stata

Abstract

Providing technology that increases the possibility of shortening the coil end section compared to conventional designs. [Solution] A stator is configured comprising an annular stator core having a plurality of teeth arranged in the circumferential direction and a plurality of slots formed between the teeth in the circumferential direction, a housing portion that is housed in the slots, and a coil end portion that protrudes axially from the end face of the stator core, wherein the coil end portion includes a straight portion and a curved portion in a front view from the radial direction, and the radii of curvature of the curved portions of the coil end portions, which are arranged at different positions in the radial direction, are different from each other.

Description

Technical Field

[0001] The present invention relates to a stator.

Background Art

[0002] Conventionally, a stator configured by winding a coil around teeth formed on a stator core is known. In such a stator, the coil generally has a housed portion that is a portion housed in a slot and a coil end portion that is a portion where the coil protrudes more than the stator core in the axial direction (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the coil end portion becomes long, the loss increases. Therefore, it is preferable that the coil end portion is as short as possible.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a technique that increases the possibility that the coil end portion becomes shorter than before.

Means for Solving the Problems

[0006] In one embodiment, the stator comprises an annular stator core having a plurality of teeth arranged in the circumferential direction and a plurality of slots formed between the teeth in the circumferential direction; a housing portion that is housed in the slots; and a coil end portion that protrudes axially from the end face of the stator core, wherein the coil end portion includes a straight portion and a curved portion in a front view from the radial direction, and the radii of curvature of the curved portions of the coil end portions, which are located at different positions in the radial direction, are different from each other.

[0007] In a coil end configuration having both a straight and a curved section, it was conventionally believed that the coil end would be shortest when the curved sections of coil end parts positioned at different locations in the radial direction had the same radius of curvature (or, if there were multiple curved sections, when each curved section had the same radius of curvature). However, it was discovered that there is a degree of freedom in the placement of the coil end parts within the space where they are located, and that there is room to make the coil end parts even shorter. Through trial and error by the applicant, it was found that if the radii of curvature of the curved sections of coil end parts positioned at different locations in the radial direction are different, the space where the coil end parts are located can be used more effectively. In other words, by making the radii of curvature of the curved sections of coil end parts positioned at different locations in the radial direction different, the possibility of making the coil end parts shorter than before can be increased. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of the status. [Figure 2] Figure 2A shows a portion of the stator viewed along the axial direction of the stator core, and Figure 2B is an enlarged cross-sectional view showing the coil cut perpendicular to the axial direction at the end face of the stator core. [Figure 3] This is a diagram showing a segment coil. [Figure 4] Figures 4A, 4B, and 4C show the first coil end portion of the coil. [Figure 5] This diagram schematically shows the arrangement of the coil's centerlines. [Modes for carrying out the invention]

[0009] Here, embodiments of the present invention will be described in the following order. (1) Stator configuration: (2) Shape identification process for the coil end: (3) Other embodiments, etc.:

[0010] (1) Stator configuration: Figure 1 is a perspective view of a stator 1 according to this embodiment. The stator 1 comprises a stator core 10 and a coil 20. Figure 2A is a view of a part of the stator 1 along the axial direction of the stator core 10. Figure 2B is an enlarged cross-sectional view showing the coil 20 cut in a direction perpendicular to the axial direction at the end face of the stator core 10. In Figure 2B, the cut surface of the coil 20 is shown with a hatch.

[0011] The stator core 10 in this embodiment is an annular member. A rotor (not shown) is arranged inside the ring formed by the stator core 10. The rotor is a member that rotates with the central axis of the ring formed by the stator core 10 as the axis of rotation Ax. In this specification, the direction parallel to the axis of rotation Ax is called the axial direction, the direction perpendicular to the axis of rotation Ax is called the radial direction, and the direction of rotation around the axis of rotation Ax is called the circumferential direction. Furthermore, in the radial direction, the direction away from the axis of rotation Ax is called the radially outward direction, and the direction approaching the axis of rotation Ax is called the radially inward direction.

[0012] The stator core 10 has a plurality of teeth 11 arranged in the circumferential direction and a plurality of slots 12 formed between the teeth 11 in the circumferential direction. In this embodiment, the teeth 11 are portions that protrude from the radially outer side to the radially inner side. The teeth 11 are formed at regular intervals in the circumferential direction around the entire inner circumference of the stator core 10. The number of teeth 11 may vary. In this embodiment, the cross-sectional shape of the teeth 11 in the direction perpendicular to the axial direction is the same at any position in the axial direction. Therefore, the teeth 11 are portions that protrude from the radially outer side to the inner side in the radial direction and extend in the axial direction with the same cross-sectional shape in the direction perpendicular to the axial direction.

[0013] The space formed between the teeth 11 in the circumferential direction is the slot 12. The coil 20 is wound around the teeth 11. Once the coil 20 is wound around the teeth 11, it is housed in the slot 12. The number of coils 20 arranged radially within the slot 12 is not limited, but in this embodiment, there are eight. In Figure 2B, the coils 20 arranged within the slot 12 are shown with turn numbers from 1 to 8. These turn numbers are for illustrative purposes only and are not inscribed on the stator core 10.

[0014] In this embodiment, the outermost diameter is designated as 1 and the innermost diameter as 8, and turn numbers are assigned accordingly. Hereafter, each coil 20 within the slot 12 may be identified by its respective turn number. For example, the innermost coil 20 may be referred to as the 8T coil 20, meaning it is the coil with turn number 8. In other words, each slot 12 contains coils 20 from 1T to 8T in sequential order.

[0015] The coil 20 includes a housing portion 21 that is housed in the slot 12 and a coil end portion 22 that protrudes axially from the end face of the stator core 10. In Figures 1 and 2A, the visible coil 20 is the coil end portion 22, as it is the part that protrudes axially from the end face of the stator core 10.

[0016] In this embodiment, the coil 20 is formed by welding a plurality of segment coils. FIG. 3 is a diagram showing a segment coil, and the segment coil is inserted into the stator core 10 with its longitudinal direction oriented in the axial direction. FIG. 3 shows the segment coil as viewed from a direction perpendicular to the axial direction (corresponding to the radial direction). In this embodiment, the state viewed from the radial direction is referred to as a front view. FIG. 3 shows the segment coils constituting the 2T coil 20 in a certain slot 12 and the 3T coil 20 in another slot 12. Although the shapes of the segment coils constituting other turn numbers are different particularly in the shape of the first coil end portion 221 described later, the general shapes are similar, so here, the general shape of each segment coil will be described using FIG. 3.

[0017] The segment coil has a housed portion 21, a first coil end portion 221, and a second coil end portion 222. In the example shown in FIG. 3, the coil end portion 22 is composed of a first coil end portion 221 and a second coil end portion 222.

[0018] The housed portion 21 is a linear portion corresponding to the axial length of the stator core 10. Two housed portions 21 are formed in one segment coil, and they are portions extending in the axial direction in a parallel state with each other. The first coil end portion 221 and the second coil end portion 222 are portions extending in opposite directions in the axial direction from the housed portion 21.

[0019] The second coil end portion 222 is a portion extending linearly from the housed portion 21, and its tip is thinner than other portions. That is, the cross-sectional area of the tip of the second coil end portion 222 in the direction perpendicular to the axial direction is smaller than other portions. The tip is the portion where the second coil end portions 222 are welded to each other. Therefore, the tip is not covered by an insulating member. On the other hand, portions other than the tip are covered by an insulating member.

[0020] The first coil end portion 221 is a portion that extends from one side of the housed portion 21 to the other side of the housed portion 21 and connects the two housed portions 21. That is, the first coil end portion 221 extends axially from the contact portions 21a with respect to each of the two housed portions 21 and is connected at the apex portion 22a.

[0021] In the present embodiment, the first coil end portion 221 has a plurality of straight portions 22b and a plurality of curved portions 22c. The straight portion 22b is a portion that is linear in a front view. The curved portion 22c is a portion that is curved in a front view. In the present embodiment, the curved portion 22c has a shape corresponding to an arc (the center line is an arc). Also, the curved portions 22c are present at a total of six locations. Specifically, between the contact portion 21a and the apex portion 22a, there are the first curved portion 22c1, the second curved portion 22c2, and the third curved portion 22c3 in order of proximity to the apex portion 22a. Since the contact portion 21a is present at each of the two housed portions 21, there are two contact portions 21a.

[0022] Therefore, three curved portions 22c (22c1, 22c2, 22c3) exist between each of the two contact portions 21a and the apex portion 22a, and the curved portions 22c exist at a total of six locations. In the present embodiment, when the apex portion 22a is above and the contact portion 21a is below, the curves formed by each of the first curved portion 22c1, the second curved portion 22c2, and the third curved portion 22c3 are convex upward (the center of curvature is located below the curved portion), convex downward (the center of curvature is located above the curved portion), and convex upward.

[0023] A plurality of such segment coils are formed in advance, each segment coil is inserted into the slot 12, and the second coil end portion 222 is welded so that the coil 20 is wound around the stator core 10. Specifically, the tip of the second coil end portion 222 is inserted into the slot 12 and moved axially, so that the housed portion 21 is in a state of being housed in the slot 12.

[0024] When multiple segment coils are inserted into predetermined slots 12, the second coil end portions 222 are bent so that their tips touch each other. Then, the tips are welded together. In Figure 1, the coil end portion 22 located at the bottom of the stator 1 is the second coil end portion 222. As shown in Figure 1, the second coil end portions 222 are bent so that their tips touch each other, and they are welded together in this state. After welding, the welded portion is insulated by an insulating material.

[0025] As described above, the segment coils that make up the coils 20 at different radial positions have different shapes from each other. The segment coils that make up the 1T and 8T coils 20, for example, coil Sc shown in Figure 1, have a significantly different shape from the segment coil shown in Figure 3. On the other hand, the segment coils that make up the 2T to 7T coils 20 have a similar shape to the segment coil shown in Figure 3, but their shape differs depending on their radial position.

[0026] In other words, the coils other than those positioned at the outermost and innermost diameters are similar in shape to each other, but their shapes differ depending on their radial position. Furthermore, these coils can be described as having a first curved section 22c1, a second curved section 22c2, and a third curved section 22c3 between the contact section 21a and the apex section 22a, in order from closest to the apex section 22a, with straight sections between each of these curved sections.

[0027] Specifically, the radii of curvature of the curved portions 22c of the first coil end portions 221, which are positioned at different locations in the radial direction, are different from each other. In this embodiment, the 2T to 7T coils 20 have different turn numbers in which the two housing portions 21 are arranged. Specifically, in the segment coil shown in Figure 3, one housing portion 21 becomes a 2T coil 20 in the slot 12, and the other housing portion 21 becomes a 3T coil 20 in the slot 12. In Figure 2A, the coil composed of this segment coil is shown as coil Sc1.

[0028] In this embodiment, in addition to coil Sc1, there are two types of segment coils, Sc2 and Sc3, as shown in Figure 2A. Coil Sc2 has one housing portion 21 that is a 4T coil 20 in the slot 12, and the other housing portion 21 that is a 5T coil 20 in the slot 12. Coil Sc3 has one housing portion 21 that is a 6T coil 20 in the slot 12, and the other housing portion 21 that is a 7T coil 20 in the slot 12. In this embodiment, each of coils Sc1 to Sc3 is arranged in the circumferential direction as shown in Figure 2A, with the pitch from one housing portion 21 to the other housing portion 21 being the same (the number of slots 12 in the circumferential direction is the same). Therefore, coils Sc1, Sc1 arranged in the circumferential direction have the same shape, coils Sc2, Sc2 arranged in the circumferential direction have the same shape, and coils Sc3, Sc3 arranged in the circumferential direction have the same shape.

[0029] The coils Sc1 to Sc3 are positioned at different radial locations when placed on the stator core 10. Figures 4A to 4C show the first coil end portions 221 of coils Sc1 to Sc3. As shown in these figures, the shapes of coils Sc1 to Sc3 are similar but different. That is, in each of the first coil end portions 221 of coils Sc1 to Sc3, there is a straight portion 22b and a curved portion 22c between the apex portion 22a and the contact portion 21a, and the shapes may differ.

[0030] The straight section 22b may be curved in the radial direction (the depth direction in the drawings of Figures 4A to 4C). For example, the straight section 22b that constitutes the vertex 22a has two curved sections when viewed from the axial direction, as indicated by the reference numeral C in Figure 2A. For this reason, it appears slightly curved when viewed from the axial direction in Figures 4A to 4C, but is almost straight in a front view. For this reason, in this specification, it is referred to as the straight section 22b in the sense that it appears almost straight in a front view.

[0031] In coils Sc1 to Sc3, the radii of curvature of at least some of the curved sections 22c are different from each other, which increases the degree of freedom in selecting the space in which the first coil end sections 221 of the multiple coils are densely arranged. Compared to a conventional configuration in which the radii of curvature of each of the multiple curved sections 22c are the same in all of coils Sc1 to Sc3, the length of the coil 20 can be shortened.

[0032] Specifically, by configuring the curved portions 22c of the first coil end portions 221 of coils Sc1 to Sc3 to have different radii of curvature, it is possible to shorten the length of the coil 20. Focusing on the curved portions 22c in Figures 4A to 4C, the arc lengths of the first curved portions 22c1 are, in descending order, coils Sc3, Sc2, and Sc1. Also, the radii of curvature of the first curved portions 22c1 are the same.

[0033] The arc lengths of the second curved section 22c2 are, in descending order, Sc2, Sc1, and Sc3 for the coils. Similarly, the radii of curvature of the second curved section 22c2 are, in descending order, Sc2, Sc1, and Sc3 for the coils. Furthermore, the arc lengths and radii of curvature of the third curved section 22c3 are equivalent for coils Sc1, Sc2, and Sc3.

[0034] In the above configuration, comparing coils Sc1 to Sc3, at least the radii of curvature of the second curved portion 22c2 are different from each other. This configuration makes it possible to shorten the length of the first coil end portion 221 in coil 20 compared to a conventional configuration in which the radii of curvature of the second curved portion 22c2 in each of coils Sc1 to Sc3 are the same.

[0035] Furthermore, the second curved portion 22c2 of the first coil end portion 221 in the innermost coil Sc3 in the radial direction has a smaller radius of curvature than the second curved portion 22c2 of the first coil end portion 221 located at other positions in the radial direction. This configuration makes it possible to shorten the length of the first coil end portion 221 in the coil 20 compared to a conventional configuration in which the radius of curvature of the second curved portion 22c2 in each of the coils Sc1 to Sc3 is the same. In other words, even if the radii of curvature of the first curved portion 22c1 and the third curved portion 22c3 are the same in coils Sc1 to Sc3, the length of the first curved portion 22c1 can be effectively shortened by changing the radius of curvature of the second curved portion 22c2.

[0036] Furthermore, focusing on the second curved section 22c2, the first coil end section 221 where the radius of curvature of the second curved section 22c2 is maximized is located between the innermost and outermost coil end sections in the radial direction. That is, the coil Sc2 with the maximum radius of curvature is located between the innermost coil Sc3 and the outermost coil Sc1 in the radial direction. With this configuration, the length of the first coil end section 221 can be minimized.

[0037] (2) Shape identification process for the coil end: As described above, the shape of the first coil end portion 221 in this embodiment differs for each coil Sc1 to Sc3, which are arranged at different positions in the radial direction. The shapes of coils Sc1 to Sc3 can be determined by various methods. That is, compared to a conventional configuration in which the radius of curvature of the curved portion 22c is the same for all coils Sc1 to Sc3, it is sufficient to individually vary the radius of curvature of the curved portion 22c in each of the coils Sc1 to Sc3 so that the length of the first coil end portion 221 is shortened.

[0038] One example of a method for determining the shape is simulation. The simulation is performed by identifying the shape of the slots in the stator core 10, determining the placement position of the coils 20 within each slot 12, identifying the cross-sectional shape and cross-sectional area of ​​the coils 20 as designed values, and repeatedly making small changes to the shape of the coils 20 reproduced in a virtual space.

[0039] Specifically, each of the coils Sc1 to Sc3 is designated as a simulation target, and two simulation target coils are placed in the virtual space. The two coils placed in the virtual space are circumferentially adjacent coils. For example, if coil Sc3 is the simulation target, Sc31 and Sc32 shown in Figure 2A are placed in the virtual space. Since coils Sc31 and Sc32 are coils with housing portions 21 of 6T and 7T, coils Sc31 and Sc32 are placed in the virtual space such that the 6th and 7th positions from the radially outer side of the stator core 10 become the contact portions 21a. In this embodiment, two coils Sc31 and Sc32 are simulation targets, but since the shapes of multiple coils Sc3 arranged in the circumferential direction are all the same, if the shapes of two circumferentially adjacent coils Sc31 and Sc32 are determined as simulation targets, the shapes of circumferentially adjacent coils Sc31 and Sc32 are determined so that they do not interfere with each other, and it is possible to arrange coils of the determined shape in the circumferential direction. Of course, simulations are also performed on coils Sc1 and Sc2.

[0040] The simulation is performed by changing the length of the center line in each part of the first coil end portion 221 that is located on the side of the apex portion 22a from the contact portion 21a. The initial shape of the coil to be simulated is predetermined, and in this embodiment, as shown in Figure 3, it has a shape in which there are a total of 5 straight sections 22b and a total of 6 curved sections 22c between the two contact portions 21a.

[0041] Figure 5 schematically shows the arrangement of the centerlines of coils Sc31 and Sc32. Coils Sc31 and Sc32 are adjacent coils in the circumferential direction. These coils Sc31 and Sc32 are arranged side by side in the circumferential direction. In Figure 5, the left portion of coil Sc31 is positioned above the left portion of coil Sc32 (on the opposite side of the stator core 10 in the axial direction), and the right portion of coil Sc31 is positioned below the right portion of coil Sc32 (towards the stator core 10 in the axial direction). In Figure 5, the straight portion 22b of coil Sc31 is shown as a dashed line, the curved portion 22c as a solid line, and coil Sc32 is shown as a dashed line.

[0042] In the initial shapes of coils Sc31 and Sc32, the lengths of each part are the same as in the conventional design. That is, the initial shape is determined such that the straight section 22b is as long as possible and the curved section 22c is as short as possible between the contact point 21a and the vertex 22a. This is based on the conventional idea that the shape connecting the contact point 21a and the vertex 22a by the shortest distance is the straight line connecting the contact point 21a and the vertex 22a, so the straight section 22b is made as long as possible and the curved section 22c is made as short as possible.

[0043] In the simulation, the shape of each coil is changed by altering the center line passing through the center of each part, as shown in Figure 5. Specifically, an objective function is defined, and an optimization process is performed to minimize the objective function. The optimization process may be carried out using various known methods, such as the annealing method.

[0044] The objective function can be defined using various methods. For example, it could be a function that minimizes the length of the coil's centerline at the first coil end portion 221 (the length from contact portion 21a to contact portion 21a), or a function that minimizes the height of the first coil end portion 221 in the axial direction (the distance from the end face of the stator core 10). In this embodiment, it is assumed that the objective function is a function that minimizes the length of the coil's centerline and minimizes the height of the first coil end portion 221.

[0045] The optimization process to minimize the objective function is a process that minimizes the objective function by repeatedly changing the variables in the equation that represents the objective function. The variables are parameters that define the shape of the coils Sc31 and Sc32, and include, for example, the radius of curvature and length (arc length) of the two first curved sections 22c1, the two second curved sections 22c2, and the two third curved sections 22c3, as well as the length and angle of each straight section 22b. The angle is the smaller of the angles of intersection between the end face of the stator core 10 and the center line of the straight section 22b. As shown in Figure 2A, when the vertex 22a of the coils Sc31 and Sc32 is viewed from the axial direction, the shape is that of two connected curved sections (indicated by symbol C in Figure 2A), so the radius of curvature and length of the curved sections may also be included in the variables.

[0046] Furthermore, various constraints may be imposed when performing the optimization process. Here, we assume an example where constraints are placed on the relationship between the angular variables and the coils Sc31 and Sc32. For example, the radius of curvature and length of the curved section 22c may be set to lower limits based on manufacturing conditions, etc. In the straight section 22b, a constraint may be imposed that it be 0 mm or more. A constraint may also be imposed that the angle is between 0° and 90°. In addition, in this embodiment, the cross-sectional shape and size of the coils Sc1, Sc2, and Sc3, and the position of the contact portion 21a are fixed.

[0047] Furthermore, regarding the relationship between coils Sc31 and Sc32, a constraint is to ensure that coils Sc31 and Sc32 do not interfere with each other when coil wires corresponding to the cross-sectional area of ​​the square wires are present around the center line. Specifically, a lower limit may be set for the distance between coils Sc31 and Sc32 in the radial direction, and a lower limit may also be set for the distance between coils Sc31 and Sc32 in the axial direction.

[0048] As described above, by defining the objective function using variables, the shapes of coils Sc31 and Sc32 can be determined by repeatedly changing their shape using known methods, while each constraint is imposed, in order to minimize the lengths of coils Sc31 and Sc32 and the height of the first curved section 22c1.

[0049] In this embodiment, the coil to be simulated is one of coils Sc1, Sc2, or Sc3 (any of the coils located at different radial positions). After optimizing one of the coils to be simulated, the process of optimizing one of the unoptimized coils as the new simulation target is repeated until all coils Sc1, Sc2, and Sc3 are optimized.

[0050] In this embodiment, with the exception of the two curved sections at the vertex 22a (indicated by the symbol C in Figure 2A), all other variables change in the direction in which coils Sc1, Sc2, and Sc3 extend. Therefore, the shapes of coils Sc1, Sc2, and Sc3 do not change radially and interfere with each other.

[0051] Furthermore, after optimizing any of the coils Sc1, Sc2, or Sc3, constraints may be set based on the optimized value. In this embodiment, coil Sc3, which is located on the innermost side in the radial direction, is optimized first, and constraints may be imposed so that the height of the first coil end portion 221 (distance from the end face of the stator core 10) identified in coil Sc3 is the same as the height of the first coil end portion 221 in the other coils Sc1 and Sc2. With this configuration, the height of the first coil end portion 221 can be set to a common value for all coils Sc1, Sc2, and Sc3. The coil that is optimized first is not limited, but coil Sc3, which is located on the innermost side in the radial direction, has the shortest distance between the contact portions 21a compared to coils Sc1 and Sc2, and has relatively less freedom in shape compared to coils Sc1 and Sc2. For this reason, optimizing coil Sc3 first increases the possibility of preventing optimization from being impossible or insufficient due to overly strict constraints during the optimization process.

[0052] Through the optimization process described above, it is possible to identify a shape that minimizes the coil length in each coil Sc1, Sc2, and Sc3, and minimizes the height of the first coil end portion 221. Furthermore, various insights into the shapes of coils Sc1, Sc2, and Sc3 can be obtained during the simulation process.

[0053] Specifically, by making some of the above-mentioned variables variable and fixing the remaining variables, it is possible to identify which parts need to be changed to shorten the length of the coil 20 compared to the conventional configuration. Furthermore, it has been found that even if the radius of curvature of the curved portion 22c of coils Sc1, Sc2, and Sc3 is made variable and the other variables are fixed to their initial values, it is possible to shorten the length of the coil 20 during the simulation process. In the coils Sc1, Sc2, and Sc3 optimized in this way, the radii of curvature of the curved portion 22c of the first coil end portion 221 are optimized to be different from each other. Therefore, if the radii of curvature of the curved portion 22c of the first coil end portion 221 are set to different values ​​in coils Sc1, Sc2, and Sc3, the length of the coil 20 can be shortened compared to the initial shape of the conventional configuration.

[0054] Furthermore, it has been found that even if the radius of curvature of the second curved section 22c2 of the curved sections 22c of coils Sc1, Sc2, and Sc3 is made variable, and other variables are fixed to their initial values, it is possible to shorten the length of the coil 20 during the simulation process. In the coils Sc1, Sc2, and Sc3 optimized in this way, the radii of curvature of the second curved section 22c2 of the first coil end section 221 are optimized to be different from each other. Therefore, if the radii of curvature of the second curved section 22c2 of the first coil end section 221 of coils Sc1, Sc2, and Sc3 are set to different values ​​from each other, the length of the coil 20 can be shortened compared to the initial shape of the conventional configuration.

[0055] Furthermore, when the radius of curvature of the second curved section 22c2 of the curved sections 22c2 of coils Sc1, Sc2, and Sc3 is made variable, and the other variables are fixed to their initial values, and when all variables are made variable, the radius of curvature of the second curved section 22c2 of coil Sc3 (the second curved section of the coil end located radially inward) becomes smaller than that of the second curved sections 22c2 of the other coils Sc1 and Sc2. Therefore, by making the second curved section of the coil end located radially inward smaller than that of the other coil ends, the length of coil 20 can be shortened.

[0056] Furthermore, in both cases—when the radius of curvature of the second curved section 22c2 of coils Sc1, Sc2, and Sc3 is made variable and the other variables are fixed to their initial values, and when all variables are made variable—the radius of curvature of the second curved section 22c2 of coil Sc2 is the largest among coils Sc1, Sc2, and Sc3. Therefore, by configuring the coil end section where the radius of curvature of the second curved section is largest to be located between the innermost and outermost coil end sections in the radial direction, the length of coil 20 can be shortened.

[0057] Of course, the objective function can be minimized more efficiently by making the radius of curvature and length of the entire curved section 22c variable rather than fixing a part of the curved section 22c, and the objective function can be minimized more efficiently by making the length and angle of the straight section 22b variable in addition to the curved section 22c.

[0058] In this embodiment, the simulation is performed under these conditions, but during the simulation process, all variables except for the two curved sections at the vertex 22a (indicated by C in Figure 2A) change in the direction in which the coils Sc1, Sc2, and Sc3 extend. Therefore, when considering stators 1 of different sizes, the size of the curved section 22c and the straight section 22b may vary due to changes in the size of the stator core 10, etc. However, this does not significantly affect the relative sizes of the radii of curvature of the curved section 22c and the straight section 22b, and it is possible to shorten the length of the coil 20 by changing the radii of curvature between coils that are located at different radial positions.

[0059] (3) Other embodiments, etc.: The embodiments described above are merely examples for carrying out the present invention, and various other embodiments can be adopted. For example, the simulation is not limited to a configuration in which it is performed for each of the coils Sc1, Sc2, and Sc3, but may be performed by placing all of the coils Sc1 to Sc3 in a virtual space and defining an objective function for all of them that minimizes the length of the coil 20 and the height of the first curved section 22c1. Furthermore, the variables used for optimization are not limited, and the variables may be defined so that the shapes of the coils Sc1, Sc2, and Sc3 can change in the radial direction.

[0060] Furthermore, the shape and arrangement of the coils are not limited to the configuration described above. For example, the coils Sc1, Sc2, and Sc3 described above are configured such that adjacent coils Sc31 and Sc32 intersect in the circumferential direction (a configuration in which the coils positioned above the axial direction on the left and right sides of Figure 5 are swapped), but the configuration is not limited to this. For example, adjacent coils in the circumferential direction do not intersect, and the larger coil is positioned above the smaller coil in the axial direction.

[0061] Furthermore, the coil winding method is not limited and can be applied to various winding methods such as slope winding, double winding, and wave winding. In addition, the configuration of the coil 20 is not limited to a segment coil as shown in Figure 3 above, and may be a configuration in which a longer coil material is bent and wound more times.

[0062] The stator core can be an annular member having multiple teeth arranged in the circumferential direction and multiple slots formed between the teeth in the circumferential direction. In other words, the stator core should be equipped with multiple teeth around which coils are wound, and should be configured so that the rotor rotates relative to the stator through the interaction between the magnetic field formed by the coils and the magnetic field formed by the rotor. The number of magnetic poles, the number of slots, the material, etc., of the stator core can be of various configurations.

[0063] The stator core only needs to be annular in its overall form. The shapes of the radially inner and radially outer surfaces of the ring formed by the stator core are not limited. For example, the radially outer surface may be circular when viewed from the axial direction, or it may have a polygonal shape. Teeth are formed on the radially inner surface, and slots are formed between the teeth. In the stator core, the general shape including the teeth can be considered annular, and the portion excluding the teeth can be considered annular.

[0064] A coil should include a housing portion that is housed in a slot and a coil end portion that protrudes axially from the end face of the stator core, and should be wound around teeth. The housing portion is the part housed in the slot, and is usually the portion within the slot that is sandwiched between the two end faces of the stator core in the axial direction. The coil end portion is the portion that protrudes axially from the end face of the stator core; that is, the coil that is on the side of the slot opposite to the end face of the stator core is the coil end portion.

[0065] The coil end portions are located at both ends of the stator in the axial direction. In the embodiment described above, the first coil end portion 221 has both a straight portion and a curved portion, but it may also be configured without a straight portion. For example, if the straight portion becomes 0 during the simulation process, the first coil end portion 221 may have a shape without a straight portion. The second coil end portion 222 may or may not have both a straight portion and a curved portion. The other coil end portion typically includes a weld where the coil end portions are welded together.

[0066] The straight and curved sections are defined by a front view of the coil end from the radial direction. The shape when viewed from the axial or circumferential direction is arbitrary, and a straight section may be curved when viewed from the axial direction. The radius of curvature of the curved section only needs to be defined by a line passing through the center of the coil.

[0067] The coil only needs to be wound around teeth, and can be made of either square or round wire; the shape of the wire itself is not limited. The number of windings and the winding method are also not limited. Of course, the coil may have an insulating coating, which insulates the coils from each other and from the stator core. The material and thickness of the insulating coating are not limited, but can be made of various resins, for example.

[0068] Since the coil is wound around teeth, multiple coils are arranged radially in the wound state. When comparing the coil ends of these radially arranged coils, the radii of curvature of their curved sections differ from one another. Conventionally, it was believed that there was an ideal shape for the coil end, which is composed of a combination of straight and curved sections, in order to shorten the coil length, and that it was ideal for all of them to have the same shape regardless of their radial position. As a result, the radii of curvature of the curved sections were all the same shape regardless of their radial position. However, if we allow for differences in the shape of the radii of curvature of the curved sections in the radial direction, the space in which the coil ends are arranged can be used more freely, allowing for optimization including multiple radially arranged coil ends. As a result, the possibility of shortening the coil end compared to conventional designs can be increased. [Explanation of Symbols]

[0069] 1... Stator, 10... Stator core, 11... Teeth, 12... Slot, 20... Coil, 21... Housing section, 21a... Contact section, 22... Coil end section, 22a... Apex section, 22b... Straight section, 22c... Curved section, 22c1... First curved section, 22c2... Second curved section, 22c3... Third curved section, 221... First coil end section, 222... Second coil end section, Ax... Rotation axis, Sc, Sc1, Sc2, Sc3, Sc31, Sc32... Coil

Claims

1. An annular stator core having a plurality of teeth arranged in the circumferential direction and a plurality of slots formed between the teeth in the circumferential direction, The stator core includes a housing portion that is housed in the slot, and a coil end portion that protrudes axially from the end face of the stator core, and comprises a coil wound around the teeth. The coil end portion includes a straight section and a curved section when viewed from the radial direction. The radius of curvature of the curved portions of the coil end portions, which are located at different positions in the radial direction, is different from that of the other. stata.

2. The aforementioned coil end portion is It extends axially from the contact points with each of the two aforementioned receiving parts and is connected at the apex. Between each of the aforementioned contact points and the aforementioned apex, there are a first curved section, a second curved section, and a third curved section in order of proximity to the apex, and in the coil end sections arranged at different positions in the radial direction, at least the radii of curvature of the second curved section are different from each other. The stator according to claim 1.

3. The second curved portion of the coil end located at the innermost radial position has a smaller radius of curvature than the second curved portion of the coil end located at other radial positions. The stator according to claim 2.

4. The coil end portion where the radius of curvature of the second curved portion is maximum is located between the innermost and outermost coil end portions in the radial direction. The stator according to claim 2.

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