JPH0997673A - Induction heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give high efficiency of an induction heating apparatus for which an iron core is used and use the heat effectively. SOLUTION: A heat resistant and heat insulating material 9 is inserted in spaces between a main body casing 1 and an iron core 2 as well as coils 3 of an excitation apparatus 4 to cover the circumference of the iron core 2 except the end parts of magnetic poles and the circumferences of the coils 3 with the heat resistant and heat insulating material 9. A surface member 5 is so installed in a plane-like way as to expose only the end faces of both magnetic poles of the iron core 1 to the surface and closely seal the excitation apparatus 4 and the heat resistant and heat insulating material 9 and a top plate 10 is installed between the iron core 2 and an object 6 to be heated. As the coils 3, heat resistant electric wires with heat resistant temperature 350-400 deg.C, e.g. glass-coated electric wires, ceramic-coated electric wires, etc., are used and as the surface member 5, glass plates, ceramic plates, heat resistant resin, etc., are used and as the top plate 10, a metal such as copper having excellent heat transmitting property is used. In the case that the apparatus is used for an electromagnetic grill, an iron plate is used as the object 6 to be heated and the object 6 to be heated is directly brought into contact with the iron core 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating apparatus for induction heating an object to be heated, such as a magnetic metal, by using an alternating magnetic flux generated from an exciting coil, and relates to effective use of heat. Yes, it is especially effective when applied to induction heating cookers and the like.

[0002]

2. Description of the Related Art An induction heating device (cooker) for induction heating a heated object (cooking pot) by applying a low frequency current such as a commercial frequency to an exciting coil to generate an alternating magnetic flux using an iron core has been known in the past. Has been. JP-B-53-37580,
The induction heating device described in JP-A-50-70941 is of this type.

As shown in FIG. 4, the induction heating cooker using an iron core is generally provided with an exciting device 4 consisting of an iron core 2 and a coil 3 inside a main body casing 1, and usually the upper surface of the exciting device 4 is a surface. It is configured such that it is covered with the member 5 and the object to be heated (special pot) 6 is placed on the surface member 5.
The heating principle is that by applying an alternating current of a low frequency (commercial frequency) to the coil 3 of the exciter 4, an alternating magnetic flux Φ having the magnetic cores of the iron core 2 and the bottom of the heated body 6 is generated,
An eddy current is induced around the alternating magnetic flux Φ by electromagnetic induction at the bottom of the heated body 6, heat is generated at the bottom of the heated body 6 by the eddy current, and the heat is used for cooking. . The surface member 5 is generally made of a non-magnetic, high-resistance metal plate such as a stainless steel plate, a heat-resistant glass plate, a ceramic plate, an inorganic or organic material such as a resin molded product, and an aluminum plate or the like. Sometimes it is. Further, the heat generated by the alternating magnetic flux Φ is also generated in the iron core 2, and unless the heat generated in the iron core 2 is released to the outside, the temperature of the coil 3 rises due to the accumulation of heat and the insulating material of the coil 3 deteriorates significantly. Therefore, ventilation holes 7 are provided in the side wall portion of the main body casing 1 so that the temperature of the coil 3 does not exceed 200 ° C. to 250 ° C. which is a general heat resistant temperature of the electric wires forming the coil 3. At the same time, a cooling fan 8 is installed inside the exciter 4
It is common to cool the heat to release heat.

[0004]

The cooking by the induction heating cooker utilizes the heat generated at the bottom of the object (dedicated pot) 6 to be heated. Conventionally, a part of the heat is applied to the surface member 5. Heat was transferred and was dissipated in the air as heat loss. Further, conventionally, it is usually necessary to install the cooling fan 8 to cool the exciter 4 as described above, and the heat generated as internal loss heat in the exciter 4 including the iron core 2 and the coil 3 is also generated. In addition, it was dissipated into the ambient air as heat loss. The conventional induction heating cooker has poor heat efficiency because a large amount of heat is dissipated in the air as heat loss without being used for cooking.

The present invention has been made in view of the above problems, and it is an object of the present invention to improve the efficiency of an induction heating device using an iron core and effectively use heat.

[0006]

In the induction heating device using an iron core, it is a conventional common sense to cool the exciting device by using a cooling fan or the like so that the coil temperature does not exceed the heat resistant temperature. Cooling the device means releasing the internal loss heat of the exciter into the ambient air as heat loss without effectively utilizing it, and sticking to the conventional wisdom is to improve the efficiency of the induction heating device. It is impossible to realize effective utilization of heat at a high level. The present invention solves the problems that cannot be solved within the range of the conventional common sense by a new idea that is not caught by the common sense. That is, according to the present invention, the heat resistant temperature of a heat resistant electric wire such as a glass covered electric wire and a ceramic covered electric wire used for a special purpose is 35
0 ° C to 400 ° C, while paying attention to the fact that the saturation temperature of the coil is about 250 ° C to 300 ° C when the exciting device of the induction heating device using the iron core is not cooled,
By using such a heat-resistant wire for the exciting coil of the induction heating device, and by configuring the induction heating device as follows,
It has been found that cooling of the exciter, which is the conventional wisdom, is unnecessary, and the internal heat loss of the exciter can be effectively used. The specific means are as follows.

The exciting device of the induction heating device is composed of an iron core and a coil to generate an alternating magnetic flux by applying an alternating current to the coil to induction-heat the object to be heated, and a heat-resistant wire is attached to the coil of the exciting device. In addition to using, the iron core and coil of the exciter are covered with a heat-resistant heat insulating material, and a metal top plate is placed between the iron core and the object to be heated, so that heat generated by the iron core and coil directly contacts the iron core and top plate. The heat is transferred to the object to be heated.

Alternatively, the exciting device of the induction heating device is made up of an iron core and a coil to generate an alternating magnetic flux by applying an alternating current to the coil to induction-heat the object to be heated. In addition to using heat-resistant wires, the core and coil of the exciter are covered with heat-resistant heat insulating material so that the iron core comes into direct contact with the object to be heated, and the heat generated by the core and coil is directly contacted with the object to be heated. The heat is transferred to the object to be heated.

When the iron core and the coil of the exciter are thus covered with the heat-resistant heat insulating material, the internal loss heat generated in the iron core and the coil is transferred to the heated object without being dissipated to the outside, and the heat can be effectively used. Becomes Then, by disposing a metal top plate between the iron core and the object to be heated and directly contacting the iron core and the top plate, or by making the iron core directly contact the object to be heated, The heat transfer is efficiently performed, and the heat efficiency is increased. Also, the temperature of the coil rises by covering the iron core of the exciter and the coil with a heat resistant heat insulating material, but since the temperature of the coil saturates at about 250 ° C to 300 ° C, it has a heat resistant temperature of 350 ° C to 400 ° C. The heat resistant wire does not deteriorate.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an induction heating cooker corresponding to claim 1. This induction heating cooker is used, for example, as a freezer gyoza, and is provided with an exciting device 4 including an iron core 2 and a coil 3 inside a main body casing 1 having an open upper part. Then, a heat-resistant heat insulating material 9 is inserted between the iron core 2 and the coil 3 of the exciting device 4 and the main body casing 1, and the heat-resistant heat insulating material around the iron core 2 and around the coil 3 excluding the ends of the pair of magnetic poles. Covered by 9. A surface member 5 is provided above the main body casing 1 so as to be flush with both magnetic poles of the iron core 2 so that only the end surfaces of the magnetic poles are exposed and the exciter 4 and the heat-resistant heat insulating material 9 are sealed. There is. The top plate 10 is arranged between the iron core 2 and the body 6 to be heated. The coil 3 is made of a heat resistant electric wire having a heat resistant temperature of 350 ° C. to 400 ° C. such as a glass covered electric wire and a ceramic covered electric wire. The surface member 5 is made of a glass plate, a ceramic plate, a heat resistant resin, or the like. The top plate 10 is made of metal such as copper having excellent heat transfer property. The object 6 to be heated is, for example, a dedicated iron pan (iron plate) for frozen gyoza.

This induction heating cooker uses a low-frequency current such as a commercial frequency, and when a low-frequency alternating current is applied to the coil 3 of the exciter 4, the bottom of the iron core 2 and the heated object 6 is heated. An alternating magnetic flux Φ having a magnetic path of is generated, and an eddy current is induced at the bottom of the heated body 6 to generate heat. You can use the heat to cook. The surface member 5 is made of a material having a poor heat transfer property, and has a structure that does not directly contact the heated body 6. Therefore, the heat loss radiated from the surface member 5 into the air is small. Further, since the iron core 2 and the coil 3 of the exciting device 4 are covered with the heat resistant heat insulating material 9, the iron core 2 and the coil 3 are
The internal loss heat generated in 1 is not dissipated to the outside, but is transferred to the heated body 6 through the top plate 10 that is in direct contact with the iron core 2, and this is also used for cooking. By thus covering the heat-resistant heat insulating material 9, the temperature of the coil 3 becomes 2
Coil 3 rises to 50 ° C to 300 ° C
There is no risk of deterioration because it is a heat resistant wire with a heat resistant temperature of 50 ° C to 400 ° C.

FIG. 2 is a graph of measurement results of measurements carried out to compare heating efficiencies of the induction heating cooker of the present invention having the structure of FIG. 1 and the conventional induction heating cooker of the structure of FIG. is there. The horizontal axis is the elapsed time (operation time) from the start of operation (heating), and the vertical axis is the temperature of the coil (winding temperature) and the temperature of the top plate (top plate temperature), and a certain amount of water evaporates due to heating. It shows the time until the end (water evaporation time). In the induction heating device according to the present invention, a copper plate having a thickness of 1.5 mm is used for the top plate 10 in the structure of FIG. 1, and this is shown as “with heat insulation” in FIG. Regarding the conventional induction heating cooker, in the structure of FIG. 4, the surface member 5 has a thickness of 1.5.
mm glass fiber mixed epoxy resin plate is used.
This is shown in FIG. 2 as "without heat insulation". Then, 100 cc of tap water is repeatedly put in the object to be heated 6 to evaporate under the same excitation device 4 and power supply conditions until 100 cc of tap water put in the object to be heated 6 is completely evaporated. Was measured each time, and the winding temperature and the top plate temperature were measured at each elapsed time from the start of operation. As can be seen from this graph, when 100 cc of water is continuously and repeatedly evaporated, the winding temperature and the top plate temperature increase and become saturated with time in any case. And an induction heating cooker (with heat insulation) according to the present invention
In the above case, after about 6 hours of continuous heating test, the top plate temperature rises to about 240 ° C and saturates, and the winding temperature rises to about 300 ° C and saturates. On the other hand, in the case of the conventional induction cooker (without heat insulation), the top plate temperature saturates at about 150 ° C and the winding temperature saturates at about 160 ° C after about 4 hours. Also, the water evaporation time is
Saturation occurs about 4 to 6 hours after the start of operation. For example, when comparison is made after 4 hours of continuous heating, the water evaporation time without insulation is 200 seconds, whereas the water evaporation with insulation is The time is 163 seconds, which is a reduction of 18.5%. This indicates that the thermal efficiency was increased by the heat transfer due to the direct contact between the iron core 2 and the top plate 10.

FIG. 3 shows an example of an induction heating cooker corresponding to claim 2. The example shown in FIG. 1 uses a dedicated pot as the object to be heated 6, but the induction heating cooker in FIG. 3 is used as, for example, an electromagnetic grill, and the object to be heated 6 is, for example, It uses iron plates. Then, the heated body 6 is brought into direct contact with the iron core 2. In this case, the main body casing 4 is also open at the top, and is provided with the exciting device 4 including the iron core 2 and the coil 3 inside. Then, a heat resistant heat insulating material 9 is also inserted between the iron core 2 and the coil 3 of the exciter 4 and the main body casing 1 so that the periphery of the iron core 2 and the periphery of the coil 3 excluding the ends of the pair of magnetic poles are heat resistant. It is covered with a material 9. A surface member 5 is provided above the main body casing 1 so as to be flush with both magnetic poles of the iron core 2 so that only the end surfaces of the magnetic poles are exposed and the exciter 4 and the heat-resistant heat insulating material 9 are sealed. There is. The body 6 to be heated is installed so as to be in direct contact with the iron core 2. And after all, in coil 3,
Withstand temperature of glass-coated electric wire, ceramic-coated electric wire, etc. is 3
A heat resistant electric wire of 50 ° C to 400 ° C is used. The surface member 5 is made of a glass plate, a ceramic plate, a heat resistant resin, or the like. Also in this case, when a low-frequency alternating current is applied to the coil 3 of the exciter 4, an alternating magnetic flux Φ having the iron core 2 and the heated body 6 as a magnetic path is generated, and an eddy current is induced in the heated body 6, Fever. Then, the heat can be used for cooking. Also in this case, the surface member 5 has poor heat transfer,
Moreover, the structure is such that it does not come into direct contact with the heated body 6. Therefore, the heat loss radiated from the surface member 5 into the air is small.
Further, since the iron core 2 and the coil 3 of the exciting device 4 are covered with the heat resistant heat insulating material 9, the internal loss heat generated in the iron core 2 and the coil 3 is not dissipated to the outside. Then, the internal loss heat is directly transferred from the iron core 2 to the heated body 6.
Therefore, the thermal efficiency is increased as in the example of FIG. Also in this case, the temperature of the coil 3 is saturated at about 250 ° C to 300 ° C. Therefore, the deterioration of the coil 3 does not occur.

The present invention is not limited to the examples shown in FIGS. 1 and 3, but can be applied to induction heating devices having various other structures and uses.

[0015]

According to the present invention, by using a heat-resistant electric wire for the exciting coil, it is possible to eliminate the limitation due to the limit of the heat-resistant temperature, and the iron core and the coil of the exciting device are covered with the heat-resistant heat insulating material to cause the internal loss. The heat can be transferred to the object to be heated without being dissipated and can be effectively used. The internal loss heat can be efficiently transmitted by direct contact between the iron core and the top plate or by direct contact between the iron core and the object to be heated, and the heat loss radiated from the surface member to the outside can be reduced. Therefore, the thermal efficiency can be improved, and the efficiency of the induction heating device can be improved and the heat can be effectively used.

Further, since the induction heating device of the present invention does not have a structure in which it is cooled by a fan, the amount of heat exhausted to the outside is small,
It is possible to reduce the load on the air conditioning in the room using this induction heating device, and to prevent dust from standing up due to the exhaust gas and to prevent water or foreign matter from entering through the ventilation holes.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an induction heating cooker showing an example of an embodiment of the present invention.

FIG. 2 is a graph showing a measurement result of a measurement for comparing the thermal efficiency of the induction heating cooker of the example of FIG. 1 and the conventional induction heating cooker.

FIG. 3 is a cross-sectional view of an induction heating cooker showing another example of the embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional induction heating cooker.

[Explanation of symbols]

 1 Main Body Casing 2 Iron Core 3 Coil 4 Exciter 5 Surface Member 6 Heated Object 9 Insulation 10 Top Plate

Claims (2)

[Claims] 1. An induction heating apparatus for inductively heating an object to be heated using an exciter, which comprises an iron core and a coil and applies an alternating current to the coil to generate an alternating magnetic flux, wherein a heat-resistant wire is provided in the coil of the exciter. While using, the core and coil of the exciter is covered with a heat-resistant heat insulating material, a metal top plate is arranged between the core and the body to be heated, the heat generated in the core and the coil An induction heating device, wherein heat is transferred to the object to be heated by direct contact between an iron core and the top plate. 2. An induction heating apparatus for inductively heating an object to be heated by using an exciter, which comprises an iron core and a coil and generates an alternating magnetic flux by applying an alternating current to the coil, wherein a heat-resistant wire is provided in the coil of the exciter. With the use of, the iron core and the coil of the exciter are covered with a heat-resistant heat insulating material, and the iron core and the coil are heated by directly contacting the iron core with the object to be heated. An induction heating device, characterized in that heat is transferred by direct contact with the object to be heated.