JP2005122984A - Induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating device capable of effectively preventing magnetic leakage flux from being generated while preventing a shield material from generating heat. <P>SOLUTION: This induction heating device has a heating coil 11 for heating an object to be heated by induction heating, and a shield material 14 comprising a metal of ferromagnetic material to cover the heating coil 11, and in the shield material 14, a plurality of slits 14a are provided in the direction in which flow of magnetic flux generated by the heating coil 11 is not hampered. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an induction heating apparatus that induction-heats an object to be heated.

  The induction heating device utilizes the fact that an eddy current is generated when a metal, which is a conductive material, is placed in a high-frequency magnetic field generated by flowing a high-frequency current of several k to 100 kHz through a heating coil. A heated object made of a metal such as iron is heated by Joule heat.

For this reason, the induction heating device is superior in safety because it does not use fire as compared with heating by a burner or the like. In addition, since the induction heating apparatus can heat the object to be heated in a short time and can also heat a specific part by current control, a hot sheet bar heating apparatus (see, for example, Patent Document 1), a copying machine Are widely used in heating apparatuses for transfer rolls (for example, see Patent Document 2), electromagnetic cookers (for example, see Patent Documents 3 and 4), and the like.
Japanese Patent Application Laid-Open No. 2-6009 JP 2002-40839 A Japanese Patent Publication No.58-37676 JP 2000-48944 A

  On the other hand, the induction heating device heats the object to be heated using the high-frequency magnetic field generated from the heating coil, so that it is inevitable that magnetic flux leaks from the induction heating device. There are concerns about the negative effects of. In particular, in recent years, steel process lines have been digitized and made compact, and electronic devices such as computers may be arranged near the lines, and there has been a growing demand for suppressing the generation of leakage magnetic flux.

  Incidentally, in the field of the electromagnetic cooker, various techniques have been proposed in order to suppress the generation of leakage magnetic flux. For example, by providing a shield ring made of a non-magnetic metal such as aluminum around the heating coil, a magnetic field opposite to the magnetic lines generated by the heating coil is generated, and the magnetic lines are enclosed in the shield ring. Techniques have been proposed for covering the power supply unit with a non-magnetic metallic material that does not obstruct the passage of magnetic flux.

  However, the former technique in the electromagnetic cooker field has a problem that the magnetic flux leaking out of the shield ring increases. In addition, a nonmagnetic metal is used as the material of the shield ring, but there is a demand for using a ferromagnetic metal from the viewpoint of workability and saturation magnetization. However, since the ferromagnetic metal has a higher electrical resistance than the nonmagnetic metal, it is necessary to suppress heat generation. Furthermore, although the latter technique can effectively shield the electromagnetic waves generated from the power supply unit, there is a problem that the leakage magnetic flux is large because the magnetic flux from the heating coil is not shielded.

  The present invention has been made based on such circumstances, and an object of the present invention is to provide an induction heating apparatus that can prevent heat generation of a shield material and effectively prevent generation of leakage magnetic flux. It is.

The present invention relates to an induction heating apparatus for induction heating an object to be heated with a heating coil, having a shield material made of a ferromagnetic metal that covers the heating coil, and the shield material is configured to reduce the flow of magnetic flux generated by the heating coil. A plurality of slits are provided in a direction not hindering.
Also, the present invention provides an induction heating apparatus for induction heating an object to be heated with a heating coil so as to surround the ferrite disposed on the opposite side of the heating surface of the heating coil and the outer periphery of the heating coil with a predetermined interval. A magnetic shielding ring made of a conductive metal, and a shield material made of a ferromagnetic metal covering the heating coil and the ferrite from the outer edge of the magnetic shielding ring, the shielding material being a magnetic flux generated by the heating coil A plurality of slits are provided in a direction that does not obstruct the flow of.

  The present invention can provide an induction heating apparatus that can prevent heat generation of the shield material and effectively prevent generation of leakage magnetic flux by providing such means.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In this embodiment, the present invention is applied to an induction heating device for a hot sheet bar. Generally, in a hot rolling line for steel, a heated plate-like slab is rolled into a thin hot sheet bar by a roughing mill, and this is further rolled to a desired product thickness by a finishing mill. Part of the heat held by the hot sheet bar is dissipated into the atmosphere between the roughing and finishing rolling processes, and the temperature distribution of the hot sheet bar is not uniform. The hot sheet bar is induction heated to keep the temperature distribution uniform. In the present embodiment, the present invention is applied to an induction heating apparatus provided on the entrance side of the finishing mill.

  FIG. 1 is a schematic view of a cross section taken along the line BB in FIG. 2 of the induction heating apparatus according to the present embodiment, and FIG. 2 is a schematic view of a cross section taken along the line AA in FIG. In the present embodiment, a pair of induction heating devices 1 and 2 are provided facing each other so as to sandwich the plate-like heated body (hot sheet bar) 3 conveyed on the hot rolling line for steel from above and below. Yes. The induction heating device 1 and the induction heating device 2 have the same configuration. Therefore, in the present embodiment, for convenience of explanation, the induction heating device 1 will be described, and the induction heating device 2 will be denoted by the same reference numerals and the detailed description thereof will be omitted.

  The induction heating apparatus 1 includes a heating coil 11 in which an electric wire is wound in a “mouth” shape, and a plurality of rod-shaped ferrites 13 that are radially attached to the surface of the heating coil 11 opposite to the heating coil surface 12; And a shielding material 14 for shielding magnetism. The heating coil surface 12 of the heating coil 11 in the induction heating device 1 and the heating coil surface 12 of the heating coil 11 in the induction heating device 2 are arranged to face each other, and the plate-like heated object 3 conveyed between them is conveyed. The entire region in the width direction is heated from above and below. In FIG. 1, an arrow C indicates the conveyance direction of the plate-shaped heated body 3.

  The shield material 14 is made of a ferromagnetic metal. The ferromagnetic material is preferably an iron-based material from the viewpoint of workability and saturation magnetization, and pure iron, electromagnetic steel sheet, cold-rolled steel sheet, hot-rolled steel sheet, galvanized steel sheet, etc. are used as the material for the shield material 14. To do. The shield material 14 is provided with a plurality of slits 14a radially from the circumferential position of a circle with a predetermined radius on a steel plate having Si = 0.1% and a plate thickness of 2 mm (point-symmetric with respect to the center of the circle with a predetermined radius). The steel plate provided with the slits 14a is deeply squeezed into a length of 1 m, a width of 1.6 m, and a depth of 50 cm, and 750 ° C. × 2 hr strain relief annealing is performed in order to remove distortion during processing. To perform molding. FIG. 3 is a view of the shield material 14 formed in this way as viewed from the opening side. As shown in the figure, the center of the circle with a predetermined radius is the central axis of the shield member 14, and the plurality of radial slits 14a from the predetermined position of the central axis in the lateral direction are point-symmetric with respect to the central axis. Is provided. As shown in FIG. 2, the shield material 14 is configured such that the opening side is directed to the plate-like heated body 3 so as to cover the ferrite 13, and the tip end portion on the opening side is separated from the outer periphery of the heating coil 11 by a predetermined distance. It is installed in. Further, the shield material 14 is installed so that the central axis of the shield material 14 and the central axis of the heating coil 11 substantially coincide. Therefore, when the shield material 14 is installed, the slit 14a is provided in a direction that does not hinder the flow of magnetic flux generated from the heating coil 11. In addition, since the magnetic flux which generate | occur | produces from the heating coil 11 can be absorbed by the ferrite 13 by providing the ferrite 13 between the heating coil 11 and the shielding material 14, it is possible to install the shielding material 14 close to the heating coil 11 side. it can.

  In the present embodiment configured as described above, a high-frequency magnetic field is generated between the heating coils 11 when a high-frequency current is supplied from a high-frequency power source (not shown) to the heating coils 11 of the pair of induction heating devices 1 and 2. When the plate-shaped heated body (hot sheet bar) 3 conveyed through the hot rolling line for steel passes through the high-frequency magnetic field, an eddy current is generated in the plate-shaped heated body 3, and the joule due to this eddy current is generated. The plate-like heated body 3 is heated by heat.

  At this time, most of the magnetic flux generated from the heating coil 11 and passing through the object to be heated in the direction of the plate surface of the plate-shaped object 3 is the opening of the shield member 14 located at a predetermined distance from the heating coil 11. It flows from the front end portion toward the center of the inner peripheral surface of the shield member 14, passes from the center portion through the center portion of the heating coil 11, and again flows so as to hit the surface to be heated of the plate-like heated body 3. That is, the magnetic flux generated from the heating coil 11 by the shield material 14 can be concentrated in the coil center direction. In addition, since a plurality of slits 14a are provided in the shield material 14 in a direction that does not interfere with the flow of magnetic flux generated from the heating coil 11, even if eddy current is locally generated between the slits 14a, Since no eddy current is generated, the eddy current in the shield material 14 can be reduced.

  Conventional magnetic shields (for example, shield rings) use nonmagnetic metals such as aluminum and copper as materials. This is because aluminum, copper, and the like have a small electrical resistance and thus generate little heat due to eddy currents. On the other hand, iron-based materials are superior from the viewpoints of workability and saturation magnetization. However, since the electric resistance is larger than that of aluminum, copper, etc., heat generation due to eddy current is large, and in particular, the plate surface of the magnetic shield material 14 When an eddy current flows in the inside, the calorific value becomes very large, and it is difficult to use an iron-based material as a magnetic shield material. In the present invention, by providing a plurality of slits 14a in a direction that does not interfere with the flow of magnetic flux in the shield material 14 for performing magnetic shielding, the eddy current in the plate surface of the shield material 14 is controlled to suppress heat generation, The shield material 14 can be made of an iron-based material.

  As described above, according to the present embodiment, the shielding material 14 is made of a ferromagnetic metal and the ferrite 13 is covered with the opening side facing the plate-like heated body 3 and the opening side end portion is a heating coil. 11 is provided at a position away from the outer periphery of the heater 11 by a predetermined distance, and a plurality of slits 14a are provided in a direction that does not hinder the flow of magnetic flux generated from the heating coil 11, thus preventing leakage magnetic flux and being generated in the shield material 14. Eddy currents can be reduced, and heat generation of the shield material 14 can be suppressed.

  Moreover, in this embodiment, the case where the present invention is applied to the induction heating device provided on the finishing rolling mill entrance side of the hot rolling line for steel is shown, but the induction heating device to which the present invention can be applied, It is not limited to this.

  FIG. 4 shows a case where the present invention is applied to the induction heating device 21 of the roll heating device 20. The roll heating device 20 simultaneously induction-heats a heated body 23 such as a hot-rolled steel plate and a cold-rolled steel plate conveyed along the outer periphery of the work roll 22 and a steel strip conveyed with the work roll 22 by the induction heating device 21. To do. The induction heating device 21 is provided with a shield material 14 made of a ferromagnetic metal.

  The shield material 14 is provided with a plurality of slits 14a radially from a circumferential position of a circle of a predetermined radius on a steel plate having Si = 0.1% and a thickness of 1 mm, and the steel plate provided with the slits 14a is 1 m in length, 1. It is formed by deep-squeezing to 2 m and a depth of 30 cm, and performing strain relief annealing at 750 ° C. × 2 hr in order to remove strain during processing. The center of the circle with a predetermined radius is the central axis of the shield member 14, and a plurality of radial slits 14a are provided so as to be point-symmetric with respect to the central axis from a predetermined position of the central axis toward the side surface. Yes. The shield material 14 is installed so that the opening side is directed toward the work roll 22 and the ferrite 13 is covered, and the opening side tip is located at a predetermined distance away from the outer periphery of the heating coil 11. The shield material 14 is installed so that the center axis of the material 14 and the center axis of the heating coil 11 substantially coincide. That is, when the shield material 14 is installed, the slit 14 a is provided in a direction that does not hinder the flow of magnetic flux generated from the heating coil 11.

  Therefore, the induction heating device 21 of the roll heating device 20 can achieve the same effect as that of the above embodiment. Incidentally, the configuration of the induction heating device 21 having the configuration shown in the figure can also be applied as an induction heating device for heating the fixing roller of the copying machine.

  FIG. 5 shows a case where the present invention is applied to the induction heating device 31 of the electromagnetic cooker 30. The electromagnetic cooker 30 induction-heats an object to be heated 33 such as an iron pan placed on a top plate 32 by an induction heating device 31 provided below the top plate 32.

  The induction heating device 31 according to this embodiment includes a heating coil 11 in which an electric wire is wound in a “mouth” shape, and a plurality of radial coils attached to the surface of the heating coil 11 opposite to the heating coil surface 12. A bar-shaped ferrite 13, a magnetic shield 15 having one end disposed substantially at the same position as the heating coil surface 12 of the heating coil 11 so as to surround the outer periphery of the heating coil 11 with a predetermined interval, and a shield The material 14 is comprised.

  The shield material 14 is provided with a plurality of slits 14a radially from a circumferential position of a circle having a predetermined radius on a steel plate having Si = 0.1% and a plate thickness of 0.6 mm, and the steel plate provided with the slits 14a has an outer diameter of 5 cm, In order to remove the strain at the time of processing, it is formed by performing strain relief annealing at 750 ° C. × 2 hr in order to remove the strain at the time of processing. FIG. 6 is a view of the shield material 14 formed in this way as seen from the opening side. As shown in the figure, the center of the circle with a predetermined radius is the central axis of the shield member 14, and the plurality of radial slits 14a from the predetermined position of the central axis in the lateral direction are point-symmetric with respect to the central axis. Is provided.

  The shield member 14 is installed so that the opening side is directed to the top plate 32 side, the tip thereof is located at the outer edge of the magnetic shield ring 15, and the ferrite 13 is covered from the outer edge of the magnetic shield ring 15. Further, the shield material 14 is installed so that the central axis of the slit of the shield material 14 and the central axis of the heating coil 11 substantially coincide. That is, when the shield material 14 is installed, the slit 14 a is provided in a direction that does not hinder the flow of magnetic flux generated from the heating coil 11.

Table 1 shows that when the shield material 14 is not installed, the slit material is not provided with the slit 14a (the above steel plate not provided with the slit 14a is formed by applying the same processing such as deep drawing). In three cases where the shield member 14 provided with 14a is installed, the leakage magnetic flux from the electromagnetic cooker 30 is measured. The temperature of the shield material 14 is measured in two ways: when a shield material not provided with the slits 14a is installed and when a shield material 14 provided with the slits 14a is installed. The magnetic flux was measured at a position 1 cm from the edge of the front surface of the top plate 32 of the electromagnetic cooker 30, and the temperature of each shield material was measured at a position corresponding to the central axis of the coil by a thermocouple thermometer. Is going.

As shown in Table 1, the leakage magnetic flux is lower when each shield material is installed than when no shield material is installed. Further, when the shield material is installed, the leakage magnetic flux is slightly larger in the case where the slit 14a is provided than in the case where the slit 14a is not provided, and the temperature is greatly increased. It can be seen that it has dropped. Therefore, the induction heating device 21 of the electromagnetic cooker 30 can achieve the same effect as that of the above embodiment.

  FIG. 7 shows a case where the shield member 14 ′ is installed in the electromagnetic cooker 30 described with reference to FIG. 5 so that the opening end protrudes from the magnetic shielding ring 15 toward the top plate 32. This shield material 14 'differs from the above-described shield material 14 in that the deep drawing process is performed at a depth of 3.5 cm and the depth is 0.5 cm deep. This shield material 14 'is installed in the same manner as described above. Therefore, the opening-side tip of the shielding material 14 ′ protrudes toward the top plate 32 by an amount corresponding to a deepening of 0.5 cm.

Table 2 shows the measurement results obtained by performing the same measurement as in Table 1 when the shielding material 14 'is installed in this way.

As shown in Table 2, when compared with the measurement results in Table 1, it can be seen that the shield material 14 'effectively prevents leakage magnetic flux. The shield material 14 'not provided with the slit 14a generates a large amount of heat due to an eddy current generated by the magnetic flux generated from the heating coil 11, and the temperature rises significantly. However, the shield material 14' provided with the slit 14a Even if an eddy current is locally generated between the slits 14a, heat generation does not increase so much, so that a rise in temperature can be suppressed. Therefore, the shield member 14 ′ whose tip protrudes from the magnetic shield ring 15 toward the top plate side 32 can suppress heat generation and effectively reduce leakage magnetic flux.

  In this embodiment, the shield materials 14 and 14 'are processed into a pan shape and used, but the present invention is not limited to this, and any shape that can form a closed magnetic path for the heated object, It may have a plate shape or a ring shape.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be modified by appropriately combining the constituent elements.

The top view of the induction heating apparatus in one embodiment of this invention. Schematic of the AA arrow cross section in FIG. The figure for demonstrating a shielding material. The schematic diagram which shows embodiment which applied this invention to the roll heating apparatus. The schematic diagram which shows embodiment which applied this invention to the electromagnetic cooker. The figure which shows the other example of a shielding material. The figure which shows the other example of a shielding material.

Explanation of symbols

1, 2, 21, 31 ... induction heating device 3, 23, 33 ... heated body 11 ... heating coil 12 ... heating coil surface 13 ... ferrite 14, 14 '... shield material 14a ... slit 15 magnetic shield ring

Claims (2)

In an induction heating apparatus for induction heating an object to be heated with a heating coil,
A shield material made of a ferromagnetic metal covering the heating coil;
The induction heating apparatus according to claim 1, wherein the shield material is provided with a plurality of slits in a direction that does not hinder the flow of magnetic flux generated by the heating coil. In an induction heating apparatus for induction heating an object to be heated with a heating coil,
A ferrite disposed on the opposite side of the heating surface of the heating coil;
A magnetic shielding ring made of a conductive metal disposed so as to surround the outer periphery of the heating coil with a predetermined interval;
A shield member made of a ferromagnetic metal covering the heating coil and the ferrite from the outer edge of the magnetic shield ring;
The induction heating apparatus according to claim 1, wherein the shield material is provided with a plurality of slits in a direction that does not hinder the flow of magnetic flux generated by the heating coil.

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