Engine cooling device

Abstract

An engine cooling device includes: a water pump; a radiator; a first cooling water channel going through the radiator; a second cooling water channel not going through the radiator; a solenoid valve provided in the second cooling water channel; and a control unit. The control unit moves, at a time of closing the solenoid valve, a valve body in a valve closing direction while the cooling water is passing at a decreased flow rate so as to close the solenoid valve to cut off passage of the cooling water in the second cooling water channel.

What is claimed is: 
     
         1 . An engine cooling device comprising:
 a water pump that controls a flow rate of cooling water for cooling an engine;   a radiator;   a first cooling water channel that passes the cooling water to the engine through the radiator;   a second cooling water channel that passes the cooling water to the engine without going through the radiator;   a solenoid valve provided in the second cooling water channel, the solenoid valve including a valve body, the valve body being moved by electric suction force to open and close the solenoid valve; and   a control unit configured to execute control, at a time of closing the solenoid valve in the second cooling water channel, to close the solenoid valve so as to cut off passage of the cooling water in the second cooling water channel by moving the valve body in a valve closing direction with at least electric suction force while the cooling water is passing at a decreased flow rate, the decreased flow rate being achieved by driving the water pump so as to decrease the flow rate of the cooling water.   
     
     
         2 . The engine cooling device according to  claim 1 , wherein
 the solenoid valve includes an urging member that urges the valve body in the valve closing direction, the valve body being configured to be moved in the valve closing direction with urging force of the urging member and the electric suction force while the water pump is driven.   
     
     
         3 . The engine cooling device according to  claim 1 , wherein:
 the control unit is configured to execute control to close the solenoid valve in the second cooling water channel by acquiring a valve-closable maximum speed of the water pump based on at least flow resistance of the cooling water and by moving the valve body while the water pump is driven at a speed equal to or less than the valve-closable maximum speed.   
     
     
         4 . The engine cooling device according to  claim 3 , further comprising a thermostat provided in the first cooling water channel, the thermostat having opening that changes based on temperature of the cooling water, wherein the control unit is configured to estimate the flow resistance of the cooling water based on the opening of the thermostat. 
     
     
         5 . The engine cooling device according to  claim 1 , wherein:
 the water pump is an electrically-operated water pump including a sensorless motor.   
     
     
         6 . The engine cooling device according to  claim 1 , wherein:
 the control unit is configured to execute control so as to increase the flow rate of the cooling water with the water pump after closing of the solenoid valve in the second cooling water channel is completed.