JPH0444808Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to an engine silencer structure.
Specifically, the present invention relates to a silencer structure in which a plurality of exhaust pipes each having a large number of small holes are provided inside a main body casing of the silencer.

[Prior art]

Exhaust gas from the engine installed in a car flows down the exhaust pipe and is muffled by a silencer before being released into the atmosphere. The exhaust noise is caused by explosions during combustion in the engine, and in order to muffle the exhaust noise, an exhaust pipe is passed through the main body casing, and a large number of small holes are drilled in the exhaust pipe within the main body casing. Silencers with the same structure have been used in the past. In such a silencer, after the exhaust gas is throttled through the small holes, it is ejected into a wide space inside the main body casing and rapidly expands, and energy is lost during the expansion. The sound is muted.

Furthermore, as described in, for example, Japanese Utility Model Application Publication No. 56-159606, a device in which a plurality of exhaust pipes are arranged in parallel within one main body casing has been known. Each exhaust pipe in this type of silencer is connected so that exhaust gas from cylinders provided in the engine that are not sequential in firing order is led out. As a result, interference of exhaust gas within each exhaust pipe is reduced, and a decrease in engine output can be avoided.

[Problem that the invention attempts to solve]

In a silencer having a structure in which a plurality of exhaust pipes pass through one main body casing as described above, a phenomenon occurs in which the exhaust gas ejected from the small hole of each exhaust pipe collides with the gas ejected from the other exhaust pipe. Due to the interference between the jet gases, a new interference sound is generated in addition to the engine combustion sound, and a cracking sound consisting mainly of high-frequency components is produced. This sound is
When it passes through the outer panel of the main body casing, it is emitted as radiated sound, and it also appears as discharge sound from the tail pipe outlet.

In order to avoid the generation of such interference noise, a silencer has also been proposed in which a partition plate is provided between the two exhaust pipes in the main body casing to isolate the jet gas from the two exhaust pipes. However, since the space after the jet gas is ejected from the small hole of the exhaust pipe becomes narrow, a sufficient expansion rate of the jet gas cannot be ensured, and there is a problem that the original exhaust sound cannot be effectively muffled. In this case, it is possible to increase the silencing effect by widening the narrow space by partitioning the interior, but problems such as increasing the size of the silencer body arise.

Furthermore, the structure of the silencer is required to not only reduce the interference noise but also not to generate exhaust resistance that would reduce engine output.

The present invention was developed in view of the above-mentioned problems, and its purpose is to eject gas from the small hole in the exhaust pipe without causing a decrease in the expansion rate of the jet gas from the small hole or in the engine output. The purpose of this invention is to suppress the generation of high-frequency radiated sound caused by mutual interference between exhaust gases and to improve the noise reduction effect.

[Means for solving problems]

Exhaust gas ejected from a small hole drilled in the exhaust pipe needs to be ejected into a space where a sufficient expansion rate can be obtained for noise reduction, but even after repeated throttling and expansion, the overall We have discovered that if we can obtain a good expansion rate, we can reduce the interference with jet gas from other exhaust pipes without reducing the silencing effect, and we can prevent any negative effects on engine output. The present invention was completed as a result of various tests in order to realize it on an actual vehicle.

That is, the present invention consists of a plurality of mutually independent exhaust pipes connected to an engine having a plurality of cylinders, and a main body casing that constitutes a sealed space and in which the plurality of exhaust pipes are arranged in parallel. This is based on the premise that a large number of small holes are formed penetrating the circumferential surface of the portion of each exhaust pipe accommodated in the main body casing. The upstream ends of the plurality of exhaust pipes are connected to each of a plurality of cylinders whose ignition order is not consecutive in the engine, and the middle portions of the plurality of exhaust pipes are extended in a straight line to the main body casing. are arranged so as to penetrate in the same direction from one end to the other. Further, an outer cylindrical tube is inserted into each part of the plurality of exhaust pipes housed in the main body casing, and between the inner circumferential surface of each of the outer cylindrical tubes and the outer circumferential surface of each of the above-mentioned exhaust pipes, A space of a predetermined size is formed in which the exhaust gas ejected through the small hole expands and diffuses. A large number of small holes are formed in the circumferential surface of each of the outer cylindrical tubes to communicate this space with the sealed space of the main body casing.

[Effect]

In the above configuration, each upstream end of the multiple exhaust pipes is connected to each of the multiple cylinders whose ignition order is not consecutive, so exhaust gas from multiple cylinders whose ignition order is consecutive is routed to one exhaust pipe. Interference between the exhaust gases from each cylinder in each exhaust pipe is suppressed compared to the case where they are gathered together.

In addition, since the outer cylindrical pipe is extrapolated to each of the exhaust pipes to form a predetermined space between the two, the exhaust gas is ejected from the small holes of each of the exhaust pipes into the respective spaces, and each small hole The energy is dissipated by throttling at , and by expansion and diffusion after ejection. At this time, since the space is formed independently for each exhaust pipe, interference with exhaust gas in other exhaust pipes is prevented from occurring.

Then, the exhaust gas in the space is ejected again into the space inside the main body casing from the numerous small holes in each of the outer cylinder tubes, and the energy is accumulated by throttling in each of the small holes and expansion and diffusion after ejection. Dissipation takes place.
The interference between the exhaust gases from each outer cylinder pipe that occurs at this stage is weakened by the above-mentioned interference suppression and interference prevention, and the high-frequency radiation sound generated through the outer panel of the main body casing is reduced. be done.

Furthermore, since the overall expansion rate of the exhaust gas within the main body casing is maintained as before, the expansion rate does not decrease, and engine combustion noise and other sounds are muffled as before.

Furthermore, because each of the multiple exhaust pipes is arranged in a straight line penetrating the main body casing, the exhaust resistance of the exhaust gas is smaller than when the exhaust pipes are bent inside the main body casing. Therefore, the effect on engine output is also reduced.

〔Example〕

Hereinafter, the silencer structure of the present invention will be explained in detail based on examples thereof.

In the exhaust system shown in FIG. 3, a pre-silencer 1A and a main silencer 1B are connected to a plurality of mutually independent exhaust pipes 2A, 2B (two in the figure).
are arranged in series on the upstream and downstream sides of the The upstream ends of these exhaust pipes 2A, 2B are, for example, V
It is connected to exhaust manifolds 5A and 5B that collect exhaust gas from three cylinders in a six-cylinder engine 3 whose ignition order is not consecutive. Therefore, each of the exhaust pipes 2A and 2B allows the high-temperature exhaust gas generated as the engine operates to flow down without interfering with each other, and then introduces the exhaust gas into the pre-silencer 1A and the main silencer 1B.

Fig. 1 shows the structure of the pre-silencer 1A, in which the main body casing 6 is an outer plate with an elliptical cross section, and the front and rear sides thereof are closed with end plates 7a and 7b (see Fig. 3). A sealed space 8 is formed within 6. Each exhaust pipe 2A, 2
B passes through the main body casing 6 in a straight line, and the peripheral wall of each exhaust pipe 2A, 2B located in the space 8 has a large number of small holes 9 as shown in FIG. It is formed through. The small holes 9 are provided around the entire circumference, for example, as shown in FIG. 2, and allow the exhaust gas flowing down each exhaust pipe 2A, 2B to be ejected and expanded and diffused into each outer cylindrical pipe 11A, 11B, which will be described later. It is becoming possible to do this.

Outer cylinder pipes 11A, 11B are provided outside the exhaust pipes 2A, 2B so as to surround the respective exhaust pipes 2A, 2B. , 11B are respectively formed with an annular space 10 of a predetermined size for reducing noise by ejecting exhaust gas from the small hole 9. And each of the above outer cylinder tubes 11
A large number of small holes 12 are formed in the peripheral walls of A and 11B, through which the exhaust gas in both annular spaces 10 and 10 is blown out into the space 8 of the main body casing 6. The jet gas can be expanded and diffused.

In this example, the pipe structure inside the silencer 1 is a double structure consisting of the exhaust pipe 2 and the outer cylindrical pipe 11, but in some cases, another outer cylindrical pipe may be added to the outer cylindrical pipe. It is also possible to adopt a triple structure. Of course, the silencer having such a configuration can be applied not only to the pre-silencer 1A described above, but also to the main silencer 1B if there is one as in this example.

According to the silencer 1 having such a configuration, the sound of exhaust gas discharged from the engine is reduced in the following manner, and the plurality of exhaust pipes 2A, 2B are
It is possible to suppress the generation of radiated sound due to interference of jet gas from the air.

That is, by operating the V-type six-cylinder engine 3, exhaust gas is introduced from each cylinder of the engine into each exhaust pipe 2A, 2B connected to each exhaust manifold 5A, 5B. At this time, each exhaust pipe 2a,
Since the exhaust gas introduced into the exhaust pipe 2b is from three cylinders whose ignition order is not consecutive, the exhaust gas from each cylinder is connected to the exhaust pipes 2a and 2b.
interference within the network can be suppressed.

The exhaust gas is first introduced into the pre-silencer 1A, where part of the exhaust gas in both the exhaust pipes 2A, 2B is ejected and diffused from a large number of small holes 9 toward each annular space 10. Ru. This dissipates the energy held by the exhaust gas and weakens the jet gas. At this time, each annular space 10 has both exhaust pipes 2
Outer tubes 11A and 11 individually inserted into A and 2B
B, one exhaust pipe 2A
Alternatively, interference between the exhaust gas in the exhaust pipe 2B and the exhaust gas in the other exhaust pipe 2B or 2A can be prevented.

Furthermore, the jet gas is supplied to each outer cylinder pipe 11A, 11
After colliding with the inner surface of B, many small holes 12
from there toward the space 8 within the main casing 6. At this time, one of the outer tubes 11A or 11B
The jet gas collides with the jet gas from the other exhaust pipe 11B or 11A arranged in parallel, but the momentum is weakened through expansion and diffusion twice in each annular space 10 and the space 8. Therefore, compared to the case where the exhaust pipes 2A and 2B are ejected directly into the space 8, the generation of interference noise due to impact can be significantly suppressed.

In addition, even if both the outer cylindrical pipes 11A and 11B are added within the main body casing 6, the same expansion rate as a whole is ensured compared to the case where they are not added, so that the exhaust gas flows through the pre-silencer 1A.
It is possible to prevent deterioration of the silencing performance such as combustion noise while flowing down.

Furthermore, since each of the exhaust pipes 2A and 2B extends in a straight line and passes through the main body casing 6 and the internal exhaust gas flows down in a straight line, the exhaust pipes are bent inside the main body casing and the exhaust gas Compared to the case where the moving direction of the engine is repeatedly reversed, the exhaust resistance can be made as small as possible, and the influence on the engine output can be reduced.

The graph in FIG. 4 compares the radiated sound generated by the above-mentioned silencer 1 with that of a conventional silencer in which the outer tube 11 is not provided, by frequency. Note that this data was obtained when the engine was varied in the range of 4000 to 5000 rpm with no load, and is the sound radiated from the outer plate of the main body casing 6 measured on the side of the silencer 1. According to this, in each frequency range, the sound pressure level of the proposed device shown by the broken line is reduced by about 5 to 10 dB compared to the conventional one shown by the solid line, and the sound pressure level is reduced by about 2 to 8 dB due to the interference of jet gas. It can be seen that the sound in the high frequency band, that is, the sound that can be heard as cracking sound, is significantly suppressed.

[Effect of idea]

As explained above, after suppressing the interference between the exhaust gas introduced from each cylinder in each exhaust pipe, the expansion and diffusion of exhaust gas into the space between the exhaust pipe and the outer tube is controlled for each exhaust pipe. After doing that, again,
Because it expands and diffuses into the space inside the main casing, it is possible to more effectively reduce the interference between the jet gases diffusing inside the main casing than with conventional structures, effectively reducing the generation of high-frequency sound. can do. Furthermore, it is possible to prevent a decrease in the expansion rate and a decrease in engine output.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the main parts of the engine silencer structure of the present invention, Fig. 2 is a sectional view when the structure is double-structured with an exhaust pipe and an outer cylinder pipe, and Fig. 3 is a diagram in which the present invention is applied. FIG. 4 is a graph comparing the radiated sound of the silencer according to the present invention with that of a conventional silencer according to frequency. 1, 1A, 1B... Silencer, 2, 2A,
2B...Exhaust pipe, 6...Body casing, 9,1
2...Small hole, 10...Predetermined space, 11, 11A,
11B...Outer tube.

Claims (1)

[Claims for Utility Model Registration] A plurality of mutually independent exhaust pipes connected to an engine having a plurality of cylinders, and a main body casing that constitutes a sealed space and in which the plurality of exhaust pipes are arranged in parallel. and an engine silencer structure in which a large number of small holes are formed penetrating the circumferential surface of a portion of each of the exhaust pipes housed in the main body casing, the upstream end of each of the plurality of exhaust pipes; is connected to each of a plurality of cylinders whose ignition order is not consecutive to the engine, and the intermediate portions of the plurality of exhaust pipes extend in a straight line in the same direction from one end of the main body casing to the other end. The outer cylindrical pipe is inserted into each part of the plurality of exhaust pipes housed in the main body casing, and the inner circumferential surface of each of the outer cylindrical pipes and each of the exhaust pipes are connected to each other. A space of a predetermined size is formed between the outer peripheral surface of the main body casing and a space of a predetermined size for expansion and diffusion of exhaust gas ejected through the small holes, and a large number of small holes communicate with the sealed space of the main body casing. is formed on the circumferential surface of each of the outer cylindrical tubes.