ELECTRIC DRIVETRAIN WITH RIM TENSION TORQUE LIMITING PROTECTION

Abstract

An electric drivetrain (120) includes an electric power source (122), an electric motor (124), and a multi-speed transmission (130). The drivetrain (120) has an electronic controller (140). The controller (140) determines a corresponding rim pull torque limit (142, 144, 146) for the operating gear of the multi-speed transmission (130) and determines whether the rim pull torque demand exceeds the rim pull torque limit.Upon determining that the rim pull torque demand exceeds the rim pull torque limit, the controller 140 acts to either (i) shift the multi-speed transmission (130) into a gear where the corresponding rim pull torque limit is at or above the rim pull torque demand, or (ii) reduce the electric motor torque command to a level at which the rim pull torque is below the corresponding rim pull torque limit for the operating gear of the multi-speed transmission (130).

Description

Technical area

[0001] This patent disclosure relates generally to a machine having an electric powertrain, and more particularly to an electric powertrain having a multi-speed transmission and a rim traction limiting protection system. State of the art

[0002] Many machines used in construction and mining environments include a drivetrain for actuating traction devices, such as tires. In particular, these drivetrains typically include a power source that provides torque via a gearbox to one or more of the machine's traction devices. An internal combustion engine is a commonly used power source for the drivetrain of such machines. The maximum transmission output of the drivetrain is generally a function of the maximum engine power applied through the various gear ratios of the transmission. An internal combustion engine has a limited range of input speed and torque to the transmission, which is determined by the internal combustion engine's inability to operate below a low idle speed.Thus, the minimum operating speed inherent in the internal combustion engine provides a design criterion for the minimum transmission input speed below which the transmission will never be operational. This results in a natural torque limit for each gear, defined by the minimum idle speed of the internal combustion engine.

[0003] Internal combustion engines can emit unwanted exhaust emissions and other pollutants during operation. In addition, increasing the fuel efficiency of machinery has also gained importance, for example due to the rising costs associated with fossil fuels. One solution to these problems is a powertrain that employs an electric motor to provide torque to the machine's traction devices. However, the use of an electric motor in a machine's powertrain can also present other challenges. For example, providing an electric motor large enough to meet a machine's torque and speed requirements can be expensive.

[0004] One way to reduce the required size of the electric motor is to use a multi-speed transmission. However, using a multi-speed transmission to transmit the torque of an electric motor brings with it other problems. For example, electric motors generally have no lower speed limit and therefore, compared to an internal combustion engine, exhibit greater power across the entire engine speed range. Batteries used to power electric motors are not speed-limited. The batteries can output full power when stationary. Thus, unlike an internal combustion engine, an electric motor can produce high torque at zero speed. Therefore, when using a multi-speed transmission with an electric motor, it is possible that each of the gears of the multi-speed transmission will be exposed to the relatively high engine torques associated with low engine speeds.However, designing the transmission's gear train to withstand such torque is very expensive.

[0005] U.S. Patent No. 7,766,791 ("the '791 patent"), assigned to the assignee of the present application, describes a drivetrain for a machine having a transmission, a differential coupled to the transmission, and a clutch connected to the differential. The clutch and differential are configured to selectively reduce overall traction available to the machine by releasing the differential in response to torque generated by the power source. In particular, the drivetrain arrangement of the '791 patent is directed to limiting torque applied to the driveline by employing an open differential between axles to reduce machine traction and prevent potentially damaging torque from being introduced into a driveline.However, the '791 patent fails to recognize the problems associated with potentially damaging torques resulting from the use of a multi-speed transmission with an electric motor in a machine's drivetrain. Brief description

[0006] This disclosure, in one aspect, describes an electric powertrain for driving a traction device of a machine. The electric powertrain includes an electric power source, an electric motor operatively connected to the electric power source, and a multi-speed transmission operatively connected to the electric motor. The multi-speed transmission is operable to shift between a plurality of gears, each of which is configured to adjust an electric motor output speed and an electric motor output torque to a corresponding transmission output speed and transmission output speed range. The electric powertrain also includes an electronic controller. The electronic controller is configured to receive a first signal indicative of the rim pull torque demand of the electric powertrain, wherein the rim pull torque demand has an associated electric motor torque command.The electronic controller is further configured to receive a second signal indicative of an operating gear in which the multi-speed transmission is operating. The electronic controller determines a corresponding rim pull torque limit for the operating gear of the multi-speed transmission. The electronic controller determines whether the rim pull torque demand exceeds the rim pull torque limit. Upon determining that the rim pull torque demand exceeds the rim pull torque limit, the controller operates to either (i) shift the multi-speed transmission to a gear where the corresponding rim pull torque limit is at or above the rim pull torque demand, or (ii) reduce the electric motor torque command to a level at which the rim pull torque is below the corresponding rim pull torque limit for the operating gear of the multi-speed transmission.

[0007] In another aspect, the disclosure describes a machine comprising a machine frame and at least one traction device mounted on the machine frame. An electric powertrain is mounted on the machine frame to drive the at least one traction device. The electric powertrain includes an electric power source, an electric motor operatively connected to the electric power source, and a multi-speed transmission operatively connected to the electric motor. The multi-speed transmission is operable to shift between a plurality of gears, each of which is configured to adjust an electric motor output speed and an electric motor output torque to a corresponding transmission output speed and transmission output speed range. The electric powertrain also includes an electronic controller.The electronic controller is configured to receive a first signal indicative of the rim pull torque demand of the electric powertrain, the rim pull torque demand having an associated electric motor torque command. The electronic controller is further configured to receive a second signal indicative of an operating gear in which the multi-speed transmission is operating. The electronic controller determines a corresponding rim pull torque limit for the operating gear of the multi-speed transmission. The electronic controller determines whether the rim pull torque demand exceeds the rim pull torque limit.Upon determining that the rim pull torque demand exceeds the rim pull torque limit, the controller acts to either (i) shift the multi-speed transmission into a gear where the corresponding rim pull torque limit is at or above the rim pull torque demand, or (ii) reduce the electric motor torque command to a level at which the rim pull torque is below the corresponding rim pull torque limit for the operating gear of the multi-speed transmission.

[0008] In another aspect, the disclosure describes a method for controlling an electric powertrain of a machine. The electric powertrain includes an electric power source, an electric motor, and a multi-speed transmission operable to shift between a plurality of gears, each of which is configured to adjust an electric motor output speed and an electric motor output torque to a corresponding transmission output speed and transmission output speed range. The method includes receiving a first signal indicative of the rim pull torque demand of the electric powertrain, wherein the rim pull torque demand has an electric motor torque command associated with it, and receiving a second signal indicative of an operating gear in which the multi-speed transmission is operating.The method further includes determining a corresponding rim pull torque limit for the operating gear of the multi-speed transmission and determining whether the rim pull torque demand exceeds the rim pull torque limit. Upon determining that the rim pull torque demand exceeds the rim pull torque limit, the method includes acting to either (i) shift the multi-speed transmission to a gear where the corresponding rim pull torque limit is at or above the rim pull torque demand, or (ii) reduce the electric motor torque command to a level at which the rim pull torque is below the corresponding rim pull torque limit for the operating gear of the multi-speed transmission. Short description of the drawings Fig. 1 is a side elevational view of an exemplary machine having an electric powertrain according to this disclosure. Fig. 2 is a schematic illustration of an electric drive train for the machine of Fig. 1. Fig. 3 is an example graph of speed versus rim pull torque for the electric drive train of Fig. 2. Fig. 4 is a flowchart illustrating an exemplary method for controlling the electric powertrain of Fig. 2 illustrates. Detailed description

[0009] Referring now to the drawings, in which like reference numbers refer to like elements where possible, Fig. 1 illustrates a mobile machine 100 in the particular embodiment of a wheel loader, which in this case is intended for loading, transporting, and delivering material at a construction site. Although the present disclosure focuses on a mobile machine 100 in the embodiment of a wheel loader, aspects of the disclosure may be applicable to other types of mobile machines that perform some type of operation associated with an industry such as mining, construction, agriculture, transportation, or the like. For example, the mobile machine 100 may be an off-highway truck, a motor grader, or other material-moving machine configured to move within a work environment.

[0010] In the illustrated embodiment, the machine 100 includes a machine frame 102. To enable maneuverability, e.g., performing sharp turns, the machine frame 102 may be an articulated frame with the front and rear ends pivotally connected at an articulation 104. To enable the machine 100 to move in a mobile manner across a work surface, the machine frame 102 may be supported on a variety of traction devices 106, such as rotatable wheels, which may include rubber tires. The wheels may be referred to as powered drive wheels for propelling the machine 100, steerable wheels for directional adjustment of the wheel loader, or combinations thereof.Other suitable embodiments of machines may include various traction devices 106, such as continuous chains with a closed belt arranged around rollers and / or sprockets, wherein the machine is supported by the translation of the belt over the work surface.

[0011] For picking up material during operation, the machine 100 may include a work tool 108, in the illustrated embodiment a bucket, which in this case is operatively connected to a lifting mechanism 110 that can vertically raise and lower the work tool 108 relative to a work surface. The lifting mechanism 110 may be a mechanical linkage composed of a plurality of rigid links connected by pivot joints that can be articulated and moved relative to one another to controllably translate or reposition the work tool 108. In particular, the work tool 108 may be pivotally mounted at the distal end of the lifting mechanism 110, which in turn may be pivotally connected (via a pivot joint 116) to the forward end of the machine frame 102. A tilt mechanism 112 may also be provided to pivot the work tool 108 relative to the lifting mechanism 110.It will be understood that in other embodiments of mobile machines, the work tool 108 may be something other than a bucket, such as a shield, a blade, an auger, and the like.

[0012] In one embodiment, the machine 100 may include a vehicle-mounted operator cab 114 to house an operator and / or the operator input devices or controls for operating the machine. For example, the input devices in the operator cab 114 may include drive inputs that control mobile operation of the machine 100, as well as lift inputs that can manipulate the work implement 108. Examples of drive and lift inputs may include handwheels, joysticks, pedals, levers, knobs, keypads, etc. The drive inputs may be configured to increase or decrease the travel speed of the machine 100 relative to the direction of travel to accelerate, decelerate, and / or stop the travel of the machine. Referring to Fig. 2, the machine 100 includes an electric powertrain 120 to power one or more of the traction devices 106. The illustrated electric powertrain 120 includes an electrical power source 122, which may, for example, comprise a battery pack supported on the machine frame 102. The battery pack may include one or more rechargeable batteries that store electrical energy that may be used to power operation of the electric powertrain 120 of the machine 100. In other embodiments, the electrical power source 122 may utilize electricity supplied, for example, by an internal combustion engine operating in series with an associated electrical generator or by a fuel cell.

[0013] The electric drivetrain 120 further includes an electric motor 124, which is also mounted on the machine frame 102. In particular, the electric drivetrain 120 may be configured such that the electrical power source 122 provides electrical energy for driving the electric motor 124. Although reference is made in the singular, more than one electric motor 124 may be used, for example, two or more electric motors mechanically connected via a gearbox or gear train. The electric motor 124 may be configured as any known AC or DC motor, for example, a permanent magnet, induction, or reluctance motor, or a hybrid configuration of the aforementioned motors, and may also be sealed, brushless, and / or liquid-cooled.Additionally, in some embodiments, the electric motor 124 may be configured and controlled to allow the machine 100 to decelerate while the electric motor 124 is used as a generator, thereby converting the kinetic energy associated with the wheel loader into electrical energy that may be stored in the electrical power source 122 or other electrical energy storage device.

[0014] In the illustrated embodiment, the electric motor 124 includes an associated inverter 126 configured to convert and control the electricity supplied from the electrical power source 122 to the electric motor 124. For example, the inverter 126 may be configured to control the frequency of the electrical power supplied to the electric motor 124 to thereby regulate the speed and output torque of the motor.

[0015] To further adjust the speed and / or torque generated by the electric motor 124, the electric powertrain 120 may include a multi-speed transmission 130. More specifically, the multi-speed transmission 130 may include a gear train or gearbox mounted on the machine frame 102 that enables regulation and transmission of the power generated by the electric motor 124 to the traction devices 106 of the machine 100. The multi-speed transmission 130 may be adapted to be operatively coupled to the electric motor 124. Such coupling may be achieved, for example, through selective use of one or more clutches, such as a forward clutch and a reverse clutch. Like the power source 122 and the electric motor 124, the multi-speed transmission 130 may be mounted on the machine frame 102.

[0016] The multi-speed transmission 130 may define a plurality of different gear ranges that may enable the machine 100 to move in both a forward and reverse direction. For example, the multi-speed transmission 130 may be configured to adjust the output speed and torque of the electric motor 124 to multiple ranges or settings, such as two, three, four, or more forward output speed and torque ranges and one reverse output speed and torque range.

[0017] The multi-speed transmission 130 may also include a transmission output shaft 132, via which the power output (e.g., rotational power output) received from the electric motor 124 may be transmitted to other components of the electric powertrain 120. The transmission output shaft 132 may, in turn, be operatively connected to a differential 134. The differential 134 may be configured to transmit the power output to the traction devices 106 to enable movement of the machine 100.

[0018] To facilitate controlled operation of the electric powertrain 120, the electric powertrain 120 may be operatively connected to a control system embodied in an electronic controller 140, sometimes referred to as an electronic control module (ECM) or electronic control unit (ECU). The electronic controller 140 may be a programmable computing device and include one or more microprocessors for executing software instructions and processing computer-readable data. Examples of suitable microprocessors include programmable logic devices such as field-programmable gate arrays ("FPGAs"), dedicated or custom logic devices such as application-specific integrated circuits ("ASICs"), gate arrays, a complex programmable logic device, or any other suitable type of circuitry or microchip.To store application software and data for the controlled operation of the electric powertrain, the electronic controller 140 may include non-volatile, computer-readable and / or writable memory, such as read-only memory ("ROM"), random access memory ("RAM"), EPROM memory, flash memory, or another more permanent storage medium such as magnetic or optical storage. To interface and network with other operational systems of the machine 100, the electronic controller 140 may include an input / output interface for electronically transmitting and receiving non-volatile data and information.The input / output interface may be physically implemented as data ports, serial ports, parallel ports, USB ports, jacks, and the like to communicate via conductive wires, cables, optical fibers, or other communicative bus systems using any suitable communication protocol such as CAN bus, Wi-Fi, Bluetooth, or cellular communication standards. Other software, including any suitable instruction sets, programs, applications, routines, libraries, databases, and the like, may be associated with the electronic controller 140 to perform its functions. Although not described in . Fig. 2 illustrates the electronic controller 140 as a single, discrete unit, in other embodiments the electronic controller 140 and its functions may be distributed among a variety of different and separate components, including various components and functionalities located onboard the machine 100 and / or at an external operator station.

[0019] In this case, the electronic control 140 is connected to the inverter 126, the electric motor 124 and the multi-speed transmission 130. The data lines of the electronic communication network between the electronic control 140 and these systems of the electric drive train 120 are in Fig. 2 are represented by dashed lines and can be implemented as CAN bus or similar protocols and use conductive wires or optical fibers as physical transmission media.

[0020] To protect the electric powertrain 120 from damage or other problems associated with excessive torque, the electronic controller 140 may be configured to limit the rim pull torque generated by the multi-speed transmission 130 under certain circumstances. Specifically, the electronic controller 140 may be configured to apply a predetermined limit to the rim pull torque in one or more of the gears in which the multi-speed transmission 130 is operating. This rim pull torque limit is a function of the gear in which the multi-speed transmission 130 is operating and represents a maximum rim pull torque for that particular gear that the electronic controller 140 allows the multi-speed transmission 130 to generate.Upon receiving a rim pull torque demand that exceeds the rim pull torque limit, the electronic controller 140 may be configured to command the multi-speed transmission 130 to downshift to a gear where the rim pull torque limit is less than the rim pull torque demand. Alternatively, the electronic controller 140 may be configured to limit the torque command to the electric motor 124 if a lower gear is unavailable for any reason (e.g., failure of one or more of the lower gears or the multi-speed transmission 130 is already in the lowest gear). The desired rim pull torque may be considered a machine performance metric that depends on the ground speed of the machine 100.When configuring the electric powertrain 120, each gear of the multi-speed transmission 130 has a theoretical maximum rim pull torque based on the operating range of maximum torque (at a given speed) multiplied by the gear ratio. Generally, this maximum rim pull curve may exceed the desired rim pull curve because the available torque / speed envelope of the electric motor 124 is not perfectly matched to the multi-speed transmission 130. Consequently, the desired rim pull curve of the machine may represent a limitation of the theoretical maximum rim pull torque capability of the machine. The rim pull torque limitation of the present disclosure does not refer to (or include) this possible difference between the desired rim pull torque and the maximum rim pull torque.

[0021] Fig. 3 provides an example graph of transmission output speed versus rim pull torque for a four-speed electric powertrain 120. In the Fig. 3, a corresponding rim pull torque limit is applied to each of the second, third, and fourth gears of the multi-speed transmission 130. The rim pull torque limit is represented by a horizontal line (labeled 142 for second gear, 144 for third gear, and 146 for fourth gear) at the bottom of the curve for each gear, showing how the rim pull torque does not increase further below a certain transmission speed. These transmission speeds may correspond to normal downshift points in each individual gear. The rim pull torque limit is particularly applicable to speeds below the normal downshift points (in Fig. 3 with 160 for the downshift point between first and second gear, 162 for the downshift point between second and third gear, and 164 for the downshift point between third and fourth gear). The rim pull torque limit is generally below the maximum rim pull torque capability of the electric motor 124. In the Fig. 3, there is no rim pull torque limit for the first gear, although in some embodiments the first gear may also have a rim pull torque limit.

[0022] For example, in a situation where the machine 100 is decelerating from its maximum travel speed, the multi-speed transmission 130 and the electronic control 140 are designed to shift gears at the corresponding shift points (e.g., 160, 162, and 164 in Fig. 3) downshift into successively lower gears so that the multi-speed transmission 130 produces the desired rim pull curve (which is defined as the smooth, continuous curve (with reference to 170) of Fig. 3 minus the horizontal rim pull torque limit lines 142, 144, 146). If the multi-speed transmission 130 fails to downshift for any reason, the desired rim pull torque, as seen by the machine, continues to increase as the ground speed decreases. In such a case, the electronic controller 140 limits the rim pull torque to the rim pull torque limit 142, 144, 146 for the currently engaged gear (based on the nominal transmission shift points 160, 162, 164) and ignores the rim pull torque increase command associated with the decelerating ground speed of the machine.

[0023] Rim pull torque is the force at the contact point between the traction device and the ground. Rim pull torque and transmission output torque are functionally equivalent, with rim pull torque representing the force that a given transmission output torque generates on the traction device. Rim pull torque and transmission output torque are used interchangeably here. Commercial applicability

[0024] The present disclosure is applicable to any type of electric powertrain. The present disclosure is particularly applicable to electric powertrains that include electric motors and multi-speed transmissions. For example, the rim pull torque limiting of the present disclosure allows one or more gears of the multi-speed transmission to be configured to withstand torques less than the full output torque capability of the electric motor. This rim pull torque limiting system can protect the multi-speed transmission from damage, as well as excessive wear and related durability issues.This can also significantly reduce the cost of the multi-speed transmission, as the rim pull torque limiting system can eliminate the need for a hardened multi-speed transmission design, where each gear and associated gear structure can withstand the full torque capability of the electric motor. The reduced rim pull torque can also signal the machine operator that, for example, there is a fault in the multi-speed transmission that prevents proper downshifting.

[0025] With reference to Fig. 4 and generally in accordance with the preceding figures, an exemplary process 150 for applying a rim pull torque limit to the electric drivetrain 120 is illustrated, which may be executed by the electronic controller 140. The process 150 depicted in the flowchart for accomplishing these tasks may include a series of steps or instructions implemented as non-transitory, computer-executable software code in the form of an application or program executed by the electronic controller 140. It should be understood that the steps of the process 150 may not necessarily be in the Fig. 4 must be carried out in the order illustrated.

[0026] In step 152 of process 150, the electronic controller 140 receives a signal indicating a rim pull torque demand of the electric powertrain 120. For example, this rim pull torque demand may be initiated by an operator of the machine 100. In step 154, the electronic controller 140 receives a signal (e.g., from the multi-speed transmission) indicating which gear the multi-speed transmission 130 is currently operating in. Next, in step 156, the electronic controller 140 determines the applicable rim pull torque limit for the current gear of the multi-speed transmission 130. For example, the applicable rim pull torque limits for each gear of the multi-speed transmission 130 may be stored in a lookup table connected to the electronic controller 140.

[0027] In step 158, the electronic controller 140 determines whether the rim pull torque demand from step 152 exceeds the rim pull torque limit from step 158. If the requested rim pull torque does not exceed the limit, the process may return to step 152, and the requested rim pull torque may be applied to the multi-speed transmission 130. If the requested rim pull torque exceeds the torque limit, the electronic controller 140 operates to reduce the rim pull torque below the rim pull torque limit. A method for doing so is described in step 160; namely, the electronic controller 140 may command the multi-speed transmission 130 to shift to a lower gear where the rim pull torque limit is higher than the current rim pull torque demand.As illustrated in step 162, if the multi-speed transmission 130 can shift to a lower gear where the rim pull torque limit is higher than the rim pull torque demand, the process 150 may return to step 152. However, as previously mentioned, there may be instances where the multi-speed transmission 130 does not or cannot successfully shift to a lower gear. In such instances, as illustrated in step 164, the electronic controller 140 may limit the torque command to the electric motor 124 to a value that is less than the rim pull torque limit for the gear in which the multi-speed transmission is operating.

[0028] It is apparent that the foregoing description provides examples of the disclosed system and technology. However, it is conceivable that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to refer to the particular example described at that point and are not intended to imply any limitation on the general scope of the disclosure. Any expression of distinction or disparagement with respect to particular features is intended to indicate no preference for those features, but is not intended to exclude them entirely from the scope of the disclosure unless otherwise indicated.

[0029] The specification of ranges of values ​​is intended merely as a shorthand for referring to each individual value falling within the range, unless otherwise specified herein, and each individual value is included in the description as if listed individually. All procedures described herein may be performed in any convenient order unless otherwise specified or the context clearly indicates otherwise.

[0030] The use of the terms "a" ... "an", "an", "an" and "the" ... "the", "the" and "at least one" or the term "one or more" and similar references in the context of describing the invention (particularly in the context of the following claims) shall be construed to cover both the singular and the plural, unless otherwise stated herein or clearly contradicted by the context. The use of the term "at least one" followed by a list of one or more items (for example, "at least one of A and B" or "one or more of A and B") shall be construed to mean the selection of one item from the listed items (A or B) or a combination of two or more of the listed items (A and B), unless otherwise stated herein or clearly contradicted by the context.Accordingly, to the extent permitted by law, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto. Furthermore, any combination of the elements described above, in all possible variations thereof, is included in the disclosure, unless otherwise stated herein or the context clearly dictates otherwise. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] US 7,766,791

[0005]

Claims

[1] An electric drive train (120) for driving a traction device (106) of a machine (100), comprising: an electrical power source (122); an electric motor (124) operatively connected to the electrical power source (122); a multi-speed transmission (130) operatively connected to the electric motor (124), the multi-speed transmission (130) operable to shift between a plurality of gears each configured to adjust an electric motor output speed and an electric motor output torque to a corresponding transmission output speed and transmission output speed range; and an electronic control (140) arranged for: Receiving a first signal indicative of the rim traction torque demand of the electric powertrain (120), the rim traction torque demand having an associated electric motor torque command; Receiving a second signal indicating an operating gear in which the multi-speed transmission (130) is operating; Determining a corresponding rim traction torque limit (142, 144, 146) for the operating gear of the multi-speed transmission (130); Determining whether the rim pull torque demand exceeds the rim pull torque limit (142, 144, 146); and after determining that the rim pull torque demand exceeds the rim pull torque limit, act to either (i) shift the multi-speed transmission (130) into a gear in which the corresponding rim pull torque limit (142, 144, 146) is at or above the rim pull torque demand, or (ii) reduce the electric motor torque command to a level at which the rim pull torque is below the corresponding rim pull torque limit (142, 144, 146) for the operating gear of the multi-speed transmission (130). [2] The electric drive train (120) of claim 1, wherein the electrical power source (122) is a battery pack. [3] Electric drive train (120) according to one of the preceding claims, wherein the rim traction torque limit (142, 144, 146) is below an output torque capability of the electric motor (124). [4] Electric drive train (120) according to one of the preceding claims, further comprising a differential (134) operatively connected to the multi-speed transmission (130) for distributing the torque generated by the electric motor (124) to the traction device (106) of the machine (100). [5] Electric drive train (120) according to any one of the preceding claims, further comprising an inverter (126) configured to convert and control the electricity supplied to the electric motor (124) from the electrical power source (122). [6] Electric drive train (120) according to claim 5, wherein the controller (140) is connected to the electric motor (124), the multi-speed transmission (130) and the inverter (126). [7] Electric drive train (120) according to one of the preceding claims, wherein the electric motor (124) is also configured for operation as a generator. [8] Electric drive train (120) according to one of the preceding claims, wherein the rim traction torque limit (142, 144, 146) is stored in the electronic control (140) for each operating gear. [9] Electric drive train (120) according to one of the preceding claims, wherein at least one lowest gear of the multi-speed transmission (130) has no rim traction torque limitation. [10] A machine (100) having an electric drive train (120) according to claim 1, the machine comprising a machine frame (102) and at least one traction device (106) carried on the machine frame (102), and wherein the electric drive train (120) is carried on the machine frame to drive the at least one traction device.

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