Axle decoupler system with mechanical synchronizer

Abstract

The axle decoupler system includes an axle decoupler configured to selectively couple an axle of a vehicle to a wheel hub of the vehicle, the axle decoupler including a sliding ring including a first spline coupled to a second spline on the axle, the sliding ring including a first position in which neither the first spline nor a third spline on the wheel hub is coupled, and a second position in which neither the first spline nor the third spline is coupled to the third spline; an electric motor for moving the sliding ring to the first position or the second position; and a one-way clutch coupling the axle and the wheel hub to each other.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 476,092, entitled "AXLE DECOUPLER SYSTEM WITH MECHANICAL SYNCHRONIZER," filed December 19, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to an axle decoupler system with mechanical synchronizers. [Background technology]

[0003] Several approaches have been attempted to selectively decouple a vehicle's wheels from its drive shaft. These approaches have been energy inefficient and distracting to vehicle occupants. For example, existing decouplers have been associated with parasitic energy losses and / or noise, vibration, and handling (NVH) issues during operation, such as clunks or other drivability concerns. Summary of the Invention

[0004] In a first aspect, an axle decoupler system includes an axle decoupler configured to selectively couple an axle of a vehicle to a wheel hub of the vehicle, the axle decoupler including a sliding ring including a first spline coupled to a second spline on the axle, the sliding ring including a first position in which neither the first spline nor a third spline on the wheel hub is coupled, and a second position in which neither the first spline nor the third spline is coupled; and an electric motor configured to move the sliding ring to the first position or the second position; and a one-way clutch coupling the axle and the wheel hub to each other.

[0005] Implementations may include any or all of the following features: The axle decoupler further includes a lead screw rotated by the electric motor, the lead screw configured to translate a shift fork to move the sliding ring to the first position or the second position. The axle decoupler further includes a guide pin for the shift fork. The axle decoupler further includes a first detent for the shift fork on the guide pin. The first detent is a ball detent or a hug ring. The first detent corresponds to the first position, and the axle decoupler further includes a second detent for the shift fork on the guide pin, the second detent corresponding to the second position. The axle decoupler system includes at least two one-way clutches connecting the axle and the wheel hub to each other. The axle decoupler further includes a one-way chamfer on the third spline of the wheel hub. The axle decoupler further includes a first bearing between the axle and the wheel hub. The axle decoupler further includes a housing and a second bearing between the housing and the axle. The axle decoupler system further includes a bushing between the axle and the wheel hub. The axle is a half shaft of a motor. The half shaft is included in a constant velocity joint assembly of the motor.

[0006] In a second aspect, a method includes receiving a first command to engage a motor of a vehicle in which a wheel hub is currently disengaged from an axle of the motor; accelerating the axle to a rotational speed of the wheel hub in response to the first command, wherein a one-way clutch connecting the axle and the wheel hub to one another is preloaded; commanding zero torque from the motor in response to the axle reaching the rotational speed of the wheel hub, wherein the axle decelerates, and moving a sliding ring connected to the axle into engagement with the wheel hub; terminating the engagement between the sliding ring and the wheel hub, wherein the axle and the wheel hub have a common rotational speed; and commanding torque from the motor according to the first command after the engagement between the sliding ring and the wheel hub has terminated.

[0007] Implementations may include any or all of the following features. When the first command is received, the rotational speed of the axle is zero. A slide ring is moved by rotating a lead screw configured to translate a shift fork that moves the slide ring between first and second positions. A first detent for the shift fork on a guide pin corresponds to the first position. A second detent for the shift fork on the guide pin corresponds to the second position. Terminating the engagement between the slide ring and the wheel hub is facilitated by a unidirectional chamfer on a spline of the wheel hub, the unidirectional chamfer causing the slide ring to move against a direction of rotation of the slide ring and the wheel hub. The method further includes receiving a second command to disengage the wheel hub from the axle, and moving the slide ring in the opposite direction toward disengagement from the wheel hub in response to the second command. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 illustrates an example of an axle decoupler system.

[0009] [Figure 2] 2 is a diagram showing an example cross section of an axle decoupler and CV joint assembly of the axle decoupler system in FIG. 1. FIG.

[0010] [Figure 3] 2 shows an example of a partial cross-sectional view of the axle decoupler system of FIG. 1 when the axle is connected to the wheel hub.

[0011] [Figure 4] 2 illustrates another example of a partial cross-sectional view of the axle decoupler system of FIG. 1 when the axle is decoupled from the wheel hub.

[0012] [Figure 5]FIG. 2 is a diagram showing an example of a partial cross-sectional view of the axle decoupler system in FIG. 1.

[0013] [Figure 6] FIG. 1 illustrates an example of a control strategy for a motor.

[0014] [Figure 7] FIG. 1 is a schematic diagram of an example vehicle axle having two axle decoupler systems.

[0015] [Figure 8] FIG. 1 is a schematic diagram of an example vehicle axle with one axle decoupler system.

[0016] Like reference symbols in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0017] This specification describes example systems and techniques that provide an axle decoupler system with a mechanical synchronizer. In some implementations, the decoupler system allows for the disconnection of a vehicle's non-drive axle, which may eliminate parasitic losses in the disconnected axle and improve overall vehicle efficiency. During engagement, the mechanical synchronizer may balance the speed of the halfshaft to the speed of the corresponding wheel, which may provide a smooth engagement and therefore improve NVH issues. The present subject matter allows axle decoupler systems to be more compact in vehicle designs and less noticeable to occupants. For example, the axle decoupler system may allow a vehicle to engage a currently disengaged wheel as fast as the motor can accelerate the component up to speed, with minimal disruption to occupants.

[0018] Ensuring the effectiveness of a decoupler system can be a key factor in maximizing vehicle efficiency. For a decoupler system, its efficiency, repeatability of disconnection and reconnection, response time, and smoothness of operation are all factors that can be considered in the mechanical design. For example, the above characteristics can help maximize the operating window over which the decoupler system can be used to eliminate parasitic losses of a disconnected axle.

[0019] A decoupler system according to the present subject matter can temporarily draw power from the vehicle to energize a rotary motor that pushes and pulls an intermediate gear to perform the primary function of coupling and decoupling between the splines on the halfshafts and the splines on the wheels. For example, this can be done via a set of self-locking lead / ball screw sets. When the intermediate gear is in either the coupled or disengaged position, a set of ball detents can ensure that the decoupler system does not consume additional power to maintain the coupled or decoupled state.

[0020] In the coupled state, the decoupler system may transfer drive unit output torque from the halfshafts to the vehicle wheels using a combination of spline connections between the halfshafts, intermediate gears, and output gears, and an overrunning clutch. In the disengaged state, the intermediate gears may be disconnected from the wheels, and the overrunning clutch may rotate freely.

[0021] During engagement, the torque transfer capability of the overrunning clutch may enable a control strategy that uses the drive unit output torque to establish a preload between the halfshafts and wheels, ensuring speed synchronization between the two, which may be combined with a unidirectional chamfer profile.

[0022] Implementations may provide one or more of the following advantages: A mechanical synchronizer (e.g., a sprag clutch) may balance the rotational speed of the axle relative to the wheel during an engagement scenario. For example, the use of an overrunning clutch may improve disengagement / reengagement repeatability, response time, and / or smoothness during spline engagement. A one-way chamfered engagement gear profile may prevent overloading of the decoupler system motor during what is sometimes referred to as a dog-on-dog situation (i.e., when the splines of gears rotating at the same speed are not currently meshing with each other). Low-friction bearings, seals, bushings, and / or sprag clutches may be used to minimize parasitic losses in both the engaged and disengaged states. A half-shaft force-responsive bearing arrangement may be used. The use of a self-locking screw and gearbox may eliminate power consumption during engaged and disengaged states.

[0023] Examples described herein refer to vehicles. A vehicle is a machine that transports passengers, cargo, or both. A vehicle may have one or more electric motors. Examples of vehicles include, but are not limited to, cars, trucks, buses, motorcycles, and scooters. The number of wheels may vary between vehicle types, and one or more (e.g., all) of the wheels may be used to propel the vehicle. A vehicle may include a passenger compartment that accommodates one or more people. By way of example, a vehicle may be powered solely by electricity, or may use one or more other energy sources in addition to electricity, or may be equipped with an internal combustion engine (ICE).

[0024] The examples described herein refer to a motor. The motor may be an electric motor or an ICE. As used herein, an electric motor may be any type of electric motor, including, but not limited to, a permanent magnet motor, an induction motor, a synchronous motor, or a reluctance motor.

[0025] FIG. 1 illustrates an example axle decoupler system 100. The axle decoupler system 100 may be used with one or more other examples described elsewhere herein. The axle decoupler system 100 includes an axle decoupler 102 and an axle that is coupled to or decoupled from a wheel by the axle decoupler 102, including, but not limited to, an outer constant velocity (CV) joint assembly 104. FIG. 2 illustrates an example cross-section of the axle decoupler 102 and the CV joint assembly of the axle decoupler system in FIG. 1. The axle decoupler 102 and the outer CV joint assembly 104 are shown separated from each other for clarity. In the following examples, components are sometimes described as being included in either component of the axle decoupler system 100; this is based on how the axle decoupler system 100 is disassembled in this illustrative description. For example, a component may be coupled to both the axle decoupler 102 and the outer CV joint assembly 104 when the axle decoupler system 100 is assembled. In some implementations, the axle connected / decoupled by the axle decoupler 102 may be a half shaft of a traction axle in a vehicle. For example, the half shaft may be included in the outer CV joint assembly 104.

[0026] The axle decoupler 102 includes an electric motor 106 that is used to couple / decouple the axles. In some implementations, the electric motor 106 can be a rotary electric motor. For example, the electric motor 106 is driven by the battery pack of an electric vehicle or by the power system in an ICE vehicle.

[0027] Axle decoupler 102 includes a slide ring 108 with radially inwardly facing splines 110 that may couple with splines 112 of outer CV joint assembly 104 and face radially outward both when the axle is coupled to the wheel and when the axle is decoupled from the wheel.

[0028] The outer CV joint assembly 104 may include, among other features, an axle nut 114, a bearing 116, one or more one-way clutches 118 and 120 (e.g., sprag clutches), and a pilot bushing 122. When the axle decoupler system 100 is assembled (i.e., when a portion of the outer CV joint assembly 104 extends partially through the opening in the axle decoupler 102), the bearing 116, the one-way clutches 118 and 120, and the pilot bushing 122 may all be positioned against the inner surface of the wheel hub (described below). As such, the one-way clutches 118 and 120 may couple the outer CV joint assembly 104 and the wheel hub to one another. For example, the one-way clutches 118 and 120 may ensure that a currently slower portion (e.g., the outer CV joint assembly 104) is not over-accelerated when the currently slower portion (e.g., the outer CV joint assembly 104) is accelerating.

[0029] The axle decoupler 102 may include a bearing 124. When the axle decoupler system 100 is assembled, an inner race of the bearing 124 may abut a surface 126 of the outer CV joint assembly 104, and an outer race of the bearing 124 may abut a housing 128 of the axle decoupler 102. Having at least two bearings in the axle decoupler system 100 (e.g., bearings 116 and 124 and, optionally, a pilot bushing 122) may enable the axle decoupler system 100 to react to a force vector from the outer CV joint assembly 104, which may have a component in the y-direction (i.e., vertical) of the vehicle coordinate system. For example, the bearings may prevent overload due to the halfshaft plunge force vector, thereby preventing excessive forces on the one-way clutches 118 and 120. Having low-friction bearings, bushings, and one-way clutches helps minimize losses.

[0030] FIG. 3 shows an example of a partial cross-sectional view of the axle decoupler system 100 in FIG. 1 when an axle is coupled to a wheel hub 300. As such, the axle decoupler system 100 is assembled here, and only a portion of the axle decoupler system 100 is shown for clarity. The axle decoupler 102 has a lead screw 302 coupled to an electric motor 106, which can rotate the lead screw 302 in either direction. A shift fork 304 engages the threads of the lead screw 302 and can translate in either direction based on the rotation of the lead screw 302. The shift fork 304 has a fork portion 304A that participates in coupling and decoupling by the axle decoupler system 100, as exemplified below. The shift fork 304 can ride on a guide pin 306 that extends along the direction of translation. As such, the axle decoupler 102 may be configured such that a lead screw 302 may be rotated by the electric motor 106 and the lead screw 302 translates a shift fork 304 that may ride on a guide pin 306 .

[0031] The axle decoupler system 100 includes a sliding ring 308 that is movable in the left-right direction of this illustration. The sliding ring 308 has radially inwardly facing splines 310 that are coupled to splines 112 on the outer CV joint assembly 104. That is, the splines 310 can be coupled to the splines 112 in all positions that the sliding ring 308 assumes. The partially illustrated wheel hub 300 has a flange 312 that can be substantially rotationally symmetrical about the axle. One or more components can be positioned between the wheel hub 300 and the outer CV joint assembly 104. For example, the pilot bushing 122 and the one-way clutch 120 are visible here and can abut the flange 312. The wheel hub 300 can have a coupler gear 314 attached to the flange 312. The coupler gear 314 has radially outwardly facing splines 316. The sliding ring 308 is now in place, whereby the splines 310 are coupled to the splines 316. The position is dictated by the current position of fork portion 304A. As such, outer CV joint assembly 104 is now coupled and engaged to wheel hub 300. Motor torque applied to outer CV joint assembly 104 can therefore drive the wheel at wheel hub 300.

[0032] To avoid an uncertain situation where the shift fork 304 inadvertently pushes back on the guide pin 306 or rotates the lead screw 302, the guide pin 306 may define an operating state, thereby creating a stable condition. One or more detents 318 or 320 may be used to ensure that the shift fork 304 remains in its intended position until intentionally changed. Any of several types of detents may be used, including a ball detent or a hook ring. For example, detent 320 corresponds to an engaged position (shown in FIG. 3 ), and detent 318 corresponds to a disengaged position, which will be described next.

[0033] FIG. 4 shows another example of the partial cross-sectional view of the axle decoupler system 100 in FIG. 1 when the axle is decoupled from the wheel hub 300. The electric motor 106 rotates the lead screw 302, translating the shift fork 304 to the right as shown, compared to the state shown in FIG. 3. The fork portion 304A has moved the sliding ring 308 to the right. The splines 310 of the sliding ring 308 no longer engage with the splines 316 of the connecting gear 314. As such, the outer CV joint assembly 104 is no longer coupled to the wheel hub 300 and is disengaged from the wheel hub 300. Therefore, the motor is no longer able to drive the wheel of the wheel hub 300. Furthermore, rotation of the wheel hub 300 no longer rotates the axle of the outer CV joint assembly 104.

[0034] The above example illustrates that an axle decoupler system (e.g., axle decoupler system 100) can include an axle decoupler (e.g., axle decoupler 102) configured to selectively couple an axle (e.g., outer CV joint assembly 104) of a vehicle to a wheel hub (e.g., wheel hub 300) of the vehicle. The axle decoupler can include a slide ring (e.g., slide ring 308) having a first spline (e.g., spline 310) coupled to a second spline (e.g., spline 112) on the axle. The slide ring has a first position (e.g., shown in FIG. 4 ) in which the first spline is not coupled to a third spline (e.g., spline 316) on the wheel hub, and a second position (e.g., shown in FIG. 3 ) in which the first spline is also coupled to the third spline.

[0035] Figure 5 shows an example of a partial cross-sectional view of the axle decoupler system 100 of Figure 1. In this illustration, the sliding ring 308 (e.g., of Figures 3-4) is omitted for clarity. As such, splines 310 on the outer CV joint assembly 104 and splines 316 on the wheel hub 300 become visible in this perspective view.

[0036] One challenge in the engagement operation can be that the splines 310 and 316 do not always mesh when the outer CV joint assembly 104 and the wheel hub 300 are rotating at the same speed. If the splines 310 and 316 do not mesh when they should, some additional functionality can be utilized. Here, a one-way chamfer 500 can be formed on some or all of the splines 316. When the sliding ring is forced into engagement, the one-way chamfer 500 allows the sliding ring to move only in the opposite direction of rotation, i.e., the negative direction. In contrast, if the sliding ring, which remains connected to the outer CV joint assembly 104, needs to move in the positive direction, this also causes additional rotation of the outer CV joint assembly 104. Such additional rotation places additional load on the one-way clutches 118 and 120, which may require a more powerful motor than the electric motor 106. Instead, using the one-way chamfer 500 reduces the load on the one-way clutches 118 and 120 upon engagement.

[0037] FIG. 6 shows an example control strategy 600 for a motor. Control strategy 600 may be used with one or more other examples described elsewhere herein. Control strategy 600 illustrates example states 602-610 that may occur while an axle engages with a wheel hub. As illustrated in the example below, full engagement occurs only at the end of control strategy 600 (e.g., upon the transition between states 608 and 610). For each state, the revolutions per minute (RPM) of the wheel and axle are listed, and graphs of axle RPM, motor torque, and sliding ring engagement position are presented.

[0038] State 602 may occur while the wheels are disengaged from the axles to conserve energy. The wheels may be at R1 RPM (e.g., corresponding to the vehicle traveling at some normal level of speed), while the axles are now at zero RPM. Given that the wheels are disengaged, there may be no torque in the system. In state 602, the motor controller may receive a command to engage the vehicle's motor. For example, the driver may command T1 newton meters (Nm) of torque (e.g., 100% of the available torque).

[0039] In state 604, the motor may apply torque such that the motor rotor accelerates to match the wheel reference speed, as shown in graph 612. Thus, the wheel may maintain R1 RPM and the axle may accelerate from zero to R1 RPM, as shown in graph 614. In this manner, the motor controller may cause the one-way clutch(es) to preload the wheel hub by an amount less than T2 Nm. For example, T2 is much less than T1.

[0040] In state 606, the motor controller commands zero torque, as shown by graph 612, so there is no torque in the system. Therefore, the rotor decelerates, as shown by graph 614. The axle may decrease from R1 RPM to R2 RPM, where R2 is lower than but substantially equal to R1. The wheel may be maintained at R1 RPM. The actuator (e.g., fork portion 304A in FIG. 3) begins to move the sliding ring into engagement with the coupler gear of the wheel hub. Graph 616 shows that the sliding ring has risen in engagement but is not yet fully engaged. For example, a unidirectional chamfer on the coupler gear may guide the sliding ring into engagement.

[0041] At state 608, the splines on the slide ring may pass through the lead-in chamfer on the coupler gear. Thus, the actuator may move the slide ring to its final position, as shown in graph 616. Here, both the wheel and axle may be at R1 RPM (i.e., they have a common rotational speed) and there is no torque in the system. That is, terminating the engagement between the slide ring and wheel hub may be facilitated by a unidirectional chamfer that moves the slide ring against the direction of rotation of the slide ring and wheel hub.

[0042] In state 610, the motor controller can command the full requested torque. As such, a torque of T1 Nm can be produced in the system, as shown in graph 612. Here, the wheels and axles can both be at R1 RPM.

[0043] The control strategy 600 may then include disengaging the axle and wheel hub from one another, which may correspond to changing from the example situation shown in Figure 3 to the example situation shown in Figure 4. With substantially no torque applied to the motor, the sliding ring may move in the opposite direction compared to when engaged.

[0044] FIG. 7 schematically illustrates an example of a vehicle axle 700 having two axle decoupler systems 702 and 704. Each of the axle decoupler systems 702 and 704 may be substantially similar to or identical to the axle decoupler system 100 in FIG. 1. The axle decoupler system 702 is coupled to a wheel hub 706 of a wheel 708, and the axle decoupler system 704 is coupled to a wheel hub 710 of a wheel 712. The vehicle axle 700 may be driven by one or more motor units 714. For example, the motor units 714 may also provide gear reduction. As such, two axle decoupler systems may be used per axle. For example, the vehicle axle 700 may be the rear or front axle of the vehicle.

[0045] FIG. 8 schematically illustrates an example of a vehicle axle 800 having one axle decoupler system 802. The axle decoupler system 802 may be substantially similar to or identical to the axle decoupler system 100 in FIG. 1. The axle decoupler system 802 is coupled to a wheel hub 804 of a wheel 806. Another wheel 808, in contrast, may not have an axle decoupler system. The vehicle axle 800 may be driven by one or more motor units 810. For example, the motor units 810 may also provide gear reduction and have an open differential. As such, one axle decoupler system may be used for the axle. For example, the vehicle axle 800 may be the rear or front axle of the vehicle.

[0046] As used throughout this specification, the terms "substantially" and "about" are used to describe and take into account small variations, such as those due to processing variations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Also, as used herein, indefinite articles such as "a" or "an" mean "at least one."

[0047] It should be understood that all combinations of the above concepts, and additional concepts discussed in more detail below, (provided that such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0048] Although several implementations have been described, it will nevertheless be understood that various modifications may be made without departing from the spirit and scope of the specification.

[0049] Additionally, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Additionally, other processes may be provided or processes may be eliminated from the described flows, and other components may be added to or deleted from the described systems. Accordingly, other implementations are within the scope of the following claims. While certain features of the described implementations are shown as described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and variations that fall within the scope of these implementations. They have been presented by way of example only, and not limitation, and it should be understood that various changes in form and details may be made. Except for mutually exclusive combinations, any portions of the apparatus and / or methods described herein may be combined in any combination. The implementations described herein may include various combinations and / or subcombinations of the functions, components, and / or features of the different described implementations.

Claims

1. an axle decoupler configured to selectively couple an axle of a vehicle to a wheel hub of said vehicle, said axle decoupler comprising: a slide ring including a first spline coupled to a second spline on the axle, the slide ring including a first position where neither the first spline nor a third spline on the wheel hub is coupled, and a second position where neither the first spline nor the third spline is coupled; and an electric motor for moving the sliding ring to the first position or the second position; and A one-way clutch connecting the axle and the wheel hub to each other 1. An axle decoupler system comprising:

2. 2. The axle decoupler system of claim 1, wherein the axle decoupler further comprises a lead screw rotated by the electric motor, the lead screw configured to translate a shift fork that moves the sliding ring to the first position or the second position.

3. The axle decoupler system of claim 2 , wherein the axle decoupler further comprises a guide pin for the shift fork.

4. 4. The axle decoupler system of claim 3, wherein the axle decoupler further comprises a first detent for the shift fork on the guide pin.

5. The axle decoupler system of claim 4 , wherein the first detent is a ball detent or a hug ring.

6. 5. The axle decoupler system of claim 4, wherein the first detent corresponds to the first position, and the axle decoupler further comprises a second detent for the shift fork on the guide pin, the second detent corresponding to the second position.

7. 7. The axle decoupler system of claim 1, comprising at least two one-way clutches connecting the axle and the wheel hub to each other.

8. 7. The axle decoupler system of claim 1, wherein the axle decoupler further comprises a unidirectional chamfer on the third spline of the wheel hub.

9. The axle decoupler system of claim 1 , wherein the axle decoupler further comprises a first bearing between the axle and the wheel hub.

10. 10. The axle decoupler system of claim 9, wherein the axle decoupler further comprises a housing and a second bearing between the housing and the axle.

11. The axle decoupler system of claim 9 further comprising a bushing between the axle and the wheel hub.

12. 7. The axle decoupler system of claim 1, wherein the axle is a motor half shaft.

13. The axle decoupler system of claim 12 , wherein the half shaft is included in a constant velocity joint assembly of the motor.

14. receiving a first command to engage a motor of a vehicle whose wheel hub is currently disengaged from the axle of the motor; accelerating the axle to a rotational speed of the wheel hub in response to the first command, a one-way clutch connecting the axle and the wheel hub to one another is preloaded; in response to the axle reaching the rotational speed of the wheel hub, commanding zero torque from the motor causing the axle to decelerate and moving a sliding ring coupled to the axle into engagement with the wheel hub; terminating the engagement between the slide ring and the wheel hub, the axle and the wheel hub having a common rotational speed; and commanding torque from the motor according to the first command after the engagement between the sliding ring and the wheel hub is terminated. A method for providing the above.

15. 15. The method of claim 14, wherein when the first command is received, the rotational speed of the axle is zero.

16. 16. The method of claim 14 or 15, wherein the slide ring is moved by rotating a lead screw configured to translate a shift fork that moves the slide ring between the first and second positions.

17. 17. The method of claim 16, wherein a first detent for the shift fork on a guide pin corresponds to the first position.

18. 18. The method of claim 17, wherein a second detent for the shift fork on the guide pin corresponds to the second position.

19. 16. The method of claim 14 or 15, wherein terminating the engagement between the slide ring and the wheel hub is facilitated by unidirectional chamfers on the splines of the wheel hub, the unidirectional chamfers causing the slide ring to move in a direction opposite to the direction of rotation of the slide ring and the wheel hub.

20. 16. The method of claim 14 or 15, further comprising receiving a second command to disengage the wheel hub from the axle, and in response to the second command, moving the sliding ring in an opposite direction toward disengagement from the wheel hub.

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