DIFFERENTIAL GEAR AND DRIVE TRAIN WITH SUCH A DIFFERENTIAL GEAR

Abstract

A differential gear with an input side that can be rotated about an axis of rotation, which has a rotary drive contour for the rotary drive engagement with a drive wheel and at least one pinion gear that can be rotated about a pinion axle, and an output side that can be rotated about the axis of rotation, which has a first axle wheel and a second axle wheel which are in rotary drive engagement with the at least one pinion gear, wherein the input side has a rotary drive section on which the rotary drive contour is provided, and a support section on which the at least one pinion gear is arranged. The rotary drive section and the support section can optionally be brought into a rotary drive connection with one another by means of a shiftable pawl freewheel.

Claims

1. A differential gear with an input side that can be rotated about an axis of rotation, which has a rotary drive contour for the rotary drive engagement with a drive wheel and at least one pinion gear that can be rotated about a pinion axle, and an output side that can be rotated about the axis of rotation, which has a first axle wheel and a second axle wheel which are in rotary drive engagement with the at least one pinion gear, wherein the input side has a rotary drive section on which the rotary drive contour is provided, and a support section on which the at least one pinion gear is arranged, wherein the rotary drive section and the support section can optionally be brought into a rotary drive connection with one another by means of a shiftable pawl freewheel.

2. The differential gear according to claim 1, wherein the pawl freewheel has an outer race, an inner race and in the radial direction between the inner and outer races pivotably arranged pawls which can be or are preferably supported in the radial direction on the inner and outer race and particularly preferably are pivotable about a pivot axis extending in the axial direction, and/or the pawl freewheel, preferably at least one pawl of the pawl freewheel, and/or the rotary drive contour is arranged nested in the radial direction with the at least one pinion gear, particularly preferably aligned with the pinion axle.

3. The differential gear according to claim 1, wherein the input side forms a gear housing in which the first and second axle wheel are arranged and/or on which the first and second axle wheel in the axial and/or radial direction, optionally by means of a plain bearing, can be or are supported, wherein the gear housing preferably has two shaft openings for axle shafts assigned to the first and second axle wheels and at least one of the shaft openings is formed in a tubular axial section of the gear housing, which particularly preferably has a smaller radial extent than an axial section accommodating the pinion gear of the gear housing.

4. The differential gear according to claim 3, wherein the rotary drive section forms the gear housing in which the support section is accommodated, which is annular and can be moved in the radial direction, preferably by means of a plain bearing or via the pawl freewheel, and/or can be or is supported in the axial direction, preferably with play, on the gear housing, wherein the inner race of the pawl freewheel is particularly preferably in one piece with the annular support section and/or the outer race of the pawl freewheel is formed in one piece with the rotary drive contour and/or the gear housing.

5. The differential gear according to claim 3, wherein the support section forms the gear housing, wherein the inner race is preferably formed in one piece with the gear housing and/or the outer race is preferably formed in one piece with the rotary drive contour or is formed separately from an input gear which has the rotary drive contour and which is fixed in a non-rotatable manner to the outer race, wherein the outer race or the input gear is particularly preferably arranged in the radial direction, preferably by means of a roller or needle bearing, and/or can be or is supported on the gear housing in the axial direction, possibly via a radial section on the outer race or the input gear and/or on the tubular axial section of the gear housing.

6. The differential gear according to claim 1, wherein the rotary drive contour is formed as an outer rotary drive contour in the radial direction or as an inner rotary drive contour in the radial direction, wherein the inner rotary drive contour is preferably in rotary drive engagement with a tubular drive wheel arranged coaxially to the axis of rotation, which is particularly preferably rotatably mounted on the gear housing, possibly the tubular axial section of the gear housing.

7. The differential gear according to claim 1, wherein an activating element which can be displaced in the axial direction is provided for shifting the pawl freewheel, wherein the activating element is arranged on the input side so that it is displaceable in the axial direction, preferably directly or via a support element fixed to the input side and particularly preferably the activating element has a tubular supporting section which can be or is slidably supported on a circumferential outer side of the input side or a tubular support element section of the support element.

8. The differential gear according to claim 7, wherein the activating element is assigned a locking device for locking the activating element in at least one axial position, preferably in at least two or at least three axial positions, relative to the pawl freewheel, wherein the latching device is arranged particularly preferably between the tubular supporting section and the circumferential outer side of the input side, between the tubular supporting section and the tubular support element section or between the activating element and a second tubular support element section of the support element lying opposite the tubular support element section in the radial direction and possibly has at least one spring-loaded latching element on the one hand, which can be latched into two or more latching depressions on the other hand.

9. The differential gear according to claim 7, wherein the activating element, optionally via axially protruding activating pins on the activating element, interacts with the pawls of the pawl freewheel, wherein the activating element is movable particularly preferably between a first axial position, in which the rotary drive section is rotary drive coupled in a first and second relative direction of rotation to the support section via the pawls, a second axial position, in which the rotary drive section is rotary drive coupled to the support section in the first relative direction of rotation, but not in the second relative direction of rotation, via at least one pawl, and a third axial position, in which the rotary drive section is rotary drive coupled neither in the first nor in the second relative direction of rotation with the support section via the pawls.

10. A drive train for a motor vehicle with a first wheel axle which can be driven by a first drive unit, possibly an electric drive unit, preferably an electric machine and/or an internal combustion engine, and a second wheel axle, wherein the second wheel axle can be optionally driven via a differential gear according to claim 1 by a second drive unit, possibly an electric drive unit, wherein the input side, particularly preferably the rotary drive contour of the rotary drive section, is in rotary drive connection preferably with the second drive unit, particularly preferably a drive wheel of the second drive unit, and the output side, particularly preferably the first and second axle wheel, is in rotary drive connection preferably with the second wheel axle, particularly preferably with a first and second axle shaft of the second wheel axle.

Description

BRIEF DESCRIPTION

[0031] The invention is explained in more detail below using exemplary embodiments with reference to the attached drawings. In the following:

[0032] FIG. 1 shows a perspective and partially cross-sectional representation of a first embodiment of a differential gear,

[0033] FIG. 2 shows a side view of the differential gear from FIG. 1 in a cross-sectional representation,

[0034] FIG. 3 shows a perspective and partially cross-sectional representation of a second embodiment of a differential gear,

[0035] FIG. 4 shows a side view of the differential gear from FIG. 3 in a cross-sectional representation,

[0036] FIG. 5 shows a side view of a third embodiment of a differential gear in a cross-sectional representation,

[0037] FIG. 6 shows a side view of a fourth embodiment of a differential gear in a cross-sectional representation, and

[0038] FIG. 7 shows a schematic representation of a drive train with a differential gear, in particular a differential gear according to one of FIGS. 1 to 6.

DETAILED DESCRIPTION

[0039] In the Figures, the mutually opposite directions of the differential gear 2 are indicated by means of corresponding arrows, namely the axial directions 4, 6, the radial directions 8, 10 and the circumferential directions 12, 14, wherein the differential gear 2 has an axis of rotation 16 extending in the axial directions 4, 6.

[0040] FIGS. 1 and 2 show a first embodiment of the differential gear 2. The differential gear 2 has an input side 18 that can be rotated about the axis of rotation 16. The input side 18, which can be rotated about the axis of rotation 16, is composed substantially of a rotary drive section 20 and a support section 22. Furthermore, the differential gear 2 has an output side 24 which can also be rotated about the axis of rotation 16. In addition, the input side 18 of the differential gear 2 has at least one differential pinion 28 that can rotate about a pinion axle 26, wherein two differential pinions 28, 30 are provided in the illustrated embodiment that can rotate about the same pinion axle 26. In addition, the pinion axle 26 extends transversely, here at right angles, to the axis of rotation 16 of the differential gear 2. The two differential pinions 28, 30 are designed as differential bevel gears. The output side 24, on the other hand, has a first axle wheel 32 and a second axle wheel 34 located opposite in the axial direction 6, which - because they belong to the output side 24 - can be rotated about the axis of rotation 16 and are in rotary drive engagement with both the differential pinion 28 and the differential pinion 30.

[0041] The input side 18 has a rotary drive contour 36 for the rotary drive engagement with a drive wheel of a drive unit, not shown in detail. The rotary drive contour 36 is provided on the rotary drive section 20 of the input side 18, wherein the rotary drive contour 36 is a rotary drive contour 36 pointing outwards in the radial direction 8, and therefore an outer rotary drive contour 36. In the illustrated embodiment, the rotary drive contour 36 is designed as a toothing, here an external toothing, wherein the external toothing shown is designed as a helical toothing, for example. The two differential pinions 28, 30, on the other hand, are arranged on the support section 22.

[0042] The input side 18 of the differential gear 2 likewise forms a gear housing, wherein the gear housing can also be referred to as a so-called differential basket. The gear housing substantially has three axial sections, namely a first axial section in the form of a tubular axial section 38, a second axial section in the form of an axial section 40 accommodating the differential pinions 28, 30 and the axle wheels 32, 34, and a third axial section in the form of a tubular axial section 42, which follow one another in the axial direction 6. As can be seen from the Figures, the two tubular axial sections 38, 42, which also form end sections of the housing, have a smaller extension in the radial direction 8, 10 than the central axial section 40. The first and second axle wheels 32, 34 are not only arranged in the gear housing formed by the input side 18, but can also be or are supported in the axial direction 4, 6 and the radial direction 8, 10, preferably by means of a plain bearing. Thus, the first axle wheel 32 is supported in the axial direction 4 via an axial bearing 44 and also in the radial direction 8, 10 on the gear housing. The second axle wheel 34, on the other hand, is supported on the gear housing via an axial bearing 46 in the axial direction 6 and also in the radial direction 8, 10.

[0043] As can be seen from FIG. 2, gear housing formed by the input side 18 has a first shaft opening 48 pointing in the axial direction 4 for a first axle shaft assigned to the first axle wheel 32 and a second shaft opening 50 pointing in the axial direction 6 for a second axle shaft assigned to the second axle wheel 34, wherein the first shaft opening 48 is formed in the tubular axial section 38, while the second shaft opening 50 is formed in the tubular axial section 42.

[0044] In the illustrated embodiment according to FIGS. 1 and 2, the rotary drive section 20 of the input side 18 forms the described gear housing, wherein the gear housing is composed of two housing halves 52, 54, here substantially identical in construction, which are fixed to one another with the interposition of an annular housing part 56, here by way of example with the aid of screw connections 58. In addition, the housing halves 52, 54 are supported on the annular housing part 56 in the axial direction 4, 6 via annular disks 60.

[0045] The previously mentioned support section 22 of the input side 18 is accommodated within the gear housing formed by the rotary drive section 20. The support section 22 is annular and has a shaft 62 which extends in the radial direction 8, 10 and on which the pinion gears 28, 30 are mounted so as to be rotatable about the pinion axle 26. In principle, each of the two pinion gears 28, 30 could also be assigned their own separate shafts. The annular support section 22 can be supported in the axial direction 4, 6 on the gear housing formed by the rotary drive section 20 of the input side 18, wherein the support section 22 is arranged with play in the axial direction 4, 6 within the gear housing. In the illustrated embodiment, the support section 22 can be or is supported in the axial direction 4 on a section of the annular disk 60 protruding in the radial direction 10 and in the axial direction 6 on a section of the opposite annular disk 60 protruding in the radial direction 10.

[0046] In order to bring the rotary drive section 20 and the support section 22 into a rotary drive connection with each other only if necessary for the purpose of transmitting a torque between the input side 18 and the output side 24, a shiftable pawl freewheel 64 is arranged between the rotary drive section 20 and the support section 22, by means of which the rotary drive section 20 and the support section 22 can be optionally brought into rotary drive connection together. The pawl freewheel 64 has an outer race 66 and an inner race 68, wherein the outer race 66 surrounds the inner race 68 in the radial direction 8 on the outside. Pivotable pawls 70, 72 are arranged in the radial direction 8, 10 between the outer and inner races 66, 68. The pawls 70, 72 are in rotary drive connection with the outer race 66, wherein the pawls 70, 72 are each pivotable from a release position into a locked position. The pawls 70, 72 can be pivoted about pivot axes 74 extending in the axial direction 4, 6, wherein the pawls 70 are pivotable in the opposite direction to the pawls 72 from the release position to the locked position and vice versa. In addition, the pawls 70, 72 can be or are supported in the radial direction 8, 10 on the sides of the inner and outer races 68, 66 that face one another in the radial direction 8, 10. The pawls 70, 72 are also pretensioned into their locked position via corresponding spring elements 76.

[0047] The outer race 66 of the pawl freewheel 64 is formed in one piece with the annular housing part 56 of the gear housing and therefore also in one piece with the rotary drive contour 36, especially since the rotary drive contour 36 is provided on the side of the annular housing part 56 pointing outwards in the radial direction 8. Furthermore, the inner race 68 of the pawl freewheel 64 is formed in one piece with the annular support section 22 to achieve a particularly compact design. In principle, the support section 22 could be or is supported by an additional radial bearing, preferably a plain bearing, in the radial direction 8 on the gear housing, but in the illustrated embodiment the annular support section 22 is supported in the radial direction 8 by the pawl freewheel 64, more precisely on the sides of the outer and inner races 66, 68 facing each other in the radial direction 8, 10, so that in this way a plain bearing is also created and the pawl freewheel 64 has a dual function.

[0048] In addition, the pawl freewheel 64, in particular its outer and inner races 66, 68, and the rotary driver contour 36 are arranged nested in the radial direction 8, 10 with the pinion gears 28, 30 in order to achieve the most direct and reliable possible torque transmission between rotary drive section 20 and support section 22. In particular, the pawls 70, 72 are arranged nested with the pinion gears 28, 30 in the radial direction 8, 10. It has proven to be particularly advantageous if-as in FIGS. 1 and 2-the pawl freewheel 64, in particular its races 66, 68 and/or the rotary drive contour 36, is aligned with the pinion axle 26 or is arranged on this pinion axle 26. In the embodiment shown, the pinion axle 26 in the side view according to FIG. 2 forms an axis of symmetry or a central axis for the pawl freewheel 64.

[0049] In order to be able to shift the pawl freewheel 64 into different shifting positions, the pawl freewheel 64 is assigned an activating element 78 that can be displaced in the axial direction 4, 6. In principle, the activating element 78 can be arranged directly on the input side 18 of the differential gear 2; in the embodiment according to FIGS. 1 and 2, however, the activating element 78 can be displaced in the axial direction 4, 6 via a support element 80 fixed to the input side 18 and is therefore arranged indirectly on the input side 18.

[0050] The activating element 78 has a tubular supporting section 82 which can be or is supported on a tubular support element section 84 of the support element 80 in the radial direction 8, 10 and in the axial direction 4, 6 in a sliding manner. The support element 80 is subsequently fixed to the gear housing, here the housing half 54, and is preferably designed as a sheet metal or shaped sheet metal part, wherein the tubular support element section 84 extends in the axial directions 4, 6. On its side facing away from the pawl freewheel 64, the activating element 78 has a radial section 86 adjoining the supporting section 82 in the axial direction 6, via which the activating element 78 can be gripped and moved in the axial direction 4, 6 by an actuating device. On a further radial section 88 of the activating element 78 adjoining the supporting section 82 in the axial direction 4, activating pins 90 of the activating element 78 protruding in the axial direction 4 are provided, which can interact directly with the pawls 70, 72 of the pawl freewheel 64 in order to convert the pawl 70, 72 into the respective release or locking position. Each pawl 70, 72 is assigned an activating pin 90 in each case.

[0051] Thus, the activating element 78 is displaceable in the axial direction 4 between a first axial position shown in FIGS. 1 and 2, a second axial position and a third axial position. In the first axial position, the rotary drive section 20 is rotary drive coupled in a first and second relative direction of rotation to the support section 22 via the pawls 70, 72, wherein the pawls 70, 72 are held in their locking position by the aforementioned spring elements 76. In the second axial position, the rotary drive section 20 is rotary drive coupled to the support section 22 via the pawls 70 or the pawls 72 in the first relative direction of rotation, but not in the second relative direction of rotation. In the third axial position, however, the rotary drive section 20 is rotary drive coupled to the support section 22 via the pawls 70, 72 neither in the first nor in the second relative direction of rotation. If the drive wheel assigned to the rotary drive contour 36 is driven by an electric machine, then it can be seen from the foregoing description that thanks to the first axial position the electric machine can also be operated as a generator which can be driven by the output side 24 of the differential gear 2.

[0052] In order to be able to set and hold the various shifting positions of the pawl freewheel 64 in a particularly targeted manner, the activating element 78 is also assigned a latching device 92 for latching the activating element 78 in at least one axial position, preferably in at least two or at least three axial positions, relative to the pawl freewheel 64, wherein the latching device 92 in the illustrated embodiment enables latching in the first, second and third axial position. In the embodiment according to FIGS. 1 and 2, the latching device 92 is arranged in the radial direction 8, 10 between the tubular supporting section 82 of the activating element 78 and the tubular support element section 84 of the support element 80 in order to act between these sections. The latching device 92 has a latching element 94 spring-pretensioned in the radial direction 8 or 10 on the one hand and two or more latching depressions 96 on the other hand, into which the latching element 94 can latch when the respective axial position is reached.

[0053] FIGS. 3 and 4 show a second embodiment of the differential gear 2, wherein the differential gear 2 in the second embodiment substantially corresponds to the differential gear according to FIGS. 1 and 2, so that the differences are substantially discussed below, the same reference numerals for the same or similar parts are used and the above description otherwise applies accordingly.

[0054] In contrast to the first embodiment, the gear housing in the second embodiment is still formed by the input side 18, but here by the support section 22 of the input side 18. The inner race 68 of the pawl freewheel 64 is formed in one piece with the support section 22 forming the gear housing. The outer race 66, on the contrary, is formed separately from an input gear 98 of rotary drive section 20 on the input side 18, which has the rotary drive contour 36, wherein the input gear 98 of rotary drive section 20 is fixed in a non-rotatable manner to the outer race 66 of the pawl freewheel 64, for example by means of screws. The input gear 98 has an outer section 100 in the radial direction 8, which is tubular here by way of example and on which the rotary drive contour 36 is provided, and an inner section adjoining the outer section 100 in the radial direction 10 in the form of a radial section 102 formed in one piece with the outer section 100. The input gear 98 can be or is supported in the radial direction 10 inwards via a radial bearing 104, which is designed here by way of example as a roller bearing or needle bearing, on the gear housing formed by the support section 22, more precisely on the tubular axial section 38 of the gear housing. In the opposite axial directions 4, 6, too, the input gear 98 is supported directly or indirectly on the gear housing and is thus fixed.

[0055] A support element 80 and a latching device 92 are also provided in the second embodiment according to FIGS. 3 and 4, but the latching device 92 together with the latching element 94 and the latching depressions 96 are arranged in the radial direction 8, 10 between the radial section 88 of the activating element 78 and a second tubular support element section 106 lying opposite the tubular support element section 84 in the radial direction 8, 10. In this embodiment, the two tubular support element sections 84 and 106 form a one-piece structural or sheet metal part, wherein the two sections 84 and 106 are connected to one another via a radial section 108.

[0056] In the second embodiment according to FIGS. 3 and 4, too, the pawl freewheel 64 is arranged nested-at least partially-in the radial direction 8, 10 with the pinion gears 28, 30, which also applies-at least slightly-to the rotary drive contour 36.

[0057] FIG. 5 shows a third embodiment of the differential gear 2, which substantially corresponds to the embodiment according to FIGS. 3 and 4, so that only the differences are discussed below, the same reference numerals are used for the same or similar parts and the above description otherwise applies accordingly.

[0058] In contrast to the second embodiment according to FIGS. 3 and 4, the rotary drive contour 36 is formed in one piece with the outer race 66 of the pawl freewheel 64, as a result of which a greater axial overlap of the rotary drive contour 36 with the pinion gears 28, 30 in the sense of a radial nesting can be achieved. The aforementioned radial section 102, however, has been subsequently fixed to the outer race 66 of the pawl freewheel 64, for example by welding. Otherwise, the radial section 102 is in a manner in the radial and axial directions 8, 10; 4, 6 is supported on the gear housing, which corresponds to the support shown in FIGS. 3 and 4.

[0059] FIG. 6 shows a fourth embodiment of the differential gear 2 in at least a partial representation, wherein the differential gear 2 in the fourth embodiment substantially corresponds to the differential gears 2 from the preceding embodiments, so that only the differences are discussed below, the same reference numerals are used for the same or similar parts and the above description otherwise applies accordingly. The pinion gears 28, 30, the shaft 62 and the axle gears 32, 34 have only been omitted for reasons of clarity.

[0060] In the fourth embodiment, the rotary drive contour 36 of the rotary drive section 20 is designed as an inner rotary drive contour 36 in the radial direction 10, thus for example as an internal toothing. In the fourth embodiment, the rotary drive contour 36 is also formed in one piece with the inner race 68 of the pawl freewheel 64. The inner rotary drive contour 36 pointing inwards in the radial direction 10 is in rotary drive engagement with a tubular drive wheel 110 which is arranged coaxially to the input and output side 18, 24 and which can preferably be driven by an electric machine. The tubular drive wheel 110 is supported and mounted via a radial bearing 112 on the gear housing, more precisely on the tubular axial section 38 of the gear housing. The radial bearing 112 is arranged nested in the radial direction 8, 10 with the rotary drive contour 36.

[0061] It can also be seen from FIG. 6 that the supporting section 82 of the activating element 78 is not arranged on an additional support element, but rather directly on the input side, here the support section 22 of the input side 18, so as to be displaceable in the axial direction 4, 6. For this purpose, the supporting section 82 of the activating element 78 is supported on an outer side 114 running around in the circumferential direction 12, 14 . In the radial direction 8, 10 between this circumferential outer side 114 and the supporting section 82 of the activating element 78, the latching device 92 with the components described above, namely the latching element 94 and latching depressions 96, is arranged. In the advantageous embodiment according to FIG. 6, the circumferential outer side 114 is formed on the side of a flange-like radial section 116 of the gear housing formed by the support section 22 that points outwards in the radial direction 8.

[0062] FIG. 7 shows the schematic representation of a drive train 118 for a motor vehicle, in particular a hybrid vehicle, wherein the drive train 118 is suitable for all-wheel drive or four-wheel drive. Thus, the drive train 118 has a first wheel axle 120 which is substantially defined by two axle shafts 122, 124 which are connected at their ends to wheels 126 of the motor vehicle. The first wheel axle 120 can be driven by a first drive unit 128, wherein the first drive unit 128 can be an internal combustion engine and/or an electric drive unit, preferably an electric machine. A hybrid drive unit as a combination of an electric machine and an internal combustion engine is particularly preferred here.

[0063] In addition, the drive train 118 has a second wheel axle 130, wherein the second wheel axle 130 is substantially defined by a first axle shaft 132 and a second axle shaft 134, at the outer ends of which wheels 126 of the motor vehicle or of the drive train 118 are in turn arranged. A differential gear 2 of the type according to the invention is arranged between the first and second axle shafts 132, 134, wherein the first axle shaft 132 protrudes through the first shaft opening 48 into the gear housing in order to be connected to the first axle wheel 32 in a non-rotatable manner. In the opposite axial direction 4, the second axle shaft 134 protrudes into the second shaft opening 50 of the gear housing in order to be connected to the second axle wheel 34 in a non-rotatable manner. The second wheel axle 130 or its axle shafts 132, 134 can be optionally driven by a second drive unit 136 via the differential gear 2, wherein the second drive unit 136 is preferably an electric drive unit, particularly preferably an electric machine, wherein an electrical machine can then also be operated advantageously as a generator. In order to ensure this drive of the second wheel axle 130, the rotary drive contour 36 of the rotary drive section 20 is in rotary drive connection with a drive wheel of the second drive unit 136, while the first and second axle wheel 32, 34 - as already explained above - are in rotary driving connection with the first and second axle shaft 132, 134 of the second wheel axle 130.

TABLE-US-00001 LIST OF REFERENCE NUMERALS 2 differential gear 41 axial direction 6 axial direction 8 radial direction 10 radial direction 12 circumferential direction 14 circumferential direction 16 axis of rotation 18 input side 20 rotary drive section 22 support section 24 output side 26 pinion axle 28 pinion gear 30 pinion gear 32 first axle wheel 34 second axle wheel 36 rotary drive contour 38 tubular axial section 40 axial section 42 tubular axial section 44 axial bearing 46 axial bearing 48 first shaft opening 50 second shaft opening 52 housing half 54 housing half 56 annular housing part 58 screw connections 60 annular disks 62 shaft 64 pawl freewheel 66 outer race 68 inner race 70 pawl 72 pawl 74 pivot axis 76 spring elements 78 activating element 80 support element 82 supporting section 84 tubular support element section 86 radial section 88 radial section 90 activating pin 92 latching device 94 latching element 96 latching depressions 98 input gear 100 outer section 102 radial section 104 radial bearing 106 second tubular support element section 108 radial section 110 drive wheel 112 radial bearing 114 circumferential outer side 116 radial section 118 drive train 120 first wheel axle 122 axle shaft 124 axle shaft 126 wheels 128 first drive unit 130 second wheel axle 132 first axle shaft 134 second axle shaft 136 second drive unit