JPS6031200Y2 - induction heating device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an induction heating device that enables static heat retention.

Conventionally, continuous feed type induction heating equipment was not able to keep warm at a standstill, so if the front and rear equipment, such as a press, breaks down, the induction heating equipment can be operated as is, the heating system bypassed, and the system can be restored at any time. If the failure persisted, the power supply would be shut off and the equipment would be placed on standby.

Of these, in the former case, power is wasted, and effort is also wasted in processing the bypassed and heated warp.

Also, in the latter case, the workpiece inside the coil must be discharged, which requires wasted labor and has the drawbacks of poor operability.

Therefore, this idea made it possible to adjust the power for each coil, and if only enough power was supplied to each coil to compensate for the heat loss corresponding to the workpiece temperature, the workpiece temperature inside the coil would become uniform. In view of this, it is an object of the present invention to provide an induction heating device that can perform static heat retention by creating a power distribution that compensates for the heat loss caused by the temperature curve within the coil.

Hereinafter, embodiments of the induction heating device of this invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the invention.
at 1 b9 1 ctld... each indicates a coil for induction heating.

A workpiece (not shown) is inserted into these coils 1a to 1d in the direction of arrow A, and the workpiece is heated by the magnetic field generated by the coils 1a to 1d.

Capacitor 2 for power factor improvement in parallel with each coil 1a to 1d
a to 2d are connected.

Adjustment of the power supplied to each coil 1a to 1d is performed by a transformer 3.
This is done by switching each of the taps a to 3d.

This switching means includes line l and each transformer 3a to 3d.
This is done by switching the switches 4a to 4d between the taps.

A transformer 5 and a transformer 6 are connected between the line 1 and a commercial frequency power source (not shown).

The transformer 6 transforms the voltage of the commercial frequency power supply and applies the output voltage to the transformer 5.

The transformer 5 receives the output voltage of the transformer 6, converts it into a predetermined frequency, and applies the current and voltage to the line 1.

As shown in FIGS. 2a to 2c, the above-mentioned filters 1a to 1d are used in which the power distribution within the coil is tapered.

Each of FIGS. 2A to 2C is a cross-sectional view, and shows the coil 10 as a whole.

First, we will discuss the case shown in FIG. 2a.

In the case of FIG. 2a, coils 8 are wound around the outer peripheral surface of a cylindrical refractory 7 at predetermined intervals, and an insulator 9 between the coil conductors is installed between each adjacent coil 8. ing.

The coil 8 is wound so that the winding width gradually increases from the left side to the right side in the figure, that is, the number of turns gradually increases from the workpiece insertion side to the exit side.

Furthermore, in other words, the coil 8 is sparse on the workpiece insertion side.
It is dense on the exit side.

By forming the coil 10 in this way, the coil 1
By making the power distribution uneven within 0, each coil 1 in FIG.
The electric power is adjusted every step a to 1d to enable stationary heat retention.

Further, in the case of the coil 10 shown in FIG. 2, the coil partially has a two-layer structure.

That is, the first layer of coils 8 having the same winding width are wound on the outer circumferential surface of the cylindrical refractory 7 at predetermined intervals, and the power is distributed toward the exit side of the coil 10 rather than the workpiece insertion side. A second layer coil 11 is wound around the outer circumferential surface near the outlet side and the center portion with an insulator 12 interposed therebetween so that the coil 11 has a large diameter.

Furthermore, in the case of FIG. 2C, the overall shape of the coil 10 is tapered, and the diameter on the exit side is smaller than that on the workpiece insertion side, and the power distribution inside this exit side is adjusted to that of the insertion port. It was designed to be larger than that.

In this case, the winding width of the coil 8 is substantially uniform over the entire length of the refractory 7.

Incidentally, the heat loss of the workpiece is composed of loss due to convection and heat dissipation loss, and if the temperature rise pattern of the workpiece in a single coil is known, the heat loss distribution can be easily calculated.

Figure 3 shows the total heat loss per unit length versus workpiece temperature when the workpiece diameter is 40 mm.

As is clear from FIG. 3, it can be seen that as the workpiece temperature rises, the heat loss increases.

'Now, in FIG. 1, assuming that each of the coils 1a to 1d uses one of the coils 10 in FIGS. 2a to 3C, the temperature rise value of the coils 1a to 1d is 750°C, 1050℃, 1200℃, 125
Assuming that the temperature is 0°C, in the coil 1a, the heat loss near the workpiece insertion port is almost 0, and the heat loss near the exit side is 5.8 (KW).
/m).

The total length of the coil 1a is 50mm, of which 175mm
Assuming that the temperature is close to that temperature, the coil may be configured to apply an extra 0.58 KW of power compared to the vicinity of the workpiece insertion side of the coil 1a.

In theory, it would be sufficient if the distribution shown in Figure 3 could be constructed within a single coil, but in reality, the inside of the coil could be divided into several points as shown in Figures 2a to 2C. , will construct a coil with a stepped power distribution that compensates for the average heat loss of each divided coil.

Here, the operation of the induction heating apparatus shown in FIG. 1 will be explained.

This transformer 6 converts the voltage of the commercial frequency power supply into a predetermined voltage and applies it to the converter 5.

This converter 5 converts the frequency of the output voltage of the transformer 6 to a predetermined frequency and applies the output voltage to the line 1.

Further, if the switches 4a to 4d are respectively switched to predetermined tap positions of the transformer 3, the voltage of the line 1 is applied to the coils 1a to 1d via the switches 4a to 4d and the transformers 3a to 3b.

As a result, the workpieces inserted into the coils 1a to 1d are heated, but during steady operation, the temperature rise curves of the coils 1a to 1d each reach 750°C! , 1050°C91200°C,
Assume that each tap of the transformers 3a to 3b is selected so that the temperature becomes 1250°C.

In this state, if it is necessary to temporarily stop the induction heating apparatus due to a failure unrelated to the induction heating apparatus shown in FIG. The coils are selected so that power can be supplied to compensate for the heat loss of the workpiece in each of the coils 1a to 1d.

At this time, in the case of a conventional induction heating device, since the power distribution within each coil is constant, the workpiece within the coil approaches each other so that every point has the same temperature.

Therefore, the temperature distribution of the workpiece cannot be maintained at the time when the induction heating device is stopped, making static heat retention impossible.

On the other hand, in the case of this invention, each of the coils 1a to 1d uses one of the coils 10 shown in FIGS. 2a to 2C, and the power distribution within the coil 10 is uneven. By providing a power distribution equal to the heat loss distribution, stationary heat retention becomes possible.

FIG. 4 shows only the coils 1a to 1d in a second embodiment of the induction heating device of this invention.

In the case of this FIG. 4, the tapered coil 10 shown in FIG. 2C is replaced with the coil 1a in the induction heating device of FIG.
~1d.

At this time, in particular, the coils 1a to 1d are sequentially stacked as shown in the figure.

That is, the workpiece outlet side of the coil 1a is inserted into the workpiece insertion port side of the coil 1b, and thereafter, the workpiece insertion side and the workpiece outlet side of adjacent coils are successively overlapped.

By doing so, the above-mentioned stationary heat retention effect can be made more reliable.

Further, FIG. 5 is a circuit diagram showing a third embodiment of the induction heating device of this invention.

In the embodiment shown in FIG. 5, full-wave phase control circuits 13a and 13b are used instead of the transformers 3a to 3d in the embodiment shown in FIG.
is used.

In FIG. 5, a transformer 6 and a transformer 5 are provided in common for coils 1a and 1b, lc and 1d, respectively.
The output of the transformer 5 is applied to the coils 1b and 1c, respectively.

Furthermore, the power supplied to the coils 1a and 1d is controlled by supplying power from the transformer 5 to the coils 1a and 1d via full-wave phase control circuits 13a and 13b, respectively.

These full-wave phase control circuits 13a and 13b have internal elements (
By controlling the firing phase of the thyristor or the number of communications,
The power supply to the coils la and ld can be controlled, and as a result, static heat retention is possible.

In the case of the embodiment shown in Fig. 5, it is possible to control continuously compared to the embodiment shown in Fig. 1, so when the variable element increases, such as a change in the material diameter of the workpiece, it can be automatically controlled. Adjustment becomes easier.

In addition, in the embodiment shown in FIG. 5, 4 of the coils 1a to 1d
Although only the case of blocks is shown, it goes without saying that it can be implemented regardless of the number of coil blocks or the number of power supplies.

As detailed above, according to the induction heating device of this invention, when supplying alternating current power to the coil to inductively heat a workpiece within the coil, the power distribution within the coil is tapered. Since we have created a power distribution that compensates for the heat loss curve due to the temperature curve generated within the coil, static heat retention can be achieved by providing a predetermined power supply to the coil even when the workpiece is stopped being fed. It is possible to maintain the temperature increase pattern within the coil, and as a result, even in the event of a failure of devices before or after the induction heating device, it is possible to prevent wasteful power consumption and reduce workpiece processing labor. In addition, it has excellent effects such as improving operability.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the induction heating device of this invention, and Figs. 2a to 2C are cross sections showing the shapes of each embodiment of the coil used in the induction heating device of this invention. Figure 3 is a diagram showing the total heat loss per unit length with respect to the workpiece temperature, Figure 4 is a diagram showing only the coil portion in the second embodiment of the induction heating device of this invention, and Figure 5 FIG. 2 is a circuit diagram showing a third embodiment of the induction heating device of this invention. 1 a~1 d9 89 109 11------ Coil, 4a~4d...Switch, 5...
・Transformer, 7... Refractory, 8, 12...
- Insulator, 13a, 13b...Full wave phase control circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (7)

[Scope of utility model registration request] (1) In an induction heating device in which multiple coils are arranged from the workpiece insertion side to the exit side, the power distribution is gradually increased from the workpiece insertion side to the exit side in order to compensate for the heat loss curve of each coil. An induction heating device characterized by having a power supply or a power adjustment means that differs in coil shape distribution and adjusts the power supplied to each coil to power equal to the heat loss of the coil to enable stationary heat retention. (2) The coil is wound more closely from the insertion side to the exit side of the workpiece, thereby tapering the power distribution to compensate for the heat loss curve of each coil. The induction heating device according to item 1. (3) The coil is multi-wound from the insertion side to the exit side of the workpiece, so that the power distribution is tapered to compensate for the heat loss curve of each coil. Claim 1 of the Utility Model Registration Claim The induction heating device described. (4) The coil is tapered so that its diameter gradually decreases from the insertion side to the exit side of the workpiece, and the power distribution is tapered to compensate for the heat loss curve of each coil. An induction heating device according to claim 1 of the patent registration claim. (5) The induction heating device according to claim 1 of the utility model registration claim, characterized in that a plurality of coils are seamlessly connected by sequentially inserting the workpiece outlet side of each coil into the workpiece insertion side of an adjacent coil. . (6) The power adjustment means adjusts the power by switching the taps of the transformer connected between each coil and the power supply using a switch.Claim 1-
The induction heating device according to any one of Item 5. (7) A utility model characterized in that the power adjustment device connects a full-wave phase control circuit between a power source and a predetermined coil, and adjusts the power supply to the coil by adjusting the phase of this full-wave phase control circuit. An induction heating device according to any one of registered claims 1 to 5.