JP2014112506A - Coil wire and coil structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coil wire capable of combining reduced eddy current loss and lightness and a coil structure using it.SOLUTION: A wire 1 comprises a plurality of element wires 3a and 3b, an insulation coating 5 and so on. The element wires 3a and 3b are composed of metals having mutually different conductivities. More specifically, the element wire 3a is made of copper or a copper alloy, and the element wire 3b is made of aluminum or an aluminum alloy. An interstitial layer 7 is formed between the element wires 3a and 3b. The element wires 3a and 3b have nearly rectangular cross sections of nearly the same width. The wire 1 has a nearly rectangular cross section as a whole, with a plurality of the element wires 3a and 3b laminated in the thickness direction. A coil wire which is light and low-cost and is less affected by resistance increase is obtainable by laminating aluminum and copper in such a way as to establish appropriate lamination conditions for aluminum.

Description

  The present invention relates to a coil structure for a motor used in, for example, an automobile and the like, and a coil wire used for the same.

  For example, a high-frequency current is passed through a motor coil used in an automobile or the like. FIG. 6A shows the coil 10. The coil 10 is configured by winding a winding 11 around the outer periphery of a coil core 13.

  FIG. 6B is a cross-sectional view taken along the line II of FIG. 6A, and is a conceptual diagram of a current density distribution flowing in the cross section of the winding 11. FIG. 7 is an enlarged view of a portion J in FIG. The winding 11 has a substantially rectangular cross-sectional shape. By doing in this way, since the coil | winding 11 can be wound around the coil core 13 without a clearance gap, a motor can be reduced in size.

  As shown in FIG. 7, the winding 11 has a portion where current concentrates (K portion in the drawing) and a non-concentrating portion (L in the drawing) where current does not flow so much. This is because when an alternating current is passed through the winding 11, an eddy current is generated in the winding 11 due to the magnetic flux interlinking with the winding 11.

  FIG. 8A is a diagram illustrating how the current flows in the thickness direction of the winding 11. In a state where the winding 11 is extended linearly, currents flowing in the thickness direction (M and N in the figure) are substantially constant. On the other hand, as shown in FIG. 8B, when a high-frequency current is passed in a state where the winding 11 is wound around the coil core 13, an eddy current (O in the figure) is generated. Therefore, due to the influence of this eddy current, the current flowing through the winding 11 has a distribution in the thickness direction as shown in FIG. 8C, the current is concentrated in the vicinity of one surface, and the current flows on the other surface. It becomes difficult to flow (P, Q in the figure).

  Thus, the AC resistance of the winding 11 increases due to the influence of the eddy current. For this reason, it becomes an obstacle to the high efficiency of a coil. As a method of reducing the influence of such an eddy current, there is a method of dividing a conductor cross section into a plurality (for example, Patent Document 1).

JP 2007-288088 A

Such eddy current loss is given by the following formula (Steinmetz's empirical formula).
Eddy current loss _{(w) = k e · (} tfBm) 2 / ρ
Where k _e : proportional constant, t: conductor thickness, f: frequency, Bm: magnetic flux density, ρ: volume resistivity.

  Therefore, a method of reducing the thickness of the conductor is effective for reducing eddy current loss. For this reason, as in Patent Document 1, eddy current loss can be reduced by reducing the thickness of each conductor. On the other hand, in order to further reduce the eddy current loss, there is a method of increasing the volume resistivity ρ. By increasing the volume resistivity ρ, eddy current loss can be reduced.

  However, if a material having a large volume resistivity is simply selected, the direct current resistance increases, so that the effect of reducing the resistance value cannot be obtained depending on the frequency. Moreover, in order to divide a conductor into a plurality of parts, it is necessary to form an insulating layer (or a low conductivity layer) between the divided conductors. May fall.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a coil wire that can achieve both reduction in eddy current loss and weight reduction, and a coil structure using the same.

  In order to achieve the above-mentioned object, the first invention is a wire for a coil, and is a second wire made of a material having a conductivity different from the conductivity of the first wire and the first wire. A conductivity of the first strand is higher than a conductivity of the second strand, and a specific gravity of the first strand is a specific gravity of the second strand. The first strand and the second strand have a substantially rectangular cross-sectional shape with substantially the same width, and the first strand and the second strand are stacked. It is the wire material for coils characterized by being made.

  It is desirable that an intervening layer having a lower conductivity than the first strand and the second strand is formed between the first strand and the second strand.

  The first strand is preferably copper or a copper alloy, and the second strand is preferably aluminum or an aluminum alloy. In this case, the intervening layer is preferably an alumite layer.

  It is desirable that the first strand is disposed on the outermost layer of each of the stacked layers. In addition, it is preferable that the first strands are not stacked so as to be adjacent to each other, and the first strands are stacked so as to be adjacent to the second strand.

  The intervening layer may be enamel, an adhesive, or an oxide film.

  When the total number of layers of the first strand and the second strand is 2, it is desirable that the thickness of the second strand is 37% to 82% of the total thickness.

  When the total number of layers of the first strand and the second strand is 3, it is desirable that the thickness of the second strand is 25% to 59% of the total thickness.

  When the total number of layers of the first strand and the second strand is 4, it is desirable that the thickness of the second strand is 19% to 45% of the total thickness. .

  In addition, when the total number of layers of the first strand and the second strand is 5, it is desirable that the thickness of the second strand is 13% to 35% of the total thickness. .

  Further, when the total number of layers of the first strand and the second strand is 6, it is desirable that the thickness of the second strand is 13% to 29% of the total thickness. .

  When the total number of layers of the first strand and the second strand is 7, it is desirable that the thickness of the second strand is 12% to 24% of the total thickness. .

  In addition, when the total number of layers of the first strand and the second strand is 8, it is desirable that the thickness of the second strand is 12% to 19% of the total thickness. .

  In addition, when the total number of layers of the first strand and the second strand is 9, it is desirable that the thickness of the second strand is 12% to 15% of the total thickness. .

  According to the first invention, since the strands made of different metals having a substantially rectangular cross section with substantially the same width are stacked, the same effect as dividing the strand into a plurality of cross sections can be obtained. In particular, although the second strand has a lower electrical conductivity than the first strand, the specific gravity is small, so that the effect of weight reduction can be obtained. Moreover, since the electrical conductivity of the 2nd strand is smaller than the electrical conductivity of the 1st strand, an eddy current loss can be reduced.

  As such a strand, for example, the first strand can be copper or a copper alloy, and the second strand can be aluminum or an aluminum alloy. Thus, by stacking dissimilar metals, the DC resistance is reduced by the first strand having high conductivity, and the eddy current loss is reduced by the second strand having relatively low conductivity. can do. Moreover, a coil can be reduced in weight by using aluminum.

  Further, since an intervening layer having a low conductivity is provided between the first strand and the second strand, the strands can be reliably divided. Since the first strand and the second strand are simply laminated, for example, compared to the case where the second strand is covered with the first strand, the manufacturing is performed. Is easy.

  Further, when aluminum or an aluminum alloy is used, the alumite layer can be made to function as an intervening layer by forming the alumite layer on the surface. Therefore, the intervening layer can be made thinner compared to the case where a normal insulating layer or the like is formed as the intervening layer. For this reason, the ratio of fastening of the conductor in the entire cross-sectional area can be increased, and high efficiency can be achieved.

  The intervening layer may be an enamel formed on the surface of the copper wires, an adhesive that bonds the wires to each other, or an oxide film formed on the surface of each wire. May be.

  2nd invention is a coil structure, Comprising: It comprises the coil core and the winding wound around the said coil core, The said winding is 1st strand which consists of copper or a copper alloy, Aluminum, or aluminum A second strand made of an alloy is laminated, and the first strand and the second strand have a substantially rectangular cross-sectional shape with substantially the same width, and are formed on the surface of the second strand. Is a coil structure in which an alumite layer is formed, and the first strand and the second strand are laminated via the alumite layer.

  According to the second invention, copper or a copper alloy and aluminum or an aluminum alloy are laminated, and the anodized layer formed on the aluminum surface functions as an intervening layer. Can be achieved.

  ADVANTAGE OF THE INVENTION According to this invention, the wire material for coils which can make reduction of an eddy current loss and weight reduction compatible, and a coil structure using the same can be provided.

(A) is sectional drawing which shows the wire 1, (b) is a figure which shows the state of the eddy current in a longitudinal direction cross section. The figure which shows the relationship between alternating current frequency and resistance. The figure which shows the resistance sum total of the range of 0-2 kHz. It is a figure which shows the relationship between an aluminum layer ratio and resistance sum total, (a) is a figure which shows the case of 2 layers, (b) is a figure which shows the case of 3 layers, (c) is a figure which shows the case of 4 layers, ( d) A diagram showing the case of five layers. It is a figure which shows the relationship between an aluminum layer ratio and resistance sum total, (a) is a figure which shows the case of 6 layers, (b) is a figure which shows the case of 7 layers, (c) is a figure which shows the case of 8 layers, ( d) The figure which shows the case of 9 layers. (A) is a figure which shows the coil 10, (b) is the II sectional view taken on the line of (a). Sectional drawing which shows the coil | winding 11. FIG. (A) is a figure which shows the direct current in the winding 11, (b) is a figure which shows the eddy current in the winding 11, (c) is a figure which shows the high frequency current which flows into the winding 11.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a cross-sectional view showing the wire 1. The wire 1 is composed of a plurality of strands 3a, 3b, an insulation coating 5, and the like. The strand 3a and the strand 3b are made of metals having different electrical conductivities. The strand 3a has higher conductivity than the strand 3b. The strand 3b has a specific gravity smaller than that of the strand 3a. For example, the strand 3a is made of copper or a copper alloy, and the strand 3b is made of aluminum or an aluminum alloy.

  An intervening layer 7 is formed between the strands 3a and 3b. The intervening layer 7 is, for example, an enamel, an adhesive, an oxide film, or the like formed on the surface of the strand 3a or the strand 3b. That is, the intervening layer 7 is made of a material having lower conductivity with respect to the strands 3a and 3b. Therefore, in the cross section of the wire 1, the conductor portion is divided into the strands 3 a and 3 b, and the wire 1 becomes a set of a plurality of different strands 3 a and 3 b.

  In addition, when the strand 3b is aluminum or aluminum alloy, it is desirable that the intervening layer 7 be an alumite layer formed on the surface thereof. The alumite layer can be easily formed as compared with other intervening layers such as enamel and can be made thinner, so that the space factor can be increased.

  The strands 3a and 3b have a substantially rectangular cross-sectional shape having substantially the same width. The wire 1 has a plurality of strands 3a and 3b stacked in the thickness direction, and has a substantially rectangular cross-sectional shape as a whole. The number of stacked wires 3a and 3b is not limited to the illustrated example, and may be a multilayer structure. However, when the strand 3a is copper or a copper alloy, the strand 3b is aluminum or an aluminum alloy, and the intervening layer 7 is an alumite layer, the strands 3a are not stacked adjacent to each other, and the strand 3a It is desirable to be laminated so as to be adjacent to the strand 3b. By doing in this way, all the intervening layers 7 can be formed with an alumite layer. For this reason, the intervening layer 7 can be reliably arrange | positioned between strands.

  When the element wire 3a is made of copper or a copper alloy and the element wire 3b is made of aluminum or an aluminum alloy and laminated in a plurality of layers, the element wire 3a comes to the outermost layer (the lowermost layer and the uppermost layer). It is desirable to laminate them. By doing so, the outermost periphery of the laminated wire is made of copper or a copper alloy, so the terminals are made by the same soldering and crimping methods as when using a conventional copper wire made only of copper. Etc. can be connected.

  A coil structure can be configured by winding the wire 1 formed in this way around the coil core 13 as shown in FIG.

  The wire 1 can be manufactured, for example, by bonding the strands 3a and 3b and then providing the insulating coating 5 on the outer periphery. Alternatively, a plurality of strands (or round wires) may be arranged and bundled, and then rolled to produce a wire 1 having a rectangular cross section.

  As shown in FIG.1 (b), since the strand 3b is provided between the strands 3a, an eddy current is disperse | distributed to each strand. For this reason, the loss due to the eddy current (A in the figure) can be reduced by the effect of reducing the conductor thickness t in the Steinmetz empirical formula described above. When the strand 3a is copper or a copper alloy and the strand 3b is aluminum or an aluminum alloy, the effect of reducing the conductor thickness t in the Steinmetz's empirical formula described above and the volume resistivity ρ are made of copper. On the other hand, the loss due to the eddy current (B in the figure) can be reduced by the effect of increasing.

  FIG. 2 is a calculation result showing the relationship between the AC frequency and the resistance in the wire configured as described above. The overall thickness of each wire shown in FIG. 2 was constant at 2.2 mm. In the figure, D represents the entire cross section of the wire made of copper. As described above, the eddy current loss increases as the frequency increases, and thus the resistance increases. On the other hand, the C-line with the entire cross-section of the wire rod made of aluminum shows a high resistance due to an increase in DC resistance at a predetermined frequency (G in the figure) or lower, but since eddy current loss is small, at a predetermined frequency or higher Resistance can be made lower than copper wire.

  On the other hand, in the case of a laminated structure in which the cross section of the copper wire was divided into a plurality of parts (thickness was divided into three equal parts), the resistance was low, as indicated by the F line in the figure. This is an effect of reducing eddy current loss by dividing the cross section. On the other hand, in the case of a laminated structure in which the central element wire is sandwiched between copper as aluminum (the thickness of each layer is divided into three equal parts of the total thickness), as shown by E line in the figure, all are made of copper. Compared with the case, the resistance is slightly larger, but the difference is small. In particular, at a predetermined frequency (H in the figure) or higher, the resistance value was lower than that of a laminated structure in which all copper was used due to the effect of reducing eddy current loss. In addition, as a wire made of copper and aluminum, a copper-coated aluminum wire having a center of aluminum and an outer periphery of copper is known. However, in the case of a copper-coated aluminum wire, copper is not divided and the entire copper is conductive, so that a large eddy current flows through the copper portion on the outer periphery. Therefore, the effect of reducing the thickness t in Steinmetz's empirical formula cannot be obtained, and eddy current loss cannot be reduced.

  As described above, according to the present embodiment, it is possible not only to divide the cross section into a plurality of parts but also to stack the dissimilar metals to reduce the eddy current loss more efficiently. Further, by sandwiching aluminum with copper, it is possible to obtain both eddy current loss reduction effect and light weight effect.

  Moreover, the thickness of the intervening layer 7 can be reduced by applying an alumite layer as the intervening layer 7. For this reason, the space factor of the wire 1 can be improved.

  In addition, the division | segmentation number of the cross section of the wire 1 and the thickness of each layer can be suitably designed according to the alternating current frequency band to be used.

Next, the change in resistance when the number of layers and the aluminum thickness occupation ratio (Al thickness / elementary wire thickness) were changed was calculated using a coil wire having a laminated structure made of copper and aluminum. As described above, the resistance of the wire includes an electric resistance in a direct current and a resistance due to an eddy current loss generated in the case of an alternating current. These are calculated by the following equations.
Total resistance _{= L · ρ / A + k} e · (tfBm) 2 / ρ
Where L: wire length, A: conductor cross-sectional area, k _e : proportional constant, t: conductor thickness, f: frequency, Bm: magnetic flux density, ρ: volume resistivity.
Incidentally, k _e may be calculated from the obtained by actually experimentally resistance. Also, when a plurality of layers of wire are formed, the direct current resistance and eddy current loss of each layer can be calculated, and the resistance value of the entire conductor can be calculated from the obtained results.

  The obtained resistance value varies depending on the frequency. In the present invention, attention was paid to the range of 0 to 2000 Hz used as a motor of an electric vehicle. As an index of resistance in the range of 0 to 2000 Hz, as shown in FIG. 3, the resistance curve of the entire conductor for each frequency described above was integrated in the range of 0 to 2000 Hz to obtain the total resistance in the range. The total resistance was calculated for each condition and evaluated. In FIG. 3, R is a DC resistance portion, and S is resistance due to eddy current loss.

  The results are shown in FIGS. The total thickness of the wires was 4 mm, and the width was 1 mm. The length of the wire was 8 m. In addition, when there were multiple layers of copper or aluminum, the thickness of each metal layer was evenly divided. The horizontal axis (Al thickness / elementary wire thickness) is the ratio of the total thickness of the aluminum layer to the total thickness of the wire. The vertical axis represents the total resistance divided by 2000 Hz as the average resistance.

  FIG. 4A shows a calculation result of a wire having a two-layer structure. In the following drawings, X is a resistance change curve when the thickness of aluminum is changed, and Y is a resistance when all are made of copper. That is, in FIG. 4A, the resistance is obtained when copper is formed in two layers. It is assumed that an insulating layer is formed between the respective layers.

  As shown in FIG. 4A, there is a region where the resistance average is smaller when a predetermined range of an aluminum layer is formed than with a wire made of only copper. As described above, this is a region in which the range of decrease in resistance value due to reduction in eddy current loss is greater than the increase in DC resistance. In the case of two layers, the resistance reduction effect could be obtained when the aluminum layer was in the range of 37 to 82% of the total thickness.

  FIG. 4B is a calculation result of a wire material having a three-layer structure. Similarly, in the case of three layers, there is a region where the resistance average is smaller when the aluminum layer in a predetermined range is formed than the wire composed of only copper. In the figure, X is a case where aluminum is one layer and copper is two layers, whereas Xa in the figure is a case where aluminum is two layers and copper is one layer. As is apparent from the figure, the resistance reduction effect is larger in Xa, but the thickness range in which the effect can be obtained is wider in X. Therefore, in the case of three layers, it was a case where the aluminum layer was one layer, and the effect of reducing the resistance could be obtained in the range of 25 to 59% of the total thickness.

  FIG.4 (c) is a calculation result of the wire of 4 layer structure. Similarly, in the case of four layers, there is a region where the resistance average is smaller when an aluminum layer in a predetermined range is formed than a wire composed only of copper. In the figure, X is a case where aluminum is one layer and copper is three layers. In the figure, Xa is a case where aluminum is two layers and copper is two layers. In the figure, Xb is In this case, aluminum is composed of three layers and copper is composed of one layer. As is apparent from the figure, the resistance reduction effect is larger in Xa and Xb, but the thickness range in which the effect can be obtained is wider in X. Therefore, in the case of four layers, the aluminum layer is one layer, and the effect of reducing the resistance can be obtained in the range of 19 to 45% of the total thickness.

  FIG.4 (d) is a calculation result of the 5-layer structure wire. Similarly, in the case of five layers, there is a region in which the resistance average is smaller when an aluminum layer in a predetermined range is formed than a wire composed only of copper. As a result of calculating the combination of the number of layers of aluminum and the number of layers of copper, the thickness range where the effect can be obtained is the widest in the case of a single layer of aluminum. Only (X) is shown. As shown in FIG. 4D, in the case of five layers, the aluminum layer is a single layer, and the effect of reducing the resistance can be obtained in the range of 13 to 35% of the total thickness.

  Fig.5 (a) is a calculation result of the wire material of 6-layer structure. Similarly, in the case of six layers, there is a region where the resistance average is smaller when the aluminum layer in a predetermined range is formed than the wire composed only of copper. As shown to Fig.5 (a), in the case of 6 layers, it was a case where the aluminum layer was 1 layer, Comprising: The effect of resistance reduction was able to be acquired in 13 to 29% of the total thickness.

  FIG.5 (b) is a calculation result of the wire material of 7-layer structure. Similarly, in the case of seven layers, there is a region where the average resistance is smaller when a predetermined range of aluminum layer is formed than with a wire composed only of copper. As shown in FIG. 5B, in the case of seven layers, the aluminum layer was one layer, and the effect of reducing the resistance could be obtained in the range of 12 to 24% of the total thickness.

  FIG.5 (c) is a calculation result of the wire material of 8 layer structure. Similarly, in the case of eight layers, there is a region where the resistance average is smaller when the aluminum layer in a predetermined range is formed than the wire composed only of copper. As shown in FIG. 5C, in the case of 8 layers, the aluminum layer is a single layer, and the effect of reducing the resistance can be obtained in the range of 12 to 19% of the total thickness.

  FIG.5 (d) is a calculation result of the wire material of 9-layer structure. Similarly, in the case of nine layers, there is a region where the resistance average is smaller when the aluminum layer in a predetermined range is formed than the wire composed only of copper. As shown in FIG. 5D, in the case of nine layers, the aluminum layer is one layer, and the effect of reducing the resistance can be obtained in the range of 12 to 15% of the total thickness.

  Note that, under the above conditions, the effect of reducing the resistance by forming the aluminum layer could not be obtained with 10 or more layers. This is because with 10 layers or more, the thickness of each layer is sufficiently thin, so that the influence of eddy current loss is reduced even with only copper.

  As described above, the desirable thickness ratio of aluminum varies depending on the number of layers. However, by stacking aluminum in an appropriate thickness range, the total resistance can be reduced as compared with the case where only copper is stacked with the same thickness and the same number of layers. Therefore, when copper is replaced with aluminum simply for weight reduction or cost reduction, deterioration of electrical resistance is inevitable. However, as in the present invention, weight reduction is achieved by laminating aluminum within an appropriate range. In addition to the cost reduction, the effect of reducing the resistance can be obtained.

  In addition, such an effect is obtained with respect to a wire in which strands having a substantially rectangular cross section are laminated. For example, an effect of reducing eddy current loss cannot be obtained with respect to a circular coaxial multi-layer wire. Therefore, it cannot be applied as it is.

  In this way, the total resistance (average resistance) in the frequency range required for each condition was calculated, the relationship between the ratio of the thickness occupied by aluminum and the total resistance was calculated, and the same number was laminated using all copper. An appropriate aluminum thickness ratio can be calculated by comparing with the total resistance. That is, the aluminum thickness ratio range in which the total resistance is lower than when all the copper is laminated can be set as appropriate aluminum lamination conditions under the conditions (total thickness, number of layers, etc.). Therefore, by laminating aluminum and copper so as to have such an aluminum thickness ratio, it is possible to obtain a coil wire that is light in weight, can be reduced in cost, and is less affected by an increase in resistance.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

DESCRIPTION OF SYMBOLS 1 ......... Wire 3a, 3b ......... Wire 5 ......... Insulation coating 7 ......... Intervening layer 10 ......... Coil 11 ......... Winding 13 ......... Coil core

Claims (18)

A wire for a coil,
A first strand and a second strand made of a material having a conductivity different from the conductivity of the first strand,
The conductivity of the first strand is higher than the conductivity of the second strand, the specific gravity of the first strand is greater than the specific gravity of the second strand,
The first strand and the second strand have a substantially rectangular cross section with substantially the same width,
A wire for a coil, wherein the first strand and the second strand are laminated.   The intervening layer having a conductivity lower than that of the first and second strands is formed between the first and second strands. 1. The coil wire according to 1.   The coil wire according to claim 2, wherein the first strand is copper or a copper alloy, and the second strand is aluminum or an aluminum alloy.   The coil wire according to claim 3, wherein the intervening layer is an alumite layer.   5. The coil wire according to claim 3, wherein the first strand is disposed on an outermost layer of each of the stacked layers.   5. The coil wire according to claim 4, wherein the first strands are not stacked so as to be adjacent to each other, and the first strands are stacked so as to be adjacent to the second strand. .   The coil wire according to claim 2, wherein the intervening layer is enamel.   The coil wire according to claim 2, wherein the intervening layer is an adhesive.   The coil wire according to claim 2, wherein the intervening layer is an oxide film.   The total number of layers of the first strand and the second strand is 2, and the thickness of the second strand is 37% to 82% of the total thickness. The coil wire according to claim 6.   The total number of layers of the first strand and the second strand is 3, and the thickness of the second strand is 25% to 59% of the total thickness. The coil wire according to claim 6.   The total number of layers of the first strand and the second strand is 4, and the thickness of the second strand is 19% to 45% of the total thickness. The coil wire according to claim 6.   4. The total number of layers of the first strand and the second strand is 5, and the thickness of the second strand is 13% to 35% of the total thickness. The coil wire according to claim 6.   The total number of layers of the first strand and the second strand is 6, and the thickness of the second strand is 13% to 29% of the total thickness. The coil wire according to claim 6.   4. The total number of layers of the first strand and the second strand is 7, and the thickness of the second strand is 12% to 24% of the total thickness. The coil wire according to claim 6.   4. The total number of layers of the first strand and the second strand is 8, and the thickness of the second strand is 12% to 19% of the total thickness. The coil wire according to claim 6.   4. The total number of layers of the first strand and the second strand is 9, and the thickness of the second strand is 12% to 15% of the total thickness. The coil wire according to claim 6. A coil structure,
A coil core;
Windings wound around the coil core;
Comprising
The winding is configured by laminating a first strand made of copper or a copper alloy and a second strand made of aluminum or an aluminum alloy,
The first strand and the second strand have a substantially rectangular cross-sectional shape with substantially the same width,
An alumite layer is formed on a surface of the second strand, and the first strand and the second strand are laminated via the alumite layer.

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