JPS6137752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating device having a multilayer coil formed by winding a tubular conductor in multiple layers.

Induction heating equipment is generally used to inductively heat billets made of aluminum or steel, and is equipped with a coil made of a tubular conductor wound around it, but the current flowing through this coil is a large current of several thousand amperes. Copper loss is extremely large. Recently, in order to improve this efficiency, the heating coil, which conventionally had a single layer winding, has been changed to a multilayer winding structure, but although a certain effect can be obtained, it is still insufficient.

FIG. 1 is a schematic front view of the coil of such a multilayer coil type induction heating device, and FIG. 2 is a schematic cross-sectional side view of the same coil. In the figure, the multilayer coil 1 has an outer layer coil 1a and an inner layer It consists of a coil 1B, these are connected in series, and cooling water is made to flow through the hollow part 4. When an AC voltage is applied to the coil 1, the outer layer coil 1A or the inner layer coil 1B
A current _i1 flows from one end and flows through the outer layer coil 1A and inner layer coil 1B as shown by the solid line arrow 2, generating magnetic flux _H0 inside the coil, which inductively heats the billet placed inside the coil. However, at this time, due to the induction effect of the current flowing through the outer layer coil 1A, an eddy current or circulating current _i2 is generated in the inner layer coil 1B as shown by the dotted arrow 3, and the copper loss due to this current is added to the copper loss due to the supply current _i1 . . For this reason, even if an attempt is made to reduce copper loss by doubling the effective cross-sectional area of the coil by winding a single-layer winding in two layers with the same current and the same number of turns, the expected efficiency improvement cannot be obtained.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a multilayer coil type induction heating device that can further improve efficiency than the conventional one. According to the present invention, in an induction heating device having a multilayer coil formed by winding a tubular conductor in multiple layers, at least the outer surface side portion of the inner wall of the tubular conductor of the inner layer coil is made of a material with low electrical resistivity. This is achieved by a multilayer coil type induction heating device characterized in that the other parts including the outer wall are made of a material with high electrical resistivity.

Hereinafter, before describing embodiments of the present invention, the current density distribution in a conventional inner layer coil, which is the starting point of the present invention, will be described.

FIG. 3A shows the current density distribution of the inner layer coil 1B in FIGS. 1 and 2, but is shown in relation to the cross-sectional view of the inner layer coil 1B shown in FIG. 3B. That is, in Fig. 3B, the left side is coil 1.
However, the current i ₁ supplied from the outside is concentrated on the inner wall of the tubular conductor due to the well-known skin effect as shown in FIG. 3A, while the current i ₁ flowing through the outer layer coil 1A As shown in FIG. 3A, the induced eddy current i ₂ concentrates on the inner wall and the outer wall and flows in a loop.

The present invention is designed to reduce the eddy current i ₂ by paying attention to the above phenomenon. Examples of the present invention will be described below.

FIG. 4 is a cross-sectional side view of a part of a multilayer coil in an induction heating device according to an embodiment of the present invention, and in this embodiment, the multilayer coil is a two-layer coil, and the entire coil is indicated by 10. ing. The coil 10 consists of an outer layer coil 10A and an outer layer coil 10B, which are connected to each other in series, and between each turn of each coil 10, 10B and between each coil 10, although not shown.
An insulating material is interposed between A and 10B. Each of the coils 10A, 10B is made of a tubular conductor in a known manner, and has a hollow portion 11 through which cooling water flows.

In the coil 10 as described above, the outer layer coil 1
Although 0A is made of a single material, such as electrolytic copper, like the conventional coil, according to this embodiment, the inner layer coil 10B is made of two materials. That is, the cooling pipe portion 12 mainly for forming the cooling water passage 11 is made of a material with high electrical resistance such as stainless steel or Cypronickel, and the other portion, that is, the outer surface side portion 13 of the inner wall of the coil 10B is made of a material with low electrical resistance, for example electrolytic copper as in the past. part 12
and 13 are integrated, for example by welding or soldering.

By configuring as described above, the supply current i ₁ as the current for induction heating is applied to the portion 1 with low resistance.
The eddy current i 2 induced by the current i ₁ flowing through the outer layer coil 10A flows concentratedly at the inner wall of the coil 10A (as in the conventional case, the eddy current i ₂ flows concentratedly at the inner wall of the outer coil 10A). Since it is made of a material with high resistance, the overall resistance is drastically reduced compared to the conventional one. Therefore, conductor loss due to eddy currents is drastically reduced, and efficiency is further improved.

In the above embodiment, the inner layer coil 10B has a shape consisting of a portion 12 having the same shape as the conventional one and an outer surface layer portion 13 joined to this.
It may be modified as shown in the figure. In this case, the inner layer coil 10B is composed of an inner wall component 15 and a cooling water passage component 14 having a U-shaped cross section, and a cooling water passage 16 is configured inside by joining these members.
The member 15 is made of a material with low electrical resistance, such as electrolytic copper, and the other member 14 is made of a material with high electrical resistance, such as stainless steel or Cypronickel. Such an inner layer coil 10B also has the same effect as the above-mentioned embodiment, and the eddy current i ₂ is drastically reduced compared to the conventional one, and the efficiency is further improved.

Although the embodiment of the present invention is configured as described above,
The present invention is, of course, not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, the cooling water passages 11, 16
The cross section of is rectangular, but may have other shapes, for example circular. Furthermore, the cross-sectional shape of the inner layer coil 10B is not limited to the illustrated example; for example, the cooling water passage component may be cylindrical, and a solid conductor having a circular cross section may be bonded to the outer surface thereof. It's okay.

Further, in the above embodiments, a two-layer winding coil has been described, but it is of course applicable to a three-layer winding coil or more.

[Brief explanation of the drawing]

Fig. 1 is a schematic front view of a coil of a conventional multilayer coil type induction heating device, Fig. 2 is a schematic partial cross-sectional side view of the same coil, and Fig. 3 shows the current density distribution of the inner layer coil of the same coil. Graphs shown in conjunction with the sectional views, FIG. 4 is a partially schematic cross-sectional side view of the coil of the multilayer coil type induction heating device according to the embodiment of the present invention, and FIG. 5 shows a modification of the inner layer coil in FIG. 4. FIG. In the figure, 10B...inner layer coil, 12
... Cooling pipe part, 13 ... Outer surface part of inner wall part,
14... Cooling water passage constituent member, 15... Inner wall constituent member.

Claims (1)

[Claims] 1. In an induction heating device having a multilayer coil formed by winding a tubular conductor in multiple layers, at least the outer surface side portion of the inner wall portion of the tubular conductor of the inner layer coil is made of a material with low electrical resistivity, and the outer wall portion is included. A multi-layer coil type induction heating device characterized in that the other parts are made of a material with high electrical resistivity.