Throttle valve controlling apparatus employing electrically controlled actuator

A throttle valve controlling apparatus for an automobile comprising:

• throttle valve means including a first throttle valve and a second throttle valve relatively rotatable to said first throttle valve, for controlling a flow of an air/fuel mixture to an engine;
• rotating means mechanically coupled to an accelerator pedal, for relatively rotating said first throttle valve with respect to said second throttle valve;
• first return spring means for biasing said first throttle valve so as to set the same to a first closed position of said throttle valve means when said accelerator pedal is released;
• relative rotation angle sensor means for detecting an actual relative rotation angle between said first and second throttle valves to output an actual relative rotation angle signal;
• rotation angle sensor means coupled to said second throttle valve, for detecting a rotation angle of said second throttle valve to produce a rotation angle signal;
• engine condition/drive condition sensor means for detecting conditions of the engine and also the automobile's drive to produce an engine condition detecting signal and a drive condition detecting signal;
• calculation controlling means for producing a rotation command signal representative of a target relative rotation angle for said first and second throttle valves, determined by said engine condition detecting signal and said drive condition detecting signal and also operation of the accelerator pedal;
• electrically controlled actuator means for relatively rotating said second throttle valve with respect to said first throttle valve in response to said rotation command signal derived from said calculation controlling means in such a manner that deviation between said target relative rotation angle and actual relative rotation angle becomes zero, and for relatively rotating said second throttle valve with respect to said first throttle valve in response to said engine condition detecting signal and drive condition detecting signal so as to reduce said actual relative rotation angle by which engine speed is reduced;
• and,
• second return spring means for biasing said second throttle valve so as to set the same to a second closed position of said throttle valve means, whereby when said electrically controlled actuator means is brought into malfunction by checking said rotation angle signal from said rotation angle sensor means, said second throttle valve is set to said second closed position at which the engine speed is rapidly reduced, and said first throttle valve is independently rotatable by said accelerator pedal.