JPH0658131A - Silencer for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce exhaust noise extending over a wide frequency region effectively by making an opening rate of influence bypass holes opened in the pipe of a silencer for an internal combustion engine larger toward downstream side so as to allow uniform interfering action. CONSTITUTION:An inlet pipe 6, inner pipes 7, 8, and an outlet pipe 9 are provided in a resonance chamber 10 and enlarging chambers 11, 12, and exhaust gas is discharged through arrows B, C, the enlarging chamber 12, and the outlet pipe 9 in order. Bypass holes 14 in the inlet pipe 6 are provided at equal spaces in a range A, and in this case, the holes 14 having a diameter becoming larger toward a downstream side is formed. The amount of exhaust gas discharged from the bypass holes 14 becomes uniform extending over a wide distribution range and interference action is carried out in main gas flow uniformly extending over a wide frequency range. Thus, the exhaust noise is reduced extending over a wide frequency region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer for an internal combustion engine.

[0002]

2. Description of the Related Art FIG. 4 shows a typical example of a conventional silencer. 1
Is an outer shell, 2 and 3 are outer plates, 4 and 5 are inner plates, 6 is an inlet pipe, 7 and 8 are inner pipes, 9 is an outlet pipe, 10 is a resonance chamber, 11
And 12 are expansion chambers.

The exhaust gas flowing into the inlet pipe 6 passes through the resonance chamber B as shown by an arrow B, passes through the inner pipe 7 into the expansion chamber 11 and becomes a main gas flow as shown by an arrow C. Pass through the inside of the expansion chamber 11 and reach the inner pipe 8
Through the expansion chamber 12 and the outlet pipe 9
Is discharged through.

A large number of bypass holes 13 are formed in the inlet pipe 6 over the range indicated by the symbol A, and the exhaust gas discharged from the bypass holes is the same as the main gas flow coming in as shown by arrows B and C. Interference reduces exhaust noise at a frequency determined by the path difference.

[0005]

SUMMARY OF THE INVENTION In the above conventional technique,
The pressure of the exhaust gas flowing to the right in the inlet pipe becomes lower toward the downstream (to the right in the drawing). Further, the pressure of the main gas flow flowing around the resonance chamber 10 as indicated by the arrow B and flowing through the inside of the extension chamber 11 as indicated by the arrow C becomes lower as it goes from right to left inside the extension chamber 11.

Therefore, the discharge amount of the exhaust gas discharged from the bypass holes 13 of the same size is larger in the upstream bypass holes,
Fewer bypass holes downstream. The discharge amount discharged from each bypass hole into the expansion chamber 11 is shown by an upward arrow in FIG. 4, but since the discharge amount is the largest in the upstream bypass hole 13,
The length of the arrow is short because the arrow is the longest and the amount of discharge is smaller toward the downstream side.

As described above, since the discharge amount of the exhaust gas from the bypass hole 13 becomes smaller in the downstream bypass hole and is not uniform over the range A, there is a problem that the frequency range in which the noise can be effectively silenced due to the interference effect is limited. There was a point.

[0008] Therefore, an object of the present invention is to provide a silencer capable of solving such a problem.

[0009]

In order to achieve the above object, the silencer for an internal combustion engine according to the present invention has an interference bypass hole (14, 14a, 14b, 14c) formed in a pipe (6).
It is characterized in that the aperture ratio of is set to be larger toward the downstream side.

[0010]

[Function] The pressure difference between the inside and the outside of the pipe is smaller in the downstream bypass hole, but the opening ratio of the bypass hole is larger in the downstream side.
The bypass discharge amount is almost uniform from upstream to downstream over the distribution range of the bypass holes.

As a result, the interference action is effectively and uniformly performed over the frequency range defined by the path difference.

[0012]

Embodiment In the embodiment of FIG. 1, 14 is an inlet pipe 6.
The bypass holes are provided at equal intervals over the range indicated by the symbol A, and the downstream (right side in the drawing) holes have larger diameters.

By doing so, the opening ratio of the bypass hole becomes larger in the range of A toward the downstream side. As in the embodiment of FIG. 1, instead of increasing the diameter of the bypass holes 14 in the downstream direction, the distance (pitch) between the bypass holes of the same diameter is decreased in the downstream direction, and The aperture ratio may be increased.

Further, the diameter of the bypass holes may be increased downstream and the interval (pitch) between the bypass holes may be decreased downstream. In the embodiment shown in FIG. 2, the bypass hole formed in the inlet pipe 6 is divided into two groups, and the upstream group has a small diameter bypass hole 14
In a, the aperture ratio is increased toward the downstream side by configuring the downstream group with the bypass hole 14b having a large diameter.

The embodiment shown in FIG. 3 is different from the embodiments shown in FIGS. 1 and 2 in the inner plate 5A and the inner pipe 7.
There are many A and expansion chambers 11A, and the bypass holes provided in the inlet pipe 6 are divided into three groups.

That is, the bypass holes 14a, 14b, 1
Since the third group consisting of 4c is composed of bypass holes having a larger diameter in the downstream side, the aperture ratio is larger in the downstream side. In addition,
In the embodiments of FIGS. 1 to 3, the parts having the same reference numerals as those of the conventional art shown by reference numerals 1 to 12 have the same operations as those of the conventional art of FIG.

[0017]

Since the silencer for an internal combustion engine of the present invention is constructed as described above, the discharge amount from the bypass hole becomes uniform over the distribution range. Therefore, it is possible to effectively and uniformly interfere with the circulated main gas flow over a wide frequency range, so that exhaust noise can be effectively reduced over a wide frequency band.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional view of another embodiment of the present invention.

FIG. 3 is a vertical sectional view of still another embodiment of the present invention.

FIG. 4 is a schematic vertical sectional view of the prior art.

[Explanation of symbols]

 6 Inlet pipe 14, 14a, 14b, 14c Bypass hole

Claims (1)

[Claims] 1. A silencer for an internal combustion engine, wherein an opening ratio of an interference bypass hole formed in a pipe is set to be larger toward a downstream side.