Cooling apparatus for internal combustion engine

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on a detection value of an intake-air temperature sensor;
• and
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established,
• wherein a state in which a driving speed of a vehicle is less than a reference speed is set to a specific driving state, the diagnosis of said operating state is prohibited when a ratio of the time of said specific driving state to the time from the starting of the internal combustion engine until the establishment of said diagnosis condition is equal to or grater than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on a detection value of an intake-air temperature sensor;
• and
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established,
• wherein the diagnosis of said operating state is prohibited when an integrated value of the intake amount drawn into the internal combustion engine from the starting of the internal combustion engine until the establishment of said diagnosis condition is less than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on a detection value of an intake-air temperature sensor;
• and
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature with said reference temperature when a predetermined diagnosis condition is established,
• wherein a variation of said reference temperature in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition is set to a first variation, and, in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition, a variation of said reference temperature at the time when the driving speed of a vehicle is less than a reference speed is set to a second variation, and wherein the diagnosis of said operating state is prohibited when a ratio of said second variation to said first variation is equal to or greater than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on a detection value of an intake-air temperature sensor;
• and
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established,
• wherein, in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition, a variation of said reference temperature at the time when the driving speed of the vehicle is equal to or greater than the reference speed is set to a first variation, and, in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition, a variation of said reference temperature at the time when the driving speed of the vehicle is less than said reference speed is set to a second variation, and wherein the diagnosis of said operating state is prohibited when a ratio of said second variation to said first variation is equal to or greater than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on a detection value of an intake-air temperature sensor;
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established;
• and
• correction means, wherein a state in which the difference between the detection value of said intake-air temperature sensor and an external air temperature is equal to or greater than an upper limit value is set to a specific state, and wherein the correction means corrects said reference temperature when the period of said specific state is equal to or longer than an upper limit period before the establishment of said diagnosis condition.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on a detection value of an intake-air temperature sensor;
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established;
• and
• correction means, wherein a state in which the driving speed of the vehicle is less than the reference speed is set to a specific driving state, and wherein the correction means corrects said reference temperature when a ratio of the time of said specific driving state to the time from the starting of the internal combustion engine until the establishment of said diagnosis condition is equal to or greater than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on a detection value of an intake-air temperature sensor;
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established;
• and
• correction means that corrects said reference temperature when an integrated value of the intake amount from the starting of the internal combustion engine until the establishment of said diagnosis condition is less than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on an detection value of an intake-air temperature sensor;
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established;
• and
• correction means, wherein a variation of said reference temperature in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition is set to a first variation, and a variation of said reference temperature when the driving speed of a vehicle is less than a reference speed in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition is set to a second variation, and wherein the correction means corrects said reference temperature when a ratio of said second variation to said first variation is equal to or greater than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on an detection value of an intake-air temperature sensor;
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established;
• and
• correction means, wherein a variation of said reference temperature when the driving speed of the vehicle is equal to or greater than the reference speed in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition is set to a first variation, and a variation of said reference temperature when the driving speed of the vehicle is less than said reference speed in the period from the starting of the internal combustion engine until the establishment of said diagnosis condition is set to a second variation, and wherein the correction means corrects said reference temperature when a ratio of said second variation to said first variation is equal to or greater than a predetermined determination value.

A cooling apparatus for an internal combustion engine, comprising:

• a thermostat that adjusts a feed rate of coolant to a radiator;
• detecting means that detects the temperature of said coolant;
• estimating means that estimates a reference temperature equivalent to the temperature of said coolant at least based on an detection value of an intake-air temperature sensor;
• diagnosis means that sets the temperature of said coolant detected through said detecting means to a detection temperature, and diagnoses an operating state of said thermostat by comparing said detection temperature and said reference temperature when a predetermined diagnosis condition is established;
• and
• correction means that calculates said reference temperature based on a value obtained by correcting the detection value of said intake-air temperature sensor to reduce it.