Gearbox arrangement with stepped planetary reducer, differential and electrically operable axle drive train

Abstract

The invention relates to a gearbox arrangement (1) comprising a planetary gearbox (4) which can be coupled to a first input shaft (5) and a differential (6) which can be coupled to a first output shaft (7) and to a second output shaft (8), the planetary gearbox (4) comprising a first sun gear (9) and a plurality of stepped planetary gears (11) which are in engagement with the first sun gear (9) and which are in each case rotatably mounted on a first planetary gear carrier (10) on a planetary gear shaft (15), each having a first set of teeth (12) and a second set of teeth (13) which move in rotation around the first sun gear (9), and a differential (6) which is arranged coaxially with respect to the first sun gear (9) and on which the planetary gears (11) roll. the planetary gear shafts (15) are each coupled to a differential balance shaft (16) of the differential (6), a first balance wheel (17) is rotatably mounted on each of the differential balance shafts (16) and in each case engages a first sun gear (18) which can be coupled to a first output shaft (7), the first balance wheel (17) further meshes with a second balance wheel (19) which in turn engages a second sun gear (20) which can be coupled to a second output shaft (8), the planetary gear shafts (15) being arranged in phase with the corresponding differential balance shafts (16).

Description

[Technical field]

[0001] The present invention relates to a transmission device for an electrically operable axle drive train of a motor vehicle, comprising a planetary transmission which can be coupled to a first drive shaft, and a differential which can be coupled to a first output shaft and to a second output shaft, the planetary transmission comprising a first sun gear, a plurality of stepped planetary gears which engage with the first sun gear and on the planetary gear shaft, in each case having a first toothing and a second toothing which are rotatably mounted on a first planetary gear carrier and which move in rotation around the first sun gear, and a ring gear which is arranged coaxially with respect to the first sun gear and on which the planetary gears roll, the first toothing being in engagement with the first sun gear. On the other hand, a second toothing having a pitch diameter smaller than the pitch diameter of the first toothing meshes with the ring gear, the planetary gear shafts are each coupled to a differential balance shaft of a differential, the first pinion gear in each case engages with a first sun gear which is rotatably arranged on the differential balance shaft and which in each case can be coupled to a first output shaft, the first pinion gear further meshes with a second pinion gear which in turn engages with a second sun gear which can be coupled to a second output shaft, the first sun gear having a tip diameter smaller than the root diameter of the second sun gear, both sun gears having the same number of teeth. The invention further relates to an electrically operable axle drive train. [Background technology]

[0002] Electric motors are increasingly being used to drive motor vehicles, creating an alternative to fossil fuel-dependent internal combustion engines. A great deal of effort has already been made to improve the suitability of electric drives for everyday use and to enable them to provide the comfortable driving to which users are accustomed.

[0003] A detailed description of an electric drive unit can be found in the article "Hochintegrativ und flexibel - Elektrische Antriebseinheit fur E-Fahrzeuge" [Highly Integrative and Flexible - Electric Drive Unit for Electric Vehicles] by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold in the German automotive magazine ATZ, volume 113 (May 2011), pages 360-365, which is probably the closest prior art. The article describes a drive unit for vehicle axles, which comprises an electric motor arranged concentrically and coaxially with a bevel gear differential, and a shiftable two-speed planetary gear set is arranged in the power train between the electric motor and the bevel gear differential and is further positioned coaxially with the electric motor or the bevel gear differential or the spur gear differential. This drive unit is very compact and, due to the shiftable two-speed planetary gear set, offers a good compromise between gradeability, acceleration and energy consumption. Such drive units are also called e-axles or electric drivetrains.

[0004] DE 102010048837 A1 discloses a drive device having at least one electric motor and at least one planetary differential that can be driven by the rotor of the electric motor, the planetary differential having at least one planet carrier operatively connected to the rotor of the electric motor, first and second planetary gears rotatably mounted on the planet carrier, and first and second sun gears each operatively connected to an output shaft of the planetary differential. In this regard, the first planetary gear engages with the first sun gear, and each of the second planetary gears engages with the second sun gear and one of the first planetary gears. Furthermore, the sun gear is arranged coaxially with the rotation axis of the rotor.

[0005] DE 10 2018 128 835 A1 shows a transmission device for a motor vehicle and a drive device which has such a transmission device.

[0006] DE 10 2015214 035 A1 shows an electronic drive unit for a motor vehicle with an electric motor and a transmission connected to the electric motor, the transmission having a transmission input stage and a differential connected to the transmission input stage via a common planet carrier, the differential having a first planetary set and a second planetary set, the first planetary set meshing with a first sun and the second planetary set meshing with a second sun, and the two planetary sets of the differential meshing with each other in pairs.

[0007] US Pat. No. 9,829,084 shows an integrated gear assembly that includes an integrated carrier assembly that couples a reduction gear set to a differential gear set.

[0008] There is a continuing need to configure such e-axles in a manner that is particularly compact and at the same time has a high power density. There is also a continuing need for such e-axles to be particularly easy to assemble. Summary of the Invention [Problem to be solved by the invention]

[0009] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to provide an improved transmission arrangement for an electrically operable axle drivetrain of a motor vehicle. [Means for solving the problem]

[0010] This object is achieved by a device according to claim 1. Further developments of the device are the subject matter of the dependent claims.

[0011] This achieves the advantage that the pinion gears of the differential gear are arranged in phase with, but not coaxially with, the stepped planetary gears of the planetary transmission, which makes it possible to achieve a particularly compact construction of the transmission arrangement. Moreover, this also improves the ease of assembly of the transmission arrangement, in particular since the ring gear can be easily slid onto the differential and thus mounted separately, which will be considered in more detail below.

[0012] Individual elements of the claimed subject matter of the present invention will be described first in the order in which they appear in the claims, followed by a description of particularly preferred embodiments of the present subject matter.

[0013] The transmission device is intended in particular for use in an electrically operable axle drive train of a motor vehicle. The electrically operable drive train comprises an electric machine and a transmission device according to the invention, which is preferably coupled to the electric machine. The transmission device and the electric machine form a structural unit. This can be formed, for example, by a drive train housing in which the transmission device and the electric machine are accommodated together.

[0014] The electric machine preferably has a motor housing and / or the transmission has a transmission housing, and the structural unit can be implemented by fixing the transmission to the electric machine. The transmission housing is a housing for accommodating the transmission. It has the task of guiding the existing shaft through bearings and giving the wheels (and cam discs, if applicable) the freedom they require under all loads without interfering with their rotation and possible path movements, as well as absorbing the bearing forces and support torques. The transmission housing can be configured as a single shell or as a multi-shell, i.e. as undivided or divided. In particular, the transmission housing must be able to damp noise and vibrations as well as safely absorb hydraulic fluids. The transmission housing is preferably formed from a metallic material, particularly preferably from aluminum, grey cast iron or cast steel, in particular by a primary forming process such as casting or die casting.

[0015] The motor housing encloses the electric machine. It may also house the control and power electronics. The motor housing may further be part of the cooling system of the electric machine and may be configured such that hydraulic fluid may be supplied to the electric machine via the motor housing and / or that heat may be dissipated to the outside via the housing surface. Furthermore, the motor housing protects the electric machine and any electronics that may be present from external influences.

[0016] The motor housing may in particular be made from a metallic material, and advantageously from a metal casting material such as die-cast aluminium, die-cast magnesium, grey cast iron or cast steel.

[0017] Electric machines are used to convert electrical energy into mechanical energy and / or vice versa and generally comprise a fixed part called a stator, stand or armature and a part called a rotor or runner, which is arranged to be movable, in particular rotatable, relative to the fixed part. Electric machines can be configured as radial flux machines or axial flux machines.

[0018] In particular, the electric machine is dimensioned such that vehicle speeds of more than 50 km / h, preferably more than 80 km / h, in particular more than 100 km / h can be achieved. Particularly preferably, the electric motor has a power output of more than 30 kW, preferably more than 50 kW, in particular more than 70 kW. Furthermore, it is preferred that the electric machine provides a speed of more than 5,000 rpm, particularly preferably more than 10,000 rpm, very particularly preferably more than 12,500 rpm.

[0019] For the purposes of this application, a motor vehicle is a land vehicle that moves under mechanical power without being tethered to a railroad track. The motor vehicle may, for example, be selected from the group of a passenger car, a truck, a minicar, a light motor vehicle, a motorcycle, a motor bus / coach or a tractor.

[0020] In particular, the transmission device can be coupled to an electric machine that is configured to generate a drive torque for the motor vehicle. Particularly preferably, the drive torque is a main drive torque, whereby the motor vehicle is driven exclusively by the drive torque.

[0021] Preferably, the drive shaft of the planetary transmission is operatively connected to a rotor of the electric machine, whereby rotation of the rotor results in rotation of the drive shaft of the planetary transmission.

[0022] In the dependent claims advantageous embodiments of the invention are specified. The features individually recited in the dependent claims can be combined with one another in a technically meaningful manner, thereby defining further embodiments of the invention. In addition, the features recited in the claims are specified and explained in more detail in the description, where further preferred embodiments of the invention are shown.

[0023] According to an advantageous embodiment of the invention, the planetary gear shafts can be arranged radially offset with respect to the corresponding differential balance shafts, it being particularly preferred if the differential balance shafts are offset radially inwards, which makes it possible to achieve a particularly compact construction of the transmission arrangement and a particularly favorable transmission ratio.

[0024] According to a further preferred development of the invention, the pinion gear can be arranged and dimensioned so that it is surrounded by the ring gear without contact. This allows the ring gear to slide axially on the differential, which makes it much easier to assemble the transmission device. Advantageously, the tip circle diameter of the internally toothed ring gear is larger than the pitch circle diameter of the pinion gear of the differential plus the tip circle diameter of the pinion gear. In this connection, it is further preferred that the teeth of the sun gear partially overlap the teeth of the ring gear in the axial direction.

[0025] Furthermore, according to an equally advantageous embodiment of the invention, the planetary gear shafts and the differential balance shafts can overlap in the axial direction. This axial nesting can also be used to provide a transmission arrangement that is particularly compact in the axial direction.

[0026] According to a further particularly preferred embodiment of the invention, the planetary gear shafts and / or the differential balance shafts can each have an axially extending end face recess, which has the particular advantage that the two shafts can be mechanically coupled to one another.

[0027] Furthermore, the invention can also be further developed in such a way that the recesses are formed to be round or flattened. A round recess can have the advantage that the planetary gear shafts do not rotate along their respective rotational axes relative to the differential balance shaft. This ensures that the position of the oil holes does not change over the service life of the drive, for example due to unintended co-rotation of the planetary gear shafts, thereby impairing the lubrication and cooling of the planetary gear transmission.

[0028] In an equally preferred embodiment of the invention, the planetary gear carrier can have in each case a first receptacle for mounting one of the planetary gear shafts and in each case a second receptacle for mounting one of the differential balance shafts, the differential balance shafts each having a contact surface with a respective corresponding planetary gear shaft of the differential balance shafts, thereby also producing a mechanical coupling between the shafts.

[0029] It may also be advantageous to further develop the invention in such a way that in each case the planetary gear shafts and the corresponding differential balance shafts are connected to one another in a form-fitting and additionally materially joined manner by a resistance welding process.

[0030] In this respect, the planetary gear shaft and the differential balance shaft can overlap in the axial direction. A circular recess is then provided for this purpose either on the differential balance shaft or on the planetary gear shaft of the stepped planetary gear set. Depending on the variant, this first creates an anti-rotation lock of either the planetary gear shaft or the differential balance shaft. In order to fix both shafts against rotation relative to each other and also axially, in particular after assembly, electrodes can be attached to the outside of the shafts and both shafts can be welded to each other by applying a direct or alternating current. By applying an axial force via the electrodes, the shafts can be pressed together partially on the end faces in a particularly advantageous manner in this respect to ensure a defined position of the materially joined connection.

[0031] It is further conceivable that the planetary gear shaft and the differential balance shaft do not overlap in the axial direction, but instead abut against each other in a partially planar manner on the end faces. In this respect, both the planetary gear shaft and the differential balance shaft can preferably be mounted in blind holes of a common carrier. The blind holes are preferably configured such that they slightly overlap in the axial direction in order to allow the shafts to contact at the end faces. In order to fix both shafts against rotation relative to each other and also axially, electrodes are attached to the outside of the shafts after assembly and both shafts are welded to each other by applying a direct or alternating current. By applying an axial force via the electrodes, the shafts are in this respect partially pressed against each other on the end faces.

[0032] Resistance heating heats the shaft until it reaches the required welding temperature. Case-hardened extruded shafts can be reworked at the weld point by removing the carbon-containing hardened layer of the bolt on the end face. This is not necessary, however, as it leads to an improvement in the quality of the welded joint due to the lower carbon content in the weld seam.

[0033] According to a further preferred embodiment of the subject matter of the present invention, the first sun gear has a number of teeth Z divisible by 3. s and the first tooth portion of the stepped planetary gear has a tooth number Z P1 and the second tooth portion of the stepped planetary gear has a tooth number Z P2 and the ratio is Z P1 =3*Z P2 Most preferably, the large planetary (Z P1 ) / The number of teeth of the first tooth section is 66, and the small planet (Z P2 ) / The number of teeth of the second tooth portion is 22.

[0034] Number of teeth of the first sun gear Z s Most preferably, the number of teeth of the ring gear (Z H ) is most preferably 97. Most preferably, the transmission ratio of the planetary transmission stages is between 6.5 and 8, preferably between 7 and 8.5, most preferably 7.93, and the transmission ratio i=Z H / Z S xZ P1 / Z P2 It is determined from +1.

[0035] It may also be preferred that the differential is configured as an asymmetric spur gear differential, with the tip diameter of the small sun gear being smaller than the root diameter of the large sun gear. The profile shift coefficient of the small sun gear is preferably <-0.8 and the profile shift coefficient of the large sun gear is preferably >0.8. Both sun gears preferably have the same number of teeth.

[0036] The object of the invention is further achieved by an electrically operable axle drive train of a motor vehicle comprising an electric machine and a transmission device that can be driven by the electric machine as claimed in any one of claims 1 to 10.

[0037] In the following, the invention will be explained in more detail with reference to the drawings, without limiting the general concept of the invention. [Brief description of the drawings]

[0038] [Figure 1] 1 shows a cross-sectional view of a transmission device. [Diagram 2] 1 shows a first embodiment of a transmission device in an axial cross-sectional view. [Diagram 3] A first variant of the first embodiment shown in FIG. 2 is shown in three different views, with a circular recess on the differential balance shaft. [Figure 4] A second variant of the first embodiment shown in FIG. 2 is shown in three different views, with a flattened recess on the differential balance shaft. [Diagram 5] 2 shows a second embodiment of a transmission device in axial section; [Figure 6] FIG. 2 shows a detailed view of the planetary gear shaft and the differential balance shaft in a perspective view. [Figure 7] 3 shows a schematic axial cross-sectional view of a third embodiment of a transmission device. [Figure 8] 1 illustrates, in a schematic block diagram, a vehicle having an electrically operable axle drivetrain; [Figure 9] 1 is a schematic block diagram of a transmission device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] FIG. 1 shows a transmission arrangement 1 of an electrically operable axle drive train 2 of a motor vehicle 3, which is also depicted by way of example in FIG.

[0040] The transmission arrangement 1 comprises a planetary transmission 4 which can be coupled to a first drive shaft 5, and a differential 6 which can be coupled to a first output shaft 7 and a second output shaft 8, which can also be easily seen in Figure 9. In this regard, the drive shaft 5 of the planetary transmission 4 is coupled to an electric machine 25 to transmit torque.

[0041] The planetary transmission 4 comprises a first sun gear 9, a plurality of stepped planetary gears 11 which engage with the first sun gear 9 and are in each case rotatably mounted on a first planetary gear carrier 10 on a planetary gear shaft 15 and which in each case have a first toothing 12 and a second toothing 13 which move in rotation around the first sun gear 9, and a ring gear 14 which is arranged coaxially with respect to the first sun gear 9 and on which the planetary gears 11 roll, the first toothing 12 engaging with the first sun gear 9 while the second toothing 13 having a pitch diameter smaller than the pitch diameter of the first toothing 12 meshes with the ring gear 14. In this respect, the planetary transmission 4 can initially be considered to be of conventional construction.

[0042] The planetary gear shafts 15 are each coupled to a differential balance shaft 16 of the differential 6, with a first pinion gear 17 in each case engaging a first sun gear 18 which is rotatably arranged on the differential balance shaft 16 and which in each case can be coupled to a first output shaft 7, the first pinion gear 17 further meshing with a second pinion gear 19 which in turn engages with a second sun gear 20 which can be coupled to a second output shaft 8. The first sun gear 18 has a tip diameter which is smaller than the root diameter of the second sun gear 20, and both sun gears have the same number of teeth.

[0043] For lubricating the plain bearings between the differential balance shaft 16 and the pinion gears 17, 19, the differential balance shaft 16 has an axially and radially extending oiling channel 40.

[0044] As can be seen particularly clearly from FIG. 1, in the transmission device 1 according to the invention, the planetary gear shafts 15 are arranged in phase with the corresponding differential balance shafts 16, i.e. the planetary gear shafts 15 are not offset from one another in the circumferential direction, but the respective rotation axes of the planetary gear shafts 15 each lie in a common radial plane.

[0045] 1-2, it can be seen, for example, that the planetary gear shaft 15 is arranged offset radially inwards with respect to the corresponding differential balance shaft 16. Figure 2 also clearly shows that the pinion gears 17, 19 are arranged and dimensioned to be surrounded by the ring gear 14 without contact, so that the ring gear 14 can slide axially on the pinion gears 17, 19 onto the planetary gear 11, i.e. from right to left in the embodiment shown in Figure 2. The teeth of the sun gear 20 partially overlap with the teeth of the ring gear 14 in the axial direction.

[0046] As shown in the embodiment of figures 2 to 5, the planetary gear shafts 15 and the differential balance shafts 16 can overlap in the axial direction. For this purpose, the planetary gear shafts 15 and / or the differential balance shafts 16 each have an end face recess 21 extending in the axial direction. Figure 3 shows an embodiment in which the recess 21 is formed so as to be circular, whereas figure 4 shows an embodiment in which the recess 21 is formed so as to be flat. In both cases, the respective shafts 15, 16 must be mounted in the correct orientation so that they can engage with each other in a corresponding form-fitting manner.

[0047] Partial view a of Fig. 3 shows an embodiment in which the planetary gear shaft 15 has a circular recess 21, while partial view c of Fig. 3 discloses a circular recess 21 on the differential balance shaft 16. The radial offset of the shafts 15, 16 relative to each other and their in-phase arrangement can also be clearly seen in partial view b of Fig. 3.

[0048] 4 shows the shafts 15, 16 in a version with in each case a flattened recess 21. Here again, the radial offset of the shafts 15, 16 relative to one another and their in-phase arrangement can be clearly seen in the subview b of FIG.

[0049] The recesses 21 thereby create in each case a form fit between the planetary gear shaft 15 and the associated differential balance shaft 16, so that the shafts 15 and 16 cannot rotate relative to one another about the respective rotation axes of the shafts 15 and 16. In addition to a form fit, it would in principle also be possible for the planetary gear shaft 15 and the associated differential balance shaft 16 to be connected to one another in such a way that they are materially joined by resistance welding.

[0050] FIG. 5 shows the embodiment known from FIGS. 2 to 4 in which the shafts 15, 16 overlap axially, but in which the planetary gear carrier 10 is shown.

[0051] 7 is a further embodiment of the transmission device 1, in which the planetary gear carrier 10 has in each case a first receptacle 22 for mounting one of the planetary gear shafts 15 and in each case a second receptacle 23 for mounting one of the differential balance shafts 16, the differential balance shafts 16 each having a contact surface 24 with the respective corresponding planetary gear shaft 15 of the differential balance shafts 16. In each case the planetary gear shaft 15 and the corresponding differential balance shaft 16 can be connected to one another in this respect so as to be materially joined by a resistance welding process.

[0052] FIG. 6 shows the arrangement of the shafts 15 , 16 without the representation of the planetary gear carrier 10 .

[0053] In the embodiment shown in FIG. 7, the planetary gear carrier 10 has two blind holes arranged in phase, the two blind holes partially overlapping in the radial direction.

[0054] Thereby, the planetary gear shaft 15 and the differential balance shaft 16 abut against each other on their ends, which can be clearly seen in Figure 7. In this embodiment, the shafts 15, 16 do not need to be mounted in alignment with each other. There is no mechanical anti-rotation lock between the shafts 15, 16, as in the exemplary embodiment of Figures 2-5. [Explanation of symbols]

[0055] 1 Transmission device 2 Axle Drivetrain 3. Automobiles 4 Planetary Transmission 5 Drive shaft 6 Differential device 7 Output shaft 8 Output shaft 9. Sun Gear 10 Planetary Gear Carrier 11 Planetary Gear 12 Teeth 13 Teeth 14 Ring Gear 15 Planetary gear shaft 16 Differential balance shaft 17 Pinion gear 18 Sun Gear 19 Pinion gear 20 Sun Gear 21 Recess 22 Receptacle 23 Receptacle 24 Contact surfaces 25 Electrical Machinery 40 Lubrication Channel

Claims

1. A transmission arrangement (1) for an electrically operable axle drive train (2) of a motor vehicle (3), comprising: a planetary transmission (4) capable of being coupled to a first drive shaft (5); and a differential (6) capable of being coupled to a first output shaft (7) and a second output shaft (8), said planetary transmission (4) comprising a first sun gear (9) and a plurality of stepped planetary gears (11) engaged with said first sun gear (9); and in each case comprising a plurality of stepped planetary gears (11) rotatably mounted on a first planetary gear carrier (10) on a planetary gear shaft (15) and having a first toothing (12) and a second toothing (13) which move in rotation around said first sun gear (9), and a ring gear (14) arranged coaxially with said first sun gear (9) and on which said planetary gears (11) roll, said first toothing (12) being in engagement with said first sun gear (9), while the second toothing (13), having a pitch diameter smaller than the pitch diameter of the first toothing (12), meshes with the ring gear (14); the planetary gear shafts (15) are each coupled to a differential balance shaft (16) of the differential device (6); a first pinion gear (17) is in each case rotatably arranged on the differential balance shaft (16) and is in each case coupled to the first output shaft (7); a first sun gear (18) that can be coupled to the second output shaft (8), said first pinion gear (17) further meshing with a second pinion gear (19) that in turn engages with a second sun gear (20) that can be coupled to the second output shaft (8), said first sun gear (18) having a tip diameter smaller than a root diameter of said second sun gear (20), and both sun gears having the same number of teeth, The planetary gear shafts (15) are arranged in phase with the corresponding differential balance shafts (16); The planetary gear shaft (15) and the differential balance shaft (16) overlap in the axial direction, the planetary gear shaft (15) and / or the differential balance shaft (16) each have an end face recess (21) extending in the axial direction; Or, said planetary gear carrier (10) has in each case a first receptacle (22) for mounting one of said planetary gear shafts (15) and in each case a second receptacle (23) for mounting one of said differential balance shafts (16), said differential balance shafts (16) each having a contact surface (24) with the respective corresponding planetary gear shaft (15) of said differential balance shafts (16), A transmission device (1).

2. 2. The transmission device (1) according to claim 1, characterized in that the planetary gear shafts (15) are arranged radially offset with respect to the corresponding differential balance shafts (16).

3. 3. A transmission device (1) according to claim 1 or 2, characterized in that the pinion gears (17, 19) are arranged and dimensioned so as to be surrounded without contact by the ring gear (14).

4. A transmission device (1) according to any one of claims 1 to 3, characterized in that in each case the planetary gear shafts (15) and the corresponding differential balance shafts (16) are connected to one another in a form-fitting and additionally materially joined manner by a resistance welding process.

5. The first sun gear (9) has a number of teeth Z divisible by 3. ｓ and the first tooth portion (12) of the stepped planetary gear (11) has a tooth number Z Ｐ１ and the second tooth portion (13) of the stepped planetary gear (11) has a tooth number Z Ｐ２ and the ratio is Z Ｐ１ = 3 * Z Ｐ２ A transmission device (1) according to any one of claims 1 to 4, characterized in that

6. The transmission device (1) according to any one of claims 3 to 9, characterized in that the toothing of the sun gear (20) partially overlaps in the axial direction with the toothing of the ring gear (14).

7. An electrically operable axle drive train (2) of a motor vehicle (3), comprising an electric machine (25) and a transmission device (1) according to any one of claims 1 to 6, capable of being driven by said electric machine (25).

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