JP2008126050A - Bottom structure of uniformly heatable induction heating type large circular cooking pot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a pot bottom structure capable of fixing a coil with high reliability, while optimally controlling a magnetic flux generated from a work coil for induction heating, for the purpose of uniformly induction-heating a large circular cooking pan and a flat-bottomed cooking pot for preparing a large volume of cooked food at once to the Self-Defense Forces, schools, various organizations, convenience stores, family restaurants, supermarkets, etc. <P>SOLUTION: On the bottom of a pot, there is formed magnetic metallic ribs that can guide an electromagnetic induction magnetic flux which is generated by a high frequency electric current of a coil. Using the ribs, a structure is formed, which can firmly fix the coil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

This invention induction heats the bottom of a large circular cooking pot installed in a cooking factory that needs to cook a large amount at once to provide food to the Self-Defense Forces, schools, various organizations, convenience stores, family restaurants, supermarkets, etc. Concerning the method, the structure of the bottom of the pot that can uniformly heat the bottom of the pot by electromagnetic induction heating, which is inherently difficult to heat evenly, and the temperature of the cooked food can be brought to the specified value all at once. About.

In high-frequency induction heating, a high-frequency magnetic field is generated in a magnetic metal disposed in the vicinity of a coil by causing a high-frequency current to flow through the coil, and an eddy current is generated as an induced current in the magnetic metal. Generate Joule heat inside.
An induction heating cooker using such an eddy current heat generating action is installed just below the bottom of the pot, which is the metal to be heated, and a high frequency current is passed through the coil in the induction heating cooker to generate an eddy current at the bottom of the pot. Thus, self-heating is generated at the bottom of the pot, and the cooked food inside the pot is heated.

An induction heating type large circular cooking pot using this type of induction heating cooker has a coil placed through a gap of several tens of millimeters from the bottom of the pot, and an induction eddy current is generated at the bottom of the pot by a high-frequency current flowing through the coil. Generate and heat the bottom of the kettle.

As a method of fixing this coil, it is conventionally fixed simply via an insulating material so as to face the bottom surface of the hook, but it is fixed to a seat directly attached to the surface of the hook bottom with a screw or the like. There are both cases where the coil is fixed by a structure different from the hook body near the surface.

However, none of these methods can generate a high-frequency magnetic field evenly on the bottom of the hook, and the magnetic field is always concentrated in a donut shape on the circular bottom, and an eddy current is generated in a donut shape, and the heating power is concentrated in a donut shape. There was a drawback. For this reason, the heat distortion at the bottom of the hook becomes extremely large, and the bottom of the hook becomes uneven, affecting the intensity of the magnetic field generated around it, and the induced eddy current density changes, resulting in non-uniform heat generation due to Joule heat. It was.

Furthermore, there is a problem that the heat given to the food in the kettle becomes uneven and the quality of the finished product is poor, and even when trying to stir the food, the bottom of the kettle is thermally distorted as described above, so that sufficient stirring is achieved. It developed into the problem of being unable.

The present invention solves the above-mentioned problems, and devise the structure of the portion that contacts the heated surface of the pot bottom and the coil fixing structure so that the bottom of the large circular cooking pot can be uniformly induction-heated, and the strength of the pot bottom An object of the present invention is to provide a structure capable of improving the uniformity of a high-frequency magnetic field while improving the above.

Means to solve the problem

In order to achieve the above-mentioned object, electromagnetic waves generated by coils placed radially under magnetic metal ribs radially from the center toward the outer diameter direction on the bottom surface of the large circular cooking pot according to claim 1 of the present invention. It functions as a magnetic path that passes the induced magnetic flux radially from the center of the hook toward the outer diameter direction, and eddy currents that are generated at right angles to the magnetic path are distributed evenly in the radial direction of the bottom of the hook. . That is, the magnetic metal as the magnetic path is fixed to the bottom of the hook by welding.

The fixing rib of claim 2 is firmly welded and fixed to the bottom of the hook so that it can also function to prevent thermal distortion at the bottom of the hook. At that time, in order not to simply improve the mechanical strength but to make the magnetic path through which the magnetic flux passes, the magnetic metal is a thin plate with a wide width and is welded in an edge shape to the bottom of the hook. It is required to uniformly distribute the angles and fix them radially from the center toward the outer diameter direction. In addition, ring-shaped ribs that are linked at right angles to the fixed ribs are appropriately arranged so that the magnetic flux generated in the radial direction does not return irregularly, thereby avoiding magnetic flux concentration near the middle in the radial direction.

As described in claim 3, by arranging two magnetic flux passing ribs in a set, the magnetic flux is evenly distributed on the circumference by giving a width to the phenomenon of approaching a magnetic material existing nearby as a property of the magnetic flux. The variation was minimized when performing angular dispersion regression.

Here, when a coil-fixing heat-resistant material is sandwiched between two fixing ribs as in claims 4 and 5 and a process for fixing the coil is applied thereto to fix the coil, the coil contacts the fixing rib. The mounting height of the heat-resistant material for fixing the coil is several mm higher than the height of the fixing rib. It is characterized by a structure that is difficult to conduct to the coil.

As described in claim 6, when a high heat-resistant insulating material is used for the coil fixing seat, both the prevention of heat conduction and ensuring insulation with the coil can be treated, but the two fixing ribs sandwiching the coil fixing seat are used. When the bolt is penetrated, an eddy current flows and the bolt heats up. Therefore, an insert screw is embedded in the high heat-resistant insulating material, the bolt is inserted from both fixing ribs, and the coil fixing bolt is fixed in an insulated state.

If a non-magnetic metal is used as the heat-resistant material for fixing the coil as described in claim 7 and the heat conducted to the coil is minimized by avoiding induction self-heating, the coil is prevented from being grounded with the coil. Insert a liner of high heat-resistant insulating material between non-magnetic metals to construct a reliable insulation with sufficient creepage distance.

As described in claim 8, there is a step for preventing rotation so that the fixing bolt can be moved and the bolt can be tightened at an appropriate position regardless of the winding pitch of the coil by the long hole processed into the coil fixing material. It features a counterbored groove that can be fixed securely.

In the ninth aspect, when an insulating material is used as the heat-resistant material for fixing the coil, the high-heat-resistant insulating material is generally very expensive and becomes cheaper as the amount of use is reduced. Therefore, it is characterized in that it is processed so that a high-temperature insulating material is used only for the high temperature portion of the bottom of the hook and the fixing rib, and a low-cost material for low temperature can be used in combination in other places.

The invention's effect

Most of the large circular cooking pots currently in use are gas or steam heating type, and the diameter of the pot is small due to gas combustion efficiency or steam pressure resistance, and the bottom of the kettle has a hemispherical shape. Since this shape makes it difficult to apply heat to the food near the center of the pot, the food is stirred inside the pot. In addition, when fried, it is necessary to remove excess water, and it is necessary to invert the food in order to remove water from the food at the bottom of the pot. It ’s hard to flip because it ’s close to the center.

According to the heating method of the large circular cooking pot with a large diameter and a flat bottom according to the present invention, the distribution of the magnetic flux at the bottom of the pot can be made uniform, eddy currents can be flowed evenly, and the entire bottom of the pot can be heated evenly. The cooked food can be cooked thinly over the entire surface of the kettle, and the boiled cooking eliminates the need for stirring and eliminates boiling. In addition, when fried cooking, the food can be spread thinly over the entire surface of the kettle, so that excess water can be easily removed and the inversion of the ingredients becomes very easy. Some of the current products have the same type as this kettle, and a method of induction heating the bottom of the large circular cooking kettle, but instead of devising the coil and generated magnetic flux passage as in this proposal, the kettle itself is rotated to equalize it. This is a heating method. When the hook rotates, the heat of the pot heated at a corner is dissipated into the air, and a heat loss of about 10% occurs. In this method, the hook is fixed and the heat loss is minimized, and the gap between the coil and the bottom of the hook does not change, and the heating power is always constant. Further, the coil position does not change and the heating mode does not change. Furthermore, it is easy to preheat the edge of the kettle to about 100 ° C. with a resistance heater or the like, which is another heat source, in order to prevent germs from growing on the food material attached to the edge of the kettle. On the other hand, since the rotary type cannot be heated efficiently except by a non-contact induction heating method, it is very difficult to take measures for heating the edge of the kettle rising from the bottom of the kettle.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a case where the bottom 5 having a conventional shape is induction-heated. When the spiral coil 1 is placed close to the bottom of the bottom and induction-heated, the distribution of the induction magnetic field 12 is changed. The case where is simulated. According to this, even if the coil is uniformly distributed around the bottom of the hook, the magnetic field strength change curve 4 shows that the magnetic field strength at the center and the outer periphery of the hook is extremely lowered and the magnetic field strength near the intermediate diameter of the bottom of the hook is increased. I understand that. That is, the induced eddy current concentrates in the vicinity of the intermediate diameter of the bottom surface of the pot, and a donut-shaped heating mode is set.

In addition, the flatness of the bottom of the hook is poor, and the space distance between the coil and the bottom of the coil is changed by several millimeters. As the density of the magnetic flux 2 that changes and changes there, eddy currents meander, and the heat distribution at the bottom of the kettle changes accordingly. Here, the isointensity curves of the magnetic field are shown as 7 and 8, 7 shows the ideal state, and 8 shows the state of change due to the relationship between the coil and the heated object.

FIG. 2 shows an example in which a magnetic path for properly passing the magnetic flux 2 is formed by welding magnetic metal ribs 12 to 16 to the bottom of the hook 5 as shown in claim 1. According to this, as shown in FIG. 3, the induced magnetic flux 2 generated by the coil is forcibly and evenly distributed by the magnetic path formed by the magnetic metal ribs 12 and 13 radially arranged from the center of the bottom of the hook to the outer diameter direction. The magnetic flux is distributed by dividing the circumference of the bottom of the hook into equal angles. As a result, the magnetic field isointensity curve 19 approximates 7 in the ideal state. Further, as described in claim 2, the magnetic flux guided by the ring-shaped ribs 14 to 16 returns so as to wrap around to the bottom side of the coil at the location, and the magnetic field strength change curve 4 becomes 17, so that the location is induced. It works to reduce the amount of eddy current and avoid concentrated heating.

FIG. 4 shows a method of fixing the coils, and as described in claim 3, the fixing ribs 12 to 16 are arranged in two rows so that the induction magnetic flux 2 can be efficiently converged and the coil fixing seats 21 and 22 are properly arranged. It is attached to the bottom of the hook so that the gap between the coils can be accurately maintained. The coil fixing seats 21 and 22 are fixed to the bottom of the hook by coil seat fixing bolts and nuts 29 as described in claim 4, and maintain a position where the coil can be fixed several millimeters higher than the fixing ribs 12 to 16 so as not to affect the heat. In addition, there is no problem in securing insulation.

FIG. 5 is a view of the coil fixing seats 21 and 22 shown in FIG. 4 as viewed from the back side, and shows a mounting surface to the hook side. If a non-magnetic aluminum material is used as the material, as described in claim 5, it is avoided from induction heating action and has the effect of not causing thermal damage to the coil. When an insulating material is used so as to produce the effect of claim 6, as shown in FIG. 6b, a blind hole that does not penetrate through the middle of the coil fixing seats 21 and 22 is made into a blind hole, and insert screws are embedded from both sides to fix the coil seat. The structure is such that two bolt nuts 29 are used in one place and can be fixed from both sides.

FIG. 6a is a detailed view of the coil fixing seats 21 and 22 as seen from the back side, but aluminum is used as the material and a through hole is machined from the side direction, and a good conductor metal bolt such as Shinchu made in claim 7 is used. It is an example of a structure in the case of fixing. Further, of this structure, the anti-rotation function structure 30 is obtained by fitting the end face of the head of the coil fixing bolt 28 into the face of the bolt fixing elongated hole of the coil fixing bolt nut 28 according to claim 8. It becomes. FIG. 6B shows an example in which a heat-resistant insulating material is used for the coil fixing seats 21 and 22, and a structure in which eddy currents to the coil seat fixing bolts and nuts 29 are interrupted to prevent thermal influence on the coil fixing seat insulation. Show.

FIG. 7 shows a method for reducing the price of the coil fixing seats 21 and 22 described in claim 9. The heat-resistant insulating materials 24 and 26 are provided only at the portions contacting the high temperature portion of the bottom 5 and the metal ribs 12 and 13. The other part is an example of a structure using a low-cost insulating seat for low temperature. It is an important point here that the high-temperature contact portion is made of the minimum necessary amount of high heat-resistant insulating materials 24 and 26, and other structures in which a clearance 27 is secured so that the low-cost insulating seat for low-temperature use is not in contact with the bottom 5 of the hook. It is included in this plan even if it exists.

Heating situation when a large circular pot bottom is heated by the conventional electromagnetic induction heating method For the purpose of improving Fig. 1, the magnetic path is evenly arranged with magnetic metal ribs on the bottom of the hook. Magnetic flux generation when a coil is placed on the bottom structure of Fig. 2 and electromagnetic induction heating is performed The coil fixing seat is fixed to the bottom of the hook and the coil is fixed on it. The figure which looked at the coil fixing seat from the back side of the state shown in FIG. 4 is shown. When the non-magnetic metal material such as aluminum material is used as shown in detail in FIG. When insulation is used as above An example of low-cost production of coil fixing seats and an example of combination of high and low cost materials

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spiral work coil 2 Inducted magnetic flux 3 Induced magnetic field strength direction 4 Inducted magnetic field strength curve or eddy current generation density curve 5 Pan or pot 6 Magnetic field strength observation axis 7 Magnetic field isointensity curve (expected mode)
8 Magnetic field isointensity curve (when meandering)
9 Center of pan or pot 10 Range of non-uniform magnetic field strength 11 Range of induced magnetic flux density 12 Magnetic metal rib for magnetic path formation (long)
13 Magnetic metal ribs for magnetic path formation (short)
14 Magnetic metal ribs for magnetic path formation (curved shape)
15 Magnetic metal rib for magnetic path formation (small ring shape)
16 magnetic metal ribs for magnetic path formation (large ring shape)
17 Inductive magnetic field strength curve after improvement or eddy current generation density curve 18 Magnetic flux return position 19 Magnetic field isointensity curve after improvement 20 Magnetic flux mode 21 converged on magnetic path (long)
22 coil fixing seat (short)
23 Coil holding seat 24 Expensive high heat resistance coil fixing seat 25 Low price low temperature coil fixing seat 26 Expensive high heat resistance coil fixing seat 27 Low price coil fixing seat does not contact the bottom of the hook 28 Coil fixing bolt nut 29 Coil seat fixing Bolt nut 30 Coil fixing bolt detent 31 Coil seat fixing bolt hole 32 Coil seat fixing insert screw hole

Claims (9)

A large circular pan or kettle (hereinafter simply referred to as the kettle) with the upper surface open and a flat bottom surface and an induction heating spiral work coil (hereinafter referred to as a coil) on the bottom surface of the kettle. An electromagnetic induction magnetic field generated by a high-frequency induction current flowing in the oven and a large circular cooking pot bottom that directly induces and heats the bottom of the pot by causing an induced eddy current to flow to the bottom of the pot by the magnetic flux. The magnetic metal ribs form a magnetic path that is evenly divided and distributed radially from the center of the circle toward the outer diameter side, and electromagnetically induced eddy currents that flow inside the pot bottom are evenly distributed. Round cooking pot bottom structure. Cooking using a large circular cooking pot is intended for all frying, frying, boiling, steaming and baking, and the bottom of the kettle must be flat to minimize thermal distortion. Arranging the reinforcing ribs radially on the bottom of the pot and evenly distributing the electromagnetic induction magnetic field are the same in terms of countermeasures and have both functions. Furthermore, by arranging several ring-shaped ribs that intersect perpendicularly to the radially arranged ribs in the radial direction of the circumference, it is possible to avoid magnetic flux concentration in a donut shape near the middle of the coil, It is characterized in that the eddy current is distributed over the entire bottom of the kettle so that the magnetic flux is concentrated at the minimum diameter and is heated evenly. The magnetic path forming / reinforcing rib (hereinafter referred to as a fixed rib) at the bottom of the hook according to claim 2 is arranged in parallel in two sets, thereby facilitating the mounting of the coil fixing seat and the width of the magnetic path through which the electromagnetic induction magnetic flux passes. It is characterized in that the uniform magnetic flux distribution can be made stable by widening. A coil fixing seat for directly fixing the coil is arranged between the two fixing ribs according to claim 3, and the surface in contact with the coil is made several mm higher than the height of the two fixing ribs so as not to contact the coil. It is characterized by that. 5. Use a high heat-resistant insulating material as the material for the coil fixing seat according to claim 4, or use a non-magnetic metal such as aluminum that is difficult to induction heat, and heat the coil insulating material so as not to contact the bottom of the hook. It is characterized by not giving any damage. The coil fixing seat is fixed to the two fixing ribs with bolts. If the coil fixing seat is a heat-resistant insulating material, insert screws are inserted and tightened from both sides of the fixing ribs so that the bolts are not heated by eddy currents. Thus, both bolts are insulated and fixed so that eddy current does not flow through the bolts. In contrast to the sixth aspect, when a non-magnetic metal is used for the coil fixing seat, an eddy current always flows through the fixing bolt, so that a good conductor metal such as Shinchu is used for the bolt material to reduce heat generation. . The coil fixing bolt and nut for machining into the coil fixing seat according to claim 5 are oblongly formed, and a bolt non-rotating groove is formed at the same time to tighten the spiral coil no matter where the winding pitch is arranged. It is easy, reliable and highly reliable. The coil fixing seat material is made of a combination type coil fixing seat structure that reduces the amount of high-priced, high-heat-resistant insulating material used, and allows the use of many low-priced, low-temperature heat-resistant materials. Characterized by price.

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