Rotor assembly with solid low friction layer and press fit sleeve

Abstract

The present invention relates to a rotor assembly with a solid low-friction layer and a press-fit sleeve. A rotor for an electric machine includes a rotor assembly having an outer surface and including a plurality of magnetic poles with permanent magnets. A solid layer is formed on the outer surface of the rotor assembly and has an outer surface with a first coefficient of friction that is lower than a second coefficient of friction of the outer surface of the rotor assembly. The rotor includes an outer sleeve. The rotor assembly is press-fit into the outer sleeve.

Description

[0001] introduction

[0002] The information provided in this section is for the purpose of generally presenting the context of this disclosure. To the extent described in this section, the works of the currently attributed inventors and aspects of the description that may not constitute prior art at the time of filing are neither explicitly nor implicitly considered to be prior art of this disclosure. Technical Field

[0003] This disclosure relates to electric motors, and more particularly to electric motors comprising rotor assemblies with press-fit sleeves. Background Technology

[0004] Electric vehicles, such as battery electric vehicles (BEVs), fuel cell vehicles, and hybrid vehicles, include one or more electric motors that operate as motors to propel the vehicle. The battery system can be recharged using mains power, from another vehicle, during regeneration, and / or by an internal combustion engine (for hybrid vehicle applications). During the operation of hybrid and / or electric vehicles, the power generated during braking can be used to recharge the vehicle's battery system. Instead of using mechanical brakes to brake the vehicle, the motor operates as a generator to brake the vehicle and generate power for recharging the battery system.

[0005] Some electric motors include a rotor assembly that comprises permanent magnets. During operation, the rotor assembly rotates within the stator to generate torque or to produce power. Webs and bridge structures are typically used for structural support in the flux path. It is understood that the rotor assembly needs to be robust because it is subjected to stresses from mechanical, electrodynamic, and magnetic forces. Summary of the Invention

[0006] A rotor for an electric motor includes a rotor assembly having an outer surface and including a plurality of magnetic poles with permanent magnets. A solid layer is formed on the outer surface of the rotor assembly and has an outer surface having a first coefficient of friction lower than a second coefficient of friction of the outer surface of the rotor assembly. The rotor includes an outer sleeve. The rotor assembly is press-fitted into the outer sleeve.

[0007] Among other features, the solid layer has a thickness of 0.2 mm or less. The outer sleeve comprises carbon fiber. The solid layer comprises a polymer material. The polymer material comprises a thermoplastic material. The thermoplastic material is selected from the group consisting of polybenzimidazole, polytetrafluoroethylene, and polyoxymethylene.

[0008] In other examples, the solid layer comprises a thermosetting material. Thermosetting materials are selected from the group consisting of epoxy resins, phenolic resins, and polyurethanes.

[0009] Among other characteristics, lubricating additives are added to the polymer material. The lubricating additives are selected from the group consisting of graphite, wax, and ceramics. The solid layer has a compressive strength greater than or equal to 50 MPa and a strength less than or equal to 30 ppm / L. 0 C is the coefficient of thermal expansion.

[0010] Among other features, the solid layer includes a ceramic material. The ceramic material is selected from the group consisting of tungsten disulfide, molybdenum disulfide, titanium nitride, and titanium carbide.

[0011] A method for manufacturing a rotor for an electric motor includes: providing a rotor assembly comprising a plurality of rotor portions and having an outer surface; and forming a solid layer on the outer surface of the rotor assembly. The solid layer has a first coefficient of friction lower than a second coefficient of friction of the outer surface of the rotor assembly. The method includes press-fitting the rotor assembly into an outer sleeve.

[0012] Among other features, the method includes performing at least one of grinding, sanding, and machining on the outer surface of the solid layer prior to press fitting. The method also includes applying a lubricant to the outer surface of the solid layer prior to press fitting.

[0013] Among other features, the method includes cooling the rotor assembly to a temperature less than or equal to -20°C before press fitting.

[0014] Among other features, the solid layer has a thickness of 0.2 mm or less. The outer sleeve comprises carbon fiber. The solid layer comprises a thermoplastic selected from the group consisting of polybenzimidazole, polytetrafluoroethylene, and polyoxymethylene.

[0015] Among other features, the solid layer includes one of the following: a thermosetting material selected from the group consisting of epoxy resin, phenolic resin and polyurethane; or a ceramic selected from the group consisting of tungsten disulfide, molybdenum disulfide, titanium nitride and titanium carbide.

[0016] The present invention provides the following technical solutions.

[0017] Technical Solution 1. A rotor for an electric motor, comprising:

[0018] A rotor assembly having an outer surface and including multiple magnetic poles with permanent magnets;

[0019] A solid layer formed on the outer surface of the rotor assembly and having an outer surface having a first coefficient of friction lower than a second coefficient of friction of the outer surface of the rotor assembly; and

[0020] Outerwear,

[0021] The rotor assembly is press-fitted into the outer sleeve.

[0022] Technical Solution 2. The rotor assembly according to Technical Solution 1, wherein the solid layer has a thickness of less than or equal to 0.2 mm.

[0023] Technical Solution 3. The rotor assembly according to Technical Solution 1, wherein the outer sleeve comprises carbon fiber.

[0024] Technical Solution 4. The rotor assembly according to Technical Solution 1, wherein the solid layer comprises a polymer material.

[0025] Technical Solution 5. The rotor assembly according to Technical Solution 4, wherein the polymer material includes a thermoplastic material.

[0026] Technical Solution 6. The rotor assembly according to Technical Solution 5, wherein the thermoplastic material is selected from the group consisting of polybenzimidazole, polytetrafluoroethylene and polyoxymethylene.

[0027] Technical Solution 7. The rotor assembly according to Technical Solution 1, wherein the solid layer comprises a thermosetting material.

[0028] Technical Solution 8. The rotor assembly according to Technical Solution 7, wherein the thermosetting material is selected from the group consisting of epoxy resin, phenolic resin and polyurethane.

[0029] Technical Solution 9. The rotor assembly according to Technical Solution 4, wherein a lubricating additive is added to the polymer material.

[0030] Technical Solution 10. The rotor assembly according to Technical Solution 9, wherein the lubricating additive is selected from the group consisting of graphite, wax and ceramic.

[0031] Technical Solution 11. The rotor assembly according to Technical Solution 5, wherein the solid layer has a compressive strength greater than or equal to 50 MPa and a compressive strength less than or equal to 30 ppm / 0 C is the coefficient of thermal expansion.

[0032] Technical Solution 12. The rotor assembly according to Technical Solution 1, wherein the solid layer comprises a ceramic material.

[0033] Technical Solution 13. The rotor assembly according to Technical Solution 12, wherein the ceramic material is selected from the group consisting of tungsten disulfide, molybdenum disulfide, titanium nitride and titanium carbide.

[0034] Technical Solution 14. A method for manufacturing a rotor for an electric motor, comprising:

[0035] A rotor assembly comprising multiple rotor sections and having an outer surface is provided;

[0036] A solid layer is formed on the outer surface of the rotor assembly.

[0037] Wherein, the solid layer has a first coefficient of friction that is lower than the second coefficient of friction of the outer surface of the rotor assembly; and

[0038] The rotor assembly is press-fitted into the outer sleeve.

[0039] Technical Solution 15. The method according to Technical Solution 14 further includes performing at least one of grinding, sanding, and machining on the outer surface of the solid layer before the press fit.

[0040] Technical Solution 16. The method according to Technical Solution 14 further includes applying a lubricant to the outer surface of the solid layer before the press fit.

[0041] Technical Solution 17. The method according to Technical Solution 14 further includes cooling the rotor assembly to a temperature less than or equal to -20°C before the press-fit.

[0042] Technical Solution 18. The method according to Technical Solution 14, wherein:

[0043] The solid layer has a thickness of less than or equal to 0.2 mm; and

[0044] The outer sleeve comprises carbon fiber.

[0045] Technical Solution 19. The method according to Technical Solution 14, wherein the solid layer comprises a thermoplastic selected from the group consisting of polybenzimidazole, polytetrafluoroethylene and polyoxymethylene.

[0046] Technical Solution 20. The method according to Technical Solution 14, wherein the solid layer comprises one of the following:

[0047] Thermosetting materials, selected from the group consisting of epoxy resins, phenolic resins, and polyurethanes; or

[0048] Ceramics, selected from the group consisting of tungsten disulfide, molybdenum disulfide, titanium nitride and titanium carbide.

[0049] Further applications of this disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0050] This disclosure will be understood more fully from the detailed description and accompanying drawings, in which:

[0051] Figure 1A This is a side view of an example rotor assembly including a press-fit sleeve;

[0052] Figure 1B This is a side view of an example of the magnetic pole portion of a rotor assembly including a press-fit sleeve;

[0053] Figure 2A This is a side view of an example rotor assembly according to the present disclosure, which includes a press-fit sleeve disposed on a solid low-friction layer;

[0054] Figure 2B This is a side view of the magnetic pole portion of an example rotor assembly according to the present disclosure, the rotor assembly including an outer sleeve disposed on a solid low-friction layer;

[0055] Figure 3 It is based on this disclosure for use in Figure 2B A flowchart illustrating an example of a method for forming a solid low-friction layer on the outer surface of a rotor assembly; and

[0056] Figure 4 This is a flowchart illustrating an example of a method for press-fitting a rotor assembly into an outer sleeve.

[0057] In the accompanying drawings, reference numerals may be used repeatedly to identify similar and / or identical elements. Detailed Implementation

[0058] The rotor assembly according to this disclosure for use in an electric motor is reinforced by an outer sleeve. The rotor assembly is press-fitted into the outer sleeve during assembly. The rotor assembly includes a solid low-friction layer formed on the outer surface of the laminations of the rotor assembly to facilitate the press-fit. In some examples, the outer sleeve is made of carbon fiber (CF). Prior to press-fitting the outer sleeve, the solid low-friction layer is applied to the outer surface of the rotor assembly at the rotor-sleeve interface to reduce friction and improve the ease of assembling the press-fit sleeve onto the rotor assembly.

[0059] The solid low-friction layer allows for the use of lower forces during assembly. This, in turn, reduces the manufacturing cost of the rotor assembly by decreasing the likelihood of damage to the sleeve and / or rotor assembly during the assembly process. The method described herein also enables the use of higher compressive stresses in the sleeve via press fitting, as the possibility of stress / damage caused by friction is reduced. Furthermore, press fitting the sleeve to a rotor assembly with a low-friction outer layer is more cost-effective and manufacturing-friendly than other processes involving directly winding the sleeve onto the rotor assembly.

[0060] Now for reference Figure 1A and Figure 1B An example of rotor assembly 6 is shown. Figure 1A In the diagram, rotor assembly 6 is shown as comprising multiple magnetic poles 8 and an outer sleeve 9, such as a carbon fiber sleeve. Figure 1BThe image shows an example of the rotor portion 10 of the rotor assembly 6. In this example, the rotor portion 10 corresponds to a single magnetic pole, and the rotor assembly 6 includes eight magnetic poles, although additional or fewer magnetic poles may be used.

[0061] The rotor portion 10 includes a plurality of laminations 11 defining a first “V”-shaped opening 12 and a second “V”-shaped opening 32. A bridge structure 15 is positioned radially across the outer portions 14 and 16 of the first “V”-shaped opening 12. Permanent magnets 20 and 22 are located in the first “V”-shaped opening 12 between the bridge structure 15 and the central portion 18 of the first “V”-shaped opening 12.

[0062] The bridge structure 43 is positioned radially across the outer portions 34 and 36 of the second “V”-shaped opening 32. Permanent magnets 40 and 42 are located in the second “V”-shaped opening 32 between the bridge structure 43 and the central portion 38 of the second “V”-shaped opening 32.

[0063] In this example, rotor portion 10 is webless. In other examples, rotor portion 10 includes a web structure (not shown). Filler material 19 is disposed in the central portion 18 of the first "V"-shaped opening 12 and the second "V"-shaped opening 32, and in other opening regions. In some examples, filler material 19 comprises a polymer, although other materials may be used.

[0064] The plurality of stacked plates 11 may include notches 46 and 48 located on opposite sides thereof. Protrusions 49 extending into the first “V” opening 12 and the second “V” opening 32 may be used to help position permanent magnets 20, 22, 40 and / or 42 therein.

[0065] The outer sleeve 9 has an interference fit to multiple laminations 11 to reinforce the rotor assembly 6. The outer sleeve 9 generates tensile stress within itself and compressive stress in the laminations and polymer material. This ensures that the deflection of the rotor assembly is sufficiently low to avoid impacting the stator. The compressive stress in the laminations typically requires the web, magnets, or polymer to support the load.

[0066] In some examples, permanent magnets 20, 22, 40, and 42 have a gap of ~0.1 mm with the first and second "V"-shaped openings in the laminations to allow insertion. Adding an outer sleeve 9 increases the effective air gap between the rotor and stator.

[0067] It is understandable that a sleeve, such as the outer sleeve 9, should provide compressive force. Therefore, the rotor assembly 6 is press-fitted into the sleeve. The advantages of this method include the fact that the sleeve can be mass-produced. Interference stress is generated relatively directly, and press-fitting is an assembly line-friendly process. The challenges of this method include the potential difficulty of achieving high levels of interference during press-fitting without damaging the sleeve.

[0068] Now for reference Figure 2A and Figure 2B An example of rotor assembly 100 is shown. Figure 2A In the diagram, the rotor assembly 100 is shown comprising a plurality of magnetic poles 104 and an outer sleeve 106 (such as a carbon fiber sleeve) disposed on a solid low-friction layer 108. Figure 2B The image shows an example of a rotor portion 110 of a rotor assembly 100. In this example, the rotor portion 110 corresponds to a single magnetic pole, and the rotor assembly 100 includes eight magnetic poles, although additional or fewer magnetic poles may be used.

[0069] The rotor portion 110 includes a plurality of laminations 111 defining a first “V”-shaped opening 112 and a second “V”-shaped opening 132. A bridge structure 115 is positioned radially across the outer portions 114 and 116 of the first “V”-shaped opening 112.

[0070] In this example, rotor assembly 100 includes a bridge and is webless. In other examples, rotor assembly 100 includes a web structure (not shown), or the rotor assembly is neither a bridge nor a web. Filler material 119 is located between permanent magnets in the central opening 118 and in other opening regions of the “V”-shaped opening. Permanent magnets 120 and 122 are located in the first “V”-shaped opening 112 between the bridge structure 115 and the central opening 118 (or, if a web structure is used, a web structure).

[0071] The bridge structure 143 is positioned radially across the outer portions 134 and 136 of the second “V”-shaped opening 132. Permanent magnets 140 and 142 are located in the second “V”-shaped opening 132 between the bridge structure 143 and the central portion 138 of the second “V”-shaped opening 132 (or a web structure if a web structure is used).

[0072] Multiple stacked plates 111 may include notches 146 and 148 located on opposite sides thereof. In some examples, one or more protrusions 149 extending inwardly into the first "V"-shaped opening 112 and the second "V"-shaped opening 132 may be used to position permanent magnets 120, 122, 140, and 142. If used, the protrusions 149 may extend from one or both facing surfaces of the first "V"-shaped opening 112 and the second "V"-shaped opening 132, such as... Figure 1B and Figure 2B As shown in the image.

[0073] A solid low-friction layer 108 is formed on the outer surface of the rotor portion 110. An outer sleeve 106 has an interference fit to the solid low-friction layer 108 to reinforce the rotor assembly 100. The press-fit outer sleeve 106 generates tensile stress within the outer sleeve 106 and compressive stress in the laminations and filler material. This ensures that the rotor deflection is sufficiently low to avoid impacting the stator.

[0074] In some examples, the permanent magnet typically has a gap of ~0.1 mm with the opening in the lamination to allow for insertion. Adding an outer sleeve 106 increases the effective air gap between the rotor and stator.

[0075] Now for reference Figure 3 This illustrates a method 200 for adding a solid low-friction layer to the outer surface of a rotor portion of a rotor assembly. At 204, the rotor assembly is assembled. In some examples, laminations are stamped, arranged, and bonded together using adhesives and / or mechanical interlocking. Permanent magnets are inserted into a "V"-shaped opening, and filler material is disposed in the opening area using molding or other processes.

[0076] At 208, a solid low-friction layer is formed on the outer surface of the rotor assembly (e.g., the radial outer surface of the laminations). At 210, the outer surface of the solid low-friction layer is optionally ground, polished, and / or machined, if desired. Grinding, polishing, or machining can be performed to provide the desired external shape and / or reduce the friction of the outer layer.

[0077] Before being press-fitted onto the outer sleeve, a solid low-friction layer is formed on the outer surface of the rotor assembly. One purpose of the outer sleeve is to reduce friction during the press-fit process to avoid damage to the rotor assembly or sleeve. The solid low-friction layer can be formed on the rotor assembly using molding processes such as transfer molding or injection molding. After curing, the molding material hardens and becomes the solid low-friction layer. A similar method is used, for example, to create slot insulation in the stator core. In some examples, the adhesion of the epoxy layer on the rotor assembly is aided by using coupling agents such as silanes.

[0078] Alternative procedures for producing the polymer layer include dip coating, spraying, or other processes. However, these alternative methods typically result in coatings with lower strength / hardness. The coatings are also often less uniform and typically require machining (unlike in the case of molding processes, where machining is optional). After application, the layer is cured or allowed to dry into a solid, low-friction layer.

[0079] After applying a solid, low-friction layer, grinding / polishing processes can be used to further smooth and round the layer. In some examples, careful machining can be performed on the outer surfaces of the rotor assembly, although care must be taken to avoid short circuits in the laminations.

[0080] In some examples, the thickness of the solid low-friction layer is sufficient to fill the distance from the lowest to the highest point on the rotor surface (relative to the radial distance from the rotor's central axis). In some examples, the solid low-friction layer has a coefficient of friction smaller than that of the outer surface of the rotor assembly's laminations. In other examples, the solid low-friction layer has a coefficient of friction less than 0.1. In some examples, the solid low-friction layer is very smooth and deformation under pressure is difficult to avoid.

[0081] In some examples, the solid low-friction layer has a thickness of less than 0.2 mm. The solid low-friction layer comprises a polymer material. In some examples, the polymer material comprises a thermoplastic. Non-limiting examples of suitable thermoplastics include polybenzimidazole, polytetrafluoroethylene, polyoxymethylene, or other thermoplastics.

[0082] In some examples, the solid low-friction layer comprises a thermosetting material. Suitable examples of thermosetting materials include epoxy resins, phenolic resins, polyurethanes, or other thermosetting materials. In other examples, the polymeric material comprises a lubricating additive, such as graphite, wax, ceramics, or other suitable lubricating additives.

[0083] In some examples, the polymer layer has a compressive strength of 50 MPa and less than 30 ppm / g due to the compressive force provided by the outer sleeve. 0 C is the coefficient of thermal expansion. In other examples, the solid low-friction layer comprises ceramics. Suitable ceramics include tungsten disulfide, molybdenum disulfide, titanium nitride, titanium carbide, or other suitable ceramics. In some examples, the solid low-friction layer is adhered to the rotor assembly surface by chemical adhesion.

[0084] In some examples, an additional lubricant, such as grease or oil, is applied to the outer surface of the low-friction surface to further reduce friction. In some examples, the rotor is cooled to -20°C or below (any temperature from -20°C to -200°C is beneficial) to reduce the outer diameter of the rotor assembly, thereby aiding press-fit operation.

[0085] exist Figure 4 In the method 250 for manufacturing a rotor assembly, the process involves producing an outer sleeve and then press-fitting the rotor assembly into the sleeve. At 260, the method includes winding filaments, such as carbon fiber, around a mandrel in the shape of the outer surface of the rotor assembly. At 262, resin is applied to the filaments and then cured. At 264, the sleeve is removed from the mandrel. At 266, the sleeve is cut to a predetermined length corresponding to the axial length of the rotor assembly. At 270, the rotor assembly having a low-friction outer layer is press-fitted into the sleeve.

[0086] Spatial and functional relationships between components (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “joined,” “linked,” “adjacent,” “right next to,” “on top of,” “above,” “below,” and “set on.” Unless explicitly described as “direct,” when describing the relationship between the first and second components in the foregoing disclosure, the relationship can be a direct relationship in which no other intermediate components exist between the first and second components, or an indirect relationship (spatially or functionally) in which one or more intermediate components exist between the first and second components. As used herein, the phrase “at least one of A, B, and C” should be interpreted as using the non-exclusive logic “OR” to represent logic (A or B or C) and should not be interpreted as representing “at least one of A, at least one of B, and at least one of C.”

[0087] In the accompanying drawings, the direction of the arrows typically indicates the flow of information (such as data or instructions) of interest. For example, when components A and B exchange various types of information, but the information transmitted from component A to component B is relevant to the illustration, the arrow can point from component A to component B. This unidirectional arrow does not imply that no other information is transmitted from component B to component A. Furthermore, for information transmitted from component A to component B, component B can send a request for the information to component A or receive an acknowledgment.

Claims

1. A rotor for an electric motor, comprising: A rotor assembly having an outer surface and including multiple magnetic poles with permanent magnets; A solid layer is formed on the outer surface of the rotor assembly and has an outer surface having a first coefficient of friction, which is lower than a second coefficient of friction of the outer surface of the rotor assembly. and Outerwear, The rotor assembly is press-fitted into the outer sleeve.

2. The rotor according to claim 1, wherein, The solid layer has a thickness of less than or equal to 0.2 mm.

3. The rotor according to claim 1, wherein, The outer sleeve comprises carbon fiber.

4. The rotor according to claim 1, wherein, The solid layer comprises a polymer material.

5. The rotor according to claim 4, wherein, The polymer material includes thermoplastic materials.

6. The rotor according to claim 5, wherein, Thermoplastic materials are polybenzimidazole, polytetrafluoroethylene, or polyoxymethylene.

7. The rotor according to claim 1, wherein, The solid layer comprises a thermosetting material.

8. The rotor according to claim 7, wherein, The thermosetting material is epoxy resin, phenolic resin, or polyurethane.

9. The rotor according to claim 4, wherein, Lubricating additives are added to the polymer material.

10. The rotor according to claim 9, wherein, The lubricating additive is graphite, wax, or ceramic.

11. The rotor according to claim 5, wherein, The solid layer has a compressive strength greater than or equal to 50 MPa and a strength less than or equal to 30 ppm / 0 C is the coefficient of thermal expansion.

12. The rotor according to claim 1, wherein, The solid layer comprises a ceramic material.

13. The rotor according to claim 12, wherein, The ceramic material is tungsten disulfide, molybdenum disulfide, titanium nitride, or titanium carbide.

14. A method for manufacturing a rotor for an electric motor, comprising: A rotor assembly comprising multiple rotor sections and having an outer surface is provided; A solid layer is formed on the outer surface of the rotor assembly. The solid layer has a first coefficient of friction that is lower than the second coefficient of friction of the outer surface of the rotor assembly; and The rotor assembly is press-fitted into the outer sleeve.

15. The method of claim 14, further comprising performing at least one of grinding, sanding, and machining on the outer surface of the solid layer prior to the press fit.

16. The method of claim 14, further comprising applying a lubricant to the outer surface of the solid layer prior to the press fit.

17. The method of claim 14, further comprising cooling the rotor assembly to a temperature less than or equal to -20°C prior to the press-fit.

18. The method of claim 14, wherein: The solid layer has a thickness of less than or equal to 0.2 mm; and The outer sleeve comprises carbon fiber.

19. The method of claim 14, wherein, The solid layer comprises a thermoplastic, which is polybenzimidazole, polytetrafluoroethylene, or polyoxymethylene.

20. The method of claim 14, wherein, The solid layer includes one of the following: Thermosetting materials, which are epoxy resins, phenolic resins, or polyurethanes; or Ceramics, which are tungsten disulfide, molybdenum disulfide, titanium nitride or titanium carbide.

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