Electric powertrain with rim-pull torque limiting protection

Abstract

The electric powertrain (120) includes a power source (122), an electric motor (124), and a multi-speed transmission (130). The powertrain (120) has an electronic controller (140). The controller (140) determines respective rim-pull torque limits (142, 144, 146) for the operating gears of the multi-speed transmission (130) and determines whether a rim-pull torque command exceeds the rim-pull torque limits. If the controller (140) determines that the rim-pull torque command exceeds the rim-pull torque limits, the controller (140) acts to either (i) shift the multi-speed transmission (130) to a gear whose respective rim-pull torque limit is equal to or greater than the rim-pull torque command, or (ii) reduce the electric motor torque command to a level where the rim-pull torque is below the respective rim-pull torque limit of the operating gear of the multi-speed transmission (130).

Description

[Technical Field]

[0001] This patent disclosure relates generally to machines having electric powertrains, and more particularly to electric powertrains having multi-speed transmissions and rim-pull limiting protection systems. [Background technology]

[0002] Many machines used in construction and mining environments include powertrains for operating traction devices, such as tires. More specifically, these powertrains typically include a power source that provides torque to one or more of the machine's traction devices via a transmission. Internal combustion engines are commonly used power sources in the powertrains of such machines. The powertrain's maximum transmission output is generally a function of the maximum engine performance applied to the transmission's various gear ratios. Internal combustion engines are limited in the range of input speeds and torques to the transmission as specified by the engine's inability to operate below a low idle speed. Therefore, the internal combustion engine's inherent minimum operating speed creates a design criterion for a minimum transmission input speed below which the transmission will never operate. As a result, there is a natural torque limit for each gear defined by the internal combustion engine's minimum idle speed.

[0003] Internal combustion engines can emit undesirable exhaust gases and other pollutants during operation. Additionally, improving the fuel efficiency of machines is becoming increasingly important due to, for example, rising costs associated with fossil fuels. One solution to these problems is a powertrain that utilizes electric motors to provide torque to the machine's traction device. However, the use of electric motors in a machine's powertrain can pose other challenges. For example, providing an electric motor of sufficient size to meet the machine's torque and speed commands can be costly.

[0004] One way to reduce the required size of an electric motor is to use a multi-speed transmission. However, using a multi-speed transmission to transfer torque from an electric motor creates other problems. For example, electric motors generally do not have a low-speed limit, resulting in higher performance across the motor's entire speed range compared to internal combustion engines. The battery powering the electric motor is not limited by speed. The battery can provide full power even at zero speed. Therefore, unlike internal combustion engines, electric motors can generate high torque even at zero speed. As a result, when using a multi-speed transmission with an electric motor, each gear in the multi-speed transmission can be exposed to the relatively high motor torque associated with low motor speeds. However, building the transmission's gear train to withstand such torque can be very costly.

[0005] U.S. Pat. No. 7,766,791 (the '791 patent), assigned to the assignee of the present application, describes a machine powertrain having a transmission, a differential coupled to the transmission, and a clutch associated with the differential. The clutch and differential are configured to selectively reduce the total tractive effort available to the machine by disengaging the differential as a function of torque generated by a power source. More specifically, the powertrain configuration of the '791 patent focuses on limiting torque applied to the powertrain by reducing the machine's tractive effort using an open differential between the shafts to prevent potentially damaging torque from being introduced into the powertrain. However, the '791 patent does not recognize the problems associated with potentially damaging torque resulting from the use of a multi-speed transmission with an electric motor in the machine's powertrain. Summary of the Invention

[0006] In one aspect, the present disclosure describes an electric powertrain for driving a traction device of a machine. The electric powertrain includes a power source, an electric motor operably coupled to the power source, and a multi-speed transmission operably coupled to the electric motor. The multi-speed transmission is shiftable among a plurality of gears, each configured to adjust the electric motor output speed and electric motor output torque to a respective 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 an electric powertrain rim-pull torque command, the rim-pull torque command having an associated electric motor torque command. The electronic controller is also configured to receive a second signal indicative of an operating gear in which the multi-speed transmission is operating. The electronic controller determines a respective rim-pull torque limit for the operating gear of the multi-speed transmission. The electronic controller determines whether the rim-pull torque command exceeds the rim-pull torque limit. If the electronic controller determines that the rim-pull torque command exceeds the rim-pull torque limit, the electronic controller acts to either (i) shift the multi-speed transmission to a gear whose respective rim-pull torque limit is equal to or greater than the rim-pull torque command, or (ii) reduce the electric motor torque command to a level where the rim-pull torque is below the respective rim-pull torque limit of the operating gear of the multi-speed transmission.

[0007] In another aspect, the present disclosure describes a machine including a machine frame and at least one traction device supported on the machine frame. An electric powertrain is supported on the machine frame for driving the at least one traction device. The electric powertrain includes a power source, an electric motor operably coupled to the power source, and a multi-speed transmission operably coupled to the electric motor. The multi-speed transmission is shiftable among a plurality of gears, each gear configured to adjust an electric motor output speed and an electric motor output torque to a respective 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 an electric powertrain rim-pull torque command, the rim-pull torque command having an associated electric motor torque command. The electronic controller is also configured to receive a second signal indicative of an operating gear in which the multi-speed transmission is operating. The electronic controller determines a respective rim-pull torque limit for the operating gear of the multi-speed transmission. The electronic controller determines whether the rim-pull torque command exceeds the rim-pull torque limit. If the electronic controller determines that the rim-pull torque command exceeds the rim-pull torque limit, the electronic controller acts to either (i) shift the multi-speed transmission to a gear whose respective rim-pull torque limit is equal to or greater than the rim-pull torque command, or (ii) reduce the electric motor torque command to a level where the rim-pull torque is below the respective rim-pull torque limit of the operating gear of the multi-speed transmission.

[0008] In yet another aspect, the present disclosure describes a method for controlling an electric powertrain of a machine. The electric powertrain includes a power source, an electric motor, and a multi-speed transmission operable to shift between a plurality of gears, each configured to regulate an electric motor output speed and an electric motor output torque to a respective transmission output speed and transmission output speed range. The method includes receiving a first signal indicative of a rim-pull torque command of the electric powertrain, the rim-pull torque command having an associated electric motor torque command, and receiving a second signal indicative of an operating gear in which the multi-speed transmission is operating. The method further includes determining a respective rim-pull torque limit for the operating gear of the multi-speed transmission and determining whether the rim-pull torque command exceeds the rim-pull torque limit. Upon determining that the rim-pull torque command exceeds the rim-pull torque limit, the method includes acting to (i) shift the multi-speed transmission into a gear whose respective rim-pull torque limit is equal to or greater than the rim-pull torque command, or (ii) reduce the electric motor torque command to a level where the rim-pull torque is less than the respective rim-pull torque limit of the operating gear of the multi-speed transmission. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an exemplary machine having an electric powertrain according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of an electric powertrain for the machine of FIG. [Figure 3] FIG. 3 is an exemplary plot of speed versus rim-pull torque for the electric powertrain of FIG. [Figure 4] FIG. 4 is a flowchart illustrating an exemplary method for controlling the electric powertrain of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Referring now to the drawings, where like reference numbers refer to like elements wherever possible, FIG. 1 illustrates a mobile machine 100, in this case in a particular embodiment of a wheel loader, for loading, transporting, and delivering material around a work site. However, while this disclosure focuses on mobile machine 100 in a wheel loader embodiment, aspects of the disclosure may be applicable to other types of mobile machines that perform some type of operation in connection with an industry, such as mining, construction, agriculture, transportation, etc. For example, mobile machine 100 may be an off-highway truck, a motor grader, or other material moving machine configured to move around a work environment.

[0011] In the illustrated embodiment, the machine 100 includes a machine frame 102. To facilitate maneuverability, such as making sharp turns, the machine frame 102 may be an articulated frame with a forward end and an aft end pivotally coupled at an articulated joint 104. To enable the machine 100 to move in a mobile manner about the work surface, the machine frame 102 may be supported on a plurality of traction devices 106, such as rotatable wheels, which may include rubber tires. The wheels may be designated as power-driven wheels for propelling the machine 100, steerable wheels for adjusting the direction of a wheel loader, or a combination thereof. Other suitable embodiments of the machine may include a different traction device 106, such as a continuous track including a closed belt disposed around rollers or sprockets, whereby movement of the belt moves the machine across the work surface.

[0012] To accommodate material during operation, the machine 100 may include a work tool 108, in this case a bucket in the illustrated embodiment, operatively associated with a lifting mechanism 110 that can vertically raise and lower the work tool 108 relative to a work surface. The lifting mechanism 110 is a mechanical linkage assembled from a plurality of rigid links connected by pivot joints that can articulate or move relative to one another to controllably displace or reposition the work tool 108. In particular, the work tool 108 is pivotally disposed at the tip of the lifting mechanism 110, which is pivotally connected to the front end of the machine frame 102 via a pivot joint 116. A tilting mechanism 112 is also provided to enable the work tool 108 to pivot relative to the lifting mechanism 110. It will be understood that in other embodiments of the mobile machine, the work tool 108 is not a bucket, but may be, for example, a fork, blade, drill auger, or the like.

[0013] In one embodiment, machine 100 may be equipped with an on-board operator cab 114 to accommodate operator input devices or controls for operating the operator and / or the machine. For example, input devices within operator cab 114 may include a drive input that controls the movement of machine 100 and a lift input that may operate work tool 108. Examples of drive inputs and lift inputs include handwheels, joysticks, pedals, levers, knobs, keypads, etc. The drive inputs may be configured to increase or decrease the drive speed of machine 100 relative to the direction of travel, and to accelerate, slow, and / or stop the movement of the machine.

[0014] 2 , machine 100 includes an electric powertrain 120 for powering one or more traction devices 106. The illustrated electric powertrain 120 includes a power source 122, which may consist of, for example, a battery pack mounted on machine frame 102. The battery pack may include one or more rechargeable batteries that store electrical energy, which may be used to drive the operation of electric powertrain 120 of machine 100. In other embodiments, power source 122 may utilize electricity provided by, for example, an internal combustion engine or a fuel cell operating in series with an associated electrical generator.

[0015] The electric powertrain 120 further includes an electric motor 124 mounted on the machine frame 102. In particular, the electric powertrain 120 may be configured such that the power source 122 provides electrical energy to power the electric motor 124. Although referred to in the singular, multiple electric motors 124 may be used, such as two or more electric motors mechanically coupled via gears or a gear train. The electric motor 124 may be any known AC or DC motor, such as permanent magnet, induction, switched reluctance, or a hybrid configuration thereof, and may be hermetically sealed, brushless, and / or liquid-cooled. Furthermore, in some embodiments, the electric motor 124 may be configured and controlled to decelerate the machine 100 while being used as a generator, thereby converting kinetic energy associated with the wheel loader into electrical energy that can be stored in the power source 122 or other power storage device.

[0016] In the illustrated embodiment, electric motor 124 has an associated inverter 126 configured to convert and control the electricity supplied to electric motor 124 by power source 122. For example, inverter 126 may be configured to control the frequency of the power supplied to electric motor 124, thereby controlling the rotational speed and output torque of the motor.

[0017] To further regulate 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 supported on the machine frame 102 that facilitates regulating and transmitting the electrical power generated by the electric motor 124 to the traction device 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 illustratively be achieved through the selective use of one or more clutches, such as a forward running clutch and a reverse running clutch. Similar to the power source 122 and the electric motor 124, the multi-speed transmission 130 may be supported on the machine frame 102.

[0018] Multi-speed transmission 130 may define multiple different gear ranges that enable machine 100 to achieve movement in both forward and reverse directions. For example, multi-speed transmission 130 may be configured to regulate the output speed and torque from electric motor 124 into multiple ranges or settings, such as two, three, four or more forward output speed and torque ranges and one reverse speed and torque range.

[0019] Multi-speed transmission 130 may also include a transmission output shaft 132 that can deliver the power output (e.g., rotational power output) received from electric motor 124 to additional components of electric powertrain 120. Transmission output shaft 132 may in turn be operably coupled to a differential 134. Differential 134 may then be configured to transfer power to traction device 106 to enable movement of machine 100.

[0020] To enable controlled operation of electric powertrain 120, electric powertrain 120 may be operatively associated with a control system embodied in electronic controller 140, also referred to as an electronic control module (ECM) or electronic control unit (ECU). Electronic controller 140 is a programmable computing device and may 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 customized logic devices such as application specific integrated circuits (“ASICs”), gate arrays, complex programmable logic devices, or any other suitable type of circuit or microchip. To store application software and data for controlled operation of the electric powertrain, electronic controller 140 may include non-transitory computer-readable and / or writable memory, such as read-only memory (ROM), random access memory (RAM), EPROM memory, flash memory, or more permanent storage media such as magnetic or optical storage. To interface and network with other operating systems on machine 100, electronic controller 140 may include input / output interfaces for electronically transmitting and receiving non-transient data and information. The input / output interfaces may be physically embodied as data ports, serial ports, parallel ports, USB ports, jacks, etc., for communicating through conductive wires, cables, fiber optics, or other communication bus systems via appropriate communication protocols such as CAN bus, WiFi, Bluetooth, or cellular communication standards. Electronic controller 140 may be associated with other software, including appropriate instruction sets, programs, applications, routines, libraries, databases, etc., to perform its functions.Although electronic controller 140 is illustrated in FIG. 2 as a single, independent unit, in other embodiments, electronic controller 140 and its functions may be distributed across multiple different, independent components, including various components and functions located on machine 100 and / or at an off-vehicle operator station.

[0021] In this case, electronic controller 140 is in communication with inverter 126, electric motor 124, and multi-speed transmission 130. The data lines of the electronic communication network between electronic controller 140 and these systems of electric powertrain 120 are represented by dashed lines in Figure 2 and may be implemented as a CAN bus or similar protocol, utilizing conductive wires or optical fibers as the physical transmission medium.

[0022] To protect electric powertrain 120 from damage or other problems associated with excessive torque, electronic controller 140 may be configured, under certain circumstances, to limit the rim-pull torque generated by multi-speed transmission 130. Specifically, 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 multi-speed transmission 130 operates. This rim-pull torque limit is a function of the gear in which multi-speed transmission 130 is operating and represents the maximum rim-pull torque for that particular gear that electronic controller 140 will permit multi-speed transmission 130 to generate. Upon receiving a rim-pull torque command that exceeds the rim-pull torque limit, electronic controller 140 may be configured to instruct multi-speed transmission 130 to downshift to a gear in which the rim-pull torque limit is below the rim-pull torque command. Alternatively, if the low gears are unavailable for some reason (e.g., one or more of the low gears fail, or the multi-speed transmission 130 is already in the lowest gear), the electronic controller 140 may be configured to limit the torque command to the electric motor 124.

[0023] The desired rim-pull torque can be considered a machine performance indicator that is a function of the ground speed of the machine 100. When configuring the electric powertrain 120, each gear in the multi-speed transmission 130 will have a theoretical peak rim-pull torque based on its maximum torque operating range (at a given speed) multiplied by the gear ratio. Typically, the available torque / speed range of the electric motor 124 will not perfectly match the multi-speed transmission 130, so this peak rim-pull curve may exceed the desired rim-pull curve. As a result, the desired rim-pull curve of the machine may limit the machine's theoretical peak rim-pull torque capability. The rim-pull torque limit in this disclosure does not refer to (or include) this potential difference between the desired rim-pull torque and the peak rim-pull torque.

[0024] FIG. 3 shows an example plot of transmission output speed versus rim-pull torque for a four-gear electric powertrain 120. In the example shown in FIG. 3, a respective rim-pull torque limit is applied to each of second, third, and fourth gears of the multi-speed transmission 130. The rim-pull torque limits are represented by horizontal lines at the low-speed end of each gear's curve (labeled 142 for second gear, 144 for third gear, and 146 for fourth gear), which indicate how the rim-pull torque stops increasing below a given transmission speed. These transmission speeds may correspond to the normal downshift points for each individual gear. The rim-pull torque limit specifically applies at speeds below those normal downshift points (in FIG. 3, the downshift point between first and second gear is labeled 160, the downshift point between second and third gear is labeled 162, and the downshift point between third and fourth gear is labeled 164). The rim-pull torque limit is generally below the maximum rim-pull torque capability of the electric motor 124. In the embodiment shown in FIG. 3, there is no rim-pull torque limit on first gear, although in some embodiments there may also be a rim-pull torque limit on first gear.

[0025] For example, in situations where the machine 100 is decelerating from maximum ground speed, the multi-speed transmission 130 and electronic controller 140 are designed to downshift to successively lower gears at appropriate shift points (e.g., 160, 162, 164 in FIG. 3 ). This causes the multi-speed transmission 130 to generate a desired rim-pull curve (which can be thought of as a smooth, continuous curve (labeled 170) in FIG. 3 minus the horizontal rim-pull torque limit lines 142, 144, 146). If the multi-speed transmission 130 does not downshift for some reason, the desired rim-pull torque from the machine's perspective continues to increase as ground speed decreases. In such a case, the electronic controller 140 limits the rim-pull torque of the currently engaged gear (based on the nominal transmission shift points 160, 162, 164) to the rim-pull torque limits 142, 144, 146, ignoring the command to increase rim-pull torque associated with the machine's decelerating ground speed.

[0026] Rim-pull torque is the force at the connection point between the traction device and the ground. Rim-pull torque and transmission output torque are functionally equivalent, and rim-pull torque represents the force that a particular transmission output torque generates on the traction device. Rim-pull torque and transmission output torque are used interchangeably herein. [Industrial Applicability]

[0027] The present disclosure is applicable to all types of electric powertrains. The present disclosure is particularly applicable to electric powertrains that include an electric motor and a multi-speed transmission. For example, the rim-pull torque limiting of the present disclosure allows one or more gears in a multi-speed transmission to be designed to withstand torques that are less than the maximum 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 tear and related durability issues. This can also significantly reduce the cost of the multi-speed transmission because the rim-pull torque limiting system reduces the need to reinforce the multi-speed transmission design to ensure that each gear and associated transmission structure can withstand the maximum torque capability of the electric motor. A reduction in rim-pull torque can also signal to a machine operator that there is a fault in the multi-speed transmission that prevents it from properly downshifting, for example.

[0028] 4, and generally in accordance with the preceding figures, an exemplary process 150 for applying rim-pull torque limiting on electric powertrain 120 executed by electronic controller 140 is illustrated. Process 150, depicted in a flow diagram 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 electronic controller 140. It will be understood that the steps of process 150 do not necessarily have to be performed in the order shown in FIG.

[0029] In step 152 of process 150, electronic controller 140 receives a signal indicative of a rim-pull torque command for electric powertrain 120. For example, this rim-pull torque command may be initiated by an operator of machine 100. In step 154, electronic controller 140 receives a signal (e.g., from the multi-speed transmission) indicative of the gear in which multi-speed transmission 130 is currently operating. Next, in step 156, electronic controller 140 determines the applicable rim-pull torque limit for the current gear of multi-speed transmission 130. For example, the applicable rim-pull torque limit for each gear of multi-speed transmission 130 may be stored in a look-up table associated with electronic controller 140.

[0030] In step 158, electronic controller 140 determines whether the rim-pull torque command from step 152 exceeds the rim-pull torque limit from step 158. If the commanded rim-pull torque does not exceed the limit, the process returns to step 152, and the commanded rim-pull torque may be applied to the multi-speed transmission 130. If the commanded rim-pull torque exceeds the torque limit, electronic controller 140 operates to reduce the rim-pull torque below the rim-pull torque limit. One way to do this is articulated in step 160, i.e., electronic controller 140 may command the multi-speed transmission 130 to shift to a lower gear whose rim-pull torque limit is higher than the current rim-pull torque command. If the multi-speed transmission 130 is able to shift to a lower gear whose rim-pull torque limit is higher than the rim-pull torque command, as reflected in step 162, process 150 returns to step 152, and the commanded rim-pull torque may be applied to the multi-speed transmission 130. However, as previously mentioned, there may be instances where the multi-speed transmission 130 does not successfully or is unable to shift into a lower gear. In such cases, as shown in step 164, the electronic controller 140 may limit the torque command to the electric motor 124 to a level below the rim-pull torque limit of the gear in which the multi-speed transmission is operating.

[0031] It will be understood that the foregoing description provides examples of the disclosed systems and techniques. However, it is contemplated that other implementations of the present disclosure may differ in detail from the foregoing embodiments. All references to the present disclosure or its embodiments are intended to refer to the specific embodiments discussed therein and do not imply limitations on the general disclosure. All language of distinction and disparagement regarding particular features is intended to indicate a lack of preference for those features, but does not entirely exclude such from the scope of the present disclosure unless otherwise indicated.

[0032] The recitation of ranges of values ​​herein is intended to serve as a shorthand method of referring individually to each individual value within that range, unless otherwise indicated herein, and each individual value is incorporated herein as if it were each individually set forth herein. Unless otherwise indicated herein or clearly contradicted by context, all methods described herein can be performed in any suitable order.

[0033] In the context of describing the present invention (particularly in the context of the claims below), the use of the terms "a," "an," "the," and "at least one," or the term "one or more," and similar reference words, should be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The term "at least one" followed by a list of one or more items (e.g., "at least one of A and B," or "one or more of A and B") shall be construed to mean one item selected from the listed items (A or B), or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context.

[0034] Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by this disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. An electric powertrain (120) for driving a traction device (106) of a machine (100), comprising: a power source (122); an electric motor (124) operably coupled to the power source (122); a multi-speed transmission (130) operably coupled to the electric motor (124), the multi-speed transmission (130) operable to shift between a plurality of gears, each gear configured to adjust electric motor output speed and electric motor output torque to a respective transmission output speed and transmission output speed range; An electronic controller (140) comprising: receiving a first signal indicative of a rim-pull torque command of the electric powertrain (120), the rim-pull torque command having an associated electric motor torque command; receiving a second signal indicative of the operating gear in which the multi-speed transmission (130) is operating; determining respective rim-pull torque limits (142, 144, 146) for the operating gears of the multi-speed transmission (130); determining whether the rim-pull torque command exceeds the rim-pull torque limit (142, 144, 146); an electronic controller configured, when determining that the rim-pull torque command will exceed the rim-pull torque limit, to: (i) shift the multi-speed transmission to a gear where the respective rim-pull torque limit (142, 144, 146) is equal to or greater than the rim-pull torque command; or (ii) act to reduce the electric motor torque command for the operating gear of the multi-speed transmission to a level where the rim-pull torque is less than the respective rim-pull torque limit (142, 144, 146).

2. The electric powertrain (120) of claim 1, wherein the power source (122) is a battery pack.

3. The electric powertrain (120) of claim 1 or 2, wherein the rim-pull torque limit (142, 144, 146) is less than the output torque capability of the electric motor (124).

4. 4. The electric powertrain (120) of claim 1, further comprising a differential (134) operably coupled to the multi-speed transmission (130) for distributing torque generated by the electric motor (124) to the traction device (106) of the machine (100).

5. The electric powertrain (120) of any one of claims 1 to 4, further comprising an inverter (126) configured to convert and control electricity supplied by the power source (122) to the electric motor (124).

6. The electric powertrain (120) of claim 5, wherein the controller (140) is in communication with the electric motor (124), the multi-speed transmission (130), and the inverter (126).

7. The electric powertrain (120) of any preceding claim, wherein the electric motor (124) is also configured to operate as a generator.

8. The electric powertrain (120) of any preceding claim, wherein the rim-pull torque limit (142, 144, 146) for each operating gear is stored in the electronic controller (140).

9. The electric powertrain (120) of any of claims 1 to 8, wherein at least a lowest gear of the multi-speed transmission (130) does not have a rim-pull torque limit.

10. 2. The machine (100) with electric powertrain (120) of claim 1, wherein the machine includes a machine frame (102) and at least one traction device (106) supported on the machine frame (102), the electric powertrain (120) being supported on the machine frame for driving the at least one traction device.

Images