JPH09160423A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve a problem that the temp. of a nip part in paper nonpassing part areas is higher than that of a paper passing part area. SOLUTION: In the thermal roller fixing system fixing device for executing fixing in such a manner that a pressure roller 3 comes into press-contact with a fixing roller 2 heated to a uniform temp. and a body to be heated of a copying paper on which toner rides passes through the nip part. When the heated body has a small size, the temp. of the paper nonpassing areas rises with respect to the paper passing part area. For preventing this a radiator roller 6 is brought into press-contact with the fixing roller 2 to rotate the radiator roller 6 with the rotation of the fixing roller 2. The central part 6a through which the small- sized body to be heated passes of the radiator roller 6 is made of a material whose thermal conductivity is comparatively low and both end parts 7 of the paper nonpassing areas are made of a material whose thermal conductivity is comparatively high. The radiator roller 6 is rotated in press-contact with the fixing roller 2, so that the temp. in the axial direction of the nip part is made uniform by the heat radiation of the temp. of the paper nonpassing regions which is made higher than that of the paper passing region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device,
More specifically, in an electrophotographic recording device such as a copying machine, a fax machine, or an electrophotographic printer, an image made of heat-meltable toner formed on the surface of a recording material such as paper has a uniform temperature distribution in the axial direction. The present invention relates to a heat fixing device that heats a fixing roller to fix a fixed image on the surface of a recording material.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a toner containing a coloring material is electrostatically absorbed by an electrostatic latent image formed on a photoconductor and then transferred to paper. Since the toner electrostatically transferred onto the toner easily peels off, it is necessary to permanently fix the toner on the paper by heating or pressurizing the toner. This step is called the fixing process. There are various fixing methods, but the heat roller fixing method is most widely used because of its high thermal efficiency and safety. This is because two rollers are pressed against each other, at least one of them is heated, and an unfixed toner image support (for example, paper or OHP sheet) is passed through these two pressed portions (hereinafter referred to as nip portions). By doing so, the unfixed toner is heated and fixed on the support. When one of the two rollers of this system is heated, the roller to be heated is called a fixing roller and the other roller is called a pressure roller. A heat source such as a halogen lamp for heating or an electric heater is installed inside the fixing roller in the axial direction of the fixing roller. A temperature sensor that detects the surface temperature of the fixing roller is attached to the outer surface of the fixing roller, and the temperature of the nip part is based on the difference between the temperature signal detected by the temperature sensor and the set temperature. The power supply amount to the heat source in the fixing roller is controlled so as to be maintained at.

However, conventionally, in such a heat fixing device, it was difficult to make the temperature distribution in the axial direction uniform. That is, in the area through which the small-sized material to be heated passes, that is, the sheet passing area, heat is consumed for heating the material to be heated (unfixed toner image support and unfixed toner on the support), Since heat is not consumed to heat the material to be heated in the non-paper passing area, heat is stored, and the temperature of the nip in the non-paper passing area is higher than the temperature of the nip in the paper passing area that is maintained and controlled at a predetermined temperature. Will also be high. For this reason, when a small-sized heated material is continuously passed and then a large-sized heated material is passed (for example, when A4 size paper is continuously passed and then A3 size paper is passed), Size Irregular fixing or wrinkles occur on the material to be heated, or the toner corresponding to the non-sheet passing area of the unfixed toner image melts too much and adheres to the fixing roller to stain the surface of the material to be heated. ,
There are problems such as hot offset).

The prior art which aims to solve such a problem by making the temperature distribution in the axial direction uniform includes the following. 1. The temperature distribution in the axial direction is made uniform by cooling the excessively heated non-sheet passing area. 2. By increasing the heat capacity of the fixing roller, the temperature rise in the non-sheet passing area is suppressed. 3. The temperature distribution in the axial direction is made uniform by increasing the thermal conductivity of the fixing roller or by bringing an object having a high thermal conductivity into contact with the fixing roller. 4. By providing a plurality of heaters having different heating widths or heating positions in the axial direction of the fixing roller and controlling each heater individually, the temperature distribution in the axial direction is made uniform. Alternatively, the temperature distribution in the axial direction is made uniform by changing the heat generation amount of one heater in the longitudinal direction. Alternatively, the heat generation portion of one heater is switched to make the temperature distribution in the axial direction uniform.

5. The heater has the characteristic that the resistance decreases as the temperature rises. 6. The control temperature is changed according to the width of the material to be heated. 7. The heat capacity and the thermal conductivity are changed along the axial direction of the fixing roller. 8. The heater is provided with a heat shield member, and the position of the shield member is controlled to change the heating position of the fixing roller to make the temperature distribution in the axial direction uniform. 9. By covering the fixing roller with a cover, heat radiation from the fixing roller is controlled. Ten. By changing the position of the sheet passing portion of the small-sized heated material, it is possible to prevent heat from being taken away only in a specific area in the axial direction of the fixing roller.

Each of these methods has advantages and disadvantages. Among these, 1. The method for cooling the excessively heated non-sheet passing portion area shown in (3) can be realized with a relatively simple mechanism and can be manufactured at a low cost. As a cooling method, an air cooling method and a method of bringing a heat radiation member into contact with the fixing roller have been proposed. As the prior art of this system, JP-A-6-250540 and JP-A-6-111983 are described below.
And JP-A-4-12383.

1) Japanese Unexamined Patent Publication No. 6-250540 A heat transfer member made of aluminum or the like is brought into contact with a pressure roller to improve the thermal conductivity in the longitudinal direction of the pressure roller, thereby improving the thermal conductivity of the pressure roller and the non-paper passage portion. The temperature difference between the parts is reduced. 2) Japanese Unexamined Patent Publication No. 6-19833 has a heat radiating member that can come into contact with the fixing roller, and the heat radiating member is brought into contact with the fixing roller according to the size of the transfer paper. 3) Japanese Unexamined Patent Publication No. 4-123383 has a fan and a duct, and cools by sucking air in the vicinity of both ends of the fixing roller or discharging outside air in the vicinity of both ends.

[0008]

However, the above-mentioned conventional technique for making the temperature distribution in the axial direction of the fixing roller uniform has the following problems. That is, JP-A-6-2505
According to Japanese Patent Laid-Open No. 40, the high heat transfer member is pressed against the pressure roller instead of the fixing roller, and the temperature uniformity effect is less than that of pressing against the heating side fixing roller. It also relates to fixing when the substrate is a film. JP-A-6-11
The 983 publication has a complicated mechanism and is costly. Further, there is no mechanism that presses the heating roller against the fixing roller and positively heats the lowered temperature of the fixing roller to compensate for the temperature difference occurrence portion. In Japanese Patent Laid-Open No. 12383/1992, the temperature at both ends of the fixing roller is cooled by sucking and exhausting air near both ends of the fixing roller by using a fan. Basically different.

According to the present invention, the above-mentioned problem that the temperature of the nip portion in the non-sheet passing portion area becomes higher than the temperature of the nip portion in the sheet passing portion area which is maintained and controlled at a predetermined temperature is efficiently achieved by a simple device. An object of the present invention is to provide a fixing device which is well solved.

[0010]

According to a first aspect of the present invention, there is provided a fixing roller having a heat source therein, and a pressure roller installed so as to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. In a fixing device configured to pass a material to be heated between the fixing roller and the pressure roller while press-contacting and heating the heat-dissipating roller, the heat-dissipating roller rotating while press-contacting the fixing roller. A portion corresponding to a region where the small-sized material to be heated does not pass is made of a material having high thermal conductivity.

According to a second aspect of the present invention, there is provided a fixing roller having a heat source therein, and a pressure roller which is installed so as to be in pressure contact with the fixing roller and rotates in cooperation with the rotation of the fixing roller. In a fixing device that allows a material to pass between the fixing roller and the pressure roller while being pressed and heated, a heat radiating roller that rotates while being in pressure contact with the fixing roller is provided, and the radiating roller has a size of the material to be heated. Accordingly, the pressure roller is moved in the axial direction of the fixing roller to make the pressure contact area with the fixing roller variable.

According to a third aspect of the present invention, there is provided a fixing roller having a heat source therein, and a pressure roller installed so as to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. A fixing device that allows a material to pass between the fixing roller and the pressure roller while being pressed and heated. The fixing device includes a heat dissipation plate that is in pressure contact with a part of the fixing roller or the pressure roller. When the small-sized object to be heated passes between the roller and the roller, in the non-passage area of the small-sized object to be heated, the radiator plate is brought into contact with the fixing roller or the pressure roller to heat the large-sized object. When the body passes, it is designed so as not to come into pressure contact with the entire area.

According to a fourth aspect of the present invention, there is provided a fixing roller having a heat source therein, and a pressure roller installed so as to be in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller. In a fixing device that allows a material to pass between the fixing roller and the pressure roller while being pressed and heated, a heating roller that is in pressure contact with the fixing roller and heats a heated body passing region of the fixing roller is provided. It is a thing.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side view for explaining a first embodiment of a fixing device according to the present invention, and FIG.
2 is a heat source, 2 is a fixing roller, 3 is a pressure roller, 4 is a paper inlet guide, 5 is a material to be heated (copy paper with toner), and 6 is a heat dissipation roller. , 7
Is the surface of the heat dissipation roller 6.

In FIG. 1 or 2, the heat source 1 is composed of a halogen lamp or the like, and is installed in the axial direction of the fixing roller 2 so as to have a length substantially equal to the entire length of the fixing roller 2, and the inner surface of the fixing roller 2 is an axis. It can be heated evenly in any direction. The pressure roller 3 has substantially the same length as the fixing roller 2 and is pressed against the fixing roller 2 in parallel with the axis by a pressing mechanism (not shown). Between the fixing roller 2 and the pressure roller 3 that are in pressure contact with each other, there is provided a heated member 5 to be fixed, that is, a paper inlet guide 4 that guides the copy paper on which toner is loaded to the nip portion.

The heat radiating roller 6 is in pressure contact with the fixing roller 2 so as to rotate in parallel with the axis of the fixing roller 2 as the fixing roller 2 rotates. The position where the heat radiating roller 6 is pressed against the fixing roller 2 may be any position, such as 8 or 9 shown by the broken line in FIG.
May be in the position. The heat radiation roller 6 has an axial length equal to or longer than that of the fixing roller 2, the central portion 6a is made of a material having a relatively low thermal conductivity, and both end portions 7 other than the central portion 6a are thermally conductive. The fixing roller 2 is made of a material having a relatively high ratio, and both end surface portions 7 are in pressure contact with the non-sheet passing portion area of the fixing roller 2.

The surface layer portions of both ends 7 are made of an elastic material such as silicon rubber, and the heat conductive material of aluminum is used except for the surface layer portions so that heat can be quickly dissipated in the axial direction of the heat radiating roller 6. To be able to However, both ends 7 are not limited to aluminum, and other materials may be used as long as they have a high thermal conductivity and a hardness that does not deform axially. A common cooler (not shown) formed by molding a material having a large thermal conductivity into a structure having a large surface area is connected to both ends 7 to prevent the ends 7 from trapping heat. It should be noted that the heat radiation roller 6 may be installed in plural instead of one. The larger the number of heat radiating rollers 6, the more the fixing roller 2
The heat dissipation effect of the non-sheet-passing part where the temperature is raised becomes large. Since the heat conductivity of the material to be heated 5 is much smaller than the heat conductivity of the both ends 7 of the heat radiating roller 6, the non-paper-passing portion removes more heat than the paper-passing portion, and the non-paper-passing portion Does not raise the temperature.

FIG. 3 is a perspective view for explaining the second embodiment of the fixing device according to the present invention. In FIG.
Reference numeral 12 is a heat-dissipating roller, and 13 is a shaft. The parts having the same functions as those in FIGS. 1 and 2 are designated by the same reference numerals as in FIGS. The same applies to the reference numbers in the drawings after FIG.

In the second embodiment of the fixing device shown in FIG. 3, the area where the heat radiating rollers 11 and 12 are in pressure contact with the fixing roller 2 can be changed according to the size of the heated body 5.
The heat radiating rollers 11 and 12 are heat radiating rollers which are movable on the shaft 13 and can be pressed against the fixing roller 2. This heat radiation roller moves on the shaft 13 in the axial direction of the fixing roller 2 by a method not shown. The heat radiating rollers 11 and 12 are configured to rotate following the rotation of the fixing roller 2.
The heat radiating rollers 11 and 12 may be pressed against the fixing roller 2 at any positions. For example, the positions 8 and 9 shown in FIG. 1 may be used. A detector (not shown) for detecting the size of the heated material 5 is provided in the vicinity of a paper feed cassette (not shown) for supplying the heated material 5. The pressure contact area between the heat radiating rollers 11 and 12 and the fixing roller 2 is changed according to the detected information, that is, the size of the supplied material 5 to suppress the temperature rise of the non-sheet passing portion.

The surface layers of the heat radiating rollers 11 and 12 are made of an elastic material such as silicon rubber, and the other parts than the surface layer are made of aluminum so that heat can be quickly dissipated in the axial direction of the heat radiating rollers 11 and 12. I am able to do it. However, the material is not limited to aluminum, and any other material may be used as long as it has a high thermal conductivity and a hardness that does not cause axial deformation. The heat radiating rollers 11 and 12 are connected to an ordinary cooler (not shown) formed by molding a material having a large thermal conductivity into a structure having a large surface area.
Prevents heat from staying inside. The heat radiation rollers 11, 1
A plurality of 2 may be installed instead of one. The larger the number of heat radiating rollers, the greater the heat radiating effect of the non-sheet-passing portion that is heated.

FIG. 4 is a perspective view for explaining a third embodiment of the fixing device according to the present invention, in which 21 is a heat radiating plate.

In the third embodiment of the fixing device shown in FIG. 4, when the size of the heated body 5 is large, the heated body 5 causes the heat dissipation plate 21 to move to the pressure roller 3 or the fixing roller 2. It is designed to prevent pressure contact. Less than,
It will be described with reference to FIG.

In FIG. 4, at the exit of the nip portion, there is a paper winding guide (not shown) for winding the heated material 5 passing through the nip portion around the pressure roller 3 or the fixing roller 2. As shown in FIG. 4, the heat radiating plate 21 has a space according to the size of a small size object to be heated.
They are separated into a and 21b, are curled together, and are in pressure contact with the pressure roller 3 or the fixing roller 2. In the case of a large-sized heated material 5, the wound heated material 5 is inserted between the heat dissipation plate 21 and the pressure roller 3 or the fixing roller 2, and the heat dissipation plate 21 and the pressure roller 3 or the fixing roller 2 are inserted. Are separated from each other to prevent the heat sink 21 from taking heat.
In the case of the small-sized heated material 5, the heated body 5 is guided between the heat radiating plates 21a and 21b, and the heat radiating plates 21a and 21b
Since b is kept in pressure contact with the pressure roller 3 or the fixing roller 2, the temperature rise is prevented and the non-sheet passing portion temperature rise is prevented.

The surface layer of the heat dissipation plate 21 is made of an elastic material such as silicon rubber, and the rest of the surface layer is made of aluminum so that heat can be quickly dissipated in the length direction of the heat dissipation plate 21. To do. However, the material is not limited to aluminum, and another material may be used as long as it has a large thermal conductivity and a hardness that does not cause deformation in the longitudinal direction. Heat sink 2
Reference numeral 1 is connected to an ordinary cooler (not shown) formed by molding a material having a large thermal conductivity into a structure having a large surface area to prevent heat from staying in the heat radiating plate 21.

FIG. 5 is a perspective view for explaining a fourth embodiment of the fixing device according to the present invention, in which 31 is a heating roller.

In the fourth embodiment of the fixing device shown in FIG. 5, a heating roller 31 having the same length as the size of the small-sized heated material 5 is pressed against the fixing roller 2 in an axially parallel manner.
This is to compensate for the temperature drop when the small-sized heated material 5 is continuously passed through the nip portion. Hereinafter, description will be given based on FIG.

In FIG. 5, the heating roller 31 is provided in pressure contact with the fixing roller 2 in a direction parallel to the axis thereof, and is rotated according to the rotation of the fixing roller 2. Heating roller 31
Has the same length as the small-sized material 5 to be heated passes through the nip portion, and a heating body 31a such as a halogen lamp for heating the heating roller 31 is installed inside the heating roller 31. Try to keep the temperature slightly higher. When the small-sized heated material 5 continuously passes through the nip portion,
Although the temperature decreases only at the nip portion, the heating roller 31 compensates for the temperature decrease. The surface layer of the heating roller 31 is made of an elastic material such as silicon rubber, and the parts other than the surface layer are made of aluminum to facilitate heat transfer. However, the material is not limited to aluminum, and any other material may be used as long as it is a material that easily transmits heat and has a hardness that does not cause axial deformation.

[0028]

【The invention's effect】

An effect corresponding to claim 1: A fixing roller having a heat source inside, and a pressure roller installed so as to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller,
A fixing device that allows a material to be heated to pass between the fixing roller and the pressure roller while being pressed and heated includes a heat dissipation roller that rotates while being pressed against the fixing roller, and the heat dissipation roller has a small size. Since the portion corresponding to the region through which the material to be heated does not pass is made of a material having high thermal conductivity, it is possible to prevent the non-sheet passing portion from rising in temperature.

An effect corresponding to claim 2: A fixing roller having a heat source inside, and a pressure roller installed so as to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. In a fixing device that allows a heating material to pass between the fixing roller and the pressure roller while being pressed and heated, a heat radiation roller that rotates while being in pressure contact with the fixing roller is provided, and the heat radiation roller is the size of the material to be heated. According to the above, the fixing roller is moved in the axial direction and the pressure contact area with the fixing roller is made variable, so that the non-sheet passing portion is prevented from rising in temperature regardless of the size of the heated material. be able to.

An effect corresponding to claim 3: A fixing roller having a heat source inside and a pressure roller which is installed so as to be in pressure contact with the fixing roller and rotates in cooperation with the rotation of the fixing roller. In a fixing device that allows a heating material to pass between the fixing roller and the pressure roller while being pressed and heated, a heat dissipation plate that is in pressure contact with a part of the fixing roller or the pressure roller is provided, and the fixing roller and the pressing roller are provided. When the small-sized object to be heated passes between the pressure roller and the pressure roller, the heat radiating plate is brought into contact with the fixing roller or the pressure roller in the non-passage area of the small-size object to be heated. When the heating element passes through, the pressure contact is prevented over the entire area, so that the temperature of the non-sheet passing portion can be suppressed by a simple device provided with a heat dissipation plate.

An effect corresponding to claim 4: A fixing roller having a heat source inside, and a pressure roller installed so as to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. In a fixing device that allows a heating material to pass between the fixing roller and the pressure roller while heating under pressure, a heating roller that presses the fixing roller and heats a heated object passage region of the fixing roller is provided. The temperature of the fixing roller whose temperature has dropped can be compensated.

[Brief description of the drawings]

FIG. 1 is a side view for explaining a first embodiment of a fixing device according to the present invention.

FIG. 2 is a perspective view of a main part of FIG.

FIG. 3 is a perspective view for explaining a second embodiment of the fixing device according to the present invention.

FIG. 4 is a perspective view for explaining a third embodiment of the fixing device according to the present invention.

FIG. 5 is a perspective view for explaining a fourth embodiment of the fixing device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat source, 2 ... Fixing roller, 3 ... Pressure roller, 4 ... Paper inlet guide, 5 ... Heated material (copy paper with toner), 6 ... Heat dissipation roller, 7 ... Surface part 1 of heat dissipation roller 6
1, 12 ... Heat dissipation roller, 13 ... Shaft, 21 ... Heat dissipation plate, 31
… Heating roller.

Claims (4)

[Claims] 1. A fixing roller having a heat source inside and a pressure roller which is installed so as to be in pressure contact with the fixing roller and rotates in cooperation with the rotation of the fixing roller. And a pressure roller between the pressure roller and the pressure roller, the heat radiating roller rotating while being in pressure contact with the fixing roller, the heat radiating roller being a region where the small-sized material to be heated does not pass. A fixing device characterized in that a portion corresponding to is made of a material having high thermal conductivity. 2. A fixing roller having a heat source inside, and a pressure roller which is installed so as to be in pressure contact with the fixing roller and rotates in cooperation with the rotation of the fixing roller. And a pressure roller, the fixing device passing the pressure roller and the pressure roller while heating the heat roller includes a heat radiation roller that rotates while pressure-contacting the fixing roller, and the heat radiation roller is fixed in accordance with the size of the material to be heated. The fixing device is characterized in that the pressure contact area with the fixing roller is made variable by moving in the axial direction. 3. A fixing roller having a heat source inside and a pressure roller which is installed so as to be in pressure contact with the fixing roller and rotates in cooperation with the rotation of the fixing roller. And a pressure roller between the fixing roller and the pressure roller, wherein a heat radiating plate is in pressure contact with a part of the fixing roller or the pressure roller. When the small-sized object to be heated passes, in the non-passage area of the small-sized object to be heated, the heat dissipation plate is brought into contact with the fixing roller or the pressure roller, and the large-sized object to be heated passes. The fixing device is characterized in that it is not pressed against the entire area. 4. A fixing roller having a heat source inside and a pressure roller which is installed so as to be in pressure contact with the fixing roller and rotates in cooperation with the rotation of the fixing roller. A fixing device for passing the pressure roller and the pressure roller while pressing and heating the fixing roller, the heating device including a heating roller that presses the fixing roller to heat a heating target passage region of the fixing roller.