JP2009301901A - Coil for induction heating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive coil for induction heating to make temperature characteristics of heating parts uniform by improving dimensional precision of a coil outer diameter. <P>SOLUTION: The coil for the induction heating is prepared by winding an electric wire of single strand of which a cross-section is flat and rectangular in a plurality of times by interposing an insulation member between these electric wires. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an induction heating coil, and more particularly to an induction heating coil suitable for use in a fixing device such as a copying machine or a printer.

  2. Description of the Related Art Conventionally, for example, an electronic copying machine using digital technology includes a fixing device that fixes a developer image on a sheet by heating in a pressurized state.

  In the electronic copying machine, a document table on which a document is placed is exposed, and reflected light from the document is guided to a photoelectric conversion element such as a CCD (charge coupled device).

  The CCD outputs an image signal corresponding to the original image. Laser light corresponding to the image signal is irradiated onto the photosensitive drum, and an electrostatic latent image is formed on the peripheral surface of the photosensitive drum. This electrostatic latent image is visualized by the adhesion of developer (toner).

  A sheet is sent to the photosensitive drum in time with the rotation of the photosensitive drum, and a visible image (developer image) on the photosensitive drum is transferred to the sheet. The sheet on which the developer image is transferred is sent to a fixing device.

  As shown in FIG. 1, a general fixing device 11 is provided with a heating roller 12 and a pressure roller 13 at a position sandwiching the conveyance path of the copy paper S up and down, and further, electromagnetic induction for heating the heating roller 12. A heating unit 14 is provided.

  The pressure roller 13 is in contact with the peripheral surface of the heating roller 12 in a pressurized state by a pressure mechanism. The contact portions of these rollers 12 and 13 have a constant nip width.

  The heating roller 12 forms a conductive material, for example, iron into a cylindrical shape, and covers the outer peripheral surface of the iron with, for example, a fluororesin such as a tetrafluoroethylene resin.

  The heating roller 12 is rotationally driven in the right direction in the figure by a drive motor 15. The pressure roller 13 receives the rotation of the heating roller 12 and rotates in the left direction in the figure.

  The copy sheet S passes through the contact portion between the heating roller 12 and the pressure roller 13 and the copy sheet S receives heat from the heating roller 12 so that the developer image T on the copy sheet S is fixed to the copy sheet S. Is done.

  An electromagnetic induction heating unit 14 is provided in the vicinity of the heating roller 12. The electromagnetic induction heating unit 14 is close to the induction heating coil 16 so as to cover a plurality of induction heating coils 16 attached to the magnetically permeable support member 19 and the induction heating coil 16. And a ferrite member 17 provided. The ferrite member 17 is for increasing the heating efficiency by the electromagnetic induction heating unit 14, has a circular cross section, and extends in the axial direction of the heating roller 12.

  In the electromagnetic induction heating unit 14, when a high-frequency current is supplied from the excitation circuit 18 to the induction heating coil 16, magnetic flux repeatedly generates and disappears around the induction heating coil 16. Here, the frequency of the high-frequency current is set to, for example, 10 to 500 kHz, and when the magnetic flux from the induction heating coil 16 crosses the heating roller 12, a magnetic field is generated on the heating roller 12 so as to prevent the magnetic field from changing. Thereby, an eddy current is generated in the heating roller 12. In the heating roller 12, Joule heat proportional to the skin resistance of the heating roller 12 is generated by the eddy current, and the heating roller 12 is heated.

  As shown in FIGS. 4 and 5, the conventional induction heating coil 16 is manufactured by winding about 10 to 30 turns of a litz wire 16a obtained by twisting several tens to several hundreds of thin copper wires having a diameter of 0.3 mm or less. Has been.

  Thus, since the conventional induction heating coil processes and twists the copper wire thinly, the litz wire is expensive, so the induction heating coil itself is also expensive, and the copper wire in the coil cross section is also expensive. Since the occupation ratio is low, the density cannot be increased, and the number of turns of the coil is large, the dimensional accuracy of the outer diameter of the coil is low, and the temperature characteristics tend to vary when the heating roller is heated.

It has been proposed that the electromagnetic induction heating unit of the fixing device is configured to wind a coil around a ferrite, but it takes time and labor to assemble and replace the electromagnetic induction heating unit (for example, Patent Document 1).
JP-A-7-114276

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide an induction heating coil that is inexpensive, improves the dimensional accuracy of the outer diameter of the coil, and makes the temperature characteristics of the heated component uniform. .

  In order to achieve the above-described object, the induction heating coil according to the present invention is characterized in that a single wire having a flat rectangular cross section is wound a plurality of times in a planar coil shape through an insulating member.

  According to the induction heating coil of the present invention, it is possible to provide an induction heating coil that is inexpensive and can make the dimensional accuracy of the outer diameter of the coil and the temperature characteristics of the heated component uniform.

  An induction heating coil according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram of a general fixing device 11 suitable for using an induction heating coil according to an embodiment of the present invention, and FIG. 2 is a plan view of the induction heating coil according to an embodiment of the present invention. 3 is a cross-sectional view taken along line AA in FIG.

  Since the general fixing device shown in FIG. 1 has been described in the background art, a detailed description thereof will be omitted.

  In the fixing device 11, a heating roller 12 and a pressure roller 13 are provided at positions where the conveyance path of the copy paper S is sandwiched up and down, and an electromagnetic induction heating unit 14 for heating the heating roller 12 is further provided.

  An electromagnetic induction heating unit 14 is provided in the vicinity of the heating roller 12, and the electromagnetic induction heating unit 14 is a plurality of induction heating coils according to an embodiment of the present invention attached to a magnetically permeable support member 19. 1 and a ferrite member 17 having an arcuate cross section that is provided close to the induction heating coil 1 so as to cover the induction heating coil 1 and increases the heating efficiency of the electromagnetic induction heating unit 14.

  In the electromagnetic induction heating unit 14, when a high-frequency current is supplied from the excitation circuit 18 to the induction heating coil 1, magnetic flux repeatedly generates and disappears around the induction heating coil 1. Here, the frequency of the high frequency current is set to 10 to 500 kHz, for example, and when the magnetic flux from the induction heating coil 1 crosses the heating roller 12, a magnetic field is generated on the heating roller 12 so as to prevent the magnetic field from changing. Thereby, an eddy current is generated in the heating roller 12. In the heating roller 12, Joule heat proportional to the skin resistance of the heating roller 12 is generated by the eddy current, and the heating roller 12 is heated.

  The induction heating coil 1 is formed by winding a single-wire electric wire 2 having a flat rectangular cross section, for example, by winding an insulating member 3 between the electric wires 2 in a planar coil shape, for example, about 5 to 20 turns.

  The electric wire 2 has a long side portion (upper and lower surfaces) of, for example, 0.2 to 3 mm and a short side portion (height) of 0.1 to 1 mm, and the long side portion becomes an upper and lower surface through the insulating member 23. It is wound in an oval shape (track shape).

  The longitudinal direction of the induction heating coil 1 corresponds to the direction parallel to the central axis of the heating roller 12, that is, the width direction of the copy sheet S perpendicular to the conveyance direction of the copy sheet S in the nip portion.

  In addition, the cross section of a flat rectangular shape does not necessarily need to be a strict rectangle, and may be a substantially rectangular shape with a corner portion rounded off.

  When the fixing device 11 using the induction heating coil according to the present embodiment is used, in the electromagnetic induction heating unit 14, when a high-frequency current is supplied from the excitation circuit 18 to the induction heating coil 16, the induction heating coil 1 The magnetic flux crosses the heating roller 12, an eddy current is generated in the heating roller 12, Joule heat is generated, and the heating roller 12 is heated.

  In this heating roller heating process, this induction heating coil has a large copper wire occupancy in the coil cross section, high density, and can reduce the number of turns of the coil. Variation in temperature characteristics of the roller can be eliminated.

  The induction heating coil is a flat rectangular single wire wound around a take-up drum, drawn out, and planar coiled and oval with an insulating member interposed between the wires. Since it is manufactured by winding, it is inexpensive, unlike the case of using an expensive litz wire obtained by twisting and twisting a copper wire like a conventional induction heating coil.

  According to the induction heating coil of the present embodiment, an induction heating coil is realized that is inexpensive and can make the dimensional accuracy of the outer diameter of the coil and the temperature characteristics of the heated component uniform.

The conceptual diagram of the general fixing device suitable for using the coil for induction heating which concerns on this invention. The top view of the coil for induction heating of one Embodiment of this invention. Sectional drawing which follows the AA line of FIG. The top view of the conventional coil for induction heating. Sectional drawing which follows the BB line of FIG.

Explanation of symbols

1 Induction heating coil 2 Electric wire 3 Insulating member

Claims (1)

A coil for induction heating, which is formed by winding a single wire having a flat rectangular cross section into a planar coil shape by interposing an insulating member between the wires.

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