Electric powertrain for a commercial vehicle with two electric motors

Abstract

The present invention relates to an electric powertrain (20) for a commercial vehicle (2) with two electric motors (22). In order to create an electric powertrain for a commercial vehicle with two electric motors, on which commercial vehicle the occurring torques can be better managed, the invention proposes arranging the electric motors (22) in motor housings (24) located on opposite sides of a transmission housing (26) located between the motor housings (24), wherein each electric motor (22) acts on a motor-side output shaft (28) that extends out of the motor housing (24) of the electric motor (22) assigned to this output shaft (28) through to and into the transmission housing (26), and in the transmission housing (26) at least one gear stage (30) is provided for each motor-side output shaft (28), via which gear stage the respective drive force introduced into the transmission housing (26) with the motor-side output shaft (28) is transferred to a respective transmission-side output shaft (32). (Fig. 2)

Description

[0001] Electric drivetrain for a commercial vehicle with two electric motors

[0002] The present invention relates to an electric drive train for a commercial vehicle with two electric motors according to the preamble of claim 1 and to a commercial vehicle with an electric drive train with two electric motors.

[0003] WO 98 / 40958 A1 discloses an electric drive unit for a motor vehicle with two electric drives arranged in a common housing and on mutually aligned rotational axes. Each electric motor drives its own rotor shaft. The output ends of the rotor shafts extend out of the drive housing on opposite sides. The ends of the rotor shafts facing each other are mounted in a bearing plate located centrally in the housing.

[0004] This design results in a drive housing that is long and must withstand considerable drive torques along its length. Significant forces are generated, particularly between the distal ends of the rotor shafts, which are absorbed by the drive housing and transmitted to the frame of the commercial vehicle in which the drive train is mounted. Vibrations occurring in the electric motors are transmitted not only via the output ends of the rotor shafts to the downstream drive components, but also via the housing fit into the drive housing.

[0005] The object of the present invention is to create an electric drive train for a commercial vehicle with two electric motors in which the occurring torques can be better controlled. Furthermore, a solution is to be found in which the vibrations from the electric motors are transmitted to the downstream drive components to a lesser extent. The unsprung masses are also to be kept low. Furthermore, an offset between the input and output shafts is to be created to enable a compact design of the drive unit.

[0006] The problem is solved for an electric drive train by the characterizing features of claim 1 and for a commercial vehicle by the characterizing features of claim 10.

[0007] The electric motors are arranged in motor housings located on opposite sides of a gearbox housing between the motor housings. The gearbox housing, arranged between the two motor housings, can effectively absorb and compensate for forces occurring between the motor housings and the resulting vibrations acting on the gearbox housing. The side walls of the gearbox housing facing the electric motors can be dimensioned sufficiently strong to attach the motor housings to them. Since each motor housing is assigned a side wall of the gearbox housing, the vibrations and drive torques for each electric motor initially only act on the side wall of the gearbox housing facing the electric motor. The side walls of the gearbox housing can be designed as solid plates made of a metallic material.The side walls of the transmission housing facing the electric motors can be connected to each other by a continuous side wall of the transmission housing. The side walls facing the electric motors can also be used to support the gears that form the gear stages in the transmission housing. This also applies to the transmission-side output shafts and the cardan shafts located outside the transmission housing, which transmit the drive forces acting on the transmission-side output shafts to the driven wheels of the commercial vehicle.

[0008] Each electric motor acts on a motor-side output shaft, which extends from the motor housing of the electric motor assigned to this output shaft into the gearbox housing. A separate output shaft is provided for each electric motor so that they can be operated independently of one another at different speeds and drive torques. With this type of design, any drive torques and vibrations that occur do not act directly on the other electric drive motor, but are transmitted from a first output shaft, at most indirectly, via the gearbox housing to the second output shaft. The rotor of the associated electric motor can be mounted directly on the respective motor-side end of an output shaft. The drive power generated by the electric motors can thus be fed directly into the gearbox housing without further transmission losses.The transmission housing contains at least one gear stage for each engine-side output shaft, via which the respective drive force introduced into the transmission housing via an engine-side output shaft is transmitted to a respective transmission-side output shaft. Each engine-side output shaft is therefore assigned its own transmission-side output shaft. The transmission-side output shafts are preferably arranged in the transmission housing such that their axes of rotation run parallel to the axes of rotation of the engine-side output shafts, but not concentrically to them, resulting in an offset between these output shafts. The offset should preferably be large enough that the cardan shafts, which transmit the drive forces acting on the transmission-side output shafts to the driven wheels of the commercial vehicle, can be connected to the transmission housing outside the peripheral shape of the engine housing.The gear stages serve the purpose of bridging the offset between the output shafts.

[0009] The drive forces applied to the transmission-side output shafts are transmitted via cardan shafts, each of which is drive-connected to one of the transmission-side output shafts and is arranged on opposite sides of the transmission housing, to the wheels of the commercial vehicle, which are drive-connected to the respective cardan shafts. The cardan shafts are designed to follow the compression and rebound movements of the wheels that they make when the commercial vehicle is in use. If the transmission housing and the engine housings are rigidly connected to the vehicle frame of the commercial vehicle, the cardan shafts are the only parts of the drivetrain whose mass is unsprung. Since the cardan shafts are comparatively light, this results in advantages for the handling and smooth running of the commercial vehicle during use. In particular, the heavy electric motors and the transmission are not part of the unsprung mass.

[0010] In the drivetrain for a commercial vehicle according to the invention, each of the two electric motors has its own transmission path for transmitting the drive power to the wheels it drives. The vibrations occurring during operation of the electric motors can be kept to a minimum. The resulting torques are easily controlled in the drivetrain designed according to the invention.

[0011] The commercial vehicle can, in particular, be a truck trailer. With truck trailers, it is particularly difficult to accommodate an electric drivetrain in the available installation space below the loading area. The available installation space is limited by legal approval regulations. In addition, axle swing arms, spring elements, shock absorbers, and brakes must be arranged in the area of ​​the wheels. The inventive design of the electric drivetrain ensures optimal use of the available installation space.

[0012] According to one embodiment of the invention, the drive train has an electronic speed control for the electric motors, which is designed to compensate for speed differences between the wheels driven by the drive train. The electronic speed control of the electric motors creates an electronic differential. If speed differences occur between opposite wheels of a commercial vehicle, which can be the case in particular when the commercial vehicle is cornering, it is possible to neutralize the speed differences by appropriate speed control of the electric motors via the decoupled transmission paths. For speed compensation, the speed of the electric motor driving an outside wheel can be increased via the electronic speed control, while the speed of the electric motor driving an inside wheel can be reduced via the electronic speed control.It is also possible to change the speed of only one of the two electric motors in a suitable direction using the electronic speed control to compensate for the speed. The change in the speed of the electric motors can be achieved via an appropriately programmed electronic control system that detects speed differences between driven wheels using suitable sensors and regulates the speeds of the electric motors to a level required for speed compensation. A mechanical differential can then be dispensed with in the drive train according to the invention, whereby the overall mass of the drive train and the unsprung masses are further reduced. Reactive power in the drive train is avoided. The electronic speed control is controlled in such a way that it neutralizes travel differences between an inside and outside wheel when cornering wherever possible.The separate drive paths of the electric motors to the wheels they drive make it possible to control each of the driven wheels individually.

[0013] According to one embodiment of the invention, the drive train has an electronic power control system for the electric motors, which is designed to generate a retarding or accelerating drive torque at the wheel driven by the electric motor affected by the power control by changing the drive torque generated by one or both electric motors. The electronic torque control is intended to influence the yaw rate of the commercial vehicle about its vertical axis in certain driving situations. It is a torque vectoring control system designed to improve the driving characteristics of the commercial vehicle. For example, the cornering behavior of the commercial vehicle can be improved if the inside wheel is slightly decelerated with a retarding torque, causing the commercial vehicle to rotate into the curve.A comparable effect, which can be achieved either as a substitute for or in support of the torque change of the inside wheel during a bend, can be achieved if the outside wheel pushes forward with an accelerating drive torque. The retarding and / or accelerating drive torque can also be used to stabilize the handling of the commercial vehicle when traveling straight ahead. This applies, for example, if the commercial vehicle tends to rock or sway in a driving situation due to driving errors, uneven road surfaces, or weather conditions. Drive torques are then specifically generated at the wheels to counteract this rocking or sway. The retarding and / or accelerating drive torques can be achieved via appropriate electronic control of the electric motor control system.The separate drive paths from the electric motors to the wheels they drive enable individual control of each driven wheel. Driving conditions in which the torque control described above is useful can be detected using suitable sensors. Yaw rate sensors, for example, can be used to detect rotational movements of the commercial vehicle about its vertical axis. The sensor data from the yaw rate sensor can be combined with other sensor data by the control electronics, for example, from wheel speed sensors, to calculate a signal indicating whether and to what extent a corresponding drive torque is necessary and / or helpful to support the commercial vehicle's handling.

[0014] According to one embodiment of the invention, the gear stages have a gear ratio that causes the speeds of the transmission-side output shafts to be unequal to the speeds of the motor-side output shafts of the electric motors. Depending on the design of the electric motors, their speeds during normal operation may be at a level where, with a gear ratio of 1:1 between the gear stages in the transmission housing, the wheels of the commercial vehicle rotate at speeds that do not correspond to the speeds at which the commercial vehicle travels during normal operation.By appropriately increasing or decreasing the speeds of the engine-side output shafts to match the changed speeds of the transmission-side output shafts using the gear ratio of the gear stages, the electric motors can be operated at speeds that, with a gear ratio of 1:1, do not match the wheel speeds expected during normal operation of the commercial vehicle. The electric motor speeds made possible by the increase or reduction ratio can be advantageous from a wear and / or energy consumption perspective. If the transmission housing contains at least one automatically or manually shiftable gear stage, the transmission-side output shafts can be driven at different speeds while maintaining the same input speed of the engine-side output shafts.

[0015] According to one embodiment of the invention, the transmission housing and / or the motor housings have one or more connecting elements with which the electric drive train can be fastened to a vehicle frame of the commercial vehicle. The connecting elements make it possible to connect the heavy components of the drive train to a vehicle frame of the commercial vehicle. Advantageously, fastening brackets can be arranged on the motor housings, via which the motor housings can be connected to the vehicle frame of a commercial vehicle. The fastening brackets can be arranged in particular at the outward-facing ends of the motor housings in order to support the weight of the electric motors there. In addition, the transmission housing can be provided with at least one connecting element in order to also support the weight of the transmission housing including the shafts and gear stages arranged therein.Alternatively, the transmission can accommodate at least two connecting elements, thus enabling one-sided attachment of the electric motors to the transmission, thereby reducing the load on the electric motor housing. The connecting elements can be designed to use known joining techniques, such as welding, screwing, riveting, gluing, and the like, to connect the drivetrain to the vehicle frame of a commercial vehicle. The heavy components of the drivetrain are thus secured to the vehicle frame of the commercial vehicle. This keeps the unsprung masses low.

[0016] According to one embodiment of the invention, the electric drive train has a torque arm as a connecting element, which is attached at one end to the transmission housing. The torque arm preferably engages the transmission housing in an area remote from the engine-side output shafts, since this is where the differential torque between input and output is greatest. The transmission housing is particularly suitable for attaching the torque arm because it must be designed to be particularly rigid in order to hold the electric motors attached to it and to prevent torsional movements of the transmission housing. The torque arm transfers the differential torque to the vehicle frame of the commercial vehicle. Furthermore, the forces caused by the torque from the torque arm are transferred centrally into the frame structure, thereby preventing torsion of the vehicle frame.A torque arm relieves the load on other fasteners connecting the drivetrain to the vehicle frame of a commercial vehicle. This allows other fasteners to be designed lighter and simpler.

[0017] According to one embodiment of the invention, the connecting element(s) comprise(s). The silent bearings are suitable for at least reducing or completely preventing the transmission of vibrations and oscillations from the drive train to the vehicle frame of a commercial vehicle. Silent bearings are components in which metallic connecting elements are connected by components made of an elastomer material in order to dampen compressive, shear and / or tensile loads and vibrations between the interconnected components. Due to their design, the silent bearings not only prevent the transmission of vibrations from the electric motors to the vehicle frame of the commercial vehicle, they also dampen shocks and impacts as well as influences from torsional movements of the vehicle frame that act from the vehicle frame onto the drive train. Alternating torques from the drive can also be at least partially absorbed by the silent bearings.In addition, the silent blocks allow the vehicle frame to be twisted without transferring the resulting forces equally to the drive structure.

[0018] According to one embodiment of the invention, in a side view, the transmission housing projects beyond the peripheral shapes of the engine housing in one direction, and the transmission-side output shafts and the connections of the cardan shafts on the transmission housing are arranged in the part of the transmission housing that projects beyond the peripheral shapes of the engine housing. With this design, the installation space required by the drive train is kept small. By attaching the cardan shafts not to the outer ends of the electric motors, but rather to the part of the transmission housing that projects beyond the engine housing, the distance over which the cardan shafts extend is increased. From the driven wheels, the cardan shafts extend further into the central area of ​​the commercial vehicle.The increased length of the cardan shafts in a direction transverse to the longitudinal axis of the commercial vehicle reduces the angles that must be compensated for by the universal joints of the cardan shafts during operation in order to bridge the distance between the engine-side output shafts and the rotational axes of the driven wheels in the longitudinal direction of the commercial vehicle and / or in the vertical direction. Furthermore, the offset allows for the deflection of the cardan shafts, which occurs due to the ride heights that must be adjusted on a commercial vehicle. This reduces wear on the universal joints of the cardan shafts. In practical operation, the cardan shafts therefore achieve a significantly longer service life.

[0019] According to one embodiment of the invention, the connections of the cardan shafts on the transmission housing are offset from the axes of rotation of the engine-side output shafts in the direction of the axes of rotation of the wheels driven by the drive train. The connections of the cardan shafts are located in particular in the part of the transmission housing in which the transmission housing projects beyond the peripheral shapes of the engine housings in a side view. Viewed in the longitudinal direction of the commercial vehicle and / or in the vertical direction, the distance between the axes of rotation of the engine-side output shafts and the axes of rotation of the driven wheels is thus shortened. The shortened distance reduces the angular degrees that the universal joints of the cardan shafts must compensate for during operation. Wear on the universal joints of the cardan shafts is thus reduced. In practical operation, the cardan shafts therefore achieve a significantly longer service life.

[0020] It is pointed out that the above-mentioned configurations of the

[0021] Invention each for itself, but also among each other with the subject matter of the

[0022] Claim 1 and the remaining subclaims can be combined, provided that there are no technical obstacles to this and no mandatory

[0023] dependencies exist.

[0024] Further modifications and embodiments of the invention can be found in the claims, the description and the drawings.

[0025] The invention will be explained in more detail below using an exemplary embodiment. The figures show:

[0026] Fig. 1 : an overall view of an electric drive train installed in a commercial vehicle from below,

[0027] Fig. 2: a front view of the electric drive train mounted in a vehicle frame with the electric motor-gearbox assembly, and

[0028] Fig. 3: a side view of the mounted in a vehicle frame

[0029] Electric motor-gearbox assembly.

[0030] Figure 1 shows an overall view of a commercial vehicle 2 in the form of a truck trailer, obliquely viewed from below, into which an electric drive train 20 is installed. The commercial vehicle 2 has a vehicle frame 4, which in the exemplary embodiment is supported on the ground by three axle structures 6. The middle axle structure 6 has the electric drive train 20; in the other two axle structures, the axle bridge or axle is omitted for reasons of simplification of the drawing. At the front, the commercial vehicle is placed with the kingpin 16 onto the fifth wheel coupling of a semi-trailer truck (not shown in detail in the drawing) and pulled over it.

[0031] The axle structures 6 each have a control arm 8 on opposite sides of the vehicle frame 4, each of which is connected to the vehicle frame 4 via a pivot bearing 10 arranged in a support bracket. A wheel carrier 12 is also attached to the control arm 8, to which the wheels of the commercial vehicle 2 can then be screwed. At their ends facing away from the pivot bearing 10, the control arms 8 are each supported on the vehicle frame via a spring element 14. The control arms 8 thus rotate around the pivot bearings 10 during spring movements, thereby counteracting the restoring forces in the flexible spring elements 14.

[0032] Fig. 2 shows a front view of an electric drive train 20 mounted in a vehicle frame 4 with the associated electric motor-gearbox assembly. The electric drive train 20 has two electric motors 22, indicated in dashed lines, each arranged in an associated motor housing 24. The two motor housings 24 are mounted on opposite sides of a gear housing 26. Each electric motor 22 has a motor-side output shaft 28, which extends from the motor housing 24 of the electric motor 22 assigned to this output shaft 28 into the gear housing 26. In the gear housing 26, there is at least one gear stage 30 for each motor-side output shaft 28, via which gear stage the respective drive force introduced into the gear housing 26 by a motor-side output shaft 28 is transmitted to a respective gear output shaft 32.The gear stages 30 can have a transmission ratio by which the speeds of the transmission-side output shafts 32 are unequal to the speeds of the engine-side output shafts 28 of the electric motors 22. The drive forces applied to the transmission-side output shafts 32 are transmitted via cardan shafts 34, each of which is drive-connected to one of the transmission-side output shafts 32 and is arranged on opposite sides of the transmission housing 26, to wheels 36 of the commercial vehicle 2, which are drive-connected to the cardan shafts 34.

[0033] Fig. 2 shows an electronics box 38, which is connected to the electric motors 22 via cables shown in dashed lines. The electronic speed control 40 and the electronic power control 42 are located in the electronics box 38. For these functions, the electronics box 38 can also be connected to additional sensors (not shown in detail in the drawing) that are located in the vehicle's electronic system 20 and / or on the commercial vehicle 2.

[0034] In the exemplary embodiment, the transmission housing 26 and / or the engine housings 24 are connected to the vehicle frame 4 of the commercial vehicle 2 via connecting elements 44. One of the connecting elements 44 is designed as a torque support 46, which is fastened at one end to the transmission housing 26 and at its other end to the vehicle frame 4 of the commercial vehicle 2. The connecting elements 44 are connected to the vehicle frame 4 via silent bearings 48. In the side view shown in Fig. 3, the transmission housing 26 projects beyond the peripheral shapes of the engine housing 24 in a downward direction. The transmission-side output shafts 32 and the connections of the cardan shafts 34 are arranged on the transmission housing 26 in the part of the transmission housing 26 that projects beyond the peripheral shapes of the engine housing 24.The connections of the cardan shafts 34 on the transmission housing 26 are also offset from the axes of rotation of the engine-side output shafts 28 in the direction of the axes of rotation of the wheels 36 driven by the drive train 20.

[0035] The invention is not limited to the embodiment described above. It will be readily apparent to those skilled in the art to modify the embodiment in a manner deemed appropriate to adapt it to a specific application.

[0036] List of reference symbols

[0037] commercial vehicle

[0038] vehicle frame

[0039] Axle construction

[0040] handlebar arm

[0041] swivel bearing

[0042] wheel carrier

[0043] Spring element electric drive train

[0044] electric motor

[0045] Engine housing

[0046] Gearbox housing engine-side output shaft

[0047] Gear stage gearbox-side output shaft

[0048] propeller shaft

[0049] wheel

[0050] Electronic box electronic speed control electronic power control

[0051] connecting element

[0052] Torque support

[0053] Silentblock

Claims

Patent claims 1 . Electric drive train (20) for a commercial vehicle (2) with two electric motors (22), characterized in that the electric motors (22) are arranged in motor housings (24) located on opposite sides of a transmission housing (26) located between the motor housings (24), each electric motor (22) acts on a motor-side output shaft (28) which extends from the motor housing (24) of the electric motor (22) assigned to this output shaft (28) into the transmission housing (26), at least one gear stage (30) for each motor-side output shaft (28) is present in the transmission housing (26), via which the respective drive force introduced into the transmission housing (26) by a motor-side output shaft (28) is transmitted to a respective transmission-side output shaft (32), and the drive forces applied to the transmission-side output shafts (32) are transmitted via cardan shafts (34),which are each drive-connected to one of the transmission-side output shafts (32) and arranged on opposite sides of the transmission housing (26), are transmitted to wheels (36) of the commercial vehicle (2) which are drive-connected to the cardan shafts (34).

2. Electric drive train (20) according to claim 1, characterized in that the drive train (20) has an electronic speed control (40) of the electric motors (22), which is designed to compensate for speed differences between the wheels (36) driven by the drive train (20).

3. Electric drive train (20) according to claim 1 or 2, characterized in that the drive train (20) has an electronic power control (42) of the electric motors (22), which is designed to generate a retarding or accelerating drive torque by changing the drive torque generated by one or both electric motors (22) at the wheel (36) driven by the electric motor (22) affected by the power control.

4. Electric drive train (20) according to one of the preceding claims, characterized in that the gear stages (30) have a transmission ratio by which the rotational speeds of the transmission-side output shafts (32) are unequal to the rotational speeds of the motor-side output shafts (28) of the electric motors (22).

5. Electric drive train (20) according to one of the preceding claims, characterized in that the transmission housing (26) and / or the motor housing (24) have one or more connecting elements (44) with which the electric drive train (20) can be fastened to a vehicle frame of the commercial vehicle (2).

6. Electric drive train (20) according to claim 5, characterized in that the electric drive train (20) has a torque support (46) as a connecting element (44), which is fastened at one end to the transmission housing (26).

7. Electric drive train (20) according to one of the preceding claims 5 or 6, characterized in that the connecting element(s) (44) comprise silent bearings (48).

8. Electric drive train (20) according to one of the preceding claims, characterized in that in a side view the transmission housing (26) projects beyond the circumferential shapes of the motor housing (24) in one direction and the transmission-side output shafts (32) and the connections of the cardan shafts (34) on the transmission housing (26) are arranged in the part of the transmission housing (26) projecting beyond the circumferential shapes of the motor housing (24).

9. Electric drive train (20) according to one of the preceding claims, characterized in that the connections of the cardan shafts (34) on the transmission housing (26) are offset from the axes of rotation of the engine-side output shafts (28) in the direction of the axes of rotation of the wheels (36) driven by the drive train (20).

10. Commercial vehicle (2) with an electric drive train (20) with two electric motors (22), characterized in that the electric drive train (20) is designed according to the features of claims 1 - 9.

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