JPH0472043B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas flow muffler for an internal combustion engine, and in particular to a main pipe forming a main exhaust passage leading directly to the outside for passing exhaust gas. The present invention relates to a gas flow muffler that is equipped with an expansion device that accumulates a portion of exhaust gas when the pressure is high and causes the accumulated gas to return to the main exhaust passage when the pressure is low to compensate for a drop in gas pressure.

[Conventional technology]

As is well known, the noise associated with the exhaust of an internal combustion engine is
This occurs because high-temperature exhaust gas is discharged from the exhaust pipe to the outside according to the output cycle of ignition → exhaust → suction → compression → ignition, going from high pressure → low pressure → high pressure → low pressure, and the exhaust gas expands rapidly. This is caused by the air hammer phenomenon.

Therefore, as one of the prior art silencers, the sixth
As shown in the figure, several expansion chambers 8, 8a, 8b, 8 are arranged inside the silencer having a closed casing 7.
c..., and each expansion chamber is connected to a plurality of communicating tubes 9, 9a, each having a large number of small holes punched in the tubular wall surface.
9b, 9c... to allow the expansion of the exhaust gas to progress gradually, and at the same time to make the pressure difference of the exhaust gas as uniform as possible,
Improves sound deadening effect. The silencer shown in Figure 6 is mainly used in automobiles, and is usually
Such an expansion type muffler is installed at two locations, front and rear of the exhaust pipe of the engine.

In addition to the expansion type muffler, the direct type muffler, which has a direct exhaust passage through which exhaust gas is directly discharged from the internal combustion engine to the outside, is used in motorcycles and other vehicles because it has a simple structure and small device volume. ing.

[Problem that the invention seeks to solve]

However, in the expansion type muffler shown in Fig. 6, the exhaust speed is significantly slowed down, which causes a back pressure phenomenon in which the exhaust gas is pushed back to the internal combustion engine, exerting an effect on the cylinder in the opposite direction. I tend to do it. When this back pressure phenomenon occurs, the vaporized fuel is exhausted in an incompletely combusted state, resulting in a decrease in fuel efficiency, an increase in fuel consumption, and a decrease in engine output. Therefore, in racing cars that seek to obtain maximum engine power from internal combustion engines, it is common to eliminate the muffler.

Therefore, a direct-type gas flow muffler that directly discharges exhaust gas to the outside is attracting attention as a muffler that can increase the muffling effect without reducing engine output. The muffling effect mainly depends on the sound-absorbing material placed on the inner wall of the muffler through which exhaust gas passes, so although it is practical for motorcycles and other vehicles with small internal combustion engines, it is useful for automobiles and other vehicles. Internal combustion engines with large rated displacements have not yet achieved sufficient silencing effects.

The present invention was made against the background of the above-mentioned circumstances, and is a direct-through type gas flow muffler that has a simple structure and a small device volume, and is suitable for internal combustion engines with relatively large rated displacements such as automobiles. The object is to provide a gas flow muffler with a novel structure that can be used.

[Means for solving problems]

In order to achieve the above object, the present invention has a main pipe constituting a main exhaust path that directly discharges exhaust gas to the outside, and a main pipe that communicates with the main exhaust path within the main pipe to allow exhaust gas to reciprocate. an expansion device including an annular expansion chamber provided around the outer peripheral surface of the main pipe;
A dispersion pipe whose end faces toward the rear of the exhaust pipe and which is wider toward the periphery than the original direct pipe leads to a dispersion pipe that is formed between the main exhaust pipe and the annular expansion chamber to disperse exhaust gas. Provided is a gas flow muffler for an internal combustion engine, characterized in that it is constituted by a communication passage.

[Effect]

To explain Fig. 5, the figure is a graph showing changes in gas pressure of exhaust gas discharged from an internal combustion engine over time, and in the figure, the solid line A is
The broken line B is the curve when the exhaust gas is discharged to the outside without passing through the muffler, and the broken line B is the curve when the exhaust gas is discharged to the outside through the muffler of the present invention.

As is well known, in internal combustion engines, the exhaust gas pressure is not a constant pressure value;
Regardless of whether it is a 2-stroke engine or a diesel engine, the suction-compression-ignition-exhaust strokes are performed in sequence (in a 2-stroke engine, intake and compression are performed simultaneously), so the exhaust gas pressure is equal to the solid line A. It is changing like this. Such changes in exhaust gas pressure cause the air hammer phenomenon, which causes intermittent noise.

Therefore, in the present invention, by employing the expansion device described above, most of the exhaust gas discharged from the internal combustion engine and accompanied by periodic pressure changes can be smoothly exhausted through the main exhaust path that communicates directly with the outside. This eliminates the back pressure phenomenon in which exhaust gas flows backward toward the internal combustion engine, preventing a drop in engine output, and at the same time, a portion of the exhaust gas that passes through the main exhaust path is accumulated inside the engine when the pressure is high. However, by installing an expansion device that naturally returns the accumulated gas to the main exhaust passage when the pressure is low and compensates for the drop in gas pressure, the exhaust gas pressure in the main exhaust passage can be kept almost constant as shown by broken line B. This eliminates the air hammer phenomenon in the exhaust of internal combustion engines.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 is a sectional view showing a first embodiment of the present invention;
2 is an end view of FIG. 1, and FIG. 3 is a sectional view taken along the - line of FIG. 1.

As shown in FIG. 1, the gas flow muffler of the present invention includes a straight main pipe 1 and an expansion pipe 2 constituting an expansion device. The expansion pipe 2 is provided so as to substantially surround the outer circumferential surface of the main pipe 1, the inside of which serves as the main exhaust path 1a. A sound absorbing material 11 such as glass fiber is attached to the inner wall surface of the main pipe 1 to improve the sound absorbing effect. During actual manufacturing, the sound absorbing material 11 is
It is sandwiched between the porous pipe 12 and the inner wall surface of the main pipe 1. This porous pipe 12 is inserted into the main pipe 1 by the front and rear ends of the main pipe 1 whose diameter has been reduced.

The expansion pipe 2 includes a tube 21 and a front plate 22 and a rear plate 23 welded to the front and rear openings of the tube 21. The front plate 22 has a central hole 24 at its center, and the rear plate 23 has a central hole 25 at its center.
Insertion notches 26, 26, 26 (Fig. 2) are provided at three locations equally spaced around the inner circumferential edge of the central hole 25 for convenience when inserting the main pipe 1 into the central hole 25. It's getting old. The main pipe 1, the front plate 22, and the rear plate 23 are welded to each other so as to maintain substantially airtightness inside.

In this way, an annular expansion chamber 13 is formed between the main pipe 1 and the expansion pipe 2, but between the front end of the main pipe 1 and the central hole 24 of the front plate 22, a part of the exhaust gas is annularly formed. A dispersion tube 14 having a triangular rear end opening cross section is interposed to feed the gas into the expansion chamber 13 (see FIG. 3). This dispersion tube 14 is
Although not shown in the figure, near its front end, it is connected to the rear end of the exhaust pipe of the internal combustion engine, and its rear end (terminus)
In the vicinity, as shown in FIG. 3, the outer circumferential surface of the main pipe 1 is welded in contact at each point dividing the outer circumferential surface into three equal parts, and the gap between the main pipe 1 and the dispersion pipe 14 widens toward the rear of the exhaust pipe. Three communication passages 15 formed in a trumpet shape are provided, and the annular expansion chamber 13 is communicated with the main exhaust passage 1a via the dispersion pipe 14. Through this communication path 15, the dispersion pipe 1
4 flows into the main exhaust path 1a in the main pipe 1, but a portion of the exhaust gas flows into the nearly sealed annular expansion chamber 13 and is accumulated, and the exhaust gas in the main exhaust path 1a flows into the main exhaust path 1a. When the gas pressure decreases, it naturally returns to the main exhaust path 1a via the communication path 15,
This will compensate for the drop in gas pressure.

Returning to FIG. 1 again, the expansion pipe 2 is provided with a small-diameter exhaust hole 27, so that when the internal combustion engine is rotated at a relatively high speed, the exhaust gas that flows into the annular expansion chamber 13 and accumulates therein is removed. This prevents the gas from becoming too high pressure.

Of course, it is also possible to separately attach a sound absorbing material (not shown) to the inner wall surface of the expansion pipe 2, and
Desirable for improving sound deadening effect.

FIG. 4 is a sectional view showing a second embodiment of the present invention. The second embodiment also includes a straight main pipe 3 and an expansion pipe 4 surrounding the outer peripheral surface of the main pipe 3. A partition plate 40 is provided in the diametrical direction approximately in the middle of the expansion pipe 4 to divide it into a first expansion chamber C1 and a second expansion chamber C2. The first expansion chamber C1 is provided behind the second expansion chamber C2.

The main pipe 3 has a main exhaust passage 3a inside thereof, and is composed of a main pipe front part 30 and a main pipe rear part 32. These main pipe front part 30 and main pipe rear part 32
are welded in the same manner as in the first embodiment. The main pipe front section 30 is connected to the exhaust pipe 5 of the internal combustion engine at its front end, and the main pipe rear section 32 is connected to the tail pipe 6 at its rear end. The main pipe 3 has a dispersion pipe 33 disposed at the rear end of the main pipe rear part 32 in the same manner as the dispersion pipe 14 of the first embodiment (see FIGS. 1 and 3), and has a 1 is in communication with the expansion chamber C1. The cross-sectional shape of the dispersion pipe 33 and the communication passage 34 is similar to the cross-sectional shape of the dispersion pipe 14 and the communication passage 15 shown in FIG. The first expansion chamber C1 and the second expansion chamber C2 are communicated with each other by a first duct D1, which has a plurality of small holes in its wall parallel to the main pipe 3. A plurality of small holes 36 are formed in the second expansion chamber C2 of the front portion 30, so that the main exhaust passage 3a and the second expansion chamber C2 can communicate with each other.

When the engine is rotating at a low speed of 600 to 1000 rpm, the gas in the first expansion chamber C1 is filled with exhaust gas flowing from the main pipe 30 and is compressed to a relatively high pressure, so the exhaust gas pressure in the main exhaust passage 3a falls, the exhaust gas in the first expansion chamber C1 flows into the main exhaust path 3a.
Natural regression occurs to compensate for the drop in gas pressure. At this time, since there is fluid resistance, only a small amount of exhaust gas flows into the second expansion chamber C2 from the first expansion chamber C1.

When the engine is rotating at a high speed of 3000 rpm or more, a large amount of exhaust gas flows into the first expansion chamber C1 from the lower end of the main pipe front section 36, and the exhaust gas flows into the first expansion chamber C1.
The exhaust gas that has become saturated therein flows into the second expansion chamber C2 through the first duct D1. When the exhaust gas pressure in the main exhaust path 3a decreases, the first expansion chamber C1
The exhaust gas accumulated in the second expansion chamber C2 naturally returns into the main exhaust passage 3a through the communication passage 34 and the plurality of small holes 36 formed in the main pipe front portion 30.

〔Effect of the invention〕

The present invention eliminates the back pressure phenomenon on the internal combustion engine by discharging most of the exhaust gas directly to the outside, thereby greatly improving the output effect and fuel efficiency of the internal combustion engine compared to conventional technology. At the same time, the air hammer phenomenon, which is one of the major causes of exhaust noise from internal combustion engines, is eliminated by an expansion device installed around the direct main exhaust path, resulting in a simpler structure and smaller size. A practical sound damping effect is achieved by a gas flow muffler with a device volume.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a rear view of FIG. 1, and FIG.
1 is a sectional view taken along the - line, FIG. 4 is a sectional view showing a second embodiment of the present invention,
Fig. 5 is a diagram showing pressure changes of exhaust gas;
The figure is a sectional view showing a conventional gas flow muffler. 1, 3... Main pipe, 1a, 3a... Main exhaust path, 1
1... Sound deadening material, 13... Annular expansion chamber, 14, 33
... Dispersion pipe, 15, 34 ... Communication path, 36 ... Small hole, C1 ... First expansion chamber, C2 ... Second expansion chamber,
D1...First duct.

Claims (1)

[Scope of Claims] 1. Main pipes 1 and 3 constituting a main exhaust passage for directly discharging exhaust gas to the outside, and communicating with main exhaust passages 1a and 3a in the main pipes 1 and 3 for reciprocating exhaust gas. an expansion device comprising annular expansion chambers 13, C1, and C2 provided around the outer peripheral surfaces of the main pipes 1 and 3 to allow
The main exhaust passages 1a, 3a are formed by dispersion pipes 14, 33 which are formed in the shape of a wrapper, the end of which faces toward the rear of the exhaust pipe and widens towards the periphery from the original direct pipe.
and an exhaust gas communication path 15, 34 formed between the annular expansion chambers 13, C1, C2. 2. The expansion device is formed so as to store a portion of the exhaust gas inside when the exhaust gas passing through the main exhaust passages 1a, 3a is at high pressure, and When the pressure of the passing exhaust gas becomes low, the accumulated exhaust gas is naturally returned to the main exhaust passages 1a and 3a,
The main exhaust paths 1a and 3a compensate for the reduced gas pressure.
2. The muffler according to claim 1, wherein the muffler is configured to maintain a substantially constant exhaust gas pressure within the muffler. 3. The muffler according to claim 1, wherein the expansion device has a gas storage capacity equal to at least the rated total exhaust capacity of the internal combustion engine. 4. The expansion device includes a first expansion chamber C1 and a second expansion chamber C2 that communicate with the main exhaust path 3a, and a first duct D1 that communicates the first expansion chamber and the second expansion chamber with each other. The muffler according to claim 1, characterized in that: 5 The first expansion chamber C1 is the second expansion chamber C2.
5. The muffler according to claim 4, wherein the first duct D1 is disposed in parallel with the main pipe 3 to return exhaust gas to the main exhaust path 3a. . 6. The silencer according to claim 5, wherein the first duct D1 has a plurality of small holes formed in its wall surface. 7 The first expansion chamber C1 and the second expansion chamber C2 are:
In both cases, an annular expansion chamber is formed around the outer peripheral surface of the main pipe 3, and a plurality of small holes are formed on the wall surface of the main pipe 3 on the second expansion chamber C2 side. The main exhaust path 3a is the second expansion chamber C
7. The muffler according to claim 4, wherein the muffler communicates with the muffler according to any one of claims 4 to 6.