Patent ID: 8189207

Claim:
A color image forming apparatus that has mode switching means for switching, on the basis of image data, image formation of which is instructed, a printing mode between a single color printing mode for performing image formation in a state in which a transfer member and a single image bearing member are set in contact with each other and a color printing mode for performing image formation in a state in which the transfer member and plural image bearing members including the single image bearing member are set in contact with each other, the color image forming apparatus comprising: a calculating unit configured to calculate, on the basis of a number of pages subjected to image formation in the image data, a number of remaining pages not subjected to image formation yet and a sheet size of image data not subjected to image formation yet, and calculate, on the basis of the number of remaining pages and the sheet size, an estimated remaining time until completion of image formation of the image data; a setting unit configured to set, on the basis of at least the estimated remaining time, the printing mode in the single color printing mode or the color printing mode; and a control unit configured to control, when image formation of the image data is performed, the mode switching means to always perform image formation in the color printing mode from the start of driving of an image bearing member that comes into contact with the transfer member in both the single color printing mode and the color printing mode until a first time, which is a predetermined time, elapses, and control the mode switching means to perform image formation in the printing mode set by the setting unit at each interval of a second time, which is a predetermined time after the elapse of the first time.