| 摘要 |
An image forming apparatus has a plurality of image forming units for forming, on an image receiving member such as a transfer sheet, toner images of a plurality of different colors such as magenta, cyan, yellow and black. Each of the image forming units includes a photosensitive drum serving as an image carrier, a developing device for developing an electrostatic latent image carried by the image carrier to form a color toner image, and a transfer device for transferring the toner image to the image receiving member. The developing device in the image forming unit for forming on the image receiving member the toner image of an (i+1)-th color is of the type capable of simultaneously performing both development and removal of residual toner. The transfer currents Ti and Ti+1 employed by the transfer units which perform transfer of the toner images of an i-th color and the (i+1)-th color satisfy the following condition (1). The sphericity factor SF of the toner used in at least one of the image forming units, defined by the following equation (2) satisfies the following condition (3):1.0<Ti+1/Ti<1.1(1)SF={(diameter of toner having greatest diameter)2/toner projection area}x( pi /4)(2)1.0</=SF</=1.3(3)
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