JPS6118171Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a muffler attached to an automobile exhaust pipe.

Utility Model Application No. 56-150812 (Utility Application No. 55-49146), in which the present applicant previously proposed an improved muffler as shown in FIG. A cylindrical tube 2 having a small diameter at the center and gradually increasing in diameter toward both ends is arranged in a sealed outer casing 1, and an enlarged section 3a that gradually decreases from one end to the center and an enlarged section 3a from the center to the other end. A small hole 4 is formed in the center of the cylindrical tube 2 to provide a resonance chamber 5 between the cylindrical tube 2 and the outer casing 1. This is a muffler with a front exhaust pipe 6 fixed to one end and a rear exhaust pipe 7 fixed to the other end by welding, and the exhaust gas sent into the muffler from the front exhaust pipe 6 is expanded to gradually decrease from one end to the center. It flows out to the rear exhaust pipe 7 through an expansion chamber 3 having a portion 3a and an expansion portion 3b that gradually increases from the center to the other end,
At this time, the smooth two-stage expansion of the expansion chamber 3 and the stretching resonance of the resonance chamber 5 effectively remove both low-frequency noise and high-frequency noise contained in the exhaust gas.

However, even with the silencing effect of the expansion chamber 3 and the silencing effect of the resonance chamber 5, a considerable amount of noise still remains, and a sufficient silencing effect may not be expected.

The present invention has been made in view of the above, and an object of the present invention is to provide a muffler that can be expected to have a sufficient muffling effect.

The silencer according to the present invention has a cylindrical tube whose diameter gradually increases from the center toward both ends in a sealed outer casing, and has an expanding section whose diameter gradually decreases from one end toward the center and the other from the center. In the cylindrical tube of the silencer, an expansion chamber having an expansion portion that gradually increases toward the end is provided, and a small hole is formed in the center of the cylindrical tube to provide a resonance chamber between the cylindrical tube and the outer casing. A through pipe is provided that penetrates between both ends of the outer casing, and a sound wave reflector is arranged in a portion of the through pipe that corresponds to the enlarged diameter portion of the cylindrical pipe. A large number of small holes are respectively formed near the exhaust discharge end, and will be explained in detail below with reference to the drawings.

In this specification, the sound wave reflector is a material that can reflect sound waves and allow gas to pass through, such as a plug with small holes, open cell material, steel wool, glass wool, etc. be. In other words, this sound wave reflector reflects 100% of the sound waves.
It does not need to reflect, nor does it need to transmit 100% of gas, and a material with appropriate sound wave reflectance and gas permeability can be selected depending on the noise level and exhaust volume.

FIG. 2 shows an embodiment of the silencer of the present invention.

The outer casing 8 is a sealed hollow cylinder, in which a cylindrical tube 9 is arranged which has a small diameter in the center and gradually increases in diameter toward both ends, and gradually decreases in diameter from one end inside the outer casing 8 toward the center. An expansion chamber 10 is provided, which has an expansion section 10a that gradually increases in size from the center toward the other end. Further, a small hole 11 is formed in the center of the cylindrical tube 9 to provide a resonance chamber 12 between the cylindrical tube 9 and the outer casing 8. The penetrating tube 13 is a tube that penetrates between both ends of the outer casing 8, and is located inside the cylindrical tube 9, that is, inside the expansion chamber 10, and inside this tube, there is a sound wave reflecting plate made of a foamed metal plate, a plug with small holes, etc. A body 14 is arranged. This reflector 14 does not necessarily have to be a perforated plate, and may be made of steel wool, glass wool, or the like. That is, this reflector 14 partially reflects sound waves and partially transmits exhaust gas. Expanded portions 10a or 10b before and after the portion where the sound wave reflector 14 is arranged
An appropriate number of small holes 15a and 15b are provided near the exhaust gas introduction end and the exhaust gas discharge end of the through pipe, respectively. In this embodiment, the front exhaust pipe 16 is fitted to one end of the through pipe 13;
A rear exhaust pipe 17 is fitted to the other end and fixed by welding.

The silencer according to the present invention has such a structure, in which exhaust gas moves from the front exhaust pipe 16 into the through pipe 18 of the silencer, and from there is divided into two parts.
Most of them pass through the expansion chamber 10 through the small hole 15a and return to the through tube 13 again through the small hole 15b, while the other part passes directly through the through tube 13, passes through the sound wave reflector 14, and passes through the small hole 15b. The exhaust gas returned into the through pipe 13 is exhausted from the rear exhaust pipe 17. The noise contained in the exhaust gas that has detoured into the expansion chamber 10 is removed by smooth two-stage expansion section 10a that gradually decreases from one end toward the center and expansion section 10b that gradually increases from the center toward the other end. Eliminate by expansion and long detour distance. Moreover, low-frequency noise contained in the exhaust gas is also eliminated at the same time by the resonance effect when the exhaust gas passes through the side surface of the resonance chamber 12. On the other hand, the noise contained in the exhaust gas that has passed orthogonally through the through pipe 13 is partially reflected by the sound wave reflector 14, which causes interference with the noise that has proceeded subsequently, and is eliminated. That is, the through pipe 13 acts as an interference chamber between the small hole 15a and the sound wave reflector 14. Therefore, since the through pipe 13 is actively used as an interference chamber, it is desirable that the sound wave reflector 14 disposed inside the through pipe 13 be located as far back as possible at the engine noise frequency. However, depending on the purpose, if you want to eliminate noise with a short frequency, it is necessary to shorten the interference part, so it is placed in the front position.

Note that the noise passing through the sound wave reflector 14 is attenuated by friction with the sound wave reflector 14.

Moreover, since the exhaust gas that has passed perpendicularly through the through pipe 13 is rectified by the sound wave reflector 14, secondary noise due to turbulent flow is less likely to be generated in the downstream region compared to exhaust gas that remains in a pulsating state. The noise contained in the exhaust gas is caused by the two-stage expansion effect of the expansion chamber 10, the resonance effect of the resonance chamber 12, and the sound wave reflector 14.
The noise is sufficiently eliminated by the interference effect, friction effect, long detour distance, etc., and when it is exhausted from the rear exhaust pipe 17, it can be exhausted as exhaust gas with extremely low noise. Further, according to the silencer of the above embodiment, the front and rear exhaust pipes 16 and 17 are fitted into the through pipe 13 passing between both ends of the outer casing 8 and fixed by welding.
The dead weight of the silencer is applied to the entire structure, eliminating local stress concentration and providing sufficient strength. Therefore, even if vibrations from the engine and road vibrations are applied to the front and rear exhaust pipes 16, 17 and the muffler, they will only vibrate as a whole, and no particular force will be applied to the welded parts, causing cracks. It becomes a durable silencer.

Note that the sound absorption characteristics vary slightly depending on the distances l and l' between both ends of the outer casing 8 and the small holes 15a and 15b formed in the through pipe 13.
5a and 15b, select the location with the best sound absorption characteristics by considering the model to which the silencer is installed, the length and diameter of the through pipe 13, the position of the muffler in the entire exhaust system, etc. It is important to form.

FIG. 3 is another embodiment of the present invention, showing a muffler in which a cylindrical tube provided within the outer casing is modified.

In this case, a cylindrical tube 19 provided in the outer casing 18 whose diameter gradually expands from the center toward both sides is shortened on one side (or both sides) to form an essentially expanded portion 20a.
This is a silencer in which the volume of the expansion part 20a and expansion chamber 20b is expanded. By doing this, it is possible to increase the noise expansion ratio and improve the silencing performance, and also to change the volume of the resonance chamber and correct the resonance frequency, making it possible to adjust for differences in noise characteristics depending on the car model. can.

Here, the expansion ratio, in the case of this embodiment, is the ratio of the expansion diameter when expanded in the small hole 15a (i.e., the inner diameter of the outer casing 18) and the diameter of the through tube 13, and the expansion ratio is large. Since sound waves have a large area and then proceed, they are susceptible to silencing effects and the amount of attenuation becomes large.
Note that by appropriately changing the distance L between one end of the outer casing 18 and the end of the cylindrical tube 19 provided inside the outer casing 18, the noise from low frequency sounds to high frequency sounds contained in the exhaust gas can be reduced. Since it is possible to change the characteristics to eliminate noise, it is desirable to select this distance L so as to obtain the optimum noise reduction effect.

According to the present invention as described in the embodiments above, the expansion chamber has a two-stage expansion action and has an expansion part that gradually decreases from one end to the other end and an expansion part that gradually increases from the center part to the other end. In addition to the resonance effect of the resonance chamber, there is a silencing effect due to the longer detour distance and an interference effect due to the sound wave reflector placed in the through pipe.
Together, the frictional effects sufficiently absorb both low- and high-frequency sounds contained in the exhaust gas, and when the exhaust gas is exhausted into the atmosphere from the exhaust pipe, it can be exhausted as extremely low-noise exhaust gas. Therefore, a sufficient sound deadening effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the muffler proposed earlier, Fig. 2 is a sectional view of a muffler according to an embodiment of the present invention, and Fig. 3 is a sectional view of a muffler according to another embodiment of the present invention. It is. 1, 8, 18... Outer casing, 2, 9, 19... Cylindrical tube, 3, 10, 20... Expansion chamber, 3a, 3b, 1
0a, 10b, 20a, 20b...Expansion chamber, 4,
11, 15a, 15b... Small hole, 5, 12... Resonance chamber, 6, 16... Front exhaust pipe, 7, 17... Rear exhaust pipe, 13... Penetration pipe, 14... Sound wave reflector.

Claims (1)

[Scope of utility model registration request] A cylindrical tube whose diameter gradually increases from the center toward both ends is arranged in a sealed outer casing, with an expansion section that gradually decreases from one end toward the center and an expansion section that gradually increases from the center toward the other end. In a silencer, an expansion chamber having an expansion part is provided, a small hole is formed in the center of the cylindrical tube, and a resonance chamber is provided between the cylindrical tube and the outer casing,
A through tube is provided in the cylindrical tube that penetrates between both ends of the outer casing, and a sound wave reflector is disposed in a portion of the through tube that corresponds to the enlarged diameter portion of the cylindrical tube, and the exhaust gas is introduced into the outer casing of the through tube. A silencer characterized in that a large number of small holes are formed near the end and near the exhaust discharge end.