JP2015108747A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus in which the occurrence of paper wrinkles of a recording medium is suppressed than before, in a belt nip system.SOLUTION: The fixing device includes a rotatable fixing roll 70, a pressure belt rotated in contact with the fixing roll 70, and a pressing pad arranged inside the pressure belt and pressing the pressure belt to the fixing roll 70 from the inner peripheral surface of the pressure belt, to form a nip part through which the recording medium passes between the fixing roll 70 and the pressure belt. The fixing roll 70 includes a metal support 71 and a surface layer 72 covered on the metal support 71. The outer diameters of both ends in the rotation axis direction of the fixing roll 70 are larger than the outer diameter of the central part in the rotation axis direction of the fixing roll 70. The elastic modulus of a surface layer 72a of the central part in the rotation axis direction is in the range of 1.0E+01 MPa or more and 1.0E+02 MPa or less and the elastic moduli of surface layers 72b of both ends in the rotation axis direction are larger than the elastic modulus of the surface layer 72a of the central part in the rotation axis direction.

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic system, an unfixed toner image formed on a recording medium such as recording paper is fixed by a fixing device to form an image. As a fixing device used in such an image forming apparatus, for example, a fixing roll and a pressure roll disposed in pressure contact with the fixing roll are provided, and an unfixed portion is provided between the fixing roll and the pressure roll. There is a fixing device that passes a recording medium on which a toner image is formed and heats and pressurizes the unfixed toner image to fix the toner image on the recording medium. Such a fixing device is called a roll nip method, a two-roll method, or a heating roll method.

  Further, for example, a rotatable rotating member, a tubular body (for example, a fixing belt such as an endless belt) that rotates in contact with the rotating member, and an inner peripheral surface of the tubular body, the tubular body is arranged as the rotating member. And a pressing member that forms a nip portion through which the recording medium passes between the rotating member and the tubular body, and there is a fixing device that allows the recording medium to pass through the nip portion. Such a fixing device is called a belt nip method.

  For example, in Patent Document 1, a rotating member (rotating member), an endless belt (tubular body), and an endless belt are disposed inside, and the endless belt is pressed against the rotating member to A pressure member (pressing member) that forms a nip portion through which the recording medium passes with the endless belt, and the rotating member is disposed on the outer side in the longitudinal direction of the paper passing region through which the recording medium passes. A fixing device in which a frictional resistance portion having a friction coefficient higher than that of the paper region is formed is disclosed.

JP 2005-265993 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus in which the occurrence of paper wrinkles on a recording medium is suppressed in the belt nip method as compared with the conventional art.

  According to a first aspect of the present invention, there is provided a rotatable rotating member, a tubular body that rotates while being in contact with the rotating member, the inside of the tubular body, and the tubular body is disposed from an inner peripheral surface of the tubular body. A pressing member that presses against the rotating member and forms a nip portion through which a recording medium passes between the rotating member and the tubular body, the rotating member on the metal support and the metal support A surface layer to be coated, wherein an outer diameter of both end portions in the rotation axis direction of the rotating member is larger than an outer diameter of a center portion in the rotating shaft direction of the rotating member, and the surface layer in the center portion in the rotating shaft direction The storage elastic modulus at 150 ° C. is in the range of 1.0E + 01 MPa to 1.0E + 02 MPa, and the elastic modulus of the surface layer at both ends in the rotational axis direction is the elasticity of the surface layer in the central part in the rotational axis direction. The fixing device is larger than the rate.

  The invention according to claim 2 is the fixing device according to claim 1, wherein the elastic modulus of the surface layer at both ends in the rotation axis direction is in a range of 1.0E + 01 MPa to 1.0E + 03 MPa.

  According to a third aspect of the present invention, the ratio of the elastic modulus of the surface layer at both ends in the rotational axis direction to the elastic modulus of the surface layer at the central portion in the rotational axis direction is in a range of more than 1 and 5 or less. The fixing device according to 1 or 2.

  According to a fourth aspect of the present invention, there is provided an image carrier, latent image forming means for forming a latent image on the surface of the image carrier, and developing the latent image using a developer for developing an electrostatic image to form a toner image. 5. A developing unit that forms, a transfer unit that transfers the toner image to a recording medium, and a fixing unit that fixes the toner image to the recording medium, wherein the fixing unit is any one of claims 1 to 4. An image forming apparatus which is the fixing device according to the item.

  According to the first aspect of the present invention, even when a hard heating member such as metal is used in the belt nip method, the occurrence of paper wrinkles on the recording medium is suppressed as compared with the case without this configuration. A fixing device is provided.

  According to the second aspect of the present invention, there is provided a fixing device in which the generation of paper wrinkles on the recording medium is further suppressed in the belt nip method as compared with the case where this configuration is not provided.

  According to the third aspect of the present invention, even when a hard heating member such as metal is used in the belt nip method, paper wrinkles of the recording medium are further generated compared to the case where this configuration is not provided. A suppressed fixing device is provided.

  According to the invention of claim 4, even when a hard heating member such as metal is used in the belt nip method, the occurrence of paper wrinkles on the recording medium is suppressed as compared with the case without this configuration. An image forming apparatus is provided.

1 is a schematic configuration diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram illustrating an example of a configuration of a fixing device according to an exemplary embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating an example of a configuration of a fixing roll used in an embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a pressure distribution in a conveyance direction of a recording sheet at a nip portion of a fixing device.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic configuration diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing an example of the configuration of the fixing device according to the embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment is roughly divided into two configurations of an image forming unit (image forming unit) X and a fixing unit (fixing unit) Y.

  The image forming unit X includes a photosensitive drum (latent image holding member) 1 that rotates in the direction of an arrow D in which a latent image due to a difference in electrostatic potential is formed on the surface by irradiating image-like light after charging. Around this, in order of rotation (arrow D direction), a charging roll (charging means) 2 for charging the surface of the photosensitive drum 1, and image-like light is applied to the photosensitive drum 1 to statically irradiate the surface. An image exposure device (latent image forming means) 3 for forming an electrostatic latent image, and a developer for selectively transferring toner to the latent image formed on the surface of the photosensitive drum 1 to form a toner image (unfixed image). (Developing means) 4, a transfer roll (transfer means) 5 that faces the photosensitive drum 1, generates a transfer bias electric field between the photosensitive drum 1 and a recording paper (recording medium) P, and toner A cleaner (cleaner) for removing toner remaining on the photosensitive drum 1 after image transfer. Grayed member) 6 and is provided.

  For example, the photosensitive drum 1 shown in FIG. 1 is formed by forming a photosensitive layer composed of an organic photosensitive material, an amorphous silicon photosensitive material, or the like on the surface of a metal pipe.

  The charging roll 2 in FIG. 1 includes, for example, an elastic layer in which a conductive agent such as stainless steel and aluminum is mixed with a conductive agent in a material such as EPDM, NBR, and ECO, a polyamide resin, and a fluorine resin. It has a surface layer in which a conductive agent is blended with a material whose main component is a resin such as a resin, an acrylic resin, or a urethane resin, and is in contact with the photosensitive drum 1 to be driven to rotate. When a predetermined voltage is applied, a continuous discharge is generated in the gap in the vicinity of the contact portion between the charging roll 2 and the photosensitive drum 1, and the surface of the photosensitive drum 1 is charged.

  The image exposure device 3 in FIG. 1 generates, for example, a blinking laser beam based on an image signal, and scans this in the main scanning direction of the photosensitive drum 1 by a polygon mirror or the like. An electrostatic latent image is formed on the surface of 1.

  The developing device 4 in FIG. 1 contains, for example, black toner, and an electrostatic latent image formed on the surface of the photosensitive drum 1 by causing a developing roll carrying the toner to approach and face the photosensitive drum 1. The toner is transferred corresponding to the above, and a visualized toner image (unfixed image) is formed (developed).

  The transfer roll 5 in FIG. 1 is composed of, for example, a conductive or semiconductive roll-shaped member, and the toner on the surface of the photosensitive drum 1 by applying a transfer bias voltage to the photosensitive drum 1. The image is transferred to the recording paper P.

  The cleaner 6 in FIG. 1 is, for example, a blade-like member that is pressed against the surface of the photosensitive drum 1, and removes toner remaining on the surface of the photosensitive drum 1. The cleaner 6 may be one that scrapes off toner with a roll-like member or sweeps out toner with a brush, instead of such a blade-like one.

  In the image forming section X having the above-described configuration, the recording paper P is supplied in the direction of arrow C from the upstream side (right side in FIG. 1) to the facing portion between the photosensitive drum 1 and the transfer roll 5. A paper feed mechanism is configured (not shown). A toner image is transferred from the photosensitive drum 1 by the transfer roll 5 to the surface of the recording paper P conveyed to the opposite portion between the photosensitive drum 1 and the transfer roll 5. That is, in the image forming unit X, a toner image (unfixed image) is formed on the surface of the recording paper P.

  The fixing unit Y located on the downstream side of the image forming unit X in the conveyance direction (arrow C direction) of the recording paper P heats and melts the toner image transferred to the surface of the recording paper P, etc. And a fixing device 90 for fixing the toner image.

  2 includes a fixing roll 70 as an example of a rotating member, a pressure belt (eg, an endless belt) 81 as an example of a tubular body that rotates while being in contact with the fixing roll 70, and a pressure belt. An example of a pressing member that presses the pressure belt 81 from the inner peripheral surface of 81 to the fixing roll 70 and forms a nip portion through which the recording paper (recording medium) P passes between the fixing roll 70 and the pressure belt 81. The pressure pad 82, the sliding member 83 disposed between the pressure belt 81 and the pressure pad 82, a guide member 86 for guiding the inner surface of the pressure belt 81, and the inner surface of the pressure belt 81 are lubricated. The lubricant supply member 87 for applying the agent, the holding member 84 for holding the pressing pad 82, and the in-belt fixed holding holder 85 for fixing the lubricant supply member 87 constitute the main part. A halogen heater 73 as an example of a heating unit is disposed inside the fixing roll 70.

  In the fixing device 90 shown in FIG. 2, a fixing roll 70 that is a rotating member is disposed on the side in contact with the unfixed toner image T, and a pressure belt 81 that is a tubular body and a pressure pad 82 are disposed on the pressure side. The configuration is not limited to this, and a tubular body (for example, a fixing belt) and a pressing member (for example, a pressing pad) are arranged on the side in contact with the unfixed toner image T, and a rotating member (for example, a pressing member). For example, the structure which has arrange | positioned the pressure roll) may be sufficient.

  Around the fixing roll 70 shown in FIG. 2, a peeling member 60 for peeling the recording paper P after fixing, a temperature sensor (not shown) for controlling the temperature of the surface of the fixing roll 70, and the like are provided. . The peeling member 60 is arranged in the direction (counter direction) opposite to the rotation direction C of the fixing roll 70 so as to be close to the fixing roll 70.

  An example of the operation of the fixing device 90 shown in FIG. 2 will be described. First, the fixing roll 70 is connected to a drive motor (not shown) and rotates in the direction of arrow C, and the pressure belt 81 also rotates following this rotation. The fixing roll 70 is heated to a predetermined temperature (fixing temperature) by radiant heat from the halogen heater 73. Then, the recording paper P is conveyed to a nip portion formed between the fixing roll 70 and the pressure belt 81. Then, when the recording paper P passes through the nip portion, pressure acting on the nip portion, heat supplied from the fixing roll 70, etc. are applied to the recording paper P, and the unfixed toner image T is fixed on the recording paper P. Is done. After fixing, the recording paper P passes through the nip portion, is peeled off from the fixing roll 70 by the peeling member 60, and is discharged from the fixing device 90.

  Next, the fixing roll 70 used in this embodiment will be described. FIG. 3 is a schematic cross-sectional view showing an example of the configuration of the fixing roll used in the embodiment of the present invention, and is a view showing the longitudinal direction of the fixing roll. As shown in FIG. 3, the fixing roll 70 has a metal support (for example, a cylindrical cored bar) 71 and a surface layer 72 coated on the metal support 71.

  The fixing roll 70 shown in FIG. 3 has a so-called flare shape in which the outer diameter of both ends in the rotation axis direction of the fixing roll 70 is larger than the outer diameter of the central portion in the rotation axis direction. More specifically, the fixing roll 70 shown in FIG. 3 has an outer diameter that decreases from one end portion in the rotation axis direction of the fixing roll 70 toward the center of the rotation axis direction. The outer diameter increases from the center toward the other end in the direction of the rotation axis.

  Further, the elastic modulus of the surface layer 72a at the central portion in the rotation axis direction of the fixing roll 70 is in a range of 1.0E + 01 MPa or more and 1.0E + 02 MPa, and the elastic modulus of the surface layer 72b at both ends in the rotation axis direction of the fixing roll 70 is It is larger than the elastic modulus of the surface layer 72 a at the center in the rotation axis direction of the fixing roll 70.

  Here, the end in the rotation axis direction is a predetermined length in the paper passing area through which the recording paper P passes from the non-paper passing area through which the recording paper P does not pass (for example, the maximum paper passing size at both ends of 5 mm to 50 mm). ) And the central portion in the rotation axis direction is a range of the sheet passing area other than the predetermined length in the sheet passing area. Further, the storage elastic modulus of the surface layer is a value measured in the state of the single surface layer 72, and the storage elastic modulus of 10 Hz at 150 ° C. with a Leo Vibron DDV-01FP dynamic viscoelasticity automatic measuring machine manufactured by Key and Day. It is. Note that the larger the elastic modulus of the surface layer 72 is, the less deformation is caused by the stress applied to the surface layer 72.

  FIG. 4 is a diagram illustrating an example of the pressure distribution in the conveyance direction of the recording paper at the nip portion of the fixing device. As shown in FIG. 4, the pressure distribution in the nip formed by the pressing pad 82 is such that the inlet side and the outlet side of the nip portion are the inlet side and the outlet side of the nip portion when the conveyance direction of the recording paper P is the horizontal axis. This is considered to be higher than the region between the sides (hereinafter sometimes referred to as the inner region of the nip portion). Thus, when the pressure on the inlet side of the nip portion is high, it is considered that the sliding resistance of the recording paper P on the inlet side of the nip portion increases. Further, in the case of a flare-shaped fixing roll in which the outer diameter at both ends in the rotation axis direction of the fixing roll is larger than the outer diameter at the central portion in the rotation axis direction, the rotation axis of the fixing roll is caused by the difference in linear velocity during rotation in the above outer diameter difference. It is considered that both end portions in the direction are more stressed than the central portion in the rotation axis direction. Therefore, on the inlet side of the nip portion, a higher pressure is applied to both ends in the rotation axis direction, so that the surface layer at both ends in the rotation axis direction of the flare-shaped fixing roll is elastically deformed, etc. It is considered that the sliding resistance of the recording paper P on the entrance side becomes larger. As a result, paper wrinkles of the recording paper P on the inlet side of the nip portion are likely to occur.

  Therefore, in the present embodiment, the elastic modulus of the surface layer 72a at the central portion in the rotation axis direction of the fixing roll 70 is in the range of 1.0E + 01 MPa to 1.0E + 02 MPa, and the surface layer 72b at both ends in the rotation axis direction of the fixing roll 70 is used. By making the elastic modulus larger than the elastic modulus of the surface layer 72a at the central portion in the rotation axis direction of the fixing roll 70, the surface layers 72b at both ends in the rotation axis direction of the fixing roll 70 on the inlet side of the nip portion having the high pressure described above. Therefore, the increase in sliding resistance of the recording paper P on the inlet side of the nip portion can be suppressed, and the occurrence of paper wrinkles on the recording paper P on the inlet side of the nip portion can be suppressed. Yeah. Further, in the case of the flare-shaped fixing roll 70 in which the outer diameters at both ends in the rotation axis direction of the fixing roll 70 are larger than the outer diameter in the central part in the rotation axis direction, Because of the difference in linear velocity at the time of rotation due to the difference in outer diameter, mainly the tensile force from the central portion in the rotation axis direction of the fixing roll 70 toward both ends acts on the recording paper P, so the recording paper P in the inner region of the nip portion It is thought that the generation of paper wrinkles can be suppressed.

  In the present embodiment, the elastic modulus of the surface layer 72a at the central portion in the rotation axis direction of the fixing roll 70 is in the range of 1.0E + 01 MPa or more and 1.0E + 02 MPa, and the elasticity of the surface layer 72b at both ends in the rotation axis direction of the fixing roll 70. The rate should be larger than the elastic modulus of the surface layer 72a at the center portion in the rotation axis direction of the fixing roll 70. However, the rotation of the fixing roll 70 from the viewpoint of suppressing the generation of paper wrinkles, the transportability of the recording paper P, and the like. The elastic modulus of the surface layer 72a in the central portion in the axial direction is preferably in the range of 2.0E + 0 MPa to 6.0E + 02 MPa. When the elastic modulus of the surface layer 72a at the central portion in the rotational axis direction of the fixing roll 70 is less than 1.0E + 01 MPa, the surface layer at the central portion in the rotational axis direction of the fixing roll 70 on the inlet side of the high pressure nip portion. It is considered that the elastic deformation of 72a occurs, the sliding resistance of the recording paper P on the inlet side of the nip portion increases, and the paper wrinkles of the recording paper P on the inlet side of the nip portion occur. Further, if the elastic modulus of the surface layer 72a at the central portion in the rotation axis direction of the fixing roll 70 exceeds 1.0E + 02 MPa, the surface layer 72a is hardly elastically deformed, so that it is difficult to form a wide nip portion, and the recording paper P It is considered that the generation of paper wrinkles and the transportability of the recording paper P deteriorate. Further, even if the elastic modulus of the surface layer 72a at the central portion in the rotation axis direction of the fixing roll 70 is 1.0E + 01 MPa or more and 1.0E + 02 MPa or less, the elastic modulus of the surface layer 72b at both ends in the rotation axis direction of the fixing roll 70 is If it is smaller than the elastic modulus of the surface layer 72a at the central portion in the rotational axis direction of the fixing roll 70, the tensile force from the central portion in the rotational axis direction of the fixing roll 70 toward both ends is caused by the difference in the linear velocity at the time of rotation in the aforementioned outer diameter difference. In addition to this, it is considered that the shrinkage force from the both end portions of the fixing roll 70 in the rotation axis direction to the central portion acts on the recording paper P and the paper wrinkles of the recording paper P are generated.

  Further, the elastic modulus of the surface layer 72b at both ends in the rotation axis direction of the fixing roll 70 is larger than the elastic modulus of the surface layer 72a at the central portion in the rotation axis direction of the fixing roll 70, and is in the range of 1.0E + 01 MPa to 1.0E + 03 MPa. It is preferable that If the elastic modulus of the surface layer 72b at both ends in the rotation axis direction of the fixing roll 70 is less than 1.0E + 01 MPa, the durability of the surface layer 72b may be lowered depending on the thickness of the surface layer 72b, and 1.0E + 03 MPa. If it exceeds 1, it is difficult to form a wide nip portion, and the transportability of the recording paper P may deteriorate.

  Further, the ratio of the elastic modulus of the surface layer 72b at both ends in the rotation axis direction of the fixing roll 70 to the elastic modulus of the surface layer 72a in the central portion in the rotation axis direction of the fixing roll 70 is preferably in the range of 1 to 5. When the ratio of the elastic modulus of the surface layer 72b at both ends in the rotational axis direction of the fixing roll 70 to the elastic modulus of the surface layer 72a at the central portion in the rotational axis direction of the fixing roll 70 is 1 or less, the nip portion at the end portion in the rotational axis direction In some cases, the shrinkage from the both ends of the entrance fixing roller 70 in the rotation axis direction toward the center acts on the recording paper P, and the paper wrinkles of the recording paper P may occur. If it exceeds 5, the pulling force toward the center or both ends of the rotational axis due to the torque at both ends becomes small, and paper wrinkles may occur.

  The difference in the outer diameter of the central portion with respect to the outer diameter of both ends in the rotation axis direction of the fixing roll 70 is preferably in the range of 0.05% to 1%, for example, 0.1% to 0.5%. The range of is more preferable. If the ratio of the outer diameter of both ends to the outer diameter of the central portion in the rotation axis direction of the fixing roll 70 is less than 0.05, the difference in linear velocity during rotation due to the difference in outer diameter decreases, and the rotation axis direction of the fixing roll 70 In some cases, the tensile force from the central portion toward both ends does not sufficiently act on the recording paper P. Also, if the ratio of the outer diameter of both ends to the outer diameter of the central portion of the fixing roll 70 in the rotational axis direction exceeds 1%, it becomes difficult to form a wide nip portion in the central portion of the rotational axis direction, and the image fixing property decreases. There is a case.

  As the metal support 71 of the fixing roll 70, for example, a cylindrical metal core is used, and in terms of mechanical strength and heat conductivity, for example, iron, aluminum (for example, A-5052 material), SUS, copper, or the like. These metals or alloys are used. Further, in order to make the fixing roll 70 flare, the metal support 71 has a shape in which the outer diameter at both ends in the rotation axis direction is larger than the outer diameter at the center portion in the rotation axis direction. The outer diameters at both ends and the center of the metal support 71 in the rotation axis direction are appropriately set according to the size of the fixing roll 70 to be used. For example, the outer diameters at both ends are φ10 or more and φ100 or less. Set by range.

  The surface layer 72 is preferably a release layer exhibiting release properties with respect to the toner image T. The material of the release layer may be appropriately selected from conventionally known materials, but preferably contains a fluororesin from the viewpoints of heat resistance and releasability with respect to the toner image T. Examples of the fluororesin include PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), and composite materials thereof. In addition, a resin containing a filler such as silicon carbide, alumina, or barium sulfate is used.

  The surface layer 72 may be a plurality of layers having an adhesive layer, an elastic layer, a release layer, and the like. Further, when the surface layer 72 is a plurality of layers, the outermost layer of the plurality of layers is a release layer exhibiting releasability with respect to the toner image T, and an adhesive layer and an elastic layer are provided between the metal support 71 and the release layer. It is preferable to arrange the layers. The material of the elastic layer of the fixing roll 70 may be appropriately selected from conventionally known materials. For example, a silicone elastomer (hereinafter sometimes referred to as silicone rubber), a fluorine-containing elastomer (hereinafter referred to as fluorine-containing rubber), and the like. May be called).

  The thickness of the surface layer 72 is not particularly limited, but is preferably in the range of 5 μm to 100 μm, for example. If the thickness of the surface layer 72 is less than 5 μm, the durability of the surface layer 72 may be reduced, and if it exceeds 100 μm, the fixing roll 70 may be enlarged.

  Next, other configurations of the fixing device 90 will be described.

  The pressure belt 81 shown in FIG. 2 is rotatably supported by a pressure pad 82 disposed inside and a guide member 86 that guides the travel of the pressure belt 81, and receives a driving force from the fixing roll 70. It is driven and rotated. As the pressure belt 81 of the present embodiment, for example, a belt member such as a seamless endless belt whose original shape is formed in a cylindrical shape or a belt with a seam is used.

  There is no restriction | limiting in particular about the structure of the pressure belt 81, a magnitude | size, etc., According to the objective, it selects suitably from conventionally well-known things. The structure of the pressure belt 81 may be a single layer structure or a multilayer structure. Examples of the pressure belt 81 having a multilayer structure include those having a base layer and a release layer. Examples of the material for the base layer of the pressure belt 81 include thermosetting polyimide, thermoplastic polyimide, polyamide, and polyamideimide. Examples of the material of the release layer of the pressure belt 81 include PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene-hexafluoropropylene copolymer). ), Composite materials thereof, and those in which fillers such as silicon carbide, alumina, and barium sulfate are blended with those resins.

  As the pressing pad 82, for example, an elastic body such as silicone rubber or fluorine-containing rubber, a heat-resistant resin such as PPS, polyimide, polyester, or polyamide, a metal such as iron, aluminum, or SUS, a leaf spring, or the like is used.

  The sliding member 83 disposed between the pressing pad 82 and the pressure belt 81 is a low friction sheet from the viewpoint of reducing the sliding resistance between the inner peripheral surface of the pressing belt 81 and the pressing pad 82. Preferably there is. Examples of the material for the low friction sheet include thermosetting polyimide, thermoplastic polyimide, polyamide, polyamideimide, silicone elastomer (silicone resin), fluororesin, and fluorine-containing elastomer.

  The lubricant supply member 87 provided in the in-belt fixed holding holder 85 is disposed so as to be in contact with the inner peripheral surface of the pressure belt 81, and lubricant such as amino-modified silicone oil or fluorine oil is applied to the pressure belt 81. Appropriate amount is supplied to the inner peripheral surface. As a result, the lubricant is supplied between the pressure belt 81 and the sliding member 83, the sliding resistance at the nip portion of the pressure belt 81 via the sliding member 83 is reduced, and the pressure belt 81 is smooth. It is thought that a smooth rotation is promoted.

  Lubricants are, for example, amino-modified silicone oil, dimethyl silicone oil, mercapto-modified silicone oil, amino-modified silicone containing antioxidants, from the viewpoints of lubricity, kinematic viscosity as an index of lubricity, heat resistance, volatility, etc. A silicone oil such as a hindered amine oil that is an oil is preferable, and an amino-modified silicone oil is more preferable from the viewpoint of wettability. In addition, methylphenyl silicone oil is also preferable from the viewpoint of superior performance due to heat resistance. In view of heat resistance, hindered amine oil is preferable.

  In this embodiment, the halogen heater 73 is used as the heating unit. However, the heating unit is not limited to the type in which the fixing roll 70 is internally heated as long as the nip portion N is heated. And the like that heat externally.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

Example 1
Using an image forming apparatus DocuPrintP350 manufactured by Fuji Xerox Co., Ltd., the test was performed under the following conditions. The fixing device mounted on the image forming apparatus DocuPrintP350 is the fixing device shown in FIG. 2, and its specific configuration is as follows.

  The fixing roll is coated with PFA resin at a thickness of 30 μm by flow coating on both ends of the φ26 mm aluminum cylindrical core metal in the rotational axis direction, and at the center of the cylindrical core metal in the rotational axis direction. PFA resin is applied by a flow coating method to a thickness of 30 μm. About the surface layer of the produced fixing roll, the storage elastic modulus of 10 Hz at 150 degreeC was measured using the Leo vibron DDV-01FP dynamic viscoelasticity automatic measuring machine made from Key & Day. As a result, the elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll is 5.5E + 01 MPa, the elastic modulus of the surface layer at the central part in the rotational axis direction is 2.6E + 01 MPa, and the surface layer at the central part in the rotational axis direction. The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of 2.1 was 2.1.

  A 600 w halogen lamp was disposed as a heating source inside the cylindrical cored bar. The pressure belt is composed of a thermosetting polyimide resin having a peripheral length of 94 mm, a wall thickness of 75 μm, and a length of 240 mm, and tetrafluoroethylene-perfluoroalkyl vinyl ether as a release layer on the outer peripheral surface of the base material. Coalescence (PFA) is applied with a thickness of 30 μm.

  Silicone rubber was used as a material constituting the pressing pad. The size of the pressure pad used was 230 mm in length (longitudinal direction), 8 mm in width (short direction) of the pressing portion, and 5 mm in thickness. As a sliding member disposed between the pressure belt and the pressure pad, a fluororesin sheet having a thickness of 20 μm was used.

(Example 2)
In Example 2, the conditions were the same as in Example 1 except that 30 μm of PFA resin was applied to both ends in the rotation axis direction of the aluminum cylindrical cored bar. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Example 2 is 4.0E + 01 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 2.6E + 01 MPa, and the surface at the central portion in the rotational axis direction. The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 1.5.

(Example 3)
In Example 3, the conditions were the same as in Example 1 except that 15 μm of PFA resin was applied to the central portion in the rotation axis direction of the aluminum cylindrical cored bar. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Example 3 is 5.5E + 01 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 1.1E + 01 MPa, and the surface at the central portion in the rotational axis direction The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 4.6.

Example 4
In Example 4, 50 μm of PFA resin was applied to the central portion of the aluminum cylindrical core metal in the rotational axis direction, and PTFE resin was applied to the central portion of the cylindrical core metal in the rotational axis direction at a thickness of 30 μm. did. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Example 4 is 3.0E + 02 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 9.1E + 01 MPa, and the surface at the central portion in the rotational axis direction The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 3.3.

(Example 5)
In Example 5, the conditions were the same as in Example 1 except that 15 μm of PFA resin was applied to both ends in the rotation axis direction of the aluminum cylindrical cored bar. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Example 5 is 2.7E + 01 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 2.6E + 01 MPa, and the surface at the central portion in the rotational axis direction The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 1.1.

(Example 6)
In Example 6, the conditions were the same as in Example 1 except that 70 μm of PFA resin was applied to both ends in the rotation axis direction of the aluminum cylindrical cored bar. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Example 6 is 1.3E + 02 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 2.6E + 01 MPa, and the surface at the central portion in the rotational axis direction The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 4.9.

(Comparative Example 1)
In Comparative Example 1, the conditions were the same as in Example 1 except that 30 μm of PFA resin was applied to both ends and the center of the aluminum cylindrical cored bar in the rotation axis direction. The elastic modulus of the surface layer at both ends and the center of the fixing roll of Comparative Example 1 was 5.5E + 01 MPa.

(Comparative Example 2)
In Comparative Example 2, the conditions were the same as in Example 1 except that 30 μm of PFA resin was applied to both ends and the center of the aluminum cylindrical cored bar in the rotation axis direction. The elastic modulus of the surface layer at both ends and the center of the fixing roll of Comparative Example 2 was 4.0E + 01 MPa.

(Comparative Example 3)
In Comparative Example 3, except that 30 μm of PFA resin was applied to both ends of the aluminum cylindrical cored bar in the rotation axis direction, and 30 μm of PFA resin was applied to the central part of the aluminum cylindrical cored bar in the rotational axis direction. The conditions were the same as in Example 1. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Comparative Example 3 is 2.6E + 01 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 5.5E + 01 MPa, and the surface at the central portion in the rotational axis direction The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 0.5.

(Comparative Example 4)
In Comparative Example 4, the PFA resin was applied to both ends of the aluminum cylindrical cored bar in the rotational axis direction at 30 μm, and the fluororesin was applied to the central part of the aluminum cylindrical cored bar in the rotational axis direction. The conditions were the same as in Example 1. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Comparative Example 4 is 4.0E + 01 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 5.5E + 01 MPa, and the surface at the central portion in the rotational axis direction The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 0.7.

(Comparative Example 5)
In Comparative Example 5, 30 μm of PTFE resin was applied to both ends of the aluminum cylindrical cored bar in the rotational axis direction, and 30 μm of PFA resin was applied to the central part of the cylindrical aluminum cored bar in the rotational axis direction. Except for this, the conditions were the same as in Example 1. The elastic modulus of the surface layer at both ends in the rotational axis direction of the fixing roll of Comparative Example 5 is 5.5E + 01 MPa, the elastic modulus of the surface layer at the central portion in the rotational axis direction is 3.0E + 02 MPa, and the surface at the central portion in the rotational axis direction The ratio of the elastic modulus of the surface layer at both ends in the rotation axis direction to the elastic modulus of the layer was 5.4.

<Evaluation of paper wrinkles>
In Examples 1 to 6 and Comparative Examples 1 to 5, the load between the pressing pad and the fixing roll (that is, the load on the nip portion) is set to 0.35 MPa, the fixing temperature is controlled to 160 ° C., and the image forming apparatus After forming a halftone image on plain paper (A4-P manufactured by Fuji Xerox Co., Ltd.) by duplex printing in the image forming unit, 20 sheets of plain paper were passed through the fixing device so that the halftone image was on the fixing roll side. . The paper wrinkle of the 20th plain paper was evaluated under the following conditions, and the results are summarized in Table 1.
A: Paper wrinkles were not observed on plain paper by visual observation.
○: Although slight paper wrinkles were observed on plain paper by visual observation, the level was satisfactory.
Δ: Paper wrinkles were observed on plain paper by visual observation.
X: Wrinkles were noticeably observed on plain paper by visual observation.

  As can be seen from Table 1, the elastic modulus at the central portion in the rotational axis direction of the fixing roll is in the range of 1.0E + 01 MPa to 1.0E + 02 MPa, and the elastic modulus at both ends in the rotational axis direction is larger than the elastic modulus at the central portion in the rotational axis direction. In Examples 1 to 6, paper wrinkles were hardly generated on plain paper, and good images were obtained. In particular, in Examples 2 and 5, no paper wrinkles occurred on the plain paper. In contrast, Comparative Examples 1 and 2 in which the elastic moduli at both ends and the center of the fixing roll are the same, and Comparative Example 3 where the elastic moduli at both ends of the rotating shaft are smaller than the elastic moduli of the central part in the rotational axis. 5, Comparative Example 4 in which the elastic modulus at both ends in the rotational axis direction is larger than that at the central part in the rotational axis direction, but the elastic modulus at the central part in the rotational axis direction is less than 1.0E + 01 MPa or more than 1.0E + 02 MPa. Paper wrinkles occurred. In particular, in Comparative Examples 3 and 5, paper wrinkles were noticeably observed on plain paper.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum, 2 Charging roll, 3 Image exposure device, 4 Developer, 5 Transfer roll, 6 Cleaner, 10 Image forming apparatus, 60 Peeling member, 70 Fixing roll, 71 Metal support, 72 Surface layer, 72a Rotating shaft Surface layer at the center in the direction, 72b surface layer at both ends in the rotation axis direction, 73 halogen heater, 81 pressure belt, 82 pressure pad, 83 sliding member, 84 holding member, 85 in-belt fixed holding holder, 86 guide member, 87 Lubricant supply member, 90 fixing device.

Claims (4)

A rotatable rotating member, a tubular body that rotates while contacting the rotating member, and disposed inside the tubular body, pressing the tubular body from the inner peripheral surface of the tubular body to the rotating member, A pressing member that forms a nip through which a recording medium passes between the rotating member and the tubular body,
The rotating member includes a metal support, and a surface layer coated on the metal support,
The outer diameter of both ends in the rotational axis direction of the rotating member is larger than the outer diameter of the central portion in the rotational axis direction of the rotating member,
The elastic modulus of the surface layer at the central portion in the rotation axis direction is in a range of 1.0E + 01 MPa to 1.0E + 02 MPa.
The fixing device according to claim 1, wherein an elastic modulus of the surface layer at both ends in the rotation axis direction is larger than an elastic modulus of the surface layer in the central portion in the rotation axis direction.   The fixing device according to claim 1, wherein an elastic modulus of the surface layer at both ends in the rotation axis direction is 1.0E + 01 MPa or more and 1.0E + 03 MPa or less.   The ratio of the elastic modulus of the surface layer at both ends in the rotational axis direction to the elastic modulus of the surface layer in the central portion in the rotational axis direction is in the range of more than 1 and 5 or less. The fixing device according to 1. An image carrier, a latent image forming unit for forming a latent image on the surface of the image carrier, a developing unit for developing the latent image using a developer for developing an electrostatic image to form a toner image, and the toner Transfer means for transferring an image to a recording medium, and fixing means for fixing the toner image to the recording medium,
The image forming apparatus according to claim 1, wherein the fixing unit is the fixing device according to claim 1.

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