A developing device includes a developing container, a feeding member, a developer carrying member, and a collecting device. A coverage which is a percentage of coating of surfaces of the carrier particles with the toner particles is 100% or more and 200% or less. The developer carrying member has a plurality of recessed portions formed on a surface thereof so that at least the toner particles having an average particle size are contactable with inner surfaces of the recessed portions, and the carrier particles having an average particle size are not contactable with the inner surfaces of the recessed portions. The recessed portions are formed so that not less than half of the toner particles having the average particle size are exposed from the recessed portions when the toner particles having the average particle size enter the recessed portions.

A developing unit includes a developing container, a developing sleeve, a developer regulating member, and a magnetic field generating portion. The magnetic field generating portion includes a drawing-up pole and a cut pole. In addition, in a peak-to-peak area, the magnetic field generating portion includes at least one of an Fr flat area in which Fr is substantially constant and an Fr attenuation area in which Fr attenuates toward the cut pole side from the drawing-up pole side, and is configured that F is oriented toward the same direction as a direction of rotation of the developing sleeve in the entire peak-to-peak area.

A developing device includes a first rotatable member; a first magnet including a first magnetic pole, a second magnetic pole, and a third magnetic pole identical in polarity to the second magnetic pole; a second rotatable member; and a second magnet including a fourth magnetic pole different in polarity from and closest to the second magnetic pole, a fifth magnetic pole, and a sixth magnetic pole identical in polarity to the fifth magnetic pole. In a rotational direction of the second rotatable member, a maximum magnetic flux density position of the fourth magnetic pole of the second magnet in a normal direction relative to an outer peripheral surface of the second rotatable member is positioned downstream of the closest position of the second rotatable member to the first rotatable member on the outer peripheral surface of the second rotatable member, and is positioned upstream of the fifth magnetic pole.

An image forming apparatus is disclosed. The image forming apparatus includes an image bearing member, a developing device, a gap retaining member and a control unit. The control unit decreases a potential difference according to an increase in the drive amounts of the image bearing member and the developer bearing member. The decrease is based on a difference according to an increase in at least one of the drive amounts of the image bearing member and the developer bearing member. The control unit is also configured to determine whether to execute a mode based on information about at least one of the driving amounts of the image bearing member and the developer bearing member from when the developing device is initially installed or the developing device is replaced.

A carrier set for electrostatic charge image developer, includes: a first carrier that satisfies Expression (1); 160 mJx200 mJ, and a second carrier that satisfies Expression (2); 210 mJy250 mJ, wherein x is a total energy amount, which is measured by a powder rheometer, of a developer which is prepared by mixing the first carrier and a toner for measurement such that a weight ratio of the toner is 8% by weight based on the developer, and y is a total energy amount, which is measured by the powder rheometer, of a developer which is prepared by mixing the second carrier and the toner for measurement such that a weight ratio of the toner is 8% by weight based on the developer.

An image forming apparatus includes a plurality of image carriers, a charging device, an exposure device, a development device, and an intermediate transfer belt. The image carrier has a surface on which an amorphous silicon photosensitive layer is formed. The intermediate transfer belt is a plastic belt having a surface resistivity of 9.5 to 10.5 (log /square). An offset amount of the primary transfer roller from the image carrier is 0 to 2 (mm), a contact surface pressure between the image carrier and the intermediate transfer belt is 0.5 to 1.5 (gf/mm.sup.2), and a charge density of primary transfer current that flows when the primary transfer voltage is applied to the primary transfer roller is 0.016 to 0.040 (C/cm.sup.2).

An image forming apparatus includes an image carrying member, a charging device, an exposure device, a development device, and a development voltage power supply. The image carrying member has an amorphous silicon photosensitive layer formed on its surface. The development device includes a developer carrying member carrying two-component developer containing toner and carrier. The development voltage power supply applies to the developer carrying member a development voltage having an alternating-current voltage superposed on a direct-current voltage. When the blank part potential on the image carrying member is V0 [V], the direct-current voltage is Vdc [V], the peak-to-peak value of the alternating-current voltage Vac is Vpp [kV], and the gap between the image carrying member and the developer carrying member is Ds [mm], 10V0Vdc90 and 1.2Vpp/Ds3.5 are fulfilled.

A developing device includes a cylindrical developing roller, a regulation member, a magnetic member, and a synthetic resin member. The regulation member includes a first opposing surface facing an outer circumferential surface of the developing roller. The magnetic member is arranged on a side surface of the regulation member. The synthetic resin member is arranged on a side surface of the magnetic member. The synthetic member includes a second opposing surface facing the outer circumferential surface of the developing roller. The second opposing surface is tilted at 40 or more but 60 or less with respect to the first opposing surface to be increasingly distant from the outer circumferential surface of the developing roller toward an upstream side in a rotating direction of the developing roller. A solubility parameter of a material of the synthetic resin member is 23 (J/cm.sup.3).sup.1/2 or more. Magnetic toner contains toner and resin fine particles.

In the first potential difference adjustment mode, the fogging toner amount is predicted from a toner charge amount and a fogging toner current sensed by a current sensing portion with a zero surface potential on the image carrying member. In the second potential difference adjustment mode, the carrier development amount is predicted from a toner concentration, a carrier charge amount calculated based on the toner charge amount, and a carrier development current sensed by the current sensing portion with a zero surface potential on the image carrying member.

A carrier contains a particle containing a core particle and a coating film that covers the core particle, wherein the carrier has a 50 percent particle diameter (D50) is between 40 m and 60 m, the content of the carrier having a particle diameter of less than 22 m is less than 0.10 percent by number, and the content of the carrier having a particle diameter of less than 24 m is between 0.10 percent by number and 5.00 percent by number.