Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1993-12-03
1997-10-14
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
Methods
60277, 60284, F01N 320
Patent
active
056759673
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The following relates to a method and an arrangement for evaluating the operability of a catalytic converter which is operated in the exhaust-gas channel of an internal combustion engine.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 3,969,932 describes a method and an arrangement wherein the operability of a catalytic converter is determined with the aid of a time measurement which is a measure of the storage capacity of the catalytic converter. The catalytic converter is first entirely charged with oxygen in that the corresponding internal combustion engine is operated lean adequately long. Then, the engine is operated rich with pregiven operating conditions whereby the oxygen stored in the catalytic converter is consumed. The exhaust gas outputted by the catalytic converter has the lambda value 1 as long as the catalytic converter can still supply oxygen to the exhaust gas conducted thereto. However, as soon as the oxygen is consumed, a lambda value measurement at the output of the catalytic converter shows a rich mixture. The time span between the start of the rich operation and the time point at which this is detected at the output of the catalytic converter is a measure for the state of deterioration of the catalytic converter. The shorter this time span is, the greater the catalytic converter has deteriorated. The catalytic converter is evaluated as no longer being operable when the measured time span drops below a pregiven time span.
The lambda value signals are set in relationship to each other in other methods for determining the operability of a catalytic converter as these signals are detected forward and rearward of a catalytic converter. Thus, for example, in U.S. Pat. No. 3,962,866, a description is provided that the operability is determined with the aid of the difference between the amplitudes of the above-mentioned two signals. The catalytic converter is determined as being no longer operable as soon as the difference drops below a threshold value. According to published German patent application 3,500,594, the ratio of the amplitudes is utilized in lieu of the difference, with this ratio also being averaged.
SUMMARY OF THE INVENTION
From the points in time of the filing of the above-mentioned patent-related literature, it can be seen that experts have, for a long time, been trying to reliably evaluate the operability of a catalytic converter. A method satisfactory for all cases could, however, still not be found. Accordingly, the desire was present to find additional methods and arrangements for evaluating the operability of a catalytic converter operated in the exhaust gas of an internal combustion engine.
A first method according to the invention is characterized in that: the engine is operated proceeding from a state in which the temperature of the catalytic converter is below the temperature at which a new catalytic converter begins to convert; a check is made as to the temperature at which the catalytic converter, which is heated by the exhaust gas of the engine, begins to convert; the determined conversion-begin temperature is compared to a pregiven comparison temperature, this comparison temperature being above the temperature at which a new catalytic converter begins to convert; and, the catalytic converter is evaluated to be operable when the determined conversion-begin temperature is below the comparison temperature.
A second method according to the invention is characterized in that: the engine has pregiven operating conditions and is operated proceeding from a state in which the temperature of the catalytic converter is below the temperature at which a new catalytic converter begins to convert; the time span is measured which the catalytic converter requires to reach a comparison temperature which is above the conversion-begin temperature for a new catalytic converter; the measured time span is compared to a pregiven comparison time span; and, the catalytic converter is evaluated to be operable when the measured time span is shorter than the comparis
REFERENCES:
patent: 3962866 (1976-06-01), Neidhard et al.
patent: 3969932 (1976-07-01), Rieger et al.
patent: 5060473 (1991-10-01), Nakagawa
patent: 5177463 (1993-01-01), Bradshaw
"Langzeitstabilitat von Katalysatoren" by E. Koberstein, VDI Berichte Nr. 639, 1987, pp. 345 to 360.
"The Effect of High Temperature Ageing on Platinum-Rhodium and Palladium-Rhodium Three Way Catalysts" by R. J. Brisley et al, SAE Technical Paper Series 910175, 1991.
Hart Douglas
Ottesen Walter
Robert & Bosch GmbH
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