JP2011020824A - Paper feeding roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeding roller for maintaining good paper feeding over a longer period than conventional one while hardly causing problems with paper feeding failures and noises. <P>SOLUTION: The paper feeding roller 1 includes an inner layer 3 formed of a porous material having an Asker C type hardness of C10-C40, and an outer layer 2 formed of a porous material having an Asker C type hardness of C40-C70 and greater rubber hardness than the inner layer, and built up on the outer periphery of the inner layer to form an outer peripheral face 6 of the paper feeding roller. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a paper feed roller used for paper feed in an electrostatic copying machine, various printers, and the like.

  For example, various paper feed rollers are incorporated in a paper feed mechanism in devices such as an electrostatic copying machine, a laser printer, a plain paper facsimile machine, an ink jet printer, and an automatic cash dispenser (ATM). Examples of the paper feed roller include a paper feed roller, a transport roller, a platen roller, and a paper discharge roller that rotate while contacting paper (including a plastic film, etc.) and convey the paper by friction. It is done.

Conventionally, the paper feed roller is a single layer made of various rubbers such as natural rubber (NR), urethane rubber, ethylene-propylene-diene rubber (EPDM), polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber and the like. Non-porous rollers are generally used.
However, the roller has a problem that the surface becomes smooth due to wear when the number of sheets to be passed increases, and the friction coefficient is greatly reduced to easily cause a paper feed failure. There is also a problem that a phenomenon called so-called “squeal” tends to occur when the paper slides on the surface of the rubber roller having a reduced friction coefficient.

The paper feed roller has a multilayer structure of two or more layers including an inner layer and an outer layer that is laminated on the outer periphery of the inner layer and constitutes the outer peripheral surface of the paper feed roller, and by making the inner layer softer than the outer layer, In order to prevent the paper feed failure from occurring by increasing the contact area with the paper, and to prevent squealing (see Patent Documents 1 to 4, etc.).
However, in all of these patent documents, the outer layer constituting the outer peripheral surface of the roller is made of non-porous rubber like the conventional single-layer rubber roller. There is no change in the smoothing and the friction coefficient greatly decreasing, and it is not possible to reliably prevent the occurrence of paper feeding failure due to the decrease in the friction coefficient.

A paper feed roller has been proposed in which both the outer layer and the inner layer are formed of a rubber porous body, and the cell diameter of the porous body is smaller than that of the inner layer in the outer layer (Patent Document 5).
Even if the outer layer made of a porous body is worn, voids existing inside are exposed to the surface one after another, so that the surface is smoothed and the friction coefficient is not greatly reduced unlike the conventional non-porous outer layer. . Therefore, it is possible to suppress to some extent the occurrence of paper feeding failure due to a decrease in the friction coefficient.

However, the paper feed roller is formed by extruding unvulcanized rubber to which a foaming agent has been added into a cylindrical shape under predetermined conditions, and then vulcanizing under specific conditions, so that the degree of foaming around the outer periphery within one roller. Is adjusted to be smaller than the inside.
Therefore, it is not easy to strictly control the thicknesses of the outer layer and the inner layer, and the ratio of the thicknesses of both layers, and variations tend to occur. If variations occur, a two-layer structure is used, and the inner layer cell diameter is increased to soften the inner layer, thereby increasing the contact area with the paper described above and preventing paper feed defects. There is also a problem that the effect of preventing squealing is likely to vary.

Moreover, Patent Document 5 attempts to ensure wear resistance by reducing the cell diameter of the outer layer. However, considering that the inner layer is provided with appropriate flexibility, the outer layer is made of the same material and has only a different cell diameter. Sufficient rubber hardness cannot be imparted and sufficient abrasion resistance cannot be imparted.
That is, in Patent Document 5, it is preferable that the total Asker C-type hardness of the paper feed roller is C23 to C37. However, when the whole is made soft as described above, the rubber hardness of the outer layer can be made only to the same extent. For this reason, although depending on the thickness of the outer layer, the outer layer is worn away at an early stage and lost, which causes a problem that good paper feeding cannot be performed in a short period of time.

JP 2001-341862 A JP 2002-347972 A JP 2006-111401 A JP 2007-137539 A JP 2004-322421 A

  It is an object of the present invention to provide a paper feed roller that is less likely to cause problems such as paper feed failure and squealing and that can maintain good paper feed for a longer period of time.

The present invention is a paper feed roller, comprising an inner layer and an outer layer laminated on the outer periphery of the inner layer to constitute the outer peripheral surface of the paper feed roller, the inner layer has an Asker C-type hardness of C10 or more, The C40 or less porous body and the outer layer are made of a porous body having an Asker C-type hardness of C40 or more and C70 or less, and the inner layer has a rubber hardness smaller than that of the outer layer.
In the paper feed roller of the present invention, by forming the outer layer with a porous body, even if it is worn, voids existing inside are successively exposed to the surface to maintain the initial surface state, and the surface is smooth. It is possible to prevent the friction coefficient from significantly decreasing. In addition, since the outer layer is formed of a porous material having an Asker C-type hardness of C40 or higher, it is possible to improve wear resistance and prevent early wear and loss.

The inner layer is formed of a porous material having an Asker C-type hardness of C10 or more and C40 or less and a rubber hardness (Asker C-type hardness) smaller than that of the outer layer, and the outer layer has an Asker C-type hardness of C70. By forming with the following porous body, the flexibility of the entire paper feed roller can be increased and the contact area with the paper can be increased.
Therefore, according to the present invention, it is possible to provide a paper feed roller that is less likely to cause problems such as paper feed failure and squealing and that can maintain good paper feed for a longer period of time.

The inner layer and the outer layer are preferably laminated by fitting an inner layer formed separately into an outer layer formed in a cylindrical shape in advance. This makes it possible to provide a paper feed roller that always has a constant effect by strictly controlling the ratio of the thicknesses of both layers and suppressing variations in the effect of preventing the paper feed failure and squealing.
The two layers are preferably fixed to each other by forming the inner diameter of the outer layer smaller than the outer diameter of the inner layer and press-fitting the inner layer into the outer layer. Thereby, the two layers can be fixed to each other by the difference in diameter and elastic force between the two layers, and the number of materials and processes can be reduced.

  The two layers may be fixed to each other by bonding with an adhesive.

  According to the present invention, it is possible to provide a paper feed roller that is unlikely to cause problems such as poor paper feed and squealing and can maintain good paper feed for a longer period of time than before.

It is a perspective view which shows an example of embodiment of the paper feed roller of this invention.

FIG. 1 is a perspective view showing an example of an embodiment of a paper feed roller of the present invention.
With reference to FIG. 1, the paper feed roller 1 of this example is inserted into a cylindrical outer layer 2, a cylindrical inner layer 3 fitted in the outer layer 2, and a through hole 4 at the center of the inner layer 3. Shaft 5 is included. The outer peripheral surface 6 of the outer layer 2 is the surface of the paper feed roller 1 that contacts the paper.
The outer layer 2 is obtained by measurement under an environment of a temperature of 23 ± 1 ° C. and a humidity of 55 ± 1% by a measurement method defined in Japan Rubber Association Standard SRIS 0101 “Physical Test Method for Expanded Rubber”. Formed by a porous body having an Asker C-type hardness of C40 or more and C70 or less.

  The Asker C-type hardness of the outer layer 2 is limited to the above range. If it is less than C40, when the paper feeding is repeated, the outer layer 2 is worn out and lost early, and a good paper is obtained in a short period of time. This is because feeding cannot be performed. Further, if it exceeds C70, the effect of preventing the noise by increasing the flexibility of the paper feed roller 1 as a whole cannot be obtained. In addition, the Asker C-type hardness of the outer layer 2 is preferably C50 or more, and preferably C60 or less, even within the above range.

  Further, the inner layer 3 is a porous material having an Asker C-type hardness of C10 or more and C40 or less, which is obtained by measurement in the environment of the temperature 23 ± 1 ° C. and humidity 55 ± 1%, and having a rubber hardness smaller than that of the outer layer Formed by the body. That is, when the outer layer 2 is made of a porous body of C40 which is the lower limit value of Asker C-type hardness, the inner layer 3 is formed of a porous body of less than C40. Moreover, when the inner layer 3 consists of a porous body of C40 which is an upper limit value of Asker C type hardness, the outer layer 2 is formed of a porous body exceeding C40.

  The reason why the Asker C-type hardness of the inner layer 3 is limited to the above range is that the inner layer 3 becomes too soft if it is less than C10. This is because it becomes easier. Further, when C40 is exceeded, the effect of preventing the noise by increasing the flexibility of the entire paper feed roller 1 cannot be obtained. The Asker C-type hardness of the inner layer 3 is preferably C30 or less even within the above range.

  The outer layer 2 is made of, for example, rubber such as EPDM, urethane rubber, acrylonitrile-butadiene rubber (NBR), thermoplastic elastomer such as polyester-based thermoplastic elastomer, styrene-based thermoplastic elastomer, urethane-based thermoplastic elastomer, or soft such as polyethylene or polypropylene. It can form by 1 type, or 2 or more types, such as resin. In particular, the outer layer 2 is preferably formed of EPDM having excellent wear resistance and the like.

The inner layer 3 may be one or two of rubbers such as NBR, butyl rubber, styrene-butadiene rubber (SBR), NR, and urethane rubber, thermoplastic elastomers such as styrene-based thermoplastic elastomer, and soft resins such as polyethylene and polypropylene. It can be formed by more than seeds.
In particular, the inner layer 3 is preferably formed of a porous body of butyl rubber. Since butyl rubber is excellent in vibration absorption performance particularly in a room temperature (5-35 ° C.) region, it is possible to more reliably suppress squealing due to friction with paper.

The elastomer forming the outer layer 2 and the inner layer 3 is for vulcanizing the rubber when the elastomer is a vulcanized rubber, such as a foaming agent or water-soluble particles for making both layers porous. Vulcanizing agents, cross-linking agents, vulcanization accelerators, vulcanization acceleration aids, etc., and further fillers, reinforcing agents, oils, plasticizers, etc. may be appropriately selected according to the type of elastomer and the like. .
It is preferable that the outer layer 2 and the inner layer 3 are separately formed in a cylindrical shape, and the inner layer 3 is fitted into the outer layer 2 to laminate both layers to constitute the paper feed roller 1. Accordingly, the ratio of the thicknesses of the two layers can be strictly controlled to suppress variations in the effect of preventing the paper feed failure and squealing, and a paper feed roller that always has a constant effect can be provided.

Both layers are formed such that the inner diameter of the outer layer 2 is slightly smaller than the outer diameter of the inner layer 3, and the inner layer 3 is press-fitted into the outer layer 2 and is fixed to each other by the difference in diameter and elasticity between the two layers. It is preferable in reducing the number of materials used and the number of steps.
However, the outer layer 2 and the inner layer 2 may be fixed to each other by bonding with an adhesive.
In order to form both the layers separately in a cylindrical shape made of a porous body, various conventionally known methods can be employed. For example, the elastomer as a raw material is kneaded with various additives as necessary and then formed into a cylindrical shape. Further, when the elastomer is a vulcanizable rubber, it is vulcanized to form both layers. At the time, for example, in the case of vulcanizable rubber, simultaneously with the vulcanization, the foaming agent previously added to the elastomer is foamed to separately form the cylindrical outer layer 2 and the inner layer 3 made of a porous body. Can be formed. The outer layer 2 and the inner layer 3 can also be formed by elution of water-soluble particles such as sodium chloride previously added to the elastomer at any time after molding, for example, in the case of a vulcanizable rubber, after elution after vulcanization.

In order to adjust the Asker C-type hardness of the two layers within the above ranges, the porous structure (whether it is a continuous pore structure or an independent pore structure, etc.) is selected, or the porosity is adjusted. You can adjust it.
Further, an elastomer as a material may be selected, or two or more kinds of elastomers may be used in combination to adjust the blending ratio.

  For example, when the elastomer is a vulcanizable (crosslinkable) rubber, the type and molecular weight of the rubber (average molecular weight, molecular weight distribution, etc.), molecular structure (straight or branched), or rubber The degree of vulcanization (degree of crosslinking) may be adjusted. The amount of oil, plasticizer, reinforcing agent, filler, etc. may be adjusted. In order to adjust the degree of vulcanization, the type and amount of vulcanizing agent, cross-linking agent, vulcanization accelerator, vulcanization acceleration aid, etc. may be adjusted.

For example, EPDM may be adjusted for ethylene, propylene, and diene content, molecular weight (average molecular weight, molecular weight distribution, etc.), molecular structure (straight or branched, etc.), or vulcanization degree (crosslinking degree). .
The thermoplastic elastomer such as polyester-based thermoplastic elastomer and styrene-based thermoplastic elastomer may be adjusted in the type and length of the blocks forming the hard segment and the soft segment, or the ratio of the quantity segment.

In addition, as the elastomer, a thermoplastic elastomer and / or a thermoplastic resin and a vulcanizable rubber can be used in combination, and the rubber can be dynamically vulcanized by heating while kneading each of the above components. In such an elastomer, the types and blending ratios of the respective components may be adjusted.
In the outer layer 2 and the inner layer 3, the outer layer 2 is thin and the inner layer 3 is thick, which is effective for increasing the flexibility of the paper feed roller 1 and preventing noise, but the outer layer 2 is too thin. It is not good to be lost in a short period of time due to wear. Therefore, the ratio of the outer layer 2 and the inner layer 3 in the radial direction of the paper feed roller 1 (outer layer) / (inner layer) is (outer layer) / (inner layer) in the individual cylinder before the inner layer 3 is fitted to the outer layer 2. It is preferable that the ratio of the inner layer 3 is larger than 50/50, and it is more preferable that (outer layer) / (inner layer) = 50/50 to 20/80.

  Further, the overall outer diameter of the paper feed roller 1 in which the inner layer 3 is fitted to the outer layer 2 can be set as appropriate according to the structure of the apparatus in which the paper feed roller 1 is incorporated. In consideration of incorporating into the space provided and taking the contact area with the paper as large as possible when feeding the paper, it is preferably 15 mm or more and 35 mm or less, particularly 20 mm or more and 30 mm or less.

Further, the thicknesses of the outer layer 2 and the inner layer 3 constituting the paper feed roller 1 whose outer diameter is within the above range are such that the outer layer 2 is 1.0 mm or more in the individual cylinder before the inner layer 3 is fitted to the outer layer 2. It is preferably 5 mm or less, particularly 2.0 mm or more and 3.0 mm or less, and the inner layer 3 is preferably 2.0 mm or more and 4.5 mm or less, particularly 3.0 mm or more and 4.0 mm or less.
If the thickness of the outer layer 2 is less than the above range, the outer layer 2 may be lost due to wear in a short period of time and the inner layer 3 may be exposed. When the above range is exceeded, there is a possibility that the effect of preventing the noise by increasing the flexibility of the entire paper feed roller 1 may not be obtained.

If the thickness of the inner layer 3 is less than the above range, the effect of preventing the squealing by increasing the flexibility of the entire paper feed roller 1 may not be obtained. On the other hand, when the above range is exceeded, the entire paper feed roller 1 becomes too soft, and the contact pressure with respect to the paper is lowered, which may cause a paper feed failure.
The ratio of the opening of the gap exposed on the outer peripheral surface 6 of the paper feed roller 1, that is, the surface of the outer layer 2, per unit area of the surface (area ratio of the opening) is 10% or more and 40% or less. preferable.

If the area occupancy is less than 10%, the outer layer 2 is made of a porous body, and the voids existing inside are exposed to the surface one after another as described above to maintain the initial surface state. There is a possibility that the effect of preventing the surface from being smoothed and greatly reducing the friction coefficient may not be sufficiently obtained.
When the area occupancy exceeds 40%, the contact area of the paper feed roller 1 with the paper becomes small, and there is a possibility that a paper feed failure is likely to occur.

  The shaft 5 can be formed of, for example, metal, ceramic, resin, or the like.

<Preparation of outer layer I>
Each component shown in Table 1 was press vulcanized at 170 ° C. for 20 minutes to obtain a cylindrical body (cot) made of a porous body having an inner diameter φ20, an outer diameter φ25, and a length of 65 mm. Then, this cylindrical body was polished to an outer diameter of φ24 using a cylindrical grinder and then cut to a length of 30 mm to produce a cylindrical outer layer I made of the porous body. The Asker C-type hardness of the outer layer I was measured in an environment of a temperature of 23 ± 1 ° C. and a humidity of 55 ± 1% by the measurement method defined in SRIS 0101 “Physical test method of expanded rubber” described above. However, it was C37.

<Preparation of outer layer II>
As shown in Table 1, a cylindrical outer layer II made of a porous body having the same dimensions was produced in the same manner as the outer layer I except that the amount of paraffin oil was 20 parts by mass. When the Asker C-type hardness of the outer layer II was measured in the same manner, it was C40.
<Preparation of outer layer III>
As shown in Table 1, the same as the outer layer I except that the amount of silicon oxide was 15 parts by mass, no paraffin oil was added, and the amount of thermally expandable microcapsules was 5.5 parts by mass. A cylindrical outer layer III made of a porous body having a size was produced. When the Asker C-type hardness of the outer layer III was measured in the same manner, it was C50.

Details of each component in Table 1 are as follows.
(Elastomer)
EPDM: Espren (registered trademark) 670F manufactured by Sumitomo Chemical Co., Ltd.
(Reinforcing agent, filler)
Silicon oxide: Nipsil (registered trademark) VN3 manufactured by Tosoh Silica Corporation
Calcium carbonate: BF300 manufactured by Bihoku Powder Chemical Co., Ltd.
Titanium oxide: Trade name Kronos KR380 manufactured by Titanium Industry Co., Ltd.
Carbon Black: Tokai Carbon Co., Ltd. trade name Seast 3
(oil)
Paraffin oil: Diana (registered trademark) process oil PW-380 manufactured by Idemitsu Kosan Co., Ltd.
(Vulcanizing additive)
Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Tsubaki, a product name manufactured by NOF Corporation Powdered sulfur: Tsurumi Chemical Co., Ltd. TET: Tetraethylthiuram disulfide [Ouchi Shinsei Chemical Industry ( Noxeller (registered trademark) TET made by Co., Ltd.]
DM: Di-2-benzothiazolyl disulfide [Noxeller (registered trademark) DM manufactured by Ouchi Shinsei Chemical Co., Ltd.]
(Foaming agent)
Thermally expandable microcapsules: Matsumoto Microsphere (registered trademark) F170D from Matsumoto Yushi Seiyaku Co., Ltd.
<Preparation of outer layer IV>
Among the components shown in Table 2, the components excluding the heat-expandable microcapsules were kneaded at 180 ° C. using a twin screw extruder (HTM38 manufactured by Ipec Co.) to dynamically crosslink EPDM, and then pelletized. A pellet of a thermoplastic elastomer composition was obtained.

  Next, the pellets and the heat-expandable microcapsules are mixed, kneaded at 180 ° C. using a φ50 single screw extruder (manufactured by Kasamatsu Chemical Research Laboratory), extruded into a cylindrical shape, and thermally expandable microcapsules. The capsule was thermally expanded to obtain a cylindrical body made of a porous body having an inner diameter of φ20 and an outer diameter of φ25. Next, this cylindrical body was polished to an outer diameter of φ24 using a cylindrical grinder and then cut to a length of 30 mm to produce a cylindrical outer layer IV made of the porous body. When the Asker C-type hardness of the outer layer IV was measured in the same manner, it was C59.

The EPDM, paraffin oil, zinc oxide, and thermally expandable microcapsules in Table 1 were the same as those used in the outer layer I. Other ingredients are as follows.
Thermoplastic elastomer: polystyrene-poly (ethylene / propylene) -polystyrene [Septon (registered trademark) 4077 manufactured by Kuraray Co., Ltd.]
Thermoplastic resin: Polypropylene [Novatech (registered trademark) PP BC6 manufactured by Nippon Polypro Co., Ltd.]
Resin cross-linking agent: Brominated alkylphenol-formaldehyde resin [Tactrol (registered trademark) 250-III manufactured by Taoka Chemical Co., Ltd.]
<Preparation of outer layer V>
Each component shown in Table 3 was press vulcanized at 170 ° C. for 20 minutes to obtain a cylindrical body (cot) made of a porous body having an inner diameter φ20, an outer diameter φ25, and a length of 65 mm. Next, this cylindrical body was polished to an outer diameter of φ24 using a cylindrical grinder and then cut to a length of 30 mm to produce a cylindrical outer layer V made of the porous body. When the Asker C-type hardness of the outer layer V was measured in the same manner, it was C70.

<Preparation of outer layer VI>
As shown in Table 3, a cylindrical outer layer VI made of a porous body having the same dimensions was produced in the same manner as the outer layer V except that the amount of the thermally expandable microcapsule was 2 parts by mass. The Asker C-type hardness of the outer layer VI was measured in the same manner as C73.

The EPDM in Table 3 is as follows.
EPDM: Esprene (registered trademark) 505A manufactured by Sumitomo Chemical Co., Ltd.
The other components were the same as those used in the outer layer I.
<Preparation of inner layer A>
Each component shown in Table 4 is extruded into a cylindrical shape from a rubber kneader and then vulcanized in a vulcanizing can at 160 ° C. for 30 minutes and foamed with a chemical foaming agent. The cylindrical inner layer A made of a porous body was produced by press-fitting the shaft and polishing it to an outer diameter of φ21 using a cylindrical grinder and cutting it to a length of 30 mm. It was C7 when the Asker C type hardness of the inner layer A was measured in the same manner.

<Preparation of inner layer B>
As shown in Table 4, a cylindrical inner layer B made of a porous body having the same dimensions was produced in the same manner as the inner layer A except that the amount of paraffin oil was 45 parts by mass. When the Asker C-type hardness of the inner layer B was measured in the same manner, it was C10.
<Preparation of inner layer C>
As shown in Table 4, a cylindrical inner layer C made of a porous body having the same dimensions was used in the same manner as the inner layer A except that no paraffin oil was added and the amount of the chemical foaming agent was 3.5 parts by mass. Produced. The Asker C-type hardness of the inner layer C was measured in the same manner as C30.

The butyl rubber, TBT-N, and chemical blowing agent in Table 4 are as follows.
Butyl rubber: Butyl 268 manufactured by ExxonMobil
TBT-N: Tetrabutylthiuram disulfide [Noxeller (registered trademark) TBT-N manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Chemical foaming agent: Neocerbon (registered trademark) N # 1000SW manufactured by Eiwa Chemical Industry Co., Ltd.
The other components were the same as those used in the outer layer I.

<Preparation of inner layer D>
Each component shown in Table 5 was extruded into a cylindrical shape from a rubber kneader and then vulcanized in a vulcanizing can at 160 ° C. for 30 minutes, and the thermally expandable microcapsule was thermally expanded. A cylindrical inner layer D made of a porous material was produced by press-fitting the shaft for machining and polishing it to an outer diameter of φ21 using a cylindrical grinder and cutting it to a length of 30 mm. The Asker C-type hardness of the inner layer D was measured in the same manner as C40.

<Preparation of inner layer E>
As shown in Table 5, a cylindrical inner layer E made of a porous body having the same dimensions was produced in the same manner as the inner layer D, except that the amount of thermally expandable microcapsules was 5.5 parts by mass. When the Asker C-type hardness of the inner layer E was measured in the same manner, it was C43.

Each component in Table 5 was the same as that used in the outer layer I.
<Example 1>
After a φ14 resin shaft (dedicated resin core) was press-fitted into the through hole of the inner layer C, the inner layer C was press-fitted into the outer layer II to manufacture a paper feed roller.
<Examples 2 to 4, Comparative Examples 1 and 2>
A paper feed roller was manufactured in the same manner as in Example 1 except that the inner layer C and the outer layer shown in Table 6 were combined.

<Example 5>
After a φ14 resin shaft (dedicated resin core) was press-fitted into the through hole of the inner layer B, the inner layer B was press-fitted into the outer layer III to manufacture a paper feed roller.
<Example 6, Comparative Examples 3 and 4>
A paper feed roller was manufactured in the same manner as in Example 5 except that the outer layer III was combined with the inner layer shown in Table 7.

About the paper feed roller of each said Example and a comparative example, the following each test was done and the characteristic was evaluated.
<Friction coefficient test and paper passing status evaluation>
A vertical feed load of 340 gf was applied to a paper feed roller of each example and comparative example placed on a Teflon (registered trademark) plate having a width of 60 mm and a length of 120 mm (GF-500 manufactured by Canon Inc.). When the paper feed roller is rotated at a peripheral speed of 105 mm / sec in a state where it is pressed while applying pressure, a conveyance force F applied to the paper is measured using a load cell, and the formula (1):
Friction coefficient = F / 340 (1)
Thus, the friction coefficient was obtained. Measurement is performed immediately after the manufacture of the paper feed roller (initial), and the paper feed roller is incorporated into a laser printer HP Laser Jet 4300n manufactured by Hewlett-Packard Japan Co., Ltd. The same paper as described above [GF-500 manufactured by Canon Inc. Was carried out after passing 50,000 sheets (after endurance). Also, by observing the passing condition at the time of passing the paper, if the paper feeding failure occurred in the middle, x evaluated that the paper feeding failure did not occur even after passing 50,000 sheets did. Also, in the case where paper feeding failure occurred midway, the friction coefficient after durability could not be measured.

<Squeal evaluation>
In each example, the paper feeding roller of the comparative example was mounted on the same laser printer as described above, and x was generated when 1000 sheets of the same paper (GF-500 manufactured by Canon Inc.) was passed, Those that did not occur were evaluated as ◯.
The above results are shown in Tables 6 and 7.

  From the results of Comparative Example 1 in Table 6, even if the inner layer has an Asker C-type hardness of C10 or more and C40 or less, the outer layer has an insufficient durability if the Asker C-type hardness of the outer layer is less than C40. Thus, it was found that the paper was worn out and lost at an early stage due to continuous paper feeding, resulting in poor paper feeding. Further, from the result of Comparative Example 2, it was found that when the Asker C-type hardness of the outer layer exceeds C70, the overall flexibility of the paper feed roller is lowered and squealing occurs.

  Also, from the results of Comparative Example 3 in Table 7, even if the outer layer Asker C type hardness is in the range of C40 or more and C70 or less, the inner layer is too soft if the inner layer Asker C type hardness is less than C10, It has been found that the contact pressure of the paper feed roller with respect to the paper decreases, resulting in poor paper feed. From the result of Comparative Example 4, it was found that when the Asker C-type hardness of the inner layer exceeds C40, the overall flexibility of the paper feed roller 1 is reduced and squealing occurs.

  On the other hand, from the results of Examples 1 to 6, the outer layer has an Asker C-type hardness of C40 or more and C70 or less, and the inner layer has an Asker C-type hardness of C10 or more and C40 or less. If the Asker C-type hardness of the outer layer is increased from the inner layer to the outer layer, it is possible to prevent problems such as poor paper feeding and squealing over a longer period than before, and maintain good paper feeding. I understood.

DESCRIPTION OF SYMBOLS 1 Paper feed roller 2 Outer layer 3 Inner layer 4 Through-hole 5 Shaft 6 Outer surface

Claims (4)

  A paper feed roller comprising an inner layer and an outer layer laminated on an outer periphery of the inner layer to constitute an outer peripheral surface of the paper feed roller, wherein the inner layer is a porous material having an Asker C-type hardness of C10 or more and C40 or less. The material body and the outer layer are made of a porous body having an Asker C-type hardness of C40 or more and C70 or less, and the inner layer has a rubber hardness smaller than that of the outer layer.   The paper feed roller according to claim 1, wherein the two layers are laminated by fitting an inner layer formed separately into an outer layer formed in a cylindrical shape in advance.   The paper feed roller according to claim 2, wherein an inner diameter of the outer layer is formed smaller than an outer diameter of the inner layer, and the inner layer is press-fitted into the outer layer.   The paper feed roller according to claim 1, wherein the inner layer and the outer layer are bonded by an adhesive.

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