JPH05288047A - Muffler - Google Patents

Abstract

PURPOSE:To provide a muffler of which the pulsation sound and the flow sound are low and catalyst is provided therein. CONSTITUTION:This muffler is partitioned by a partition plate 201 into a plurality of expansion chambers therein. An inlet pipe 3 with many exhaust passage holes formed on the outlet side is inserted into a first expansion chamber 21, and a structure 211 having many thin passages for supporting catalyst is arranged to penetrate at least one partition plate to be attached thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust muffler suitable for reducing pollution of exhaust gas used in general-purpose gasoline engines and the like.

[0002]

2. Description of the Related Art A first conventional example will be described with reference to FIG.
This first conventional example is a porous silencer. 1 in the figure
Is the muffler body. A partition plate 101 partitions the inside of the muffler body 1 into a first expansion chamber 31 and a second expansion chamber 32.
A plurality of small holes 12 are formed in the partition plate 101. 3 is an inlet pipe, the center line of which is parallel to the partition plate 101, is fixed through the wall of the muffler body 1, and the inner end is fixed to the muffler body 1.
Fixed and closed to the wall. Reference numeral 2 is a flange that is attached to the outer end of the inlet pipe 3 and is joined to the attachment surface of the exhaust port of the engine (not shown). A plurality of small holes 11 are formed in the wall of the inlet pipe 3 in the first expansion chamber 31. Reference numeral 4 denotes a tail pipe which is vertically fixed through an outer wall parallel to the partition plate 101 of the second expansion chamber 32, and the other end of the second expansion chamber 32 is fixed to the partition plate 101. A plurality of small holes 13 are formed in the tail tube wall in the second expansion chamber 32.

The operation of the first conventional example will be described. The flange 2 is attached to the exhaust port of the engine. The inlet pipe 3 introduces the exhaust gas of the engine and discharges it from the small hole 11 to the first expansion chamber 31. Exhaust gas enters the second expansion chamber 32 from the first expansion chamber 31 through the small hole 12, and then is discharged from the tail pipe 4 to the outside air through the small hole 13. A second conventional example will be described with reference to FIG. FIG. 8 is a sectional view of the second conventional example. Second
The conventional example of is an insertion tube type. In the figure, parts corresponding to those in FIG. 7 are assigned the same reference numerals as those in FIG. 7 and their explanations are omitted. Both 102 and 103 are partition plates that partition the inside of the muffler body 1 into a first expansion chamber 31, a second expansion chamber 32, and a third expansion chamber 33. Reference numeral 6 is an insertion tube, which is a short tube fixed vertically through the partition plate 102. Reference numeral 7 denotes an insertion tube, which has the same shape as the insertion tube 6 and is vertically fixed through the partition plate 103. Reference numeral 5 is a short tail tube which is vertically fixed through the outer wall of the third expansion chamber 33 facing the partition plate 102. Since the operation of the second conventional example is known, the description is omitted.

A third conventional example will be described with reference to FIG. FIG. 9 is a sectional view of the third conventional example. The third conventional example is a combination of the porous type and the insertion tube type. In the figure 104
The partition plate partitions the inside of the muffler body 1 into a first expansion chamber 31 and a second expansion chamber 32. Reference numeral 8 denotes an insertion tube which is a short tube which is vertically fixed through the partition plate 104 and fixed and whose end on the second expansion chamber 32 side is closed. A plurality of holes 12 are formed in the wall of the insertion tube 8 in the second expansion chamber. Since the operation of the third conventional example is well known, the description thereof will be omitted. Although the drawing of the fourth conventional example is omitted, the muffler body is provided with an increased number of partition plates to provide four or more expansion chambers. Since the function and effect are the same as those of the other conventional examples, a detailed description will be omitted.

[0005]

The engine exhaust sound is composed of a sound due to pressure fluctuation of the exhaust, that is, a pulsating sound and a flow sound when the exhaust gas is ejected at a high speed. FIG. 10 shows an example of frequency analysis of exhaust noise. Pulsating sound is less than 1kHz, flowing sound is 2kHz
It consists of the above frequency components. The purpose of the exhaust silencer is to keep both sounds low without compromising engine performance. However, in a general-purpose engine, the volume is often about 5 times the exhaust volume of the engine due to mounting and design problems, and excessive throttling has sufficient effects such as increasing the back pressure of the engine and causing a reduction in output. I have difficulty getting it. Furthermore, excessive throttling is accompanied by an increase in flow noise due to an increase in flow velocity. In order to solve these problems, as shown in FIG. 7, a perforated type, which produces less flow noise even at the same flow rate, is used, but the amount of reduction of pulsating noise, especially 160-300 kHz components, is small. Further, the insertion pipe type of FIG. 8 can reduce the sound of 160 to 300 kHz, but the flow noise is large and the exhaust sound level is high as a whole.

Further, it cannot be said that the combination type shown in FIG. 9 is sufficiently reduced. Next, regarding exhaust emission regulations expected in the future, it will be necessary to apply catalysts used in gasoline engines for automobiles. Moreover, in a general-purpose engine, it is difficult to mount the catalyst alone as in an automobile because of mounting problems. An object of the present invention is to solve the above problems and to provide an exhaust silencer in which both pulsation noise and flow noise are low and a catalyst can be installed inside.

[0007]

The engine performance and exhaust noise largely depend on the structure of the exhaust silencer. The acoustic characteristics of the silencer are also affected by the length of the insertion pipe, etc., and the muffler volume must be increased overall to obtain sufficient noise reduction characteristics.
It is necessary to reduce the cross-sectional area of the insertion tube and increase its length. However, if the cross-sectional area is made smaller, the engine back pressure will become excessive and output will be reduced. Therefore, the inlet pipe outlet will have many small holes, and the insertion pipe will have a thin passage structure such as a honeycomb shape, and the back pressure at this time will not rise. Set the total cross-sectional area of the passage. In addition, this structure has a narrow passage structure instead of an insertion pipe having a large cross-sectional area, and thus suppresses the generation of jet noise due to jet discharge, and is also effective in suppressing the flow noise. Further, the insertion pipe has a narrow passage structure, and at the same time, a catalyst for purifying exhaust gas is supported on the narrow passage portion. The exhaust silencer of the present invention has a plurality of expansion chambers internally partitioned by a partition plate, and has an inlet pipe inserted into the first expansion chamber and having a large number of exhaust passage holes formed on the outlet side; It is characterized in that it has a structure provided with a large number of narrow passages for supporting a catalyst, the structure being provided through the partition plate.

[0008]

[Function] The inlet pipe has a large number of small holes and the insertion pipe is divided into narrow passages, but the entire area is set so as not to excessively increase the back pressure. The characteristics are obtained. FIG. 11 shows the sound reduction characteristics. A large amount of purification of exhaust gas can be obtained by a catalyst supported on a structure having a narrow passage.

[0009]

EXAMPLE A first example will be described with reference to FIG. Figure 1
[FIG. 3] is a sectional view of the first embodiment. In the figure, 1 is a muffler body, which is box-shaped. A partition plate 201 divides the inside of the muffler body 1 into a first expansion chamber 21 and a second expansion chamber 22. Three
Is fixed through an outer wall of the first expansion chamber in parallel with the partition plate 201 by an inlet pipe, and the end on the first expansion chamber side is fixed and closed to the outer wall. A small hole 11 is provided in a large number in the pipe wall of the inlet pipe 3 in the first expansion chamber. The small hole 11 may be a long hole. Two
Is attached to the outer end of the inlet pipe 3 by a flange and fits on the attachment surface of the exhaust port of the engine (not shown). A passage structure 211 has a number of narrow passages formed therein, and is fixed through the partition plate 201. This passage is configured substantially parallel to the flow of exhaust gas. The passage structure 211 carries a catalyst for removing harmful components of the exhaust gas. The passage structure 211 is like a honeycomb structure. Reference numeral 5 denotes a tail pipe, which is vertically fixed through an outer wall parallel to the partition plate 201 of the second expansion chamber 23.

The operation of the first embodiment will be described. The inlet pipe 3 which is attached to the exhaust port of the engine by the flange 2 introduces the engine exhaust and discharges it from the small hole 11 to the first expansion chamber 21. The exhaust gas that has entered the first expansion chamber 21 flows through the passage structure 211 and is purified by the action of the catalyst, so that the second expansion chamber 22
Enter The exhaust gas in the second expansion chamber 22 is reduced in noise and the tail pipe 5
Is released to the outside air. A second embodiment will be described with reference to FIG. FIG. 2 is a sectional view of the second embodiment. In the second embodiment, the muffler body is divided into three expansion chambers by two partition plates. In the figure, the first expansion chamber 21, the second expansion chamber 22 and their internal structures are the same as in the first embodiment. A partition plate 202 partitions the inside of the muffler body 1. A third expansion chamber 23 is separated from the second expansion chamber by a partition plate 202. Reference numeral 8 denotes an insertion tube which is a short tube which is vertically penetrated through the partition plate 202 and fixed and whose end on the third expansion chamber side is closed. A plurality of small holes 12 are formed in the tube wall of the insertion tube 8 in the third expansion chamber. Since the operation of the second embodiment is similar to that of the first embodiment, its explanation is omitted.

A third embodiment will be described with reference to FIGS. FIG. 3 is a sectional view of the third embodiment, and FIG. 4 is a sectional view taken along the arrow A of FIG. In the figure, a partition plate 202 partitions the muffler main body 1 perpendicularly to the inlet pipe 3, and the inlet pipe 3 is fixed through it. Reference numeral 24 is a first expansion chamber. The small hole 11 is open to the first expansion chamber 24.
Reference numeral 25 is a second expansion chamber. The inlet pipe 3 penetrates the second expansion chamber 25. The passage structure 211 is fixed by vertically penetrating the partition plate 202. The tail pipe 5 is parallel to the partition plate 202 and vertically fixed through the outer wall of the second expansion chamber 25.
The operation of the third embodiment will be described. The exhaust gas introduced into the inlet pipe 3 flows from the small hole 11 into the first expansion chamber 24, then bends its path at a substantially right angle, and passes through the passage structure 211. While passing through the passage structure 211, it is purified by the action of the catalyst and flows out to the second expansion chamber 25. It is discharged from the second expansion chamber 25 to the outside air through the tail pipe 5. The emitted exhaust is reduced in sound.
The operation of the third embodiment is the same as the operation of the first embodiment.

A fourth embodiment will be described with reference to FIG. Since the vertical cross section of the fourth embodiment is the same as that of FIG. 3, it is also used in FIG. FIG. 5 is a cross-sectional view taken along the arrow A of FIG. The inlet pipe 3 is the muffler body 1
It is attached to the outer wall of the car at an angle. The operation of the fourth embodiment is the same as that of the third embodiment. A fifth embodiment will be described with reference to FIG. FIG. 6 is a vertical sectional view of the fifth embodiment. In the figure, the structures of the elements having the same reference numerals as those in FIG. 3 are the same as those in FIG. Reference numeral 10 denotes a tail tube that vertically penetrates the outer wall of the second expansion chamber and is fixed, and the inner end of the second expansion chamber 24 is closed. A plurality of small holes 14 are formed in the tube wall of the second expansion chamber 24 of the tail tube 10. In all of the above-mentioned embodiments, the first expansion chamber and the second expansion chamber are communicated with each other through a narrow passage structure, and a catalyst is carried in the passage portion.

[0013]

Since the present invention is constructed as described above, sufficient noise reduction characteristics can be obtained as shown in FIG. 11 without lowering the output, and the catalyst can be installed in a large area within the silencer, resulting in a large purification. The effect is obtained. FIG. 12 is a diagram showing the components of the exhaust gas from the muffler. Oxidizes CO, THC and N
The three-way catalyst for reducing O _X is an example of when carrying. Therefore, the present invention can provide an exhaust silencer in which the pulsating sound and the flowing sound are both low and a catalyst is installed inside.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a sectional view of a third embodiment.

FIG. 4 is a sectional view taken along the arrow A of the third embodiment, taken along the center line of the inlet pipe in FIG.

FIG. 5 is a cross-sectional view taken along arrow A of the fourth embodiment including an inlet pipe.

FIG. 6 is a sectional view of a fifth embodiment.

FIG. 7 is a sectional view of a first conventional example.

FIG. 8 is a sectional view of a second conventional example.

FIG. 9 is a sectional view of a third conventional example.

FIG. 10 is a diagram showing a factor analysis of engine exhaust sound by frequency analysis.

FIG. 11 is a diagram showing acoustic theoretical sound reduction characteristics of the present invention.

FIG. 12 is a diagram showing removal of harmful components of exhaust gas according to the present invention.

[Explanation of symbols]

1 ... Muffler body, 21 ... 1st expansion chamber, 22 ... 2nd expansion chamber, 24 ... 1st expansion chamber, 25 ... 2nd expansion chamber, 201 ... Partition plate, 202 ... Partition plate, 3 ... Inlet pipe, 11 ... small holes, 21
1 ... (passage) structure.

Claims (1)

[Claims] 1. An inner partition which is partitioned into a plurality of expansion chambers by partition plates; an inlet pipe inserted into the first expansion chamber and having a number of exhaust passage holes formed on the outlet side; and at least one of said partitions. An exhaust silencer for an engine, comprising: a structure that is provided through a plate and has a large number of narrow passages carrying a catalyst.