Patent ID: 7773900

Claim:
An image forming apparatus, comprising: a plurality of image forming parts, each of the plurality of image forming parts including: an image bearing member on which an electrostatic image is formed; a charging device that charges said image bearing member; and a developing device having a developer bearing member that bears developer including carrier and toner, wherein said developing device develops the electrostatic image by applying a developing bias to the developer bearing member; an intermediate transfer member in which images, formed by each of said plurality of image forming parts, are sequentially superposed and transferred at transfer positions, wherein each of the transfer positions is a position in which one of said image bearing members of said plurality of image forming parts and said intermediate transfer member face each other; a transfer member that transfers a toner image on said intermediate transfer member to a transfer material; cleaning means to clean at least one of said intermediate transfer member and said transfer member; and a controller that, in each of said plurality of image forming parts, when application of developing bias into the developer bearing member is started according to a start of image forming, controls an operation of each of said plurality of image forming parts so as to start applying the developing bias before a leading edge of a charging area on said image bearing member charged by said charging device reaches a developing area in which the developer bearing member and said image bearing member face each other; wherein, in each of said plurality of image forming part, a primary area is defined as an area in which said corresponding image bearing member faces the developer bearing member when a developing bias is applied into the developer bearing member according to the start of image forming, and in said intermediate transfer member, secondary areas are each defined as an area in which said intermediate transfer member faces the corresponding primary area of each of said image forming parts when the corresponding primary area passes through each of the transfer positions, and wherein said controller controls the operations of said plurality of image forming parts so that all of the secondary areas are not overlapped, or in a case where the secondary areas are overlapped, at least one of the secondary areas is not overlapped in an area in which all of the other secondary areas are all overlapped.