RU2837373C2 - Stacked core and rotating electric machine - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: stacked core comprises multiple stacked sheets of electrical steel and multiple adhesive layers located between sheets of electrical steel next to each other in direction of laying. Electrotechnical steel sheet includes annular body. At least one of the plurality of adhesive layers (41) is a first adhesive layer. In one sheet of two sheets of electrical steel, placing in the middle the first adhesive layer in the laying direction, when the imaginary axis crossing the central axis of the annular body and continuing in the easy magnetization direction is set as the L-axis, imaginary axis intersecting with central axis and intersecting with L-axis is set as C-axis, and the electrical steel sheet is divided into a plurality of sections (S) in the circumferential direction of the annular body by the L-axis and the C-axis. At least one section of the plurality of sections is the first section. In the first section, the area of the first adhesive layer in the first section (P1) of the electrical steel sheet, in which the main magnetic flux is formed in the L-axis direction, is less than the area of the first adhesive layer in the second section (P2) of the electrical steel sheet, in which the main magnetic flux is formed is formed in direction along C-axis.

EFFECT: reduction of losses in iron and losses in copper at maintenance of holding force for laying and fixation of stacked core.

18 cl, 16 dwg, 2 tbl

Description

Field of technology to which the invention relates

[0001] The present invention relates to a core assembly and to a rotating electric machine.

This application claims priority from Japanese Patent Application No. 2021-191446, filed in Japan on November 25, 2021, the contents of which are incorporated herein by reference.

Description of the Prior Art

[0002] The rotation speed of the main machine (rotating electric machine, electric motor or engine) for EV/HEV, the number of uses of which is expected to increase in the future, becomes higher to reduce the size and weight. As the rotation speed increases, the iron loss of the rotor core or stator core increases, resulting in a decrease in efficiency. The main factor for the increase in iron loss due to high-frequency excitation is the increase in eddy current loss, and a measure to improve it is thinning the electrical steel sheet.

On the other hand, when a rotor core or a stator core formed by punching etc. is stacked, edge folding is generally used, but it is very difficult to stack and fix ultra-thin electrical steel sheets by edge folding. At this time, tying and fixing is one method for stacking and fixing ultra-thin electrical steel sheets (see, for example, the following Patent Document 1).

List of cited documents

Patent documents

[0003] Patent Document 1

Unexamined Patent Application Japan, First Publication No. 2008-78346

The essence of the invention

Problems solved by the invention

[0004] However, in the conventional bonding and fixing method, when the electrical steel sheet is fixed using an adhesive material, the elastic compressive stress generated in the electrical steel sheet due to the shrinkage during solidification of the adhesive material may deteriorate the magnetic characteristics (excitation characteristics and iron loss characteristics), resulting in an increase in loss. It should be noted that such a problem occurs not only in the electric motor but also in the entire rotating electric machine including the generator.

[0005] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a stacking core capable of suppressing an increase in loss (iron loss and copper loss) while maintaining a holding force for stacking and fixing.

Solution to the problem

[0006] <1> A composite core according to an aspect of the present invention includes: a plurality of composite sheets of electrical steel; and a plurality of adhesive layers disposed between the electrical steel sheets adjacent to each other in the stacking direction, wherein the electrical steel sheet includes an annular body, at least one adhesive layer of the plurality of adhesive layers is a first adhesive layer in one electrical steel sheet of two electrical steel sheets disposing the first adhesive layer in the middle in the stacking direction, when an imaginary axis intersecting with the central axis of the annular body and extending in the easy magnetization direction is defined as the L-axis, an imaginary axis intersecting with the central axis and intersecting with the L-axis is defined as the C-axis, and the electrical steel sheet is divided into a plurality of sections in the circumferential direction of the annular body by the L-axis and the C-axis, at least one section of the plurality of sections is the first section, and in the first section, an area of the first adhesive layer in the first portion of the electrical steel sheet in which the main magnetic flux is formed in the direction along the L-axis, less than the area of the first adhesive layer in the second section of the electrical steel sheet, in which the main magnetic flux is formed in the direction along the C-axis.

[0007] As a result of intensive research, the present inventor has come to the following conclusions. In other words, in a stacked core in which electrical steel sheets adjacent to each other in the stacking direction are bonded and attached to each other by means of an adhesive material, a compressive mechanical stress is applied to the electrical steel sheets due to the adhesive material, and this compressive mechanical stress affects the deterioration (the amount of increase in iron loss, etc.) of the magnetic characteristics of the electrical steel sheets. The present inventor has discovered for the first time that the degree of this influence varies depending on the direction of the main magnetic flux generated in the electrical steel sheets. More specifically, in the case where the direction of the main magnetic flux is the L direction (the easy magnetization direction), compared with the case where the direction of the main magnetic flux is the C direction (the direction intersecting with the L direction, the direction which is not the easy magnetization direction), the higher the area ratio of the adhesive in the electrical steel sheet, the larger the deterioration ratio in terms of iron loss, and the higher the compressive stress applied per unit area of the electrical steel sheet, the larger the deterioration ratio in terms of iron loss (see, for example, Figs. 13, 14 and 16 described below). It should be noted that the main magnetic flux is a general term for magnetic fluxes generated in the rotor core or the stator core.

[0008] Based on the above findings, the inventor of the present application has achieved that in a composite core including a ring body, an electrical steel sheet is divided into a plurality of sections by an L-axis and a C-axis, and in at least one of the plurality of sections, the area of the adhesive layer has become different depending on the direction in which the main magnetic flux is generated. In other words, the inventor of the present application has achieved that, in the first section, which is at least one of the plurality of sections, the area of the first adhesive layer in the first portion in which the main magnetic flux is generated in the L direction has become smaller than the area of the first adhesive layer in the second portion in which the main magnetic flux is generated in the C direction. As a result, instead of forming a large adhesive layer in a portion having a large influence on the iron loss in the electrical steel sheet, a large adhesive layer can be formed in a portion having a small influence on the iron loss. Therefore, it is possible to suppress the increase in losses while ensuring the required holding force.

[0009] <2> In the composite core according to <1>, in the first section, when a region relatively close to the C-axis is called a "region on the C-axis side" and a region relatively close to the L-axis is called a "region on the L-axis side", the first portion may include a portion located in a region on the C-axis side of the annular body, and the second portion may include a portion located in a region on the L-axis side of the annular body.

[0010] In a composite core including an annular body, a main magnetic flux is generated mainly in the circumferential direction in the annular body. The relative relationship between the main magnetic flux generated in the annular body and the L direction or the C direction differs depending on the position at which the main magnetic flux is generated in the circumferential direction. For example, in a portion of the annular body located on the L-axis side, the number of components of the main magnetic flux in the C direction increases. On the other hand, in a portion of the annular body located on the C-axis side, the number of components of the main magnetic flux in the L direction increases.

[0011] <3> In the composite core according to <2>, the first adhesive layer may include a first adhesive portion located on at least one of the inner peripheral edge and the outer peripheral edge of the annular body, and in the first section, the area of the first adhesive portion in the region on the C-axis side may be smaller than the area of the first adhesive portion in the region on the L-axis side.

[0012] The first adhesive portion is located at least on one of the inner peripheral edge and the outer peripheral edge of the annular body, and extends mainly in the circumferential direction. Accordingly, the first adhesive portion extends, in a region on the C-axis side, in a direction closer to the L direction than to the C direction (having a gentle slope), and extends, in a region on the L-axis side, in a direction closer to the C direction than to the L direction (having a gentle slope). Accordingly, with respect to the first adhesive portion, as the number of portions located in the region on the L-axis side increases, the ratio of the first adhesive portion extending in a direction close to the C direction increases, and the effect on the iron loss decreases.

Therefore, in the composite core, in the first section, the area of the first adhesive portion in the region on the C-axis side is smaller than the area of the first adhesive portion in the region on the L-axis side. Therefore, the influence of the first adhesive portion on the iron loss can be suppressed so that it is small.

[0013] <4> In the composite core according to <3>, the first adhesive portion may extend in a tape shape along at least one of the inner peripheral edge and the outer peripheral edge of the annular body, and in the first section, the width of the first adhesive portion may be equal regardless of the position in the circumferential direction or may decrease from the L-axis to the C-axis along the circumferential direction.

[0014] <5> In the composite core according to <4>, in the first section, the width of the first adhesive portion may decrease from the L-axis to the C-axis along the circumferential direction.

[0015] In the first section, the width of the first adhesive portion is equal regardless of the position in the circumferential direction or decreases from the L-axis to the C-axis along the circumferential direction. It should be noted that the width of the first adhesive portion preferably decreases from the L-axis to the C-axis along the circumferential direction. The above-described advantages are demonstrated largely due to the above.

[0016] <6> In the composite core according to any one of <1> to <5>, the electrical steel sheet may further include a plurality of teeth protruding from the annular body inward in a radial direction of the annular body and arranged at intervals in a circumferential direction of the annular body, the first portion may include a portion of teeth arranged in a region on the L-axis side, and the second portion may include a portion of teeth arranged in a region on the C-axis side.

It should be noted that, as described above, when the electrical steel sheet includes not only the annular body but also the teeth, the first adhesive layer bonds not only the annular bodies but also the teeth of the electrical steel sheet, the first section is defined not only for the annular body but also for the teeth, and each of the first portion and the second portion includes not only a part or all of the annular body but also a part or all of the teeth.

[0017] In a composite core including teeth, a main magnetic flux is mainly generated in a radial direction in the teeth. A relative relationship between the main magnetic flux generated in the teeth and the L direction or the C direction differs depending on a position at which the main magnetic flux is generated in the circumferential direction of the teeth. For example, the number of components of the main magnetic flux in the L direction increases in the teeth located on the L-axis side of the plurality of teeth. On the other hand, the number of components of the main magnetic flux in the C direction increases in the teeth located on the C-axis side of the plurality of teeth.

[0018] <7> In the composite core according to <6>, the first adhesive layer may include a second adhesive portion located on the peripheral edge of the teeth, and in the first section, the area of the second adhesive portion in the region on the C-axis side may be larger than the area of the second adhesive portion in the region on the L-axis side.

[0019] The second adhesive portion is located at the peripheral edge of the teeth and extends mainly in the radial direction. Therefore, the second adhesive portion extends, in the region on the C-axis side, in a direction closer to the C direction than to the L direction (having a gentle slope), and extends, in the region on the L-axis side, in a direction closer to the L direction than to the C direction (having a gentle slope). Therefore, with respect to the second adhesive portion, as the number of portions located in the region on the C-axis side increases, the ratio of the second adhesive portion extending in a direction close to the C direction increases, and the effect on the iron loss decreases.

Therefore, in the composite core, in the first section, the area of the second adhesive portion in the region on the C-axis side is larger than the area of the second adhesive portion in the region on the L-axis side. Therefore, the influence of the second adhesive portion on the iron loss can be suppressed so that it is small.

[0020] <8> In the composite core according to <7>, the second adhesive portion may extend in the form of a tape along the peripheral edge of the teeth, and in the first section, the width of the second adhesive portion may be equal regardless of the positions of the teeth in the circumferential direction or may be larger for the teeth located closer to the side along the C-axis than for the teeth located closer to the side along the L-axis along the circumferential direction.

[0021] <9> In the composite core according to <8>, in the first section, the width of the second adhesive portion may be larger for the teeth located closer to the side along the C-axis than for the teeth located closer to the side along the L-axis along the circumferential direction.

[0022] In the first section, the width of the second adhesive portion is equal regardless of the positions of the teeth in the circumferential direction, or is larger for the teeth located closer to the side along the C-axis than for the teeth located closer to the side along the L-axis along the circumferential direction. It should be noted that in the first section, the width of the second adhesive portion is preferably larger for the teeth located closer to the side along the C-axis than for the teeth located closer to the side along the L-axis along the circumferential direction. The above-described advantages are demonstrated largely due to the above.

[0023] <10> In the composite core according to any one of <2> to <5>, in the first section, when an imaginary axis extending in a direction dividing a central angle formed by the C-axis and the L-axis around the central axis into two equal parts is defined as a base axis, a region on the C-axis side and a region on the L-axis side may have a symmetrical relationship in a circumferential direction with respect to the base axis.

[0024] The region on the C-axis side and the region on the L-axis side are symmetrical in the circumferential direction with respect to the basal axis. Therefore, the above-described advantages are demonstrated to a large extent.

[0025] <11> In the stacked core according to any one of <2> to <10>, the first adhesive layer may include a tape adhesive portion, in a region on the L-axis side, a total area of the tape adhesive portions in which the circumferential direction is the longitudinal direction may be larger than a total area of the tape adhesive portions in which the radial direction of the annular body is the longitudinal direction, and in a region on the C-axis side, a total area of the tape adhesive portions in which the circumferential direction is the longitudinal direction may be smaller than a total area of the tape adhesive portions in which the radial direction is the longitudinal direction.

[0026] <13> In the composite core according to any one of <1> to <11>, all of the plurality of adhesive layers may be first adhesive layers.

[0027] In the case where all of the plurality of adhesive layers are first adhesive layers including the first section, in other words, in the case where such a condition that all of the plurality of adhesive layers are first adhesive layers is satisfied, the above-described advantages are demonstrated to a significant extent, for example, compared with the case in which a part of the plurality of adhesive layers does not satisfy such a condition that the adhesive layers are first adhesive layers.

[0028] <14> In the composite core according to any one of <1> to <12>, all of the plurality of sections may be first sections.

[0029] In the case where all of the plurality of sections in the first adhesive layer are first sections, in other words, in the case where such a condition that all of the plurality of sections are first sections is satisfied, the above-described advantages are demonstrated to a significant extent, for example, compared to the case in which a part of the plurality of sections does not satisfy such a condition that the sections are first sections.

[0030] <14> In the composite core according to any one of <1> to <13>, the electrical steel sheet may be a non-oriented electrical steel sheet.

[0031] <15> In the composite core according to any one of <1> to <13>, the sheet of electrical steel may be a grain-oriented sheet of electrical steel.

[0032] <16> In the composite core according to any one of <1> to <15>, only one easy magnetization direction may exist in one sheet of electrical steel, and the L-axis and the C-axis may be orthogonal to each other.

[0033] <17> In the composite core according to any one of <1> to <15>, two or more easy magnetization directions may exist in one sheet of electrical steel, the L-axis may extend in the two or more easy magnetization directions with the possibility of intersecting with each other on the central axis, and the C-axis may extend in a direction in which a central angle formed around the central axis by the L-axes next to each other in the circumferential direction is divided into two equal parts.

[0034] <18> A rotating electric machine according to an aspect of the present invention includes a composite core according to any one of <1> to <17>.

Advantages of the invention

[0035] According to the present invention, it is possible to suppress the increase in loss in maintaining the holding force for laying and fixing.

Brief description of the drawings

[0036] Fig. 1 is a cross-sectional view of a rotating electrical machine according to an embodiment of the present invention.

Fig. 2 is a top view of a stator included in the rotating electrical machine illustrated in Fig. 1.

Fig. 3 is a side view of a stator included in the rotating electrical machine illustrated in Fig. 1.

Fig. 4 is a top view of an electrical steel sheet and an adhesive layer of a stator included in the rotating electrical machine illustrated in Fig. 1.

Fig. 5 is a plan view of the electrical steel sheet and the adhesive layer and is an enlarged view of one section divided by the L-axis and the C-axis.

Fig. 6 is a photograph for explaining the roll impression and is a photograph showing a common sheet of electrical steel.

Fig. 7 is an enlarged photograph of a portion of the photograph shown in Fig. 7.

Fig. 8 is a side view illustrating an example of manufacturing equipment for manufacturing a stator included in the rotating electric machine illustrated in Fig. 1.

Fig. 9 is a top view according to a first example of modification of a stator included in the rotating electric machine illustrated in Fig. 1, and is a view corresponding to the enlarged view illustrated in Fig. 5.

Fig. 10 is a top view according to a second example of modification of a stator included in the rotating electric machine illustrated in Fig. 1, and is a view corresponding to the enlarged view illustrated in Fig. 4.

Fig. 11 is a top view according to a second example of modification of a stator included in the rotating electric machine illustrated in Fig. 1, and is a view corresponding to the enlarged view illustrated in Fig. 5.

Fig. 12 is a photograph for explaining the rotational stacking and is a photograph showing the overall stacking core.

Fig. 13 is a graph illustrating the relationship between the adhesive area ratio and the iron loss when the magnetic flux is generated in the L direction in the first verification test.

Fig. 14 is a graph illustrating the relationship between the area ratio of the adhesive and the iron loss when the magnetic flux is generated in the C direction in the first verification test.

Fig. 15 is a top view of a stator electrical steel sheet as a target for simulating iron loss in the second verification test, and is a view corresponding to the enlarged view illustrated in Fig. 5.

Fig. 16 is a graph illustrating the result of the second verification test.

Embodiment of the invention

[0037] Hereinafter, a rotating electric machine according to an embodiment of the present invention will be described with reference to the drawings. It should be noted that in the present embodiment, an electric motor, namely, an AC electric motor, more specifically, a synchronous electric motor, and even more specifically, a permanent magnetic field electric motor, will be described as an example of a rotating electric machine. This type of electric motor is suitably adapted for, for example, an electric vehicle.

[0038] As illustrated in Fig. 1 and 2, the rotating electric machine 10 includes a stator 20, a rotor 30, a housing 50 and a rotary shaft 60. The stator 20 and the rotor 30 are housed in the housing 50. The stator 20 is attached to the housing 50.

In the present embodiment, an internal rotor machine in which the rotor 30 is disposed in the stator 20 is used as the rotating electric machine 10. However, an external rotor machine in which the rotor 30 is disposed outside the stator 20 can be used as the rotating electric machine 10. In the present embodiment, the rotating electric machine 10 is a three-phase AC motor having 12 poles and 18 slots. However, for example, the number of poles, the number of slots, the number of phases, etc. can be appropriately changed. It should be noted that, for example, the rotating electric machine 10 can rotate at a rotation speed of 1000 rpm by applying an excitation current having an effective value of 10 A and a frequency of 100 Hz to each phase.

[0039] The stator 20 includes a stator core 21 and a winding (not illustrated).

The stator core 21 includes a cylindrical core back 22 (annular body) and a plurality of teeth 23. Hereinafter in this document, the axial direction (the direction of the central axis O of the stator core 21) of the stator core 21 (the core back 22) is referred to as "simply the axial direction," the radial direction (the direction orthogonal to the central axis O of the stator core 21) of the stator core 21 (the core back 22) is referred to as "simply the radial direction," and the circumferential direction (the direction going around the central axis O of the stator core 21) of the stator core 21 (the core back 22) is referred to as "simply the circumferential direction."

[0040] The back 22 of the core has a ring shape in a top view, when viewing the stator 20 from the axial direction.

A plurality of teeth 23 project inward in the radial direction from the back 22 of the core (towards the central axis O of the back 22 of the core along the radial direction). The plurality of teeth 23 are arranged at equal intervals in the circumferential direction. In the present embodiment, 18 teeth 23 are arranged every 20 degrees of the central angle centered on the central axis O. The plurality of teeth 23 have the same shape and the same size.

The winding is wound around the teeth 23. The winding can be wound using a concentrated winding or a distributed winding.

[0041] The rotor 30 is located in the stator 20 (in the stator core 21) in the radial direction. The rotor 30 includes a rotor core 31 and a plurality of permanent magnets 32.

The rotor core 31 is located coaxially with the stator 20 and has a cylindrical shape. The rotational shaft 60 is located in the rotor core 31. The rotational shaft 60 is attached to the rotor core 31 in such a way that it rotates together with the rotor core 31.

A plurality of permanent magnets 32 are attached to the rotor core 31. In the present embodiment, a pair of permanent magnets 32 functions as one magnetic pole. A plurality of pairs of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In the present embodiment, 12 pairs (24 in total) of permanent magnets 32 are arranged at every 30 degrees of the central angle centered on the central axis O.

[0042] In the present embodiment, a built-in magnet motor is used as a permanent magnetic field motor. A plurality of through cavities 33 penetrating the rotor core 31 in the axial direction are formed in the rotor core 31. The plurality of through cavities 33 are formed according to a plurality of permanent magnets 32. Each of the permanent magnets 32 is attached to the rotor core 31 in a state of being located in a corresponding through cavity 33. Each of the permanent magnets 32 can be attached to the rotor core 31 by, for example, bonding the outer surface of the permanent magnet 32 to the inner surface of the through cavity 33 using an adhesive material. It should be noted that, as a permanent magnetic field motor, a surface magnet motor can be used instead of a built-in magnet motor.

[0043] The stator core 21 and the rotor core 31 are composite cores. The composite core is formed by stacking a plurality of electrical steel sheets 40.

It should be noted that each of the stator core 21 and the rotor core 31 has a stacking thickness of, for example, 50.0 mm. The stator core 21 has an outer diameter of, for example, 250.0 mm. The stator core 21 has an inner diameter of, for example, 165.0 mm. The rotor core 31 has an outer diameter of, for example, 163.0 mm. The rotor core 31 has an inner diameter of, for example, 30.0 mm. It should be noted that these values are just examples, and the stacking thickness, the outer diameter and the inner diameter of the stator core 21 and the stacking thickness, the outer diameter and the inner diameter of the rotor core 31 are not limited to these values. Here, the inner diameter of the stator core 21 is based on the end portions of the teeth 23 in the stator core 21. The internal diameter of the stator core 21 is the diameter of an imaginary circle inscribed in the end sections of all teeth 23.

[0044] Each of the electrical steel sheets 40 forming the stator core 21 and the rotor core 31 is formed, for example, by punching an electrical steel sheet serving as a base metal. As the electrical steel sheet 40, a known electrical steel sheet may be used. The chemical composition of the electrical steel sheet 40 is not particularly limited. In the present embodiment, a non-oriented electrical steel sheet is used as the electrical steel sheet 40. As the non-oriented electrical steel sheet, a non-oriented electrical steel strip of JISC2552:2014 may be used. However, as the electrical steel sheet 40, a grain-oriented electrical steel sheet may be used instead of a non-oriented electrical steel sheet. As the grain-oriented electrical steel sheet, a grain-oriented electrical steel strip according to JIS C 2553:2012 may be used. In addition, as the 40 grain-oriented electrical steel sheet, an Fe-based amorphous alloy may be used instead of the non-grain-oriented electrical steel sheet. As the Fe-based amorphous alloy, for example, an iron-based amorphous strip according to JIS C 2534:2017 may also be used.

[0045] Insulating coatings are formed on both surfaces of the electrical steel sheet 40 in order to improve the workability of the electrical steel sheet and the iron loss of the composite core. As a substance constituting the insulating coating, for example, (1) an inorganic compound, (2) an organic resin, (3) a mixture of an inorganic compound and an organic resin can be used. Examples of the inorganic compound include (1) a complex compound of dichromate and boric acid and (2) a complex compound of phosphate and silicon dioxide. Examples of the organic resin include epoxy resin, acrylic resin, acrylic styrene resin, polyester resin, silicon resin and fluorine resin.

[0046] In order to ensure the insulating performance between the electrical steel sheets 40 stacked on each other, the thickness of the insulating coating (the thickness per surface of the electrical steel sheet 40) is preferably 0.1 μm or more.

On the other hand, as the insulating coating becomes thicker, the insulating ability is saturated. In addition, as the insulating coating becomes thicker, the filling factor decreases and the performance as a composite core deteriorates. Therefore, the insulating coating is preferably thin within a range in which the insulation performance can be ensured. The thickness of the insulating coating (the thickness per side of the electrical steel sheet 40) is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 2 μm or less.

[0047] As the electrical steel sheet 40 becomes thinner, the advantage in terms of improving the iron loss gradually saturates. In addition, as the electrical steel sheet 40 becomes thinner, the manufacturing cost of the electrical steel sheet 40 increases. Therefore, the thickness of the electrical steel sheet 40 is preferably 0.10 mm or more in consideration of the advantage in terms of improving the iron loss and the manufacturing cost.

On the other hand, when the electrical steel sheet 40 is too thick, the press punching operation of the electrical steel sheet 40 is difficult. Therefore, the thickness of the electrical steel sheet 40 is preferably 0.65 mm or less in consideration of the press punching operation of the electrical steel sheet 40.

In addition, as the electrical steel sheet 40 becomes thicker, the iron loss increases. Therefore, the thickness of the electrical steel sheet 40 is preferably 0.35 mm or less, and more preferably 0.20 mm or 0.25 mm in consideration of the iron loss characteristics of the electrical steel sheet 40.

The thickness of each of the electrical steel sheets 40 is, for example, 0.10 mm or more and 0.65 mm or less, preferably 0.10 mm or more and 0.35 mm or less, and more preferably 0.20 mm or 0.25 mm in view of the above aspects. In addition, the thickness of the electrical steel sheet 40 also includes the thickness of the insulating coating.

[0048] A plurality of electrical steel sheets 40 forming the stator core 21 are bonded to each other by an adhesive layer 41. The adhesive layer 41 is disposed between the electrical steel sheets 40 next to each other in the stacking direction. The adhesive layer 41 includes adhesive portions 42 and 43 which are curable adhesive materials. As the adhesive material, for example, a thermosetting adhesive material using polymerization bonding is used. As the composition of the adhesive material, a composition containing (1) an acrylic resin, a composition containing (2) an epoxy resin, a composition containing (3) an acrylic resin and an epoxy resin, and the like can be used. As such an adhesive material, in addition to a thermosetting adhesive material, an adhesive material based on radical polymerization and the like can be used, and it is desirable to use a room temperature curing adhesive material from the viewpoint of performance. The room temperature curing adhesive material is cured at 20 to 30°C. As the room temperature curing adhesive material, an acrylic adhesive material is preferable. A typical acrylic adhesive material is a second generation acrylic adhesive material (SGA) and the like. All of an aerobic adhesive material, an instant adhesive material, and an elastomer-containing acrylic adhesive material can be used as long as the advantages of the present invention are not impaired. It should be noted that the adhesive material here means an adhesive material before curing, and the adhesive material becomes an adhesive layer 41 after the adhesive material is cured.

[0049] The adhesive layer 41 has an average tensile elastic modulus E of 1500 MPa to 4500 MPa at a normal temperature (20-30°C). When the average tensile elastic modulus E of the adhesive layer 41 is less than 1500 MPa, a problem arises that the rigidity of the composite core decreases. Therefore, the lower limit value of the average tensile elastic modulus E of the adhesive layer 41 is 1500 MPa, and more preferably 1800 MPa. On the other hand, when the average tensile elastic modulus E of the adhesive layer 41 exceeds 4500 MPa, a problem arises that the insulating coating formed on the surface of the electrical steel sheet 40 peels off. Therefore, the upper limit value of the average tensile elastic modulus E of the adhesive layer 41 is 4500 MPa, and more preferably 3650 MPa.

In addition, the average tensile modulus E is measured by the resonance method. Specifically, the tensile modulus is measured in accordance with JIS R 1602:1995.

More specifically, a measurement sample (not illustrated) is first produced. This sample is obtained by bonding two sheets 40 of electrical steel with an adhesive material to be measured and curing the adhesive material so as to form an adhesive layer 41. When the adhesive material is a thermosetting adhesive material, the curing is performed by heating and pressurizing under the conditions of heating and pressurizing in the actual operation. On the other hand, when the adhesive material is a room temperature curing adhesive material, this curing is performed by pressurizing at room temperature.

Then, the tensile elastic modulus of this specimen is measured by the resonance method. The method for measuring the tensile elastic modulus by the resonance method is carried out in accordance with JIS R 1602:1995 as described above. After that, the influence of the electrical steel sheets 40 itself is removed from the tensile elastic modulus (measured value) of the specimen by calculation, so as to obtain the tensile elastic modulus of the adhesive layer 41 only.

Since the tensile modulus obtained from the sample in this way is equal to the average value as the entire stacked core, this numerical value is considered as the average tensile modulus E. The composition is set in such a way that the average tensile modulus E does not change substantially depending on the laying position along the laying direction or the position of the stacked core in the circumferential direction around the central axis. Therefore, the average tensile modulus E can also be set as a numerical value obtained by measuring the cured adhesive layer 41 in the upper end position of the stacked core.

[0050] As the bonding method, for example, a method in which an adhesive material is applied to the electrical steel sheets 40, and then the electrical steel sheets 40 are bonded by one or both of heating and pressure bonding may be used. It should be noted that the heating means may be any means such as heating in a high-temperature tank or an electric furnace, or a direct power supply method.

[0051] In order to stably obtain sufficient adhesive strength, the thickness of the adhesive layer 41 is preferably 1 μm or more.

On the other hand, when the thickness of the adhesive layer 41 exceeds 100 μm, the adhesive force is saturated. In addition, as the adhesive layer 41 becomes thicker, the fill factor decreases, and the magnetic characteristics such as the iron loss of the stacked core deteriorate. Therefore, the thickness of the adhesive layer 41 is preferably 1 μm or more and 100 μm or less, and more preferably 1 μm or more and 10 μm or less.

It should be noted that in the above description, the thickness of the adhesive layer 41 means the average thickness of the adhesive layer 41.

[0052] The average thickness of the adhesive layer 41 is more preferably 1.0 μm or more and 3.0 μm or less. When the average thickness of the adhesive layer 41 is less than 1.0 μm, sufficient adhesive force cannot be ensured as described above. Therefore, the lower limit value of the average thickness of the adhesive layer 41 is 1.0 μm, and more preferably 1.2 μm. On the other hand, when the average thickness of the adhesive layer 41 is more than 3.0 μm, a problem such as a significant increase in the tension amount of the electrical steel sheet 40 due to shrinkage during heat curing occurs. Therefore, the upper limit value of the average thickness of the adhesive layer 41 is 3.0 μm, and more preferably 2.6 μm.

The average thickness of the adhesive layer 41 is an average value as the entire stacked core. The average thickness of the adhesive layer 41 does not change substantially depending on the laying position along the laying direction or the position of the stacked core in the circumferential direction around the central axis. Therefore, the average thickness of the adhesive layer 41 can be set as an average value of the numerical values measured at ten or more locations in the circumferential direction in the upper end position of the stacked core.

[0053] It should be noted that the average thickness of the adhesive layer 41 can be adjusted, for example, by changing the amount of adhesive material applied. In addition, the average tensile modulus E of the adhesive layer 41 can be adjusted, for example, in the case of a thermosetting adhesive material, by changing one or both of the heating and pressurization conditions applied during bonding and the type of curing agent.

[0054] It should be noted that in the present embodiment, a plurality of electrical steel sheets 40 forming the rotor core 31 are attached to each other by a folded edge 51 (tongue). However, a plurality of electrical steel sheets 40 forming the rotor core 31 can be bonded to each other by an adhesive layer 41.

It should be noted that a composite core such as the stator core 21 or the rotor core 31 may be formed by so-called rotational stacking. It should be noted that in the present embodiment, the stator core 21 is not obtained by rotational stacking. Therefore, the rolling directions of the plurality of electrical steel sheets 40 forming the stator core 21 coincide with each other.

[0055] Here, as illustrated in Fig. 3 and 4, in the present invention, in the stator core 21, the electrical steel sheets 40 adjacent to each other in the stacking direction are bonded to each other by an adhesive layer 41. In the illustrated example, the electrical steel sheets 40 adjacent to each other in the stacking direction are fixed only by bonding and are not fixed by another means (for example, folding of edges). It should be noted that the electrical steel sheets 40 may be bonded to each other by an adhesive layer 41 after being fixed to each other by another means.

[0056] As illustrated in Fig. 4 and 5 (the same applies to Fig. 9, 10, 11 and 15 described below), in the present embodiment, the electrical steel sheets 40 adjacent to each other in the stacking direction are bonded to each other by an adhesive layer 41. It should be noted that, in the present embodiment, the shapes in a plan view of all the adhesive layers 41 arranged between the electrical steel sheets 40 are identical. The shape in a plan view of the adhesive layer 41 means the entire shape of the adhesive layer 41 in a plan view when viewing the electrical steel sheet 40 including the adhesive layer 41 from the stacking direction. The identical shapes in the plan view of all the adhesive layers 41 arranged between the electrical steel sheets 40 include not only the case in which the shapes in the plan view of all the adhesive layers 41 arranged between the electrical steel sheets 40 are completely identical, but also the case in which the shapes in the plan view are substantially identical. The case in which the shapes in the plan view are substantially identical is the case in which the shapes in the plan view of all the adhesive layers 41 arranged between the electrical steel sheets 40 are common in 90% or more of the areas.

[0057] Each of the adhesive layers 41 includes a first adhesive portion 42 and a second adhesive portion 43. The first adhesive portion 42 is located on at least one of the inner peripheral edge and the outer peripheral edge of the back 22 of the core. The first adhesive portion 42 continues in the form of a tape along at least one of the inner peripheral edge and the outer peripheral edge of the back 22 of the core. The second adhesive portion 43 is located on the peripheral edge of the teeth 23. The second adhesive portion 43 continues in the form of a tape along the peripheral edge of the teeth 23.

[0058] Here, the tape shape includes a shape in which the width of the tape changes in the middle, and a shape in which the middle position of the tape is divided. For example, a shape in which each of the individual portions has a predetermined shape, for example, a round shape or a quadrangular shape, but the individual portions are continuous in one direction without division, and a shape in which two adjacent individual portions are separated from each other, but the separation distance between them is relatively small, and which is a tape shape as a whole (as a set of the individual portions described above), are also included in the tape shape continuing in one direction. In the tape adhesive portions 42 and 43, for example, the aspect ratio (the ratio of the long and short side) of each of the adhesive portions 42 and 43 is five or more (the long side has a length five times or more than the short side). The arrangement of the adhesive portions 42 and 43 along the peripheral edge is not based on the premise that the adhesive portions 42 and 43 have a shape continuous in one direction. For example, a case in which a plurality of adhesive portions 42 and 43 are intermittently arranged in one direction is also included. It should be noted that in this case, the interval (length in one direction) between a pair of adhesive portions 42 and 43 adjacent to each other in one direction preferably exceeds the size (length in one direction) of each pair of adhesive portions 42 and 43. In such tape adhesive portions 42 and 43, one direction is a longitudinal direction. The longitudinal direction of the tape adhesive portions 42 and 43, for example, is a direction in which the long side of each of the adhesive portions 42 and 43 having an aspect ratio of five or more continues.

The arrangement of the adhesive portions 42 and 43 along the peripheral edge includes not only the case in which the adhesive portions 42 and 43 are arranged without a gap from the peripheral edge, but also the case in which the adhesive portions 42 and 43 are arranged with a gap with respect to the peripheral edge of the electrical steel sheet 40. It should be noted that in this case, the arrangement of the adhesive portions 42 and 43 along the peripheral edge means that the adhesive portions 42 and 43 extend substantially parallel to the target peripheral edge. In other words, the arrangement of the adhesive portions 42 and 43 along the peripheral edge includes not only the case in which the adhesive portions 42 and 43 are completely parallel to the peripheral edge, but also the case in which the adhesive portions 42 and 43 have an inclination of, for example, five degrees or less to the peripheral edge. The arrangement of the adhesive portions 42 and 43 along the peripheral edge does not include the case in which the adhesive portions 42 and 43 are arranged with a gap exceeding a certain width with respect to the peripheral edge of the electrical steel sheet 40. Specifically, the adhesive portions 42 and 43 are arranged in a range not exceeding a width three times the size corresponding to the sheet thickness of the electrical steel sheet 40 from the peripheral edge of the electrical steel sheet 40. The distance (width) between the adhesive portions 42 and 43 and the peripheral edge of the electrical steel sheet 40 is preferably equal to or less than the sheet thickness of the electrical steel sheet 40, and should only be equal to or less than three times the sheet thickness. It should be noted that when the distance is 0, the adhesive portions 42 and 43 are arranged without a gap on the peripheral edge of the electrical steel sheet 40.

[0059] In the present embodiment, as illustrated in Figs. 4 and 5, the first adhesive portion 42 includes both an inner adhesive portion 42a located on the inner peripheral edge of the back 22 of the core and an outer adhesive portion 42b located on the outer peripheral edge of the back 22 of the core. Each of the inner adhesive portion 42a and the outer adhesive portion 42b extends in the circumferential direction. The inner adhesive portion 42a and the outer adhesive portion 42b are arranged at equal positions in the circumferential direction. The inner adhesive portion 42a is located in the outer adhesive portion 42b in the radial direction. The inner adhesive portion 42a discontinuously extends in the circumferential direction. The outer adhesive portion 42b continuously extends in the circumferential direction.

[0060] The inner adhesive portion 42a is located in a portion in which the teeth 23 are not located on the inner peripheral edge of the back 22 of the core. The inner adhesive portion 42a includes partial adhesive portions 42c located at intervals in the circumferential direction. The partial adhesive portion 42c is located between the teeth 23 adjacent in the circumferential direction on the inner peripheral edge of the back 22 of the core. The partial adhesive portion 42c continues along the entire length between the teeth 23 on the inner peripheral edge of the back 22 of the core.

It should be noted that, as illustrated in Fig. 5, the width of the inner adhesive portion 42a may be smaller than the width of the outer adhesive portion 42b. In the back 22 of the core, the magnetic flux is more likely to be generated at the inner peripheral edge than at the outer peripheral edge, and the iron loss is reduced by decreasing the width (area) of the adhesive portion at the inner peripheral edge.

[0061] The second adhesive portions 43 are intermittently arranged in the circumferential direction. The second adhesive portion 43 includes a plurality of tooth adhesive portions 43a arranged on the teeth 23, respectively. The tooth adhesive portion 43a has a U-shape in a plan view when viewing the electrical steel sheet 40 from the laying direction. The tooth adhesive portion 43a includes two side edge portions 43b and one end edge portion 43c. The two side edge portions 43b are arranged on two side edges of one tooth 23. The two side edge portions 43b are arranged at intervals in the circumferential direction. Each of the side edge portions 43b continues in the form of a tape in the radial direction. One end edge portion 43c is arranged at the end (the inner end in the radial direction in the illustrated example) of one tooth 23. Each of the side edge portions 43b extends in the form of a tape in the radial direction. The end edge portion 43c extends in the form of a tape in the circumferential direction. It should be noted that the end edge portion 43c prevents delamination of the end of the tooth 23 when an external force is applied to the end of the tooth 23. The external force, for example, can be applied to the tooth 23 when the winding is inserted into the groove.

[0062] In the present embodiment, the first adhesive portion 42 and the second adhesive portion 43 are arranged alternately in the circumferential direction. In the illustrated example, the end portion of the first adhesive portion 42 (the inner adhesive portion 42a) in the circumferential direction and the end portion of the second adhesive portion 43 (the side edge portion 43b) in the circumferential direction are continuous in the circumferential direction. The first adhesive portion 42 and the second adhesive portion 43 are arranged alternately along the entire circumference in the circumferential direction. Two first adhesive portions 42 and two second adhesive portions 43 are arranged. Each of the first adhesive portion 42 and the second adhesive portion 43 is arranged approximately 1/4 from the circumference.

[0063] Here, the L-axis and the C-axis are defined. Both the L-axis and the C-axis are imaginary axes intersecting with the central axis (the central axis O) of the back portion 22 of the core. The L-axis extends in the easy magnetization direction. It should be noted that, in the present embodiment, the electrical steel sheet is a non-oriented electrical steel sheet, and the L-axis extends in the rolling direction and in the easy magnetization direction. In other words, in the present embodiment, the easy magnetization direction and the rolling direction coincide with each other. The C-axis is orthogonal to (intersected with) the L-axis. Hereinafter in this document, the direction in which the L-axis extends is called the "L direction", and the direction in which the C-axis extends is called the "C direction".

[0064] It should be noted that in the present embodiment, only one direction of easy magnetization exists in one electrical steel sheet 40. The direction of easy magnetization can be determined, for example, by (1) confirming the grains of the electrical steel sheet 40 or (2) magnetically measuring the electrical steel sheet 40. In any of the above-mentioned methods of (1) and (2) determining, for example, first, the electrical steel sheet 40 to be measured is removed from the stator core 21, for example, by peeling.

Thereafter, in the method (1) for confirming the grains of the electrical steel sheet 40, for example, a pattern (100) with a reverse curve is created in the direction parallel to the rolled surface using a reflection electron microscope (EBSD), and the direction with the highest strength can be used as the easy magnetization direction (reference document: "EBSD Reader=In Using OIM=(B4.00)", written by Seiichi Suzuki, TSL Solutions, Inc., URL: https://www.tsljapan.com/archives/3380).

On the other hand, as the method (2) for magnetic measurement of the electrical steel sheet 40, for example, a method is provided in which a rectangular or square steel sheet inclined at a predetermined angle with respect to the rolling direction is cut out to obtain a measurement sample, and the measurement is performed based on the method for magnetic measurement of an electrical steel strip using a single sheet tester specified in JIS C 2556:2015. In this case, the direction of easy magnetization can be determined by preparing a plurality of the above-described measurement samples with different inclination angles with respect to the rolling direction and comparing the measurement results of the plurality of measurement samples.

Here, in the present invention, when the number of easy magnetization directions is counted (for example, whether or not the number of easy magnetization directions is one or more), the directions opposite by 180° around the central axis O are counted as an identical direction (one direction). For example, the direction at 0° and the direction at 180° are counted as an identical direction (one direction). For example, the direction at +X° and the direction at +(X+180)° in the same direction around the central axis O with respect to the rolling direction are counted as an identical direction (one direction).

[0065] The rolling direction can be determined by means of a roll imprint 40a illustrated in Fig. 6 and 7. Fig. 6 and 7 are photographs illustrating a common electrical steel sheet 40Z. It should be noted that a similar roll imprint 40a can also be confirmed in the electrical steel sheet 40 included in the stator core 21.

The roll mark 40a is a linear defect formed on the surfaces of the electrical steel sheets 40 and 40Z by the rolling roll during the rolling of the electrical steel sheets 40 and 40Z. It can also be said that the roll mark 40a is a stripe continuing in the rolling direction. The roll mark 40a can be visually confirmed by a person. For example, in the electrical steel sheet 40 illustrated in Figs. 6 and 7, it can be confirmed that there is a roll mark 40a (defect, stripe) continuing in the direction from left to right relative to the surface of the paper (for example, the roll mark 40a is easily visually recognized in the R range in Fig. 7).

It should be noted that when the rolling direction of the electrical steel sheet 40 included in the stator core 21 is determined, for example, preferably the electrical steel sheet 40 is removed from the stator core 21, and then the electrical steel sheet 40 is observed in a state in which the adhesive layer 41 is removed from the surface of the electrical steel sheet 40.

[0066] As illustrated in Fig. 4 and 5, the above-described two first adhesive portions 42 (see Fig. 4) are linearly symmetrical with respect to the C-axis (or L-axis). The two second adhesive portions 43 are linearly symmetrical in the C direction with respect to the L-axis.

[0067] Furthermore, as illustrated in Fig. 5, the electrical steel sheet 40 is divided into a plurality of sections S. In the embodiment illustrated in Fig. 5, the electrical steel sheet 40 is divided into four sections. The four sections S are sections S obtained by segmenting the electrical steel sheet 40 into four equal parts by an L-axis and a C-axis. Of the four sections S, two sections adjacent to each other with a C-axis (or L-axis) arranged between them are linearly symmetrical with each other about the C-axis (or L-axis). Of these four sections S, two sections arranged at positions rotated by 180 degrees around a central axis (central axis O) are point-symmetrical with each other around the central axis (central axis O).

[0068] Here, in each of the four sections S, a reference axis R, a region SC on the C-axis side, and a region SL on the L-axis side are defined. The reference axis R is an imaginary line passing through the center (the center in the circumferential direction) of the C-axis and the L-axis, and in the present embodiment, the reference axis R is an imaginary axis continuing at an inclination of 45° with respect to each of the C-axis and the L-axis. The reference axis R continues in a direction that divides a central angle formed by the C-axis and the L-axis around the central axis O into two equal parts. The region SC on the C-axis side is a region relatively close to the C-axis. In other words, at each position belonging to the region SC on the C-axis side, the distance to the C-axis is smaller than the distance to the L-axis. In other words, the SC region on the C-axis side is the region located midway between the basal axis R and the C-axis. The SL region on the L-axis side is the region relatively close to the L-axis. In other words, at each position belonging to the SL region on the L-axis side, the distance to the L-axis is less than the distance to the C-axis. In other words, the SL region on the L-axis side is the region located midway between the basal axis R and the L-axis. The SC region on the C-axis side and the SL region on the L-axis side have identical areas. The region SC on the C-axis side and the region SL on the L-axis side are linearly symmetrical with each other with respect to the base axis R. In the present embodiment, the region SC on the C-axis side is the entire region located in a range of a predetermined central angle from the C-axis to the L-axis around the central axis O. The region SL on the L-axis side is the entire region located in a range of a predetermined central angle from the L-axis to the C-axis around the central axis O. In the present embodiment, the central angle of each of the region SC on the C-axis side and the region SL on the L-axis side is 45°. The region SC on the C-axis side is the entire region located on the L-axis side with respect to the base axis R. The region SL on the L-axis side is the entire region located on the C-axis side with respect to the base axis R.

[0069] Incidentally, the author of the present application comes to the following conclusions (1) and (2).

(1) In the stator core 21 including the core back 22, the main magnetic flux M is generated mainly in the circumferential direction in the core back 22. In the core back 22, the direction in which the main magnetic flux M is generated is the circumferential direction. The relative relationship between the main magnetic flux M generated in the core back 22 and the L direction or the C direction differs depending on the position in which the main magnetic flux M is generated in the circumferential direction. For example, in a portion of the core back 22 located on the L-axis side, the number of components of the main magnetic flux M in the C direction increases. On the other hand, in a portion of the core back 22 located on the C-axis side, the number of components of the main magnetic flux M in the L direction increases.

(2) In the stator core 21 including the teeth 23, the main magnetic flux M is generated mainly in the radial direction in the tooth 23. In the tooth 23, the direction in which the main magnetic flux M is generated is the radial direction. The relative relationship between the main magnetic flux M generated in the tooth 23 and the L direction or the C direction differs depending on the position of the tooth 23 in which the main magnetic flux M is generated in the circumferential direction. For example, the number of components of the main magnetic flux M in the L direction increases in the tooth 23 located on the L-axis side of the plurality of teeth 23. On the other hand, the number of components of the main magnetic flux M in the C direction increases in the tooth 23 located on the C-axis side of the plurality of teeth 23.

[0070] Therefore, the inventor of the present application sets a portion of the electrical steel sheet 40 in which the main magnetic flux M is generated in the L direction as a first portion P1. The inventor of the present application sets a portion of the electrical steel sheet 40 in which the main magnetic flux M is generated in the C direction as a second portion P2. For example, in each portion of the electrical steel sheet 40, when the main magnetic flux M is decomposed into a component in the L direction and a component in the C direction in the electrical steel sheet 40, a portion in which the number of components of the main magnetic flux M in the L direction increases may be set as the first portion P1, and a portion in which the number of components of the main magnetic flux M in the C direction increases may be set as the second portion P2.

Based on the above conclusions (1) and (2), the author of the present application defines each of the first portion P1 and the second portion P2 by whether the direction of the main magnetic flux M flowing through each portion of the target electrical steel sheet 40 is relatively close to the L direction or the C direction. Specifically, the author of the present application defines the first portion P1 and the second portion P2 as follows (see Fig. 5). In other words, the first portion P1 includes a <1-1> portion SC1 of the core back 22 located in the SC region on the C-axis side, and a <1-2> portion SL1 of the teeth 23 located in the SL region on the L-axis side. The second portion P2 includes a <2-1> portion SL2 of the core back 22 located in the SL region on the L-axis side, and a <2-2> portion SC2 of the teeth 23 located in the SC region on the C-axis side. As illustrated in Fig. 5, when the base axis R passes through one tooth 23, one tooth 23 is divided into two sections in the form of sections SL1 and SL2.

[0071] In the present embodiment, the area of the adhesive layer 41 in the first portion P1 is smaller than the area of the adhesive layer 41 in the second portion P2 in all of the above-described four sections S.

Here, the adhesive layer 41 in the first portion P1 includes a <1-1> adhesive layer 41 disposed in a portion SC1 of the core back 22 located in the SC region on the C-axis side, and a <1-2> adhesive layer 41 disposed in a portion SL1 of the teeth 23 located in the SL region on the L-axis side. In other words, the adhesive layer 41 in the first portion P1 includes a <1-1> first adhesive portion 42 in the SC region on the C-axis side (the SC1 portion) and a <1-2> second adhesive portion 43 in the SL region on the L-axis side (the SL1 portion).

The adhesive layer 41 in the second portion P2 includes a <2-1> adhesive layer 41 arranged in a portion SL2 of the core back 22 located in the SL region on the L-axis side, and a <2-2> adhesive layer 41 arranged in a portion SC2 of the teeth 23 located in the SC region on the C-axis side. In other words, the adhesive layer 41 in the second portion P2 includes a <2-1> first adhesive portion 42 in the SL region on the L-axis side (portion SL2) and a <2-2> second adhesive portion 43 in the SC region on the C-axis side (portion SC2).

It should be noted that in the example illustrated in Fig. 5, the area of the electrical steel sheet 40 in each of the first portion P1 and the second portion P2 and the area of the adhesive layer 41 in each of the first portion P1 and the second portion P2 can be set as illustrated in Table 1 below.

[0073] In addition, as illustrated in Table 1, the area of the first adhesive portion 42 in the region SC on the C-axis side (the area of the adhesive layer 41 in the region SC1) is smaller than the area of the first adhesive portion 42 in the region SL on the L-axis side (the area of the adhesive layer 41 in the region SL2). The area of the second adhesive portion 43 in the region SC on the C-axis side (the area of the adhesive layer 41 in the region SC2) is larger than the area of the second adhesive portion 43 in the region SL on the L-axis side (the area of the adhesive layer 41 in the region SL1).

[0074] It should be noted that, in the example illustrated in Fig. 5, the area of the electrical steel sheet 40 in each of the region on the L-axis side and the region on the C-axis side of each section S and the area of the adhesive layer 41 in each of the region on the L-axis side and the region on the C-axis side of each section S may also be set as illustrated in Table 2 below. As described above, in each section S, the area of the adhesive layer 41 in the region SC on the C-axis side is different from the area of the adhesive layer 41 in the region SL on the L-axis side.

[0076] In the illustrated example, in all of the above-described four sections S, the width of the first adhesive portion 42 is equal regardless of the position in the circumferential direction, or decreases from the L-axis to the C-axis along the circumferential direction. In the present embodiment (see Figs. 4 and 5), the width of each of the plurality of partial adhesive portions 42c constituting the first adhesive portion 42 and the width of the outer adhesive portion 42b are equal regardless of the position in the circumferential direction. The widths of the plurality of partial adhesive portions 42c are equal to each other. It should be noted that in another embodiment, the width of at least one of the plurality of partial adhesive portions 42c may differ from the width of the other partial adhesive portions 42c.

[0077] Here, the width of the adhesive portion (for example, the first adhesive portion 42) is a size of the adhesive portion extending in a tape shape in a direction orthogonal to the pulling direction (longitudinal direction) of the adhesive portion. An equal width of the adhesive portion, regardless of the position in the circumferential direction, includes not only a case in which the width of the adhesive portion is completely equal regardless of the position in the circumferential direction, but also a case in which the width of the adhesive portion is substantially equal regardless of the position in the circumferential direction. The case in which the width of the adhesive portion is substantially equal is a case in which the width of the adhesive portion varies by approximately 10% relative to the average width of the corresponding adhesive portion.

In addition, in the illustrated example, in all of the above-described four sections S, the width of the second adhesive portion 43 is equal regardless of the position of the tooth 23 in the circumferential direction, or is larger for the tooth 23 located closer to the side along the C-axis than for the tooth 23 located closer to the side along the L-axis along the circumferential direction. It should be noted that in the present embodiment, the width of the second adhesive portion 43 is equal regardless of the position of the tooth 23 in the circumferential direction.

[0078] In the SL region on the L-axis side, the total area of the tape adhesive portions 42 and 43 whose circumferential direction is the longitudinal direction is larger than the total area of the tape adhesive portions 42 and 43 whose radial direction is the longitudinal direction. Further, in the SC region on the C-axis side, the total area of the tape adhesive portions 42 and 43 whose circumferential direction is the longitudinal direction is smaller than the total area of the tape adhesive portions 42 and 43 whose radial direction is the longitudinal direction. Here, examples of the tape adhesive portions 42 and 43 whose circumferential direction is the longitudinal direction include the inner adhesive portion 42a, the outer adhesive portion 42b, and the end edge portion 43c. Examples of the tape adhesive portions 42 and 43 whose radial direction is the longitudinal direction include the side edge portion 43b. The tape adhesive portions 42 and 43 whose circumferential direction is the longitudinal direction include not only the adhesive portions 42 and 43 continuing in a curved shape parallel to the circumferential direction, but also, for example, the adhesive portions 42 and 43 continuing linearly in the circumferential direction. The tape adhesive portions 42 and 43 whose radial direction is the longitudinal direction include not only the adhesive portions 42 and 43 continuing linearly in the radial direction, but also, for example, the adhesive portions 42 and 43 continuing in a curved shape in the radial direction.

[0079] It should be noted that the area of the adhesive layer 41 is the area of the region in which the adhesive portions 42 and 43 are arranged in the electrical steel sheet 40. This area is obtained, for example, by photographing the surfaces of adjacent electrical steel sheets 40 after the electrical steel sheets 40 are peeled off from each other, and performing image analysis for the photographing result.

[0080] The stator core 21 is manufactured, for example, using the manufacturing equipment 100 illustrated in Fig. 8. Hereinafter, a method for manufacturing the stator core 21 is described. It should be noted that the manufacturing method is not limited to this.

First, the manufacturing equipment 100 will be described below. In the manufacturing equipment 100, when feeding the electrical steel sheet P from the coil 101 (hoop) in the direction of the arrow F, perforation is performed repeatedly by a die arranged at each stage so as to gradually form the electrical steel sheet P into the shape of the electrical steel sheet 40, an adhesive material is applied to the lower surface of the electrical steel sheet 40, and the perforated electrical steel sheets 40 are stacked on top of each other and bonded under pressure while the temperature is raised so as to form each adhesive layer 41.

[0081] The manufacturing equipment 100 includes a first-stage punching station 110 located closest to the coil 101, a second-stage punching station 12 0 located below the punching station 110 in the conveying direction of the electrical steel sheet P such that it is adjacent to the punching station 110, and a station 130 for applying an adhesive material located further below the punching station 120 such that it is adjacent to the punching station 12 0.

The punching station 110 includes a negative matrix 111 located below the electrical steel sheet P and a positive matrix 112 located above the electrical steel sheet P.

The punching station 120 includes a negative matrix 121 located below the electrical steel sheet P and a positive matrix 122 located above the electrical steel sheet P.

The station 130 for applying the adhesive material includes an applicator 131 including a plurality of injectors arranged according to a pattern for applying the adhesive material.

[0082] The manufacturing equipment 100 further includes a laying station 140 below the station 130 for applying the adhesive material. The laying station 140 includes a heating device 141, an outer peripheral perforating negative matrix 142, a heat-insulating element 143, an outer peripheral perforating positive matrix 144 and a spring 145.

The heating device 141, the outer peripheral perforating negative matrix 142 and the heat-insulating member 143 are arranged below the electrical steel sheet P. On the other hand, the outer peripheral perforating positive matrix 14 4 and the spring 145 are arranged above the electrical steel sheet P. It should be noted that the reference number 21 denotes the stator core.

[0083] In the manufacturing equipment 100 having the configuration described above, first, the electrical steel sheet P is sequentially fed from the coil 101 in the direction of the arrow F in Fig. 8. Then, the electrical steel sheet P is first perforated by the perforating station 110. Then, the electrical steel sheet P is perforated by the perforating station 120. By perforation, the electrical steel sheet P is given the shape of the electrical steel sheet 40 including the core back 22 and the plurality of teeth 23 illustrated in Figs. 2 and 3. It should be noted that the electrical steel sheet P is not completely perforated at this point in time, and therefore the process proceeds to the next step along the direction of the arrow F. In the adhesive material applying station 130, as the next step, the adhesive material fed from each injector of the applicator 131 is applied pointwise.

[0084] Finally, the electrical steel sheet P is fed to the stacking station 140, punched by the outer peripheral punching positive die 144, and stacked with high precision. During this stacking, the electrical steel sheet 40 receives a constant pressure from the spring 145. By sequentially repeating the punching step, the adhesive material application step, and the stacking step as described above, a predetermined number of electrical steel sheets 40 can be stacked on top of each other. In addition, the stacked core formed by stacking the electrical steel sheets 40 in this manner is heated to, for example, a temperature of 200°C by the heating device 141. Due to this heating, the adhesive material is cured to form the adhesive layer 41.

Through the above steps, the stator core 21 is completely prepared.

[0085] As a result of intensive investigation, the present inventor arrives at the following conclusions. In other words, the present inventor discovers for the first time that, in the stator core 21 in which the electrical steel sheets 40 are bonded and attached to each other by means of an adhesive material next to each other in the stacking direction, a compressive mechanical stress is applied to the electrical steel sheets 40 due to the adhesive material, and this compressive mechanical stress affects the deterioration (the amount of increase in iron loss, etc.) of the magnetic characteristics of the electrical steel sheets 40. The degree of this influence varies depending on the direction of the main magnetic flux M formed in the electrical steel sheets 40. More specifically, in the case where the direction of the main magnetic flux M is the L direction, compared with the case where the direction of the main magnetic flux M is the C direction, the higher the area ratio of the adhesive in the electrical steel sheet 40, the larger the deterioration ratio in terms of iron loss, and the higher the compressive mechanical stress applied per unit area of the electrical steel sheet 40, the larger the deterioration ratio in terms of iron loss (see Figs. 13, 14 and 16 described below).

[0086] Based on the above findings, the author of the present application achieved that, in a stator core 21 including a core back 22, an electrical steel sheet 40 is divided into four sections S by an L-axis and a C-axis, and, in at least one of the four sections S, an area of an adhesive layer 41 becomes different depending on the direction in which the main magnetic flux M is generated. For example, in the four sections S, the area of the adhesive layer 41 in a first portion P1 in which the main magnetic flux M is generated in the L direction is set smaller than the area of the adhesive layer 41 in a second portion P2 in which the main magnetic flux M is generated in the C direction. As a result, instead of forming a large adhesive layer 41 in a portion having a large influence on the iron loss in the electrical steel sheet 40, a large adhesive layer 41 can be formed in a portion having a small influence on the iron loss iron. Therefore, it is possible to suppress the increase in loss while ensuring the required holding force. It can be said that such a configuration is achieved only when attention is paid to the application of mechanical stress in compression to the electrical steel sheet 40 due to the compression of the adhesive material. In other words, it can be said that such a configuration cannot be achieved under the premise of a composite core that fixes the electrical steel sheet 40 in a direction different from the adhesion (for example, by hemming or welding).

[0087] The first adhesive portion 42 is located at least on one of the inner peripheral edge and the outer peripheral edge of the back 22 of the core, and extends mainly in the circumferential direction. Accordingly, the first adhesive portion 42 extends, in the region SC on the C-axis side, in a direction closer to the L direction than to the C direction (having a gentle slope), and extends, in the region SL on the L-axis side, in a direction closer to the C direction than to the L direction (having a gentle slope). Accordingly, with respect to the first adhesive portion 42, as the number of portions located in the region SL on the L-axis side increases, the ratio of the first adhesive portion 42 extending in a direction close to the C direction increases, and the effect on the iron loss decreases.

Therefore, in the stator core 21, in each section S, the area of the first adhesive portion 42 in the region SC on the C-axis side is smaller than the area of the first adhesive portion 42 in the region SL on the L-axis side. Therefore, the influence of the first adhesive portion 42 on the iron loss can be suppressed so that it is small.

[0088] The second adhesive portion 43 is disposed on the peripheral edge of the teeth 23 and extends mainly in the radial direction. Therefore, the second adhesive portion 43 extends, in the region SC on the C-axis side, in a direction closer to the C direction than to the L direction (having a gentle inclination), and extends, in the region SL on the L-axis side, in a direction closer to the L direction than to the C direction (having a gentle inclination). Therefore, with respect to the second adhesive portion 43, as the number of portions disposed in the region SC on the C-axis side increases, the ratio of the second adhesive portion 43 extending in a direction close to the C direction increases, and the effect on the iron loss decreases.

Therefore, in the stator core 21, in each section S, the area of the second adhesive portion 43 in the region SC on the C-axis side is larger than the area of the second adhesive portion 43 in the region SL on the L-axis side. Therefore, the influence of the second adhesive portion 43 on the iron loss can be suppressed so that it is small.

[0089] It should be noted that the scope of the present invention is not limited to only the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0090] For example, similar to the stator 20A according to the first modification example illustrated in Fig. 9, the width of the first adhesive portion 42 may decrease from the L-axis to the C-axis along the circumferential direction. The width of the second adhesive portion 43 may be larger for the tooth 23 located closer to the side along the C-axis than for the tooth 23 located closer to the side along the L-axis along the circumferential direction. Here, in the first modification example illustrated in Fig. 9, the width of the first adhesive portion 42 gradually decreases from the L-axis to the C-axis along the circumferential direction. It should be noted that the width of the first adhesive portion 42 may continuously decrease from the L-axis to the C-axis along the circumferential direction. Similarly, the width of the second adhesive portion 43 may continuously decrease.

It should be noted that in the enlarged view illustrated in Fig. 9, the positions of the L-axis and the C-axis are reversed relative to the enlarged view illustrated in Fig. 5. Here, in the stator 20 according to the embodiment illustrated in Fig. 5, as described above, the width of the first adhesive portion 42 and the width of the second adhesive portion 43 are constant (equal) regardless of the position in the circumferential direction.

[0091] In an embodiment, in all four sections, the area of the adhesive layer 41 in the region SC on the C-axis side is different from the area of the adhesive layer 41 in the region SL on the L-axis side, the area of the first adhesive portion 42 in the region SC on the C-axis side is smaller than the area of the first adhesive portion 42 in the region SL on the L-axis side, and the area of the second adhesive portion 43 in the region SC on the C-axis side is larger than the area of the second adhesive portion 43 in the region SL on the L-axis side. However, another configuration may be used in which at least one of the four sections S is the first section, which is the S section satisfying the above condition. For example, only one of the four sections S may be the first section, and the remaining three sections S may be S sections that do not satisfy the above condition.

[0092] In an embodiment, the shapes in the top view of all the adhesive layers 41 are identical in the top view, but the shapes in the top view of all the adhesive layers 41 do not necessarily have to be identical.

In an embodiment, each of the adhesive layers 41 has a first section, but this shape can be suitably changed to another shape including at least one first adhesive layer, which is an adhesive layer 41 having a first section.

[0093] The adhesive layer 41 does not necessarily have to include both the first adhesive portion 42 and the second adhesive portion 43. For example, the adhesive layer 41 may include only one of the first adhesive portion 42 and the second adhesive portion 43.

The region SC on the C-axis side and the region SL on the L-axis side are not limited to the shapes described in the embodiment. In each section S, it is possible to appropriately change the shape to another shape in which a region relatively close to the C-axis is set as the region SC on the C-axis side, and a region having an area identical to that of the region SC on the C-axis side and relatively close to the L-axis is set as the region SL on the L-axis side.

[0094] The shape of the stator core 21 is not limited to only the shapes described in the embodiment. Specifically, the dimensions of the outer diameter and the inner diameter of the stator core 21, the stacking thickness, the number of grooves, the proportion between the size in the circumferential direction and the size in the radial direction of the tooth 23, the proportion between the size of the tooth 23 and the size of the back 22 of the core in the radial direction, and the like can be arbitrarily calculated according to the required characteristics of the rotating electric machine.

[0095] In the rotor 30 in the embodiment, a pair of permanent magnets 32 forms one magnetic pole, but the present invention is not limited to this. For example, one permanent magnet 32 may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0096] In the embodiment, a permanent magnetic field electric motor is described as an example of a rotating electric machine, but the structure of the rotating electric machine is not limited to this as illustrated below, and further, various known structures not illustrated in particular below can also be used.

In the embodiment, a permanent magnetic field electric motor is described as an example of a synchronous electric motor, but the present invention is not limited to this. For example, the rotating electric machine may be a magnetic resistance electric motor or an electromagnetic field electric motor (a winding field electric motor).

In the embodiment, a synchronous electric motor is described as an example of an AC electric motor, but the present invention is not limited to this. For example, a rotating electric machine can be an induction electric motor.

In the embodiment, an AC motor is described as an example of an electric motor, but the present invention is not limited to this. For example, a rotating electric machine may be a DC motor.

In the embodiment, the electric motor is described as an example of a rotating electric machine, but the present invention is not limited to this. For example, the rotating electric machine can be a generator.

[0097] In the above embodiment, a case is roughly illustrated in which the composite core according to the present invention is applied to a stator core, but the composite core can also be applied to a rotor core.

[0098] It should be noted that the direction (L direction) in which the L-axis extends is the easy magnetization direction as described above. Here, the relationship between the easy magnetization direction and the rolling direction is appropriately set according to, for example, the type of electrical steel sheet. For example, the easy magnetization direction may or may not necessarily coincide with the rolling direction. In the case where the magnetic flux is generated in the direction in which the L-axis extends (the easy magnetization direction), the amount of increase in iron loss is smaller than the amount in the case where the magnetic flux is generated in the direction in which the C-axis extends. It should be noted that, in the case where the elastic compressive stress is applied in the direction in which the L-axis extends, the amount of increase in iron loss is larger than the amount in the case where the elastic compressive stress is applied in the direction in which the C-axis extends. Furthermore, when the plastic tension is applied in the direction in which the L-axis continues, the magnitude of the increase in iron loss is greater than that when the plastic tension is applied in the direction in which the C-axis continues.

[0099] In the present embodiment, the electrical steel sheet 40 is divided into four sections S, but the present invention is not limited to this. For example, similar to the stator 20C according to the second modification example illustrated in Figs. 10 and 11, the electrical steel sheet 40 can be segmented into eight sections S. In the stator 20C according to the second modification example, two or more easy magnetization directions exist in one electrical steel sheet 40. The two easy magnetization directions are orthogonal to each other. In such a 40 electrical steel sheet, the L-axes extend in two easy magnetization directions, respectively, and are orthogonal to each other on the central axis O. The L-axes (easy magnetization directions) are arranged at equal intervals of 90 degrees around the central axis O. The C-axis extends in a direction (in the 45-degree direction) in which a central angle (90 degrees) formed around the central axis O by the L-axes next to each other in the circumferential direction is divided into two equal parts. It should be noted that, in the present modification example, the L-axis (easy magnetization direction) does not necessarily have to coincide with the rolling direction. The direction in which the L-axis (easy magnetization direction) extends may be a 45° direction or a 135° direction relative to the rolling direction. The direction in which the C-axis extends may coincide with the rolling direction or may coincide with a direction perpendicular to the rolling direction.

It should be noted that whether or not there are two directions of easy magnetization in one electrical steel sheet 40 can be determined, for example, in the following manner. In other words, for example, a square or rectangular sample for measurement is cut out from the electrical steel sheet 40 with the possibility of having a plurality of angles with respect to the rolling direction according to the above-described direction of determining the direction of easy magnetization. By magnetically measuring the cut out sample by the above-described method for magnetically measuring an electrical steel strip using a single sheet tester, it is possible to confirm the existence of the direction of easy magnetization.

[0100] In the above embodiment, the stator cores 21 are not obtained by rotational stacking, but may be obtained by rotational stacking. Whether or not the stator cores 21 are obtained by rotational stacking can be determined by confirming the appearance of the stator cores 21, for example.

Fig. 12 is a photograph for explaining the definition of rotational stacking. This photograph shows a common stator 20Z. In the stator 20Z, the electrical steel sheets 40 are rotationally stacked every predetermined number of electrical steel sheets 40. In the stator 20Z, the stator 20Z includes six stacking bodies A1-A6, including a first stacking body A1 - a sixth stacking body A6. In each of the stacking bodies A1-A6, the electrical steel sheets 40 are stacked on top of each other. The stator 20Z is formed by stacking the six stacking bodies A1-A6.

The orientations of the electrical steel sheets 40 forming each of the built-up bodies A1-A6 are common. Therefore, in the electrical steel sheets 40 forming each of the built-up bodies A1-A6, the L-axis and the C-axis overlap with each other in a plan view. As a result, the adhesive layer 41 provided in each of the built-up bodies A1-A6 functions as a first adhesive layer for both of the two electrical steel sheets 40 to which the adhesive layer 41 is bonded, and satisfies, for example, the above-described relationship of the area ratio of the adhesive in the present invention.

On the other hand, the orientations of the electrical steel sheets 40 differ between the A1-A6 stacked bodies adjacent to each other in the stacking direction. Therefore, in the electrical steel sheets 40 forming the A1-A6 stacked bodies adjacent to each other in the stacking direction, the L-axis and the C-axis do not overlap with each other in a plan view in some cases. As a result, the adhesive layer 41 located at the boundary of any adjacent two of the A1-A6 stacked bodies functions as the first adhesive layer only for the electrical steel sheet 40 of one of the adjacent two of the A1-A6 stacked bodies, and, for example, the above-described relationship of the area ratio of the adhesive in the present invention can be satisfied.

As illustrated in Fig. 12, the gloss of the outer peripheral surface of each of the composite bodies A1-A6 changes at the boundary of adjacent two of the composite bodies A1-A6 to such a degree that it can be visually recognized by a person. Therefore, it is possible to determine whether or not the stator 20Z includes the composite bodies A1-A6 (i.e., whether or not the electrical steel sheets are rotationally stacked) by visually recognizing the outer peripheral surface of the stator 20Z.

[0101] Furthermore, it is possible to appropriately replace the constituent elements in the embodiment with known constituent elements without departing from the essence of the present invention, and the above-described examples of modifications can be appropriately combined with each other.

[0102] Next, a verification test is performed to verify the above-described benefits.

[0103] First Verification Test

In this verification test, a plurality of test specimens are prepared. Each of the test specimens is a non-oriented electrical steel sheet made of identical material. Each of the test specimens has a square shape with a side of 100 mm. In the square shape formed by the test specimen, the first side is parallel to the L direction, which is the easy magnetization direction (rolling direction), and the second side is parallel to the C direction, which is the direction orthogonal to the rolling direction.

An adhesive material is intermittently applied dotwise to the entire surface of each of these test specimens. The plurality of dots of the adhesive material have the same shape and the same size and are arranged at identical intervals. In addition, the size of the dots of the adhesive material and the interval between the dots of the adhesive material are set to be different, and the occupied area fraction (i.e., the area ratio of the adhesive) of the adhesive material on the surface of the test specimen is set to be different for the plurality of test specimens.

In addition, a test sample is also prepared on which no adhesive material is applied. This test sample is a test sample that serves as a baseline for iron loss.

[0104] In each of a plurality of test specimens, (1) the iron loss is measured when the magnetic flux moves in the L direction, and (2) the iron loss is measured when the magnetic flux moves in the C direction.

Fig. 13 and 14 are graphs illustrating the relationship between the adhesive area ratio and the iron loss in (1) and (2), respectively. In these graphs, the horizontal axis represents the adhesive area ratio (%), and the vertical axis represents the change rate of W15/50 (%). The higher the value on the vertical axis, the greater the iron loss. It should be noted that W15/50 represents the iron loss when the absolute maximum value of the magnetic flux density is 1.5 T, and a fluctuating magnetic flux varying at 50 Hz is formed.

[0105] From these graphs, it is confirmed that in the case (2) in which the magnetic flux moves in the C direction (Fig. 14), the iron loss is suppressed such that it is lower (by about half), in particular, as the area ratio of the adhesive is higher compared to the case (1) in which the magnetic flux moves in the L direction (Fig. 13).

[0106] Second Verification Test

This verification test is performed by simulation using software. The software used is JMAG software for electromagnetic field analysis based on finite element method, manufactured by JSOL Corporation.

[0107] In this verification test, the premise is set as follows.

- 12 poles, 18 slots, concentrated winding, IPM electric motor

- Stator core outer diameter: φ 260 mm, rotor core outer diameter: φ 164 mm

- Test material: 35A300

- Speed and torque: 1000 rpm and 28.9 Nm/m

[0108] Under the above premise, one stator core is designed as each of the example and the comparative example. In the stator core of the example, the shape in the plan view of the adhesive layer is the shape illustrated in Figs. 4 and 5. On the other hand, in the stator core of the comparative example, the shape in the plan view of the adhesive layer is a shape in which the positions of the L-axis and the C-axis are interchanged with the shape in the plan view illustrated in Figs. 4 and 5. In other words, similar to the stator 20B illustrated in Fig. 15, the shape in the plan view of the adhesive layer 41 is interchanged between the region SC on the C-axis side and the region SL on the L-axis side in each of the above-described four sections S.

[0109] The simulation is performed for the iron loss in the example and the comparative example. The results are illustrated in Fig. 16. In Fig. 16, the vertical axis represents the deterioration ratio in terms of the stator iron loss. A deterioration ratio of 1 indicates a case in which there is no adhesive layer, and it is indicated that the iron loss increases as the value of the deterioration ratio increases.

[0110] From the above graph, it is confirmed that the iron loss in the example is suppressed to a greater extent than the iron loss in the comparative example.

[0111] Furthermore, it is possible to appropriately replace the constituent elements in the embodiment with known constituent elements without departing from the spirit of the present invention, and the above-described examples of modifications can be appropriately combined with each other.

List of reference positions

[0112] 10 - rotating electric machine

23 - tooth

40 - electrical steel sheet

41 - adhesive layer

42 - first adhesive section

43 - second adhesive section

P1 - first section

P2 - the second section

R - base axis

S - section

SC - area on the side along the C-axis

SL - area on the side along the L-axis

Claims (51)

1. A composite core containing: a plurality of sheets of electrical steel; and a plurality of adhesive layers located between sheets of electrical steel next to each other in the direction of laying, wherein: the electrical steel sheet includes a ring body, at least one adhesive layer of the plurality of adhesive layers is a first adhesive layer, in one electrical steel sheet of two electrical steel sheets, arranging the first adhesive layer in the middle in the laying direction, when the imaginary axis intersecting with the central axis of the annular body and extending in the easy magnetization direction is set as the L-axis, the imaginary axis intersecting with the central axis and intersecting with the L-axis is set as the C-axis, and the electrical steel sheet is divided into a plurality of sections in the circumferential direction of the annular body by the L-axis and the C-axis, at least one section of the plurality of sections is a first section, and in the first section, the area of the first adhesive layer in the first section of the electrical steel sheet, in which the main magnetic flux is formed in the direction along the L-axis, is less than the area of the first adhesive layer in the second section of the electrical steel sheet, in which the main magnetic flux is formed in the direction along the C-axis. 2. A composite core according to item 1, in which: in the first section, when the region relatively close to the C-axis is called the "region on the C-axis side", and the region relatively close to the L-axis is called the "region on the L-axis side": the first section includes a section located in the region on the C-axis side of the annular body, and the second section includes a section located in the region on the L-axis side of the annular body. 3. A composite core according to item 2, in which: the first adhesive layer includes a first adhesive portion located on at least one of the inner peripheral edge and the outer peripheral edge of the annular body, and in the first section, the area of the first adhesive portion in the region on the side along the C-axis is less than the area of the first adhesive portion in the region on the side along the L-axis. 4. A composite core according to item 3, in which: the first adhesive portion extends in the form of a tape along at least one of the inner peripheral edge and the outer peripheral edge of the annular body and in the first section, the width of the first adhesive portion is equal regardless of the position in the circumferential direction or decreases from the L-axis to the C-axis along the circumferential direction. 5. A composite core according to item 4, in which: in the first section, the width of the first adhesive portion decreases from the L-axis to the C-axis along the circumferential direction. 6. A composite core according to any one of paragraphs 2-5, in which: the electrical steel sheet further includes a plurality of teeth protruding from the annular body inward in the radial direction of the annular body and arranged at intervals in the circumferential direction of the annular body, the first section includes a section of teeth located in the region on the side along the L-axis, and the second section includes a section of teeth located in the region on the side along the C-axis. 7. A composite core according to item 6, in which: the first adhesive layer includes a second adhesive portion located on the peripheral edge of the teeth, and in the first section, the area of the second adhesive portion in the region on the C-axis side is greater than the area of the second adhesive portion in the region on the L-axis side. 8. A composite core according to item 7, in which: the second adhesive section continues in the form of a tape along the peripheral edge of the teeth and in the first section, the width of the second adhesive section is equal regardless of the positions of the teeth in the circumferential direction or is greater for the teeth located closer to the side along the C-axis than for the teeth located closer to the side along the L-axis along the circumferential direction. 9. A composite core according to item 8, in which: in the first section, the width of the second adhesive portion is greater for the teeth located closer to the side along the C-axis than for the teeth located closer to the side along the L-axis along the circumferential direction. 10. A composite core according to any one of paragraphs 2-9, in which: in the first section, when the imaginary axis extending in the direction dividing the central angle formed by the C-axis and the L-axis around the central axis into two equal parts is given as the reference axis, the region on the C-axis side and the region on the L-axis side have a symmetrical relationship in the circumferential direction relative to the basal axis. 11. A composite core according to any one of paragraphs 2-10, in which: the first adhesive layer includes a tape adhesive portion, in the region on the L-axis side, the total area of the tape adhesive portions in which the circumferential direction is the longitudinal direction is greater than the total area of the tape adhesive portions in which the radial direction of the annular body is the longitudinal direction, and in the region on the C-axis side, the total area of the tape adhesive portions in which the circumferential direction is the longitudinal direction is less than the total area of the tape adhesive portions in which the radial direction is the longitudinal direction. 12. A composite core according to any one of claims 1-11, wherein all of the plurality of adhesive layers are first adhesive layers. 13. A composite core according to any one of claims 1-12, wherein all of the plurality of sections are first sections. 14. A composite core according to any one of claims 1 to 13, wherein the electrical steel sheet is a non-oriented electrical steel sheet. 15. A composite core according to any one of paragraphs. 1-13, in which the sheet of electrical steel is a grain-oriented sheet of electrical steel. 16. A composite core according to any one of paragraphs 1-15, in which: only one direction of easy magnetization exists in one sheet of electrical steel and The L-axis and C-axis are orthogonal to each other. 17. A composite core according to any one of paragraphs 1-15, in which: two or more directions of easy magnetization exist in one sheet of electrical steel, each L-axis extends in two or more easy magnetization directions with the possibility of crossing each other at the central axis, and The C-axis extends in a direction in which the central angle formed around the central axis by the L-axes next to each other in the circumferential direction is divided into two equal parts. 18. A rotating electric machine comprising a composite core according to any one of paragraphs 1-17.