JPS6337467Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) This invention relates to an improvement in a muffler that attenuates noise contained in engine exhaust gas.

(Background Art) In order to reduce the exhaust noise of an automobile engine, a muffler is connected in the middle of an exhaust pipe for discharging the exhaust gas from the engine into the atmosphere. In addition to the main silencer, such silencers usually include a front silencer and a rear silencer.
Although they are connected in series in the middle of the exhaust pipe, they all have a considerably larger cross-sectional area than the exhaust pipe, so
When installing under the floor of a car, there are restrictions on where it can be installed. However, the ability of a silencer to attenuate low-frequency components of noise changes depending on where it is installed, so conventionally it has not been possible to fully demonstrate the original performance of the silencer. Furthermore, the structure of the muffler itself tends to generate high-frequency secondary noise due to eddy currents inside the muffler, and this secondary noise results in unsatisfactory high-frequency muffling performance.

As a muffler for solving such inconveniences, the mufflers disclosed in U.S. Pat. These silencers are
The exhaust pipe is branched into two parallel pipes,
At least one of a throttle tube and a closing plate is fitted in the middle of one tube. Furthermore, as a muffler that improved these mufflers, a practical application was made in 1983.
There is a silencer related to No. 49888. This muffler is constructed, for example, as shown in Fig. 1, in which an inlet pipe section 1 into which exhaust gas from the engine is sent from the left as shown by the arrow is parallel to each other by a first branch section 2. It branches into a first pipe part 3 and a second pipe part 4. The rear end portions of the first and second pipe portions 3 and 4 (the end on the far side from the engine, the right end portion in the drawing) each communicate with a first throttle merging portion 5 having a small cross-sectional area. Further, the first throttle merging section 5 is branched by a second branching section 6 into a third pipe section 7 and a fourth pipe section 8 which are parallel to each other. Further, the rear end portions of the third and fourth pipe portions 7 and 8 each communicate with a second throttle merging portion 9. This second throttle merging section 9 further includes a third branching section 1
0, it branches into two parallel pipes 11 and 12. The rear ends of these tubes 11, 12 are open, and a large number of small holes 13, 13 are bored around them. A cover pipe 14 is attached to each of them. The inner peripheral surface of this tube 14 and each tube 11,
A cylindrical space between the outer peripheral surface of the sound absorbing material 15 and the outer peripheral surface of the sound absorbing material 15 is filled. Further, a closing plate 16 is fixed to the middle of the second tube section 4 and the third tube section 7, respectively, and closes the cross sections of the second and third tube sections 4 and 7.
Therefore, the second pipe section 4 and the third pipe section 7 are connected to the closing plate 16.
Therefore, the left and right chambers 4L, 4R, 7L, 7 respectively
It is divided into R. Each room 4L, 4R, 7
Exhaust gas does not flow through L and 7R, and each chamber acts as a branch pipe for attenuating sound waves. If a branch pipe of length lx with the end blocked is installed on the side of the exhaust flow path, the frequency x of the noise attenuated by this branch pipe becomes x=c/4lx (c: speed of sound), so the blockage By appropriately varying the lengths of the chambers 4L, 4R, 7L, and 7R depending on the position where the plate 16 is provided, it is possible to attenuate noise at various frequencies. That is, FIG. 2 shows a structure that functions similarly to the silencer shown in FIG. 1, and parts equivalent to those in FIG. To explain the function of the silencer shown in FIG. 1 with reference to FIG. 2, the exhaust gas that has entered the inlet pipe portions 1 and 1a is
It flows towards the first pipe portions 3 and 3a through the chambers 4L and 4La, which have a length of l ₁ and act as branch pipes, so that the frequency _{is 1} (=c/4l ₁ )
noise is attenuated. The exhaust gas that has flowed through the first pipe portions 3, 3a then flows to the first throttle merging portions 5, 5a,
It then flows into the second branch portions 6, 6a, at which time the noise is attenuated by contraction and expansion of the flow path. Further, the rear side of the first throttle merging section 5, 5a has a length l ₂
The chambers 7L and 7La are on the front side, and the chambers _4R and 4Ra are on the front side.
are branched, so the frequency ₂ during exhaust
(=c/4l ₂ ), ₃ (=c/4l ₃ ) noise is attenuated. The exhaust gas further flows from the second branch portions 6, 6a into the fourth pipe portions 8, 8a, and further flows into the second throttle merging portions 9, 9a.
through which it flows into the third branch 10, 10a. During this time, the exhaust air repeatedly contracts and expands to attenuate noise. . In addition, since chambers 7R and 7Ra having a length _l4 are branched on the front side of the second throttle merging sections 9 and 9a, the frequency of the exhaust air before passing through the second throttle merging sections 9 and 9a is ₄ (=c/4l ₄ ) of noise is attenuated. The exhaust gas further flows into the pipes 11, 11a, 12, 12a from the third branch part 10, 10a, and is dissipated into the atmosphere from the rear end openings of both pipes.
Many small holes 1 in the middle of 1, 11a, 12, 12a
3, 13a, the noise components in the exhaust, especially high frequency components, are attenuated by the surrounding sound absorbing materials 15, 15a. Therefore, when dissipating into the atmosphere from the rear end openings of both pipes 11, 11a, 12, 12a, the noise in the exhaust is well suppressed over all frequencies,
No more exhaust noise spreading around. In particular, engines often generate noise in a specific frequency range depending on their displacement, normal rotation speed, etc., but as mentioned above, each chamber 4L, 4La, 4R,
By changing the lengths of 4Ra, 7L, 7La, 7R, and 7Ra, the frequency of the noise to be attenuated can be easily changed, making it easy to obtain the best silencer for the engine. Furthermore, if the lengths _l1 to _l4 of each chamber are varied stepwise, noises of different frequencies ₁ to ₄ can be attenuated, as shown in FIG.

However, even with the previously invented muffler constructed and operated as described above, the following problems still occur. That is, in order to attenuate a particularly low part of the low frequency components of noise with such a muffler, one of the chambers 4L, 4R,
7L and 7R must be formed sufficiently long, but in the case of a silencer installed in a limited space such as under the floor of a car, there is a limit to the length of each pipe part 4 and 7, so the length shown in Fig. 1 is The tube portion 4,
7, for example, if one chamber 4L provided in the pipe section 4 is made sufficiently long, the other chamber 4R will become extremely short, making it impossible to attenuate the slightly higher part of the low frequency component in the noise. I get used to it.

(Purpose of the present invention) In order to solve the above-mentioned inconveniences, the present invention
The total length of the pair of chambers provided at both ends of the tube can be made longer than the length of the tube by the blocking plate, and low frequency components of noise can be effectively attenuated over a wide frequency range. The purpose is to provide a silencer that can.

(Structure of the present invention) The silencer of the present invention has pipes for guiding the exhaust gas of the engine that are parallel to each other and communicate with each other at both the front and rear ends.
By branching into a pair of tubes and partitioning one tube in the middle in the length direction by biting into each other, a pair of chambers whose inner parts are closed in the one tube can be created. is forming.

With this configuration, each chamber acts as a branch pipe having a length from the inlet to the inner surface including the biting portion, and the total length of both chambers becomes longer by the length of the biting portion.

(Embodiments of the present invention) Next, the present invention will be explained in more detail while explaining the illustrated embodiments.

FIG. 4 shows an embodiment of the silencer of the present invention. The same reference numerals are given to the same parts as those of the silencer according to the previous invention described above, and redundant explanation will be omitted, and the characteristic parts of the present invention will be explained below. A closing plug 17 is fitted in the middle of each of the second pipe part 4 and the third pipe part 7 that constitute the muffler. As shown in FIG.
An outward flange 19 is provided at the open end of the bottomed cylindrical portion 18 which has a diameter sufficiently smaller than the inner diameter of the tube 7 and which is closed at one end. A short cylindrical portion 20 that can be fitted inside is formed. Such a closing plug 17 is
As shown in FIG. 4, the outer peripheral surface of the short cylindrical portion 20 is brought into close contact with the inner peripheral surface of the tube portion 4 or
The center of the tube 4 and the center of the tube portions 4 and 7 are made to coincide with each other, and the tube portions 4 and 7 are fixed inside each other. In this way, each pipe section 4,
By fixing the blocking plug 17 in the middle of the tube 7, each tube part 4, 7 is connected to the left and right chambers 4L, 4R, 7L,
It is divided into 7Rs, and each chamber acts as a branch chamber.
To explain the frequency attenuated by each chamber, taking the chambers 4L and 4R of the second pipe section 4 as an example, the length of the left chamber 4L is from the entrance of the chamber 4L to the plug 1.
7 to the outward facing flange 19, and the length of the right chamber 4R is the length _l3 from the entrance of the chamber 4R to the depth of the bottomed cylindrical portion 18 of the plug ₁₇ .
Since the cross-sectional area of each chamber 4L and 4R changes in the middle,
The frequency x attenuated in each chamber 4L, 4R is not exactly c/4lx, but if the ratio of the cross-sectional area change is not extremely large, it is approximated by x≈c/4lx. Therefore, the bottomed cylindrical portion 1 of the closing plug 17
If the cross-sectional area of 8 is set to about 1/2 of the cross-sectional area of each tube part 4, 7, the ratio of the above-mentioned cross-sectional area change can be kept small on either side of the chamber.
It is possible to attenuate the noise component of frequency _1≈c /4l ₁ in room L, and the noise component of frequency _3≈C /4l ₃ in room 4R. Length of chamber 4L l ₁
The sum (l ₁ +l ₃ ) of the length l ₃ of the chamber 4R is the second pipe part 4
Because it is longer than the length by the length of the biting part of both chambers 4L and 4R (the length of the short cylindrical part 18),
Even if the length of the second pipe section 4 is limited, the lengths of both chambers 4L and 4R can be made sufficiently large, so that even considerably low frequency parts of the noise components in the exhaust can be effectively attenuated. become. This means that the third pipe section 7
The same applies to the chambers 7L and 7R provided in the above.

Next, FIGS. 6 and 7 show a second embodiment of the present invention. In this embodiment, as shown in FIG. 7, semicircular folded walls 21b are provided at both ends of a flat plate portion 21a having a width that matches the inner diameter of the second tube portion 4 (the third tube portion 7 is also the same). As shown in FIGS. 6A and 6B, the partition plate 21, which is formed by bending the partition plates 21b at right angles in opposite directions, is fixed in the middle of the second pipe part 4. is partitioned into left and right chambers 4L, 4R, and a portion of both chambers 4L, 4R are wedged into each other in the length direction. In the case of this second embodiment as well, the total length of both chambers 4L and 4R is the length of the biting part (partition plate 2
1 length).

In the first and second embodiments described above, the thickness of the second pipe portion 4 itself was configured so as not to change midway, but as in the third embodiment shown in FIG. Alternatively, the second pipe portion 4 may be constructed by connecting a small diameter pipe 22a and a large diameter pipe 22b, and the ends of both pipes may be closed, and a biting portion may be provided at the connecting portion.

Further, as in the fourth embodiment shown in FIG. 9, the deep parts of each chamber 4L, 4R may be filled with a sound absorbing material 23 such as glass wool, steel wool, rock wool, etc. The surface of the sound absorbing material 23 is made of punching metal,
It is held down with a porous holding plate 24 such as forming metal. When the sound absorbing material 23 is filled in the depths of the chambers 4L and 4R in this way, the length of each chamber 4L and 4R becomes shorter by the thickness of the sound absorbing material 23, and the frequency of the noise to be attenuated becomes a little higher, but the sound absorption Due to the action of the material 23, the amount of noise attenuation is improved as a whole, and good silencing performance can be obtained. That is, when the sound absorbing material 23 is not provided, in each chamber 4L, 4R, the 10th
Although the sound deadening effect as shown by the solid line in the figure can be obtained, if the sound absorbing material 23 is filled in the deep part of each chamber 4L, 4R, the sound deadening effect as shown by the chain line in the figure can be obtained. By filling the sound absorbing material 23,
Although the attenuation frequency moves to the high frequency side and the maximum attenuation decreases, it becomes possible to obtain a relatively large amount of attenuation over a wide frequency range, and the overall silencing performance improves.

Note that the silencer of the present invention only needs to have at least one pair of pipe portions that are parallel to each other, and as in the illustrated example, there are two pairs of pipe portions that are parallel to each other.
There is no need to exist. Further, the structure of the portions other than the pair of parallel tube portions, such as the rear end tubes 11 and 12, is not limited to such a structure.

(Effects of the present invention) Since the silencer of the present invention is constructed and operates as described above, it can be constructed without particularly increasing the cross-sectional area, and the degree of freedom is increased when it is installed under the floor of an automobile. In addition, since a long muffler can be constructed that spans the entire length of the underfloor, it is possible to effectively attenuate low-frequency noise, which was previously considered difficult, and due to the structure, it is possible to effectively attenuate high-frequency noise caused by eddy currents inside the floor. In addition to the same effect as the previous design, which was said to be difficult to achieve, it is also possible to effectively attenuate even lower frequency noise components without increasing the overall length of the muffler.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing a muffler according to an earlier invention;
Fig. 2 is a schematic sectional view showing a muffler equivalent to the muffler shown in Fig. 1, Fig. 3 is a diagram showing the state of noise attenuation in the branch pipe portion of the muffler shown in Figs. The figure is a schematic cross-sectional view showing the first embodiment of the silencer of the present invention, FIG. 5 is a perspective view of the plug, FIGS. 7 is a partial schematic sectional view of the pipe portion, FIG. 7 is a sectional view taken along the line X-X in FIG.
9 is a sectional view similar to FIG. 8 showing the fourth embodiment, and FIG. 10 is a diagram showing the noise damping effect obtained by the structure of FIG. 9. 1: Inlet pipe part, 2: First branch part, 3: First pipe part, 4: Second pipe part, 4L, 4R: Chamber, 5: First throttle merging part, 6: Second branch part, 7: Third pipe section, 7
L, 7R: chamber, 8: fourth pipe section, 9: second throttle merging section, 10: third branch section, 11, 12: pipe, 13:
Small hole, 14: Covered pipe, 15: Sound absorbing material, 16: Closure plate,
17: Closing plug, 18: Bottomed cylindrical part, 19: Outward flange, 20: Short cylindrical part, 21: Partition plate, 2
1a: flat plate part, 21b: folded wall, 22a: small diameter pipe, 22b: large diameter pipe, 23: sound absorbing material, 24: restraining plate.

Claims (1)

[Scope of utility model registration request] The pipe that guides the exhaust from the engine is branched into a pair of pipe parts that are parallel to each other and communicate with each other at both the front and rear ends, and one pipe part is partitioned by cutting into each other in the length direction, and this pipe part has a deep part. A silencer consisting of a pair of closed chambers.