Roller-bearing-mounted motor vehicle drive unit

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 device housing; a 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 two other 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; these bearings each have a fixed bearing for absorbing axial forces and at least one floating bearing designed exclusively to absorb radial forces; said three fixed bearings are mounted in the traction transmission cover (14); and at least three of said floating bearings are mounted in the traction transmission housing.

Description

[0001] Rolling bearing motor vehicle drive device

[0002] The invention relates to a roller-bearing 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 102019 127 242 A1 discloses an electric drive device for a motor vehicle according to the preamble of claim 1, including a transmission.

[0003] A general requirement for a motor vehicle drive is that it has a long service life and is highly efficient. 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 what is known as an involute toothing. Although such a toothing is less sensitive to deviations from the planned center distance (so-called center distance errors), a rigid (low load-dependent displacement) and efficient bearing is also advantageous here. A particularly rigid bearing for transmission shafts can be achieved with what is known as an adjusted bearing, but such a bearing exhibits a significant degree of loss, particularly compared to a non-adjusted bearing.

[0004] The invention proposes a roller-bearing motor vehicle drive system that simultaneously enables the transmission of drive power with high efficiency and low displacement of the transmission shafts. This object is achieved by an object according to claim 1, with preferred developments of the invention being the subject of the dependent claims. In particular, the invention proposes considering the bearings of the transmission shafts as a whole in order to be able to provide a particularly low-displacement and efficient motor vehicle drive system.

[0005] In the sense of the invention, a motor vehicle drive system is to be understood as a system for driving a motor vehicle, preferably a passenger car, wherein the drive power is used to overcome driving resistances such as friction, rolling,

[0006] 17.08.2022 the air and the so-called acceleration resistance is provided by an 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.

[0007] The motor vehicle drive system further comprises a traction transmission device, wherein this transmission device is configured to transmit and adapt drive power to a load requirement of the motor vehicle, which results in particular from the driving resistances. 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 in particular to mean a motor vehicle drive axle, in particular a front or rear axle. 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 configured to accommodate the electric drive motor.A traction gear drive shaft is rotatably mounted in this traction gear housing, whereby this traction gear drive shaft can be regarded as the first gear shaft or also as the input shaft into the traction gear device with regard to power transmission from the electric drive motor to the motor vehicle axle drive, 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 is arranged downstream of the traction gear drive shaft with respect to the motor drive direction, preferably directly downstream of the latter. 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. Furthermore, the traction gear device has

[0010] 17.08.2022 also has a traction transmission output shaft, which is arranged downstream of the traction transmission intermediate shaft with respect to the motor drive direction, preferably directly downstream of it. Furthermore, the traction transmission output shaft is rotatably mounted in the traction transmission housing device and is preferably arranged axially parallel and radially spaced from the other two traction transmission shafts.

[0011] 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.

[0012] 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 roller bearings for rotatably supporting 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 or assembly.

[0013] In particular, to achieve sufficient rigidity of the bearings of the transmission shafts (traction gear input shaft, traction gear output shaft, traction gear intermediate

[0014] 17.08.2022 (shaft), these three traction gear shafts are each supported in the traction gear housing device with a so-called fixed-loose bearing arrangement. For the purposes of the invention, a fixed-loose bearing arrangement is understood in particular to mean a bearing arrangement which 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, axial and radial being understood in each case 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 point can also have several rolling bearings; in particular, the fixed bearing can have a radial and an axial bearing.

[0015] The term "fixed-loose bearing" as such is known from the prior art. It is therefore further proposed that such a fixed-loose bearing each comprise at least one fixed bearing for absorbing axial forces, and that this fixed bearing be 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.

[0016] In a preferred embodiment of the invention, the traction transmission drive gear and the first traction transmission intermediate gear engage with each other to transmit drive power and thus form a first traction transmission gear stage.

[0017] In a preferred embodiment of the invention, the second traction transmission intermediate gear and the traction transmission output gear engage with each other to transmit drive power and thus form a second traction transmission gear stage.

[0018] In a preferred embodiment, at least two gears of the first and second traction gear stage are designed as helical spur gears, which preferably have so-called involute toothing.

[0019] The traction gear drive shaft is mounted in the traction gear housing device by means of a fixed-loose bearing, i.e. a bearing which has a fixed bearing at least 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 drive shaft, and further preferably, this bearing is designed as a so-called four-

[0020] 17.08.2022 point bearing and 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 floating bearing of this fixed-floating bearing of the traction gear drive shaft. This floating bearing is preferably designed as a cylindrical roller bearing and preferably as a deep groove ball bearing. In a preferred embodiment, both the fixed bearing and the floating bearing of the traction gear drive shaft are designed as deep groove ball bearings. Particularly in an embodiment with such rolling bearings, high efficiency in power transmission can be achieved. Preferably, the fixed bearing of the traction gear drive shaft bearing is arranged in the traction gear cover and, in particular, is fixed therein. Further preferably, the traction gear housing is designed such that the electric drive motor is arranged on it or in it.In particular, with such a design, easy assembly of the motor vehicle drive system and high efficiency in transmitting drive power can be achieved.

[0021] The traction gear intermediate shaft is mounted in the traction gear housing by means of a fixed-loose bearing, i.e. with a bearing having 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 and 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. 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 intermediate shaft are designed as deep groove ball bearings.Particularly in a design with such rolling bearings, high power transmission efficiency can be achieved. Preferably, the fixed bearing for the traction transmission intermediate shaft is located in the traction transmission cover.

[0022] The traction transmission output shaft is mounted in the traction transmission 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 point, and at least one loose bearing. The fixed-loose bearing for supporting the traction transmission output shaft preferably comprises more than two 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.

[0023] 17.08.2022, in addition to two cylindrical roller bearings, the fixed-floating bearing of the traction transmission output shaft also has a rolling bearing designed as a fixed bearing, preferably a rolling bearing with 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 free 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 arrangement 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, of the traction transmission output shaft bearing arrangement is arranged in the traction transmission cover. In particular, such a configuration enables efficient and rigid mounting of the traction transmission output shaft.

[0024] Individual features and embodiments of the invention are explained in more detail below with reference to the figures, in which:

[0025] Fig.1 : a schematic cross-sectional view of the proposed motor vehicle drive system orthogonal to the traction gear drive shaft,

[0026] Fig.2: a first longitudinal section of the proposed motor vehicle drive system parallel to the traction transmission drive shaft,

[0027] Fig.3: a second longitudinal section of the proposed motor vehicle drive system parallel to the traction transmission intermediate shaft,

[0028] Figure 1 shows a cross-section through a motor vehicle drive system, i.e. a section orthogonal to the traction gear drive axle 1 at the level of the traction gear wheel set. The electromechanical energy converter in such a motor vehicle drive system is designed 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 axle 2 and the traction gear output gear 3. The traction gear drive shaft 1 and the traction gear output shaft 2 of the

[0029] 17.08.2022 The traction gear device is rotatably mounted in the traction gear housing assembly (not shown). The traction gear drive shaft 1 is connected to the electric drive motor via a shaft-hub connection.

[0030] 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 gearwheel is arranged on the traction gear drive shaft 1 and meshes with a first traction gear intermediate gearwheel 6. The traction gear drive gearwheel is not visible in the sectional view shown, as it is located behind the traction gear drive shaft fixed bearing 7.Furthermore, a second traction gear intermediate gear 8 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.

[0031] The three illustrated traction transmission shafts (traction transmission input shaft 1, traction transmission intermediate shaft 4, traction transmission output shaft 2) are each mounted in the traction transmission housing assembly with a fixed-loose bearing. A bearing of this type 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 assembly.

[0032] 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.

[0033] The output shaft of the electric drive motor 15 is directly connected 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 device 13, 14. The traction gear drive shaft fixed bearing 7 is arranged in the traction gear cover 14 and absorbs axial forces occurring on the traction gear drive shaft 1. Furthermore,

[0034] 17.08.2022 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, with a traction gear drive shaft centering seat 21 achieving centering of 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, thus achieving improved efficiency compared to independent support of both shafts with two roller bearings each.

[0035] 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.

[0036] 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.

[0037] August 17, 2022 Figure 3 shows a further longitudinal section of the motor vehicle drive system, with this longitudinal section representing 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 designed to drive a motor vehicle in the forward direction 5 and in the opposite direction (reverse). The electric drive motor 15 transmits 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.

[0038] 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.

[0039] 17.08.2022 List of reference symbols

[0040] 17.08.2022

Claims

Claims Motor vehicle drive system (24) with an electromechanical energy converter as an electric drive machine (15) and with a traction gear device for transmitting drive power to a motor vehicle axle drive, wherein the traction gear device has a traction gear housing device and wherein a traction gear drive 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 latter, and with a traction gear intermediate shaft (4) which is rotatably mounted in the traction gear housing device and which is arranged axially parallel and radially spaced from the traction gear drive shaft (1), and with a traction gear output shaft (2) which is rotatably mounted in the traction gear housing device and which is arranged axially parallel and radially spaced from the two other traction gear shafts (1, 4),wherein a traction gear drive gear (19) is arranged on the traction gear drive shaft (1), which engages with a first traction gear intermediate gear (6) 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 engages with a traction gear output gear (3) 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 these bearings each have a fixed bearing for absorbing axial forces and at least one loose bearing,which are designed exclusively to absorb radial forces, and in that these three fixed bearings are arranged in the traction gear cover (14), and in that at least three of these floating bearings are arranged in the traction gear housing. A motor vehicle drive system according to claim 1, characterized in that at least one of the floating bearings of the traction gear intermediate shaft, the traction gear output shaft, and the traction gear input shaft are designed as cylindrical roller bearings, or all of these floating bearings are designed as cylindrical roller bearings. 17.08.2022 Motor vehicle drive system according to one of the preceding claims, characterized in that, in the bearing of the traction transmission input shaft (1), both the fixed bearing and the floating bearing of this bearing are designed as deep groove ball bearings. Motor vehicle drive system according to one of the preceding claims, characterized in that, in the bearing of the traction transmission intermediate shaft (4), both the fixed bearing and the floating bearing of this bearing are designed as deep groove ball bearings. Motor vehicle drive system according to one of the preceding claims, characterized 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 on different sides of the traction transmission output gear (3) in an axial direction of the traction transmission output shaft (2), and in that the fixed bearing of this bearing is designed as a deep groove ball bearing or as a four-point contact bearing. 17.08.2022

Images