JP2005122986A - Induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating device capable of more effectively restraining leakage of magnetic flux. <P>SOLUTION: A plurality of conductive non-magnetic metal plates 15 are arrayed on a heating coil surface of a heating coil 11 with a space between them in a peripheral direction of the heating coil 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  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 steel slab heating apparatus (see, for example, Patent Document 1) and transfer in a copying machine Widely used in roll heating devices (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, in the former technique, there is a magnetic flux that leaks to the outside of the shield ring, and further reduction in magnetic flux leakage has been demanded. In the latter technique, although electromagnetic waves generated from the power supply unit can be effectively shielded, the magnetic flux from the heating coil is not shielded, so that there is a problem that the leakage magnetic flux is large.

  This invention is made | formed based on such a situation, The place made into the objective is providing the induction heating apparatus which can suppress magnetic flux leakage more effectively.

  The present invention relates to an induction heating apparatus that induction-heats an object to be heated with a heating coil. In view of the fact that a magnetic flux leakage is reduced by appropriately disposing a conductive nonmagnetic metal above the heating coil, the heating coil of the heating coil A conductive nonmagnetic metal plate is disposed on a part of the surface.

  According to the present invention, a plurality of conductive nonmagnetic metal plates are arranged on the heating coil surface of the heating coil so as to be spaced apart from each other in the circumferential direction of the heating coil.

  In the present invention, the shape of each conductive nonmagnetic metal plate is rectangular, circular, or the like.

  Moreover, as for the plate | board thickness of each electroconductive nonmagnetic metal plate, it is desirable to make a center part thicker than the both ends in the circumferential direction of a heating coil.

  Furthermore, it is preferable that each conductive non-magnetic metal plate is aligned on the heating coil surface so as to be pointed with respect to the center of the heating coil.

  The present invention can provide an induction heating device capable of suppressing magnetic flux leakage more effectively by taking such means.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In addition, this embodiment is a case where this invention is applied to the induction heating apparatus of the hot sheet bar in the steel industry. 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 plan view of the induction heating apparatus in 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.

  FIG. 3 is a bottom view of the induction heating apparatus 1. As shown in FIGS. 1 to 3, the induction heating device 1 is attached in a radial manner to a heating coil 11 in which an electric wire is wound in a “mouth” shape, and a surface of the heating coil 11 opposite to the heating coil surface. The plurality of ferrite rods 12, the metal tube 13, the insulating sheet 14, and the plurality of conductive nonmagnetic metal plates (hereinafter simply referred to as metal plates) 15. The heating coil surface of the heating coil 11 in the induction heating device 1 and the heating coil surface of the heating coil 11 in the induction heating device 2 are arranged to face each other, and the width direction of the plate-like heated body 3 conveyed between them. The substantially entire area is heated from above and below. In FIG. 1, an arrow B indicates the conveyance direction of the plate-shaped heated body 3.

  On the heating coil surface of the heating coil 11, as shown in FIG. 3, a plurality (eight in the figure) of circular metal plates 15 are spaced in the circumferential direction of the heating coil 11 via the insulating sheet 14. They are arranged in a row. Each metal plate 15 covers about 50% of the area of the heating coil surface of the heating coil 11. Each metal plate 15 is formed of a conductive nonmagnetic metal such as stainless steel or plastic. The metal plates 15 are arranged at equal intervals so as to be point targets with respect to the center point of the heating coil 11, and are electrically insulated from each other.

  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, as shown in FIG. 4, an induced current Q in the direction opposite to the current P flowing through the heating coil 11 is generated on each metal plate 15 arranged on the heating coil surface of the heating coil 11. Since the induction current Q generates a magnetic field opposite to the high-frequency magnetic field generated from the heating coil 11, the high-frequency magnetic field is weakened. However, since the current is closed in one metal plate 15, in each metal plate 15, induced currents P1 and P2 opposite to the induced current Q flowing in the central portion thereof flow in the outer peripheral portion. . The induction currents P1 and P2 suppress the weakening of the high-frequency magnetic field.

  In FIG. 5, the solid line H <b> 1 indicates the magnetic field strength distribution when the metal plate 15 is not disposed on the heating coil surface of the heating coil 11, and the broken line H <b> 2 is the same as when the plurality of metal plates 15 are disposed. The magnetic field strength distribution is shown. When the metal plate 15 is not disposed, a strong high-frequency magnetic field is generated at the center of the heating coil 11. The high frequency magnetic field is important for generating an eddy current in the heated body 3, but if it is locally strong, the leakage magnetic flux to the outside increases.

  On the other hand, when a plurality of conductive and non-magnetic metal plates 15 are arranged on the heating coil surface of the heating coil 11 as in the present embodiment, induction in the reverse direction is performed on each metal plate 15 as described above. Since the current Q and the induced currents P1 and P2 in the positive direction flow, the magnetic flux can be generated uniformly, and the magnetic field distribution becomes a broadband. Thereby, although the peak strength of the magnetic field in the central portion of the heating coil 11 is reduced, the integrated value of the magnetic field strength is substantially equal to that in the case where the metal plate 15 is not disposed, so that the heating efficiency is not lowered. In addition, since the peak strength of the magnetic field is suppressed, the magnetic flux leaking to the outside is reduced.

  By the way, in the present embodiment, the metal cylinder 13 is provided around the heating coil 11. The metal tube 13 is disposed so as to surround the outer periphery of the heating coil 11 with a predetermined interval, and one end portion is positioned closer to the heated surface side of the heated body than the heating coil surface of the heating coil 11. The substantially rectangular column-shaped cylinder 131 and a flat surface provided at one end of the cylinder 131 on the heated surface side and extending from the end to the inside and outside of the cylinder 131 with a certain width. And is provided at the other end opposite to the heated surface side of the cylindrical body 131, and is extended so as to protrude a certain amount from the end to the inside of the cylindrical body 131. And an annular member 133. The cylindrical body 131, the annular flat plate member 132, and the annular member 133 are all formed of a conductive metal. The cylinder 131, the annular flat plate member 132, and the annular member 133 may be integrally formed, or may be separately molded and bonded to form the metal cylinder 13.

  The metal cylinder 13 is arranged so that the central axis of the cylindrical body 131 is coaxial with the central axis of the heating coil 11. Further, the end of the flat surface extending inward of the cylindrical body of the annular flat plate member 132 does not overlap vertically with the heating coil surface, and the end of the flat surface extending outward of the cylindrical body is a hot rolling line for steel. The width of the annular flat plate member 132 is set so as to be located sufficiently outside the end of the plate-like heated body 3 that is conveyed. Further, the height of the cylindrical body 131 and the thickness of the annular flat plate member 132 are set so that the distance between the heating coil surface and the plate-like heated body 3 is not too large. Further, the width of the annular member 133 is set so that the end of the ferrite rod 12 is substantially in contact with the tip of the annular member 133.

  Here, when the metal cylinder 13 is cut in the longitudinal direction with the annular flat plate member 132 facing upward, the cut surface has a “τ” shape. The shape of the metal cylinder 13 is not limited to the “τ” type, and may be a “T” type in which the annular member 133 is omitted or a “−” type in which the cylinder 131 is omitted.

  Thus, in the present embodiment, in addition to the metal plate 15 made of a conductive nonmagnetic material, the cylindrical body 131 made of a conductive metal is provided so as to surround the outer periphery of the heating coil 11 with a predetermined interval, The cylindrical body 131 is arranged so that one end of the cylindrical body 131 is located closer to the plate-shaped heated body 3 than the heating coil surface of the heating coil 11, and the one end of the cylindrical body 131 is connected to the end from the end. An annular flat plate member 132 made of a conductive metal having a flat surface extending inward and outward of the cylindrical body 131 is provided. Therefore, the magnetic flux diffused by hitting the surface to be heated of the plate-like heated body 3 can be absorbed by the flat portion of the annular flat plate member 132 without leakage, and the leakage magnetic flux can be further effectively suppressed.

  In addition, since the magnetic flux absorbed by the flat portion of the annular flat plate member 132 and returned to the ferrite rod 12 via the cylindrical body 131 is effectively returned to the central portion of the heating coil 11, the heating efficiency is also reduced from this point. There is an effect that can be prevented.

  In the above embodiment, the case where the number of the metal plates 15 is eight is illustrated. However, the number of the metal plates 15 is not limited to eight, and two or more metal plates are arranged on the heating coil surface. The effect of reducing the leakage magnetic flux can be obtained by arranging them at intervals. In this case, the ratio of covering the area of the heating coil surface with the metal plate 15 is not limited to about 50%. Moreover, the shape of the metal plate 15 is not limited to a circle, and may be, for example, a quadrangle (square, rectangle), a pentagon, a hexagon, or the like.

  Another embodiment of the induction heating apparatus 1 in which four metal plates 15 having a rectangular shape are arranged on the surface of the heating coil via the insulating sheet 14 and spaced from each other with respect to the center point of the heating coil 11. Is shown in FIG. Also in this other embodiment, as shown in FIG. 7, when a current P flows through the heating coil 11, an induced current Q in the direction opposite to the current P is generated at the center of each metal plate 15, and each metal plate Since the induced currents P1 and P2 in the same direction as the current P are generated at both ends of the circuit 15, the same effects as those of the above-described embodiment are obtained.

  Further, as shown in FIG. 8, the first conductive nonmagnetic metal plate 15a having a rectangular shape has an equal length to the first conductive nonmagnetic metal plate 15a and a short width at a substantially central portion in the upper surface width direction. A rectangular second conductive nonmagnetic metal plate 15b is bonded to form a thick metal plate 15 'at the center. Then, as shown in FIG. 9, a plurality (four in the drawing) of the metal plates 15 ′ are arranged on the heating coil surface via the insulating sheet 14. At this time, the metal plates 15 ′ are arranged at intervals so that the thick portions of the metal plates 15 ′ are aligned in the circumferential direction of the heating coil 11. By doing so, the current density of the induced currents P1 and P2 generated at both end portions is larger than the induced current Q generated at the central portion of each metal plate 15 ', so that the magnetic flux leaking to the outside can be more effectively prevented. It is possible to reduce the heating efficiency.

  The first metal plate 15a and the second metal plate 15b are bonded together to form a thick metal plate 15 'at the center, but the metal plate 15' having a thick center at one member. Even if it is molded and used as shown in FIG. 9, the same effect can be obtained. Further, the shape of the metal plate 15 ′ is not limited to a rectangle, and for example, the central portion of the circular metal plate may be thick.

  Moreover, in the said embodiment, although each metal plate 15 was arrange | positioned through the insulating sheet 14 on the heating coil surface of the heating coil 11, the outer periphery of the electric wire which forms the heating coil 11 is coat | covered with the insulator. Therefore, the insulating sheet 14 can be omitted.

  By the way, in the said embodiment, although the case where this invention was applied to the induction heating device provided in the finishing rolling mill entrance side of the hot rolling line for steel was shown, the induction heating device which can apply the present invention, It is not limited to this.

  FIG. 10 shows a case where the present invention is applied to the induction heating device 41 of the roll heating device 40. The roll heating device 40 induction-heats a heated body 43 such as a hot-rolled steel plate and a cold-rolled steel plate conveyed along the outer periphery of the work roll 42 from the outer periphery of the work roll 42 by the induction heating device 41. In this induction heating device 41 as well, the leakage magnetic flux can be reduced by arranging a plurality of circular or rectangular conductive nonmagnetic metal plates 15 on the heating coil surface of the heating coil 11 at intervals. it can.

  Incidentally, the induction heating device 41 having the configuration shown in FIG. 10 can also be applied as an induction heating device for heating the fixing roller of the copying machine.

  FIG. 11 shows a case where the present invention is applied to the induction heating device 51 of the electromagnetic cooker 50. The electromagnetic cooker 50 induction-heats a heated object 53 such as an iron pan placed on the top plate 52 by an induction heating device 51 provided below the top plate 52. In this induction heating device 51 as well, leakage magnetic flux can be reduced by arranging a plurality of circular or rectangular conductive nonmagnetic metal plates 15 on the heating coil surface of the heating coil 11 at intervals. it can.

The top view of the induction heating apparatus in one embodiment of this invention. Schematic of the AA arrow cross section in FIG. The bottom view of the induction heating apparatus in the embodiment. The schematic diagram used for action | operation description of the same embodiment. The figure which shows intensity distribution of the magnetic field in the embodiment. The top view which shows the induction heating apparatus in other embodiment of this invention. The schematic diagram used for action | operation description of other embodiment. The perspective view which shows the other structural example of a rectangular metal plate. The top view which shows the induction heating apparatus using the rectangular metal plate shown in FIG. 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.

Explanation of symbols

1, 2, 41, 51 ... induction heating device 3, 43, 53 ... heated object 11 ... heating coil 12 ... ferrite rod 13 ... metal cylinder 131 ... cylinder body 132 ... annular flat plate member 133 ... annular member 14 ... insulating sheet 15 , 15 '... Metal plate

Claims (5)

In an induction heating apparatus for induction heating an object to be heated with a heating coil,
An induction heating apparatus, wherein a conductive nonmagnetic metal plate is disposed on a part of the heating coil surface of the heating coil. In an induction heating apparatus for induction heating an object to be heated with a heating coil,
An induction heating apparatus, wherein a plurality of conductive non-magnetic metal plates are aligned on the heating coil surface of the heating coil at intervals in the circumferential direction of the heating coil.   The induction heating apparatus according to claim 1 or 2, wherein the shape of each conductive nonmagnetic metal plate is rectangular or circular.   3. The induction heating apparatus according to claim 1, wherein the thickness of each of the conductive nonmagnetic metal plates is such that a central portion is thicker than both ends in the circumferential direction of the heating coil.   3. The induction heating apparatus according to claim 1, wherein each of the conductive nonmagnetic metal plates is arranged on the surface of the heating coil so as to be pointed with respect to a center point of the heating coil.

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