Stator

Abstract

Provided is a resin-molded stator capable of suppressing the occurrence of injection molding defects and voids caused by residual air without increasing magnetic resistance. The stator includes: a stator core having a cylindrical core back, and first core teeth and second core teeth alternately arranged in a circumferential direction on an inner circumferential surface of the core back; and a coil provided on one of the first core tooth and the second core tooth, the first core tooth having a rectangular cross-sectional shape and the second core tooth having a trapezoidal cross-sectional shape, the first core tooth and the second core tooth including the coil being molded by a molding resin, a hole into which the molded resin can flow is formed on the inside of a triangular region formed between two imaginary lines extending from the center of the tip of the second core tooth in the circumferential direction toward the outer periphery of the core back and parallel to the two bevel edges of the second core tooth. At least a portion of the outer periphery of the hole is disposed on the second core tooth side inside the triangular region.

Description

Technical Field

[0001] This disclosure relates to the stator. Background Technology

[0002] Previously, stators were known to be formed by resin molding the entire core teeth containing the coil, with the aim of improving the heat dissipation of the stator and fixing the coil. It is also known to form holes in the magnetic yoke (back of the core) on the outer periphery of the stator core, so that resin can enter the holes for resin molding, thereby suppressing the deformation of the stator core (for example, see Patent Document 1).

[0003] Furthermore, a stator is known in which rectangular and trapezoidal cross-section teeth are alternately arranged circumferentially on the inner circumferential surface of the back of a cylindrical iron core. The coil is mounted on the rectangular core teeth. This reduces the gap between the coil and the core teeth, thus improving the heat dissipation of the stator (see, for example, Patent Document 2).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-159648

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-184820 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] When resin molding a stator with alternating rectangular and trapezoidal core teeth arranged circumferentially, the gap between the coil and the core teeth is narrower compared to using a typical stator core with only rectangular core teeth. Therefore, resin has difficulty entering the gap, and air in the resin has difficulty escaping. As a result, not only does the resin injection time increase, but the resin also fails to distribute throughout the entire stator, potentially leading to poor injection molding and voids caused by residual air.

[0010] However, if holes are formed on the back of the stator core as described in Patent Document 1 in order to ensure that the molding resin is distributed throughout the stator and to expel air from the resin, it may increase the magnetic saturation of the stator and thus increase the magnetic reluctance. If a region with high magnetic reluctance is locally generated in the stator, it will become a bottleneck in the characteristics of the rotating machine constructed from that stator, and may lead to a decrease in the characteristics of the rotating machine.

[0011] The purpose of this disclosure is to provide a resin-molded stator that can suppress poor injection molding and voids caused by residual air without increasing magnetic resistance.

[0012] Solution for solving the problem

[0013] This disclosure relates to a stator comprising: a stator core having a cylindrical core back, first core teeth arranged circumferentially on the inner circumferential surface of the core back, and second core teeth arranged circumferentially alternately with the first core teeth on the inner circumferential surface of the core back; and a coil disposed on one of the first core teeth and the second core teeth. When viewed along the central axis of the stator core, the first core tooth has a rectangular cross-sectional shape, and when viewed along the central axis of the stator core, the second core tooth has a trapezoidal cross-sectional shape. The first core tooth and the second core tooth, including the coil, are molded from molding resin. A hole through which the molding resin can flow is formed on the inner side of a triangular region formed between two imaginary lines. The two imaginary lines extend from the circumferential center of the inner end of at least one second core tooth toward the outer periphery of the core back and are parallel to the two hypotenuses of the second core tooth. At least a portion of the outer periphery of the hole is disposed on the inner side of the triangular region near the second core tooth. Attached Figure Description

[0014] Figure 1 This is a perspective view showing a portion of the stator of an electric motor according to one embodiment.

[0015] Figure 2 It means Figure 1 A top view of a portion of the stator core in the stator shown.

[0016] Figure 3 It is an enlarged representation Figure 2 The top view of the first and second core teeth in the stator core shown.

[0017] Figure 4 This is a top view showing another embodiment of the hole provided in the second core tooth.

[0018] Figure 5 This is a top view showing another embodiment of the hole provided in the second core tooth.

[0019] Figure 6 This is a top view showing another embodiment of the hole provided in the second core tooth.

[0020] Figure 7 This is a top view showing another embodiment of the hole provided in the second core tooth.

[0021] Figure 8 This is a top view showing another embodiment of the hole provided in the second core tooth.

[0022] Figure 9 This is to explain the... Figure 1A diagram showing the method of resin molding the stator.

[0023] Figure 10 It is after resin molding Figure 1 The stator is shown in cross-sectional view.

[0024] Figure 11 This is a diagram showing the magnetic analysis results of a reference example stator without holes in the core teeth.

[0025] Figure 12 This is a diagram showing the magnetic analysis results of the stator in the first embodiment, where the core teeth have holes with circular cross-sections.

[0026] Figure 13 This is a graph showing the magnetic analysis results of a stator in a comparative example where the core teeth have holes with circular cross-sections.

[0027] Figure 14 This is a diagram showing the magnetic analysis results of the stator in the second embodiment, where the core teeth have holes with quadrilateral cross-sections.

[0028] Figure 15 This is a diagram showing the magnetic analysis results of the stator in the third embodiment, where the core teeth have holes with quadrilateral cross-sections.

[0029] Figure 16 It is a graph showing the relationship between the width ratio (b / a) of the opening location and the front end of the core tooth and the torque ratio.

[0030] Figure 17 This is a diagram illustrating the width ratio (b / a) between the opening location and the front end of the core tooth. Detailed Implementation

[0031] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Figure 1 In this context, the stator 100 is, for example, the stator of a rotary electric machine. The rotary electric machine consists of a stator 100 and a rotor 8 rotatably disposed inside the stator 100. The stator 100 has a stator core 1 and coils 6.

[0032] Here, the X direction indicated by the two arrows in the figure represents the circumferential direction of the stator 100 and stator core 1. The Y direction indicated by the two arrows represents the radial direction of the stator 100 and stator core 1. The Y1 direction is the radially outer side of the stator 100 and stator core 1, and the Y2 direction is the radially inner side of the stator 100 and stator core 1. Z represents the direction of the central axis of the stator 100 and stator core 1.

[0033] The stator core 1 is formed by concentrically stacking multiple thin, ring-shaped electromagnetic steel plates. The stator core 1 has a cylindrical core back 2 located on the outermost periphery, first core teeth 3 and second core teeth 4 located on the inner periphery surface 2b of the core back 2 and projecting radially inward towards the inner Y2. Multiple first core teeth 3 and second core teeth 4 are respectively provided on the stator core 1. Figure 2 as well as Figure 3 As shown, the first core tooth 3 and the second core tooth 4 have different cross-sectional shapes. This cross-sectional shape is the shape shown in the cross-section perpendicular to the central axis of the stator core 1.

[0034] Viewed along the central axis Z of the stator core 1, the cross-sectional shape of the first core tooth 3 (the shape of the cross-section cut by a plane perpendicular to the central axis) is rectangular. Specifically, the cross-sectional shape of the first core tooth 3 has a front end 3a facing the radially inner side Y2 of the stator core 1 and two sides 3b, 3b extending parallel to the inner circumferential surface 2b of the back surface 2 of the core from both ends of the front end 3a in the circumferential direction X. Thus, the first core tooth 3 is formed with the same width along the radial Y direction of the stator core 1. All of the multiple first core teeth 3 provided on the stator core 1 are of the same shape and size.

[0035] Viewed along the central axis Z of the stator core 1, the cross-sectional shape of the second core tooth 4 (the shape of the cross-section cut by a plane perpendicular to the central axis) is trapezoidal. Specifically, the cross-sectional shape of the second core tooth 4 has a front end 4a facing the radially inner side Y2 of the stator core 1, and two inclined sides 4b, 4b extending obliquely from both ends of the front end 4a toward the inner circumferential surface 2b of the back surface 2 of the core 1 in a manner expanding in the circumferential direction X. Thus, the second core tooth 4 is formed such that its width continuously narrows from the radially outer side Y1 of the stator core 1 toward the radially inner side Y2. All of the plurality of second core teeth 4 provided on the stator core 1 are of the same shape and size.

[0036] The width of the front end 3a of the first core tooth 3 along the circumferential direction X of the stator core 1 is the same as the width of the front end 4a of the second core tooth 4. The two sides 3b, 3b of the first core tooth 3 are arranged parallel to the two inclined sides 4b, 4b of the second core tooth 4.

[0037] The first core tooth 3 and the second core tooth 4 are alternately arranged along the circumferential direction X of the stator core 1. A groove 5 is formed between the first core tooth 3 and the second core tooth 4. The groove 5 is open on the radial inner side Y2 of the stator core 1 and on the two end faces 1a, 1a in the direction of the central axis of the stator core 1.

[0038] like Figure 1As shown, the coil 6 is wound into a ring shape and inserted into the slot 5. The coil 6 is inserted from the radially inner side Y2 of the stator core 1 toward the radially outer side Y1 into the two slots 5, 5 located on both sides of the circumferential X of the first core tooth 3. Thus, the coil 6 is assembled to the first core tooth 3. Since the two sides 3b, 3b of the cross-sectional shape of the first core tooth 3 are parallel to the two inclined sides 4b, 4b of the cross-sectional shape of the second core tooth 4, the coil 6 is in close contact with the side of the first core tooth 3 and the side of the second core tooth 4 in the slot 5, covering approximately the entire area of ​​the side of the first core tooth 3 and the second core tooth 4. Therefore, the heat of the coil 6 is easily transferred to the stator core 1, resulting in high heat dissipation. The duty cycle of the coil 6 in the slot 5 is increased, thus increasing the torque of the stator 100. An insulating paper (not shown) is provided between the coil 6 and the first core tooth 3 and the second core tooth 4. However, the coil 6 can also be assembled in the second core tooth 4 instead of the first core tooth 3.

[0039] like Figures 1-3 As shown, the stator core 1 has holes 7 for filling with molding resin. Holes 7 are circular holes with a circular cross-section. Holes 7 extend from one end face 1a of the stator core 1 to the other end face 1a. Holes 7 are correspondingly provided with the second core teeth 4 in the first core tooth 3 and the second core tooth 4 of the stator core 1. No holes are provided at the locations corresponding to the first core tooth 3. Because the inner circumferential surface of the circular hole 7 is curved, the flow of molding resin into the hole 7 becomes smooth, and air in the resin is easily expelled.

[0040] exist Figure 3 The diagram shows two imaginary lines L1, L1 extending radially from the central portion P of the circumferential direction X of the front end 4a of the cross-sectional shape of the second core tooth 4 toward the outer periphery 2a of the back core 2. The imaginary lines L1, L1 are straight lines extending parallel to the two hypotenuses 4b, 4b in the cross-sectional shape of the second core tooth 4. Between the two imaginary lines L1, L1, a triangular region R is formed from the second core tooth 4 to the back core 2. A hole 7 is formed inside the triangular region R.

[0041] exist Figure 3 The diagram also shows an imaginary line L2 extending circumferentially along the inner circumferential surface 2b of the back of the core 2 in the circumferential direction X. The imaginary line L2 is formed by a curve along the boundary between the back of the core 2 and the first core tooth 3 and the second core tooth 4. The imaginary line L2 traverses the triangular region R formed by the imaginary lines L1 in the circumferential direction X. Thus, the triangular region R is divided into a front region R1, composed of triangles, which is radially inward (Y2) from the imaginary line L2, and a rear region R2, composed of quadrilaterals (trapezoidal shapes), which is radially outward (Y1) from the imaginary line L2. The front region R1 is located at the second core tooth 4, and the rear region R2 is located at the back of the core 2. Furthermore, since the imaginary line L2 is a curve, the triangular region R is not a strictly geometric triangle, but rather an approximate triangular shape.

[0042] Hole 7 is disposed at least in the front end region R1, inside the triangular region R. Specifically, as... Figure 3 As shown, the outer periphery 7a of the hole 7 is arranged around the entire circumference of the inner side of the front end region R1, but not in the rear end region R2. Therefore, in the cross-sectional shape of the second core tooth 4, as... Figure 17 As shown, the width a of the circumferential X from the central portion P of the front end 4a to the inclined side 4b has a relationship of a≤b with respect to the width b of the circumferential X from the outer periphery 7a of the hole 7 to the inclined side 4b. Therefore, even when the second core tooth 4 forms the hole 7, the second core tooth 4 retains a width greater than the width of the front end 4a along the circumferential X. Figure 3 The outer periphery 7a of the hole 7 shown is tangent to two imaginary lines L1, L2 and one imaginary line L2 respectively, and has a=b relationship.

[0043] Since the front end 3a of the first core tooth 3 and the front end 4a of the second core tooth 4 have the same width, even if the hole 7 is formed inside the front end region R1 of the second core tooth 4, there is almost no difference in the circumferential width X of the remaining portion after the hole 7 is formed in the first core tooth 3 and the second core tooth 4. Therefore, the local increase in the magnetic reluctance of the stator 100 can be suppressed. In addition, in the stator 100 where the rectangular first core tooth 3 and the trapezoidal second core tooth 4 are arranged alternately along the circumferential X, the magnetic reluctance of each core tooth is uniform, and thus the torque fluctuation (torque fluctuation caused by rotor phase) is also reduced.

[0044] like Figure 4 As shown, hole 7 can also be separated from the back of the iron core 2 and positioned on the front end 4a side of the second core tooth 4. That is, the outer periphery 7a of hole 7 is tangent to the radial imaginary lines L1, L2, but not to the circumferential imaginary line L2. In this case, the diameter of hole 7 is... Figure 3 The diameter of hole 7 shown is small.

[0045] Hole 7 is not limited to a circular hole with a circular cross-section. For example, as shown... Figure 5 As shown, hole 7 can also be a trapezoidal cross-section. (Construction) Figure 5 Three of the four sides of the outer periphery 7a of the hole 7 shown are tangent to the radial imaginary lines L1, L2 and the circumferential imaginary line L2. The hole 7 is not located on the back of the core 2. Figure 5 The hole 7 shown is a trapezoid with a longer radial length Y along the stator core 1. The front end 7b of the hole 7 is closer to the front end 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 flow of molding resin becomes smooth, and air in the resin is easily expelled. Furthermore, since the imaginary line L2 is a curve, the trapezoidal hole 7 is not a geometrically strict trapezoid, but rather an approximate trapezoid.

[0046] like Figure 6As shown, the trapezoidal hole 7 can also be a trapezoid with a shorter radial Y along the stator core 1. In this case, the front end 7b of the hole 7 is closer to the imaginary line L2 than the front end 4a of the second core tooth 4. The opening area of ​​the hole 7 is greater than... Figure 5 The hole 7 shown is small, but the increase in magnetic resistance is further suppressed.

[0047] like Figure 7 As shown, hole 7 can also be elliptical in cross-section or elongated in cross-section. Hole 7 with elliptical or elongated cross-section is shorter in the circumferential direction X of the stator core 1 and longer in the radial direction Y. Figure 7 The outer periphery 7a of the hole 7 shown is tangent to the radial imaginary lines L1, L2 and the circumferential imaginary line L2. The hole 7 is not located on the back of the core 2. Since the inner circumferential surface of the hole 7, which has an elliptical or elongated cross-section, is curved, the flow of molding resin into the hole 7 becomes smooth, similar to the case of a circular hole with a circular cross-section, and air in the resin is easily expelled.

[0048] The hole 7 is preferably disposed inside the front end region R1 of the triangular region R, but at least a portion of the outer periphery 7a of the hole 7 may be disposed inside the front end region R1 of the second core tooth 4 on the inner side of the triangular region R. That is, for example, in the case of a stator core 1 with a sufficiently wide radial Y width of the back 2 of the core and low magnetic reluctance in the back 2 of the core, such as Figure 8 As shown, a portion of the outer periphery 7a of the hole 7 can also be positioned radially outward Y1 beyond the imaginary circumferential line L2 in the rear end region R2 on the back side 2 of the stator core. In this case, since most of the hole 7 is positioned inside the front end region R1 in the triangular region R, the local increase in magnetic reluctance of the stator core 1 can also be suppressed.

[0049] Thus, a hole 7 is formed in the second core tooth 4, and a stator 100 with coil 6 is assembled thereon. Figure 9 The jig 200 shown is installed for injection molding of molding resin. The jig 200 is configured to block the inner circumferential side and the lower surface side of the stator 100. A cylindrical sheath 9 is disposed on the outer circumferential side of the stator 100. The molding resin 300 is a thermosetting resin such as epoxy resin, which is injected between the jig 200 and the sheath 9. The injected molding resin 300 covers the entire first core tooth 3 and the second core tooth 4 of the stator core 1 including the coil 6, and also flows into the hole 7 formed in the second core tooth 4. The molding resin 300 flows down in the hole 7 and also spreads to the lower surface side of the stator 100, so that even if there is no gap in the groove 5 for the molding resin 300 to pass through, the molding resin 300 can spread to the entire stator 100, thereby reducing the likelihood of injection molding defects. Air in the molding resin 300 rises in the hole 7 and is released from between the jig 200 and the sheath 9.

[0050] The molding resin 300 covering the stator 100 is cured by heating. Thus, as... Figure 10 As shown, a stator 100 covered by cured resin 301 is obtained. Residual air in the molding resin 300 rises and is released in the holes 7, thus suppressing the formation of voids in the cured resin 301.

[0051] Next, refer to Figures 11-16 The effects of the stator disclosed herein will be explained. Figures 11-15 This is a contour map showing the magnetic flux density as a result of magnetic analysis of the stator core. Figures 11-15 In the middle, the annotation and Figures 1-8 The parts of the stator 100 shown with the same reference numerals indicate parts of the same structure.

[0052] first, Figure 11 A stator 100A (reference example) is shown, formed from a stator core 1A without holes formed in the core teeth. In the stator core 1A, rectangular first core teeth 3 and trapezoidal second core teeth 4 are alternately arranged along the circumferential direction X. A rotor 8 is rotatably arranged on the inner circumference of the stator 100A. The rotor 8 has a plurality of permanent magnets 82 arranged along the circumferential direction X in a cylindrical rotor core 81. In this stator 100A, even when the rotor 8 is rotated, no local increase in magnetic reluctance is visible.

[0053] Figure 12 This indicates that a tooth 4 is formed on the second core tooth 4 with a tooth 4. Figure 3 A stator 100 (Example 1) is constructed from a stator core 1 with the same hole 7. In this hole 7, Figure 17 The relationship between width a and width b (b / a) shown is 100%. In this stator 100, Figure 11 The torque of the stator 100A without holes shown is set to 100%, for example... Figure 17 As shown, 99% of the data indicates that even when rotor 8 is rotated, no local increase in magnetic reluctance was found.

[0054] Figure 13 The stator 100B (Comparative Example 1) is composed of a stator core 1B. This stator core 1B has a hole 70 formed on its second core tooth 4, consisting of a circular hole of a size extending radially from imaginary lines L1 and L2, not from the circumferential direction of the imaginary line L2. In this hole 70, Figure 17 The relationship between width a and width b (b / a) shown is 65%. In this stator 100B, Figure 11 The torque of the stator 100A without holes shown is set to 100%, for example... Figure 17 As shown, 90% is observed, indicating a significant reduction in torque. When rotor 8 is rotated, a localized increase in magnetic reluctance was found at point S.

[0055] Figure 14This indicates that a tooth 4 is formed on the second core tooth 4 with a tooth 4. Figure 6 A stator 100 (Example 2) is constructed from a stator core 1 with the same hole 7. In this hole 7, Figure 17 The relationship between width a and width b (b / a) shown is 100%. In this stator 100, Figure 11 The torque of the stator 100A without holes shown is set to 100%, for example... Figure 17 As shown, 99% of the data indicates that even when rotor 8 is rotated, no local increase in magnetic reluctance was found.

[0056] Figure 15 This indicates that a tooth 4 is formed on the second core tooth 4 with a tooth 4. Figure 5 A stator 100 (Example 3) is constructed from a stator core 1 with the same hole 7. In this hole 7, Figure 17 The relationship between width a and width b (b / a) shown is 100%. In this stator 100, Figure 11 The torque of the stator 100A without holes shown is set to 100%, for example... Figure 17 As shown, 99% of the data indicates that even when rotor 8 is rotated, no local increase in magnetic reluctance was found.

[0057] In the above embodiments, the hole 7 is formed to penetrate the stator core 1 along the central axis direction Z, but the hole 7 can also be a hole that does not penetrate the stator core 1 along the central axis direction Z (a hole with a bottom).

[0058] The following notes are also disclosed regarding the above-described embodiments and variations.

[0059] (Note 1)

[0060] A stator (100) comprises: a stator core (1) having a cylindrical core back (2), first core teeth (3) arranged circumferentially (X) on the inner circumferential surface (2b) of the core back (2), and second core teeth (4) arranged alternately with the first core teeth (3) on the inner circumferential surface (2b) of the core back (2) along the circumferential direction (X); and a coil (6) disposed on one of the first core teeth (3) and the second core teeth (4), wherein the cross-sectional shape of the first core tooth (3) perpendicular to the central axis of the stator core (1) is rectangular, and the cross-sectional shape of the second core tooth (4) perpendicular to the central axis of the stator core (1) is rectangular. The trapezoidal shape, including the first core tooth (3) and the second core tooth (4) of the coil 6, is molded from molding resin (300). A hole (7) is formed on the inner side of the triangular region (R) formed by two imaginary lines (L1) through which the molding resin (300) can flow. The two imaginary lines (L1) extend from the center (P) of the circumferential (X) of the front end (4a) of the second core tooth (4) toward the outer periphery (2a) of the back of the iron core (2) and are parallel to the two hypotenuses (4b) of the second core tooth (4). At least a portion of the outer periphery (7a) of the hole (7) is located on the inner side of the triangular region (R) near the second core tooth (4).

[0061] (Note 2)

[0062] In the stator (100) of Appendix 1, the hole (7) is positioned on the inside of the triangular region (R) near the second core tooth (4).

[0063] (Note 3)

[0064] In the stator (100) of Appendix 1 or 2, the hole (7) passes through the stator core (1).

[0065] (Note 4)

[0066] In any of the stator (100) in notes 1 to 3, the cross-section of the hole (7) is circular.

[0067] (Note 5)

[0068] In any of the stator (100) in notes 1 to 3, the cross-section of the hole (7) is trapezoidal.

[0069] (Note 6)

[0070] In any of the stator (100) in notes 1 to 3, the hole (7) is elliptical in cross section or elongated in cross section.

[0071] Explanation of reference numerals in the attached figures

[0072] 1: Stator core; 2: Back of core; 2a: Outer periphery of the back of core; 3: First core tooth; 4: Second core tooth; 4a: Front end of the second core tooth; 4b: Hydrate; 6: Coil; 7: Hole; 7a: Outer periphery of the hole; 100: Stator; 300: Molded resin; L1, L2: Imaginary lines; P: Central part of the circumference; R: Triangular area.

Claims

1. A stator having: A stator core having a cylindrical core back, first core teeth arranged circumferentially on the inner circumferential surface of the core back, and second core teeth arranged circumferentially alternately with the first core teeth on the inner circumferential surface of the core back; and A coil, which is disposed on one of the first core tooth and the second core tooth. When viewed along the central axis of the stator core, the cross-sectional shape of the first core tooth is rectangular. When viewed along the central axis of the stator core, the cross-sectional shape of the second core tooth is trapezoidal. The first core tooth and the second core tooth, which include the coil, are molded from molding resin. In the stator, An inlet is formed on the inner side of the triangular region formed between the two imaginary lines, allowing the molding resin to flow in. The two imaginary lines extend from the circumferential center of the front end of the second core tooth toward the outer periphery of the back of the iron core and are parallel to the two hypotenuses of the second core tooth. At least a portion of the outer periphery of the hole is disposed on the inner side of the triangular region, near the second core tooth side.

2. The stator according to claim 1, wherein, The hole is positioned on the inner side of the triangular region, near the second core tooth.

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

4. The stator according to any one of claims 1 to 3, wherein, The hole is circular when viewed in section.

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

6. The stator according to any one of claims 1 to 3, wherein, The hole is elliptical or elongated in cross-section.

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