| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing a high-background density phenomenon in which a developer is attached to a photoreceptor of an image forming unit unrelated to an image forming while switching image forming modes between a first image forming mode for forming a first type image by using a part of plural image forming units and a second image forming mode for forming a second type image by using all of the plural image forming devices. <P>SOLUTION: Control means controls a developer hold-transporting member of a developing device of an image forming unit unrelated to an image forming in a first image forming mode so as to stop rotation, or to relatively decelerate or accelerate the rotation speed. When switching from a first image forming mode to a second image forming mode, the control means controls an AC inter-peak voltage of a developing bias of a developing device of an image forming unit unrelated to the image forming during periods of necessary rise time and fall time for rotary-driving the developer hold-transporting member to be higher than the voltage during a period of executing development. Also, an absolute value of DC developing bias during the periods of the rise and fall time is controlled to be smaller than that during a period of executing development. <P>COPYRIGHT: (C)2012,JPO&INPIT |
