JPS63202880A - Induction heating coil for metal pipe - 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 A. Field of Industrial Application The present invention relates to an induction heating coil for a metal pipe that improves the heating efficiency of the edge of the metal pipe in which a slit is formed.

13. Summary of the Invention The present invention provides an induction heating coil for a metal pipe that faces an edge of a metal pipe in which a slit is formed and sequentially inductively heats the edges along the longitudinal direction of the metal pipe. A first coil part and a second coil part to be heated are respectively provided along the outer circumferential surface of the metal vibrator, and each coil part is connected to a main part facing the edge and a main part formed on the outside thereof. The width of the main part is set small and the width of the base part is set large, and the direction of the current flowing through both main parts is opposite to each other. By arranging it along the outer circumferential surface within 2/3 of the circumferential slit of the pipe, the induced current generated in the metal pipe is focused at the edge and generates a lot of heat, while the edge Other parts are dispersed to reduce heat generation and power consumption, so that only the edges are efficiently heated by induction.

C1 Prior Art There are various means for heating the edges of metal pipes, such as preheating when manufacturing electric resistance welded pipes, to form slits formed by bending metal plates.

Conventionally, induction heating coils shown in FIGS. 8 and 9 have been used to heat the edge of a metal vibrator.

The induction heating coil 1 shown in FIG. 8(a) sequentially inductively heats the edges 2a of a small-diameter metal pipe 2 while conveying it in its longitudinal direction, so that the induction heating coil 1 surrounds the metal vibrator 2. is formed. On the other hand, Fig. 9 (
The induction heating coil 3 shown in a) sequentially inductively heats the edges 2a of the large-diameter metal vibrator 2 while conveying it in its longitudinal direction. Used facing each other.

When a bender is used, the induction heating coil l is placed at a position facing each part of the induction heating coil l, as shown in FIG. 8(b).
An induced current flows in the opposite direction to the direction of the current flowing through the edge 2a, that is, the current i flowing through the edge 2a and the current i flowing in the circumferential direction of the metal vibrator 2 form a circulating flow path.
The edge 2a is heated by the current i flowing through the edge 2a. The current i flowing in the circumferential direction heats parts other than the edge 2a and is not used for heating the edge 2a, so that most of the electrical energy is used for heating the parts other than the edge 2a. The power efficiency of using electric power to heat the edge 2a is determined by the coil efficiency ((amount of electric power induced in the vibrator/power input to the coil fi Overall heat generation f
f1)X10Q), and the induction heating coil l
The in-pipe efficiency of is 35% to 50%. Note that the coil efficiency is about 75%.

The back or the latter is placed along the circumferential direction of the metal vibrator 2.
When a bent wire is used as in the induction heating coil 1 of FIG. 9(a), the conductors 3c and 3d of the heating coil 3 extend in the longitudinal direction of the metal pipe 2 as shown in FIG. 9(b). and an induced current ic flowing in the opposite direction along the longitudinal direction of the metal vibrator 2 in response to the current flowing through the metal pipe 2, or a current ia flowing in the edge direction along the circumference of the metal pipe 2 and a current ib flowing in the opposite direction. The current ia flows through the edge 2a and forms a circulating flow path that heats the edge 2a. The same applies to the other opposing edge 2a. The other current ib flows around the circumference of the metal pipe 20 to the side opposite to the edge 2a, merges with the current ic on the opposite side of the metal pipe 2, and forms a circulation flow path that flows around the circumference again to the side opposite to the edge 2a. In other words,
Three circulation channels are formed.

Even when this induction heating coil 3 is used, the induced current flows in a wide range other than the edges, so much power is consumed in areas other than the edges, and as with the former, the efficiency inside the pipe is 35 to 50%, and the coil efficiency is is about 75%.

When the metal pipe 2 is induction heated using the induction heating coil 3 shown in FIG. 9(a), the temperature change at each part of the outer peripheral surface P, Q, and H in the circumferential direction of the metal pipe 2 is measured by induction heating. As a result, the results shown in Fig. 1θ were obtained.

In the figure, P, Q, and R correspond to the respective parts P, Q, and R of the metal pipe 2 in FIG. 9(a). That is, P is the tip of the edge 2a, R is the region where the most induced current ic flows, and Q is the intermediate region. As shown in the figure, the temperature rises quickly in the order of P, II, and Q, but it can be seen that the temperatures of P, Q, and H approach each other immediately after passing the end of the coil.

D0 Problems that the invention aims to solve If the efficiency inside the coil is low as in the past, parts of the metal pipe other than the edges are heated, which not only wastes electrical energy, but also increases the temperature only at the edges. However, there is a problem in that parts other than the edges also rise in temperature.

SUMMARY OF THE INVENTION An object of the present invention is to provide an induction heating coil for metal pipes that solves these problems.

Means for Solving Problem E1 The structure of the present invention for achieving the above object is to attach the edge of a metal pipe formed with a slit extending in the longitudinal direction at one location in the circumferential direction to the edge of the metal pipe. In the induction heating coil for a metal pipe that sequentially heats the metal pipe in the longitudinal direction, it is composed of a first coil part that induction heats the edge on the -blade side and a second coil part that induction heats the edge on the other side,
Each coil part is formed into a shape close to a closed circuit by a main part facing the edge along the outer circumferential surface of the metal pipe and a mallet part integrated with the main part on the outside thereof, so that the width of the main part is small and The width of the mallet part is set large so that the directions of the currents flowing through both main parts are opposite to each other, and the width of the mallet part is set to be large, and the current flowing through both main parts is configured to be opposite to each other. It is also characterized in that it is arranged along the outer peripheral surface within 2/3 of the range.

F1 action The magnetic flux φ due to the current flowing in each adjacent part of the heating coil acts in the same direction between each part and strengthens each other, as shown in Fig. 2, and intersects with the metal pipe, so the first coil part, An induced current is efficiently induced on the surface of the metal pipe facing the second coil section, and since each coil section has a shape close to a closed circuit, each induced current flows individually into the first circulation flow path, A second circulation flow path is formed within at most two-thirds of the circumferential slit of the metal pipe to prevent the induced current from flowing to the surface of the metal pipe on the opposite side of the slit. Prevent power loss. In each coil part, the width of the main part is set to be small and the width of the hammer part is set to be large, so that the density of the induced current flowing through each circulation channel is also dispersed in parts other than the edges and converged at the edges. Therefore, there is less heat generation and power loss in parts other than the edges, whereas the edges generate heat effectively.
The edges are heated intensively. Furthermore, since the direction of the current flowing through the main part of the first coil and the direction of the current flowing through the main part of the second coil are mutually opposite, the directions of the induced currents flowing through both edges are also mutually opposite. , the induced current flowing through the edge is focused due to the proximity effect, promoting heat generation at the edge.

G. Examples Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

FIG. 2 is a front view of the first embodiment in which an induction heating coil is arranged to face the outer peripheral surface of a metal vibrator that is conveyed in the longitudinal direction, and FIG. 1 shows the metal vibrator and induction heating coil developed. FIG. 3 is a plan view showing an expanded flow path of an induced current flowing through a metal vibrator.

As shown in FIG. 1, the induction heating coil 6 has a first coil portion 4 for heating the edge 2a on the left side with respect to the slit 12.
and a second coil portion 5 for heating the right edge 2a. Each coil part 4, 5 has an edge 2
a main part 7 for serving opposite to a, and hammer parts 8, 9.1 that form a rectangular circuit close to a closed circuit integrally with the main part 7.
0. The first coil section 4 and the second coil section 5 are connected to a single power source 13. In other words,
The left hammer part 9 in FIG. The first coil part 4 and the second coil part 5 are integrated by being connected through the first coil part 4.

The width of the main portion 7 is set to be small, and the width of the hammer portions 8 to 10 is set to be large. If the width of each main part 7 is Wl, and the width of the hammer parts 8 to IO is W, to W4, then W, = W, = 4
．． W,,W3=8W,Wt compared to Wl,
W4 and W3 are much larger.

Note that by connecting the main parts 7 with each other through the connecting part 11 as described above, the directions of the currents flowing through both main parts 7 are set to be opposite to each other. The induction heating coil 6 in parentheses is formed along the outer circumferential surface of the metal vibrator 2 within a range of 1/2 to 2/3 at most around the circumferential slit 12 of the metal vibrator 2, as shown in FIG. .

Next, the function of the induction heating coil of such a metal vibrator will be explained.

The metal vibrator 2 is conveyed in the direction of the arrow while a current is applied to the induction heating coil 6 to heat the edge 2a by induction. In FIG. 1, when the current flows in the direction of the arrow in the induction heating coil 6, the edge 2a of the metal vibrator 2, the slit 12. S and N to edge 2a in order.

By forming the S magnetic pole, the magnetic flux φ of each part acts to strengthen each other as shown in FIG. Since the current is an alternating current, S, N, N in S, S, N repeats, and due to the change in alternating alternating magnetic flux that acts to strengthen each other, a third
The induced current I shown in the figure is efficiently induced. First coil part 4. The second coil portion 5 has a circuit configuration close to a closed circuit with the main portion 7 and the mallet portions 8 to IO, respectively, so that the surface of the metal pipe 2 where the first coil portion 4 and the second coil portion 5 face each other is , a current in the opposite direction to the direction of the current flowing through the coil ■
flow, the first circulation channel 21. The second circulation flow path 22 is formed in a range from within 1/2 to at most 2/3 of the slit 12 in the circumferential direction of the metal pipe 2.

First coil part 4. Diameter portion 8 in each of the second coil portions 5
~Since the width of IO is large, the corresponding positions r and g
, h, the path for the induced current I is also wide (and the resistance R of the current path through which these induced currents flows is small. Since the heat loss is given by I3R, the heat generation outside edge 2a is reduced, and the edge Power consumption in areas other than 2a is also reduced.On the other hand, since the width of the main part 7 is small,
At a, the induced current I flows in a concentrated manner, and since the induced currents I flowing through the opposing edges 2a are opposite in direction and are close to each other, the proximity effect causes the induced current I to flow in a concentrated manner at the tip of the edge 2a. Heat efficiently.

Further, the second coil section 4. The first circulation flow path 2 of the induced current on the outer surface of the metal pipe 2 by the second coil part 5! and a second circulation flow path 22 are formed, but the first coil part 4 and the second coil part 5 are connected to the slit 12 in the circumferential direction of the metal pipe 2.
Since these circulation channels are formed along the outer circumferential surface within a range of 1/2 to 2/3 at most around
In addition, there is a flow path f of the induced current I other than the edge 2a.

Since the widths of g and h are wide and the electric resistance is small, the induced current flows easily, so the induced current flows through these circulation channels and hardly flows to the outer periphery on the opposite side from the slit 12, and the edge does not flow from this side either. Edge 2 has less heat loss in areas other than 2a.
The heating efficiency at point a is high.

As mentioned above, the first coil part 4 and the second coil part 5 are arranged in a range from within 1/2 to at most 2/3 of the slit 12 in the circumferential direction of the metal pipe 2. , the distances of the induced current circulation channels f, g, and h other than the edge 2a are made as short as possible to minimize heat loss in these parts, and the induced current is distributed to the outer circumference on the opposite side of the slit 12. This is to make the route length along the outer periphery shown by the chain line j in FIG. When the current was placed within a range of 273, almost no shunt to the outer periphery indicated by flow path j was observed, but when it exceeded 2/3, the amount of induced current that shunted and flowed through flow path j rapidly increased. As a result, the temperature of the outer circumferential branch on the opposite side to the slit 12 rose.

Using this induction heating coil, the outer circumferential surface P, Q, H of the metal pipe 2 in the circumferential direction is measured as shown in the graph shown in FIG.
The graph shown in FIG. 4 was obtained by measuring the temperature change at each part. As shown in the figure, the temperature rise in the P part that passed through the induction heating coil was much higher than in the past, whereas the temperature rise in the Q and H parts was sufficiently low that it did not become red hot. The in-coil efficiency of such an induction heating coil was 75%.

In order to focus the induced current further on the edge than the induction heating coil 6, the following second to fourth embodiments are available.

The induction heating coil of the second embodiment (see FIG. 5) is constructed by attaching an iron core 14 to the main portion 7°7 of the induction heating coil 6 shown in the first embodiment to cover both sides and the back of the metal vibrator 2. This is intended to improve the heating efficiency of the edge 2a.

The induction heating coil of the third embodiment (see FIG. 6) has two turns in the main portion 7 of the induction heating coil 6 shown in the first embodiment. That is, by replacing the main part 7 with the main part 15.17 and then the main part 16.18 and connecting them at the connecting parts 19 to 21, the current flows from the diameter part 8 to the main part I5 to the main part 16.
→Main part 17 →Main part 18--diameter part 8. The main part that heats one edge 2a is the main part 15.
．． 17 and the main portions 16 and 18, each of which has two currents flowing in the same direction, intersects with the edge 2a.

The alternating magnetic flux is further increased and the heating efficiency of the edge 2a is higher than that of the first embodiment.

The induction heating coil of the first embodiment (see Fig. 7) is
The coil part 4 and the second coil part 5 are separated,
The lower end of the main portion 7 in each coil portion is located at the respective diameter portion lO.
The diameter portion 9 of the second coil portion 5 is divided and connected to the power source I3, respectively. In such an induction heating coil 6, it is necessary to synchronize the power supplies 13, 13 in order to cause currents in opposite directions to the phase σ to flow in each main portion 7.

Although the first to fourth embodiments have been shown here, the second embodiment and the third embodiment may be combined, or the fourth embodiment may be combined with the second embodiment, the third embodiment, or both. Efficiency can be increased.

■ Effects of the invention As explained above, according to the induction heating coil according to the present invention, the first coil part and the second coil part face the edge of the metal vibrator, and the main part and the diameter part provided on the outside thereof. The metal vibrator is formed into a shape close to a closed circuit and placed along the outer periphery within 2/3 of the circumferential slit of the metal vibrator. Since the width is set large and the directions of the 7IX flows flowing through both main parts are opposite to each other, the magnetic flux caused by the current flowing through each part of the induction heating coil acts to effectively strengthen each other, An induced current is efficiently induced in the metal vibrator by this induction heating coil, and the induced current flows forming a first circulation passage and a second circulation passage at relatively close portions on both sides of the edge, respectively. This induced current is concentrated at the tip of the edge because the width of the main part of the induction heating coil is narrow at the edge, and the directions of the induced current flowing through both opposing edges are opposite to each other, causing a proximity effect. Effectively heats and raises the temperature. On the other hand, in areas other than the edges, the induced current is widely dispersed and flows at a low current density, corresponding to the wide diameter portion of the induction heating coil, so heat loss is suppressed in areas other than the edges. In addition, since almost no flow is diverted to the outer peripheral portion on the opposite side from the edge, heat loss in this portion is also suppressed. As a result, the heating of parts other than the edges is minimized, the edges are heated efficiently, and the efficiency within the vibrator is improved to 75% or more.

[Brief explanation of the drawing]

1 to 6 relate to an induction heating coil for a metal pipe according to the present invention, and FIGS. 1 to 3 show a first embodiment, and FIG. 1 is a plan view of the induction heating coil shown in an expanded state. Figure, 2nd
The figure is a front view of the induction heating coil, Figure 3 is an expanded plan view of the flow path of the induced current flowing through the metal pipe, and Figure 4 is the relationship between the circumferential position of the outer surface of the metal pipe and temperature. 5 is an expanded plan view of the second embodiment of the induction heating coil, FIG. 6 is an expanded plan view of the third example of the induction heating coil, and FIG. 7 is an expanded plan view of the second embodiment of the induction heating coil. 4th coil
8(a) and 8(b) are plan views showing the developed example.
) and FIGS. 9(a) and (b) are perspective views showing the flow of induced current in a conventional induction heating coil and metal pipe, and FIG. It is a graph showing the relationship between circumferential position and temperature. 2... Metal pipe, 2a... Edge, 4... First coil part, 5... Second coil part, 6... Induction heating coil, 7.15.17, 1.8...・Main part, 8, 9.1
0... Machine part, 12... Slit, 13... Power supply. Fig. 1 Inductive extramaxillary coil
1) 2-1--All genus pipes 7,15.1
6.17.18---Single part 2a---1 horn
8.9.10 - 111 Ward Section 4----Yuichi Coil Section 12---Hitori Wato 5----Kuzu Nikoil Section 13---t Uo 6----Shohide Thin 7
Fig. 2 Front view of the coil (Embodiment 1 of the present invention) Fig. 3 A top view showing an expanded metal pipe (Example 1 of the invention)
Fig. 4 5IIl Kamo coil's propensity 1, final graph (true brother 12 to story n)! <Eve's spear and hat stand! Expanding the dielectric 4 heating coil, i, and the horizontal plane (Embodiment 2 of the present invention) Fig. 8 t! To #7 + o road carp 2v and t Yuukiden 7 tile flow 6 child 11 Toboku diagram (Juto) (a) Figure 10 Graph showing the induction coil's output and negative heat (1 foot east) pipe Noro U old 1! Procedural Amendment (Target.Showa.!To.Monday, 2nd

Claims (1)

[Claims] In an induction heating coil for a metal pipe that sequentially heats the edge of a metal pipe in the longitudinal direction of the metal pipe formed by forming a slit extending in the longitudinal direction at one location in the circumferential direction, one side a first coil part that induction heats the edge of the metal pipe and a second coil part that induction heats the edge of the other side, and a main part in which each coil part faces the edge along the outer peripheral surface of the metal pipe On the outside, the main part and the integral slave part are formed into a shape similar to a closed circuit, and the width of the main part is set small and the width of the slave part is set large, so that the directions of the currents flowing through both main parts are mutual. If you configure it so that it is opposite to
2/ centered around the circumferential slit of the metal pipe
An induction heating coil for a metal pipe, characterized in that the induction heating coil is arranged along the outer peripheral surface within a range of 3.