JP2017157806A - Wound core and method of manufacturing wound core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wound core which has an excellent iron loss characteristic, and a method of manufacturing the wound core.SOLUTION: A wound core 10 is provided that has wound thickness of 40 mm or more and is comprised of: an inner iron core which is arranged in an inner surface 11 side; and an outer iron core which is arranged on an outer surface side of the inner iron core. The wound thickness of the inner iron core is an inner dimension shown by the following formula (1), 19*Ln(t)-54-0.05*t≤v≤19*Ln(t)-54+0.05*t ---(1) (In the formula (1), v is an inner dimension, t is the wound thickness of the wound core, and Ln() is a logarithm with natural logarithm as a base). A grain-oriented magnetic steel sheet forming an inner iron core 13 of grain-oriented magnetic steel sheets, includes a plurality of curved bent parts in side view. In an outer iron core 23, a space factor of the grain-oriented magnetic steel sheet is higher than that of the inner iron core.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wound core and a method for manufacturing the wound core.

A wound iron core is used as a magnetic core for a reactor, a filter, or a transformer.
Conventionally, as a wound iron core, for example, there are those described in Patent Documents 1 to 4.
Patent Document 1 describes a wound core in which the space factor of the iron core material in the corner portion is lower than the space factor of the iron core material in the side portion excluding the corner portion. In the wound iron core described in Patent Document 1, since it is possible to prevent the joint portion formed by each iron core material from opening, an increase in iron loss can be suppressed.

In Patent Document 2, when a wound iron core is manufactured through a strain relief annealing process after laminating metal ribbons, the dew point of the stress relief annealing atmosphere is set to 0 ° C. or less to provide a wound iron core with low iron loss. The manufacturing technique is described.
In Patent Document 3, linear or point-strain distortion approximately perpendicular to the rolling direction of the steel sheet is applied to the surface of the steel sheet constituting the iron core at a substantially constant interval in the rolling direction by laser irradiation. Describes a technique for reducing iron loss.
Patent Document 4 describes a wound iron core formed by overlapping a plurality of magnetic steel plates bent in an annular shape and having different lengths in the outer circumferential direction.

  Non-Patent Document 1 describes a method of manufacturing a wound core in which a steel sheet is sheared into a predetermined length, wound into a circle, and pressed into a predetermined shape. Non-Patent Document 1 describes a wound iron core in which the shape of a portion deformed by press working is not a constant curvature.

Japanese Patent Laying-Open No. 2015-141930 Japanese Patent Laid-Open No. 10-256065 JP 2003-347128 A Utility Model Registration No. 3081863

Insulation / Circuits July 1975 `` A Case for Die Formed Transformer Cores ''

However, the conventional wound core has been required to further reduce the iron loss.
This invention is made | formed in view of said situation, and makes it a subject to provide the manufacturing method of a wound iron core with favorable iron loss characteristics, and a wound iron core.

[1] A wound iron core having a winding thickness of 40 mm or more in which a plurality of directional electrical steel sheets having a ring shape in a side view are laminated in a plate thickness direction;
It consists of an inner iron core disposed on the inner surface side and an outer iron core disposed on the outer surface side of the inner iron core, and the winding thickness of the inner iron core is an inner dimension represented by the following formula (1),
The directional electrical steel sheet forming the inner iron core among the directional electrical steel sheets has a plurality of bent portions that are curved in side view and formed of a metal structure including twins.
The outer iron core has a higher space factor of the grain-oriented electrical steel sheet than the inner iron core.
19 * Ln (t) −54−0.05 * t ≦ v ≦ 19 * Ln (t) −54 + 0.05 * t (1)
(In formula (1), v represents the inner dimension, t represents the winding thickness of the wound core, and Ln () represents the logarithm with the natural logarithm as the base.)

[2] The wound iron core according to [1], wherein the shortest distance among the distances between adjacent bent portions in the inner iron core is 6 mm or more.
[3] The wound core according to [1] or [2], wherein a radius of curvature of the bent portion is 0.1 mm to 100 mm.
[4] A bending that satisfies the following formula (2) in which the directional electrical steel sheet forming the inner iron core is alternately arranged with straight portions and curved portions having one vertex in the outer surface direction in a side view. The wound core according to any one of [1] to [3], which has a shape in which four shapes are connected.
Φ × m (2 ≦ m) = 90 °
(In Formula (2), Φ indicates the angular difference in the extending direction of two linear portions adjacent to each other through the curved portion, and m indicates the number of curved portions.)

[5] A method for producing a wound core according to any one of [1] to [4],
A plurality of strip-shaped directional electrical steel sheets are each bent and formed into an annular similar shape in side view, and laminated in the thickness direction so that the inner thickness is the inner dimension represented by the following formula (1) An inner core forming process for forming an iron core;
An outer core forming step in which a strip-shaped directional electrical steel sheet is sheared to a predetermined length, wound into a circle, formed into an annular shape in a side view by pressing, and then subjected to strain relief annealing to form an outer iron core; ,
A method of manufacturing a wound iron core, comprising: a step of filling the inner iron core into the center of the outer iron core to form a wound iron core having a winding thickness of 40 mm or more.
19 * Ln (t) −54−0.05 * t ≦ v ≦ 19 * Ln (t) −54 + 0.05 * t (1)
(In formula (1), v represents the inner dimension, t represents the winding thickness of the wound core, and Ln () represents the logarithm with the natural logarithm as the base.)

[6] In the inert gas atmosphere, at the temperature of 700 ° C. to 1000 ° C., for 0.01 to 30 hours, the directional electrical steel sheet before lamination after the bending process, and the inner iron core before being inserted into the center of the outer iron core The method for producing a wound core according to [5], including an annealing step of annealing any of the wound cores after the filling step.
[7] The method for manufacturing a wound iron core according to [5] or [6], wherein the bending process is performed at a plate temperature of the grain-oriented electrical steel sheet of 3 ° C or lower or 200 ° C or higher.

The wound core of the present invention has a winding thickness of 40 mm or more, and is composed of an inner core disposed on the inner surface side and an outer core disposed on the outer surface side of the inner core, and the winding thickness of the inner core is represented by the following formula (1 ), And the grain-oriented electrical steel sheet forming the inner iron core has a plurality of bent portions formed in a metal structure including twins in a side view. It is good.
Moreover, in the wound iron core of the present invention, the outer iron core has a higher space factor of the grain-oriented electrical steel sheet than the inner iron core. For this reason, the iron loss characteristic which was excellent compared with the wound iron core which consists of said inner iron core which made winding thickness 40 mm or more, for example is acquired.

It is the schematic diagram which looked at the wound iron core of this embodiment from the side surface side of a grain-oriented electrical steel sheet. It is the enlarged view which looked at a part of one grain-oriented electrical steel plate which forms the inner core of the wound iron core shown in FIG. It is the enlarged view which looked at a part of one grain-oriented electrical steel plate which forms the inner core of the wound iron core shown in FIG. In the manufacturing method of the wound iron core of this embodiment, it is explanatory drawing for demonstrating an inner iron core formation process. In the manufacturing method of the wound iron core of this embodiment, it is explanatory drawing for demonstrating an outer iron core formation process. It is an optical microscope photograph of the grain-oriented electrical steel sheet which forms the inner side iron core (iron core B) used for (iron core B'-1). It is an optical microscope photograph of the grain-oriented electrical steel sheet which forms the inner side iron core (iron core B-1) used for (iron core B'-2). It is an optical microscope photograph of the grain-oriented electrical steel sheet which forms (iron core A).

  In order to solve the above-mentioned problems, the present inventors sheared a band-shaped grain-oriented electrical steel sheet to a predetermined length, wound it into a circle, formed it into an annular shape in a side view by pressing, and then removed the distortion. The wound iron core formed by annealing was intensively studied and the following knowledge was obtained.

  In the wound iron core obtained by the above-described manufacturing method, there is a case where the working strain of the grain-oriented electrical steel sheet disposed on the inner surface side is not sufficiently released in spite of performing strain relief annealing. Since the magnetic resistance is small on the inner surface side of the wound core, the magnetic flux is concentrated. Therefore, the working strain remaining on the grain-oriented electrical steel sheet disposed on the inner surface side of the wound iron core tends to cause iron loss deterioration.

  Further, in the wound iron core obtained by the above manufacturing method, there is a case where working strain remains only in a curved portion in a side view in the grain-oriented electrical steel sheet arranged on the inner surface side. The working strain remaining on the grain-oriented electrical steel sheet deteriorates the magnetostriction. For this reason, when the wound iron core is excited, the volume of the portion where the processing strain remains locally expands, and stress may be applied to the grain-oriented electrical steel sheet disposed on the outer surface side, leading to deterioration of the iron loss. there were.

Then, the present inventors diligently studied to suppress the iron loss deterioration caused by the working strain remaining in the grain-oriented electrical steel sheet disposed on the inner surface side.
As a result, the grain-oriented electrical steel sheet (hereinafter sometimes referred to as “twinned steel sheet”) having a plurality of bent portions with a curved side view formed of a metallographic structure including twins on the inner surface side of the wound iron core. It has been found that a plurality of cores may be formed of iron cores laminated in the thickness direction. Moreover, it discovered that each twin-containing steel plate used for the inner surface side of a wound iron core was obtained by bending a directional electromagnetic steel plate and forming it into an annular shape when viewed from the side.

  However, an iron core formed by laminating a plurality of twin-containing steel plates in the thickness direction has a low space factor of grain-oriented electrical steel plates. For this reason, when the inner surface side of the wound iron core is formed of an iron core obtained by laminating the twin-containing steel sheet in the thickness direction, the ratio of the winding thickness of the iron core made of the twin-containing steel sheet in the wound thickness of the wound iron core If the amount is excessively increased, the space factor of the directional electromagnetic steel sheet of the whole wound core becomes low, and the iron loss characteristic of the wound core is deteriorated.

Therefore, the present inventors formed the outer surface side of the wound iron core with an iron core having a higher space factor of the directional electromagnetic steel sheet than the iron core in which the twin-containing steel sheets are laminated in the plate thickness direction, and the outer surface side iron core. To optimize the position of the boundary between the inner core and the inner core.
That is, from the viewpoint of the space factor of the grain-oriented electrical steel sheet, the position of the boundary between the outer surface side iron core and the inner surface side iron core is preferably set to the inner surface side. However, if the position of the boundary between the outer surface side iron core and the inner surface side iron core is too much on the inner surface side, the shape of the grain-oriented electrical steel sheet arranged on the inner surface side in the outer surface side core becomes small. For this reason, the working strain of the grain-oriented electrical steel sheet disposed on the inner surface side of the outer iron core cannot be sufficiently reduced, and the iron loss deterioration due to the work strain of the grain-oriented electrical steel sheet cannot be sufficiently suppressed.

  Therefore, the present inventors have further studied, and by making the winding thickness of the wound core 40 mm or more, the side view shape of the grain-oriented electrical steel sheet disposed on the inner surface side of the outer core is sufficiently increased. On the other hand, after sufficiently securing the ratio of the iron core on the outer surface side in the entire wound iron core, the winding thickness of the iron core on the inner surface side was set to the inner dimension represented by the following formula (1). In this case, the effect of improving the iron loss characteristic by suppressing the processing strain of the grain-oriented electrical steel sheet arranged on the inner surface side of the iron core formed on the outer surface side is the iron loss characteristic due to the lower space factor of the iron core on the inner surface side. Thus, a wound core having an excellent iron loss characteristic can be obtained.

Hereinafter, the wound core and the manufacturing method of the wound core of the present invention will be described in detail.
"Maki iron core"
Drawing 1 is a mimetic diagram which looked at the wound iron core of this embodiment from the side of the grain-oriented electrical steel sheet.
A wound iron core 10 of the present embodiment shown in FIG. 1 is obtained by laminating a plurality of grain-oriented electrical steel sheets having a ring-like similarity type in the thickness direction.
As shown in FIG. 1, the wound core 10 includes an inner iron core 13 disposed on the inner surface 11 side and an outer iron core 23 disposed on the outer surface side of the inner iron core 13.

The winding thickness t of the wound core 10 is 40 mm or more. In the present embodiment, the winding thickness t (total winding thickness) means the total width m (kg) of the iron core, the steel core length l (m) and the electromagnetic steel sheet density ρ (= 7650 kg / m ³ ). defined by the product of m) (t = m / (l * ρ * w)). Here, the iron core length l (m) is an average value of the outermost and innermost circumferences of the iron core.
The winding thickness t of the wound core 10 can be changed depending on the thickness of the grain-oriented electrical steel sheets forming the inner core 13 and the outer core 23 and the number of laminated sheets. The winding thickness t should just be 40 mm or more, and can be suitably determined according to the voltage (capacity) at the time of exciting the wound core 10.

The winding thickness of the inner iron core 13 is an inner dimension v represented by the following formula (1).
19 * Ln (t) −54−0.05 * t ≦ v ≦ 19 * Ln (t) −54 + 0.05 * t (1)
(In formula (1), v represents the inner dimension, t represents the winding thickness of the wound core, and Ln () represents the logarithm with the natural logarithm as the base.)

The winding thickness of the inner iron core 13 is the product of the thickness of the grain-oriented electrical steel sheet used for the inner iron core 13 and the number of laminated sheets. The winding thickness of the inner iron core 13 is preferably in the state shown below.
That is, the number of laminated directional electrical steel sheets used for the inner iron core 13 is the number that minimizes the value represented by the following formula (3).
| V ₀ −k × n | (3)
(In Formula (3), v ₀ represents the target inner dimension represented by the following Formula (5), k represents the thickness of the grain-oriented electrical steel sheet, n represents the number of laminated grain-oriented electrical steel sheets, and | Indicates absolute value.)
v ₀ = 19 * Ln (t) −54 (5)
(In Expression (5), v ₀ represents the target inner dimension, t represents the winding thickness of the wound core, and Ln () represents the logarithm with the natural logarithm as the base.)

  In the wound iron core 10 shown in FIG. 1, the directional electromagnetic steel sheet forming the inner iron core 13 among the directional electromagnetic steel sheets includes a plurality of bent portions having a curved shape in a side view formed of a metal structure including twins. It has a twin-containing steel plate. FIG. 2 is an enlarged view of a part of one grain-oriented electrical steel sheet (twinned steel sheet 17) forming the inner core 13 of the wound core 10 shown in FIG. In FIG. 2, one bending part 18 of the some bending part which the twin-containing steel plate 17 has, and its periphery are shown. The bent portion in the present embodiment refers to a region s surrounded by points D, E, F, and G on the twin-containing steel plate 17 shown in FIG. means.

The bent portion 18 (region s) shown in FIG. 2 is determined as follows. First, the center point A of the radius of curvature r (the radius of curvature of the bent portion 18) in the side-curved portion of the twin-containing steel plate 17 shown in FIG. 2 is arranged on both sides of the side-curved portion. The intersection point B with the extending direction of the straight line portion in side view is connected by a line. The point where the line connecting the center point A of the radius of curvature r and the intersection point B intersects the inner surface of the twin-containing steel plate 17 is defined as the origin C. Next, the points moved along the inner surface of the twin-containing steel plate 17 on both sides of the origin C by the distance m represented by the following formula (4) are designated as point D and point E, respectively. The intersections of the vertical lines drawn from the outer surface of the twin-containing steel sheet 17 toward the points D and E and the outer surface of the twin-containing steel sheet 17 are defined as a point F and a point G, respectively.
m = r * (1 + π / 4) (4)
(In Expression (4), m represents a distance, and r represents a radius of curvature.)

The density of twins included in the metal structure of the bent portion of the twin-containing steel sheet 17 is not particularly limited.
Whether or not the metal structure of the bent portion of the twin-containing steel sheet 17 contains twins can be confirmed by observing the cross section of the twin-containing steel sheet 17 with an optical microscope. As the optical microscope, a commercially available general optical microscope can be used. When observing the cross section of the twin-containing steel plate 17 with an optical microscope, a sample having the cross-section as the observation surface is cut out from the twin-containing steel plate 17, and the observation surface is mirror-polished and then corroded with acid. What is necessary is just to process to such an extent that a field can be observed.

  In the metallographic structure of the twin-containing steel sheet 17, there may be dislocations resulting from bending the grain-oriented electrical steel sheet. In the metal structure of the twin-containing steel plate 17, a transition may exist or a transition may not exist. When there is no transition in the metal structure of the twin-containing steel plate 17, it is preferable because a more excellent iron loss characteristic can be obtained.

  Whether or not dislocations are present in the metal structure of the twin-containing steel sheet 17 is the same as in the case of confirming whether the metal structure of the bent portion contains twins or not. This can be confirmed by observing with an optical microscope. As the optical microscope, a commercially available general optical microscope can be used. When observing the cross section of the twin-containing steel plate 17 with an optical microscope, a sample having the cross-section as the observation surface is cut out from the twin-containing steel plate 17, and the observation surface is mirror-polished and then corroded with acid. What is necessary is just to process to such an extent that a field can be observed.

  The shortest distance among the distances between adjacent bent portions in the inner iron core 13 is preferably 6 mm or more. When the distance is 6 mm or more, it is possible to prevent the strain introduced by bending the grain-oriented electrical steel sheet from overlapping with the strain introduced to form the adjacent bent portion and becoming difficult to come off. . For this reason, even more excellent iron loss characteristics can be obtained.

  FIG. 3 is an enlarged view of a part of one grain-oriented electrical steel sheet (twinned steel sheet 17) forming the inner core 13 of the wound core 10 shown in FIG. FIG. 3 shows two bent portions 18 and 18 ′ of the plurality of bent portions of the twin-containing steel plate 17 and the periphery thereof. 3, the same members as those in FIG. 2 are denoted by the same reference numerals as those in FIG.

  In this embodiment, the shortest distance among the distances between adjacent bent portions in the inner iron core 13 is points C and C on the inner surface of the twin-containing steel plate 17 shown in FIG. It means the shortest distance among the distances along the inner surface of the twin-containing steel plate 17 between. The origin C ′ on the inner surface of the twin-containing steel plate 17 shown in FIG. 3 is determined in the same manner as the origin C. That is, the intersection of the center point A ′ of the radius of curvature r ′ of the bent portion 18 ′ adjacent to the bent portion 18 and the extending direction of the side-view straight line portions respectively disposed on both sides of the side-view curved portion. Connect B 'with a line. The point where the line connecting the center point A ′ of the radius of curvature r ′ and the intersection point B ′ intersects the inner surface of the twin-containing steel sheet 17 is defined as the origin C ′.

  In addition, since the inner iron core 13 is formed by laminating a plurality of twin-containing steel plates 17 formed in a ring-like similar shape in the side view in the thickness direction, the shortest distance among the distances between the adjacent bent portions. Varies depending on each twin-containing steel plate 17. The shortest distance among the distances between adjacent bent portions in the present embodiment is the twin-containing steel sheet 17 arranged on the innermost surface side among the twin-containing steel sheets 17 forming the inner core 13. It means the shortest distance among the distances along the inner surface of the twin-containing steel plate 17 between the points C and C ′.

  The radius of curvature of the bent portion is preferably 0.1 mm to 100 mm. When the curvature radius of the bent portion is 0.1 mm or more, the insulating coating applied to the twin-containing steel plate 17 is peeled off by the fine shape undulation (unevenness) of the steel plate surface layer introduced by the bending process. Can be prevented. Further, when the curvature radius of the bent portion is 0.1 mm or more, by laminating the twin-containing steel plates 17, fine shape undulations existing on the surface layer of each twin-containing steel plate 17 overlap, and the use of the wound core At times, a huge eddy current can be generated to prevent deterioration of characteristics. Moreover, when the curvature radius of the bending part shape | molded by the bending process is 100 mm or less, since the twin is fully introduce | transduced into the twin-containing steel plate 17, the much more excellent iron loss characteristic is acquired. Furthermore, when the radius of curvature of the bent portion is 100 mm or less, since the amount of strain introduced by the bending process is small, the bent portion is elastically deformed when the twin-containing steel sheet 17 is laminated, and stress is generated. It is possible to prevent the iron loss from deteriorating.

As shown in FIG. 1, each twin-containing steel plate 17 forming the inner iron core 13 is formed by alternately arranging straight portions 14 and curved portions 15 having one vertex in the outer surface direction in a side view. It is preferable to have a shape in which four bending shapes 16 satisfying the following formula (2) are connected.
Φ × m (2 ≦ m) = 90 °
(In Formula (2), Φ indicates the angular difference in the extending direction of two linear portions adjacent to each other through the curved portion, and m indicates the number of curved portions.)

  As shown in FIGS. 1 to 3, in this embodiment, each twin-containing steel sheet 17 has an angle difference Φ in the extending direction between two straight portions 14 and 14 adjacent to each other via the curved portion 15 in a side view. Is 45 °, and has four bent shapes 16 in which the number of curved portions 15 is two. Said angle difference (PHI) should just be 2 or more of the curve parts 15, for example, 30 degrees may be sufficient and 10 degrees may be sufficient. It is preferable that the angle difference Φ is 45 ° or 30 ° (that is, when the number of the curved portions 15 is 2 or 3) because an even better iron loss characteristic can be obtained. When the angle difference Φ is 45 ° or more, the processing strain caused by bending the grain-oriented electrical steel sheet becomes large, and even if the twin-containing steel sheet 17 is annealed, the processing strain in the bent portion is increased. Is not preferred because it tends to remain.

The outer iron core 23 forming the wound iron core 10 has a higher space factor of the grain-oriented electrical steel sheet than the inner iron core 13. The space factor of the outer iron core 23 and the inner iron core 13 indicates the ratio of the area occupied by the iron core material to the cross-sectional area of the wound iron core, and its definition is as follows.
The space factor in the present embodiment is a value (%) obtained by multiplying the value of S _eff / S _im obtained by dividing the actual cross-sectional area S _eff by the apparent cross-sectional area S _im of the iron core by 100. Here, the substantial cross-sectional area S _eff is a value obtained by dividing the product of the total weight m (kg) of the iron core and the density of the magnetic steel sheet ρ (= 7650 kg / m ³ ) by the iron core length l (m) (S _eff = m * l * ρ). The iron core length l (m) is an average value of the outermost circumference and the innermost circumference of the iron core. The apparent cross-sectional area S _im of the iron core is a product (S _im = κ * w * n) of the nominal plate thickness κ, the plate width w, and the number n of stacked layers.

  Further, as shown in FIG. 1, the outer iron core 23 is preferably substantially rectangular in a side view, and the four corner portions 25 preferably have a constant radius of curvature.

"Method of manufacturing wound core"
Next, the manufacturing method of the wound iron core 10 of this embodiment is demonstrated.
To manufacture the wound core 10 of the present embodiment shown in FIG. 1, an inner core forming process for forming the inner iron core 13, an outer core forming process for forming the outer iron core 23, and the inner iron core at the center of the outer iron core 23. 13 is carried out.

"Inner iron core formation process"
In the inner iron core forming step, first, a plurality of strip-shaped directional electrical steel sheets are respectively bent as shown in FIG. 4 (a), and as shown in FIG. To mold. As a result, a plurality of twin-containing steel plates 17 having a plurality of bent portions that are curved in a side view and formed of a metal structure containing twins are formed. Next, the obtained twin-containing steel plate 17 is laminated in the plate thickness direction, thereby forming the inner iron core 13 whose winding thickness is the inner dimension v represented by the formula (1).

The shape of the twin-containing steel sheet 17 formed by bending is preferably a shape in which four bent shapes 16 satisfying the formula (2) are connected.
In the present embodiment, the thickness and the number of twin-containing steel plates 17 formed by bending are determined so that the winding thickness of the inner iron core 13 becomes the inner dimension v represented by the formula (1). Specifically, the number of laminated twin-containing steel plates 17 (orientated electrical steel plates) used for the inner iron core 13 is preferably set to a number that minimizes the value represented by the above formula (3).
As a processing machine used when bending the grain-oriented electrical steel sheet in the inner core forming step, a conventionally known machine such as a unicore processing machine can be used.

  In the inner iron core forming step, it is preferable to perform the bending process by setting the plate temperature of the grain-oriented electrical steel sheet to 3 ° C. or lower or 200 ° C. or higher. When the plate temperature of the grain-oriented electrical steel sheet is 3 ° C. or lower or 200 ° C. or higher, the mechanical strain generated by the bending process tends to change into twins. For this reason, it is possible to prevent dislocations from being formed in the metal structure of the twin-containing steel sheet 17 due to mechanical strain caused by bending. Therefore, the deterioration of the iron loss characteristic due to the transition existing in the metal structure of the twin-containing steel sheet 17 is suppressed, and the wound core 10 having even more excellent iron loss characteristics can be obtained.

"Outer iron core formation process"
In the outer iron core forming step, the band-shaped directional electromagnetic steel sheet 24 (hoop material) (see FIG. 5A) is sheared to a predetermined length and wound into a circle (see FIG. 5B). After forming into an annular shape in a side view by press working, strain relief annealing is performed to form the outer iron core 23 (see FIG. 5C).
As conditions for the press working and strain relief annealing performed in the outer iron core forming step, the same conditions as conventionally known conditions for manufacturing a wound iron core can be used.
In the outer iron core forming step, it is preferable to perform shape correction after strain relief annealing.

  The total thickness of the winding thickness of the inner iron core 13 and the winding thickness of the outer iron core 23 is 40 mm or more by adjusting the thickness of the grain-oriented electrical steel sheet used for the outer iron core 23 and the number of laminated layers. To be.

"Filling process"
Next, the inner core 13 is inserted into the center of the outer core 23 to form the wound core 10 having a winding thickness of 40 mm or more.
Through the above steps, the wound core 10 shown in FIG. 1 is obtained.

In the manufacturing method of the present embodiment, the grain-oriented electrical steel sheet after being bent in the inner core formation step and before lamination in an inert gas atmosphere at a temperature of 700 to 1000 ° C. for 0.01 to 30 hours, preferably 1 to 4 hours. (Twinned steel sheet 17) It is preferable to include an annealing step in which any one of the inner core 13 before being inserted into the center of the outer iron core and the wound core 10 after being inserted is included in the embedding step. An annealing process may be performed only once and may be performed twice or more.
By performing such an annealing step, the mechanical strain generated by the bending process can be removed from the twin-containing steel plate 17, and the wound core 10 having even more excellent iron loss characteristics can be obtained.

  By setting the temperature in the annealing process to 1000 ° C. or less, the mechanical strain generated by the bending process can be removed without losing the twins contained in the metal structure of the twin-containing steel sheet 17. Moreover, the mechanical distortion which arose by the bending process from the twin-containing steel plate 17 can fully be removed because the temperature in an annealing process shall be 700 degreeC or more.

Moreover, it is preferable that the annealing time in an annealing process is 1-4 hours. When the annealing time is 1 hour or longer, the above-described effect due to the annealing process becomes remarkable. When the annealing time is 4 hours or less, the wound core 10 can be manufactured efficiently.
Examples of the inert gas atmosphere in the annealing step include a nitrogen atmosphere and an argon atmosphere. Moreover, you may use the mixed atmosphere which consists of nitrogen and / or argon, and a trace amount hydrogen as inert gas atmosphere. When an atmosphere containing hydrogen is used as the inert gas atmosphere, oxidation of the steel sheet forming the wound iron core in the annealing process can be suppressed, which is preferable. On the other hand, in consideration of equipment costs and addition accompanying the management of hydrogen gas, it is preferable to use a nitrogen atmosphere as the inert gas atmosphere.

The wound core 10 according to the present embodiment has a winding thickness of 40 mm or more, and includes an inner iron core 13 disposed on the inner surface 11 side and an outer iron core 23 disposed on the outer surface side of the inner iron core 13. The directional electromagnetic steel sheet having a thickness of the inner dimension represented by the formula (1) and forming the inner iron core 13 includes a plurality of bent portions having a curved shape in a side view formed of a metal structure including twins. Therefore, the iron loss characteristics are good.
Moreover, in the wound core 10 of this embodiment, the outer iron core 23 has a higher space factor of the grain-oriented electrical steel sheet than the inner iron core 13. For this reason, the iron loss characteristic which was excellent compared with the wound iron core which consists of said inner iron core 13 which made winding thickness 40 mm or more, for example is acquired.

  In the manufacturing method of the wound core 10 of the present embodiment, a plurality of strip-shaped directional electrical steel sheets are each bent and formed into a similar shape with an annular shape when viewed from the side, and stacked in the thickness direction, whereby the winding thickness is calculated. The inner iron core 13 having the inner dimension indicated by (1) is formed. Further, the outer iron core 23 is formed by shearing the belt-shaped grain-oriented electrical steel sheet to a predetermined length, winding it into a circular shape, forming it into an annular shape by pressing, and then performing strain relief annealing. And the wound iron core 10 of this embodiment is obtained by inserting the inner iron core 13 in the center of the obtained outer iron core 23, and forming a wound core with a winding thickness of 40 mm or more.

  In the above-described embodiment, the case where the shapes of the plurality of bent portions in the grain-oriented electrical steel sheet forming the inner iron core 13 are all the same has been described as an example, but the inner iron core 13 is formed. Different shape may be sufficient as the shape of the some bending part in the grain-oriented electrical steel plate which is, and one part or all may be the same shape.

Hereinafter, the present invention will be specifically described by way of examples.
"Example 1"
The wound cores of the following (iron core A) (iron core A ') (iron core B) (iron core B-1) (iron core B'-1) (iron core B'-2), which are the total thicknesses shown in Tables 1 to 4, are shown below. Then, the “iron core loss” and “material iron loss” were measured as the iron loss characteristics by the method shown below, and “BF” was calculated. The results are shown in Tables 1-4.

(Iron Core A)
A band-shaped grain-oriented electrical steel sheet having a width of 152.4 mm and a thickness of 0.23 mm is sheared to a predetermined length and wound into a circular shape, formed into an annular shape in a side view by pressing, and then subjected to strain relief annealing. Thereafter, the iron core A was formed by performing shape correction. The iron core A has a substantially rectangular shape when viewed from the side, and the four corner portions have a constant radius of curvature. The space factor of the iron core A was 97%.

(Iron Core A ')
The grain-oriented electrical steel sheet was removed from the inner surface side of the iron core A with the thickness corresponding to the inner winding thickness shown in Tables 1 to 4. Thereafter, another iron core having an outer shape along the inner surface shape of the iron core A after removing the grain-oriented electrical steel sheet was formed. Another iron core was formed by annealing the iron core formed in the same manner as the iron core A to completely remove the processing strain. Then, another iron core was fitted as the inner iron core into the portion of the iron core A from which the grain-oriented electrical steel sheet was removed, and the iron core A ′ was obtained.

(Iron Core B)
A plurality of belt-shaped grain-oriented electrical steel sheets having a width of 152.4 mm and a thickness of 0.25 mm are each bent at room temperature (25 ° C.) to form an annular similar type having a plurality of bent portions in a side view. The iron core B was formed by laminating in the plate thickness direction. In the directional electrical steel sheet of the iron core B, as viewed from the side, the angle difference Φ in the extending direction of two linear portions adjacent to each other through the curved portion is 45 °, and the number of curved portions is two (2) It shall have the shape which connected the bending shape which satisfy | fills four. In the iron core B, the shortest distance among the distances between adjacent bent portions was 6 mm, and the radius of curvature of the bent portion was 1 mm. The space factor of the iron core B was 95.5%.
(Iron Core B-1)
The iron core B was annealed in a nitrogen atmosphere at a temperature of 800 ° C. for 2 hours to obtain an iron core B-1. The space factor of the iron core B-1 was 95.5%.

(Iron core B'-1)
The grain-oriented electrical steel sheet was removed from the inner surface side of the iron core A with the thickness corresponding to the inner winding thickness shown in Tables 1 to 4. Thereafter, another iron core having an outer shape along the inner surface shape of the iron core A after removing the grain-oriented electrical steel sheet was formed. Another iron core was formed in the same manner as the iron core B. Then, another iron core was fitted as an inner iron core into the portion of the iron core A from which the directional electromagnetic steel sheet was removed, and an iron core B′-1 was obtained.

(Iron core B'-2)
As another iron core, an iron core B′-2 was formed in the same manner as the iron core B′-1 except that the iron core B-1 was formed.

  In (Iron Core A ′) (Iron Core B′-1) (Iron Core B′-2), the product of the thickness of the grain-oriented electrical steel sheet forming the inner iron core and the number of laminated sheets is shown in Tables 1 to 4. It was formed by adjusting the number of laminated directional electrical steel sheets so as to have a dimension closest to the inner winding thickness of (iron core A ′) (iron core B′-1) (iron core B′-2) shown.

"Core loss"
Using the excitation current method described in JIS C 2550-1, the iron loss value of the iron core at W17 / 50 (W / kg) (conditions where the set magnetic flux density at 50 Hz is 1.7 T) was measured.
"Material iron loss"
A single plate having a width of 60 mm and a length of 300 mm is taken from a portion other than the bent portion of the grain-oriented electrical steel sheet disposed from the inner surface side of the iron core to the position corresponding to the thickness of the inner winding thickness shown in Tables 1 to 4, and a nitrogen atmosphere Inside, it annealed at the temperature of 800 degreeC for 2 hours. Thereafter, the single plate iron loss was measured by the H coil method described in JIS C2556.
In addition, (Iron Core A) (Iron Core B) (Iron Core B-1) is not inserted with another iron core as the inner iron core, and from the inner surface side to the position of the thickness of the inner winding thickness, , The same material.
"BF"
The iron core loss measured by the above method was divided by the material iron loss measured by the above method to calculate BF (building factor) (iron core loss / material iron loss).

In order to evaluate the relationship between the iron loss characteristics shown in Tables 1 to 4 and the inner winding thickness, the numerical value of the target inner dimension v _{0 represented by} the following formula (5) with respect to the winding thickness (total winding thickness) of the wound core was calculated. . The results are shown in Table 5.
v ₀ = 19 * Ln (t) −54 (5)
(In Expression (5), v ₀ represents the target inner dimension, t represents the winding thickness of the wound core, and Ln () represents the logarithm with the natural logarithm as the base.)

Whole volume thickness 40mm shown in Table 5, 50 mm, 100 mm, with reference to the target inner dimension _{v 0} of the formula (5) at 250 mm, in particular of the Tables 1, whole volume is an inner dimension which satisfies the equation (1) As a result of the thickness of 40 mm, the inner winding thickness of 15 mm, the total winding thickness of 50 mm, the inner winding thickness of 20 mm, the total winding thickness of 100 mm, the inner winding thickness of 30 mm, the total winding thickness of 250 mm, and the inner winding thickness of 50 mm. Iron loss characteristics of (iron core B′-1) (iron core B′-2) among (iron core A ′) (iron core B) (iron core B-1) (iron core B′-1) (iron core B′-2) It turns out that is excellent.

  (Iron core B'-1) (Iron core B'-2) is formed by inserting the iron core B or the iron core B-1 as an inner iron core in the portion where the directional electromagnetic steel sheet of the iron core A is removed. The iron core B and the iron core B-1 are formed by bending to form an annular similar shape having a plurality of bent portions that are curved in side view, and are laminated in the thickness direction. In particular, in the case of (iron core B'-2) using (iron core B-1) obtained by annealing (iron core B) as the inner iron core, excellent iron loss characteristics were obtained.

On the other hand, when the total winding thickness was 20 mm, the effect of improving the iron loss characteristics in (iron core B′-1) (iron core B′-2) could not be confirmed.
Moreover, even if the inner winding thickness was larger or smaller than the inner dimension v shown by the formula (1), the iron loss characteristic was deteriorated.

From these facts, it was confirmed that excellent iron loss characteristics were obtained by using a wound core satisfying the following (A) to (E).
(A) The total winding thickness should be 40 mm or more.
(B) A wound core composed of an inner iron core and an outer iron core disposed on the outer surface side of the inner iron core.
(C) The inner winding thickness is set to the inner dimension v represented by the formula (1).
(D) Use (Iron Core B) or (Iron Core B-1) as the inner iron core.
(E) As the outer iron core (iron core A), use one having a higher space factor of the grain-oriented electrical steel sheet than the inner iron core (iron core B) or (iron core B-1).

  Moreover, the directional electrical steel sheet which forms (iron core A) shown in Tables 1-4, and another iron core (inner iron core) used for (iron core B'-1) (iron core B'-2) are formed. The cross-section of the curved portion in side view was observed with an optical microscope (trade name: ECLIPSE LD100V, manufactured by Nikon Corporation) at a magnification of 100 times. The observation sample was produced by cutting out a sample from the grain-oriented electrical steel sheet with the cross section of the curved portion in the side view as the observation surface, mirror-polishing the observation surface, and then corroding with an acid. The results are shown in FIGS.

  FIG. 6 is an optical micrograph of the grain-oriented electrical steel sheet forming the inner iron core (iron core B) used for (iron core B′-1). As shown in FIG. 6, a metal structure including twins was formed on the grain-oriented electrical steel sheet. From this, it was confirmed that a grain-oriented electrical steel sheet having a plurality of bent portions having a curved shape in a side view formed of a metal structure including twins can be obtained by bending. Moreover, as shown in FIG. 6, the dislocation resulting from the bending process existed in the metal structure of the grain-oriented electrical steel sheet.

  FIG. 7 is an optical micrograph of the grain-oriented electrical steel sheet forming the inner iron core (iron core B-1) used in (iron core B′-2). As shown in FIG. 7, a metal structure including twins was formed on the grain-oriented electrical steel sheet by bending. However, as shown in FIG. 7, there was no dislocation resulting from the bending process in the metallographic structure of the grain-oriented electrical steel sheet. From this, (iron core B) was annealed under the above conditions to make (iron core B-1), and it was produced by bending from grain-oriented electrical steel sheets without losing twins contained in the metal structure. It was confirmed that mechanical strain could be removed.

  FIG. 8 is an optical micrograph of the grain-oriented electrical steel sheet forming (Iron Core A). As shown in FIG. 8, twins were not observed in the metallographic structure of the grain-oriented electrical steel sheet. From this, when the directional electrical steel sheet is sheared to a predetermined length and wound into a circular shape, and formed into an annular shape in a side view by pressing, the directional electrical steel sheet is subjected to strain relief annealing. It was confirmed that a metal structure containing twins was not formed.

  From the results of Tables 1 to 4 and FIGS. 6 to 8, (iron core B′-1) (iron core B′-2) is a metal structure in which the grain-oriented electrical steel sheet forming the inner iron core includes twins. Since it has a plurality of bent portions formed in a side view, it has been found that good iron loss characteristics can be obtained.

"Example 2"
Angular difference Φ shown in Table 6 which is (iron core B′-2) having a total winding thickness of 80 mm and an inner winding thickness of 30 mm, and the directional electrical steel sheet forming the inner core satisfies the following formula (2) in side view: The wound iron cores each having a shape in which four bent shapes, which are several m in the curved portion, are connected to each other were formed. In addition, the curvature radius of the some bending part in each inner iron core was made into the curvature radius of all the bending parts shown in Table 6.
Φ × m (2 ≦ m) = 90 °
(In Formula (2), Φ indicates the angular difference in the extending direction of two linear portions adjacent to each other through the curved portion, and m indicates the number of curved portions.)

  About each obtained wound iron core, it carried out similarly to Example 1, and measured "iron core iron loss." Subsequently, each wound iron core after measuring “iron core loss” was annealed in a nitrogen atmosphere at a temperature of 800 ° C. for 2 hours. Thereafter, “material iron loss” was measured in the same manner as in Example 1, and “BF” was calculated in the same manner as in Example 1. The results are shown in Table 6.

As shown in Table 6, when the angle difference Φ in the formula (2) is 45 ° or 30 ° (that is, the number of the curve portions 15 is 2 or 3), it is found that even better iron loss characteristics can be obtained. It was.
Moreover, as shown in Table 6, when the curvature radius of the bending part was 0.1 mm-100 mm, it turned out that the further outstanding iron loss characteristic is acquired.

"Example 3"
Folded part adjacent to the directional electromagnetic steel sheet arranged on the innermost surface side among the directional electromagnetic steel sheets that are (iron core B′-2) having a total winding thickness of 80 mm and an inner winding thickness of 30 mm. As shown in Table 7, the wound cores were formed by varying the shortest distance among the distances between them. In addition, the grain-oriented electrical steel sheet forming the inner iron core has a shape obtained by connecting four bending shapes in which the angle difference Φ satisfying the formula (2) is 45 ° and the number m of curved portions is 2 in a side view. It was supposed to have. Moreover, all the curvature radii of the some bending part in each inner side iron core were 1 mm.

  About each obtained wound iron core, it carried out similarly to Example 2, and measured "iron core iron loss" and "material iron loss", and calculated "BF". The results are shown in Table 7.

  As shown in Table 7, it was found that when the shortest distance among the distances between adjacent bent portions in the inner iron core is 6 mm or more, even better iron loss characteristics can be obtained.

Example 4
Except for performing the bending process with the plate temperature of the grain-oriented electrical steel sheet set to the temperature shown in Table 8, similarly to the wound iron core in which the distance between adjacent bent portions of Example 3 shown in Table 7 is 6 mm, A wound core was formed.
About each obtained wound iron core, it carried out similarly to Example 2, and measured "iron core iron loss" and "material iron loss", and calculated "BF". The results are shown in Table 8.

  As shown in Table 8, it was found that even better iron loss characteristics can be obtained by bending the grain-oriented electrical steel sheet at a temperature of 3 ° C. or lower or 200 ° C. or higher. This is because when the plate temperature is 3 ° C. or lower or 200 ° C. or higher, the mechanical strain generated by the bending process is likely to change into twins, so that many twins are introduced into the grain-oriented electrical steel sheet. Presumed.

  10 cores, 11 inner surfaces, 13 inner cores, 14 straight sections, 15 curved sections, 16 bent shapes, 17 twinned steel sheets, 18, 18 'bent sections, 23 outer cores, winding thickness of t core (total thickness) ), V Inside dimensions.

Claims (7)

A plurality of grain-oriented electrical steel sheets that are annular in a side view are wound cores having a winding thickness of 40 mm or more laminated in the thickness direction,
It consists of an inner iron core disposed on the inner surface side and an outer iron core disposed on the outer surface side of the inner iron core, and the winding thickness of the inner iron core is an inner dimension represented by the following formula (1),
The directional electrical steel sheet forming the inner iron core among the directional electrical steel sheets has a plurality of bent portions that are curved in side view and formed of a metal structure including twins.
The outer iron core has a higher space factor of the grain-oriented electrical steel sheet than the inner iron core.
19 * Ln (t) −54−0.05 * t ≦ v ≦ 19 * Ln (t) −54 + 0.05 * t (1)
(In formula (1), v represents the inner dimension, t represents the winding thickness of the wound core, and Ln () represents the logarithm with the natural logarithm as the base.)   2. The wound core according to claim 1, wherein the shortest distance among adjacent bent portions in the inner iron core is 6 mm or more.   The wound core according to claim 1 or 2, wherein a curvature radius of the bent portion is 0.1 mm to 100 mm. The directional electrical steel sheet forming the inner iron core has a bent shape satisfying the following formula (2) in which a straight line portion and a curved portion having one vertex in the outer surface direction are alternately arranged in a side view, The wound core according to any one of claims 1 to 3, wherein the wound core has four connected shapes.
Φ × m (2 ≦ m) = 90 °
(In Formula (2), Φ indicates the angular difference in the extending direction of two linear portions adjacent to each other through the curved portion, and m indicates the number of curved portions.) It is a manufacturing method of the volume iron core according to any one of claims 1 to 4,
A plurality of strip-shaped directional electrical steel sheets are each bent and formed into an annular similar shape in side view, and laminated in the thickness direction so that the inner thickness is the inner dimension represented by the following formula (1) An inner core forming process for forming an iron core;
An outer core forming step in which a strip-shaped directional electrical steel sheet is sheared to a predetermined length, wound into a circle, formed into an annular shape in a side view by pressing, and then subjected to strain relief annealing to form an outer iron core; ,
A method of manufacturing a wound iron core, comprising: a step of filling the inner iron core into the center of the outer iron core to form a wound iron core having a winding thickness of 40 mm or more.
19 * Ln (t) −54−0.05 * t ≦ v ≦ 19 * Ln (t) −54 + 0.05 * t (1)
(In formula (1), v represents the inner dimension, t represents the winding thickness of the wound core, and Ln () represents the logarithm with the natural logarithm as the base.)   In an inert gas atmosphere, at a temperature of 700 ° C. to 1000 ° C., for 0.01 to 30 hours, after the bending, before the lamination, the grain-oriented electrical steel sheet, the inner iron core before filling the center of the outer iron core, the filling The manufacturing method of the wound iron core of Claim 5 including the annealing process which anneals either of the said wound iron cores after a setting process.   The method for manufacturing a wound core according to claim 5 or 6, wherein the bending process is performed at a plate temperature of the grain-oriented electrical steel sheet of 3 ° C or lower or 200 ° C or higher.