JPH1130924A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly heat a portion in contact with a transfer paper by using iron or a stainless alloy as a heat generating portion for an outer layer as a core metal structure of an induction heating roller. The rise time is shortened to save energy, and the inner layer is made of aluminum in consideration of heat conduction to prevent temperature unevenness. SOLUTION: In a fixing device for fixing by a heating roller 1 and a pressure roller 2, wherein the heating roller is an induction type heating roller, the heating roller is a fixed side on which an induction coil is wound around an outer peripheral surface. A bobbin part 3 and a cored bar 4 coaxially and rotatably arranged in the outer diameter direction of the bobbin part;
The core is made of a first layer 30 made of a material having a high linear expansion coefficient.
And a second layer 31 made of a material having a low coefficient of thermal expansion fixed to the outer surface of the first layer, wherein the axial length of the first layer is greater than the axial length of the second layer. And a movement preventing member 22 for preventing the movement of the second layer in the axial direction is provided on the first layer side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fixing device used in an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile machine, etc., and more particularly to a fixing device using an induction type heat roller utilizing electromagnetic induction. .

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus,
After transferring the toner image formed on the photoreceptor onto transfer paper, the transfer paper is guided into a fixing device to fix the toner image, and then discharged outside the apparatus. The fixing device generally includes a heating roller provided with a heater and a pressure roller that nips the peripheral surface of the heating roller. When the transfer paper is passed between the two rollers, pressure is applied while heating. Thus, the toner is fixed. As means for causing the heating roller to generate heat, an induced coil is generated by an induction coil disposed inside the core, and an induced current is generated in the core (conductive layer) on the outer peripheral portion of the roller by the induced magnetic flux. There is known an induction heating roller configured to generate a desired temperature on the roller surface by Joule heat. As a configuration of the conventional induction-type heating roller as described above, Japanese Patent Application Laid-Open No. S60-38494 discloses a core bar using iron as an inner layer and aluminum as an outer layer. In the method, first, the inner iron layer is heated, and then heat is supplied to the surface of the heating roller through the outer aluminum layer. Therefore, there was a disadvantage that the rise time was delayed. Heating rollers having a two-layered core have different thermal expansion coefficients of the materials constituting each layer, and thus have different lengths when heated, resulting in repeated heating and cooling. As a result, there is a drawback that the axial position shift between the two layers occurs, and the heating performance shifts, thereby deteriorating the fixing performance.
In other words, since the outer aluminum layer was fixed to the outer peripheral surface of the inner iron layer by the crimping method, the crimping at the boundary was loosened due to repeated heating and cooling, and relative displacement in the axial direction and the like was likely to occur. Was. Also, the core of the conventional induction-type heating roller is made of aluminum, but if the outer peripheral surface of aluminum is supported by bearings, the aluminum part will wear out. However, there is also a drawback that the aluminum part is worn down due to abrasion and the core metal itself cannot be used.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a core of an induction-type heating roller, in which iron or a stainless alloy serving as a heat generating portion is formed on an outer layer. Direct heating of the part in contact with the transfer paper by using it to speed up the rise time and save energy, while using aluminum as the inner layer in consideration of heat conduction, the axial temperature which is a drawback of iron roller The purpose is to prevent unevenness. Also, even if such a laminated structure is adopted, the displacement of the iron layer caused by the difference in the coefficient of linear expansion caused by the repetition of heating / cooling at the boundary between the iron layer and the aluminum layer can be prevented or the heating roller can be used. Another object is to prevent problems at the time of attaching to a fixing unit. Another object of the present invention is to provide iron or stainless steel for the bearing portion so as to eliminate wear over time and eliminate problems in regeneration of the heating roller.

[0004]

As described above, according to the first aspect of the present invention, a transfer sheet having a toner image to be fixed is transferred while the transfer sheet having the toner image to be fixed is held between a heating roller and a pressure roller. A fixing device for fixing on paper, wherein the heating roller is an induction-type heating roller, wherein the heating roller has a fixed bobbin around which an induction coil is wound around an outer peripheral surface, and an outer diameter of the bobbin. A metal core arranged coaxially and rotatably in the direction, the metal core having a first layer made of a material having a high linear expansion coefficient, and a linear expansion fixed to an outer surface of the first layer. A second layer made of a material having a small ratio, wherein the axial length of the first layer is set longer than the axial length of the second layer, and the axial length of the second layer in the axial direction is set. A movement preventing member for preventing movement is provided on the first layer side. The invention of claim 2 is characterized in that the material of the first layer is an aluminum-based material and the material of the second layer is an iron-based or stainless-based material. The invention according to claim 3 is characterized in that the core metal is rotatably supported by slidingly contacting the outer peripheral surface of the second layer made of the iron-based or stainless-based material with a bearing.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. FIG. 1A is a schematic diagram of a main part of a fixing device of the present invention, and FIG. 1B is an enlarged sectional view of the main part.
The fixing device includes a heating roller 1 and a pressure roller 2 that rotates while being in contact with the outer peripheral surface of the heating roller 1. The transfer paper P holding the toner T is passed through a nip between the rollers 1 and 2. In the process, the toner T is fixed on the transfer paper P by the heat from the heating roller 1 and the pressure from the pressure roller 2. The heating roller 1 has a configuration in which a cylindrical roller body (core metal) 4 is rotatably supported coaxially with a predetermined gap in the outer diameter direction of the fixed bobbin portion 3. FIG. 2 is a side longitudinal sectional view of an example of the induction heating roller of the present invention. The bobbin portion 3 is formed integrally with, for example, a heat-resistant resin, and the central portion in the axial direction has a large-diameter portion 11. A power source (not shown), which is a hollow cylindrical body, in which an induction coil 12 is wound around an outer peripheral surface of a large diameter portion 11 and lead wires 14a, 14b disposed inside both small diameter end portions 13a, 13b are connected to the induction coil 12. Is configured to supply a high-frequency current from. The outer peripheries of both ends 13a, 13b of the bobbin 3 are fixedly supported by brackets 15a, 15b of the image forming apparatus main body. The roller body (core bar) 4 includes ball bearings 21a and 21a fitted to the side plates 20a and 20b of the fixing device.
It is rotatably supported by 21b. Roller body 4
Is a first layer (inner layer) 30 which is relatively thick and directly faces the induction coil 12, and a second layer which is laminated over the entire outer peripheral surface of the first layer 30 over a predetermined axial length. Layer (outer layer) 31
And a release layer 32 laminated over the entire outer peripheral surface of the second layer 31 over a predetermined axial length. First layer 3
Numeral 0 is a layer made of a material having a good thermal conductivity and a high coefficient of linear expansion such as aluminum or an aluminum alloy (aluminum-based). (A linear expansion coefficient is smaller than that of aluminum-based materials).

In this embodiment, iron or a stainless steel alloy is used as the second layer 31 as the outer layer, so that the portion in contact with the transfer paper is directly induction-heated to increase the rise time and save energy. In addition, by using an aluminum alloy in consideration of thermal conductivity as the material of the first layer 30 as the inner layer, it is possible to prevent the temperature unevenness in the axial direction of the second layer 31 made of iron or the like. . The outer peripheral surfaces of both ends in the axial direction of the second layer 31 are supported by ball bearings 21a and 21b.
Retaining rings (movement preventing members) 22a and 22b fixed to the outer peripheral surface of the first layer 30 are located at positions outside the both ends in the axial direction, and the second layer 31 moves outward in the axial direction. Has been blocked. The release layer 32 is dimensioned such that the axial length is shorter than the second layer 31. First
A gear 35 for receiving a driving force is fixed to the outer peripheral surface of one end of the layer 30 in the axial direction by a retaining ring 36 and meshes with a driving gear (not shown) to receive a rotational driving force. In addition,
For example, as the first layer 30, aluminum or an aluminum alloy (aluminum-based material) having a thickness of about 1 to 5 mm and having good thermal conductivity is used, and as the second layer 31, a thickness of 0.1
About 2 mm of iron (iron-based material), stainless steel or stainless alloy (stainless-based material), and a release layer 32
For example, a fluororesin containing a magnetic material having a thickness of about 10 to 40 μm is used. Note that silicone rubber or fluorine rubber may be used for the release layer 32 instead of the fluorine resin. In this case, the thickness of the rubber layer is 0.3 mm
About 3 mm is appropriate.

[0007] The induction-type heating roller having the above configuration is
By using an iron-based material or a stainless-based material such as a stainless alloy as a heat-generating portion for induction heating in the second layer (outer layer) 31, the portion in contact with the transfer paper is directly heated to shorten the rise time. Energy saving. In addition, by using a material having good heat conductivity such as an aluminum alloy in consideration of heat conduction as the first layer (inner layer) 30, it is possible to prevent temperature unevenness in the axial direction which is a defect of the iron layer. it can. In addition, when such a laminated structure is employed, axial displacement occurs between the iron layer and the aluminum layer due to a difference in linear expansion coefficient due to repeated heating / cooling at the boundary between the two layers. However, in the present embodiment, since the axial movement of the second layer is regulated by the retaining ring fixed to the inner first layer, such a displacement is eliminated, and the heating portion is removed. It is possible to prevent a decrease in fixing performance caused by the deviation. Further, since the bearing for rotatably supporting the heating roller main body is supported by the second layer made of iron or stainless steel alloy, wear over time is eliminated, and this has conventionally occurred when the heating roller is recycled. It is possible to solve the problem that the durability of the core metal is lowered.

Further, a first material made of a material having a large linear expansion coefficient
Since the length of the layer in the axial direction is increased, the elongation of the material during heating can be easily absorbed, and an inexpensive fixing unit can be provided. That is, in the production of the heating roller, the heating roller is assembled at a cold time, but the surface of the heating roller is 18
The temperature is raised to about 0 to 200 ° C. At this time, in the present invention, since the first layer made of aluminum or the like having a large coefficient of linear expansion in the axial direction is used, the retaining ring 22 fixed to the first layer is used.
When a and 22b are displaced axially outward due to thermal expansion, iron and the like (the linear expansion coefficient is smaller than aluminum) constituting the second layer interfere with the retaining ring even if displaced in the same direction. It is not possible. As a result, problems such as bending of the roller can be eliminated. On the other hand, if the first layer is made of iron or the like, and the second layer is made of aluminum, and the first layer is provided with a retaining ring, the linear expansion of the second layer made of aluminum will occur. Since the rate is higher, the second layer interferes with the retaining ring, causing the roller to bend and deform.

[0009]

As described above, in the first aspect of the present invention, the outer layer having the release layer is prevented because the aluminum material or the like constituting the outer layer of the induction heating roller is prevented from moving in the thrust direction. Does not move in the axial direction over time, and a stable fixing quality can be obtained. According to the second aspect of the present invention, the inner layer of the heating roller is made of aluminum or an alloy thereof, and the outer layer in contact with the transfer paper is made of iron or stainless steel. Thereby, the temperature distribution unevenness of the outer layer can be reduced. According to the third aspect of the present invention, the first layer made of a material having a large coefficient of linear expansion has a long axial length, so that the elongation of the material at the time of heating can be easily absorbed, and an inexpensive fixing unit can be provided. According to the fourth aspect of the present invention, since the bearing portion is in sliding contact with the second layer made of an iron-based or stainless-based material, the friction of the heating roller is reduced and it can be recycled.

[Brief description of the drawings]

1 (a) and 1 (b) are a front view of a main part of a fixing device of the present invention and an enlarged view of a main part of a heating roller.

FIG. 2 is a side longitudinal sectional view of the fixing device of FIG.

[Explanation of symbols]

1 heating roller, 2 pressure roller, 3 bobbin section, 4
Roller body (core), 11 large diameter portion, 12 induction coil, 13a, 13b both ends, 14a, 14b lead wire, 15a, 15b bracket, 20a, 20b side plate, 21a, 21b ball bearing, 22a, 22b retaining ring,
30 first layer (inner layer), 31 second layer (outer layer), 32 release layer, 35 gear, 36 retaining ring,

Claims (3)

[Claims] 1. A fixing device for fixing a toner image on a transfer sheet while nipping and transferring a transfer sheet having a toner image to be fixed between a heating roller and a pressure roller, wherein the heating roller is an induction type heating device. In the roller, the heating roller has a fixed-side bobbin around which an induction coil is wound on an outer peripheral surface, and a core metal coaxially and rotatably arranged in an outer diameter direction of the bobbin. A first layer made of a material having a high linear expansion coefficient, a second layer made of a material having a low linear expansion coefficient fixed to an outer surface of the first layer,
The first layer has a length in the axial direction longer than the length of the second layer, and a movement preventing member that prevents the second layer from moving in the axial direction is provided with a first layer. A fixing device provided on the side. 2. The fixing device according to claim 1, wherein the material of the first layer is an aluminum-based material, and the material of the second layer is an iron-based or stainless steel-based material. 3. The core metal is rotatably supported by slidingly contacting an outer peripheral surface of the second layer made of an iron-based or stainless-based material with a bearing.
The fixing device as described in the above.