| 摘要 |
<P>PROBLEM TO BE SOLVED: To more precisely determine the lifetime of a cleaning unit, based on the pixel density of each block. Ž<P>SOLUTION: The image forming apparatus forms an image, by forming an electrostatic latent image on a charged image carrier, developing the electrostatic latent image and transferring a toner image to paper, and prepares for next image formation by cleaning untransferred toner by the cleaning unit; and the image forming apparatus specifies the pixel-existing spot in a writable area to a small area of prescribed unit during image forming operation, to calculate the pixel density in the small area (S3 to S5), subjects the pixel density of each area to weighting (S6) on the basis of the calculated write-in pixel density in the small area, and integrates the pixel density subjected to weighting (S7), and compares the integrated value with a lifetime threshold to determine the lifetime of the cleaning unit (S8, S9 and S10). Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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