JP2019101213A - Conductive sponge roller and image forming apparatus - Google Patents

Abstract

To provide a conductive sponge roller that comprises an elastic layer having a small difference in density in a thickness direction, and has a satisfactorily improved durability despite its low hardness, and an image forming apparatus including the conductive sponge roller.SOLUTION: There is provided a conductive sponge roller 1 comprising: a shaft body 2; and an elastic layer 3 provided on an outer peripheral surface of the shaft body 2, where the shaft body 2 is formed of a synthetic resin in which a conductive filler is dispersed, the shaft body 2 has a thermal conductivity of 5 W/(m K) or less, and the elastic layer 3 has an Asker F hardness of 25 or more and 75 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive sponge roller and an image forming apparatus, and more specifically, a conductive sponge roller having a good improvement in durability while having a small difference in density in the thickness direction of an elastic layer and low hardness, The present invention relates to an image forming apparatus provided with the conductive sponge roller.

  Various image forming apparatuses using an electrophotographic system have been adopted for laser printers, copying machines, video printers, facsimiles, and multi-functional machines thereof. An image forming apparatus using an electrophotographic method has a shaft and an elastic layer formed on the outer peripheral surface thereof. For example, a cleaning roller, a charging roller, a developer conveyance roller, a developing roller, a transfer roller, a pressure roller, A sponge roller for various types of printing such as a paper feed conveyance roller and a fixing roller is provided.

  Among these sponge rollers, the cleaning roller, the developer conveyance roller, and the development roller have conductivity for the purpose of suction and conveyance of the developer, and are used by being crimped with other sponge rollers. In order to reduce the load and friction on the developer, low hardness is required.

  As a sponge roller having low hardness, for example, Patent Document 1 discloses that the developing mechanism portion of the image forming apparatus accompanied by the developing operation with the developer rotates in contact with the surface of the developing roller and the developer in the developer reservoir. A developer conveying roller that carries and conveys on the outer peripheral surface and supplies the developer to the surface of the developing roller, wherein at least the outer peripheral surface is formed of a foam, and a predetermined range excluding the both ends of the roller is crushed There is disclosed a developer transport roller characterized in that the cell film of the foam is broken and the predetermined range of the roller central portion is set to be lower in hardness than both roller end portions.

  Further, Patent Document 2 includes a shaft having conductivity and a cylindrical conductive rubber having conductivity and provided on an outer peripheral surface of the shaft, and the conductive rubber has Disclosed is a conductive roller characterized in that a metal fiber aggregate in which metal fibers having flexibility are gathered and wound in such a manner as to conduct the shaft and the outer peripheral surface of the conductive rubber body. There is.

JP 2007-65103 A Unexamined-Japanese-Patent No. 2007-256410

  Here, in order to lower the hardness of the sponge roller, there is a method of reducing the content of silica contained in the elastic layer, but in that case, the elastic layer tends to tear and there is a problem that the durability is lowered. . Further, in the sponge rollers described in Patent Document 1 and Patent Document 2, since the difference in density in the thickness direction of the elastic layer is large, it is not sufficient in terms of low hardness, and there is a difference in density as described above. In addition, the density of the outer peripheral surface of the sponge roller changes with time due to wear, and the amount of developer supplied and the amount of scraping change with time, so there was a problem that the durability was not sufficient. Therefore, the present invention has been made in view of the above problems, and there is a small difference in density in the thickness direction of the elastic layer, and a conductive sponge roller whose durability is favorably improved while having low hardness, and An object of the present invention is to provide an image forming apparatus provided with the conductive sponge roller.

  The inventors of the present invention conducted intensive studies to solve the above problems. As a result, in the conductive sponge roller, it is found that the above problem can be solved by adjusting the thermal conductivity of the shaft using a synthetic resin in which the conductive filler is dispersed in the shaft, and the present invention is completed. It came to Specifically, the present invention provides the following.

  (1) A first aspect of the present invention is a conductive sponge roller having a shaft and an elastic layer provided on the outer peripheral surface of the shaft, wherein the shaft is dispersed with a conductive filler. The conductive sponge roller is made of the synthetic resin, the thermal conductivity of the shaft is 5 W / (m · K) or less, and the Asker F hardness of the elastic layer is 25 or more and 70 or less.

(2) A second aspect of the present invention is the conductive sponge roller according to (1), wherein the density of the elastic layer is 50% of the thickness of the elastic layer from the outer peripheral surface of the shaft The difference between the density of the elastic layer and the density of the elastic layer on the outer peripheral surface of the elastic layer is 0.03 g / cm ³ or less.

(3) A third aspect of the present invention is the conductive sponge roller according to (1) or (2), wherein the density of the shaft is 3 g / cm ³ or less. is there.

  (4) A fourth aspect of the present invention is an image forming apparatus comprising the conductive sponge roller according to any one of (1) to (3).

  The conductive sponge roller according to the present invention uses, as a shaft, a shaft made of a synthetic resin having a thermal conductivity of 5 W / (m · K) or less, in which a conductive filler is dispersed, and the thickness direction of the elastic layer While the difference in the density is small and the hardness is low, the durability is well improved.

It is an explanatory view showing a conductive sponge roller concerning an embodiment of the present invention. FIG. 1 is an explanatory view showing an example of an image forming apparatus into which a conductive sponge roller according to an embodiment of the present invention is incorporated. In the electroconductive sponge roller of this invention, it is drawing which shows a compression tester which measures the outer diameter reset rate of an elastic layer.

<Conductive sponge roller>
The electroconductive sponge roller 1 which is an example of this invention has the axial body 2 and the elastic layer 3 provided on the outer peripheral surface of the axial body 2 as FIG. 1 shows. The code | symbol 4 is a coating layer provided in the surface of the elastic layer 3 as needed.

[Shaft]
The shaft 2 used in the present invention is made of a synthetic resin in which a conductive filler is dispersed. In the case where a so-called core metal formed of iron, aluminum, stainless steel, brass or the like is used as the shaft of the conductive sponge roller by using a synthetic resin in which the conductive filler is dispersed as the shaft 2 In comparison, the thermal conductivity can be reduced. As a result, the heat transfer between the shaft 2 and the elastic layer 3 becomes small, and the elastic layer 3 foams stably, so the density difference in the thickness direction of the elastic layer 3 becomes small, and the conductive sponge roller 1 with low hardness You can get In addition, since the density difference in the thickness direction of the elastic layer 3 is reduced, it is possible to suppress the temporal change in the developer supply amount and the scraping amount of the conductive sponge roller 1. Durability can be improved.

  The shaft 2 is adjusted to an appropriate diameter and axial length in accordance with the attached image forming apparatus. When the sponge roller is incorporated into the image forming apparatus, the shaft 2 usually has a diameter of 5.0 mm or more and 40 mm or less, and the axial length from one end to the other end is usually 120 mm or more and 1000 mm or less. The outer peripheral surface of the shaft 2 may be subjected to treatments such as washing treatment, degreasing treatment, and primer treatment in order to improve the adhesion to the elastic layer 3.

  The synthetic resin used for the shaft 2 is not particularly limited, but can be selected from general-purpose resins and engineering plastics. Examples of engineering plastics include polyacetal, polyamide resin (polyamide 6, polyamide 6.6, polyamide 12, polyamide 4.6, polyamide 6.10. Polyamide 6, 12 polyamide 11, polyamide MXD6), polybutylene terephthalate, polyphenylene Ether, polyphenylene sulfide, polyether sulfone, polycarbonate, polyimide, polyamide imide, polyether imide, poly sulfone, polyether ether ketone, polyethylene terephthalate, polyarylate, liquid crystal polymer or polytetrafluoroethylene, etc. may be mentioned. Moreover, as a general purpose resin, polypropylene, an ABS (acrylonitrile-butadiene-styrene) resin, polystyrene, and further polyethylene, etc. may be mentioned. Besides, melamine resin, phenol resin, silicone resin and the like can also be mentioned. One of these may be used alone, or two or more of these may be used in combination.

  The conductive filler used for the shaft 2 is not particularly limited as long as it is a component that can impart conductivity to the elastic layer 3. The conductive filler may be, for example, a conductive powder containing conductive carbon, carbons for rubber, metals, conductive polymers and the like. The conductive powder is preferably carbon black. Examples of carbon black include furnace black such as ketjen black (registered trademark), acetylene black, channel black, thermal black and the like.

  The content of the conductive filler is preferably 3% by mass or more and 50% by mass or less with respect to the total mass of the shaft 2. By adjusting the content of the conductive filler to the above range, the shaft body 2 has appropriate conductivity and thermal conductivity. The content of the conductive filler is more preferably 5% by mass or more and 45% by mass or less, and still more preferably 5% by mass or more and 40% by mass or less with respect to the total mass of the shaft 2.

(Thermal conductivity)
In the present invention, the thermal conductivity of the shaft body 2 is 5 W / (m · K) or less. By setting the thermal conductivity of the shaft 2 in the above range, the density difference in the thickness direction of the elastic layer 3 can be reduced. As a result, the elastic layer can be made to have a low hardness, and further, the temporal change in the developer supply amount and the scraping amount of the conductive sponge roller 1 can be suppressed, and the durability of the conductive sponge roller 1 can be reduced. It is possible to improve the quality. The thermal conductivity can be measured using a thermal conductivity meter (trade name QTM-500, manufactured by Kyoto Denshi Co., Ltd.). The thermal conductivity of the shaft 2 is preferably 0.1 W / (m · K) or more and 5 W / (m · K) or less 0.1 W / (m · K) or more 1 W / (m · K) Or less) is more preferable.

(Density of shaft)
The density of the shaft body 2 is smaller than that of the shaft body using the metal core made of the above metal, and is preferably ³ g / cm ³ or less. As described above, since the density of the shaft 2 is small, processing time such as polishing can be shortened and productivity can be improved as compared with the case of using a metal core made of the above metal as the shaft. Moreover, since the density is small, it is possible to suppress that the elastic layer 3 formed on the outer peripheral surface of the shaft 2 is crushed by its own weight. The density of the shaft 2 is more preferably 0.8 g / cm ³ or more and 3 g / cm ³ or less, and still more preferably 1 g / cm ³ or more and 2 g / cm ³ or less.

[Elastic layer]
The elastic layer 3 is made of a rubber material containing silicone rubber. In the present embodiment, since the elastic layer 3 contains silicone rubber, the compression set can be reduced, and an effect of excellent flexibility in a low temperature environment can be obtained.

Examples of the silicone rubber include crosslinked products of organopolysiloxanes such as dimethylpolysiloxane and diphenylpolysiloxane. The silicone rubber may also be a modified product of these.
Moreover, as the silicone rubber in the present invention, specifically, KE-571-U, KE-1571-U, KE-904FU, KE-951-U, KE-541-U, manufactured by Shin-Etsu Chemical Co., Ltd., KE-551-U, KE-561-U, KE-961T-U, KE-1541-U, KE-1551-U, KE-941-U, KE-971T-U, etc. can be used.

  The rubber material preferably comprises mainly silicone rubber. Specifically, the content of silicone rubber in the rubber material is preferably 60% by mass or more based on the total mass of the rubber material. 30 mass% or more may be sufficient as content of silicone rubber, and 40 mass% or more may be sufficient.

  The rubber material may contain components other than the rubber component. For example, the rubber material may further contain a conductivity imparting agent. The same base material as the above-mentioned conductive filler can be used for the conductivity imparting agent.

  In the conductive sponge roller 1, the elastic layer 3 is formed such that the outer peripheral surface of the shaft 2 is exposed at both ends in the axial direction of the shaft 2. That is, on the outer peripheral surface of the shaft 2, there is a region where the elastic layer 3 is not provided. In the present invention, the aspect of the elastic layer 3 is not limited to this, and the elastic layer 3 may be provided so as to cover the entire outer peripheral surface of the shaft 2.

  The thickness of the elastic layer 3 is preferably 0.5 mm or more and 10 mm or less, and preferably 1 mm or more and 5 mm, from the viewpoint of ensuring a uniform nip width with the abutted body in the abutted state. The following are more preferable. In the present specification, “thickness” means the thickness in the direction perpendicular to the axial direction of the conductive sponge roller 1. The outer diameter of the elastic layer 3 is not particularly limited. The outer diameter may be, for example, 5 mm or more and 20 mm or less. In the present specification, the “outer diameter” means the outer diameter in a cross section perpendicular to the axial direction of the conductive sponge roller 1. The thickness and outer diameter of the elastic layer 3 may be adjusted by adjusting the amount of the rubber composition used when forming the elastic layer 3 or by polishing or grinding the outer peripheral surface of the elastic layer 3 after the elastic layer 3 is formed. It can be adjusted.

  The outer peripheral surface of the elastic layer 3 may be subjected to surface treatment such as primer treatment, corona treatment, plasma treatment, excimer treatment, UV treatment, intro treatment, frame treatment and the like.

  The rubber material constituting the elastic layer 3 may be a cured product of a rubber composition.

(Rubber composition)
The rubber composition contains a rubber component that constitutes a silicone rubber by crosslinking. As such a rubber component, silicone gum, such as organopolysiloxane, is mentioned, for example.

As organopolysiloxane, the organopolysiloxane etc. which are represented by the following average composition formula are mentioned, for example.
R _n SiO _{(4-n) / 2}
[R represents a monovalent hydrocarbon group which may be substituted. 1 or more and 12 or less are preferable, and, as for carbon number of a hydrocarbon group, 1 or more and 8 or less are more preferable. Plural R may be the same or different. n is an integer of 1.95 or more and 2.05 or less. ]

  In the above formulae, R is, for example, an alkyl group such as methyl, ethyl, propyl, butyl, hexyl and dodecyl, a cycloalkyl such as cyclohexyl, a vinyl, allyl, butenyl and hexenyl Alkenyl groups such as aryl groups, aryl groups such as phenyl and tolyl groups, aralkyl groups such as β-phenylpropyl group, and part or all of hydrogen atoms bonded to carbon atoms of these groups as halogen atoms or cyano groups And the like, for example, chloromethyl group, trifluoropropyl group and cyanoethyl group substituted by

  The organopolysiloxane is preferably an organopolysiloxane containing at least two alkenyl groups bonded to a silicon atom in one molecule. For example, in the above formula, at least two Rs preferably have the above alkenyl group. More preferably, the organopolysiloxane has a vinyl group.

  Specific examples of the organopolysiloxane include dimethylpolysiloxane and diphenylpolysiloxane.

  The organopolysiloxane is preferably terminated at its molecular chain end with a trimethylsilyl group, a dimethylvinylsilyl group, a dimethylhydroxysilyl group, a trivinylsilyl group or the like.

  The rubber composition may contain various additives. As such additives, for example, auxiliary agents such as conductivity imparting agents, chain extenders and crosslinking agents, catalysts such as addition reaction catalysts, reaction control agents, dispersants, anti-aging agents, antioxidants, fillers And pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardancy improvers, acid acceptors, heat conductivity improvers, mold release agents, solvents and the like.

  As the foaming agent, any foaming agent conventionally used for forming an elastic layer may be used. Examples of inorganic foaming agents include sodium bicarbonate, ammonium carbonate and the like, and organic foaming agents such as diazoamino derivatives and azonitrile derivatives, Organic azo compounds such as azodicarboxylic acid derivatives and the like can be mentioned. Among the organic azo compounds, azodicarboxylic acid amide, azobis-isobutyronitrile and the like are suitably used. In particular, azobis-isobutyronitrile can be suitably used. When a foaming agent is used to form the elastic layer 3, the average cell diameter of the cells formed by the foaming agent in the cross section of the elastic layer which appears when the elastic layer is cut in the direction perpendicular to the central axis of this elastic layer. Is preferably 100 μm or more and 350 μm or less. The compression set can be reduced by adjusting the average cell diameter to the above range. The foaming agent is preferably contained in an amount of 4 parts by mass or more and 8 parts by mass or less, and more preferably 6 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass of the base rubber material. By setting the content of the foaming agent in the above range, the density difference in the thickness direction of the elastic layer 3 can be further reduced, and the hardness of the elastic layer 3 can be further lowered.

  The rubber composition preferably contains a conductivity imparting agent. The same base material as the above-mentioned conductive filler can be used for the conductivity imparting agent.

  Examples of the crosslinking agent include addition reaction type crosslinking agents such as organohydrogenpolysiloxane and organic peroxide reaction crosslinking agents such as benzoyl peroxide. These crosslinking agents may be used alone or in combination of two or more.

  The organohydrogenpolysiloxane may be linear, branched or cyclic. Specifically, methyl hydrogen polysiloxane and the like can be mentioned.

  The organohydrogenpolysiloxane preferably has two or more SiH groups (SiH bonds) in one molecule.

  The addition reaction catalyst may, for example, be a platinum catalyst comprising a support such as silica, alumina or silica gel and platinum supported on the support.

  A well-known reaction control agent can be used as a reaction control agent. The reaction control agent may be, for example, acetyl vinyl alcohols such as methyl vinyl cyclotetrasiloxane, ethynyl cyclohexanol, siloxane-modified acetyl alcohol, hydroperoxide and the like.

  The rubber composition may be a liquid rubber composition, and may be a millable rubber composition.

  As the rubber composition according to the present embodiment, the “addition-curable millable conductive silicone rubber composition” described in JP-A-2008-058622 can be used, and the contents described therein are incorporated in the present specification. Be

<Method of manufacturing conductive sponge roller>
The conductive sponge roller of the present invention can be produced, for example, by the following method. First, each raw material of the rubber composition described above is uniformly mixed, for example, by using a two-roll, three-roll, roll mill, a Banbury mixer, a dough mixer (kneader), or another rubber kneader. The mixture can be obtained by kneading at normal temperature or under heating for a few minutes to several hours, preferably 5 minutes or more and 1 hour or less.

  Next, the obtained mixture is thermoformed on the outer peripheral surface of a shaft for constituting a sponge roller by continuous thermoforming by extrusion molding, molding by a press, injection or the like.

  After the mixture is formed into a cylindrical shape on the outer surface of the shaft, the cylindrical mixture, in other words, a cylindrical formed body, is heated and vulcanized together with the shaft (heat curing).

  It is particularly preferable to heat the molded body in heating and vulcanization as follows. That is, as primary vulcanization, heat at 100 ° C. to 300 ° C., particularly 150 ° C. to 250 ° C. for 5 minutes to 30 minutes, then as secondary vulcanization 180 ° C. to 250 ° C., especially 200 ° C. to 230 ° C., 1 hour It is good to heat for 10 hours. Such heating with a plurality of times is preferable because it is possible to control the decomposition of the chemical blowing agent, the curing of the silicone rubber, and the removal of the residual low molecular weight siloxane as necessary.

  The heating necessary for vulcanization can be performed by a heating furnace such as an infrared heating furnace or a hot air furnace, a heating machine such as a dryer, or the like.

  The conductive sponge roller thus obtained may be further subjected to the polishing step. In the polishing process, the shape of the conductive sponge roller formed on the outer peripheral surface of the shaft is gradually increased toward the center of the shaft in the axial direction of the shaft, so that the shaft is moved from the center of the shaft to the shaft Step of adjusting to a shape that gradually decreases toward the tip of the body, that is, a crown shape, or a shape that increases the thickness of the sponge roller from the center of the shaft toward both ends of the shaft, that is, an inverse crown shape or a straight shape It is.

(Asker F hardness)
The elastic layer 3 has an Asker F hardness of 25 or more and 70 or less, and preferably 30 or more and 60 or less. If the Asker F hardness falls within such a range, a conductive sponge roller with low hardness can be obtained, and the load and friction on the developer at the time of pressure bonding of the rollers can be reduced. Asker F hardness is a value obtained by pressing the center of the pressing element of the hardness tester against the curved surface of the roller that is the object to be measured and reading the scale at the moment the reference surface contacts the surface of the roller. is there. In fact, it is possible to measure with "Asker rubber hardness meter F type" manufactured by Kobunshi Keiki Co., Ltd.

(Density of elastic layer)
In the elastic layer 3, the difference between the density of the elastic layer 3 at a position 50% of the thickness of the elastic layer 3 from the outer peripheral surface of the shaft 2 and the density of the elastic layer 3 at the outer peripheral surface of the elastic layer 3 is 0 It is preferable that it is .03 g / cm ³ or less. When the difference in density of the elastic layer 3 at the above two points is in the above range, the elastic layer 3 can be made to have low hardness, and furthermore, the amount of developer supplied and scraped off of the conductive sponge roller 1 Changes with time can be suppressed, and the durability of the conductive sponge roller 1 can be improved. Further, the difference between the density of the elastic layer 3 at a position 50% of the thickness of the elastic layer 3 from the outer peripheral surface of the shaft 2 and the density of the elastic layer 3 at the outer peripheral surface of the elastic layer 3 is 0.005 g / cm. more preferably ³ or more 0.03 g / cm ³ or less, and more preferably not more than 0.005 g / cm ³ or more 0.025 g / cm ^3.

[Outside diameter return rate]
In the conductive sponge roller 1 of the present invention, the outer diameter return ratio after one hour of the elastic layer 3 using the compression tester 60 is 90% or more and 100% or less. By adjusting the outer diameter return ratio to this range, it is possible to obtain the conductive sponge roller 1 having low hardness and improved strain characteristics and improved durability. In the method of measuring the outer diameter return rate, a compression tester 60 shown in FIG. 3 is used. First, the outer diameter of the conductive sponge roller 1 is measured by a laser measuring machine at normal temperature. As shown in FIG. 3, the conductive sponge roller 1 is sandwiched between the compression plate 61 and the compression plate 61, and the handle 63 is turned to tighten. The thickness of the spacer 62 (the length from the upper end surface of the spacer 62 in contact with the upper compression plate 61 to the lower end of the spacer 62 in contact with the lower compression plate 61) is 10 mm. Then turn the handle 63 and tighten. With the conductive sponge roller 1 clamped by the compression tester 60, the compression tester 60 is placed in a dryer at 100 ° C. and heated for 8 hours as it is. After 8 hours have passed, take out the compression device from the drier, immediately remove the conductive sponge roller 1 from the compression tester 60, and leave it for 1 hour at normal temperature to measure the outer diameter of the conductive sponge roller 1 Measure by The value calculated by the formula of the outer diameter of the conductive sponge roller 1 after compression / the outer diameter of the conductive sponge roller 1 before compression × 100 is defined as an outer diameter return rate (%).

<Image forming apparatus>
The conductive sponge roller 1 according to the present invention can be incorporated into, for example, the developing unit 40 or the fixing unit 35 of the image forming apparatus.

  Next, referring to FIG. 2, an example of an image forming apparatus 30 (hereinafter, may be referred to as an image forming apparatus 30 according to the present invention) incorporating the developing means 40 provided with the conductive sponge roller according to the present invention. To explain.

  As shown in FIG. 2, the image forming apparatus 30 according to the present invention is disposed around a rotatable image carrier 31, such as a photosensitive member, on which an electrostatic latent image is formed, and the image carrier 31. The charging unit 32, the exposure unit 33, the developing unit 40, the transfer unit 34, the cleaning unit 37, and the fixing unit 35 are provided downstream of the recording medium 36 in the conveyance direction. The developing unit 40 is basically formed in the same manner as the conventional developing unit. Specifically, as shown in FIG. 2, the developer storage portion 41 and the developer 42 are supplied to the image carrier 31. The developer carrier 44, the developer supply means 43 for supplying the developer 42 to the developer carrier 44, and the developer regulating member 45 for charging the developer 42 are provided.

  The fixing unit 35 includes an endless belt supporting roller disposed in the vicinity of the fixing roller 53 and the fixing roller 53 in a case 50 having an opening 52 through which the recording medium 36 passes, as a cross section thereof is shown in FIG. 54, endless belt 55 wound around fixing roller 53 and endless belt supporting roller 54, pressure roller 56 pressed against fixing roller 53 via endless belt 55, and non-contact with endless belt 55 The heating device is disposed, and includes heating means for heating the fixing roller 53 from the outside via the endless belt 55, and the fixing roller 53 and the pressure roller 56 are rotatable so as to abut or press against each other via the endless belt 55. It is a pressure heat fixing device supported.

  The endless belt support roller 54 may be any roller that is usually used in an image forming apparatus, and for example, an elastic roller or the like is used. The endless belt 55 may be, for example, an endless belt formed of a resin such as polyamide and polyamideimide, and the thickness and the like can be appropriately adjusted to be suitable for the fixing means 35. The pressure roller 56 is in pressure contact with the fixing roller 53 via the endless belt 55 by urging means (not shown) such as a spring. As the heating means, a radiation heating method using a halogen heater, a reflection plate or the like, a direct contact heating method in which the heater is brought into direct contact and heating, an induction heating method or the like is adopted. The heating means is a member having a length substantially the same as the length in the axial direction of the fixing roller 53, and may be disposed in any of the fixing means 35, but as shown in FIG. It is preferable that the fixing roller 53 be disposed substantially parallel to the fixing roller 53 at a more constant interval. In the induction heating method, a heating coil is used, and the heating coil is a ferromagnetic material such as ferrite and is a typical shape used for a switching power supply, and it is an I-type, an E-type and a U-type. Etc., and the conducting wire is wound. The recording material 36 passes while being in pressure contact with the endless belt 55 and the pressure roller 56, so that the developer 42 (electrostatic latent image) transferred to the recording material 36 is fixed while being simultaneously heated. be able to.

  The image forming apparatus 30 according to the present invention operates as follows. First, in the image forming apparatus 30, the image carrier 31 is uniformly charged by the charging unit 32, and an electrostatic latent image is formed on the surface of the image carrier 31 by the exposure unit 33. Next, the developer 42 is supplied from the developing means 40 to the image carrier 31 to develop the electrostatic latent image, and the developer image is conveyed between the image carrier 31 and the transfer means 34 on the recording material 36 Is transferred to The conductive sponge roller 1 of the present invention can be suitably used, for example, for the developer supply means 43 and the developer carrier 44, and since the hardness is low, the load and friction on the developer are reduced. Furthermore, since the strain characteristics are also improved, the durability is excellent. The recording medium 36 is conveyed to the fixing means 35, and the developer image is fixed on the recording medium 36 as a permanent image. Thus, an image can be formed on the recording body 36.

  The conductive sponge roller and the image forming apparatus according to the present invention are not limited to the above embodiments, and various modifications can be made as long as the object of the present invention can be achieved.

  For example, in the conductive sponge roller 1, the elastic layer 3 has a single-layer structure, but may have a multilayer structure of two or more layers in the present invention.

  Although the image forming apparatus 30 is an electrophotographic image forming apparatus, in the present invention, the image forming apparatus is not limited to the electrophotographic system, and may be, for example, an electrostatic image forming apparatus. Good. In addition, although the image forming apparatus 30 is a monochrome image forming apparatus in which only developing agent 42 of a single color is accommodated in the developing unit 40, in the present invention, the image forming apparatus is not limited to the monochrome image forming apparatus. It may be an image forming apparatus. As a color image forming apparatus, for example, a four cycle type color image forming apparatus in which a developer image carried on an image carrier is sequentially and sequentially transferred to an intermediate transfer member, and a plurality of image carriers having developing units of respective colors. And a tandem type color image forming apparatus in which an intermediate transfer member and a transfer conveyance belt are arranged in series. The image forming apparatus 30 is, for example, an image forming apparatus such as a copying machine, a facsimile, or a printer.

  Further, in the fixing means 35 and the image forming apparatus 30, as the developer 42, a one-component type developer is advantageously used, but a two-component type developer containing a toner and a carrier such as iron or nickel is also used. can do.

  Although the present invention has been described above using the embodiment, it goes without saying that the technical scope of the present invention is not limited to the scope of the invention described in the above embodiment, and various modifications or changes may be made to the above embodiment. It will be apparent to one skilled in the art that improvements can be made. It is also apparent from the scope of the claims that the invention added with such changes or improvements can be included in the technical scope of the present invention.

  Hereinafter, the present invention will be described in detail by way of examples. The present invention is not limited to the examples shown below.

  Example 1

(Preparation of conductive sponge roller)
After applying a silicone primer (trade name: Primer No. 4, Shin-Etsu Chemical Co., Ltd.) to the surface of the shaft (diameter 6 mm, length 230 mm) in which the content of the conductive filler is dispersed in the synthetic resin And dried at 150 ° C. in a gear oven. By this operation, a primer layer was formed on the outer periphery of the shaft.

  Next, the following materials were mixed to prepare an addition-curable millable conductive silicone rubber composition. A product made by Shin-Etsu Chemical Co., Ltd. as a "cross-linking agent" with respect to 100 parts by mass of a base rubber material using a millable silicone having a trade name "KE-551U" manufactured by Shin-Etsu Chemical Co., Ltd. as a base rubber material. 2 parts by mass of an addition reaction crosslinking agent having a name C-25B, 10 parts by mass of carbon black having a trade name of Asahi Thermal Black manufactured by Asahi Carbon Co., Ltd. as a conductivity imparting agent, and Shin-Etsu Chemical Co., Ltd. as a “catalyst” 2 parts by mass of a platinum catalyst having a trade name of C-25A manufactured by the company and 5 parts by mass of AIBN of a trade name of AZO series manufactured by Otsuka Chemical Co., Ltd. as a "chemical blowing agent" are mixed and kneaded using a pressure kneader Thus, an addition-curable mirable conductive silicone rubber composition was prepared.

  Next, the shaft on which the primer layer was formed and the addition-curable millable conductive silicone rubber composition were integrally separated by a crosshead extruder, and heated at 250 ° C. for 30 minutes using a gear oven. Thereafter, secondary heating was further performed at 200 ° C. for 4 hours using a gear oven, and left at normal temperature for 24 hours. Next, the surface of the elastic layer was polished with a cylindrical grinder such that the diameter of the formed elastic layer was 13 mm.

(Example 2)
A conductive sponge roller of Example 2 was obtained by the same method as Example 1 except that the amount of AIBN was 8 parts by mass.

(Comparative example 1)
A conductive sponge roller of Comparative Example 1 was obtained by the same method as Example 1, except that a shaft (diameter 6 mm, length 230 mm) made of free-cutting steel SUM23 was used as the shaft. .

  Configuration of the shaft, thermal conductivity and density, Asker F hardness of the elastic layer, and 50% of the thickness of the elastic layer from the outer peripheral surface of the shaft in the example and the comparative example manufactured in this way Table 1 shows the difference between the density of the elastic layer at the position of and the density of the elastic layer on the outer peripheral surface of the elastic layer (described as “the difference in density at two points” in Table 1) and the outer diameter return rate.

  From the above, according to the present invention, it is possible to obtain a conductive sponge roller in which the durability is favorably improved while the difference in density in the thickness direction of the elastic layer is small and the hardness is low.

DESCRIPTION OF SYMBOLS 1 conductive sponge roller 2 shaft 3 elastic layer 4 coating layer 30 image forming apparatus 31 image carrier 32 charging unit 33 exposure unit 34 transfer unit 35 fixing unit 36 recording member 37 cleaning unit 40 developing unit 41 developer storage portion 42 development Agent 43 Developer Supply Means 44 Developer Carrier 45 Developer Regulating Member 50 Case 52 Opening 53 Fixing Roller 54 Endless Belt Support Roller 55 Endless Belt 56 Pressure Roller 60 Compression Tester 61 Compression Plate 62 Spacer 63 Handle

Claims (4)

A conductive sponge roller comprising a shaft and an elastic layer provided on the outer peripheral surface of the shaft,
The shaft is made of a synthetic resin in which a conductive filler is dispersed,
The thermal conductivity of the shaft is 5 W / (m · K) or less,
The conductive sponge roller whose Asker F hardness of the said elastic layer is 25 or more and 70 or less. The difference between the density of the elastic layer at a position 50% of the thickness of the elastic layer from the outer peripheral surface of the shaft and the density of the elastic layer at the outer peripheral surface of the elastic layer is 0.03 g / cm ³ or less The conductive sponge roller according to claim 1. The conductive sponge roller according to claim 1, wherein the density of the shaft is 3 g / cm ³ or less.   An image forming apparatus comprising the conductive sponge roller according to any one of claims 1 to 3.