| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing device that can suppress image unevenness and scattering of toner without providing magnetic seals at ends of a developing sleeve.SOLUTION: There is provided a developing unit 1 including a developing container 2, a developing sleeve 3, and a magnetic roller 4 having a plurality of magnetic poles including a peeling pole N3 and a pump-up pole N1 having the same polarity in the circumferential direction, a low magnetic field area having a magnetic force of 10 mT or less is provided between the peeling pole and the pump-up pole; the distribution of the magnetic force in the longitudinal direction at a position where the magnetic flux density of the low magnetic field area becomes minimum has a difference of 3 mT or less between the maximum magnetic flux density within a range from a maximum position where the attenuation factor of the magnetic flux density becomes maximum to a position in the central direction of the developing sleeve by 30 mm, and the magnetic flux density on the central side with respect to the range; the absolute value of the magnetic flux density in the longitudinal direction outside the maximum position is set to 3 mT or less. The developing device includes an electric field forming member that is arranged in a space between the developing container and the developing sleeve and in an area on the periphery of the ends of the developing sleeve, and can form an electric field that repulsive to a normal charge polarity of a toner. |
