Apparatus, Method, and System for Diagnosing Reductant Deposits in an Exhaust Aftertreatment System

Abstract

An exhaust gas treatment system for an internal combustion engine may have a reductant delivery system that delivers reductant to an exhaust stream in an exhaust aftertreatment system. A temperature sensor may be positioned in or near the flow of reductant and exhaust to measure the temperature of the reductant and exhaust. A change in temperature over time, such as an increase, decrease, or change in variation amplitude, may indicate the presence of a reductant deposit in the system. Detection of the deposit may initiate a regeneration cycle in which the operating characteristics of the system change to eliminate the reductant deposit to prevent it from hindering the performance of the exhaust aftertreatment system.

What is claimed is: 
     
         1 . A method for diagnosing existence of a reductant deposit in an exhaust aftertreatment system that delivers reductant to exhaust gas produced by an internal combustion engine to provide a mixture of exhaust gas and reductant, the method comprising:
 sampling a temperature of the mixture of exhaust gas and reductant with a temperature sensor positioned in or near the exhaust aftertreatment system;   determining when the temperature is below a predetermined temperature value;   in response to the determined temperature being below the predetermined threshold value, determining a presence of a reductant deposit in the exhaust aftertreatment system; and   in response to determining the presence of the reductant deposit, initiating a regeneration cycle of the internal combustion engine to increase a temperature of the exhaust gas flowing through the exhaust aftertreatment system to at least partially remove the reductant deposit.   
     
     
         2 . The method of  claim 1 , further comprising, before sampling the temperature of the mixture of exhaust gas and reductant, positioning the temperature sensor in or near the exhaust aftertreatment system. 
     
     
         3 . The method of  claim 1 , wherein the predetermined temperature value is a value corresponding to a temperature indicative of impeded heat transfer due to the reductant deposit. 
     
     
         4 . The method of  claim 1 , wherein the temperature sensor is positioned near a boss that extends from a decomposition chamber of the exhaust aftertreatment system, and a reductant delivery system of the exhaust aftertreatment system delivers reductant to the exhaust gas through the boss. 
     
     
         5 . The method of  claim 1 , wherein the predetermined temperature value is less than a value for a normal temperature region. 
     
     
         6 . The method of  claim 1 , wherein sampling the temperature occurs at a predetermined time increment. 
     
     
         7 . The method of  claim 1 , wherein the temperature sensor is positioned outside of an exhaust line of the exhaust aftertreatment system. 
     
     
         8 . The method of  claim 1 , wherein the predetermined temperature value is between 100 degrees Celsius and 200 degrees Celsius. 
     
     
         9 . An on-board diagnostic apparatus for diagnosing an existence of a reductant deposit in an exhaust aftertreatment system, the apparatus comprising:
 a sampling circuit configured to sample a temperature of a mixture of exhaust gas and reductant with a temperature sensor;   a comparison circuit configured to:
 determine when the temperature is below a predetermined temperature value; and 
 in response to determining that the temperature is below the predetermined temperature value, determine a presence of a reductant deposit in an exhaust aftertreatment system; and 
   a regeneration circuit configured to, in response to determining the presence of a reductant deposit, initiate a regeneration cycle of an internal combustion engine to increase a temperature of exhaust gas flowing through the exhaust aftertreatment system to at least partially remove the reductant deposit.   
     
     
         10 . The apparatus of  claim 9 , wherein the predetermined temperature value is a value corresponding to a temperature indicative of impeded heat transfer due to the reductant deposit. 
     
     
         11 . The apparatus of  claim 9 , wherein the temperature sensor is positioned near a boss that extends from a decomposition chamber of the exhaust aftertreatment system, and a reductant delivery system of the exhaust aftertreatment system delivers reductant to the exhaust gas through the boss. 
     
     
         12 . The apparatus of  claim 9 , wherein the predetermined temperature value is less than a value for a normal temperature region. 
     
     
         13 . The apparatus of  claim 9 , wherein sampling the temperature occurs at a predetermined time increment. 
     
     
         14 . The apparatus of  claim 9 , wherein the temperature sensor is positioned outside of an exhaust line of the exhaust aftertreatment system 
     
     
         15 . The apparatus of  claim 9 , wherein the predetermined temperature value is between 100 degrees Celsius and 200 degrees Celsius. 
     
     
         16 . A system comprising:
 an exhaust aftertreatment system in fluid communication with the internal combustion engine to receive exhaust gas from the internal combustion engine, the exhaust aftertreatment system injecting reductant into the exhaust gas to create a mixture of exhaust gas and reductant,   a temperature sensor positioned in or near the exhaust aftertreatment system; and   an onboard diagnostic system including:
 a sampling circuit configured to sample a temperature of a mixture of exhaust gas and reductant with the temperature sensor; 
 a comparison circuit configured to:
 determine when the temperature exceeds a predetermined temperature value; and 
 in response to determining that the temperature exceeds the predetermined temperature value, determine a presence of a reductant deposit in an exhaust aftertreatment system; and 
 
 a regeneration circuit configured to, in response to determining the presence of a reductant deposit, initiate a regeneration cycle to increase a temperature of exhaust gas flowing through the exhaust aftertreatment system to at least partially remove the reductant deposit. 
   
     
     
         17 . The system of  claim 16 , wherein the predetermined temperature value is a value corresponding to a temperature indicative of impeded heat transfer due to the reductant deposit. 
     
     
         18 . The system of  claim 16 , wherein the temperature sensor is positioned near a boss that extends from a decomposition chamber of the exhaust aftertreatment system, and a reductant delivery system of the exhaust aftertreatment system is configured to deliver reductant to the exhaust gas through the boss. 
     
     
         19 . The system of  claim 16 , wherein sampling the temperature occurs at a predetermined time increment. 
     
     
         20 . The system of  claim 16 , wherein the predetermined temperature value is less than a value for a normal temperature region.