JP2003151747A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating cooker induction-heating various kinds of objects to be heated without switching induction heating coils and additionally miniaturizing a device casing. SOLUTION: This induction heating cooker comprises a high frequency inverter 7, a boosting means 8 for supplying a boosting power to the high frequency inverter 7, a switching element 9 and induction heating coil 10, and a resonance condenser 11 connected with the high frequency inverter 7, and an object 12 to be heated by the induction heating coil 10. The boosting means 8 supplies to the induction heating coil 10 a resonance current of a frequency as twice as or higher than that for driving the switching element 9 and thereby the object 12 is induction-heated without switching the induction heating coil 10 regardless of material of the object 12 to be heated, and miniaturization of the device casing can be realized.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an induction heating cooker used in general households.

[0002]

2. Description of the Related Art A conventionally known induction heating cooker is one in which a high frequency magnetic field is generated from an induction heating coil and an object to be heated such as a cooking pot is heated by an eddy current caused by electromagnetic induction.

Hereinafter, a conventional induction heating cooker is shown in FIG.
An example will be described based on 0. In the figure, 1 is a high frequency inverter, 2 is a switching element that constitutes the high frequency inverter 1, 3 is an induction heating coil connected to the high frequency inverter 1, 4 is a resonance capacitor connected in series with the induction heating coil 3, and 5 is induction heating. An object to be heated such as a cooking pot heated by the coil 3, and 6 are power sources.

In this structure, a high-frequency magnetic field is generated from the induction heating coil 3 by the high-frequency current supplied from the high-frequency inverter 1, and an eddy current due to electromagnetic induction flows in the object to be heated 5, which causes Joule heat. Heated object 5
Is heated and can be cooked.

[0005]

In the above conventional structure, the Joule heat generated in the heated body 5 is determined by the material of the heated body 5 and the high frequency magnetic field generated by the induction heating coil 3 depending on the heating structure. And is generally represented by (Equation 1).

[0006]

[Formula 1] Here, P is Joule heat generated in the heated body 5, Rs is the skin resistance of the heated body 5, N is the number of turns of the induction heating coil 3, I is the current of the induction heating coil 3, and ρ is the heated body 5. Of the material, μ is the same permeability, and f is the induction heating coil 3
Is the frequency of the current.

When iron, which is conventionally used as the material to be heated 5, is used as a reference, if non-magnetic stainless steel that is also conventionally used and aluminum that has been difficult to be heated by induction are applied to this formula (Table It becomes as 1).

[0008]

[Table 1] Here, the number of turns of the induction heating coil 3, the current of the induction heating coil 3, and the frequency are the same. As is clear from this table, non-magnetic and low-resistance metals such as aluminum are
It is more difficult to generate Joule heat than other metals. Induction heating of such a metal requires at least Joule heat equivalent to that of non-magnetic stainless steel capable of induction heating, and Rs (NI) ² may be increased by 5.2 times. I understand.

Here, induction heating is possible by increasing Rs, that is, increasing the frequency. However, as shown in FIG. 11, according to the conventional control method,
Since the drive frequency of the switching element 2 and the current frequency of the induction heating coil 3 are almost the same, increasing the frequency also increases the drive frequency of the switching element 2 and increases the loss. The same applies to other parts.

Further, when the number of turns of the induction heating coil 3 is increased, the inductance is increased, so that it is difficult to increase the current of the induction heating coil 3 and it is also difficult to increase NI. Further, there is also known one that switches the induction heating coil depending on the material of the object to be heated, but there is a problem that the volume of the induction heating coil becomes large and the housing of the induction heating cooker needs to be large, resulting in high cost. It was

The present invention is to solve the above-mentioned conventional problems. Induction heating that realizes downsizing of a device by induction heating the object to be heated without switching the induction heating coil regardless of the material of the object to be heated. It is intended to provide a cooking device.

[0012]

In order to achieve the above object, the induction heating cooker of the present invention supplies a boosting power source to a high frequency inverter by a boosting means to drive a switching element at a frequency twice or more. A resonance current that is to be supplied to the induction heating coil.

With this, regardless of the material of the object to be heated, the object to be heated can be induction-heated without switching the induction heating coil, and the miniaturization of the device can be realized.

[0014]

A first aspect of the present invention is a high frequency inverter, boosting means for supplying boosting power to the high frequency inverter, a switching element connected to the high frequency inverter, an induction heating coil, and a resonance capacitor. And an object to be heated by the induction heating coil, wherein the boosting means is an induction heating cooker for supplying to the induction heating coil a resonance current having a frequency that is at least twice the frequency that drives the switching element. This makes it possible to both increase the number of turns of the induction heating coil and increase the current of the induction heating coil to generate a stronger magnetic field and also to increase the frequency of the magnetic field. Increases the epidermal resistance of the body and allows more effective induction heating. Therefore, induction heating can be performed regardless of the material of the object to be heated without switching the induction heating coil and the resonance capacitor, and the size of the device can be reduced.

According to a second aspect of the present invention, there is provided a switching means for switching a plurality of resonance capacitors and a material discriminating means of the object to be heated, and the switching means selects the resonant capacitor according to the discrimination result of the material discriminating means. By using the induction heating cooker according to Item 1, a plurality of resonance capacitors having smaller component volumes are switched and used as compared with the induction heating coil, so that the high frequency with respect to the material of the object to be heated while keeping the equipment volume small. It is possible to increase the degree of freedom in designing the inverter.

The invention according to claim 3 is the induction heating cooker according to claim 2, wherein the switching means is connected in series to all or a part of the plurality of resonant capacitors connected in parallel, whereby the object to be heated is heated. Since it is possible to freely select the resonance capacitor according to the material of the body, it is possible to further increase the degree of freedom in designing the high frequency inverter.

According to a fourth aspect of the present invention, the induction heating cooker according to the second aspect has the switching means connected in parallel to all or some of the plurality of resonance capacitors connected in series, whereby the object to be heated is heated. Even when the voltage of the resonance capacitor greatly rises depending on the material of the body, it is possible to cope with the series connection of the resonance capacitors, which has a low withstand voltage and is low in cost.

According to a fifth aspect of the present invention, there is provided the induction heating cooker according to the fourth aspect, wherein a part of the plurality of switching means is connected in series with a part of the plurality of resonance capacitors.
When a withstand voltage is provided by connecting multiple resonant capacitors with small capacity in series, the resonant capacitor capacity connected in series with a part of the multiple switching means is increased to design a high-frequency inverter for the material to be heated. It is possible to increase the degree of freedom.

In a sixth aspect of the present invention, any one of the third to fifth aspects is characterized in that a switching means in which a plurality of changeover switches are connected in series is connected in parallel to all or some of the plurality of series-connected resonant capacitors. By using the induction heating cooker according to the item 1, even when the resonant capacitor voltage greatly increases due to the material of the object to be heated, it is possible to design within the withstand voltage of the switching means.

According to a seventh aspect of the present invention, any one or more of the third to fifth aspects is characterized in that a switching means in which a plurality of selector switches are connected in parallel is connected in parallel to all or some of the plurality of resonance capacitors connected in series. By using the induction heating cooker described in the item 1, even when the resonance capacitor current is large, it is possible to design within the current capacity of the switching means.

An eighth aspect of the present invention is the induction heating cooker according to any one of the second to seventh aspects, wherein the resonance capacitor, which is not switched by the switching means, is provided with a voltage detecting means for the resonance capacitor. With this, it is possible to detect the voltage applied to the whole or a part of the resonance capacitor regardless of switching of the resonance capacitor.

[0022]

Embodiment 1 Embodiment 1 of the present invention will be described below with reference to the drawings. In FIG. 1, 7 is a high-frequency inverter, 8 is boosting means for supplying boosting power to the high-frequency inverter 7, and 9, 10, 11 are switching elements connected in series and connected to the high-frequency inverter 7, an induction heating coil, and Resonant capacitor, 12
Is a heated object such as a cooking pot heated by the induction heating coil 10, and 13 is a power source.

Further, as shown in FIG. 2, the boosting means 8 supplies a resonance current having a frequency twice or more the frequency for driving the switching element 9 to the induction heating coil 10 and the resonance capacitor 11 connected in series. To supply.

In the above structure, the high frequency inverter 7
By boosting the power supply of No. 2, both the increase in the number of turns of the induction heating coil 10 and the increase in the current of the induction heating coil 10 can be achieved, and a stronger magnetic field can be generated, and the magnetic field itself can have a higher frequency. . Therefore, the skin resistance of the object to be heated 12 is increased, and the induction heating can be performed more effectively. Therefore,
Induction heating of the heated body 12 made of non-magnetic metal such as aluminum, which has been difficult in the past, becomes possible. Further, due to the predetermined high frequency inverter design, control of the boosting means, etc., it is not necessary to switch the induction heating coil 10 and the resonance capacitor 11 regardless of the material of the object to be heated 12, so the size of the induction heating cooker can be reduced. Can be suppressed.

In this embodiment, the high frequency inverter 7
However, the present invention is not limited to this, and the same effect can be obtained even if a part of the high-frequency inverter also serves as a part of the booster.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to the drawings. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only different points will be described.

In FIG. 3, 14 is a plurality of capacitors 1.
4a and 14b are connected in parallel to the resonance capacitor, and 15 is a changeover switch 1 corresponding to the capacitors 14a and 14b.
Switching means having 5a and 15b, 16 is a heated body 1
2 is a material discriminating means for controlling the switching means 15 by discriminating the material.

As an example, the material discriminating means 22 detects the resonance current flowing through the induction heating coil 10 and the resonance capacitor 14 and the voltage of the switching element 9, and discriminates the material of the heated body 12 based on the detected values. Based on the determination result, the switching unit 15 is controlled to select the plurality of capacitors 14a and 14b.

In the above structure, when the heated body 12 is made of iron, the combined inductance of the heated body 12 and the induction heating coil 10 becomes lower when the heated body 12 is made of aluminum. The resonance current frequency flowing through the heating coil 10 and the resonance capacitor 14 becomes high. Also,
When the drive frequency of the switching element 9 and the phase of this resonance current frequency match, that is, when the resonance current frequency is an integral multiple of the frequency for driving the switching element 9,
Sufficient resonance occurs and the heated body 12 is likely to be induction-heated.

Therefore, the drive frequency of the switching element 9 in which the heated body 12 is easily heated by induction varies depending on the material of the heated body 12. When the high-frequency inverter 7 is designed to match the object 12 to be heated of a certain material, the object 12 to be heated of another material may be less likely to be heated by induction heating. It is necessary to boost the power source of No. 7 to a predetermined voltage and generate a strong magnetic field.

However, at the same time, the switching element 9
The voltage is also raised, so a limit is set from the breakdown voltage.
Therefore, in the present embodiment, induction heating can be performed regardless of the material of the object to be heated 12 by changing the resonance current frequency. Switching of the induction heating coil 13 and switching of the resonance capacitor 14 can be considered for changing the resonance current frequency, but by switching and using a plurality of resonance capacitors 14 having a smaller component volume than the induction heating coil 13, The object to be heated 12 while keeping the enclosure volume of the device small.
It is possible to increase the degree of freedom in designing the high frequency inverter with respect to the material.

In the present embodiment, the heated body 12
Induction heating coil 10 and resonance capacitor 1
Although the example in which the resonance current flowing in 4 and the voltage of the switching element 9 are detected is given, the resonance current frequency flowing in the induction heating coil 13 and the resonance capacitor 14, the voltage of the resonance capacitor 14, the input current, etc. The material of the heated object 19 can be discriminated also by the combination.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings. The same parts as those in the second embodiment are designated by the same reference numerals, the description thereof will be omitted, and only different points will be described.

In FIG. 4, the resonance capacitor 14 has a plurality of capacitors 14a to 14c connected in parallel.
The switching means 15 is connected in series only to 4a and 14b. There is no particular problem even if the switching means 15 is connected in series to all of the capacitors 14a to 14c.

In the above structure, the resonance capacitors 14a to 14c can be freely designed according to the material of the object to be heated 12,
Since it becomes selectable, the degree of freedom in designing the high frequency inverter can be increased.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to the drawings. The same parts as those in the second embodiment are designated by the same reference numerals, the description thereof will be omitted, and only different points will be described.

In FIG. 5, the resonance capacitor 14 is formed by connecting a plurality of capacitors 14a to 14c in series.
The switching means 15 is connected in parallel only to 4a and 14b. Note that, as in the third embodiment, the capacitors 14a-14
There is no particular problem if the switching means 15 is connected in parallel to all of c.

In the above structure, even when the voltage of the resonance capacitor 14 greatly increases depending on the material of the object to be heated 12, the breakdown voltage is low, and it is possible to provide the breakdown voltage by connecting a plurality of resonance capacitors in series at low cost. Becomes

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described with reference to the drawings. The same parts as those in the fourth embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only different points will be described.

In FIG. 6, the resonance capacitors are the first,
The second resonance capacitors 14 and 17 are provided, and the switching means is provided with the first and second switching means 15 and 18.
Then, the second resonance capacitor 17 and the second switching means 18 are connected in series.

In the above structure, the voltage applied to the first resonance capacitor 14 greatly increases depending on the material of the object 12 to be heated, and a plurality of resonance capacitors having a small capacitance are connected in series to provide a withstand voltage. By increasing the capacity of the resonance capacitor 17, the degree of freedom in designing the high frequency inverter 7 with respect to the material of the heated body 12 can be increased.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described with reference to the drawings. The same parts as those in the fourth embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only different points will be described.

In FIG. 7, the resonance capacitor 14 is composed of a plurality of capacitors 14a to 14c connected in series.
The switching means 15 is connected in parallel only to 4a and 14b. The changeover means 15 has a plurality of changeover switches 15a and 15b connected in series. There is no particular problem even if the switching means 15 is connected in parallel to all of the capacitors 14a to 14c.

In the above structure, even when the voltage of the resonance capacitor 14 greatly rises due to the material of the heated body 12, it is possible to design within the withstand voltage of the changeover switches 15a and 15b of the changeover means 15, respectively.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described with reference to the drawings. The same parts as those of the sixth embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only different points will be described.

In FIG. 8, the resonance capacitor 14 is formed by connecting a plurality of capacitors 14a to 14c in series.
The switching means 15 is connected in parallel only to 4a and 14b. The changeover means 15 has a plurality of changeover switches 15a and 15b connected in parallel. There is no particular problem even if the switching means 15 is connected in parallel to all of the capacitors 14a to 14c.

In the above structure, even when the current of the resonance capacitor 14 is large, it is possible to design within the current capacity of the changeover switches 15a and 15b of the changeover means 15, respectively.

(Embodiment 8) Next, an embodiment 8 of the invention will be described with reference to the drawings. The same parts as those in the fourth embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only different points will be described.

In FIG. 9, the resonance capacitor voltage detection means 19 is connected in parallel to the resonance capacitor 14c which is not switched.

In the above structure, the voltage applied to the whole or a part of the resonance capacitor can be detected regardless of the switching of the resonance capacitor 14, so that the circuit can be simplified.

[0051]

As described above, according to the induction heating cooker of the present invention, the object to be heated can be induction-heated without switching the induction heating coil, and the miniaturization of the housing of the device can be realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an induction heating cooker according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an induction heating coil current and a switching element drive signal of the induction heating cooker.

FIG. 3 is a schematic configuration diagram of an induction heating cooker according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an induction heating cooker according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an induction heating cooker according to a fourth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of an induction heating cooker according to a fifth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of an induction heating cooker according to a sixth embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of an induction heating cooker according to a seventh embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of an induction heating cooker according to an eighth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a conventional induction heating cooker.

FIG. 11 is a diagram showing the relationship between the induction heating coil current and the switching element drive signal of the induction heating cooker.

[Explanation of symbols]

7 High frequency inverter 8 boosting means 9 switching elements 10 induction heating coil 11, 14 Resonant capacitor 12 Heated object 15 Switching means 16 Material discrimination means 19 Voltage detection means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takahiro Miyauchi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yuji Fujii             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 3K051 AA02 AA07 AB05                 5H007 BB04 CA01 CB09 CB17 DB01

Claims (8)

[Claims] 1. A high frequency inverter, boosting means for supplying boosting power to the high frequency inverter, a switching element connected to the high frequency inverter, an induction heating coil,
And a resonance capacitor and an object to be heated by the induction heating coil, wherein the boosting means supplies the resonance heating current having a frequency twice or more the frequency for driving the switching element to the induction heating coil. Cooking device. 2. The induction heating according to claim 1, further comprising a switching means for switching a plurality of resonance capacitors and a material discriminating means for the object to be heated, wherein the switching means selects the resonant capacitor according to a discrimination result of the material discriminating means. Cooking device. 3. The induction heating cooker according to claim 2, wherein the switching means is connected in series to all or some of the plurality of resonance capacitors connected in parallel. 4. The induction heating cooker according to claim 2, wherein the switching means is connected in parallel to all or some of the plurality of resonance capacitors connected in series. 5. The induction heating cooker according to claim 4, wherein a part of the plurality of switching means is connected in series with a part of the plurality of resonance capacitors. 6. The induction heating cooking according to claim 3, wherein a switching means in which a plurality of changeover switches are connected in series is connected in parallel to all or a part of the plurality of resonance capacitors connected in series. vessel. 7. The induction cooking according to any one of claims 3 to 5, wherein all or some of the plurality of resonance capacitors connected in series are connected in parallel with a switching means in which a plurality of changeover switches are connected in parallel. vessel. 8. The induction heating cooker according to any one of claims 2 to 7, wherein a resonance capacitor voltage detection means is provided to the resonance capacitor which is not switched by the switching means.