PURPOSE: To obtain torque transmission characteristics linear to relative rotation by adopting, for the fluid regulating means which generates fluid pressure, a means operated by a plate valve which is fully closed on ring contact with the peripheral edge of the end of an opening of a fluid channel and opens with the flexible deformation in response to the pressure of a fluid chamber.

CONSTITUTION: A plate valve 90 changes its opening in response to the differential pressure between the internal pressure of a cylinder chamber 50 and the internal pressure of an accumulator chamber 70. On occurrence of any rotational speed difference between both output shafts 15, 16, relative rotation is caused on a cover 20 and a rotor 30, which in turn causes a piston 40 circumferentially in contact with a cam surface 21 to make reciprocal movements in the radial direction. When such a movement is directed toward the center of the axis of rotation to compress the volumetric capacity of the cylinder chamber 50, the pressure inside the cylinder chamber 50 increases due to the flow resistance caused by the outflow restriction by the valve 90. A hydraulic force of oil pressure generated then, multiplied by the pressure receiving area of the piston 40, acts as a force pushing against the cam surface 21 of the piston 40. Acting as a differential limiting torque, this lessens the distribution of driving force on high speed revolution side and increases the same on low speed revolution side to limit the differential.