PURPOSE: To prevent any drop in torque from occurring, to be hard to cause the seizure or binding of a valve element to make durability improvable and embody the promotion of miniaturization and the cost reduction in addition to ease of production, in regard to a hydraulic power transmission coupling in use for a distribution of car driving force.
CONSTITUTION: This power transmission coupling is provided with a third port 19 being installed on a valve surface of a valve element 11 and closed by the end face of a rotor 4, while at the case of being tuned to a high-pressure state, releasing the coheringness between the rotor 4 and the valve element 11, a high pressure chamber 15 being installed in the valve element 11 and made up of interconnecting a discharge port 13, two control valves 33 and 31 controlling conductingness between the third port 19 and a low pressure chamber in a coupling and another conductingness between the third port 19 and the high pressure chamber 15, and an actuator operating these control valves 33, 31 by a signal from the outside, respectively. In succession, pressure in the third port 19 is constituted so as to make it selectable to both high and low pressure states.
YAMADA TAKEHISA