JPS6131951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating inductor with low leakage magnetic flux.

For example, during the hot rolling process, the end portions of a metal piece being rolled undergo a greater temperature drop than the center portion in the width direction during the period between rolling in a rough rolling mill and rolling in a finishing rolling mill. For this reason, depending on the steel type of the metal piece, defects such as edge cracks may occur during rolling, which is undesirable in terms of product quality, so the ends of the metal piece are heated by induction heating.

In addition, recently, in hot rolling, there has been an attempt to directly convey metal pieces from a continuous casting device or a blooming mill to a hot rolling mill and roll them without heating them in a heating furnace. In this case, various measures to prevent the temperature drop have been studied, and induction heating inductors are attracting attention and being used frequently as an energy-saving heating means for the temperature drop section. By the way, an induction heating inductor heats a metal piece that is being transported due to its heating function.

A conventional induction heating inductor will be described with reference to FIGS. 1 to 6. 1 and 1' are the iron cores of the inductor, which are generally made of laminated silicon steel plates. These iron core legs are called magnetic poles 2, 2', and coils 3, 3' are wound around the magnetic poles 2, 2'. When a current is passed through the coils 3, 3', a magnetic field is generated by the magnetomotive force caused by the current, a magnetic flux 4 is induced, and the magnetic flux 4 passes between the magnetic poles 2, 2'. When this magnetic flux 4 penetrates the metal piece 5 to be heated, an eddy current is generated in the metal piece 5 to be heated, and the metal piece 5 to be heated is heated due to the eddy current loss and hysteresis loss.

Inductor A that heats this metal piece 5 to be heated
is provided between the transfer rollers 6 of the metal piece 5 to be heated, and the inductor A has three legs and three windings in FIG. 1, the inductor A has four legs and four windings in FIG. 2, and the inductor A in FIG. For inductor A with three legs and one winding, magnetic flux 4 shown by a solid line passing between upper iron core 1 → upper magnetic pole 2 → lower magnetic pole 2' → lower iron core 1' and upper and lower inductors A, and inductor A There is a leakage magnetic flux 8 shown by a broken line leaking outward from the inductor, and since there is a large amount of the leakage magnetic flux 8 in these inductors, the following problems occur. In other words, one of the main problems in practical induction heating is damage to peripheral devices where the inductor is installed, such as transfer rollers, center aprons of transfer lines, etc., due to heating due to leakage magnetic flux. This is heat loss called heating. Since the principle of induction heating is the application of electromagnetic phenomena, especially magnetic induction and the resulting eddy currents and hysteresis losses, this problem is caused by phenomena that are inherent to the nature of induction heating. That is, this is a problem that has continued since the beginning of industrial use of induction heating to this day. When peripheral devices are heated by leakage magnetic flux and reach a temperature of several hundred degrees, their mechanical strength may decrease and become deformed, or the rotating and sliding parts may seize up and become unable to rotate, leading to the suspension of the production line. In order to suppress such a temperature rise in the inductor peripheral device, it is necessary to take measures such as increasing the separation distance between the inductor and the peripheral device, or using non-magnetic steel. However, on the actual production line,
For various reasons, it is often not possible to secure the necessary separation distance. In a roller table that conveys a piece of metal to be heated 5, for example, a steel material, the roller pitch is determined by the shape, size, transfer speed, etc. of the steel material.
If the roller pitch is increased, smooth conveyance of the steel material will be hindered. Furthermore, if non-magnetic steel is used for peripheral equipment, equipment costs will increase.

When adding and installing an induction heating device to existing equipment, it is almost always necessary to make a fairly extensive modification of the existing equipment in order to ensure the above-mentioned separation distance.
In order to prevent the above-mentioned troubles caused by heating of peripheral devices due to leakage magnetic flux of the inductor,
Up until now, it has been common practice to perform forced cooling using water, air, etc. Therefore, in addition to the energy loss of unnecessary heating of the peripheral devices, energy for cooling the peripheral devices, the refrigerant supply device thereof, and the drive energy and maintenance of the entire device are added.

By the way, the inductor input is also
When excited at 100 kW and frequency f = 500 Hz, the leakage magnetic flux density distribution was as shown in Figure 4. At that time, the temperature of the transfer roller 6 reached approximately 800°C. Note that a in FIG. 4 shows the leakage magnetic flux distribution at a distance from the wall 7 of the inductor 1 in the direction of transfer of the heated metal piece (X direction), and b in FIG. The leakage magnetic flux density distribution in the direction perpendicular to the direction (Y direction) is shown.

In order to reduce the influence of such leakage magnetic flux, a four- or two-winding inductor as shown in FIG. 5 has been proposed. This inductor has magnetic poles 2, 2' by winding coils around the middle two of the four legs, and the legs 10-1, 10- at both ends.
1' is used as an auxiliary magnetic pole. In this inductor, when a current is passed through the coil 3, a magnetic field is generated and a magnetic flux 4 flows, but since the coil 3 is wound only around the middle leg, the flow of the magnetic flux 4 is as follows.
Upper iron core 1 → Upper magnetic pole 2 → Lower magnetic pole 2' →
Lower iron core 1' → lower magnetic pole 2' → upper blank pole 2 →
The upper iron core 1 and the circular flow are the main flow.

On the other hand, since no coil is wound around the auxiliary magnetic poles 10-1 and 10-1' at both ends, they do not have the function of driving the magnetic flux 4. Therefore, most of the magnetic flux 4 induced by the magnetomotive force of the magnetic poles 2, 2'
2', and due to the unbalance of magnetic resistance, the magnetic flux leaking from these magnetic poles 2, 2' flows through the auxiliary magnetic fluxes 10-1, 10-1'.
The outside of this auxiliary magnetic pole is air, and since the magnetic resistance is much greater than the auxiliary magnetic flux, the amount of leakage magnetic flux 8 generated outside the auxiliary magnetic pole is sufficiently small.

FIG. 6a shows the measurement results of the leakage magnetic flux in the X direction of the four-legged, two-winding inductor, together with the results for the three-legged, one-winding inductor. At this time, the input power of the four-legged two-winding inductor was 150KW, and the excitation frequency was 500Hz.

In this way, in the case of a four-legged two-winding inductor,
The leakage magnetic flux in the X direction is significantly reduced by the effect of the auxiliary magnetic poles 10-1 and 10-1'.

However, as shown in Figure 6b, although the leakage magnetic flux in the Y direction is much lower in the 4-leg 2-winding inductor than in the 3-leg 1-winding inductor, it is still very high compared to the X-direction. It's on the level. Therefore, peripheral devices located in the Y direction, such as the center apron, will be heated to a high temperature even if they are separated from the inductor side wall by 100 mm or more, causing various problems as described above.

The present invention solves the above problems and provides an induction heating inductor in which leakage magnetic flux to the outside of the inductor is further reduced.

That is, in the inductor of the present invention, at least four legs are provided in a row on an iron core made of laminated metal plates, the outermost two of the legs serve as auxiliary magnetic poles with no coil wound around them, and the remaining legs The induction heating inductor is characterized in that a coil is wound around the leg portion to form a magnetic pole, and an auxiliary magnetic pole is provided along the leg portion in parallel to the arrangement direction of the leg portion.

The present invention will be explained below based on the embodiments shown in FIGS. 7 and 10.

FIGS. 7a and 7b are a plan view and a side view showing an embodiment of the present invention;
A second auxiliary magnetic pole 1 is added to the wire-wound inductor.
1 and 11' are provided along the arrangement direction (X direction) of the magnetic poles 2 and 2'.

The shape of the inductor of this example as viewed from the front, the magnetic circuit, and the manner of outward leakage magnetic flux are the same as those in FIG. 5, and therefore illustration thereof is omitted.

7b shows the shape of the second auxiliary magnetic poles 11, 11' and the leakage magnetic flux to the side (Y direction), and 13 in the figure shows the center apron provided between the transfer rollers 6. It is. As shown in the plan view of FIG. 9, the center apron 13 is located between the rollers 6 to prevent the tip of the rolled material from falling downward.

According to the inductor of this embodiment, due to the effect of the second auxiliary magnetic poles 11 and 11', leakage magnetic flux in the Y direction is almost eliminated, and the center apron is not heated.

FIG. 8 shows the inductor leakage magnetic flux of this example,
This is a graph showing the conventional method. The second auxiliary magnetic poles 11, 11' and the magnetic pole 2 in this inductor,
2', a distance of about 80 to 100 mm is practically sufficient.

10a and 10b are a plan view and a side view showing another embodiment of the present invention, in which the inductor of FIG. 7 is further provided with third auxiliary magnetic poles 12, 12'.
is provided on the other side symmetrically with the second auxiliary magnetic poles 11, 11'. In this case, in addition to the center apron, the pedestal 14 (for example, an inductor support pedestal or a measuring device pedestal) installed close to the roller table is prevented from being heated.

As described above, the present invention has much less leakage magnetic flux than the conventional one, performs efficient heating, does not damage the peripheral devices installed with the inductor, and does not damage the peripheral devices unlike the conventional ones. This has many advantages, such as eliminating the need to use expensive non-magnetic steel.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, FIG. 3, and FIG. 5 are front views (partially perspective views) showing conventional induction heating inductors, respectively. FIGS. 4 and 6 are graphs showing the leakage magnetic flux distribution of a conventional inductor. FIG. 7 is a drawing showing an embodiment of the present invention, in which a is a plan view and b is a side view. FIG. 8 is a graph showing the leakage magnetic flux distribution of the inductor of this embodiment and the conventional one, and FIG. 9 is a plan view showing the arrangement position of the inductor of the present invention. FIG. 10 is a drawing showing another embodiment of the present invention, in which a is a plan view;
b is a side view. 1, 1': Iron core, 2, 2': Magnetic pole, 3, 3': Coil, 4: Magnetic flux, 5: Metal piece, 6: Transfer roller, 8: Leakage magnetic flux, 10-1, 10-1': Leg (auxiliary magnetic pole), 11, 11': second auxiliary magnetic pole, 1
2, 12': Third auxiliary magnetic pole.

Claims (1)

[Claims] 1 At least four legs are arranged in a row on an iron core made of stacked metal plates, the outermost two of the legs serve as auxiliary magnetic poles without winding a coil, and the remaining legs are wound with a coil. An induction heating inductor, characterized in that an auxiliary magnetic pole is provided along the leg portions in parallel to the arrangement direction of the leg portions.