Transmission for electric drive train of motor vehicle, electric drive train and motor vehicle

Abstract

The invention relates to a transmission (10) for an electric drive train of a motor vehicle, comprising a transmission input shaft (12) which is provided for rotationally fixed connection to a rotor shaft (18) of an electric traction machine; an intermediate shaft (14) that meshes with the transmission input shaft (12); a transmission output shaft (16) meshing with the intermediate shaft (14); and a transmission housing on which the intermediate shaft (14) and / or the transmission output shaft (16) are / is rotatably mounted by means of two cylindrical roller bearings (36, 38) at the respective ends thereof and by means of a four-point bearing (40).

Description

Technical Field

[0001] The invention relates to a transmission for an electric drive train of a motor vehicle, an electric drive train for a motor vehicle and a motor vehicle having an electric drive train. Background Art

[0002] The use of transmissions in the drive train of a corresponding motor vehicle for adjusting the rotational speed or torque is already known in series vehicle construction.

[0003] DE 10 2004 043 386 B4 discloses a transmission device of countershaft construction, which comprises a transmission input central shaft and a transmission input hollow shaft arranged concentrically with the transmission input central shaft. In addition, the transmission device comprises a corresponding countershaft, which is supported in a housing. The transmission input central shaft is directly supported in the housing via a first bearing device in the region of its end facing away from the power unit. Summary of the invention

[0004] The object of the present invention is to provide a solution which allows a particularly efficient and acoustically optimized design of a transmission for an electric drive train of a motor vehicle.

[0005] This object is solved by the technical solution of the independent claim. Other possible solutions of the present invention are disclosed in the dependent claims, the description and the drawings. The features, advantages and possible solutions set forth in the description of one of the technical solutions of the independent claim can be regarded at least similarly as the features, advantages and possible solutions of the corresponding technical solutions of the other independent claims and any possible combination of the technical solutions of the independent claims, if necessary in combination with one or more dependent claims.

[0006] The invention relates to a transmission for an electric drive train of a motor vehicle, in particular a car, in particular a passenger car. The motor vehicle is arranged to be driven by electric energy by means of the electric drive train. The motor vehicle is therefore an electric vehicle or a hybrid vehicle. The motor vehicle may comprise an electric traction machine as part of the electric drive train, which is arranged to provide a torque for driving the motor vehicle. The electric traction machine may be arranged to generate a torque using the electric energy of a battery, in particular a high-voltage battery of the motor vehicle. In order to adapt the torque generated by the electric traction machine to a desired torque and thus convert it into the desired torque, a transmission is provided. The transmission is in particular a non-shiftable transmission.

[0007] The transmission comprises a transmission input shaft, which is arranged to be connected to the rotor shaft of the electric traction machine in a non-rotatable manner. This means that the torque generated by the electric traction machine is transmitted to the transmission input shaft through the non-rotatable connection of the rotor shaft to the transmission input shaft. The transmission input shaft is assigned to the drive side of the transmission. The transmission also comprises an intermediate shaft meshing with the transmission input shaft. The intermediate shaft is connected to the transmission input shaft in a permanent force-transmitting manner, in particular. Therefore, the torque introduced into the transmission by the transmission input shaft can be transmitted from the transmission input shaft to the intermediate shaft. In particular, not only the transmission input shaft but also the intermediate shaft have respective gears, which mesh with each other for the purpose of transmitting force. The transmission also comprises a transmission output shaft meshing with the intermediate shaft. The transmission output shaft is in particular permanently meshed with the intermediate shaft. For this meshing, not only the intermediate shaft but also the transmission output shaft can have respective gears, which mesh with each other for the purpose of transmitting force. The transmission output shaft is assigned to the output side of the transmission. The transmission output shaft can be operatively connected to the corresponding wheels of the motor vehicle and thus provide the torque converted in the transmission for the wheels of the motor vehicle. The transmission therefore comprises two transmission stages. The first transmission ratio is formed by the meshing between the transmission input shaft and the countershaft, and the second transmission ratio is formed by the meshing between the countershaft and the transmission output shaft.

[0008] The transmission also includes a transmission housing, on which the intermediate shaft is rotatably supported by two cylindrical roller bearings at its respective ends and by a four-point bearing. This means that the first cylindrical roller bearing is arranged on the first end of the intermediate shaft and the second cylindrical roller bearing is arranged on the opposite second end of the intermediate shaft. The four-point bearing is arranged on one of the two ends of the intermediate shaft, in particular axially next to the cylindrical roller bearing assigned to the same end. This means that a four-point bearing is arranged on one end of the intermediate shaft and no four-point bearing is arranged on the other end of the intermediate shaft. Therefore, the first end of the intermediate shaft is supported on the transmission housing by a cylindrical roller bearing and a four-point bearing, while the second end of the intermediate shaft is rotatably supported on the transmission housing only by a cylindrical roller bearing. The cylindrical roller bearings serve as corresponding floating bearings, which enable reliable radial support of the intermediate shaft in the transmission housing. The four-point bearing serves as a fixed bearing and enables axial support of the intermediate shaft on the transmission housing. The axial direction and the radial direction each relate to the rotation axis of the corresponding assigned shaft, wherein the axial direction extends parallel to the rotation axis and the radial direction extends perpendicular to the rotation axis. The respective shaft rotates about an associated axis of rotation during operation of the motor vehicle.

[0009] In the described arrangement, a cylindrical roller bearing is used as a radial bearing and a four-point bearing is used as an axial bearing. The cylindrical roller bearing enables a very rigid support of the respective shaft (intermediate shaft or transmission output shaft) and thus enables only particularly small displacements of the tooth meshing between the respective shafts. Since the cylindrical roller bearing cannot absorb axial loads, a four-point bearing is additionally provided as an axial bearing arrangement. By providing a combination of two cylindrical roller bearings and the four-point bearing, a particularly small cylindrical roller bearing or a four-point bearing can be selected for supporting the intermediate shaft on the transmission housing. Since these bearing arrangements are particularly small, a particularly space-saving and lightweight support of the intermediate shaft can be achieved, whereby the transmission can be designed to be particularly compact and particularly light. In addition, due to their small size, only particularly low friction losses occur in the bearings.

[0010] In a possible extension of the present invention, it is provided that the transmission output shaft is part of a differential. The differential is a planetary gear transmission having a drive shaft and two output shafts. Here, the intermediate shaft can directly mesh with the planetary gear carrier of the differential, which can also be called a cage or basket. The transmission output shaft can therefore be constructed as a planetary gear carrier or have a planetary gear carrier. Through the differential, the torque regulated by the transmission can be directly transmitted to the corresponding wheels of the motor vehicle. Here, the differential can rotate the wheels of the motor vehicle at different speeds. Thus, multiple wheels of the motor vehicle can be driven by a single electric traction machine. As an alternative to designing the transmission output shaft as a part of the differential, the transmission output shaft can be directly connected to the individual wheels of the motor vehicle in a torque-transmitting manner and a separate electric traction machine and a separate transmission can be provided for each wheel of the motor vehicle. By designing the transmission output shaft as a part of the differential, the electric drive transmission system of the motor vehicle can be constructed particularly compactly and saves structural space.

[0011] In another possible design of the present invention, it is provided that the transmission output shaft and the intermediate shaft are rotatably supported on the transmission housing by two cylindrical roller bearings at their respective ends and by a four-point bearing. A relatively high torque is generated in the intermediate shaft and the transmission output shaft by the first and second transmission stages. For example, the torque present on the intermediate shaft is more than three times the torque on the transmission input shaft and the torque present on the transmission output shaft is more than three times the torque on the intermediate shaft. Therefore, there are particularly high forces in the intermediate shaft and the transmission output shaft, which should be supported on the transmission housing by corresponding bearing structures. The cylindrical roller bearings enable a very rigid support of the intermediate shaft and the transmission output shaft, thereby achieving a particularly small displacement of the tooth meshing between the transmission input shaft and the intermediate shaft and between the intermediate shaft and the transmission output shaft. Therefore, the inclination of the shaft and / or the deformation of the shaft can be kept particularly small. Therefore, the transmission is particularly quiet during operation.

[0012] In another possible embodiment of the invention, it is provided that the four-point bearing and one of the cylindrical roller bearings are arranged directly next to each other in the axial direction and thus form a bearing unit. This means that the four-point bearing rests on the cylindrical roller bearings assigned to the same end of the respective shaft. With the aid of the bearing unit, the respective shaft with the bearing unit can be mounted particularly easily on the transmission housing, and the bearing unit can be fixed in the transmission housing particularly compactly. In addition, the bearing unit allows particularly good stabilization of the respective shaft mounted on the transmission housing via the bearing unit.

[0013] In another possible embodiment of the invention, it is provided that the cylindrical roller bearing is arranged axially further outward along the intermediate shaft than the four-point bearing. If the transmission output shaft is also rotatably supported on the transmission housing by two cylindrical roller bearings at its respective ends and by a four-point bearing, the cylindrical roller bearing can also be arranged axially further outward along the transmission output shaft than the four-point bearing. In other words, the cylindrical roller bearing is arranged closer to the nearest end of the intermediate shaft or the transmission output shaft than the four-point bearing assigned to it. Therefore, the four-point bearing is arranged axially further inward than the cylindrical roller bearing. Along the corresponding length of the intermediate shaft or the transmission output shaft, the cylindrical roller bearing is arranged axially further outward and the four-point bearing is arranged axially further inward. As a result, the corresponding cylindrical roller bearing can be designed to be particularly small and the transmission can be particularly easily installed. When installing the transmission, it is provided that, starting from the transmission cover, the cylindrical roller bearing on the cover side is first positioned and then the four-point bearing is positioned. Then the corresponding gear is positioned and then the cylindrical roller bearing on the housing side is positioned. As a result, a particularly compact cylindrical roller bearing can be used. If the cover-side cylindrical roller bearing and the four-point bearing are arranged opposite each other and are therefore interchanged in the axial direction, the outer bearing raceway of the cylindrical roller bearing must be larger than the outer diameter of the four-point bearing in order to be able to mount the transmission and to connect the four-point bearing via the pre-mounted outer ring of the cylindrical roller bearing. The cylindrical roller bearing is therefore significantly larger than would be necessary from a load perspective. Furthermore, an additional retaining ring can be omitted if the four-point bearing is arranged axially between two cylindrical roller bearings.

[0014] In another embodiment of the present invention, it is provided that the intermediate shaft and the transmission output shaft are arranged parallel to each other and the four-point bearings are assigned to the same end of these shafts or to different ends of these shafts. This means that it is provided that not only the intermediate shaft but also the transmission output shaft are supported on the transmission housing at their ends by two cylindrical roller bearings and additionally by a corresponding four-point bearing. This means that the corresponding four-point bearings of the intermediate shaft and the transmission output shaft can be arranged axially on the corresponding same end and thus on the same side of the transmission, or can be arranged on the ends of the intermediate shaft and the transmission output shaft that are opposite to each other. The intermediate shaft and the transmission output shaft are especially arranged parallel to each other and each have a first end assigned to the first side and a second end assigned to the second side opposite to the first side. For example, the intermediate shaft can have a four-point bearing at its first end, while the transmission output shaft has a four-point bearing at its second end. Alternatively, the intermediate shaft can have a four-point bearing at its second end, while the transmission output shaft has a four-point bearing at its first end. If the intermediate shaft and the transmission output shaft have a four-point bearing at the same end, both the intermediate shaft and the transmission output shaft can each have an associated four-point bearing at their first end or at their second end. If the four-point bearing is arranged on the intermediate shaft and on the transmission output shaft on the same side and therefore at the same end, the transmission can be mounted particularly simply, since the fixed bearings are thus arranged on the same side of the transmission.

[0015] In particular, the respective shafts can be particularly well stabilized if the four-point bearing is arranged particularly close to the gears of the second transmission stage. This means that the four-point bearing on the intermediate shaft is arranged closer to the gears meshing with the transmission output shaft than to the gears meshing with the transmission input shaft. On the transmission output shaft, the four-point bearing is arranged closer to the gears meshing with the intermediate shaft than to the other gears of the transmission output shaft. In particular, the four-point bearing can be arranged axially directly next to the gears of the transmission output shaft meshing with the intermediate shaft. As a result, the intermediate shaft and the transmission output shaft can be particularly well stabilized in the region in which the shafts are particularly heavily loaded due to the force transmission from the intermediate shaft to the transmission output shaft.

[0016] In another possible design of the present invention, it is provided that the transmission input shaft is rotatably supported on the transmission housing by at least one deep groove ball bearing assigned to one of its ends. The deep groove ball bearing is a very efficient bearing structure in which particularly small friction occurs. Therefore, the deep groove ball bearing can realize particularly efficient support of the transmission input shaft. The deep groove ball bearing can be arranged on the first end of the transmission input shaft, and the other end is connected to the rotor shaft in a non-rotatable manner. The rotor shaft can be rotatably supported on the transmission housing by a so-called A bearing, and the A bearing is especially another deep groove ball bearing. Since the minimum torque in the transmission occurs in the transmission input shaft, a very efficient deep groove ball bearing can be used because it is sufficient to support the transmission input shaft. In addition, this deep groove ball bearing is a particularly low-cost rolling bearing, which can additionally support the transmission input shaft not only axially but also radially.

[0017] The invention further relates to an electric drive train for a motor vehicle, which has a transmission as already described with respect to the transmission according to the invention. The electric drive train further comprises an electric traction machine, whose rotor shaft is connected to a transmission input shaft of the transmission in a torque-transmitting manner. The electric traction machine is provided for driving the motor vehicle by means of electrical energy from a battery, in particular a high-voltage battery, of the motor vehicle, in that the torque generated by the electric traction machine is transmitted via the transmission to at least one wheel of the motor vehicle. The electric drive train is therefore provided for driving the motor vehicle by means of electrical energy.

[0018] The invention also relates to a motor vehicle having an electric drive train as has been described with respect to the electric drive train. The motor vehicle is an electric vehicle or a hybrid vehicle.

[0019] Other features of the invention can be derived from the claims, the drawings and the description of the drawings. The features and feature combinations mentioned above in the description and the features and feature combinations shown below in the description of the drawings and / or in the drawings alone can be used not only in the respectively given combination but also in other combinations or alone without departing from the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The only attached picture ( Figure 1 ) shows a transmission for an electric drive train of a motor vehicle in a schematic sectional view. DETAILED DESCRIPTION

[0021] exist Figure 11 shows a transmission 10 for an electric drive train of a motor vehicle, in particular a car, in particular a passenger car. The transmission 10 is provided for converting a torque received from an electric traction machine of the motor vehicle and transmitting the converted torque to at least one wheel of the motor vehicle. The transmission 10 is provided for converting the torque received from the electric traction machine in a plurality of transmission stages, in the present case two transmission stages 28, 30.

[0022] The transmission 10 comprises a transmission input shaft 12, an intermediate shaft 14 and a transmission output shaft 16. Force in the form of torque can be introduced into the transmission 10 via the transmission input shaft 12, which force is in turn provided to the corresponding wheels of the motor vehicle via the transmission output shaft 16. At present, the transmission output shaft 16 is part of a differential. For this purpose, the transmission output shaft 16 has a differential basket 32. The torque introduced into the transmission 10 via the transmission input shaft 12 is guided to the transmission output shaft 16 via the intermediate shaft 14 in the corresponding transmission stages 28, 30. The transmission input shaft 12 is currently connected to the rotor shaft 18 of the electric traction machine in a force-transmitting manner, in particular in a non-rotatable manner. The transmission input shaft 12 has a first pinion 20 on the outside, which meshes with a first gear 22 of the intermediate shaft 14 in a force-transmitting manner. The first pinion 20 and the first gear 22 mesh with each other permanently. The gear with the smaller diameter of the two meshing gears in a gear transmission is called a pinion. The intermediate shaft 14 has a second pinion 24 which meshes, in particular permanently meshes, with a second gear 26 of the transmission output shaft 16. The transmission 10 is therefore a non-shiftable transmission. The transmission ratio of the transmission 10 is therefore fixed and predetermined. Thus, in an electric drive train, the torque or the rotational speed at the wheels is regulated by the torque provided by the electric traction machine or by the rotational speed of the rotor shaft 18.

[0023] The first pinion 20 and the first gear wheel 22 form a first transmission stage 28 , while the second pinion 24 and the second gear wheel 26 form a second transmission stage 30 .

[0024] The transmission input shaft 12 is supported in the present case by means of corresponding deep groove ball bearings 34 on the transmission 10. Figure 11. The transmission housing is not shown in the figure. The deep groove ball bearing 34 is used not only for radial support but also for axial support of the transmission input shaft 12. In the present case, the transmission input shaft 12 is rotatably supported on the transmission housing by two deep groove ball bearings 34. In the present case, the transmission input shaft 12 is directly supported on the transmission housing by the first deep groove ball bearing of the deep groove ball bearings 34 and indirectly supported on the transmission housing via the rotor shaft 18 by the second deep groove ball bearing 34. In the present case, the transmission input shaft 12 is inserted into the shaft end of the rotor shaft 18 and the shaft end of the rotor shaft 18 is rotatably supported on the transmission housing by the second deep groove ball bearing 34. The second deep groove ball bearing 34 is a so-called A bearing. The deep groove ball bearing 34 is a particularly efficient bearing, which means that particularly low friction occurs in the deep groove ball bearing 34. The first deep groove ball bearing 34 is a so-called C bearing, which holds the transmission input shaft 12 axially and radially, but has clearance.

[0025] In the present case, both the intermediate shaft 14 and the transmission output shaft 16 are rotatably supported on the transmission housing via a first cylindrical roller bearing 36, a second cylindrical roller bearing 38 and a four-point bearing 40. In this case, the respective cylindrical roller bearing 36, 38 is arranged axially further outward on the respective shaft than the four-point bearing 40 assigned to the same end of the respective shaft. The respective cylindrical roller bearing 36, 38 serves as a floating bearing, while the four-point bearing 40 serves as a fixed bearing for the respective shaft. Thus, the four-point bearing 40 serves to axially support the respective shaft, while the cylindrical roller bearings 36, 38 serve to radially support the respective shaft. The respective cylindrical roller bearings 36, 38 are assigned to the ends of the respective shaft that are opposite to each other. This means that the first cylindrical roller bearing 36 is arranged on the first end of the respective shaft and the second cylindrical roller bearing 38 is arranged on the second end of the respective shaft that is opposite to the first end. The four-point bearing 40 is assigned to one of the ends of the respective shaft. In the present case, the four-point bearing 40 is also assigned to the first end of the respective shaft. The four-point bearing 40 forms a bearing unit together with the first cylindrical roller bearing 36. In the bearing unit, the four-point bearing 40 and the first cylindrical roller bearing 36 are arranged directly side by side in the axial direction. This means that the first cylindrical roller bearing 36 and the four-point bearing 40 can contact each other laterally.

[0026] As in Figure 1 It can be seen particularly clearly that the transmission input shaft 12, the intermediate shaft 14 and the transmission output shaft 16 are oriented parallel to one another with their respective rotational axes 42. The corresponding bearing unit formed by the first cylindrical roller bearing 36 and the four-point bearing 40 is arranged in the present case both on the intermediate shaft 14 and on the transmission output shaft 16 on the same side and thus on the same side. Figure 1Alternatively, the bearing units can also be arranged at different ends on the intermediate shaft 14 and on the transmission output shaft 16. For example, the bearing unit can be arranged at a first end of the intermediate shaft 14 and at a second end of the transmission output shaft 16 or vice versa. In particular, the arrangement of the bearing units depends on the orientation of the respective shaft or the arrangement of the respective gear or pinion on the shaft.

[0027] In order to keep the tilt of the intermediate shaft 14 relative to the transmission input shaft 12 or the transmission output shaft 16 relative to the intermediate shaft 14 particularly small, it is provided that the respective four-point bearing 40 or the respective bearing unit is arranged closer to the second transmission stage 30 than to the first transmission stage 28. This means that the four-point bearing 40 on the intermediate shaft 14 is arranged closer to the second pinion 24 than to the first gear 22. In this case, the four-point bearing 40 is arranged in the axial direction on the side of the second pinion 24 facing away from the first gear 22. On the transmission output shaft 16, the four-point bearing 40 is arranged directly next to the second gear 26 in the axial direction. As in Figure 1 It can be further seen that the four-point bearing 40 on the transmission output shaft 16 can be arranged radially inside the toothed ring of the second gear 26. This means that the four-point bearing 40 is covered or surrounded radially outward by the toothed ring of the second gear 26 at least in an axial length section. The four-point bearing 40 is therefore arranged particularly close to the force introduction point of the transmission output shaft 16, via which the torque is introduced into the transmission output shaft 16 via the second transmission stage 30. Since the torque acting in the second transmission stage 30 is greater than in the first transmission stage 28, the respectively assigned shaft, in the present case the intermediate shaft 14 or the transmission output shaft 16, can be particularly well stabilized by arranging the respective four-point bearing 40 particularly close to the second transmission stage 30, so that the risk of a tilting of the shaft can be kept particularly low.

[0028] The respective four-point bearing 40 is fixed to the transmission housing and serves as a fixed bearing for the respective assigned shaft. The transmission 10 can be mounted particularly simply if all fixed bearings and therefore all four-point bearings 40 are arranged on the same side of the transmission 10. The four-point bearing 40 has no or only a particularly small amount of play, thus achieving axial fixation of the respective assigned shaft. The four-point bearing 40 prevents axial displacement of the assigned shaft, the respective four-point bearing 40 being able to move radially in the transmission housing.

[0029] The torque introduced into the transmission 10 via the rotor shaft 18 is increased by the respective transmission stages 28, 30, so that the forces acting in the second transmission stage 30 are greater than in the first transmission stage 28. Therefore, particularly strong bearings are advantageous for stabilizing the shaft that realizes the second transmission stage 30. The four-point bearing 40 is particularly compact and particularly light and therefore has weight advantages and structural space advantages. Since the four-point bearing 40 is not used to absorb radial forces well, cylindrical roller bearings 36, 38 with high radial rotational forces are additionally provided. By providing a combination of cylindrical roller bearings 36, 38 and four-point bearings 40, particularly small bearings can be used in each case, which are designed to be particularly compact and lightweight. In addition, these bearings have particularly low friction due to their particularly small size.

[0030] Instead of a transmission 10 design with a differential basket 32, the transmission 10 can have a transmission output shaft 16 that is connected to only one wheel of the motor vehicle in a torque-transmitting manner. Thus, the transmission 10 can have a transmission input shaft 12, an intermediate shaft 14, and a transmission output shaft 16 according to the described arrangement for each wheel to be driven of the motor vehicle.

[0031] The described transmission 10 is based on the technical requirement to produce a transmission for an electric drive train that is as efficient and acoustically optimized as possible.

[0032] Known rolling bearing designs are either very rigid and thus cause small deformations of the transmission shaft and small displacements of the tooth meshing, or they are very efficient. Very rigid bearing designs, such as tapered roller bearings, cause small displacements of the tooth meshing, but are disadvantageous in terms of efficiency. Very efficient bearing designs, such as pure deep groove ball bearings, are very efficient and thus have low loss or friction torques, but cause relatively large deformations and / or tilting of the transmission shaft and thus displacements of the tooth meshing. As a result, a large load-bearing area is produced in relation to the torque, which results in acoustic disadvantages.

[0033] The transmission 10 has a combination of a highly efficient four-point bearing 40 as axial bearing and cylindrical roller bearings 36, 38 as radial bearings. The cylindrical roller bearings 36, 38 result in a very rigid support and therefore in small displacements of the corresponding tooth meshing. Since the cylindrical roller bearings 36, 38 cannot absorb axial loads, at least one four-point bearing 40 is additionally provided as an axial bearing arrangement. In the combination of this bearing concept on the differential and thus on the transmission output shaft 16 and on the intermediate shaft 14 and the deep groove ball bearing arrangement of the transmission input shaft 12, Figure 1 In the two transmission stages 28 , 30 of the arrangement shown in FIG. 8 , a very small displacement of the tooth meshing is achieved.

[0034] The motor vehicle can have an electric drive train with an electric machine, a first gear stage 28, a second gear stage 30 and a differential. Alternatively, the motor vehicle can have an electric drive train with two electric machines and a first gear stage 28 and a second gear stage 30 respectively and without a differential.

[0035] The transmission input shaft 12 is supported by means of a deep groove ball bearing 34, the first deep groove ball bearing 34 arranged next to the first pinion 20 serving as a fixed bearing. The intermediate shaft 14 is supported by means of a four-point bearing 40 as a fixed bearing on the transmission cover side of the transmission housing and by means of two cylindrical roller bearings 36, 38 as floating bearings or radial bearings. The transmission output shaft 16 or the differential basket 32 ​​is supported by means of a four-point bearing 40 as a fixed bearing on the transmission cover side and by means of two cylindrical roller bearings 36, 38 as floating bearings or radial bearings. The respective four-point bearings 40 are radially exposed in the transmission cover of the transmission housing or on the transmission shaft, respectively. Therefore, no radial forces are transmitted to the four-point bearings 40 and they serve purely as axial bearings or fixed bearings. The proposed arrangement achieves elastic deformation of the respective bearing locations in the same direction and thus tilting or deformation of the transmission shaft in the same direction and thus small radial displacements and angular deviations of the gears in meshing with each other and thus small deviations in the tooth meshing.

[0036] By arranging the bearing arrangement of the spur gear in the structural space or in the transmission 10, the accessibility of the locking element of the fixed bearing is limited. The standard snap ring in the transmission 10 cannot be connected to the differential 10 and can only be connected to the intermediate shaft 14 to a certain extent. Therefore, a recess can be made in the transmission cover in the region of the snap ring, through which the corresponding snap ring can be operated from the outside. The recess can be closed after the snap ring is connected.

[0037] In summary, the present invention shows how a rolling bearing concept with a separate radial and axial bearing design can be realized for a transmission 10 of an electric drive.

[0038] Reference numerals list

[0039] 10 Transmission

[0040] 12 Transmission input shaft

[0041] 14Intermediate shaft

[0042] 16 Transmission output shaft

[0043] 18 Rotor shaft

[0044] 20First pinion

[0045] 22 First gear

[0046] 24 Second small gear

[0047] 26 Second gear

[0048] 28 First gear stage

[0049] 30 Second gear stage

[0050] 32 Differential Basket

[0051] 34 deep groove ball bearings

[0052] 36 Cylindrical roller bearings

[0053] 38 Cylindrical roller bearings

[0054] 40 four point bearing

[0055] 42 Rotation axis

Claims

1. A transmission (10) for an electric drive train of a motor vehicle, the transmission comprising: - a transmission input shaft (12) which is provided for a rotationally fixed connection to a rotor shaft (18) of an electric traction machine; - an intermediate shaft (14) meshing with the transmission input shaft (12); - a transmission output shaft (16) meshing with the intermediate shaft (14); and - a transmission housing, on which the intermediate shaft (14) is rotatably supported via two cylindrical roller bearings (36, 38) at its respective ends and via a four-point bearing (40).

2. The transmission (10) according to claim 1, characterized in that: The transmission output shaft (16) is part of the differential.

3. The transmission (10) according to claim 1 or 2, characterized in that: The transmission output shaft (16) and the intermediate shaft (12) are rotatably supported on the transmission housing via two cylindrical roller bearings (36, 38) at their respective ends and via a four-point bearing (40).

4. The transmission (10) according to any one of the preceding claims, characterized in that The four-point bearing (40) and one of the cylindrical roller bearings (36, 38) are arranged directly adjacent to each other in the axial direction and thus form a bearing unit.

5. The transmission (10) according to any one of the preceding claims, characterized in that The cylindrical roller bearings (36, 38) are arranged axially further outward along the intermediate shaft (14) than the four-point bearing (40).

6. A transmission (10) according to claim 3 or according to claim 4 or 5 as dependent on claim 3, characterized in that The intermediate shaft (14) and the transmission output shaft (16) are arranged parallel to one another and the four-point bearing (40) is assigned to the same end of the shafts or to different ends of the shafts.

7. The transmission (10) according to any one of the preceding claims, characterized in that The transmission input shaft (12) is rotatably supported on the transmission housing via at least one deep groove ball bearing (34) assigned to one of its ends.

8. An electric drive train for a motor vehicle, comprising a transmission (10) according to any one of the preceding claims and an electric traction machine, the rotor shaft (18) of which is connected in a torque-transmitting manner to a transmission input shaft (12) of the transmission (10).

9. A motor vehicle comprising an electric drive train according to claim 8.

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