JP2006267900A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device using a heat transfer belt excellent in durability and thermal conductivity and to provide an image forming apparatus having the fixing device. <P>SOLUTION: The fixing device includes: a fixing means for fixing an unfixed toner image held on paper subjected to recording; a pressure means for exerting pressure in conjunctive with the fixing means; an external heating means for heating the unfixed toner image in order to fix the unfixed toner image; and the heat transfer belt heated by the external heating means. The fixing device directly or indirectly heats the unfixed toner image by the heat transfer belt. In such a fixing device, the heat transfer belt has: a release layer 91 formed on the surface of the belt; a base layer 92 formed on the back of it and made of a resin; and a highly thermally conductive layer 93 disposed between the release layer 91 and the base layer 92 and composed by adding thermally conductive filler to a resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device that heats and fixes an unfixed toner image on a recording sheet, and an image forming apparatus including the fixing device, in an image forming apparatus such as a copying machine or a facsimile machine.

  In general, in an image forming apparatus such as a copying machine, a printer, or a facsimile, a recording sheet carrying an unfixed toner image is nipped and conveyed to a nip formed by a heating roller and a pressure roller of the fixing device. The unfixed toner image is fixed on the recording paper by heating and pressurizing. In such a fixing device, a heating unit is incorporated in the middle space portion of the heating roller, and the heating unit is configured to heat a nip portion formed by press-contacting the heating roller and the pressure roller. Therefore, there is a disadvantage that it takes time for the fixing device to raise the temperature to a desired fixing temperature.

Conventionally, as a countermeasure, an apparatus using an external heating means has been proposed to heat a rotatable fixing means for fixing an unfixed toner image. As this external heating means, for example, a heat transfer belt stretched by a plurality of rolls and in contact with the surface of the fixing means in a predetermined area is used, and the fixing means is heated from the outside by this heat transfer belt. There are some (see, for example, Patent Document 1).
Japanese Patent No. 2004-198659

  However, in the one described in Patent Document 1 described above, a nickel electroformed belt coated with silicon rubber or a polyimide coated silicon rubber is used as the heat transfer belt. For this reason, a nickel electroformed belt coated with silicon rubber exhibits excellent thermal conductivity. However, in order to provide heat capacity, increasing the thickness reduces the flexibility and durability due to the higher Young's modulus. There is a problem that it is bad. In addition, when polyimide is coated with silicon rubber, it is made of a resin with low thermal conductivity, so there is a temperature difference in the heat transfer from the heating means to the fixing means, and the thermal conductivity is poor. There is.

  The present invention has been made to solve the above-described problems, and provides a fixing device using a heat transfer belt excellent in durability and thermal conductivity, and an image forming apparatus including the fixing device. For the purpose.

  In order to achieve the above object, in the present invention, a fixing means for fixing an unfixed toner image carried on a recording paper, a pressure means for pressing together with the fixing means, and an unfixed toner image are fixed. And an external heating means for heating the unfixed toner image and an endless heat transfer belt heated by the external heating means, and directly or indirectly heating the unfixed toner image by the heat transfer belt. In the fixing device, the heat transfer belt has a release layer on the front surface and a base layer made of resin on the back surface, and contains a heat conductive filler in the resin between the release layer and the base layer. It has the formed high heat conductive layer, It is characterized by the above-mentioned.

  According to this configuration, since the base layer is formed of resin, the base layer has overall strength and heat capacity as a heat transfer belt, and the high heat conductive layer as the upper layer contains a heat conductive filler in the resin. Forming. Therefore, heat can be efficiently conducted from the base layer to the release layer on the surface. As a result, a heat transfer belt excellent in durability and thermal conductivity can be obtained. Moreover, since the surface is formed of a release layer, the toner is excellent in releasability at the contact portion with the recording paper or the fixing means that carries the unfixed toner image that comes into contact with the heat transfer belt, and the toner. This is convenient because it is difficult for dust and paper dust to adhere to it.

  Here, the present invention is characterized in that the heat conductive filler content of the high heat conductive layer is formed so as to increase sequentially from the base layer side toward the release layer side. According to this configuration, the heat heated from the base layer side is more efficiently conducted through the high thermal conductive layer, reaches the release layer, and the recording sheet carrying the unfixed toner image or the fixing unit is more efficiently performed. This is preferable because it can be heated.

  In the present invention, the release layer is made of a fluororesin, and the layer pressure of the release layer is thinner than that of the high thermal conductive layer. According to this configuration, the release layer made of the fluororesin on the surface has excellent release properties and is thinner than the high heat conductive layer, so that the heat conducted through the high heat conductive layer is more efficiently determined. It can be conducted to a recording paper carrying a contacted toner image or a fixing means and heated more efficiently. Furthermore, it is preferable because toner, paper powder, and the like are less likely to adhere to the heat transfer belt.

  In the present invention, the base layer contains a heat conductive filler in the resin, and the content of the heat conductive filler in the base layer is lower than the content of the heat conductive filler in the high heat conductive layer. . According to this configuration, since the heat conductive filler is also contained in the resin layer of the base layer, the heating efficiency from the heating source is improved, and the content rate is lower than that of the high heat conductive layer. It is preferable because sufficient strength and heat capacity can be provided without increasing the Young's modulus as a whole.

  Furthermore, in the present invention, there is provided an image forming apparatus comprising a fixing device having any one of the above-described configurations. Therefore, according to this configuration, it is possible to obtain an image forming apparatus that exhibits the same action as the fixing device having any one of the above-described configurations.

  According to the configuration of the present invention, it is possible to obtain a fixing device using a heat transfer belt excellent in durability and thermal conductivity, and an image forming apparatus including the fixing device.

(First embodiment)
A specific first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic configuration diagram showing a schematic configuration when applied to a copying machine as an image forming apparatus using the fixing device according to the first embodiment of the present invention.

  As shown in FIG. 1, a copying machine 1, which is an image forming apparatus, includes a document conveying unit 3 that automatically conveys a document to an image reading unit 2, an image reading unit 2 that reads image information of a document, and a recording target. An image forming unit 4 that forms an image read by the image reading unit 2 on a sheet P, a fixing device 5 to be described later, and a sheet feeding unit 6 in which the recording sheet P is stored are provided. Further, a paper transport path 7 is formed for transporting the recording paper P to the paper discharge unit 71 via the image forming unit 4 and the fixing device 5.

  As is well known, the image reading unit 2 irradiates light from an exposure lamp to an original that has been conveyed from the original conveying unit 3 on the contact glass, and reflects the light through a reflecting mirror. By guiding the light to a photoelectric conversion unit comprising a CCD sensor or the like, the image information of the document is read and read.

  The document conveying means 3 includes a document placing table 31 for placing a document, a document feeding unit that feeds a document loaded on the document placing table 31, and a document feeding unit for transporting the fed document. A paper conveyance path and a document discharge section 32 for discharging the document that has been read are provided.

  The paper feeding means 6 includes a plurality of paper feeding cassettes 61 in which recording paper P is accommodated, and a paper feeding cassette 61 selected from among the plurality of paper feeding cassettes 61 by the rotation operation of the paper feeding roller 62. The recording paper P is sent out to the paper conveyance path 7 side. With this configuration, the recording paper P is reliably fed to the paper transport path 7 one by one. These paper feed cassettes 61 are configured to be detachable from the copying machine 1.

  The recording paper P fed to the paper transport path 7 is transported toward the image forming unit 4 via the paper transport path 7. The image forming means 4 forms a predetermined toner image on the recording paper P by an electrophotographic process, and is an image end holder that is rotatably supported in a predetermined direction (the arrow direction in the figure). And a charging device 42, an exposure device 43, a developing device 44, a transfer device 45, a cleaning device 46, and a charge eliminating device 47 are provided around the photoconductor 41 in the rotation direction.

  The charging device 42 includes a charging wire to which a high voltage is applied. By applying a predetermined potential to the surface of the photoconductor 41 by corona discharge from the charging wire, the surface of the photoconductor 41 is uniformly charged. It is done. Then, the exposure device 43 irradiates the photoconductor 41 with light based on the image data of the original read by the image reading unit 2, whereby the surface potential of the photoconductor 41 is selectively attenuated, and this photosensitivity. An electrostatic latent image is formed on the surface of the body 41. Next, toner is attached to the electrostatic latent image by the developing device 44 to form a toner image on the surface of the photoconductor 41, and the toner image on the surface of the photoconductor 41 is transferred from the photoconductor 41 to the transfer device by the transfer device 45. 45 is transferred onto the recording paper P supplied between the two.

  The recording paper P to which the toner image is transferred is conveyed from the image forming unit 4 to the fixing device 5. The fixing device 5 is disposed on the downstream side of the image forming unit 4 in the paper conveyance direction, and the recording paper P on which the toner image is transferred by the image forming unit 4 is heated and pressed by the fixing device 5 described later. Then, the toner image is fixed on the recording paper P. Next, the recording paper P on which the image is formed in the fixing device 5 from the image forming unit 4 is discharged onto the paper discharge unit 71. On the other hand, after the transfer, the toner remaining on the surface of the photoconductor 41 is removed by the cleaning device 46, and the residual charge on the surface of the photoconductor 41 is removed by the charge eliminating device 47. The photosensitive member 41 is charged again by the charging device 42, and image formation is performed in the same manner.

  Next, a specific configuration of the fixing device according to the characterizing portion of the present invention will be described with reference to FIGS. 2 is a conceptual diagram showing a schematic configuration of the fixing device shown in FIG. 1, and FIG. 3 is an enlarged sectional view showing a laminated structure of a heat transfer belt of the fixing device shown in FIG.

  In this embodiment, an unfixed toner image carried on a recording sheet is indirectly heated by an endless heat transfer belt heated by an external heating unit. That is, as shown in FIG. 2, the fixing device 5 fixes the unfixed toner image carried on the recording paper P, for example, a fixing unit 51 including a fixing roller rotatably supported by the rotation shaft 53. And a pressurizing unit 52 that presses and rotates in cooperation with the fixing unit 51, for example, a pressure roller 52 that is rotatably supported by a rotating shaft 54, and an external heating unit that heats the fixing unit 51 from the outside 8 and.

  The external heating means 8 includes, for example, two belt support rollers 81 and 82 and an endless heat transfer belt 9 that is stretched between the belt support rollers 81 and 82. And a heating source 83 made of, for example, a halogen heater or the like built in a belt support roller 81 that functions as a heat roller. The heat transfer belt 9 is disposed on the surface of the fixing unit 51 so as to be in close contact with the belt-like region L extending in the longitudinal direction having a length in the outer peripheral direction of the fixing unit 51. With this configuration, as described above, the fixing device 5 sandwiches and conveys the recording paper P carrying the unfixed toner image in the nip formed by the fixing unit 51 and the pressure unit 52, and the unfixed toner image Is fixed to the recording paper P.

  When the fixing unit 51 is rotated clockwise in FIG. 2 by the electric motor 55, the pressurizing unit 52 is rotated counterclockwise. At the same time, the belt support roller 81 is rotated counterclockwise by the fixing means 51 via the heat transfer belt 9, and accordingly, the belt support roller 82 is also driven counterclockwise via the heat transfer belt 9. It is rotated. At this time, when the heating source 83 is energized and heat generation is started, the heat from the heating source 83 heats the belt support roller 81 that is a heat roller, and accordingly, the heat transfer belt 9 is also heated. The heated heat transfer belt 9 conducts heat to the fixing unit 51 through the belt-like region L that is in close contact with the fixing unit 51, and the temperature of the fixing unit 51 is increased so as to be in a predetermined fixing temperature range. The heating source 83 is controlled by control means (not shown).

  Thus, according to the present invention, the endless heat transfer belt 9 has a release layer 91 on the surface in contact with the fixing means 51 and a base layer 92 made of resin on the back surface as shown in FIG. Between the layer 91 and the base layer 92, a high thermal conductive layer 93 formed by containing a thermal conductive filler in the resin is provided.

  As the release layer 91, for example, a fluororesin can be used, and examples thereof include polytetrafluoroethylene (PTFE) and perfluoroalkoxyalkane resin (PFA). Examples of the resin of the base layer 92 and the high thermal conductive layer 93 include heat-resistant resins such as polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, and polyphenylene sulfide. Examples of the heat conductive filler mixed in the resin of the high heat conductive layer 93 include silver, copper, aluminum, alumina, silicon carbide, silica, graphite carbon, and a mixture of two or more of these. In order to form the heat transfer belt 9 having such a multi-layer structure, for example, a resin containing a heat conductive filler is sprayed onto the upper layer of the base layer 92 and then baked to form the high heat conductive layer 93. Thereafter, the fluororesin forming the release layer 91 may be sprayed and applied.

  Here, the release layer 91 is preferably made of a fluororesin, and the layer pressure of the release layer 91 is made thinner than that of the high thermal conductive layer 93. According to this configuration, the release layer 91 made of a fluororesin on the surface has excellent release properties and is thinner than the high thermal conductive layer 93, so that the heat conducted through the high thermal conductive layer 93 can be reduced. Therefore, the heat can be more efficiently conducted to the fixing means 51 and heated more efficiently. Furthermore, it is preferable because toner, paper powder, and the like are difficult to adhere.

  Further, the base layer 92 contains a heat conductive filler in the resin, and the content of the heat conductive filler in the base layer 92 is set to the content of the heat conductive filler in the high heat conductive layer 93 (for example, 20% to 40%). You may form so that it may become lower. According to this configuration, since the resin of the base layer 92 also contains the heat conductive filler, the heating efficiency from the heating source 83 is improved, and the content is lower than that of the high heat conductive layer 93. This is preferable because sufficient strength and heat capacity can be provided without increasing the Young's modulus of the heat transfer belt 9 as a whole.

  According to the above configuration, since the base layer 92 is made of resin, the base layer 92 has the entire strength and heat capacity as the heat transfer belt 9, and the high heat conductive layer 93 as an upper layer is a heat conductive filler in the resin. It contains and is formed. Therefore, heat can be efficiently conducted from the base layer 92 to the release layer 91 on the surface. As a result, a heat transfer belt excellent in durability and thermal conductivity can be obtained. In addition, since the surface is formed of the release layer 91, it is excellent in the releasability of the contact portion with the fixing means 51 that comes into contact with the heat transfer belt 9, and it is difficult for toner, paper powder, etc. to adhere to it. preferable.

(Example)
In the following, according to the present invention, as shown in FIG. 3, an endless heat transfer belt having a multilayer structure in which a heat conductive filler is contained in a resin and a high heat conductive layer 93 is formed between a release layer 91 and a base layer 92. Based on the experimental example using 9, the excellent effect of the present invention will be described. For comparison, a comparative example using the heat transfer belt 9 in which the high heat conductive layer 93 is not formed is also shown.

(Experimental example 1)
A 65 μm thick highly heat conductive layer 93 containing polyimide resin and 40% aluminum filler as a heat conductive filler is formed on the upper layer of a 65 μm thick base layer 92 containing 20% graphite filler as a heat conductive filler. The heat transfer belt 9 in which PTFE having a thickness of 15 μm was formed as a release layer 91 on the upper layer was used.

(Comparative Example 1)
A heat transfer belt in which PTFE having a thickness of 15 μm was formed as a release layer on a resin layer having a thickness of 130 μm made of polyimide resin was used.

  A fixing device 5 as shown in FIG. 2 was manufactured by using the heat transfer belt 9 described above, and the temperatures of the point A of the external heating unit 8 and the point B of the fixing unit 51 were measured by temperature sensors. The temperature difference is shown in Table 1. The table also shows the thermal conductivity (W / m · K) of the heat transfer belt.

実験例１と、比較例１との対比により、本発明に従い、離型層９１と基層９２との間に、樹脂に熱伝導性フィラーを含有して高熱伝導層９３を形成した多層構造の熱伝達ベルト９を用いた実験例１では、外部加熱手段８から定着手段５１への温度差を、比較例１に比べ約３０％縮めることができ、効率良く熱移動し、熱伝導性が極めて優れていることが認められた。

In comparison with Experimental Example 1 and Comparative Example 1, in accordance with the present invention, a heat having a multilayer structure in which a high thermal conductive layer 93 is formed between the release layer 91 and the base layer 92 by containing a thermal conductive filler in the resin. In Experimental Example 1 using the transmission belt 9, the temperature difference from the external heating means 8 to the fixing means 51 can be reduced by about 30% compared to Comparative Example 1, and the heat transfer is efficiently performed, and the thermal conductivity is extremely excellent. It was recognized that

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. 4 is a conceptual diagram showing a schematic configuration of a fixing device according to a second embodiment of the present invention, and FIG. 5 is an enlarged cross-sectional view showing a laminated structure of heat transfer belts of the fixing device shown in FIG. 4 and FIG. 5, the portions denoted by the same reference numerals as those in FIGS. 1 to 3 described above are substantially the same, and thus detailed description thereof is omitted here. Hereinafter, the difference from the above-described embodiment will be mainly described.

  In this embodiment, an endless heat transfer belt heated and rotated by an external heating unit is used as a fixing belt, and an unfixed toner image carried on a recording paper is directly heated by the heat transfer belt. It is what you do. That is, as shown in FIG. 4, the fixing device 5 includes a fixing unit 51 having an endless heat transfer belt 9 for fixing an unfixed toner image carried on the recording paper P, a pressure unit 52, and a fixing unit. And an external heating means 8 for heating 51 from the outside.

  The fixing unit 51 includes a heat transfer belt 9 that functions as a fixing belt, and a fixing roller 511 that presses the heat transfer belt 9 against the recording paper P, for example, is rotatably supported by a rotation shaft 53. I have. The heat transfer belt 9 is stretched between the fixing roller 511 and the support roller 85, heated by the external heating unit 8, and sandwiched between the fixing roller 511 and the pressure unit 52 and circulated. The

  The external heating means 8 is composed of, for example, a halogen heater or the like disposed inside the circulating travel of the heat transfer belt 9, for example, in the internal space of the support roller 85 so as to heat the endless heat transfer belt 9. A heating source 83 is provided. With this configuration, as described above, the fixing device 5 sandwiches and conveys the recording paper P carrying the unfixed toner image in the nip formed by the heat transfer belt 9 of the fixing unit 51 and the pressing unit 52. And has a function of fixing the unfixed toner image onto the recording paper P.

  When the fixing roller 511 is rotated clockwise in FIG. 4 by an electric motor (not shown), the pressure unit 52 is driven and rotated counterclockwise. At the same time, the heat transfer belt 9 is also rotated in the clockwise direction. At this time, when the heat source 83 is energized and heat generation is started, the heat transfer belt 9 is heated to increase the temperature, and the heat source 83 is controlled by a control means (not shown) so that the temperature becomes a predetermined fixing temperature range. Be controlled.

  Thus, according to the present invention, the endless heat transfer belt 9 has a release layer 91 on the surface in contact with the recording paper P and a base layer 92 made of resin on the back surface, as shown in FIG. Between the mold layer 91 and the base layer 92, a high thermal conductive layer 93 formed by containing a thermal conductive filler in a resin is provided. And the content rate of the heat conductive filler of the high heat conductive layer 93 is formed so that it may increase sequentially toward the mold release layer 91 side from the base layer 92 side. For example, the content of the heat conductive filler in the first layer 931 on the base layer 92 side is 20%, and the content of the heat conductive filler in the second layer 932, the third layer 933, and the fourth layer 934 is Then, 25%, 30%, and 35% are sequentially set, and the content of the heat conductive filler of the fifth layer 935 is set to 40%.

  According to the present embodiment having the above-described configuration, since the base layer 92 is formed of a resin as in the above-described embodiment, the base layer 92 has the overall strength and heat capacity as the heat transfer belt 9 and is a high heat layer serving as the upper layer. The conductive layer 93 is formed by containing a heat conductive filler in a resin. Therefore, heat can be efficiently conducted from the base layer 92 to the release layer 91 on the surface. As a result, a heat transfer belt excellent in durability and thermal conductivity can be obtained. In addition, since the surface is formed by the release layer 91, it is excellent in releasability at the contact portion with the recording paper P carrying the unfixed toner image in contact with the heat transfer belt 9, and toner or paper It is preferable because powder or the like hardly adheres. Further, the heat heated from the base layer 92 side is conducted more efficiently through the high heat conductive layer 93 in which the content of the heat conductive filler is sequentially increased from the base layer 92 side to the release layer 91. The recording paper P that reaches the release layer 91 and carries the unfixed toner image can be efficiently heated, which is preferable.

The above-described embodiment is a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.
For example, in the above-described embodiment, the copying machine has been described as an example. However, the present invention can be applied to, for example, a facsimile machine or a multifunction machine having various functions such as a copying function, a printer function, a scanner function, and a facsimile function. It can also be applied to.

  In the above-described embodiment, the drum-shaped photoconductor 41 is used. However, the shape of the photoconductor 41 is not limited, and a known shape other than the above-described drum shape can be used. Examples of the shape include a sheet shape, a belt shape, and a web shape.

  Examples of use of the present invention include a fixing device that heat-fixes an unfixed toner image carried on a recording paper, and an image forming apparatus including the fixing device.

1 is a schematic configuration diagram illustrating a schematic configuration when applied to a copying machine as an image forming apparatus using a fixing device according to a first embodiment of the present invention. FIG. 2 is a conceptual diagram illustrating a schematic configuration of the fixing device illustrated in FIG. 1. FIG. 3 is an enlarged sectional view showing a laminated structure of a heat transfer belt of the fixing device shown in FIG. 2. FIG. 6 is a conceptual diagram illustrating a schematic configuration of a fixing device according to a second embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view showing a laminated structure of a heat transfer belt of the fixing device shown in FIG. 4.

Explanation of symbols

P: recording paper, 1 ... image forming apparatus, 5 ... fixing device, 8 ... external heating means, 9 ... heat transfer belt, 51 ... fixing means, 52 ... pressure means, 91 ... release layer, 92 ... base layer, 93 ... High thermal conductive layer

Claims (5)

A fixing unit for fixing an unfixed toner image carried on a recording paper; a pressure unit for pressing together with the fixing unit; and an external unit for heating the unfixed toner image to fix the unfixed toner image. In a fixing device comprising a heating unit and an endless heat transfer belt heated by the external heating unit, wherein the unfixed toner image is directly or indirectly heated by the heat transfer belt. ,
The heat transfer belt has a release layer on the front surface and a base layer made of resin on the back surface, and a high heat conductive layer formed between the release layer and the base layer by containing a heat conductive filler in the resin. And a fixing device.   The fixing device according to claim 1, wherein the content of the heat conductive filler in the high heat conductive layer is formed so as to sequentially increase from the base layer side toward the release layer side.   The fixing device according to claim 1, wherein the release layer is made of a fluororesin, and a layer pressure of the release layer is formed to be thinner than that of the high thermal conductive layer.   The base layer contains a heat conductive filler in a resin, and the content of the heat conductive filler in the base layer is lower than the content of the heat conductive filler in the high heat conductive layer. The fixing device according to claim 3.   An image forming apparatus comprising the fixing device according to claim 1.

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