Method and device for detecting auto-ignitions on the basis of measured and estimated internal cylinder pressure values of an internal combustion engine

A device for detecting and reducing auto-ignition in a combustion chamber of a spark-ignited internal combustion engine, the device configured to:

• during a compression stroke of the internal combustion engine, acquire values for a combustion chamber pressure in the combustion chamber at defined crankshaft angles within an evaluation window,
• determine a filtered pressure value from the acquired values for the combustion chamber pressure,
• determine, for the defined crankshaft angles, theoretical pressure values in the combustion chamber that would occur if no combustion were to take place in the combustion chamber,
• determine a value of the pressure difference between the filtered pressure value and the theoretical pressure values,
• compare the value of the pressure difference with a predefined threshold value,
• if the pressure difference exceeds the predefined threshold value, increasing a counter value associated with a counter of the control device by an increment corresponding to the defined crankshaft angle associated with the corresponding acquired value for the combustion chamber pressure, wherein a lower crankshaft angle generates a larger increment,
• determine an auto-ignition in the combustion chamber if the counter value exceeds a predefined counter threshold value, and
• if auto-ignition is detected, initiate measures to decrease the temperature in the combustion chamber.

A spark-ignited internal combustion engine comprising:

• at least one cylinder which, together with a piston connected to a crankshaft, bounds a combustion chamber, a combustion chamber pressure sensor configured to measure a pressure in the combustion chamber,
• a crankshaft angle sensor that supplies a signal which represents a rotation angle of the crankshaft,
• a control device configured to perform open-loop and/or closed-loop control of the internal combustion engine, and
• a device for detecting auto-ignition in the combustion chamber by:
• during a compression stroke of the internal combustion engine, acquiring values for a combustion chamber pressure in the combustion chamber at defined crankshaft angles within an evaluation window,
• determining a filtered pressure value from the acquired values for the combustion chamber pressure,
• determining, for the defined crankshaft angles, theoretical pressure values in the combustion chamber that would occur if no combustion were to take place in the combustion chamber,
• determining a value of the pressure difference between the filtered pressure value and the theoretical pressure values,
• comparing the value of the pressure difference with a predefined threshold value, and
• if the pressure difference exceeds the predefined threshold value, increasing a counter value associated with a counter of the control device by an increment corresponding to the defined crankshaft angle associated with the corresponding acquired value for the combustion chamber pressure, wherein a lower crankshaft angle generates a larger increment,
• determining an auto-ignition in the combustion chamber if the counter value exceeds a predefined counter threshold value,
• wherein the control device responds to a determination of auto-ignition by initiating measures to decrease the temperature in the combustion chamber.