| 摘要 |
<P>PROBLEM TO BE SOLVED: To arrange a bypass catalyst converter performing exhaust emission control just after cold starting on the upstream side; and to prevent leakage of the exhaust gas through a flow passage switching valve 4. <P>SOLUTION: The flow passage switching valve 4 is arranged in a merging part wherein four upstream side main passages connected to each of cylinders are gathered as downstream side main passages. As a bypass flow passage, an upstream side bypass passage diverges from each of the respective upstream side main passages, and the bypass catalyst converter intervenes in a halfway of a downstream side bypass passage. When the flow passage switching valve 4 is closed, the main flow passage is shut off, and simultaneously, the upstream side main passages of the respective cylinders are in the non-communication state. The flow passage switching valve 4 is provided with a valve base 21 having four opened valve openings 25 and a valve element 26, and a metal pipe 22 for the upstream side main passage is welded to a partition wall 35 of the valve base 21 after processing of a seal surface 25a and assembling of the valve element 26. The welded part is separated from the seal surface 25a, and thereby sealing performance is not lowered by distortion. <P>COPYRIGHT: (C)2007,JPO&INPIT |
