Axle drive of a vehicle with an electric machine

Abstract

The invention relates to an axle drive for a vehicle (1), comprising an electric motor (2), a drive shaft (3), an intermediate shaft (4) arranged axially parallel to the drive shaft (3), and output shafts arranged axially parallel to the drive shaft (3) and the intermediate shaft (4) for driving vehicle wheels. The drive shaft (3) is connectable to the intermediate shaft (4) via a switchable spur gear (6), the intermediate shaft (4) is connected via at least one planetary gear (13) to an output differential (14) for driving the output shafts, and a lockable parking lock shaft (8) is arranged coaxially to the intermediate shaft (4) and is connected to the intermediate shaft (4) in a rotationally fixed manner. A vehicle (1) having at least one electric axle drive is also proposed.

Description

The present invention relates to an axle drive of a vehicle, having an electric machine, having a drive shaft, having an intermediate shaft arranged axially parallel to the drive shaft and having output shafts arranged axially parallel to the drive shaft and to the intermediate shaft for driving vehicle wheels, wherein the drive shaft can be connected to the intermediate shaft via a shiftable spur gear mechanism, and wherein the intermediate shaft is connected to an output differential for driving the output shafts via at least one planetary gear mechanism.Such a final drive is known, for example, from the publication DE 11 2017 002 206 T5.The present invention is based on the object of further improving a final drive described at the beginning and a vehicle with the final drive.This object is achieved according to the invention by the features of patent claims 1 and 11. Advantageous and claimed developments are evident from the dependent claims and the description and the drawings.Thus, an electric final drive of a vehicle, having an electric machine, having a drive shaft, having an intermediate shaft arranged axially parallel to the drive shaft and having output shafts arranged axially parallel to the drive shaft and to the intermediate shaft for driving vehicle wheels, is proposed, wherein the drive shaft can be connected to the intermediate shaft via a shiftable spur gear transmission, and wherein the intermediate shaft is connected to an output differential for driving the output shafts via at least one planetary gear transmission. In order to further improve the proposed electric final drive, it is provided that a fixable parking lock shaft is arranged coaxially to the intermediate shaft and connected to the intermediate shaft in a rotationally fixed manner.In this way, a very compactly constructed final drive with an electric machine of, for example, a high-speed, parallel-axis design is realized, wherein the final drive realizes a plurality of gear stages via the shiftable spur gear transmission and transmits them via the intermediate shaft and the planetary gear to the output differential, wherein a parking lock shaft is provided in the intermediate shaft for the advantageous integration of the parking lock function, whereby advantages result not only with regard to costs but also with regard to the required installation space in the proposed final drive. In addition, the advantage results that, due to the positioning of the parking lock shaft between the output shaft or the output shafts on the one hand and the shiftable spur gear transmission on the intermediate shaft on the other hand, a permanent connection of the parking lock shaft to the vehicle wheels is ensured.An arrangement which is particularly advantageous in terms of installation space is realized in the proposed final drive in that the intermediate shaft is designed as a hollow shaft, wherein the parking lock shaft is arranged in the interior of the hollow shaft. This results in a particularly space-saving arrangement in the proposed final drive.In particular in the case of electric machines rotating up, a high transmission ratio in the first gear results due to the low torque, as a result of which high engaging rotational speeds can also result when the parking lock is engaged. These high engaging rotational speeds can lead to undesired torque impacts during the engagement of the parking lock because of the high torques occurring between the drive shaft of the electric machine and the parking lock. In order to prevent these undesired loads without additional components and additional installation space, it is provided that the parking lock shaft is designed at least in sections as a torsion spring or the like. Due to this soft connection of the parking lock shaft, loads are absorbed by the parking lock shaft designed as a torsion spring and possible torque impacts are advantageously reduced or minimized. Depending on the loads occurring, in the proposed final drive the parking lock shaft can be designed as a torsion spring over its entire length or only in sections.In order to realize the rotationally fixed connection between the parking lock shaft and the intermediate shaft in a manner as simple and easy to assemble as possible, it is provided that the rotationally fixed connection between the parking lock shaft and the intermediate shaft is designed as a spline or the like.In the embodiment of a spline as a rotationally fixed connection between the parking lock shaft and the intermediate shaft, it is particularly advantageous if the spline has axial passages, openings or the like for the oil passage, and the intermediate shaft has at least one radial bore for the oil supply of the shiftable spur gear transmission. In this way, an engine-side oil supply can be implemented in a structurally simple manner by the parking lock shaft and the intermediate shaft. The passages or openings can be realized particularly cost-effectively by removing some teeth of the spline.In order to realize a particularly structurally simple transmission-side oil supply through the parking lock shaft and the intermediate shaft, it is provided in the proposed final drive that the parking lock shaft has an axial bore and a radial bore for oil passage and that the intermediate shaft has a radial bore for oil supply of the shiftable spur gear transmission.A particularly structurally simple and cost-effective shift without required synchronizing elements is realized in the proposed final drive in that the shiftable spur gear transmission comprises a first spur gear stage with a first fixed gear of the drive shaft and with a first loose gear of the intermediate shaft as well as a second spur gear stage with a second fixed gear of the drive shaft and a second loose gear of the intermediate shaft, wherein a claw shift with several shift positions is assigned to the loose gears of the intermediate shaft for connection to the intermediate shaft in a rotationally fixed manner.However, another construction of the shiftable spur gear transmission is also conceivable. The prescribed arrangement of the spur gear with the claw gear with the idler gears arranged on the intermediate shaft, however, has the advantage that high rotational speeds on the idler gears are prevented compared with a positioning of the idler gears on the drive shaft. In addition, in the above-described positive dog shift, various shift positions and a neutral position can be realized, so that in the neutral position, speed adjustment for synchronization can be performed via the electric machine. Decoupling the drive from the output shafts is also advantageous, for example, when towing the vehicle or for saving energy in all-wheel drive vehicles (so-called disconnect function).The intermediate shaft can preferably be connected to an element of the planetary gear set via a transmission stage, in particular via a spur gear stage, wherein an element of the planetary gear set is connected to the output differential. On the one hand, the axial offset between the intermediate shaft and the output shafts is thus bridged and, on the other hand, a pretransmission for the planetary transmission is advantageously provided via the spur gear stage, which leads to a particularly high torque density with a small radial installation space requirement in the region of the output shafts.The object on which the invention is based is also achieved by a vehicle having at least one electric final drive described above, with the result that the advantages already described and further advantages are obtained.The invention is explained in more detail below with reference to the drawings.The following are shown: FIG. 1 shows a sectional view of a possible embodiment of an electric final drive according to the invention of a vehicle; FIG. 2 shows a sectional view of an intermediate shaft with a parking lock shaft of the final drive arranged in the interior of the intermediate shaft, with an oil feed on the motor side; FIG. 3 is a cross-sectional view of the intermediate shaft connected to the parking lock shaft via a spline, with axial passages for oil supply; and FIG. 4 shows a sectional view of the intermediate shaft with the parking lock shaft arranged in the interior of the intermediate shaft with an oil feed on the transmission side.FIGS. 1 to 4 show various views of an electric final drive according to the invention of a vehicle 1 by way of example.The electric final drive illustrated in FIG. 1 comprises an electric machine 2 having a drive shaft 3 and having an intermediate shaft 4 arranged axially parallel to the drive shaft 3. The intermediate shaft 4 is connected via a spur gear stage 12 to a sun gear as element of a planetary gear set 13, wherein a planetary gear carrier as element of the planetary gear set 13 is connected to an output differential 14 and wherein a ring gear as element of the planetary gear set 13 is fixed on the housing side. The output shafts arranged axially parallel to the drive shaft 3 and to the intermediate shaft 4 are driven via the output differential 14 for driving vehicle wheels, not shown in greater detail, wherein the output shafts are schematically indicated merely by an output shaft axis 5.The drive shaft 3 driven by the electric machine 2 can be connected to the intermediate shaft 4 via a spur gear transmission 6 with a claw connection 7. The intermediate shaft 4 is designed as a hollow shaft in which a parking lock shaft 8 is arranged coaxially with the intermediate shaft 4. The parking lock shaft 8 is connected in a rotationally fixed manner to the intermediate shaft 4 via a spline 9.In order to avoid undesirable torque impacts when engaging a locking pawl 10 on the housing into a parking lock wheel 11 connected to the parking lock shaft 8 in a rotationally fixed manner, the parking lock shaft 8 is designed at least in sections as a torsion spring. The parking lock gear 11 is arranged at a first end of the parking lock shaft 8, while the spline 9 for rotationally fixed connection to the intermediate shaft 4 is arranged at a second end of the parking lock shaft 8 opposite the first end. In this way, a torque shock occurring on the motor side or also on the output side can be absorbed over its entire length via the spline 9 by the parking lock shaft 8 designed as a torsion spring. Due to the torsionally flexible design of the parking lock shaft 8, both the parking lock mechanism and the transmission components are protected against unnecessary loads when the parking lock is engaged.The spur gear transmission 6 comprises a first spur gear stage and a second spur gear stage, wherein the first spur gear stage comprises a first fixed gear 15 on the drive shaft 3, which is in engagement with a first loose gear 16 of the first spur gear stage on the intermediate shaft 4. The second spur gear stage comprises a second fixed gear 17 on the drive shaft 3, which is in engagement with a second loose gear 18 of the second spur gear stage on the intermediate shaft 4. The pawl circuit 7 comprises a switching pawl which is movable between three switching positions axially on the intermediate shaft 4. In a shift position shifted to the left in the drawing plane, the first loose wheel 16 is connected to the intermediate shaft 4 in a rotationally fixed manner in order to realize a second gear stage having an exemplary transmission ratio i equal to 16. In the middle shift position shown, the claw circuit 7 is in a neutral position, so that the intermediate shaft 4 is decoupled from the drive shaft 3. In a shift position shifted to the right in the drawing plane, the second idler gear 18 is connected to the intermediate shaft 4 in a rotationally fixed manner in order to realize a first gear stage having an exemplary transmission ratio i equal to 31.FIG. 2 shows, by way of example, an engine-side oil feed via the parking lock shaft 8 and the intermediate shaft 4 for the spur gear transmission 6 by means of a plurality of arrows. For this purpose, the oil is supplied on the motor side via a feed hopper 19 axially on the spline 9 between the parking lock shaft 8 and the intermediate shaft 4. For this purpose, the spline 9 has a plurality of axial passages 20 through, for example, missing teeth of the spline 9, as is indicated, for example, in FIG. 3. The oil is guided axially through the axial passages 20 in the interior space formed between the parking lock shaft 8 and the intermediate shaft 4 until the oil reaches radial bores 21 on the intermediate shaft 4 and is fed through the radial bores 21 to bearings of the spur gear transmission 6.In FIG. 4, an oil supply on the transmission side via the parking lock shaft 8 and the intermediate shaft 4 for the spur gear transmission 6 is indicated by means of a plurality of arrows by way of example. For this purpose, the oil is supplied on the axial side to an axial bore 22 of the parking lock shaft 8. The axial bore 22 is adjoined by a transversely running radial bore 23 of the parking lock shaft 8, through which the oil is continued until the oil reaches the radial bores 21 on the intermediate shaft 4 and is fed through the radial bores 21 to bearings of the spur gear transmission 6.For mounting the proposed final drive, according to FIG. 1, two rotor shaft bearings L 1, L 2 are provided on both sides in the housing in the electric machine. The drive shaft 3 is connected to the rotor shaft in a rotationally fixed manner and is supported at the second rotor shaft bearing L 2 as well, so that a drive shaft bearing L 3 of smaller dimensions on the left in the drawing plane and a drive shaft bearing L 4 of larger dimensions are sufficient for the drive shaft 3. The intermediate shaft 4 is supported in the drawing plane via a left intermediate shaft bearing L 5 and a right intermediate shaft bearing L 6. The parking lock shaft 8 arranged in the interior of the intermediate shaft 4 advantageously has a right parking lock bearing L 7 and only one centering seat 23, so that an additional parking lock shaft bearing can be dispensed with. The two idler gears 16, 18 on the intermediate shaft 4 are rotatably mounted on the intermediate shaft 4 via associated idler bearings. The spur gear stage 12 connected to the intermediate shaft 4 in a rotationally fixed manner has a left spur gear bearing L 8 and a right spur gear bearing L 9. The ring gear of the planetary gear set 13 connected to the housing is connected to the housing via a spline. The planetary gear set 13 comprises a planet carrier bearing L 10, two planet bearings L 11, L 12 and an axial bearing L 13 on the sun shaft, wherein the output differential 14 comprises a differential bearing L 14.Reference numerals denote reference numerals1 Vehicle 2 Electric machine 3 Drive shaft 4 Intermediate shaft or countershaft 5 Output shaft axis 6 Spur gear transmission 7 Claw gear 8 Parking lock shaft 9 Spline toothing 10 Pawl 11 Parking lock gear 12 Spur gear stage 13 Planetary gear 14 Output differential 15 First fixed gear 16 First loose gear 17 Second fixed gear 18 Second loose gear 19 Feed funnel 20 Axial passages 21 Radial bore of the intermediate shaft 22 Axial bore of the parking lock shaft 23 Radial bore of the parking lock shaft L 1 Rotor shaft bearing L 2 Rotor shaft bearing L 3 Drive shaft bearing L 4 Drive shaft bearing L 5 Intermediate shaft bearing L 6 Intermediate shaft bearing L 7 Parking lock bearing L 8 Spur gear bearing L 9 Spur gear bearing L 10 Planetary gear carrier bearing L 11 Planetary bearing L 12 Planetary bearing L 13 Axial bearing L 14 Differential bearingReferences 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 citedDE 11 2017 002 206 T5

[0002]

Claims

Final drive of a vehicle (1), having an electric machine (2), having an input shaft (3), having an intermediate shaft (4) arranged axially parallel to the input shaft (3) and having output shafts arranged axially parallel to the input shaft (3) and to the intermediate shaft (4) for driving vehicle wheels, wherein the input shaft (3) can be connected to the intermediate shaft (4) via a shiftable spur gear transmission (6), and wherein the intermediate shaft (4) is connected via at least one planetary gear transmission (13) to an output differential (14) for driving the output shafts, characterized in that a fixable parking lock shaft (8) is arranged coaxially to the intermediate shaft (4) and is connected rotationally fixedly to the intermediate shaft (4).Final drive according to Claim 1, characterized in that the intermediate shaft (4) is designed as a hollow shaft, the parking lock shaft (8) being arranged in the interior of the hollow shaft.Final drive according to Claim 1 or 2, characterized in that the parking lock shaft (8) is designed at least in sections as a torsion spring.Final drive according to one of the preceding claims, characterized in that a parking ratchet wheel (11) which can be fixed on the housing side via a pawl (10) is arranged on a first end of the parking ratchet shaft (8) in a rotationally fixed manner, and in that the rotationally fixed connection to the intermediate shaft (4) is provided on a second end of the parking ratchet shaft (8).Final drive according to one of the preceding claims, characterized in that the rotationally fixed connection between the parking lock shaft (8) and the intermediate shaft (4) is designed as a spline (9).Final drive according to Claim 5, characterized in that the spline toothing (9) between the parking lock shaft (8) and the intermediate shaft (4) has axial passages (20) for oil passage, the intermediate shaft (4) having at least one radial bore (21) for supplying oil to the shiftable spur gear transmission (6).Final drive according to one of the preceding claims, characterized in that the parking lock shaft (8) has at least one axial bore (22) and at least one radial bore (23) for oil passage, and in that the intermediate shaft (4) has at least one radial bore (21) for supplying oil to the shiftable spur gear transmission (6).Final drive according to one of the preceding claims, characterized in that the shiftable spur gear transmission (6) comprises a first spur gear stage with a first fixed gear (15) of the drive shaft (3) and with a first loose gear (16) of the intermediate shaft (4) as well as a second spur gear stage with a second fixed gear (17) of the drive shaft (3) and a second loose gear (18) of the intermediate shaft (4), wherein a claw shift (7) with several shift positions is assigned to the loose gears (16, 18) of the intermediate shaft (4) for connection to the intermediate shaft (4) in a rotationally fixed manner.Final drive according to Claim 8, characterized in that the claw shift (7) comprises a first shift position as the first gear stage, a second shift position as the neutral position and a third shift position as the second gear stage.Final drive according to one of the preceding claims, characterized in that the intermediate shaft (4) is connected via a spur gear stage (12) to an element of the planetary gear set (13), and in that an element of the planetary gear set (13) is connected to the output differential (14).Vehicle (1) having at least one electric final drive according to one of the preceding claims.

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