JPH07125101A - Feed roller - Google Patents

Abstract

PURPOSE:To maintain the friction coefficient, to eliminate defective feeding, and to improve durability of a feed roller by making it of silicone rubber with a specified crosslinking density. CONSTITUTION:The friction coefficient of a feed roller is adjusted at 1.5 or more by controlling the crosslinking density of silicone rubber at 2.0X10<-4>mol/ cm<3> or more. Either method of addition or heat curing can be applied to the crosslinking of silicone rubber. General type peroxide such as bis(2,4- dichlorobenzoyl) peroxide and dicumyl peroxide can be used for the heat curing. As a result, the feed roller can keep its performance with improved durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies various types of terminals such as electronic copying machines and laser beam printers (hereinafter abbreviated as LBP), or pickup rollers, field rollers, reverse rollers, etc. in a sheet feeding portion of a facsimile (FAX). Related to rollers for paper.

[0002]

2. Description of the Related Art Most of paper feeding mechanisms such as electronic copying machines employ a paper feeding / conveying system utilizing friction between a rubber roller and paper. The paper feeding unit, which should be called the heart of the paper feeding mechanism, is a paper feeding roller using a material having a friction coefficient of about 1.5 to 2.0 in order to avoid problems such as poor paper feeding and double feeding. Has been adopted. Therefore, a rubber material with relatively low hardness is required,
Usually, the one of 20 to 40 degrees (JISA) is often used. Further, the paper feed roller is required to have durability against ozone generated inside the copying machine and to be inert to a cleaning solvent such as isopropyl alcohol used at the time of maintenance or overhaul, which meets these requirements. As the material, polynorbornene rubber, a blended product of polynorbornene rubber and ethylene propylene rubber (hereinafter abbreviated as EPDM), EPDM and the like are used.

[0003]

In recent years, in an electronic copying machine or a color copying machine having a double-sided copying function, oil resistance against silicone oil used as a releasing oil in the fixing section is required. That is, a small amount of the silicone oil used in the fixing unit adheres to the paper when the toner is fixed, and the silicone oil that adheres to the paper accumulates on the surface of the paper feed roller made of polynorbornene rubber or the like during paper passing, and therefore the roller There was a problem that the coefficient of friction was extremely reduced and paper could not be passed. In this case, by using silicone rubber as the material of the paper feed roller, it is possible to avoid the reduction of the friction coefficient due to the adhesion of silicone oil. This is because when the silicone oil adheres to the surface of the paper feed roller made of silicone rubber, the friction coefficient temporarily decreases, but since the compatibility of silicone rubber and silicone oil is good, the silicone oil is absorbed and absorbed by the silicone rubber. The coefficient of friction is restored and the performance of the paper feed roller is maintained.

On the other hand, polynorbornene rubber and EP
Since materials such as DM have poor compatibility with silicone oil, they do not have the above-described effect of adsorbing silicone oil. However, when a standard silicone rubber such as KE941U (trade name of Shin-Etsu Chemical Co., Ltd.) is applied to the paper feed roller, the initial coefficient of dynamic friction is at most 1.0.
However, since the friction coefficient gradually decreases as the number of passed sheets increases, there is a problem that a sheet passing defect occurs even in the initial stage when the number of passed sheets is about 10,000. Therefore, an object of the present invention is to provide a paper feed roller that solves the above problems, maintains the friction coefficient, eliminates paper passing defects, and has excellent durability.

[0005]

In order to achieve the above-mentioned object, the paper feed roller according to the present invention has a silicone rubber having a cross-linking density of 2.0 × 10 ⁻⁴ mole / cc or more, which causes abrasion. The inventors have found that a silicone rubber having a coefficient of 1.5 or more can be obtained, and completed the present invention.

In the present invention, the method for crosslinking the silicone rubber is not particularly limited, and any type of addition type and thermal vulcanization type can be used. Further, in the case of the thermal vulcanization type, a commonly used peroxide can be used, and
-Dichlorobenzoyl peroxide, dicumyl peroxide, ditertiary butyl peroxide, 2,
5-Dimethyl-2,5 bis (t-butylperoxy)-
Hexane and the like are exemplified.

The hardness of the rubber cured product of the silicone composition of the present invention is not particularly limited and can be arbitrarily selected in the range of 15 to 50 degrees by the JISA hardness tester, but the balance between the physical strength and the friction coefficient can be selected. From the top, about 20 to 35 degrees is desirable. There are various types of paper feed rollers such as a metal shaft with a rubber piece inserted and a rubber piece inserted with a resin piece, but the physical strength is such that rubber cracks do not occur during assembly. It is desirable that the rubber has a tensile strength of 2 MPa and an elongation of 350% or more. Further, in the case of silicone rubber, paper powder tends to be less likely to adhere to it when it is highly stretched, so from this viewpoint as well, the elongation is preferably 350% or more.

Also in the present invention, it is essential to mix and formulate the filler and the like, and in order to balance the mechanical characteristics of the cured silicone composition, that is, the physical strength, the rubber strength and the like with the friction coefficient, Aerosil or Cab-O. -It is better to mainly use dry silica (fumed silica) represented by Sil, wet silica such as Hi-Sil and Nipsil, diatomaceous earth such as Celite and Radiolite, and quartz powder such as Minusil and Crystallite. Fillers such as may be used if necessary. Further, a plasticizer such as a non-functional silicone oil may be added.

[0009]

EXAMPLES The present invention will be described below based on examples.
In FIG. 1, 1 is a paper feed roller, 2 is a core metal of the paper feed roller 1, 3 is a silicone rubber layer fixed to the core metal 2, and the method for measuring the crosslink density of the silicone rubber is JP-B-4-38579, and is measured by the toluene swelling method. Ie 2
A 5 mm × 20 mm sample is cut out from a rubber sheet vulcanized and molded to have a thickness of mm, immersed in 50 ml of toluene at room temperature, and the weight of the sample containing toluene is measured at predetermined appropriate intervals. Then, when the difference between the two measurement values measured over 24 hours is 1% or less of the sample weight, the sample weight is defined as W (g). Then after air-drying the sample,
Dry at 120 ° C for 3 hours to remove toluene and weigh W
₀ (g) was measured and placed on a platinum boat to
The sample is heated to 900 ° C. at a heating rate of 0 ° C./min or less, held at 900 ° C. for 10 minutes, cooled, and the weight W _f (g) of the remaining sample is measured. Using the above measured values, the number of cross-links contained in 1 cc of vulcanized rubber is N ₀ / V ₀ (mole / c
c) is calculated and used as the crosslink density.

[0010]

[Equation 1] here,

[Equation 2]

The crosslink density as used herein means the crosslink formed by vinyl groups in methylvinylsilicone rubber,
This includes both the crosslinks formed between silica and the siloxane polymer in the silicone rubber, and is the number of crosslinks contained in 1 cc of the silicone rubber after crosslinking, which is the vinyl in the methyl vinyl silicone raw rubber. It can be adjusted by changing the ratio of the groups.

The dynamic friction coefficient in this example was measured by the e method of ASTM D1894. That is, the e method of ASTM D1894 will be described with reference to the schematic view shown in FIG. 2. The method is screwed with a screw rod 10 rotated by a motor (not shown), and forward / backward rotation is performed by forward / reverse rotation of the screw rod 10. The PPC paper 12 is placed on the sample table 11 which can be freely moved, while the rolled rubber sample 13 is placed on the PPC paper 12 without any load on the PPC paper 12. From that state, the vertical load W ₀ is applied again, and the vertical load W ₀ is applied to the PPC paper 12.
_Make sure ₀ is present. Further, 14 is a measuring rod fixedly mounted on the rubber sample 13, 15 is a strain gauge with which the measuring rod 14 contacts, 16 is an amplifier, and 17 is a recorder.

When the screw rod 10 is rotated by the operation of the above-mentioned motor and the sample table 11 screwed to the screw rod 10 is moved in the direction of the arrow, the PPC paper 12 placed on the sample table 11 is moved by this movement. The mounted rubber sample 13 also moves together with the measuring rod 14, and the movement causes the tip of the measuring rod 14 to contact the strain gauge 15. However, even if the tip of the measuring rod 14 comes into contact with the strain gauge 15, the sample stage 11 still moves, and the strain gauge 15 has a frictional force F.
To detect. The frictional force F is low in the case of a sample having a good slip property and is high in the case of a sticky one. Therefore, the friction coefficient μ is calculated from the above W ₀ and F by μ = F / W ₀ , whereby the friction coefficient can be measured.

[0014]

Example 1 100 parts by weight of a rubber compound obtained by adding dry silica to 5 types of methyl vinyl-based raw rubber having different vinyl group contents was added to 100 parts by weight of a vulcanizing agent C-8A [trade name of Shin-Etsu Chemical Co., Ltd., 2,5- A sample was prepared by kneading 0.5 parts by weight of 80% silicone base of dimethyl-2,5-di (t-butylperoxy) hexane. In addition, 170
A rubber sheet having a thickness of 2 mm was vulcanized under the condition of 10 ° C for 10 minutes, the crosslink density was measured by the above-mentioned method, and the physical properties of rubber were determined according to JIS K6301 to obtain the results shown in Table 1.

[0015]

[Table 1]

Next, a rubber roller having an inner diameter of 7 mm and an outer diameter of 21 mm was prepared, cut into a width of 15 mm, fitted into a mandrel and polished to an outer diameter of 19 mm to prepare a paper feed roller, and the measurement shown in FIG. After measuring the dynamic friction coefficient with the device, a paper passing test was conducted on each sample, and the results shown in Table 2 were obtained, with a crosslink density of 2.0 × 10 ^-4 mole / cc or more, 50,000 sheets. Even after the paper passing test, no defects such as defective feeding of paper and double feeding were observed.

[0017]

[Table 2]

From the above results, the higher the crosslink density is, the higher the dynamic friction coefficient of silicone rubber is, and in order to obtain a stable paper feed roller having an initial dynamic friction coefficient of 1.5 or more, the crosslink density is 2.0 ×. It turns out that more than 10 ^-4 mole / cc is required.

As described in detail above, according to this embodiment, the cross-linking density of the silicone rubber of the paper feed roller 1 is 2.0.
Since it was set to × 10 ^-4 mole / cc or more, a high dynamic friction coefficient could be obtained. Therefore, even if the number of sheets to be passed is large, the dynamic friction coefficient does not decrease and good sheet passing can be maintained. Therefore, it is possible to obtain excellent durability as the paper feed roller.

[0020]

EFFECTS OF THE INVENTION Since the paper feed roller according to the present invention has a cross-linking density of silicone rubber of 2.0 × 10 ⁻⁴ mole / cc or more, it is possible to obtain a silicone rubber having a high friction coefficient of 1.5 or more. It is possible to obtain a paper feed roller which is capable of maintaining the performance as a paper feed roller and has extremely excellent durability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a paper feed roller

FIG. 2 is a schematic diagram of a dynamic friction coefficient measuring device.

[Explanation of symbols]

 1 Paper feed roller 2 Core metal 3 Silicone rubber layer

Claims (2)

[Claims] 1. A paper feed roller made of silicone rubber, wherein the silicone rubber has a crosslinking density of 2.0 × 10 ^−4.
A paper feed roller characterized by a mole / cc or higher. 2. The paper feed roller according to claim 1, wherein the silicone rubber contains methyl vinyl silicone raw rubber and dry silica.