Patent ID: 7677357

Claim:
A muffler comprising a conduit that passes through an expansion chamber, wherein the conduit comprises: a partition wall at a central section of the conduit; an upstream section upstream from the partition wall having an outflow section with a side surface in which outflow holes are formed that allow exhaust gas to flow out to the expansion chamber, and having a head section upstream from the outflow section, wherein an inner diameter of the upstream section is maintained without size reduction from the head section to the partition wall; and a downstream section downstream from the partition wall having an inflow section with a side surface formed with inflow holes that allow exhaust gas to flow in from the expansion chamber, wherein at least one section of the downstream section has a smaller inner diameter than the inner diameter of the outflow section, the upstream section is connected to the downstream section so that the upstream section and the downstream section constitute a single conduit, the downstream section has a tail section downstream from the inflow section, the conduit comprises an upstream pipe comprising the head section and the outflow section, and a downstream pipe comprising the inflow section and the tail section and connected to the upstream pipe, a downstream end of the upstream pipe is open, an upstream end of the downstream pipe has a closed end defining the partition wall, and the upstream end of the downstream pipe is inserted into and connected by welding to the open downstream end of the upstream pipe.