JPS5942438B2 - induction heating device - Google Patents

Description

Detailed Description of the Invention This invention installs a heated object made of a metal material in an alternating magnetic field, and uses eddy current loss and hysteresis loss generated in the heated object by electromagnetic induction to This invention relates to an induction heating device that heats the mouth.

Generally, in this type of induction heating device, due to its heating principle, the inductor coil often generates noise accompanied by vibration.

The disadvantages of the conventional method will be explained below with reference to the drawings. The first figure is a sectional view of a conventional induction heating device of this type, in which 1 is a cylindrical inner cylinder made of heat-resistant concrete that houses a heated object 2 and has an inductor coil 3 wound around its outer circumference; , 4 is this inner cylinder 1
A pair of support plates are fitted and attached to both ends of the inner cylinder 1 along with the contact plates 5, 5, and the support plates 4, 4 are fixed to the inner cylinder 1 together with the contact plates 5, 5 by a plurality of connecting bolts 6 spanning these. has been done. Reference numeral 7 denotes a fixture for fixing the support plates 4, 4 to the support stand 8.

Figure 2 shows the inductor coil 3 extracted.
It is shown that a coil 3 having terminals A and A' is wound around the inner cylinder 1. When a power frequency voltage is applied to terminals A and A' of this coil 3, the coil 3
A current having a waveform shown by the solid line flows, and the object 2 to be heated within the alternating magnetic field generated thereby generates heat due to overcurrent and hysteresis loss, and the object 2 to be heated becomes high temperature.
In the above operation, when a current (solid line in Fig. 4a) flows through the coil 3, the object 2 to be heated is heated, and at the same time, the coil 3 receives an alternating current with a frequency twice that of the alternating power supply current. Electromagnetic force (dotted line in Figure 4a) acts.

This force is composed of two forces: the force that causes the coil 3 to expand and contract in the axial direction, and the force that causes the coil 3 to expand and contract in the radial direction.
It can be divided into two parts. The former force is applied through the inner cylinder 1. Alternatively, the vibration is transmitted directly from the coil 3 to the support plates 4, 4, causing the support plates 4, 4 and the contact plates 5, 5 to vibrate greatly, and this vibration is radiated as a loud noise. On the other hand, regarding the radial excitation force of coil 3, it is the coil that vibrates in response to this force.
In the file 3 itself, the acoustic radiation area is the supporting plates 4, 4, the contact plate 5,
Since it is not as wide as 5, it is not important as a cause of noise generation.
good. This invention was made focusing on this point,
It is an object of the present invention to provide an induction heating device that reduces noise as described above. Examples of this invention will be described below. That is, instead of the coil 3 wound around the cylinder 1 shown in Figs. 1 and 2, there are two coils 9 which are divided into two as shown in Fig. 3 and whose terminals are B, B', C, and C'. ,
9 is wound around cylinder 1.

The total number of turns and winding direction of the coils 9 and 9 are the same as those of the coil 3. When operating this device, coil end B-B
A current having the phase shown in FIG. 4b is passed through the coil end C-C', and a current having the same magnitude as shown in FIG. Since the induction heating device of the present invention is constructed as described above, the electromagnetic force Fb due to the current flowing through the coil end B-B' is generated by the electromagnetic force Fb.

The electromagnetic force FO due to the current flowing through the coil end C-C' is.

However, A is a proportionality constant, ω is the power angular frequency, t is time, and I
is the magnitude of the current. Since the electromagnetic force 1FT acting in the longitudinal direction of the axis is the sum of Fb and FO, calculating this using equations 1 and 2 gives The vibration force that tries to expand and contract in the axial direction will not work.

This can also be understood from Figure 4d. Therefore, the cylinder 1 does not vibrately expand or contract in the axial direction, and the support plates 4, 3 and contact plates 5, 5 that are in contact with the cylinder 1 do not vibrate, so no large noise is generated, and the noise is drastically reduced. The coils 9, 9 in the present invention expand and contract in the radial direction, but as mentioned earlier, vibration in this direction does not pose a problem because the acoustic radiation area is small.
It goes without saying that shifting the phase of the applied voltage of the power source by 900 as shown in FIGS. 4B and 4C can be easily realized when a thyristor power source is used.

According to the induction heating device of the present invention, as described above, two identical inductor coils 9, 9 are wound around the inner cylinder 1, and alternating currents having a phase shift of 90 degrees are passed through the coils. The cylindrical axial excitation force generated from the two coils 9, 9 is canceled and disappears, and the supporting plates 4, 4, the contact plate 5,
5 no longer vibrates. Therefore, the noise radiated to the outside has an excellent effect of being significantly reduced compared to the conventional one.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the outline of a conventional induction heating device, Figure 2
Figure 3 is a coil configuration diagram of a conventional device, Figure 3 is a coil configuration diagram showing an embodiment of the present invention, Figure 4 a is a current waveform and electromagnetic force waveform of a conventional coil, Figure 4 B, c, and d. 1 is a diagram of current waveforms and electromagnetic force waveforms according to an embodiment of the present invention. In the figure, 1 is a cylinder, 2 is an object to be heated, 3 is an inductor coil, 4
is a support plate, 5 is a backing plate, 6 is a connecting bolt, 7 is a fixing metal fitting,
8 is a support base, and 9 is a split inductor coil.

Claims (1)

[Claims] 1. An object to be heated is housed inside, and an inner cylinder is provided with two similar inductor coils wound side by side around the outer periphery, and an alternating current with a phase difference of 90° is passed through the two inductor coils to generate vibration. An induction heating device that is characterized by canceling out noise and reducing noise.