Knock suppressing apparatus and method

A knock suppressing method for an internal combustion engine comprising:

• generating a knock signal indicative of engine vibrations;
• amplifying the knock signal with an amplification gain;
• generating a vibration level signal indicative of the level of the amplified knock signal over a first period;
• generating a threshold indicative of the level of the vibration level signal over a second period;
• comparing the vibration level signal with the threshold signal;
• controlling an engine operating parameter based on the result of comparison so as to suppress knocking;
• and
• controlling the amplification gain based on the level of the threshold signal, wherein controlling the gain comprises:
• decreasing the gain when the threshold becomes greater than or equal to an upper limit;
• measuring an upper rotational speed of the engine corresponding to the upper limit;
• determining a lower rotational speed smaller than the upper rotational speed;
• increasing the gain when the threshold becomes less than or equal to the lower rotational speed.

A knock suppressing apparatus for an internal combustion engine comprising:

• a knock sensor for generating a knock signal indicative of engine vibrations;
• a variable gain amplifier connected to the knock sensor for amplifying the knock signal and generating an output signal;
• means for generating a vibration level signal indicative of the level of the amplifier output signal;
• means for generating a threshold signal indicative of the level of the vibration level signal;
• a comparator for comparing the vibration level signal and the threshold signal;
• engine control means responsive to the comparator for controlling an engine operating parameter so as to suppress knocking based on the result of comparison by the comparator;
• and
• gain control means for varying the gain of the amplifier based on the threshold signal, further comprising a speed sensor for sensing an engine operating condition indicative of the engine rotational speed and generating a corresponding output signal, wherein the gain control means comprises:
• means for decreasing the gain when the threshold signal is greater than or equal to an upper limit;
• means responsive to the speed sensor for determining an upper engine rotational speed corresponding to the upper limit;
• means for calculating a lower engine rotational speed smaller than the upper engine rotational speed;
• and
• means for increasing the gain when the engine rotational speed becomes less than or equal to the lower engine rotational speed.

A knock suppressing method for an internal combustion engine comprising:

• generating a knock signal indicative of engine vibrations;
• amplifying the knock signal with an amplification gain;
• generating a vibration level signal indicative of the level of the amplified knock signal over a first period;
• generating a threshold indicative of the level of the vibration level signal over a second period;
• comparing the vibration level signal with the threshold signal;
• controlling an engine operating parameter based on the result of comparison so as to suppress knocking;
• and
• controlling the amplification gain based on the level of the threshold signal in a step-wise manner between at least two different levels, with hysteresis.