JPS61184575A - Fixing device - Google Patents

Abstract

PURPOSE:To improve release characteristic and durability by using rollers each having >=2 layers of elastic layers on a mandrel and a surface layer consisting of a fluororesin thereon in which the elastic material layers nearer the mandrel have the smaller rubber hardness. CONSTITUTION:The heating roller 1 consists of the constitution in which the low-hardness elastic layer 1b is provided on the mandrel 1a holding internally a halogen heater and the high-hardness layer 1c is provided thereon and further the surface layer 1d consisting of the fluororesin such as polytetrafluoroethylene is provided thereon. The heating roller 2 consists also of the constitution in which the low-hardness elastic layer 2b is provided on the mandrel 2a and the high-hardness elastic layer 2c thereon and further the surface layer 2d consisting of the fluororesin such as polytetrafluoroethylene is provided thereon. The durability of he rollers is improved and the generation of cracking and offsetting is eliminated by using the rollers each having the surface layer consisting of the fluororesin and the elastic material layers having he smaller rubber hardness nearer the mandrel under said layer. The stable and satisfactory fixing is thus made possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fixing device used in an electrophotographic copying machine, etc., and in particular, a fixing device that clamps a recording material between a pair of rollers, at least one of which is a heating roller. Regarding the fixing device.

[Prior art]

Conventionally, the roller of the above-mentioned fixing device has been provided with an elastic layer on a core metal and a surface layer made of tetrafluoroethylene resin on the elastic layer (Reference No. 57-89785); an elastic layer and a surface layer made of fluororubber containing tetrafluoroethylene resin (Japanese Patent Laid-Open No. 58-577)
No. 0, No. 58-27175, and No. 58-90673] are used.

Of these, the former roller has excellent mold release properties, but because there is a large difference in the elastic modulus between the surface layer and the elastic layer, when recording material such as cardboard is passed continuously, both the left and right ends of the recording material pass through. There is a problem in that cracks are likely to occur in the surface layer due to shearing force. In addition, in the latter roller, the surface layer also exhibits relatively large elasticity and there is little difference in the elastic modulus between the surface layer and the elastic layer, so cracks do not occur in the surface layer, but tetrafluorocarbon formation in the surface layer The problem is that the ethylene resin layer is very thin, resulting in poor durability and easy offset.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a heat roller type fixing device that has excellent mold releasability and durability.

[Structure of the invention]

The present invention provides a fixing device that presses and feeds a recording material between a pair of rollers, at least one of which is a heating roller. The above object is achieved by a fixing device having a roller having an elastic layer having a rubber hardness smaller as the layer is closer to the core metal.

〔Example〕

The present invention will be explained below using illustrated examples.

The figure is a sectional view of essential parts showing an example of the fixing device of the present invention.
is a heating roller that comes into contact with the toner image adhesion side of the recording material P;
2 is a pressure roller that comes into contact with the back side of the recording material P.

The heating roller 1 has a low-hardness elastic layer 1b on a core metal 1a that holds a nitrogen heater 3 inside, a high-hardness elastic layer IC on top of that, and a fluororesin such as polytetrafluoroethylene on top of that. The pressure roller 2 also has a low hardness elastic layer 2b on a core metal 2a, a high hardness elastic layer 2c on top of that, and a surface layer 1d made of polytetrafluoroethylene on top of that. The structure includes a surface layer 2d made of a fluororesin. Note that silicone rubber is preferably used for the elastic layers of the heating roller 1 and the pressure roller 2, and the high hardness elastic layer has a rubber hardness in the range of 70° to 90°, and the low hardness elastic layer has a rubber hardness in the range of 70° to 90°. Those having a hardness in the range of 25° to 40° are preferably used.

In the fixing device of the present invention as described above, the heating roller 1
and the surface layer 1d and 2dO layer thickness of the pressure roller 2 are both 20μ.
The layer thickness of the high-hardness elastic layer IC made of silicone rubber of the heating roller 1 is 100μ, the layer thickness of the low-hardness elastic layer N1b is 200μ, and the high-hardness elastic layer IC of the pressure roller 2' is made of the same silicone rubber as the heating roller 1. The layer thickness of layer 2C is 1 t.
m, when the toner image on the recording material P was fixed by this fixing device with the layer thickness of the low hardness elastic layer 2b being 4 mm,
Even when the recording material P is thin paper or thick paper, the heating roller 1 and the pressure roller 2 have excellent durability, and no cracking or offset occurs, and stable and good fixing is achieved. Further, even when the pressure roller was replaced with a conventional pressure roller, the above-mentioned heating roller 1 showed the same durability.

On the other hand, the surface layer on the heating roller is the above-mentioned surface layer 1d.
In a fixing device using a roller whose elastic layer consists only of a low-hardness elastic layer, when a recording material was passed under the same conditions, cracks occurred in the heating roller when the recording material was cardboard. Further, in a fixing device using a heating roller whose surface layer is a fluororubber layer containing a tetrafluoroethylene resin, the surface of the heating roller becomes dirty and becomes unusable after a short period of time.

〔Effect of the invention〕

The fixing device of the present invention uses a roller having a surface layer of fluororesin and an elastic layer below the surface layer, the rubber hardness of which is lower as the layer is closer to the core metal, so that the roller has excellent durability and does not crack easily. An excellent effect will be achieved if stable and good fixing can be achieved without the occurrence of offset or offset.

Note that the present invention is not limited to the example in which the above-mentioned rollers are used for both of the pair of rollers, but the above-described roller may be used for only one roller. In that case, it goes without saying that it is preferable to use the above-mentioned roller as the roller that comes into contact with the toner image-attached surface of the recording material.

Moreover, the above-mentioned roller may be one in which the rubber hardness of the elastic layer changes continuously. Furthermore, in the embodiment, the low hardness elastic layer it), 2b and the high hardness elastic layer 1a,
Although silicone rubber was used in both cases 2c, the low hardness elastic layer may be formed of silicone rubber, and the high hardness elastic layer may be formed of fluororubber.

[Brief explanation of the drawing]

The figure is a sectional view of essential parts showing an example of the fixing device of the present invention. 1...Heating roller, 2...Pressure roller, l
a, 2a... Core bar, 1b, 2b... Low-altitude elastic layer, 10.20... High-hardness elastic layer, ld, 2d... Surface! , 3...Halogen heat, P...Recording material.

Claims (1)

[Claims] A fixing device that presses and feeds a recording material between a pair of rollers, at least one of which is a heating roller, which has two or more elastic layers on a core metal and a surface layer made of a fluororesin thereon,
A fixing device characterized by using a roller in which the elastic layer is closer to the core metal, the harder the rubber is.