JP4891360B2 - Scarf - Google Patents

Description

  The present invention relates to a muffler.

  Conventionally, as described in Patent Document 1, a muffler has passed exhaust gas from an internal combustion engine through a large number of expansion chambers and inner pipes to reduce noise.

JP 2001-271627 A

In particular, agricultural machinery such as tractors and construction machinery vehicles such as power shovels are operated within a predetermined range such as farmland and construction sites, so exhaust noise can easily enter the ears of nearby residents and give discomfort. It has been desired to reduce the exhaust sound on the low and high sound side. Further, reduction of back pressure and cost reduction for improving fuel efficiency have been desired.
However, the structure in which the interior of the muffler body is divided into a large number of spaces and these spaces are connected by a plurality of communication pipes requires many manufacturing processes, parts, and materials. In addition, the short piece of glass fiber used in conventional mufflers may scatter to the atmosphere along with the exhaust, and requires a scattering prevention member such as a metal plate or metal fiber. effort and costs there is a problem that is that whether.

  Accordingly, an object of the present invention is to provide a muffler that can be manufactured at a low cost with a simple structure while reducing exhaust sound and back pressure on the low sound range side and high sound range side.

In order to achieve the above object, a muffler of the present invention includes a muffler main body having a cylindrical wall member and a pair of side wall members that respectively cover both end openings of the cylindrical wall member in a cover shape, and exhaust the exhaust to the muffler main body. connecting an exhaust introduction pipe for introducing, and an exhaust discharge pipe for discharging exhaust from the muffler body, in the interior of the muffler body, a first expansion chamber which is connected to the exhaust inlet tube, and the exhaust discharge pipe A second extension chamber, a communication pipe connecting the first extension chamber and the second extension chamber and having a number of through holes in the peripheral wall, and being arranged between the first extension chamber and the second extension chamber. A sound absorbing chamber that surrounds the outer periphery of the communication pipe, and the exhaust introduction pipe has the tip end side passing between the one side opening of the communication pipe and the side wall member on one side. It is inserted from the wall member into the first expansion chamber, and the tip is closed. In addition, the exhaust introduction pipe has a large number of introduction holes in the peripheral wall of the first expansion chamber, and the introduction to the side wall member on one side so that the exhaust does not immediately flow to the communication pipe. The exhaust discharge pipe has an opening end on the base end side inserted into the second expansion chamber from the cylindrical wall member and exhausted from the other opening of the communication pipe on the peripheral wall. The through-holes are arranged in a staggered manner in the communication pipe, the aperture ratio of the peripheral wall in the sound absorption chamber is 18% to 30%, and the long glass fiber is provided in the sound absorption chamber. Ru der those filled with.

  According to the muffler of the present invention, it can be manufactured inexpensively with a simple structure and a small number of parts. Exhaust sound on the low and high frequencies can be reduced. By using the long glass fibers, it is possible to prevent the fragmented glass fibers from being scattered and the noise reduction effect from being lowered. It is possible to reduce the back pressure and improve the fuel efficiency of the counterpart internal combustion engine.

It is a section front view showing an embodiment of the invention. It is a side view which shows embodiment of this invention. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is a section front view of a comparative example.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
As shown in FIGS. 1 and 2, the muffler according to the embodiment of the present invention is an expansion type sound absorbing muffler connected to an internal combustion engine of an agricultural work machine (vehicle) such as a tractor or a construction vehicle (machine) such as a power shovel. A muffler body 1 filled with glass long fibers 20, an exhaust introduction pipe 2 for introducing exhaust (sound) into the muffler body 1, an exhaust discharge pipe 3 for exhausting exhaust from the muffler body 1 to the atmosphere, It has.

  The muffler body 1 is formed in an oval or elliptical column shape. It has a cylindrical wall member 7 made of an ellipse or an elliptic cylindrical sheet metal, and side wall members 8, 8 made of sheet metal that cover both ends of the cylindrical wall member 7 in a cover shape.

  The inside of the muffler main body 1 surrounded by the cylindrical wall member 7 and the pair of side wall members 8 and 8 (inside the main body) includes a first expansion chamber 11 into which an exhaust introduction pipe 2 of a metal thin pipe is inserted and connected, and a metal In the longitudinal direction N of the muffler body 1 (in the direction of arrow N), the second expansion chamber 14 into which the exhaust pipe 3 of the thin-walled pipe is inserted and connected, the first expansion chamber 11 and the second expansion chamber 14 are connected. A communication pipe 12 arranged with the axis L1 aligned, and a sound absorption chamber 13 arranged between the first expansion chamber 11 and the second expansion chamber 14 and surrounding the outer periphery (wall) of the communication pipe 12; Have. The sound absorbing chamber 13 is filled with long glass fibers 20.

In other words, inside the main body, a pair of partition members 9 and 9 made of sheet metal are arranged in parallel in the longitudinal direction N, and are divided into three spaces.
A space surrounded by the side wall member 8 (8a) on one side in the longitudinal direction N, the partition member 9 (9a) on one side, and the cylindrical wall member 7 is defined as a first expansion chamber 11.
Further, the longitudinal direction N of the other side of the wall member 8 (8b), the partition member 9 of the other side (9 b), and a space surrounded by the cylindrical wall member 7 as the second expansion chamber 14.
Further, a communication pipe 12 of a thin metal pipe that penetrates between the pair of partition members 9 and 9 in the longitudinal direction N is provided, and is surrounded by the outer peripheral walls of the pair of partition members 9 and 9, the cylindrical wall member 7, and the communication pipe 12. The sound absorption chamber 13 is defined as the space.

The base end 2b side of the exhaust introduction pipe 2 is attached to an exhaust discharge port of an internal combustion engine (not shown). The distal end 2 a side is inserted into the cylindrical wall member 7 from the radial direction of the communication pipe 12. It is inserted from the side inserted into the cylindrical wall member 7 to the facing side, and the tip 2a is closed. In other words, the exhaust introduction pipe 2 is disposed so as to skew the first expansion chamber 11 so as to pass between the side wall member 8 a on one side and the opening 12 a on one side of the communication pipe 12.

  Further, the exhaust introduction pipe 2 has an introduction hole 2 c in a peripheral wall in contact with the first expansion chamber 11. As shown in FIG. 3, a large number of introduction holes 2c are concentrated near the side wall member 8a on one side so that the exhaust gas does not flow into the communication pipe 12 immediately. That is, the center line of the introduction hole 2c is disposed in a semicircle near the side wall member 8a on one side.

  The communication pipe 12 is disposed at a substantially central position inside the main body with its axis L1 aligned with the longitudinal direction N of the muffler main body 1. A large number of through holes 12c are formed in a staggered pattern on the peripheral wall in contact with the sound absorbing chamber 13, and the aperture ratio is set to be 18% to 30%. It is more preferable to set the aperture ratio to 20%. This is because if the aperture ratio is less than 18%, exhaust (sound) does not sufficiently flow into the sound absorbing chamber 13 and a sound absorbing effect cannot be obtained. This is because if it exceeds 30%, the long glass fiber 20 may be exposed and scattered in the communication pipe 12 in a large amount.

  The through hole 12c has a diameter of 2.5 mm or more and 4 mm or less. More preferably, the diameter is 3.5 mm. This is because if it is less than 2.5 mm, the exhaust sound is not sufficiently transmitted to the sound absorbing chamber 13 (the exhaust does not flow), and the sound absorbing effect cannot be obtained. This is because if the length exceeds 4 mm, the long glass fibers 20 may enter the communication pipe 12 in a large amount.

  As shown in FIG. 4, the sound absorbing chamber 13 is formed in an annular chamber whose outer shape is an oval or elliptical cross section. And countless long glass fibers 20 are filled. The long glass fiber 20 means one glass fiber having a length of 100 m or more.

The bulk density of the long glass fibers 20 filled in the sound absorption chamber 13 is 100 kg / m ³ or more and 200 kg / m ³ or less, more preferably 120 kg / m ³ or more and 170 kg / m ³ or less. For example, it is filled at 150 kg / m ³ . If the bulk density is less than 100 kg / m ³ , a sufficient sound absorbing effect cannot be obtained, and if it exceeds 200 kg / m ³ , the filling operation becomes very difficult.

The diameter of the long glass fiber 20 is desirably 15 μm or more and 50 μm or less, and more preferably 20 μm or more and 30 μm or less.
If the diameter of the long glass fiber 20 is less than 15 μm, the strength may be weakened and the glass fiber 20 may be finely broken and scattered. On the other hand, if the thickness exceeds 50 μm, the surface area of the filled glass long fiber 20 as a whole is reduced and a sufficient silencing effect cannot be obtained.

For example, the long glass fibers 20, SiO ₂ is 55-56% CaO is 18 to 25% _Al 2 _{O 3} is 10 to 15% Mg0 is 0-5%, others less than 2%, of a component What is constructed is preferred. Specifically, Advantex (trade name: Ovantex, manufactured by Owens Corning Japan) having an average fiber diameter of 24 μm is applicable.

  The exhaust discharge pipe 3 is inserted into the cylindrical wall member 7 from the radial direction of the communication pipe 12 at the open end 3 a on the base end side. The opening end 3 a is inserted deeper than the other side opening 12 b of the communication pipe 12. That is, the exhaust from the other opening 12b of the communication pipe 12 does not immediately flow into the exhaust discharge pipe 3, but is once arranged to collide with the peripheral wall of the exhaust discharge pipe 3.

The use method (action) of the muffler of the embodiment of the present invention described above will be described.
Exhaust gas (sound) discharged from an internal combustion engine of an agricultural or construction machine vehicle is introduced into the muffler body 1 by an exhaust introduction pipe 2. The exhaust sound discharged from the introduction hole 2c of the exhaust introduction pipe 2 does not immediately flow into the communication pipe 12, but collides with the side wall member 8a on one side and is absorbed (muffled). Further, the first expansion chamber 11 is sufficiently expanded to absorb sound.

  The exhaust sound enters the communication pipe 12 and comes into contact with the long glass fiber 20 through the through hole 12c and is absorbed. At this time, the long glass fiber 20 tends to be drawn into the communication pipe 12 due to the air flow of the exhaust gas, etc., but since one is a long continuous (not short fragment) fiber, the sound absorption is performed through the through hole 12c. It is not discharged together with the exhaust from the chamber 13 and is not scattered into the atmosphere. Since the long glass fiber 20 is not reduced by scattering, the silencing effect is stably continued and the sustainability of the quality (sound absorbing effect) is improved.

  Exhaust sound from the other opening 12b of the communication pipe 12 collides with the outer peripheral wall of the exhaust discharge pipe 3 and is absorbed, and is expanded into the second expansion chamber 14 to be absorbed. That is, the outer peripheral wall of the exhaust discharge pipe 3 near the other opening 12b of the communication pipe 12 is also used as a collision wall member for sound absorption (especially for sound absorption on the low sound side). In addition, since the number of chambers inside the main body is small, each one (the first and second expansion chambers 11 and 14 and the sound absorbing chamber 13) is sufficiently wide so that not only a sound absorbing effect can be obtained but also exhaust from the internal combustion engine. Flows smoothly and back pressure decreases. Exhaust air that has been sufficiently absorbed (quiet exhaust) is discharged to the atmosphere via the exhaust discharge pipe 3.

Table 1 below shows the results of comparative verification of the sound absorption effect and the back pressure reduction effect of the above-described embodiment (example) of the present invention and the comparative example shown in FIG. In the comparative example, the inside of the muffler main body 61 is provided in a two-layer tube structure, and the annular space between the outer cylinder member 67 and the inner cylinder member 60 is filled with a short piece of glass fiber 70 to prevent scattering. . The outer dimensions of the example and the comparative example are formed equally.
The comparison results in Table 1 are values obtained by subtracting the db value of the comparative example from the db value of the example, and a negative value means that the effect is improved. Further, the exhaust sound was measured a plurality of times at a position 45 degrees and 150 mm apart in the discharge direction with respect to the axial center of the outlet portion of the exhaust discharge pipe 3 and the exhaust discharge pipe 63 of the comparative example. The back pressure was measured a plurality of times inside the vicinity of the inlet of the exhaust introduction pipe 2 and the exhaust introduction pipe 62 of the comparative example. The numerical values shown in Table 1 are average values.

  As is clear from Table 1 above, the embodiment according to the present invention is a comparative example for the low frequency range (low frequency sound) of 250 Hz or less and the high frequency range (high frequency sound) of 2 k (2000) Hz or more. It is more effective in absorbing sound. Moreover, it can be said that the reduction | decrease effect of a back pressure is fully exhibited. Further, the sound pressure level is sufficiently reduced even in the entire exhaust sound, and a noise prevention effect is obtained.

  As described above, the present invention includes the first expansion chamber 11 connected to the exhaust introduction pipe 2, the second expansion chamber 14 connected to the exhaust discharge pipe 3, the first expansion chamber 11, and the second expansion chamber 14. And a communication pipe 12 having a large number of through holes 12c in the peripheral wall, and a sound absorption chamber 13 disposed between the first expansion chamber 11 and the second expansion chamber 14 and surrounding the outer periphery of the communication pipe 12. In addition, since the sound absorbing chamber 13 is filled with the glass long fibers 20, the sound pressure level of the high frequency (2000 Hz or more) and low frequency (250 Hz or less) exhaust sound can be reduced while having a simple, light and compact structure. The number of parts is small, the number of man-hours can be reduced, and it can be manufactured at low cost. By using the long glass fiber 20, it is possible to prevent the sound absorption effect from being lowered due to scattering. It is possible to reduce the back pressure and improve the fuel efficiency of the counterpart internal combustion engine. It is possible to reliably reduce the sound pressure level in the annoying sound range (high frequency side of 2000 Hz or higher and low frequency side of 250 Hz or lower) that gives a person discomfort. The filling operation of the long glass fiber 20 into the sound absorbing chamber 13 has an advantage that it can be performed with high efficiency by compressor air (compressed air).

  Further, the through holes 12c are arranged in a staggered manner, and the opening ratio of the peripheral wall in contact with the sound absorbing chamber 13 is set to 18% to 30%, so that the exhaust sound can be reliably absorbed. The long glass fiber 20 is prevented from entering the communication pipe 12 by the exhaust airflow. It is possible to prevent scattering and improve the sustainability of the sound absorption effect. A stable sound absorption effect can be obtained over a long period of time.

1 Muffler body 2 Exhaust pipe
3 exhaust exhaust pipe
7 cylinder wall member
8a, 8b pair of side wall members
11 1st extension room
12 communication pipe
12a one side opening
12b Opening on the other side
12c through hole
13 Sound absorption chamber
14 Second extension room
20 Long glass fiber

Claims (1)

A muffler main body (1) having a cylindrical wall member (7) and a pair of side wall members (8a) (8b) that respectively cover both end openings of the cylindrical wall member (7) in a cover shape, and the muffler main body (1 ) And an exhaust exhaust pipe (2) for exhausting exhaust from the muffler body (1),
Inside of the muffler body (1), the exhaust inlet pipe (2) and connected to the first expansion chamber a and (11), the exhaust discharge pipe (3) and connected to the second expansion chamber (14), A communication pipe (12) for connecting the first expansion chamber (11) and the second expansion chamber (14) and having a large number of through holes (12c) in the peripheral wall, the first expansion chamber (11) and the first expansion chamber A sound absorption chamber (13) disposed between the two expansion chambers (14) and surrounding the outer periphery of the communication pipe (12);
The exhaust introduction pipe (2) has the cylindrical wall member (2a) so that the tip (2a) side passes between the one side opening (12a) of the communication pipe (12) and the side wall member (8a) on one side. 7) is inserted into the first expansion chamber (11) and the tip (2a) is closed,
Further, the exhaust introduction pipe (2) has a large number of introduction holes (2c) in the peripheral wall inside the first expansion chamber (11), and the exhaust does not immediately flow to the communication pipe (12). The introduction hole (2c) is concentrated and formed near the side wall member (8a) on one side,
The exhaust discharge pipe (3) has a base-side open end (3a) inserted from the cylindrical wall member (7) into the second expansion chamber (14), and a peripheral wall of the communication pipe (12). The exhaust from the other side opening (12b) is arranged to collide,
In the communication pipe (12), the through holes (12c) are arranged in a staggered manner, and the opening ratio of the peripheral wall in the sound absorbing chamber (13) is 18% to 30%.
A muffler characterized in that the sound absorbing chamber (13) is filled with a long glass fiber (20).

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