JP2024086581A - Induction Cooker - Google Patents

Abstract

By suppressing positional deviation of a sensor coil relative to a heating coil, it is possible to improve the accuracy of detecting the position of an object to be heated while reducing the number of parts.
[Solution] An induction heating cooker 100 that inductively heats an object to be heated placed on a top plate 1, and is equipped with a sheet-shaped heating coil 2 for heating the object to be heated, which is provided on a substrate B arranged on the back side of the top plate 1, and a sensor coil 3 that is provided integrally with the heating coil 2 and for detecting the position of the object to be heated.
[Selected figure] Figure 4

Description

The present invention relates to an induction heating cooker that inductively heats a heated object such as a pot.

As shown in Patent Document 1, a conventional induction heating cooker uses a coil of litz wire as a heating coil for heating an object to be heated.

Recently, induction cookers have been developed that allow the food to be heated to be placed anywhere on the top plate (hereafter referred to as "Any Place cookers").

In addition to the heating coil described above, this Any Place cooker also has a sensor coil for detecting the position of the object to be heated.

However, in the induction heating cooker shown in Patent Document 1, the heating coil and the sensor coil are separate structures, and the position of the sensor coil is prone to misalignment with respect to the heating coil, making it impossible to detect, for example, slight differences in the eddy currents flowing in the heated object or the precise position of the heated object.

As a result, problems arise such as poor accuracy in detecting the position of the heated object and an increase in the number of sensor coils required to ensure accuracy in detecting the position.

Furthermore, as shown in Patent Document 1, if a litz wire is used as a heating coil, a member is required to maintain the litz wire in a coil shape, increasing the number of parts.

Furthermore, in Patent Document 1, the heating coil is provided on a flexible substrate, but the component cost of the flexible substrate itself is high, and since it must be configured as a separate component from the heating coil, there is also the problem that the reliability of the heating coil itself cannot be guaranteed.

Patent Application No. 2016-77445

The present invention was developed to solve all of the above problems at once, and aims to reduce the number of parts while improving the accuracy of detecting the position of the heated object by suppressing the misalignment of the sensor coil relative to the heating coil.

That is, the induction heating cooker of the present invention is an induction heating cooker that inductively heats an object to be heated placed on a top plate, and is characterized by having a sheet-shaped heating coil that is provided on a substrate arranged on the back side of the top plate and heats the object to be heated, and a sensor coil that is provided integrally with the heating coil and detects the position of the object to be heated.

In an induction heating cooker configured in this manner, the heating coil and the sensor coil are integrally provided, which makes it possible to prevent the sensor coil from misaligning with the heating coil. Furthermore, because a sheet-shaped heating coil is used, the number of parts can be reduced compared to conventional configurations that use Litz wire.

It is preferable that at least two of the sensor coils are provided for one of the heating coils, and the two sensor coils are arranged diagonally across the center of the heating coil.
With this configuration, it is possible to realize high accuracy in detecting the position of the heated object using as few sensor coils as possible.

At least two heating coils are disposed on the substrate, and the distance between the two heating coils is preferably narrower than half the outer diameter of the heating coils.
With this configuration, it is possible to ensure heating efficiency while suppressing the effect of the heating coil on the sensor coil.

It is preferable that the substrate has two or more heating coil layers insulated from each other and provided with the heating coil, a sensor layer in which the sensor coil is provided, and an insulating layer interposed between the heating coil layer and the sensor layer, and that, of the two or more heating coil layers, the heating coil layer connected to the resonant capacitor is positioned farther from the sensor layer than the other heating coil layers.
With this configuration, the heating coil layer closer to the sensor layer can be designed to withstand low voltage, and the insulating layer can be designed to be thin.

It is preferable that the device further comprises a temperature sensor provided integrally with the heating coil and the sensor coil.
With this configuration, since the temperature sensor is integrally provided with the heating coil and the sensor coil, it is possible to reduce product costs by reducing wiring, etc.

It is preferable that the temperature sensor is disposed at or near the center of the heating coil, or near a connector to which the heating coil is connected.
With this configuration, the temperature sensor is located at the location where the temperature is most likely to become high, making it possible to detect the temperatures of the heating coil and the connecting connector themselves, and thus enabling the heating coil to be controlled with high reliability.

It is preferable that a connector to be connected to another control board is mounted on the board, and that the connector is mounted in a reverse orientation with respect to the top plate.
With this configuration, the distance between the object to be heated and the heating coil is narrower than in a configuration in which the connecting connector is mounted facing the top plate, so the object to be heated can be heated more efficiently.

When the sensor coil is placed on the heating coil, an induced voltage is generated in the sensor coil when the heating coil is driven. This induced voltage may destroy the drive circuit connected to the sensor coil. Therefore, it is desirable that the induction heating cooker of the present invention is provided with a protection circuit between the sensor coil and the drive circuit connected to the sensor coil, which protects the drive circuit from the induced voltage generated in the sensor coil.

The output value of the sensor coil changes depending on the ambient temperature. Specifically, the output value of the sensor coil changes as the resistance value of the sensor coil changes depending on the ambient temperature. For example, as the ambient temperature rises, the output value of the sensor coil decreases. If this happens, the value will drop to the same state as "no pot" during heating, resulting in a false detection of "no pot" and stopping heating. For this reason, it is desirable for the induction heating cooker of the present invention to correct the output value of the sensor coil using the temperature detected by the temperature sensor.

When the heating coil is not driven, no resonant circuit is formed in the heating coil, so the sensor coil is less susceptible to the influence of the heating coil. On the other hand, when the heating coil is driven, a resonant circuit is formed in the heating coil, so that the magnetic flux generated in the sensor coil near the heating coil is absorbed by the heating coil. As a result, the accuracy of detecting the position of the heated object may deteriorate. Therefore, it is desirable for the induction heating cooker of the present invention to correct the change in the output value of the sensor coil caused by the magnetic flux absorption of the heating coil when the heating coil starts to be driven.

The present invention, configured in this way, can reduce the number of parts while improving the accuracy of detecting the position of the heated object by suppressing the positional deviation of the sensor coil relative to the heating coil.

1 is a schematic diagram showing an overall configuration of an induction heating cooker according to an embodiment of the present invention; FIG. 2 is a schematic diagram showing the configuration of a position detection sensor according to the embodiment; FIG. 2 is a schematic diagram showing a substrate of the induction heating cooker according to the embodiment. FIG. 2 is a schematic diagram showing a substrate of the induction heating cooker according to the embodiment. FIG. 2 is a functional block diagram showing functions of a control device according to the embodiment. FIG. 2 is a diagram for explaining the arrangement of sensor coils in the embodiment; FIG. 2 is a schematic diagram showing the arrangement of sensor coils in the embodiment; 6A and 6B are diagrams showing the results of calculating eddy current loss for different arrangements of the sensor coil in the embodiment; FIG. 2 is a schematic diagram showing the arrangement of sensor coils in the embodiment; FIG. 13 is a schematic diagram for explaining the configuration of a substrate when a conventional Litz wire is used. FIG. 4 is a schematic diagram showing the configuration of a substrate when the heating coil of the embodiment is used. FIG. 13 is a circuit diagram showing the configuration of a sensor coil, a drive circuit, an MUX, and a protection circuit according to a modified embodiment. 3A to 3C are diagrams illustrating the operation states of a protection circuit section; 13A and 13B are diagrams showing count values without temperature compensation in a modified embodiment; 13A shows count values when magnetic flux absorption is not corrected, and FIG. 13B shows count values when magnetic flux absorption is corrected, in a modified embodiment.

Below, one embodiment of the induction heating cooker according to the present invention will be described with reference to the drawings.

The induction heating cooker according to this embodiment inductively heats an object to be heated, such as a cooking pot or other cooking utensil, placed on a top plate, and is configured so that the object to be heated can be placed anywhere on the top plate and heated.

Specifically, as shown in FIG. 1, the induction heating cooker 100 includes a top plate 1 on which an object to be heated is placed, a plurality of heating coils 2 for heating the object to be heated, a sensor coil 3 for detecting the position of the object to be heated, an inverter circuit 4 for supplying an alternating current to the heating coils 2, and a control device 5 for controlling the inverter circuit 4.

The top plate 1 has a flat surface on which an object to be heated is placed, and is a flat plate made of an electrically insulating material such as glass or ceramic.

The heating coil 2 is provided on the back side of the top plate 1, and as shown in FIG. 1, multiple heating coils 2 are arranged in a two-dimensional array (vertical and horizontal matrix) in a plan view.

More specifically, as shown in FIG. 1, a pair of heating coils 2 is provided on a common substrate B arranged on the back side of a top plate 1, and this substrate B is laid out so as to form a two-dimensional array (vertical and horizontal matrix) in a plan view.

Each heating coil 2 is in the form of a sheet provided on a substrate B, specifically formed as a printed circuit board made of photoresist or the like. Here, two heating coils 2 are provided on one substrate B, and the distance between those heating coils 2 is narrower than half the outer diameter dimension of each heating coil 2 (specifically, for example, the maximum or minimum value of the outer dimension). Here, each of the multiple heating coils 2 has the same shape and size, but the shape and size may be changed as appropriate.

The sensor coil 3 is provided on the back side of the top plate 1, and is specifically an inductive proximity coil provided on the substrate B described above.

This sensor coil 3 is used to detect the position of the heated object placed on the top plate 1, and as shown in Figure 2, it constitutes a position detection sensor 30 together with a resonance capacitor 31, an oscillation amplifier 32, an oscillation frequency detection circuit 33, and a control unit 34.

Here, as shown in Figures 3 and 4, the above-mentioned substrate B has a heating coil layer B1 in which a heating coil 2 is provided, and a sensor layer B2 in which a sensor coil 3 is provided, and these layers are laminated and integrated with an insulating layer B3 interposed therebetween.

With this configuration, the heating coil 2 and the sensor coil 3 are integrally provided, and the sensor coil 3 is positioned relative to the heating coil 2. In other words, the relative positional relationship between the heating coil 2 and the sensor coil 3 is the same for each of the multiple substrates B that are laid out.

Here, as shown in FIG. 3, the sensor layer B2 is located on the top plate 1 side, and the heating coil layer B1 is stacked so that it is located on the opposite side of the top plate 1 from the sensor layer B2.

More specifically, as shown in Figures 3 and 4, the heating coil layer B1 is equipped with a connector CN that is connected to the control board 6, and this connector CN is mounted in the opposite direction to the top plate 1.

Furthermore, as shown in Figures 1, 3, and 4, the induction heating cooker 100 of this embodiment is equipped with a temperature sensor T provided on the substrate B or between adjacent substrates B, so that the temperature of the object to be heated and the heating coil 2 can be detected.

The temperature sensor T here is integral with the heating coil 2 and the sensor coil 3, and is located at or near the center of the heating coil 2, or near the above-mentioned connector CN for connecting the heating coil 2 to the control board 6.

The inverter circuit 4 converts the AC voltage supplied from the power source into an arbitrary drive frequency and outputs it to the heating coil 2. The inverter circuit 4 here is of a half-bridge type using switching elements, but a full-bridge type may also be used.

The control device 5 physically comprises a CPU, memory, input means, etc., and functionally performs the functions of a position detection unit 51 and an inverter control unit 52 as shown in FIG. 5 by the CPU and its peripheral devices working together in accordance with the program stored in the memory.

The position detection unit 51 detects the position of the object to be heated based on the output value of the position detection sensor 30 described above, and detects the position and size of the object to be heated placed on the top plate 1.

Here, the position detection sensor 30 of this embodiment outputs the inductance value of the sensor coil 3, and this inductance value varies depending on whether or not a heated object is located above the sensor coil 3.

More specifically, the inductance value output from the position detection sensor 30 is a value that varies depending on the distance from the heated object to the sensor coil 3. For example, when a heated object located far away from the sensor coil 3 is brought closer to the sensor coil 3, the inductance value decreases.

Therefore, the position detection unit 51 compares the inductance value output from the position detection sensor 30 with a preset threshold value to detect the position and size of the heated object.

Specifically, the position detection unit 51 determines that the object to be heated is located above a sensor coil 3 with an inductance value lower than the threshold value, and outputs the area above the sensor coil 3 as the detected position where the object to be heated is placed.

The inverter control unit 52 calculates the actual power, which is the actual power supplied from the power source, and controls the above-mentioned drive frequency so that the actual power approaches the target power corresponding to the heating power set by the user. However, the inverter control unit 52 may also control the on/off duty ratio of the above-mentioned switching element.

This inverter control unit 52 is configured to selectively energize only the heating coil 2 located below the object to be heated placed on the top plate 1.

Now, let us consider the arrangement of the sensor coil 3 relative to the heating coil 2 with reference to Figure 6. Note that the shaded area in Figure 6 indicates the position where the object to be heated is placed.

First, as shown in FIG. 6(a), when one sensor coil 3 is provided for one heating coil 2, the number of sensor coils 3 is too small to ensure the accuracy of detecting the position of the heated object.

On the other hand, if multiple sensor coils 3 are provided for one heating coil 2 in order to ensure position detection accuracy, as shown in FIG. 6(b), the number of parts increases, resulting in higher costs.

Also, as shown in FIG. 6(c), when two sensor coils 3 are arranged horizontally for one heating coil 2, the number of parts can be reduced, but the vertical position detection accuracy cannot be guaranteed. Also, as shown in FIG. 6(d), when two sensor coils 3 are arranged vertically for one heating coil 2, the number of parts can be reduced, but the horizontal position detection accuracy cannot be guaranteed.

Therefore, in this embodiment, as shown in FIG. 7, two sensor coils 3 are provided for one heating coil 2, and these sensor coils 3 are arranged diagonally across the center of the heating coil 2.

In other words, when the area in which the heating coil 2 is formed is divided vertically and horizontally into four areas by two imaginary lines Z that pass through the center of the heating coil 2 and are perpendicular to each other, the two sensor coils 3 are arranged in diagonal areas (quadrants).

Now, to give a more specific example of the arrangement, as shown in FIG. 8(a), the closer the sensor coil 3 is to the corner of the heating coil 2, the greater the eddy current loss. However, as mentioned above, the arrangement shown in FIG. 8(c) cannot guarantee the accuracy of lateral position detection.

Therefore, in this embodiment, as shown in FIG. 8(b) and the change from the upper part of FIG. 9 to the lower part of FIG. 9, two sensor coils 3 are arranged diagonally with respect to one heating coil 2, and both of these sensor coils 3 are arranged closer to the center than the corners of the heating coil 2, that is, closer to each other.

This arrangement ensures position detection accuracy while keeping the number of parts to a minimum, and also reduces eddy current loss.

Next, we will consider the laminated structure of the heating coil layer B1 and the sensor layer B2 described above.

First, as shown in Figure 10, a conventional Litz wire is coiled into a heating coil 2', and the heating coil layer B1' is formed therein. In this configuration, the output of the inner circumference of the heating coil 2' is high, for example up to 1000V, so the voltage difference with the low-voltage sensor layer B2' becomes large. As a result, a thick insulating layer B3' needs to be interposed between the heating coil layer B1' and the sensor layer B2', which places a limit on how thin the substrate B' can be made.

As shown in Figures 11(a) and (b), the substrate B of this embodiment has two or more heating coil layers B1 insulated from each other and provided with a heating coil 2, a sensor layer B2 in which a sensor coil 3 is provided, and an insulating layer B3 interposed between the heating coil layer B1 and the sensor layer B2. Of the two or more heating coil layers B1, the heating coil layer B1 connected to the resonant capacitor is positioned farther from the sensor layer B2 than the other heating coil layers B1.

In other words, in this embodiment, multiple heating coil layers B1 are stacked so that the current flows back and forth in a predetermined direction. Each heating coil layer B1 is insulated from the other by a core layer B4, and among these heating coil layers B1, the heating coil layer B1 on the output side is positioned farther from the sensor layer B2 than the heating coil layer B1 on the input side.

With this configuration, for example, as shown in FIG. 11( a ), if the heating coil layer B1 has a two-layer structure that causes the current to go back and forth once, the output of the inner circumference of the heating coil layer B1 can be suppressed to about 500 V even with a coil design that provides the same output as the Litz wire shape described above. Alternatively, as shown in FIG. 11( b ), if the heating coil layer B1 has a four-layer structure that causes the current to go back and forth twice, the output of the inner circumference of the heating coil layer B1 can be suppressed to about 250 V.
As a result, the thickness required for the insulating layer B3 interposed between the heating coil layer B1 and the sensor layer B2 can be reduced, and the substrate B can be made thinner.

In the above-mentioned configuration, the high voltage portion of the heating coil 2 is applied to the through hole TH for connecting the heating coil layer B1, the sensor layer B2, and the insulating layer B3, so the sensor coil 3 of the sensor layer B2 is provided so as not to overlap this portion. This design also makes it possible to reduce the thickness of the insulating layer B3, which in turn contributes to making the substrate B thinner.

In the induction heating cooker 100 configured as described above, the heating coil 2 and the sensor coil 3 are integrally provided, so that the positional deviation of the sensor coil 3 relative to the heating coil 2 can be suppressed, and furthermore, because a sheet-shaped heating coil 2 is used, the number of parts can be reduced compared to the conventional configuration using Litz wire.

In addition, since the two sensor coils 3 are arranged diagonally around the center of the heating coil 2, it is possible to achieve high accuracy in detecting the position of the heated object using as few sensor coils 3 as possible.

Furthermore, since the distance between the two heating coils 2 provided on one substrate B is narrower than half the outer diameter dimension of the heating coil 2, it is possible to ensure heating efficiency while suppressing the effect of the heating coil 2 on the sensor coil 3.

In addition, of the stacked heating coil layers B1, the heating coil layer B1 on the output side that is connected to the resonant capacitor is positioned farther away from the sensor layer B2 than the heating coil layer B1 on the input side, so the heating coil layer B1 closer to the sensor layer B2 can be designed to withstand low voltages, making it possible to design the insulating layer B3 to be thin.

In addition, the temperature sensor T is integrated with the heating coil 2 and the sensor coil 3, which reduces product costs by reducing wiring, etc.

In addition, the temperature sensor T is placed at or near the center of the heating coil 2, or near the connection connector CN to which the heating coil 2 is connected. This means that the temperature sensor T is placed in the location where the temperature is most likely to become high, making it possible to detect the temperature of the heating coil 2 and the connection connector CN themselves, and allowing the heating coil 2 to be controlled with high reliability.

In addition, the connector CN on the substrate B is mounted in the opposite direction to the top plate 1, so the distance between the object to be heated and the heating coil 2 is narrower than in a configuration in which the connector CN is mounted facing the top plate 1, allowing the object to be heated more efficiently.

The present invention is not limited to the above embodiment.

For example, in the above embodiment, two heating coils 2 are provided on one substrate B, but a single heating coil 2 may be provided, or three or more heating coils 2 may be provided.

In addition, in the above embodiment, two sensor coils 3 are provided for one heating coil 2, but three or more sensor coils 3 may be provided.

Furthermore, in the above embodiment, the sensor coil 3 is provided closer to the center than the corner of the heating coil 2, but it may be provided at the corner.

In addition, in the induction heating cooker 100 of the above embodiment, as shown in FIG. 12, a protection circuit section 35 is provided between the sensor coil 3 and the drive circuit section 3D connected to the sensor coil 3 to protect the drive circuit section 3D from the induced voltage (maximum ±80V) generated in the sensor coil 3.

Here, the drive circuit section 3D has the resonance capacitor 31, oscillation amplifier 32, oscillation frequency detection circuit 33, control section 34, etc. of the above embodiment. Also, in FIG. 12, multiple sensor coils 3 are connected to one drive circuit section 3D via a multiplexer (MUX section) 36. Then, the protection circuit section 35 is provided between each sensor coil 3 and the MUX section 36 connected to each sensor coil 3. In other words, the protection circuit section 35 is provided for each of the multiple sensor coils 3.

Specifically, the protection circuit unit 35 includes a protection element 351 having a diode 351a such as a Schottky diode and a field effect transistor (FET) 351b such as a MOSFET. The protection element 351 is connected in series to both sides of the sensor coil 3. In each protection element 351, the drain of the FET 351b is connected to the sensor coil 3 side. In each protection element 351, the diode 351a is connected to the source side of the FET 351b, with the cathode of the diode 351a connected to the sensor coil 3 side and the anode of the diode 351a connected to ground (GND). In this protection element 351, when the source voltage of the FET 351b becomes 5V or more, the FET 351b is automatically turned off.

Figure 13 shows each operating state of the protection circuit unit 35. Figure 13 (a) shows the protection circuit unit 35 in the off state (FET 351b is on). Figure 13 (b) shows the protection circuit unit 35 in the on state (FET 351b is off). Figure 13 (b) shows the state in which an induced voltage occurs in the sensor coil 3 that is not selected by the MUX unit 36, the source voltage of FET 351b becomes 5V, and FET 351b is off. In addition, the protection circuit unit 35 is in the on state (FET 351b is off) when, for example, the MUX unit 36 is disabled and an induced voltage occurs in the sensor coil 3 and the source voltage of FET 351b becomes 5V, or when an error occurs in the MUX unit 36, the drive circuit unit 3D, etc. and an induced voltage occurs in the sensor coil 3 and the source voltage of FET 351b becomes 5V.

The protection circuit unit 35 configured as above can protect the MUX unit and the drive circuit unit 3D from the induced voltage even if an induced voltage occurs in the sensor coil 3. Furthermore, the protection circuit unit 35 is configured to protect the MUX unit and the drive circuit unit 3D from the induced voltage using the withstand voltage of the FET 351b without consuming the induced voltage, and can handle even large induced voltages.

Furthermore, in the induction heating cooker 100 of the above embodiment, the output value (count value) of the sensor coil 3 may be corrected using the temperature detected by the temperature sensor T.

Here, the resistance Rp in the resonant circuit is expressed as follows:
Rp = L / (Rs x C)
Here, L is the inductance of the sensor coil 3 , Rs is the resistance of the sensor coil, and C is the capacitance of the resonance capacitor 31 .

Then, the drive circuit section 3D of the sensor coil 3 controls the sensor coil 3 with a constant current and outputs the ratio of the frequency due to the change in inductance value as a count value. In other words, the count value is proportional to the resistance Rp of the resonant circuit.

Furthermore, when the coil material of the sensor coil 3 is constant, the temperature change of the resistance Rp of the resonant circuit can be expressed as follows: where α is the resistance temperature coefficient.
Rp(t) = Rp(t0) x (1 + α(t-t0))

That is, the count value decreases linearly with respect to the temperature change. Therefore, the count value is corrected using the temperature change (T-T0) with respect to a predetermined reference temperature (T0) and a previously obtained temperature correction coefficient k, for example, based on the following formula:
Count value after correction=count value before correction+k×(T−T0)

The temperature correction of the count value may be performed by the oscillation frequency detection circuit 33 or the control unit 34 of the position detection sensor 30, or by the position detection unit 51 of the control device 5.

Figure 14 shows the change in count value with and without temperature compensation. Figure 14 (a) shows the fluctuation in the detection value when no temperature compensation is applied. In this case, the count value decreases after heating begins, and falls below the threshold for determining "no pot present" even though a pot is present, resulting in a false detection. On the other hand, Figure 14 (b) shows the fluctuation in the detection value when temperature compensation is applied. In this case, the decrease in the count value is suppressed even after heating begins, and false detection does not occur.

Furthermore, the induction heating cooker 100 of the above embodiment may be configured to correct the change in the output value (inductance value) of the sensor coil 3 that occurs due to the magnetic flux absorption of the heating coil 2 when the heating coil 2 starts to be driven.

Specifically, the amount of change in the output value (inductance value) of the sensor coil 3 caused by the magnetic flux absorption of the heating coil 2 when the heating coil 2 starts to drive is measured, and the measured amount of change is added to the output value (inductance value) of the sensor coil 3 after the heating coil 2 starts to drive. This compensates for the change in the output value (inductance value) of the sensor coil 3 caused by the magnetic flux absorption of the heating coil 2.

The effect of magnetic flux absorption on the output value (inductance value) may be corrected by the oscillation frequency detection circuit 33 or the control unit 34 of the position detection sensor 30, or by the position detection unit 51 of the control device 5.

Figure 15 shows the change in count value with and without magnetic flux absorption compensation. Figure 15(a) shows the fluctuation in the detection value when magnetic flux absorption is not compensated for, in which case the count value drops as magnetic flux is absorbed by the heating coil after heating begins. On the other hand, Figure 15(b) shows the fluctuation in the detection value when magnetic flux absorption is compensated for, in which the drop in count value due to magnetic flux absorption by the heating coil is compensated for.

It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

REFERENCE SIGNS LIST 100 induction heating cooker 1 top plate 2 heating coil 3 sensor coil 4 inverter circuit 5 control device B substrate B1 heating coil layer B2 sensor layer B3 insulating layer T temperature sensor CN connection connector 3D drive circuit section 35 protection circuit section

Claims (10)

An induction heating cooker that induction heats an object to be heated placed on a top plate,
A sheet-shaped heating coil is provided on a substrate arranged on the back side of the top plate to heat the object to be heated;
13. An induction heating cooker comprising: a sensor coil provided integrally with the heating coil for detecting a position of the object to be heated. At least two of the sensor coils are provided for one of the heating coils,
2. The induction heating cooker according to claim 1, wherein the two sensor coils are disposed diagonally across the center of the heating coil. The induction heating cooker according to claim 1, characterized in that at least two heating coils are arranged on the substrate, and the distance between the two heating coils is narrower than half the outer diameter of the heating coils. the substrate has two or more heating coil layers insulated from each other and provided with the heating coil, a sensor layer in which the sensor coil is provided, and an insulating layer interposed between the heating coil layer and the sensor layer,
2. The induction heating cooker according to claim 1, wherein, of the two or more heating coil layers, a heating coil layer connected to a resonant capacitor is positioned farther from the sensor layer than the other heating coil layers. The induction heating cooker according to claim 1, further comprising a temperature sensor integrally provided with the heating coil and the sensor coil. The induction heating cooker according to claim 5, characterized in that the temperature sensor is disposed at or near the center of the heating coil, or near the connector to which the heating coil is connected. A connector is mounted on the board to be connected to another control board,
2. The induction heating cooker according to claim 1, wherein the connector is mounted in an inverted manner on the top plate. The induction heating cooker according to claim 1, wherein a protection circuit is provided between the sensor coil and a drive circuit connected to the sensor coil, the protection circuit protecting the drive circuit from an induced voltage generated in the sensor coil. The induction heating cooker according to claim 5 or 6, wherein the output value of the sensor coil is corrected using the temperature detected by the temperature sensor. The induction heating cooker according to claim 1, which corrects the change in the output value of the sensor coil caused by the magnetic flux absorption of the heating coil when the heating coil starts to be driven.