JPH0772754A - Pressure roller - Google Patents

Abstract

PURPOSE:To obtain a pressure roller having low hardness and excellent permanent compressive strain. CONSTITUTION:This pressure roller 1 consists of a metal core 2, a silicone sponge rubber layer 3 covering the core, and a fluorocarbon resin layer 4 as the surface layer. In the silicone sponge rubber layer 3, several slits 5 are formed periodically in the circumference direction of the roller 1 in such a manner that these slits are continuously formed along the longitudinal direction of the roller 1 and that in the cross section of the roller 1, the slits 5 are radially arranged and tilted by a specified angle from the radial line penetrating the center of the core 2.

Description

Detailed Description of the Invention

[0001]

This invention relates to an electronic copying machine and an LBP.
The present invention relates to a pressure roller in a fixing unit of a (laser beam printer).

[0002]

2. Description of the Related Art Conventionally, a roller in which a fluorocarbon resin sleeve is coated on the outer circumference of a rubber roller containing a core metal has been known as a pressure roller in a regular part of an electronic copying machine or an LBP in order to improve the releasability of toner. There is.

In recent years, miniaturization of electronic copying machines and LBPs using a fixing roller has progressed, and the outer diameter of the heat roller and the pressure roller has been reduced to about 10 to 25 mm. Especially, the pressure roller has a small diameter. Therefore, in order to secure the nip width at the time of fixing, there is a tendency to reduce the hardness of the elastic layer coated on the outer periphery of the metal core, and the elastic layer as disclosed in Japanese Patent Publication No. 04-77315. The one using a porous elastic body (sponge rubber) is often used.

Recently, in order to maintain the releasability of the pressure roller from the toner, a roller whose surface layer is covered with a fluororesin sleeve is used.

[0005]

In a pressure roller in which the outer circumference of a metal core bar is covered with silicone sponge rubber and the surface layer is covered with a fluororesin layer, it is necessary to secure a nip width during fixing as the outer diameter becomes smaller. Because there is
It is necessary to use a lower hardness silicone sponge rubber.

However, in order to obtain a silicone sponge rubber having a lower hardness, it is necessary to increase the foaming ratio, and usually a foaming agent such as AIBN (azobisisobutyronitrile) is added, but as a result, compression is performed. There was a problem that deterioration of durability strain was caused.

As shown in FIG. 4, the deterioration of the compression endurance strain in the silicone sponge rubber tends to be abruptly deteriorated when the sponge hardness (Asker C) falls below about 20 degrees.

Therefore, although a silicone sponge having a sponge hardness of less than about 20 degrees can secure a nip width, it has a drawback that it cannot be practically used as a pressure roller because of its poor compression set.

Further, in the pressure roller in which the outer circumference of such a silicone sponge layer is coated with a fluororesin layer, the heat generated during the heat fixing causes the bubbles in the inside as well as the sponge material to expand due to the heat, so that in the axial direction of the roller. There was a problem that the distribution of the expansion degree of was reflected as it was in the axial roller shape.

That is, the gas expanded in the center of the roller has no escape because the roller surface is coated with the fluororesin, whereas at the end of the roller, the gas escapes from both end surfaces through the bubble film. You can

Therefore, there is a phenomenon that the outer diameter at the center of the roller becomes larger than the outer diameter at the end of the roller.

Due to the change in the roller shape, paper wrinkles were sometimes induced on the recording paper.

The paper wrinkles in this case are not of the nature that they occur in any state, but they tend to occur when the first copy immediately after the power is turned on or when the paper quality is poor, and they are also induced by environmental conditions. Sometimes it was easy.

That is, there is a tendency that paper wrinkles are likely to occur when a moisture-absorbed paper is passed, such as when the high-temperature and high-humidity paper is passed.

[0015]

As a result of earnest research for solving the above-mentioned problems, the present invention covers a metal sponge rubber layer 3 on a metal cored bar 2 and a fluororesin layer 4 on its surface. In the pressure roller 1, the silicone sponge layer 3 has a plurality of radial lines which are inclined at a required angle with respect to a radial line passing through the center of the cored bar 2 in a cross section of the roller and which are continuous in the longitudinal direction of the roller. The present invention proposes a pressure roller in which the slits 5 are provided at equal intervals in the circumferential direction of the roller.

[0016]

The gas in the silicone sponge layer 3 that has been expanded in volume by heating becomes easy to escape in the end direction along the radial slits 5 provided in the sponge layer 3 and continuous in the longitudinal direction. Since the difference in the outer diameter change in the axial direction is small, the occurrence of paper wrinkles on the recording paper can be significantly reduced.

Particularly, it is very effective in eliminating paper wrinkles that occur when papers of different sizes are passed immediately after papers of a certain size are continuously passed, and paper wrinkles that occur in a high temperature environment.

[0018]

EXAMPLE A pressure roller 1 comprises a metal cored bar 2, a silicone sponge layer 3 covering the metal cored bar 2 and a fluororesin sleeve layer 4 covering the surface layer thereof.

The material of the fluororesin sleeve 4 is PF
A (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) is used, and the inner surface of the fluororesin sleeve 4 is made of sodium-
It is used after being surface-treated by the naphthalene-tetrahydrofuran method or the sodium-liquid solution method.

The metal cored bar 2 and the silicone sponge layer 3 are adhered to each other by pressing a silicone rubber extruded with a foaming agent with an extruder to form a raw rubber tube, and then applying H
AV (Hot Air Vulcanization) method and FBV (Fluidized Be)
A silicone sponge tube is formed by heat-foaming by a method such as d Vulcanization), and a metal cored bar 2 to which an additive type adhesive such as TSE322 (Toshiba Silicone Co., Ltd.) is previously applied is inserted into the silicone sponge tube. After that, the method of further heating to cure the adhesive and adhering the silicone sponge tube to the metal cored bar 2 may be used, or Primer No. 8 (trade name of Shin-Etsu Chemical Co., Ltd.) on the surface.
A metal cored bar 2 coated with an adhesive such as the above is passed through a crosshead die of an extruder to form a silicone rubber layer in which the foaming agent and the vulcanizing agent on the metal cored bar 2 are kneaded, and then this is kept at a constant temperature. You may heat and foam in a tank or a heated mold, and at the same time, bond them.

In any of the bonding methods, after forming the silicone sponge layer 3 on the metal cored bar 2, the outer periphery of the sponge is polished to remove the skin layer formed on the surface and to obtain the accuracy of the outer diameter. There is a need.

"Example 1"

First, a metal core bar 2 having an overall length of 330 mm and an outer diameter of 20 mm
The outer periphery of was coated with a silicone sponge rubber having a hardness of 25 degrees (Asker C) and then polished to an outer diameter of 38 mm.

Silicone sponge layer 3 thus prepared
In addition, as shown in FIGS. 1 and 2, in a cross section of the roller, a linear or arc-shaped radial pattern inclined at a required angle with respect to a radial line passing through the center of the cored bar 2 is formed and is continuous in the longitudinal direction of the roller. Twenty slits (cuts) 5 were made at equal intervals in the circumferential direction of the roller.

After that, the surface of the silicone sponge layer 3 was covered with a fluororesin sleeve 4 via an adhesive.

The roller hardness at this time was 35 degrees (Asker C).

Next, when this roller was attached to NP6030 (trade name), which is a copying machine manufactured by Canon Inc., and an actual machine durability test was conducted, it was found that there would be a problem even after a paper running durability test of 70,000 sheets. Image defects, uneven fixing, and paper wrinkles did not occur at all.

Then, again under high temperature and high humidity (32 ° C, 85%)
Although 20 sheets were continuously fed, no paper wrinkles occurred.

Further, the fixing unit was subjected to an energization latch test for 3 days, and the pressure roller had a sag of 0.1.
It was found to be usable as a pressure roller without causing uneven fixing, paper wrinkles and abnormal noise.

[Example 2]

As shown in FIG. 2, a roller similar to that of Example 1 was formed except that the slit 5 was formed in an arcuate radial shape, and this roller was a copying machine manufactured by Canon Inc., NP6030 (trade name). ), And the same actual equipment endurance test as in Example 1 was performed, and the same results as in Example 1 were obtained. "Comparative Example 1"

As in Example 1, except that the slit 5 was not formed in the silicone sponge layer 3, the metal sponge layer 3 having a hardness of 25 degrees (Asker C) was coated on the metal cored bar 2 and then the fluororesin sleeve 4 was formed. And the roller (see FIG. 3) was molded.

The product hardness of the roller thus produced is 39.
It was degree.

Next, when this roller was attached to NP6030 (manufactured by Canon Inc.) and a paper passing test was carried out, image distortion occurred at the early stage of paper passing. The cause was investigated and investigated, and the product hardness was high. Therefore, the fixing rate of the toner was found to be poor.

"Comparative Example 2"

In the same manner as in Comparative Example 1 except that a silicone sponge having a hardness of 20 degrees (Asker C) was used, a roller was formed in the silicone sponge layer 3 without slits 5.

The product hardness of the roller thus produced is 35
It was degree.

Next, when this roller was attached to NP6030 (manufactured by Canon Inc.) and a paper passing test was carried out, there was no problem in the early stage of paper passing, but image disturbance occurred at 30,000 sheet passing. It was

Then, when a current-carrying latch test was carried out for 3 days, it was found that the roller had a large settling amount of 0.3 mm and the compression set was poor, so that it had no durability as a pressure roller.

"Comparative Example 3"

As in Example 2, except that the silicone sponge layer was not slit, the metal sponge layer 3 of 25 degrees (Asker C) was coated on the metal cored bar 2, and the fluororesin sleeve 4 was put on the roller to cover the roller. Molded.

The product hardness of the roller thus produced is 39.
It was degree.

Next, when this roller was attached to NP6030 (manufactured by Canon Inc.) and a paper passing test was carried out, image distortion occurred at the early stage of paper passing. When the cause was investigated and investigated, the product hardness was high. Therefore, the fixing rate of the toner was found to be poor.

"Comparative Example 4"

A roller was formed in the same manner as in Comparative Example 3 except that the silicone sponge having a hardness of 20 degrees (Asker C) was not used and the slits 5 were not formed in the silicone sponge layer 3.

The product hardness of the roller thus prepared was 35 degrees.

Next, when this roller was attached to NP6030 (manufactured by Canon Inc.) and a paper-passing test was carried out, there was no problem in the early stage of paper-passing, but image distortion occurred at 30,000 sheets.

Then, when a current-carrying latch test was carried out for 3 days, it was found that the roller had a large settling amount of 0.3 mm and the compression set was poor, so that it was not durable as a pressure roller.

[0049]

As described above, according to the present invention, it is possible to obtain a low-hardness pressure roller coated with a fluororesin, which is extremely excellent in durability.

[Brief description of drawings]

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

FIG. 2 is a vertical sectional side view showing another embodiment of the pressure roller of the present invention.

FIG. 3 is a vertical sectional side view showing another aspect of the pressure roller of Comparative Examples 1 to 4.

FIG. 4 is a diagram showing the relationship between compression durability strain and sponge hardness (Asker C) in silicone sponge rubber.

[Explanation of symbols]

 1 Pressure roller 2 Metal core 3 Silicone sponge layer 4 Fluororesin sleeve layer 5 Slit

Claims (1)

[Claims] 1. A pressure roller in which a silicone sponge layer coated on the outer periphery of a metal core bar is coated with a fluororesin sleeve having a thickness of 0.1 mm or less, wherein the silicone sponge layer has the core on the cross section of the roller. Form a radial pattern inclined by a required angle with respect to a radial line passing through the center of gold,
A pressure roller characterized in that a plurality of slits continuous in the longitudinal direction of the roller are provided at equal intervals in the circumferential direction of the roller.