Abnormality determination apparatus and abnormality determination method for coolant temperature sensor, and engine cooling system
When a temperature difference between intake air temperature that detected by an intake air temperature sensor and engine coolant temperature thw 1 detected by an engine coolant temperature sensor is greater than a threshold value, a coolant temperature sensor abnormality determination apparatus opens a changeover valve to cause the coolant to flow into an engine coolant passageway, thereby mixing the coolant in an engine and the coolant in a heater passageway (bypass passageway). If the temperature difference between the engine coolant temperature thw 1 and a heater inlet coolant temperature (bypass coolant temperature) thw 2 occurring after the changeover valve opens is less than or equal to a predetermined value, the apparatus determines that the engine coolant temperature sensor is normal. If the temperature difference is greater than the predetermined value, the apparatus determines that the engine coolant temperature sensor is abnormal.
1. A coolant temperature sensor abnormality determination apparatus for use with an engine cooling system having: (i) a coolant passageway including an engine coolant passageway and a bypass passageway that bypasses an engine, (ii) a control valve configured to be in an open state to allow mixing of coolant from the engine coolant passageway and coolant from the bypass passageway at a confluence between the engine coolant passageway and the bypass passageway and configured to be in a closed state to restrict the mixing of the coolant from the engine coolant passageway and the coolant from the bypass passageway at the confluence between the engine coolant passageway and the bypass passageway, (iii) an engine coolant temperature sensor configured to detect an engine coolant temperature in the engine coolant passageway, and (iv) a bypass coolant temperature sensor arranged in the coolant passageway, downstream of the confluence between the engine coolant passageway and the bypass passageway, the coolant temperature sensor abnormality determination apparatus comprising:
an electronic control unit configured to:
open the control valve when a difference between an atmospheric temperature around the engine and the engine coolant temperature detected by the engine coolant temperature sensor at the time of starting the engine is greater than a threshold value; and
determine only after the control valve is opened that the engine coolant temperature sensor is abnormal, if the difference between: (i) a temperature detected by the engine coolant temperature sensor, and (ii) a temperature detected by the bypass coolant temperature sensor, is greater than a predetermined value.
2. The coolant temperature sensor abnormality determination apparatus according to claim 1 , wherein the electronic control unit determines that the bypass coolant temperature sensor is normal if the difference between the atmospheric temperature and the temperature detected by the bypass coolant temperature sensor, in the closed state of the control valve, is within a predetermined range.
3. The coolant temperature sensor abnormality determination apparatus according to claim 1 , wherein:
the control valve is a temperature-sensitive operation valve that has a temperature sensitive portion configured to displace a valve body; and
the electronic control unit is configured to determine that the control valve has opened when an estimated value of ambient coolant temperature of the control valve becomes equal to or greater than a valve-opening temperature of the control valve.
4. The coolant temperature sensor abnormality determination apparatus according to claim 1 , wherein the electronic control unit executes the determination on whether the engine coolant temperature sensor is abnormal after a predetermined time elapses following the opening of the control valve.
5. A coolant temperature sensor abnormality determination method for use in an engine cooling system having: (i) a coolant passageway including an engine coolant passageway and a bypass passageway that bypasses an engine, (ii) a control valve configured to be in an open state to allow mixing of coolant from the engine coolant passageway and coolant from the bypass passageway at a confluence between the engine coolant passageway and the bypass passageway and configured to be in a closed state to restrict the mixing of the coolant from the engine coolant passageway and the coolant from the bypass passageway at the confluence between the engine coolant passageway and the bypass passageway, (iii) an engine coolant temperature sensor configured to detect an engine coolant temperature in the engine coolant passageway, and (iv) a bypass coolant temperature sensor arranged in the coolant passageway, downstream of the confluence between the engine coolant passageway and the bypass passageway, the coolant temperature sensor abnormality determination method comprising:
opening the control valve when a difference between an atmospheric temperature around the engine and the engine coolant temperature detected by the engine coolant temperature sensor at the time of starting the engine is greater than a threshold value; and
determining only after the control valve is opened that the engine coolant temperature sensor is abnormal, if the difference between: (i) a temperatures detected by the engine coolant temperature sensor, and (ii) a temperature detected by the bypass coolant temperature sensor, is greater than a predetermined value.
6. The coolant temperature sensor abnormality determination method according to claim 5 , further comprising:
determining that the bypass coolant temperature sensor is normal if the difference between the atmospheric temperature and the temperature detected by the bypass coolant temperature sensor, in the closed state of the control valve, is within a predetermined range.
7. An engine cooling system comprising:
a coolant passageway having an engine coolant passageway and a bypass passageway that bypasses an engine;
a control valve configured to be in an open state to allow mixing of coolant from the engine coolant passageway and coolant from the bypass passageway at a confluence between the engine coolant passageway and the bypass passageway and configured to be in a closed state to restrict the mixing of the coolant from the engine coolant passageway and the coolant from the bypass passageway at the confluence between the engine coolant passageway and the bypass passageway;
an engine coolant temperature sensor configured to detect an engine coolant temperature in the engine coolant passageway;
a bypass coolant temperature sensor that is arranged in the coolant passageway, downstream of the confluence between the engine coolant passageway and the bypass passageway; and
an electronic control unit configured to:
open the control valve when a difference between an atmospheric temperature around the engine and the engine coolant temperature detected by the engine coolant temperature sensor at the time of starting the engine is greater than a threshold value; and
determine only after the control valve is opened that the engine coolant temperature sensor is abnormal, if the difference between: (i) a temperature detected by the engine coolant temperature sensor, and (ii) a temperature detected by the bypass coolant temperature sensor, is greater than a predetermined value.
8. The coolant temperature sensor abnormality determination apparatus according to claim 1 , wherein the threshold value is set at 70° C.
9. The coolant temperature sensor abnormality determination apparatus according to claim 1 , wherein the predetermined value is set in a range between −20° C. to 20° C.
10. The coolant temperature sensor abnormality determination method according to claim 5 , wherein the threshold value is set at 70° C.
11. The coolant temperature sensor abnormality determination method according to claim 5 , wherein the predetermined value is set in a range between −20° C. to 20° C.
12. The engine cooling system according to claim 7 , wherein the threshold value is set at 70° C.
13. The engine cooling system according to claim 7 , wherein the predetermined value is set in a range between −20° C. to 20° C.