Transmission and drivetrain for a vehicle

Abstract

The invention relates to a transmission (3) for a drive train (2) of an at least partially electrically driven vehicle (1), comprising a planetary gear set (P) with a first planetary gear set (P1) and a second planetary gear set (P2), wherein a first gear set element of the first planetary gear set (P1) is rotationally fixed to an input shaft (4) which is provided to be operatively connected to a rotor (5) of an electric machine (11), wherein a second gear set element of the first planetary gear set (P1) is rotationally fixed to a second gear set element of the second planetary gear set (P2), wherein a third gear set element of the first planetary gear set (P1) is fixed to the housing, and wherein a first gear set element of the second planetary gear set (P2) is rotationally fixed to a first output shaft (14) of the transmission (3).and wherein a third gear set element of the second planetary gear set (P2) is rotationally fixed to a second output shaft (15) of the transmission (3). Furthermore, the invention relates to a drive train (2) comprising such a transmission (3).

Description

[0001] The invention relates to a transmission for a drive train of an at least partially electrically powered vehicle. The invention further relates to a drive train comprising such a transmission.

[0002] From the publication WO 2014 / 139 744 A1, a drive train for a vehicle is known, comprising at least one electric drive that can be coupled to at least a first gear ratio and a second gear ratio via a drive shaft. At least one shifting device is provided for shifting the gear ratios, wherein the shifting device comprises at least one positive shifting element and at least one frictional shifting element for performing power shifts. Each of the gear ratios can be shifted using the positive shifting element, wherein at least one of the gear ratios can be shifted using both the positive shifting element and the frictional shifting element.

[0003] The object of the present invention is to provide a transmission that offers improved power density while simultaneously requiring less installation space. This object is achieved according to a first aspect of the invention with a transmission according to claim 1. The object is further achieved according to a second aspect of the invention with a drive train according to claim 8. Advantageous embodiments emerge from the dependent claims.

[0004] According to a first aspect of the invention, a transmission for a drive train of an at least partially electrically driven vehicle comprises a planetary transmission with a first planetary gear set and a second planetary gear set, wherein a first gear set element of the first planetary gear set is connected in a rotationally fixed manner to an input shaft which is intended to be operatively connected to a rotor of an electric machine, wherein a second gear set element of the first planetary gear set is connected in a rotationally fixed manner to a second gear set element of the second planetary gear set, wherein a third gear set element of the first planetary gear set is arranged fixedly to the housing, wherein a first gear set element of the second planetary gear set is connected in a rotationally fixed manner to a first output shaft of the transmission, and wherein a third gear set element of the second planetary gear set is connected in a rotationally fixed manner to a second output shaft of the transmission.

[0005] The second planetary gear set performs the function of an integrated differential, with the differential input being formed by the second gear set element of the second planetary gear set and the differential outputs by the first and third gear set elements of the second planetary gear set. Two of the three gear set elements of the second planetary gear set are drivingly connected to a respective output shaft, with the remaining gear set element transferring the drive power from the first planetary gear set to the second planetary gear set, which acts as a differential. With such a transmission, the transferable power in electric drives can be significantly increased compared to conventional electric drives, which, for example, comprise single- or multi-stage spur gear stages that transfer drive power to a differential for distribution to output shafts. This allows the power density to be increased.In addition, the transmission can be designed much more compactly and / or manufactured more cost-effectively. Instead of making the transmission more compact, the transmittable power can be increased within the same installation space.

[0006] The two planetary gear sets are preferably arranged axially adjacent to one another. This enables a radially compact design of the transmission. The first gear set element of the respective planetary gear set is preferably a sun gear, the second gear set element of the respective planetary gear set is a planet carrier, and the third gear set element of the respective planetary gear set is a ring gear. Accordingly, the first sun gear of the first planetary gear set is connected in a rotationally fixed manner to the input shaft of the transmission, the planet carriers of the two planetary gear sets are connected in a rotationally fixed manner to one another, and the first ring gear of the first planetary gear set is arranged fixedly with the housing or is connected in a rotationally fixed manner to the housing of the transmission or the chassis of the vehicle.The second sun gear of the second planetary gear set is rotationally fixedly connected to the first output shaft of the transmission, while the second ring gear of the second planetary gear set is rotationally fixedly connected to the second output shaft of the transmission. The output shafts are each operatively connected at least indirectly to a wheel of a common axle of the vehicle.

[0007] Furthermore, the two planetary gear sets preferably form a stepped planetary gear set, wherein the planet carriers of the planetary gear sets are connected to one another in one piece. The planet carriers are thus combined to form a single structural unit. According to one exemplary embodiment, at least two stepped planetary gears are rotatably mounted on the planet carriers, each comprising a first gear that meshes with the first sun gear and the first ring gear of the first planetary gear set, and a second gear that is non-rotatably connected thereto and meshes with the second sun gear and the second ring gear of the second planetary gear set. Each of the stepped planetary gears is rotatable about a planetary pin and, in the case of a rotating planet carrier or stepped planetary gear carrier, is rotatable about a transmission axis of the planetary gear set.The two gears are arranged coaxially to each other and can be connected to each other via an intermediate shaft or directly in a rotationally fixed manner.

[0008] The two gears of each stepped planetary gear have different diameters and numbers of teeth. In particular, the first gear has a larger diameter than the second gear. Gears that mesh or mesh with each other transmit speed and torque via their intermeshing teeth. The advantage of a stepped planetary gear set is that the planet carriers, which are connected in a rotationally fixed manner, do not require any connection to other transmission components, thus providing a cost-optimized transmission. Furthermore, the stepped planetary gear set exhibits comparatively good mechanical characteristics—i.e., speed and torque—while maintaining high efficiency at a high conversion ratio.

[0009] Preferably, one of the sun gears extends axially at least partially through the other sun gear. Thus, at least one of the sun gears, and preferably both sun gears depending on the design of the drive train, is hollow and connected to a respective hollow shaft.

[0010] The second planetary gear set serves as an integrated differential and is connected to the first planetary gear set by the second gear set elements, which are connected to one another in a rotationally fixed manner. At the second planetary gear set, the drive power coming from the first planetary gear set is distributed between the two output shafts, preferably 50% each. In other words, the integral differential allows the input torque coming from the first planetary gear set to be converted and distributed or transmitted to the two output shafts in a defined ratio. Preferably, the input torque is transmitted 50% each, i.e., half, to the output shafts.While the first ring gear supports the drive torque on the housing, the first sun gear transmits a first portion of the drive power with a respective gear ratio, at least indirectly, to the first output shaft, while the second ring gear transmits a second portion of the drive power with a respective gear ratio, at least indirectly, to the second output shaft. The output shafts are arranged coaxially to an output axle. By eliminating additional components for a differential and by saving on screw and / or welded connections, a compact transmission design can be achieved.

[0011] Preferably, a maximum of five stepped planetary gears are rotatably mounted on the planetary carriers. In other words, the planetary gear set can be equipped with any number of stepped planetary gears. A variable configuration of the planetary gear sets enables a modular transmission system. This allows for the creation of a basic transmission that can be adapted for different vehicle and / or torque classes with minimal modifications. This significantly reduces the manufacturing costs of the transmission, especially for large production runs.

[0012] An "operative connection" or "drive connection" is understood to mean a connection between two torque-carrying parts that allows torque or power to be transmitted between these parts. In particular, both parts are mounted so that they can rotate. Drive connections include both those that have no gear ratio or intermediate components, as well as those that do have gear ratios or intermediate components. For example, additional shafts and / or gears can be arranged between two shafts or two gears in a drive-effective manner. Such a connection can also be a non-rotatable connection.

[0013] The term "at least indirectly" means that two components are connected to each other via at least one additional component arranged between the two components, or are directly and thus immediately connected to each other. Thus, additional components can be arranged between shafts or gears that are operatively connected to the shaft or gear.

[0014] A "shaft," be it an input shaft, an output shaft, an intermediate shaft, or the like, is a rotatable component of the transmission through which the associated components of the transmission are connected to one another in a rotationally fixed manner. The respective shaft can connect the components axially or radially, or even both axially and radially. A shaft is not exclusively understood to mean, for example, a cylindrical, rotatably mounted machine element for transmitting torque, but rather also general connecting elements that connect individual components or elements to one another, in particular connecting elements that connect several elements to one another in a rotationally fixed manner.

[0015] According to a second aspect of the invention, a drive train for an at least partially electrically powered vehicle comprises a transmission according to the first aspect of the invention, as well as an electric machine whose rotor is connected in a rotationally fixed manner to the input shaft of the transmission. The rotor shaft or the rotor of the electric machine serves as the output shaft of the electric machine during rotor operation of the electric machine. The input shaft of the transmission can be connected in a rotationally fixed manner to the rotor shaft or form the rotor shaft. During rotor operation of the electric machine, electrical energy is fed into the electric machine, for example from an energy storage device, in particular a battery or the like, which results in rotation of the rotor relative to a stator of the electric machine to generate drive power, wherein the drive power is provided for rotationally driving the first gear set element of the first planetary gear set.In generator mode, however, the electric motor generates electrical energy. In generator mode, the transmission's output shafts act as input shafts, while the input shaft is the transmission's output shaft. In this case, the vehicle's drive power is fed into the electric motor via the transmission, allowing the electric motor to generate electrical energy, which can then be fed into the energy storage device for storage. In generator mode, power from the vehicle's rotating wheels, which are operatively connected to the output shafts, is fed into the electric motor via the transmission.

[0016] Preferably, the electric motor is arranged coaxially with the output shafts. Accordingly, the input shaft, which is arranged coaxially with the rotor of the electric motor, is also arranged coaxially with the output shafts. The drive train is thus designed in a coaxial manner.

[0017] The drivetrain according to the invention and the transmission according to the invention can be used in purely electrically powered vehicles as well as in hybrid-powered vehicles that are partially electrically powered and optionally partially driven by a separate combustion engine. Depending on the design and number of driven axles, the vehicle can also comprise two or more such drivetrains or transmissions, whereby one axle, several axles, or all axles of the vehicle can be equipped with the respective drivetrain according to the invention and thus designed to be drivable. Such a vehicle is therefore understood to mean motor vehicles, in particular passenger cars, commercial vehicles, or trucks.

[0018] It is understood that features of the solutions described above or in the claims and / or figures may also be combined if necessary in order to be able to implement the advantages and effects mentioned here cumulatively.

[0019] The invention is described below with reference to the figures, which show a preferred embodiment of the invention. In detail: Fig. 1 a vehicle comprising a drive train according to the invention with a transmission according to the invention according to a first embodiment; and Fig. 2 a schematic representation of the transmission according to the invention according to Fig. 1;

[0020] Fig. Figure 1 shows an electrically powered vehicle 1 with a drive train 2 according to the invention, in accordance with a preferred embodiment. The drive train 2 is arranged on one of the axles of the vehicle 1, thus making this axle a driven axle. The drive train 2 comprises an electric machine 11, which generates drive power and transmits it to a transmission 3. The transmission 3 is in Fig. 2, wherein the transmission 3 has an integrated differential, by means of which a drive power of the electric machine 11 can be divided between two output shafts 14, 15. The vehicle 1 can further comprise an energy storage device (not shown here) that supplies the electric machine 11 with electrical energy and that is supplied with electrical energy by the electric machine 11 during reverse power flow, i.e., in generator mode. The energy storage device can be, for example, a battery or the like. In addition, the electric machine 11 is connected to power electronics (also not shown here).

[0021] In Fig. 2 is the Fig. 1, a highly schematic representation of the transmission 3 according to the invention is shown. The transmission 3 comprises an input shaft 4 which is connected in a rotationally fixed manner to a rotor 5 of the electric machine 11. The rotor 5 is rotatably mounted relative to a stator 6 fixed to the housing. The transmission 3 comprises a planetary transmission P with two planetary gear sets P1, P2, wherein a transmission ratio is set by means of the first planetary gear set P1 and wherein a differential function is performed by means of the second planetary gear set P2. The planetary gear sets P1, P2 of the planetary transmission P, which are arranged axially adjacent to one another, are designed as a stepped planetary gear set. A first sun gear 7a of the first planetary gear set P1 is connected in a rotationally fixed manner to the input shaft 4. A first planet carrier 9a of the first planetary gear set P1 and a second planet carrier 9b of the second planetary gear set P2 form a coherent, one-piece component.When "a planetary carrier" is referred to below, this refers to the structural unit consisting of the two planetary carriers 9a, 9b. A first ring gear 8a of the first planetary gear set P1 is fixedly arranged on a housing 19. A second sun gear 7b of the second planetary gear set P2 is rotationally fixedly connected to the first output shaft 14, and a second ring gear 8b of the second planetary gear set P2 is rotationally fixedly connected to the second output shaft 15. At least two and at most five rotatably mounted stepped planetary gears 10 are arranged on the planetary carrier 9a, 9b. Each stepped planetary gear 10 comprises a first gear 12, which meshes with the first sun gear 7a and the first ring gear 8a of the first planetary gear set P1, and a second gear 13, which is connected in a rotationally fixed manner thereto and meshes with the second sun gear 7b and the second ring gear 8b of the second planetary gear set P2.

[0022] The second planetary gear set P2 is designed in such a way that the drive power coming from the first planetary gear set P1 via the first planet carrier 9a is distributed by means of the second planetary gear set P2 to the first output shaft 14 and the second output shaft 15, which in turn are each driven according to Fig. 1 are drivingly connected to a wheel 18 of the vehicle 1. At the stepped planetary gears 10, the drive power is distributed among the meshing gear set elements of the second planetary gear set P2. The electric machine 11, the planetary gear sets P1, P2 and the output shafts 14, 15 are located on a common drive axle 16 and output axle 17, respectively, with the first output shaft 14, which in Fig.2, is guided axially through the electric machine 11. Thus, the electric machine 11, the input shaft 4, the planetary gear sets P1, P2, and the output shafts 14, 15 are arranged coaxially with one another. With such a transmission 3, an axially compact drive train 2 can be realized. Additional intermediate components, such as drive shafts, transmission gears, spring and damping elements, or the like, can be arranged between the output shafts 14, 15 and the wheels 18 of the vehicle 1 that are operatively connected thereto. Reference symbol 1 vehicle 2 Drivetrain 3 gearboxes 4 Input shaft 5 Rotor of the electric machine 6 Stator of the electric machine 7a First sun gear 7b Second sun gear 8a First ring gear 8b Second ring gear 9a First planet carrier 9b Second planet carrier 10 stepped planetary gears 11 Electric machine 12 First gear 13 Second gear 14 First output shaft 15 Second output shaft 16 drive axle 17 Output axle 18 Wheel of the vehicle 19 housings P planetary gear P1 First planetary gear set P2 Second planetary gear set QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2014 / 139 744 A1

[0002]

Claims

[1] Transmission (3) for a drive train (2) of an at least partially electrically driven vehicle (1), comprising a planetary transmission (P) with a first planetary gear set (P1) and a second planetary gear set (P2), wherein a first gear set element of the first planetary gear set (P1) is connected in a rotationally fixed manner to an input shaft (4) which is intended to be operatively connected to a rotor (5) of an electric machine (11), wherein a second gear set element of the first planetary gear set (P1) is connected in a rotationally fixed manner to a second gear set element of the second planetary gear set (P2), wherein a third gear set element of the first planetary gear set (P1) is arranged fixedly to the housing, wherein a first gear set element of the second planetary gear set (P2) is connected in a rotationally fixed manner to a first output shaft (14) of the transmission (3), and wherein a third gear set element of the second planetary gear set (P2) is connected to a second output shaft (15) of the transmission (3) is connected in a rotationally fixed manner. [2] Transmission (3) according to claim 1, wherein the first gear set element of the respective planetary gear set (P1, P2) is a sun gear (7a, 7b), the second gear set element of the respective planetary gear set (P1, P2) is a planet carrier (9a, 9b) and the third gear set element of the respective planetary gear set (P1, P2) is a ring gear (8a, 8b). [3] Transmission (3) according to claim 2, wherein the two planetary gear sets (P1, P2) form a stepped planetary gear set, wherein the planet carriers (9a, 9b) of the planetary gear sets (P1, P2) are connected to one another in one piece. [4] Transmission (3) according to claim 3, wherein at least two stepped planetary gears (10) are rotatably mounted on the planet carriers (9a, 9b), each comprising a first gear (12) which meshes with the first sun gear (7a) and the first ring gear (8a) of the first planetary gear set (P1), and a second gear (13) which is connected in a rotationally fixed manner thereto and which meshes with the second sun gear (7b) and the second ring gear (8b) of the second planetary gear set (P2). [5] Transmission (3) according to claim 4, wherein at most five stepped planetary gears (10) are rotatably mounted on the planet carriers (9a, 9b). [6] Transmission (3) according to one of the preceding claims, wherein the two planetary gear sets (P1, P2) are arranged axially adjacent to one another. [7] Transmission (3) according to one of the preceding claims, wherein the input shaft (4) and the output shafts (14, 15) are arranged coaxially to one another. [8] Drive train (2) for an at least partially electrically driven vehicle (1), comprising a transmission (3) according to one of the preceding claims and an electric machine (11), the rotor (5) of which is connected in a rotationally fixed manner to the input shaft (4) of the transmission (3). [9] Drive train (2) according to claim 8, wherein the electric machine (11) is arranged coaxially to the output shafts (14, 15).

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