초록 ▼

A system and method for controlling an air-fuel ratio of an internal combustion engine using a ratio of cylinder pressures measured within at least one cylinder. The air-fuel ratio control system includes an electronic control module (ECM) which computes a measured cylinder pressure ratio of the cyl

A system and method for controlling an air-fuel ratio of an internal combustion engine using a ratio of cylinder pressures measured within at least one cylinder. The air-fuel ratio control system includes an electronic control module (ECM) which computes a measured cylinder pressure ratio of the cylinder pressure measured at a predetermined crank angle before top dead center and the cylinder pressure measured at a predetermined crank angle after top dead center. The measured cylinder pressure ratio is compared with an optimal cylinder pressure ratio. Based upon the results of this comparison, the ECM then determines an adjusted air-fuel ratio which would modify the measured pressure ratio to equal the optimal pressure ratio. This system controls the air-fuel ratio by measuring the quality of combustion without the need to measure the amount of air or fuel actually delivered to the engine. The measured pressure ratio corresponds to an excess air ratio of the internal combustion engine at those operating conditions, wherein a measured excess air ratio of the engine may be obtained from the computed pressure ratio. The measured excess air ratio may be compared with an optimal excess air ratio for the specific engine operating conditions currently being sensed, wherein the ECM then determines the adjusted air-fuel ratio which would modify the measured excess air ratio to equal the stored optimal excess air ratio.

대표청구항 ▼

[ What is claimed is:] [1.] A system for controlling an air-fuel ratio of an internal combustion engine, comprising:a cylinder pressure sensor for detecting a first cylinder pressure measured at a predetermined crank angle before top dead center and a second cylinder pressure measured at a predeterm

[ What is claimed is:] [1.] A system for controlling an air-fuel ratio of an internal combustion engine, comprising:a cylinder pressure sensor for detecting a first cylinder pressure measured at a predetermined crank angle before top dead center and a second cylinder pressure measured at a predetermined crank angle after top dead center in a combustion chamber of the internal combustion engine; said cylinder pressure sensor providing signals indicative of the cylinder pressure detected;control means for controlling at least one of a quantity of air and a quantity of fuel delivered to the engine to control an actual air-fuel ratio;operation detecting means for sensing at least one engine operating condition and providing output signals indicative of the operating conditions sensed;an electronic control module including:receiving means for receiving said signals from said cylinder pressure sensor;computing means for computing a measured pressure ratio of said first cylinder pressure and said second cylinder pressure from signals received from said cylinder pressure sensor;a cylinder pressure ratio information storage means for storing optimal cylinder pressure ratios for various engine operating conditions;an excess air ratio information storage means containing optimal excess air ratios for various engine operating conditions; each of said optimal excess air ratios in said information storage means corresponding to one of said stored optimal cylinder pressure ratios for a specific set of engine operating conditions;comparison means for comparing said measured pressure ratio with an optimal cylinder pressure ratio stored in said cylinder pressure ratio information storage means corresponding to a specific set of engine operating conditions sensed by said operation detecting means and determining an adjusted air-fuel ratio;adjusting means for controlling said control means to adjust at least one of the quantity of air and the quantity of fuel delivered to the engine to thereby achieve said adjusted air-fuel ratio corresponding to said stored optimal pressure ratio.