Measuring and testing – Test stand – For engine
Patent
1990-06-21
1992-07-14
Myracle, Jerry W.
Measuring and testing
Test stand
For engine
G01M 1500
Patent
active
051292580
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for determining the temperature of a lambda sensor and/or the temperature of the exhaust gas surrounding it. The invention also relates to an apparatus for determining the exhaust gas temperature.
BACKGROUND OF THE INVENTION
It is known that the internal resistance of a lambda sensor drops significantly with increasing temperature. There is a definite relationship between the sensor temperature and the internal resistance. This relationship is used to determine the sensor temperature from a measurement of the internal resistance, as described, for example, in U.S. Pat. No. 4,419,190.
The temperature of the lambda sensor is determined in the case of an unheated sensor exclusively and in the case of a heated sensor predominantly by the temperature of the exhaust gas surrounding it. This temperature is determined according to the state of the art with the aid of a separate measuring sensor.
It is the object of the invention to specify methods for determining the temperatures of a lambda sensor and/or of the exhaust gas surrounding it with the methods being simple but nevertheless operating precisely. Furthermore, the invention is based on the object of specifying an apparatus of simple configuration for determining the exhaust gas temperature.
SUMMARY OF THE INVENTION
The method of the invention is for determining the temperature of the exhaust gas of an internal combustion engine and includes the steps of: measuring the internal resistance of a lambda sensor arranged in the exhaust gas; and, determining the exhaust gas temperature with the aid of a known relationship between internal resistance and exhaust gas temperature for the steady-state case.
The sensor temperature is determined with the aid of a known relationship between internal resistance and sensor temperature. The temperature of the lambda sensor is determined by detecting the lambda value; and, in the case of a rich mixture, a relationship between internal resistance and sensor temperature is used which was determined for a rich mixture, and in the case of a lean mixture, a relationship between internal resistance and sensor temperature is used which was determined for a lean mixture.
Both methods are distinguished by the fact that they perform a temperature determination with the aid of the internal resistance of a lambda sensor arranged in the exhaust gas. The method according to the invention for determining the exhaust gas temperature is based on the recognition that not only is the relationship between internal resistance and sensor temperature definite, but also that, provided there are steady-state conditions, the relationship between sensor temperature and exhaust gas temperature is definite for a particular present arrangement. Accordingly, there is, for the steady-state case, a definite relationship between internal resistance and exhaust gas temperature. This makes it possible initially to measure the relationship between exhaust gas temperature and internal resistance and then to determine, with the aid of this known relationship, the exhaust gas temperature for the steady-state case from the internal resistance measured in the normal manner. In this connection, it is irrelevant whether the sensor is heated or unheated. Resulting differences in the relationship between internal resistance and exhaust gas temperature are automatically taken into account if the relationship between internal resistance and exhaust gas temperature is measured.
In order to be able to determine the exhaust gas temperature from the internal resistance even in the non-steady-state case, the temperature obtained from the steady-state relationship is corrected with the aid of the increase of the time/temperature curve at the particular instant.
It is also advantageous to perform a correction which allows for the fact that different relationships between internal resistance and exhaust gas temperature exist for leaner and richer mixtures, to the effect that with a particular identical exhaust gas t
REFERENCES:
patent: 4376026 (1983-03-01), Hoffman et al.
patent: 4419190 (1983-12-01), Dietz et al.
patent: 4742808 (1988-05-01), Blumel et al.
Myracle Jerry W.
Ottesen Walter
Robert & Bosch GmbH
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