JPH08203662A - Induction heating equipment - Google Patents

Abstract

PURPOSE: To provide an induction heating equipment having a larger heating value with the same power, or having the same heating value with a lesser power. CONSTITUTION: A member 1 to be induction-heated is arranged on the upper part of an induction heating coil 2, and a U-shaped core 3 consisting of a soft magnetic material is arranged on the lower part of the coil 2. As the U-shaped core 3, a core having a form for partially enclosing the side surface part of the coil 2 is arranged to minimize the space between the member 1 to be induction-heated and the opened end surface of the outer leg part of the U-shaped core 3. Thus, the core and the member to be induction-heated are arranged closer to a closed magnetic path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device in which a member made of a soft magnetic core is arranged under a coil for induction heating.

[0002]

2. Description of the Related Art Conventionally, an induction heating apparatus of this type is one in which an eddy current is generated in a portion to be induction-heated by causing an alternating current to flow through a coil and heat is generated by Joule heat.

As shown in FIG. 2, the conventional induction heating apparatus has an induction heating coil 2 having an induction heating member 1 disposed above the induction heating coil 2 and a soft magnetic core 3 disposed below the coil 2. . The soft magnetic core 3 is rod-shaped.

That is, the distance between the induction heating member 1 and each part of the soft magnetic core 3 is constant, and when an electric current is applied to the coil 2, a magnetic field is generated around the coil 2 and the magnetic field is generated. As a result, the core 3 and the induction-heated member 1 are excited, and a magnetic flux that circulates around the coil 2 is generated.

[0005]

However, in the case of the conventional induction heating apparatus of this type, the core 3 cannot be in contact with the coil 2 and a predetermined space is provided between the core 3 and the induction heating member 1. Due to the large gap, a large demagnetizing field is generated in the core 3 and the core 3 is not excited much. Therefore,
The magnetic flux density generated in the induction heated member also decreases,
As a result, there is a drawback that the calorific value is small.

The present invention eliminates these drawbacks by providing:
Induction heating equipment with the same electric power and having a larger calorific value,
Alternatively, it is another object of the present invention to provide an induction heating device having the same heat generation amount with less electric power.

[0007]

SUMMARY OF THE INVENTION The present invention is an induction heating apparatus in which an induction heating member is arranged above an induction heating coil, and a U-shaped core made of a soft magnetic material is arranged below the coil. , Arranging a U-shaped core having a shape surrounding a part of the side surface of the coil, and bringing the induction-heated member into contact with the open end surface of the outer leg of the U-shaped core, or by reducing the interval thereof, The present invention relates to an induction heating device characterized by having a structure close to a closed magnetic path between a U-shaped core and a member to be induction-heated, and with the same electric power as compared with an induction heating device using a conventional rod-shaped core. It is characterized by having a larger calorific value or having the same calorific value with less electric power.

That is, the present invention provides an induction heating apparatus in which a plate-shaped induction heating member is arranged above an induction heating coil, and a bar-shaped core made of a soft magnetic material is arranged below the coil. A U-shaped core having outer leg portions provided in the vertical direction with respect to the induction-heated member at both ends of the coil, and the coil is provided inside the U-shaped core so as not to stick out from the open end surface of the outer leg portion. The cores are arranged at a predetermined distance from each other, and the open end surfaces of the outer legs of the core are arranged in parallel with the lower surface of the induction-heated member so that the gap length is as small as possible or in contact with the lower surface. And induction heating equipment.

[0009]

The at least one outer leg portion is provided upright on both ends of the core in a direction perpendicular to the surface of the induction heating member. In this way, by providing the outer leg portions at both ends, and by making the core surround a part of the side surface portion of the coil, the distance between the open end surface of the outer leg portion of the U-shaped core and the induction-heated member, It is possible to make it smaller than the distance between the conventional rod-shaped core and the induction-heated member. Further, if the U-shaped core is used, it is possible to make contact with the induction-heated member, so that a structure closer to a closed magnetic path is formed between the U-shaped core and the induction-heated member. Therefore, the demagnetizing field generated in the U-shaped core becomes small, and the magnetic flux density excited in the U-shaped core becomes large. Therefore,
The magnetic flux density generated in the induction-heated member also increases, and as a result, the amount of heat generated increases.

The power loss due to induction heating is proportional to the square of the magnetic flux density when the electromagnetic field is uniformly applied to the entire induction-heated member. Therefore, the amount of heat generation depends on the magnitude of the magnetic flux density, and the larger the magnetic flux density, the greater the amount of heat generation.

As described above, in the present invention, the U-shaped core is formed so as to surround a part of the side surface of the coil,
By approaching a closed magnetic circuit structure, an induction heating device with the same electric power and a larger calorific value, or an induction heating device with a smaller electric power and the same calorific value than the conventional induction heating device using a rod-shaped core. A heating device can be provided.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 3 is a schematic bottom view of the induction heating device according to the embodiment of the present invention as viewed from below. As shown in FIG. 3, a disk-shaped induction-heated member 1 was placed above the induction heating coil 2, and a U-shaped core 3 made of a soft magnetic material was placed below the coil 2.

FIG. 1 is a sectional view of an induction heating device according to an embodiment of the present invention, taken along the line A and the line B in FIG. As shown in FIG. 1, an induction heating member 1 is arranged above an induction heating coil 2, and a U-shaped core 3 in which two outer leg portions made of a soft magnetic material are erected is provided below the coil 2. I arranged it. In this case, in order to prevent the coil 2 from protruding from the open end surface of the outer leg portion inside the U-shaped core 3, the coil 2 is arranged in the center with a predetermined interval, and the core 3
The U-shaped cores 3 are arranged so that the open end surfaces of the outer legs are parallel to the lower surface of the induction-heated member in FIG.

By the way, since the amount of heat generated is generally proportional to the square of the magnetic flux density, it can be obtained by calculating the magnetic flux density distribution of the induction-heated member. But,
In the case of an arbitrary shape, the magnetic flux density distribution is complicated and an analysis method such as the finite element method is necessary.

This time, a general-purpose finite element method analysis software A
Using NSYS (manufactured by Swanson Analysys Systems), the magnetic flux density distribution of the induction-heated member was calculated, and the effect of improving the heat generation amount was quantitatively evaluated.

The induction heating member was divided into minute volumes Vi, the magnetic flux density Bi in each minute volume was calculated, and the following value Wc was calculated as an index proportional to the amount of heat generation. Wc = Σ
(Vi · Bi ² ) / (μ ₀ · ΣVi) [J / m ³ ] and μ ₀ is the magnetic permeability in vacuum.

In calculating the distribution of magnetic flux density, in both the case of FIG. 1 showing the induction heating apparatus of the present invention and FIG. 2 showing the conventional induction heating apparatus, the induction heating coil 2 is a 0.5 mm copper wire. Ten bundle wires of 25 bundles were used, and the current value was 3 A per bundle.

The induction heating member 1 is made of magnetic stainless steel (S
US403), and the magnetic permeability μ was set to 120 from the actually measured value.

The U-shaped core 3 made of a soft magnetic material is M
It is n-Zn ferrite, and μ is 1500 from the measured value.

The thickness h of the U-shaped core 3 is 5 mm, the length of the bottom plate portion of the U-shaped core 3 is 70 mm, the radius of the disk-shaped induction heating member 1 is 120 mm, and the total width of the coil 2 is 50 m.
The distance between the induction heating member 1 and the bottom plate portion of the U-shaped core 3 was 10 mm.

In the case of FIG. 1, the gap g between the open end surface of the outer leg of the U-shaped core 3 and the induction-heated member is 2
mm.

In calculating the distribution of the magnetic flux density, the magnetic flux density distribution in the acute angle portion between the line segment AB and the line segment AC, which is the minimum unit of the symmetrical shape in FIG. 3, is used in both cases of FIG. 1 and FIG. Only calculated.

FIG. 4 shows the calculation result of the magnetic flux density distribution of the induction-heated member 1 in the induction heating instrument of this embodiment shown in FIG. Table 1 shows the magnetic flux densities corresponding to the numbers indicating the equal magnetic flux density regions of the induction heating member of FIG.

[0025]

As a comparative example, FIG. 5 and Table 1 show the calculation results of the magnetic flux density distribution of the induction heating member in the conventional induction heating device shown in FIG.

When the U-shaped core 3 of the present invention has a shape surrounding a part of the side surface of the induction heating coil 2 (FIG. 4 and Table 1), the conventional core 3 as a comparative example has a rod shape (FIG. 5
Also, compared with Table 1), the magnetic flux density of the whole induction-heated member 1 is increased. 4 and 5, the drawing of the induction heating coil 2 is omitted.

Table 2 shows Wc calculated from the magnetic flux density distributions of FIGS. 4 and 5.

[0029]

The difference in the calculation conditions when calculating the magnetic flux density distribution shown in FIGS. 4 and 5 is that the outer leg portion surrounding a part of the side surface portion of the induction heating coil is located at both ends of the rod-shaped core shown in FIG. Is additionally provided, and the other calculation conditions, for example, the input power and the coil position are the same.

As described above, by forming the U-shaped core 3 so as to surround a part of the side surface of the induction heating coil, the heat generation amount is increased by about 80% as compared with the conventional rod-shaped core 3. Results were obtained.

The induction heating apparatus according to the present invention shown in FIG. 1 and the conventional induction heating apparatus shown in FIG. 2 were manufactured by using members having the same material and shape as those used in the simulation by the finite element method. 1,500 ml of water at 25 ° C. was placed in an Erlenmeyer flask having a bottom diameter of φ200 mm, placed on the induction heating member 1 and heated to measure the temperature.

As a result, as shown in FIG. 6, in the conventional induction heating device (heating curve 21), the time required for the water temperature to reach about 100 ° C. is about 20 minutes, whereas the induction heating according to the present invention is performed. About 12 for the fixture (heating curve 11)
It was min. Converting the result of this experiment into the ratio of the amount of heat generation, the increase was about 60%.

In order to prevent the coil from protruding from the open end surface of the outer leg portion inside the U-shaped core, the coil is arranged at the center with a predetermined interval, and the open end surface of the outer leg portion is When the U-shaped core is arranged so as to come into contact with the lower surface of the induction-heated member, there is an advantage that the heat generation amount is higher or the power consumption is higher than the case where the U-shaped core is arranged with a certain gap length. It goes without saying that an induction heater can be provided.

[0035]

As described above, according to the present invention,
It is possible to bring the open end surfaces of the outer legs of the U-shaped core into contact with the induction-heated member or to reduce the distance between them, and to approach the closed magnetic circuit structure, the demagnetizing field generated in the U-shaped core Becomes smaller, and the magnetic flux density excited by the U-shaped core increases, so the magnetic flux density generated in the induction-heated member also increases, which is higher than the conventional induction heating device using a rod-shaped core. It has become possible to provide induction heating appliances that have the advantage of heat generation or power saving.

[Brief description of drawings]

FIG. 1 is a sectional view showing an induction heating device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a conventional induction heating device.

FIG. 3 is a schematic bottom view of the induction heating instrument according to the embodiment of the present invention or the induction heating instrument when viewed from below.

FIG. 4 is a magnetic flux density distribution diagram of the induction-heated member of the induction heating device according to the embodiment of the present invention.

FIG. 5 is a magnetic flux density distribution diagram of an induction heating member of a conventional induction heating device.

FIG. 6 is a diagram showing the results of an example of a heating experiment using the induction heating device of the present invention and the conventional induction heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Induction heating member 2 (For induction heating) Coil 3 (Soft magnetic or U-shaped) core 11 (Invention) heating curve 21 (Conventional) heating curve g Gap length h Core thickness

Claims (1)

[Claims] 1. An induction heating apparatus in which a plate-shaped induction heating member is arranged above an induction heating coil and a bar-shaped core made of a soft magnetic material is arranged below the coil, and both ends of the bar-shaped core are covered. A U-shaped core having outer leg portions provided in the vertical direction with respect to the induction heating member is formed, and the coils are provided with a predetermined distance so as not to project from the open end surface of the outer leg portion inside the U-shaped core. Induction heating characterized in that it is arranged in the center, and the open end surface of the outer leg of the core is arranged in parallel with the lower surface of the induction-heated member so that the void length is as small as possible or in contact with the lower surface of the induction-heated member. Equipment.