Patent ID: 7543794

Claim:
A torque-transmitting device for transmitting a torque from a driving source to a valve for opening and closing a valve port, the torque-transmitting device comprising: a casing; a gear train supported in the casing and disposed between the driving source and a valve shaft connected to the valve, the gear train including a rotating body having an axis supported in the casing, the rotating body being coupled to the valve shaft for driving the valve shaft; and a coil spring disposed around the axis to supply a biasing force to the rotating body in a predetermined direction, wherein: the rotating body includes a cylindrical core portion rotatably supported on the axis and a large-diameter portion having a diameter larger than a diameter of the cylindrical core portion, the large-diameter portion being connected to the cylindrical core portion; a space for accommodating the coil spring is formed between the casing and the cylindrical core portion, and a cylindrical space is formed between an inner circumference of the coil spring and the cylindrical core portion; and the large-diameter portion includes a through-space connecting an axial outside of the large-diameter portion and the cylindrical space, wherein the through-space comprises a plurality of U-shaped slits formed in the large-diameter portion, each U-shaped slit having a radially outer open end, open at a radially outer periphery of the large-diameter portion, and a radially inner closed end, positioned at an outer periphery of the cylindrical core portion.