Patent ID: 7886584

Claim:
A stroke detection apparatus of a 4-cycle engine for detecting an intake stroke and a power stroke based on a time period during which a crankshaft of the engine is rotated through a predetermined crank angle which is sensed via monitored crank pulses, said stroke detection apparatus comprising: a rotary engine speed detection unit for calculating rotary engine speeds based on respective crank-pulse time intervals measured at two crank positions which are located before and after a top dead center orientation of said crankshaft; a speed difference determination unit for calculating a difference between the sensed rotary engine speeds at said two crank positions detected by said rotary engine speed detection unit; a throttle position sensor for detecting a throttle opening; and a stroke detection unit operable to distinguish between an intake stroke and a power stroke depending on the detected throttle opening according to either change in a pressure in an intake pipe or sensed rotary engine speeds at two said crank positions for two successive rotations of said crankshaft including a successive top dead center and a preceding top dead center; wherein when said detected throttle opening is less than a predetermined throttle opening, said stroke detection unit performs stroke detection based on a change of a negative pressure of said intake pipe of the engine in an operation region; and when said detected throttle opening is greater than said predetermined throttle opening, said stroke detection unit performs stroke detection based on said difference between the crank-pulse time intervals measured with respect to two successive rotations of said crankshaft including a successive top dead center and a preceding top dead center.