| 摘要 |
An improved method of assessing the catalyst warm-up rate of a motor vehicle catalytic converter is based on the response rates of fast warm-up exhaust gas sensors located in the exhaust gas upstream and downstream of the catalytic converter. The method essentially measures an oxygen storage characteristic of the catalyst that increases as the catalyst temperature rises to its ideal operating temperature. In one method, a ratio of switching frequency between the upstream and downstream exhaust gas sensors is periodically computed and compared to a threshold during catalyst warm-up. In another method, the response times of the exhaust gas sensors to a known air/fuel ratio transition are detected to form a measure of the oxygen storage characteristic that is compared to a threshold. In each method, the threshold varies as a function of cumulative airflow through the engine to compensate for different engine airflow levels.
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