Electric axle drive for a motor vehicle with two stepped planetary gear sets on the output shafts

Abstract

Drive device for a motor vehicle, comprising an electric machine (1) which is operatively connected via a drive shaft (2) with a first and a second sun gear (14a, 14b) arranged thereon non-rotatably to a transmission device (3), wherein the transmission device (3) comprises a first stepped planetary gear set with several first stepped planetary gears (4) and a second stepped planetary gear set with several second stepped planetary gears (5), wherein each of the stepped planetary gears (4, 5) comprises a first and a second gear (4a, 4b, 5a, 5b) non-rotatably connected to each other, wherein the first stepped planetary gears (4) are rotatably arranged on a first planet carrier (6a), wherein the second stepped planetary gears (5) are rotatably arranged on a second planet carrier (6b), and wherein the first stepped planetary gears (4) are in tooth mesh with the first sun gear (14a) and a first ring gear (8a) which is non-rotatably connected to a first output shaft (7a). stand,wherein the second stepped planetary gears (5) are in tooth mesh with the second sun gear (14b) and a second ring gear (8b), which is non-rotatably connected to a second output shaft (7b), and wherein the two planet carriers (6a, 6b) are operatively connected to each other via a fixed negative gear ratio, characterized in that the first planet carrier (6a) is non-rotatably connected to a spur gear (9), wherein a first toothing (16a) on a balance shaft (16) is in tooth mesh with the spur gear (9), wherein the second planet carrier (6b) is non-rotatably connected to a third ring gear (8c), wherein a second toothing (16b) on the balance shaft (16) is in tooth mesh with the third ring gear (8c).

Description

[0001] The invention relates to a drive device for a motor vehicle, comprising a transmission device and an electric machine.

[0002] For example, DE 10 2018 101 408 B3 discloses a drive device for a motor vehicle, comprising an electric motor operatively connected to a transmission device via a drive shaft, wherein the transmission device has at least one stepped planetary gear set and a differential stage. The stepped planetary gear set has a plurality of stepped planetary gears, each stepped planetary gear having a first and a second gear connected to one another in a rotationally fixed manner.

[0003] US 2016 / 0 153 537 A1 shows a drive device for a motor vehicle.

[0004] US 5 390 751 A shows a drive device for a construction vehicle, whereby each wheel of the axle can be steered and driven independently of the other.

[0005] WO 2017 / 107 848 A1 shows several transmission diagrams for a drive device of a motor vehicle.

[0006] DE 29 17 430 A1 or AT 355 920 B shows a steering gear for tracked vehicles. The object of the present invention is to further develop a drive device comprising a transmission device and an electric motor, in particular to design it in a weight-optimized, compact, and torsionally rigid manner. This object is achieved by the subject matter of patent claim 1. Preferred embodiments can be found in the dependent claims.

[0007] A drive device according to the invention for a motor vehicle comprises an electric machine which is operatively connected to a transmission device via a drive shaft having a first and a second sun gear arranged thereon in a rotationally fixed manner, wherein the transmission device has a first stepped planetary gear set with a plurality of first stepped planetary gears and a second stepped planetary gear set with a plurality of second stepped planetary gears, wherein each of the stepped planetary gears has a first and a second gear connected to one another in a rotationally fixed manner, wherein the first stepped planetary gears are rotatably arranged on a first planet carrier, wherein the second stepped planetary gears are rotatably arranged on a second planet carrier, and wherein the first stepped planetary gears mesh with the first sun gear and a first ring gear which is rotationally fixedly connected to a first output shaft,wherein the second stepped planetary gears mesh with the second sun gear and a second ring gear which is non-rotatably connected to a first output shaft, and wherein the two planetary carriers are operatively connected to one another via a fixed negative transmission ratio.

[0008] A fixed negative gear ratio means that the gear ratio is not variable or changeable, but has a fixed value, which is negative. Thus, the two planetary carriers are operatively connected to each other via a negative gear.

[0009] The term "operatively connected" means that two gear elements can be directly connected to one another, or that additional gear elements, such as one or more shafts or gears, are located between two gear elements. Two meshing gears are designed to transmit torque and speed from one gear to the other. A gear includes, for example, a gear of a stepped planetary gear, a sun gear, a ring gear, a spur gear, and a toothed system.

[0010] According to the invention, the electric machine has a single drive shaft which has two sun gears formed thereon in a rotationally fixed manner and is designed to drive the motor vehicle. The drive shaft is therefore connected in a rotationally fixed manner, in particular in one piece, to a rotor of the electric machine. A stator of the electric machine is formed fixedly to the housing. The respective output shaft is connected at least indirectly to a respective wheel of a drive axle of the motor vehicle. A differential function is realized in that respective stepped planetary gears are arranged in the power flow between the respective sun gear and the respective output shaft, which are operatively connected to one another via a fixed negative transmission ratio between the planet carriers. In other words, the transmission device has two transmission halves which are drive-connected to the electric machine via the drive shaft and the respective sun gear.

[0011] According to a first alternative according to the invention, the first planet carrier is rotationally fixedly connected to a spur gear, with a first toothing on a balance shaft meshing with the spur gear. The second planet carrier is rotationally fixedly connected to a third ring gear, with a second toothing on the balance shaft meshing with the third ring gear. The respective toothing is preferably designed as a fixed gear on the balance shaft. In particular, the balance shaft is rotatably mounted in a housing of the drive device.

[0012] The respective wheel of the drive axle can be driven at least indirectly via the first and second ring gears. Thus, each of the two ring gears transmits only half the torque of the electric motor and can thus be designed to be lightweight and compact, particularly torsionally rigid. Likewise, all gearing components of the transmission between the two planetary carriers can be designed to be lightweight and compact, since each of them transmits only half the torque of the electric motor.

[0013] The terms "lightweight" and "compact" are particularly to be used in relation to drive devices that comprise an electric motor with a single drive shaft, a differential gear, and two output shafts. Compared to these drive devices, the drive device or drive train according to the invention is both lighter and more compact, as well as more torsionally rigid.

[0014] Preferably, the first sun gear meshes with the first gear of the first stepped planetary gears, while the second sun gear meshes with the first gear of the second stepped planetary gears. In particular, the two sun gears are identically constructed.

[0015] Preferably, the first ring gear meshes with the second gear of the first stepped planetary gears, and the second ring gear meshes with the second gear of the second stepped planetary gears. For this purpose, each ring gear has a respective toothing on its inner circumferential surface.

[0016] According to a second solution according to the invention, the first planet carrier is connected in a rotationally fixed manner to a first spur gear, wherein a first toothing on a first balance shaft meshes with the first spur gear, wherein the second planet carrier is connected in a rotationally fixed manner to a second spur gear, wherein a first toothing on a second balance shaft meshes with the second spur gear and a second toothing on the first balance shaft, and wherein a second toothing on the second balance shaft meshes with the first toothing on the first balance shaft. Thus, the two balance shafts are operatively connected to one another via two common toothing sections. The respective toothing is preferably designed as a fixed gear on the respective balance shaft. In particular, the respective balance shaft is rotatably mounted in a housing of the drive device.

[0017] According to a third solution according to the invention, the first planet carrier is connected in a rotationally fixed manner to a third ring gear, wherein a first toothing on a first balance shaft meshes with the third ring gear, wherein the second planet carrier is connected in a rotationally fixed manner to a fourth ring gear, wherein a first toothing on a second balance shaft meshes with the fourth ring gear, and wherein the first balance shaft has a second toothing which meshes with a second toothing on the second balance shaft. Thus, the two balance shafts are operatively connected to one another via a common toothing section. The respective toothing is preferably designed as a fixed gear on the respective balance shaft. In particular, the respective balance shaft is rotatably mounted in a housing of the drive device.

[0018] The invention includes the technical teaching that the electric machine is arranged coaxially with the first and second stepped planetary gears, wherein the electric machine is arranged axially between the first and second stepped planetary gears. In other words, the drive shaft protrudes from the electric machine toward a first end face and a second end face of the electric machine. The drive shaft and the two output shafts, like the first and second stepped planetary gears, rotate about a common axis of rotation.

[0019] Preferably, a diameter of the first gear of the first stepped planetary gears is larger than a diameter of the second gear of the first stepped planetary gears, and a diameter of the first gear of the second stepped planetary gears is larger than a diameter of the second gear of the second stepped planetary gears. In particular, the first stepped planetary gears are structurally identical to the second stepped planetary gears.

[0020] Preferably, several balance shafts or pairs of balance shafts are arranged distributed around the circumference and are effectively connected to the two ring gears. For example, three balance shafts or pairs of balance shafts are arranged distributed around the circumference and are effectively connected to the two ring gears. This has the advantage that any resulting meshing forces between the balance shafts and the ring gears are canceled out.

[0021] Further measures improving the invention are described in more detail below together with the description of four preferred embodiments of the invention with reference to the figures, wherein like elements are provided with the same reference numerals. Fig. 1 a simplified schematic representation to illustrate the structure of a drive device according to the invention according to a first embodiment, Fig. 2 a simplified schematic representation to illustrate the structure of a drive device according to the invention according to a second embodiment, Fig. 3 a simplified schematic representation to illustrate the structure of a drive device according to the invention according to a third embodiment, and Fig. 4 a simplified schematic representation to illustrate the structure of a drive device not according to the invention according to a fourth embodiment.

[0022] According to the Fig. 1, Fig. 2, and Fig. 3 shows a respective drive device according to the invention and according to the Fig. 4 shows a drive device not according to the invention for a motor vehicle (not shown here), comprising an electric machine 1 and a transmission device 3. The electric machine 1 is designed as a prime mover and comprises a stator fixed to the housing and a rotor. The drive power of the electric machine 1 is introduced into the transmission device 3 via a single drive shaft 2 which is connected in a rotationally fixed manner to the rotor and is arranged between the electric machine 1 and the transmission device 3 and has a first and a second sun gear 14a, 14b arranged thereon in a rotationally fixed manner. Thus, a rotational speed and a torque for driving the motor vehicle are fed into the transmission device 3 via the two sun gears 14a, 14b. The drive shaft 2 can be designed either as a solid shaft or as a hollow shaft. The electric machine 1 can advantageously be cooled via a cavity in the drive shaft 2.

[0023] The transmission device 3 comprises a first stepped planetary gear set with a plurality of first stepped planetary gears 4 and a second stepped planetary gear set with a plurality of second stepped planetary gears 5, wherein each of the stepped planetary gears 4, 5 has a first and a second gear 4a, 4b, 5a, 5b connected to one another in a rotationally fixed manner. Due to the schematic representation, only a first and a second stepped planetary gear 4, 5 is shown here. A diameter of the first gear 4a of the first stepped planetary gears 4 is larger than a diameter of the second gear 4b of the first stepped planetary gears 4. Furthermore, a diameter of the first gear 5a of the second stepped planetary gears 5 is larger than a diameter of the second gear 5b of the second stepped planetary gears 5. The first and second stepped planetary gears 4, 5 are designed identically to one another.

[0024] The first stepped planetary gears 4 are rotatably mounted on a first planet carrier 6a and mesh with the first sun gear 14a and a first ring gear 8a, with the first ring gear 8a being rotationally fixedly connected to a first output shaft 7a. The second stepped planetary gears 5 are rotatably mounted on a second planet carrier 6b and mesh with the second sun gear 14b and a second ring gear 8b, with the second ring gear 8b being rotationally fixedly connected to a second output shaft 7b. The two ring gears 8a, 8b have internal gearing. The two planet carriers 6a, 6b are operatively connected to one another via a fixed negative gear ratio. The electric machine 1 is arranged coaxially with the first and second stepped planetary gears 4, 5. Thus, the input shaft 2 and the stepped planetary gears 4, 5 rotate about a common axis of rotation 15.Furthermore, the electric machine 1 is arranged axially between the first and second planetary gears 4, 5. The two sun gears 14a, 14b always rotate at the same speed.

[0025] According to Fig. 1, the first planet carrier 6a is non-rotatably connected to a spur gear 9. In contrast, the second planet carrier 6b is non-rotatably connected to a third ring gear 8c. A balance shaft 16 with first and second gearings 16a, 16b is operatively arranged between the two planet carriers 6a, 6b. The balance shaft 16 is rotatably mounted in a housing 13 of the transmission device 3. The first gearing 16a on the balance shaft 16 meshes with the spur gear 9, while a second gearing 16b on the balance shaft 16 meshes with the third ring gear 8c. For this purpose, the third ring gear 8c has internal gearing. The fixed negative transmission ratio between the two planet carriers 6a, 6b is realized via the balance shaft 16, which is operatively connected to the spur gear 9 and the third ring gear 8c.Even if only a single balance shaft 16 is shown here, several such balance shafts 16 can be arranged distributed over the circumference and operatively connected to the respective planet carrier 6a, 6b in order to realize the fixed negative transmission ratio between the two planet carriers 6a, 6b.

[0026] According to Fig. 2, the first planet carrier 6a is rotationally fixedly connected to a first spur gear 10a. In contrast, the second planet carrier 6b is rotationally fixedly connected to a second spur gear 10b. A first and a second balance shaft 11, 12 are arranged between the two planet carriers 6a, 6b. The first balance shaft 11 has first and a second toothing 11a, 11b. The second balance shaft 12 also has first and a second toothing 12a, 12b. The two balance shafts 11, 12 are rotatably mounted in a housing 13 of the transmission device 3. The first toothing 11a on the first balance shaft 11 meshes with the first spur gear 10a.The first toothing 12a on the second balance shaft 12 meshes with the second spur gear 10b and the second toothing 11b on the first balance shaft 11, wherein the second toothing 12b on the second balance shaft 12 meshes with the first toothing 11a on the first balance shaft 11. The fixed negative gear ratio between the two planet carriers 6a, 6b is realized via the two balance shafts 11, 12, which are operatively connected to one another and to the respective spur gear 10a, 10b. Even if only one balance shaft pair, consisting of the first and second balance shafts 11, 12, is shown here, several such balance shaft pairs can be arranged distributed over the circumference and operatively connected to the respective planet carrier 6a, 6b in order to realize the fixed negative gear ratio between the two planet carriers 6a, 6b.

[0027] According to Fig. 3, the first planet carrier 6a is rotationally fixedly connected to a third ring gear 8c. In contrast, the second planet carrier 6b is rotationally fixedly connected to a fourth ring gear 8d. A first and a second balance shaft 11, 12 are arranged between the two planet carriers 6a, 6b. The first balance shaft 11 has first and a second toothing 11a, 11b. The second balance shaft 12 also has first and a second toothing 12a, 12b. The two balance shafts 11, 12 are rotatably mounted in a housing 13 of the transmission device 3. The first toothing 11a on the first balance shaft 11 meshes with the third ring gear 8c. The first toothing 12a on the second balance shaft 12 meshes with the fourth ring gear 8d. The second toothing 11b on the first balance shaft 11 meshes with the second toothing 12b on the second balance shaft 12.The fixed negative gear ratio between the two planetary carriers 6a, 6b is realized via the two balance shafts 11, 12, which are operatively connected to each other and to the respective third and fourth ring gears 8c, 8d. Although only one balance shaft pair, consisting of the first and second balance shafts 11, 12, is shown here, several such balance shaft pairs can be arranged distributed over the circumference and operatively connected to the respective planetary carrier 6a, 6b in order to realize the fixed negative gear ratio between the two planetary carriers 6a, 6b.

[0028] According to Fig.4, the first planet carrier 6a is non-rotatably connected to a first spur gear 10a. In contrast, the second planet carrier 6b is non-rotatably connected to a second spur gear 10b. A first and a second balance shaft 11, 12 are arranged between the two planet carriers 6a, 6b. The first balance shaft 11 has first and a second toothing 11a, 11b. The second balance shaft 12 also has first and a second toothing 12a, 12b. The two balance shafts 11, 12 are rotatably mounted in a housing 13 of the transmission device 3. The first toothing 11a on the first balance shaft 11 meshes with the first spur gear 10a. The first toothing 12a on the second balance shaft 12 meshes with the second spur gear 10b. The second toothing 11b on the first balance shaft 11 meshes with the second toothing 12b on the second balance shaft 12.The fixed negative gear ratio between the two planetary carriers 6a, 6b is realized via the two balance shafts 11, 12, which are operatively connected to each other and to the respective spur gear 10a, 10b. Although only one balance shaft pair, consisting of the first and second balance shafts 11, 12, is shown here, several such balance shaft pairs can be arranged distributed over the circumference and operatively connected to the respective planetary carrier 6a, 6b in order to realize the fixed negative gear ratio between the two planetary carriers 6a, 6b. List of reference symbols 1 electric machine 2 drive shaft 3 planetary gears 4 first stepped planetary gear 4a, 4b Gear on the first stepped planetary gear 5 second stepped planetary gear 5a, 5b Gear on the second stepped planetary gear 6a, 6b planet carrier 7a, 7b Output shaft 8a - 8d ring gear 9 Spur gear 10a, 10b Spur gear 11 first balance shaft 11a, 11b Gearing on the first balance shaft 12 second balance shaft 12a, 12b Gearing on the second balance shaft 13 housings 14a, 14b Sun gear 15 axis of rotation 16 balance shaft 16a, 16b Gearing on the balance shaft

Claims

[1] Drive device for a motor vehicle, comprising an electric machine (1) which is operatively connected to a transmission device (3) via a drive shaft (2) with a first and a second sun gear (14a, 14b) arranged thereon in a rotationally fixed manner, wherein the transmission device (3) has a first stepped planetary gear set with a plurality of first stepped planetary gears (4) and a second stepped planetary gear set with a plurality of second stepped planetary gears (5), wherein each of the stepped planetary gears (4, 5) has a first and a second gear (4a, 4b, 5a, 5b) connected to one another in a rotationally fixed manner, wherein the first stepped planetary gears (4) are arranged rotatably on a first planet carrier (6a), wherein the second stepped planetary gears (5) are arranged rotatably on a second planet carrier (6b), and wherein the first stepped planetary gears (4) are connected to the first sun gear (14a) and a first ring gear (8a) which is connected in a rotationally fixed manner to a first output shaft (7a). is in meshing engagement,wherein the second stepped planetary gears (5) are in meshing engagement with the second sun gear (14b) and a second ring gear (8b) which is connected in a rotationally fixed manner to a second output shaft (7b), and wherein the two planetary carriers (6a, 6b) are operatively connected to one another via a fixed negative transmission ratio, , characterized by in that the first planet carrier (6a) is connected in a rotationally fixed manner to a spur gear (9), wherein a first toothing (16a) on a balance shaft (16) is in tooth engagement with the spur gear (9), wherein the second planet carrier (6b) is connected in a rotationally fixed manner to a third ring gear (8c), wherein a second toothing (16b) on the balance shaft (16) is in tooth engagement with the third ring gear (8c). [2] Drive device according to claim 1, characterized bythat the first sun gear (14a) is in meshing engagement with the first gear (4a) of the first stepped planetary gears (4), wherein the second sun gear (14b) is in meshing engagement with the first gear (5a) of the second stepped planetary gears (5). [3] Drive device according to one of the preceding claims, characterized by that the first ring gear (8a) is in meshing engagement with the second gear (4b) of the first stepped planetary gears (4), wherein the second ring gear (8b) is in meshing engagement with the second gear (5b) of the second stepped planetary gears (5). [4] Drive device according to the preamble of claim 1 and one of claims 2 or 3, characterized byin that the first planet carrier (6a) is connected in a rotationally fixed manner to a first spur gear (10a), wherein a first toothing (11a) on a first balance shaft (11) is in tooth engagement with the first spur gear (10a), wherein the second planet carrier (6b) is connected in a rotationally fixed manner to a second spur gear (10b), wherein a first toothing (12a) on a second balance shaft (12) is in tooth engagement with the second spur gear (10b) and a second toothing (11b) on the first balance shaft (11), and wherein a second toothing (12b) on the second balance shaft (12) is in tooth engagement with the first toothing (11a) on the first balance shaft (11). [5] Drive device according to the preamble of claim 1 and one of claims 2 or 3, characterized byin that the first planet carrier (6a) is connected in a rotationally fixed manner to a third ring gear (8c), wherein a first toothing (11a) on a first balance shaft (11) is in tooth engagement with the third ring gear (8c), wherein the second planet carrier (6b) is connected in a rotationally fixed manner to a fourth ring gear (8d), wherein a first toothing (12a) on a second balance shaft (12) is in tooth engagement with the fourth ring gear (8d), and wherein the first balance shaft (11) has a second toothing (11b) which is in tooth engagement with a second toothing (12b) on the second balance shaft (12). [6] Drive device according to one of claims 1 to 5, characterized by that the respective balance shaft (11, 12, 16) is rotatably mounted in a housing (13) of the transmission device (3). [7] Drive device according to one of the preceding claims, characterized bythat a diameter of the first gear (4a) of the first stepped planetary gears (4) is greater than a diameter of the second gear (4b) of the first stepped planetary gears (4), wherein a diameter of the first gear (5a) of the second stepped planetary gears (5) is greater than a diameter of the second gear (5b) of the second stepped planetary gears (5).

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