JP2014026748A - Interference effect suppression induction heating coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an induction heating coil capable of suppressing failure due to magnetic flux interference so that a wide area of large circle can be induction heated uniformly, or a pipeline of extended length can be induction heated uniformly at equal interval, by using a plurality of commercially available induction heating inverters of relatively small capacity having different oscillation frequencies.SOLUTION: Interference failure is suppressed by splitting one induction heating coil into two, and combining two split coils so that a current flows through each coil in a direction for creating an induction heating flux properly, and electromotive forces generated by magnetic interference can be cancelled in the same coil. Since induction of a high voltage due to interference flux induction can be suppressed by using the interference effect suppression induction heating coil, even if the interval to other adjoining coil is shortened, uniform heating can be ensured.

Description

  The present invention relates to a high-frequency current generating inverter (referred to as an IH inverter) for induction heating by a high-frequency current of 20 kHz or higher and an induction heating work coil (referred to as a coil) connected to the inverter. When heating, the magnetic flux interlinked with the metal to be heated induces other metals and coils while induction heating, and has a number of adverse effects. Another IH inverter is connected to a coil connected to another IH inverter that is installed adjacent to the other coil that causes trouble to other coils, and induces a high voltage in the coil of another IH inverter to increase the terminal voltage of the coil. There is an effect of applying a high voltage to the IGBT, which is a switching element, to cause destruction. The present invention relates to a coil that is wound so that a magnetic flux having a completely opposite phase to that of the interference magnetic flux can be generated by the coil itself so as to eliminate the influence of the interference magnetic flux.

  High-frequency induction heating is a method in which a high-frequency current is passed through a coil to generate a magnetic field, and a magnetic flux is interlinked in a magnetic metal placed close to the coil surface to cause an induced eddy current to flow in the magnetic metal. To generate Joule heat in the magnetic metal.

There are many induction heating applications that use the heat generated by induced eddy currents in the world, and it is possible to efficiently heat shaped objects such as iron plates, steel bars, containers, and pipes that are to be heated. It is an optimal means that can be converted into heat.

However, in order to perform high-frequency induction heating, a power source for supplying high-frequency current and the high-frequency current are converted into magnetic flux and linked to the metal to be heated, and induced eddy current is caused to flow inside the metal. Although a coil for generating Joule heat is required, the frequency of the power source is unique to each power source. If a plurality of power sources are used, high-frequency current flows at different frequencies corresponding to the number of power sources. For this reason, when a plurality of power supplies are used, there is a problem that magnetic flux interference occurs in the coil portion due to the different frequencies.

  As an improvement measure, the magnetic flux that interferes by mutual induction is forcibly corrected by reverse phase shift in a reactor wound in reverse polarity while controlling the frequency of the high-frequency current output from multiple power sources to be synchronized. There is a method of configuring a load circuit, etc., however, the special auxiliary reactor used for this and the configuration of the cooling device require enormous costs and fine adjustment, and the device itself becomes large and at the same time power loss due to auxiliary equipment such as the reactor However, the energy efficiency is greatly reduced.

JP 2006-49332 A JP 2004-259665 A

Naoki Uchida and two other authors "150kW Zone Control High Frequency Inverter for Induction Heating" 2006 IEEJ Industrial Application Conference

  The problem to be solved is to obtain a good quality uniform heating mode at a low price by enabling the coil itself to suppress the influence of magnetic flux interference due to the difference in the high-frequency current frequency output from a plurality of power supplies.

An induction heating type large circular container or induction heating type long pipe cannot be heated uniformly by a single coil or a single IH inverter. Therefore, by using multiple coils and multiple IH inverters side by side, the required heating distribution and heating power can be obtained for optimal heating, but multiple IH inverters such as large circles or long pipes can be used. Heated objects that require coils cause damage to the IH inverter and unpleasant high-frequency interference due to the difference in the transmission frequency of each IH inverter and the influence of the induction magnetic field from the coil. It was the minimum necessary operating condition. For this reason, there has been a drawback that an extreme difference occurs in the heating temperature of the object to be heated, so that the heating uniformity cannot be obtained and the necessary heating power cannot be obtained.

Naturally, the thermal distortion due to the non-uniform temperature of the object to be heated became extremely large, and the bottom of the container became uneven and the pipe was deformed and bent.
The serious problem was that the object to be heated deformed during heating operation, the heating constant changed, the interference magnetic flux between adjacent coils increased, high voltage was induced in the coil, and the IH inverter was suddenly destroyed.

Even if multiple IH inverters and coils are arranged on a common heated object and heated at the same time, there is no unpleasant interference sound due to no magnetic flux interference between different coils, but different coils The coil can be placed close to each other easily to make the heating uniform, and the interference high voltage induced in the coil can be extinguished by the coil itself. The purpose is to provide.

  The present invention is characterized in that, when winding a plurality of coils in a spiral shape with a common winding center as in the contents of claim 1, each coil is divided into two and each coil is wound in a spiral shape. . Each of the two divided coils spirals in a half-moon shape and is connected and used so that currents in opposite directions flow on the circumference. At that time, if it was affected by the interference magnetic flux from another coil, the electromotive voltage can be canceled in its own coil. That is, a circuit was formed that extinguishes the electromotive voltage induced by the interference magnetic flux so that the electromotive voltage induced by the interference magnetic flux generated on the circumference is generated in the opposite direction in each of the two divided coils. This is the main feature.

As in the case of 0012, when a plurality of cylindrical coils are arranged side by side when heating a long pipe equally according to the contents of claim 2, two rectangular plate coils having the same winding direction are formed in forming this cylindrical coil. As a rectangular plate coil wound in the same direction when viewed from the front side, it was smoothly bent toward the back side to form a cylinder by abutting two colls. And These two divided cylindrical coils are used in combination so that currents in opposite directions flow on the circumference of the cylinder. If it was affected by the interference magnetic flux from another coil, the electromotive voltage could be canceled in its own coil. In other words, a circuit was formed to extinguish the electromotive voltage induced by the interference magnetic flux so that the electromotive voltage induced by the interference magnetic flux generated on the circumference of the cylinder was generated in the opposite direction in each of the two divided coils. It is characterized by that.

  According to the induction heating coil of the interference influence suppression type of the present invention, the heating power of a plurality of IH inverters is used when it is desired to control the convection direction of the fluid evenly by heating the fluid placed in a large circular tank of ~ φ1000 class. Since each can be freely controlled, there is an advantage that can be easily performed.

In addition, this interference-induction induction heating coil is used for induction heating of pipes for transporting fluids such as oil that will solidify and clog the pipe if it is not transported and transported while maintaining the overall length at a few tens of degrees Celsius in a long-distance pipeline etc. Pipelines using, which has the advantage of being able to control the temperature with high accuracy, can use multiple IH inverters and can evenly heat pipes that are extended indefinitely.

FIG. 1 is a diagram of a conventional method in which two or more coils are arranged with a common winding center of a flat coil. Fig. 2 shows a ferrite core inserted in the magnetic path between coils for the purpose of improving Fig. 1. Fig. 3 is a diagram showing an interference heating suppression induction heating coil. FIG. 4 is a diagram in which a ferrite core is inserted in the winding center of the interference heating type induction heating coil and the magnetic path between the coils. FIG. 5 is a diagram for explaining the effect of the interference influence suppressing induction heating coil. FIG. 6 shows a combination of an interference heating suppression induction heating coil and a flat plate coil. FIG. 7 is a diagram illustrating the effect of the interference heating suppression induction heating coil in the cylindrical coil. FIG. 8 shows a combination of an interference heating suppression induction heating coil and a general cylindrical coil.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a flat plate coil having a conventional shape, which is an induction heating device composed of two coils and two IH inverters. The first coil and the second coil have different frequencies. Is driven by IH inverters 4 and 5. As a result, magnetic flux interference occurs between 1 and 2, and a high voltage due to the interference induced voltage may be applied to 4 and 5, which may damage the inverter. You must drive with a large separation between 3 and 8. Although the distance is 150 mm or more, when the object to be heated is heated on the distance, the heating distribution of the object to be heated becomes inhomogeneous due to the inductive effect buffering band of 150 mm or more.

  FIG. 2 is an improvement of FIG. 1 in which ferrite cores 9, 10, and 11 are inserted between the spiral coils. According to this method, even if 3 coils are arranged in addition to 1 and 2 coils, the distance 8 between the coils mentioned in the previous section can be reduced from about 150 mm to about 50 mm. The heating power can be increased with respect to the same object to be heated.

  FIG. 3 shows an example of a basic type in which flat coils 12 to 15 are arranged as alternative coils of 2 and 3 shown in FIG. 1 and FIG. is there. When the interference magnetic flux from the coil 1 affects the coil 2 as shown in claim 1, the electromotive voltage caused by the interference magnetic flux generated in one of the coils 2 is completely counter-electromotive force generated by the other coil 2. As a result, they cancel each other, and the interference magnetic flux electromotive voltage disappears. The principle during this time will be described with reference to FIG.

  FIG. 4 is a powerful version of the effect of FIG. 3, and the effect of the ferrite core applied in FIG. 2 is applied as it is. The difference from Fig. 2 is that a magnetic path for passing magnetic flux is formed so that the magnetic flux generated by the coil can be returned by inserting the ferrite cores 19 to 22 in the gap at the beginning of winding of the interference heating suppression induction heating coils 12 to 15 The interference magnetic flux from each coil is prevented from being generated, and at the same time, the back electromotive voltage is appropriately generated so that the influence of the interference magnetic flux from the other coil can be surely eliminated.

  FIGS. 5 and 6 show the interference effect suppression type induction by omitting 14 and 15 of the interference effect suppression type induction heating coils 12 to 15 configured in FIG. 4 and forming a general spiral coil 3. This explains that the heating coil function can be performed. That is, a high-frequency current flows from each coil terminal 16 to 18 and a magnetic field is formed in each coil, but interference magnetic fluxes 30 and 30a due to the high-frequency currents 29 and 29a of the central flat coil 1 are induced to suppress interference effects. Even if it works to induce a high voltage on the coil 12 side as seen in the coil current directions 23 and 25 when linked to the heating coils 12 and 13, the induced voltage becomes a low voltage on the coil 13 side. In the same interference influence suppression type induction heating coil, they are in a direction to cancel each other, and the influence of the interference magnetic flux disappears. On the other hand, since the interference magnetic fluxes in the opposite directions are always influenced by the coils 12 and 13 from the interference influence suppressing induction heating coils 12 and 13 to the flat coil 1 side, the interference influence suppressing induction heating coils 12 and 13 are applied to the flat coil 1 side. There will be no influence from 13.

  Similarly, when a high-frequency current flows from each coil terminal 16 to 18 and a magnetic field is formed in each coil, the interference magnetic flux 27 / 27a due to the high-frequency current 28 / 28a of the outer-diameter plate coil 3 is suppressed. Inductive voltage that causes low voltage on the coil 13 side even if it works to induce a high voltage on the coil 12 side as seen in the coil current directions 24 and 26 when interlinking with the type induction heating coils 12 and 13 In the same interference effect suppressing induction heating coil, the directions cancel each other and the influence of the interference magnetic flux disappears. As described above, there is no influence on the flat coil 3 side from the interference influence suppressing induction heating coils 12 and 13.

  FIG. 6 shows the ferrite cores 9 to 11 between the three windings and the beginning of winding of the interference effect suppressing induction heating coils 12 and 13 in order to more firmly execute the principle described in FIG. Example with 19 and 20 inserted

FIG. 7 shows an example of formation of the interference heating suppression type induction heating coil 31 by the cylindrical coil described in claim 2, and this coil is used alternately with the general cylindrical coil 32.
The interference influence suppression type induction heating coil 31 has two rectangular plate coils wound in the same direction, and both coils are semicircular when viewed from the front side so that the winding direction is the same. Combining this with bending produces a figure. The winding end sides of the two same coils are connected as shown by a wiring 31a in the drawing, and the IH inverter 36 is connected to the winding start sides of both coils to supply power.

  Pipes for transportation such as molten aluminum hot water must be kept at several hundred degrees Celsius, but high-precision temperature control is possible with a pipeline using a water-cooled interference effect suppression induction heating coil. This also has the advantage that multiple IH inverters can be used, so it can be transported from a molten aluminum furnace to a die-cast type even at long distances. Further, it becomes possible to heat a long cylindrical metal billet such as a billet heater while partially controlling the whole.

1 Flat coil (center arrangement)
2 Flat coil (intermediate arrangement)
3 Flat coil (peripheral arrangement)
4 IH inverter for centrally arranged coil 5 IH inverter for outer circumferentially arranged coil 6 IH inverter for intermediately arranged coil 7 Coil fixing base 8 Distance between flat coil and flat coil 9 Magnetic path forming ferrite core for coil center 10 Magnetic for intermediate arrangement between different coils Path forming ferrite core 11 Same as above 12 One piece of induction heating coil divided into two intermediate interference influence suppression 13 One piece of induction heating coil divided into two intermediate interference influences 14 One piece of induction heating coil divided into two outer circumference interference influence suppression pieces 15 Interference-inhibition-type induction heating coil divided into two pieces 16 Central coil lead-out terminal 17 Intermediate coil lead-out terminal 18 Peripheral coil lead-out terminal 19 Ferrite core for intermediate interference effect-suppression type induction heating coil winding core 20 Same as above 21 Ferrite core for heating coil core 22 Same as above 23 Interference effect suppression type induction heating coil current direction 24 Same as above 25 Same as above 26 Same as above 27 and 27a Interference magnetic flux generated by outer peripheral plate coil 28 and 28a Current direction of outer peripheral plate coil 29 and 29a Current direction of central plate coil 30 and 30a Interference magnetic flux generated by central plate coil 31 Cylindrical coil current direction 33a Cylindrical coil leakage magnetic flux 34 Cylindrical coil current flux 34a Cylindrical coil leakage magnetic flux 35 IH inverter for cylindrical coil 36 IH inverter for induction heating cylindrical coil

Claims (6)

A spiral work coil for electromagnetic induction heating (hereinafter referred to as a flat plate coil) is placed on a flat horizontal surface with its winding center aligned and arranged in a concentric circle, and each coil is used to generate a high-frequency induction current of several tens of kHz or more. Regarding the heating operation by individually connecting switching power supplies (hereinafter referred to as IH inverters), the magnetic flux interference phenomenon occurs between the coils due to the difference in the transmission frequency of the inverter connected to each adjacent coil. One coil is divided into two so that it always crosses the magnetic flux in the opposite phase and becomes non-inductive, each coil is wound in a half-moon shape, and when the two coils are combined, it is formed to be a perfect circle, It is characterized in that the outer peripheral currents of the respective coils that hit the inner and outer diameter sides of the perfect circle are connected so as to face each other. When a plurality of cylindrical coils are arranged side by side on the coaxial cylindrical surface in the same manner as described above, a flat plate coil divided into two as a cylindrical coil shape is bent into a curved semi-cylindrical shape, and the two coils are abutted to form a cylinder. The outer circumferential currents of the cylindrical end face coil formed in such a manner are connected so as to face each other. The winding start center of the coil according to claim 1 and claim 2 is formed into an ellipse, and a ferrite core is arranged at the center thereof so that the magnetic flux is concentrated at the coil winding center. A ferrite core is also disposed between the coil and a magnetic flux capable of exhibiting the effect of preventing interference can be effectively generated by currents flowing in the opposite directions of the vector flowing on the outer periphery of the coil. The coil according to claim 1 and claim 2 is characterized in that the conventional general flat plate coil or cylindrical coil are alternately arranged in the adjacent coil so that the generation of the interference magnetic flux can be canceled by the combination thereof.
A combination of this two-divided coil and a conventional general flat plate coil or cylindrical coil is alternately and repeatedly arranged to complete an unlimited number of interference effect induction heating coil arrays. By continuously combining the coil combination according to claim 4 from a flat plate to a cylinder, a large drum-shaped tank can be heated with a uniform heating force from the flat bottom to the cylinder rise, and the coil is individually controlled by an interference heating suppression induction heating coil effect. It is characterized in that the intensity of heating can be freely adjusted partially by being able to connect separate inverters. When the coils according to claim 1 and claim 2 are continuously arranged, the generation of the interference magnetic flux can be surely canceled by combining the butt portions divided into two at 90 ° angles. However, as shown in the explanatory diagram, this displacement angle can be arbitrarily changed, and naturally, the combination in that case is also included in the content of the claim.