| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent leakage of exhaust gas via a flow passage switching valve 4, by arranging a bypass catalytic converter 18 on the further upstream side for controlling exhaust emission just after cold starting. <P>SOLUTION: The flow passage switching valve 4 for simultaneously opening and closing four upstream side main passages 2, is arranged in a confluent part for merging the four upstream side main passages 2 connected with every cylinder 1 into one downstream side main passage 3. An upstream side bypass passage 11 branches off from the respective upstream side main passages 2 as a bypass flow passage, and the bypass catalytic converter 18 is interposed in the middle of a downstream side bypass passage 16. When closing the flow passage switching valve 4, a main flow passage is cut off, and at the same time, the mutual upstream side main passages 2 become an uncommunicating state, and a second seal surface for partitioning mutual four valve opening parts for opening and closing one valve element, is retreated to a first seal surface of the outer periphery, and even if a partition wall part having the second seal surface thermally expands, the valve element is not push-opened. <P>COPYRIGHT: (C)2007,JPO&INPIT |
