Axle driving device

Abstract

The invention relates to a drive device for an axle of a two-track vehicle. According to the invention, instead of conventional wheel brakes, the axle is equipped with exactly one central disc brake (57) serving as a wheel brake, by means of which disc brake vehicle braking can be carried out.

Description

Technical Field

[0001] The invention relates to a drive device for a vehicle axle according to the preamble of claim 1 . Background Art

[0002] To improve efficiency and range, braking of electrified vehicles is performed by the electric drive in generator mode (hereinafter referred to as recuperation mode) as long as certain boundary conditions are met.

[0003] Such axle drive has an axle differential, which can achieve a 50 / 50 power distribution. Its input side is drive-connected to the electric motor, while its output side is output on a flange shaft leading to the two wheels.

[0004] In the aforementioned prior art, different braking torques cannot be set at the wheels during recuperation mode. This means that braking torque redistribution is not possible during recuperation mode. For safety reasons, the recuperation range is limited. If this range is exceeded, recuperation is deactivated and the conventional vehicle braking system takes over. In this case, in the prior art, the conventional vehicle braking system is used to perform vehicle dynamics control, with a control unit selectively controlling the wheel brakes of each wheel with different braking torques to influence driving behavior.

[0005] Therefore, no recuperation occurs when braking torque redistribution is performed. As a result, recuperation performance and therefore consumption or electric range are limited for driving safety reasons.

[0006] Sports vehicles, in particular, often have a torque vectoring system on the rear axle. This directs the drive torque directly to the wheels via the differential. This allows for free distribution of the drive torque to the corresponding axles. In addition to the usual drive with differential, this torque vectoring system also features two superposition gears, two force-locking control clutches, two actuators, a control unit, and often its own hydraulic system.

[0007] A differential gear with a torque vectoring function is known from DE 10 200 9 013 293 A1. A device for controlling a differential with slip limitation is known from DE 10 201 5 112 924 A1. An axle with an electric drive motor is known from DE 10 201 8 133 223 A1.

[0008] The object of the present invention is to provide a drive device for an axle of a two-track vehicle, in which the recuperation power during driving is increased compared to the prior art and / or the drive device is designed to save space.

[0009] This object is achieved by the features of claim 1. Preferred developments of the invention are disclosed in the dependent claims.

[0010] The present invention is based on a drive system for the axle of a two-wheel vehicle, which features an axle differential. Its input side is drive-connected to the electric motor, while its output side drives flanged shafts leading to both wheels. Each wheel of the axle has a superposition transmission with a disc clutch. The superposition transmission allows the electric motor to be directly connected to the wheel flange shafts and bridges the axle differential. When the vehicle accelerates, the electric motor can be operated in engine mode, and when the vehicle decelerates, it can be operated in recuperation mode.

[0011] According to the present invention, during recuperation mode, not only can the drive torque be redistributed between the two wheels, but also the braking torque can be redistributed. When redistributing the braking torque, the corresponding disc clutches are controlled to divide the braking torque path extending between the wheels and the electric motor into a differential braking torque path, which directs the differential braking torque from the wheels via the axle differential to the electric motor, and a superposition braking torque path, which directs the superposition braking torque from the wheels via the axle differential and the superposition gear mechanism to the electric motor. This allows the wheels to be subjected to different braking torques during recuperation mode, enabling them to be braked to varying degrees.

[0012] If the axle is designed without wheel brakes, recuperation must always be fully effective. This means that full braking or downhill braking must be reliably guaranteed, even when the battery is fully charged. Braking functions are subject to high safety requirements. Drives must be developed in accordance with these requirements.

[0013] Against this backdrop, according to the characterizing portion of claim 1, the axle is equipped with precisely one central disc brake serving as a wheel brake, enabling even braking of the vehicle on both sides. The central disc brake allows vehicle braking to be performed as an alternative to or in addition to a disc clutch. Thus, if the electric motor is unable or only partially capable of recuperation, the disc brake can at least partially or completely take over the braking task. For example, the disc brake can brake the vehicle based on the current recuperation capacity.

[0014] When braking evenly on both sides of the vehicle, for safety reasons, the braking intervention can preferably be mainly taken over by the central disc brake. On the contrary, in the case of uneven braking on both sides of the vehicle, the disc clutch preferably mainly takes over the braking intervention.

[0015] In one technical embodiment, the disc brake consists of an inner disc carrier, an outer disc carrier, and a disc pack arranged therebetween. The electric motor can be connected directly or indirectly to the input side of the axle differential via its rotor shaft. According to a first embodiment variant, the disc brake can act directly on the rotor shaft. In this case, the inner disc carrier can be connected to the rotor shaft in a rotationally fixed manner, while the outer disc carrier is also connected to the transmission housing wall in a rotationally fixed manner.

[0016] In a specific embodiment, the rotor shaft of the electric motor can be connected to an intermediate shaft via an intermediate stage. The intermediate shaft can be oriented axially parallel to the rotor shaft. In the case of an axially short transmission housing, the intermediate shaft can extend on one side from the intermediate stage in the direction opposite to the rotor shaft towards the motor end side. The electric motor can be installed transversely in the axle so that the rotor shaft of the electric motor is aligned axially parallel to the flange shaft. With regard to space-saving positioning, it is advantageous if an installation space is provided at the motor end side, between the intermediate stage and the intermediate shaft and the rotor shaft, in which installation space a disc brake can be positioned in a space-saving manner. Preferably, the transmission stage can be implemented as an axially short intermediate spur gear stage, which consists of a fixed gear arranged on the rotor shaft and an input gear meshing therewith, which is connected to the differential housing axle differential in a rotationally fixed manner.

[0017] In a second embodiment variant, the disc brake can act directly on the differential housing of the axle differential. In this case, the inner disc carrier can be connected to the differential housing in a rotationally fixed manner, while the outer disc carrier is connected to the transmission housing wall in a rotationally fixed manner.

[0018] By providing a disc brake, the use of conventional wheel brakes, each of which is formed by a brake disc positioned on the wheel drive shaft and a brake caliper interacting therewith, can be dispensed with. This avoids brake wear debris, which would otherwise be discharged into the environment in conventional vehicles.

[0019] Two exemplary embodiments of the present invention are described below with reference to the accompanying drawings.

[0020] The accompanying drawings show:

[0021] Figures 1 to 5 Different illustrations of axles with integrated central disc brakes are shown.

[0022] Figure 1 An electrified axle, in particular the rear axle, is shown, which has a drive unit 1 consisting of an electric motor EM and a transmission 3. The electric motor EM is connected to a high-voltage battery 2. Figure 1As can be seen in the figure, conventional wheel brakes are omitted from the axle. Instead of such conventional wheel brakes, the axle has a central disc brake 57 and a disc clutch 33 described later. As an alternative to or in addition to the disc clutch 33, the central disc brake 57 causes vehicle braking. The axle has a drive unit 1 consisting of an electric motor EM and a transmission 3, via which the electric motor EM supplies power to the rear wheels HR, HL. The electric motor EM is connected via its rotor shaft 5 to the input side 8 of the axle differential 9 with an intermediate stage 7 connected in between. The output side of the axle differential is drive-connected to the rear wheels HR, HL of the vehicle. Figure 1 In the embodiment, the electric motor EM is mounted transversely in the axle. Therefore, the rotor shaft 5 and the flange shaft 27 are axially parallel to one another, leading from the output side of the axle differential 3 to the vehicle's rear wheels HL and HR. Similarly, the disc clutch 33 and the disc brake 57 mounted in the axle are oriented axially parallel to one another in the vehicle transverse direction y.

[0023] Viewed in the vehicle transverse direction y, the axle has a superposition transmission 11 on each vehicle side, via which the electric motor EM can be directly connected to one of the flange shafts 27, while bridging the axle differential 9. With the help of two superposition transmissions 11, the electric motor EM can thus be driven directly to the wheels HR, HL via the load paths L1, L2 indicated by dashed lines, while bridging the axle differential 9.

[0024] Figure 2 The detailed transmission structure of the axle transmission 3 is shown. The intermediate stage 7 thus consists of two spur gear stages 19, 20. The rotor shaft 5 of the electric motor EM is connected to the intermediate shaft 13 via a first spur gear stage 19. The first spur gear stage 19 consists of a fixed gear 15 arranged on the rotor shaft 5 and a fixed gear 17 arranged on the intermediate shaft 13, which meshes with the fixed gear 15. The intermediate shaft 13 is connected to the input side 8 of the axle differential 9 via a second spur gear stage 20. The second spur gear stage 20 consists of a fixed gear 21 arranged on the intermediate shaft 13 and an axle differential gear 23 on the input side. The axle differential gear 23 is connected to a rotating differential housing 25 in a rotationally fixed manner. According to Figure 2 The axle differential 9 delivers power in the vehicle transverse direction y in a 50 / 50 distribution on both sides of the two flange shafts 27 leading to the wheels HL, HR.

[0025] The two superposition transmissions 11 are designed as mirror images with respect to a central longitudinal plane of the vehicle passing through the axle differential 9. Each of the two superposition transmissions 11 has a transmission stage 28, which is designed in the manner of a planetary gear (but without an outer ring gear), with a sun gear 47 on the vehicle's outer side, viewed in the vehicle transverse direction y, which is located rotationally fixed on the flange shaft 27, and a sun gear 29 on the vehicle's inner side, which is arranged rotatably on the flange shaft 27 as a floating gear. The sun gear 29 on the vehicle's inner side meshes with planet gears 41 on the vehicle's inner side, each of which is arranged in a rotationally fixed manner on a carrier shaft 43. Each carrier shaft 43 has a planet gear 45 on the vehicle's outer side, which meshes with a sun gear 47 on the vehicle's outer side. The sun gear 29 on the vehicle's outer side, the sun gear 47 on the vehicle's outer side, and the planet gears 41, 45 have Figure 3 and Figure 4 The teeth shown are numbered z1 to z4.

[0026] The sun gear 29 on the vehicle's inner side (i.e., the floating gear) sits on a hollow shaft, through which the flange shaft 27 passes, along with the inner plate carrier 31 of the plate clutch 33. The inner plate carrier 31 interacts via a plate pack with an outer plate carrier 39, which is connected to the differential case 25 in a rotationally fixed manner. The plate pack between the outer plate carrier 39 and the inner plate carrier 31 can be pressurized by an annular piston (not shown), whose horizontal stroke can be adjusted by a hydraulic cylinder to actuate the plate clutch 33 to a predetermined clutching degree. The plate clutch 33 is power-shiftable and can be controlled by slipping.

[0027] The core of the invention lies in the axially shortened geometry of the transmission 3 in the transverse direction y, which is axially shortened in the transverse direction y of the vehicle. The intermediate stage 7 is thus formed by two axially short spur gear stages 19, 20. The intermediate shaft 31 is Figure 2 The disc brake 57 extends in the vehicle transverse direction y on one side from the intermediate shaft and spur gear stage 19 (opposite the rotor shaft 5) toward the motor end face 51. Specifically, it extends while forming a structural space 53, which is delimited axially between the motor end face 51 and the intermediate shaft and spur gear stage 19 and radially between the intermediate shaft 13 and the outer transmission housing wall 55. A disc brake 57 is positioned in the installation space 53 and consists of an inner disc carrier 59 and an outer disc carrier 61, with a disc package interposed therebetween. The inner disc carrier 59 is arranged on the rotor shaft 5 in a rotationally fixed manner, while the outer disc carrier 61 is connected to the transmission housing wall 55 in a rotationally fixed manner.

[0028] exist Figure 3 The figure shows the axle in an operating situation in the drive mode during straight-ahead driving, in which a torque request is present, in which a drive torque M is applied to the right wheel HR. R Greater than the driving torque M applied to the left wheel HLL .

[0029] In order to meet the torque requirement, the total driving torque M an From Motor EM through Intermediate Level 7 to Figure 3 In the input gear 23 of the axle differential 9. Figure 3 In the operating condition shown, the right disk clutch 33 is closed to the extent that the clutch allows slip. On the other hand, the left disk clutch 33 is fully open. As a result, the total drive torque M at the input gear 23 is an is divided into the differential torque M which is directed to the axle differential 9 D and superimposed moment M U , the superimposed moment M U It is guided to the right flange shaft 27 through the right disk clutch 33 and the right transmission stage 28. In order to ensure that the driving torque flows to the right wheel HR through the right disk clutch 33, it is important that there is a speed difference between the input gear 23 of the axle differential 9 and the inner disk carrier 31, where the speed n of the input gear 23 is D Greater than the speed n of the inner disc support 31 IR It is also important that the speed n of the inner disc support 31 IR Greater than the speed n of the right wheel HR R This is for example in Figure 3 The conditions shown are achieved, namely

[0030] z2>z3

[0031] z4>z1

[0032] n L =n R =n D

[0033] n iR =n R ∙(z1∙z3) / (z2∙z4)

[0034] n iR <n D .

[0035] Figure 3 The differential torque M is guided from the input gear 23 to the differential case 25. D In the axle differential 9, the partial torque M is distributed between the two flange shafts 27 in a 50 / 50 distribution. DL The left flange shaft 27 is guided to the left wheel HL, and the same magnitude of the partial torque M DR The torque is then directed to the right wheel HR via the right flange shaft 27. The torque addition occurs on the sun gear 47 on the outside of the vehicle, where part of the torque M DR and superimposed moment MU Added together to form the driving torque M R , the driving torque M R Applied to the right wheel HR.

[0036] exist Figure 4 The operating situation in braking mode and when driving straight ahead with the vehicle dynamics control system is shown in FIG. 1 , in which a braking torque request is present, in which a braking torque M is applied to the right wheel HR. R Greater than the braking torque M applied to the left wheel HL L .

[0037] In order to meet the braking torque requirement, Figure 4 The left disc clutch 33 in the clutch is closed to the extent that the clutch allows slip. On the other hand, the right disc clutch 33 remains fully open. In this way, the following objectives are achieved: the braking torque M that can be applied to the right wheel HR R is completely introduced into the axle differential 9 (i.e. up to the axle bevel gear 67 of the right flange shaft 27). In addition, partial load paths L1, L2 are formed: the differential housing 25, the left disk clutch 33 and the left transmission stage 28 are integrated in the partial load path L1. The superimposed torque M U The load path L1 is directed to the sun gear 47 of the left transmission stage 28 on the outside of the vehicle. There, torque addition is performed, wherein the braking torque M applied by the left wheel HL L With the superimposed moment M U Added together to form the total moment M S , the total moment M S is guided into the axle differential 9 (ie to the axle bevel gear 65 ) on the left flange shaft 27 ). Braking torque M Br The energy is transferred via the partial load path L2 to the electric motor EM and recovered there.

[0038] Due to the 50 / 50 distribution in the axle differential 9 , the total torque M directed from the left flange shaft 27 into the axle differential 3 is S and the right braking torque M directed from the right flange shaft 27 to the axle differential 3 R have the same magnitude. Therefore, the braking torque M applied to the right side of the vehicle R Than the braking torque M applied to the left side of the vehicle L The superposition torque M generated on the left disc clutch 33 is large U .

[0039] In order to ensure that the torque flows from the differential housing 25 via the left disk clutch 33 and the left transmission stage 28 to the left flange shaft 27 in the load path L1, it is relevant that there is a speed difference between the differential housing 25 and the inner disk carrier 31, wherein the speed n of the differential housing 25 isD Greater than the speed n of the inner disc support 31 IL It is also important that the speed n of the inner disc support 31 IL Greater than the speed n of the left flange shaft 27 L This is in Figure 4 is achieved under the conditions shown, i.e.

[0040] z2>z3

[0041] z4>z1

[0042] n L =n R =n D

[0043] n iL =n R ∙(z1∙z3) / (z2∙z4)

[0044] n iR <n D .

[0045] Figure 5 To correspond to Figure 2 The diagram of FIG. 1 shows a second exemplary embodiment of the present invention. Figure 2 Different, in Figure 5 In the embodiment, the disc brake 57 acts directly on the differential housing 25 of the axle differential 9. Figure 5 In the embodiment, the inner disc support 59 of the disc brake 57 is connected to the differential housing 25 in a rotationally fixed manner, while the outer disc support 61 is connected to the transmission housing wall 55 in a rotationally fixed manner. In other respects, the further transmission structure and the functions achieved with the transmission 3 are similar to those of the reference transmission 3. Figure 2 、 Figure 3 and Figure 4 Same as described.

[0046] List of reference numerals:

[0047] 1 drive unit

[0048] 3 transmission

[0049] 5 rotor shaft

[0050] 7Intermediate

[0051] 8 Input side

[0052] 9-axle differential

[0053] 11Superposition transmission mechanism

[0054] 13 intermediate shaft

[0055] 15,17 fixed gear

[0056] 19,20 spur gear stages

[0057] 21 fixed gear

[0058] 23 Input gear

[0059] 25 differential housing

[0060] 27 flange shaft

[0061] 31 inner disc bracket

[0062] 33 disc clutch

[0063] 39 outer disc bracket

[0064] 41 Vehicle inner planetary gear

[0065] 29 Vehicle inner sun gear

[0066] 43 support shaft

[0067] 45 vehicle outer planetary gear

[0068] 47 Vehicle outer sun gear

[0069] 51 motor end side

[0070] 53 installation space

[0071] 55 Transmission housing wall

[0072] 57 disc brake

[0073] 59 inner disc bracket

[0074] 61 external disc bracket

[0075] 65 left shaft bevel gear

[0076] 67 left shaft bevel gear

[0077] n L ,n R Wheel speed

[0078] n D Differential case speed

[0079] n iR , n iL Speed of the disc clutch inner disc support 31

[0080] M an Total driving torque

[0081] M R Output torque / braking torque that can be applied to the right wheel

[0082] M LOutput torque / braking torque that can be applied to the left wheel

[0083] M D Differential torque

[0084] M U Superposition torque

[0085] M DL , M DR Partial torque

[0086] M S Total torque

[0087] Number of teeth from z1 to z4

Claims

1. A drive device for an axle of a two-wheel tread vehicle, the drive device comprising an axle differential (9), the input side (8) of the axle differential being drive-connected to an electric machine (EM) and the output side of the axle differential being output on a flange shaft (27) leading to two wheels (HL, HR), wherein: Each flange shaft (27) is assigned a superposition transmission (11), by means of which the electric machine (EM) can be connected directly to the flange shaft (27) while bridging the axle differential (9), wherein the superposition transmission (11) can be controlled by a control unit for torque redistribution between the wheels (HL, HR), in particular for braking torque redistribution during a recuperation operation of the electric machine (EM). It is characterized by: The axle is equipped with precisely one central disk brake (57) serving as a wheel brake, by means of which the vehicle can be braked.

2. The driving device according to claim 1, It is characterized by: The disc brake (57) is composed of an inner disc support (59), an outer disc support (61) and a disc assembly arranged therebetween.

3. The driving device according to claim 1 or 2, It is characterized by: The electric machine (EM) is indirectly or directly drive-connected with its rotor shaft (5) to the input side (8) of the axle differential (9), and in particular the disk brake (57) acts directly on the rotor shaft (5).

4. The driving device according to claim 3, It is characterized by: The inner disc support (59) is connected to the rotor shaft (5) in a rotationally fixed manner, while the outer disc support (61) is connected to the transmission housing wall (55) in a rotationally fixed manner.

5. A drive device according to any one of the preceding claims, It is characterized by: The rotor shaft (5) is connected to an intermediate shaft (13) via an intermediate stage (7), in particular an intermediate spur gear stage, the intermediate shaft (13) being oriented axially parallel to the rotor shaft (5) and / or the intermediate shaft (13) extending on one side from the intermediate stage (7) in the direction of the motor end side (51), in particular forming a disk brake installation space (53) between the motor end side (51), the intermediate stage (7) and the intermediate shaft (13) as well as the rotor shaft (5).

6. A drive device according to any one of the preceding claims, It is characterized by: The electric machine (EM) is mounted transversely in the axle so that the rotor shaft (5) is oriented axially parallel to the flange shaft (27).

7. A drive device according to any one of the preceding claims, It is characterized by: The input side (8) of the axle differential (9) has an input gear (23) which is connected to the differential housing (25) in a rotationally fixed manner, and in particular the intermediate shaft (13) is connected to the differential housing (25) in a driving manner via a spur gear stage (20), which preferably consists of a fixed gear (21) formed on the intermediate shaft (13) and an input gear (23) of the differential housing (25) which meshes with the fixed gear.

8. A drive device according to any one of the preceding claims, It is characterized by: The disc brake (57) acts directly on the differential housing (25) of the axle differential (9).

9. The driving device according to claim 8, It is characterized by: The inner disc support (59) is connected to the differential housing (25) in a rotationally fixed manner, and the outer disc support (61) is connected to the transmission housing wall (55) in a rotationally fixed manner.

10. A drive device according to any one of the preceding claims, It is characterized by: Disc brakes (57) are used as a replacement for conventional wheel brakes on axles.

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