Patent ID: 9046824
Filing Date: 2015-06-02
Classification: G03G

Abstract:
1. A developing device comprising: a sleeve arranged so as to face an image carrier on which an electrostatic latent image is formed, the sleeve having a cylindrical shape and being rotated in a circumferential direction, the image carrier facing only one sleeve, which is the sleeve; and a magnet roller supported in a fixed state in the sleeve, the magnet roller having a plurality of magnetic poles arranged in the circumferential direction and magnetically attracting developer containing a magnetic material so that the developer is held on a peripheral surface of the sleeve, the magnetic poles including a first magnetic pole and a second magnetic pole that is disposed adjacent to the first magnetic pole and downstream of the first magnetic pole in a rotation direction of the sleeve and that has a polarity opposite to a polarity of the first magnetic pole, wherein a distribution of magnetic attraction applied to the developer on the peripheral surface of the sleeve in a region from the first magnetic pole to the second magnetic pole of the magnet roller is such that the magnetic attraction decreases from a position where the first magnetic pole is disposed toward the downstream side in the circumferential direction, a gradient of change in the magnetic attraction decreases in a region downstream of a region in which a gradient of reduction in the magnetic attraction temporarily increases, thereby forming an attraction reduction region in which the magnetic attraction is reduced so that the developer cannot be held on the peripheral surface of the sleeve, and the gradient of change in the magnetic attraction increases in a region downstream of the attraction reduction region so that the magnetic attraction increases to a position where the second magnetic pole is provided.