Rotary shaft coupler with rotary valve plate position dependent on direction of shaft rotation

A hydraulic power transmission joint for transmitting a torque according to a difference between rotational speeds of shafts of left and right drive wheels, comprising:

• a cam housing provided between input and output shafts capable of rotating relative to one another, said cam housing being connected to one of said input and output shafts and having a cam face which includes at least two cam noses formed on an inside surface thereof;
• a rotor connected to the other one of said input and output shafts, said rotor being rotatably enclosed in said cam housing, in which a plurality of plunger chambers are formed in a direction of an axis thereof;
• a plurality of plungers enclosed in said plurality of plunger chambers, respectively, in such a manner as to be able to perform a reciprocative movement in response to a pressing force of a corresponding return spring, said plungers being driven by said cam face upon a relative rotation of one of said input and output shafts with respect to the other of said input and output shafts;
• intake/discharge holes formed in said rotor and communicating with said plunger chambers;
• a rotary valve rotatably and slidably brought into contact with an end surface of said rotor and being positioned in such a way as to have a positional relationship with said cam housing, said rotary valve having a plurality of intake and discharge ports formed in surface portions thereof and acting as intake and discharge valves, respectively, according to a positional relationship thereof with said intake/discharge holes;
• and
• a valve structure, provided in said rotary valve, for providing an automatic lock characteristic in response to oil pressure supplied from one of said discharge ports, wherein said valve structure comprises:
• a valve element which is enclosed in a high-pressure chamber formed in said rotary valve;
• a pin member capable of operatively holding and releasing said valve element in relation to oil pressure supplied from said high-pressure chamber;
• and
• a spring biasing said pin member towards said valve element;
• a collar member made of a hard material, said collar member partitioning said high-pressure chamber from a low-pressure chamber;
• and
• an orifice formed in said collar member, wherein said orifice and is open when said valve element is held by said pin member, and said orifice generates fluid resistance to a flow of discharge oil driven by said plungers, and said orifice is closed when said valve element is seated thereon upon being released from said pin member.