JP3759483B2 - Radiation noise reduction device in engine exhaust system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiated sound reducing device for reducing radiated sound emitted from functional parts such as a flexible tube, a catalytic converter, a main, and a sub silencer provided in an exhaust system of an engine.
[0002]
[Prior art]
In the exhaust system of an engine provided with functional parts such as the silencer, the shock wave component of the sound in the exhaust pipe generated by the pressure pulsation of the exhaust grows in each upstream exhaust pipe such as the silencer. It has been conventionally known that when a wall such as a silencer is vibrated in a pulsed manner and the air around the wall is vibrated, a radiated sound including an unpleasant high-frequency component is generated. ing.
[0003]
And the technical means for reducing such a radiated sound has already been proposed (for example, refer patent document 1).
[0004]
[Patent Document 1]
Japanese Patent No. 2744896
[Problems to be solved by the invention]
By the way, in the conventional radiation noise reduction technology, a sound absorption material such as glass wool is specially wound around an outer cylinder of a silencer or the like, or the outer cylinder has a complicated double tube structure having a large number of partition walls inside. It was something to do.
[0006]
However, in the former, there are problems such as an increase in cost and weight associated with the use of the sound absorbing material, and the sound absorbing material is deteriorated at an early stage. There are problems such as cumbersome manufacturing and high manufacturing costs and poor mass productivity.
[0007]
The present invention has been made in view of such circumstances, and provides a radiated sound reduction device in an exhaust system of an engine having a simple structure that can effectively reduce the generation of the radiated sound at a light weight and at a low cost. It is an object.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is characterized in that a radiated sound generating section that generates a radiated sound when a wall surface is vibrated by a shock wave generated by pressure pulsation of exhaust flowing in the exhaust pipe is provided in the middle of the exhaust pipe or in the exhaust system of the engine located downstream end of the exhaust pipe, the upstream portion than the radiated sound generating unit, the radiation sound generation from the radiation sound generating unit to suppress the growth of the shock wave at the upstream portion Forming an enormous tube portion for reducing the enlarging tube portion, the axial length of the enormous tube portion being shorter than the inner diameter, and the upper and downstream ends so that the upper and downstream ends of the enormous tube portion are respectively squeezed Each of which is integrally provided with an expansion chamber, and is provided with an expansion chamber inside thereof, and is formed on the inner periphery of the upstream connection cylinder portion with a diameter smaller than that of the enormous cylinder portion and on the downstream side. When an inner pipe whose end has entered the middle of the expansion chamber is fitted and connected In, wherein the annular space is formed between the inner periphery of the outer peripheral and the enormous tubular portion of the downstream end. According to this feature, the exceptionally wide pipe section rapidly increases changing the exhaust passage cross-sectional area in the interior of, since it is possible to suppress the growth of the shock wave on the upstream side of the radiant sound generating unit, from the radiated sound generator Ru can be reduced in generation of the sound radiated effectively.
[0009]
In the present invention, the “radiant sound generator” corresponds to functional parts such as a flexible tube, a catalytic converter, a main, and a sub silencer that are provided in the exhaust system of the engine and in which the generation of the radiated sound is a problem. . Further, the “radiated sound” of the present invention does not include the discharge sound of exhaust from the tail end of the exhaust pipe.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the embodiments of the present invention shown in the accompanying drawings.
[0011]
In this embodiment, the present invention is applied to a vehicle equipped with an in-line four-cylinder engine. FIG. 1 is a side view showing the main part of the engine E and its exhaust system Ex, and FIG. 2 is an enlarged view of FIG. 3, FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. 2, FIG. 4 is a sectional view taken along line 4-4 in FIG. 3, and FIG. FIG. 6 is a graph showing the relationship with the area ratio, FIG. 6 is a graph showing a time-series pressure waveform change of the pressure inside the tube when a shock wave is input into the flexible tube, and FIG. 7 is a frequency distribution of the sound radiated from the flexible tube. FIG. 8 is a graph corresponding to FIG. 1 showing another embodiment in which the arrangement portion of the enormous tube portion is changed.
[0012]
In FIG. 1, a traveling engine E for a vehicle V is mounted horizontally on a vehicle body frame 1 of the vehicle V via front and rear engine mounts. The engine E is a four-cycle in-line four-cylinder engine, and four exhaust ports 2 are opened in parallel on the rear side (right side in FIG. 1), and the exhaust system according to the present invention is connected to these exhaust ports 2. Ex is connected.
[0013]
The exhaust system Ex includes an exhaust manifold 3 whose upstream end is integrally connected to the exhaust port 2 and an exhaust pipe 4 connected to its downstream end.
[0014]
The exhaust pipe 4 includes a first exhaust pipe portion 4A on the upstream side and a second exhaust pipe portion 4B on the downstream side, and a spherical joint J is provided between the exhaust manifold 3 and the first exhaust pipe portion 4A. And a flexible tube 5 is interposed between the first exhaust pipe portion 4A and the second exhaust pipe portion 4B. Further, in the middle of the second exhaust pipe portion 4B, a catalytic converter 6 and a sub silencer ( A main silencer (not shown) and a main silencer (not shown) are interposed in series in this order with a space therebetween.
[0015]
Next, the structure of the exhaust pipe 4 will be described with reference to FIGS. The first exhaust pipe portion 4A includes a first exhaust pipe portion main body 10 made of a heat-resistant rigid material (for example, cast iron) made of a hollow double tube and an enormous amount of heat-resistant rigid material (for example, stainless steel) connected to the upstream end thereof. It is comprised with the pipe part 11. FIG.
[0016]
The enormous tube portion 11 includes an enormous tube portion 11m located in the central portion in the axial direction, and tapered tapered connecting tube portions 11a and 11b integrally connected to both ends of the enormous tube portion 11m. The internal space is an expansion chamber C. The distal end portion of the upstream connecting tube portion 11a, that is, the inlet end of the enormous tube portion 11 is fitted and welded (welded) over the entire circumference to the downstream end of a second connection flange f2 (described later) of the spherical joint J. The The downstream end of the connecting tube portion 11b on the downstream side, that is, the outlet end of the enormous tube portion 11, is also fitted and connected (welded) to the upstream end of the first exhaust pipe portion body 10 over the entire circumference.
[0017]
The enormous tube portion 11 is internally provided with an inner tube 12 made of a cylindrical tube that is substantially the same diameter as the tip end of the upstream connecting tube portion 11a, that is, a sufficiently small diameter compared with the enormous tube portion 11m. The inner pipe 12 functions as a passage cross-sectional area changing means for abruptly increasing the exhaust passage cross-sectional area inside the enormous pipe portion 11, and its upstream end is upstream of the enormous pipe portion 11 in the illustrated example. It is fitted and connected (welded) to the tip of the side connecting cylinder 11a in an airtight manner over the entire circumference.
[0018]
The downstream end 12d of the inner pipe 12 enters the expansion chamber C up to a substantially central region of the enormous cylinder part 11m, and the outer peripheral surface of the inner pipe 12 and the enormous pipe part 11 (particularly the enormous cylinder part 11). An annular gap s is interposed between the portion 11m and the inner peripheral surface of the upstream connecting cylinder portion 11a).
[0019]
Thus, the huge pipe portion 11 is formed in the exhaust pipe 4 (that is, the first exhaust pipe portion 4A) on the upstream side of the flexible tube 5 as the radiated sound generating portion, and the huge pipe portion of the present invention. Is configured.
[0020]
By the way, in the exhaust system Ex, when the spherical joint J and the flexible tube 5 are provided side by side, the engine E is largely subjected to rolling vibration, that is, rolling displacement, due to traveling of the vehicle V, particularly traveling such as sudden start, sudden acceleration, and sudden deceleration. In this case, the displacement can be effectively absorbed to reduce the vehicle vibration caused by the rolling displacement of the engine E as much as possible. An exhaust system upstream of the exhaust pipe 4 will be described below. The configuration of Ex will be specifically described.
[0021]
As clearly shown in FIGS. 2 and 3, the four distribution pipes 3 a of the exhaust manifold 3 are curved in an elbow shape with their upstream ends connected to the four exhaust ports 2 of the engine E, respectively. Ascending gradually toward the rear, the engine E extends downwardly adjacent to the rear surface thereof, and its downstream end opens downward, and its downstream end is integrally connected to one exhaust collecting part 3b. Has been. As shown in FIG. 1, the exhaust collecting portion 3b is located near the rear surface of the engine E, and is connected to the upstream end of the first exhaust pipe portion 4A via the spherical joint J (in the illustrated example, the enlarged pipe portion 11). Connected to the upstream end).
[0022]
As shown in FIGS. 3 and 4, the spherical joint J includes a first connection flange f1 constituting a joint half on the exhaust manifold side, a second connection flange f2 constituting a joint half on the exhaust pipe side, and And a gasket G sandwiched between the flanges f1 and f2. The gasket G is formed of a heat-resistant material such as carbon, and has an opening Ga for exhaust gas circulation at the center and a spherical portion Gb surrounding the opening on one side surface. The gasket G has a flat other side surface Gc in contact with the first connection flange f1, and the spherical surface portion Gb is slidable on a spherical seating surface formed on the second connection flange f2. Touched. The first and second connection flanges f1 and f2 are elastically connected via a spring 8 by a plurality of sets of bolts and nuts 7.
[0023]
An exhaust collecting portion 3b at the downstream end of the exhaust manifold 3 is fitted and connected (welded) in an airtight manner to the center portion of the first connection flange f1 of the spherical joint J. In addition, an upstream end (upstream end of the enormous pipe portion 11) of the first exhaust pipe portion 4A that opens upward is integrally connected to the center portion of the second connection flange f2. Therefore, the exhaust gas flowing through the exhaust manifold 3 flows through the spherical joint J to the first exhaust pipe portion 4A.
[0024]
The first connection flange f <b> 1 of the spherical joint J is detachably fixed to the rear surface of the engine E via the stay 9. Therefore, when the engine E performs the rolling displacement, the second connection flange f2 is rotationally displaced via the gasket G with respect to the first connection flange f1.
[0025]
As described above, the exhaust pipe body 10 of the first exhaust pipe portion 4A, the upstream end of which is connected to the spherical joint J, has a curved portion that curves convex toward the engine E side, and the upstream side thereof. A half portion extends downward with respect to the engine E, and a downstream half portion thereof extends rearward with respect to the engine E, and is formed in an elbow shape in a side view. The front end of the flexible tube 5 is fitted and connected (welded) over the entire circumference to the downstream end of the first exhaust pipe portion 4A that opens toward the rear.
[0026]
The flexible tube 5 is formed in a bellows shape that can be expanded and contracted in the front-rear direction, and absorbs mainly the component in the front-rear direction among the rolling displacement of the engine E by the expansion and contraction. In the illustrated example, a protective blade 15 made of a metal mesh is wound around the outer periphery of the bellows-shaped wall surface 5w of the flexible tube 5, but this protective blade may be omitted. In addition, since the conventionally well-known thing is employ | adopted for the said flexible tube 5, the detailed description beyond this is abbreviate | omitted.
[0027]
The second exhaust pipe portion 4B connected to the downstream end of the flexible tube 5 extends substantially horizontally in the front-rear direction of the vehicle V. In the middle of the second exhaust pipe portion 4B, the catalytic converter 5 is connected. A sub silencer and a main silencer (not shown) are connected to the second exhaust pipe portion 4B on the downstream side, and a tail pipe (not shown) that opens to the atmosphere is connected to the outlet side of the main silencer. Is done.
[0028]
In the illustrated example, the upstream end portion of the second exhaust pipe portion 4B is supported by the vehicle body of the vehicle V via the elastic support means 14.
[0029]
Next, the operation of this embodiment will be described.
[0030]
The exhaust gas generated by the operation of the engine E is the exhaust manifold 3, the spherical joint J, the first exhaust pipe portion 4A, the flexible tube 5, the upstream portion of the second exhaust pipe portion 4B, the catalytic converter 6, and the second exhaust pipe portion 4B. , And a sub silencer and a main silencer (not shown), while harmful components such as HC and CO are purified and exhaust sound is silenced and released to the atmosphere.
[0031]
By the way, when the vehicle V travels, particularly when it suddenly starts, suddenly accelerates, or suddenly decelerates, the engine E undergoes rolling displacement as described above, and this rolling displacement is caused by the first, It is effectively absorbed by the relative rotational displacement of the second connection flanges f1, f2. That is, since the spherical joint J is disposed between the exhaust manifold 3 and the first exhaust pipe portion 4A at a position close to the engine E, the spherical joint J is as close as possible to the rolling shaft of the engine E. Even when the engine E undergoes a large rolling displacement, the small rotational displacement of the spherical joint J can reliably absorb the large rolling displacement and prevent the displacement from being transmitted to the flexible tube 5. it can. Accordingly, the length of the flexible tube 5 can be set to a relatively short length that is sufficient to absorb the displacement component in the front-rear direction of the rolling displacement that occurs during normal travel of the vehicle V, thereby reducing cost and durability. Improvement is achieved.
[0032]
Further, the enormous pipe portion 11 of the exhaust pipe 4 is located upstream of the flexible tube 5 as a radiated sound generating portion that generates a radiated sound when the wall surface is vibrated by a shock wave of the sound in the exhaust pipe generated by the pressure pulsation of the exhaust. is doing. Then, in the process of exhaust gas flowing into the expansion chamber C from the downstream end 12d of the inner tube 12 inside the enormous tube unit 11, the exhaust passage is rapidly increased and the exhaust gas is rapidly expanded, and the shock wave Thus, the growth of the shock wave on the upstream side of the tube 5 is effectively suppressed, and the generation of the radiated sound from the tube 5 is effectively reduced.
[0033]
Such a reduction effect of the radiated sound by the special provision of the enormous tube portion 11 has been confirmed by an experiment conducted by the present inventors. Here, the pressure ratio of the exhaust pressure (exit side pressure) immediately upstream of the flexible tube 5 as the radiated sound generating unit to the exhaust pressure (inlet side pressure) immediately upstream of the enormous pipe portion 11 is the sound pressure in the exhaust pipe. This is an index representing the strength of the shock wave, and the smaller the pressure ratio, the smaller the shock wave.
[0034]
Therefore, when the inner diameter of the inner tube 12 is A and the inner diameter of the enlarged tube portion 11m of the enlarged tube portion 11 is B, the opening cross-sectional area ratio (so-called M ratio) represented by (B / A) ² When the relationship with the pressure ratio was confirmed with an actual machine, a graph as shown in FIG. 5 was obtained. According to this graph, the pressure ratio decreased as the opening cross-sectional area ratio increased, and was maximum in the range of the opening cross-sectional area ratio of 1 to 1.5. From this result, the pressure ratio decreases, that is, the shock wave is reduced, and the effect of reducing the radiated sound is better as the opening cross-sectional area ratio is larger, that is, the sudden increase change ratio of the exhaust passage cross-sectional area in the huge pipe portion 11 is larger. Was confirmed. In the graph, plot a corresponds to the conventional example, both A and B are 48.6 mm, plot b is 48.6 mm and B is 60 mm, and plot c is 48.6 mm in A. B is 70 mm, and plot d is 48.6 mm for A and 90 mm for B.
[0035]
FIG. 6 shows a time-series pressure waveform change of the pressure in the tube when a shock wave is inputted into the flexible tube 5 under the above plot conditions. Further, FIG. 7 shows the flexible under the conditions of plots a and c. The frequency distribution of the radiated sound from the tube 5 (engine speed is 4000 rpm) is shown. From these graphs, it can be seen that the shock wave of the sound in the exhaust pipe is reduced by the special provision of the enormous pipe portion 11, and the effect of reducing the radiated sound is good.
[0036]
The experiment described that the effect of reducing the radiated sound of the flexible tube 5 due to the special provision of the enormous tube portion 11 as described above is deteriorated if the length of the exhaust passage from the radiated sound generating portion, that is, the flexible tube 5 to the enormous tube portion 11 is too long. It was confirmed in. This is considered to be because when the exhaust passage length exceeds a predetermined limit length, the shock wave grows again during that time and vibrates the radiated sound generating portion. Further, it has been confirmed by experiments that if the exhaust passage length is equal to or shorter than a predetermined limit length, the effect of reducing the radiated sound by the huge pipe portion can be sufficiently obtained regardless of the length.
[0037]
FIG. 8 shows an embodiment in which the enormous tube portion is arranged at a site different from the above embodiment. For example, in FIG. 8A, the enormous tube portion 11 is disposed immediately upstream of the flexible tube 5 as the radiated sound generating portion, and in this arrangement, the flexible tube 5 and other radiated sound generating portions are used. This is effective for reducing each radiated sound from the catalytic converter 6.
[0038]
In FIG. 8B, the enormous tube portion 11 is disposed immediately downstream of the flexible tube 5 serving as a radiated sound generating portion (that is, immediately upstream of the catalytic converter 6). However, it is not effective in reducing the radiated sound from the flexible tube 5.
[0039]
Further, in order to reduce the radiated sound from a silencer (not shown) located downstream of the catalytic converter 6, a huge pipe portion is provided on the upstream side from the silencer. In this case, the silencer and the huge pipe are provided. The length of the exhaust passage between the parts does not exceed the predetermined limit length.
[0040]
As mentioned above, although one Example of this invention was described, this invention is not limited to the Example, A various Example is possible within the scope of the present invention.
[0041]
For example, in the above-described embodiment, the case where the radiated sound reduction device in the exhaust system according to the present invention is implemented in an in-line four-cylinder four-cycle engine has been described, but it is needless to say that this can be implemented in other types of engines. .
[0042]
【The invention's effect】
As described above, according to the present invention, the engine in which the radiated sound generating portion that generates the radiated sound when the wall surface is vibrated by the shock wave generated by the pressure pulsation of the exhaust flowing in the exhaust pipe exists in the middle or downstream end of the exhaust pipe. In the exhaust system of the present invention, an enormous tube for reducing the generation of the radiated sound from the radiated sound generating unit by suppressing the growth of the shock wave in the upstream part of the exhaust pipe upstream of the radiated sound generating unit The enormous tube portion is connected to the upper and downstream ends so as to constrict the upper and downstream ends of the enormous cylinder portion whose axial length is shorter than the inner diameter, and the enlarging tube portion, respectively. The connecting cylinder part is integrally provided, and an expansion chamber is provided inside. The connecting cylinder part on the upstream side of the connecting cylinder part is formed to have a smaller diameter than the enormous cylinder part, and the downstream end is the expansion chamber. The inner pipe that has penetrated to the middle part is fitted and connected to the outer end of the downstream end. The annular gap is formed between the inner periphery of the large cylindrical portion and, the inside of the large tube portion sharply increases changing the exhaust passage cross-sectional area, wherein the upstream side of the radiant sound generator The growth of the shock wave can be suppressed , whereby the generation of the radiated sound from the radiated sound generating unit can be effectively reduced. In addition, the above-mentioned effect can be obtained with a relatively simple structure in which the huge pipe part is provided in the exhaust pipe upstream of the radiated sound generating part, and the peripheral wall of a functional part such as a silencer as the radiant sound generating part is specially modified. There is no need to use a special sound absorbing material such as glass wool, so the increase in cost and weight due to the special installation of the radiated sound reduction device can be suppressed as much as possible, and the radiated sound reduction effect is effectively demonstrated over a long period of time. The
[Brief description of the drawings]
1 is a side view showing an essential part of an engine E and its exhaust system Ex. FIG. 2 is an enlarged view taken along arrow 2 in FIG. 1. FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. Fig. 5 is a cross-sectional view taken along line 4-4. Fig. 5 is a graph showing the relationship between the exhaust pressure ratio and the opening cross-sectional area ratio of the enormous tube. Fig. 6 Time series of pipe pressure when a shock wave is input into the flexible tube. Graph showing pressure waveform change [FIG. 7] Graph showing an example of frequency distribution of radiated sound from flexible tube [FIG. 8] FIG. 1 corresponding to FIG. Explanation of]
4 .... exhaust pipe 4A ... first exhaust pipe part (upstream part)
4B ... 2nd exhaust pipe part 5 ... Flexible tube (radiation sound generation part)
6 ... Catalyst converter (radiated sound generator)
11... Enlarged pipe part 11a... Upstream connecting cylinder part 11b... Downstream connecting cylinder part 11m... Enlarged cylinder part 12.
12d ... downstream end C ... expansion chamber E ... engine Ex ... exhaust system s ... annular gap

Claims (1)

When the wall surface is vibrated by a shock wave generated by pressure pulsation of the exhaust gas flowing in the exhaust pipe (4), a radiated sound generating portion (5, 6) is generated in the middle or downstream end of the exhaust pipe (4). In the existing engine exhaust system,
The exhaust pipe (4), wherein the upstream portion than radiated sound generator (5, 6) (4A), the upstream portion and the suppressing the growth of the shock wave the radiated sound generator in (4A) (5, large tube portion for reducing the occurrence of the sound radiated from 6) (11) is formed,
The enormous tube portion (11) has an axial length that is shorter than the inner diameter (B), and the upper and downstream sides of the enormous tube portion (11m) and the upper and downstream ends of the enormous tube portion (11m). It has integrally connecting tube portions (11a, 11b) connected to the ends respectively, and has an expansion chamber (C) inside,
On the inner periphery of the upstream connecting tube portion (11a), the downstream tube portion (12d) has a diameter smaller than that of the enormous tube portion (11m) and enters the expansion chamber (C) to the middle portion thereof. The inner tube (12) is fitted and connected, and an annular gap (s) is formed between the outer periphery of the downstream end (12d) and the inner periphery of the enormous cylinder portion (11m). that, radiated sound reducing equipment in the exhaust system of the engine.

Images