Engine control system and control method thereof
First Claim
1. An engine control system comprising:
- intake air amount control means for controlling the amount of air taken into an engine;
an intake airflow sensor for detecting the amount of air taken into the engine;
an EGR path for returning part of exhaust gas, the EGR path being connected to an exhaust path and an intake path in the engine;
an EGR flow sensor for detecting the flow rate of an EGR gas that passes through the EGR path;
EGR flow rate control means for controlling the flow rate of the EGR gas that passes through the EGR path;
an intake pressure sensor for detecting the pressure in an intake pipe of the engine; and
a fuel supply unit for supplying the engine with fuel;
wherein said engine control system further comprises;
first EGR rate estimation means for estimating the EGR rate of the engine on the basis of the output result of the intake airflow sensor and the output result of the EGR flow sensor; and
second EGR rate estimation means for estimating the EGR rate of the engine on the basis of the detection result of the EGR flow sensor and the detection result of the intake pressure sensor.
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Accused Products
Abstract
An engine that re-circulates its exhaust gas suffers decreased accuracy in estimating an EGR rate real-time especially while the operating state of the engine is in a transitional state, which often results in torque fluctuations and deteriorated exhaust gas.
A sensor for directly detecting an EGR flow rate is disposed in an EGR path. An EGR rate and in-cylinder oxygen concentration are calculated from the output value of that sensor. In addition, when this EGR rate calculation method is used, the calculation is properly switched between a steady operation state characterized by a low load and small rotational fluctuations and a transitional operating state including the acceleration and deceleration. This makes it possible to correctly estimate the EGR rate and the in-cylinder oxygen concentration under a wide range of engine operation conditions, and thereby to avoid the fluctuation of torque and the deterioration of exhaust gas.
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Citations
19 Claims
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1. An engine control system comprising:
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intake air amount control means for controlling the amount of air taken into an engine; an intake airflow sensor for detecting the amount of air taken into the engine; an EGR path for returning part of exhaust gas, the EGR path being connected to an exhaust path and an intake path in the engine; an EGR flow sensor for detecting the flow rate of an EGR gas that passes through the EGR path; EGR flow rate control means for controlling the flow rate of the EGR gas that passes through the EGR path; an intake pressure sensor for detecting the pressure in an intake pipe of the engine; and a fuel supply unit for supplying the engine with fuel; wherein said engine control system further comprises; first EGR rate estimation means for estimating the EGR rate of the engine on the basis of the output result of the intake airflow sensor and the output result of the EGR flow sensor; and second EGR rate estimation means for estimating the EGR rate of the engine on the basis of the detection result of the EGR flow sensor and the detection result of the intake pressure sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification