| 摘要 |
PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus capable of detecting conditions apt to cause scumming, in advance, and decreasing toner concentration, accordingly, thereby preventing occurrence of the scumming. SOLUTION: In the image forming apparatus, a reference pattern is formed on an image carrier, the reflected density of the reference pattern is detected, and then, the toner concentration in a developing device is controlled based on the detection result, and also, the apparatus includes a function to count an image forming operation period for every image forming job and a function to count the number of printed sheets. Provided that the image forming operation period is expressed by A (second) and the number of printed sheets is expressed by B (page), the toner concentration is controlled in accordance with A/B as a calculated value. COPYRIGHT: (C)2009,JPO&INPIT
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