Electric motor and assembly method thereof

Abstract

An electric motor assembly includes a stator having a plurality of stator laminations. Each stator lamination includes an annular body and a plurality of stator teeth extending radially inward from the annular body to an opening. A rotor is located in the opening. Each stator tooth defines a pocket, and a damping element is located in the pocket. The damping element includes a viscoelastic material. The pocket and the damping element are located in a position where the magnetic flux of the stator tooth is less than an adjacent area of ​​the stator tooth.

Description

Technical Field

[0001] The present disclosure relates to an electric motor, and more particularly to an electric motor with vibration reduction characteristics and an assembly method thereof. Background Art

[0002] Electric motors are used in a wide range of applications to convert electrical energy into mechanical rotation. Electric motors typically include a stator and a rotor. The stator generates a magnetic field via the application of an electric current, which is applied as a torque on the rotor, causing the rotor to rotate. The stator can generate a magnetic field via a direct current (DC) or alternating current (AC) configuration. The magnetic field both attracts and repels the rotor, generating a torque that causes it to rotate.

[0003] In some configurations, the electric motor includes a rotor with multiple permanent magnet poles and a stator with a multi-phase winding located in multiple stator slots. These electric motors are generally referred to as permanent magnet motors. The combination of the number of rotor poles and the number of stator slots determines the performance of the motor, such as output torque, power, torque ripple, and vibration / noise. A permanent magnet motor with a fractional number of stator slots per rotor, i.e., a fractional slot permanent magnet motor, provides high torque density, generally provides low torque ripple by skewing the rotor / stator poles, and provides high flux weakening capability. For example, some popular configurations include 9 slots and 6 poles, 12 slots and 8 poles, or 12 slots and 10 poles. Compared with the traditionally used electric motors with 12 slots, 8 poles, or 9 slots and 6 poles, electric motors with 12 slots and 10 poles have been shown to have advantageous characteristics. In fact, even without skewing, electric motors with 12 slots and 10 poles generally have lower torque ripples, higher power / torque density, and lower cogging torque. These attributes can result in lower costs and smaller packages compared to other configurations. However, the low order mode shape of the deflection of this electric motor configuration makes it more challenging in terms of noise, vibration and harshness (NVH). Various approaches have been proposed to address this problem, including electromagnetic solutions and structural solutions.

[0004] Electromagnetic solutions typically focus on reducing radial forces in the machine, or eliminating specific harmonics that contribute to low-order mode shapes. However, these solutions typically have a negative impact on the magnetic properties of the motor, including a negative impact on the average torque and the cogging torque. On the other hand, structural solutions have less impact on the electromagnetic performance of the motor. Physical components or features are implemented to dampen vibrations. Various implementations have been proposed, including profiling the outer circumference of the stator, using spring devices as dampers between the stator and the housing, and other implementations. However, these structural solutions typically include increasing the cost, weight, and complexity of the electric motor to only provide limited reductions in NVH.

[0005] Therefore, there has been a lot of interest in developing solutions to minimize NVH in electric motors. Summary of the invention

[0006] The present disclosure generally relates to a stator tooth for an electric motor. The stator tooth includes a base, a body portion extending radially inwardly from the base, and an interface portion extending from the body portion opposite the base. The interface portion defines a surface adjacent to a provided rotor. A pocket is defined by the stator tooth, and a damping element is located in the pocket.

[0007] One aspect of the disclosed embodiment includes a stator for an electric motor. The stator includes a plurality of stator laminations. Each of the plurality of stator laminations includes an annular body and a plurality of stator teeth extending radially inward from the annular body to an opening for placement of a provided rotor. At least one of the plurality of stator teeth defines a pocket in which a damping element is located.

[0008] Another aspect of the disclosed embodiment includes an electric motor assembly. The electric motor assembly includes a stator, the stator including a plurality of stator laminations. Each of the plurality of stator laminations includes an annular body and a plurality of stator teeth extending radially inward from the annular body to an opening. A rotor is located in the opening. At least one of the plurality of stator teeth defines a pocket, and a damping element is located in the pocket.

[0009] These and other aspects of the disclosure are disclosed in the following detailed description of the embodiments, the appended claims and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present disclosure can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, as is customary, the various features of the drawings are not drawn to scale. Instead, the sizes of the various features are arbitrarily enlarged or reduced for clarity.

[0011] Figure 1 An electric motor assembly according to the principles of the present disclosure is generally shown.

[0012] Figure 2 A stator tooth is generally shown according to a first embodiment of the present disclosure.

[0013] Figure 3 A stator tooth is generally shown according to a second embodiment of the present disclosure.

[0014] Figure 4 is a graphical representation of the normalized vibration response of various stator tooth configurations.

[0015] Figure 5 The magnetic flux passing through the stator teeth is shown when the electric motor assembly is powered by operation.

[0016] Figure 6 is a flow chart generally illustrating a method of forming stator teeth according to the principles of the present disclosure. DETAILED DESCRIPTION

[0017] The following discussion is directed to various embodiments of the present disclosure. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted or otherwise used to limit the scope of the present disclosure (including the claims). In addition, those skilled in the art will understand that the following description has a wide range of applications, and the discussion of any embodiment is only meant as an example of that embodiment, and is not intended to imply that the scope of the present disclosure (including the claims) is limited to that embodiment.

[0018] As mentioned above, electric motors are used in a wide range of applications to convert electrical energy into mechanical rotation. Electric motors generally include a stator and a rotor. The stator generates a magnetic field via the application of an electric current, which is applied as a torque on the rotor, causing the rotor to rotate. The stator can generate a magnetic field via a direct current (DC) or alternating current (AC) configuration. The magnetic field both attracts and repels the rotor to generate torque and cause it to rotate.

[0019] The electric motor includes poles in the form of permanent magnets or bundled wires in the stator. The number of poles generally corresponds to the torque output, where a larger number of poles produces a larger torque. The electric motor also includes slots, which determine the number of phases of available power. In applications that require a large amount of torque and multiple phases, such as in the automotive industry, there are usually a large number of poles and slots. For example, an electric motor with 12 slots and 10 poles has been shown to have characteristics superior to conventional electric motors with 12 slots, 8 poles or 9 slots, 6 poles. More specifically, even without deflection, an electric motor with 12 slots and 10 poles generally has lower torque ripple, higher power / torque density, and lower cogging torque. These properties can result in lower costs and smaller packages compared to other configurations. However, the low-order modal shape of the deflection of this electric motor makes it more challenging in terms of noise, vibration, and harshness (NVH). Various methods have been proposed to solve this problem, including electromagnetic solutions and structural solutions.

[0020] Electromagnetic solutions typically focus on reducing radial forces in the machine, or eliminating specific harmonics that contribute to low-order mode shapes. However, these solutions typically have a negative impact on the magnetic properties of the motor, including a negative impact on the average torque and the cogging torque. On the other hand, structural solutions have minimal impact on the electromagnetic performance of the motor. Physical components or features are implemented to suppress vibrations. Various implementations have been proposed, including profiling the outer circumference of the stator, using spring devices as dampers between the stator and the housing, and other implementations. However, these structural solutions typically include increasing the cost, weight, and complexity of the electric motor to only provide limited reductions in NVH.

[0021] Therefore, there may be a need for an electric motor assembly and method of assembling the same, such as described herein, that is configured to mitigate NVH. In some embodiments, the electric motor assembly includes a plurality of slots and a plurality of poles, and at least one damping feature integrated into the stator back-iron design to mitigate vibration without compromising the electromagnetic performance of the electric motor. In some embodiments, the electric motor assembly includes 12 slots and 10 poles.

[0022] In operation, the electric motor assembly can be used in a vehicle, such as a car, a truck, a SUV, a crossover, a minivan, a ship, an airplane, an all-terrain vehicle, a recreational vehicle, or other suitable vehicle. The vehicle can include any suitable propulsion system, including an internal combustion engine, one or more electric motors (e.g., an electric vehicle), one or more fuel cells, a hybrid (e.g., a hybrid vehicle) propulsion system, including a combination of an internal combustion engine, one or more electric motors, and / or any other suitable propulsion system. The vehicle can also include a steering system, such as a wire steering system, which converts a steering input into an output and ultimately turns the vehicle. The electric motor assembly described herein can be used in a variety of automotive applications, such as a steering system or a propulsion system. For example, the electric motor can be used in a wire steering system, a steering assist assembly, an autonomous driving steering, and other applications. In some embodiments, the electric motor assembly 10 can be configured as an AC or DC electric motor, and can be further configured for reverse flow of current to provide a generator function. In some embodiments, the electric motor assembly can also be used in other situations.

[0023] Figure 1 An electric motor assembly 10 is generally shown. The electric motor assembly 10 includes a stator 12 and a rotor 14. The stator 12 may define a plurality of stator laminations 13 that define a channel 16 along an axis A, and the rotor 14 is located within the channel 16. The stator laminations 13 of the stator 12 include a plurality of stator teeth 18 disposed circumferentially about the axis A. The stator laminations 13 may be stacked along the axis A. A plurality of slots 20 circumferentially space each stator tooth 18. The stator 12 includes at least one magnetic field actuator 22, such as a wound coil located in at least one of the slots 20, for generating a magnetic field. In some embodiments, the at least one magnetic field actuator 22 includes a wound coil in each slot 20. The rotor 14 may also include a plurality of magnetic elements 24 located within or around its outer surface for reacting to the generated magnetic field and causing the rotor 14 to rotate. The rotor 14 may be integral with a component of the vehicle, such as a drive shaft of a propulsion system, or otherwise attached to a component of the vehicle. Each stator lamination 13 also includes an annular body 26, and the stator teeth 18 may be integrally formed with or otherwise connected to the annular body 26 and extend radially inward from the annular body toward the rotor 14. More specifically, each stator tooth 18 includes a base portion 28 on the annular body 26, a body portion 30 extending radially inward, and an interface portion 32 tapering outward from the body portion 30 to define a circular cam surface that is approximately equal to or slightly larger than the circumference of the rotor 14. The stator laminations 13, the magnetic field actuator 22, and the rotor 14 are located within an electric motor housing 34. At least one mounting bracket 36 may connect the electric motor housing 34 to a larger component, such as a component of an automobile.

[0024] In operation, the magnetic field actuator 22 generates a magnetic field that interacts with the rotor 14 (e.g., magnetic element 24) to generate torque and cause the rotor 14 to rotate about the axis A. During rotation, the interaction between the magnetic field of the rotor 14 and the magnetic field actuator 22 generates a magnetic force on the teeth 18, which is then transmitted to the motor housing 34 and causes vibrations in the motor housing 34, and ultimately causes vibrations in the mounting bracket 36 and larger components connected thereto. When the electric motor assembly 10 is connected to a vehicle, such undesirable vibrations can negatively affect performance and the ride experience of the occupants. To absorb these vibrations, at least one of the teeth 18 includes a bag 38 that deforms when receiving the vibration force applied to the tooth 18 and blocks a portion of the vibration transmitted to the housing 34. Each bag 38 may also include a damping element 40, which is located in the bag 38 to further dampen the vibration. The damping element 40 may be formed of a material that exhibits viscosity, elasticity, or both. For example, the damping element 40 may include an elastic material such as a viscoelastic material. The viscoelastic material may provide both viscous and elastic damping properties. In some embodiments, the damping element 40 includes an amorphous polymer, a semi-crystalline polymer, a biopolymer, an asphalt material, or a combination thereof. In some embodiments, only one tooth 18 includes a pocket 38, each tooth 18 may include a pocket 38, only alternating teeth 18 may include a pocket 38, or only one of each pair of diametrically opposed teeth 18 may include a pocket 38. In some embodiments, each pocket 38 may include a damping element 40, alternating pockets 38 may include a damping element 40, or diametrically opposed teeth 18 may include two pockets 38 but only one damping element 40.

[0025] Reference now Figure 2, a first embodiment of a stator tooth 118 is shown, wherein the stator tooth 118 has been isolated from the stator laminations 113. The stator tooth 118 includes: a base 128; a body portion 130 extending radially inward; and an interface portion 132 tapering outwardly from the body portion 130 to define a circular cam surface that is substantially equal to or slightly larger than the circumference of the rotor 14. A pocket 138 is located in the center of the base 128 and defines a triangular shape. The triangle may include a circular head 142 located near the outer circumference of the annular body 126 and a tail 144 extending toward the axis A. The stator tooth 118 also includes a spring strip 145 located between the pocket 138 and the outer circumference of the annular body 126. The tail 144 may be defined by opposing edges 146, which may be symmetrical and rounded from the head 142 to the vertex 148. The head 142 may be rounded to define a circumference that is greater than, equal to, or less than the outer circumference of the annular body 126. In the illustrated arrangement, the head 142 is rounded to define a radius that is slightly less than the outer circumferential radius of the annular body 126. The opposing edge 146 of the tail 144 may be rounded radially inward from the head 142 at a radius that is less than the radius defined by the outer edge 150 of the head 142. The damping element 140 may be located in the pocket 138 and fill the entire pocket 138 or at least the entire cross-section of the pocket 138. As described, in some embodiments, the damping element 140 may not be disposed in the pocket 138, may be disposed in selected pockets 138, or may be disposed in each pocket 138.

[0026] Reference now Figure 3 , a second embodiment of a stator tooth 218 is shown, wherein the stator tooth 218 has been isolated from the stator laminations 213. The stator tooth 218 includes: a base portion 228; a body portion 230 extending radially inward; and an interface portion 232 tapering outwardly from the body portion 230 to define a circular cam surface that is approximately equal to or slightly larger than the circumference of the rotor 214. The pocket 238 is located in the center of the base 228 and defines a partially circular shape, such as a semi-elliptical shape. The semi-circular shape may include a substantially flat top edge 248 and a circular bottom edge 250 extending radially outward from opposite ends of the top edge 248. The circular bottom edge 250 may be defined by one radius (i.e., circular) or more than one radius (i.e., elliptical). The damping element 240 may be located in the pocket 238 and fill the entire pocket 238 or at least the entire cross-section of the pocket 238. Stator tooth 218 also includes spring bars 245 between pockets 238 and the outer circumference of annular body 226. As described, in some embodiments, damping element 240 may not be disposed in pockets 238, may be disposed in selected pockets 238, or may be disposed in each pocket 238.

[0027] In some embodiments, the annular body 26 may include embodiments of both stator teeth 138, 238 that are arranged alternately, or in diametrically opposed positions. In operation, the damping effect may be aggregated between various combinations of pockets, spring bars, damping elements, and additional portions of stator teeth. Referring now to Figure 4 , provides a graphical representation of simulation test results comparing the effectiveness of various configurations of a single tooth. During the simulation, a unit force with a fixed frequency is applied to the interface portion of the tooth, while the rest of the tooth is calculated as a fixed support. At the interface portion, the surface deformation is calculated as a function of the surface velocity. The graph illustrates the embodiment with a damping element ( Figure 2 and Figure 3 ), an embodiment with a bag but no damping element ( Figure 2 and Figure 3 ) and the normalized vibration response (e.g., radial velocity) per unit force exerted by the tooth without any pockets. The term "Original" refers to the design without any pockets, the term "Void" refers to the design with pockets but no damping element, "High LF" refers to the damping element comprising a viscoelastic material with a high loss factor, and "Stiff" refers to the stiffness of the damping element.

[0028] Reference now Figure 5 , shows the magnetic flux density of the tooth 18 when the damping pocket 38 is not considered. As shown, a location 60 substantially located in the center of the tooth 18 receives less magnetic flux than the surrounding area. It is expected that removing stator material at this location will have the least impact on motor performance. Therefore, pockets (e.g., pockets 138 and pockets 238), damping elements 40, and spring bars (e.g., spring bars 145 and spring bars 245) can be located in this area for damping purposes without affecting the magnetic performance of the motor. As such, before forming a tooth 18 with pockets (e.g., pockets 138 and pockets 238), the magnetic flux distribution can be considered to guide the location of the pockets (e.g., pockets 138 and pockets 238) for future similar configurations.

[0029] Reference now Figure 6, a method 300 for assembling stator teeth is provided. At 302, the method 300 includes modeling a stator assembly (e.g., a stator tooth) without a bag or a damping element to determine a magnetic flux in the stator tooth. At 304, the method 300 includes determining a location in the stator tooth with a smaller magnetic flux than other areas of the stator tooth (e.g., adjacent areas or surrounding areas). At 306, the method includes: forming a single stator tooth or multiple stator teeth with a bag in the location of the stator tooth with a smaller magnetic flux. At 308, the method 300 includes depositing a damping element in the bag. Step 308 may include injection, molding, or other strategies for placing the damping element. At 310, the method includes: modeling the formed single stator tooth or the formed multiple stator teeth with the bag and the damping element to determine the effect of the bag (i.e., the damping bag) and the damping element of the damping material on the vibration at the rear of the tooth. Repeating the assembly may only repeat steps 304 and 306 and may include forming stator laminations including at least one stator tooth having a pocket and a damping element.

[0030] The above discussion is meant to illustrate the principles and various embodiments of the present disclosure. Once the above disclosure is fully understood, many changes and modifications will become apparent to those skilled in the art. It is intended that the following claims be interpreted as including all such changes and modifications.

[0031] The word "example" is used herein to mean used as an example, instance, or illustration. Any aspect or design described herein as an "example" is not necessarily to be construed as being superior or advantageous to other aspects or designs. On the contrary, the use of the word "example" is intended to present concepts in a specific way. The term "or" used in this application is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clear from the context, "X includes A or B" is intended to mean any natural inclusive arrangement. That is, if X includes A; X includes B; or X includes A and B, then "X includes A or B" is satisfied in any of the above cases. In addition, unless otherwise specified or clearly pointed to a singular form from the context, the articles "one" and "an" used in this application and the appended claims should generally be interpreted as meaning "one or more". In addition, unless so described, the use of the term "one embodiment" or "an embodiment" throughout does not mean the same embodiment or embodiment.

[0032] The above-mentioned various embodiments, various implementations and various aspects have been described to allow easy understanding of the present disclosure and are not intended to limit the present disclosure. On the contrary, the present disclosure is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is given the broadest interpretation to cover all such modifications and equivalent structures permitted by law.

Claims

1. A stator tooth for an electric motor, comprising: base; a body portion extending radially inwardly from the base portion; an interface portion extending from the body portion opposite the base portion, the interface portion defining a surface adjacent to a provided rotor; a pocket defined by said stator teeth; as well as a damping element disposed in the bag; in The pocket and the damping element are located centrally within the base and adjacent an outer edge of the base opposite the body portion to define a spring bar.

2. The stator tooth according to claim 1, wherein: The damping element comprises an elastic material.

3. The stator tooth according to claim 1, wherein: The damping element includes a viscous material.

4. The stator tooth according to claim 1, wherein: The damping element comprises a viscoelastic material.

5. The stator tooth according to claim 1, wherein: The bag includes a head portion and a tail portion, wherein the head portion is located near an outer edge of the base portion opposite the body portion, and the tail portion extends toward the body portion.

6. The stator tooth according to claim 5, wherein: The head is at least partially defined by an outer edge of the head adjacent an outer edge of the base, wherein the outer edge of the head is rounded.

7. The stator tooth according to claim 6, wherein: The tail is defined by symmetrically opposed edges that are rounded from the head to the apex.

8. The stator tooth according to claim 7, wherein: The damping element extends between an outer edge of the head portion and an opposite edge of the tail portion.

9. The stator tooth according to claim 1, wherein: The bag includes a top edge located adjacent an outer edge of the base opposite the body portion and a bottom edge extending toward the body portion.

10. The stator tooth according to claim 9, wherein: The top edge is flat and the bottom edge is rounded.

11. The stator tooth according to claim 10, wherein: The damping element extends between the top edge and the bottom edge.

12. The stator tooth according to claim 1, wherein: The pocket is located in a location where the magnetic flux of the stator tooth is less than at least one adjacent region of the stator tooth.

13. A stator for an electric motor, comprising: a plurality of stator laminations; Each of the plurality of stator laminations includes an annular body and a plurality of stator teeth extending radially inwardly from the annular body to an opening for receiving a provided rotor; at least one of the plurality of stator teeth defines a pocket; as well as a damping element located in the bag; wherein The stator tooth includes a base portion and a body portion extending radially inward from the base portion; the pocket and the damping element are located in the center of the base portion and adjacent to an outer edge of the base portion opposite the body portion to define a spring bar.

14. The stator for an electric motor according to claim 13, wherein: Each of the plurality of stator teeth includes a pocket.

15. The stator for an electric motor according to claim 14, wherein: Each of the pockets includes a damping element positioned therein.

16. The stator for an electric motor according to claim 13, wherein: The pocket is located in a location where the magnetic flux of the stator tooth is less than at least one adjacent region of the stator tooth.

17. The stator for an electric motor according to claim 13, wherein: The damping element comprises a viscoelastic material.

18. An electric motor assembly comprising: a stator, comprising a plurality of stator laminations; Each of the plurality of stator laminations includes an annular body and a plurality of stator teeth extending radially inwardly from the annular body to an opening; a rotor located in the opening; at least one of the plurality of stator teeth defines a pocket; as well as a damping element located in the bag; wherein The stator tooth includes a base portion and a body portion extending radially inward from the base portion; the pocket and the damping element are located in the center of the base portion and adjacent to an outer edge of the base portion opposite the body portion to define a spring bar.

19. The electric motor assembly of claim 18, wherein: The damping element comprises a viscoelastic material.

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