Drive unit for a vehicle

Abstract

The invention relates to a drive unit (10) for a vehicle, comprising an electric machine (12) with a rotor shaft (14) and a transmission (16) with a transmission shaft (18), wherein the transmission shaft (18) is rotatably supported in a first housing section (22) by means of a first rolling bearing (20) and the rotor shaft (14) is rotatably supported in a second housing section (26) by means of a second rolling bearing (24). It is proposed that the transmission shaft (18) and the rotor shaft (14) are coupled to one another against rotation, wherein a third rolling bearing (28) is arranged at the transition between the transmission shaft (18) and the rotor shaft (14), which third rolling bearing has a bearing inner ring (30), wherein the bearing inner ring (30) abuts with its inner surface (32) both at the rotor shaft (14) and at the transmission shaft (18).

Description

Technical Field

[0001] The present invention relates to a drive unit for a vehicle as described in the preamble of claim 1. Background Technology

[0002] A drive unit for a vehicle is known from DE 10 2016 206 479 A1. This drive unit has a motor with a rotor shaft and a transmission device with a transmission mechanism input shaft, the transmission mechanism input shaft being double-supported and having an integrated pinion, wherein the rotor shaft and the transmission mechanism input shaft are interlocked. In the assembly using an assembly mandrel and first assembling the transmission device into the transmission mechanism housing, a precise assembly sequence must be followed. Summary of the Invention

[0003] The problem upon which this invention is based is solved by a drive unit for a vehicle having the features of claim 1. Advantageous improvements of the invention are set forth in the dependent claims.

[0004] According to the present invention, a drive unit for a vehicle is provided, the drive unit having a motor with a rotor shaft and a transmission mechanism with a drive shaft (separate from the rotor shaft). The drive shaft is rotatably supported in a first housing section by means of a first rolling bearing, and the rotor shaft is rotatably supported in a second housing section by means of a second rolling bearing.

[0005] The drive shaft and the rotor shaft are connected to each other in an anti-rotational manner, wherein a third rolling bearing is arranged at the (axial) transition between the drive shaft and the rotor shaft, the third rolling bearing having an inner ring, wherein the inner surface of the inner ring abuts against the rotor shaft and the drive shaft.

[0006] Therefore, the drive shaft and rotor shaft (partially along the axial direction) are received in the inner ring of the third bearing, and the inner ring of the third rolling bearing supports the drive shaft and rotor shaft radially. Thus, alignment of the two shafts can be achieved directly in the third rolling bearing at the inner surface of the bearing's inner ring.

[0007] This allows for the independent assembly of the motor and transmission mechanism. This enables greater flexibility in the assembly sequence of the drive unit, as the motor can be selectively constructed before assembling the transmission mechanism, or vice versa. By aligning the drive shaft and rotor shaft within the inner rings of the bearings, additional alignment elements (e.g., alignment surfaces) for guiding the two shafts relative to each other can be eliminated. Furthermore, guiding these shafts with a third rolling bearing allows for higher operating accuracy (smaller coaxial tolerances) compared to guiding the rotor shaft using a drive shaft.

[0008] The inner surface of the bearing inner ring can be an inner surface with a continuously constant inner diameter (along the axial direction) or a stepped inner surface with different inner diameters. The first housing section can be the housing of a transmission mechanism (transmission mechanism housing). The second housing section can be the housing of a motor (motor housing).

[0009] As already shown, the rotor shaft and the drive shaft are arranged coaxially with each other. The drive shaft can be the input shaft of the transmission mechanism.

[0010] The rotor shaft and drive shaft are constructed separately from each other and are connected to each other in a rotationally resistant manner when assembling the drive unit. By designing the drive shaft and rotor shaft separately, the shaft material can be selected according to the load. Furthermore, the shafts can be machined separately and, if necessary, heat-treated separately (resulting in a smaller shaft mass compared to a one-piece design). Additionally, greater flexibility is achieved in the design of the running gear diameter, seal diameter, bearing diameter, or parking lock connection.

[0011] The first rolling bearing can be arranged at the end of the drive shaft away from the rotor shaft. The second rolling bearing can be arranged at the end of the rotor shaft away from the drive shaft. The third rolling bearing can be arranged axially between the first rolling bearing and the second rolling bearing.

[0012] In order to transmit torque, a drive shaft can be engaged with another drive shaft, for example, by means of gears mounted on the drive shaft or by teeth, for example, cut out in the drive shaft.

[0013] The drive unit can have additional components. The motor can then have a rotor that is anti-rotatingly connected to a rotor shaft. Furthermore, the motor can have a stator that interacts electromagnetically with the rotor. The transmission mechanism can be a single-stage or multi-stage transmission mechanism, such as a cylindrical gear transmission mechanism. The drive unit can form a tram axle for a vehicle.

[0014] According to an improved design, the third rolling bearing can be located primarily on the drive shaft, particularly axially, with its inner ring abutting against a radially protruding portion on a side facing away from the rotor shaft. This allows radial and axial forces acting on the drive shaft, for example from teeth or a parking lock at the drive shaft, to be directly directed into the third rolling bearing. Therefore, an additional interface for force transmission can be eliminated. The protrusion can be constructed by a shoulder projecting radially relative to the bearing housing or by a separate element, such as a retaining ring, mounted on the drive shaft. The third rolling bearing can be arranged in the first housing section and thus rotatably supports the drive shaft and rotor shaft within the first housing section.

[0015] According to one improved design, the first and third rolling bearings can be arranged in an X-type or O-type configuration within the first housing section. Therefore, axial forces, such as those originating from the running teeth, during push-pull operation can be guided from the drive shaft to the first housing section (e.g., the transmission mechanism housing) via the rolling bearings. Radial forces acting on the drive shaft are directly supported by the drive shaft through the rolling bearings in the first housing section.

[0016] Optionally, the first, second, and / or third rolling bearings can be preloaded axially relative to the housing section where the respective rolling bearings are located, particularly by means of springs or washers. This helps to absorb axial forces.

[0017] According to an improved design, the drive shaft and rotor shaft can be axially fastened to each other (axially fixed connection), wherein one of the first and third rolling bearings is constructed as a floating bearing and the other is constructed as a fixed bearing. Therefore, stress can be relieved and manufacturing tolerances can be compensated for through thermal expansion.

[0018] According to an improved embodiment, the rotor shaft can abut its outer circumferential surface against the inner surface of the inner ring of the third rolling bearing. The rotor shaft is axially supported at the inner ring of the third rolling bearing or at the drive shaft by a radial shoulder (an end face oriented axially). Therefore, the axial force of the rotor shaft toward the drive shaft can be supported by the inner ring of the bearing. The bearing housing of the drive shaft, i.e., the section of the drive shaft where the inner ring of the third rolling bearing is located, and the outer circumferential surface of the rotor shaft can have the same outer diameter. Therefore, the inner ring of the third rolling bearing can have an inner diameter that remains constant axially.

[0019] According to one improvement, the third rolling bearing can have an axially extended inner ring that extends axially from the third rolling bearing. Therefore, with the same radial structural dimensions of the rolling bearing, more reliable contact with the rotor shaft and the drive shaft can be achieved through a sufficiently large contact surface. This contributes to a radially compact structural design.

[0020] Alternatively, the third rolling bearing can be designed to be larger than both the first and third rolling bearings (e.g., in terms of standard width). Therefore, conventional rolling bearings can be used with a sufficiently large contact area with both the rotor shaft and the drive shaft. This contributes to a cost-effective design. With a standard width, the inner and outer rings of the bearing can have the same axial dimensions.

[0021] According to an improved embodiment, the third rolling bearing can have a shoulder with an increased inner diameter at the axially extended inner ring, wherein the outer circumferential surface of the rotor shaft abuts against this shoulder at the inner ring. Therefore, axial force can be transmitted from the rotor shaft to the inner ring with little or no weakening of the rotor shaft's cross-section. The shoulder is particularly constructed at the end of the inner ring facing the rotor shaft.

[0022] According to an improved design, the rotor shaft can have a stepped portion with a reduced outer diameter, wherein the inner ring of the third rolling bearing abuts against this stepped portion on the rotor shaft with its inner circumference. Therefore, axial force can be transmitted from the rotor shaft to the inner ring of the third rolling bearing without weakening the cross-section of the inner ring. The stepped portion on the rotor shaft and the bearing housing on the drive shaft, i.e., the section of the drive shaft where the third rolling bearing's inner ring is located, can have the same diameter. The stepped portion is particularly constructed at the end of the rotor shaft facing the drive shaft.

[0023] According to one improvement, the drive shaft can be constructed as a hollow shaft, either partially or completely along the axial direction. Therefore, the drive shaft can have a central opening or a central through portion. This allows for oiling or cooling of the rotor shaft and / or shaft connections, such as interlocking teeth. Radial channels can be constructed in the drive shaft and / or the rotor shaft. This allows for oiling or cooling of the bearings and / or seals. Independently, it is conceivable that the rotor shaft can be constructed as a hollow shaft, either partially or completely along the axial direction.

[0024] According to one improvement, the rotor shaft and the drive shaft can be connected to each other in a material-locking manner (e.g., by means of welding), a form-locking manner (e.g., by means of interlocking teeth), and / or a force-locking manner (e.g., by means of extrusion joints). Therefore, a structurally simple and stable connection of the shafts can be achieved.

[0025] The drive shaft and rotor shaft can overlap each other axially and connect to each other in the overlap area. An axially projecting journal can be constructed on the rotor shaft, extending into the opening or through portion of the drive shaft in the assembled state. Internal teeth can be constructed on the inner periphery of the drive shaft, and external teeth can be constructed on the outer periphery of the journal. The internal and external teeth, when interlocked, form an interlocking toothed section. Attached Figure Description

[0026] The following explanation describes feasible embodiments of the present invention with reference to the accompanying drawings. Wherein:

[0027] Figure 1 A schematic cross-sectional view of a drive unit for a vehicle is shown; and

[0028] Figures 2a-2dThe image shows the rotor shaft and drive shaft in the form of... Figure 1 A feasible design scheme for the support portion at the third rolling bearing of the drive unit. Detailed Implementation

[0029] The drive unit for the vehicle Figure 1 The reference numeral 10 generally pertains to the drive unit 10. The drive unit 10 includes a motor 12 with a rotor shaft 14 and a transmission mechanism 16 with a drive shaft 18 separate from the rotor shaft 14. The drive shaft 18 is rotatably supported in a first housing section 22 (not shown) by means of a first rolling bearing 20, and the rotor shaft 14 is rotatably supported in a second housing section 26 (not shown) by means of a second rolling bearing 24. The first housing section 22 can be the housing of the transmission mechanism 16, and the second housing section 26 can be the housing of the motor 12 (the housing is correspondingly not shown). The housing can have one or more housing walls (again not shown) in which bearing housings (without reference numerals) for the rolling bearings 20, 24, 28 are constructed (the bearing housings are indicated by shaded lines).

[0030] The drive shaft 18 and the rotor shaft 14 are connected to each other in a rotationally inert manner. A third rolling bearing 28 is arranged at the axial transition between the drive shaft 18 and the rotor shaft 14. This third rolling bearing has an inner ring 30, the inner ring 30 of which abuts against the rotor shaft 14 and the drive shaft 18 with its inner surface 32 (see [link]). Figure 2a ).

[0031] The inner surface 32 of the bearing inner ring can be an inner surface 32 with a continuously constant inner diameter (along the axial direction) or a stepped inner surface 32 with different inner diameters. The rotor shaft 14 and the drive shaft 18 are arranged coaxially with each other. The drive shaft 18 can be the input shaft of the transmission mechanism.

[0032] The first rolling bearing 20 is arranged at the end of the drive shaft 18 opposite to the rotor shaft 14. The second rolling bearing 24 is arranged at the end of the rotor shaft 14 opposite to the drive shaft 18. The third rolling bearing 28 is arranged axially between the rolling bearings 20 and 24. The drive shaft 18 has, for example, teeth 34 cut in the drive shaft 18 for transmitting torque.

[0033] The motor 12 has a rotor 36 that is anti-rotatingly connected to the rotor shaft 14. Furthermore, the motor 12 has a stator (not shown) that electromagnetically interacts with the rotor 36. The drive unit 10, for example, constitutes a tram axle for a vehicle.

[0034] The third rolling bearing 28 is mostly located on the drive shaft 18 along the axial direction, wherein the inner ring 30 of the bearing abuts against a radially protruding portion 38 on the side opposite to the rotor shaft 14. The protruding portion 38 is constructed, for example, by a shoulder that protrudes radially relative to the bearing housing 40, i.e., the section of the drive shaft 18 in which the inner ring 30 of the third rolling bearing 28 is located.

[0035] The third rolling bearing 28 is arranged in the first housing section 22 and rotatably supports the drive shaft 18 and the rotor shaft 14 in the first housing section 22. The first rolling bearing 20 and the third rolling bearing 28 are arranged in the first housing section 22, for example, in an X-shaped arrangement. Optionally, the rolling bearings 20, 24, and 28 can be preloaded axially, as explained above.

[0036] The drive shaft 18 and the rotor shaft 14 are fastened to each other axially, wherein one of the first rolling bearing 20 and the third rolling bearing 28 is constructed as a floating bearing and the other bearing is constructed as a fixed bearing (not shown in detail).

[0037] exist Figure 2a The enlarged view shows the pressing Figure 1 The support portion is located at the third rolling bearing 28. The third rolling bearing 28 has an axially extending inner ring 30 that extends axially from the rolling bearing 28. The rotor shaft 14 has a stepped portion 42 with a reduced outer diameter relative to the outer peripheral surface 41, wherein the inner ring 30 of the third rolling bearing 28 abuts against the stepped portion 42 at the rotor shaft 14 with its inner surface 32. The rotor shaft 14 is supported at the end side of the (extended) inner ring 30 of the rolling bearing 28 by a radial shoulder 44. The bearing housing 40 of the drive shaft 18 and the stepped portion 42 of the rotor shaft 14, for example, have the same outer diameter. The inner ring 30 has an inner diameter that remains constant axially at its inner surface 32.

[0038] Drive shaft 18 is constructed as a hollow shaft with a central through portion 46 (see...) Figure 1 Therefore, the rotor shaft 14 and, if necessary, the shaft connection can also be oiled or cooled, as explained above.

[0039] The rotor shaft 14 and the drive shaft 18 are connected to each other, for example, by form-fitting, or more precisely by means of interlocking teeth 48 (see...). Figure 1 The drive shaft 18 and the rotor shaft 14 overlap each other axially and are connected to each other in the overlapping area. A journal 50 extending axially is constructed at the rotor shaft 14, which extends into the through portion 46 of the drive shaft 18 in the assembled state of the shafts 14 and 18.

[0040] An internal toothed portion 54 is constructed at the inner periphery 52 of the drive shaft 18, and an external toothed portion 58 is constructed at the outer periphery 56 of the journal 50. The internal toothed portion 54 and the external toothed portion 58 form an interlocking toothed portion 48 when they are inserted together.

[0041] Figures 2b to 2d Different design options for the support portion at the third rolling bearing 28 are shown. Identical or functionally identical elements are given the same reference numerals, thus referring to the foregoing embodiments to avoid repetition.

[0042] Press Figure 2b At the support part, different Figure 2a The rotor shaft 14 does not have a radial shoulder 44. Instead, the third rolling bearing 28 has a shoulder 60 at the (axially extended) inner ring 30, which has an increased inner diameter, wherein the rotor shaft 14 abuts against the shoulder 60 at the inner ring 30 with its outer circumferential surface 41. The shoulder 60 is constructed at the end of the rotor shaft 14 facing the drive shaft 18.

[0043] Press Figure 2c In the support part, different Figure 2a The inner ring 30 of the bearing does not extend axially, and therefore does not extend axially beyond the third rolling bearing 28. The inner ring 30 abuts against the stepped portion 42 at the rotor shaft 14 with its inner surface 32. The rotor shaft 14 is supported at its end by a radial shoulder 44 at the inner ring 30 of the rolling bearing 28. Compared to Figure 2a The support part in the middle, Figure 2c The rolling bearing 28 moves further toward the rotor shaft 14.

[0044] Press Figure 2d In the support part, different Figure 2a The rotor shaft 14 does not have a radial shoulder 44 at its end against the inner ring 30 of the bearing. Instead, the rotor shaft 14 is supported at the end of the drive shaft 18 by the radial shoulder 44. The outer circumferential surface 41 of the rotor shaft 14 and the bearing housing 40 of the drive shaft 18 have the same outer diameter. The inner ring 30 does not extend axially, and thus does not extend axially from the rolling bearing 30. The inner ring 30 has an inner diameter that remains constant axially at its inner surface 32.

Claims

1. A drive unit (10) for a vehicle, the drive unit having a motor (12) with a rotor shaft (14) and a transmission mechanism (16) with a drive shaft (18), wherein, The drive shaft (18) is rotatably supported in the first housing section (22) by means of a first rolling bearing (20), and the rotor shaft (14) is rotatably supported in the second housing section (26) by means of a second rolling bearing (24). The drive shaft (18) and the rotor shaft (14) are anti-rotationally connected to each other, wherein a third rolling bearing (28) is arranged at the transition between the drive shaft (18) and the rotor shaft (14), the third rolling bearing having an inner ring (30), wherein the inner ring (30) is formed by its inner surface... (32) Abutting against the rotor shaft (14) and the drive shaft (18), wherein the third rolling bearing (28) is located on the drive shaft (18), wherein the inner ring (30) of the bearing abuts against a radial protrusion (38) on a side away from the rotor shaft (14), such that radial and axial forces acting on the drive shaft (18) from the teeth or parking lock at the drive shaft (18) are directly guided into the third rolling bearing (28), and wherein the protrusion (38) is configured as a radially protruding shoulder of the drive shaft (18).

2. The driving unit (10) according to claim 1, characterized in that, The first rolling bearing (20) and the third rolling bearing (28) are arranged in the first housing section (22) in an X-shaped arrangement or an O-shaped arrangement.

3. The driving unit (10) according to claim 1 or 2, characterized in that, The drive shaft (18) and the rotor shaft (14) are fastened to each other axially, wherein one of the first rolling bearing (20) and the third rolling bearing (28) is configured as a floating bearing and the other is configured as a fixed bearing.

4. The driving unit (10) according to claim 1 or 2, characterized in that, The rotor shaft (14) abuts against the inner surface (32) of the inner ring (30) of the third rolling bearing (28) on its outer peripheral surface (41), wherein the rotor shaft (14) is axially supported by a radial shoulder (44) at the inner ring (30) of the third rolling bearing (28) or at the drive shaft (18).

5. The driving unit (10) according to claim 1 or 2, characterized in that, The third rolling bearing (28) has an axially extending inner ring (30) that extends axially from the third rolling bearing (28), or the third rolling bearing (28) is designed to be a larger rolling bearing than the first rolling bearing (20) and the second rolling bearing (24).

6. The driving unit (10) according to claim 5, characterized in that, The third rolling bearing (28) has a shoulder (60) with an increased inner diameter at the inner ring (30) of the bearing, wherein the outer circumferential surface (41) of the rotor shaft (14) abuts against the shoulder (60) at the inner ring (30) of the bearing.

7. The driving unit (10) according to claim 1 or 2, characterized in that, The rotor shaft (14) has a stepped portion (42) with a reduced outer diameter, wherein the inner ring (30) of the third rolling bearing (28) abuts against the stepped portion (42) at the rotor shaft (14) with its inner surface (32).

8. The driving unit (10) according to claim 1 or 2, characterized in that, The drive shaft (18) is partially or completely hollow along the axial direction.

9. The driving unit (10) according to claim 1 or 2, characterized in that, The rotor shaft (14) and the transmission shaft (18) are connected to each other in a material-locking, form-locking and / or force-locking manner.

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