Multi-speed electric powertrain with stepped splines that allow additional degrees of freedom

Various methods and systems are provided for a multi-speed electric axle assembly. The multi-speed electric axle assembly includes a grounding plate with an outer interface coupled to a housing interface and an inner stepped splined interface designed to selectively mate with a clutch sleeve. In the assembly, the inner stepped splined interface includes a plurality of steps that each include a first side that perpendicularly intersects a second side and the first side of each step in the inner stepped splined interface includes a clearance between the first side and a stepped surface of the clutch sleeve.

TECHNICAL FIELD

The present disclosure relates to a multi-speed electric powertrain with a transmission having a grounding plate.

BACKGROUND AND SUMMARY

Many electric powertrains include single speed transmissions that mechanically attach to a motor. Due to the single gear ratio, the powertrains are forced to make tradeoffs between off the line acceleration and top speed. To diminish the extent of these unwanted tradeoffs, multi-speed gearboxes have been provided for operating the powertrain in discrete gear ratios. Because of the gear ratio adjustability, the motor may be operated within a desired speed/torque range to increase motor efficiency and operational range, for example.

Certain transmissions have made use of epicyclic gears that compactly provide discrete gear reductions. To adjust the gear ratio of these transmissions, one of the epicyclic gears may be mechanically grounded to inhibit gear rotation. The shifting components may experience binding during certain conditions. The inventor has found that in some transmissions the binding is caused by the over-constraint of the shifting components. For instance, tilt of a sliding sleeve in a dog clutch and the positional tolerance stack-up of the shifting components may lead to sleeve jamming which hampers the sleeve's ability to axially translate. The inventor has identified an unmet need to strategically increase selected degrees of freedom of the clutch sleeve to prevent binding while providing durable sleeve grounding functionality.

The inventor has recognized the aforementioned issues with previous electric powertrains and developed a multi-speed electric powertrain system that includes a grounding plate with an outer interface coupled to a housing interface, in one example. In this example, the grounding plate includes an inner stepped splined interface designed to selectively mate with a clutch sleeve. Further, the inner stepped splined interface includes a plurality of steps that each include a first side that perpendicularly intersects a second side. Even further, the second side of each step in the inner stepped splined interface includes a vertical clearance between the second side and a stepped surface of the clutch sleeve. Further, in one example, the outer interface may also be a stepped splined interface with a horizontal clearance between the sides of the steps. In this way, the stepped spline interfaces accommodate for some vertical and, in certain cases horizontal, movement and tilt of the sliding sleeve in the corresponding plane, which permits the clutch sleeve to find its equilibrium with respect to the grounding plate to reduce the chance of binding. Further, the inclusion of multiple vertical, and in some cases horizontal, steps may allow a torque reaction load that is transferred between the splined interfaces to be dispersed over greater contact areas to reduce stress occurring at any given contact point. Consequently, the likelihood of grounding plate, clutch sleeve, and/or housing degradation is reduced, thereby increasing the system's longevity.

As one example, the first side of the steps of the grounding plate or the clutch sleeve may include a curved profile, such as an elliptical or involute shape. Further, in some cases, both the steps in the grounding plate and the clutch sleeve may include a curved profile. In this way, edge loading, which may result when the clutch sleeve mates with the inner stepped splined interface is under a torque load, may be reduced. In another example, the plurality of steps may have varying widths, which may allow for desired load distribution in the grounding plate.

In another example, the multi-speed electric powertrain system may further include a shoe. The shoe has a flat surface adjacent to a stepped surface in the outer or inner splined interface as well as a convex surface mated in a concave receptacle. In this way, the shoe may be used as an additional tool for reducing edge loading and contact stress.

DETAILED DESCRIPTION

In some electric vehicle (EV) systems, the powertrain utilizes clutch units that include a sliding shift sleeve and an inner hub to ground one or more gears in a transmission, to operate the vehicle in a variety of different gear ratios. The shift sleeve may have concentric splines engaging a grounding plate. The shift sleeve may transmit torque transferred from one or more gears in the transmission to the grounding plate, the torque being transmitted in a plane normal to the axis of translation. In these systems, the shift sleeve may experience binding issues due to the radial positional tolerance stack-up within the shifting assembly, gravitational effects, and/or tilting of the shift sleeve during operation, which may hinder the ability of the sleeve to translate axially. For instance, the shift sleeve may become jammed, or pinched, between the inner hub and the grounding plate in a vertical plane when the outer and/or inner diameter splines present over-constraints.

A transmission system is described herein that at least partially addresses the over-constraint issues of previous transmissions. The transmission system includes a clutch shift sleeve with outer and inner diameter splines, at least one of which may include stepped vertical or horizontal flanks. The stepped spline configuration reduces over-constraints, particularly those which restrict movement of the clutch shift sleeve in a vertical direction and restrict rotation (e.g., tilting) of the clutch shift sleeve in a vertical plane, to allow for some vertical movement and a small amount of tilting of the clutch sleeve. Further, in some cases, the splines may be designed to allow axial translation and the transmission of torque from a gear component to a grounding plate, and to resist horizontal movement normal to a translation axis and rotational movement in a horizontal plane. In this way, the ability of the clutch shift sleeve to translate axially may be increased, while maintaining some restriction of axial and rotational movement of the clutch shift sleeve, to avoid binding issues that may arise from excessive tilting and/or gravitational effects combined with radial positional tolerance.

FIG. 1depicts a vehicle with a powertrain including a grounding assembly having a clutch sleeve and grounding plate assembly for shifting operation in a transmission.FIGS. 2-4depict a transmission of a powertrain including a grounding plate and clutch sleeve according to a first example.FIGS. 5A-5Cillustrate a housing, grounding plate, and clutch sleeve, respectively, andFIGS. 6-7Billustrate interfaces between the housing, grounding plate, and clutch sleeve, in the first example.FIGS. 8A-8Idepict various alternative configurations of the interfaces shown inFIGS. 6-7B.FIGS. 9-10illustrate a second example of a grounding assembly having a grounding plate and a clutch sleeve.FIGS. 11-12depict an example configuration for retaining a grounding plate within a housing, in one example.FIG. 13depicts a table representing restricted and over-constrained degrees of freedom which may be present in various use-case examples of a grounding plate and a clutch sleeve.

FIG. 1schematically illustrates a multi-speed electric powertrain100with a transmission111for providing power to an axle assembly106in a vehicle101. The vehicle may take a variety of forms in different examples, such as a light, medium, or heavy duty vehicle. Additionally, the powertrain100may be adapted for use in front and/or rear axles, as well as steerable and non-steerable axles. To generate power, the powertrain100may include an electric motor-generator102. The electric motor-generator102may include conventional components such as a rotor, a stator, a housing, and the like for generating mechanical power as well as electrical power during a regenerative mode, in some cases. In some examples, the powertrain100may include a second electric motor-generator, such that each of the first and second electric motor-generators may provide power which can drive the axle assembly106. In other examples, the vehicle101may further include an internal combustion engine for providing mechanical power to another axle. As such, the powertrain100may be utilized in a hybrid or electric vehicle (EV) (e.g., battery electric vehicle (BEV)).

In the illustrated example, a first shaft104is operably coupled to the electric motor-generator102for rotation. The first shaft104may extend from the electric motor-generator102into a first gear assembly110of the transmission111. Power transferred to the first gear assembly110from the electric motor-generator102may be transmitted by the first shaft104into one side109of the first gear assembly110. The first gear assembly110and the electric motor-generator102may be situated in a housing108with first shaft104extending axially within the housing from the electric motor-generator to the first gear assembly110.

In some examples, the first gear assembly110may be a planetary gearset such as a Ravigneaux gearset. In this way, the compactness of the system may be increased when compared to non-planetary gear reductions. In the Ravigneaux example, the first gear assembly110may include a first sun gear112operably coupled to the first shaft104for rotation therewith. Further, the first sun gear112may be in meshing engagement with a first set of planet gears114. Even further, the first set of planet gears114may be in meshing engagement with a second set of planet gears116. In addition to meshing engagement with the first set of planet gears114, the second set of planet gears116may be in meshing engagement with a second sun gear118and a ring gear122. In one example, the first sun gear112may have an outermost diameter that is smaller than an outermost diameter of the second sun gear118. Both of the first and second sets of planet gears114,116may be coupled to a common planet carrier120and may rotate independently of the planet carrier. The first set of planet gears114and the second set of planet gears116may co-rotate with a fixed gear ratio with respect to each other and may each include multiple planet gears.

The first gear assembly110may include clutches that are selectively engageable with different portions of the first gear assembly110, thereby permitting the vehicle101to operate at multiple discrete gear ratios. Specifically, in one example, the powertrain may be a three speed powertrain. However, two speed powertrains or powertrains with greater than three ratios have been contemplated. Clutches in the powertrain may not include synchronizer rings, in some examples. Specifically, in one example, the clutches may be sleeved dog clutches with synchronizer rings, omitted. In the illustrated example, a clutch assembly142may be selectively engageable with at least a portion of the planet carrier120. However, the clutch assembly142may ground other suitable gears or be omitted from the transmission111, in other examples. When the clutch assembly142is engaged with the planet carrier120, the planet carrier is mechanically grounded and does not rotate. As described herein, mechanical grounding a component infers that the component is held substantially stationary.

Another clutch assembly143may be selectively engageable with at least a portion of the first sun gear112and the second sun gear118. When the clutch assembly143is engaged with the first sun gear112and the second sun gear118, the first sun gear and the second sun gear are held and rotate together. A clutch assembly160, which may include a grounding assembly, may be selectively engageable with at least a portion of the second sun gear118. When the clutch assembly160is engaged with the second sun gear118, the second sun gear is mechanically grounded and does not rotate. Further, the clutch assemblies142,143and160may be shifted between their respective positions of engagement and, a neutral position. In this way, different planetary components in the geartrain may be engaged to achieve different gear ratios (e.g., a first, second or third gear ratio). Other clutch arrangements in the transmission have been envisioned.

The mechanical grounding described above may be accomplished via a grounding plate162that is schematically depicted inFIG. 1. However, the grounding plate has greater structural complexity that is elaborated upon herein. The grounding plate162may be coupled to the housing108at an outer interface of the grounding plate. Further, the grounding plate162may include an inner interface designed to selectively mate with a clutch shift sleeve161of the clutch assembly160, so that the clutch shift sleeve is axially movable within the grounding plate. Further, the clutch shift sleeve161may be splined to an inner hub for selectively achieving the aforementioned grounding configurations within first gear assembly110to operate the transmission111in one of the different gear ratios. Specifically, the clutch shift sleeve161may be engaged with the planet carrier120or the second sun gear118and grounded via the grounding plate162while the transmission operates in a first or second gear, for example. As such, the planet carrier and second sun gears may be selectively grounded to operate the transmission in a desired operating mode.

Exemplary structures and details of the interfaces of the grounding plate and clutch shift sleeve are elaborated on herein with reference to various examples depicted inFIGS. 2-13. In each example, the grounding assembly may be designed to avoid binding issues and prevent over-constraint of the clutch shift sleeve during operation (e.g., under torque loading). More particularly, the grounding plate162may allow for some vertical movement of the clutch sleeve with respect to the grounding plate, where clearances at the interface of the clutch sleeve and grounding plate may be large enough to accommodate a vertical component of a tolerance stack (e.g., radial positional tolerance stack).

The ring gear122may serve as the output of the first gear assembly110and may be fixedly coupled to a second gear assembly130. The second gear assembly130may include a first gear132in meshing engagement with a second gear134, which may be operably coupled with a second shaft136. The second shaft136may be supported for rotation with one or more bearings. In some examples, the second shaft136may be provided in a parallel relationship, or, in some instances, the second shaft may be provided in a concentric relationship with the first shaft104. A third gear138may be disposed at an end of the second shaft136. Further, the third gear138may be of in meshing engagement with the fourth gear149disposed on a differential140. Specifically, the third and fourth gears may form a bevel or hypoid gearset. The differential140may be operatively attached to an axle assembly106. The axle assembly106may include a first and second axle shafts144,146, for providing rotational power to a first drive wheel145and a second drive wheel147via a first axle shaft144and a second axle shaft146, respectively. As such, the differential140may distribute rotational driving force received, from the first and second gear assemblies110,130of the powertrain100, to the drive wheels145,147, during certain operating conditions.

In some examples, the first shaft104may be supported at both ends for rotation by one or more bearings105(e.g., ball bearings, needle roller bearings, etc.). The bearings105may support and locate the first shaft104, while also reducing friction to allow for smoother rotation thereof. Further, the bearings105which may contribute to positioning of downstream components in the transmission111, particularly the hub, which is radially positioned to shaft104through the second sun gear118shaft. The bearings may also constrain downward movement of the inner hub which may reduce the likelihood of the shift sleeve being pushed to the bottom of the grounding plate.

The transmission111may operate in at least a first gear ratio, a second gear ratio, and a third gear ratio. The first gear ratio may be higher than the second gear ratio, which may be higher than the third gear ratio. In the first gear ratio, the planet carrier120may be held stationary (e.g., grounded) and does not rotate. In the second gear ratio, the second sun gear118may be held stationary and does not rotate. In the third gear ratio, the first sun gear112and the second sun gear118may rotate together. However, the gear ratios may be derived using other gear configurations which may be selected based on the end-use gear reduction objectives.

As illustrated inFIG. 1, the powertrain100and axle assembly106may be in a perpendicular configuration. As used herein, the phrase “perpendicular configuration” refers to the electric motor-generator providing power that is transmitted perpendicular to the orientation of the axle driving wheel rotation. However, in other examples, the powertrain and axle may be in a parallel configuration, wherein the electric motor-generator provides power that is transmitted parallel to the orientation of the axle driving wheel rotation.

The vehicle101may also include a control system150with a controller152. The controller152may include a processor153and a memory154. The memory may hold instructions stored therein that when executed by the processor cause the controller152to perform various methods, control techniques, etc. described herein. The processor153may include a microprocessor unit and/or other types of circuits. The memory154may include known data storage mediums such as random access memory, read only memory, keep alive memory, combinations thereof, etc. The controller152may receive various signals from sensors156positioned in different locations in the vehicle101and powertrain100. The controller152may also send control signals to various actuators158coupled at different locations in the vehicle101and powertrain100.

An input device159may be in communication with the controller152. For instance, the input device159may be a gear selector or drive mode selector. In some examples, the clutches configured as rotation locking assemblies in first gear assembly110may be operated by one or more actuators of the actuators158coupled to controller152. In response to a user input via input device159and/or based on automatic shift control strategies stored in memory154, the controller152may send a signal causing one or more of the clutches to selectively engage a portion of the first gear assembly110. To elaborate, in one use-case scenario to shift from neutral to a first gear, the clutch assembly142may receive a first gear shift command and in response, move the clutch sleeve161to ground the planet carrier120. Further, to shift from the first gear to a second gear, the clutch assembly160may receive a second shift command and in response move the clutch sleeve161past the neutral position and into a position that grounds the second sun gear118. The controller may transition the transmission between discrete gear ratios based on operating conditions such as vehicle speed, vehicle load, battery state of charge (SOC), etc.

An axis system170is provided inFIG. 1, as well asFIGS. 2-12where relevant, for reference. The y-axis may be a vertical axis (e.g., parallel to a gravitational axis), the z-axis may be a lateral axis (e.g., a horizontal axis), and/or the x-axis may be a longitudinal axis, in one example. However, the axes may have other orientations, in other examples. Further, a first rotational axis175is illustrated extending through the first gear assembly110, first shaft104, electric motor-generator102and the clutch assembly160. A second rotational axis180is also illustrated extending through the differential140, the axle shafts144,146of axle assembly106, and the driving wheels145,147. In one example, where the powertrain and axle are in the perpendicular configuration described above, the first rotational axis175and the second (e.g., driving) rotational axis180may be oriented perpendicularly to one another in the x-y plane, as shown inFIG. 1.

FIGS. 2-4show an example of an electric powertrain200with a transmission211. The transmission includes a planetary geartrain210with a grounding assembly230enclosed within a housing208.FIGS. 3 and 4provide cross-sectional views of the transmission housing208ofFIG. 2. The cross-sectional views, as shown inFIGS. 3A and 3B, are defined by a lateral cut plane taken along a dashed line3-3, respectively, as indicated inFIG. 2. The powertrain200may share common structural and functional features with the powertrain100, shown inFIG. 1and vice-versa. For instance, the planetary geartrain210, as shown inFIG. 3A, which may be similar to the first gear assembly110depicted inFIG. 1. As such, the geartrain210may be a Ravigneaux gearset. In other examples, the geartrain210may have different arrangements, such as, a compound type planetary gearset (e.g., multi-stage planetary (e.g., a two-stage or three-stage planetary system)), a simple planetary, and the like. However, it will be understood that the use of a multi-stage planetary system may increase complexity and costs associated with assembly, as well as the size of the geartrain and housing. In other examples, non-planetary arrangements for the geartrain have been contemplated.

Turning specifically toFIGS. 2 and 3A, the housing208may be a multi-section housing with sections that removably attached to one another to enclose an electric motor coupled to the geartrain210. The sections of the housing may be coupled via bolts209and/or other suitable fasteners.

Referring toFIG. 3A, the geartrain210may receive rotational power via input shaft204and transfer the power via an output shaft206. The input shaft204may be designed to receive power from an electric motor, such as the electric motor-generator102in the powertrain100ofFIG. 1. Further, the output shaft206may provide power to final drive components downstream of the geartrain210, such as a differential. The input and output shafts204,206as well as various gear components within the geartrain210may be supported by bearings, such as needle roller bearings.

Also shown inFIGS. 2-4is a shift fork assembly212coupled to the housing208. The shift fork assembly212may include a pronged shift fork214mounted to a shaft216. The shift fork214may be engaged with the clutch sleeve240and displaced by an actuator via the shaft216, whereby displacement of the shift fork214is translated into axial translation of the clutch sleeve240for shifting the powertrain into different gear ratios. Specifically, the clutch sleeve may be adjusted by the shift fork to place the transmission in a first gear, a neutral state, and a second gear.

The grounding assembly230of the powertrain200may further include a clutch sleeve240and a grounding plate260. In some examples, the clutch sleeve and grounding plate may cooperate to receive torque transmitted in a plane perpendicular to a rotational axis175from one or both of a planet carrier297and a second sun gear296of the geartrain210, and hold these components stationary while the transmission operates in different gears.

Turning briefly toFIG. 4, the grounding assembly230is again illustrated with the grounding plate260, clutch sleeve240, and hub290positioned within the housing208. More particularly,FIG. 4illustrates the interface285between the clutch sleeve240and the grounding plate260, as well as the interface280between the grounding plate260and the housing208. The housing208, grounding plate260, and clutch sleeve240are depicted separately inFIGS. 5A-5C, respectively. A more detailed view of the interfaces is illustrated inFIG. 6. Further, the interfaces285and280are separately illustrated inFIGS. 7A and 7B, respectively. As such, the first example of the interfaces and grounding assembly components may be described with reference to any ofFIGS. 4-7B, and common numbering of components may be used accordingly.

FIGS. 3B and 4show views of an example of the grounding plate260having an outer stepped splined surface262, mating with an inner stepped splined surface282of the housing208at the interface280, and an inner stepped splined surface264, mating with an outer stepped splined surface244of the clutch sleeve240at an interface285. The interface280may include a plurality of horizontal steps on each of the outer stepped splined surface262of the grounding plate260and the inner stepped splined surface282of the housing208. Additionally, the interface285includes a plurality of vertical steps on each of the outer stepped splined surface244of the clutch sleeve240and the inner stepped splined surface264of the grounding plate260. Particularly illustrated inFIGS. 3B and 4is a relative positioning of the grounding plate260, clutch sleeve240, and hub290and the respective steps or splines provided thereon. For instance, the grounding plate260, clutch sleeve240, and hub290may be generally coaxially arranged, due to the splined engagement between the components.

In some examples, the outer splined surface262on the grounding plate may extend radially outward from a main body261of the grounding plate260and be positioned at an axial middle portion of the main body261. Further, the main body261of the grounding plate260may include one or more openings263for allowing movement of a shift fork214therethrough as the shift fork moves (e.g., axially translates) the clutch sleeve240to shift between various grounding configurations (e.g., to achieve different gear ratios). Accordingly, the clutch sleeve240may be designed to be axially translated due to movement of the shift fork214.

The clutch sleeve240may further include an inner splined surface242mating with an outer splined surface292of the inner hub290at an interface295, as indicated inFIGS. 3B and 4. In some cases, the interface295may include a tapered splined connection, such that the inner splined surface242of the clutch sleeve240and an outer splined surface292of the inner hub290each include axially extending teeth tapered at their axial ends and designed to mate with one another, or may each include involute splines. In this way, the weight of the clutch sleeve240may be supported by the inner hub290. Further, the inner hub290may be positioned coaxially within the clutch sleeve240, so that inner hub290may radially position the clutch sleeve240with respect to the input shaft204and/or second sun gear296shaft.

The clutch sleeve240and inner hub290may be designed to selectively ground the planet carrier, or a gear via the grounding plate to operate the vehicle in a desired gear ratio, as previously indicated. During a shifting transient, the clutch sleeve may move into the engaged position, the clutch sleeve, gear, and inner hub are locked together, grounding the engaged gear to the housing via the grounding plate. In this way, the clutch sleeve may smoothly engage a gear during a shifting event, thereby reducing noise, vibration, and harshness (NVH). In the illustrated embodiment, the transmission does not include synchronizer rings. However, in other embodiments, the transmission may utilize synchronizer rings.

In one example, interface285between the grounding plate260and the clutch sleeve240may be defined by an inner stepped splined surface264that includes vertical steps265at an inner periphery of the grounding plate260. The inner stepped splined surface264mates with an outer stepped splined surface244of the clutch sleeve240. As such, the outer stepped splined surface244of the clutch sleeve240may include vertical steps245at an outer periphery of the clutch sleeve.

Each of the vertical steps265of the inner stepped splined surface264of the grounding plate260may include a first side266that intersects a second side267at an angle268, as particularly illustrated inFIGS. 6 and 7A. In some examples, the angle268may be 90 degrees. For instance, the first and second sides266,267may be perpendicularly intersecting horizontal and vertical sides, respectively. However, other substantially perpendicular orientations have been contemplated, in other examples, wherein the angle268is near 90 degrees, though such orientations may lead to undesirable loading at the interface285and may consequently hinder the ability of the clutch sleeve240to axially translate. Similarly, each of the vertical steps245of the outer stepped splined surface244of the clutch sleeve240may have a first side246intersecting a second side247at an angle248. Again, the first and second sides246,247may be horizontal and vertical sides, respectively, perpendicularly intersecting such that the angle248is 90 degrees or approximately 90 degrees.

When the clutch sleeve240is positioned within the grounding plate260, as shown inFIG. 4, the outer stepped splined surface244of the clutch sleeve may mate with the inner stepped splined surface264of the grounding plate. As such, the first and second sides266,267of the grounding plate may be positioned adjacent to the first and second sides246,247, respectively, of the clutch sleeve. Further, the inner hub290may be coaxially positioned within the clutch sleeve240, where the outer splined surface292of the inner hub meshes with the inner splined surface242of the clutch sleeve. In this way, torque from the planetary geartrain (e.g., the planet carrier or second sun gear) may be received at the inner hub and transmitted through the splines of the inner hub outer splined surface292and clutch sleeve inner splined surface242, and then transmitted through the clutch sleeve to the grounding plate260via the vertical steps245of the clutch sleeve outer splined surface244and the vertical steps265of the grounding plate inner splined surface264. Further, the mating engagement between the inner splined surface264of the grounding plate260and the outer splined surface244of the clutch sleeve240may permit axial translation of the clutch sleeve240with respect to the grounding assembly.

Referring toFIGS. 5B and 5C, the vertical steps265and245of the grounding plate260and the clutch sleeve240, respectively, may be partitioned into four quadrants along the inner stepped splined surface264(e.g., quadrants510,512,514,516) and outer stepped splined surface244(e.g., quadrants520,522,524,526), respectively, in one example.

Referring toFIGS. 4 and 5B-5C, the grounding plate260is shown having a number of vertical steps265provided in each of the quadrants, shown inFIG. 4as quadrants201,202,203, and205(i.e., corresponding to quadrants510-516and520-526inFIGS. 5A and 5B, respectively), the clutch sleeve240also having a number of vertical steps245provided in each of the four quadrants and designed to mate with the interface defined by the vertical steps of the grounding plate. However, in other examples, other numbers of vertical steps may be provided on each of the grounding plate and the clutch sleeve, and/or different numbers of vertical steps may be provided in different quadrants, so long as the vertical steps of the stepped splined surfaces264,244of the grounding plate260and clutch sleeve240, respectively, cooperate to form a suitable mating interface285.

Continuing withFIGS. 4 and 5B-5C, the vertical steps265,245provided in each of the quadrants described above may allow torque reaction loads between the stepped splined surfaces264,244of the grounding plate260and the clutch sleeve240, respectively, to be dispersed over more contact area, thus reducing contact stress at any given point of the contact areas. Further, when vertical steps are provided in each of the four quadrants, opposing quadrants may react torque. For instance, opposing portions of interface285in quadrants202and205(e.g., vertical steps265of grounding plate260in quadrants512,516, shown inFIG. 5B, and vertical steps245of clutch sleeve240in quadrants522,524, shown inFIG. 5C) may react torque having a clockwise direction at the clutch sleeve240. Further, opposing portions of interface285in quadrants201and203(e.g., vertical steps265of grounding plate260in quadrants510,514, shown inFIG. 5B, and vertical steps245of clutch sleeve240in quadrants520,526, shown inFIG. 5C) may react torque having a counterclockwise (CCW) direction at the clutch sleeve240. Hence, the transmission may react torque in both clockwise (CW) and CCW rotations. In one specific embodiment, a minimum of one step may be used in each quadrant to react both the CW and CCW torque.

The interface285may further include a clearance287, as illustrated inFIGS. 6 and 7A. The clearance287may be a vertical clearance formed between pairs of adjacent vertical steps265,245(i.e., between first (e.g., horizontal) sides266,246) of the grounding plate260and the clutch sleeve240, respectively. The clearance287may allow for some vertical movement of the clutch sleeve240within the grounding plate260and a small amount of tilt of the clutch sleeve240in the vertical plane (e.g., about the z-axis), which may help to avoid binding issues that would hinder the ability of the clutch sleeve240to slide axially with respect to the grounding plate260. Further, the clearance287may allow the clutch sleeve240to find its equilibrium with respect to the grounding plate so as to avoid being pinched between an outer diameter of the inner hub and the inner stepped splined surface264of the grounding plate260. Even further, the clearance287may be of a dimension sufficient to accommodate a full vertical component of a radial positional tolerance stack, further avoiding (e.g., preventing) binding. In some examples, the dimension may be selected based on various structural considerations. For instance, the clearance may be greater than or equal to a component (e.g., the vertical component) of the radial positional tolerance stack of the grounding plate and clutch sleeve assembly. In one use-case example, the positional tolerance stack value may be 1.362 millimeters (mm) and the clearance may therefore be greater than 1.362 mm.

Further, in some examples, the interface285may include a flank gap289, which may be a horizontal flank gap defined between the second (e.g., vertical) sides267of the grounding plate260and curved surfaces249of the clutch sleeve240. The flank gap289may, in some cases, vary along the interface285at each step of the mating vertical steps265,245. In one example, the flank gap289may incrementally decrease at each step as the steps approach a horizontal plane extending through the center of the clutch sleeve240and/or grounding plate260. In this way, the flank gap289may be varied for more balanced loading between each of the steps of the grounding plate and the clutch sleeve as they react torque and the components flex. In one example, the flank gap289may be designed differently at each step to further allow for more equal loading of the steps265,245as the clearance287is taken up (e.g., decreases) and the components flex. Thus, backlash between the vertical steps265,245may be controlled (e.g., restricted) by varying the flank gap289. Further, the flank gap289may change as the clutch sleeve240moves vertically within the grounding plate260, and a size of the flank gap289may be selected accordingly, taking this change into account, so as to maintain some flank gap space to reduce the chance of the components binding or wedging.

The vertical steps265,245of the grounding plate260and the clutch sleeve240may, in some examples, have varying widths (e.g., as defined along the first sides266,246, respectively), which may allow for desired placement of the vertical steps along respective outer and inner peripheries of the grounding plate and the clutch sleeve to more evenly disperse load distribution, thereby increase the assembly's durability. In other embodiments, however, the vertical steps may have the same width. Further, the vertical steps265,245of the grounding plate260and the clutch sleeve240may, in some examples, have different depths (e.g., as defined along second sides267,247, respectively) and, in other examples, may have the same depth. The profile of the steps may be selected based on expected loading of the different components in the assembly, the material construction of the components, ease of placement, manufacturability, etc. Thus, the specific contours of the steps may be chosen to increase grounding plate durability.

In some examples, the vertical steps265,245of the grounding plate260and the clutch sleeve240may include a first and second side each having a flat (e.g., straight) profile. However, in one example, as particularly illustrated inFIGS. 6 and 7A, the second (e.g., vertical) sides247of the vertical steps245of the clutch sleeve240may include a curved (e.g., elliptical or involute) profile along a portion of their surfaces, as indicated at249inFIG. 7A. In other examples, other configurations of vertical steps including one or more curved profiles have been contemplated. For instance, in addition or as an alternative to the curved surface on the second sides247of the clutch sleeve's vertical steps245, the second sides267of the vertical steps265of the grounding plate260may include a curved (e.g., elliptical or involute) surface along a portion of their profile. In still other examples, the first and/or second sides of one or both of the vertical steps265,245of the grounding plate260and the clutch sleeve240, respectively, may include a tapered profile. The inclusion of a curved and/or tapered profile, particularly on the second side of one or both of the different sets of vertical steps may reduce or eliminate edge loading when the clutch sleeve and grounding plate interface is under a torque load during operation, thus reducing a chance of uneven wear and/or component degradation. Various configurations of the vertical step profiles at the interface285will be shown and discussed further with reference toFIGS. 8A-8C.

Returning toFIG. 4, the interface280between the grounding plate260and the housing208may be defined by an outer stepped splined surface262on grounding plate260and an inner stepped splined surface282of the housing208. The grounding plate260may further include horizontal steps270along outer stepped splined surface262designed to mate with the inner stepped splined surface282of the housing208. As such, the inner stepped splined surface282of the housing208may include horizontal steps250at an inner periphery of the housing.

Each of the horizontal steps270of the outer stepped splined surface262of the grounding plate260may include a first side271intersecting a second side272at an angle273, as particularly illustrated inFIGS. 6 and 7B. In some examples, the angle273may be 90 degrees. For instance, the first and second sides271,272may be perpendicularly intersecting horizontal and vertical sides, respectively. However, other substantially perpendicular orientations have been contemplated, in other examples, wherein the angle273is near 90 degrees. Similarly, each of the horizontal steps250of the inner stepped splined surface282of the housing208may include a first side251intersecting a second side252at an angle253. Again, the first and second sides251,252may be horizontal and vertical sides, respectively, perpendicularly intersecting such that the angle253is 90 degrees.

When the grounding plate260is positioned within the housing208, as shown inFIGS. 4, 6 and 7B, the outer stepped splined surface262of the grounding plate may mate with the inner stepped splined surface282of the housing. As such, first sides271of the grounding plate horizontal steps270may be adjacent the first sides251of the housing horizontal steps250, and the second sides272of the grounding plate horizontal steps may be adjacent the second sides252of the housing horizontal steps. Further, the grounding plate260may be supported by the housing208, such that the weight of the grounding plate260may be transferred through the lower horizontal steps270,250of the grounding plate260and the housing208, respectively.

Similar to the partitioning of the vertical steps245and265described above with respect to the clutch sleeve240and grounding plate260, respectively, the horizontal steps may be partitioned into four quadrants. Referring toFIGS. 5A and 5B, the horizontal steps270,250of the grounding plate260and the housing208, respectively, may be partitioned into four quadrants along the outer stepped splined surface262(e.g., quadrants530,532,534,536) and the inner stepped splined surface282(e.g., quadrants510,512,514,516), respectively.

In the illustrated example, referring toFIG. 4, the grounding plate260and the housing208are shown having horizontal steps270,250, respectively, provided in each of the quadrants201,202,203, and205. However, in other examples, other numbers of horizontal steps may be provided on each of the grounding plate and the housing, and/or different numbers of horizontal steps may be provided in different quadrants, so long as the horizontal steps of the stepped splined surfaces262,282of the grounding plate260and the housing208, respectively, cooperate to form a suitable mating interface280.

Referring toFIGS. 4 and 5A-5B, the horizontal steps provided in each of the quadrants may allow torque reaction loads between the stepped splined surfaces262,282of the grounding plate260and the housing208, respectively, to be dispersed over more contact area, thus reducing contact stress at any given point of the contact areas. Further, when horizontal steps are provided in each of the four quadrants, opposing quadrants may react torque. For instance, opposing portions of interface280in quadrants202and205(e.g., horizontal steps270of the grounding plate260in quadrants512,516, as shown inFIG. 5B, and horizontal steps250of the housing208in quadrants532,536, as shown inFIG. 5A) may react torque having a clockwise direction at the grounding plate260. On the other hand, opposing portions of interface280in quadrants201and203(e.g., horizontal steps270of the grounding plate260in quadrants510,514, as shown inFIG. 5B, and horizontal steps250of the housing208in quadrants530,534, as shown inFIG. 5A) may react torque having a CCW direction at the grounding plate260. In one specific embodiment, a minimum of one step may be used in each quadrant to react both the CW and CCW torque. Further, the grounding plate260may react torque to prevent rotation of the clutch sleeve240about the x-axis.

The interface280may further include a clearance255, as illustrated in the detail views ofFIGS. 6 and 7B. The clearance255may be a horizontal clearance formed between pairs of adjacent horizontal steps270,250(i.e., between vertical sides272,252) of the grounding plate260and the housing208, respectively. The clearance255may thus provide some horizontal positional tolerance, allowing for some horizontal movement of the grounding plate260with respect to the housing208. Such a configuration may further allow the clutch sleeve240, slidably held within the grounding plate260, to find its equilibrium (e.g., desired operating center) so as to avoid being pinched between an outer diameter of the inner hub290and the inner stepped splined surface264of the grounding plate260. The inner hub290, in splined engagement with the clutch sleeve240, may further contribute to radial positioning (e.g., centering) and guiding the axial translation of the clutch sleeve240during a shift event. Additionally, in one example, when the horizontal stepped splined interface280is used in conjunction with the vertical stepped splined interface285, horizontal and vertical displacement over-constraint may be avoided, which may allow the inner hub to find its operating center. Again, the clearance255may be selected to accommodate for the horizontal tolerance stack of the assembly, which may help to further prevent binding issues.

The interface280may include a flank gap257, which may be a vertical flank gap defined between the first (e.g., horizontal) sides271of the grounding plate260, and curved surfaces259of the housing208, respectively. Further, the flank gap257may vary in size along the interface280at each step of the mating horizontal steps270,250. In one example, the flank gap257may be designed differently at each step to allow a more equal loading of steps270,250as the clearance255is taken up (e.g., decreases) under a torque load, such that backlash between the horizontal steps270,250may be controlled (e.g., restricted) by varying the flank gap257. Further, the flank gap257may change as the grounding plate260moves horizontally within the housing208, and the size of the flank gap257may be selected accordingly, taking this change into account, to provide sufficient space to reduce the chance of binding of the components.

The horizontal steps270,250of the grounding plate260and the housing208may, in some examples, have the same widths (e.g., as defined along the first sides271,251, respectively). However, in other examples, the horizontal steps may have varying widths, which may allow for a desired placement of the steps along the respective outer and inner peripheries of the grounding plate and the housing. Further, the horizontal steps270,250may, in some examples, have different depths (e.g., as defined along the second sides272,252, respectively) and, in other examples, may have the same depth.

In some examples, the horizontal steps270,250of the grounding plate260and the housing208may include first and second sides each having a flat profile. However, in one example, as particularly illustrated inFIGS. 6 and 7B, the first (e.g., horizontal) sides271of the horizontal steps270of the grounding plate260may include a curved (e.g., elliptical or involute) profile, as indicated at259inFIG. 7B. In other examples, other configurations of horizontal steps including one or more curved profiles have been contemplated. For instance, in addition or as an alternative to the curved profile on the first sides271of the grounding plate's horizontal steps270, the first sides251of the horizontal steps250of the housing may include a curved (e.g., elliptical or involute) profile. In still other examples, the first and/or second sides of one or both of the horizontal steps270,250of the grounding plate260and the housing208, respectively, may include a tapered profile. The inclusion of a curved and/or tapered profile, particularly on the first sides of one or both of the sets of horizontal steps, may reduce or eliminate edge loading that may result when the outer stepped splined surface262of the grounding plate260is under a torque load, thus reducing a chance of uneven wear and/or component degradation. Various configurations of the horizontal step profiles at the interface will be shown and discussed further with reference toFIGS. 8D-8I.

The combined effect of the vertical stepped splined surfaces, at the interface285of the grounding plate260and the clutch sleeve240, and the horizontal stepped splined surfaces, at the interface280of the grounding plate260and the housing208, provides for vertical positional tolerance of the clutch sleeve240with respect to the grounding plate260and horizontal positional tolerance of the clutch sleeve240with respect to the housing208through the horizontal positional tolerance of the grounding plate260with respect to the housing208. In other words, the clutch sleeve240and the grounding plate260may be allowed some vertical and horizontal movement, respectively. The vertical steps245,265of the clutch sleeve240and the grounding plate260, respectively, may further allow for some tilting of the clutch sleeve240in a vertical plane (e.g., some rotation about the z-axis in the x-y plane). The horizontal steps270,250of the grounding plate260and the housing208, respectively, may further allow for some tilting of the clutch sleeve240in a horizontal plane (e.g., some rotation about the y-axis in the x-z plane). In this way, the clutch sleeve240, with the inner hub290splined to the interior surface thereof, may be better able to find its equilibrium. In this way, the clutch sleeve240, with the inner hub290splined to the interior surface thereof, may be better able to find its equilibrium. Further, by allowing for smoother axial translation of the clutch sleeve240and inner hub290, the chance of binding within the assembly may be reduced.

Turning toFIGS. 8A-8C and 8H, examples of an interface between mating vertical steps of a grounding plate860and a clutch sleeve840are depicted. It will be understood that, in some examples, the vertical spline steps of the grounding plate860and the clutch sleeve840, designed to mate at an interface885as shown inFIGS. 8A-8C and 8H, may be included in the clutch sleeve240shown inFIGS. 2-7A, representing a lower left quadrant section of the interface285shown inFIG. 4. As such, a vertical step845on an inner stepped splined surface864of the grounding plate860may include a first (e.g., horizontal) side866. Further, the vertical step865of the outer stepped splined surface844of the clutch sleeve840may include a first side846. Further, as shown inFIGS. 8A and 8Bthe vertical step845include a second (e.g., vertical side)867and the vertical step865include a second (e.g., vertical) side847. In other examples, the splined surface profiles described inFIGS. 8A-8C and 8Hmay be implemented in the different interfaces described herein.

As depicted inFIG. 8A, the second side847of the clutch sleeve vertical step845may include a curved section851and a flat section852, while the second side867of the grounding plate vertical step865may include a continuous flat section.FIG. 8Bdepicts the second side847of the clutch sleeve vertical step845may include a continuous flat section, and the second side867of the grounding plate vertical step865may include a curved section868and a flat section869.FIG. 8Cdepicts a third example, where both of the second sides867,847of the grounding plate and clutch sleeve vertical steps865,845include the curved sections868,851, respectively. In any of the examples ofFIGS. 8A-8C, curved sections868and/or851may each include a curved profile, such as an elliptical or involute profile. Further, the curved sections868and/or851may be positive (e.g., convex) curved sections extending from the second side867or847, respectively, and therefore have a radius of curvature. However, in different examples, the use of other curved profiles has been contemplated.

In some examples, the curved section851on a vertical step845of the clutch sleeve840may be provided at an outer end portion of the second side847with respect to a central horizontal plane extending through the clutch sleeve. As such, the flat section852may be provided at an inner end portion of the second side847, adjacent to the curved section851.

Further, the curved section868on a vertical step865of the grounding plate860may be provided at an inner end portion of the second side867with respect to a central horizontal plane extending through the grounding plate, and the flat section869may be provided at an outer end portion of the second side867, adjacent to the curved section868. For instance, for mating vertical steps845,865in a lower quadrant, as illustrated inFIGS. 8A-8C, a curved section851on the second side847of the clutch sleeve840may be positioned below the flat section852(i.e., at an outer portion of the second side847), and a curved section868on the second side867of the grounding plate860may be positioned above the flat section869(at an inner portion of the second side867). Conversely, for mating vertical steps845,865in an upper quadrant, a curved section851on the second side847of the clutch sleeve840may be positioned above the flat section852(i.e., at an outer portion of the second side847), and a curved section868on the second side867of the grounding plate860may be positioned below the flat section869(at an inner portion of the second side867). However, in other examples, any of the sides having a curved section may not include a flat section, such that the entirety of the second side includes a curved profile.

The inclusion of a curved surface on one or both of inner periphery of the grounding plate or outer diameter of the clutch sleeve, in the examples described herein, may help to reduce edge loading at an interface between the clutch sleeve and the grounding plate, such as interface285between clutch sleeve240and grounding plate260inFIGS. 4, 6, and 7A, when the components are under a torque load. However, to reduce cost and complexity associated with manufacturing of the components, the curved surface may be provided on one of the second side of the inner vertical steps of the grounding plate or the second side of the outer vertical steps of the clutch sleeve, and a substantially flat surface may be provided on the other of the second side of the inner vertical steps of the grounding plate or the first side of the outer vertical steps of the clutch sleeve, such as, for instance, in the manner depicted viaFIG. 8A. Further,FIG. 8Hshows an embodiment of a stepped interface where the horizontal and vertical sides in the grounding plate860and the clutch sleeve840have substantially planar profiles.

Turning toFIGS. 8D-8F and 8I, examples of an interface between mating horizontal steps of a grounding plate860and a housing808are depicted. The steps shown inFIGS. 8D-8F and 8Imay be included in the horizontal steps shown inFIG. 7B, such that the interface880shown inFIGS. 8D-8F and 8Imay be included in the interface280between the grounding plate260and housing208, shown inFIGS. 4, 6 and 7B. As such, a horizontal step870on an outer stepped splined surface862of the grounding plate860may include a first (e.g., horizontal) side871and a second (e.g., vertical) side874. Further, a horizontal step850on an inner stepped splined surface882of the housing808may include a first (e.g., horizontal) side856and a second (e.g., vertical) side859.FIG. 8Dillustrates the first side871of the horizontal step870on the grounding plate860may include a curved section872and a flat section873, while the first side856of the horizontal step850on the housing808may include a continuous flat section.FIG. 8Edepicts a second example where the first side871of the horizontal step870on the grounding plate860may include a continuous flat section, and the first side856of the horizontal step850on the housing808may include a curved section857and a flat section858.FIG. 8Fdepicts a third arrangement, where both of the first sides871,856of the horizontal steps870,850, respectively, include the curved sections872,857, respectively. In any of the examples shown inFIGS. 8D-8F, curved sections872and/or857may each have a curved profile, such as an elliptical or involute profile. Further, the curved sections872and/or857may be positive (e.g., convex) curved sections extending from the first side871or856, respectively, and having a radius of curvature. However, in different examples, the use of other curved profiles has been contemplated, in different examples.

Continuing withFIGS. 8D-8F, a curved section872on a horizontal step870of the grounding plate860may be provided at an outer end portion of the first side871, with respect to a central vertical plane extending through the grounding plate860, so as to be located away from the central vertical plane with respect to the flat section873provided at an inner end portion of the first side871, adjacent to the curved section872. Further, a curved section857on a horizontal step850of the housing may be provided at an inner end portion of the first side856, with respect to a central vertical plane extending through the housing808, so as to be located closer to the central vertical plane with respect to the flat section858provided at an outer end portion of the first side856, adjacent to the curved section857. For instance, for mating horizontal steps870,850on the grounding plate860and housing808, respectively, in a left quadrant of the interface880, as illustrated inFIGS. 8D-8F, a curved section872on the first side871of the grounding plate horizontal step870may be positioned to the left of the flat section873(i.e., at an outer portion of the first side871), and a curved section857on the first side856of the housing horizontal step850may be positioned to the right of the flat section858(i.e., at an inner portion of the first side856). Conversely, for mating horizontal steps870,850in a right quadrant, a curved section872on the first side871of the grounding plate horizontal step870may be positioned to the right of the flat section873(i.e., at an outer portion of the first side871), and a curved section857on the first side856of the housing horizontal step850may be positioned to the left of the flat section858(i.e., at an inner portion of the first side856). However, in other examples, any side(s) having a curved section may not include a flat section, such that the entirety of the second side includes a curved profile.

In the examples described herein referring toFIGS. 8D-8F, the inclusion of a curved surface on one or both of first sides856,871of the horizontal steps850,870of the housing808or grounding plate860, respectively, may help to reduce edge loading at the interface880between the housing and the grounding plate when the components are under a torque load. However, in one example, to reduce cost and complexity associated with manufacturing of the components, the curved surface may be provided on one of the first side856of the horizontal steps850of the inner stepped splined surface882on the housing808, or the first side871of the horizontal steps870of the outer stepped splined surface862of the grounding plate860. In this example, a substantially flat surface may be provided on the other of the first side856of horizontal step850and first side871of horizontal step870, such as, for instance, in the manner depicted inFIG. 8D. Further,FIG. 8Ishows an embodiment of a stepped interface where the horizontal and vertical sides in the housing808and the grounding plate860have substantially planar profiles.

Referring toFIGS. 8A-8F, collectively, it will be understood that one or more curved surfaces may be included at some or all of the second sides847,867of the vertical steps865,845on the clutch sleeve840and the grounding plate860, respectively, at the interface885, and/or at some or all of the first sides871,856of the horizontal steps870,850on the grounding plate860and the housing808, respectively, at the interface880, in any of the manners described inFIGS. 8A-8F. In one example, each pair of mating steps may include the same type of curved profile. However, in other examples, different curved profiles may be provided at different pairs of mating steps. For instance, in one example, a curved profile on one step may have a width different from a curved profile on another one of the steps. In still other examples, some pairs of mating steps may include one or more curved profiles and flat profiles, while others may include a continuous flat profile. In this way, the curved profile may reduce edge loading at particular contact areas where excessive edge loading is expected to occur when the respective interface885or880is under a torque load during operation, thus reducing a chance of uneven wear and component degradation in the housing, grounding plate, and/or clutch sleeve.

Turning toFIG. 8G, another example of a stepped spline is shown. Specifically,FIG. 8Gshows an example of an interface880between mating horizontal steps870,850on outer and inner stepped splined surfaces862,882of the grounding plate860and the housing808, respectively. In some examples, the grounding plate860and the housing808may be made of a metal (e.g., aluminum, steel, etc.). In one example, the grounding plate860and the housing808may be made of the same metal, thus sharing similar material properties (e.g., hardness, yield strength, etc.). In other examples, however, the grounding plate860and the housing808may be made of different metal materials, thus having dissimilar material properties. For instance, the grounding plate860may be made of a ductile cast iron material, and the housing808may be made of aluminum. In such a scenario, the grounding plate860may, under certain conditions, degrade (e.g., deform) the housing808due to torque transmitted through the grounding plate860to the housing808at the interface880. It may therefore be desired to reduce edge loading and contact stress at the interface880, and/or at the interface885, such as, for instance, by increasing the contact width at the interface via the configurations shown inFIG. 8G.

The horizontal step870of the grounding plate860is shown inFIG. 8Gto include perpendicularly intersecting first and second sides871,874, respectively, and the horizontal step850on the housing808includes perpendicularly intersecting first and second sides856,859, respectively, similar to the configurations of horizontal steps870and850previously described with reference toFIGS. 8D-8F. As such, additional discussion of the general relative arrangement of the first and second sides of the steps is omitted for brevity.

The first side871of the horizontal step870on the outer stepped splined surface862of the grounding plate860may include a negative (e.g., concave) curved surface810, defining a receptacle811in the first side871. Further, a shoe812may be provided that slides along the first side856of the horizontal step850on the inner stepped splined surface882. The shoe812may include a positive (e.g., convex) curved surface813corresponding to the negative curved surface810of the horizontal step870. Further, the receptacle811defined by the negative curved surface810may have a radius that is slightly larger than the positive curved surface813of the shoe812, such that the shoe812may be received in the receptacle811when the horizontal steps850,870are engaged at interface880. In some examples, the depth of the receptacle811(e.g., as defined between the first side871and a middle point of negative curved surface810) may be designed so as to allow the negative curved surface810to push laterally against the positive curved surface813of the shoe812, under certain loading conditions where the grounding plate860moves horizontally, without causing the shoe812to become wedged or jammed between the receptacle811and first side856as it moves. In one example, the shoe812may have a tapered end configuration or include other features to aid in aligning and positioning of the shoe while assembling the interface880between mating horizontal steps870,850on outer and inner stepped splined surfaces862,882of the grounding plate860and the housing808.

In some cases, a small radial difference between the positive curved surface813of the shoe812and the negative curved surface810of the receptacle811may be desired, so as to allow the shoe812to pivot within the receptacle to find its equilibrium. Further, the space between the positive curved surface813and the negative curved surface810may be small enough to provide a contact width sufficient to reduce edge loading and contact stress at the interface880. In other words, a smaller radial difference between the positive and negative curved surfaces813,810, respectively, provides a greater amount of contact width, thus offering a greater reduction in edge loading and contact stress at the interface880between the shoe curved surface813and the negative curved surface810of the receptacle811.

In some examples, the shoe812may have a flat side814, on an opposite side from a positive curved surface813. As such, an additional contact area may be provided between the flat side814of the shoe812and a flat surface815of the first side856of the horizontal step850. The additional contact area provides a greater amount of contact width, thus offering a greater reduction in contact stress at the interface880between the shoe flat side814of the shoe812and the flat surface of the first side856of the horizontal step850, as compared to the positive (e.g., convex) curved sections against a flat surface as described previously inFIGS. 8A-8F. Furthermore, an attachment device may be used for retaining the shoe812in place in the grounding plate860receptacle811while assembling the interface880between mating horizontal steps870,850on outer and inner stepped splined surfaces862,882of the grounding plate860and the housing808respectively. Examples of a suitable attachment device may thus include retaining rings, pins, and other mating features. In one example, the shoe812, grounding plate860, or both, may further include protrusions, cuts, and/or cutouts to facilitate retention of the shoe812. In some examples, the shoe812may be formed of a metal (e.g., a similar or different metal of the housing808). As such, the shoe812may be formed by various processes, including, for instance, machining from a billet, casting, powdered metal sintering, etc.

In one example, as illustrated inFIG. 8G, the shoe812may be provided on all of the horizontal steps870of the outer stepped splined surface862on the grounding plate860, so as to be provided in the four quadrants of the housing808. In some cases, the same number of shoes may be provided in each quadrant. However, in some cases, opposing quadrants may have an equal number of shoes, while the adjacent quadrants may have a greater or lesser number of shoes. For instance, a quadrant handling counterclockwise torque from the grounding plate860may have more or less shoes than a quadrant handling clockwise torque from the grounding plate860. As such, the number of shoes provided on the outer stepped splined surface862may be determined based on the contact stress anticipated at the corresponding interface880.

Further, while the shoe812is discussed as being provided on a horizontal step870on the grounding plate860, other configurations including shoes have been envisioned, in different examples. For instance, converse to the depiction shown inFIG. 8G, the shoe812, may be included on the first side856of the horizontal step850on the inner stepped splined surface882of the housing808. As such, the negative curved surface810, and thus the receptacle811, may be provided on a first side856of the horizontal step850on the inner stepped splined surface882of the housing808. In other examples, the shoes may be implemented on vertical steps (e.g., on a second side847of a vertical step845on the outer stepped splined surface844of the clutch sleeve840, or on a second side867of the vertical step865on the inner stepped splined surface864of the grounding plate860, at interface885depicted inFIGS. 8A-8C). Accordingly, in such examples, a receptacle811defined by the negative curved surface810may be provided on a corresponding side of a vertical step so as to receive (e.g., retain) the shoe812. In still further examples, the shoes and receptacle may be provided, in any of the configurations described above, as an alternative to, or in conjunction with, any of the positive curved surface examples described with reference toFIGS. 8A-8F, so as to reduce contact stress and edge loading at a corresponding interface between either or both of the housing and the grounding plate or the grounding plate and the clutch sleeve.

FIGS. 9-10illustrate another example of a grounding plate960mated at an outer and inner interface with a housing908and a clutch sleeve940, respectively. An interface980is illustrated between the grounding plate960and the housing908, and an interface985is illustrated between the grounding plate960and the clutch sleeve940. Further, the clutch sleeve940is in splined engagement with an inner hub990at an interface995. The interface995may include a tapered or involute splined surface992on an outer periphery of the inner hub990designed to mate with a tapered or involute splined surface942on an inner periphery of the clutch sleeve940. Further, the interface985may be defined by an inner stepped splined surface964at an inner periphery of the grounding plate960including vertical steps965designed to selectively mate with vertical steps945of an outer stepped splined surface944at an outer periphery of the clutch sleeve940.

The interfaces995and985may be substantially identical to the interfaces295and285, respectively, described herein with relation toFIGS. 3B-8G, and repeated discussion of the tapered (or involute) spline and vertical stepped spline interfaces will be omitted for brevity. Thus, the vertical stepped splined interface995may allow for some vertical movement and tilting of the clutch sleeve940within the grounding plate960which may increase the ability of the clutch sleeve to axially translate therein, and, in conjunction with the tapered splined interface995radially positioning the clutch sleeve940about the inner hub990, may further allow the clutch sleeve940to find its equilibrium, to reduce the chance of binding of the components.

The grounding plate960illustrated inFIGS. 9 and 10may include an outer splined engagement surface962designed to mate with an inner splined engagement surface982of the housing908at an interface980, in addition to the aforementioned inner stepped splined surface964designed to mate with the outer stepped splined surface944of the clutch sleeve940at interface985. The outer splined engagement surface962may include involute splines963positioned about an outer periphery of the grounding plate960. Similarly, the inner splined engagement surface982of the housing908may include corresponding involute splines983radially positioned about an inner periphery of the housing908. In some examples, the involute splines963,983may be provided along the entire outer or inner periphery of the grounding plate960and housing908, respectively. However, in other examples, the involute splines963,983may be provided in non-contiguous segments, separated by non-splined circumferential segments. In some cases, the segments of involute splines963,983provided on the grounding plate960or the housing908, respectively, may have equal or non-equal lengths, and may have equal or non-equal numbers of involute splines accordingly.

In the illustrated example, the involute splines963of the outer splined engagement surface962are provided in three segments910,920, and930on the grounding plate960, as indicated inFIG. 10. However, in other examples, a different number of segments (e.g., two segments, four segments, etc.) of involute splines963may be provided. In some examples, the housing908may have a similar number of segments of involute splines983corresponding to the number of segments of involute splines963on the grounding plate960, though other examples have been contemplated where different numbers of segments of involute splines983,963are provided on the housing908and the grounding plate960, respectively. Further, the segments of involute splines963,983on the grounding plate960and the housing908may be radially aligned to increase the effectiveness and load distribution of the splined engagement. However, in different examples, other arrangements having radially offset segments of the involute splines963,983have been envisioned.

The inclusion of involute splines at the interface980between the grounding plate960and the housing908may restrict horizontal and vertical movement of the grounding plate960within the housing908, and may further restrict rotation about a vertical axis (e.g., y-axis) and a horizontal axis (e.g., z-axis). This may, in turn, allow for a secure, stable engagement between the housing908and the grounding plate960to maintain a desired position of the grounding plate960. However, in some cases, such a configuration may constrain the assembly, particularly when some horizontal positional tolerance of the grounding plate960is desired to accommodate radial positional tolerance stack-up within the assembly to allow the clutch sleeve940to find its operating center.

In still other examples, the grounding plate960may be positioned vertically in the housing908via dowel pins, shoulder screws, or similar means. In one example, three dowel pins, separated by selected angles may be used to attach the grounding plate to the housing, though other numbers of dowel pins have been envisioned. The dowel pins may axially extend through an inner periphery of the housing908into the outer periphery of the grounding plate960through horizontally slotted holes, thus attaching the grounding plate960to the housing908at a desired vertical position. In some examples, the use of dowel pins may allow for some horizontal movement of the grounding plate960with respect to the housing908in a horizontal plane, providing some positional tolerance.

FIGS. 11 and 12illustrate another example for positioning a grounding plate1160with respect to a housing1108. In this example, the grounding plate1160may include an outer engagement surface1162designed to mate with an inner engagement surface1109of the housing1108at an interface1180. The outer surface1162and the inner surface1109may include any of the splined engagement configurations described herein, such as the horizontal stepped splined interface or the involute splined interface, or, in some cases, may include a non-splined surface. Similarly, there may be an inner engagement surface of the grounding plate1160and the housing1108. The rear side surface of the housing1108may be a step in the housing or a retaining ring groove for the retaining ring1110.

As shown inFIG. 11, two retaining rings1110,1120may be provided on opposing axial sides of the grounding plate1160along the x-axis. The retaining rings may be provided at or near the inner engagement surface1109of the housing1108, extending inwardly towards the grounding plate1160. In one example, the outer engagement surface1162of the grounding plate1160may include a splined surface. The splined surface extends outward from a main body of the grounding plate1160(e.g., similar to the outer stepped splined surface262of grounding plate260shown inFIG. 4). Further, the retaining ring1110may be positioned on one side of the outwardly extending splined surface, while retaining ring1120may be positioned on the other axial side of the outwardly extending splined surface, so as to maintain an axial position of the grounding plate1160with respect to the housing1108.FIG. 12further illustrates the retaining ring1120, shown in front of the outer engagement surface1162of the grounding plate1160, which is depicted via a dashed line to represent its position behind retaining ring1120. Thus, with the retaining ring1120disposed on a front side of the grounding plate1160, it will be understood that the retaining ring1110may be disposed on a rear side of the grounding plate1160, positioned coaxially with the retaining ring1120. In this way, the grounding plate1160may be axially captured in a simple, cost-effective manner, while allowing for a targeted amount of the grounding plate movement in a horizontal direction (e.g., along the z-axis), if wanted. Axially capturing the grounding plate1160constrains the ability of the grounding plate to tilt about the y-axis, removing a degree of freedom. In some instances, the grounding plate's tilt ability about the y-axis could be regained by increasing the clearance between the retaining rings1110and1120with the inner and outer engagement surfaces1109and1162. In some instances, a wave spring may be added between retaining rings1110and1120, and the inner and outer engagement surfaces1109and1162respectively, to allow tilt ability of the grounding plate1160about the y-axis while reducing axial backlash of the grounding plate1160between retaining rings1110and1120. The horizontal positional tolerance may further allow for positioning of a clutch sleeve1140engaged with the grounding plate1160at an interface1185, which may allow for the clutch sleeve1140to find its equilibrium (e.g., intended operating center along the axis of rotation) to reduce the chance of binding of the components.

FIG. 13shows a table1300depicting how various degrees of freedom of a sliding sleeve in a clutch are restricted or, in some cases, over-constrained due to various engagement configurations between the sleeve and a grounding plate and between a grounding plate and a housing, some of which may be similar to other examples described herein with relation toFIGS. 2-12. However, it will be understood that the configurations described with reference to the table1300are representative of different use-case examples.

Example configurations are indicated in the rows of the table1300, including first through fourth examples1310-1340. Further, six degrees of freedom (DOF) of a clutch sleeve and/or a grounding plate corresponding to translation and rotation about x, y and z axes are considered for each example. The x, y, and z axes described with relation toFIG. 13may be the same as x, y, and z axes of the axis system170shown inFIGS. 2-12. As such, the x-axis may be a longitudinal axis (e.g., horizontal axis extending through a longitudinal axis of a clutch sleeve, grounding plate, and/or housing), the z-axis may be a lateral axis (e.g., a horizontal axis oriented normally to the longitudinal axis), and the y-axis may be a vertical axis (e.g., parallel to a gravitational axis).

The first example1310corresponds to a previously known configuration wherein a clutch sleeve and a grounding plate both include involute splines at their respective outer diameters. The involute splines of the clutch sleeve may be designed to mate with an inner surface of the grounding plate, and the involute splines of the grounding plate may be designed to mate with an inner surface of a housing. In this example, one sliding sleeve DOF is provided without restriction (i.e., axial displacement along the x-axis), while five of six sliding sleeve DOF are restricted: axial displacement along the z-axis, vertical displacement along the y-axis, torsional reaction about the x-axis, a binding moment about the y-axis, and a binding moment about the z-axis. In some cases, some of the restricted DOF may be excessively restricted, i.e., over-constrained. These over-constraints may be recognized in: the axial displacement along the z-axis, the vertical displacement along the y-axis, the binding moment about the y-axis, and the binding moment about the z-axis. Further, these over-constraints may cause binding issues, where the clutch sleeve may become jammed within the grounding plate, hindering its ability to translate axially in a desired manner. Thus, each of the examples1320-1340may address over-constraints by either eliminating the restriction entirely or eliminating the over-constraint.

In the second example1320, the clutch sleeve includes a vertical stepped spline at its outer diameter for mating with a vertical stepped spline on an inner diameter of the grounding plate. The grounding plate outer diameter and housing inner diameter include involute splines. Thus, it will be understood that example1320may be similar to the configuration of clutch sleeve940and grounding plate960discussed with reference toFIGS. 9-10. In the second example1320, two over-constraints present in first example1310may be eliminated. However, three of the six sliding sleeve DOF: axial displacement along the z-axis, torsional reaction about the x-axis, and a binding moment about the y-axis) may remain restricted and/or over-constrained, while three DOF: axial displacement along the x-axis, vertical displacement along the y-axis, and a binding moment about the z-axis, may still be provided without restriction.

In the third example1330, the grounding plate may include horizontal stepped splines at an outer diameter thereof, which may be similar to the configuration of the grounding plate260described with reference toFIG. 7B. The sliding sleeve outer diameter and grounding plate inner diameter include involute splines. The horizontal stepped-spline configuration of the fourth example1340may restrict and/or over-constrain three of the six sliding sleeve DOF: vertical displacement along the y-axis, torsional reaction about the x-axis, and the binding moment about the z-axis. Thus, three of the six DOF may be provided without restriction: axial displacement along the x-axis, axial displacement along the z-axis, and the binding moment about the y-axis.

In the fourth example1340, the clutch sleeve may include a vertical stepped spline at its outer diameter, and the grounding plate may include a horizontal stepped spline at its outer diameter. As such, it will be understood that the configuration of the fourth example1340may be substantially similar to the configuration described with reference toFIGS. 2-6(e.g., including the clutch sleeve240having vertical steps245designed to mate with the grounding plate260at interface285, and the grounding plate260having horizontal steps270designed to mate with the housing). However, in some cases, the fourth example1340may include a different clutch sleeve and grounding plate having vertical and horizontal steps, respectively, along their respective outer diameters. Further, the fourth example1340may include the grounding plate retaining rings1110and1120used for positioning a grounding plate with respect to a housing as described inFIGS. 11-12.

The fourth example1340may provide four DOF without restriction: axial displacement along the x-axis, axial displacement along the z-axis, vertical displacement along the y-axis, and the binding moment about the z-axis. Thus, the other two of the six DOF may be restricted. Specifically, the torsional reaction about the x-axis may be restricted, and the binding moment about the y-axis may be restricted. However, by eliminating many of the restrictions and/or over-constraints observed in previous examples, and particularly by providing the binding moment about the z-axis without restriction, the combined vertical and horizontal step configuration of the fourth example1340may reduce a chance of binding of the clutch sleeve and/or grounding plate, when compared to previous examples.

Although the aforementioned examples describe a grounding assembly which may include a horizontal stepped splined interface between a grounding plate and a housing, and a vertical stepped splined interface between the grounding plate and a clutch sleeve, other examples have been envisioned where a horizontal stepped splined interface may be provided between the grounding plate and the clutch sleeve, and a vertical stepped splined surface may be provided between the housing and the grounding plate. In such an example, however, the grounding plate may have some vertical positional tolerance within the housing, which may lead to undesired weight distribution of the grounding plate carried by the clutch sleeve, in some cases. Further, although the various examples described herein refer to “vertical” and “horizontal” stepped splined interfaces comprising pluralities of “vertical” and “horizontal” steps, respectively, other examples for use in different applications may include stepped splined surfaces with a plurality of steps oriented at a different angle (e.g., an angle between the vertical and horizontal). In such cases, the application may involve another type of torque loading and/or external biasing force(s) other than gravity which may be adequately addressed via stepped surfaces oriented in this manner.

The invention will be further described in the following paragraphs. In one aspect, a multi-speed electric powertrain system is provided that comprises a grounding plate including an outer interface coupled to a housing interface and an inner stepped splined interface designed to selectively mate with a clutch sleeve, wherein the inner stepped splined interface includes a plurality of steps that each include a first side that perpendicularly intersects a second side, and wherein the first side of each step in the inner stepped splined interface includes a clearance between the first side and a stepped surface of the clutch sleeve.

In another aspect, a method for operating a multi-speed electric powertrain is provided that comprises mechanically grounding a clutch sleeve via a grounding plate, wherein the grounding plate includes an outer interface coupled to a housing interface; and an inner stepped splined interface designed to selectively mate with the clutch sleeve, wherein the inner stepped splined interface includes a plurality of steps that each include a first side that perpendicularly intersects a second side, and wherein the first side of each step in the inner stepped splined interface includes a clearance between the first side and a stepped surface of the clutch sleeve.

In yet another aspect, a multi-speed electric axle system is provided that comprises a grounding plate including an outer splined interface comprising a plurality of stepped splines that are mated with a housing interface, and an inner splined interface including a plurality of stepped splines that are designed to mate with a clutch sleeve, wherein the outer splined interface includes a clearance on one side of each of the plurality of stepped splines, and wherein the inner splined interface includes a clearance on one side of each of the plurality of stepped splines.

In any of the aspects or combinations of the aspects, the outer interface may be a stepped splined interface that comprises a plurality of steps that each include a first side that perpendicularly intersects a second side and the first side of each step in the outer interface may include a clearance between the first side and a stepped surface of the housing interface.

In any of the aspects or combinations of the aspects, the first side of the one or more of the plurality of steps may include a curved profile.

In any of the aspects or combinations of the aspects, the curved profile may be an elliptical or involute shape.

In any of the aspects or combinations of the aspects, the plurality of steps may have varying widths.

In any of the aspects or combinations of the aspects, a magnitude of the clearance may be greater than or equal to a positional tolerance stack of a clutch assembly that includes the clutch sleeve.

In any of the aspects or combinations of the aspects, the clearance between the first side of the inner stepped splined surface and the stepped surface of the clutch sleeve may vary between the plurality of steps in the inner stepped splined surface.

In any of the aspects or combinations of the aspects, one or more dowel pins may be included for attaching the outer interface of the grounding plate to the housing interface.

In any of the aspects or combinations of the aspects, a pair of retaining rings may be included that axially capture the grounding plate.

In any of the aspects or combinations of the aspects, the plurality of steps in the inner stepped splined surface may be partitioned into quadrants.

In any of the aspects or combinations of the aspects, an inner hub may be designed to selectively couple to the clutch sleeve.

In any of the aspects or combinations of the aspects, the clutch sleeve may be mechanically coupled to a gear, or a carrier in a planetary gearset.

In any of the aspects or combinations of the aspects, the multi-speed electric powertrain may be in one of a plurality of drive gears while the clutch sleeve is mechanically grounded.

In any of the aspects or combinations of the aspects, the clearance in the outer splined interface may be a horizontal clearance, wherein the clearance in the inner splined surface may be a vertical clearance.

In any of the aspects or combinations of the aspects, the outer splined surface may include a flank gap between a curved surface and the housing interface, wherein the flank gap may sequentially decrease.

In any of the aspects or combinations of the aspects, the plurality of stepped splines in the outer splined interface and the plurality of stepped splines in the inner splined interface may each include a first side that perpendicularly intersects a second side.

In any of the aspects or combinations of the aspects, the first side or the second side of one or more of the plurality of stepped splines in the outer or inner splined interface may include a curved surface adjacent to a stepped surface.

In any of the aspects or combinations of the aspects, the clutch sleeve may be designed to selectively ground one gear, or one carrier in a planetary assembly.

In any of the aspects or combinations of the aspects, the outer stepped splined interface may include mated convex and concave surfaces.

In any of the aspects or combinations of the aspects, the multi-speed electric powertrain system may further comprise a shoe including: a flat surface adjacent to a stepped surface in the outer or inner (stepped) splined interface; and a convex surface mated in a concave receptacle.

In any of the aspects or combinations of the aspects, the outer and inner splined interfaces may each include a flank gap between a curved surface and the housing interface and the clutch sleeve, respectively and wherein the flank gaps may sequentially decrease.

In another representation, a multi-speed gearbox is provided that includes a planetary gearset and a clutch with a sleeve designed to axially engage and disengage at least a first gear and a carrier in the planetary gearset in different positions, wherein during clutch sleeve engagement of the first gear or carrier the sleeve is grounded via a plate with stepped contours that have gaps, wherein the gaps permit horizontal and vertical movement of the sleeve with regard to the plate.

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 used herein, the terms “substantially” and “approximately” are construed to mean plus or minus five percent of the range unless otherwise specified.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to a variety of vehicles such as vehicles with hybrid electric powertrains, combustion engine powertrains, electric powertrains, and the like. Moreover, unless explicitly stated to the contrary, the terms “first,” “second,” “third,” and the like are not intended to denote any order, position, quantity, or importance, but rather are used merely as labels to distinguish one element from another. 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.

Further, it will be appreciated that the configurations 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 transmissions. 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.