EXHAUST SYSTEM OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To facilitate assembling work of a flow passage switching valve 4, and to improve dimensional accuracy, by arranging a bypass catalytic converter on the further upstream side for performing exhaust emission control just after cold starting. SOLUTION: The flow passage switching valve 4 is arranged in a confluent part of gathering four upstream side main passages connected with every cylinder. The bypass catalytic converter is interposed in a bypass passage branching off from the respective upstream side main passages. When closing the flow passage switching valve 4, simultaneously when cutting off a main flow passage, the mutual upstream side main passages of the respective cylinders are put in an non-communicating state. The flow passage switching valve 4 has a housing 21 of opening four valve opening parts 22 and a valve element 24, and the two valve elements 24 are installed in a common valve support 25. In this valve support 25, two arm parts 25B for respectively fixing the valve elements 24 are integrally formed in a shaft part 25A integrally rotating with a rotary shaft rotatably supported in the housing 21. COPYRIGHT: (C)2008,JPO&INPIT