Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1990-06-11
1992-01-07
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
Methods
60276, 60285, F01N 320
Patent
active
050779702
ABSTRACT:
A method of on-board detection of the degradation of an automotive catalyst which receives the emissions from an engine placed in a closed-loop feedback control with an A/F characteristic sensor immersed in the emissions. The method comprises: (a) artificially modulating the frequency and/or amplitude of the control for a predetermined burst period; (b) sensing an A/F characteristic by an independent sensor substantially immediately downstream of the catalyst at events prior to and during the burst period; and (c) determining if there is an absence of a substantial change between events in the independently sensed A/F characteristic, thus indicating a degraded catalyst. The artificial modulation changes the oxygen exposure of the catalyst during a short catalyst interrogation period in a manner to magnify the oxygen absorption characteristic of the noble metals within the catalyst. The artificial modulation may comprise a frequency change of a fixed uniform increase, such as 2-3 times the normal limit cycle frequency of the engine control, preferably about 2-4 Hz, or may comprise a variable change of frequency or amplitude such as ramping with or without steps or interruptions.
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patent: 4007589 (1977-02-01), Neidhard et al.
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patent: 4761950 (1988-08-01), Nagai et al.
SAE Paper #800826, Hamburg et al., "A Closed-Loop A/F Control Model for Internal Combustion Engines", Jun. 1980.
SAE Paper #841297, Gamberg et al., "Adaptive Air/Fuel Control Applied to a Single Point Injection System for SI Engines", 1984.
Ford Motor Company
Hart Douglas
Malleck Joseph W.
May Roger L.
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