| 摘要 |
PURPOSE:To maintain constant air-fuel ratio at a certain value by a method wherein an output of an air flow sensor which generates frequency proportional to an intake air amount is controlled to change proportionally in accordance with the operational condition of an engine, thereby changing the operating frequency of an electromagnetic valve. CONSTITUTION:An air flow sensor 1 provided within an intake manifold 3 of an engine 16 comprises a triangle column 2, an ultrasonic wave transmitter 4 and a receiver 5 and provides a frequency output which is proportional to the air flow rate. This output signal is sent through an amplifier 6 and a circuit changing switch 7 and then converted into a pulse signal of a frequency proportional to the measured frequency while passing through a frequency dividing circuit 11, one time circuit 12 or multiplier circuit 13. Thus obtained pulse signal drives an electromagnetic valve 14, and therefore, a certain air-fuel ratio A11- A13 can be maintained constantly. In addition, the circuit changing switch 7 is selected in accordance with the operational condition of the engine 16, so that an appropriate air-fuel ratio A11-A13 can be adopted selectively. |
