Bearing assembly for electric vehicle drive motor

Abstract

The bearing assembly 20 comprises a first ring 22 defining a first rolling surface and a second ring 24 defining a second rolling surface opposite the first rolling surface. A plurality of rolling elements 26 are arranged between the first ring and the second ring in a manner that they roll-engage with the first and second rolling surfaces. A cup 50 is positioned outside one of the associated rings 22 and 24. Insulating sheet materials 48a to 48c are placed between the cup 50 and the associated ring 22 and 24 and are held in place by the cup 50.

Description

Technical Field

[0001] This application claims priority based on U.S. Provisional Patent Application No. 63 / 463,811, filed on May 3, 2023, which is hereby incorporated by reference in its entirety for all purposes.

[0002] The present invention generally relates to electric vehicles (EVs), and more particularly to an insulated bearing assembly used to rotatably support the shaft of an EV drive motor.

Background Art

[0003] As is well known, EVs utilize an electric motor instead of an internal combustion engine to effect wheel rotation. The motor has a stator that generates a magnetic flux to rotate a rotor. The rotor is typically held by a shaft supported by bearings for rotation. It is known that bearings used in such environments may experience pitching on the rolling surfaces. Specifically, the current passing through the bearing may generate a spark between the raceway and the rolling elements. Thereby, the surface metal may melt at the location where the spark occurs, which is known as "pitching". Such pitching may, in some cases, make the rolling surfaces wavy, and in any case, is considered harmful to the function of the bearing.

[0004] In many cases, the bearings used in electric motors are insulated to reduce pitching. In previous attempts to insulate bearings, an insulating coating or polymer material has been used on the OD or ID of the bearing. In other cases, the components of the bearing have been manufactured from non-conductive (ceramic) materials to impede current.

Summary of the Invention

Problems to be Solved by the Invention

[0005] This invention recognizes and addresses matters that should be considered in the configuration and methods of the prior art. [Means for solving the problem]

[0006] One aspect of the present invention provides a bearing assembly comprising a first ring defining a first rolling surface and a second ring defining a second rolling surface opposite to the first rolling surface. A plurality of rolling elements are arranged between the first and second rings in such a manner that they roll-engage with the first and second rolling surfaces. A cage is positioned outside one of the associated rings. An insulating sheet material is placed between the cage and the associated ring. Preferably, the insulating sheet material is held in place by the cage.

[0007] In some exemplary embodiments, the retainer includes a cylindrical portion. For example, the retainer may be in the shape of a cup having a radial flange at one end.

[0008] In some exemplary embodiments, the first ring and the second ring each have a first end face, a second end face, and a cylindrical surface between the first and second end faces. According to such embodiments, the cup has a first flange, a second flange, and a cylindrical portion that hold insulating sheet material to the first end face, the second end face, and the cylindrical portion of the associated first and second rings, respectively.

[0009] In some exemplary embodiments, the insulating sheet material may include a single insulating sheet material cut into a selected pattern. For example, the selected pattern may have a central hub from which a plurality of radial arms extend integrally. Each of these radial arms may have first and second tapering portions that act as hinges.

[0010] In some exemplary embodiments, the cup may be a drone cup. Furthermore, the first flange and cylindrical portion of the cup may be cured, while the second flange of the cup may not be cured.

[0011] Another aspect of the present invention provides a method for insulating a bearing having an inner ring, an outer ring, and a plurality of rolling elements between the inner and outer rings. One step of this method includes providing a cup having a first radial flange and an open end. Another step includes inserting a single insulating sheet material into the cup, having a central hub from which a plurality of radial arms extend integrally, such that the central hub is adjacent to the first flange and the radial arms fold in perpendicular to the central hub. This method also includes inserting a bearing into the cup so that the insulating sheet material fits between the outer ring of the bearing and the adjacent inner surfaces of the cup. A portion of the cup may be folded in to close the open end so that the bearing is held in place by the cup.

[0012] In yet another embodiment, the present invention provides a bearing assembly comprising a first ring defining a first rolling surface. A second ring is also provided defining a second rolling surface opposite to the first rolling surface. In this embodiment, each of the first and second rings has a first end face, a second end face, and a cylindrical surface between the first and second end faces. A plurality of rolling elements are arranged between the first and second rings in such a manner that they roll-engage with the first and second rolling surfaces. A cup is positioned outside one of the associated rings, the first and second rings, and the cup has a first flange, a second flange, and a cylindrical portion. An insulating sheet material is placed between the cup and the associated ring, the first and second rings, and the insulating sheet material is held in place by the cup.

[0013] The accompanying drawings incorporated herein and constituting part thereof illustrate one or more embodiments of the present disclosure and, together with the description, are useful in illustrating various principles of the present invention.

[0014] A complete and implementable disclosure of the present invention, including the best mode of the invention, is described herein, with reference to the accompanying drawings, and is intended for those skilled in the art. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram of an electric motor that can utilize one or more bearing assemblies configured according to the present invention. [Figure 2] This is a partial cross-sectional view of a conventional bearing assembly used in electric motors for electric vehicles (EVs). [Figure 3] This is a schematic diagram of a bearing assembly configured according to the present invention and usable in an electric motor. [Figure 4] This figure shows the insulating inserts that can be used in the bearing assembly shown in Figure 3. [Figure 5] This is a cross-sectional view obtained along line 5-5 in Figure 4. [Figure 6A] This figure shows a specific step in the manufacturing of the bearing assembly shown in Figure 3. [Figure 6B] This figure shows a specific step in the manufacturing of the bearing assembly shown in Figure 3. [Figure 6C] This figure shows a specific step in the manufacturing of the bearing assembly shown in Figure 3. [Modes for carrying out the invention]

[0016] The repeated use of reference numerals in this specification and drawings is intended to represent identical or similar features or elements of the inventions described herein.

[0017] Next, preferred embodiments of the present invention will be described in detail, one or more of which are shown in the accompanying drawings. Each embodiment is provided for illustrative purposes only, and not to limit the invention. In fact, it will be apparent to those skilled in the art that it is possible to modify or change the invention without departing from the scope and spirit of the invention. For example, further embodiments can be obtained by using features illustrated or described as part of one embodiment in another embodiment. Thus, the present invention encompasses such modifications and changes within the scope of the appended claims and their equivalents.

[0018] When used herein, but not limited to, terms referring to the orientation or position of a bearing assembly, such as “vertical,” “horizontal,” “top,” “bottom,” “above,” or “below,” refer to the orientation and relative position with respect to the orientation of the bearing assembly shown in Figure 1. Furthermore, as used in this disclosure and the appended claims, the term “or” means inclusive, not exclusive. That is, unless otherwise specified or as is evident from the context, the expression “X uses A or B” is intended to mean any of the natural and inclusive sortings. Thus, the expression “X uses A or B” is satisfied by any of the following: “X uses A,” “X uses B,” or “X uses both A and B.” Furthermore, the articles "a," "an," and "the" used in this document should generally be interpreted as meaning "one or more" unless otherwise specified or unless the context makes it clear that they refer only to singular nouns. The meaning of "in" may include "in" and "on." The word "at" may include "at," "adjacent to," and "on." The expression "in one embodiment" used herein may refer to the same embodiment, although it does not necessarily mean the same embodiment. The meanings established above are not necessarily limiting, but merely provide examples to help explain the terminology.

[0019] FIG. 1 is a schematic view of an electric motor 10 that can be used, for example, to provide propulsion force to an EV. The motor 10 includes a housing 12 that houses a fixed stator 14. The stator 14 generates a magnetic flux that causes the rotation of a rotor 16 that is concentric with the stator 14. The rotor 16 is held by a shaft 18, and the shaft 18 is supported for rotation by a pair of bearing assemblies 20 attached to the housing 12 at a fixed position relative to the housing 12. As will be understood by those skilled in the art, the shaft 18 extends outside the housing 12 so as to be appropriately connected to the drive train of the EV.

[0020] Before discussing the structure of the bearing assembly 20, it is helpful to explain in more detail a particular aspect of the prior art. Referring now to FIG. 2, a prior art bearing assembly 100 is attached to a housing 102 so as to rotatably support a shaft 104. The bearing assembly 100 has an inner ring 106 and an outer ring 108. As shown, the inner ring 106 and the outer ring 108 are concentric with each other and define opposing raceways in which a plurality of rolling elements 110 are disposed. The inner ring 106 is fixed to the shaft 104 between a radial surface 112 and a restraint ring 114. Similarly, the outer ring 108 is fixed to the housing 102 between a radial surface and a restraint ring 118. The rings 114 and 118 can be attached to the shaft 104 and the housing 102, respectively, by means such as screw connection, press fitting, snap ring, etc. As previously mentioned, the bearing assembly 100 can be made insulating by an insulating coating or polymer material on the OD or ID of the bearing, or by forming the components of the bearing from a non-conductive (ceramic) material.

[0021] A particular aspect of the bearing assembly 20 can be most easily described by referring to FIG. 3. As shown, the bearing assembly 20 has an inner ring 22 and an outer ring 24 that define opposing rolling surfaces (raceways), and a plurality of rolling elements 26 are disposed on the rolling surfaces. (For the sake of brevity, only a portion of the bearing assembly 20 is shown here, but those skilled in the art will understand that the rings 22 and 24 together completely surround the shaft 18.) In this embodiment, the rings 22 and 24 are concentric with each other, and the rolling elements 26 are formed as balls. However, those skilled in the art will understand that aspects of the present invention can be used in various types of bearings, including needle bearings, tapered roller bearings, and thrust bearings. The rolling elements themselves can take various forms, including the balls (shown), needles, cylindrical rollers, and tapered rollers.

[0022] The inner ring 22 is fixed to the shaft 18, and the outer ring 24 is fixed to the housing 12. In this regard, the shaft 18 defines a reduced-diameter portion 28 that defines a radial surface 30. During assembly, the inner ring 22 is slid and fitted onto the reduced-diameter portion 28 and held in contact with the radial surface 30 by a restraint ring 32. Similarly, the outer ring 24 is held between the radial surface 38 of the pocket 36 and a restraint ring 40 within an annular pocket 36 of the housing 12. In this case, the restraint ring 32 is screwed onto the shaft 18 via a thread 42. Similarly, the restraint ring 40 is screwed onto the housing 12 via a thread 44. However, those skilled in the art will understand that in various embodiments, other suitable means for holding the restraint rings 32 and 40, such as press-fitting, snap rings, etc., can be provided as necessary or desired. Further, the reduced-diameter portion 28 and / or the pocket 36 can include a function of facilitating the slidable arrangement of the bearing assembly 20. For example, in this embodiment, the pocket 36 defines a chamfer 46 that facilitates the insertion of the bearing assembly 20.

[0023] The bearing assembly 20 also includes a function to electrically isolate it from currents such as stray currents that may occur within the housing 12. In this regard, one or more insulators are provided between one or both of the bearing rings and the external structure. Preferably, the insulator can be a sheet-like structure made of a flexible insulating material that is held in contact with the surface of the bearing rings by a cup. In this regard, Figure 3 shows insulating sheets 48a and 48b adjacent to the end faces of the outer ring 24, and a sheet 48c adjacent to the outer cylindrical surface of the outer ring 24. It will be understood that sheets 48a and 48c have a radial orientation, and sheet 48c has a cylindrical orientation. Sheets 48a-48c are held in this position by suitable retaining elements in the form of a cup 50 having end flanges 50a and 50b arranged axially spaced together with the cylindrical portion 50c. The cup 50 can be formed as a metal drone cup, as will be described in more detail below. The cup 50 itself is conductive, but the bearing ring and rollers are isolated from the current by an insulating sheet.

[0024] In some embodiments, it will be understood that sheets 48a to 48c may be separate elements. For example, sheets 48a and 48b may be formed as discs having appropriate inner diameter (ID) and outer diameter (OD), and sheet 48c may have a tubular shape of a suitable ID. Such shapes may be continuous or non-continuous throughout the annular portion, as long as the gaps are not large enough to allow metal-to-metal contact and sufficient separation between the metal components is possible. For example, sheet 48c may be formed with slits that allow it to be easily wrapped around the outside of the outer ring 24.

[0025] Referring next to Figures 4 and 5, the insulating sheets 48a-c can be parts of a larger sheet 48 made of a flexible insulating material (e.g., a suitable polymer material with a thickness of about 500 μm or other suitable thickness) cut into a suitable pattern. For example, the sheets 48 can be punched out in large quantities at low cost from a continuous sheet of insulating material. In this embodiment, the sheet 48 has a rosette pattern in which a plurality of radial arms 52 extend from a central hub (or base ring) 54. The sheet 48 is preferably configured to avoid wrinkles or in-plane deformation which are necessary when wrapping it around the ends and OD of the bearing ring. In this case, the base ring 54 has an ID and OD that substantially match the face diameter of the bearing ring to be protected. Here there is a bendable transition section in the form of a first tapered section 56, which forms a hinge for folding the arms 52 against the OD of the bearing ring. The radially outer sheet section 58 of the tapered section 56 matches the axial length and is close to the circumference of the OD of the bearing ring to be protected as a whole. Here, the second bendable transition portion in the form of a second narrowing portion 60 forms a hinge for folding in an end pie portion 62 that protects the opposite side of the bearing ring. Thus, it will be understood by those skilled in the art that in this embodiment the base ring 54 corresponds to sheet 48a, the sheet portion 58 as a whole corresponds to sheet 48c, and the pie portion 62 as a whole corresponds to sheet 48b.

[0026] The sum of the widths of the seat portions 58 is preferably about 90% or more of the OD of the bearing ring, but the seat portions 58 should not overlap each other. It will be understood that the slightly uncovered portion of the OD of the bearing ring may have a gap the thickness of the shim of the cup 50, and that this gap should, in many cases, provide sufficient insulation to prevent current. Similarly, the gaps between the narrowed portions 56 and 60 at the corners between the OD and the end face of the bearing ring should also provide sufficient insulation to prevent current. If necessary or desired, the drone cup may also be formed with narrowed regions such as regions 64a-b (Figure 3), and the thickness of the gap at these locations may be increased.

[0027] Figures 6A-6C show a particular embodiment of the assembly of a bearing assembly according to an embodiment of the present invention. In this case, the cup 50 may be a drone cup formed from an annular metal sleeve, for example, made from low-carbon steel. Before assembling the other components to the cup 50, a first end flange 50a is formed on one end of the cup 50. At this point, the flange 50a and the cylindrical portion 50c may be heat-treated, while the portion that will become the end flange 50b may be left untreated. Alternatively, the portion that will become the end flange 50b may utilize a hot curl end method or a lower cost curl method. Next, the seat 48 is inserted into the open end of the cup 50, and the base ring 54 is adjacent to the first end flange 50a. As shown, the radial arm 52 is folded at a right angle at the narrowed portion 56.

[0028] As indicated by the arrows in Figure 6A, the inner ring 24 is then slidably inserted into the cup 50 until one of its end faces is adjacent to the base ring 54. As indicated by the arrows in Figure 6B, a portion 66 of the cup 50 is then folded in to capture the bearing ring 24, thereby forming the end flange 50b. The seat 48 is folded in accordingly at the reduced width portion 60 so that the fan-shaped portion 62 covers the opposite end face of the bearing ring 24.

[0029] In particular, since some anticipated applications utilize bearings pressed into aluminum housings, embodiments using unhardened drone cups are intended. The drone cups ensure good press-fitting within the housing bore, which is not lost over time. Press-fitting the drone cups onto the insulator should similarly maintain the insulator's contact with the bearing ring. If creep needs to be prevented, an end shape or contour can be provided on one of the bearing's end faces to allow the drone cups to bend (roughly similar to the keyways in bearings and keys made on the drone cups to prevent rotation).

[0030] While one or more preferred embodiments of the present invention have been described so far, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope and spirit of the invention.

Claims

1. A first ring defining the first rolling surface, A second ring defining a second rolling surface opposite to the first rolling surface, Between the first ring and the second ring, there are a plurality of rolling elements arranged in such a manner that they engage with the first rolling surface and the second rolling surface, A retainer positioned on the outside of the associated first ring and the second ring, An insulating sheet material is placed between the retainer and the associated one of the first ring and the second ring, and is held in a predetermined position by the retainer. A bearing assembly equipped with the following features.

2. The bearing assembly according to claim 1, wherein the retainer includes a cylindrical portion.

3. The bearing assembly according to claim 2, wherein the retainer is in the shape of a cup having a radial flange at one end thereof.

4. Each of the first ring and the second ring has a first end face, a second end face, and a cylindrical surface between the first end face and the second end face. The retainer is formed as a cup having a first flange, a second flange, and a cylindrical portion, which hold the insulating sheet material with respect to the first end face, the second end face, and the cylindrical portion of the first ring and the second ring, respectively. The bearing assembly according to claim 1.

5. The bearing assembly according to claim 4, wherein the insulating sheet material includes a single insulating sheet material cut into a selected pattern.

6. The selected pattern is the bearing assembly according to claim 5, having a central hub from which a plurality of arms extend integrally.

7. The bearing assembly according to claim 6, wherein each of the arms has first and second retractable portions that act as hinges.

8. The bearing assembly according to claim 4, wherein the cup is a drone cup.

9. The bearing assembly according to claim 8, wherein the first flange and the cylindrical portion of the cup are hardened.

10. The bearing assembly according to claim 9, wherein the second flange of the cup is not hardened.

11. A method for insulating a bearing having an inner ring, an outer ring, and a plurality of rolling elements between the inner ring and the outer ring, To provide a cup having a radial first flange and an open end, Insert a single insulating sheet material having a central hub from which multiple radial arms extend integrally into the cup, such that the central hub is adjacent to the first flange and the radial arms are folded perpendicular to the central hub, and Insert the bearing into the cup so that the insulating sheet material is contained between the outer ring of the bearing and the adjacent inner surface of the cup. A method that includes this.

12. The method according to claim 11, further comprising folding a portion of the cup to close the open end so that the bearing is held in place by the cup.

13. A first ring defining the first rolling surface, A second ring defining a second rolling surface opposite to the first rolling surface, Between the first ring and the second ring, there are a plurality of rolling elements arranged in such a manner that they engage with the first rolling surface and the second rolling surface, A cup having a first flange, a second flange, and a cylindrical portion, positioned on the outside of the associated first ring and the second ring, An insulating sheet material is placed between the cup and the associated one of the first ring and the second ring, and is held in a predetermined position by the cup. Equipped with, A bearing assembly in which each of the first ring and the second ring has a first end face, a second end face, and a cylindrical surface between the first end face and the second end face.

14. The bearing assembly according to claim 13, wherein the insulating sheet material is held with respect to the first end face, the second end face, and the cylindrical portion of the first and second rings, respectively.

15. The bearing assembly according to claim 14, wherein the insulating sheet material includes a single insulating sheet material having a central hub from which a plurality of arms extend integrally.

16. The bearing assembly according to claim 15, wherein each of the arms has first and second retractable portions that act as hinges.

17. The bearing assembly according to claim 13, wherein the cup is a drone cup.

18. The bearing assembly according to claim 17, wherein the first flange and the cylindrical portion of the cup are hardened.

19. The bearing assembly according to claim 18, wherein the second flange of the cup is not hardened.

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