Optimized ball bearing with reduced mass and improved lubrication features

Abstract

An optimized ball bearing for an electric vehicle is provided, the ball bearing having an inner ring or an outer ring having a radial thickness at least equal to the diameter of the ball, the ball bearing being provided with at least one annular recessed surface to reduce the mass of the ring. Each annular recessed surface may be formed as a chamfer, a fillet, or a groove. The annular recessed surface may be disposed on both the inner ring and the outer ring to improve lubricant flow.

Description

Technical Field

[0001] The present invention relates to bearings, and more particularly to ball bearings. Background Art

[0002] Ball bearings are well known and include at least an inner ring with an inner raceway, an outer ring with an outer raceway, and a plurality of balls arranged between the two rings and rolling on both the inner raceway and the outer raceway. The ball bearing selected for a particular application is generally based on the diameter of the shaft on which the bearing is to be mounted and the amount of load supported by the bearing. The appropriate bearing size is then selected from one of several commercially available ball bearings that are typically capable of fitting on the specified shaft size and supporting the indicated load.

[0003] Although this ball bearing selection process has proven to be very effective since the beginning of the ball bearing industry, it often results in the use of bearings that are larger and heavier than actually necessary to support the specified load. Particularly for applications such as electric vehicles, there is an incentive to reduce the size and weight of the various mechanical components to reduce energy consumption. Summary of the invention

[0004] In one aspect, the present invention is a ball bearing for an electric vehicle, the ball bearing supporting a load applied to a shaft of an electric motor of the vehicle and rotatably coupling the shaft to a housing. The ball bearing includes an inner ring having a centerline, an inner circumferential surface sized to fit on the shaft of the electric motor, an outer circumferential surface, a radial thickness defined between the inner circumferential surface and the outer circumferential surface, a first axial end, an opposite second axial end, and an inner raceway formed in the outer circumferential surface. An outer ring is arranged around the inner ring and has an outer circumferential surface, an inner circumferential surface, a radial thickness defined between the inner circumferential surface and the outer circumferential surface, a first axial end, an opposite second axial end, and an outer raceway formed in the inner circumferential surface. A plurality of balls are arranged between the inner raceway and the outer raceway, each ball having a ball diameter. If the ratio between the radial thickness of the inner ring and the ball diameter is at least 1.0, the inner ring includes at least one annular recessed surface formed between the outer circumferential surface and the first axial end and / or between the outer circumferential surface and the second axial end. Alternatively, if the ratio between the radial thickness of the outer ring and the ball diameter is at least 1.0, the outer ring includes at least one annular recessed surface formed between the inner circumferential surface and the first axial end and / or between the inner circumferential surface and the second axial end.

[0005] In addition, the plurality of balls traverse a pitch circle extending about the centerline, the pitch circle having a pitch circle diameter. The particular number of the plurality of balls and the ball diameter are selected to provide a value of the pitch circle diameter that satisfies the following formula:

[0006] X=π 2 *BD 2 *PD*ID; where LL≤X≤UL;

[0007] UL=(-2.4815*ID 3 )+(211.6*ID 2 )-(4568.1*ID)+38956; and

[0008] LL=(-23.511*ID 2 )+(2235.9*ID)-2856;

[0009] Among them, X is the suitability factor, BD is the ball diameter, PD is the pitch diameter, ID is the inner diameter of the inner ring, LL is the lower limit, and UL is the upper limit, thereby providing an optimized ball bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The foregoing summary of the invention and the detailed description of the preferred embodiments of the invention will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, there are shown in the accompanying drawings presently preferred illustrative embodiments. However, it should be understood that the invention is not limited to the precise configurations and instrumentalities shown. In the accompanying drawings:

[0011] Figure 1 is an axial cross-sectional view of a ball bearing optimized according to the present invention;

[0012] Figure 2 yes Figure 1 An enlarged view of the upper portion of

[0013] Figure 3 It passes through Figure 2 A view of line 3-3;

[0014] Figure 4 is an axial cross-sectional view of an alternative optimized ball bearing showing an outer ring sized to fit within a conventionally sized bore of a seat;

[0015] Figure 5 is an axial cross-sectional view of an optimized ball bearing showing an adapter sleeve for fitting the bearing into a conventionally sized bore of a seat;

[0016] Figure 6is a more diagrammatic, partially cut-away view of an electric vehicle and electric motor incorporating the bearing of the present invention;

[0017] Figure 7 is a perspective view of a preferred cage for use with an optimized ball bearing;

[0018] Figure 8 is a cutaway axial cross-sectional view of the upper portion of an optimized ball bearing showing a portion of a preferred cage mounted on a ball;

[0019] Fig. 9 is a cutaway axial cross-sectional view of an upper portion of an optimized ball bearing mounted about a shaft and within a seat, showing an external lubricant source having a passage through the shaft;

[0020] Fig.10 is a cutaway axial cross-sectional view of an upper portion of an optimized ball bearing mounted about a shaft and within a seat, showing an external lubricant source having a passage through the seat;

[0021] Fig.11 is a cutaway axial cross-sectional view of an upper portion of an optimized ball bearing having an inner ring with a relatively large radial thickness, showing an annular concave surface formed as chamfers;

[0022] Fig.12 is a cutaway axial cross-sectional view of an upper portion of an optimized ball bearing having an outer ring with a relatively large radial thickness, showing an annular concave surface formed as a chamfer;

[0023] Fig.13 is a cutaway axial cross-sectional view of an upper portion of an optimized ball bearing having an outer ring with a relatively large radial thickness, showing the outer ring having an asymmetric chamfer and the inner ring having a single chamfer; and

[0024] Fig.14 is a cutaway axial cross-sectional view of the upper portion of an optimized ball bearing having an inner ring with a relatively large radial thickness, showing that the inner ring has fillets and grooves, and the outer ring has symmetrical chamfers. DETAILED DESCRIPTION

[0025] Referring now in detail to the drawings, wherein like numerals are used to refer to like elements throughout, Figures 1 to 14 1 shows a ball bearing 10 for supporting a load L applied to a shaft S. The load L has a predetermined value and may be radial, axial, moment or any combination thereof, and the shaft S has an outer diameter OD SThe bearing 10 is preferably used in an electric vehicle V, and in particular for supporting a load L applied to an output shaft S of an electric motor 1 of the vehicle V, the shaft S being rotated about a central axis A. C More specifically, the ball bearings 10 are preferably arranged in a housing 2 that surrounds an electric motor stator 3 arranged around an electric motor rotor 4 mounted on a shaft S, with two of the bearings 10 each being positioned adjacent to a separate axial end of the rotor 4, such as Figure 6 As shown. The ball bearing 10 is formed according to the method of the present invention, as described in detail below, wherein the bearing 10 is designed to optimize the material usage of the bearing 10, in particular to optimize the number and size of the plurality of balls 12 required to support the load L, and to position the balls 12 on a pitch circle PC that is generally "smaller" (i.e., having a smaller pitch circle diameter PD value) compared to prior art design principles. Specifically, the ball bearing 10 is formed with a selected inner ring inner diameter ID, a determined number N of balls 12 having a specific diameter BD, to provide an optimized pitch circle diameter PD that satisfies the following formula:

[0026] X=π 2 *BD 2 *PD*ID; where LL≤X≤UL;

[0027] UL=(-2.4815*ID 3 )+(211.6*ID 2 )-(4568.1*ID)+38956; and

[0028] LL=(-23.511*ID 2 )+(2235.9*ID)–2856;

[0029] Where X is the fitness coefficient, LL is the lower limit, and UL is the upper limit, as described in further detail below.

[0030] Basically, the ball bearing 10 includes an inner ring 14 and an outer ring 16 arranged around the inner ring 14 and an optimized number N of balls 12, which are preferably retained in a cage 13, as described below. Specifically, the inner ring 14 has an axis A with respect to the shaft. C Coaxial center line CL( Figure 2 ), an inner circumferential surface 15A having an inner diameter ID, an opposite outer circumferential surface 15B having an outer diameter (not indicated), a first axial end 14a and an opposite second axial end 14b. The inner raceway 18 extends inwardly from the outer surface 15B and has an inner track diameter TD at a central position on the inner raceway 18. IThe inner raceway 18 is preferably centered between the axial ends 14a, 14b of the inner ring 14. In addition, the inner ring 14 has an axial length LA between the first axial end 14a and the second axial end 14b. I and a radial thickness TR defined between the inner circumferential surface 15A and the outer circumferential surface 15B I Preferably, the inner diameter ID is sized approximately equal to a designated outside diameter ODS of the shaft S, but most preferably, the inner diameter ID is sized to reduce a desired amount of interference between the inner race 14 and the shaft S.

[0031] In addition, the outer ring 16 includes an outer circumferential surface 17A having an outer diameter OD, an inner circumferential surface 17B having an inner diameter (not indicated), a first axial end 16a and an opposite second axial end 16b. The outer raceway 20 extends outward from the inner surface 17B and has an outer track diameter TD at a central position on the outer raceway 20. O The outer raceway 20 is preferably centered between the axial ends 16a, 16b of the outer ring 16. In addition, the outer ring 16 has an axial length LA between the first axial end 16a and the second axial end 16b. O and a radial thickness TR defined between the inner circumferential surface 17B and the outer circumferential surface 17A O .

[0032] In the preferred application of the electric vehicle V, the balls 12 are preferably made of a ceramic material, but may also be made of any other suitable material for other applications, such as bearing steel, etc. The number N of balls 12 is determined or calculated to provide only the amount / number of balls 12 required to support a specific load L with a certain safety factor (i.e., the balls 12 will support a certain amount of load in excess of the specific load L to avoid failure). Therefore, the bearing 10 is designed to have a minimum acceptable number N of balls 12 that will provide the required load L support and enable the other dimensions of the bearing 10 to be sized to provide the required strength and structural integrity of the ball bearing 10.

[0033] More specifically, the balls 12 have a specific ball diameter BD and are preferably selected from a plurality of standard ball sizes, each standard ball size having a ball diameter of a different value than the ball diameter of each other standard ball size. Each ball 12 of a particular standard size is known to have a certain "load capacity" or ability to safely support up to a certain amount of load. In addition, a larger ball formed from a given material (e.g., bearing steel, ceramic, etc.) has the ability to support a greater load than a smaller ball formed from the same material, and vice versa. However, as another option, the balls 12 can be manufactured specifically for the bearing 10 and can each have a non-standard ball diameter BD.

[0034] In either case, once a particular ball size having a particular ball diameter BD has been selected, the number N of balls 12 required to support the particular load L can be determined by dividing the load L by the load capacity of each ball 12 having the selected ball size. That is:

[0035] Number of balls (N) = load (L) / ball load capacity

[0036] Once the number N of balls 12 is calculated or determined, the circumference of the pitch circle PC can be determined, which is a theoretical circle extending through the center of each ball 12 as the ball 12 circulates between the inner race 14 and the outer race 16. Specifically, the circumference CP of the pitch circle PC is calculated by multiplying the determined number N of balls 12 by the ball diameter BD, or:

[0037] CP=N*BD

[0038] Since there is usually a desired spacing distance SD between each pair of two adjacent balls 12 (usually established or maintained by a ball cage (not shown)), the circumference CP of the pitch circle PC spacing can be more accurately calculated as follows:

[0039] CP=(N*BD)+(N*SD)

[0040] Next, after determining the circumference CP of the pitch circle PC, the diameter of the pitch circle or "pitch diameter" PD can be calculated by dividing the calculated value of the circumference CP of the pitch circle PC by the value of the mathematical constant pi or "π", as is known under basic geometric principles. The calculation of the pitch circle diameter can be represented by the following formula:

[0041] PD=CP / π=(N*BD) / π

[0042] Alternatively, taking into account the spacing distance SD between the balls 12, the pitch circle diameter PD may alternatively be calculated as follows:

[0043] PD=CP / π=[(N*BD)+(N*SD)] / π

[0044] Once the pitch diameter PD for the desired number N of balls 12 having a selected ball size is known, the appropriateness or "suitability" of a particular value of the pitch diameter PD is determined by calculating a "suitability factor" X for the calculated pitch diameter PD based on the selected ball size (i.e., ball diameter BD) and the determined inner diameter ID of the inner ring 14. The suitability factor X has been determined taking into account various factors of the bearing design such as the minimum required radial thickness of the inner ring 14 between the inner raceway 18 and the inner circumferential surface 15A for a specific inner ring inner diameter ID, the minimum axial length LA of the inner ring 14 for a specific ball diameter BD and inner ring inner diameter ID. I Etc. Using these and other factors, a detailed discussion of which is beyond the scope of this disclosure, the suitability coefficient X is represented by the following formula:

[0045] X=π 2 *BD 2 *PD*ID

[0046] Furthermore, a particular value of the pitch circle diameter PD calculated or derived as discussed above is determined to be acceptable or "validated" when the value of the suitability coefficient X is between an upper limit UL and a lower limit LL (which is calculated as follows):

[0047] UL=(-2.4815*ID 3 )+(211.6*ID 2 )–(4568.1*ID)+38956; and

[0048] LL=(-23.511*ID 2 )+(2235.9*ID)–28567.

[0049] Thus, when a particular value of the pitch diameter PD based on the selected ball size (i.e., ball diameter BD) is verified or found to be acceptable using the suitability factor X, the remaining dimensions of the ball bearing 10 can be designed or planned based on the available envelope or space of the bearing 10 between the shaft S and the external member M (e.g., seat, hub, etc.) and other conventional bearing design factors. Such dimensions include the inner race diameter TD I 、Outer track diameter TD O , the axial length LA of the inner ring 14 I and the axial length LA of the outer ring 16 O, the outer diameter OD of the outer ring 16, etc. In any case, it is preferred to manufacture at least one ball bearing 10 having a verified pitch circle diameter PD, a selected ball diameter BD and a determined number N of balls 12, as well as other calculated bearing dimensions discussed above and discussed in further detail below.

[0050] More specifically, the inner raceway diameter TD of the inner raceway 18 of the inner ring 14 is I Calculated by subtracting the specific ball diameter BD from the pitch circle diameter PD. Similarly, the outer raceway diameter TD of the outer raceway 20 of the outer ring 16 is O It can be calculated by adding the pitch circle diameter PD to the specific ball diameter BD. In addition, the axial length LA of the inner ring 14 is I can be calculated as the sum of the ball diameter BD and twice the value of the desired shoulder axial length (not indicated), and the axial length LA of the outer ring 16 O It can be calculated as the sum of the ball diameter BD and twice the value of the desired shoulder axial length (not indicated). Preferably, the axial lengths of the inner ring 14 and the outer ring 16 are equal to provide a common bearing axial length SLB, but as an alternative, in certain applications, the axial lengths of the inner ring 14 and the outer ring 16 may be different from each other.

[0051] In addition, the outer diameter OD of the outer ring 16 can have a commercially available bearing (especially a bearing whose inner diameter of the inner ring is equal to the determined inner diameter ID of the inner ring, such as Figure 3 When the customer has formed the opening or hole B for the bearing 10 based on conventional bearing design principles, the overall size of such a bearing 10 may be appropriate. However, the outer diameter OD of the bearing outer ring 16 preferably has a value smaller than the outer diameter of commercially available bearings and larger than the sum of the pitch circle diameter PD and the ball diameter OD, as shown in FIG. Figure 1 In other words, the outer diameter OD is smaller than the outer track diameter TD. O The value of φ is greater than the appropriate radial thickness between the outer raceway 20 of the bearing outer ring 16 and the outer circumferential surface 17A.

[0052] As described above, the second method for determining the outer ring outer diameter OD takes advantage of the primary benefit of the present invention, which is the reduction in overall bearing size due to the calculation and implementation of a pitch circle diameter PD that is significantly reduced compared to the typical pitch circle diameter of prior art commercial bearings. This reduced bearing ring outer diameter OD not only reduces the weight of the bearing outer ring 16 (typically formed of a relatively heavy bearing steel), but also this reduced size allows for a corresponding increase in the material of the seat or hub in which the outer ring 16 is mounted, which seat or hub can be formed of a significantly lighter material (such as aluminum or even a rigid polymer material). In addition, even if the optimized bearing 10 is installed in an existing bore B or orifice sized by a conventional bearing selection process, an annular sleeve SL of a lightweight material (e.g., aluminum) can be provided to fill the space between the reduced size outer ring 16 and the existing bore / hole, such as Figure 5 shown.

[0053] However, if the pitch circle diameter PD determined for the selected ball size (i.e., ball diameter BD) is found to be unsuitable or invalid through the calculations discussed above or even when verified, another standard ball size having another specific ball diameter BD2 may be selected. Preferably, the other ball diameter BD2 is selected from a plurality of standard ball sizes, but as an alternative the other ball diameter BD2 may be selected or specified with a non-standard ball diameter BD2. The number N2 of balls 12 of the other ball size required to support the load L is then determined, and based on the determined number N2 of balls 12 of the other standard ball size, another pitch circle diameter PD2 of an alternative pitch circle PC2 of the ball bearing 10 is calculated as described above. Another fitness coefficient X2 may then be derived using the following formula:

[0054] X2=π 2 *BD2 2 *PD2*ID

[0055] Finally, when another suitability coefficient X2 has a value between the upper limit UL and the lower limit LL as described above, another pitch circle diameter PD2 is verified to be suitable for the ball bearing 10, and the upper limit UL and the lower limit LL are based only on the selected inner ring inner diameter ID and are therefore the same for all pitch circle diameters in a specific design application.

[0056] The process of selecting a particular ball size and calculating the pitch diameter PD based on the ball diameter BD, the determined inner ring inside diameter ID, and the applied load L can be repeated for as many different ball bearing diameters BD (i.e., standard ball sizes) as desired by a particular designer of the ball bearing 10. The ball bearing designer can then select one of the particular verified pitch diameters PD, PD2, etc. and the associated ball bearing diameters BD, BD2, etc. and then calculate or select the remaining size of the ball bearing 10 (as described above or as known from conventional bearing design factors). The selection of a particular ball diameter and pitch diameter combination can be based on which design produces the lowest friction as determined by an appropriate simulation tool.

[0057] Furthermore, since the design process is preferably iterative for many different ball sizes / diameters BD and involves various bearing sizes based on the calculated pitch diameter PD, the process is preferably automated by using an appropriate software program or other computerized means. In other words, preferably a computer software program is provided that is configured to receive the shaft outer diameter OD S and the value of the load L as input. The program is configured to perform the following steps: select the inner diameter ID of the inner ring 14 of the bearing, select a standard ball size / diameter BD, determine the number N of balls 12, calculate the pitch circle diameter PD, calculate the acceptability coefficient X, and then verify the calculated pitch circle diameter PD. The software program then provides at least one verified pitch circle diameter PD as output, and most preferably provides multiple verified pitch circle diameters PD, PD2, etc. and other bearing dimensions corresponding to each verified pitch circle diameter PD, such as the inner ring inner diameter ID, the bearing axial length LA, the recommended outer ring outer diameter OD, etc. The software program can also determine which combination of various bearing sizes produces the least amount of friction.

[0058] The bearing design process of the present invention produces a ball bearing 10 having a reduced pitch diameter PD and using balls 12 having a smaller ball diameter BD, thereby enabling a reduction in both the axial length LA of the bearing 10 and the outer diameter of the bearing 10 (i.e., the outer diameter OD of the outer ring of the bearing). This reduction in overall bearing size reduces the weight of the assembly into which the bearing 10 is mounted, and thus reduces energy consumption, and also generally results in reduced friction within the bearing 10, as compared to a bearing selected for a particular application in a previously known bearing selection process.

[0059] Reference Figure 7 and Figure 8The bearing retainer 13 used with the optimized ball bearing 10 formed according to the present invention is preferably "open-ended" for reasons discussed below. Specifically, the bearing retainer 13 preferably includes an annular "backbone" or base 30 and a plurality of arms 32 extending axially from the annular base 30. A plurality of pockets 34 are each defined between a single pair of adjacent arms 32, and each pocket 34 is configured to retain a single one of the balls 12. With this retainer structure, the annular base or skeleton 30 is located on one axial side of the ball 12, i.e., between the ball 12 and one axial end 14a or 14b of the inner race 14 and one axial end 16a or 16b of the outer race 16. Thus, the other axial side of the ball 12 is "open" and allows unimpeded access of lubricant to the ball 12, as discussed further below.

[0060] like Figures 9 and 10 As shown, the optimized ball bearing 10 is preferably used with an external lubricant source 40, which is configured to direct lubricant into the annular opening 19 defined between the first axial end 14a of the inner ring 14 and the first axial end 16a of the outer ring 16. The lubricant source 40 preferably includes a reservoir 42 containing a certain amount of lubricant and a channel 44 formed in the shaft S (such as Fig. 9 as shown) or formed in the seat 2 (as shown Fig.10 ), and has an outlet port 46. The outlet port 46 is axially spaced from the first axial ends 14a, 16a of the inner and outer rings 14, 16, and is configured to direct or discharge lubricant into the annular opening 19, as discussed further below.

[0061] Specific reference Fig.10 In certain applications, a particular ball bearing 10 optimized by the method of the present invention produces a ball 12 having a ball diameter BD that is proportional to the axial length LA of the inner ring 14. I and the axial length LA of the outer ring 16 O For example, the size of the bearing 10 can be designed so that the axial length LA of the inner ring 14 is I The ratio of LA to the ball diameter BD (i.e. I / BD) is at least 2.0 and can be greater than 2.5. Similarly, the axial length LA of the outer ring 16 O The ratio of LA to the ball diameter BD (i.e. O / BD) is at least 2.0 and can be greater than 2.5, the two axial lengths LA I , LA O Preferably they are equal. Using the axial length LA of the rings 14, 16 I , LA OWith this relative size to ball diameter BD, annular gap GA between outer surface 15B of inner race 14 and inner surface 17B of outer race 16 is relatively long and narrow, making a path (not indicated) provided between races 14, 16 for lubricant from an external source to reach ball 12 relatively constricted.

[0062] When the optimized ball bearing 10 produces such a long and narrow annular gap GA, the bearing 10 is preferably used and assembled with a cage 13 formed as described above so that the skeleton / base 30 of the cage 13 is located on the axial side of the ball 12 opposite the annular opening 19 into which the lubricant is directed. In other words, the lubricant supplier 40 is configured to direct the lubricant into the annular opening 19 formed between the first axial ends 14a, 16a of the rings 14, 16, and the cage annular base 30 is axially arranged between the plurality of balls 12 and the second axial ends 14b, 16b of the inner ring 14 and the outer ring 16. Therefore, the structure and positioning of the cage 13 provide an unobstructed path for the lubricant to reach the ball 12, thereby improving the lubrication efficiency of the bearing 10.

[0063] Reference Figures 11 to 14 In certain applications, an optimized ball bearing 10 may result in a ball 12 of a certain size and location, i.e., a ball 12 having a certain ball diameter BD and located at a certain pitch diameter PD, which results in an inner ring 14 or an outer ring 16 sized to accommodate the ball size and pitch diameter PD having a relatively large radial thickness TR, respectively, compared to the ball diameter BD. I or TR O For example, a particular bearing 10 may be sized such that the radial thickness TR of the inner ring 14 is I The ratio of the ball diameter BD (i.e., TR I / BD) is at least 1.0, or the radial thickness TR of the outer ring 16 O The ratio of the ball diameter BD (i.e., TR O / BD) is at least 1.0. Such a relatively "thick" inner ring 14 or outer ring 16 may result in a ring mass that is greater than desired, thereby resulting in undesirable dynamic conditions, such as increased moment of inertia.

[0064] In order to reduce this adverse effect of a “massive” inner ring 14 or outer ring 16, the radial thickness TR of the ring I ,TR OAt least one of the rings 14 or 16 having a ratio to the ball diameter BD of at least 1.0 is preferably provided with at least one annular recessed surface 50 to reduce the mass of the particular ring 14 or 16. Specifically, when provided on the inner ring 14, the recessed surface 50 is formed between the outer circumferential surface 15B of the inner ring 14 and at least one of the first axial end 14a and / or the second axial end 14b of the ring 14, and extends completely around the centerline CL in the circumferential direction. Alternatively or additionally, the annular recessed surface 50 may be formed on the outer ring 16 between the inner circumferential surface 17B of the outer ring 16 and at least one of the first axial end 16a and / or the second axial end 16b of the ring 16. The recessed surface(s) 50 may be formed during the forging process used to produce the bearing rings 14, 16, or may be machined into the rings 14, 16 when the bearing material is in a relatively "soft" state.

[0065] Special reference Fig.11 and Fig.12 , by providing (one or more) annular concave surfaces 50 to reduce the mass of either or both of the rings 14, 16, each ring 14, 16 having at least one concave surface 50 having a reduced radial thickness TR adjacent each axial end 14a, 14b and / or 16a, 16b of the concave surface 50 (i.e., the axial end 14a, 14b, 16a or 16b from which the concave surface 50 extends) RI or TR RO Preferably, the reduced radial thickness TR RI ,TR RO is less than the radial thickness TR of the rest of the rings 14, 16 on which the surface 50 is formed. I ,TR O Most preferably, each reduced radial thickness TR RI ,TR RO The value is significantly smaller than the radial thickness TR of the ring I ,TR O , such as less than seventy percent, less than fifty percent, etc. Therefore, it is apparent that the concave surface 50 provided in accordance with the present invention removes a significantly greater amount of material than the chamfers or radii provided on typical bearing rings to remove sharp edges or to facilitate the installation of bearings.

[0066] In addition, each annular concave surface 50 may be formed as a chamfer 52 ( Figures 11 to 14 )、fillet 54( Fig.14 )、Opening slot 54( Fig.14, shown as a rectangular step), or in any other suitable manner that reduces the amount of material of the rings 14 and / or 16 and thus also reduces the mass of the rings 14 and / or 16, such as by way of example a complex shaped surface including a combination of one or more flat surfaces and / or one or more curved surfaces. The concave surface 50 may be symmetrical ( Fig.11 and Fig.12 ) or asymmetrically ( Fig.13 and Fig.14 ) is formed on each ring 14 and / or 16 provided with such a surface 50. Furthermore, since the annular concave surface 50 also increases the size or width of the annular opening 19 for receiving lubricant, the concave surface 50 can be provided on the first axial ends 14a, 16a of both rings 14, 16 (and even also on the second axial ends 14b, 16b) to improve the flow of lubricant to the balls 12 and subsequently out of the bearing 10.

[0067] Representative non-limiting examples of the present invention are described in detail above with reference to the accompanying drawings. This detailed description is only intended to teach those skilled in the art further details for practicing the preferred aspects of the present teachings, and is not intended to limit the scope of the present invention.

[0068] In addition, the combination of features and steps disclosed in the above detailed description may not be necessary for practicing the present invention in the broadest sense, but is merely taught to particularly describe representative examples of the present invention. In addition, the individual features of the above representative examples and the attached individual independent claims and dependent claims may be combined in a manner not specifically and explicitly listed to provide additional useful embodiments of the present teaching.

[0069] For the purpose of original written disclosure and for the purpose of limiting the claimed subject matter, all features disclosed in the description and / or claims are intended to be disclosed individually and independently of each other, without relying on the combination of features in the embodiments and / or claims. In addition, for the purpose of original written disclosure and for the purpose of limiting the claimed subject matter, all value ranges or indications of entity groups are intended to disclose every possible intermediate value or intermediate entity. The present invention is not limited to the above-described embodiments and may vary within the scope of the appended claims.

Claims

1. A ball bearing (10) for an electric vehicle (V), the ball bearing (10) supporting a load (L) applied to a shaft (S) of an electric motor (1) of the vehicle (V), the ball bearing (10) comprising: An inner ring (14) having a center line (CL), an inner circumferential surface (15A) sized to fit on a shaft (S) of the electric motor (1), an outer circumferential surface (15B), a radial thickness (TR) defined between the inner circumferential surface (15A) and the outer circumferential surface (15B), I ), a first axial end portion (14a), an opposite second axial end portion (14b), and an inner raceway (18) formed in the outer circumferential surface (15B); An outer ring (16) is arranged around the inner ring (14) and has an outer circumferential surface (17A), an inner circumferential surface (17B), a radial thickness (TR) defined between the inner circumferential surface (17B) and the outer circumferential surface (17A) O ), a first axial end portion (16a), an opposite second axial end portion (16b), and an outer raceway (20) formed in the inner circumferential surface (17B); as well as A plurality of balls (12) arranged between the inner raceway (18) and the outer raceway (20), each ball having a ball diameter (BD); This includes one of the following: The radial thickness (TR) of the inner ring (14) I ) to the ball diameter (BD) is at least 1.0, and the inner ring (14) includes at least one annular concave surface (50) formed between the outer circumferential surface (15B) and the first axial end (14a) and / or between the outer circumferential surface (15B) and the second axial end (14b); and The radial thickness (TR) of the outer ring (16) O ) to the ball diameter (BD) is at least 1.0, and the outer ring (16) includes at least one annular recessed surface (50) formed between the inner circumferential surface (17B) and the first axial end (16a) and / or between the inner circumferential surface (17B) and the second axial end (16b).

2. The ball bearing (10) according to claim 1, characterized in that Each of the inner ring (14) and the outer ring (16) having at least one annular concave surface (50) has a reduced radial thickness (TR) at each of the first axial end (14a), (14b) and the second axial end (14a), (14b) or (16a), (16b) adjacent to the annular concave surface (50). RI )、(TR RO ), the reduced radial thickness (TR RI )、(TR RO ) is smaller than the radial thickness (TR) of the rest of the inner ring (14) or the outer ring (16). I )、(TR O )’s value.

3. The ball bearing (10) according to claim 1 or 2, characterized in that: The inner ring (14) has an inner diameter (ID) whose size is designed so that the inner ring (14) fits on the shaft (S) of the electric motor (1); The plurality of balls (12) pass through a pitch circle (PC) extending about the centerline (CL), the pitch circle (PC) having a pitch circle diameter (PD); and The number (N) of the plurality of balls (12) and the ball diameter (BD) are selected to provide a value of the pitch diameter (PD) that satisfies the following formula: X=π 2 *BD 2 *PD*ID; where LL≤X≤UL; UL=(-2.4815*ID 3 )+(211.6*ID 2 )-(4568.1*ID)+38956; and LL=(-23.511*ID 2 )+(2235.9*ID)-2856; Where X is the fitness factor, BD is the ball diameter, PD is the pitch diameter, ID is the inside diameter of the inner ring, LL is the lower limit, and UL is the upper limit.

4. The ball bearing (10) according to claim 3, characterized in that: Each ball (12) is formed of ceramic, and the ball diameter (BD) has a value between three millimeters (3 mm) and six millimeters (6 mm); and The inner diameter (ID) of the inner ring (14) has a value between twenty millimeters (20 mm) and sixty millimeters (60 mm).

5. The ball bearing (10) according to claim 3, characterized in that: The number (N) of the balls (12) is determined by dividing the value of the load (L) by the load capacity of each ball (12) having the ball diameter (BD); The circumference (CP) of the pitch circle (PC) is determined by multiplying the number (N) of the balls (12) by the ball diameter (BD); and The pitch circle diameter (PD) is determined by dividing the circumference (CP) of the pitch circle (PC) by the value of pi (π).

6. The ball bearing (10) according to any one of claims 1 to 5, characterized in that: The inner ring (14) has a first annular concave surface (50) formed between the outer circumferential surface (15B) and the first axial end (14a) and a second annular concave surface (50) formed between the outer circumferential surface (15B) and the second axial end (14b); and / or The outer ring (14) has a first annular concave surface (50) formed between the inner circumferential surface (17B) and the first axial end (16a) and a second annular concave surface (50) formed between the inner circumferential surface (17B) and the second axial end (16b).

7. The ball bearing (10) according to any one of claims 1 to 6, characterized in that Each annular concave surface (50) is one of a chamfer (52), a fillet (54), and a groove (56).

8. The ball bearing (10) according to any one of claims 1 to 7, characterized in that: The inner ring (14) has an axial length (LA) defined between a first axial end (14a) and a second axial end (14b) of the inner ring (14). I ), the size of the inner ring (14) is designed so that the axial length (LA) of the inner ring (14) I ) to the ball diameter (BD) is at least 2.0; and The outer ring (16) has an axial length (LA) defined between a first axial end (16a) and a second axial end (16b) of the outer ring (16). O ), the size of the outer ring (16) is designed so that the axial length (LA) of the outer ring (16) O ) to the ball diameter (BD) is at least 2.

0.

9. The ball bearing (10) according to any one of claims 1 to 8, characterized in that Further including: a lubricant source (40) configured to direct lubricant into an annular opening (19) defined between a first axial end (14a) of the inner race (14) and a first axial end (16a) of the outer race (16); and A bearing retainer (13) comprises an annular base (30), a plurality of arms (32) extending axially from the annular base (32), and a plurality of cavities (34) each defined between a single pair of adjacent arms (32), each cavity (34) retaining a single one of the balls (12), the annular base (30) of the retainer (13) being axially arranged between the plurality of balls (12) and the second axial ends (14b), (16b) of the inner ring (14) and the outer ring (16).

10. The ball bearing (10) according to claim 8, characterized in that The lubricant source (40) includes a channel (44) formed in the shaft (S) or the seat (2) and connected to a lubricant reservoir (42), the channel (44) having an outlet port (46) axially spaced from first axial ends (14a), (16a) of the inner ring (14) and the outer ring (16) and configured to direct lubricant into an annular opening (19) between the inner ring (14) and the outer ring (16).

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