drive device

Abstract

Drive device (1) with an electric motor (3) and a gearbox (4), wherein a rotor shaft (5) of the electric motor (3) is non-rotatably connected to an input shaft (6) of the gearbox (4) at a torque transmission point (7) via a splined connection (8), wherein the rotor shaft (5) is supported at one longitudinal end at the torque transmission point (7) by a fixed bearing (9) and at the opposite longitudinal end by a floating bearing (10), characterized in that: - the input shaft (6) is supported in the region of one end facing away from the rotor shaft (5) by a gearbox bearing (11), - the torque transmission point (7) is designed such that an angular and / or coaxiality deviation (12) between the rotor shaft (5) and the input shaft (6) can be compensated, - the input shaft (6) has a toothed race (24) which is arranged in the axial direction (15) directly next to the gearbox bearing (11) of the input shaft (6). is.

Description

The present invention relates to a drive device having an electric motor and a transmission, wherein a rotor shaft of the electric motor is connected in a rotationally fixed manner to an input shaft of the transmission at a torque transmission point via a spline, according to the preamble of claim 1.DE 10 2018 104 685 A1 discloses a drive device of the generic type having an electric motor and a transmission, wherein a rotor shaft of the electric motor is connected in a rotationally fixed manner to an input shaft of the transmission via a toothing. In addition, the rotor shaft is mounted in a housing via a fixed bearing and a movable bearing, and the input shaft is likewise mounted in the housing in the region of an end facing away from the output shaft. In addition, the input shaft is mounted on the rotor shaft in the region of the end facing the rotor shaft. As a result, both the rotor shaft and the gear shaft are each mounted at two points, as a result of which an increased number of bearing points and, associated therewith, also production costs are produced.DE 197 38 293 A1 discloses a joint for connecting free ends of two articulated shafts which are arranged substantially flush with one another and which transmit a torque. It is provided that the free ends of the articulated shafts abut each other with portions facing each other and these portions are not connected to each other. Thus, in addition to a torque, axial pressure forces can also be transmitted via the joint.DE 101 17 749 A1 discloses a vehicle drive having an arcuate toothed clutch which is connected between a motor shaft and a pinion shaft. The arc clutch has a first clutch portion with an internal toothing and a second clutch portion with an external toothing, wherein the first clutch portion is fixedly connected to the pinion shaft and the second clutch portion is fixedly connected to the motor shaft. When the motor is mounted on the transmission, the clutch sections can thus be inserted comparatively easily into one another.From DE 10 2018 118 069 A1, a further drive device with an electric motor and a transmission is known, wherein a rotor shaft of the electric motor is connected in a rotationally fixed manner to an input shaft of the transmission via a spline. The input shaft is rotatably supported in a housing via a fixed bearing and a movable bearing, while the rotor shaft is rotatably supported in the housing via a bearing in the region of an end facing away from the input shaft.DE 10 2008 052 760 A1 discloses an electric vehicle having an electric motor which has a motor shaft and a transmission, wherein the transmission has, on the input side, a transmission input shaft driven by the electric motor. The electric motor is rotatably coupled to the transmission via a torque transmission device. The torque transmission device is designed to compensate for coaxiality tolerances which exist between the motor shaft and the transmission input shaft and occur during dynamic operation.DIETZ Peter; SCHÄFER Gunther: Mitteilungen der Institute fur Machineischen University of Clausthal, No. 31, 2006, pp. 11-14, ISSN 0947-2247, discloses a spline connection for the length compensation of two shafts connected to one another.Drive devices of the generic type having an interface between an electric motor and a transmission can in principle be divided into one-part, two-part or multi-part solutions of rotor and transmission input shafts. In particular in the case of two- or multi-part shafts, component tolerances, for example with regard to coaxiality, can have an appreciable influence on the overall system behavior. For example, component deviations within a torque transmission point, such as a spline, can cause oscillations and result in an unacceptable behavior or evaluation of the overall system with regard to acoustics, bearing forces, etc. Moreover, an inclination or a deviation of a coaxiality of two shafts with respect to one another can also lead to forces and displacements in the interface, which in turn result in oscillations and forces, which can likewise have a disadvantageous effect on the overall system with regard to acoustics, bearing loads, rotational speed strengths, oscillations, wear, etc. In order to optimize efficiency and to reduce costs and effort, a reduction of bearings and bearing points is also sought, but in some cases with undesirable effects on the overall system on account of the aforementioned relationships.The present invention is therefore concerned with the problem of specifying an improved or at least one alternative embodiment for a drive device of the generic type, which in particular allows a reduced sensitivity to manufacturing tolerances and structural deviations and additionally represents an optimum overall system with regard to outlay, weight, costs, efficiency, acoustics, etc.This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject of the dependent claims.The present invention is based on the general idea of forming a torque transmission point between the rotor shaft and the input shaft in a drive device of the generic type having an electric motor and a transmission and having a rotor shaft and an input shaft of the transmission connected thereto in a torque-transmitting manner such that tolerances caused by assembly and production can be compensated there. At the same time, a bearing is dispensed with, namely a bearing of the input shaft of the transmission in the region of the torque transmission point, as a result of which not only a more cost-effective, since less expensive, bearing concept but also at the same time the compensation of the angular and / or coaxiality deviation between rotor shaft and input shaft can be achieved. The drive device according to the invention has an electric motor and a transmission, wherein a rotor shaft of the electric motor is connected to an input shaft of the transmission in a torque-transmitting manner at the aforementioned torque transmission point via a spline toothing. The rotor shaft is mounted in a known manner at one longitudinal end at the torque transmission point via a fixed bearing and at the opposite longitudinal end via a movable bearing. According to the invention, the input shaft is now mounted via a transmission bearing in the region of an end facing away from the rotor shaft, but not, as is known from the prior art, additionally in the region of the end facing the rotor shaft via a bearing previously present there. Furthermore, the torque transmission point is designed in such a way that angular and / or coaxiality deviations between the rotor shaft and the input shaft can be compensated. With the drive device according to the invention, it is thus possible for the first time to design the entire drive device in a less structurally complicated manner, since at least one bearing point is dispensed with and at the same time also less complicated with regard to manufacturing and / or assembly tolerances to be observed, since the torque transmission point is now capable of compensating at least certain coaxiality tolerances or coaxiality deviations between the shafts connected to one another in a rotationally fixed manner, that is to say the rotor shaft and the input shaft. Manufacturing and assembly tolerances which are particularly unavoidable cannot be compensated for in this way, wherein at the same time fewer oscillations which can lead to noises or even to damage, for example, are produced overall in the drive device.In an advantageous development of the solution according to the invention, the rotor shaft has an internal toothing and the input shaft has an external toothing which is formed in a complementary manner thereto and is inserted into the rotor shaft for the transmission of torque. Such a spline toothing permits, on the one hand, easy assembly and, on the other hand, reliable and play-free or low-play torque transmission. Purely theoretically, it is of course also conceivable that the rotor shaft has an external toothing and the input shaft has an internal toothing formed complementarily thereto and is inserted into the input shaft for torque transmission.Expediently, the external toothing and / or the internal toothing have a width crowning on tooth flanks. Such a wide crowning permits a certain angular deviation of the axis of the rotor shaft relative to the input shaft of the transmission without the risk of unpleasant noise generation or even damage. By virtue of such a width crowning, coaxiality deviations and / or an angular deviation of the axial positions can thus be tolerated or compensated comparatively easily. A further possibility is offered in that the external toothing of the transmission input shaft is formed comparatively short in the axial direction and only just as long that the required torque can be transmitted via the spline toothing. By reducing the axial length of the external toothing of the input shaft, a certain tolerance with respect to angular and / or coaxiality deviations can likewise be achieved.Expediently, the axial articulated bearing has a pivot point about which the input shaft can be rotated or pivoted relative to the rotor shaft, wherein the pivot point is arranged in the axial direction preferably centrally of the toothing. An axially central arrangement of the pivot point in cooperation with a width crowning of the spline enables a coaxiality deviation between an axis of the rotor shaft and an axis of the input shaft of the transmission and / or an angular deviation of the axis positions to be compensated without any problem.In a further advantageous embodiment of the drive device according to the invention, a spherical segment-like or spherical bearing element is arranged on the front end of the input shaft and a bearing socket formed in a complementary manner thereto is arranged on the rotor shaft, or vice versa, which together form an axial articulated bearing. The interaction of the spherical bearing element with the bearing socket thereby enables an axial sliding bearing and at the same time a deviation with respect to the coaxiality and / or an angular position of the axes of the two shafts to be supported on one another, wherein such an axial articulated bearing enables an axial bearing of the input shaft of the transmission without however no longer being able to compensate any manufacturing-related or assembly-related tolerances. By arranging the pivot point substantially in the axial direction in the center of the torque transmission point, axial displacements of the rotor shaft or of the input shaft and thus oscillations and additional forces in the shafts, possible shaft bearings, in the housing and in the overall system can furthermore be avoided. This makes it possible to reduce, in particular, noise emission and wear.In a further advantageous embodiment of the drive device according to the invention, the rotor shaft is of hollow design and has, in the region of the internal toothing, a fluid channel via which a cooling medium can flow from an interior of the rotor shaft to the toothing. Oil can be used here as the cooling medium, for example, which can be used not only for cooling and thus for increasing the output of the electric motor, but at the same time also for lubricating the toothing, whereby a high-performance, smooth and low-friction operation is made possible.In a further advantageous embodiment, a spring device is provided which applies a force directed away from the fixed bearing of the rotor shaft to the movable bearing of the rotor shaft. A sufficiently high bearing reduction load is of decisive importance for a satisfactory functioning of a rotor shaft bearing of an electric motor in any conceivable operating state of the drive device and of the electric motor. The bearing load must always be so high that all rolling bodies of the individual bearings roll on their raceways on the bearing rings, impermissible sliding between rolling bodies and bearing rings is avoided, no play occurs in the individual bearings and the rolling bodies lose contact with the bearing rings. The spring device provided in this embodiment, as well as the force exerted by it, is dimensioned such that due to external loads or influences, the bearing prestress force applied by the spring device is not reduced or is only reduced to a permissible extent. In this way, in particular, negative effects of the torque transmission point can also be at least substantially reduced. Axial forces caused by tensile or shear force due to a helical toothing arranged on the input shaft can be supported in an optimized manner via the fixed bearing of the rotor shaft or, for example, via the axial joint bearing arranged between the input shaft and the rotor shaft, by the axial prestress by the spring device. A support via the transmission bearing, via which the input shaft is mounted at its end facing away from the rotor shaft, is also conceivable.According to the invention, the input shaft has a running toothing, for example a helical toothing, which is arranged directly next to the fixed bearing of the input shaft in the axial direction. High-performance electric drives, in particular with an insert at a rear axle of an electric vehicle, generally transmit significantly higher drive torques in traction operation than in coasting operation, since the transmitted torques are lower in coasting operation and permissible limits of driving stability due to the dynamic wheel load distribution of the electric vehicle must be taken into account. Toothing forces and thus also axial forces from the running toothing, here usually a helical toothing, are thus less effective in the coasting mode than in the pulling mode. By the direct adjacent arrangement of the running toothing next to the transmission bearing, an improved mounting of the toothing can be made possible. Due to the distance between the running toothing of the input shaft of the transmission and the fixed bearing of the rotor shaft, the fixed bearing is loaded comparatively little by toothing forces. This is advantageous in particular in traction operation, provided that the axial forces of the running toothing are transmitted via the fixed bearing on the rotor side, since the fixed bearing of the input shaft or the transmission bearing thereof is relieved as a result. An axial force transmission from the input shaft to the rotor shaft takes place via the axial articulated bearing. Due to the greatest possible distance of the running toothing from the torque transmission point, backlash or unavoidable manufacturing tolerances of the torque transmission point also have no or only a marginal influence on the running toothing.In a further advantageous embodiment of the drive device according to the invention, the transmission is a planetary transmission and the input shaft is connected to its sun gear in a rotationally fixed manner. In this case, the gear bearing is an axial bearing. The drive device according to the invention can thus also be used together with a transmission designed as a planetary transmission, wherein in this case too, due to the configuration of the torque transmission point such that said angular and / or coaxiality deviations between the input shaft of the transmission and the rotor shaft can be compensated for, positive influence can be exerted on wear, noise emission and manufacturing and assembly tolerances to be observed.The present invention is further based on the general idea of equipping an electric or hybrid vehicle with a drive device described in the previous paragraphs and thereby obtaining an electric or hybrid vehicle which can avoid oscillations which arise as a result of unavoidable manufacturing and assembly tolerances and which can lead, for example, to noises or even damage. This makes it possible to achieve an electric or hybrid vehicle with a significantly longer service life.Further important features and advantages of the invention are evident from the dependent claims, from the drawings and from the associated description of the figures with reference to the drawings.It is understood that the features mentioned above and those still to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the invention.Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally the same components.In each case, diagrammatically show, FIG. 1 shows a sectional illustration through a drive device according to the invention, FIG. 2 shows an illustration as in FIG. 1, but in a view onto a rotor shaft and an input shaft of a transmission connected thereto in a torque-transmitting manner, FIG. 3 is an exploded view, partly in section, of the drive device, FIG. 4 shows an exploded view of the drive device with a cut rotor shaft, FIG. 5 shows a possible angular and / or coaxiality deviation between the input shaft of the transmission and the rotor shaft, FIG. 6 shows a drive device according to the invention with a transmission designed as a planetary transmission.Corresponding to FIGS. 1, 2, 3, 4, 5 to 6, a drive device 1 according to the invention, for example for an electric or hybrid vehicle 2, has an electric motor 3 and a transmission 4. A rotor shaft 5 of the electric motor 3 is connected in a rotationally fixed manner to an input shaft 6 of the transmission 4 at a torque transmission point 7 via a spline 8. The rotor shaft 5 is moreover mounted at one longitudinal end of the torque transmission point 7 via a fixed bearing 9 and at the opposite longitudinal end via a movable bearing 10. According to the invention, the input shaft 6 is now mounted via a transmission bearing 11 in the region of an end facing away from the rotor shaft 5, and at the same time the torque transmission point 7 is designed to compensate for angle and / or coaxiality deviations 12 (see FIG. 5 ) or coaxiality tolerances and / or angle tolerances which exist between the rotor shaft 5 and the input shaft 6 or occur during dynamic operation. In this way, it is possible in particular to at least reduce oscillations and damage or noise arising as a result, for example. By the inventive design of the torque transmission point 7, a bearing with high rigidity and thus a high rotational speed can be achieved and at the same time tolerances and tolerance chains can be minimized. The rotor shaft 5 is fixedly mounted via its fixed bearing 9 and movable bearing 10, wherein the input shaft 6 of the transmission 4 is mounted only via its transmission bearing 11 and in the radial direction in the torque transmission point 7, whereby any angular and / or coaxiality deviations 12 that may occur can be compensated.The rotor shaft 5 has an internal toothing 13 while the input shaft 6 has an external toothing 14 formed complementarily thereto and is inserted into the rotor shaft 5 for torque transmission. Of course, a reverse configuration is also conceivable purely theoretically, so that in this case the external toothing 14 would be arranged on the rotor shaft 5 and the internal toothing 13 on the input shaft 6. By mounting the input shaft 6 in the rotor shaft 5, a previously separate bearing, for example a further fixed or floating bearing, can be dispensed with. This allows assembly and cost advantages to be achieved.In order to be able to tolerate an angular and / or coaxiality deviation 12, the external toothing 14 and / or the internal toothing 13 can have a wide crowning on the tooth flanks, as a result of which forces, oscillations and wear can be minimized. In addition, the external toothing 14 can be embodied comparatively short in the axial direction 15, as a result of which both an adequate torque transmission capacity is provided and the possibility of not having to align an axis 16 of the input shaft 6 exactly coaxially with an axis 17 of the rotor shaft 5 (cf. FIG. 5 ).If FIGS. 1 and 3 to 6 are further viewed, it can be seen that a spherical-segment-like or spherical bearing element 18 is arranged on the input shaft 6 facing the rotor shaft 5 on the front end side and a bearing socket 19 formed in a complementary manner thereto is arranged on the rotor shaft 6, said bearing socket together forming an axial articulated bearing 33. By means of such an axial articulated bearing 33, both a support of the input shaft 6 of the transmission 4 on the rotor shaft 5 in the axial direction 15 and a deviation of the coaxiality of the axles 16 and 17 can take place. The axial articulated bearing 33 furthermore has a rotation pivot point 20, about which the input shaft 6 can be rotated or pivoted relative to the rotor shaft 5, wherein the rotation pivot point 20 is arranged in the axial direction 15 centrally of the spline 8. When the axles 16 and 17 are inclined or when they are tilted, for example as a result of tolerances, forces, etc., sliding movements or displacements (coaxiality deviations 12) occur within the torque transmission point 7, wherein axial displacements of the input shaft 6 due to oscillations or additional forces, shaft bearings, etc., can be avoided due to the arrangement of the pivot point 20 centrally in the spline 8. By means of a short spline toothing 8 with respect to its axial extension and an optimized microgeometry of the individual teeth of the external toothing 14 and / or of the internal toothing 13, such as a wide crowning on the tooth flanks, oscillations, forces and wear can likewise be reduced.If the rotor shaft 5 is viewed further, it can be seen that it is of hollow design and has a fluid channel 21 in the region of the internal toothing 13, via which fluid channel a cooling medium can flow from an interior 22 of the rotor shaft 5 to the spline toothing 8. As a result, for example, a rotor interior cooling of the electric motor 3 is possible, as is a lubrication of the spline 8, as a result of which the power of the electric motor 3 can be increased. By lubricating, for example with oil, the spline 8 the risk of a matching grid can also be avoided.A sufficiently high bearing reducing load in any conceivable operating state of the drive device 1 or of the electric motor 3 is also of decisive importance for a satisfactory function of a rotor shaft bearing of an electric motor 3. In addition, no play should be established in the individual bearings 9, 10, 11 and the rolling bodies must also not lose contact with the bearing rings.In order to achieve this, a spring device 23 can be provided, by means of which a biasing force F acting axially on the movable bearing 10 is applied. The arrangement of the fixed bearing 9, the movable bearing 10 and the axial prestressing force F and their direction of action are selected in such a way that external loads or influences do not reduce the bearing prestressing force F, or only to a permissible extent. Negative effects in the region of the spline toothing 8 or of the bearing element 18 on the bearing prestressing force F can be avoided or reduced to the greatest possible extent by a special embodiment (described further above). Forces from the drive train, the transmission 4 or a transmission toothing can lead to an increase in the bearing loads of the rotor shaft bearings 9, 10 (fixed bearing 9 and movable bearing 10), but not to an impermissible reduction.According to FIGS. 1, 2, 3, 4, 5 to 6, it can be seen that the input shaft 6 has a helical gearing 24, which is designed as a helical gearing 25 and which is arranged directly next to the transmission bearing 11 of the input shaft 6 in the axial direction 15.High-performance electric drives at a rear axle of an electric or hybrid vehicle 2 generally transmit significantly higher drive torques in traction mode 26 than in coasting mode 27, since the transmitted torques are lower in coasting mode 27 and permissible limits of the driving stability due to the dynamic wheel load distribution of the electric or hybrid vehicle 2 must be taken into account. Toothing forces and thus also axial forces from the helical toothing 25 are thus less noticeable in the thrust mode 27 than in the traction mode 26. For optimum load distribution or dimensioning of the components and a bearing life and an efficiency, it is advantageous to arrange the transmission bearing 11 directly next to the helical toothing 24 or the helical toothing 25 of the input shaft 6, whereby a very good bearing of the helical toothing 25 is made possible. Only higher radial forces are to be absorbed by the transmission bearing 11 in this case.Due to the distance between the helical toothing 25 and the fixed bearing 9 of the rotor shaft 5, the fixed bearing 9 is at the same time loaded comparatively little by the toothing forces of the helical toothing 25. It is thus advantageous if the axial forces of the helical toothing 25 act in the direction of the fixed bearing 9 in the traction mode 26 and are transmitted by the latter, since the transmission bearing 11 is relieved as a result. An axial force transmission from the input shaft 6 to the rotor shaft 5 takes place via the bearing element 18 and the associated bearing socket 19.If reference is now made to FIG. 6, it can be seen there that the transmission 4 is designed as a planetary transmission 28 and the input shaft 6 is connected to its sun gear 34 in a rotationally fixed manner. The planet gears 29 rotate in a ring gear 30. A planet carrier 31 is supported via a bearing 32. In this case, the transmission bearing 11 is designed as an axial needle bearing.With the drive device 1 according to the invention, it is possible to easily compensate for assembly- or production-related angular and / or coaxiality deviations 12, whereby wear and noise emission can be reduced in particular.

Claims

Drive device (1) having an electric motor (3) and a transmission (4), wherein a rotor shaft (5) of the electric motor (3) is connected to an input shaft (6) of the transmission (4) at a torque transmission point (7) in a rotationally fixed manner via a spline toothing (8), wherein the rotor shaft (5) is mounted at one longitudinal end at the torque transmission point (7) via a fixed bearing (9) and at the opposite longitudinal end via a movable bearing (10), characterized - in that the input shaft (6) is mounted via a transmission bearing (11) in the region of an end facing away from the rotor shaft (5), - in that the torque transmission point (7) is designed such that an angular and / or coaxiality deviation (12) between the rotor shaft (5) and the input shaft (6) can be compensated, - in that the input shaft (6) has a running toothing (24), which is arranged directly next to the transmission bearing (11) of the input shaft (6) in the axial direction (15).Drive device according to Claim 1, characterized in that the rotor shaft (5) has an internal toothing (13) and the input shaft (6) has an external toothing (14) which is formed in a complementary manner thereto and is inserted into the rotor shaft (5) for the transmission of torque.Drive device according to Claim 2, characterized in that the external toothing (14) and / or the internal toothing (13) have a wide crowning.Drive device according to one of the preceding claims, characterized in that a spherical-segment-like or spherical bearing element (18) is arranged on the front end side of the input shaft (6) and a bearing socket (19) formed in a complementary manner thereto is arranged on the rotor shaft (5), or vice versa, which together form an axial articulated bearing (33).Drive device according to Claim 4, characterized in that the axial articulated bearing (33) has a rotation / pivot point (20) about which the input shaft (6) can be rotated or pivoted relative to the rotor shaft (5), wherein the rotation / pivot point (20) is arranged in the axial direction (15) preferably centrally of the spline toothing (8).Drive device according to one of Claims 1 to 5, characterized in that the rotor shaft (5) is of hollow design and has, in the region of the internal toothing (13), a fluid duct (21) via which a cooling medium can flow from an interior space (22) of the rotor shaft (5) to the plug toothing (8).Drive device according to one of Claims 1 to 6, characterized in that a spring device (23) is provided which acts on the movable bearing (10) of the rotor shaft (5) with a force (F) preferably directed away from the fixed bearing (9) of the rotor shaft (5).Drive device according to one of Claims 1 to 7, characterized in that the running toothing (24) is designed as helical toothing (25).Drive device according to one of Claims 1 to 8, characterized - in that the transmission (4) is a planetary transmission (28) and the input shaft (6) is connected to its sun wheel (34) in a rotationally fixed manner, - in that the transmission bearing (11) is an axial bearing.Electric or hybrid vehicle (2) having a drive device (1) according to one of the preceding claims.

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