| 摘要 |
PURPOSE:To actuate a valve in a stable manner, by a method wherein, when a taper needle valve mounted to an air bleed to control the air-fuel ratio of a carburetter is closed, the speed of a step motor for drive is gradually reduced from a high value to a low value to bring it into a full closed state, and thereafter the opening thereof is decreased to a minimum value. CONSTITUTION:Taper needle valves 11 driven by a step motor 10 are mounted in a main air bleed 13 and a low speed air bleed passage 14 of a carburetter 12. The step motor 10 is driven by means of a signal from a control circuit 9, based on an output from an oxygen sensor 3 mounted to an exhaust system 2, so that a given air-fuel ratio is provided based on outputs from a negative pressure sensor 5, a water temperature detecting sensor 7, and a rotation sensor 8 of an ignition coil. When the taper needle valve 11 is closed, the step motor 10 is gradually varied from a high speed to a low speed, and after the valve is fully closed, the step motor 10 is reversed, and the valve is opened to a given minimum opening prevailing during full closing. |
