Electric axle drive for a motor vehicle

Abstract

Electric axle drive (1) for a motor vehicle, comprising a transmission arrangement with two gears, an electric machine (2) for driving at least one output shaft (28, 29) of the axle (30) of the motor vehicle, a first spur gear stage (4) driven by the electric machine (2) and a second spur gear stage (10) driven by the electric machine (2), and at least one planetary gear set (13, 15), characterized in that a gear (9) forming the output of the second spur gear stage (10) is part of an assembly (11) comprising this gear (9), a ring gear (12) of a first planetary gear set (13) and a planet carrier (14) of a second planetary gear set (15), wherein in one of the gears the torque flow to the at least one output shaft (28, 29) is via the first planetary gear set (13) and in the other of the gears the torque flow to the at least one output shaft (28, 29) is via both planetary gear sets (13, 15) is divided,wherein in first gear a freewheel (23) blocks a sun gear (16) of the first planetary gear set and a ring gear (21) of the second planetary gear set (15) and a brake (24) for locking a sun gear (20) of the second planetary gear set (15) is open, or wherein in second gear a freewheel (23) releases the sun gear (16) of the first planetary gear set (13) and a ring gear (21) of the second planetary gear set (15) and a brake (24) for locking the sun gear (20) of the second planetary gear set (15) is closed, wherein the freewheel (23) can be combined with a clutch for recuperation.

Description

[0001] The invention relates to an electric axle drive for a motor vehicle, said axle drive comprising a transmission arrangement with two gears, an electric machine for driving at least one output shaft of the axle of the motor vehicle, a first spur gear stage drivable by means of the electric machine and a second spur gear stage drivable via said first spur gear stage, and at least one planetary gear.

[0002] Such an axle drive for a motor vehicle is known from DE 10 2013 102 161 A1. This axle drive uses a single planetary gear. A first spur gear stage is provided on the electric machine side of the axle drive, with an intermediate shaft serving as the output of this spur gear stage being connected to a planet carrier of the planetary gear. A ring gear of the planetary gear is connected to a spur gear of the second spur gear stage, the other spur gear of which serves, via a differential gear, to drive two output shafts of the motor vehicle's axle. Each output shaft is assigned a gear of this axle. Shifting means are assigned to the planetary gear, which enable shifting under load and ensure that, particularly in a first gear of the motor vehicle, which is a primary gear, the planetary gear is shifted as a block, thus rotating as a block and not in the power flow.In the second gear, which is therefore the secondary gear, the gear ratio is shifted in the planetary gear.

[0003] DE 11 2006 000 969 T5 discloses an electric axle drive for a motor vehicle, comprising a transmission arrangement having gears, an electric motor for driving an output shaft of the motor vehicle's axle, and a first and a second planetary gear set. The electric motor drives an assembly consisting of a ring gear of the first planetary gear set and a planet carrier of the second planetary gear set. In one gear, the torque flow to the output shaft is via the first planetary gear set. In the other gear, the torque flow to the output shaft is divided between both planetary gear sets.

[0004] The object of the present invention is to create an electric axle drive for a motor vehicle that is compact, particularly in the output area of ​​the transmission assembly. It should be possible to transmit a relatively high torque to the output area of ​​the transmission assembly with a relatively small design of gears.

[0005] The object is achieved by an electric axle drive which is designed according to the features of patent claim 1 and by an electric axle drive which is designed according to the features of patent claim 3.

[0006] The electric axle drive has a gear arrangement with two gears. An electric motor drives at least one output shaft of the motor vehicle's axle. A first spur gear stage can be driven by the electric motor, and via this, a second spur gear stage. The electric axle drive also features two planetary gears. A gear forming the output of the second spur gear stage is part of an assembly comprising this gear, a ring gear of a first planetary gear of the planetary gears, and a planet carrier of a second planetary gear of the planetary gears. In one of the gears, the torque flow to the at least one output shaft is via the first planetary gear. In the other gear, the torque flow to the at least one output shaft is split between the two planetary gears.

[0007] According to claim 1, in first gear, a freewheel blocks a sun gear of the first planetary gear and a ring gear of the second planetary gear and a brake is opened to fix the sun gear of the second planetary gear, or in second gear, the freewheel releases a sun gear of the first planetary gear and a ring gear of the second planetary gear and a brake is closed to fix the sun gear of the second planetary gear, wherein the freewheel can be combined with a clutch, in particular a dog clutch, for recuperation.

[0008] According to claim 3, the planetary gears are switched by means of a single actuator.

[0009] Preferably, in the first gear of the motor vehicle, the torque flow occurs only via the first planetary gear and in the second gear of the motor vehicle, the torque flow is divided between the first planetary gear and the second planetary gear.

[0010] The electric axle drive thus features a planetary final drive via two planetary gears that interact differently depending on the gearshift state. The planetary final drive design ensures high torque capacity with compact dimensions.

[0011] In particular, the axle drive is designed such that a center axis of the planetary gear is arranged coaxially to a center axis of the at least one output shaft.

[0012] The assembly is mounted in a housing for rotation. Due to the mounting of the various components combined in the assembly, the influence of the second spur gear stage or both spur gear stages on the planetary gears can be minimized, thus ensuring optimized acoustics for the electric axle drive.

[0013] According to a preferred development of the invention, it is provided that the first planetary gear has the ring gear, a sun gear, planetary gears meshing with the ring gear and the sun gear, and a planetary carrier for receiving the planetary gears, wherein the torque flow to at least one output shaft in both gears takes place via the planetary carrier of the first planetary gear.

[0014] According to a preferred development of the invention, it is further provided that the second planetary gear set comprises a ring gear, a sun gear, planetary gears meshing with the ring gear and the sun gear, and a planetary carrier for receiving the planetary gears. A further assembly is provided that comprises a sun gear of the first planetary gear set and the ring gear of the second planetary gear set. This further assembly allows a kinematic coupling of the two planetary gear sets in the region of the planetary gear sets of the planetary gear sets to be created in a structurally simple manner.

[0015] The switching of the two planetary gears for the purpose of operating the transmission arrangement in the two gears is carried out by switching elements, which can have different designs and different functionalities. Thus, according to claim 4, it can be provided that in first gear, a freewheel or a brake blocks a sun gear of the first planetary gear and a ring gear of the second planetary gear, and a brake for securing the sun gear of the second planetary gear is opened. Furthermore, according to claim 4, it can be provided that in second gear, a freewheel or a brake releases a sun gear of the first planetary gear and a ring gear of the second planetary gear, and a brake for securing the sun gear of the second planetary gear is closed.For example, the shifting element for second gear is a friction brake, and the shifting element for first gear is a freewheel for traction operation and an optional clutch, preferably a dog clutch, for overrun operation, thus operation during recuperation. All shifting elements are designed to lock to the transmission housing.

[0016] In an alternative design, the shift elements for first and second gear are friction-locked brakes. These shift elements also lock to the transmission housing.

[0017] In the variant that uses two brakes, recuperation is possible in both first and second gear. In the other variant, which uses a freewheel, recuperation is only possible in second gear. In first gear, such recuperation is only possible when combined with an optional clutch, especially a dog clutch.

[0018] Depending on the performance requirements, the respective brake can be designed as a dry brake, resulting in low drag losses and thus high efficiency. For high performance requirements, the brake should preferably be designed as a wet switching element, especially an oil-immersed switching element.

[0019] When using a brake and a freewheel, power shifting during traction shifting is preferably achieved using a single actuator. However, if two brakes are provided, power shifting is preferably achieved using two actuators.

[0020] The electric motor drives an intermediate shaft via the first spur gear stage, which is formed by two meshing spur gears, to which a spur gear of the second spur gear stage is connected in a rotationally fixed manner. This spur gear meshes with a spur gear of this spur gear stage, which is part of the assembly comprising this gear, the ring gear of the first planetary gear, and the planet carrier of the second planetary gear. The at least one output shaft of the electric axle drive is driven via the planet carrier of the first planetary gear. This at least one output shaft drives one or more wheels (road wheels) of the axle. Preferably, two output shafts are provided, which can be driven by the electric motor. The electric motor thus drives the two wheels / road wheels of the axle, each of which is assigned to an output shaft.

[0021] According to a particular development of the invention, a bevel gear differential or a planetary differential, whose output is assigned to two output shafts, can be driven via the output of the first planetary gear. The planetary differential is designed, in particular, as a planetary differential with a Ravigneaux set.

[0022] Additionally, a torque vectoring unit can be provided with the electric axle drive. This torque vectoring unit comprises, in particular, another electric motor and a superposition gear to achieve a differential torque between the two drive shafts. The torque vectoring unit can also have a gear ratio stage located between the other electric motor and the superposition gear.

[0023] From the perspective of a particularly compact design of the electric axle drive, also from the perspective of its compact arrangement relative to at least one output shaft, in particular the two output shafts, it is considered particularly advantageous if the center axes of the planetary gears and / or the planetary differential and / or the superposition gear and / or the transmission stage and / or the other electric machine are identical.

[0024] The invention, including its further developments, thus proposes an electric, powershiftable 2-speed axle drive with an optional torque vectoring unit.

[0025] Further features of the invention will become apparent from the dependent claims, the accompanying drawings, and the description of the two preferred embodiments shown in the drawings, without being limited thereto. It shows: Fig. 1 shows a schematic representation of the drive components of the electric axle drive for a first embodiment, Fig. 2 a nomogram illustrating the speeds of the components of the planetary gears of the electric drive unit, Fig. 3 shows a schematic representation of the drive components of the electric axle drive for a second embodiment.

[0026] The electric axle drive is particularly used in passenger cars. The axle drive powers two wheels, i.e., the road wheels of one axle of the vehicle.

[0027] Fig. Figure 1 illustrates, with regard to the first exemplary embodiment, the basic structure of the electric axle drive 1. It shows an electric machine 2—a traction electric machine—with its output shaft 3. This interacts with a spur gear stage 4 comprising gears 5 and 6. The relatively smaller gear 5 is connected in a rotationally fixed manner to the output shaft 3, and the relatively larger gear 6 is connected in a rotationally fixed manner to an intermediate shaft 7. Also connected in a rotationally fixed manner to the intermediate shaft 7 is a gear 8 whose diameter is significantly smaller than that of the gear 6. The gear 8 meshes with a gear 9 and forms a second spur gear stage 10.

[0028] The gear 9 forms part of an assembly 11 which comprises this gear 9, a ring gear 12 of a first planetary gear 13 and a planet carrier 14 of a second planetary gear 15.

[0029] The first planetary gear 13 includes the ring gear 12, a sun gear 16, planetary gears 17 meshing with the ring gear 12 and the sun gear 16, and a planet carrier 18 for receiving the planetary gears 17. The second planetary gear 15 includes the planet carrier 14, planetary gears 19 received therein, a sun gear 20, and a ring gear 21. The planetary gears 19 mesh with the sun gear 20 and the ring gear 21. The sun gear 16 of the first planetary gear 13 and the ring gear 21 of the second planetary gear 15 form a further assembly 22.

[0030] The electric axle drive 1 has two gears. In the motor vehicle's first gear, a freewheel 23 blocks the assembly 22 and thus the sun gear 16 of the first planetary gear 13 and the ring gear 21 of the second planetary gear, wherein a brake 24 for braking the sun gear 20 of the second planetary gear 15 is opened, allowing this sun gear 20 to rotate. In second gear, the brake 24 is closed, whereby the sun gear 20 is stationary and a higher speed is applied to the assembly 22 than to the assembly 11, thereby overtaking the freewheel. In this variant, recuperation in second gear is possible. Recuperation in first gear is only possible in combination with an optional clutch, in particular a dog clutch 25, by means of which the assembly 22 can be secured to a housing 26.The freewheel 23 is also effective between this housing 26 and the assembly 22, and the brake 24 is effective between the housing 26 and the sun gear 20.

[0031] In this embodiment, the radially inner diameter of the ring gears 12 and 21 is identical, furthermore the radially outer diameter of the sun gears 16 and 20 is identical and furthermore the diameter of the planet gears 17 and 19 is identical.

[0032] In the illustrated embodiment, the planetary gears 13, 15 are shifted by means of a single actuator that engages the brake 24. If a dog clutch 25 is present, the same actuator that engages the brake 24 is preferably provided for this.

[0033] Instead of the freewheel 23, another brake can also be used. In this case, no claw clutch 25 is required for recuperation operation. In this variant (not illustrated), in first gear, the preferably friction-locked brake between the housing 26 and the assembly 22 is active and the other brake 24 is open, while in second gear, the brake 24 is closed and the other brake located between the housing 26 and the assembly 22 is open. In this variant, the planetary gears 13, 15 are preferably switched by means of two actuators, each of which switches one of the brakes.

[0034] Regardless of whether the electric axle drive is in one gear or the other, the output in the area of ​​the two planetary gears 13, 15 occurs via the planet carrier 18 of the first planetary gear 13. The planet carrier 18 interacts with a differential gear 27, which is in particular a bevel gear differential gear or planetary differential gear. Two output shafts 28, 29 of the electric axle drive 1 are driven by means of the differential gear 27, with the respective output shaft 28 or 29 serving to drive a (road) wheel of the axle 30 of the motor vehicle. The output shafts are thus output shafts of the electric axle drive or output shafts of the transmission unit for driving the respective wheel / road wheel of the passenger car in the area of ​​the vehicle axle.

[0035] The Fig. 1 shows that the two planetary gears 13, 15 and the differential 27 have the same center axis 31.

[0036] In recuperation mode, i.e., when torque is introduced via the planetary carrier 18 into the first planetary gear 13 and from there into the spur gear stages 10 and 4, the claw clutch 25 is switched to its closed position, thus establishing a positive connection to the electric motor 2 for generator operation. If a brake is used instead of the claw clutch, this is switched to its closed position.

[0037] Fig. 2 shows in a nomogram the rotational speeds of sun gear 16, sun gear 20, ring gear 12 and planet carrier 18 for the first gear and the second gear of the motor vehicle.

[0038] The embodiment according to Fig.3 shows a modification of the torque transmission from the planet carrier 18 of the first planetary gear 13 to the two output shafts 28, 29: The differential gear 27, specifically a ring gear 32 of a differential gear designed as a planetary differential gear, is driven via the planetary carrier 18. This ring gear 32 is connected in a rotationally fixed manner to the planetary carrier 18. The two output shafts 28, 29 are assigned to an output 33 of the planetary differential 27. The planetary differential 27 is designed as a planetary differential with a Ravigneaux set.

[0039] Furthermore, the electric axle drive 1, in particular optionally, has a torque vectoring unit 34. This unit has a further electric motor 35 and a superposition gear 36 for generating a differential torque between the two output shafts 28, 29. Furthermore, the torque vectoring unit 34 has a gear ratio stage 37 between the electric motor 35 and the superposition gear 36.

[0040] The output shafts 28, 29, the planetary differential 27, the torque vectoring unit 34, the additional electric motor 35, the superposition gear 36, and the transmission gear 37 are arranged coaxially to the center axis 31. The output shaft 3 and the intermediate shaft 7 are arranged axially parallel to the center axis 31. List of reference symbols 1 axle drive 2 electric machine 3 Output shaft 4 spur gear stage 5 gear 6 gear 7 Intermediate shaft 8 gear 9 gear 10 spur gear stage 11 Assembly 12 ring gear 13 First planetary gear 14 planet carriers 15 Second planetary gear 16 Sun gear 17 Planetary gear 18 planet carriers 19 Planetary gear 20 Sun gear 21 ring gear 22 Assembly 23 Freewheel 24 Brake 25 claw coupling 26 housings 27 differential gears 28 Output shaft 29 Output shaft 30 axis 31 Center axis 32 ring gear 33 Exit 34 Torque vectoring unit 35 Additional electric machine 36 superposition gears 37 gear ratios

Claims

[1] Electric axle drive (1) for a motor vehicle, wherein said axle drive has a transmission arrangement with two gears, with an electric machine (2) for driving at least one output shaft (28, 29) of the axle (30) of the motor vehicle, with a first spur gear stage (4) drivable by means of the electric machine (2) and a second spur gear stage (10) drivable via said first spur gear stage, and with at least one planetary gear (13, 15), characterized bythat a gear (9) forming the output of the second spur gear stage (10) is part of an assembly (11) comprising this gear (9), a ring gear (12) of a first planetary gear set (13), and a planet carrier (14) of a second planetary gear set (15), wherein in one of the gears the torque flow to the at least one output shaft (28, 29) takes place via the first planetary gear set (13), and in the other of the gears the torque flow to the at least one output shaft (28, 29) is distributed between both planetary gear sets (13, 15), wherein in the first gear a freewheel (23) blocks a sun gear (16) of the first planetary gear set and a ring gear (21) of the second planetary gear set (15), and a brake (24) for fixing a sun gear (20) of the second planetary gear set (15) is opened,or wherein in the second gear, a freewheel (23) releases the sun gear (16) of the first planetary gear (13) and a ring gear (21) of the second planetary gear (15) and a brake (24) for fixing the sun gear (20) of the second planetary gear (15) is closed, wherein the freewheel (23) can be combined with a clutch for recuperation. [2] Electric axle drive according to claim 1, characterized by that the switching of the planetary gears (13, 15) takes place by means of a single actuator. [3] Electric axle drive (1) for a motor vehicle, wherein said axle drive has a transmission arrangement with two gears, with an electric machine (2) for driving at least one output shaft (28, 29) of the axle (30) of the motor vehicle, with a first spur gear stage (4) drivable by means of the electric machine (2) and a second spur gear stage (10) drivable via said first spur gear stage, and with at least one planetary gear (13, 15), characterized byin that a gear (9) forming the output of the second spur gear stage (10) is a component of an assembly (11) which has this gear (9), a ring gear (12) of a first planetary gear (13) and a planet carrier (14) of a second planetary gear (15), wherein in one of the gears the torque flow to the at least one output shaft (28, 29) takes place via the first planetary gear (13) and in the other of the gears the torque flow to the at least one output shaft (28, 29) is divided between the two planetary gears (13, 15), wherein the switching of the planetary gears (13, 15) takes place by means of a single actuator. [4] Electric axle drive according to claim 3, characterized by , that In first gear, a freewheel (23) or a brake blocks a sun gear (16) of the first planetary gear and a ring gear (21) of the second planetary gear (15), and a brake (24) for fixing a sun gear (20) of the second planetary gear (15) is opened, or in the second gear, a freewheel (23) or a brake releases the sun gear (16) of the first planetary gear (13) and a ring gear (21) of the second planetary gear (15) and a brake (24) for fixing the sun gear (20) of the second planetary gear (15) is closed. [5] Electric axle drive according to one of claims 1 to 4, characterized by that a center axis (31) of the planetary gears (13, 15) is arranged coaxially to a center axis (31) of the at least one output shaft (28, 29). [6] Electric axle drive according to one of claims 1 to 5, characterized by that the assembly (11) is rotatably mounted in a housing (26). [7] Electric axle drive according to claim 1, 2 or 4, characterized by that the first planetary gear (13) has the ring gear (12), the sun gear (16), planetary gears (17) meshing with the ring gear (12) and the sun gear (16), and a planetary carrier (18) for receiving the planetary gears (17), wherein the torque flow to at least one output shaft (28, 29) in both gears takes place via the planetary carrier (18) of the first planetary gear (13). [8] Electric axle drive according to claim 1, 2 or 4, characterized by that the second planetary gear (15) has a ring gear (21), the sun gear (20), planetary gears (19) meshing with the ring gear (21) and the sun gear (20), and a planet carrier (14) for the planetary gears (19), wherein a further assembly (22) is provided which has the sun gear (16) of the first planetary gear (13) and the ring gear (21) of the second planetary gear (15). [9] Electric axle drive according to one of claims 1 to 8, characterized by that in first gear the torque flow occurs only via the first planetary gear (13) and in second gear the torque flow is divided between the first planetary gear (13) and the second planetary gear (15). [10] Electric axle drive according to one of claims 1 to 9, characterized by that a differential gear (27) can be driven via the planet carrier (18) of the first planetary gear (13), the output (33) of which is assigned to two output shafts (28, 29), the differential gear (27) being designed as a planetary differential with a Ravigneaux set or as a bevel gear differential gear. [11] Electric axle drive according to one of claims 1 to 10, characterized by that it has a torque vectoring unit (34). [12] Electric axle drive according to claim 11, characterized bythat the torque vectoring unit (34) has a further electric machine (35) and a superposition gear (36) for generating a differential torque between the two output shafts (28, 29). [13] Electric axle drive according to claim 12, characterized by that the torque vectoring unit (34) has a transmission stage (37) which is arranged between the further electric machine (35) and the superposition gear (36). [14] Electric axle drive according to claim 10 and claim 13, characterized by that the planetary gears (13, 15) and / or the differential gear (27) and / or the superposition gear (36) and / or the transmission stage (37) and / or the further electric machine (35) have the same central axis (31).

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