| 摘要 |
PROBLEM TO BE SOLVED: To prevent the simultaneous rotation of developer by making the magnetism of magnetic poles related to the transfer of the developer between developing rollers for forming a magnetic brush arranged in parallel different and specifying the difference of flux density between the respective magnetic poles. SOLUTION: The developing rollers 5 and 6 are arranged on the upstream side and a downstream side in the moving direction of a photoreceptor drum 2, respectively. The magnetic poles P11 to P15 of the roller 5 and the magnetic poles P21 to P23 of the roller 6 are provided by odd number in a peripheral direction, respectively, and the different poles are arranged alternately. Then, the flux density of the magnetic poles P12 and P23 is set to <=0mT. It is preferable to set the flux density of the magnetic pole P23 of the roller 6 to >=70mT. Even when a copying machine is operated at high speed, the simultaneous rotation of the developer is prevented, and the irregular image density is avoided. |
