Electric axle drive with two output planetary gear sets for a motor vehicle

Abstract

Drive device for a motor vehicle, comprising an electric machine (1) with a rotor, which is operatively connected to a transmission device (3) via a drive shaft (2) designed as a hollow shaft and a single drive shaft (2) non-rotatably connected to the rotor with a first and a second sun gear (14a, 14b) arranged non-rotatably thereon, wherein the transmission device (3) has a first planetary gear set with several first planet gears (4) and a second planetary gear set with several second planet gears (5), wherein the first planet gears (4) are rotatably arranged on a first planet carrier (6a) and are in mesh with the first sun gear (14a) and a first ring gear (8a) which is non-rotatably connected to a first output shaft (7a), wherein the second planet gears (5) are rotatably arranged on a second planet carrier (6b) and are in mesh with the second sun gear (14b) and a second ring gear (8b),which is non-rotatably connected to a second output shaft (7b), in tooth mesh, 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 2011 007 259 A1 discloses a drive device with an electric machine, a first planetary gear, a differential, and an operative connection between a drive shaft of the electric machine and a first sun gear of the first planetary gear. The first sun gear meshes with first planetary gears, which mesh with a stationary first ring gear and are rotatably mounted on a first planetary carrier, which is non-rotatably connected to a differential carrier of the differential. Furthermore, a second planetary gear is operatively connected to at least one second sun gear, which is non-rotatably connected to the drive shaft and meshes with second planetary gears.The second planetary gears mesh with a stationary second ring gear and are rotatably mounted on a second planet carrier, which is non-rotatably connected to the first sun and by an engageable and disengageable rotary connection between the second sun and the second ring gear.

[0003] US 2016 / 0 153 537 A1 shows a transmission device.

[0004] US 4 784 232 A shows an electromechanical axle drive train.

[0005] US 4 813 506 A shows a steering gear. DE 29 17 430 A1 also shows a steering gear.

[0006] DE 10 2017 004 837 A1 discloses a drive device for a motor vehicle, comprising an electric machine having a stator and a rotor which is drivable by the stator and is thereby rotatable about a rotational axis relative to the stator and has a rotor shaft via which at least one torque for driving wheels of the motor vehicle can be provided by the electric machine, wherein in the axial direction of the electric machine on both sides of the latter respective planetary gears are arranged, which have sun gears drivable by the rotor shaft, planet carriers drivable by the rotor shaft via the sun gears as outputs of the drive device, planet gears rotatably mounted on the planet carrier and meshing with the sun gears, and ring gears meshing with the planet gears, which are coupled to one another in such a way thatthat a rotation of one of the ring gears in a first direction of rotation results in a rotation of the other ring gear in a second direction of rotation opposite to the first direction of rotation.

[0007] 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 features of the independent claims. Preferred embodiments can be found in the dependent claims.

[0008] 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 planetary gear set with a plurality of first planet gears and a second planetary gear set with a plurality of second planet gears, wherein the first planet gears are rotatably arranged on a first planet carrier and mesh with the first sun gear and a first ring gear which is rotationally fixedly connected to a first output shaft, wherein the second planet gears are rotatably arranged on a second planet carrier and mesh with the second sun gear and a second ring gear which is rotationally fixedly connected to a second output shaft, and wherein the two planet carriers are operatively connected to one another via a fixed negative transmission ratio.

[0009] A fixed negative gear ratio means that the gear ratio is not variable or adjustable, but has a fixed value, which is negative. Thus, the two planetary carriers are operatively connected to each other via a negative gear.

[0010] 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 the two gear elements. Two meshing gears are designed to transmit torque and speed from one gear to the other. A gear can be, for example, a planetary gear, a sun gear, a ring gear, a spur gear, or a toothed system.

[0011] 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 planetary gears are arranged in the power flow between the respective sun gear and the respective output shaft, which planetary gears are operatively connected to one another via a fixed negative gear 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.

[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] According to a first solution according to the invention, the first planetary carrier is rotationally fixedly connected to a spur gear, with a first toothing on a balance shaft meshing with the spur gear. The second planetary 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.

[0014] According to a second 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.

[0015] The invention includes the technical teaching that the drive shaft protrudes from the electric machine to a first end face and a second end face of the electric machine. The drive shaft and the two output shafts, as well as the first and second planetary gears, rotate about a common axis of rotation.

[0016] Preferably, the first and second planetary gears are identically designed. In other words, the first and second planetary gears have the same dimensions and the same number of teeth.

[0017] Preferably, several balance shafts or pairs of balance shafts are arranged distributed around the circumference and effectively connected to the two planetary carriers. For example, three balance shafts or pairs of balance shafts are arranged distributed around the circumference and effectively connected to the two planetary carriers. This has the advantage that any resulting meshing forces between the balance shafts and the planetary carriers are canceled out.

[0018] 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 not 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.

[0019] According to the Fig. 1 and Fig. 3, a respective drive device according to the invention for a motor vehicle (not shown here) comprises an electric machine 1 and a transmission device 3. The Fig. 2 and Fig. 4 each have a drive device not according to the invention for a motor vehicle (not shown here), an electric machine 1 and a transmission device 3, but with identical components. The electric machine 1 is designed as a prime mover and comprises a stator fixed to the housing and a rotor. A 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 is designed as a hollow shaft.Advantageously, cooling of the electric machine 1 can be effected via a cavity in the drive shaft 2.

[0020] The transmission device 3 comprises a first planetary gear set with a plurality of first planetary gears 4 and a second planetary gear set with a plurality of second planetary gears 5. Due to the schematic representation, only one first and one second planetary gear 4, 5 are shown here. The first and second planetary gears 4, 5 are identical to one another.

[0021] The first planet gears 4 are rotatably arranged on a first planet carrier 6a and mesh with the first sun gear 14a and a first ring gear 8a, wherein the first ring gear 8a is rotationally fixedly connected to a first output shaft 7a. The second planet gears 5 are rotatably arranged on a second planet carrier 6b and mesh with the second sun gear 14b and a second ring gear 8b, wherein the second ring gear 8b is rotationally fixedly connected to a second output shaft 7b. The two ring gears 8a, 8b have internal teeth. The two planet carriers 6a, 6b are operatively connected to one another via a fixed negative gear ratio. The two sun gears 14a, 14b always rotate at the same speed.

[0022] 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 the second gearing 16b on the balance shaft 16 meshes with the third ring gear 8c. For this purpose, the third ring gear 8c has an 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.

[0023] 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 a 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 that 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.

[0024] 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.

[0025] 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 planetary gear 5 second planet 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) with a rotor, which is operatively connected to a transmission device (3) via a single drive shaft (2) designed as a hollow shaft and connected in a rotationally fixed manner to the rotor, 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 planetary gear set with a plurality of first planet gears (4) and a second planetary gear set with a plurality of second planet gears (5), wherein the first planet gears (4) are rotatably arranged on a first planet carrier (6a) and mesh with 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), wherein the second planet gears (5) are rotatably arranged on a second planet carrier (6b) and mesh with the second sun gear (14b) and a second ring gear (8b),which is connected to a second output shaft (7b) in a rotationally fixed manner, are in tooth engagement, and wherein the two planet 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 the preamble of claim 1, 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). [3] Drive device according to one of the preceding claims, characterized by that the respective balance shaft (11, 12, 16) is rotatably mounted in a housing (13) of the transmission device (3). [4] Drive device according to one of the preceding claims, characterized by that the first and second planet gears (4, 5) are identical.

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