Internal-combustion engines – Cooling – Indicators and safety devices
Reexamination Certificate
2000-07-20
2001-11-27
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
Indicators and safety devices
C073S118040
Reexamination Certificate
active
06321696
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for diagnosing a thermostat trouble in an engine cooling system.
2. Description of the Background Art
In the engine cooling system, a radiator and a thermostat (a thermostat valve) are provided. This thermostat is opened or closed in response to a cooling water temperature. It is opened when the cooling water temperature for the engine becomes more than a predetermined temperature (ex. 80° C.), whereby the cooling water flows through a radiator to be cooled by the radiator. The thermostat is closed when the cooling water temperature becomes less than the predetermined temperature, whereby the cooling water bypasses the radiator so that the cooling water temperature may rise rapidly.
However, the cooling water temperature will not rise rapidly if the thermostat is caused to remain open (an opening lock) due to a problem with the thermostat. In this case the cooling water flows through the radiator and thus the engine would be actuated under a cold condition. This condition is not suitable for keeping the engine operation stable nor for improving specific fuel consumption and taking measures regarding exhaust gas.
To determine whether the thermostat trouble has occurred, Japanese Public Disclosure No.Hei 10-184433 discloses the thermostat trouble detecting device for detecting whether the actual cooling water temperature is less than the predetermined temperature a predetermined number of hours after the engine starts, namely, whether the opening trouble has occurred.
However, the above device is likely to cause the incorrect determination that a opening trouble has occurred even though actually the thermostat is not out of order, since the cooling water temperature does not rise very much even if the cooling water is not cooled by the radiator when an operating condition under which there is a small heat amount from the engine such as an idling operation continues after the engine starts.
To prevent the above incorrect determination, the present inventors developed an apparatus that determines that the opening trouble has occurred when an integrating value of deviation between the predicted cooling water temperature and the actual cooling water temperature detected by a temperature sensor is more than the predetermined temperature at the point that the cooling water temperature predicted based on the engine operating condition reaches the predetermined temperature. According to the device for determining, the incorrect determination that the thermostat opening trouble has occurred can be prevented since it takes a longer time until the predicted temperature reaches the predetermined temperature even if an operating condition under which there is a small heat amount from the engine such as an idling operation continues after the engine starts.
However, in the device for determining using the predicted temperature as described above, the predicted temperature reaches the predetermined temperature for a short period if an operating condition under which the cooling water temperature rises rapidly continues, for example, if the acceleration of a vehicle up a steep ascent continues directly after the engine starts, and thus the determining device is likely to determine incorrectly that the thermostat is normal since the integrating value becomes small even if the opening trouble occurs.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention overcomes the above problems. It is an object of the present invention to provide an apparatus for diagnosing a thermostat trouble in an engine cooling system to be able to determine more precisely whether the thermostat trouble has occurred.
The present invention includes an apparatus for diagnosing a thermostat trouble in an engine cooling system including a thermostat which opens a valve to direct a cooling water to flow through a radiator when the cooling water temperature for an engine becomes more than a predetermined temperature, and closes the value to direct the cooling water to bypass the radiator when the temperature becomes less than the predetermined temperature with the apparatus including a mechanism for calculating a radiation heat amount from a radiator based on a predicted cooling water temperature calculated by using operating parameters indicating a condition of the engine operation and an actual cooling water temperature detected by a detector for detecting a temperature of the water, and based on an integrated value of deviation between the predicted temperature and the actual temperature, and a deviation between a present predicted temperature and the actual temperature, and a mechanism for determining whether the thermostat trouble has occurred based on a result of a comparison between the actual or predicted temperature and the predetermined temperature and the radiation heat amount calculated by the calculating mechanism.
Further, the present invention may include a second calculating mechanism for calculating the heat amount from the engine received by the cooling water for the engine, wherein the detector is configured to determine whether the thermostat trouble has occurred based on a relation between the radiation heat amount and the received heat amount.
The integrated value is a value derived from multiplying the deviation between the predicted temperature and the actual temperature by a vehicle speed wherein the second calculating mechanism calculates the heat amount from the engine received by the cooling water for the engine with the determining mechanism being configured to determine if the thermostat trouble has occurred by comparing a ratio of the radiation heat amount to the received heat amount with a predetermined threshold for determination. Further, the determining mechanism may be configured to determine that thermostat trouble has occurred and that the valve has been left open when the predicted temperature or the actual temperature is less than an opening set temperature of the thermostat and when the ratio of the heat amount is more than the threshold for determination. Additionally, the determining mechanism may be configured to determine that the thermostat trouble has occurred and left the valve closed when the predicted temperature or the actual temperature is more than the opening set temperature of the thermostat and when the ratio of the heat amount is less than the threshold for determination.
Additionally, the present invention may include a mechanism for stopping the determination of whether the thermostat trouble has occurred by the determining mechanism when the cooling water temperature is less than the predetermined value or when the vehicle speed is less than the predetermined value.
Moreover, in accordance with the present invention, the apparatus for diagnosing thermostat trouble includes a controller which is configured to calculate a radiation heat amount from a radiator based on a predicted cooling water temperature calculated by using operating parameters indicating a condition of the engine operation and an actual cooling water temperature, and also based on an integrated value of deviation between the predicted temperature and the actual temperature, and a deviation between a present predicted temperature and the actual temperature and a mechanism for determining whether the thermostat trouble has occurred based on the result of a comparison between the actual or predicted temperature and a predetermined temperature, and the calculated radiation heat amount. The controller is further configured to calculate the heat amount received by the cooling water for the engine and determining whether the thermostat trouble has occurred based on a relation between the radiation heat amount and the received heat amount. Furthermore, when the integrated value is a value derived from multiplying the deviation between the predicted temperature and the actual temperature utilizing a vehicle speed, the controller is configured to calculate the heat amount from the engine received by the cool
Hosokai Tetsushi
Makimoto Seiji
Nishioka Futoshi
Kamen Noah P.
Mazda Motor Corporation
Nixon & Peabody LLP
Studebaker Donald R.
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