Rotor core, rotor, and motor
By tilting the magnet slots on the rotor core and setting holes of a specific shape, the problems of magnetic flux flow obstruction and weight increase are solved, achieving lightweighting and inertia reduction, and improving the torque and high-speed performance of the motor.
Patent Information
- Application Number
- CN202380099490.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-28
- Publication Date
- 2026-02-13
AI Technical Summary
In existing technologies, the magnetic flux flow in the rotor core is impeded, resulting in reduced torque, while it is difficult to achieve lightweighting and reduced inertia.
Multiple pairs of magnet slots are formed on the rotor core along the axial direction. The magnet slots are arranged at an angle and holes of a specific shape are set in between, including a first hole and a second hole, to enhance magnetic flux flow and reduce weight.
This achieves lightweighting and reduced inertia of the rotor core without reducing torque, thereby improving the controllability and high-speed capability of the motor.
Smart Images
Figure CN121532929A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a rotor core, a rotor, and a motor. BACKGROUND
[0002] Pairs of magnet grooves configured in a V shape are formed in an end surface of a rotor core of a motor, and a magnet is inserted in each of the magnet grooves. Further, for the purpose of weight reduction of the rotor core and the purpose of reducing inertia, a hole is formed in the rotor core (for example, refer to Japanese Patent No. 6987310). However, when a hole is formed inside each pair of magnet grooves configured in a V shape, the flow of magnetic flux is hindered, and the torque is reduced.
[0003] PRIOR ART DOCUMENTS
[0004] PATENT DOCUMENTS
[0005] Japanese Patent No. 6987310 SUMMARY
[0006] PROBLEMS TO BE SOLVED BY THE INVENTION
[0007] In order to increase the torque, it is considered to extend the V-shaped top end portion of each pair of magnet grooves to the inside in the radial direction of the rotor core. However, in this case, the area of the rotor core in which a hole can be formed is reduced. As a result, it is difficult to reduce the weight, and it is also difficult to reduce the inertia. In addition, in this case, even if the rotor is inserted into the inner cylinder of the yoke, it is difficult to sufficiently magnetize a portion of the magnet located inside in the radial direction, which becomes a cause of reduction in torque.
[0008] Therefore, it is desirable to have a light-weight rotor core, a rotor, and a motor that can reduce the inertia without reducing the torque and sufficiently magnetize.
[0009] SOLUTION TO PROBLEM
[0010] According to a first technical solution of the present disclosure, there is provided a rotor core in which a plurality of pairs of magnet grooves extending along an axial direction of the rotor core are formed in the rotor core, the plurality of pairs of magnet grooves are arranged equidistantly along a circumferential direction of the rotor core in a radial cross section of the rotor core, each pair of magnet grooves of the plurality of pairs of magnet grooves includes a first magnet groove that is inclined counterclockwise with respect to a radius of the rotor core and a second magnet groove that is inclined clockwise with respect to the radius of the rotor core, in the each pair of magnet grooves, one end of the first magnet groove and one end of the second magnet groove are separated from each other, and the other end of the first magnet groove and the other end of the second magnet groove are adjacent to each other at a position that is located more radially inward than the one end of the first magnet groove and the one end of the second magnet groove, and a first hole is formed adjacent to the each pair of magnet grooves, the first hole includes a first portion that corresponds to at least a portion of a region between the other end of the first magnet groove and the other end of the second magnet groove, and a second portion that is continuous with the first portion and is located more radially inward than the first portion.
[0011] The objects, features, and advantages of the present disclosure will become more apparent from the following description of embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0012] Figure 1 is an axial cross-sectional view of a motor provided with a rotor core based on the present disclosure.
[0013] Figure 2 is a radial cross-sectional view of a rotor core based on the first embodiment.
[0014] Figure 3 is Figure 2 is a partial cross-sectional view of the rotor core shown in
[0015] Figure 4 is a partial cross-sectional view of a portion of Figure 3 enlarged.
[0016] Figure 5 is a radial cross-sectional view of the same rotor core as Figure 2 .
[0017] Figure 6 is another partial cross-sectional view of the rotor core shown in Figure 2 .
[0018] Figure 7 is a partial cross-sectional view of a portion of Figure 6 enlarged.
[0019] Figure 8A is a partial cross-sectional view showing magnetic flux in a motor in the related art.
[0020] Figure 8B This is a graph showing the relationship between time and torque in electric motors in the prior art.
[0021] Figure 9A This is a partial cross-sectional view showing the magnetic flux of the electric motor based on the first embodiment.
[0022] Figure 9B This is a graph showing the relationship between time and torque of the electric motor based on the first embodiment.
[0023] Figure 10A This is a partial cross-sectional view showing the magnetic susceptibility of an electric motor in the prior art.
[0024] Figure 10B This is a partial cross-sectional view showing the magnetic susceptibility of the electric motor based on the first embodiment. Detailed Implementation
[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the drawings, corresponding constituent elements are labeled with common reference numerals. Figure 1 This is a cross-sectional view along the axial direction of an electric motor having a rotor core based on this disclosure. For example... Figure 1 As shown, the electric motor 1 includes a stator 9 and a rotor 10 rotatably supported on the stator 9. A first bearing 7 and a second bearing 8 are arranged on the inner circumferential surface of the stator 9. Furthermore, a shaft 5 passing through the rotor 9 is rotatably supported on the stator 9 by the first bearing 7 and the second bearing 8. In addition, a detector 6 for detecting the rotational speed of the shaft 5 is installed at one end of the stator 9.
[0026] Figure 2 This is a radial cross-sectional view of the rotor core based on the first embodiment. Figure 2 The rotor core 10a shown is generally annular in shape with a through hole for the shaft portion 5 in the center. However, as will be described later, it is preferable that the outer peripheral surface of the rotor core 10a is not smooth. Furthermore, the rotor core 10a is typically stacked. Figure 2 Multiple magnetic plates of the shape shown, such as iron plates, carbon steel plates, electromagnetic steel plates, or formed from pressed iron cores.
[0027] In the rotor core 10a, multiple pairs of magnet slots 20 extending along the axial direction of the rotor core 10a are formed at equal intervals in the circumferential direction. Each pair of magnet slots 20 includes a first magnet slot 21 inclined counterclockwise with respect to the radius of the rotor 10 and a second magnet slot 22 inclined clockwise with respect to the aforementioned radius of the rotor 10. Preferably, the absolute values of the inclination angles of the first magnet slot 21 and the second magnet slot 22 with respect to the radius are equal to each other.
[0028] Figure 3 yes Figure 2A partial cross-sectional view of the rotor core is shown. Permanent magnets 91 and 92 are inserted into the magnet slots 21 and 22 of the rotor core 10a, respectively. Therefore, the magnet slots 21 and 22 are approximately rectangular, corresponding to the shapes of the permanent magnets 91 and 92, and preferably have the same shape. In addition, for the sake of simplicity, the illustrations of the permanent magnets 91 and 92 are sometimes omitted.
[0029] Each pair of magnet slots 20 is arranged in a manner that converges towards each other in the radial direction inwards toward the rotor core 10a. In other words, the magnet slots 21 and 22 are formed in a generally V-shape. The angle formed by the magnet slots 21 and 22 in each pair of magnet slots 20 in this disclosure is an obtuse angle, for example, 120°. In addition, these magnet slots 21 and 22 do not need to be connected to each other in the radial direction inwards toward the rotor core 10a.
[0030] In addition, Figure 2 In this rotor core 10a, the outer periphery is composed of a plurality of first outer peripheral portions 11 and a plurality of second outer peripheral portions 12 connecting the plurality of first outer peripheral portions 11 respectively. That is, the plurality of first outer peripheral portions 11 and the plurality of second outer peripheral portions 12 are alternately arranged in the circumferential direction of the rotor core 10a. Figure 2 It can be seen that the multiple first outer peripheral portions 11 roughly correspond to the respective regions of the multiple pairs of magnet slots 20. Strictly speaking, the first outer peripheral portions 11 correspond to the other end 21x of the magnet slot 21 and the other end 22x of the second magnet slot 22 on the inner side of the rotor core 10a in the radial direction. Furthermore, the multiple second outer peripheral portions 12 correspond to the regions between two adjacent pairs of magnet slots 20. Strictly speaking, the aa of the second outer peripheral portion 12 corresponds to one end 21y of the magnet slot 21 and one end 22y of the second magnet slot 22 on the outer side of the rotor core 10a in the radial direction.
[0031] Furthermore, the outermost portion of the first outer peripheral portion 11 is located radially outward of the outermost portion of the second outer peripheral portion 12 compared to the outermost portion of the second outer peripheral portion 12. In other words, the plurality of first outer peripheral portions 11, which are protrusions, and the plurality of second outer peripheral portions 12, which are concave portions, are alternately arranged in the circumferential direction of the rotor core 10a. The entire first outer peripheral portion 11 lies within a circle with a radius equal to the line segment connecting the center O of the rotor core 10a and the outermost portion of the first outer peripheral portion 11. Figure 2 A radial cross-sectional view of the same rotor core, i.e. Figure 5 In the diagram, the circle mentioned above is represented by a dashed line.
[0032] Since the outer circumference of the rotor core 10a is not a perfect circle, the change in the magnetic flux linkage number is reduced when the motor 1 with the rotor core 10a is driven. As a result, it is possible to prevent the cogging torque and torque fluctuation from increasing. Therefore, in the first embodiment of the present invention, the controllability of the motor 1 with the rotor core 10a can be improved.
[0033] In addition, Figure 2 In this configuration, the outermost portions of the first outer perimeter 11 are each formed by at least one curve. In one example, the first outer perimeter 11 is defined by the formula r = D - E / cos(Fθ) (where D, E, and F are positive numbers). In this case, the first outer perimeter 11 is reliably located inside the aforementioned circle and becomes smooth. Furthermore, the outermost portions of the second outer perimeter 12 can also be formed by at least one straight line.
[0034] In embodiments not shown, the outermost portion of the first outer peripheral portion 11 may be formed by at least one straight line, and the outermost portion of the second outer peripheral portion 12 may be formed by at least one curve. Furthermore, both the outermost portions of the first outer peripheral portion 11 and the outermost portions of the second outer peripheral portion 12 may be formed by at least one straight line, or both may be formed by at least one curve. Additionally, at least one of the outermost portions of the first outer peripheral portion 11 and the outermost portions of the second outer peripheral portion 12 may be formed by at least one straight line and at least one curve. In such cases, the outermost portions of the plurality of first outer peripheral portions 11 are also located radially outward from the outermost portions of the plurality of second outer peripheral portions 12, thus the outer periphery of the rotor core 10a becomes a shape different from a perfect circle. Therefore, it is understood that the same effect as described above can be obtained.
[0035] Furthermore, in a variation of the first embodiment (not shown), the first outer peripheral portion 11 may be located radially inward of the rotor core 10a compared to the second outer peripheral portion 12. Even in such a case, the same effects as described above can be obtained, which is within the scope of the first embodiment.
[0036] like Figure 2 As shown, on the end face of the rotor core 10a, a plurality of first holes 31 extending axially along the rotor core 10a are formed at equal intervals along the circumferential direction. According to Figure 2 and Figure 3 As can be seen, multiple first holes 31 are formed in the regions of the rotor core 10a corresponding to the first outer peripheral portion 11. Strictly speaking, the first hole 31 is formed on a radius of the rotor core 10a between the first magnet slot 21 and the second magnet slot 22 of a pair of magnet slots 20. The shape of the first hole 31 will be described later.
[0037] On the end face of the rotor core 10a, a plurality of second holes 32 are formed at equal intervals along the circumferential direction. Each of the second holes 32 is formed on a radius as described above. Therefore, the first holes 31 and the second holes 32 are arranged on the same radius of the rotor core 10a. Therefore, from... Figure 3It can be seen that the second hole 32 is formed at a position further outward in the radial direction than the first hole 31 in the rotor core 10a. Strictly speaking, the first hole 31 is formed at a position further in the radial direction than the pair of magnet slots 20 in the rotor core 10a, and the second hole 32 is formed at a position further outward in the radial direction than the pair of magnet slots 20 in the rotor core 10a. The shape of the second hole 32 will be described later.
[0038] Furthermore, from Figure 2 As can be seen, multiple groups consisting of the third hole 33 and the fourth hole 34 are formed at equal intervals along the circumference of the rotor core 10a. The groups consisting of the third hole 33 and the fourth hole 34 are formed between two adjacent pairs of magnet slots 20. The third hole 33 and the fourth hole 34 are arranged on the same radius of the rotor core 10a. Furthermore, the third hole 33 is formed at a position further outward in the radial direction than the fourth hole 34 of the rotor core 10a. The shapes of the third hole 33 and the fourth hole 34 will be described later.
[0039] The first hole 31 will be described below. For example... Figure 3 As shown, the first hole 31 is an approximately isosceles triangle with an acute apex. The apex of the approximately isosceles triangle is located outside the radial direction of the rotor core 10a, and the base of the approximately isosceles triangle is located inside the radial direction of the rotor core 10a. In addition, the base of the approximately isosceles triangle is perpendicular to one radius of the rotor core 10a.
[0040] Furthermore, the reason for specifying it as "approximately isosceles triangle" is to include cases where the vertices of an isosceles triangle have rounded corners, where the two hypotenuses of an isosceles triangle are each composed of multiple straight lines, and where the two hypotenuses of an isosceles triangle each contain curves, which are different from a perfect isosceles triangle. The same applies to the other holes 32, 33, and 34.
[0041] Figure 4 It is Figure 3 A magnified partial sectional view. (By...) Figure 3 and Figure 4 It can be seen that the first hole 31 is composed of a first portion 31a containing the acute angle of a roughly isosceles triangle and a second portion 31b containing the base of a roughly isosceles triangle. The first portion 31a has a shape similar to the first hole 31. The boundary line between the first portion 31a and the second portion 31b is preferably parallel to the base.
[0042] like Figure 4As shown, the boundary line between the first part 31a and the second part 31b corresponds to a portion of line segment L0 connecting the other end 21x of the first magnet slot 21 and the other end 22x of the second magnet slot 22, which are located radially inward of the rotor core 10a. Strictly speaking, line segment L0 connects the innermost part of the other end 21x of the first magnet slot 21 located radially in the rotor core 10a with the innermost part of the other end 22x of the second magnet slot 22 located radially in the rotor core 10a.
[0043] Furthermore, it is preferable that the other end 21x of the first magnet slot 21 is approximately parallel to the hypotenuse of the approximately isosceles triangle adjacent to it. Similarly, it is preferable that the other end 22x of the first magnet slot 22 is approximately parallel to the hypotenuse of the approximately isosceles triangle adjacent to it.
[0044] Thus, the regions between the first hole 31 and the first magnet slots 21 and 22 in this disclosure are formed adjacent to each other. Furthermore, a first portion 31a of the first hole 31 is formed between the other end 21x of the first magnet slot 21 and the other end 22x of the second magnet slot 22. And a second portion 31b of the first hole 31 is formed at a position radially inward of the rotor core 10a compared to the first portion 31a.
[0045] In other words, the first hole 31 based on this disclosure must include not only the first portion 31a formed between the first magnet slot 21 and the second magnet slot 22, but also the second portion 31b. Therefore, in this disclosure, a large first hole 31 can be formed. As a result, the rotor core 10a can be made lighter, and the motor 1 can be made to run at high speed.
[0046] In addition, such as Figure 3 As shown, a gap 21g is formed on one end 21y of the first magnet groove 21. The gap 21g is formed to partially protrude from one end 21y along the length of the first magnet groove 21. A gap 22g of the same shape is formed on one end 22y of the second magnet groove 22.
[0047] Furthermore, a gap 21p is also formed at the other end 21x of the first magnet slot 21. Similarly, a gap 22p is formed at the other end 22x of the second magnet slot 22. The gaps 21p and 22p protrude locally from the other ends 21x and 22x along the length of the first magnet slot 21 and the second magnet slot 22.
[0048] The gaps 21g and 21p in the first magnet slot 21 and the gaps 22g and 22p in the second magnet slot 22 serve as magnetic flux barriers to suppress magnetic flux leakage from both ends of the magnets 91 and 92 along their long sides to the rotor core. Furthermore, the gaps 21g, 22g, 21p, and 22p also facilitate the insertion and removal of the permanent magnets 91 and 92 relative to their corresponding magnet slots 21 and 22. Moreover, by forming the aforementioned gaps 21g, 21p, 22g, and 22p, the rotor core 10a is made lighter.
[0049] exist Figure 4 In the diagram, line segment L0' represents the line segment connecting a portion of the other end 21x of the first magnet slot 21 located radially outside the rotor core 10a, and a portion of the other end 22x of the second magnet slot 22 located radially outside the rotor core 10a. Figure 4 It can be seen that portions of gaps 21p and 22p extend beyond line segment L0' and protrude outwards in the radial direction of rotor core 10a. In other words, gaps 21p and 22p are formed to protrude from the other ends 21x and 22x in two directions: perpendicular to the length of the first magnet slot 21 and the second magnet slot 22, and along the length of the magnet slots 21 and 22, respectively. Furthermore, gaps 21p and 22p are connected to the first magnet slot 21 and the second magnet slot 22, respectively. Additionally, as shown in the figure, gaps 21p and 22p are not interconnected.
[0050] like Figure 4 As shown, the shortest distance between the gap 21p at the other end 21x of the first magnet slot 21 and the first hole 31 is defined as distance a. The shortest distance between the gap 22p at the other end 22x of the second magnet slot 22 and the first hole 31 is also the same distance a. Furthermore, the shortest distance between the other end 21x of the first magnet slot 21 and the first hole 31 is defined as distance a'. The shortest distance between the other end 22x of the second magnet slot 22 and the first hole 31 is also the same distance a'. Distance a can be less than half of distance a', preferably less than 1 / 4. In a typical example, these distances a are greater than 0 and less than 1 mm.
[0051] As described above, the angle formed by the magnet slots 21 and 22 is an obtuse angle, making it difficult for the motor 1 equipped with the rotor core 10a to output high torque. However, the rotor core 10a of the present invention has a first hole 31 and gaps 21p and 22p of the aforementioned shape and size. Therefore, magnetic flux leakage is reduced when the motor 1 is driven, and thus, even when the angle formed by the magnet slots 21 and 22 is an obtuse angle, the torque of the motor 1 can be maintained at a high level. In addition, by forming the first hole 31 and the gaps 21p and 22p, the rotor core 10a can be made lighter.
[0052] Here, during magnetization, the rotor 10, with magnets 91 and 92 inserted into all magnet slots 21 and 22 respectively, is positioned within the inner cylinder of the yoke (not shown). At this time, a portion of magnets 91 and 92 located radially inward of the rotor 10 is positioned away from the yoke. Therefore, particularly when the angle formed by the first magnet slot 21 and the second magnet slot 22 is acute, it is difficult to sufficiently magnetize the aforementioned portion of magnets 91 and 92.
[0053] However, compared to the case where the angle formed by the magnet slots is acute, in this disclosure, the angle formed by the magnet slots 21 and 22 is obtuse, so the other ends 21x and 22x of the magnet slots 21 and 22 are located closer to the outer peripheral surface of the rotor core 10a. Therefore, in this disclosure, a portion of the magnets 91 and 92 located near the other ends 21x and 22x of the magnet slots 21 and 22 can be magnetized more easily. In other words, in this disclosure, the angle formed by the magnet slots 21 and 22 is obtuse, thus providing the additional effect of easily magnetizing the magnets. Regarding this, using Figure 10A and Figure 10B To be described later.
[0054] Next, the second hole 32 will be explained. For example... Figure 3 As shown, the first hole 31 and the second hole 32 are arranged on the same radius of the rotor core 10a. Furthermore, the first hole 31 is formed at a position inside the rotor core 10a in the radial direction relative to the pair of magnet slots 20, and the second hole 32 is formed at a position outside the rotor core 10a in the radial direction relative to the pair of magnet slots 20.
[0055] The second hole 32 is formed by a first portion 32a and a second portion 32b located radially outward of the first portion 32a relative to the rotor core 10a. The boundary line between the first portion 32a and the second portion 32b of the second hole 32 is preferably parallel to the base of the approximately isosceles triangle of the first hole 31.
[0056] like Figure 3As shown, the first part 32a is a generally isosceles triangle with its apex pointing towards the center O of the rotor core 10a. Preferably, the apex angle of the generally isosceles triangle of the first part 32a is an acute angle, and larger than the apex angle of the generally isosceles triangle of the first part 31a of the first hole 31. Furthermore, the second part 32b is an arc, such as a semicircle, protruding outward from the base of the isosceles triangle in the radial direction of the rotor core 10a. The first part 32a and the second part 32b are preferably smoothly connected to each other. In other words, at the junction between the first part 32a and the second part 32b, preferably the hypotenuse of the generally isosceles triangle of the first part 32a and the tangent of the second part 32b are the same. Additionally, the arc of the second part 32b can be longer or shorter than the arc of a semicircle. Furthermore, the arc of the second part 32b can also be an elliptical arc.
[0057] exist Figure 3 In this design, the line segment connecting one end 21y of the first magnet slot 21 and one end 22y of the second magnet slot 22, located radially outward of the rotor core 10a, is designated as the first line segment L1. Strictly speaking, the first line segment L1 connects the outermost portion of one end 21y of the first magnet slot 21 located radially outward of the rotor core 10a to the outermost portion of one end 22y of the second magnet slot 22 located radially outward of the rotor core 10a. Figure 3 It is known that the boundary line B1 between the first part 32a and the second part 32b of the second hole 32 is preferably parallel to the first line segment L1 and located inside the rotor core 10a in the radial direction than the first line segment L1.
[0058] In other words, at least a portion of the second part 32b of the second hole 32 is located radially outward of the rotor core 10a compared to the first line segment L1. Therefore, in this disclosure, a large second hole 32 can be formed, resulting in a lighter rotor core 10a and enabling high-speed operation of the electric motor 1. Furthermore, by making the second part 32b an arc, the flow of magnetic flux is not obstructed when the electric motor 1 with the rotor core 10a is driven. Additionally, to increase the area of the second hole 32, the boundary line B1 can also be located on the first line segment L1, or the boundary line B1 can be located radially outward of the rotor core 10a compared to the first line segment L1.
[0059] As described above, the first outer peripheral portion 11 with the second hole 32 preferably protrudes outward in the radial direction relative to the second outer peripheral portion 12 of the rotor core 10a. In this case, the second hole 32 can be made longer outward in the radial direction of the rotor core 10a, corresponding to the protrusion of the first outer peripheral portion 11. Therefore, it is known that the second hole 32 can be enlarged, and correspondingly, the rotor core 10a can be made lighter.
[0060] likeFigure 4 As shown, the shortest distance between the gap 21p at the other end 21x of the first magnet slot 21 and the second hole 32 is defined as distance b. The shortest distance between the gap 22p at the other end 22x of the second magnet slot 22 and the second hole 32 is also the same distance b. These distances b are measured from the portion of the gaps 21p and 22p that protrudes outward in the radial direction from the line segment L0' towards the rotor core 10a to the second hole 32.
[0061] These distances b can also be less than half of the distance a', preferably less than 1 / 4. In a typical example, these distances a are greater than 0 and less than 1 mm. Thus, the same effect as described above can be obtained.
[0062] Next, the third hole 33 will be explained. Figure 6 yes Figure 2 Other partial sectional views of the rotor core are shown. (See also...) Figure 6 As shown, a pair of magnet slots 20a includes a first magnet slot 21a and a second magnet slot 22a. Another pair of magnet slots 20b includes a first magnet slot 21b and a second magnet slot 22b. A third hole 33 is formed between the second magnet slot 22a of the magnet slot 20a and the first magnet slot 21b of the magnet slot 20b.
[0063] Depend on Figure 6 It is understood that the third hole 33 comprises a generally isosceles triangle, such as an obtuse isosceles triangle, whose vertex angle 33a is defined by an arc. The vertex angle 33a of the generally isosceles triangle of the third hole 33 faces outward in the radial direction of the rotor core 10a. Furthermore, preferably, the two hypotenuses of the generally isosceles triangle of the third hole 33 are parallel to the second magnet slot 22a and the first magnet slot 21b, respectively.
[0064] Furthermore, the portion of the roughly isosceles triangle corresponding to the two base angles of the third hole 33 can be omitted, and the hypotenuse and base can be connected near the base. Figure 6 In the middle, the portion corresponding to the bottom angle is formed by a right angle. Alternatively, the portion corresponding to the bottom angle can also be formed by an arc. By forming the third hole 33 in this way, the flow of magnetic flux will not be obstructed.
[0065] Furthermore, a protrusion 33b may be formed, protruding from the base of the approximately isosceles triangle of the third hole 33 toward the radial direction inward of the rotor. The protrusion 33b is preferably formed at approximately the center of the base of the approximately isosceles triangle.
[0066] Figure 7 It is Figure 6 A partially enlarged sectional view. Figure 7The diagram primarily shows the second magnet slot 22a of a pair of magnet slots 20a and the first magnet slot 21b of another pair of magnet slots 20b. Furthermore, a second line segment L2 is defined as the line segment connecting the innermost part of the second magnet slot 22a (radially inward) to the other end 22x of the first magnet slot 21b. Strictly speaking, the second line segment L2 connects the innermost part of the second magnet slot 22x (radially inward) to the innermost part of the first magnet slot 21b (radially inward) to the other end 22y of the first magnet slot 21b. At this time, the third hole 33 is located entirely outside the radial direction of the rotor core 10a, relative to the second line segment L2.
[0067] like Figure 7 As shown, the third hole 33 is formed in the region surrounded by the second magnet slot 22a of one pair of magnet slots 20a, the first magnet slot 21b of another pair of magnet slots 20b, and the second line segment L2. In other words, the third hole 33 is not formed on or near the second line segment L2. Therefore, the strength of the rotor core 10a can be ensured. Moreover, it is known that when the motor 1 including the rotor core 10a is driven, the flow of magnetic flux is not impeded.
[0068] In addition, such as Figure 7 As shown, the third hole 33 is formed between the second magnet slot 22a of a pair of magnet slots 20a and the first magnet slot 21b of another pair of magnet slots 20b. Furthermore, the shortest distance between the third hole 33 and the first magnet slot 21b is greater than the shortest distance c between the third hole 33 and the second magnet slot 22a.
[0069] The shortest distance c is preferably more than half the thickness t of magnets 91 and 92. In a typical example, the shortest distance is more than 2 mm. When the third hole 33 is more than half the thickness t of magnets 91 and 92 away from magnets 91 and 92, the above-mentioned magnetization can be performed without being affected by the third hole 33.
[0070] And, as Figure 7 As shown, the line segment connecting one end 22y of the second magnet slot 22a and one end 21y of the first magnet slot 21b, which is located on the innermost side of the rotor core 10a in the radial direction, is designated as the third line segment L3. Strictly speaking, the third line segment L3 connects the innermost part of one end 21y of the first magnet slot 22a located on the innermost side of the rotor core 10a in the radial direction with the innermost part of one end 22y of the second magnet slot 21b located on the innermost side of the rotor core 10a in the radial direction.
[0071] The third line segment L3 is parallel to the second line segment L2. Furthermore, the third hole 33 has a dimension d on the center line between the second magnet slot 22a and the first magnet slot 21b, which is also the center line of the radius of the rotor core 10a. Dimension d does not necessarily have to be on the center line of the third hole 33. The dimension between the second line segment L2 and the third line segment L3 is defined as dimension e. In this case, dimension e is preferably more than twice the dimension d.
[0072] The reason for designing and arranging the third hole 33 in this way is to ensure the strength of the area between the third hole 33 and the second magnet slot 22a and the first magnet slot 21b, and to ensure smooth magnetic flux flow. Furthermore, in a motor 1 equipped with such a rotor core 10a, inertia can be reduced.
[0073] Next, the fourth hole, 34, will be explained. Figure 7 It is known that a third hole 33 and a fourth hole 34 are arranged on the radius of the center between the second magnet slot 22a of one pair of magnet slots 20a and the first magnet slot 21b of another pair of magnet slots 20b in the rotor core 10a. The group formed by the third hole 33 and the fourth hole 34 is formed between two adjacent pairs of magnet slots 20a and 20b in the plurality of pairs of magnet slots 20. The third hole 33 and the fourth hole 34 can also be formed axially symmetrically with respect to the aforementioned radius. In addition, the fourth hole 34 is formed at a position that is more radially inward than the second line segment L2 in the rotor core 10a.
[0074] The fourth hole 34 has a generally oblong or generally elliptical shape, with its major axis parallel to line segment L2. Furthermore, the fourth hole 34 preferably has protrusions 34a and 34b extending along the aforementioned radius. For example... Figure 7 As shown, protrusion 34a extends outward in the radial direction of rotor core 10a, and protrusion 34b extends inward in the radial direction of rotor core 10a. By forming these protrusions 34a and 34b, the fourth hole 34 can be enlarged, resulting in a lighter rotor core 10a. Alternatively, one of the protrusions 34a and 34b can be omitted.
[0075] Here, Figure 8A This is a partial cross-sectional view showing the magnetic flux of an electric motor in the prior art. Figure 9A This is a partial cross-sectional view showing the magnetic flux of an electric motor having a rotor core based on the first embodiment. Figure 8A The electric motor 1' shown includes a stator 9' and a rotor 10'. The rotor 10' does not have the first hole 31 to the fourth hole 34 formed therein. On the other hand, Figure 9A The electric motor 1 shown includes a stator 9 and the aforementioned rotor 10. The construction of rotors 10 and 10' is well known, so a description is omitted.
[0076] CompareFigure 8A and Figure 9A It can be seen that even when the first hole 31 to the fourth hole 34 are formed as in motor 1, the flow of magnetic flux will not be obstructed by the first hole 31, etc. Moreover, motor 1 has a lighter amount of the first hole 31 to the fourth hole 34 than motor 1'.
[0077] and, Figure 8A The angle between the first magnet slot 21' and the second magnet slot 22' in the pair of magnet slots 20' is an acute angle, for example, 60°. Therefore, the number of magnets 91' and 92' inserted into the first magnet slot 21' and the second magnet slot 22' respectively is... Figure 9A The number of magnets 91 and 92 shown is large.
[0078] Figure 8A The diameter of the rotor 10' shown is the same as Figure 9A The diameters of the rotors 10 shown are all equal. However, Figure 8A The width W0 of the magnets 91' and 92' shown is, for example, 31.4 mm. In contrast, Figure 9A The width W1 of the magnets 91 and 92 shown can be, for example, 22.5 mm.
[0079] Thus, in this disclosure, the number of magnets 91 and 92 can be reduced compared to the prior art, and the size of magnets 91 and 92 can be reduced. As a result, motor 1 can be significantly lighter than motor 1'. In the illustrated embodiment, the total weight of magnets 91 and 92 in motor 1 can be, for example, about 28% less than the total weight of magnets 91' and 92' in motor 1'.
[0080] and then, Figure 8B This is a graph showing the relationship between time and torque in existing electric motors. Figure 9B These are graphs showing the relationship between time and torque in the electric motor of the first embodiment. In these figures, the horizontal axis represents time, and the vertical axis represents the torque of motors 1 and 1'. Figure 8B In this case, the maximum torque of motor 1' is between 100 Nm and 101 Nm. In contrast, in... Figure 9B In this configuration, the maximum torque of motor 1 is between 91.5 Nm and 92 Nm. That is, even with the first hole 31 to the fourth hole 34 formed, the torque reduction is suppressed to less than 10%.
[0081] Thus, even when the first hole 31 to the fourth hole 34 are formed on the rotor 10, the torque will not be significantly reduced, and a practical torque will be generated. Furthermore, it will be obvious to those skilled in the art that the same effect can be obtained when only at least one of the first hole 31 to the fourth hole 34 is formed.
[0082] Furthermore, if we express the ratio of the D-axis current to the stall current in motor 1 and motor 1' as a percentage, it is as follows.
[0083] [Table 1]
[0084] According to the table, the limit is exceeded in motor 1' at a speed of 2500 rpm, but in motor 1, stable operation can be achieved even when the speed is increased to, for example, 3000 rpm. This is because the D-axis current is relatively small in motor 1. Furthermore, copper losses, which increase proportionally to the square of the load current, are suppressed in motor 1 compared to motor 1'. Therefore, the motor 1 of this disclosure can rotate at a higher speed.
[0085] in addition, Figure 10A This is a partial cross-sectional view showing the magnetic susceptibility of an electric motor in the prior art. Figure 10B These are partial cross-sectional views showing the magnetic susceptibility of the electric motor in the first embodiment. In these figures, three levels of magnetic susceptibility are shown, with higher susceptibility areas represented by darker colors. Specifically, areas with low magnetic susceptibility (magnetic flux density of 0.0T to 1.7T) are represented in white, areas with moderate magnetic susceptibility (magnetic flux density of 2.2T to 3.3T) are represented in light colors, and areas with high magnetic susceptibility (magnetic flux density of 3.5T to 5.0T) are represented in dark colors.
[0086] exist Figure 10A In the prior art electric motor 1' shown, only a portion of magnets 91' and 92' located on the outer side of rotor 10' in the radial direction is magnetized, while the remaining portions on the inner side of magnets 91' and 92' are unmagnetized. Because the angle formed by the first magnet slot 21 and the second magnet slot 22 where magnets 91' and 92' are inserted is acute, the distance between the other end of magnets 91' and 92' located on the inner side of rotor 10' and the outer circumferential surface of rotor 10' is relatively long. Therefore, in the prior art, even if rotor 10' is positioned within the inner cylinder of a yoke (not shown), it is difficult to magnetize the other end of magnets 91' and 92'. Therefore, in the prior art, the magnetization rate of magnets 91' and 92' is approximately 30%.
[0087] In contrast, Figure 10BIn the electric motor 1 shown, magnets 91 and 92 are magnetized almost entirely, with a magnetization rate of approximately 100%. In other words, in this disclosure, even when the rotor 10 is positioned within the inner cylinder of the yoke (not shown), the ends of magnets 91 and 92 located radially inward of the rotor 10 can be sufficiently magnetized. Therefore, in this disclosure, where the angle between the first magnet slot 21 and the second magnet slot 22 is obtuse, magnetization of magnets 91 and 92 can be reliably achieved.
[0088] Furthermore, in this disclosure, as long as the first hole 31 and the gaps 21p and 22p are formed, the second hole 32 to the fourth hole 34 may not be formed. Moreover, a structure in which at least one of the second hole 32 to the fourth hole 34 is formed in addition to the first hole 33 and the gaps 21p and 22p is also included in the scope of this disclosure.
[0089] Therefore, in at least one embodiment, by forming the first hole 31, the rotor 10 can be made lightweight without significantly reducing torque, allowing for sufficient magnetization and reducing inertia. In other words, a lightweight rotor 10 can be provided that reduces inertia and allows for sufficient magnetization without reducing torque. Therefore, high acceleration of the electric motor 1 having the rotor 10 can be achieved.
[0090] The embodiments of this disclosure have been described in detail, but this disclosure is not limited to the various embodiments described above. Various additions, substitutions, modifications, and partial deletions can be made to these embodiments without departing from the spirit and essence of the invention, or without departing from the spirit and essence of the invention derived from the claims and their equivalents. For example, in the embodiments described above, the order of each action and the order of each process are shown as examples only, and are not limited to these. The same applies to cases where numerical values or formulas are used in the description of the embodiments described above. Furthermore, suitable combinations of the foregoing embodiments are included within the scope of this disclosure.
[0091] Regarding the above-described embodiments and variations, the following notes are also disclosed. (Note 1)
[0092] A rotor core (10a), wherein,
[0093] Multiple pairs of magnet slots (20) extending along the axial direction of the rotor core (10a) are formed in the rotor core (10a).
[0094] The plurality of pairs of magnet slots (20) are arranged at equal intervals along the circumference of the rotor core (10a) in the radial direction section of the rotor core (10a).
[0095] Each of the multiple pairs of magnet slots (20) includes a first magnet slot (21) that is inclined counterclockwise relative to the radius of the rotor core (10a) and a second magnet slot (22) that is inclined clockwise relative to the radius of the rotor core (10a).
[0096] In each pair of magnet slots (20), one end of the first magnet slot (21) is separated from one end of the second magnet slot (22), and the other end of the first magnet slot (21) and the other end of the second magnet slot (22) are adjacent to each other in the radial direction inward of the rotor core (10a) than the ends of the first magnet slot (21) and the second magnet slot (22).
[0097] Furthermore, a first hole (31) is formed adjacent to each pair of magnet slots (20).
[0098] The first hole (31) includes: a first portion (31a) corresponding to at least a portion of the region between the other end of the first magnet slot (21) and the other end of the second magnet slot (22); and a second portion (31b) continuous with the first portion (31a) and located radially inward of the first portion (31a) from the rotor core (10a).
[0099] (Note 2)
[0100] According to the rotor core (10a) described in Appendix 1, wherein,
[0101] Gaps (21p, 22p) are formed at the other end of the first magnet slot (21) and the other end of the second magnet slot (22), respectively.
[0102] The gaps (21p, 22p) protrude locally outward in the radial direction of the rotor core (10a) relative to the line segment (L0') connecting the other end of the first magnet slot (21) located radially outside the rotor core (10a) and the other end of the second magnet slot (22) located radially outside the rotor core (10a).
[0103] (Note 3)
[0104] According to Appendix 1 or 2, the rotor core (10a) wherein,
[0105] The distance (a) between the gap (21p) formed at the other end of the first magnet slot (21) and the first hole (31) is less than half of the distance (a') between the other end of the first magnet slot (21) and the first hole (31).
[0106] The distance (a) between the gap (22p) formed at the other end of the second magnet slot (22) and the first hole (31) is less than half of the distance (a') between the other end of the second magnet slot (22) and the first hole (31).
[0107] (Note 4)
[0108] According to any one of Appendices 1-3, the rotor core (10a) wherein,
[0109] The outer periphery of the rotor core (10a) is composed of a plurality of first outer periphery portions (11) and a plurality of second outer periphery portions (12) respectively connecting the plurality of first outer periphery portions (11).
[0110] The plurality of first peripheral portions (11) correspond to the respective regions of the plurality of pairs of magnet slots (20).
[0111] The plurality of second peripheral portions (112) correspond to the regions between two adjacent pairs of magnet slots (20a, 20b) in the plurality of pairs of magnet slots (20), respectively.
[0112] The outermost portion of the plurality of first peripheral portions (11) is located outside the rotor core (10a) in the radial direction than the outermost portion of the plurality of second peripheral portions (12).
[0113] (Note 5)
[0114] According to any one of Annexes 1-4, the rotor core (10a) wherein,
[0115] The plurality of first peripheral portions (11) are formed by at least one curve.
[0116] The plurality of second peripheral portions (12) are formed by at least one straight line.
[0117] (Note 6)
[0118] According to any one of Annexes 1-5, the rotor core (10a) wherein,
[0119] Furthermore, a second hole (32) is formed adjacent to each pair of magnet slots (20).
[0120] Each of the first holes (31) and each of the second holes (32) are arranged in the radial direction of the rotor core (10a).
[0121] (Note 7)
[0122] According to any one of Annexes 1-6, the rotor core (10a) wherein,
[0123] In the radial cross-section of the rotor core (10a), the second hole (32) is formed by an approximately isosceles triangle whose apex (32a) faces the center of the rotor core (10a) and an arc protruding from the base of the isosceles triangle outward in the radial direction of the rotor core (10a).
[0124] At least a portion of the arc of the second hole (32) is located outside the rotor core (10a) in the radial direction than the first line segment (L1), the first line segment (L1) connecting one end of the first magnet slot (21) and one end of the second magnet slot (22) outside the radial direction of the rotor core (10a).
[0125] (Note 8)
[0126] According to any one of Annexes 1-6, the rotor core (10a) wherein,
[0127] The distance (b) between the gap (21p) formed at the other end of the first magnet slot (21) and the second hole (32) is less than half of the distance (a') between the other end of the first magnet slot (21) and the first hole (31).
[0128] The distance (b) between the gap (22p) formed at the other end of the second magnet slot (22) and the second hole (32) is less than half of the distance (a') between the other end of the second magnet slot (22) and the first hole (31).
[0129] (Note 9)
[0130] According to any one of Appendices 1-8, the rotor core (10a) wherein,
[0131] A third hole (33) is formed between two adjacent pairs of magnet slots (20a, 20b) in the plurality of pairs of magnet slots (20).
[0132] The third hole (33) is formed at a position on the outer side of the rotor core (10a) in the radial direction, which is closer to the second line segment (L2). The second line segment (L2) connects the other end of the second magnet slot (22a) in one pair of magnet slots (20a, 20b) to the other end of the first magnet slot (21b) in the other pair of magnet slots (20b).
[0133] (Postscript 10)
[0134] According to any one of notes 1-9, the rotor core (10a) wherein,
[0135] The distance (c) between the third hole (33) and the first magnet slot (21) or the second magnet slot (22) is more than half the thickness (t) of the magnet that should be inserted into the first magnet slot (21) or the second magnet slot (22).
[0136] (Postscript 11)
[0137] The rotor core (10a) according to any one of Appendices 1-10, wherein,
[0138] The distance (e) between the third line segment (L3) connecting one end of the second magnet slot (22a) in one pair of magnet slots (20a, 20b) and one end of the first magnet slot (21b) in the other pair of magnet slots (20b) and the second line segment (L2) is more than twice the length (d) of the rotor core (10a) of the third hole (33) in the radial direction.
[0139] (Postscript 12)
[0140] According to any one of Appendices 1-11, the rotor core (10a) wherein,
[0141] Furthermore, a fourth hole (34) is formed at a position that is radially inward of the rotor core (10a) compared to the third hole (33).
[0142] Each of the third holes (33) and each of the fourth holes (34) are arranged in the radial direction of the rotor core (10a).
[0143] (Postscript 13)
[0144] A rotor (10), wherein,
[0145] The rotor (10) has:
[0146] Rotor core (10a) according to any one of Appendix 1-12;
[0147] Magnets (91, 92), which are respectively inserted into the plurality of pairs of magnet slots (20), (20); and
[0148] Shaft (5), which is inserted into the rotor core.
[0149] (Postscript 14)
[0150] An electric motor (1), wherein,
[0151] The electric motor (1) has the following features:
[0152] The rotor (10) described in Appendix 13; and
[0153] The stator (9) is configured around the rotor (10).
[0154] Explanation of reference numerals in the attached figures
[0155] 1. Electric motor; 5. Shaft; 9. Stator; 10. Rotor; 10a. Rotor core; 11. First outer peripheral portion; 12. Second outer peripheral portion; 20, 20a, 20b. A pair of magnet slots; 21, 21a, 21b. First magnet slot; 21g, 21p. Gap; 22, 22a, 22b. Second magnet slot; 22g, 22p. Gap; 31. First hole; 31a. First part; 31b. Second part; 32. Second hole; 32a. First part; 32b. Second part; 33. Third hole; 33a. Apex; 33b. Protrusion; 34. Fourth hole; 34a, 34b. Protrusion; 91, 92. Magnet; L0, L0'. Line segment; L1. First line segment; L2. Second line segment; L3. Third line segment.
Claims
1. A rotor core, wherein a plurality of pairs of magnet grooves extending in an axial direction of the rotor core are formed in the rotor core, the plurality of pairs of magnet grooves are arranged at equal intervals in a circumferential direction of the rotor core in a radial cross section of the rotor core, each of the pairs of magnet grooves includes a first magnet groove inclined counterclockwise with respect to a radius of the rotor core and a second magnet groove inclined clockwise with respect to the radius of the rotor core, in the each of the pairs of magnet grooves, one end of the first magnet groove and one end of the second magnet groove are separated from each other, and the other end of the first magnet groove and the other end of the second magnet groove are adjacent to each other at a position closer to an inner side in a radial direction of the rotor core than the one end of the first magnet groove and the one end of the second magnet groove, and a first hole is formed adjacent to the each of the pairs of magnet grooves; the first hole includes a first portion corresponding to at least a portion of a region between the other end of the first magnet groove and the other end of the second magnet groove, and a second portion continuous with the first portion and located at a position closer to the inner side in the radial direction of the rotor core than the first portion.
2. The rotor core according to claim 1, wherein a gap is formed in the other end of the first magnet groove and the other end of the second magnet groove, respectively; the gap locally protrudes to an outer side in a radial direction of the rotor core with respect to a line segment connecting the other end of the first magnet groove located on an outer side in the radial direction of the rotor core and the other end of the second magnet groove located on the outer side in the radial direction of the rotor core.
3. The rotor core according to claim 2, wherein a distance between the gap formed in the other end of the first magnet groove and the first hole is half or less of a distance between the other end of the first magnet groove and the first hole, a distance between the gap formed in the other end of the second magnet groove and the first hole is half or less of a distance between the other end of the second magnet groove and the first hole.
4. The rotor core according to claim 1, wherein an outer periphery of the rotor core is constituted by a plurality of first outer periphery portions and a plurality of second outer periphery portions connecting the plurality of first outer periphery portions, respectively, the plurality of first outer periphery portions correspond to regions of the plurality of pairs of magnet grooves, respectively, the plurality of second outer periphery portions correspond to regions between two pairs of magnet grooves adjacent to each other among the plurality of pairs of magnet grooves, respectively, an outermost portion of the plurality of first outer periphery portions is located at a position closer to an outer side in a radial direction of the rotor core than an outermost portion of the plurality of second outer periphery portions.
5. The rotor core according to claim 4, wherein the plurality of first outer periphery portions are constituted by at least one curved line, the plurality of second outer periphery portions are constituted by at least one straight line.
6. The rotor core according to claim 1, wherein and a second hole is formed adjacent to the each of the pairs of magnet grooves, each of the first holes and each of the second holes are arranged in the radial direction of the rotor core.
7. The rotor core according to claim 6, wherein In a radial cross section of the rotor core, the second hole is composed of a substantially isosceles triangle whose apex angle faces the center of the rotor core and a circular arc that protrudes from the base of the isosceles triangle to the radial outer side of the rotor core, At least a portion of the circular arc of the second hole is located at a position that is on the radial outer side of the rotor core than a first line segment that links the one end of the first magnet slot and the one end of the second magnet slot on the radial outer side of the rotor core.
8. The rotor core according to claim 6, wherein A distance between the gap formed at the other end of the first magnet slot and the second hole is half or less of a distance between the other end of the first magnet slot and the first hole, A distance between the gap formed at the other end of the second magnet slot and the second hole is half or less of a distance between the other end of the second magnet slot and the first hole.
9. The rotor core according to claim 1, wherein A third hole is formed between two pairs of magnet slots that are adjacent to each other among the plurality of pairs of magnet slots, The third hole is formed at a position that is on the radial outer side of the rotor core than a second line segment that links the other end of the second magnet slot in one pair of magnet slots among the two pairs of magnet slots and the other end of the first magnet slot in the other pair of magnet slots among the two pairs of magnet slots.
10. The rotor core according to claim 9, wherein A distance between the third hole and the first magnet slot or the second magnet slot is half or more of a thickness of a magnet to be inserted into the first magnet slot or the second magnet slot.
11. The rotor core according to claim 9, wherein A distance between a third line segment that links the one end of the second magnet slot in one pair of magnet slots among the two pairs of magnet slots and the one end of the first magnet slot in the other pair of magnet slots among the two pairs of magnet slots and the second line segment is two times or more of a length in the radial direction of the rotor core of the third hole.
12. The rotor core according to claim 9, wherein and a fourth hole is formed at a position that is on the radial inner side of the rotor core than the third hole, Each of the third holes and each of the fourth holes are arranged in the radial direction of the rotor core.
13. A rotor, wherein The rotor includes: The rotor core according to any one of claims 1 to 12; Magnets that are respectively inserted into the plurality of pairs of magnet slots; and A shaft portion that is inserted into the rotor core.
14. An electric motor, wherein The electric motor includes: The rotor according to claim 13; and A stator that is disposed around the rotor.