Patent ID: 9574471
Date: 2017-02-21
CPC Classifications: F01N

Claim:
1. An exhaust muffler whose sound silencing characteristics are made variable by causing a change in a flow channel of an exhaust gas from an internal combustion engine, comprising: a casing in which an upstream chamber and a downstream chamber are defined with a partition interposed therebetween; a discharge pipe configured to discharge an exhaust gas in said downstream chamber out of said casing; a first conduit having one end into which the exhaust gas from the internal combustion engine is introduced and extending through said partition with an other end thereof being open into said upstream chamber, said first conduit having a pierced region including a plurality of fluid communication holes held in fluid communication with said downstream chamber; a second conduit, different from the first conduit, having one end into which the exhaust gas from the internal combustion engine is introduced and extending through said partition with an other end thereof being open into said upstream chamber; valve means configured to open and close said first conduit upstream of said pierced region and to open and close said second conduit; and valve actuating means actuating said valve means to switch open and closed states of the first and second conduits to cause a change in the flow channel of the exhaust gas in said casing; wherein said valve actuating means actuates said valve means to switch between a short channel mode discharging the exhaust gas from said internal combustion engine from at least said first conduit through said pierced region into said downstream chamber, and through said discharge pipe out of the casing and a long channel mode discharging the exhaust gas from said internal combustion engine from said second conduit through said upstream chamber, into said first conduit, through said pierced region into said downstream chamber, and through said discharge pipe out of the casing, and wherein the pierced region is only formed in the first conduit.