JP2002089230A - Outflow pipe of muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an outflow pipe assembled in a muffler, capable of minimizing the exhausting resistance and improving the tone quality. SOLUTION: An inflow port 17 and a flowing port 18 are formed on a pipe member 13, and the inflow port 17 and the flowing port 18 are smoothly connected by means of a connecting pipe 19. A number of draft holes 22 are formed on a pipe outer peripheral part of the inflow port, and further a number of draft holes 21 are formed on an end cover plate 20. Further an inner diameter of the inflow port 17 is enlarged in comparison with an inner diameter of the flowing port 18, and an area of a channel (diameter D2) in the inflow port 17 is determined corresponding to the inner diameter of the flowing port 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In an exhaust silencer for an internal combustion engine, it is necessary to devise an exhaust outlet pipe so that the internal back pressure is as low as possible and the silencing function is enhanced. The present invention belongs to such a technical field.

[0002]

2. Description of the Related Art Prior art that is closely related to the present invention includes:
There is one described in JP-A-8-49521.
The point is described in FIG. A resistance plate 3 having a large-diameter hole 2 is mounted in a casing 1, thereby forming expansion chambers 4 and 5. At the center of the expansion chambers 4, 5, a conduit 6 is arranged, in which a number of flow holes 7 are drilled. The conduit 6 is divided by the resistance plate 3 without communicating left and right.

[0003] Exhaust gas entering the conduit 6 flows from the flow hole 7 to the expansion chamber 4, where the expansion phenomenon at this time silences the sound. Thereafter, the gas flows into the next expansion chamber 5 from the large-diameter hole 2, flows again into the conduit 6 from the communication hole 7, and flows out to the outside or the exhaust pipe while performing a noise reduction function. The outflow pipe 8
Is set smaller than that of the conduit 6, but nothing is described here.

[0004]

Since the conduit 6 is closed by the resistance plate 3, the exhaust gas flowing into the conduit 6 from the flow hole 7 has a directional component of the inflow as shown in FIG. The tendency to go diametrically rather than axially of conduit 6 is increased. As a result, a release layer as indicated by reference numeral 9 is formed on the inner wall of the conduit 6 so as to be large in the diameter direction, and the flow passage area to be formed in the longitudinal direction of the conduit 6 is substantially reduced. become. That is, the substantial flow path area is extremely reduced like the diameter D1. In addition, a stagnation area indicated by reference numeral 10 occurs near the center of the resistance plate 3. In the stagnation region 10, a vortex is generated at a high pressure and becomes a stagnation region for the exhaust gas flow.

[0005] As described above, the decrease in the flow path area due to the separation layer hinders the smooth flow of the exhaust gas. Will be reduced. Further, the tone of the exhaust sound has been tuned to a soundly comfortable one or a sporty one.
The length of the portion or the inner diameter thereof is appropriately selected.
However, in FIGS. 4 and 5, no technical considerations regarding tuning as described above are made.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the invention of claim 1 is to reduce the exhaust gas inside the muffler to the outside of the muffler. A pipe member that guides the flow member, wherein an inflow portion and a flow portion are formed in the pipe member, and an inner diameter of the inflow portion is set to a value larger than an inner diameter of the flow portion set to a predetermined value. A plurality of ventilation holes are formed in the outer peripheral portion and the end cover plate.

The exhaust gas flowing from the outer peripheral portion of the inflow portion is
The direction is changed to the downstream side by the exhaust gas flow from the vent hole of the end cover plate. Therefore, the substantial flow passage area in the inflow section can be made as large as possible. By doing so, the resistance of the exhaust gas flow at the inflow section is reduced, and the back pressure upstream of the inflow section is reduced. In other words, the direction of the exhaust gas entering from the outer periphery of the inflow portion is corrected by the longitudinal exhaust gas flow from the end cover plate, so that the flow path area can be enlarged. At the same time, since the vent holes are also formed in the end cover plate, the flow area of the entire inflow portion can be increased, which contributes to the reduction of the back pressure.

In the distribution section, a tone that is comfortable to listen to and a tone full of sports sensation are originally sought by selecting the inner diameter and the length of the distribution section. In general, the length of the circulation section must be set to a predetermined length.
As described above, the inner diameter and the length of the flow portion are set to predetermined values in advance, so that the inflow portion needs to enlarge its inner diameter in conformity with the behavior of the exhaust gas flow there. Such expansion causes an exhaust gas flow having an appropriate flow passage area in the inflow portion, smoothly shifts the flow state to the circulation portion, and smoothens the exhaust gas flow from the inflow portion to the circulation portion. It is a plan. If the flow area of the exhaust gas entering the circulation part is larger than the inner diameter of the circulation part, turbulence occurs immediately before the circulation part, and the selection of the timbre is appropriate. Will not be realized. At the same time, the decrease in the back pressure becomes slow.

A second aspect of the present invention is characterized in that, in the first aspect, the inflow portion and the flow portion are communicated with each other by a connection pipe whose inner diameter gradually changes.

[0010] By doing so, the exhaust gas flow set in the inflow section enters the distribution section without being disturbed by the gradual change in the cross-sectional area of the connection pipe, and the tone color in the distribution section is favorably adjusted.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the embodiments shown in FIGS. Symbol 11 is
This is the silencer casing. An inflow pipe 12 and a pipe member 13 for guiding exhaust gas to the outside of the muffler are disposed therein. The interior of the casing 11 is defined as an expansion chamber 14, and a stay member 15 disposed therein is provided with an inflow pipe 12 and a pipe member 13.
Is fixed in the casing 11. The connection of each part of the stay member 15 is performed by welding. Inflow pipe 1
The other end of 2 is welded through the end plate of casing 11. The other end of the pipe member 13 is also welded in the same structure as the inflow pipe 12. A large number of ventilation holes 16 are opened in the inflow pipe 12, and the exhaust gas that has entered the inflow pipe 12 is expanded and resonated by the ventilation holes 16.
A silencing effect is achieved.

The pipe member 13 is formed of a steel pipe having a circular cross section, and has an inflow portion 17 and a flow portion 18 formed therein.
The two are connected by a connection pipe 19. Distribution Department 1
At 8, a timbre is selected. Therefore, as described above, the inner diameter and the length of the flow portion 18 are determined in advance,
Good tones and sporty tones are selected.

On the other hand, an end cover plate 20 is welded to the end of the inflow portion 17 to form a large number of ventilation holes 21. Also,
A large number of ventilation holes 22 are also formed in the outer peripheral portion of the pipe of the inflow portion 17. The ventilation holes 22 are arranged in a staggered pattern. In addition, in FIG. 2, the vent hole 22 is shown only in the cross-section of the steel plate. The portion connecting the inflow portion 17 and the flow portion 18, that is, the connection pipe 19, has a shape in which the inner diameter gradually changes, and both portions 17, 18 are smoothly connected.

In the distribution section 18, by selecting its inner diameter and length, a comfortable timbre,
To obtain a tone full of sports sensation, for that purpose, pay attention to the inner diameter of the circulation part 18 in relation to the back pressure,
It is common to make it smaller. In addition, the length of the distribution section 18 must also be a predetermined length suitable for tone color selection. As described above, since the inner diameter and the length of the flow portion 18 are set in advance to predetermined values, the inflow portion 17 needs to enlarge its inner diameter in conformity with the behavior of the exhaust gas flow there. Such enlargement causes an exhaust gas flow having an appropriate flow passage area in the inflow portion 17, smoothly transitions the flow state to the circulation portion 18, and allows the exhaust gas to flow from the inflow portion 17 to the circulation portion 18. This is to facilitate the flow.
If the flow area of the exhaust gas entering the circulation part 18 is larger than the inner diameter of the circulation part 18, turbulence may occur immediately before the circulation part 18,
The selection of the tone cannot be properly realized. At the same time, the back pressure decreases slowly.

The flow phenomenon in the inflow portion 17 is such that an axial flow along the longitudinal direction of the pipe member 13 is obtained from the vent hole 21 of the end cover plate 20, and this is combined with the inflow gas flow from the vent hole 22. Working. The exhaust gas flow flowing from the vent hole 22 forms the peeling layer described with reference to FIG. 5. Here, the exhaust gas from the vent hole 22 flows in the axial direction immediately after the inflow due to the gas flow from the vent hole 21. , The thickness of the release layer becomes thin as indicated by reference numeral 23 in FIG. Therefore, the substantial flow passage area is enlarged like the diameter D2.

As described above, even if the flow path area (diameter D2) is enlarged, since the peeling layer 23 exists with a certain thickness, the inner diameter of the inflow portion 17 is enlarged to flow the diameter D2 there. It is necessary to set a value suitable for the inner diameter of the portion 18. Under such circumstances, the inner diameter of the inflow section 17 is set to a value larger than the inner diameter of the flow section 18 which is a predetermined value.

The operation of this embodiment is clear from the above description, but will be briefly described as follows. The exhaust gas flowing from the vent hole 22 is immediately diverted in the axial direction by the axial flow from the vent hole 21. Therefore, the peeling layer 23 has an extremely thin layer pressure, and the diameter D2 of the flow path becomes large. The back pressure is reduced by such a large diameter D2. At the same time, since the ventilation holes are opened at both the outer peripheral portion of the pipe and the end cover plate, the total area of the ventilation holes is increased, thereby also reducing the back pressure.

The amount of expansion of the inner diameter of the inflow portion 17 is determined by the diameter D of the flow path.
2 is set to be substantially the same as or slightly larger than the inner diameter of the flow portion 18, and such a gas flow is gradually reduced by the connection pipe 19 and smoothly moves to the flow portion 18. Go on. Such a smooth flow is advantageous for setting the silencer back pressure low.

The pipe member 13 shown in FIG. 1 has its rear end protruding out of the casing 11, but in the case of FIG. 3, the pipe member 13 is installed in the muffler, and "exhaust gas is supplied to the outside of the muffler. Function that leads to ". In this figure, members denoted by the same reference numerals as in FIG. 1 perform the same functions as those described above. Reference numeral 24 denotes a partition plate, by which expansion chambers 25 and 26 are formed. Further, reference numeral 27 is also a partition plate, by which an expansion chamber 28 is formed. In addition. Reference numeral 29 denotes an outlet pipe.

In such an embodiment, the role played by the pipe member 13 is the same as that described above.

[0021]

According to the present invention, the gas flow entering from the outer peripheral side of the inflow portion is deflected by the axial flow from the end cover plate, and the flow path diameter in the inflow portion can be set large. The gas flow in the inflow section is very smooth, and therefore, the back pressure upstream of the inflow section is reduced, which is effective in increasing the exhaust efficiency. Since the vent hole of the inflow portion has a large flow path area as a whole, a muffler with low back pressure can be obtained from this surface.

The inner diameter and length of the flow section are determined in advance from the point of sound quality. By expanding the inner diameter of the flow section in association with the inner diameter of the flow section, the flow from the flow section to the flow section is increased. Can be made smoother, which is also advantageous for lowering the back pressure. Further, since the flow from the inflow section to the circulation section is further smoothed by the connecting pipe, the back pressure is similarly reduced.

The amount of expansion of the inner diameter of the inflow portion depends on the relationship with the thickness of the release layer. As in the present invention, when the release layer is thinned by the axial flow from the end cover plate side, the amount of increase in the inner diameter can be reduced. This means that the inner diameter difference between the inflow portion and the circulation portion is reduced, and therefore, the flow from the inflow portion to the circulation portion is less likely to be disturbed, which is advantageous in reducing the back pressure. Become.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional side view showing a part of a pipe member in an enlarged manner.

FIG. 3 is a simplified vertical side view showing another embodiment.

FIG. 4 is a vertical sectional side view showing a conventional technique.

FIG. 5 is an enlarged longitudinal side view of a part of FIG. 4;

[Explanation of symbols]

 13 Pipe member 17 Inflow section 18 Flow section 22, 21 Vent hole 19 Connection pipe

Claims (2)

[Claims] 1. A pipe member for guiding exhaust gas inside a muffler to the outside of the muffler, wherein the pipe member has an inflow portion and a flow portion, and an inner diameter of the inflow portion has a predetermined value. An outlet pipe for an exhaust silencer, wherein the outlet pipe is set to a value larger than the inner diameter of the section, and has a plurality of ventilation holes formed in an outer peripheral portion of the pipe at an inflow section and an end cover plate. 2. The outflow pipe of an exhaust silencer according to claim 1, wherein the inflow section and the flow section are connected by a connection pipe whose inner diameter changes gradually.