side of the developer bearing member, the collection chamber comprising a collection conveyer to collect the two-component developer from the developer bearing member at a downstream side from the developing area while conveying the two-component developer in the axial direction of the developer bearing member within the collection chamber, wherein the multiple magnetic poles includes three developer bearing poles capable of bearing the developer on its surface, the three developer bearing poles consisting of a developing pole, a pre-developing pole, and a post-developing pole, the developing pole generating a magnetic field in the developing area, the pre-developing pole generating a magnetic field that conveys the developer supplied from the supply chamber to the developing area, the post-developing pole generating a magnetic field that separates the developer from the developer bearing member at a downstream side from the developing area and an upstream side from the developing pole, and the magnetic carrier particles have a surface roughness Ra of 0.38 to 0.90 μm.