Exhaust gas purification apparatus of internal combustion engine

Abstract

An exhaust gas purification apparatus of an internal combustion engine of the invention includes an electrical heating catalyzer. The catalyzer includes a catalyst carrier which produces heat when the catalyst carrier is energized, a pair of electrodes provided on the catalyst carrier, a casing which houses the catalyst carrier and at least one insulation member provided between the catalyst carrier and the casing. The apparatus executes a PM removal control for increasing a temperature of the electrical heating catalyzer by using energy discharged from the engine to an exhaust passage to remove particulate matter from the catalyzer in response to temperature of the particulate matter and an insulation resistance value between the catalyst carrier and the casing satisfying a predetermined removal condition.

What is claimed is: 
     
         1 . An exhaust gas purification apparatus of an internal combustion engine, the exhaust gas purification apparatus comprising:
 an electrical heating catalyzer provided in an exhaust passage of the internal combustion engine, the electrical heating catalyzer including:
 a catalyst carrier which carries catalyst, the catalyst carrier producing heat when the catalyst carrier is energized; 
 a pair of electrodes provided on the catalyst carrier, the electrodes being provided to energize the catalyst carrier; 
 a casing which houses the catalyst carrier provided with the electrodes; and 
 at least one insulation member provided between the catalyst carrier and the casing; and 
   an electronic control unit configured to apply potential difference to the electrodes to energize the catalyst carrier when energization of the catalyst carrier is requested,   
       wherein the electronic control unit is configured:
 to acquire an insulation resistance value corresponding to an electric resistance value between the catalyst carrier and the casing as a acquired resistance value; 
 to estimate a temperature of accumulating particulate matter which is particulate matter accumulating in the electrical heating catalyzer as an estimated PM temperature; and 
 to execute a PM removal control for increasing a temperature of the electrical heating catalyzer by using energy discharged from the internal combustion engine to the exhaust passage to remove the accumulating particulate matter in response to the estimated PM temperature and the acquired resistance value satisfying a predetermined removal condition which is satisfied when the accumulating particulate matter should be removed in the state that the catalyst carrier is not energized. 
 
     
     
         2 . The exhaust gas purification apparatus of the internal combustion engine according to  claim 1 , wherein the electronic control unit is configured to execute the PM removal control in response to the electronic control unit estimating that no water adheres to the electrical heating catalyzer and the estimated PM temperature and the acquired resistance value satisfying the predetermined removal condition. 
     
     
         3 . The exhaust gas purification apparatus of the internal combustion engine according to  claim 1 , wherein the electronic control unit is configured:
 to acquire the estimated PM temperature acquired at a time of acquiring the acquired resistance value as a particular PM temperature;   to convert the acquired resistance value on the basis of the particular PM temperature to acquire a converted resistance value corresponding to the acquired resistance value to be acquired when the particular PM temperature corresponds to a predetermined base temperature;   to determine that the predetermined removal condition is satisfied and execute the PM removal control when the converted resistance value is smaller than a predetermined first resistance threshold which is a threshold of the insulation resistance value used for determining whether the accumulating particulate matter should be removed when the particular PM temperature corresponds to the predetermined base temperature;   to acquire the converted resistance value which increases as the particular PM temperature increases when the particular PM temperature is higher than or equal to the predetermined base temperature; and   to acquire the converted resistance value which decreases as the particular PM temperature decreases when the particular PM temperature is lower than the predetermined base temperature.   
     
     
         4 . The exhaust gas purification apparatus of the internal combustion engine according to  claim 1 , wherein the electronic control unit is configured:
 to acquire the estimated PM temperature acquired at a time of acquiring the acquired resistance value as a particular PM temperature;   to convert a base resistance threshold on the basis of the particular PM temperature to acquire a second resistance threshold which corresponds to a threshold of the insulation resistance value used for determining whether the accumulating particulate matter should be removed on the basis of the acquired resistance value, the base resistance threshold being a threshold of the insulation resistance value used for determining whether the accumulating particulate matter should be removed when the particular PM temperature corresponds to a predetermined base temperature;   to determine that the predetermined removal condition is satisfied and execute the PM removal control when the acquired resistance value is smaller than the second resistance threshold; and   to acquire the second resistance threshold such that the second resistance threshold acquired when the particular PM temperature is relatively high, is smaller than the second resistance threshold acquired when the particular PM temperature is relatively low.   
     
     
         5 . The exhaust gas purification apparatus of the internal combustion engine according to  claim 1 , wherein the exhaust gas purification apparatus further comprises a voltage measuring device for measuring a voltage between the catalyst carrier and the casing and the electronic control unit is further configured to acquire the acquired resistance value on the basis of the voltage.