JPH11117723A - Muffler loaded with catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler loaded with catalyst, which does not cause a problem of reduction in the engine performance and which provides a sufficient exhaust gas purifying function and a muffling function. SOLUTION: In a muffler in which the inside of a muffler body 2 is divided into plural expansion chambers 5, 6, 7, the respective expansion chambers are connected by communicating pipes 8, 9, and a monolith catalyst 11 for purifying exhaust gas is provided at least in one communicating pipe 8, a diameter- reduced pipe 12 consisting of a hollow expansion pipe part 12a having the same diameter as that of the communicating pipe 8, a tapered pipe part 12b, the diameter of which is drawn into a conical shape, and a small diameter pipe part 12c, the diameter of which is reduced, is provided on the outlet side of the communicating pipe 8 provided with catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler (muffler) mounted on an exhaust pipe of an internal combustion engine, and more particularly to a muffler provided with an exhaust gas purifying catalyst.

[0002]

2. Description of the Related Art A muffler for reducing exhaust noise is mounted on an exhaust pipe of an internal combustion engine. FIG. 5 shows the structure of a general muffler to which the present invention is applied. An exhaust pipe 1 connected to an engine (not shown) has a rear end portion whose diameter gradually increases, and a cylindrical muffler main body 2 is attached to the rear end portion. The muffler main body 2 includes a first expansion chamber 5 on the rear end side, a second expansion chamber 6 on the front end side, and a third expansion chamber 7 in the center by two parallel first and second partition walls 3 and 4. It is divided into three expansion chambers. A first communication pipe 8 is provided through the first and second partition walls 3 and 4 to communicate the first and second expansion chambers 5 and 6, and the second and third expansion chambers 6 and 7 are provided.
Penetrates the first partition wall 3 to communicate with the second communication pipe 9
Is provided. The third expansion chamber 7 communicates with the outside through a tail pipe 10.

In such a structure, the exhaust gas discharged from the rear end of the exhaust pipe 1 in the muffler main body 2 has a first expansion chamber 5 → a first communication pipe 8 → a second expansion chamber 6 → a second communication pipe. 9 →
It flows in the order of the third expansion chamber 7 → the tail pipe 10 and is discharged to the outside. In such an exhaust passage, the exhaust gas rapidly expands in the first, second, and third expansion chambers 5, 6, 7, and suddenly expands in the first and second communication pipes 8, 9, and the tail pipe 10. By repeating the contraction alternately, the sound is released to the outside due to the silencing effect.

In such a muffler structure, optimal values are selected for the volume of each expansion chamber and the diameter and length of the communication pipe in accordance with the frequency to be silenced, and the vibration of the sound to be silenced can be efficiently reduced. Decay.

On the other hand, in order to efficiently provide a monolith catalyst for purifying exhaust gas in a space-efficient manner, a catalyst-mounted muffler mounted in a muffler is used. FIG. 6 shows the configuration of such a muffler equipped with a catalyst. This muffler has the same structure as that of the example of FIG. 5 except that the first communication pipe 8 of the muffler having the same configuration as that of FIG. 5 is filled with the monolith catalyst 11. The monolithic catalyst 11 is, for example, a honeycomb-shaped catalyst metal or a corrugated sheet-shaped (corrugated) catalyst wound in a roll shape and inserted into the communication pipe 8, and the entire internal space is filled with the catalyst to be integrated with the communication pipe 8. It is a thing. The exhaust gas passes through a gap between the catalysts in the communication pipe 8 and comes into contact with the catalysts and undergoes a purifying action.

[0006]

However, when a monolithic catalyst is filled in the communicating pipe, the pipe diameter must be increased in order to obtain a predetermined purifying action within a limited pipe length. For this reason, the pipe diameter of the communication pipe filled with the monolith catalyst is larger than the optimum pipe diameter for noise reduction, and a predetermined noise reduction function cannot be obtained, and the problem of exhaust noise has increased. In this case, if the length is increased without increasing the diameter of the tube in order to increase the amount of contact with the catalyst, the passage resistance of the communication tube is increased and the engine performance is reduced.

The present invention has been made in view of the above-mentioned prior art, and provides a catalyst-mounted muffler capable of obtaining a sufficient exhaust gas purifying function and a silencing function without causing a problem of deterioration in engine performance. With the goal.

[0008]

In order to achieve the above object, according to the present invention, the inside of the muffler body is divided into a plurality of expansion chambers, and each of the expansion chambers is connected with a communication pipe. In a muffler equipped with a monolithic catalyst for purifying exhaust gas, on the outlet side of a communication tube equipped with the catalyst, a hollow extension tube portion having the same diameter as the communication tube, a tapered tube portion whose diameter is conically narrowed, Provided is a catalyst mounting muffler characterized in that a reduced-diameter pipe including a small-diameter pipe portion having a reduced diameter is provided.

According to this configuration, a reduced-diameter pipe composed of a funnel-shaped extension pipe, a tapered pipe, and a small-diameter pipe is mounted on the outlet side of the communication pipe on which the catalyst is mounted. By providing this reduced-diameter pipe, the diameter of the communicating pipe is reduced by the small-diameter pipe part, so that a sufficient noise reduction function is obtained.The diameter of the communicating pipe is tapered rather than stepped by the tapered pipe part. Since the throttle is smoothly reduced, a decrease in engine performance is sufficiently prevented, and since the extension pipe is provided immediately after the catalyst, the diameter is not reduced immediately after passing through the catalyst, so that a sufficient exhaust gas purification function can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment,
The muffler body is divided into three expansion chambers by two parallel partition walls, and a communication pipe is provided in these expansion chambers so that exhaust gas flows in the order of a rear end side, a front end side, and a central expansion chamber, and a rear end side. The catalyst is mounted on a communication pipe that communicates the expansion chamber of the above with the expansion chamber on the front end side.

Since the communicating pipe is supported by the two partition walls by applying the reduced diameter pipe of the present invention to the catalyst mounting muffler having such a configuration, the catalyst position is extended from the partition wall by mounting the reduced diameter pipe. Even if the entire length of the protrusion protrudes, the communication tube is held sufficiently stably, and the present invention can be easily applied to an existing muffler.

[0012]

FIG. 1 is a diagram showing the basic configuration of an embodiment of the present invention.
This basic configuration example is an example in which the present invention is applied to the above-described catalyst mounting muffler of FIG.
The reduced diameter pipe 12 according to the present invention is mounted on the outlet side of the communication pipe 8. The reduced diameter pipe 12 is connected to the first communication pipe 8.
And a tapered tube portion 12b whose diameter is reduced conically, and a small-diameter tube portion 12c whose diameter is reduced. The length L of the extension tube portion 12a is
Is appropriately set based on the type of the catalyst, the amount of exhaust gas passing, and the like so as not to lower the exhaust gas purification function due to the exhaust gas. The taper angle α of the tapered pipe portion 12b is set in consideration of the space dimension and the like in accordance with the engine characteristics so as to prevent a decrease in engine performance. The diameter and length of the small-diameter pipe portion 12c are set so that the sound attenuation efficiency is maximized in accordance with the frequency of the exhaust sound to be silenced.

FIG. 2 is an overall configuration diagram of a scooter provided with a catalyst mounting muffler to which the present invention is applied. The basic frame structure of the scooter 21 includes a head pipe 24 that rotatably supports a steering shaft 23 of a handle 22,
The main pipe 25 includes a main pipe (down tube) 25 fixed to the head pipe 24 and side pipes 27 connected to the left and right sides of the lower end of the main pipe 25 and extending obliquely rearward below the seat 26. A front fork 28 is connected to the head pipe 24, and a front wheel 29 is mounted. Left and right side pipes 2 are located below the seat 26.
The swing-type engine unit 30 supported by 7 is mounted. The engine unit 30 includes the side pipe 2
7 and a link plate 32 bolted to the bracket 31, the front upper portion is suspended and supported, and the rear side is connected to a rear side pipe 27 a together with a rear wheel 34 via a cushion 33. It is swingably supported. For example, a front portion 35a, a footrest portion 35b, and an under portion 3
5c, a seat lower portion 35d, left and right side portions 35e, a rear cowl portion 35f, and the like.

The engine unit 30 is mounted on one side (left side) of the rear wheel 34, and has a cylinder head 36 at the front thereof.
An air cleaner 37 is mounted adjacent to one side (left side) of the air cleaner. Further, an exhaust pipe 38 is drawn out from the cylinder head 36 on the opposite side of the air cleaner 37. This exhaust pipe 3
At the end of 8, a catalyst mounting muffler 39 according to the present invention,
It is attached to the rear wheel 34 on the right side opposite to the engine unit 30.

FIG. 3 is an internal structural view of the catalyst mounting muffler 39 according to the present invention, and FIGS. 4 (A) and 4 (B) are cross-sectional views taken along AA and BB of FIG. 3, respectively. The catalyst mounting muffler 39 is composed of a substantially cylindrical muffler main body 40, the inside of which is formed by a first partition wall 41 and a second partition wall 42, the first expansion chamber 43 on the rear end side in the front-rear direction, and the first expansion chamber 43 on the front end side. It is divided into three chambers, two expansion chambers 44 and a third expansion chamber 45 in the middle. The muffler main body 40 is formed by, for example, welding a half-cylindrical body divided into right and left parts.

In the muffler main body 40, an exhaust pipe connecting pipe 46 is provided, which is connected to the end of the exhaust pipe 38 connected to the engine, and gradually increases in diameter. Open to the rear. This exhaust pipe connection pipe 46
4A and 4B, as shown in FIGS. 4A and 4B.
1 and 42 penetrate the lower center. A punch hole 55 is formed at the base of the exhaust pipe connection pipe 46, and the periphery thereof is covered with a glass wool 57 whose outside is sealed by a non-perforated plate 56. By providing such a glass wool 57, a part of the exhaust gas passes through the inside of the glass wool 57 via the punched holes 55, so that the noise reduction effect is enhanced. Such a glass wool 57 is further mounted on the inner surfaces of the first expansion chamber 43 and the second expansion chamber 44 of the muffler body 40 via a punching metal 59. As a result, part of the exhaust gas passes through the glass wool 57 through the holes of the punching metal 59, and the sound deadening effect is enhanced. The glass wool 57 on the inner surface side of the muffler main body 40 has a sound insulating function as well as a silencing effect, and prevents overheating of the outer surface of the muffler main body 40. It should be noted that 49 in FIGS. 4A and 4B indicate partition walls 41 and 42.
This is a thick portion for reinforcement (bead) formed in the above. Also, 50
Is a bracket for attaching the silencer to the vehicle body.

A support frame 47 is provided at an intermediate portion of the first expansion chamber 43 having a large capacity, and supports an exhaust pipe connection pipe 46 and a tail pipe 48. The support frame 47 has an opening (not shown) in the frame and does not obstruct the flow of the exhaust gas in the first expansion chamber 43. The tail pipe 48 has its front end supported by the second partition 42 and faces the third expansion chamber 45. The tail pipe 48 is drawn out of the third expansion chamber 45 and passes through the first expansion chamber 43. It is exposed from the main body 40 to the outside. In the middle of the tail pipe 48, the resonator 63
Communicates through a small hole (not shown) provided in the tail pipe, and further attenuates sound of a predetermined frequency.

As shown in FIG. 4B, a tail pipe 48 and an exhaust pipe connecting pipe 46 penetrate the second partition 42, and a first communication pipe 60 penetrates the second partition 42. This first
The communication tube 60 is filled with a monolith catalyst 61. On the outlet side (front end side) of the first communication pipe 60, the reduced diameter pipe 12 of the present invention is mounted. As described above, the diameter-reduced pipe 12 includes a hollow extension pipe part 12a having substantially the same diameter as the first communication pipe 60, a tapered pipe part 12b whose diameter is conically narrowed, and
The reduced-diameter pipe 1 is configured by a small-diameter pipe portion 12c having a reduced diameter, and a portion of the extension pipe portion 12a penetrating the first partition wall 41.
2 is supported by the first partition 41.

As shown in FIG. 4A, the first partition wall 41 supports the reduced-diameter pipe 12 and the exhaust pipe connecting pipe 46, and penetrates and supports the second communication pipe 62. . The second communication pipe 62 is connected to the first partition 41.
To allow the second expansion chamber 44 and the third expansion chamber 45 to communicate with each other.

In the catalyst mounting muffler 39 having the above structure, the exhaust gas from the engine is introduced from the exhaust pipe 38 through the exhaust pipe connection pipe 46 in the muffler body 20 to the rear end of the first expansion chamber 43 from the rear end 46a. Inflates rapidly. Thereafter, the exhaust gas passes forward through the inside of the catalyst 61 in the first communication pipe 60 and undergoes a catalyst purification action.
The exhaust gas that has passed through the catalyst 61 is introduced into the reduced-diameter pipe 12 at the outlet thereof, and as described above, the hollow extension pipe 1
2a prevents the reduction of the exhaust gas purifying action of the catalyst 61, the tapered pipe section 12b prevents a decrease in engine performance due to smooth diameter reduction, and the small-diameter pipe section 12c reliably achieves the muffler function which is the original muffler function. I do. This small diameter pipe section 12
Exhaust gas having exited from c is rapidly expanded in the second expansion chamber 44, is rapidly contracted through the second communication pipe 62, enters the third expansion chamber 45, and is rapidly expanded. Thereafter, the air is discharged from the third expansion chamber 45 through the tail pipe 48 to the outside.

[0021]

As described above, according to the present invention, a reduced-diameter pipe comprising a funnel-shaped extension pipe section, a tapered pipe section, and a small-diameter pipe section is mounted on the outlet side of a communication pipe having a catalyst mounted thereon. Because the diameter of the communication pipe is reduced by the small diameter pipe part, a sufficient noise reduction function is obtained, and the diameter of the communication pipe is smoothly reduced to a tapered shape without a step by the tapered pipe part. The deterioration of engine performance is sufficiently prevented, and the extension tube is provided immediately after the catalyst,
Since the diameter is not narrowed immediately after passing through the catalyst, a reduction in the exhaust gas purification function is prevented. As a result, the exhaust noise can be sufficiently reduced and the exhaust gas can be sufficiently purified without causing the problem of deterioration in engine performance.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is an external view of a scooter to which the present invention is applied.

FIG. 3 is a configuration diagram of a muffler according to the embodiment of the present invention.

FIG. 4 is a sectional view of an AA section and a BB section of FIG. 3;

FIG. 5 is a general structural view of a muffler to which the present invention is applied.

FIG. 6 is a configuration diagram showing a state where a catalyst is mounted on the muffler of FIG. 5;

[Explanation of symbols]

1, 38: exhaust pipe, 2, 40: muffler body, 3, 4
1: first partition, 4, 42: second partition, 5, 43: first expansion chamber, 6, 44: second expansion chamber, 7, 45: third expansion chamber,
8, 60: first communication pipe, 9, 62: second communication pipe, 10,
48: tail pipe, 12: reduced diameter pipe, 12a: extended pipe, 12b: tapered pipe, 12c: small diameter pipe, 11,
61: monolithic catalyst, 39: catalyst-mounted muffler, 57:
Glass wool, 59: punching metal.

Claims (2)

[Claims] 1. The inside of a muffler body is divided into a plurality of expansion chambers,
A communication pipe connects the expansion chambers to each other, and a muffler in which a monolithic catalyst for purifying exhaust gas is mounted in at least one of the communication pipes, wherein an outlet of the communication pipe in which the catalyst is mounted has the same diameter as the communication pipe. A muffler equipped with a catalyst, comprising: a reduced-diameter pipe comprising a hollow extension pipe section, a tapered pipe section conically narrowed in diameter, and a small-diameter pipe section narrowed in diameter. 2. The muffler body is divided into three parallel partitions.
A communication pipe is provided so that exhaust gas flows in the order of the rear end side, the front end side, and the central expansion chamber, and the rear end side expansion chamber and the front end side expansion chamber are connected to each other. The catalyst-mounted muffler according to claim 1, wherein the catalyst is mounted on a communication pipe.