Patent ID: 9235158
Filing Date: 2016-01-12
CPC Classification: G03G

Claim Text:
1. A developing device, comprising: a developing container configured to store a developer including a non-magnetic toner and a magnetic carrier; a cylindrical developing sleeve having a plurality of grooves which are respectively formed in a direction which intersects a circumferential direction of the developing sleeve on an outer surface thereof and configured to rotate while carrying the developer on the outer surface; a developer regulating member configured to regulate an amount of the developer carried by the developing sleeve; and a magnetic field generating portion disposed on an inner side of the developing sleeve and including a plurality of fixed magnetic poles which have at least a drawing-up pole which draws up the developer in the developing container and bears the developer on the outer surface of the developing sleeve, and a cut pole which is disposed to be adjacent to the drawing-up pole on a downstream side of the drawing-up pole in a direction of rotation of the developing sleeve and to be in the vicinity of the developer regulating member, wherein the plurality of fixed magnetic poles are configured to form a Fr attenuation area in which Fr attenuates toward the cut pole side from the drawing-up pole side between a peak of a magnetic flux density of the drawing-up pole and a peak of a magnetic flux density of the cut pole, and a Fθ reverse area in which Fθ is oriented towards an opposite direction to the direction of rotation of the developing sleeve between the peak of the magnetic flux density of the drawing-up pole and the peak of the magnetic flux density of the cut pole where Fr is a magnetic force in a direction toward the center of the developing sleeve and Fθ is a magnetic force in a tangential direction of the outer surface of the developing sleeve, wherein a pitch interval of the plurality of grooves of the developing sleeve is shorter than a length of the Fθ reverse area in the direction of rotation of the developing sleeve.