Abstract: A transfer case is disclosed for a four-wheel drive vehicle. The transfer case includes an interaxle differential and a transfer clutch for controlling speed differentiation and torque biasing across the interaxle differential. A mode shift mechanism is provided for selectively coupling one or more components of the interaxle differential to the input shaft for establishing a full-time four-wheel drive mode, a locked four-wheel drive mode, and a Neutral mode. A controller controls actuation of the transfer clutch and the mode shift mechanism in response to a mode signal indicating which drive mode has been selected by the vehicle operation.

Abstract: A viscous coupling apparatus having enhanced torque progression characteristics. The viscous coupling apparatus includes two sets of viscous coupling plates which are interleaved and mounted with rotatable members for relative rotation therebetween. Each plate is a generally circular ring of thin plate material and has one or more openings formed therein. The openings include coined edge surfaces that form an inclined surface and an arcuate wiping surface. The coined edges of inner and outer coupling plates oppose one another and facilitate the removal of viscouse fluid from in between and wiping of viscous fluid from the surface of adjacent coupling plates when relative rotation and frictional contact occurs between adjacent plates without generating excessive wear on either one of the plates. The removal of the viscous fluid promotes enhanced frictional contact between the facing adjacent plate surfaces and results in an increased torque transmission characteristic.

Abstract: A viscous coupling apparatus having enhanced torque progression characteristics. The viscous coupling apparatus includes two sets of viscous coupling plates which are interleaved and mounted with rotatable members for relative rotation therebetween. Each plate is a generally circular ring of thin plate material and has one or more openings formed therein. The openings include coined edge surfaces that form an inclined surface and an arcuate wiping surface. The coined edges facilitate the wiping and removal of viscous fluid from the surface of an adjacent coupling plate when relative rotation and frictional contact occurs between adjacent plates without generating excessive wear on one of the mating plates. The removal of the viscous fluid promotes enhanced frictional contact between the facing adjacent plate surfaces and results in an increased torque transmission characteristic.

Abstract: A method of hardening and flattening a viscous coupling plate generally combining a heat treatment process followed by roller leveling is disclosed. The heat treatment process produces an epsilon iron nitride surface layer of the desired hardness on the plate. Subsequent to the heat treatment, the plates are passed through a series of leveling rolls to produce a sufficiently flat plate. The flat rolling process can incorporate a single pass or multiple passes through the leveling rolls. The method of the present invention eliminates any distortion in the plates and brings them within any required flatness specifications, as well as producing viscous coupling plates that exhibit improved resistance to permanent deformation under operating conditions.