JPH0552653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of manufacturing an iron core made of an amorphous magnetic alloy plate used in a transformer, etc., by annealing the iron core.

[Technical background of the invention and its problems]

Recently, consideration has been given to using amorphous magnetic alloy plates as materials for wound cores and laminated cores used in transformers and the like. Amorphous magnetic alloy plates are made of metals (Fe, Co, Ni, etc.) and semimetallic elements (B, C, Si,
It is manufactured using an ultra-quenching method with P, etc. as its main component, and has low iron loss (loss) of 1/3 to 1/4 compared to silicon steel sheets, which are conventional core materials, and has excellent magnetic properties. Are better.

However, since amorphous magnetic alloy plates are manufactured using an ultra-quenching method, their magnetic properties are extremely degraded due to distortion during rapid cooling, such as increased core loss, and the originally excellent magnetic properties cannot be obtained. For this reason, iron cores made of amorphous magnetic alloy plates undergo strain-relief annealing after core assembly to remove the strain on the amorphous magnetic alloy plates, thereby reducing core loss and reducing the inherent magnetic properties of amorphous magnetic alloys. Efforts are being made to restore the characteristics. This annealing is a method for improving magnetic properties by placing an iron core in a magnetic field to impart magnetic anisotropy.

However, when performing this annealing, the following points are important. Amorphous magnetic alloy plates have narrow annealing temperature conditions, and if the temperature is not raised to make the temperature distribution inside the core uniform, the magnetic properties will deteriorate due to thermal stress, and the original excellent magnetic properties must be recovered. I can't. In addition, since amorphous magnetic alloy plates have the property of becoming brittle after annealing, when handling the iron core after annealing, the amorphous magnetic alloy plates may be damaged by external force (creating cracks or fragments), which may occur while the transformer is in use. There is a risk of dielectric breakdown, etc., which is unfavorable in terms of the quality of the iron core. Therefore, it is necessary to assemble the iron core before annealing, reduce the number of assembly steps after annealing, and reduce the chances of external force being applied to the amorphous magnetic alloy plate. In this case, the work of winding the transformer coil around the iron core places a large degree of stress on the iron core.

Conventionally, for annealing an iron core made of an amorphous magnetic alloy plate, a method has been adopted in which the iron core is heated by an external heat source. That is, as shown in FIG. 2, a coil 3 for applying a magnetic field is wound around an iron core 1 made of an amorphous magnetic alloy plate 2, for example, a wound iron core made by winding the amorphous magnetic alloy plate 2. is housed inside a constant temperature bath 4 whose heat source is an electric heater (not shown).
Then, a direct current is passed through the coil 3 by the DC power source 5 to apply a magnetic field to the iron core 1, and the inside of the constant temperature bath 4 is raised to a predetermined annealing temperature by heating with an electric heater to heat the iron core 1, thereby annealing it. Do the following.

The annealing temperature for amorphous magnetic alloy materials varies depending on the type, but the annealing temperature for amorphous magnetic alloy materials varies depending on the type, but the annealing temperature for amorphous magnetic alloy materials is currently considered to be the most suitable as a core material for transformers.
For METGLAS2605S2, a temperature of about 360 to 410°C is appropriate. Further, it is considered appropriate that the annealing temperature is maintained for about 2 hours.

However, in such an annealing method, since the iron core 1 is heated from the outside by the radiant heat of the electric heater that is the heat source, the inside of the iron core is not properly heated, and the temperature distribution on the surface and inside of the iron core 1 becomes uneven. . Therefore, the magnetic properties of the amorphous magnetic alloy plate 2 of the iron core 1 deteriorate due to thermal stress, and it is difficult to restore the original magnetic properties. In addition, the iron core 1 is heated to a predetermined annealing temperature using an electric heater.
In order to heat up to about 400℃, the temperature inside the constant temperature oven 4 will also rise to the same temperature, so if you put the iron core 1 wound with the transformer coil inside the constant temperature oven 4 and perform annealing, the coil will also be heated at the same temperature. It is heated externally to 400℃. However, the insulating material used for the insulation coating of the coil generally has a low limit of heat resistance, and when heated to a temperature of 400° C., the insulating material is damaged and becomes impractical. For this reason, it is difficult to wind the transformer coil around the iron core 1 in the process before annealing and then perform annealing because it will damage the coil. It turns out. However, since the iron core 1 after annealing is accompanied by the embrittlement phenomenon of the amorphous magnetic alloy plate 2, when the assembly work of winding a coil around the iron core 1 after annealing is performed, the amorphous magnetic alloy plate 2 is damaged by external force. This increases the chance that the quality of the iron core 1 will deteriorate.

Therefore, an excitation coil is provided on the iron core made of an amorphous magnetic alloy plate, and an excitation alternating current is passed through this excitation coil to excite the iron core.The loss that occurs in the iron core due to this excitation causes the iron core itself to generate heat and heat up, annealing it. A method has been proposed. This method has the advantage that most of the winding of the transformer coil and the assembly of the transformer contents can be performed in the process prior to annealing, so that handling of the amorphous magnetic alloy plate, which becomes brittle due to annealing, can be minimized as much as possible.

However, in this method, when the temperature rises due to the heat generated by the iron core itself, heat is radiated from the surface of the iron core, so if this method continues, the power consumption for excitation will increase.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is capable of economically and favorably annealing an iron core made of an amorphous magnetic alloy plate, with the result that the quality is such that the excellent magnetic properties inherent to the amorphous magnetic alloy can be sufficiently exhibited. The purpose of this invention is to provide a method for manufacturing an iron core that can obtain an iron core with good quality.

[Summary of the invention]

The method for manufacturing an iron core according to the present invention includes, when annealing an iron core made of an amorphous magnetic alloy thin plate, placing the iron core around which an excitation coil is wound in a constant temperature bath, and exciting the iron core by passing a high-frequency alternating current through the excitation coil. The loss that occurs in the core due to this excitation causes the core itself to generate heat, and the core is heated by a heating element installed in the thermostatic oven.Furthermore, after the temperature inside the thermostatic oven has risen to a preset temperature, the core is heated by high-frequency excitation. The feature is that the iron core is annealed by raising it to a predetermined annealing temperature using its own heat generation. In other words, the present invention can raise the temperature of the iron core with a uniform temperature distribution by using the heat generated by the iron core itself due to excitation and the heating of the constant temperature bath, and also speeds up the annealing work by suppressing the heat radiation of the iron core and raising the temperature of the iron core in a short time. can be done. In this case, by setting the temperature in the thermostatic chamber to a temperature that does not deteriorate the insulation,
It becomes possible to attach a transformer coil to an iron core and perform annealing without damaging the transformer coil.

[Embodiments of the invention]

Embodiments of the present invention illustrated in the drawings will be described below.

FIG. 1 shows an embodiment of the method of the present invention.
In this embodiment, two-phase wound cores formed by winding amorphous magnetic alloy thin plates are arranged, and a transformer coil is commonly wound around the central leg of each wound core.

Each winding core 11 is a strip-shaped amorphous magnetic alloy thin plate 12
is formed by winding it into a rectangular shape. Each winding core 11 is arranged side by side, and a transformer coil 13 is commonly wound around its central leg.

When the wound core 11 is annealed, a pre-wound coil 14 is wound around the outer leg portion of each wound core 11 to cause an excitation high-frequency alternating current to flow therethrough. The temporary winding coils 14 are wound in opposite directions to each other, and the number of turns is set so as to provide a voltage that does not cause problems in terms of the dielectric strength of the transformer coil 13. Note that for the temporary coil 14, an inorganic insulated wire made of ceramic or the like is used in consideration of voltage resistance and heat resistance.

Next, transformer coil 13 and temporary winding coil 1
Each of the cores 11 wound with 4 is placed inside the thermostatic chamber 15. The temporarily wound coils 14 of each wound core 11 placed in the thermostatic chamber 15 are connected to a high frequency AC power source 18 and a DC power source 19 via a changeover switch 17, respectively.
20 is a voltage regulator that adjusts the voltage of the AC power supply 18. The thermostatic oven 15 includes an electric heater 16 as a heat generating element, and the heat generated by the electric heater 16 maintains the inside at a predetermined set temperature.

Then, in order to sinter and purify the wound core 11, a constant temperature bath 1 is used.
5, the internal temperature at which the insulating material used in the transformer coil 13 does not cause thermal deterioration, for example,
Set the temperature to about 100-150℃. This set temperature can be changed as appropriate depending on the type of insulator, and it can be set to a higher temperature if an H type insulator is used. That is, the electric heater 16 is made to generate heat so that the inside of the constant temperature bath 15 reaches the set temperature. For this reason, the wound core 11 placed inside the thermostatic chamber 15 is heated from the outside by the electric heater 16 and its temperature rises.

In addition, the temporary winding coil 14 is set by the changeover switch 17.
is connected to the high frequency AC power supply 18, and the voltage regulator 20 is connected to the high frequency AC power supply 18.
The voltage is adjusted by , and a high-frequency alternating current for excitation is caused to flow through the temporary coil 14 . The frequency of this alternating current is selected to be, for example, 2 to 4 KHz. For this reason, by flowing an alternating current through the temporarily wound coil 14, magnetic flux is generated and eddy current flows through the wound iron core 11, and Joule heat is generated in the wound iron core 11 due to power loss accompanying this eddy current. Therefore, the wound core 11 is heated by its own internal heat generation and its temperature rises.

In this way, the temperature of the wound core 11 rises due to both internal heat generation due to high frequency excitation and external heating due to the electric heater 16 of the constant temperature oven 15. That is,
The temperature of the wound core 11 rises up to the set temperature range of the thermostatic oven 15 by a combination of internal heat generation due to excitation and external heating of the thermostatic oven 15. Then, from the time when the temperature of the wound core 11 rises to the set temperature (100 to 150° C.) of the constant temperature bath 15, the temperature of the wound core 11 increases due to heat generation of the core itself due to high frequency excitation. When the temperature of the wound core 11 rises to 400°C, which is the appropriate annealing temperature for the amorphous magnetic alloy thin plate 12, the voltage is adjusted by the voltage regulator 20 to keep the temperature of the wound core 11 at 400°C constant for an appropriate temperature holding time. Hold. In addition, each winding core 1
Since the temporary winding coil 14 of No. 1 is connected with opposite polarity, even if an alternating current is applied to the temporary winding coil 14 to excite it, no induced voltage is generated in the transformer coil 13 due to the magnetic flux.

Next, by switching the changeover switch 17, the temporary coil 14 is disconnected from the AC power source 18 and connected to the DC power source 19. For this reason, the supply of alternating current to the temporarily wound coil 14 is gradually stopped, the excitation of the wound core 11 is stopped, and the wound iron core 11 begins to cool down. At the same time, a DC current flows from the DC power supply to the temporary winding coil 14 and forms a magnetic field with respect to the winding core 11. In this way, the wound core 11 is cooled in the magnetic field.

After the annealing is completed, the wound core 11 is taken out from the constant temperature bath 15, and the temporarily wound coil 14 is removed from the wound iron core 11 to complete the work.

Note that the constant temperature bath 15 is preferably filled with an inert atmosphere such as nitrogen gas in order to prevent oxidation of the wound core 11.

If the wound core 11 is manufactured in this way, when the temperature of the wound core 11 is in a range lower than the set temperature of the thermostatic oven 15, the core can be wound by both heat generation of the core itself due to high frequency excitation and external heating from the thermostatic oven 15. The temperature of the iron core 11 rises, and from the time when the temperature of the wound iron core 11 becomes equal to the set temperature of the thermostatic chamber 15, the wound iron core 1 increases due to heat generation of the iron core itself due to high frequency excitation.
1 rises in temperature. Therefore, the amount of heat dissipated from the wound core 11 is determined by the difference between the core temperature and the set temperature of the constant temperature bath 15, and the amount of heat dissipated is smaller than when excited at room temperature, allowing the wound core 11 to be annealed in a short time. Can be raised to temperature.

That is, the calorific value of the wound core 11 is Q ₁ (Kcal),
The amount of heat dissipated from the winding core 11 is Q ₂ (Kcal), and the heat radiation from the winding core 1 is
If the amount of heat stored inside 1 is Q ₃ (Kcal), then Q ₃ =Q ₁ −Q ₂ (1).

Q ₁ and Q ₂ are expressed by the following equations.

Q ₁ = k ₁ Wqt ……(2) Q ₂ = k ₂ W (Om−On) ……(3) k ₁ , k ₂ : Constant of proportionality W: Iron core weight (Kg) q: Iron core unit weight, unit time Calorific value per unit (Kcal/Kg・h) t: Current energization time (h) Om: Iron core temperature (℃) On: Temperature in constant temperature chamber (℃) As is clear from the above formula, the winding core temperature Om is
In order to effectively use the heat generation amount Q ₁ to increase the heat storage amount Q ₂ to raise the temperature to about 400° C., it is necessary to reduce the heat radiation amount Q ₂ . On the other hand, the amount of heat dissipation Q ₂ ′ when the wound core is excited at room temperature is Q ₂ ′ = k ₂ W (Om−Oa) ……(4) Oa: ambient temperature (room temperature) °C.

In the present invention, when annealing the wound core 11,
Since this is a method of exciting and annealing the wound core 11 in a constant temperature bath 15 heated to a temperature of ~150°C, there is a difference in the amount of heat dissipated compared to when the wound core 11 is excited at room temperature.
From equations (3) and (4), Q ₂ ′ becomes Q ₂ ″=k ₂ W (Om−Oa), and since the amount of heat dissipation is small, the wound core 11 can be raised to the annealing temperature in a short time. In other words, if the iron core unit weight expressed by equation (2) and the calorific value q per unit time are constant, the energization time required to raise the temperature to about 400°C can be significantly shortened. The iron core 11 can be annealed quickly.On the other hand, when the current application time t is constant, the calorific value q
can be made small, and q∝f ⁿ B ^m (f: alternating current frequency,
B: magnetic flux density), the frequency of the alternating current may be low, and in the case of the same iron core weight, the power supply capacity of the alternating current power supply 18 may be small. Note that by reducing the amount of heat dissipated from the wound core 11 and also using external heating, the temperature distribution inside and outside the wound core 11 can be made more uniform.
Strain removal by annealing can be performed well and deterioration of magnetic properties can be prevented.

Furthermore, when the wound core 11 is placed in the thermostatic oven 15 for annealing, the temperature inside the thermostatic oven 15 is set at a temperature that does not cause thermal deterioration of the insulation of the transformer coil 13. Even if the transformer coil 13 is wound and annealed, the transformer coil 13 can be annealed without being damaged.

In addition, in the above-mentioned embodiment, in order to excite the wound iron core at high frequency, a temporarily wound coil is used, but the present invention is not limited to this, and a transformer coil wound around the wound iron core may also be used. good. However, in this case, since the problem of dielectric breakdown occurs in the transformer coil when used for high voltage use, it is possible to employ it for low voltage transformers.

In addition to using a temporary winding coil, it is also possible to use a transformer coil to apply a DC magnetic field to the winding core when cooling the winding core.
Furthermore, it is also possible to apply a DC magnetic field to the wound iron core during the process of heating the wound iron core.

The core to be annealed is not limited to a wound core, and the same effect can be obtained with a laminated core made of laminated amorphous magnetic alloy thin plates.

When performing sintering, it is advantageous in terms of quality and manufacturing to wind the transformer coil around the iron core. However, the present invention is not limited to this, and it is also possible to perform annealing without winding the transformer coil around the iron core.

〔Effect of the invention〕

As explained above, according to the method for manufacturing an iron core of the present invention, an iron core made of an amorphous magnetic alloy thin plate is heated with a uniform temperature distribution to economically anneal it.
Deterioration of the magnetic properties of the amorphous magnetic alloy thin plate due to annealing can be prevented, and annealing can be performed quickly and in a short time. In addition, annealing can be performed without damaging the transformer coil even when the transformer coil is wound around the iron core, reducing the number of assembly steps to be performed after annealing and preventing damage due to embrittlement of the amorphous magnetic alloy thin plate. can. Therefore, a high quality iron core made of amorphous magnetic alloy thin plate can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the manufacturing method of the present invention, and FIG. 2 is an explanatory diagram showing a conventional example. 11... Wound iron core, 12... Amorphous magnetic alloy thin plate, 13... Transformer coil, 14... Pre-wound coil, 15... Constant temperature oven, 16... Electric heater, 18
...AC power supply, 19...DC power supply.

Claims (1)

[Scope of Claims] 1. When annealing an iron core made of an amorphous magnetic alloy thin plate, the iron core around which an excitation coil is wound is placed in a constant temperature bath, and a high-frequency alternating current is passed through the excitation coil to anneal the iron core. is excited, the iron core itself generates heat due to the loss that occurs in the iron core due to this excitation, the iron core is heated by a heating element provided in the thermostatic oven to raise the temperature of the iron core, and then the temperature of the iron core in the thermostatic oven is increased. A method for manufacturing an iron core, characterized in that after the temperature rises to a set value, the iron core is raised to an annealing temperature and annealed only by the heat generated by the iron core itself due to the excitation. 2. The method of manufacturing an iron core according to claim 1, wherein the temperature in the constant temperature layer is set to a temperature at which the insulator does not deteriorate.