JPH0544455A - Exhaust gas purifying device for two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To improve exhaust gas purifying performance even during the starting of cold-start of a two-cycle internal combustion engine. CONSTITUTION:The upper stream end of a muffler 3 is integrally connected to the exhaust gas port 2 of a two-cycle internal combustion engine 1. The muffler 3 comprises an exhaust gas pipe part 4, an expansion pipe part 5, a cylindrical part 6, and contraction pipe part 7, and support stays 8 and 9 are fitted internally in the expansion pipe 5 and the cylindrical part 6, respectively. A guide pipe 20 and a table pipe 22 are fitted to the central parts of the support stays 8 and 9, respectively, and the upper stream end of the guide pipe 20 is opened toward an exhaust gas pipe part 4. A downstream part 21 of the guide pipe 20 is expanded and the upper stream end of a catalyst body 10 having an outer shape in the shape of a cylinder is fitted to the downstream end of the guide pipe. An upper stream part 23 of a tail pipe 22 is also expanded, the upper stream end thereof is fitted to the lower stream end of the catalyst body 10, and the downstream end of the tail pipe 22 is fitted to the downstream end of the contraction part 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus in which a catalyst is arranged in a muffler of a two-cycle internal combustion engine mounted on a small vehicle such as a motorcycle.

[0002]

2. Description of the Related Art A conventional exhaust gas purifying apparatus is constructed as shown in FIG. In FIG. 8, the upstream end of the exhaust pipe portion 04 of the first muffler 03 is connected to the exhaust port 02 of the two-cycle internal combustion engine 01, and in the first muffler 03, the exhaust pipe portion 04 along the exhaust flow, Expanding part 05 and tubular part 06
And the contracted tube portion 07 are integrally connected. Further, the tail pipe 08 facing the tubular portion 06 is integrally fitted in the downstream end of the contracted pipe portion 07 of the first muffler 03, and the second muffler 09 is connected to the downstream end of the tail pipe 08. An exhaust gas permeable catalyst 010 is attached to the upstream end of the tail pipe 08, and when the exhaust gas passes through the exhaust gas permeable catalyst 010 in the first muffler 03, carbon monoxide (CO ), Nitrogen oxides (NOx), hydrocarbons (HC), etc., are brought into contact with the catalyst 010 and are oxidized and reduced to be purified.

[0003]

Since the exhaust gas temperature in the first muffler 03 decreases linearly as it goes away from the exhaust port 02, as shown in FIG. 8, the central part of the first muffler 03 or the downstream thereof. Exhaust gas permeation type catalyst 010 on the side
In some cases, the exhaust gas purifying performance at the time of cold engine start may be reduced. To avoid this, if the exhaust gas permeable catalyst 010 is placed close to the exhaust port 02,
The dynamic effect of exhaust gas is significantly impaired, and the output of the internal combustion engine 01 is greatly reduced.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an improvement of an exhaust gas purifying apparatus for a two-cycle internal combustion engine which overcomes the above-mentioned problems, and a catalyst is provided at a substantially central portion in a muffler of the two-cycle internal combustion engine. Is provided, and a guide tube opened toward the upstream side of the muffler is connected to the upstream end of the catalyst. In the present invention, 2
Since the guide pipe opened toward the upstream side of the muffler is connected to the upstream end of the catalyst disposed in the substantially central portion of the muffler of the cycle internal combustion engine, even when the cold start is performed, the outer wall of the muffler is Hot exhaust gas flowing through the uncooled central portion of the muffler can be guided to the catalyst by the guide pipe. Further, in the present invention, since the catalyst is disposed in the substantially central portion having a large cross-sectional area in the muffler, a decrease in engine output is avoided, and the heat generated from the catalyst increases the temperature of the muffler outer wall. Can be prevented.

[0005]

EXAMPLES An example of the present invention shown in FIGS. 1 to 3 will be described below. Reference numeral 1 denotes a two-cycle internal combustion engine mounted on an off-road motorcycle (not shown), and an exhaust port 2 of the two-cycle internal combustion engine 1 is integrally connected to an upstream end of a muffler 3, and the muffler 3 has A catalyst body 10 is provided. Further, the muffler 3 is connected to the exhaust pipe portion 4 on the upstream side thereof and the expanded pipe portion 5 connected to the downstream end of the exhaust pipe portion 4 and having a diameter gradually increasing toward the downstream side.
And a cylindrical portion 6 having a substantially constant diameter connected to the downstream end of the pipe expanding portion 5, and a contracted pipe portion connected to the downstream end of the cylindrical portion 6 and having a diameter gradually decreasing toward the downstream side. It consists of seven.

Further, support stays 8 and 9 are fitted in the expanded pipe portion 5 and the cylindrical portion 6 of the muffler 3, respectively, and the guide pipe 20 is fitted in the central portion of the support stay 8 and the support stay 9 is attached. The tail pipe 22 is fitted in the center of the
The upstream end of 20 is open toward the exhaust pipe portion 4, the downstream portion 21 of the guide pipe 20 is enlarged, and its downstream end is fitted to the upstream end of the catalyst body 10, and the upstream of the tail pipe 22. The portion 23 is also enlarged so that the upstream end thereof is fitted to the downstream end of the catalyst body 10 and the downstream end of the tail pipe 22 is fitted to the downstream end of the contracted pipe portion 7.

However, in the catalyst body 10, as shown in FIGS. 2 and 3, the strip-shaped flat plates 12 and the strip-shaped corrugated plates 14 are alternately stacked, and the strip-shaped flat plates 12 and the strip-shaped corrugated plate 14 are spirally wound. The core portion 11 is turned to form three strip-shaped flat plates 12a, 12b and 12c from the peripheral surface of the central cylindrical portion 16 in a spiral shape at intervals of a central angle of 120 ° in the circumferential direction. For example, the end portion 15a of the strip-shaped corrugated plate 14a between the tip portion 13a of the strip-shaped flat plate 12a protruding from the peripheral surface and the tip portion 13b of the strip-shaped flat plate 12b that extends next, that is, in the circumferential direction of the central angle 120 °. So that the heights of the strips gradually increase as the distance from the branching portion 17 increases,
The tips 15a, 15b, 15c of 14b, 14c are formed, and the height of the strip-shaped corrugated plates 14a, 14b, 14c at the outer peripheral portion is made constant (see FIG. 3). Furthermore, the outer cylinder 18 is integrally fitted to the outer periphery of the core portion 11, and in the catalyst body 10, the exhaust gas is parallel to the center line of the central cylindrical portion 16 in the inner space of the core portion 11 inside the outer cylinder 18. It is designed to flow in any direction.

Moreover, the band-shaped flat plate 12 and the band-shaped corrugated plate 14 are metal plates which have a catalytic action themselves, and a brazing material is interposed at the joint between the band-shaped flat plate 12 and the band-shaped corrugated plate 14.
After fitting the core portion 11 into the outer cylinder 18, the catalyst body 10 is heated to melt the brazing material, so that the joining portion of the strip flat plate 12 and the strip corrugated plate 14 is brazed. There is.

Further, the strip-shaped flat plate 12 and the strip-shaped corrugated plate 14 may be, for example, a metal plate made of Ce-Fe-Al-based ferrite stainless steel which does not have a catalytic action by itself. An oxide film is formed on the surface, and strip-shaped flat plate 1
2. After forming the core portion 11 by spirally winding the band-shaped corrugated plate 14, the core portion 11 is immersed in a slurry obtained by stirring activated alumina, an alumina-based binder, and water, dried, and then baked. By doing so, the catalyst body 10 may be configured.

Further, the diameter of the upstream open end of the guide tube 20 is about 20.
mm, the inner diameter of the pipe expanding portion 5 in that portion is set to about 50 mm, and the opening area of the guide tube 20 is the pipe expanding portion 5 of that portion.
The cross-sectional area is about 16%. Furthermore, the tail pipe 22 protrudes rearward longer than the downstream end of the contracted pipe portion 7 of the muffler 3, contacts the downstream end of the contracted pipe portion 7, and has a second muffler 24 at the downstream protruding portion (not shown) of the tail pipe 22.
The upstream portion 25 of the is fitted.

Since the embodiment shown in FIGS. 1 to 3 is constructed as described above, the two-stroke internal combustion engine 1
The exhaust gas discharged from the exhaust port 2 of the exhaust pipe 2 and passing through the muffler 3 expands in the expanded pipe portion 5 thereof, and before the heat is taken from the outer peripheral portion, the exhaust gas is guided from the upstream opening of the guide pipe 20.
Since it flows into the inside of the muffler 3, the high-temperature exhaust gas is also introduced into the catalyst body 10 arranged on the downstream side of the central portion of the muffler 3 in the longitudinal direction.
Can keep good purification function.

Further, since the catalyst body 10 having a large diameter is not arranged in the expanded pipe portion 5 having a narrow cross-sectional area but is arranged in the cylindrical portion 6 having a wide cross-sectional area behind it, the expanded pipe portion 5 of the muffler 3,
It is possible to sufficiently maintain the dynamic effect of exhaust by the cylindrical portion 6 and the contracted pipe portion 7 and prevent the output from decreasing.

Further, the guide tube 20, the tail pipe 22, and the support stay 8 are provided in the substantially central portion of the cylindrical portion 6 having a large diameter without directly contacting the catalytic body 10 which is heated to a high heat by the oxidation reaction. Since it is supported via the support stays 9, it is possible to prevent the muffler 3, particularly the cylindrical portion 6 from being heated to a high temperature, and to eliminate the need to provide a heat insulating structure on the surface of the muffler 3, thereby reducing the cost. You can

Further, in the catalyst body 10, three strip-shaped flat plates 12a, 12b, 12c are splayed from the peripheral surface of the central cylindrical portion 16 at circumferential intervals of a central angle of 120 ° to form a spiral shape. For example, the tip of the strip-shaped flat plate 12a extending from the peripheral surface of 16
The height of the tip portion 15a of the strip-shaped corrugated plate 14a between the strip portion 13a and the tip portion 13b of the strip-shaped flat plate 12b which is next diverged, that is, in the circumferential direction with the central angle of 120 °, increases gradually as the distance from the branch portion 17 increases. So that the tips 15a of the strip-shaped corrugated plates 14a, 14b, 14c,
Since 15b and 15c are formed, the strip-shaped corrugated plates 14a, 14b and 14c
Also, the arrangement density of the tip portions 15a, 15b, 15c, that is, the density of the central portion of the core portion 11 can be significantly reduced as compared with the conventional one, and as a result, it is difficult to dissipate heat and the core is easily heated to a high temperature. It is possible to prevent the temperature of the central portion of the portion 11 from rising.

Next, the exhaust pipe on the upstream side of the muffler is long,
If the exhaust gas temperature decreases before the exhaust gas reaches the catalyst and a sufficient purification function cannot be exerted, another embodiment shown in FIGS. 4 to 5 may be applied. The exhaust pipe attachment portion 30 is attached to the two-cycle internal combustion engine 1 so that the exhaust passage 31 of the exhaust pipe attachment portion 30 communicates with the exhaust port 2 of the two-cycle internal combustion engine 1, and the control valve 32 can be opened and closed in the exhaust passage 31. And the bypass passage 33 is formed from the upstream portion of the exhaust passage 31 with respect to the control valve 32. In addition, the exhaust pipe mounting portion 30 has 2
A thermostat 34 that detects the temperature of the cooling water passing through the cycle internal combustion engine 1 and closes the control valve 32 when the temperature is lower than a certain temperature and opens the control valve 32 when the temperature is higher than a certain temperature is provided. There is. Furthermore, the exhaust pipe attachment part 30 has an exhaust pipe
The upstream end of 35 is connected, and the exhaust pipe 35 is composed of an inner pipe 37 having a large number of small holes 36 and an outer pipe 38 having a diameter larger than that of the inner pipe 37. The inner pipe 37 communicates with the exhaust passage 31. Together with inner tube 37
An annular passage 39 surrounded by the outer pipe 38 communicates with the bypass passage 33, and a catalyst 40 is provided in the annular passage 39. Furthermore, the downstream end of the exhaust pipe 35 is connected to the muffler 3 via the connecting portion 41.
It is connected to the muffler 42 of the same structure as.

Since the embodiment shown in FIGS. 4 to 5 is configured as described above, the temperature of the cooling water is low and the control valve 32 is closed at the time of starting the cooling machine, and the control valve 32 is closed. The discharged exhaust gas flows from the bypass passage 33 into the annular passage 39, is in contact with the catalyst 40 in the annular passage 39, is oxidized and reduced, and is reliably purified. Further, when the required time has elapsed since the engine was started, the two-cycle internal combustion engine 1 is warmed and the exhaust pipe 35 is also sufficiently heated, so that the thermostat 34
The control valve 32 in the closed state is opened by the operation of 1. and most of the exhaust gas passes through the inside of the inner pipe 37 and flows into the muffler 42. In the muffler 42, as compared with the embodiment shown in FIGS. Similar purifying action is performed. Then, in a normal operation state in which a large amount of exhaust gas is discharged as compared with at the time of starting, most of the exhaust gas does not flow through the annular passage 39 with large flow resistance and passes through the inside pipe 37 with small flow resistance, The power loss is small and a large output can be generated.

Further, in the embodiment shown in FIGS. 4 to 5, the inner tube 37 is provided with a large number of small holes 36.
As shown in FIG. 3, the small hole 36 may not be provided in the inner pipe 37, and the small hole 36 may be provided in the connecting portion 41 between the portions where the inner pipe 37 and the outer pipe 38 are fitted to the connecting portion 41. In the embodiment, at the time of cold start,
Since all the exhaust gas is made to pass through the annular passage 39 in which the catalyst 40 exists, the exhaust gas purifying action can be performed more reliably.

[Brief description of drawings]

FIG. 1 is a partially longitudinal side view showing an embodiment of an exhaust gas purifying apparatus for a two-cycle internal combustion engine of the present invention.

FIG. 2 is a transverse cross-sectional view cut along the line II-II in FIG.

FIG. 3 is an explanatory diagram during the manufacture of the core portion of the catalyst body in the above-mentioned embodiment.

FIG. 4 is a side view, partly in vertical section, at the time of starting the cold machine in another embodiment of the present invention.

5 is a side view, partly in vertical section, during normal operation in the embodiment shown in FIG.

FIG. 6 is a side view, partly in vertical section, at the time of starting the cold machine in still another embodiment of the present invention.

FIG. 7 is a partially longitudinal side view of the embodiment shown in FIG. 6 during normal operation.

FIG. 8 is a partially longitudinal side view of an exhaust gas purifying apparatus for a conventional two-cycle internal combustion engine.

[Explanation of Codes] 1 ... Two-cycle internal combustion engine, 2 ... Exhaust port, 3 ... Muffler, 4 ... Exhaust pipe section, 5 ... Expanded section, 6 ... Cylindrical section, 7 ... Reduced section, 8, 9 ... Support stay , 10 ... Catalyst body, 11 ... Core part,
12 ... band flat plate, 13 ... tip part, 14 ... band corrugated plate, 15 ... tip part, 16 ... central cylindrical part, 17 ... branch part, 18 ... outer cylinder, 20 ... guide tube, 21 ... downstream part, 22 ... Tailpipe, 23 ... Upstream, 24 ...
2nd muffler, 25 ... upstream part, 30 ... exhaust pipe mounting part, 31 ...
Exhaust passage, 32 ... Control valve, 33 ... Bypass passage, 34 ... Thermostat, 35 ... Exhaust pipe, 36 ... Small hole, 37 ... Inner pipe, 38 ... Outer pipe, 39 ... Annular passage, 40 ... Catalyst body, 41 ... Connection Department, 42 ... Muffler.

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[Procedure amendment]

[Submission date] May 15, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

Title: Exhaust gas purification device for a two-cycle internal combustion engine

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (1)

[Claims] 1. A catalyst is disposed at a substantially central portion in a muffler of a two-cycle internal combustion engine, and a guide pipe opened toward an upstream side of the muffler is connected to an upstream end portion of the catalyst. Exhaust gas purification device for a two-cycle internal combustion engine.