Cooling control system for engine

Abstract

A cooling control system for an engine is provided. Cooling water circulate within a cooling circuit via a water pump and the engine, and a bypass circuit is formed to circulate the cooling water without passing through the engine. A first temperature sensor is disposed on the cooling circuit, and a second temperature sensor is disposed on the bypass circuit to detect a temperature of the cooling water. A switching valve controls a flow rate of the cooling water flowing through the cooling circuit, and the switching valve is provided with a water passage that allows the cooling water to flow therethrough when is closed. The cooling control system is configured to estimate an amount of clogging of the water passage based on a temporal change in a temperature difference between temperatures of the cooling water detected by the first temperature sensor and the second temperature sensor, under a condition in that the engine is stopped, the switching valve is closed, and the water pump is driven.

1 . A cooling control system for an engine, comprising:
 a cooling circuit for circulating cooling water via a water pump and the engine to cool the engine;   a bypass circuit for circulating the cooling water without passing through the engine;   a first temperature sensor that is disposed on the cooling circuit to detect a temperature of the cooling water flowing therethrough;   a second temperature sensor that is disposed on the bypass circuit to detect a temperature of the cooling water flowing therethrough;   a switching valve that is closed to reduce a flow rate of the cooling water flowing through the cooling circuit, and that is opened to increase the flow rate of the cooling water flowing through the cooling circuit; and   a water passage that allows the cooling water to flow through the cooling circuit in a small amount when the switching valve is closed, and   a controller that is configured to estimate an amount of clogging of the water passage based on a temporal change in a temperature difference between a temperature of the cooling water detected by the first temperature sensor and a temperature of the cooling water detected by the second temperature sensor, under a condition in that the engine is stopped, the switching valve is closed, and the water pump is driven.   
     
     
         2 . The cooling control system as claimed in  claim 1 ,
 wherein the controller is further configured to estimate the amount of clogging of the water passage by subtracting the temperature difference of a case in which the water pump is not driven from the temperature difference of a case in which the water pump is driven, in case an external temperature is lower than a predetermined temperature.   
     
     
         3 . The cooling control system as claimed in  claim 1 , wherein the controller is further configured to:
 estimate a current amount of clogging of the water passage while reducing a drive frequency of the water pump to be less than the previous value if a current estimated value of the amount of clogging is smaller than a first threshold value, and   estimate a current amount of clogging of the water passage while increasing the drive frequency of the water pump to be more than that of the previous case if the current estimated value of the amount of clogging is larger than the first threshold value.   
     
     
         4 . The cooling control system as claimed in  claim 1 ,
 wherein the controller is further configured to estimate the amount of clogging of the water passage by increasing the drive frequency of the water pump with an increase in a speed of a vehicle having the engine.   
     
     
         5 . The cooling control system as claimed in  claim 1 , wherein the controller is further configured to:
 estimate the amount of clogging of the water passage while increasing the drive frequency of the water pump if the estimated value of the amount of clogging is larger than the first threshold value but smaller than a second threshold value, and   open the switching valve if the estimated value of the amount of clogging is smaller than the second threshold value.