JPH06212964A - Exhaust device of engine - Google Patents

Abstract

PURPOSE:To enhance an ejector effect in a simple structure so as to supply secondary air efficiently, reduce the cost and the noise of exhaust and prevent oxidation and deterioration due to high temperature of a muffler main body so as to improve the durability and obtain high reliability. CONSTITUTION:Exhaust gas discharged from an engine is introduced into a first expansion chamber 6, a second expansion chamber 7 and a third expansion chamber 8 disposed in a muffler main body 2 through a manifold 3, and then further increased in the flow velocity at an ejector part 5 to generate negative pressure, so that the secondary air is sucked from an air introducing pipe 16. While exhaust gas and secondary air are mixed in a diffuser pipe 17, it is discharged to a catalyst chamber 10 to be purified by a catalyst 21 and released to the air through an exhaust pipe 4. At this time, as a muffler part having large resistance is not provided in the downstream of the ejector part 5, the ejector effect can be enhanced so as to improve the exhaust gas purifying performance and miniaturize the whole device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system of an engine for purifying exhaust gas by introducing secondary air to promote an oxidation reaction on a catalyst.

[0002]

2. Description of the Related Art Conventionally, there is known a technique for promoting secondary exhaust gas purification reaction in a post-treatment device such as a catalyst or a thermal reactor by introducing secondary air into the exhaust gas of an engine operated at a rich air-fuel ratio. As a means for supplying the secondary air to the exhaust system, there is one that positively supplies the auxiliary air by using auxiliary equipment such as a pump.

However, the amount of secondary air introduced, which is commensurate with the amount of exhaust gas discharged, must be properly controlled by a control means such as a throttle valve, which complicates the control and increases the size of the entire apparatus, resulting in cost reduction. There is a problem that causes soaring prices.

On the other hand, the structure in which the secondary air is introduced by utilizing the ejector effect at the time of discharging the exhaust gas has a simple structure, and the secondary air corresponding to the discharge amount of the exhaust gas can be introduced. It is used in many engines because it can. For example, U.S. Pat. No. 3,468,124 discloses a technique in which secondary air is taken into each cylinder by an ejector effect on the upstream side of an exhaust manifold.

[0005]

[Problems to be Solved by the Invention]
When taking in secondary air by the ejector effect, as described in the above-mentioned prior art, an ejector is provided upstream of the exhaust manifold, and a silencer is provided downstream of this ejector to reduce exhaust noise. Since it is a silencer with a large resistance, a sufficient ejector effect cannot be obtained. Furthermore, as shown in FIG. 9, since the exhaust pressure of the engine has a small negative pressure portion, there is a problem that the ejector effect is weakened by the positive pressure.

Further, there is a problem in durability such that the muffler main body is heated by the reaction heat when the exhaust gas reacts with the secondary air at the catalyst, resulting in oxidative deterioration.

The present invention has been made in view of the above circumstances, and it is possible to enhance the ejector effect with a simple structure to efficiently supply the secondary air, at low cost, and to reduce exhaust noise. It is also an object of the present invention to provide an exhaust system for an engine capable of suppressing the oxidation deterioration of the muffler main body due to high temperature and improving durability and high reliability.

[0008]

According to a first aspect of the present invention, a muffler body connected to an exhaust side of an engine is provided with a muffling section communicating with an exhaust gas introduction port of the muffler body and a secondary air introduced from the outside. The ejector section that mixes with the exhaust gas that has passed through the muffling section and the catalyst that purifies the exhaust gas from the ejector section are provided.

According to a second aspect of the invention, in a muffler body connected to the exhaust side of the engine, a muffling section communicating with the exhaust gas introduction port of the muffler body and secondary air introduced from the outside through a check valve. An ejector section that mixes the exhaust gas that has passed through the muffling section and a catalyst that purifies the exhaust gas from the ejector section are arranged.

According to a third aspect of the present invention, in a muffler body connected to the exhaust side of the engine, a muffling section communicating with the exhaust gas introduction port of the muffler body and secondary air introduced from the outside to pass through the muffling section. Ejector mixed with the exhaust gas, a catalyst for purifying the exhaust gas from the ejector, and a part of the exhaust gas passing through the silencer around the holder holding the catalyst to pass the catalyst. A bypass passage for mixing with the exhaust gas afterward is provided.

According to a fourth aspect of the present invention, in a muffler body connected to the exhaust side of the engine, a muffling section communicating with the exhaust gas introduction port of the muffler body and secondary air introduced from the outside through a check valve. An ejector part that mixes with the exhaust gas that has passed through the muffling part, a catalyst that purifies the exhaust gas from the ejector part, and a part of the exhaust gas that has passed through the muffling part around the retainer that holds the catalyst. And a bypass passage for mixing with the exhaust gas after passing through the catalyst.

[0012]

In the first aspect of the invention, the exhaust gas discharged from the engine is introduced into the muffler in the muffler body to reduce the exhaust noise, and the exhaust gas from the muffler is guided to the ejector section to generate secondary air. It is introduced and mixed, and then introduced into a catalyst for purification.

According to the second aspect of the invention, the exhaust gas discharged from the engine is introduced into the muffler in the muffler body to reduce the exhaust noise, the exhaust gas from the muffler is guided to the ejector section, and the check valve is opened. It is mixed with the secondary air introduced through and further introduced to the catalyst for purification.

In the third aspect of the invention, the exhaust gas discharged from the engine is introduced into the muffler in the muffler body to reduce the exhaust noise, and the exhaust gas from the muffler is guided to the ejector section to form secondary air. The catalyst is mixed and guided to the catalyst, and a part of the exhaust gas from the muffling section is bypassed to be guided to the periphery of a holder holding the catalyst to cool the periphery of the catalyst.

According to the fourth aspect of the invention, the exhaust gas discharged from the engine is introduced into the muffler in the muffler body to reduce exhaust noise, and the exhaust gas from the muffler is guided to the ejector section to form a check valve. It mixes with the secondary air introduced via the above and guides it to the catalyst, and also bypasses a part of the exhaust gas from the above-mentioned muffling section and guides it to the periphery of the holder that holds the catalyst to cool the periphery of the catalyst.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show a first embodiment of the present invention, FIG. 1 is a sectional view of an exhaust device, FIG. 2 is an external view of the exhaust device, FIG. 3 is a front view of an ejector portion, and FIG. 4 is exhaust gas at the ejector portion. FIG. 5 is an explanatory diagram showing flows of gas and secondary air, and FIG. 5 is an explanatory diagram showing exhaust pressure generated in the ejector portion.

In FIG. 2, reference numeral 1 is an exhaust device,
A manifold 3 is attached to the upper end of the cylindrical muffler body 2 so as to circulate in the radial direction and communicate with the inside, and is connected to an exhaust port such as a general-purpose engine (not shown) via a flange 3a at the tip of the manifold 3. It is like this.

An exhaust pipe 4 for discharging purified exhaust gas to the atmosphere is attached to a lower end portion of the muffler body 2, and an ejector portion 5 is provided at a substantially central portion of the muffler body 2. The secondary air is taken into the muffler body 2 from the ejector section 5.

The muffler body 2 is, as shown in FIG.
A first expansion chamber 6 communicating with the manifold 3 serving as an exhaust gas introduction port, and a third expansion chamber 8 formed below the first expansion chamber 6 are provided inside the outer cylinder 2a in which cup-shaped cylinders are vertically joined. And a second expansion chamber 7 formed below the third expansion chamber 8 and communicating with the first expansion chamber 6 through the guide pipe 9, and further, the second expansion chamber 7 is provided. It has a catalyst chamber 10 formed in the lower part, and a lowermost exhaust chamber 11 communicating with the exhaust pipe 4.

The first expansion chamber 6 and the third expansion chamber 8 are partitioned by a partition plate 12, and the third expansion chamber 8 and the second expansion chamber 7 are partitioned by a partition plate 13. . The outer circumferences of the upper and lower open ends of the guide pipe 9 are
The first expansion chamber 6 and the second expansion chamber 7 are connected to each other by being fixed to the partition plate 11 and the partition plate 12, respectively, and further, through a large number of holes 13 a formed in the partition plate 13. The second expansion chamber 7 and the third expansion chamber 8 are communicated with each other.

The ejector section 5 is housed in the second expansion chamber 7, and the ejector section 5 is a cylindrical swivel tube 14 arranged laterally with respect to the muffler body 2.
An exhaust gas introducing pipe 15 for communicating the inside of the swirl cylinder 14 with the third expansion chamber 8, an air introducing pipe 16 for taking in secondary air from the outside, and an exhaust gas and a secondary air for mixing. And an elbow-shaped diffuser pipe 17 leading to the catalyst chamber 10.

The exhaust gas introducing pipe 15 penetrates through the partition plate 13a and has one end opening into the third expansion chamber 8 and the other end located at the axial center of the swivel cylinder 14 as shown in FIG. On the other hand, they are fixed to the outer peripheral portion of the swivel cylinder 14 so as to be orthogonal to each other with an offset, and open inside the swivel cylinder 14.

The air introducing pipe 16 is the swivel cylinder 1
4 is fixed so as to be concentric with the swirl cylinder 14 by penetrating an outer front wall thereof, and inside the swirl cylinder 14, a straight pipe portion of the diffuser pipe 17 having a diameter larger than that of the air introduction pipe 16 is provided. A double tube is formed with the open ends flush or slightly overlapping.

The diffuser pipe 17 is fixed so that the straight pipe portion that penetrates the rear wall of the swivel cylinder 14 and projects into the swivel cylinder 14 is concentric with the swirl cylinder 14, and the second expansion chamber 7 is provided. A curved pipe portion extending inward penetrates a partition plate 18 that divides the second expansion chamber 7 and the catalyst chamber 10 along the vertical direction of the muffler body 2 and is opened in the catalyst chamber 10. ing.

The catalyst chamber 10 has the exhaust chamber 11
The catalyst holder 20 attached to the partition 19 accommodates a catalyst (oxidation catalyst) 21 having a small flow resistance. Then, the exhaust gas purified by the catalyst 21 is released from the exhaust chamber 11 to the atmosphere through the exhaust pipe 4.

Next, the operation of the exhaust device 1 having the above structure will be described.

When the engine is started, the exhaust gas discharged from the engine passes through the manifold 3 and the muffler body 2
Is discharged to the first expansion chamber 6 provided in the first expansion chamber 6 and is discharged to the second expansion chamber 7 by the guide pipe 9. Further, the exhaust gas discharged into the second expansion chamber 7 is separated by the partition plate 1 above the second expansion chamber 7.
It is squeezed by a large number of holes 13 a bored in the hole 3 and introduced into the third expansion chamber 8. As a result, the exhaust gas discharged from the engine repeatedly expands and contracts, and exhaust noise can be efficiently reduced by the small-capacity silencer.

Next, the exhaust gas in the third expansion chamber 8 is introduced into the swirl cylinder 14 through the exhaust gas introduction pipe 15 of the ejector section 5. At this time, as shown in FIG. 3, since the exhaust gas introduction pipe 15 is offset and orthogonal to the axial center of the swirl cylinder 14, the exhaust gas introduced into the swirl cylinder 14 swirls while accelerating the flow velocity. Swivel.

Then, as shown in FIG. 4, the exhaust gas swirled in the swirling cylinder 14 enters the inside of the diffuser pipe 17 from the annular gap formed between the opening of the diffuser pipe 17 and the opening of the air introducing pipe 16. invade. As a result, the flow velocity of the exhaust gas is further increased, a negative pressure is generated, and fresh air (secondary air) outside is sucked from the air introduction pipe 16.

After that, while the exhaust gas and the secondary air are mixed in the diffuser pipe 17, they are discharged into the catalyst chamber 10 and enter the catalyst 21, and the oxidation reaction in the catalyst 21 purifies toxic HC and CO. And is discharged from the exhaust pipe 4 to the atmosphere.

That is, by arranging a muffling section consisting of the first expansion chamber 6, the second expansion chamber 7, and the third expansion chamber 8 having a large resistance on the upstream side of the ejector unit 5, the exhaust pressure in the engine shown in FIG. 5, the negative pressure generated in the ejector unit 5 can be increased as a positive and negative total as shown in FIG. 5, and the suction amount of the secondary air can be greatly increased.

As a result, the engine noise can be efficiently reduced, the ejector effect can be further enhanced, and the exhaust gas purification performance can be greatly improved, and the overall size can be reduced. is there.

FIG. 6 shows a second embodiment of the present invention and is a sectional view of an exhaust system.

In the second embodiment, a check valve is provided on the secondary air introduction side in order to enhance the ejector effect with respect to the exhaust device 1 of the first embodiment. In each of the following embodiments, the same members as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 6, the exhaust device 3 of this embodiment.
0 is the air introduction pipe 16 of the ejector unit 5 of the first embodiment.
At the tip of the air introduction pipe 31 extending the open end of
A check valve 32 is provided. The check valve 32 is integrally formed of a reed valve 33, a stopper 34, and a seat 35. The check valve 32 is held by a suction pipe 36 and a lid 37 and connected by a bolt or the like (not shown). Is attached to the tip of.

In the present embodiment, as shown in FIG. 9, the check valve prevents exhaust gas before purification from being discharged from the air introduction pipe 31 to the atmosphere due to the positive pressure with respect to the exhaust pressure of the engine having many positive pressure portions. 32, the secondary air can be effectively introduced to further enhance the ejector effect. Other functions and effects are similar to those of the first embodiment described above.

FIG. 7 shows a third embodiment of the present invention and is a sectional view of an exhaust system.

In the third embodiment, the catalyst 21 generated inside the muffler main body 2 is different from the exhaust device 1 of the first embodiment.
The surroundings of the catalyst 21 are cooled in order to prevent heat damage due to the reaction heat.

That is, in the exhaust device 40 of this embodiment,
As shown in FIG. 7, the peripheral edge of the catalyst holder 42 accommodating the catalyst 21 extends and contacts the partition plate 41 in the lower portion of the second expansion chamber 7 corresponding to the partition plate 18 of the first embodiment, and the ejector. The catalyst chamber 10 in which the diffuser pipe 43 of the part 5 is opened is formed.

The diffuser pipe 43 is shown in FIG.
In the first embodiment, the bend of the elbow-shaped conduit is slightly different from that of the diffuser pipe 17 of the first embodiment, but the ejector portion 5 may be slightly extended in the lateral direction, and the attachment position of the diffuser pipe 17 may be shifted. .

The outer cylinder 2 is provided below the second expansion chamber 7.
a, the partition plate 41, the catalyst holder 42 side wall, and the space surrounded by the partition plate 44 (corresponding to the partition plate 19 of the first embodiment) to which the catalyst holder 20 is attached, the fourth expansion. A chamber 45 is formed.

A hole 41a is formed in the partition plate 41 at a position between the outer cylinder 2a and the outer wall of the catalyst holder 42. Further, the partition plate 44, like the partition plate 41, has the above-mentioned structure. A hole 44 is provided at a position between the outer cylinder 2a and the outer wall of the catalyst holder 42.
a is provided in the exhaust chamber 1 through the fourth expansion chamber 45 through the second expansion chamber 7 by the holes 41a and 44a.
A bypass passage communicating with 1 is formed.

In this embodiment, as in the first embodiment, the exhaust gas from the second expansion chamber 7 is mixed with the secondary air in the ejector section 5 and guided to the catalyst 21, while the second expansion chamber 7 is exhausted. Part of the exhaust gas is introduced into the fourth expansion chamber 45 through the hole 41a of the partition plate 41, further passes through the hole 44a of the partition plate 44, reaches the exhaust chamber 11, and is purified by the catalyst 21. It is mixed with exhaust gas and released into the atmosphere.

That is, a part of the exhaust gas flows between the outer cylinder 2a and the catalyst holder 42 to cool the high temperature part due to the heat of oxidation reaction in the catalyst 21, and the exhaust gas passing through the catalyst 21 When mixing, the excess oxygen is small and the reactor reaction does not occur. Therefore, it is possible to prevent the excessive temperature rise of each part and keep the whole muffler at a relatively low temperature. Therefore, it is possible to reduce the total cost, enhance safety, and improve durability without using an expensive heat-resistant alloy.

FIG. 8 shows a fourth embodiment of the present invention and is a sectional view of an exhaust system.

In the fourth embodiment, the check valve is provided in the exhaust device 40 of the third embodiment, whereas the check valve is provided in the exhaust device 1 of the first embodiment in the fourth embodiment. It is equipped with a valve.

That is, the exhaust device 50 of the fourth embodiment is
As shown in FIG. 8, the air introduction pipe 16 of the ejector unit 5
Is an air introducing pipe 31 similar to that of the second embodiment, and a check valve 32 similar to that of the second embodiment is provided at the tip of this air introducing pipe 31 to prevent heat damage due to the heat of oxidation reaction in the catalyst. The ejector effect can be further enhanced while preventing it.

In each of the above embodiments, the ejector that swirls the exhaust gas spirally has been described, but the present invention is not limited to this.

[0049]

As described above, according to the present invention, the exhaust gas discharged from the engine is introduced into the muffler in the muffler body to reduce the exhaust noise, and the exhaust gas from the muffler is ejected. After introducing the secondary air and mixing it, the secondary air is introduced into the catalyst for purification, so the ejector effect is not weakened by the silencing part with high resistance, and the ejector effect is enhanced by a simple structure to generate secondary air. It can be supplied efficiently, at low cost, and exhaust noise can be reduced.

Further, since the secondary air is introduced into the ejector section through the check valve, the ejector effect is not weakened by the positive exhaust pressure.

Further, since a part of the exhaust gas from the muffling section is bypassed and guided to the periphery of the holder for holding the catalyst to cool the periphery of the catalyst, the oxidation deterioration due to the high temperature of the muffler body is suppressed and the durability is improved. And an excellent effect such as high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an exhaust device according to a first embodiment of the present invention.

FIG. 2 Same as above, external view of the exhaust device

FIG. 3 is a front view of the ejector portion of the above.

FIG. 4 is an explanatory diagram showing the flow of exhaust gas and secondary air in the ejector section.

FIG. 5 is an explanatory diagram showing the exhaust pressure generated in the ejector section.

FIG. 6 is a sectional view of an exhaust device according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view of an exhaust device according to a third embodiment of the present invention.

FIG. 8 is a cross-sectional view of an exhaust device according to a fourth embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an exhaust pressure of an engine according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust device 2 Muffler main body 5 Ejector part 6 1st expansion chamber (silencer part) 7 2nd expansion chamber (silencer part) 8 3rd expansion chamber (silencer part) 21 Catalyst 32 Check valve 41a hole (bypass passage) 42a hole (Bypass passage)

Claims (4)

[Claims] 1. A muffler body connected to an exhaust side of an engine, and a muffler communicating with an exhaust gas introduction port of the muffler body, and an exhaust gas introduced from the outside by secondary air and passing through the muffler. An exhaust system for an engine, comprising: an ejector section for mixing; and a catalyst for purifying exhaust gas from the ejector section. 2. A muffler body connected to the exhaust side of the engine, and a muffling section communicating with the exhaust gas introduction port of the muffler body, secondary air introduced from the outside through a check valve, and the muffling section. An exhaust system for an engine, comprising: an ejector section that mixes the exhaust gas that has passed through; and a catalyst that purifies the exhaust gas from the ejector section. 3. A muffler body connected to the exhaust side of the engine, and a muffling section communicating with an exhaust gas introduction port of the muffler body, and an exhaust gas that has introduced secondary air from the outside and passed through the muffling section. An ejector part for mixing, a catalyst for purifying exhaust gas from the ejector part, and a part of the exhaust gas that has passed through the muffling part around the retainer for holding the catalyst to guide the exhaust gas after passing through the catalyst. An exhaust system for an engine, wherein an exhaust passage for mixing with the exhaust passage is provided. 4. A muffler body connected to an exhaust side of an engine, and a muffler section communicating with an exhaust gas introduction port of the muffler body, secondary air introduced from the outside through a check valve, and the muffler section. The ejector section that mixes the exhaust gas that has passed through, a catalyst that purifies the exhaust gas from the ejector section, and a portion of the exhaust gas that has passed through the muffling section is guided around the holder that holds the catalyst. An exhaust system for an engine, comprising: a bypass passage for mixing with exhaust gas after passing through a catalyst.