Patent ID: 8571449
Filing Date: 2013-10-29
Classification: G03G

Abstract:
1. A development device, comprising: a developer containing part containing two-component developer including toner and magnetic carrier particles; a cylindrical developer carrier to carry by rotation the developer supplied from the developer containing part to a development range where the developer carrier faces an image carrier; a first developer transport member disposed in the developer containing part, to supply the developer to the developer carrier while transporting the developer in an axial direction of the developer carrier; and a magnetic field generator disposed inside the developer carrier, having three developer-carrying magnetic poles each capable of generating a magnetic field to keep the developer on a circumferential surface of the developer carrier, the three developer-carrying magnetic poles consisting of a development pole to generate a first magnetic field in the development range, a pre-development pole to generate a second magnetic field to transport the developer supplied from the developer containing part to the development range, and a post-development pole to generate a third magnetic field disposed between the first magnetic field and the second magnetic field, wherein the second magnetic field causes the developer supplied from the developer containing part to be attracted to the circumferential surface of the developer carrier at a developer attraction position, the first magnetic field and the second magnetic field keep the developer on the circumferential surface of the developer carrier from the developer attraction position to the development range, and the first magnetic field and the third magnetic field keep the developer on the circumferential surface of the developer carrier from the development range to a release position where the developer is separated from the developer carrier, and each of the developer-carrying magnetic poles has a maximum density of magnetic flux in a normal direction to the circumferential surface of the developer carrier of 10 mT or greater.