Patent ID: 9020403
Filing Date: 2015-04-28
Classification: G03G

Abstract:
1. A developing device comprising: a developer carrying member for carrying a developer containing a magnetic carrier and a non-magnetic toner and for developing an electrostatic latent image formed on an image bearing member, with said developer carrying member having a direction of rotation; a magnet, provided in said developer carrying member and including a plurality of magnetic poles disposed along a circumferential direction of said developer carrying member, for carrying the developer on said developer carrying member; and a regulating member, provided opposite to said developer carrying member with a predetermined spacing in a region in which the magnetic poles are disposed such that magnetic poles different in polarity are adjacent to each other, for regulating an amount of the developer carried on said developer carrying member, wherein the magnetic poles are disposed so that a circumferential direction component of a magnetic force acting on the magnetic carrier contacting at least a part of an upstream regulating surface of said regulating member with respect to the direction of rotation of said developer carrying member is opposite from the direction of rotation, wherein the magnetic poles include a first magnetic pole closest to said regulating member, a second magnetic pole provided adjacent to and downstream of the first magnetic pole with respect to the rotational direction of said developer carrying member, and a third magnetic pole adjacent to and upstream of the first magnetic pole with respect to the rotational direction of said developer carrying member, wherein the second magnetic pole and the third magnetic pole are different in polarity from the first magnetic pole, and wherein a maximum of a component of the magnetic force, with respect to a radial direction of said developer carrying member, acting on the magnetic carrier between a peak position of a magnetic flux density of the first magnetic pole and a peak position of a magnetic flux density of the third magnetic pole is larger than a component of the magnetic force, with respect to the radial direction of said developer carrying member, acting on the magnetic carrier between the peak position of the magnetic flux density of the first magnetic pole and a peak position of a magnetic flux density of the second magnetic pole.