| 摘要 |
PROBLEM TO BE SOLVED: To greatly reduce a CO component by forcibly supplying external air into a muffler expansion room by a diaphragm pump and increasing the amount of oxygen in a first expansion room. SOLUTION: A diaphragm pump 70 performs pumping action based on the pressure fluctuation of the crank room 6 of an internal combustion engine 1, sucks external air from an air introducing pipe 82 and discharges the air to an air discharge pipe 83. The air introduced to the air discharge pipe 83 is guided to the air flow-in pipe 53 of a muffler 20 via a connecting tube 84, and the air is jetted out from the air flow-in pipe 53 into the first expansion room 31 of the muffler 20. Exhaust gas introduced to the first expansion room 31 is mixed with the air jetted out from the air flow-in pipe 53, then, by a pressure difference between the first expansion room 31 and an adjacently disposed second expansion room 32 which are partitioned by a partition plate 40, it enters the inside of the exposed side face of an oxidation catalyst 50 and then guided through a small hole formed in the inside thereof to the second expansion room 32.
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