Patent ID: 7536993

Claim:
A throttle device for an internal combustion engine, comprising: a throttle body defining therein an intake air channel; a throttle valve having a throttle shaft and disposed within the intake air channel; an electrically-driven actuator operable to rotate the throttle shaft for opening and closing the throttle valve; a gear transmission mechanism constructed to transmit a drive force of the actuator to the throttle shaft and including a final stage gear fixedly mounted to the throttle shaft; an opener rotatably mounted to the throttle shaft; a back spring comprising a torsion coil spring and interleaved between the throttle body and the opener, so that the opener is biased in a closing direction of the throttle valve by the back spring; an opener open angle setting stopper disposed on the throttle body and constructed to prevent the opener from rotating to such an open angle that is smaller than an opener open angle, the opener open angle being larger than the open angle of the throttle valve at a fully closed position of the throttle valve; a relief spring comprising a torsion coil spring and interleaved between the final stage gear and the opener, so that (a) the final stage gear and the opener engage with each other and rotate together when the open angle of the throttle valve is equal to or larger than the opener open angle, and (b) the final stage gear can rotate in a direction for disengagement with the opener when the open angle of the throttle valve is smaller than the opener open angle; wherein the throttle valve is held at the opener open angle when no power is supplied to the actuator; wherein the relief spring has a terminal end on the side of the opener, the terminal end being bent radialy outward or inward of a coil portion of the relief spring; wherein the opener has an engaging recess that can receive the terminal end of the relief spring, wherein the engaging recess is configured to permit movement of the terminal end in a circumferential direction of the opener and to be able to engage the terminal end at a predetermined position with respect to the circumferential direction.