Electric power system for commercial vehicle with two electric motors

Abstract

The invention relates to an electric power system (20) for a commercial vehicle (2) having two electric motors (22). In order to create an electric drive train for a commercial vehicle having two electric motors, on which the torque occurring can be better managed, the invention proposes that the electric motors (22) are arranged in motor housings (24) located on opposite sides of a transmission housing (26), the transmission housing being located between the motor housings (24), each electric motor (22) acts on a motor-side output shaft (28) which extends from a motor housing (24) of the electric motor (22) associated with the output shaft (28) into the transmission housing (26), and in the transmission housing (26), each motor-side output shaft (28) has at least one gear stage (30) by means of which the output shaft (28) is driven by the transmission housing (26). The respective driving force introduced into the transmission housing (26) by means of the motor-side output shaft (28) is transmitted to the respective transmission-side output shaft (32).

Description

[0001] The invention relates to an electric drive train for a commercial vehicle having two electric motors according to the preamble of claim 1 , and to a commercial vehicle having an electric drive train having two electric motors.

[0002] Document WO 98 / 40958 A1 discloses an electric drive unit for a motor vehicle, which has two electric drives arranged in a common housing and aligned with each other on the rotation axis. Each electric motor drives its own rotor shaft. The output-side ends of the rotor shaft are led out of the drive housing on opposite sides. The ends of the rotor shaft facing each other are mounted in a bearing shield arranged in the center of the housing.

[0003] This design results in a long drive housing which must withstand considerable drive torques over its length. In particular, considerable forces are generated between the distal ends of the rotor shaft, which are absorbed by the drive housing and transmitted to the frame of the commercial vehicle on which the powertrain is installed. The vibrations generated in the electric motor are not only transmitted to the downstream drive components via the output-side end of the rotor shaft, but also to the drive housing via the housing fit.

[0004] The aim of the invention is to create an electric powertrain for a commercial vehicle with two electric motors in which the torque generated can be better controlled. Furthermore, a solution is to be found in which the vibrations of the electric motors are transmitted less to the downstream drive components. The unsprung masses should also be kept low. An offset should also be created between the drive shaft and the output shaft in order to achieve a compact design of the drive unit.

[0005] This object is achieved by the characterizing features of claim 1 for an electric drive system and by the characterizing features of claim 10 for a commercial vehicle.

[0006] The electric motor is arranged in a motor housing, which is located on opposite sides of a transmission housing arranged between the motor housings. The transmission housing arranged between the two motor housings can easily absorb and compensate for the forces generated between the motor housings and the vibrations generated acting on the transmission housing. The side wall of the transmission housing facing the motor can be designed to have sufficient strength to attach the motor housing thereto. Since each motor housing is assigned a side wall of the transmission housing, the vibration and driving torque of each motor initially act only on the side wall of the transmission housing facing the motor. The side wall of the transmission housing can be designed as a solid plate made of a metal material. The side walls of the transmission housing facing the motor can be connected to each other through the peripheral side walls of the transmission housing. The side walls facing the motor can also be used to support the gears forming the gear stage in the transmission housing. This also applies to the transmission-side output shaft and the cardan shaft arranged outside the transmission housing, which transmits the driving force acting on the transmission-side output shaft to the driven wheel of the commercial vehicle.

[0007] Each electric motor acts on a motor-side output shaft, which extends from the motor housing of the electric motor assigned to the output shaft and enters the transmission housing. A separate output shaft is provided for each electric motor so that they can be operated independently of each other at different speeds and drive torques. In this arrangement, any drive torque and vibrations that occur do not act directly on the other electric drive motor, but are at most transmitted indirectly from the first output shaft to the second output shaft via the transmission housing. The rotor of the associated electric motor can be mounted directly on the corresponding motor-side end of the output shaft. In this way, the drive force generated by the electric motor can be introduced directly into the transmission housing without further transmission losses.

[0008] In the transmission housing, at least one gear stage is provided for each motor-side output shaft, by means of which the corresponding driving force introduced into the transmission housing by means of the motor-side output shaft is transmitted to the corresponding transmission-side output shaft. Therefore, each motor-side output shaft is assigned its own transmission-side output shaft. The transmission-side output shafts are preferably arranged in the transmission housing so that their rotation axes are parallel to the rotation axes of the motor-side output shafts, but are not concentric with them, so that there is an offset between these output shafts. The offset is preferably large enough so that the cardan shaft that transmits the driving force acting on the transmission-side output shaft to the driven wheels of the commercial vehicle can be connected to the transmission housing outside the peripheral shape of the motor housing. The gear stage serves to bridge the offset between the output shafts.

[0009] The driving force applied to the transmission-side output shaft is transmitted via cardan shafts, each of which is drivingly 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 drivingly connected to the corresponding cardan shaft. The cardan shaft is suitable for following the compression and rebound movements of the wheels when the commercial vehicle is in use. If the transmission housing and the motor housing are rigidly connected to the frame of the commercial vehicle, the cardan shaft is the only component of the powertrain whose mass is unsprung. Since the cardan shaft is relatively light, this has advantages for the driving properties and smooth running of the commercial vehicle during use. In particular, the heavy electric motor and the transmission are not part of the unsprung mass.

[0010] In the power system for commercial vehicles according to the present invention, each of the two electric motors thus has its own transmission path for transmitting the driving force to the wheels it drives. The vibrations generated during the operation of the electric motors can be kept to a minimum. The torque generated in the power system designed according to the present invention can be easily controlled.

[0011] The commercial vehicle may be, in particular, a truck trailer. In the case of a truck trailer, it is particularly difficult to accommodate an electric drivetrain in the available installation space below the loading area. The available installation space width is limited by legal approval regulations. In addition, axle swing arms, suspension elements, shock absorbers and brakes must be arranged in the wheel area. The design of the electric drivetrain according to the invention makes optimal use of the available installation space.

[0012] According to one embodiment of the invention, the power system has an electronic speed control device for an electric motor, which is designed to compensate for the speed difference between the wheels driven by the power system. The electronic speed control device for the electric motor generates an electronic differential. If a speed difference occurs between the relative wheels of a commercial vehicle, especially when the commercial vehicle is turning, the speed difference can be eliminated by controlling the speed of the electric motor via a decoupled transmission path. In order to equalize the speed, the speed of the electric motor driving the outer wheel of the curve can be increased by the electronic speed control device, while the speed of the electric motor driving the inner wheel of the curve can be reduced by the electronic speed control device. It is also possible to change the speed of only one of the two electric motors by the electronic speed control device, so that it is directed to a direction suitable for speed compensation. The speed of the electric motor can be changed by a suitably programmed electronic control system, which detects the speed difference between the driven wheels by suitable sensors and adjusts the speed of the electric motor to the level required for speed compensation. Then, the mechanical differential can be omitted in the power system according to the invention, which further reduces the total mass and unsprung mass of the power system. Reactive power in the power system is avoided. The electronic speed control device is controlled to eliminate the travel difference between the inner and outer wheels of the curve as much as possible. Individual drive paths from the electric motor to the wheels it drives enable individual control of each driven wheel.

[0013] According to one embodiment of the invention, the power system has an electronic power control device for the electric motor, which is designed to generate a deceleration or acceleration drive torque by changing the drive torque generated by one or two electric motors at the wheels driven by the corresponding electric motors affected by the power control. The electronic torque control is intended to influence the yaw rate of the commercial vehicle about its vertical axis in certain driving situations. This is a torque vector control system that is intended to improve the driving characteristics of the commercial vehicle. For example, if the wheel on the inside of the curve is slightly decelerated with a deceleration torque, the turning performance of the commercial vehicle can be improved, so that the commercial vehicle can turn into the curve. If the wheel on the outside of the curve is pushed forward with an acceleration drive torque, an effect comparable to the torque change of the wheel on the inside of the curve can be achieved, which can replace or support the torque change of the wheel on the inside of the curve. The deceleration and / or acceleration drive torque can also be used to stabilize the handling of the commercial vehicle when driving in a straight line. This applies, for example, if the commercial vehicle tends to sway or swing in the driving situation due to driving errors, uneven road surfaces or weather conditions. Then, the drive torque is specifically generated at the wheel to counteract any sway or swing. The deceleration and / or acceleration drive torque can be achieved by electronically controlling the electric motor. Individual drive paths from the electric motor to the respective wheels driven thereby enable individual control of the individual driven wheels. Suitable sensor systems can be used to detect driving conditions in which the above-mentioned torque control is useful. For example, a yaw rate sensor can be used to detect a rotational movement of the commercial vehicle about its vertical axis. The sensor data of the yaw rate sensor can be offset by the electronic control unit with other sensor data (e.g. from wheel speed sensors) in order to calculate therefrom a signal which indicates whether and / or to what extent a corresponding drive torque is required to support the drivability of the commercial vehicle.

[0014] According to one embodiment of the invention, the gear stage has a transmission ratio by which the speed of the transmission-side output shaft is not equal to the speed of the motor-side output shaft of the electric motor. Depending on the design of the electric motor, there may be a situation where, in normal operation, their speed is at such a level that, when the transmission ratio of the gear stage in the transmission housing is 1:1, the wheels of the commercial vehicle rotate at a speed that does not correspond to the speed at which the commercial vehicle is driven in normal operation. By increasing or reducing the speed of the motor-side output shaft accordingly to the changed speed of the transmission-side output shaft by means of the transmission ratio of the gear stage, the electric motor can be operated at a speed that, in the case of a transmission ratio of 1:1, does not match the wheel speed expected during normal operation of the commercial vehicle. The speed of the electric motor achieved by the reduction ratio or reduction ratio may be advantageous in terms of wear and / or energy consumption. If there is at least one gear stage in the transmission housing for automatic or manual shifting, the transmission-side output shaft can be driven at different speeds at the same input speed of the motor-side output shaft.

[0015] According to one embodiment of the invention, the transmission housing and / or the motor housing has one or more connecting elements, by means of which the electric powertrain can be attached to the frame of the commercial vehicle. Using the connecting elements, the heavy components of the powertrain can be connected to the frame of the commercial vehicle. Advantageously, a fastening bracket can be arranged on the motor housing, by means of which the motor housing can be connected to the frame of the commercial vehicle. In particular, the mounting bracket can be arranged at the outward end of the motor housing in order to support the weight of the motor 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 and the shafts and gear stages arranged therein. Alternatively, the transmission can accommodate at least two connecting elements, so that the motor can be attached to the transmission on one side, thereby reducing the load on the motor housing. The connecting elements can be designed to use known connection techniques, such as welding, screwing, riveting, gluing, etc., to connect the powertrain to the frame of the commercial vehicle. As a result, the heavy components of the powertrain are fixed to the frame of the commercial vehicle. This keeps the unsprung mass low.

[0016] According to one embodiment of the invention, the electric powertrain has a torque bracket as a connecting element, one end of which is attached to the transmission housing. Preferably, the torque bracket engages the transmission housing in an area away from the output shaft on the motor side, because this is where the differential torque between input and output is greatest. The transmission housing is particularly suitable for attaching the torque bracket, because it must be designed to be particularly strong in order to fix the electric motor attached to it and prevent torsional movements of the transmission housing. The torque bracket transmits the differential torque to the frame of the commercial vehicle. In addition, the force is concentratedly transmitted into the frame structure by the torque from the torque bracket, which prevents torsion of the frame. The torque bracket reduces the strain on other connecting elements used to connect the powertrain to the frame of the commercial vehicle. As a result, the other connecting elements can be lighter and simpler.

[0017] According to one embodiment of the invention, the connecting element has a silencer pad. The silencer pad is suitable for at least reducing or completely avoiding the transmission of vibrations and oscillations from the power system to the frame of the commercial vehicle. The silencer pad is a component in which the metal connecting elements are connected to each other by a component made of an elastomeric material in order to dampen pressure, shear and / or tensile loads and vibrations between the connecting components. Due to their design, the silencer pads not only prevent the transmission of vibrations from the electric motor to the frame of the commercial vehicle, they also dampen the effects of shocks and impacts and torsional movements from the frame, which act from the frame on the power system. The alternating torque from the drive can also be at least partially absorbed by the silencer pad. In addition, the silencer pad allows the frame to twist without equally transmitting the generated forces to the drive structure.

[0018] According to one embodiment of the present invention, in a side view, the transmission housing exceeds the peripheral shape of the motor housing in one direction, and the connection of the transmission side output shaft and the cardan shaft on the transmission housing is arranged in the portion of the transmission housing that exceeds the peripheral shape of the motor housing. This design keeps the installation space required for the power system to a minimum. Due to this design, the cardan shaft is not attached to the outer end of the motor, but to the portion of the transmission housing that exceeds the motor housing, thereby increasing the distance that the cardan shaft extends. Starting from the driven wheel, the cardan shaft extends further to the central area of ​​the commercial vehicle. The greater length of the cardan shaft in a direction transverse to the longitudinal axis of the commercial vehicle reduces the angle that must be compensated by the cardan joint of the cardan shaft during the operation of the cardan shaft, so as to bridge the distance between the motor side output shaft and the rotation axis of the driven wheel when viewed in the longitudinal direction and / or vertical direction of the commercial vehicle. In addition, the offset enables the cardan shaft to deflect due to the ride height that must be set on the commercial vehicle. This reduces the wear of the cardan joint of the cardan shaft. In actual operation, the cardan shaft thus achieves a significantly longer service life.

[0019] According to one embodiment of the invention, the connection of the cardan shaft on the transmission housing deviates from the rotation axis of the motor-side output shaft in the direction of the rotation axis of the wheels driven by the power system. The connection of the cardan shaft is particularly located in the portion of the transmission housing in which the transmission housing exceeds the peripheral shape of the motor housing in a side view. The distance between the rotation axis of the motor-side output shaft and the rotation axis of the driven wheel is thus shortened when viewed in the longitudinal direction and / or vertical direction of the commercial vehicle. The shortened distance reduces the angle that the universal joint of the cardan shaft must compensate during operation. This reduces the wear of the universal joint of the cardan shaft. Therefore, in actual operation, the cardan shaft achieves a significantly longer service life.

[0020] It should be noted that the embodiments of the invention described above, each of which itself, can also be combined with each other, with the subject matter of claim 1 and other dependent claims, provided that there are no technical obstacles and no mandatory dependencies.

[0021] Further modifications and embodiments of the invention can be found in the claims, the description and the drawings.

[0022] The present invention will be explained in more detail below based on exemplary embodiments, in which:

[0023] Figure 1 : An overall view of the electric powertrain installed in a commercial vehicle is shown from diagonally below.

[0024] Figure 2 : shows a front view of the electric powertrain mounted in a vehicle frame with an electric motor / transmission assembly, and

[0025] Figure 3 : Shows a side view of the motor / transmission assembly mounted in the vehicle frame.

[0026] Figure 1 An overall view of a commercial vehicle 2 in the form of a truck trailer is shown from below, in which an electric drive train 20 is installed. The commercial vehicle 2 has a frame 4, which in the exemplary embodiment is supported on the ground via three axle structures 6. The intermediate axle structure 6 has the electric drive train 20, while the axle bridges or axles have been omitted from the other two axle structures for the sake of simplicity. In the front area, the commercial vehicle with the traction pin 16 rests on the fifth wheel coupling of a semitrailer, which is not shown in detail in the figure, and is towed by it.

[0027] The axle structures 6 each have a link arm 8 on opposite sides of the frame 4, which is connected to the frame 4 via a pivot bearing 10 arranged in a retaining bracket. A wheel carrier 12 is also attached to the link arm 8, to which the wheel 36 of the commercial vehicle 2 can then be bolted. At their ends facing away from the pivot bearing 10, the link arms 8 are each supported on the frame 4 via a spring element 14. The link arms 8 thus rotate around the pivot bearing 10 during the spring movement and resist the restoring force in the flexible spring element 14.

[0028] Figure 2 A front view of an electric powertrain 20 mounted in a vehicle frame 4 with an associated motor / transmission assembly is shown. The electric powertrain 20 has two electric motors 22 (indicated by dashed lines), each of which is arranged in an associated motor housing 24. The two motor housings 24 are mounted on opposite sides of a transmission 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 associated with the output shaft 28 into the transmission housing 26. In the transmission housing 26, at least one gear stage 30 is provided for each motor-side output shaft 28, through which the corresponding driving force introduced into the transmission housing 26 by means of the motor-side output shaft 28 is transmitted to the corresponding transmission-side output shaft 32. The gear stage 30 can have a transmission ratio, through which the rotation speed of the transmission-side output shaft 32 is not equal to the rotation speed of the motor-side output shaft 28 of the electric motor 22. The driving force applied to the transmission-side output shafts 32 is transmitted via cardan shafts 34 , each of which is drivingly 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 drivingly connected to the cardan shafts 34 .

[0029] Figure 2, an electronic box 38 is shown, which is connected to the electric motor 22 via lines shown in dashed lines. An electronic speed control device 40 and an electronic power control device 42 are arranged in the electronic box 38. For these functions, the electronic box 38 can also be connected to other sensors, not shown in detail in the figure, which are arranged in the electric vehicle train 20 and / or on the commercial vehicle 2.

[0030] In the exemplary embodiment, the transmission housing 26 and / or the motor housing 24 are connected to the 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 attached at one end to the transmission housing 26 and at the other end to the frame 4 of the commercial vehicle 2. The connecting element 44 is connected to the frame 4 via a sound-absorbing spacer 48.

[0031] exist Figure 3 In the side view shown, the transmission housing 26 projects downwardly in one direction beyond the peripheral shape of the motor housing 24. The connection of the transmission-side output shaft 32 and the cardan shaft 34 on the transmission housing 26 is arranged in the portion of the transmission housing 26 that projects beyond the peripheral shape of the motor housing 24. The connection of the cardan shaft 34 on the transmission housing 26 is also offset from the rotation axis of the motor-side output shaft 28 in the direction of the rotation axis of the wheels 36 driven by the powertrain 20.

[0032] The present invention is not limited to the exemplary embodiments described above. A person skilled in the art will have no difficulty in modifying the exemplary embodiments in a manner they deem appropriate in order to adapt them to a particular application.

[0033] Reference numerals list

[0034] 2 Commercial vehicles

[0035] 4 Frame

[0036] 6-axis structure

[0037] 8 Link arm

[0038] 10 Pivot bearing

[0039] 12 Wheel Rack

[0040] 14 Spring element

[0041] 20 Electric Powertrain

[0042] 22 Electric Motor

[0043] 24 Motor housing

[0044] 26 Transmission housing

[0045] 28 Motor side output shaft

[0046] 30 gear stages

[0047] 32 Transmission side output shaft

[0048] 34 Cardan shaft

[0049] 36 Wheels

[0050] 38 Electronic Box

[0051] 40 Electronic speed control

[0052] 42 Electronic power control device

[0053] 44 Connecting elements

[0054] 46 Torque bracket

[0055] 48 Silencer pad

Claims

1. An electric powertrain (20) for a commercial vehicle (2) having two electric motors (22), characterized in that: The electric motor (22) is arranged in a motor housing (24) located on opposite sides of a transmission housing (26), the transmission housing (26) being located between the motor housings (24), each electric motor (22) acting on a motor-side output shaft (28), the motor-side output shaft (28) extending from the motor housing (24) of the electric motor (22) assigned to the output shaft (28) and entering the transmission housing (26), at least one of which is provided for each motor-side output shaft (28) in the transmission housing (26). A gear stage (30), through which the corresponding driving force introduced into the transmission housing (26) by means of the motor-side output shaft (28) is transmitted to the corresponding transmission-side output shaft (32), and the driving force acting on the transmission-side output shaft (32) is transmitted to the wheels (36) of the commercial vehicle (2) drivingly connected to the cardan shaft (34) via cardan shafts (34), each cardan shaft (34) drivingly connected to one of the transmission-side output shafts (32) and arranged on opposite sides of the transmission housing (26).

2. The electric powertrain (20) according to claim 1, characterized in that: The powertrain (20) has an electronic speed control (40) for the electric motor (22), the electronic speed control (40) being designed to compensate for speed differences between the wheels (36) driven by the powertrain (20).

3. The electric powertrain (20) according to claim 1 or 2, characterized in that: The powertrain (20) has an electronic power control device (42) for the electric motor (22), and the electronic power control device (42) is designed to produce a decelerating or accelerating driving torque by varying the driving torque produced by one or both electric motors (22) at the wheels (36) driven by the corresponding electric motor (22) affected by the power control.

4. An electric powertrain (20) according to any one of the preceding claims, characterised in that The gear stage (30) has a transmission ratio, by which the speed of the transmission-side output shaft (32) is not equal to the speed of the motor-side output shaft (28) of the electric motor (22).

5. An electric powertrain (20) according to any one of the preceding claims, characterised in that The transmission housing (26) and / or the motor housing (24) have one or more connecting elements (44), by means of which the electric drive train (20) can be fastened to the frame of the commercial vehicle (2).

6. The electric powertrain (20) of claim 5, wherein: The electric powertrain (20) has a torque bracket (46) as a connecting element (44), the torque bracket (46) being fastened to the transmission case (26) at one end.

7. The electric powertrain (20) according to claim 5 or 6, characterized in that The connecting element (44) includes a sound-absorbing pad (48).

8. An electric powertrain (20) according to any one of the preceding claims, characterised in that In a side view, the transmission housing (26) extends beyond the peripheral shape of the motor housing (24) in one direction, and the connection between the transmission-side output shaft (32) and the universal joint (34) on the transmission housing (26) is arranged in a portion of the transmission housing (26) that extends beyond the peripheral shape of the motor housing (24).

9. An electric powertrain (20) according to any one of the preceding claims, characterised in that The connection of the cardan shaft (34) to the transmission housing (26) is offset from the rotation axis of the motor-side output shaft (28) in the direction of the rotation axis of the wheels (36) driven by the power system (20).

10. A commercial vehicle (2) having an electric powertrain (20) with two electric motors (22), characterized in that: The electric powertrain (20) is designed according to the features of claims 1 to 9.

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