JP2004132203A - Soundproof structure of engine room - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soundproof structure of an engine room which can reduce a noise in a compartment and a noise out of a vehicle by efficiently absorbing a resonance sound in the room and which is not disturbed by a disposed sound absorber. <P>SOLUTION: In the engine room 1 in which an engine 2 with a supercharger is disposed at a lateral central part, the sound absorber 20 for absorbing the resonant sound by resonating with a frequency of a standing wave generated in the room 1 is provided integrally with an inter-cooler cover 10 of an inter-cooler 3 provided at an upper side of the engine 2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a soundproof structure of an engine room that can efficiently absorb noise radiated from an automobile engine.
[0002]
[Prior art]
The noise of cars, trucks, buses, and other vehicles can be broadly divided into the noise inside the vehicle felt by the driver and the occupants, and the noise outside the vehicle felt by people outside the vehicle. Engine noise. Since the engine noise is transmitted to the vehicle interior via the engine room and radiated outside the vehicle, the acoustic characteristics of the engine room, which corresponds to the propagation path, greatly affect the propagation of the noise. Therefore, it is important to reduce engine noise, which is a main sound source of a vehicle, in order to ensure quietness in the vehicle compartment and reduce noise outside the vehicle.
[0003]
The engine room of a general automobile has an engine hood at the top, a hood ridge and fenders at the side, and a body such as a cowl whose both ends are connected to the vehicle body structural members at both ends and a dash panel that is a partition from the cabin. Parts around the engine. In addition, a shielding cover with sound absorbing and sound insulating properties is provided on the side and lower part of the engine to absorb and shield noise in the engine room radiated from the engine, and It prevents propagation and reduces outside noise.
[0004]
However, in the case of a passenger car class vehicle in which quietness is particularly important, the width of the engine room in the left-right direction is approximately 1.2 m to 1.4 m from the relation of the entire width of the vehicle, which is a problem in vehicle interior noise. Sound waves in the frequency range of 200 Hz to 500 Hz cause resonance in the left and right directions of the engine room and become standing waves (standing waves).
[0005]
The standing wave in the left-right direction is generated by reflection of a sound wave at a hood ridge portion on a side surface on which almost no sound absorption processing is performed. Regarding the strength of the standing wave in the left-right direction in the front-rear direction, the noise level is low in front of the engine room due to the presence of a radiator through which sound waves can easily escape, and the noise level is high near the rear dash panel.
[0006]
On the other hand, with respect to the standing wave in the front-rear direction and the vertical direction, there is a gap between the radiator and the lower gap, and the sound pressure leaks to the outside in the process of generating resonance, so that a standing wave that causes a problem does not occur. .
[0007]
In order to cope with such standing wave noise in the left and right direction of the engine room, conventionally, a resonance tube having an opening on one side and resonating with the standing wave is arranged in the engine room, and the resonance tube is defined by the resonance tube. The sound wave of the standing wave is absorbed to reduce the noise. Then, as shown in FIGS. 6 and 7, the resonance tubes 31, 32, and 33 are disposed on the lower surface of the engine hood 5, and as shown in FIGS. 8 and 9, the resonance tubes 34, 35, 36, and 37 are provided. Is disposed in the vicinity of the dash panel 6 (for example, see 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 tubes, it is necessary to avoid interference with other parts in the engine room, and it is difficult to secure a sufficient cross-sectional area of the resonance tubes due to the spatial layout in the engine room. In other words, there is a problem that the sound absorbing power that increases according to the cross-sectional area of the resonance tube cannot be sufficiently secured, and that a sufficient noise reduction effect cannot be obtained.
[0010]
In addition, since the resonance tube is formed separately from the engine parts and arranged as a single component in the engine room, it is difficult to secure 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 in order to solve the above-mentioned problems, and an object of the present invention is to efficiently absorb resonance noise in an engine room to reduce vehicle interior noise and vehicle exterior noise, and furthermore, the arranged sound absorbers An object of the present invention is to provide a soundproof structure of an engine room that does not interfere.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the soundproof structure of the engine room is provided in an engine room in which an engine with a supercharger is arranged in the center in the width direction of the engine room. The cooler cover is integrally provided with a sound absorber that resonates with a frequency of a standing wave generated in the engine room and absorbs sound.
[0013]
The term "integrally provided" means not only the integrally molded product, but also the one molded separately and joined together by screwing or bonding, etc., and the combination of the sound absorber and the intercooler cover is considered as one It means that it can be handled.
[0014]
According to this configuration, the intercooler cover generally aims 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 on the back side of the intercooler cover. By installing a sound absorber (resonator) integrally with the intercooler cover, the wasted space of the intercooler cover is effectively used, and the sound absorber can be easily arranged even in a narrow engine room space. Therefore, the noise reduction effect of the sound absorber can reduce the engine noise. In addition, by integrating it with the intercooler cover, it is possible to prevent an increase in cost caused by the installation of the sound absorber.
[0015]
In the soundproof structure of the engine room, it is preferable that the sound absorber and the intercooler cover are manufactured by integral molding. With this structure, it is not necessary to attach the sound absorber to the intercooler cover again. Cost can be reduced.
[0016]
In the above-mentioned soundproof structure for an engine room, the intercooler cover is formed in a flat plate shape having an intercooler opening, is disposed above the intercooler, and the sound absorber is connected to the intercooler opening. Place on both sides of the. With this configuration, the intercooler cover and the sound absorber can be easily integrated.
[0017]
Further, in the above-described soundproof structure of the engine room, the sound absorber is formed by a resonance tube having an opening on one side. According to this configuration, since the sound absorber is formed of a simple cylindrical body, manufacturing and mounting are easy, manufacturing costs can be reduced, and a standing wave sound wave that resonates with the resonance tube is absorbed to reduce engine noise. Can be reduced.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
In the soundproof structure of the engine room 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 absorbs sound. A resonance tube 20, which is a kind of a vessel (resonator), is provided integrally.
[0020]
The intercooler cover 10 is provided around the intercooler 3 in order to improve the view of the engine room 1. Resonance tubes are provided on both sides of the intercooler opening 12 of the intercooler cover 10. 20 is installed.
[0021]
The resonance tube 20 has an opening 21 at one end and is formed in a tubular shape with the other end closed, and is installed with the opening 21 facing the dash panel 6. 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 arranged in the front-rear direction of the engine room 1, and the opening 21 is 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 and right direction of the engine room 1. In addition, it is formed with an appropriate size of the diameter dr or the cross-sectional shape so as not to interfere with the intercooler 3. Note that the cross-sectional shape of the resonance tube 20 does not necessarily have to be circular, and the cross-sectional shape is appropriately selected according to the shape of the settable space.
[0023]
The resonance pipe 20 has a sound absorbing function at a resonance frequency frm. A resonance sound generated in the engine room 1 by using the engine 2 as a sound source is absorbed by the resonance pipe 20 so that a sound pressure due to resonance in the engine room 1 is generated. The rise is suppressed.
[0024]
More specifically, assuming that the width of the resonance room of the engine room 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 sound speed.
[0025]
Further, for a one-sided opening resonance tube, if m is a natural number (m = 1, 2, 3,...), The resonance frequency frm of the m mode is frm = (2m-1) c / (4Lrm), and is constant. The length Lrm of the resonance tube 20 that resonates with the standing wave needs to be corrected for the open end, but if this is omitted, then frm = fen, and Lrm = (2m-1) B / (2n).
[0026]
When 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 waves in the two-node mode and the three-node mode are λ2 = For B, 1.2 m to 1.4 m, and for λ3 = B, 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 for the resonance frequencies fe2 and fe3 are m = 1, and Lr1 = λ2 / 4 = B / 4 and Lr2 = λ3 / 6 = without correction of the open end. B / 6, which is 0.3 m to 0.4 m and 0.2 m to 0.23 m.
[0027]
Note that the sound absorption power depends on the cross-sectional area of the resonance tube, and as this cross-section increases, the sound absorption increases, so that the resonance tube length Lr is usually selected in relation to the resonance frequency, and the cross-sectional shape and cross-section Is selected from the positional relationship with the intercooler cover 10 and the intercooler 3 so that the cross-sectional area is as large as possible in order to obtain a large noise reduction effect.
[0028]
In the soundproof structure of the engine room, the sound absorbing function of the resonance tube 20 absorbs standing waves in the left and right (lateral) directions generated by resonating with the engine room 1 using the engine 2 as a sound source to reduce acoustic energy. Thus, noise can be reduced. In addition, since the opening 21 of the resonance tube 20 is arranged near the dash panel, which is a high noise level portion, in the front-back direction of the engine room 1, the standing wave is absorbed very efficiently, The pressure level can be reduced.
[0029]
Therefore, it is possible to enhance the sound absorbing effect while avoiding interference with other components in the engine room 1, suppress a rise in sound pressure caused by engine noise resonating in the engine room 1, and reduce the noise reduction effect. Can be raised.
[0030]
Although the soundproof structure of the engine room according to the present invention has been described by taking the resonance tube 20 as an example, the resonance tube is not necessarily a one-sided opening type resonance tube, but may be a two-sided opening resonance tube or a Helmholtz type resonance type sound absorber. Or any other sound absorbing device that can provide a resonance effect.
[0031]
【The invention's effect】
As described above, according to the engine room soundproofing structure of the present invention, since the sound absorber (resonator) is integrally disposed in the wasted space behind the intercooler cover, this waste is eliminated. By effectively utilizing the space, the sound of standing waves in the engine room can be absorbed and the engine noise can be reduced. In addition, by integrating the sound absorber with the intercooler cover, manufacturing and mounting become easy, 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 showing the soundproof structure of the engine room shown in FIG. 1 and viewed from the direction of the arrow Y in which a radiator and an air cleaner are omitted.
FIG. 3 is a plan view showing a structure of an intercooler cover according to the present invention.
FIG. 4 is a view in the direction of arrow A in FIG. 3 showing the structure of the intercooler cover of FIG. 3;
FIG. 5 is a sectional view taken along the line BB ′ of FIG. 3;
FIG. 6 is a schematic plan view showing a conventional engine room with a muffler.
FIG. 7 is a view as viewed in the direction of the arrow UU in FIG. 6;
FIG. 8 is a schematic plan view showing another engine room with a silencer according to the related art.
FIG. 9 is a view on arrow VV of FIG. 8;
[Explanation of symbols]
REFERENCE SIGNS LIST 1 engine room 2 engine 3 intercooler 10 intercooler cover 11 cover body 20 resonance tube (sound absorber)
21 Opening M Central part L Left end R Right end

Claims (1)

In the engine room where the supercharged engine is arranged in the center in the width direction, the intercooler cover of the intercooler provided on the upper side of the engine resonates with the frequency of the standing wave generated in the engine room. A soundproof structure for an engine room, which is provided with a sound absorber for sound absorption.

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