Stator and electric motor having the same

Abstract

The stator (1) of the electric motor has a cylindrical stator core (3). On the inner circumferential surface of the stator core (3), first core teeth (5) and second core teeth (6) are alternately arranged along the circumferential direction. The cross-sectional shape of the second core tooth (6) perpendicular to the central axis of the stator core (3) is different from the cross-sectional shape of the first core tooth (5). A coil (9) is mounted on the first core tooth (5). A coil (9) is mounted on one of the first core tooth (5) and the second core tooth (6). At the boundary between the front end portion of the second core tooth (6) and the rear portion of the front end portion, the width of the second core tooth (6) is narrowed in a step-like or curved manner.

Description

Technical Field

[0001] The invention relates to a stator and an electric motor having the stator. Background Art

[0002] In an electric motor such as a motor or a generator, a stator is provided to generate a rotating magnetic field to rotate a rotor. Figure 8 As shown, the stator 101 has a substantially cylindrical stator core 103. On the inner circumferential surface of the stator core 103, rectangular core teeth 105 are arranged in the circumferential direction. The coil 109 is inserted into the slot 107 between adjacent core teeth 105 and is mounted on the core teeth 105.

[0003] When current flows through the coil 109, the coil 109 generates heat due to its resistance, and the temperature of the coil 109 rises. If the temperature of the coil 109 rises excessively, problems such as the coil film being damaged, short circuiting, and heating may occur. Therefore, the coil 109 needs to be cooled. The cooling of the coil 109 is partially performed by dissipating heat to the stator core 103 through the core teeth 105.

[0004] like Figure 8 As shown, in a structure in which core teeth 105 are evenly arranged and have a rectangular cross-sectional shape perpendicular to the central axis of the stator core 103, the coil 109 is in contact with the core teeth 105 on its inner side, so the heat dissipation is high, but on the outer side of the coil 109, a gap is generated between the core teeth 105, so the heat dissipation is reduced.

[0005] like Fig. 9 As shown, there is also a structure in which core teeth 105 with a rectangular cross-section and core teeth 106 with a trapezoidal cross-section are alternately arranged along the circumferential direction on the inner circumferential surface of the stator core 103. In this structure, both sides of the coil 109 are in contact with the core teeth 105, so high heat dissipation can be ensured.

[0006] From the perspective of heat dissipation, Figure 8 Compared with the uniform arrangement structure of the rectangular core teeth 105 shown, Fig. 9 The alternating arrangement of the rectangular core teeth 105 and the trapezoidal core teeth 106 shown is advantageous. Fig.10 As shown in FIG. 1 , since the distance between the permanent magnet 121 of the rotor 120 and the side of the trapezoidal core tooth 106 is closer than the distance between the permanent magnet 121 and the side of the rectangular core tooth 105, the magnetic attraction F2 received by the trapezoidal core tooth 106 from the permanent magnet 121 of the rotor 120 is stronger than the magnetic attraction F1 received by the rectangular core tooth 105 from the permanent magnet 121 of the rotor 120. Therefore, as Fig.11As shown, compared with the uniform arrangement structure of the rectangular core teeth 105, the alternating arrangement structure of the rectangular core teeth 105 and the trapezoidal core teeth 106 has the opposite property of increasing the cogging torque.

[0007] In the stator of the electric motor, there is a trade-off between the coil heat dissipation performance and the cogging torque.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Unexamined Patent Application Publication (PCT Application Translation) No. 2009-5288811 Summary of the invention

[0011] A stator for a motor is desired that can ensure heat dissipation of a coil and suppress an increase in cogging torque.

[0012] The stator of an electric motor of one embodiment of the present disclosure has a cylindrical stator core. On the inner circumferential surface of the stator core, first core teeth are arranged along the circumferential direction. On the inner circumferential surface of the stator core, second core teeth are arranged alternately with the first core teeth along the circumferential direction. The cross-sectional shape of the second core tooth perpendicular to the central axis of the stator core is different from the cross-sectional shape of the first core tooth. A coil is installed on the first core tooth or the second core tooth. At the boundary between the front end portion of the second core tooth and the rear portion of the front end portion, the width of the second core tooth is narrowed in a step or curved manner, the front end portion of the second core tooth has the same shape and the same size as the front end portion of the first core tooth, one side of the coil can contact the side of the first core tooth in the entire area, and the other side of the coil can contact the side of the second core tooth in the rear portion of the front end portion.

[0013] According to this method, the coil can be brought into contact with the side surface of the first core tooth, and although the front end portion of the second core tooth and the coil are not brought into contact due to a gap, the coil can be brought into contact with the second core tooth at the rear portion of the front end portion. Thus, the heat dissipation of the coil can be improved compared to a case where a gap is formed between the coil and the second core tooth over almost the entire area.

[0014] In addition, the width of the front end of the first core tooth is the same as the width of the front end of the second core tooth, and the shape of the front end portion of the second core tooth is the same as the shape of the front end portion of the first core tooth, so that the magnetic attraction between the second core tooth and the magnet of the rotor can be made similar to the magnetic attraction between the first core tooth and the magnet of the rotor. As a result, the increase in the cogging torque can be suppressed.

[0015] Furthermore, instead of simply forming the front end portions of the first core tooth and the second core tooth into the same shape, the front end portion of the second core tooth is formed into the same shape as the front end portion of the first core tooth by digging out the side surface of the front end portion of the second core tooth, thereby making the front end portion of the second core tooth thinner, thereby improving the insertion operability of the coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a perspective view of a part of a stator of a motor according to an embodiment.

[0017] Figure 2 yes Figure 1 A cross-sectional view of a portion of an electric motor.

[0018] Figure 3 yes Figure 1 An enlarged cross-sectional view of a rectangular core tooth and a trapezoidal core tooth.

[0019] Figure 4 This is a supplementary diagram for explaining the heat dissipation of the coil of the stator according to the present embodiment.

[0020] Figure 5 It is shown Figure 1 A diagram of the magnetic attraction that the trapezoidal core teeth and the rectangular core teeth receive from the permanent magnets of the rotor.

[0021] Figure 6 This is a diagram showing the cogging torque of the stator according to the present embodiment.

[0022] Figure 7 is shown for coverage Figure 1 Figure 4. A diagram of a cover with trapezoidal core teeth.

[0023] Figure 8 This is a supplementary diagram for explaining the heat dissipation of a coil in a conventional uniformly arranged structure of rectangular core teeth.

[0024] Fig. 9 This is a supplementary diagram for explaining the heat dissipation of a coil in a conventional structure in which rectangular core teeth and trapezoidal core teeth are alternately arranged.

[0025] Fig.10 It is shown Fig. 9 A diagram of the magnetic attraction between the trapezoidal core teeth and the rectangular core teeth and the permanent magnets of the rotor.

[0026] Fig.11 It is shown Fig. 9 , Fig.10 Graph of the cogging torque of the respective stators. DETAILED DESCRIPTION

[0027] Hereinafter, a stator according to the present embodiment and a motor having the stator will be described with reference to the drawings.

[0028] like Figure 1 , Figure 2 , Figure 3 As shown, the stator 1 and the rotor 2 having permanent magnets 21 constitute a motor. The stator 1 has a substantially cylindrical stator core 3, inside which the rotor 2 is accommodated. The rotor 2 has: a substantially cylindrical core 20 with a rotating shaft passing through the center; and permanent magnets 21 arranged at equal intervals along the circumferential direction of the core 20.

[0029] On the inner circumferential surface of the stator core 3, a plurality of types of core teeth having different cross-sectional shapes perpendicular to the center axis R are protruding toward the center axis R of the stator core 3, and are two types of first core teeth 5 and second core teeth 6. The first core teeth 5 and the second core teeth 6 are alternately arranged along the circumferential direction of the stator core 3. The first core teeth 5 and the second core teeth 6 are radially arranged with the center axis R of the stator core 3 as the center in such a manner that their respective center lines C1 and C2 coincide with the radius of the cylinder. The coil 9 is inserted into the gap (slot) 7 between the first core teeth 5 and the second core teeth 6, and is mounted on the first core teeth 5. The coil 9 can also be mounted on the second core teeth 6.

[0030] The first core teeth 5 have the same shape and size, and the second core teeth 6 have the same shape and size. The second core teeth 6 are shaped differently from the first core teeth 5. Typically, the cross-sectional shape of the first core teeth 5 perpendicular to the central axis R of the stator core 3 is a rectangle. The width W1 of the front end of the first core tooth 5 facing the rotor 2 is constant toward the radially outer direction (depth direction).

[0031] On the other hand, the second core tooth 6 has a substantially trapezoidal cross-sectional shape, so that the side surface of the second core tooth 6 is parallel to the side surface of the first core tooth 5 adjacent thereto, and the groove 7 therebetween is made into a parallel groove. Although it is formed into a trapezoidal shape in which the width W2 of its upper base is configured to be the same as the width W1 of the front end of the first core tooth 5, and the width of the trapezoid continuously narrows from its lower base toward the front end, the width has a step difference in the middle and narrows to a width W2, and the width W2 continues to the front end. The portion from the position where the width narrows with a step difference to the front end is referred to as the front end portion 8. In other words, in the second core tooth 6, the width W2 of the front end is continued within the range of the specified depth length, and the front end portion 8 of the second core tooth 6 is made to have the same shape and the same size as the front end portion of the first core tooth 5, so that the two side surfaces of the second core tooth 6 are hollowed into a narrow concave shape. Furthermore, although the boundary between the front end portion 8 of the second core tooth 6 and the rear portion of the front end portion 8 has a step and narrows to the width W2, it may be formed to have a curved surface and gradually narrow to the width W2.

[0032] On the first core tooth 5, a rectangular coil is installed as the coil 9. When installed on the second core tooth 6, the coil 9 is set as a trapezoidal coil. Here, the former example is explained. In either case, one side of the coil 9 is in contact with the side of the first core tooth 5 in the entire area, and on the other hand, the other side of the coil 9 is in contact with the side of the second core tooth 6 in the rear part of the front end part 8. In addition, in fact, there is insulating paper between the coil 9 and the first core tooth 5 and the second core tooth 6.

[0033] like Figure 4 As shown in FIG. 1 , a gap is formed between the front end portion 8 which is hollowed out into a concave shape and the coil 9, and the coil 9 is not in contact with the coil 9. However, in the portion on the radially outer side (inner side) relative to the front end portion 8, the coil 9 is in contact with the side surface of the second core tooth 6. Therefore, as shown in FIG. Figure 8 The coil 9 shown in the figure has improved heat dissipation performance compared to a structure in which the coil 9 has a gap with the side surface of the second core tooth 6 over the entire region and does not contact the side surface of the second core tooth 6 .

[0034] The cross-sectional shape of the first core tooth 5 is a rectangle, so its two side surfaces are parallel to the cylinder radius like the center line C1. Similarly, for the second core tooth 6, only the front end portion 8 is parallel to the cylinder radius. Moreover, the widths of the two core teeth are also equal. Figure 5 As shown in FIG. 1 , when focusing on a certain position on the side surface near the front end of the first core tooth 5, the shortest distance D1 between the focus position and the permanent magnet 21 when the rotor 2 is in a certain phase is the same as the shortest distance D2 between the same position on the side surface near the front end of the second core tooth 6 and the permanent magnet 21. This distance D2 is the same as the distance D2 between the two side surfaces of the front end portion 8 of the second core tooth 6 when the front end portion 8 is not concave. Fig. 9 Therefore, the distance between the focus position on the side surface near the front end of the first core tooth 5 and the permanent magnet 21 changes with the phase shift of the rotor 2, but in contrast, the change in the distance between the corresponding position on the side surface near the front end of the second core tooth 6 and the permanent magnet 21 is almost equal.

[0035] Since the magnetic attraction is inversely proportional to the square of the distance, the magnetic attraction F3 received by the second core tooth 6 from the permanent magnet 21 is greater than the magnetic attraction F1 received by the first core tooth 5 from the permanent magnet 21, but smaller than Fig. 9 In the case of the structure, the magnetic attraction force F2 is small.

[0036] therefore, Figure 6 The toothing torque of the structure in which the rectangular first core teeth 5 and the trapezoidal second core teeth 6 (which are hollowed out so that the cross section of the front end portion is rectangular) are alternately arranged is similar to that of the embodiment shown in FIG. Figure 8The cogging torque of the rectangular core teeth evenly arranged structure shown in the figure is increased compared to that of the Fig. 9 The rectangular core teeth shown can suppress the toothing torque compared to the alternate arrangement structure of trapezoidal core teeth whose front end portions are not hollowed out.

[0037] In addition, by extending the front end portion 8 of the second core tooth 6, the increase in the cogging torque can be more effectively suppressed, and the cogging torque of the structure in which the rectangular core teeth are evenly arranged can be approximated. However, on the contrary, the range of contact between the coil 9 and the side of the front end portion 8 of the second core tooth 6 becomes narrower, and the heat dissipation will be reduced. The length L of the concave front end portion 8 of the second core tooth 6 can be determined in consideration of the balance between the cogging torque and the heat dissipation.

[0038] The toothing torque can be suppressed even when the front end portion 8 of the second core tooth 6 is not hollowed out into a concave shape, but the front end portion of the first core tooth 5 is expanded into a trapezoidal shape in a widened manner so that the front end shapes of the two core teeth are configured to be the same shape and the same size. However, in the present embodiment, the front end portion 8 of the second core tooth 6 is hollowed out into a concave shape and configured to be the same shape and the same size as the front end portion of the first core tooth 5, thereby improving the efficiency of the insertion operation of the coil 9.

[0039] like Figure 7 As shown, the front end portion 8 of the second core tooth 6 can also be covered with a cover 11 to prevent the coil 9 from falling off. As the material of the cover 11, a non-magnetic resin can be used so as not to affect the tooth torque. More specifically, an epoxy resin with improved thermal conductivity by adding fillers such as Al2O3, AlN, BN, BeO, an elastic EVA resin or other resins can be used. If it is the former, the heat dissipation can be improved. In addition, if it is the latter, the coil 9 can be effectively prevented from falling off. The cover 11 can be pre-formed into a short cylinder with a prism-shaped shape to fill the gap between the concave front end portion 8 of the second core tooth 6 and the coil 9. After covering the second core tooth 6, the coil 9 can be inserted. Alternatively, after the coil 9 is inserted into the first core tooth 5, it can be injected into the gap between the concave front end portion 8 of the second core tooth 6 and the coil 9 and cured.

[0040] Although certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. In fact, the new methods and systems described herein may be embodied in various other forms, and in addition, various omissions, substitutions, and changes may be made to the forms of the methods and systems described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover forms or modifications that fall within the scope and spirit of the invention.

Claims

1. A stator, characterized in that: have: The cylindrical stator core The first core teeth are arranged along the circumferential direction on the inner circumferential surface of the stator core. The second core teeth are arranged alternately with the first core teeth along the circumferential direction on the inner circumferential surface of the stator core, and the cross-sectional shape of the second core teeth perpendicular to the central axis of the stator core is different from the cross-sectional shape of the first core teeth, and A coil, mounted on the first core tooth or the second core tooth; The width of the second core tooth is narrowed in a stepped or curved manner at a boundary between a front end portion and a portion behind the front end portion. The front end portion of the second core tooth has the same shape and the same size as the front end portion of the first core tooth, One side surface of the coil contacts the side surface of the first core tooth over the entire area, and the other side surface of the coil contacts the side surface of the second core tooth at a portion behind the front end portion.

2. The stator according to claim 1, characterized in that: The first core tooth has a rectangular cross-sectional shape, and the second core tooth has a trapezoidal cross-sectional shape.

3. The stator according to claim 2, characterized in that: The tip portion of the second core tooth has the same width as the tip portion of the first core tooth, and has a shape such that the width continues for a predetermined depth.

4. The stator according to claim 1, characterized in that: The second core tooth has the cross-sectional shape such that a groove between the first core tooth and the second core tooth becomes a parallel groove.

5. The stator according to any one of claims 1 to 4, characterized in that The front end portion of the second core tooth is covered by a cover, and the cover is a non-magnetic body.

6. The stator according to claim 5, characterized in that: The cover is an epoxy resin with a filler of a specific material added to improve thermal conductivity.

7. The stator according to claim 5, characterized in that: The cover is elastic.

8. An electric motor having the stator according to any one of claims 1 to 7.

9. A stator, characterized in that: have: The cylindrical stator core A plurality of types of core teeth are arranged along the circumferential direction on the inner circumferential surface of the stator core, and have different cross-sectional shapes perpendicular to the central axis of the stator core, and A coil mounted on the core teeth; The multiple types of core teeth include specific types of core teeth and other types of core teeth, wherein, at the boundary between the front end portion of the other type of core teeth and the portion behind the front end portion, the width of the other type of core teeth is narrowed in a step or curved manner, so that the front end portion of the other type of core teeth has the same shape and the same size as the shape of the front end portion of the specific type of core teeth.

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