Cooling system for internal combustion engine

Abstract

A cooling system for an internal combustion engine includes a coolant flow passage through which coolant flows between the internal combustion engine and a heat exchanger, a flow amount control valve incorporated in the coolant flow passage and configured to control flow of the coolant flowing in the coolant flow passage, and a control section configured to effect switchover from a full opened state to a full closed state of the flow amount control valve based on a supply of a negative pressure produced in the internal combustion engine and to effect also switchover from the full closed state to the full opened state over a second period longer than a first period required for the switchover for the flow amount control valve from the full closed state to the full opened state, in response to stop of the supply of the negative pressure.

1 . A cooling system for an internal combustion engine, the cooling system comprising:
 a coolant flow passage through which coolant flows between the internal combustion engine and a heat exchanger;   a flow amount control valve incorporated in the coolant flow passage and configured to control flow of the coolant flowing in the coolant flow passage; and   a control section configured to effect switchover from a full opened state to a full closed state of the flow amount control valve based on a supply of a negative pressure produced in the internal combustion engine and to effect also switchover from the full closed state to the full opened state over a second period longer than a first period required for the switchover for the flow amount control valve from the full closed state to the full opened state, in response to stop of the supply of the negative pressure.   
     
     
         2 . The cooling system for an internal combustion engine of  claim 1 , wherein:
 the system further comprises   a switching valve for switching a pressure to be fed to the control section to either one of a first pressure comprised of the negative pressure produced in the internal combustion engine or a second pressure higher than the first pressure; and   a constricted portion for constricting an opening area of a feed passage for feeding a fluid having the second pressure to the switching valve is incorporated in the feed passage.   
     
     
         3 . The cooling system for an internal combustion engine of  claim 1 , wherein the control section is configured such that when the flow amount control valve is switched from the full closed state to the full opened state, the control section firstly provides alternation between the full closed state and a released state of the full closed state and then provides switchover to the full opened state. 
     
     
         4 . The cooling system for an internal combustion engine of  claim 1 , wherein:
 the flow amount control valve includes:   a communication passage for communicating an inlet port through which the coolant enters the flow amount control valve to an outlet port through which the coolant flows out of the flow amount control valve; and   a bypass passage that communicates the inlet port to the outlet port, with bypassing the communication passage; and   the control section firstly establishes communication between the inlet port and the outlet port via the bypass passage and then establishes communication between the inlet port and the outlet port via the communication passage.