JP2005144683A - Mold for molding elastic roller and molding method of elastic roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for efficiently and stably molding an elastic roller enhanced in outer diameter precision and outer diameter deflection precision, and a molding method of the elastic roller. <P>SOLUTION: A cylindrical mold and a piece mold are provided and the holding recessed part 8 of a core is provided to the piece mold. A dividing surface 10 for dividing the piece mold into two piece mold pieces 11 and 12 is provided to the piece mold in a direction traversing the depth direction of the holding recessed part 8. A mounting part 17 in which an O-ring is fitted is provided to the piece mold piece 11 so as to surround the holding recessed part 8. The mounting part 17 is slightly narrower than the O-ring and the O-ring is formed so that a part thereof is protruded when the O-ring is mounted so as to be freely brought into contact with the periphery of the core under pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a molding die for an elastic roller used for conveying / transferring colorants, printing paper, and the like, and a method for molding an elastic roller using the same, for example, an electrostatic roller formed on a latent image carrier. The present invention relates to a mold that can be particularly preferably used for forming a developing elastic roller used in a developing device for visualizing a latent image, and a method for forming an elastic roller using the same.

  There are several image forming methods. One of the general-purpose methods is an electrophotographic method. The electrophotographic method is a mainstream method for developing devices such as a copy, a printer, and a facsimile. In this method, various elastic rollers are used around the photosensitive drum which is the center of image formation.

  In the electrophotographic system, image quality and full color have been improved. Increasing the image quality has increased the tendency to make the particle size of the toner finer.

  Higher image quality and finer particles require high adhesion accuracy of the toner layer on the photosensitive drum, and on the other hand, lowering of the contact pressure on the photosensitive drum by the developing roller is required. In order to satisfy a low contact pressure and high adhesion accuracy of the toner layer, the developing roller is required to have a cylindrical shape with an ideal balance. The degree of uniformity of the cylindrical shape can be quantified by the concept of outer diameter accuracy and outer diameter deflection accuracy. The developing roller uniformly transfers the frictionally charged toner on the photosensitive drum in a thin layer. The developing roller is fatal if there is even a slight distortion in the central axis. Actually, every time the electrophotographic process is repeated, density unevenness and white streaks occur in the obtained image. In order to level the surface of the roller, the roller is molded and shaped, and then the obtained molded product is usually polished to adjust the dimensions.

  In the polishing operation, each molded roller is individually processed. Polishing is not an easy operation.

In order to improve the outer diameter accuracy and outer diameter runout accuracy of the developing roller, as one method, a resin ring having a high linear expansion coefficient is provided on the inner surface of the piece mold, and the core is utilized by utilizing the difference in thermal expansion from the piece metal. There is a method of centering gold (see Patent Document 1). FIG. 7 is a sectional view showing the conventional method. The cylindrical mold 1 and the frame molds 4 and 5 for closing both open ends 2 and 3 of the cylindrical mold 1 are provided. A cored bar receiving member 40 is provided in the block molds 4 and 5 so as to surround the recess 8. For the metal core receiving member 40, polyether ether ketone, polyphenylene sulfide, or the like is used.
JP 2001-96485 A

  Polyetheretherketone, polyphenylene sulfide, and the like have a much lower thermal conductivity than that of metal, so that it takes time to sufficiently expand them, and production efficiency is not good. Further, when the resin ring is fitted to the inner surface of the piece mold, the installation and the cleaning of the mold are time-consuming and need to be devised.

  Accordingly, an object of the present invention is to provide an elastic roller molding die and an elastic roller molding method capable of efficiently and stably molding an elastic roller having high outer diameter accuracy and outer diameter deflection accuracy. .

  The present invention employs the following means in order to solve the above problems.

  The invention according to claim 1 includes a cylindrical shape and a piece shape, the cylindrical shape is open at both ends, and is formed hollow so as to be able to fill the elastic part forming material, and the piece shape is a cylindrical opening. An elastic roller molding metal having a closing portion for closing the end, and a holding recess for holding the end portion of the core metal in the closing portion, and forming an elastic roller having the core metal as a central axis in a cylindrical mold In the mold, the piece shape has a dividing surface that is divided into two piece-shaped pieces in a direction crossing the depth direction with respect to the depth direction of the holding recess, and at least one divided surface of the two piece-shaped pieces includes: A fitting portion for fitting the centering elastic member for the metal core is provided so as to surround the outer periphery of the holding recess, and the fitting portion has a slightly smaller fitting width than the centering elastic member to be fitted. Narrow, when the centering elastic member is fitted, a part of the elastic member extends around the cored bar from the opening end of the fitting part. It is formed so as to project freely against an elastic roller mold according to claim.

  The invention according to claim 2 is formed in addition to the structure according to claim 1, and the fitting portion has a structure in which two piece-shaped pieces are joined together at a dividing surface to form an O-ring fitting groove. The O-ring fitting groove is formed such that when an O-ring, which is an elastic member to be fitted, is fitted, at least a part of the O-ring protrudes from the opening end of the fitting groove in an annular manner so that the core metal can be pressed into a ring. The elastic roller molding die according to claim 1.

  In the invention described in claim 3, in addition to the configuration described in claim 1 or 2, the elastic member to be fitted is formed of an elastic heat-resistant resin.

  In the invention described in claim 4, in addition to the structure described in claim 3, the elastic heat-resistant resin is silicone rubber, fluorine rubber, or EPDM rubber.

  According to a fifth aspect of the present invention, in addition to the structure according to any one of the first to fourth aspects, the elastic member to be molded in the cylindrical mold is a silicone rubber or other liquid polymer.

  According to a sixth aspect of the present invention, there is provided a step of assembling the elastic roller molding die according to any one of the first to fifth aspects, a step of fitting a centering elastic member to the fitting portion, and a cored bar. Inserting a mold, preheating the mold, injecting a material for forming the elastic portion into the mold, heating the mold, cooling the mold, and taking out the molded product This is a method for forming an elastic roller.

  With the above configuration, the present invention has the following effects.

  According to the first aspect of the present invention, when the elastic roller is molded in the cylindrical mold, the cylindrical mold can be filled with the elastic part forming material. An end portion of the cored bar can be held in the piece shape that closes the cylindrical opening end. At the time of manufacturing the elastic roller, a part of the centering elastic member for the centering of the cored bar protrudes from the opening of the fitting part so as to be freely pressable around the end of the cored bar. This will center the core. The fitting portion of the centering elastic member is on the piece-shaped dividing surface and is separated from the elastic portion molding material of the elastic roller. The heat in the cylindrical mold does not directly transfer to the centering elastic member.

  Generally, the inner diameter of the piece part of the elastic roller molding die is larger than the outer diameter of the core bar in order to allow insertion and extraction of the core bar. The piece type is held with backlash only by the large fitting tolerance. If the core bar can be centered at the center of the fitting portion provided on the piece-shaped dividing surface, the positional accuracy of the roller is improved. An elastic roller with improved outer diameter deflection accuracy is obtained.

  According to the second aspect of the present invention, when the elastic roller is manufactured, a part of the O-ring for centering the cored bar protrudes around the end of the cored bar so that the cored bar can be pressed in a ring shape. I do.

  The invention according to claim 3 is used for an elastic member to which a heat-resistant resin is to be fitted.

  In the invention according to claim 4, since the elastic heat-resistant resin uses silicone rubber, fluorine rubber, or EPDM rubber, it is soft and rich in elastic deformation, and can be used at a high temperature.

  The invention according to claim 5 is scheduled to be formed in a cylindrical shape in a solid form, such as silicone rubber, urethane rubber, epoxy resin and the like. Urethane rubber, epoxy resin and the like are introduced into the cylindrical mold in the form of a liquid polymer, for example.

  According to the sixth aspect of the present invention, the centering elastic member provided on the piece-shaped dividing surface partially projects from the opening end of the fitting portion to center the cored bar.

  According to this invention, the elastic member for centering the metal core, part of which protrudes from the fitting portion opening end so as to be press-contactable, performs the centering of the metal core. Centering depends on the elasticity of the elastic member. There is no need to wait for the thermal expansion of the elastic member. The fitting portion is on the piece-shaped dividing surface. If the dividing surface is separated from the cylindrical part where the elastic part forming material of the elastic roller is formed, it is not necessary to raise the temperature of the fitting part. There is almost no possibility that part of the elastic member will be eluted. Eliminates the hassle of cleaning the fitting part. It is possible to provide an elastic roller molding die and an elastic roller molding method capable of efficiently and stably molding an elastic roller having high outer diameter accuracy and outer diameter deflection accuracy.

  The elastic roller manufactured as described above can be used as a developing roller used in a developing device of an electrophotographic apparatus. By using the elastic roller obtained in the present invention as a developing roller, high quality without image unevenness can be obtained. An image can be formed.

  In the invention according to claim 2, since an O-ring is used in addition to the above effect, it is easy to obtain and the operation is simple.

  In the invention according to claim 3, the elastic member for centering the cored bar extends its life.

  Since the invention according to claim 4 uses silicone rubber, fluorine rubber, or EPDM rubber, it can be used repeatedly when forming an elastic roller.

  In the invention according to claim 5, since the moldability of the material itself is good, the elastic roller can be molded more easily.

  According to the sixth aspect of the present invention, it is possible to stably form an elastic roller having high outer diameter accuracy and outer diameter deflection accuracy.

  The best mode for carrying out the present invention will be described below. FIG. 1 is a partially exploded external view showing an embodiment for implementing an elastic roller molding die according to the present invention, and FIG. 2 is a sectional view of the assembled state.

  Both ends 2 and 3 are opened, and a cylindrical mold 1 is provided by being hollowly formed so as to be filled with an elastic part forming material. At both ends 2 and 3 of the cylindrical mold 1, detachable piece molds 4 and 5 are provided, respectively. The cylindrical mold 1 and the piece molds 4 and 5 form a mold for forming an elastic roller.

  In the frame shapes 4 and 5, a small-diameter disk body portion 6 and a large-diameter disk body portion 7 are coaxially stacked in a staircase pattern. The large-diameter disk portion 7 has a sufficient extent to close the peripheral edge of the cylindrical mold 1. The small-diameter disk body portion 6 can be fitted into the cylindrical mold 1 with only a slight gap and with almost no gap, and forms a closed insertion portion that can close both ends 2 and 3.

  A holding recess 8 is formed at the center of the disk in the closed fitting portion formed by the small-diameter disk body portion 6. The back end of the holding recess 8 bites into a part of the large-diameter disk part 7. The holding concave portion 8 formed in the small-diameter disk body portion 6 is formed with a size that allows the end of the core bar of the elastic roller to be molded to enter and exit with almost no gap. At the time of molding the elastic roller, Hold the end of the mandrel.

  FIG. 2 is a cross-sectional view showing a state in which the end portions of the cylindrical mold 1 are closed by the piece molds 4 and 5. FIG. 3 is an external view of the piece 4 divided by the dividing surface 10.

  The piece 4 has a dividing surface 10 on a large-diameter disk body portion 7 that is separated from a small-diameter disk body portion 6 that is a closed fitting portion. The piece type 5 also has the same structure and the same function as the piece type 4. The dividing surface 10 divides the depth of the holding recess 8 at a right angle and bisects the holding recess 8 in the perpendicular direction, and the frame 4 is divided into a frame-shaped piece 11 and a frame-shaped piece 12. The dividing surface 10 includes a dividing surface 13 on the piece-shaped piece 11 side and a dividing surface 14 on the piece-shaped piece 12 side. Both dividing surfaces 10 have a step between the peripheral edge portion and the central portion. The piece-shaped piece 11 has a small-diameter disc body portion 6 forming a closed fitting portion, and its dividing surface 13 bulges a peripheral edge portion 15 to form a concave portion. The other piece-shaped piece 12 forms a convex shape in which the peripheral edge portion 16 is recessed at the dividing surface 14. The piece-shaped piece 11 and the piece-shaped piece 12 are fitted to each other such that the dividing surface 13 and the dividing surface 14 face each other.

  The split surface 13 of the piece-shaped piece 11 digs up an O-ring mounting portion 17 around the holding recess 8 in an annular shape. The O-ring mounting portion 17 is a place where an O-ring for centering is mounted when forming an elastic roller. The O-ring to be mounted has a circular cross section, and the inner diameter of the ring is equal to the inner diameter of the holding recess 8. The ring outer diameter is equal to the outer periphery of the annular O-ring mounting portion 17. The O-ring mounting portion 17 has such a size, that is, the mounting portion width of the O-ring mounting portion 17 is equal to the cross-sectional diameter of the O-ring.

  The O-ring mounting portion 17 provided on the piece-shaped piece 11 is arranged around the holding recess 8 in the piece-shaped piece 12 when the divided surface 13 of the piece-shaped piece 11 and the divided surface 13 of the piece-shaped piece 12 are fitted to each other. Is added to form the O-ring fitting groove 18. The groove width of the O-ring fitting groove 18, that is, the width measured in the length direction of the holding recess 8 is slightly smaller than the diameter of the O-ring to be fitted. For example, 0.9 to 0.5 times. If it becomes 0.9 times or more, it is difficult to obtain a sufficient deformation effect to the center. If it is 0.5 times or less, there is a possibility of deformation outside the groove, and conversely the centering effect cannot be obtained.

  When the O-ring is inserted into the O-ring fitting groove 18 and the piece-shaped piece 11 and the piece-shaped piece 12 are pressed against each other, the O-ring is slightly deformed and a part protrudes toward the holding recess 8 side.

  Such a mold is used as follows to produce an elastic roll.

  FIG. 4 is a cross-sectional view showing a state in which an O-ring and a cored bar are mounted on a mold.

  The O-ring 20 is attached to the O-ring attachment portion 17 of the piece-shaped piece 11 on the piece shape 4 side. The material of the O-ring is preferably soft and can be used particularly at high temperatures. For example, silicone rubber, fluorine rubber, EPDM rubber and the like can be mentioned.

  In the cylindrical mold 1, usually, solid molding such as silicone rubber, urethane rubber, and epoxy resin is often planned. Urethane rubber, epoxy resin, and the like are introduced into the cylindrical mold 1 in the form of a liquid polymer.

  The end of the cored bar 21 is inserted into the holding recess 8 on the piece-shaped piece 11 side of the piece 4 and the holding recess 8 on the piece-shaped piece 12 side is attached to the end protruding to the opposite side. The cylindrical mold 1 is combined with the piece mold 4. The same applies to the piece type 5 side. When the piece-shaped piece 11 and the piece-shaped piece 12 are pressed against each other, the width of the O-ring fitting groove 18 is narrowed and the O-ring 20 is deformed. As a result, the core 21 is centered.

  Preheat the mold 1. A material for forming the elastic part of the elastic roll is poured into the mold, the mold is heated, the mold is then cooled, and the molded product is taken out.

  FIG. 5 is an external view showing an example of an elastic roller formed by such an elastic roller molding die. The core bar 21 and the elastic part 22 are formed.

  The above shows an example in which an O-ring is used as an elastic member for centering the cored bar 21. The O-ring can be used as an elastic member for centering the cored bar 21. Elastic balls may be used. FIG. 6 shows an example using elastic balls. FIG. 6A shows a state before the elastic ball is installed, and FIG. 6B shows a state after the elastic ball is installed.

  In place of the O-ring fitting groove 18, three, preferably four or more elastic ball installation portions 24 are provided around the pre-installation holding recess 8. There, for example, rubber balls 25 are arranged.

  Next, specific examples of the present invention will be described.

  A mold was designed and manufactured according to the above embodiment. A silicone rubber O-ring was attached to this.

  A material obtained by adding carbon to LTV silicone rubber (trade name KE-1950A, B: manufactured by Shin-Etsu Chemical Co., Ltd.) as a raw material rubber for molding the elastic part was cast into a cylindrical shape at room temperature using a casting machine. After casting, the mold was placed in a heating furnace at 150 ° C. for 30 minutes to cure the rubber material. The mold was taken out from the heating furnace, and after cooling, the obtained molded product was taken out from the mold.

  Thereafter, heat treatment was performed at 200 ° C. for 4 hours to obtain a rubber roller having a hardness of 40 degrees. Forty rubber rollers were made in the same manner. The outer diameter and runout of the obtained roller were measured with a non-contact laser length measuring device. The results are shown in Table 1.

A roller was prepared in the same manner as in Example 1 except that the mold was preheated at 150 ° C. for 15 minutes before casting. Measurements similar to those in Example 1 were performed.
(Comparative Example 1)

A roller was produced in the same manner as in Example 1 except that a conventional integrated piece type having no dividing surface 10 was used and an O-ring was not used. Measurements similar to those in Example 1 were performed.
(Comparative Example 2)

  A roller was manufactured in the same manner as in Example 2 except that a conventional integrated piece type having no dividing surface 10 was used and an O-ring was not used. Measurements similar to those in Example 1 were performed.

  From Table 1, the elastic roller manufactured by using the molds of Examples 1 and 2 was removed from the center of the piece-shaped dividing surface by fitting the elastic member for centering the metal core effectively. It was found that the radial runout accuracy was significantly improved over the conventional elastic roller.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially exploded external view showing an embodiment for implementing an elastic roller molding die according to the present invention. It is sectional drawing of the state which obstruct | occluded the edge part of the cylindrical shape with the piece shape of the same elastic roller shaping die. It is the external view which divided | segmented the piece type | mold of the same elastic roller shaping | molding metal mold | die with the division surface. It is sectional drawing which shows a mode that the O ring and the core metal were mounted | worn with the same metal mold | die for elastic roller shaping | molding. It is an external view which shows an example of the elastic roller shape | molded with the same metal mold | die for elastic roller shaping | molding. It is a figure which shows the example before the elastic ball installation which uses an elastic ball for the elastic member for centering of the metal core of the same elastic roller molding die. It is a figure which shows the example after the elastic ball installation which uses an elastic ball for the elastic member for centering of the metal core of the same elastic roller molding die. It is sectional drawing which shows the conventional centering method.

Explanation of symbols

1 Cylindrical type 2, 3 Cylindrical type open end 4, 5 piece type 6 Small-diameter disc body part (blocking insertion part)
7 Large-diameter disk body part 8 Holding recess 11 Piece-shaped piece A
12 piece type B
18 O-ring fitting groove (fitting part)
20 O-ring (centering elastic member)
21 Core

Claims (6)

A cylindrical shape and a piece shape, the cylindrical shape is hollow at both ends opening so as to be able to fill the elastic part forming material, and the piece shape has a closing portion that closes the opening of the cylindrical shape. The closing portion has a holding recess for holding an end portion of the core metal, and an elastic roller molding die for molding an elastic roller having the core metal as a central axis in the cylindrical mold,
The piece shape has a dividing surface that is divided into two piece-shaped pieces in a direction crossing the depth direction with respect to the depth direction of the holding recess, and at least one dividing surface of the two piece-shaped pieces includes: A fitting portion for fitting the elastic member for centering the cored bar is provided surrounding the outer periphery of the holding recess, and the fitting portion has a slightly smaller fitting width than the elastic member to be fitted. For forming an elastic roller, wherein the elastic member is formed so that a part of the elastic member protrudes from the opening end of the fitting portion so as to be press-contactable freely when the elastic member is fitted. Mold. The fitting portion has a structure in which two piece-shaped pieces are joined together at a dividing surface to form an O-ring fitting groove, and the formed O-ring fitting groove is an elastic member to be fitted. 2. The elastic roller according to claim 1, wherein when the ring is fitted, at least a part of the O-ring protrudes from the opening end of the fitting groove so as to be able to press-contact the cored bar annularly. Mold for molding. The elastic roller molding die according to claim 1 or 2, wherein the elastic member to be fitted is formed of an elastic heat resistant resin. 4. The elastic roller molding die according to claim 3, wherein the elastic heat-resistant resin is silicone rubber, fluorine rubber, or EPDM rubber. The elastic roller molding die according to any one of claims 1 to 4, wherein the elastic portion to be molded in the cylindrical mold is made of silicone rubber or other liquid polymer. A step of assembling the elastic roller molding die according to any one of claims 1 to 5, a step of fitting an elastic member for centering in the fitting portion, a step of inserting a cored bar, and a die A method for forming an elastic roller, comprising: a step of preheating; a step of injecting a material for forming an elastic portion into a mold; a step of heating the mold; and a step of cooling the mold and taking out a molded product.

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