Power plants – Internal combustion engine with treatment or handling of... – Having means analyzing composition of exhaust gas
Patent
1997-05-19
1999-12-14
Denion, Thomas E.
Power plants
Internal combustion engine with treatment or handling of...
Having means analyzing composition of exhaust gas
60277, 60274, 60285, 123688, 123691, F01N 300
Patent
active
060002182
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a system for monitoring the functional ability of catalytic converters and/or lambda sensors in detoxification systems for exhaust.
Systems of this kind are known especially for exhaust from internal combustion engines in a plurality of embodiments (for example DE 23 04 464 C2).
These known systems suffer from the disadvantages that they cannot monitor functional ability sufficiently reliably since indirect measurement is performed either with two lambda sensors (DE 40 39 429) or by temperature probes. In particular, reliable determination of functional ability is not possible in aged catalytic converters because of the conversion rate of hydrocarbons and other pollutants that no longer correlate with the oxygen storage capacity.
A device is also known (DE 42 11 116) with which the lambda value of a mixture can be modulated to determine the functional ability of the catalytic converter in such fashion that an oxygen excess periodically alternates with an oxygen deficiency. On the basis of the sudden reaction of a lambda sensor located downstream from the catalytic converter in the flow direction, the functional ability and/or degree of conversion capacity of the catalytic converter is detected. Here again the indirect acquisition of information about the function of the catalytic converter is disadvantageous.
SUMMARY OF THE INVENTION
Hence the goal of the invention is to design a system for monitoring the functional ability of catalytic converters and/or lambda sensors in detoxification systems for exhaust that reacts more reliably as well as rapidly.
This goal is achieved according to the invention in a system according to the species in accordance with the preamble of the main claim, by virtue of its characterizing features.
Thus, according to the present invention it is not a lambda sensor or a temperature sensor that is provided for monitoring, but an emission sensor in the flow direction of the exhaust, downstream from or in the catalytic converter. In addition, a rapid, defined change in the load and/or the rpm of an engine or of the lambda value and/or the oxygen content in the exhaust is performed, for example by defined leaning out or enrichment of the exhaust from internal combustion engines according to a specific procedure or cycle and the electrical output signal from the emission sensor is compared with a value profile that is stored and corresponds to the defined change in lambda value. If the electrical output signal lies within a certain tolerance range in the stored value profile, it is assumed that both the catalytic converter and the lambda sensors are in a functioning state. If the values fall outside a tolerance range, it provides an indirect indication of a defect in either the catalytic converter or the lambda sensors. Advantageously, the defined change in lambda value can occur by adding secondary air in the flow direction upstream from the catalytic converter so that its function and/or that of the emission sensor itself can be checked as well. Otherwise, only the function of the emission sensor itself is determined.
Advantageously it is also possible to locate the emission sensor between two or more individual catalytic converters because then the defined change reaches higher values of the emission peaks, but these comparatively higher concentrations can be reduced in the catalytic converter located downstream so that determination of the functional ability does not result in an increased emission figure.
BRIEF DESCRIPTION OF THE DRAWINGS
One preferred embodiment will now be described in greater detail with reference to the drawing, which provides a schematic diagram.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Initially, direction arrow 10 indicates the exhaust flowing from an internal combustion engine of a motor vehicle, which passes through a catalytic converter designated by 11 as a whole. Reference numeral 12 refers to an emission sensor located in flow direction 10 of the exhaust downstream from catalyti
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patent: 5103640 (1992-04-01), Nada et al.
patent: 5105651 (1992-04-01), Gutmann
patent: 5265417 (1993-11-01), Visser et al.
patent: 5291673 (1994-03-01), Hamburg et al.
patent: 5357749 (1994-10-01), Ohsuga et al.
Denion Thomas E.
Heraeus Electro-Nite International N.V.
Tran Binh
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