JPH01155013A - Gas flow silencer for internal combustion engine - Google Patents

Abstract

PURPOSE: To improve noise suppressing effect by arranging an expansion member connected to a main pipe constituting a main exhaust path. CONSTITUTION: An expansion pipe 2 is arranged surrounding the outer periphery of a main pipe 1 that constitutes a main exhaust path 1a. A passage 15 is formed between the main exhaust path 1a and a circular expansion chamber 13 in the expansion pipe 2. At high pressure, a part of the exhaust gas in the main exhaust path 1a is released to the expansion chamber 13 and accumulated there, and at low pressure, the accumulated gas returns back to the main exhaust path 1a. By this constitution, the air hammer phenomenon disappears, the noise suppressing effect is improved.

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 caused by high-temperature exhaust gas flowing out from the exhaust pipe and following the output cycle of ignition-exhaust-intake-compression-ignition, high pressure - low pressure - high pressure - low pressure - and the exhaust gas exits the exhaust pipe. This is due to the air hammer phenomenon that occurs due to rapid expansion as it is discharged.

Therefore, as one of the prior art mufflers, as shown in FIG. 9, a muffler with a closed casing 7 has several expansion chambers 8.8a, 8b.

A plurality of communication tubes 9.9a partition each expansion chamber into 8c... and have a large number of small holes punched in the tubular wall surface of each expansion chamber.

9b, 9c, . . . communicate with each other to gradually advance the expansion of the exhaust gas, and at the same time make the pressure difference of the exhaust gas as uniform as possible, thereby improving the muffling effect. The muffler shown in FIG. 9 is mainly used in automobiles, and such an expansion muffler is normally installed at two locations, one at the front and the other at 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. 9, the exhaust speed is significantly slowed down, so the exhaust gas is pushed back to the internal combustion engine, causing a hack pressure phenomenon that applies an acting force in the opposite direction to the cylinder. It becomes difficult. When this pack pressure phenomenon occurs, 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 a sufficient silencing effect.

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 solve the above problems, the present invention has a main pipe constituting a main exhaust passage that directly discharges exhaust gas to the outside, and a main exhaust passage in the main pipe that communicates with the exhaust gas so that the exhaust gas can reciprocate. , when the exhaust gas passing through the main exhaust passage is at high pressure, a part of the exhaust gas is stored inside, and when the exhaust gas passing through the main exhaust passage becomes low pressure, an expansion device formed to naturally return the accumulated exhaust gas into the main exhaust passage, compensate for the reduced gas pressure and keep the exhaust gas pressure in the main exhaust passage almost constant; The main purpose is to have the following.

Below is the margin [Function] To explain Figure 8, the figure is inside! ! This is a graph showing the change in gas pressure of exhaust gas discharged from eight engines over time. In the diagram, the solid line A is the curve when the exhaust gas is discharged outside without passing through the muffler, and the dashed line B is a curve when exhaust gas is discharged to the outside through the muffler of the present invention.

As is well known, in an internal combustion engine, the exhaust gas pressure is not a constant pressure value (regardless of whether it is a 4-cycle engine, a 2-cycle engine or a diesel engine, the intake gas pressure is not constant).
The steps of compression, ignition, and exhaust are performed in sequence (in 2-stroke engines, intake and compression are performed at the same time).
Therefore, the exhaust gas pressure changes as shown by solid line A.

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, most of the exhaust gas with periodic pressure changes discharged from the internal combustion engine is smoothly exhausted through the main exhaust path that communicates directly with the outside. This eliminates the back pressure phenomenon in which gas flows backwards toward the internal combustion engine, preventing a drop in engine output.At the same time, a portion of the exhaust gas passing through the main exhaust path is accumulated internally when the pressure is high, and when the pressure is low. By providing an expansion device that compensates for the drop in gas pressure by allowing the gas to naturally return to the main exhaust passage, the exhaust gas pressure in the main exhaust passage can be kept almost constant as shown by broken line B, and the internal combustion engine can be improved. This eliminates the air hammer phenomenon in the exhaust.

〔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, FIG. 2 is an end view of FIG. 1, and FIG. 3 is a sectional view taken along the line ■-■ in FIG. be.

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. In actual manufacturing, the sound absorbing material 11 is sandwiched between the porous pipe 12 and the inner wall surface of the main pipe 1. This porous vibe 12 is inserted into the main pipe 1 by the front and rear ends of the main pipe 1 whose diameter is reduced.

The expansion pipe 2 includes a tube 21 and this tube 2.
The vehicle is provided with a front plate 22 and a rear plate 23 welded to the front and rear openings of the vehicle. The front plate 22 has a center hole 24 at its center, and the rear plate 23 has a center hole 25 at its center.
3 is further provided with insertion notches 26, 26, 26 (Fig. 2) at three equally spaced locations around the inner peripheral edge of the central hole 25, and the main pipe 1 is inserted into the central hole 25. It is very convenient. 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 vibrator 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). Although not shown, this dispersion pipe 14 is connected to the rear end of the exhaust pipe of the internal combustion engine near its front end, and as shown in FIG. Since the main pipe 1 and the dispersion pipe 14 are welded in contact at each point, three communication passages 15 are provided between the main pipe 1 and the dispersion pipe 14, and the annular expansion chamber 13 and the dispersion pipe 14 (that is, the main exhaust passage 1
a) will be communicated with. Through this communication path 15, most of the exhaust gas passing through the dispersion pipe 14 is transferred to the main pipe 1.
However, a portion of the exhaust gas flows into the nearly sealed annular expansion chamber 13 and is accumulated therein, and when the exhaust gas pressure in the main exhaust path la decreases, it is discharged through the communication path 15. The gas naturally returns to the main exhaust path la to 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 to prevent exhaust gas from flowing into the annular expansion chamber 13 and being accumulated when the internal combustion engine is rotated at a relatively high speed. 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, which is also desirable in terms of improving the sound deadening effect.

FIG. 4 is a diagram showing another modification of the annular expansion chamber 13. The main pipe 1 has one branch pipe 28, which is a tubular body with a closed tip, branched as shown in the figure. tube 28
The interior and the main exhaust path 1a inside the main pipe 1 are in communication, thereby increasing the silencing effect of gas pressure compensation. In this case, the capacity of the branch pipe 28 portion needs to be approximately equal to the rated total displacement of the internal combustion engine.

FIG. 5 is a sectional view showing a second embodiment of the present invention. The second embodiment also includes a linear main pipe 3 and an expansion vibrator 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 this expansion vibe 4, and the first
It is divided into an 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 its interior as a main exhaust path 3a, and
It 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 has an exhaust pipe 5 of an internal combustion engine at its front end.
The main pipe rear part 32 is connected to the tail vibro at its rear part. The main pipe 3 is connected to the dispersion pipe 14 of the first embodiment (see FIGS. 1 and 3) at the rear end of the main pipe rear part 32.
(see figure), it communicates with the first expansion chamber C1 through three communication passages 34. First expansion chamber C1 and second expansion chamber C
2 and 2 communicate with each other by a first duct D1 having a plurality of small holes in its wall that are installed in parallel with the main pipe 3, and in the second expansion chamber C2 of the main pipe front part 30, Since a plurality of small holes 36 are provided, the main exhaust path 3a and the second expansion chamber C2 can communicate with each other.

When the engine is rotating at a low speed of 600 to 11,000 rpm, the gas in the first expansion chamber C1 is filled with exhaust gas that has flowed in from the main pipe 30 and is compressed to a relatively high pressure, so that the exhaust gas in the main exhaust passage 3a When the pressure drops, the first expansion chamber C
1 naturally returns to the main exhaust path 3a to compensate for the drop in gas pressure. At this time, the exhaust gas only slightly flows into the second expansion chamber C2 from the first expansion chamber CI because there is fluid resistance.

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 that has become saturated in the first expansion chamber C1 is It flows into the second expansion chamber C2 through the first duct D1. When the exhaust gas pressure in the main exhaust passage 3a decreases, the exhaust gas accumulated in the first expansion chamber C1 and the second expansion chamber C2 is discharged through the plurality of small holes opened in the communication passage 34 and the front part 30 of the main pipe. 36 and naturally returns to the main exhaust path 3a.

FIG. 6 is a sectional view showing a third embodiment of the present invention. The third embodiment differs from the second embodiment in that the expansion pipe 4 is
A third expansion chamber C3 is extended to the rear of the expansion chamber C1. This third expansion chamber C3 is communicated with the second expansion chamber C2 through a second duct D2 provided in parallel with the main exhaust passage 3a. Furthermore, three discharge passages 38 are newly provided to interconnect the third expansion chamber C3 and the main exhaust passage 3a. This discharge path 38 corresponds to the dispersion pipe 14 of the first embodiment.
(see Figure 3), even if the engine is rotated at a high speed of 5000 rpm or more, this third
By providing the expansion chamber C3, high-pressure exhaust gas can be accumulated in the third expansion chamber C3, and the main exhaust path 3a
As soon as the gas pressure drops, the high-pressure exhaust gas can be returned by the discharge passage 38.

FIG. 7 is a sectional view showing a fourth embodiment of the present invention. In this fourth embodiment, the first duct DI and the second duct D2 of the third embodiment include a branch pipe 31, which is a tubular body branched from the main pipe 3, and a plurality of branch pipes 31 in a portion where the branch pipe 31 becomes the main pipe 3. Although it has been replaced by the newly opened small hole 33,
Through these plurality of small holes 33, the first expansion chamber C1 and the second expansion chamber C2 are communicated with each other as in the third embodiment. Moreover, since the main pipe 3 also has a plurality of small holes 35 in the second expansion chamber C2, it is possible to achieve the same noise reduction effect as in the third embodiment.

〔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 device volume. The four-gas flow muffler achieves a practical sound muffling effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the present invention;
Fig. 2 is a rear view of Fig. 1, Fig. 3 is a sectional view taken along the line III-I in Fig. 1, and Fig. 4 shows main pipes and expansion tubes having different configurations. 5 is a sectional view showing a second embodiment of the present invention, FIG. 6 is a sectional view showing a third embodiment of the present invention, and FIG. 7 is a sectional view showing a modification of the device. FIG. 8 is a cross-sectional view showing a fourth embodiment of the present invention, FIG. 8 is a diagram showing pressure changes in exhaust gas, and FIG. 9 is a cross-sectional view showing a conventional gas flow muffler. 1.3... Main pipe, 1a... Main exhaust path, 1
1... Sound deadening material, 13... Annular expansion chamber, 1
5.34...Communication path, 28.31...Branch pipe, 33.35.36...Small hole, 38...Discharge path, CI...First expansion chamber, C2...No. 2 expansion chamber, C3... 3rd expansion chamber, Dl... 1st duct,
D2...Second duct. Below is the daylight of life

Claims (1)

[Scope of Claims] 1. A main pipe constituting a main exhaust passage that directly discharges exhaust gas to the outside, and a main exhaust passage that communicates with the main exhaust passage in the main pipe so that the exhaust gas can reciprocate. When the exhaust gas passing through the main exhaust passage is at high pressure, a part of the exhaust gas is accumulated inside the main exhaust passage, and when the exhaust gas passing through the main exhaust passage becomes low pressure, the accumulated part is stored inside the main exhaust passage. and an expansion device configured to naturally return the exhausted exhaust gas into the main exhaust passage to compensate for the reduced gas pressure and keep the exhaust gas pressure in the main exhaust passage almost constant. Gas flow silencer. 2. 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. 3. The muffler according to claim 1, wherein the main pipe has a layer of sound absorbing material provided on an inner wall surface forming the main exhaust passage inside the main pipe. 4. The muffler according to claim 1 or 3, wherein the expansion device is one annular expansion chamber provided around the outer peripheral surface of the main pipe. 5. The noise reduction device according to claim 4, wherein the expansion device is a tubular body branching from the main pipe and includes a communication path that communicates the main exhaust path and the annular expansion chamber. vessel. 6. The expansion device is a tubular body that branches from the main pipe, and is a branch pipe that communicates with the main exhaust passage at its front end and has a closed end that does not communicate with either of its rear ends. A silencer according to claim 1 or 2. 7. The expansion device is characterized by comprising a first expansion chamber and a second expansion chamber that communicate with the main exhaust passage, and a first duct that communicates the first expansion chamber and the second expansion chamber with each other. A silencer according to claim 1. 8. The first expansion chamber is connected immediately behind the second expansion chamber, and the first duct is interposed in parallel with the main pipe to return exhaust gas to the main exhaust path. A muffler according to claim 7 characterized by: 9. The silencer according to claim 8, wherein the first duct has a plurality of small holes in its wall surface. 10. The first expansion chamber and the second expansion chamber both form an annular expansion chamber provided around the outer peripheral surface of the main pipe, and a plurality of small holes are formed on the second expansion chamber side of the main pipe wall surface. 9. The muffler according to claim 7, wherein the main exhaust path of the main pipe communicates with the second expansion chamber by opening the muffler. 11. The expansion device has a third expansion chamber connected thereto, and
Claim 1, characterized in that a second duct is provided to communicate the second expansion chamber and the third expansion chamber.
The silencer according to any one of Items 7, 8, 9, and 10. 12. The third expansion chamber is provided annularly around the outer peripheral surface of the main pipe, and is connected immediately behind the first expansion chamber, and has a discharge path through which exhaust gas returns to the main exhaust path. 12. A muffler according to claim 11, characterized in that it is formed. 13. The expansion device is a branch pipe of a tubular body branched from the main pipe, and communicates with the third expansion chamber, thereby returning exhaust gas from the third expansion chamber to the main exhaust path. A muffler according to any one of claims 1, 11, and 12, characterized in that the muffler is provided with a channel. 14. The expansion device includes a branch pipe whose one front end communicates with the main pipe and whose one rear end communicates with the third expansion chamber, and which is connected at its front end to an exhaust pipe on the internal combustion engine side. A plurality of small holes are opened in the wall surface of a portion parallel to the main pipe, and the main pipe opens a plurality of small holes in the wall surface of the second expansion chamber, so that the first expansion chamber 14. The muffler according to claim 13, wherein the second expansion chamber and the third expansion chamber are communicated with each other.