Sätt och anordning för att bestämma cylindertryck vid en förbränningsmotor

摘要

The pressure in a cylinder of a combustion engine is determined on the basis of vibrations in the engine which are generated during movement of the piston. A vibration signal (S) from a vibration sensor situated on a cylinder is filtered in the region about the piston top dead center position, at the transition from compression to expansion, in a special filter in which a half Hanning filter acts upon the vibration signal before and an exponential filter acts upon the vibration signal after the piston top dead center position. The filtered signal (U) is thereafter converted to a pressure signal (P) on the basis of an established relationship between vibration and pressure. The half Hanning filter has a significantly shorter time window (T_H) than the exponential filter (T_E). The filter cleans the vibration signal in an advantageous manner and makes more reliable pressure determination possible.