ROTOR CORE, ROTOR AND ELECTRIC MOTOR

Abstract

The present invention provides a rotor core (10a) provided with a plurality of pairs of magnetic slots (20) shaped to assume a V-shape. A plurality of holes (30) are formed between each pair of magnetic slots. A hole (30) comprises an approximately isosceles triangle (T, 31) whose vertex angle is directed towards the center of the rotor core, and an arc (32) connected to the base of the isosceles triangle. At least one region of the arc is positioned radially along the rotor core on the outer side of a first line segment connecting the outermost regions of the magnetic slots.

Description

TECHNICAL FIELD

[0001] Embodiments of the present invention relate to a rotor core, a rotor and an electric motor. STATE OF THE ART

[0002] A plurality of pairs of V-shaped magnetic slots are formed in one end face of a rotor core of a motor, and magnets are inserted into each magnetic slot. To reduce the weight and inertia of the rotor core, holes are formed in the rotor core (see, for example, Japanese Patent JP 6,987,310). However, if holes are formed in each pair of V-shaped magnetic slots, the flow of magnetic flux is obstructed, thereby reducing torque.

[0003] Patent Document 1: Japanese Patent JP 6,987,310 Summary of the inventionTechnical problem

[0004] To increase torque, it is possible to extend the V-shaped tip of each pair of magnetic slots radially inward relative to the core. However, this reduces the area of ​​the rotor core where holes can be formed. As a result, it is difficult to reduce weight and inertia.

[0005] Therefore, there is a demand for a lightweight rotor core, rotor and electric motor that can reduce inertia without reducing torque. Solution to the problem

[0006] According to a first aspect of the present invention, there is provided a rotor core wherein a plurality of pairs of magnetic slots extending in an axial direction of the rotor core are formed in the rotor core, the plurality of pairs of magnetic slots being arranged at equal intervals in a circumferential direction of the rotor core in a radial cross section of the rotor core, each pair of magnetic slots of the plurality of pairs of magnetic slots including a first magnetic slot inclined counterclockwise relative to a radius of the rotor core and a second magnetic slot inclined clockwise relative to the radius of the rotor core, further comprising a plurality of holes extending in the axial direction of the rotor core between the first magnetic slot and the second magnetic slot in each pair of magnetic slots.In the radial cross section of the rotor core, each of the plurality of holes is formed by an approximately isosceles triangle whose apex angle faces the center of the rotor core and an arc protruding from the base of the isosceles triangle toward the radially outer side of the rotor core. At least a portion of the arc in each of the plurality of holes in the radial cross section of the rotor core is positioned on the radially outer side of the rotor core relative to a first line segment between a portion of the first magnetic slot positioned at the outermost position of the rotor core and a portion of the second magnetic slot positioned at the outermost position of the rotor core.

[0007] The objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an axial cross-sectional view of an electric motor according to a first embodiment of the present invention; Fig. 2 is a radial cross-sectional view of a rotor of an electric motor based on the first embodiment; Fig. 3 is an enlarged view of a first portion of the Fig. 2 rotor shown; Fig. 4 is an enlarged view of a second portion of the Fig. 2 rotor shown; Fig. 5 is an enlarged view of a third area of ​​the Fig. 2 rotor shown; Fig. 6A is a cross-sectional view showing a part of the magnetic flux of a prior art electric motor; Fig. 6B is a view showing the relationship between time and torque of a prior art electric motor; Fig. 7A is a cross-sectional view showing a magnetic flux range of an electric motor based on the first embodiment; Fig. Fig. 7B is a view showing the relationship between time and torque of an electric motor based on the first embodiment, and Fig. 8 is a radial cross-sectional view of a rotor core of an electric motor based on the first embodiment. DESCRIPTION OF THE EMBODIMENTS

[0008] Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, corresponding components are designated by the same reference numerals. Fig. 1 is an axial cross-sectional view of an electric motor based on a first embodiment of the present invention. As shown in Fig. As shown in Figure 1, the electric motor 1 includes a stator 9 and a rotor 10 rotatably supported by the stator 9. A first bearing 7 and a second bearing 8 are arranged on the inner peripheral surface of the stator 9. 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. A detector 6 for detecting the rotational speed of the shaft 5 or the like is attached to one end of the stator 9.

[0009] Fig. Figure 2 is a radial cross-sectional view of the rotor of the electric motor based on the first embodiment. Fig. The rotor 10 shown in Fig. 2 is substantially annular and includes a through hole in the center thereof for the shaft 5. However, as will be described later, it is preferable that the outer peripheral surface of the rotor 10 is not smooth.

[0010] A plurality of pairs of magnetic slots 20 extending in the axial direction of the rotor 10 are formed in the rotor 10 at equal intervals in the circumferential direction. Each pair of magnetic slots 20 includes a first magnetic slot 21 inclined counterclockwise relative to the radius of the rotor 10 and a second magnetic slot 22 inclined clockwise relative to the radius of the rotor 10. It is preferable that the absolute values ​​of the inclination angles of the first magnetic slot 21 and the second magnetic slot 22 relative to the radius be equal to each other.

[0011] Permanent magnets 21a, 21b are inserted into the magnet slots 21, 22, respectively. Therefore, the magnet slots 21, 22 are preferably substantially rectangular, corresponding to the shapes of the permanent magnets 21a, 21b, and preferably have the same shape. Furthermore, it is preferable that additional notches or the like be formed in the magnet slots 21, 22 to facilitate the insertion / removal of the permanent magnets 21a, 21b.

[0012] The magnetic slots 21, 22 are arranged such that they converge toward the radially inner side of the rotor 10. In other words, the magnetic slots 21, 22 are formed to form a substantially V-shape. However, the magnetic slots 21, 22 do not need to be connected to each other on the radially inner side.

[0013] In Fig. 2, the outer circumference of the rotor 10 consists of a plurality of first outer circumferences 11 and a plurality of second outer circumferences 12 connecting the plurality of first outer circumferences 11. In particular, the plurality of first outer circumferences 11 and the plurality of second outer circumferences 12 are arranged alternately in the circumferential direction of the rotor 10. As can be seen from Fig. 2, the plurality of first outer peripheries 11 correspond to the respective areas of the plurality of pairs of magnetic slots 20. The plurality of second outer peripheries 12 correspond to the respective areas between two adjacent pairs of magnetic slots 20 of the plurality of pairs of magnetic slots 20.

[0014] The outermost portion of each first outer circumference 11 is positioned on the radially outer side of the rotor 10 relative to the outermost portion of each second outer circumference 12. In other words, the first outer circumference 11 as convex portions and the second outer circumference 12 as concave portions are arranged alternately in the circumferential direction of the rotor 10. The entire first outer circumference 11 is within a circle (represented by the dashed line in Fig. 8, which will be described later) with a radius of a line segment connecting the center O of the rotor 10 and the outermost portion of the first outer circumference 11. It is preferable that the outermost portion of the second outer circumference 12 be positioned on the radially outer side of the rotor 10 relative to the permanent magnet 21b of one pair and the permanent magnet 21a of the other pair of the two pairs of magnetic slots 20 adjacent to the second outer circumference 12.

[0015] Since the first outer circumference of the rotor 10 is not a perfect circle, the change in magnetic flux linkage during the driving of the electric motor 1 including the rotor 10 is small, and as a result, it is possible to prevent an increase in cogging torque and torque ripple. Thus, in the first embodiment of the present invention, it is possible to improve the control of the electric motor 1 including the rotor 10.

[0016] In Fig. 2, each of the outermost regions of the first outer circumferences 11 consists of at least one curve. In one example, the first outer circumference 11 is defined by the formula r = DE / cos(Fθ) (where D, E, and F are positive numbers). In this case, the first outer circumference 11 is reliably positioned within the aforementioned circle and is smooth.

[0017] Each of the outermost regions of the second outer periphery 12 consists of at least one straight line. In the illustrated embodiment, the outermost region of the second outer periphery 12 includes a straight line that runs substantially parallel to one side of the permanent magnet 21a of one of the two pairs of magnetic slots 20 adjacent to the second outer periphery 12 and one side of the permanent magnet 21b of the other pair.

[0018] In an embodiment not shown, the outermost region of the first outer circumference 11 can be formed by at least one straight line, and the outermost region of the second outer circumference 12 can be formed by at least one curved line. Both the outermost region of the first outer circumference 11 and the outermost region of the second outer circumference 12 can be formed by at least one straight line, or both the outermost region of the first outer circumference 11 and the outermost region of the second outer circumference 12 can be formed by at least one curved line. Furthermore, at least one of the outermost regions of the first outer circumference 11 and the outermost region of the second outer circumference 12 can be formed by at least one straight line and at least one curved line.In such a case, the outer circumference of the rotor 10 has a shape that deviates from a perfect circle because the outermost regions of the first outer circumference 11 are positioned on the radially outer side of the rotor 10 relative to the outermost regions of the second outer circumference 12. Thus, it should be clear that the same effects as described above can be achieved.

[0019] In a modification example of the first embodiment (not shown), the first outer periphery 11 may be positioned radially inward of the rotor 10 relative to the second outer periphery 12. Even in such a case, the same effects as those described above can be achieved and are included within the scope of the first embodiment.

[0020] As in Fig. 2, a plurality of holes 30 extending in the axial direction of the rotor 10 are formed in the end surface of the rotor 10 at equal intervals in the circumferential direction. Fig. 3 is an enlarged view of the first area of ​​the Fig. 2. As can be seen from the Fig. 2 and Fig. As can be seen from Figure 3, each of the plurality of holes 30 is formed in a region of the rotor 10 corresponding to the first outer periphery 11. Specifically, the hole 30 is formed between the first magnetic slot 21 and the second magnetic slot 22 of the pair of magnetic slots 20. The shape of the hole 30 will be described later.

[0021] Likewise, a plurality of sets of holes 41, 42 extending in the axial direction of the rotor 10 are formed in the end surface of the rotor 10 at equal intervals in the circumferential direction. As can be seen from the Fig. 2 and Fig. 3, each of the plurality of sets of holes 41, 42 is formed in a region of the rotor 10 corresponding to the second outer circumference 12. The hole 41 is formed in the radially outer side of the rotor 10 relative to the hole 42, and the hole 41 is smaller than the hole 42. In one example, the hole 41 is circular, and the hole 42 is an ellipse whose width decreases from the inside to the outside in the radial direction of the rotor 10. Alternatively, at least one of the holes 41, 42 may be elliptical or oval.

[0022] The shapes of the holes 30 are described below. As in Fig. 3, each hole 30 consists of a first region 31 and a second region 32, which is positioned relative to the first region 31 on the radially outer side of the rotor 10. The center lines of the first region 31 and the second region 32 are positioned on a radius R of the rotor 10. It should be noted that the "radius R" in the present description is a region of a straight dashed line extending from the center point O of the rotor 10 and passing through the center line of the hole 30 in Fig. 8, which will be described later. In other words, the "radius R" is a line segment connecting the center O of the rotor 10 and the edge of the first outer circumference 11 from the center O.

[0023] As in Fig. As shown in Figure 3, the first region 31 has the shape of an approximately isosceles triangle T, whose apex angle points toward the center O of the rotor 10. The second region 32 has the shape of an arc, for example, a semicircle, projecting from the base of the isosceles triangle T toward the radially outer side of the rotor 10. It is preferable that the first region 31 and the second region 32 be smoothly connected to each other.

[0024] The reason for using the term "approximately isosceles triangle" is that it includes cases that differ from a perfect isosceles triangle, e.g., when the vertex region of the isosceles triangle T is rounded, when each of the two hypotenuses 33 of the isosceles triangle T consists of a plurality of straight lines, and when each of the two hypotenuses 33 of the isosceles triangle T contains a curve. Furthermore, the arc as the second region 32 may be longer or shorter than the arc of a semicircle. Furthermore, the arc as the second region 32 may be an elliptical arc.

[0025] In Fig. 3, in a pair of magnetic slots 20, a portion of the first magnetic slot 21 positioned on the outermost side of the rotor 10 is denoted as "X", and a portion of the magnetic slot 22 positioned on the outermost side of the rotor 10 is denoted as "X'". At least one portion of the arc, for example, the second portion 32, point A, is positioned on the radially outer side of the rotor 10 relative to the straight line XX'.

[0026] Since at least a portion of the hole 30 is positioned further on the radially outer side of the rotor 10 than the straight line XX', the length of the hole 30 on the radius R is longer than the length of the surface of the permanent magnets 21a, 21b facing the hole 30 (corresponding to the width of the permanent magnets). Thus, in the first embodiment, a large hole 30 can be formed, and as a result, the rotor 10 can be made lighter and the electric motor 1 can be made faster. In addition, since the second portion 32 is an arc, the flow of the magnetic flux is not obstructed when the electric motor 1 including the rotor 10 is driven / energized.

[0027] As described above, it is preferable that the first outer circumference 11 in which the hole 30 is formed protrudes further toward the radially outer side of the rotor 10 than the second outer circumference 12. In this case, the hole 30 can be formed to be longer in the radial direction of the rotor 10 by the protruding portion of the first outer circumference 11. Thus, it should be clear that the hole 30 can be made larger, and the rotor 10 can be made lighter.

[0028] Fig. 4 is an enlarged view of the second area of ​​the Fig. 2 shown rotor. In Fig. 4, each hypotenuse 33 of the first portion 31 of the hole 30 has a first straight section 33a extending from the base of the approximately isosceles triangle T, and a second straight section 33b extending from the distal end of the first straight section 33a toward a point B at the apex of the approximately isosceles triangle T. As can be seen from the Fig. 3 and Fig. As can be seen in Figure 4, the first straight section 33a is connected to the second region 32. The intersection point B between the two second straight sections 33b may be rounded.

[0029] In Fig. 4, the first straight section 33a and the second straight section 33b intersect at an intersection point C. As can be seen from the Fig. 3 and Fig. 4, the intersection point C is located outside the approximately isosceles triangle T relative to the hypotenuse corresponding to the intersection point C. In other words, the angle formed by the radius R and the first straight section 33a, as in Fig. 4, is smaller than the angle formed by the radius R and the second straight section 33b.

[0030] Therefore, the first region 31 having the shape described above is larger than the first region 31 as a perfect isosceles triangle T. Therefore, the hole 30 is larger, and the rotor 10 can be made lighter accordingly. Although the second straight section 33b extends from the vicinity of point B to enlarge the hole 30, the first straight section 33a extends so as to suppress the enlargement of the hole 30. In other words, it is preferable that the hole 30 be shaped to be larger on the radially inner side of the rotor 10 and smaller on the radially outer side of the rotor 10. This prevents the hole 30 from becoming excessively large and suppresses the flow of magnetic flux from being obstructed on the radially outer side of the rotor 10.

[0031] In Fig. 4, in the pair of magnetic slots 20, a portion of the first magnetic slot 21 closest to the radius R is denoted as "Y," and a portion of the second magnetic slot 22 closest to the same radius R is denoted as "Y'." The vertex B on the vertex angle side of the approximately isosceles triangle T is positioned near the straight line YY'. The vertex B can be positioned at the intersection point of the straight line YY' and the radius R, or radially inward of the rotor 10 relative to the straight line YY'. In this way, the hole 30 can be made larger because the end of the hole 30 positioned radially inward of the rotor 10 is positioned near the straight line YY', and as a result, the rotor 10 can be made lighter.

[0032] It is preferable that the apex B is positioned more on the radially outer side of the rotor 10 than on the straight line YY'. This can ensure the strength of the rotor 10. When the rotor 10 is formed by stacking a plurality of magnetic plates in the axial direction of the rotor 10, the above configuration is particularly preferable because it can ensure the strength of the plurality of magnetic plates.

[0033] Fig. 5 is an enlarged view of a third area of ​​the Fig. 2. In the rotor shown in Fig. In the example shown in Figure 5, the maximum width L2 of the hole 30 corresponds perpendicular to the radius R (see Fig. 3 and Fig. 4) substantially the base of the above-described approximately isosceles triangle T. This maximum width L2 is preferably 1 / 3 or less of the length L1 of the straight line XX'. This can prevent the hole 30 from becoming excessively large while suppressing the magnetic flux on the radially outer side of the rotor 10.

[0034] The Fig. The line segment L3 shown in Fig. 5 is the length between the edge 5a of the through hole of the rotor 10, into which the shaft 5 is inserted, and the outermost portion of the rotor 10, and represents the length of a portion on the radius R described above. The line segment L4 represents the length between the outermost portion of the hole 30 in the radial direction of the rotor 10 and the outermost portion in the radial direction of the rotor 10. In other words, the line segment L4 is the shortest distance between the first outer circumference 11 and the second portion 32 of the hole 30.

[0035] In Fig. 5, the length of line segment L3 is preferably less than ten times the length of line segment L4. In one example, the length of line segment L3 is ten times the length of line segment L4. In such a case, the flow of magnetic flux on the radially outer side of rotor 10 can be prevented from being obstructed while maintaining the size of hole 30.

[0036] Fig. 6A is a partial cross-sectional view showing the magnetic flux of a prior art electric motor, and Fig. Fig. 7A is a partial cross-sectional view showing the magnetic flux of an electric motor based on the first embodiment. Fig. The electric motor 1' shown in Figure 6A comprises a stator 9' and a rotor 10'. Fig. The electric motor 1 shown in Figure 7A includes a stator 9 and the rotor 10 described above. Since the structures of the rotors 10 and 10' are generally known, a description has been omitted. As can be seen by comparing Fig. 6A and Fig. As can be seen from Fig. 7A, the flow of magnetic flux is not obstructed by the holes 30 or the like, even if the holes 30, 41, and 42 are formed in the manner of the electric motor 1. Furthermore, the electric motor 1 is lighter than the electric motor 1' by the amount required to form the holes 30, 41, and 42.

[0037] Fig. Fig. 6B is a view showing the relationship between time and torque of a prior art electric motor, and Fig. Figure 7B is a view showing the relationship between time and torque of an electric motor based on the first embodiment of the invention. In these drawings, the horizontal axis represents time, and the vertical axis represents the torque of the electric motors 1 and 1'. Fig. 6B, the maximum torque value of the electric motor 1' is between 100 Nm and 101 Nm. In contrast, in Fig. 7B, the maximum torque value of the electric motor 1 is between 91.5 Nm and 92 Nm. In particular, even with the formation of holes 30, 41, and 42, the torque reduction is suppressed to less than 10%.

[0038] Even if the holes 30, 41, and 42 are formed in this way, the torque is not significantly reduced, and a practical torque can be generated. It would be obvious to one skilled in the art that the same effects can be achieved even if only the hole 30 of the first embodiment is formed.

[0039] Thus, in the first embodiment of the present invention, the rotor 10 is made lighter by forming the holes 30, and the inertia can be reduced without a significant decrease in torque. In particular, it is possible to provide a lightweight rotor 10 that can reduce inertia without a decrease in torque. Therefore, high acceleration of the electric motor 1 can be achieved with the rotor 10.

[0040] Fig. Fig. 8 is a radial cross-sectional view of a rotor core of an electric motor based on the first embodiment. Fig. The rotor core 10a of the rotor 10 shown in Fig. 8 is the one shown in Fig. 2, in which all permanent magnets 21a, 21b and the rotor 5 have been removed. Others in Fig. 8 are identical to those shown in relation to Fig. 2. Such a Fig. 8 shown rotor core 10a and the one in Fig.1, etc. are also included in the scope of the first embodiment of the present invention.

[0041] Although the embodiments of the present invention have been described in detail, the present invention is not limited to the individual embodiments described above. Various additions, replacements, modifications, or partial deletions may be made to these embodiments within the spirit of the invention or within the scope of the idea and purpose of the present invention, which can be particularly seen from the content described in the claims and their equivalents. For example, the order of each operation and the order of each process of the above-described embodiments are shown as examples and are not limited to them. The same applies when numerical values ​​or formulas are used in the description of the above-described embodiments. Furthermore, suitable combinations of some of the above-described embodiments are included within the scope of the present invention. List of reference symbols 1 electric motor 5 Wave 9 Stator 10 Rotor 10a Rotor core 11 first outer circumference 12 second outer circumference 20 magnetic slot 21 first magnetic slot 22 second magnetic slot 21a, 21b Permanent magnet 30 holes 31 first area 32 second area 33 Hypotenuse 33a first straight section 33b second straight section 41, 42 holes T approximately isosceles triangle QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 6.987.310 [0002, 0003]

Claims

[1] Rotor core, where a plurality of pairs of magnetic slots extending in an axial direction of the rotor core are formed in the rotor core, the plurality of pairs of magnetic slots are arranged at equal intervals in a radial cross section of the rotor core in the circumferential direction of the rotor core, each pair of magnetic slots of the plurality of pairs of magnetic slots includes a first magnetic slot inclined counterclockwise relative to a radius of the rotor core and a second magnetic slot inclined clockwise relative to the radius of the rotor core, a plurality of holes extending in the axial direction of the rotor core are further formed between the first magnetic slot and the second magnetic slot in each pair of magnetic slots, in the radial cross-section of the rotor core, each of the plurality of holes is formed by an approximately isosceles triangle whose apex angle faces the center of the rotor core and by an arc projecting from the base of the isosceles triangle toward the radially outer side of the rotor core, and at least a portion of the arc in each of the plurality of holes in the radial cross-section of the rotor core is positioned on the radially outer side of the rotor core relative to a first line segment between a portion of the first magnetic slot positioned at the outermost position of the rotor core and a portion of the second magnetic slot positioned at the outermost position of the rotor core. [2] The rotor core according to claim 1, wherein the outer periphery of the rotor core consists of a plurality of first outer peripheries and a plurality of second outer peripheries connecting each of the plurality of first outer peripheries, the plurality of first outer peripheries correspond to corresponding areas of the plurality of pairs of magnetic slots, the plurality of second outer peripheries correspond to regions between two pairs of magnetic slots that are adjacent to each other among the plurality of pairs of magnetic slots, and outermost regions of the plurality of first outer circumferences are positioned on the radially outer side of the rotor core relative to the outermost regions of the plurality of second outer circumferences. [3] Rotor core according to claim 2, wherein the plurality of first outer circumferences by at least one curve and the plurality of second outer circumferences is formed by at least one straight line. [4] The rotor core according to any one of claims 1 to 3, wherein each of the two hypotenuses of the approximately isosceles triangle has a first straight section extending from the base and a second straight section extending from a distal end of the first straight section toward the apex of the approximately isosceles triangle, and the intersection point between the first straight section and the second straight section is positioned outside the approximately isosceles triangle relative to the hypotenuse corresponding to the intersection point. [5] The rotor core according to any one of claims 1 to 4, wherein the length of the base of the approximately isosceles triangle is 1 / 3 or less of the length of the first line segment. [6] The rotor core according to any one of claims 1 to 5, wherein a through hole for a shaft to be inserted into the rotor core is formed, and the length of a third line segment positioned on the radius of the rotor core and connecting the outer edge of the through hole to the first outer circumference is shorter than ten times the distance from the first outer circumference to the arc on the third line segment. [7] Rotor having: the rotor core according to one of claims 1 to 6, a shaft inserted into the rotor core and magnets inserted into each of the pairs of magnetic slots of the rotor core. [8] Electric motor having: the rotor according to claim 7 and a stator arranged around the rotor.

Images