대표
청구항
▼
What is claimed is: 1. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system comprising: an exhaust pipe coupled with the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst disposed at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst disposed at the second lo...
What is claimed is: 1. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system comprising: an exhaust pipe coupled with the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst disposed at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst disposed at the second location in the exhaust pipe a set distance downstream of the first catalyst, the second catalyst configured to provide an oxidation action; a secondary air induction pipe for introducing air into the exhaust pipe at the third location, the secondary air induction pipe being connected to the exhaust pipe between the first and the second catalysts at a location where the secondary air induction pipe is in fluid communication with the first catalyst and a temperature difference between the first and the second catalysts in a cold start transient phase is within a predetermined range; and a muffler that surrounds a portion of the exhaust pipe, wherein the first catalyst is disposed upstream of the muffler, and the second catalyst is disposed inside the muffler; wherein the third cross-sectional area is less than at least one of the first and the second cross-sectional areas. 2. The engine system of claim 1, wherein the cold start transient phase extends form an engine cold start until a predetermined operation time elapses. 3. The engine system of claim 1, wherein the secondary air induction pipe is connected to the exhaust pipe at a location where the flow velocity of the exhaust gas in the exhaust pipe is increased. 4. The engine system of claim 1, further comprising a flow regulator associated with the secondary air induction pipe to control the flow of secondary air therein. 5. The engine system of claim 1, wherein the engine has a displacement of about 50 cubic centimeters, the first catalyst is located within about 500 mm from the exhaust port, the second catalyst is located about 200 mm from the first catalyst, and the secondary air induction pipe is connected to the exhaust pipe within about 120 mm of the first catalyst. 6. The engine system of claim 1, wherein the secondary air induction pipe is connected to a part of the exhaust pipe outside the muffler. 7. The engine system of claim 1, further comprising a four-cycle engine comprising said exhaust port. 8. The engine system of claim 1, wherein the exhaust pipe comprises an upstream portion and a downstream portion, the downstream portion comprising a U-shaped construction. 9. The engine system of claim 8, wherein the first catalyst is situated in the upstream portion and the second catalyst is situated in the downstream portion. 10. The engine system of claim 1, wherein the exhaust pipe comprises an enlarged portion and a constricted portion wherein the flow velocity of exhaust gas increases. 11. The engine system of claim 10, wherein the constricted portion of the exhaust pipe is between the first and second catalysts. 12. The engine system of claim 10, wherein at least one of the first and second catalysts is located in the enlarged portion of the exhaust pipe. 13. The engine system of claim 10, wherein the enlarged portion includes a first section and a second section and wherein the constricted portion is located between the first and second sections of the enlarged portion. 14. The engine system of claim 10, wherein the secondary air induction pipe is connected to the constricted portion of the exhaust pipe. 15. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system comprising: an exhaust pipe coupled with the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst disposed at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst disposed at the second location in the exhaust pipe a set distance downstream of the first catalyst, the second catalyst configured to provide an oxidation action; a secondary air induction pipe for introducing air into the exhaust pipe at the third location, the secondary air induction pipe being connected to the exhaust pipe between the first and the second catalysts at a location where the secondary air induction pipe is in fluid communication with the first catalyst and a temperature difference between the first and the second catalysts in a cold start transient phase is within a predetermined range; and a muffler that surrounds a portion of the exhaust pipe, the muffler being disposed downstream of the first catalyst, and the second catalyst being disposed inside the muffler, wherein the secondary air induction pipe is connected to a part of the exhaust pipe inside the muffler; wherein the third cross-sectional area is less than at least one of the first and the second cross-sectional areas. 16. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system comprising: an exhaust pipe coupled with the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst disposed at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst disposed at the second location in the exhaust pipe a set distance downstream of the first catalyst, the second catalyst configured to provide an oxidation action; a secondary air induction pipe for introducing air into the exhaust pipe at the third location, the secondary air induction pipe being connected to the exhaust pipe between the first and the second catalysts at a location where the secondary air induction pipe is in fluid communication with the first catalyst and a temperature difference between the first and the second catalysts in a cold start transient phase is within a predetermined range; wherein the exhaust pipe comprises an enlarged portion and a constricted portion wherein the flow velocity of exhaust gas increases; wherein the third cross-sectional area is less than at least one of the first and the second cross-sectional areas; and wherein the secondary air induction pipe is connected to the enlarged portion of the exhaust pipe downstream of the first catalyst. 17. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system comprising: an exhaust pipe coupled with the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst disposed at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst disposed at the second location in the exhaust pipe a set distance downstream of the first catalyst, the second catalyst configured to provide an oxidation action; a secondary air induction pipe for introducing air into the exhaust pipe at the third location, the secondary air induction pipe being connected to the exhaust pipe between the first and the second catalysts at a location where the secondary air induction pipe is in fluid communication with the first catalyst and a temperature difference between the first and the second catalysts in a cold start transient phase is within a predetermined range; and wherein the exhaust pipe comprises an enlarged portion and a constricted portion wherein the flow velocity of exhaust gas increases; wherein the third cross-sectional area is less than at least one of the first and the second cross-sectional areas; and wherein exhaust pipe includes a longitudinal axis and a transition portion having a transverse size that varies along the longitudinal axis, the transition portion located between the enlarged portion and the constricted portion, wherein the secondary air induction pipe is connected to the transition portion. 18. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system comprising: an exhaust pipe coupled with the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst disposed at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst disposed at the second location in the exhaust pipe a set distance downstream of the first catalyst, the second catalyst configured to provide an oxidation action; a secondary air induction pipe for introducing air into the exhaust pipe at the third location, the secondary air induction pipe being connected to the exhaust pipe between the first and the second catalysts at a location where the secondary air induction pipe is in fluid communication with the first catalyst and a temperature difference between the first and the second catalysts in a cold start transient phase is within a predetermined range; wherein the third cross-sectional area is less than at least one of the first and the second cross-sectional areas; and wherein the temperature difference between the first and second catalyst is within about 100 degrees Celsius. 19. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system guiding exhaust pulsations, comprising: an exhaust pipe coupled to the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst arranged at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst arranged at the second location in the exhaust pipe a set distance downstream of the first catalyst, the second catalyst configured to provide an oxidation action; a secondary air induction pipe for introducing the secondary air into the exhaust pipe at the third location, the secondary air induction pipe being connected to the exhaust pipe between the first and the second catalysts at a position where the secondary air induction pipe is in fluid communication with the first catalyst and the secondary air acts on the first catalyst due to the exhaust pulsation; and a muffler that surrounds a portion of the exhaust pipe, wherein the first catalyst is disposed upstream of the muffler, and the second catalyst is disposed inside the muffler; wherein the third cross-sectional area is less than at least one of the first and the second cross-sectional areas. 20. The engine system of claim 19, further comprising a four-cycle engine comprising said exhaust port. 21. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system guiding exhaust pulsations, comprising: an exhaust pipe coupled to the exhaust port, the exhaust pipe comprising a first location having a first cross-sectional area, a second location having a second cross-sectional area, and a third location having a third cross-sectional area; a first catalyst arranged at the first location in the exhaust pipe, the first catalyst configured to provide a reduction action; a second catalyst arranged at the second location in the exhaust pipe a set distance downstream of the first catalyst, the second catalyst configured to provide an oxidation action; a secondary air induction pipe for introducing the secondary air into the exhaust pipe at the third location, the secondary air induction pipe being connected to the exhaust pipe between the first and the second catalysts at a position where the secondary air induction pipe is in fluid communication with the first catalyst and the secondary air acts on the first catalyst due to the exhaust pulsation; and a muffler that surrounds a portion of the exhaust pipe, the muffler being disposed downstream of the first catalyst, and the second catalyst being disposed inside the muffler, wherein the secondary air induction pipe is connected to a part of the exhaust pipe inside the muffler. 22. An engine system, comprising: an exhaust port for releasing combusted gas from an engine; an exhaust system comprising: an exhaust pipe comprising a secondary air induction port and being coupled with the exhaust pipe; a first catalyst disposed in the exhaust pipe; a second catalyst disposed in the exhaust pipe a set distance downstream of the first catalyst; and a secondary air induction pipe coupled with the exhaust pipe at the secondary air induction port, the secondary air induction pipe being configure for introducing air into the exhaust pipe; wherein the secondary air induction port is positioned between the first and second catalysts and air delivered therethrough causes the first and second catalysts to be heated during a cold start transient phase such that the temperature difference between the first and the second catalysts is less than about 100�� C. 23. The engine system of claim 22, wherein the secondary air induction pipe is connected to the exhaust pipe between a constriction in the exhaust pipe and the first catalyst. 24. The engine system of claim 22, wherein the secondary air induction pipe is connected to the exhaust pipe at a location that is closer in the flow path to the first catalyst than to the second catalyst. 25. The engine system of claim 22, wherein the secondary air induction pipe is connected to the exhaust pipe at a location that is closer in the flow path to the second catalyst than to the first catalyst. 26. The engine system of claim 22, wherein the first catalyst is configured to provide a reduction action and the second catalyst is configured to provide an oxidation action. 27. The engine system of claim 22, further comprising a muffler that surrounds a portion of the exhaust pipe, wherein the first catalyst is disposed upstream of the muffler, and the second catalyst is disposed inside the muffler. 28. The engine system of claim 22, wherein the secondary air induction port is positioned such that at least some air delivered therethrough enters the first catalyst.
