Method of on-board detection of automotive catalyst degradation
First Claim
1. A method of on-board detection of the degradation of an automotive catalyst which receives the emissions from the engine placed in a closed-loop feedback control with an A/F characteristic sensor, comprising:
- (a) artificially modulating at least one of the frequency and amplitude of said control for a predetermined burst;
(b) sensing an A/F characteristic by an independent sensor substantially immediately downstream of said catalyst at A/F modulation events prior to and during said burst; and
(c) determining if there is an absence of a substantial change in the independently sensed A/F characteristic when changing from one such event to the other, thus indicating a degraded catalyst.
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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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Citations
28 Claims
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1. A method of on-board detection of the degradation of an automotive catalyst which receives the emissions from the engine placed in a closed-loop feedback control with an A/F characteristic sensor, comprising:
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(a) artificially modulating at least one of the frequency and amplitude of said control for a predetermined burst; (b) sensing an A/F characteristic by an independent sensor substantially immediately downstream of said catalyst at A/F modulation events prior to and during said burst; and (c) determining if there is an absence of a substantial change in the independently sensed A/F characteristic when changing from one such event to the other, thus indicating a degraded catalyst. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification