JP2010046814A - Mold for molding elastic roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a change of an outer diameter generated in a longitudinal direction of a rubber roller formed by injecting a rubber material into a mold for molding. <P>SOLUTION: The mold for molding has: a pipe mold body 2 with a cylindrical inner surface; and a pair of end dowels 1 and 3 which are fitted into both ends of the pipe mold body 2 to support a roller shaft 4 arranged in the pipe mold body 2, respectively. A hole 3a for injecting is provided in the end dowel 3 in an injecting side of the rubber material. An air vent 1b to discharge air in a cavity and not to leak the injected rubber material is formed in the end dowel 1 in a non-injecting side. In the mold for molding of the rubber roller molded by hardening the rubber material after injecting the rubber material into the cavity, by arranging the roller shaft 4 in the cavity, the cylindrical inner surface of the pipe mold body 2 is formed in a taper shape in which an inside diameter becomes gradually smaller toward the non-injecting side from the injecting side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, when manufacturing various elastic rollers used for OA (office automation) equipment such as printers and copiers, a liquid elastic material is injected into a molding die and cured to be molded. The present invention relates to a mold for elastic rollers.

  Generally, a rubber roller manufactured by injecting a rubber material as an elastic material into a molding die has at least three cylindrical pipe dies and a pair of end pieces fitted to both ends of the pipe dies. It is provided with a member. One of the pair of end pieces is provided with at least one injection port for injecting a rubber material. Further, at the time of molding the rubber roller, the molding die is heated up to the curing temperature of the rubber material by a hot air furnace or a heating plate cut out in a die shape. When liquid rubber is used as the rubber material, it is necessary to prevent bubbles from being mixed during material injection, that is, so-called bubble biting. For this reason, generally, the molding die is placed in an upright state, the rubber material is injected from the lower side of the molding die, and the air in the cavity is provided with an air escape and a non-injection end piece. Escape from material overflow hole. Then, the rubber material is finally overflowed and molded so as not to cause insufficient injection due to dimensional accuracy of the molding die and the shaft body and variations in the injection of the rubber material.

  However, this method has a problem that the yield of the rubber material is lowered. For this reason, there is known a molding method in which the end piece on the non-injection side is configured in a closed system so that air in the cavity is released and the injected rubber material is not released (for example, Patent Document 1). However, in the case of this method, the rubber material does not leak from the non-injection side due to thermal expansion or the like during heat curing, but since the end piece on the injection side is an open system, the injected material is injected. Leak slightly outside the mold from the end piece on the side. Therefore, the outer diameter of the molded rubber roller tends to be larger on the non-injection side than on the injection side. In today's high-definition office automation equipment such as copiers and printers, the difference in the outer diameter of both ends of the rubber roller causes a defect that causes image unevenness and the like, and it is preferable to keep it below 10 μm. Is no longer meeting current requirements.

On the other hand, a method has been proposed in which the temperature of the heating plate that heats the mold when the rubber roller is molded is changed with respect to the longitudinal direction, and the difference in the longitudinal direction of the outer diameter is absorbed by thermal contraction (for example, Patent Document 2).
JP 2007-185857 A JP-A-11-129353

  However, in the method of Patent Document 2, since the thermal expansion of the heating plate itself is different in the longitudinal direction, the heating plate itself may be warped. Even when a predetermined temperature distribution is applied to the heating plate, the temperature difference with respect to the longitudinal direction of the molding die is reduced by heat conduction, so it is necessary to set the temperature difference with respect to the longitudinal direction of the heating plate to be even larger. Therefore, there is a high possibility that the heating panel will be warped. There is also a method in which the heating panel is divided into a plurality of parts according to the temperature setting distribution in the longitudinal direction in order to prevent the heating panel from warping. However, when the heating plate is divided into a plurality of parts, the molding die itself thermally expands non-uniformly in the longitudinal direction, so that the molding die itself may be bent.

  In addition, when a temperature distribution is given to the heating panel, it is necessary to provide a temperature measuring element and a temperature adjustment mechanism for each temperature according to the temperature setting distribution in order to accurately control the temperature. This leads to an increase in cost. In such a situation, further improvement of the roller mold has been desired.

  Therefore, the present invention provides a molding die for an elastic roller that can reduce a change in outer diameter with respect to the longitudinal direction of the elastic roller by forming the cylindrical inner surface of the pipe die body into a tapered shape. The purpose is to do.

  In order to achieve the above-mentioned object, a molding die for an elastic roller according to the present invention is a pipe die that supports a pipe die body having a cylindrical inner surface and a shaft body disposed in the pipe die body. A pair of end pieces that are respectively fitted to both ends of the main body, and an injection hole is provided in the end piece on the injection side of the elastic material, and the end piece on the non-injection side is provided in the cavity The air vent part that releases the air and does not leak the elastic material injected into the cavity is provided, the shaft is placed in the cavity, and after the elastic material is injected into the cavity, the elastic material is cured and molded In the molding die for the elastic roller, the cylindrical inner surface of the pipe mold body is formed in a tapered shape in which the inner diameter gradually decreases from the injection side toward the non-injection side.

  According to the present invention, since it is not necessary to set a temperature gradient in the heating panel, it is possible to prevent the heating panel from being warped due to the temperature gradient. Further, according to the present invention, it is possible to suppress a difference in outer diameter that occurs in the longitudinal direction of the elastic roller due to the structure of the end piece on the injection side and the non-injection side.

  Hereinafter, specific embodiments according to the present invention will be described with reference to the drawings.

  The molding die of the present invention includes a pipe mold body having a cylindrical inner surface, and a pair of ends that are respectively fitted to both ends of the pipe mold body while supporting a roller shaft disposed in the pipe mold body. It has a part piece. The end piece on the injection side is provided with an injection hole. The end piece on the non-injection side is provided with an air vent that allows air in the cavity to escape and does not leak the injected rubber material as the elastic material. In this molding die, a roller shaft is disposed in the cavity, and after the rubber material is injected into the cavity, the rubber material is cured to form a rubber roller as an elastic roller. The cylindrical inner surface of the pipe mold body is formed in a tapered shape in which the inner diameter gradually decreases from the injection side toward the non-injection side.

  Next, the present invention will be described in more detail with reference to preferred embodiments.

  The inner diameter and length of the pipe mold main body 2 are not particularly limited, but in the case of a rubber roller used in an image forming apparatus such as a general electrophotographic apparatus, for example, those corresponding to A4 paper or A3 paper size are mainly used. It is. The inner diameter and length of such a rubber roller is about φ8 mm to φ25 mm, and the length is about 210 mm to 250 mm for A4 paper size, and about 300 mm to 350 mm for A3 size paper. is there.

  As a method of processing the cylindrical inner surface of the pipe mold main body 2 into a tapered shape, for example, the cylindrical inner surface of the pipe mold main body 2 has a tapered inner surface that is several μm to several tens μm smaller than a desired dimension. After being processed in advance, the honing machine is used. There is a method of finishing the taper shape of a desired dimension by adjusting the amount of widening of the grindstone in conjunction with the pushing stroke of the honing machine.

  For example, a vertical honing machine is used, and the pipe mold body 2 is set up on the honing machine. For example, the cylindrical inner surface of the pipe mold body 2 is tapered from the upper side toward the lower side. A method for forming a shape is mentioned. In this case, a grindstone is inserted from the upper side of the pipe mold body 2, honing is performed, and as the stroke of the grindstone is advanced downward, the widening amount of the grindstone is gradually increased in conjunction with the stroke. Thus, a taper shape having a desired dimension is finished. Conversely, there is a method of forming a tapered shape on the cylindrical inner surface of the pipe mold body 2 so that the inner diameter gradually decreases from the upper side to the lower side. In this case, a grindstone is inserted from the upper side of the pipe mold body 2 to perform honing, and as the stroke of the grindstone is advanced downward, the widening amount of the grindstone is gradually reduced in conjunction with the stroke. Finish the taper shape with the desired dimensions.

  Further, as another processing method, a plurality of straight portions having a step of about 2 μm to 7 μm in diameter are formed on the cylindrical inner surface of the pipe mold body 2 by lathe processing, and a predetermined inner diameter difference is made with respect to the longitudinal direction. The method of attaching in advance is mentioned. And the taper shape of a desired dimension is formed by adjusting the amount of widening of the grindstone of a honing machine according to the internal diameter of a straight part, and connecting a level | step-difference part smoothly by a honing process.

  At this time, the inner diameter difference of the cylindrical inner surface of the pipe mold body 2 needs to be determined in consideration of heat shrinkage, curing shrinkage, etc., based on the outer diameter difference of the rubber roller formed by the straight pipe mold body. There is. However, when the inner diameter difference is less than 5 μm, the inner diameter difference falls within the range of variations in processing accuracy, or the difference in image quality using an actually molded rubber roller is less likely to appear. The effect obtained by this will be reduced. For this reason, the pipe mold body preferably has a difference of 5 μm or more between the inner diameter on the injection side and the inner diameter on the non-injection side on the cylindrical inner surface.

  Also, a molding die in which the end piece on the injection side is an open system and the end piece on the non-injection side is a closed system, and the cylindrical inner surface of the pipe mold body 2 is formed in a straight shape. When a mold is used, material leakage due to thermal expansion may occur on the injection side. For this reason, the rubber roller molded by such a molding die generally has a tendency that the outer diameter on the non-injection side is relatively larger than the outer diameter on the injection side. The rate at which the outer diameter increases depends on the coefficient of thermal expansion of the material, the molding temperature, etc., but the maximum is about 0.5%. For this reason, the inner diameter of the pipe mold main body 2 of the molding die is reduced by about 0.5% at the maximum on the non-injection side with respect to the injection side having a large inner diameter as a reference (100%). A rubber roller in which the difference in outer diameter of the rubber roller is suppressed to 10 μm or less can be obtained.

  As a method of molding a rubber roller, in general, a roller shaft body 4 is provided in a molding die having a pipe die body 2 and a pair of end pieces 1 and 3 fitted to both ends of the pipe die body 2. The rubber material is injected into the cavity from one end piece 3.

  The end piece 3 on the injection side is provided with at least one hole 3a for injecting a rubber material. Further, the end piece 1 on the non-injection side is a closed system having an air vent part 1b that escapes air in the cavity but does not leak the injected rubber material, and is provided with at least one air vent part 1b. . The air vent 1b is a hole provided through the non-injection side end piece 1 or a groove formed in the outer periphery of the non-injection side end piece 1.

  After injecting the rubber material, after separating the material injection nozzle 12 from the molding die, the molding die is heated in a hot air oven or a heating block 6a, 6b, 6c or the like sandwiching the molding die, The rubber material is cured. After the rubber material is heat-cured, generally, after cooling the molding die, the rubber roller is taken out from the molding die.

The air vent 1b provided in the end piece 1 on the non-injection side has a depth of 0 in a hole having a diameter of 0.2 mm or less or a fitting portion of the end piece 1 on the non-injection side, depending on the rubber material to be injected. It is formed by cutting into a groove shape of about .05 mm. The air vent 1b can escape only the air in the cavity without leaking the injected rubber material. Also, within the cross-sectional area perpendicular to the ventilation direction in the grooves or holes forming the air vent portion 1b is of the order of 0.01mm ² ~0.05mm ^2, preferably within the range of about 0.01mm ² ~0.03mm ² is there. The number of locations where the air vent 1b is provided functions as long as there is at least one. However, in consideration of the workability of the molding die, the number is preferably 4 or less.

  As a rubber material for molding the rubber roller, any of natural rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, ethylene-propylene rubber, butyl rubber, silicone rubber, urethane rubber, fluorine rubber, chlorine rubber, etc. may be used. good. Moreover, as an elastic material, as needed, for example, a conductive material, a filler, a curing agent, a catalyst, and the like may be appropriately dispersed and used.

  Examples of the conductive material that can be dispersed in the elastic material include carbons such as carbon black and conductive carbon, and metal powder, conductive fiber, or semiconductive metal oxide powder such as tin oxide. Any of these may be used. The electric resistance can be appropriately adjusted depending on the content of the conductive material.

  An embodiment in which the rubber roller molding die of the present invention is applied to molding of a developing roller for an electrophotographic apparatus will be described. In forming the developing roller, the pipe has a cylindrical mold body 2 having a cylindrical inner surface, and a pair of end pieces 1 and 3 that are fitted to both ends of the pipe mold body 2 and support the roller shaft body 4. A mold was prepared. The material of the molding die is CENA1, a prehardened steel manufactured by Hitachi Metals.

As an example, the inner surface of the pipe mold body 2 of the molding die is formed so that the inner diameter on the injection side is φ16.34 mm, the inner diameter on the non-injection side is φ16.32 mm, and the length of the cylindrical portion is 240 mm. The formed mold was used. At this time, the inner diameter difference of the cylindrical inner surface is 20 μm in diameter, and the inner diameter difference is 0.12% based on the injection side having a large inner diameter. The end piece 3 on the injection side is provided with eight holes of φ1.8 mm as injection holes 3a. Further, in the end piece 1 on the non-injection side, grooves as an air vent part 1b are formed by being cut at a depth of 0.05 mm at four places of the fitting part with the pipe mold body 2. The air in the cavity was formed to escape and not to leak the injected rubber material. At this time, the cross-sectional area of the groove forming the air escape portion 1b is 0.023 mm ² . The outer diameters of the pipe mold body 2 and the pair of end pieces 1 and 3 are all unified to 26 mm.

  In the developing roller molding process, as shown in FIGS. 4 and 5, the above-described molding die is supported by the die receiver 10 and the die holder 11. In the molding process, a rubber material is injected into the molding die using an injection nozzle 12, an injection valve 13, an injection syringe 14, an injection motor 15, a static mixer 16, a mixing block 17, a material pump 18, and the like. Is called.

  First, after setting the roller shaft 4 (made of free cutting steel SUM24L) having an outer diameter of φ8 mm × length of 260 mm in the cavity of the molding die, the molding die is formed into a die shape as shown in FIG. It was sandwiched between two punched duralumin heating blocks 6 and preheated for 3 minutes. Subsequently, 37 cc of a two-component mixed thermosetting silicone rubber material containing conductive carbon was injected from the end piece 3 on the injection side, and the silicone rubber material was heated for 3 minutes to be cured. At this time, the heating block 6 made of duralumin is divided into three in the longitudinal direction, and a heater 7 and a temperature measuring body 8 are provided in each heating block 6, and the heating temperature is arbitrarily set in each heating block 6. It is configured to be configurable. Moreover, about the heating block 6 made from duralumin, all the temperature settings of the three heating blocks 6 of the injection | pouring side block 6c, the center part block 6b, and the non-injection side block 6a were set to 115 degreeC.

  After the rubber material is cured, the molding die is taken out of the heating block 6 made of duralumin, cut into the shape of the molding die, and molded by the two duralumin cooling blocks in which cooling water adjusted to 20 ° C circulates. The mold was sandwiched for 3 minutes to cool the mold. After cooling the molding die, the molded developing roller was taken out.

  In addition, the inner diameter difference when the injection side having a large inner diameter is set as a reference is 0.5% or less as an application range of the present embodiment, but depending on the roller length, the material injection pressure, the temperature of the heating block, and the like, This is an experimentally controllable range. That is, when the injection pressure of the rubber material is increased, the pressure difference between the injection side and the non-injection side when the injection nozzle 12 is removed becomes higher, so that the inner diameter of the pipe mold body 2 on the injection side and the non-injection side is increased. The difference needs to be further increased, and the inner diameter difference (%) takes a larger value than in this embodiment. Further, when the heating temperature of the heating block 6 is higher than that of the present embodiment, material leakage due to the influence of thermal expansion becomes large. For this reason, in this case, correction is made in the direction of increasing the inner diameter difference of the pipe mold body. In this way, when considering the embodiment, the inner diameter difference considered to be compatible is limited to 0.5%.

  As a comparative example, a molding die in which the inner surface shape of the pipe die body 2a of the molding die was formed into a straight shape with a diameter of 16.34 mm was used. Further, the outer diameter of the pipe mold body 2a was φ26 mm as in the first embodiment, and the length of the cylindrical portion was 240 mm as in the first embodiment. In addition, as the end piece 3 on the injection side and the end piece 1 on the non-injection side, those having the same shape as in Example 1 were used. Further, the temperature setting of the heating block 6 made of duralumin was set to 115 ° C. for the three blocks 6a, 6b and 6c in the same manner as in Example 1. Other conditions such as the preheating time of the molding die, the injection amount of the rubber material, the curing time of the developing roller, and the cooling conditions are all the same as those in the first embodiment.

  As a reference example, a molding die in which the inner surface shape of the pipe die body 2a of the same molding die as that of the comparative example is formed in a straight shape having a diameter of 16.34 mm was used. Moreover, the temperature setting of the heating block 6 made from duralumin was set to 115 ° C. for the injection side block 6c and the central block 6b, and the non-injection side block 6a was set to 120 ° C. Further, the outer diameter of the pipe mold body 2a is set to 26 mm as in the first embodiment, and the end piece 3 on the injection side of the rubber material and the end piece 1 on the non-injection side are of the same shape as in the embodiment. Using. Other conditions such as the preheating time of the molding die, the injection amount of the rubber material, the curing time of the developing roller, and the cooling conditions are all the same as in the embodiment.

  The outer diameters of the developing rollers respectively molded in these examples, comparative examples, and reference examples were measured using an outer diameter measuring device LS-7000 (sensor head unit LS-7030M) manufactured by Keyence Corporation. As measurement points of the outer diameter of the developing roller, five points of 55 mm and 110 mm from the central portion and the center of the developing roller were measured, and the outer diameter differences were compared.

  As shown in FIG. 6, the outer diameter of the developing roller 5 is D1, D2, D3, D4, and D5 in order from the injection side for convenience, and Table 1 shows the measurement results of the outer diameter at each point. As a developing roller for an electrophotographic apparatus with high definition in recent years, the outer diameter difference in the longitudinal direction is preferably 10 μm or less, and in this embodiment, a non-defective product having an outer diameter difference of 10 μm or less is used. OK).

  The developing roller formed in the embodiment has an outer diameter difference of 3 μm between the injection side D1 and the non-injection side D5, which is almost straight, and the difference between the maximum diameter and the minimum diameter is also 5 μm or less. There was a difference in the outer diameter within the range where there was no problem as a product.

  On the other hand, in the molding die of the comparative example, the end piece on the non-injection side is a closed system, while the end piece on the injection side becomes an open system by removing the injection nozzle after the injection of the rubber material, and so on. Caused leakage of the rubber material on the injection side. For this reason, in the developing roller molded in the comparative example, the outer diameter of the non-injection side D5 is about 14 μm larger than that of the injection side D1.

  That is, according to the embodiment, the outer diameter of the non-injection-side rubber roller that occurs in the comparative example is increased by gradually reducing the inner diameter of the cylindrical inner surface of the pipe mold body toward the non-injection-side. As a result, a developing roller having a substantially straight shape could be obtained.

  Since the reference example corresponds to a supplementary test that has been performed in the prior art, a desirable result can be obtained as the dimension of the developing roller. In the reference example, since the heat shrinkage was increased by increasing the temperature of the heating block on the non-injection side, the phenomenon that the outer diameter of the injection side of the rubber roller was reduced due to the leakage of the rubber material as described in the comparative example was solved. It was done. Therefore, the rubber roller molded in the reference example is reduced so that the outer diameter of the non-injection side D5 is close to a desired dimension, and the difference in outer diameter between the injection side D1 and the non-injection side D5 is 8 μm. It settled in the level without a problem. However, the reference example still has a problem relating to the generation of distortion due to the setting of the temperature difference of the heating block.

From the above, in the embodiment, an almost straight rubber roller can be formed by forming the inner diameter of the pipe mold body into a taper shape of about 10 μm to 20 μm without giving a temperature distribution to the heating block. did it. Therefore, in the example, the outer diameter difference could be suppressed to 10 μm or less as in the case where the temperature distribution was given to the heating block.

It is sectional drawing which shows the metal mold | die used in the Example. It is sectional drawing which shows the metal mold | die used by the comparative example and the reference example. It is a perspective view which shows the edge part piece of the non-injection side used by the Example, the comparative example, and the reference example. It is a perspective view which shows the heating block used by the Example, the comparative example, and the reference example. It is a schematic diagram which shows the shaping | molding apparatus of the developing roller used by the Example, the comparative example, and the reference example. It is a side view which shows the measuring point of the outer diameter of the developing roller shape | molded by the Example, the comparative example, and the reference example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 End piece on the non-injection side 1b Air vent part 2 Pipe mold main body 3 End piece on the injection side 3a Hole for injection 4 Roller shaft

Claims (5)

A pipe mold body having a cylindrical inner surface, and a pair of end pieces that are respectively fitted to both ends of the pipe mold body to support a shaft body disposed in the pipe mold body, The end piece on the injection side of the elastic material is provided with an injection hole, and the end piece on the non-injection side releases air in the cavity and does not leak the elastic material injected into the cavity. In the molding die of the elastic roller, the shaft body is disposed in the cavity, and the elastic material is cured after being injected into the cavity.
A molding die for an elastic roller, wherein the cylindrical inner surface of the pipe die body is formed in a tapered shape in which an inner diameter gradually decreases from the injection side toward the non-injection side.   In the pipe mold main body, the difference between the inner diameter on the injection side and the inner diameter on the non-injection side on the cylindrical inner surface is 5 μm or more, and the difference is 0.5% or less based on the inner diameter on the injection side. A molding die for an elastic roller according to claim 1. ^2. The molding die for an elastic roller according to claim 1, wherein a cross-sectional area of the air vent part is in a range of 0.01 mm ² to 0.05 mm ² , and the number of places provided with the air vent part is 4 or less. .   4. The air vent according to claim 1, wherein the air vent is a hole formed through the end piece on the non-injection side or a groove formed in an outer peripheral portion of the end piece on the non-injection side. 2. A molding die for an elastic roller according to item 1.   The elastic roller molding die according to any one of claims 1 to 4, wherein the elastic roller is a rubber roller used in an electrophotographic apparatus.

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