JP2008117726A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight induction heating cooker small in heat capacity without hindering air cooling of a coil, easily manufacturable, and surely reducing a leakage magnetic field. <P>SOLUTION: A shield ring is structured to bend downward the whole or a part of both ends of the inner and outer peripheries of a ring-like plate, the ring can be formed by bending a sheet metal, whereby a material cost and a manufacturing time can be reduced, the shield ring small in heat capacity can be provided, reduction effect of a leakage current can be enhanced by doubly absorbing electromagnetic waves in a side surface direction, and a coil surface can be cooled without hindering the flow of air by keeping the upper surface of the shield ring flat. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an induction heating cooker for cooking a magnetic pot placed on a top plate by electromagnetic induction of a heating coil.

  Conventionally, this type of induction heating cooker generates a high-frequency magnetic field (hereinafter referred to as a magnetic field) by flowing a high-frequency current from an inverter circuit to a heating coil, and the magnetic field causes a vortex on the bottom of a magnetic pan placed on a top plate. An electric current is generated and the bottom of the pan generates heat due to its electrical resistance (see, for example, Patent Document 1).

  Most of the magnetic field generated from the heating coil is absorbed by the pan and converted to heat, but there is also a magnetic field that leaks from the periphery of the pan (leakage magnetic field). This leakage magnetic field may affect nearby electrical appliances. Recently, there are reports of concern about the impact on the human body, and each company is working to reduce the leakage magnetic field.

  FIG. 5 is a cross-sectional view showing a configuration of a conventional induction heating cooker.

Reference numeral 3 denotes a top plate on which an object to be heated such as a pan is placed, and a heating coil 5 supported by a coil base 6 is provided below the top plate. In order to reduce the leakage magnetic field from the heating coil 5 as one of the efforts to reduce the leakage magnetic field, a cast shield ring 7 is provided on the outer periphery of the heating coil 5 to absorb the magnetic flux from the lateral direction of the heating coil 5. I am letting. Further, a control board for controlling the heating coil 5 and the like, a component on the board, a fan motor 12 for cooling the heating coil, and the like are arranged below the heating coil 5 (for example, Patent Document 2). reference).
Japanese Patent Laid-Open No. 10-302953 JP 2006-120338 A

  However, the conventional configuration has a problem that since it is made of casting, the material cost and the manufacturing time are large, and the heat capacity is large, so that the thermal efficiency for heating the pan is lowered.

  To solve this problem, there is a method of forming a shield ring by making a sheet metal into a ring. However, the effect of reducing the leakage magnetic field is affected by the cross-sectional area of the shield ring. The reduction effect is small, and if the end face of the sheet metal is on the upper surface, there is a problem that the flow of air for cooling the coil surface is hindered.

  The present invention solves the above-described conventional problems, and is an induction heating cooker that is lightweight, has a small heat capacity, is easy to manufacture, and reliably reduces the leakage magnetic field without obstructing the wind for cooling the coil. The purpose is to provide.

  In order to solve the above-described conventional problems, an induction heating cooker according to the present invention includes a top and a bottom case that are divided into upper and lower parts and an outer case, and a top that is provided on the case and on which a heated object is placed. A plate, a heating coil disposed below the top plate, a coil base for holding the heating coil, a shield ring disposed in a ring shape on the outer periphery of the heating coil, and a substrate for supplying current to the heating coil A fan motor for cooling the components on the substrate and the heating coil, an air inlet provided under the case, and an air outlet provided under the case and / or on the case, and the shield ring Is a configuration in which the entire circumference or part of both ends of the inner periphery and the outer periphery of the ring-shaped plate is bent downward.

  As a result, since the ring can be formed by bending a sheet metal, the material cost and the manufacturing time can be reduced, and the electromagnetic wave in the side direction is absorbed twice to enhance the effect of reducing leakage current, and the upper surface of the ring is kept flat. Thus, the coil surface can be cooled without hindering the flow of the wind.

  The induction heating cooker of the present invention can reduce the material cost and the manufacturing time, and can provide a shield ring with a small heat capacity. In addition, since the sheet metal is doubled in the side surface direction, electromagnetic wave can be absorbed twice and the effect of reducing leakage current can be enhanced. Furthermore, by keeping the upper surface of the ring flat, the coil surface can be cooled without hindering the flow of wind.

  According to a first aspect of the present invention, there are provided a case upper and lower cases that are divided into upper and lower parts, a top plate that is provided on the case and on which an object to be heated is placed, and a heating coil disposed below the top plate. A coil base that holds the heating coil, a shield ring arranged in a ring shape on the outer periphery of the heating coil, a substrate that supplies current to the heating coil, and components on the substrate and the heating coil are cooled. A fan motor, an intake port provided under the case, and an exhaust port provided under the case and / or on the case, and the shield ring includes all of the inner and outer ends of the ring-shaped plate. The circumference or part of the structure is bent downward. Accordingly, since the ring can be formed by bending a sheet metal, material costs and manufacturing time can be reduced as compared with casting. In addition, since the sheet metal is doubled in the side surface direction, electromagnetic wave can be absorbed twice and the effect of reducing leakage current can be enhanced. Also, by providing a rib on the lower side and keeping the upper surface of the ring flat, the coil surface can be cooled without hindering the flow of wind.

  In the second invention, the bent shape of the shield ring is a part of the circumference on both the outer circumference and the inner circumference, and the rib ends are not on the same normal line on the inner circumference and the outer circumference. This prevents the escape shape necessary for the end of the bending in press working from being formed at the same position on the inner and outer circumferences, thereby preventing a portion from being extremely constricted and electromagnetic waves from leaking there. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
In FIG. 1, a case upper 1 and a case lower 2 are combined vertically to form a product outline, and a heated object such as a magnetic pot made of heat-resistant tempered glass or ceramic is placed on the case 1. The top plate 3 is adhered. Although the top plate 3 in the figure is a rectangular plane, there is no particular problem even if it is round or grooved. An operation unit 4 having a liquid crystal display window is provided on the front surface of the case 1 at a lower surface than the top plate 3.

  FIG. 2 is a top view of the case 1 with the case 1 removed. A heating coil 5 held by the coil base 6 is provided in the approximate center of the case lower 2. A substrate 8 is placed, a substrate 9 of the operation unit is placed in the front, and a substrate 10 of the power supply unit is placed in the right rear. Further, a fan motor 11 is provided on the left front side of the heating coil 5, and a heat sink (not shown) to which a heat generating component attached to the substrate 8 of the inverter unit is fixed, other components on the substrate, and the heating coil 5 are provided. Cooling air for cooling is sent in. Therefore, there is a circular squirrel-cage intake port 13 below the fan motor 11 under the case 2, and an exhaust port 14 is provided on the side surface and bottom surface of the case lower 2 away from the intake port 13. The rotation direction of the fan motor 11 is clockwise when viewed from above the main body, and a rib (not shown) constituting a casing (not shown) connected by R so that the radius gradually increases in the blowing direction. Are provided on the lower case 2 and a part of the upper case 1.

  The heating coil 5 is formed by winding a strand of bundled strands in a disk shape, and is placed on a coil base 6 made of an insulator in which ferrite (not shown) is radially arranged. It is pinched and fixed. On the outer periphery of the heating coil 5, a shield ring 7 made of a conductor that is not heated by induction heating such as aluminum or copper is provided at a certain distance so as to be below the surface of the heating coil 5. Yes.

  As shown in FIG. 3, the cross-sectional shape of the shield ring 15 is configured such that the upper part is a flat plate and the inner and outer ends are bent downward. This cross-sectional shape is substantially the same throughout the entire circumference, but the portion located above the fan motor 11 (in the left front direction in FIG. 2) remains flat to reduce the height of the main body. . As shown in FIG. 4, the end portion of the bent shape which is the boundary between the bent portion and the flat plate portion is not provided with the outer peripheral bent shape end portion 7a and the inner peripheral bent shape end portion 7c on the same normal line of the shield ring 7. In this case, they are shifted.

  About the induction heating cooking appliance comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, a high frequency current flows from the substrate 8 of the inverter part to the heating coil 5 to generate a magnetic field. Due to this magnetic field, an eddy current is generated at the bottom of a magnetic pot (not shown) placed on the top plate 3, and the pot itself generates heat due to electric resistance to the current. A magnetic field is uniformly generated from the inside to the outside around the heating coil 5 through which a high-frequency current flows. However, ferrite is radially arranged on the coil base 6 holding the heating coil 5 and repels itself. By doing so, the magnetic flux density above the heating coil 5 (top plate 3 side) is increased, and the magnetic field received by the pan is increased.

  When the pan is larger than the diameter of the heating coil 5, most of the magnetic flux is absorbed by the pan, and the leakage magnetic field is reduced. However, as the pan becomes smaller, the magnetic field generated from the outer periphery of the heating coil 5 is not absorbed by the pan. Leak out from the pan. When the shield ring 7 made of a conductor such as aluminum is provided on the outer periphery of the heating coil 5 against the magnetic field leaking from the lateral direction of the heating coil 5, it absorbs the magnetic flux that goes out of the pan. Can do.

  As shown in FIG. 3, by folding the inner and outer circumferences of the shield ring 15 downward, the magnetic flux can be absorbed twice inside and outside. In addition, since the upper surface can be kept flat by bending the end portion downward, the air flowing through the upper surface of the heating coil 5 is not hindered and the cooling performance is maintained. Moreover, since the thickness becomes uniform and can be processed by press molding by using such a shape, the production time can be shortened as compared with casting.

  In the portion where the shield ring 15 and the fan motor 11 overlap vertically, the bent shape of the shield ring 15 is not formed on the inner periphery and the outer periphery in order to keep the body height low. In order to bend the end of the bent shape cleanly, it is known to create a relief shape. Providing such a relief shape reduces the cross-sectional area of the shield ring at that portion. If the outer and inner peripheral bent ends are provided on the same normal line, the relief shape is also provided on the same normal line, and the cross-sectional area of the shield ring becomes extremely small in that part, and magnetic flux leaks from that position. End up.

  Therefore, as shown in FIG. 4, by providing the outer peripheral bent shape end portion 7a and the inner peripheral bent shape end portion 7c so as to be shifted, the outer peripheral escape shape 7b and the inner peripheral escape shape 7d are also provided shifted so that the magnetic flux leaks. The extreme constriction cannot be constituted. In the figure, the bent shape of the inner periphery is larger than the bent shape of the outer periphery, but conversely, the bent shape of the outer periphery may be provided larger and the bent shape of the inner periphery may be reduced.

  As described above, the induction heating cooker according to the present invention can efficiently reduce leakage of electromagnetic waves by the shield ring formed by sheet metal processing, and can also maintain the cooling performance of the coil. It can be applied to all induction heating cookers where reduction of the temperature is desired.

External view of the heating cooker in Embodiment 1 of the present invention The internal block diagram of the heating cooker in Embodiment 1 of this invention Sectional drawing of the principal part of the heating cooker in Embodiment 1 of this invention The perspective view of the shield ring in Embodiment 1 of this invention Sectional view of the main part of a conventional induction heating cooker

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case top 2 Case bottom 3 Top plate 4 Operation part 5 Heating coil 6 Coil base 7 Shield ring 8 Inverter part board 9 Operation part board 10 Power supply part board 11 Fan motor 12 Coil holder 13 Inlet 14 Outlet

Claims (2)

A case that is divided into upper and lower parts and forms an outer case; a top plate that is provided on the case and on which an object to be heated is placed; a heating coil disposed below the top plate; and the heating coil A coil base to be held; a shield ring arranged in a ring shape on the outer periphery of the heating coil; a substrate that supplies current to the heating coil; a fan motor that cools the components on the substrate and the heating coil; An intake port provided under the case and an exhaust port provided under the case and / or on the case, and the shield ring faces down all or part of the inner and outer ends of the ring-shaped plate An induction heating cooker that is folded into two. The induction heating cooker according to claim 1, wherein the bent shape of the shield ring is a part of the outer periphery and the inner periphery, and the rib ends are not on the same normal line at the inner periphery and the outer periphery.

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