Drive device with two gear stages

Abstract

Drive device for a motor vehicle, comprising an electric machine (1) with a rotor shaft (17) which is operatively connected to a transmission device (3) via a coupling unit (2), wherein the transmission device (3) has a stepped planetary gear set (4) and a differential stage (6), wherein the differential stage (6) is configured to distribute a drive power of the electric machine (1) to a first and second output shaft (12a, 12b), wherein the stepped planetary gear set (4) has several stepped planetary gears (5), each stepped planetary gear (5) having a first and a second gear (5a, 5b), wherein the stepped planetary gears (5) are rotatably arranged on a planet carrier (7), wherein the first gear (5a) is in mesh with a first sun gear (8a), and wherein the second gear (5b) is in mesh with a second sun gear (8b) and a ring gear (9), wherein the first and second sun gears (8a,8b) are operatively connected to the clutch unit (2), wherein a freewheel device (10) is arranged in a first power path between the clutch unit (2) and the second gear (5b) via the first sun gear (8a) and the first gear (5a) to the second gear (5b), which is designed to couple the second gear (5b) to the clutch unit (2) via the first gear (5a) in a first switching position in order to realize a first gear stage, and in a second switching position to decouple the first power path from the second gear (5b) in order to realize a second gear stage via a second power path from the clutch unit (2) via the second sun gear (8b) to the second gear (5b).

Description

[0001] The invention relates to a drive device for a motor vehicle, comprising an electric machine which is operatively connected to a transmission device via a clutch unit.

[0002] For example, DE 10 2014 215 455 A1 discloses a transmission with a spur gear having a first and a second sub-transmission, which can be coupled to an output element of a drive motor via a clutch. Torque is transmitted to an output shaft of the transmission via one of the sub-transmissions, with a powershift transmission arranged between the input shaft and the output shaft in the torque flow, which transmits torque during a shift between the sub-transmissions. The powershift transmission can be coupled to the shafts of the transmission or sub-transmissions by means of a shifting device. According to an alternative proposal in the description, the shifting unit can be replaced by a switchable freewheel.

[0003] DE 10 2009 041 085 A1 shows an automatic transmission for a motor vehicle with a first planetary gear set and with a second planetary gear set and with at least one shifting element, wherein the two planetary gear sets each have a ring gear, at least one planet gear and a sun gear, and wherein the two planetary gear sets can be coupled to one another by means of the shifting element.

[0004] The object of the present invention is to further develop a drive device, particularly to design it in a compact and performance-optimized manner. This object is achieved by the subject matter of patent claim 1. Preferred embodiments can be found in the dependent claims.

[0005] A drive device according to the invention for a motor vehicle comprises an electric machine with a rotor shaft, which is operatively connected to a transmission device via a clutch unit, wherein the transmission device has a stepped planetary gear set and a differential stage, wherein the differential stage is designed to distribute a drive power of the electric machine to a first and second output shaft, wherein the stepped planetary gear set has a plurality of stepped planetary gears, wherein each stepped planetary gear has a first and a second gear, wherein the stepped planetary gears are rotatably arranged on a planet carrier, wherein the first gear is in meshing engagement with a first sun gear, and wherein the second gear is in meshing engagement with a second sun gear and a ring gear, wherein the first and second sun gears are operatively connected to the clutch unit, wherein in a first power path,which extends from the clutch unit via the first sun gear and the first gear to the second gear, a freewheel device is arranged which is designed to drive-couple the second gear to the clutch unit via the first gear in a first switching position in order to realize a first gear stage, and to drive-decouple the first power path from the second gear in a second switching position in order to realize a second gear stage via a second power path which extends from the clutch unit via the second sun gear to the second gear stage.

[0006] The freewheel device therefore enables, on the one hand, the drive coupling of the second gear to the clutch unit via the first gear and the first sun gear, and, on the other hand, the drive decoupling of the first power path. This means that the power flow in a coupled state or according to the first switching position of the freewheel device occurs via the first power path from the clutch unit via the first sun gear and the first gear to the second gear, whereby the power flow in a decoupled state or according to the second switching position of the freewheel device occurs via the second power path from the clutch unit via the second sun gear to the second gear. A gear ratio in the first power path is not the same as a gear ratio in the second power path.

[0007] The invention includes the technical teaching that the freewheel device has a first element which is intended to be connected in a rotationally fixed manner to an input-side element, a second element which is intended to be connected in a rotationally fixed manner to an output-side element, and a third element which is switchably arranged between the first and the second element.

[0008] In a first switching state, the third element is provided to connect the first and second elements in a rotationally fixed manner, depending on a direction of rotation between the first and second elements, and to transmit a torque and a rotational speed between the first and second elements. Furthermore, in a second switching state, the third element is provided to decouple the first and second elements in an opposite direction of rotation between the first and second elements, in order to prevent any torque or rotational speed from being transmitted between the first and second elements. The two gear stages can be represented by the two switching positions of the freewheel device.

[0009] The exact position of the freewheel device in the first power path is irrelevant. What is important is that the freewheel device is arranged in the first power path between the clutch unit and the second gear. For example, the freewheel device can be arranged between the clutch unit and the first sun gear, with the freewheel device then being connected to the clutch unit on the one hand and to the first sun gear on the other. Alternatively, the freewheel device can be arranged between the first gear and the second gear, with the freewheel device then being connected to the first gear on the one hand and to the second gear on the other.

[0010] The clutch unit is preferably designed as a powershift clutch. A “powershift clutch” is understood to mean a device that has at least one open and one closed state and can be switched between the at least two states under load. In the open state, the clutch unit does not transmit any torque. Thus, the clutch unit only transmits torque between two shafts operatively connected to the clutch unit in an at least partially closed state, wherein the two shafts are connected to one another in a rotationally fixed manner when the clutch unit is closed. Thus, in the closed state of the clutch unit, the electric machine and the second sun gear are drive-connected, wherein in the open state of the clutch unit, the electric machine is decoupled from the second sun gear and the power is fed into the transmission device solely via the first sun gear.

[0011] In particular, the clutch can be actuated by an actuator to initiate opening or closing of the clutch. The actuator can be hydraulically, electromechanically, electromagnetically, or even pneumatically actuated, for example. In particular, the actuator is integrated into the clutch unit.

[0012] The invention includes the technical teaching that a gear ratio between the first sun gear and the first gear is greater than a gear ratio between the second sun gear and the second gear. In particular, the first gear has a larger diameter than the second gear.

[0013] 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, and a ring gear.

[0014] Preferably, the ring gear is fixedly mounted on a housing of the transmission device. Thus, the ring gear is connected to the housing in a rotationally fixed manner.

[0015] In particular, each stepped planetary gear is rotatably mounted on a respective pin, with the respective pin being non-rotatably connected to the planetary carrier. Preferably, the planetary carrier is operatively connected to the differential stage.

[0016] According to a measure further improving the invention, the differential stage comprises a first planetary gear set with a plurality of first planetary gears and a second planetary gear set with a plurality of second planetary gears, wherein the planetary gears of both planetary gear sets are rotatably arranged on the planet carrier. In other words, both the stepped planetary gears of the stepped planetary gear set and the first and second planetary gears of the differential stage are arranged on the planet carrier. In particular, a stepped planetary gear of the stepped planetary gear set is rotatably mounted together with a first or second planetary gear of the differential stage on a common bolt, wherein the common bolt is connected in a rotationally fixed manner to the planet carrier.

[0017] Preferably, the stepped planetary gears of the stepped planetary gear set are arranged on a common axis with the first planetary gears of the first planetary gear set or with the second planetary gears of the second planetary gear set. This provides particular advantages in the manufacture and assembly of the transmission device.

[0018] Preferably, the first planetary gears mesh with a toothing on the first output shaft, the second planetary gears mesh with a toothing on the second output shaft, and the planetary gears of both planetary sets mesh with each other in pairs. Thus, a first planetary gear always meshes with a second planetary gear and the toothing on the first output shaft, and a second planetary gear always meshes with a first planetary gear and the toothing on the second output shaft.

[0019] Furthermore, the electric machine preferably has a stator and a rotor, wherein the rotor is connected to the clutch unit via a rotor shaft. Thus, the rotor shaft serves as a drive shaft arranged between the electric machine and the clutch unit.

[0020] According to a preferred embodiment, the electric machine is arranged coaxially with the differential stage, with the rotor shaft being designed as a hollow shaft and the first output shaft passing through the rotor shaft. Alternatively, an additional transmission device is arranged in the power flow between the electric machine and the clutch unit, with the rotor shaft being arranged parallel to the two output shafts. Preferably, both output shafts are arranged on a common axis and form an electric drive axle of the motor vehicle.

[0021] Advantageously, the clutch unit is designed to be power-shiftable and has a first and a second clutch pack, wherein the first clutch pack is connected in a rotationally fixed manner to the first sun gear and the rotor shaft, and wherein the second clutch pack is connected in a rotationally fixed manner to the second sun gear. In particular, the clutch unit is designed as a friction-disk clutch, wherein the first clutch pack forms, in particular, the outer friction plates and the second clutch pack forms, in particular, the inner friction plates. The clutch unit is closed by actuation, wherein the friction plates come into contact with their end faces in order to connect the rotor shaft in a rotationally fixed manner to the first and second sun gear.

[0022] Further measures improving the invention are described in more detail below together with the description of two preferred embodiments of the invention with reference to the two figures. Fig. 1 a simplified schematic representation to illustrate the structure of a drive device according to the invention according to a first embodiment, and Fig. 2 a simplified schematic representation to illustrate the structure of a drive device according to the invention according to a second embodiment.

[0023] According to the Fig. 1 and Fig. 2, a respective drive device according to the invention for a motor vehicle (not shown here) comprises an electric machine 1, a clutch unit 2, and a transmission device 3. The electric machine 1 is designed as a prime mover and comprises a stator 15 and a rotor 16. A drive power of the electric machine 1 is introduced via a rotor shaft 17, which is arranged between the electric machine 1 and the clutch unit 2, into the clutch unit 2 and therefrom into the transmission device 3 in order to drive the motor vehicle. The transmission device 3 comprises a stepped planetary gear set 4 and a differential stage 6. The differential stage 6 is designed to distribute a drive power of the electric machine 1 between a first and second output shaft 12a, 12b.

[0024] The differential stage 6 has a first planetary gear set with a plurality of first planetary gears 6a and a second planetary gear set with a plurality of second planetary gears 6b.

[0025] Due to the simplified schematic representation, only a first and a second planetary gear 6a, 6b are shown here. The planetary gears 6a, 6b of both planetary sets are rotatably mounted on a planetary carrier 7. The first planetary gears 6a mesh with a toothing 13a on the first output shaft 12a, while the second planetary gears 6b mesh with a toothing 13b on the second output shaft 12b. Furthermore, the planetary gears 6a, 6b of both planetary sets mesh with each other in pairs.

[0026] The stepped planetary gear set 4 has a plurality of stepped planetary gears 5, each stepped planetary gear 5 having a first and a second gear 5a, 5b. Due to the simplified schematic representation, only one stepped planetary gear 5 is shown here, the stepped planetary gears 5 being identical to one another. Furthermore, the stepped planetary gears 5 are also rotatably mounted on the planet carrier 7. The stepped planetary gears 5 of the stepped planetary gear set 4 are arranged on a common axis with the first planetary gears 6a of the first planetary gear set. The first gear 5a meshes with a first sun gear 8a, while the second gear 5b meshes with a second sun gear 8b and a ring gear 9. The ring gear 9 is stationary on a housing 11 of the transmission device 3. The first and second sun gears 8a, 8b are operatively connected to the clutch unit 2.

[0027] A first power path, in which a freewheel device 10 is arranged, extends from the clutch unit 2 via the first sun gear 8a and the first gear 5a to the second gear 5b. A second power path extends from the clutch unit 2 via the second sun gear 8b to the second gear 5b. The freewheel device 10 is designed to drive-couple the second gear 5b via the first gear 5a and the first sun gear 8a to the clutch unit 2 in a first switching position in order to realize a first gear stage, and to drive-decouple the first power path from the second gear 5b in a second switching position in order to realize a second gear stage via the second power path.

[0028] According to Fig. 1, the freewheel device 10 is arranged between the first gear 5a and the second gear 5b. Alternatively, the freewheel device 10 could be arranged between the clutch unit 2 and the first sun gear 8a. Furthermore, the electric machine 1 is arranged coaxially to the differential stage 6, wherein the rotor shaft 17 is designed as a hollow shaft and the first output shaft 12a is guided through the rotor shaft 17. The clutch unit 2 is designed to be power-shiftable and has a first and second clutch pack 14a, 14b, wherein the first clutch pack 14a is connected in a rotationally fixed manner to the first sun gear 8a and the rotor shaft 17, and wherein the second clutch pack 14b is connected in a rotationally fixed manner to the second sun gear 8b.

[0029] According to Fig. 2, the freewheel device 10 is arranged between the clutch unit 2 and the first sun gear 8a. Alternatively, the freewheel device 10 could be arranged between the first gear 5a and the second gear 5b. Furthermore, an additional transmission device 18 is arranged in the power flow between the electric machine 1 and the clutch unit 2, wherein the rotor shaft 17 is arranged parallel to the two output shafts 12a, 12b. The additional transmission device 18 is represented in a simplified form by a fixed gear 19, wherein the fixed gear 19 is arranged on a shaft 20 and meshes with a fixed gear 21 on the rotor shaft 17 and with a fixed gear 22 on a shaft 23 that connects the clutch unit 2 and the first sun gear 8a in a rotationally fixed manner.The clutch unit 2 is designed to be power-shiftable and has a first and a second clutch pack 14a, 14b, wherein the first clutch pack 14a is connected to the first sun gear 8a via the shaft 23 in a rotationally fixed manner, and wherein the second clutch pack 14b is connected to the second sun gear 8b via a shaft 24 which connects the clutch unit 2 and the second sun gear 8b in a rotationally fixed manner.

[0030] According to the Fig. 1 and Fig. 2, the clutch unit 2 is designed as a friction-disk clutch and enables powershift capability. In this case, the first clutch pack 14a is designed as an outer disk pack, while the second clutch pack 14b is designed as an inner disk pack. The clutch unit 2 is actuated by an actuator (not shown here).

[0031] The freewheel device 10 automatically closes in a first direction of rotation and opens in a second direction of rotation. The first direction of rotation is defined as the direction of rotation for forward travel of the motor vehicle. Accordingly, the second direction of rotation is defined as the direction of rotation for reverse travel of the motor vehicle.

[0032] If the clutch unit 2 is open, the first gear is active, with the first and second power paths being mechanically decoupled from one another. When the electric machine 1 initiates a rotary movement in the first direction of rotation into the transmission device 3, this movement is transmitted via the first power path, with the freewheel device 10 closing. The drive power is transmitted via the first sun gear 8a to the first gear 5a and then to the second gear 5b, with the drive power being transmitted via the planet carrier 7 to the differential stage 6 and therefrom to the output shafts 12a, 12b. The first gear has a higher gear ratio than the second gear. When the clutch device 2 is open, no drive power can be transmitted to the differential stage 6 because the freewheel unit 10 opens automatically in the second direction of rotation.To engage a reverse gear, the clutch unit 2 would have to be closed and the electric machine 1 would have to initiate a rotational movement in the transmission device 3 according to the second direction of rotation.

[0033] If the clutch unit 2 is closed and the electric machine 1 initiates a rotational movement in the first direction of rotation into the transmission device 3, the second gear stage becomes active, whereby the first and second power paths are coupled to one another via the clutch unit 2. However, the freewheel device 10 opens simultaneously and automatically due to the gear ratio between the first sun gear 8a and the first gear 5a, which is greater than the gear ratio between the second sun gear 8b and the second gear 5b. The power flow no longer occurs via the first power path, but only via the second power path, which has a different gear ratio than the first power path. List of reference symbols 1 electric machine 2 coupling unit 3 Gear device 4-stage planetary gear set 5-stage planetary gear 5a, 5b gear 6 Differential stage 6a, 6b planetary gear 7 planet carriers 8a, 8b sun gear 9 ring gear 10 Freewheel device 11 housings 12a, 12b Output shaft 13a, 13b Gearing 14a, 14b clutch pack 15 Stator 16 Rotor 17 Rotor shaft 18 additional gear device 19 Fixed gear 20 Wave 21 Fixed gear 22 Fixed gear 23 Wave 24 Wave

Claims

[1] Drive device for a motor vehicle, comprising an electric machine (1) with a rotor shaft (17) which is operatively connected to a transmission device (3) via a clutch unit (2), wherein the transmission device (3) has a stepped planetary gear set (4) and a differential stage (6), wherein the differential stage (6) is designed to distribute a drive power of the electric machine (1) to a first and second output shaft (12a, 12b), wherein the stepped planetary gear set (4) has a plurality of stepped planetary gears (5), wherein each stepped planetary gear (5) has a first and a second gear (5a, 5b), wherein the stepped planetary gears (5) are rotatably arranged on a planet carrier (7), wherein the first gear (5a) is in meshing engagement with a first sun gear (8a), and wherein the second gear (5b) is in meshing engagement with a second sun gear (8b) and a ring gear (9), wherein the first and second sun gear (8a,8b) are operatively connected to the clutch unit (2), wherein a freewheel device (10) is arranged in a first power path between the clutch unit (2) and the second gear (5b) via the first sun gear (8a) and the first gear (5a) up to the second gear (5b), which freewheel device is designed to drive-couple the second gear (5b) via the first gear (5a) to the clutch unit (2) in a first switching position in order to realize a first gear stage, and to drive-decouple the first power path from the second gear (5b) in a second switching position in order to realize a second gear stage via a second power path from the clutch unit (2) via the second sun gear (8b) to the second gear (5b). [2] Drive device according to claim 1, characterized by that the freewheel device (10) is arranged between the clutch unit (2) and the first sun gear (8a). [3] Drive device according to claim 1, characterized by that the freewheel device (10) is arranged between the first gear (5a) and the second gear (5b). [4] Drive device according to one of the preceding claims, characterized by that the ring gear (9) is fixed stationary to a housing (11) of the transmission device (3). [5] Drive device according to one of the preceding claims, characterized byin that the differential stage (6) has a first planetary gear set with a plurality of first planetary gears (6a) and a second planetary gear set with a plurality of second planetary gears (6b), wherein the planetary gears (6a, 6b) of both planetary gear sets are rotatably arranged on the planet carrier (7), wherein the first planetary gears (6a) are in tooth engagement with a toothing (13a) on the first output shaft (12a), wherein the second planetary gears (6b) are in tooth engagement with a toothing (13b) on the second output shaft (12b), and wherein the planetary gears (6a, 6b) of both planetary gear sets are in tooth engagement with one another in pairs. [6] Drive device according to claim 5, characterized by that the stepped planetary gears (5) of the stepped planetary gear set (4) are arranged on a common axis with the first planetary gears (6a) of the first planetary gear set or with the second planetary gears (6b) of the second planetary gear set. [7] Drive device according to one of the preceding claims, characterized by that an additional transmission device (18) is arranged in the power flow between the electric machine (1) and the clutch unit (2), wherein the rotor shaft (17) is arranged parallel to the two output shafts (12a, 12b). [8] Drive device according to one of claims 1 to 6, characterized by that the electrical machine (1) is arranged coaxially to the differential stage (6), wherein the rotor shaft (17) is designed as a hollow shaft and the first output shaft (12a) is guided through the rotor shaft (17). [9] Drive device according to one of the preceding claims, characterized by that a gear ratio between the first sun gear (8a) and the first gear (5a) is greater than a gear ratio between the second sun gear (8b) and the second gear (5b). [10] Drive device according to one of the preceding claims, characterized byin that the clutch unit (2) is designed to be power-shiftable and has a first and a second clutch pack (14a, 14b), wherein the first clutch pack (14a) is connected in a rotationally fixed manner to the first sun gear (8a) and the rotor shaft (17), and wherein the second clutch pack (14b) is connected in a rotationally fixed manner to the second sun gear (8b).

Images