JPS60230393A - Induction heating coil unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an induction heating coil device used in electromagnetic induction equipment, such as an electromagnetic cooker.

Prior Art and Its Problems As an electromagnetic cooker using high-frequency induction heating, for example, as shown in FIG. An induction heating coil device consisting of coils 2 arranged in a spiral shape on a plane is assembled in case 3, and coil 2 is heated to 20 to 40K.
A high frequency high power of 8 degrees Hz is supplied to a load 5 such as a pan placed on a heat-resistant insulating plate 4 above the coil 2.
A method is known in which direct heating is performed by generating eddy current loss and hysteresis loss due to electromagnetic induction.

However, if the coil support board l is made of a simple heat-resistant insulating material, the same amount of magnetic flux as that on the load 5 side will leak to the back side of the coil support board l, and the electronic circuit device 1 disposed on the back side will leak. For example, a problem arises in that an inverter section provided for driving this induction heating coil device generates electricity.

Therefore, as a means to solve this problem, as shown in FIGS. 2 and 3, a plurality of ferrite magnetic plates 6 extending in the radial direction of the coil winding are provided at appropriate intervals on the back side of the coil support substrate l. , a structure has been proposed that reduces magnetic flux leakage to the back surface side and at the same time concentrates the magnetic flux to the upper surface side where the load 5 is located. However, this second
In the case of the conventional example shown in Figures and Figure 3, the ferrite magnetic plate 6
In the area without , magnetic flux leaks to the back side. If the number of ferrite magnetic plates 6 is increased, magnetic flux leakage to the back side can be reduced, but the overall weight and cost will increase.

In addition, in the part where the ferrite magnetic plate 6 is present, the load 5 (
However, concentration of magnetic flux does not occur in areas where there is no ferrite magnetic plate 6, resulting in uneven heating. There are also problems such as changes in inductance and susceptibility to load fluctuations.

Further, in induction heating, the coil support substrate 1 and the ferrite magnetic plate 6 attached to the coil support substrate 1 are heated due to heat generation of the induction heating coil 2 and temperature rise of the load 5 such as a cooking pot.

The ferrite magnetic plate 6 has a Curie temperature as a temperature characteristic, and loses magnetism when the temperature exceeds the Curie temperature. When the ferrite magnetic plate 1 loses its magnetism, the inductance of the coil 2 drops significantly.

In this type of induction heating device, the LC of the inductance of the coil 2 and the capacitor connected externally is
Since a high frequency current is supplied to the coil 2 using a resonance circuit, when the temperature of the ferrite magnetic plate l exceeds the Curie temperature and loses its magnetism, the inductance of the coil 2 decreases significantly, and the frequency of the induction heating current decreases. fluctuates, and the induction heating effect fluctuates significantly. However, in the past, sufficient studies have not been made regarding the Curie temperature of the ferrite magnetic substrate 6, and the ferrite magnetic substrate 6 has been constructed exclusively using ferrite magnetic materials with high magnetic permeability and high saturation magnetic flux density. . For this reason, conventionally, there was a risk that the ferrite magnetic plate 6 attached to the coil support substrate 1 would be heated beyond its Curie temperature.

In order to suppress the temperature rise, measures such as installing an air cooling fan, heating protection mechanism, etc., or improving the heat dissipation effect are taken in conventional electric A cookers, etc., but in this case, the set temperature is The temperature is set for heating normal foods containing a lot of water, so if oil is used for cooking or if it is used continuously for a long time, the temperature may rise above the set temperature. Resulting in. For example, when frying tempura (±, 3,0 minutes to 60 minutes, the induction heating coil 2
The temperature of the coil support substrate 1 rises to about 140 to 15.0 degrees Celsius.For this reason, conventionally, even if there is a means to prevent overheating such as a double series, the coil support substrate 1 cannot be attached to the coil support substrate 1. There was still a risk that the ferrite magnetic plate 6 would be heated above its Curie temperature.

Purpose of the Invention Therefore, the present invention solves the above-mentioned conventional problems, reduces and uniformizes the magnetic flux leakage to the back side, eliminates heating unevenness and load fluctuation, and further reduces the inductance of the induction heating coil due to temperature rise. It is an object of the present invention to provide an induction heating coil device that can reduce the change in frequency and the accompanying frequency fluctuation, and stabilize the induction heating action.

Structure of the present invention 1 To achieve the above-mentioned object 1 The present invention provides an induction heating coil device in which a coil for induction heating is spirally wound on one side of a coil support substrate and arranged in a planar manner. The substrate is made of a mixture of heat-resistant insulating resin and sintered ferrite magnetic powder, and is characterized by being made of composite ferrite having a Curie temperature of 150° C. or higher.

Embodiment FIG. 4 is a front sectional view of an induction heating coil device according to the present invention, and FIG. 5 is a back view thereof.

In the figures, the same reference numerals as in FIGS. 1 to 3 indicate the same components. The coil support substrate 1 has conventionally been constructed using a heat-resistant insulating resin, but in the present invention, it is molded using a composite ferrite material in which a heat-resistant insulating resin is mixed with sintered ferrite magnetic powder. As the heat-resistant insulating resin, for example, unsaturated polyester resin or phenol resin is suitable.

As described above, when the coil support substrate 1 is made of a composite ferrite material, leakage of magnetic flux to the back side of the coil support substrate 1 is reduced and made uniform. Therefore, the heating effect caused by leakage magnetic flux on the electronic circuit devices and the like disposed on the back surface side is prevented, and at the same time, heating unevenness, load fluctuations, etc. are reduced.

The composite ferrite has a Curie temperature Tc of 150°C or higher, preferably 180°C or higher. As mentioned above, when using oil for cooking or when using continuously for a long time, the heating temperature of the coil support substrate 1 is a maximum of 150°C.
Before and after. Therefore, by forming the coil support substrate 1 using a composite ferrite having a Curie temperature Tc of 150° C. or higher.

The composite ferrite that makes up the coil support substrate maintains magnetism, not only when heating ordinary foods containing a lot of water, but also when using oil for cooking or when using continuously for a long time. It is possible to stabilize the induction heating effect by suppressing changes in the induction heating frequency due to fluctuations in inductance.

Furthermore, the sintered ferrite magnetic powder is mixed so that the initial magnetic permeability (magnetic permeability at room temperature and frequency IKHz, hereinafter the same in this specification) pI as a composite ferrite satisfies i≧7. If the initial permeability i is smaller than 7, the inductance of the induction heating coil 2 will be smaller than the value required for practical use, making it impractical.

By the way, in general, when the Curie temperature Tc of a ferrite magnetic material is increased, magnetic properties such as initial magnetic permeability μi and saturation magnetic flux density tend to decrease.

Therefore, in order to obtain a composite ferrite having the characteristics according to the present invention, a ferrite magnetic material that satisfies the required characteristics is selected from Ni-Zn ferrite magnetic materials, In-Zn ferrite magnetic materials, or Cu-Mg ferrite magnetic materials. be able to. In addition, it can be manufactured by combining and pulverizing several types of ferrite magnetic materials. This is done in combination with a ferrite magnetic material that has low magnetic flux. With such a combination, a composite i-lite with Curie temperature T c > 150° C. and initial magnetic permeability i≧7 can be easily realized. In addition, the Curie temperature and initial permeability pL of the ferrite magnetic material
Since the control of i is well known, the explanation will be omitted.

The appropriate mixing ratio of the sintered ferrite magnetic powder to the heat-resistant insulating resin is about 75 to 85% by weight. The higher the mixing ratio of magnetic flux leakage powder to the back side of the coil support substrate l, the better. However, in composite ferrite materials, if the mixing ratio of sintered ferrite magnetic powder is low, thermosetting insulating resin (heat-resistant It is possible to obtain a coil support substrate l with excellent heat resistance and mechanical strength by adding fillers, thickeners, etc. to a base resin (resin), but as the mixing ratio of sintered ferrite magnetic powder increases, this The advantages are lost, manufacturing becomes difficult, and the magnetic properties are even worse. On the other hand, the mixing ratio of sintered ferrite magnetic powder is 75 to 85.
When it is selected as % by weight, the above-mentioned problems in composite ferrite can be solved and the magnetic properties can be improved without impairing heat resistance and mechanical strength.

Furthermore, in this embodiment, the coil support substrate l is connected to the coil 2.
A plurality of ribs 12 extending in the winding diameter direction of the coil 2 are provided at appropriate intervals on the surface opposite to the surface 11 on which the coil 2 is arranged. From the standpoint of preventing magnetic flux leakage, increasing mechanical strength, etc., the larger the thickness of the coil support substrate 1, the better.However, simply increasing the thickness of the coil support substrate 1 would result in a significant increase in the overall weight and at the same time. , the cost will be high.

Therefore, in this embodiment, by providing the ribs 12, the mechanical strength is increased, and at the same time, the magnetic flux leakage prevention effect is improved by increasing the thickness of the ribs 12. Furthermore, due to the increase in mechanical strength due to the ribs 12, the wall thickness t1 of the fan-shaped portion 13 between the ribs 12 is reduced, and the overall substantial thickness is reduced, thereby achieving weight reduction and cost reduction. I can do it. for example,
Even if the thickness t2 of the rib 12 is 5 m and the thickness tl of the fan-shaped portion 13 is 3.5 m, the thickness of the support substrate 1 is 5 m.
Mechanical strength and magnetic properties similar to those obtained with a uniform thickness of 7II11 were obtained.

The number of ribs 12 is preferably four or more, particularly about six to eight ribs. If the amount is less than this, the practically required magnetic flux leakage prevention effect, mechanical strength, etc. cannot be ensured, and in order to compensate for this, the thickness of the coil support substrate 1 must be increased.

Although not shown in the drawings, it is also possible to adopt a structure in which a ferrite magnetic plate as shown in FIGS. 2 and 3 is combined with a coil support substrate l made of composite ferrite.

Effects of the Invention As described above, the present invention provides an induction heating coil device in which an induction heating coil is spirally wound on one side of a coil support substrate and arranged in a planar manner. It is made by mixing heat-resistant insulating resin and sintered ferrite magnetic powder, and is characterized by being composed of composite ferrite that has a Curie temperature of 150°C or more, which reduces magnetic flux leakage to the back side and creates a uniform magnetic flux. , eliminating heating unevenness and load fluctuations, and reducing changes in the inductance of the induction heating coil due to temperature rise and accompanying frequency fluctuations.
It is possible to provide an induction heating coil device in which the induction heating effect is stabilized.

Furthermore, as shown in the example, by providing a plurality of ribs extending in the winding diameter direction of the coil on the side of the coil support substrate opposite to the coil arrangement surface, the mechanical strength is increased and at the same time It is possible to provide an induction heating coil device that improves the magnetic flux leakage prevention effect at the rib portion and further reduces weight and cost.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view schematically showing the structure of an electromagnetic cooker;
FIG. 2 is a rear view of a conventional induction heating coil device, FIG. 3 is a sectional view taken along line A 1-A in FIG. 2, FIG. 4 is a rear view of an induction heating device according to the present invention, and FIG. is a sectional view taken along line A2-A2 in FIG. 4. 1... Coil support board 2... Coil 12-... Rib Fig. 1 Fig. 2m

Claims (4)

[Claims] (1) In an induction heating coil device in which an induction heating coil is spirally wound and arranged on one side of a coil support substrate, the coil support substrate is made of heat-resistant insulating resin and sintered ferrite magnetic powder. What is claimed is: 1. An induction heating coil device comprising a composite ferrite having a Curie temperature of 150° C. or higher. (2) The composite ferrite has an initial magnetic permeability JLi of gi
The induction heating coil device according to claim 1, wherein ≧7. (3) The induction heating coil device according to claim 1 or 2, wherein the body heat insulating resin is selected from unsaturated polyester or phenol resin. (4) The coil support substrate has a plurality of lips extending in the winding diameter direction of the induction heating coil on a side opposite to the surface on which the induction heating coil is arranged. The induction heating coil device according to item 1, item 2, or item 3.