US Patent 7144347 Differential limiting device

A differential limiting device includes a planetary gear mechanism, in which a planetary carrier rotatably distributes the rotational power of a front housing to a ring gear and a sun gear through planetary gears and hence, to a first inner shaft and a second inner shaft which are rotatable respectively with the ring gear and the sun gear. A pilot clutch, when in friction engagement, brings about relative rotation between a cam ring and the second inner shaft to axially move the second inner shaft by the action of a cam mechanism provided therebetween. The axial movement of the second inner shaft causes the first inner shaft to be axially moved, whereby a main clutch arranged between the front housing and the first inner shaft is brought into friction engagement. When in friction engagement, the main clutch limits the relative rotation between the ring gear and the planetary carrier.