DRIVE UNIT FOR A VEHICLE

Abstract

The invention relates to a drive unit (10) for a vehicle comprising an electric machine (12) having a rotor shaft (14) and a transmission (16) with a transmission shaft (18), wherein the transmission shaft (18) is rotatably mounted in a first housing section (22) by means of a first rolling bearing (20) and the rotor shaft (14) is rotatably mounted in a second housing section (26) by means of a rolling second bearing (24). According to the invention, the transmission shaft (18) and the rotor shaft (14) are coupled to another in a rotationally fixed manner, wherein a third rolling bearing (28) which has an inner bearing ring (30) is arranged at the transition between the transmission shaft (18) and the rotor shaft (14), wherein the inner bearing ring (30) is in contact with the rotor shaft (14) and the transmission shaft (18) with its inner surface (32).

Claims

1. A drive unit (10) for a vehicle comprising: an electric machine (12) having a rotor shaft (14) and a transmission (16) having a transmission shaft (18), wherein the transmission shaft (18) is rotatably mounted in a first housing section (22) by a first rolling bearing (20) and the rotor shaft (14) is rotatably mounted in a second housing section (26) by a second rolling bearing (24), wherein the transmission shaft (18) and the rotor shaft (14) are coupled to one another in a rotationally fixed manner, wherein a third rolling bearing (28) which comprises an inner bearing ring (30) is disposed at the transition between the transmission shaft (18) and the rotor shaft (14), wherein an inner surface (32) of the inner bearing ring (30) abuts the rotor shaft (14) and the transmission shaft (18).

2. The drive unit (10) according to claim 1, wherein the third rolling bearing (28) is seated on the transmission shaft (18), wherein the inner bearing ring (30) abuts a radial projection (38) on a side facing away from the rotor shaft (14).

3. The drive unit (10) according to claim 1, wherein the first rolling bearing (20) and the third rolling bearing (28) are disposed in the first housing section (22) in an X arrangement or an O arrangement.

4. The drive unit (10) according to claim 1, wherein the transmission shaft (18) and the rotor shaft (14) are fastened to one another axially, wherein one bearing of the first rolling bearing (20) and the third rolling bearing (28) is configured as a floating bearing and the respective other bearing as a fixed bearing.

5. The drive unit (10) according to claim 1, wherein the rotor shaft (18) abuts the inner surface (32) of the inner bearing ring (30) of the third rolling bearing (28) with an outer peripheral surface (41), wherein the rotor shaft (14) is supported axially on the inner bearing ring (30) of the third rolling bearing (28) or on the transmission shaft (18) with a radial shoulder (44).

6. The drive unit (10) according to claim 1, wherein the third rolling bearing (28) comprises an axially extended inner bearing ring (30) which projects axially from the third rolling bearing (28) or that the third rolling bearing (28) is implemented as a larger rolling bearing than the first rolling bearing (20) and the second rolling bearing (24).

7. The drive unit (10) according to claim 6, wherein the third rolling bearing (28) comprises a shoulder (60) having an enlarged inner diameter on the inner bearing ring (30), wherein the rotor shaft (14) abuts the inner bearing ring (30) with an outer peripheral surface (41) in this shoulder (60).

8. The drive unit (10) according to claim 1, wherein the rotor shaft (14) comprises a step (42) having a reduced outer diameter, wherein the inner surface (32) of the inner bearing ring (30) of the third rolling bearing (28) abuts the rotor shaft (14) at this step (42).

9. The drive unit (10) according to claim 1, wherein the transmission shaft (18) is configured axially in sections or entirely as a hollow shaft.

10. The drive unit (10) according to claim 1, wherein the rotor shaft (14) and the transmission shaft (18) are connected to one another in a material-locking, form-locking and/or force-locking mariner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Possible embodiments of the invention are explained in the following with reference to the accompanying drawings. The figures show:

[0026] FIG. 1 a schematic section through a drive unit for a vehicle; and

[0027] FIGS. 2a-2d options for configuring the mounting of the rotor shaft and the transmission shaft on the third rolling bearing of the drive unit of FIG. 1.

DETAILED DESCRIPTION

[0028] In FIG. 1, a drive unit for a vehicle bears the overall reference sign 10. The drive unit 10 comprises an electric machine 12 having a rotor shaft 14 and a transmission 16 having a transmission shaft 18 which is separate from the rotor shaft 14. The transmission shaft 18 is rotatably mounted in a first housing section 22 (not shown) by means of a first rolling bearing 20 and the rotor shaft 14 is rotatably mounted in a second housing section 26 (not shown) by means of a second rolling bearing 24. The first housing section 22 can be a housing of the transmission 16, and the second housing section 26 can be a housing of the electric machine 12 (housing not shown in each case). The housings can comprise one or more (likewise not shown) housing walls, in which bearing seats (without reference signs) for the rolling bearings 20, 24, 28 are configured (bearing seats indicated by hatching).

[0029] The transmission shaft 18 and the rotor shaft 14 are coupled to one another in a rotationally fixed manner, wherein a third rolling bearing 28 which comprises an inner bearing ring 30 is disposed at the axial transition between the transmission shaft 18 and the rotor shaft 14, wherein the inner bearing ring 30 abuts the rotor shaft 14 and the transmission shaft 18 with its inner surface 32 (see FIG. 2a).

[0030] The inner surface 32 of the inner bearing ring can be an inner surface 32 having an (axially) uniform inner diameter throughout or a stepped inner surface 32 having different inner diameters. The rotor shaft 14 and the transmission shaft 18 are disposed coaxially with one another. The transmission shaft 18 can be an input shaft of the transmission.

[0031] The first rolling bearing 20 is disposed on the end of the transmission shaft 18 facing away from the rotor shaft 14. The second rolling bearing 24 is disposed on the end of the rotor shaft 14 facing away from the transmission shaft 18. The third rolling bearing 28 is disposed axially between the rolling bearings 20, 24. In this example, the transmission shaft 18 comprises a toothing 34 cut into the transmission shaft 18 for torque transmission.

[0032] The electric machine 12 comprises a rotor 36 that is coupled to the rotor shaft 14 in a rotationally fixed manner. The electric machine 12 also comprises a (not shown) stator that interacts electromagnetically with the rotor 36. In this example, the drive unit 10 forms an electrical axle for a vehicle.

[0033] The third rolling bearing 28 is positioned on the transmission shaft 18 for the axially predominant part, wherein the inner bearing ring 30 abuts a radial projection 38 on the side facing away from the rotor shaft 14. In this example, the projection 38 is formed by a shaft shoulder which projects radially relative to the bearing seat 40, i.e., the portion of the transmission shaft 18 on which the third rolling bearing 28 with the inner bearing ring 30 is seated.

[0034] The third rolling bearing 28 is disposed in the first housing section 22 and rotatably supports the transmission shaft 18 and the rotor shaft 14 in the first housing section 22. In this example, the first rolling bearing 20 and the third rolling bearing 28 are disposed in the first housing section 22 in an X arrangement. The rolling bearings 20, 24, 28 can optionally be axially pretensioned as discussed above.

[0035] The transmission shaft 18 and the rotor shaft 14 are fastened to one another axially, wherein one bearing of the first rolling bearing 20 and the third rolling bearing 28 is configured as a floating bearing and the respective other bearing as a fixed bearing (not shown in detail).

[0036] The mounting on the third rolling bearing 28 according to FIG. 1 is shown enlarged in FIG. 2a. The third rolling bearing 28 comprises an axially extended inner bearing ring 30 that projects axially from the rolling bearing 28. The rotor shaft 14 comprises a step 42 having an outer diameter which is reduced compared to the outer peripheral surface 41, wherein the inner bearing ring 30 of the third rolling bearing 28 abuts the rotor shaft 14 with its inner surface 32 in this step 42. The rotor shaft 14 is supported on the front side on the (extended) inner bearing ring 30 of the rolling bearing 28 with a radial shoulder 44. In this example, the bearing seat 40 of the transmission shaft 18 and the step 42 of the rotor shaft 14 have an identical outer diameter. On the inner surface 32, the inner bearing ring 30 has an axially uniform inner diameter.

[0037] The transmission shaft 18 is configured as a hollow shaft comprising a centric passage 46 (see FIG. 1). Oiling or cooling of the rotor shaft 14, and optionally also the shaft connection, is thus possible as discussed above.

[0038] In this example, the rotor shaft 14 and the transmission shaft 18 are connected to one another in a form-locking manner, specifically by means of a spline 48 (see FIG. 1). The transmission shaft 18 and rotor shaft 14 overlap axially and are connected to one another in the overlapping region. An axially projecting pin 50, which projects into the passage 46 of the transmission shaft 18 when the shafts 14, 18 are assembled, is formed on the rotor shaft 14.

[0039] An inner toothing 54 is configured on the inner perimeter 52 of the transmission shaft 18 and an outer toothing 58 is configured on the outer perimeter 56 of the pin 50. When mated, the inner toothing 54 and the outer toothing 58 form the spline 48.

[0040] FIGS. 2b to 2d show different options for configuring the mounting on the third rolling bearing 28. Same or functionally same elements are provided with identical reference signs, so that reference is made to the explanations above in order to avoid repetition.

[0041] Unlike in FIG. 2a, for the mounting according to FIG. 2b, the rotor shaft 14 does not comprise a radial shoulder 44. Instead, the third rolling bearing 28 comprises a shoulder 60 having an enlarged inner diameter on the (axially extended) inner bearing ring 30, wherein the rotor shaft 14 abuts the inner bearing ring 30 with its outer peripheral surface 41 in this shoulder 60. The shoulder 60 is configured on the end of the rotor shaft 14 facing the transmission shaft 18.

[0042] Unlike in FIG. 2a, for the mounting according to FIG. 2c, the inner bearing ring 30 is not axially extended, so that it does not project axially beyond the third rolling bearing 28. The inner bearing ring 30 abuts the rotor shaft 14 in the step 42 with its inner surface 32. The rotor shaft 14 is supported on the front side on the inner bearing ring 30 of the rolling bearing 28 with a radial shoulder 44. Compared to the mounting in FIG. 2a, the rolling bearing 28 in FIG. 2c is shifted further in the direction of the rotor shaft 14.

[0043] Unlike in FIG. 2a, for the mounting according to FIG. 2d, the rotor shaft 14 does not comprise a radial shoulder 44 with which the rotor shaft 14 abuts on the front side on the bearing inner ring 30. Instead, the rotor shaft 14 is supported on the front side on the transmission shaft 18 with a radial shoulder 44. The outer peripheral surface 41 of the rotor shaft 14 and the bearing seat 40 of the transmission shaft 18 have an identical outer diameter. The inner bearing ring 30 is not axially extended, so that it does not project axially from the rolling bearing 30. On the inner surface 32, the inner bearing ring 30 has an axially uniform inner diameter.