JPH086429A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To provide a thermal fixing device capable of keeping toner fixability in the central part and edge part of a recording paper constant and further, eliminating the generation of a problem such as paper wrinkles caused by a heat shrinkage. CONSTITUTION:In the thermal fixing device for an electrophotographic device provided with a fixing roller 11 supplying heat from a heat source 12 and a pressure roller 16 press-contacting with the fixing roller 11 and holding/carrying a transfer material by the fixing roller 11 and the pressure roller 16, to heat/fix unfixed toner on the transfer material, a temperature distribution control means 17 controlling the temperature distribution of the roller surface in the longitudinal direction of the pressure roller 11 is provided thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device for an electrophotographic apparatus.

[0002]

2. Description of the Related Art FIG. 9 shows a schematic view of a conventional electrophotographic apparatus. Around the organic photosensitive drum (hereinafter, referred to as OPC drum) 1 rotated by a drive mechanism (not shown), a charger 2, an exposure device 3, and an exposure device 3 in the order of the rotation direction of the drum 1.
The developing device 4, the transfer device 5, and the cleaner 6 are provided, and the OPC is charged to a predetermined potential by the charger 2.
An electrostatic latent image is formed on the surface of the drum 1 by the exposure device 3, and the electrostatic latent image is visualized with toner attached by the developing device 4 and passes between the OPC drum 1 and the transfer device 5. The transfer device 5 transfers the toner image onto a transfer material (hereinafter referred to as recording paper). Then, the residual toner adhering to the OPC drum 1 is removed by the cleaner 6, and the recording paper onto which the toner image has been transferred is heated and fixed by the thermal fixing device 10.

FIG. 10 is a diagram showing the details of the heat fixing device 10, in which (a) is a front view and (b) is a side sectional view.
The heat fixing device 10 includes a fixing roller 11 and the fixing roller 1.
1, a heater 12 as a heat source for supplying heat to the fixing roller 11, a thermistor 13, which is a temperature sensor for measuring the surface temperature of the fixing roller 11, and a cleaner for removing toner adhering to the surface of the fixing roller 11. The pad 14 and the fixing roller 11 are provided with a pressure roller 16 pressed against the fixing roller 11 by a spring 15. When the temperature of the fixing roller 11 detected by the thermistor 13 is lower than or equal to a predetermined temperature, the heater 12 is turned on, and when it is higher than or equal to the predetermined temperature, it is turned off, and the temperature of the fixing roller 11 is used for fixing the toner. It is kept at a suitable predetermined temperature. In addition, the fixing roller 11
Since both ends in the longitudinal direction of the are easier to radiate heat than the central part,
The heat generation amount of the heater 11 is adjusted so that the central portion is smaller than the both end portions of the fixing roller 11, so that the surface temperature of the fixing roller is made uniform in the longitudinal direction.

The recording paper on which the toner image is adhered is passed between the fixing roller 11 and the pressure roller 16 of the fixing device 10 while the toner image is in contact with the fixing roller 11 side. Therefore, a predetermined amount of heat is supplied to the toner image and the recording paper, and the toner image is fixed on the recording paper. However, the fixing device 10 has the following problems.

As described above, the surface temperature of the fixing roller 11 is made uniform in the roller longitudinal direction as shown in FIG. Therefore, the amount of heat applied from the fixing roller 11 to the pressure roller 16 that is in pressure contact with the fixing roller 11 is also made uniform along the longitudinal direction of the pressure roller 16. However, also in the pressure roller 16, heat is more likely to escape from both ends than from the central portion, so that the temperature distribution on the surface of the pressure roller 16 is higher in the central portion in the longitudinal direction as shown in FIG. Both ends are low. Therefore, when passing between the fixing roller 11 and the pressure roller 16, both rollers 1
The sum of the amounts of heat supplied to the recording paper from Nos. 1 and 16 is the portion of the recording paper that passes through the central parts of both rollers 11 and 16 (hereinafter,
A portion (hereinafter referred to as an end portion of the recording paper) that passes through both ends of both rollers 11 and 16 is smaller than a central portion of the recording paper. Therefore, when the temperature of the pressure roller 16 is extremely different between the both end portions and the central portion, there is a difference in the amount of shrinkage due to heat between the central portion and the end portion of the recording paper, which causes problems such as paper wrinkles. Occurs.

Further, in order to avoid the above problems, FIG.
As shown in FIG. 5, the heat generation amount at both ends of the heater 12 is increased so that the temperature at both ends of the fixing roller 11 becomes higher than that at the central portion. It is also conceivable that the sum of the amounts of heat supplied from the pressure roller 16) is approximately the same in the central portion and the end portion of the recording paper. However, in such a configuration, the main heating source for fixing the toner on the recording paper is the fixing roller 11
Therefore, there arises a problem that the fixing property of the toner is different between the end portion and the central portion of the recording paper.

[0007]

As described above, in the conventional fixing device, if the toner fixing property at the central portion and the end portion of the recording paper is to be made constant, the amount of shrinkage due to heat at the central portion and the end portion of the recording paper is caused. Therefore, a problem such as paper wrinkling occurs, and conversely, if it is attempted to make the amount of shrinkage due to heat in the central portion and the end portion of the recording paper constant, the toner fixing property in the central portion and the end portion of the recording paper There was a problem that there was a difference.

The present invention has been made to solve the above-mentioned conventional drawbacks, and the toner fixing property at the central portion and the end portion of the recording paper can be made constant, and the problem such as paper wrinkling is also caused. An object is to provide a heat fixing device that does not occur.

[0009]

According to the present invention, there is provided a fixing roller to which heat is supplied from a heat source and a pressure roller in pressure contact with the fixing roller, and the transfer material is nipped and conveyed by the fixing roller and the pressure roller. In a heat fixing device of an electrophotographic apparatus that heat-fixes unfixed toner on a transfer material, the pressure roller is provided with temperature distribution control means for controlling the temperature distribution on the roller surface in the longitudinal direction of the pressure roller. Has become.

[0010]

In the present invention, the pressure roller is provided with temperature distribution control means for controlling the temperature distribution on the roller surface in the longitudinal direction of the pressure roller. Therefore, when the fixing roller is heated by the heat source so that the toner fixing property at the central portion and the end portion of the recording paper can be made constant, and thus the temperature distribution can uniformly heat the recording paper, With respect to the temperature distribution in the longitudinal direction of the pressure roller supplied with heat from the fixing roller, the temperature distribution control means corrects heat radiation from both ends to obtain a temperature distribution capable of uniformly heating the recording paper. it can.

[0011]

Embodiments of the present invention will be described in detail below with reference to FIGS.

1 to 3 are views showing a first embodiment, FIG. 1 (a) is a front view of a heat fixing device, and FIG. 1 (b) is a sectional view taken along line AA of FIG. 1 (a). 2 and 3 are schematic diagrams of the electrophotographic apparatus, and FIG. 3 is a diagram showing temperature distributions of the fixing roller and the pressure roller.

The electrophotographic apparatus, as shown in FIG.
The C drum 1, the charging device 2, the exposure device 3, the developing device 4, the transfer device 5, the cleaner 6, and the heat fixing device 10 are provided, and these configurations are the same as those of the conventional example except the heat fixing device 10. Since the configurations are the same, description thereof will be omitted.

As shown in FIG. 1, the heat fixing device 10 measures the surface temperature of the fixing roller 11, the heater 12 arranged in the fixing roller 11 as a heat source for supplying heat to the fixing roller 11, and the surface temperature of the fixing roller 11. Temperature sensor, a thermistor 13, a cleaner pad 14 for removing toner adhering to the surface of the fixing roller 11, a fixing roller 11
The pressure roller 16 pressed against the
And a blower 17 which is a temperature distribution control means (heat dissipation means) provided in the longitudinal center of the pressure roller 16.
It is equipped with. The blower 17 includes a fan 17a and a fan 17a.
It has a guard 17b which surrounds a and guides the air blown by the fan 17a to the center of the roller 16. This heat fixing device 10
The configuration is similar to that of the conventional example except that the blower 17 is arranged. The reason why the blower 17 is arranged is as follows.

In order to obtain a uniform toner fixing property in the longitudinal direction of the fixing roller 11, the heat generation amount of the heater 12 is adjusted so that the surface temperature is uniform at both ends and the central part. For this reason, the pressure roller 16 heated by the fixing roller 11 has a temperature distribution that is higher in the central portion in the longitudinal direction and lower in both ends because the heat is more likely to escape at the both end portions than at the central portion. Therefore, by air-cooling the central portion of the pressure roller 16 by using the blower 17, the heat radiation amounts at the both end portions and the central portion become approximately the same. As shown in FIG. 3, the temperature distribution of the pressure roller 16 when the fan 17a of the blower 17 is stopped is high in the central portion, but the temperature distribution of the pressure roller 16 is made uniform by operating the fan 17a. Can be Therefore, the recording paper is the fixing roller 11 and the pressure roller 1.
It is uniformly heated by 6. Therefore, the toner fixing property at the central portion and the end portion of the recording paper can be made constant, and the problem such as paper wrinkling does not occur due to the difference in heat shrinkage.

4 and 5 are views showing a second embodiment of the present invention. In the first embodiment, the blower 17 is provided in the central portion of the pressure roller 16 in order to radiate heat from the central portion of the pressure roller 16, but in the present embodiment, the temperature inside the electrophotographic apparatus is equal to or higher than the predetermined temperature. The figure shows a case in which heat is radiated from the central portion of the pressure roller 16 by using a fan that also functions as an air-cooling device that is controlled so as not to become the same and an air circulation device that discharges ozone generated in the device to the outside of the device.

On the side surface of the casing 110 of the electrophotographic apparatus 100, an air discharge port 110a is provided on the upper side and an air suction port 110b is provided on the lower side. Air outlet 110a
Is provided with a fan 111 that also serves as an air cooling device and an air circulation device, and the air suction port 110b is positioned below the recording paper discharge port 112. Also, the air suction port 110b
A guide portion 115 and an air passage 116 are provided so that the cold air sucked from the center of the pressure roller 16 flows but not both ends.

With such a structure, when the fan 111 is operated, the inside of the apparatus 100 is cooled by the outside cool air, and the ozone generated in the apparatus is discharged to the outside of the apparatus, and the pressure roller is also used. The cool air passing through the central portion of 16 dissipates heat in the central portion of the pressure roller 16, and the surface temperature distribution of the pressure roller 16 becomes uniform in the longitudinal direction.

6A and 6B are views showing a third embodiment of the present invention. FIG. 6A is a front view of the heat fixing device, and FIG. 6B is a sectional view taken along the line BB of FIG. 6A. It is a figure. In this example, a heat radiating means is used as the temperature distribution control means of the pressure roller 16,
A heat radiator 18 is used as the heat radiating means. The other structure is similar to that of the first embodiment.

The radiator 18 is formed of a plate material having a good thermal conductivity, and is in contact with the central portion of the pressure roller 16. Therefore, the heat in the central portion of the pressure roller 16 is taken away by the radiator 18, so that the temperature distribution of the pressure roller 16 becomes uniform in the longitudinal direction. 7A and 7B are views showing a fourth embodiment of the present invention. FIG. 7A is a front view of the heat fixing device, and FIG. 7B is a sectional view taken along line CC of FIG. 7A. . In this example, the heating means is used as the temperature distribution control means of the pressure roller 16, and the heater 20 is used as the heating means. The other structure is similar to that of the first embodiment.

The heaters 20 are disposed at both ends of the pressure roller 16, and the heater 20 replenishes the heat escaping from the ends of the pressure roller 16 so that the pressure roller 1
The temperature distribution of No. 6 is made uniform in the longitudinal direction.

In the above four embodiments, the pressure roller 1
The temperature distribution in the longitudinal direction of the pressure roller 16 is made uniform by radiating heat from the central portion of 6 or by heating both end portions, but this is to the end as compared with the central portion of the pressure roller 16. This is a means when a large amount of heat is dissipated in the section. For example, depending on the device, there is a case where the central portion of the pressure roller 16 dissipates more heat than the both end portions thereof due to the influence of wind or the like flowing in the device. In such a case, the temperature distribution of the pressure roller 16 is controlled by cooling both ends or heating the central part.

8A and 8B are views showing a fifth embodiment of the present invention. FIG. 8A is a front view of a heat fixing device, and FIG. 8B is a sectional view taken along line D-D of FIG. 8A. It is a figure. In the above four embodiments, only the temperature distribution of the pressure roller 16 is controlled. However, in this embodiment, the temperature distribution of the fixing roller 11 also changes due to the influence of the temperature distribution of the pressure roller 16. Considering this, the temperature distribution of the fixing roller 11 is also controlled.

In this example, the pressure roller 16 is provided with a blower 17 at the center and heaters 20 at both ends.
In addition, three thermistors 13 are brought into contact with the corresponding portions of the pressure roller 16 in order to measure the temperatures of the pressure roller 16 in the central portion and at both end portions. Further, in addition to the heater 12 which is the heat source of the roller 11, the fixing roller 11 is provided with heaters 24 which are auxiliary heat sources at both ends thereof, and the temperature of the fixing roller 11 at the central portion and at both ends thereof is controlled. For the measurement, three thermistors 13 are brought into contact with corresponding portions of the fixing roller 11.

In this example, the three rollers provided on the fixing roller 11 are used.
By turning on / off the auxiliary heater 24 by a signal detected by each thermistor 13, the fixing roller 11
The temperature distribution in the longitudinal direction of can be made suitable for heat fixing of the toner. Further, the temperature distribution in the longitudinal direction of the pressure roller 16 can be made uniform by turning on and off the air blower 17 and the heater 20 according to the signals detected by the three thermistors provided on the pressure roller 16. Therefore, even when the usage environment of the electrophotographic apparatus changes, the temperature distributions in the longitudinal direction of the fixing roller 11 and the pressure roller 16 can be always maintained in an optimum state.

In each of the above embodiments, the temperature distribution control means controls the temperature distribution of the fixing roller 11 and the pressure roller 16 so as to be uniform in the longitudinal direction, but the present invention is not limited to this. . That is, in the present invention,
It is important to uniformly heat and fix the toner on the recording paper and to uniformly heat the entire recording paper. Therefore, when the fixing roller and the pressure roller have a special shape such as a concave shape and a convex shape, the temperature distribution in the longitudinal direction of the fixing roller and the pressure roller does not necessarily have to be uniform, and the fixing roller and the pressure roller do not have to be uniform. Both pressure rollers may be controlled so that the recording paper can be uniformly heated.

[0027]

As described above, in the heat fixing device of the present invention, when the fixing roller is heated by the heat source so that the recording paper has a uniform temperature distribution, the heat amount is supplied from the fixing roller. The temperature distribution in the longitudinal direction of the pressure roller can also be corrected by the temperature distribution control means so that the recording paper can be uniformly heated. Therefore, the toner fixing property at the central portion and the end portion of the recording paper can be made constant, and the problem such as paper wrinkling due to heat shrinkage does not occur.

[Brief description of drawings]

FIG. 1 is a diagram showing a heat fixing device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an electrophotographic apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a temperature distribution in a roller longitudinal direction in the thermal fixing device of FIG.

FIG. 4 is a front sectional view of an electrophotographic apparatus according to a second embodiment of the present invention.

5 is a left side view of the electrophotographic apparatus of FIG.

FIG. 6 is a diagram showing a third embodiment of the present invention.

FIG. 7 is a diagram showing a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a fifth embodiment of the present invention.

FIG. 9 is a schematic view of a conventional electrophotographic apparatus.

FIG. 10 is a diagram showing a conventional heat fixing device.

FIG. 11 is a diagram showing a temperature distribution of a roller in a conventional heat fixing device.

FIG. 12 is a diagram showing another example of the roller temperature distribution in the conventional heat fixing device.

[Explanation of symbols]

 10 Thermal Fixing Device 11 Fixing Roller 12 Heat Source 13 Thermistor 16 Pressure Roller 17 Blower Device 18 Radiator 20 Heating Means 24 Auxiliary Heat Source

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G05D 23/19 H

Claims (12)

[Claims] 1. A fixing roller which is supplied with heat from a heat source and a pressure roller which is in pressure contact with the fixing roller, and the transfer material is nipped and conveyed by the fixing roller and the pressure roller to heat unfixed toner to the transfer material. In the heat fixing device of the electrophotographic apparatus for fixing, the pressure roller is provided with temperature distribution control means for controlling the temperature distribution on the roller surface in the longitudinal direction of the pressure roller. . 2. The heat fixing device according to claim 1, wherein the temperature distribution control means is a heat radiation means for releasing heat from a predetermined portion of the pressure roller. 3. The heat fixing device according to claim 2, wherein the predetermined portion is a central portion in the longitudinal direction of the pressure roller. 4. The heat fixing device according to claim 2, wherein the heat radiating means is a blower for blowing cool air to the pressure roller. 5. The temperature distribution control means is a heating means provided at a predetermined portion of the pressure roller.
The heat fixing device described in 1. 6. The heat fixing device according to claim 5, wherein the predetermined portions are both end portions in the longitudinal direction of the pressure roller. 7. The thermal fixing device according to claim 1, wherein the temperature distribution control means is operated by a signal of a temperature sensor brought into contact with the surface of the pressure roller. 8. The heat fixing device according to claim 2, wherein the heat radiating means is a heat radiating member brought into contact with the pressure roller. 9. The heat fixing device according to claim 4, wherein the air blowing device also serves as an air cooling device for controlling the temperature in the electrophotographic apparatus. 10. The heat fixing device according to claim 4, wherein the air blowing device also serves as an air circulating device used for removing ozone generated in the electrophotographic device. 11. The fixing roller has, in addition to a heat source for supplying heat to the entire fixing roller, an auxiliary heat source for partially heating the fixing roller, and the auxiliary heat source has a temperature contacted with the surface of the fixing roller. The thermal fixing device according to claim 1, wherein the thermal fixing device is operated by a signal from a sensor. 12. The thermal fixing device according to claim 11, wherein the auxiliary heat source is provided at both ends of the fixing roller in the longitudinal direction.