Drive unit for a motor vehicle, and motor vehicle

Abstract

The invention relates to a drive unit (1) and to a motor vehicle having the drive unit (1). The drive unit (1) has a drive machine (2) with a machine output shaft (6), a transmission (3) with a transmission drive shaft (7), and a shaft connecting device (8). By means of the shaft connecting device (8), the two shafts (6, 7) are frictionally and / or interlockingly connected to each other at the end faces in order to transmit a torque along a common shaft axis (9). The shaft connecting device (8) comprises a centering bearing (10), the bearing outer ring (12) of which is provided in a bearing seat (15) of the drive unit (1), a bearing inner ring (11) of the centering bearing (10) sitting both directly in an output shaft bearing seat (16) of the machine output shaft (6) and directly in a drive shaft bearing seat (17) of the transmission drive shaft (7). Mutually facing shaft end faces (18, 19) of the shafts (6, 7) are situated axially along the shaft axis (9), in each case between a first axial end (20) of the centering bearing (10) and a second axial end (21) of the centering bearing (10).

Description

[0001] Drive unit for a motor vehicle as well as motor vehicle

[0002] The present invention relates to a drive unit for a motor vehicle and to a motor vehicle comprising such a drive unit or two or more such drive units.

[0003] In automotive engineering, a transmission input shaft of a gearbox unit is supported by a first bearing, and a crankshaft or rotor shaft of a drive engine is supported by a second bearing in separate housings. The housings are axially positioned and fixed relative to each other along a common main axis, with the transmission input shaft and the rotor / crankshaft being rotationally fixed to one another. In this configuration, positioning errors between the two shafts accumulate due to assembly and manufacturing tolerances of the components – resulting in an undesirable offset between the longitudinal center axis of the transmission input shaft and the longitudinal center axis of the rotor or crankshaft. Conventional torque-transmitting shaft connections between a drive engine and a gearbox unit of a motor vehicle are shown, for example, in DE 102 12 033 B3 and DE 102021 115 521 B3.

[0004] The object of the present invention is to align two shafts axially to one another in a particularly simple and cost-effective manner and to connect them together in a rotationally fixed manner with particular reliability, especially in the manufacture of an engine-transmission combination for a motor vehicle. This object is achieved by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, across categories and embodiments as features, advantages, and possible embodiments of the respective subject matter of the other independent claims and of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0005] According to the invention, a drive unit for a motor vehicle is proposed, wherein the drive unit comprises a drive motor with a motor output shaft and a transmission with a transmission input shaft. The motor output shaft and the transmission input shaft (i.e., the shafts) are connected to each other for torque transmission. The motor vehicle incorporates the drive unit; thus, the drive unit, in its intended installation position, forms an integral part of the motor vehicle. Although this text focuses specifically on an electric drive motor, it should be understood that the drive motor could just as easily be an internal combustion engine. If the drive motor is an electric motor, the motor output shaft is a rotor shaft of the drive motor or the electric motor.In contrast, the machine output shaft is a crankshaft if the drive engine is an internal combustion engine. The motor vehicle can be designed as a purely internal combustion engine vehicle, a purely electric vehicle, or a hybrid-electric vehicle. In the case of a purely electric or hybrid-electric vehicle, the drive engine of the drive unit forms the traction machine of the motor vehicle.

[0006] The drive machine comprises, in particular, a machine housing, and the gearbox comprises, in particular, a gearbox housing. Furthermore, the gearbox may have one or more disengaging clutches. In addition to the drive machine and the gearbox, the drive unit also comprises a shaft connection device by means of which the two shafts are connected end-to-end by means of a force-fit and / or positive-locking connection for torque transmission along a common shaft axis.For the force-fit and / or positive-locking connection of the machine output shaft and the transmission input shaft, all shaft connections known to those skilled in the art that act in a positive-locking and / or force-locking manner are suitable, such as a splined shaft-splined hub connection, a toothed shaft-splined hub connection, a keyway connection, a face gear connection, a pin connection, a transverse press fit, an axial screw connection (designed centrally and / or along a bolt circle), etc. The shaft connection device of the drive unit further comprises a centering bearing, which is designed in particular as a rolling element bearing. An outer bearing ring of the centering bearing is arranged in a bearing seat of the drive unit, whereas an inner bearing ring of the centering bearing sits both directly in an output shaft bearing seat of the machine output shaft and directly in an output shaft bearing seat of the transmission input shaft.In this configuration, both shafts terminate within the centering bearing along their common axis. In other words, one end face of the machine output shaft and one end face of the transmission input shaft, which are opposite each other along their common axis, are each positioned between a first bearing axial end and a second bearing axial end of the centering bearing. The bearing axial ends of the centering bearing are spaced apart along a longitudinal center axis of the centering bearing, which coincides with the shaft axis, by an axial width of the centering bearing.

[0007] Thanks to the drive unit's design, at least one bearing can be omitted, as the centering bearing functions as both a radial bearing for the machine output shaft and a radial bearing for the transmission input shaft. Two separate bearings—one for the machine output shaft and the other for the transmission input shaft—are deliberately avoided, resulting in a drive unit with a significantly reduced number of individual components and a particularly efficient mass design. Furthermore, the inner ring of the centering bearing ensures precise axial alignment of the machine output shaft and the transmission input shaft along their common axis, thus preventing any offset between the two shafts.Furthermore, manufacturing the shafts is simplified because the elements that connect them to each other in a rotationally fixed manner can be manufactured with larger tolerances than before, since the two shafts are positively aligned by being inserted into the shared inner ring of the centering bearing. According to a possible further development, the bearing seat of the drive unit is formed entirely by the gearbox housing or entirely by the machine housing. This makes it particularly easy to manufacture the housing that does not include the bearing seat of the drive unit.Furthermore, embodiments of the drive unit are conceivable in which the bearing seat of the drive unit is neither formed or arranged on the gearbox housing nor on the machine housing, but for example on a drive unit housing in which the gearbox or gearbox housing and / or the drive machine or the machine housing are arranged.

[0008] In an alternative embodiment, the bearing seat of the drive unit is formed partially by the gearbox housing and partially by the machine housing. This means that the centering bearing projects along its longitudinal center axis into both the gearbox housing and the machine housing. The centering bearing is seated in a partial bearing seat on the gearbox side and a partial bearing seat on the machine side, with the bearing seat of the drive unit being formed by these two partial bearing seats. In this way, the drive unit and the gearbox are radially aligned with respect to the shaft axis, as both housings bear against the same outer bearing race of the centering bearing. Thus, the centering bearing acts as a positioning aid for both shafts and also as a positioning aid for both housings.

[0009] According to another possible embodiment, the shaft connection is free of any material bond connecting the shafts. This makes manufacturing the drive unit, in particular the axial connection of the two shafts, especially simple, and also allows for particularly easy disassembly of the drive unit. As a result, the drive unit is particularly easy and / or inexpensive to repair and / or maintain.

[0010] In another possible embodiment of the drive unit, the inner ring of the centering bearing is designed to be a single piece, or monolithic. This prevents tilting of the two inner ring components relative to each other, ensuring that the two shafts are aligned with exceptional security and precision along their common axis. However, it is also conceivable that the inner ring could be assembled from two separately manufactured inner ring components, which are then bonded together, for example, by welding.

[0011] According to another possible embodiment of the drive unit, the opposing shaft ends are arranged between a first axial end of a rolling element set of the centering bearing and a second axial end of the rolling element set. The rolling element set of the centering bearing comprises a plurality of cylindrical or tapered rollers or balls, arranged in a single or double row. If the centering bearing is, for example, a single-row cylindrical roller bearing, the respective cylinder of the rolling element or cylindrical roller set is long enough that the shaft ends are positioned along the shaft axis between a first and a second axial end of the respective cylindrical roller.If the centering bearing is a double-row bearing, for example a double-row ball, tapered roller, or cylindrical bearing, this embodiment provides that the shaft end faces are arranged along the shaft axis or along the longitudinal center axis of the centering bearing between the two rows of rolling elements. This ensures that the two shafts are arranged and centered particularly securely and precisely relative to each other along the common shaft axis.

[0012] According to another possible embodiment of the drive unit, it features a positive-locking housing device by means of which the gearbox housing and the machine housing are directly and rotationally fixed to one another. In other words, the gearbox is directly flanged to the drive machine. This makes the drive unit particularly compact in the axial direction, and also allows the two shafts to be advantageously designed to be particularly short.

[0013] In a possible further development, the positive locking device for the housings is provided with a threadless fitting element that engages positively in a fitting element receptacle of the positive locking device. According to one possible embodiment, the positive locking device for the housings has exactly one fitting element that locks the housings together in a rotationally fixed manner. Alternatively, the positive locking device for the housings can have two or more fitting elements and a corresponding number of fitting element receptacles. The respective fitting element receptacle is formed on one or both of the housings. The respective fitting element can be completely or partially threadless. In other words, the respective fitting element can have a threadless section as well as a threaded section.For example, the fitting elements are screwed to one of the two housings by means of their threaded section, or screwed into one of the two housings. With their unthreaded section, the fitting elements then project into the corresponding other housing, specifically into the fitting element receptacles located there. This connects the two housings in a rotationally fixed manner and also aligns them radially with respect to the shaft axis. The fitting elements and fitting element receptacles are provided, in particular, in addition to a screw clamping connection by means of which the housings are clamped together axially. This means that, according to this embodiment, the drive unit has, in particular, screw elements by means of which the housings are clamped together axially, and also the fitting elements / fitting element receptacles.The respective fitting element, which can also be called a dowel pin, should not be confused with a screw element of a screw connection; in particular, the fitting element does not have a clamping head. Thanks to the fitting elements or fitting element receptacles, the two housings can be aligned with exceptional precision during the assembly or manufacturing of the drive unit, and the two shafts are also aligned with exceptional precision.

[0014] Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0015] In the following, a drive unit 1 and a motor vehicle (not shown) comprising the drive unit 1 are described jointly with reference to the single figure (designated Fig. 1). In Fig. 1, identical and functionally equivalent elements are designated with the same reference numeral.

[0016] According to the present example, the motor vehicle is designed as a purely electric or hybrid-electric vehicle. Consequently, the motor vehicle has an electric machine as its traction machine or drive machine 2. The drive machine 2 is part of the drive unit 1, which also includes a transmission 3. Fig. 1 shows a highly schematic and sectional view of the drive unit 1, revealing that the drive machine 2 has a machine housing 4, and the transmission 3 has a transmission housing 5. Furthermore, the drive machine 2 has a machine output shaft 6, and the transmission 3 has a transmission input shaft 7. The drive unit 1 also includes a shaft connection device 8, by means of which the two shafts 6 and 7 are connected to each other in a force-fit and / or positive-locking manner – but not by material bond – along a common shaft axis 9 for torque transmission.

[0017] The shaft connection device 8 has a centering bearing 10, which comprises an inner bearing ring 11, an outer bearing ring 12, and a set of rolling elements 13 with a plurality of rolling elements 14. The outer bearing ring 12 of the centering bearing 10 is arranged in a bearing seat 15 of the drive unit 1, with the inner bearing ring 11 of the centering bearing 10 sitting directly in an output shaft bearing seat 16 of the machine output shaft 6 and directly in an input shaft bearing seat 17 of the transmission input shaft 7. The shaft bearing seats 16, 17 are each formed, for example, by a respective outer circumferential surface of the shafts 6, 7. A shaft end face 18 of the machine output shaft 6 and a shaft end face 19 of the transmission input shaft 7 face each other along the shaft axis 9 of the drive unit 1 and, in particular, abut directly against each other.The shaft end faces 18, 19 are both arranged between a first bearing axial end 20 and a second bearing axial end 21 of the centering bearing 10.

[0018] As can be seen in Fig. 1, the bearing seat 15 of the drive unit 1 is formed entirely by the gearbox housing 5 in the present example. In an alternative embodiment (not shown), the bearing seat 15 of the drive unit 1 is formed entirely by the machine housing 4. Furthermore, another alternative embodiment of the drive unit 1, also not shown, is formed in which the bearing seat 15 of the drive unit 1 is formed partly by the machine housing 4 and partly by the gearbox housing 5.

[0019] In the present example, the inner ring 11 of the centering bearing 10 is a single piece. It can also be seen that the centering bearing 10 is designed as a single-row cylindrical roller bearing. Variants of the drive unit 1 in which the centering bearing 10 is designed as a single- or double-row ball, tapered, or cylindrical roller bearing are not shown. The rolling elements 14 of the rolling element set 13 of the centering bearing 10 are therefore each designed as a cylindrical roller, according to the present example. The opposing shaft end faces 18, 19 are both arranged between a first rolling element axial end 22 of the rolling element set 13 and a second rolling element axial end 23 of the rolling element set 13. This is shown in Fig.

[0020] 1 to recognize that the rolling elements 14 or cylindrical rollers of the centering bearing 10 radially overlap or span both the machine output shaft 6 and the transmission input shaft 7 along the shaft axis 9.

[0021] By means of a positive locking device 24, the housings 4, 5 are directly and rotationally fixed to one another. According to the present example, the positive locking device 24 has threadless fitting elements 25, each of which is positively inserted into corresponding fitting element receptacles 26 of the positive locking device 24. As can be seen in Fig. 1, each fitting element 25 is inserted into a fitting element receptacle 26 of the respective housing 4, 5, thereby preventing the housings 4, 5 from rotating relative to each other about the shaft axis 9. In addition, the positive locking device 24 in the present example has a screw arrangement 27 by means of which the housings 4, 5 are clamped together axially along the shaft axis 9.

[0022] The drive unit 1 and the motor vehicle comprising the drive unit 1 each demonstrate a way in which the problem described at the outset – namely, to align two shafts axially in a particularly simple and cost-effective manner and to connect them together reliably and in a rotationally fixed way – can be solved. The core concept of the invention is that the two shafts 6, 7 meet in a common bearing – namely, in the centering bearing 10. Thus, there is no radial displacement / deviation in the area of ​​this bearing, which means that the two shafts 6, 7 are aligned with particular precision along the shaft axis 9. This results in a particularly advantageous and uniform concentricity of the shafts 6, 7 during operation of the drive unit 1 and the motor vehicle, respectively. Both shafts are supported together by means of the centering bearing 10 and are connected to each other in a rotationally fixed manner via a suitable positive-locking and / or frictional connection.The material connection between waves 6 and 7 is deliberately omitted. Reference list.

[0023] 1 drive unit

[0024] 2 Drive machine

[0025] 3 gearboxes

[0026] 4 machine housings

[0027] 5 Gearbox housing

[0028] 6 Machine output shaft

[0029] 7 Gearbox drive shaft

[0030] 8 Shaft connection device

[0031] 9 Shaft axis

[0032] 10 centering bearings

[0033] 11 Inner bearing ring

[0034] 12 Outer bearing ring

[0035] 13 Rolling element set

[0036] 14 rolling elements

[0037] 15 bearing seat

[0038] 16 Output shaft bearing seat

[0039] 17 Drive shaft bearing seat

[0040] 18 Wave face

[0041] 19 Wave face

[0042] 20 Bearing axial end

[0043] 21 Bearing axial end

[0044] 22 rolling element axial end

[0045] 23 rolling element axial end

[0046] 24 Housing positive locking device

[0047] 25 Fitting element

[0048] 26 Fitting element receptacle

[0049] 27 Screw arrangement

Claims

Patent claims 1. Drive unit (1) for a motor vehicle, comprising: - a drive machine (2) with a machine output shaft (6), - a gearbox (3) with a gearbox drive shaft (7), - a shaft connection device (8) by means of which the two shafts (6, 7) are connected to each other end-to-end by means of force and / or form locking for torque transmission along a common shaft axis (9), wherein the shaft connection device (8) has a centering bearing (10) whose outer bearing ring (12) is arranged in a bearing seat (15) of the drive unit (1), and an inner bearing ring (11) of the centering bearing (10) sits both directly in an output shaft bearing seat (16) of the machine output shaft (6) and directly in an input shaft bearing seat (17) of the transmission input shaft (7), wherein the opposing shaft end faces (18, 19) of the shafts (6, 7) are arranged along the shaft axis (9) between a first bearing axial end (20) of the centering bearing (10) and a second bearing axial end (21) of the centering bearing (10).

2. Drive unit (1) according to claim 1 , characterized in that the bearing seat (15) of the drive unit (1) is formed completely by a gearbox housing (5) of the gearbox (3) or completely by a machine housing (4) of the drive machine (2).

3. Drive unit (1) according to claim 1 , characterized in that the bearing seat (15) of the drive unit (1) is formed partly by a gearbox housing (5) of the gearbox (3) and partly by a machine housing (4) of the drive machine (2).

4. Drive unit (1) according to one of the preceding claims, characterized in that the shaft connection device (8) is free of a material connection connecting the shafts (6, 7).

5. Drive unit (1) according to one of the preceding claims, characterized in that the inner bearing ring (11) of the centering bearing (10) is a single piece.

6. Drive unit (1) according to one of the preceding claims, characterized in that the shaft end faces (18, 19) facing each other are arranged between a first rolling element axial end (22) of a rolling element set (13) of the centering bearing (10) and a second rolling element axial end (23) of the rolling element set (13).

7. Drive unit (1) according to one of the preceding claims, characterized in that a gearbox housing (5) of the gearbox (3) and a machine housing (6) of the drive machine (2) are fixed directly to each other in a rotationally fixed manner by means of a housing positive locking device (24).

8. Drive unit (1) according to claim 7, characterized in that the housing form-locking device (24) has a threadless fitting element (25) which engages in a form-locking manner in fitting element receptacles (26) of the housing form-locking device (24) which is formed on one or both of the housings (4, 5).

9. Motor vehicle with the drive unit designed according to one of claims 1 to 8

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