JPH06337610A - Press roller - Google Patents

Abstract

PURPOSE:To provide a press roller having low hardness and excellent compression set. CONSTITUTION:This press roller 1 is formed by coating the surface of a metallic arbor 2 with a silicone sponge roller layer 3 and coating the surface of this layer with a fluororesin layer 4. The silicone sponge roller layer 3 is provided with plural pieces of slits 5 continuous in the longitudinal direction of the roller radially from the center of the arbor 2 and at equal intervals or spiral slits 5 continuous in the longitudinal direction of the roller.

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. 5, the deterioration of the compression endurance strain of 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 core 2 and a fluororesin layer 4 on the surface thereof. In this pressure roller 1, a plurality of slits 5 which are continuous with the silicone sponge layer 3 from the center of the cored bar 2 in the longitudinal direction of the roller radially and at equal intervals, or a spiral slit 5 which is continuous in the longitudinal direction of the roller. A pressure roller provided with is proposed.

[0016]

The gas in the silicone sponge layer 3 which has been expanded in volume by heating becomes easy to escape in the end direction along the radial or spiral slits 5 provided in the sponge layer 3 and continuous in the longitudinal direction. Since the difference in the outer diameter change of the pressure roller 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)
The silicone sponge tube is made by heat-foaming by a method such as d Vulcanization), and the 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
As shown in FIG. 1, 20 slits (cuts) 5 were made in the longitudinal direction and radially from the cored bar 2 at equal intervals.

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.

"Comparative Example 1"

As in Example 1, except that the slits 5 were not formed in the silicone sponge layer 3, the silicone 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 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"

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

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 at the beginning of the paper passing, but image disturbance occurred at 30,000 paper passing. It was

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

"Example 2"

First, a metal cored bar having a total length of 330 mm and an outer diameter of 20 mm 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.

The sponge roller thus prepared was provided with spiral slits 5 at intervals of 3 mm in the longitudinal direction as shown in FIG.

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 a copying machine manufactured by Canon Inc., NP6030 (trade name), and an actual machine durability test was carried out, 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, when a current-carrying latch test was carried out for 3 days in the fixing unit, the pressure roller was found to have a sag of 0.1.
It was found to be usable as a pressure roller without causing uneven fixing, wrinkling of wrinkles, abnormal noise, etc.

As shown in FIG. 2, the spiral slits 5 are arranged at equal intervals in the axial direction, and the clearance can be arbitrarily determined, but from the balance with the sponge hardness, 1 to
7mm spacing is preferred.

That is, since the sponge layer 3 is easily peeled off from the core metal 2, it is difficult to form it as a roller, and a gap of 7 mm or more has no effect of lowering the product hardness in the present invention.

Further, as shown in FIG. 4, a plurality of slits 5 may be provided in parallel in the longitudinal direction at equal intervals.
As described above, a plurality of slits 5 may be tilted rightward and leftward with respect to the axis so as to intersect with each other.

"Comparative Example 3"

As in Example 2, except that the silicone sponge layer was not slit, the metal sponge layer 3 having a temperature 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. 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 4"

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

The product hardness of the roller thus produced 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 disturbance occurred at 30,000 sheets.

Therefore, 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.

[0059]

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 embodiment of the pressure roller of the present invention.

FIG. 4 is a vertical sectional side view showing another embodiment of the pressure roller of the present invention.

FIG. 5 is a diagram showing the relationship between compression endurance 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 (2)

[Claims] 1. A pressure roller in which a silicone resin sponge layer coated on the outer periphery of a metal cored bar is coated with a fluororesin sleeve having a thickness of 0.1 mm or less, wherein the silicon sponge layer is radiated from the center of the cored metal. A pressure roller characterized in that a plurality of continuous slits are provided at equal intervals in the longitudinal direction of the roller. 2. A pressure roller in which a silicone resin sponge layer coated on the outer periphery of a metal core bar is coated with a fluorine resin sleeve having a thickness of 0.1 mm or less, wherein the silicon sponge layer has a spiral continuous in the longitudinal direction of the roller. A pressure roller having a slit.