Bearing support for parallel electric axle gear assembly

Abstract

Bearing (72, 74) arrangements for a drive unit (10) having an electric motor for providing drive for an electric axle and wheel assembly of a vehicle. The drive unit includes a pair of bearings and a reduction gear assembly (12) having a first drive gear mounted to and coaxial with a main shaft of the motor, and a first driven gear rotatably coupled to the first drive gear and mounted to and coaxial with an intermediate shaft to form an intermediate shaft assembly. The reduction gear assembly includes a second drive gear mounted to and coaxial with the intermediate shaft, and a second driven gear rotatably coupled with the second drive gear. A first bearing of the pair of bearings is mounted to a bulkhead and to the intermediate shaft assembly between the first driven gear and the second drive gear to reduce a distance between the first bearing and a second bearing.

Description

Technical Field

[0001] This disclosure relates to a gear assembly for an electric vehicle axle in a vehicle. Background Technology

[0002] The drive unit of an electric axle for a motor vehicle typically includes a reduction gearbox, or more generally, a reduction gear assembly or gear unit, to reduce the speed or rotational motion of the motor. This reduced speed translates into increased torque transmitted to the vehicle's wheels. The gear assembly is typically supported by multiple bearings and must fit within the limited space available for the vehicle's drive unit. An electric axle can be part of an electric motor vehicle or a hybrid electric vehicle (HEV). Summary of the Invention

[0003] According to one embodiment, a drive unit for an electric vehicle axle of a vehicle is disclosed, the drive unit having an electric motor for providing drive to a wheel assembly. The drive unit includes a housing having a partition portion, a main shaft driven by the motor, and a reduction gear assembly coupled to the main shaft. The reduction gear assembly has a first-stage gear assembly, an intermediate shaft, and a second-stage gear assembly. The first-stage gear assembly has a first drive gear mounted to and coaxial with the main shaft, and a first driven gear rotatably coupled to the first drive gear and mounted to and coaxial with the intermediate shaft. The second-stage gear assembly has a second drive gear mounted to and coaxial with the intermediate shaft, and a second driven gear rotatably coupled to the second drive gear. The first driven gear, the second drive gear, and the intermediate shaft form an intermediate shaft assembly. The intermediate shaft assembly includes a pair of bearings. The first bearing of the pair of bearings is mounted to the partition portion of the housing and is mounted to the intermediate shaft assembly between the first driven gear and the second drive gear.

[0004] In some embodiments, the first bearing is mounted between the partition portion of the housing and the first driven gear. The first driven gear and the second drive gear may also be integral with the intermediate shaft.

[0005] In some embodiments, a first driven gear and a first bearing are mounted to the proximal end of the intermediate shaft adjacent to the motor axial direction, and a second bearing of the paired bearings is mounted between the housing and the distal end of the intermediate shaft. The bearings can be any combination of fixed bearing pairs, floating bearing pairs, or adjusting bearing pairs.

[0006] In some embodiments, the first bearing is configured to support an axial load in a direction toward the proximal end of the intermediate shaft, and the second bearing is configured to support an axial load in a direction toward the distal end of the intermediate shaft. The intermediate shaft may extend continuously from the first driven gear to the second drive gear and may be parallel to and radially spaced from the main shaft.

[0007] In some embodiments, the partition portion of the housing is configured to rotatably support one end of a differential unit connected to a second driven gear via bearings, for transmitting drive to the wheel assembly. The rotational speed of the second driven gear may be less than that of the first driven gear. The spindle may be directly or indirectly connected to a motor. Attached Figure Description

[0008] Reference will now be made to the accompanying drawings, which illustrate exemplary embodiments of this application, by way of example, wherein:

[0009] Figure 1 A cross-sectional view of a drive unit for an electric vehicle axle according to an embodiment of the present disclosure is shown;

[0010] Figure 2 It shows Figure 1 A close-up cross-sectional view of a portion;

[0011] Figure 3 A graph showing bearing damage compared to the axial distance from the first bearing to the first driven gear, according to one embodiment of this disclosure, is shown; and

[0012] Figure 4 A graph showing bearing damage compared to the axial distance from the first bearing to the first driven gear, according to another embodiment of this disclosure, is shown.

[0013] Similar reference numerals can be used in different accompanying drawings to denote similar parts. Detailed Implementation

[0014] This disclosure relates to a drive unit for an electric vehicle axle in a motor vehicle, including battery electric motor vehicles (BEVs) and hybrid electric vehicles (HEVs). Specifically, this disclosure relates to the construction of a bearing for supporting a reduction gear assembly in the drive unit.

[0015] Some electric vehicle axles (eAxles) include a reduction gearbox or gear assembly that is coupled to an electric motor to increase torque and reduce the speed to be transmitted to the vehicle's wheels. The gearbox typically consists of two stages of helical or spur gears arranged on parallel axes. The driven gear of the first stage and the drive gear of the second stage can be attached to an intermediate shaft supported by two bearings. A conventional arrangement is to have the gears adjacent to each other and a bearing supporting each outer end of the intermediate shaft. This arrangement can be axially fixed using a fixed / floating, floating, or adjustable bearing arrangement.

[0016] According to embodiments of this disclosure, the bearing arrangement for a reduction gear assembly is improved by moving the position of a bearing supporting an intermediate shaft near the driven gear of the first stage. Specifically, the bearing is mounted to a partition portion of the housing and to an intermediate shaft assembly positioned between the driven gear of the first stage and the drive gear of the second stage. In one embodiment, the bearing is mounted to the housing and to the driven gear of the first stage. Thus, the housing supports the intermediate shaft via the bearing. A second bearing is located at the distal end of the intermediate shaft. By reducing the distance between the first bearing and the second drive gear, the fatigue life of each bearing is more balanced. The load on the pinion (drive gear of the second stage) is typically much higher than the load on the gear (driven gear of the first stage). Reducing the distance between the bearings also improves the drive unit by enabling a more compact package. Tolerance stacking can also be reduced, thereby reducing bearing noise.

[0017] Figure 1 This is a cross-sectional view of a drive unit 10 and a reduction gear assembly 12 according to an embodiment of the present disclosure. The drive unit 10 has a housing 14. The housing 14 may be composed of housing segments. The housing 14 contains an electric motor 16 and a reduction gear assembly 12. Although Figure 1 The reduction gear assembly 12 is shown located on the left side of the motor 16; however, it should be understood that, depending on the frame of reference, the reduction gear assembly 12 may be located on the right side of the motor 16. Therefore, directional references used in this specification or claims, such as left, right, top, bottom, upper, lower, etc., are for ease of description and are not intended to limit the scope of the invention in any way.

[0018] Left output shaft 20 and right output shaft 22 extend from housing 14 and support left wheel hub 24 and right wheel hub 26 for connecting and transmitting torque to corresponding left and right wheel assemblies (not shown). Left output shaft 20 and right output shaft 22 are connected to reduction gear assembly 12 and motor 16 via an assembly such as differential unit 30. As shown, right output shaft 22 is coaxial with and rotatably supported within main shaft 32 of drive unit 10. Main shaft 32 may also be referred to as and can be equivalent to the motor shaft or drive shaft of drive unit 10.

[0019] The reduction gear assembly 12 operates to reduce the rotational speed and increase the torque supplied to the differential unit by the motor 16. The reduction gear assembly 12 includes a first-stage gear assembly 38 and a second-stage gear assembly 40 arranged around an intermediate shaft 42. Specifically, the first-stage gear assembly 38 includes a first drive gear 50 and a first driven gear 52. The first driven gear 52 and the intermediate shaft 42 form an intermediate shaft assembly. The first drive gear 50 is mounted to and coaxial with the main shaft or motor shaft 32. In one embodiment, the first drive gear 50 is integral with the main shaft or motor shaft 32 and forms part of the main shaft or motor shaft. The first driven gear 52 is mounted to and coaxial with the intermediate shaft 42 and is rotatably connected to the first drive gear 50. In some embodiments, the first driven gear 52 is integral with the intermediate shaft 42 and forms part of the intermediate shaft. As shown, the first driven gear 52 is mounted to the proximal end 54 of the intermediate shaft 42, i.e., the end of the shaft axially adjacent to the motor 16.

[0020] The intermediate shaft 42 is radially spaced from and parallel to the main shaft or motor shaft 32. The first drive gear 50 of the first-stage gear assembly 38 is connected to the motor 16, and the first driven gear 52 of the first-stage gear assembly 38 is connected to the intermediate shaft 42. The second drive gear 58 of the second-stage gear assembly 40 is connected to the intermediate shaft 42, and the second driven gear 60 of the second-stage gear assembly 40 is also connected to the housing 44 of the differential unit 30, for driving the left output shaft 20 and the right output shaft 22. The gears 50 and 52 of the first-stage gear assembly 38 and the gears 58 and 60 of the second-stage gear assembly 40 can be helical gears or spur gears.

[0021] As described above, the second-stage gear assembly 40 includes a second drive gear 58 and a second driven gear 60. The second drive gear 58 is mounted to and coaxial with the intermediate shaft 42. In one embodiment, the second drive gear 58 is integral with and forms part of the intermediate shaft 42. Therefore, the second drive gear 58 and the first driven gear 52 have the same axis of rotation. In one embodiment, the intermediate shaft 42 extends continuously from the first driven gear 52 to the second drive gear 58. The second driven gear 60 is rotatably connected to the second drive gear 58. The second driven gear 60 is also mounted to and supported by the housing 44 of the differential unit 30 to transmit torque from the reduction gear assembly 12 to the differential unit 30 and the left and right wheels.

[0022] like Figure 1As shown, the differential unit 30 is supported by a housing wall partition 62, which may be part of the housing 14 and has the same axis of rotation as the main shaft 32. The differential unit 30 is typically supported by two bearings 64 and 66, which may be tapered roller bearings, deep groove ball bearings, angular contact ball bearings, or a combination of deep groove and cylindrical roller bearings. Similarly, the main shaft or motor shaft 32 is supported by at least two bearings 68 and 70 axially spaced on opposite sides of the motor 16. Similar to bearings 64 and 66, the bearings 68 and 70 supporting the main shaft or motor shaft 32 may be ball bearings, tapered roller bearings, deep groove ball bearings, angular contact ball bearings, or a combination of deep groove and cylindrical roller bearings.

[0023] A pair of bearings for intermediate shaft 42 Figure 1 and Figure 2 The image is shown in a close-up view. The pair includes a first bearing 72 and a second bearing 74. The first bearing 72 and the second bearing 74 can be deep groove ball bearings, cylindrical roller bearings, angular contact ball bearings, or tapered roller bearings. The first bearing 72 is mounted near the proximal end of the intermediate shaft 42 to the housing 14 and the first driven gear 52. The second bearing 74 is mounted at the distal end 76 of the intermediate shaft 42 between the housing 14 and the intermediate shaft 42.

[0024] Specifically, in one embodiment, the inner ring 80 of the first bearing 72 is mounted to the outer circumferential surface of the shaft portion 82 of the first driven gear 52. The inner ring 80 can be axially fixed relative to the intermediate shaft 42 between the retaining ring 84 and the first shoulder 86 defined by the first driven gear 52. The outer ring 88 of the first bearing 72 is mounted to the housing 14, and specifically to a portion 90 of the housing 14 extending radially inward toward the reduction gear assembly 12. In one embodiment, as... Figure 1 As shown, this portion 90 of the housing 14 can also form a housing wall partition 62 that supports the differential unit 30. In one embodiment, the outer ring 88 is axially fixed to the right (i.e., in the direction toward the proximal end 54 of the intermediate shaft 42) against a first shoulder 92 defined by the partition portion 90 of the housing 14.

[0025] The second bearing 74 can be held between the housing 14 and the intermediate shaft 42 in a known configuration, such as Figure 1 and Figure 2 As shown. In one embodiment, the inner ring 98 of the second bearing 74 is mounted adjacent to the distal end 76 to the intermediate shaft 42. The outer ring 100 of the second bearing 74 is mounted to the inner surface of the housing 14. The outer ring 100 of the second bearing 74 can be axially fixed to the left (i.e., in the direction toward the distal end of the intermediate shaft 42) against a second shoulder 102 defined by the housing 14.

[0026] Therefore, in one embodiment, each of the first bearing 72 and the second bearing 74 may be fixed in one direction relative to the respective proximal end 54 and distal end 76 of the intermediate shaft 42. In other embodiments, the first bearing 72 may be a fixed bearing, and the second bearing 74 may be configured as a floating bearing. Alternatively, the second bearing 74 may be a fixed bearing, while the first bearing 72 may be a floating bearing.

[0027] In some embodiments, the first bearing 72 and the second bearing 74 may be of the types and configurations shown in Table 1 below.

[0028]

[0029]

[0030] Table 1: Construction of the first and second bearings 72, 74 according to embodiments of the present disclosure

[0031] Figure 3 and Figure 4 The graphs 300 and 400 illustrate the reduction in bearing damage at different axial positions of the first bearing 72 and the second bearing 74 relative to the first driven gear 52. The first bearing 72 is indicated as a right-hand or RH bearing, and the second bearing 74 as a left-hand or LH bearing. As the distance "x" decreases and becomes negative, i.e., the first bearing 72 is positioned to the left relative to the first driven gear 52, it can be seen that damage to both bearings is reduced. The reduction in damage to LH or the second bearing 74 is more significant than the increase in damage to RH or the first bearing 72, thus balancing the damage between the first bearing 72 and the second bearing 74. Figure 3 This indicates a fixed first bearing 72 and a floating second bearing 74. Figure 4 This indicates that each of the first bearing 72 and the second bearing 74 is fixed in one direction and preloaded relative to the respective proximal and distal ends of the intermediate shaft 42 (referred to as adjusting the bearing arrangement).

[0032] Certain adaptations and modifications can be made to the described embodiments. Therefore, the embodiments discussed above are considered illustrative rather than limiting. Other combinations and configurations of drive unit components and bearings described herein may be included within the scope of this disclosure.

Claims

1. A drive unit for an electric vehicle axle of a vehicle, the drive unit having an electric motor for providing drive to a wheel assembly, the drive unit comprising: The outer casing has a partition section; The main spindle is driven by the motor; A reduction gear assembly connected to the main shaft, the reduction gear assembly having a first-stage gear assembly, an intermediate shaft, and a second-stage gear assembly; and Paired bearings; The intermediate shaft has a proximal end that is axially adjacent to the motor and a distal end that is axially spaced from and opposite to the proximal end. The first-stage gear assembly has, A first drive gear, which is mounted to and coaxial with the main shaft, and A first driven gear, rotatably coupled to the first drive gear and mounted to the proximal end of the intermediate shaft and coaxial with the intermediate shaft, The second-stage gear assembly has, The second drive gear is mounted to and coaxial with the intermediate shaft, and The second driven gear is rotatably connected to the second driving gear, and the first driven gear, the second driving gear, and the intermediate shaft form an intermediate shaft assembly; and The first bearing of the paired bearings has an outer ring mounted to a partition portion of the housing and an inner ring mounted to the first driven gear, wherein the first driven gear and the first bearing are mounted to a proximal end of the intermediate shaft adjacent to the axial direction of the motor; and The second bearing of the paired bearings is mounted between the housing and the distal end of the intermediate shaft.

2. The driving unit according to claim 1, wherein, The first bearing is mounted between the partition portion of the housing and the first driven gear.

3. The driving unit according to claim 1 or 2, wherein, The first driven gear is integral with the intermediate shaft.

4. The driving unit according to claim 1, wherein, The first bearing includes one of a fixed bearing or a floating bearing, and the second bearing includes the other of a fixed bearing or a floating bearing.

5. The driving unit according to claim 1, wherein, The first bearing is configured to support an axial load in a direction toward the proximal end of the intermediate shaft, and the second bearing is configured to support an axial load in a direction toward the distal end of the intermediate shaft.

6. The drive unit according to any one of claims 1 to 5, wherein, The second drive gear is integral with the intermediate shaft.

7. The driving unit according to claim 6, wherein, The intermediate shaft extends continuously from the first driven gear to the second drive gear.

8. The drive unit according to any one of claims 1 to 7, wherein, The paired bearings are configured to support only the intermediate shaft assembly within the housing.

9. The drive unit according to any one of claims 1 to 8, wherein, The intermediate shaft is parallel to the main shaft and radially spaced from the main shaft.

10. The driving unit according to claim 9, wherein, The partition portion of the housing is configured to rotatably support one end of the differential unit connected to the second driven gear for transmitting drive to the wheel assembly.

11. The drive unit according to any one of claims 1 to 10, wherein, The rotational speed of the second driven gear is less than that of the first driven gear.

12. The drive unit according to any one of claims 1 to 11, wherein, The first drive gear is integral with the main shaft.

13. The drive unit according to any one of claims 1 to 12 further includes a spline operably connected to the main shaft and the first driven gear for driving the first driven gear.

14. The drive unit according to any one of claims 1 to 13, wherein, The spindle is directly and operably connected to the motor.

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