| 摘要 |
A diagnosis system for an engine including an exhaust pipe, a hydrocarbon (HC) absorbent arranged within the exhaust pipe, an upstream air/fuel ratio sensor arranged upstream of the HC absorbent and detecting a wide range air/fuel ratio of an exhaust gas, a downstream air/fuel ratio sensor arranged downstream of the HC absorbent and detecting rich or lean with respect to stoichiometric air/fuel ratio of the exhaust gas, and a control unit, the control unit includes means for correcting an air/fuel ratio upstream of the HC absorbent, means for correcting an air/fuel ratio downstream of the HC absorbent, and means for predicting a HC absorbing amount of the HC absorbent, the means for correcting the air/fuel ratio upstream of the HC absorbent correcting and controlling an output value of the upstream air/fuel ratio sensor toward lean, the means for predicting the HC absorbing amount of the HC absorbent predicting an absorbing performance of the HC absorbent on the basis of a difference between an output value of the upstream air/fuel ratio sensor and a predetermined value C during a period from a timing where a temperature of the HC absorbent becomes higher than or equal to a predetermined value A and the output value of the upstream air/fuel ratio sensor is corrected and controlled toward lean to a timing where the temperature becomes lower than or equal to a predetermined value B. |
