This application claims the benefit of priority to Japanese Patent Application Number 2022-056856 filed on Mar. 30, 2022. The entire contents of the above-identified application are hereby incorporated by reference.
The disclosure relates to a coil wire rod, a manufacturing method for the coil wire rod, a stator, and an electric motor.
When a magnetic flux interlinks with a conductor, current is generated to generate a magnetic flux in a direction opposite to the magnetic flux in the conductor. A loss due to the current is generally called an eddy current loss. For reducing the eddy current loss, it is effective to reduce the conductor dimension in the direction perpendicular to the magnetic flux.
In a known coil of an electric motor with a plurality of wires bundled and wound, a difference in inductance due to a difference in wire positions occurs, and a deviation in magnitude of current flowing through the wires occurs particularly in a high frequency range. Deviation of the current increases a copper loss occurring in the coil as compared with uniform flow of the current. This increased loss is generally called a circulating current loss.
For reducing the circulating current loss, it is effective to reduce the difference in wire positions. Known techniques for this include a configuration using a litz wire in which a plurality of wires is twisted and a technique called transposition of forming a coil while changing a relative position of a wire conductor (for example, see JP 2020-514960 T).
The sum of the eddy current loss and the circulating current loss described above is generally called an alternating-current loss.
Unfortunately, in achieving the transposition as described above, the stranded wire is formed by twisting the wires, causing irregularities on the outer surface of the stranded wire. This decreases a space factor in a slot when the stranded wire is accommodated in the slot. As a result, the copper loss of the direct current may increase.
The disclosure has been made to solve the above problems, and an object of the disclosure is to provide a coil wire rod that can further suppress copper loss, a manufacturing method for the coil wire rod, a stator, and an electric motor.
To solve the above problems, a coil wire rod according to the disclosure includes a conductor formed of a conductive material, having a uniform outer peripheral shape, and extending in a direction of an axis. The conductor is divided by a division region having a radial shape around the axis in a cross-sectional view orthogonal to the direction of the axis and includes a plurality of stranded wires each extending in the direction of the axis. The division region is twisted about the axis toward the direction of the axis in at least a part in the direction of the axis.
A manufacturing method for a coil wire rod according to the disclosure, which is a method for manufacturing the coil wire rod described above, includes a step of sequentially forming, by additive manufacturing, the plurality of stranded wires until being divided by the division region.
A stator according to the disclosure includes a yoke having an annular shape and extending in the direction of the axis, a plurality of teeth protruding inward in a radial direction from an inside surface of the yoke and arrayed at intervals in a circumferential direction, and coils having the coil wire rod wound around the teeth. The teeth include a tooth body connected to the inside surface of the yoke and extending in a radial direction and a flange portion overhanging in a circumferential direction from an end portion inward in the radial direction of the tooth body. In the coil wire rod located at a connection portion between the tooth body and the flange portion of a plurality of the coil wire rods included in the coils, at least one corner facing an outer periphery side with respect to the axis of outside surfaces of the plurality of stranded wires forms an arc shape when viewed from the direction of the axis.
A stator according to the disclosure includes a yoke having an annular shape and extending in the direction of the axis, a plurality of teeth protruding inward in a radial direction from an inside surface of the yoke and arrayed at intervals in a circumferential direction, and coils having the coil wire rod wound around the teeth. The teeth include a tooth body connected to the inside surface of the yoke and extending in a radial direction and a flange portion overhanging in a circumferential direction from an end portion inward in the radial direction of the tooth body. In the coil wire rod located outside in a circumferential direction of the flange portion of a plurality of the coil wire rods included in the coils, at least one corner facing an outer periphery side with respect to the axis of outside surfaces of the plurality of stranded wires forms an arc shape when viewed from the direction of the axis.
An electric motor according to the disclosure includes a rotor extending along a center axis and the stator covering the rotor from an outer periphery side.
The disclosure can provide a coil wire rod that can further suppress copper loss, a manufacturing method for the coil wire rod, a stator, and an electric motor.
The disclosure will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, a coil wire rod 40 according to a first embodiment of the disclosure, a manufacturing method for the coil wire rod 40, a stator 20, and an electric motor 1 will be described with reference to
As illustrated in
The stator 20 covers the rotor 10 from an outer periphery side. The stator includes a stator core 21 and a coil 22. The stator core 21 includes a yoke 23 and teeth 24. The yoke 23 has an annular shape around the center axis A. The plurality of teeth 24 protrudes inward in a radial direction from an inside surface of the yoke 23 and is arrayed at equal intervals in the circumferential direction. In the present embodiment, nine teeth 24 are provided as an example, but the number of the teeth 24 may be 8 or less or 10 or more.
The teeth 24 include a tooth body 25 and a flange portion 26. The tooth body 25 extends in a radial direction from the inside surface of the yoke 23. The circumferential dimension (that is, width dimension) of the tooth body 25 is constant over the entire area in the radial direction. An end portion (tip end) inward in a radial direction of the tooth body 25 is provided with a flange portion 26. The flange portion 26 overhangs from the tip end of the tooth body 25 to both sides in the circumferential direction. The flange portion 26 is provided to prevent the coil 22 attached to the tooth body 25 from falling off.
A space between a pair of the teeth 24 adjacent to each other in the circumferential direction is called a slot 27. The coil 22 is arranged in the slot 27. The volume occupied by the coil 22 in the slot 27 may be referred to as a space factor.
The coil 22 is formed by winding the coil wire rod 40 described later around the tooth body 25 multiple times. When current is supplied to the coil 22, an electromagnetic force is generated by a magnetic field occurring between a permanent magnet of the rotor 10 and the coil 22 of the stator 20, and the rotor is rotationally driven about the center axis A. Rotation of the rotor 10 is taken out from the shaft end and used for various uses.
By having a tubular shape around the center axis A, the housing 30 covers the stator 20 from the outer periphery side. As an example, the stator 20 is fixed to the inside surface of the housing 30 by press-fit.
Next, the configuration of the coil wire rod 40 will be described with reference to
As illustrated in
The conductor 50 includes a plurality of (four) stranded wires 41. The four stranded wires 41 are annularly arranged side by side in the circumferential direction with reference to the axis X. A gap is formed between each of the stranded wires 41. This gap is a division region 42. That is, this division region 42 divides the cross section of the conductor 50 into four. The division region 42 extends radially around the axis X. In the present embodiment, the division region 42 has a cross shape when viewed from the axis X direction.
As illustrated in
Next, a manufacturing method for the coil wire rod 40 will be described with reference to
In step S1, fine powder of a conductive material such as copper described above is prepared. In subsequent step S2, the coil wire rod 40 is shaped to have the above-described shape by additive manufacturing. This shaping method gives a predetermined shape by melting copper fine powder by irradiating the copper fine powder with laser and then curing the copper fine powder. By repeating this treatment over a plurality of successive layers, the coil wire rod 40 is obtained in a state where the above-described shape is maintained. For example, when the coil wire rod 40 additively manufactures the coil 22, a method of laminating in the direction of the central line of the coil 22 having an annular shape is conceivable.
Here, in a coil where a plurality of wires is bundled and wound, it is known that a difference occurs in inductance due to a difference in magnetic flux interlinked with the coil of each wire, and a deviation occurs in magnitude of current flowing through the wires particularly in a high frequency range. When the current is deviated, copper loss occurring in the coil increases as compared with a case where the current uniformly flows. This increased loss is generally called an alternating-current loss.
In order to reduce alternating-current loss, it is effective to reduce the difference in amount of interlinkage magnetic flux between the wires. As a technique for this, a configuration using a litz wire in which a plurality of wires is twisted has been known. However, when wires are twisted to form a stranded wire, irregularities occur on the outer surface of the stranded wire. That is, spiral irregularities occur between the stranded wires, and the outer peripheral shape changes (becomes not uniform) as compared with that before twisting. This decreases the space factor in the slot when the coil is accommodated in the slot. As a result, the copper loss of the direct current may increase.
Therefore, the coil wire rod 40 according to the present embodiment adopts the above-described configuration. According to the above configuration, the conductor 50 is formed of the plurality of stranded wires 41 while the outer peripheral shape (contour of the cross section) of the conductor 50 is uniformly square over the entire area in the axis X direction. This reduces irregularities occurring on the outside surface as compared with the case where the wire rod is formed by twisting wires having a rectangular cross-sectional shape, for example. As a result, when forming the coil 22 in the slot 27, the gap between the coil wire rods 40 can be reduced. In other words, the space factor of the coil 22 in the slot 27 can be increased. This makes it possible to greatly reduce the copper loss occurring in the coil 22. Therefore, the efficiency of the electric motor 1 using the coil wire rod 40 can be improved.
These stranded wires 41 are divided into one another by the division region 42 extending radially around the axis X. Furthermore, the division region 42 is twisted about the axis X toward the axis X direction. When such a shape is achieved by additive manufacturing, no residual stress occurs in each of the stranded wires 41, and therefore the loss (iron loss) occurring by the residual stress can also be reduced. On the other hand, in a case where a wire rod is formed by twisting wires that initially has a linear shape, residual stress occurs inside the wire on the basis of plastic deformation when the wire is twisted. As a result, there is a possibility of an increase in the iron loss. The configuration and the manufacturing method according to the present embodiment can reduce the possibility of occurrence of such a loss.
The first embodiment of the disclosure has been described above. Note that various changes and modifications can be made to the above-described configurations without departing from the gist of the disclosure.
Next, a coil wire rod 140 and the stator 20 according to the second embodiment of the disclosure will be described with reference to
As illustrated in
According to the above configuration, since the corner facing the outer periphery side of the stranded wire 41 has an arc shape, it is possible to reduce the eddy current loss occurring in a large amount at the right-angled corners as compared with the case where the corner has a right angle shape, that is, the stranded wire 41 has a square cross section. By forming the coil 22 using such the coil wire rod 140, the loss occurring in the coil 22 can further greatly be reduced. As a result, the efficiency of the electric motor 1 using the coil 22 can further be improved.
The coil wire rod 140 is particularly desirably used in the position illustrated in
The second embodiment of the disclosure has been described above. Note that various changes and modifications can be made to the above-described configurations without departing from the gist of the disclosure.
For example, as illustrated in
Next, a coil wire rod 240 according to the third embodiment of the disclosure will be described with reference to
Furthermore, a recessed groove 243 extending in the axis X direction and recessed toward the inner periphery side is formed on one of the surfaces between the pair of flat parts adjacent to each other.
According to the above configuration, since the corner facing the outer periphery side of the stranded wire 41 has a flat shape, it is possible to reduce the eddy current loss that occurs frequently when the corner has a right-angled shape.
Furthermore, according to the above configuration, when configuring the coil 22, by arranging the recessed groove 243 of the conductor 50 to face the rotor 10 side of the electric motor 1, it is also possible to reduce local copper loss based on the magnetic force of the rotor 10. That is, it is particularly desirable that the recessed groove 243 is formed on a surface facing the center axis A side of the electric motor 1. This can further improve the efficiency of the electric motor 1.
The third embodiment of the disclosure has been described above. Note that various changes and modifications can be made to the above-described configurations without departing from the gist of the disclosure. For example, as described in the second embodiment, the eddy current loss is likely to occur at the connection portion between the tooth body 25 and the flange portion 26. Therefore, in the coil wire rod 240 located at the connection portion, as illustrated in
As a simpler aspect, as illustrated in
Next, modification examples common to each embodiment will be described with reference to
As illustrated in
Thus, the use of the coil wire rod 140 or the coil wire rod 240 only in a minimum necessary region can further improve the space factor of the coil 22, further improving the efficiency of the electric motor 1. In the coil wire rod 140 and the coil wire rod 240, since the division region 42 transitions twisting in the axis X direction as described above, the cross-sectional area of the conductor 50 increases or decreases depending on the position of the axis X depending on the area occupied by the division region 42. That is, the space factor becomes slightly smaller than that of the coil wire rod 340.
Furthermore, in each of the above-described embodiments, an example in which the division region 42 has a cross shape to form the four stranded wires 41 has been described. However, as in a coil wire rod 440 illustrated as a modification example in
The coil wire rod 40 described in each embodiment, the manufacturing method for the coil wire rod 40, the stator 20, and the electric motor 1 are understood as follows, for example.
According to the above configuration, the conductor 50 is formed of the plurality of stranded wires 41 while the outer peripheral shape of the conductor 50 is uniform. This can increase the space factor of the coil 22 when the coil 22 is formed in the slot 27. As a result, the copper loss can be reduced.
According to the above configuration, since the corner facing the outer periphery side of the stranded wire 41 has an arc shape, it is possible to reduce the eddy current loss that occurs frequently when the corner has a right-angled shape.
According to the above configuration, since the corner facing the inner periphery side of the stranded wire 41 has an arc shape, it is possible to reduce the eddy current loss that occurs frequently when the corner has a right-angled shape.
According to the above configuration, since the corner facing the outer periphery side of the stranded wire 41 has a flat shape, it is possible to reduce the eddy current loss that occurs frequently when the corner has a right-angled shape.
According to the above configuration, since the corner facing the inner periphery side of the stranded wire 41 has a flat shape, it is possible to reduce the eddy current loss that occurs frequently when the corner has a right-angled shape.
According to the above configuration, arranging the recessed groove 243 of the conductor 50 to face the rotor 10 side of the electric motor 1 can reduce local copper loss based on the magnetic force of the rotor 10.
According to the above configuration, the recessed groove 243 has an asymmetric cross-sectional shape, and thus, for example, when the recessed groove 243 is arranged opposite to the corner formed by the teeth 24 and the flange portion 26 it is possible to reduce the eddy current loss that is likely to occur at the corner.
According to the above method, since additive manufacturing is used, the plurality of stranded wires 41 can be shaped in a twisted state from the beginning. This reduces manufacturing cost. Since no residual stress occurs inside the stranded wire 41, iron loss based on the residual stress can also be reduced.
According to the above configuration, in the coil wire rod 40 located at the connection portion formed by the tooth body 25 and the flange portion 26, since the corner facing the outer periphery side of the stranded wire 41 is cut out, it is possible to reduce the eddy current loss that is likely to occur at the connection portion.
According to the above configuration, in the coil wire rod 40 located at the connection portion formed by the tooth body 25 and the flange portion 26, since the corner facing the outer periphery side of the stranded wire 41 has an arc shape, it is possible to reduce the eddy current loss that is likely to occur at the connection portion.
According to the above configuration, in the coil wire rod 40 located at the connection portion formed by the tooth body 25 and the flange portion 26, since the corner facing the outer periphery side of the stranded wire 41 has a flat shape, it is possible to reduce the eddy current loss that is likely to occur at the connection portion.
According to the above configuration, in the coil wire rod 40 in contact with any one of the tooth body 25 and the flange portion 26, since the corner facing the outer periphery side of the stranded wire 41 is cut out, it is possible to reduce the eddy current loss that is likely to occur in the region.
According to the above configuration, in the coil wire rod 40 in contact with any one of the tooth body 25 and the flange portion 26, since the corner facing the outer periphery side of the stranded wire 41 forms an arc shape, it is possible to reduce the eddy current loss that is likely to occur in the region.
According to the above configuration, in the coil wire rod 40 in contact with any one of the tooth body 25 and the flange portion 26, since the corner facing the outer periphery side of the stranded wire 41 forms a flat shape, it is possible to reduce the eddy current loss that is likely to occur in the region.
According to the above configuration, in the coil wire rod 40 located at the connection portion formed by the tooth body 25 and the flange portion 26, since the corner facing the inner periphery side of the stranded wire 41 is cut out, it is possible to reduce the eddy current loss that is likely to occur at the connection portion.
Here, the magnetic flux interlinked with the coil wire rod 40 located outside the flange portion 26 temporally changes with rotation of the rotor 10. According to the above configuration, in the coil wire rod 40 located outside the flange portion 26, a corner on the outer periphery side of the stranded wire 41 is cut out. This can reduce the eddy current loss based on the temporal change.
Here, the magnetic flux interlinked with the coil wire rod 40 located outside the flange portion 26 temporally changes with rotation of the rotor 10. According to the above configuration, in the coil wire rod 40 located outside the flange portion 26, a corner on the outer periphery side of the stranded wire 41 is cut out. This can reduce the eddy current loss based on the temporal change.
The above configuration can provide the electric motor 1 that can be efficiently driven by further reducing the copper loss.
While preferred embodiments of the invention have been described as above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the invention. The scope of the invention, therefore, is to be determined solely by the following claims.
Number | Date | Country | Kind |
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2022-056856 | Mar 2022 | JP | national |