Motor vehicle drive device

Abstract

The invention relates to a motor vehicle drive system (24) comprising: an electromechanical energy converter as an electric drive machine (15); a traction transmission device for transmitting drive power to a motor vehicle axle drive, wherein the traction transmission device has a traction transmission housing device and wherein a traction transmission drive shaft (1), which is connected to the electric drive machine (15) for conjoint rotation therewith or can be selectively connected thereto for conjoint rotation therewith, is rotatably mounted in said traction transmission housing device; an traction transmission intermediate shaft (4) which is rotatably mounted in the traction transmission housing device and which is arranged axially parallel to and radially spaced apart from the traction transmission drive shaft (1); a traction transmission output shaft (2) which is rotatably mounted in the traction transmission housing device and which is arranged axially parallel to and radially spaced apart from the other two traction transmission shafts (1, 4), wherein a traction transmission drive gear (19), which engages with a first traction transmission intermediate gear (6) which is mounted on the traction transmission intermediate shaft (4), is mounted on the traction transmission drive shaft (1), and wherein a second traction transmission intermediate gear (20), which engages with a traction transmission output gear (3) which is mounted on the traction transmission output shaft (2), is mounted on the traction transmission intermediate shaft (4), and wherein the traction transmission housing device has a traction transmission housing (13) and a traction transmission cover (14). The motor vehicle drive system is characterised in that: the three traction transmission shafts (1, 2, 4) are each mounted in the traction transmission housing device with a fixed / floating bearing; such a bearing has in each case at least one fixed bearing for absorbing axial forces; and at least two of these fixed bearings are mounted in the traction transmission cover (14).

Description

[0001] Motor vehicle drive device

[0002] The invention relates to an electric motor vehicle drive system for overcoming motor vehicle driving resistances such as rolling resistance, air resistance, and the like, and to a motor vehicle with such a drive system. DE 10 2019 127 242 A1 discloses an electric drive device for a motor vehicle according to the preamble of claim 1, comprising a transmission, as well as a drive arrangement comprising a transmission and an electric motor.

[0003] A general requirement for a motor vehicle drive is that it delivers the required drive power comfortably and efficiently. However, these two properties, or rather their achievement, can have a negative impact on each other. The invention is explained below using a motor vehicle drive system with a gear transmission, wherein the gears of this transmission have so-called involute toothing. With such toothings, it is known that so-called deep toothings, in particular gear pairs with a profile overlap >= 2.0 and a step overlap >= 2.0, enable a particularly comfortable drive. With a gear pair with a smaller profile overlap and a different overlap combination, efficiency can be improved compared to the deep toothing explained above, but this generally leads to an acoustic disadvantage and thus impairs the comfort of power transmission.Furthermore, it is generally possible to reduce noise in a motor vehicle drive by means of additional insulation materials, but this has a negative impact on the vehicle weight, means additional expenditure and thus reduces the efficiency of the vehicle.

[0004] In contrast, the invention proposes a motor vehicle drive system which simultaneously permits the transmission of drive power with high efficiency and high comfort. This object is achieved by an object according to patent claim 1, and by a motor vehicle according to patent claim 9, wherein preferred developments of the invention are each the subject of the dependent patent claims. In the invention, it is particularly proposed to consider not only the toothing of the individual gearwheels, but the entire system, in particular the bearing of the transmission shafts in a transmission housing. In particular, the combination of bearing concept and toothing design then results in a drive system with high comfort and high efficiency.

[0005] For the purposes of the invention, a motor vehicle drive system is understood to be a system for driving a motor vehicle, preferably a passenger car, wherein the drive power for overcoming driving resistances such as friction, rolling, air, and so-called acceleration resistance is provided by means of a preferably electromechanical energy converter. For the purposes of the invention, such an electromechanical energy converter is understood to be an electric drive machine, in particular an electric motor / generator, whereby such an electric drive machine is known in various designs.

[0006] The motor vehicle drive system further comprises a traction transmission device, which is configured to transmit and adapt drive power to a load requirement of the motor vehicle, which results in particular from the driving resistance. The traction transmission device is thus configured to transmit drive power in the form of speed and torque to a motor vehicle axle drive. This motor vehicle axle drive is understood to mean, in particular, a motor vehicle drive axle, in particular a front or rear axle.

[0007] The traction transmission device comprises a traction transmission housing device. In particular, the traction transmission housing device consists of several components and is preferably also designed to accommodate the electric drive motor. A traction transmission drive shaft is rotatably mounted in this traction transmission housing. This traction transmission drive shaft can be considered the first or input shaft of the traction transmission device with respect to power transmission from the electric drive motor to the motor vehicle axle drive, the so-called motor drive direction.

[0008] In a first embodiment of the invention, the traction transmission drive shaft is rotationally fixedly connected to the electric drive motor, preferably aligned coaxially therewith, and more preferably directly coupled thereto. In a further embodiment, the traction transmission drive shaft can be selectively rotationally fixedly connected to the electric drive motor, preferably by means of a coupling device. In particular, a permanently rotationally fixed connection of the electric drive motor to the traction transmission drive shaft makes it possible to eliminate a bearing point, and drag losses can be reduced with a selectively coupled electric drive motor.

[0009] In addition to the traction gear drive shaft, the traction gear device also has a traction gear intermediate shaft, which, with respect to the motor drive direction, is arranged downstream of the traction gear drive shaft, preferably directly downstream thereof. The traction gear intermediate shaft is rotatably mounted in the traction gear housing device and is arranged axially parallel and radially spaced from the traction gear drive shaft. The traction gear device also has a traction gear output shaft, which, with respect to the motor drive direction, is arranged downstream of the traction gear intermediate shaft, preferably directly downstream thereof. The traction gear output shaft is rotatably mounted in the traction gear housing device and is preferably arranged axially parallel and radially spaced from the other two traction gear shafts.

[0010] To form the traction transmission device, in particular a transmission device with two gear stages for transmitting power from the electric drive motor to the motor vehicle axle drive, a traction transmission drive gear is arranged on the traction transmission input shaft, which engages with a first traction transmission intermediate gear arranged on the traction transmission intermediate shaft. The traction transmission drive gear and the first traction transmission intermediate gear thus form a first gear stage with the traction transmission input shaft and the traction transmission intermediate shaft, by means of which drive power can be transmitted from one of these shafts to the other. A second traction transmission intermediate gear is also arranged on the traction transmission intermediate shaft, which engages with a traction transmission output gear arranged on the traction transmission output shaft.The second traction gear intermediate gear and the traction gear output gear thus form a second gear stage with the traction gear intermediate shaft and the traction gear output shaft, by means of which drive power can be transferred from one of these shafts to the other.

[0011] The traction gear housing assembly comprises a traction gear housing and a traction gear cover as its main components. In particular, the traction gear housing and the traction gear cover are configured to accommodate bearings, preferably roller bearings, to rotatably support the traction gear drive shaft, traction gear intermediate shaft, and traction gear output shaft relative to the traction gear housing assembly. The traction gear housing is preferably configured such that, in the assembled state of the motor vehicle drive system, it covers at least one of these gear stages in the axial direction of the traction gear drive shaft, preferably both gear stages. Furthermore, the traction gear cover is preferably configured as a so-called bearing plate. The traction gear cover, like the traction gear housing, can be configured as a multi-part component.

[0012] In particular, to achieve sufficient rigidity in the bearings of the transmission shafts (traction transmission input shaft, traction transmission output shaft, traction transmission intermediate shaft), these three traction transmission shafts are each mounted in the traction transmission housing device with a so-called fixed-loose bearing. For the purposes of the invention, a fixed-loose bearing is understood in particular to mean a bearing that has two bearing points for a shaft relative to a housing, one of these bearing points being designed to absorb axial and radial forces and the other to absorb radial forces, with axial and radial being understood to mean each relative to the axis of rotation of the shaft to be supported, and the bearing point at which the axial forces can be absorbed being understood to be the fixed bearing.A single such bearing location can also have several bearings, preferably several rolling bearings, in particular the so-called fixed bearing can have a radial and an axial bearing.

[0013] The term "fixed-loose bearing" as such is known from the prior art. It is therefore further proposed that such a fixed-loose bearing comprise at least one fixed bearing for absorbing axial forces, with at least two of these fixed bearings being arranged in the traction gear cover or supported by it and positioned opposite the traction gear housing. In particular, such a design of the motor vehicle drive system enables simple assembly of the traction gear device.

[0014] In a preferred embodiment, all fixed bearings provided for supporting the traction gear drive shaft, traction gear intermediate shaft, and traction gear output shaft are arranged in this traction gear cover, or are supported by it, and are thus positioned and held relative to the traction gear housing. In particular, such an embodiment of the invention enables simple assembly of the traction gear device.

[0015] In a preferred embodiment of the invention, the traction transmission drive gear and the first traction transmission intermediate gear mesh with one another to transmit drive power, thus forming a first traction transmission gear stage. Further preferably, the profile contact ratio of this first traction transmission gear stage is greater than 1.70, preferably greater than or equal to 1.76, and preferably, this profile contact ratio is less than 1.90 and preferably less than or equal to 1.84. Further preferably, the step contact ratio of the first traction transmission gear stage is greater than 3.10, preferably greater than or equal to 3.16, and further preferably, this step contact ratio is less than 3.30 and preferably less than or equal to 3.24.In particular, in combination with the previously described bearing concept (fixed-loose bearing) and the profile or jump overlap selected in this way, the traction gear device is easy to install and the drive power is transmitted quietly, while at the same time the power transmission is highly efficient.

[0016] In a preferred embodiment of the invention, the second traction transmission intermediate gear and the traction transmission output gear mesh with one another to transmit drive power, thus forming a second traction transmission gear stage. Further preferably, the profile contact ratio of this second traction transmission gear stage is greater than 1.40, preferably greater than or equal to 1.46, and preferably, this profile contact ratio is less than 1.60 and preferably less than or equal to 1.54. Further preferably, the step contact ratio of the second traction transmission gear stage is greater than 2.40, preferably greater than or equal to 2.46, and further preferably, this step contact ratio is less than 2.50 and preferably less than or equal to 2.54.In particular, in combination with the previously described bearing concept (fixed-loose bearing) and the profile or jump overlap of the second traction gear stage selected in this way, the traction gear device is easy to install, as well as a low-noise transmission of drive power and, at the same time, high efficiency.

[0017] In a preferred embodiment, at least two gears of at least one of the two traction gear stages are designed as helical spur gears, which preferably have so-called involute gearing. Preferably, all gears of these gear stages are designed as such, in particular helical, spur gears. In such an embodiment with at least two, preferably with all, helical spur gears, the first traction gear intermediate gear preferably has a first helical gearing with a first helix angle, and the second traction gear intermediate gear preferably has a second helical gearing with a second helix angle.Furthermore, these first and second helix angles are directed in opposite directions, so that axial forces occurring during power transmission, particularly due to these helix angles, at least partially cancel each other out, or axial forces occurring during the transmission of drive power are directed in opposite directions. In particular, due to the opposite directions of the axial forces of the first and second traction transmission intermediate gears, the load on the fixed bearing of the fixed-loose bearing of the traction transmission intermediate shaft is reduced, thus extending its service life. Furthermore, the power loss caused by this bearing can be reduced.

[0018] In a preferred embodiment of the invention, the traction gear drive shaft is mounted in the traction gear housing by means of a fixed-loose bearing, i.e., a bearing comprising a fixed bearing, at least for absorbing axial forces, and a loose bearing. Preferably, at least one of these bearings of this fixed-loose bearing is arranged only indirectly on the traction gear drive shaft. Preferably, the traction gear drive shaft is accommodated in a further shaft, and this loose bearing of the fixed-loose bearing of the traction gear drive shaft is accommodated on this further shaft or is configured to support this further shaft and thus indirectly to support the traction gear drive shaft.Preferably, the traction gear drive shaft is connected to this further shaft in a rotationally fixed manner and preferably by means of a positive shaft-hub connection and particularly preferably a fit, preferably a transition fit and preferably a press fit, is provided for positioning the traction gear drive shaft relative to the further shaft.

[0019] Preferably, the floating bearing of the fixed-floating bearing of the traction gear drive shaft is thus designed as a so-called common floating bearing for the traction gear drive shaft and for this further shaft and, in particular, by means of such a design of the bearing of the traction gear drive shaft, a particularly efficient bearing of this shaft is made possible.

[0020] Further preferably, a rolling bearing with balls as rolling elements is provided as the fixed bearing of this fixed-loose bearing of the traction gear drive shaft, and further preferably, this bearing is designed as a so-called four-point bearing and preferably as a so-called deep groove ball bearing. Further preferably, this fixed bearing, in particular via the connection of the traction gear drive shaft to this further shaft, also forms the fixed bearing for this further shaft. Further preferably, a rolling bearing with cylindrical rolling elements or preferably with balls is provided as the loose bearing of this fixed-loose bearing of the traction gear drive shaft. Preferably, this loose bearing is designed as a cylindrical roller bearing and preferably as a deep groove ball bearing. In a preferred embodiment, both the fixed bearing and the loose bearing of the bearing of the traction gear drive shaft are designed as deep groove ball bearings.Particularly in an embodiment with such rolling bearings, high power transmission efficiency can be achieved. Preferably, the fixed bearing for the traction gear drive shaft is arranged in the traction gear cover and, in particular, is secured therein.

[0021] Further preferably, the traction transmission housing is designed such that the electric drive motor is arranged on or within it. In particular, such a design allows for easy assembly of the motor vehicle drive system and high efficiency in transmitting drive power.

[0022] In a preferred embodiment of the motor vehicle drive system, the traction gear intermediate shaft is mounted in the traction gear housing by means of a fixed-loose bearing, i.e., a bearing with a fixed bearing for absorbing axial forces and a loose bearing. Further preferably, a rolling bearing with balls as rolling elements is provided as the fixed bearing of this fixed-loose bearing of the traction gear intermediate shaft, and further preferably, this bearing is designed as a so-called four-point bearing, preferably as a so-called deep groove ball bearing. Further preferably, a rolling bearing with cylindrical rolling elements or, preferably, with balls is provided as the loose bearing of this fixed-loose bearing of the traction gear intermediate shaft. This loose bearing is preferably designed as a cylindrical roller bearing, preferably as a deep groove ball bearing.In a preferred embodiment, both the fixed bearing and the floating bearing of the traction transmission intermediate shaft are designed as deep groove ball bearings. Particularly in an embodiment with such rolling bearings, high power transmission efficiency can be achieved. The fixed bearing of the traction transmission drive shaft is preferably arranged in the traction transmission cover.

[0023] In a preferred embodiment, the traction gear output shaft is mounted in the traction gear housing by means of a fixed-loose bearing. Further preferably, this fixed-loose bearing, in particular for absorbing axial forces, comprises a fixed bearing, or a fixed bearing location, and at least one loose bearing. The fixed-loose bearing for supporting the traction gear output shaft preferably comprises, in particular, two or more rolling bearings, wherein the rolling elements of at least two of these rolling bearings are designed as cylindrical rolling elements, and these rolling bearings are thus preferably designed as cylindrical roller bearings. Preferably, in addition to two cylindrical roller bearings, the fixed-loose bearing of the traction gear output shaft also comprises a rolling bearing designed as a fixed bearing, preferably a rolling bearing having balls as rolling elements.Further preferably, the fixed bearing of the traction transmission output shaft bearing is designed as a deep groove ball bearing, preferably as a four-point contact bearing. This fixed bearing is, in particular, radially exposed, or in other words, the bearing seat on the traction transmission output shaft, which is designed to accommodate this fixed bearing, has a smaller diameter than a bearing inner ring of this fixed bearing, or further preferably, the bearing seat in the traction transmission housing device, which is designed to accommodate this fixed bearing, has a larger diameter than the bearing outer diameter of this fixed bearing. Further preferably, these cylindrical roller bearings of the fixed-loose bearing of the traction transmission output shaft are arranged in an axial direction on different sides of the traction transmission output gear.Further preferably, the fixed bearing, in particular the deep groove ball bearing or the four-point contact bearing, for supporting the traction transmission output shaft is arranged in the traction transmission cover. In particular, such a configuration allows for efficient and rigid support of the traction transmission output shaft.

[0024] Furthermore, a motor vehicle is proposed which has at least one motor vehicle drive system of the proposed design. In particular, the motor vehicle drive system is configured to drive the motor vehicle in a main direction of travel and preferably also counter to this, wherein this main direction of travel is understood to be the forward direction of travel of a passenger car. Preferably, the motor vehicle can be driven with only one of these motor vehicle drive systems and is thus designed as a motor vehicle with front-wheel drive or rear-wheel drive. Further preferably, the motor vehicle is equipped with two of these motor vehicle drive systems and is thus designed as an all-wheel drive vehicle.

[0025] In a preferred embodiment, at least the second traction transmission gear stage is designed as a helical gear stage. In particular, the traction transmission output gear has helical output teeth with an output helix angle and is thus designed as a helical spur gear. Further preferably, the output helix angle is selected such that the axial force of the traction transmission output gear, which arises when the motor vehicle is driven in the forward direction due to the helical toothing of the traction transmission output gear, is directed in the direction of the traction transmission output shaft extension, i.e., in the axial direction from the traction transmission cover toward the traction transmission housing. In particular, such a design enables efficient transmission of drive forces with a high level of comfort, while at the same time, the motor vehicle drive system is easy to assemble and thus cost-effective to manufacture.

[0026] In other words, a basic idea of ​​the invention is that the engagement ratios of the gearing of the first spur gear stage (first traction gear stage) and the second spur gear stage (second traction gear stage) are selected to achieve high efficiency while simultaneously achieving good comfort in the transmission of drive power, in particular good acoustics. For the proposed motor vehicle drive system, the gearing of the first and second traction gear stages are designed such that the engagement ratios of this gearing are preferably as follows:

[0027] - first traction gear stage, profile contact ratio in the range 1.76 - 1.84, step contact ratio in the range 3.16 - 3.24;

[0028] - second traction gear stage, profile contact ratio in the range 1.46 - 1.54, step contact ratio in the range 2.46 - 2.54.

[0029] It is further proposed that the helix direction of the teeth of the second traction transmission gear stage is preferably selected such that the resulting axial force of the traction transmission output gear during forward motorized travel of the motor vehicle is directed toward the traction transmission housing. It is further proposed that the traction transmission output gear is preferably designed as a so-called final drive gear. For the purposes of the invention, the so-called final drive gear is understood to mean a gear in which an axle differential of a motor vehicle drive axle is accommodated, or which is rotationally fixedly connected to a differential cage of such an axle differential.

[0030] Furthermore, the traction transmission drive gear, and thus also the first traction transmission intermediate gear, are preferably designed as helical spur gears, as are preferably the traction transmission output gear and the second traction transmission intermediate gear. It is further proposed that the helical direction of the toothing of the first traction transmission gear stage can preferably be selected such that the axial forces of the gear of the first traction transmission gear stage and the gear of the second traction transmission gear stage act in opposite axial directions on the traction transmission intermediate shaft, thus at least partially canceling each other out.It is further proposed that a fixed-loose bearing can be used for the bearing of the traction transmission intermediate shaft, as is also the case for the traction transmission output shaft; in addition, the traction transmission input shaft can also be mounted with such a fixed-loose bearing, wherein in particular the loose bearing of the bearing of the traction transmission input shaft can simultaneously be used as a bearing for another shaft such as the output shaft of an electric drive machine, preferably the rotor shaft.

[0031] Furthermore, a special geometric arrangement of the transmission shafts (traction transmission input shaft, traction transmission intermediate shaft, and traction transmission output shaft) is proposed, depending on the planned forward direction of travel and the resulting direction of rotation of the traction transmission input shaft. The installation space requirements in a motor vehicle, in which certain functions must be provided, in this case the drive function, result in boundary conditions that must be observed for the arrangement of components. Furthermore, the quality of the fulfillment of the function can depend on the arrangement of the components in the specified installation space, in this case in particular the aforementioned transmission shafts. For the reasons stated, two alternatives for the arrangement of this transmission shaft are proposed.

[0032] The first of these alternatives thus represents a preferred embodiment of the invention in which, with respect to this forward direction of travel of the motor vehicle in the plane and in the planned installation position of the motor vehicle drive system, the traction gear input shaft is arranged in front of the traction gear intermediate shaft and furthermore, in this first alternative, the traction gear output shaft is arranged behind the traction gear intermediate shaft.

[0033] Further preferably, in this embodiment, relative to the forward direction of travel, in a direction of view from the right, orthogonal (relative to a rotational axis of the traction transmission drive shaft) to an end face of the traction transmission drive shaft, the direction of rotation of this transmission shaft is directed clockwise to generate a movement of the motor vehicle in the forward direction of travel. Thus, the traction transmission intermediate shaft has an opposite direction of rotation, and the traction transmission output shaft rotates in the same direction as the traction transmission drive shaft. In particular, with such an embodiment of the invention, a slight displacement of the gears involved in the transmission of drive forces can be achieved, thus enabling an efficient and reliable transmission of drive forces with the motor vehicle drive system in the planned forward direction of travel.In a preferred embodiment of the invention, with respect to this forward direction of travel in the plane and in the planned installation position of the motor vehicle drive system, the traction transmission intermediate shaft is arranged geometrically higher than the traction transmission input shaft, and more preferably, the traction transmission output shaft is arranged lower than the traction transmission intermediate shaft, and preferably, the latter is also arranged lower than the traction transmission input shaft. In particular, such a configuration results in minimal displacement of the gears involved in the transmission of drive forces, thus enabling efficient and reliable transmission of these drive forces with the motor vehicle drive system in the planned forward direction of travel.

[0034] The second of these alternatives represents a further preferred embodiment of the invention, in which, with respect to this forward direction of travel in the plane and in the planned installation position of the motor vehicle drive system, the traction gear input shaft is arranged behind the traction gear intermediate shaft and further preferably the traction gear output shaft is arranged in front of the traction gear intermediate shaft.

[0035] Further preferably, in this embodiment (second alternative), relative to the forward direction of travel, in a viewing direction from the left, orthogonally (relative to a rotational axis of the traction gear drive shaft) to an end face of the traction gear drive shaft, the direction of rotation of this gear shaft for generating a movement of the motor vehicle in the forward direction of travel is directed counterclockwise and thus the traction gear intermediate shaft has a clockwise direction of rotation and the traction gear output shaft rotates in the same direction as the traction gear drive shaft.

[0036] Further preferably, in this embodiment, relative to this forward direction of travel on the plane and in the planned installation position of the motor vehicle drive system, the traction gear intermediate shaft is arranged lower than the traction gear output shaft, and preferably the traction gear input shaft is arranged higher than the traction gear output shaft, and further preferably the traction gear input shaft is arranged higher than the traction gear intermediate shaft. In particular, with such an embodiment of the invention, a minimal displacement of the gears involved in the transmission of drive forces can be achieved, as well as low noise during power transmission with the traction gear stages, and thus an efficient and reliable transmission of drive forces with the motor vehicle drive system in the planned forward direction of travel can be achieved.

[0037] Further preferably, in this embodiment, with respect to this forward direction of travel on the plane and in the planned installation position of the motor vehicle drive system, the traction gear intermediate shaft is arranged higher than the traction gear output shaft, and preferably the traction gear input shaft is arranged higher than the traction gear output shaft, and further preferably the traction gear input shaft is arranged lower than the traction gear intermediate shaft. In particular, with such an embodiment of the invention, a minimal displacement of the gears involved in the transmission of drive forces and a low center of gravity for the motor vehicle drive system can be achieved, thus enabling efficient and reliable transmission of drive forces with the motor vehicle drive system in the planned forward direction of travel.

[0038] Individual features and embodiments of the invention are explained in more detail below with reference to the figures, in which:

[0039] Fig.1 : a schematic cross-sectional view of the proposed motor vehicle drive system orthogonal to the traction gear drive shaft,

[0040] Fig.2: a first longitudinal section of the proposed motor vehicle drive system parallel to the traction transmission drive shaft,

[0041] Fig.3: a second longitudinal section of the proposed motor vehicle drive system parallel to the traction transmission intermediate shaft,

[0042] Fig.4: highly schematic plan view of a motor vehicle with the proposed motor vehicle drive system,

[0043] Fig. 5a: a schematic plan view of the motor vehicle drive system in a first embodiment,

[0044] Fig. 5b is a schematic side view of the motor vehicle drive system in the first embodiment in a planned installation position,

[0045] Fig. 6a: a schematic plan view of the motor vehicle drive system in a second embodiment,

[0046] Fig. 6b: a schematic side view of the motor vehicle drive system in the second embodiment in a planned installation position,

[0047] Fig. 7a: a schematic plan view of the motor vehicle drive system in a modified variant of this second embodiment, Fig. 7b: a schematic side view of the motor vehicle drive system of this modified variant of this second embodiment in a planned installation position.

[0048] Figure 1 shows a cross-section through a motor vehicle drive system, i.e., a section orthogonal to the traction gear drive shaft 1 at the level of the traction gear wheel set. The electromechanical energy converter in such a motor vehicle drive system is embodied as an electric drive motor (not shown). Drive power for driving a motor vehicle can be transmitted from the electric drive motor via the traction gear device shown in section to a motor vehicle axle drive, in particular to the traction gear output shaft 2 and the traction gear output gear 3. The traction gear drive shaft 1 and the traction gear output shaft 2 of the traction gear device are rotatably mounted in the traction gear housing device (not shown).The traction gear drive shaft 1 is connected in a rotationally fixed manner to the electric drive machine, in particular to the rotor shaft of such a machine, by means of a shaft-hub connection.

[0049] The traction gear device further comprises the traction gear intermediate shaft 4, which is also rotatably mounted in the traction gear housing. The gear shafts of the traction gear device are each arranged axially parallel to one another and radially spaced from one another and are shown here in the intended installation position in a motor vehicle. Furthermore, the intended forward direction of travel 5 is shown with reference to this installation situation. A traction gear drive gear 19 is arranged on the traction gear drive shaft 1 and meshes with a first traction gear intermediate gear 6. The traction gear drive gear 19 is not visible in the sectional view shown in Figure 1, since it is located behind the traction gear drive shaft fixed bearing 7.Furthermore, a second traction gear intermediate gear 20 is arranged on the traction gear intermediate shaft 4, which engages with the traction gear output gear 3, which is arranged on the traction gear output shaft 2.

[0050] The three traction transmission shafts shown (traction transmission input shaft 1, traction transmission intermediate shaft 4, traction transmission output shaft 2) are each mounted with a fixed-loose bearing in the traction transmission housing device and are each connected in a rotationally fixed manner to the transmission shaft on which they are arranged. A bearing of the type described as such is known from the prior art for supporting transmission shafts and has at least one fixed bearing for absorbing axial forces. In the proposed motor vehicle drive system, at least two of these fixed bearings are arranged in the traction transmission cover, which, together with the traction transmission housing, forms the traction transmission housing device or is a component thereof.

[0051] Figure 2 shows a longitudinal sectional view of the motor vehicle drive system, with the sectional plane A being visible in Figure 1. The drive power is provided by the electric drive motor 15, which is accommodated in the traction gear housing device 13, 14, whereby the traction gear housing device is only partially shown.

[0052] The output shaft of the electric drive motor 15 is directly connected in a rotationally fixed manner to the traction gear drive shaft 1 via a shaft-hub connection 16. The traction gear drive shaft 1 is rotatably mounted in the traction gear housing assembly 13, 14. The traction gear drive shaft fixed bearing 7 is arranged in the traction gear cover 14 and absorbs axial forces acting on the traction gear drive shaft 1. Furthermore, the traction gear drive shaft 1 is mounted in the traction gear housing 13 via the traction gear drive shaft floating bearing 10.Structurally, the traction gear drive shaft floating bearing 10 is designed as a common bearing for the electric drive motor 15 and the traction gear drive shaft 1, wherein a traction gear drive shaft centering seat 21 is used to center the drive shaft of the electric drive motor 15 and the traction gear drive shaft 1. Thus, a bearing arrangement with three bearings can be used for the support of these two shafts, and thus improved efficiency can be achieved compared to an independent support of both shafts with two roller bearings each.

[0053] The traction transmission drive gear 19, which is arranged on the traction transmission drive shaft 1, meshes with the first traction transmission intermediate gear, which is not shown in this sectional view, to transmit drive power. The traction transmission housing assembly 13, 14 is connected to the motor vehicle structure (not shown) via the assembly bearings 17 and is thus positioned in the motor vehicle.

[0054] Drive power is transmitted from the traction gear input shaft 1 to the traction gear output shaft 2 via the traction gear intermediate shaft, which is not located in the illustrated sectional plane A and therefore not shown in Figure 2. The traction gear output gear 3 is arranged on the traction gear output shaft 2; this gear is designed as a final drive gear and transmits the drive power to the axle differential 18. The traction gear output shaft 18 is rotatably mounted in the traction gear housing device 13, 14 via a fixed-loose bearing. The fixed bearing device 8 of the traction gear output shaft 2 is accommodated in the traction gear cover 14 and has a traction gear output shaft radial bearing 8a and a traction gear output shaft axial bearing 8b.The traction gear output shaft axial bearing 8b is radially exposed from the traction gear cover 14, so that it does not transmit any radial forces between the traction gear output shaft 2 and the traction gear cover. Furthermore, the traction gear output shaft axial bearing 8b is designed as a four-point bearing and has a common outer ring with the traction gear output shaft radial bearing 8a, which is designed as a cylindrical roller bearing. The traction gear output shaft floating bearing 11 is accommodated in the traction gear housing and is designed as a cylindrical roller bearing. When the motor vehicle is driven in the forward direction 5, the helical gearing creates favorable force ratios on the traction gear shaft 1, 2, 4, enabling efficient operation of the motor vehicle drive system.

[0055] Figure 3 shows a further longitudinal section of the motor vehicle drive system, this longitudinal section being a section along section plane B (see Figure 1). The motor vehicle drive system is connected to the motor vehicle structure (not shown) via the assembly mounts 17 and is configured to drive a motor vehicle in the forward direction 5 and in the opposite direction (reverse). The electric drive motor 15 outputs power via the traction transmission intermediate shaft 4, which, with respect to the power transmission from the electric drive motor 15, is arranged between the traction transmission input shaft 1 and the traction transmission output shaft 2.For transferring the drive power by means of the traction gear intermediate shaft 4, the latter has the first traction gear intermediate gear 6 and the second traction gear intermediate gear 20, wherein the first traction gear intermediate gear 6 is in engagement with the traction gear drive gear 19 and the second traction gear intermediate gear 20 is in engagement with the traction gear output gear 3 for power transmission.

[0056] The traction transmission intermediate shaft is also mounted with a fixed-loose bearing in the traction transmission housing assembly 13, 14, as are the traction transmission input shaft 1 and the traction transmission output shaft 2. The fixed bearing for both traction transmission intermediate shafts 4 is also arranged in the traction transmission cover 14. The traction transmission intermediate shaft fixed bearing 9, like the traction transmission intermediate shaft loose bearing 12, is designed as a deep groove ball bearing. The traction transmission intermediate shaft fixed bearing is designed to absorb axial forces on the traction transmission intermediate shaft 4 and is fixed in the traction transmission cover 14 for this purpose. The traction transmission intermediate shaft loose bearing 12 is accommodated in the traction transmission housing 13 for axial movement.

[0057] Figure 4 shows a highly schematic plan view of a motor vehicle with the proposed motor vehicle drive system 24. The driven front axle 22 can be supplied with drive power via the motor vehicle drive system 24, so that the motor vehicle can be driven in the forward direction 5 or opposite to this direction, i.e., backward. Furthermore, the motor vehicle has a non-driven rear axle 22, so that the motor vehicle shown is designed as a front-wheel drive vehicle.

[0058] Figure 5a shows a schematic plan view of a first embodiment of the motor vehicle drive system. A motor vehicle is driven by the electric drive motor 15, of which only the rotor, or rather the rotor shaft, is shown here. The electric drive motor 15 has a rotor shaft bearing 26, which is designed as a floating bearing. Furthermore, a parking lock gear 25 is arranged on the traction transmission drive shaft 1, in particular to enable mechanical locking of the motor vehicle drive system. The traction transmission drive shaft 1 is connected in a rotationally fixed manner to the rotor shaft of the electric drive motor 15 by a shaft-hub connection, and the traction transmission drive shaft floating bearing, which is arranged on the rotor shaft of the electric drive motor, is thus used as the floating bearing for the traction transmission drive shaft support.

[0059] In the view shown, the direction of rotation for the traction gear drive gear 19 and thus of the traction gear drive shaft 1 in the planned forward direction 5 is in the direction of arrow 28, whereby the helix angle of this traction gear drive gear 19 is selected such that the resulting axial force is in the direction of arrow 27 and is thus directed against the traction gear drive shaft fixed bearing 7. To transmit drive power, the traction gear drive gear 19 meshes with the first traction gear intermediate gear 6, where the direction of rotation is in the direction of arrow 30 and an axial force in the direction of arrow 29; the traction gear intermediate shaft 4 thus has the same direction of rotation (direction of arrow 30).The helix angle of the second traction gear intermediate gear 20 is selected such that the axial force resulting from the second traction gear intermediate gear 20 during power transmission for the planned forward direction 5 is in the direction of arrow 31 and thus counteracts the axial force on the first traction gear intermediate gear (arrow direction 29), so that these axial forces on the traction gear intermediate shaft 4 are at least partially canceled out. The traction gear intermediate shaft 4 is rotatably mounted by means of the traction gear intermediate shaft fixed bearing 9 and the traction gear intermediate shaft floating bearing 12.

[0060] The second traction gear intermediate shaft gear 20 meshes with the traction gear output gear 3 on the traction gear output shaft 2 for power transmission, whereby to provide drive power for the planned forward direction 5, a direction of rotation of the traction gear output shaft is set in the direction of arrow 34 and an axial force results in the direction of arrow 33. The traction gear output shaft 2 is mounted by means of the traction gear output shaft fixed bearing device 8, which has the traction gear output shaft radial bearing 8a and the traction gear output shaft axial bearing 8b, and the traction gear output shaft floating bearing 11.

[0061] Figure 6a shows a schematic plan view of a second embodiment of the motor vehicle drive system. In contrast to the first embodiment (Figures 5a and 5b), in which the electric drive motor 15 is arranged at the front in the planned forward direction of travel 5, in the second embodiment it is arranged at the rear. The drive of a motor vehicle is still provided by the electric drive motor 15, of which only the rotor, or rather the rotor shaft, is shown here.

[0062] The following essentially focuses on the differences between the first (Figures 5a / 5b) and the second embodiment (Figures 6a / 6b) of the proposed motor vehicle drive system. The traction transmission intermediate shaft 4, which in the first embodiment represents the uppermost transmission shaft relative to its rotational axis, represents the lowermost transmission shaft in the second embodiment relative to the planned installation position, particularly relative to a flat road surface.

[0063] Furthermore, a grounding ring 35 and a radial shaft seal 36 are arranged on the traction gear intermediate shaft 4; these can also be used in the first embodiment. As explained, the helix angles of the gears are selected such that the axial force during drive in the planned forward direction is directed against the traction gear drive shaft fixed bearing 8 and that the axial forces on the traction gear intermediate shaft 4 at least partially cancel each other out in this drive mode, i.e., have opposite directions. Figures 7a and 7b show a variation of the second embodiment of the motor vehicle drive system shown in Figures 6a and 6b.In this variation, the traction gear intermediate shaft 4 is not the lowest-positioned gear shaft of the traction gear device; rather, it is arranged above the traction gear input shaft 1 and above the traction gear output shaft 2, and the traction gear input shaft is arranged above the traction gear output shaft 2 but below the traction gear intermediate shaft 4. Otherwise, reference is made essentially to the explanations of the second embodiment of the motor vehicle drive system shown in Figures 6a and 6b.

[0064] List of reference symbols

Claims

Claims 1. A motor vehicle drive system (24) comprising an electromechanical energy converter as the electric drive machine (15) and comprising a traction transmission device for transmitting drive power to a motor vehicle axle drive, wherein the traction transmission device comprises a traction transmission housing device and wherein a traction transmission input shaft (1) is rotatably mounted therein, which is connected in a rotationally fixed manner to the electric drive machine (15) or can be selectively connected in a rotationally fixed manner to the electric drive machine (15), and comprising a traction transmission intermediate shaft (4) which is rotatably mounted in the traction transmission housing device and which is arranged axially parallel and radially spaced from the traction transmission input shaft (1), and comprising a traction transmission output shaft (2) which is rotatably mounted in the traction transmission housing device and which is arranged axially parallel and radially spaced from the two other traction transmission shafts (1, 4),wherein a traction gear drive gear (19) is arranged on the traction gear drive shaft (1), which is in engagement with a first traction gear intermediate gear (6) which is arranged on the traction gear intermediate shaft (4), and wherein a second traction gear intermediate gear (20) is arranged on the traction gear intermediate shaft (4), which is in engagement with a traction gear output gear (3) which is arranged on the traction gear output shaft (2), and wherein the traction gear housing device has a traction gear housing (13) and a traction gear cover (14), characterized in that the three traction gear shafts (1, 2,4) are each mounted with a fixed-loose bearing in the traction gear housing device and that such a bearing has at least one fixed bearing for absorbing axial forces and that at least two of these fixed bearings are arranged in the traction gear cover (14).

2. Motor vehicle drive system according to claim 1, characterized in that all fixed bearings of the traction gear shafts (1, 2, 4) are arranged in this traction gear cover (14).

3. Motor vehicle drive system according to one of the preceding claims, characterized in that the traction transmission drive gear (19) and the first traction transmission intermediate gear (6) form a first traction transmission gear stage and that the profile overlap of this first traction transmission gear stage is greater than 1.70 and less than 1.90 and that the step overlap of the first traction transmission gear stage is greater than 3.10 and less than 3.

30.

4. Motor vehicle drive system according to one of the preceding claims, characterized in that the second traction transmission intermediate gear (20) and the traction transmission output gear (3) form a second traction transmission gear stage and that the profile overlap of this second traction transmission gear stage is greater than 1.40 and less than 1.60 and that the step overlap of the second traction transmission gear stage is greater than 2.40 and less than 2.

60.

5. Motor vehicle drive system according to one of the preceding claims, characterized in that the first traction gear intermediate gear (6) has a first helical toothing with a first helix angle and the second traction gear intermediate gear (20) has a second helical toothing with a second helix angle and that the first and the second helix angle are directed in the same direction, so that axial forces occurring at the two traction gear intermediate gears (6, 20) during power transmission at least partially cancel each other out.

6. Motor vehicle drive system according to one of the preceding claims, characterized in that the traction gear drive shaft (1) is mounted by means of a fixed-loose bearing with a fixed bearing for absorbing axial forces and a loose bearing in the traction gear housing device, that both the fixed bearing and the loose bearing of this bearing are designed as deep groove ball bearings, that this fixed bearing is arranged in the traction gear cover (14) and that the An electric drive motor (15) is arranged on or in the traction gear housing (13). Motor vehicle drive system according to one of the preceding claims, characterized in that the traction gear intermediate shaft (4) is mounted in the traction gear housing device by means of a fixed-loose bearing arrangement with a fixed bearing for absorbing axial forces and a loose bearing, that both this fixed bearing and this loose bearing are designed as deep groove ball bearings, and that this fixed bearing is arranged in the traction gear cover (14).Motor vehicle drive system according to one of the preceding claims, characterized in that the traction transmission output shaft (2) is mounted in the traction transmission housing device by means of a fixed-loose bearing with a fixed bearing for absorbing axial forces and a loose bearing, in that the bearing of the traction transmission output shaft (2) has a first and a second cylindrical roller bearing, wherein these cylindrical roller bearings are arranged in an axial direction on different sides of the traction transmission output gear (3), and in that this fixed bearing is designed as a deep groove ball bearing or as a four-point bearing and is arranged in the traction transmission cover (14). Motor vehicle with at least one motor vehicle drive system (24) according to one of the preceding claims and with a forward travel direction (5) in which the motor vehicle can be driven by this motor vehicle drive system (24).Motor vehicle according to claim 9, characterized in that, with respect to this forward direction of travel (5) in the plane and with the planned installation position of the motor vehicle drive system, the traction transmission input shaft (1) is arranged in front of the traction transmission intermediate shaft (4), and that the traction transmission output shaft (2) is arranged behind the traction transmission intermediate shaft (4). Motor vehicle according to claim 9 or 10, characterized in that, with respect to this forward direction of travel (5) in the plane and with the planned installation position of the motor vehicle drive system (24), the traction transmission intermediate shaft (4) is arranged higher than the traction transmission input shaft (1). that the traction transmission output shaft (2) is arranged lower than the traction transmission input shaft (1). Motor vehicle according to claim 9, characterized in that, with respect to this forward direction of travel (5) in the plane and with the planned installation position of the motor vehicle drive system, the traction transmission input shaft (1) is arranged behind the traction transmission intermediate shaft (4) and that the traction transmission output shaft (2) is arranged in front of the traction transmission intermediate shaft (4). Motor vehicle according to claim 9 or 12, characterized in that, with respect to this forward direction of travel (5) in the plane and with the planned installation position of the motor vehicle drive system (24), the traction transmission intermediate shaft (4) is arranged lower than the traction transmission output shaft (2) and that the traction transmission input shaft (1) is arranged higher than the traction transmission output shaft (2).Motor vehicle according to claim 9 or 12, characterized in that, with respect to this forward direction of travel (5) in the plane and in the planned installation position of the motor vehicle drive system (24), the traction transmission intermediate shaft (4) is arranged higher than the traction transmission output shaft (2), and that the traction transmission input shaft (1) is arranged higher than the traction transmission output shaft (2). Motor vehicle according to one of claims 9 to 14, characterized in that the traction transmission output gear (3) has helical output teeth with an output helix angle such that this output helix angle is selected such that axial forces of the traction transmission output gear (3) when driving the motor vehicle in the forward direction of travel (5) are directed in the axial direction of the traction transmission output shaft (2) from the traction transmission cover (14) to the traction transmission housing (13).

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