Patent ID: 7054584
Filing Date: 2006-05-30
Classification: G03G

Abstract:
1. A developing apparatus for developing an electrostatic image formed on an image bearing member, comprising: a first developer bearing member having a cylindrical shape for bearing and conveying magnetic developer to a first developing portion to develop the electrostatic image; first magnetic field generating means stationarily provided in said first developer bearing member; a second developer bearing member having a cylindrical shape for bearing and conveying the magnetic developer to a second developing portion downstream of the first developing portion in a movement direction of the image bearing member to develop the electrostatic image, said second developer bearing member developing the electrostatic image developed by said first developer bearing member; and second magnetic field generating means stationarily provided in said second developer bearing member, wherein a peak position of a magnetic force in a direction perpendicular to a surface of said second developer bearing member is set in a range of 5° to 10° on a downstream side of a portion closest to said image bearing member with respect to a rotating direction of said second developer bearing member, and wherein the magnetic force is defined by differentiating partially a value of (Br where Br is a component, perpendicular to the surface of said second developer bearing member, of a magnetic flux density caused by said second magnetic field generating means, and where Bθ is a component, tangential to the surface of said second developer bearing member, of the magnetic flux density caused by said second magnetic field generating means.