EGR apparatus of engine

Abstract

An EGR apparatus includes an EGR passage to allow part of exhaust gas discharged from an engine to an exhaust passage to flow as EGR gas into an intake passage; an EGR valve to regulate an EGR flow rate in the EGR passage; various sensors for detecting an engine running state; and an ECU to control the EGR valve based on the detected running state to diagnose abnormality in the EGR valve. The ECU calculates a reference intake pressure according the detected engine rotation speed and load by reference to a reference intake pressure map showing a relationship of the reference intake pressure to engine rotation speed, and engine load, and determine whether or not the EGR valve has abnormality in opening/closing by comparing the reference intake pressure with the detected intake pressure.

What is claimed is: 
     
       1. An EGR apparatus of an engine, the EGR apparatus comprising:
 an EGR passage configured to allow part of exhaust gas discharged from the engine to an exhaust passage to flow as EGR gas from the exhaust passage to an intake passage in order to recirculate the EGR gas into the engine; 
 an EGR valve configured to regulate a flow rate of the EGR gas in the EGR passage, the EGR valve including a valve seat, a valve element provided to be seatable on the valve seat, and an actuator to move the valve element; 
 a running-state detecting unit configured to detect a running state of the engine; 
 an EGR valve control unit configured to control the EGR valve based on the detected running state; and 
 an EGR valve abnormality diagnosing unit configured to diagnose an abnormality in opening/closing between the valve seat and the valve element of the EGR valve based on the detected running state, wherein 
 the running-state detecting unit includes:
 an intake pressure detecting unit configured to detect intake pressure in the intake passage downstream of a position where the EGR gas flows from the EGR passage into the intake passage; 
 a rotation speed detecting unit configured to detect a rotation speed of the engine; and 
 a load detecting unit configured to detect a load of the engine, 
 
 the EGR valve abnormality diagnosing unit is configured to determine whether or not the EGR valve has the abnormality by comparing a reference intake pressure calculated based on the detected rotation speed and the detected load with the detected intake pressure or by comparing a reference opening degree of the EGR valve calculated based on the detected rotation speed, the detected load, and the detected intake pressure with a control opening degree of the EGR valve under control by the EGR valve control unit, 
 the EGR valve abnormality diagnosing unit is provided with a reference function map or a reference function expression previously set to show a relationship of the reference intake pressure to the rotation speed and the load, and 
 the EGR valve abnormality diagnosing unit is configured to calculate the reference intake pressure according to the detected rotation speed and the detected load by reference to the reference function map or the reference function expression, and determine whether or not the EGR valve has the abnormality by comparing the calculated reference intake pressure with the detected intake pressure, 
 when the engine is in deceleration and the EGR valve control unit the EGR valve to close to a valve-closed state, and 
 the EGR valve abnormality diagnosing unit is configured to determine whether or not the EGR valve has the abnormality by comparing a decrease rate of the detected intake pressure with a predetermined decrease rate. 
 
     
     
       2. An EGR apparatus of an engine, the EGR apparatus comprising:
 an EGR passage configured to allow part of exhaust gas discharged from the engine to an exhaust passage to flow as EGR gas from the exhaust passage to an intake passage in order to recirculate the EGR gas into the engine; 
 an EGR valve configured to regulate a flow rate of the EGR gas in the EGR passage, 
 the EGR valve including a valve seat, a valve element provided to be seatable on the valve seat, and an actuator to move the valve element; 
 a running-state detecting unit configured to detect a running state of the engine; 
 an EGR valve control unit configured to control the EGR valve based on the detected running state; and 
 an EGR valve abnormality diagnosing unit configured to diagnose an abnormality in opening/closing between the valve seat and the valve element of the EGR valve based on the detected running state, wherein 
 the running-state detecting unit includes:
 an intake pressure detecting unit configured to detect intake pressure in the intake passage downstream of a position where the EGR gas flows from the EGR passage into the intake passage; 
 a rotation speed detecting unit configured to detect a rotation speed of the engine; and 
 a load detecting unit configured to detect a load of the engine, 
 
 the EGR valve abnormality diagnosing unit is configured to determine whether or not the EGR valve has the abnormality by comparing a reference intake pressure calculated based on the detected rotation speed and the detected load with the detected intake pressure or by comparing a reference opening degree of the EGR valve calculated based on the detected rotation speed, the detected load, and the detected intake pressure with a control opening degree of the EGR valve under control by the EGR valve control unit, 
 the EGR valve abnormality diagnosing unit is provided with a reference function map or a reference function expression previously set to show a relationship of the reference intake pressure to the rotation speed and the load, and 
 the EGR valve abnormality diagnosing unit is configured to calculate the reference intake pressure according to the detected rotation speed and the detected load by reference to the reference function map or the reference function expression, and determine whether or not the EGR valve has the abnormality by comparing the calculated reference intake pressure with the detected intake pressure, 
 the EGR apparatus further includes a foreign-matter removal control unit, and 
 when it is determined that the EGR valve has the abnormality, the foreign-matter removal control unit is configured to:
 obtain an opening degree corresponding to a diameter of a foreign matter lodged between the valve seat and the valve element based on a foreign-matter diameter equivalent ratio obtained by dividing the detected intake pressure by the calculated reference intake pressure; and 
 execute a foreign-matter removal control that controls the actuator to open the valve element at a larger opening degree than the obtained opening degree corresponding to the diameter of the foreign matter to remove the foreign matter from between the valve seat and the valve element. 
 
 
     
     
       3. An EGR apparatus of an engine, the EGR apparatus comprising:
 an EGR passage configured to allow part of exhaust gas discharged from the engine to an exhaust passage to flow as EGR gas from the exhaust passage to an intake passage in order to recirculate the EGR gas into the engine; 
 an EGR valve configured to regulate a flow rate of the EGR gas in the EGR passage, 
 the EGR valve including a valve seat, a valve element provided to be seatable on the valve seat, and an actuator to move the valve element; 
 a running-state detecting unit configured to detect a running state of the engine; 
 an EGR valve control unit configured to control the EGR valve based on the detected running state; and 
 an EGR valve abnormality diagnosing unit configured to diagnose an abnormality in opening/closing between the valve seat and the valve element of the EGR valve based on the detected running state, wherein 
 the running-state detecting unit includes:
 an intake pressure detecting unit configured to detect intake pressure in the intake passage downstream of a position where the EGR gas flows from the EGR passage into the intake passage; 
 a rotation speed detecting unit configured to detect a rotation speed of the engine; and 
 a load detecting unit configured to detect a load of the engine, and 
 
 the EGR valve abnormality diagnosing unit is configured to determine whether or not the EGR valve has the abnormality by comparing a reference intake pressure calculated based on the detected rotation speed and the detected load with the detected intake pressure or by comparing a reference opening degree of the EGR valve calculated based on the detected rotation speed, the detected load, and the detected intake pressure with a control opening degree of the EGR valve under control by the EGR valve control unit, 
 the EGR valve abnormality diagnosing unit is provided with a reference function map or a reference function expression previously set to show a relationship of the reference opening degree of the EGR valve to the rotation speed, the load, and the intake pressure, 
 the EGR valve abnormality diagnosing unit is configured to calculate the reference opening degree according to the detected rotation speed, the detected load, and the detected intake pressure by reference to the reference function map or the reference function expression, and determine whether or not the EGR valve has the abnormality by comparing the calculated reference opening degree with the control opening degree, 
 the EGR apparatus further includes a foreign-matter removal control unit, and 
 when it is determined that the EGR valve has the abnormality, the foreign-matter removal control unit is configured to:
 obtain an opening degree corresponding to a diameter of a foreign matter lodged between the valve seat and the valve element according to the calculated reference opening degree, and 
 execute a foreign-matter removal control that controls the actuator to open the valve element at a larger opening degree than the obtained opening degree corresponding to the diameter of the foreign matter to remove the foreign matter from between the valve seat and the valve element. 
 
 
     
     
       4. The EGR apparatus of an engine according to  claim 2 , wherein
 the foreign-matter removal control unit is configured such that 
 when the engine is in deceleration and fuel supply to the engine is cut off, the foreign-matter removal control unit immediately executes the foreign-matter removal control, and 
 when the engine is in deceleration and the fuel supply is not cut off, the foreign-matter removal control unit executes the foreign-matter removal control when an opening degree of the valve element needed to remove the foreign matter is smaller than a predetermined upper limit opening degree. 
 
     
     
       5. The EGR apparatus of an engine according to  claim 3 , wherein
 the foreign-matter removal control unit is configured such that 
 when the engine is in deceleration and fuel supply to the engine is cut off, the foreign-matter removal control unit immediately executes the foreign-matter removal control, and 
 when the engine is in deceleration and the fuel supply is not cut off, the foreign-matter removal control unit executes the foreign-matter removal control when an opening degree of the valve element needed to remove the foreign matter is smaller than a predetermined upper limit opening degree. 
 
     
     
       6. The EGR apparatus of an engine according to  claim 4 , wherein the foreign-matter removal control unit configured to correct the upper limit opening degree according to the running state of the engine related to combustion proof stress in the engine. 
     
     
       7. The EGR apparatus of an engine according to  claim 5 , wherein the foreign-matter removal control unit is configured to correct the upper limit opening degree according to the running state of the engine related to combustion proof stress in the engine. 
     
     
       8. An EGR apparatus of an engine, the EGR apparatus comprising:
 an EGR passage configured to allow part of exhaust gas discharged from the engine to an exhaust passage to flow as EGR gas from the exhaust passage to an intake passage in order to recirculate the EGR gas into the engine;   an EGR valve configured to regulate a flow rate of the EGR gas in the EGR passage, the EGR valve including a valve seat, a valve element configured to be seatable on the valve seat, and an actuator configured to move the valve element;   a throttle valve disposed in the intake passage;   an intake pressure sensor configured to detect an intake pressure in the intake passage downstream of the throttle valve;   a rotation speed sensor configured to detect a rotation speed of the engine;   a load sensor configured to detect a load of the engine; and   a processor programmed to
 determine whether or not the EGR valve has an abnormality in opening/closing between the valve seat and the valve element by comparing (i) the detected intake pressure with (ii) an addition result, the addition result having been obtained by adding a pressure increase allowance according to the detected rotation speed of the engine to a reference intake pressure, the reference intake pressure having been calculated based on the detected rotation speed and the detected load; and 
 in response to determining the EGR valve has the abnormality,
 obtain an opening degree corresponding to a diameter of a foreign matter lodged between the valve seat and the valve element based on a foreign-matter diameter equivalent ratio obtained by dividing the detected intake pressure by the reference intake pressure, and 
 execute a foreign-matter removal control that controls the actuator to open the valve element at a larger opening degree than the obtained opening degree corresponding to the diameter of the foreign matter to remove the foreign matter from between the valve seat and the valve element. 
 
   
     
     
       9. An EGR apparatus of an engine, the EGR apparatus comprising:
 an EGR passage configured to allow part of exhaust gas discharged from the engine to an exhaust passage to flow as EGR gas from the exhaust passage to an intake passage in order to recirculate the EGR gas into the engine;   an EGR valve configured to regulate a flow rate of the EGR gas in the EGR passage, the EGR valve including a valve seat, a valve element configured to be seatable on the valve seat, and an actuator configured to move the valve element;   a throttle valve disposed in the intake passage;   an intake pressure sensor configured to detect an intake pressure in the intake passage downstream of the throttle valve;   a rotation speed sensor configured to detect a rotation speed of the engine; and   a load sensor configured to detect a load of the engine; and   a processor programmed to
 control the EGR valve based on the detected intake pressure, the detected rotation speed, and the detected load; and 
 determine whether or not the EGR valve has an abnormality in opening/closing between the valve seat and the valve element by comparing (i) the detected intake pressure with (ii) an addition result, the addition result having been obtained by adding a pressure increase allowance according to the detected rotation speed of the engine to a reference intake pressure, the reference intake pressure having been calculated based on the detected rotation speed and the detected load.