Automatic temperature and humidity regulation – Thermostatic – With indicator or alarm
Reexamination Certificate
1999-10-22
2001-09-04
Tanner, Harry B. (Department: 3744)
Automatic temperature and humidity regulation
Thermostatic
With indicator or alarm
C236S034500, C123S041150, C123S479000
Reexamination Certificate
active
06283381
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a diagnostic apparatus of a coolant temperature sensor, a diagnostic apparatus of a cooling apparatus and method, and particularly to those applied to an engine of a vehicle.
In Japanese Patent Application Laid-open No. H10-73047, there is disclosed that a counter for measuring the time after an engine started is provided, and that when the measured time exceeds a predetermined value, if the coolant temperature detected by a water temperature sensor does not reach a judgment value, it is judged that a trouble of output drop occurs in the water temperature sensor.
SUMMARY OF THE INVENTION
Meanwhile, according to such a conventional trouble diagnostic system, when a trouble that the output of the sensor sticks to a value exceeding the judgment value used for diagnosis of the water temperature sensor even though the actual water temperature is lower than the judgment value, it is impossible to judge that the water temperature sensor is in trouble.
This will be explained below. When a trouble of output drop occurs in the water temperature sensor, as shown in
FIG. 12A
, rising movement of water temperature TWN is slow or gentle (see broken line) as compared when the water temperature sensor is normal (see solid line). At that time, the coolant temperature at a judging timing t is smaller than a judgment value TW
D
, and it is judged that a trouble occurs in the water temperature sensor. Whereas, in the case of trouble that the sensor output sticks to a value exceeding the judgment value TW
D
, as shown in
FIG. 12B
, the coolant temperature TWN at the judging timing t becomes equal to or greater then the judgment value TW
D
as in
FIG. 12A
, so it is not judged that the trouble occurs.
Thereupon, in diagnosis of a water temperature (a coolant temperature sensor), it is an object of the present invention to supply a diagnostic apparatus and a diagnostic method of a coolant temperature sensor capable of diagnosing the trouble of output drop of the water temperature sensor, by judging that the water temperature sensor is in trouble when the output of the water temperature sensor is not varied more than a predetermined value until a predetermined time is elapsed or a sufficient heat is generated after the engine started, and capable of diagnosing a trouble that the output from the sensor sticks to a value exceeding the judging value (judging value used for conventional diagnosing system of the sensor).
Further, in order to utilize the result of diagnosis of the water temperature sensor for diagnosing a thermostat such as leakage, it is another object of the invention to provide a diagnostic apparatus and a diagnostic method of a cooling apparatus which prevent error in diagnosis of the thermostat, due to the influence of trouble of the water temperature, by prohibiting the diagnosis of the thermostat when the water temperature sensor is in trouble.
In the present invention, a diagnostic apparatus of a coolant temperature sensor sending out an output in correspondence to a temperature of a coolant of an engine, comprises: a setting section setting, as a measuring timing, a time when a predetermined time is elapsed after the engine started or a time when a predetermined heat is generated; a calculating section calculating a variation amount of the output of the coolant temperature sensor from a start of the engine to the measuring timing; and a judging section judging that a trouble occurs in the coolant temperature sensor when the variation amount is smaller than a predetermined value.
When the trouble of output drop occurs in the sensor, the water temperature rises from the start of the engine more slowly as compared when the sensor is in normal. At that time, the variation amount of the sensor output from the start of the engine to the measuring timing becomes smaller than the predetermined value and thus, it is judged that a trouble occurs in the sensor. On the other hand, also when the trouble that the output of the sensor sticks to a value exceeding the judgment value (judgment value used for conventional trouble diagnosis of the sensor), the variation amount of the sensor output from the start of the engine to the measuring timing becomes smaller than the predetermined value and thus, it is also judged that a trouble occurs in the sensor.
According to this structure, it is possible to judge the trouble that the output of the sensor sticks to a value exceeding the judgment value (judgment value used for conventional trouble diagnosis of the sensor), in addition to the trouble of output drop of the sensor.
In other words, in the present invention, a diagnostic apparatus of a coolant temperature sensor sensing a temperature of a coolant of an engine, comprises: setting means for setting a measuring timing; calculating means for calculating a variation amount of the temperature of the coolant from a start of the engine to the measuring timing; and judging means for judging that a trouble occurs in the coolant temperature sensor when the variation amount is smaller than a predetermined value.
Besides, in the present invention, a diagnostic method of a coolant temperature sensor sensing a temperature of a coolant of an engine, comprises: setting a measuring timing; calculating a variation amount of the temperature of the coolant from a start of the engine to the measuring timing; and judging that a trouble occurs in the coolant temperature sensor when the variation amount is smaller than a predetermined value.
Further, a diagnostic apparatus of a cooling apparatus of the invention is applied to a cooling apparatus provided with a cooling section carrying off heat of an engine by coolant to cool the engine, a radiator radiating the heat carried off by the coolant, and a thermostat controlling a flow rate of the coolant which circulates through the cooling section and the radiator. The diagnostic apparatus comprises: a coolant temperature sensor sending out an output in correspondence to a temperature of the coolant; a setting section setting, as a measuring timing, a time when a predetermined time is elapsed after the engine started or a time when a predetermined heat is generated; a sampling section sampling the temperature of the coolant at the measuring timing based on the output of the coolant temperature sensor; a judging section judging that a trouble occurs in the thermostat when the temperature of the coolant at the measuring timing sampled by the sampling section is smaller than a first predetermined value; a calculating section calculating a variation amount of the output of the coolant temperature sensor from start of the engine to the measuring timing; and a prohibiting section prohibiting the judging section from judging when the variation amount is smaller than a second predetermined value.
If the leakage diagnosis of the thermostat is carried out using the output of the sensor which is in trouble, it may be erroneously diagnosed that thermostat has leakage. However, when the variation amount of the output of the sensor from the start of the engine to the measuring timing is smaller than the predetermined value, the leakage diagnosis of the thermostat is prohibited as the sensor has a trouble, and thus, it is possible to prevent the erroneous judgment that the thermostat has leakage.
In other words, a diagnostic apparatus of a cooling apparatus of the invention is applied to the above cooling apparatus, too, and comprises: temperature detecting means sending out an output in correspondence to a temperature of the coolant; setting means for setting a measuring timing; sampling means for sampling the temperature of the coolant at the measuring timing based on the output of the temperature detecting means; judging means for judging that a trouble occurs in the coolant control means when the temperature of the coolant at the measuring timing sampled by the sampling means is smaller than a first predetermined value; calculating means for calculating a variation amount of the output of the temperature detecting means
Foley & Lardner
Nissan Motor Co,. Ltd.
Tanner Harry B.
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