Patent ID: 7219635

Claim:
A four-cycle engine comprising: a crankshaft provided with a first gear; a camshaft provided with a second gear, wherein the second gear has twice as many teeth as the first gear, such that a pitch angle of each tooth of the second gear is half as large as a pitch angle of each tooth of the first gear; an endless rotation transmission that is installed around the first and second gears and is configured to transmit rotation of the crankshaft to the camshaft; a crank phase detecting device configured to detect a rotational phase of the crankshaft to a degree that is equal to or less than the pitch angle of the tooth of the first gear; a cam phase detecting device configured to detect at least one rotational phase of the camshaft; and a phase difference detecting device configured to detect a phase difference between the first gear and second gear to a degree corresponding to one tooth of the second gear, based on input from the crank phase detecting device and the cam phase detecting device.