JP3264131B2 - Automotive exhaust silencer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an exhaust silencer disposed under a floor of an automobile.

[0002]

2. Description of the Related Art An exhaust silencer for reducing the exhaust noise of an internal combustion engine of an automobile is usually arranged under the floor of the automobile. 7 and 8 show a configuration example of a conventional exhaust silencer 21. The exhaust silencer 21 includes a flat, substantially cylindrical shell 22 and front and rear end plates 23 for closing both ends thereof. And one continuous exhaust pipe 24 penetrating both end plates 23.
A large number of small holes 25 are formed in the exhaust pipe 24. Therefore, in this example, the chamber 26 inside the shell 22 communicating through the small hole 25 functions as an expansion chamber (see Japanese Utility Model Laid-Open No. 3-89920). The shell 22 and the end plate 23 are both made of a steel plate and are integrally joined by welding. Further, the space between the exhaust pipe 24 and the opening edge of the end plate 23 through which the exhaust pipe 24 passes is also welded.

By the way, in the noise reduction device 21 of an internal combustion engine, it is desirable to secure the internal volume as large as possible from the viewpoint of the noise reduction performance, in other words, to increase the cross-sectional area of the substantially elliptical cross section as much as possible. There is a need. On the other hand, as shown in FIG. 7, this type of silencer 21 is arranged in a limited space between various members arranged under the floor of the automobile, for example, the fuel tank 27, the propeller shaft 28, and the like. It is necessary to keep the vehicle above the line L which is the minimum ground clearance of the vehicle.

Accordingly, in order to secure the largest cross-sectional area under the constraints of securing the clearance with the fuel tank 27, the propeller shaft 28, and the like, and securing the minimum ground clearance, recently, FIG. As shown in the figure, as the cross-sectional shape of the shell 22, the upper surface side portion 22a is curved with a certain degree of curvature, the curvature is maximized in the left and right portions 22b, and the curvature of the lower surface side portion 22c is In many cases, a vertically asymmetric configuration is used so as to be smaller than the curvature of the upper surface side portion 22a. That is, the lower surface side portion 22c is gently curved in a shape close to a plane.

[0005]

However, if the curvature of the lower surface side portion 22c of the exhaust silencer 21 is set to be small as in the prior art, the rigidity of the exhaust silencer 21 becomes low.
There is a problem that the lower surface side portion 22c of the shell 22 vibrates with the flow of the exhaust gas, and radiated sound is generated loudly. If the curvature of the lower surface side portion 22c is secured in the same manner as the upper surface side portion 22a to reduce the radiated sound, the above-described restrictions such as the minimum ground clearance of the vehicle shown in FIG. As a result, the capacity of the exhaust silencer 21 is reduced, so that the silencing effect is reduced and the exhaust noise is deteriorated.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has a flat, substantially cylindrical shell, and end plates which are closed at both end surfaces and have front and rear ends through which an exhaust pipe penetrates. Alternatively, in an exhaust muffler for an automobile having one or a plurality of resonance chambers, the curvature of the lower surface portion of the shell is set smaller than the curvature of the upper surface portion, and the shaft is provided substantially at the center of the lower surface portion. It is characterized by providing a reinforcing portion along the direction.

[0007] In particular, according to the second aspect of the present invention, a bent line portion extending in the axial direction is formed in the shell as the reinforcing portion.

According to the third aspect of the present invention, a bead having a partially bulged or concave cross-sectional shape is formed as the reinforcing portion.

Further, according to the invention of claim 4, the inside of the shell is
The exhaust pipe that passes through is placed in the shell cross-section and offset downward,
The lower part of the peripheral surface of the exhaust pipe extends over almost the entire length of the shell.
Thus, the shell was brought into contact with the inner wall surface of the lower surface side portion .

[0010]

As described above, by providing the reinforcing portion composed of a broken line portion or a bead, the surface rigidity along the axial direction of the lower surface side portion of the shell having a small curvature is improved. Therefore, the vibration of the lower surface side portion of the shell is suppressed.

Further, if the inner wall surface of the lower surface side portion of the shell having a small curvature is brought into contact with the peripheral surface of the exhaust pipe passing through the inside of the shell, the axial direction of the shell lower surface side portion is similarly increased. The rigidity along the surface is improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the present invention. The exhaust silencer 1 comprises a shell 2 having a flat and substantially cylindrical shape, and end plates 3 before and after closing both ends thereof, and a single continuous exhaust pipe penetrating the end plates 3. 4 are arranged. A large number of small holes 5 are formed in the exhaust pipe 4. As a result, the chamber 6 inside the shell 2 that communicates through the small hole 5 is configured as an expansion chamber. The shell 2 and the end plate 3
Are made of a steel plate and are integrally joined by welding. Also, an exhaust pipe 4 and an end plate 3 through which the exhaust pipe 4 penetrates.
Is also welded to the opening edge. Note that a plurality of expansion chambers and resonance chambers may be formed inside the shell 2, and a plurality of exhaust pipes may be arranged to appropriately connect the plurality of chambers.

The exhaust silencer 1 is interposed at an appropriate position in an exhaust system from an exhaust manifold of an internal combustion engine to an exhaust outlet at the rear end of the vehicle, and is disposed under the floor of the vehicle. In particular,
As described above, it is disposed in a limited space between various members disposed under the floor of the vehicle, for example, a fuel tank and a propeller shaft, and is located near a line which is a minimum ground clearance of the vehicle. become.

In order to secure the largest cross-sectional area under the constraints of securing the clearance with the fuel tank and the propeller shaft and the like, and securing the minimum ground clearance, the sectional shape of the shell 2 is set as follows. The upper surface side portion 2a is curved with a certain degree of curvature, the curvature is maximized in the left and right portions 2b, and the curvature of the approximate shape of the lower surface side portion 2c is smaller than the curvature of the upper surface side portion 2a. Thus, it is configured vertically asymmetrically.

Here, the lower surface side portion 2c has a general cross-sectional shape similar to a conventional loosely curved shape which swells downward, but in detail, each cross-section has a linear shape. It is composed of a pair of inclined surfaces, and a broken line portion 7 is formed at the center thereof along the axial direction. The broken line portion 7 is formed by bending a steel plate constituting the shell 2 at a slight angle, and is formed over the entire length of the shell 2 in the front-rear direction. And this shell 2
The end plate 3 that closes both ends has the same shape as that of FIG. In order to increase the cross-sectional area while securing the minimum ground clearance, it is preferable to reduce the bending angle of the broken line portion 7 so as to be almost flat as a whole, and on the other hand, the bending angle is excessively large. If it is small, the effect of improving the surface rigidity, which will be described later, is lost. Therefore, the angle should be set to a small angle as long as the surface rigidity can be ensured.

Further, in the above embodiment, the portions on both sides of the broken line portion 7 are flat as described above.
The curved surface may have a very small curvature.

Next, the operation of the above configuration will be described.

In a conventional vehicle exhaust silencer,
In a frequency band of 1 kHz or less where the radiated sound level is large, there is a resonance system showing a vibration mode as shown in FIG.
Such a vibrating force that excites the resonance system is not actually generated, and the sound pressure distribution mode in the silencer, which becomes the vibrating force of the radiated sound, is, as shown in FIG. Distributed only in Therefore, as shown in FIG. 11 or FIG. 12, as a vibration mode for generating radiation sound, a vibration mode generated only in the axial direction becomes a problem, and it is not necessary to consider a vibration mode as shown in FIG. . Therefore, increasing the surface rigidity in the axial direction of the lower surface side portion 2c having a small curvature, which generates a large radiation sound, greatly contributes to the reduction of the radiation sound.

According to the structure of the above embodiment, the axial rigidity of the shell 2 is improved by forming the broken line portion 7 along the axial direction at the center of the lower surface side portion 2c of the shell 2. Therefore, radiation sound from the lower surface side portion 2c is reduced.
Moreover, in the above configuration, the sectional area of the shell 2 is hardly reduced and the same capacity can be secured as compared with the case where the lower surface side portion 2c is configured to have a gentle curved surface as in the related art.
The noise reduction effect does not decrease. That is, it is possible to greatly reduce the radiated sound without deteriorating the sound deadening characteristics.

Next, FIGS. 3 and 4 show a second embodiment of the present invention.
An example is shown. In this embodiment, the shell 2
Has a gentle curved surface with a small curvature. A bead 8 having a partially expanded cross-sectional shape is formed in the center of the lower surface side portion 2c along the axial direction. In this embodiment, the bead 8 has a U-shaped or C-shaped cross section, but may be bent into a V-shape, for example. Further, in the present embodiment, the bead 8 is bulged outward in order to maximize the cross-sectional area of the shell 2, but it is also possible to form the bead 8 by depressing inward.

In addition, the lower portion 2c of the lower surface of the shell 2
May be fixed to the outer surface or the inner surface of the shell 2 by welding or the like, for example, a reinforcing member made of another member, for example, a channel member having an L-shaped cross section.

Next, FIGS. 5 and 6 show a third embodiment of the present invention.
An example is shown. In this embodiment, the shell 2
An exhaust pipe 4 penetrating through the shell 2 is arranged below the shell 2 so as to be offset, and a lower portion of its peripheral surface is in contact with the inner wall surface of the shell 2. In a state where the exhaust pipe 4 and the shell 2 are in contact with each other, both ends of the shell 2 and the exhaust pipe 4 are rigidly connected. Specifically, an annular cap 9 is firmly welded to the front and rear end plates 3, and the cap 9 is attached to the exhaust pipe 4.
Are welded.

In this embodiment, since the exhaust pipe 4 is located along the axial direction in contact with the inner wall surface of the lower portion 2c of the shell 2, the axial rigidity of the lower portion 2c is reduced. improves. Therefore, the sound radiation from the lower surface side portion 2c is reduced without reducing the capacity of the shell 2 at all.

In order to more firmly support the lower surface portion 2c of the shell 2, the lower surface portion 2c of the shell 2 and the exhaust pipe 4 may be welded to each other.

[0026]

As is apparent from the above description, according to the exhaust silencer for an internal combustion engine according to the present invention, the surface rigidity in the axial direction of the lower surface side portion of the shell can be increased without substantially reducing the capacity of the shell. This makes it possible to reduce the sound radiated from the lower surface side while maintaining the noise reduction performance.

In particular, according to the configuration of the second or third aspect, the radiation sound can be reduced only by slightly changing the sectional shape of the shell without using a separate member.

According to the fourth aspect of the present invention, the exhaust pipe itself having a large sectional area is used as a reinforcing member.
Effective rigidity improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment of the present invention, taken along line AA of FIG. 2;

FIG. 2 is a longitudinal sectional view of the first embodiment.

FIG. 3 is a cross-sectional view showing a second embodiment, taken along line BB of FIG. 4;

FIG. 4 is a longitudinal sectional view of the second embodiment.

FIG. 5 is a cross-sectional view of the third embodiment, taken along line CC of FIG. 6;

FIG. 6 is a longitudinal sectional view of the third embodiment.

FIG. 7 is a cross-sectional view of a conventional exhaust silencer.

FIG. 8 is a longitudinal sectional view of a conventional exhaust silencer.

FIGS. 9A and 9B are explanatory diagrams showing examples of vibration modes of the exhaust silencer viewed from the side and the front-rear direction, respectively.

FIG. 10 is an explanatory diagram showing a distribution of sound pressure modes in the exhaust silencer.

FIGS. 11A and 11B are explanatory diagrams showing another example of the vibration mode of the exhaust silencer viewed from the side and the front-back direction, respectively.

FIGS. 12A and 12B are explanatory views showing still another example of the vibration mode of the exhaust silencer viewed from the side and the front-rear direction, respectively.

[Explanation of symbols]

 2 ... shell 3 ... end plate 4 ... exhaust pipe 7 ... broken line part 8 ... bead

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-87312 (JP, U) JP-B-42-26660 (JP, B1) (58) Fields surveyed (Int. Cl. ⁷ , DB name) F01N 1/02 F01N 7/00

Claims (4)

(57) [Claims] 1. A flat, substantially cylindrical shell, and an end plate before and after the exhaust pipe penetrating both end surfaces of the shell, and one or more expansion chambers or resonance chambers are formed therein. In the automobile exhaust silencer, the curvature of the lower surface side portion of the shell is set smaller than the curvature of the upper surface side portion, and a reinforcing portion along the axial direction is provided substantially at the center of the lower surface side portion. A vehicle exhaust silencer characterized by the following. 2. A broken line portion formed in the shell along the axial direction as the reinforcing portion.
A vehicle exhaust silencer according to any of the preceding claims. 3. A vehicle exhaust silencer according to claim 1, wherein a bead having a partially bulged or recessed cross-sectional shape is formed as said reinforcing portion. 4. A flat, substantially cylindrical shell, and an end plate before and after the exhaust pipe penetrating both end surfaces of the shell, and one or more expansion chambers or resonance chambers are formed therein. In the exhaust muffler for an automobile, the curvature of the lower surface portion of the shell is set smaller than the curvature of the upper surface portion, and the exhaust pipe passing through the inside of the shell is sealed.
In the cross section of the exhaust pipe,
The lower part of the shell over almost the entire length of the shell.
An exhaust muffler for an automobile, wherein the exhaust silencer is in contact with an inner wall surface of a surface side portion .