JP2008293888A - Induction-heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker capable of more efficiently heating a heated cooking utensil formed of a material with low magnetic permeability. <P>SOLUTION: An induction heating element 21 and a heat-insulation insulator 23 are arranged in layers in this order from a top plate 3 side at a position corresponding to a loading part 4 at the underside of the top plate 3. The induction heating element 21 has slits extended in a direction crossing the winding direction of a heating coil 6, and a heating coil 8 are wound around so as not to cross the slits. When a high-frequency current is supplied to the heating coil 8, an induction current flows in the induction heating element 21 by magnetic flux generated at the heating coil 8, and indirectly heats the heated cooking utensil 10 by thermal conduction. On the other hand, when a high-frequency current is supplied to the heating coil 6, the induction current scarcely flows in the induction heating element 21 due to the action of the slits. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an induction heating cooker including an induction heating coil for heating a cooked object to be heated placed on a top plate that constitutes the upper surface of a cooker body.

  In induction heating cookers, pans made of materials with low magnetic permeability and high electrical conductivity, such as aluminum and copper, are less likely to absorb magnetic flux from heating coils (induction heating coils) than pans of magnetic materials such as iron. There is a problem of inefficiency. In addition, so-called pot floating tends to occur due to the interaction between the induced current flowing through the pot bottom and the magnetic flux. In order to solve such a problem, Patent Document 1 discloses an induction heating apparatus in which an annular aluminum plate having a slit is disposed between an aluminum pan and a heating coil.

According to this induction heating device, a part of the magnetic flux generated from the heating coil is linked to the aluminum plate before reaching the aluminum pan, and the induction series flows through the aluminum plate, thereby increasing the equivalent series resistance of the heating coil. To do. In addition, since the magnetic flux detoured from the periphery of the aluminum plate is linked to the aluminum pan and induction heating is performed, when heating the aluminum pan with the same power consumption, the current flowing through the heating coil can be reduced. As a result, the above-described pan floating can be suppressed.
Japanese Patent No. 3465712 (FIG. 1)

  In the induction heating device of Patent Document 1, when heating a pan having low skin resistance and high electrical conductivity such as an aluminum pan, the heating coil generates heat due to its own loss. In addition, the aluminum plate is also heated by induction heating in the same manner as the pan, so that the heating coil is heated by the aluminum plate to a higher temperature.

  In order to reduce such a temperature rise of the heating coil, for example, it is necessary to provide a heat insulating material between the aluminum plate and the heating coil and to have a structure in which cooling air flows between them. However, with such a structure, the gap between the heating coil and the pan that is the object of induction heating is 11 to 12 mm including the top plate (thickness 4 mm), which is larger than the gap 6 to 7 mm in a general induction heating cooker. About 5 mm larger. As a result, the magnetic flux generated from the heating coil is less likely to reach the aluminum pan where the magnetic flux is harder to reach than a magnetic pan such as iron, and the aluminum pan cannot be sufficiently heated.

  In addition, since pans with low skin resistance, such as aluminum and copper, have low resistance, a multi-stage winding structure in which the number of turns of the heating coil is increased to, for example, about three times, or a three-stage winding structure is flowed to the heating coil. It is also conceivable to increase the equivalent series resistance of the heating coil by increasing the frequency of the alternating current. However, in the former case, the gap between the aluminum pan and the heating coil is further increased, making it difficult for the magnetic flux to reach the pan. In the latter case, in the inverter circuit for supplying high-frequency current to the heating coil and the heating coil. Since the loss increases, the heating efficiency deteriorates.

  This invention is made | formed in view of the said situation, The objective is to provide the induction heating cooking appliance which can heat the to-be-heated cooking appliance comprised with the material of a low magnetic permeability more efficiently. .

The induction heating cooker of the present invention includes a cooker body,
A top plate that constitutes the upper surface of the cooker body, and on which the cooked utensils are placed,
A first induction heating coil, a second induction heating coil and an induction heating element provided below the top plate for heating the cooked utensil;
High-frequency current supply means for supplying a high-frequency current to the first and second induction heating coils;
Heating control means for controlling the heating of the cooked utensil by controlling the high-frequency current supply means according to the material of the cooked utensil;
The induction heating element is thermally connected to the top plate, and an induction current blocking unit that blocks an induction current generated in the induction heating element when a high frequency current is supplied to the first induction heating coil. Have
The second induction heating coil has an annular shape arranged so as not to cross the induction current interrupting portion of the induction heating element.

  If comprised in this way, if a high frequency current is supplied to a 1st induction heating coil by a high frequency current supply means, induction heating will be performed with respect to a to-be-heated cooking appliance. At this time, no induced current flows through the induction heating element due to the action of the induced current blocking unit. Further, when a high frequency current is supplied to the second induction heating coil by the high frequency current supply means, an induction current is generated in the induction heating element thermally connected to the top plate, and the induction heating element generates heat. Indirect heating by heat conduction is performed on the cooked utensil. And since a heating control means controls a high frequency current supply means according to the material of a to-be-heated cooking appliance, and controls induction heating or indirect heating with respect to a to-be-heated cooking appliance, it heats various kinds of to-be-heated cooking appliances It becomes possible.

  According to the present invention, the first induction heating coil or the second induction heating coil and the induction heating element are used to perform heating suitable for the material of the cooked utensil. In addition to cooking utensils, it is possible to efficiently heat cooked utensils made of various materials such as cooked utensils made of a material with low magnetic permeability.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a front sectional view of an induction heating cooker body. As for the cooking appliance main body 1, the outer shell is the main body case 2, and the top plate 3 comprises the top plate 3 by having the top plate 3 located above this. Inside the main body case 2, heating coils 6 and 7 for induction heating (corresponding to the first induction heating coil) and a heating coil for indirect heating are respectively provided below the mounting portions 4 and 5 of the top plate 3. 8, 9 (corresponding to the second induction heating coil) are disposed. By these, cooked utensils such as a pan placed on the placing portions 4 and 5 (shown with reference numeral 10 in FIG. 2) are heated.

  An operation panel 11 and an oven door 12 are provided on the front surface of the main body case 2, and the user can perform various operations related to heating of the cooked utensil 10 by the operation panel 11. Yes. An oven (not shown) continues behind the oven door 12 (inside the main body case 2). In the lower surface of the top plate 3, temperature detection units 13 and 14 (corresponding to temperature detection means) constituted by a thermistor or the like are provided, particularly at a position directly below the center of the placement units 4 and 5. The heating coils 6 and 8 and the heating coils 7 and 9 are supported by coil bases 15 and 16, and the coil bases 15 and 16 receive magnetic fluxes from the heating coils 6, 8 and 7, 9 as will be described later. Ferrites 17 and 18 for forming a magnetic path are arranged.

  On the lower surface side of the top plate 3, heating portions 19 and 20 are provided at portions corresponding to the placement portions 4 and 5. In the following description, the configuration of the portion corresponding to the mounting portion 4 will be described. However, the portion corresponding to the mounting portion 5 is also configured in the same manner. For those shown in 1, reference numerals are shown in parentheses.

  FIG. 2 shows an enlarged view of the mounting portion 4 in FIG. As shown in FIGS. 1 and 2, an induction heating element 21 (22) and a heat insulating insulator 23 (24) are arranged in this order from the top plate 3 side below the mounting portion 4 (5). The coil base 15 (16) is positioned below the layer. A heating coil 8 (9) wound in an annular plate shape is arranged on the upper surface of the coil base 15 (16), and a heating coil 6 (7) wound in an annular plate shape is arranged on the lower surface. Has been placed.

  The induction heating element 21 (22) and the heat insulating insulator 23 (24) are pressed against the top plate 3 by the coil base 15 (16) via a spacer (not shown), and the induction heating element 21 (22) is It arrange | positions so that it may closely_contact | adhere to the lower surface side of 3. The induction heating element 21 (22) is provided so as to cover the entire top surface of the heating coil 8 (9), and the gap between them is set to be 2 mm to 3 mm. A ferrite 17 (18) is disposed under the heating coil 6 (7) so as to cover the entire lower surface thereof. The heating unit 19 (20) is configured as described above.

  FIG. 3 shows a detailed configuration of a part of the heating unit 19. The induction heating element 21 is made of, for example, a nonmagnetic material such as nonmagnetic stainless steel (nonmagnetic SUS), carbon, or silicon nitride. The induction heating element 21 is provided with a slit 21b extending in a vertical direction (a direction intersecting a winding direction of a heating coil 6 to be described later) in FIG. 3 on an annular thin plate having a circular opening 21a at the center. Thereby, it has the structure which has the reverse C-shaped heat generating part 21c and the C-shaped heat generating part 21d which were made into the left-right symmetric shape. In the present embodiment, the slit 21b functions as an induced current blocking unit. The heat insulation insulator 23 is formed as an annular thin plate having a circular opening 23a at the center.

  The heating coil 6 is wound so as to avoid the opening 21a of the induction heating element 21, and the coil bundle is formed in an annular plate shape. On the other hand, the heating coil 8 includes a winding portion 8a wound from a position along the inner periphery of each of the heat generating portions 21c and 21d of the induction heating element 21 to an intermediate position between the peripheral portion and the peripheral portion. A winding portion 8b is provided. The ring formed by the coil bundle of the winding part 8a has an inverted C shape, and the ring formed by the coil bundle of the winding part 8b has a C shape. That is, the heating coil 8 has a shape that avoids (does not cross) the opening 21a and the slit 21b. In addition, the coil | winding part 8a and the coil | winding part 8b are electrically connected in series at each edge part (refer FIG. 4).

  When a high frequency current is supplied to the heating coil 8, the induction heating element 21 generates heat due to the induction current flowing due to the magnetic flux generated in the heating coil 8 (see the description of operation described later). Joule heat generated in the induction heating element 21 is conducted to the cooking utensil 10 via the top plate 3 disposed in close contact with the entire upper surface. In addition, by arranging the heat insulating insulator 23 in close contact with the entire lower surface of the induction heating element 21, the heating coils 6 and 8 are hardly heated by the Joule heat. The induction current in the induction heating element 21 flows to a position corresponding to the path through which the high-frequency current flows in the heating coil 8. For this reason, the path through which the induction current flows becomes long, and the equivalent resistance of the heating coil 8 in a state where the high-frequency current is supplied to the heating coil 8 increases.

  On the other hand, when a high frequency current is supplied to the heating coil 6, the induction heating element 21 hardly generates heat due to the action of the slit 21 b, and the induction heating element 21 hardly generates heat (see the explanation of the action described later).

  FIG. 4 is a functional block diagram showing the configuration of the control system. In addition, since the heating parts 19 and 20 are the same structures, the heating part 20 and the other structure corresponding to this are abbreviate | omitted in FIG. The induction heating control device 24 (corresponding to a heating control means and a material determination means) is provided inside the main body case 2 described above, and is configured mainly with a microcomputer. The induction heating control device 24 receives an operation signal from the operation unit 25 disposed on the operation panel 11 and a temperature detection signal from the temperature detection unit 13. This operation unit 25 has a clay pot selection switch 25b (corresponding to the operation means) used when heating a non-metal pot such as a heating power adjustment dial 25a or a clay pot described later (see FIG. 1).

  The induction heating control device 24 controls the operation of the display unit 26 arranged on the operation panel 11 and controls an inverter 27 (corresponding to high-frequency current supply means) based on these input signals and a previously stored control program. To control the heating of the cooking utensil 10 by supplying a high-frequency current to the heating coils 6 and 8. The inverter 27 is supplied with a drive power supply that is converted from a commercial AC power supply 28 into a direct current via a rectifier circuit 29. In the present embodiment, the frequency of the high-frequency current is about 25 kHz.

  The high-frequency current output from the inverter 27 is supplied to the heating coil 6 or 8 via the changeover switch 30 s of the relay 30. That is, a high-frequency current is supplied to the heating coil 6 when the contact c-a of the changeover switch 30s is turned on, and a high-frequency current is supplied to the heating coil 8 when the contact c-b is turned on. It has become. The induction heating control device 24 detects the material of the cooking utensil 10 to be heated, and controls the switching of the changeover switch 30s of the relay 30 according to the material.

  The terminals of the heating coils 6 and 8 opposite to the changeover switch 30 s are connected in common, and a resonance capacitor 31 is connected in series between this common connection point and the inverter 27. Thereby, the resonance circuit which comprises a part of inverter 27 by the heating coil 6 or 8, the resonant capacitor 31, and the to-be-heated cooking appliance 10 or the induction heating body 21 is comprised. In the heating coil 8 in this embodiment, the winding portion 8a and the winding portion 8b are connected in series. However, the winding portion 8a and the winding portion 8b are connected in parallel (the heating coil 6). Connected in parallel).

  A current transformer 32 is disposed on the input side of the rectifier circuit 29, and a current transformer 33 is disposed on the output side of the inverter 27, and these detection signals are given to the induction heating control device 24. When the induction heating control device 24 detects the material of the cooking utensil 10 to be heated, it turns on between the contacts ca of the changeover switch 30s of the relay 30, and the input current ip to the cooking utensil 10 to be heated and the output of the inverter 27 are turned on. The current (coil current) ic is detected.

Next, the operation of the present embodiment will be described with reference to FIGS.
First, the induced current flowing through the cooked appliance 10 and the induction heating element 21 will be described. When a high frequency current is supplied to the heating coil 6, a magnetic flux B1 is generated as shown in FIG. FIG. 5 schematically shows the state of the induced current flowing through the bottom portion (pan bottom) 10a of the cooking utensil 10 at this time and the induction heating element 21. Although the magnetic flux B1 passes through the induction heating element 21, the induction current does not flow through the induction heating element 21 as shown in FIG. Therefore, the induction heating element 21 is not induction heated. On the other hand, when the magnetic flux B1 passes through the cooked appliance 10 to be heated, an induction current I1 flows through the bottom 10a, and the cooked appliance 10 to be heated is induction-heated.

  On the other hand, when a high frequency current is supplied to the heating coil 8, a magnetic flux B2 is generated as shown in FIG. FIG. 6 schematically shows the state of the induced current flowing through the pan bottom 10a and the induction heating element 21 at this time. As the magnetic flux B2 passes through the heat generating portions 21c and 21d of the induction heating element 21, the induction current I2 flows through the heat generating portions 21c and 21d, respectively, as shown in FIG. The induced current I2 flows along the peripheral portion of the induction heating element 21, and flows along the opening 21a and the slit 21b. In this case, the magnetic flux B <b> 2 is canceled by the magnetic flux based on the induced current I <b> 2 flowing through the induction heating element 21, and thus does not reach the cooked utensil 10. Therefore, an induction current does not flow through the cooked utensil 10, and the cooked utensil 10 is not induction heated.

FIG. 7 is a flowchart showing the contents of control by the induction heating control device 24 for the portion according to the gist of the present invention. In addition, below, although the control content at the time of heating the to-be-heated cooking utensil 10 mounted in the mounting part 4 is demonstrated, it becomes the same control content also about the mounting part 5. FIG.
When the induction heating control device 24 reads the set value of the input power set by operating the heating power adjustment dial 25a (step S1), the induction heating control device 24 determines whether or not the earthenware pot selection switch 25b is turned on (step S2). If it is determined that the earthenware pot selection switch 25b is on (YES), the process proceeds to step S10 described later.

  On the other hand, if it is determined that the earthenware pot selection switch 25b is off (NO), the contact c-a of the changeover switch 30s of the relay 30 is turned on (step S3), and the material determination of the cooking utensil 10 is performed (step S4). ). In steps S5 and S7, it is determined whether or not the material is a high resistance metal material and whether or not the material is a low resistance metal material.

For example, in order to determine whether or not the material is a high resistance metal material such as iron or stainless steel (SUS), a high frequency current having a constant voltage and frequency is supplied to the heating coil 6 by the inverter 27, as shown in FIG. The determination is made based on the relationship between the input current ip and the coil current ic.
That is, when the material of the cooking utensil 10 is a magnetic material such as iron, the magnetic flux generated by the heating coil 6 easily passes through the cooking utensil 10 and is easily linked to the cooking utensil 10. As a result, the leakage magnetic flux is reduced, and the equivalent inductance L (see FIG. 8B) of the heating coil 6 is reduced. In addition, since the magnetic material has a large specific resistance and a skin effect (an effect of eddy current concentration on the top plate 3 side of the pan bottom), the equivalent resistance R of the heating coil 6 is increased.

  On the other hand, in the case of a nonmagnetic and low specific resistance material such as aluminum or copper, the magnetic flux generated in the heating coil 6 becomes difficult to pass through the cooked appliance 10 and the leakage flux increases, so the equivalent inductance L of the heating coil 6 is increased. Becomes larger. Since the specific resistance is small and the skin effect is small, the equivalent resistance R is also small. Further, in the case of a non-metal pan such as a clay pan or no load, since the induced current does not flow at all, the equivalent inductance L becomes the largest and the equivalent resistance R becomes the smallest.

The coil current ic is inversely proportional to the equivalent impedance Z of the heating coil 6, and the input current ip is proportional to the coil current ic and R / Z. As a result, a relationship as shown in FIG. That is,
Material Coil current ic Input current ip
Iron Small (R is large → Z is large) Large (R / Z is large)
Aluminum Large (R is small → Z is small) Small (R / Z is small)
Non-metal (earthen pot) Small (ωL is large → Z is large) Small (R / Z is small)
Therefore, the material of the cooked utensil 10 can be determined based on the magnitude relationship between the input current ip and the coil current ic.

  When it is determined in step S5 that the material is a high resistance metal material (YES), the induction heating control device 24 performs induction heating cooking using the input power set value read in step S1 as input power to the inverter 27 ( Step S6). That is, it is the usual induction heating cooking performed conventionally. In this case, as described above, the induced current hardly flows through the induction heating element 21. Therefore, most of the input power to the inverter 27 is consumed by the cooked appliance 10 to be heated.

On the other hand, when the material is not a high-resistance metal material (step S5, “NO”), the induction heating control device 24 is a non-magnetic metal material with a low resistance such as aluminum or copper, or a non-metal such as a clay pot. It is determined whether the pan (or no load) (step S7).
If it is a low resistance metal material (YES), the induction heating control device 24 turns on between the contacts c-b of the changeover switch 30s of the relay 30 (step S8). And the induction heating control apparatus 24 supplies a high frequency current to the heating coil 8 by making the input electric power setting value read by step S1 into the input electric power with respect to the inverter 27 (step S9). Then, the induction current I2 flows through the induction heating element 21 according to the magnetic flux B2 generated by the high-frequency current flowing through the heating coil 8, and the induction heating element 21 is induction-heated. The heat-generating induction heating element 21 indirectly heats the cooked utensil 10 made of aluminum or copper via the top plate 3 by heat conduction.
In this case, as described above, the magnetic flux B2 does not reach the cooked utensil 10. Therefore, most of the input power to the inverter 27 is consumed for heating by the induction heating element 21.

  If it is determined in step S7 that the material is not a low-resistance metal material (NO), or if it is determined in step S2 that the clay pot selection switch 25b is turned on (YES), the material is a non-metallic material. Other cases include no load. In this case, similarly to steps S8 and S9, the induction heating control device 24 turns on the contact c-b of the changeover switch 30s of the relay 30 (step S10), and heats the induction heating element 21 to indirectly generate heat. Heating is performed (step S11).

By the way, it is not possible to discriminate between a non-metallic material and no load from the relationship between the input current ip and the coil current ic described above. Therefore, the temperature detection unit 13 detects the temperature rise degree from the start of indirect heating in step S10 (step S12).
That is, as shown in FIG. 9, for example, when a clay pot or the like is placed on the placement portion 4 of the top plate 3, the heat capacity of the load is large, and therefore the degree of temperature rise (rise) from the start of heating is relatively moderate. become. On the other hand, when there is no load, since there is only the heat capacity of the top plate 3, the degree of temperature rise from the start of heating becomes relatively abrupt. Based on such a difference in temperature rise, non-metallic material and no load are determined (step S13).

  When the induction heating control device 24 determines that there is no load (“YES” in step S13), it stops indirect heating (step S14) and determines that the material is a non-metallic material (“NO” in step S13). Returning to step S1 as it is, indirect heating by the induction heating element 21 is continued.

As described above, according to the present embodiment, the following effects can be obtained.
When the induction heating cooker heats a pan having a large skin resistance, which is made of a magnetic metal, induction heating is performed by the heating coil 6, and a pan or nonmetal having a low skin resistance, which is made of a nonmagnetic metal. In the case of heating the made pot, indirect heating is performed by the heat generation of the induction heating element 21. Accordingly, it is possible to heat pans made of various materials such as metal pans such as iron, stainless steel (SUS), aluminum, and copper, and non-metal pans such as earthen pans and glass pans.

  When heating a pan having a small skin resistance such as an aluminum pan, the induction heating element 21 is induction-heated by the magnetic flux B2 generated by the heating coil 8, and the aluminum pan is indirectly heated by the heat generation. Since the induction heating is not directly performed on the pan having a low skin resistance such as an aluminum pan, the pan does not float due to the interaction between the induced current flowing through the bottom of the pan and the magnetic flux. Therefore, the cooking power is not changed by the pan, and good cooking performance can be obtained, and safe and efficient heating can be performed.

  Since the induction heating element 21 is arranged close to the heating coil 8 and the path of the induction current flowing through the induction heating element 21 is lengthened, the equivalent series resistance of the heating coil 8 in a state where a high frequency current is supplied to the heating coil 8. Becomes larger. For this reason, the number of turns of the heating coil 8 can be reduced, the loss in the heating coil 8 is reduced, and the efficiency when heating the aluminum pan can be further increased. Moreover, the heating coil 6 is used when heating the pot with a large skin resistance comprised with the magnetic body metal as above-mentioned. Therefore, the equivalent series resistance of the heating coil 6 in a state where a high-frequency current is supplied to the heating coil 6 also increases. For this reason, the heating coil 6 can reduce the number of turns, like the heating coil 8.

  And by reducing the number of turns of the heating coils 6 and 8, the resonance voltage in the inverter 27 can be lowered to about 1/5. Therefore, the leakage current that occurs due to the stray capacity between the heating coils 6 and 8 and the cooked appliance 10 to be heated and the human body touches the pan can reduce the leakage current that flows to the ground via the human body, further improving safety. It is done. Further, an electrostatic shield for reducing leakage current is not necessary, and the number of parts can be reduced.

  Further, by increasing the equivalent series resistance of the heating coils 6 and 8, the oscillation frequency in the inverter 27 can be lowered to about 25 kHz. Accordingly, even when a non-magnetic metal pan such as an aluminum pan is heated, the loss of the semiconductor switching elements such as IGBTs and the heating coils 6 and 8 constituting the inverter 27 can be greatly reduced.

  Furthermore, the gap between the induction heating element 21 and the heating coil 8 was set to 2 to 3 mm, and the induction heating element 21 was disposed so as to cover the entire upper surface of the heating coil 8. For this reason, when indirectly heating an aluminum pan, a copper pan, or the like, the leakage magnetic flux when induction heating the induction heating element 21 by the magnetic flux generated by the heating coil 8 becomes very small. In addition, since the amount of magnetic flux generated is reduced by reducing the number of turns of the heating coil 8, an induction heating cooker with less leakage of electromagnetic waves can be configured.

  In order to reduce the loss due to the skin effect, the conventional heating coil uses a litz wire in which 1000 to 2000 fine wires having a diameter of about 50 μm are twisted, and further a litz wire to withstand the withstand voltage between the windings of the heating coil due to the resonance voltage. Was insulated with a Teflon (registered trademark) tube. On the other hand, in the present embodiment, the diameter of the heating coils 6 and 8 can be reduced to about 300 μm by reducing the oscillation frequency and the resonance voltage in the inverter 27, and the number of twisted litz wires is also 1/36 of the conventional one. Can be about. Furthermore, the insulation between the litz wires can be eliminated.

  By using the above-described configuration, the heating efficiency in heating a pan having a low skin resistance, such as an aluminum pan or a copper pan, is greatly improved as compared to the conventional one, and the reliability is also improved. If an example is shown regarding this heating efficiency, if the heating efficiency by the conventional structure was 60%, in this embodiment, it can improve to about 70%.

  When a high frequency current is supplied to the heating coil 6, the magnetic flux B <b> 1 generated thereby passes through the cooking utensil 10, whereby an induction current I <b> 1 flows through the bottom 10 a, and the cooking utensil 10 is induction heated. At this time, the magnetic flux B1 passes through the induction heating element 21, but since the conduction path of the induction current is blocked by the slit 21b, the induction current hardly flows through the induction heating element 21. Accordingly, when heating a high-resistance magnetic metal pan such as iron or stainless steel, most of the electric power of the heating coil 6 is consumed in the pan, and the heating efficiency is improved.

  The induction heating control device 24 turns on the contact c-a of the changeover switch 30s of the relay 30, supplies a high frequency current to the heating coil 6, and detects the input current ip and the coil current ic, whereby the top plate 3 The cooking utensil 10 to be heated is a pan with a large skin resistance made of a magnetic metal such as iron or stainless steel, or a pan with a low skin resistance made of a non-magnetic metal such as aluminum or copper. Is determined. Therefore, when the metal cookware 10 is heated, it is automatically determined whether the material is a magnetic metal or a non-magnetic metal, and the optimum and efficient heating according to the material is performed. It can be carried out. Furthermore, when this material detection is performed, that is, when a high-frequency current is supplied to the heating coil 6, almost no induced current flows through the induction heating element 21 as described above, so that it is possible to detect the material with high accuracy.

  A clay pot selection switch 25b is provided on the operation panel 11, and the clay pot selection switch 25b is turned on to perform indirect heating by heat generation of the induction heating element 21. Therefore, non-metallic pots such as earthen pots and glass pots that cannot be directly induction heated can also be heated.

  Moreover, the induction heating control apparatus 24 performs indirect heating by heat_generation | fever of the induction heating element 21, when it is judged that the to-be-heated cooking appliance 10 mounted in the top plate 3 is not metal. And the temperature rise degree (rise) is detected based on the detected temperature from the temperature detection part 13, and when this temperature rise degree is comparatively moderate, it judges that the non-metallic pan is mounted and is indirect. Continue heating. On the other hand, if the temperature rise is relatively rapid, it is determined that there is no load, and indirect heating is stopped. Accordingly, it is possible to detect a no-load state that could not be detected by the conventional material detection method using the equivalent impedance of the heating coil 6, and when the cooking utensil 10 to be heated is not placed on the top plate 3, the induction heating element is immediately generated. The indirect heating by the heat generation of 21 can be stopped, and wasteful power consumption can be eliminated.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 10 and 11.
FIGS. 10 and 11 are diagrams corresponding to FIGS. 2 and 3 in the first embodiment. The same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, different parts will be described. .
The heating unit 41 shown in FIGS. 10 and 11 is different from the heating unit 19 shown in FIGS. 2 and 3 in that the heating coil 6 and the heating coil 8 are disposed and that a ferrite 42 is provided instead of the ferrite 17. Is different. That is, the heating coil 6 is disposed on the upper surface of the coil base 15, and the heating coil 8 is disposed on the lower surface. And the ferrite 42 which makes | forms the shape which covers the whole lower surface is arrange | positioned under this heating coil 8. FIG.

  As in the above configuration, when the heating coils 6 and 8 are disposed in the opposite positions with respect to the first embodiment, the gap between the heating coil 8 and the induction heating element 21 is slightly larger than that of the first embodiment. However, since it is sufficiently smaller than the gap between the heating coil and the pan that is the induction heating target in the prior art, the same operations and effects as in the first embodiment can be obtained. Moreover, according to the said structure, since the gap of the heating coil 6 and the to-be-heated cooking appliance 10 becomes a little smaller than 1st Embodiment, when heating high resistance magnetic metal pans, such as iron and stainless steel, Since the magnetic flux from the heating coil 6 can easily reach the cooking utensil 10 to be heated, the heating efficiency is improved.

(Third embodiment)
FIG. 12 is a partial configuration diagram of a heating unit showing a third embodiment of the present invention.
The heating unit 51 shown in FIG. 12 is different from the heating unit 19 shown in FIG. 3 in that an induction heating element 52 is provided instead of the induction heating element 21, and a heating coil 53 (second However, the other components are the same, and are given the same reference numerals as in FIG.

  The induction heating element 52 is formed in an annular thin plate having a circular opening 52a at the center similar to the induction heating element 21, and a slit 52b (induction current) extending from the upper center of the induction heating element 52 to the opening 52a. Is provided in an annular shape with the central upper part opened. The heating coil 53 is configured to be wound from a position along the inner periphery of the induction heating element 52 to an intermediate position between the peripheral portion and the peripheral portion. That is, the heating coil 53 has a shape that avoids (does not cross) the opening 52a and the slit 52b. Even with such a configuration, the same operations and effects as the first embodiment can be obtained.

(Fourth embodiment)
FIG. 13 is a partial configuration diagram of a heating unit showing a fourth embodiment of the present invention.
13 is different from the heating unit 51 shown in FIG. 12 in that an induction heating element 52 is provided instead of the induction heating element 52, and a heating coil 63 (second second) is used instead of the heating coil 53. However, the other components are the same, and the same reference numerals as those in FIG. 12 are given.

  The induction heating element 62 is provided with a slit 62b (corresponding to an induction current blocking part) extending from the upper center of the induction heating element 62 to the opening 62a in an annular thin plate having a circular opening 62a at the center. By doing so, it is formed in an annular shape with the central upper part opened. However, the slit 62b has a shape that expands in an arc shape toward the upper end portion and the lower end portion. For this reason, the open end at the upper center of the induction heating element 62 has a rounded shape. The heating coil 63 has three winding portions 63 a to 63 c wound from a position along the inner periphery of the induction heating element 62 to an intermediate position between the peripheral portion and the peripheral portion. The winding portions 63a to 63c have a shape that avoids (does not cross) the opening 62a and the slit 62b. Even with such a configuration, the same operations and effects as the first embodiment can be obtained.

(Fifth embodiment)
FIG. 14 is a partial configuration diagram of a heating unit showing a fifth embodiment of the present invention.
The heating unit 71 shown in FIG. 14 differs from the heating unit 19 shown in FIG. 3 in that an induction heating element 72 is provided instead of the induction heating element 21 and the shape of the second induction heating coil is different. However, the other components are the same, and are given the same reference numerals as in FIG. The induction heating element 72 is formed as an annular thin plate having a circular opening 72a at the center. In addition, the induction heating element 72 is provided with slits 72b to 72e (corresponding to the induction current blocking section) extending from the upper, lower, left and right peripheral portions toward the central opening 72a, thereby generating the heating portions 72f to 72f. 72i.

  Thin portions are present at the ends of the slits 72b to 72e, and the heat generating portions 72f to 72i are integrally formed. Although not shown, the second induction heating coil in the present embodiment is wound from a position along the inner periphery of each of the heat generating portions 72f to 72i to an intermediate position between the peripheral portion and the peripheral portion. One having four winding portions is used. That is, the second induction heating coil used in this embodiment has a shape that avoids (does not cross) the opening 72a and the slits 72b to 72e in the induction heating element 72. Even with such a configuration, the same operations and effects as the first embodiment can be obtained.

(Other embodiments)
The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following modifications or expansions are possible.
The shape of the induced current blocking part in the induction heating element may be any shape that can block the induced current. In addition, the shape of the second induction heating coil may be an annular shape that is arranged so as not to cross the induction current blocking portion of the induction heating element. That is, these shapes are not limited to those disclosed in each of the above-described embodiments, and may be appropriately changed according to individual designs as long as they are within a range satisfying the above conditions.

The material of the cooked utensil 10 is not limited to the one that the induction heating cooker automatically discriminates. For example, the user may input and set the material. Moreover, what is necessary is just to provide the earthenware pot selection switch 25b as needed.
In the above embodiment, the relay 30 is used to switch the supply of high-frequency current from the inverter 27 to the first induction heating coil and the second induction heating coil. However, the first and second induction heating coils A dedicated inverter may be provided for each, and the induction heating control device 24 may control these two inverters to control energization to the first and second induction heating coils.

Front sectional drawing of the induction heating cooker main body which shows the 1st Embodiment of this invention FIG. 1 is an enlarged view of one mounting portion side. The figure which shows the partial composition of the heating section Functional block diagram showing the configuration of the control system The figure which shows typically the state of the induction current when it supplies with electricity to the 1st induction heating coil. The figure which shows typically the state of the induction current when supplying with electricity to the 2nd induction heating coil The flowchart which shows the control content by the induction heating control apparatus about the part which concerns on the summary of this invention (A) is a figure which shows the relationship between the input current ip according to the material of a to-be-heated cooking appliance, and the coil current ic, (b) is an equivalent circuit schematic of an induction heating coil The figure explaining the difference in the temperature rise degree from a heating start in the case where a to-be-heated cooking utensil is a nonmetallic material, and the case of no load. FIG. 2 equivalent view showing the second embodiment of the present invention 3 equivalent figure FIG. 3 equivalent view showing a third embodiment of the present invention FIG. 12 equivalent diagram showing a fourth embodiment of the present invention FIG. 3 equivalent view showing the fifth embodiment of the present invention

Explanation of symbols

  In the drawings, 1 is a cooker body, 3 is a top plate, 6 and 7 are heating coils (first induction heating coils), 8, 9, 53 and 63 are heating coils (second induction heating coils), 10 is Cooked utensils, 13 and 14 are temperature detection units (corresponding to temperature detection means), 21, 22, 52, 62 and 72 are induction heating elements, 21b, 52b, 62b and 72b to 72e are slits (induction current blocking units). ), 24 is an induction heating control device (heating control means, material judgment means), 25b is a clay pot selection switch (operation means), and 27 is an inverter (high frequency current supply means).

Claims (6)

The cooker body,
A top plate that constitutes the upper surface of the cooker body, and on which the cooked utensils are placed,
A first induction heating coil, a second induction heating coil and an induction heating element provided below the top plate for heating the cooked utensil;
High-frequency current supply means for supplying a high-frequency current to the first and second induction heating coils;
Heating control means for controlling the heating of the cooked utensil by controlling the high-frequency current supply means according to the material of the cooked utensil;
The induction heating element is thermally connected to the top plate, and an induction current blocking unit that blocks an induction current generated in the induction heating element when a high frequency current is supplied to the first induction heating coil. Have
The induction heating cooker characterized in that the second induction heating coil has an annular shape arranged so as not to cross the induction current blocking portion of the induction heating element. The induction current interrupter provided in the induction heating element extends in a direction intersecting with the winding direction of the first induction heating coil,
The induction heating cooker according to claim 1, wherein the second induction heating coil is wound so that a high-frequency current flows along the induction current cut-off portion. The heating control means
A material determining means for detecting the input impedance of the first induction heating coil and determining the material of the cooked utensil based on the input impedance;
When the material determining means determines that the material of the cooked utensil is a high resistance metal, the first induction heating coil is energized, and when it is determined that the material is a low resistance metal, the second The induction heating cooker according to claim 1 or 2, wherein the high-frequency current supply means is controlled so as to energize the induction heating coil. The heating control means
Comprising a material judgment means capable of judging whether or not the material of the cooked utensil is non-metallic,
The high-frequency current supply means is controlled so as to energize the second induction heating coil when the material judging means judges that the material of the cooked utensil is non-metallic. The induction heating cooking appliance in any one of thru | or 3. Temperature detecting means for detecting the temperature of the cooked utensils,
The material determining means is based on the degree of increase in temperature detected by the temperature detecting means, the material of the cooked utensil is non-metallic, or is in an unloaded state where there is no cooked utensil. The induction heating cooker according to claim 4, wherein the induction heating cooker is determined. Comprising an operation means for selectively performing heating of the non-metallic cooked utensil;
The heating control means controls the high-frequency current supply means so as to energize the second induction heating coil when heating of the non-metal heated cooking utensil is selected by the operation means. The induction heating cooker according to any one of claims 1 to 5.

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