JP7803293B2 - Laminated iron core, manufacturing method of laminated iron core, and transformer - Google Patents

Description

This disclosure relates to laminated cores, methods for manufacturing laminated cores, and transformers.

There are many requirements for the cores used in transformers. Among these, reducing transformer noise is a particularly strong requirement. Therefore, a method for reducing transformer noise using laminated cores is known (see Patent Document 1).

Japanese Patent Application Laid-Open No. 2003-077747

In Patent Document 1, transformer noise is reduced by applying an adhesive such as resin to the lamination end surfaces of the laminated core. However, applying an adhesive such as resin to the lamination end surfaces may reduce the space factor of the laminated core. A reduced space factor of the laminated core may increase iron loss in the transformer.

The purpose of this disclosure, made in light of these circumstances, is to provide a laminated core, a manufacturing method for a laminated core, and a transformer that reduce transformer noise while suppressing increases in iron loss in the transformer.

(1) A laminated core according to one embodiment of the present disclosure includes:
A laminated core in which a plurality of steel plates are laminated, the core having a yoke portion and a leg portion,
the steel plate includes a first steel plate member included in the yoke portion and a second steel plate member included in the leg portion,
The ratio of the maximum peak height Rp on the surface of the second steel plate member to the maximum peak height Rp on the surface of the first steel plate member exceeds 1.

(2) In the laminated core of (1) above,
A ratio of a maximum peak height Rp on a surface of the second steel plate member to a maximum peak height Rp on a surface of the first steel plate member may be 1.15 or more.

(3) In the laminated core of (1) or (2),
A ratio of a maximum peak height Rp on a surface of the second steel plate member to a maximum peak height Rp on a surface of the first steel plate member may be 1.15 or more and 1.45 or less.

(4) A method for manufacturing a laminated core according to one embodiment of the present disclosure includes:
In the manufacturing method of any one of the laminated cores (1) to (3) above, chemical polishing, shot blasting, or emery polishing is performed on the second steel plate member or on the steel plate before forming the second steel plate member.

(5) A transformer according to an embodiment of the present disclosure includes:
The motor includes a laminated core of any one of (1) to (3) above.

One embodiment of the present disclosure provides a laminated core, a manufacturing method for a laminated core, and a transformer that reduce transformer noise while suppressing an increase in iron loss in the transformer.

1 is a diagram showing a schematic configuration of a laminated core according to an embodiment of the present disclosure. FIG. FIG. 2 is a diagram showing the steel plate shown in FIG. 1 .

Embodiments of the present disclosure will be described below with reference to the drawings. Each drawing is a schematic representation and may differ from the actual product.

(Configuration of laminated core)
The transformer according to this embodiment includes a laminated core 1 as shown in Fig. 1. The laminated core 1 can be used in a three-phase, three-limbed transformer. The laminated core 1 includes yoke portions 2A and 2B and leg portions 3A, 3B, and 3C.

Hereinafter, when there is no need to distinguish between yoke portions 2A and 2B, they will also be referred to simply as "yoke portion 2." When there is no need to distinguish between leg portions 3A, 3B, and 3C, they will also be referred to simply as "leg portion 3."

The laminated core 1 according to this embodiment has three legs 3. However, the number of legs 3 provided in the laminated core 1 is not limited to three. The laminated core 1 may have any number of legs 3 depending on the type and configuration of the transformer in which the laminated core 1 is used. As another example, if the laminated core 1 is used in a three-phase five-limbed transformer, the laminated core 1 may have five legs 3. As yet another example, if the laminated core 1 is used in a single-phase transformer, the laminated core 1 may have two legs 3.

A coil is wound around leg 3. Yoke 2A connects one end of legs 3A to 3C. Yoke 2B connects the other end of legs 3A to 3C.

The laminated core 1 includes multiple stacked steel plates 10. Figure 1 shows an example in which the laminated core 1 includes five stacked steel plates 10. However, the laminated core 1 may include any number of steel plates 10 depending on the application of the transformer in which the laminated core 1 is used, etc.

The material of steel sheet 10 is, for example, grain-oriented electrical steel sheet. Grain-oriented electrical steel sheet has a crystalline structure in which the <001> orientation, the easy axis of iron magnetization, is highly aligned in the rolling direction of the steel sheet. However, the material of steel sheet 10 may be any material. As another example, the material of steel sheet 10 may be an electrical steel sheet that exhibits a given magnetic flux density B8 when excited at a magnetic field strength of 800 A/m, or a steel sheet that exhibits a given iron loss when excited. The magnetic field strength of 800 A/m is an index for measuring the degree of orientation of crystal grains in the electrical steel sheet. As yet another example, the material of steel sheet 10 may be a steel sheet that has undergone magnetic domain refinement treatment. The magnetic domain refinement treatment is, for example, a process of forming grooves on the surface of the steel sheet by performing electrolytic etching, gear rolling, laser etching, or the like on the surface of the steel sheet. As yet another example, the material of steel sheet 10 may be a non-heat-resistant magnetic domain refinement material into which thermal distortion has been introduced using a laser, electron beam, plasma jet, or the like, before or after surface treatment to increase the maximum peak height Rp, as described below.

The steel plate 10 has a rectangular outer shape. As shown in FIG. 2, the steel plate 10 has first steel plate members 11 and 12 and second steel plate members 13, 14, and 15. Hereinafter, when there is no particular distinction between the first steel plate members 11 and 12, they will also be referred to simply as "first steel plate members." Hereinafter, when there is no particular distinction between the second steel plate members 13 to 15, they will also be referred to simply as "second steel plate members."

The first steel plate member 11 is included in the yoke portion 2A of the laminated core 1. The extension direction of the first steel plate member 11 corresponds to the magnetization direction in the yoke portion 2A. The first steel plate member 11 is formed so that the <001> orientation of the grain-oriented electromagnetic steel sheet corresponds to the extension direction of the first steel plate member 11. The first steel plate member 11 includes joints 11A, 11B, and 11E. Joint 11A has an inclined shape that is inclined with respect to the extension direction of the first steel plate member 11. Joint 11B has an inclined shape that is inclined with respect to the extension direction of the first steel plate member 11. The inclined shape of joint 11A and the inclined shape of joint 11B are axisymmetric. Joint 11E has a V-shape.

The first steel plate member 12 is included in the yoke portion 2B of the laminated core 1. The extension direction of the first steel plate member 12 corresponds to the magnetization direction in the yoke portion 2B. The first steel plate member 12 is formed so that the <001> orientation of the grain-oriented electromagnetic steel sheet corresponds to the extension direction of the first steel plate member 12. The first steel plate member 12 includes joints 12C, 12D, and 12F. Joint 12C has an inclined shape that is inclined with respect to the extension direction of the first steel plate member 12. Joint 12D has an inclined shape that is inclined with respect to the extension direction of the first steel plate member 12. The inclined shape of joint 12C and the inclined shape of joint 12D are axisymmetric. Joint 12F has a V-shape.

The second steel plate member 13 is included in the leg 3A of the laminated core 1. The extension direction of the second steel plate member 13 corresponds to the magnetization direction of the leg 3A. The second steel plate member 13 is formed so that the <001> orientation of the grain-oriented electromagnetic steel plate corresponds to the extension direction of the second steel plate member 13. The second steel plate member 13 includes joints 13A and 13D. Joint 13A has an inclined shape that is inclined with respect to the extension direction of the second steel plate member 13. Joint 13D has an inclined shape that is inclined with respect to the extension direction of the second steel plate member 13. The inclined shape of joint 13A and the inclined shape of joint 13D are axisymmetric.

The second steel plate member 14 is included in leg 3B of the laminated core 1. The extension direction of the second steel plate member 14 corresponds to the magnetization direction in leg 3B. The second steel plate member 14 is formed so that the <001> orientation of the grain-oriented electromagnetic steel plate corresponds to the extension direction of the second steel plate member 14. The second steel plate member 14 includes joints 14E and 14F. Joints 14E and 14F are V-shaped. The shape of joint 14E is substantially the same as the shape of joint 11E. The shape of joint 14F is substantially the same as the shape of joint 12F.

The second steel plate member 15 is included in leg 3C of the laminated core 1. The extension direction of the second steel plate member 15 corresponds to the magnetization direction in leg 3C. The second steel plate member 15 is formed so that the <001> orientation of the grain-oriented electromagnetic steel plate corresponds to the extension direction of the second steel plate member 15. The second steel plate member 15 includes joints 15B and 15C. Joint 15B has an inclined shape that is inclined with respect to the extension direction of the second steel plate member 15. Joint 15C has an inclined shape that is inclined with respect to the extension direction of the second steel plate member 15. The inclined shape of joint 15B and the inclined shape of joint 15C are axisymmetric.

When assembling the steel plates 10, joints 11A and 13A are butted together, joints 11B and 15B are butted together, joints 15C and 12C are butted together, and joints 12D and 13D are butted together. Furthermore, when assembling the steel plates 10, joints 11E and 14E are butted together, and joints 12F and 14F are butted together. Joints 11A, 13A, etc. may be butted together without the use of adhesive or the like. By butting joints 11A, 13A, etc. together without the use of adhesive or the like, the space factor of the steel plates 10 in the laminated core 1 can be increased compared to when joints 11A, 13A, etc. are butted together using adhesive or the like.

The multiple steel plates 10 are stacked without the use of adhesives or the like. By stacking the multiple steel plates 10 without the use of adhesives or the like, the space factor of the steel plates 10 in the laminated core 1 can be increased compared to when the multiple steel plates 10 are stacked with adhesives or the like. The multiple steel plates 10 may be stacked in any manner. For example, the multiple steel plates 10 may be stacked in a step-lap format at butt joints 11A, 13A, etc.

In the laminated core 1 according to this embodiment, the ratio of the maximum peak height Rp on the surface of the second steel plate member to the maximum peak height Rp on the surface of the first steel plate member exceeds 1. The maximum peak height Rp is an index of surface roughness. In this embodiment, the maximum peak height Rp is the highest peak on the profile curve within the reference length. A peak is a portion higher than the mean line. In this embodiment, the maximum peak height Rp refers to the maximum peak height Rp specified in JIS B0601:2001 (ISO 4287:1997). The minimum value of the maximum peak height Rp on the surface of the second steel plate member is preferably 14.0 μm, as shown in Table 6 below.

In this manner, in the laminated core 1 according to this embodiment, the ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member exceeds 1, so that the surface of the second steel plate member is rougher than the surface of the first steel plate member. By roughening the surface of the second steel plate member included in the leg 3 in this manner, the frictional force between the multiple second steel plate members in the laminated core 1 can be increased. By increasing the frictional force between the multiple second steel plate members in the laminated core 1, the multiple steel plates 10 in the laminated core 1 are less likely to slip sideways, even when stacked without adhesive or the like. By reducing the resistance of the multiple steel plates 10 to slip sideways in the laminated core 1, the rigidity of the laminated core 1 can be increased. By increasing the rigidity of the laminated core 1, the natural vibration of the laminated core 1 can be reduced. Here, the natural vibration of the laminated core 1 refers to the vibration of the laminated core 1 as a single structure at a specific frequency. Therefore, in this embodiment, by reducing the natural vibration of the laminated core 1, it is possible to reduce the noise of a transformer equipped with the laminated core 1. Furthermore, in the laminated core 1 according to this embodiment, by stacking multiple steel plates 10 without using an adhesive or the like, it is possible to increase the space factor of the steel plates 10 in the laminated core 1. By increasing the space factor of the steel plates 10 in the laminated core 1, it is possible to suppress an increase in iron loss in a transformer equipped with the laminated core 1.

Furthermore, in a transformer including the laminated core 1 according to this embodiment, the legs 3 are wound with coils. Therefore, the legs 3 are not fastened by components or the like. In contrast, the yoke 2 is fastened by components such as clamps or brackets. Fastening the yoke 2 in this manner makes it less likely for the multiple steel plates 10 in the laminated core 1 to slide sideways, even without increasing the maximum peak height Rp of the first steel plate member. In this embodiment, by ensuring that the maximum peak height Rp of the surface of the first steel plate member is not greater than the maximum peak height Rp of the surface of the second steel plate member, an increase in iron loss in the transformer can be suppressed. In other words, in this embodiment, by ensuring that the ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member exceeds 1, an increase in iron loss in the transformer can be suppressed.

Therefore, in the laminated core 1 according to this embodiment, the ratio of the maximum peak height Rp on the surface of the second steel plate member to the maximum peak height Rp on the surface of the first steel plate member exceeds 1, thereby suppressing an increase in iron loss in a transformer equipped with the laminated core 1 while reducing noise from the transformer. See also the results of Experiment 2 for more information on this effect.

(Experiment 1: Skidding)
An experiment was conducted to examine the relationship between the maximum peak height Rp of a steel sheet, which is an iron core material, and lateral slippage. A grain-oriented electrical steel sheet with a phosphorus hydrochloride-based insulating coating was used as the iron core material. This grain-oriented electrical steel sheet was manufactured using a known method. This grain-oriented electrical steel sheet was divided into rectangular steel sheet members. Each rectangular steel sheet member measured 30 mm in width, 280 mm in length, and 0.23 mm in thickness. Some of the divided steel sheet members were subjected to a surface treatment to roughen the surface. The surface treatment involved immersing the steel sheet members in a 1 mol/L aqueous solution of sodium hydroxide for 2 minutes. This resulted in the preparation of surface-treated steel sheet members and untreated steel sheet members.

Surface-treated and untreated steel plate members were stacked to prepare a laminate made of surface-treated steel plate members and a laminate made of untreated steel plate members. Each of these two laminates had 70 layers. The ease of sliding of these two laminates was measured. The measurement method used was to place the laminate on a horizontal table and tilt the table in 1-degree increments from the horizontal up to a maximum of 90 degrees, measuring the angle at which the steel plate members in the laminate began to move. With this measurement method, the closer the table angle was to 90 degrees when the steel plate members in the laminate began to move, the less likely the laminate was to slide. In the experiment, the laminate behaved as a single rigid body, and a stopper half the height of the laminate was placed on the table to prevent the laminate from moving without sliding.

Table 1 shows the results of Experiment 1. The maximum peak height Rp on the surface of the steel plate member was measured by surface roughness measurement using a laser microscope VK-X100 manufactured by Keyence Corporation.

As shown in Table 1, the maximum peak height Rp of the untreated steel plate members was 12.2 μm. The angle at which the steel plate members in the stack made of untreated steel plate members began to move was 35 degrees. The maximum peak height Rp of the surface-treated steel plate members was 16.5 μm. The angle at which the steel plate members in the stack made of surface-treated steel plate members began to move was 48 degrees.

From the results of Experiment 1 above, the inventors have found that a stack made of steel plate members whose surfaces have been roughened by surface treatment is less prone to skidding than a stack made of steel plate members whose surfaces have not been treated.

(Experiment 2: Transformer noise and iron loss)
In Experiment 2, the noise and iron loss of a transformer equipped with a laminated core were measured. First, a laminated core was assembled using steel plate members under conditions 1 to 4 shown in Table 2. The steel plate members included a first steel plate member included in the yoke portion and a second steel plate member included in the leg portion. As in Experiment 1, the surface treatment involved immersion in a 1 mol/L sodium hydroxide aqueous solution for 2 minutes. To assemble the laminated core, 70 layers of the steel plate members under conditions 1 to 4 were stacked in a 5-layer step-lap format consisting of pairs of sheets with a lap length of 2 mm.

Under Condition 1, no surface treatment was performed on any of the steel plate members, i.e., the first steel plate member and the second steel plate member. In other words, all of the steel plate members were surface untreated.

Under condition 2, surface treatment was performed on all steel plate members, i.e., the first steel plate member and the second steel plate member.

In condition 3, surface treatment was performed on the first steel plate member included in the yoke portion, but not on the second steel plate member included in the leg portion.

In condition 4, surface treatment was performed on the second steel plate member included in the leg portion, but not on the first steel plate member included in the yoke portion.

The sizes of the steel plate members under conditions 1 to 4 were as shown in Table 3. Height a is the height of the laminated core, as shown in Figure 2. Width b is the width of the laminated core, as shown in Figure 2. Length c is the height of the gap between the two legs, as shown in Figure 2. Distance d is the distance between the two legs, as shown in Figure 2. Length e is the length of the central second steel plate member. Angle f is the angle at which the joint is inclined with respect to the extension direction of the first steel plate member. Thickness is the thickness of the steel plate. In other words, for the steel plate members under conditions 1 to 4, height a was 500 mm, width b was 500 mm, length c was 300 mm, distance d was 100 mm, length e was 400 mm, angle f was 45 degrees, and thickness was 0.23 mm.

After assembling the laminated core, backing plates were placed on the front and back of the yoke, and clamps were used to apply a uniform pressure of 0.2 MPa. The legs were secured in place by wrapping glass tape around them so as not to interfere with winding the coil around them. A 50-turn primary coil and a 50-turn secondary coil were wound around each of the three legs, creating a laminated core for a three-phase, three-limbed transformer. This laminated core was subjected to three-phase excitation at a frequency of 50 Hz and a maximum excitation magnetic flux density of 1.7 T, and the noise and iron loss of the transformer were measured.

When measuring the noise of a transformer, noise was measured at eight equally spaced locations surrounding the laminated core. These eight locations were located at half the height of the laminated core and 30 cm from the surface of the laminated core. The average value of these eight locations was taken as the noise of the transformer.

When measuring the transformer's iron loss, the primary current and secondary voltage during three-phase excitation were measured with a wattmeter to calculate the no-load loss. Furthermore, the transformer's iron loss was calculated (measured) by dividing the no-load loss by the weight of the laminated core.

Table 4 shows the results of Experiment 2. The maximum peak height Rp on the surface of the steel plate member was measured by surface roughness measurement using a laser microscope VK-X100 manufactured by Keyence Corporation, as in Experiment 1.

Under Condition 1, the maximum peak height Rp on the surface of the first copper plate member was 12.4 μm. The maximum peak height Rp on the surface of the second steel plate member was 12.2 μm. The noise level of the transformer was 62.2 dBA. The iron loss of the transformer was 1.02 W/kg.

Under condition 2, the maximum peak height Rp on the surface of the first steel plate member was 16.7 μm. The maximum peak height Rp on the surface of the second steel plate member was 16.5 μm. The noise level of the transformer was 57.3 dBA. The iron loss of the transformer was 1.10 W/kg.

Under condition 3, the maximum peak height Rp on the surface of the first steel plate member was 16.5 μm. The maximum peak height Rp on the surface of the second steel plate member was 12.2 μm. The noise level of the transformer was 62.0 dBA. The iron loss of the transformer was 1.11 W/kg.

Under condition 4, the maximum peak height Rp on the surface of the first steel plate member was 12.3 μm. The maximum peak height Rp on the surface of the second steel plate member was 16.8 μm. The noise level of the transformer was 57.5 dBA. The iron loss of the transformer was 1.01 W/kg.

Under conditions 2 to 4, transformer noise was reduced more than under condition 1. These results demonstrate that transformer noise can be reduced by increasing the maximum peak height Rp of the surface of the steel plate member. However, under condition 3, the degree of transformer noise reduction was smaller than under condition 1. This is because, by tightening the yoke portion, the multiple steel plates in the laminated core are less likely to slip sideways, even without increasing the maximum peak height Rp of the first steel plate member included in the yoke portion.

Under Conditions 2 and 3, the transformer's iron loss was greater than under Condition 1. From this result, it can be seen that, from the perspective of transformer iron loss, it is better not to increase the maximum peak height Rp of the first steel plate member included in the yoke portion.

From the results of Experiment 2 above, the inventors discovered that when the ratio of the maximum peak height Rp on the surface of the second steel plate member to the maximum peak height Rp on the surface of the first steel plate member exceeds 1, it is possible to reduce transformer noise while suppressing an increase in transformer iron loss.

(Experiment 3: Transformer noise and iron loss)
In Experiment 3, the optimum ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member was evaluated. In Experiment 3, the noise and iron loss of the transformer were measured while varying the maximum peak heights Rp of the first and second steel plate members. The sizes of the steel plate members used in the laminated core were as shown in Table 5. That is, the height a was 700 mm, the width b was 700 mm, the length c was 420 mm, the spacing d was 140 mm, the length e was 560 mm, the angle f was 45 degrees, and the thickness was 0.23 mm. The laminated core was assembled using 70 layers of steel plate members with the sizes shown in Table 5, stacked in a 10-layer step-lap format with a lap length of 2 mm, consisting of two pairs of sheets. After assembly, a 50-turn primary coil and a 50-turn secondary coil were wound around each of the three legs, forming a laminated core for a three-phase, three-limbed transformer. This laminated core was subjected to three-phase excitation under the conditions of a frequency of 50 [Hz] and a maximum excitation magnetic flux density of 1.7 [T], and the noise and iron loss of the transformer were measured.

Table 6 shows the results of Experiment 3. The maximum peak height Rp of the surfaces of the first steel plate member and the second steel plate member was measured by surface roughness measurement using a laser microscope VK-X100 manufactured by Keyence Corporation, as in Experiment 1.

In Nos. 1 to 15, the maximum peak height Rp of the surface of the first steel plate member was 12.2 μm. Among Nos. 1 to 15, No. 1 is a comparative example, and Nos. 2 to 15 are working examples. In Nos. 2 to 4 (working examples), the change in the ratio of maximum peak height Rp was small compared to No. 1 (comparative example). Therefore, in this experiment, Nos. 2 to 4 (working examples) did not demonstrate significant improvements in suppressing the increase in iron loss and reducing noise in the transformer. However, in Nos. 5 to 15 (working examples), in which the ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member was 1.15 or greater, significant improvements in suppressing the increase in iron loss and reducing noise in the transformer were observed compared to No. 1 (comparative example). In particular, good results were obtained in Examples No. 5 to 11, in which the ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member was 1.15 or greater and 1.45 or less. The reason the results of Examples No. 12 to 15, in which the ratio of maximum peak height Rp was 1.45 or greater, were worse than those of Examples No. 5 to 11 is thought to be because the surface of the second steel plate member was roughened by the surface treatment. In other words, in Examples No. 12 to 15, the surface of the second steel plate member was roughened by the surface treatment, which is thought to have reduced the contact area between the second steel plate members rather than increasing the frictional force between the second steel plate members.

In Nos. 16 to 34, the maximum peak height Rp of the surface of the first steel plate member was 13.8 μm. Among Nos. 16 to 34, Nos. 16 to 19 are comparative examples, and Nos. 20 to 34 are working examples. In Nos. 20 to 23 (working examples), the change in the ratio of maximum peak height Rp was smaller than in No. 16 (comparative example). Therefore, in Experiment 3, Nos. 20 to 23 (working examples) did not demonstrate significant improvements in suppressing the increase in iron loss and reducing noise in the transformer. However, in Nos. 24 to 34 (working examples), in which the ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member was 1.15 or greater, significant improvements in suppressing the increase in iron loss and reducing noise in the transformer were observed compared to No. 16 and other comparative examples. In particular, good results were obtained in Examples No. 24 to 32, in which the ratio of the maximum peak height Rp on the surface of the second steel plate member to the maximum peak height Rp on the surface of the first steel plate member was 1.15 or greater and 1.45 or less. The reason the results of Examples No. 33 to 34, in which the ratio of maximum peak height Rp was 1.45 or greater, were worse than those of Examples No. 24 to 32 is thought to be because, as mentioned above, the surface of the second steel plate member became rough due to the surface treatment.

In Nos. 35 to 45, the ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member was maintained at approximately 1, while the maximum peak height Rp of the first steel plate member and the second steel plate member was increased. Of Nos. 35 to 45, Nos. 36 to 45 are comparative examples, and No. 35 is an example. The results for Nos. 35 to 45 show that when the ratio is approximately 1, no significant improvement is seen in suppressing the increase in iron loss in the transformer or reducing noise.

(Manufacturing method of laminated iron core)
A method for manufacturing a laminated core will be described. First, a grain-oriented electrical steel sheet is prepared that has been applied with an insulating coating after finish annealing. Next, a first steel sheet member and a second steel sheet member are formed from the grain-oriented electrical steel sheet that has been applied with an insulating coating after finish annealing. After the second steel sheet member is formed, a surface treatment is performed on the second steel sheet member. The surface treatment is a process for increasing the maximum peak height Rp of the second steel sheet member. Examples of the surface treatment include chemical polishing, shot blasting, and emery polishing. On the other hand, the first steel sheet member is not surface-treated. For example, the second steel sheet member may be surface-treated so that the ratio of the maximum peak height Rp of the second steel sheet member to the maximum peak height Rp of the surface of the first steel sheet member is 1.15 or more and 1.45 or less. By performing the surface treatment on the second steel sheet member without performing the surface treatment on the first steel sheet member, the manufacturing cost of the laminated core can be reduced. However, the grain-oriented electrical steel sheet may be surface-treated before the second steel sheet member is formed.

Other processes included in the manufacturing method of the laminated core may be publicly known processes.

Although embodiments of the present disclosure have been described based on various drawings and examples, it should be noted that those skilled in the art would easily be able to make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications and alterations are included within the scope of the present disclosure.

1 Laminated core 10 Steel plate 11, 12 First steel plate member 11A, 11B, 11E, 12C, 12D, 12F Joint part 13, 14, 15 Second steel plate member 13A, 13D, 14E, 14F, 15B, 15C Joint part 2, 2A, 2B Yoke part 3, 3A, 3B, 3C Leg part

Claims (5)

A laminated core in which a plurality of steel plates are laminated without adhesive , the laminated core comprising a yoke portion and a leg portion,
The steel plate includes a first steel plate member included in the yoke portion and a second steel plate member included in the leg portion, and the first steel plate member and the second steel plate member are butted together without an adhesive,
A laminated core, wherein the ratio of the maximum peak height Rp of the surface of the second steel plate member to the maximum peak height Rp of the surface of the first steel plate member exceeds 1. The laminated core of claim 1, wherein the ratio of the maximum peak height Rp on the surface of the second steel plate member to the maximum peak height Rp on the surface of the first steel plate member is 1.15 or greater. A laminated core as described in claim 1, wherein the ratio of the maximum peak height Rp on the surface of the second steel plate member to the maximum peak height Rp on the surface of the first steel plate member is 1.15 or more and 1.45 or less. A method for manufacturing a laminated iron core according to any one of claims 1 to 3, wherein chemical polishing, shot blasting or emery polishing is performed on the second steel plate member or only on the steel plate before forming the second steel plate member, in order to obtain the maximum peak height Rp on the surface of the second steel plate member . A transformer comprising a laminated core according to any one of claims 1 to 3.