JP2013109889A - Induction heating apparatus - Google Patents

Abstract

An induction heating apparatus capable of uniformly heating a pan and switching to a high efficiency heating mode is provided.
A resonance frequency of a first resonance circuit formed by a first heating coil and a first resonance capacitor among a plurality of heating coils and 57 and a plurality of resonance capacitors is determined by: The value of the first heating coil 55 or the first resonance capacitor 56 is set so as to be higher than the resonance frequency of the second resonance circuit 45 formed by the second heating coil 57 and the second resonance capacitor 58. The first resonance circuit 44 and the second resonance circuit 45 are connected to a single inverter circuit 43, and the first heating coil 55 and the second resonance circuit 44 are controlled by the control means 59 by the control of the inverter circuit 43. The high frequency current flowing in the heating coil 57 is changed at the same time, and the same number of frequency regions as the number of resonance circuits connected to the inverter circuit 43 are switched at regular intervals to be heated. Induction heating.
[Selection] Figure 1

Description

  The present invention relates to an apparatus using induction heating such as an induction heating cooker.

  Conventionally, in this type of induction heating apparatus, there is one in which one heating region is constituted by a plurality of heating coils arranged in a plane, and each heating coil is energized with a time difference provided sequentially (see, for example, Patent Document 1). ).

  In the induction heating apparatus described in Patent Document 1, since a specific place is not heated by changing the coil that is sequentially energized, the temperature distribution of the object to be heated is averaged so that a doughnut-shaped heating unit is not generated. can do.

  In addition, in the induction heating apparatus constituted by a central coil and four peripheral coils in which one heating region is arranged in a plane, two peripheral coils are turned on, and the other two peripheral coils are turned off. There is also a control that repeats the step A in which A and two peripheral coils that have been turned on are turned off and the other two peripheral coils that have been turned off are turned on (for example, patents). Reference 2).

  Since the induction heating apparatus described in Patent Document 2 alternately heats a pan whose peripheral coil is an object to be heated, predetermined convection is formed in cooking utensils such as moisture contained in the pan. Is done. Thereby, the cooking utensil material in a pan is heated uniformly, and it can suppress that a part of cooking utensil material is overheated, and can prevent scorching.

JP-A-63-291387 International Publication No. 2010/101202

  However, in order to achieve the above-described effect, an inverter circuit for controlling the energization state of each of the plurality of heating coils is required, resulting in an expensive induction heating apparatus with a large number of circuit components.

  In Patent Document 1 (FIG. 3), a switching element (inverter circuit) is connected to each of a plurality of heating coils, and the energization state is controlled by operating each switching element sequentially with a time difference. It can be seen that the same number of switching elements (inverter circuits) as the heating coils are required.

  Similarly, in Patent Document 2 (FIG. 6), an inverter circuit is provided in each of the plurality of heating coils, so that the number of parts of the circuit is large and the induction heating apparatus is expensive.

Moreover, in patent document 1 (FIG. 6), although only one switching element (inverter circuit) is connected with respect to several heating coils, a relay is provided between each heating coil and a power supply, and connection with a power supply is carried out. By sequentially switching, the energization state to each heating coil can be controlled. However, when a relay that mechanically switches contacts is used, a new problem arises that the relay is burdened and the life of the induction heating device is shortened. In addition, when using a relay,
When switching from one energization state to the next heating coil, the time required to switch the contacts is longer compared to a circuit system consisting only of semiconductor switching elements. It is not possible to switch to the above, and a pause period in which no power is supplied to any heating coil becomes longer, a sufficient amount of heating cannot be obtained, and the performance of the induction heating device is deteriorated. Furthermore, if the switching frequency of the relay is increased in order to uniformly heat the object to be heated, the sound generated at the contact point at the time of switching the relay frequently occurs and becomes annoying.

  The present invention solves the above-described conventional problems, and provides an induction heating apparatus that can uniformly heat a heated object or convect liquid stored in a container of the heated object and does not increase an inverter circuit. The purpose is to do.

  In order to solve the above-described conventional problems, an induction heating apparatus according to the present invention includes a plurality of heating coils that induction-heat a single object to be heated, and a plurality of resonance capacitors that form a resonance circuit with the plurality of heating coils. A single inverter circuit for supplying a high-frequency current to the plurality of heating coils; and a control means for controlling the operation of the inverter circuit by outputting a drive signal to the inverter circuit, wherein the control means is at least the inverter A function of controlling an operating frequency of the circuit, and the resonance frequency of the first resonance circuit formed by the first heating coil and the first resonance capacitor among the plurality of heating coils and the plurality of resonance capacitors is The first heating coil to be higher than the resonance frequency of the second resonance circuit formed by the second heating coil and the second resonance capacitor Alternatively, the value of the first resonance capacitor is set, and the first resonance circuit and the second resonance circuit are connected to the single inverter circuit. By controlling the operation, the high-frequency current flowing in the first heating coil and the second heating coil is changed at the same time, and the same number of frequency regions as the number of resonance circuits connected to the inverter circuit are switched at regular intervals to be heated. An object is heated by induction.

  According to the induction heating device of the present invention, since the current flowing through the plurality of heating coils can be controlled by a single inverter circuit, the number of components required for the inverter circuit is reduced and an inexpensive induction heating device is realized. can do.

  Further, by switching the operating frequency at regular intervals, the heating coil through which the high-frequency current mainly flows can be switched to generate convection in the contents of the container that is the object to be heated. By applying this induction heating device, the cooking performance can be improved by accelerating the passage of heat and taste into the cooked food.

Circuit diagram of induction heating apparatus according to Embodiment 1 The figure which shows the resonance characteristic by the heating coil and resonance capacitor which concern on Embodiment 1 Arrangement of first heating coil and second heating coil according to Embodiment 1 Transition diagram of drive frequency during convection according to Embodiment 1 Transition diagram of drive frequency during uniform heating according to the first embodiment The figure which shows the electric power balance of the 1st heating coil which concerns on Embodiment 1, and a 2nd heating coil Other arrangement views of the first heating coil and the second heating coil according to the first embodiment Arrangement of three heating coils according to Embodiment 1 Arrangement of four heating coils according to the second embodiment Circuit diagram of induction heating apparatus according to Embodiment 2 The figure which shows the heating area | region in each mode which concerns on Embodiment 2. FIG. Circuit diagram of induction heating apparatus according to Embodiment 3 The figure which shows the heating area | region in each mode which concerns on Embodiment 3. FIG. Circuit diagram of induction heating apparatus according to Embodiment 4 The figure which shows the heating area | region in each mode which concerns on Embodiment 4. FIG. The figure which shows the heating area | region in each mode in the 2nd connection state which concerns on Embodiment 4. FIG. The figure which shows the heating area | region in each mode in the 3rd connection state which concerns on Embodiment 4. FIG. Arrangement of other heating coils according to Embodiment 4 The figure which shows the resonance characteristic by the heating coil and resonance capacitor which concern on Embodiment 5

  A first invention supplies a plurality of heating coils for induction heating a single object to be heated, a plurality of resonance capacitors that form a resonance circuit with the plurality of heating coils, and a high-frequency current to the plurality of heating coils. Comprising a single inverter circuit and a control means for controlling the operation of the inverter circuit by outputting a drive signal to the inverter circuit, the control means having a function of controlling at least the operating frequency of the inverter circuit; Among the plurality of heating coils and the plurality of resonance capacitors, the resonance frequency of the first resonance circuit formed by the first heating coil and the first resonance capacitor is the second heating coil and the second resonance capacitor. The value of the first heating coil or the first resonance capacitor is set to be higher than the resonance frequency of the second resonance circuit formed by The first resonance circuit and the second resonance circuit are connected to the single inverter circuit, and the control circuit controls the operation of the inverter circuit to control the first heating coil and the second resonance circuit. The high-frequency current flowing through the second heating coil is changed simultaneously, and the same number of frequency regions as the number of resonance circuits connected to the inverter circuit are switched at regular intervals to inductively heat the object to be heated.

  As a result, the current flowing through the plurality of heating coils can be controlled by a single inverter circuit, so that the number of components required for the inverter circuit can be reduced and an inexpensive induction heating apparatus can be realized.

  Further, by switching the operating frequency at regular intervals, the heating coil through which the high-frequency current mainly flows can be switched to generate convection in the contents of the container that is the object to be heated. By applying this induction heating device, the cooking performance can be improved by accelerating the passage of heat and taste into the cooked food.

  In addition, since a component having a mechanical contact such as a relay is not used, the heating coil that supplies a high-frequency current can be switched at high speed. Furthermore, the life of the induction heating device can be extended. Furthermore, it is possible to realize an induction heating device that eliminates the noise generated at the contact point when the relay is switched, thereby reducing the noise.

  According to the second invention, in particular, in the induction heating apparatus of the first invention, a plurality of intervals for switching a plurality of frequency regions are provided.

  As a result, it is possible to perform both heating for uniformly heating the object to be heated by controlling the switching period of the operating frequency and for generating convection by heating non-uniformly. The object to be heated can be heated with a heating pattern to improve cooking performance.

  According to a third invention, in particular, in the induction heating device of the first or second invention, the first heating coil and / or the second heating coil is constituted by a plurality of heating coils.

As a result, the number of resonance circuits is less than the number of heating coils and the number of inverter circuits is one even in a configuration in which a plurality of heating coils are distributed and heated in a uniform manner. The induction heating device can be realized with a small number of parts that constitute the inverter circuit and at a low cost and with a small volume.

  Moreover, electric power can be simultaneously supplied by connecting the heating coil with the same increase / decrease timing of the electric current which flows into a heating coil in the same resonance circuit. The current sensors can be unified and made inexpensive, and the controllability of power can be improved.

  In the fourth aspect of the invention, in particular, in the induction heating apparatus according to any one of the first to third aspects, the plurality of heating coils are arranged so as to be point-symmetric from the center of the heating region of the object to be heated, and are point-symmetric. Are connected to the same resonance circuit. Thereby, since the heating coil located farthest diagonally is driven at the same time, the pan can be easily heated uniformly. Moreover, a big convection can be generated in the whole pan.

  In the fifth aspect of the invention, in particular, in the induction heating apparatus according to any one of the first to third aspects, the plurality of heating coils are arranged so as to be symmetrical with respect to the center of the heating region of the object to be heated, and are adjacent to each other. The heating coil is connected to the same resonance circuit. Thereby, the heating region and the non-heating region of the object to be heated can be clearly separated, and a large convection can be generated in the liquid in the object to be heated, so that, for example, the taste can be quickly infused into the food.

  In particular, the sixth aspect of the invention is an induction heating apparatus according to any one of the first to fifth aspects, and mainly appears in the first resonance circuit at an operating frequency for supplying power to the object to be heated from the first heating coil. The resistance value and the resistance value appearing in the second resonance circuit at the operating frequency at which power is mainly supplied from the second heating coil to the object to be heated are substantially the same. As a result, the maximum power that can be supplied from each of the two resonance circuits can be made substantially the same, so that heating with good balance can be performed.

  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 1)
FIG. 1 is a circuit diagram of the induction heating apparatus according to Embodiment 1 of the present invention, and shows an example of a method for connecting an inverter circuit, a plurality of heating coils, and a plurality of resonance capacitors.

  FIG. 2 is a diagram showing the resonance characteristics of the heating coil and the resonance capacitor according to Embodiment 1 of the present invention, and shows the relationship between the operating frequency of the inverter circuit of the induction heating device and the power that can be supplied to the object to be heated. It is.

  In FIG. 1, a power source supplied from an outlet or the like is an AC power source 41, and a diode bridge 46 is connected to convert the AC power source 41 into a DC power source. A choke coil 47 and a capacitor 48 are connected to the output terminal of the diode bridge 46 in order to smooth the DC power output from the diode bridge 46 and prevent the electromagnetic noise generated from the induction heating device from propagating to the AC power supply 41. ing. The diode bridge 46, the choke coil 47, and the capacitor 48 constitute a rectifying means 42.

  On the output side of the capacitor 48, a first switching element 51 having a reverse conducting diode 52 connected in parallel and a second switching element 53 having a reverse conducting diode 54 connected in parallel are electrically connected in series. The inverter circuit 43 is connected.

At the connection point of the first switching element 51 and the second switching element 53, one end of the first resonance circuit 44 including the first heating coil 55 and the first resonance capacitor 56 and the second heating coil 57 are connected. One end of the second resonance circuit 45 including the second resonance capacitor 58 is connected.

  The other terminal of the first resonance circuit 44 and the other terminal of the second resonance circuit 45 are connected to the negative potential side of the DC voltage. In addition, the snubber capacitor 60 is electrically connected in parallel with the second switching element 53 in order to reduce switching loss caused by the switching operation of the first switching element 51 and the second switching element 53.

  Moreover, by having the control means 59 which drive-controls the 1st switching element 51 and the 2nd switching element 53, the circuit of the induction heating apparatus of this Embodiment is formed.

  About the induction heating apparatus formed as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The inverter circuit 43 of the induction heating device shown in the first embodiment controls the operating frequency of the first switching element 51 and the second switching element 53, the ratio of conduction (on) time to non-conduction (off) time, and the like. As a result, the high-frequency current flowing through the first resonance circuit 44 and the high-frequency current flowing through the second resonance circuit 45 are changed and supplied from the first heating coil 55 and the second heating coil 57 to the object to be heated. The power can be adjusted. The first switching element 51 and the second switching element 53 are exclusively turned on so that the power supply is not short-circuited.

  When adjusting the power supplied to the object to be heated from the heating coil by controlling the operating frequency of the inverter circuit 43, the applied voltage to the inverter circuit 43 is constant at the resonance frequency of the resonance circuit as shown in FIG. The resonance (power) characteristic is such that the power supplied to the object to be heated is maximized when the inverter circuit 43 is operated.

  In FIG. 2, a waveform 71 is a power characteristic supplied to the object to be heated from the first heating coil 55 included in the first resonance circuit 44, and a waveform 72 is the first characteristic included in the second resonance circuit 45. This is a characteristic of power supplied from the second heating coil 57 to the object to be heated. In the induction heating device of the present invention, the value of the first heating coil 55 or the first resonance capacitor 56 is set so that the resonance frequency of the first resonance circuit 44 is higher than the resonance frequency of the second resonance circuit 45. Therefore, the waveform 71 indicating the power characteristic in the first resonance circuit 44 appears on the higher frequency side than the waveform 72 indicating the power characteristic in the second resonance circuit 45.

  An operation area A in FIG. 2 indicates an operation frequency range of the inverter circuit 43 when electric power is mainly supplied from the first heating coil 55 to the object to be heated, and an operation area B is mainly the second heating coil. The operating frequency range of the inverter circuit 43 when electric power is supplied from 57 to the object to be heated is shown.

By the way, when the resonant circuit is operated by the inverter circuit 43, if the operating frequency of the inverter circuit 43 is higher than the resonant frequency of the resonant circuit, the current is delayed in phase with respect to the voltage applied to the resonant circuit. On the other hand, when the operating frequency of the inverter circuit 43 is lower than the resonant frequency of the resonant circuit, the current advances and becomes a phase with respect to the voltage applied to the resonant circuit. When the power supply to the inverter circuit 43 is a voltage source, the operation frequency of the inverter circuit 43 is made higher than the resonance frequency of the resonance circuit to make the resonance current a lagging phase, and the switching element is connected by the connection of the snubber capacitor 60. The switching loss that occurs when the switching element is turned off when the voltage applied to the switching element becomes gentle due to the current flowing through the switching element flowing through the snubber capacitor 60 when the switching element is switched from on to off. Can be suppressed. From this viewpoint, it is desirable that the operating frequency of the inverter circuit 43 be higher than the resonant frequency of the resonant circuit.

  In addition, since the induction heating device according to the first embodiment of the present invention shares the inverter circuit 43 and connects the two resonance circuits in parallel, the switching element constituting the inverter circuit has a current flowing through the two resonance circuits. The sum will flow. However, as shown in the operation region B, when the electric power supplied from the second heating coil 57 to the object to be heated is larger than the electric power supplied from the first heating coil 55 to the object to be heated, the first heating coil Since the current value flowing through the second heating coil 57 is also considered to be larger than the current value flowing through the second heating coil 57, the sum of the current flowing through the two resonance circuits has a strong phase lag component and suppresses the switching loss as described above. be able to.

  From this point of view, the operation region B is equal to or higher than the resonance frequency of the second resonance circuit 45 and the power supplied from the first heating coil 55 and the power supplied from the second heating coil 57 as shown in FIG. Below the intersection. Here, if the range in which the sum of the current values flowing through the heating coil shows a delayed phase is shifted from the intersection of the power characteristics due to the difference in characteristics between the first heating coil 55 and the second heating coil 57, the operation The maximum frequency of region B may be shifted from the intersection of the power characteristics.

  FIG. 3 shows an example of the arrangement of the first heating coil 55 and the second heating coil 57. The first heating coil 55 and the second heating coil 57 are arranged concentrically.

  In the induction heating apparatus according to Embodiment 1 of the present invention, the first heating coil 55 and the second heating coil 57 heat a single object to be heated. The second heating coil 57 is combined.

  In the induction heating apparatus according to Embodiment 1 of the present invention, by operating the operating frequency of the inverter circuit 43 alternately in the operation area A and the operation area B, for example, when the object to be heated is a pan, A predetermined convection is formed in cooking utensils such as moisture stored in the container. Thereby, the cooking utensil material in a pan is heated uniformly, and it can suppress that a part of cooking utensil material is overheated, and can prevent scorching.

  In addition, by heating only a part of the pan, after the heated liquid such as water has risen to the upper part of the liquid, the liquid smoothly flows to the unheated part, and the flow rate of the liquid is increased. It is possible to cook in a short time by accelerating the transmission of heat to the ingredients and the soaking of taste.

  Furthermore, since there is only one inverter circuit that supplies high-frequency current to the two heating coils, it can be realized at low cost by not increasing the inverter circuit 43. In addition, a compact configuration can be realized without increasing the volume of the inverter circuit.

  Moreover, since the fragile part which has mechanical contacts, such as a relay, is not used for the structure of the inverter circuit 43, a long life and cheap induction heating apparatus is realizable.

  The induction heating apparatus according to Embodiment 1 of the present invention has a mode in which the inverter circuit 43 is operated in the operation region A and a mode in which the inverter circuit 43 is operated in the operation region B, and the time and operation in which the operation is performed in the operation region A. There are a plurality of times or ratios for operating in the region B.

As described above, when convection is desired in boiled food cooking or the like, as shown in FIG. 4, the inverter circuit 43 is operated in the operation area A that is mainly supplied to the first heating coil 55 at regular intervals (for example, 10 seconds). Inverter circuit 4 in the operating mode and operating region B that is mainly supplied to the second heating coil 57
The convection is generated by switching the mode in which 3 is operated.

  Moreover, it may be desirable to heat uniformly depending on cooking contents, such as fried food cooking. When uniform heating is required, a mode in which the inverter circuit 43 is operated in an operation region A mainly supplied to the first heating coil 55 and a second heating coil 57 as shown in FIG. Since the interval for switching the mode for operating the inverter circuit 43 in the operation region B to be supplied is shorter (for example, 2 seconds) than in the case of the cooked food, the object to be heated repeats heating and non-heating at high speed. The temperature distribution of the heated product is averaged and can be heated uniformly.

  In addition, when heating an object to be heated having a diameter larger than that of the heating coil, the outside of the object to be heated is not heated, and the amount of heat released increases, resulting in a decrease in temperature. The street tends to be insufficient. In such a case, as shown in FIG. 6, the electric power supplied to the second heating coil 57 located outside by fixing the operating frequency in the operating region B and in the high frequency region, Control without switching, such as maintaining higher than the 1st heating coil 55 located inside, is also possible, and usability can further be improved according to cooking performance.

  Furthermore, the arrangement of the heating coils is not limited to a concentric circle. For example, the same effect can be obtained by arranging the heating coils side by side in the heating region 11 as shown in FIG.

  Further, as shown in FIG. 8, the number of resonance circuits and the number of heating coils may be any combination, such as three resonance circuits and three heating coils.

(Embodiment 2)
FIG. 9 is an arrangement diagram of the heating coils of the induction heating device according to the second embodiment of the present invention, and shows an example of a method of arranging the heating coils in point symmetry from the center of the heating region.

  FIG. 10 is a circuit diagram of the induction heating apparatus according to Embodiment 2 of the present invention, and shows an example of a method for connecting an inverter circuit, a plurality of heating coils, and a plurality of resonance capacitors.

  FIG. 11 shows the supply state of power to the heating coil according to the operating conditions of the inverter circuit of the induction heating apparatus according to Embodiment 2 of the present invention.

  Here, in the second embodiment, only the parts different from the first embodiment will be described, and the description of the same parts as the first embodiment will be omitted.

  FIG. 9 heats one object to be heated using the first to fourth four heating coils 81 to 84. The four heating coils 81 to 84 are disposed in the heating region 11 where the object to be heated can be heated, and the heating coils are disposed so as to be symmetric with respect to the center point of the heating region 11.

  FIG. 10 shows a circuit diagram of an induction heating device for heating the four heating coils 81 to 84 shown in FIG. 1 is different from the inverter circuit shown in FIG. 1 of Embodiment 1 in that two heating coils connected in series are connected as a heating coil of a resonance circuit.

  In the second embodiment, the first heating coil 81 and the third heating coil 83 that are point-symmetrical from the center of the heating region 11 are connected in series as the heating coil of the first resonance circuit 44. The second heating coil 82 and the fourth heating coil 84 connected in series are used as the heating coil of the second resonance circuit 45, and a high-frequency current is supplied from the same inverter circuit 43 to the heating coil.

  About the induction heating apparatus formed as mentioned above, the operation | movement and an effect | action are demonstrated below.

  As shown in FIG. 10, by connecting the heating coils so as to form a common resonance circuit with a plurality of heating coils, the number of resonance circuits composed of the heating coils and the resonance capacitors is smaller than the number of heating coils. An induction heating device can be realized. Thereby, since a high frequency current can be supplied to all the heating coils with less resonance capacitors than the number of heating coils, an inexpensive induction heating device can be provided. Further, by setting the value of the heating coil or the resonance capacitor so that the resonance frequencies of the plurality of resonance circuits are different, the power characteristic as shown in FIG. 2 of the first embodiment can be obtained.

  When the operating frequency is set to 20 kHz or more, which is a human audible sound, in order not to be concerned about the operating sound of the induction heating device, the operating frequency of the inverter circuit increases as the number of resonant circuits increases. If a resonance capacitor is connected to each of the first to fourth heating coils 81 to 84 to have four resonance circuits, the power characteristics of the third and fourth resonance circuits are higher than that of the operation region A. It will be located in the frequency side, and the switching loss of the switching element which forms an inverter circuit will become large.

  Further, if the difference in the resonance frequency of the resonance circuit is reduced in order to avoid an increase in switching loss even if the number of resonance circuits increases, the operation region B becomes smaller and the inverter circuit is operated in the operation region B. When operated, the high-frequency current value supplied to the first heating coil included in the first resonance circuit is increased, and the controllability of power is deteriorated.

  Therefore, by adopting a configuration having a plurality of heating coils in one resonance circuit, the number of resonance circuits can be reduced as compared with the conventional case, switching loss can be reduced, and power controllability can be maintained at a high level. it can.

  In the induction heating apparatus according to the second embodiment, as shown in FIGS. 9 and 11, the heating coils that are point-symmetrical from the center of the heating region are connected to the same resonance circuit. Thereby, for example, the on and off periods and ratios of the high-frequency current flowing in the second heating coil 82 and the fourth heating coil 84 are the same. The same applies to the first heating coil 81 and the third heating coil 83.

  As shown in FIG. 11, the heating coil at a point-symmetrical position from the center of the heating region 11, that is, the heating coil farthest from a certain heating coil shares an on / off period and the like, as shown in FIG. 4. Thus, by switching between mode 1 and mode 2 at regular intervals, for example, when a pan containing a cooked product containing liquid as the object to be heated is used, the convection source is distributed in a well-balanced manner, and the slow convection is panned. By generating it throughout, cooking without scorching can be performed. In addition, since the convection can be changed, when noodles such as pasta are boiled, the noodles are entangled without stirring the contents because the convection moves to the next convection before trying to entangle it. An induction heating device that does not occur can be realized.

  Furthermore, as shown in FIG. 5, the temperature of the object to be heated is changed quickly between heating and non-heating by making the period Tb of mode 1 shorter than the period Ta of mode 1 shown in FIG. The distribution is averaged and the object to be heated can be heated uniformly. Therefore, when it is better for cooking performance to uniformly heat non-heated items such as grilled foods, it is possible to perform heating optimal for cooking contents by switching between mode 1 and mode 2 in a short time.

(Embodiment 3)
FIG. 12 is a circuit diagram of the induction heating apparatus according to Embodiment 3 of the present invention, and shows an example of a method for connecting an inverter circuit, a plurality of heating coils, and a plurality of resonance capacitors.

  FIG. 13 shows the supply state of power to the heating coil according to the operating conditions of the inverter circuit of the induction heating apparatus according to Embodiment 3 of the present invention.

  Here, in the third embodiment, only parts different from the first and second embodiments will be described, and the description of the same parts as the first and second embodiments will be omitted.

  FIG. 12 shows an inverter circuit for heating the four heating coils 81 to 84 shown in FIG. 1 is different from the inverter circuit shown in FIG. 1 in that two heating coils connected in series are connected as a heating coil of a resonance circuit.

  In the third embodiment, two adjacent first heating coils 81 and fourth heating coils 84 connected in series are used as the heating coil of the first resonance circuit 44, and the second heating coil 82 A high frequency current is supplied from the same inverter circuit 43 to the heating coil as a heating coil of the second resonance circuit 45 by connecting the third heating coil 83 in series.

  About the induction heating apparatus formed as mentioned above, the operation | movement and an effect | action are demonstrated below.

  As an effect of the induction heating device in the third embodiment, as in the second embodiment, it is possible to provide an inexpensive induction heating device by reducing the number of resonance capacitors than the number of heating coils, and to reduce switching loss. It is possible to maintain high controllability of power.

  In the induction heating device according to the third embodiment, two adjacent heating coils are connected to the same resonance circuit. Thereby, for example, the on and off periods and ratios of the high-frequency current flowing in the first heating coil 81 and the fourth heating coil 84 are the same. The same applies to the second heating coil 82 and the third heating coil 83.

  As shown in FIG. 13, two adjacent heating coils share an on / off period and the like, and by switching between mode 1 and mode 2 at regular intervals as shown in FIG. If you have a pan with food containing food, you can generate a large convection with a high flow rate by providing a convection source locally. Can be accelerated.

  Furthermore, as shown in FIG. 5, the temperature of the object to be heated is changed quickly between heating and non-heating by making the period Tb of mode 1 shorter than the period Ta of mode 1 shown in FIG. It seems that the distribution is averaged and the object to be heated is heated uniformly. Therefore, when it is better for cooking performance to be uniform in non-heated materials such as grilled foods, optimal heating for cooking contents can be performed by switching between mode 1 and mode 2 in a short time.

(Embodiment 4)
FIG. 14 is a circuit diagram of an induction heating apparatus according to Embodiment 4 of the present invention, and shows an example of a method for connecting an inverter circuit, a plurality of heating coils, and a plurality of resonance capacitors.

  FIG. 15 shows the supply state of power to the heating coil according to the operating conditions of the inverter circuit of the induction heating apparatus according to Embodiment 4 of the present invention.

  Here, in the fourth embodiment, only the parts different from the first to third embodiments will be described, and the description of the same parts as the first to third embodiments will be omitted.

  FIG. 14 shows a connection method of the inverter circuit in the case where there are six heating coils arranged in the heating region 11, and FIG. 1 shows that three resonance circuits are connected to one inverter circuit. 10 and FIG. 12 are different.

  In the fourth embodiment, two adjacent first heating coils 81 and a fourth heating coil 84 are connected in series as the heating coil of the first resonance circuit 44, and the second heating coil 82 The fifth heating coil 85 connected in series is used as the heating coil of the second resonance circuit 45, and the third heating coil 83 and sixth heating coil 86 are connected in series to the third resonance circuit 91. As described above, a high-frequency current is supplied from the same inverter circuit 43 to the heating coil.

  FIG. 15 shows the supply state of electric power to the heating coil when the first to sixth six heating coils 81 to 86 are used to heat one object to be heated.

  By connecting the heating coils in series so as to be symmetric with respect to the center point of the heating region 11, a total of three heating coil groups can be formed. By connecting a resonant capacitor to each of the three heating coil groups, A resonance circuit is formed and connected to one inverter circuit 43 to constitute an inverter circuit.

  About the induction heating apparatus formed as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The induction heating device in the fourth embodiment has three resonance circuits. As described in the above embodiment, in the induction heating apparatus of the present invention, each of the plurality of resonance circuits has a different resonance frequency. Therefore, when the number of resonance circuits increases, the waveform of the power characteristics shown in FIG. One characteristic appears on the higher frequency side than the resonance characteristic 71 of the first resonance circuit (not shown). Similarly, when there are three or more resonant circuits, the number of modes shown in FIG. 4 and FIG. 5 is the same as the number of resonant circuits, so that a high-frequency current is supplied to each heating coil group by switching the operating frequency. Since the period and size can be controlled, the same effect as described in the above embodiment can be obtained.

  Further, by increasing the number of the plurality of heating coils for heating one object to be heated, it is possible to increase the number of heating places and disperse the heating part, so that the object to be heated can be heated more uniformly. .

  Furthermore, even if the number of heating coils increases, only one inverter circuit is required for the induction heating apparatus of the present invention, so that an induction heating apparatus having high cooking performance can be realized with a low cost and compact configuration.

  In addition, in this Embodiment 4, although the connection method of the inverter circuit at the time of connecting the heating coil in the position which becomes a point symmetry from the center point of the heating area | region 11 in series, and the heating condition of each mode were shown, FIG. As shown in FIG. 3, the adjacent heating coils may be connected to form three resonance circuits, and the effect is the same as that described in the above embodiment, and is uniform by increasing the number of heating coils. Uniformity when heating can be improved.

  Also, as shown in FIG. 17, three adjacent heating coils may be connected in series, and the six heating coils may be heated by two resonance circuits. In short, the number of resonance circuits is smaller than the number of heating coils. By heating with one inverter circuit, the present invention is useful in that it is possible to realize an induction heating device having both uniform / convection control of heating distribution and controllability of power with an inexpensive circuit configuration.

  Furthermore, as shown in FIG. 18, even when the heating coil is arranged around the central portion of the heating region 11, the heating coil arranged at the central portion independently forms a resonance circuit, By connecting two heating coils to form one resonance circuit, the heating coil can be controlled by one inverter circuit with five heating coils as three resonance circuits.

(Embodiment 5)
FIG. 19 is a diagram showing the resonance characteristics of the heating coil and the resonant capacitor according to the fifth embodiment of the present invention, showing the relationship between the operating frequency of the inverter circuit of the induction heating device and the power that can be supplied to the object to be heated. It is.

  Here, in the fifth embodiment, only the parts different from the above embodiment will be described, and the description of the same parts as the above embodiment will be omitted.

  FIG. 19 differs from FIG. 2 in that the maximum value of the resonance characteristic 73 of the first resonance circuit is equivalent to the maximum value of the resonance characteristic 72 of the second resonance circuit.

  About the induction heating apparatus formed as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The induction heating device according to the fifth embodiment periodically switches the operating frequency of the inverter circuit. By adjusting the operating time in one mode, convection is generated in the contents of the object to be heated. The object to be heated can be heated uniformly. At this time, if a plurality of heating coils for heating one object to be heated are configured with heating coils having the same characteristics, the resistance component of the object to be heated viewed from the heating coil included in the resonance circuit having a high resonance frequency is resonant. Compared with a low frequency, it becomes large and it becomes difficult for a high frequency current to flow into a heating coil. Then, as shown in FIG. 19, the maximum value of the waveform 71 of the first resonance circuit when the heating coil having the same characteristics is applied to all the heating coils is the maximum value of the waveform 72 of the second resonance circuit. Smaller than.

  Since the induction heating apparatus according to the fifth embodiment heats the same object to be heated, it is desirable to heat in a balanced manner. For this purpose, it is necessary to reduce the difference in power that can be supplied from the respective resonance circuits to the object to be heated.

  Therefore, in the induction heating apparatus according to the fifth embodiment, the resistance component of the object to be heated as viewed from the heating coil included in the resonance circuit that mainly supplies power has other resonances in the frequency region that mainly supplies power. It is set so as to be equivalent to the resistance component of the object to be heated as seen from the operating frequency of the circuit and the heating coll in the region.

  That is, in the fifth embodiment, the resistance value of the object to be heated near the resonance frequency viewed from the first heating coil group included in the first resonance circuit and the second resistance circuit included in the second resonance circuit. By setting the heating coil so that the resistance value of the object to be heated in the vicinity of the resonance frequency viewed from the heating coil group becomes equal, as shown in the waveform 73 of the power characteristic of the first resonance circuit in FIG. The maximum value of the power characteristic of one resonance circuit is equivalent to the maximum value of the power characteristic of the second resonance circuit, and the power that can be supplied from each heating coil group to the object to be heated is the same level and heats in a balanced manner. be able to. Thereby, it can suppress that a difference arises according to a heat | fever by the bias | inclination of the non-heating thing in a cooking container, the bias | inclination of the mounting place of a cooking container, etc.

Here, the resistance value of the object to be heated as viewed from the first heating coil group that mainly supplies power at a high operating frequency, and the object to be heated as viewed from the second heating coil group that mainly supplies power at a low operating frequency. As a method of lowering the resistance value, the number of turns of the first heating coil is made smaller than that of the second heating coil, or the distance between the first heating coil and the object to be heated is set to the second heating coil and the object to be heated. Any method may be used for the method, such as disposing it away from the object.

  As described above, the first to fifth embodiments of the present invention are inverter circuits using two switching elements, and the first resonance circuit and the second resonance circuit are connected to the negative potential side of the rectifier circuit. However, the connection method of the inverter circuit and the resonance circuit is not limited to this, and a plurality of resonance circuits can be controlled simultaneously by changing the operating frequency of at least one switching element constituting the inverter circuit. Any configuration may be used.

  Moreover, although the said Embodiments 1-5 demonstrated the arrangement | positioning and connection method of up to six heating coils, and how to put in electric power, if the number of heating coils is plural, it may be whatever.

  Also, the arrangement of the heating coils is not limited to that shown in the figure, and if they are arranged point-symmetrically or line-symmetrically, the same effects as those described in the above embodiment can be obtained. Needless to say, even if there is a slight shift, the effect of the present invention is not greatly affected.

  In the induction heating cooker, since the object to be heated can be heated uniformly and the heating method for generating convection can be performed without changing the connection of the inverter circuit. This is useful not only for home appliances, but also for all induction heating devices for which the heating balance is appropriately changed, such as for business use and industrial use.

DESCRIPTION OF SYMBOLS 11 Heating area 41 AC power supply 42 Rectification means 43 Inverter circuit 44 1st resonance circuit 45 2nd resonance circuit 55 1st heating coil 56 1st resonance capacitor 57 2nd heating coil 58 2nd resonance capacitor 59 Control Means 60 Snubber capacitor 71 Power characteristic of first resonance circuit 72 Power characteristic of second resonance circuit 73 Power characteristic of first resonance circuit 81 First heating coil 82 Second heating coil 83 Third heating coil 84 Fourth heating coil 85 Fifth heating coil 86 Sixth heating coil 91 Third resonance circuit

Claims (6)

A plurality of heating coils for induction heating a single object to be heated;
A plurality of resonant capacitors forming a resonant circuit with the plurality of heating coils;
A single inverter circuit for supplying a high-frequency current to the plurality of heating coils;
Control means for controlling the operation of the inverter circuit by outputting a drive signal to the inverter circuit;
The control means has a function of controlling at least the operating frequency of the inverter circuit,
Among the plurality of heating coils and the plurality of resonance capacitors, the resonance frequency of the first resonance circuit formed by the first heating coil and the first resonance capacitor is the second heating coil and the second resonance capacitor. Setting the value of the first heating coil or the first resonance capacitor to be higher than the resonance frequency of the second resonance circuit formed by
The first resonance circuit and the second resonance circuit are connected to the single inverter circuit,
By controlling the operation of the inverter circuit by the control means, simultaneously changing the high-frequency current flowing through the first heating coil and the second heating coil,
An induction heating apparatus that induction-heats an object to be heated by switching frequency regions equal to the number of resonance circuits connected to the inverter circuit at regular intervals.   The induction heating device according to claim 1, wherein the induction heating device has a plurality of intervals for switching a plurality of frequency regions.   3. The induction heating apparatus according to claim 1, wherein the first heating coil and / or the second heating coil includes a plurality of heating coils.   The plurality of heating coils are disposed so as to be point-symmetric from the center of the heating region of the object to be heated, and the heating coils positioned symmetrically are connected to the same resonance circuit. The induction heating device described in 1.   The said some heating coil is arrange | positioned so that it may become line symmetrical from the center of the heating area | region of a to-be-heated material, and an adjacent heating coil is connected to the same resonance circuit. Induction heating device.   The resistance value that appears in the first resonance circuit at the operating frequency that supplies power to the object to be heated mainly from the first heating coil, and the first that is at the operating frequency that supplies power to the object to be heated mainly from the second heating coil. The induction heating device according to any one of claims 1 to 5, wherein resistance values appearing in the two resonance circuits are substantially the same.