JP2009117200A - Induction heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating apparatus which generates no uncomfortable sounds at the time of use of apparatus and lessens circuit loss and is effective and easy to use. <P>SOLUTION: When switching means 4, 14 supply power to one of heating coils 3, 13, they are respectively connected with one end of a DC power supply 1. When simultaneously supplying power to both heating coils 3, 13, they are respectively connected with each other so that the heating coils 3, 13 and resonance capacitors 2, 12 form a series circuit. Thus, when one of the heating coils 3, 13 independently heats a load or both the heating coils 3, 13 simultaneously heat the same load, a circuit method is switched to heat the load while an interference sound caused by a difference of mutual operation frequencies is not existed, and circuit loss can be lessened. Consequently, the interference sound and air capacity of a cooling fan can be lessened, an optimal heating structure suitable for a load can be realized, and it is effective and easy to use. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an induction heating apparatus that heats a load such as a pan using induction heating by a high-frequency magnetic field.

Conventionally, this type of induction heating apparatus is well known (see, for example, Patent Document 1).
JP-A-5-114474

  However, in the conventional induction heating device, for example, when a pan having a large outer diameter is heated simultaneously using a plurality of heating coils, when each heating coil operates independently, the pan is supplied to each heating coil. When the frequency of the current is different, the difference between the frequencies of the currents flowing in the heating coils can be heard by the device user, which makes the user feel uncomfortable. Further, when a plurality of heating coils are used, if an attempt is made to obtain a high output with only one heating coil, the loss of the semiconductor switch increases, resulting in a problem that cooling design becomes difficult.

  On the other hand, when a heating coil adapted to a pan with a large outer diameter is used alone, when the pan with a small outer diameter is heated, the outer diameter of the heating coil becomes larger and efficient heating cannot be performed.

  An object of the present invention is to solve the above-mentioned conventional problems, and to provide an induction heating apparatus that is efficient and easy to use without causing an unpleasant noise when using the apparatus and with little circuit loss.

  In order to solve the conventional problem, an induction heating apparatus of the present invention includes a DC power source, a series body of first and second semiconductor switches connected in parallel to the DC power source, and one end of the first and second semiconductor switches. A series circuit of a first heating coil, a first resonance capacitor, and a first switching means connected to a midpoint in a series body of second semiconductor switches, and third and fourth connected in parallel to the DC power source. A series body of semiconductor switches, a second heating coil having one end connected to a midpoint of the series body of the third and fourth semiconductor switches, a series circuit of a second resonance capacitor, and a second switching means. I have. The first and second switching means are connected to one end of the DC power source when supplying power to only one of the first and second heating coils, respectively, and the first and second heating means are respectively connected. When power is simultaneously supplied to the coil, the first and second heating coils and the first and second resonance capacitors are connected so as to form a series circuit.

  As a result, when the first and second heating coils heat the same load independently, they can be operated as independent half-bridge circuits, and one load can be simultaneously applied to the first and second heating coils. When heating is performed, the first and second heating coils and the first and second resonant capacitors are connected in series and operate as a full bridge circuit. Therefore, since the same current flows through the first and second heating coils, heating can be performed in a state where there is no interference sound caused by a difference in the operating frequency of each other, and circuit loss can be reduced. The air volume of the fan can be reduced, and an optimum heating configuration suitable for the load can be realized, and the fan can be made efficient and easy to use.

  The induction heating device of the present invention can select a heating coil to be used according to the shape of a load such as a pan, and there is no unpleasant noise when using the heating coil at the same time. By switching, there is little circuit loss, and it can be made efficient and easy to use.

  The first invention is a DC power supply, a series body of first and second semiconductor switches connected in parallel to the DC power supply, and one end at a midpoint in the series body of the first and second semiconductor switches. A series circuit of a connected first heating coil, a first resonance capacitor, and a first switching means, a series body of third and fourth semiconductor switches connected in parallel to the DC power supply, and one end of the first heating coil A second heating coil connected to the midpoint of the series body of the third and fourth semiconductor switches, a second resonance capacitor, and a series circuit of second switching means are provided. The first and second switching means are connected to one end of the DC power source when supplying power to only one of the first and second heating coils, respectively, and the first and second heating means are respectively connected. When power is simultaneously supplied to the coil, the first and second heating coils and the first and second resonance capacitors are connected so as to form a series circuit.

  As a result, when the first and second heating coils heat the same load independently, they can be operated as independent half-bridge circuits, and one load can be simultaneously applied to the first and second heating coils. When heating is performed, the first and second heating coils and the first and second resonant capacitors are connected in series and operate as a full bridge circuit. Therefore, since the same current flows through the first and second heating coils, heating can be performed in a state where there is no interference sound caused by a difference in the operating frequency of each other, and circuit loss can be reduced. The air volume of the fan can be reduced, and an optimum heating configuration suitable for the load can be realized, and the fan can be made efficient and easy to use.

  According to a second aspect of the invention, in particular, in the first aspect of the invention, the first and second switching means can switch the circuit system at low cost by using an electromagnetic switch.

  In the third invention, in particular, in the first invention, since the first and second switching means can use the semiconductor switch, the durability at the time of switching can be remarkably improved, so that the reliability is high. Can be.

  In a fourth aspect of the invention, in particular, in any one of the first to third aspects of the invention, at least one of the first and second semiconductor switches and at least one semiconductor switch of the third and fourth semiconductor switches are connected in parallel. By connecting the capacitor, the loss of the semiconductor switch can be reduced and the noise during the switching operation can be reduced. Therefore, the efficiency can be improved and the noise can be reduced.

  According to a fifth invention, in particular, in any one of the first to fourth inventions, the first and second heating coils are arranged concentrically to heat the same load, and the outer diameter of the first heating coil By making the diameter smaller than the inner diameter of the second heating coil, one load can be heated with good distribution, so that the cooking performance can be improved.

  According to a sixth invention, in particular, in any one of the first to fourth inventions, the first and second heating coils are arranged in parallel on a concentric plane so as to heat the same load. Can be arranged on a single table, and a magnetic-shielding component such as ferrite arranged on the back surface of the heating coil can be shared, so that an inexpensive configuration can be realized.

  In a seventh aspect of the invention, in particular, in any one of the first to sixth aspects of the invention, the first and second switching means connect the series circuit including the first and second heating coils to one end of the DC power supply. In the case where the first and second switching means connect the series circuit including the first and second heating coils in series, the generated electric energy is increased, so that the inductance of the heating coil is high at the time of high output. Therefore, it is possible to obtain a magnetic field necessary for heating with a small current, and to improve efficiency with little circuit loss.

  In the eighth invention, in particular, in any one of the first to seventh inventions, when the first and second switching means are operated, the heating is stopped for a certain period of time. Since the switching unit can be switched in a state where there is no electric charge stored in the resonance capacitor, an overcurrent does not occur in the switching unit, and the reliability can be improved.

  The ninth aspect of the invention includes, in particular, in any one of the first to eighth aspects of the invention, provided with load detection means for detecting the outer diameter of the load, and when the outer diameter is larger than a predetermined value, The switching means connects the series circuit including the first and second heating coils in series to increase the shape of the heating coil when the outer diameter of a load such as a pan is large, and to increase the maximum heating power, When the outer diameter of the load is small, the shape of the heating coil can be reduced and the maximum heating power can be reduced, and heating suitable for the shape of the pan can be performed. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment)
The figure shows an induction heating device in an embodiment of the present invention.

  As shown in FIG. 1, the induction heating apparatus according to the present embodiment includes a DC power source 1, a series body of first and second semiconductor switches 5 and 6 connected in parallel to the DC power source 1, and one end at a first end. A series circuit of a first heating coil 3, a first resonant capacitor 2, and a first switching means 4 connected to a midpoint in a series body of the first and second semiconductor switches 5 and 6, and a DC power supply 1 in parallel A series body of third and fourth semiconductor switches 15 and 16 to be connected, and a second heating coil 13 and a second terminal, one end of which is connected to a midpoint of the series body of third and fourth semiconductor switches 15 and 16. Resonance capacitor 12 and a series circuit of second switching means 14.

  The first to fourth semiconductor switches 5, 6, 15, 16 are controlled by the control means 8 so that predetermined power is applied to a load such as a pan magnetically coupled to the first heating coil 3 and the second heating coil 13. The conduction time and operating frequency are controlled so that they can be supplied.

  In the present embodiment, the first switching means 4 and the second switching means 14 are composed of electromagnetic switches such as relays. Taking the first switching means 4 as an example, the first switching means 4 The fixed end of the relay 4 is connected to one end of a series circuit of the first heating coil 3 and the first resonance capacitor 2, and the movable end is one end of the DC power source 1 or the second heating coil 13 and the second resonance. It is connected to one end of a series circuit with the capacitor 12. That is, the first and second switching means 4 and 14 are connected to one end of the DC power source 1 when supplying power to only one of the first and second heating coils 3 and 13, respectively. When supplying power to the two heating coils 3 and 13 simultaneously, the first and second heating coils 3 and 13 and the first and second resonant capacitors 2 and 12 are connected so as to form a series circuit. I have to.

  The first to fourth semiconductor switches 5, 6, 15 and 16 are usually a semiconductor switch for controlling a forward current, such as an IGBT or an FET, and a reverse element diode for passing a current in the reverse direction to the semiconductor switch. However, the present invention is not limited to this configuration.

  A first snubber capacitor 7 and a second snubber capacitor 17 are connected in parallel to at least one of the first and second semiconductor switches 5 and 6 and at least one of the third and fourth semiconductor switches 15 and 16, respectively. Since the rise of the voltage when the first to fourth semiconductor switches 5, 6, 15, 16 are turned off can be moderated by connecting to the switch, the switching loss at turn-off can be reduced. In addition, noise generated from the semiconductor switch can be suppressed to a low level.

  Here, when the first and second heating coils 3 and 13 heat a load such as the same pan, when heating is performed by supplying power to only one heating coil or alternately to the heating coil, The first and second switching means 4, 14 are connected to one end of the DC power source 1 by connecting a series circuit of the first heating coil 3 and the first resonance capacitor 2 and the second heating coil 13 and the second resonance capacitor 12. By connecting a series circuit, the necessary power is supplied to a load such as a pan through individual heating coils. At this time, in order to obtain a predetermined power, the control means 8 can independently vary the drive frequency of the first and second semiconductor switches 5 and 6 and the drive frequency of the third and fourth semiconductor switches 15 and 16. As a result, electric power required for each heating coil is generated.

  On the other hand, when the first and second heating coils 3 and 13 simultaneously heat the same load, the first and second switching means 4 and 14 include the first heating coil 3 and the first resonance capacitor. 2 and a series circuit of the second heating coil 13 and the second resonant capacitor 12 are switched so that they are connected in series with each other, so that the first to fourth semiconductor switches 5, 6, 15, 16 Since both the heating coils 3 and 13 and the first and second resonant capacitors 2 and 12 are connected between the points, a full bridge circuit is formed. At this time, in order to obtain a predetermined power, the control means 8 operates the first to fourth semiconductor switches 5, 6, 15 and 16 alternately, and the first heating coil 3 and the second heating switch 3 The same current flows through the heating coil 13. In this case, the power distribution on the load such as the pan depends on the ratios of the shapes and the number of turns of the first and second heating coils 3 and 13.

  Further, as shown in FIG. 2, the first and second heating coils 3 and 13 are arranged concentrically so that a heating distribution can be obtained evenly with respect to the load. Furthermore, by arranging in parallel on the same plane, the heating coil can be arranged on one stand, and a magnetic-shielding component such as ferrite arranged on the back surface of the heating coil can be shared.

  Further, when the first heating coil 3 and the second heating coil 13 are connected in series, the heating coil operates by a full bridge circuit, so even if the inductance of the heating coil is large, twice the voltage is applied to the heating coil. The generated power can be made larger than in the case of a half-bridge circuit that heats the heating coil 3 or 13 alone. As a result, a large amount of generated magnetic field can be obtained with a small current, and circuit loss can be reduced. Therefore, when large power is required, the circuit can be cooled with a small amount of cooling air by adopting a configuration in which the first heating coil 3 and the second heating coil 13 are arranged in series, and the operation sound is quiet. An induction heating device can be provided.

  When the outer diameter of the load such as a pan is small, heating is performed by the inner heating coil (first heating coil 3 in FIG. 2) alone, and when the outer diameter of the load becomes larger, the inner heating coil (The first heating coil 3 in FIG. 2) and the outer heating coil (the second heating coil 13 in FIG. 2) are configured in series so that an optimum heating configuration that matches the shape of the pan can be realized. is there. When the same load is heated by the first and second heating coils 3 and 13, each can be operated as an independent half-bridge circuit.

  Thereby, since the same current flows through the first and second heating coils 3 and 13, heating can be performed in a state where there is no interference sound caused by a difference in operating frequency, and circuit loss can be reduced. It is possible to reduce the interference sound and the air volume of the cooling fan, realize an optimal heating configuration suitable for the load, and make it efficient and easy to use.

  In this embodiment, load detecting means (not shown) for detecting the outer diameter of the pan is provided, and as a detection method thereof, a method of detecting a leakage magnetic field from the heating coil with a pickup coil. Although there is a method of detecting the temperature distribution on the top plate on which the pan is loaded, or a method of estimating from the relationship between the current flowing through the heating coil and the generated voltage, there is no particular limitation.

  Further, when a relay is used as the first and second switching means 4 and 14, particularly when the relay is switched, the power supply to a load such as a pan is stopped for a certain period of time, and then heating is performed. It is also desirable from the point of increasing the reliability of the relay.

  FIG. 3 shows a configuration in which the first and second switching means 4 and 14 use semiconductor switches without using relays. The first semiconductor switching means 18 is used to determine whether or not the series circuit of the first heating coil 3 and the first resonant capacitor 2 is connected to one end of the DC power source 1, and the second semiconductor switching means 19 is the second semiconductor switching means 19. Whether the series circuit of the heating coil 13 and the second resonance capacitor 12 is connected to one end of the DC power source 1 or not, the third semiconductor switching means 20 further includes the first heating coil 3 and the first resonance capacitor 2. Are used to connect the series circuit of the second heating coil 13 and the second resonant capacitor 12. By using the semiconductor switching means in this way, the durability with respect to the number of times of use is improved as compared with the mechanical contact switching means, so that the reliability can be improved.

  The first and second switching means 4 and 14 and the first to third semiconductor switching means 18 to 20 perform a switching operation based on a command to the control means 8.

  As described above, according to the present embodiment, the first heating coil 3 and the second heating coil 13 are independently applied to the same load by the switching method between the first switching unit 4 and the second switching unit 14. When heating with the first and second heating coils 3, 13, the first and second heating coils 3, 13 simultaneously heat the same load. 13 and the first and second resonant capacitors 2 and 12 are connected in series, and the first to fourth semiconductor switches 5, 6, 15 and 16 operate as a full bridge circuit. Therefore, since the same current flows through the first and second heating coils 3 and 13, heating can be performed in a state where there is no interference sound caused by a difference in operating frequency, and circuit loss can be reduced. It is possible to reduce the sound and the air volume of the cooling fan, realize an optimum heating configuration suitable for the load, and make it efficient and easy to use.

  As described above, the induction heating device according to the present invention can select a heating coil to be used according to the shape of a load such as a pan, and there is no unpleasant noise when using the heating coil at the same time. By switching the circuit system at high thermal power, circuit loss is reduced, and it can be made efficient and easy to use. Therefore, it can be applied to induction heating apparatuses such as induction heating cookers.

The circuit block diagram of the induction heating apparatus in embodiment of this invention (A) Perspective view of heating coil of induction heating device (b) Side sectional view of heating coil Circuit diagram showing a modification of the induction heating apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 1st resonance capacitor 3 1st heating coil 4 1st switching means 5 1st semiconductor switch 6 2nd semiconductor switch 7 1st snubber capacitor 8 Control means 12 2nd resonance capacitor 13 1st 2 heating coil 14 2nd switching means 15 3rd semiconductor switch 16 4th semiconductor switch 17 2nd snubber capacitor 18 1st semiconductor switching means 19 2nd semiconductor switching means 20 3rd semiconductor switching means

Claims (9)

A DC power source, a series body of first and second semiconductor switches connected in parallel to the DC power source, and a first heating having one end connected to a midpoint in the series body of the first and second semiconductor switches A series circuit of a coil, a first resonance capacitor and a first switching means, a series body of third and fourth semiconductor switches connected in parallel to the DC power supply, and one end of the third and fourth semiconductors A second heating coil connected to a midpoint in the series body of switches, a second resonance capacitor, and a series circuit of second switching means are provided, and the first and second switching means are the first and second switching means. When supplying electric power to only one of the heating coils, it is connected to one end of the DC power source, and when supplying electric power to the first and second heating coils simultaneously, the first and second heating coils are connected. Coil and first Induction heating apparatus spare second resonant capacitor is connected to form a series circuit. The induction heating apparatus according to claim 1, wherein the first and second switching means use electromagnetic switches. The induction heating apparatus according to claim 1, wherein the first and second switching means use semiconductor switches. The induction heating apparatus according to any one of claims 1 to 3, wherein a capacitor is connected in parallel to at least one of the first and second semiconductor switches and at least one of the third and fourth semiconductor switches. The first and second heating coils are concentrically arranged to heat the same load, and the outer diameter of the first heating coil is made smaller than the inner diameter of the second heating coil. The induction heating device described in 1. The induction heating device according to any one of claims 1 to 4, wherein the first and second heating coils are arranged in parallel on a concentric plane so as to heat the same load. When the first and second switching means connect the series circuit including the first and second heating coils to one end of the DC power supply, the first and second switching means connect the first and second heating coils. The induction heating apparatus according to any one of claims 1 to 6, wherein the amount of generated electric power is increased when a series circuit including the series circuit is connected in series. The induction heating apparatus according to any one of claims 1 to 7, wherein when the first and second switching means are operated, heating is stopped for a predetermined time. A load detection means for detecting the outer diameter of the load is provided, and when the outer diameter is larger than a predetermined value, the first and second switching means connect a series circuit including the first and second heating coils in series. Item 9. The induction heating apparatus according to any one of Items 1 to 8.

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