Patent Description:
In automotive applications, an electronically actuated locking differential of the related art may be actuated electronically and is designed for forward-wheel-drive (FWD), rear-wheel-drive (RWD), all-wheel-drive (AWD), and four-wheel-drive (4WD) vehicles to allow the differential to be locked or unlocked when it is so desired. The driver can lock the front and/or rear wheels by manually activating a switch or button mounted to a dash or console of the vehicle. However, as vehicles and associated systems become more complex, vehicle component packaging also becomes more challenging. Accordingly, it is desirable to provide a more compact electronically actuated locking differential. In <CIT> there is disclosed a lock plate for an electronically actuated locking differential, wherein the lock plate comprises a base portion having a first side and an opposite second side; a plurality of radially spaced teeth extending outwardly from the first side; and a plurality of standoffs extending outwardly from the second side. <CIT> further discloses an electronically actuated locking differential comprising: a gear case having opposite first and second ends and a plurality of slots formed in the first end; a differential gear set disposed in the gear case; a lock plate disposed at the gear case first end and configured to selectively engage the differential gear set, wherein the lock plate includes a plurality of standoffs extending through the plurality of slots formed in the gear case first end; and an electronic actuator disposed at the gear case first end and having a stator and an armature, wherein the electronic actuator is operable between an unlocked first mode where the lock plate does not lockingly engage the differential gear set, and a locked second mode where, when the stator is energized, the armature is pulled toward the gear case first end such that the lock plate is pushed into locking engagement with the differential gear set to thereby lock a pair of axle shafts.

The background description provided herein is for the purpose of generally presenting the context of the invention. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.

In one aspect, the present invention is a combination of a lock plate and an armature for an electronically actuated locking differential as it is defined in claim <NUM>.

In addition to the foregoing, the described lock plate may include one or more of the following features: wherein each of the plurality of standoffs are integrally formed with the base portion; wherein each of the plurality of standoffs are circumferentially spaced about the base portion; and wherein each standoff includes an outer lip, the groove disposed between the outer lip and the shoulder portion.

In another aspect, the present invention is an electronically actuated locking differential as it is defined in claim <NUM>. The electronically actuated locking differential includes a gear case having opposite first and second ends and a plurality of slots formed in the first end, a differential gear set disposed in the gear case, and a lock plate disposed at the gear case first end and configured to selectively engage the differential gear set. Each of the plurality of standoffs extends through the plurality of slots formed in the gear case first end. An electronic actuator is disposed at the gear case first end and includes a stator and the armature. The electronic actuator is operable between an unlocked first mode where the lock plate does not lockingly engage the differential gear set, and a locked second mode where, when the stator is energized, the armature is pulled toward the gear case first end such that the lock plate is pushed into locking engagement with the differential gear set for thereby locking a pair of axle shafts.

In addition to the foregoing, the described electronically actuated locking differential may include one or more of the following features: wherein the differential gear set includes a first side gear and a second side gear, the lock plate selectively lockingly engaging the first side gear in the locked second mode.

In addition to the foregoing, in the described electronically actuated locking differential each of the plurality of slots may include a pair of opposed straight walled portions and a pair of opposed rounded portions.

In addition to the foregoing, the described electronically actuated locking differential may include one or more of the following features: a biasing mechanism disposed between the first side gear and the lock plate, the biasing mechanism biasing the lock plate out of engagement with the first side gear; wherein each slot formed in the gear case includes a pair of opposed straight wall portions and a pair of rounded end portions; wherein the lock plate is disposed between the first side gear and the stator; and wherein the stator and armature are disposed outside of the gear case and the lock plate base portion is disposed within the gear case.

With initial reference to <FIG>, an electronically actuated locking differential is generally indicated at <NUM>. The electronically actuated locking differential <NUM> generally includes a gear case <NUM> formed by coupling (e.g., bolting) a hub portion (not shown) and a housing portion <NUM>. In other embodiments, gear case <NUM> may be a one-piece housing <NUM>. Torque input to the differential is typically by an input ring gear (not shown), which may be attached to a flange (not shown) of the gear case <NUM>. Each of the hub portion and the housing portion <NUM> of the gear case <NUM> may be mounted to a bearing set (not shown) to provide rotational support for the differential <NUM> relative to an outer housing or carrier (not shown).

The gear case <NUM> defines a gear chamber <NUM>, which generally supports a differential gear set including a pair of input pinion gears (not shown) rotatably mounted on a pinion shaft (not shown), which is secured relative to the gear case <NUM> by any suitable mechanism. The pinion gears are meshingly engaged with a respective pair of left and right side gears <NUM> (only one shown). The side gears <NUM> define respective sets of internal, straight splines that are adapted to be in splined engagement with mating external splines on a respective pair of left and right axle shafts (not shown).

The electronically actuated locking differential <NUM> further includes a rotation prevention mechanism <NUM> configured to selectively prevent relative rotation of the left and right axle shafts. The rotation prevention mechanism <NUM> is disposed at least partially within gear case <NUM> and generally includes a lock plate <NUM> operably associated with side gear <NUM> (the first output gear), and an electronic actuator <NUM>.

As illustrated in <FIG>, in the example embodiment, the lock plate <NUM> is near net forged for reduced weight and tapered for die release. The near net forged lock plate <NUM> is subsequently worked (e.g., machined) to form the lock plate <NUM> shown in <FIG> and <FIG>.

With additional reference to <FIG> and <FIG>, the lock plate <NUM> is spaced apart from the side gear <NUM> and is slidable along the outer surface of side gear <NUM>. In the example embodiment, the lock plate <NUM> generally includes a base portion <NUM> and a plurality of standoffs <NUM>. The lock plate <NUM> is biased toward a non-actuated, unlocked mode by a biasing mechanism <NUM> such as, for example, a wave spring <NUM> (see <FIG>).

As shown in <FIG>, the base portion <NUM> is generally annular and includes a first side <NUM>, an opposite second side <NUM>, and a generally circular central aperture <NUM>. The first side <NUM> includes a plurality of radially spaced dog teeth <NUM> configured to selectively engage the side gear <NUM>, as described herein in more detail. As illustrated, the plurality of standoffs <NUM> extend outwardly from the base portion second side <NUM>.

In the example embodiment, each standoff <NUM> includes a proximal end <NUM> and a distal end <NUM>. The proximal end <NUM> is integrally coupled with the base portion second side <NUM> such that standoffs <NUM> extend orthogonal to or substantially orthogonal thereto. The distal end <NUM> generally defines an outer lip <NUM>, a groove <NUM>, and a shoulder portion <NUM> formed therein as the standoff <NUM> extends from the distal end <NUM> toward the proximal end <NUM>.

With continued reference to <FIG>, in the example embodiment, the electronic actuator <NUM> is disposed primarily external to the gear case <NUM> in a location opposite the flange at a bell end of the gear case <NUM> and adjacent to side gear <NUM>. The electronic actuator <NUM> generally includes an armature <NUM> and a stator <NUM>, which defines a cavity <NUM> configured to receive an electromagnetic coil <NUM>. The coil <NUM> is configured to be energized via electrical leads (not shown) and receive a current, such as direct current (DC), from a power source such as a vehicle battery (not shown).

As shown in <FIG>, in the example embodiment, an inner diameter portion of the armature <NUM> abuts against lock plate shoulder portion <NUM>. The armature <NUM> is secured in place to the lock plate <NUM> by a snap ring <NUM>, which is received within the groove <NUM> located between the outer lip <NUM> and the shoulder portion <NUM> of the standoff <NUM>. That stator <NUM> is generally annular and spaced apart from the armature <NUM> by a gap <NUM>. When energized, the stator <NUM> generates a magnetic field, which draws the armature <NUM> toward the stator <NUM> to close the gap <NUM>. This movement of armature <NUM> is subsequently imparted to the lock plate <NUM> and slides the lock plate <NUM> leftward (as shown in <FIG>) into locking engagement with the side gear <NUM>.

With additional reference to <FIG>, the gear case <NUM> is formed with circumferentially spaced slots <NUM> each configured to receive one standoff <NUM>. In the example embodiment, each slot <NUM> includes rounded end portions <NUM> and generally straight wall portions <NUM>. The lock plate standoffs <NUM> have radial features <NUM> (<FIG>) corresponding to the rounded end portions <NUM> that are cut back with a reduced radial angle of center to allow for lash. Such an arrangement with standoffs <NUM> extending through the slots <NUM> of gear case <NUM> advantageously enables higher loads and reduced stresses. In this way, all or substantially all of the torque goes through the standoffs <NUM>.

During normal, straight-ahead operation of a vehicle within which the differential <NUM> is employed, no differentiation occurs between the left and right axle shaft or side gears <NUM>. Therefore, the pinion gears do not rotate relative to the pinion shaft. As a result, the gear case <NUM>, pinion gears, and side gears <NUM> all rotate about an axis of rotation as if the gear case <NUM>, pinion gears, and side gears <NUM> are a solid unit.

When direct current (DC) power is supplied to the electromagnetic coil <NUM>, magnetic energy is generated within the stator <NUM>, which creates an attractive force between the stator <NUM> and the armature <NUM>, thereby causing the armature <NUM> to move toward the gear case <NUM>. This in turn causes the lock plate <NUM> to move leftward (as shown in <FIG>) toward and into locking engagement with side gear <NUM> as it compresses biasing mechanism <NUM>. In this way, lock plate teeth <NUM> meshingly engage side gear teeth <NUM> (<FIG>) until lock plate <NUM> exerts a required retarding torque on the side gear <NUM>, locking it to the differential case <NUM> and thus locking the left and right axle shafts independent of driveline rotation.

The differential <NUM> may be controlled manually, wherein a driver of the vehicle manually selects "locked" mode (rather than "unlocked" mode) to operate the differential <NUM>. For example, when, say the vehicle is at rest, the driver simply manually activates a switch or button (not shown), such as a simple momentary-type "on/off" toggle or rocker switch or push button, mounted to a dash or console (not shown) of the vehicle. In this way, an electric circuit (not shown) is closed, thereby turning on current in the circuit and a lamp (not shown) located in or near the toggle switch or push button to indicate to the driver that the differential is actuated. Current flows in the circuit and ultimately to the electromagnetic coil <NUM> of the differential <NUM>. The differential <NUM> then operates in the "locked" mode (i.e., when the vehicle is in first gear or reverse). In this way, the first output gear <NUM> is locked relative to the gear case <NUM>, preventing any further differentiation between the first output gear <NUM> and gear case <NUM>.

Described herein are systems and methods for a lock plate of an electronic locking differential. The lock plate includes near net -forged integrated standoffs on an opposing surface from the lock teeth. The standoffs are straight walled and orthogonal to the differential centerline. The standoffs increase the interface area between the lock plate and differential case to reduce contact stress and provide a robust design. The lock plate improves unlock performance, provides allowance for lock detection integration, and reduces bill of material complexity. Additionally, the lock plate accommodates the use of lower cost materials and heat treatment options, as well as improves compatibility assembling the differential into a one-piece differential case.

Claim 1:
A combination of a lock plate (<NUM>) and an armature (<NUM>) for an electronically actuated locking differential (<NUM>), comprising:
an armature (<NUM>), and
a lock plate (<NUM>) comprising:
a base portion (<NUM>) having a first side (<NUM>) and an opposite second side (<NUM>);
a plurality of radially spaced teeth (<NUM>) extending outwardly from the first side (<NUM>); and
a plurality of standoffs (<NUM>) extending outwardly from the second side (<NUM>), each of the plurality of standoffs (<NUM>) extending from a proximal end (<NUM>) to a distal end (<NUM>) and at the distal end (<NUM>) having an outer diameter and an inner diameter, the outer diameter including (i) a groove (<NUM>) that receives a snap ring (<NUM>) and (ii) a shoulder portion (<NUM>) arranged closer to the proximal end (<NUM>) than the groove (<NUM>), wherein a portion of the armature (<NUM>) is disposed between each of the plurality of standoffs (<NUM>) and the snap ring (<NUM>) at the shoulder portion (<NUM>).