Electric portal axle for the electric drive of a motor vehicle

Abstract

Electric portal axle (1) for the electric drive of a motor vehicle, with two spur gear stages (13, 14) for driving two wheels of the axle, wherein the portal axle (1) has a single electric machine (2) to which a transmission (5) and a differential (7) are arranged, and wherein the portal axle (1) further comprises a housing (28), characterized by the fact that the transmission (5) is a switchable transmission (5) with freewheel (6), the switchable transmission (5) is designed as a planetary gear set, and for switching two gear stages of the portal axle (1) the latter has a switching means (23), wherein in a first gear stage a ring gear (9) of the transmission (5) and a housing-fixed clutch body (27) are connected and a clutch (29) which is arranged between the ring gear (9) and a planet carrier (11) of the transmission (5) is open, and wherein in a second gear stage the ring gear (9) and the housing-fixed clutch body (27) are separated and the clutch (29) is closed, the clutch (29) is designed as a friction-fit clutch, wherein the clutch (29) is arranged between the switching means (23) which is connected to the ring gear (9) in a torque-transmitting manner and the planet carrier (11).

Description

[0001] The invention relates to an electric portal axle for the electric drive of a motor vehicle, with two spur gear stages for driving two wheels of the axle.

[0002] Such an electric portal axle is known from DE 10 2009 036 299 A1. This portal axle has two electric motors, with a wheel rotatably mounted at each end of the portal axle, and each wheel being driven by a rotor of its associated electric motor. A reduction gear, designed as a spur gear stage, is arranged between each electric motor and its associated wheel. The input shaft of each spur gear stage is located closer to the ground on which the vehicle stands than the output shaft of the spur gear stage. Consequently, the area between the spur gear stages is lowered, so that the electric motors are lowered relative to the underbody of the vehicle, resulting in a lowering of the vehicle's center of gravity.

[0003] An electric portal axle can also be designed in such a way that the area between the spur gear stages is not lowered, but raised, so that the vehicle can be used particularly well off-road.

[0004] Electrically powered vehicles having portal frames are also known from US 6 843 750 B1, US 6 978 853 B2 and US 7 350 602 B2.

[0005] DE 10 2010 050 217 A1 discloses an electric axle for the electric drive of a motor vehicle, comprising an electric machine with an output shaft and a switchable transmission and a differential. The switchable transmission is designed as a planetary gear set, with the portal axle having a switching device for switching between two gear stages.

[0006] DE 42 12 324 A1 discloses a drive device with an electric motor and a gearbox. The gearbox has spur gears and a freewheel in the area of ​​a spur gear designed as a loose gear.

[0007] DE 10 2010 017 966 A1 discloses an electric portal axle according to the preamble of claim 1.

[0008] DE 10 2011 007 262 A1 discloses further state of the art.

[0009] The object of the present invention is to create a two-stage switchable electric portal axle for the electric drive of a motor vehicle.

[0010] The problem is solved by an electric portal axis which has the features of claim 1.

[0011] The portal axle according to the invention comprises a single electric motor and a switchable transmission with freewheel and differential. The transmission with freewheel and differential is arranged downstream of the single electric motor. Furthermore, the portal axle has two spur gear stages for driving the two wheels of the axle, as well as a housing. The switchable transmission is designed as a planetary gear set. The portal axle has a shifting device for shifting between two gear stages. In a first gear stage, a ring gear of the planetary gear set and a housing-mounted clutch body are connected, and a clutch between the ring gear and a planet carrier of the planetary gear set is open. In a second gear stage, the ring gear and the housing-mounted clutch body are disengaged, and the clutch is closed.

[0012] The clutch is designed as a friction-based clutch and is positioned between the shift element, which is connected to the ring gear for torque transmission, and the planet carrier. This allows for a very compact design. Preferably, the clutch is designed as a multi-plate clutch.

[0013] It is particularly advantageous if, during the shifting process, the electric motor's power is transmitted via the freewheel, and after the clutch engages, the freewheel is disengaged and the electric motor's power is transmitted via the clutch. Consequently, the electric portal axle enables a load-shiftable 2-speed transmission.

[0014] The portal axle is designed such that, in the first gear stage, the ring gear is fixed to the housing in the pulling direction via the freewheel and in the pushing direction via the clutch body. In the second gear stage, the ring gear is preferably disengaged from the clutch body, the clutch is engaged, and the freewheel is disengaged.

[0015] From the perspective of optimal power flow, the planetary gear system is designed so that the output is transmitted via the planet carrier to the differential.

[0016] The switching element is, in particular, a switching sleeve. This preferably also serves as the outer plate carrier of the multi-plate clutch.

[0017] The electric portal axle is preferably designed such that the single electric motor, the planetary gear set, the freewheel, the differential, and the two spur gear stages are arranged within a common housing. Consequently, the electric portal axle constitutes a single unit.

[0018] The wheels of the axle can preferably be driven via cardan shafts using the electric portal axle.

[0019] The invention thus proposes a load-shiftable 2-speed gearbox in planetary-spur gear design for an electric portal axle, enabling a purely electric drive in a portal design. Shifting is achieved via a single actuator – the switching device. The electric motor can recuperate energy in both gears. Compared to 1-speed versions, the construction effort is only slightly increased. Overall, the portal axle according to the invention is characterized by a very compact design. This 2-speed concept represents optimized performance and efficiency compared to 1-speed concepts.

[0020] 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. It shows: Fig. 1. A schematic diagram of the electric portal axle for the electric drive of a motor vehicle, Fig. 2 which according to the principle Fig. 1 working electric portal axis, Fig. 3 concerning the representation of the electric portal axis according to Fig. 2, whose switching range is shown in an enlarged view, Fig. Figure 4 shows a schematic diagram of the area of ​​the electric portal axle showing the circuitry of the electric portal axle, illustrated for the switched first gear stage. Fig. 5 the schematic diagram according to Fig. 4, illustrated for the shifting process from first gear to second gear, Fig. 6 the schematic diagram according to the Fig. 4 and Fig. 5, illustrated for the engaged second gear.

[0021] Fig. Figure 1 shows the basic structure of the electric portal axle 1 for the electric drive of a motor vehicle. The portal axle 1 has a single electric motor 2, which is installed transversely to the vehicle. A stator of the electric motor 2 is designated by reference numeral 3, and a rotor of the electric motor 2 by reference numeral 4. A switchable planetary gear 5 with a freewheel 6 and a differential 7 is connected to the electric motor 2. Regarding the planetary gear 5, an inner sun gear 8, an outer ring gear 9, and planet gears 10 meshing with the sun gear 8 and ring gear 9 are illustrated. The planet gears 10 are mounted in a planet carrier 11. The sun gear 8 is non-rotatably connected to a rotor-side output shaft 12 of the electric motor 2. The ring gear 9 interacts with the freewheel 6.

[0022] The planet carrier 11 interacts with the differential 7. The right and left sides of the output are connected via this differential 7. A spur gear stage 13 or 14 is provided on each output side. The spur gear stage 13 located on the right output side is connected to a differential-side output shaft 16 in the area of ​​a gear 15 of relatively small diameter. A gear 17 of the spur gear stage 13 meshes with the gear 15. This gear 17 is rotationally fixed to an output shaft 18 and has a larger diameter than the gear 15. A driveshaft, which is rotationally fixed to the output shaft 18 and drives a wheel (also not shown) on the right side of the vehicle, is not shown.

[0023] On the side of the differential 7 opposite the output shaft 16 for the spur gear stage 13, an output shaft 19 for the left spur gear stage 14 is arranged. This differential-side output shaft 19 passes through the output shaft 12, which is connected to the rotor 4 of the electric machine 2. The left spur gear stage 14 is designed in accordance with the configuration of the right spur gear stage 13 and thus has a smaller gear 20, a larger gear 21 meshing with it, and an output shaft 22. The output shaft 22 interacts with a driveshaft (not shown) that drives the wheel on the left side of this axle.

[0024] The spur gear stages, designed as reduction gears, allow the electric motor to be lowered relative to the underbody of the vehicle, thus lowering the vehicle's center of gravity.

[0025] The electric portal axle 1 has a switching device, designed as a switching sleeve 23, for switching between two gear stages of the portal axle 1. A switching actuator 24 serves to switch the switching sleeve 23 in the axial direction of the output shaft 12 of the electric machine 2. The switching sleeve 23 has a sliding projection 25 in the region of its end facing the ring gear 9, which interacts with a guide sleeve 26 arranged on the outer radial circumference of the ring gear 9, such that the switching sleeve 23, and thus the sliding projection 25, is axially displaceable relative to the ring gear 9, but rotationally fixed to it. In the region of the end facing away from the ring gear 9, the switching sleeve 23 can be connected to a coupling body 27, which is rigidly connected to a housing 28 of the portal axle 1.Furthermore, a clutch 29, which is designed as a multi-plate clutch, is arranged between the ring gear 9, specifically the shift sleeve 23 which is connected to the ring gear 9 in a torque-transmitting manner, and the planet carrier 11.

[0026] Fig. 2 illustrates the in Fig. The components of the electric portal axis 1 shown in the schematic diagram are depicted in a specific embodiment. In this respect, the Fig. 2 the components which are related to those according to Fig. 1, designated with the same reference numerals. In particular, the ring gear 9 with guide sleeve 26 and backstop, which forms the freewheel 6, and the shift sleeve 23 including the outer plates 30 of the clutch 29 are illustrated. Furthermore, the planet carrier 11 including the inner plates 31 of the clutch 29 and the input of the differential 7 are shown. Finally, the clutch body 27, which is fixed to the housing, including backlash control, is illustrated.

[0027] Fig. Figure 3 shows the actual switching range of the electric portal axis 1 according to Fig. 2 in an enlarged view.

[0028] The Fig. Figures 4 to 6 show the different switching states of the portal axle, which can be switched in two gear stages: Fig. Figure 4 illustrates the shift state in first gear. In this state, the ring gear 9 of the planetary gear set 5 and the housing-mounted clutch body 27 are rigidly connected, with the clutch 29 open. The gear ratio is determined by the planetary gear set 5. In the pulling direction, the ring gear 9 is fixed to the housing via the freewheel 6, and in the pushing direction via the clutch body 27. This allows for recuperation in the pushing direction. The output is via the planet carrier 11 to the differential 7, and from there via the output shaft 16 to the spur gear stage 13, and via the output shaft 19 to the spur gear stage 14. The wheels of the axle are driven via the spur gear stages 13 and 14.

[0029] Fig. Figure 5 illustrates the shifting process when shifting from first to second gear. Here, the connection between the ring gear 9 and the clutch body 27 is disengaged via the shift actuator 24. The drive torque is transmitted via the freewheel 6. The clutch 29 is engaged, with the kiss point of the clutch 29 being frictionally engaged as its outer and inner plates approach each other. The clutch 29 is frictionally engaged, thereby overriding the freewheel 6. This occurs when the speed of the electric motor 2 is adjusted. Power is then frictionally transmitted via the clutch 29.

[0030] Fig.Figure 6 illustrates the state when second gear is engaged. Here, the ring gear 9 is disengaged from the clutch body 27, and the clutch 29 is frictionally engaged between the ring gear 9 and the planet carrier 11. The freewheel 6 is disengaged because an inner ring of the freewheel overrides an outer ring of the freewheel. Recuperation is possible in this second gear. The output is via the planet carrier 11 to the differential 7.

[0031] An electric portal axle 1 for the electric drive of a motor vehicle is thus proposed, in which, during the shifting process, the power of the electric motor 2 is transmitted via the freewheel 6, and after the clutch 29 is engaged, the freewheel 6 is disengaged and the power of the electric motor 2 is transmitted via the clutch 29. In the first gear stage, the ring gear 9 is fixed to the housing in the pulling direction via the freewheel 6 and in the pushing direction via the clutch body 27. In the second gear stage, the ring gear 9 is disengaged from the clutch body 27, the clutch 29 is engaged, and the freewheel 6 is disengaged. The shift actuator 24 serves to axially displace the shifting element 23 or the shift sleeve 23. The shifting element 23 can be fixed with respect to rotation by means of the clutch body 27, and the shifting element 23 is fixed with respect to rotation within the ring gear 9 and is axially displaceable relative to the ring gear 9.

[0032] The electric machine 2, the planetary gear 5, the freewheel 6, the differential 7 and the two spur gear stages 13, 14 are arranged within the common housing 28.

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