ELECTRIC DRIVE UNIT WITH REMOVABLE THROUGH SHAFT

A system for an electric drive unit. The electric drive unit includes, in one example, a first shaft with a through shaft opening and a second shaft axially aligned with the first shaft. The electric drive unit further includes a through shaft that axially extends through the through shaft opening and removably attaches to the first shaft and the second shaft.

TECHNICAL FIELD

The present disclosure relates to an electric drive unit with a removable through shaft that when removed prevents a traction motor from receiving rotational input.

BACKGROUND AND SUMMARY

Electric powertrains include motors that generate motive power for electric vehicles (EVs). These electric powertrains provide an attractive alternative in terms of hydrocarbon emissions in relation to vehicles that solely rely on internal combustion engines to generate motive power. Certain electric powertrains include transmissions that allow the power output of the motor to be transferred to drive wheels.

It may be desirable to prevent electric motors from rotating during certain operating conditions, such as when the EV is being towed. Specifically, when the electric motor spins during towing operation, the motor generates electromagnetic fields (EMFs) while electrical power supplied to the motor is inhibited. The EMFs have the potential to degrade some motor components.

To prevent EMF generation, the EV may be placed on a flatbed trailer during towing. However, this type of towing may be costly and impractical for certain types of vehicles that have comparatively large heights and/or weights, for example.

U.S. Pat. No. 11,433,765 B2 to Perry et al. teaches an electric axle architecture with an axle disconnect device that allows powertrain rotation and specifically traction motor rotation to be stopped to avoid EMF generation. Perry's axle disconnect device mounts to one output of a differential.

The inventors have recognized several potential issues with the axle disconnect device disclosed in U.S. Pat. No. 11,433,765 B2. For instance, Perry's disconnect device is electronically actuated via a controller which allows the powertrain to be quickly disconnected via electronic control signal. However, if the controller or battery is not operational, the axle disconnect device may be correspondingly non-operational. As such, under certain conditions, the axle disconnect device may not function when needed. Further, when the axle disconnect device is activated, the differential will continue to spin during towing, thereby increasing differential wear and the likelihood of differential degradation.

The inventors have recognized the abovementioned issues and developed an electric drive unit to at least partially overcome the issues. The electric drive unit, in one example, includes a first shaft with a through shaft opening and a second shaft that is axially aligned with the first shaft. The electric drive unit further includes a through shaft that axially extends through the through shaft opening and removably attaches to the first shaft and the second shaft. Designing an electric drive unit with a removable through shaft that exhibits these features enables the through shaft to be reliably and manually removed prior to towing or other operating conditions where it is desirable to avoid rotation of a traction motor in the electric drive unit. Further, the through shaft is able to be removed regardless of the state of a controller, battery, and the like that may be included in the electric drive system, if desired.

Further, in one example, to achieve the removable attachment between the through shaft and the first and second shafts, the through shaft may be splined to the first and second shafts. In this way, a strong and detachable connection is formed between the through shaft, the first shaft, and the second shaft.

Further, in one example, the first shaft may be a rotor shaft in a traction motor and the second shaft may be an input shaft of a gearbox and where the input shaft has a gear fixedly coupled thereto. It this way, the through shaft is efficiently incorporated into the traction motor and may be more easily accessed.

DETAILED DESCRIPTION

An electric drive unit with a removable through shaft, that when removed inhibits a traction motor from receiving rotational input, when desired, is described herein. Using the through shaft to inhibit motor rotation allows a vehicle operator or other personnel to reliably and effectively disable the motor during selected conditions such as vehicle towing. The through shaft may be removably connected to a rotor shaft and an input shaft, in one example. However, in other examples, the through shaft may be removably coupled to another pair of shafts in the electric drive unit. Splines and/or a shaft flange may be used to achieve the removable attachment between the through shaft and the rotor and input shafts. In this way, a strong connection between the through shaft and the input and rotor shafts is formed that can be effectively disconnected, when desired, such as prior to towing operation to avoid electromagnetic field (EMF) generation and component degradation.

FIG.1shows a schematic depiction of an electric drive unit with a removable through shaft that enables rotational input to a traction motor to be effectively inhibited.FIGS.2A and2Bshow detailed views of an example of an electric drive unit with a through shaft mated with a rotor shaft and an input shaft, inFIG.2A, and decoupled from the rotor shaft and the input shaft inFIG.2B.FIG.3shows a detailed view of a splined interface between shafts in an electric drive unit.

FIG.1depicts an example of an electric drive unit100(e.g., an electric axle) that may be included in an electric vehicle (EV)101. The electric drive unit100may specifically be an electric axle, in one example, which can be more easily incorporated into a variety of vehicle platforms when compared to other types of electric drives. To elaborate, the electric axle may be an electric beam axle that is coupled to a dependent suspension system to increase axle durability and articulation when compared to axles that are coupled to independent suspension systems. However, the axle may be coupled to an independent suspension system, in other examples.

The EV101may be an all-electric vehicle in one example, although alternative examples are possible such as a hybrid electric vehicle (HEV) that utilizes an internal combustion engine for propulsion and/or recharging of an energy storage device. Further, the EV101may be a light, medium, or heavy duty vehicle, for instance. To elaborate, the vehicle may be a commercial vehicle (e.g., a vehicle that has a gross weight which is greater than or equal to 4,536 kilograms (kg)).

The electric drive unit100includes a traction motor102with a stator104which electromagnetically interacts with a rotor106to generate motive power during motor operation. The rotor106includes a rotor shaft108. Further in one example, the traction motor102may be a motor-generator which is designed to generate electrical energy during regeneration operation.

The traction motor102may be electrically coupled to one or more energy storage device(s)110(e.g., one or more traction batteries, capacitor(s), fuel cell(s), combinations thereof, and the like) by way of an inverter112when the machine is designed as alternating current (AC) machine. However, a direct current (DC) electric machine may be used in alternate examples.

Arrows114denote the electrical connection between the traction motor102, the inverter112, and the energy storage device(s)110. The inverter112may be designed to convert DC to AC and vice versa. In one use-case example, the traction motor102and the inverter112may be three-phase devices which can achieve greater efficiency when compared to other types of motors. However, motors and inverters designed to operate using more than three phases have been envisioned.

A through shaft116is removably coupled to the rotor shaft108and an input shaft118of a gearbox120, in the illustrated example. However, it will be appreciated that the through shaft116may be removably coupled to another pair of shafts in the gearbox120. For instance, the through shaft may be removably coupled to a pair of adjacent shafts that are downstream of the input shaft. To enable the removable coupling between the through shaft116, the rotor shaft108, and the input shaft118, splines, flanges, and/or fasteners may be used. A detailed example of a through shaft is expanded upon herein with regard toFIGS.2A-2B. A removable cover122may further be included in the traction motor102. The removable cover122may allow the through shaft to be accessed and reduce the likelihood of contamination of interior motor components.

The input shaft118may include a gear124fixedly coupled thereto. The gear124may mesh with a gear126that is fixedly coupled to a shaft128. The gearbox120is illustrated as a multi-speed gearbox120with clutches130and132that are designed to shift between different gear combinations in the gearbox. However, multi-speed gearboxes with a different number of clutches (e.g., a single clutch or more than two clutches) or a single speed gearbox may be used in the electric drive unit100, in other embodiments.

The clutch130is designed to selectively engage a gear134and a gear136that are idly mounted to the shaft128. Likewise, the clutch132is designed to selectively engage a gear138and a gear140that are idly mounted to a shaft142(e.g., output shaft). The gear138meshes with the gear134and the gear140meshes with the gear136in the illustrated example. However, numerous gear layouts are possible in the gearbox.

The shaft142may include a gear144that meshes with a gear146in a differential148. The differential148may be rotationally coupled to drive wheels via axle shafts (e.g., half shafts).

The electric drive unit100may further include a control system190with a controller192as shown inFIG.1. The controller192may include a microcomputer with components such as a processor193(e.g., a microprocessor unit), input/output ports, an electronic storage medium194for executable programs and calibration values (e.g., a read-only memory chip, random access memory, keep alive memory, a data bus, and the like). The storage medium may be programmed with computer readable data representing instructions executable by a processor for performing methods and control techniques.

The controller192may receive various signals from sensors195coupled to various regions of the EV101and the gearbox120. For example, the sensors195may include a pedal position sensor designed to detect a depression of an operator-actuated pedal such as an accelerator pedal and/or a brake pedal, a speed sensor at the gearbox output shaft, energy storage device state of charge (SOC) sensor, clutch position sensors, and the like. Motor speed may be ascertained from the amount of power sent from the inverter to the electric machine. An input device199(e.g., accelerator pedal, brake pedal, drive mode selector, combinations thereof, and the like) may further provide input signals indicative of an operator's intent for vehicle control.

Upon receiving the signals from the various sensors195ofFIG.1, the controller192processes the received signals, and employs various actuators196of vehicle and/or electric drive unit components to adjust the components based on the received signals and instructions stored on the memory of controller192. For example, the controller192may receive an accelerator pedal signal indicative of an operator's request for increased vehicle acceleration. In response, the controller192may command operation of the inverter112to adjust electric machine mechanical power output and increase the power delivered from the traction motor102to the gearbox120. The controller192may during certain operating conditions, be designed to send commands to the clutches130and132, to engage and disengage the clutches. For instance, a control command may be sent to one of the clutches and in response to receiving the command, an actuator in the clutch may adjust the clutch based on the command for clutch engagement or disengagement. The other controllable components in the vehicle may function in a similar manner with regard to sensor signals, control commands, and actuator adjustment, for example.

An axis system is provided inFIG.1as well asFIGS.2A,2B, and3, for reference. The z-axis may be a vertical axis (e.g., parallel to a gravitational axis), the x-axis may be a lateral axis (e.g., horizontal axis), and/or the y-axis may be a longitudinal axis, in one example. However, the axes may have other orientations, in other examples.

It will be appreciated that the electric drive unit100shown inFIG.1discloses one or many possible architectures. For instance, the electric drive unit may include a single speed gearbox with a different number of shafts and gears, in one example, or the number of operating gears in the gearbox may be increased, in another example.

FIGS.2A and2Bshow an example of an electric drive unit200(e.g., electric axle) with a traction motor202with a through shaft204installed in the traction motor and removed from the traction motor respectively. The electric drive unit200may include at least some structural and/or functional features that are similar to the electric drive unit100, shown inFIG.1. Redundant description of the overlapping components is omitted for brevity.

The traction motor202includes a stator205and a rotor206with a rotor shaft208. The rotor shaft208includes through shaft opening210. Further, the rotor shaft208may be coupled to a spider212which may be coupled to laminations, for instance.

The electric drive unit200further includes an input shaft214of a gearbox216. The input shaft214includes a through shaft recess218. The through shaft recess218may only partially extend through the input shaft214. However, in other examples, the through shaft recess may extend axially from one end of the shaft to the other end. In alternate examples, the through shaft may include an input shaft recess that mates with an axial extension of the input shaft. In other words, a portion of the through shaft may circumferentially surround and mate with a portion of the input shaft.

The through shaft204is removably coupled to the rotor shaft208and the input shaft214via mating with the through shaft opening210and the through shaft recess218. In this way, the through shaft204is able to be manually and reliably removed from the rotor shaft208and the input shaft214or vice versa.

The gearbox216may include a gear219coupled to or otherwise integrally formed on the input shaft214. The gear219may mesh with a gear221that is fixedly coupled to a shaft223. The shaft223may be rotationally coupled to downstream components such as gears, clutches, and/or a differential, for instance.

A housing262of the traction motor202may be coupled to a housing225of the gearbox216via attachment devices227. The housing225may at least partially enclose the gears219,221.

In the illustrated example, the through shaft204includes a first section of splines220, a second section of splines222, and a third section of splines224. Each of the sections of splines include multiple splines226. The first and second section of splines220,222mate with a first section of splines228and a second section of splines230, respectively, in the rotor shaft208. Further, the third section of splines224mates with a third section of splines232in the input shaft214, in the illustrated example. The mating between the splines form splined interfaces238,240, and242. Further, the through shaft204includes an un-splined section243between the first and second section of splines220,222, in the illustrated example.

However, alternate spline configurations in the through shaft are possible. For instance, the through shaft204may include one set of splines that extend from a flange234on a proximal end245to a distal end236of the shaft. Further, in an alternate example, the through shaft may include one set of splines that mates with splines in the input shaft and one set of splines that mates with splines in the rotor shaft. Even further in other examples, the through shaft may include more than three sets of splines.

The abovementioned splines may be involute splines, in one example, to increase the strength of the shaft connection when compared to straight splines. However, in other examples, straight splines may be used.

Bearings244(e.g., thrust bearings) are directly coupled to the input shaft214in the illustrated example. Further, bearings246(e.g., ball bearings) are directly coupled to the rotor shaft208in the illustrated example. To elaborate, the bearings244,246are coupled to opposing ends of the respective shafts. The bearings allow for shaft support and rotation. As described herein, a bearing may include inner and outer races as well as roller elements (e.g., balls, cylinders, tapered cylinders, and the like). The first section of splines220axially extends across the section of the rotor shaft208that is coupled to one of the bearings246. Likewise, the second section of splines222axially extends across the section of the rotor shaft208that is coupled to one of the bearings246. However, in alternate examples, the sections of splines may be axially offset from the bearings246.

The through shaft204includes the flange234in the illustrated example. The flange234has a diameter248that is greater than a diameter250of the first section of splines220of the through shaft204. Further, a diameter251of the third section of splines224may be less than the diameter250of the first section of splines220. Further, a diameter253of the second section of splines222may be equal to the diameter250of the first section of splines220. Designing the through shaft with these contours allows the through shaft to be efficiently installed and removed from the rotor shaft208and the input shaft214. However, in other examples, the through shaft204may include one section of splines that extends from the flange234to the distal end236and in such an example, the diameter of the splined section may be constant, along its axial length.

Further, an axial length270of the through shaft204may be greater than an axial length of the rotor shaft208to allow the through shaft to removably attach to both the rotor shaft and the input shaft. However, in other examples, the input shaft may include an extension that mates with a recess in the through shaft and the length of the through shaft may be less than or equal to a length of the rotor shaft.

Further, the flange234includes openings252through which attachment devices254(e.g., bolts) extend. The attachment devices254are further profiled to attach to a section256of the rotor shaft208. Further, a surface257of the flange234may abut a surface261of the rotor shaft208, when the through shaft is installed in the motor. In this way, the rotor shaft may axially delimit the through shaft. The flange234allows the strength of the attachment between the through shaft204and the rotor shaft208to be increased and may reduce an amount of axial play between the rotor shaft208and the through shaft204as well as reduce the likelihood of unintended decoupling of the through shaft from the rotor shaft and the input shaft. However, in other examples, the flange234may be removed from the shaft.

The traction motor202further includes a removable cover258that removably attaches to a section260of the housing262. The section260of the housing262is on an axial side264of the motor that includes an electrical interface266. The electrical interface266serves as an electrical connection between end windings in the stator205and an inverter and/or energy storage device. A seal259may be included in the removable cover258to form a seal between the cover and the traction motor housing, to reduce the likelihood of the interior of the motor becoming contaminated. To elaborate, the seal may circumferential surround the cover.

To remove the through shaft204, as shown inFIG.2B, the cover258may be initially removed. Subsequently, the attachment devices254may be decoupled from the input shaft214and the flange234. Next, the through shaft204is axially slid in direction268until the splines in the through shaft204are decoupled from the splines in both the input shaft214and the rotor shaft208. The steps of cover removal, attachment device removal, and through shaft removal may be sequentially implemented by a vehicle operator or other personnel while the traction motor202is shutdown. The steps may be reversed to re-install the through shaft and allow the electric drive unit to be again operated to transfer mechanical power from the traction motor to the drive wheels. In this way, the through shaft may be effectively and reliably removed and reinstalled from the rotor shaft and the input shaft.

FIG.3shows a detailed illustration of a splined interface300between a through shaft302and a shaft304(e.g., a rotor shaft or an input shaft of a gearbox). Splines306in the through shaft302are shown mating with splines308in the shaft304. The splines306,308are depicted as involute splines. However, straight splines may be used in alternate examples, as previously discussed.

FIGS.2A and2Bare drawn approximately to scale, aside from the schematically depicted components, although other relative component dimensions may be used in other embodiments.

The invention will be described in the following paragraphs. In one aspect, an electric drive unit is provided that comprises a first shaft with a through shaft opening; a second shaft axially aligned with the first shaft; and a through shaft that axially extends through the through shaft opening and removably attaches to the first shaft and the second shaft.

In another aspect, an electric axle is provided that comprises a traction motor with a rotor shaft that includes a through shaft opening; a gearbox with an input shaft that has a gear coupled thereto; and a through shaft that axially extends through the through shaft opening and removably attaches to the rotor shaft and the input shaft.

In another aspect, a traction motor is provided that comprises a stator; a rotor at least partially circumferentially surrounded by the stator and including a rotor shaft with a through shaft opening; and a removable through shaft splined to the through shaft opening and including a distal section that is configured to spline to a splined recess in an input shaft of a gearbox.

In any of the aspects or combinations of the aspects, the first shaft may be a rotor shaft in a traction motor and the second shaft may be an input shaft of a gearbox and wherein the input shaft has a gear fixedly coupled thereto.

In any of the aspects or combinations of the aspects, the gearbox may be a multi-speed gearbox wherein the traction motor is a multi-phase motor.

In any of the aspects or combinations of the aspects, the through shaft may be splined to the first shaft and the second shaft.

In any of the aspects or combinations of the aspects, the splines in the through shaft may include: a first set of splines with a larger diameter that mate with the first shaft; and a second set of splines with a smaller diameter that mate with the second shaft.

In any of the aspects or combinations of the aspects, the splines may be involute splines.

In any of the aspects or combinations of the aspects, the through shaft may include a flange at a first end that is opposite to a second end that removably attaches to the second shaft;

and the flange may removably attach to the first shaft.

In any of the aspects or combinations of the aspects, the electric drive unit may further comprise a cover that extends across the first end of the through shaft and removably attaches to a section of a housing of a traction motor.

In any of the aspects or combinations of the aspects, the section of the housing may include an electrical interface electrically coupled to a stator.

In any of the aspects or combinations of the aspects, the electric drive unit may be included in an all-electric vehicle.

In any of the aspects or combinations of the aspects, the all-electric vehicle may be a commercial vehicle.

In any of the aspects or combinations of the aspects, the through shaft may include: a first splined section that mates with splines in the through shaft opening; and a second splined section that mates with splines in the input shaft.

In any of the aspects or combinations of the aspects, the second splined section may have a smaller diameter than the first splined section.

In any of the aspects or combinations of the aspects, the splines in the through shaft opening may be positioned on opposing axial sides of the through shaft opening.

In any of the aspects or combinations of the aspects, the through shaft may include a flange at a first end that is opposite a second end that extends into the input shaft; and a plurality of attachment devices may extend through the flange and are removably coupled to a section of the rotor shaft.

In any of the aspects or combinations of the aspects, the through shaft may include a flange at a proximal end and the traction motor may further comprise a removable cover that encloses the proximal end of the through shaft.

In any of the aspects or combinations of the aspects, the removable cover may include a gasket sealing with a section of a housing.

In any of the aspects or combinations of the aspects, the splines may have varying diameters.

While various embodiments have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant arts that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The embodiments described above are therefore to be considered in all respects as illustrative, not restrictive. As such, the configurations and routines disclosed herein are exemplary in nature, and that these specific examples are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to powertrains that include different types of propulsion sources including different types of electric machines and/or internal combustion engines. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.