JP2012103613A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that is configured to suppress temperature rise in both edge areas of a heating roller in a fixing process of a small-sized recording member, and an image forming apparatus.SOLUTION: A heating roller of a fixing device includes a release layer 221 having a first passage area L1 and a second passage area L2, which is provided at a position where the first passage area L1 is held between both sides in the shaft direction of a core member 223. The heat radiation rate of the release layer 221 of the second passage area L2 is set to be larger than the heat radiation rate of the release layer 221 of the first passage area L1.

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a fixing device that fixes a toner image formed on a recording member and an image forming apparatus including the fixing device.

  In a fixing device provided in an image forming apparatus or the like, a recording member having a toner image formed on the surface thereof is introduced, and an area where the recording member is sandwiched between a pressure roller and a heating roller provided in the fixing device. By passing, the toner image on the recording member is heated and fixed to the recording member.

  Conventionally, in a fixing device, in order to reduce heat loss radiated from a pressure roller and a heating roller, for example, a means for covering the periphery of the pressure roller and the heating roller with a heat radiation (radiation) reflector has been taken. It was. However, the provision of the heat radiation (radiation) reflector has a disadvantage that the fixing device is enlarged.

  In order to avoid such inconvenience, in Patent Document 1, a release layer having a thickness of 5 μm to 10 μm is provided on the surface of the heating roller. This release layer is made of PTFE (polytetrafluoroethylene) on nickel, which is a metal exhibiting good thermal conductivity, so that the emissivity in the infrared wavelength region corresponding to the fixing temperature in the fixing device is 0.65 or less. And PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer). By configuring the release layer with such a material, it is intended to suppress the amount of heat (radiant energy) radiated from the surface of the heating roller.

JP 09-080952 A

  Here, at the time of fixing a toner image formed on a small-sized recording member (for example, B5 vertical size), the recording member does not deprive the heat amount in both end regions of the heating roller that are not in contact with the recording member of the heating roller. For this reason, the temperature of both end regions tends to increase as compared to the central region of the heating roller through which the recording member passes.

  This tendency becomes more prominent as the conveyance speed of the recording member increases. Therefore, it is necessary to reduce the conveyance speed of the recording member in order to suppress the temperature rise in the both end regions of the heating roller. However, when the conveyance speed of the recording member is lowered, the image forming processing capability (productivity) of the image forming apparatus is lowered. Such a problem appears conspicuously when a technique such as that described in Patent Document 1 is used.

  The present invention has been made in order to solve the above-described problem, and does not reduce the image forming processing capability (productivity) of the image forming apparatus. It is an object of the present invention to provide a fixing device and an image forming apparatus having a structure capable of suppressing a temperature rise in a region.

  In the fixing device according to the present invention, a pressure roller and a heating roller are provided, and a plurality of recording members having different widths are passed through a region sandwiched between the pressure roller and the heating roller, and A fixing device that pressurizes and heats a toner image on a recording member to fix the toner image on the recording member, wherein the heating roller includes a heating source and a cylindrical core member that includes the heating source. A release layer that is in contact with the recording member and formed on the core member, and the release layer includes a first contact region that contacts the recording member having a minimum width, and the first contact region. A second contact region that contacts the recording member having a larger width than the recording member having the minimum width, and a third contact region located on both sides of the first contact region in the second contact region. And the third contact area Thermal emissivity of the release layer is provided greater than the emissivity of the heat of the release layer of the first contact region.

  In another embodiment, the third contact region has a region provided thicker than the film thickness of the first contact region.

  In another embodiment, the release layer contains a low thermal emissivity material having a lower heat emissivity than the release layer, and the content of the low thermal emissivity material in the first contact region is It is greater than the content of the low thermal emissivity material in the 3-contact region.

  In another form, as for the surface roughness of the said core member, the surface roughness corresponding to the said 3rd contact area is provided more largely than the surface roughness corresponding to the said 1st contact area.

  An image forming apparatus according to the present invention includes the above-described fixing device.

  According to the fixing device and the image forming apparatus based on the present invention, the both end regions of the heating roller can be fixed even in the fixing process of a small-sized recording member without reducing the image forming processing capability (productivity) of the image forming apparatus. It is possible to suppress the temperature rise.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment. 1 is a block diagram of an image forming apparatus according to an embodiment. 1 is a perspective view of a fixing device according to an embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. 1 is an overall view of a heating roller employed in a fixing device in an embodiment. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. It is sectional drawing along the axis line of the heating roller employ | adopted as the fixing device in embodiment. It is sectional drawing along the axis line of the other heating roller employ | adopted as the fixing device in embodiment. It is sectional drawing along the axis line of the other heating roller employ | adopted as the fixing device in embodiment. It is sectional drawing along the axis line of the other heating roller employ | adopted as the fixing device in embodiment. It is sectional drawing along the axis line of the other heating roller employ | adopted as the fixing device in embodiment. It is sectional drawing along the axis line of the other heating roller employ | adopted as the fixing device in embodiment. FIG. 6 is a cross-sectional view of a heating roller employed in a fixing device according to another embodiment, corresponding to a VI-VI line arrow in FIG. 5. FIG. 6 is a cross-sectional view of a heating roller employed in a fixing device according to another embodiment, corresponding to the view taken along line VI-VI in FIG. 5.

  Hereinafter, a fixing device and an image forming apparatus according to each embodiment based on the present invention will be described with reference to the drawings. Note that in the embodiments described below, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated. In addition, it is planned from the beginning to use the structures in the embodiments in appropriate combinations.

  In this embodiment, a tandem color printer that forms a color image is shown as an example of an image forming apparatus. The image forming apparatus according to the present invention only needs to include a fixing device, and may be a monochrome printer.

[Overall Configuration of Image Forming Apparatus 100]
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 100 including a fixing device 110 according to the present embodiment. Referring to FIG. 1, an image forming apparatus 100 includes an exterior cover 101 that forms an appearance, and a recording member (hereinafter referred to as a transfer sheet) printed inside the image forming apparatus 100 is carried out from a discharge port 108. Is done.

  The image forming apparatus 100 includes four photosensitive members 104 that rotate, and an intermediate transfer belt 105 that sequentially stacks and transfers toner images formed at respective transfer positions of the photosensitive member 104 for image formation. And a transfer roller 106 provided at a transfer position set around the moving surface of the intermediate transfer belt 105.

  The transfer paper stored in the paper feed cassette 102 is conveyed to the transfer position using the paper feed roller 103. Although not shown, the paper feed cassette 102 is provided with a sensor for detecting the presence or absence of transfer paper. If the paper feed cassette 102 is not set or the transfer paper runs out, a display panel (not shown) or the like is used. The user is notified.

  In the image forming apparatus 100, an electrostatic latent image is formed on the photoconductor 104 based on image data to be printed on a transfer sheet. The electrostatic latent image formed on the photoconductor 104 is visualized with toner by development, and sequentially laminated on the intermediate transfer belt 105. The toner image that has been electrostatically transferred onto the intermediate transfer belt 105 and has been combined is electrostatically and collectively transferred onto the transfer sheet based on the electrostatic suction from the transfer roller 106 at the transfer position. .

  The transfer sheet on which the toner image is transferred passes through the fixing device 110. Due to the passage of the fixing device 110, heat and pressure are applied to the transfer paper on which the toner image has been transferred, and the toner image on the transfer paper is fixed. This process completes image formation on the transfer paper. Thereafter, the transfer sheet is discharged from the discharge port 108.

[Block Diagram of Image Forming Apparatus 100]
FIG. 2 is a block diagram of the image forming apparatus 100. Referring to FIG. 2, image forming apparatus 100 includes a central control unit 1 that controls the operation of image forming apparatus 100 as a whole. The central control unit 1 includes a CPU (Central Processing Unit).

  The image forming apparatus 100 includes a ROM (Read Only Memory) 3 including data such as a program executed by the central control unit 1 and a RAM (Random Access Memory) 2 serving as a working area when the central control unit 1 executes the program. A memory 4 for storing various data such as setting values when the central control unit 1 executes the program, a display unit for displaying the state of the image forming apparatus 100, buttons for inputting information from the outside, and the like. An operation unit 5 including an input unit and a network I / F (interface) 9 serving as an interface when communicating with an external device via the network 9A are included.

  In the image forming apparatus 100, formation of an electrostatic latent image on the photosensitive member 104, rotation of the intermediate transfer belt 105, rotation of the transfer roller 106, rotation of the paper feed roller 103, presence / absence of transfer paper in the paper feed cassette 102, and the like. Processing is performed until an electrostatic latent image is formed and developed in an image forming operation, such as processing of a detection signal by a sensor, a toner image is transferred to a transfer sheet of the paper feed cassette 102, and the transfer sheet is introduced into the fixing device 110. The image forming unit 6 executes processing until the transfer sheet that has passed through the fixing device 110 is discharged from the discharge port 108. The operation of the image forming unit 6 is controlled by the central control unit 1.

  The fixing device 110 includes a fixing device control unit 310 that controls the operation of the fixing device 110 as a whole. In the fixing device 110, the fixing device control unit 310 controls the operation of the halogen heater 313 (heating source) and the various motors 314 based on the detection outputs of the various sensors 315.

[Configuration of Fixing Device 110]
3 is a perspective view of the fixing device in each embodiment according to the present embodiment, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG.

  Referring to FIGS. 3 and 4, fixing device 110 includes a housing 28 that covers an outline of the fixing device 110. In the fixing device 110, a carry-out port 24 is provided on the upper side of the housing 28 (downstream side in the transfer sheet conveyance direction), and a carry-in port 26 is provided on the lower side on the opposite side (upstream side in the transfer sheet conveyance direction).

  A guide member 42 is provided at the carry-in port 26. If the guide member 42 is configured to be driven by the drive mechanism, it can also function as a shutter that opens and closes the carry-in port 26.

  Inside the housing 28, a pressure roller (pressure member) 20 and a heating roller (heating member) 22 incorporating a halogen heater 313 are provided.

  The transfer sheet carried in from the carry-in port 26 on the lower side of the housing 28 passes through a region sandwiched between the pressure roller 20 and the heating roller 22. As a result, the toner image on the transfer paper is pressurized and heated, and the toner image is fixed on the transfer paper. Thereafter, the transfer sheet is sent out of the fixing device 110 from the carry-out port 24.

  In the fixing device 110, the transfer paper is pressed by the pressure roller 20 and the heating roller 22 so as to form a nip region. The nip region is formed so that no gap is generated in a region other than the transfer paper when the transfer paper is passed.

  Referring again to FIG. 2, the fixing device 110 includes a temperature sensor (not shown) that detects the surface temperature of the heating roller 22. The fixing device control unit 310 controls on / off of the halogen heater 313 based on the temperature detected by the temperature sensor.

  In addition, the fixing device control unit 310 drives a motor (not shown) (included in various motors 314) that rotates the heating roller 22 and the pressure roller 20 in accordance with the timing at which the transfer sheet is introduced into the fixing device 110. Control.

[Configuration of Heating Roller 22]
5 is an overall view of the heating roller 22 employed in the fixing device 110, and FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. Referring to FIGS. 5 and 6, the heating roller 22 has a cylindrical outer shape having an outer diameter of about 30 mm. A halogen heater 313 is provided inside the cylinder. The heating roller 22 is provided with a hollow cylindrical core member 223 so as to enclose the halogen heater 313. A release layer 221 having a thickness of about 40 μm is provided on the outer periphery of the core member 223.

  The core member 223 is made of a material having good heat conduction characteristics such as aluminum. In the present embodiment, the release layer 221 is made of a material having a high transmittance in the infrared wavelength range of 2 to 10 μm. Examples of such a material include PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) and PTFE (polytetrafluoroethylene).

  In the fixing device 110 having the pressure roller 20 and the heating roller 22, the core member 223 inside the heating roller 22 is heated by heat radiation emitted from the halogen heater 313, and the release layer 221 is heated by heat conduction. The Heat is transferred from the surface of the release layer 221 to the inside and outside of the transfer sheet and the fixing device 110. The heat generated in the fixing unit is used to melt the toner image on the transfer paper. Other than that, heat is radiated out of the heating roller 22 by heat radiation from the surface of the heating roller 22.

  Here, as shown in FIG. 5, the heating roller 22 includes a first contact region L1 with which the recording member having the minimum width comes into contact, and a width larger than the recording member having the minimum width, including the first contact region L1. A second contact region L2 that is in contact with the recording member and a third contact region L3 located on both sides of the first contact region L1 in the second contact region L2.

  When the maximum sheet is continuously contacted, the heat radiated from the heating roller 22 is evenly removed by the transfer roller 22 because the transfer sheet uniformly removes the heat in the entire third contact region L3. There is no rising area. However, when the minimum sheet is continuously contacted, heat is taken away by the transfer sheet in the first contact area L1 of the heating roller 22, but the transfer sheet does not contact in the third contact area L3. In addition, the transfer paper is not deprived of heat.

  For this reason, the temperatures of the third contact regions L3 on both sides tend to increase as compared to the first contact region L1 of the heating roller that contacts the recording member. This tendency becomes prominent when the heat roller 22 is provided with a heat dissipation suppression function for the purpose of reducing the power consumption energy of the fixing device 110 and the image forming apparatus 100.

  Therefore, the heating roller 22 according to the present embodiment employs the structure shown in FIG. FIG. 7 is a cross-sectional view along the axis of the heating roller 22. In the heating roller 22, the thickness of the release layer 221 provided on the surface of the core member 223 is larger in the thickness of the third contact region L3 on both sides than the thickness of the first contact region L1. It is provided as follows. The thickness difference (t3) is preferably 5 μm or more.

  Thus, by providing the film thickness of the release layer 221 such that the thickness of the third contact region L3 on both sides is greater than the thickness of the first contact region L1, the third contact region L3. The heat emissivity of the release layer 221 is greater than the heat emissivity of the release layer 221 in the first contact region L1. As a result, even when the minimum sheet is continuously contacted, the third contact area L3 is more easily cooled than the first contact area L1, and the temperature increase of the third contact area L3 can be suppressed. Become.

  In addition, in the heating roller 22, as another configuration in which the heat emissivity of the release layer 221 in the third contact region L3 is larger than the heat emissivity of the release layer 221 in the first contact region L1, The configuration shown in FIGS. 8 to 12 can be given. Hereinafter, a description will be given with reference to FIGS. 8 to 12 are cross-sectional views along the axis of another heating roller.

  Referring to FIG. 8, the release layer 221 in the third contact region L3 shown in FIG. 7 has a uniform thickness over the entire third contact region L3. In the heating roller 22 shown in FIG. 8, the film thickness of the third contact area L3 on the side in contact with the first contact area L1 is the largest, and the film thickness of the third contact area L3 gradually decreases toward the outside. It has a tapered shape.

  With this configuration, the heat emissivity of the release layer 221 in the third contact region L3 on the side in contact with the first contact region L1 is the highest, and the emissivity can be gradually decreased toward the outside. .

  Referring to FIG. 9, the configuration of heating roller 22 shown in FIG. 9 is opposite to the configuration shown in FIG. In the heating roller 22 shown in FIG. 9, the thickness of the third contact region L3 of the release layer 221 on the side in contact with the first contact region L1 is the same as the thickness of the release layer 221 of the first contact region L1. And has a tapered shape in which the film thickness of the third contact region L3 gradually increases toward the outside.

  With this configuration, the emissivity can be gradually increased from the third contact region L3 on the side in contact with the first contact region L1 toward the outside.

  Referring to FIG. 10, in the configuration of the heating roller 22, only the release layer 221 in the first contact region L <b> 1 contains a low thermal emissivity material 221 a having a heat emissivity smaller than that of the release layer 221. . The emissivity of the low thermal emissivity material 221a is preferably 0.5 or less. The amount of the low thermal emissivity material 221a added to the release layer 221 is preferably 5% by mass to 20% by mass.

  As the low thermal emissivity material 221a, a metal, a metal alloy, or the like is preferable, and specific examples include aluminum, copper, silver, and the like. Further, the low thermal emissivity material 221a may be uniformly dispersed in the release layer 221 in the first contact region L1. It is preferable that the particles of the low thermal emissivity material 221a are not deposited on the outermost surface of the release layer 221 in contact with the transfer paper.

  Even with this configuration, when the emissivity of the first contact region L1 of the release layer 221 is compared with the emissivity of the third contact region L3, the emissivity of the third contact region L3 is higher. As a result, the heat emissivity of the release layer 221 in the third contact region L3 can be made larger than the heat emissivity of the release layer 221 in the first contact region L1.

  In addition, in the heating roller 22 shown in FIG. 10, the case where the low thermal emissivity material 221a whose heat emissivity is smaller than the release layer 221 is not included in the release layer 221 of the third contact region L3 is shown. However, as shown in FIG. 11, the ratio of the low thermal emissivity material 221a contained in the first contact region L1 and the third contact region L3 of the release layer 221 is set to be higher than that in the third contact region L3. Also by increasing the amount of L1, the heat emissivity of the release layer 221 in the third contact region L3 is made larger than the heat emissivity of the release layer 221 in the first contact region L1. Is possible.

  Referring to FIG. 12, the configuration of the heating roller 22 is such that the surface roughness of the core member 223 is the surface corresponding to the third contact region L3 rather than the surface roughness corresponding to the first contact region L1. The roughness is larger. For example, the surface roughness at the position corresponding to the first contact region L1 is preferably Ra = 0.1 μm or less, and the surface roughness at the position corresponding to the third contact region L3 is preferably Ra = 0.4 μm or more. Ra represents the centerline average roughness.

  Thus, by making the surface roughness of the core member 223 corresponding to the third contact region L3 rougher than the surface roughness of the core member 223 in the region corresponding to the first contact region L1, the radiation area increases, The amount of radiation increases. As a result, this effect is also reflected in the release layer 221 formed on the core member 223, and the heat emissivity of the release layer 221 in the third contact region L3 is changed to that of the release layer 221 in the first contact region L1. It becomes possible to make it larger than the emissivity of heat.

  In addition, although the above-mentioned heating roller 22 has demonstrated the case where the mold release layer 221 is formed in the core member 223, as shown in FIG. It is also possible to adopt a configuration in which an elastic layer 222 is provided between the layer 221 and a configuration in which a low heat radiation layer 225 is further provided between the elastic layer 222 and the release layer 221 as shown in FIG.

  For the elastic layer 222, heat-resistant elastic rubber such as silicon rubber or fluorine rubber may be used. The low heat radiation layer 225 is preferably made of a material having a low heat emissivity, such as aluminum, copper, or silver. The emissivity of the low heat radiation layer 225 is preferably about 0.3 when iron or the like is used, and more preferably 0.1 or less, such as aluminum, copper, or silver. In addition, since the emissivity of the low heat radiation layer 225 becomes lower as the surface becomes smoother, the surface of the low heat radiation layer 225 is preferably mirror-finished.

  As described above, according to the fixing device 110 and the image forming apparatus 100 using the fixing device according to the present embodiment, the release layer 221 has the first contact region L1 in the heating roller 22 employed in the fixing device 110. And a third contact region L3 provided at a position sandwiching the first contact region L1 from both axial sides of the core member 223, and the heat emissivity of the release layer 221 of the third contact region L3 is It is larger than the heat emissivity of the release layer 221 in the one contact region L1.

  As a result, it is possible to suppress the temperature increase in the third contact regions L3 of the heating roller 22 even in the fixing process of the small size recording member.

  In the image forming apparatus shown in FIG. 1, the recording member is conveyed in the vertical direction (from bottom to top) with respect to the arrangement of the fixing device 110, but the present invention is limited to this conveyance direction. Is not to be done. For example, the configuration of the present invention can also be applied to a fixing device and an image forming apparatus that employ a configuration in which a recording member is conveyed in the lateral direction (left-right direction).

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 central control unit, 4 memory, 5 operation unit, 6 image forming unit, 20 pressure roller, 22 heating roller, 24 carry-out port, 26 carry-in port, 28 housing, 42 guide member, 100 image forming apparatus, 101 exterior cover, DESCRIPTION OF SYMBOLS 102 Paper feed cassette, 103 Paper feed roller, 104 Photoconductor, 105 Intermediate transfer belt, 106 Transfer roller, 108 Outlet, 110 Fixing device, 221 Release layer, 221a Low heat emissivity material, 222 Elastic layer, 223 Core member, 225 Low heat radiation layer, 310 fixing device control unit, 313 halogen heater, 314 various motors, 315 various sensors.

Claims (5)

A pressure roller and a heating roller are provided, and a plurality of recording members having different widths are passed through a region sandwiched between the pressure roller and the heating roller to press the toner image on the recording member. A fixing device that heats and fixes the toner image on the recording member,
The heating roller includes a heating source, a cylindrical core member containing the heating source, and a release layer formed on the core member in contact with the recording member,
The release layer includes a first contact region that contacts the recording member having the minimum width, and a first contact region that contacts the recording member having a larger width than the recording member having the minimum width. Two contact areas, and in the second contact area, a third contact area located on both sides of the first contact area,
The fixing device, wherein an emissivity of heat of the release layer in the third contact region is set larger than an emissivity of heat of the release layer in the first contact region.   The fixing device according to claim 1, wherein the third contact region has a region provided thicker than the film thickness of the first contact region. The release layer contains a low thermal emissivity material having a lower heat emissivity than the release layer,
The fixing device according to claim 1, wherein a content rate of the low thermal emissivity material in the first contact region is larger than a content rate of the low thermal emissivity material in the third contact region.   2. The fixing device according to claim 1, wherein the surface roughness of the core member is larger in the surface roughness corresponding to the third contact area than in the surface roughness corresponding to the first contact area. .   An image forming apparatus comprising the fixing device according to claim 1.

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