Image forming device

Abstract

[Problem] To provide an image forming device that can suppress contamination of a charging device and dielectric breakdown for photosensitive bodies by maintaining a prescribed range for a ratio of metal particles in recovered toner. [Solution] The image forming device, which forms a color image by sequentially superimposing color toner images formed on photosensitive drums (1) onto an intermediate transfer belt (5), is provided with a plurality of photosensitive drums (1), a charging device (4) that comes into contact with and charges each of the photosensitive drums (1), a developing device (21) for making toner that includes metal particles, which are polishing particles, adhere and developing a latent image, and a cleaning device (3) for eliminating residual toner from the surface of the photosensitive drums (1). The image forming device is provided with a primary transfer bias control unit (53) wherein a primary transfer bias outside of the image forming time on the photosensitive drums (1) is switched to the same polarity or the opposite polarity as the charge of the toner according to an average printing rate for the previous prescribed number of sheets for each color.

Description

technical field [0001] The present invention relates to image forming apparatuses used in, for example, copiers, printers, facsimile machines, and the like. Background technique [0002] In a full-color image forming device, on the peripheral surface of a plurality of photoreceptor drums corresponding to the respective colors of yellow (Y), magenta (M), cyan (C) and black (BK) An electric latent image is formed by using a laser scanning unit, and toner images of each color are respectively generated from toners of each color. [0003] The toner images of the respective colors formed on the peripheral surfaces of the respective photoreceptor drums are successively overlapped and transferred onto the intermediate transfer belt that runs continuously, whereby a color image is synthesized on the intermediate transfer belt. Next, the color image synthesized on the intermediate transfer belt is transferred to a sheet made of paper or the like by a transfer roller, and then pressu...

AI Technical Summary

Problems solved by technology

[0006] In the tandem color machine, there are multiple photoreceptor units such as yellow, cyan, magenta, and black, but the printing rate of each color is mostly different. Therefore, each image forming station (hereinafter referred to as "station") The ratio of metal particles in the recovered toner in the cleaning device is different, and the pollution level of the charged device is prone to difference

[0007] On the other hand, if the ratio of metal particles in the recycled toner is low, the photoreceptor is prone to dielectric breakdown.

That is, the metal particles in the recovered toner have the effect of releasing electric charges. Therefore, if the ratio of metal particles in the recovered toner is low, the toner will be excessively charged due to friction in the cleaning device, and the cleaning blade will remove the charge from the photoreceptor. When peeling off, the photoreceptor is discharged, and the photoreceptor is prone to dielectric breakdown

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