Abnormality diagnosis apparatus and method for water temperature sensor

• US 20060093014A1
• Filed: 10/28/2005
• Published: 05/04/2006
• Est. Priority Date: 10/29/2004
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Mizutani, Koichi, Satoya, Koichi, Higashiyama, Norikazu
• Granted Patent: US 7,524,106 B2
• Time in Patent Office: Days
• US Class Current: 374/1
• CPC Class Codes: F01P 11/16 concerning coolant temperature F01P11/20 takes precedence
• CPC Class Codes: F01P 2025/13 Ambient temperature
• CPC Class Codes: F01P 2031/00 Fail safe
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

There are occasions when an intermittent abnormality occurs in a water temperature sensor that is of a type that does not cause a sudden change in a detection value of the water temperature sensor. The movement of the detection value of the water temperature sensor when this type of abnormality occurs may be, for example, a movement in which the detection value of the water temperature sensor becomes lower even through warm up has been proceeding after engine start up has begun. When this type of movement of the detection value occurs, if the detection value of the water temperature sensor reduces, after engine start up has begun, to a value lower than that when start up began, it is immediately determined based on this fact that an abnormality of the water temperature sensor is occurring.

Claims

1. An abnormality diagnosis apparatus comprising:

a water temperature sensor that detects a coolant temperature of an internal combustion engine; and

a controller that determines whether an abnormality of the water temperature sensor is occurring based on if, after start up of the internal combustion engine has begun, a detection value of the water temperature sensor has become a value lower than that when start up began.

2. The abnormality diagnosis apparatus according to claim 1, wherein abnormality determination of the controller is only performed when a change amount of an intake air temperature of the internal combustion engine is small.

3. The abnormality diagnosis apparatus according to claim 1, wherein, in addition to the abnormality determination, the controller determines whether an abnormality of the water temperature sensor is occurring based on if the detection value of the water temperature sensor changes suddenly.

4. An abnormality diagnosis apparatus comprising:

a water temperature sensor that detects a coolant temperature of an internal combustion engine;

an intake air temperature sensor that detects an intake air temperature of the internal combustion engine; and

a controller that determines whether an abnormality of the water temperature sensor is occurring based on if a detection value of the water temperature sensor has become a value lower than the intake air temperature after start up of the internal combustion engine has begun.

5. The abnormality diagnosis apparatus according to claim 4, wherein, in addition to the abnormality determination, the controller determines whether an abnormality of the water temperature sensor is occurring based on if the detection value of the water temperature sensor changes suddenly.

6. An abnormality diagnosis apparatus comprising:

a water temperature sensor that detects a coolant temperature of an internal combustion engine; and

a controller that determines whether an abnormality of the water temperature sensor is occurring based on if a change amount of the detection value of the water temperature sensor per unit time has become equal to or less than a predetermined negative value after start up of the internal combustion engine has begun.

7. The abnormality diagnosis apparatus according to claim 6, wherein the predetermined negative value is set to a value that is smaller than the smallest value that might conceivably be obtained for the change amount of the detection value of the water temperature sensor per unit time when the coolant temperature reduces due to decrease of an intake air temperature.

8. The abnormality diagnosis apparatus according to claim 6, wherein, in addition to the abnormality determination, the controller determines whether an abnormality of the water temperature sensor is occurring based on if the detection value of the water temperature sensor changes suddenly.

9. An abnormality diagnosis method for a water temperature sensor that detects a coolant temperature of an internal combustion engine, comprising:

determining whether an abnormality of the water temperature sensor is occurring based on if, after start up of the internal combustion engine has begun, a detection value of the water temperature sensor has become a value lower than that when start up began.

10. The abnormality diagnosis method according to claim 9, wherein abnormality determination is only performed when a change of an intake air temperature of the internal combustion engine is small.

11. The abnormality diagnosis method according to claim 9, further comprising:

determining whether an abnormality of the water temperature sensor is occurring based on if the detection value of the water temperature sensor changes suddenly.

12. An abnormality diagnosis method for a water temperature sensor that detects a coolant temperature of an internal combustion engine, comprising:

determining whether an abnormality of the water temperature sensor is occurring based on if a detection value of the water temperature sensor has become a value lower than an intake air temperature after start up of the internal combustion engine has begun.

13. The abnormality diagnosis method according to claim 12, further comprising:

determining whether an abnormality of the water temperature sensor is occurring based on if the detection value of the water temperature sensor changes suddenly.

14. An abnormality diagnosis method for a water temperature sensor that detects a coolant temperature of an internal combustion engine, comprising:

determining whether an abnormality of the water temperature sensor is occurring based on if a change amount of the detection value of the water temperature sensor per unit time has become equal to or less than a predetermined negative value after start up of the internal combustion engine has begun.

15. The abnormality diagnosis method according to claim 14, wherein the predetermined negative value is set to a value that is smaller than the smallest value that might conceivably be obtained for the change amount of the detection value of the water temperature sensor per unit time when the coolant temperature is reduced due to decrease of an intake air temperature.

16. The abnormality diagnosis method according to claim 14, further comprising:

determining whether an abnormality of the water temperature sensor is occurring based on if the detection value of the water temperature sensor changes suddenly.