JPS6217087B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates primarily to an exhaust system for automobiles.

[Conventional technology]

Conventionally, in this type of exhaust system, a pre-muffler 1 and a main muffler 2 are installed in the middle of one exhaust pipe P, as shown in Fig. 1, and these are attached to the underfloor surface of the vehicle body to absorb exhaust gas. The various noises included are removed by the pre-muffler 1 and main muffler 2.

However, since the above-mentioned exhaust system must be provided with a relatively large pre-muffler 1 in addition to the large main muffler 2, the entire system becomes large and heavy, which is a problem. Furthermore, the underfloor surface of the vehicle body to which the exhaust system is attached has a complicated uneven structure, making it difficult to install the exhaust system.

Furthermore, recent research has revealed that the muffler's silencing performance is affected by its mounting position in the exhaust system. In other words, the muffler has an optimal mounting position in the exhaust system, and if that position is incorrect, there will be a big difference in the silencing effect even if the same muffler is installed (Journal of the Acoustical Society of Japan)
35, No. 6 [1979], pp. 322 to 332 (see "Optimum mounting device for expansion type silencers and prediction of required silencing performance").

However, in the actual car body structure, the underfloor surface has a complex uneven structure as mentioned above, so even if the optimal mounting position of the pre-muffler 1 and the main muffler 2 is known, it will not be possible due to the constraints of the car body structure. However, it is difficult to install the pre-muffler 1 and the main muffler 2 at appropriate positions where they can fully exhibit their silencing effect, and as a result, there has been a problem in that a satisfactory silencing effect cannot be obtained.

In addition, unlike the above-mentioned exhaust system, multiple sets of two parallel exhaust pipes are connected with multiple communication parts,
There is also known an exhaust system in which one pipe is provided with various noise reduction mechanisms, the other pipe is left straight, and these exhaust pipes are installed so that their installation positions can be changed alternately at the communication part ( (See Japanese Patent Publication No. 46-32373, Japanese Patent Publication No. 51-15747, and Japanese Patent Publication No. 54-38689).

In this device, there is no main muffler or pre-muffler, and the exhaust gas flows down alternately through a plurality of straight exhaust pipes arranged alternately through a communicating section of two parallel pipes. Further, noise is muted by a plurality of pipes which are arranged alternately and have a muting function. Therefore, according to such a device, there is no problem such as poor attachment to the underfloor surface of the vehicle body.

[Problem that the invention seeks to solve]

However, since pipes equipped with a noise reduction function are completely closed pipes or are filled with sound-absorbing material, the exhaust gas only flows down the straight pipe, but such a straight pipe is one narrow exhaust pipe. Because it is a pipe, there is a large amount of back pressure and a large pressure loss, which causes problems such as large consumption of fuel.

In order to solve this problem, the diameter of the exhaust pipe through which the exhaust gas flows can be increased.
On the other hand, increasing the diameter will have an adverse effect on the ease of installation, and the pipe diameter will be different from that of the exhaust pipe provided with a noise-reducing function, which will complicate the structure of the communicating portion between the two pipes and increase the number of production steps. Moreover, if the diameters of both exhaust pipes were both made larger, the ease of mounting would further deteriorate, and the silencing performance would be adversely affected, which was undesirable.

Therefore, there has been a need for an exhaust system that is comprised of an exhaust pipe with a diameter that has been conventionally used and is superior in terms of ease of installation, productivity, and noise reduction performance.

[Purpose of the invention]

The present invention was devised in view of the above circumstances.
It is an object of the present invention to provide an exhaust system that can sufficiently absorb noise, can be easily attached to the underfloor surface of a vehicle body, and can reduce fuel consumption.

[Problem that the invention seeks to solve]

In order to achieve such an object, the exhaust system according to the present invention includes an exhaust pipe consisting of a hollow straight pipe, and a perforated plate in the pipe or a throttle pipe in which the exhaust gas exit side is diffused in parallel with the exhaust pipe. Either one of the exhaust pipes is connected to the exhaust pipe at a plurality of communicating portions via short convergence pipes.

[Action of the invention]

According to the present invention, exhaust noise is attenuated by the contraction and expansion of the exhaust pipe and the converging short pipe, and the exhaust noise is attenuated by the contraction and expansion of the exhaust pipe and the converging short pipe, and the exhaust noise is attenuated by the constriction pipe and perforated plate provided in the exhaust pipe. Since there is a difference in the degree of attenuation with the noise energy and a difference in phase, the exhaust noise is further attenuated due to the interference effect of the sound waves with different phases in the merging short pipe.

Moreover, since the exhaust gas flows down the exhaust pipe made of a hollow straight pipe, and a portion of the exhaust gas flows down the exhaust pipe provided with a throttle pipe or a perforated plate, an increase in back pressure is prevented.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 shows a first embodiment of the present invention, in which 3a is an exhaust pipe made of a hollow straight pipe, 3b is an exhaust pipe arranged in parallel with the branch pipe 3a, and there is an exhaust pipe in the pipe. A throttle pipe 5 whose gas exit side is expanded is arranged, and the noise flowing into the exhaust pipe 3b is
When flowing down the throttle tube 5, the damping constant increases due to tube wall friction and the frequency changes. And these exhaust pipes 3a, 3b,
An exhaust system is constructed by connecting a plurality of communicating portions via a short confluence pipe 4 such that the installation positions are alternately changed.

The short merging pipe 4 is a short single pipe that combines the pipe ends of the exhaust pipes 3a and 3b and allows exhaust gas to flow together. In addition, the manifold p directly connected to the engine (not shown) is configured as a straight exhaust pipe 3a in order to smoothly send exhaust gas discharged from each cylinder rearward without applying back pressure to the engine.
are arranged in parallel.

As shown in FIG. 3, such an exhaust system is assembled by first bending the pipe ends of each exhaust pipe 3a and 3b inward, and then crushing the overlapping inner half of each connecting end to form a flat surface. 6a and 6b are formed. Then, the two flat surfaces 6a and 6b are overlapped and fitted into one end of the short merging pipe 4, and the rear exhaust pipes 3a and 3b are successively connected to the other end of the short merging pipe 4. be done. In assembling this exhaust system, it is sufficient to connect a necessary number of exhaust pipes of appropriate lengths depending on the vehicle type, and to connect exhaust pipes that are bent to conform to the uneven shape of the underfloor surface of the vehicle body.

Since this embodiment is configured in this way, the exhaust noise generated by the engine is expanded when flowing down inside the manifold p and merging into the short merging pipe 4, and then from this short merging pipe 4 to this pipe. After being contracted when flowing into the fitting ends of the exhaust pipes 3a, 3b fitted into the short pipe 4, it is expanded again at the regular cylindrical parts of the exhaust pipes 3a, 3b. These expansions and contractions are repeated each time it passes through each of the short merging pipes 4 and exhaust pipes 3a and 3b located downstream, and the exhaust noise is successively muted and the noise level is sufficiently reduced before it is released from the pipe end. released into the atmosphere. Moreover, the exhaust noise is contracted and expanded within the exhaust pipe 3b by the throttle pipe 5, and due to pipe wall friction when flowing down the throttle pipe 5, its attenuation constant increases and its frequency changes. I'm starting to do that. Therefore, the exhaust noise flowing into the exhaust pipe 3b having the throttle pipe 5 is further attenuated within this exhaust pipe 3b, while this attenuated noise is caused by the above-mentioned change in frequency to the hollow exhaust pipe. Since there is a difference in phase with the noise flowing down 3a, interference occurs between the noise and this noise at the downstream merging short pipe 4. This resulted in further attenuation of exhaust noise.

In addition, the exhaust gas already flows down the exhaust pipe 3a made of a hollow straight pipe, but a part of it flows down the exhaust pipe 3b provided with a throttle pipe.

Note that this exhaust system includes an exhaust pipe 3a made of a hollow straight pipe, an exhaust pipe 3b provided with a throttle pipe, and
A single unit consisting of the short confluence pipe 4 cannot be expected to have the same silencing performance as the main muffler, but by installing multiple units in series, the main muffler,
It exhibits noise reduction performance equivalent to or better than an exhaust system equipped with a pre-muffler.

Moreover, in this embodiment, as mentioned above, the exhaust gas flows down even in the exhaust pipe 3b provided with the throttle pipe, so one of the parallel exhaust pipes is closed as in the conventional case, or the structure is filled with sound-absorbing material. Overall, the exhaust gas flows down smoothly and no back pressure is applied to the engine. Furthermore, there is no need to specially attach a large main muffler or pre-muffler, and the entire structure can be constructed from a substantially uniform tube body, making it extremely easy to attach to the underfloor surface of the vehicle body. Moreover, the present exhaust system has a sound-reducing performance as a whole, so unlike an exhaust system having a main muffler or a pre-muffler, there is no need to consider the mounting position of the main muffler or pre-muffler. Furthermore, you can connect the required number of exhaust pipes of the appropriate length depending on the vehicle type, or connect exhaust pipes that bend according to the uneven shape of the underfloor of the car body, so it can be used with a variety of vehicles with different body types. Can be easily installed.

In the above embodiment, the throttle pipe 5 is provided in the exhaust pipe 3b, but as shown in FIG. 4, a perforated plate 7 having open cells or small holes is provided in the exhaust pipe 3b. Good too. Also, in this embodiment, as in the above-mentioned embodiments, it is possible to achieve the intended purpose and effects. Further, in each of the above embodiments, the exhaust system is constructed with two exhaust pipes 3a and 3b, but it goes without saying that it may be constructed with three or more exhaust pipes. The functions will be improved.

〔Effect of the invention〕

As described above, according to the present invention, exhaust noise can be reduced by expanding and contracting in one unit consisting of an exhaust pipe made of a hollow straight pipe, an exhaust pipe provided with a throttle pipe or a perforated plate, and a merging short pipe. Since the noise is efficiently attenuated by the interference effect, the entire system in which a plurality of these units are installed in series can achieve a sufficient noise reduction effect of the same number or more than a conventional exhaust system. Moreover, since the entire exhaust system is constructed of a tube body, it is very easy to attach to the underfloor surface of the vehicle body. Furthermore, even if an exhaust pipe with a conventionally used diameter is used, back pressure will not increase and fuel consumption will not increase.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional exhaust system, FIG. 2 is a partial cross-sectional perspective view of a first embodiment of the exhaust system according to the present invention, and FIG. 3 is an exhaust pipe in the exhaust system according to the present invention. FIG. 4 is an exploded perspective view of the connecting portion of the short merging pipe, and FIG. 4 is a partially sectional perspective view of another embodiment of the exhaust system according to the present invention. 3a, 3b...exhaust pipe, 4...merging short pipe, 5...throttle pipe, 7...perforated plate.

Claims (1)

[Claims] 1. An exhaust pipe consisting of a hollow straight pipe and an exhaust pipe parallel to this in which either a perforated plate or a throttle pipe with an enlarged exhaust gas outlet side is arranged inside the pipe are connected via a converging short pipe. An exhaust system characterized in that the exhaust system is connected by a plurality of communicating portions.