JP2007187223A - Method of manufacturing conductive elastic body roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction in uniform electrostatic property even in long-term use when used for a charging roller, by forming a uniform smooth surface without a recess on an outer peripheral surface of an elastic body roller. <P>SOLUTION: This conductive elastic body roller is composed of core metal and a nonlinear cylindrical or cylindrical elastic body on its outside, and integrates the elastic body and the core metal after fitting and inserting the core metal in a hollow part of the elastic body of a free state. A hollow part inner diameter of the elastic body of the free state is formed in the size of 70% to 95% of a core metal outer diameter. A hollow part shape of the elastic body of the free state is molded and vulcanized in advance so that the hollow part inner diameter successively becomes large over both end parts of a central part of the hollow part in the thrust direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an elastic roller used in electrophotography, an electrophotographic plate making system, and the like. More specifically, it is used in electrophotography and electrophotographic plate making systems such as copying machines, laser beam printers, LED printers, etc., and is a conductive material that integrates the elastic body and the core metal by inserting the core metal into the hollow portion of the elastic body. It is related with the manufacturing method of this elastic body roller.

  Conventionally, in electrophotographic apparatuses such as copying machines, laser beam printers, and LED printers, and electrophotographic plate making system apparatuses, the conductive elasticity of a form suitable for each application, such as a charging roller, a developing roller, and a transfer roller. Body rollers are used. As shown in FIG. 3, the conductive elastic roller 101 used in these electrophotographic apparatuses has an elastic roller main body 102 and a cored bar 103 at the center, and a hollow portion of a cylindrical roller main body. A part of the cored bar 103 penetrating through is protruded at both ends.

  The conductive elastic roller has a predetermined core metal portion protruding from both ends in order to bring the surface of the elastic roller body 102 into close contact with a photosensitive member, an image carrier such as a transfer belt, and a transfer material (paper). Is pressed and rotated in the radial direction about the central axis of the cored bar. In addition, in order to ensure a stable contact state with the image carrier, transfer material, etc., the elastic roller is made of a material such as rubber, elastomer or the like and formed into a solid or a foam having a fine cell diameter. It is composed of a hard elastic body.

  Further, the elastic body roller is deformed by applying a predetermined pressure to the cored bar portion projecting at both ends, so that the pressure contact area between the image bearing member and the elastic roller is equal to the central part of the elastic roller body 102. Since both ends are small and large, the outer diameter shape of the elastic roller main body 102 is often polished into a crown shape in which the outer diameter of the central portion is larger than the outer diameter of both ends because it differs in the thrust direction.

  A conductive elastic roller used in contact with a photoconductor and biased is supplied with power from a core bar projecting at both ends to charge an image carrier such as a photoconductor from the surface of the elastic roller body.

  In recent years, the electrophotographic apparatus has been increased in speed and definition, and in order to obtain a high-quality image, the conductive elastic roller is required to be a conductive uniform roller.

  The conductive elastic roller may not obtain a good image only by making the conductivity of the elastic roller main body uniform. For example, in the charging roller, if there is a dent on the outer peripheral surface of the elastic roller body, a good image cannot be obtained in the dent, or residual toner, paper dust, etc. are likely to partially adhere to the dent. When used for a long period of time, an image defect (for example, a decrease in uniform chargeability with respect to the photoreceptor) due to a decrease in conductivity may occur. One cause of this dent is that the adhesion between the cored bar and the elastic roller body is partially insufficient, or the adhesive force is partially insufficient.

  In these elastic body rollers, a rubber composition is first formed into a cylindrical shape and then vulcanized to produce a cylindrical elastic body. The inner diameter of the hollow portion of the cylindrical elastic body is formed so as to be smaller than the outer diameter of the cored bar.

  Next, the cored bar is inserted into the hollow part of the cylindrical elastic body while inflating the cylindrical elastic body by sending air under pressure into the hollowed part of the cylindrical elastic body vulcanized from the opposite side of the cored bar insertion side. The core metal and the cylindrical elastic body are integrated. There is also an elastic roller that applies an adhesive to the outer peripheral surface of the core metal as necessary and integrates the core metal and the cylindrical elastic body and then heats them to bond them more firmly. Thereafter, the outer peripheral surface of the cylindrical elastic body is polished to finish the dimensions of the desired elastic roller body. Furthermore, there is also a two-layer charging roller that adjusts the roller resistance by applying a thin film conductive paint on the outer peripheral surface of the ground elastic roller, and the outer peripheral surface of the elastic roller has smoothness. It has been demanded.

  In these elastic rollers, when the outer peripheral surface of the cylindrical elastic body is formed into an arbitrary shape by polishing after the core metal is inserted, partial adhesion or partial adhesion between the core metal and the cylindrical elastic body If the force could not be secured, there was a problem that the elastic roller main body portion in the gap portion and the portion with weak adhesive force was deformed more greatly than the other portions by the polishing force, resulting in dents on the surface and a good image could not be obtained.

In order to solve the above-mentioned problems, the cylindrical elastic body is accommodated in the chamber, and a sealed space is formed between the outer peripheral surface of the cylindrical elastic body and the inner wall surface of the chamber, and the sealed space is vacuum-sucked to thereby form the cylindrical elastic body. Enlarge the inner diameter of the body. Then, after inserting the cored bar into the enlarged inner diameter, there is a method in which air is sequentially introduced into the sealed space to bring the cylindrical elastic body into close contact with the cored bar. (For example, refer to Patent Document 1.)
JP2003-112372

  However, in order to gradually switch from the vacuum state to the atmospheric state from the front end portion to the rear end portion of the cylindrical elastic body before insertion, as in the conventional example (Patent Document 1), the outer periphery of the cylindrical elastic body The sealed space formed between the surface and the inner wall surface of the chamber must be divided and sequentially switched from the vacuum state to the atmospheric state, which complicates the apparatus. In addition, air residue may occur in the divided sealed space.

  The present invention solves the problems that occur when a cored bar is inserted into the hollow portion of such a conventional cylindrical elastic body, can form a uniform smooth surface without dents on the outer peripheral surface of the elastic body, and An object of the present invention is to provide a method for producing an elastic roller having high productivity regardless of the roller shape.

In order to achieve the above object, the invention according to the present application includes a cored bar and a non-cylindrical cylindrical or cylindrical elastic body on the outer side thereof, and the elastic body after the cored bar is inserted into the hollow part of the elastic body in a free state In the conductive elastic roller integrating the core and the core metal, the inner diameter of the hollow part of the elastic body in the free state is 70% to 95% of the outer diameter of the core metal, and the hollow part shape of the elastic body in the free state is A method for producing a conductive elastic roller, characterized in that molding and vulcanization are performed so that the inner diameter of the hollow portion increases sequentially from the center to both ends in the thrust direction.

  That is, when a cored bar is inserted into the hollow part of the elastic body, the compressed air is stopped and the inner and outer diameters of the elastic body contract to make a close contact with the cored bar. The problem that occurs in the elastic body, that is, the gap between the cored bar and the elastic roller body due to the remaining air is eliminated by preventing the hollow part from sticking to the cored bar at least at either end. There is. Alternatively, the generation of a portion that is not bonded due to air remaining between the adhesive surface applied to the outer peripheral surface of the core metal and the elastic roller body is eliminated.

  As described above, according to the present invention, in the conductive elastic roller of the present invention, the space layer is formed over the entire interface between the outer peripheral surface of the core metal and the inner peripheral surface of the hollow portion of the elastic body. Since it does not exist, the adhesion between the cored bar and the elastic body is good, and there is no dent on the surface of the roller in surface polishing or the like, and it is stable and good even when used for a conductive elastic body roller. An image can be obtained.

  Furthermore, if it is used as the base layer of the charging roller, it is possible to provide a charging roller that is free from contamination even after long-term use.

  Next, an embodiment for manufacturing a conductive elastic roller using the manufacturing method according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a diagram for explaining the configuration of the elastic body according to the present embodiment in a free state. FIG. 2 is a cross-sectional view illustrating a state in which the elastic body in the free state according to the present embodiment is inserted into the cored bar.

  The configuration will be described with reference to FIG. 1. 1 is a cylindrical cored bar, and 2 is an elastic body in a free state. The elastic body 2 in a free state before the core metal 1 is inserted is provided with a hollow portion 3 having a circular cross section and penetrating. D is the outer diameter of the cored bar, D1 and D2 are inner diameters at both ends of the hollow part of the elastic body facing each other in the thrust direction, and D3 is the inner diameter of the central part located substantially at the center in the thrust direction of the hollow part 3. . The cross-sectional shape of the hollow portion 3 of the elastic body is a circular shape having an inner diameter that gradually increases from the center to both ends of the hollow portion 3 in the thrust direction. The inner diameters D1, D2, and D3 of the hollow portion 3 are configured to be 70% to 95% of the outer diameter D of the cored bar.

  Further, the inner diameter D3 of the central portion of the hollow portion is configured to be 96% or less with respect to the inner diameters D1 and D2 of the end portions of the hollow portion. The core 1 is a metal such as iron with nickel on the surface for rust prevention. The elastic body 2 is an Asker C hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) and is composed of an elastic body of 20 to 90 degrees.

  Next, the process of inserting and inserting the elastic body of the present embodiment into the cored bar will be described.

  The process flow will be described with reference to FIG. 2. Reference numeral 4 denotes an air injection jig having a through-hole 5 serving as a flow path for compressed air. The air injection jig is pressed against the end surface of the elastic body 2 in order to send the compressed air to the end 6a of the hollow portion 3 of the elastic body 2.

  In the configuration described above, an example of the operation of the embodiment will be described. The end of the cored bar 1 is press-fitted into the end 4b of the hollow part 3 of the elastic body 2 by 1 to 10 mm, and then the other end 4a of the hollow part of the elastic body 2 is inserted from the opposite side to the insertion side of the cored bar 1. The cored bar 1 is inserted into the hollow portion 3 while inflating the elastic body 2 by sending air under a pressure of 0.1 to 0.4 MPa. The metal core 1 is inserted to a desired position, and then the compressed air is stopped to integrate the metal core and the elastic body 2. If necessary, a conductive adhesive is applied to the outer peripheral surface of the core metal, and the core metal and the elastic body are integrated, and then heated at a temperature of 120 to 200 ° C. for 10 to 120 minutes to bond more firmly.

  In this embodiment, if the central part inner diameter D3 at which the inner diameter of the hollow part is the minimum is 70% or more of the outer diameter D of the cored bar, the cored bar can be easily inserted into the elastic body, and the inner diameter of the hollow part is maximized. If either of the end inner diameters D1 and D2 is 95% or less, sufficient adhesion between the core metal and the elastic body can be secured. Then, the central portion inner diameter D3 of the hollow portion is configured to be 96% or less with respect to the end portion inner diameters D1 and D2 of the hollow portion, so that the core metal is inserted into the hollow portion of the elastic body and then pumped. When the air is stopped and the inner and outer diameters of the elastic body contract and come into close contact with the cored bar, it is possible to prevent the inner diameter of the central part of the elastic body from coming into close contact with the cored bar first to cause air remaining. That is, it is possible to eliminate the generation of a gap due to the air remaining between the core metal and the elastic body.

  Furthermore, the elastic body having the hollow portion described above is manufactured as follows.

  The rubber raw materials are mixed with a kneader such as a bunley, kneader or open roll. Next, by using an extruder, a cross section is formed into a ring shape from an extrusion head having a circular inner diameter and a die having a circular inner diameter located at the tip end of the extruder, and at the same time, the extrusion speed is changed to change the hollow portion. The preform of the elastic body having the above is continuously molded. For example, in both-end molding of an elastic preform, the extrusion speed is increased sequentially from the center of the elastic preform by sequentially increasing the rotational speed of the screw compared to the molding of the center. The shape of the hollow part of the preform can be molded so that the inner diameter increases sequentially from the central part to both ends of the hollow part in the thrust direction.

  Thereafter, the outer peripheral surface of the conductive elastic roller body in which the elastic body and the core metal are integrated is polished using a known cylindrical grinding machine to finish the dimensions of the desired conductive elastic roller. As a cylindrical grinding machine that cylindrically grinds the outer peripheral surface of an elastic roller, a traverse NC cylindrical grinding machine that moves and grinds a grindstone or an elastic roller in the thrust direction of the elastic roller, and the elastic roller is a core metal shaft. A plunge cut type NC cylindrical grinder that cuts a grinding wheel having a width close to the width in the thrust direction of the elastic roller body while revolving to the center without reciprocating may be used.

Further, the shape of the elastic roller 101 is a roller type used in an image forming apparatus such as an electrophotographic apparatus or an electrophotographic plate making system, and the outer diameter shape is a straight shape or the outer diameter of the central portion of the elastic roller body 102 is the end. Suitable for non-cylindrical crowns that are larger than the outer diameter of the part, those that have a tapered shape, or those that have a reverse crown shape in which the outer diameter of the central part of the roller body is smaller than the outer diameter of the end part Applied.
The cored bar 103 is not particularly limited by the present invention, and can be used in the present invention as long as it is used in an image forming apparatus. For example, a metal such as stainless steel, iron, or iron whose surface is nickel or nickel / chrome plated for rust prevention can be used as the core metal 103. The adhesive applied to the core metal is preferably conductive and more preferably lower than the volume resistance of the elastic body. The film thickness of the conductive adhesive is selected from 5 to 20 μm.

  NBR (acrylonitrile-butadiene rubber), EPDM (ethylene-propylene-diene-copolymer), polybutadiene, natural rubber, polyisoprene, SBR (styrene butadiene rubber), CR (chloroprene) as polymer raw materials used for elastic bodies There are rubbers such as silicon rubber, epichlorohydrin rubber and urethane rubber. These rubbers can also be used as a mixture, and are not particularly limited.

  The conductive material added to the polymer raw material includes conductive carbon black, metal oxide such as TiO2, SnO2, and ZnO, solid oxide of SnO2 and Sb2O5, double oxide such as a solid solution of ZnO and Al2O3, Cu -Metal powders, such as Ag, etc. are mentioned, Usually, it adds in the range of 5-200 weight part with respect to 100 weight part of said polymer raw materials. In addition to conductive particles, surfactants such as metal salts such as LiBF4 and NaSCN and quaternary ammonium salts can be used as the ion conductive material. Usually, 0.02 to 20 parts by weight is added to 100 parts by weight of the polymer raw material. To do.

  Further, a filler, a reinforcing material, a plasticizer, a vulcanizing agent, a vulcanization accelerator, and the like are added to the polymer raw material as necessary. The roller hardness is preferably applied to a 20 to 90 degree roller with an Asker C hardness meter.

(Examples 1-3)
Next, a bias voltage is applied as a method of manufacturing a conductive elastic roller in which a cored bar is inserted into the hollow part of the elastic body and the elastic body and the cored bar are integrated. The manufacturing method of the present invention will be described in detail by taking as an example a charging roller for charging the surface of a photoreceptor having an outer diameter of Φ30 mm.

  The elastic body in the free state was prepared as follows.

  Epichlorohydrin rubber (trade name: Epichromer CG102, manufactured by Daiso Corporation), 100 parts by mass, calcium carbonate 25 parts by mass, MT carbon 2 parts by mass, zinc oxide 5 parts by mass, plasticizer 10 parts by mass, stearin 1 part by weight of acid, 2 parts by weight of quaternary ammonium perchlorate and 1 part by weight of antioxidant (tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate methane]) 1 part by weight of vulcanization accelerator (DM), 0.5 part by weight of vulcanization accelerator (TS), 0.5 part by weight of sulfur as a vulcanizing agent, and 1 part by weight of vulcanization accelerator (DM: dibenzothiazyl disulphide) In addition, rubber material kneaded by sheeting and kneading for 15 minutes with an open roll. Got.

  In order to form the kneaded rubber material into an elastic preform, a nipple having an outer diameter of φ3.6 and a die having an inner diameter of φ9.0 were set in an extruder. Furthermore, the extrusion speed was set by changing the number of rotations of the screen. In Examples 1 to 3, the tip portion extrusion speed corresponding to the end of the elastic preform is selected from 1 to 6 m / min, and then the central portion extrusion speed is sequentially reduced from the tip portion extrusion speed to 0.5 to After selecting from 4 m / min, the rear end pushing speed corresponding to the other end was sequentially accelerated from the center pushing speed and selected from 1 to 6 m / min. By continuously repeating the extrusion speed cycle of the preform, the hollow portion shape of the preform is gradually increased from the center to both ends in the thrust direction of the preform, which is the extrusion direction. It can shape | mold continuously so that it may become. Thereafter, the continuous body of the preform was cut by a cutting machine to obtain a length dimension.

  Further, the cut preform of elastic body is vulcanized in a vulcanizer at 160 ° C for 40 minutes, and then subjected to secondary vulcanization in a hot air oven at 160 ° C for 30 minutes. The elastic body in a free state was cut and vulcanized.

  The elastic bodies obtained in Examples 1 to 3 were cut at a pitch of 60 mm in the thrust direction, and the inner diameter of the hollow portion was measured with a cylindrical pin gauge.

  FIG. 4 shows the inner diameter of the elastic body in the free state prepared in Examples 1 to 3. 100 elastic bodies each having an average value of the inner diameter of the elastic body at each position in the thrust direction and a tolerance of ± 0.02 mm were produced.

  Further, a conductive vulcanized adhesive was applied to a core metal having an outer diameter of Φ6.0 mm with an average film thickness of 10 μm and dried.

  The end of the cored bar was pressed into the end of the hollow part of the elastic body obtained in Examples 1 to 3 by 2 mm, and then the other end of the hollow part of the elastic body was inserted from the side opposite to the insertion side of the cored bar. The cored bar and the elastic body were integrated by inserting the cored bar into the hollow part while inflating the elastic body by feeding air under a pressure of 0.25 MPa, and then stopping the pressurized air. Next, the unground elastic rollers of Examples 1 to 3 were heated using a hot air oven at 160 ° C. for 15 minutes, and heat-bonded with a conductive adhesive, and then both ends were cut off. The overall length was adjusted to 230 mm. Next, the unground elastic roller obtained in Examples 1 to 3 was ground by an NC cylindrical grinder into an elastic roller having an outer peripheral surface of Φ12 mm and a crown amount of 100 μm at the center.

  A surface layer was applied to the ground elastic roller of Examples 1 to 3 by dipping coating using the following paint to prepare a two-layer charging roller. As the preparation of the coating for the surface layer, first, 100 parts by mass of lactone-modified acrylic polyol, 220 parts by mass of methyl isobutyl ketone, 90 parts by mass of conductive tin oxide (surface treatment of silane coupling agent, powder resistance 100 Ωcm, average particle size 0.02 μm), After a mixed liquid blended in a proportion of 40 parts by mass of crosslinked polymethyl methacrylate fine particles (average particle size 5 μm, SF-1 110) and 0.08 parts by mass of modified dimethyl silicone oil was dispersed in a bead mill, hexamethylene diisocyanate (HDI) A 1: 1 mixture of each butanone oxime block of isophorone diisocyanate (IPDI) was added so that NCO / OH = 1.0 and dissolved to prepare a coating for the surface layer. On the elastic roller ground in Examples 1 to 3 above, the surface layer paint was first dipped and air dried for 10 minutes, then turned upside down, dipped and air dried for 30 minutes, and then 150 ° C. Were dried for 1 hour to obtain charging rollers of Examples 1 to 3 having a surface layer having a thickness of 15 μm.

(Comparative Examples 1-4)
Next, in Comparative Example 1 and Comparative Example 2, the extrusion speed was selected from 0.5 to 6 m / min, and the extrusion speed was kept constant. did. FIG. 4 shows the inner diameter dimension of the elastic body in the free state prepared in Comparative Example 1 and Comparative Example 2.

  Further, the charging rollers of Comparative Example 1 and Comparative Example 2 were obtained in the same manner as in Example.

  Further, in Comparative Example 3 and Comparative Example 4, the extrusion speed was changed in the same manner as in Example, but in Comparative Example 3, the inner diameter of the central portion was 68.3% with respect to the outer diameter of the core metal of Φ6, and in Comparative Example 4, The inner diameter of both ends was 96.7% with respect to the outer diameter of the core metal of Φ6. FIG. 4 shows the inner diameter of the elastic body in the free state prepared in Comparative Example 3 and Comparative Example 4.

  Further, the charging rollers of Comparative Example 3 and Comparative Example 4 were obtained in the same manner as in Example.

  And the evaluation of the elastic body rollers obtained in Examples 1 to 3 and Comparative Examples 1 to 4 is shown in FIG. 4, and the determination was made based on the insertion property, the adhesiveness, and the dent occurrence rate.

  Insertability is determined by the ease of press-fitting when inserting the metal core. Adhesion is fixed by fixing the metal core after insertion and applying a force of 0.4 Mpa to the elastic body in the radial direction. Judgment was made based on whether or not it was made. Also, measure the gap with a rubber roller gap inspection machine (GM1000 manufactured by OPTRON) that measures the gap with a laser while rotating the outer peripheral surface of the charging roller with a surface layer on the elastic roller against a Φ30 mm metal drum at 1000 gr. did. The occurrence rate of the charging roller was detected by detecting a gap having a gap height of 4 μm or more and a length of 0.2 mm or more with a gap inspection machine.

  In Comparative Example 2 and Comparative Example 3, it was difficult to press-fit when inserting the metal core. In Comparative Example 4, there was an elastic roller in which the core metal and the elastic body could not be firmly fixed due to poor adhesion at the ends.

  Next, for the charging roller in Examples 1 to 3 and the charging roller in which the gap height is 4 μm or more and the length is 0.2 mm or more in Comparative Example 1 and Comparative Example 4, the conductivity uniformity is evaluated. did. Each charging roller was allowed to stand for 24 hours in a measurement environment (N / N temperature 23 ° C., relative humidity 60%), and then the resistance value was measured under the following conditions.

  A load of 500 gr is applied to both ends of each core of the charging roller, and each charging roller is pressed against a cylindrical aluminum drum having a diameter of 30 mm and rotated, and a DC voltage of 200 V is applied to the core of the charging roller. A DC voltage is applied using a power source. In this state, the voltage applied to the resistor was measured at both ends of the resistor connected in series to the aluminum drum, and the amount of current injected from each charging roller to the aluminum drum was evaluated. From the current value, the resistance value of each charging roller was calculated, and the average of the maximum value and the minimum value of the resistance value distribution was defined as the average resistance value. Further, the resistance value distribution in the circumferential direction of each charging roller was obtained. The ratio between the maximum value and the minimum value (maximum value / minimum value) of the resistance value distribution in the circumferential (radial) direction was used as an index of resistance value unevenness.

  In the charging rollers of Examples 1 to 3, the average resistance value is 2 to 3 × E05Ω and the resistance unevenness is 1.08 to 1.09. In Comparative Examples 1 and 4, the gap height is 4 μm or more and the length is 0.2 mm or more. In the charging roller in which a certain gap was detected, the average resistance value was 2 to 3 × E05Ω, and the uneven resistance value was 1.09 to 1.10. There was little difference in uneven resistance.

  Next, using the charging roller in Examples 1 to 3 and the charging roller in which the gap height is 4 μm or more and the length is 0.2 mm or more in Comparative Example 1 and Comparative Example 4 is detected as follows. Image evaluation was performed.

  The electrophotographic laser printer used in this test is an A4 vertical output machine, the output speed of the recording medium is 94 mm / sec, and the image resolution is 600 dpi. The photoreceptor is a reversal development type photosensitive drum in which an aluminum cylinder is coated with an OPC layer having a film thickness of 18 μm, and the outermost layer is a charge transport layer using a modified polycarbonate as a binder resin. The toner was obtained by polymerizing a random copolymer of styrene and butyl acrylate containing a charge control agent, a pigment and the like centering on wax, and further polymerizing a thin polyester layer on the surface to externally add silica fine particles. This toner is a polymerized toner having a glass transition temperature of 63 ° C. and a volume average particle diameter of 6 μm. All images are evaluated in a low-temperature, low-humidity environment (L / L: 10 ° C x 15% Rh), and a halftone image (an image that draws a horizontal line with a width of 1 dot and a spacing of 2 dots in the direction perpendicular to the rotation direction of the photoconductor). , And continuous durability of 20000 sheets before and after the endurance, uniform image evaluation before and after the endurance, and whether or not the charging roller was partially soiled. The charging roller having the surface layer applied to Examples 1 to 3 was free from contamination even after 20,000 sheets of continuous durability, and good images were obtained. In Comparative Example 1 and Comparative Example 4, the charging roller in which a gap height of 4 μm or more and a length of 0.2 mm or more was detected produced a black haze image from the beginning. Further, a dent was visually confirmed on the surface of the charging roller corresponding to the black haze image portion.

It is the schematic explaining the structure in the free state of the cylindrical elastic body which concerns on 1st Example of this invention. It is sectional drawing explaining the state which inserts the cylindrical elastic body which concerns on 1st Example of this invention in a metal core. It is a figure explaining an elastic body roller. It is a table | surface which shows the evaluation of an elastic body roller.

Explanation of symbols

101 Elastic roller
102 Elastic roller body
103 cored bar
2 Elastic body in free state
3 Hollow part D Outer diameter of core metal D1, D2 Inner diameter of both ends of hollow part D3 Inner diameter of central part of hollow part

Claims (3)

  In a conductive elastic roller comprising a core metal and a non-cylindrical cylindrical or cylindrical elastic body on the outer side thereof, and integrating the elastic body and the core metal after the core metal is inserted into the hollow portion of the elastic body in a free state The inner diameter of the hollow portion of the elastic body in the free state is not less than 70% and not more than 95% of the outer diameter of the core metal, and the hollow portion shape of the elastic body in the free state is extended from the central portion of the hollow portion to both ends in the thrust direction. A method for producing a conductive elastic roller, characterized in that molding and vulcanization are performed so that the inner diameter of the hollow portion increases in order.   The conductive elastic body according to claim 1, wherein the elastic body is molded and vulcanized so that the inner diameter of the central portion of the hollow portion is 96% or less with respect to the inner diameter of the end portion of the hollow portion. Body roller manufacturing method.   The elastic body in a free state according to claim 1, wherein an extrusion speed is adjusted using an extruder to form a hollow part shape as a pre-formed body of the elastic body so that the inner diameter is gradually increased from the center part to both end parts in the thrust direction. A method for producing a conductive elastic roller, characterized in that it is molded as follows.

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