Kraftstoff-Luftverhältnis-Regeleinrichtung und Verfahren zum Regeln des Kraftstoff-Luftverhältnisses eines Motors

摘要

In a horizontally opposed type engine, right and left exhaust pipes 4, 6 are provided on right and left cylinder banks 2, 3 respectively and a collecting pipe 8 is disposed to collect these two exhaust pipes. Further, in a two-stage catalytic converter system, two main catalysts 21, 22 are provided for the two exhaust pipes 4, 6, respectively and a subsidiary catalyst 23 is provided in the collecting pipe 8. An oxygen sensor 25, 26 is provided in each of the exhaust pipes 4, 6 on the upstream side of the main catalyst 21, 22, respectively. The air-fuel ratios of both the banks are controlled simultaneously on the basis of the output of the oxygen sensor 25 of one of the cylinder banks and the air-fuel ratio of the other bank is corrected on the basis of a phase difference between the outputs of the two oxygen sensors 25, 26. Accordingly, the air-fuel ratios of both right and left banks can be controlled appropriately, without use of any auxiliary oxygen sensor. As a result, it is possible to improve the purification capability of the auxiliary catalyst 23 in the collecting pipe 8. <IMAGE>