JPH05107985A - Pressure fixing device - Google Patents

Abstract

PURPOSE:To enable the uniform fixing of toner by imparting uniform pressure to the contact part of a roller with simple constitution. CONSTITUTION:The outer periphery of at least one roller of a pressure fixing device which fixes a toner image by passing an image support 4 having the unfixed toner image between a pair of the rollers 1 and 2 in contact with each other in pressurization is coated with a soft elastic body 3 having 20 to 100kg/mm<2> modulus in compression. The value a/t obtd. by dividing the modulus in compression (a) kg/mm<2> of the soft elastic body 3 by the thickness (t)mm of the soft elastic body 3 is specified to 2 and 200. The thickness of the soft elastic body 3 is preferably 0.5 to 10mm. The nonuniformity of the micro- pressure distribution by the ruggedness of the image support 4 passing between a pair of the roller 1 and 2 is eliminated by such constitution. The uniform pressure is thus imparted to the image support 4 and the toner image is fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure fixing device for fixing a toner image on a supporting surface of an image support. Further, the present invention relates to a roller coated with a soft elastic body, which is used as such a pressure fixing device and other various pressure rollers that need to apply a uniform pressure over the entire length.

[0002]

2. Description of the Related Art Conventionally, a pair of rollers contacting each other under pressure are provided, an image support having an unfixed toner image is passed between the pair of rollers, and the toner image is fixed on the support surface of the image support. There is a pressure fixing device. Paper or an OHP sheet is usually used as the image support, and paper is taken as an example in the following description, but the image support is not limited to paper and may be other than paper. In a copying machine using this type of pressure fixing device, as a toner, a viscous wax-type toner containing wax as a main component, a capsule composed of a core material composed of a binder and a colorant and an outer shell covering the core material. Type of toner is used. In the case of wax type toner, it is necessary to apply high pressure to the pair of rollers in order to squeeze and fix the toner on the paper. Further, for the capsule type toner as well, it is necessary to apply a high pressure to the pair of rollers because it is necessary to break the outer shell in order to let the core material flow out.

Since a high pressure is required, the pressure fixing device uses a metal roller plated with hard chrome to keep its surface rigid. In this case, if the pressure distribution of the metal roller is not uniform, there are portions where the fixing is not sufficient. In order to make the pressure distribution of the pressure contact part of the metal roller uniform, measures such as intersecting the axis of the metal roller, or making the diameter of the metal roller small at the central part and large at both ends to taper It is possible to make the pressure of the pressure contact portion uniform. However, when the paper is passed through the pressure contact portion between the metal rollers, a minute unevenness of the pressure is generated due to the minute unevenness of the paper itself, and a portion where the toner image is hard to be uniformly pressure-fixed on the transfer paper is formed. .. Therefore, in order to eliminate such an insufficiently fixed portion, one of the rollers is made of an elastic roller, or the elastic roller member is covered with a fixing roller so as to make the pressure uniform and The aim is to improve the image quality by eliminating insufficient parts and increasing the fixing strength of the toner image. This type of pressure fixing device is disclosed, for example, in Japanese Patent Publication No. 46-15876 and Japanese Patent Laid-Open No. 62-1.
No. 53988.

[0004]

However, when the elastic modulus of the elastic body is high as in Japanese Patent Publication No. 46-15876, the effect of uniformizing the pressure by coating the elastic body becomes small. Further, as in JP-A-58-62677, when the compression elastic modulus of the elastic body is smaller than that of paper,
Since a high pressure is applied to the pair of rollers, the elastic body is deformed and the required fixing pressure cannot be obtained, and if high pressure is continuously applied during non-operation, the elastic part is deformed, which causes a malfunction of the roller rotation. Therefore, it is necessary to provide a mechanism for releasing the pressure contact during non-fixing. Further, even if the compressive elastic modulus is relatively small, if the coating layer is too thin, the effect of the base metal and the amount of deformation cannot be made large, so that a sufficient pressure equalizing effect does not appear.

Further, when the compressive elastic modulus is relatively large and the coating layer is too thick, the coating layer may be deformed depending on the pressure applied to the pair of rollers as in the case where the hardness is small. There is a problem with the rotation of the. Thus, the thickness of the soft elastic body (the length of the pressing force transmitted from the roller in the pressing direction) is largely related to the pressing force applied to the roller and the compression elastic modulus of the soft elastic body, and the pressing force applied to the roller is It is necessary to select the optimum value depending on the compression elastic modulus of the soft elastic body. An object of the present invention is to provide a pressure fixing device for applying a pressure to an image support having an unfixed toner image between a pair of rollers to fix a toner image, by applying uniform pressure to the contact portion of the rollers with a simple configuration. It is an object of the present invention to provide a pressure fixing device capable of uniformly fixing a toner image.

[0006]

In order to achieve the above object, the present invention comprises a pair of rollers which come into contact with each other under pressure, and pass an image support having an unfixed toner image between the rollers. In a pressure fixing device for fixing a toner image on a supporting surface of an image support, the soft elastic body covering the outer periphery of the at least one roller has a compression elastic modulus of 20 to 100.
[Kg / mm ² ] and the compression elastic modulus a [k of the soft elastic body
The value a / t divided by the thickness t [mm] of the soft elastic body covering g / mm ² ] is 2 or more and 200 or less. The soft elastic body that covers at least one of the rollers has a thickness of 0.5 mm to 10 mm.

[0007]

Function: The unevenness of minute pressure distribution due to the unevenness of the paper itself which is the image support passing between the pair of rollers is eliminated,
The image support can be fixed by applying uniform pressure.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the accompanying drawings. FIG. 1 shows a pressure fixing device used in an embodiment of the present invention. The pressure fixing device includes a device frame body whose ends are swingably supported, and the frame body includes a pressure roller 2 covered with a metal both-end fixing roller 1 and a soft elastic body 3 via a bearing. Is rotatably supported, and the image support 4 passes between the rollers. The rotation axes of the rollers are arranged so as to intersect each other at a predetermined angle, for example, 1.4 degrees. The fixing roller 1 is provided with a mechanism for applying a load in the pressure roller 2 direction. Both end support rollers are
For example, it is formed of substantially cylindrical hardened steel.

The soft elastic body 3 covering the pressure roller 2 has a compression elastic modulus of 20 to 100 [Kg / mm ² ]. The compression elastic modulus of the soft elastic body is a [kg / m
m ² ] and the thickness of the soft elastic body to be coated is t [mm], the material and the thickness satisfy the relationship of 2 ≦ a / t ≦ 200. As a result, the unevenness of minute pressure distribution due to the unevenness of the paper itself which is the image support passing between the pair of rollers is eliminated, and uniform pressure can be applied to the image support to fix it. Preferably, the soft elastic body to be coated has a thickness of 0.5 to 10 mm. This is shown in FIG. 4, where the compression elastic modulus is a = 20 [kg / mm ² ] and a = 1.
It is within a range surrounded by a line of 00 [kg / mm ² ] and curves of E = 200t and E = 2t.

2 and 3 show the experimental results regarding the fixing strength and the fixing uniformity in which the compression elastic modulus and the thickness of the coated soft elastic body are changed in the pressure fixing device having the above structure.
Shown in. Here, the fixing strength was examined by the fixing degree of the character image, and the fixing uniformity was examined by the fixing degree of the solid image. The capsule toner used in this experiment is a capsule toner containing a relatively soft polymer as a core material, for example, a lauryl methacrylate polymer as a core material, a polyurethane resin as an outer shell, and carbon black as a colorant,
In addition, a charging treatment material is added to the surface to improve charging.

In order to destroy the toner capsule, it is necessary to apply a pressure of approximately 100 kg / cm ² or more when the transfer paper carrying the unfixed toner image is passed between a pair of pressured rollers. In the case of a soft elastic covered roller, FIG.
As shown in, when a soft elastic body having a compression elastic modulus of 100 Kg / cm ² or more is used, minute deformation of the roller surface is small and there is no effect of improving uniformity. Looking at the remaining toner after the tape is attached to the fixed image of the solid image and peeled off, it is the way the toner escapes with a uniform pressure, and the spotted toner escapes with a fixed image to which pressure is applied unevenly. Becomes This state is shown in FIG. On the other hand, the compression modulus is 20 kg
If a soft elastic body having a pressure of not more than / cm ² is used, if high pressure is continuously applied during non-operation, the elastic body is deformed, causing a problem in rotation of the roller. Looking at the residual toner after the tape is adhered and peeled off to the fixed image to which uniform pressure is applied in this way, the residual toner is the same as that of the fixed image fixed by the thermal fixing device.

In the pressure fixing device of the present invention, the roller not covered with the soft elastic body may be any roller that applies a predetermined pressing force to the contact portion between the rollers, and is not particularly limited. For example, it may be formed of steel and subjected to induction hardening followed by hard chrome plating. Furthermore, as a soft elastic body that covers the outer periphery,
The material is not particularly limited as long as it has a compressive elastic modulus of 20 to 100 kg / mm ² , but is made of, for example, fluorine resin, hard urethane, polypropylene, nylon, silicon rubber or the like.

[0013]

As described above, according to the present invention, the compression elastic modulus of the soft elastic body covering the outer periphery of at least one roller is 20 to 100 Kg / mm ^2, and the compression elastic modulus a [ kg / mm ² ], the thickness t of the soft elastic body
Since the value a / t divided by [mm] is set to 2 or more and 200 or less, a minute pressure distribution due to unevenness of the paper itself when the paper, which is the image support having the unfixed toner image, passes through the pressure contact portion. By eliminating the nonuniformity, it is possible to apply a uniform pressure to uniformly fix the toner image.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a central axis of both rollers showing a main part of a pressure fixing device according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing the fixing strength of a character image when the compression elastic modulus and the thickness of the coated soft elastic body are changed.

FIG. 3 is a diagram showing the fixing uniformity of a solid image when the compression elastic modulus and the thickness of the coated soft elastic body are changed.

FIG. 4 is a diagram showing a relationship between a compression elastic modulus of a coating material and a coating thickness.

FIG. 5 is a diagram showing how an image of a solid image remains after tape peeling.

[Explanation of symbols]

1 fixing roller, 2 pressure roller, 3 soft elastic body, 4
Image support

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Mizomi 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zero Tux Co., Ltd.

Claims (1)

[Claims] 1. A pressure fixing device comprising a pair of rollers which are in contact with each other under pressure, and pass an image support having an unfixed toner image between the rollers to fix the toner image on a support surface of the image support. The compression elastic modulus of the soft elastic body covering the outer periphery of the at least one roller is 20 to 100.
[Kg / mm ² ] and the compression elastic modulus a [k of the soft elastic body
The pressure fixing device is characterized in that the value a / t divided by the thickness t [mm] of the soft elastic body covering g / mm ² ] is 2 or more and 200 or less.