JP4095565B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to a leakage magnetic flux reduction method for an induction heating cooker.

FIG. 4 is a front sectional view showing the configuration of a general leakage magnetic flux reducing means of the induction heating cooker, FIG . 5A is a plan view of the heating coil and the conductive ring, and FIG. 4B is a heating coil surface and conductivity. Sectional drawing which shows the positional relationship with a ring, (c) is a side view of a conductive ring.

  As a principle of the induction heating cooker, a high frequency current is supplied to the heating coil 2 disposed on the lower side of the top rate 1 to generate a high frequency magnetic flux, and a metal pan or the like disposed on the upper side of the top plate 1 by this magnetic flux. An eddy current is generated in the article 3 to be heated, and cooking is performed by Joule heat generated by the eddy current and the resistance of the article 3 to be heated.

  Here, a conductive ring 4 is disposed around the heating coil 2. An induction current flows through the conductive ring 4 due to the high-frequency magnetic flux generated from the heating coil 2 or the object to be heated 3. The canceling magnetic flux (high-frequency magnetic flux) due to this induction current is generated from the heating coil 2 or the object to be heated 3. Since the magnetic flux is generated in the direction of canceling out, the leakage magnetic flux to the outside can be reduced. The conductive ring 4 is disposed outside and in the vicinity of the heating coil 2. This is for the purpose of generating more canceling magnetic flux due to the induced current of the conductive ring 4.

FIG. 6 shows the calculation results of the self-inductance L of the conductive ring 4, the induced current IA, and the generated canceling magnetic flux Z due to the difference in radius of the conductive ring 4. As a calculation condition, a high frequency current of 25 kHz / 1 A is passed through the heating coil 2 having a radius of 90 mm and a winding number of 25 T. The canceling magnetic flux indicates a value generated at a distance of 300 mm from the center of the heating coil 2. In addition, the influence of the to-be-heated material 3 is disregarded.

  As the radius of the conductive ring 4 increases, the induced current IA of the conductive ring 4 decreases due to the influence of the decrease of the flux linkage Z1 from the heating coil 2 and the increase of the self-inductance L of the conductive ring 4. As a result, the canceling magnetic flux Z is also reduced.

Here, in the case of a built-in type induction heating cooker, considering the housing size and the like, the conductive ring 4 cannot be set to have a radius of 200 mm or more, and therefore can be disposed in the vicinity of the heating coil 2 with a radius of 100 mm. It turns out that it is effective. Therefore, conventionally, as shown in FIG. 5 , the conductive ring 4 is disposed very close to the heating coil 2.

  However, even when the conductive ring 4 is arranged in the vicinity of the heating coil 2 and the canceling magnetic flux is effectively generated as in the conventional example, the induced current of the conductive ring 4 is generated by the heating coil 2 or the object to be heated. There is a problem that a canceling magnetic flux sufficient to cancel the high-frequency magnetic flux from 3 cannot be generated.

  In order to solve this problem, Patent Document 1 proposes a method of supplying a current necessary for canceling the leakage magnetic flux from the outside. However, a current supply means such as a high-frequency inverter is separately required. As a result, the configuration becomes complicated and the number of electronic components increases.

On the other hand, as shown in FIG. 7 , the heating coil 2 is housed in a metal casing of the induction heating cooker, and a part of the leakage magnetic flux from the heating coil 2 is shielded by the metal casing. However, part of the canceling magnetic flux from the conductive ring 4 disposed in the vicinity of the heating coil 2 is also shielded by the metal casing. As a result, there is a further problem that the leakage flux canceling effect is reduced.
JP-A-6-260272

    This invention solves said subject and aims at provision of the induction heating cooking appliance which can fully reduce a leakage magnetic flux.

In order to solve the above-mentioned problems, the present invention provides an induction heating cooker in which an object to be heated is electromagnetically heated by a heating coil, and a conductor is arranged on the outer periphery of the heating coil in a loop shape so as to surround the heating coil. The conductor includes a strip-shaped horizontal portion whose strip surface is disposed substantially parallel to the coil surface of the heating coil, and a conductive portion made of a wire.

  According to the above configuration, the loop shape of the conductor can be flexibly formed in an effective arrangement, and the leakage magnetic flux can be effectively reduced.

  Note that a part of the conductor can be in contact with the back surface of the top plate on which the object to be heated is placed. Thereby, the influence on the leakage magnetic flux reduction effect by a metal cooker main body can be avoided.

As described above, according to the present invention , the canceling magnetic flux can be generated effectively.

EMBODIMENT OF THE INVENTION Embodiment of the induction heating cooking appliance which concerns on this invention below is described based on drawing. 1 to 3 show a first embodiment of an induction heating cooker according to the present invention, FIG. 1 is a plan view of the induction heating cooker, and FIG . 2 (a) is a set of heating coils and conductors. FIG. 3B is a side view of the conductor , and FIG. 3 is a diagram showing the relationship between the loop radius of the conductor and the canceling magnetic flux.

  As shown in FIGS. 1 and 2, the induction heating cooker according to the present embodiment is provided with a top plate 1 made of a nonmagnetic material on the upper surface of a cooker body 5 made of a metal casing. Under the front side, one or more sets (two sets in this embodiment) of the heating coil 2 and the conductor 4 for canceling an unnecessary magnetic field radiated from the heating coil 2 to the outside are arranged, and the rear of the top plate A radial heater 8 made of a spiral nichrome wire is disposed below the side.

  The heating coil 2 energizes a high-frequency current capable of inductively heating a metal heated object 3 (see FIG. 9) placed on the top plate 1, and is not shown as an electronic circuit for controlling the heating coil 2. However, an inverter circuit for supplying a high-frequency current to the heating coil 2 and inverter control means for controlling the output power of the inverter circuit are provided.

A loop-shaped conductor 4 is provided outside the heating coil 2 so as to surround the heating coil 2. The conductor 4 is disposed in a half-circular portion on the front side of the heating coil 2, and is disposed in a strip-shaped horizontal portion 4 b substantially parallel to the coil surface of the heating coil 2, and in a semi-circular portion on the rear side of the heating coil 2, The conductive portion 4e using a wire is electrically connected to each other .

In this embodiment, a band-shaped front horizontal portion 4b made of a metal plate is closely attached to the back surface of the top plate 1, and a litz wire obtained by twisting fine wires such as enamel wires is used as the rear conductive portion, and the vicinity of the heating coil 2 is used. It is arranged in.

As the wire, various wires such as a copper wire, an aluminum wire, a copper alloy wire, and an aluminum alloy wire may be used in addition to the litz wire.

  FIG. 3 shows the radius of the loop-shaped conductor 4 and the canceling magnetic flux value generated at a distance of 300 mm from the center of the heating coil 2 when an induction current of the same magnitude flows through them.

It can be understood from FIGS . 3 and 6 that if the induced current can be increased, increasing the radius of the conductive ring exhibits the effect of reducing the leakage magnetic flux. Therefore, as shown in FIG. 2, the conductor 4 is disposed only in the vicinity of the heating coil 2 so that a large amount of induced current flows on the rear side of the heating coil 2, and the front side is induced as far as possible from the center of the heating coil. By disposing the conductor 4 so as to allow current to flow, it is possible to effectively generate a canceling magnetic flux on the front side and reduce leakage magnetic flux.

  In addition, about the back side of the heating coil 2, the reduction effect of the same level as the near side of the heating coil 2 is not acquired, but in a normal built-in type induction heating cooker, as shown in FIG. 2 is an arrangement that is biased toward the front side of the main body 5, and the distance to the rear is farther than the front side of the main body. Therefore, it is more effective to place importance on the reduction effect on the front side.

In the above configuration, the rear conductive portion 4e of the conductor 4 is disposed only in the vicinity of the heating coil 2 so that a large amount of induced current flows on the rear side of the heating coil 2, and the front side is located as far as possible from the center of the heating coil. The front horizontal portion 4b is disposed so as to cause an induced current to flow and to avoid canceling magnetic flux shielding by the cooker body 5 made of a metal casing, and this is effective for the front horizontal portion 4b. Therefore, a canceling magnetic flux can be generated and leakage magnetic flux can be reduced.

However, when adhering the front side horizontal portion 4b to the top plate, at the time of product incorporation, dimensional tolerance in the height direction of the conductor 4 affects the distance between the heating coil 2 and the top plate 1.

  For example, when the finish of the conductor 4 is large, the distance between the heating coil 2 and the top plate 1 becomes larger than the design value. On the other hand, when the finish of the conductor 4 is small, the conductor 4 does not adhere to the back surface of the top plate 1. In any case, it affects the leakage electromagnetic wave reduction effect and the basic characteristics of induction heating.

  However, in the present embodiment, by configuring the rear conductive portion 4e with a wire material such as a litz wire that is more flexible than the metal plate, the height position of the rear wire material can be freely selected, and the above problem It can be avoided.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added within the scope of the present invention.

The top view of the induction heating cooking appliance which shows embodiment of this invention (A ) is a plan view of a pair of heating coil and conductor, (b) is a side view of the conductor. Diagram showing the relationship between conductor loop radius and cancellation flux Sectional drawing which shows the outline of the conventional induction heating cooking appliance (A) is a top view of a heating coil and a conductor of a conventional induction heating cooker, (b) is a sectional view showing the positional relationship between the heating coil and the conductor, and (c) is a side view of the conductor. Diagram showing the relationship between the radius of the conductive ring and the canceling magnetic flux Outline appearance of induction heating cooker

Explanation of symbols

1 Top plate 2 Heating coil 3 Object to be heated (cooking pan)
4 Conductor 4b Horizontal part 4c End part 4e Rear conductive part 5 Cooker body

Claims (3)

In an induction heating cooker that electromagnetically heats an object to be heated by a heating coil, a conductor is disposed on the outer periphery of the heating coil in a loop shape so as to surround the heating coil, and the conductor is disposed on the front side of the heating coil. The belt-shaped front horizontal part, which is disposed in the half-circular part and whose band surface is substantially parallel to the coil surface of the heating coil, and the rear conductive part, which is disposed in the half-circular part on the rear side of the heating coil, are electrically connected to each other. An induction heating cooker characterized by being connected to each other . The induction heating cooker according to claim 1, wherein the front horizontal portion has a structure in contact with a back surface of a top plate on which an object to be heated is placed . The induction heating cooker according to claim 1 or 2 , wherein the wire is a litz wire formed by twisting fine wires .

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