JPS5919779Y2 - Silencer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an improvement in a muffler incorporated into an automobile exhaust system.

Background of the Technology As shown in FIG. 2, a conventionally used simple structure muffler 1 has a closed casing 5 formed by closing both ends of a cylindrical can body 2 with end plates 3.4. .

An inlet side exhaust conduit 6 and an outlet side exhaust conduit 7 are inserted into the casing 5 from the end plates 3 and 4, and both the exhaust conduits 6 and 7 are supported by a partition plate 8.9.

In this muffler 1, a large number of small holes 10 are provided in the inlet side exhaust conduit 6 and the partition plate 8, and the small holes 10 are used to expand and contract the exhaust gas.

A resonator pipe 11 is communicated with a chamber formed by the partition plate 9 and a part of the sealed casing 5, and this chamber is used as a resonance chamber 12, so that the sound is muffled by the resonance effect.

Furthermore, since the aperture ratio (the ratio of the total value of the hole area to the entire surface area) of the small holes 10 provided in the inlet side exhaust pipe 6 and the partition plate 8 is 20% or more, the small holes have a large effect on the propagation of sound waves. Inlet side exhaust pipe 6 or partition plate 8 provided
The boundary conditions can be considered by assuming that the part does not exist.

In particular, in this muffler 1, the boundary condition position (indicated by position a in the figure, where the sound waves flowing down in the inlet pipe 6 are first radiated to the outside from this exhaust pipe), where the aperture ratio of the small hole 10 is 20
% or more, this position a coincides with the position of the small hole 10 on the leftmost side in the figure (hereinafter referred to as the initial radiation position), but it is located to the right in the figure compared to the position of the inlet 13 of the outlet side exhaust conduit 7. be.

Moreover, if we also take into account this pipe end correction of the outlet side exhaust pipe 7 (generally expressed as 0.3D when the inner diameter of the outlet side exhaust pipe 7 is D), we can consider that when a sound wave enters the outlet side exhaust pipe 7, The boundary condition position (already shown in the figure, hereinafter referred to as the sound wave introduction position) is on the left side of the outlet side exhaust pipe 7, and the pipe length from the end plate 3 to the initial radiation position a and the partition plate 9
The overlapped portion R with the pipe length from the point to the sound wave introduction position becomes large.

In this way, in a silencer having a wrapped portion R between the initial radiation position a and the sound wave introduction position, the main traveling wave of the sound wave (specifically, from the population side exhaust pipe 6 to the exit side exhaust pipe In the artificial side exhaust pipe 6, there is a so-called branch B between the initial radiation position a and the partition plate 9.
1, and in the outlet side exhaust conduit 7, the sound wave is generated between the end plate 3 and the end plate 3 at B2.

Problems with the Prior Art In this type of silencer, the silencing effect improves in principle if both the first branch B1 and the second branch B2 are long;
Most silencers are in the m range, and the overall length of this muffler is severely limited due to the structure of the automobile.

Moreover, if the length of the first branch B1 is more than about 185 mm, a so-called squeaking sound will occur, so the length must be less than this, and the length of the second branch B2 is about 80 mm.
If it is less than mm, a new problem arises in that the back pressure on the engine side increases.

In particular, when muffling noise using the branch effect as described above, if the branch length is L and the frequency at which the sound speed is attenuated by C1 is f, then there is a relationship: f, = C/4 L, and this relational expression can be used. Then, 300~8
If we calculate the length of the branch that attenuates the intermediate frequency of 00 Hz, it will be about 100 to 300 mm.

Manufacturing a silencer so that the length of the branch fits within such a narrow range (approximately 100 to 300 mm) is difficult because the overall length of the silencer is limited depending on the vehicle model, so it is difficult to manufacture a silencer so that the length of the branch fits within such a narrow range (approximately 100 to 300 mm). In a silencer having such a portion R, the degree of freedom in designing the silencer is narrowed accordingly, and manufacturing becomes even more troublesome.

Additionally, experiments have shown that the above-described muffler having the wrapped portion R has a poor muffling effect at intermediate frequencies, and improvements in this respect are desired.

Purpose of the invention Therefore, the present invention was made in consideration of such requests.
The length of the pipe from the end plate on the inlet side to the initial radiation position where the sound waves are emitted in the exhaust pipe on the inlet side does not overlap with the length of the pipe from the partition plate forming the resonance chamber to the position where the sound waves are introduced in the exhaust pipe on the discharge side. The purpose of the present invention is to provide a muffler with improved muffling effect.

Composition of the Device In order to achieve the above object, the present invention provides a large number of small holes of the inlet side exhaust pipe in the first expansion chamber and the second expansion chamber (the opening ratio of the small holes is 20% or more), and The pipe length from the end plate to the small hole with an aperture ratio of 20% or more opened in the inlet side exhaust pipe and the pipe length from the exit side partition plate to the sound wave introduction position of the outlet side exhaust pipe are made so that they do not overlap. be.

Example Hereinafter, the silencer according to the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing one embodiment of the same muffler 20, and the same members as in FIG. 2 are given the same reference numerals.

This muffler 20 forms a sealed casing 5 by closing both ends of the cylindrical can body 2 with end plates 3.4,
An inlet side exhaust conduit 21 and an outlet side exhaust conduit 22 are provided through the end plate 3 or 4, and both exhaust conduits 21 and 22 are supported by partition plates 8 and 9.

Furthermore, the partition plate 8 divides the inside of the silencer 20 into the first expansion chamber 15 and the second expansion chamber 15.
The partition plate 9 forms a resonance chamber 12.

A large number of small holes 10.10a are formed in each of the inlet side exhaust conduit 21 and the partition plate 8.

Since the aperture ratio of this small hole 10.10H is over 20%,
When determining boundary conditions regarding the propagation of sound waves, the propagation of sound waves may be considered assuming that the entrance side exhaust pipe 21 and the partition plate 8 do not exist in the portion where the small holes 10, 10a are opened.

In particular, in the present invention, the initial radiation position a is the boundary condition position where the sound wave is first radiated from the inlet side exhaust conduit 21.
The length B1 of the pipe from the end plate 3 to the end plate 3 (this length corresponds to the branch to the artificial side exhaust pipe) and the sound wave introduction position where the sound wave enters the outlet side exhaust pipe 22 from the root of the partition forming the resonance chamber 12. The length B2 of the pipes (this length corresponds to the branch to the outlet-side exhaust conduit) is configured so that they do not overlap.

Here, the reason why the position of the branch with respect to the inlet side exhaust pipe and the outlet side exhaust pipe has changed compared to the conventional example is as follows.
The main traveling wave of the sound wave in the silencer (specifically, the shortest distance traveling wave of the sound wave in the silencer 20 propagating from the inlet side exhaust pipe 21 to the outlet side exhaust pipe, that is, from the position a to the position b in the figure) This is because the direction of the sound wave (progressing to) has been reversed, and the position of the so-called branch, which forms an interference region with the main traveling wave of the sound wave and exerts a silencing effect, changes.

Unlike what is shown in FIG. 2, if the overlapping portion R is eliminated, the first branch B1 generated in the inlet side exhaust pipe 21 will be generated between the end plate 3 and the initial radiation position a, and the first branch B1 will be generated between the end plate 3 and the initial radiation position a, and The second branch B2 on the exhaust pipe 22 side is formed between the sound wave introduction position and the partition plate 9.

The branch is the part that becomes the muffling area for the main traveling wave of the sound wave, so when the sound wave returns from the initial radiation position a to the sound wave introduction position as in the case of a muffler as shown in Fig. 2, the position of the branch is is different, as shown in FIG.

Therefore, when trying to keep the length of the branch within a narrow range, it is not necessary to consider the length of the wrapped portion R, making design and manufacturing easy, and moreover, the length of the branch can be adjusted to the wrapped portion R. You can take an extra R.

According to the present invention, since the branch length can be freely selected, the most preferable frequency (300 to 800 Hz) at which noise can be suppressed by this muffler as shown in FIG.
), the overall muffling by this branch will be further improved if the branch length is chosen to produce a peak effect of attenuation at ).

That is, for example, if the frequency at which the peak effect occurs is set to 550
If the branch length is selected and designed so that
Since the peak effect appears exactly in the middle of 00 to 800 Hz, the silencing effect is improved over almost the entire intermediate frequency where the muffling effect of this muffler is most expected.

Further, this inlet side exhaust pipe 21 has a non-porous section 24 following the section 23 in which the small hole 10 is interposed, and this non-porous section 2
4 has a portion thereof protruding into the resonance chamber 12.

Therefore, in the resonance chamber 12, the capacity within the resonance chamber changes depending on the length t by which the non-porous section 24 protrudes from the partition plate 9, and the resonance effect here allows tuning of the frequency at which the sound is muted.

In particular, since the inlet side exhaust conduit 21 also functions as the resonator pipe 11 shown in FIG. 2, the resonator pipe shown in FIG. 2 is not required, and the structure can be simplified.

In the above-mentioned embodiment, the outlet side exhaust conduit 22 is non-porous, but the present invention is not limited to this in any way, and the pipe 22 may be provided with a large number of small holes.

In this case, the length of the branch B2 is naturally equal to the length from the partition plate 9 to the small hole plus the tube end correction.

Effects of the invention As is clear from the above explanation, according to the invention, the length of the pipe from the end plate on the artificial side to the initial radiation where sound waves are emitted from the inlet side exhaust pipe, and the length from the partition plate forming the resonance chamber to the outlet. The length of the exhaust pipe up to the sound wave introduction point was made to not overlap, so that the sound waves from the inlet exhaust pipe entered the outlet exhaust pipe without returning, so the length of the branch was adjusted to take into account the above-mentioned overlapped part. In this case, the length of the branch can be made longer by the wrapped portion, which improves the silencing characteristics, especially the intermediate frequency that should be the most muted, and facilitates design and manufacturing.

In addition, since a part of the non-porous part formed at the end of the inlet-side exhaust conduit on the inside of the muffler protrudes into the resonance chamber provided in the muffler, there is no need to provide a separate resonator pipe, and the internal structure of the simple muffler This results in extremely excellent effects such as further simplification and easier production.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a simple muffler according to the present invention, Fig. 2 is a schematic longitudinal cross-sectional view of a conventional simple muffler, and Fig. 3 shows the amount of attenuation for intermediate frequencies of the muffler according to the present invention. It is a graph. 2...Tubular can body, 3, 4...End plate,
5... Sealed casing, 8, 9... Partition plate, 10, 10a... Small hole, 12...
・Resonance chamber, 15... First expansion chamber, 16...
...Second expansion room, 20...Silencer, 21...
... Inlet side exhaust pipe, 22 ... Outlet side exhaust pipe, 24 ... Non-porous part, a ... Initial radiation position, b ... Sound wave Inlet, Bl, B! ...
···branch.

Claims (2)

[Scope of utility model registration request] (1) It has a sealed casing 5 in which both ends of the cylindrical can body 2 are closed by end plates 3 and 4, and the tube ends are opened in the end plates 3 and 4, respectively, and the opening ratio is set at a predetermined position on the tube circumferential surface. An inlet side exhaust conduit 21 having a small hole 10 of 20% or more and an outlet side exhaust conduit 22 having an open end are inserted through each other, and both exhaust conduits 21 and 22 are held and the inlet side exhaust conduit 21 is provided. A non-perforated partition plate 9 forms a resonance chamber 12 with open tube ends, and a non-porous partition plate 9 holds both the exhaust conduits 21 and 22 and connects the inside of the sealed casing 5 to a first expansion chamber 15 and a second expansion chamber 16.
In the muffler, the airtight casing 5 is provided with a partition plate 8 having a large number of small holes 10a that partition the small holes 10 of the inlet side exhaust pipe into the first expansion chamber 15 and the second expansion chamber 15.
A large number of pipe lengths B1 are provided in the expansion chamber 16 from the end plate 3 on the inlet side to the small holes 10 with an opening ratio of 20% or more opened in the inlet exhaust pipe 21, and from the partition plate 9 to the outlet. A silencer characterized in that the pipe length B2 of the side exhaust pipe up to the sound wave introduction position does not overlap. (2) The inlet side exhaust pipe 21 connects a part of the non-porous part formed at the inboard end of the exhaust pipe 21 to the resonance chamber 12.
1. A silencer as set forth in claim 1 of the utility model registration claim, which protrudes from the interior of the vehicle.