JP2021108259A - Induction heating cooker - Google Patents

Abstract

To suppress the generation of unpleasant interference noise in an induction heating cooker equipped with a plurality of heating coils.SOLUTION: An induction heating cooker 10 includes a first heating coil 16 and a second heating coil 20, a plurality of inverters that are provided corresponding to the first heating coil 16 and the second heating coil 20 and supply a high-frequency current, and a control unit 60 that controls a drive frequency of each of the inverters 30. The control unit 60 includes a random number generation unit 62 that generates random numbers over time in a predetermined range, and modulates at least one of the plurality of first inverters 30a and the second inverter 30b by the random number generated by the random number generation unit 62 to diffuse the frequency of the interference sound when a difference between the drive frequencies of the plurality of first inverters 30a and the second inverter 30b is within an audible frequency range.SELECTED DRAWING: Figure 2

Description

The present invention relates to an induction heating cooker.

Conventionally, an induction heating cooker provided with a plurality of heating coils has been provided. Such an induction heating cooker includes a plurality of inverters provided corresponding to each of the plurality of heating coils, and by driving each of them at a predetermined drive frequency, a set heating output can be obtained. It is supposed to be. In such an induction heating cooker, when a plurality of heating coils are used at the same time, the frequency corresponding to the difference between the drive frequencies of the respective inverters becomes an audible frequency, and an unpleasant interference sound is generated.

Therefore, a method is generally used in which the output of each inverter is fixed at the same frequency, and the output is controlled by changing the current time flowing through the heating coil in a fixed frequency cycle. Further, in the induction heating cooker disclosed in Patent Document 1 below, the sweep state in which the drive frequency difference between a plurality of inverter drive circuits fluctuates continuously is controlled to be continued, and the interference sound heard by the user is reduced. I'm going to let you.

Japanese Patent No. 5832129

However, the above-mentioned method of fixing to the same frequency requires a current resonance inverter of a half-bridge circuit that requires two switching elements or a full-bridge circuit that requires four switching elements, and a simple voltage resonance inverter with one switching element is required. I can not use it. Further, in the induction heating cooker of Patent Document 1, even if it is possible to make it difficult for the user to hear the interference sound, it cannot be said that the interference sound is converted into white noise. In Patent Document 1, as an example of the case where the drive frequency is continuously swept, an example of using a triangular wave waiting for periodicity is given. However, even if the interference sound can be reduced by sweeping the drive frequency in this way, it is considered that the frequency due to the repetition period of the triangular wave and its harmonic frequency component become the audible frequency. Therefore, there is a concern that the sound generated by the audible frequency component may be unpleasant.

Therefore, an object of the present invention is to solve the above-mentioned problems and suppress the generation of unpleasant interference noise in an induction heating cooker provided with a plurality of heating coils.

(1) In the induction heating cooker of the present invention, a plurality of heating coils, a plurality of inverters provided corresponding to the plurality of heating coils, and a plurality of inverters for supplying a high frequency current, and a plurality of the inverters are set respectively. The control unit is provided with a control unit that controls the drive frequency so as to be an output, and the control unit is provided with the condition that the difference between the drive frequencies of the plurality of inverters is within the range of the audible frequency. It is characterized in that the frequency of the interference sound is diffused by randomly modulating at least one drive frequency of the inverters in a predetermined frequency width.

In the induction heating cooker of the present invention, at least one drive frequency of the plurality of inverters is randomly modulated on the condition that the difference between the drive frequencies of the plurality of inverters is within the range of the audible frequency. The frequency of the interference sound can be diffused. Therefore, according to the present invention, it is possible to suppress the generation of unpleasant interference noise in an induction heating cooker provided with a plurality of heating coils.

(2) The above-described induction heating cooker has a random number generation unit that generates random numbers over time in a predetermined range, and the control unit generates at least one drive frequency of the plurality of inverters. It is preferable that the frequency of the interfering sound is diffused by modulating with the random number generated in the above.

The induction heating cooker of the present invention has a random number generator, and is capable of generating random numbers over time within a predetermined range. Further, the control unit uses a random number generated in the random number generator to set at least one drive frequency of the plurality of inverters, provided that the difference between the drive frequencies of the plurality of inverters is within the range of the audible frequency. It can be modulated and the interfering sound can be frequency diffused. Therefore, according to the present invention, it is possible to suppress the generation of unpleasant interference noise in an induction heating cooker provided with a plurality of heating coils.

(3) In the above-mentioned induction heating cooker, the control unit drives and controls the inverter with the highest output (lowest frequency) without modulating the drive frequency with a random number, and drives the other inverters with a random number. It is preferable that the frequency is modulated.

According to this configuration, the input fluctuation width can be reduced under the same condition as the frequency diffusion width (the wider the diffusion width, the greater the interference sound suppression effect), and the drive frequency is modulated by a random number for the inverter having the highest output. No need to do. Therefore, according to the present invention, it is possible to provide an induction heating cooker capable of suppressing the generation of unpleasant interference noise by simple control.

(4) In the induction heating cooker described above, the control unit is characterized in that the random numbers that modulate the drive frequencies of the plurality of inverters are random numbers that cancel each other out. It would be nice to have it.

According to such a configuration, the frequency spread width can be doubled, and the frequency of occurrence of the drive frequency difference within the frequency spread width is the same. Therefore, it is possible to significantly suppress the interference noise generated when a plurality of inverters are driven by different drive frequencies. In addition, the input fluctuations are also offset (although not 100% offset) between the inverters, and the effect of suppressing the input fluctuation range can be expected. In the case of random numbers that are independent of each other, the frequency of occurrence of the frequency difference becomes maximum at the center frequency of the diffusion width, and the effect of suppressing the interference sound is diminished.

(5) In the induction heating cooker described above, the control unit controls the center frequency so that the average value of the inputs for each of the plurality of inverters becomes a predetermined input according to the set output. good.

According to such a configuration, it is possible to provide an induction heating cooker capable of obtaining an output as set while suppressing the generation of unpleasant interference noise.

(6) In the induction heating cooker described above, if the random number generator is an M-sequence pseudo-random number generator, random numbers can be easily generated by a general-purpose microcomputer.

According to the present invention, in an induction heating cooker provided with a plurality of heating coils, it is possible to provide an induction heating cooker capable of suppressing the generation of unpleasant interference noise.

It is a figure which shows the induction heating cooker which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the induction heating cooker of FIG. It is a circuit diagram which shows an example of the inverter used in the induction heating cooker of FIG. It is a graph which shows an example of the transition of the drive frequency of each inverter at the time of performing frequency diffusion control in the induction heating cooker of FIG. It is a graph which shows another example of the transition of the drive frequency of each inverter at the time of performing frequency diffusion control in the induction heating cooker of FIG.

Hereinafter, the induction heating cooker 10 according to the embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the outline of the basic configuration of the induction heating cooker 10, the inverter 30 which is an example of the circuit for driving, and the control unit 60 will be described, and then the induction heating cooker 10 will be used. The characteristic control method used will be described.

<< About the basic configuration of the induction heating cooker 10 >>
The induction heating cooker 10 shown in FIG. 1 has a first heating port 14 and a second heating port 16 on the left and right sides of a top plate 12 on which a pot or the like can be placed. The induction heating cooker 10 includes a first heating coil 18 and a second heating coil 20 at positions corresponding to the first heating port 14 and the second heating port 16 on the lower side of the top plate 12.

The induction heating cooker 10 is a pot placed on the first heating port 14 and the upper part of the second heating port 16 by a high frequency magnetic field generated by energizing the first heating coil 18 and the second heating coil 20. Etc. can be induced and heated. In the induction heating cooker 10, for example, the output of the first heating port 14 and the second heating port 16 can be set by the operation panel 22 provided on the top plate 12 or the like.

≪About inverter 30≫
As shown in FIG. 2, the induction heating cooker 10 includes a plurality of (two in this embodiment) inverters 30. The inverter 30 is connected to an AC power supply 24 such as a commercial power supply. The inverter 30 includes a first inverter 30a for the first heating coil 18 and a second inverter 30b for the second heating coil 20. Since the first inverter 30a and the second inverter 30b have the same configuration, they will be collectively referred to as the inverter 30 in the following description and FIG. 3, and will be described without any particular distinction between the two.

As shown in FIGS. 2 and 3, the inverter 30 is connected to the first heating coil 18 or the second heating coil 20 and an AC power supply 24 such as a commercial power supply. As shown in FIG. 3, the inverter 30 includes a non-smoothing DC voltage circuit 40 and an inverter circuit 42.

The non-smoothing DC voltage circuit 40 includes a full-wave rectifier circuit 44, a choke coil 46, and a capacitor 48. The full-wave rectifier circuit 44 is composed of a diode bridge. The full-wave rectifier circuit 44 is connected to the AC power supply 24 on the input side. Further, the full-wave rectifier circuit 44 is connected to one end of the capacitor 48 via the choke coil 46 on one output side (DC power supply line 40a) and to the other end of the capacitor 48 on the other side (DC power supply line 40b). ing.

The inverter circuit 42 is connected to the output side of the non-smoothing DC voltage circuit 40 (DC power supply lines 40a, 40b). The inverter circuit 42 includes a switching element 50, a free hole diode 52, and a capacitor 54. The switching element 50 is connected between the DC power supply lines 40a and 40b. The free hole diode 52 is connected in parallel with the switching element 50. Further, the capacitor 54 is connected in parallel to the first heating coil 18 or the second heating coil 20.

<< About control unit 60 >>
The control unit 60 controls the drive frequency so that a plurality of (two in the present embodiment) inverters 30 (first inverter 30a and second inverter 30b) each have a set output. The control unit 60 is supposed to include, for example, a microcomputer. By controlling the operation of the inverter circuit 42 described above, the control unit 60 can apply a high-frequency current to the first heating coil 18 or the second heating coil 20 to generate a high-frequency magnetic field.

The control unit 60 includes a random number generation unit 62, a frequency modulation unit 64, and a drive frequency control unit 66. The random number generation unit 62 generates a random number for modulating the drive frequency of the inverter 30. The random number generation unit 62 generates random numbers in a predetermined range so as to randomly fluctuate with time (continuously generated at predetermined time intervals). The random number generator 62 may be configured by, for example, an M-sequence pseudo-random number generator or the like. The frequency modulation unit 64 modulates the drive frequency of at least one of the plurality of inverters 30 (the first inverter 30a and the second inverter 30b in the present embodiment) with the random numbers generated by the random number generation unit 62. be. The drive frequency control unit 66 adjusts the center value of the drive frequency according to the set output of the first inverter 30a and the second inverter 30b.

The control unit 60 controls the frequency (audible sound frequency) of the interference sound generated by the difference in the drive frequency by operating the inverter 30 at the drive frequency modulated by the frequency modulation unit 64 (frequency diffusion control). You can. Hereinafter, frequency diffusion control, which is a control peculiar to the induction heating cooker 10 performed by the control unit 60, will be described in detail with reference to the drawings.

≪Frequency diffusion control≫
Hereinafter, the frequency diffusion control performed by the control unit 60 in the induction heating cooker 10 will be described in detail with reference to the drawings.

Here, when a plurality of inverters 30 (first inverter 30a and second inverter 30b in the present embodiment) exist as in the induction heating cooker 10 described above, the set outputs of each are different and a plurality of inverters 30 are present. If the difference in the drive frequencies of the inverter 30 is within the range of the audible frequency, there is a concern that an unpleasant interference sound may be generated. Therefore, in the induction heating cooker 10 of the present embodiment, by performing frequency diffusion control, it is possible to suppress the discomfort given to the user or the like by the interference sound.

Specifically, in the induction heating cooker 10 of the present embodiment, two random number generation units 62 (first random number generation unit 62a, second random number generation unit 62a, second random number generation unit 62) corresponding to each of the first inverter 30a and the second inverter 30b. Part 62b) is provided. The first random number generation unit 62a and the second random number generation unit 62b have a relationship in which the frequency modulation portions determined by the random numbers cancel each other out. For example, the relationship between the modulation frequency (fra) generated by the first random number generation unit 62a and the modulation frequency (frb) generated by the second random number generation unit 62b is set to fla = −frb. The modulation frequency range is a predetermined range (± M), and a random frequency is generated within this frequency range. The inverter of this embodiment is an inverter that can reduce the output and reduce the input by increasing the frequency.

More specifically, as shown in FIG. 4, the frequency modulation unit 64 randomly modulates the drive frequency of the first inverter 30a over time based on the random numbers generated by the first random number generation unit 62a (FIG. a) See). Further, the frequency modulation unit 64 also modulates the drive frequency of the second inverter 30b over time in the second random number generation unit 62b based on the random numbers according to the relationship with the first random number generation unit described above (FIG. FIG. See (b)). Further, the drive frequency control unit 66 sets the center (fca) or (fca) of each drive collection frequency so that the average input value of each of the first inverter 30a and the second inverter 30b becomes a predetermined input according to the set output. fcb) is controlled. Since the drive frequency and the input have the above-mentioned relationship, the average value of the input becomes smaller when the center of the drive frequency is made higher, and becomes larger when the center of the drive frequency is made lower.

Here, as described above, in the first random number generation unit 62a and the second random number generation unit 62b, the modulation frequency portions (fra, frb) corresponding to the random numbers generated at each timing are assumed to cancel each other out. There is. Therefore, the sum of the drive frequencies of the first inverter 30a and the second inverter 30b within a predetermined time is at or near the center (fca) and (fcb) of the respective drive frequencies.

Further, the difference in drive frequencies between the first inverter 30a and the second inverter 30b is such that the frequency range is doubled (± 2M) with the difference in the centers of the respective drive frequencies (fca-fcb) as the center from the above-mentioned relationship. Become. This is the frequency spread width of the interfering sound. The frequency of occurrence of the interference sound frequency within this diffusion width is only a value obtained by doubling the random number in the first random number generation unit 62b and has no effect on the randomness, so it is generated in the first random number generation unit 62a. It will be a random number similar to the random number. Therefore, in the induction heating cooker 10, the discomfort caused by the interference sound can be suppressed.

Further, when the first inverter 30a increases the drive frequency (the input decreases), the second inverter 30b decreases the drive frequency (increases the input), so that the fluctuation of the input due to the frequency modulation can be suppressed.

As described above, in the induction heating cooker 10 of the present embodiment, the random number generation unit 62 included in the control unit 60 can generate random numbers over time within a predetermined range. Further, in the induction heating cooker 10, the control unit 60 sets the first inverter 30a and the second inverter 30b on the condition that the difference between the drive frequencies of the first inverter 30a and the second inverter 30b is within the range of the audible frequency. The drive frequency of the second inverter 30b can be modulated by the random number generation unit 62 with the random number having the above-mentioned relationship, and the frequency of the interference sound can be diffused. Therefore, according to the present embodiment, it is possible to suppress the generation of unpleasant interference noise in the induction heating cooker 10 provided with the plurality of first heating coils 16 and the second heating coils 20. Further, since the fluctuation of the input can be suppressed, it becomes easy to take measures against the outflow of the modulated wave to the power supply.

The induction heating cooker 10 of the present embodiment includes two inverters 30, a first inverter 30a for the first heating port 14 and a second inverter 30b for the second heating port 16. Further, a large number of heating ports and inverters 30 may be provided. Even when the induction heating device 10 is provided with three or more inverters 30, the generation of unpleasant interference noise can be suppressed by performing the same control as described above.

Further, in the present embodiment, both the first inverter 30a and the second inverter 30b are provided on the condition that the difference between the drive frequencies of the first inverter 30a and the second inverter 30b is within the range of the audible frequency. Although an example of modulating the drive frequency with a random number generated by the random number generation unit 62 has been shown, the present invention is not limited to this. That is, the induction heating cooker 10 may be any one that modulates the drive frequency of at least one of the plurality of inverters 30 with a random number, and it is not always necessary to modulate the drive frequencies of all the inverters 30 with a random number. do not have. In this case, the same frequency width as the frequency modulation width is the diffusion frequency width. Moreover, there is no effect of suppressing input fluctuations.

Specifically, as shown in FIG. 5, among a plurality of inverters 30 (first inverter 30a and second inverter 30b in this embodiment), the drive frequency of the first inverter 30 having the highest output is driven by a random number. The drive frequency of the second inverter 30b, which is another inverter 30, may be modulated by a random number by controlling the drive without performing the modulation of the above. In this case, since the output of the second inverter 30b is low, the drive frequency is high, so that the input fluctuation width can be reduced under the condition that the diffusion frequency width is the same.

According to such a configuration, it is not necessary to modulate the drive frequency with a random number for the first inverter 30a having the highest output. This makes it possible to suppress the generation of unpleasant interference sounds while further simplifying the control of the induction heating cooker 10.

In the example shown in FIG. 5, an example in which the inverter 30 having the highest output is selected as the inverter 30 that does not modulate the drive frequency by a random number is shown. For example, the inverter 30 having the lowest output has a drive frequency by a random number. The drive frequency of the other inverter 30 may be modulated by a random number without modulation. Further, as described above, when three or more inverters 30 are provided, the drive frequency of the inverter 30 having an intermediate set output is not modulated by a random number, and the maximum output inverter 30 and the minimum output inverter 30 are provided. The drive frequency of the other inverter 30 may be modulated by a random number.

Further, the above-mentioned induction heating cooker 10 controls so that the random numbers that modulate the drive frequencies of the first inverter 30a and the second inverter 30b cancel each other out. By performing such control, it is possible to significantly suppress the interference sound generated by driving the first inverter 30a and the second inverter 30b at different drive frequencies. In the present embodiment, an example is shown in which the random numbers that modulate the drive frequencies of the first inverter 30a and the second inverter 30b cancel each other out, but as in the example shown in FIG. 5, for example, They may not cancel each other out. In this case, the frequency of appearance of the interference sound frequency within the diffusion frequency width increases at the median value within the diffusion frequency width, but the diffusion frequency width is the same as the above-mentioned case of canceling each other, and the interference sound can be suppressed. ..

The induction heating cooker 10 described above controls the center frequency so that the average value of the inputs for each of the first inverter 30a and the second inverter 30b becomes a predetermined input according to the set output. Since the induction heating cooker 10 performs such control, it is possible to obtain an output as set while suppressing the generation of an unpleasant interference sound.

The above-mentioned induction heating cooker 10 exemplifies a random number generator 62 including an M-sequence pseudo-random number generator, but the present invention is not limited to this, and other methods, devices, and the like are used. Random numbers may be output by.

The present invention is not limited to those shown as the above-described embodiments, modifications, and the like, and there may be other embodiments from the teaching and spirit within the scope of the claims. The components of the above-described embodiment may be arbitrarily selected and combined. Further, any component of the embodiment and any component described in the means for solving the invention, or a component embodying any component described in the means for solving the invention are optional. It may be configured in combination. We also intend to acquire the rights to these in the amendment of the present application or in the divisional application.

The present invention can be suitably used in all induction heating cookers having a plurality of heating coils.

10: Induction heating cooker 18: First heating coil 20: Second heating coil 24: AC power supply 30: Inverter 30a: First inverter 30b: Second inverter 60: Control unit

Claims (6)

With multiple heating coils,
A plurality of inverters provided corresponding to each of the plurality of heating coils to supply a high frequency current, and
It is provided with a control unit that controls the drive frequency so that the plurality of inverters have set outputs.
The control unit
The frequency of the interference sound is diffused by randomly modulating at least one drive frequency of the plurality of inverters, provided that the difference between the drive frequencies of the plurality of inverters is within the range of the audible frequency. thing,
An induction heating cooker featuring. It has a random number generator that generates random numbers over time in a predetermined range.
The control unit diffuses the frequency of the interference sound by modulating at least one drive frequency of the plurality of inverters with a random number generated in the random number generator.
The induction heating cooker according to claim 1. The control unit
For the inverter with the highest output, drive control is performed without modulating the drive frequency with random numbers.
Modulating the drive frequency with random numbers for other inverters,
The induction heating cooker according to claim 1 or 2. The control unit
Modulation of the drive frequencies of the plurality of inverters by random numbers so as to cancel each other out.
The induction heating cooker according to any one of claims 1 to 3. The control unit
Controlling the drive frequency so that the average value of the inputs for each of the plurality of inverters becomes a predetermined input according to the set output.
The induction heating cooker according to any one of claims 1 to 4. The random number generator
It is composed of M-sequence pseudo-random number generators,
The induction cooking apparatus according to any one of claims 1 to 5.

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