JP2015227973A - Roller for fixing apparatus, fixing apparatus, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roller for a fixing apparatus, configured to reduce warm-up time, to improve durability, and to extend the service life of a fixing belt.SOLUTION: A roller for a fixing apparatus includes an elastic layer formed of a porous body having bubbles on an outer peripheral surface of a cylindrical core bar. In the porous body, a bubble diameter of a bubble existing in a cross section including an axis of the core bar and parallel to the axis is 0.1-50 μm. Bubbles existing in a 200-μm square area in the cross section are arranged with the highest periodicity. The porous body has an angle of 60-120 degrees with respect to the axis.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device roller for fixing an unfixed toner image used in an electrophotographic copying machine, printer, facsimile, and the like, a fixing device including such a roller, and an image forming apparatus. It is.

  As a fixing device used in various image forming apparatuses such as a copying machine, a printer, a facsimile, or a complex machine of these, a belt fixing method and a film heating method are widely known. An example of the fixing device is shown in FIG.

  The fixing device 20 is composed of, for example, the following members. A fixing belt 21 constituted by a thin and flexible endless belt-like member or a film-like member as a fixing member. A pipe-shaped heat conduction member 22 provided in the fixing belt 21. A halogen heater 25 which is a heating member. A thermistor 28 that is a temperature sensor that detects the surface temperature in contact with the fixing belt 21. A pressure roller 31 as a pressure member that forms a fixing nip N in contact with the fixing belt 21. A heat dissipating member 40 having a circular arc cross section disposed opposite to a part of the outer periphery of the fixing belt 21.

  Here, FIG. 4 schematically shows a cross section of an example 31 of the pressure roller.

  In this example, an elastic layer 2 made of a porous body and a release layer 3 made of polytetrafluoroethylene are sequentially provided on the side surface of a cylindrical metal core 1. In such a pressure roller 31, a foamed elastic heat insulating layer by the so-called water-foamed silicone technology, which has open cells using a water emulsion silicone rubber composition containing water as a dispersant, has been proposed in Patent Document 1. According to this technology, the elastic layer is made of fine bubbles and continuous cells, so that not only the warm-up time can be shortened but also the increase in the outer diameter of the roller due to thermal expansion during heating and the decrease in hardening due to bubble breakage can be prevented. The durability is improved.

  However, when an endless fixing belt is used as a fixing member in the fixing device of the belt (film) fixing method as described above, the fixing belt is shifted toward one side in the rotation axis direction (thrust direction) (hereinafter referred to as “belt shifting”). "). ) Is likely to occur. The cause of this belt misalignment is the parallelism of the nip constituent members (fixing member and pressure member) that make up the nip, and both end surfaces from the center of the nip due to the symmetry of the shape and physical characteristics of each member. Is the non-uniformity of the axial force applied to. However, it is actually difficult to completely eliminate these factors.

  Various countermeasures have been proposed for the above-mentioned belt side. For example, Patent Document 2 proposes attachment of a deviation regulating member on the inner peripheral surface of the belt, installation of a belt deviation retaining ring at the end of the roller shaft, and installation of a belt support member control mechanism. However, in this method, when a fast belt shift (strong shift force) occurs, there is a problem that the member is easily peeled off, the belt rides up, or the belt end portion is easily damaged due to buckling.

  As described above, there has been a demand for a fixing device roller that can shorten the warm-up time and have a superior durability, and can extend the life of the fixing belt.

  The present invention solves the above-described problem, that is, has a roller for a fixing device capable of extending the life of a fixing belt while shortening warm-up time and having an advantage in durability, and has such a roller. It is an object of the present invention to provide a fixing device and an image forming apparatus.

  In order to solve the above problems, the fixing device roller according to the present invention has an elastic layer made of a porous body having air bubbles formed on the outer peripheral surface of a cylindrical core metal as described in claim 1. In the fixing device roller, a bubble diameter of a bubble present in a cross section including the shaft of the core metal and parallel to the axis of the porous body is 0.1 μm or more and 50 μm or less, and one side in the cross section Is characterized in that the angle with respect to the axis at which the periodicity of the array of bubbles existing in a square region of 200 μm is the strongest is 60 ° or more and 120 ° or less.

  In order to solve the above problems, the fixing device roller according to the present invention has an elastic layer formed of a porous body having air bubbles formed on the outer peripheral surface of a cylindrical cored bar as described in claim 1. In the fixing device roller, a bubble diameter of a bubble present in a cross section including the shaft of the core metal and parallel to the axis of the porous body is 0.1 μm or more and 50 μm or less, and one side in the cross section Has a configuration in which the angle with respect to the axis at which the periodicity of the bubble array existing in the 200 μm square region is the strongest is 60 ° or more and 120 ° or less, so that the warm-up time is shortened and the durability is improved. While having superiority, it is possible to extend the life of the fixing belt.

FIG. 1 is a diagram illustrating an example of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an example of the fixing device of the present invention. FIG. 3 is a model cross-sectional view of an example of a fixing belt. FIG. 4 is a model cross-sectional view in a cross section perpendicular to the axis of an example of the fixing device roller of the present invention. FIG. 5 is a cross-sectional view of the model including a shaft of the fixing device roller of FIG. FIG. 6 is an explanatory diagram relating to a method for evaluating the periodicity of the arrangement of bubbles. FIG. 6A is a model analysis image (135-degree direction). FIG. 6B is an analysis result with respect to FIG. FIG. 6C shows a model analysis image (135 degree direction + random). FIG. 6 (d) shows the analysis result for FIG. 6 (c). It is an example of the cross-sectional photograph of a porous body. FIG. 7A is a photograph before binarization. FIG. 7B is a photograph after binarization. FIG. 8 is an electron micrograph of the cross section of the porous body of the rollers of Examples 1-4 and Comparative Examples 1-3. 8 (a) Example 1, FIG. 8 (b) Example 2, FIG. 8 (c) Example 3, FIG. 8 (d) Example 4, FIG. 8 (e) Comparative Example 1, FIG. 8 (f) Comparative Example 2, FIG. 8 (g) Comparative Example 3 FIG. 9 is a diagram showing the bubble distribution analysis results of Example 1 and Comparative Example 3. It is a graph which shows the belt shift speed reduction effect in the roller of an Example.

  The present invention will be described below with reference to the drawings.

  FIG. 1 is an overall schematic configuration diagram of an example of an image forming apparatus for explaining an embodiment of the present invention.

  In this example, a tandem color printer is shown as the image forming apparatus.

  In FIG. 1, four toner bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably attached to a bottle accommodating portion 101 installed above the main body of the image forming apparatus 1 ( It is installed freely. An intermediate transfer unit 85 is disposed below the bottle housing portion 101.

  Image forming portions 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 installed in the intermediate transfer unit 85. Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing device 76, a cleaning unit 77, a charge eliminating unit (not shown), and the like are disposed.

  The photosensitive drums 5Y, 5M, 5C, and 5K rotate, and the following image forming processes (charging process, exposure process, developing process, transfer process) are performed on the photosensitive drums 5Y, 5M, 5C, and 5K. , Cleaning process). Then, an image of each color is formed on each photosensitive drum 5Y, 5M, 5C, 5K.

  The image forming process for the photosensitive drums 5Y, 5M, 5C, and 5K will be described below.

  The photosensitive drums 5Y, 5M, 5C, and 5K are driven to rotate clockwise in FIG. 1 by a drive motor (not shown). Then, in the charging unit 75 (only one corresponding to the photosensitive drum 5K is shown in FIG. 1), the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged (charging process).

  After being charged, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are irradiated and exposed with laser light emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed (exposure process). The photosensitive drums 5Y, 5M, 5C, and 5K on which the latent images are formed are developed with toner developed by the developing device 76 (only those corresponding to the photosensitive drum 5K are shown in FIG. 1). A toner image of each color is formed (development process).

  The toner images on the photosensitive drums 5Y, 5M, 5C, and 5K are transferred onto the intermediate transfer belt 78 by the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K (primary transfer process). In this way, the toner image is transferred onto the intermediate transfer belt 78 so that a color image is formed on the intermediate transfer belt 78.

  After the transfer, the photosensitive drums 5Y, 5M, 5C, and 5K reach the cleaning unit 77, and the untransferred toner remaining on the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K is removed by the cleaning blade of the cleaning unit 77. It is recovered mechanically (cleaning process). FIG. 1 shows only the cleaning unit corresponding to the photosensitive drum 5K.

  Thereafter, the residual potential on the surface of the photoconductive drums 5Y, 5M, 5C, and 5K is removed by the static eliminating unit. Thus, a series of image forming processes for the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

  Next, a series of transfer processes performed on the intermediate transfer belt 78 will be described.

  The intermediate transfer unit 85 includes, for example, the following members. An endless intermediate transfer belt 78. Four primary transfer bias rollers 79Y, 79M, 79C, and 79K. Secondary transfer backup roller 82. Cleaning backup roller 83. Tension roller 84. Intermediate transfer cleaning unit 80.

  The intermediate transfer belt 78 is stretched and supported by the secondary transfer backup roller 82, the cleaning backup roller 83, and the tension roller 84, and is moved in the direction of the arrow in FIG. The primary transfer bias rollers 79Y, 79M, 79C, and 79K form primary transfer nips such that the intermediate transfer belt 78 is sandwiched between the photosensitive drums 5Y, 5M, 5C, and 5K. A primary transfer bias roller 79Y, 79M, 79C, 79K is applied with a transfer bias opposite to the polarity of the toner.

  The intermediate transfer belt 78 travels in the direction of the arrow, and sequentially passes through the primary transfer nip between the intermediate transfer belt 78 and the photosensitive drums 5Y, 5M, 5C, and 5K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are superimposed on the intermediate transfer belt 78 and primary transfer is performed.

  After the primary transfer, the intermediate transfer belt 78 reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 forms a secondary transfer nip so as to sandwich the intermediate transfer belt 78 with the secondary transfer roller 89. At the secondary transfer nip, the four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P being conveyed.

  After the transfer, the intermediate transfer belt 78 reaches the intermediate transfer cleaning unit 80, and the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

  Here, the recording medium P conveyed to the position of the secondary transfer nip is conveyed from the paper supply unit 12 disposed below the image forming apparatus main body 1 via the paper supply roller 97 and the registration roller 98. Is. That is, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in a stacked manner.

  When the paper feed roller 97 is driven to rotate counterclockwise in FIG. 1, the paper is fed to the registration rollers 98 in order from the top recording medium P. The recording medium P conveyed to the registration roller 98 is temporarily stopped at the position of the roller nip of the registration roller 98 that has stopped rotating.

  The registration roller 98 is rotationally driven in synchronization with the toner image on the intermediate transfer belt 78, whereby the recording medium P is conveyed toward the secondary transfer nip. In this way, the toner image is transferred onto the recording medium P.

  The recording medium P on which the color image has been transferred at the secondary transfer nip is conveyed to the fixing device 20, where the toner image transferred to the surface by being heated and pressed by the fixing belt 21 and the pressure roller 31 in the fixing device 20. Is fixed on the recording medium P. Thereafter, the recording medium P is discharged out of the apparatus main body 1 through the paper discharge roller 99 and is sequentially stacked on the stack unit 100.

  Next, an example of the fixing device of the present invention will be described with reference to FIG.

  In FIG. 2, the fixing device 20 is composed of the following members in this example, for example. A fixing belt 21 comprising an endless belt-like member as a fixing member. A pipe-shaped heat conduction member 22 provided in the fixing belt 21. A halogen heater 25 which is a heating member. Fixing bell. A thermistor 28 that is a temperature sensor that detects the surface temperature in contact with 21. Fixing bell. 21. A pressure roller 31 as a pressure member that contacts and forms a fixing nip N. A heat dissipating member 40 having a circular arc cross section disposed opposite to a part of the outer periphery of the fixing belt 21.

  The heat conducting member 22 has a recess 22 a at a position facing the fixing nip N. In this recess 22 a, a nip forming member 26, a mesh-like sliding sheet 23 disposed between the fixing belt 21 and the nip forming member 26, and a gap between the bottom of the recess 22 a of the heat conducting member 22 and the nip forming member 26 are provided. A heat insulating material 27 is disposed.

  The nip forming member 26 is made of an elastic body such as silicone rubber or fluorine rubber, and is slid indirectly with respect to the inner surface of the fixing belt 21 via the sliding sheet 23. The nip forming member 26 may slide directly on the inner surface of the fixing belt 21.

  The hollow heat conducting member 22 is made of a pipe-shaped metal such as aluminum, iron or stainless steel. The heat conducting member 22 of the present embodiment has a circular shape with a bubble diameter smaller than the bubble diameter of the fixing belt 21 by about 1 mm. A nip forming member 26 and a heat insulating material 27 are housed inside the recess 22a of the heat conducting member 22, and a substantially T-shaped holding member 30 is provided inside the heat conducting member 22 to support them. It has been. Although the illustrated halogen heater 25 may be used as a heat source for raising the temperature of the heat conducting member 22, an IH (induction heating) method, a resistance heating element, a carbon heater, or the like can also be used.

  A fixing belt example 21 will be described with reference to the model cross-sectional view of FIG. From FIG. 3, the elastic layer 2 and the release layer 3 are laminated | stacked on the base material 1, The whole thickness is 1 mm or less. Further, the bubble diameter is set to be about 15 to 120 mm, and is set to about 30 mm in the present embodiment.

  The fixing belt base material layer 41 has a layer thickness of 30 to 50 μm and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide (PI). The elastic layer 42 is formed for the purpose of giving flexibility to the belt surface in order to obtain a uniform image without uneven glossiness, and the thickness is preferably 100 to 300 μm. Moreover, silicone rubber, foamed silicone rubber, fluorosilicone rubber or the like is used as a material because of heat resistance at the fixing temperature. Examples of the material used for the release layer 43 include the following. Tetrafluoroethylene resin (PTFE). Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA). Tetrafluoroethylene / hexafluoropropylene copolymer (FEP). A mixture of fluororesins. A product in which these fluororesins are dispersed in a heat-resistant resin.

  The pressure roller 31 is a roller for a fixing device of the present invention, and its configuration will be described with reference to FIGS. 4 and 5. An elastic layer 33 made of foamed silicone rubber and a surface release layer 34 made of PFA or PTFE are laminated in this order on a metal core 32 made of a metal cylindrical member. In the vicinity of both end portions of the elastic layer 33, instead of the surface release layer 34, a grip layer 35 made of a rubber material that prevents slippage with the fixing belt is formed.

  The cored bar 32 is made of a highly rigid metal material such as stainless steel or carbon steel. With respect to the thickness of the cored bar, the present invention has a heat insulating property by applying foamed silicone rubber to the elastic layer, and it does not matter whether it is hollow or solid. In this example, a STKM material having a thickness of 2 mm was used.

  By using foamed silicone rubber for the elastic layer 33, heat insulation can be obtained, and by reducing the heat transfer to the pressure roller, the start-up time of the device can be shortened and energy saving (TEC value reduction) can be achieved.

  The porous body constituting the elastic layer 33 preferably has a thermal conductivity of 0.1 to 0.2 W / (m · K) and a hardness of 20 to 60 ° (Asker C).

  This porous body needs to have a bubble diameter of 0.1 μm or more and 50 μm or less of a bubble present in a cross section including a cylindrical cored bar axis and parallel to the axis. Furthermore, it is necessary that the angle at which the periodicity of the arrangement of the bubbles present in a square region having a side of 200 μm in the cross section is the strongest with respect to the axis of the core is 60 ° or more and 120 ° or less. If these are not satisfied, the effect of extending the life of the fixing belt cannot be obtained.

  Further, it is preferable that the area ratio of the composite bubbles formed by overlapping the bubbles partially in the square region is 60% or more and 70% or less. Here, unlike the spherical shape of single bubbles, the composite bubbles are partially overlapped with each other. Therefore, by observing the cross section of the porous body with a microscope or the like, it can be easily distinguished from single bubbles. it can.

  Furthermore, among the bubbles, when the bubble size is 5 μm or more and 50 μm or less, when the bubbles are 5 μm or more and 10 μm or less when fractionated every 5 μm, high durability is obtained. preferable.

  Further, when the number of bubbles having a size of 5 μm or more and 10 μm or less is defined as 100, and the number ratio of the bubbles having a size of 10 μm or more and 20 μm or less is 50 or more, the pressure stress is more evenly distributed. Since it can be dispersed, higher durability can be obtained.

  Here, as a manufacturing method of the porous body, a chemical foaming method in which a foaming agent is added to form a foamed structure, and water foaming in which water is volatilized by emulsifying water in liquid silicone rubber and heating to form a foamed structure. The silicone method is generally known.

  Among these, the chemical foaming method has a large cell size, so when used as a fixing rotating body of an image forming apparatus, it is difficult to apply a uniform pressure to the toner. There is a problem that the hardness tends to decrease and breakage easily occurs. On the other hand, the water-foamed silicone method is advantageous in terms of durability because fine cells can be uniformly formed, so that a uniform pressure can be applied to the toner and the pressure can be applied evenly.

  The porous body forming the elastic layer in the present invention can be obtained by applying the technique proposed as water-foamed silicone, for example.

  Specifically, the water-foamed silicone composition disclosed in Patent Document 1 is used. However, in the porous body that is finally formed, air bubbles are present in a cross section including the axis of the cored bar and parallel to the axis. Stirring is carried out so that the bubble diameter is 0.1 μm or more and 50 μm or less. During the stirring, it is preferable to adjust so that bubbles having a bubble diameter of 5 μm or more and 50 μm or less are most frequently present when the bubble diameter is fractionated every 5 μm. Further, when the number of bubbles having a bubble diameter of 5 μm or more and 10 μm or less is defined as 100, the number ratio of the bubbles having a bubble diameter of 10 μm or more and 20 μm or less is adjusted to be 50 or more. Is preferred.

  More specifically, a catalyst, a surfactant, and a crosslinking agent are added to and mixed with a commercially available two-component liquid silicone rubber. And an additive, a filler, a dispersing agent, etc. are mixed with water (add alcohol as needed), and it stirs together with the mixed solution made into the viscosity equivalent to liquid silicone rubber, and prepares an emulsion composition.

  Here, the blending ratio of the liquid silicone rubber and the mixed solution is adjusted by a desired porosity. For example, when the blending ratio of the liquid silicone rubber and the mixed solution is 1: 1, the particulate water in the emulsion is evaporated to form cells, so that a porous body having a porosity of 50% can be obtained.

  For the emulsion, use a homogenizer or, if necessary, a stirrer with ultrasonic treatment, and various stirring such as stirring means, stirring time, stirring speed (for example, 300 to 1500 rpm) so as to obtain a bubble distribution that satisfies the above conditions. Adjust the conditions. Thereafter, the prepared emulsion composition is poured into a mold and heated to cure the silicone rubber without evaporating moisture in the emulsion composition (primary heating).

  Here, the heating temperature is in the range of 80 to 130 ° C., and the heating time is in the range of 30 to 120 minutes. A heating temperature of 90 to 110 ° C. and a heating time of 60 to 90 minutes are desirable. Next, secondary heating is performed in order to remove moisture from the porous body after the primary heating. The heating temperature is 150 to 300 ° C., and the heating time is 1 to 24 hours. A heating temperature of 200 to 250 ° C. and a heating time of 3 to 5 hours are preferable. By performing such secondary heating, moisture is removed from the porous body, the bubbles are of the continuous foam type, and the final curing of the silicone rubber is terminated. It should be noted that by adjusting the temperature raising conditions during the molding, the angle at which the periodicity of the arrangement of bubbles existing in a square region having a side of 200 μm on the cut surface is the strongest can be made a desirable range. This is because the moisture in the emulsion composition escapes in the direction in which the rate of temperature rise (temperature) is high (consecutive foaming).

  A one-component thermosetting adhesive is uniformly applied on the molded elastic layer, and the PFA tube is covered to form a release layer. For the release layer, a material having good release properties and heat resistance such as PTFE and FEP can be used.

  The grip layer has a width of about 1 to 15 mm and is formed from a portion outside the paper passing area on the release layer side to the roller end. As the molding method, spray coating, dip coating, roll coating or the like is used. The material of the grip layer is required to have three characteristics: a tack property for obtaining a grip force, an elastic body for forming a nip portion, and a heat resistance against a fixing temperature. Examples of such a material include rubber materials such as silicone rubber and fluorine rubber.

  Here, the method for measuring the number of bubbles and the method for evaluating the periodicity of the arrangement of bubbles in the present invention will be described.

  First, a method for evaluating the periodicity of the arrangement of bubbles (an arrangement of bubbles and a solid layer (silicone rubber)) will be described.

  The porous body formed of water-foamed silicone is a so-called open-cell body that is connected by fine passages formed when water (and alcohol), which is a dispersant, escapes from the molded body. In addition, even when the photographed image (see FIG. 7A) is visually observed, it is impossible to determine in which direction the solid layer and the bubbles (continuous foam) have the periodicity. Therefore, this time, we decided to evaluate the periodicity of the arrangement of bubbles (and the solid part) by two-dimensional Fourier analysis of the image. An example of the evaluation method is shown below.

  Here, as an example, a two-dimensional Fourier analysis is performed on an image (FIG. 6A) in which black and white patterns are arranged in an oblique direction of 135 degrees. As can be seen visually, the periodicity of the black and white pattern has a peak in the direction of 135 degrees (FIG. 6B). Here, white lines are arranged so that it is impossible to determine in which direction the black-and-white pattern is lined up randomly in the image of FIG. 6A (FIG. 6C). Even if the analysis is performed in the same manner as described above, the periodic peak is extracted in the direction of 135 degrees (FIG. 6D).

  In this way, by applying the evaluation method described above (the white line in FIG. 5 is regarded as a bubble (continuous foam) and the black line is regarded as a solid layer (silicone rubber)), the arrangement of the bubbles (continuous foam) with respect to the solid layer is arranged. It is possible to evaluate the periodicity of the bubbles (the direction of the bubble bubbles).

  As an actual evaluation procedure, first, a porous body constituting an elastic layer with a sharp blade is cut along a plane including the axis of the cored bar and parallel to the axis. The cross section is photographed with a laser microscope (LSM) or an electron microscope (SEM) so that a square region with a side of 200 μm can be clearly seen (see FIG. 7A).

  The obtained image is subjected to image processing so that the bubble portion is black and the solid layer (silicone rubber) portion is white and binarized into black and white (see FIG. 7B). A two-dimensional Fourier analysis is performed on the binarized image, and an angle at which the periodicity of the black and white (bubble and solid portion) arrangement is the strongest is extracted. The periodicity of the bubble arrangement is evaluated by the above method.

  Next, a method for measuring the number of bubbles will be described. An image is captured in the same manner as described above, and an image binarization process is performed. After extracting the bubble portion, an opening process, which is one of image processing methods, is performed using each bubble diameter as a constituent element, and the extracted bubbles are screened to each bubble diameter. By taking the difference between the results before and after each opening process, the number of pixels of the constituent elements (bubble diameter) that have been screened can be known.

  By dividing this number of pixels by the number of pixels of the constituent elements, the number contained in each diameter range (the number of bubbles present in each fractionated fraction) can be known, and the distribution can be obtained.

  As described above, the porous body constituting the elastic layer in the present invention has an area occupied by a composite bubble formed by overlapping spherical bubbles partially with respect to a square region having a side of 200 μm in the cross section. The ratio is preferably 60% or more and 70% or less. Here, such an area ratio cuts out a square area having a side of 200 μm in the image data obtained by the microscope (the square area can be used as it is). Then, after visually erasing the image related to the bubble other than the composite bubble formed in this region, the image is erased while visually checking, and then binarized into black and white, and the area ratio of the black portion in the entire region (image Calculated by the processing software).

  Although the present invention has been described with reference to the preferred embodiment, the fixing device roller, the fixing device, and the image forming apparatus of the present invention are not limited to the configuration of the above embodiment.

  A person skilled in the art can appropriately modify the fixing device roller, the fixing device, and the image forming apparatus of the present invention in accordance with conventionally known knowledge. Of course, such modifications are included in the scope of the present invention as long as they include the configurations of the fixing device roller, the fixing device, and the image forming apparatus of the present invention.

  A STKM material having a diameter of 24 mm and a wall thickness of 2 mm was used as the core metal, and a foamed silicone rubber was formed on the outer surface of the foamed silicone rubber with a wall thickness of 4 mm using a water-foamed silicone composition manufactured by Toray Dow Corning Silicone. Further, a PFA tube having a thickness of 30 μm was coated as a surface release layer on a portion to be a paper passing area, and a grip layer was uniformly formed with a thickness of 50 μm on the exposed elastic layer at both ends of the roller.

  Seven types of rollers having different stirring conditions and heating conditions are prepared for the water-foamed silicone composition, and Examples 1 to 4 and Comparative Examples 1 to 3 are used. After measuring the shifting speed of each roller, a cross section obtained by cutting the porous body, which is an elastic layer, in the axial direction was photographed with a scanning electron microscope. The periodicity of the layers was evaluated.

  FIGS. 8A to 8G show micrographs of cross sections of the elastic layers of the fixing device rollers of Examples 1 to 4 and Comparative Examples 1 to 3, respectively, and FIG. 9 shows bubbles of Example 1 and Comparative Example 3. The survey results of the distribution of are shown. Evaluation items A to E in the table are the following items. A: An angle with respect to the axis at which the periodicity of the arrangement of bubbles (and the solid part) existing in the cross section is the strongest. B: Range of bubble size (bubble diameter). C: Area ratio of a composite bubble formed by overlapping spherical bubbles partially overlapping each other in a square region having a side of 200 μm in the cross section. D: The largest fractionation range when bubbles having a bubble diameter of 5 μm or more and 50 μm or less present in a cross section obtained by cutting the porous body are fractionated every 5 μm. E: The ratio of the number of bubbles in a fraction that is one step larger than the fraction, where 100 is the number of bubbles in the largest fraction range.

  In addition, the heat conductivity of the elastic layer of the rollers of Examples 1 to 4 and Comparative Examples 1 to 3 is in the range of 0.100 to 0.110 W / (m · K), and the hardness is 34 to 38 ° (Asker C). there were. These are at the same level, and the influence on the evaluation results described later due to these differences is negligible.

  In each example and comparative example, a durability test and a measurement of the belt shift speed were performed.

  In the test, in the fixing unit shown in FIG. 2, the urging of the pressure roller was controlled so that the nip width was 10 mm, the belt surface temperature was controlled to 140 ° C., and the linear velocity was controlled to 256 mm / second. Carried out.

  In conducting the test, only the pressure roller of the fixing device shown in FIG. 2 was replaced with the roller of the example and the comparative example. The belt shift speed is measured by measuring the position of one end of the fixing belt with a laser displacement meter, and the moving distance (positive when moving to the measuring side, and negative when moving to the other side) Calculated by dividing by elapsed time. The durability test was performed for 300 hours under the test conditions described above, and the pressure roller hardness reduction indicates a change in hardness before and after the test.

  Regarding the life of the fixing belt, “◯” was evaluated as being sufficient when there was no end face destruction and no abnormal noise, and “X” was evaluated as being insufficient when end face destruction or abnormal noise occurred. In addition, the pressure roller life is sufficient when the hardness (Asker C) decreases within 2 ° and there is no bubble breakage (the solid part (wall-like part) between the bubbles of the porous body is broken). As “◯”. When the hardness decrease exceeded 2 ° or bubble breakage occurred, it was evaluated as “x” as insufficient. Further, as a comprehensive judgment, “◯” was evaluated as being sufficient only when both the life of the pressure roller and the life of the fixing belt were sufficient, and “x” was evaluated as being insufficient otherwise. The results are shown in Table 2.

  In all the examples and comparative examples described above, the belt shift itself occurred, but there was a difference in the shift speed. In Comparative Examples 1 and 2, the belt end surface interfered with the regulating member, so that abnormal noise was generated, and in Comparative Example 2, destruction was caused. On the other hand, in Examples 1 to 4, it was confirmed that the belt shifting speed was reduced.

  Here, the relationship between the angle at which the periodicity of the arrangement of bubbles existing in a square region having a side of 200 μm in the cross section of the porous body with respect to the roller axis (periodic peak angle) and the belt shifting speed is shown in FIG. Indicated. It is understood that there is a very strong correlation between them. As described above, it was confirmed that the present invention is effective in reducing the shifting speed.

  The reason for the shift speed reduction by the fixing device roller of the embodiment is considered as follows. The foamed rubber used in the examples is in the form of continuous bubbles, and it is considered that the number of bubbles is continuous at a certain angle based on the periodicity evaluation of the arrangement of the bubbles. Here, if the bubbles are connected to the roller axis other than 60 to 120 degrees in an oblique direction, the force applied to the roller during nip formation is decomposed into a vertical component and an axial component, It is considered that the belt is pushed by the force acting in the axial direction at that time, causing a deviation. In the fixing apparatus roller according to the embodiment, the angle at which the bubbles are continuously connected (periodicity of the bubble arrangement) is controlled to reduce the force acting in the axial direction. It is thought that this leads to longer life.

  Further, as a result of the durability test, the roller of Comparative Example 3 had a large decrease in hardness and inferior durability performance as compared with the roller of Example.

  As described above, according to the present invention, a fixing device roller that can achieve a longer life of a fixing belt by reducing the belt shifting speed while having an advantage in durability, a fixing device having such a roller, and an image forming apparatus It became possible to provide.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20 Fixing apparatus 31 Pressure roller (Fixing apparatus roller)
32 Metal core 33 Elastic layer 34 Surface release layer

JP 2013-164458 A JP 2000-199550 A

Claims (9)

In a roller for a fixing device in which an elastic layer composed of a porous body having bubbles is formed on the outer peripheral surface of a cylindrical cored bar,
The porous body has a bubble diameter of 0.1 μm or more and 50 μm or less of bubbles present in a cross section including the axis of the cored bar and parallel to the axis, and
The fixing device roller, wherein an angle with respect to the axis at which the periodicity of the arrangement of the bubbles existing in a square region having a side of 200 μm in the cross section is the strongest is 60 ° or more and 120 ° or less.   2. The fixing device roller according to claim 1, wherein a composite bubble formed by the bubbles partially overlapping each other has an area ratio of 60% to 70% with respect to the square region.   The bubble having a bubble diameter of 5 μm or more and 10 μm or less is most present when the bubbles having a bubble diameter of 5 μm or more and 50 μm or less are fractionated every 5 μm. The fixing device roller according to 2.   4. The number ratio of bubbles having a bubble diameter of 10 μm or more and 20 μm or less is 50 or more, where the number of bubbles having a bubble diameter of 5 μm or more and 10 μm or less is defined as 100. 2. A roller for a fixing device according to 1.   The fixing device roller according to claim 1, wherein the porous body is made of water-foamed silicone rubber.   6. A release layer composed of a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer or polytetrafluoroethylene is formed on the outermost layer. 2. A roller for a fixing device according to 1.   The fixing device roller according to any one of claims 1 to 6, wherein a grip layer made of an elastic body is provided on both ends of the roller outside the sheet passing region.   A fixing device comprising the roller according to claim 1.   An image forming apparatus comprising the fixing device according to claim 8.