JP2005152400A - Rice cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rice cooker which easily reduces low-frequency leaking magnetic fields contained in a heating coil. <P>SOLUTION: A low-frequency magnetic field cancelling means 12 which is located in a high-frequency oscillating section 11, has the same frequency component as a low-frequency component of a current which flows on a side surface heating coil 1b, and is arranged in such a manner that a current may flow in the direction opposite to that of the side surface heating coil 1b is constituted by being laminated into a coil shape a plurality of times with the same diameter. In a vicinity of the side surface heating coil, and on the internal side of an electromagnetic shield ring 2, the low-frequency magnetic filed cancelling means 12 is arranged in parallel with the electromagnetic shield ring. Thus, leaking magnetic fields of low frequencies and high frequencies can greatly be reduced, and at the same time, the assembly can be facilitated when a leaking magnetic field remedy is taken. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an induction heating rice cooker used for home use and business use.

  In a conventional induction heating rice cooker, an induction heating device (see, for example, Patent Document 1) will be described with reference to the drawings as a method of reducing a leakage magnetic field from a heating coil. FIG. 5 shows a conventional induction heating apparatus in which the leakage magnetic field of the heating coil is reduced. In this conventional example, an electromagnetic shield ring 2 is arranged on the outer peripheral portion of the heating coil 1 to constitute an induction heating device. In the induction heating apparatus having this configuration, an induction current flows through the electromagnetic shield ring 2 by being induced by the high-frequency magnetic field generated in the heating coil 1, and further, the induction current causes a high-frequency magnetic field generated from the heating coil 1 to be generated in the electromagnetic shield ring 2. Produces a reverse high-frequency magnetic field. As a result, the high-frequency magnetic field generated from the electromagnetic shield ring 2 acts so as to cancel out the high-frequency magnetic field generated on the outer peripheral portion of the heating coil 1, so that the 20 k to 50 kHz high-frequency leakage magnetic field leaking from the heating coil 1 is reduced. The electromagnetic shield ring 2 is known to have an aluminum plate, a lead wire or the like made into a ring.

An induction heating apparatus (see, for example, Patent Document 2) that reduces a leakage magnetic field generated from another heating coil will be described. FIG. 6 shows a conventional induction heating apparatus with a reduced leakage magnetic field. The inductance 5 is formed by winding the vicinity of the outer periphery of the heating coil 1, and the high-frequency magnetic field generated from the heating coil 1 and the high-frequency magnetic field component generated by the inductance 5 are arranged to cancel each other. FIG. 7 shows a circuit example of a conventional induction heating apparatus. The induction heating apparatus of FIG. 7 includes a power supply unit 3 configured by a commercial power supply, a high-frequency oscillation unit 11 that converts power from the power supply unit 3 into high-frequency power, and a heating coil 1 that converts power from the high-frequency oscillation unit 11 into a high-frequency magnetic field. The high frequency oscillating unit 11 includes a rectifier 4 that rectifies the commercial power supply, an inductor 5 that smoothes the output of the rectifier 4, and a smoothing capacitor 6. And a semiconductor switch 8 that controls power supply to the heating coil 1 and a resonant capacitor 7 that smoothes the switching operation of the semiconductor switch 8. In the conventional example of FIG. 7, the inductor 5 is composed only of windings, which eliminates the need for the core material of the inductance 5 and reduces the size of the device, and also has the effect of reducing high-frequency noise.
JP-A-57-115795 Japanese Patent Publication No. 63-7672

  However, in the induction heating apparatus in which the leakage magnetic field from the conventional heating coil as shown in FIG. 5 is reduced, the high-frequency leakage magnetic field can be reduced by the effect of the electromagnetic shield ring 2 but is generated from the heating coil 1. A magnetic field having a power frequency or twice the frequency of the power source (hereinafter referred to as a low-frequency magnetic field) cannot be suppressed by the electromagnetic shield ring 2 and is therefore hardly absorbed by the inner pot 15 and released to the outside, and the electromagnetic shield ring 2 generates a reverse magnetic field. Since it does not generate enough, the low frequency magnetic field does not decrease.

  On the other hand, in the conventional induction heating apparatus of FIG. 6, since the winding is operated as an inductance (about several hundred μH), the number of turns of the winding increases. At this time, the low-frequency magnetic field emitted from the winding becomes larger than the low-frequency magnetic field emitted from the heating coil, resulting in an increase in the low-frequency magnetic field emitted to the outside. In addition, the conventional induction heating device aims to cancel the high-frequency magnetic field, and the winding for reducing the leakage magnetic field is limited to the vicinity of the heating coil and has no freedom of arrangement, and is further arranged near the heating coil. The magnetic field distribution to the heated object such as changes, particularly in the case of a rice cooker, the problem of greatly affecting the rice cooking performance arises. Further, as described above, the conventional induction heating apparatus reduces the high-frequency leakage magnetic field, and has not paid attention to the reduction of the low-frequency leakage magnetic field. However, by reducing the low-frequency leakage magnetic field, the user's anxiety about the effects on the human body of the low-frequency magnetic field, which is not clear in the causal relationship but is concerned in some investigations, can be removed. It is also possible to eliminate the risk of malfunction of an electronic device in the immediate vicinity of.

  In order to solve the above problems, the present invention focuses on a low-frequency leakage magnetic field that has not been recognized by a conventional induction heating apparatus, and reduces the emission of a low-frequency magnetic field from a heating coil and reduces the high frequency. The purpose is to provide a rice cooker that can suppress the leakage magnetic field of the components and reduce unnecessary electromagnetic waves generated from the equipment and has good assembly workability.

  In order to solve the above problems, a rice cooker of the present invention includes an inner pot, an inner frame that holds the inner pot, a bottom surface heating coil that is disposed on the outer surface of the inner frame and induction-heats the bottom of the inner pot, A side heating coil disposed on the outer surface of the inner frame for inductively heating the side surface of the inner pot; a high-frequency oscillating unit for receiving a power supply of commercial frequency and supplying a high-frequency current to the bottom heating coil and the side heating coil; An electromagnetic shield ring is provided on the outer periphery of the side surface heating coil, and the high frequency oscillating unit has a wiring having the same frequency component as the low frequency component of the current flowing in the side surface heating coil, opposite to the side surface heating coil. A low-frequency magnetic field canceling means arranged so that a current flows, wherein the low-frequency magnetic field canceling means is configured by laminating a plurality of coils in the same diameter and in the vicinity of the side heating coil. Is obtained is assumed to be cooker arranged in parallel with the shield ring inside the ring.

  As a result, the magnetic field generated from the low-frequency magnetic field canceling means arranged in the high-frequency oscillating unit so that the current flows in the opposite direction to the side heating coil with the same frequency component as the low frequency component of the current flowing in the side heating coil is reduced. The leakage magnetic field from the side heating coil that generates a lot of leakage magnetic field cancels each other to greatly reduce the low frequency leakage magnetic field, and the high frequency magnetic field can also be greatly reduced between the electromagnetic shields, and the low frequency magnetic field canceling means Can be handled as a single component, so that it can be handled easily and the assembly workability can be improved.

  The rice cooker of this invention can reduce the low frequency and high frequency leakage magnetic field which generate | occur | produce from a heating coil by simple structure.

  According to a first aspect of the present invention, there is provided an inner pot, an inner frame that holds the inner pot, a bottom surface heating coil that is disposed on the outer surface of the inner frame and induction-heats the bottom of the inner pot, and is disposed on the outer surface of the inner frame. A side heating coil that induction-heats the side surface of the inner pot, a high-frequency oscillation unit that receives a commercial frequency power supply and supplies a high-frequency current to the bottom heating coil and the side heating coil, and an outer peripheral portion of the side heating coil The high frequency oscillating unit includes a wiring having the same frequency component as the low frequency component of the current flowing in the side surface heating coil, and arranged so that a current flows in a direction opposite to the side surface heating coil. A low-frequency magnetic field canceling means, wherein the low-frequency magnetic field canceling means is configured by laminating a plurality of coils in the same diameter and in the vicinity of the side surface heating coil, inside the electromagnetic shield ring. By arranging in parallel with the ring, from the low frequency magnetic field canceling means arranged so that the current flows in the opposite direction to the side heating coil with the same frequency component as the low frequency component of the current flowing in the side heating coil in the high frequency oscillation part The generated magnetic field cancels each other with the leakage magnetic field from the side heating coil that generates a lot of low-frequency leakage magnetic field, greatly reducing the low-frequency leakage magnetic field, and the high-frequency magnetic field can also be greatly reduced by the electromagnetic shield ring. Moreover, since the low-frequency magnetic field canceling means is laminated on the coil, it can be handled as one component, so that it can be handled easily and the assembly workability can be improved.

  In the second invention, the rice cooker of the first invention is particularly produced by winding the wire rods constituting the bottom surface heating coil and the side surface heating coil so that the current flows in the same direction, thereby reducing the low frequency leakage magnetic field canceling means. Since the low-frequency leakage magnetic field generated from the bottom heating coil and the low-frequency leakage magnetic field generated from the side heating coil cancel each other, more low-frequency leakage magnetic fields can be reduced.

  In the third aspect of the invention, in particular, the rice cooker of the first or second aspect of the invention is arranged at the lower part of the magnetic-shielding ferrite in which the low-frequency canceling means is arranged in the vicinity of the heating coil. Since the low frequency canceling means is arranged outside the closed magnetic field composed of ferrite, the high frequency component contained in the low frequency canceling means does not prevent the pan from absorbing the high frequency magnetic field generated from the heating coil, It is possible to take a leakage magnetic field countermeasure that does not disturb the magnetic field distribution entering the pan and has little influence on the rice cooking performance.

  4th invention makes especially the rice cooker of 1st-3rd invention the diameter of the wiring on the coil which comprises a low frequency magnetic field cancellation means larger than the diameter of the inner periphery of a side surface heating coil. As a result, the low-frequency magnetic field generated from the low-frequency canceling means increases, so that more low-frequency leakage magnetic fields can be canceled.

  In the fifth aspect of the invention, in particular, the rice cooker of the first to fourth aspects of the present invention is provided with a recess for housing the low-frequency canceling means in a part of the electromagnetic shield ring, thereby winding the coil on the coil constituting the low-frequency canceling means. Since the wire can be arranged along the electromagnetic shield ring and the electromagnetic shield ring and the low-frequency canceling means can be handled integrally, assembly workability can be improved when taking measures against leakage magnetic fields.

  The sixth invention is the rice cooker of the first to fourth inventions in particular, and the conductor constituting the electromagnetic shield ring is provided with supporting means for supporting the low frequency canceling means in part, whereby the low frequency magnetic field canceling means is provided. Since it can be arranged simply and inexpensively, leakage magnetic field countermeasures can be performed at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited by this embodiment.

(Embodiment 1)
FIG. 1 shows a block diagram of a rice cooker in an embodiment of the present invention. In FIG. 1, a power supply unit 1 including a commercial power supply is connected to a high-frequency oscillation unit 11, and the high-frequency oscillation unit 11 is connected to a bottom surface heating coil 1a and a side surface heating coil 1b. The bottom surface heating coil 1 a and the side surface heating coil 1 b are disposed on the bottom surface and the side surface of the inner frame 16, and are installed so as to be magnetically coupled to the inner pot 15 placed on the upper surface of the inner frame 16. Magnetostatic ferrite 13 is disposed below the bottom heating coil 1a and the side heating coil 1b to enhance the magnetic coupling with the inner pot 15, and the electromagnetic shield ring surrounds the heating coil and a part of the pot on the outer periphery of the side heating coil 1b. 2 is arranged. The high-frequency oscillation unit 11 includes a rectifying unit 4 connected to the power source unit 3, a series connection of an inductor 5 and a smoothing capacitor 6 connected in series with the rectifying unit 4, and a resonant capacitor connected in parallel to the smoothing capacitor 6. 7 and the semiconductor switch 8 are connected in series, and the resonant capacitor 7 is connected in parallel with the bottom surface heating coil 1a and the side surface heating coil 1b. The bottom surface heating coil 1a and the side surface heating coil 1b are connected in series when simultaneous energization is performed (hereinafter referred to as the heating coil 1), and the bottom surface heating coil 1a and the side surface heating coil 1b are preferably wound in the same direction. On the other hand, the inductor 5 has a configuration in which the wiring of the inductor 5 is wound inside the electromagnetic shield ring 2 in the vicinity of the side surface heating coil 1b and wound in a plurality of times opposite to the winding direction of the side surface heating coil 1b. It is arranged in parallel and constitutes a low frequency canceling means.

  In this embodiment, a general circuit configuration used for the induction heating apparatus is shown, but there is no particular limitation as long as the circuit configuration is such that a low-frequency magnetic field component is superimposed on the heating coil 1.

  About the rice cooker comprised as mentioned above, the operation | movement and an effect | action are demonstrated below. FIG. 2 is a diagram showing a current path in each section of the inverter circuit. I3 is an input current, I5 is a current flowing through the inductor 5 and the low-frequency magnetic field canceling means 12, and I1 is a current flowing through the heating coil 1. The power supply unit 3 is composed of a commercial power source or the like, and supplies commercial frequency power to the high-frequency oscillation unit 11. Therefore, the input current I3 is a current having a commercial frequency component. In the high-frequency oscillating unit 11, the commercial power is rectified by the rectifying means 4 to be converted into power having a frequency component twice that of the commercial power supply, and further converted into high-frequency power of about 20 k to 50 kHz using the semiconductor switch 8. And this high frequency electric power is supplied to the heating coil 1, and is supplied to the inner pot 15 from the heating coil 1 in the form of a high frequency magnetic field. In the inner pot 15, an eddy current is generated in the surface layer portion according to the high frequency magnetic field, and as a result, heat is generated. For this reason, the current I5 having a frequency twice the commercial frequency flows through the inductor 5 and the low-frequency magnetic field canceling means 12, and when the semiconductor switch 8 is turned on in the heating coil 1b, the power source 1 → rectifier A current I11 in which a low-frequency current having a component twice the commercial frequency generated in the loop of means 4 → heating coil 1 → semiconductor switch 8 and a high-frequency component flowing in the heating coil 1 according to the frequency of the semiconductor switch 8 flows. Therefore, the low frequency magnetic field generated from the heating coil 1 can be canceled by arranging the heating coil 1 and the low frequency magnetic field canceling means 12 so that the low frequency magnetic fields cancel each other. At this time, the side surface heating coil 1b has a larger coil diameter than the bottom surface heating coil 1a, and is difficult to be coupled with the inner pot 15, so that the leakage magnetic field is large. For this reason, it is desirable that at least the side surface heating coil 1b and the low frequency magnetic field canceling means 12 are arranged so as to cancel each other. The magnetic field canceling effect of 12 can be further increased.

  On the other hand, by arranging the electromagnetic shield ring 2 so as to cover the outer periphery of the side surface heating coil 1b from the heating coil 1 to a part of the side surface of the inner pot 15, the electromagnetic shield ring is induced by the high frequency magnetic field generated in the heating coil 1. An induced current flows through 2, and further, a high frequency magnetic field opposite to the high frequency magnetic field generated from the heating coil 1 is generated in the electromagnetic shield ring 2 by this induced current. As a result, the high-frequency magnetic field generated from the electromagnetic shield ring 2 acts so as to cancel out the high-frequency magnetic field generated on the outer peripheral portion of the heating coil 1, so that the 20 k to 50 kHz high-frequency leakage magnetic field leaking from the heating coil 1 is reduced. The electromagnetic shield ring 2 may be an aluminum plate, a lead wire, or the like that is annular.

  Here, as shown in FIG. 3, the low-frequency magnetic field canceling means 12 is configured by stacking the low-frequency canceling means 12 in a tandem configuration in a ring shape, and is disposed in the vicinity of the electromagnetic shield ring 2 in the vicinity of the side surface heating coil 1b. By arranging such an arrangement, the low-frequency canceling means 12 can be arranged in the vicinity of the side surface heating coil 1b where a large amount of leakage magnetic field is generated, and is arranged inside the electromagnetic shield ring 2. The housing can be made compact without becoming large. Further, by adopting a configuration in which the low-frequency canceling means 12 are stacked in the vertical direction, the low-frequency magnetic field canceling means 12 can be configured in a coil shape with the maximum diameter that can be mounted, thereby increasing the canceling effect on the leakage magnetic field. Can do. Therefore, it is desirable that at least the low frequency canceling means 12 is larger than the inner diameter of the side surface heating coil 1b. Furthermore, in the rice cooker of this Embodiment, since the electromagnetic shield ring 2 and the low frequency cancellation means 12 can be handled independently, workability | operativity at the time of taking a countermeasure against a leakage magnetic field can be improved.

  Further, the low frequency canceling means 12 includes a slight high frequency component. In the configuration of this embodiment, the low-frequency component generated from the heating coil 1 is canceled and the high-frequency component is slightly canceled. Therefore, it is desirable to arrange outside the magnetic field loop of the inner pot 15, the heating coil 1 and the magnetic shield ferrite 13, and therefore, it is desirable to arrange the low frequency canceling means 12 below the magnetic shield ferrite 13.

  As described above, in the present embodiment, the low-frequency magnetic field cancellation in which the wiring having the same frequency component as the low-frequency component of the current flowing through the side surface heating coil 1b is arranged to flow in the opposite direction to the side surface heating coil 1b. The means 12 is constructed by laminating the coil 12 in the same diameter and a plurality of times in the form of a coil, and by arranging in parallel with the electromagnetic shield ring inside the electromagnetic shield ring 2 in the vicinity of the side surface heating coil 1b, a lot of low-frequency leakage magnetic fields are generated. The leakage magnetic field from the side heating coil 1b that cancels each other cancels each other to greatly reduce the low-frequency leakage magnetic field, and the high-frequency magnetic field can also be greatly reduced by the electromagnetic shield ring 2, and the low-frequency magnetic field canceling means 12 is provided on the coil. Since it can be handled as a single component, it is easy to handle and is assembled when taking measures against leakage magnetic fields. It is possible to improve the workability.

(Embodiment 2)
FIG. 4 is a configuration diagram of the rice cooker according to the embodiment of the present invention. The rice cooker of the present embodiment is different from that of the first embodiment in that a concave portion 18 for disposing the low frequency canceling means 12 is provided in the lower part of the electromagnetic shield ring 2.

  About the rice cooker comprised as mentioned above, the operation | movement and an effect | action are demonstrated below. The low frequency canceling means 12 generates more canceling magnetic fields as the number of windings is larger and the diameter is larger. Therefore, it is desirable to arrange in a place where the diameter can be increased. On the other hand, when the diameter is increased, the size of the rice cooker increases, so that the installation location is limited. Therefore, as shown in FIG. 4, by providing the recess 18 that can accommodate the low-frequency magnetic field canceling means 12 inside the electromagnetic shield ring 2, it is possible to store the low-frequency magnetic field canceling means 12 with a large diameter and in a compact manner. become. In addition, since the electromagnetic shield ring 2 and the low-frequency magnetic field canceling means 12 can be handled integrally, the workability when taking measures against leakage magnetic fields is improved.

  As described above, according to the present embodiment, the recess on the low-frequency canceling means 12 is provided in a part of the electromagnetic shield ring 2 so that the winding on the coil constituting the low-frequency canceling means 12 is electromagnetically Since it can arrange | position along the shield ring 2 and the electromagnetic shield ring 2 and the low frequency cancellation means 12 can be handled integrally, when taking a countermeasure against a leakage magnetic field, assembly workability can be improved.

(Embodiment 3)
FIG. 5 is a configuration diagram of the rice cooker according to the embodiment of the present invention. The rice cooker of the present embodiment is different from the first embodiment in that a support portion 17 is provided in a part of the electromagnetic shield ring 2 and the low frequency canceling means 12 is fixed to the electromagnetic shield ring 2.

  About the rice cooker comprised as mentioned above, the operation | movement and an effect | action are demonstrated below. The low frequency canceling means 12 generates more canceling magnetic fields as the number of windings is larger and the diameter is larger. Therefore, it is desirable to arrange in a place where the diameter can be increased. On the other hand, when the diameter is increased, the size of the rice cooker increases, so that the installation location is limited. Therefore, as shown in FIG. 5, the low frequency magnetic field canceling means 12 is disposed inside the electromagnetic shield ring 2, and a support portion 17 for fixing the low frequency magnetic field reducing means 12 is provided and fixed to a part of the electromagnetic shield ring 2. It is supposed to be. Thus, the low-frequency magnetic field canceling means 12 can be fixed by a simple method. In particular, the electromagnetic shield ring 2 is cut and the cut is protruded and sandwiched between the electromagnetic shield ring 2 and the electromagnetic shield ring 2. By adopting the configuration, it is possible to easily and inexpensively take measures against magnetic shielding.

  As described above, according to the present embodiment, the low-frequency magnetic field canceling means 12 can be simplified by providing the support means 17 that supports the low-frequency canceling means 12 in a part of the conductor constituting the electromagnetic shield ring 2. Since it can arrange | position cheaply, a leakage magnetic field countermeasure can be performed cheaply.

The figure which shows the structure of the rice cooker in Embodiment 1 of this invention. The figure which shows the operation | movement waveform of the rice cooker in Embodiment 1 of this invention. The figure which shows the structure of the rice cooker in Embodiment 1 of this invention. The figure which shows the structure of the rice cooker in Embodiment 2 of this invention. The figure which shows the structure of the rice cooker in Embodiment 3 of this invention. The figure which shows the structure of the conventional induction heating apparatus The figure which shows the structure of the conventional induction heating apparatus The figure which shows the circuit structure of the conventional induction heating heating apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating coil 1a Bottom surface heating coil 1b Side surface heating coil 2 Electromagnetic shield ring 3 Power supply part 4 Rectification means 5 Inductor 6 Smoothing capacitor 7 Resonance capacitor 8 Semiconductor switch 11 High frequency oscillation part 12 Low frequency magnetic field cancellation means 13 Magnetostatic ferrite 15 Inner pan 16 Inside Frame 17 Support 18 Recess

Claims (6)

An inner pot, an inner frame for holding the inner pot, a bottom heating coil disposed on the outer surface of the inner frame for induction heating the bottom of the inner pot, and a side surface of the inner pot disposed on the outer surface of the inner frame. A side heating coil that performs induction heating, a high-frequency oscillation unit that receives a power supply of commercial frequency and supplies a high-frequency current to the bottom heating coil and the side heating coil, and an electromagnetic shield ring disposed on an outer periphery of the side heating coil The high-frequency oscillating unit includes a low-frequency magnetic field canceling unit in which a wiring having the same frequency component as the low-frequency component of the current flowing in the side surface heating coil is arranged so that the current flows in a direction opposite to the side surface heating coil. The low frequency magnetic field canceling means is configured by laminating a plurality of times in a coil shape, and in parallel with the electromagnetic shield ring inside the electromagnetic shield ring in the vicinity of the side surface heating coil. Location the rice cooker. The rice cooker according to claim 1, wherein the wires constituting the bottom heating coil and the side heating coil have the same direction of current flowing through the wire. The rice cooker according to claim 1 or 2, wherein the low-frequency canceling means is disposed below a magnetic-shielding ferrite disposed near the heating coil. The rice cooker of any one of Claims 1-3 which made the diameter of the wiring on the coil which comprises a low frequency magnetic field cancellation means larger than the diameter of the inner periphery of a side surface heating coil. The rice cooker of any one of Claims 1-4 which provided the recessed part which accommodates a low frequency cancellation means in a part of electromagnetic shield ring. The rice cooker according to any one of claims 1 to 4, wherein a conductor constituting the electromagnetic shield ring is provided with support means for supporting low-frequency canceling means in part.

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