JP5582595B2 - Elastic roller and fixing device used in image forming apparatus - Google Patents

Description

The present invention relates to an elastic roller and a fixing device used in an image forming apparatus, and more particularly to an elastic roller and a fixing device excellent in durability used in an image forming apparatus .

  Various image forming apparatuses using an electrophotographic system are employed in printers such as laser printers and video printers, copiers, facsimiles, and multi-function machines thereof. The image forming apparatus includes a fixing device having a fixing roller and / or a heating roller in order to fix the developer image transferred to the recording member to the recording member. A fixing roller and a heating roller employed in such a fixing device usually include a foamed elastic layer formed on the outer peripheral surface of the shaft body.

  Examples of the fixing roller provided with the foamed elastic layer formed on the outer peripheral surface of the shaft include, for example, “a metal cored bar and a foamed silicone rubber layer that covers the metal cored bar, and the foamed silicone rubber Patent Document 1 describes “a sponge roll characterized in that the average cell diameter of the core metal side region in the layer is smaller than the average cell diameter of the outer region”.

  However, when the sponge roll described in Patent Document 1 is mounted as a fixing roller on the fixing device of the image forming apparatus and the image forming apparatus is operated, the surface of the mounted sponge roll, particularly the foamed silicone rubber layer, is destroyed. In some cases, cracks are likely to occur, and the deterioration may occur such that a desired function cannot be exhibited in a short time. Therefore, the fixing device and the image forming apparatus to which such a sponge roll is attached cannot be used for a long period of time, and it has been desired to improve the durability of the sponge roller.

JP 2007-170473 A

It is an object of the present invention to provide an elastic roller and a fixing device that are used in an image forming apparatus and have excellent durability.

As means for solving the problems,
Claim 1 is an elastic roller comprising a shaft body and a foamed elastic layer formed on the outer peripheral surface of the shaft body, wherein the foamed elastic layer is a first region in order from the outer peripheral surface side of the shaft body, When divided into the second region and the third region, the average cell diameter A of the cells included in the first region, the average cell diameter B of the cells included in the second region, and included in the third region An elastic roller used in an image forming apparatus, wherein the average cell diameter C of the cells satisfies the following relationship:
B>A> C
The elastic foam used in the image forming apparatus according to claim 1, wherein the foamed elastic layer is formed by curing a silicone rubber composition.
According to a third aspect of the present invention, there is provided a fixing device comprising an elastic roller used in the image forming apparatus according to the first or second aspect.

The elastic roller used in the image forming apparatus according to the present invention includes a cell included in the first region when the elastic roller is divided into a first region, a second region, and a third region in order from the outer peripheral surface side of the shaft body. The average cell diameter A, the average cell diameter B of the cells included in the second region, and the average cell diameter C of the cells included in the third region are provided with a foamed elastic layer that satisfies the above relationship. It is possible to achieve high adhesion to the body and hardness required for the elastic roller used in the image forming apparatus, and the fixing device is provided by the third region in which the cells having the smallest average cell diameter C are formed. It is possible to prevent the structure of the third region from being broken due to the distribution of the load when mounted on the. Therefore, according to the present invention, it is used in an image forming apparatus, Durable elastic roller, and comprising an elastic roller for use in an image forming apparatus according to the present invention, fixing Durable An apparatus can be provided.

As shown in FIGS. 1 and 2, an elastic roller used in the image forming apparatus according to the present invention (hereinafter, “an elastic roller used in the image forming apparatus” may be simply referred to as an “elastic roller”). elastic roller 1A as an example of.) is composed includes a shaft body 2, and a foamed elastic layer 3 formed on the outer peripheral surface of the shaft body 2.

  The shaft body 2 only needs to have good conductive properties, and is usually a so-called “core” composed of iron, aluminum, stainless steel, brass, or the like. Further, the shaft body 2 may be a shaft body that is made conductive by plating an insulating core body such as a thermoplastic resin or a thermosetting resin. Furthermore, the shaft body 2 may be a thermoplastic resin or a thermosetting resin. The shaft body may be formed of a conductive resin in which carbon black or metal powder is blended as a conductivity imparting agent.

  The foamed elastic layer 3 is formed in a single layer structure on the outer peripheral surface of the shaft body 2 and has cells (not shown in FIG. 1) inside and / or on the outer surface thereof. When the foamed elastic layer 3 has cells, the hardness of the foamed elastic layer 3 is reduced, and the function of the elastic roller 1 can be improved. Here, the cell which the foaming elastic layer 3 has refers to the hollow area | region which arises by foaming or decomposition | disassembly of the foaming agent contained in the below-mentioned rubber composition which forms the foaming elastic layer 3. FIG. The plurality of cells of the foamed elastic layer 3 are in a state where they do not contact or communicate with other cells (referred to as independent cell states), a state where they contact or communicate with other cells (communication cell state) Or the independent cell state and the communication cell state may coexist. The foamed elastic layer 3 has a cell size, a presence rate, and the like determined according to various rollers used in the image forming apparatus.

  As shown in FIG. 2 (in FIG. 2, hatching indicating a cross section is omitted), the foamed elastic layer 3 includes the first region 3 </ b> A and the second region in order from the outer peripheral surface side of the shaft body 2. When divided into the region 3B and the third region 3C, the average cell diameter A of the cells 7A included in the first region 3A, the average cell diameter B of the cells 7B included in the second region 3B, and the first The average cell diameter C of the cells 7C included in the three regions 3C satisfies the relationship B> A> C. Thus, when the foamed elastic layer 3 is divided into three regions from the outer peripheral surface side of the shaft body 2 in the thickness direction, the inner peripheral surface side of the foamed elastic layer 3 (the outer peripheral surface side of the shaft body 2). ) To the outer peripheral surface side, the average cell diameter of the cells included in the region is small, large, or medium.

  When the foamed elastic layer 3 has such characteristics, the inventor of the present application maintains the hardness required for the elastic roller mounted on the image forming apparatus while ensuring high adhesion with the shaft body 2. In addition, the third region in which cells having the smallest average cell diameter C are formed disperses the load when attached to the fixing device and destroys the structure of the third region over a long period of time. The present invention has been completed by finding that it can be prevented.

  That is, the inventor of the present application finds the following functions of the first region 3A, the second region 3B, and the third region 3C in the foamed elastic layer 3 and further synergistically exhibits these functions, It was found that the objective can be achieved well.

  The first region 3 </ b> A in the foamed elastic layer 3 mainly contributes to the expression of hardness in the foamed elastic layer 3 and the securing of adhesion to the shaft body 2. The second region 3 </ b> B in the foamed elastic layer 3 mainly contributes to the development of hardness in the foamed elastic layer 3. The third region 3 </ b> C in the foamed elastic layer 3 mainly contributes to prevention of surface deterioration in the foamed elastic layer 3. That is, if the third region in the vicinity of the surface of the foamed elastic layer 3 has such cells 7C, even if the foamed elastic layer 3 is loaded with a large load, the fine cells 7C are attached. In other words, in other words, since the load is evenly distributed on the cell wall where the cell 7C is not formed, the cell structure in the vicinity of the surface of the foamed elastic layer 3 is destroyed and the occurrence of cracks or the like is prolonged. Can be prevented over time.

  In the present invention, the first region 3A, the second region 3B, and the third region 3C divided as described above are arranged in the thickness direction of the foamed elastic layer 3 in order from the outer peripheral surface side of the shaft body 3: 6: It is preferable that the area is divided at a ratio of 1. If the cell diameters A, B, and C satisfy the relationship when the first region 3A, the second region 3B, and the third region 3C are divided by the ratio, the first region 3A, the second region 3B, and the third region The effects of 3C are exhibited synergistically to achieve higher adhesion to the shaft body 2 and the desired hardness required for the elastic roller, and the load when mounted on the fixing device is uniform. It can be highly prevented over a long period that the structure of the third region is destroyed by being dispersed.

The average cell diameter or the like of the cells formed in the foamed elastic layer 3 is not particularly limited as long as the above relationship is satisfied, and is appropriately adjusted according to the application. For example, when the elastic roller 1 is used as a fixing roller or a heating roller in the fixing device of the image forming apparatus, the average cell diameter of the cells of the foamed elastic layer 3 is within the following range so as to satisfy the relational expression. It is preferred that it be selected. That is, the average cell diameter of the cells 7A existing in the first region 3A is preferably 80 to 750 μm, and particularly preferably 150 to 450 μm. The average cell diameter of the cells 3B existing in the second region 3B is preferably 100 to 800 μm, and particularly preferably 200 to 500 μm. The average cell diameter of the cells 7C existing in the third region 3C is preferably 60 to 700 μm, and particularly preferably 100 to 400 μm. When the average cell diameters of the cells 7A, 7B, and 7C existing in the first region 3A, the second region 3B, and the third region 3C are selected from the following ranges so as to satisfy the relational expression, the shaft body 2 In addition, the hardness required for the fixing roller or the heating roller can be sufficiently maintained while the durability of the elastic roller 1 can be further improved. The average cell diameter of the cell is determined by observing an area of about 20 mm ² with an electron microscope or the like on the surface of each of the regions 3A, 3B and 3C of the foamed elastic layer 3 or a cut surface obtained by cutting an arbitrary surface. Is measured as the average length obtained by arithmetically averaging the measured maximum length. In addition, the average cell diameter in the foamed elastic layer 3 can be adjusted by the blending amount of the foaming agent contained in the rubber composition to be described later that forms the foamed elastic layer 3, the curing conditions of the rubber composition, and the like.

  The foamed elastic layer 3 preferably has an Asker C hardness of 20 to 60, and particularly preferably has an Asker C hardness of 25 to 45. When the foamed elastic layer 3 has Asker C hardness in the above range, the function as an elastic roller attached to an image forming apparatus or the like can be sufficiently exhibited. Asker C hardness can be measured according to JIS K6253.

  The thickness of the foamed elastic layer 3 is not particularly limited, but is usually preferably adjusted to 2 to 20 mm, and particularly preferably adjusted to 3 to 12 mm.

  The rubber composition forming the foamed elastic layer 3 may be a composition containing rubber, a foaming agent, and various additives as required. For example, a foamed silicone rubber composition and a foamed urethane rubber composition A thing etc. are mentioned preferably. The foamed silicone rubber-based composition is a suitable rubber composition that is excellent in heat resistance, durability, residual strain resistance, and the like and can withstand high-speed operation of the image forming apparatus. As such a foamed silicone rubber composition, an addition reaction type foamed silicone rubber composition is particularly preferred. The foaming agent may be any foaming agent conventionally used for foamed rubber. Examples of the inorganic foaming agent include sodium bicarbonate and ammonium carbonate. Examples of the organic foaming agent include diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acids. And organic azo compounds such as acid derivatives. Usually, an inorganic foaming agent is used when forming a continuous cell in rubber, and an organic foaming agent is used when forming an independent cell. In the elastic roller 1, the foaming agent is preferably an organic foaming agent in that it can form a cell in an independent cell state. Specifically, for example, azodicarboxylic acid amide, azobis-isobutyrate is used. An azo compound such as ronitrile is preferably used. In particular, dimethyl-1,1'-azobis (1-cyclohexanecarboxylate) can be preferably used.

  The addition reaction type foamed silicone rubber composition contains a vinyl group-containing silicone raw rubber, a silica-based filler, the foaming agent, an addition reaction crosslinking agent, an addition reaction catalyst, and a reaction control agent. Furthermore, you may contain an organic peroxide crosslinking agent, a heat resistance improver, and various additives. As such an addition reaction type | mold foaming silicone rubber composition, the addition reaction type | mold foaming silicone rubber composition described in Unexamined-Japanese-Patent No. 2008-076751 is mentioned, for example. In addition, as a silicone rubber composition containing the vinyl group-containing silicone raw rubber, the silica-based filler, and the various additives, for example, trade names “KE series” and “KEG series” manufactured by Shin-Etsu Chemical Co., Ltd. It can be easily obtained.

  As shown in FIG. 3, an elastic roller 1 </ b> B as another embodiment of the elastic roller according to the present invention includes a shaft body 2, a foamed elastic layer 3 formed on the outer peripheral surface thereof, and a foamed elastic layer 3. And a tube layer 4 formed on the outer peripheral surface. The shaft body 2 and the foamed elastic layer 3 in the elastic roller 1B are basically the same as the shaft body 2 and the foamed elastic layer 3 in the elastic roller 1A. Therefore, the foamed elastic layer 3 of the elastic roller 1B is included in the average cell diameter A of the cells 7A included in the first region 3A, the average cell diameter B of the cells 7B included in the second region 3B, and the third region 3C. The average cell diameter C of the cell 7C satisfies the relationship B> A> C.

  The tube layer 4 is formed on the outer peripheral surface of the foamed elastic layer 3 with a material to be described later. If the tube layer 4 is formed on the outer surface of the foamed elastic layer 3, the releasability of the developer can be improved. The tube layer 4 is formed to a thickness of 1 to 100 μm, for example.

  The material for forming the tube layer 4 is not particularly limited, but the elastic roller 1B is preferably in contact with or pressed against the contacted body, and thus is preferably a material that is not easily permanently deformed. For example, alkyd resin , Alkyd resin modified products such as phenol modified / silicone modified, oil free alkyd resin, acrylic resin, silicone resin, epoxy resin, fluororesin, phenol resin, polyamide resin, urethane resin, polyamideimide resin, and mixtures thereof It is done. The tube layer 4 may be a metal sleeve, and examples of the metal forming the tube layer 4 include metals having high thermal conductivity such as iron, stainless steel, and nickel.

  The tube layer 4 may have a single layer structure or a laminated structure in which two or more layers are laminated, and is formed to have a thickness of 1 to 100 μm, for example. When the tube layer 4 is made of metal, it is preferable that the tube layer 4 has a tensile strength of about 800 to 1300 MPa because it is difficult to be deformed by pressure contact from the inner peripheral surface of the foamed elastic layer 3. The measuring method of the tensile strength is based on JIS Z 2241.

  In this elastic roller 1B, since the tube layer 4 is a thin layer, even if the tube layer 4 is formed on the outer peripheral surface of the foamed elastic layer 3, the elastic roller 1B has the characteristics of the foamed elastic layer 3 in the tube layer 4. It can be demonstrated through. Therefore, also in this elastic roller 1B, the same effect as the elastic roller 1A can be sufficiently obtained.

  In order to manufacture the elastic rollers 1A and 1B, first, the shaft body 2 is prepared by a known method using the material. The shaft body 2 is coated with a primer layer on the outer peripheral surface as desired. The rubber composition is heat molded on the outer peripheral surface of the shaft body 2 thus produced by continuous heat molding by extrusion molding, pressing, mold molding by injection, or the like. In the heat molding of the rubber composition, first, the rubber composition is disposed on the outer peripheral surface of the shaft body 2. As a method of disposing the rubber composition on the outer peripheral surface of the shaft body 2, for example, the shaft body 2 and the rubber composition are integrally extracted by an extruder or the like, and the rubber composition is disposed on the outer peripheral surface of the shaft body 2. And a method of injecting a rubber composition into a mold for housing the shaft body 2 and disposing the rubber composition on the outer peripheral surface of the shaft body 2. Among these, the method of dispensing the shaft body 2 and the rubber composition integrally with an extruder or the like is preferable in terms of easy work and continuous work.

  Thus, after arrange | positioning a rubber composition to the outer peripheral surface of the shaft body 2, a rubber composition is heated, maintaining this state. The heating of the rubber composition may be performed under conditions sufficient for the rubber contained in the rubber composition, for example, the vinyl group-containing silicone raw rubber to crosslink and the foaming agent to decompose or foam. For example, the rubber composition is usually heated to about 170 to 500 ° C., particularly 200 to 400 ° C. by a heating furnace such as an infrared heating furnace or a hot air oven, a heating machine such as a dryer, and the like. In particular, it is heated for 5 to 30 minutes.

  At this time, in order to form three regions in the heat-curing rubber composition, for example, a method of selecting a heating method of the rubber composition disposed on the outer peripheral surface of the shaft body 2 or the rubber composition is contained in the rubber composition. A method of adjusting the temperature and method of heating the rubber composition according to the curing temperature of the rubber and the foaming temperature of the foaming agent contained in the rubber composition may be mentioned. That is, the rubber composition is simultaneously heated from the outer peripheral surface of the shaft body 2 and the outer peripheral surface of the shaft body 2, and preferably, the outer peripheral surface side of the rubber composition is located closer to the shaft body 2 side than the shaft body 2 side. By heating to a high temperature, cells having a smaller average cell diameter than the substantially central portion can be formed on the shaft body 2 side and the outer peripheral surface side of the foamed elastic layer 3. In the method of appropriately selecting the rubber and the foaming agent contained in the rubber composition, in order to form cells having a small average cell diameter in the foamed elastic layer 3, foaming having a foaming temperature higher than the curing temperature of the rubber. After selecting the agent and heating the rubber composition to cure the rubber to some extent, the method of increasing the heating temperature as necessary to foam the foaming agent, etc., on the other hand, the average cell diameter in the foamed elastic layer 3 In order to form a large cell, a foaming agent having a foaming temperature lower than the curing temperature of the rubber is selected, the rubber composition is heated to foam the foaming agent to some extent, and then the heating temperature is increased as necessary. And a method of curing the rubber.

  As a method of simultaneously heating the rubber composition from the outer peripheral surface of the shaft body 2 and the outer peripheral surface of the shaft body 2, specifically, the shaft body 2 and the addition reaction type foamed silicone rubber composition By heating the outer peripheral surface of the object to, for example, 150 to 350 ° C., cells 7A and 7C having a small average cell diameter can be formed in the first region 3A and the third region 3C that are quickly heated to a predetermined temperature. At the same time, a cell 7B having a large average cell diameter can be formed in the second region 3B, which is gradually heated to a temperature lower than a predetermined temperature by heat conduction of the addition reaction type foamed silicone rubber composition. In the case where the addition reaction type foamed silicone rubber composition or the like is used, for example, the shaft body 2 can be formed at 100 to 300 ° C. at a temperature of the rubber composition in that three regions can be easily formed in the foamed elastic layer 3. In order to increase the average cell diameter of the cells 7A in the first region 3A to be larger than the average cell diameter of the cells 7C in the third region 3C, a heating condition for heating the outer peripheral surface to 150 to 350 ° C is preferable. Preferably, a means for setting the heating temperature of 2 lower than the outer peripheral surface heating temperature of the rubber composition is mentioned. For example, the temperature difference between the heating temperature of the shaft body 2 and the outer peripheral surface heating temperature of the rubber composition is 1 to Heating conditions adjusted to a range of 100 ° C are preferable, and heating conditions adjusted to a range of 40 to 100 ° C are particularly preferable.

  If desired, the rubber composition may be further subjected to secondary heating. In the secondary heating, for example, the rubber composition cross-linked under the above-described conditions is further in an extruded state, for example, 180 to 250 ° C, preferably 190 to 230 ° C, for 1 to 24 hours. Heating again for 3 to 10 hours or using a mold, for example, at 130 to 200 ° C., preferably 150 to 180 ° C. for 5 minutes to 24 hours, preferably 10 minutes to 10 hours or less Is done.

  The rubber cured body thus molded is subjected to a grinding process, a polishing process and / or a cutting process, etc., which are adjusted to a desired size and shape, if desired. The grinding process, the polishing process, and / or the cutting process can be performed according to a conventional method using a conventionally used grinder, cylindrical grinder, file, or the like.

  If desired, a tube layer 4 is formed on the outer periphery of the foamed elastic layer 3 formed as described above. Specifically, the tube layer 4 is formed by inserting the foamed elastic layer 3 into a tubular body previously formed in a cylindrical shape having the same inner diameter as the outer diameter of the foamed elastic layer 3. Forming on the outer surface is preferable in that the tube layer 4 having a smooth surface can be formed without being greatly affected by the uneven shape present on the surface of the foamed elastic layer 3. Of course, the tube layer 4 may be formed by applying the material to the outer peripheral surface of the foamed elastic layer 3 according to, for example, a dip method, a spray method, etc., and then curing and / or crosslinking.

  Thus, the elastic rollers 1A and 1B provided with the foamed elastic layer 3 having the above characteristics on the outer peripheral surface of the shaft body 2 can be manufactured.

  The foamed elastic layer 3 in the elastic rollers 1A and 1B is a cell included in the first region 3A when it is divided into the first region 3A, the second region 3B, and the third region 3C in this order from the outer peripheral surface side of the shaft body 2. Since the average cell diameter A of 7A, the average cell diameter B of the cells 7B included in the second region 3B, and the average cell diameter C of the cells 7C included in the third region 3C satisfy the relationship, the shaft body 2 The third region 3C disperses the load when it is mounted on the fixing device and destroys the structure of the third region 3C. This can be prevented. Thus, the foamed elastic layer 3 can exhibit high durability. Since the elastic rollers 1A and 1B have the above-described effects, they are preferably used as an elastic roller mounted on the image forming apparatus, for example, a fixing roller, a heating roller, a cleaning roller, a recording material conveying roller, and the like. It is preferably used as a heating roller.

  The elastic roller according to the present invention is not limited to the above-described embodiments, and various modifications can be made within a range in which the object of the present invention can be achieved. For example, the foamed elastic layer 3 in the elastic rollers 1A and 1B is formed in a single layer structure. However, in the present invention, the foamed elastic layer may be formed in a laminated structure of two or more layers. A three-layer structure in which the two regions and the third region are separately formed may be employed.

  Moreover, although the foamed elastic layer 3 in the elastic rollers 1A and 1B is formed of a rubber composition having the same composition, in this invention, the foamed elastic layer may be formed of rubber compositions having different compositions. For example, the foamed elastic layer can be formed from rubber compositions containing foaming agents having different foaming temperatures.

  Furthermore, in the elastic rollers 1A and 1B, the tube layer 4 is directly provided on the outer peripheral surface of the foamed elastic layer 3. In this invention, the tube layer is formed on the outer peripheral surface of the foamed elastic layer via an adhesive layer or the like. May be.

  The elastic roller according to the present invention is disposed, for example, as the image forming apparatus 40 shown in FIG. 4, more specifically, as a fixing roller 61 or a heating roller 62 built in the fixing apparatus 60 of the image forming apparatus 40. Is done.

  As shown in FIG. 4, the image forming apparatus 40 includes a rotatable image carrier 41 on which an electrostatic latent image is formed, such as a photosensitive member, and a charging unit 42, which is disposed around the image carrier 41. A charging roller, an exposure unit 43, a developing unit 50, a transfer unit 44 such as a transfer roller and a cleaning unit 45, and a fixing unit 60 such as a fixing device are provided on the downstream side in the conveyance direction of the recording body 46. The developing means 50 is formed basically in the same manner as the conventional developing means. Specifically, as shown in FIG. 4, the developer 52 is supplied to the developer accommodating portion 51 and the image carrier 41. A developer carrier 54, a developer regulating member 55 that charges the developer 52, and a stirrer 53 that uniformly stirs the developer 52 are provided. As long as the developer 52 is a one-component developer, the developer 52 may be a dry developer or a wet developer, and may be a non-magnetic developer or a magnetic developer.

  As shown in FIG. 4, the fixing device 60 includes a fixing roller 61, a pressure roller 62 arranged to face the fixing roller 61, and a fixing roller in a housing 64 having an opening 65 through which the recording body 46 passes. An external heating means 63 for heating 61 from the outside is provided, and the fixing roller 61 and the pressure roller 62 are rotatably supported so as to contact or press against each other. The pressure roller 62 is in contact with or in pressure contact with the fixing roller 61 by an urging means (not shown) such as a spring. The fixing device 60 is equipped with a heating coil as the external heating means 63 and employs an induction heating method. The heating coil as the external heating means 63 is a member having a length substantially the same as the axial length of the fixing roller 61, and is disposed substantially parallel to the fixing roller 61 at a certain interval from the surface of the fixing roller 61. Has been. Although not shown, this heating coil is usually made of a ferromagnetic material such as ferrite and is formed into I-type, E-type, U-type, etc., which are typical shapes used for a switching power source, and a conducting wire is wound. It is made up of. When a high-frequency alternating current is applied to the conducting wire of the heating coil 63, an eddy current is generated in the sleeve 4 and the sleeve 4 is induction-heated by the Joule heat. As a result, the fixing roller 61 is heated.

  In the fixing device 60, the external heating unit 63 employs, in addition to the induction heating method, a radiant heating method using a halogen heater, a reflector, or the like, a direct contact heating method in which heating is performed by directly contacting a heater or the like. The position where the external heating means 63 is arranged is not particularly limited. The fixing device 60 may employ an internal heating unit instead of the external heating unit 63 or in addition to the external heating unit 63.

  The image forming apparatus 40 operates as follows. First, as shown by the arrow in FIG. 4, the image carrier 41 rotates in the clockwise direction, and after the developer 52 and / or dust and the like on the surface thereof are removed by the cleaning unit 45, the charging unit 42 removes it. Then, the image is exposed by the exposure means 43, and an electrostatic latent image is formed on the surface of the image carrier 41.

  On the other hand, in the developing means 50, the developer carrier 54 is rotated in the direction of the arrow shown in FIG. 4, whereby the developer 52 is supplied to the developer carrier 54, and the supplied developer 52 is supplied to the developer carrier. Passing between 54 and the developer regulating member 55, it is regulated to a desired layer thickness and charged as desired.

  Next, a developer 52 having a desired layer thickness and charge amount is supplied to the image carrier 41 via the developer carrier 54, and the electrostatic latent image formed on the image carrier 41 is developed by the developer 52. This electrostatic latent image is visualized as a developer image. Next, the developer image developed on the image carrier 41 is transferred by the transfer unit 44 onto the recording body 46 conveyed between the image carrier 41 and the transfer unit 44. The recording body 46 to which the developer image has been transferred is conveyed to the fixing device 60 and heated when passing through a contact portion or a pressure contact portion between the pressure roller 62 and the fixing roller 61 heated by the heating coil 63. The developer image (electrostatic latent image) transferred by being pressed and / or pressed is fixed on the recording body 46 as a permanent image. In this way, an image can be formed on the recording body 46.

  In the image forming apparatus 40, the elastic roller 1 is mounted as the fixing roller 61 or the heating roller 62. However, the elastic roller 1 can achieve the hardness required for the elastic roller 1 as described above. In addition, since the durability is excellent, even if the image forming apparatus 40 is operated for a long period of time, the function of the fixing device 60 is not impaired in a short time due to the breakage of the elastic roller 1 or the like. Therefore, the fixing device 60 and the image forming apparatus 40 can be operated for a long period of time and have excellent durability. That is, according to the present invention, the object of providing a fixing device and an image forming apparatus excellent in durability can be achieved.

  The image forming apparatus 40 is an electrophotographic image forming apparatus. However, the image forming apparatus in which the elastic roller 1 is disposed is not limited to the electrophotographic system. For example, the electrostatic image forming apparatus. It may be. Further, the image forming apparatus 40 is a monochrome image forming apparatus in which only a single color developer is accommodated in the developing unit, but the image forming apparatus in which the elastic roller 1 is disposed is not limited to the monochrome image forming apparatus. A color image forming apparatus may be used. Examples of the color image forming apparatus include a four-cycle color image forming apparatus that sequentially repeats primary transfer of a developer image carried on an image carrier to an intermediate transfer body, and a plurality of image carriers provided with developing means for each color. Examples thereof include a tandem type color image forming apparatus in which a body is arranged in series on an intermediate transfer body or a transfer conveyance belt. The image forming apparatus 40 is an image forming apparatus such as a copying machine, a facsimile machine, or a printer.

  In this invention, the fixing device 60 is an external heating system. In this invention, however, the fixing device uses a fixing roller 61 and a pressure roller 62 in which a heater such as a heater is housed instead of the external heating means 63. An internal heating method may be used.

Example 1
First, an electroless nickel-plated shaft (diameter 12 mm x length 350 mm, SUM22) was washed with toluene, and primer “No. 101A / B” (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name) was applied. did. The primer-treated shaft was fired at 180 ° C. for 30 minutes using a gear oven, and then cooled at room temperature for 30 minutes or more to form a primer layer.

  Subsequently, 100 parts by mass of a silicone rubber composition “KE-904FU” (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name) containing a vinyl group-containing silicone raw rubber and a silica-based filler, and an addition reaction crosslinking agent “C-153A” ( Shin-Etsu Chemical Co., Ltd .: trade name: 2.0 parts by mass; Organic foaming agent: Azobis-isobutyronitrile “KEP-13” (Shin-Etsu Chemical Co., Ltd .: trade name): 2.5 parts by mass An appropriate amount of platinum catalyst as an addition reaction catalyst, 0.5 parts by mass of a reaction control agent “R-153A” (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), and an organic peroxide cross-linking agent “C-3” (Shin-Etsu) Chemical Industry Co., Ltd .: trade name) appropriate amount and heat resistance improver “KEP-12” (Shin-Etsu Chemical Co., Ltd .: trade name) 1.0 part by mass sufficiently kneaded with two rolls, Preparation of addition reaction type foamed silicone rubber composition It was.

  Next, the shaft body 2 on which the primer layer is formed and the addition reaction type foamed silicone rubber composition are integrally extracted by an extruder, and the addition reaction type foamed silicone rubber composition is disposed on the outer peripheral surface of the shaft body 2. did. In this way, the shaft body 2 is heated to 150 ° C. with the electric heater connected to the shaft body 2 of the roller base material in which the addition reaction type foamed silicone rubber composition is disposed on the outer peripheral surface of the shaft body 2. The raw roller body was placed in a heater adjusted to 200 ° C. and heated simultaneously from the shaft body 2 side and the outer peripheral surface side of the addition reaction type foamed silicone rubber composition for 30 minutes. After that, the roller base material from which the electric heater was removed from the shaft body 2 was further heated in a gear oven at 200 ° C. for 7 hours, and the addition reaction type foamed silicone rubber composition after secondary foaming was secondarily heated, and 1 Left for hours. The elasticity of Example 1 in which the addition reaction type foamed silicone rubber composition obtained by secondary heating was adjusted to an outer diameter of 29 mm with a cylindrical grinder, and the foamed elastic layer 3 was provided on the outer peripheral surface of the shaft body 2. A roller was produced. The Asker C hardness of this elastic roller was 30.

(Comparative Example 1)
A roller original was produced in the same manner as in Example 1. After the roller body shaft body 2 was heated to 250 ° C. for 10 minutes, the roller body was placed in a heater adjusted to 200 ° C. and heated for 30 minutes. Thereafter, secondary heating and grinding were performed in the same manner as in Example 1 to produce an elastic roller of Comparative Example 1. The Asker C hardness of this elastic roller was 30.

  The elastic rollers of Example 1 and Comparative Example 1 manufactured in this way were cut along a plane perpendicular to the axis, and the average cell shape of the cells formed in each region on the cut surface of the foamed elastic layer 3 was determined by the above method. It was measured. In each area of the foamed elastic layer 3, the thickness of the foamed elastic layer 3 is 8.5 mm. Therefore, the first area 3A is an area having a thickness from the outer peripheral surface of the shaft body 2 to about 2.6 mm. The second region 3B is a region having a thickness of about 2.6 to 7.6 mm from the outer peripheral surface of the shaft body 2, and the third region 3C is about 7.6 to 8.5 mm from the outer peripheral surface of the shaft body 2. It was set as the area | region which has thickness.

  As a result, in the elastic roller of Example 1, the average cell diameter of the first region 3A was 410 μm, the average cell diameter of the second region 3B was 480 μm, and the average cell diameter of the third region 3C was 360 μm. In the elastic roller of Comparative Example 1, the average cell diameter of the first region 3A was 430 μm, the average cell diameter of the second region 3B was 520 μm, and the average cell diameter of the third region 3C was 530 μm. The elastic roller of Comparative Example 1 corresponds to Patent Document 1, and the average cell diameter in the region on the shaft body 2 side (region from the outer peripheral surface of the shaft body 2 to about 4.3 mm) is the outer region (shaft body). 2 from the outer peripheral surface of 2 to an area of about 4.3 to 8.5 mm).

(Durability test)
The durability test of the elastic roller of Example 1 and Comparative Example 1 was performed by the following method using the durability test apparatus 70 described in FIG. Specifically, the durability test apparatus 70 is fixed to the lower surface inside the housing and is provided on both sides of the heating roller 71 provided with an internal heater 72 along the axial direction of the heating roller 71. A test roller mounting portion 74 provided on the upper surface inside the housing so as to be movable up and down so as to face the heat insulating material 73 and the heating roller 71, and a pressing force adjusting means 75 capable of moving the test roller mounting portion 74 up and down. For example, a pressure adjusting micrometer is provided. As the heating roller 71, a metal (stainless steel, SUS304) roller having a diameter of 20 mm was used.

  Each manufactured elastic roller is mounted on the bearing of the test roller mounting portion 74, and as shown in FIG. 5, the pressing force adjusting means 75 is operated to mount the mounted elastic roller (“elastic roller 76” in FIG. 5). ) Is pressed against the heating roller 71, and the elastic roller 76 is fixed at the pressure-contact portion between the heating roller 71 and the elastic roller 76 so that the foamed elastic layer of the elastic roller 76 is recessed 3 mm inside (that is, the elastic roller 76). The distance d between the central axis of the elastic roller 76 and the central axis of the heating roller 71 was adjusted to be 3 mm shorter than the sum of the outer diameter of the heating roller 71 and the outer diameter of the heating roller 71). Subsequently, the heat insulating material 73 and the internal heater 72 were started, and the surface temperature of the heating roller 71 was adjusted to 180 ° C. Thereafter, the elastic roller 76 was rotationally driven at a rotational speed of 180 rpm by a driving means (not shown) provided in the test roller mounting portion 74 until the surface of the elastic roller 76 was cracked. The occurrence of cracks was confirmed by visually stopping the surface of the elastic roller 76 after a predetermined time had elapsed.

  As a result, the elastic roller of Comparative Example 1 required 210 hours before the surface cracked, whereas the elastic roller 1 of Example 1 required 1.5 hours or more, 330 hours. .

FIG. 1 is a schematic perspective view showing an elastic roller which is an embodiment of the elastic roller according to the present invention. FIG. 2 is a schematic cross-sectional view showing a cross section taken along line AA in FIG. FIG. 3 is a schematic perspective view showing an elastic roller which is another embodiment of the elastic roller according to the present invention. FIG. 4 is a schematic explanatory view showing an image forming apparatus including a fixing device according to an embodiment of the fixing device according to the present invention. FIG. 5 is a schematic view showing a durability test apparatus suitably used for carrying out the durability test of the elastic roller according to the present invention.

DESCRIPTION OF SYMBOLS 1A, 1B Elastic roller 2 Shaft body 3 Foamed elastic layer 3A 1st area | region 3B 2nd area | region 3C 3rd area | region 4 Tube layer 7A, 7B, 7C Cell 40 Image forming apparatus 41 Image carrier 42 Charging means 43 Exposure means 44 Transfer means 45 Cleaning means 46 Recording body 50 Developing means 51 Developer storage section 52 Developer 53 Stirrer 54 Developer carrier 55 Developer regulating member 60 Fixing device 61 Fixing roller 62 Pressure roller 63 External heating means 64 Housing 65 Opening 70 Durability Property testing device 71 heating roller 72 internal heater 73 heat insulating material 74 test roller mounting portion 75 pressing force adjusting means

Claims (3)

An elastic roller comprising a shaft body and a foamed elastic layer formed on the outer peripheral surface of the shaft body,
When the foamed elastic layer is divided into a first region, a second region, and a third region in order from the outer peripheral surface side of the shaft body, the average cell diameter A of the cells included in the first region, the second An elastic roller used in an image forming apparatus , wherein an average cell diameter B of cells included in an area and an average cell diameter C of cells included in the third area satisfy the following relationship:
B>A> C The elastic roller used in the image forming apparatus according to claim 1, wherein the foamed elastic layer is formed by curing a silicone rubber composition. A fixing device comprising an elastic roller used in the image forming apparatus according to claim 1.

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