The present invention generally relates to a differential with improved lubrication flow to a set of clutch plates.
Cutch-type limited slip differentials typically have two clutch packs each of which being mounted between the differential case and an associated side gear. Each clutch pack can include a set of first clutch plates, which can be non-rotatably coupled to the differential case, and a set of second clutch plates that can be non-rotatably coupled to an associated side gear and interleaved with the first clutch plates. The first and second clutch plates can be engaged to and released from one another depending on the amount of torque that is transmitted through the differential. With increasing torque transmission, meshing engagement of the side gears with the pinion gears of the differential can urge the side gears axially apart from one another so as to compress the clutch packs so that the first and second clutch plates frictionally engage one another. It will be appreciated that frictional engagement of the first and second clutch plates will couple the side gears to the differential case to prevent speed differentiation between the side gears when the counter-torque acting on the side gears is smaller than the clutch torque produced by the clutch packs.
Lubrication for the clutch packs in a clutch-type limited slip differential can be introduced through large openings in the sides of the differential case. In such situations, it is desired that the lubrication entering the differential case migrate around and behind the side gears and travel to and between the first and second clutch plates. We have noted, however, that the path for this lubrication is frequently complex and that in some situations, the complexity of this path may limit the amount of lubrication that can be transmitted to the first and second clutch plates.
Another drawback with the known lubrication systems for the clutch packs in a clutch-type limited slip differential concerns the effectiveness with which the first and second clutch plates can be lubricated. In this regard, the first and second clutch plates tend to be best lubricated when the differential is operated at different rotational speeds so that the first and second clutch plates are alternately squeezed together and then allowed to disengage or separate. In situations where the differential is operated at a moderate (or higher) rotational speed that is relatively consistent (e.g., as when a vehicle is operated on a relatively flat and straight highway with the cruise control set to cause the vehicle to travel at a desired highway speed), the amount of lubrication that is received by the clutch plates can be less than desired, which can lead to undesired noise or shudder when the differential is operated in a cornering event (i.e., when a vehicle equipped with the differential travels around a corner).
In view of the above remarks, there remains a need in the art for an improved differential. There also remains a need in the art for an improved method for providing lubrication to the clutch plates in a clutch-type limited slip differential.
This section provides a general summary of some aspects of the present disclosure and is not a comprehensive listing or detailing of either the full scope of the disclosure or all of the features described therein.
In one form, the present teachings provide a differential with a differential case, a differential gear set and a clutch pack. The differential case has a first end, a second end opposite the first end and an internal cavity between the first and second ends. A plurality of first lubrication apertures are formed through the first end and extend into the internal cavity. The differential gear set is mounted to the differential case in the internal cavity and includes a first side gear disposed proximate the first end of the differential case. The first clutch pack is disposed between the first end and the first side gear. The clutch pack includes a plurality of first clutch plates and a plurality of second clutch plates. The first clutch plates are non-rotatably coupled to the differential case, while the second clutch plates are non-rotatably coupled to the first side gear. Each of the plurality of first and second clutch plates include a plurality of second lubrication apertures extend axially therethrough.
In another form, the present teachings provide a method for operating an axle assembly having an axle housing, a differential and a pair of differential bearings that support the differential on the axle housing for rotation about an axis. The differential has a differential case, a pair of friction clutches and a differential gear set with a pair of side gears. The method includes: rotating the differential about the first axis; directing a lubricant onto the differential bearings, the lubricant being passed through the differential bearing toward the differential due to centrifugal force; and passing the lubricant passed through the differential bearing axially through the differential case and axially through at least a portion of the friction clutches.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application and/or uses in any way.
The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. The drawings are illustrative of selected teachings of the present disclosure and do not illustrate all possible implementations. Similar or identical elements are given consistent identifying numerals throughout the various figures.
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The differential assembly 34 can be a clutch-type limited slip differential and can include a differential case 100, a pair of differential bearings 102, a ring gear 104, a differential gear set 106 and a pair of clutch packs 108. In the particular example provided, the differential case 100 includes is unitarily formed, but those of ordinary skill in the art will appreciate that the differential case 100 may be unitarily formed or may be formed from two or more case components. The differential case 100 can comprise a first end 112, a second end 114, a mounting flange 116, a pair of trunnions 118 and a gear cavity 120 into which the differential gear set 106 can be received. The gear cavity 120 can be shaped to define a pair of locking elements 122 (
The differential bearings 102 can be any type of bearings, such as angular contact ball bearings (e.g., single row angular contact ball bearings, dual row angular contact ball bearings) or tapered roller bearings, and can include an inner bearing race 130, a plurality of rollers 132, and an outer bearing race 134. The inner bearing race 130 of each differential bearing 102 can be coupled (e.g., press-fit) to a corresponding one of the trunnions 118. The outer bearing race 134 of each differential bearing 102 can be received in a corresponding one of the differential bearing journals 80 (i.e., between a bearing cap 56 and an associated one of the bearing journals 72). In the example provided, the bearing cap 56 can apply a clamping force to the outer bearing race 134 that clamps the outer bearing race 134 to the differential bearing journal 80.
The differential gear set 106 can include a pinion shaft 140, which can extend through the differential case 100 generally perpendicular to the first axis 82, a pair of pinion gears 142, which can be rotatably mounted on the pinion shaft 140, and a pair of side gears 144 that can be in meshing engagement with the pinion gears 142. A bore 145 can be formed through each of the side gears 144. The bore 145 can be configured with a plurality of spline teeth 146. Each of the side gears 144 can include a hub portion 147 that can include a locking element, such as a plurality of spline teeth 148.
Each of the clutch packs 108 can be received in the gear cavity 120 between an associated one of the first and second ends 112, 114 and an associated one of the side gears 144. Each clutch pack 108 can include a set of first friction or clutch plates 150 and a set of second friction or clutch plates 152 that can be interleaved with the first clutch plates 150. The clutch packs 108 can be configured to engage the side gears 144 to the differential case 100 via frictional engagement between the first and second clutch plates 150 and 152, which can be affected by the amount of torque transmitted through a respective one of the side gears 144. More specifically, the side gears 144 can translate axially along the first axis 82 in an amount that depends on the magnitude of the torque that is transmitted from the pinion gears 142 to the side gears 144, to compress or release the clutch packs 108.
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The axle shafts 38 can be received through the axle tubes 58 (
During operation of the vehicle 10 (
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The first lubrication apertures 158 in the first clutch plates 150 can be aligned to the apertures 260 in the differential case 100. It will be appreciated that as the second clutch plates 152 are coupled for rotation with the side gears 144, the second lubrication apertures 168 can be rotated into alignment with the first lubrication apertures 158 to permit fluid communication through the clutch pack 108 and further into the gear cavity 120 to facilitate lubrication of the differential gear set 106. It will also be appreciated that the apertures 260 in the differential case 100 and the first and second lubrication apertures 158 and 168 can be disposed in-line with a space between the inner race 132 and the outer race 134 of the differential bearings 102. Configuration of the lubrication path for lubricating the clutch pack 108 is less complex so that better lubrication can be achieved.
It will be appreciated that third oil galleries (not specifically shown) could be coupled in fluid communication to the first oil gallery 64 and/or second oil gallery 66 to distribute a portion of the lubricant 90 received into the first oil gallery 64 into openings (not specifically shown) in the carrier housing 54 so that such lubricant 90 can be received into the axle tubes 58. The lubricant 90 that is received into the axle tubes 58 can be employed to lubricate wheel bearings and seals, as well as to reject heat to the axle tubes to thereby aid in the cooling of the lubricant 90.
While the second oil galleries 66 have been illustrated as being fed lubricant from the one of the pinion bearings 172 that is closest to the teeth T of the input pinion 170 (i.e., the head bearing), it will be appreciated that the second oil galleries 66 could be fed lubricant from the other one of the pinion bearings 172 (i.e., the tail bearing, which is axially further from the teeth T of the input pinion 170) as shown in
Moreover, while the axle assembly 22 (
It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein, even if not specifically shown or described, so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular examples illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the teachings of the present disclosure, but that the scope of the present disclosure will include any embodiments falling within the foregoing description and the appended claims.