| 摘要 |
<p>PROBLEM TO BE SOLVED: To make it possible to evaluate the deterioration of performance of a double functional occlusion catalyst by measuring a time difference during a change in air ratios on the upstream and downstream of the occlusion catalyst to evaluate its occlusion functions. SOLUTION: Oxygen sensors 1, 2 are severally arranged in exhaust gas pipes on the upstream and downstream sides of an occlusion catalyst. A signal from the sensor 1 follows the change of an air-fuel ratio through an engine electronic system, but a signal from the sensor 2 is influenced by the occlusion characteristics of the catalyst. An elapsed termΔt1 until the recording of reduction component by the sensor 2 depends upon the rate of the quantity of a nitrogen oxide occluded in the occlusion catalyst and oxygen occlusion component contained in a test piece. After the end of a thick mixture stage, the air- fuel ratio increases in value more than 1. But the sensor 2 indicates a value smaller than a stoichiometrical air-fuel ratio on the downstream side of the catalyst for a specified timeΔt2. Since a time intervalΔt2 depends only upon the oxygen occlusion capacity of the catalyst, the oxygen occlusion function of the catalyst can be evaluated by measuring the above time.</p> |
