JP7167779B2 - Method for manufacturing iron core, wound iron core, method for manufacturing stacked iron core, and method for manufacturing electromagnetic steel sheet for iron core - Google Patents

Description

TECHNICAL FIELD The present invention relates to an iron core, a method for producing a wound iron core, a method for producing a laminated iron core, and a method for producing an electromagnetic steel sheet for an iron core.

BACKGROUND ART Grain-oriented electrical steel sheets (hereinafter referred to as "steel sheets") in which the axes of easy magnetization are aligned in one direction are used as materials for iron cores for transformers. Iron cores are required to reduce iron loss, and as a technique for reducing iron loss, a technique of magnetic domain refining that reduces the width of the magnetic domain of a steel sheet is known. Known techniques for magnetic domain refining include, for example, a technique of applying a laser beam to the surface of a grain-oriented electrical steel sheet to introduce strain, and a technique of forming a plurality of grooves at predetermined intervals on the surface of the steel sheet.

The wound iron core is obtained by winding a laminated steel sheet, and then press-molding it into a predetermined shape. In order to remove the unnecessary distortion that occurs in the steel sheet at this time, the wound iron core after pressure forming is annealed. Since the annealing also removes strain for refining the magnetic domains, the magnetic domain refining is generally performed by forming grooves in the wound iron core.

On the other hand, there is a known technique for improving iron loss in the entire wound core by using steel sheets with different magnetic properties in the inner and outer peripheral portions of the wound core (see Patent Documents 1 to 3). ). In Patent Literatures 1 and 2, the steel plate in the inner peripheral portion of the iron core has a lower magnetic permeability than the steel plate in the outer peripheral portion, thereby making the magnetic flux density distribution in the iron core uniform. Further, in Patent Document 3, the magnetostriction of the steel plate in the inner peripheral portion of the iron core by the 0-peak method is configured to be less than the magnetostriction of the steel plate in the outer peripheral portion.

JP-A-6-120044 JP 2006-185999 A JP-A-8-203746

By the way, when producing the iron cores as in Patent Documents 1 to 3, a plurality of steel sheets with different magnetic properties are required, and these plural types of steel sheets must be laminated to produce a wound iron core. . Therefore, there is a problem that the manufacturing process of the wound iron core is complicated. In addition, it is not easy to manufacture a plurality of steel sheets with finely adjusted magnetic properties, and there is also the problem that a sufficient effect of reducing iron loss cannot be obtained.

The present invention has been made in view of the above circumstances, and an iron core capable of easily reducing iron loss, a method for manufacturing a wound iron core, a method for manufacturing a laminated iron core, and a method for manufacturing an electrical steel sheet for an iron core. intended to provide

The iron core of the present invention is an iron core for a transformer comprising a laminated body in which a plurality of steel plate pieces are laminated, wherein the steel plate piece has grooves intersecting with the rolling direction on the surface, and the steel plate piece has the above-described By changing at least one of the depth of the groove, the width of the groove, and the pitch of the groove, a closed magnetic circuit formed when the iron core is used in a transformer is formed from the inside to the outside. , the groove cross-sectional area ratio η represented by the formula (1) changes continuously or stepwise.
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece.

A method for manufacturing a wound iron core of the present invention is a method for manufacturing a wound iron core for a transformer comprising a laminate in which a plurality of steel plate pieces are laminated, in which the plurality of steel plate pieces are cut from a hoop of a grain-oriented electrical steel sheet. a groove forming step of forming grooves in the cut steel plate pieces that intersect with the rolling direction of the steel plate pieces; laminating the steel plate pieces; and a molding step of forming the wound iron core, and the groove forming step includes changing at least one of the depth of the groove, the width of the groove, and the pitch of the groove, so that the The groove cross-sectional area ratio η represented by the formula (1) is changed continuously or stepwise from the inner side to the outer side of the closed magnetic circuit formed when the wound iron core is used in the transformer.
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece.

A method for manufacturing a laminated iron core according to the present invention is a method for manufacturing a laminated iron core for a transformer comprising a laminate in which a plurality of steel plate pieces are laminated, wherein the plurality of steel plate pieces are cut from a hoop of a grain-oriented electrical steel plate. a groove forming step of forming grooves in the cut steel plate pieces that intersect with the rolling direction of the steel plate pieces; and a forming step of laminating the steel plate pieces to form the laminated iron core, In the groove forming step, by changing at least one of the depth of the groove, the width of the groove, and the pitch of the groove, a closed magnetic field is formed when the laminated iron core is used in a transformer. The groove cross-sectional area ratio η represented by the formula (1) is changed continuously or stepwise from the inner side to the outer side of the channel.
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece.

A method for manufacturing an electromagnetic steel sheet for an iron core according to the present invention is a method for manufacturing an electromagnetic steel sheet for an iron core for a transformer composed of a laminate in which a plurality of steel sheet pieces are laminated, wherein the plurality of steel sheet pieces are formed. A groove forming step of forming a plurality of grooves in each of the plurality of steel plate piece regions, wherein the groove forming step changes at least one of the depth of the groove, the width of the groove, and the pitch of the groove. , the groove cross-sectional area ratio η represented by the formula (1) is continuously or stepwise changed from the inside to the outside of the closed magnetic circuit formed when the iron core is used in the transformer. It is.
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece.

According to the present invention, by changing at least one of the depth, the width, and the pitch of the grooves formed in the steel plate piece, the groove cross-sectional area ratio of the steel plate piece can be changed to that of the iron core. The magnetic flux density distribution generated inside the iron core is easily improved because the magnetic flux density is reduced continuously or stepwise from the inside to the outside in the direction intersecting the closed magnetic circuit formed when used in iron loss can be reduced.

It is a perspective view which shows the external appearance of the wound iron core which concerns on 1st Embodiment. FIG. 3 is an explanatory view showing a steel plate piece that forms a wound iron core and has a plurality of grooves formed along the longitudinal direction of the steel plate piece. FIG. 4 is a cross-sectional view of a wound core showing grooves formed in steel plate pieces of the wound core. It is a cross-sectional view of a steel plate piece explaining the depth, width, and pitch of grooves. It is explanatory drawing which shows an example of the process of manufacturing a wound iron core. 1 is a perspective view showing an example of a groove forming device provided in a continuous processing facility for grain-oriented electrical steel sheets; FIG. It is a perspective view which shows the external appearance of the laminated iron core which concerns on 2nd Embodiment. FIG. 4 is an explanatory view showing grooves formed in each steel plate piece of the laminated iron core; It is explanatory drawing which shows the example which gradually decreases the depth of a groove|channel toward an outer periphery from an inner periphery. FIG. 5 is an explanatory view showing an example in which each portion of the steel plate piece divided in the width direction has a different groove cross-sectional area ratio. It is explanatory drawing which shows an example of the process of manufacturing a laminated iron core. 4 is a graph showing the relationship between groove cross-sectional area ratio, effective magnetic permeability, and core loss measured in Examples.

[First embodiment]
In FIG. 1, the wound iron core 10 is obtained by laminating M (M is 2 or more) layers of steel plate pieces 14 ₁ to 14 _M (see FIG. 3) in order from the inner periphery to the outer periphery. The lengths of the steel plate pieces 14 ₁ to 14 _M in the rolling direction are different from each other, and gradually increase from the steel plate piece on the inner peripheral side of the wound iron core 10 toward the steel plate piece on the outer peripheral side. The length of 14 ₁ is the shortest, and the length of the outermost steel plate piece 14 _M is the longest. A plurality of grooves 16 _i (see FIG. 3) are formed on the surface of the steel plate piece 14 _i where i is 1, 2, . In the following description, the steel plate pieces 14 ₁ to 14 _M are collectively referred to as the steel plate pieces 14 when they are not distinguished. Similarly, grooves 16 ₁ to 16 _M are collectively referred to as grooves 16 when not distinguished.

The wound iron core 10 is molded into a substantially square tubular shape having a hollow portion. The four corners of the wound iron core 10 are rounded with a predetermined curvature. The wound iron core 10 is made into a transformer by _winding a _primary winding P and a secondary winding S, for example. A magnetic circuit of magnetic flux that circulates around the hollow portion, that is, a closed magnetic circuit is formed.

A grain-oriented electrical steel sheet is used as the steel sheet pieces 14 ₁ to 14 _M. A grain-oriented electrical steel sheet is an electrical steel sheet in which the direction of the axis of easy magnetization of crystal grains (the <100> direction of a body-centered cubic crystal) is substantially aligned in the rolling direction at the time of manufacture, and the magnetization is directed in the rolling direction. has a structure in which magnetic domains are arranged with domain walls in between. Such a grain-oriented electrical steel sheet is suitable as an iron core material for a transformer in which magnetic lines of force are oriented in a fixed direction. The axes of easy magnetization of the steel plate pieces 14 ₁ to 14 _M are in the circumferential direction of the wound iron core 10 (the direction of circulation around the hollow portion).

As shown in FIG. 2, the steel plate piece _14i has a rectangular shape elongated in the rolling direction (direction of arrow A). A plurality of grooves 16 _i are formed on the surface of the steel plate piece 14 _i . Each groove 16 _i extends in the plate width direction (arrow B direction) orthogonal to the rolling direction of the steel plate piece 14 _i . The plurality of grooves 16 _i are formed at a predetermined pitch in the rolling direction of the steel plate piece 14 _i . Here, as for the forming direction of the grooves 16, it is preferable that the angle θ between the grooves 16 and the rolling direction is a right angle, that is, 90°. However, when producing a wound iron core, there is a possibility that cracks will occur starting from the groove 16 at the location where the bending process is performed. , less than 90°. Further, if the angle θ formed by the grooves 16 and the rolling direction is larger than 45°, it is possible to suppress significant deterioration of the iron loss improvement characteristic. Therefore, the angle θ between the grooves 16 and the rolling direction is preferably greater than 45° and less than or equal to 90°.

The grooves _16i are formed, for example, by irradiation with laser light. However, the method of forming the grooves _16i is not limited to laser light irradiation, and etching, machining, or the like can also be used. The method of forming the grooves 16 _i by irradiating laser light is a preferable method because the shape and pitch of the grooves can be easily controlled by changing the output of the laser, the focused diameter, the scanning speed, and the like.

In this example, the grooves 16 _i are formed in the entire region of the steel plate piece 14 _i in the rolling direction at a predetermined pitch _. You can also Such a configuration is advantageous in preventing cracking of the steel plate pieces 14 ₁ to 14 _M when the steel plate pieces 14 ₁ to 14 _M are bent into the shape of the wound iron core 10 . For example, forming shallow grooves or grooves extending in a direction inclined with respect to the width direction in the steel plate pieces 14 ₁ to 14 _M is also effective in suppressing cracking of the steel plate pieces 14 ₁ to 14 _M. be.

In FIG. 3, as described above, the wound iron core 10 has steel plate pieces 14 ₁ , 14 ₂ , . . . . It is a laminate in which _14M is layered. In this example, the steel plates 14 ₁ to 14 _M have the same thickness and width. The grooves 16 _i may be formed on at least one surface of each steel plate piece 14 _i . In this example, the grooves 16 i are formed on the inner peripheral surface of the wound iron core 10 , but are formed on the outer peripheral surface. You may Further, in each steel plate piece 14 _i layered on the wound iron core 10, the groove 16 _i is formed on the inner peripheral side without aligning the surface on which the groove 16 _i is formed on the inner peripheral side or the outer peripheral side. 14 _i may be combined with a steel plate piece 14 _i having a groove 16 _i formed on the outer peripheral side. An insulating film (not shown) is formed on the surfaces of the steel plate pieces 14 _i , but the grooves 16 _i are formed in the steel plate pieces 14 _i themselves. The trench _16i is preferably covered with an insulating film.

In order to reduce the iron loss, the wound iron core 10 is arranged in a direction intersecting the direction of a closed magnetic circuit formed when the wound iron core 10 is used in a transformer (hereinafter simply referred to as the direction of the magnetic circuit). For each closed magnetic circuit formed, the magnetic resistance along the closed magnetic circuit is made substantially equal (substantially the same). That is, in the wound iron core 10, since the steel plate pieces 14 ₁ to 14 _M are laminated between the inner circumference and the outer circumference, the magnetic resistances of the steel plate pieces 14 ₁ to 14 _M are substantially the same. In order to make the magnetic resistance substantially the same, the effective magnetic permeability of the steel plate pieces 14 ₁ to 14 _M is continuously or stepwisely decreased from the inner periphery to the outer periphery.

The magnetic resistance R _i along the closed magnetic path in the steel plate piece 14 _i is defined by μ _{e i} as the effective permeability of the steel plate piece 14 i , L _i as the magnetic path length (the length of the steel plate piece 14 _i ), and the section of the steel plate piece 14 i Assuming that the area is s _i , it can be expressed as "R _i =L _i /(μ _{e i} ×s _i )".

As described above, the length of the steel plate pieces _{14 1} to 14 _M in the rolling direction gradually increases from the inner circumference to the outer circumference _. A certain magnetic path length gradually increases from the inner circumference to the outer circumference of the wound iron core 10, the magnetic path length at the innermost circumference being the shortest and the magnetic path length at the outermost circumference being the longest. For this reason, the steel plate piece 14 _i on the inner peripheral side having a shorter magnetic path length _Li has a larger effective magnetic permeability μe _i , and the steel plate piece 14 _i on the outer peripheral side having a longer magnetic path length _Li has a smaller effective magnetic permeability μe _i . By doing so, the magnetic resistances of the steel plate pieces 14 ₁ to 14 _M can be substantially the same.

Therefore, by making the magnetic resistance of the steel plate pieces 14 ₁ to 14 _M approximately the same, the magnetic flux densities generated by the steel plate pieces 14 ₁ to 14 _M are made uniform. can be reduced.

The effective magnetic permeability μe _i of the steel plate piece 14 can be increased or decreased by changing at least one of the depth, width and pitch of the grooves 16 _i formed in the steel plate piece 14 _i . The inventors defined the groove cross-sectional area ratio (details will be described later) of the grooves 16, and when the groove cross-sectional area ratio is changed, the effective permeability does not change even if the iron loss does not change substantially. found to get. _{Based on} this, the effective _{permeability μe i} By configuring the wound iron core 10 by laminating in the order of, the magnetic resistance along the magnetic path inside the wound iron core 10 is made uniform (the magnetic resistance along each magnetic path is made the same), It was found that iron loss can be made lower.

The groove cross-sectional area ratio η of the groove 16 can be obtained, for example, by the formula (1).
η=(π・d・W)/(2・P・t) (1)
That is, focusing on one steel plate piece 14 _i , the groove cross-sectional area ratio η _i of the groove 16 _i can be obtained by the formula (1a).
η _i =(π· _di ·W _i )/(2·P _i ·t) (1a)

As shown in FIG. 4, the value W _i in the formula (1a) is the width of the groove 16 _i and the length of the opening in the surface of the steel plate piece 14 _i in the direction along the closed magnetic circuit. The value P _i is the pitch of the grooves 16 _i in the direction along the closed magnetic circuit, and the length of the interval between corresponding portions of adjacent grooves 16 _i in the direction along the closed magnetic circuit. The value d _i is the depth of the groove 16 _i and the length from the surface of the steel plate piece 14 _i to the bottom of the groove 16 _i . The value t is the thickness (plate thickness) of the steel plate piece _14i . More precisely, the values of the width W _i , the pitch P _i , and the depth d _i are different (non-uniform) in each of the plurality of grooves 16 _i on the steel plate piece 14 _i due to manufacturing variations. However, in such a case, by obtaining the average value of each value for the plurality of grooves 16 _i on the steel plate piece 14 _i , the average value is used in formula (1a), width W _i , pitch It is also possible to let P _i be the value of the depth d _i . As in the case where the grooves 16 _i are not formed in the regions corresponding to the four corners of the wound iron core 10 , the values of the width W _i , the pitch P _i , and the depth d _i are intentionally different for each portion on the steel plate piece 14 _i . , the average values can also be used as the values of width W _i , pitch P _i , and depth d _i used in equation (1a).

As the depth d _i increases, the width W _i increases, and the pitch P _i decreases, the groove cross-sectional area ratio η _i increases, and the effective permeability of the steel plate piece 14 _i can be reduced. This is because the formation of the grooves _16i creates voids with low magnetic permeability on the surfaces of the steel plate pieces _14i , thereby lowering the effective magnetic permeability.

For each required effective permeability, the depth, width and pitch of the grooves 16 _{1 -16M} to be formed in the steel plate pieces 14 _{1 -14M} can be determined experimentally, for example. In the example shown in FIG. 4, the depth d _i and the width W _i of each groove 16 _i formed in the same steel plate piece 14 _i are the same, and the pitch P _i between the plurality of grooves 16 _i is constant.

In the example shown in FIG. 4, the depth d _i , width W _i , and pitch P _i of each groove 16 _i in one steel plate piece 14 _i are constant as described above. In 14 _i , the depth d _i and width W _i of each groove 16 _i may be different, and the pitch P _i may be changed, and the effective permeability may be set to a required value.

In order to suppress the fluctuation width of the magnetic flux density in the steel plate pieces 14 ₁ to 14 _M , the fluctuation width of the magnetic resistance is preferably small, and the fluctuation rate of the magnetic resistance is preferably 5% or less, for example, 1% The following are more preferable.

As described above, in this embodiment, at least one of the depth d _i of the grooves 16 _i , the width W _i of the grooves 16 _i , and the pitch P _i of the grooves 16 _i is changed, and the steel plate pieces 14 ₁ to 14 By controlling the effective magnetic permeability of _M , the magnetic resistance in the direction crossing the rolling direction between the steel plate pieces 14 in the wound iron core 10 is made substantially the same. As a result, the magnetic flux densities of the steel plate pieces 14 ₁ to 14 _M in each layer of the wound iron core 10 become uniform, and iron loss is reduced. Since the effective permeability of the steel plate pieces 14 ₁ to 14 _M is adjusted by the groove cross-sectional area ratio, that is, the depth, width and pitch of the grooves 16 ₁ to 16 _M , the required effective permeability can be easily obtained. can be obtained, and the iron loss of the wound iron core 10 can be reduced.

In this example, the effective magnetic permeability is changed for each steel plate piece 14, but the steel plate pieces 14 constituting the wound iron core 10 are divided into a plurality of groups in the direction from the inner circumference to the outer circumference of the wound iron core 10, and the group The effective permeability may be set and changed for each. In this case, the effective magnetic permeability of each steel plate piece 14 in the group is the same, but the effective magnetic permeability of each group is made smaller from the inner circumference to the outer circumference. A group is composed of one or more steel strips 14 .

Next, a method for manufacturing the wound iron core 10 will be described with reference to FIG. In addition, the manufacturing method described below is an example, and does not limit the manufacturing method of the wound iron core 10 . First, as shown in FIG. 5A, a hoop 31 is prepared. The hoop 31 is formed by rolling a long grain-oriented electrical steel sheet 32 in which the grooves 16 are not formed. The width of the grain-oriented electrical steel sheet 32 of the hoop 31 is, for example, the same as the width of the steel plate piece 14, and the longitudinal direction of the grain-oriented electrical steel sheet 32 is the rolling direction. Next, the grain-oriented electrical steel sheet 32 is unwound from the hoop 31, and the grain-oriented electrical steel sheet 32 is sequentially cut into the respective lengths of the steel sheet pieces 14 ₁ to 14 _M to obtain the steel sheet pieces 14 ₁ to 14 _M ( cutting process). For example, by sequentially shortening the cutting length, the steel plate piece _14M on the outermost circumference to the steel plate piece 141 _on the innermost circumference can be obtained in order.

A steel sheet piece 14 cut from a grain-oriented electrical steel sheet 32 is scanned in the width direction with a laser beam from a laser device 33 to form grooves 16 extending in the width direction and intersecting the rolling direction (groove forming process). For example, while continuously moving the steel plate piece 14 _i in the rolling direction, the laser beam is scanned in the plate width direction at a scanning frequency corresponding to the pitch P _i of the grooves 16 _i . As a result, a plurality of grooves 16 _i are formed at corresponding pitches P _i in each steel plate piece 14 _i . Further, by irradiating a laser beam adjusted to a laser output and a focal diameter determined for each steel plate piece _14i , a groove _16i having a corresponding depth _di and width _Wi is formed for each steel plate piece _14i . is formed. The scanning frequency can be adjusted, for example, by the rotation and vibration frequencies of a rotating polygon mirror and a galvano motor mirror, which are laser beam scanning mechanisms. The condensed diameter of the laser beam can be realized by focus adjustment by moving a condensing lens or a condensing mirror, for example. Note that the adjustment device and adjustment method are not limited to these.

By forming the grooves 16 _i immediately after the cutting step in this manner, the grooves 16 ₁ to 16 _M having the predetermined groove cross-sectional area ratio for each of the steel plate pieces 14 ₁ to 14 _M can be reliably and easily formed. can be formed. It is also preferable to form the grooves 16 in the grain-oriented magnetic steel sheet 32 unwound from the hoop 31 and then cut the grain-oriented magnetic steel sheet 32 to form the steel sheet pieces 14 . In addition, the steel plate piece 14 may be coated with an insulating coating in order to improve the insulation between the laminated steel plates. In that case, the insulating coating may be formed after forming the grooves 16 and before the next lamination step.

As shown in FIG. 5B, steel plate pieces 14 ₁ to 14 _M having grooves 16 ₁ to 16 _M are sequentially laminated to form a laminate 35 (lamination step). The laminate 35 is wound into a roll (winding step), as shown in FIG. 5(C). After that, as shown in FIG. 5(D), the roll-shaped laminated body 35 is pressure-molded to form the wound iron core 10 having a substantially square tubular shape having a hollow portion (molding step). In addition, in the forming process, the wound iron core 10 is annealed in order to remove the distortion of the deformed portion after pressure forming.

In this manner, the wound core 10 can be manufactured by forming the corresponding grooves 16 ₁ to 16 _M in the steel plate pieces 14 ₁ to 14 _M in the process of manufacturing the individual wound cores 10 .

In the above example, the groove 16 is formed in the steel plate piece 14 obtained by cutting the grain-oriented electrical steel sheet 32 unwound from the hoop 31. You may form the groove|channel 16 by.

FIG. 6 shows an example of forming grooves 16 in a wide grain-oriented electrical steel sheet 41 . The grain-oriented electrical steel sheet 41 has a width (for example, 1 m to 1.5 m) several times that of the steel sheet pieces 14 forming the wound iron core 10, for example. The grooving device 42 is provided in a continuous processing facility for continuously threading and processing the grain-oriented electrical steel sheet 41 to finally form, for example, a coil shape. The direction in which the grain-oriented electrical steel sheet 41 is passed is the rolling direction.

The groove forming device 42 is composed of a plurality of laser devices 33, a marker device 43, a process computer 44, a tracking device 45, and the like. The plurality of laser devices 33 are arranged side by side in the width direction of the grain-oriented electromagnetic steel sheet 41 , and divide the grain-oriented electromagnetic steel sheet 41 in the width direction to form the grooves 16 . Control data including the length and width of each steel plate piece 14 of the wound iron core 10 and the depth, width, pitch, etc. of the groove 16 of each steel plate piece 14 is input to the process computer 44 in advance.

The tracking device 45 is composed of, for example, an encoder or the like attached to a transport roll 46 that rotates following the transport of the grain-oriented electrical steel sheet 41, and outputs the number of revolutions of the transport roll 46 as a detection signal. Based on the detection signal from the tracking device 45 and the irradiation position of the laser beam of each laser device 33, the process computer 44 identifies the threading position in the threading direction of the grain-oriented electrical steel sheet 41 on each irradiation position. . Similarly, the process computer 44 identifies the threading position of the grain-oriented electrical steel sheet 41 on the marking position based on the detection signal from the tracking device 45 and the marking position by the marker device 43 .

The process computer 44 forms a groove in each steel plate piece region corresponding to each steel plate piece 14 of the grain-oriented electromagnetic steel plate 41 based on the passing position of the grain-oriented magnetic steel plate 41 on the irradiation position of the laser beam specified as described above. Each laser device 33 is individually controlled to form 16 . As a result, a steel plate piece region corresponding to the steel plate piece _14-1 , _a steel plate piece region corresponding to the steel plate piece _14-2 , . are formed side by side. In each steel strip area, a groove 16 _i of the corresponding steel strip 14 _i is formed by the laser device 33 . After forming each steel plate piece region corresponding to one set of steel plate pieces 14 ₁ to 14 _M , each laser device 33 forms each steel plate piece region corresponding to the next one set of steel plate pieces 14 ₁ to 14 _M. to form Thus, grooves 16 are formed in grain-oriented electrical steel sheet 41 .

In addition, the process computer 44 drives the marker device 43 based on the identified strip threading position to record marks, for example, on the boundaries of the respective steel plate strip regions (marking step). For this marker, something that can be confirmed visually or with a camera, such as sprayed paint, is used. Also, the markers may be recorded in a pattern that enables automatic identification of individual steel strip regions. Furthermore, by stopping the irradiation of the laser beam from the laser device 33 in a certain section as the boundary of each steel plate piece region, a non-formation section of the groove 16 is formed, and this non-formation section is used as a marker as a boundary of each steel plate section region. good too.

When manufacturing the wound iron core 10, the grain-oriented electrical steel sheet 41 as the electrical steel sheet for the core is cut in its longitudinal direction (sheet threading direction) based on the markers manufactured as described above, and the steel sheet pieces are cut. It is cut into 14 widths and divided widthwise. As a result, a plurality of sets of steel plate pieces 14 ₁ to 14 _M for manufacturing a plurality of wound iron cores 10 are obtained. In this way, since the grooves 16 are formed in accordance with the steel plate pieces 14 of the wound core 10 at the stage of manufacturing the coil of the grain-oriented electrical steel sheet 41, it is possible to easily manufacture a wound core with reduced iron loss and excellent characteristics. can.

Although the case of forming grooves in the steel plate pieces of the wound iron core has been described above, grooves can be formed in the steel plate pieces of the laminated iron core, which will be described later, in a continuous processing facility by a similar method.

[Second embodiment]
2nd Embodiment aims at reduction of the iron loss of a laminated iron core. In FIG. 7, a laminated iron core 50 is composed of a central leg 51 and a pair of side legs 52, which are iron core legs, and four yokes (yokes) 53 connecting the central leg 51 and the side legs 52, respectively. be done. The central leg 51 and the side legs 52 are arranged side by side in one direction so that the pair of side legs 52 sandwich the central leg 51 therebetween. The center leg 51 is formed by stacking N (N is 2 or more) steel plate pieces 51a. Similarly, each side leg 52 and each yoke 53 are formed by stacking N steel plate pieces 52a and 53a, respectively.

As shown in FIG. 8, the steel plate pieces 51a to 53a are cut out from a grain-oriented electrical steel plate so that the axis of easy magnetization, that is, the rolling direction, is parallel to the closed magnetic circuit circulating inside the core 50. be. The closed magnetic circuit in this case is formed (closed) in one layer consisting of the steel plate pieces 51a, 52a, and 53a among the laminated steel plate pieces when the laminated iron core 50 is used in a transformer. It means a line of magnetic force, and it is assumed that a plurality of closed magnetic circuits are generated in the one layer.

The direction of the closed magnetic path in the central leg 51 and the side legs 52 is the direction in which the pair of yokes 53 are sandwiched (direction of arrow X), and the direction of the closed magnetic path in each yoke 53 is the direction in which the central leg 51 and the side legs 52 are aligned. (arrow Y direction).

A plurality of grooves 56 are formed in each of the stacked steel plate pieces 51a. Each groove 56 extends in the width direction of the steel plate piece 51a (the direction perpendicular to the rolling direction), that is, the direction perpendicular to the closed magnetic circuit, and is provided at predetermined intervals in the rolling direction. Similarly, each steel plate piece 52a has a plurality of grooves 57 extending in its width direction, and each steel plate piece 53a has a plurality of grooves 58 extending in its width direction. , are provided at predetermined intervals in the rolling direction. Note that the groove 56 may extend in a direction crossing the magnetic path.

In the laminated iron core 50, a closed magnetic circuit CM is formed around each hollow portion surrounded by the central leg 51, the side legs 52 and the yoke 53, respectively. In FIG. 8, only one closed magnetic circuit CM is drawn around each hollow portion for the sake of convenience. A lot of closed magnetic circuits are formed so that Moreover, each layer of the laminated iron core 50 has such a structure.

In general, the closer to the inner circumference of the closed magnetic circuit, the shorter the circumference of the closed magnetic circuit and the smaller the magnetic resistance, so that the magnetic flux density tends to concentrate more on the inner circumference. Therefore, iron loss increases in the closed magnetic path on the inner peripheral side. The grooves 56 to 58 are formed so that their magnetic resistances are substantially the same. In this example, as shown in FIG. 9, the groove 57 formed in each steel plate piece 52a has a depth extending from the inside to the outside of the closed magnetic circuit formed when the iron core is used in a transformer. It has a shape that gradually decreases with time. As a result, the width and pitch of the grooves 57 in the plate width direction of the steel plate piece 52a are constant, while the groove cross-sectional area ratio η in the direction of the magnetic path gradually decreases from the inner peripheral side to the outer peripheral side. Similarly, the groove 58 formed in each steel plate piece 53a has a shape whose depth gradually decreases from the inner peripheral side toward the outer peripheral side. As a result, the steel plate piece 53a keeps the groove width and pitch of the grooves 57 constant in the width direction, while continuously decreasing the groove cross-sectional area ratio η in the direction of the magnetic path from the inner peripheral side to the outer peripheral side. there is

The groove 56 formed in each steel plate piece 51a of the central leg 51 has a shape in which the depth of the groove 56 gradually decreases from the center toward the outside. That is, the groove cross-sectional area ratio η in the direction of the magnetic path is continuously decreased from the inner peripheral side to the outer peripheral side.

By forming the grooves 56 to 58 in each of the steel plate pieces 51a to 53a as described above, the effective magnetic permeability in the plate width direction is controlled, and the magnetic resistance of each closed magnetic circuit in the plate width direction is made substantially the same. As a result, the magnetic flux densities of the respective portions of the steel plate pieces 51a to 53a in the plate width direction are made uniform, and iron loss is reduced. Since the effective magnetic permeability of the steel plate pieces 51a-53a is adjusted by the groove cross-sectional area ratio, that is, the depth, width and pitch of the grooves 56-58, the required effective magnetic permeability can be easily obtained. Iron loss of the laminated iron core 50 can be reduced. The groove cross-sectional area ratio can be obtained, for example, by the formula (1) as in the first embodiment.

In the above example, the depth of the groove of each steel plate piece is made to gradually decrease from the inner peripheral side to the outer peripheral side (that is, toward the direction intersecting the closed magnetic circuit), and the magnetic resistance in each closed magnetic circuit is reduced to approximately Although they are made the same, when making the magnetic resistance substantially the same, the depth, width, and pitch of the grooves formed in the steel plate piece can be adjusted as in the case of the first embodiment. Further, the groove cross-sectional area ratio in the direction of the magnetic path may be decreased stepwise. Moreover, although the above-mentioned laminated iron core has a three-legged structure, it may have a two-legged structure.

In FIG. 10, the steel plate piece 52a is divided into an inner peripheral portion 61, an intermediate portion 62, and an outer peripheral portion 63 in order from the inner peripheral side. The groove cross-sectional area ratio of is adjusted. The inner peripheral portion 61 has the largest groove cross-sectional area ratio in the steel plate piece 52a, that is, the depth, width, and pitch determined so that the groove cross-sectional area ratio η is larger than that of the intermediate portion 62 and the outer peripheral portion 63. groove 61a is formed. The outer peripheral portion 63 has the smallest groove cross-sectional area ratio in the steel plate piece 52a, that is, the depth, width, and pitch determined so that the groove cross-sectional area ratio η is smaller than that of the inner peripheral portion 61 and the intermediate portion 62. groove 63a is formed. The intermediate portion 62 is formed with a plurality of grooves 62a having a depth, width, and pitch determined so as to satisfy the groove cross-sectional area ratio η between the inner peripheral portion 61 and the outer peripheral portion 63 . By forming the grooves 61a to 63a in the inner peripheral portion 61, the intermediate portion 62, and the outer peripheral portion 63, respectively, the magnetic resistance is increased in the order of the outer peripheral portion 63, the intermediate portion 62, and the inner peripheral portion 61. Therefore, the magnetic flux density is made uniform and iron loss is reduced.

When manufacturing the laminated iron core 50, as shown in FIG. 11A, for example, steel plate pieces 51a to 53a are sequentially cut from a grain-oriented electrical steel plate 32 unwound from a hoop 31, and these pieces are cut. The grooves 56 to 58 are formed by irradiating the steel plate pieces 51a to 53a with laser light from the laser device 33, respectively. At this time, the depth, width, pitch, etc. of the grooves 56 to 58 are controlled so as to obtain the required groove cross-sectional area ratio η. In general, since the laminated iron core is used for a large transformer, the size of each steel plate piece is large. Therefore, it is relatively easy to form grooves by changing laser irradiation conditions for each part of the steel plate piece. After that, as shown in FIG. 11(B), steel plate pieces 51a to 53a having grooves 56 to 58 formed thereon are laminated to form a laminated iron core 50. Next, as shown in FIG. Also, an insulating coating may be applied between the groove formation process and the lamination process to increase the insulation between the layers.

First, a steel plate piece of a grain-oriented electrical steel sheet with a plate thickness t of 0.230 mm was prepared, and a plurality of samples with different groove depths, widths, and pitches were prepared on the steel plate piece, and the groove cross-sectional area ratio and the effective The relationship between magnetic permeability and iron loss W _17/50 (W/kg) was investigated. Iron loss W _17/50 is iron loss generated in an alternating magnetic field with a maximum magnetic flux density of 1.7 T and a frequency of 50 Hz.

A laser device was used to form the grooves. As a laser device, a fiber laser with a wavelength of 1.1 μm is used, and the output is changed within the range of 1000 W to 2000 W, the diameter of the focused laser beam is 0.005 mm to 0.150 mm, and the scanning speed is changed within the range of 5 to 50 m / s. did. As a result, the grooves formed have a depth of 0.005 mm to 0.05 mm, a width of 0.01 mm to 0.200 mm, a pitch of 2 mm to 10 mm, and a groove cross-sectional area ratio of approximately 0.01 to 0.01 mm. 400 range. The groove cross-sectional area ratio was determined by the formula (1). FIG. 12 shows the relationship between the groove cross-sectional area ratio η, the effective magnetic permeability μe, and the core loss W _17/50 , depending on the combinations of groove depths, widths, and pitches within these ranges. The effective magnetic permeability μe was obtained by measuring the magnetic flux density B ₈ (T) generated at a magnetic field strength H ₈ (=800 (A/m)) and obtaining “μe=B ₈ /H ₈ ”.

From the above results, the relationship between the groove cross-sectional area ratio η and the effective permeability μe was approximated by the formula (A). Further, the iron loss W _17/50 was almost constant within the above range of the groove cross-sectional area ratio η.
μe=0.568η ² −0.4621η+2.4005 (A)
However, 0.02<η<0.400
η=(π・d・W)/(2・P・t)

Next, as Example 1, a transformer using the wound iron core 10 was produced and the iron loss W _17/50 was measured. Based on the above _- mentioned formula "R _i = _{L i} /(μ _{e i} ×s _i )" showing the relationship between the magnetic resistance R _i and the effective magnetic permeability μ _{e i The} effective magnetic permeability _{μe i} such that .theta. The groove cross-sectional area ratio η _i corresponding to each effective permeability μ _{e i} is obtained from the relationship of formula (A), and based on the formula (1), the depth, width, The grooves 16 were formed by adjusting the pitch. The groove cross-sectional area ratio in each steel plate piece 14 is assumed to be constant. The fluctuation range of the magnetic resistance R of the steel plate pieces 14 ₁ to 14 _M was adjusted to be within ±5% of the average value.

Further, as Comparative Example 1, a transformer was manufactured using a wound iron core in which the groove cross-sectional area ratio was constant between the steel plate pieces, that is, the depth, width, and pitch were the same between the steel plate pieces. Iron loss was compared. The groove depth of each steel plate piece in Comparative Example 1 was 0.02 mm, the width was 0.05 mm, and the pitch was 5 mm. Other conditions of the transformer of Comparative Example 1 were the same as those of the transformer of Example 1.

In addition, as Example 2, a transformer using the laminated iron core 50 was manufactured and the iron loss was measured. 10, each steel plate piece 52a, 53a is divided into an inner peripheral portion 61, an intermediate portion 62, and an outer peripheral portion 63 in the width direction. The depth, width, and pitch of the grooves 61a to 63a were adjusted so that the cross-sectional area ratio of the grooves decreased in the order of the outer peripheral portion 63. FIG. Further, as Comparative Example 2, a transformer using a laminated iron core having a constant groove cross-sectional area ratio η in the width direction of each steel plate piece was manufactured, and iron loss was measured. Other conditions of the transformer of Comparative Example 2 were the same as those of the transformer of Example 2.

The transformer of Example 1 using the wound iron core 10 had a core loss lower than that of the transformer of Comparative Example 1 by about 10%. In addition, the transformer of Example 2 using the laminated iron core 50 had an iron loss lower than that of the transformer of Comparative Example 2 by about 8%.

10 Wound iron core 14, 51a-53a Steel plate piece 16, 56-57 Groove 31 Hoop 32, 41 Directional electromagnetic steel plate 50 Laminated iron core 56-57 Groove

Claims (5)

In an iron core for a transformer composed of a laminated body in which a plurality of steel plate pieces are laminated,
The steel plate piece has grooves crossing the rolling direction on the surface,
By changing at least one of the depth of the groove, the width of the groove, and the pitch of the groove, the steel plate piece forms a closed magnetic circuit when the iron core is used in a transformer. An iron core in which the groove cross-sectional area ratio η represented by the formula (1) changes continuously or stepwise from the inside to the outside.
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece. 2. The iron core according to claim 1, wherein the magnetic resistance along said closed magnetic path is substantially the same in each of said arbitrary closed magnetic paths formed when said iron core is used in a transformer. In a method for manufacturing a wound iron core for a transformer composed of a laminated body in which a plurality of steel plate pieces are laminated,
a cutting step of cutting a plurality of steel plate pieces from a hoop of a grain-oriented electrical steel plate;
a groove forming step of forming a groove in the cut steel plate piece that intersects with the rolling direction of the steel plate piece;
A molding step of laminating the steel plate pieces, winding the laminated laminate, and then pressure-molding it to form the wound iron core;
has
In the groove forming step, by changing at least one of the depth of the groove, the width of the groove, and the pitch of the groove, a closed magnetic field is formed when the wound iron core is used in a transformer. A method for manufacturing a wound iron core, wherein the groove cross-sectional area ratio η represented by the formula (1) is changed continuously or stepwise from the inner side to the outer side of the passage.
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece. In a method for manufacturing a laminated iron core for a transformer comprising a laminate in which a plurality of steel plate pieces are laminated,
a cutting step of cutting a plurality of steel plate pieces from a hoop of a grain-oriented electrical steel plate;
a groove forming step of forming a groove in the cut steel plate piece that intersects with the rolling direction of the steel plate piece;
A forming step of laminating the steel plate pieces to form the laminated iron core;
has
In the groove forming step, by changing at least one of the depth of the groove, the width of the groove, and the pitch of the groove, a closed magnetic field is formed when the laminated iron core is used in a transformer. A method for manufacturing a laminated iron core, wherein the groove cross-sectional area ratio η represented by the formula (1) is changed continuously or stepwise from the inner side to the outer side of the channel.
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece. In a method for manufacturing an electromagnetic steel sheet for an iron core for a transformer iron core composed of a laminate in which a plurality of steel plate pieces are laminated,
A groove forming step of forming a plurality of grooves in each of the plurality of steel plate piece regions to be the plurality of steel plate pieces,
In the groove forming step, by changing at least one of the depth of the groove, the width of the groove, and the pitch of the groove, a closed magnetic circuit is formed when the iron core is used in a transformer. A method for manufacturing an electrical steel sheet for an iron core, wherein the groove cross-sectional area ratio η represented by the formula (1) is changed continuously or stepwise from the inside to the outside of the .
η=(π・d・W)/(2・P・t) (1)
Here, π is the circular constant, d is the depth of the groove, W is the width of the groove, P is the pitch of the groove, and t is the thickness of the steel plate piece.

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