JPH11224767A - Induction heating cooking appliance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating cooking appliance which is high in heating efficiency, easy in manufacture, and low in cost. SOLUTION: A heating coil 1A to induction-heat a work 20 to be heated comprises a plurality of coils 2-5 which are concentrically and successively wound from the inner side to the outer side, and one or plurality of coils among the coils 2-5 according to the material and the size of the work 20 to be heated are selected in a DC-connecting manner. The heating coil 1A comprises a first coil and a second coil concentrically wound therearound on its outer side. When the work 20 is low in resistance and magnetic permeability, the first coil is connected to the second coil in series, and when the work 20 is high in resistance and/or magnetic permeability, and small in diameter, the first coil is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker for inductively heating an object to be heated by supplying a high-frequency current to a heating coil.

[0002]

2. Description of the Related Art As a conventional induction heating cooker, for example, a plurality of spirally wound coils are vertically stacked in multiple layers with an insulator interposed between the coils, so that the number of turns can be increased. There is a heating coil provided with such a heating coil, and the number of turns of the heating coil is switched according to the material of a load such as a low-resistance pot or a high-resistance pot (Japanese Utility Model Publication No. 3-19192).

[0003]

However, in order to further improve the efficiency of the induction heating cooker, it is necessary to consider the electromagnetic coupling between the heating coil and the pan. It is necessary to increase the space factor of the wire, that is, the ratio of the wire to the entire volume of the heating coil.
In the multi-stage heating coil as described above, there is unevenness on the coil surface between the coils, a gap is made between them, and an insulator must be inserted between the plurality of coils. The rate cannot be improved and it is difficult to increase efficiency. Further, in order to form a multi-stage coil, since a high voltage is applied between the coils, it is necessary to bond after inserting an insulator, which is difficult to manufacture and increases the cost.

[0004] The present invention has been made in view of the above,
An object of the present invention is to provide an induction heating cooker that has a high heating efficiency, is easy to manufacture, and is low in cost.

[0005]

In order to solve the above-mentioned problems, according to the present invention, a plurality of coils in which a heating coil for inductively heating an object to be heated is sequentially concentrically wound from the inside to the outside. The point is that one or a plurality of coils are selected and configured according to the material of the object to be heated among the plurality of coils. With this configuration, the input impedance of the heating coil is proportional to the product of the skin resistance of the object to be heated and the square of the number of turns of the heating coil, and the efficiency is high when matching with the rated input. Since the skin resistance of the object to be heated changes depending on its material, by changing the number of turns of the heating coil in accordance with the material of the object to be heated, the input impedance is maintained at an appropriate value and efficient heating can be performed.

According to a second aspect of the present invention, a heating coil for inductively heating an object to be heated is constituted by a plurality of coils concentrically wound from the inner side to the outer side, and among the plurality of coils, the heated coil is provided. The gist is that one or more coils are selected and configured according to the size of the body. With this configuration, the current flowing through the object to be heated such as a pan flows through a portion corresponding to an intermediate portion between the inner diameter and the outer diameter of the substantially heating coil shape. In the case of a pot having a large diameter, such as a pot, by using a heating coil having a large diameter, the path length of the current flow becomes long, and the input resistance of the heating coil increases, resulting in high efficiency.

According to a third aspect of the present invention, in the induction heating cooker according to the first or second aspect, the litz wire constituting the heating coil has a multi-stage twist structure in which twisted wires are further twisted. The gist is that the volume of the wire covered with the insulating layer in the litz wire is 40% or more of the entire volume of the heating coil. With this configuration, if the ratio of the volume of the wires to the entire volume of the heating coil, that is, the space factor, is increased, the coupling between the wires becomes denser, the inductance becomes larger, and the electromagnetic coupling with the object to be heated is increased. Increase. By increasing the space factor to 40% or more,
Sufficient electromagnetic coupling is obtained, and substantially constant high heating efficiency can be achieved.

According to a fourth aspect of the present invention, a heating coil for inductively heating an object to be heated is constituted by a first coil and a second coil concentrically wound around the outside of the first coil. When the object to be heated has low resistance and low magnetic permeability, the first coil and the second coil are connected in series, and when the object to be heated has high resistance and / or high magnetic permeability, the second coil is used. The gist of the present invention is that: With this configuration, when a high-resistance or high-permeability object to be heated such as iron or stainless steel is heated, if the outer second coil is used, the path length of current flow increases, and the input resistance of the heating coil increases. . At this time, since the loss of only the heating coil is constant, the efficiency is high.

According to a fifth aspect of the present invention, the heating coil for inductively heating the object to be heated is constituted by a first coil and a second coil concentrically wound outside the first coil. When the object to be heated has low resistance and low magnetic permeability, the first coil and the second coil are used in series, and when the object to be heated has high resistance or / and high magnetic permeability and a small diameter, The gist is that the first coil is configured to be used.
With this configuration, when heating a small-diameter object to be heated having high resistance or high magnetic permeability such as iron and stainless steel, the magnetic flux is effectively linked to the object to be heated by using the inner first coil. Heating can be performed efficiently.

According to a sixth aspect of the present invention, the heating coil for inductively heating the object to be heated is constituted by a first coil and a second coil concentrically wound outside the first coil. When the diameter of the object to be heated is small, the first coil is used,
The gist is such that when the diameter of the object to be heated is large, the second coil is used. With this configuration, by changing the size of the heating coil according to the size of the object to be heated, the magnetic flux is effectively linked to the object to be heated, and efficient heating can be performed.

According to a seventh aspect of the present invention, a heating coil for inductively heating an object to be heated is provided with a first coil, a second coil concentrically wound outside the first coil, and a second coil. A third coil concentrically wound around the outside of the coil, and when the object to be heated has low resistance and low magnetic permeability, the first coil, the second coil, and the third coil are connected in series. The gist of the present invention is that the second coil is used when it is connected and used and has high resistance and / or high magnetic permeability. With this configuration, a high-resistance or high-permeability target such as iron or stainless steel has a lower thermal conductivity than a low-resistance or low-permeability target such as aluminum or copper. When heating a high-resistance or high-permeability standard-sized object to be heated, by using the intermediate second coil, the path of the current flowing to the bottom of the object to be heated is shifted to the center of the object to be heated. Around the middle of the outer peripheral portion, the temperature of the bottom of the heated object is made uniform, and efficient heating can be performed.

According to the present invention, the heating coil for inductively heating the object to be heated is provided with a first coil, a second coil concentrically wound outside the first coil, and the second coil. 2
And a third coil concentrically wound around the outside of the coil. When the resistance and / or the magnetic permeability are high, the first coil and the third coil are connected in series and used. The gist is to constitute. According to this configuration, it is possible to prevent the occurrence of uneven heating as compared with a case where the object to be heated having high resistance and / or high magnetic permeability is heated using the first coil or the third coil.

According to an eleventh aspect of the present invention, in the induction heating cooker according to any one of the first to tenth aspects, each of the coils constituting the heating coil is molded. With this configuration, it is necessary to increase the number of turns of the heating coil in order to heat a low-resistance, low-permeability object to be heated such as aluminum or copper. As a result, the voltage of the heating coil is increased, and the conductor for shielding maintained at a low voltage is usually arranged on the top plate. By molding each coil, insulation of the heating coil between the coil and the shield conductor is improved.

According to a twelfth aspect of the present invention,
In the induction heating cooker described above, the gist is that the litz wire constituting each of the coils is manufactured by directly winding it around an epoxy mold. With this configuration, each coil is configured in a single-stage configuration such that the second coil is concentrically wound around the outside of the first coil. Is wound, and each coil is formed, and further, it is possible to integrally mold it by epoxy molding.

The invention according to claim 13 is the invention according to claim 11.
In the induction heating cooker described above, a gist of the present invention is that a heat shrink tube is previously placed on a connection terminal extraction portion of each coil from a molding die to cast a molding material. With this configuration, at the time of heating for solidifying the molding material such as epoxy, the heat-shrinkable tube shrinks and the outflow of the molding material is prevented, so that the molding material does not solidify in the connection terminal extracting portion. As a result, breakage of the connection terminal extraction portion due to solidification of the molding material is prevented.

The invention according to claim 14 is the invention according to claim 13.
In the induction heating cooker described above, the litz wire of the connection terminal take-out portion of each coil is filled with silicon and covered with the heat-shrinkable tube. With this configuration, by infiltrating silicon into the litz wire, outflow of the molding material is more reliably prevented, and breakage of the connection terminal extraction portion is eliminated.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

In the induction heating cooker, a high-frequency current is applied to a heating coil wound in a spiral shape to generate a magnetic flux, and an eddy current is applied to the bottom of the pan to be heated to heat the pan. Improving the electromagnetic coupling between the heating coil and the pan improves the heating efficiency. As a method, if the ratio (occupancy ratio) of the volume of the wire (including the insulating layer) to the total volume of the heating coil is increased, the wires are first tightly coupled with each other, and the inductance is increased. Electromagnetic coupling increases. In addition, the distance between the heating coil and the pan cannot be brought closer than necessary in view of the heat countermeasure and the top plate. Therefore, in the single-stage coil capable of increasing the space factor, the current and the space between the pots are close to each other, the electromagnetic coupling is increased, and the efficiency is improved. In particular, when heating an aluminum or copper pan, the heating efficiency is improved by reducing the current flowing through the heating coil and the distance between the pans due to the non-magnetic material.

The embodiments will be described below in order.

FIG. 1 to FIG. 3 are views showing a first embodiment of the present invention. The description will be started from the heating coil 1A with reference to FIG. The heating coil 1A is configured such that the second coil 3 is wound outside the first coil 2, the third coil 4 is wound outside the second coil 3, and the fourth coil 5 is wound concentrically outside the outside. Have been. The number of turns of each coil is, for example, 12T (turn) for the first coil 2, 8T for the second coil 3,
The third coil 4 has 60T, and the fourth coil 5 has 5T. 18 is a top plate. In order to efficiently heat the pan 20 which is the object to be heated, as shown in Table 1, the skin resistance of the pan 20 varies depending on its material. It is necessary to match the skin resistance, and the number of turns of each coil is as described above.

[0021]

[Table 1] The input impedance of the heating coil 1A is (skin resistance)
X (the square of the number of turns of the heating coil). Therefore, efficiency is good when the input impedance matches the rated input. In the case of iron having a large skin resistance, the number of turns may be small, and the fourth coil 5 of 5T is used, and the terminal 17 is used.
A high-frequency current flows between a and 17b. Next, in the case of an 18-8 stainless steel pan having a small skin resistance, terminals 17b and 17c are used.
And the third coil 4 and the fourth coil 5 are connected in series such that the total is 65 T, and a high-frequency current is passed between the terminals 17a and 17d. For aluminum, a total of 7
The second coil 3, the third coil 4, and the fourth coil 5 are connected in series so as to be 3T, and a high-frequency current flows between the terminals 17a and 17f. In the case of a copper pot having the smallest skin resistance, the first to fourth coils 2, 3, 4, and 5 are connected in series so as to have a total of 85T, and a high-frequency current flows between the terminals 17a and 17h. In this way, heating can be efficiently performed with the number of turns of the heating coil 1A that matches the material of the pan 20. Here, as shown in FIG. 1, for example, the fourth coil 5 is shown slightly closer to the top plate 18 side, the upper surfaces of the plurality of coils 2, 3, 4, and 5 are not coplanar but have irregularities. You may. However, it is more efficient to bring the fourth coil 5 having a smaller number of turns closer to the top plate 18 in accordance with the number of turns of each of the coils 2, 3, 4, and 5, such as approaching the top plate 18 side. Get better.

Next, the circuit configuration and operation of the induction heating cooker will be described with reference to FIG. 27 is a commercial AC power supply, 28
Is a diode bridge, 29 is a smoothing capacitor, and the diode bridge 28 and the capacitor 29 constitute a DC power supply circuit. Switching elements Q ₁ and Q ₂ alternately turn on / off in response to a drive signal from inverter drive circuit 23, and periodically turn on / off a DC voltage from a DC power supply circuit, thereby supplying a high-frequency current to heating coil 1A. Shed. At this time, control of the inverter, the phase of the switching element Q ₂ voltage and the voltage of the resonance capacitor C ₁ is detected by the phase comparator circuit 21 is carried out in the PLL feedback circuit for inputting it to the voltage control oscillator 22. Optionally Thus, it is possible to make constant a phase difference between the current flowing through the voltage and the resonant circuit of the switching element Q _2, it is changed when the user performs the input setting by the input setting means the phase difference by the phase difference setting circuit 24 Input. The material detection circuit 25 detects the current value of the inverter by CT, and switches the capacitance of the heating coil to an appropriate number of turns and an appropriate frequency to the pan material.

First, at the start of operation, first to fourth coils ₂ , ₃ , ₄ , 5 and capacitors C ₁ , C ₂ , C ₃ , C ₄
Switches SW ₁ , SW ₂ , SW so that
₃ to 17b-17c, 17d-17e, 17f respectively
Switch to -17g connection. At this time, when the copper pot is placed, a normal inverter current flows, and the heating can be performed efficiently and the operation can be continued. Other pots (aluminum, iron,
(Stainless steel) has a small skin current and therefore low current. Thus, stopping the operation, it is necessary to reduce the number of turns of heating coil 1A, the second to fourth coils 3, 4, 5 and the capacitor C _1, C _2, C ₃ has a switch SW ₃ to be connected in series The connection is switched to be a 17f-17k connection. At this time, if an aluminum pot is placed, normal inverter current flows and heating can be performed efficiently to continue operation. Other pots (iron, stainless steel) have low skin current and therefore low current. Thus, stopping the operation, it is necessary to reduce the number of turns of heating coil 1A, third, the switch SW ₂ as the fourth coil 4, 5 and the capacitor C _1, C ₂ is connected in series to 17d-17j connected Switch so that At this time, if a stainless steel pan is placed, a normal inverter current flows and heating can be performed efficiently to continue the operation. At this time, since the iron pot has a larger skin resistance than stainless steel, the current is small. Therefore, it is necessary to stop the operation and reduce the number of turns of the heating coil 1A.
Switching of such coil 5 and the capacitor C ₁ is the switch SW ₁ to be connected in series 17b-17i connected. At this time, if an iron pot is placed, normal inverter current flows and heating can be performed efficiently to continue operation. As described above, any pot can be efficiently heated by using the number of turns of the heating coil that matches the pot material. FIG.
Shows the relationship between the space efficiency and the heating efficiency when the aluminum pan is heated, when the space factor is increased by integrating the heating coil 1A into one stage as described above. Space factor 40
%, The heating efficiency can be increased at a substantially constant value. When the space factor is about 40% or less, the heating efficiency is extremely deteriorated. This is because the coupling coefficient has become smaller.

FIGS. 4 and 5 show a second embodiment of the present invention. 4, the heating coil 1B is concentrically wound with a second coil 7 outside the first coil 6, a third coil 8 outside the second coil 7, and a fourth coil 9 outside the outside. Turned and configured. Each coil 6, 7, 8,
The diameter of the first coil 6 is 100 mm, the second coil 7 is 160 mm, the third coil 8 is 200 mm, and the fourth coil 9 is 220 mm. In order to heat the pan 20 efficiently, it is necessary to heat the pan 20 with a heating coil corresponding to the diameter of the pan 20. If the diameter of the aluminum pan is 220mm or more,
Using the fourth coil 9, a high-frequency current flows between the terminals 17a and 17b. Next, in the case of an aluminum pan having a diameter of 200 mm to 220 mm, the third coil 8 is used, and 17c and 17c are used.
A high-frequency current flows between d. In the case of an aluminum pan having a diameter of 160 mm to 200 mm, the second coil 7 is used,
The first coil 6 is used for an aluminum pan of mm or less. Especially,
In the case of an aluminum pan, if the distance between the heating coil 1 </ b> B and the pan 20 is large, the heating efficiency will be reduced. Pot 20
Flows through the middle portion between the inner diameter and the outer diameter of the shape of the heating coil. Therefore, if the pot diameter is large and the coil size is large, the path length of the current flow is long, the input resistance of the heating coil 1B is increased, and the efficiency is improved. That is, the input resistance Rin of the pan which is proportional to the input for heating the pan 20 is: Rin∝Rs · L (1) Rs: skin resistance, L; path length of current flowing through the pan,
The skin resistance Rs is as follows: Rs = √ (f · μr · ρ) (2) f; frequency, μr; relative magnetic permeability, ρ; If the loss of the heating coil is the same, the larger the input resistance Rin, the higher the heating efficiency. In particular, in the case of an aluminum or copper pan, it is necessary to increase both the number of turns and the frequency of the heating coil. With such a shape, the efficiency is greatly improved. on the other hand,
When heated by a heating coil having an inner diameter larger than the diameter of the aluminum / copper pot, the magnetic flux of the heating coil does not enter the pot due to the non-magnetic material, so that the efficiency is remarkably deteriorated.

Next, the circuit configuration and operation of the induction heating cooker will be described with reference to FIG. Nabe径detection circuit 26, the current value of the inverter is detected by CT, a suitable heating coil shape that matches the pot diameter, switches the switch SW _5. At this time, the coil is sequentially switched from a coil having a larger diameter to a coil having a smaller diameter. First, at the start of operation, switches to the fourth coil 9 and the capacitor C ₅ is a changeover switch SW ₅ to be connected in series to 17j-17a connected.
At this time, when an aluminum pan having a diameter of 220 mm or more is placed, a normal inverter current flows and heating can be performed efficiently to continue the operation. Pots smaller than this have low input resistance and high current because no magnetic flux enters the pot. Therefore, it is necessary to stop the operation and switch the heating coil 1B.
And switching to the capacitor C ₅ is a changeover switch SW ₅ to be connected in series to 17j-17c connected. At this time, if an aluminum pan having a diameter of 200 mm to 220 mm or more is placed, a normal inverter current flows and the operation can be continued with efficient heating. Pots smaller than this have low input resistance and large current because magnetic flux does not enter the pot effectively. Thus, stopping the operation, it is necessary to switch the heating coil 1B, the second coil 7 and 17j-17e changeover switch SW ₅ to the capacitor C ₅ is connected in series
Switch to connect. At this time, diameter 160mm
If a 200-mm aluminum pan is placed on it, normal inverter current flows and heating can be performed efficiently to continue operation. Pots smaller than this have low input resistance and large current because magnetic flux does not enter the pot effectively. Thus, stopping the operation, it is necessary to switch the heating coil 1B, the first coil 6 and the changeover switch S to the capacitor C ₅ is connected in series
Switch the W ₅ so that the 17j-17g connection. At this time, if an aluminum pan having a diameter of about 160 mm or less is placed, a normal inverter current flows and heating can be performed efficiently, and the operation continues. In this way, when heating using a heating coil of the size that matches the pot diameter, low-resistance, non-magnetic aluminum,
Even a copper pot can be efficiently heated. This method is also effective for iron and stainless steel.

FIG. 6 shows a third embodiment of the present invention. A low-resistance non-magnetic pot 20 made of aluminum, copper, or the like is heated by a heating coil 1C in which a first coil 10 (for example, 65T) and a second coil 11 (for example, 20T) are connected in series.
A high-resistance or magnetic pot 20 made of iron, stainless steel, or the like uses the outer second coil 11. At this time, the input resistance Rin for heating the iron or stainless steel pot is expressed by the above equation (1), and the skin resistance Rs is expressed by the above equation (2). Therefore, if the inverter frequency is the same, the input resistance Rin has a fixed value. When a high resistance or magnetic pot coil made of iron or stainless steel is wound outside, the path length of current flow becomes longer (FIG. 6B), and the input resistance Rin increases. Therefore,
Since the loss of only the heating coil 1C is constant, the efficiency is improved. Therefore, the iron and stainless steel heating uses the outer second coil 11.

FIG. 7 shows a fourth embodiment of the present invention. A low-resistance non-magnetic pot 20 made of aluminum, copper, or the like is heated by a heating coil 1D in which a first coil 12 (for example, 20T) and a second coil 13 (for example, 65T) are connected in series.
The iron or stainless steel high resistance or magnetic pot 20 uses the inner first coil 12. When heating the small-diameter pan 20 with iron or stainless steel, the diameter of the heating coil 1D is
If it is too large compared to 0, the magnetic flux does not enter the pot 20 effectively, and heating cannot be performed efficiently. When the small-diameter pot is heated by the first coil 12 wound inside, FIG.
As shown in (b), the magnetic flux is effectively linked to the pot 20 and the pot 20 can be efficiently heated.

A fifth embodiment of the present invention will be described with reference to FIG. The large-diameter pan 20 uses the second coil 13 and the small-diameter pan 20 has
Is used. The pot 20 allows efficient heating by changing the size of the heating coil.

FIG. 8 shows a sixth embodiment of the present invention. A low-resistance, non-magnetic pot 20 made of aluminum, copper, or the like is provided with a heating coil in which a first coil 14 (for example, 30T), a second coil 15 (for example, 20T), and a third coil 16 (for example, 35T) are connected in series. Heated at 1E, a high resistance or magnetic pot 20 of iron or stainless steel uses an intermediate second coil 15. Iron and stainless steel pans have lower thermal conductivity than aluminum and the like. Therefore, in the pan 20 having a standard size, the path of the current flowing through the bottom of the pan 20 may flow around the center between the center and the outer periphery of the pan 20 (FIG. 8B). Cooking performance is improved.

FIG. 9 shows a seventh embodiment of the present invention. A low-resistance, non-magnetic pot made of aluminum, copper, or the like includes a first coil 41 (for example, 10T) and a second coil 42 (for example, 6T).
5T) and a third coil 43 (for example, 10T) are heated by a heating coil 1G connected in series, and a high-resistance or magnetic pan made of iron or stainless steel connects the first coil 41 and the third coil 43 in series. Used. In a single-stage coil that can heat not only iron and stainless steel pots but also aluminum and copper pots, the number of coil turns is smaller when heating iron and stainless steel pots than when heating aluminum and copper pots. . Further, in the pan, the current flows through the heating coil in the upper portion where the current flows through the heating coil, and the pan generates heat. Therefore, when heating an iron or stainless steel pot, if induction heating is performed using a single coil, only that portion may generate heat and cause uneven heating. In particular, in the case of a hot cake or the like in which the object to be heated hardly moves during heating, the upper surface of the coil to which an electric current is applied is burned, but otherwise, there is a possibility that a problem of burning may occur. Therefore, by supplying a current to the inner first coil 41 and the outer third coil 43, it is possible to reduce the occurrence of uneven heating.

Next, the circuit configuration and operation of an induction heating cooker using a heating coil 1G according to a seventh embodiment will be described with reference to FIG. The material detection circuit 25 detects the current value of the inverter by CT, and sets the number of turns of the heating coil appropriate for the material of the pan and the capacitance of the capacitor so as to obtain an appropriate frequency suitable for the material of the pan, by means of the switch SW _6.
And by controlling the SW _7, it switches.

First, at the start of operation, the switches SW ₆ and SW ₇ are set to 17a so that the first to third coils 41, 42 and 43 and the capacitors C ₆ and C ₇ are connected in series.
The connection is switched so that the connection becomes -17b, 17d-17e. At this time, when a pot made of aluminum, copper, or the like is placed, a normal inverter current flows, the heater can be efficiently heated, and the operation continues. Other pots (iron, stainless steel) stop operating,
First, so that the third coil 41, 43 and the capacitor C ₇ and the switch SW ₆ in order to serially connected to 17a-17c connected and switched so that the switch SW ₇ to 17d-17f connected.

FIG. 11 is a modification of FIG. 10 in which one switch SW is used to switch the number of turns of the heating coil appropriate for the material of the pan and the capacitance of the capacitor so as to obtain an appropriate frequency suitable for the material of the pan. _This is the configuration realized in ₈ . That is, aluminum, when heating the pot such as copper, so as to switch SW ₈ becomes 17a-17b connected, iron, when heating the stainless steel pot, the switch SW ₈ 17
a-17c. According to this configuration, the cost can be reduced as compared with the configuration of FIG.

FIG. 12 shows an eighth embodiment of the present invention. A low-resistance non-magnetic pot such as aluminum or copper is heated by a heating coil 1H in which a first coil 51 (for example, 10T) and a second coil 52 (for example, 75T) are connected in series,
A high resistance or magnetic pot made of iron or stainless steel is used by connecting the first coil 51 and the third coil 53 (for example, 10T) in series. Thus, it is possible to reduce the occurrence of uneven heating as in the embodiment shown in FIG.

Next, the circuit configuration and operation of an induction heating cooker using a heating coil 1H according to an eighth embodiment will be described with reference to FIG. Material detection circuit 25, the current value of the inverter is detected by CT, the capacitance so that the appropriate frequency appropriate to the appropriate heating coil turns and pans material of which matches the material of the pot, controls the switch SW ₉ To switch.

Firstly, at the start of operation, switches to the first and second coils 51 and 52 and capacitor C _8, C ₉ is a switch SW ₉ so as to be connected in series 17a-17b connected. At this time, when a pot made of aluminum, copper, or the like is placed, a normal inverter current flows, the heater can be efficiently heated, and the operation continues. Other pan (iron, stainless steel) is stopped operation, first, switch SW ₉ to 17a-1 in order to the third coil 51, 53 and the capacitor C ₉ connected in series
Switch to 7c connection.

With such a circuit configuration, the switch
Requires only pieces, it is possible to reduce the cost, also aluminum, at the time of pot heating, such as copper, with the switching of the switch SW _9, a voltage of about 5kV outside the second coil 52 is generated, the coil The insulation process can be easily performed on the outside of the outside 52.

In the eighth embodiment, a low-resistance, non-magnetic pot made of aluminum, copper, or the like is used for the first coil 51.
(For example, 10T) and the second coil 52 (for example, 75T).
T) is heated by a heating coil 1H connected in series, and a high-resistance or magnetic pan made of iron or stainless steel is placed in the first coil and the third coil.
The coil 53 (for example, 10T) is used in series, but a low-resistance, non-magnetic pot such as aluminum or copper is used for the heating coil 1H in which the third coil 53 and the second coil 52 are connected in series. And a high-resistance or magnetic pot made of iron or stainless steel may be used by connecting the first coil 51 and the third coil 53 in series. This is because the width of the inner or outer coil used for heating an iron pot or the like is smaller in number of turns than the second coil 52, is about 1 cm, and the diameter of the entire coil is about 19 cm. This is because the influence of uneven heating is small without using either the inner or outer coil during heating. In this case, the circuit configuration shown in FIG.
And the connection position of the third coil 53 may be reversed.

FIG. 14 shows a ninth embodiment of the present invention. Heating coil 1 in aluminum and iron combined single-stage coil
Mold F. In order to heat a low-resistance, non-magnetic pot, it is necessary to increase the number of turns of the heating coil because the skin resistance of the pot is small, and the voltage of the heating coil increases. Therefore, it is necessary to arrange the shield conductor 30 on the top plate 18 and connect it to the low-voltage section. Therefore, it is necessary to perform epoxy molding between the coil and the shield to prevent dielectric breakdown. 31 is a ferrite.

FIGS. 15 to 17 show a tenth embodiment of the present invention. When performing epoxy molding, in the case of a one-stage heating coil, coil molding can be easily performed using an epoxy mold and integral molding can be performed. As shown in FIG. 15, the litz wire 32 of the heating coil is directly wound around the mold 33a capable of releasing the epoxy such as aluminum, the litz wire 32 is drawn out halfway, the first coil is made, and then the second coil is started to be wound. . This mold can be turned about a central axis. Next, as shown in FIG. 16A, it is set in a mold 33b into which an epoxy resin can be poured, and epoxy casting is performed.
At that time, the coil litz wire 32 is exposed on the upper surface of the coil, and there is a possibility that insulation breakdown may occur with the shielding conductor on the top plate. Therefore, as shown in FIG. 17, the coil is placed again in the mold 33c with the top open, and epoxy casting is performed. At this time, the ferrite 31 is bonded to the lower surface of the coil. If the litz wire 32a of the one-stage heating coil and the litz wire 32b at the beginning and end of the winding are exposed to the outside of the mold 33b by capillary action due to the capillary phenomenon, the part may be broken when moved. . Therefore, when the heat-shrinkable tube 34 is attached to the portion and the epoxy resin is heated to harden the epoxy, the heat-shrinkable tube 34 is shrunk to shrink the portion, thereby preventing the outflow of the epoxy. At this time, the litz wire 32
a, 32b by infiltrating the silicon 35 (FIG. 1).
6 (b)), it is possible to more reliably prevent the epoxy from flowing out.

[0041]

As described above, according to the first aspect of the present invention, the heating coil for inductively heating the object to be heated is constituted by a plurality of coils concentrically wound sequentially from the inside to the outside, Since the number of coils corresponding to the material of the object to be heated is selected and connectable among the plurality of coils, the input impedance can be maintained at an appropriate value even when the material of the object to be heated changes. Heating with high efficiency.

According to the second aspect of the present invention, the heating coil for inductively heating the object to be heated is constituted by a plurality of coils concentrically wound sequentially from the inside to the outside. Since the number of coils according to the size of the object to be heated is selected and connectable, when heating a large-diameter pot, etc., the path length of current flow becomes longer, and the input resistance of the heating coil increases, resulting in higher efficiency. Can be improved.

According to the third aspect of the present invention, the litz wire constituting the heating coil has a multi-stage twisted structure in which a twisted wire is further twisted, and a wire covered with an insulating layer in the litz wire. Is 40% or more of the volume of the entire heating coil, so that the space factor is large, sufficient electromagnetic coupling is obtained, and a substantially constant high heating efficiency can be achieved.

According to the present invention, the heating coil for inductively heating the object to be heated is constituted by the first coil and the second coil concentrically wound outside the first coil. ,
When the object to be heated has a low resistance and a low magnetic permeability, the first coil and the second coil are connected in series and used to provide a high resistance or / and a low resistance.
And when the magnetic permeability is high, the second coil is used. Therefore, when heating a high-resistance or high-permeability object such as iron or stainless steel, the length of a path through which a current flows becomes longer, resulting in heating. The input resistance of the coil increases, and the efficiency can be improved.

According to the fifth aspect of the present invention, the heating coil for inductively heating the object to be heated is constituted by the first coil and the second coil concentrically wound around the outside of the first coil. ,
When the object to be heated has low resistance and low magnetic permeability, the first coil and the second coil are connected in series, and when the object to be heated has high resistance and / or high magnetic permeability and a small diameter, Since the first coil is used, when heating a small-diameter object to be heated having high resistance or high magnetic permeability such as iron and stainless steel, the magnetic flux is effectively linked to the object to be heated to increase the efficiency. be able to.

According to the present invention, the heating coil for inductively heating the object to be heated is constituted by the first coil and the second coil concentrically wound outside the first coil. ,
When the diameter of the object to be heated is small, the first coil is used. When the diameter of the object to be heated is large, the second coil is used. Therefore, the magnetic flux effectively links to the object to be heated. And can be efficiently heated.

According to the seventh aspect of the present invention, the heating coil for inductively heating the object to be heated is provided with the first coil and the second coil concentrically wound around the outside of the first coil. And a third coil concentrically wound around the outside of the second coil. When the object to be heated has low resistance and low magnetic permeability, the first coil is used.
, The second coil and the third coil are connected in series, and when the resistance is high and / or the magnetic permeability is high, the second coil is used.
When heating a high-resistance or high-permeability and standard-sized object to be heated, the path of the current flowing through the bottom of the object to be heated is changed between the center and the outer periphery of the object to be heated. Around the middle, the temperature of the bottom of the object to be heated is made uniform, and heating can be performed efficiently.

According to the present invention, the heating coil for inductively heating the object to be heated is composed of the first coil and the second coil concentrically wound around the outside of the first coil. A third coil concentrically wound around the outside of the second coil, and when the resistance and / or the magnetic permeability are high, the first coil and the third coil are connected in series. Since the first coil or the third coil is used to heat the object to be heated having high resistance and / or high magnetic permeability, it is possible to reliably prevent the occurrence of uneven heating. .

According to the eleventh aspect of the present invention, since each coil constituting the heating coil is molded, the insulation of the heating coil can be improved without an insulating sheet, and the cost can be reduced.

According to the twelfth aspect of the present invention, since the litz wire constituting each of the coils is manufactured by directly winding it around a die for epoxy molding, it is easy to manufacture.

According to the thirteenth aspect of the present invention, since the heat shrinkable tube is previously placed on the connection terminal take-out portion of each coil from the molding die, the molding material is cast. Is prevented from flowing out, the breakage of the connection terminal extraction portion due to solidification of the molding material is prevented, the yield is improved, and the manufacturability can be improved.

According to the fourteenth aspect of the present invention, since the litz wire of the connection terminal take-out portion of each of the coils is filled with the heat-shrinkable tube after being filled with silicon, the molding material can be more reliably formed. The outflow is prevented, the breakage of the connection terminal take-out portion is eliminated, and the productivity can be further improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a heating coil part in a first embodiment of an induction heating cooker according to the present invention.

FIG. 2 is a circuit diagram of the first embodiment.

FIG. 3 is a characteristic diagram showing a relationship between a space factor and heating efficiency in the first embodiment.

FIG. 4 is a sectional view of a heating coil portion according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of the second embodiment.

FIG. 6 is a diagram illustrating a heating coil portion according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a heating coil portion according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating a heating coil portion according to a sixth embodiment of the present invention.

FIG. 9 is a sectional view of a heating coil part according to a seventh embodiment of the present invention.

FIG. 10 is a circuit diagram of the seventh embodiment.

FIG. 11 is another circuit diagram of the seventh embodiment.

FIG. 12 is a sectional view of a heating coil part according to an eighth embodiment of the present invention.

FIG. 13 is a circuit diagram of the eighth embodiment.

FIG. 14 is a sectional view of a heating coil portion according to a ninth embodiment of the present invention.

FIG. 15 is a view for explaining a step in which a litz wire is directly wound around a mold to perform coil forming in the tenth embodiment of the present invention.

FIG. 16 is a diagram illustrating a step of epoxy-molding a coil after molding in the tenth embodiment.

FIG. 17 is a diagram for explaining a step of performing epoxy casting again on the coil upper surface in the tenth embodiment.

[Explanation of symbols]

 1A-1H Heating coil 2-16 Coil 18 Top plate 20 Pot (heated object) 32 Litz wire 33a-33c Mold 34 Heat shrink tube 35 Silicon

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Teruo Kobuna 3-3-9, Shimbashi, Minato-ku, Tokyo Inside Toshiba Abu E Corporation (72) Inventor Shojiro Sato 3-chome, Shimbashi, Minato-ku, Tokyo No. 9 Toshiba Abu E Co., Ltd.

Claims (14)

[Claims] 1. A heating coil for induction heating a body to be heated,
It is constituted by a plurality of coils concentrically wound sequentially from the inside to the outside, and one or a plurality of coils corresponding to the material of the object to be heated are selected from among the plurality of coils. An induction heating cooker characterized by the following. 2. A heating coil for inductively heating an object to be heated,
It is constituted by a plurality of coils concentrically wound sequentially from the inside to the outside, and one or a plurality of coils according to the size of the object to be heated are selected from among the plurality of coils. An induction heating cooker characterized in that: 3. A litz wire constituting the heating coil,
The multi-strand structure in which the stranded wires are further twisted, and the volume of the wire covered with the insulating layer in the litz wire is 40% or more of the volume of the entire heating coil. Item 3. An induction heating cooker according to Item 1 or 2. 4. A heating coil for induction heating a body to be heated,
A first coil and a second coil concentrically wound around the outside of the first coil, and when the object to be heated has low resistance and low magnetic permeability, the first coil and the second coil An induction heating cooker characterized in that the coil is connected in series and the second coil is used when the resistance is high and / or the magnetic permeability is high. 5. A heating coil for inductively heating an object to be heated,
A first coil and a second coil concentrically wound around the outside of the first coil, and when the object to be heated has low resistance and low magnetic permeability, the first coil and the second coil An induction heating cooker, wherein the first coil is used when a coil is used in series and the object to be heated has high resistance and / or high magnetic permeability and a small diameter. . 6. A heating coil for induction heating a body to be heated,
A first coil and a second coil concentrically wound around the outside of the first coil, wherein the first coil is used when the diameter of the object to be heated is small, An induction heating cooker characterized in that when the diameter is large, the second coil is used. 7. A heating coil for inductively heating an object to be heated,
The heating target comprises a first coil, a second coil concentrically wound outside the first coil, and a third coil concentrically wound outside the second coil. Body has low resistance,
When the magnetic permeability is low, the first coil, the second coil and the third coil are connected in series, and when the magnetic resistance is high or / and the magnetic permeability is high, the second coil is used. An induction heating cooker characterized by being made. 8. A heating coil for inductively heating an object to be heated,
The heating target comprises a first coil, a second coil concentrically wound outside the first coil, and a third coil concentrically wound outside the second coil. Body has low resistance,
When the magnetic permeability is low, the first coil, the second coil, and the third coil are used in series, and when the magnetic resistance is high or / and the magnetic permeability is high, the first coil and the third coil are used. Characterized in that they are connected in series and used. 9. A heating coil for inductively heating an object to be heated,
The heating target comprises a first coil, a second coil concentrically wound outside the first coil, and a third coil concentrically wound outside the second coil. Body has low resistance,
When the magnetic permeability is low, the first coil and the second coil are connected in series, and when the resistance is high and / or the magnetic permeability is high, the first coil and the third coil are connected in series. An induction heating cooker characterized by being configured to be used. 10. A heating coil for inductively heating an object to be heated, a first coil, a second coil concentrically wound around the outside of the first coil, and a concentric coil outside the second coil. And when the object to be heated has a low resistance and a low magnetic permeability, the second coil and the third coil are connected in series to use a high resistance and / or a high resistance. An induction heating cooker characterized in that the first coil and the third coil are connected in series and used when the magnetic permeability is high. 11. The induction heating cooker according to claim 1, wherein each coil constituting the heating coil is molded. 12. A litz wire forming each of the coils,
The induction heating cooker according to claim 11, wherein the induction heating cooker is directly wound around a mold for epoxy molding and manufactured. 13. The molding material is cast by placing a heat-shrinkable tube on a connection terminal extraction portion of each coil from a molding die in advance.
2. The induction heating cooker according to 1. 14. The induction heating cooker according to claim 13, wherein the heat-shrinkable tube is covered after filling the litz wire of the connection terminal take-out portion of each coil with silicon.