WO2015058788A1

WO2015058788A1 - Drive assembly and method of controlling a drive assembly

Info

Publication number: WO2015058788A1
Application number: PCT/EP2013/072019
Authority: WO
Inventors: Mark Schmidt; Robert Maslowski; Marc Absenger; Anja Häniche; Colin Zaers
Original assignee: Gkn Driveline International Gmbh
Priority date: 2013-10-22
Filing date: 2013-10-22
Publication date: 2015-04-30
Also published as: DE112013007520T5; DE112013007520B4

Abstract

The invention relates to a drive assembly for a motor vehicle, comprising a first gear and a second gear 6, wherein the first gear 5 and the second gear 6 are drivingly connected to one another; a lubricant filling which, in a static built-in condition of the drive assembly 2, defines a lubricant level; a first reservoir 3 which is arranged above the lubricant level and which, when the drive assembly 2 is being driven, can be filled with lubricant as a result of the rotation of the first gear 5; a second reservoir 4 which is arranged above the lubricant level and which, when the drive assembly 2 is being driven, can be filled with lubricant as a result of the rotation of the second gear 6. The invention also relates to a process of controlling such a drive assembly.

Description

Drive assembly and method of controlling a drive assembly

Description

The invention relates to a drive assembly for being used in the driveline of a motor vehicle, more particularly a motor vehicle which comprises an electric motor as a driving source. Furthermore, the invention relates to a process of controlling such a drive assembly which can form part of an electric drive.

An electric drive can serve as the only drive unit for a motor vehicle or it can be provided in addition to an internal combustion engine, wherein the electric drive and the internal combustion engine can, either individually or jointly superimposed on one another, drive the motor vehicle. Such drive concepts are also referred to as a "hybrid drive". Normally, an electric drive comprises an electric motor and a subsequent reduction gear which translates an introduced rotational movement from high speeds to low speeds. The reduction gear is drivingly connected to a differential drive which is disposed in the power path downstream to the reduction gear. The differential drive divides the introduced torque on to two sideshafts for driving the vehicle wheels.

Electric drives for optionally drivable secondary axles in hybrid all-wheel drive vehicles usually use disconnection systems for the purpose of disconnecting the electric motor from the wheels at higher vehicle speeds. This permits the electric motor to be designed advantageously in respect of traction and, at higher vehicle speeds, it reduces the friction losses.

Supplying all rotating components of a drive with lubricants is frequently problemati- cal. It is necessary to set a high static oil level in order to ensure adequate lubrication and cooling of upper shafts and bearings. This results in relatively high splashing losses, which, in turn, leads to an increase in the formation of heat as a result of the circulation of a relatively large quantity of oil. Particularly in a disconnected condition of a disconnectable electric drive having an upper driving source, a sufficient quantity of lubricant can reach the driveshaft bearings and seals rotating at high speeds only when the lubricant level is very high.

From JP 2006 275 164 A a differential gear is known with a device for supplying a rolling contact bearing with lubricant. The interior of the gear housing is divided into two chambers by a plate, wherein one chamber accommodates the input gear and the other chamber forms an oil reservoir. When the input gear rotates, lubricant reaches the oil reservoir. The lubricant can flow through a channel from the oil reservoir to the bearing of the differential carrier.

From JP 2004 176 744 A a lubricant device for a gearbox is known. The lubricant device comprises a reservoir at the input end, which reservoir supplies bearings at the engine end with lubricant, as well as a reservoir at the output end, which supplies bearings at the gearbox output with lubricant.

US 5 634 530 proposes a lubricant device for a motor vehicle drive. Sprayed oil is conveyed from a cover element to a passage from where it reaches a bearing bush.

It is an object of the present invention to propose a drive assembly having components which run in a lubricant, which drive assembly ensures a reliable supply of lubricant, in particular also when the driving source is disconnected, and thus features a long service life. Furthermore, it is an object of the invention to propose a process of controlling such a drive assembly for a motor vehicle, more particularly as part of an electric drive for an optionally drivable secondary driving axle of a motor vehicle.

The objective is achieved by providing a drive assembly for a motor vehicle, compris- ing: a first gear and a second gear, wherein the first gear and the second gear are drivingly connected to one another; a lubricant filling which, in a static built-in condition of the drive assembly, defines a lubricant level; a first reservoir which is arranged above the lubricant level and which, when the drive assembly is being driven, can be filled with lubricant as a result of the rotation of the first gear; a second reservoir which is arranged above the lubricant level and which, when the drive assembly is being driven, can be filled with lubricant as a result of the rotation of the second gear. By means of the reservoirs the oil sump, respectively at least a part of the lubricant, can be displaced into upper regions of the drive assembly under operational conditions. For this purpose, the pumping effect of the gears is used which convey lubricant from the oil sump upwardly. By using two gears for conveying oil, two different main oil flow directions can be used . In particular, it is possible to fill two separate reservoirs simultaneously, so that even different regions of the drive assembly, which are spacially separated from each other, can be reliably filled with lubricant. The first reservoir with supplying means is preferably configured such that any lubricant received and again discharged during rotation of the first gear, substantially reaches the first reservoir. Accordingly, the second reservoir with supply means is preferably configured such that any lubricant received and again discharged upon rotation of the second gear substantially reaches said second reservoir. The filling levels of the reservoirs can be configured to have a fixed ratio relative to one another, which however can be modified by respective constructive design. Overall, the design of the drive assembly allows a considerable reduction in the quantity of oil required. In addition, under driving conditions, any splashing losses are reduced, which splashing losses may occur under driving conditions as a result of the gears and shafts splashing in the oil sump. The drive efficiency is improved overall, with the driveshaft bearings and seals being oiled when the drive unit is discon- nected. The drive assembly is meant to include any kind of torque transmitting apparatus comprising gears and a lubricant for cooling and lubricating the gears. To that extent, the drive assembly can also be referred to as transmission, gearing or gearbox assembly. For transmitting torque, the first gear and the second gear are indirectly or directly drivingly connected to one another, so that upon introduction of torque into the drive assembly they both rotate jointly. The transmission of torque can be effected directly in that the two gears engage one another, or indirectly in that one or more driving elements are connected in between. It is also conceivable that a coupling is arranged in the power path between the two gears. As far as referece is made to a power path, this is intended to include the path via which torque is transmitted from an input to an output. Thus, the power path can also be referred to as transmission path.

According to a preferred embodiment, the first gear and the second gear are arranged axially offset relative to one another, which means that a central plane of the first gear is axially spaced from a central plane of the second gear. The axis of rotation of the first gear is preferably arranged parallel to the axis of rotation of the sec- ond gear. According to one embodiment, the first gear and the second gear rotate in opposed directions of rotation. It is thus possible to use two main oil flow paths individually for filling one reservoir each, said flow paths resulting from the rotational movement of the respective gear and the lubricant conveyed therefrom, so that two reservoirs are reliably filled with lubricant. However, a different arrangement is also conceivable, wherein two reservoirs are filled by gears rotating in the same direction of rotation. For example, such an arrangement could comprise an intermediate gear between the first and second gear.

The lubricant level is defined by the static built-in condition of the drive assembly in a motor vehicle, i.e. when the rotatingly drivable components stand still. The lubricant level is preferably configured such that at least one of the first and the second gear is partially immersed in the lubricant. In order to avoid splashing losses, the second gear can be arranged in its entirety above the lubricant level. However, it is also conceivable for the second gear, too, to be partially immersed in the lubricant.

According to a preferred embodiment, it is proposed that the first reservoir and the second reservoir are arranged axially spaced apart from one another. Thus, it is ensured that also spatially remote regions of the drive assembly can easily be supplied with lubricant, for example two axially opposed bearing regions of one or several ro- tating parts of the drive assembly.

The drive assembly can comprise a housing with a first housing part and a second housing part which are connected to one another in a joining plane, wherein the first reservoir and the second reservoir are preferably positioned on different sides of the joining plane. This measure ensures a simple assembly procedure. More particularly, it is proposed that the first reservoir is laterally delimited by a cover element towards the second reservoir. The cover element ensures that the two reservoirs and the supply channels leading to the reservoirs are spatially separated from one another. The cover element is preferably positioned axially between the central plane of the first gear and the central plane of the second gear, more particularly with a slight axial overlap relative to the first gear. It is thus ensured that at least most of the lubricant which is centrifuged upwards by the first gear reaches the first reservoir and that at least most of the lubricant centrifuged upwards by the second gear reaches the second reservoir.

According to a preferred embodiment, at least one of the two reservoirs comprises at least one channel through which the lubricant can flow towards a drive assembly re- gion which has to be lubricated and cooled, respectively. The first reservoir preferably serves to lubricate a first bearing region, whereas the second reservoir serves to lubricate a second bearing region. For this purpose, a channel is provided at the first and/or at the second reservoir, which channel connects the respective reservoir to the respective bearing region. For instance, the channel can end in a region between a seal and a radial bearing for a shaft, so that components which rotate relative to one another are reliably supplied with lubricant.

The drive assembly comprises an input element through which torque can be introduced, and at least one output element via which the torque can be transmitted to one or more driven components. The input element can also be referred to as input part or driving part. Accordingly, the output element can also be referred to as output part or driven part. Input element and output element can be any component suitable for transmitting torque, such as a shaft or a gear. In a preferred embodiment, the first gear is arranged on an intermediate shaft in the transmission path between the input element and an output element. The second gear can be connected to a differential housing, wherein the output element can be provided in the form of a differential carrier which is rotatably supported in the differ- ential housing around an axis of rotation. According to an embodiment, the first and the second reservoir can be designed for supplying lubricant to the two bearing regions of the sideshafts in the drive assembly housing and in the differential housing, respectively. In other words, there is/are provided one or several bores through which lubricant can flow from the respective reservoir to the associated bearing region, where the bearing means and sealing means can be supplied with oil. For supplying the first reservoir with oil centrifuged upwards by the first gear, a supply channel is provided in the housing. The supply channel extends in the drive housing, more particularly in the circumferential direction around the differential housing rotatably sup- ported in the drive housing, and ends in the first reservoir. The supply channel can be closed laterally by a cover plate. As a result of the circumferential speed of the intermediate gear, oil is conveyed upwardly into the supply channel and flows through same into the first reservoir. According to a preferred embodiment, at least one of the following conditions applies in the built-in condition of the drive assembly: the axis of rotation of the second gear is positioned above the axis of rotation of the first gear; and/or the axis of rotation of the second gear is positioned above the axis of rotation of the input element; and/or the axis of rotation of the second gear is positioned above the lubricant level; and/or the second gear, in its entirety, is positioned above the lubricant level. These conditions each feature a reduced quantity of lubricant, little splashing losses and thus a high performance of the drive assembly.

The drive assembly is particularly suitable for installation concepts, respectively de- sign concepts, in which the output is positioned above the input. Since lubricant is conveyed into the first and second reservoir by the first and second gears, the upper drive elements can be lubricated and cooled reliably, too. Splashing losses can be kept low, because the second gear is positioned largely or entirely above the lubricant level, which also has an advantageous effect on the aging process of the lubri- cant. In a preferred embodiment, the axis of rotation of the intermediate gear, in the built-in condition of the drive assembly, is positioned below the axis of rotation of the input element and, respectively, the axis of rotation of the input element is arranged above the lubricant level. This, too, contributes towards a reduction in splashing losses in the drive.

According to a preferred embodiment, a coupling is provided in the power path between the input element and the output element, so that a transmission of torque can optionally be effected or interrupted. The coupling is preferably arranged in the power path between a differential housing connected to the second gear and a differential carrier freely rotatable in said housing. A controllable actuator can be provided for actuating the coupling, wherein said actuator can be connected to an electronic control unit for control purposes. The differential drive comprises two sideshaft gears which are arranged in the differential housing and which are rotatably supported around the axis of rotation and a plurality of differential gears which are rotatably connected with the differential carrier and which, at least indirectly, engage the side- shaft gears. One sideshaft each is connected to one of the sideshaft gears for transmitting torque to an associated vehicle wheel. The differential housing is rotatably supported relative to a stationary drive housing by rolling contact bearings. Also, one sideshaft or both sideshafts can be rotatably supported in the drive housing via bearing means. The first and the second reservoir serve to supply at least one of these bearing regions with lubricant. The drive assembly can form part of an electric drive which serves to drive a vehicle axle and which comprises an electric motor as a driving source. The electric drive can be provided in the form of a secondary drive for the motor vehicle which comprises an internal combustion engine as primary drive (hybrid drive). The electric drive can be used for driving the front axle or the rear axle. Insofar, the above- mentioned objective is also achieved by providing such an electric drive with an inventive drive assembly and an electric motor. In this case, the drive assembly preferably comprises a reduction gear, a coupling and a differential drive which can be driven by the electric motor via the reduction gear. By means of the electric drive it is possible to achieve the above-mentioned advantages of reducing the quantity of oil that is required as well as the splashing losses and, thus, of improving the efficiency of the drive assembly. All rotating components are reliably supplied with lubricant, both in the connected and disconnected condition of the electric drive. Furthermore, the objective is achieved by providing a process of controlling a drive assembly which comprises a coupling in the power path between an input element and an output element, by means of which coupling a transmission of torque can optionally be effected or interrupted, with the following process stages: determining a switching condition of the coupling; rotatingly driving the input element during time intervals during which the coupling is open, so that at least one gear of the drive assembly conveys lubricant into at least one reservoir; finishing the process of rotatingly driving the drive element after a defined period of time. The process can be carried out by the above-mentioned drive assembly which, more particularly, can be provided in the form of one or several of the above-mentioned embodiments. Having "at least one reservoir" means that the drive assembly can comprise one or several reservoirs which is/are filled by the rotation of an associated gear. If two reservoirs are used, both are filled when the input element is driven. Reference to a, one or the reservoir is thus meant to include one, two or more reservoirs which each can be filled with lubricant by one or more respective gears. To the extent that reference is made to a gear or the gear, this is intended to mean that at least one gear is provided for filling a respective reservoir.

A reservoir of the drive assembly is only filled with lubricant if lubricant is conveyed into the reservoir by a rotating gear. If the secondary axle comprising the drive assembly shall be driven, the coupling is closed, so that torque can be transmitted from the driving source to the vehicle wheels of the optionally drivable (secondary) axle. The gears arranged in the power path rotate, so that also the reservoir/s is/are supplied with lubricant, from which reservoir/s oil can reach the regions to be lubricated.

However, if the secondary axle shall not be driven, the power path between the driving axle and the driving source is interrupted by opening the coupling. Thus, the differential housing and all rotatable, respectively drivable components included upstream in the power path become stationary, inter alia also the gears which, when rotating, convey lubricant into the reservoir/s. On the other hand, the components arranged downstream, in particular the sideshafts, the sideshaft gears connected thereto, the differential gears and the differential carrier continue to rotate due to the rolling action of the vehicle wheels. In order to ensure an adequate degree of lubrication and cooling of the components which rotate relative one another, even in this disconnected condition of the driving source, it is proposed that during certain time intervals, when the coupling is open, the driving source is activated, so that, as a result of the rotation of the gears, the reservoir/s is/are filled with lubricant. When the at least one reservoir is at least partially filled, the driving source is disconnected again after a predetermined time. Now the lubricant can flow from the reservoir to the region to be lubricated, with the reservoir emptying progressively. After a certain period of time, the driving source is again connected, so that the at least one reservoir is again filled with lubricant. The driving source can be configured in the form of an electric motor.

According to a preferred embodiment, it is proposed that the period between two filling intervals which follow one another is longer than the actual filling process during which the drive assembly is idling for the purpose of filling the reservoir. The filling process can take 20 to 40 seconds. The time interval during which the driving source is disconnected depends on the speed at which the lubricant flows out of the reservoir for the purpose of lubricating the rotating parts. The period between two filling processes can possibly be controlled or set in dependence of the vehicle speed. Preferred embodiments will be explained below with reference to the Figures wherein:

Figure 1 is a cross-section of an inventive drive assembly; Figure 2 is a first perspective view of a first housing part of the drive assembly according to Figure 1 ;

Figure 3 is a second perspective view of the first housing part according to Figure 1 ; Figure 4 is an axial view of the first housing part according to Figure 1 ;

Figure 5 shows a detail of the first housing part according to sectional line V-V of Figure 4 with a drawn-in sideshaft, differential housing part, bearing and seal; Figure 6 shows a detail of the first housing part according to sectional line VI-VI of Figure 4; Figure 7 shows the first housing part of Figure 1 in an axial view with a drawn-in driving gear and intermediate gear;

Figure 8 shows the first housing part according to Figure 1 in an axial view with a drawn-in driving gear, intermediate gear and cover;

Figure 9 shows the first housing part according to Figure 1 in an axial view with a drawn-in driving gear, intermediate gear, cover and ring gear;

Figure 10 shows a second housing part of the drive assembly according to Figure 1 in a first perspective view;

Figure 1 1 shows the second housing part according to Figure 1 in a second perspective view; Figure 12 is an axial view of the second housing part according to Figure 1 ;

Figure 13 shows a detail of the second housing part according to sectional line XIII-

XIII of Figure 12; Figure 14 shows a detail of the second housing part according to sectional line XIV-

XIV according to Figure 12;

Figure 15 shows a detail of the drive assembly according to Figure 1 in a sectional view which is similar to that of Figure 14, with a drawn-in sideshaft, differential hous- ing part, bearing and seal; and

Figure 16 shows a detail of the drive assembly according to Figurer 1 in an axial view from the inside on to the second housing part. Figures 1 to 16 will be described jointly below. They show an inventive drive assembly 2 which comprises a first and a second reservoir 3, 4 which, under operational conditions, can be filled with lubricant as a result of the rotation of a first and a sec- ond gear 5, 6. The drive housing 7 contains a quantity of lubricant which, in the static built-in condition of the drive assembly, defines a lubricant level. More particularly, the drive assembly forms part of an electric drive which serves to drive an optionally drivable secondary driving axle of a motor vehicle. The driving source for the drive assembly 2 is provided in the form of an electric motor (not shown) which can be at- tached to the drive housing 7 via a flange connection. The electric drive serves as an optionally connectable driving source for optionally driving the motor vehicle which can comprise an internal combustion engine as the main driving source for permanently driving the vehicle. The drive assembly 2 comprises a reduction gear 9, a differential drive 10 and a coupling 12 which can be actuated by an actuator 13. The reduction gear 9 comprises a first pair of gears 14, 5 and a second pair of gears 22, 6, so that a rotational movement introduced by the driving source via a driveshaft 18 is translated from a high speed to a low speed. The driveshaft 18 is rotatably supported in the drive housing around a driving axis A18 by bearing means. The driving gear 14 is connected to the driveshaft 18 in a rotationally fixed way and can also be produced so as to be integral therewith.

Furthermore, the reduction gear 9 comprises an intermediate shaft 19 which, via bea- ring means 20, 21 , is rotatably supported around an axis of rotation extending parallel to the driving axis A18. The first gear 5, which can also be referred to as intermediate gear, is connected to the intermediate shaft 19 in a rotationally fixed way. The connection can be effected in the form of a form-fitting connection, for example by splines, or as a material-fitting connection such as a welded connection. Further- more, the intermediate shaft 19 comprises a pinion 22 which is integrally connected with the intermediate shaft. The pinion 22 of the intermediate shaft 19 engages the second gear 6 which can also be referred to as ring gear and which serves to drive the differential drive 10. The driving gear 14 and the first intermediate gear 5 engaging same form the first pair of gears 14, 5 of the reduction gear 9 with a first reduction ratio. The pinion 22 and the ring gear 6 engaging same form a second pair of gears 22, 6. It can be seen that the driving gear 14 comprises a smaller diameter and a smaller number of teeth than the diameter and, respectively, the number of teeth of the first intermediate gear 5. In this way a reduction into a lower speed is achieved. Also, the pinion 22 comprises a smaller diameter and a smaller number of teeth than the ring gear 6, so that a further reduction towards a lower speed is achieved.

The ring gear 6 is fixedly connected to the differential housing 23. In the present embodiment, the connection between the annular gear 6 and the differential housing 23 is a welded connection, with other connecting means such as a bolted connection also being conceivable. The differential housing 23 has a two-part design and com- prises a first housing part 24 which is substantially dish-shaped, and a second housing part 25 which is substantially cover-shaped. In the region of their openings, the two housing parts 24, 25 each comprise a flange portion which are inserted into a corresponding receiving portion of the ring gear 6 and connected to same. The differential housing 23 is rotatably supported in the drive housing 7 around the axis of rotation A23 by bearing means 26, 27.

An annular differential carrier 28 is supported in the differential housing 23 so as to be rotatable around the axis of rotation A23. The differential carrier 28 comprises radial bores into which a journal 29 is inserted and fixed by suitable fixing means, for instance a securing pin. Two differential gears 30 are rotatably supported on the journal 29 around the journal axis. The two differential gears 30 engage a first and a second sideshaft gear 32, 33 which are arranged coaxially relative to the axis of rotation A23. The two sideshaft gears 32, 33 comprise means to achieve a rotationally fixed connection with the associated sideshaft 34, 35, for example splines, so that torque can be transmitted to the vehicle wheels. The two sideshaft gears 32, 33 are axially supported relative to the differential housing 23 via friction reducing sliding discs. The coupling 12 is provided in the form of a form-fitting coupling, more particularly as a toothed coupling, with the use of other types of coupling also being conceivable, for example a friction coupling. The coupling 12 comprises a first coupling part 36 which is firmly connected to the differential carrier 28, more particularly forms one part therewith, as well as a second coupling part 37 which is axially movable relative to the first coupling part 36 and which is connected to the differential housing 23 in a rotationally fixed way. For transmitting torque, the second coupling part 37 can be made to engage the first coupling part, so that a form-fitting connection between the two coupling parts is achieved. By disengaging the second coupling part 37, the transmission of torque can be interrupted again. The first coupling part 36, as a form- fitting part, comprises a toothed ring which is integrally formed on to the end face of the differential carrier 28. Accordingly, the second coupling part 37 comprises a corresponding toothed ring which is arranged inside the differential housing 23. Furthermore, the second coupling part 37 comprises a plurality of circumferentially dis- tributed axial projections 38 which pass through corresponding through-apertures of the differential housing 23. By suitably controlling the actuator 13, the second coupling part 37 can be axially moved relative to the first coupling part 36, wherein torque is transmitted from the annular gear 6 to the differential carrier 28 in the engaged condition, whereas the transmission of torque is interrupted in the disengaged condition.

The actuator 13 comprises an electro-magnet 39 and a piston 40. When the electromagnet is supplied with current, the piston 40 is loaded towards the coupling 12, so that the latter is closed. A target element 42 is fixed to the second coupling part 37, which target element 42 cooperates with a sensor so that the switching condition of the coupling 12 can be identified. The sensor detects a signal representing the distance between the sensor and the target element 42 which can also be referred to as sensor object. A returning spring 43 is arranged between the differential housing 23 and the target element 42. If the electro-magnet 39 is switched off, the second cou- pling part 37 is moved into its initial position so that the coupling 12 is opened again.

The differential housing 23 comprises a first sleeve projection 44 and a second sleeve projection 45 which, via the bearings 26, 27 are rotatably supported in the drive housing 7. The two bearings 26,27 are provided in the form of ball bearings, with other suitable types of bearing also being conceivable. The sideshafts 34, 35 each extend through the sleeve projections 44, 45 and, at their inner ends, are each connected to an associated sideshaft gear 32, 33. The sideshaft 34, which is arranged on the side of the drive assembly to which the driving source is connected, is rotata- bly supported in the sleeve projection 44, which thus forms a plain bearing. Figure 1 shows lubricant grooves for lubricating the plain bearing which can also be referred to as friction bearing 41 . Said sideshaft 34, more particularly, is provided in the form of an intermediate shaft whose outer end, which faces the wheel, can be rotatingly supported in a stationary component. Towards the outside, the annular space between the sideshaft 34 and the drive housing 7 is sealed by a shaft sealing ring 46. The opposed sideshaft 35 comprises a first portion which, by means of a first rolling contact bearing 47, is rotatably supported in the sleeve projection 45 of the differential housing 23, as well as a second portion which, by means of a second rolling con- tact bearing 48, is rotatably supported in a second rolling contact bearing 48 in the drive housing 7. It can be seen in Figure 15 that said sideshaft 35 is provided in the form of a short shaft, wherein the wheel-facing end of the short shaft forms the outer joint part of a constant velocity joint. Towards the outside, the annular space between the sideshaft 35 and the drive housing 7 is sealed by a shaft sealing ring 49.

The drive assembly 2 can comprise a driving source (not illustrated) which can be provided in the form of an electric motor. The driving source drives the differential drive 23 by which - when the coupling 12 is closed - the introduced torque is transmitted to the two sideshafts 35, 36. When the coupling 12 is open, the sideshafts 35, 36, the sideshaft gears 32, 33, the differential gears 30 and the differential carrier 28 rotate jointly with the vehicle wheels rolling on the road surface. On the other hand, all the driving parts arranged in front (upstream) of the torque flow, such as the coupling part 37, the differential housing 23, the reduction gear 9 and the driving source are disconnected and thus stand still.

One advantage, more particularly, of the drive assembly 2 consists in that even when the coupling 12 is open, it is ensured that those components which rotate relative to one another, more particularly the bearing regions of the sideshafts 34, 35, are relia- bly lubricated and cooled. For this purpose, there is provided the first reservoir 3 which supplies the bearing region 41 of the first sideshaft 34 with lubricant; there is also provided the second reservoir 4 which supplies the bearing regions 47, 48 of the second sideshaft 35 with lubricant. When the coupling 12 is closed and when the drive unit is running, lubricant is permanently conveyed from the oil sump to the reservoirs 3, 4 arranged at an upper level; this leads to a reduction in splashing losses and, overall, leads to a reduction in the quantity of oil required.

The first reservoir 3 is filled as a result of the rotation of the first gear 5. This is ef- fected in that the gear 5 receives lubricant from the oil sump, which lubricant, as a result of centrifugal forces occurring during continued rotation, is again centrifuged off the gear 5. Said conveying effect of the lubricant is illustrated in Figure 7 by arrows P. The lubricant, through the supply channel 17, reaches the first reservoir 3 which extends in an upper portion of the housing part 56 in an approximately C-shaped way. A circumferentially extending wall portion 50 of the housing part 56 forms a radially inner end of the first reservoir 3. In a mounted condition, the differential housing 23 is arranged radially inside said circumferentially extending wall portion 50. Figures 2 to 8 show further details of the reservoir 3. It can be seen that the reservoir 3 comprises a first portion 51 which, via a first channel 52, is connected to a first circumfer- ential portion of an annular chamber 53 formed between the housing 7 and the side- shaft 34. The annular chamber 53 is positioned axially between the shaft sealing ring 46 and the bearings 26, 41 , so that said components are lubricated with the lubricant. The reservoir 3 comprises a second portion 54 which is circumferentially offset relative to the first portion 51 , more particularly it is approximately diametrically opposed thereto. A second channel 55 connects the second portion 54 to the annular chamber 53, wherein the mouth of the second channel 55 is circumferentially offset relative to the mouth of the first channel 52. In this way, it is ensured that a sufficient amount of lubricant reaches the bearing and sealing regions of the first sideshaft 34. The first reservoir 3 and the second reservoir 4 are axially spaced from one another, i.e. arranged in different planes in the housing 7. It can be seen that the housing 7 comprises a first housing part 56 and a second housing part 57 which are connected to one another in a joining plane E via flange connections 58, 59. The first reservoir 3 is formed in the first housing part 56 and is positioned at least partially in a plane which is defined by the first gear 5. The second reservoir 4 is formed in the second housing part 57, wherein a stripping device 61 for supplying the second reservoir 4 with lubricant extends into a plane of the second gear 6.

A cover element 60 laterally closes the first reservoir 3 towards the interior of the drive, which can be seen in Figures 5 and 8. In the mounted condition, the cover element 60 is positioned in the first housing part 56, at a small distance laterally adjoining and parallel to the joining plane E of the two housing parts 56, 57. The shape of the cover element 60 is adapted to the shape of the reservoir 3 and is approximately C-shaped in an axial view. For fixing purposes, bolts can be passed through holes 62 in the cover element 60 and threaded into threaded bores 63 of the first housing part 56. The cover element 60 forms a side wall of the reservoir 3, so that any lubricant conveyed through the supply channel 17 into the reservoir 3 is pre- vented from escaping axially towards the ring gear 6. The only path which the lubricant can take out of the reservoir 3 passes through the bores 52, 55 which end in the region of the bearing and seal of the sideshaft 34. At the upper end of the housing part 56 there is provided a labyrinth seal 64 for ventilation purposes. Figures 2 to 4 show further details of the first housing part 56, inter alia the bearing region 65 for supporting the driveshaft 18, the bearing region 66 for supporting the intermediate shaft 19 and the bearing region 67 for supporting the differential housing 23. The opposed bearing regions of the second housing part 57 have been given the same reference numbers provided with an apostrophe (65', 66', 67'). Figures 7 and 8 show the drive assembly in the position in which it is arranged in the built-in condition. The lubricant level is defined in this condition, more particularly with stationary driving parts and emptied reservoirs 3, 4. The lubricant level is preferably selected such that the first gear 5 (intermediate gear) and the pinion 22 are immersed in the lubricant when rotating. In order to avoid any splashing losses, the second gear 6 (ring gear) is positioned in its entirety above the lubricant level. It can be seen that the axis of rotation A19 of the intermediate shaft 19 is arranged below the axis of rotation A18 of the driveshaft 18 and below the axis of rotation A23 of the differential housing 23. The axis of rotation A23 of the differential housing is positioned above the axis of rotation A18 of the driveshaft.

The second reservoir 4 is formed in the second housing part 57 which is shown more particularly in Figures 10 to 16. In an upper portion of the housing part 57 the strip- ping device 61 can be seen which covers the second gear 6 (ring gear) in the axial direction. Thus, any lubricant at the gear 6 is stripped off at an edge 68 of the device 61 from where it is able to flow off along the web 69 towards the second chamber 4.

Figures 10 to 14 show further details of the second reservoir 4. The reservoir 4 com- prises a first portion 76 which, via a first channel 77, ends in an annular chamber 78 formed between the housing 7 and the second sideshaft 35. The annular chamber 78 is positioned axially between the bearing 48 of the sideshaft 35 and the bearing 27 of the differential housing 23. The reservoir 4 comprises a second portion 79 which is circumferentially offset relative to the first portion 76. At a lower region of the second portion 79 there is provided the mouth of the second channel 80 which connects the second portion 79 to the annular chamber 78. The mouths of the two channels 77, 80 are circumferentially offset relative to one another, so that, accordingly, lubricant can reach the bearing regions in different circumferential areas. A second cover element 70 laterally delimits the second reservoir 4 towards the interior of the drive assembly, as can be seen in Figures 15 and 16. In the circumferential direction, the second reservoir 4 is delimited by radially extending webs 72, 73. Radially inside, the second reservoir 4 is delimited by a sleeve-like wall portion 31 of the housing part 57. The shape of the cover element 70 is adapted to the contour of the reservoir 4. In an axial view, the reservoir 4 extends in an approximately C-shaped way around an upper portion of the bearing region 67' for the differential housing 23 and the sideshaft 35. For fixing the cover element 70, bolts can be threaded into corresponding threaded bores 74, 75 of the housing part 57. The cover element 70 forms a side wall of the reservoir 4, so that any lubricant conveyed into the reservoir 4 remains therein until it flows off through the bores 77, 80 into the annular chamber 78 and into the region of the bearings 27, 48 and the seal 49 of the sideshaft 35, respectively. The cover element 70 comprises a projecting groove portion 71 on an upper side which, in the mounted condition, is arranged below the web 69, so that any lubricant dripping off the web is caught by the groove portion 71 and passed on to the reservoir 4. The two cover elements 60, 70 can be produced in the form of formed sheet metal parts. The first gear 5 (intermediate gear) and the second gear 6 (ring gear) are arranged so as to be axially offset relative to one another, i.e. they are positioned in parallel planes. The second gear 6 engages the pinion 22 which is arranged adjacent to the first gear 5. Thus, the first and the second gear 5, 6 rotate in opposed directions, as can be seen in Figure 9. The toothed engagement between the pinion 22 and the second gear 6 generates a pumping effect so that lubricant is conveyed upwardly in the direction of rotation of the second gear.

To ensure that even in the disconnected condition of the secondary drive the components rotating relative to one another are sufficiently lubricated, a process of control- ling the drive assembly 2 is proposed such that in defined time intervals the drive assembly is driven in idling condition, i.e. when the coupling 12 is open in order to again fill the reservoirs 3, 4 with lubricant. For this purpose, the electric motor introduces torque into the driveshaft 18, so that the gears of the reduction gear 9 rotate under no load. In this way, the first and the second gear 5, 6 convey lubricant into the associ- ated reservoirs 3,4. After a predetermined period of time, which is sufficient for at least partially filling the reservoirs, the electric motor is switched off again. The electric motor can be controlled by an electronic control unit as a function of time or rule- based. Said interval-controlled method of driving the drive assembly is only necessary when the coupling 12 is open because, in this condition, the gears generally stand still so that no lubricant is conveyed into the chambers 3, 4. When the coupling 12 is closed, the gears rotate, so that the chambers 3, 4 are permanently supplied with lubricant. Overall, the driveline assembly and the process ensure a passive, requirement-orientated supply of lubricant to the rotating components. List of reference numbers

2 gearbox assembly

3 first reservoir

4 second reservoir

5 first gear (intermediate gear)

6 second gear (annular gear)

7 gearbox housing

8 connecting flange

9 reduction gear

10 differential drive

12 coupling

13 actuator

14 driving gear

17 supply channel

18 driveshaft

19 intermediate shaft

20 bearing

21 bearing

22 pinion

23 differential housing

24 first housing part

25 second housing part

26 bearing

27 bearing

28 differential carrier

29 journal

30 differential gear

31 wall portion

32 sideshaft gear

33 sideshaft gear

34 first sideshaft

35 second sideshaft 36 first coupling part

37 second coupling part

38 axial offset

39 electro-magnet

40 piston

41 bearing

42 transducer element

43 returning spring

44 first sleeve projection

45 second sleeve projection

46 shaft sealing ring

47 first rolling contact bearing

48 second rolling contact bearing

49 shaft sealing ring

50 wall portion

51 first portion

52 channel

53 annular chamber

54 second portion

55 second channel

56 first housing part

57 second housing part

58 flange

59 flange

60 cover element

61 stripping device

62 bore

63 threaded bore

64 labyrinth seal

65 bearing region

66 bearing region

67 bearing region

68 edge web

cover element groove portion web

web

threaded bore threaded bore first portion first channel annular chamber second portion second channel axis of rotation plane

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Claims

1 . A drive assembly for a motor vehicle, comprising:

a first gear (5) and a second gear (6), wherein the first gear (5) and the second gear (6) are drivingly connected to one another;

a lubricant filling which, in a static built-in condition of the drive assembly (2), defines a lubricant level;

a first reservoir (3) which is arranged above the lubricant level and which, when the drive assembly (2) is being driven, can be filled with lubricant as a result of the rotation of the first gear (5);

a second reservoir (4) which is arranged above the lubricant level and which, when the drive assembly (2) is being driven, can be filled with lubricant as a result of the rotation of the second gear (6).

2. A drive assembly according to claim 1 , characterised in that the first gear (5) and the second gear (6) are arranged axially offset relative to one another.

3. A drive assembly according to claim 1 or 2, characterised in that the first gear (5) and the second gear (6) rotate in opposed directions of rotation.

4. A drive assembly according to any one of claims 1 to 3, characterised in that the first reservoir (3) and the second reservoir (4) are arranged axially spaced from one another.

5. A drive assembly according to any one of claims 1 to 4, characterised in that a housing (7) is provided comprising a first housing part (56) and a second housing part (57) which are connected to one another in a joining plane (E), wherein the first reservoir (3) and the second reservoir (4) are positioned on different sides of the joining plane (E).

6. A drive assembly according to any one of claims 1 to 5, characterised in that the first reservoir (3) is laterally delimited by a cover (60) towards the second reservoir (4).

7. A drive assembly according to any one of claims 1 to 6, characterised in that at least one first channel (52, 55) is provided through which lubricant can flow from the first reservoir (3) to first bearing means (41 ).

8. A drive assembly according to any one of claims 1 to 7, characterised in that at least one second channel (77, 80) is provided through which lubricant can flow from the second reservoir (4) to second bearing means (27, 48).

9. A drive assembly according to any one of claims 1 to 8, characterised in that at least one of the first and second bearing means (41 , 48) is configured to ro- tatably support a component (34, 35) which is drivingly connected to the second gear (6).

10. A drive assembly according to any one of claims 1 to 9, characterised in that the first gear (5) is arranged on an intermediate shaft (16) in the power path between an input element (18) and a output element (28).

1 1 . A drive assembly according to any one of claims 1 to 10, characterised in that the second gear (6) is connected to a differential housing (23), wherein the output element (28) is provided in the form of a differential carrier which is ro- tatably supported in the differential housing (23).

12. A drive assembly according to any one of claims 1 to 1 1 , characterised in that the first and the second bearing means (41 , 48) which are supplied with lubricant via the first and the second channels (52, 55, 77, 80) are configured for rotatably supporting sideshafts (34, 35) relative to the drive housing (7) or relative to the differential housing (23).

13. A drive assembly according to any one of claims 1 to 12, characterised in that a supply channel (17) is provided in the housing (7) for supplying the first reservoir (3) with lubricant.

14. A drive assembly according to any one of claim 1 to 13, characterised in that in the built-in condition of the drive assembly (2) at least one of the following conditions applies:

the axis of rotation (A23) of the second gear (6) is positioned above the axis of rotation (A19) of the first gear (5);

the axis of rotation (A23) of the second gear (6) is positioned above the axis of rotation (A18) of the input element (18);

the axis of rotation (A23) of the second gear (6) is positioned above the lubricant level;

the second gear (6) is completely positioned above the lubricant level.

15. A drive assembly according to any one of claims 1 to 14, characterised in that, in the built-in condition of the drive assembly, the axis of rotation (A19) of the first gear (5) is positioned underneath the axis of rotation (A18) of the input element (18).

16. A drive assembly according to any one of claims 1 to 15, characterised in that a coupling (12) is provided in the power path between the input element (18) and the output element (28) by means of which coupling (12) a transmission of torque can be optionally effected or interrupted.

17. A drive assembly according to any one of claims 1 to 16, characterized in that an electric motor is provided as the driving source for driving the drive assembly (2).

18. A process of controlling a drive assembly, more particularly according to any one of claims 1 to 17,

said drive assembly comprising a coupling (12) in the power path between an input element (18) and an output element (28) for optionally effecting or interrupting a transmission of torque,

the process comprising the following process steps:

determining a switching condition of the coupling (12);

when the coupling (12) is in an open condition, rotatingly driving the input element (18) so that at least one gear (5, 6) of the drive assembly conveys lubricant into at least one reservoir (3, 4) of the drive assembly (2);

stopping the input element (18) after a period of time so that the at least one gear (5, 6) stands still;

repeating the process steps of rotatingly driving the input element (18) and stopping the input element (18) alternately, while the coupling is in an open condition.

19. A process according to claim 18, characterised in that the process step of driving the input element (18) for conveying lubricant into the at least one reservoir (3, 4) is performed for a first period of time, and that the process step of stopping the input element (18) is performed for a second period of time which is larger than the first period.

20. A process according to claim 18 or 19, characterised in that the second period of time between two first periods of time in which lubricant is conveyed into the reservoir (3, 4) by the gear (5, 6) is set as a function of the vehicle speed.