Method for detecting detonation phenomena in an internal combustion engine

1. A method for detecting the development of detonation phenomena in an internal combustion engine ( 1 ) provided with a number of cylinders ( 2 ), a control unit ( 16 ), and a number of detonation sensors connected to the control unit ( 16 ); wherein, detonation sensors include at least one of an accelerometer and a voltage gauge which is connected and arranged in series to the electric circuit of a spark plug ( 15 ) to measure the voltage at the terminals of the electrodes of the spark plug ( 15 ) during combustion and/or a pressure gauge which measures the maximum amplitude pressure oscillation (MAPO) of the intensity of the pressure waves generated in the cylinders ( 2 ) during combustion; the method comprises the steps of:

acquiring the signal (S) coming from said number of detonation sensors connected to the control unit ( 16 );

processing the signal (S) coming from said number of detonation sensors connected to the control unit ( 16 ) so as to obtain the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point;

filtering the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point;

calculating the mean detonation energy (μ i _ m ) for a given cylinder ( 2 ) and in a given engine point with the filtered value of the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point;

comparing the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point with the mean detonation energy (μ i _ m ) for a given cylinder ( 2 ) and in a given engine point;

determining the variance (σ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point as a function of the comparison between the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point and the mean detonation energy (μ i _ m ) for a given cylinder ( 2 ) and in a given engine point;

calculating the maximum variance (σ i _ max ) for a given cylinder ( 2 ) and in a given engine point with a reduction of the spark advance actuated in the given cylinder ( 2 );

comparing the maximum variance (σ i _ max ) for a given cylinder ( 2 ) and in a given engine point with the variance (σ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point; and

determining the development of detonation phenomena for each combustion taken into account for a given cylinder ( 2 ) and in a given engine point as a function of the comparison between the maximum variance (σ i _ max ) for a given cylinder ( 2 ) and in a given engine point and the variance (σ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point.

2. The method as set forth in claim 1 , wherein the step of calculating the maximum variance (σ i _ max ) for a given cylinder ( 2 ) and in a given engine point with a reduction of the spark advance actuated in the given cylinder ( 2 ) is performed by degrading the spark advance actuated in the given cylinder ( 2 ) up to a value that is such that no detonation phenomena will occur.

3. An electronic control unit ( 16 ), which is suited to implement a method for detecting the development of detonation phenomena in an internal combustion engine ( 1 ) performed as set forth in claim 1 .

4. The method as set forth in to claim 1 , including the further steps of:

initializing, in a preliminary adjustment and set up phase, a first map (MAPS 1 ) with the values of the mean detonation energy (μ i _ m ) for a given cylinder ( 2 ) and in a given engine point; and

updating the first map (MAPS 1 ) with the filtered value of the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point.

5. The method as set forth in claim 4 , wherein at least one of the first map (MAPS 1 ), the second map (MAPS 2 ), the third map (MAPS 3 ), and the fourth map (MAPS 4 ) have a number of cells that varies as a function of the number (N cyl ) of cylinders ( 2 ) and of the engine points identified by the number of revolutions per minute (rpm) and by the load (load).

6. The method as set forth in claim 4 , further including the further step of updating the first map (MAPS 1 ) with the filtered value of the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point with a weighted mean between the filtered value of the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point and the value of the mean detonation energy (μ i _ m ) for a given cylinder ( 2 ) and in a given engine point contained in the first map (MAPS 1 ).

7. The method as set forth in claim 6 , including the further steps of:

initializing, in a preliminary adjustment and set up phase, a second map (MAPS 2 ) of counters of the combustions taken into account for a given cylinder ( 2 ) and in a given engine point; and

determining the weights to be assigned to the filtered value of the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) and in a given engine point and to the value of the mean detonation energy (μ i _ m ) for a given cylinder ( 2 ) and in a given engine point contained in the first map (MAPS 1 ) as a function of the second map (MAPS 2 ) of counters of the combustions taken into account for a given cylinder ( 2 ) and in a given engine point.

8. The method as set forth in claim 7 , wherein the filtered value of the detonation energy (μ i ) of each combustion taken into account for a given cylinder ( 2 ) has a gradually decreasing value.

9. The method as set forth in claim 1 , including the further steps of:

initializing, in a preliminary adjustment and set up phase, a third map (MAPS 3 ) with the values of the maximum variance (σ i _ max ) for a given cylinder ( 2 ) and in a given engine point; and

updating, during a learning phase, the third map (MAPS 3 ) with the nominal value of the noise peak of the i-th combustion taken into account for a given cylinder ( 2 ) and in a given engine point.

10. The method as set forth in claim 9 , including the further step of updating the third map (MAPS 3 ) with the nominal value of the noise peak of the i-th combustion taken into account for a given cylinder ( 2 ) and in a given engine point with a weighted mean between the nominal value of the noise peak of the i-th combustion taken into account for a given cylinder ( 2 ) and in a given engine point and the value of the maximum variance (σ i _ max ) for a given cylinder ( 2 ) and in a given engine point contained in the third map (MAPS 3 ).

11. The method as set forth in claim 10 , including the further steps of:

initializing, in a preliminary adjustment and set up phase, a fourth map (MAPS 4 ) of counters of the combustions taken into account for a given cylinder ( 2 ) and in a given engine point; and

determining the weights to be assigned to the nominal value of the noise peak of the i-th combustion taken into account for a given cylinder ( 2 ) and in a given engine point and to the value of the maximum variance (σ i _ max ) for a given cylinder ( 2 ) and in a given engine point contained in the third map (MAPS 3 ) as a function of the fourth map (MAPS 4 ) of counters of the combustions taken into account for a given cylinder ( 2 ) and in a given engine point.

12. The method as set forth in claim 11 , wherein the nominal value of the noise peak of the i-th combustion taken into account for a given cylinder ( 2 ) and in a given engine point has a gradually increasing value.