Thermostat with failure diagnosis function and mehod for failure diagnosis of thermostat using the same

Abstract

Disclosed are a thermostat with a failure diagnosis function and methods for diagnosing a failure in a thermostat. The thermostat is to be installed between an engine and a radiator to control cooling water to bypass back to the engine or to circulate to the radiator by means of a valve operated depending on temperatures in the cooling water circulated between the engine and the radiator. The thermostat may include a plurality of water temperature sensors installed before and after the valve to measure the temperatures in the cooling water before and after the valve, for determining whether or not the valve is normally operated by comparing a difference of the temperatures in the cooling water before and after the valve with a preset temperature.

What is claimed is: 
     
         1 . A thermostat with a failure diagnosis function, wherein the thermostat is to be installed between an engine and a radiator to control cooling water to bypass back to the engine or to circulate to the radiator by means of a valve operated depending on temperatures in the cooling water circulated between the engine and the radiator, the thermostat comprising:
 a plurality of water temperature sensors installed before and after the valve to measure the temperatures in the cooling water before and after the valve, for determining whether or not the valve is normally operated by comparing a difference of the temperatures in the cooling water before and after the valve with a preset temperature.   
     
     
         2 . The thermostat of  claim 1 , wherein if a temperature in the cooling water introduced from the engine to the thermostat is lower than a closed completion temperature at which the valve is set to be fully closed and the difference of the temperatures in the cooling water before and after the valve is lower than a preset closed-failing determination temperature, the valve is determined to be closed-failing which is not closed despite of being closed. 
     
     
         3 . The thermostat of  claim 2 , wherein the closed-failing determination temperature is set as about 10° C. 
     
     
         4 . The thermostat of  claim 1 , wherein if the temperature in the cooling water introduced from the engine to the thermostat is higher than an open completion temperature at which the valve is set to be opened and the difference of the temperatures in the cooling water before and after the valve is higher than a preset open-failing determination temperature, the valve is determined to be open-failing which is not opened despite of being opened. 
     
     
         5 . The thermostat of  claim 4 , wherein the open-failing determination temperature is set as about 10° C. 
     
     
         6 . The thermostat of  claim 1 , wherein the water temperature sensors comprise a first water temperature sensor installed at a side to which the cooling water is introduced from the engine to the thermostat and a second water temperature sensor installed at a side from which the cooling water passing through the valve is discharged to the radiator. 
     
     
         7 . A method for diagnosing a failure in a thermostat, wherein the thermostat is to be installed between an engine and a radiator to control cooling water to bypass back to the engine or to circulate to the radiator by means of a valve operated depending on temperatures in the cooling water circulated between the engine and the radiator and measured by water temperature sensors installed before and after the valve, the method comprising:
 performing closed completion estimation by comparing a temperature in the cooling water at a side to which the cooling water is introduced from the engine with a closed completion temperature at which the valve of the thermostat is set to be fully closed;   performing closed-failing determination in which, if the temperature in the cooling water introduced from the engine is lower than the closed completion temperature at the performing of the closed completion estimation, a difference of the temperatures in the cooling water before and after the valve is compared with a closed-failing determination temperature; and   performing closed-failing confirmation in which, if the difference of the temperatures in the cooling water before and after the valve is lower than the closed-failing determination temperature at the performing of the closed-failing determination, the valve is confirmed to be closed-failing which is not closed despite of being closed.   
     
     
         8 . The method of  claim 7 , further comprising:
 prior to the performing of the closed completion estimation, performing diagnosis beginning determination to determine whether or not the temperature in the cooling water introduced from the engine is higher than a preset diagnosis beginning temperature,   wherein if the temperature in the cooling water introduced from the engine is higher than the diagnosis beginning temperature, the performing of the closed completion estimation is carried out.   
     
     
         9 . The method of  claim 8 , wherein the diagnosis beginning temperature is set to be higher than an atmospheric temperature by a preset temperature. 
     
     
         10 . The method of  claim 7 , wherein the closed completion temperature is set to be lower than a closed beginning temperature at which the valve is set to be closed by a preset temperature. 
     
     
         11 . The method of  claim 7 , further comprising:
 performing normally closed confirmation in which, if the temperature in the cooling water introduced from the engine is not lower than the closed completion temperature at the performing of the closed completion estimation, the valve is confirmed to be normally closed when having to be closed.   
     
     
         12 . The method of  claim 7 , further comprising:
 performing normally closed confirmation in which, if the difference of the temperatures in the cooling water before and after the valve is not lower than the closed-failing determination temperature at the performing of the closed-failing determination, the valve is confirmed to be normally closed when having to be closed.   
     
     
         13 . A method for diagnosing a failure in a thermostat, wherein the thermostat is to be installed between an engine and a radiator to control cooling water to bypass back to the engine or to circulate to the radiator by means of a valve operated depending on temperatures in the cooling water circulated between the engine and the radiator and measured by water temperature sensors installed before and after the valve, the method comprising:
 performing open completion estimation by comparing a temperature in the cooling water at a side to which the cooling water is introduced from the engine with an open completion temperature at which the valve of the thermostat is set to be fully opened;   performing open-failing determination in which, if the temperature in the cooling water introduced from the engine is higher than the open completion temperature at the performing of the open completion estimation, a difference of the temperatures in the cooling water before and after the valve is compared with an open-failing determination temperature; and   performing open-failing confirmation in which, if the difference of the temperatures in the cooling water before and after the valve is higher than the open-failing determination temperature at the performing of the open-failing determination, the valve is confirmed to be open-failing which is not opened despite of being opened.   
     
     
         14 . The method of  claim 13 , further comprising:
 performing normally open confirmation in which, if the temperature in the cooling water introduced from the engine is not higher than the open completion temperature at the performing of the open completion estimation, the valve is confirmed to be normally opened when having to be opened.   
     
     
         15 . The method of  claim 13 , further comprising:
 performing normally open confirmation in which, if the difference of the temperatures in the cooling water before and after the valve is not higher than the open-failing determination temperature at the performing open-failing determination, the valve is confirmed to be normally opened when having to be opened.