JP2004258567A - Fixing device for electrophotographic printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and low-cost fixing device for an electrophotographic printer which is free of thermal breakage on a heat roller surface and can perform high-speed printing by thermal fixation with stable high temperature setting. <P>SOLUTION: The fixing device is constituted by arranging two temperature detectors detecting the surface temperature of a heat roller and the heat roller includes one main heating element which always operates and two subordinate heating elements. The fixing device selects and operates one of the two subordinate heating elements according to information obtained by a form size detector detecting the size of a form in use and independently controls the respective heating elements according to detection information of the temperature detectors corresponding to the heating elements. Here, the ratio of the heating range of the main heating element, the heating range of one subordinate heating element, and the heating range of the other subordinate heating element is 2:2:1 to 10:2:1 and the ratio of outputs is 2:2:1 to 16:2:1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device for an electrophotographic printing device.
[0002]
[Prior art]
In a conventional fixing device in which toner on a sheet is thermally fixed to the sheet by the surface heat of the heating roller, when the passage width of the sheet is narrow, the surface temperature of a portion of the heating roller where the sheet does not pass abnormally rises, and the It is known that a roller and its surface coating material are damaged. In order to avoid this, two temperature detectors 1 for detecting the surface temperature of the heating roller are arranged, and two heating elements built in the heating roller are detected by the corresponding temperature detectors. It is controlled independently based on the information to keep the surface temperature of the heating roller within a specified range.
[0003]
[Problems to be solved by the invention]
In order to increase the printing speed without changing the size of the electrophotographic printing apparatus, it is necessary to increase the rotation speed of the heating roller without changing the outer dimensions of the heating roller.
[0004]
However, if the rotation speed of the heating roller is increased without changing the outer dimensions of the heating roller, the contact area between the heating roller and the paper remains the same, and only the contact time is shortened. However, a sufficient amount of heat cannot be given, resulting in insufficient fixing strength. In order to solve the problem, there is known a means for increasing the contact area by increasing the pressing force of the pressure roller. Alternatively, there is known a means for reducing the rubber hardness of the pressure roller to increase the contact area. However, any of these methods causes a short life of the pressure roller due to an increase in the load of the pressure roller.
[0005]
Further, as another solution, it is known that a necessary heat amount can be given by setting the surface temperature of the heating roll higher than before, while keeping the contact area unchanged. However, if the set value of the surface temperature is increased while keeping the variation width of the surface temperature of the heating roll the same, if the paper passage width is narrow, the heating roller due to the abnormal temperature rise in the portion where the paper does not pass through the heating roller In addition, there is a possibility of causing thermal damage to the surface coating material.
[0006]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to reduce a variation width of a heating roll surface temperature due to a change in a paper passage width, thereby providing a heating roller and a heating roller. A small and inexpensive electrophotographic printer fixing device that maintains high surface temperature settings without causing thermal damage to the surface coating material and features high-speed printing with a minimum number of temperature detectors and heating elements. Is to provide.
[0007]
[Means for solving the problem]
The above object is to dispose two temperature detectors for detecting the surface temperature of the heating roller, wherein the heating roller comprises one main heating element which is always operated, and two sub-heating bodies. Based on the information obtained from the paper size detector that detects the size of the paper being used, a heating element is built in, and one of the two sub-heating elements is selected and activated. The ratio of the heating range of the main heating body, the heating range of the one sub-heating body, and the heating range of the other sub-heating body is 2: 2: 1 to 10: 2: 1. The output ratio is in the range of 2: 2: 1 to 16: 2: 1, and the respective heating elements are independently controlled based on the detection information of the temperature detectors corresponding to the respective heating elements. It is characterized by controlling.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS.
[0009]
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 charges the photosensitive drum 16 rotating by the motor 15. Thereafter, the CPU 10 controls the optical unit 19 to form a latent image on the photosensitive drum 16, and electrostatically attaches the toner 6 from the developing device 20 to the latent image. Thereafter, the toner 6 is transferred onto the paper 5 by the transfer unit 22 to which the high voltage is applied by the high voltage power supply 21. The paper 5 is peeled off from the photosensitive drum 16 by a peeler 24 to which a high voltage is applied by a high voltage power supply 23, and the paper 5 is rotated by a motor 27 by a paper transport belt 23 rotated by a motor 25. Is transported between the heating roller 1 and the pressing roller 4. In FIG. 1, reference numeral 11 denotes a driver, and 12 denotes a heating power supply.
[0010]
FIG. 1 is a schematic diagram showing a cross section and a circuit of a fixing roller according to an embodiment of the present invention.
[0011]
Two temperature detectors 13 and 14 are arranged to detect the surface temperature of the heating roller 1. One is disposed at a position where one main heating element 2 can be controlled, and the other is disposed at a position where both two sub-heating elements 3a and 3b can be controlled. One main heating element 2 that is always operated and two sub heating elements 3a and 3b are arranged inside the heating roller 1. Only one of the two sub-heating bodies 3a and 3b is selected based on the information obtained from the paper size detectors 7, 8, and 9, which detect the size of the paper being used. It is working.
[0012]
The length and position of the main heating element 2 are set in accordance with the area of the minimum sheet passage width Lmin. The length and position of one of the sub-heating elements 3a are set in accordance with the area obtained by subtracting Lmin from the maximum sheet passage width Lmax. The length and position of the other sub-heating body 3b are set in accordance with the area obtained by subtracting Lmin from the sheet passing width Lmid which is approximately halfway between the minimum sheet passing width Lmin and the maximum sheet passing width Lmax.
[0013]
The temperature detectors 14 corresponding to the two sub-heating bodies 3a and 3b are disposed at a position of the sheet passing width Lmid approximately halfway between the minimum sheet passing width Lmin and the maximum sheet passing width Lmax. Thus, both the heating element 3a and the other heating element 3b can be controlled.
[0014]
The CPU 10 recognizes the width Lp of the paper 5 based on the information of the paper size detectors 7, 8, and 9 when the paper 5 is set in the electrophotographic printing apparatus and the printing preparation operation is being performed. Based on the information obtained from the paper size detectors 7, 8, and 9, when the paper passage width is Lmid or smaller, the heating element 3b is selected and energized to operate. When the paper passage width exceeds Lmid based on the information obtained from the paper size detectors 7, 8, and 9, the heating element 3a is selected and energized to operate. Then, based on the information of the respective temperature detectors corresponding to the main heating element 2 and the sub-heating elements 3a and 3b, each heating element is controlled independently, and the surface temperature of the heating roller 1 is controlled. Is kept within the specified range.
[0015]
The ratio of the heating range W1 of the heating element 2, the heating range W2 of the heating element 3a, and the heating range W3 of the heating element 3b is 2: 2: 1 to 10: 2: 1, and the output ratio is 2: 2: It ranges from 1 to 16: 2: 1.
[0016]
In the conventional method, in the case of Lmin <Lp <Lmid, the temperature rise in the non-sheet passing area becomes large because the heating element 3a is used, and the variation width of the surface temperature of the heating roller is large. However, according to the present embodiment, in the case of Lmin <Lp <Lmid, the temperature rise in the non-sheet passing area is small because the heating element 3b is used, and the variation width of the surface temperature of the heating roller is small. You can do it.
[0017]
In addition, if the set value of the surface temperature of the temperature detector 14 is changed based on the information obtained from the paper size detector, the variation width of the surface temperature of the heating roller can be further reduced. It is. For example, when Lmid <Lp <Lmax and Lp is a sheet width close to Lmid, the control value of the temperature detector 14 is set to be lower than when Lp is close to Lmax. The temperature rise can be reduced, and as a result, the variation width of the surface temperature of the heating roller can be reduced.
[0018]
Therefore, the surface temperature set value of the heating roller can be set to a higher value close to the breakage limit temperature than in the conventional method, and high-speed printing can be performed without changing the size of the apparatus.
[0019]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the variation width of the surface temperature of the heating roller due to the difference in the paper width, and it is possible to secure stable fixing quality. Further, the surface temperature set value of the heating roller can be set to a high value close to the breakage limit temperature as compared with the conventional method. As a result, a small and high-speed electrophotographic apparatus can be provided.
[0020]
Further, since it can be constituted by 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 showing a configuration of an electrophotographic apparatus according to one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heating roller, 2, 3a, 3b ... Heating body, 5 ... Paper, 6 ... Toner, 7, 8, 9 ... Paper size detector, 10 ... CPU, 11 ... Driver, 12 ... Heating power supply, 13, 14 ... temperature detector, 15 ... motor, 16 ... photosensitive drum, 17 ... high voltage power supply, 18 ... charger, 19 ... optical unit, 20 ... developing machine, 21 ... high voltage power supply, 22 ... transfer unit, 23 ... high voltage power supply, 24 ... Peeler, 25 ... Motor, 26 ... Paper transport belt, 27 ... Motor.

Claims (1)

Two temperature detectors that detect the surface temperature of the heating roller are arranged, and the heating roller has one main heating element that is always operated and two auxiliary heating elements. Then, based on the information obtained from the paper size detector that detects the size of the paper being used, one of the two sub-heating bodies is selected and operated, and the main heating is performed. The ratio of the heating range of the body, the heating range of the one sub-heating body, and the heating range of the other sub-heating body is 2: 2: 1 to 10: 2: 1, and the output ratio is Each of the heating elements is independently controlled based on detection information of a temperature detector corresponding to each of the heating elements within a range of 2: 2: 1 to 16: 2: 1. A fixing device for an electrophotographic printing apparatus.

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