Engine self-diagnosis system

Abstract

An engine self-diagnosis system capable of performing diagnosis of the light-off performance of a catalyst at a low cost and high accuracy without requiring addition or improvement of a sensor, etc. The engine self-diagnosis system comprises a unit for directly or indirectly detecting performance A of an exhaust cleaning catalyst when temperature of the catalyst is within a predetermined temperature range, and a unit for, based on the detected catalyst performance A, estimating performance B of the catalyst, which is resulted when the temperature of the catalyst is outside the predetermined temperature range.

1 . An engine self-diagnosis system comprising: 
 means for directly or indirectly detecting performance A of an exhaust cleaning catalyst when temperature of said catalyst or temperature of exhaust gas flowing into said catalyst is within a predetermined temperature range; and    means for, based on the detected catalyst performance A, estimating performance B of said catalyst which is resulted, when the temperature of said catalyst is outside the predetermined temperature range.    
   
   
       2 . The engine self-diagnosis system according to  claim 1 , wherein said catalyst has at least three-way performance.  
   
   
       3 . The engine self-diagnosis system according to  claim 1 , wherein said catalyst is an HC adsorbing combustion catalyst that adsorbs HC when the catalyst temperature is within a predetermined temperature range, desorbs the adsorbed HC when the catalyst temperature exceeds the predetermined temperature range, and cleans the adsorbed and desorbed HC.  
   
   
       4 . The engine self-diagnosis system according to  claim 1 , wherein said catalyst is a lean NOx catalyst.  
   
   
       5 . The engine self-diagnosis system according to  Claim 1 , further comprising: 
 means for directly or indirectly detecting the temperature of said catalyst;    means for directly or indirectly detecting the catalyst performance A when the catalyst temperature detected by said detecting means is within a temperature range in which an exhaust cleaning rate is not smaller than a predetermined value; and    means for, based on the detected catalyst performance A, estimating the catalyst performance B resulted when the catalyst temperature detected by said detecting means is within a temperature range in which the exhaust cleaning rate is smaller than the predetermined value.    
   
   
       6 . The engine self-diagnosis system according to  claim 1 , wherein the catalyst performance B is a catalyst temperature T 0  at which the exhaust cleaning rate is not smaller than the predetermined value.  
   
   
       7 . The engine self-diagnosis system according to  claim 6 , further comprising catalyst deterioration determining means for determining that said catalyst has deteriorated, when the catalyst temperature T 0  at which the exhaust cleaning rate is not smaller than the predetermined value exceeds a predetermined temperature.  
   
   
       8 . The engine self-diagnosis system according to  claim 7 , wherein said catalyst is an HC adsorbing combustion catalyst, and said catalyst deterioration determining means determines that said HC adsorbing combustion catalyst has deteriorated, when the catalyst temperature T 0  at which the exhaust cleaning rate is not smaller than the predetermined value exceeds a predetermined temperature.  
   
   
       9 . The engine self-diagnosis system according to  claim 7 , wherein said catalyst is a lean NOx catalyst, and said catalyst deterioration determining means determines that said lean NOx catalyst has deteriorated, when the catalyst temperature T 0  at which the exhaust cleaning rate is not smaller than the predetermined value exceeds a predetermined temperature.  
   
   
       10 . The engine self-diagnosis system according to  claim 1 , wherein the catalyst performance A is exhaust cleaning capacity.  
   
   
       11 . The engine self-diagnosis system according to  claim 1 , wherein the catalyst performance A is oxygen storage capacity.  
   
   
       12 . The engine self-diagnosis system according to  claim 1 , wherein the catalyst performance A is given as exhaust cleaning capacity, and the catalyst performance B is given as the catalyst temperature T 0  at which the exhaust cleaning rate is not smaller than the predetermined value.  
   
   
       13 . The engine self-diagnosis system according to  claim 1 , wherein the catalyst performance A is given as oxygen storage capacity, and the catalyst performance B is given as the catalyst temperature T 0  at which the exhaust cleaning rate is not smaller than the predetermined value or the oxygen storage capacity is not smaller than a predetermined value.  
   
   
       14 . The engine self-diagnosis system according to  claim 1 , further comprising exhaust component detecting means disposed downstream of said catalyst.  
   
   
       15 . The engine self-diagnosis system according to  claim 1 , further comprising an O 2  sensor or an A/F sensor downstream of said catalyst.  
   
   
       16 . The engine self-diagnosis system according to  claim 15 , further comprising means for detecting oxygen storage capacity of said catalyst based on an output signal from said O 2  sensor or said A/F sensor.  
   
   
       17 . The engine self-diagnosis system according to  claim 15 , further comprising: 
 means for oscillating an O 2  concentration or an air/fuel ratio upstream of said catalyst at a predetermined frequency;    means for computing a component at the predetermined frequency of the output signal from said O 2  sensor or said A/F sensor; and    means for detecting oxygen storage capacity of said catalyst based on the computed component at the predetermined frequency.    
   
   
       18 . The engine self-diagnosis system according to  claim 15 , further comprising: 
 means for changing an O 2  concentration or an air/fuel ratio upstream of said catalyst by a predetermined value;    response delay time computing means for computing a response delay time from a time at which the O 2  concentration or the air/fuel ratio upstream of said catalyst is changed by a predetermined value to a time at which an output signal from said O 2  sensor downstream of said catalyst is changed by a predetermined value; and    means for detecting oxygen storage capacity of said catalyst based on the computed response delay time.    
   
   
       19 . The engine self-diagnosis system according to  claim 1 , further comprising: 
 means for raising temperature of said catalyst;    catalyst temperature estimating means;    an O 2  sensor, an A/F sensor, or an exhaust sensor disposed downstream of said catalyst;    means for directly detecting, based on an output signal from said O 2  sensor, said A/F sensor, or said exhaust sensor, whether the exhaust cleaning rate of said catalyst is not smaller than a predetermined value and said catalyst is in a light-off state; and    abnormality determining means for determining said catalyst temperature raising means to be abnormal, when said means for directly detecting catalyst light-off does not detect that said catalyst is in the light-off state, in spite of the catalyst temperature estimated by said catalyst temperature estimating means reaching an estimated light-off temperature representing the catalyst performance B.    
   
   
       20 . The engine self-diagnosis system according to  claim 1 , further comprising means for indicating the catalyst performance A and/or B or information related to the catalyst performance A and/or B.  
   
   
       21 . The engine self-diagnosis system according to  claim 1 , further comprising means for modifying an engine control parameter based on the catalyst performance A and/or B.  
   
   
       22 . The engine self-diagnosis system according to  claim 21 , further comprising means for modifying a control parameter for said catalyst temperature raising means based on the catalyst performance B represented by a catalyst temperature T 0  at which an exhaust cleaning rate is not smaller than the predetermined value.  
   
   
       23 . The engine self-diagnosis system according to  claim 21 , wherein the control parameter for said catalyst temperature raising means is a retard amount of ignition timing and/or a period during which the ignition timing is retarded.  
   
   
       24 . An automobile equipped with the engine self-diagnosis system according to any one of  claims 1  to  23 .