| 摘要 |
The exhaust sensor (26) signals exhaust NOx concentration (first signal) and exhaust air/fuel ratio (second signal). The signal analyzer (33) selects one signal for output, to control engine air/fuel ratio using an air fuel/ratio controller (31). PREFERRED FEATURES:- The controller (31) outputs the first or second signal, during lean and rich engine operation respectively. Further variants are described, with key features as follows. Continuous monitoring by a transition detector (33) determines transition from lean-to-rich ratio, from the first signal. The reverse transition is detected from the second signal. Based on the results, the controller adjusts the air-fuel ratio. The controller includes lean and rich controllers maintaining air/fuel ratio under rich control, to displace NOx absorbed by the NOx storage catalyst (13) during lean burn operation. The controller assesses the NOx stored during lean burn; it then controls fuel injection during rich operation, in correspondence with NOx absorbed, to precisely displace it. The sensor is a composite type, giving both NOx and oxygen concentration as first and second signals respectively.
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