Engine control system and the method thereof

Claim 1

A control system of an engine having a cylinder, an intake manifold, a fuel injector for injecting fuel into said cylinder, a throttle valve for controlling an intake air and an EGR valve for controlling an EGR gas, comprising: engine speed calculating means for calculating an engine speed; accelerator angle calculating means for calculating an accelerator opening angle; control parameter establishing means for establishing target values of control parameters based on said engine speed and said accelerator opening angle; initial set value establishing means for establishing initial set values of a basic fuel injection amount, an EGR rate and an in-cylinder equivalent ratio, respectively, based on said target values; equivalent ratio assuming means for assuming an EGR gas equivalent ratio from said initial set value of said in-cylinder equivalent ratio; control target value establishing means for establishing a first control target value with respect to an air components partial pressure of intake manifold pressure and a second control target value with respect to a non-air components partial pressure of intake manifold pressure, respectively, based on said set value of said in-cylinder equivalent ratio, said initial set value of said basic fuel injection amount and said initial set value of said EGR rate; non-air components partial pressure assuming means for assuming said non-air components partial pressure based on an air flow passing through said throttle valve and air components and non-air components of said EGR gas; EGR gas flow establishing means for establishing an EGR gas flow based on a difference between thus assumed non-air components partial pressure and said second control target value of said non-air components partial pressure; air components partial pressure assuming means for assuming said air components partial pressure based on said air flow passing through said throttle valve and air components of and non-air components of said EGR gas; air flow establishing means for establishing an air flow passing through said throttle valve based on a difference between thus assumed air components partial pressure and said first control target value of said air components partial pressure and based on said air components of said EGR gas; an EGR actuator for actuating said EGR valve so as to control said EGR gas; EGR actuator means for calculating an operating amount of said EGR actuator based on said established value of said EGR gas flow and said intake manifold pressure and for actuating said EGR valve according to said operating amount of said EGR actuator; a throttle actuator for actuating said throttle valve so as to control said intake air; throttle actuator means for calculating an operating amount of said throttle actuator based on said established value of said air flow passing through said throttle valve and said intake manifold pressure and for actuating said throttle valve according to said operating amount of said throttle actuator; and fuel injection amount establishing means for calculating an operating amount of said fuel injector and establishing a final basic fuel injection amount.