Manufacturing method of stator for rotary electric machine

Abstract

To facilitate molding of a resin portion in such an uneven shape to some extent and, on the other hand, to keep an insulation property of a welded portion in an end of a conductor segment when forming a resin portion 11 formed in a projected shape from projections in a region 12 covering a welded portion 20 in the end of a conductor segment 13 aligned in a radial direction and formed in a recessed shape from recesses in the other region 12 over a circumferential direction of a stator on one end face 10 of the stator in an axial direction in a manufacturing method of a stator 1 for a rotary electric machine.SOLUTION: In the step of forming a resin portion which is formed in a projected shape in a region covering a welded portion in an end of a conductor segment and formed in a recessed shape in a region, in which there is no welded portion, on an end face of a stator in an axial direction in a manufacturing method of the stator, in a casting mold 30 having a shape complementary to the shape of the resin portion, a surface of a projection in a projected portion 31 opposed to the region, in which there is no welded portion, is formed coarser than a surface of a recess in a recessed portion 31 opposed to the region covering the welded portion in the end of the conductor segment.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a stator for a rotating electric machine, and more specifically, to a method for a stator having a coil wound around the teeth (stator teeth) of a stator core, the method including a step of forming a resin portion on the end face of the stator to cover the welded portion of the conductor segment located on the axial end face of the stator. [Background technology]

[0002] As one method for winding a coil around the teeth (stator teeth) of a stator core of a rotating electric machine, a method is adopted in which a plurality of annularly curved conductor segments are inserted into slots between the stator teeth so as to surround the stator teeth, and the ends of the conductor segments are welded to each other in sequence on the axial end face of the stator core to form a single coil wound around the stator teeth. In such a configuration, the conductor segments are covered with an insulating coating except for both ends, but an end (welded portion) that is welded to an end of another conductor segment on one axial end face of the stator core is exposed in a bare wire state. Therefore, in order to insulate the welded portions of adjacent conductor segments from each other, a configuration is sometimes adopted in which the end face of the stator core on which the welded portions of the conductor segments are lined up is immersed in liquid resin and the resin is hardened in a state in which the resin coating is formed. Regarding the process of forming the resin portion on the end face of such a stator core, for example, Patent Document 1 proposes that the resin be cured under a positive pressure environment in order to suppress the occurrence of voids in the resin portion (molded portion) that is hardened on the end face of the stator core. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-136787 [Non-patent literature]

[0004] [Non-Patent Document 1] Ryoji Kitada, Journal of the Japan Society of Electrical Machining Engineers, Vol. 44, No. 106 (2010) Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned configuration in which the welded portions of the ends of a plurality of annular wire segments surrounded by stator teeth are covered with resin on the axial end face of the stator, in order to save the amount of resin used, a configuration may be adopted in which the resin portion is patterned in a convex shape in the circumferential direction of the stator in the region covering the welded portions of the wire segment ends aligned along the radial direction and in a concave shape in the other region (see FIG. 2(A)). In such a configuration, when the resin portion is formed on the axial end face of the stator, a mold having a shape complementary to the shape of the resin portion patterned in the concave and convex shapes as described above is placed with its opening facing up, and the stator end face on which the welded portions of the wire segment ends are aligned is placed facing down in the mold, and liquid resin is poured in the mold so as to cover the entire area of ​​the stator end face, and then, when the resin hardens, the mold is removed from the resin portion on the stator end face covered with the resin (see FIGS. 3(A) to 3(C)).

[0006] Generally, the "mold release force" required to remove a resin formed in a mold that has hardened therein is lower as the roughness of the inner surface of the mold increases (see Non-Patent Document 1), making the molding process easier. Therefore, by appropriately roughening the inner surface of the mold in the process of forming the resin part on the stator end face, it is expected that molding of the resin part having an uneven shape as illustrated in FIG. 2(A) will be easier. However, according to research by the inventors of the present invention, if the entire inner surface of the mold is roughened in the process of forming the resin part on the stator end face, minute unevenness is formed on the resin surface, and cracks are generated starting from the minute unevenness due to stress concentration during use of the rotating electric machine, and if such cracks reach the welded part of the end of the conductor segment where the conductor is exposed, the insulation of the welded part is impaired.

[0007] In view of the above circumstances, the main object of the present invention is to provide a method for manufacturing a stator for a rotating electric machine, which provides a resin portion on one axial end face of the stator that is convex in the areas covering the welded portions of the ends of the wire segments that are aligned radially around the stator, and concave in other areas, which facilitates to a certain extent the molding of such concave-convex shaped resin portion while ensuring the insulation of the welded portions of the ends of the wire segments. [Means for solving the problem]

[0008] According to the present invention, the above problem is solved by a method for manufacturing a stator for a rotating electric machine, the stator having a coil wound around stator teeth protruding radially inward from a stator core, the coil being formed by connecting a plurality of annular conductor segments in a single line, both ends of the plurality of conductor segments being welded to ends of another adjacent conductor segment on one axial end face of the stator, and the welded portions of the ends of the plurality of conductor segments being aligned along the stator teeth, forming a resin portion on the axial end surface of the stator, the resin portion being shaped in a convex shape in a region covering the welded portion of the wire segment end and being shaped in a concave shape in a region not including the welded portion; In the step of forming the resin portion, placing the axial end face in a mold having a shape complementary to a shape of the resin portion; injecting a liquid resin into the mold so as to cover the entire axial end surface, and hardening the resin; releasing the hardened resin portion on the axial end surface from the mold after the resin is hardened; Including, This is achieved by forming the mold such that the surface of the convex portion opposite the area without the weld is rougher than the surface of the concave portion opposite the area covering the weld of the wire segment end.

[0009] In the above configuration, the "rotating electric machine" may be any type of rotating electric machine (generator, electric motor, motor-generator) that uses a stator wound with a coil. In the present invention, the "coil" is, as described above, a plurality of conductor segments, i.e., wires made of conductive material (copper, aluminum, etc.) that are connected in sequence to form a single spiral. Each conductor segment is entirely insulated except for the portions welded to other conductor segments at both ends, so that they are not conductive even when they come into contact with each other. Note that the above stator core may have a plurality of coils wound thereon, and in that case, each coil is formed by connecting a plurality of conductor segments in a single spiral (i.e., the stator of the present invention also includes a case where a plurality of coils are wound around the stator core). In addition, the resin material of the resin portion applied to the end face of the stator on the side where the welded portions of the conductor segments are aligned may be any insulating resin that hardens from a liquid state, for example, one-liquid thermosetting epoxy. The mold may be a mold formed from conventional materials used in the art.

[0010] In the above-described configuration of the present invention, in a mold for forming the resin portion on the axial end face of the stator in a convex shape in the region covering the welded portion of the wire segment end and in a concave shape in the region without the welded portion, the surface of the convex portion facing the region without the welded portion is formed rougher than the surface of the concave portion facing the region covering the welded portion of the wire segment end, which allows the concave-shaped resin portion to be easily released from the mold, while cracks are less likely to occur in the convex resin portion enclosed within the welded portion of the wire segment, thereby ensuring insulation in the welded portion without insulating coating of the wire segment. In addition, in the concave region of the resin part that can be easily released from the mold, as described above, cracks are likely to occur starting from the minute irregularities on the surface, but since the conductor segments contained in that region are covered with an insulating coating, the insulation of the coil is not impaired, and it is also advantageous in that if a crack occurs in the concave region of the resin part, it is possible to release the strain stress acting on the entire resin part. The surface roughness of the convex part of the mold (the part that abuts on the concave region of the resin part) and the surface smoothness of the concave part of the mold (the part that abuts on the convex region of the resin part) may be determined experimentally. That is, the smoothness of the surface of the concave part of the mold is set to a degree that cracks do not occur in the convex region of the resin part during use of the electric machine, and the surface roughness of the convex part of the mold is set to a degree that cracks occur in the concave region of the resin part during use of the electric machine. Effect of the Invention

[0011] Thus, according to the configuration of the present invention, in the resin portion formed at the axial end face where the welded portions of the stator wire segments are aligned, the surface is smoother in the convex region, making the resin less likely to crack and ensuring insulation, thereby avoiding a ground fault failure mode (discharge between the stator and the case). On the other hand, the concave region can be more easily released from the mold and is more susceptible to cracking, allowing the distortion stress generated in the stator to be released. Thus, according to the present invention, it is possible to achieve both ease of molding the resin portion and a safe design for the product.

[0012] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief description of the drawings]

[0013] [Figure 1] Fig. 1(A) is a schematic perspective view of a stator to which this embodiment is applied, and Fig. 1(B) is a schematic view of a coil formed by sequentially connecting both ends of a circularly curved conductor segment to the ends of another conductor segment. [Diagram 2] Fig. 2(A) is a schematic enlarged perspective view of a resin portion formed on a stator end face by the method of the present embodiment, and Fig. 2(B) is a schematic cross-sectional view along the circumferential direction of the stator of the resin portion formed on the stator end face by the method of the present embodiment. [Diagram 3] 3A to 3C are schematic diagrams showing the steps of forming a resin portion on a stator end surface by the method of the present embodiment, and Fig. 3D and Fig. 3E are schematic plan and enlarged cross-sectional views, respectively, of a mold used in the steps of forming the resin portion by the method of the present embodiment. [Explanation of symbols]

[0014] 1 ... stator, 10 ... stator axial end surface, 11 ... resin part, 11 (L) ... liquid resin, 12 convex ... convex area of ​​resin part, 12 concave ... concave area of ​​resin part, 13 ... wire segment, 15, 16 ... end of wire segment, 20 ... welded part, 21 ... bare wire part, 30 ... mold, 31 convex ... convex area of ​​mold, 31 concave ... concave area of ​​mold, BEST MODE FOR CARRYING OUT THEINVENTION

[0015] The present invention will now be described in detail with reference to some preferred embodiments thereof with reference to the accompanying drawings, in which like reference numerals indicate like parts.

[0016] Overview of coils wound around stator teeth In the stator of a rotating electric machine manufactured by applying the method of this embodiment, as in the case of Patent Document 1, as shown in Fig. 1(A), the coil wound around a plurality of teeth (stator teeth) protruding inward in the radial direction of an annular stator core 1 is a coil formed by sequentially connecting a plurality of conductor segments made of a conductive material in a spiral shape. More specifically, as shown in Fig. 1(B), the coil according to this embodiment is arranged such that a plurality of annularly curved conductor segments 13 are aligned so as to surround a stator tooth (not shown), and both ends 15, 16 of the conductor segment 13 are sequentially connected by welding to ends 16, 15 of another conductor segment 13 adjacent to each other side, to form a single coil wound around the stator tooth (note that the winding of the coil around the stator tooth may be in any manner (concentrated winding, distributed winding, etc.)). Therefore, the welded portions 20 of the conductor segments 13 are aligned along the extending direction of the stator teeth on one end face in the axial direction Ax of the stator, as shown in FIG. 1(B).

[0017] Conductor segment 13 is formed by appropriately bending or curving a wire made of a conductive material such as copper or aluminum into a ring shape, and its surface, except for the tip portion, is covered with an insulating coating. The cross section of the conductor segment may be, for example, a rectangle of 3 mm x 2 mm or 3 mm x 4 mm, and the length is, for example, 100 to 150 mm, but is not limited thereto.

[0018] Formation of resin part on the stator end face As described above, in the configuration in which the coil surrounding the stator teeth is connected by welding the ends of multiple conductor segments in sequence, the insulating coating is removed from the welded portion 20 of the conductor segment and its vicinity, exposing the conductor. Therefore, in order to ensure insulation at the welded portion 20 and its vicinity, the axial end face 10 of the stator, where the welded portions of the conductor segments are lined up, is covered with a resin portion 11 (see Figure 1(A)) as already mentioned.

[0019] In the process of forming the resin portion 11 covering the axial end surface 10 of the stator, first, as shown in FIG. 3(A), an annular mold 30 having a container portion with a shape complementary to the shape of the resin portion 11 is placed with its opening facing up, and the axial end surface 10 of the stator 1 on the side where the welded portions 20 are aligned is placed downward, and the portion of the wire segment 13 protruding from the stator end surface 10 is placed in the container portion of the mold 30, and liquid resin 11(L) is poured therein, as shown in FIG. 3(B). The liquid resin may be, for example, a one-part thermosetting epoxy. After that, when the resin is cured in the state shown in FIG. 3(B), the stator 1 is lifted by a release pin or the like, and the mold 30 is released from the resin portion 11 formed on the axial end surface 10 (FIG. 3(C)).

[0020] In the process of forming the resin portion 11 on the stator end face 10, in order to save the amount of resin used, the resin portion 11 is formed so that the area including the welded portion 20 of the conductor segment end and its vicinity 21 is formed in a convex shape (12 convex), and the other area is formed in a concave shape (12 concave), as shown in Fig. 2(A). Therefore, in order to model the shape of the resin portion 11, the annular mold 30 is formed with a concave portion 31 (concave) and a convex portion 31 (convex) so that the shape is complementary to the concave-convex shape of the resin portion 11, as can be seen from Figs. 3(D) and (E).

[0021] As mentioned in the section of the invention, generally, when a resin formed in a mold that has hardened from a liquid state to a solid state is released from the mold, the rougher the inner surface of the mold, the lower the release force, and the resin part that has hardened in the mold can be easily removed from the mold, facilitating the molding process. However, if the inner surface of the mold is rough, minute irregularities are formed on the surface of the resin part molded there, and cracks will occur starting from the minute irregularities due to stress concentration. If such cracks reach the welded parts of the ends of the conductor segments where the conductor is exposed, the insulation of the welded parts will be impaired.

[0022] In this embodiment, in order to make the molding process of the resin portion as easy as possible while ensuring the insulation of the welded portion and its vicinity, the mold 30 is formed so that the surface of the concave portion 31 (concave) is smoother (area marked with F in FIG. 3(E)), while the surface of the convex portion 31 (convex) is rougher (area marked with R in FIG. 3(E)). As a result, the surface of the convex region 12 (convex) of the resin portion 11 is smoother (area marked with F in FIG. 2(B)), with almost no minute irregularities formed, cracks are less likely to occur, and the insulation of the welded portion 20 and its vicinity 21 is more assured. Meanwhile, the concave portion 12 (concave) of the resin portion 11 can be easily released from the mold (area marked with R in FIG. 2(B)). Thus, according to this embodiment, it is possible to make it easier to mold the resin portion having an uneven shape to a certain extent, while ensuring the insulation of the welded portion of the wire segment end.

[0023] In addition, in the recess of region 12 of resin portion 11 formed in this embodiment, minute unevenness is formed, and as shown in Fig. 2(B), cracks C are likely to occur, but even if cracks C occur in this region, the conductor portion forming the coil directly below the cracks will not break down because it is covered with an insulating coating. In addition, the occurrence of cracks C in the recess of region 12 is advantageous in that the distortion stress occurring in resin portion 11 is alleviated, improving the mechanical stability of the stator.

[0024] The smoothness of the concave surface of the concave portion 31 of the mold 30 may be experimentally determined to a degree that prevents cracks from occurring in the convex area of ​​the resin portion during use of the electric appliance, and the roughness of the convex surface of the convex portion 31 of the mold may be experimentally determined to a degree that causes cracks to occur in the concave area of ​​the resin portion during use of the electric appliance.

[0025] The above description has been given in relation to the embodiment of the present invention, but it will be apparent to those skilled in the art that many modifications and changes can be easily made thereto, and that the present invention is not limited to the embodiment exemplified above, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A method for manufacturing a stator for a rotating electric machine, comprising: a stator core having a coil wound around a stator tooth protruding radially inward from the stator core; the coil being formed by connecting a plurality of annular conductor segments in a single line; both ends of the plurality of conductor segments are welded to ends of adjacent other conductor segments on one axial end face of the stator; and the welded portions of the ends of the plurality of conductor segments are aligned along the stator tooth, forming a resin portion on the axial end surface of the stator, the resin portion being shaped in a convex shape in a region covering the welded portion of the wire segment end and being shaped in a concave shape in a region not including the welded portion; In the step of forming the resin portion, placing the axial end face in a mold having a shape complementary to a shape of the resin portion; injecting a liquid resin into the mold so as to cover the entire axial end surface, and hardening the resin; releasing the hardened resin portion on the axial end surface from the mold after the resin is hardened; Including, The mold may have a convex surface facing the non-welded area that is rougher than a concave surface facing the area covering the weld of the wire segment end.

Images