Apparatus and method for preventing overheating of exhaust purification filter

Abstract

An apparatus for preventing a filter for purifying exhaust gas emitted by a vehicle diesel engine from overheating is provided. The filter filters particulate matter in exhaust gas. Particulate matter that is accumulated in the filter through filtering is burned and purified by executing a temperature increase process in which the filter is heated. The apparatus includes an electronic control unit as overheat prevention means. During the temperature increase process, the overheat prevention means executes an increase process for increasing the flow rate of exhaust gas when the filter is likely to overheat. As a result, the filter is effectively prevented from overheating.

1 . An apparatus for preventing a filter for purifying exhaust gas emitted by an internal combustion engine from overheating, wherein the filter filters particulate matter in exhaust gas, particulate matter that is accumulated in the filter through filtering is burned and purified by executing a temperature increase process in which the filter is heated, the apparatus comprising: 
 overheat prevention means, wherein, during the temperature increase process, the overheat prevention means executes an increase process for increasing the flow rate of exhaust gas when the filter is likely to overheat.    
   
   
       2 . The apparatus according to  claim 1 , wherein the increase process includes reducing, when the exhaust flow rate is decreasing, the rate at which the exhaust flow rate decreases.  
   
   
       3 . The apparatus according to  claim 1 , wherein the increase process of exhaust gas includes maintaining, when the exhaust flow rate is decreasing, the exhaust flow rate so that the exhaust flow rate stops decreasing.  
   
   
       4 . The apparatus according to  claim 1 , wherein the overheat prevention means executes the exhaust flow rate increase process by executing an intake flow rate increase process for increasing the flow rate of air that is drawn into the internal combustion engine.  
   
   
       5 . The apparatus according to  claim 4 , wherein the internal combustion engine includes an intake system, a throttle valve disposed in the intake system, an exhaust system, an exhaust gas recirculation passage connecting the exhaust system with the intake system, and an exhaust gas recirculation valve disposed in the exhaust gas recirculation passage, and wherein the intake flow rate increase process includes at least one of increasing an opening degree of the throttle valve and reducing an opening degree of the exhaust gas recirculation valve.  
   
   
       6 . The apparatus according to  claim 5 , wherein the increasing of the opening degree of the throttle valve includes maximizing the opening degree of the throttle valve, and wherein the reducing of the opening degree of the exhaust gas recirculation valve includes minimizing the opening degree of the exhaust gas recirculation valve.  
   
   
       7 . The apparatus according to  claim 1 , wherein the exhaust flow rate increase process includes increasing an idle speed when the internal combustion engine is idling.  
   
   
       8 . The apparatus according to  claim 1 , wherein the overheat prevention means determines that the filter is likely to overheat when the temperature of exhaust gas that flows out of the filter is higher than an overheat determination temperature.  
   
   
       9 . The apparatus according to  claim 1 , wherein the overheat prevention means determines that the filter is likely to overheat when at least one of situations occurs, the situations being a situation where the temperature of exhaust gas that flows into the filter is higher than a first overheat determination temperature and a situation where the temperature of exhaust gas that flows out of the filter is higher than a second overheat determination temperature.  
   
   
       10 . The apparatus according to  claim 1 , wherein the internal combustion engine includes an exhaust system and a fuel adding valve disposed in the exhaust system, wherein the overheat prevention means estimates the temperature of the filter based on the exhaust flow rate, an amount of fuel added to exhaust gas from the fuel adding valve, the temperature of exhaust gas that flows into the filter, and the temperature of exhaust gas that flows out of the filter, and wherein, when the estimated temperature of the filter is higher than an overheat determination temperature, the overheat prevention means determines that the filter is likely to overheat.  
   
   
       11 . The apparatus according to  claim 1 , wherein the overheat prevention means determines that the filter is likely to overheat when an amount of particulate matter accumulated in the filter is greater than a reference accumulation amount during the temperature increase process.  
   
   
       12 . The apparatus according to  claim 1 , wherein the overheat prevention means determines that the filter is likely to overheat when, during the temperature increase process, the internal combustion engine decelerates and the highest temperature of the filter that is estimated based on an operating state of the internal combustion engine exceeds an overheat determination temperature.  
   
   
       13 . The apparatus according to  claim 1 , wherein the overheat prevention means determines that the filter is likely to overheat when, during the temperature increase process, the highest temperature of the filter that is estimated based on an operating state of the internal combustion engine is higher than an overheat determination temperature.  
   
   
       14 . The apparatus according to  claim 13 , wherein the overheat prevention means estimates the highest temperature based on a decrease amount of the flow rate of air that is drawn into the internal combustion engine per unit time, and an amount of particulate matter accumulated in the filter.  
   
   
       15 . The apparatus according to  claim 1 , wherein the overheat prevention means determines that the filter is likely to overheat when the internal combustion engine decelerates and an amount of particulate matter accumulated in the filter exceeds a reference accumulation amount during the temperature increase process.  
   
   
       16 . The apparatus according to  claim 11 , wherein the temperature increase process includes a process for releasing sulfur collected on the filter.  
   
   
       17 . The apparatus according to  claim 13 , wherein the temperature increase process includes a process for releasing sulfur collected on the filter.  
   
   
       18 . An apparatus for preventing a filter for purifying exhaust gas emitted by an internal combustion engine from overheating, wherein the filter filters particulate matter in exhaust gas, particulate matter that is accumulated in the filter through filtering is burned and purified by executing a temperature increase process in which the filter is heated, the apparatus comprising: 
 means for reducing the rate of decrease of the flow rate of exhaust gas when the filter is likely to overheat during the temperature increase process.    
   
   
       19 . A method for preventing a filter for purifying exhaust gas emitted by an internal combustion engine from overheating, the method comprising: 
 filtering particulate matter in exhaust gas with the filter;    burning and purifying particulate matter that is accumulated in the filter through filtering by executing the temperature increase process in which the filter is heated; and    executing an increase process for increasing the flow rate of exhaust gas when the filter is likely to overheat during the temperature increase process.    
   
   
       20 . The method according to  claim 19 , wherein the increase process is executed by executing an intake flow rate increase process for increasing the flow rate of air that is drawn into the internal combustion engine.