| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device in which the variation of turbocharging pressure by rich spike is suppressed without impairing supercharging effect in a turbocharged engine in which the portion of an exhaust system where an engine body is connected to the turbine of an exhaust turbosupercharger is composed of a first exhaust passage and a second exhaust passage and an NOx control device is installed in an exhaust passage on the downstream side of the turbine. <P>SOLUTION: An ECU 30 of the air-fuel ratio control device opens a waste gate valve in at least one of first and second exhaust passages 20a, 20b on the exhaust passage side when the predetermined requirements for lean operation to lean air-fuel ratio are satisfied to control the air-fuel ratio of the air-fuel mixture supplied to the cylinder corresponding to one exhaust passage to lean and the other air-fuel ratio to the theoretical air-fuel ratio. When the predetermined requirements for rich spike are satisfied during the lean operation, one air-fuel ratio is controlled to the theoretical air-fuel ratio. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
