Multi-stage axle drive with a planetary gear set featuring stepped planetary gear sets and an axially adjacent ring gear

Abstract

Multi-speed axle drive (1) of a motor vehicle, comprising a drive unit (2) and a planetary gear set (4) operatively connected thereto, which has at least a first planetary gear stage (5) with a first stepped planetary gear set (14) and a second planetary gear stage (6) with a second stepped planetary gear set (15), wherein the stepped planetary gear sets (14, 15) each have individual planets (14a, 14b, 15a, 15b) of different outer diameters connected to one another in a rotationally fixed manner via a web (25, 26), wherein a differential gear (8) is connected to an output shaft (7) of the second planetary gear stage (6), which is rotationally fixed to a second web (26) of the second planetary gear stage (6), characterized in that the stepped planetary gear sets (14, 15) are arranged relative to one another in such a way that the smallest planets (14a, 15a) of the stepped planetary gear sets (14, 15) in a meshing interaction with ring gears (24) are,which are arranged axially next to each other, wherein the output shaft (9) of the drive unit (2) is connected to the planetary gear (4) via a coupling unit (10).

Description

[0001] The invention relates to a multi-gear axle drive of a motor vehicle, with a drive unit and a planetary gear operatively connected thereto, which has at least a first planetary gear stage with a first stepped planetary gear set and a second planetary gear stage with a second stepped planetary gear set, wherein the stepped planetary gear sets each have individual planets of different outer diameters which are connected to one another in a rotationally fixed manner via a web, wherein a differential gear is connected to an output shaft of the second planetary gear stage, which is rotationally fixedly coupled to a second web of the second planetary gear stage.

[0002] A planetary gear system, as is generally known, comprises at least one sun gear, at least one planet gear, at least one ring gear, and at least one planet carrier. The interaction of these individual gear components will not be discussed below, as the expert is familiar with this from his or her work and the relevant literature.

[0003] Multi-gear electric axle drives of this type are used to convert the speeds of at least one electric motor to the desired output. Such electric axle drives require high overall gear ratios.

[0004] A planetary gear transmission with a high overall transmission ratio is known from DE 10 2016 202 723 A1. This discloses a planetary gear transmission with a power input, a power output, a pre-stage transmission driven by the power input, with a fixed transmission ratio including a pre-stage sun gear, a pre-stage planetary gear set, a pre-stage planetary carrier, and a pre-stage ring gear, a load-stage transmission driven by the pre-stage transmission, with a first load-stage sun gear, a second load-stage sun gear, load-stage planetary gears, a first load-stage planetary carrier, and a first load-stage ring gear.

[0005] DE 10 2016 202 723 A1 also discloses a dual clutch device with a first clutch for selectively coupling the first load-stage sun gear to the pre-stage planetary carrier, and a second clutch for selectively coupling the second load-stage sun gear to the pre-stage planetary carrier. The dual clutch device is arranged between the pre-stage transmission and the load-stage transmission.

[0006] DE 10 2015 016 010 A1 shows a drive train device with an electric motor and a transmission.

[0007] DE 10 2014 101 726 A1 shows a multi-speed planetary transmission for use in passenger vehicles, trucks, commercial vehicles, agricultural machinery, construction vehicles, diesel locomotives, wind turbines, bicycles, motorcycles, mopeds, motorcycles or pedal-operated bicycles.

[0008] DE 10 2015 205 264 A1 shows a drive unit for an industrial truck, comprising a first gear stage designed as a first planetary stage and a second gear stage designed as a second planetary stage, wherein the first planetary stage comprises first rotating gears and at least two first stationary gears and wherein the second planetary stage comprises second rotating gears and at least two second stationary gears.

[0009] Although this state-of-the-art arrangement already enables relatively high overall gear ratios, this usually comes at the expense of mechanical efficiency.

[0010] Another problem with the current state of the art is the high degree of individuality that every technical implementation of a multi-speed electric axle drive requires. Changing conditions generally require a redesign of the entire drive system.

[0011] Against this background, the present invention is based on the object of eliminating or at least mitigating the disadvantages of the prior art. In particular, the present invention aims to increase power density and create additional gear ratios. A further object is to ensure the aforementioned objectives while simultaneously developing a modular system.

[0012] This is achieved according to the invention in that the stepped planetary gear sets are arranged in such a way, i.e., such that the circumferentially smallest planets of the stepped planetary gear sets are in meshing engagement with ring gears, which ring gears are arranged axially adjacent to one another. In this way, the power density is increased and an additional gear ratio is created.

[0013] According to the invention, the output shaft of the drive unit is connected to the planetary gear via a clutch unit. This enables a space-optimized arrangement between the drive unit and the planetary gear.

[0014] Advantageous embodiments are the subject of the dependent claims. These are discussed below.

[0015] It is advantageous if the first carrier of the first planetary gear stage is non-rotatably connected to the first sun gear of the second planetary gear stage. This increases compactness, for example.

[0016] It is particularly advantageous if the ring gears have a common supporting structure that is firmly connected to the housing, which promotes the axially adjacent structure.

[0017] As soon as a first output shaft of a first electric motor is connected in a rotationally fixed manner to an output shaft of the drive unit and the first output shaft is arranged coaxially to the output shaft of the drive module, the power density is further increased.

[0018] Advantageously, a second output shaft of a second electric motor is connected to the output shaft of the drive unit via a first spur gear stage and the second output shaft of the second electric motor is arranged parallel to the output shaft of the drive unit.

[0019] In the embodiment in which the output shaft of the drive unit is connected to the planetary gear by a clutch unit, it is also advantageous if the second output shaft of the second electric motor is operatively connected to clutch elements of the clutch unit via spur gear stages with different gear ratios.

[0020] Further preferably, the clutch unit has a first clutch element and a second clutch element, wherein the first clutch element can be brought into operative connection with the first web of the first planetary gear stage and the second clutch element can be brought into operative connection with a first sun gear of the first planetary gear stage.

[0021] In particular, when the clutch unit has a second clutch element and a third clutch element, wherein the second clutch element can be brought into operative connection with a first sun of the first planetary gear stage and the third clutch element can be brought into operative connection with a second sun gear of the first planetary gear stage, the power density is increased.

[0022] Another advantageous multi-gear axle drive is characterized by the fact that the individual planets of the first stepped planetary gear set consist of three planets that are connected to one another in a rotationally fixed manner, so that the planetary gear set is triple-stepped.

[0023] Advantageously, the clutch unit comprises a further clutch element that can be operatively connected to a third sun gear that meshes with the third planet. Furthermore, it is advantageous if the clutch unit is variably composed of the clutch elements and is designed as a double clutch, triple clutch, or quadruple clutch.

[0024] Within the scope of the invention, it is also possible to arrange the differential gear coaxially to the center axis of the planetary gear and to design it as a coaxial differential. Alternatively, the differential gear is arranged as an axially parallel differential parallel to the center axis of the planetary gear and meshes with the output shaft of the planetary gear via an additional spur gear stage. Finally, it is also possible for the differential gear to be arranged as an angularly offset differential orthogonal or transverse to the center axis of the planetary gear and meshes with the output shaft of the planetary gear via an angular stage.

[0025] Using (partially different) terms, a further aspect - which may be independently claimable - is described below.

[0026] In this preferred aspect of the invention, a multi-speed electric axle drive of a motor vehicle is disclosed, comprising an electric module having at least a first electric motor, and a planetary gear connected to the electric module, which planetary gear has at least a first planetary gear stage and a second planetary gear stage and to whose output shaft a differential gear is connected.

[0027] This aspect of the disclosure is particularly characterized by the fact that an electric module output shaft can be coupled to the first and second planetary gear stages via at least one dual clutch. Consequently, the dual clutch is now arranged between the electric module and the planetary gear in the torque transmission path. This increases the modularity of the arrangement because the individual components are interchangeable for varying applications.

[0028] In a further preferred embodiment, the first output shaft of the first electric motor is connected to a second output shaft of a second electric motor via a gear connection. In this way, two electric motors are responsible for the drive power, which increases the drive power and the speed range of the multi-speed electric axle drive. In this embodiment, the electric module output shaft, into which the power of both electric motors is fed, implements both input stages of the dual clutch. Consequently, depending on the engaged clutch, a varying transmission ratio of the speed of the electric module output shaft is achieved.

[0029] As an alternative to the first output shaft of the first electric motor being connected to a second output shaft of a second electric motor via a gear connection, in a further preferred embodiment, a first gear stage and a second gear stage are arranged on the first output shaft. In this way, a single electric motor ensures two different input speeds for the respective clutch inputs of the dual clutch.

[0030] This increases the power density and the achievable gear ratio of the multi-speed electric axle drive.

[0031] In the embodiment with the first gearing stage and the second gearing stage on the first output shaft, the first and second gearing stages further preferably directly represent the two input stages of the dual clutch. This achieves a high degree of compactness with very high gear ratios.

[0032] It is advantageous if the electric module output shaft is rigidly connected to a first output shaft of the first electric motor. More preferably, the electric module output shaft is connected in one piece to the first output shaft of the first electric motor. This increases the power density because the first output shaft of the first electric motor represents a direct input variable of the dual clutch, free of transmission losses.

[0033] A particularly preferred embodiment of the multi-gear electric axle drive is characterized in that the first planetary unit has a first stepped planetary gear set, and the second planetary unit has a second stepped planetary gear set. In these stepped planetary gear sets, the respective planetary gear of the planetary transmission has a step change, resulting in two gearing levels. This allows for particularly high gear ratios with only one gear.

[0034] In the embodiment in which the multi-gear electric axle drive has at least two stepped planetary gear units, the first stepped planetary gear set and the second stepped planetary gear set are preferably arranged mirror-symmetrically to one another. This enables a compact, space-optimized gear ratio.

[0035] Further preferably, in the embodiment in which the multi-gear electric axle drive has at least two stepped planetary units, the first stepped planetary gear set and the second stepped planetary gear set roll in a common ring gear. In this way, the planetary gear is further optimized in terms of installation space and component count. In a particularly preferred embodiment, the ring gear is directly connected to the housing in a rotationally fixed manner.

[0036] To further increase the achievable gear ratio, the first planetary unit of the multi-speed electric axle drive, in a preferred variant, has more than one sun gear, preferably two sun gears. The second sun gear of the first planetary unit meshes with the planet carrier driven by the first sun gear, which is configured, for example, as a stepped planetary gear set. This further increases the power density not only of the planet carrier, but of the entire multi-speed electric axle drive.

[0037] In yet another embodiment of the multi-speed electric axle drive according to the invention, the dual clutch has additional stages in order to be configured as a triple clutch or a quadruple clutch, so as to be coupled to a third planetary unit and a fourth planetary unit as the output variable of the triple clutch or quadruple clutch. The term dual clutch in the context of this disclosure is not to be understood as limiting the number. Rather, it implies that at least two input and output stages can be coupled. Once a triple clutch or quadruple clutch is implemented, the power density and the achievable gear ratio from the electric module to the output are further increased.

[0038] In other words, this invention aims to arrange a dual clutch between an electric motor and a first planetary gear set. This general operating principle increases power density and enables the implementation of additional gear ratios.

[0039] This overarching inventive concept has been further developed through various technical embodiments. For example, it is preferably possible to engage a through drive through the first planetary gear set. In this case, the drive is realized via the sun gear of the first planetary gear set. Further preferably, the stepped planetary gear sets are arranged mirror-symmetrically, and a common ring gear of the double stage is fixed, in particular, in a rotationally fixed manner relative to the housing.

[0040] Within the scope of the invention, it is further possible to connect the carrier of the first stage to the sun of the second stage and optionally realize the output via the carrier of the second planetary gear set. The motor driving the electric module is preferably arranged coaxially to the electric module output shaft. Alternatively, the motor is arranged axially parallel to the electric module output shaft.

[0041] The transmission output shaft represents the input to the differential. Differentials can be implemented in various designs. Examples include a coaxial design, a parallel-axis design, or an angular drive. For example, the differential can be integrated into a planetary design as an alternative to a bevel gear differential.

[0042] The present invention will be explained below with reference to the figures, which show: Fig. 1 a schematic view of a multi-speed electric axle drive according to the invention with a dual clutch in a first embodiment; Fig. 2 a schematic view of the multi-gear electric axle drive according to the invention in a second embodiment with two gear stages on an output shaft; Fig. 3 a schematic view of the multi-gear electric axle drive according to the invention in a third embodiment with a second sun on a first planetary gear set; Fig. 4 is a schematic view of the multi-gear electric axle drive according to the invention in a fourth embodiment with a triple clutch; and Fig. 5 a schematic view of the multi-speed electric axle drive according to the invention in a fifth embodiment with a quadruple clutch.

[0043] The figures are merely schematic in nature and serve solely to facilitate understanding of the invention. The individual components of the various embodiments are interchangeable, provided they are covered by the inventive concept. The same elements are provided with the same reference numerals.

[0044] Fig. 1 shows a multi-speed electric axle drive 1 of a motor vehicle. The multi-speed electric axle drive 1 has a drive unit 2, which has at least a first electric motor 3, and a planetary gear 4 connected to the drive unit 2, which has at least a first planetary gear stage 5 and a second planetary gear stage 6, and to whose output shaft 7 a differential gear 8 is connected. According to the invention, an output shaft 9 of the drive unit 2 can be coupled to the first and second planetary gear stages 5, 6 via at least one clutch unit 10 (e.g., as a dual clutch 30a). Consequently, the clutch unit 10 is arranged between the drive unit 2 and the planetary gear 4.

[0045] The first electric motor 3 has a first output shaft 11. This is coupled via a gear connection to a second output shaft 12 of a second electric motor 13. The power of the first output shaft 11 and the second output shaft 12 is fed into the output shaft 9 and transmitted to the planetary gear 4 via one of the transmission paths of the clutch unit 10.

[0046] In order to increase the gear ratio of the planetary gear 4, the first planetary gear stage 5 has a first stepped planetary gear set 14. This is composed of two individual planets 14a, 14b, with the smaller of the two individual planets 14a, 14b being referenced to 14a. For this purpose, the second planetary gear stage 6 has a second stepped planetary gear set 15, which is mirror-symmetrical. This is composed of two individual planets 15a, 15b, with the smaller of the two individual planets 15a, 15b being referenced to 15a. The input variable to the first planetary gear stage 5 is implemented by a first sun gear 16a in the first planetary gear stage 5 and a planet carrier 16b in the first planetary gear stage 5. The input variable to the second planetary gear stage 6 is implemented by a first sun gear 17a in the second planetary gear stage 6.

[0047] Differential 8 can be implemented in various ways. The figures show three examples: a coaxial differential 21, an axially parallel differential 22, and an angularly offset differential 23.

[0048] A ring gear 24, which is immovable relative to a housing 27, meshes with both planetary gear sets 15, 16. A first web 25 and a second web 26 are indicated schematically.

[0049] The clutch unit 10 can be switched as required. With regard to Fig. 1, at a higher gear ratio, the first planetary gear stage 5 is to be engaged, the output of which acts on the second sun gear 17a of the second planetary gear stage 6. At a lower gear ratio, the second planetary gear stage 6 can be engaged directly, which bridges the first planetary gear stage 5.

[0050] It should be noted that the clutch unit 10 is arranged between the drive unit 2 and the planetary gear 4 with respect to the torque flow. Optionally, the clutch is also arranged axially between the drive unit 2 and the planetary gear 4.

[0051] This in connection with Fig. The basic functional principle of the present invention described in Figure 1 also applies to the further embodiments in the Fig. 2 to 5. These use the same reference numerals for the same components as mentioned above. Therefore, for the sake of conciseness, only the individual differences between the respective embodiments are pointed out in the present description of the figures. For a detailed description of the respective functional principle, please refer to the description of Fig. 1.

[0052] In Fig. 2 schematically shows an embodiment in which two pinions are arranged on the output shaft 9 of the drive unit 2, which represent a first spur gear stage 28 and a second spur gear stage 29. The first and second spur gear stages 28, 29 are the direct input stages of the clutch 10. Consequently, a high degree of compactness is achieved. Regarding the other components of the multi-speed electric axle drive 1, reference is made to the description of Fig. 1.

[0053] In the embodiment from Fig. 3, a third sun gear 18 is arranged in the first planetary gear stage 5 next to the first sun gear 16a. This allows a higher and more variable transmission ratio, which can be realized by the multi-speed electric axle drive 1 according to the invention. The third sun gear 18 meshes with the first stepped planetary gear set 14. Regarding the other components of the multi-speed electric axle drive 1, reference is made to the description of Fig. 1.

[0054] In the embodiment from Fig. 4 is the drive unit 2 (as in the embodiment of Fig. 1) consists of the first electric motor 3 and the second electric motor 13. The output shaft 9 finally has three input paths for a triple clutch 30b. The first stepped planetary gear set 14 is accordingly triple-stepped, resulting in the first planetary gear stage 5 and a third stage 19. Regarding the other components of the multi-speed electric axle drive 1, please refer to the description of Fig. 1.

[0055] In the embodiment from Fig. 5 is the drive unit 2 (as in the embodiment of Fig. 1) is composed of the first electric motor 3 and the second electric motor 13. The output shaft 9 finally has four input paths for a quadruple clutch 30c. The first stepped planetary gear set 14 is accordingly quadruple-stepped, resulting in the first planetary gear stage 5, the third stage 19, and a fourth stage 20. Regarding the other components of the multi-speed electric axle drive 1, reference is made to the description of Fig. 1. In addition to the two individual planets 14a, 14b, a third individual planet 14c is also part of this embodiment. List of reference symbols 1 Multi-gear axle drive 2 drive unit 3 First electric motor 4 planetary gears 5 First planetary gear stage 6 Second planetary gear stage 7 Output shaft 8 differential gears 9 Output shaft drive unit 10 Coupling unit 11 First output shaft 12 Second output shaft 13 Second electric motor 14 First stepped planetary gear set 14a First single planet 14b Second single planet 14c Third single planet 15 Second stepped planetary gear set (15a,b,c) 15a First single planet 15b Second single planet 16a First sun gear of the first planetary gear stage 16b Planet carrier of the first planetary gear stage 17a First sun gear of the second planetary gear stage 17b Planet carrier of the second planetary gear stage 18 Third sun gear 19 Third stage 20 Fourth Stage 21 Coaxial differential 22 Axle-parallel differential 23 Angle-offset differential 24 ring gear 25 First jetty 26 Second jetty 27 housings 28 First spur gear stage 29 Second spur gear stage 30a double clutch 30b triple coupling 30c quadruple clutch

Claims

[1] Multi-gear axle drive (1) of a motor vehicle, comprising a drive unit (2) and a planetary gear (4) operatively connected thereto, which comprises at least a first planetary gear stage (5) with a first stepped planetary gear set (14) and a second planetary gear stage (6) with a second stepped planetary gear set (15), wherein the stepped planetary gear sets (14, 15) each comprise individual planets (14a, 14b, 15a, 15b) of different outer diameters which are connected to one another in a rotationally fixed manner via a web (25, 26), wherein a differential gear (8) is connected to an output shaft (7) of the second planetary gear stage (6), which is rotationally fixedly coupled to a second web (26) of the second planetary gear stage (6), characterized bythat the stepped planetary gear sets (14, 15) are arranged relative to one another in such a way that the circumferentially smallest planets (14a, 15a) of the stepped planetary gear sets (14, 15) are in a meshing operative relationship with ring gears (24) which are arranged axially next to one another, wherein the output shaft (9) of the drive unit (2) is connected to the planetary gear (4) by a clutch unit (10). [2] Multi-gear axle drive (1) according to claim 1, characterized by that the planet carrier (16b) of the first planetary gear stage (5) is connected in a rotationally fixed manner to the first sun gear (17a) of the second planetary gear stage (6). [3] Multi-gear axle drive (1) according to claims 1 or 2, characterized by that the ring gears (24) have a common supporting structure which is firmly connected to the housing (27). [4] Multi-gear axle drive (1) according to one of claims 1 to 3, characterized bythat a first output shaft (11) of a first electric motor (3) is connected in a rotationally fixed manner to an output shaft (9) of the drive unit (2) and the first output shaft (11) is arranged coaxially to the output shaft (9) of the drive unit (2). [5] Multi-gear axle drive (1) according to one of claims 1 to 3, characterized by that a second output shaft (12) of a second electric motor (13) is connected to the output shaft (9) of the drive unit (2) via a first spur gear stage (28) and the second output shaft (12) of the second electric motor (13) is arranged parallel to the output shaft (9) of the drive unit (2) [6] Multi-gear axle drive (1) according to claim 1, characterized by that the second output shaft (12) of the second electric motor (13) is operatively connected to clutch elements of the clutch unit (10) via spur gear stages (28, 29) with different gear ratios. [7] Multi-gear axle drive (1) according to one of claims 1 or 6, characterized by that the clutch unit (10) has a first clutch element and a second clutch element, wherein the first clutch element can be brought into operative connection with the planet carrier (16b) of the first planetary gear stage (5) and the second clutch element can be brought into operative connection with a first sun gear (16a) of the first planetary gear stage (5). [8] Multi-gear axle drive according to the preceding claims, characterized by that the individual planets of the first stepped planetary gear set (14) consist of three planets (14a, 14b, 14c) connected to one another in a rotationally fixed manner.

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