Abstract: An image forming apparatus of the present invention includes a developing device including a rotatable, nonmagnetic developer carrier and a magnetic field forming device. In a developing region where the developer carrier faces an image carrier, the magnetic field forming device causes a developer made up of toner and magnetic grains to rise on the developer carrier in the form of a magnet brush. In the developing region, the magnet brush on the developer carrier is caused to move at a higher speed than the surface of the image carrier in the same direction as and in contact with the surface of the image carrier, thereby developing the latent image. The toner of the developer is magnetic toner. Flux density set up in the developing region outside of the surface of the developer carrier in a normal direction has an attenuation ratio of 50% or above.

Abstract: A developing device including a developer supporter, and a napping unit for napping the developer on the developer supporter by magnetic poles. The napping unit further includes a developing main magnetic pole installed at a location opposite to a latent image supporter, and a developing auxiliary magnetic pole located at a downstream side of the developing main magnetic pole in a rotational direction of the developer supporter. The developing main magnetic pole has a half-value width equal to or less than 22°. The composite magnetic flux density of the developing main magnetic pole and the developing auxiliary magnetic pole is equal to or greater than 80 mT. In this way, the disclosure can prevent voids in a back end from occurring to improve the fine line reproduction, and additionally, the carrier adhesion can be also prevented.

Abstract: A developing device is provided. The developing device comprises a developer supporter; and a napping unit for napping the developer on the developer supporter by magnetic poles. The napping unit further comprises a developing main magnetic pole installed at a location opposite to a latent image supporter, and a developing auxiliary magic pole located at a downstream side of the developing main magnetic pole in a rotational direction of the developer supporter. The developing main magnetic pole has a half-value width equal to or less than 22°. The composite magnetic flux density of the developing main magnetic pole and the developing auxiliary magnetic pole is equal to or greater than 80 mT. In this way, the disclosure can prevent voids in a back end from occurring to improve the fine line reproduction, and additionally, the carrier adhesion can be also prevented.

Abstract: A developing device capable of obviating carrier deposition on an image carrier and uniformly distributing toner on a developer carrier is disclosed. A developer deposited on the developer carrier and moved away from a metering member rises in the form of a magnet brush, falls down, and again rises in accordance with the movement of the developer carrier. The toner of the developer is efficiently agitated in the axial direction of the developer carrier in a narrow zone between the first metering member and a developing zone.

Abstract: An image forming apparatus of the present invention includes a developing device including a rotatable, nonmagnetic developer carrier and a magnetic field forming device. In a developing region where the developer carrier faces an image carrier, the magnetic field forming device causes a developer made up of toner and magnetic grains to rise on the developer carrier in the form of a magnet brush. In the developing region, the magnet brush on the developer carrier is caused to move at a higher speed than the surface of the image carrier in the same direction as and in contact with the surface of the image carrier, thereby developing the latent image. The toner of the developer is magnetic toner. Flux density set up in the developing region outside of the surface of the developer carrier in a normal direction has an attenuation ratio of 50% or above.