Stator

Abstract

The present invention provides a resin-molded stator capable of suppressing the generation of voids due to residual air and casting defects without increasing magnetic resistance. This stator comprises: a stator core having a cylindrical core back, a first core tooth, and a second core tooth, the first and second core teeth being alternately arranged along a circumferential direction on an inner peripheral surface of the core back; and a coil provided on either the first core tooth or the second core tooth. The cross-sectional shape of the first core tooth is rectangular, and the cross-sectional shape of the second core tooth is trapezoidal. The first and second core teeth including the coil are molded by resin molding. A hole through which molding resin can flow is formed inside a triangular region formed between two imaginary lines extending from the circumferential center at the tip of the second core tooth toward the outer circumference of the core back, parallel to the two oblique sides of the second core tooth. At least part of the periphery of the hole is located on the second core tooth side inside the triangular region.

Description

Stator

[0001] The present disclosure relates to a stator.

[0002] Conventionally, a stator has been known in which the core teeth including the coil are entirely resin-molded for the purpose of improving the heat dissipation of the stator and fixing the coil. It is also known to form holes in a yoke (core back) on the outer periphery of the stator core and resin-mold the resin so that the resin fills the holes, thereby suppressing deformation of the stator core (see, for example, Patent Document 1).

[0003] Another known stator has core teeth with rectangular and trapezoidal cross sections perpendicular to the central axis of the stator core arranged alternately in the circumferential direction on the inner peripheral surface of a cylindrical core back. Coils are attached to the rectangular core teeth. This reduces the gap between the coils and the core teeth, improving the heat dissipation of the stator (see, for example, Patent Document 2).

[0004] JP 2015-159648 A JP 2020-184820 A

[0005] When resin-molding a stator with rectangular and trapezoidal core teeth arranged alternately in the circumferential direction, the gaps between the coils and core teeth are narrower than when using a stator core with only typical rectangular core teeth. This makes it difficult for resin to penetrate the gaps, and for air in the resin to escape through the gaps. As a result, not only does the resin injection time increase, but the resin is not easily distributed throughout the stator, which can lead to molding defects and voids due to residual air.

[0006] However, forming holes in the core back of the stator core as described in Patent Document 1 to allow the molding resin to spread throughout the stator and to allow air to escape from the resin may increase magnetic saturation in the stator, resulting in increased magnetic resistance. If a portion of the stator has high magnetic resistance locally, this may limit the characteristics of the rotating electric machine formed by that stator, potentially resulting in a deterioration in the characteristics of the rotating electric machine.

[0007] An object of the present disclosure is to provide a resin-molded stator that can suppress the occurrence of voids due to casting defects and residual air without increasing magnetic resistance.

[0008] The present disclosure relates to a stator comprising: a cylindrical core back; first core teeth arranged circumferentially on the inner peripheral surface of the core back; and second core teeth arranged alternately with the first core teeth circumferentially on the inner peripheral surface of the core back; and a coil provided on one of the first core teeth or the second core teeth, wherein the first core teeth have a rectangular cross-sectional shape when viewed in the direction of the central axis of the stator core, and the second core teeth have a trapezoidal cross-sectional shape when viewed in the direction of the central axis of the stator core, and the first core teeth and the second core teeth including the coil are molded with a molded resin, and a hole into which the molded resin can flow is formed inside a triangular region formed between two imaginary lines extending from a circumferential center of an inner end of at least one of the second core teeth toward the outer periphery of the core back and parallel to two hypotenuses of the second core tooth, and at least a part of the outer periphery of the hole is positioned on the side of the second core tooth inside the triangular region.

[0009] 1 is a perspective view showing a portion of a stator of an electric motor according to an embodiment; FIG. 2 is a plan view showing a portion of a stator core in the stator shown in FIG. 1; FIG. 3 is an enlarged plan view showing first core teeth and second core teeth in the stator core shown in FIG. 2; FIG. 4 is a plan view showing another embodiment of holes provided in the second core teeth; FIG. 5 is a plan view showing another embodiment of holes provided in the second core teeth; FIG. 6 is a plan view showing another embodiment of holes provided in the second core teeth; FIG. 7 is a plan view showing another embodiment of holes provided in the second core teeth; FIG. 8 is a diagram explaining a method of resin-molding the stator shown in FIG. 1; FIG. 9 is a cross-sectional view of the resin-molded stator shown in FIG. 1; FIG. 10 is a diagram showing magnetic analysis results of a stator according to a reference example in which no holes are provided in the core teeth; FIG. 11 is a diagram showing magnetic analysis results of a stator according to a first example in which holes with circular cross sections are provided in the core teeth; FIG. 12 is a diagram showing magnetic analysis results of a stator according to a comparative example in which holes with circular cross sections are provided in the core teeth; FIG. 13 is a diagram showing magnetic analysis results of a stator according to a second example in which holes with square cross sections are provided in the core teeth. 1 is a graph showing the results of magnetic analysis of a stator according to a third embodiment in which a hole with a square cross section is provided in the core tooth; FIG. 2 is a graph showing the relationship between the torque ratio and the ratio (b / a) of the holed portion to the width of the tip of the core tooth; and FIG. 3 is a diagram explaining the ratio (b / a) of the holed portion to the width of the tip of the core tooth.

[0010] An embodiment of the present disclosure will be described in detail below with reference to the drawings. In Fig. 1, a stator 100 is, for example, a stator for a rotating electric machine. The rotating electric machine is configured with the stator 100 and a rotor 8 rotatably disposed inside the stator 100. The stator 100 has a stator core 1 and coils 6.

[0011] Here, the X direction indicated by the double-headed arrow in the drawing indicates the circumferential direction of the stator 100 and the stator core 1. The Y direction indicated by the double-headed arrow indicates the radial direction of the stator 100 and the stator core 1. The Y1 direction is the radially outer side of the stator 100 and the stator core 1, and the Y2 direction is the radially inner side of the stator 100 and the stator core 1. Z indicates the central axis direction of the stator 100 and the stator core 1.

[0012] The stator core 1 is formed by concentrically stacking a plurality of thin, annular electromagnetic steel sheets. The stator core 1 has a cylindrical core back 2 located on the outermost side, and first core teeth 3 and second core teeth 4 provided on an inner peripheral surface 2b of the core back 2 and protruding radially inward in the radial direction Y2. A plurality of the first core teeth 3 and a plurality of the second core teeth 4 are provided on the stator core 1. As shown in FIGS. 2 and 3 , the first core teeth 3 and the second core teeth 4 have different cross-sectional shapes. These cross-sectional shapes are shapes indicated by a cross section perpendicular to the central axis of the stator core 1.

[0013] When viewed in the central axis direction Z of the stator core 1, the cross-sectional shape of each first core tooth 3 (the shape of a cross section cut along a plane perpendicular to the central axis) is rectangular. More specifically, the cross-sectional shape of each first core tooth 3 has a tip 3a facing the radially inner side Y2 of the stator core 1, and two sides 3b, 3b extending in parallel from both ends of the tip 3a in the circumferential direction X toward the inner circumferential surface 2b of the core back 2. As a result, each first core tooth 3 is formed with the same width along the radial direction Y of the stator core 1. All of the multiple first core teeth 3 provided on the stator core 1 have the same shape and dimensions.

[0014] When viewed in the central axis direction Z of the stator core 1, the cross-sectional shape of each second core tooth 4 (the shape of a cross section cut along a plane perpendicular to the central axis) is trapezoidal. More specifically, the cross-sectional shape of each second core tooth 4 has a tip 4a facing the radially inner side Y2 of the stator core 1 and two oblique sides 4b, 4b extending obliquely in the circumferential direction X from both ends of the tip 4a in the circumferential direction X toward the inner circumferential surface 2b of the core back 2. As a result, the second core tooth 4 is formed so that its width continuously narrows from the radially outer side Y1 to the radially inner side Y2 of the stator core 1. All of the multiple second core teeth 4 provided on the stator core 1 have the same shape and dimensions.

[0015] The width of the tip 3 a of the first core tooth 3 and the width of the tip 4 a of the second core tooth 4 along the circumferential direction X of the stator core 1 are the same. The two sides 3 b, 3 b of the first core tooth 3 and the two oblique sides 4 b, 4 b of the second core tooth 4 are arranged parallel to each other.

[0016] The first core teeth 3 and the second core teeth 4 are arranged alternately along the circumferential direction X of the stator core 1. Slots 5 are formed between the first core teeth 3 and the second core teeth 4. The slots 5 are open to the radially inner side Y2 of the stator core 1 and to both end faces 1a, 1a of the stator core 1 in the central axis direction.

[0017] As shown in FIG. 1 , the coil 6 is wound in an annular shape and inserted into the slot 5. The coil 6 is inserted into two slots 5, 5 arranged on both sides of the first core tooth 3 in the circumferential direction X from the radially inner side Y2 of the stator core 1 toward the radially outer side Y1. This allows the coil 6 to be attached to the first core tooth 3. Because two sides 3 b, 3 b in the cross-sectional shape of the first core tooth 3 and two oblique sides 4 b, 4 b in the cross-sectional shape of the second core tooth 4 are parallel, the coil 6 is in close contact with almost the entire side surface of the first core tooth 3 and almost the entire side surface of the second core tooth 4 within the slot 5. This facilitates heat transfer from the coil 6 to the stator core 1, resulting in high heat dissipation. The space factor of the coil 6 within the slot 5 is improved, thereby improving the torque of the stator 100. Insulating paper (not shown) is provided between the coil 6 and the first and second core teeth 3 and 4. However, the coil 6 may be assembled to the second core teeth 4 instead of the first core teeth 3 .

[0018] As shown in FIGS. 1 to 3 , holes 7 are provided in the stator core 1, into which molding resin is filled. The holes 7 are circular holes with a circular cross section. The holes 7 penetrate from one end face 1 a of the stator core 1 to the other end face 1 a. The holes 7 are provided to correspond to each of the second core teeth 4 out of the first core teeth 3 and second core teeth 4 provided in the stator core 1. No holes are provided in the areas corresponding to the first core teeth 3. Because the inner circumferential surface of the circular cross section hole 7 is a curved surface, the molding resin flows smoothly into the hole 7, and air in the resin also easily escapes.

[0019] 3 shows two imaginary lines L1, L1 extending radially from a central portion P in the circumferential direction X of the tip 4a of the cross-sectional shape of the second core tooth 4 toward the outer periphery 2a of the core back 2. The imaginary lines L1, L1 are straight lines extending parallel to two oblique sides 4b, 4b of the cross-sectional shape of the second core tooth 4. A triangular region R is formed between the two imaginary lines L1, L1 from the second core tooth 4 to the core back 2. The hole 7 is formed inside the triangular region R.

[0020] FIG. 3 also shows a single imaginary line L2 extending in the circumferential direction X along the inner circumferential surface 2b of the core back 2. The imaginary line L2 is a curved line that follows the boundaries between the core back 2 and the first and second core teeth 3 and 4. The imaginary line L2 crosses the triangular region R formed by the imaginary lines L1, L1 in the circumferential direction X. This divides the triangular region R into a leading end region R1 that is a triangle located radially inward Y2 from the imaginary line L2, and a trailing end region R2 that is a rectangle (trapezoid) located radially outward Y1 from the imaginary line L2. The leading end region R1 is located at the second core tooth 4, and the trailing end region R2 is located at the core back 2. Note that because the imaginary line L2 is a curved line, the triangular region R is not a strict triangle in a geometric sense, but is an approximately triangular shape.

[0021] The hole 7 is located at least in the tip region R1 inside the triangular region R. More specifically, as shown in FIG. 3 , the entire outer periphery 7a of the hole 7 is located inside the tip region R1, and is not located in the rear region R2. Therefore, in the cross-sectional shape of the second core tooth 4, as shown in FIG. 17 , the width a in the circumferential direction X from the center P of the tip 4a to one of the hypotenuses 4b and the width b in the circumferential direction X from the outer periphery 7a of the hole 7 to one of the hypotenuses 4b satisfy the relationship a≦b. Therefore, even if the hole 7 is formed in the second core tooth 4, a width in the circumferential direction X of the second core tooth 4 that is equal to or greater than the width of the tip 4a remains. The outer periphery 7a of the hole 7 shown in FIG. 3 is tangent to two imaginary lines L1, L1 and one imaginary line L2, and the relationship a=b holds.

[0022] Because the tips 3 a of the first core teeth 3 and the tips 4 a of the second core teeth 4 have the same width, even if the holes 7 are formed inside the tip regions R1 of the second core teeth 4, there is almost no difference in width in the circumferential direction X between the first core teeth 3 and the remaining portions of the second core teeth 4 after the holes 7 are formed. This prevents the magnetic resistance of the stator 100 from increasing locally. Furthermore, in the stator 100 in which the rectangular first core teeth 3 and the trapezoidal second core teeth 4 are alternately arranged along the circumferential direction X, the magnetic resistance of each core tooth is made uniform, thereby reducing torque ripple (torque pulsation due to rotor phase).

[0023] 4, the hole 7 may be disposed on the tip 4a side of the second core tooth 4, away from the core back 2. That is, the outer periphery 7a of the hole 7 is in contact with the imaginary lines L1, L1 in the radial direction but is not in contact with the imaginary line L2 in the circumferential direction. In this case, the diameter of the hole 7 is smaller than the diameter of the hole 7 shown in FIG.

[0024] The hole 7 is not limited to a circular hole with a circular cross section. For example, as shown in FIG. 5 , the hole 7 may have a trapezoidal cross section. Three of the four sides constituting the outer periphery 7a of the hole 7 shown in FIG. 5 are in contact with the radial imaginary lines L1, L1 and the circumferential imaginary line L2. The hole 7 is not disposed in the core back 2. The hole 7 shown in FIG. 5 is a trapezoid that is elongated along the radial direction Y of the stator core 1. The tip 7b of the hole 7 is closer to the tip 4a of the second core tooth 4 than the imaginary line L2. Since the hole 7 can be formed as large as possible in the second core tooth 4 without increasing magnetic resistance, the molding resin flows smoothly and air in the resin can easily escape. Note that because the imaginary line L2 is a curve, the trapezoidal hole 7 is not a strict trapezoid in a geometric sense, but is an approximate trapezoid.

[0025] As shown in Fig. 6, the hole 7 having a trapezoidal cross section may be a short trapezoid along the radial direction Y of the stator core 1. In this case, the tip 7b of the hole 7 is closer to the imaginary line L2 than the tip 4a of the second core tooth 4. The opening area of ​​the hole 7 is smaller than that of the hole 7 shown in Fig. 5, but the increase in magnetic resistance is further suppressed.

[0026] As shown in Fig. 7 , the hole 7 may have an elliptical or elongated cross section. The hole 7 having an elliptical or elongated cross section is short in the circumferential direction X of the stator core 1 and long in the radial direction Y. The outer periphery 7a of the hole 7 shown in Fig. 7 is in contact with imaginary radial lines L1, L1 and an imaginary circumferential line L2. The hole 7 is not disposed in the core back 2. Because the inner circumferential surface of the hole 7 having an elliptical or elongated cross section is curved, the molding resin flows smoothly into the hole 7 and air in the resin easily escapes, just as in the case of a circular hole.

[0027] It is most desirable that the hole 7 be disposed inside the tip region R1 of the triangular region R, but it is sufficient if at least a part of the outer periphery 7 a of the hole 7 is disposed in the tip region R1 on the second core tooth 4 side inside the triangular region R. That is, for example, in the case of a stator core 1 in which the width of the core back 2 along the radial direction Y is sufficiently wide and the magnetic resistance of the core back 2 is small, as shown in Fig. 8 , a part of the outer periphery 7 a of the hole 7 may be disposed radially outward Y1, beyond the circumferential imaginary line L2, in the rear end region R2 on the core back 2 side. Even in this case, most of the hole 7 is disposed inside the tip region R1 of the triangular region R, so that a local increase in the magnetic resistance of the stator core 1 is suppressed.

[0028] As shown in FIG. 9 , the stator 100 with the holes 7 formed in the second core teeth 4 and the coils 6 assembled thereto is mounted on a mold resin casting jig 200. The jig 200 is positioned so as to cover the inner circumferential side and the underside of the stator 100. A cylindrical jacket 9 is positioned on the outer circumferential side of the stator 100. The mold resin 300 is a thermosetting resin such as epoxy resin, and is injected between the jig 200 and the jacket 9. The injected mold resin 300 covers the entire first core teeth 3 and second core teeth 4 of the stator core 1, including the coils 6, and also flows into the holes 7 formed in the second core teeth 4. The mold resin 300 flows down the holes 7 and reaches the underside of the stator 100. Therefore, even if there are no gaps in the slots 5 through which the mold resin 300 can pass, the mold resin 300 can be spread throughout the entire stator 100, reducing the likelihood of molding defects. The air in the molding resin 300 rises through the hole 7 and is released from between the jig 200 and the jacket 9 .

[0029] The molding resin 300 covering the stator 100 is hardened by heating, thereby obtaining the stator 100 covered with the hardened resin 301, as shown in Fig. 10. The residual air in the molding resin 300 rises and is released through the holes 7, thereby suppressing the generation of voids in the hardened resin 301.

[0030] Next, the effects of the stator of the present disclosure will be described with reference to Figures 11 to 16. Figures 11 to 15 are contour plots of magnetic flux density showing the results of magnetic analysis of the stator core. In Figures 11 to 15, parts with the same reference numerals as those of stator 100 shown in Figures 1 to 8 indicate parts with the same configuration.

[0031] First, Fig. 11 shows a stator 100A (reference example) formed by a stator core 1A in which no holes are formed in the core teeth. The stator core 1A has rectangular first core teeth 3 and trapezoidal second core teeth 4 arranged alternately along the circumferential direction X. A rotor 8 is rotatably arranged on the inner periphery of the stator 100A. The rotor 8 has a cylindrical rotor core 81 and multiple permanent magnets 82 arranged along the circumferential direction X. This stator 100A does not have any areas where magnetic resistance increases locally even when the rotor 8 is rotated.

[0032] Fig. 12 shows a stator 100 (Example 1) configured with a stator core 1 in which a hole 7 similar to that shown in Fig. 3 is formed in the second core tooth 4. In this hole 7, the relationship (b / a) between width a and width b shown in Fig. 17 is 100%. In this stator 100, the torque ratio when the torque of stator 100A shown in Fig. 11, which has no hole formed, is taken as 100%, is 99% as shown in Fig. 17, and no areas where magnetic resistance increases locally were observed even when rotor 8 was rotated.

[0033] Figure 13 shows a stator 100B (Comparative Example 1) constructed using a stator core 1B in which a circular hole 70 is formed in the second core tooth 4. The hole 70 is large enough to extend beyond the imaginary line L2 in the circumferential direction but not beyond the imaginary lines L1 and L2 in the radial direction. For this hole 70, the relationship between width a and width b (b / a) shown in Figure 17 is 65%. For this stator 100B, the torque ratio is 90%, as shown in Figure 17, when the torque of the stator 100A shown in Figure 11, which does not have a hole, is taken as 100%, indicating a clear decrease in torque. When the rotor 8 is rotated, a region S where magnetic resistance increases locally is observed.

[0034] Fig. 14 shows a stator 100 (Example 2) configured with a stator core 1 in which a hole 7 similar to that shown in Fig. 6 is formed in the second core tooth 4. In this hole 7, the relationship (b / a) between width a and width b shown in Fig. 17 is 100%. In this stator 100, the torque ratio when the torque of stator 100A shown in Fig. 11, which has no hole formed, is taken as 100%, is 99% as shown in Fig. 17, and no areas where magnetic resistance increases locally were observed even when rotor 8 was rotated.

[0035] Fig. 15 shows a stator 100 (Example 3) configured with a stator core 1 in which a hole 7 similar to that shown in Fig. 5 is formed in the second core tooth 4. In this hole 7, the relationship (b / a) between width a and width b shown in Fig. 17 is 100%. In this stator 100, the torque ratio when the torque of stator 100A shown in Fig. 11, which has no hole formed, is taken as 100%, is 99% as shown in Fig. 17, and no areas where magnetic resistance increases locally were observed even when rotor 8 was rotated.

[0036] In the above embodiment, the hole 7 is formed so as to penetrate the stator core 1 in the central axis direction Z, but the hole 7 may also be one that does not penetrate the stator core 1 in the central axis direction Z (a hole with a bottom).

[0037] The following supplementary notes are further disclosed regarding the above-described embodiment and modified examples. (Supplementary Note 1) A stator core (1) includes a cylindrical core back (2), first core teeth (3) arranged along a circumferential direction (X) on an inner peripheral surface (2b) of the core back (2), and second core teeth (4) arranged alternately with the first core teeth (3) along the circumferential direction (X) on the inner peripheral surface (2b) of the core back (2), and a coil (6) provided on one of the first core teeth (3) and the second core teeth (4), wherein the cross-sectional shape of the first core teeth (3) perpendicular to the central axis of the stator core (1) is rectangular, and the cross-sectional shape of the second core teeth (4) perpendicular to the central axis of the stator core (1) is trapezoidal, and the coil (6) is The stator (100) has a first core tooth (3) and a second core tooth (4) including the first core tooth (3) and the second core tooth (4) molded with a molded resin (300), and a hole (7) into which the molded resin (300) can flow is formed inside a triangular region (R) formed by two imaginary lines (L1) extending from a central portion (P) in the circumferential direction (X) at the tip (4a) of the second core tooth (4) toward the outer periphery (2a) of the core back (2) and parallel to two oblique sides (4b) of the second core tooth (4), and at least a part of the outer periphery (7a) of the hole (7) is arranged on the second core tooth (4) side inside the triangular region (R).

[0038] (Supplementary Note 2) In the stator (100) of Supplementary Note 1, the entire hole (7) is arranged on the second core tooth (4) side inside the triangular region (R).

[0039] (Supplementary Note 3) In the stator (100) of Supplementary Note 1 or 2, the hole (7) penetrates the stator core (1).

[0040] (Supplementary Note 4) In the stator (100) of any one of Supplementary Notes 1 to 3, the hole (7) has a circular cross section.

[0041] (Supplementary Note 5) In the stator (100) of any one of Supplementary Notes 1 to 3, the hole (7) has a trapezoidal cross section.

[0042] (Supplementary Note 6) In the stator (100) of any one of Supplementary Notes 1 to 3, the hole (7) has an elliptical cross section or an oblong cross section.

[0043] REFERENCE SIGNS LIST 1 stator core 2 core back 2a outer periphery of core back 3 first core tooth 4 second core tooth 4a tip of second core tooth 4b oblique side 6 coil 7 hole 7a outer periphery of hole 100 stator 300 molded resin L1, L2 imaginary lines P circumferential center R triangular area

Claims

1. A stator comprising: a cylindrical core back; first core teeth arranged along the circumferential direction on the inner peripheral surface of the core back; second core teeth arranged alternately with the first core teeth along the circumferential direction on the inner peripheral surface of the core back; and a coil provided on one of the first core teeth and the second core teeth. When viewed in the central axis direction of the stator core, the cross-sectional shape of the first core teeth is rectangular, and when viewed in the central axis direction of the stator core, the cross-sectional shape of the second core teeth is trapezoidal. The stator in which the first core teeth and the second core teeth including the coil are molded by a molding resin, and a hole into which the molding resin can flow is formed inside a triangular region formed between two virtual lines extending from the central portion in the circumferential direction at the tip of the second core teeth toward the outer periphery of the core back and parallel to the two hypotenuses of the second core teeth. At least a part of the outer periphery of the hole is disposed on the second core teeth side inside the triangular region.

2. The stator according to claim 1, wherein the whole of the hole is disposed on the second core teeth side inside the triangular region.

3. The stator according to claim 1 or 2, wherein the hole penetrates the stator core in the central axis direction.

4. The stator according to any one of claims 1 to 3, wherein the hole is circular in cross-sectional view.

5. The stator according to any one of claims 1 to 3, wherein the hole is trapezoidal in cross-sectional view.

6. The stator according to any one of claims 1 to 3, wherein the hole is elliptical in cross-sectional view or slot-shaped in cross-sectional view.

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