Vehicle axle for a two-track vehicle

Abstract

The invention relates to a vehicle axle for a two-track vehicle, comprising an axle differential (9), the input side (8) of which is drivingly connected to an electric motor (EM), and the two output sides of which drive output shafts (27), each leading to a vehicle wheel (HL, HR), wherein each output shaft (27) is assigned a superposition gear (11), by means of which the electric motor (EM) can be directly connected to the respective output shaft (27), bypassing the axle differential (9). According to the invention, the vehicle axle comprises a total of three multi-disk brakes (33, 57), namely a central multi-disk brake (57), which acts, for example, as a vehicle brake, and two auxiliary multi-disk brakes (33), each of which is installed in one of the superposition gears (11).

Description

The invention relates to a vehicle axle for a two-track vehicle according to the preamble of claim 1.To increase the efficiency and the range, braking operations of an electrified vehicle are carried out by an electric drive in generator operation (referred to below as recuperation mode), provided that certain boundary conditions are fulfilled.A drive device of the generic type for a vehicle axle has an axle differential, by means of which a 50 / 50 distribution can be carried out. Its input side is drivingly connected to an electric machine, while its output sides drive off on output shafts which are guided to the two vehicle wheels.In the above related art, different braking torques cannot be set at the vehicle wheels during the recuperation mode. Thus, brake torque redistribution is not available during the recuperation mode. For safety reasons, the recuperation range is restricted. If this range is left, recuperation is deactivated and the conventional vehicle brake system is taken over. In this case, in the prior art, driving dynamics control is carried out by means of the conventional vehicle brake system, in which a control unit actuates the vehicle wheel brakes of the vehicle wheels in a targeted manner with different braking torques in order to influence the driving behavior.During the execution of the brake torque redistribution, therefore, no recuperation takes place. Accordingly, the recuperation power and thus the consumption or the e-range is limited due to driving safety aspects.Sports vehicles in particular usually have a torque vectoring system on the rear axle of the vehicle. This directs drive torque past the differential directly to the vehicle wheels. As a result, the drive torques can be distributed freely on the respective vehicle axle. In addition to the usual drive with differential, such a torque vectoring system also has two superimposed gears, two force-lockingly regulated clutches, two actuators, a control unit and usually its own hydraulic system.AT 520430 A4 discloses a vehicle having an electric drive and a brake system, which is designed as a multi-disk brake system having at least one brake disk pack having a plurality of brake disks arranged one behind the other in an axial direction. From DE 10 2018 112 880 A1 an electric vehicle drive system is known, which has an electric motor, first and second planetary gear sets including sun gear, planet carrier and ring gear elements, first and second output shafts and a housing. The elements of the first planetary gear set are connected to the electric motor, the first output shaft and an element of the second planetary gear set. The elements of the second planetary gear are connected to the first planetary gear, the housing, and the second output shaft. The first planetary gear provides a differential reduction device and the second planetary gear provides a reversal and reduction device. Optional clutches may provide the function of a limited slip differential and distribute torque preferentially to an output shaft or the other.The object of the invention is to provide a drive device for a vehicle axle of a two-lane vehicle, in which the recuperation power during the driving operation is increased in comparison to the prior art and / or the drive device is designed to be space-saving.The object is achieved by the features of claim 1. Preferred developments of the invention are disclosed in the dependent claims.The invention relates to a vehicle axle for a two-track vehicle, which axle axle has an axle differential. Its input side is drivingly connected to an electric machine, while its two output sides drive off on output shafts, which each lead to a vehicle wheel. Each output shaft is assigned a superposition gear, by means of which the electric machine can be directly connected to the respective output shaft, bypassing the axle differential. The two superposition gears arranged on each vehicle side can be controlled by a control unit in order to carry out a torque redistribution during driving operation. By way of example, a brake torque redistribution during a recuperation mode of the electric machine or a drive torque redistribution during a normal driving mode, that is to say a driving dynamics control, can be carried out. According to the characterizing part of claim 1, the vehicle axle has a total of three multi-disk brakes, namely a central multi-disk brake acting as a vehicle brake, for example, and two further auxiliary multi-disk brakes, each auxiliary multi-disk brake of which is installed in one of the superposition transmissions. The two disk brakes installed in the superposition transmissions can be controlled by the control unit for torque redistribution.According to the invention, not only a drive torque redistribution but additionally a brake torque redistribution between the two vehicle wheels of the vehicle axle can be carried out during the recuperation operating mode. In the event of the brake torque redistribution, a brake torque load path running between the vehicle wheel and the electric machine can be divided by actuating the respective multi-disk brake, to be precise into a differential brake torque path which leads a differential brake torque from the vehicle wheel via the axle differential to the electric machine, and into a superposition brake torque path which leads a superposition brake torque from the vehicle wheel past the axle differential via the superposition transmission to the electric machine. In this way, in the recuperation operating mode, the vehicle wheels can be subjected to braking torques of different magnitudes, so that the vehicle wheels can brake to different extents.In an embodiment of the vehicle axle without conventional vehicle wheel disc brakes, it is necessary that the braking function is ensured even when the battery is fully charged, in which no recuperation is available. The vehicle axle according to the invention is developed in accordance with these requirements. With the aid of the central multi-disk brake, vehicle braking can be carried out uniformly on both vehicle sides. Alternatively and / or additionally, vehicle braking can likewise be carried out with the two auxiliary multi-disk brakes. If, therefore, the electric machine is not capable of recuperation or is only partially capable of recuperation, then the central multi-disk brake and / or the secondary multi-disk brakes installed in the superposition gearing can take the braking task. The multi-disk brakes may provide vehicle braking, for example, depending on the current recuperation capability.Preferably, in the case of uniform braking on both vehicle sides, for safety reasons, the braking engagement can be adopted primarily by the central multi-disk brake. In contrast, in the case of uneven braking on both vehicle sides, it is preferred if the auxiliary multi-disk brakes primarily take over the braking intervention.In a technical realization, each of the disk brakes consists of an inner disk carrier, an outer disk carrier and an intermediate disk pack. The electric machine can be connected with its rotor shaft indirectly or directly in a driving manner to the input side of the axle differential. According to a first embodiment variant, the central disk brake can act directly on the rotor shaft. In this case, the inner plate carrier can be connected to the rotor shaft in a rotationally fixed manner, while the outer plate carrier is connected to a transmission housing wall in a rotationally fixed manner.In one technical implementation, the differential housing has, on both sides, a hub section, as viewed in a vehicle transverse direction, through which one of the output shafts is guided to the vehicle wheel in each case. Each of the hub sections of the differential housing is drivingly connected to the output shaft by means of the superposition gearing.The superposition gear can have a transmission stage which is designed in the manner of a planetary gear of axially short construction. The planetary gear can have a rotatable planetary gear carrier which can be braked with the aid of the assigned auxiliary multi-disk brake.In a specific embodiment variant, the rotatable planet carrier of the superposition transmission is connected to the inner plate carrier of the auxiliary plate brake in a rotationally fixed manner, while the outer plate carrier is connected to a transmission housing in a rotationally fixed manner.The superposition gear can have, for example, the following components, namely a sun gear which is on the outside of the vehicle in the transverse direction of the vehicle and is seated in a rotationally fixed manner on one of the output shafts, and a sun gear which is on the inside of the vehicle and is seated in a rotationally fixed manner on one of the hub sections of the differential housing. In addition, a support shaft is provided on which a planetary gear, which meshes with the sun gear on the vehicle interior, and a planetary gear, which meshes with the sun gear on the vehicle exterior, are seated in a rotationally fixed manner. In a structurally simple embodiment, the support shaft can be a hollow shaft which is rotatably mounted on the planet wheel carrier.In a first variant embodiment, the rotor shaft of the electric machine can be connected to an intermediate shaft via a countershaft stage. The intermediate shaft can be oriented axially parallel to the rotor shaft. With regard to a transmission housing of axially short construction, the intermediate shaft can extend on one side from the countershaft stage in the opposite direction to the rotor shaft back in the direction of the electric machine end side. The electric machine can be installed in the transverse installation in the vehicle axle, so that the rotor shaft of the electric machine is oriented axially parallel to the output shafts. With regard to space-saving positioning, it is advantageous if an installation space can be provided between the electric machine front side, the countershaft stage and the intermediate shaft and the rotor shaft, in which installation space the multi-disk brake can be positioned in a manner favorable for installation space. The countershaft stage can preferably be realized as an axially short countershaft spur gear stage which is constructed from a fixed gearwheel arranged on the rotor shaft and an input gearwheel which meshes therewith and is connected to the differential housing of the axle differential in a rotationally fixed manner.In a second embodiment variant, the central multi-disk brake can act directly on the differential housing of the axle differential. In this case, the inner disk carrier can be connected to the differential housing in a rotationally fixed manner, while the outer disk carrier is connected to a transmission housing wall in a rotationally fixed manner.By providing the central disk brake and the secondary disk brakes, it is possible to dispense with the use of conventional vehicle wheel disk brakes which are each formed from a brake disk positioned on the vehicle wheel drive shaft and having a brake caliper interacting therewith. This makes it possible to avoid brake abrasion which is otherwise emitted into the environment in conventional vehicle brakes.Exemplary embodiments of the invention are described below with reference to the attached figures.The following are shown: FIGS. 1 to 3 show different representations of a vehicle axle with integrated multi-disk brakes.FIG. 1 shows a block diagram of an electrified vehicle axle, in particular rear axle, having a drive unit 1 consisting of an electric machine EM and a transmission 3, via which the electric machine EM drives off onto the rear wheels HR, HL. The electric machine EM is connected to a high-voltage battery 2. As further shown in FIG. 1, conventional vehicle wheel disc brakes are omitted from the vehicle axle. Instead of such conventional vehicle wheel brakes, the vehicle axle in FIG. 2 or 3 has a central multi-disk brake 57 and secondary multi-disk brakes 33. The central disk brake 57 brings about a vehicle braking as an alternative or in addition to the secondary disk brakes 33.The electric machine EM is connected via its rotor shaft 5 with the interposition of a countershaft stage 7 to an input side 8 of an axle differential 9. Its output sides are in driving connection with the vehicle rear wheels HR, HL via output shafts 27 (FIG. 2 ). In FIG. 1, the electric machine EM is installed in the vehicle axle in transverse installation. Accordingly, in FIG. 2 or 3, the rotor shaft 5 and the output shafts 27 are axis-parallel to each other, which lead from the output sides of the axle differential 3 to the vehicle rear wheels HL, HR. Likewise, the auxiliary disk brakes 33 installed in the vehicle axle and the central disk brake 57 are oriented axially parallel to one another in the vehicle transverse direction y, as can be seen from FIG. 2.The vehicle axle has, as viewed in the vehicle transverse direction y, on each vehicle side, a superposition transmission 11 by means of which the electric machine EM can be connected directly to one of the output shafts 27, bypassing the axle differential 9. With the aid of the two superposition transmissions 11, the electric machine EM can therefore drive directly away to the vehicle wheels HR, HL via the load paths L 1, L 2 indicated by dashed lines in FIG. 1, bypassing the axle differential 9.FIG. 2 shows a specific transmission structure of the transmission 3 of the vehicle axle. Consequently, the countershaft stage 7 consists of two spur gear stages 19, 20. The first spur gear stage 19 is constructed from a fixed gearwheel 15 arranged on the rotor shaft 5 and a fixed gearwheel 17 which meshes therewith and is arranged on the intermediate shaft 13. The intermediate shaft 13 is connected via a second spur gear stage 20 to the input side 8 (FIG. 1 ) of the axle differential 9. The second spur gear stage 20 is constructed from a fixed gearwheel 21 arranged on the intermediate shaft 13 and an input-side axle differential gearwheel 23. The axle differential gearwheel 23 is connected to a rotating differential housing 25 in a rotationally fixed manner. According to FIG. 2, the axle differential 9 in the vehicle transverse direction y drives in a 50 / 50 distribution on both sides onto the two output shafts 27 leading to the vehicle wheels HL, HR.The two superposition gears 11 are embodied in mirror images with respect to a vehicle central longitudinal plane which passes through the axle differential 9. Thus, each of the two superposition gears 11 has a transmission stage 28 which is designed in the manner of a planetary gear (but without an outer ring gear). The planetary gear has a sun wheel 47 on the outside of the vehicle, as viewed in the transverse direction y of the vehicle, which sun wheel is seated on the output shaft 27 in a rotationally fixed manner, and a sun wheel 29 on the inside of the vehicle. The sun wheel 29 on the inside of the vehicle is connected in a rotationally fixed manner to a hub section 30 of the differential housing 25, through which one of the output shafts 27 is guided to the vehicle wheel HR, HL in each case. The sun wheel 29 on the inside of the vehicle is in toothed engagement with a planetary wheel 41 on the inside of the vehicle, which is arranged on a support shaft 43 in a rotationally fixed manner. The support shaft 43 also has a planet wheel 45 on the outside of the vehicle, which meshes with the sun wheel 47 on the outside of the vehicle.As can be further seen from FIG. 2, the support shaft 43 is realized as a hollow shaft which is rotatably mounted on a planetary gear carrier 48. The planet carrier 48 is in turn mounted rotatably about the axis of the two output shafts 27. In addition, the rotatable planetary gear carrier 48 is connected in a rotationally fixed manner to an inner disk carrier 31 of the auxiliary disk brake 33. The inner disk carrier 31 interacts via a disk pack with an outer disk carrier 39 which is connected fixedly to the housing on a transmission housing wall 55. The disk set located between the outer disk carrier 39 and the inner disk carrier 31 can be pressurized via an annular piston, not shown, which can be adjusted by a horizontal stroke by means of a hydraulic cylinder in order to actuate the auxiliary disk brake 33 up to a predefined clutch degree. The auxiliary multi-disk brake can be power-shifted and controlled with slip by means of a control unit. The same applies to the central disk brake 57.One core of the invention consists in the geometry of the transmission 3 which is of axial short construction in the transverse direction y of the vehicle. Accordingly, the countershaft stage 7 is formed from the two spur gear stages 19, 20 of axial short construction. In FIG. 2, the intermediate shaft 13 extends in the transverse direction y of the vehicle on one side from the countershaft spur gear stage 19-counter to the rotor shaft 5-in the direction of the electric machine end side 51, specifically forming an installation space 53 which is axially delimited between the electric machine end side 51 and the countershaft spur gear stage 19 and is delimited in the radial direction between the intermediate shaft 13 and an outer transmission housing wall 55. The central disk brake 57 is positioned in the installation space 53, which is constructed from an inner disk carrier 59 and an outer disk carrier 61 with an interposed disk pack. The inner plate carrier 59 is arranged on the rotor shaft 5 in a rotationally fixed manner, while the outer plate carrier 61 is connected to the transmission housing wall 55 in a rotationally fixed manner.FIG. 3 shows a second exemplary embodiment of the invention. In contrast to FIG. 2, in FIG. 3, the central disk brake 57 acts directly on the differential housing 25 of the axle differential 9. the inner disk carrier 59 of the central disk brake 57 is connected in a rotationally fixed manner to the differential housing 25 in FIG. 3, while the outer disk carrier 61 is connected in a rotationally fixed manner to a transmission housing wall 55. Otherwise, the further transmission construction and the function achieved with the transmission 3 are identical as described with reference to FIGS. 1 and 2.LIST OF REFERENCE CHARACTERS:1 Drive assembly 3 Transmission 5 Rotor shaft 7 Countershaft stage 8 Input side 9 Axle differential 11 Superposition transmission 13 Intermediate shaft 15, 17 Fixed gearwheels 19, 20 Spur gear stage 21 Fixed gearwheel 23 Input gearwheel 25 Differential housing 27 Output shafts 29 Vehicle-interior sun wheel 30 Hub portion 30 Hub portion 31 Inner disk carrier 33 Secondary disk brake 39 Outer disk carrier 41 Vehicle-interior planetary gearwheel 43 Support shaft 45 Vehicle-exterior planetary gearwheel 47 Vehicle-exterior sun wheel 48 Planetary gearwheel carrier 51 Electric machine end face 53 Installation space 55 Transmission housing wall 57 Central disk brake 59 Inner disk carrier 61 Outer disk carrierReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedAT 520430 A4

[0007] DE 10 2018 112 880 A1

[0007]

Claims

Vehicle axle for a two-track vehicle, which has an axle differential (9), the input side (8) of which is drivingly connected to an electric machine (EM), and the two output sides of which are driven off on output shafts (27), which each lead to a vehicle wheel (HL, HR), wherein each output shaft (27) is assigned a superposition transmission (11), by means of which the electric machine (EM) can be connected directly to the respective output shaft (27), bridging the axle differential (9), wherein in particular the superposition transmissions (11) can be controlled by a control unit for torque redistribution, for example a braking torque redistribution during a recuperation mode of the electric machine or a driving torque redistribution during a normal driving mode, characterized in that the vehicle axle has a total of three disc brakes (33, 57), namely a central disc brake, For example, a multi-disk brake (57) acting as a vehicle brake and two auxiliary multi-disk brakes (33), of which each auxiliary multi-disk brake (33) is installed in one of the superposition gears (11) and can be controlled in particular by the control unit for torque redistribution.Vehicle axle according to Claim 1, characterized in that each of the disc brakes (33, 57) is formed from an inner disc carrier (31, 59), an outer disc carrier (39, 61) and an intermediate disc pack.Vehicle axle according to Claim 1 or 2, characterized in that the electric machine (EM) is connected by its rotor shaft (5) indirectly or directly in terms of drive to an input-side axle differential gearwheel (23) which is connected in a rotationally fixed manner to a rotating differential housing (25) of the axle differential (9), and in that the differential housing (25) has, on both sides in a vehicle transverse direction (y), a hub section (30) through which in each case one of the output shafts (27) is guided to the vehicle wheel (HR, HL), and in that each of the hub sections (30) of the differential housing (25) can be connected in terms of drive to the output shaft (27) by means of the superposition gearing (11).Vehicle axle according to one of the preceding claims, characterized in that the superposition gearing (11) has a transmission stage (28) which is designed in the manner of a planetary gearing which has a rotatable planet wheel carrier (48) which can be braked by means of the auxiliary multi-plate brake (33).Vehicle axle according to Claim 4, characterized in that the rotatable planet wheel carrier (48) of the superposition transmission (11) is connected to the inner disc carrier (31) of the auxiliary disc brake (33) in a rotationally fixed manner, and in that the outer disc carrier (39) is connected to a transmission housing (55) in a rotationally fixed manner.Vehicle axle according to Claim 5, characterized in that the planetary transmission of the superposition transmission (11) has the following components: - a sun wheel (47) which is on the outside of the vehicle in the transverse direction (y) of the vehicle and is seated in a rotationally fixed manner on one of the output shafts (27), and a sun wheel (29) which is on the inside of the vehicle and is seated in a rotationally fixed manner on one of the hub sections (30) of the differential housing (25), and - at least one support shaft (43) on which a planetary wheel (41) which meshes with the sun wheel (29) on the inside of the vehicle and a planetary wheel (45) which meshes with the sun wheel (47) on the outside of the vehicle are seated in a rotationally fixed manner, and in that the support shaft (43) is a hollow shaft which is mounted in a rotationally fixed manner on the planetary carrier (48).Vehicle axle according to one of Claims 3 to 6, characterized in that the central disc brake (57) acts directly on the differential housing (25) of the axle differential (9), and in that in particular the inner disc carrier (59) is connected to the differential housing (25) in a rotationally fixed manner, and the outer disc carrier (61) is connected to a transmission housing (55) in a rotationally fixed manner.Vehicle axle according to one of Claims 3 to 6, characterized in that the central disc brake (57) acts directly on the rotor shaft (5) of the electric machine (EM), and in that in particular the inner disc carrier (59) is connected to the rotor shaft (5) in a rotationally fixed manner, while the outer disc carrier (61) is connected to the transmission housing (55) in a rotationally fixed manner.

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