JPH0736303A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device for fixing an image by use of heating means which never cause a roller period unevenness in a fixed image or an excessive temperature rise in non-paper passing area by the continuous feed of a small-sized paper when at least a pressure roller is used, which result from the high heat capacity and low heat conductivity of the roller consisting of a material such as rubber. CONSTITUTION:A fixing roller 4 has a release layer consisting of a PFA tube 2 formed on an aluminum core metal 1 internally having a halogen lamp 3, and a pressure roller 6 arranged to be pressed onto the fixing roller 4 has an elastic layer consisting of silicone rubber 5, a high heat conductive layer 10 having a metal thin film evaporated thereon, and a surface release layer formed by another PFA tube 2 formed on another aluminum core metal 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an image formed on a recording material using a thermoplastic developer by utilizing thermal energy.

[0002]

2. Description of the Related Art Conventionally, in a copying machine or a printer using an electrophotographic recording technique, a toner made of a thermoplastic resin is used as a developer, and a heating means is used to fix an image formed by this toner. The fixing device having the above is used.

The fixing device widely used at present is shown in FIG.
As shown in FIG. 1, a fixing roller 4 in which a halogen lamp 3 as a heat source is inserted into a roller having a release layer composed of a PFA tube 2 on a core metal 1 made of aluminum, and a core metal 1 on the fixing roller 4. It is composed of a pressure roller 6 provided with an elastic layer made of silicone rubber 5 and a release layer made of PFA tube 2, and heat and pressure are applied to the unfixed toner 9 on the recording material 8 at the nip portion 7 to complete fixing. To do.

Further, in a fixing device for fixing a color image, a plurality of toners are laminated and formed on a recording material, and the fixing roller surface also needs elasticity in order to sufficiently mix the toners of respective colors. Therefore, as shown in FIG. 5, at least one layer of silicone rubber 5 having a thickness of 1 mm or more is provided as a releasing layer of the fixing roller 4.

Further, in the on-demand type fixing device using the heat-resistant thin layer film 15 instead of the fixing roller as shown in FIG. 6, the pressure roller 6 is a silicone rubber type roller having a releasing layer on its surface. Is used. The on-demand heating means 11 is composed of a heater substrate 12, a heating resistance portion 13, a surface protective layer 19, a thermistor 14, and a film guide member 18, and the heat resistant thin film 15 is applied to the heating portion by a driving roller 16 and a driven roller 17. It is conveyed and fixed at a nip portion with the pressure roller 6.

According to each of the conventional examples described above, a good fixing operation can be performed.

[0007]

However, according to the above-mentioned conventional example, it is necessary to provide an elastic layer at least on the surface of the pressure roller to widen the width of the nip portion to secure the fixing property. As a result, the heat capacity of the roller as a whole is increased, causing the following problems. First, when the heat capacity becomes large, it takes a long time for the entire pressure roller to be sufficiently warmed up, and the startup time and the temperature recovery time from the standby state to the printing state are extended, resulting in deterioration of responsiveness. On the contrary, if it is used without taking a sufficient time or if high-speed printing is continuously performed, the temperature distribution in the circumferential direction of the roller becomes uneven, and the fixability of the image on one page changes.
As a result, there is a risk of causing unevenness in density and gloss. Also, if you print continuously with a small size paper and then switch to a large size paper for printing, the temperature difference between the paper passing part and the non-paper passing part of the first paper is large, so There have been problems that uneven fixing occurs in the image and that the temperature of the non-sheet passing portion increases and the roller and its peripheral members are thermally deteriorated.

The present invention solves the above problems and, in a fixing device for fixing an image using a heating means, at least when a pressure roller is used, the roller made of a material such as rubber has a high heat capacity and a low heat capacity. It is an object of the present invention to provide a fixing device that does not cause roller cycle unevenness in a fixed image due to thermal conductivity and does not cause an excessive temperature rise in a non-paper passing area due to continuous passing of small size paper.

[0009]

According to the present invention, the above object is to provide a heating means that generates heat when energized, a conveying means that is arranged in contact with or in close proximity to the heating means, and is endlessly movable, and the conveying means. A pressure roller having a releasable surface layer, which is arranged so as to be in pressure contact with the heating means directly or through the transportation means, and the pressure roller and the pressure contact portion of the transportation means or Fixing for fixing the unfixed developer on the recording material by sandwiching and conveying the recording material carrying the unfixed developer at the pressure contact portion of the pressure roller and the heating means formed via the conveying means. In the apparatus, it is achieved by providing a high thermal conductive layer below the releasable surface layer of the pressure roller.

[0010]

According to the present invention, since the high thermal conductive layer is provided under the releasable surface layer of the pressure roller, the temperature distribution in the circumferential direction and the axial direction of the pressure roller is made uniform, and high-speed continuous fixing is performed. In this case, it is possible to prevent the fixing pitch unevenness of the pressure roller cycle at the time and the temperature rise of the recording material non-passing area after the continuous fixing of the small-sized recording material.

[0011]

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

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIG. First Embodiment FIG. 1 is a sectional view showing a schematic configuration of a fixing device according to a first embodiment of the present invention. Note that FIG.
The same parts as those of the conventional example shown in FIG.

In this embodiment, the pressure roller 6 used is one in which the high thermal conductive layer 10 is provided under the surface releasing layer formed of the PFA tube 2 having a thickness of about 50 μm. In this embodiment, the high thermal conductive layer 10 is formed of a metal thin film of aluminum by vapor deposition and has a thickness of about 1 μm. By using such a thin film, there is little influence on the hardness of the roller, and a sufficient nip width can be obtained. By using this configuration, the temperature distributions in the circumferential direction and the axial direction of the pressure roller 6 are made uniform, and the fixing pitch unevenness of the pressure roller cycle during high-speed continuous printing and the non-sheet passing after the continuous feeding of small size paper are performed. Part temperature rise can be prevented. Further, according to the present configuration, sufficient fixing property can be obtained only by heating the roller surface, so that it is not necessary to heat the entire pressure roller 6 having a large heat capacity, and as a result, the temperature rising speed of the pressure roller 6 is accelerated. Therefore, it is possible to contribute to shortening the startup time of the fixing device. Further, in this configuration, as described above, the temperature rise in the non-sheet-passing portion and the startup time of the fixing device do not depend so much on the heat capacity of the roller itself, so a material with high heat insulation such as sponge can be selected as the elastic layer. It is possible to realize an energy-saving type configuration with less heat leak from the roller bearing portion and the like.

In this embodiment, after the metal thin film layer 10 is formed on the surface of the silicone rubber 5 by vapor deposition, PFA is used.
Although the tube 2 is laminated with the primer by heat shrinkage, a tube of metal foil having a film thickness of several hundreds of μm may be used instead of the vapor deposition film, and each layer may be adhered by a primer.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. Note that the same parts as those of the first embodiment and the conventional example shown in FIG.

FIG. 2 is a sectional view showing the schematic arrangement of a fixing device according to the second embodiment of the present invention. In this embodiment, a high-heat conductive layer 10 is provided between the silicone rubber layer 5 of the fixing roller 4 in addition to the pressure roller 6 in the color fixing device, and the upper and lower silicone rubber layers 5 are made of a material. The lower side is HTV silicone rubber and the upper side is RTV silicone rubber.

By using this structure, the temperature distribution of the pressure roller 6 as well as the temperature distribution of the fixing roller 4 in the circumferential direction and the axial direction can be made uniform by the fixing device for color, and the unevenness of the fixing property is more uneven than that of the monochrome image. This improves the fixability of color images, which makes it more noticeable, and contributes to speeding up, measures to raise the temperature of non-sheet passing areas, and shortening of the fixing device startup time.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment and the conventional example shown in FIG.

In this embodiment, the high thermal conductive layer 10 is provided on the pressure roller 6 of the on-demand type fixing device. In the on-demand type fixing device, since there is a heater at the nip facing portion, uneven fixing is unlikely to occur in the sheet passing direction, but the non-sheet passing portion temperature rises significantly after continuously passing small size sheets. The main factor of this phenomenon is that the pressure roller 6 has a large thermal conductivity defect, and by using this configuration, the temperature difference between the paper passing portion and the non-paper passing portion can be quickly reduced.

[0020]

As described above, according to the present invention,
Fixing in which an image is formed on a recording material using a thermoplastic developer, and the recording material is nipped and conveyed by a fixing roller or a fixing film having a heating means and the fixing roller or a pressure roller pressed against the fixing film. In the apparatus, by providing a high thermal conductive layer at least under the release surface layer of the pressure roller, the roller cycle unevenness that occurs on the fixed image and the excessive non-paper passing area due to continuous feeding of small size paper It is possible to prevent a rise in temperature. Further, since the heat of the fixing roller can be uniformly and efficiently transferred from the periphery of the pressure roller, it is possible to shorten the startup time of the fixing device. Furthermore, since the temperature distribution is made uniform, sufficient fixing performance can be obtained by warming only the surface layer of the pressure roller, which saves the time and energy required to warm the entire roller as in the conventional case, and the temperature of the previous multi-rotation etc. The homogenization process can also be simplified.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a first exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a second exemplary embodiment of the present invention.

FIG. 3 is a sectional view illustrating a schematic configuration of a fixing device according to a third exemplary embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a schematic configuration of a conventional fixing device.

FIG. 5 is a cross-sectional view showing a schematic configuration of a conventional color fixing device.

FIG. 6 is a sectional view showing a schematic configuration of a conventional on-demand fixing device.

[Explanation of symbols]

 3 Halogen lamp (heating means) 4 Fixing roller (conveying means) 5 Silicone rubber (releasing surface layer) 6 Pressure roller 8 Recording material 9 Unfixed toner (unfixed developer) 10 High thermal conductive layer 11 On-demand heating Means (Heating Means) 15 Heat Resistant Film (Conveying Means)

Claims (4)

[Claims] 1. A heating means which generates heat when energized, a conveying means which is disposed in contact with or in the vicinity of the heating means and is endlessly movable, and the heating means which is directly connected to the conveying means or through the conveying means. A pressure roller having a releasable surface layer arranged so as to be in pressure contact with the means, and the pressure roller and the pressure roller formed through the pressure contact portion of the conveying means or the conveying means. A fixing device for fixing the unfixed developer on the recording material by sandwiching and transporting the recording material carrying the unfixed developer at the pressure contact portion of the heating means,
A fixing device comprising a high thermal conductive layer provided under the releasable surface layer of the pressure roller. 2. The fixing device according to claim 1, wherein a metal thin film is used as the high thermal conductivity layer. 3. The fixing roller having three layers of a heat resistant elastic layer, a high thermal conductive layer and a heat resistant elastic layer formed on a cored bar is used as the transporting means. The fixing device described. 4. The fixing device according to claim 1, wherein a heat-resistant film is used as the conveying means.