Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
1998-11-20
2001-05-15
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
C073S116070, C073S117020
Reexamination Certificate
active
06230553
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for diagnosing an abnormality of an engine cooling system.
2. Description of Related Art
Among abnormalities generated in an engine cooling system, there are, for example, defects in a cooling water sensor or in a thermostat valve. If there is generated an open stuck trouble in which a leakage is generated in the thermostat valve and the valve is kept open and can not be closed, the cooling water circulates through the radiator during warming up of the engine and the warm up is delayed.
There is a conventional apparatus for diagnosing an abnormality of the engine cooling system of this type in which a cooling liquid temperature TW, which is reached after a set warming up driving time is elapsed is compared with a reference value, and if the cooling liquid temperature TW does not reach the criteria value, it is diagnosed that there is an abnormality in the engine cooling system as disclosed in Japanese Patent Applications Laid-open Nos. 4-187854 and 7-34943, for example.
However, in such a conventional abnormality diagnosis apparatus of the engine cooling system, even if there is an abnormality such as leakage in the thermostat valve, if the engine is driven at high load during warming up, since the cooling liquid temperature TW abruptly rises, this abnormality can not be judged. Further, even if the thermostat valve is normally operated, if the engine is driven at an idle speed during warming up, since the rise of the cooling liquid temperature TW is delayed, there is a possibility that it is misjudged that the thermostat is abnormal.
In an abnormality diagnosis apparatus of an engine cooling system disclosed n Japanese Utility Model Application Laid-open No. 55-135983, a plurality of cooling water sensors are provided for detecting leakage of the thermostat valve.
In an abnormality diagnosis apparatus of an engine cooling system disclosed in Japanese Patent Application Laid-open No. 58-8225, a movable contact is provided in the thermostat valve to detect open stuck or close stuck.
However, in such a conventional apparatus of an engine cooling system, it is necessary to provide a sensor or the like, increases the cost to manufacture the apparatus.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above problem, and it is an object of the present invention to enhance the precision of diagnosis in an abnormality diagnosis apparatus of an engine cooling system.
To achieve the object described above, there is provided an abnormality diagnosis apparatus of an engine cooling system comprises; a cooling liquid temperature sensor for detecting a cooling liquid temperature; a first section for calculating a rise value of the cooling liquid temperature in a measuring section; a second section for judging a liquid temperature convergence time at which the rise value of the cooling liquid temperature in the measuring section becomes smaller than a predetermined value; and a third section for diagnosing that there is an abnormality in the cooling system when the cooling liquid temperature in the liquid temperature convergence time is smaller than a criteria value.
In this abnormality diagnosis apparatus of the engine cooling system, the rise value of the cooling liquid temperature in the measuring section is calculated, a liquid temperature convergence time at which said rise value of said cooling liquid temperature in said measuring section becomes smaller than the predetermined value is judged; it is judged that there is an abnormality in the cooling system when said cooling liquid temperature in said liquid temperature convergence time is smaller than the criteria value.
For example, when the engine is driven at an idle during warming up of the engine, a timing of the abnormality diagnosis of the cooling system is delayed in correspondence with the fact that the cooling liquid temperature slowly rises and convergence of the cooling liquid temperature is delayed. Therefore, it is possible to precisely diagnose whether the thermostat valve and the like are normally operated.
Further, since the abnormality diagnosis of the cooling system is conducted based on the detection value of the cooling water temperature sensor, it is unnecessary to newly add the sensor or the like, and the structure can be simplified.
In a preferred embodiment, the abnormality diagnosis apparatus of an engine cooling system comprises: a unit for detecting a load of the engine; a fourth section for integrating the load of the engine detected in the measuring section to calculate a heat value of the engine; and a fifth section for judging whether the cooling liquid temperature is converging by the calculated heat value of the engine.
In this abnormality diagnosis apparatus of an engine cooling system, the load of the engine detected in the measuring section is integrated to calculate the heat value of the engine, and it is judged whether the cooling liquid temperature is converging by the calculated heat value of the engine.
For example, when the engine is driven at high load during warming up of the engine, and the measuring section is shortened with increase of the heat value of the engine, and the engine is driven at an idle speed during warming up so that the temperature rise of the cooling liquid temperature is delayed, since the measuring section is increased, it is possible to accurately judge whether the thermostat valve and the like are normally operated without being influenced by increase or decrease the heat value of the engine.
By using the existing air flow meter or signal of fuel injection amount as the unit for detecting a load of the engine, it is unnecessary to newly add the sensor or the like, and the structure can be simplified.
The reference value for judging the completion time of the measuring section based on the heat value of the engine is corrected in accordance with the vehicle speed or the intake air temperature.
In this case, by correcting the reference value for judging the completion time of the measuring section in accordance with a vehicle speed or an intake air temperature, it is possible to calculate the measuring section suitable for the heat value of the engine in accordance with the radiation of heat of the radiator or the engine, and the precision of the diagnosis can be enhanced.
Further, the criteria value may be corrected in accordance with a vehicle speed or an intake air temperature.
In this case, by correcting the criteria value which diagnoses the abnormality in the cooling system based on the cooling liquid temperature at the time of the convergence of the liquid temperature, in accordance with a vehicle speed or an intake air temperature, the precision of the diagnosis can be enhanced without being influenced by an increase or a decrease in the heat value of the engine.
Further, the heat value of the engine may be corrected in accordance with at least one of a vehicle speed, an ignition timing, a mixing ratio and the engine revolution number.
In this case, by correcting the heat value of the engine in accordance with at least one of a vehicle speed, an ignition timing, a mixing ratio and the engine revolution number, the heat value of the engine can be calculated at high accuracy, and the precision of the diagnosis can be enhanced.
In another preferred embodiment, the abnormality diagnosis apparatus of an engine cooling system comprising: a unit for detecting a load of an engine; a fourth section for integrating a detected load of the engine to calculate a heat value of the engine; and a sixth section for diagnosing whether an abnormality is generated in the cooling system in accordance with a detected cooling liquid temperature Tw and the heat Value of the engine.
In this abnormality diagnosis apparatus of an engine cooling system, the load of the engine is integrated to calculate the heat value of the engine, and it is judged whether the abnormality is generated in the cooling system in accordance with a detected cooling liquid tempera
Kawamura Katsuhiko
Uchiyama Katsuaki
Davis Octavia
Foley & Lardner
Fuller Benjamin R.
Nissan Motor Co,. Ltd.
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