Powertrain of a purely electric motor vehicle with two electric motors

Abstract

Drive train (1) of a purely electrically powered motor vehicle, with an axle (2) having a differential (35) and with two electric motors (13, 14), wherein the axle (2) can be driven by the electric motors (13, 14) via at least one transmission (15, 16), characterized in that a first electric motor (13) interacts with a first transmission (15) and a second electric motor (14) with a second transmission (16), wherein the first transmission (15) can be connected via a first switchable clutch (36) to an input gear (34) of the differential (35) for driving two axle sections (4, 5) of the axle (2) connected to different outputs of the differential (35), and the first transmission (15) can be connected via a second clutch (37) to a first axle section (4) of the axle (2) when the first clutch (36) is open, and the second transmission (16) via a third coupling (38) with a second axle section (5) of the axle (2),with the first clutch (36) open, the transmissions (15, 16) are designed as spur gear transmissions, the second transmission (16) interacts with a spur gear (26), the spur gear (26) being freely rotatable in the second shaft section (5) of the shaft (2), the spur gear (26) being rotationally fixed to a clutch part (27) of the third clutch (38), which can be brought into an operative position with a clutch part (28) of the third clutch (38), the first transmission (15) interacts with a spur gear (29) modified compared to the spur gear (26) interacting with the second transmission (16), the spur gear (29) of the first transmission (15) being freely rotatable in the first shaft section (4) of the shaft (2), the spur gear (29) being rotationally fixed to a clutch part (30) of the second clutch (37), which in an operative position can be brought with a coupling part (31) of the second coupling (37), whereby the spur gear (29),The spur gear (29) assigned to the first axle section (4) differs from the spur gear (26) assigned to the second axle section (5) in that the spur gear (29) assigned to the first axle section (4) receives a coupling part (32) of the first switchable clutch (36) in a rotationally fixed manner, which can be brought into operative connection with a switchable coupling part (33) of the first switchable clutch (36), thereby establishing a rotationally fixed connection between the spur gear (29) and an input gear (34) of the differential (35).

Description

The invention relates to a drive train of a purely electrically drivable motor vehicle, having an axle which has a differential, and two electric machines, wherein the axle can be driven by means of the electric machines via at least one transmission.Such a drive train, which is used for an electrically drivable earthmoving vehicle or for an agricultural vehicle with four-wheel drive, is known from DE 600 13 340 T2. This drive train has two electric machines which are arranged above the rear axle of the motor vehicle in the direction of travel and cooperate with a spur gear transmission which is arranged in front of the rear axle. The transmission is connected via one shaft or two shafts to the differentials which are assigned to the two axles, thus to the rear axle and the front axle of the motor vehicle.From DE 10 2010 005 789 A1, a device for driving a vehicle is known, wherein the device has two electric machines, a differential gear mechanism and two planetary gear mechanisms, wherein one of the electric machines interacts with one of the planetary gear mechanisms in each case, wherein the planetary carriers can be connected to the differential gear mechanism or connected to output shafts of the differential gear mechanism in each case via a clutch, or the planetary carriers can be connected neither to the differential gear mechanism nor to output shafts of the differential gear mechanism.It is an object of the present invention to provide a drive train in a purely electrically operated motor vehicle, by means of which different driving states can be driven with particularly good efficiency.The object is achieved by a drive train which is designed according to the features of patent claim 1.The drive train of the purely electrically drivable motor vehicle thus has two electric machines. One of the two electric machines, referred to below as the first electric machine, interacts with a first transmission, and the other of the two electric machines, referred to below as the second electric machine, interacts with a second transmission. The first transmission is connectable via a first shiftable clutch to an input wheel of the differential for driving two axle sections of the axle connected to different outputs of the differential. The first transmission is connectable via a second clutch to a first axle section of the axle, when the first clutch is disengaged, and the second transmission is connectable via a third clutch to a second axle section of the axle, when the first clutch is disengaged.This configuration of the drive train with the two electric machines, the two transmissions assigned to them and the three clutches makes it possible either to drive the two axle sections of the axle by driving only the first electric machine via the first transmission assigned to it and the differential assigned to it, or else not to introduce the driving force into the differential and instead to drive each axle section directly by means of the electric machine assigned to it. This independent drive of the respective axle section of the axle enables an individual wheel drive of the wheel of the motor vehicle assigned to the respective axle section, thus of the running wheel of the motor vehicle. This allows torque vectoring of the axle sections of the axle or of the wheels of the axle. This torque vectoring does not cause any loss due to braking intervention on the axle section of one or the other wheel.During driving operation, in which the transmission of force takes place via the differential, only one electric machine-first electric machine-is operated, with the first clutch closed, while the two other clutches-second and third clutches-are opened. In the case of single-wheel drive, on the other hand, the first clutch is opened and the second and third clutches are closed.The drive of the motor vehicle only with the one electric machine-first electric machine-is advantageous when driving states are to be managed in which low energy consumption is important. In particular, when driving-dynamically critical driving states are to be managed, a switch is made to the single-wheel drive. These driving-dynamic critical driving states are in particular those which are critical from a safety aspect and which require a stabilizing intervention on the vehicle.Preferably, the two electric machines and the three clutches have control means by means of which, when the first electric machine is in operation, the first clutch is closed and the second and third clutches are open, or, when the electric machines are in operation, the first clutch is open and the second and third clutches are closed.The gears are designed as spur gears. They can be accommodated in a relatively small installation space. In particular, the gears have identical transmission ratios.The electric machines are arranged in particular transversely to the direction of travel of the motor vehicle.The drive train is preferably used in a motor vehicle which is designed as a passenger car. This passenger vehicle is in particular a sport car. This motor vehicle, in particular the passenger car or the sport car, is preferably designed with a rear drive. The two electric machines are thus arranged in the rear region of the motor vehicle or drive train. It is considered to be particularly advantageous if the two electric machines are arranged behind the rear axle.In principle, however, the motor vehicle can be designed as a front drive.The wheels assigned to the drive train are suspended in particular individually via articulated shafts. The drive train thus does not have a rigid axle.Further features of the invention are evident from the dependent claims, the attached drawing and the description of the preferred embodiment shown in the drawing, without being limited thereto. It shows: FIG. 1 shows a schematic illustration of a preferred embodiment of the drive train according to the invention.The exemplary embodiment according to FIG. 1 illustrates a drive train for a purely electrically drivable motor vehicle, which is in particular a passenger car, specifically a sport car. The drive train assigned to the rear axle of the motor vehicle is shown, as well as a non-driven front axle of the motor vehicle.The drive train 1 with independent wheel suspension has the first, rear axle 2. With respect to the forward travel direction 3 of the motor vehicle, referred to below as the travel direction, the rear axle 2 has a left axle section 4 and a right axle section 5. Reference numeral 6 denotes left and right wheels of the rear axle 2, and reference numeral 7 denotes bearings for the axle sections 4 and 5 of the rear axle 2. The axle sections 4 and 5 of the rear axle 2 have articulated shafts.The motor vehicle further has a second, front axle 8, which is not driven. This axle 8 also has an independent wheel suspension. The front axle 8 has a left axle section 9 and a right axle section 10. Reference numeral 11 denotes the left and right wheels of the front axle 8, and reference numeral 12 denotes the bearings for the axle sections 9 and 10 of the front axle 8. The axle sections 9 and 10 of the front axle 8 likewise have articulated shafts.The rear axle 2 can be driven by means of two electric machines 13 and 14. Here, the electric machine 13 interacts with a transmission 15 and the electric machine 14 interacts with a transmission 16. The transmissions 15 and 16 are arranged substantially behind the rear axle 2, and the two electric machines 13 and 14 are each arranged transversely to the direction of travel 3. The axis of rotation of the respective electric machine 13 or 14, represented by its output shaft 17, is thus arranged in the direction of travel 3.The stator of the respective electric machine 13 or 14 is denoted by the reference numeral 18, the rotor of the respective electric machine 13 or 14, to which the output shaft 17 is connected, is denoted by the reference numeral 19. The respective output shaft 17 is mounted in bearings 20.The output shaft 17 of the two electric machines 13, 14 are arranged on the same geometric axis, whereby the axis of rotation of the stators 18 of the electric machines 13 and 14 corresponds to this geometric axis.The two transmissions 15, 16, apart from the slight difference to be described below, are arranged mirror-symmetrically to the longitudinal axis of the vehicle and are of identical design. They thus have identical transmission ratios. The gears are designed as spur gears.The respective transmission 15 or 16 has a pinion 21 which is connected in a rotationally fixed manner to the output shaft 17 and is designed as a spur gear. This pinion 21 meshes with a spur gear 22 of the respective transmission 15 or 16, which is connected to a shaft 23 in a rotationally fixed manner. This is mounted at the end in bearings 24. Next to the spur gear 22, a pinion 25 is arranged and connected to the shaft 23 in a rotationally fixed manner. The pinion 25 of the transmission 16 meshes with a spur gear 26 which is mounted in a freely rotatable manner in the right axle section 5 of the axle 2. The spur gear 26 is connected in a rotationally fixed manner to a coupling part 27 which can be brought into the operative position with a coupling part 28 which is connected in a rotationally fixed manner to the right axle section 5.A spur gear 29 modified with respect to the spur gear 26 interacts with the pinion 25 of the other transmission 15. This, like the spur gear 26, is mounted freely rotatably in the axle section of the axle 2, in the present case the left axle section 4, and connected in a rotationally fixed manner to a coupling part 30, which is designed in a manner corresponding to the coupling part 27. This coupling part 30 can be brought into the operative position with a coupling part 31 which is connected in a rotationally fixed manner to the left axle section 4 and in this respect corresponds with respect to the construction and arrangement of the coupling part 28.The spur gear 29 which is assigned to the left axle section 4 differs in principle from the spur gear 26 which is assigned to the right axle section 5, in that the spur gear 29 receives a coupling part 32 in a rotationally fixed manner. This can be brought into operative connection with a coupling part 33, which can be shifted and with the aid of which a rotationally fixed connection can be produced between the spur gear 29 and an input gear 34 of a differential 35. The two axle sections 4 and 5 are connected in a rotationally fixed manner to two outputs of the differential 35.Consequently, the clutch parts 32 and 33 form a first switchable clutch 36, the clutch parts 30 and 31 form a second switchable clutch 37 and the clutch parts 27 and 28 form a third switchable clutch 38. The electric machine 14 is switched off. Consequently, only the electric machine 13 transmits the torque to the differential 35 via the transmission 15 and consequently the spur gear 29 and the clutch 36 and from there to the wheels 6 via the two axle sections 4 and 5.If, on the other hand, control of a driving-dynamic critical situation is important, the wheels 6 of the rear axle 2 can be individually driven. The first clutch 36 is opened and the second and third clutches 37, 38 are closed. In this case, there is no transmission of force via the differential 35 to the axle sections 4 and 5 of the rear axle 2, but rather there is transmission in a first torque train from the electric machine 13 via the transmission 15 assigned to it to the clutch 37 and from there to the left axle section 4 to the wheel 6 assigned to it. Via a second torque path, the electric machine 14 is connected via the transmission 16 to the closed clutch 38, so that the right axle section 5 and the wheel 6 assigned to it are driven via these. Different torques can be introduced into the two axle sections 4 and 5 by different torques of the electric machines 13, 14, whereby torque vectoring of the rear axle 2 by means of single-wheel drive is possible.The two electric machines 13 and 14 and the three clutches 36, 37, 38 have control means by means of which, when the first electric machine 13 is in operation, the first clutch 36 is caused to be closed and the second and third clutches 37, 38 are opened, or, when the two electric machines 13, 14 are in operation, the first clutch 36 is opened and the second and third clutches 37, 38 are closed.

Claims

Drive train (1) of a purely electrically drivable motor vehicle, having an axle (2) which has a differential (35), and having two electric machines (13, 14), wherein the axle (2) can be driven by means of the electric machines (13, 14) via at least one transmission (15, 16), characterized in that a first electric machine (13) interacts with a first transmission (15) and a second electric machine (14) interacts with a second transmission (16), wherein the first transmission (15) can be connected to an input wheel (34) of the differential (35) via a first switchable clutch (36), for driving two axle sections (4, 5) of the axle (2) which are connected to different outputs of the differential (35), and the first transmission (15) interacts via a second clutch (37) with a first axle section (4) of the axle (2), when the first clutch (36) is open, The invention also provides a device for connecting the two gears to one another, wherein the second transmission (16) can be connected via a third clutch (38) to a second axle section (5) of the axle (2), when the first clutch (36) is open, wherein the transmissions (15, 16) are designed as spur gear transmissions, wherein the second transmission (16) interacts with a spur gear (26), wherein the spur gear (26) is mounted freely rotatably in the second axle section (5) of the axle (2), wherein the spur gear (26) is connected non-rotatably to a clutch part (27) of the third clutch (38), which clutch part can be brought into the active position with a clutch part (28) of the third clutch (38), wherein the first transmission (15) interacts with a spur gear (29) modified with respect to the spur gear (26) interacting with the second transmission (16), wherein the spur gear (29) of the first transmission (15) is mounted freely rotatably in the first axle section (4) of the axle (2), wherein the spur gear (29) is connected in a rotationally fixed manner to a coupling part (30) of the second clutch (37), which coupling part can be brought into the operative position with a coupling part (31) of the second clutch (37), wherein the spur gear (29) which is assigned to the first axle section (4) differs from the spur gear (26) which is assigned to the second axle section (5), characterized in that the spur gear (29) which is assigned to the first axle section (4) receives in a rotationally fixed manner a coupling part (32) of the first switchable clutch (36), which coupling part can be brought into an operative connection with a switchable coupling part (33) of the first switchable clutch (36), as a result of which a rotationally fixed connection can be produced between the spur gear (29) and an input gear (34) of the differential (35).Drive train according to Claim 1, characterized in that the axle (2) is a rear axle of the motor vehicle.Drive train according to Claim 2, characterized in that the electric machines (13, 14) are arranged close to the rear axle (2), in particular behind the rear axle.Drive train according to one of Claims 1 to 3, characterized in that it is a drive train (1) of a passenger car, in particular of a sports car.Drive train according to one of Claims 1 to 4, characterized in that the two electric machines (13, 14) and the three clutches (36, 37, 38) have control means by means of which, when the first electric machine (13) is in operation, the first clutch (36) is closed and the second and third clutches (37, 38) is open or, when the electric machines (13, 14) are in operation, the first clutch (36) is open and the second and third clutches (37, 38) is closed.Drive train according to one of Claims 1 to 5, characterized in that the transmissions (15, 16) have identical transmission ratios.Drive train according to one of Claims 1 to 6, characterized in that the electric machines (13, 14) are arranged transversely with respect to the direction of travel of the motor vehicle.Drive train according to one of Claims 1 to 7, characterized in that the first axle (2) has two axle sections (4, 5) having articulated shafts.

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