| 摘要 |
A muffler comprises a casing and an exhaust pipe penetrating the casing. An exhaust gas chamber 4 is defined between the outer wall surface of the exhaust pipe and the inner wall surface of the casing. In the exhaust pipe positioned in the casing, an enlarged chamber for accommodating a particulate filter is formed. A downstream side portion of the exhaust pipe and the exhaust gas chamber are communicated with each other by a branch pipe. A communicating port is formed on the wall of an upstream side portion of the exhaust pipe positioned in the exhaust gas chamber. Until the pressure difference between the upstream and downstream of the communication control valve reaches a threshold value, the communication control valve is kept closed to close the communicating port and, thus, the exhaust gas flows through the particulate filter. When the pressure difference has reached the threshold value, the communication control valve is opened by the pressure in the upstream side portion to open the communicating port and, thus, a part of the exhaust gas bypasses the particulate filter. |
