Combustion state control apparatus for internal combustion engine

Claim 1

A control apparatus for an internal combustion engine comprising: a) first means for detecting an engine operating condition; b) second means for setting a basic EGR rate on the basis of the detected engine operating condition; c) third means for detecting an inner cylinder pressure of the engine and outputting a signal waveform representing the inner cylinder pressure variation; d) fourth means for detecting a combustion state variable on the basis of the inner cylinder pressure variation signal waveform for each combustion of the engine; e) fifth means for detecting an air/fuel mixture ratio of the engine; f) sixth means for averaging the combustion state variable for each predetermined period of a rich state and lean state of the air/fuel mixture ratio based on the output signal of said fifth means; g) seventh means for correcting the basic EGR rate on the basis of an average value of the combustion variable derived by said sixth means to derive a final EGR rate; and, h) eighth means for controlling an exhaust gas recirculation from an exhaust gas system of the engine to an intake air system thereof on the basis of the final EGR rate.

Claim 12

An apparatus for controlling an EGR rate with a variation in air/fuel mixture ratio of an internal combustion engine taken into consideration, having an EGR control valve located in a passage communicated from an exhaust gas passage and intake air passage of the engine, said EGR rate controlling apparatus comprising: a) an air fuel mixture ratio sensor which is located in an exhaust gas passage of the engine so as to provide an output signal indicating the air/fuel mixture ratio of the engine; b) an engine operating condition sensor which is so constructed to detect an engine operating condition including an engine load and engine revolution speed; c) basic EGR rate calculating means for deriving a basic EGR rate on the basis of the engine load and engine revolution speed; d) combustion state determining factor detecting means for detecting a combustion state determining factor on the basis of each inner cylinder pressure variation of each engine cylinder; e) rich/lean period determining means for determining a reverse of the air/fuel mixture ratio from a rich state to a lean state and vice versa on the basis of the variation in the detected air/fuel mixture ratio; f) final EGR rate determining means for determining a final EGR rate for each rich/lean period on the basis of an average value of the combustion state determining factor for each rich/lean period and the basic EGR rate; and g) duty ratio signal output means for producing and outputting a pulse signal having a duty ratio corresponding to the final EGR rate to an electromagnetic valve associated with an EGR control valve.

Claim 13

An apparatus for controlling an EGR rate with a variation in air/fuel mixture ratio of an internal combustion engine taken into consideration, having an EGR control valve located in a passage communicated from an exhaust gas passage and intake air passage of the engine, said EGR rate controlling apparatus comprising: a) an air fuel mixture ratio sensor which is located in an exhaust gas passage of the engine so as to provide an output signal indicating the air/fuel mixture ratio of the engine; b) an engine operating condition sensor which is so constructed to detect an engine operating condition including an engine load and engine revolution speed; c) basic EGR rate calculating means for deriving a basic EGR rate on the basis of the engine load and engine revolution speed; d) combustion state determining factor detecting means for detecting a combustion state determining factor on the basis of each inner cylinder pressure variation of each engine cylinder; e) rich/lean period determining means for determining a reverse of the air/fuel mixture ratio from a rich state to a lean state and vice versa on the basis of the variation in the detected air/fuel mixture ratio; f) final EGR rate determining means for determining a final EGR rate for each rich/lean period on the basis of an average value of the combustion state determining factor for each rich/lean period and the basic EGR rate; and g) duty ratio signal output means for producing and outputting a pulse signal having a duty ratio corresponding to the final EGR rate to an electromagnetic valve associated with an EGR control valve.