BEARING ASSEMBLY

Abstract

A bearing assembly for supporting a drive shaft of an electric drive motor includes at least one inner ring, at least one outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring. The bearing assembly is an angular contact ball bearing, and the plurality of rolling elements include a first row of rolling elements and a second row of rolling elements. Also a shaft assembly supported by the bearing assembly and an electric motor including the shaft assembly.

Claims

1. A bearing assembly for supporting a drive shaft of an electric drive motor, the bearing assembly comprising: at least one inner ring, at least one outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, wherein the bearing assembly comprises an angular contact ball bearing, and wherein the plurality of rolling elements comprise a first row of rolling elements and a second row of rolling elements.

2. The bearing assembly according to claim 1, wherein a diameter of the plurality of rolling elements falls between 0.2*(D-d) and 0.4*(D-d), where D is an outer diameter of the bearing assembly, and d is an inner diameter of the bearing assembly.

3. The bearing assembly according to claim 1, wherein a diameter of the rolling elements falls between 0.25*(D-d) and 0.35*(D-d), where D is an outer diameter of the bearing assembly, and d is an inner diameter of the bearing assembly.

4. The bearing assembly according to claim 1, wherein a contact angle of the angular contact ball bearing falls between 15° and 40°.

5. The bearing assembly according to claim 1, wherein a contact angle of the angular contact ball bearing falls between 15° and 25°.

6. The bearing assembly according to claim 1, wherein a contact angle of the first row of rolling elements is different than a contact angle of the second row of rolling elements.

7. The bearing assembly according to claim 1 including an electrically conducting brush disposed between the inner ring and the outer ring.

8. The bearing assembly according to claim 1, wherein the at least one inner ring comprises a first inner ring and a second inner ring, wherein the at least one outer ring comprises a first outer ring and a second outer ring, wherein the first row of rolling elements is disposed between the first inner ring and the first outer ring, and wherein the second row of rolling elements is disposed between the second inner ring and the second outer ring.

9. The bearing assembly according to claim 1, wherein the at least one inner ring comprises a first inner ring and a second inner ring, wherein the at least one outer ring comprises no more than one outer ring, wherein the first row of rolling elements is disposed between the first inner ring and the outer ring, and wherein the second row of rolling elements is disposed between the second inner ring and the outer ring.

10. A shaft assembly for an electric drive motor, comprising: a shaft supported on both ends by a bearing assembly according to claim 1.

11. An electric motor comprising the shaft assembly according to claim 10.

12. A method comprising: operating the electric motor according to claim 11 at a rotational speed having an n*dm value greater than 700,000 mm/min.

13. A method comprising: operating the electric motor according to claim 11 at a rotational speed having an n*dm value greater than 1,000,000 mm/min.

14. The bearing assembly according to claim 1, wherein a diameter of the plurality of rolling elements falls between 0.2*(D-d) and 0.4*(D-d), where D is an outer diameter of the bearing assembly, and d is an inner diameter of the bearing assembly, and wherein a contact angle of the angular contact ball bearing falls between 15° and 40°.

15. A shaft assembly for an electric motor comprising: a shaft supported on both ends by a bearing assembly according to claim 14.

16. An electric motor comprising the shaft assembly according to claim 15.

17. A method comprising: operating the electric motor according to claim 16 at a rotational speed having an n*dm value greater than 700,000 mm/min.

18. A method comprising: mounting the shaft assembly according to claim 16 in an electric motor, and operating the electric motor at a rotational speed having an n*dm value greater than 1,000,000 mm/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a cross-sectional view of a first embodiment of a bearing assembly for supporting a drive shaft of an electric drive motor.

[0024] FIG. 2 is a cross-sectional view of a second embodiment of a bearing assembly for supporting a drive shaft of an electric drive motor.

DETAILED DESCRIPTION

[0025] In the following, identical or functionally equivalent elements are designated by the same reference numbers.

[0026] FIG. 1 shows a cross-sectional view of a first embodiment of a bearing assembly 1 for supporting a drive shaft of an electric drive motor. The bearing assembly 1 is configured as a double row angular contact ball bearing and includes a split inner ring 2-1, 2-2. The bearing assembly 1 furthermore includes a single, common outer ring 4. Two rows of rolling elements 6-1 and 6-2 are disposed between the split inner ring 2-1, 2-2 and the outer ring 4.

[0027] Due to the use of an angular contact ball bearing 1 for supporting a drive shaft of an electric drive motor, higher rotational speeds can be realized in the motor than were possible with previous bearing assemblies that use deep groove ball bearings. Due to the use of the angular contact ball bearings 1, it is possible for the drive shaft and thus the motor to be operated at very high rotational speeds up to 1,500,000 mm/min, or even higher. With the deep groove ball bearings used to date, only rotational speeds of up to 700,000 mm/min could be achieved. Due to the higher rotational speeds, the motor can be built smaller and lighter in comparison to previous motors.

[0028] In the angular contact ball bearing 1 depicted in FIG. 1, the contact angle α=30°. Instead of two identical contact angles as is shown here, different contact angles can also be used. This has the advantage that the row having the smaller contact angle generates a greater radial rigidity, while the row having the larger contact angle generates a greater axial rigidity.

[0029] The angular contact ball bearing 1 is used to support a drive shaft of an electric drive motor. For this purpose the drive shaft is supported on each end by a bearing assembly, as is depicted in FIG. 1 or FIG. 2. The inner rings 2-1, 2-2 of the angular contact ball bearing 1 are disposed on the drive shaft, whereas the outer rings 4 are disposed in a housing of the drive motor in order to support the drive shaft in the housing.

[0030] In comparison to conventional angular contact ball bearings, the diameter D.sub.W of the rolling elements 6-1, 6-2 is selected smaller. In particular, the diameter D.sub.W in such a double row angular contact ball bearing 1 can be 0.303*(D-d), wherein D is the bearing outer diameter and d is the bearing inner diameter.

[0031] The rolling elements 6-1, 6-2 can be held by respective cages 8-1, 8-2. In particular, these can be one-piece cages. The cages 8-1, 8-2 can be manufactured from plastic or from metal. Outwardly the bearing assembly 1 can be sealed by respective seal assemblies 10.

[0032] Instead of a double row angular contact ball bearing, two single row angular contact ball bearings 1-1, 1-2 can also be used, as is depicted in FIG. 2. Here the two single row angular contact ball bearings 1-1, 1-2 are installed in pairs. In contrast to the double row angular contact ball bearing 1 of FIG. 1, in this case the angular contact ball bearing 1 is thus configured with two inner rings 2-1, 2-2, and two outer rings 4-1, 4-2.

[0033] In the embodiment depicted, the two angular contact ball bearings 1-1, 1-2 are depicted in a back-to-back arrangement. Alternatively the two single row angular contact ball bearings 1-1, 1-2 can also be installed in a face-to-face arrangement.

[0034] In this case the diameter D.sub.W of the rolling elements 6-1, 6-2 can preferably be 0.33*(D-d). The rolling elements 6-1, 6-2 can be held by respective cages 8-1, 8-2.

[0035] In this bearing assembly 1 the contact angle α is also 30°. However, it should be noted that the contact angle of the angular contact ball bearing of FIG. 1 and FIG. 2 can be between 15° and 40°. A smaller contact angle has the advantage that the bearing assembly 1 can withstand higher rotational speeds. The contact angle α can also differ between the two rolling-element rows 6-1, 6-2. The row having the smaller contact angle increases the radial rigidity, whereas the row having the larger contact angle increases the axial rigidity.

[0036] As explained above, the disclosed bearing assembly makes it possible to realize very high rotational speeds of 1,400,000 or mm/min or 1,500,000 mm/min or higher in motors in which the bearing assembly is used for supporting the drive shaft. This is achieved by using angular contact ball bearings instead of the previous deep groove ball bearings. Due to these high rotational speeds, the motors can in turn be built lighter and more compact.

[0037] Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved bearing assemblies for electric motors.

[0038] Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

[0039] All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

REFERENCE NUMBER LIST

[0040] 1 Bearing assembly [0041] 2 Inner ring [0042] 4 Outer ring [0043] 6 Rolling elements [0044] 8 Cage [0045] 10 Seal assembly [0046] α Contact angle [0047] D.sub.W Rolling-element diameter