JPH04116677A - Fixing device - Google Patents

Abstract

PURPOSE:To form a fixing device having superior durability by bringing a heating roll into contact with the surface of at least one of a pair of rolls having the same structure without incorporating heating sources into the rolls. CONSTITUTION:A pair of rolls 7 having the same structure and performing fixing on transfer paper during conveyance between them are used without incorporating heating sources into the rolls 7 and heating rolls 1 are brought into contact with the surfaces of the rolls 7 so that the rolls 1 follow the rolls 7. Since the surfaces of the rolls 7 are heated to a temp. fit for fixing but heat does not reach the depths of the rolls 7, thermal efficiency can be increased. Since a large temp. difference is not produced between the lower layer 10 and the core metal 5 of each of the rolls 7, exfoliation and damage are prevented and the service life of the rolls can be prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat roller fixing device for an electrophotographic image forming apparatus, and particularly to a fixing device in which a nip portion between a pair of rollers is flat.

As a fixing device for transfer paper in an electrophotographic image forming apparatus such as an electrophotographic copying machine or an electrostatic printer, an unfixed toner image is carried at the nip between a heating roller and a pressure roller that are in pressure contact with each other. A heat roller fixing device that fuses a toner image to a transfer paper by nipping and conveying the transfer paper is widely used. In this type of fixing device, in order to obtain the nip width, an elastic layer is usually provided on the surface of the pressure roller so that the fixing roller bites into it. There are disadvantages in that wrinkles occur when paper consisting of several sheets of paper is passed as a transfer paper, and thick paper is difficult to pass.

In order to solve this problem, Japanese Unexamined Patent Publication No. 1-142779 discloses that, as shown in FIG. It is constructed by providing a heat-resistant elastic layer 105 around a core bar 104 having the same outer diameter, and a release resin layer 106 thereon, and forming a nip portion 1 between both rollers.
A fixing device having a flat surface is disclosed.

However, in this configuration, the heat source 101 of the heating roller 102
exists at the center of the roller 102, the ohm-up time becomes longer, the temperature difference between the core metal part 104 and the heat-resistant elastic layer 105 becomes larger, and the adhesive part that bonds them together becomes hot due to the high temperature. There is a problem of deterioration and MR, and the disadvantage is that the life of the heating roller is significantly shorter than that of a normal fixing device where the surface layer of the heating roller is made of Teflon.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned pressure points of conventionally proposed heat roller fixing devices in which the nip portion is substantially flat, and provides a fixing device with excellent durability. Another object of the present invention is to provide a fixing device with short warm-up time.

5. The present invention provides a heat roller fixing device in which the nip portion of a pair of rollers is generally flat, in which the pair of rollers have the same configuration, do not have an internal heating source, and at least The present invention is characterized in that a heated roller is provided which is driven and comes into contact with the outer peripheral surface of one of the rollers.

It is preferable that each roller has a foam layer having heat insulating properties around a core metal, a thin elastic layer having good thermal conductivity thereon, and a mold-releasing resin layer on the surface.

Furthermore, instead of providing a heating roller that is in circumferential contact with the above-mentioned roller, a deformable heating element layer may be provided between the above-mentioned heat-resistant foamed elastic layer and the good thermally conductive elastic thin layer of both rollers. good.

As mentioned above, since both of the pair of rollers have the same configuration, the nip portion is generally flat, and since the heating roller is provided in circumferential contact with at least one of the rollers, the heating roller is in contact with the roller. The surface reaches a temperature suitable for fusing, but the heat is not connected to the deep part of the roller, improving thermal efficiency.
Since there is no large temperature difference between the lower layer and the core metal, there is no possibility of them peeling off or breaking each other, and the life of the roller is improved.

If a deformable heating element is provided near the surface of both rollers instead of the circumscribed heating roller, when a nip is formed due to pressure contact between the two rollers, the heating element will easily follow this and deform. , no excessive force is applied. In addition, since the heating element is installed near the surface layer, the roller surface temperature easily reaches the fixing temperature, but the heat does not reach the deep part of the roller, improving thermal efficiency and creating a large gap between the lower layer and the core metal. As there is no temperature difference, there is no possibility of peeling off or damage from each other, as in the case of the above-mentioned configuration.

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

FIG. 1 is a diagram showing a first embodiment of the present invention, in which both rollers 7 of a pair of rollers that nip and convey transfer paper and perform fixing are of the same construction.

Inside the roller 7, a heating roller 1 is provided which does not have a heat source and is in contact with the outer peripheral surface of the roller 7 and driven. The roller 7 is provided with a foamed elastic material layer 10 having heat resistance and heat insulation properties such as silicone sponge around the core metal 5, and a layer 10 of a foamed elastic material having heat resistance and heat insulation properties such as silicone sponge, and a layer 10 of a foamed elastic material having heat resistance and heat insulation properties, for example, a layer of a good heat conductive elastic material such as alumina or silica in rubber. A thin layer 9 of a material filled with a highly thermally conductive filler is provided, and a releasable resin layer 8 such as a PFA tube is provided on the surface layer.

The heating roller 1 that comes into pressure contact with each roller rough is configured as a metal roller 5 with a heater 6 provided at the center. When the heater 6 is energized to generate heat, the temperature of the metal roller 5 rises, and the heat is transferred to the thermally conductive elastic layer 9 on the surface of both rollers 7 with which it comes into pressure contact, and the temperature of the roller 7 rises. However, since the foam layer 10 on the inside has heat insulating properties, heat is not transmitted to the inner part, and heat is not transmitted to the core bar 5, improving thermal efficiency and shortening the fixing start-up time. The temperature difference between the core bar 5 and the foam layer 10 in contact with it is small, and there is no fear that the adhesive between the two will peel off or be damaged. or,
Since the structures of the pair of roller lugs are the same, when they are pressed against each other, the nip is generally flat. In addition, since the roller is constructed by laminating a foam layer 10, a good heat conductive elastic layer 9, and a release resin layer 8 on a core metal 5, it can be elastically deformed even with a small pressure force, and can form a large nip. Obtainable.

Note that the heating roller 1 may be provided only on the roller rough that contacts the side of the transfer paper having the toner image.Next, a second embodiment of the present invention will be described with reference to FIG.

Also in this embodiment, the pair of rollers that press against each other have the same structure. Each roller 20 has a metal shaft 27
A heat-resistant foamed elastic layer 28 such as silicone sponge rubber,
Two deformable heating element layers, a thin elastic layer 30 with good thermal conductivity made of an elastic and good heat conductive metal such as copper, brass, stainless steel, or aluminum, and an offset prevention layer 31 made of fluororesin or silicone rubber. are laminated in this order. The above deformable heating element layer 29 is
As shown in a developed view in FIG. 3, heating wires 29b are evenly embedded in a flexible insulating material 29a having good thermal conductivity.

Both rollers 20 have the same configuration and are constructed by laminating elastic layers, so when pressed against each other, a substantially flat wide nip can be formed with not too much pressure. By rotating the transfer material at the same circumferential speed using a drive means that does not have any wrinkles, it is possible to nip and convey a transfer material made of multiple sheets of paper, such as an envelope, without wrinkles, and fix the unfixed toner image carried thereon. . In addition,
The heating element layer 29 is energized by the roller 2 as shown in FIG.
This is achieved by providing slip rings 33, 34 at both ends of the machine, connecting both ends of the heating wire 29b to these, and pressing an elastically deformable brush 35, 36 fixed to the machine frame onto the slip rings 33, 34. can.

Next, a method for manufacturing the roller 20 of this embodiment is shown in FIG.
), (b), (c), (d), (e).

The process will be explained step by step using (f).

First, as shown in Fig. (a), a heating element is formed by placing the surface heating element 29 on the inner surface of a cylinder made of thin metal or the like that will become the thermally conductive layer 30, overlapping as shown in Fig. (b), and then forming a heating element (C). As shown in FIG. 3, an anti-offset layer 31 is formed by coating with a fluorocarbon resin or a silicone resin. As shown in figure (d), the cylindrical body 81 thus formed is fitted into a cylindrical bottomed container 80 for roll molding, the shaft 27 is inserted through its center, and the raw material for the heat-resistant foamed elastic body 28 is poured into it. Heat and shape. (d) Instead of pouring as shown in the figure, as shown in (e) figure, a shaft 2 on which the raw material for the heat-resistant elastic foam roll layer is pre-attached to a cylinder 81 fitted into a roll forming container 80.
A cylindrical body 81 that may be heated and molded after passing through the cylindrical body 81.
The molding order may also be reversed to the above, forming the offset prevention layer 31 first, and then forming the heat generating layer 29. Note that the layers forming the roller 20 described above are bonded together by appropriate means. When the molded product is removed from the molding container 80, a molded and laminated roller 20 is obtained as shown in FIG. Finally, as shown in FIG. 4, slip rings 33 and 34 are attached to both ends and the heating wire 29b is connected.

As mentioned above, this roller has a large flat nip area without applying a large pressing force, and the heat generating layer is placed close to the surface of the roller, resulting in high thermal efficiency and extremely short warm-up time. It's over. In addition, the temperature difference between the surface layer and the heat source does not become large as in the conventional case, and the temperature of each layer can be lowered. Furthermore, the temperature difference between adjacent eyebrows is also reduced, resulting in a longer service life.

Circle-1 As described above, according to the present invention, it is possible to form a flat, large-area nip between both rollers without applying a large pressing force, so that transfers made of multiple sheets of paper such as envelopes can be It is possible to reliably pass and fix paper without wrinkles even when using paper, and it is also effective in improving the life of the roller.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a pair of rollers in a fixing device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view showing the configuration of a pair of rollers in a fixing device according to a second embodiment, and FIG. FIG. 4 is a developed plan view showing the configuration of the heat generating layer; FIG. 4 is a side view including a partial cross section showing an example of a means for supplying electricity to the heat generating layer; FIGS.
(f) is an explanatory diagram explaining the method of manufacturing the roller of the second embodiment step by step, and FIG. 6 is a sectional view showing an example of a conventionally known fixing device having a pair of rollers with a flat nip portion. be. DESCRIPTION OF SYMBOLS 1...Heating roller, 5...Core metal, 6...Heater, 7...Roller, 8...Releasable resin layer, 9...Good heat conductive elastic thin layer, 10. ...Heat-resistant foamed elastic material layer, 20...Roller, 27...Metal shaft, 28...Heat-resistant foamed elastic material layer, 2...Heating element layer, 30...Good heat conduction Elastic layer 31...Releasable resin layer Fig. 1 Fig. 25

Claims (3)

[Claims] (1) In a thermal roller fixing device in which the nip portion of a pair of rollers that are in pressure contact with each other is generally flat, and the transfer sheet is conveyed between the nip portions and fixed, the above-mentioned pair of rollers have the same configuration. A fixing device, characterized in that it does not have a heating source inside, but is provided with a heated roller that is driven and in contact with the outer peripheral surface of at least one of the rollers. (2) A claim characterized in that both of the rollers have a heat-resistant foam layer around a core metal, a thin elastic layer with good thermal conductivity thereon, and a releasable resin layer on the surface. 1. The fixing device according to 1. (3) Instead of the heating roller of the fixing device according to claim 2, a deformable heat generating layer is provided between the heat-resistant foamed elastic layer and the good heat conductive elastic thin layer of both rollers. A fixing device characterized by: