Patent ID: 7377343

Claim:
A vehicle drive train comprising: a first drive system that is adapted to transmit rotary power from a first power source to a first set of vehicle wheels; and a second drive system that is adapted to selectively transmit rotary power to a second set of vehicle wheels, the second drive system including a pair of drive units, each drive unit having a motor, a friction clutch, a first gear, a second gear and a wheel hub, the motor having a motor output shaft, the friction clutch including a first portion, which is coupled for rotation with the motor output shaft, a second portion, which is coupled for rotation with the first gear, a plurality of sliders received between the first and second portions, and a plurality of springs that bias the sliders in a radially inward direction toward one of the first and second portions, each of the sliders being received between a pair of radially extending wall members, each of the springs being received between an associated one of the sliders and the other one of the first and second portions between two of the radially extending wall members, the first gear being meshingly engaged to the second gear, the second gear driving the wheel hub; wherein the sliders move radially outward at a predetermined rotational speed to disengage the one of the first and second portions to rotationally decouple the motor output shaft from the wheel hub.