JPH06260270A - Heating coil - Google Patents

Abstract

PURPOSE:To provide a heating coil in which the self-loss at high frequency induction heating is more reduced by forming a second litz wire by stranding two or more first litz wires formed by stranding a plurality of element wires having insulating layers on conductors. CONSTITUTION:The optimum diameter and necessary number of an element wire 11 having an insulating layer 14 are determined from the sectional area obtained from the depth of penetration determined by the frequency per unit length of a conductor 13 and the conductor area and outer form required to carry the whole current. Thereafter, a plurality of the element wires 11 are stranded to form a first litz wire 12, and two or more litz wires 12 are stranded to constitute a second litz wire 16. The wires 16 are successively spirally wound from the center so that the element wire number and outer form of the wire 16 are conformed to the required number and outer form to form a heating coil. Thus, the effective resistance value by neighborhood effect of the surface skin effect when a high frequency current is carried at induction heating can be suppressed at minimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating coil which reduces self-loss during high frequency induction heating.

[0002]

2. Description of the Related Art A conventional heating coil will be described below. In FIGS. 4 and 5, reference numeral 1 is a wire, which has an insulating layer 4 on the conductor 3. Reference numeral 2 is a litz wire, which is obtained by twisting the strands 1 together and collecting them. Reference numeral 5 is a heating coil produced by winding the litz wire 2 in a spiral shape from the center so as to have a required outer shape.

The heating coil configured as described above will be described below. Conventionally, when the wire of the heating coil is a single wire, when a high-frequency current is passed, the current gathers on the surface due to the skin effect, the effective resistance value increases, and the loss increases accordingly. From the cross-sectional area of the conductor obtained from the penetration depth determined by the frequency, the conductor area required to flow the entire current, and the outer shape, find the optimum diameter and the required number of strands, and By using a litz wire that is gathered together by twisting together, the effective resistance is reduced to reduce the loss of the heating coil during induction heating, improve the efficiency of the equipment and reduce the burden on the cooling structure. It was

[0004]

However, in the above-mentioned conventional structure, as the number of strands increases, the effective resistance due to the skin effect decreases and the effect of the increase in effective resistance due to the proximity effect also increases. The resistance value is obtained by multiplying the skin effect and the proximity effect, and the relationship between the number of strands and the loss is the minimum at a certain number of strands.Therefore, the loss can be reduced by reducing the strand diameter. Had a problem that there was a limit.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to further reduce the loss when a high-frequency current flows during induction heating to improve the efficiency of the equipment and reduce the load on the cooling structure. And

[0006]

In order to achieve this object, the heating coil of the present invention comprises, as a first means, a second litz in which two or more first litz wires obtained by twisting a plurality of strands are twisted together. A line is formed, and as a second means,
The first litz wire is covered with a flexible insulating material.

[0007]

With this structure, since the increase in effective resistance due to the proximity effect is suppressed, the high frequency at the time of induction heating is higher than that of the heating coil made from the wire diameter and the number of wires obtained by considering only the skin effect. The loss due to current is further reduced. For this reason, the efficiency of the device is improved and the heat generation is reduced at the same time, so that the cooling capacity can be relaxed, and the device can be made smaller and thinner. Further, by covering the litz wire obtained by twisting a plurality of strands with a flexible insulating material, the effect can be more reliably obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the wire 11 is a conductor 1.
3 has an insulating layer 14 on it, a plurality of strands 11 are twisted together to form a first litz wire 12, and two or more first litz wires are twisted to form a second litz wire 16. , A heating coil.

The heating coil having the above-described structure will be described in detail below. Conductor 13
Based on the cross-sectional area of the conductor 13 obtained from the penetration depth determined by the frequency, the conductor area required to flow the entire electric current, and the outer shape per unit length of Calculate the number. Then, a plurality of strands 11 are twisted together to form a first litz wire 12, and two or more first litz wires 12 are twisted together to form a second litz wire 16. This second litz wire 16 is arranged so that the total number of wires matches the required number of the above-mentioned wires.
A heating coil is manufactured by sequentially winding the coil from the center so that it has the required outer shape.

As described above, the wire 11 is connected to the first litz wire 12
After twisting the first Litz wire 12 again, the first Litz wire 12 is twisted again to form the second Litz wire 16 and is finished into a heating coil, so that the skin effect and the proximity effect when a high frequency current is applied during induction heating Since the effective resistance value can be suppressed to a minimum, as shown in FIG. 2, when the number of wires is equal to or more than a certain number, the conventional twisting of the wires in consideration of only the skin effect is performed multiple times in the present embodiment. The method reduces loss, improves the efficiency of the device, and at the same time reduces self-heating of the heating coil, so that the cooling capacity required by the device can be mitigated, so the device can be made smaller and thinner. It will be possible.

Next, a second embodiment will be described with reference to the drawings. In FIG. 3, 21 is a wire, a conductor 23 is present inside the wire 21, and an insulating layer 24 is present at the outer circumference.
A plurality of the strands 21 are twisted to form a first litz wire 22. The first litz wire 22 is covered with an insulating tube 27 having flexibility, and the first litz wire covered with the insulating tube 27 is formed. The wire 22 is twisted again to form the second litz wire 26.
In the same manner as in the first embodiment, a heating coil is formed by sequentially winding the coil from the center so as to have a required outer shape.

The operation of the above structure will be described. Since the first litz wire 22 is surrounded by the insulating tube 27 when a plurality of heating coils are manufactured, the average distance between the conductors 23 in the second litz wire 26 is increased. As in the first embodiment, the current flows to the surface of the conductor 23 due to the skin effect due to the high frequency current during the induction heating, but due to the configuration of the first litz wire 22, the permeation determined by the frequency. Depending on the depth, the area through which the current flows per unit length becomes larger than that of a single wire, so the effective resistance value decreases, and the distance between the conductors 23 increases on average, so that the resistance value due to the proximity effect increases. The effect of suppressing the rise to a minimum is surely obtained.

As described above, according to this embodiment, the wire 21
Is twisted on the first litz wire 22, and then the first litz wire 22
Is covered with an insulating tube 27, and then twisted again to form a second litz wire 26, which is then finished into a heating coil, thereby minimizing loss when a high-frequency current is passed through the heating coil and simultaneously heating a plurality of heating elements. This variation in the loss can be suppressed for the coil, and workability is also improved.

Although the first litz wire 22 is covered with the insulating tube 27 as an insulating material in the second embodiment, a flexible adhesive may be used instead of the insulating tube 27. Good. Further, both the first and second embodiments have a structure in which two or more litz wires are twisted again.
It goes without saying that it is also possible to use a structure in which twists are made more than once.

[0015]

As described above, according to the present invention, in the heating coil in which the high frequency current flows during the induction heating, the strands are twisted to form the first litz wire, and the litz wire is twisted again to form the second litz wire. Since the increase in the effective resistance due to the proximity effect is suppressed by forming the, the high-frequency current during induction heating is higher than that of a heating coil made from the wire diameter and the number of wires obtained by considering only the skin effect. Since the loss due to is further reduced, the efficiency of the device is improved, and at the same time, the heat generation is also reduced, so that the cooling capacity is relaxed, and the device can be made smaller and thinner.

Further, by covering the first litz wire in which a plurality of strands are twisted with a flexible insulating material, a further effect can be surely obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a litz wire of a heating coil according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the number of strands of the heating coil and loss.

FIG. 3 is a sectional view of a litz wire of a heating coil according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a litz wire of a conventional heating coil.

5A is a plan view of a conventional heating coil, and FIG. 5B is a cross-sectional view of the same heating coil.

[Explanation of symbols]

 11, 21 Elementary wire 12, 22 First litz wire 13, 23 Conductor 14, 24 Insulating layer 16, 26 Second litz wire 27 Insulating tube

Claims (2)

[Claims] 1. A heating coil in which a plurality of strands having an insulating layer are twisted together on a conductor to form a first litz wire, and two or more of these litz wires are twisted to form a second litz wire. 2. The heating coil according to claim 1, wherein the first litz wire is covered with a flexible insulating material.