| 摘要 |
PROBLEM TO BE SOLVED: To preclude an effect of exhaust gas pulsation and improve detection accuracy by detecting concentration of oxygen in exhaust gas discharged in the exhaust stroke in a single cylinder 4-cycle engine having an oxygen concentration sensor upstream from an exhaust gas purifying catalyst. SOLUTION: This engine is equipped with a first pulse generator which generates a pair of pulse signals a, b per one rotation of a crankshaft and a second pulse generator which generates pulse signals c, d at every minute angle of rotation of the crankshaft. Angular velocity of the crankshaft is detected from an interval between the pulse signals c and d. A pulse signal a which is output when the angular velocity is low is judged to be output in the compression stroke, and is used as an ignition signal a1. Also, a pulse signal a which is output when the angular velocity is high is judged to be output in the exhaust stroke, and is used as a signal a2 for detecting the concentration of oxygen.
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