Arrangement for transmitting a torque from a transmission to sideshafts

The present invention relates to an arrangement for transmitting a torque to side- shafts in a motor vehicle and to a joint outer body of a constant velocity joint for use in an arrangement according to the invention.

Solutions for the transmission of torque for front axles of front wheel drive vehi- cles are known from the prior art, which solutions have a differential which is integrated into the transmission and intermediate shafts which, in order to connect the transmission to those wheels of the motor vehicle which are fastened to the side- shafts, are connected via a flange connection or a plug-in connection firstly to the lateral gears of the differential and secondly to the joint outer bodies of constant velocity joints.

As a consequence of the arrangement of the differential in the transmission, an adaptation of diverse components, in particular the intermediate shaft and the differential, to lower or higher torques is possible only if the transmission is addition- ally adapted. Accordingly, the design of the components is oriented toward the transmission of higher torques, the result of which are a higher weight of the overall arrangement and uneconomical material application.

Furthermore, in most cases, the differential is arranged in the lower region of the transmission and therefore moves in the transmission oil sump. This leads to churning losses and an overall poorer degree of efficiency in comparison with an arrangement of a differential outside the transmission body.

In addition, in the case of transversely mounted engines, in which the differential does not usually coincide with the central vehicle longitudinal axis, equally long

intermediate shafts between the differential and the constant velocity joint or e- qually long sideshafts between the constant velocity joint and the wheel cannot be realized, with the result that the torsional spring rigidity of the shaft arrangement is not identical for each wheel of the motor vehicle. A different response behavior of the driven wheels can therefore occur, in particular in the case of high acceleration values of the vehicle.

It is therefore an object of the invention to solve at least partially the problems which are described in the prior art and, in particular, to provide an arrangement which makes more flexible adaptation possible of the individual components to the technical boundary conditions, permits a higher degree of energy efficiency and restricts the part diversity, and, furthermore, to provide a joint outer body which can be used in the arrangement which is proposed here.

These objects are achieved by an arrangement according to the features of patent claim 1 and by a joint outer body as claimed in claim 9. Further advantageous refinements of the invention are specified in the dependent patent claims. Reference is made to the fact that the features which are described individually in the dependent patent claims can be combined with one another in any desired, technologically appropriate manner and define further refinements of the invention. Moreover, the features which are described in the patent claims are specified and explained more precisely in the description, further preferred refinements of the invention being illustrated.

In the present case, the object is achieved by an arrangement for transmitting a torque from a transmission of a motor vehicle to a sideshaft, comprising at least one transmission having at least one transmission housing, one sideshaft assembly having at least one differential with a differential housing, a hollow shaft, a first sideshaft and a second sideshaft, the sideshaft assembly extending partially through the transmission housing and the differential being arranged outside the transmission housing.

Here, an arrangement is described, in particular, which is suitable for use in front axles in the case of front wheel drive motor vehicles, in which a transmission transmits the torques via a differential to the sideshafts of the front wheels of the motor vehicle.

The arrangement will be described with an open (nonlocked) differential in the following text. It has, in particular, two planetary bevel gears which rotate with the differential housing about a central rotational axis of the sideshaft assembly, and two bevel gears which are in engagement with the planetary gears and are arranged on the central rotational axis. Here, one (second) bevel gear is connected to an intermediate shaft, which extends through a hollow shaft to a second joint outer body, and therefore transmits the transmission torques via the intermediate shaft and a second joint outer body to the second sideshaft. The other (first) bevel gear forms a structural unit with a first joint outer body and therefore transmits the transmission torques to the first sideshaft.

As an alternative, however, any differential which is known from the prior art can be used. In particular, the transmission of the torques from the differential housing via intermediate gearwheels (worm gearwheels, bevel gearwheels, helical gearwheels, etc.) to further gearwheels which are arranged on output shafts can be of different design. What is continuously significant here for the application is only the transfer of the torques from the differential housing to two shafts (an intermediate shaft and a first joint outer body here) via gearwheels which are arranged in the differential. For example, multiple disk locking differentials, electronically controlled differentials, locking differentials with a friction cone, locking differentials with helical gearwheels, locking differentials with worm gearwheels, locking differentials with a viscous coupling and also locking differentials without toothing can be used.

The sideshaft assembly comprises, in particular, a common central rotational axis for the joint outer bodies which are connected to one another via the differential, inter alia. The sideshaft assembly then penetrates a part of the transmission housing, with the result that the sideshafts of the sideshaft assembly extend toward the wheels on both sides of the transmission. The differential of the sideshaft assembly is additionally arranged outside the transmission housing, that is to say, in other words, between the transmission and the wheel and/or the constant velocity joint. The problems which were mentioned in the introduction can therefore be overcome, as will also be explained in the following text in relation to the further de- sign variants and the figures.

In order to decouple the vehicle and the drive unit (engine, etc.), inter alia also from the transmission and the differential, from the translatory wheel movements, the torques of the drive unit are transmitted via constant velocity joints to the side- shafts and therefore to the wheels. Here, the constant velocity joints can be configured as plunge joints or fixed joints.

Accordingly, one development of the arrangement according to the invention is proposed, the first sideshaft having a first joint with a first joint outer body and the second sideshaft having a second joint with a second joint outer body, and the first sideshaft being connected to the differential via the first joint and the second sideshaft being connected to the differential via the second joint. The joints which are mentioned here and connect the two sideshafts can in principle be configured according to the known design for motor vehicles or comparably driven vehicles, similar or even identical designs being proposed for both joints of a sideshaft assembly, in particular. For example, what are known as plunge joints are preferred which reliably ensure a transmission of torque even in the case of deflected shafts and an axial relative movement of the shafts with respect to one another.

It is proposed according to a further refinement that the first joint outer body is integrated at least partially into the differential. A movement of the joint outer body within the differential occurs as a consequence of different movements of the

drive wheels of the motor vehicle (for example, when driving around bends). The joint outer body is therefore arranged in the differential housing such that it can be rotated with respect to the differential and is sealed with respect to the surroundings via sealing elements between the differential housing and the joint outer body.

In particular, the joint outer body is mounted within the differential in such a way that any forces which act on the joint outer body via the sideshaft are dissipated via the differential housing, and/or via the sideshaft assembly and the transmission housing. According to a further refinement, the joint outer body can also be moun- ted outside the differential housing, with the result that any forces of the sideshafts via the joint outer body are dissipated not via the differential, but rather via bearings outside the differential housing, for example to the body of the vehicle.

According to a further expedient embodiment, the differential housing is in en- gagement with the hollow shaft, and the hollow shaft transmits a torque of the transmission via drive means of the hollow shaft and via output means of the transmission. Here, the drive means and output means can be configured as gearwheels, belts or disks which are connected to one another nonpositively, in particular. Here, the hollow shaft is connected fixedly to the differential housing and is mounted in the transmission housing.

According to a further advantageous embodiment, the drive means of the hollow shaft is a main drive gearwheel and the output means of the transmission is an output gearwheel, and the main drive gearwheel is in engagement with the output gearwheel. Here, the main drive gearwheel of the hollow shaft or the sideshaft assembly is connected to the hollow shaft, with the result that torques can be transmitted via the transmission to the drive gearwheel and/or to the differential outer body.

Furthermore, the hollow shaft serves to make it possible for the second joint to be connected via a coupler shaft to the differential and/or the bevel gear in the differ-

ential, the coupler shaft being guided through the hollow shaft and being supported in the latter. The coupler shaft also serves to make it unnecessary for different spacings between the differential and the wheels to be compensated for by different sideshaft lengths, with the result that a symmetrical arrangement of the joint outer bodies with respect to the respective wheels is possible. The coupler shaft makes it possible to provide an arrangement which makes it possible to equalize the torsional spring rigidity of the components for the transmission of the torques to the wheels of the motor vehicle in such a way that the driven wheels exhibit a very uniform response behavior, in particular in the case of pronounced load chan- ges.

According to a further refinement, the differential housing has at least one supporting face for at least one bevel gear which is connected to the joint outer body.

Here, the supporting face serves to fix the bevel gear and/or the joint outer body within the differential housing, with the result that firstly the joint outer body is arranged rotatably in the differential housing and secondly it is impossible for the joint outer body to fall out of the differential housing. The bevel gear has a face which lies opposite the supporting face and is configured so as to correspond. The bevel gear is preferably attached on a shoulder or on the circumference of the joint outer body and is advantageously shaped as a bevel gear disk which is mounted on the outside (so as to lie opposite the joint ball tracks) and can thus interact with a planetary gear of the differential which is likewise of beveled configuration here.

According to a further refinement, the transmission has a first lubricating system and the differential has a second lubricating system, the first lubricating system and the second lubricating system being configured independently of one another. In other words, this means, in particular, that the lubricants of both components are not mixed (directly). In principle, in particular, separate lubricants, lubricant reser- voirs, lubricant feed lines and discharge lines or the like can be provided. Firstly, a reduction in the churn losses and therefore an improvement in the degree of efficiency of the drive unit occur as a result of the arrangement of the differential out-

side the first lubricating system of the transmission. Secondly, the lubrication of the differential can be adapted in a particularly satisfactory manner to the requirements of said assembly. In particular, grease lubrication can therefore also be realized in the second lubricating system.

According to a further advantageous refinement, the differential and at least the first joint form a common second lubricating system. This feature leads to a further cost advantage of the compact arrangement of the differential and the first joint. In this refinement, the first joint outer body can have at least one aperture to the dif- ferential housing, in order thus to make common lubrication possible with the same lubricant firstly of the first joint and secondly of the differential.

As a result of the arrangement of the differential outside the transmission, they can be combined with one another independently of one another for a very wide variety of applications or loads. Here, in particular, the transmissions can be designed independently of the respective differential type or the overall size.

A joint outer body, to which the invention, furthermore, relates, can in principle be used in the arrangement according to the invention and is distinguished by the fact that the joint outer body has a bevel gear. Here, the joint outer body on the opposite side from the receptacle of the sideshaft has on the outside an integrated (for example, machined) and/or separate (and fastened on the outside) bevel gear. Here, the bevel gear can be produced, in particular, together with the joint outer body and can accordingly have the same material. However, it can also be connected to the latter by different joining techniques and can accordingly comprise different materials, with the result that the bevel gear can be designed specifically for the application. Finally, the bevel gear is driven as a consequence of the rotation of the differential body by the planetary gears which are fastened in the differential body, with the result that torques are transmitted via the transmission and the differential body to the joint outer body and therefore to the sideshaft.

It is to be noted for the sake of completeness that, in special cases (as an alternative or cumulatively), identically acting transmission elements can be provided on the outside of the joint outer body, in particular other gearwheel types, wedge shaped toothing systems, positively locking elements, etc.. These are preferably config- ured as a separate component and are connected to the joint outer body; however, this is not necessary, with the result that optionally a single piece variant can exist.

According to a further development of the invention, the bevel gear is connected releasably to the joint outer body. A replacement or a repair of the differential is therefore likewise possible optionally - the joint outer bodies can therefore likewise be integrated later into other differentials, after the correspondingly required gearwheel has been mounted again.

Additionally, the invention particularly preferably relates to a motor vehicle having at least one arrangement according to the invention for the transmission of torque from an engine via the transmission and the sideshafts toward the wheels.

The invention and the technical background will be explained in the following text using the figures. Reference is made to the fact that the figures show particularly preferred design variants, to which said invention is not restricted, however. In the figures, in a diagrammatic manner:

fig. 1 shows a cross section through a first design variant of the arrangement,

fig. 2 shows a cross section through a further exemplary embodiment of a transmission having a sideshaft assembly, and

fig. 3 shows a cross section through a differential having an integrated joint.

Fig. 1 diagrammatically shows, as a constituent part of a motor vehicle 3, a cross section of an arrangement 1 comprising a sideshaft assembly 4 and a transmission 2 which is delimited by a transmission housing 5, the sideshaft assembly 4 being mounted in the transmission housing 5 and being sealed with respect to the trans- mission 2. The sideshaft assembly 4 is driven via drive means 27, in the present exemplary embodiment by a main drive gearwheel 9 which is arranged in the transmission housing 5. The main drive gearwheel 9 transmits a torque of the transmission 2 via a hollow shaft 16 of the sideshaft assembly 4 to the differential housing 8 of a differential 7, which differential housing 8 is connected to the hol- low shaft 16.

The differential 7 is configured as a bevel gear differential in this exemplary embodiment. Planetary gears 21 are arranged in a rotatably mounted manner in the differential housing 8, which planetary gears 21 drive the bevel gears 18 (other gearwheels can be used depending on the differential type) in the same direction and at the same speed as a consequence of a rotation of the differential housing 8. In the event of a different rotational movement of the first sideshaft 10 and the second sideshaft 11, for example as a result of the motor vehicle 3 driving around a bend, the planetary gears 21 compensate for the differential movement between the first sideshaft 10 and the second sideshaft 11 and the bevel gears 18.

Furthermore, a first joint 12 having a first joint outer body 13 is arranged within the differential 7, the first joint 12 being configured as a plunge joint and receiving the sideshaft 10 within itself. The torques which are transmitted from the transmis- sion 2 via the main drive gearwheel 9 and the hollow shaft 16 to the differential outer housing 8 are forwarded via the bevel gears 18 firstly to the first joint outer body 13 and secondly to a coupler shaft 22 which is guided through the hollow shaft 16 and is connected to a second joint 14 which, as a plunge joint, receives the second sideshaft 11 in an articulated manner.

Accordingly, the sideshaft assembly 4 forms a common rotational axis 23 for the first sideshaft 10, the second sideshaft 11, the first joint 12, the second joint 14 and the planetary gears 21 of the differential 7.

Fig. 2 shows a cross section through a transmission 2 and a sideshaft assembly 4 of the arrangement 1, an output means 28, here an output gearwheel 6, being arranged within the transmission 2 in such a way that it is in engagement with a drive means 27, here a main drive gearwheel 9, of the sideshaft assembly 4. Here, the main drive gearwheel 9 is received within the transmission housing 5, said main drive gearwheel 9 transmitting torques of the output gearwheel 6 via the hollow shaft 16 to the differential housing 8, the hollow shaft 16 being mounted in the transmission housing 5. Here, the transmission 2 has a first lubricating system 19 which is separate from the differential (likewise described as a bevel gear differential here), only the drive gearwheel 9 of the sideshaft assembly 4 being moved in the lubricating sump of the transmission 2.

Two bevel gears 18 which lie opposite one another and two planetary gears 21 which lie opposite one another are arranged within the differential 7, and furthermore a first joint 12 having a first joint outer body 13. The first sideshaft 10 is re- ceived in an articulated manner within the first joint 12 which is configured here as a plunge joint, the supporting face 17 serving firstly to mount and fix the bevel gear 18 and/or the first joint outer body 13 within the differential housing 8 and it being possible secondly to use said supporting face 17 as a friction cone for use as a locking differential. The bevel gears 18 which are driven via the differential hou- sing 8 and via the planetary gears 21 drive firstly the first joint outer body 13 and secondly the coupler shaft 22 which for its part is connected directly or indirectly to the second joint outer body 15. In particular in the case of an indirect connection of the coupler shaft 22 and the second joint outer body 15, for example by a corresponding wedge-shaped toothing system and plug in connection, the coupler shaft 22 is to be mounted rotatably in the hollow shaft 16 in such a way that an unde- sired excitation of the arrangement is avoided which is familiar to a person skilled in the art as "humming". At the same time, asymmetrical elements of the transmission arrangement can be compensated for via the coupler shaft 22, which asymmet-

rical elements would have to be used as a consequence of the first sideshafts 10 and second sideshafts 11 of different size of said transmission arrangement, with the result that different torsional spring rigidities of the drive components would be the consequence.

The second sideshaft 11 is received in an articulated manner in the second joint 14 which is configured as a plunge joint, with the result that translatory movements of the wheels of the motor vehicle 3 can be absorbed by the second joint 14.

Fig. 3 shows a cross section through a differential 7, likewise configured as a bevel gear differential in the present exemplary embodiment, having the integrated first joint 12 as a constituent part of the sideshaft assembly 4, and also shows the two planetary gears 21 which lie opposite one another and are connected to the differential housing 8 and the bevel gears 18 which are arranged opposite one another and are in engagement with the planetary gears 21. The torques of the transmission 2 are transmitted from the hollow shaft 16 via the differential housing 8 and the planetary gears 21 to the bevel gears 18 and then firstly via the first joint outer body 13 to the first sideshaft 10 and secondly via the coupler shaft 22 and the second joint outer body 15 to the second sideshaft 11. The first joint outer body 13 is received rotatably here in the differential housing 8 which can be of single part or else multiple part configuration. In particular, the first joint 12 and the differential 7 can have separate lubricating systems, it also being possible to produce a common second lubricating system 20 via apertures 25 between the joint outer body 13 and the differential 7, the second lubricating system 20 being independent of the first lubricating system 19 of the transmission 4.

In particular, the second lubricating system 20 is then delimited by the differential housing 8 and the first joint outer body 13, and the first lubricating system 19 is delimited via the transmission housing 5. The second lubricating system 20 is sea- led with respect to the surroundings by suitable sealing elements 24.

In the case of plug-in connections 26 and/or journal connections firstly between the hollow shaft 16 and the differential housing 8 and secondly between the coupler shaft 22 and the second joint outer body 15, what is known as "humming" should be avoided, in particular, by corresponding mounting of the coupler shaft 22 in the hollow shaft 16 and of the hollow shaft 16 in the transmission housing 5.

In the exemplary embodiment which is shown here, the supporting faces 17 are arranged on the inner side of the differential housing 8, with the result that the bevel gears 18 can be supported on said inner face by way of their beveled circum- ferential face. The bevel gears 18 are therefore mounted radially in the differential housing 8 and are fixed axially at the same time by the supporting face 17 and the planetary gears 21. With a corresponding design, the supporting faces 17 can generate an additional frictional moment, with the result that the differential 7 is also suitable for use as a locking differential.

The present invention is not restricted to the exemplary embodiments which are shown. Rather, a large number of modifications of the invention are possible within the scope of the patent claims. This relates, in particular, to the design of the joints as plunge joints or fixed joints of any known type.

List of Designations

1 Arrangement

2 Transmission 3 Motor vehicle

4 Sideshaft assembly

5 Transmission housing

6 Output gearwheel

7 Differential 8 Differential housing

9 Main drive gearwheel

10 First sideshaft

11 Second sideshaft

12 First joint 13 First joint outer body

14 Second joint

15 Second joint outer body

16 Hollow shaft

17 Supporting face 18 Bevel gear

19 First lubricating system

20 Second lubricating system

21 Planetary gear

22 Coupler shaft 23 Rotational axis

24 Sealing element

Aperture Plug in connection Drive means Output means