JP2012099429A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating cooker which can reduce generation of interference sound regardless of the drive frequency of a heating coil.SOLUTION: The induction heating cooker comprises a top plate 2 on which a pot is mounted, a plurality of heating coils 3, 7 provided under the top plate 2 and heating pots 6, 10, a drive circuit 8 which feeds a high frequency current to the heating coils 3, 7 by converting an AC voltage into a high frequency voltage, and a ring-shaped magnetic shield ring 12 arranged to surround the heating coils 3, 7. The magnetic shield ring 12 is formed so that the amount of magnetic flux to be shielded increases for a part of a portion facing the adjoining heating coils 3, 7 when compared with a portion not facing the adjoining heating coils 3, 7.

Description

  The present invention relates to an induction heating cooker.

  In the conventional induction heating cooker, for example, for the purpose of preventing the interference sound, for example, "a difference in transmission frequency between adjacent heating coils among the heating coils is set to at least 20 kHz" has been proposed. (For example, refer to Patent Document 1).

JP 59-25193 A (Claims)

In general, the electric power to the heating coil is controlled by changing the drive frequency. For example, when the heating coil A and the heating coil B that are adjacent to each other are driven together, in order to avoid interference noise, the heating coil A is controlled by changing the driving frequency in the range of the driving frequency from 20 kHz to 40 kHz. When the heating coil B needs to change the frequency in the range of 60 kHz to 80 kHz, the frequency difference being 20 kHz or more larger than the audible range.
However, in this case, there is a problem that the heating coil loss of the heating coil B driven at a high frequency and the loss of the drive circuit increase.

  This invention is made in order to solve the above subjects, and obtains the induction heating cooking appliance which can suppress generation | occurrence | production of an interference sound irrespective of the drive frequency of a heating coil.

  An induction heating cooker according to the present invention includes a top plate on which an object to be heated is placed, a plurality of heating coils that are provided under the top plate and heats the object to be heated, and an alternating voltage is converted to a high-frequency voltage A drive circuit for converting the high-frequency current to flow through the heating coil and a ring-shaped magnetic shield means disposed so as to surround the heating coil, the magnetic shield means being a portion facing the adjacent heating coil Are formed so that the amount of magnetic flux to be shielded is larger than that of the non-opposing portions.

  The present invention can suppress the generation of interference sound regardless of the driving frequency of the heating coil.

It is the block diagram which looked at the induction heating cooking appliance explaining the generation | occurrence | production mechanism of interference sound from the side. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 1 from the side. 1 is a perspective view of a magnetic shield ring showing Embodiment 1. FIG. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 2 from the side. 5 is a perspective view of a magnetic shield ring showing a second embodiment. FIG. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 3 from the side. 10 is a perspective view of a magnetic shield ring showing a third embodiment. FIG. 10 is a perspective view of a magnetic shield ring showing a third embodiment. FIG. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 4 from the side. FIG. 10 is a perspective view of a magnetic shield ring showing a fourth embodiment. FIG. 10 is a top view of a magnetic shield ring showing a fifth embodiment. It is a figure explaining the other shape of a magnetic shielding means. It is a figure explaining the other shape of a magnetic shielding means. It is a figure explaining the other shape of a magnetic shielding means. It is a figure explaining the other shape of a magnetic shielding means. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 6 from the side. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 7 from the side. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 7 from the side. It is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 8 from the side. It is a top view of the induction heating cooking appliance which shows Embodiment 9. FIG.

Embodiment 1 FIG.
FIG. 1 is a block diagram of an induction heating cooker illustrating a mechanism for generating interference sound as seen from the side.
In FIG. 1, 1 is an AC power source, 2 is a top plate on which an object to be heated such as a pan is placed, 3 is a heating coil, 4 is a drive coil 3 by converting the AC voltage of the AC power source 1 into a high-frequency voltage. A drive circuit 5 for controlling the drive circuit 4, and a heated object (pan) 6 placed on the heating coil 3.
Further, 7 is a heating coil, 8 is a drive circuit for driving the heating coil 7 by converting the AC voltage of the AC power source 1 into a high frequency voltage, 9 is a control circuit for controlling the drive circuit 8, and 10 is the heating coil 7 This is the object to be heated (pan).
In addition, the heating coils 3 and 7 shown in FIG. 1 have shown the cross section of the coil divided | segmented into the inner side and the outer side, and arrange | positioned concentrically.
A dotted line 11 indicates a magnetic flux leaking from the heating coil 7 toward the heating coil 3 (hereinafter also referred to as “leakage magnetic flux”).

In FIG. 1, for example, when the pan 10 is heated at a maximum power of 3 kW by an operation of an operation unit (not shown) by a user, the control circuit 9 controls the drive circuit 8 to supply power to the heating coil 7. Is controlled to be 3 kW. Since the input power is inversely proportional to the frequency, for example, when 3 kW is input in the frequency variable range from 20 kHz to 40 kHz, the driving is performed at 20 kHz.
At this time, a leakage magnetic flux that does not contribute to heating of the pan 10 is radiated from the heating coil 7 to the surroundings. Since this leakage magnetic flux is proportional to the input power, the leakage magnetic flux indicated by the dotted line 11 also increases.

When heating one pan 6 with medium power of about 800 W while heating the pan 10 with the maximum power of 3 kW, the control circuit 5 controls the drive circuit 4 so that the power supplied to the heating coil 3 is 800 W. To control. Since the input power is in inverse proportion to the frequency, when 800 W is input in the frequency variable range from 20 kHz to 40 kHz, the driving is performed at about 30 kHz.
At this time, a leakage magnetic flux is also generated from the heating coil 3 (not shown). However, since the input power is as weak as 800 W, the leakage magnetic flux from the heating coil 7 increases in this case.

The leakage magnetic flux from the heating coil 7 indicated by the dotted line 11 reaches the pan 6 and becomes an eddy current of 20 kHz in the pan 6. For this reason, a 30 kHz eddy current due to the magnetic flux from the heating coil 3 and a 20 kHz eddy current due to the leakage magnetic flux from the heating coil 7 flow through the pan 6.
At this time, since an oscillating force is also generated in the pan 6 simultaneously with the generation of eddy current due to the magnetic flux, the pan 6 vibrates at a frequency of 20 kHz and 30 kHz, and the difference of 10 kHz is heard as an unpleasant interference sound.
As described above, the interference sound is an unpleasant interference sound that can be heard by humans when two kinds of excitation force are generated in the pan due to the leakage magnetic flux from the adjacent heating coil and the frequency difference is in the audible frequency range. .

As described above, it has been clarified through experiments and analyzes that the interference sound is caused by the leakage magnetic flux.
From this result, in order to prevent interference noise, it is effective to reduce the leakage magnetic flux to the adjacent heating coil.
Hereinafter, the induction heating cooker according to the present embodiment, which reduces the leakage magnetic flux to the adjacent heating coil and suppresses the generation of interference noise, will be described.

FIG. 2 is a block diagram of the induction heating cooker showing the first embodiment as seen from the side.
FIG. 3 is a perspective view of the magnetic shield ring showing the first embodiment.
As shown in FIG. 2, a ring-shaped magnetic shield ring 12 is installed so as to surround each of the heating coil 3 and the heating coil 7. The magnetic shield ring 12 is made of a nonmagnetic metal such as aluminum.
Other configurations are the same as those in FIG. 1 described above, and the same portions are denoted by the same reference numerals.
The “magnetic shield ring 12” corresponds to “magnetic shield means” of the present invention.

  In the present embodiment, the case where there are two heating coils will be described. However, the present invention is not limited to this, and an arbitrary number of three or more may be used. In this case, the magnetic shield ring 12 may be arranged in each heating coil, or the magnetic shield ring 12 may be arranged only in a part of the heating coils.

As shown in FIGS. 2 and 3, the magnetic shield ring 12 is formed by extending at least a part of the portion facing the adjacent heating coil downward as compared to the portion not facing.
In other words, the magnetic shield ring 12 arranged so as to surround the periphery of the heating coil 7 has a part of the portion facing the adjacent heating coil 3 (left side of the drawing) compared with a portion not facing the heating coil 3 (right side of the drawing). And extended downward.
Further, the magnetic shield ring 12 arranged so as to surround the periphery of the heating coil 3 has a part of the portion facing the adjacent heating coil 7 (right side of the drawing) compared with a portion not facing the heating coil 7 (left side of the drawing). And extended downward.

As described above, in the present embodiment, the magnetic shield ring 12 is formed by extending at least a part of the portion facing the adjacent heating coil downward as compared with the portion not facing.
For this reason, the amount of magnetic flux shielded by the part facing the adjacent heating coil can be increased compared to the part not facing, for example, heating compared to the case where the height of the magnetic shield ring is constant. Magnetic flux leaking from the coil to the adjacent pan can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

  In addition, since the portion facing the adjacent heating coil is extended downward and the portion not facing is not extended downward, the cooling air path and circuit board of the heating coil can be arranged while reducing the leakage magnetic flux to the adjacent pan. The space under the heating coil can be used effectively.

  Further, by configuring the magnetic shield ring 12 with a nonmagnetic metal such as aluminum, it is possible to suppress heat generation due to an eddy current generated inside the magnetic shield ring 12 due to the interrupted magnetic flux.

The upper end of the magnetic shield ring 12 may be arranged above the lower end of the heating coil winding. Further, the upper end of the magnetic shield ring 12 may be disposed in contact with the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

Embodiment 2. FIG.
FIG. 4 is a block diagram of the induction heating cooker showing the second embodiment as viewed from the side.
FIG. 5 is a perspective view of a magnetic shield ring showing the second embodiment.
The magnetic shield ring 12 in the present embodiment is formed by laminating at least a part of a portion facing an adjacent heating coil in the diameter direction.
Other configurations are the same as those in the first embodiment, and the same reference numerals are given to the same portions.

As shown in FIGS. 4 and 5, the magnetic shield ring 12 arranged so as to surround the periphery of the heating coil 7 has a portion facing the adjacent heating coil 3 (on the left side of the drawing) separated by a space in the diametrical direction. In addition, the magnetic shield ring 12 arranged so as to surround the periphery of the heating coil 3 has a portion facing the adjacent heating coil 7 (on the right side in the drawing) separated by a space (air layer) in the diameter direction. It has a heavy structure.
In addition, although it was set as the double structure here over the air layer, this invention is not limited to this, The structure which does not provide an air layer may be sufficient. Moreover, it is good also as a structure more than triple.

As described above, in this embodiment, the magnetic shield ring 12 is formed by laminating at least a part of a portion facing the adjacent heating coil in the diameter direction.
For this reason, the amount of magnetic flux shielded by the portion facing the adjacent heating coil can be increased compared to the portion not facing, for example, adjacent to the heating coil compared to the case where the magnetic shield ring is a single layer. The magnetic flux leaking into the pot to be reduced can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

  Moreover, since the magnetic shield ring 12 is laminated | stacked on the diameter direction, the leakage magnetic flux to the adjacent pan can be reduced, without extending below, The said magnetic shield ring 12 can be comprised thinly. Therefore, since the cooling air path of the heating coil and the circuit board can be arranged under the magnetic shield ring 12, space can be used effectively.

  Further, by configuring the magnetic shield ring 12 with a nonmagnetic metal such as aluminum, it is possible to suppress heat generation due to an eddy current generated inside the magnetic shield ring 12 due to the interrupted magnetic flux.

The upper end of the magnetic shield ring 12 may be arranged above the lower end of the heating coil winding. Further, the upper end of the magnetic shield ring 12 may be disposed in contact with the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

Embodiment 3 FIG.
FIG. 6 is a block diagram of the induction heating cooker showing Embodiment 3 as seen from the side.
7 and 8 are perspective views of the magnetic shield ring showing the third embodiment.
The magnetic shield ring 12 in the present embodiment is formed such that at least a part of a side surface of a portion facing an adjacent heating coil is inclined so that the upper side approaches the center.
Other configurations are the same as those in the first embodiment, and the same reference numerals are given to the same portions.

As shown in FIGS. 6 and 7, the magnetic shield ring 12 arranged so as to surround the periphery of the heating coil 7 has a portion facing the adjacent heating coil 3 (on the left side of the drawing), a portion not facing the heating coil 3 ( Compared to the right side of the drawing), the ring is extended downward, and the side surface of the ring extended downward is inclined so that the upper side approaches the center.
In addition, the magnetic shield ring 12 arranged so as to surround the periphery of the heating coil 3 has a portion facing the adjacent heating coil 7 (on the right side in the drawing) lower than a portion not facing the heating coil 7 (on the left side in the drawing). The side surface of the ring that is extended and further downward is inclined so that the upper side is closer to the center.

The shape of the magnetic shield ring 12 is not limited to this, and it may be formed by inclining at least a part of the side face of the portion facing the adjacent heating coil.
For example, as shown in FIG. 8, the height of the magnetic shield ring 12 in the vertical direction may be constant, and the side surface of the portion facing the adjacent heating coil may be inclined so that the upper side approaches the center. .

As described above, in the present embodiment, the magnetic shield ring 12 is formed such that at least a part of the side surface of the portion facing the adjacent heating coil is inclined so that the upper side approaches the center.
For this reason, the amount of magnetic flux shielded by the portion facing the adjacent heating coil can be increased compared to the portion not facing, for example, compared with the case where the side surface of the magnetic shield ring is not inclined, Magnetic flux leaking to the adjacent pan can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

  Further, by forming the side surfaces to be inclined, it is possible to increase the area of the side surfaces without increasing the height of the magnetic shield ring 12, and to reduce the leakage magnetic flux to the adjacent pan. Therefore, since the cooling air path of the heating coil and the circuit board can be arranged under the magnetic shield ring 12, space can be used effectively.

  Further, by configuring the magnetic shield ring 12 with a nonmagnetic metal such as aluminum, it is possible to suppress heat generation due to an eddy current generated inside the magnetic shield ring 12 due to the interrupted magnetic flux.

The upper end of the magnetic shield ring 12 may be arranged above the lower end of the heating coil winding. Further, the upper end of the magnetic shield ring 12 may be disposed in contact with the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

Embodiment 4 FIG.
FIG. 9 is a block diagram of the induction heating cooker showing the fourth embodiment as viewed from the side.
FIG. 10 is a perspective view of a magnetic shield ring showing the fourth embodiment.
In the magnetic shield ring 12 in the present embodiment, at least a part of the portion facing the adjacent heating coil is formed thicker than the portion not facing.
Other configurations are the same as those in the first embodiment, and the same reference numerals are given to the same portions.

As shown in FIG. 9 and FIG. 10, the magnetic shield ring 12 arranged so as to surround the heating coil 7 is formed so that the portion facing the adjacent heating coil 3 (on the left side of the drawing) is formed with a large thickness. The surface parallel to the plate 2 is formed to be wide.
In addition, the magnetic shield ring 12 disposed so as to surround the periphery of the heating coil 3 is formed so that the portion facing the adjacent heating coil 7 (on the right side in the drawing) is formed thick and the surface parallel to the top plate 2 is wide. It is formed to become.

As described above, in the present embodiment, the magnetic shield ring 12 is formed such that at least a part of the part facing the adjacent heating coil is thicker than the part not facing.
For this reason, the amount of magnetic flux shielded by the portion facing the adjacent heating coil can be increased compared to the portion not facing, for example, compared with the case where the thickness of the magnetic shield ring is constant, the heating coil Can reduce the magnetic flux leaking to the adjacent pan. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

Further, since the thickness of the magnetic shield ring 12 is increased and the surface parallel to the top plate 2 is widened, the leakage magnetic flux from the oblique lower surface of the top plate 2 toward the adjacent pan can be effectively reduced. .
Moreover, the leakage magnetic flux to the adjacent pan can be reduced without increasing the height of the magnetic shield ring 12, and the magnetic shield ring 12 can be made thin. Therefore, since the cooling air path of the heating coil and the circuit board can be arranged under the magnetic shield ring 12, space can be used effectively.

  Further, by configuring the magnetic shield ring 12 with a nonmagnetic metal such as aluminum, it is possible to suppress heat generation due to an eddy current generated inside the magnetic shield ring 12 due to the interrupted magnetic flux.

The upper end of the magnetic shield ring 12 may be arranged above the lower end of the heating coil winding. Further, the upper end of the magnetic shield ring 12 may be disposed in contact with the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

Embodiment 5 FIG.
FIG. 11 is a top view of the magnetic shield ring showing the fifth embodiment.
The magnetic shield ring 12 in the present embodiment is a portion facing an adjacent heating coil, and is formed so as to cover at least a part of the upper surface of the heating coil surrounded by the magnetic shield ring 12.
Other configurations are the same as those in the first embodiment, and the same reference numerals are given to the same portions.

As shown in FIG. 11, the magnetic shield ring 12 arranged so as to surround the periphery of the heating coil 7 is a portion facing the adjacent heating coil 3 (on the left side in the drawing), and a part of the upper surface of the heating coil 7 is formed. It is formed to cover.
The magnetic shield ring 12 disposed so as to surround the periphery of the heating coil 3 is a portion facing the adjacent heating coil 7 (on the right side in the drawing) and is formed so as to cover a part of the upper surface of the heating coil 3. ing.

As described above, in the present embodiment, the heating coil is formed so as to cover at least a part of the upper surface of the heating coil that is opposed to the adjacent heating coil and is surrounded by the magnetic shield ring 12.
For this reason, the amount of magnetic flux shielded by the portion facing the adjacent heating coil can be increased compared to the portion not facing, for example, the heating coil compared with the magnetic shield ring that does not cover the upper surface of the heating coil. Magnetic flux leaking from the upper surface to the adjacent pan can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
In addition, when the magnetic shield ring 12 is installed on the upper surface of the heating coil, the magnetic flux for heating the pan is also reduced, and the heating efficiency is reduced. However, since the portion to be covered is limited, the reduction in the heating efficiency is minimized. It can be suppressed.

  Further, by configuring the magnetic shield ring 12 with a nonmagnetic metal such as aluminum, it is possible to suppress heat generation due to an eddy current generated inside the magnetic shield ring 12 due to the interrupted magnetic flux.

Note that the upper end of the magnetic shield ring 12 may be disposed in contact with the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

In the first to fifth embodiments, the ring-shaped magnetic shield means of the present invention has been described. However, the present invention is not limited to this, and at least a part of the portion facing the adjacent heating coil is used. Any shape may be used as long as it is formed so as to increase the amount of magnetic flux to be shielded compared to the non-opposing portions.
For example, a rectangular shape may be used as shown in FIG. 12, an arc shape as shown in FIG. 13, or a U shape as shown in FIG.
Also in such an arbitrarily shaped magnetic shield means, the side surface facing the adjacent heating coil may be formed to extend downward compared to the side surface not facing (see, for example, FIG. 15).
Also, in the magnetic shield means having an arbitrary shape, a plurality of side surfaces facing adjacent heating coils may be laminated.
Also, in the magnetic shield means having an arbitrary shape, the side surface facing the adjacent heating coil may be made thicker than the side surface not facing.
Further, the magnetic shield means having an arbitrary shape may be formed so as to cover at least a part of the upper surface of the heating coil that is surrounded by the magnetic shield means on the side surface facing the adjacent heating coil.
Even if it is such a structure, there can exist an effect similar to Embodiment 1-5 mentioned above.

  In the first to fifth embodiments, the case where both the magnetic shield ring 12 arranged in the heating coil 3 and the magnetic shield ring 12 arranged in the heating coil 7 are shaped to reduce the leakage magnetic flux has been described. Only one of them may have a shape that reduces the above-described leakage magnetic flux, and the other may have a cylindrical ring or a configuration that is not provided.

Embodiment 6 FIG.
FIG. 16: is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 6 from the side surface.
As shown in FIG. 16, in the induction heating cooker in the present embodiment, a ring-shaped magnetic shield ring 12 is installed so as to surround each of the heating coil 3 and the heating coil 7. As the magnetic shield ring 12, the magnetic shield ring 12 of any of the first to fifth embodiments may be used, or a magnetic shield ring having a constant height and thickness may be used.
A flat magnetic shield plate 13 made of a nonmagnetic metal such as aluminum is disposed between the heating coil 3 and the heating coil 7. Further, the magnetic shield plate 13 in the present embodiment is disposed substantially perpendicular to the top plate 2.
Other configurations are the same as those in FIG. 1 described above, and the same portions are denoted by the same reference numerals.
The “magnetic shield plate 13” corresponds to “magnetic shield means” of the present invention.

  In the present embodiment, the case where there are two heating coils will be described. However, the present invention is not limited to this, and an arbitrary number of three or more may be used. Also in this case, the flat magnetic shield plate 13 is disposed between adjacent heating coils among the plurality of heating coils.

As described above, in the present embodiment, the flat magnetic shield plate 13 disposed between adjacent heating coils is provided, and the magnetic shield plate 13 is disposed substantially perpendicular to the top plate 2. Yes.
For this reason, the magnetic flux which leaks from the heating coil to the adjacent pan can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

  Moreover, it is not necessary to provide a configuration for reducing the leakage magnetic flux to the pan adjacent to each heating coil, and interference sound can be prevented with an inexpensive configuration.

  In addition, since the magnetic shield plate 13 is made of a nonmagnetic metal such as aluminum, heat generation due to an eddy current generated inside the magnetic shield plate 13 due to the interrupted magnetic flux can be suppressed.

Note that the upper end of the magnetic shield plate 13 may be disposed above the lower end of the heating coil winding. Further, the upper end of the magnetic shield plate 13 may be disposed in contact with the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

Embodiment 7 FIG.
FIG. 17: is the block diagram which looked at the induction heating cooking appliance which shows Embodiment 7 from the side surface.
As shown in FIG. 17, the magnetic shield plate 13 in the present embodiment is disposed substantially horizontally with respect to the top plate 2.
Other configurations are the same as those in the sixth embodiment, and the same reference numerals are given to the same portions.

As described above, in the present embodiment, the flat magnetic shield plate 13 disposed between the adjacent heating coils is provided, and the magnetic shield plate 13 is disposed substantially horizontally with respect to the top plate 2. Yes.
For this reason, the magnetic flux which leaks from the heating coil to the adjacent pan can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

  Moreover, it is not necessary to provide a configuration for reducing the leakage magnetic flux to the pan adjacent to each heating coil, and interference sound can be prevented with an inexpensive configuration.

  In addition, since the magnetic shield plate 13 is installed so as to be substantially horizontal with respect to the top plate 2, a cooling air path and a circuit board for the heating coil can be disposed under the magnetic shield plate 13, so that the space can be used effectively. .

  In addition, since the magnetic shield plate 13 is made of a nonmagnetic metal such as aluminum, heat generation due to an eddy current generated inside the magnetic shield plate 13 due to the interrupted magnetic flux can be suppressed.

In addition, you may make it arrange | position the upper end (upper surface) of the magnetic shield board 13 above the lower end of a heating coil winding. Further, the upper end (upper surface) of the magnetic shield plate 13 may be disposed so as to contact the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

For example, as shown in FIG. 18, the magnetic shield plate 13 may be disposed so as to cover a part of the upper surface of the heating coils 3 and 7. With such an arrangement, the magnetic flux leaking from the upper surface of the heating coil to the adjacent pan can be further reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Moreover, when the magnetic shield plate 13 is installed on the upper surface of the heating coil, the magnetic flux for heating the pan is also reduced, and the heating efficiency is reduced. However, since the portion to be covered is limited, the reduction in the heating efficiency is minimized. It can be suppressed.

Embodiment 8 FIG.
FIG. 19 is a block diagram of the induction cooking device showing the eighth embodiment as viewed from the side.
As shown in FIG. 19, the magnetic shield plate 13 in the present embodiment is disposed obliquely with respect to the top plate 2.
Other configurations are the same as those in the sixth embodiment, and the same reference numerals are given to the same portions.

As described above, in the present embodiment, the flat magnetic shield plate 13 disposed between adjacent heating coils is provided, and the magnetic shield plate 13 is disposed obliquely with respect to the top plate 2. .
For this reason, the magnetic flux which leaks from the heating coil to the adjacent pan can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

  Moreover, it is not necessary to provide a configuration for reducing the leakage magnetic flux to the pan adjacent to each heating coil, and interference sound can be prevented with an inexpensive configuration.

  In addition, since the magnetic shield plate 13 is installed obliquely with respect to the top plate 2, the magnetic shield plate 13 having a large area can be installed, and the leakage magnetic flux to the pan placed on the adjacent heating coil is further reduced. It is possible to increase the magnetic shielding effect.

  In addition, since the magnetic shield plate 13 is made of a nonmagnetic metal such as aluminum, heat generation due to an eddy current generated inside the magnetic shield plate 13 due to the interrupted magnetic flux can be suppressed.

Note that the upper end of the magnetic shield plate 13 may be disposed above the lower end of the heating coil winding. Further, the upper end of the magnetic shield plate 13 may be disposed in contact with the lower surface of the top plate 2.
Thereby, the leakage magnetic flux to the pan placed on the adjacent heating coil can be further reduced.

Embodiment 9 FIG.
FIG. 20 is a top view of the induction heating cooker showing the ninth embodiment.
As shown in FIG. 20, below the heating coil 3 and the heating coil 7, a plurality of ferrites 14 each formed in a rod shape are arranged radially.
The ferrite 14 serves to guide the magnetic flux emitted from the lower surface of the heating coil to the top plate 2 side on which the pan is placed.

In the present embodiment, among the plurality of ferrites 14 arranged radially, at least a part of the ferrite arranged in the portion facing the adjacent heating coil is made longer than the ferrite arranged in the non-opposing portion. It is shortened.
For example, as shown in FIG. 20, among the ferrites 14 arranged radially below the heating coil 7, the ferrite 14 arranged in the portion facing the adjacent heating coil 3 (left side of the drawing) is compared with other ferrites 14. Thus, the length is shortened.
Further, among the ferrites 14 arranged radially below the heating coil 3, the length of the ferrite 14 arranged on the portion facing the adjacent heating coil 7 (on the right side of the drawing) is shorter than that of other ferrites 14. Forming.

  In addition, you may make it not arrange | position the ferrite 14 to at least one part facing the adjacent heating coil among the some ferrite 14 arrange | positioned radially.

  In the ninth embodiment, the case where the rod-like ferrites 14 are arranged radially has been described, but the present invention is not limited to this. What is necessary is just to make it the area | region which arrange | positioned the ferrite in the side facing an adjacent heating coil among the bottoms of a heating coil decrease compared with the range which has arrange | positioned the ferrite in the non-opposing side. For example, the ferrite 14 may have an arbitrary shape, and may be disposed at an arbitrary position so that the arrangement range on the adjacent heating coil side is reduced.

As described above, in the present embodiment, among the plurality of ferrites 14, at least a part of the ferrite 14 disposed in the portion facing the adjacent heating coil is longer than the ferrite 14 disposed in the portion not facing. Shortened the length.
For this reason, the magnetic flux radiated | emitted above a heating coil from the side facing an adjacent heating coil can be weakened, and the magnetic flux which leaks from the heating coil upper surface to an adjacent pan can be reduced. Therefore, interference noise can be prevented regardless of the driving frequency of the heating coil.
Therefore, it is not necessary to separate the driving frequencies of the heating coils from each other by 20 kHz or more, and it is possible to prevent an increase in coil loss and driving circuit loss due to an increase in driving frequency.

Embodiment 10 FIG.
According to the configurations of the first to ninth embodiments, interference noise can be prevented without operating one of the plurality of heating coils at a frequency separated by 20 kHz or more. Further, since it is not necessary to operate at a high frequency, it is not necessary to increase the eddy current loss of the heating coil and the switching loss of the drive circuit.
On the other hand, an eddy current flows through the magnetic shield ring 12 or the magnetic shield plate 13 that blocks the leakage magnetic flux. The magnetic shield ring 12 and the magnetic shield plate 13 are made of a nonmagnetic metal material that does not easily generate heat, but are accompanied by slight heat generation. Further, in the configuration in which the length of the ferrite 14 is partially shortened, the magnetic flux to the pan to be heated is also weakened. Therefore, it is necessary to increase the input in order to heat the pan, and there is a slight loss of the drive circuit. However, it will increase.
As a result, the internal temperature of the casing (not shown) in which the heating coils 3 and 7, the drive circuits 4 and 8, the magnetic shield ring 12 and the magnetic shield plate 13 are housed increases slightly.

In the present embodiment, at least a part or all of the switching elements and diodes constituting the drive circuits 4 and 8 are formed of a wide band gap semiconductor. Examples of the wide band gap semiconductor include silicon carbide, a gallium nitride-based material, and diamond.
Other configurations are the same as those in any of the first to ninth embodiments.

As described above, in the present embodiment, at least a part or all of the switching elements and diodes constituting the drive circuits 4 and 8 are formed of a wide band gap semiconductor.
For this reason, switching loss and on-loss can be reduced, and heat generation inside the housing containing the heating coils 3 and 7, the drive circuits 4 and 8, the magnetic shield ring 12 and the magnetic shield plate 13 can be suppressed.
In addition, since switching elements and diode elements formed of wide band gap semiconductors have high voltage resistance and high allowable current density, the switching elements and diode elements can be miniaturized. By using a diode element, a semiconductor module incorporating these elements can be miniaturized.

  Further, since the heat resistance is high, the heat radiation fins of the heat sink can be downsized and the water cooling part can be air cooled, so that the semiconductor module can be further downsized.

  Furthermore, since the power loss is low, it is possible to increase the efficiency of the switching element and the diode element, and further increase the efficiency of the semiconductor module.

  Although both the switching element and the diode element are desirably formed of a wide band gap semiconductor, either one of the elements may be formed of a wide band gap semiconductor, and the effects described in this embodiment Can be obtained.

  1 AC power source, 2 top plate, 3 heating coil, 4 drive circuit, 5 control circuit, 6 pan, 7 heating coil, 8 drive circuit, 9 control circuit, 10 pan, 11 dotted line, 12 magnetic shield ring, 13 magnetic shield plate 14 Ferrite.

Claims (18)

A top plate on which an object to be heated is placed;
A plurality of heating coils provided under the top plate for heating the object to be heated;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
A ring-shaped magnetic shield means arranged so as to surround the heating coil,
The magnetic shield means includes
An induction heating cooker characterized in that at least a part of a portion facing the adjacent heating coil is formed such that a larger amount of magnetic flux is shielded than a portion not facing the heating coil. The magnetic shield means includes
The induction heating cooker according to claim 1, wherein at least a part of a portion facing the adjacent heating coil is formed to extend downward as compared with a portion not facing the heating coil. The magnetic shield means includes
The induction heating cooker according to claim 1, wherein a plurality of portions facing each of the adjacent heating coils are stacked in a diametrical direction. The magnetic shield means includes
2. The induction heating cooker according to claim 1, wherein at least a part of a side surface of the portion facing the adjacent heating coil is inclined so that the upper side approaches the center. The magnetic shield means includes
The induction heating cooker according to claim 1, wherein at least a part of a portion facing the adjacent heating coil is formed to be thicker than a portion not facing the heating coil. The magnetic shield means includes
2. The induction heating cooker according to claim 1, wherein the induction heating cooker is formed so as to cover at least a part of an upper surface of the heating coil that is adjacent to the adjacent heating coil and is surrounded by the magnetic shield means. A top plate on which an object to be heated is placed;
A plurality of heating coils provided under the top plate for heating the object to be heated;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
A magnetic shield ring arranged to surround the heating coil;
An induction heating cooker comprising a flat magnetic shield means arranged between adjacent heating coils among the plurality of heating coils. The induction heating cooker according to claim 7, wherein the magnetic shield means is disposed substantially perpendicular to the top plate. The induction heating cooker according to claim 7, wherein the magnetic shield means is disposed substantially horizontally with respect to the top plate. The induction heating cooker according to claim 7, wherein the magnetic shield means is disposed obliquely with respect to the top plate. The magnetic shield means includes
The induction heating cooker according to any one of claims 1 to 10, wherein an upper end is disposed above a lower end of the heating coil. The magnetic shield means includes
The induction heating cooker according to any one of claims 1 to 11, wherein an upper end is disposed so as to contact a lower surface of the top plate. The induction heating cooker according to any one of claims 1 to 12, wherein the magnetic shield means is made of a nonmagnetic metal. A top plate on which an object to be heated is placed;
A plurality of heating coils provided under the top plate for heating the object to be heated;
Ferrite disposed under the heating coil;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
An induction heating cooker characterized in that the range in which the ferrite is disposed on the side facing the adjacent heating coil is less than the range in which the ferrite is disposed on the non-facing side under the heating coil. The ferrite is formed in a rod shape, and a plurality of radials are arranged under the heating coil,
The at least part of the ferrite disposed in a portion facing the adjacent heating coil among the plurality of ferrites is shorter in length than the ferrite disposed in a portion not facing the ferrite. Item 15. The induction heating cooker according to Item 14. The ferrite is formed in a rod shape, and a plurality of radials are arranged under the heating coil,
The induction heating cooker according to claim 14, wherein the ferrite is not disposed in at least a part of a portion facing the adjacent heating coil. The induction heating cooker according to any one of claims 1 to 16, wherein at least part or all of the switching elements and diodes constituting the drive circuit are formed of a wide band gap semiconductor. The induction heating cooker according to claim 17, wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material, or diamond.

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