JP2003029570A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing the heat damage of the surface of a heating roller and performing stable thermal fixing. SOLUTION: Two temperature detectors are arranged to detect the surface temperature of the heating roller, and two heating bodies incorporated in the heating roller and having a different range to heat the heating roller are independently controlled based on the information detected by the temperature detectors with respect to the respective heating bodies.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an electrophotographic printing device. 2. Description of the Related Art A conventional technique will be described with reference to FIG. In a fixing device in which the toner 6 on the paper 5 is thermally fixed to the paper 5 by the surface heat of the heating roller 1 heated by the heating body 2 or 3 incorporated in the heating roller 1,
Roller 1 caused by a change in the passing width Lp of the paper 5
In order to avoid breakage of the heating roller due to an abnormal rise in the temperature of the surface of the heating roller 1 in the portion Ln through which the sheet 5 does not pass, the CPU 10 controls the heating roller 1 based on the detection information of the sheet size detectors 7, 8, and 9. Recognizing the passage width Lp of the sheet 5,
At the same time, the heating unit 2 in the heating range W3 or the heating unit 3 in the heating range W4 contained in the heating roller 1 is selected, and the output of the heating unit power supply 12 is
Alternatively, there is known a fixing device of an electrophotographic printing apparatus that sets the surface temperature of the heating roller 1 within a specified range by controlling the supply to the heating roller 3. [0003] According to the prior art,
When the type of paper to be used increases, the type of paper passing width of the heating roller also increases due to the difference in the type of paper. Therefore, the number of heating elements corresponding to the type increases, and there is a possibility that the apparatus becomes expensive. Therefore, in general, a single heating element is made to correspond to the passage width of several types of sheets, and is constituted by as few heating elements as possible. If the passage width is narrow and the difference is large, there is a possibility that thermal damage to the surface of the heating roller may be caused due to an abnormal temperature rise in a portion of the heating roller where the paper does not pass. If the heating range of the heating element is narrowed to solve the above-mentioned problem, the surface temperature of a part of the heating roller through which the paper passes may be abnormally lowered, which may lead to defective fixing of the toner to the paper. was there. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to keep the surface temperature of a heating roller within a specified value range at all times and to minimize the number of temperature detectors. It is an object of the present invention to provide a fixing device for an electrophotographic printing apparatus characterized in that it can be handled by a heating element. In order to achieve the above object, according to the present invention, two temperature detectors are arranged so as to detect the surface temperature of a heating roller, and the temperature detector is built in the heating roller. The two heating elements were independently controlled based on the detection information of the corresponding temperature detectors, so that the surface temperature of the heating roller was within a specified range. Further, in the above configuration, since the amount and range of heat taken by the paper from the surface of the heating roller differ depending on the width of the paper passing through the heating roller, the temperature distribution on the surface of the heating roller also differs. If the temperature of the heating element is controlled by the same control value, the surface temperature of the heating roller has a wide fluctuation range, and the surface temperature of the heating roller outside the detection range of the temperature detector may deviate from the specified range. For this reason, in addition to the above configuration, based on the detection information of the sheet passing through the heating roller obtained by the sheet size detector, the temperature of each heating element is controlled by a control value corresponding to the passage width of each sheet. Thus, the surface temperature of the heating roller is configured to be within a narrower specified range. FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIGS. FIG. 2 is a schematic diagram showing the operation of the electrophotographic apparatus of the present invention. The charger 18 to which the high voltage is applied by the high voltage power supply 17 is rotating by the motor 15. The surface of the photosensitive drum 16 is charged. Then, C
The PU 10 controls the optical system 19 to form a latent image on the photosensitive drum 16, electrostatically attaches the toner 6 from the developing device 20 to the latent image, and transfers the toner image to the transfer device 22 to which a high voltage is applied by the high voltage power supply 21. The toner 6 is transferred to the paper 5 by the following. The sheet 5 is separated from the photosensitive drum 1 by a peeler 24 to which a high voltage is applied by a high voltage power supply 23.
6 is conveyed between the heating roller 1 and the pressure roller 4 rotating by the motor 27 by the paper conveying belt 23 rotating by the motor 25. FIG. 1 is a schematic diagram showing a section and a circuit of a fixing roller according to an embodiment of the present invention. FIG. 4 shows an example in which the heating range is changed. The conveyed sheet 5 has two temperature detectors 1 arranged to detect the nipping and conveying force between the heating roller 1 and the pressing roller 4 and the surface temperature of the heating roller 1.
The surface temperature of the heating roller 1 is detected by the sensor 3 and the temperature detector 14, and the heating element 2 and the heating element 3 incorporated in the heating roller 1 are independently controlled based on the detection information. At this time, the ratio of the heating range W1, W3 of the heating element 2 to the heating range W2, W4 of the heating element 3 is from 1: 1 to 5:
1, the output ratio ranges from 1: 1 to 8: 1. As described above, according to this embodiment, the heating roller 1 is controlled by keeping the surface temperature of the heating roller 1 within a specified range.
Irrespective of the passing width Lp of the sheet 5, the abnormal temperature rise of the portion Ln of the heating roller 1 where the sheet 5 does not pass or the heating roller 1
The printed image of the toner 6 on the sheet 5 can be thermally fixed without causing an abnormal decrease in the surface temperature of a portion within the passage width Lp through which the sheet 5 passes. As described above, according to the present invention, regardless of the width of the sheet passing through the surface of the heating roller,
The fixing heat can always be controlled within a specified value range, and stable fixing quality can be secured. Further, since it can be composed of a minimum number of temperature detectors and heating elements, an inexpensive fixing device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a cross section and a circuit of a fixing device according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of an electrophotographic apparatus according to one embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a cross section and a circuit of a fixing device according to the related art. FIG. 4 is a schematic diagram illustrating a cross section and a circuit of a fixing device according to another embodiment of the present invention. [Description of Signs] 1 ... heating roller, 2, 3 ... heating body, 5 ... paper, 6 ... toner, 10 ... CPU, 11 ... DRV, 12 ... heating power supply,
13, 14 ... temperature detectors.

Continuation of front page    (72) Inventor Osamu Nishino             1060 Takeda, Hitachinaka City, Ibaraki Prefecture Hitachi             Machine Co., Ltd. (72) Inventor Masato Miwa             1060 Takeda, Hitachinaka City, Ibaraki Prefecture Hitachi             Machine Co., Ltd. F-term (reference) 2H033 AA24 AA26 BA27 BA32 BB18                       CA07 CA17 CA30 CA48                 3K058 AA71 BA18 CA12 CA23 CA92                       DA06

Claims (1)

Claims: 1. Two temperature detectors are arranged so as to detect a surface temperature of a heating roller, and two temperature detectors built in the heating roller are provided.
In a fixing device of an electrophotographic apparatus, wherein the two heating elements are independently controlled based on the detection information of the corresponding temperature detectors and the surface temperature of the heating roller is controlled within a specified range. In addition to the detection information of the temperature detector for detecting the surface temperature of the heating roller having a heating range ratio of 1: 1 to 5: 1 and an output ratio of 1: 1 to 8: 1, the paper to be used A fixing device for controlling the surface temperature of the heating roller based on information on the sheet width of the heating roller obtained from detection information of a sheet size detector for detecting the size of the heating roller.