Patent ID: 7454149

Claim:
An image forming apparatus comprising: a plurality of image forming parts, each of said plurality of image forming parts including: an image bearing member on which an electrostatic image is formed; charging means to charge said image bearing member; and developing means which bears developer including carrier and toner on a developer bearing member and develops an electrostatic image by applying a developing bias to the developer bearing member; transfer means which superposes toner images formed by each of said plurality of image forming parts on an intermediate transfer member and, after that, collectively transfers them on a transfer material; means to clean at least said intermediate transfer member or said transfer means; and control means to control the operation of said charging means and said developing means, wherein said control means, at the image forming operation starting time, after starting the charging by said charging means in each of said plurality of image forming parts, starts the application of said developing bias before the top end of the charging portion of said image bearing member surface reaches a developing area in which said image bearing member and said developer bearing member are set against each other, wherein, from among the areas on said image bearing member where the charging is not yet performed by said charging means in each of said plurality of image forming parts, in case each area having passed the developing area when said developing bias is applied is brought into contact with said intermediate transfer member, the contact area with said each area in the intermediate transfer member is controlled so as not to be superposed on said intermediate transfer member, and wherein when a time from the application starting time of said developing bias until the top end portion of the image forming area on said image bearing member reaches said developing area is taken as Ts (sec), said image bearing member moving direction width of said developing area as H (mm), and the peripheral speed of said image bearing member as Vdr (mm/sec), said time Ts in said each image forming part becomes different more than H/Vdr between said each image forming parts.