Positive Drive Differential

A differential assembly for a four wheel drive vehicle, the four wheel drive vehicle having a primary drive axle and a secondary drive axle, the secondary drive axle having two drive axle segments, the differential assembly configured to operably couple to the secondary drive axle, the differential assembly comprising:

• a differential housing;
• an input pinion including a pinion gear and a pinion input shaft attached to the pinion gear, the pinion gear located within the differential housing with a portion of the pinion input shaft extending out of an opening in the differential housing, the pinion input shaft configured to operably engage with a drive shaft so as to permit the drive shaft to rotate the pinion shaft;
• a bi-directional overrunning clutch assembly located within the differential housing and configured to engage with the two drive axle segments, the bi-directional overrunning clutch assembly configured to transmit torque, when engaged, between the pinion gear and the drive axle segments, the bi-directional overrunning clutch assembly including:
• a ring gear engaged to the pinion gear;
• a clutch housing attached to or formed integral with the ring gear wherein the ring gear is positioned radially outward from an inner surface of the clutch housing, the inner surface having a contoured surface formed on at least a portion of the inner surface;
• two roller clutch assemblies located radially inward from the inner surface of the clutch housing, each roller clutch assembly including a roll cage with a plurality of spaced apart slots that extend radially through the roll cage from its outer surface to its inner surface, a roll located in each slot and sized so that it can rotate within the slot, and at least one spring biasing the rolls against movement radially outward relative to the roll cage;
• and
• a roll cage coupler positioned between the two roller clutch assemblies for intermittently coupling the two roll cages to limit relative motion of the roll cages with respect to one another;
• and
• two hubs, each hub located radially inward of one of the roller clutch assemblies, the hubs being axially aligned with one another so as to rotate about a common axis, each hub configured to engage with an end of a corresponding drive axle segment, each hub located radially inward from a plurality of the rolls of the associated roller clutch assembly, each hub having a contoured exterior portion with a plurality of recessed channels formed on the contoured exterior portion of the hub, the recessed channels each extending axially along the contoured exterior portion parallel to a longitudinal axis of the hub, the recessed channels are each sized so that a portion of a roll can seat within the channel, the recessed channels are spaced about the circumference of the contoured exterior portion of the hub;
• the at least one spring biasing the rolls in its roller clutch assembly such that each of the rolls is seated in one of the recessed channels when the roll in the roller clutch assembly is not overrunning, the seating of the rolls in the recessed channels providing a connection between the associated roll cage and hub so as to cause the roll cage to initially move with its associated hub.