JPS6155233B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to an induction heating device that heats an object to be heated by the electromagnetic induction action of an induction heating coil. The present invention provides an induction heating device in which only the inner surface of the casting mold is heated by the eddy current generated therein by the magnetic flux flowing through the iron core.

Generally, when rolling rollers such as rolling rollers are cast, a mold release agent such as graphite is applied to the surface of the cylindrical mold before casting. Because the entire mold, which is extremely heavy, is heated to a predetermined temperature using a gas furnace or heavy oil furnace, it takes a considerable amount of time (about 4 hours or more) to heat it.
It is extremely difficult to match the timing of removing the mold with the timing of tapping the metal during casting, which not only requires long waiting times for workers and advanced technology, but also wastes a lot of energy to heat the mold. It was.

This invention has been made with attention to this point, and its principle will be explained with reference to FIG. That is, one leg of the rectangular iron core 1 is passed through approximately the center of the cylindrical casting mold 5, and a magnetic flux is caused to flow through this to induce a voltage in the casting mold 5. By allowing current to flow, the mold itself generates heat due to Joule loss.The commercial frequency power supply is converted to the optimum power frequency by the frequency converter 4, and the power factor correction capacitor is The heating coil 2 is configured to be supplied with electric power via the heating coil 3 .

Now, assuming that the cross-sectional area of the iron core 1 is S and the length of the iron core 1 is l, a magnetic flux Φ of the following formula is generated within the iron core 1.

Φ=IcNcμsS/l … [1] However, Ic is the coil current flowing through the heating coil 2 Nc is the number of turns of the heating coil 2 μs is the magnetic permeability of the iron core 1 Therefore, the casting mold 5 is In order to cancel the magnetic flux Φ, a voltage according to the following formula [2], that is, E=-dΦ/dt... [2] is induced, and an eddy current according to the impedance of the casting mold 5 flows into this casting mold. flows. Therefore, a joule loss proportional to the resistance of the casting die 5 occurs, and the casting die 5 rapidly generates heat to a high temperature.

Due to the skin effect, the current flowing through the casting mold 5 flows only to the inner skin portion determined by the frequency generated by the frequency converter 4, so that the heat generation occurs on the inner surface of the casting mold 5. Since the heating is concentrated in one area, the heating efficiency of the casting mold is extremely good, and it is possible to prevent heating of unnecessary areas.

Comparing the heating of a casting mold according to the present invention described above and the heating by the conventional means described above (gas furnace or heavy oil furnace), there is a significant difference in heating time and energy consumption. For example, the casting mold 5 has an outer diameter of 700 m/m, a length of 1100 m/m, and an inner diameter of 420 m/m.
m/m, in this invention, only the inner surface of the mold is heated to a depth of 10 m/m, so the heating weight only needs to be 5.4% of the total, and the heating energy can be saved by 94.6%. Moreover, the heating time is
Conventionally, it took about 4 hours to heat up the entire furnace using a gas furnace or a heavy oil furnace, but according to the present invention, depending on the heater capacity, according to one design example,
With a power supply of about 200KW, it is possible to raise the temperature to 300℃ in about 5 minutes.

Note that FIG. 2 shows a specific embodiment of the present invention.As for the iron core 1, since a square-shaped closed circuit cannot actually be used, a long U-shaped fixed core 1a and a short U-shaped fixed core 1a are used. The fixed core 1a is fixed to a fixed part, and the movable core 1b is detachably divided into a U-shaped movable core 1b.
is fixed. Further, in order to increase the heater capacity, the casting mold 5 is installed by a movable cart 6 so as to be coaxial with the heating coil 2 at the heating position. That is, the movable trolley 6 on which the casting mold 5 is removably placed and the movable iron core 1b are integrally constructed, and after the movable trolley 6 is moved away from the heating coil 2, the casting is carried out on the movable trolley 6. Place the mold 5 for
By moving this movable trolley 6 in the direction of arrow A on a guide rail installed on the fixed part in parallel with the central axis of the heating coil 2, the casting mold 5 is set at the heating position and at the same time movable. The iron core 1b is configured to abut against the fixed iron core 1a via a thin insulator 9 to form a closed magnetic circuit.

Note that in FIG. 2, the power factor improving capacitor 3 and the frequency converter 4 are not shown. Furthermore, the core is not limited to the U-shape, but may be divided into an L-shaped fixed core and an L-shaped movable core.

As described above, according to the present invention, only the necessary parts of the casting mold can be heated due to the skin effect, so the heating time is extremely short.
This not only has the effect of greatly reducing heating energy, but also significantly improves workability, so it has the effect of greatly reducing the amount of manpower required for a series of casting operations.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the principle of the invention, and FIG. 2 is a front view showing a specific embodiment of the invention. In the drawing, 1 is an iron core, 1a is a fixed iron core, 1b is a movable iron core, 2 is a heating coil, 3 is a power factor correction capacitor, 4 is a frequency converter, 5 is a casting mold, 6
is a moving trolley. Note that the same reference numerals in the figures indicate the same parts.

Claims (1)

[Claims] 1. A fixed iron core that is fixed to a fixed part and forms a part of the mouth-shaped magnetic path, a heating coil wound around this fixed iron core, and a heating coil arranged on the fixed part parallel to the central axis of this heating coil. a movable core that contacts the fixed core to form a closed circuit of the mouth-shaped magnetic path; the movable core is fixed, and the movable core is moved by being guided by the guide rail; A trolley on which a casting mold that is brought into contact with a fixed iron core and is heated by induction during contact is placed coaxially with the heating coil, and a commercial power source is converted to high frequency to supply power to the heating coil. An induction heating device equipped with a frequency converter.