Method for detecting combustion misfires

Claim 1

A method for detecting misfires in the combustion of a z-cylinder four stroke internal combustion engine, the engine including a transducer wheel coupled to the crankshaft of the engine and rotating in phase synchronism with said crankshaft, the method comprising the steps of: causing said transducer wheel to have z/2 segments; scanning said segments with a sensor device to supply a segment-time signal reflecting the nonuniformity of the rotational movement of the crankshaft with respect to individual ones of the cylinders of the engine; forming rough-running values for each cylinder on the basis of the segment times with each of said rough-running values including a component occurring at the frequency of said crankshaft; filtering out said component by forming differences between segment times which are assigned to the same transducer wheel segment; then, comparing the filtered rough-running value to a threshold value; determining a misfire to be present when said filtered rough-running value exceeds said threshold value; for an even number of cylinders, detecting a segment time for each ignition; for an uneven number of cylinders, additionally detecting the segment time for the mechanically same segment shifted by one crankshaft revolution; and, forming the difference of segment times, which segment times were detected for segments each shifted by 360° crankshaft angle.

Claim 2

A method for detecting misfires in the combustion of a z-cylinder four stroke internal combustion engine, the engine including a transducer wheel coupled to the crankshaft of the engine and rotating in phase synchronism with said crankshaft, the method comprising the steps of: causing said transducer wheel to have z/2 segments; scanning said segments with a sensor device to supply a segment-time signal reflecting the nonuniformity of the rotational movement of the crankshaft with respect to individual ones of the cylinders of the engine; forming rough-running values for each cylinder on the basis of the segment times with each of said rough-running values including a component occurring at the frequency of said crankshaft; filtering out said component by forming differences between segment times which are assigned to the same transducer wheel segment; then, comparing the filtered rough-running value to a threshold value; determining a misfire to be present when said filtered rough-running value exceeds said threshold value; for an even number of cylinders, detecting a segment time for each ignition; for an uneven number of cylinders, additionally detecting the segment time for the mechanically same segment shifted by one crankshaft revolution; and, forming the difference of segment times, which segment times were detected for segments each shifted by 360° crankshaft angle.

Claim 3

A method for detecting misfires in the combustion of a z-cylinder four stroke internal combustion engine, the engine including a transducer wheel coupled to the crankshaft of the engine and rotating in phase synchronism with said crankshaft, the method comprising the steps of: causing said transducer wheel to have z/2 segments; scanning said segments with a sensor device to supply a segment-time signal reflecting the nonuniformity of the rotational movement of the crankshaft with respect to individual ones of the cylinders of the engine; forming rough-running values for each cylinder on the basis of the segment times with each of said rough-running values including a component occurring at the frequency of said crankshaft; filtering out said component by forming differences between rough-running values which are assigned to the same transducer wheel segment; then, comparing the filtered rough-running value to a threshold value; determining a misfire to be present when said filtered rough-running value exceeds said threshold value; and, compensating the influences of changes in rpm on said rough-running values.

Claim 4

A method for detecting misfires in the combustion of a z-cylinder four stroke internal combustion engine, the engine including a transducer wheel coupled to the crankshaft of the engine and rotating in phase synchronism with said crankshaft, the method comprising the steps of: causing said transducer wheel to have z/2 segments; scanning said segments with a sensor device to supply a segment-time signal reflecting the nonuniformity of the rotational movement of the crankshaft with respect to individual ones of the cylinders of the engine; forming rough-running values for each cylinder on the basis of the segment times with each of said rough-running values including a component occurring at the frequency of said crankshaft; filtering out said component by forming differences between rough-running values which are assigned to the same transducer wheel segment; then, comparing the filtered rough-running value to a threshold value; determining a misfire to be present when said filtered rough-running value exceeds said threshold value; and, compensating the influences of changes in rpm on said rough-running values.