JP4084448B2 - Automotive exhaust muffler - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automobile exhaust muffler, and in particular, includes an inner pipe connected to an exhaust pipe of an engine and having a large number of through holes in a peripheral wall, and an outer shell that defines a silencer chamber on the outer periphery of the inner pipe. The present invention relates to improvement of an exhaust muffler installed under the floor.
[0002]
[Prior art]
In such an exhaust muffler for automobiles, a partition cylinder that has a large number of through holes in the peripheral wall and surrounds the inner pipe is disposed in the outer shell, and the partition cylinder is wound while metal wool is wound around the outer peripheral surface of the inner pipe. It is known that the inside is a hollow expansion chamber and the outside of the partition tube is a sound absorbing chamber filled with a sound absorbing material (see, for example, JP-A-8-144735).
[0003]
[Problems to be solved by the invention]
In the conventional exhaust muffler, the hollow expansion chamber contributes to the attenuation of the low and medium frequency exhaust sound, and the sound absorption chamber filled with the sound absorbing material contributes to the absorption of the medium and high frequency exhaust sound. Further, the high heat of the exhaust gas is blocked by the metal wool so that the sound absorbing material is not deteriorated by the high heat.
[0004]
By the way, the expansion chamber can increase the attenuation effect of low and medium frequency exhaust noise as the cavity volume is large. However, in the conventional exhaust muffler, metal wool is arranged on the outer peripheral surface of the inner pipe. Therefore, the metal wool reduces the cavity volume of the expansion chamber, and lowers the low and medium frequency attenuation performance. Therefore, if a sufficient cavity volume is taken, the size of the outer shell will inevitably be increased.
[0005]
The present invention has been made in view of such circumstances, and provides the above-described automobile exhaust muffler capable of effectively attenuating and absorbing low-frequency to high-frequency exhaust sound without causing an increase in the outer shell size. The purpose is to do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 defines an inner pipe connected to an exhaust pipe of an engine and having a large number of through holes in the peripheral wall in the entire circumferential direction , and a sound deadening chamber is defined around the inner pipe. An exhaust muffler for an automobile having an outer shell that is installed under the floor of the automobile, wherein the silencer chamber has a plurality of through holes except for its lower portion in a peripheral wall, and a partition cylinder surrounding the inner pipe. The partition tube is divided into a hollow expansion chamber that does not have a sound absorbing material, and a sound absorbing chamber that occupies the outside of the partition tube and is filled with a sound absorbing material. Wool layers are gathered together, and the outer shell cylinder is formed so that its cross section is elliptical with its long axis oriented horizontally, while the axis of the inner pipe is below the long axis and the Than the axis of the partition cylinder Characterized in that arranged on the side.
[0007]
According to this feature, the expansion chamber is a large volume cavity that does not have a sound absorbing material, so the expansion effect of the exhaust gas that has migrated from the inner pipe to the partition tube is large, and low and medium frequency exhaust noise is effective. As a result, the exhaust temperature can be greatly reduced. Next, the pressure in the expansion chamber shifts to the sound absorption chamber, and mainly medium and high frequency exhaust sounds are absorbed by the metal wool layer and the sound absorbing material. In this case, the metal wool layer prevents the exhaust gas entering the sound absorption chamber from coming into direct contact with the sound absorption material and protects the sound absorption material from the heat damage of the exhaust gas. Since it is descending, an expensive metal wool layer is sufficient to protect the sound absorbing material, which contributes to cost reduction. In addition, the metal wool layer absorbs mid- and high-frequency exhaust sound in cooperation with the sound-absorbing material, so there is no need for a special, large-volume sound absorbing chamber for the metal wool layer, and the outer shell is enlarged. Can be avoided.
[0008]
Also the cylindrical body of the outer shell, while formed so that cross-section has an elliptical shape with its major axis in the horizontal direction, the lower side of the axis of and partition cylinder the axis of the inner pipe under sides of the major axis With this arrangement, when the recess for accommodating the exhaust pipe and the exhaust muffler is formed on the floor plate of the automobile, the ground height of the exhaust muffler can be sufficiently secured while making the recess as shallow as possible.
[0009]
Furthermore, since the peripheral wall of the partition tube is provided with a large number of through holes except for its lower part, even if an inner pipe in which a large number of through holes are provided in the peripheral wall in the entire circumferential direction is close to the lower part of the partition tube, The exhaust gas ejected from the through hole in the lower part of the pipe is blocked by the lower part of the partition tube without the through hole and does not directly enter the sound absorbing chamber. Therefore, the high-pressure exhaust gas does not have the metal wool layer and sound absorbing material in the sound absorbing chamber. Can be prevented from scattering them.
[0010]
According to a second aspect of the present invention, in addition to the feature of the first aspect of the invention, between the opposing surfaces of the end plate constituting the end wall of the outer shell and the small end plate constituting the end wall of the partition tube. The glass wool is filled with reinforcing ribs formed on the end plate and the small end plate, respectively. According to this feature, the small end is formed by the plate glass wool. The sound emitted from the plate can be absorbed, and the plate-like glass wool is held in place by the reinforcing ribs of the end plate and the small end plate biting into the end surface.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.
[0012]
First, in FIG. 1, an exhaust pipe 1 suspended under the floor of a vehicle body is connected to an exhaust manifold M of an engine installed in an engine room E of an automobile A. The exhaust pipe 1 is connected to an upstream side, that is, an exhaust. From the manifold M side, an exhaust purification primary catalytic converter 2 ₁ , an exhaust purification secondary catalytic converter 2 ₂ , a primary exhaust muffler 3 ₁ and a secondary exhaust muffler 3 ₂ are sequentially interposed. In this embodiment, the present invention in the primary exhaust muffler 3 ₁ is applied as follows.
[0013]
As shown in FIGS. 2 to 4, defines a primary exhaust muffler 3 _1, an inner pipe 5 having a hole 6 in a large number on the peripheral wall, the silencing chamber 7 between it surrounds the inner pipe 5 An outer shell 8 that surrounds the inner pipe 5 and a partition cylinder 9 that divides the silencer chamber 7 into an inner expansion chamber 7a and an outer sound absorption chamber 7b. The upstream portion 1a and the downstream portion 1b of the pipe 1 are connected by welding.
[0014]
The outer shell 8 has an oval outer cylinder 10 whose cross section is oriented with the long axis X in the horizontal direction, and a pair of ends that are caulked to both ends of the outer cylinder 10 and welded to the outer peripheral surface of the inner pipe 5. The end plates 11 are formed with reinforcing ribs 12 (see FIGS. 1 and 5) that protrude outward. The inner pipe 5 is arranged so that its axis S is below the long axis X and below the axis of the partition tube 9 .
[0015]
The partition tube 9 includes a cylindrical body 14 having a circular cross section, and a pair of non-holed small end plates 15 that connect both ends of the cylindrical body 14 and the outer peripheral surface of the inner pipe 5. A large number of through holes 16 are provided except for the lower portion 14a. In the case of the illustrated example, the range of the lower portion 9 a without the through hole 16 of the cylindrical body 14 is a portion that is below the horizontal plane including the axis S of the inner pipe 5. When the partition tube 9 is formed by rounding a steel plate and butt welding both ends thereof, the welding can be performed easily and reliably if the both end butt portions are arranged in the range of the lower portion 9a without the through holes 16. Can be done.
[0016]
In addition, the small end plate 15 is formed with reinforcing ribs 13 (see FIGS. 4 and 5) protruding upward.
[0017]
A heat-resistant metal wool layer, for example, a stainless wool layer 18 is arranged on the outer peripheral surface of the cylindrical body 14.
[0018]
Thus, the expansion chamber 7a is a hollow portion having no sound deadening material, while the sound absorbing chamber 7b is filled with glass wool 19 so as to surround the stainless wool layer 18 as a sound absorbing material. A plate-like glass wool 20 is filled between the plate 11 and the small end plate 15 of the partition tube 9. At that time, the glass wool 19 and the plate-like glass wool 20 are held in place by the reinforcing ribs 12 and 13 of the end plate 11 and the small end plate 15 biting into the end surfaces thereof.
[0019]
The operation of this embodiment will be described.
[0020]
As shown in FIG. 4, the floor plate Af of the automobile A has a recess 21 for accommodating the exhaust pipe 1 suspended thereby and the primary exhaust muffler 3 _{1 and} other accessory devices 2 ₁ , 2 ₂ , 3 _{2 connected} thereto. , 22 are provided. At that time, the primary exhaust muffler 3 ₁ of the outer shell 8, since forms an oval with its major axis X in the horizontal direction, the recess 2 2 floorboards Af accommodating this can be relatively shallow. Further, since the axis S of the inner pipe 5 connected to the exhaust pipe 1 is arranged on the lower side of the major axis X, the recess 2 1 floorboards Af for accommodating the exhaust pipe 1 can be shallower. Thus, while as much as possible shallow recesses 21, 22 of the floor plate Af, can be sufficiently secured primary exhaust muffler 3 ₁ of ground clearance.
[0021]
When high-temperature and high-pressure exhaust gas discharged from the engine to the exhaust pipe 1 arrives in the inner pipe 5, the pressure is transferred to the expansion chamber 7 a through the many through holes 6 of the inner pipe 5, and the exhaust gas rapidly expands. Due to the pressure drop due to, mainly low and medium frequency exhaust sounds are attenuated. In particular, since the expansion chamber 7a is a large volume cavity having no sound absorbing material, the expansion effect of exhaust gas is large, and low and medium frequency exhaust sounds can be effectively attenuated. At the same time, the exhaust temperature can be greatly reduced.
[0022]
Next, the pressure in the expansion chamber 7 a passes through the numerous through holes 16 of the partition tube 9 and enters the sound absorption chamber 7 b, and mainly the middle and high frequency exhaust sounds are absorbed by the stainless wool layer 18 and the glass wool 19. In this case, the stainless wool layer 18 prevents the exhaust gas that has entered the sound absorbing chamber 7b from directly contacting the glass wool 19 and protects the glass wool 19 from the heat damage of the exhaust gas. Since the temperature has already dropped in the expansion chamber 7a, even with a relatively thin stainless steel wool layer 18, heat damage to the glass wool 19 can be prevented, and the expensive stainless steel wool layer 18 can be thin. It will also contribute to cost reduction. In addition, since the stainless wool layer 18 cooperates with the glass wool 19 to absorb medium and high frequency exhaust sound, it is not necessary to form a special sound absorbing chamber 7b for the stainless wool layer 18 with a large volume, and the outer shell. 8 can be avoided.
[0023]
Incidentally, as described above, while as much as possible shallow recesses 21, 22 of the floor plate Af, in order to sufficiently ensure the primary exhaust muffler 3 ₁ ground clearance, the axis S of the inner pipe 5 is the outer shell 8 oval long When arranged below the axis X, the inner pipe 5 comes close to the lower part of the partition tube 9, so that the exhaust gas ejected from the through hole 16 at the lower part of the inner pipe 5 is hardly decompressed and is separated from the partition tube. However, since the lower hole 9a of the partition tube 9 is not provided with the through hole 16, the exhaust gas ejected from the lower hole 6 of the inner pipe 5 is separated from the partition tube without the through hole 16. 9 does not directly enter the sound absorbing chamber 7b and is depressurized in the expansion chamber 7a before moving to the sound absorbing chamber 7b. Therefore, it is possible to prevent the high-pressure exhaust gas from acting on the stainless wool layer 18 and the glass wool 19 in the sound absorbing chamber 7b and scattering them.
[0024]
Further, since the plate-like glass wool 22 is interposed between the end plate 11 of the outer shell 8 and the small end plate 15 of the partition tube 9, the radiated sound from the small end plate 15 is absorbed by the glass wool 19. Can do.
[0025]
The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, a through hole 16 can be provided in the small end plate 15 of the partition tube 9. Further, the present invention can also be applied to the secondary exhaust muffler 3 _2.
[0026]
【The invention's effect】
As described above, according to the present invention, the inner pipe is connected to the exhaust pipe of the engine and has a large number of through holes in the circumferential wall in the entire circumferential direction, and the outer shell that defines the sound deadening chamber on the outer periphery of the inner pipe. In the exhaust muffler for automobiles installed under the floor of an automobile, the inside of the partition cylinder is surrounded by a partition cylinder that has a large number of through holes except for the lower portion of the peripheral wall and surrounds the inner pipe. It divides into a hollow expansion chamber that does not have a sound absorbing material and a sound absorbing chamber that occupies the outside of the partition tube and is filled with the sound absorbing material, and a metal wool layer is arranged on the outer peripheral surface of the partition tube, The outer shell cylinder is formed so that its cross section is elliptical with its long axis oriented in the horizontal direction, while the inner pipe axis is below the long axis and below the partition cylinder axis. Having disposed, the sound absorbing material Tanai The expansion chamber of large volume, large expansion effects of the exhaust gas, low, dissipate effectively attenuate the exhaust noise of the middle frequency can be lowered significantly even the exhaust temperature. In the sound absorbing chamber, the metal wool layer and the sound absorbing material mainly absorb the middle and high frequency exhaust sound, and the metal wool layer can prevent the heat damage of the exhaust gas to the sound absorbing material. At that time, since the temperature of the exhaust gas has already dropped sufficiently in the expansion chamber, it is sufficient that the expensive metal wool layer is relatively thin, which contributes to cost reduction. In addition, the metal wool layer absorbs mid- and high-frequency exhaust sound in cooperation with the sound-absorbing material, so there is no need for a special, large-volume sound absorbing chamber for the metal wool layer, and the outer shell is enlarged. Therefore, it is possible to provide an exhaust muffler for automobiles that is compact and has high noise reduction performance.
[0027]
In addition, while the outer shell cylinder is formed so that its cross section is elliptical with its long axis oriented in the horizontal direction, the axis of the inner pipe is arranged under the long axis, so that When the recess for accommodating the exhaust pipe and the exhaust muffler is formed, the ground height of the exhaust muffler can be sufficiently secured while making the recess as shallow as possible.
[0028]
Furthermore, since the peripheral wall of the partition tube is provided with a large number of through holes except for its lower part, even if an inner pipe in which a large number of through holes are provided in the peripheral wall in the entire circumferential direction is close to the lower part of the partition tube, The exhaust gas ejected from the through hole in the lower part of the pipe is blocked by the lower part of the partition tube without the through hole and does not directly enter the sound absorbing chamber. Therefore, the high-pressure exhaust gas does not have the metal wool layer and sound absorbing material in the sound absorbing chamber. Can be prevented from being scattered, and their durability can be increased.
[0029]
In particular, according to the invention of claim 2, plate-like glass wool is filled between the opposing surfaces of the end plate constituting the end wall of the outer shell and the small end plate constituting the end wall of the partition tube, Since the reinforcing ribs formed respectively on the end plate and the small end plate are bitten, the plate-like glass wool can absorb the radiated sound from the small end plate. By holding the reinforcing ribs of the end plate and the small end plate into the end surface, the end plate is held in place.
[Brief description of the drawings]
FIG. 1 is a perspective view of an exhaust system of an automobile engine equipped with an exhaust muffler according to the present invention.
2 is an enlarged sectional view taken along line 2-2 of FIG.
3 is a cross-sectional view taken along line 3-3 in FIG.
4 is an enlarged sectional view taken along line 4-4 of FIG.
5 is a cross-sectional view taken along line 5-5 of FIG.
[Explanation of symbols]
A ... car 1 ... exhaust pipe 3 ₁ .... primary exhaust muffler 5 ... inner pipe 6 ... inner pipe through hole 9 ... .... Partition tubes
11. End plate
12, 13, ... Reinforcing ribs
15 .... Small end plate 16 .... Partition hole 18 of the partition tube ... Stainless steel wool layer 19 as a metal wool layer ...... Glass wool as a sound absorbing material
20 ... Plate glass wool

Claims (2)

An inner pipe (5) having a large number of through holes (6) extending in the circumferential direction on the peripheral wall connected to the engine exhaust pipe (1), and a sound deadening chamber (7) is defined on the outer periphery of the inner pipe (5). An exhaust muffler for an automobile, comprising an outer shell (8) that is installed under the floor of the automobile (A),
The silencer chamber (7) is divided into a partition tube (9) by a partition tube (9) having a number of through holes (16) except for the lower portion (9a ) on the peripheral wall and surrounding the inner pipe (5). ) And a hollow expansion chamber (7a) that does not have a sound absorbing material, and a sound absorbing chamber (7b) that occupies the outside of the partition tube (9) and is filled with the sound absorbing material (19), A metal wool layer (18) is arranged on the outer peripheral surface of the partition tube (9), and the cylinder (10) of the outer shell (8) is arranged with its long axis (X) oriented in the horizontal direction. while formed to be elliptical, that is arranged below the axis of and the partition cylinder below the axis of the inner pipe (5) (S) the long axis (X) (9) An exhaust muffler for automobiles. A plate-like glass wool (20) is provided between the opposing surfaces of the end plate (11) constituting the end wall of the outer shell (8) and the small end plate (15) constituting the end wall of the partition tube (9). The glass wool (20) is filled and reinforced with ribs (12, 13) formed on the end plate (11) and the small end plate (15), respectively. The automobile exhaust muffler described.

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