Abstract
A power transmission device is provided with a casing drivingly coupled to the power source to create a rotation about an axis, and a differential gear set supported by the casing to rotate with the casing about the axis. The differential gear set includes a pair of side gears capable of making a differential motion from each other, a friction section interposed between the casing and the differential gear set, or internal to the differential gear set, to frictionally limit the differential motion, a disconnect device coupled to one of output shafts for connectably disconnecting one of the side gears from the one of the output shafts, and a cam structure coupled directly or indirectly to the friction section to convert a torque in a direction for accelerating the rotation into a thrust force in an axial direction to exert the thrust force on the friction section.