Catalyst deterioration detecting system and catalyst deterioration detecting method of internal combustion engine

Abstract

A catalyst deterioration detecting system of an internal combustion engine includes a measuring unit that measures the oxygen storage capacity of a catalyst, a detector that detects or estimates the temperature of the catalyst, and a detector that detects poisoning of the catalyst based on the relationship between a change in the catalyst temperature and a change in the oxygen storage capacity corresponding to the change in the catalyst temperature. The change in the oxygen storage capacity corresponding to the change in the catalyst temperature varies depending on the presence or absence of poisoning of the catalyst. Thus, the catalyst deterioration detecting system is able to favorably detect poisoning of the catalyst by utilizing this relationship, and distinguish temporary deterioration due to catalyst poisoning from permanent deterioration. A method of detecting deterioration of the catalyst is also provided.

1 . A catalyst deterioration detecting system of an internal combustion engine which detects deterioration of a catalyst disposed in an exhaust passage of the internal combustion engine, comprising:
 a storage capacity measuring unit that measures an oxygen storage capacity of the catalyst;   a catalyst temperature detector that detects or estimates a temperature of the catalyst; and   a poisoning detector that detects poisoning of the catalyst, based on a relationship between a change in the catalyst temperature detected or estimated by the catalyst temperature detector, and a change in the oxygen storage capacity measured by the storage capacity measuring unit, which change corresponds to the change in the catalyst temperature.   
   
   
       2 . The catalyst deterioration detecting system according to  claim 1 , wherein the poisoning detector detects poisoning of the catalyst based on an amount of change of the oxygen storage capacity between at least two points of the catalyst temperature. 
   
   
       3 . The catalyst deterioration detecting system according to  claim 2 , wherein the poisoning detector detects poisoning of the catalyst by comparing a value based on the amount of change of the oxygen storage capacity with a predetermined value, and the predetermined value is changed in accordance with a value of the oxygen storage capacity measured at a point of the catalyst temperature in a lowest temperature range. 
   
   
       4 . The catalyst deterioration detecting system according to  claim 1 , further comprising a permission/inhibition determining unit that permits or inhibits detection of deterioration of the catalyst depending on a result of detection by the poisoning detector. 
   
   
       5 . The catalyst deterioration detecting system according to  claim 1 , further comprising a poisoning removal controller that performs poisoning removal control so as to regenerate the catalyst from poisoning when poisoning of the catalyst is detected by the poisoning detector. 
   
   
       6 . A catalyst deterioration detecting system of an internal combustion engine which detects deterioration of a catalyst disposed in an exhaust passage of the internal combustion engine, comprising:
 an active air/fuel ratio controller that performs active air/fuel ratio control for causing an air/fuel ratio of an exhaust gas entering the catalyst to be changed to a rich side or a lean side relative to a predetermined central air/fuel ratio;   a storage capacity measuring unit that measures an oxygen storage capacity of the catalyst during execution of the active air/fuel ratio control; and   a poisoning detector that detects poisoning of the catalyst based on a relationship between a change in a rich-side or lean-side amplitude established during the active air/fuel ratio control, and a change in the oxygen storage capacity measured by the storage capacity measuring unit, which change corresponds to the change in the rich-side or lean-side amplitude.   
   
   
       7 . The catalyst deterioration detecting system according to  claim 6 , wherein the poisoning detector detects poisoning of the catalyst based on an amount of change of the oxygen storage capacity between at least two points of the rich-side or lean-side amplitude. 
   
   
       8 . The catalyst deterioration detecting system according to  claim 7 , wherein the poisoning detector detects poisoning of the catalyst by comparing a value based on the amount of change of the oxygen storage capacity with a predetermined value, and the predetermined value is changed in accordance with a value of the oxygen storage capacity measured at a point at which the rich-side or lean-side amplitude is at a minimum. 
   
   
       9 . The catalyst deterioration detecting system according to  claim 6 , further comprising a permission/inhibition determining unit that permits or inhibits detection of deterioration of the catalyst depending on a result of detection by the poisoning detector. 
   
   
       10 . The catalyst deterioration detecting system according to  claim 6 , further comprising a poisoning removal controller that performs poisoning removal control so as to regenerate the catalyst from poisoning when poisoning of the catalyst is detected by the poisoning detector. 
   
   
       11 . A catalyst deterioration detecting method of an internal combustion engine for detecting deterioration of a catalyst disposed in an exhaust passage of the internal combustion engine, comprising:
 measuring an oxygen storage capacity of the catalyst;   detecting or estimating a temperature of the catalyst; and   detecting poisoning of the catalyst based on a relationship between a change in the detected or estimated catalyst temperature, and a change in the oxygen storage capacity corresponding to the change in the catalyst temperature.   
   
   
       12 . A catalyst deterioration detecting method of an internal combustion engine for detecting deterioration of a catalyst disposed in an exhaust passage of the internal combustion engine, comprising:
 performing active air/fuel ratio control for causing an air/fuel ratio of an exhaust gas entering the catalyst to be changed to a rich side or a lean side relative to a predetermined central air/fuel ratio;   measuring an oxygen storage capacity of the catalyst during execution of the active air/fuel ratio control; and   detecting poisoning of the catalyst based on a relationship between a change in a rich-side or lean-side amplitude established during the active air/fuel ratio control, and a change in the oxygen storage capacity corresponding to the change in the rich-side or lean-side amplitude.