Single-cylinder 4-cycle engine

摘要

In a single-cylinder engine (E) including an oxygen concentration sensor (34) provided at a location upstream of an exhaust emission control catalyst (33), the influence of pulsation of the exhaust gas is eliminated to enhance the detection accuracy by detecting of the concentration of oxygen in the exhaust gas. A first pulse generator (35) generates a pair of pulse signals a and b per one rotation of a crankshaft (19), and a second pulse generator (36) generates pulse signals c and d at every very small angle of rotation of the crankshaft (19). The angular speed of the crankshaft (19) is detected from the interval of the pulse signals c and d. The pulse signal output a when the angular speed is smaller is determined as being the output during a compression stroke, and is used as an ignition signal a1. The pulse signal output a when the angular speed is larger is determined as being the output during an exhaust stroke, and is used as an oxygen concentration detecting signal a2.