JPH0643774A - Heat roller fixing device - Google Patents

Abstract

PURPOSE:To improve the passing stability of recording paper so that good images are obtd. by forming the heat resistant elastic material layer on the surface of a press roller to the surface roughness smaller than the surface roughness of a heating roller. CONSTITUTION:The surface roughness of the heat resistant elastic material layer 13 forming the surface of the heating roller 1 is set in a 1<=Rz<=5 range and the surface roughness of the heat resistant elastic material layer 23 forming the surface of a press roller is set at Rz<=2 smaller than the surface roughness of the heat resistant elastic material layer 13 of the heating roller 1. The heat resistant elastic material layer 23 of the press roller 2 is constituted of a heat resistant elastic material contg. silica of the amt. equal to or larger than the amt. of the heat resistant elastic material constituting the heat resistant elastic material layer 13 of the heating roller 1. As a result, the tendency to the electrostatic charge of both rollers 1, 2 and the recording paper is controlled by the surface roughness and silica content of the two rollers 1, 2, by which the recording paper is sucked or attracted to the press roller 2 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller fixing device used in a fixing portion of an electronic copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, as a heat roller fixing device for an electronic copying machine, a heating roller having a heat resistant elastic body layer formed on a core material and having a built-in heater, and a heat roller having a heat resistant elastic body layer formed on the core material. And a pressure roller that presses the toner image onto the copy sheet by passing the copy sheet holding the charged toner image between the rollers so that the holding surface of the toner image faces the heating roller. Things are known.

In recent years, there has been an increasing demand for a full-color image forming apparatus that reproduces all colors by using four types of toner in which black is added to the three primary colors, and in forming a single image in this apparatus, A full-color image is formed by superposing the four color toner images and fixing the toner images once. Therefore, in order to satisfy the characteristics such as the gloss of the full-color image, the image quality, and the color reproducibility of the transmitted image, it is necessary to use a toner having a high light-transmitting property and having a low viscosity in order to increase the toner adhesion amount. In order to ensure the transparency of the fixed toner image,
It is necessary to make the surface of the fixed toner image a uniform surface. In order to satisfy such characteristics, as a fixing roller, a release agent is applied to the surface of the low-viscosity toner so that offset does not occur, and the surface of the fixed toner image is made uniform. A fixing roller with high surface smoothness is used.

On the other hand, in an ordinary image forming apparatus, a separating claw is provided on the heating roller side in order to improve the stability of sheet passing, or the thickness of the heating roller on the image side is increased to change the sheet passing direction in the roller nip. The paper-passing property is improved by setting the non-image side. Also, in order to prevent the recording paper from wrapping around the heating roller of the type covered with the heat-resistant release layer, the surface roughness of the pressure roller is made smaller than that of the heating roller, and the pressure roller and the recording paper are There is known a technique in which the suction force acting between the heat roller and the recording paper is made larger than the suction force acting between the heating roller and the recording paper (Japanese Patent Publication No. 3-14351).

[0005]

However, when the separating claw is provided as described above, the image surface comes into contact with the separating claw to deteriorate the image, or the separating claw comes into contact with the roller surface to damage the roller surface. However, there is a problem that the image is deteriorated. On the other hand, when the roller thickness on the image surface side is increased in order to make the sheet passing direction in the roller nip toward the non-image surface side, there arises a problem that the thermal response deteriorates.

When the surface roughness of the pressure roller is made smaller than the surface roughness of the heating roller to prevent the recording paper from wrapping around the heating roller, when the surface roughness of both rollers becomes close to each other, the toner adheres. Force is more likely to act,
There is a problem in that good paper passing properties cannot be obtained. In particular, in the case of a full-color image, the toner adhesion amount increases as described above, so that it is difficult to secure good paper feeding reliability.

The present invention has been devised in view of the above problems, and secures the paper feeding stability and obtains a good image without deteriorating the thermal response of the roller and the image deterioration due to the separating claw. This is a technical issue to be solved.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, the charging property generated between the heat resistant elastic layer constituting the roller surface and the recording paper depends on the surface roughness of the heat resistant elastic layer, and the heat resistant elasticity thereof. This was made by discovering that the silica contained in the body layer and the recording paper are charged, and it is possible to ensure the paper feeding stability by controlling the charging tendency of the roller and the recording paper. . It is considered that calcium carbonate contained in the recording paper influences the cause of the charging.

That is, the thermal roll fixing device of the present invention is
The toner image includes a heating roller formed by laminating a heat resistant elastic layer on a core material, and a pressure roller arranged by being pressed against the heating roller and formed by laminating a heat resistant elastic layer on the core material. A heat roller fixing device for fixing the toner image on the recording paper by passing the recording paper carrying the recording paper between the rollers so that the toner image faces the heating roller. The surface roughness of the layer is in the range of 1 ≦ Rz ≦ 5, the heat resistant elastic layer of the pressure roller has a surface roughness of Rz ≦ 2 and is smaller than the surface roughness of the heat resistant elastic layer of the heating roller, Further, the heat-resistant elastic layer of the pressure roller is composed of a heat-resistant elastic material containing silica in an amount equal to or larger than that of the heat-resistant elastic material forming the heat-resistant elastic layer of the heating roller. To do.

[0010]

In the heat roller fixing device of the present invention, since the surface roughness of the heat resistant elastic body layer constituting the surface of the pressure roller is smaller than the surface roughness of the heat resistant elastic body layer constituting the surface of the heating roller, the space between both rollers is reduced. When the recording paper passes through, the pressure roller side is charged with a higher potential than the heating roller side, and the recording paper is largely attracted or attracted to the pressure roller side. Since the heat-resistant elastic material forming the heat-resistant elastic layer of the pressure roller contains silica in an amount equal to or larger than that of the heat-resistant elastic material forming the heat-resistant elastic layer of the heating roller, the recording paper When the silica and silica are charged, the recording paper is more easily attracted or adsorbed by the pressure roller side. In this way
By controlling the electrification tendency between both rollers and the recording paper by controlling the surface roughness and silica content of both rollers, the separation property of the recording paper from the heating roller is improved and good paper passing stability is secured. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) As shown in FIG. 1, the heat roller fixing device according to the present embodiment includes an aluminum core metal 1 having a heater 11 built therein.
A heating roller 1 formed by laminating a heat resistant elastic body layer 13 on the heat roller 2.
A pressure roller 2 formed by laminating a heat resistant elastic body layer 23 on an aluminum cored bar 22 containing a heater 21, cleaning rollers 3 and 4, an oil application unit 5, and provided on the pressure roller 2 side. The separating claw 6 and the oil recovery blade 7 are mainly configured.

The heat resistant elastic layer 13 of the heating roller 1 is made of silicone rubber laminated on the core metal 12 having an outer diameter of 60 mm to a thickness of 2 mm. The basic composition of this silicone rubber is that the viscosity at room temperature is 5000 centistokes, and the particle size of the organosiloxane with both ends vinyl group blocked is 50.
Inorganic silica having a specific surface area of 100 m ² / g or more at a particle size of 1 μm or less and inorganic silica having a specific surface area of 10 m ² / g or more at a particle size of 1 to 50 μm or less are mixed in a ratio of 1: 1 and further used as a crosslinking agent. It is a mixture of a hydrogen polysiloxane and a platinum catalyst, and the content of silica is 20% by weight. The heat-resistant elastic body layer 13 is formed by applying a silicone rubber composition onto the cored bar 12 and then heat-curing the same, and is subjected to polishing treatment so that the surface roughness Rz becomes 2 μm.

The heat resistant elastic layer 23 of the pressure roller 2 is made of silicone rubber laminated on the core metal 22 having an outer diameter of 60 mm to a thickness of 2 mm. This heat resistant elastic layer 23
Is similarly formed of silicone rubber having the same silica content of 20% by weight as the heat resistant elastic layer 13 of the heating roller 1, but its surface roughness Rz is 1 μm. When the heat roller fixing device configured as described above is mounted on a copying machine CF-70 manufactured by Minolta Camera Co., and 200 sheets of copy paper A (neutral paper containing calcium carbonate) are passed, a jam occurs. It showed stable paper passing property.

In the heat roller fixing device of this embodiment, the surface roughness of the heat resistant elastic layer 23 of the pressure roller 2 is smaller than the surface roughness of the heat resistant elastic layer 13 of the heating roller 1, and the heat resistance of the pressure roller 2 is reduced. Since the elastic layer 23 contains a larger amount of silica than the heat resistant elastic layer 13 of the heating roller 1, when the copy paper A passes between the rollers 1 and 2, the heating roller 1 is placed on the pressure roller 2 side. Since the copying paper A is charged with a potential higher than that on the side, the copying paper A is surely attracted or adsorbed to the pressure roller 2 side.
After that, copy paper A sent out between the rollers 1 and 2
Is reliably separated from the pressure roller 2 by the separation claw 6 provided on the pressure roller 2 side.

Therefore, according to the heat roller fixing device of the present embodiment, it is possible to secure good paper feeding stability by controlling the charging tendency of both rollers 1, 2 and the recording paper. Further, since the copy paper A is not attracted to the heating roller 1 on the image surface side, it is not necessary to provide a separating claw on the heating roller 1 side, and image deterioration due to the separating claw can be avoided.

(Embodiment 2) The heat roller fixing device of this embodiment is basically the same as that of the above embodiment 1 as shown in FIG. The difference is that the elastic layer 14 has a two-layer structure. Therefore, since the structure other than the heat resistant elastic body layer 14 is the same as that of the first embodiment, the common members are referred to by the reference numerals and the description thereof is omitted.

The heat resistant elastic body layer 14 of the heating roller 1 includes an inner silicone rubber layer 14a laminated on the cored bar 12 with a thickness of 1 mm, and 1 mm on the inner silicone rubber layer 14a.
The outer silicone rubber layer 14b is laminated to have a thickness of. The inner silicone rubber layer 14a has the same silica content as the heat resistant elastic body layer 14 of the pressure roller 2 of 20.
Whereas it is made of silicone rubber by weight,
The outer silicone rubber layer 14b is formed of the silicone rubber having a silica content of 10% by weight. The surface roughness Rz of the outer silicone rubber layer 14b is 2 μm.
m.

The thermal roller fixing device of the present embodiment having the above-described structure is mounted on a copying machine CF-70 manufactured by Minolta Camera Co., Ltd., and 200 sheets of copying paper A (neutral paper containing calcium carbonate) are passed. As a result, a stable paper-passing property was exhibited without causing a jam, and the same results as in the case of Example 1 were obtained. Further, in this embodiment, the heat-resistant elastic body layer 14 has a two-layer structure, and the inner silicone rubber layer 14 having a large silica content is used.
Since a is disposed inside, the silicone rubber can compensate for the drawback that the heat resistance, the material strength, and the like decrease when the silica content decreases. In this case, the heating roller 1
Since the relationship between the surface roughness and the surface potential of Si and the relationship between the silica content and the jam occurrence rate depend on the characteristics of the outer silicone rubber layer 14b of the heat resistant elastic layer 14, the same as in the case of the single layer structure. The result is obtained.

(Evaluation of Surface Roughness and Chargeability of Roller) In order to investigate the relationship between the surface roughness and chargeability of the roller, the surface roughness of the heating roller was compared with that of the pressure roller having a surface roughness Rz of 2 μm. And copy paper (calcium carbonate content 1
The surface potential of the heating roller when 2% by weight) was passed was measured. The measurement environment was a temperature of 20 ° C. and a humidity of 65%. The result is shown in FIG.

As is apparent from FIG. 3, when the value of the surface roughness Rz of the heating roller is smaller than about 4 μm, the surface potential of the heating roller rises sharply, and the surface roughness greatly affects the charging property. Recognize. (Evaluation of Roller Surface Roughness and Paper Stability) Further, the heat roller fixing device according to the present invention is used as a copying machine C manufactured by Minolta Camera Co.
Mounted on F-70, the surface roughness of the heating roller was changed with respect to a pressure roller having a surface roughness Rz value of 0.5 μm.
The jam occurrence rate was measured by passing 1000 copy papers at each surface roughness. The measurement environment was an air temperature of 20 ° C. and a humidity of 65%, and the same copy paper was used by leaving it in this environment for 24 hours. The content of silica in the heat resistant elastic layer was 20% by weight for both the heating roller and the pressure roller. The results are shown in Table 1.

[0021]

[Table 1] As is clear from Table 1, the occurrence of jam is 5% when the value of the surface roughness Rz of the heating roller is 1 μm, and the surface roughness (surface potential) of the heating roller greatly affects the jam occurrence rate. I understand.

Further, the surface roughness of the heating roller was changed with respect to the pressure roller having the surface roughness Rz of 1 μm, and the jam occurrence rate of the copy paper was measured under the same conditions as above. The results are shown in Table 2.

[0023]

[Table 2] As is clear from Table 2, when the surface roughness Rz of the heating roller is 1 μm, as much as 50% of the jam occurs, and when the surface roughness of the heating roller is larger than that of the pressure roller, the jam occurrence rate is high. It became 0%.

(Evaluation of Silica Content and Paper Stability) Using a pressure roller and a heating roller having a surface roughness Rz of the heat-resistant elastic layer of 2 μm, the heat-resistant elastic layer has a silica content of 20. %, The silica content of the heat-resistant elastic layer of the heating roller (weight ratio with respect to the total amount of silica contained in the pressure roller) is changed with respect to the pressure roller, and copy paper jam occurs under the same conditions as above. The rate was measured. The result is shown in FIG.

As is clear from FIG. 4, the smaller the silica content, the lower the jam occurrence rate, and when the silica content is less than 20%, the jam occurrence rate sharply decreases. From this, it is understood that the silica content contributes to the reduction of the jam occurrence rate. (Evaluation of roller surface roughness and offset occurrence rate) The offset occurrence rate was examined by changing the surface roughness of the heating roller. This measurement was performed under the same conditions as in the case of measuring the occurrence of jam. The result is shown in FIG.

As is clear from FIG. 5, when the surface roughness Rz of the heating roller reaches about 5 μm, an offset occurs, and when it exceeds 5 μm, the offset occurrence rate rises extremely rapidly. Therefore, the value of the surface roughness Rz is 5 μm.
It can be seen that those of m or more are not suitable for the heating roller. Further, when the surface roughness of the pressure roller was changed and the offset occurrence rate was examined in the same manner, the offset occurrence rate sharply increased when the value of the surface roughness Rz was 5 μm or more, and the same result was obtained.

[0027]

According to the fixing device of the present invention, the heat-resistant elastic layer of the heating roller has a surface roughness in the range of 1≤Rz≤5, and the heat-resistant elastic layer of the pressure roller has a surface roughness. Rz ≦ 2
And smaller than the surface roughness of the heat resistant elastic body layer of the heating roller, and the heat resistant elastic body layer of the pressure roller is equal to or more than the heat resistant elastic material forming the heat resistant elastic body layer of the heating roller. Since it is composed of a heat-resistant elastic material containing silica, the charging tendency between both rollers and the recording paper is controlled by the surface roughness of both rollers and the silica content so that the recording paper is sucked or adsorbed on the pressure roller side. It is possible to improve the passage stability of the recording material.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view of a heat roller fixing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a roller portion of a heat roller fixing device according to a second embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the surface roughness of the heating roller and the surface potential.

FIG. 4 is a graph showing a relationship between a silica content rate of a heating roller and a jam occurrence rate.

FIG. 5 is a graph showing the relationship between the surface roughness of the heating roller and the offset occurrence rate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating roller 2 ... Pressure roller 6 ... Separation claw 12, 22 ... Core metal (core material) 13, 14, 23 ... Heat resistant elastic body layer

Claims (3)

[Claims] 1. A heating roller having a heat resistant elastic layer laminated on a core material, and a pressure roller having a heat resistant elastic layer laminated on the core material, the pressure roller being arranged in pressure contact with the heating roller. A heat roller fixing device for fixing the toner image on the recording paper by passing the recording paper carrying the toner image between the two rollers so that the toner image faces the heating roller. The surface roughness of the heat resistant elastic layer of the roller is 1 ≦ R.
z ≦ 5, the heat-resistant elastic layer of the pressure roller has a surface roughness Rz ≦ 2 and is smaller than the surface roughness of the heat-resistant elastic layer of the heating roller, and the heat-resistant elastic layer of the pressure roller. The heat roller fixing device, wherein the body layer is made of a heat resistant elastic material containing silica in an amount equal to or larger than that of the heat resistant elastic material forming the heat resistant elastic body layer of the heating roller. 2. The heat roller fixing device according to claim 1, wherein each heat resistant elastic body layer of the heating roller and the pressure roller is made of silicone rubber. 3. A heat-resistant elastic body layer of at least one of the heating roller and the pressure roller is formed by laminating a plurality of heat-resistant elastic materials having different silica contents.
The heat roller fixing device described.