PURPOSE: To improve the purification of an exhaust gas by projecting one end of a conductive central line from the end face of a cylindrical fitting by a fixed dimension while a light receiving element is provided on the end face of a light transmitting optical fiber at the other end thereof and a high frequency coaxial line terminal somewhere before the light receiving element in the conductive central line separate from the light transmitting fiber.
CONSTITUTION: As a piston 16 rises to a point before or after the upper dead point and the common frequency of a main combustion chamber 17 and a subcombustion chamber 18 coincides with the oscillation frequency of a microwave oscillator 19, a part of radio waves is inputted into the subcombustion chamber 18 and the main combustion chamber 17 from a sensing plug 20. After suffering a loss in the combustion chambers, the radio waves reflected to a receiving diode 21 drop in the level and two resonance points 23 before and after the upper dead point are indicated on a display 22. The signal thereof is amplified 24 to give an advance angle condiion and a fuel injection timing signal for the subsequent cycle is outputted from a processing circuit 25 to control a fuel injection nozzle 26. This can make the fuel injection timing so accurate to improve the combustion efficiency and the operation performance.
ENDOU AKIRA
HARADA KOUJI
KANEKO YOUICHI
