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AssigneeSharp Kabushiki Kaisha
InventorsKazushige Morita, Yuriko Shindoh, Hiroko Ishibashi, Yoshihide Shimoda, Masanori Matsumoto
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An electrophotographic color image forming apparatus including a multiple number of photoreceptors for multiple development colors including black, is constructed such that the photoreceptors satisfy the following relation:— 0.5<(X/Y)<0.8, where X represents the reduction in film thickness (Å) per 1×107 mm of the traveling distance of the photoreceptor for black development and Y represents the reduction in film thickness (Å) per 1×107 mm of the traveling distance of the photoreceptors for the other development colors. This limitation is aimed at differentiating the abrasion resistance of the photoreceptors between that for black and that for colors and designating the reduced amounts of the film thickness per unit traveling distance to fall within the predetermined ranges, whereby it is possible to prevent the drum for black development, which is used most frequently, alone, from being worn away at an earlier time. Accordingly, both the drums for black and for colors can be replaced at approximately the same time, to the maintenance cost can be reduced.
A color image forming apparatus comprising a multiple number of electrophotographic image forming stations for multiple development colors including black, arranged in line in the paper feed direction, each image forming station having a photoreceptor, a charger, an exposure device, a developing device, a transfer device and a cleaning device, characterized in that the photoreceptors satisfy the following relation:
Dependencies are inferred from the claim text.