JP5836743B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker that induction-heats a cooking vessel by supplying a high-frequency current to a heating coil.

As a conventional induction heating cooker, a load impedance is adjusted using a mutual inductance between a small-diameter inner heating coil and a large-diameter outer heating coil, and a non-magnetic cooking vessel can also be induction-heated (for example, , See Patent Document 1).
In addition, as another induction heating cooker, a magnetic material based on a current flowing through each heating coil is provided by arranging a concave magnetic material having high permeability in the inner heating coil and the outer heating coil having the same axis. Prevents the mutual influence between the induced currents generated in both of them and efficiently links the magnetic flux to the cooking container (see, for example, Patent Document 2).

JP 2007-12482 (abstract, FIG. 1) JP 2009-129737 A (page 3, FIG. 1)

  In the techniques described in Patent Documents 1 and 2 described above, induction heating is enabled by controlling the phase difference of each coil according to the magnetism and nonmagnetism of the cooking container by providing an inner heating coil and an outer heating coil. However, the magnetic fields generated from the inner heating coil, the outer heating coil, and other heating coils adjacent to the outer heating coil interfere with each other, resulting in deterioration in heating efficiency and heating unevenness. There was a problem that interference sound was generated by induction heating.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an induction heating cooker that can suppress interference of a leakage magnetic field that occurs between heating coils.

An induction heating cooker according to the present invention includes a top plate provided with at least two heating ports adjacent to each other indicating a placement position of a cooking container, and a shaft disposed below one of the heating ports. An annular inner heating coil and an outer heating coil having the same core, an annular heating coil disposed below the other heating port among the heating ports, an inner heating coil, an outer heating coil, and a heating coil, respectively. Among the ferrites arranged in the inner heating coil and the outer heating coil, the ferrite located on the heating coil side is more than the ferrite arranged on the opposite side. It is characterized by a large number.

  According to the present invention, since the concave ferrite is disposed in the circumferential direction at the lower part of each of the inner heating coil and the outer heating coil and the heating coil, leakage of the magnetic field generated from each heating coil can be reduced. Thus, mutual interference due to a leakage magnetic field can be prevented and heating unevenness can be improved. Moreover, the interference sound of a cooking container which arises by the mutual interference by a leakage magnetic field can be suppressed.

3 is a circuit diagram of the induction heating cooker according to Embodiment 1. FIG. It is a wave form diagram of the drive signal of the full bridge type inverter circuit shown in FIG. It is a top view which shows arrangement | positioning and energization direction of each heating coil in the induction heating cooking appliance of Embodiment 1. FIG. It is a schematic diagram which shows the arrangement | positioning of the ferrite of each heating coil and the direction of a magnetic field in the induction heating cooking appliance of Embodiment 1. FIG. It is a figure which shows the example of arrangement | positioning of the ferrite of the left inner / outer heating coil in the induction heating cooking appliance of Embodiment 1. FIG. It is a schematic diagram which shows the arrangement | positioning of the ferrite of each heating coil and the direction of a magnetic field in the induction heating cooking appliance of Embodiment 2. FIG. It is a figure which shows the example of arrangement | positioning of the ferrite of the left inner / outer heating coil in the induction heating cooking appliance of Embodiment 2. FIG.

Embodiment 1 FIG.
1 is a circuit diagram of an induction heating cooker according to Embodiment 1. FIG.
As shown in FIG. 1, the induction heating cooker according to the present embodiment is connected between DC power supplies 1 and 70, reactor 2 disposed on the positive electrode side of DC power supply 1, and the output of reactor 2 and the negative electrode of DC power supply 1. Smoothing capacitor 16, full-bridge inverter circuit 14 connected in parallel with smoothing capacitor 16, inner heating coil 40 and outer heating coil 44, resonant capacitor 43 connected in series with inner heating coil 40, outer heating coil 44 in series with the resonance capacitor 41, the reactor 71 arranged on the positive electrode side of the DC power source 70, the smoothing capacitor 76 connected between the output of the reactor 71 and the negative electrode of the DC power source 70, and in parallel with the smoothing capacitor 76. A half-bridge inverter circuit 82 connected to the heating coil 80, the heating coil 80, and the resonant capacitor 8 connected in series with the heating coil 80. And and the like as the main electrical components.

  The induction heating cooker also includes an input current detection circuit 11 that detects an input current input to the inverter circuit 14, an input voltage detection circuit 50 that detects an input voltage of the inverter circuit 14, and an input current that is input to the inverter circuit 82. An input current detection circuit 74 for detecting the input current, an input voltage detection circuit 73 for detecting the input voltage of the inverter circuit 82, an output current detection circuit 45 for detecting a current flowing through the inner heating coil 40, and a current flowing through the outer heating coil 44. The output current detection circuit 46, the output current detection circuit 79 for detecting the current flowing through the heating coil 80, the output voltage detection circuit 51 for detecting the voltage applied to the inner heating coil 40 and the resonance capacitor 43, the outer heating coil 44 and the resonance capacitor Output voltage detection circuit 52 for detecting the voltage applied to 41, heating coil 80, and resonant capacitor Output voltage detection circuit 78 for detecting a voltage applied to 1, the control circuit 26, operation unit 27, a display section 28.

  The DC power sources 1 and 70 described above are composed of, for example, a rectifier circuit that converts an AC voltage of a commercial power source into a DC voltage. The full-bridge type inverter circuit 14 includes six switching elements 31, 32, 33, 34, 35, and 36 (for example, IGBT) connected in series between two positive and negative buses, and the switching elements. It consists of three sets of arms 60, 61, 62 composed of diodes connected in antiparallel to 31, 32, 33, 34, 35, 36, respectively.

  Hereinafter, one of the three sets of arms 60, 61, 62 is referred to as a common arm 60, and the other two sets are referred to as an inner heating coil arm 61 and an outer heating coil arm 62. The switching elements 31, 33, 35 on the positive bus side of the arms 60, 61, 62 are the upper switches 31, 33, 35, the switching elements 32, 34, 36 on the negative bus side are the lower switches 32, 34, 36.

  The common arm 60 is an arm to which a resonance circuit composed of the inner heating coil 40 and the resonance capacitor 43 and a resonance circuit composed of the outer heating coil 44 and the resonance capacitor 41 are connected. The common arm 60 includes the upper switch 31 and the lower switch 32. The connection point between the upper switch 31 and the lower switch 32 is the output point of the common arm 60. The inner heating coil arm 61 is an arm to which the other end of the resonance circuit composed of the inner heating coil 40 and the resonance capacitor 43 is connected, and is composed of an upper switch 33 and a lower switch 34. The outer heating coil arm 62 is an arm to which the other end of the resonance circuit constituted by the outer heating coil 44 and the resonance capacitor 41 is connected, and is constituted by an upper switch 35 and a lower switch 36.

  The control circuit 26 turns off the lower switch 32 while the upper switch 31 of the common arm 60 is turned on, turns the lower switch 32 on while the upper switch 31 is turned off, and alternately turns on and off. Drive signal to output. The control circuit 26 outputs a drive signal for alternately turning on and off the upper switch 33 and the lower switch 34 of the inner heating coil arm 61 and the upper switch 35 and the lower switch 26 of the outer heating coil arm 62.

  The inner heating coil 40 is between the output point of the common arm 60 (the connection point of the upper switch 31 and the lower switch 32) and the output point of the arm 61 for the inner heating coil (the connection point of the upper switch 33 and the lower switch 34). It is connected. The external heating coil 44 is connected between the output point of the common arm 60 and the output point of the external heating coil arm 62 (the connection point between the upper switch 35 and the lower switch 26).

  The inner heating coil 40 is formed in a ring shape with a small diameter, and the outer heating coil 44 is formed in a ring shape with a larger diameter than the diameter of the inner heating coil 40, and the inner heating coil is centered on the axis of the inner heating coil 40. It is provided so as to surround the outer periphery of 40. The inner heating coil 40 and the outer heating coil 44 are adjusted so that there is no difference in impedance value in a state where the large-diameter pan is placed.

  The inner heating coil 40 and the outer heating coil 44 are wound in the same circumferential direction as viewed from the common arm 60. For example, the inner heating coil 40 is wound clockwise from the inner side to the outer side, and the inner coil is connected to the output point of the inner heating coil arm 61 and the outer coil is connected to the output point of the common arm 60. ing. The outer heating coil 44 is wound clockwise from the outer side to the inner side, and the outer coil is connected to the output point of the common arm 60 and the inner coil is connected to the output point of the arm 62 for the outer heating coil. ing.

  The inner / outer heating coils 40 and 44 are installed below the top plate together with the heating coil 80 described above, and are opposed to a heating port provided on the upper surface of the top plate. The heating port is formed in a circular shape indicating the placement position of the cooking container.

  The control circuit 26 controls the induction heating cooker as a whole. The control circuit 26 includes a timer counter 26 a therein, displays an operation state on the display unit 28 according to an input instruction from the operation unit 27, and also detects the input current detection circuit 11. The heating output is adjusted according to the detected value. The drive signal output to each arm 60, 61, 62 has a drive frequency higher than the resonance frequency of the inner heating coil 40 and the outer heating coil 44, and the current flowing through the load circuit is compared with the voltage applied to the load circuit. Control to flow in a delayed phase. The phase difference is determined using the timer counter 26a.

Next, drive signals output from the control circuit 26 to the arms 60, 61, 62 will be described with reference to FIG. FIG. 2 is a waveform diagram of drive signals of the full bridge type inverter circuit shown in FIG.
The control circuit 26 outputs a high-frequency drive signal to the upper switch 31 and the lower switch 32 of the common arm 60, and outputs a drive signal whose phase is advanced from the drive signal to the upper switch 33 and the lower switch of the arm 61 for the inner heating coil. 34, and output to the upper switch 35 and the lower switch 36 of the arm 62 for the external heating coil, respectively. The output point of each arm 60, 61, 62 (the connection point between the upper switch and the lower switch) has a positive-side bus potential that is the output of the DC power source 1, according to the on / off state of the upper switch and the lower switch, Alternatively, the bus potential on the negative electrode side is switched to a high frequency and output. A potential difference between the common arm 60 output point and the inner heating coil arm 61 output point is applied to the inner heating coil 40, and a potential difference between the common arm 60 output point and the outer heating coil arm 62 output point is applied to the outer heating coil 44. Is applied.

  Therefore, the phase difference between the drive signal to the common arm 60 and the drive signals to the inner heating coil arm 61 and the outer heating coil arm 62 is increased or decreased to be applied to the inner heating coil 40 and the outer heating coil 44. The high frequency voltage can be adjusted, and the high frequency output current and the input current flowing through the inner heating coil 40 and the outer heating coil 44 can be controlled.

Next, the half-bridge type inverter circuit 82 will be described. The description of the same parts as those of the inverter circuit 14 described above will be omitted.
The half-bridge type inverter circuit 82 includes two switching elements 75 and 77 (hereinafter referred to as “upper arm 75 and lower arm 77”) connected in series between the positive and negative buses, Each diode is connected to the lower arm 77 in antiparallel. Between the connection point of the upper arm 75 and the lower arm 77 and the negative bus line side, a heating coil 80 and a resonance capacitor 81 connected in series are inserted.

  The control circuit 26 turns off the lower switch 77 while the upper switch 75 is turned on, and outputs a drive signal that turns on / off alternately. The drive signals output to the upper and lower switches 75 and 77 are controlled so that the current flowing through the load circuit flows at a delayed phase as compared with the voltage applied to the load circuit as the drive frequency higher than the resonance frequency of the heating coil 80. To do. When the heating coil 80 of the inverter circuit 82 and the three heating coils 40 and 44 of the full bridge type inverter circuit 14 are driven in the vicinity, an interference sound is generated.

FIG. 3 is a plan view showing the arrangement and energization direction of each heating coil in the induction heating cooker according to the first embodiment.
The inner / outer heating coils 40 and 44 and the heating coil 80 are arranged close to the left and right direction when the induction cooking device is viewed from the front. When the left and right heating coils 40 and 44 and the right heating coil 80 are energized and the pan placed on the top plate 24 above these coils is induction-heated, each heating coil 40, 44, and 80 is mutually heated. There is a possibility that the pan is induction-heated due to the leakage magnetic field generated from. In this case, one pan is induction-heated by two types of magnetic fields generated from the heating coils 40, 44, and 80. When an induced current of a different frequency is generated in one pan, the difference in frequency of the induced current appears as vibration as it is. When the vibration component, which is the difference, reaches the audible range, the user recognizes it as high-frequency noise. In addition, when only the left outer heating coil 44 and the right heating coil 80 are energized, more of the magnetic field generated from the outer heating coil 44 leaks, and the pan placed on the heating coil 80 is induction-heated. It is considered a thing.

FIG. 4 is a schematic diagram showing the arrangement of the ferrite and the direction of the magnetic field in each heating coil in the induction cooking device of the first embodiment.
In the present embodiment, as shown in FIG. 4, a plurality of concave-shaped ferrites 20, 21, and 22 in which the heating coils 40, 44, and 80 are housed are arranged in the circumferential direction. In a rod-like ferrite extending radially from the central portion as in the past, the magnetic field leaked from the left heating coil 40, 44 reaches the pan 91 placed on the top plate 24 on the right heating coil 80. (Thick arrow in the figure). However, by arranging a plurality of concave shaped ferrites 20, 21, 22 in which the heating coils 40, 44, 80 are accommodated in the circumferential direction, the magnetic field generated in the left and right heating coils 40, 44, 80 can be reduced. The magnetic flux passes through the ferrites 20, 21, and 22 as magnetic paths, respectively, and the pots 90 and 91 are induction-heated while suppressing the magnetic field leaking from the heating coils 40, 44, and 80, respectively.
This makes it possible to reduce the magnetic field leaked from the external heating coil 44 even when only the large-diameter external heating coil 44 is energized among the left internal / external heating coils 40, 44 as shown in FIG. Induction heating to the pan 91 on the right side heating coil 80 can be prevented.

Next, an arrangement example of the ferrites 20 and 21 of the left and right inner and outer heating coils 40 and 44 will be described with reference to FIG. FIG. 5 is a diagram showing an example of the arrangement of ferrite in the left and right inner and outer heating coils in the induction heating cooker according to the first embodiment.
Concave-shaped ferrites 20 and 21 arranged in the circumferential direction in the left and right inner and outer heating coils 40 and 44 are arranged on the coil side adjacent to the right heating coil 80 in the inner and outer heating coils 40 and 44, respectively. It is more concentrated than the other side. In addition, in the right heating coil 80, the concave-shaped ferrite 22 is disposed at substantially equal intervals.

  Thereby, reduction of the leakage magnetic field reaching the pan 90 on the right heating coil 80 can be achieved. By arranging the inner and outer heating coils 40 and 44 so as to be individually wrapped with the concave shaped ferrites 20 and 21, not only can the interference between the inner and outer heating coils 40 and 44 having the same central axis be prevented. The mutual interference with the right heating coil 80 can also be prevented. Therefore, uneven heating can be reduced, and interference noise generated by induction heating of the pots 90 and 91 by the mutual leakage magnetic field can also be reduced.

  In the present embodiment, it has been described that the concave-shaped ferrite 22 is arranged in the heating coil 80 on the right side at almost equal intervals. However, the present invention is not limited to this. For example, the concave-shaped ferrite 22 may be intensively arranged on the coil side adjacent to the outer heating coil 44 located on the left side of the right side heating coil 80 as compared with the opposite coil side.

Embodiment 2. FIG.
FIG. 6 is a schematic diagram showing the arrangement of the ferrite and the direction of the magnetic field of each heating coil in the induction heating cooker according to the second embodiment. FIG. 7 is a diagram of the left and right inner / outer heating coils in the induction heating cooker according to the second embodiment. It is a figure showing an example of arrangement of ferrite.

  In this embodiment, as shown in FIGS. 6 and 7, the concave-shaped ferrite 23 arranged on the coil side adjacent to the right heating coil 80 in the outer heating coil 44 is arranged on the opposite side. Compared with the ferrite 21, many are concentrated. Among the protrusions provided on both sides of the heating coil 44, the ferrite 23 has a height of one protrusion on the heating coil 80 side that is higher than the other protrusion, and the width of one protrusion is the other. It is formed wider than the protruding portion. That is, the ferrite 23 has a larger mass than the ferrite 21. Further, in the vicinity of the ferrite 23, for example, a rectangular parallelepiped ferrite 25 is disposed. In addition, in the right heating coil 80, the concave-shaped ferrite 22 is disposed at substantially equal intervals.

  The magnetic flux in the magnetic field generated in the outer heating coil 44 by the ferrite 23 described above is directed to the pan 90 side using one projecting portion of the ferrite 23 as a magnetic path. And the magnetic flux which leaked from the magnetic path goes to the pan 90 on the heating coil 44 by the rectangular parallelepiped-shaped ferrite 25 almost without going to the adjacent pan 91 side.

  As described above, the ferrite 23 having a large mass is arranged on the coil side adjacent to the right heating coil 80 in the outer heating coil 44, and the rectangular parallelepiped ferrite 25 is provided in the vicinity of the ferrite 23. Therefore, a leakage magnetic field from the left outer heating coil 44 toward the right heating coil 80 can be prevented. Thereby, the heating unevenness can be reduced, the mutual interference of the magnetic fields can be reduced, and accordingly, the interference sound generated by induction heating of the pans 90 and 91 by the mutual leakage magnetic field can be suppressed.

In the present embodiment, it has been described that the rectangular parallelepiped ferrite 25 is disposed in the vicinity of the ferrite 23, but the ferrite 25 may not be disposed.
Further, in the present embodiment, it has been described that the concave-shaped ferrite 22 is arranged at substantially equal intervals in the right heating coil 80, but the present invention is not limited to this. For example, the ferrite 23 may be disposed on the coil side adjacent to the left outer heating coil 44 in the right heating coil 80, and a rectangular parallelepiped ferrite 25 may be provided in the vicinity of the ferrite 23.

  1, 70 Commercial power supply, 2, 71 reactor, 11, 74 Input current detection circuit, 14 Full bridge type inverter circuit, 82 Half bridge type inverter circuit, 16, 76 Smoothing capacitor, 26, Control circuit, 26a Timer counter, 27 Operation unit, 28 Display unit, 31, 32, 33, 34, 35, 36, 75, 77 Switching element, 40 internal heating coil, 44 external heating coil, 80 heating coil, 41, 43, 81 Resonance capacitor, 45, 46, 79 Output current detection circuit, 50, 73 Input voltage detection circuit, 51, 52, 78 Output voltage detection circuit, 60 Common arm, 61 Inner heating coil arm, 62 Outer heating coil arm, 24 Top plate, 20, 21, 22, 23, 25 Ferrite, 90, 91 Pan.

Claims (5)

A top plate provided with at least two heating ports adjacent to each other indicating the placement position of the cooking container;
An annular inner heating coil and an outer heating coil having the same axial center disposed below one of the heating ports;
An annular heating coil disposed below the other heating port of the heating ports;
The inner heating coil and the outer heating coil, and a concave-shaped ferrite disposed in the circumferential direction below each of the heating coils ,
Among the ferrites arranged in the inner heating coil and the outer heating coil, the number of ferrites located on the heating coil side is larger than the number of ferrites arranged on the opposite side . Of the ferrite disposed in the heating coil, ferrite located in the outer heating coil side, induction heating cooker of claim 1, wherein the number is larger than a ferrite disposed on the opposite side. 3. The induction heating cooker according to claim 1, wherein among the ferrites arranged in the outer heating coil, the ferrite located on the heating coil side has a larger mass than the ferrite arranged on the opposite side. 4. . Wherein among the arranged heating coil ferrite, ferrite located in the outer heating coil side, to any one of claims 1-3, characterized in that the mass is greater than the ferrite disposed opposite The induction heating cooker described. The induction heating cooker according to claim 3 or 4 , wherein a rectangular parallelepiped ferrite is disposed in the vicinity of the ferrite having a large mass.

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