JP6910114B2 - Induction heating cooker - Google Patents

Description

The present invention relates to an induction heating cooker that induces and heats an object to be heated placed on a top plate.

Conventionally, a heating cooker that includes an inner heating coil and an outer heating coil arranged adjacent to each other around the inner heating coil and determines the material of the load located above the inner heating coil and the outer heating coil is known. Has been done. In such a heating cooker, when the load located above the inner heating coil is determined to be a magnetic material and the load located above the outer heating coil is determined to be a non-magnetic material, it is output to the inverter of the outer heating coil. A technique has been proposed in which the frequency of the switch drive signal to be driven is driven at a frequency higher than the upper limit of the audible frequency than the frequency of the switch drive signal output to the inverter of the inner heating coil (see, for example, Patent Document 1).

According to the induction heating cooker described in Patent Document 1, it is possible to suppress the interference sound caused by the frequency difference of the high frequency magnetic field generated from the adjacent heating coils.

Japanese Unexamined Patent Publication No. 2011-258339 (pages 4-6)

Recently, with the spread of induction heating cookers that induce and heat an object to be heated placed on a top plate, there is an increasing demand from users who want to use cooking containers (objects to be heated) of various shapes and sizes. There is. Therefore, it has been desired to improve the degree of freedom in arranging the object to be heated on the top plate. At the same time, it is also desired to suppress the interference sound caused by the frequency difference of the high frequency magnetic field generated from the adjacent heating coil.

The present invention has been made against the background of the above problems, and provides an induction heating cooker capable of increasing the degree of freedom in arranging the object to be heated. Further, the present invention provides an induction heating cooker capable of suppressing an interference sound caused by a frequency difference of a high frequency magnetic field generated from an adjacent heating coil.

The induction heating cooker according to the present invention has a top plate on which an object to be heated is placed, a plurality of heating coils arranged in a grid pattern or a staggered pattern below the top plate, and the plurality of heating coils, respectively. The same number of inverters as the plurality of heating coils that supply high-frequency currents, and whether or not the object to be heated is placed in the region of the top plate corresponding to each of the heating coils, and whether or not the object to be heated is placed to be heated. When a load detection unit that periodically detects the material of an object and a control unit that controls the plurality of inverters based on the detection result of the load detection unit are provided, and different materials are simultaneously detected by the load detection unit. , The heating coils corresponding to different materials among the plurality of heating coils are adjacent to each other, and the difference between the drive frequencies corresponding to the materials corresponding to the adjacent heating coils is within the first range. If at least one or more of the heating coil for the adjacent, supply of the high-frequency current from the inverter corresponding to themselves is the also Ru stopped.

According to the present invention, the degree of freedom in arranging the object to be heated on the top plate can be improved. Further, it is possible to suppress the interference sound caused by the frequency difference of the high frequency magnetic field generated from the adjacent heating coils.

It is a perspective view of the induction heating cooker which concerns on Embodiment 1. FIG. It is a perspective view which shows the other arrangement example of the heating coil of the heating cooker which concerns on Embodiment 1. FIG. It is a figure which shows the structure of the main part of the induction heating cooker which concerns on Embodiment 1. FIG. It is a figure explaining the example of the drive frequency of each heating coil of the induction heating cooker which concerns on Embodiment 1. FIG. It is a figure which shows the state which the heated object of a magnetic material and the heated object of a high resistance non-magnetic material are placed on the top plate of the induction heating cooker which concerns on Embodiment 1. FIG. It is a figure explaining the heating coil which is driven against the interference sound of the induction heating cooker which concerns on Embodiment 1. FIG. It is a figure explaining another example of the heating coil which is driven against the interference noise of the induction heating cooker which concerns on Embodiment 1. FIG. It is a control flowchart of the induction heating cooker which concerns on Embodiment 1. FIG. It is a figure which shows the structure of the main part of the induction heating cooker which concerns on Embodiment 4.

Hereinafter, embodiments of the induction heating cooker according to the present invention will be described with reference to the drawings. The present invention is not limited to the form of the drawings shown below. Further, in the following description, terms indicating directions (for example, "top", "bottom", "right", "left", "front", "rear", etc.) are appropriately used for ease of understanding. This is for illustration purposes only and these terms are not intended to limit the invention. Further, in each figure, those having the same reference numerals are the same or equivalent thereof, which are common in the entire text of the specification. In each drawing, the relative dimensional relationship or shape of each component may differ from the actual one.

Embodiment 1.
FIG. 1 is a perspective view of the induction heating cooker according to the first embodiment. The induction heating cooker 1 has a substantially box-shaped housing 2, and a top plate 3 on which an object to be heated such as a pan or a frying pan is placed is provided on the housing 2. The top plate 3 is made of a non-metal material such as ceramics, heat-resistant glass, and crystallized glass. An operation unit 4 for receiving an operation input from a user is provided on the front side of the upper surface of the induction heating cooker 1 and the front wall of the housing 2. The operation unit 4 is composed of, for example, a push button, a dial switch, a capacitive touch switch, or the like. A display unit 5 is provided on the front side of the top plate 3. The display unit 5 has a device for visually notifying information such as a liquid crystal display and an LED, and allows the user to input the operating state such as the heating power of the induction heating cooker 1 and the timer time, and the operation unit 4. Notify choices, warnings and alerts to users. The number, arrangement, and specific configuration of the operation unit 4 and the display unit 5 are not limited to the present invention, and are specific except those illustrated in the present embodiment as long as they exhibit the same functions. The configuration can be adopted.

Inside the housing 2, a plurality of heating coils C formed by winding a conducting wire are provided on the lower side of the top plate 3. In FIG. 1, the heating coil C arranged in the housing 2 is shown by a broken line. The plurality of heating coils C of the present embodiment illustrated in FIG. 1 are arranged in a grid pattern of 7 rows and 13 columns. The number of the plurality of heating coils C is not limited to the one shown in the drawing, and a grid-like arrangement of N rows and M columns (N and M are two or more positive numbers) can be adopted.

FIG. 2 is a perspective view showing another arrangement example of the heating coil of the heating cooker according to the first embodiment. In the example shown in FIG. 2, the plurality of heating coils C are arranged in a staggered pattern. The number of the plurality of heating coils C is not limited to the one shown in the figure.

The shape of each heating coil C may be a polygonal shape or a star shape, in addition to a circular shape like the heating coils C exemplified in FIGS. 1 and 2. The outer diameter of the heating coil C can be 30 mm to 70 mm. The shapes and dimensions of the plurality of heating coils C are all the same in this embodiment, but either or both of the shapes and dimensions of some of the heating coils C may be different. The shape and dimensions of the heating coil C are not limited to the present invention.

In the arrangement example of the plurality of heating coils C shown in FIGS. 1 and 2, the distances between the adjacent heating coils C are equal. By doing so, uneven heating of the object to be heated can be suppressed, but the distance between adjacent heating coils C may be different depending on the position of each heating coil C.

As a conventional induction heating cooker, one or a plurality of heating ports are provided at a predetermined position on a top plate, and an object to be heated is placed on the heating ports. The induction heating cooker 1 of the form is not provided with a heating port at a fixed position. In the induction heating cooker 1 of the present embodiment, an object to be heated placed at an arbitrary position on the top plate 3 can be induced and heated by a combination of a plurality of heating coils C.

The induction heating cooker 1 may be provided with a display function for the user to grasp the position of the heating coil C from the outside. For example, the front surface or the back surface of the top plate 3 may be printed to indicate the position of each heating coil C, or a display device such as an LED indicating the position of each heating coil C may be provided on the lower side of the top plate 3. You may.

FIG. 3 is a diagram showing a configuration of a main part of the induction heating cooker according to the first embodiment. In FIG. 3, for the sake of explanation, the reference numerals of the plurality of heating coils C are shown separately from C1 to C6 and Cn. In the following description, when the matters common to each heating coil will be described, it will be referred to as a heating coil C, and when one unspecified heating coil will be described, it will be referred to as a heating coil Cn, and the illustrated specific heating coil will be referred to. When explaining, a number is added like the heating coil C1. Further, although FIG. 3 shows two objects to be heated 30 placed on the top plate 3 for explanation, the objects to be heated 30 do not constitute the present invention.

As shown in FIG. 3, the induction heating cooker 1 includes inverters INV1 to INV6 and INVn that supply high-frequency currents to the heating coils C1 to C6 and Cn, respectively, a control unit 6, and a load detection unit 7. In the following description, when the matters common to each inverter are described, the inverter INV is referred to, when one unspecified inverter is described, the inverter INVn is referred to, and when the illustrated specific inverter is described, the inverter INV1 is used. The explanation will be given by adding numbers as in. Each inverter INVn is connected to each heating coil Cn on a one-to-one basis, and the number of inverter INVs and the number of heating coils C are the same.

The inverter INV receives a current input from the commercial power source 20 and supplies a high frequency current to the corresponding heating coil C. The inverter INV includes a set of switching elements, and turns on / off the set of switching elements based on the drive signal from the control unit 6 to supply a high frequency current to the heating coil C.

The control unit 6 supplies a drive signal having a frequency based on the load detection result output from the load detection unit 7 to each inverter INV. The control unit 6 is composed of dedicated hardware or a CPU (also referred to as a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microprocessor, a microprocessor, or a processor) that executes a program stored in a memory. ..

The load detection unit 7 detects whether or not the object to be heated is placed in the region of the top plate 3 corresponding to each heating coil C, and the material of the object to be heated on which the object to be heated is placed. Specifically, for example, the load detection unit 7 detects the input current value to the inverter INVn and the coil current value flowing through the heating coil Cn when the inverter INVn corresponding to the heating coil Cn is driven. Here, the impedance on the output side as seen from the inverter INVn differs depending on the presence or absence of the object to be heated in the region of the top plate 3 corresponding to the heating coil Cn and the material of the object to be heated on which the heating coil Cn is placed. Utilizing this fact, based on the input current value and the coil current value, the presence or absence of the heated object in the region of the top plate 3 corresponding to each heating coil Cn and the material of the heated object are detected. Materials to be heated are roughly classified into magnetic materials such as iron and magnetic stainless steel (for example, SUS430), high resistance non-magnetic materials such as non-magnetic stainless steel (for example, SUS304), and low resistance non-magnetic materials such as aluminum and copper. NS. The load detection unit 7 detects whether the material to be heated is a magnetic material, a high-resistance non-magnetic material, or a low-resistance non-magnetic material.

Further, as an example of the object to be heated, there is one in which a sticking material made of magnetic metal is stuck to the central portion of the bottom outer surface of the aluminum cooking container. Such an object to be heated will be referred to as a sticking pan in the following description. When the sticking pot is placed on the top plate 3, the heating coil Cn located below the aluminum is detected to be a low-resistance non-magnetic material, and the heating coil Cn located below the sticking material is detected. Is detected that the object to be heated is a magnetic material.

FIG. 4 is a diagram illustrating an example of a drive frequency of each heating coil of the induction heating cooker according to the first embodiment. In FIG. 4, each heating coil C is hatched differently depending on the drive frequency. Further, in FIG. 4, the object to be heated 30B is a high-resistance non-magnetic material, the object to be heated 30C is a sticking pot, and reference numeral 31 indicates a sticking material of the sticking pot.

As shown in FIG. 4, in a state where the object to be heated 30B and the object to be heated 30C are placed on the top plate 3, the load detection unit 7 has the object to be heated placed on each heating coil Cn. Whether or not it is present, and the material of the object to be heated on which it is placed are detected. The control unit 6 supplies each inverter INV that supplies a high-frequency current to each heating coil C based on the presence / absence and material of the object to be heated in the region of the top plate 3 corresponding to each heating coil C output from the load detection unit 7. Determine the drive frequency of.

In the example shown in FIG. 4, three types of drive frequencies S, T, and U are predetermined according to the material of the object to be heated. The drive frequency S is a frequency for a magnetic material, the drive frequency T is a frequency for a high resistance non-magnetic material, and the drive frequency U is a frequency for a low resistance non-magnetic material. Since the magnetic material has a larger equivalent resistance that contributes to heating than the non-magnetic material, it is easily heated, and since the equivalent inductance is large, the drive frequency S for the magnetic material is smaller than the drive frequencies T and U for the non-magnetic material. Is. Since the low-resistance non-magnetic material has a smaller equivalent resistance than the high-resistance non-magnetic material and the eddy current is less likely to change to Joule heat, the drive frequency U for the low-resistance non-magnetic material is set to the high-resistance non-magnetic material in order to increase the equivalent resistance. It is a value larger than the driving frequency T for the target. In the present embodiment, the drive frequencies S, T, and U will be described as being 22 kHz, 30 kHz, and 80 kHz, respectively.

In FIG. 4, the inverter INVn of the heating coil Cn on which the object to be heated 30B is mounted has a drive frequency T, and the inverter INVn of the heating coil Cn on which the magnetic material 31 of the object to be heated 30C which is a sticking pot is mounted is The inverter INVn of the heating coil Cn on which the aluminum material of the drive frequency S and the object to be heated 30C is placed is driven by the drive frequency U. Further, the inverter INVn of the heating coil Cn on which the object to be heated is not placed is driven and stopped.

Here, it is known that when the frequencies of high-frequency currents flowing between adjacent heating coils Cn are different, electromagnetic interference sounds corresponding to the differences in frequencies are generated. In the example of FIG. 4, between the heating coil C1 corresponding to the magnetic material and the heating coil C2 corresponding to the low resistance non-magnetic material, Δf = drive frequency U (80 kHz) − drive frequency S (22 kHz) = 58 kHz. Electromagnetic interference noise is generated. Further, electromagnetic interference of Δf = drive frequency U (80 kHz) − drive frequency T (30 kHz) = 50 kHz between the heating coil C2 corresponding to the low resistance non-magnetic material and the heating coil C3 corresponding to the high resistance non-magnetic material. Sound is generated. Further, an electromagnetic interference sound of Δf = drive frequency T (30 kHz) − drive frequency U (22 kHz) = 8 kHz is generated between the heating coil C1 corresponding to the magnetic material and the heating coil C3 corresponding to the high resistance non-magnetic material. appear. Generally, human audible sound is 20 kHz or less. Therefore, in the case of the present embodiment, when the heating coil C1 corresponding to the magnetic material and the heating coil C3 corresponding to the low resistance non-magnetic material are adjacent to each other, an electromagnetic interference sound of 8 kHz is generated as an audible sound. ..

It is also known that the sound pressure of the electromagnetic interference sound decreases according to the magnitude of the distance between the heating coils having different frequencies.

Therefore, in the present embodiment, when the frequency difference between the adjacent heating coils Cn is 20 kHz or less, which is the range of the human audible range, one or both of the adjacent heating coils Cn The inverter INVn corresponding to the above is driven as a countermeasure against interference noise. In the present embodiment, 20 kHz, which is the range of the audible range, corresponds to the first range of the present invention. Hereinafter, the interference noise countermeasure drive will be described.

FIG. 5 is a diagram showing a state in which a magnetic material to be heated and a high resistance non-magnetic material to be heated are placed on the top plate of the induction heating cooker according to the first embodiment. The object to be heated 30A is a magnetic material, and the object to be heated 30B is a high resistance non-magnetic material. As shown in FIG. 5, the drive frequency determined based on the result of load detection for each heating coil Cn is the drive frequency S and high resistance for the heating coil Cn on which the object to be heated 30A of the magnetic material is placed. The drive frequency T is for the heating coil Cn on which the non-magnetic material to be heated 30B is placed. In the example of FIG. 5, the heating coils C1 and C2 having the drive frequency S include the heating coils C3 and C4 having the drive frequency T in which the difference in the drive frequencies is in the audible range in the heating coils adjacent to each of the heating coils C1 and C2. .. On the contrary, when viewed from the heating coils C3 and C4, it can be said that the heating coils C1 and C2 having the drive frequency S in which the difference in the drive frequencies is in the audible range are included in the heating coils adjacent to each of the heating coils C3 and C4. In such a situation, the interference sound countermeasure drive is performed.

FIG. 6 is a diagram illustrating a heating coil driven to prevent interference noise in the induction heating cooker according to the first embodiment. FIG. 7 is a diagram illustrating another example of a heating coil driven to prevent interference noise in the induction heating cooker according to the first embodiment. In the example of FIG. 6, two heating coils C3 and C4 on which the object to be heated 30B, which is a high-resistance non-magnetic material, is placed are driven to prevent interference noise. In the example of FIG. 7, two heating coils C1 and C2 on which the object to be heated 30A, which is a magnetic material, is placed are driven to prevent interference noise.

The interference noise countermeasure drive of the present embodiment is a drive stop. That is, the inverter INVn corresponding to the heating coil Cn that is the target of the interference noise countermeasure drive is stopped, and the high frequency current does not flow through the target heating coil Cn and does not contribute to the heating of the object to be heated. Either heating is performed by driving and stopping the heating coils C3 and C4 by driving against interference noise as shown in FIG. 6, or by driving and stopping the heating coils C1 and C2 by driving against interference noise as shown in FIG. As for the coil Cn, the difference in drive frequency from the adjacent heating coil Cn is a value outside the audible range. Therefore, it is possible to suppress the generation of an interference sound that becomes an audible sound.

Here, when the heating coils Cn are adjacent to each other, the range of the heating coils Cn to be referred to as adjacent can be determined according to the arrangement and size of the heating coils Cn. In the present embodiment, when focusing on a certain heating coil Cn, eight heating coils Cn (upper, lower, left, right, upper left, lower left, upper right, lower right) arranged around the heating coil Cn are adjacent to each other. It is called a heating coil. In addition, when focusing on a certain heating coil Cn, the four heating coils Cn arranged on the top, bottom, left, and right of the heating coil Cn can also be referred to as adjacent heating coils. In a certain heating coil Cn, when the difference in drive frequency from the heating coil Cn adjacent to itself is a value of 20 kHz or less, which is within the range of the human audible range, the heating coil Cn is subject to interference noise countermeasure drive. .. Therefore, when one or more heating coils Cn are driven to prevent interference noise, the distance between the heating coil groups driven at different drive frequencies (distance between outer shapes) is the distance at which interference noise in the audible range is not generated. The range adjacent to the heating coil Cn is defined so as to be.

Of the adjacent heating coils Cn, which of the heating coils Cn whose drive frequency difference is within the range of the audible sound is to be the target of the interference sound countermeasure drive is determined in the first to third examples below. It can be determined in this way.

As a first example, the heating coil Cn having the larger drive frequency can be targeted for the interference noise countermeasure drive. The fact that the drive frequency is higher than that of the adjacent heating coil means that an object to be heated with relatively low heating efficiency is placed on the heating coil Cn, so that the heating coil Cn Is the target of the interference noise countermeasure drive, and the other object to be heated with good heating efficiency is preferentially heated at the drive frequency according to the material. FIG. 6 is consistent with this first example.

As a second example, the heating coil Cn having the smaller drive frequency can be the target of the interference noise countermeasure drive. The fact that the drive frequency is smaller than that of the adjacent heating coil means that an object to be heated having a relatively high heating efficiency is placed on the heating coil Cn. For example, when there is a heating coil Cn driven by the drive frequency S and a heating coil Cn driven by the drive frequency T, the region of the heating coil Cn driven by the lower drive frequency S is relative to the region. It can be said that a magnetic material to be heated, which has high heating efficiency, is placed on the surface. Looking at the power density applied to the object to be heated, the power density per coil of the heating coil Cn having the lower drive frequency is higher than the power density per coil of the heating coil Cn having the higher drive frequency. Is also expensive. Therefore, when one heating object is heated by a plurality of heating coils Cn having a smaller driving frequency, some of the heating coils Cn having a smaller driving frequency are targeted for interference noise countermeasure driving. Even if the drive is stopped, it does not easily affect the heating of the object to be heated, which is a material with relatively high heating efficiency. FIG. 7 is consistent with this second example.

As a third example, the heating coil Cn belonging to the one having the larger number of heating coils Cn driven at the same drive frequency can be targeted for the interference noise countermeasure drive. Since the number of heating coils Cn driven at the same drive frequency is large, it is expected that the bottom area of the object to be heated is large, so even if the heating coils Cn are driven and stopped as the target of the interference noise countermeasure drive. It does not easily affect the heating of the object to be heated. FIG. 7 is also consistent with this third example.

Focusing on each heating coil Cn in this way, when it is detected that an object to be heated is placed in the region of the top plate 3 corresponding to the heating coil Cn, the object corresponding to the heating coil Cn is covered. Either a high-frequency current is supplied from the inverter INVn at a drive frequency according to the material of the heated object, or the drive is stopped as a target of interference noise countermeasure drive. Countermeasures against interference noise When the heating coil Cn, which is the target of driving, is stopped, the difference in frequency between the adjacent heating coils Cn becomes out of the audible range.

FIG. 8 is a control flowchart of the induction heating cooker according to the first embodiment. A control example for realizing the operation shown in FIGS. 5 to 7 will be described with reference to FIG.

(Step S1)
Upon receiving the instruction to start heating, the load detection unit 7 detects the load on the top plate 3 corresponding to each heating coil Cn, and the control unit 6 detects the planned frequency fn_s for each heating coil Cn based on the load detection result. To determine. Specifically, the control unit 6 drives each inverter INVn to pass a high-frequency current for load detection through each heating coil Cn. At this time, all the inverter INVs may be driven at the same time, the grouped inverter INVs may be driven simultaneously for each group, or each inverter INV may be driven sequentially. The load detection unit 7 of the top plate 3 corresponding to each heating coil Cn is based on the input current to the inverter INVn when the high frequency current for load detection is supplied and the coil current value flowing through the corresponding heating coil Cn. Whether or not the object to be heated is placed in the region and the material of the placed object to be heated are detected. Based on the load detection result for each heating coil Cn, the control unit 6 sets one of the drive frequencies S, T, and U corresponding to the material of the placed object to be heated to the planned frequency fn_s of the heating coil Cn. To determine as.

(Step S2)
The control unit 6 has, for each heating coil Cn, a heating coil having a planned frequency fn_s in which the difference between the planned frequencies fn_s is within the audible range in one or a plurality of heating coils C adjacent to the heating coil Cn. Detects whether or not there is C.

(Step S3)
The control unit 6 determines the drive frequency f of the inverter INV corresponding to each heating coil Cn. Specifically, the heating coil Cn determined in step S1 that the object to be heated is not placed in the corresponding region of the top plate 3 is driven and stopped. Further, in step S2, the heating coil Cn detected that there is a heating coil C having a planned frequency fn_s in which the difference between the planned frequencies fn_s is within the audible range among the adjacent heating coils Cn is stepped. The scheduled frequency fn_s determined in S1 is determined as the drive frequency f, or the drive is stopped as the target of the interference sound countermeasure drive. For the other heating coils Cn, the scheduled frequency fn_s determined in step S1 is determined as the drive frequency f of the corresponding inverter INVn.

(Step S4)
Unless instructed to stop heating (S4; NO), the induction heating cooker 1 periodically executes the processes of steps S1 to S3. That is, the object to be heated in the region of the top plate 3 corresponding to each heating coil Cn is periodically detected, and the drive frequency of the corresponding inverter INVn is updated based on the detection result. Therefore, for example, even if a new object to be heated is placed on the top plate 3 or the object to be heated is moved after the start of heating, depending on the state of the object to be heated at that time. , The inverter INVn of each heating coil Cn is driven and controlled. When instructed to stop heating (S4; YES), the control unit 6 drives and stops the inverter INV to stop heating.

As described above, according to the present embodiment, a plurality of heating coils C are arranged in a grid pattern or in a staggered pattern below the top plate 3, and the region of the top plate 3 corresponding to each heating coil C is heated. Whether or not an object is placed and the material of the object to be heated on which the object is placed are periodically detected. When different materials are simultaneously detected by the load detection unit 7, the heating coils Cn corresponding to the different materials among the plurality of heating coils Cn are adjacent to each other, and the materials corresponding to the adjacent heating coils Cn. When the difference between the drive frequencies corresponding to the above is within the audible range, at least one or more of the adjacent heating coils C are stopped from supplying the high frequency current from the inverter INVn corresponding to them. Therefore, the degree of freedom in the arrangement and shape of the object to be heated can be increased, and the generation of interference sound due to the difference in the driving frequency of the high-frequency magnetic field between the adjacent heating coils Cn can be suppressed.

In the above, the control of the inverter INV of the heating coil C has been described with a focus on the material of the object to be heated and the suppression of the interference sound in the audible range. The thermal power when heating the object to be heated can be adjusted by changing the on-duty of the drive signal of the inverter INV corresponding to each heating coil C.

The switching element included in the inverter INV may be made of a silicon semiconductor, but may also be made of a wide bandgap semiconductor made of SiC (silicon carbide) or GaN (gallium nitride based material). As described above, in the induction heating cooker 1 of the present embodiment, a plurality of heating coils C are arranged in a grid pattern or a staggered pattern so that the object to be heated can be induced and heated at any position on the top plate 3. There is an inverter INV driven at a drive frequency U (for example, 80 kHz) for induction heating of a low resistance non-magnetic material such as aluminum. Here, the loss of the silicon semiconductor increases as the drive frequency increases, and cooling becomes difficult. On the other hand, SiC (silicon carbide), which is a wide bandgap semiconductor, has a higher heat resistant temperature than silicon semiconductors, so by using SiC as the switching element of the inverter INV, the cooling means such as heat dissipation fins and cooling fan can be miniaturized. And it can be reduced in weight. In addition, since GaN (gallium nitride based material) has a significantly smaller loss than silicon semiconductors, by using GaN as the switching element of the inverter INV, the loss is small even when the drive frequency is high, so heat dissipation fins and cooling Cooling means such as a fan can be made smaller and lighter. As a result, the weight of the induction heating cooker 1 provided with the plurality of heating coils C and the plurality of inverter INVs can be reduced, and the workability of the induction heating cooker 1 can be improved.

Embodiment 2.
In the above-described first embodiment, it has been described that the inverter INVn of the target heating coil Cn is driven and stopped as an example of the interference noise countermeasure driving. In the present embodiment, as another example of the interference noise countermeasure drive, a control example in which the difference between the drive frequency of the adjacent heating coil C and its own drive frequency is set to a value outside the audible range is set. This will be described with reference to FIGS. 6 and 7. In the present embodiment, the differences from the first embodiment will be mainly described.

In FIG. 6, the heating coils C3 and C4 are the targets of the interference noise countermeasure drive. The drive frequencies of the heating coils C3 and C4 are set so that the difference from the drive frequency S is outside the audible range. Specifically, the drive frequency of the heating coils C3 and C4 is changed from the drive frequency T (30 kHz) determined according to the material of the object to be heated, and is set to, for example, 52 kHz. By doing so, the frequency difference between the heating coils C3 and C4 and the heating coils C1 and C2 is Δf = 52 kHz-drive frequency S (22 kHz) = 30 kHz, and the electromagnetic interference sound is out of the audible range. Further, the difference between the drive frequencies of the heating coils C3 and C4 and the drive frequency T is Δf = 52 kHz − drive frequency T (30 kHz) = 22 kHz, and the electromagnetic interference sound is also out of the audible range.

Further, in FIG. 7, the heating coils C1 and C2 are the targets of the interference noise countermeasure drive. The drive frequencies of the heating coils C1 and C2 are set so that the difference from the drive frequency T is outside the audible range. Specifically, the drive frequency of the heating coils C1 and C2 is changed from the drive frequency S (22 kHz) determined according to the material of the object to be heated, and is set to, for example, 52 kHz. By doing so, the frequency difference between the heating coils C1 and C2 and the heating coils C3 and C4 is Δf = 52 kHz − drive frequency T (30 kHz) = 22 kHz, and the electromagnetic interference sound is out of the audible range. Further, the difference between the drive frequencies of the heating coils C1 and C2 and the drive frequency S is Δf = 52 kHz − drive frequency S (22 kHz) = 30 kHz, and the electromagnetic interference sound is also out of the audible range.

According to the second embodiment, the same effect as that of the first embodiment can be obtained. Further, the heating coil Cn, which is the target of the interference noise countermeasure drive, is driven at a higher frequency than the drive with a drive frequency according to the material, so that the heating power is low, but the heated object is heated. Since it continues, the heating efficiency of the object to be heated can be improved as compared with the first embodiment.

Embodiment 3.
In the third embodiment, a control example in which the drive frequency of the heating coil C driven to prevent interference noise is changed with time will be described with reference to FIGS. 6 and 7. In this embodiment, the differences from the first and second embodiments will be mainly described.

In FIG. 6, the drive frequencies of the heating coils C3 and C4 are changed over time in a range of drive frequencies in which the difference from the drive frequency S is outside the audible range. Specifically, the drive frequencies of the heating coils C3 and C4 are changed over time in the range of 32 kHz to 34 kHz, which is a value larger than the drive frequency T. By doing so, the frequency difference between the drive frequencies of the heating coils C3 and C4 and the drive frequency T (30 kHz) fluctuates in the range of 2 kHz to 4 kHz and does not become a constant value. Further, the difference between the drive frequency of the interference sound countermeasure drive and the drive frequency S (22 kHz) fluctuates in the range of 10 kHz to 12 kHz and does not become a constant value.

Further, in FIG. 7, the drive frequencies of the heating coils C1 and C3 are changed with time in the range of the drive frequencies in which the difference from the drive frequencies T is outside the audible range. Specifically, the drive frequencies of the heating coils C1 and C2 are changed over time in the range of 24 to 26 kHz, which is a value larger than the drive frequency S. By doing so, the frequency difference between the drive frequencies of the heating coils C1 and C2 and the drive frequency S (22 kHz) fluctuates in the range of 2 kHz to 4 kHz and does not become a constant value. Further, the difference between the drive frequency of the interference sound countermeasure drive and the drive frequency T (30 kHz) fluctuates in the range of 4 kHz to 6 kHz and does not become a constant value.

According to the present embodiment, the drive frequency of the heating coil C, which is the target of the interference noise countermeasure drive, fluctuates with time. Therefore, the difference from the drive frequency of the other heating coil C does not become a constant value, and it is possible to suppress the generation of annoying electromagnetic interference sound due to the frequency difference. Further, by changing the drive frequency of the heating coil Cn, which is the target of the interference noise countermeasure drive, in a range close to the drive frequency determined according to the material, the heating coil Cn is placed in the region of the top plate 3 corresponding to the heating coil Cn. It is possible to suppress a decrease in the heating efficiency of the placed object to be heated.

Embodiment 4.
In this embodiment, another hardware configuration example of the heating coil C, the inverter INV, and the control unit 6 of the induction heating cooker 1 described in the first to third embodiments will be described. The present embodiment can be combined with the first to third embodiments, and the differences from the first to third embodiments will be mainly described in the present embodiment.

FIG. 9 is a diagram showing a configuration of a main part of the induction heating cooker according to the fourth embodiment. FIG. 9 schematically shows the heating coil C and its auxiliary members arranged under the top plate 3, and also illustrates the functional connection relationship between the main control unit 6A and the sub control unit 6B. In the present embodiment, the heating coil Cn is formed on the substrate 8 as a pattern coil. An inverter INVn that supplies a high-frequency current to the heating coil Cn and a sub-control unit 6B that controls the inverter INVn are mounted on the substrate 8. That is, the heating coil Cn, the inverter INVn, and the sub-control unit 6B are all mounted on the substrate 8, and these are modularized. A plurality of such modularized heating coils C are arranged in a grid pattern or a staggered pattern under the top plate 3.

The sub-control unit 6B of the present embodiment has the function of the load detection unit 7 shown in the first embodiment, and the object to be heated is placed in the region of the top plate 3 corresponding to the heating coil Cn. Whether or not it is present, and the material of the object to be heated on which it is placed are detected.

The plurality of sub-control units 6B corresponding to the plurality of heating coils C are all connected to the main control unit 6A. The main control unit 6A outputs a control command to each sub control unit 6B to control the sub control unit 6B, and there is a master-slave relationship between the main control unit 6A and each sub control unit 6B. There is. The main control unit 6A and the sub control unit 6B include a CPU (Central Processing Unit, a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, and a processor) that execute programs stored in dedicated hardware or memory. It is composed of). The main control unit 6A and the sub control unit 6B transmit and receive signals by wired communication or wireless communication.

The main control unit 6A outputs a load detection execution command to each sub control unit 6B at the timing of the load detection that is periodically executed. The sub-control unit 6B that has acquired the load detection execution command executes the load detection and outputs the detection result to the main control unit 6A. The main control unit 6A outputs a control command to each sub control unit 6B based on the load detection result output from the sub control unit 6B. This control command is information on whether or not each sub-control unit 6B drives the corresponding inverter INVn, and the frequency at the time of driving.

According to the present embodiment, it is possible to realize the interference noise countermeasure drive of the induction heating cooker 1 shown in the first to third embodiments. Further, since the heating coil Cn and the inverter INVn are mounted on the same substrate 8 and modularized, the wiring in the induction heating cooker 1 can be simplified. Further, since the sub-control unit 6B is also mounted on the same board 8 and modularized, the wiring between the sub-control unit 6B and the inverter INVn can be simplified. Further, since the heating coil C is made into a pattern coil, the size, particularly the thickness of the heating coil C can be reduced, and the degree of freedom in arranging the substrate 8 and other parts in the housing 2 of the induction heating cooker 1 can be increased. Can be enhanced.

Although the structural example in which the heating coil C is a pattern coil formed on the substrate 8 is shown in the present embodiment, the heating coil formed by winding the conducting wire shown in the first embodiment is not a pattern coil. C may be combined with the same control as the control by the sub control unit 6B and the main control unit 6A described above.

1 Induction heating cooker, 2 housing, 3 top plate, 4 operation unit, 5 display unit, 6 control unit, 6A main control unit, 6B sub-control unit, 7 load detector, 8 board, 20 commercial power supply, 30 covers Heated object, 30A heated object, 30B heated object, 30C heated object, 31 magnetic material, C heating coil, INV inverter.

Claims (6)

The top plate on which the object to be heated is placed and
A plurality of heating coils arranged in a grid pattern or a staggered pattern below the top plate,
The same number of inverters as the plurality of heating coils that supply high-frequency current to the plurality of heating coils, respectively.
A load detection unit that periodically detects whether or not the object to be heated is placed in the region of the top plate corresponding to each of the heating coils, and the material of the object to be heated.
A control unit that controls the plurality of inverters based on the detection result of the load detection unit is provided.
When different materials are detected at the same time by the load detection unit,
When the heating coils corresponding to different materials among the plurality of heating coils are adjacent to each other, and the difference between the drive frequencies corresponding to the materials corresponding to the adjacent heating coils is within the first range. for,
At least one or more of the adjacent heating coils
An induction heating cooker characterized in that the supply of high-frequency current from the inverter corresponding to itself is stopped. The control unit
A sub-control unit that is provided corresponding to each of the plurality of inverters and controls the corresponding inverters.
The induction heating cooker according to claim 1, further comprising a main control unit that outputs a control command to the sub control unit based on the detection result of the load detection unit. The control unit
A sub-control unit that is provided corresponding to each of the plurality of inverters and controls the corresponding inverters.
The sub-control unit has a main control unit that outputs a control command.
The plurality of heating coils are arranged as pattern coils on the substrate.
The induction heating cooker according to claim 1, wherein the heating coil, which is the pattern coil, the inverter, and the sub-control unit are mounted on the substrate. The main control unit on the basis of the detection result of the load detection unit, the induction heating cooker of claim 3 Symbol mounting and outputs a control command to the sub controller. The induction heating cooker according to any one of claims 1 to 4 , wherein the inverter includes a switching element formed of a wide bandgap semiconductor. The induction heating cooker according to claim 5 , wherein the wide bandgap semiconductor is a silicon carbide or gallium nitride-based material.

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