Leak check for fuel vapor purge system

Abstract

A leak check system executes a leak check processing. In the leak check processing, the system closes a canister valve and a purge valve to close the fuel vapor purge system. Then, the system detects and monitors a pressure in the fuel vapor purge system. During the leak check processing, the system detects a rapid change of the pressure that is caused by a deformation of a wall of a fuel tank. The system cancels or suspends the processing to avoid erroneous detection of the leak. If the leak check is canceled, the system opens the canister valve to open the fuel vapor purge system.

1. An apparatus of checking a leak in a fuel vapor purge system comprising:
 pressure detecting means for detecting a pressure of a fuel vapor purge system including a fuel tank;  
 leak checking means for checking presence or absence of the leak in the fuel vapor purge system based on the pressure of the fuel vapor purge system detected by the pressure checking means when the fuel vapor purge system is maintained in a hermetically closed state;  
 erroneous check avoiding means for avoiding an erroneous check caused by a deformation of the fuel tank;  
 restricting means for restricting the pressure of the fuel vapor purge system into a predetermined restricted value when the leak checking means checks the leak;  
 temperature determining means for determining a temperature in the fuel tank or a temperature around the fuel tank or information related thereto; and  
 means for changing the restricted value based on the temperature determined by the temperature determining means.  
 
     
     
       2. The apparatus of checking a leak of a fuel vapor purge system according to  claim 1 , wherein the restricting means restricts increase of the pressure. 
     
     
       3. An apparatus of checking a leak in a fuel vapor purge system comprising:
 pressure detecting means for detecting a pressure of a fuel vapor purge system including a fuel tank;  
 leak checking means for checking presence or absence of the leak in the fuel vapor purge system based on the pressure of the fuel vapor purge system detected by the pressure checking means when the fuel vapor purge system is maintained in a hermetically closed state;  
 erroneous check avoiding means for avoiding an erroneous check caused by a deformation of the fuel tank;  
 restricting means for restricting the pressure of the fuel vapor purge system into a predetermined restricted value when the leak checking means checks the leak; and  
 means for correcting the restricted value in a direction of approaching an atmospheric pressure when the pressure of the fuel vapor purge system detected by the pressure detecting means is rapidly changed in checking the leak by the leak checking means.  
 
     
     
       4. The apparatus of checking a leak of a fuel vapor purge system according to  claim 3 , wherein the restricting means restricts increase of the pressure. 
     
     
       5. An apparatus of checking a leak of a fuel vapor purge system which is a fuel vapor purge system for purging fuel vapor generated by evaporating a fuel in a fuel tank to an intake system of an engine, said apparatus comprising:
 pressure detecting means for detecting a pressure of the fuel vapor purge system including the fuel tank;  
 a first valve for opening and closing an atmosphere communicating path of the fuel vapor purge system;  
 leak checking means for checking presence or absence of a leak of the fuel vapor purge system based on the pressure detected by the pressure detecting means when at least the first valve is closed to thereby maintain the fuel vapor purge system in a hermetically closed state in stopping to operate the engine; and  
 valve controlling means for temporarily releasing the hermetically closed state of the fuel vapor purge system by temporarily opening the first valve after finishing to check the leak and thereafter closing the first valve again.  
 
     
     
       6. The apparatus of checking a leak of a fuel vapor purge system according to  claim 5 , wherein the valve controlling means closes the first valve at a time point at which the pressure detected by the pressure detecting means becomes lower than a predetermined determinant when the first valve is opened after finishing to check the leak. 
     
     
       7. The apparatus of checking a leak of a fuel vapor purge system according to  claim 5 , wherein the valve controlling means does not open the first valve when the pressure detected by the pressure detecting means becomes equal to or smaller than a predetermined determinant in finishing to check the leak. 
     
     
       8. A method of checking a leak in a fuel vapor purge system, the method comprising:
 detecting a pressure of a fuel vapor purge system including a fuel tank;  
 checking presence or absence of a leak in the fuel vapor purge system based on the detected pressure of the fuel vapor purge system when the fuel vapor purge system is maintained in a hermetically closed state;  
 avoiding an erroneous check caused by a deformation of the fuel tank;  
 restricting the pressure of the fuel vapor purge system into a predetermined restricted value when the leak is checked;  
 determining a temperature in the fuel tank or a temperature around the fuel tank; and  
 changing the restricted value based on the determined temperature.  
 
     
     
       9. The method of checking a leak of a fuel vapor purge system according to  claim 8 , wherein restricting the pressure of the fuel vapor purge system includes restricting an increase of the pressure. 
     
     
       10. A method of checking a leak in a fuel vapor purge system, the method comprising:
 detecting a pressure of a fuel vapor purge system including a fuel tank;  
 checking presence or absence of a leak in the fuel vapor purge system based on the detected pressure of the fuel vapor purge system when the fuel vapor purge system is maintained in a hermetically closed state;  
 avoiding an erroneous check caused by a deformation of the fuel tank;  
 restricting the pressure of the fuel vapor purge system into a predetermined restricted value when the leak is checked; and  
 corrected the restricted value in a direction of approaching an atmospheric pressure when the detected pressure is rapidly changed in the checking of the leak.  
 
     
     
       11. The method of checking a leak of a fuel vapor purge system according to  claim 10 , wherein restricting the pressure of the fuel vapor purge system includes restricting an increase of the pressure. 
     
     
       12. A method of checking a leak of a fuel vapor purge system which is a fuel vapor purge system for purging fuel vapor generated by evaporating a fuel in a fuel tank to an intake system of an engine, said method comprising:
 detecting a pressure of the fuel vapor purge system including the fuel tank;  
 opening and closing an atmosphere communicating path of the fuel vapor purge system via a first valve;  
 checking presence or absence of a leak of the fuel vapor purge system based on the detected pressure when at least the first valve is closed to thereby maintain the fuel vapor purge system in a hermetically closed state in stopping to operate the engine; and  
 temporarily releasing the hermetically closed state of the fuel vapor purge system by temporarily opening the first valve after finishing to check the leak and thereafter closing the first valve again.  
 
     
     
       13. The method of checking a leak of a fuel vapor purge system according to  claim 12 , wherein the first valve is closed at a time point at which the detected pressure becomes lower than a predetermined determinant when the first valve is opened after finishing to check the leak. 
     
     
       14. The method of checking a leak of a fuel vapor purge system according to  claim 12 , wherein the first valve is not opened when the detected pressure becomes equal to or smaller than a predetermined determinant in finishing to check the leak. 
     
     
       15. An apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine comprising:
   a first valve for opening and closing an atmosphere communicating path of the fuel vapor purge system;        leak checking means for checking the presence or absence of a leak in the fuel vapor purge system based on a pressure in the fuel vapor purge system when the fuel vapor purge system is in a hermetically closed state with the first valve closed while the engine is stopped; and        valve control means for temporarily releasing the hermetically closed state of the fuel vapor purge system by temporarily opening the first valve after finishing checking the leak and thereafter closing the first valve again.      
     
     
       16. The apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 15 , wherein the valve control means closes the first valve at a time point at which the pressure in the fuel vapor purge system becomes lower than a predetermined determinant when the first valve is opened after finishing checking the leak.  
     
     
       17. The apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 15 , wherein the valve control means does not open the first valve when the pressure in the fuel vapor purge system becomes equal to or smaller than a predetermined determinant in finishing checking the leak.  
     
     
       18. The apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 15 , wherein the leak checking means checks whether the pressure is lowered to be equal to or smaller than a predetermined pressure.  
     
     
       19. A method of checking a leak in a fuel vapor purge system for an internal combustion engine, the method comprising:
   stopping the internal combustion engine;        hermetically closing the fuel vapor purge system by closing a first valve that opens and closes an atmosphere communicating path of the fuel vapor purge system;        checking the presence or absence of a leak in the fuel vapor purge system based on a pressure in the fuel vapor purge system;        temporarily opening the first valve after finishing checking the leak; and        closing the first valve again.      
     
     
       20. The method of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 19 , wherein the first valve is closed at a time point at which the pressure in the fuel vapor purge system becomes lower than a predetermined determinant when the first valve is opened after finishing checking the leak.  
     
     
       21. The method of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 19 , wherein the first valve is not opened when the pressure in the fuel vapor purge system becomes equal to or smaller than a predetermined determinant in finishing checking the leak.  
     
     
       22. The method of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 19 , wherein checking the presence or absence of a leak in the fuel vapor purge system includes checking whether the pressure is lowered to be equal to or smaller than a predetermined pressure.  
     
     
       23. An apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine comprising:
   a first valve for opening and closing an atmosphere communicating path of the fuel vapor purge system; and        leak checking means for checking the presence or absence of a leak in the fuel vapor purge system based on a pressure in the fuel vapor purge system when the fuel vapor purge system is in a hermetically closed state with the first valve closed while the engine is stopped;        wherein the leak checking means checks a leak when a condition that fuel vapor is liable to generate at a time when the engine is stopped is satisfied.      
     
     
       24. The apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 23 , wherein the condition is that a fuel temperature is equal to or higher than a predetermined temperature.  
     
     
       25. The apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 23 , wherein the condition is that an engine running time is equal to or longer than a predetermined time before the engine is stopped.  
     
     
       26. The apparatus of checking a leak in a fuel vapor purge system for an internal combustion engine of a vehicle according to  claim 23 , wherein the condition is that a running distance of the vehicle is equal to or larger than a predetermined value before the engine is stopped.  
     
     
       27. A method of checking a leak in a fuel vapor purge system for an internal combustion engine, the method comprising:
   stopping the internal combustion engine;        hermetically closing the fuel vapor purge system by closing a first valve that opens and closes an atmosphere communicating path of the fuel vapor purge system; and        checking the presence or absence of a leak in the fuel vapor purge system based on a pressure in the fuel vapor purge system;        wherein the leak is checked when a condition that fuel vapor is liable to generate at a time when the engine is stopped is satisfied.      
     
     
       28. The method of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 27 , wherein the condition is that a fuel temperature is equal to or higher than a predetermined temperature.  
     
     
       29. The method of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 27 , wherein the condition is that an engine running time is equal to or longer than a predetermined time before the engine is stopped.  
     
     
       30. The method of checking a leak in a fuel vapor purge system for an internal combustion engine according to  claim 27 , wherein the condition is that a running distance of the vehicle is equal to or larger than a predetermined value before the engine is stopped.