JP2006302683A - High-frequency heating coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the concentration of current on an angular pipe corner part in the bent inner side of a bent part of a high-frequency heating coil by an inexpensive means without degrading dimensional accuracy. <P>SOLUTION: By forming the cross-sectional shape of each angular pipe of circular heating conductor parts 2 and a semi-circular heating conductor part 4 connected to each other at respective bent parts 5a and 5b into a pentagon-shaped cross section having one peak 2a or 4a between angular pipe corner parts in the bent inner side of the bent part, a current concentrated on the angular pipe corner parts in the bent inner side is dispersed to parts of the peaks 2a and 4a formed between the angular pipe corner parts; and thus the concentration of the current on the angular pipe corner parts in the bent inner side can be prevented with an inexpensive means without degrading dimensional accuracy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-frequency heating coil formed by connecting square pipes.

  A high-frequency heating coil formed by connecting square pipes has a linear or arc-shaped heating conductor portion that runs around the object to be heated between a pair of lead conductor portions connected to a high-frequency power source. Cooling water is passed through the lead conductor portion and the heating conductor portion. Normally, the square pipes forming these lead conductor portions and heating conductor portions have a rectangular cross section and are connected by brazing (see, for example, Patent Document 1).

  In such a high-frequency heating coil, a bent portion is often formed at a connection portion between the lead conductor portion and the heating conductor portion or a connection portion between the heating conductor portions. It is known that the current from the high-frequency power source is concentrated at the corner pipe corner inside the bend at the bent portion of the high-frequency heating coil. For this reason, a high-frequency heating coil that is repeatedly energized to heat a large number of objects to be heated has a temperature amplitude due to heating and cooling at the corner pipe corner inside the bent portion where this current is concentrated, compared to other portions. It becomes large, and the brazing of the square pipe corner part is peeled off, the square pipe itself is cracked, and the life is shortened due to leakage of internal cooling water.

  As a means for preventing current concentration at the corner pipe corner inside the bend at the bent portion of the high-frequency heating coil, there is a method of connecting by connecting a separate connecting conductor that is curved at a portion corresponding to the bent portion. It has been proposed (see, for example, Patent Document 2).

Japanese Utility Model Publication No. 58-164196 (Fig. 1) Japanese Patent No. 2614167 (FIGS. 1-8)

  As described in Patent Document 2, a high-frequency heating coil that is connected by incorporating a separate connecting conductor that is curved in a portion corresponding to a bent portion increases the number of conductors and the number of connecting portions, so that the connecting portion There is a problem that the manufacturing cost increases due to an increase in the time and labor of the processing and brazing. In addition, it is difficult to bend the connecting conductor formed of a square pipe with high accuracy, and there is a problem that the dimensional accuracy of the high-frequency heating coil is lowered.

  Accordingly, an object of the present invention is to prevent current concentration on the corner pipe corner portion inside the bent portion of the high-frequency heating coil without lowering the dimensional accuracy by an inexpensive means.

  In order to solve the above-described problems, the present invention provides a high-frequency heating coil formed by connecting square pipes and having a bent portion formed at a connecting portion of the square pipe. A configuration was adopted in which the cross-sectional shape of the square pipe was a polygonal cross section having apexes between the corner pipe corners inside the bent portion.

  That is, by making the cross-sectional shape of at least one of the square pipes connected at the bent portion into a polygonal cross section having a vertex between the corner pipe corner portions on the inner side of the bent portion, the corner pipe corner portion on the inner side of the bent portion is formed. Disperse the concentrated current to the apex part provided between the corner pipe corners, and prevent current concentration on the corner pipe corners inside the bend without reducing the dimensional accuracy with inexpensive means. did.

  By making the polygonal cross section of the square pipe having a vertex between the corner pipe corner portions on the inner side of the bend into a pentagonal cross section having one vertex between the corner pipe corner portions on the inner side of the bend, the square pipe having a polygonal cross section is obtained. Can be formed at low cost.

  In the high-frequency heating coil of the present invention, the cross-sectional shape of at least one of the square pipes connected at the bent portion is a polygonal cross section having apexes between the corner pipe corner portions inside the bent portion. Disperses the current concentrated on the corner pipe corners to the apex portion provided between the corner pipe corners, and concentrates the current on the corner pipe corners inside the bend without reducing dimensional accuracy with inexpensive means. It is possible to prevent the peeling of brazing at the corner pipe corner and the occurrence of cracks in the square pipe itself, and to ensure a long life of the high-frequency heating coil.

  By making the polygonal cross section of the square pipe having a vertex between the corner pipe corner portions on the inner side of the bend into a pentagonal cross section having one vertex between the corner pipe corner portions on the inner side of the bend, the square pipe having a polygonal cross section is obtained. Can be formed at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 (a) and 1 (b), the high-frequency heating coil is placed around the object A to be heated between a pair of lead conductors 1 connected to a high-frequency power source (not shown). A pair of arc-shaped heating conductor portions 2, a linear heating conductor portion 3, and a semi-arc-shaped heating conductor portion 4 are connected by brazing. Each lead conductor portion 1 and each heating conductor portion 2, 3, 4 are formed of copper square pipes, and cooling water is passed through the inside thereof.

  Right-angled bent portions 5a and 5b are formed at connection points between the linear heating conductor portions 3, the arc-shaped heating conductor portions 2 and the semicircular arc-shaped heating conductor portions 4, respectively. The square pipes of the heating conductors 2 and 4 connected by these bent portions 5a and 5b have a pentagonal cross section having one apex 2a and 4a between the corner pipe corner portions inside the bent portions. The cross-sectional shape of the lead conductor portion 1 connected to each heating conductor portion 2 is also a pentagonal cross section having the same apex 1 a as the heating conductor portion 2. The square pipe of the linear heating conductor portion 3 has a rectangular cross section.

  As an example, the square pipe of the pentagonal cross section of the lead conductor portion 1 and each of the heating conductor portions 2 and 4 has the cross sectional dimensions shown in FIG. 2A, and the rectangular pipe of each heating conductor portion 3 has the rectangular cross section of FIG. A high-frequency heating coil having a cross-sectional dimension shown in b) was prepared. As a comparative example, a high-frequency heating coil was prepared in which all the square pipes forming the lead conductor part and each heating conductor part had the same cross-sectional dimensions as the square pipe of the heating conductor part 3 shown in FIG. The thickness of each square pipe is 1 mm.

First, for the high-frequency heating coils of the above-described example and comparative example, the current density distribution when a high-frequency current was passed at the same current and frequency was numerically analyzed using a general-purpose analysis simulator based on the finite element method. 3A and 3B are color images of an analysis simulator showing current density distributions of the high-frequency heating coils of the example and the comparative example, respectively. In this color image, the bent portion 5a of the connecting portion between the heating conductor portion 2 and the heating conductor portion 3 is viewed from the inside, but in the comparative example, the corner pipe corner portion inside the bent portion 5a is bent. The current density is as high as about 1700 A / mm ² . On the other hand, in the example, the current density is slightly higher at the corner pipe corner portion inside the bent portion 5a and the apex 2a portion of the pentagonal cross section of the heating conductor portion 2, but this value Is about 800 A / mm ² at most.

  From the numerical analysis of the current density distribution using the above analysis simulator, the high-frequency heating coil of the example shows that the current concentrated on the corner pipe corner portion inside the bend is the apex portion of the pentagonal cross section provided between the corner pipe corner portions It was confirmed that it was dispersed.

Next, as shown in FIG. 4A, an induction hardening experiment was conducted in which a high-frequency current indicated by an arrow was passed through each of the high-frequency heating coils of the above-described example and comparative example, and the object A to be heated was induction-quenched. The dimension and quenching pattern of the article A to be heated are as shown in FIG. The number N of the high-frequency heating coils of the example and the comparative example was three, and the life of each coil was investigated. The coil life was evaluated by the number of quenching objects A to be heated that had been quenched before breakage (cooling water leakage). The induction hardening conditions of the examples and comparative examples are as follows.
・ High frequency power: 120kW
・ Frequency: 10 kHz
・ Heating time: 4 seconds

  The results of the induction hardening experiment are shown in Table 1. The table also shows the average number of quenching of each of the three induction heating coils of the example and the comparative example. In all of the comparative examples, leakage of cooling water occurred in the corner pipe corner portion inside the bent portion, and in the example, one was a corner pipe corner portion inside the bent portion, and the other. In the two, a leakage of cooling water occurred at the apex of the pentagonal cross section of the angle pipe inside the bend. As can be seen from these results, the example in which the current concentration at the corner pipe corner inside the bent part is prevented is more than twice the average quenchable number compared to the comparative example. It can be seen that the coil life is significantly improved.

  In the embodiment described above, the cross-sectional shape of one of the square pipes connected by the bent portion is a pentagonal cross section having one apex between the corner pipe corner portions inside the bent portion. The shape may be a polygonal cross section having two or more vertices between the corner pipe corners inside the bend, and the vertices may be rounded. Moreover, it is good also considering the cross-sectional shape of both the square pipes connected by a bending part as such a polygonal cross section.

a is a perspective view from below showing an embodiment of a high-frequency heating coil, b is a partially cutaway perspective view of a a is a cross-sectional view showing the cross-sectional dimensions of the square pipe of the lead conductor portion and the arc-shaped heating conductor portion of the embodiment, b is a cross-sectional view showing the cross-sectional dimensions of the square pipe of the linear heating conductor portion of the embodiment a and b are color images of an analysis simulator showing current density distributions of the example and the comparative example, respectively. a is a perspective view showing an induction hardening test method for an object to be heated, and b is a cross-sectional view showing dimensions and a quenching pattern of the object to be heated in a.

Explanation of symbols

1 Lead conductor part 2, 3, 4 Heating conductor part 1a, 2a, 4a Vertex 5a, 5b Bending part

Claims (2)

  In a high-frequency heating coil formed by connecting square pipes and having a bent portion formed at the connecting portion of the square pipe, the cross-sectional shape of at least one of the square pipes connected by the bent portion is the inner side of the bent portion. A high-frequency heating coil having a polygonal cross section having apexes between corner pipe corner portions.   The high-frequency heating coil according to claim 1, wherein a polygonal cross section of the square pipe having a vertex between the bent inner corner pipe corner portions is a pentagonal cross section having one apex between the bent inner corner pipe corner portions. .