Engine exhaust purifying apparatus

Abstract

The present invention has its object to judge the establishment of conditions influencing on the evaluation of performance of a NOx catalyst, whereby when being established, the evaluation of performance of the NOx catalyst is stopped to thereby prevent the performance of the NOx catalyst from being erroneously judged. The aforementioned object is realized by an engine exhaust purifying apparatus comprising a NOx trap which is provided in an exhaust passage of an engine to trap NOx in exhaust gases by adsorption or absorption when the air/fuel ratio of a mixture gas is lean, and to release or reduce NOx when the air/fuel ratio is rich, and NOx trapping quantity judging means for evaluating the exhaust purifying performance including the NOx trapping quantity of the NOx trap, wherein the operating state of the NOx trap is measured directly or indirectly, and when the measured operating state is judged to be beyond a predetermined range, the purifying performance evaluation of the NOx trap is inhibited or stopped. Further, the aforementioned object is realized by an engine exhaust purifying apparatus comprising a NOx trap which is provided in the engine exhaust passage to trap such as adsorption or absorption NOx of exhaust gases when the air/fuel ratio of exhaust gases is lean, and to release or reduce NOx when the air/fuel ratio is rich, and NOx trapping quantity judging means for evaluating the exhaust purifying performance including the NOx trapping quantity of the NOx trap, characterized in that the operating state of the NOx trap is measured directly or indirectly, and when the measured operating state is judged to be beyond the predetermined range, the purifying performance evaluation of the NOx trap is inhibited or stopped. According to the present invention, since the release of oxygen stored and the timing of the release of NOx trapped are detected separately by the output of the air/fuel ratio sensor at the downstream of the NO trap for trapping NOx, it is possible to provide an engine exhaust purifying apparatus capable of detecting the NOx trap quantity and the oxygen storage capacity separately with good accuracy. Under the circumstances that the aforesaid detection accuracy cannot be secured, it is possible to prevent an erroneous detection by inhibiting or stopping the detecting operation.

What is claimed is:  
     
         1 . An engine exhaust purifying apparatus, comprising: 
 an exhaust component trap which is provided in an exhaust passage of an engine and having a trapping function to adsorb or absorb an exhaust component; and    means for evaluating the performance of said exhaust component trap;    wherein when at least one of an operating state of an engine system, the operating state of said exhaust component trap, and said means for evaluating the performance of said exhaust component trap is judged to be beyond a predetermined operating range, the performance evaluation of said exhaust component trap is inhibited or stopped.    
     
     
         2 . An engine exhaust purifying apparatus, comprising: 
 a NOx trap which is provided in an exhaust passage of an engine to trap NOx in exhaust gases by adsorption or absorption when the air/fuel ratio of a mixture gas is lean, and to release or reduce NOx when the air/fuel ratio is rich; and    NOx trapping quantity judging means for evaluating the exhaust purifying performance including the NOx trapping quantity of said NOx trap;    wherein the operating state of said NOx trap is measured directly or indirectly, and when said measured operating state is judged to be beyond a predetermined range, the purifying performance evaluation of said NOx trap is inhibited or stopped.    
     
     
         3 . The engine exhaust purifying apparatus according to  claim 2 , wherein as the operating state of said NOx trap, the internal temperature of said NOx trap is measured directly or indirectly, and when said measured temperature is judged to be beyond a predetermined range, the purifying performance evaluation of said NOx trap is inhibited or stopped.  
     
     
         4 . The engine exhaust purifying apparatus according to  claim 2 , wherein the internal air/fuel ratio of said NOx trap is measured directly or indirectly, and when said measured air/fuel ratio is judged to be beyond a predetermined range, the purifying performance evaluation of said NOx trap is inhibited or stopped.  
     
     
         5 . The engine exhaust purifying apparatus according to  claim 2 , wherein the component ratio of the internal exhaust gases of said NOx trap is measured directly or indirectly, and when said measured component ratio is judged to be beyond a predetermined range, the purifying performance evaluation of said NOx trap is inhibited or stopped.  
     
     
         6 . An engine exhaust purifying apparatus, comprising: 
 a NOx trap which is provided in an exhaust passage of an engine to trap NOx in exhaust gases by adsorption or absorption when the air/fuel ratio of a mixture is lean, and to release or reduce NOx when the air/fuel ratio is rich; and    NOx trapping quantity judging means for evaluating the exhaust purifying performance including the NOx trapping quantity of said NOx trap;    wherein an operating state of an engine system is measured directly or indirectly, and when said measured operating state is judged to be beyond a predetermined range, the purifying performance evaluation of said NOx trap is inhibited or stopped.    
     
     
         7 . The engine exhaust purifying apparatus according to  claim 6 , wherein as the operating system of said engine system, when an engine parameter influencing on at least one of the exhaust temperature of the engine, the exhaust air/fuel ratio, the exhaust component, and the exhaust gas quantity is judged to be beyond a predetermined range, the purifying performance evaluation of said NOx trap is inhibited or stopped.  
     
     
         8 . An engine exhaust purifying apparatus, comprising: 
 a NOx trap which is provided in an exhaust passage of an engine to trap NOx in exhaust gases by adsorption or absorption when the air/fuel ratio of a mixture is lean, and to release or reduce NOx when the air/fuel ratio is rich; and    NOx trapping quantity judging means for evaluating the exhaust purifying performance including the NOx trapping quantity of said NOx trap;    wherein the operating state of said NOx trap performance evaluation means is judged directly or indirectly, and the purifying performance evaluation of said NOx trap is inhibited or stopped on the basis of said judged operating state.