JP2652594B2 - Muffler structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler structure for exhausting acoustic energy of exhaust gas of an engine to reduce noise.

[0002]

2. Description of the Related Art A muffler structure used for silencing exhaust noise of an automobile engine or the like includes, for example, those shown in FIGS.

FIG. 5 is a partial sectional view showing the internal structure of a muffler, and shows a double-walled drum 2 with a glass wool 1 interposed.
Are closed at both ends by end plates 3. The inside of the drum 2 is divided into a plurality of rooms by a separator 4 arranged in parallel with the end plate 3. Further, an inner pipe 5 is provided so as to pass through the center portions of the end plate 3 and the separator 4. The inner pipe 5 is provided with one or a plurality of closing plates 6 at appropriate positions so as to block the internal flow path and prevent pulsation noise, and is provided near the upstream side and the downstream side of the closing plate. A large number of holes 7 and 8 serving as exhaust passages are formed. The white arrow 9 indicates the flow direction of exhaust gas to the muffler.

FIG. 6 is an enlarged partial cross-sectional perspective view of a portion B in FIG. 5, in which the flow of exhaust gas whose flow path is blocked by the closing plate 6 is indicated by arrows. That is, the exhaust gas flowing through the inside of the inner pipe 5 is prevented from traveling straight by the closing plate 6, flows out of the hole 7 once to the outside of the inner pipe, and then returns from the hole 8 to the inside of the inner pipe again. .

[0005]

In the above-described conventional muffler structure, a flange surface 6a obtained by bending the circumferential portion of the closing plate 6 at a substantially right angle is fixed to the inner pipe 5 by spot welding. Was. In such a fixed structure, a narrow gap is often generated between the flange surface 6a and the inner surface of the inner pipe 5 due to the dynamic pressure of the exhaust flow, thermal deformation during welding, and dimensional errors. With this gap, some of the exhaust will pass through it at high speed,
When the wind noise at this time causes resonance, FIG.
5KHz as shown in the frequency analysis diagrams of (A) and (B)
There was a large noise level peak near the muffler noise. In order to prevent such a phenomenon, measures were taken to reduce the gap as much as possible by increasing the number of spot welding points, but it was difficult to completely eliminate the gap and reliably prevent muffler noise. .

Therefore, an object of the present invention is to provide a muffler structure capable of reliably preventing muffler noise caused by resonance of wind noise, without being limited to eliminating a gap between the flange surface and the inner surface of the inner pipe. Is to do.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an upstream side near and a downstream side of a closing plate provided with a flow path blocked inside an inner pipe penetrating the inside of a drum. A muffler structure in which a hole serving as an exhaust passage is formed in the vicinity, and exhaust gas flowing through the inner pipe is configured to once exit the inner pipe from the upstream hole and return to the inner pipe again from the downstream hole. The muffler structure according to any one of claims 1 to 3, wherein a communication hole for communicating an upstream side and a downstream side is provided in a circumferential portion of the closing plate.

[0008]

According to the above-mentioned means, the idea of eliminating the gap between the flange surface and the inner surface of the inner pipe is changed. Conversely, a communication hole larger than the conventional gap is provided in the circumferential portion to reduce wind noise. We have succeeded in making it smaller. That is, by providing a communication hole of an appropriate size in the circumferential portion of the closing plate and actively flowing a part of the exhaust gas from the upstream side to the downstream side, the gap between the flange surface and the inner pipe inner surface is reduced.
The noise generated by the wind is eliminated, and muffler noise is prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a muffler structure according to the present invention will be described with reference to FIGS. The same parts as those in the conventional structure are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a view corresponding to FIG. 6 of a conventional structure, in which a closing plate 11 is provided so as to block a flow path of exhaust gas flowing inside the inner pipe 5 to prevent pulsation noise. ing. The circumferential portion of the closing plate 11 is bent at a substantially right angle to form a flange surface 11a, but four communication holes 12 are formed by cutting out a part of the circumferential portion. The closing plate 11 is inserted to a predetermined position in the inner pipe 5, and the flange surface 11a and the wall surface of the inner pipe 5 are fixed by spot welding. Thus, the upstream side and the downstream side of the closing plate 11 communicate with each other through the communication hole 12, and a part of the exhaust gas can pass through the closing plate 11 through the communication hole 12. In addition,
In principle, the communication hole 12 formed in the closing plate 11 is provided in a circumferential portion. Further, the area of the communication hole 12 with respect to the cross-sectional area of the inner pipe 5 does not always show a constant value depending on various conditions such as conditions on the engine side and other structures of the muffler, but 80 to 120% of the area of the hole 7. Of degree
The range is a rough guide. At this time, what is most important is the length d in the radial direction of the communication hole 12 (see FIG. 2), and it is a rough guide to set d to a value substantially equal to the diameter of the hole 7.

According to the muffler structure having the above-described structure, the main flow of exhaust gas flowing inside the inner pipe 5 goes straight to the closing plate 11 attached for the purpose of preventing pulsation noise as shown in FIG. Partially, one part flows out of the pipe through the hole 7. At the same time, the remaining exhaust gas flows through the communication hole 12 in the circumferential portion, and merges with the flow flowing from the hole 8 on the downstream side of the closing plate 11. For this reason,
Even if there is a small gap between the flange surface 11a and the inner surface of the inner pipe 5, the exhaust gas that travels straight in the inner pipe 5 passes through the communication hole 12 with less resistance. Therefore, the wind noise generated when the exhaust gas passes through the small gap at a high speed is prevented, and as shown in the test results shown in FIGS. Is eliminated.

In the above embodiment, four band-shaped communication holes 12 are provided, but in other embodiments,
Other shapes such as a circle or an ellipse may be used, and the number is not limited to four. However, if the communication hole 12 is too large or too close to the center of the closing plate 11, the pulsating sound silencing effect, which is the purpose of the closing plate 11, is reduced. Holes need to be set.

[0013]

According to the muffler structure of the present invention described above,
Converting the conventional idea of eliminating the gap generated in the mounting part of the closing plate attached to the inner pipe for the purpose of preventing pulsation noise, providing a communication hole of an appropriate size on the circumference of the closing plate By positively flowing a part of the exhaust gas, the wind noise can be prevented without reducing the pulsation noise silencing effect. As a result, the peak of the noise level near 5 KHz is eliminated, and a muffler structure having good performance without muffler noise is obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view showing a main part of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing a flow of exhaust gas in the muffler structure of the present invention.

4A and 4B are frequency analysis diagrams showing the effect of the present invention, wherein FIG. 4A shows a case at 1,400 rpm, and FIG. 4B shows a case at 1,600 rpm.

FIG. 5 is a partial sectional view showing an example of a muffler having a conventional structure .

FIG. 6 is a partial cross-sectional perspective view of a main part of a conventional structure.

[Explanation of symbols]

 2 Drum 5 Inner pipe 7, 8 hole 11 Closing plate 11a Flange surface 12 Communication hole

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuyoshi Takasaka 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Automotive Industries, Ltd. (56) References Fully open Showa 56-171616 (JP, U) Fully open Showa 61-70522 (JP, U) Actually open Hei 2-119916 (JP, U) Actually open Showa 57-3816 (JP, U)

Claims (1)

(57) [Claims] 1. A hole serving as an exhaust passage is formed in the vicinity of an upstream side and a downstream side of a closing plate provided in the inner pipe penetrating through the inside of the drum so as to block a flow path, and flows through the inner pipe. In a muffler structure in which the exhaust gas is configured to once exit the inner pipe from the upstream hole and return to the inner pipe again from the downstream hole, an upstream side and a downstream side are provided on a circumferential portion of the closing plate. A muffler structure characterized by having a communication hole through which the holes communicate.