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An exhaust gas control apparatus for an engine and a method for producing the same are provided. The exhaust gas control apparatus includes a valve portion, an absorption portion, and a catalyst portion. The valve portion includes a valve that opens/closes a main exhaust passage. The absorption por

An exhaust gas control apparatus for an engine and a method for producing the same are provided. The exhaust gas control apparatus includes a valve portion, an absorption portion, and a catalyst portion. The valve portion includes a valve that opens/closes a main exhaust passage. The absorption portion includes a hydrocarbon-absorbent that absorbs hydrocarbons. The catalyst portion includes a three-way catalyst that purifies exhaust gas. The valve portion, absorption portion, and the catalyst portion are independent of each other. The valve portion, the absorption portion, and the catalyst portion are connected to each other in series. With this configuration, any individual component can be replaced with another corresponding component that achieves a required level of performance while minimizing the number of other components.

대표청구항 ▼

What is claimed is: 1. An exhaust gas control apparatus for an engine, comprising: an absorption portion that includes a first exhaust passage and a second exhaust passage, the respective openings of which are located at different positions, and through which exhaust gas flows into the absorption p

What is claimed is: 1. An exhaust gas control apparatus for an engine, comprising: an absorption portion that includes a first exhaust passage and a second exhaust passage, the respective openings of which are located at different positions, and through which exhaust gas flows into the absorption portion; wherein the first exhaust passage is provided therein with a hydrocarbon-absorbent, which absorbs hydrocarbons present in the exhaust gas; a valve portion that includes a valve that opens and closes the second exhaust passage, thereby changing a mode where the exhaust gas flows; and a catalyst portion that includes a catalyst that purifies the exhaust gas, wherein the absorption portion, the valve portion, and the catalyst portion are independent of each other; the absorption portion, the valve portion, and the catalyst portion are connected to each other in series, and the first exhaust passage communicates with a space upstream of the second exhaust passage through an upstream-opening positioned upstream of the hydrocarbon-absorbent, and communicates with a space downstream of the second exhaust passage through a downstream-opening positioned downstream of the hydrocarbon-absorbent, when the valve is open, the exhaust gas flows from the valve through the second exhaust passage to the catalyst and a portion of the exhaust gas flows back from the downstream-opening through the first exhaust passage and the upstream-opening to the space upstream of the valve. 2. The exhaust gas control apparatus for an engine, according to claim 1, wherein the valve portion, the absorption portion, and the catalyst portion are disposed from an upstream side to a downstream side. 3. The exhaust gas control apparatus for an engine according to claim 1, wherein, when the valve is closed, the exhaust gas flows from the space upstream of the valve through the upstream-opening, the first exhaust passage and the downstream-opening to catalyst. 4. The exhaust gas control apparatus for an engine according to claim 1, wherein, when the valve is open, the downstream-opening facilitates the flow of the exhaust gas between the first exhaust passage and a space where pressure of the exhaust gas is stable. 5. The exhaust gas control apparatus for an engine according to claim 1, wherein the downstream-opening is positioned at a distance from a boundary between a space where the exhaust gas swirls or stagnates and a space where the exhaust gas does not swirl or stagnate when the valve is open, and the distance is sufficient for the exhaust gas to flow between the first exhaust passage and the space where the exhaust gas does not swirl or stagnate when the valve is open. 6. The exhaust gas control apparatus for an engine according to claim 1, wherein an inlet port, through which the exhaust gas flows into the exhaust gas control apparatus, is positioned such that a straight flow of the exhaust gas from the inlet port does not pass through the upstream-opening. 7. The exhaust gas control apparatus for an engine according to claim 1, wherein the exhaust gas flows into the exhaust gas control apparatus; and the upstream-opening is positioned such that a straight flow of the exhaust gas from the inlet port does not pass through the upstream-opening. 8. The exhaust gas control apparatus for an engine according to claim 1, wherein an inlet port of an exhaust pipe that allows the exhaust gas from the engine to flow therethrough is disposed immediately upstream of the valve, and the exhaust gas flows into the exhaust gas control apparatus through the inlet port. 9. The exhaust gas control apparatus for an engine according to claim 1, wherein an auxiliary-exhaust pipe, which is independent of an exhaust pipe that allows the exhaust gas from the engine to flow therethrough, is connected to a downstream end of the exhaust pipe and disposed immediately upstream of the valve so that a downstream-opening of the auxiliary-exhaust pipe is disposed immediately upstream of the valve to form an inlet port, through which the exhaust gas flows into the exhaust gas control apparatus. 10. The exhaust gas control apparatus for an engine according to claim 9, wherein the auxiliary-exhaust pipe includes a hole which radially communicates between an inside and an outside of the auxiliary-exhaust pipe so as to allow the exhaust gas to flow therethrough. 11. The exhaust gas control apparatus for an engine according to claim 8, wherein a downstream-opening of the exhaust pipe is disposed immediately upstream of the valve to function as the inlet port. 12. The exhaust gas control apparatus for an engine according to claim 11, wherein the exhaust pipe includes a hole, positioned inside the valve portion, which radially communicates between an inside and an outside of the exhaust pipe so as to allow the exhaust gas to flow therethrough. 13. The exhaust gas control apparatus for an engine according to claim 2, wherein the upstream-opening is positioned near the valve, and the downstream-opening is positioned near the catalyst. 14. The exhaust gas control apparatus for an engine according to claim 1, wherein, when the valve is open, the upstream-opening facilitates the flow of the exhaust gas between the first exhaust pipe and a space where the exhaust gas does not swirl or stagnate and the downstream-opening facilitates the flow of exhaust gas between the first exhaust passage and a space where the exhaust gas swirls or stagnates. 15. The exhaust gas control apparatus for an engine according to claim 1, wherein a restrictive element, which reduces a flow speed of the exhaust gas flowing toward the downstream side through the downstream-opening,is provided downstream of the downstream-opening. 16. The exhaust gas control apparatus for an engine according to claim 15, wherein the restrictive element is the catalyst. 17. The exhaust gas control apparatus for an engine according to claim 15, wherein the restrictive element is a sound-absorbing material. 18. The exhaust gas control apparatus for an engine according to claim 1, wherein a relation between a cross sectional area of the upstream-opening and a cross sectional area of the downstream-opening is set so that a flow speed of the exhaust gas flowing in the first exhaust passage is reduced to a speed that is equal to or lower than an upper limit flow speed, at or below which the hydrocarbon-absorbent can absorb all hydrocarbons present in the exhaust gas, when the valve is closed. 19. An exhaust gas control apparatus for an engine, comprising: an absorption portion that includes an external cylinder, disposed at an outermost position thereof, a first exhaust passage and a second exhaust passage, the respective openings of which are located at different positions, and through which exhaust gas flows into the abosorption portion; and the first exhaust passage is provided with a hydrocarbon-absorbent which absorbs hydrocarbons present in the exhaust gas, and a partition that is provided downstream of the hydrocarbon-absorbent and that separates the first exhaust passage from a first space, the first space being positioned on a downstream side of the absorption portion and on a downstream side of the second exhaust passage, the partition portion being provided with at least one hole through which the exhaust gas flows between the first exhaust passage and the first space; a valve portion that includes an external cylinder, disposed at an outermost position thereof, and a valve, connected to the external cylinder to face the second exhaust passage, that opens and closes the second exhaust passage, thereby changing a mode where the exhaust gas flows; and a catalyst portion that includes an external cylinder, disposed at an outermost position thereof, and a catalyst that purifies the exhaust gas, wherein the absorption portion, the valve portion, and the catalyst portion are independent of each other; and the absorption portion, the valve portion, and the catalyst portion are connected to each other with the external cylinders. 20. The exhaust gas control apparatus for an engine according to claim 19, wherein the catalyst is disposed so that all of the exhaust gas flowing into a space inside the external cylinder of the catalyst portion passes through the catalyst. 21. The exhaust gas control apparatus for an engine according to claim 19, further comprising: a heat-insulating portion that suppresses heat transmission from the second exhaust pipe to the hydrocarbon-absorbent. 22. The exhaust gas control apparatus for an engine according to claim 19, wherein the absorption further includes an internal cylinder disposed inside the external cylinder; the first exhaust passage is provided between the external cylinder and the internal cylinder of the absorption portion; and the second exhaust passage is provided inside the internal cylinder. 23. The exhaust gas control apparatus for an engine according to claim 22, wherein the internal cylinder includes a plurality of pipes that are concentrically disposed; and a space is formed between the adjacent pipes. 24. The exhaust gas control apparatus for an engine according to claim 23, wherein the heat-insulating material is disposed in the space between any two adjacent pipes. 25. The exhaust gas control apparatus for an engine according to claim 19, wherein the second exhaust passage has a tapered shape; and a cross sectional area of the second exhaust passage orthogonal to an axis thereof increases from an upstream side toward a downstream side. 26. The exhaust gas control apparatus for an engine according to claim 19, wherein the second exhaust passage allows the exhaust gas to flow therethrough without passing through the hydrocarbon-absorbent. 27. The exhaust gas control apparatus for an engine according to claim 1, wherein the first structure includes an upstream-opening positioned upstream of the hydrocarbon-absorbent, and a downstream-opening positioned downstream of the hydrocaron-absorbent; the upstream-opening allows the exhaust gas to communicate between a space in which the hydrocarbon-absorbent is provided and a space upstream of the upstream-opening and the downstream-opening allows the exhaust gas to communicate between a space in which the hydrocarbon-absorbent is provided and a space downstream of the downstream-opening; and the downstream-opening is positioned so as to stabilize a flow speed of the sidestream. 28. The exhaust gas control apparatus for an engine according to claim 27, wherein, when the second mode is selected, pressure in a space downstream of the downstream-opening is increased so as to be higher than pressure in a space upstream of the upstream-opening. 29. The exhaust gas control apparatus for an engine according to claim 1, wherein the exhaust gas flows through an inlet port into the exhaust gas control apparatus from an exhaust pipe located upstream of the exhaust gas control apparatus; and the inlet port is positioned so that a hydrocarbon concentration in the exhaust gas in the mainstream is equal to or less than an upper limit concentration, at or below which the catalyst can remove all hydrocarbons present in the exhaust gas. 30. The exhaust gas control apparatus for an engine according to claim 1, wherein the exhaust gas flows into the exhaust gas control apparatus through an inlet port; a diameter of the inlet port is set so that a hydrocarbon concentration in the exhaust gas of the mainstream is equal to or less than an upper limit concentration, at or below which the catalyst can remove all hydrocarbons present in the exhaust gas. 31. An exhaust gas control apparatus for an engine, comprising; a first structure that includes an external cylinder, disposed at an outermost position thereof, a first exhaust passage and a second exhaust passage, the respective openings of which are located at different positions, and through which exhaust gas flows into the first structure; and the first exhaust passage is provided with a hydrocarbon-absorbent, which absorbs hydrocarbons present in exhaust gas discharged from an engine, and a partition that is provided downstream of the hydrocarbon-absorbent and that separates the first exhaust passage from a first space, the first space (1) being positioned on a downstream side of the first structure and on a downstream side of the second exhaust passage and being radially outside an extended cross-section of the second passage, the partition portion being provided with at least one hole through which the exhaust gas flows between the first exhaust passage and the first space, the at least one hole being positioned radially outside of the second passage; and a second structure disposed downstream of the first structure, the second structure including an external cylinder, disposed at an outermost position thereof, and a catalyst, that purifies the exhaust gas discharged from the engine, wherein the first structure and the second structure are independent of each other; and the first structure and the second structure are disposed in series, and are joined to each other, and the first structure and the second structure are connected to each other with the external cylinders. 32. A method for producing an exhaust gas control apparatus for an engine, comprising; selecting an absorption portion that achieves a required level of performance from among different absorption portions that achieve different levels of performance, wherein each of the absorption portions includes an external cylinder, disposed at an outermost position thereof, a first exhaust passage and a second exhaust passage, the respective openings of which are located at different positions, and through which the exhaust gas flows into the absorption portion; and the first exhaust passage is provided with a hydrocarbon-absorbent that absorbs hydrocarbon present in the exhaust gas, and a partition that is provided downstream of the hydrocarbon-absorbent and that separates the first exhaust passage from a first space, the first space being positioned on a downstream side of the absorption portion and on a downstream side of the second exhaust passage, the partition portion being provided with at least one hole through which the exhaust gas flows between the first exhaust passage and the first space; selecting a valve portion that achieves a required level of performance from among different valve portions that achieve different levels of performance, wherein each of the valve portions includes an external cylinder, disposed at an outermost position thereof, and a valve, connected to the external cylinder to face the second exhaust passage, that opens and closes the second exhaust passage; and each of the valve portions changes a mode where the exhaust gas flows by opening and closing the second exhaust passage, using the valve; selecting a catalyst portion that achieves a required level of performance from among different catalyst portions that achieve different levels of performance, wherein each of the catalyst includes an external cylinder, disposed at an outermost position thereof, and a catalyst that purifies the exhaust gas; and disposing, in series, the absorption portion selected in the first step, the valve portion selected in the second step and the catalyst portion selected in the third step, and that are independent of each other, and the absorption portion, the valve portion, and the catalyst portion are connected to each other with the external cylinders. 33. The method for producing the exhaust gas control apparatus for an engine according to claim 32, wherein an auxiliary-exhaust pipe, which is independent of an exhaust pipe positioned upstream of the exhaust gas control apparatus, is connected to an end at a downstream side of the exhaust pipe; the auxiliary-exhaust pipe includes an opening positioned at a downstream side thereof; and the opening of the auxiliary-exhaust pipe is disposed immediately upstream of the valve. 34. The method for producing the exhaust gas control apparatus for an engine according to claim 33, wherein a hole, which allows the exhaust gas to radially flow between an inside and an outside of the auxiliary-exhaust pipe, is formed in the auxiliary-exhaust pipe before the auxiliary-exhaust pipe is connected to the exhaust pipe. 35. The method for producing the exhaust gas control apparatus for an engine according to claim 34, wherein the exhaust pipe includes an opening positioned at a downstream side thereof, and the opening of the exhaust pipe is disposed immediately upstream of the valve. 36. The method for producing the exhaust gas control apparatus for an engine according to claim 35, wherein a hole, which allows the exhaust gas to radially flow between an inside and an outside of the exhaust pipe, is formed in a portion of the exhaust pipe located inside the valve portion, before the exhaust pipe is disposed immediately upstream the valve portion.