JP4243523B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a fixing device that employs an electromagnetic induction heating method and is used in an image forming apparatus such as a copying machine, a facsimile machine, or a printer.

  In recent years, there has been an increasing demand for higher speed image forming apparatuses such as copying machines. As one means for achieving this, a technique for constructing a fixing device using what is called an IH belt formed by providing a heat-resistant belt base material with a thin film layer having heat generation by electromagnetic induction has been proposed. ing. However, the belt having such a structure is expensive because it undergoes a very troublesome manufacturing process of forming a heat generating layer having a thickness of several μm, and it is technically necessary to uniformly form the thin film layer as described above. In addition, when a belt having a layer structure is slid around a roller while generating heat, a load is applied between the layers constituting the belt, which may cause delamination.

On the other hand, as a fixing device having no problem in the belt having the above-described layer structure, a heating roller that forms a roller by adhering a thin conductive layer, a heat insulating layer, and a support layer to each other in order from the surface to the inside. An exciting coil that excites and heats the thin conductive layer from outside, and a pressurizing unit that presses against the heating roller to form a nip, and passes a recording material carrying an image through the nip to pass the image. There is an apparatus that heats (see, for example, Patent Document 1).
JP 2001-5315 A

However, as a result of intensive studies by the inventor of the present application, the thermal expansion amount of the heat generation layer and the thermal expansion of the support layer are obtained by using Al for the support layer of the roller that generates heat as in the example described in Patent Document 1 above. If you take a configuration with a different amount,
(1) Peeling easily occurs between the layers constituting the heat generating roller,
(2) The heat generating roller is likely to be wavyly deformed,
(3) Accordingly, there arises a problem that the glossiness of the image may vary, and there may be a state in which the above-described problem in the belt having the layer configuration cannot be solved.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device that can solve the problems associated with heating layers other than the heat generating layer as described above, and an image forming apparatus using the same.

According to a first aspect of the present invention, there is provided a fixing nip between a heating roller having heat generation due to electromagnetic induction heating, a belt having no heat generation due to electromagnetic induction heating around the heating roller, and the belt. In a fixing device comprising a pressure roller that forms a portion and a heating means that heats the heating roller from the outer periphery thereof by electromagnetic induction , the heating roller generates heat on a non-heat generating material that also serves as a support as a roller. A material layer is formed, and a magnetic layer is provided on the inner peripheral side of the non-heat-generating material body .

The fixing device according to claim 2 is the fixing device according to claim 1, wherein a magnetic layer is provided between the heat generating material layer and the non-heat generating material body .

A fixing device according to the claim 3 is the fixing device according to claim 1 or 2, before Symbol nonpyrogenic material body is characterized Rukoto also serves as a heat insulating layer.

The fixing device according to claim 4 includes a heating roller, a fixing roller arranged in parallel to the heating roller, and an endless belt-like toner that is wound around the heating roller and the fixing roller and is heated by the heating roller. A heating medium, a pressure roller that is pressed against the fixing roller via the toner heating medium and forms a fixing nip portion with the toner heating medium, and the heating roller is heated from the outer peripheral side by electromagnetic induction. In the fixing device comprising a heating means, the heating roller is formed by forming a heat generating material layer on a non-heat generating material body that also serves as a support as a roller, and a magnetic layer is formed on the inner peripheral side of the non-heat generating material body. It is provided.

Fixing device according to the claim 5 is the Fixing device according to claim 4, characterized in Rukoto such provided magnetic layer between the non-heat generating material member and the heat generating material layer.

Fixing device according to the claim 6 is the fixing device according to claim 4 or 5, before Kihi exothermic material body is characterized Rukoto also serves as a heat insulating layer.

The image forming apparatus according to the claim 7 characterized by using either of the fixing device of claims 1 to 6.

  The present invention is a structure that is inexpensive and does not cause problems such as delamination, and heat transfer from a heating roller having heat generation by electromagnetic induction heating to a belt having no heat generation by electromagnetic induction heating. There is an effect that the efficiency can be increased.

The present invention, by functionally separated into a non-heat generating member and the heat generating material layer in the structure of the pressurized heat roller, has achieved thermal conductivity improvement of the fixing belt side by the insulating effect of the heating roller internally and heating The roller is less likely to cause delamination or undulating deformation between the non-heating element and the heating material layer. Further, by providing a magnetic layer on the inner side (axial side) of the heat generating material layer, the magnetic flux can be concentrated on the heat generating material layer. Therefore, like a conventional IH belt fixing device, a thin film is formed on the fixing belt. There is an effect that it is possible to solve problems caused by providing a heating element, that is, breakage due to repeated deformation of the belt , occurrence of delamination due to heat, poor durability, and the like .

  FIG. 1 is a schematic cross-sectional view of an embodiment of an image forming apparatus including a fixing device according to the present invention. In the figure, 1 is an image carrier, 2 is a charging means, 3 is a laser writing unit, 4 is a developing device, 5 is a transfer roller, and 6 is a cleaning device. In the figure, reference numeral 7 denotes a paper feed unit, 8 denotes a paper feed roller, 9 denotes a registration roller pair, 10 denotes a fixing device, 11 denotes a paper discharge unit, and 12 denotes an image forming apparatus main body.

  The image carrier 1 is rotationally driven in the direction of the arrow in the figure by a driving means (not shown), and the surface thereof is uniformly charged by the charging means 2, and then a latent image is formed on the surface by exposure from the laser writing unit 3. The latent image is visualized by the developing device 4 and the toner image is transferred by the transfer device 5 to a transfer body P such as paper supplied from the paper supply unit 7 via the paper supply roller 8 and the registration roller pair 9. . The toner remaining on the surface of the image carrier 1 after the transfer of the toner image is removed by the cleaning device 6.

  The transfer body P to which the image has been transferred is introduced into the fixing device 10, the toner image is fixed to the transfer body P by heating and pressurization, and then discharged to the paper discharge unit 11. Of course, the present invention is not limited to the illustrated image apparatus, and can be applied to various types.

  FIG. 2A is a schematic sectional view showing an embodiment of the fixing device according to the present invention. The fixing device 10 is hung on a heating roller 21 heated by electromagnetic induction of an induction heating unit 20, a fixing roller 22 arranged so that the axis of the heating roller 21 is parallel to the heating roller 21, and the heating roller 21 and the fixing roller 22. The rotating belt includes an endless fixing belt 23 that is rotated, and a pressure roller 24 that rotates while being pressed against the fixing roller 22 via the fixing belt 23.

  The induction heating means 20 heats the heating roller 21 by electromagnetic induction, and includes an excitation coil 25 that is a magnetic field generation means, a coil guide plate 26 around which the excitation coil 25 is wound, a ferrite disposed outside the excitation coil 25, and the like. This is composed of a semi-cylindrical excitation coil core 27 made of a ferromagnetic material and an excitation coil core support member 28 for fixing and supporting the excitation coil core 27. The excitation coil 25 is connected to a driving power supply (not shown) (for example, an oscillation circuit whose frequency is variable).

  The coil guide plate 26 has a semi-cylindrical shape arranged close to the outer peripheral surface of the heating roller 21, and the excitation coil 25 has a single excitation coil wire along the coil guide plate 26 as shown in FIG. As shown in FIG. 3C, a magnetic field E is generated in a direction perpendicular to the axis of the coil so that the heating roller 21 is electromagnetically induced. To heat. The coil is wound in an area where the fixing belt 23 and the heating roller 21 are in contact with each other. In this way, the area of the heating roller 21 that performs electromagnetic induction heating is increased, and the range in which the heat generating material layer 31 on the surface of the heating roller 21 that is generating heat can contact the fixing belt 23 is increased. Heat transfer efficiency can be increased.

  FIG. 2B is an enlarged partial sectional view showing the structure of the heating roller 21 in FIG. The heating roller 21 is made of, for example, a heat-insulating material such as ceramic, a heat-insulating material in which a balloon (hollow body) such as phenol resin or glass is dispersed and mixed in super engineering plastic, or a low thermal conductive material made of silica. A hollow cylindrical non-heating element 30 made of a material or the like and a heating material layer 31 provided on the outer peripheral surface (contact surface to the fixing belt 23) side thereof.

  Since the hollow cylindrical non-heating element 30 also serves as a support as the heating roller 21, the hollow cylindrical non-heating element 30 has a required rigidity as a support, such as 0.3 mm or 0.4 mm. On the other hand, the heat-generating material layer 31 is formed by forming a heat-generating material such as SUS430 or nickel on the non-heat generating body 30 in a thickness of about 1 to 10 μm by vapor deposition or the like.

  The fixing roller 22 is configured by covering a metal core such as stainless steel with a heat-resistant silicone rubber in a solid or foamed state. The pressure roller 24 is configured by providing an elastic member having heat resistance and high toner releasability on the surface of a cored bar made of a metal cylindrical member having high heat conductivity such as copper or aluminum. SUS or the like is used for the core metal. The fixing roller 22 and the pressure roller 24 are pressed against each other via the fixing belt 23 to form a nip portion for fixing the transfer body P and the toner T thereon by heating and pressing. It is set as the structure which has thickness.

  As the fixing belt 23, any suitable belt can be used as long as it has good thermal conductivity and hardly undergoes deformation such as bending. For example, those having heat resistance such as fluorine resin such as PFA, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, and PPS resin can be used. In the present invention, the fixing belt 23 does not require heat generation due to electromagnetic induction. Therefore, the fixing belt 23 does not have to be made of a magnetic metal or alloy such as iron, cobalt, or nickel, which is used in a conventionally known IH fixing device. It is not necessary to have a thin film layer for heat generation. In the figure, reference numeral 40 denotes a temperature sensor, which is arranged inside the wound fixing belt 23 so that the temperature of the fixing belt 23 can be detected.

  With such a configuration, the exciting coil 25 is fed with a high-frequency alternating current from a drive power source to generate a magnetic field E, and the heat generating material layer 31 of the heating roller 21 is heated by electromagnetic induction. The fixing belt 23 receives heat conduction from the heat generating material layer 31 by contact with the heating roller 21. Then, the heat generating material layer 31 is continuously heated over the whole by the rotation of the heating roller 21 and the fixing roller 22 to raise the temperature. At this time, heat transfer from the heat-generating material layer 31 to the hollow interior is substantially blocked by the non-heat-generating body 30 having thermal insulation or low thermal conductivity, and is efficiently transferred to the fixing belt 23.

  According to the results of experiments conducted by the inventors of the present application, heat generation is observed when the heat generating material layer 31 is 1 μm or more, the degree of heat generation increases as the thickness increases, and the thickness is saturated at about 10 μm. For the purpose of making the time required for raising the temperature to the required fixing temperature, that is, the so-called rise time as short as possible, a thickness of about 5 μm is suitable. Of course, the thickness of the heat generating material layer 31 of the heating roller 23 in the present invention is not limited to this example, and may be appropriately selected according to the material. Incidentally, a layer made of, for example, engineering plastic or the like having a thickness of about 2 to 3 μm is provided on the outer periphery of the heat generating material layer 31 by vapor deposition or the like to improve the contact property with the pressure roller 24 and the releasability with the transfer body P You may plan. In any case, the time for raising the temperature to the fixing temperature can be significantly shortened by electromagnetic induction heating of the thin heat generating material layer 31.

  FIG. 4 is an enlarged partial cross-sectional view showing another configuration example of the heating roller that can be used in the fixing device according to the present invention. The heating roller 21 in this example is configured such that the magnetic layer 32 is provided between the non-heating element 30 and the heating material layer 31 similar to the heating roller 21 described above, and the magnetic field E generated by the excitation coil 25 is likely to concentrate. The heating property is enhanced by making it difficult to leak from the gap between the exciting coil 25 and the non-heating element 30.

  FIG. 5 is an enlarged partial sectional view showing a modification of the example shown in FIG. The heating roller 21 in this example is provided with a magnetic layer 32 inside a hollow cylindrical non-heating element 30. Others are the same as the example of FIG.

  That is, in the fixing device according to the present invention, by separating the function into the non-heating element 30 and the heating material layer 31 in the structure of the heating roller, the heat conductivity to the fixing belt 23 side is improved by the heat insulating effect inside the heating roller 21. In addition, the non-heating element 30 and the heating material layer 31 in the heating roller 21 are less likely to be delaminated and wavy. Also. By providing the magnetic layer 32 on the inner side (axial center side) of the heat generating material layer 31, the magnetic flux can be concentrated on the heat generating material layer 31. Therefore, as in the case of the conventional IH belt fixing device, there is a problem caused by providing a thin film heating element on the fixing belt, that is, damage due to repeated deformation of the belt, occurrence of delamination due to heat, poor durability, etc. Has solved.

  In the fixing device manufactured according to the present invention, the cost of forming a heating element on the belt is comparatively effective in the conventional type compared to the conventional IH fixing belt type that generates heat from the belt. Therefore, it can be realized at a cost of about 30%, and can be realized at a cost of about 50% as compared with a type in which a heater is built in the heating roller.

  In the present invention, the non-heating element 30 of the heating roller 21 may be a solid roller, and a separate support is provided, for example, in the shape of a shaft inside the hollow cylindrical non-heating element 30 to provide further support. May be raised.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus including a fixing device according to the present invention. FIG. 3 is an enlarged partial sectional view (B) showing the structure of the heating roller, together with a schematic sectional view (A) showing an embodiment of the fixing device according to the present invention. It is sectional drawing (A) which shows the structure of an induction heating means, a side view (B), and an expanded sectional view (C). It is an expanded sectional fragmentary view which shows the other structural example of the heating roller which can be used for the fixing apparatus which concerns on this invention. It is an expanded sectional fragmentary view which shows the modification of the example shown in FIG.

Explanation of symbols

1: image carrier 2: charging means 3: laser writing unit 4: developing device 5: transfer roller 6: cleaning device 7: paper feeding unit 8: paper feeding roller 9: registration roller pair 10: fixing device 11: paper ejection unit 12: Image forming apparatus body 20: Induction heating means 21: Heating roller 22: Fixing roller 23: Fixing belt 24: Pressure roller 25: Excitation coil 26: Coil guide plate 27: Excitation coil core 28: Excitation coil core support member 30: Non Heating element 31: Heating material layer 32: Magnetic layer 40: Temperature sensor P: Transfer body T: Toner

Claims (7)

A heating roller having heat generation due to electromagnetic induction heating, a belt not having heat generation due to electromagnetic induction heating around the heating roller, a pressure roller forming a fixing nip portion between the belt, and the heating roller In the fixing device comprising heating means for heating from the outer peripheral side by electromagnetic induction , the heating roller forms a heat-generating material layer on a non-heat-generating material body that also serves as a support as a roller, and the non-heat-generating material A fixing device comprising a magnetic layer provided on an inner peripheral side of a body . 2. The fixing device according to claim 1, wherein a magnetic layer is provided between the heat generating material layer and the non-heat generating material body . The fixing device according to claim 1 or 2, a fixing device before Symbol nonpyrogenic material body is characterized Rukoto also serves as a heat insulating layer. A heating roller, a fixing roller arranged in parallel with the heating roller, an endless belt-like toner heating medium that is wound around the heating roller and the fixing roller and heated by the heating roller, and the toner heating medium A fixing device comprising: a pressure roller that is in pressure contact with the fixing roller and forms a fixing nip portion with the toner heating medium; and a heating unit that heats the heating roller from the outer peripheral side thereof by electromagnetic induction. A fixing device in which a heating roller is formed with a heat generating material layer on a non-heat generating material body that also serves as a support as a roller, and a magnetic layer is provided on the inner peripheral side of the non-heat generating material body . In Fixing device according to claim 4, the fixing device according to claim Rukoto such provided magnetic layer between the non-heat generating material member and the heat generating material layer. The fixing device according to claim 4 or 5, a fixing device before Kihi heating material body is characterized Rukoto also serves as a heat insulating layer. An image forming apparatus characterized by using either of the fixing device of claims 1 to 6.

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