JPH10325316A - Exhaust gas emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs, promote reaction of a catalyst carrier, prevent reduction of an output, and improve durability. SOLUTION: An exhaust gas emission control device is provided with a catalyst carrier 3 formed in a cylindrical shape along an inner surface of a muffler 1. The catalyst carrier 3 is arranged on a position near an engine in the muffler 1, and is fixed to the muffler 1 through a bellows part 33 provided with a plurality of recessed/projection (a wave part) parts 33a formed integratedly with one end part 32 of its large diameter side while fixing to the muffler 1 through the other end part 31 of its small diameter side.

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 for an internal combustion engine having a catalyst carrier in a muffler.

[0002]

2. Description of the Related Art As an exhaust gas purifying apparatus for an internal combustion engine of this type, for example, in a two-stroke engine, there is known an exhaust apparatus (muffler) provided with a catalyst carrier in order to purify exhaust gas. I have. Regarding the installation position of the catalyst carrier, if it is too close to the exhaust port of the engine, the resistance will decrease and the output will decrease, but if it is too far from the exhaust port of the engine, the reaction start time will be delayed. It is often provided in a close part (diffuser part).

FIG. 6 shows a first conventional example in which a catalyst carrier 2 is provided in a muffler 1 of a two-cycle engine. The muffler 1 includes an exhaust portion 11 connected to an exhaust port of the engine, a chamber portion 12, a tail pipe portion 13, and a silencer (not shown) attached to a rear portion of the tail pipe portion 13.

The catalyst carrier 2 has a first catalyst carrier 21 fixed in the exhaust portion 11 by welding and a second catalyst carrier 22 fixed in the front taper portion 121 of the chamber portion 12 by welding. It is configured to have: These first and second catalyst carriers 21 and 22
Extends in each of the exhaust portion 11 and the front taper portion 121 along the longitudinal direction. Further, as shown in FIGS. 7 and 8, these catalyst carriers 21 and 22 have a shape protruding inward.

A second conventional example is disclosed in Japanese Unexamined Patent Publication No.
No. 93461 is known. Although not shown, a tapered catalyst carrier is provided at a position corresponding to the front taper portion 121 via a heat-resistant elastic member.

A third conventional example is disclosed in Japanese Unexamined Patent Publication No.
The thing shown in 8-163862 is known. Although not shown, the bellows is provided on the gasket portion to absorb the thermal expansion of the catalyst carrier.

[0007]

However, in the first conventional example, since the catalyst carrier 2 protrudes inside the diffuser portion such as the exhaust portion 11 and the front taper portion 121, the exhaust gas resistance is generated due to the exhaust resistance. Is reduced.

In addition, since the catalyst carrier 2 extends along the longitudinal direction of the exhaust pipe portion 11 and the front tapered portion 121 and is fixed to the exhaust pipe portion 11 and the front tapered portion 121 by welding. Stress is generated due to a temperature difference between the first catalyst carrier 21 and the exhaust portion 11 or between the second catalyst carrier 22 and the front taper portion 121, resulting in poor durability. .

Further, the catalyst carrier 2 extends along the longitudinal direction of the exhaust portion 11 and the tapered portion 121, and the exhaust portion 11 and the tapered portion 121 are extended.
Is fixed by welding, the heat in the muffler 1 tends to escape to the outside, and the reaction of the catalyst takes time. For this reason, as shown in FIG. 6, it is necessary to take measures to extend the catalyst carrier 2 to the vicinity of the exhaust port of the engine, which causes a problem that the output is reduced.

On the other hand, in the second conventional example, the number of parts is increased by the heat-resistant elastic member and the like, and it is troublesome to incorporate the heat-resistant elastic member, so that the cost is increased. In addition, when the heat-resistant elastic member is loose, the catalyst carrier is in a state of being suspended in the air, so that there is a problem that vibration is generated and durability is deteriorated.

On the other hand, the third conventional example has a problem in that the number of assembling steps for supporting the catalyst carrier with the gasket increases, while the bellows itself is small (the number of peaks is small), so that the durability is poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to reduce the cost, promote the reaction of the catalyst carrier, and prevent the output from lowering. It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine, which is capable of achieving excellent durability.

[0013]

In order to achieve the above object, the present invention relates to an exhaust gas purifying apparatus for an internal combustion engine having a catalyst carrier formed in a cylindrical shape along an inner surface of a muffler. Is a bellows arranged at a position near the engine in the muffler, and fixed to the muffler through one end on the small diameter side, and having a plurality of irregularities integrally formed on the other end on the large diameter side. It is characterized in that it is fixed to the muffler via a part.

In the invention configured as described above, the structure is simple because the bellows portion is formed integrally with the catalyst carrier. Moreover, since a heat-resistant elastic member is not required and the catalyst carrier is not supported by the gasket, the number of parts is small and assembly is simple. Therefore, cost can be reduced.

Further, the catalyst support has one end portion and the bellows portion on the other end side fixed to a muffler. Since the number of contact portions between the catalyst support and the muffler is small, heat in the muffler is reduced to outside. Difficult to escape. Therefore, the reaction time of the catalyst is short, and the reaction of the catalyst can be promoted. Further, since the catalyst carrier is located at a position near the engine in the muffler, the reaction of the catalyst can be promoted. Furthermore, since the catalyst carrier is formed in a cylindrical shape along the inner surface of the muffler and does not protrude inward, a decrease in output can be prevented.

Further, even if the catalyst carrier thermally expands,
The thermal expansion allowance can be sufficiently absorbed by the bellows portion having a plurality of irregularities. Therefore, the durability can be improved. Moreover, since the heat-resistant elastic member is not used to absorb the thermal expansion allowance of the catalyst carrier, there is no deterioration due to a change in diameter. Therefore, the durability can be improved, and the occurrence of vibration and abnormal noise as shown in the second conventional example can be prevented.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. This embodiment shows an exhaust gas purifying apparatus for a two-cycle engine (internal combustion engine). This exhaust gas purifying apparatus is provided in a muffler 1 of a motorcycle shown in FIG. However, components common to those shown in FIGS. 6 to 8 shown as the first conventional example are denoted by the same reference numerals, and description thereof will be simplified.

The exhaust gas purifying apparatus shown in this embodiment has a catalyst carrier 3 formed in a cylindrical shape along the inner surface of the muffler 1, as shown in FIGS. Are arranged at a position near the engine in the muffler 1 and are fixed to the muffler 1 via one end 31 on the small diameter side thereof, and are formed integrally with the other end 32 on the large diameter side. It is fixed to the muffler 1 via a bellows portion 33 having a wave portion (irregularities) 33a.

As shown in FIGS. 1 and 2, the muffler 1 has an exhaust pipe section 11, a chamber section 12, a tail pipe section 13, and a silencer 14 (see FIG. 5). The exhaust pipe section 11, the chamber section 12, the tail pipe section 13, and the silencer 14
Are formed separately from each other, and are connected to each other by welding. Further, the chamber section 12
Is a front taper portion (diver jet cone) 121
And a body portion 122 and a rear taper portion (conver jet cone) 123 connected by welding.

The front side taper portion 121 is
The diameter of the torso is gradually increased from 1 to a conical shape.
It is connected to 2. The upstream end 121a of the front taper 121 is fitted to the outer periphery of the downstream end 11a of the exhaust pipe 11 and fixed by welding. Further, the downstream end 12 of the front taper 121
1b, as shown in FIG.
24 is fitted to the inner periphery of the upstream end 124a and fixed by welding. The body 122 includes the outer cylinder 124 described above,
It has a three-layer structure of an inner cylinder 125 provided inside the outer cylinder 124, and a heat-resistant sound absorbing material 126 sandwiched between the inner cylinder 125 and the outer cylinder 124.

As shown in FIGS. 1 and 3, the catalyst carrier 3 is formed in a cylindrical shape that gradually expands in a conical shape while gradually bending along the inner surface of the front tapered portion 121.
A plurality of through holes 3a are formed in the peripheral wall. This catalyst carrier 3 has an outer surface, an inner surface, and a through-hole 3a in a range L (a region sandwiched by dashed lines in FIG. 1) excluding the one end 31, the other end 32, and the bellows 33. A catalyst is supported. And this catalyst carrier 3 is
As shown in FIG. 1, one end portion 31 is fitted to the inner periphery of the downstream end portion 11a of the exhaust portion 11 and connected by welding.

As shown in FIG. 4, the bellows portion 33 has three wave portions 33a projecting radially outward with respect to the other end portion 32, and each wave portion 33a is provided downstream of these wave portions 33a. Reduced diameter portion 33 having substantially the same inner diameter as the bottom of portion 33a
b. Each wave portion 33a is formed continuously in a curved shape.

The bellows portion 33 has a reduced diameter portion 3
3b is fitted on the inner periphery of the downstream end portion 121b of the front taper portion 121, and is fixed to the downstream end portion 121b by welding. Further, the inner cylinder 125 of the body 122 has its upstream end 125a fitted to the inner surface of the reduced diameter portion 33b of the bellows portion 33 and fitted to the bottom of the wave portion 33a. It extends upstream to cover the inside. The reduced diameter portion 33b and the upstream end 1 of the inner cylinder 125
Although they are not welded to 25a, they may be fixed by welding. Further, in FIG. 4, all of the wave portion 33a is not covered with the upstream end portion 125a, but may be entirely covered.

Further, as shown in FIG. 1, a main catalyst 4 is provided in the rear tapered portion 123 of the chamber portion 12. The main catalyst 4 is formed of, for example, a honeycomb catalyst or the like.

In the exhaust gas purifying apparatus constructed as described above, the bellows portion 33 is formed integrally with the catalyst carrier 3, so that the structure is simple. In addition, since a conventionally used heat-resistant elastic member is not required and the catalyst carrier 3 is not supported by the gasket, the number of parts is small and the assembly is simple. Therefore, cost can be reduced.

Further, the bellows portion 33 on one end 31 and the other end 32 of the catalyst carrier 3 is fixed to the muffler 1 and the contact portion between the catalyst carrier 3 and the muffler 1 is small. It is difficult for the heat inside the muffler 1 to escape to the outside. Therefore, the reaction time of the catalyst is short, and the reaction of the catalyst can be promoted. Further, since the catalyst carrier 3 is located closest to the engine in the chamber 12 of the muffler 1, the reaction of the catalyst can be promoted. Further, since the catalyst carrier 3 is formed in a cylindrical shape along the inner surface of the muffler 1 and does not protrude inward, a decrease in output can be prevented. Further, since the wave portion 33a is covered with the upstream end portion 125a of the inner cylinder 125, the exhaust gas is
a. Therefore, it is possible to prevent the output from being reduced by the wave portion 33a.

Further, even when the catalyst carrier 3 thermally expands, a plurality of thermal expansions (in this embodiment, 3
) Can be absorbed with a sufficient margin. Therefore, the durability can be improved. Further, the increase in stress on the bellows portion 33 due to thermal expansion is smaller as it is on the larger diameter side. This is because the load per unit area is reduced. At this point, since the bellows portion 33 is provided at the position of the maximum diameter of the catalyst carrier 3, the stress acting on the bellows portion 33 is small. Therefore, the durability can be improved from this point as well.

Moreover, since the heat-resistant elastic member is not used to absorb the thermal expansion allowance of the catalyst carrier 3, there is no deterioration due to a change in diameter. Therefore, the durability can be improved, and the occurrence of vibration and abnormal noise as shown in the second conventional example can be prevented.

In the above embodiment, the catalyst carrier 3 is provided with a plurality of through holes 3a, but these through holes 3a need not be provided. If the through holes 3a are not provided, the catalyst is supported only on the inner surface of the catalyst carrier 3.

The upstream end 125a of the inner cylinder 125 covers the inside of the wave portion 33a, but the upstream end 125a is stopped by the reduced diameter portion 33b of the bellows 33.
You may comprise so that the inside of the wave part 33a may not be covered. However, even in this case, since the inner diameter of the bottom of the wave portion 33b is substantially equal to the inner diameter of the inner cylinder 125 of the body portion 122, and therefore substantially equal to the maximum inner diameter of the muffler 1, the exhaust acting on the wave portion 33a is exhausted. The pressure of the gas is much lower than the pressure acting on the upstream end 121a of the front taper 121, for example. Therefore, even if the corrugated portion 33a is exposed, resistance to the flow of the exhaust gas is small. That is, the wave portion 33a has little effect on the flow of the exhaust gas.

Further, the main catalyst 4 is provided in the rear tapered portion 123 in the chamber portion 12, but the main catalyst 4 may not be provided.

Further, the above embodiment has been described with respect to an example in which the present invention is applied to a muffler of a two-cycle engine.

[0033]

According to the present invention, since the bellows portion is formed integrally with the catalyst carrier, the structure is simple.
Moreover, since a heat-resistant elastic member is not required and the catalyst carrier is not supported by the gasket, the number of parts is small and assembly is simple. Therefore, cost can be reduced.

Further, the catalyst support has one end portion and the bellows portion on the other end side fixed to a muffler. Since there are few contact portions between the catalyst support and the muffler, the heat inside the muffler is reduced to the outside. Difficult to escape. Therefore, the reaction time of the catalyst is short, and the reaction of the catalyst can be promoted. Further, since the catalyst carrier is located at a position near the engine in the muffler, the reaction of the catalyst can be promoted. Furthermore, since the catalyst carrier is formed in a cylindrical shape along the inner surface of the muffler and does not protrude inward, a decrease in output can be prevented.

Further, even if the catalyst carrier thermally expands,
The thermal expansion allowance can be sufficiently absorbed by the bellows portion having a plurality of irregularities. Therefore, the durability can be improved. Moreover, since the heat-resistant elastic member is not used to absorb the thermal expansion allowance of the catalyst carrier, there is no deterioration due to a change in diameter. Therefore, the durability can be improved, and the occurrence of vibration and abnormal noise as shown in the second conventional example can be prevented.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view of a main part of an exhaust gas purifying apparatus for an internal combustion engine shown as one embodiment of the present invention.

FIG. 2 is a perspective view of the exhaust gas purifying apparatus for the internal combustion engine.

FIG. 3 is a view showing the exhaust gas purifying apparatus for the internal combustion engine, and is a cross-sectional view along the line III-III in FIG. 1;

4 is a view showing the exhaust gas purifying apparatus for the internal combustion engine, and is a cross-sectional view showing a main part IV of FIG. 1;

FIG. 5 is a side view showing a motorcycle equipped with the exhaust gas purifying apparatus for the internal combustion engine.

FIG. 6 is a perspective view of an exhaust gas purifying apparatus for an internal combustion engine shown as a first conventional example.

FIG. 7 is a view showing the exhaust gas purifying apparatus for the internal combustion engine, and is a cross-sectional view along the line VII-VII of FIG. 6;

FIG. 8 is a view showing the exhaust gas purifying apparatus for the internal combustion engine, and is a cross-sectional view along the line VIII-VIII in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Muffler 3 Catalyst support 31 One end 32 Other end 33 Bellows part 33a Unevenness (wave part)

Claims (1)

[Claims] 1. An exhaust gas purifying apparatus for an internal combustion engine having a catalyst carrier formed in a cylindrical shape along an inner surface of a muffler, wherein the catalyst carrier is arranged at a position closer to the engine in the muffler and has a small diameter side. The internal combustion engine is fixed to the muffler via one end of the internal combustion engine and is fixed to the muffler via a bellows portion having a plurality of irregularities formed integrally with the other end on the large diameter side. Engine exhaust gas purification equipment.