Patent ID: 7289754
Filing Date: 2007-10-30
Classification: G03G

Abstract:
1. An image forming apparatus comprising: an image forming body; a latent image forming section to form an electrostatic latent image on the image forming body; and a developing unit to form a toner image by developing the electrostatic latent image, wherein the developing unit comprises: a developer carrier, arranged to face the image forming body, for transporting developer to a developing area and for forming a developer layer in the developing area by rotation of the developer carrier; a magnetic field generating member arranged inside the developer carrier; a restriction member to restrict an amount of the developer to be transported by the developer carrier; a first conveyer to agitate the developer while transporting the developer in a rotation axis direction of the first conveyer; and a second conveyer to receive the developer transported by the first conveyer and to supply the developer to the developer carrier while transporting the developer in a rotation axis direction of the second conveyer, wherein the magnetic field generating member comprises: a main magnetic pole for generating a magnetic field to form the developer layer on the developer carrier in the developing area; a pickup magnetic pole to hold the developer from the second conveyer onto the developer carrier; and a strip-off magnetic pole to strip off the developer having passed through the developing area from the developer carrier, wherein the developing unit satisfies following conditions of a, b, c, and d: a: the second conveyer is a screw conveyer having an outer diameter of not less than 24 mm and not more than 30 mm, which rotates with a rotating speed of not less than 300 rpm (revolutions per minute) and not more than 500 rpm, b: the pickup magnetic pole is arranged at an angle of not less than 25° and not more than 60° downstream with respect to a line connecting a center of the developer carrier axis and a center of the second conveyer axis, the line being perpendicular to the center of the developer carrier axis, and the developer carrier axis being parallel to the second conveyer axis, c: the strip-off magnetic pole is arranged at an angle of not less than 60° and not more than 80° upstream with respect to the line, d: a transporting capability of the first conveyer is larger than a transporting capability of the second conveyer.