Muffler for an internal combustion engine
A muffler has a housing enclosing a plurality of chambers. A first flow path extends from an inlet to an outlet passing through a bypass chamber. A flow tube has a plurality of perforations being open to a chamber other than the bypass chamber. A second in flow path passes from the inlet to the outlet without passing through the bypass chamber and passing through the perforations. Exhaust gas is introduced into the muffler via the inlet and discharged therefrom via the outlet. A first portion of the exhaust gas flows from the inlet to the outlet along the first flow path. A second portion of the exhaust gas flows from the inlet to the outlet along the second flow path, the first and second portions mixing at least in the outlet chamber. A semi-closed tube has an open end being open to one of the chambers and a closed end.
1. A muffler for an internal combustion engine, the muffler comprising:
a housing enclosing a plurality of chambers including an outlet chamber and a bypass chamber;
an inlet for receiving exhaust gas from the engine;
an outlet for discharging exhaust gas from the muffler, the outlet opening to the outlet chamber;
at least the inlet, the outlet, the outlet chamber, and the bypass chamber defining a first flow path extending from the inlet to the outlet and passing through the bypass chamber;
a flow tube defining at least in part the first flow path, the flow tube defining a passage upstream of the bypass chamber along the first flow path; and
a plurality of perforations defined in a portion of the flow tube, each of the plurality of perforations being open to one of the plurality of chambers other than the bypass chamber;
at least the inlet, the outlet, the outlet chamber, and the plurality of perforations defining a second flow path extending from the inlet to the outlet without passing through the bypass chamber, the second flow path passing through the plurality of perforations,
whereby
exhaust gas is introduced into the muffler via the inlet and discharged from the muffler via the outlet;
a first portion of the exhaust gas flows from the inlet to the outlet along the first flow path and a second portion of the exhaust gas flows from the inlet to the outlet along the second flow path, the first portion mixing with the second portion at least in the outlet chamber; and
a semi-closed tube having an open end and a closed end opposite the open end, the open end of the semi-closed tube being open to one of the plurality of chambers.
2. The muffler of claim 1 , wherein:
the plurality of chambers is at least three chambers including an inlet chamber, the outlet chamber and the bypass chamber;
the inlet opens into the inlet chamber;
each perforation of the plurality of perforations is open to one of the at least three chambers other than the inlet chamber and the bypass chamber.
3. The muffler of claim 2 , wherein the inlet is defined by an inlet tube extending from a first end being open to the inlet chamber to a second end being open outside the muffler.
4. The muffler of claim 2 , wherein the flow tube comprises:
a first end open to the inlet chamber; and
a second end opposite the first end being open to one of the at least three chambers other than the outlet chamber and the inlet chamber.
5. The muffler of claim 4 , wherein the second end of the flow tube is open to the bypass chamber, the flow tube fluidly communicating the inlet chamber with the bypass chamber.
6. The muffler of claim 2 , wherein the plurality of perforations is open to the outlet chamber.
7. The muffler of claim 6 , wherein:
the at least three chambers is three chambers;
the flow tube is a first flow tube fluidly communicating the inlet chamber with the bypass chamber;
the passage defined by the first flow tube is a first passage;
the muffler further comprises a second passage fluidly connecting the bypass chamber with the outlet chamber,
the first flow path passing from the inlet to the inlet chamber, from the inlet chamber via the first passage to the bypass chamber, from the bypass chamber via the second passage to the outlet chamber and from the outlet chamber out of the muffler via the outlet;
the second flow path passing from the inlet to the inlet chamber, from the inlet chamber via a portion of the first passage and through the plurality of perforations into the outlet chamber and from the outlet chamber out of the muffler via the outlet.
8. The muffler of claim 7 , further comprising a second flow tube fluidly connecting the bypass chamber to the outlet chamber and defining the second passage.
9. The muffler of claim 2 , wherein:
the bypass chamber is disposed adjacent a first end of the housing;
the inlet chamber is disposed adjacent a second end of the housing opposite the first end of the housing; and
the outlet chamber is disposed between the inlet chamber and the bypass chamber.
10. The muffler of claim 2 , wherein the at least three chambers is four chambers including the inlet chamber, the outlet chamber, the bypass chamber and a fourth chamber.
11. The muffler of claim 10 , wherein the plurality of perforations is open to the fourth chamber.
12. The muffler of claim 1 , wherein the bypass chamber is disposed adjacent a first end of the housing.
13. The muffler of claim 2 , wherein the open end of the semi-closed tube is open to the inlet chamber.
14. The muffler of claim 1 , wherein:
the flow tube extends from the inlet to one of the plurality of chambers other than the outlet chamber.
15. The muffler of claim 14 , wherein the plurality of perforations is open to the outlet chamber.
16. The muffler of claim 1 , further comprising an outlet tube extending from a first end being open to the outlet chamber to a second end being open outside the muffler, the outlet being defined by the outlet tube.
17. The muffler of claim 16 , wherein the outlet tube further comprises a spark arrestor.
18. The muffler of claim 1 , wherein:
the first flow path and the second flow path join at least in the outlet chamber and are configured to provide a first resonant attenuation frequency for attenuation of sound waves, and
the semi-closed tube is configured to provide a second resonant attenuation frequency for attenuation of sound waves.
19. The muffler of claim 18 , wherein the second resonant attenuation frequency is greater than the first resonant attenuation frequency.
20. The muffler of claim 18 , wherein the second resonant attenuation frequency is an anti-resonant frequency with respect to the first resonant attenuation frequency.