JPH0627850A - Pressurizing roller - Google Patents

Abstract

PURPOSE:To provide the pressurizing roller which satisfies all of necessary conditions, such as wrinkling of paper, envelope wrinkling, fixability, release property of toners and reduction of warming up time, by forming the roller of multilayered structures coated with a silicone layer, silicone sponge layer and fluororesin tube later successive ly from an arbor in the central part toward outer layers and by forming the silicone sponge layer with the open cellular sponge layer. CONSTITUTION:This pressurizing roller is constituted in the multilayered structures coated with the silicone rubber layer 2, the open cellular silicone sponge layer 3 and the fluororesin tube layer 4 successively from the arbor 1 in the central part. The change in the outside diameter of the roller by heating is absorbed by the elasticity of the silicone sponge layer 3 in the constitution and, therefore, the wrinkling of the paper does not arise any more. In addition, the silicone sponge layer 3 is formed of the open cellular sponge, by which the gas expanded by heating is escaped from the end through the inside of the open cells regardless of the difference in the central part and the end part of the roller and therefore, the difference in the shape change in the axial direction of the roller is lessened and the reliability on the paper wrinkling is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure roller used in a fixing device for heating and fixing an unfixed image in an electrostatic recording type copying machine, printer, facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, as a pressure roller used in an image fixing device such as a copying machine, a roller having a core metal coated with silicone rubber, or a roller having a core metal coated with silicone rubber and then coated with a fluororesin is used. It is commonly used.

The outer diameter of the conventional pressure roller changes depending on the temperature, and when the paper is nipped and conveyed between the heating roller and the heating roller, the outer diameter of the roller in the axial direction of the roller is in contact with the paper. The change appeared as a difference in the sheet conveyance speed, and wrinkles were generated on the sheet.

In particular, when a large amount of paper of a certain size is passed and then a paper of a different size is passed, heat is taken away by the paper in the front paper width portion in the roll axis direction, so that the surface is more than the other portion. The phenomenon that paper wrinkles were generated due to the low temperature and the small outer diameter of the roll was remarkable.

Further, since the surface of the conventional pressure roller is made of silicone rubber, there is a problem that toner adheres and the surface is easily soiled.

On the other hand, in order to solve the stain on the toner, a method of coating the surface with a fluororesin (for example, polytrafluoroethylene; PTFE) or a method for coating the surface with a fluororesin (for example, tetrafluoroethylene and perfluoroalkyl vinyl ether) A method of coating a tube made of a copolymer of PFA resin), especially a fluororesin tube of about 50 μm is known.

However, the roller of this fluororesin tube not only has the above-mentioned paper wrinkle problem, but also its surface hardness becomes high, so that the contact width with the fixing roller, that is, the nip width is reduced, so that the toner image is transferred to the fixing roller. However, there was a problem in that it was not possible to bring them into close contact with each other in a sufficiently pressurized state, and it was not possible to obtain a high-quality fixed image.

Therefore, a roller in which the hardness of the silicone rubber has been lowered to around 15 degrees in JIS A in order to make the nip width wide has been considered, but it is difficult at present to make the material hardness less than this.

In addition, in the above-mentioned two types of conventional pressure rollers, the heat of the fixing roller escapes to the pressure roller side through the connecting portion, so that it requires a long warm-up after the switch is turned on until the first copy. There was also the problem of

Recently, with the spread of direct mail, the demand for printing on the surface of an envelope having a certain amount of thickness has increased, and the above two types of pressure rollers, which have no tolerance for the thickness of the sheet, are used for the envelope. Wrinkles and other defects cannot be avoided.

That is, the nip width of the envelope paper passing portion becomes larger than the nip width of other portions due to the thickness of the envelope, which causes a difference in peripheral speed between the paper passing portion and the non-paper passing portion, which causes repulsion elasticity. With the relatively high pressure rollers of the two types, slipping occurs on the paper contact surface inside the envelope in an attempt to correct the difference in peripheral speed, which causes wrinkles in the envelope.

In order to solve these problems,
A pressure roller has been developed in which a core metal is directly coated with silicone sponge and the outside is coated with a fluororesin tube. According to this, changes in the outer diameter of the pressure roller and the envelope thickness are absorbed by the elasticity of the sponge layer, and It has been considered possible to eliminate paper wrinkles.

However, since the silicone sponge of the pressure roller is a closed cell, the heat generated during the heat fixing causes the sponge material and the internal bubbles to thermally expand, and the expansion degree of the bubbles in the axial direction of the roller may vary. There is a drawback that the uneven distribution is reflected as it is in the axial roller shape.

That is, the expanded gas at the center of the roller has no escape because the surface is covered with the coating layer, whereas at the end of the roller, the gas easily escapes to both end faces through the bubble film. As a result, the roller shape changes between the central part and the end part.

This change in the roller shape is not a decisive factor that induces paper wrinkles in any case, but it adversely affects the paper transportation during the first copying after the power is turned on or when the paper quality is poor. Paper wrinkles are generated depending on environmental conditions.

Further, this roller has a wide nip width with a low load, but on the other hand, the pressure applied to the nip portion is absorbed by the sponge layer, so that the toner image cannot be sufficiently pressed.

Further, in order to satisfy the fixing, a method of increasing the sponge hardness and a method of increasing the load can be considered, but the former cannot avoid the problem such as paper wrinkles by losing the sponge effect, and the latter is the silicone sponge. The problem that the roller is permanently deformed by accelerating the compression set of 1 is inevitable.

[0018]

SUMMARY OF THE INVENTION The present invention is directed to paper wrinkles of paper, toner releasability in the above conventional pressure roller,
It is to solve all the problems by fixing the toner image, shortening the warming-up time, and wrinkling the envelope.

[0019]

In order to solve the above-mentioned conventional problems, the present invention provides a silicone rubber layer 2 and a silicone sponge layer 3 from a core metal 1 at the center of a roller toward an outer layer.
The present invention proposes a pressure roller having a multi-layer structure in which a fluororesin tube layer 4 is coated in this order, and the silicone sponge layer 3 is an open-cell sponge.

[0020]

The change in roller outer diameter due to heating is absorbed by the elasticity of the silicone sponge layer, so that paper wrinkles are eliminated.

Particularly, it is very effective in eliminating paper wrinkles that occur when sheets of different sizes are passed immediately after passing a large amount of sheets of a certain size.

Further, since the silicone sponge layer is made into a sponge having open cells, the gas volume-expanded by heating passes through the open cells regardless of the difference between the center and the end of the roller and escapes from the end surface. The difference in the change in shape is small and the reliability against paper wrinkles is significantly increased.

Moreover, the impact resilience can be reduced by using the silicone sponge, the above-mentioned peripheral speed difference caused by the thickness of the envelope can be allowed, and the envelope wrinkle can be eliminated.

Further, since the surface of this roller is made of fluororesin, the releasing property of the toner is good and the roller surface is not contaminated with the toner.

Further, in addition to the advantage that a wide nip width can be obtained under a low load by the silicone sponge layer, a sufficient pressure can be obtained by increasing the hardness of the silicone rubber layer thereunder.

Moreover, by changing the thickness ratio of the silicone rubber layer and the silicone sponge layer, the nip width and the pressure applied thereto can be adjusted, so that an image with a higher fixing property can be pursued.

Further, as a great effect of using the silicone sponge layer, the temperature rise of the fixing roller at the time of start-up is accelerated due to its heat insulating property, and the warming-up time can be greatly shortened.

[0028]

FIG. 1 shows an embodiment of a pressure roller of the present invention, in which a silicone rubber layer 2, an open-cell silicone sponge layer 3 and a core metal 1 at a central portion are sequentially arranged toward an outer layer. The fluororesin tube layer 4 is covered to form a multilayer structure.

As the silicone rubber layer 2 in the embodiment of the present invention, an addition type silicone rubber KE1330A / B (JIS A hardness of 40 degrees) manufactured by Shin-Etsu Chemical Co., Ltd. and a silicone sponge layer 3 manufactured by Shin-Etsu Chemical Co., Ltd. are used. 30 with Asker C obtained by adding KE904FU as a base and giving a crush after foaming
The open cell sponge used was PFA 50 μm for the fluororesin tube.

In the embodiment of the present invention, the pressure roller having a diameter of 24 mm was manufactured by setting the core metal 1 to 14 mm, the thickness of silicone rubber to 4 mm, and the thickness of silicone sponge to 1 mm.

In order to compare and contrast with the above-mentioned embodiment, three kinds of pressure rollers as comparative examples having different structures were manufactured.

That is, as shown in FIG. 2, the roller of Comparative Example 1 has a core metal 5 and a silicone rubber 6 (X-34-201A / Shin-Etsu Chemical Co., Ltd.).
As shown in FIG. 3, the roller coated with B) and the roller of Comparative Example 2 have a core metal 7 and a silicone rubber 8 (KE931U manufactured by Shin-Etsu Chemical Co., Ltd.).
Which is then coated with a fluororesin tube 9 made of PFA having a thickness of 50 μm. The roller of Comparative Example 3 has a core metal 10 and a silicone sponge 11 (base material; KE904FU manufactured by Shin-Etsu Chemical Co., Ltd.) as shown in FIG. 50 after coating
The fluororesin tube 12 of μm is coated.

These samples were used as samples and mounted on a laser printer 4105 manufactured by Fuji Xerox to actually carry out a paper feeding experiment to observe the fixability, paper wrinkles, roller surface stains, and envelope wrinkles.

The results are shown in Table 1.

[0035]

[Table 1]

As shown in Table 1, according to the pressure roller of the present invention, the amount of deformation in the roller axial direction due to heating is uniform due to the effect of the sponge of open cells, and the deformation is also due to the elasticity of the silicone sponge layer. The paper does not wrinkle because it is absorbed, and the presence of the silicone rubber as the base allows the unfixed toner to be sufficiently pressed onto the paper, and because the silicone sponge layer provides a wide nip width, the fixability is also good. Results were obtained.

Further, since the fluororesin tube layer is provided on the outermost shell, the roller surface is not contaminated by toner, and the roller life is improved as compared with Comparative Example 1 in which the surface is not coated with fluororesin. I understand.

Furthermore, the temperature of the roller rises quickly due to the heat insulating effect of the silicone sponge, and the warming-up time from the machine start-up to the first sheet passing can be greatly shortened.

In the above embodiment, the hardness of the silicone rubber is 40 degrees in JIS A hardness and the silicone sponge hardness is 30 degrees in Asker C hardness. However, the present invention is not limited to this and the nip width and It may be freely set within the range compatible with the pressure.

Further, in the embodiment, the thickness ratio of silicone rubber: silicone sponge in the elastic layer is 4: 1, but the invention is not limited to this.

However, this ratio is 2: 2 when the silicone sponge layer having open cells is set to 1 because the effect of using this structure is diminished when either one is made extremely thin.
Other experiments have shown that it should be set from 1 to 7: 1, preferably from 3: 1 to 5: 1.

[0042]

As described above, according to the present invention, a multilayer structure in which a silicone rubber layer, a silicone sponge layer, and a fluororesin tube layer are coated from the cored bar at the center of the roller toward the outer layer, and the silicone sponge layer is formed. Since it is an open-cell sponge, it is possible to solve wrinkles on paper, envelope wrinkles, fixability, toner releasability, which could not be solved by conventional rollers.
It is possible to obtain a roller that satisfies all the preferable conditions required for the pressure roller, such as shortening the warming-up time.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a roller of an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a roller of Comparative Example 1 used in a comparative experiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a roller of Comparative Example 2 used in a comparative experiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a roller of Comparative Example 3 used in a comparative experiment of the present invention.

[Explanation of symbols]

 1 core metal 2 silicone rubber layer 3 continuous-cell silicone sponge layer 4 fluororesin tube layer 5 core metal 6 silicone rubber 7 core metal 8 silicone rubber 9 fluororesin tube 10 core metal 11 silicone sponge 12 fluororesin tube

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Claims (1)

[Claims] 1. A multi-layer structure in which a silicone rubber layer, a silicone sponge layer, and a fluororesin tube layer are sequentially coated from a core metal bar in the central portion toward an outer layer, and the silicone sponge layer is an open-cell sponge. A pressure roller characterized by.