Stroke determination device for 4-stroke engine

A stroke determination device for a four-stroke engine for establishing whether a stroke carried out in cylinders of the four-stroke engine is an exhaust stroke or a compression stroke when an ignition operation is carried out in the cylinders, the four-stroke engine comprising an engine body having at least one cylinder, and an ignition device that has an ignition coil provided for each cylinder and induces a high voltage in a secondary coil of the ignition coil by controlling a primary current of the ignition coil, and ignition being performed by applying, to a spark plug provided in each cylinder, a high voltage induced in the secondary coil of the ignition coil of the ignition device, wherein

• the stroke determination device is provided with
• parameter detection means for stroke determination, in which a parameter that shows the characteristics of a waveform of voltage appearing at both ends of the secondary coil of the ignition coil or a waveform of current flowing through the secondary coil of the ignition coil at the time of the ignition operation, and shows a different value when the stroke carried out in the cylinders of the engine is the exhaust stroke and when the stroke is the compression stroke when the ignition operation is carried out in the cylinders, is detected as a stroke determination parameter, and
• stroke determination means for establishing whether the stroke carried out when the ignition operation was carried out in each cylinder of the engine is the exhaust stroke or the compression stroke on the basis of the fact that the stroke determination parameter shows a different value between when the stroke carried out in each cylinder when the ignition operation is carried out in each cylinder is the exhaust stroke and when the stroke is the compression stroke;
• the secondary coil of the ignition coil comprises a first coil portion, and a second coil portion that has fewer windings than does the first coil portion and is connected in series to the first coil portion, and a tap is drawn out from a boundary part between the first coil portion and the second coil portion, and
• the parameter detection means for stroke determination is configured so as to detect the stroke determination parameter from the voltage at both ends of the second coil portion of the secondary coil of the ignition coil detected by way of the tap.