Exhaust device for engine

1. An exhaust device for an engine, said exhaust device including: an exhaust pipe having a curved portion;

a flow rectifying means for rectifying a flow of an exhaust gas, said flow rectifying means being disposed in an upstream end of an inner pipe, said flow rectifying means comprising protrusions projecting inwardly, and being attached to an inner surface of the inner pipe, said inner pipe being connected to an end of the exhaust pipe,

wherein the exhaust gas engaging said flow rectifying means has passed through the curved portion of the inner pipe, and wherein the inner pipe also includes a muffler having a plurality of vent holes disposed in an inner portion thereof, and an outer pipe surrounding the inner pipe, defining an angular chamber therebetween, and wherein said flow rectifying means comprises a first flow rectifying member attached to the inner surface of the inner pipe, outwardly of a curved direction of the curved portion of the exhaust pipe, and a second flow rectifying member attached to the inner surface of the inner pipe, downstream of the first flow rectifying member, said first and second flow rectifying members having the protrusions projecting integrally therewith, inwardly from an inner surface of the upstream end of the inner pipe, wherein the flow rectifying means uniformizes exhaust gas pressure in the inner pipe.

2. The exhaust device according to claim 1 , wherein said flow rectifying means is disposed downstream of said curved portion, on an outwardly disposed section thereof.

3. The exhaust device according to claim 1 , wherein one of said protrusions is angularly disposed so as to be progressively spaced from the inner surface of the inner pipe downstream with respect to the direction in which the exhaust gas flows, and wherein the distance between the projecting end of the at least one protrusion and the inner surface of the inner pipe in a region where a pressure distribution of the exhaust gas in the inner pipe exhibits a highest pressure is greater than distances at other portions of the projecting end.

4. The exhaust device according to claim 1 , wherein the first and second flow rectifying members include an arcuate cross-sectional shape in a plane perpendicular to an axis of the inner pipe.

5. An exhaust device for an engine, comprising:

an exhaust pipe having an inner surface thereof and a curved portion configured to be attached to the engine at an upstream portion thereof, and configured to be attached to a muffler at a downstream portion thereof;

a protrusion projecting inwardly from an inner surface of the exhaust pipe, said protrusion disposed downstream of said curved portion,

wherein the protrusion is configured to rectify flow of exhaust gas which has passed through the curved portion by uniformizing exhaust gas pressure in the exhaust pipe.

6. The exhaust device according to claim 5 , wherein said protrusion is disposed downstream of said curved portion, on an outwardly disposed section thereof.

7. An exhaust device for an engine, said exhaust device comprising:

an exhaust pipe having an upstream curved portion at one end thereof and a downstream curved portion at another end thereof, said upstream curved portion being configured to be attached to an engine, said downstream curved portion being configured to be attached to a muffler, whereby the muffler comprises an inner pipe having a number of vent holes thereupon, and an outer pipe surrounding the inner pipe, thereby defining an angular chamber between the outer pipe and the inner pipe;

a first flow rectifying protrusion disposed on an inner surface of an upstream end of the inner pipe, said first protrusion being configured to rectify flow of exhaust gas which has passed through the downstream curved portion,

said device further comprising a second flow rectifying protrusion, with the first flow rectifying protrusion being attached to the inner surface of the inner pipe, and the second flow rectifying protrusion being fixed to the inner surface of the inner pipe downstream of the first flow rectifying protrusion, with the first and second flow rectifying protrusions projecting integrally inwardly from the upstream end of the inner pipe, wherein the first and second flow rectifying protrusions uniformize exhaust gas pressure in the inner pipe.

8. The exhaust device according to claim 7 , wherein the first protrusion is angularly disposed so as to be progressively from the inner surface of the inner pipe downstream with respect to the direction in which the exhaust gas flows there through, and wherein a distance between a projecting end of the first protrusion and the inner surface of the inner pipe, in a region where a pressure distribution of the exhaust gas in the inner pipe exhibits a highest pressure, is greater than the distances at other portions of the projecting end.

9. The exhaust device according to claim 8 , wherein the first and second flow rectifying protrusions comprise an arcuate cross-sectional shape in a plane perpendicular to an axis of the inner pipe.

10. The exhaust device according to claim 9 , wherein the at least one flow rectifying protrusion is disposed downstream of the downstream curved portion, on an outwardly disposed section thereof.

11. An exhaust device for an engine, comprising:

an exhaust pipe having a curved portion at an upstream end thereof; and

at least one flow rectifying protrusion projecting inwardly from an inner surface of the exhaust pipe, said flow rectifying protrusion disposed downstream of the curved portion, said protrusion configured to rectify a flow of an exhaust gas which has passed through the curved portion by uniformizing exhaust gas pressure in the exhaust pipe.

12. The exhaust device according to claim 11 , wherein the flow rectifying protrusion is disposed to project inwardly from an outward section of the exhaust pipe.