Skew rotor for an electric motor

Abstract

The electric motor comprises a stator having slots; and a rotor including a stack of rotor laminations, the rotor having: a first sub-stack of the rotor laminations, wherein the rotor laminations within the first sub-stack include a first rivet hole and a first magnet hole having a first permanent magnet; and a second sub-stack of the rotor laminations, wherein the rotor laminations within the second sub-stack include a second rivet hole and a second magnet hole having a second permanent magnet, and the orientation of the first sub-stack and the second sub-stack relative to each other provides a skew to the rotor.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 368,191, filed on July 12, 2022, entitled "SKEWED ROTOR FOR ELECTRIC MOTOR", the disclosure of which is hereby incorporated by reference in its entirety.

[0002] This specification relates to a skewed rotor for an electric motor.

Background Art

[0003] In recent years, transportation worldwide has been beginning to shift from power trains mainly driven by fossil fuels to more sustainable energy sources. Such increasingly popular power trains include electric motors powered by on - board energy storage units. The quality of the customer experience of a vehicle is at least partially determined by the performance of the electric motor, including factors such as noise, vibration, and harshness (NVH). Improving the performance of the power train regarding NVH provides an advantage to vehicle manufacturers.

Summary of the Invention

[0004] In one aspect, an electric motor comprises a stator having slots; and a rotor including a stack of rotor laminations, the rotor having: a first sub - stack of the rotor laminations, wherein the rotor laminations within the first sub - stack include a first rivet hole and a first magnet hole having a first permanent magnet; and a second sub - stack of the rotor laminations, wherein the rotor laminations within the second sub - stack include a second rivet hole and a second magnet hole having a second permanent magnet, and the orientation of the first sub - stack and the second sub - stack relative to each other provides a skew to the rotor.

[0005] The implementation may include any or all of the following features. The skew is based on the angle between adjacent slots of the stator. The skew is equal to approximately one half of the angle between the adjacent slots of the stator. All of the rotor laminations in the first and second sub-stacks have a common stamping pattern, and the second sub-stack is oriented opposite to the first sub-stack to provide the skew. The common stamping pattern includes an asymmetry of at least one subset of the first and second magnet holes with respect to the rotor radius. The first and second rivet holes do not have the asymmetry. The asymmetry includes that the subset of the first and second magnet holes is offset from the rotor radius in the rotor rotation direction. The rotor laminations in the first sub-stack have a first stamping pattern, and the rotor laminations in the second sub-stack have a second stamping pattern different from the first stamping pattern. The first stamping pattern is asymmetric with respect to the rotor radius, and the second stamping pattern is symmetric with respect to the rotor radius. The first and second rivet holes are symmetric with respect to the rotor radius. The electric motor further includes a first key in each of the rotor laminations of the first sub-stack and a second key in each of the rotor laminations of the second sub-stack. The first and second keys are symmetric with respect to the rotor radius. Each of the first and second magnet holes has a substantially trapezoidal shape, and the trapezoidal shape has a pair of parallel sides and a pair of non-parallel sides. Each of the parallel sides of the trapezoidal shape is offset from the rotor rotation direction. At least one of the non-parallel sides of the trapezoidal shape is substantially parallel to the rotor radius.

Brief Description of the Drawings

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[0012] Like reference numerals in the various drawings indicate like elements.

DETAILED DESCRIPTION OF THE INVENTION

[0013] This specification describes examples of systems and techniques for providing skew within a rotor of an electric motor. In some implementations, a common stamping pattern can be used for all rotor laminations within an electric motor, and each sub-stack of rotor laminations can be oriented relative to one another to provide skew to the rotor to cancel out slot harmonics and / or other targeted harmonics. In other implementations, the sub-stacks of rotor laminations can have different stamping patterns from one another, and the sub-stacks can be oriented relative to one another to provide skew to the rotor.

[0014] When an electric motor generates a rotating magnetic field using a stator, the stator has a finite number of slots. Any of a variety of numbers of slots can be used, including, but not limited to, 72 or 48 slots. Due to the finite number of slots, the magnetic field generated by the electric motor has a ripple of, for example, on the order of (72±p) or (48±p), where p is the number of pole pairs, corresponding to the number of stator slots. Such a ripple in the magnetic field can produce force and torque pulsation / ripple on the order of the number of slots. This can affect the NVH of a vehicle. The present subject matter presents an approach for addressing this and other situations and providing an improved electric motor.

[0015] The examples described herein refer to a vehicle. A vehicle is a machine that transports passengers or cargo, or both. A vehicle can have one or more motors that use at least one type of fuel or other energy source (e.g., electricity). Examples of vehicles include, but are not limited to, cars, trucks, and buses. The number of wheels can vary among different types of vehicles, and one or more (e.g., all) of the wheels can be used for vehicle propulsion. A vehicle can include a passenger compartment that accommodates one or more persons.

[0016] The examples described herein refer to a top, bottom, front, or back. These and similar expressions identify things or aspects relatively based on an explicit or arbitrary concept of perspective. That is, these terms are merely illustrative used for the purpose of explanation and do not necessarily indicate the only possible positions, directions, etc.

[0017] Figure 1 shows an example of an electric motor 100. The electric motor 100 can be used together with one or more other examples described elsewhere in this specification. The electric motor 100 is shown schematically, and some components are not shown for the sake of brevity. In particular, a rotor lamination 102 that is part of a rotor 104 within the electric motor 100 is shown. Also, a portion of a stator lamination 106 that is part of a stator 108 within the electric motor 100 is shown.

[0018] The rotor 104 can include a plurality of rotor laminations including, but not limited to, the rotor lamination 102, which together form a rotor body. The rotor 104 can also have a rotor shaft (not shown) positioned within an opening 110 and one or more end plates (not shown) at either or both ends of the rotor body.

[0019] The stator 108 can include a plurality of stator laminations including, but not limited to, the stator lamination 106, which together form a stator body. The stator 108 can also have stator windings (not shown) positioned within each of a plurality of slots 112 arranged in a pattern such that poles are formed by the stator laminations. The slots 112 can have any of a plurality of shapes including, but not limited to, substantially the shape shown. Each of the slots 112 can be positioned along a corresponding one of radii 114 from the center of the stator 108. Adjacent ones of the slots 112 can form an angle 117 with each other. Similarly, adjacent ones of the stator teeth 118 can form the above angle 117 with each other.

[0020] The geometry of the rotor lamination 102 can be defined by a stamping pattern. In some implementations, the manufacture of the rotor lamination 102 can begin with a metal sheet stock, which is then stamped or otherwise machined (e.g., cut) into its final shape in one or more operations. Here, the spatial configuration of the rotor lamination 102 is described in terms of the stamping pattern, regardless of the specific operations that can be performed in the manufacture of the rotor lamination 102. In the following, the stamping pattern is illustrated with reference to the rotor radius or rotor diameter. Here, rotor diameters 116A - 116B are shown for illustration purposes, and rotor diameters 116A - 116B are perpendicular to each other.

[0021] The rotor lamination 102 can include holes for one or more purposes. Here, the rotor lamination 102 includes a plurality of magnet holes that can accommodate permanent magnets (not shown for clarity) for the rotor 104. Some of these magnet holes will be discussed as an example to illustrate the stamping pattern. The rotor lamination 102 includes magnet holes 118A - 118B, and these positions can be characterized with reference to the rotor diameter 116A. Similarly, the rotor lamination 102 includes magnet holes 120A - 120B, and these positions can be characterized in the same way with reference to the rotor diameter 116A.

[0022] Here, the rotor lamination 102 also includes rivet holes 122A - 122B among other rivet holes. Each of the rivet holes 122A - 122B can accommodate a rivet that extends axially through the rotor body to compress the rotor 104. Here, the rotor lamination 102 also includes keys 124A - 124B positioned at the edge of the opening 110. Each of the keys 124A - 124B can function to ensure proper orientation between the rotor 104 and other structures (e.g., a rotor shaft extending through the opening 110).

[0023] At least some of the magnet holes of the rotor lamination 102 may be offset with respect to the rotor diameters 116A and / or 116B. Here, the magnet holes 118A and 120A are positioned such that their respective edges abut the rotor diameter 116A. In contrast, the magnet holes 118B and 120B are rotated such that their respective edges are located at an angle 126 away from the rotor diameter 116A. The angle 126 is defined with reference to the center of the rotor 104. That is, the stamping pattern may have an asymmetry in at least one subset of the magnet holes 118A - 118B and 120A - 120B with respect to the rotor diameter 116A (or the rotor radius of the rotor diameter 116A). This asymmetry may include that the subset of magnet holes is offset from the rotor radius in the rotational direction of the rotor 104. For example, due to the angle 126, the magnet holes 118B and 120B may be characterized as being positioned with an offset in the rotor rotation direction from the rotor radius. Other offsets may be used additionally or alternatively.

[0024] That is, here, the offset between the magnet holes 118A - 118B extends to the right side of the rotor diameter 116A, while here the offset between the magnet holes 120A - 120B extends to the left side of the rotor diameter 116A. The perspective from which the current plan view of the rotor lamination 102 is shown may, in that case, optionally be referred to as the front side. In the view from the opposite side, the other surface of the rotor lamination 102 is visible, and these offsets may, in that case, alternatively be characterized as extending to the left and right sides of the rotor diameter 116A, respectively. The view from the opposite side may, in that case, optionally be referred to as the back side.

[0025] The magnet holes of the rotor lamination 102 can have one or more shapes. In some implementations, at least one of the magnet holes has a substantially trapezoidal shape. Here, all of the magnet holes within the rotor lamination 102 have a substantially trapezoidal shape of various sizes. The magnet hole 118A can have a trapezoidal shape with sides 128A - 128D. Sides 128A and 128C can be referred to as a pair of non - parallel sides since they are not parallel to each other. Sides 128B and 128D can be referred to as a pair of parallel sides since they are substantially parallel to each other. Here, sides 128B and 128D are not tangential to the rotor rotation direction of the rotor 104. Sides 128B and 128D are thus offset from the rotor rotation direction. Side 128A, which is part of the pair of non - parallel sides, is here substantially parallel to the rotor radius of the rotor diameter 116A.

[0026] In the stamping pattern of the rotor lamination 102, the rivet holes may not be offset or may not be asymmetric. Here, the rivet holes 122A - 122B are symmetric with respect to the rotor diameter 116A. Therefore, the rivet holes 122A - 122B do not have the asymmetry that some other aspects of the stamping pattern (e.g., the magnet holes 118A - 118B and 120A - 120B) may have.

[0027] In the stamping pattern of the rotor lamination 102, the keys may not be offset or may not be asymmetric. Here, the keys 124A - 124B are symmetric with respect to the rotor diameter 116A. Therefore, the keys 124A - 124B are symmetric, unlike one or more other aspects of the stamping pattern (e.g., the magnet holes 118A - 118B and 120A - 120B).

[0028] FIG. 2 shows an example of a rotor 200 having sub-stacks 202A and 202B arranged with skew. Sub-stack 202A and / or 202B can be used with one or more other examples described elsewhere in this specification. Here, sub-stacks 202A to 202B are shown separated from each other for illustration purposes. Each of sub-stacks 202A and 202B includes a plurality of rotor laminations arranged within their respective stacks. In particular, here, the rotor laminations of sub-stacks 202A to 202B have a common stamping pattern. For example, here, the rotor laminations of sub-stacks 202A to 202B can all have the stamping pattern of rotor lamination 102 in FIG. 1. Also, here, the rotor laminations 102 within sub-stack 202A are oriented in a direction opposite to those of sub-stack 202B. Here, in sub-stack 202A, the rotor laminations 102 are oriented such that the front side of the rotor laminations 102 (e.g., the side visible in FIG. 1) faces outward in the figure. Here, on the other hand, in sub-stack 202B, the rotor laminations 102 are oriented such that the back side of the rotor laminations 102 (e.g., the side not visible in FIG. 1) is visible in the figure. This orientation of sub-stacks 202A to 202B with respect to each other provides skew to the rotor 200. The skew can be based on the angle between adjacent slots of the stator used with the rotor 200 (or equivalently, the angle between adjacent teeth of the stator). In some implementations, the skew is based on angle 117 in FIG. 1. For example, to eliminate slot harmonics when the stator has 72 slots, the skew angle can be approximately half of 360 degrees divided by 72 slots, which is 2.5 degrees. This can be achieved by making angle 126 (in FIG. 1) within rotor lamination 102 approximately one-fourth (e.g., about 25%) of the angle between adjacent slots of the stator.

[0029] Figure 3 schematically shows the stamping patterns of the sub-stacks 202A to 202B of Figure 2. Here, the stamping pattern shows the positions of the magnet holes when superimposed on each other in the superposition 300 and viewed along the rotation axis of the rotor. Regarding the rivet holes, the stamping pattern can be symmetric when viewed from the front side and the back side. Therefore, here, the rivet holes 322A and 322B are common to the stamping patterns within the superposition 300.

[0030] On the other hand, the magnet holes do not have to be symmetric within the stamping pattern. Therefore, the magnet holes from each of the sub-stacks 202A to 202B may be individually visible within the superposition 300. Here, the magnet holes 318A and 318B belong to the sub-stack 202A and correspond to the magnet holes 118A and 118B in Figure 1 when viewed from the front side of the rotor lamination 102, respectively. Also, the magnet holes 318A' and 318B' belong to the sub-stack 202B and correspond to the magnet holes 118A and 118B in Figure 1 when viewed from the back side of the rotor lamination 102, respectively. Similarly, the magnet holes 320A and 320B belong to the sub-stack 202A and correspond to the magnet holes 120A and 120B in Figure 1 when viewed from the front side of the rotor lamination 102, respectively; the magnet holes 320A' and 320B' belong to the sub-stack 202B and correspond to the magnet holes 120A and 120B in Figure 1 when viewed from the back side of the rotor lamination 102, respectively. Therefore, the orientation of the sub-stacks 202A to 202B relative to each other causes a skew in the rotor.

[0031] Figures 4 - 5 show examples of rotor laminations 400 and 500 having different stamping patterns from each other. Rotor lamination 400 may have an asymmetric stamping pattern, similar to that of rotor lamination 102 in FIG. 1. Rotor lamination 400 has magnet holes that are asymmetric with respect to rotor diameters 402A and / or 402B. For example, magnet holes 404 and 406 within rotor lamination 400 are rotated such that their respective edges are located at an angle of 126' away from rotor diameter 402A. However, the asymmetry in rotor lamination 400 can be approximately twice as large as that of rotor lamination 102. For example, angle 126' can be approximately twice that of angle 126 in FIG. 1. Rotor lamination 400 has rivet holes and / or keys that are symmetric with respect to rotor diameters 402A and / or 402B.

[0032] In contrast, rotor lamination 500 may have a stamping pattern different from that of rotor lamination 400. For example, rotor lamination 500 has magnet holes that are symmetric with respect to rotor diameters 502A and / or 502B. As another example, rotor lamination 500 has rivet holes and / or keys that are similarly symmetric with respect to rotor diameters 502A and / or 502B.

[0033] FIG. 6 shows an example of a rotor 600 having sub-stacks 602A and 602B, each having the rotor laminations 400 and 500 of FIGS. 4-5 arranged with skew. Sub-stack 602A and / or 602B can be used with one or more other examples described elsewhere in this specification. Here, sub-stacks 602A-602B are shown separated from each other for illustrative purposes. Each of sub-stacks 602A and 602B includes a plurality of rotor laminations arranged within their respective stacks. For example, here, the rotor laminations of sub-stack 602A can all have the stamping pattern of rotor lamination 500. Since rotor lamination 500 is symmetric with respect to the magnet holes, rivet holes, and key, rotor lamination 500 shows the same stamping pattern when viewed from either the front side or the back side. As another example, here, the rotor laminations of sub-stack 602B can all have the stamping pattern of rotor lamination 400. Rotor lamination 400 is asymmetric with respect to the magnet holes and symmetric with respect to the rivet holes and key. Rotor lamination 400 can thus be oriented such that either the front side or the back side is visible in this view. Sub-stacks 602A-602B can be oriented relative to each other to provide skew to rotor 600. The skew can be based on the angle of the slots of the stator used with rotor 600. For example, to eliminate slot harmonics when the stator has 72 slots, the skew angle can be approximately one-half of 360 degrees divided by 72 slots, which is 2.5 degrees. This can be achieved by setting the angle 126' (FIG. 4) within rotor lamination 400 to be approximately one-half (e.g., approximately 50%) of the angle of the slots of the stator.

[0034] FIG. 7 schematically shows the stamping patterns of the sub-stacks 602A to 602B in FIG. 6. Here, the stamping pattern shows the positions of the magnet holes when superposed on each other in the superposition 700 and viewed along the rotation axis of the rotor. Regarding the rivet holes, the stamping pattern may be symmetric when viewed from the front side and the back side. Therefore, here, the rivet holes 722A and 722B are common to the stamping pattern within the superposition 700.

[0035] On the other hand, the magnet holes do not have to be symmetric within the stamping pattern. Therefore, the magnet holes from each of the sub-stacks 602A to 602B may be individually visible within the superposition 700. Here, the magnet holes 718A and 718B belong to the sub-stack 602A and correspond to the stamping pattern of the rotor lamination 500. Also, the magnet holes 718A' and 718B' belong to the sub-stack 602B and correspond to the stamping pattern of the rotor lamination 400. Therefore, the orientation of the sub-stacks 602A to 602B relative to each other causes a skew in the rotor.

[0036] The terms "substantially" and "about" as used throughout this specification are used to account for and take into consideration minor variations such as those due to variations during processing. For example, they can refer to less than or equal to ±5%, for example less than or equal to ±2%, for example less than or equal to ±1%, for example less than or equal to ±0.5%, for example less than or equal to ±0.2%, for example less than or equal to ±0.1%, for example less than or equal to ±0.05%. Also, as used herein, indefinite articles such as "a" or "an" mean "at least one".

[0037] It is to be understood that all combinations of the above concepts and additional concepts discussed in more detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the subject matter of the invention disclosed herein. In particular, all combinations of the claimed subject matter that appear at the end of this disclosure are contemplated as being part of the subject matter of the invention disclosed herein.

[0038] A number of implementations have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of this specification.

[0039] In addition, the logical flows shown in the figures do not require the particular order, or sequential order, shown to achieve desirable results. In addition, other processes may be provided to, or processes may be eliminated from, the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.

[0040] Certain features of the described implementations have been shown as described herein, but now many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. Accordingly, it should be understood that the appended claims are intended to cover all such modifications and changes that fall within the scope of these implementations. They are presented by way of example only and not of limitation, and it should be understood that various changes in form and detail can be made. Except for mutually exclusive combinations, any part of the apparatus and / or method described herein can be combined in any combination. The implementations described herein can include various combinations and / or sub-combinations of the functions, components, and / or features of the different implementations described.

Claims

1. A stator having slots; and A rotor including a stack of rotor laminations, wherein the rotor comprises: A first sub-stack of the rotor laminations, wherein the rotor laminations within the first sub-stack include a first rivet hole and a first magnet hole having a first permanent magnet; and A second sub-stack of the rotor laminations, wherein the rotor laminations within the second sub-stack include a second rivet hole and a second magnet hole having a second permanent magnet, and an orientation of the first sub-stack and the second sub-stack with respect to each other provides a skew to the rotor, An electric motor.

2. The electric motor according to claim 1, wherein the skew is based on an angle between adjacent slots of the stator.

3. The electric motor according to claim 2, wherein the skew is equal to approximately one half of the angle between the adjacent slots of the stator.

4. All of the rotor laminations within the first sub-stack and the second sub-stack have a common stamping pattern, and the second sub-stack is oriented opposite to the first sub-stack to provide the skew, the electric motor according to claim 1.

5. The electric motor according to claim 4, wherein the common stamping pattern includes an asymmetry of at least one subset of the first magnet hole and the second magnet hole with respect to the rotor radius.

6. The electric motor according to claim 5, wherein the first rivet hole and the second rivet hole do not have the asymmetry.

7. The electric motor according to claim 5, wherein the asymmetry includes that the subset of the first magnet hole and the second magnet hole is offset from the rotor radius in the rotor rotation direction.

8. The rotor laminations within the first sub-stack have a first stamping pattern, and the rotor laminations within the second sub-stack have a second stamping pattern different from the first stamping pattern, the electric motor according to claim 1.

9. The electric motor according to claim 8, wherein the first stamping pattern is asymmetric with respect to the rotor radius, and the second stamping pattern is symmetric with respect to the rotor radius.

10. The electric motor according to claim 9, wherein the first rivet hole and the second rivet hole are symmetric with respect to the rotor radius.

11. The electric motor according to claim 1, further comprising a first key in each of the rotor laminations of the first sub-stack and a second key in each of the rotor laminations of the second sub-stack.

12. The electric motor according to claim 11, wherein the first key and the second key are symmetric with respect to the rotor radius.

13. The electric motor according to claim 1, wherein each of the first magnet hole and the second magnet hole has a substantially trapezoidal shape, and the trapezoidal shape has a pair of parallel sides and a pair of non-parallel sides.

14. The electric motor according to claim 13, wherein each of the parallel sides of the trapezoidal shape is offset from the rotor rotation direction.

15. The electric motor according to claim 13, wherein at least one of the non-parallel sides of the trapezoidal shape is substantially parallel to the rotor radius.

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