ELECTRIC DRIVE AND DRIVELINE ASSEMBLY

Abstract

An electric drive for driving a motor vehicle comprises an electric machine, a transmission gearing and a differential drive; wherein the electric machine comprises a motor shaft that is rotatably driveable around a first rotational axis A1; wherein the transmission gearing comprises a drive gear connected to the motor shaft, at least one intermediate gear rotatingly drivable by the drive gear around a second rotational axis A2, a crown gear rotatingly drivable by the intermediate gear around a third rotational axis A3, and a driven gear connected to the crown gear; wherein the driven gear and the crown gear are arranged coaxially relative to one another and are connected to one another in a rotationally fixed way so that they rotate jointly around the third rotational axis A3, wherein the third rotational axis A3 crosses the first rotationally axis A1. A driveline assembly can have such an electric drive.

Claims

1.-15. (canceled)

16. An electric drive for driving a motor vehicle, comprising: an electric machine, a transmission gearing and a differential drive; wherein the electric machine comprises a motor shaft configured as a hollow shaft that is rotatingly driveable around a first rotational axis; wherein the transmission gearing comprises a drive gear connected to the motor shaft, at least one intermediate gear rotatingly drivable by the drive gear around a second rotational axis, a crown gear rotatingly drivable by the at least one intermediate gear around a third rotational axis, and a driven gear connected to the crown gear; and wherein the driven gear and the crown gear are arranged coaxially relative to each other and are connected to each other in a rotationally fixed way so that they rotate jointly around the third rotational axis, wherein the third rotational axis crosses the first rotationally axis.

17. An electric drive according to claim 16, wherein the third rotational axis crosses at least one of the first rotational axis and of the second rotational axis at a distance.

18. An electric drive according to claim 16, wherein the third rotational axis intersects at least one of the first rotational axis and of the second rotational axis.

19. An electric drive according to claim 16, wherein the second rotational axis of the intermediate gear is arranged parallel to the first rotational axis.

20. An electric drive according to claim 16, wherein exactly one intermediate gear is provided that meshingly engages the drive gear driven by the electric machine as well as the crown gear.

21. An electric drive according to claim 16, wherein the crown gear comprises a greater diameter and a greater number of teeth then the drive gear, and a transmission ratio between the drive gear and the crown gear is between 3 and 4.

22. An electric drive according to claim 16, wherein the driven gear comprises a smaller diameter and a smaller number of teeth than the crown gear, and a transmission ratio between the crown gear and the driven gear is between 2 and 3.

23. An electric drive according to claim 16, wherein the driven gear and the crown gear of the transmission gearing are firmly connected to one another.

24. An electric drive according to claim 16, wherein the driven gear and the crown gear are firmly connected to a drive shaft.

25. An electric drive according to claim 16, wherein the differential drive comprises a differential carrier that is rotatingly drivable by the driven gear around the first rotational axis, a plurality of differential gears that rotate jointly with the differential carrier around the first rotational axis, and output gears that are drivingly connected to the differential gears.

26. An electric drive according to claim 16, wherein the differential drive comprises a ring gear that is arranged coaxially relative to the differential carrier and is firmly connected thereto, wherein the annular gear and the electric machine are arranged on different sides with respect to a central plane of the differential drive.

27. An electric drive according to claim 26, wherein one of the output gears of the differential drive is connected to an output shaft in a rotationally fixed way, wherein the output shaft extends through the hollow shaft of the electric machine.

28. An electric drive according to claim 16, wherein the electric machine, the transmission gearing and the differential drive comprise a common housing.

Description

[0025] Example embodiments will be explained below with reference to the drawings wherein

[0026] FIG. 1 is a diagrammatic illustration of an electric drive in a plan view;

[0027] FIG. 2 shows the electric drive according to FIG. 1 in an axial view;

[0028] FIG. 3 shown an a further example electric drive in an axial view.

[0029] FIG. 4 shows a yet further example electric drive in an axial view in a further modified embodiment, and

[0030] FIG. 5 schematically shows in a plan view an example driveline assembly having an example electric drive.

[0031] FIGS. 1 and 2 will be described jointly below. FIG. 1 shows an example electric drive 2 having an electric machine 3 and a transmission unit 4 rotatingly drivable by the electric motor. The transmission unit 4 comprises a transmission gearing 5 and a differential drive 6 arranged downstream in the power path. The electric drive 2 can serve as a primary driving source, or as a secondary driving source for driving an optionally drivable secondary driving axle of a motor vehicle that comprises a primary driving source for driving a primary driving axle.

[0032] The electric motor 3 comprises a stator 7 and a rotor 8 rotatable thereto that, when the electric motor is supplied with current, rotatingly drives a motor shaft 9. The rotational movement of the motor shaft 9 is transmitted, via the transmission gearing 5 following in the performance path, to the differential drive 6. The electric motor 3 is supplied with electric current by a battery (not illustrated), wherein the battery can be charged with electric current when the electric machine operates as generator. Furthermore, the electric drive 2 comprises a housing 10 in which the electric motor 3 and the transmission unit 4 are arranged.

[0033] The transmission gearing 5 is configured such that a rotational movement introduced by the motor shaft 9 is translated from a high speed into a slow speed, which is the reason that the gearing can also be referred to as step-down gearing. The motor shaft 9 is provided in the form of a hollow shaft and is supported in the housing 10 so as to be rotatable around a first rotational axis Al by means of bearings (not illustrated). A drive gear 14 (first gear) is connected to the driveshaft 9 in a rotationally fixed way, for example by splines, wherein it is understood that other connecting possibilities, like welding, can also be used.

[0034] The transmission gearing 5 comprises the drive gear 14, an intermediate gear 15 (second gear) rotatingly drivable by the drive gear around a second rotational axis A2, as well as a crown gear 16 (third gear) that is rotatingly drivable by the intermediate gear 15 around a third rotational axis (A3) and a driven gear 17 (fourth gear) that is fixedly connected to the crown gear. The driven gear 17 engages the ring gear 18 of the differential drive 6 for driving same and can thus also be referred to as drive gear or drive pinion. The gear set including the drive pinion 17 and the ring gear 18 can be provided in the form of a hypoid set. In the power path between the electric machine 3 and the output parts of the differential drive 6 a controllable clutch (not illustrated) can be provided which, optionally, can effect or interrupt a transmission of torque between the electric machine 3 and the output parts of the differential drive.

[0035] The differential drive 6 comprises a differential carrier 19 fixed to the annular gear 18, a plurality of differential gears 20 connected to the differential carrier 19 that are rotatably supported on one or several journals connected to the differential carrier 19, as well as a first and a second side shaft gear 23, 24 forming the output parts which are rotatably driveable by the differential gears 20 around the rotational axis A1. In the present example, the differential drive is configured in the form of a bevel gear differential, wherein the differential gear set 19, 23, 24 is arranged in the differential carrier 19 which thus can also be referred to at a differential cage. The first sideshaft gear 23 is connected to a first output shaft 25 in a rotationally fixed way that is arranged coaxially relative to the rotational axis A1 and that passes through the motor shaft 9 configured as a hollow shaft. The output shaft 25 comprises an end portion arranged at the transmission side that is connected to the sideshaft gear 23 in a rotationally fixed way, as well as an end portion arranged away from the transmission, that is supported in the housing 10 so as to be rotatable around the rotational axis Al and that is connected to a constant velocity joint 26. The constant velocity joint 26 serves to transmit torque from the first output shaft 25 to the first sideshaft 27 of the motor vehicle while carrying out angular movements. Via a further constant velocity joint 28 at the wheel end, the first sideshaft 27 is connected to a first vehicle wheel 29 for transmitting torque while carrying out angular movement. The first sideshaft 27 is connected to a first vehicle wheel via a wheel-sided further constant velocity joint 28 for transmitting torque under angular movement. The second sideshaft gear 24 drives the opposed second vehicle wheel 29′ via a second output shaft 30, a constant velocity joint 26′, a second sideshaft 27′ and a constant velocity joint 28′ at the wheel end.

[0036] The transmission gearing 5 is configured such that, between the electric machine 3 and the differential carrier 19, a translation from a high speed to a low speed is effected. The transmission ratio between the motor drive gear 14 and the differential carrier 19 can amount to between 8 and 12, for example. For this, the crown gear 16 can comprise a greater diameter and a greater number of teeth than the drive gear 14 and the driven gear 17 of the differential drive 6 can comprise a smaller diameter and a smaller number of teeth than the crown gear 16 arranged coaxially thereto. To achieve a total transmission ratio iges of 8 to 12, a first transmission ratio i1 formed between the drive gear 14 and the crown gear 16 can be between 3 and 4 for example, and a second transmission ratio i2 formed between the crown gear 16 and the driven gear 17 can be between 2 and 3, for example.

[0037] The driven gear 17 and the crown gear 16 of the transmission gearing are rotationally fixed to each other so that they jointly rotate around the rotational axis A3. The connection can be effected by form-locking, force-locking, and/or material locking. The unit consisting of the driven gear 17 and the crown gear 16 comprises a shaft journal 21 that can be supported in a sleeve portion of the housing 10 so as to be rotatable around the rotational axis A3. The shaft journal 21 can be drivingly connected to a driveshaft of a driveline (not illustrated) of the motor vehicle, so that torque can be introduced into the unit via both said driveshaft as well as by the electric machine 3, individually or in a superimposed manner.

[0038] The crown gear 16 comprises face teeth 32 that face towards the differential drive 6 and are arranged on a greater diameter than the teeth of the driven gear 17. The crown gear 16 engages the intermediate gear 15 which comprises teeth 33 corresponding to the crown gear teeth 32. The individual teeth of the crown gear teeth 32 can comprise, in a longitudinal extension, a variable cross-section and a height that varies with respect to the tooth base line. The teeth can widen radially outwardly with respect to the crown gear axis A3 to achieve a uniform engagement with the teeth of the intermediate gear 15. The central lines of the tooth flanks of the crown gear teeth are positioned in a plane that is normal relative to the rotational axis A3 of the crown gear, so that the contact lines of the tooth engagement between the crown gear 16 and the intermediate gear 15 meshing therewith extend parallel relative to the axis A2 of the intermediate gear. The intermediate gear 15 is provided in the form of a cylindrical gear with cylindrical teeth. The crown teeth 32 and the intermediate gear teeth 33 can be configured as straight teeth or helical teeth.

[0039] With reference to the first rotational axis Al radially inside, the intermediate gear 15 engages the motor drive gear 14. The intermediate gear 15 is dimensioned such that the radial distance between the motor gear 14 and the crown gear 16 is bridged. In the present example, exactly one intermediate gear 15 is provided in the power path between the drive gear 14 and the crown gear 16. It is understood, however, that, depending on space conditions or other technical requirements, it is also possible to provide several intermediate gears for transmitting torque from the drive gear to the crown gear. It can be seen in particular in FIG. 2 that the rotational axis A2 of the intermediate gear 15 extends parallel to the rotational axis A1 of the drive gear 14 and intersects the rotational axis A3 of the crown gear 16. In this case, an axial offset V is formed between the rotational axis A3 and the rotational axis A1. Said offset V refers to both the pair of gears formed by the driven gear 17 and the annular gear 18, which can also be referred to as hypoid gear set, and to the pair formed by the intermediate gear 15 and the crown gear 16 which can also be referred to as the crown gear set.

[0040] FIG. 3 shows an example assembly that is slightly modified relative to the example according to FIG. 2. A plan view of the example according to FIG. 3 would correspond to that according to FIG. 1 and is therefore not shown again. The example according to FIG. 3 largely corresponds to that shown in FIG. 2 so that in respect of common features it is referred to the above description. Identical details are provided with the same reference numbers as in FIGS. 1 and 2. The only difference of the example according to FIG. 3 is that the third rotational axis A3 crosses the second rotational axis A2 that extends parallel to the first rotational axis A1 at a distance. The distance in the present example corresponds to the axial offset V between the third axis A3 and the first axis A1, i.e. the first and the second Axes A1, A2 jointly form a plane that extends parallel to the third axis A3. In technical terms, this means that an axial offset is provided only in the hypoid set 17, 18, but not in the crown gear set 15, 16.

[0041] FIG. 4 shows a further example assembly which, again, is slightly modified relative to FIGS. 2 and 3 respectively. A plan view of the example according to FIG. 4 would correspond to that according to FIG. 1 and is therefore not shown again. The example according to FIG. 4 largely corresponds to that in FIGS. 2 and 3 respectively, so that in respect of common features reference is made to the above description, with identical details are provided with the same reference numbers as in FIGS. 1 to 3. The only difference of the example according to FIG. 4 is that the third rotational axis A3 intersects the first rotational axis A1 and the second rotational axis A2. This means that all three rotational axes A1, A2, A3 are arranged in the same plane. This also means that neither the hypoid set 17, 18 nor the crown gear set comprise an axial offset.

[0042] FIG. 5 shows an example driveline assembly 34 for a multi-axle driven motor vehicle. A first drive assembly 35 with an internal combustion engine 36 is provided, as well as an example electric drive 2 according to one of the embodiments according to FIGS. 1 to 4 as a second drive assembly. The driveline assembly 34 comprises a first driveline for driving a first driving axle 37 and a second driveline for driving a second driving axle 38. The internal combustion engine 36, via a multi-step transmission 39, drives a transfer case 40 via which torque is introduced into the first driveline and the second driveline respectively.

[0043] The first driveline 5 comprises a differential drive (not illustrated) via which an introduced torque is transmitted to the two sideshafts 41, 41′ for driving the associated wheels 42, 42′. The sideshafts 41, 41′ each comprise a constant velocity joint 43, 43′, 44, 44′ at the transmission end and at the wheel end respectively, which each permit a transmission of torque under angular movements.

[0044] The second driveline can be driven permanently (permanent four-wheel drive) or can be connected, as required, by a clutch arranged in the power path (on-demand drive). The second driveline comprises a propeller shaft 45 by which torque can be transmitted to the input part 21 of the second driveline assembly 2. The propeller shaft 45 is provided in the form of a multi-component shaft which comprises a first shaft portion with a first joint 46 at an end, a central joint 47, and a second shaft portion with a second joint 48 at an end.

[0045] The first driving axle 37 and the second driving axle 38 can be driven selectively via the first drive assembly 35 and/or the second drive assembly 2. When the vehicle is braked, the electric machine 3 of the second drive assembly can convert in a generator mode mechanical energy into electric energy. A special feature of the present driveline assembly 34 is that, because of the coaxial alignment of the electric machine 3 and the differential drive 6 and because of the transmission gearing 5 having the crown gear 16, the example drive assembly 2 has a particularly compact design and can therefore easily be integrated into the rear axle. In the present example, the first drive assembly 35 with internal combustion engine 36 being the primary driving source is associated to the front axle, whereas the second drive assembly 2 with electric motor 3 is associated to the rear axle. However, it is understood that depending on the type of vehicle, a reversed arrangement would also be possible, i.e. the electric drive 2 would be associated with the front axle and the primary drive 35 with the rear axle.