Patent ID: 9695736
Date: 2017-07-04
CPC Classifications: F01P

Claim:
1. A cooling device for an internal combustion engine, comprising: a coolant water passage formed in said internal combustion engine; a radiator configured to cool coolant water; a radiator circulation passage configured to allow coolant water discharged from said coolant water passage to pass through said radiator and return to said coolant water passage; a bypass passage configured to allow coolant water discharged from said coolant water passage to return to said coolant water passage without passing through said radiator; and a thermostat valve connected to said radiator circulation passage and said bypass passage, said thermostat valve being switched in accordance with a temperature of coolant water flowing in said thermostat valve to either a closed state of interrupting coolant water from said radiator circulation passage and outputting coolant water from said bypass passage to said coolant water passage or an opened state of outputting coolant water from said radiator circulation passage and coolant water from said bypass passage to said coolant water passage, said cooling device further comprising: a pump configured to circulate coolant water; a first temperature sensor configured to detect a temperature of coolant water in said coolant water passage; a second temperature sensor configured to detect a temperature of coolant water in said radiator circulation passage; and a diagnosis unit configured to estimate a temperature of coolant water in said radiator circulation passage based on a leakage flow rate, which is set as a flow rate flowing through said radiator circulation passage even when said thermostat valve is in the closed state, and an output of said first temperature sensor, and perform a failure diagnoses for said thermostat valve based on a difference between an estimated temperature and a detected temperature of said second temperature sensor, said leakage flow rate during operation of said pump being set to be a larger value as compared to said leakage flow rate during stopping of said pump.