Electric axle drive for a motor vehicle

Abstract

Electric axle drive (1) for a motor vehicle, comprising an electric machine (2) for driving at least one output shaft (15, 16) of the axle (13) of the motor vehicle, and a spur gear transmission (5), wherein the electric axle drive (1) has two gears, wherein a planetary gear transmission (14) can be driven by means of the electric machine (2) via two spur gear stages (6, 7), wherein the planetary gear transmission (14) is switchable between two gears, wherein in the first gear a reduction is engaged in the planetary gear transmission (14) and in the second gear the planetary gear transmission (14) is engaged as a unit, characterized in that an output gear (12) of the spur gear transmission (5) is connected to a ring gear (17) of the planetary gear transmission (14), planet gears (19) of the planetary gear transmission (14) mounted in a planet carrier (18) with the ring gear (17) and a sun gear (20) of the planetary gear transmission (14) comb,wherein the planet carrier (18) forming one output of the planetary gear (14) can drive at least one output shaft (15, 16); in first gear, a freewheel (30) blocks the sun gear (20) and a clutch (22) is open for coupling the sun gear (20) and ring gear (17) and / or in second gear, a freewheel (30) releases the sun gear (20) and a clutch (22) is closed for coupling the sun gear (20) and ring gear (17), the freewheel (30) being combinable with a clutch for recuperation.

Description

[0001] The invention relates to an electric axle drive for a motor vehicle, comprising an electric machine for driving at least one output shaft of the axle of the motor vehicle, and a spur gear transmission.

[0002] Such an electric axle drive is known from WO 2011 / 076542 A1. The electric axle drive comprises an electric motor whose output shaft runs parallel to the axle of the vehicle. The torque of the electric motor is transmitted to a differential located on the axle via an upstream gear stage in the form of a single-stage spur gear transmission. Additionally, a torque vectoring unit is provided, which acts on a reduction gear stage, allowing the torque to be distributed individually to each wheel within the axle. The reduction gear stage consists of two identically dimensioned, parallel-connected, power-split planetary gear sets. The wheel-specific torque distribution is continuously adjustable via the torque of one of the electric motors in the torque vectoring unit.A load-balancing gear stage, also in the form of a planetary gear, is connected downstream of the power-splitting planetary gears as an active stage to combine the torque flow divided by the power-splitting planetary gears to the output.

[0003] The object of the present invention is to further develop an electric axle drive for a motor vehicle of the type mentioned above in such a way that a vehicle can be driven purely electrically over a wide speed range, with optimal efficiency of the axle drive.

[0004] The problem is solved by an electric axle drive designed according to the features of claim 1.

[0005] The electric axle drive according to the invention is provided to have two gears, wherein a planetary gear can be driven by means of the electric machine via two spur gear stages of the spur gear transmission, and the planetary gear can be switched between two gears, wherein in the first gear a reduction is switched in the planetary gear and in the second gear the planetary gear is switched as a block.

[0006] In the second gear, which is primarily the primary gear, only the two spur gear stages are in motion and transmitting power. The switchable planetary gear set rotates as a unit. This allows for efficiency gains. Because the electric axle drive can operate in two gears, it is possible to propel the vehicle purely electrically over a wide speed range.

[0007] It is advantageous, particularly with regard to a compact design, if the central axis of the planetary gear is arranged coaxially to the central axis of the at least one output shaft.

[0008] The electric motor drives at least one output shaft via an intermediate shaft. This output shaft drives one or more 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 of the axle, each of which is assigned to one output shaft.

[0009] It is considered particularly advantageous if an output gear of the spur gear unit is connected to a ring gear of the planetary gear unit. In a further development of this design, it is specifically provided that planet gears of the planetary gear unit, mounted in a planet carrier, mesh with the ring gear and a sun gear of the planetary gear unit, wherein the at least one output shaft can be driven by means of the planet carrier forming the output of the planetary gear unit.

[0010] This design of the planetary gear set, in particular its connection to the spur gear set and to the at least one output shaft, makes it possible to implement shift states for the individual gears that ensure very good fail-safe behavior. In a first preferred embodiment, a brake is engaged to lock the sun gear, and a clutch is open to engage the sun gear and ring gear. In a second gear, a brake is open to lock the sun gear, and a clutch is engaged to engage the sun gear and ring gear. Preferably, this is a normally-open brake for the first gear and a normally-closed clutch for the second gear, with this normally-closed clutch preferably being frictionally engaged.In a second preferred embodiment, a freewheel blocks the sun gear in first gear, and a clutch for engaging the sun gear and ring gear is open. In second gear, a freewheel releases the sun gear, and a clutch for engaging the sun gear and ring gear is closed. Thus, this embodiment provides a freewheel for first gear and a normally closed clutch, preferably a friction clutch, for second gear.

[0011] The brake / clutch is either designed as a dry brake / clutch, which ensures low drag losses and consequently high efficiency. Alternatively, the brake / clutch is designed as a wet brake / clutch, which enables high performance.

[0012] Accordingly, the electric axle drive can be shifted under load using a clutch and brake or freewheel. With a combination of clutch and freewheel, load shifting is preferably achieved with only one actuator. With a combination of brake and clutch(es), preferably two actuators are provided, one for the clutch(es) and one for the brake.

[0013] In the first variant, which uses the brake and clutch, recuperation is possible in both first and second gear. In the second variant, because a freewheel is used, recuperation is only possible in second gear. Recuperation in first gear is possible when combined with an optional clutch, particularly a dog clutch.

[0014] According to a particular embodiment of the invention, a planetary differential can be driven via the output of the planetary gear set, the output of which is assigned to two output shafts. The planetary differential is specifically designed as a planetary differential with a Ravigneaux set.

[0015] Additionally, the electric axle drive can be equipped with a torque vectoring unit. This torque vectoring unit comprises, in particular, another electric motor and a superimposed gearbox to generate a differential torque between the two output shafts. The torque vectoring unit can also include a transmission stage located between the additional electric motor and the superimposed gearbox.

[0016] From the perspective of a particularly compact design of the electric axle drive, and also from the perspective of its compact arrangement to the at least one output shaft, in particular the two output shafts, it is considered particularly advantageous if the center axis of the planetary gear is coaxial to the respective center axis of the planetary differential and / or the superimposed gear and / or the transmission stage and / or the other electric machine.

[0017] The invention, including its further developments, thus proposes an electric, load-switchable two-speed axle drive with an optional torque vectoring unit.

[0018] Further features of the invention will become apparent from the dependent claims, the accompanying drawing and the description of the preferred embodiments shown in the drawing, without being limited thereto.

[0019] It shows:

[0020] Fig. 1 For a first embodiment, a schematic representation of the drive components of the electric axle drive,

[0021] Fig. 2 For a second embodiment, a schematic representation of the drive components of the electric axle drive.

[0022] Electric axle drives are primarily used in passenger cars. They drive two wheels on one axle of the vehicle.

[0023] Fig. Figure 1 illustrates, with regard to the first embodiment, the basic structure of the electric axle drive. 1 An electric machine is illustrated. 2 – Traction electric machine – with its rotor 3 and the rotor shaft connected to it 4 This operates with a spur gear transmission. 5 together, the two spur gear stages 6 and 7 features the spur gear stage 6a small spur gear 8 up, which is rotationally fixed to the rotor shaft 4 is connected and with a large spur gear 9 the spur gear stage 6 combs. The spur gear 9 is with an intermediate shaft 10 connected in a rotationally fixed manner, which in turn connected a small spur gear in a rotationally fixed manner 11 the spur gear stage 7 absorbs this spur gear 11 combs with a large spur gear 12 the spur gear stage 7 The spur gear 12 rotates during operation of the electric machine 2 around an axis 13 , which simultaneously forms the central axis of a planetary gear 14 represents that by means of the electric machine 2 is propellable.

[0024] This axis 13 or center axis 13 also represents the axis of rotation of two output shafts 15 , 16 of the electric axle drive 1This describes a system where each output shaft drives a wheel of the vehicle's axle. The output shafts are therefore the output shafts of the electric axle drive or the output shafts of the transmission unit for driving the respective wheel of the passenger car in the area of ​​the vehicle axle.

[0025] The planetary gear 14 a hollow gear 17 , in a planetary carrier 18 planetary gears mounted on bearings 19 and a sun wheel 20 up. The spur gear 12 the spur gear stage 7 is with the hollow gear 17 connected. The planetary gears 19 comb with the ring gear 17 and the sun wheel 20 . By means of the output of the planetary gear 14 forming planetary carrier 18 are the output shafts 15 and 16 can be driven in a manner that will be described in more detail below.

[0026] The electric axle drive 1 It has two gears. There is a brake in first gear. 21 to block the sun wheel 20 closed and a clutch 22 for coupling sun wheel 20 and ring gear 17 opened. The brake 21 and the clutch 22 They are switched via a common actuator, which is not illustrated. In second gear, the brake is engaged. 21 to block the sun wheel 20 opened and the clutch 22 for coupling sun wheel 20 and ring gear 17 Closed. This results in good fail-safe behavior due to a preferably normally-open brake for first gear and a normally-closed clutch, preferably frictionally engaging, for second gear. Here, recuperation in first and second gear is possible because of the rotationally rigid connection provided by the brake. 21 or existing clutch 22possible.

[0027] In first gear, the sun wheel 20 fixed so that the torque flow from the spur gear 12 and ring gear 17 formed unit via the planetary gears 19 into the planetary carrier 18 and from there to the output shafts 15 , 16 This occurs. In the second gear, however, which is mainly used, the planetary gear is used. 14 connected as a block. Therefore, only the two gear stages, i.e., the two spur gear stages, are present. 6 , 7 , arranged in the power flow. In first gear, the gear ratio is in the planetary gear system. 14 realized through the use of brakes 21 with the clutch open 22 .

[0028] Via the output of the planetary gear 14 , specifically the planetary carrier 18 , is a planetary differential 23 , specifically a hollow gear 24 of the planetary differential23 propellable. The exit 25 of the planetary differential 23 are the two drive shafts 15 , 16 assigned. The planetary differential 23 is designed as a planetary differential with a Ravigneaux set.

[0029] Furthermore, the electric axle drive features 1 , especially optionally, a torque vectoring unit 26 This one has another electric motor. 27 and a superimposed gearbox 28 up, to generate a differential torque between the two output shafts 15 , 16 Furthermore, the torque vectoring unit exhibits 26 between the electric machine 27 and the superimposed gear 28 a translation stage 29 on.

[0030] The axis or center axis 13 of the planetary gear 4 is coaxial to the one also with the reference numeral 13designated central axis of electric machine 27 , superimposed gear 28 and translation stage 29 arranged.

[0031] The exemplary embodiment according to the Fig. 2 is in that it is different from the one after the Fig. 1 modified so that instead of the brake 21 a free run 30 is intended. In first gear, the freewheel is blocked. 30 the sun wheel 20 and it's the clutch 22 for coupling sun wheel 20 and ring gear 17 open. In second gear, the freewheel engages. 30 the sun wheel 20 free and it is the clutch 22 for coupling sun wheel 20 and ring gear 17Closed. Particularly good fail-safe behavior with this variant is achieved with freewheeling for first gear and a normally closed clutch, preferably a positive-locking clutch, for second gear. With this variant, recuperation is possible in second gear. Recuperation in first gear is only possible in combination with an optional clutch, especially a dog clutch.

[0032] Furthermore, in the exemplary embodiment according to the Fig. 2 the same reference numbers for corresponding components according to Fig. 1 has been used. QUOTES INCLUDED IN THE DESCRIPTION

[0033] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0034] WO 2011 / 076542 A1

[0002]

Claims

[1] Electric axle drive ( 1 ) for a motor vehicle, with an electric motor ( 2 ) to drive at least one output shaft ( 15 , 16 ) of the axis ( 13 ) of the motor vehicle, as well as with a spur gear transmission ( 5 ), characterized by that the electric axle drive ( 1 ) has two gears, using the electric motor ( 2 ) via two spur gear stages ( 6 , 7 ) a planetary gear ( 14 ) is driveable, as well as the planetary gear ( 14 ) is switchable between two gears, with the first gear having a gear ratio in the planetary gear system ( 14 ) is switched on and in second gear the planetary gear ( 14 ) is connected as a block. [2] Electric axle drive according to claim 1, characterized by that the central axis ( 13 ) of the planetary gear ( 14 ) coaxial to the central axis ( 13) of at least one output shaft ( 15 , 16 ) is arranged. [3] Electric axle drive according to claim 1 or 2, characterized by that an output gear ( 12 ) of the spur gear drive ( 5 ) with a ring gear ( 17 ) of the planetary gear ( 14 ) is connected. [4] Electric axle drive according to claim 3, characterized by that in a planetary carrier ( 18 ) planetary gears mounted on bearings ( 19 ) of the planetary gear ( 14 ) with the ring gear ( 17 ) and a sun wheel ( 20 ) of the planetary gear ( 14 ) comb, whereby the output of the planetary gear ( 14 ) forming planetary carrier ( 18 ) which has at least one output shaft ( 15 , 16 ) is propellable. [5] Electric axle drive according to claim 4, characterized by that a brake is applied in first gear ( 21 ) to block the sun wheel ( 20) is closed and a coupling ( 22 ) for coupling sun wheel ( 20 ) and ring gear ( 17 ) is open. [6] Electric axle drive according to claim 4 or 5, characterized by that a brake is applied in second gear ( 21 ) to block the sun wheel ( 20 ) opened and a clutch ( 22 ) for coupling sun wheel ( 20 ) and ring gear ( 17 ) is closed. [7] Electric axle drive according to claim 4, characterized by that in first gear there is a freewheel ( 30 ) the sun wheel ( 20 ) blocked and a clutch ( 22 ) for coupling sun wheel ( 20 ) and ring gear ( 17 ) is open. [8] Electric axle drive according to claim 4 or 7, characterized by that in second gear there is a freewheel ( 30 ) the sun wheel ( 20 ) releases and a coupling ( 22 ) for coupling sun wheel ( 20 ) and ring gear ( 17) is closed. [9] Electric axle drive according to claim 7 or 8, characterized by that the freewheel ( 30 ) can be combined with a coupling, in particular a claw coupling, for recuperation. [10] Electric axle drive according to one of claims 7 to 9, characterized by that the planetary gear system ( 14 ) is achieved using a single actuator. [11] Electric axle drive according to any one of claims 1 to 10, characterized by that about the exit ( 18 ) of the planetary gear ( 14 ) a planetary differential ( 23 ) is driveable, whose output ( 25 ) two output shafts ( 15 , 16 ) are assigned, in particular the planetary differential ( 23 ) as planetary differential ( 23 ) is trained in the Ravigneaux set. [12] Electric axle drive according to any one of claims 1 to 11, characterized by that a torque vectoring unit ( 26) is planned. [13] Electric axle drive according to claim 12, characterized by that the torque vectoring unit ( 26 ) another electric machine ( 27 ) and a superimposed gear unit ( 28 ) exhibits, to generate a differential torque between two output shafts ( 15 , 16 ). [14] Electric axle drive according to claim 13, characterized by that the torque vectoring unit ( 26 ) a translation stage ( 29 ) exhibits, which between the other electric machine ( 27 ) and the superimposed gear ( 28 ) is arranged. [15] Electric axle drive according to any one of claims 2 to 14, characterized by that the central axis ( 13 ) of the planetary gear ( 14 ) coaxial to the respective center axis ( 13 ) of the planetary differential ( 23 ) and / or the superimposed gear ( 28 ) and / or the translation level ( 29) and / or the other electric machine ( 27 ) is arranged.

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