JP4192548B2 - Soundproof structure of engine room - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a soundproof structure for an engine room that can efficiently absorb noise radiated from an automobile engine.
[0002]
[Prior art]
The noise of automobiles such as passenger cars, trucks, and buses can be broadly divided into in-car noise felt by drivers and passengers and outside-car noise felt by people outside the car, both of which are mainly caused in the engine room. Engine noise. Since the engine noise is transmitted to the vehicle interior via the engine room and radiated to the outside of the vehicle, the acoustic characteristics of the engine room hitting the propagation path greatly affect the propagation of the noise. For this reason, it is important to reduce engine noise, which is the main sound source of an automobile, in order to ensure quietness in the passenger compartment and to reduce noise outside the vehicle.
[0003]
The engine room of a general automobile has an engine hood at the top, a hood ridge and fender at the side, a cowl that is connected at both ends to the body structure member at the rear and a vehicle body such as a dash panel that is a partition from the passenger compartment Parts surround the engine. In addition, a shielding cover with sound absorption characteristics and sound insulation characteristics is installed on the side and lower part of the engine to absorb and shield the noise in the engine room radiated from the engine. Propagation is prevented and external noise is reduced.
[0004]
However, in passenger car class automobiles where quietness is particularly important, the width in the left-right direction of the engine room is approximately 1.2 m to 1.4 m due to the total vehicle width, which is a problem with vehicle interior noise. Sound waves in the frequency range of 200 Hz to 500 Hz resonate in the left-right direction of the engine room and become standing waves (stationary waves).
[0005]
This standing wave in the left-right direction is generated when the sound wave is reflected at the side of the hood ridge where the sound absorption process is hardly performed. The front-rear strength of the standing wave in the left-right direction has a low noise level in front of the engine room because there is a radiator in which sound waves easily escape, and a high noise level in the vicinity of the rear dash panel.
[0006]
On the other hand, with respect to standing waves in the front-rear direction and the up-down direction, there is a gap between the radiator and the lower gap, and the sound pressure leaks to the outside during the process of resonance, so no problematic standing waves are generated. .
[0007]
In order to cope with such standing wave noise in the left-right direction of the engine room, conventionally, a resonance tube that has an opening on one side and resonates with the standing wave is arranged in the engine room and is defined by this resonance tube. The existing sound waves are absorbed to reduce noise. Then, as shown in FIGS. 6 and 7, the resonance tubes 31, 32, 33 are arranged on the lower surface of the engine hood 5, or as shown in FIGS. 8 and 9, the resonance tubes 34, 35, 36, 37. Are arranged in the vicinity of the dash panel 6 (see, for example, Patent Document 1).
[0008]
[Patent Document 1]
JP 2001-233244 A (Claims 1 and 2, FIGS. 1 to 4)
[0009]
[Problems to be solved by the invention]
However, in such an arrangement of the resonance tube, it is necessary to avoid interference with other parts in the engine room, so it is difficult to secure a sufficient cross-sectional area of the resonance tube due to the spatial layout in the engine room. Therefore, there is a problem that a sufficient sound absorbing force that increases in accordance with the cross-sectional area of the resonance tube cannot be secured, and a sufficient silencing effect cannot be obtained.
[0010]
In addition, since the resonance tube is formed separately from the engine parts and disposed in the engine room as a single part, it is difficult to ensure a sufficient cross-sectional area, and work for mounting the resonance tube occurs. There is also a problem that the manufacturing cost increases accordingly.
[0011]
The present invention has been made to solve the above-described problems, and an object of the present invention is to efficiently absorb the resonance sound in the engine room to reduce vehicle interior noise and vehicle exterior noise. It is to provide an engine room soundproof structure that does not get in the way.
[0012]
[Means for Solving the Problems]
The soundproof structure of the engine room for achieving the above object is an engine room in which an engine with a supercharger is arranged at the center in the width direction of the engine room. On the back side of the cooler cover and on both sides of the intercooler opening, a sound absorber that absorbs sound by resonating with the frequency of a standing wave generated in the engine room is integrally provided.
[0013]
This integral provision includes not only the integrally molded one but also the one molded separately by screwing or bonding, etc., and combining the sound absorber and intercooler cover as one It means that it can be handled.
[0014]
According to this configuration, the intercooler cover is generally intended to improve the appearance of the engine room, and since the outer surface is molded as a smooth surface, there is a lot of wasted space behind the intercooler cover. In addition, the sound absorber (resonator) is integrated with the intercooler cover so that the wasted space of the intercooler cover can be used effectively, and the sound absorber can be easily placed even in a narrow and limited engine room space. Therefore, engine noise can be reduced by the silencing effect of the sound absorber. In addition, by integrating with the intercooler cover, it is possible to prevent an increase in cost caused by mounting the sound absorber.
[0015]
In the soundproof structure of the engine room, it is preferable to manufacture the sound absorber and the intercooler cover by integral molding. With this structure, it is not necessary to reattach the sound absorber to the intercooler cover. Cost can be reduced.
[0016]
In the engine room soundproof structure, the intercooler cover is formed in a flat plate shape having an intercooler opening, and is disposed above the intercooler, and the sound absorber is connected to the intercooler opening. Place on both sides. This configuration facilitates integration of the intercooler cover and the sound absorber.
[0017]
Furthermore, in the soundproof structure of the engine room, the sound absorber is formed of a resonance tube having an opening on one side. With this configuration, since the sound absorber is formed of a simple cylindrical body, it is easy to manufacture and attach, and the manufacturing cost can be reduced, and the sound wave of the standing wave resonating with the resonance tube is absorbed to reduce the engine noise. Can be reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
In the engine room soundproof structure according to the embodiment of the present invention, as shown in FIGS. 1 to 5, the intercooler 3 of the engine 2 in the engine room 1 is covered with the intercooler cover 10, and the intercooler cover 10 has sound absorption. A resonance tube 20 which is a kind of a resonator is integrally provided.
[0020]
The intercooler cover 10 is provided around the intercooler 3 in order to improve the scenery of the engine room 1, and resonance pipes are provided on both sides of the intercooler opening 12 of the intercooler cover 10. 20 is installed.
[0021]
The resonance tube 20 is formed in a cylindrical shape having an opening 21 at one end and closed at the other end, and the opening 21 is installed with the dash panel 6 side. That is, in order to obtain a large noise reduction effect with the resonance tube 20, it is necessary to provide the opening 21 at a portion where the sound pressure is large. Therefore, the resonance tube 20 is disposed in the front-rear direction of the engine room 1, and the opening 21 is the most. It is provided so as to be closer to the dash panel 6 in the center of the engine room 1 where a large sound pressure is generated.
[0022]
The length Lr is set so that the resonance frequency fr of the resonance tube 20 matches the resonance frequency fe of the standing wave in the left-right direction of the engine room 1. At the same time, it is formed with a diameter dr or a cross-sectional shape of an appropriate size so as not to interfere with the intercooler 3. The cross-sectional shape of the resonance tube 20 is not necessarily circular, and the cross-sectional shape is appropriately selected according to the shape of the space that can be set.
[0023]
The resonance tube 20 has a sound absorbing action at the resonance frequency frm, and the resonance sound generated in the engine room 1 using the engine 2 as a sound source is absorbed by the resonance tube 20 and thereby the sound pressure due to resonance in the engine room 1 is obtained. The rise is suppressed.
[0024]
More specifically, if the width of the engine room as a resonance chamber is B, the wavelength λn of the standing wave is λn = 2B in the n mode, where n is a natural number (n = 1, 2, 3,...). / N and the resonance frequency fen is fen = c / λn = nc / 2B, where c is the speed of sound.
[0025]
For a resonance tube with one side opening, if m is a natural number (m = 1, 2, 3,...), The m-mode resonance frequency frm is frm = (2m−1) c / (4Lrm). The length Lrm of the resonance tube 20 that resonates with the standing wave needs to be corrected at the opening end. If this is omitted, frm = fen and Lrm = (2m−1) B / (2n).
[0026]
Then, assuming that the resonance width B of the engine room 1 of the automobile is 1.2 m to 1.4 m and the sound speed c is 340 m / s, the wavelengths λ2 and λ3 of the standing wave in the two-node mode and the three-node mode are λ2 = B is 1.2 m to 1.4 m, and λ3 = B is 0.8 m to 0.93 m, and the resonance frequencies fe2 and fe3 are 283 Hz to 243 Hz and 364 Hz to 425 Hz. The shortest lengths L2 and L3 of the resonance tube 20 with respect to the resonance frequencies fe2 and fe3 are set to m = 1, and Lr1 = λ2 / 4 = B / 4 and Lr2 = λ3 / 6 = without correction of the opening end. B / 6, 0.3 m to 0.4 m, and 0.2 m to 0.23 m.
[0027]
The sound absorbing force depends on the cross-sectional area of the resonance tube, and as the cross-sectional area increases, the sound absorbing force increases. Therefore, the resonance tube length Lr is usually selected in relation to the resonance frequency, and the cross-sectional shape and cross-sectional area are selected. Is selected from the arrangement relationship with the intercooler cover 10 and the intercooler 3 so that the cross-sectional area becomes as large as possible in order to obtain a large silencing effect.
[0028]
In this engine room soundproof structure, the sound absorption of the resonance tube 20 absorbs the standing wave in the left and right (lateral) direction generated by resonating with the engine room 1 using the engine 2 as a sound source, thereby reducing acoustic energy. Thus, noise can be reduced. In addition, since the opening 21 of the resonance tube 20 is arranged in the vicinity of the dash panel, which is a portion with a high noise level, in the front-rear direction of the engine room 1, the standing wave is absorbed very efficiently, The pressure level can be lowered.
[0029]
Therefore, it is possible to increase the sound absorption effect while avoiding interference with other components in the engine room 1, and to suppress an increase in sound pressure caused by the engine noise resonating in the engine room 1, thereby reducing the noise. Can be raised.
[0030]
The soundproof structure of the engine room according to the present invention has been described by taking the resonance tube 20 as an example. However, the resonance tube 20 is not necessarily a single-sided opening type resonance tube, and is not necessarily a double-sided resonance tube or a Helmholtz-type resonance type sound absorber. Or a sound absorber that can obtain a resonance effect.
[0031]
【The invention's effect】
As described above, according to the soundproof structure of the engine room according to the present invention, the sound absorber (resonator) is integrally disposed in the wasted space portion on the back side of the intercooler cover. This makes it possible to effectively reduce the engine noise by absorbing the standing wave in the engine room. In addition, by integrating the sound absorber with the intercooler cover, manufacturing and mounting are facilitated, and manufacturing costs can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a soundproof structure of an engine room according to an embodiment of the present invention.
FIG. 2 is a view in the Y direction showing the soundproof structure of the engine room of FIG. 1 with a radiator and an air cleaner omitted.
FIG. 3 is a plan view showing a structure of an intercooler cover according to the present invention.
4 is a view taken in the direction of arrow A in FIG. 3 showing the structure of the intercooler cover in FIG. 3;
5 is a cross-sectional view taken along the line BB ′ of FIG.
FIG. 6 is a schematic plan view showing an engine room with a silencer according to the prior art.
7 is a view taken in the direction of arrows U-U in FIG. 6;
FIG. 8 is a schematic plan view showing another engine room with a silencer according to the prior art.
9 is a VV arrow view of FIG. 8;
[Explanation of symbols]
1 Engine room 2 Engine 3 Intercooler 10 Intercooler cover 11 Cover body 20 Resonance tube (sound absorber)
21 Opening M Center part L Left end part R Right end part

Claims (1)

In the engine room in which the engine with a supercharger is arranged in the center in the width direction, the engine room is provided on the back side of the intercooler cover of the intercooler provided on the upper side of the engine and on both sides of the opening for the intercooler. A soundproof structure for an engine room, which is integrally provided with a sound absorber that absorbs sound by resonating with the frequency of a standing wave generated inside.

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