Patent ID: 6520125
Filing Date: 2003-02-18
Classification: F01P

Abstract:
A cooling syst em for a liquid-cooled internal combustion engine cooled by coolant comprising:a radiator for cooling the coolant which flows out from the liquid-cooled internal combustion engine cooled by coolant and which flows into the engine; a bypass circuit by which the coolant flowing out from the engine bypasses the radiator; a pump for circulating the coolant between the radiator and the engine, the pump being operated independently from the engine rotation; a blower for blowing air to the radiator; a flow rate control valve for controlling a bypass flow rate of coolant flowing in the bypass circuit and a radiator flow rate of coolant flowing in the radiator; a control means for controlling the operations of the pump, the blower and the flow rate control valve; a coolant temperature sensor for detecting the temperature of the coolant; wherein the control means determines a combination of the cooling effect by the pump and the cooling effect by the blower to get a required cooling effect determined according to a load given to the engine, the control means further comprising: a first map for determining a target coolant temperature (Tmap) according to a load given to the engine; a second map for determining control quantities used for controls of the pump and the blower according to a load given to the engine; a coolant temperature judging means for judging whether or not the detected coolant temperature detected by the coolant temperature sensor is higher than the target coolant temperature determined by the first map, by comparing the detected coolant temperature with the target coolant temperature, and whether or not the detected coolant temperature is within a predetermined range in which the target coolant temperature is used as a reference value; a feedback control means for feedback controlling the flow rate of discharge of the pump, the quantity of the air blown by the blower and the degree of opening of the flow rate control valve, based on the detected coolant temperature, when judging that the detected coolant temperature is not within the predetermined range in which the target coolant temperature is used as a reference value, the feedback control means comprising a coolant temperature-fall control means and a coolant temperature-rise control means, wherein, when the detected coolant temperature is higher than the target coolant temperature, the coolant temperature-fall control means preferentially controls the flow rate control valve to increase the degree of opening of the valve in increments of a predetermined value from initial degree of opening of the valve so as to increase the flow rate of the coolant flowing in the radiator, and after the degree of opening of the valve substantially reaches a full-open state, the coolant temperature-fall control means then increases the flow rate of discharge of the pump and the quantity of the air blown by the blower, and wherein, when the detected coolant temperature is lower than the target coolant temperature, the coolant temperature-rise control means decreases the flow rate of discharge of the pump and the quantity of the air blown by the blower and controls the degree of opening of the valve so as to decrease the flow rate of the coolant flowing in the radiator; a map-based control means for controlling the flow rate of discharge of the pump and the quantity of the air blown by the blower, based on the control quantities determined by the second map, when judging that the detected coolant temperature is within the predetermined range in which the target coolant temperature is used as a reference value.