Axle assembly

1. An axle assembly comprising:

an axle housing;

a locking differential assembly received in the axle housing, the locking differential assembly having a differential input member, first and second differential output members, first and second clutch dogs, at least one return spring, a movable member, a clutch fork and a linear motor, the differential input member and the first and second differential output members being rotatable about a rotary axis, the first clutch dog being coupled to the second differential output member for rotation therewith, the second clutch dog being non-rotatably but axially slidably coupled to the differential input member, the second clutch dog being movable between a first position, in which the first and second clutch dogs are engaged to one another to thereby inhibit relative rotation between the differential input member and the second differential output member, and a second position in which the first and second clutch dogs are disengaged from one another to thereby permit relative rotation between the differential input member and the second differential output member, the at least one return spring biasing the second clutch dog toward the second position, the movable member defining a clutch fork groove and being movable between a third position, which physically positions the second clutch dog in the first position, and a fourth position, which permits the second clutch dog to be moved by the at least one return spring into the second position, a clutch fork received in the clutch fork groove and pivotable about the rotary axis, the linear motor being coupled to the axle housing and having a motor output member that engages the clutch fork but which is not fixedly coupled to the clutch fork; and

at least one guide pin coupled to the axle housing and engaging the clutch fork, the at least one guide pin being configured to guide the clutch fork along a desired path of movement that is parallel to the rotary axis.

2. The axle assembly of claim 1 , wherein the at least one guide pin is threadably coupled to the axle housing.

3. The axle assembly of claim 1 , wherein the at least one guide pin comprises first and second guide pins that are disposed along guide pin axes that are parallel to the desired path of movement and wherein the motor output member of the linear motor contacts the clutch fork at a location that is disposed between the guide pin axes.

4. The axle assembly of claim 1 , wherein the linear motor comprises a compliance spring and an intermediate output member and wherein the compliance spring permits movement of the intermediate output member relative to the motor output member.

5. A front axle assembly comprising:

an axle housing;

a locking differential assembly received in the axle housing, the locking differential assembly having a differential case, a helical gearset, which is received in the differential case, and first and second clutch dogs, the differential case defining a plurality of pinion bores, the helical gearset having first and second helical side gears and a plurality of pinion sets, each of the pinion sets being received in an associated one of the pinion bores and having a first helical pinion, which is meshingly engaged to the first helical side gear, and a second helical pinion that is meshingly engaged with the second helical side gear, the first and second helical pinions of each pinion set being meshingly engaged to one another, the first clutch dog being coupled to the second helical side gear for rotation therewith, the second clutch dog being non-rotatably but axially movably coupled to the differential case, the second clutch dog being movable between a first position, in which the first and second clutch dogs are engaged to one another to thereby inhibit relative rotation between the second helical side gear and the differential case, and a second position in which the second clutch dog is disengaged from the first clutch dog to thereby permit relative rotation between the second helical side gear and the differential case; and

an electrically operated linear motor coupled to the axle housing, the linear motor having a motor output member that is selectively movable to urge the second clutch dog toward the first position.

6. An axle assembly comprising:

a housing; and

a locking differential assembly having a differential case, a helical gearset and a locking mechanism, the differential case being mounted in the housing for rotation about an axis and defining a plurality of pinion bores, the helical gearset comprising first and second helical side gears and a plurality helical pinions, the first and second helical side gears being rotatable about the axis, the helical pinions being received in the pinion bores and transmitting rotary power between the differential case and the first and second helical side gears, the locking mechanism having first and second clutch dogs and a plurality of return springs, the first clutch dog being fixed to the first helical side gear for rotation therewith, the second clutch dog being non-rotatably but axially slidably coupled to the differential case and movable between a first position, in which the first and second clutch dogs are engaged to one another to inhibit relative rotation between the first helical side gear and the differential case, and a second position in which the first and second clutch dogs are separated axially along the axis to permit relative rotation between the first helical side gear and the differential case, each of the return springs being received in the differential case and disposed between the second clutch dog and an associated one of the helical pinions, the return springs cooperating to bias the second clutch dog toward the second position.

7. The axle assembly of claim 6 , wherein the helical pinions comprise a plurality of pinion gear sets, each of the pinion bores housing an associated one of the pinion gear sets, each of the pinion gear sets comprising a first helical pinion, which is meshingly engaged to the first helical side gear, and a second helical pinion that is meshingly engaged to the second helical side gear, the first and second helical pinions of each pinion gear set being meshingly engaged, and wherein the return springs are disposed between the second clutch dog and the first helical pinions.

8. The axle assembly of claim 7 , wherein each of the second helical pinions comprises a gear member and a brake shoe, the brake shoe being received in an associated one of the pinion bores and being mounted on the gear member.

9. The axle assembly of claim 8 , wherein each of the return springs is received through an associated one of the brake shoes.

10. The axle assembly of claim 7 , wherein the first clutch dog defines a plurality of teeth that are spaced circumferentially apart about the axis, and wherein each of the teeth has a root and is formed with a feature that is configured to reduce stress at the root.

11. The axle assembly of claim 10 , wherein the feature comprises a groove that is formed centrally on an associated one of the teeth in a circumferential direction, the groove extending from a radially inward point on the associated one of the teeth and through an outer circumferential end of the associated one of the teeth.

12. A method for assembling an axle assembly, the method comprising:

providing an axle housing that defines a differential cavity and an aperture that intersects the differential cavity;

securing a linear motor to the axle housing to close the aperture, the linear motor having a motor output member;

installing a locking differential assembly into the differential cavity, the locking differential assembly having a differential input member, first and second differential output members, first and second clutch dogs, at least one return spring, a movable member and a clutch fork, the differential input member and the first and second differential output members being rotatable about a rotary axis, the first clutch dog being coupled to the second differential output member for rotation therewith, the second clutch dog being non-rotatably but axially slidably coupled to the differential input member, the second clutch dog being movable between a first position, in which the first and second clutch dogs are engaged to one another to thereby inhibit relative rotation between the differential input member and the second differential output member, and a second position in which the first and second clutch dogs are disengaged from one another to thereby permit relative rotation between the differential input member and the second differential output member, the at least one return spring biasing the second clutch dog toward the second position, the movable member defining a clutch fork groove and being movable between a third position, which physically positions the second clutch dog in the first position, and a fourth position, which permits the second clutch dog to be moved by the at least one return spring into the second position, the clutch fork being received in the clutch fork groove such that the clutch fork is pivotable about the rotary axis, the clutch fork abutting but not being fixedly coupled to the movable member; and

installing at least one guide pin to the axle housing, the at least one guide pin engaging the clutch fork and being configured to guide the clutch fork along a desired path of movement that is parallel to the rotary axis.

13. The method of claim 12 , wherein the at least one guide pin comprises first and second guide pins that are disposed along guide pin axes that are parallel to the desired path of movement and wherein the motor output member of the linear motor contacts the clutch fork at a location that is disposed between the guide pin axes.