Bearing concept of a superimposed gearbox for an electric torque vectoring system

Abstract

Proposed is an electrically actuated torque vectoring unit (1) with an input gear stage (2) and two planetary gear stages (3, 4) as a superimposed transmission (16), each having an output shaft (5, 6), and the two planetary gear stages (3, 4) being torque-transmittingly coupled to the input gear stage (2), wherein the input gear stage (2) is driven by an electric motor (7), wherein each planetary gear stage (3, 4) of the superimposed transmission (16) has at least one flanking axial roller bearing (51, 52, 53), wherein each planetary gear stage (3, 4) is supported only radially via its gear teeth, and the axial roller bearing (51, 52, 53) axially supports the two planet carriers (32, 33) relative to each other and / or connects one of the planet carriers (32, 33) to the common ring gear (15) of the superimposed transmission. (16) axially supported.

Description

[0001] DE 10 2015 223 131 A1 shows a drive device for a motor vehicle, comprising a differential gear and a torque vectoring unit with an electric machine, wherein the differential gear has a first and a second planetary gear set rotatably mounted on a common web, wherein the first planetary gear set meshes with at least a first sun gear, the second planetary gear set meshes with at least a second sun gear and the two planetary gear sets mesh with each other at least in pairs, and wherein at least the second sun gear is connected to the torque vectoring unit for redistributing the torque between the first and second sun gears.

[0002] WO 2015 / 169837 A1 and US 2015 / 0152947 A1 each show a torque vectoring arrangement in a transmission that can be actuated by an electric motor.

[0003] DE 10 2022 001 679 B3 shows an electric drive device for a motor vehicle, in particular for a motor vehicle with two electric motors and torque vectoring function.

[0004] The object is to provide an improved bearing in a superposition gear of a torque vectoring unit, which is achieved with the features of claim 1. Further developments of the device are the subject of the subclaims.

[0005] The torque vectoring unit has an input gear stage with its own output shaft, which also serves as the drive shaft for transferring the torque from the input gear stage to the superposition gear of the torque vectoring unit. This means that the torque vectoring unit according to the invention has an electric motor, an input gear stage, and a superposition gear.

[0006] A differential gear is not included in the torque vectoring unit. The difference between the superposition gear according to the invention and the differential gear is that the superposition gear of a torque vectoring unit acts on a drive shaft with the applied torque of the electric motor in such a way that the speed of the wheel on the drive shaft is accelerated relative to the speed of the wheel opposite along the wheel axis. In a differential gear, the drive torque is usually introduced to the planet carrier and delivered equally to the left and right wheels, assuming the same road friction coefficients at both wheels. If there are different road friction coefficients at the two wheels of an axle with a differential gear in between, a wheel with the higher road friction coefficient "brakes" due to the higher friction.The corresponding differential gear (in a bevel gear differential) or the sun gear (in a spur gear differential) then has a different speed than the gear assigned to the other gear. The differential gear, as a planetary gear with one input and two outputs, is able to convert these speed differences, ensuring that the wheel with the lower road friction coefficient does not receive a disproportionate amount of drive torque and transition to sliding friction (wheel spin).

[0007] The superposition gear is provided with two planetary gears, whereby, in contrast to the conventional differential gear, the torque is introduced via the sun gear of one of the planetary gears (first sun gear), transmitted via a common ring gear to the other (second) planetary gear and both (first and second) planetary gears have an interface to a (first and second) shaft via their (first and second) planet carrier.

[0008] The electromechanical axle drive train typically features an electric motor designed to propel the vehicle (electric drive unit). This is typically connected to the planetary carrier of a differential gear, so that the torque from the electric motor (optionally with the interposition of a reduction gear to convert a high speed of the electric motor into a lower speed for the differential gear, thus converting a low torque from the electric motor into a higher torque for the differential gear) is transmitted to the differential gear to drive two wheels on an axle.

[0009] The first and second shafts of the superposition gear are operatively connected in the drive train so that the torque vectoring unit can incorporate its function into the driving behavior and can superimpose the drive torque path with the torque introduced by the electric motor of the torque vectoring unit (superposition gear).

[0010] The superposition gear is implemented in the drivetrain as follows. The electric motor of the torque vectoring unit is not energized.

[0011] The first planet carrier of the first planetary gear of the superposition gear is torque-fixedly connected to the planet carrier of the differential gear via a first shaft, so that the torque input by the electric drive motor into the differential gear is simultaneously transmitted via the first shaft through the first planet carrier of the first planetary gear of the superposition gear to the second planetary gear of the superposition gear, so that the second planet carrier of the second planetary gear, as the output of the superposition gear, is transmitted to the first output shaft of the first wheel. Because the electric motor of the torque vectoring unit is de-energized, no "manipulation" of the first output shaft of the differential gear occurs.

[0012] When the electric motor of the torque vectoring unit is energized, it delivers a direction-dependent torque through the input gear of the input stage via the output shaft of the input stage to the (first) sun gear of the first planetary gear of the superposition gearing – this output shaft of the input gear is also the input sun gear for the superposition gearing. The first planetary gear thus has two input torques: one from the electric drive motor to the first planet carrier of the first planetary gearing, and one from the electric motor of the torque vectoring unit to the (first) sun gear of the first planetary gearing. The stepped-up / step-down torque is transferred from the first planetary gearing via the ring gear shared with the second planetary gearing from the first planetary gearing and subsequently into the second planetary gearing.Since the (second) sun gear of the second planetary gear is fixed to the frame, i.e., is non-rotatably supported on a housing part, the only torque output for the second planetary gear is at its second planet carrier, which is non-rotatably connected to the first output shaft of the differential gear. Consequently, the additional torque input by the superposition gear accelerates or decelerates the first wheel relative to the second output shaft of the differential gear, and thus also relative to the second wheel. Advantageously, the control is such that cornering is detected, and thus the electric motor of the torque vectoring unit is energized in such a way that the first wheel rotates faster or slower relative to the second wheel.

[0013] For example, the steering angle during cornering can be determined as a control variable, and the electric motor of the torque vectoring unit can be energized in the desired direction of rotation, so that either the output of the first planetary gear overtakes the output of the second planetary gear, or vice versa. This creates a torque vectoring function that allows the outside wheel to rotate faster, reducing slippage and instability when cornering at high vehicle speeds and improving driving dynamics.

[0014] This creates a clear difference between a differential gear and the torque vectoring unit according to the invention with its superposition gear.

[0015] The superposition gear unit consists of two planetary gears coupled to each other via a common ring gear. Each planetary gear unit has a shaft that is rotationally fixedly coupled to its planet carrier.

[0016] One shaft is provided for each driven wheel of the vehicle. Within the scope of this invention, one shaft is the output shaft of the differential gear, and the other shaft is a shaft non-rotatably coupled to a planetary carrier. Thus, a drive torque variation can be applied to the two wheels of one axle of the vehicle through the operation of the electric motor, which drives the input gear stage.

[0017] The bearing of the drive sun shaft is floating, meaning there are no locking elements for axially fixing the rolling bearings, so that each rolling bearing no longer has any degree of freedom in either axial direction. According to the invention, each ring of each rolling bearing has a restriction of its axial degree of freedom in only one axial direction. The rolling bearings of the drive sun shaft support each other axially. Forces in the axial direction are transmitted from one rolling bearing ring through the rolling elements to the other rolling bearing ring of the one rolling bearing. Furthermore, the outer rings of the rolling bearings find their axial contact with two interconnectable housing halves as peripheral components, so that the absolute position of the bearing of the drive sun shaft is determined. In order to achieve the preload of the bearing of the drive sun shaft, the rolling bearings used for the bearing can be clamped together using shims.

[0018] Advantageously, the torque vectoring unit can be provided with an electric motor driving it.

[0019] According to the invention, the torque vectoring unit has an improved bearing for its superposition gearing. The superposition gearing comprises two (first and second) planetary gears coupled to one another via a common ring gear. To achieve good load distribution within the system, each planet carrier is provided without its own radial bearing in the form of an additional rolling bearing. The radial determination of the position of the two shafts, which are non-rotatably connected to the planet carriers, is achieved via the planetary gear sets and the common ring gear. Since the second sun gear is non-rotatably mounted relative to the housing and the first sun gear is connected to the input gearing in a torque-transmitting manner, and the ring gear is formed jointly via both planetary gears of the superposition gearing, the first and second planet carriers can be radially released without an additional rolling bearing.The two shafts, each torque-fixedly connected to the first and second planet carrier, are axially centered and radially determined to the respective first and second sun gear.

[0020] The axial support of the two planetary carriers of the superposition gear is provided by three axial rolling bearings. A first axial rolling bearing is located between the first planetary carrier and the common ring gear that fits over it. A second axial rolling bearing is located between the two planetary carriers, and a third axial rolling bearing is located between the second planetary carrier and the common ring gear that fits over it. All three axial rolling bearings have sheet metal raceways and are designed as needle roller bearings.

[0021] The axial roller bearings, each located between a planet carrier and a component of the ring gear—for example, a cover connected to the ring gear—are received by this component of the ring gear and placed in a corresponding receptacle in the component. The component is advantageously a ring-disk-shaped cover that has the receptacle for accommodating the axial roller bearing. The cover is secured axially to the ring gear, which overlaps both planetary gears, for example with a retaining ring. The shared ring gear thus advantageously has two such covers placed at its ends, which accommodate both planetary gears. The covers of the ring gear have no further radial guiding function.

[0022] The axial roller bearing positioned between the two planetary gears is held by one of the two planetary carriers via a recess formed by the planetary carrier. The recess may be formed by the planetary carrier cover.

[0023] Advantageously, the axial roller bearings have an inner diameter that allows oil projected radially from the inside (from the rotational axis) to the outside to be blocked by the axial roller bearing or to be projected onto this axial roller bearing, so that excess oil is redirected axially to the planetary gear bearings and can lubricate them. This eliminates the need for a separate oil collector in the form of an oil collecting plate.

[0024] Advantageously, the receptacle of the planet carrier for receiving the axial rolling bearing further comprises an oil flow guide contour which is capable of redirecting and supplying the oil thrown away from the axis of rotation to the bearings of the planets of the planetary gear.

[0025] In particular, at least two of the three axial rolling bearings are designed as identical parts, i.e. they have at least the same shape and number of needles as rolling elements, whereby the raceway discs can vary due to the connection to the peripheral components.

[0026] The common ring gear advantageously has a uniform toothing for both planetary gears. Furthermore, the axial ends of the common ring gear are sealed with cover rings, allowing the shaft to extend through its respective cover.

[0027] The common ring gear is mounted relative to the housing by a fixed bearing designed as a rolling bearing.

[0028] Advantageous embodiments of the invention are shown in the figures.

[0029] Show with: Fig. 1 a torque vectoring unit according to the invention, Fig. 2 a planet carrier with a cover for receiving an axial rolling bearing spaced apart before assembly, Fig. 3 the planet carrier Fig. 2 with the mounted axial rolling bearing, Fig. 4 a section through the planet carrier according to Fig. 3, Fig. 5 the axial rolling bearing between the planet carrier Fig. 3 and a ring gear cover and Fig. 6 the section through the superposition gear with the axial rolling bearings.

[0030] Fig. 1 shows a torque vectoring unit 1 with an input gear stage 2 designed as an input gear 18 and a superposition gear 16. The superposition gear 16 has two first and second planetary gear stages 3 and 4 connected to one another via a common ring gear 15, which respectively contain the first and second planetary gear of the preceding general description.

[0031] The input gear stage 2 has two axially parallel, offset spur gears which mesh with each other. The torque from the electric motor 7 of the torque vectoring unit 1 is applied to a double gear shaft 24 via a first gear 22 of the spur gear chain and passed on to the second gear 25 of the spur gear chain via a pinion 23 seated on this double gear shaft 24. This causes the output shaft 17 of the input gear stage 2 to rotate. The output shaft 17 from the input gear stage 2 is also the drive sun shaft 26. The two first and second rolling bearings 8 and 9 support the drive sun shaft 26 relative to the housing 10. The rolling bearings 8, 9 are positioned axially on the drive sun shaft 26 such that the rolling bearings 8, 9 flank the input gear 18.The inner rings 11 and 12 of the rolling bearings 8, 9 are mounted on the drive sun shaft 26 and each rests on one side only against a diametrical shoulder formed by the drive sun shaft 26. The diametrical shoulder is located axially between the two rolling bearings 8 and 9. The outer rings 13 and 14 of the rolling bearings 8, 9 are inserted into the housing 10 and each rests on one side only against a diametrical shoulder of the mount for the rolling bearing 8, 9. This contact is located on the axially opposite side of the contact on the diametrical shoulder of the respective rolling bearing 8, 9.

[0032] Away from the area of ​​the rolling bearings with the rolling bearings 8 and 9, the sun gear of the first planetary gear stage 3, formed in one piece with the drive sun shaft 26, is located. The first planetary gear stage 3 further has a first planet carrier 32 and associated planet gears. The planet carrier 32 of the first planetary gear stage 3 is connected to the shaft 27 driven by the drive motor 20, which also drives the differential gear 19 via its own planet carrier. The differential gear 19 has two first and second output shafts 5 and 6, with the second output shaft 6 passing through this shaft 27 and projecting through the superposition gear 16 to transmit the drive torque from the drive motor 20 to one of the wheels.The second output shaft 6 is connected in a rotationally fixed manner to the second planet carrier 33 of the second planetary gear stage 4 via a rotationally fixed connection 21 (indicated here by a second spline 41). The schematically indicated sun gear 28 of the second planetary gear stage 4 is fixed to the frame. Thus, when the electric motor 7 manipulates the second output shaft 6 with the superposition gear 16, the drive for propelling the vehicle is transmitted from the drive electric motor 20 to both the left and right wheels (not further shown here) at the ends of the first and second output shafts 5, 6.

[0033] If the electric motor 7 is energized and, through its torque, influences the second output shaft 6 via the input gear stage 2 to the superposition gear 16, a torque difference can be introduced between the first and second output shafts 5, 6. This process is called torque vectoring, since one of the two wheels on an axle is driven more than the other, thus increasing the vehicle's stability when cornering.

[0034] The section also reveals the screw connection below the centerline. The dowel sleeve 45 is arranged both in a receptacle of the second leg 43 of the second leg part 37 and in a receptacle of the second cover 35, so that the screw 31 can extend through the dowel sleeve 45 and connect the second cover 35 to the second leg part 37 in an axially loadable manner. Torque is transmitted via the dowel sleeve 45 or via the dowel sleeves 45 of each second leg 43. This screw connection is also designed in an analogous manner for the first planet carrier 32.

[0035] The section further shows two opposing screw connections of the first and second planet carrier 32, 33. Both planet carriers 32, 33 can now be placed closer to each other by means of the countersunk head screws 30, 31, since no screw heads of the screws 30, 31 protrude from the respective cover 34, 35. In the circumferential direction, the installation space that would otherwise be unusable due to a few screw heads can thus be used, for example, for the placement of an axial needle bearing, which can support both planet carriers 32, 33 relative to each other, which is particularly advantageous in the inventive design of the torque vectoring unit 1 according to Fig. 1 the advantage of a superposition gear 16 with reduced axial installation space can be realized.

[0036] The Fig. 2 shows a planet carrier 33 with a cover 35 for receiving an axial roller bearing 53 spaced apart before assembly. The planet carrier 33 is the second planet carrier 33 of the arrangement according to Fig. 1. The receptacle 29 for the axial rolling bearing 53 is formed by the second stilt part 37. The receptacle 29 consists of several circular arc segments that are regularly distributed around the circumference and protrude in the axial direction from the second stilt part 37. These circular arc segments of the receptacle 29, which are regularly distributed around the circumference, are integral with the stilt part 37. The axial rolling bearing 53 is received via its axial rolling bearing inner ring on the circular arc-shaped outer surfaces of the receptacle 29, which are present on the radial outside. The outer surfaces of the receptacle 29 on the radial inside serve to guide the oil thrown off the axis of rotation during operation to the bearings of the planets. The outer surfaces of the receptacle 29 on the radial inside are therefore also integral with the stilt part 37.

[0037] The Fig. 3 shows the planet carrier 33 after Fig. 2 with the mounted axial roller bearing 53. The part of the receptacle 29 dotted here with the reference line shows in this embodiment the radially inner surface made up of two circular arc segments, which on the one hand are intended to guide the oil better to the planetary bearings and on the other hand do not have to have a solid construction for reliable support of the axial roller bearing 53, since the radial support of the planetary gear stage 4 is only provided via its gearing.

[0038] The Fig. 4 shows a section through the planet carrier 33 according to Fig. 3. The axial roller bearing 53 only partially covers the planetary bearing so that the oil on the radial inside of the axial roller bearing 53 can be deflected by it and enter the planetary bearing.

[0039] The Fig. 5 shows the axial rolling bearing 53 between the planet carrier 33 Fig. 3 and a ring gear cover 47. The ring gear cover 47 and the second stilt part 37 of the planet carrier 33 axially directly limit the axial rolling bearing 53. It is also alternatively conceivable that the second planetary gear stage 4 or the second planet carrier 33 are mirror-inverted, so that instead of the second stilt part 37, the second cover 35 forms the receptacle 29 for the axial rolling bearing 51.

[0040] The Fig. 6 shows the section through the superposition gear 16 according to Fig.1 with the axial roller bearings 51, 52, 53. All three axial roller bearings 51, 52, 53 are designed as identical parts. The axial roller bearing 53, as mentioned in the preceding figure descriptions, is located between the second stilt part 37 and the ring gear cover 47 and is received by a receptacle 29 of the second stilt part 37. The ring gear cover 47 is axially secured to the common ring gear 15 with a retaining ring 49. Approximately centrally in the superposition gear 16, in any case axially between the two planetary gear stages 3 and 4, is the second axial roller bearing 52, which is received by at least one receptacle of one of the planet carriers 32, 33 in a manner analogous to that described above. The third axial rolling bearing 51 is located axially between the first planetary gear stage 3 and the ring gear cover 46. Both axial rolling bearings 51 and 53 can additionally be accommodated by a circular receptacle of the ring gear covers 46, 47.Beyond the ring gear cover 46 and axially outside the planetary gear stages 3 and 4, the common ring gear 15 is supported by a roller bearing 50 designed as a radial roller bearing to the housing 10. Support is provided solely by the one roller bearing 50 at the end of the common ring gear 15 and thus corresponds to a floating bearing of the ring gear 15. Thus, the planetary gear stages 3 and 4 are radially supported via their gearing. Via the gearing, the radial support is determined on the one hand by the drive sun shaft 26 (for the first planetary gear 3) and on the other hand by the frame-mounted sun gear (not shown here) of the second planetary gear 4. List of reference symbols 1 torque vectoring unit 2 input gear stage 3 first planetary gear stage 4 second planetary gear stage 5 first output shaft 6 second output shaft 7 Electric motor 8 first rolling bearing 9 second rolling bearing 10 housings 11 first inner ring 12 second inner ring 13 first outer ring 14 second outer ring 15 common ring gear 16 superposition gears 17 Output shaft (input gear stage) 18 input gears 19 differential gears 20 drive electric motor 21 non-rotatable connection 22 first gear 23 pinions 24 Double gear shaft 25 second gear 26 Drive sun shaft 27 Wave 28 Sun gear 29 recording 30 screw 31 Screw 32 first planet carrier (of the first planetary gear stage) 33 second planet carrier (of the second planetary gear stage) 34 first cover (of the first planet carrier) 35 second cover (of the second planet carrier) 36 first stilt part (of the first planet carrier) 37 second stilt part (of the second planet carrier) 38 first tube (of the first cover) 39 second tube (of the second cover) 40 first spline (of the first tube) 41 second spline (of the second tube) 42 stilts 43 stilts 44 fitting sleeve 45 fitting sleeve 46 first ring gear cover 47 second ring gear cover 48 first retaining ring 49 second retaining ring 50 rolling bearings 51 thrust rolling bearings 52 thrust rolling bearings 53 thrust rolling bearings

Claims

[1] Electrically operated torque vectoring unit (1) with an input gear stage (2) and two planetary gear stages (3, 4) as superposition gears (16), wherein the two planetary gear stages (3, 4) are coupled to the input gear stage (2) in a torque-transmitting manner, wherein the input gear stage (2) is driven by / by an electric motor (7), characterized by that each planetary gear stage (3, 4) of the superposition gear (16) has at least one axial rolling bearing (51, 52, 53) flanking it, wherein the planetary gear stages (3 and 4) are radially supported via their toothing and the axial rolling bearing (51, 52, 53) axially supports one of the planet carriers (32, 33) to the common ring gear (15) of the superposition gear (16). [2] Torque vectoring unit (1) according to claim 1, characterized bythat at least one planet carrier (32, 33) of the respective planetary gear stage (3, 4) has a receptacle for receiving one of the axial rolling bearings (51, 52, 53). [3] Torque vectoring unit (1) according to one of the preceding claims, characterized by that the common ring gear (15) is connected at the end to ring gear covers (46, 47) which house both planetary gear stages (3, 4). [4] Torque vectoring unit (1) according to one of the preceding claims, characterized by that all axial rolling bearings (51, 52, 53) are of identical design. [5] Torque vectoring unit (1) according to one of the preceding claims, characterized by that the common ring gear (15) is mounted relative to the housing (10) only by a single rolling bearing (50) designed as a radial rolling bearing, wherein the rolling bearing (50) is arranged at the end of the common ring gear (15). [6] Torque vectoring unit (1) according to one of claims 3 to 5, characterized bythat an axial roller bearing (51, 52, 53) is arranged between a ring gear cover (46, 47) and a planet carrier (32, 33) adjacent to the latter of the respective planetary gear stage (3, 4). [7] Torque vectoring unit (1) according to one of claims 3 to 6, characterized by that at least one ring gear cover (46, 47) is axially secured to the common ring gear (15) via a retaining ring (48, 49). [8] Torque vectoring unit (1) according to one of claims 5 to 7, characterized by that the rolling bearing (50) is placed axially between a ring gear cover (46, 47) and a retaining ring (48, 49). [9] Torque vectoring unit (1) according to one of the preceding claims, characterized by that each axial rolling bearing (51, 52, 53) can introduce an oil flow into the adjacent planetary gear stage (3, 4) with one of its components.

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