| 摘要 |
PURPOSE:To enable cooling of a catalyst holding part and exhaust gas after passage of it through a catalyst by means of engine cooling water, by a method wherein a catalyst holding part is situated in an exhaust gas passage, and an engine cooling water passage is disposed around an exhaust gas passage located down a line from a catalyst. CONSTITUTION:A catalyst 36 is disposed at a position facing an exhaust port 32 of an engine 16, and a branch exhaust gas passage 38 is formed on the back of the catalyst 36. In this case, the catalyst 36 is held in a holding part 42 formed to an inner cover 40 forming a part of an exhaust gas passage 34 through a mat 44. Meanwhile, a water jacket 29 is communicated with a water chamber 43 formed within the inner cover 40 in a manner to surround the holding part 42, and the water chamber 43 is communicated to a water passage 57 formed between a partition plate 54 and an outer cover 52 through a hole 54 of a partition plate 50. The water passage 57 is communicated to a communication passage 58 formed in the inner cover 40 through a hole 56 of a partition plate 54. This constitution feeds cooling water to the surroundings of the holding part 42 of the catalyst 36. |
