JPH08170119A - Annealing of iron core - Google Patents

Abstract

PURPOSE: To uniformly execute annealing of an iron core with high-frequency current by arranging an auxiliary magnetic path to the iron core having recessed/projecting parts at either the inner periphery or outer periphery. CONSTITUTION: An auxiliary magnetic path 9, which is formed to the shape of a slot, is placed in the slot 8a of the inner periphery of a stator core, annealing of the stator core 8 is executed by using the iron loss generated by electromagnetic induction action due to high-frequency current, thus, large difference of magnetic flux density between teeth 8b and a yoke 8c is not generated and irregular heat generation is not generated, thus sufficient annealing effect is given to the stator core 8 by heat approximately uniformly generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron core annealing method for annealing an iron core by electromagnetic induction.

[0002]

2. Description of the Related Art Generally, it is known that an iron core manufactured from silicon steel and used for an electromagnetic induction device or the like has its magnetic characteristics improved by annealing. A method for annealing such an iron core is described in, for example, Japanese Patent Laid-Open No. 61-61.
-215212, which will be described with reference to FIG.

In this case, as an iron core of an electromagnetic induction device, a stator iron core formed by laminating silicon steel plates of an electric motor is taken as an example. A leg of an annealing iron core 2 forming a closed magnetic circuit is inserted into the hollow portion of the stator iron core 1, and a coil 3 is wound around the other leg of the annealing iron core 2. An alternating current is supplied to the coil 3 from an alternating current power source 4. Then, a short-circuit current I flows through the stator iron core 1 by the electromagnetic induction action, and the stator iron core 1 is heated by the heat generated by the Jules loss. in this way,
As the AC power supply, a commercial AC power supply can be used as it is, and there is an advantage that the temperature rising rate of the stator core 1 can be controlled by controlling the AC current value.

A similar method is disclosed in Japanese Patent Laid-Open No. 61-6.
No. 8671 is disclosed, which will be described with reference to FIG. In this case, as the iron core of the electromagnetic induction device, a transformer iron core including a wound iron core is taken as an example.
Coils 6 and 6 are wound around the iron cores 5 and 5, and a high frequency current is supplied from the power source 7 to the coils 6 and 6. The iron cores 5, 5 are heated by the iron loss generated by the high-frequency magnetic flux induced in the iron cores 5, 5 by the high-frequency current.

In this case, a special power source called a high frequency power source is required as the power source 7. However, the iron loss generated in the iron cores 5 and 5 is mainly eddy current loss when the frequency of the current is high to some extent, and since the eddy current loss is proportional to the square of the frequency, a larger loss than the former method. That is, heat can be given and the annealing time can be shortened. Further, by controlling the frequency of the power supply 7, variable loss control can be performed over a wide range, and there is an advantage that the temperature rising rate can be easily controlled.

[0006]

However, when an iron core having an uneven portion on its inner peripheral portion such as a stator iron core of an electric motor is targeted, there are the following problems. That is, the former method has a problem that the short-circuit current flows only in the circumferential direction and does not flow in the radial direction, so that the convex portion on the inner circumferential side of the stator core 1, that is, the tooth portion cannot be heated.

In the latter method, the amount of high-frequency magnetic flux flowing around the teeth of the iron core is small, and sufficient iron loss cannot be obtained, resulting in insufficient heating. If iron loss is increased by increasing the frequency of the high-frequency current in order to compensate for insufficient heating of the teeth portion of the iron core, excessive heat is generated in the outer peripheral portion of the iron core, that is, the yoke portion, and the iron core is melted at worst. It is not preferable because it causes such a situation.

As described above, when the stator core of an electric motor is targeted, not only in the method of JP-A-61-215212 but also in the method of JP-A-61-68671, the temperature distribution fluctuates due to uneven heating, and the temperature is appropriate. There is a possibility that a sufficient annealing effect may not be obtained due to the appearance of a portion that does not reach the appropriate temperature.

The present invention solves the above problems, and an object of the present invention is to heat a convex portion of an iron core having an uneven portion such as a stator iron core of an electric motor when the iron core is annealed by an electromagnetic induction action by a high frequency current. By making the temperature distribution of the iron core uniform by supplementing the above, it is an object of the present invention to provide a method of annealing the iron core which can give a sufficient annealing effect to the iron core.

[0010]

In order to solve the above-mentioned problems, the method of annealing an iron core according to claim 1 is such that a hollow portion of a cylindrical iron core having an inner peripheral portion or an outer peripheral portion with irregularities is formed. In the annealing method of the iron core, which is annealed by iron loss generated in the iron core, by applying a high-frequency current to the conductor penetrated in
It is characterized in that an auxiliary magnetic path formed in conformity with the shape of the concave and convex portions is arranged and annealed.

According to a second aspect of the present invention, there is provided a method for annealing an iron core, wherein a cylindrical iron core having an uneven portion formed on an inner peripheral portion or an outer peripheral portion of a cylinder is provided with two concave portions of the uneven portion and convex portions existing therebetween. Inserting a U-shaped conductor so as to sandwich it, and arranging a ring-shaped auxiliary magnetic path so as to be in contact with the tip of the convex part, and performing annealing by iron loss generated in the iron core by passing a high-frequency current through the U-shaped conductor. It is characterized by.

According to a third aspect of the present invention, there is provided a method of annealing an iron core, wherein a high frequency current is applied to a conductor which penetrates a hollow portion of a cylindrical iron core having an inner peripheral portion or an outer peripheral portion having an uneven portion. In the method of annealing an iron core which is annealed by the iron loss generated in 1), a short-circuit ring is attached to each of the outer circumference and the inner circumference of the iron core, and the annealing is performed.

[0013]

According to the iron core annealing method of the first aspect, since the auxiliary magnetic path formed according to the shape of the concave and convex portions of the iron core is arranged and the annealing is performed by the high frequency current, the magnetic flux generated in the iron core is generated. Flows sufficiently not only to the outer or inner peripheral portion but also to the convex portion of the iron core through the auxiliary magnetic path, so the amount of iron loss generated in the convex portion of the iron core is approximately the same as that of the outer or inner peripheral portion. The uniform annealing can be performed on the entire iron core.

According to the iron core annealing method of claim 2,
The magnetic flux generated by passing a high-frequency current through the U-shaped conductor inserted in the two recesses of the uneven portion of the iron core causes the protrusions adjacent to the recesses and the outer peripheral portion (or inner peripheral portion) forming the bases thereof and the convex portions. Since the ring-shaped auxiliary magnetic path that is in contact with the tip of the core flows as a magnetic path, both the convex portion and the outer peripheral portion (or the inner peripheral portion) of the iron core are heated due to iron loss, and the same effect as in claim 1 is obtained.

According to the iron core annealing method of claim 3,
Since the Joule loss generated by the short-circuit current flowing in the short-circuit between the outer circumference and the inner circumference of the iron core formed by the short-circuit ring can compensate for the shortage of the heating amount of the convex portion of the iron core, the same as claim 1. Can be obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. The stator core (iron core) 8 of the electric motor, which is formed by stacking silicon steel plates into a cylindrical shape, is such that the rotor is housed in the hollow portion of the cylinder when assembled as an electric motor. A large number of concave and convex portions are provided in a portion facing a so-called gap with the child. A winding conductor is wound around the slot 8a, which is the concave portion of the uneven portion.

An auxiliary magnetic path 9 formed to match the shape of the slot 8a is arranged in each slot 8a.
The conductor 10 is passed through the hollow portion of the stator core 8 in which the rotor is housed. The conductor 10
Is connected to a high frequency power source (not shown), and the high frequency current is supplied from the power source.

Next, the operation of this embodiment will be described. Conductor 1
When a high-frequency current i is supplied from a high-frequency power source (not shown in FIG. 0), when the high-frequency current i is flowing from the side facing the paper toward the front, as shown in FIG. Counterclockwise by stator core 8
Occurs in the circumferential direction. The magnetic field H generated is H = i
It is represented by / (2πr).

Here, r is a distance with the conductor 10 as the center. That is, since the magnetic field H decreases in inverse proportion to the distance r, the teeth portion 8 that is a convex portion near the center of the stator core 8 is formed.
The magnetic field applied to b is large, and the magnetic field applied to the outer peripheral yoke portion 8c is small. Conventionally, the slot 8a was present as a gap with respect to the magnetic flux induced by the magnetic field, and therefore the magnetic flux density induced in the tooth portion 8b was very small.

However, in this embodiment, since the gap is filled by the auxiliary magnetic path 9, the magnetic flux density induced is increased. Also, the teeth portion 8b
The amount of magnetic flux decreases due to the existence of the contact surface between the auxiliary magnetic path 9 and the auxiliary magnetic path 9, but since the strength of the magnetic field is strong in this portion as described above,
The magnetic flux densities of the tooth portion 8b and the yoke portion 8c are substantially equal. Therefore, the iron loss generated in the stator core 8 is generated in substantially the same manner in each part, the calorific value, that is, the temperature distribution is substantially uniform, and the stator core 8 can be given a sufficient annealing effect.

The material of the auxiliary magnetic path 9 is the stator core 8
Similarly to the above, it is made of a material having a small iron loss, such as a thin silicon steel plate or ferrite, so that the temperature does not rise. Therefore, even if the stator core 8 made of a silicon steel plate is heated to near the Curie point, the auxiliary magnetic path 9 can continue to be heated while being kept at a relatively low temperature.

As described above, according to this embodiment, the auxiliary magnetic path 9 is arranged in the slot 8a in the inner peripheral portion of the stator core 8,
Since the stator core 8 is annealed by the iron loss caused by the electromagnetic induction effect of the high frequency current, unlike the conventional case, a large difference in magnetic flux density does not occur between the teeth portion 8b and the yoke portion 8c. It is possible to obtain a substantially uniform heat generation state without causing heat generation unevenness, and to give a sufficient annealing effect to the stator core 8.

Next, the second embodiment of the present invention will be described with reference to FIG.
And FIG. 4 will be described. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below. The U-shaped conductor 11 shown in FIG. 4 is insulated on its surface other than the power supply terminal portion, and has two teeth 8b between two adjacent slots 8a instead of the auxiliary magnetic path 9 of the first embodiment. It is inserted so as to sandwich it. Here, for the sake of explanation, the slot 8a has n (n is an even number).
Assuming that there are individual items, numbers 1 to n are assigned to identify them.

First, the first U-shaped conductor 11 is inserted into the first slot 8a (1) and the second slot 8a (2) in the direction from the side facing the page to the front side. The second U-shaped conductor 11 is inserted into the second slot 8a (2) and the third slot 8a (3). The third U-shaped conductor 11 is inserted into the third slot 8a (3) and the fourth slot 8a (4).

Thereafter, the slots 8a are sequentially shifted one by one, and the U-shaped conductors 11 are inserted into the n-shaped U-shaped conductors 11.
Is inserted in the stator core 8. The n U-shaped conductors 11 are energized by a high frequency power source (not shown). In addition, the ring-shaped auxiliary magnetic path 12 is provided in the hollow portion of the stator core 8 in the teeth portion 8b.
It is arranged so as to contact the tip of the.

Next, the operation of the second embodiment will be described. First slot 8a (1) to nth slot 8a
The U-shaped conductor 11 inserted up to (n) is supplied with a high-frequency current i from a high-frequency power source (not shown), and the two U-shaped conductors 11 inserted into the same slot 8a have the same direction and are inserted into the adjacent slot 8a. The two U-shaped conductors 11 are energized in the opposite directions. Then, the generated magnetic flux φ is generated along the loop of the magnetic path formed by the adjacent tooth portion 8b and yoke portion 8c and the auxiliary magnetic path 12. Along with that, iron loss is generated in the teeth portion 8b and the yoke portion 8c to generate heat. Therefore, when the teeth portion 8b and the yoke portion 8c are annealed in accordance with the same magnetic flux flow, iron loss is similarly generated in both and annealing is performed substantially uniformly.

In the above description, the U-shaped conductor 11 is inserted into the two adjacent slots 8a for annealing for the sake of convenience. However, when the U-shaped conductor 11 is actually inserted, the teeth 8b and the yoke are inserted. Considering that the amount of magnetic flux flowing to the portion 8c is substantially the same, the plurality of tooth portions 8b are positioned between both arm portions of the U-shaped conductor 11, and the width of the plurality of tooth portions 8b is set. The total dimension is determined to be substantially equal to the width dimension D of the yoke portion 8c.

As described above, according to the second embodiment, the U-shaped conductor 11 is inserted into the two slots 8a of the stator core 8 and the auxiliary magnetic path 12 is brought into contact with the tips of the teeth 8b. Since the stator core 8 is annealed by generating magnetic flux in the magnetic path centering on the tooth portion 8b formed by arranging the tooth portion 8b in the same manner as in the first embodiment.
And the yoke portion 8c can be provided with substantially the same amount of heat generation.

Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described below. 5, which shows a cross-sectional view of the stator core 8, the auxiliary magnetic path 9 is not installed, a short-circuit ring 13a made of a conductive material is attached to the outer periphery of the stator core 8, and the stator core 8 is attached. A short-circuit ring 13b made of a conductive material is attached to the hollow portion of the iron core 8 so as to come into contact with the tips of the teeth portion 8b which is the inner periphery thereof.

Next, the operation of the third embodiment will be described. When the exciting conductor 10 is energized and a high-frequency current i flows,
Similar to the first embodiment, the magnetic flux φ is induced around the yoke portion 8c, which is the outer peripheral portion, and iron loss occurs in the stator core 8. At the same time, since the short-circuit rings 13a and 13b are installed, the stator core 8 has the teeth portion 8b to the yoke portion 8c.
Since a short circuit leading up to is formed, a short circuit current I flows through the short circuit and Joule loss occurs due to the resistance value of the stator core 8 itself.

Since the Joule loss is inversely proportional to the cross-sectional area of the portion where the current flows, the generated loss is large in the tooth portion 8b having a small cross-sectional area and small in the yoke portion 8c having a large cross-sectional area. Therefore, the Joule loss due to the short-circuit current is generated so as to supplement the heat generation amount of the teeth portion 8b having a small iron loss, and as a result, the heat generation amounts of the teeth portion 8b and the yoke portion 8c are substantially equal.

As described above, according to the third embodiment, by mounting the short-circuit rings 13a and 13b so as to contact the outer periphery of the stator core 8 and the tips of the teeth 8b, the conductor 1
The short-circuit current I flows in the short-circuit circuit formed by the short-circuit rings 13a and 13b in response to the high-frequency current i flowing to 0, and a large Joule loss is applied to the tooth portion 8b. The calorific value of the portion 8c is substantially equal, and the temperature distribution of the stator core 8 becomes uniform, so that a sufficient annealing effect can be provided.

The present invention is not limited to the embodiments described above and shown in the drawings, but the following modifications are possible. Although the stator core of the electric motor has been described as the iron core, it may be a rotor iron core having an uneven portion on the outer peripheral portion, and not limited to the iron core of the electric motor, the point is that the outer peripheral portion or the inner peripheral portion is cylindrical. Any iron core having an uneven portion on at least one side can be appropriately applied.

[0034]

Since the present invention is as described above,
The following effects are obtained. According to the iron core annealing method of claim 1, the auxiliary magnetic path formed in conformity with the shape of the concave and convex portions formed on the inner peripheral portion or the outer peripheral portion of the iron core is arranged to perform annealing by a high frequency current. Therefore, the magnetic flux generated in the iron core flows not only to the outer peripheral portion or the inner peripheral portion but also to the convex portion of the iron core through the auxiliary magnetic path, and the amount of iron loss generated in the convex portion of the iron core is equal to that of the outer peripheral portion or the inner peripheral portion. The heat generation becomes almost equal to that of the inner peripheral portion, a uniform heat generation state can be obtained, and a sufficient annealing effect can be given to the iron core.

According to the iron annealing method of claim 2,
The magnetic flux generated by passing a high-frequency current through the U-shaped conductor inserted in the two concave portions of the concave and convex portions formed on the inner or outer peripheral portion of the iron core forms the convex portions adjacent to the concave portions and their bases. The ring-shaped auxiliary magnetic path that is in contact with the outer peripheral portion or the inner peripheral portion and the tip of the convex portion flows as a magnetic path, so iron loss occurs in both the convex portion and the outer peripheral portion or the inner peripheral portion, and the same effect as in claim 1 is obtained. Is obtained.

According to the iron core annealing method of claim 3,
By the Joule loss generated by the short-circuit current flowing in the short-circuit between the outer circumference and the inner circumference of the iron core formed by the short-circuit ring, it is possible to compensate for the shortage of heating amount due to the shortage of iron loss of the convex portion of the iron core, The same effect as that of the item 1 is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of a stator core with an auxiliary magnetic path installed according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the same.

FIG. 3 is a view corresponding to FIG. 2 in a state in which a U-shaped conductor showing a second embodiment of the present invention is installed.

FIG. 4 is a perspective view of a U-shaped conductor.

FIG. 5 is a view corresponding to FIG. 2 showing a state in which a short-circuit ring is installed showing a third embodiment of the present invention.

FIG. 6 is a diagram showing a first example of a conventional technique.

FIG. 7 is a diagram showing a second example of the prior art.

[Explanation of symbols]

8 is a stator core (iron core), 8a is a slot (recess), 8
b is a tooth portion (convex portion), 8c is a yoke portion (outer peripheral portion),
Reference numeral 9 is an auxiliary magnetic path, 10 is a conductor, 11 is a U-shaped conductor, 12 is an auxiliary magnetic path, and 13a and 13b are short-circuit rings.

Claims (3)

[Claims] 1. An iron core having a cylindrical iron core having an inner peripheral portion or an outer peripheral portion having irregularities formed thereon, a high-frequency current is passed through a conductor penetrating the hollow portion, and the core is annealed by iron loss generated in the iron core. The annealing method of the iron core, wherein the annealing is performed by disposing an auxiliary magnetic path formed in conformity with the shape of the concave portion of the uneven portion. 2. A U-shaped conductor is inserted into two concave portions of the concave and convex portion so as to sandwich the convex portion existing between the cylindrical iron core having the concave and convex portions formed on the inner peripheral portion or the outer peripheral portion. A method for annealing an iron core is characterized in that a ring-shaped auxiliary magnetic path is arranged so as to be in contact with the tip of the convex portion, and a high-frequency current is passed through the U-shaped conductor to perform annealing by iron loss generated in the iron core. 3. An iron core which is annealed by iron loss generated in a core, in which a high frequency current is applied to a conductor which penetrates the hollow portion of a cylindrical iron core having an inner peripheral portion or an outer peripheral portion having irregularities. The annealing method of the iron core, wherein the annealing is performed by mounting short-circuit rings that are in contact with the outer circumference and the inner circumference of the iron core, respectively.