Fixing unit

Abstract

In one embodiment, in a standby mode, an endless heating belt is caused to move apart from a hot roller. Furthermore, in color mode, the endless heating belt is caused to contact the hot roller to make possible thermal conduction between the endless heating belt and the hot roller, and a surface temperature of the endless heating belt is adjusted within a prescribed range of 200 DEG C. to 210 DEG C. being higher than a fixing temperature of 180 DEG C. Further still, in monochrome mode, a length (or a surface area) of a heating contact region between the endless heating belt and the hot roller is set to a maximum to increase a thermal conduction efficiency between the endless heating belt and the hot roller, and a surface temperature of the endless heating belt is adjusted within a prescribed range of 210 DEG C. to 220 DEG C. being sufficiently higher than the fixing temperature of 180 DEG C.

Description

technical field [0001] The present invention relates to a fixing device used in electrophotographic image forming devices such as copiers, facsimile machines, and printers. Background technique [0002] Generally, in an image forming apparatus such as a copying machine, a printer, or a facsimile apparatus, an electrostatic latent image is formed on a photoreceptor, a toner is supplied from a developing device to the photoreceptor, and the electrostatic latent image on the photoreceptor is developed by the toner. A toner image is formed on a photoreceptor, the toner image is transferred from the photoreceptor to recording paper, and the recording paper is heated and pressurized to fix the toner image on the recording paper. [0003] The fixing device sandwiches the recording paper between a heating roller and a pressure roller (also called a fixing roller), heats and presses it, and heats and fuses the toner image on the recording paper to fix it. In order to reliably fix th...

AI Technical Summary

Problems solved by technology

[0009] However, when the surface temperature of the fixing roller is controlled by bringing the heating belt or the external heating roller into contact with the fixing roller as in the above-mentioned (Japanese) Patent Application Publication No. 2004-198659 and (Japanese) Patent Application Publication No. 2004-85601 , as described above, When the surface temperature of the fixing roller decreases as the conveying speed or processing speed of the recording paper increases, the temperature of the heat source such as the heating belt or the external heating roller must be raised rapidly to suppress the decrease in the surface temperature of the fixing roller. and the load on the control circuit of the heat source becomes larger

[0010] In addition, since the contact area between the heating belt or the externally heating roller and the fixing roller is maintained constant, even if the temperature of the heating belt or the externally heating roller rises, the heat of the heating belt or the externally heating roller does not always transfer to the fixing roller quickly. Difficulty in controlling surface temperature of transfer and fixing rollers

Therefore, it is considered to expand the contact area between the heating belt or the external heating roller and the fixing roller to improve the heat conduction between the two, but in this way, the resistance to the rotation of the fixing roller is steadily increased, and the fixing roller rotation mechanism, etc. The load becomes larger

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