JP2007065518A - Image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt fixing device capable of restraining the deterioration of the glossiness of an image by appropriately removing toner adhering to a belt. <P>SOLUTION: The fixing device 110 has: a fixing belt 114 for heating a toner image on recording material; a heating roller 112 for heating the belt 114; a cooling fan 116 for cooling the already heated recording material moving together with the belt 114 before separation; and a cleaning roller 120 for cleaning the surface of the belt 114. The cleaning roller 120 is installed in the temperature area of the belt 114, where the loss modulus of toner is 10<SP>3</SP>to 10<SP>7</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image heating apparatus that heats a toner image on a recording material. Examples of the image heating device include a fixing device that fixes an unfixed toner image on a recording material, and a gloss adjusting device that adjusts the glossiness of an image by heating the toner image fixed on the recording material. Can do.

  2. Description of the Related Art Conventionally, image forming apparatuses using an electrophotographic method have been commercialized not only for monochrome but also for forming color images. As this electrophotographic image forming apparatus is used in various fields, the demand for image quality is becoming higher and higher. Here, one of the factors that determine the image quality, particularly the glossiness of a color image, is the smoothness of the output image. As a technique for obtaining a color image having excellent glossiness, for example, a color toner made of a thermoplastic resin is transferred to a recording material provided with a transparent resin layer made of a thermoplastic resin, and heated and melted. An image forming method for forming a color image is known.

  A belt fixing device (image heating device) employing such an image forming method has been proposed. For example, in the belt fixing device disclosed in Patent Document 1, a recording material carrying an unfixed toner image is heated and pressed while being in close contact with a fixing belt made of a heat-resistant film. The toner is solidified by forcibly cooling the recording material while keeping the recording material in close contact with the fixing belt. Thereafter, the recording material on which the toner image is fixed and solidified is peeled off from the fixing belt. As a result, the toner image is fixed while being embedded in the transparent resin layer of the recording material, and both the transparent resin layer on the surface of the recording material and the toner image are solidified according to the surface shape of the fixing belt, and the entire surface of the recording material Becomes a smooth surface. Thereby, a color image excellent in glossiness can be obtained.

  In the belt fixing device, a technique for removing toner adhering to the fixing belt has been proposed. For example, in the belt fixing device disclosed in Patent Document 2, the cleaning roller is in contact with the tension roller provided in the recording material separating portion among the two rollers that stretch the fixing belt. . The cleaning roller has a built-in halogen heater.

JP-A-4-362679 Japanese Patent Laid-Open No. 11-352819 JP-A-5-72925

  However, since the belt fixing device of Patent Document 2 has a halogen heater built in the cleaning roller, it is an inefficient system that requires a new heater for cleaning, and is cooled. When the heated object comes into contact with the existing roller, the cooling roller is slightly warmed up, making it difficult to maintain good separation, and because the heating roller is in contact with the cooling roller, heating is performed sufficiently. Accordingly, it has been difficult to sufficiently heat the toner image on the recording material and collect the offset toner from the belt to the cleaning roller. Accordingly, a part of the toner image on the recording material is transferred to the fixing belt at the time of separation (so-called offset), the smoothness of the image is lowered, the glossiness is deteriorated, and sufficient cleaning is not performed. There was a drawback.

  Further, in the belt fixing device of Patent Document 3, a cleaning roller is installed at a position facing the heating roller. However, with the arrangement of the cleaning roller, the belt is not sufficiently heated, and the toner on the belt at the cleaning position is in a solidified state. Therefore, the cleaning by the cleaning roller cannot be performed sufficiently, and there is a possibility that the toner may pass through the belt. As a result, the toner remaining on the belt may affect the next fixing, leading to an image defect and a decrease in glossiness.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image heating apparatus that can appropriately remove toner adhering to a belt and suppress a decrease in glossiness of an image.

In order to achieve the above object, a typical configuration of the present invention includes an endless belt that heats a toner image on a recording material, a heating unit that heats the belt, and a heated recording material that moves with the belt before separation. And a cleaning member for cleaning the belt surface, wherein the cleaning member is installed in the temperature region of the belt where the loss elastic modulus of the toner is 10 ³ to 10 ^7. To do.

  According to the present invention, it is possible to appropriately remove the toner adhering to the belt and to suppress a decrease in glossiness of the image.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In addition, what attached | subjected the same code | symbol in each drawing has the same structure or effect | action, The duplication description about these was abbreviate | omitted suitably.

  FIG. 1 shows an example of an image forming apparatus. In FIG. 1, an electrophotographic color printer using a rotary 4A on which one image carrier 1 and a plurality of developing devices 4 (developing devices 41 to 46) provided around the image carrier 1 are mounted. Hereinafter, it is referred to as an “image forming apparatus”.

  First, a schematic configuration of the image forming apparatus will be described with reference to FIG. The image forming apparatus 10 includes a digital color image printer unit (hereinafter referred to as “printer unit”) A and a digital color image reader unit (hereinafter referred to as “reader unit”) B provided on the upper part of the printer unit A. ing.

  In the printer unit A, a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier is disposed so as to be rotatable in an arrow direction. Around the photosensitive drum 1, a primary charger 2 as a charging means, a laser exposure optical system 3 as an exposure means, a developing device 4 as a developing means, and an intermediate as an intermediate transfer body are arranged almost in order along the rotation direction. A transfer belt 5 and a cleaning device 6 as a cleaning unit are disposed.

  The developing device 4 described above has a rotatable rotary 4A and a plurality of developing devices mounted on the rotary 4A. Here, six developing devices 41 to 46 are illustrated as a plurality of developing devices. The six developing devices 4 include a cyan developing device 41 containing dark cyan toner as a developer, a magenta developing device 42 containing dark magenta toner, a yellow developing device 43 containing yellow toner, and a black toner. Is a black developing device 44 in which a light cyan toner is stored, a light cyan developing device 45 in which a light cyan toner is stored, and a light magenta developing device 46 in which a light magenta toner is stored.

  That is, the image forming apparatus of this example has a combination of magenta and cyan with the same hue and different brightness. That is, dark toner developing devices 41 and 42 containing light magenta and light cyan as low-lightness toners (dark color toner) and light magenta and light cyan as high-lightness toners (light color toner), respectively, and light color Two types of toner developing devices 45 and 46 are provided. Here, the yellow developing device 43 and the black toner developing device 44 having the same hue and not having different lightness are also dark toner developing devices.

  The toners having the same hue and different lightness usually refer to toners having the same spectral characteristics and different amounts of the coloring component (pigment) contained in the toner based on the resin and the coloring component (pigment). . The toner having a high lightness means a toner having a relatively low density among a combination of toners having the same hue and different lightness.

The same hue means that the color developing components (pigments) have the same spectral characteristics as described above, but generally they are not exactly the same, such as magenta, cyan, yellow, black, etc. In addition, a range that can be called the same color in terms of the normal color concept. Toner having the same hue and high brightness has an optical density after fixing of less than 1.0 per 0.5 mg / cm ² of toner on the recording material, and low toner has a toner amount of 0 on the recording material. The optical density after fixing is 1.0 or more per 0.5 mg / cm ² . In this example, dark toners, dark cyan, dark magenta, yellow, and black, have a post-fixing optical density of 1.6 when the applied amount of toner on the recording material is 0.5 mg / cm ^2. So that the amount of pigment is adjusted. Further, light cyan and light magenta, which are light color toners, are designed such that the applied density is 0.5 mg / cm ² and the optical density after fixing is 0.9. The two gradations of toner are mixed well to reproduce the gradation of each color toner.

  Further, the developer contained in each of the developing devices 41 to 46 is a two-component developer used by mixing toner and carrier, but there is no problem even if the toner is a single-component developer. In addition, as the toner types, combinations with different brightness are provided for two colors of cyan and magenta. However, the present invention is not limited to these two types, and the brightness is different for all colors for cyan only, magenta only, yellow only, and the like. A combination may be provided. In other words, any hue may have a combination with different brightness. Accordingly, the number of developing devices is six in this example, but is not limited thereto.

  The above-described intermediate transfer belt 5 is stretched around a driving roller 51, tension rollers 52 and 54, and a secondary transfer counter roller 53. A primary transfer roller 50 that presses the intermediate transfer belt 5 against the photosensitive drum 1 is disposed inside the intermediate transfer belt 5. A secondary transfer roller 55 is disposed at a position corresponding to the secondary transfer counter roller 53 outside the intermediate transfer belt 5.

  Further, in the lower part of the printer unit A, the feeding cassettes 11, 12, 13, feeding rollers 14, 15, 16 and the conveying rollers are sequentially arranged from the upstream side along the conveying direction of the recording material to be image formed. 17, 18, 19 and a registration roller 20 are disposed. Further, a conveying belt 21 stretched around the rollers 22 and 23, a heat roller fixing device 9 as a first image heating device, a discharge roller 24, and the like are disposed. The heat roller fixing device 9 is provided with a fixing roller 91, a pressure roller 92, and a fixing roller cleaner 93. Further, the printer unit A is provided with a duplex conveyance path 25, a manual feed tray 26, a feeding roller 27, and the like.

  In the reader section B, an original table glass 31, an original pressing plate 32, an exposure lamp 33, reflection mirrors 34, 35, and 36, a lens 37, a full color CCD sensor 38, and the like are disposed.

  In the image forming apparatus, at the time of image formation, the document is placed on the platen glass 31 with the image surface facing downward in the reader unit B and pressed by the document pressing plate 32. The image surface of the original is exposed and scanned by the exposure lamp 33. The reflected light image from the original is condensed on the full color CCD sensor 38 by the lens 37 to obtain a color separation image signal. The color-separated image signal is subjected to image processing by a video processing unit (not shown) through an amplifier circuit (not shown), and sent to the printer unit A via an image memory (not shown).

  In addition to the signal from the reader unit B, an image signal from a computer as an external device, an image signal from a FAX, and the like are similarly sent to the printer unit A.

  Here, as an example, the operation of the printer unit A based on the signal from the reader unit B will be described.

  At the time of image formation, the photosensitive drum 1 is rotationally driven at a predetermined process speed (circumferential speed) in a direction indicated by an arrow by a driving unit (not shown), and the surface thereof is uniformly charged to a predetermined polarity and potential by a primary charger 2. (Charging process).

  An electrostatic latent image is formed on the surface of the photosensitive drum 1 after charging by the laser exposure optical system 3. An image signal from the reader unit B is converted into an optical signal by a laser output unit (not shown). The laser beam converted into the optical signal is reflected by the polygon mirror 3a, and irradiated to the charged photosensitive drum 1 surface through the lens 3b and each reflecting mirror 3c. As a result, each separation color is exposed by the laser exposure optical system 3 to form an electrostatic latent image on the photosensitive drum 1 (exposure process).

  Next, the rotary 4A is rotated, and a predetermined developing device is moved to the developing position on the photosensitive drum 1. Then, the developing device at the development position is operated to develop the latent image on the photosensitive drum 1, and a developer image (toner image) based on resin and pigment is formed on the photosensitive drum 1 (developing step). .

  As shown in FIG. 1, the toner in each developing device is a ratio of the toner in each developing device 41 to 46 from the toner container (hopper) 61 to 66 for each color disposed on the laser exposure optical system 3. (Or toner amount) is replenished as needed at a desired timing. Further, a photo sensor 70 as density detecting means is arranged on the photosensitive drum 1 so that the toner amount on the photosensitive drum 1 can be detected.

  The toner image thus formed on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5 by the primary transfer roller 50 (primary transfer process). After the toner image is transferred, the toner (residual toner) remaining on the surface of the photosensitive drum 1 is removed by the cleaning device 6 (cleaning process), and is used for image formation of the next color. The above-described image forming processes of charging, exposure, development, primary transfer, and cleaning are similarly repeated for the necessary colors from among the six colors. As a result, toner images of a plurality of colors are superimposed on the intermediate transfer belt 5.

  The toner images superposed on the intermediate transfer belt 5 in this way are collectively secondary-transferred onto the recording material by the secondary transfer roller 55. The recording material is selectively fed from the feeding cassettes 11 to 13, and the registration roller 20 matches the timing of the toner image on the intermediate transfer belt 5, so that the intermediate transfer belt 5 and the secondary transfer roller 55 Is supplied to the secondary transfer section. After the toner image has been transferred, the toner (residual toner) remaining on the surface of the intermediate transfer belt 5 is removed by a belt cleaner 56 and used for the next primary transfer.

  In the intermediate transfer belt 5, a detection sensor 57 that detects the positional deviation and density of the image transferred from the photosensitive drum 1 is disposed opposite the driven roller 52. The image forming apparatus main body control unit (not shown) corrects the image density, the toner supply amount, the image writing timing, the image writing start position, and the like at any time based on the detection result of the detection sensor 57.

  The recording material on which the toner image is transferred as described above is conveyed to the heat roller fixing device 9 by the conveying belt 21. In the heat roller fixing device 9, the recording material is supplied to a fixing nip portion between the fixing roller 91 and the pressure roller 92 pressed against the recording material, and is heated and pressed to fix the toner image on the surface. .

  Further, when images are formed on both sides of the recording material, a conveyance path guide (not shown) is driven immediately after the recording material passes through the heat roller fixing device 9, and the recording material passes through the conveyance path 28 and the reverse path 29. To once. After that, the recording material is retreated in the direction opposite to the feeding direction from the trailing edge when fed by the reverse rotation of the reversing roller 30 and sent to the duplex conveyance path 25. Thereafter, the recording material passes through the double-sided conveyance path 25, skew correction and timing are performed by the double-sided conveyance roller, and conveyed to the registration roller 20 at a desired timing. Thereafter, the toner image is transferred to the other surface again by the above-described image forming process, and then fixed. Thereby, the image formation on both sides of the recording material is completed.

  Further, as shown in FIG. 1, an optional unit 100 having an image heating device 110 for forming an image on a recording material having a transparent resin layer made of a thermoplastic resin on the surface is attached to and detached from the image forming apparatus described above. It is installed freely. In other words, the image forming apparatus of FIG. 1 to which the option unit 100 is attached includes the heat roller fixing device 9 as the first image heating device and the belt fixing device 110 as the second image heating device described later. It is installed.

  Here, details of the option unit 100 including the belt fixing device 110 will be described.

  In addition to the belt fixing device 110, a switching guide 101 is disposed in the option unit 100. The switching guide 101 conveys the recording material fixed by the heat roller fixing device 9 as it is toward the discharge tray 102 provided on the upper surface of the option unit 100 or toward the belt fixing device 110. Switch between. A discharge tray 103 on which the recording material fixed by the belt fixing device 110 is placed is disposed on the side surface of the option unit 100. In addition, roller pairs 104, 105, and 106 for conveying the recording material are arranged at appropriate positions.

  FIG. 2 is a schematic cross-sectional view of the belt fixing device 110. The belt fixing device 110 includes a fixing belt 114 as an endless belt that heats the toner image on the recording material, and a heating unit that heats the belt 114. In this example, a heating roller 111 as a heating rotator having a heat source is used as the heating means. In this example, a halogen lamp built in the heating roller is used as the heat source, but another heat source may be used. In addition, the belt fixing device 110 includes a separation roller 112 disposed at a predetermined interval from the heating roller 111. A fixing belt 114 is stretched between the two rollers 111 and 112. A pressure roller 115 as a pressure rotator is pressed against the heating roller 111 across the fixing belt 114. In addition, a cooling fan 116 and a cooling duct 121 are provided as cooling means for cooling the recording material that moves together while being in close contact with the fixing belt 114 between the heating roller 111 and the separation roller 112 inside the fixing belt 114. Is provided. The cooling duct 121 is provided with cooling fins 121a that slide on the back surface of the fixing belt. The recording material that moves together while being in close contact with the fixing belt 114 is sufficiently cooled by the cooling means and then separated from the fixing belt 114 at a separation position facing the separation roller 112.

  The heating roller 111 adopts a concentric three-layer structure, and has a core portion, an elastic layer, and a release layer. This core portion is constituted by an aluminum hollow pipe having a diameter of 44 mm and a thickness of 5 mm. The elastic layer is made of silicon rubber having a JIS-A hardness of 50 degrees and a thickness of 300 μm. The release layer is made of PFA having a thickness of 50 μm. A halogen lamp 117 as a heat source (roller heater) is disposed inside the hollow pipe of the core portion. The heat source is not limited to the halogen heater, and a heating roller having a configuration in which the heating roller is heated by electromagnetic induction using a magnetic flux generated from an exciting coil may be adopted.

  The pressure roller 115 also has a substantially similar configuration. The elastic layer is made of silicon rubber having a thickness of 3 mm. This is because the elastic layer increases the width of the heating nip portion N (length in the recording material conveyance direction). A halogen lamp 118 as a heat source (roller heater) is also disposed inside the hollow pipe in the core portion of the pressure roller 115.

  The heating roller 111 and the pressure roller 115 are pressed against each other with a predetermined pressing force across the fixing belt 114 to form a heating nip portion N as a heating / pressing portion having a predetermined width in the recording material conveyance direction. Here, the pressure applied to the heating roller 111 by the pressure roller 115 is set to 490 N (50 kgf) as a total pressure. At this time, the width of the heating nip portion N (length in the recording material conveyance direction) was 5 mm.

  The fixing belt 114 has a mirror surface with a belt surface in close contact with the image formed on the recording material in order to form a high gloss image. The fixing belt 114 of this example has a silicone rubber as an elastic layer on a polyimide resin, and a polyimide silicon resin is coated thereon as a release layer.

  In this example, the fixing belt 114 is cooled by cooling air flowing in the cooling duct 121 when the cooling fan 116 is operated. As a result, the recording material (toner image) that moves together while being in close contact with the fixing belt 114 is sufficiently forcibly cooled. The cooling means is not limited to the configuration using the above-described cooling fins, and may be a configuration of only a cooling fan that cools the fixing belt in a non-contact manner. Further, a Peltier element, a heat pipe, or a water circulation type cooling device that cools in contact with the fixing belt may be used.

A recording material used for such a belt cooling and fixing device is a recording material (resin coated paper or the like) in which a thermoplastic resin serving as a toner receiving layer is coated on top and bottom of a recording material base layer such as paper. The recording material of this example is formed by coating a polyethylene resin on the recording material base layer, and further coating a polyester resin (the same resin as the toner) that is compatible with the toner. The amount of the polyester resin is about 15 g / m ² , and the basis weight of the entire recording material is 200 g / m ² . The toner receiving layer of this recording material is compatible with the toner, and has a property of being softened (melted) together with the toner when heated by the belt fixing device 110. In this example, the same polyester resin as the resin constituting the toner is used as the resin of the toner receiving layer.

  As described above, the toner receiving layer is softened together with the toner during heating, the toner image is embedded in the toner receiving layer, and the recording material is separated from the fixing belt after the toner image on the recording material is sufficiently cooled. As a result, the smoothness of the image surface of the recording material is improved, and the glossiness of the image of the recording material can be improved.

  A toner image is formed on such a recording material by the image forming method described above. That is, a toner image is formed on the polyester resin layer (toner receiving layer), and is assumed by the heat roller fixing device 9 of the image forming apparatus main body 10. In this state, the toner image is only fixed on the polyester resin layer by heating, and does not reach a state where each color toner is melted and mixed. Further, the toner receiving layer of the recording material is not melted even when heated. Thereafter, the belt fixing device 110 shown in FIG. 2 is entered. As described above, by assuming the unfixed toner image on the recording material, the toner image on the recording material is prevented from being offset to the conveyance roller or the like while reaching the belt fixing device.

  The heating roller 111 is rotationally driven at a predetermined speed in a clockwise direction by a driving mechanism (not shown). By the rotation driving of the heating roller 111, the fixing belt 114 is rotated in a clockwise direction at a predetermined speed (in this example, 50 mm / s). The separation roller 112 and the pressure roller 115 are driven to rotate as the fixing belt 114 rotates. The separation roller 112 also functions as a tension roller that applies a predetermined tension to the fixing belt 114.

  Electric power is supplied to the halogen lamps 117 and 118 disposed inside the heating roller 111 and the pressure roller 115, respectively, and the heating roller 111 and the pressure roller 115 are heated by the heat generated by the halogen lamps 117 and 118, so that the surface temperature is increased. To rise. The surface temperatures of the heating roller 111 and the pressure roller 115 are respectively detected by a thermistor (not shown), and the detected temperatures of the thermistors are fed back to the control circuit (in this example, the CPU of the image forming apparatus main body). The control circuit controls the power supplied to the halogen lamps 117 and 118 so that the detected temperature input from each thermistor is maintained at a predetermined target temperature set for each of the heating roller 111 and the pressure roller 115. That is, the temperature control of the heating roller 111 and the pressure roller 115 is controlled to a predetermined target temperature, and the temperature of the heating nip portion N is controlled to a predetermined fixing temperature (about 180 ° C. in this example).

  Here, the control unit (CPU shown in FIG. 1) on the image forming apparatus main body side is used to perform control on the option unit side, but the present invention is not limited to this. For example, a dedicated control unit may be provided on the option unit side, or a control unit may be provided on both the image forming apparatus main body and the option unit.

  The recording material sent to the belt fixing device 110 is introduced into a heating nip portion N formed by the fixing belt 114 and the pressure roller 115 and is nipped and conveyed. At that time, due to the heat from the heating roller 111 and the pressure roller 115, the temperature of the transparent resin layer (toner receiving layer) rises and becomes soft with the toner, and further, pressure from the heating roller 111 and the pressure roller 115 is applied. As a result, the toner image is buried in the high-temperature transparent resin layer. At the same time, the recording material adheres to the surface of the fixing belt 114. At this time, the image surface of the recording material on which the toner image is formed is made uniform so as to follow the surface property (mirror surface shape) of the fixing belt 114.

The recording material in which the toner image is embedded in the transparent resin layer is conveyed to the separation portion by the separation roller 112 while keeping in close contact with the surface of the fixing belt 114. The recording material in close contact with the fixing belt 114 is efficiently and forcibly cooled by the cooling fan 116 until it reaches the separation portion (cooling region). That is, the toner image is cooled to a temperature (about 35 ° C.) lower than the softening point temperature of the toner (glass transition temperature: about 50 ° C.). As a result, the recording material is easily peeled off from the fixing belt in combination with the releasability of the fixing belt surface. Note that the belt temperature at the separating portion has a substitute when 10 ⁹ to loss modulus G "of the toner to be described later.

  Then, the recording material in close contact with the surface of the fixing belt 114 is sufficiently cooled in the cooling region and then separated from the fixing belt 114 by its own rigidity (strain) at the separation portion where the curvature of the fixing belt 114 is changed by the separation roller 112. Stripped (curvature separation).

  By performing the cooling separation in this manner, the surface of the recording material can be finished in a state having no irregularities substantially corresponding to the mirror-like surface of the fixing belt 114. Therefore, if the above-described belt fixing device 110 is used, a high-quality image having a gloss level comparable to that of a silver-lead photograph can be obtained.

  During the fixing operation as described above, the thermoplastic resin (polyester resin) on the surface of the recording material may slightly ooze out around the recording material on the fixing belt and may cause an offset phenomenon that adheres to the fixing belt. This is because the recording material is heated and pressurized in the heating nip portion N, and the thermoplastic resin on the surface of the recording material is melted and spreads around. Alternatively, an offset phenomenon may occur in which the toner that forms an image on the surface of the recording material or the polyester resin on the surface of the recording material that is the same resin (thermoplastic resin) as the toner adheres to the fixing belt. The deposit (thermoplastic resin) that adheres to the fixing belt includes a toner and a transparent resin layer that forms the surface layer of the recording material. In the following description, the deposit that adheres to the fixing belt is referred to as toner. If the toner offset on the fixing belt is left as it is, it may circulate around the fixing belt and adhere to the next recording material. This damages the image of the next recording material.

  Therefore, the belt fixing device 110 of this example has a cleaning roller 120 as a cleaning member that contacts the fixing belt 114 and removes toner adhering to the fixing belt 114.

  The cleaning roller 120 is a metal roller. Specifically, in this example, a SUS roller processed with a diameter of 30 mm and a surface roughness Rz of about 0.1 to 1.0 μm is used as the cleaning roller. The contact pressure of the cleaning roller 120 against the fixing belt 114 is set to 196 N (20 kgf) as a total pressure. Since the adhered toner is transferred from the higher surface energy to the lower one, the toner is transferred from the fixing belt to the cleaning roller 120. The surface roughness Rz of the cleaning roller is preferably a value that can maintain the specularity of the surface of the fixing belt 114.

  The cleaning roller 120 is driven to rotate by a drive mechanism (not shown) so as to be driven at substantially the same speed as the fixing belt 114. The rotation direction of the cleaning roller 120 is a direction that moves in the same direction as the fixing belt at the cleaning position.

  If the cleaning roller 120 is configured to rotate following the fixing belt 114, the surface of the fixing belt 114 becomes slippery when wax or the like in the toner adheres to the fixing belt 114. That is, the cleaning roller 120 may slip on the surface of the fixing belt. If the cleaning roller 120 slips and scratches the surface of the fixing belt, the scratch is transferred to the image surface of the recording material, resulting in an image defect (decrease in glossiness). In order to prevent this, as described above, the cleaning roller 120 is driven to rotate at substantially the same speed as the fixing belt 114.

The cleaning roller 120 is disposed in the temperature region of the fixing belt 114 where the loss elastic modulus G ″ of the toner is 10 ³ to 10 ^{7. This} will be described in detail below.

  The toner loss elastic modulus G ″ was measured using a dynamic viscoelasticity measuring device such as Rheometric RMS-800. As a measuring method, about 1 g of a sample was fixed between the plates on a parallel plate test fixture. (Heated at about 110 ° C. for several minutes), and a strain of 62.8 rad / sec of torsional reciprocating motion is applied from one side, and the stress for this strain is detected on the other side. The temperature was raised in the state, and the temperature dependence of viscoelasticity was measured.

  This result is linked to the relationship between the toner temperature at each point ag on the belt (see FIG. 2) and the loss elastic modulus G ″ of the toner at that time.

  The result is shown in FIG. FIG. 3A is a diagram showing the relationship between the position of the fixing belt on the heating roller and the temperature of the fixing belt at that position, and FIG. 3B is the relationship between the toner temperature and the loss elastic modulus G ″ of the toner. In addition, the temperature of the fixing belt and the temperature of the toner attached to the fixing belt are assumed to be equal, and the point at which the toner temperature of the fixing belt in the portion around which the heating roller is wound is detected. 2, the points a to g are located at intervals of 30 °.

  As shown in FIG. 3 (a), the temperature change of the fixing belt in the portion around which the heating roller having the heater is wound changes from the point a at approximately 12:00 when the cooled fixing belt contacts the heating roller to the heating nip portion N. The temperature increases toward the point g at 6 o'clock. This change in the temperature of the fixing belt is a change in the temperature of the toner attached to the fixing belt. The loss elastic modulus G ″ of the toner with respect to the temperature change of the toner decreases as the temperature increases as shown in FIG.

Here, the toner on the fixing belt is removed by the cleaning roller at points a, d, f, and g corresponding to 10 ⁹ , 10 ⁷ , 10 ³ , and 10 ² in the toner loss elastic modulus G ″ shown in FIG. An experiment was conducted on the durability of the fixing belt, and the results were as follows.

First, the point a of toner loss modulus G "is 10 ⁹ the temperature of the fixing belt becomes low temperature side, the number of durable sheets of the fixing belt is in the order of about 1,000, was not a desirable result as resistance of the fixing belt. This is presumably because the toner adhering to the fixing belt is in a solidified state and cannot be sufficiently removed by the cleaning roller and accumulated on the fixing belt.

Also, the point g temperature hot side to become toner loss modulus G "of 10 ² of the fixing belt, the number of durable sheets of the fixing belt is in the order of about 5,000 sheets, was not a desirable result as resistance of the fixing belt. This is presumably because the toner adhering to the fixing belt was excessively heated and the viscosity of the toner became too low to be easily removed by the cleaning roller.

On the other hand, when the temperature of the fixing belt is the points d and f where the toner loss elastic modulus G ″ is 10 ⁷ and 10 ³ , the durable number of the fixing belt is about 100,000 and about 30,000, respectively. The result was sufficient.

In other words, cleaning cannot be performed when the toner is hard such that the toner loss elastic modulus G ″ is less than 10 ^7, and cleaning is not performed when the toner is completely melted such that the toner loss elastic modulus G ″ exceeds 10 ^3. I found it difficult.

From the above results, in the belt fixing device 110, as described above, the cleaning roller 120 is disposed in the temperature region of the fixing belt 114 in which the loss elastic modulus G ″ of the toner is 10 ³ to 10 ⁷ .

In the belt fixing device 110, as shown in FIG. 2, the cleaning roller 120 is installed in a region facing the heating roller 111. More specifically, based on the above results, the cleaning roller 120 is moved from 3 o'clock on the heating roller 111 to 5 o'clock, which corresponds to the temperature region of the belt 114 where the loss elastic modulus G ″ of the toner is 10 ³ to 10 ^7. It is disposed at the time position (within the range of points d to f).

  As a result, the toner adhering to the fixing belt can be appropriately removed by the cleaning roller, and deterioration of the glossiness of the image can be suppressed. Further, the durability until the fixing belt reaches the end of its life is as long as 30,000 to 100,000. Therefore, it is possible to obtain a color image excellent in gloss while obtaining a sufficient cleaning effect.

In the above-described embodiment, the position of the fixing belt 114 on the heating roller 111 from 3 o'clock to 5 o'clock (within the range of points df) is exemplified as the contact position of the cleaning roller 120 with respect to the fixing belt 114. However, the present invention is not limited to this. That is, the cleaning roller 120 may be in any other position as long as the cleaning roller 120 is in contact with the fixing belt 114 at a position where the loss elastic modulus G ″ of the toner is 10 ³ to 10 ⁷ .

  In the belt fixing device described above, the cleaning roller is fixed at a predetermined position and the cleaning roller is always in contact with the fixing belt. However, the configuration is not limited thereto. The cleaning roller may be configured to be able to contact and separate from the fixing belt. According to this configuration, the possibility of scratching the fixing belt is reduced, which is particularly preferable.

  In the belt fixing device described above, a metal roller having no layer structure by coating or the like is exemplified as the cleaning means. According to this configuration, the configuration is simple and the cost is low. However, the cleaning means is not limited to this. For example, a belt-like cleaning member that is in contact with the fixing belt by a roller may be used. Further, although the SUS roller is exemplified as the cleaning roller, the present invention is not limited to this. Other rollers or belts may be used as long as they have a metal surface layer.

  In the belt fixing device described above, both the heating roller as the heating rotator and the pressure roller as the pressure rotator have the heat sources. However, the present invention is not limited to this, and at least the heating rotator. As long as the configuration has a heat source.

  In the above-described embodiments, the image heating apparatus provided with the endless belt is exemplified as the image heating apparatus that can be attached to and detached from the image forming apparatus main body. However, the present invention is not limited to this. For example, the image forming apparatus may be an image heating apparatus integrally provided, and the same effect can be obtained by applying the present invention to the image heating apparatus.

  In the embodiment described above, as the image forming apparatus, as shown in FIG. 1, a plurality of developing devices are supported by a rotating member, and the rotating member is rotated and moved so that a predetermined developing device is used. Although an apparatus was illustrated, it is not limited to this. For example, as shown in FIG. 4, a tandem type image forming apparatus using a plurality of developing devices arranged in parallel may be used. Further, as shown in FIGS. 1 and 4, an intermediate transfer member is used, toner images of necessary colors are sequentially transferred onto the intermediate transfer member, and the toner image carried on the intermediate transfer member is used as a recording material. The present invention is not limited to an image forming apparatus that performs batch transfer. For example, an image forming apparatus that uses a recording material carrier and sequentially superimposes and transfers toner images of necessary colors on the recording material carried on the recording material carrier. Further, the printer is exemplified as the image forming apparatus. However, the present invention is not limited to this. For example, other image forming apparatuses such as a copying machine and a facsimile machine, or a multifunction machine combining these functions, etc. Other image forming apparatuses may be used. A similar effect can be obtained by applying the present invention to an image heating apparatus provided with an endless belt member used in these image forming apparatuses.

  Further, the hue and number of the developer contained in the developing device are not limited to this, and the hue having a combination with different brightness is not limited to magenta or cyan.

  In addition, the dimensions, materials, shapes, and relative positions of the components of the image forming apparatus described above are not intended to limit the scope of the present invention to those unless otherwise specified. Absent.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus. It is a schematic cross-sectional view of a belt fixing device. It is explanatory drawing of a toner loss elastic modulus. It is a schematic block diagram which shows the other example of an image forming apparatus.

Explanation of symbols

A ... Printer B ... Reader G "... toner loss elastic modulus N ... heating nip 1 ... photosensitive drum 4 ... developing device 4A ... rotary 5 ... intermediate transfer belt 9 ... heat roller fixing device 10 ... image forming devices 41 to 46 ... Developer 100 ... Option unit 110 ... Belt fixing device 111 ... Heating roller (heating rotator)
112 ... Separation roller (rotating body)
114 .. fixing belt (endless belt)
115 ... pressure roller (pressure rotating body)
116 ... Cooling fan (cooling means)
117, 118 ... halogen lamp 120 ... cleaning roller (cleaning means)
121 ... Cooling duct 121a ... Cooling fin

Claims (5)

An endless belt for heating the toner image on the recording material, a heating means for heating the belt, a cooling means for cooling the heated recording material moving with the belt before separation, a cleaning member for cleaning the belt surface, In an image heating apparatus having
An image heating apparatus, wherein a cleaning member is provided in a temperature region of a belt in which a loss elastic modulus of toner is 10 ³ to 10 ⁷ .   The image heating apparatus according to claim 1, wherein the heating unit includes a heating rotator over which the belt is suspended, and the cleaning member is disposed in a region facing the heating rotator.   The image heating apparatus according to claim 1, wherein the cleaning member includes a rotating body that rotates at a substantially constant speed with the belt in the same direction at the contact position.   The image heating apparatus according to claim 1, wherein the belt has a surface roughness Rz of 0.1 to 1.0 μm.   The image heating apparatus according to claim 1, wherein the cleaning member is detachable from the belt.

Images