JP2001247055A - Soundproof engine hood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soundproof engine hood capable of reducing cabin inside noise and car outside noise by efficiently absorbing a resonance sound in an engine room by arranging resonance sound absorbing pipes having opening parts on both sides in an air passage for an intercooler arranged in an engine hood. SOLUTION: In this engine hood 3 for arranging the air passage 30 up to the intercooler 9 on the under surface side from an outside air introducing port 30a arranged in front of a vehicle of an automobile, the resonance sound absorbing pipes 41 to 43 having a resonance frequency of a lateral directional standing wave generated by cavity resonance of the engine room 1 and having the opening parts 41a to 43a, 41b to 43b on both sides, are arranged in the air passage 30 to constitute the soundproof engine hood.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soundproof engine hood capable of efficiently absorbing noise radiated from an automobile engine.

[0002]

2. Description of the Related Art Noise of automobiles such as passenger cars, trucks, and buses can be roughly classified into interior noises felt by drivers and occupants and exterior noises felt by people outside the vehicle.
The main cause is engine noise generated in the engine room. This engine noise is transmitted to the vehicle interior via the engine room and radiated outside the vehicle, so that the acoustic characteristics of the engine room, which corresponds to the propagation path, have a significant effect.

[0003] As schematically shown in Fig. 8, the structure of an engine room 1 of a general automobile has an engine hood (bonnet) 3 at an upper portion, a hood ridge 4 and a fender 5 at a side portion, and a body structure at a rear portion. Body parts such as a cowl 2 having both ends connected to a member 7 and a dash panel 6 which is a partition from a vehicle compartment, and surrounds an engine 10 which is a noise source installed in a central portion.

[0004] Regarding vehicle interior noise, generally,
The problem is the sound of relatively low frequency components of 500 Hz or less, and particularly the main component that is perceived as engine noise is the medium frequency sound of 200 Hz to 500 Hz.
In addition, regarding the noise outside the vehicle, the sound of a component having a relatively high frequency of 500 Hz or more mainly affects the noise.

On the other hand, the width of the engine room in the left-right direction is approximately 1.2 m to 1.4 m in view of the overall width of the vehicle in a passenger car class vehicle in which quietness is particularly important. A part of the problematic sound in the middle frequency range resonates in the left and right directions of the engine room and becomes a standing wave (standing wave).

Considering the strength of the standing wave in the left-right direction with respect to the front-rear direction of the vehicle, the noise level is low in front of the engine room due to the presence of a radiator from which sound can easily escape. The noise level is high.

[0007] The standing waves in the middle frequency range that are particularly problematic are standing waves in the two-node mode and the three-node mode in the left-right direction of the engine room 1 as shown in FIG. In the two-bar mode, the center M of the engine room 1 and the right end R and the left end L of the engine room 1
, And in the three-bar mode, one-third and two-thirds of the parts M ′ and M ′, and the right end R of the engine room 1,
An antinode of the acoustic mode in which the amplitude of the sound pressure is maximum occurs at the left end L, and the noise of the amplified frequency propagates to the vehicle interior and exterior.

In order to cope with such a noise in the two-bar mode, Japanese Patent Application No. 10-358055 discloses a Helmholtz type resonance sound absorber installed in an engine room to reduce noise.

As shown in FIG. 9 to FIG. 12, in the engine rooms 11 and 21 with the sound deadening device, resonance-type sound absorption in which the resonance frequency is matched in accordance with the frequency of the standing wave in the left-right two-node mode. The devices 18C, 18R and 18L are installed in the space inside the cowl 12, and the resonance type sound absorbers 28C, 28R and 28L are installed on the upper surface of the engine hood 23.

The resonance type sound absorbers 18C, 18R, 18
The openings of the necks 82 of the L, 28C, 28R, and 28L face the portions corresponding to the antinodes of the standing waves, that is, the central portions M and both ends R, L of the engine rooms 11, 21 in the left-right direction. Has been established.

[0011]

However, the Helmholtz type resonance type sound absorbers 18C to 28L have a neck portion 82 and a resonance chamber 81, and the resonance chamber 81 requires a volume V corresponding to the resonance frequency f. Therefore, the structure becomes relatively large and the structure becomes complicated.

This resonance frequency f involves several factors.
This is a complicated calculation, where c is the speed of sound, d is the diameter of the introduction hole, and k is
When the number of introduction holes, V is the volume, and tc is the thickness of the introduction hole,
In this case, f = (c / 2π) × SQRT (C0 / V).
You. Where C0 = kπ (2d) ^Two/ (Tc + β × d /
2), β = π / 2.

The resonance type sound absorbers 18C to 18L
In the cowl 2 for disposing the sound absorber, there is a problem that it is difficult to install the resonance type sound absorbers 18C to 18L while securing a sufficient volume suitable for silencing since the wiper system is usually installed. In addition, when installed in the engine hood 3, there is a problem that the resonance type sound absorbers 28C to 28L obstruct the driver's view.

On the other hand, as shown in FIGS.
In the case of an engine with a supercharger or the like, when the intercooler 9 is equipped, in addition to the outside air inlet 1a for the engine 10 provided in front of the engine hood 3, the engine hood 3
In some cases, an air bulge 35b is provided at the center of the air cooler, and an outside air inlet 35a for the intercooler 10 is provided in front of the air bulge 35b.

An intercooler is provided from the outside air inlet 35a.
The air passage 35 leading to 10 is close to the engine 10,
Since the outside air inlet 35a has a relatively large opening area, there is a problem that engine noise of a high-frequency component of 500 Hz or more leaks out of the vehicle from the outside air inlet 35a to deteriorate outside noise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. An object of the present invention is to dispose a resonance sound absorbing tube having openings on both sides in an air passage for an intercooler provided in an engine hood. It is an object of the present invention to provide a soundproof engine hood capable of efficiently absorbing resonance in an engine room and reducing vehicle interior noise and vehicle exterior noise.

[0017]

SUMMARY OF THE INVENTION A soundproof engine hood for achieving the above object is constituted as follows.

1) In an engine having an intercooler, in order to provide an outside air inlet for the intercooler in front of the vehicle and to reduce noise caused by standing waves in the left and right directions caused by cavity resonance in the engine room,
A sound absorbing tube having openings on both sides and also serving as an air passage is provided on the lower surface of the engine hood and between the outside air inlet and the opening of the intercooler.

According to the soundproof type engine hood having these constructions, the outside air inlet for the intercooler is provided in front of the vehicle, and the resonance sound absorbing tube which resonates with the standing wave in the left and right direction of the engine room is provided in the air passage for the intercooler. To
Since the opening of the resonance sound absorbing tube is disposed at the antinode of the acoustic mode in which the sound pressure of the resonance sound, which is a standing wave, is maximized, the opening of the resonance sound absorbing tube is also provided. Sound energy is efficiently reduced by the resonance sound absorbing tube.

This resonance sound absorbing tube is an open-ended resonance tube having openings on both sides. The relationship between the length Lr of the resonance sound absorbing tube and the resonance frequency fr is such that c is the sound speed, and n is a natural number (n =
1, 2, 3,...), Fr = (nc) / (2L
r).

Further, the sound absorbing power is determined by the cross-sectional area of the passage of the resonance sound absorbing tube, and as this cross-sectional area increases, the sound absorbing power increases. Usually, this cross-sectional area is limited by the place where it can be arranged, but within that limit, based on the frequency analysis of noise, considering the sound pressure level of each frequency to be silenced, the most efficient overall The cross-sectional area of each resonance sound absorbing tube will be determined so that the noise level is reduced.

When the sound absorbing device is constituted by the resonance sound absorbing tubes having the openings on both sides, the resonance sound absorbing tubes have an elongated cylindrical shape and are open at both ends, so that they can be used as air passages. Therefore, it is used here as an air passage for taking in outside air of the intercooler.

Also, since the air inlet for the intercooler is provided in front of the vehicle away from the engine,
Leakage of engine noise outside the vehicle is reduced.

Since the resonance sound absorbing tube is housed in the engine hood, it can be easily installed in a narrow engine room without requiring a special installation space.

2) In the soundproof type engine hood having the above-described configuration, the opening of the resonance sound absorbing tube is disposed at a position where an antinode of the acoustic mode of the standing wave is generated in the left-right direction of the engine room. Be composed.

That is, in the left-right direction of the engine room, antinodes of standing waves of even mode such as two-node mode are formed in the center of the engine room, and one-node mode and two-node mode are formed near the hood ridge. The antinode of the standing wave mode of each mode such as the knot mode is formed, and the noise level is high near the dash panel in the front and rear direction of the engine room, and the opening of the resonance sound absorbing tube is arranged in this part Therefore, the target standing wave is efficiently absorbed.

3) In the soundproof type engine hood having the above structure, the first resonance frequency of the standing wave in the two-node mode and the second resonance frequency of the standing wave in the three-node mode generated in the left and right directions of the engine room are respectively set. A soundproof engine hood in which a first sound absorbing tube and a second sound absorbing tube are disposed on a lower surface of an engine hood, wherein an opening of the first sound absorbing tube is disposed substantially at a center in a left-right direction of an engine room, The second
The opening of the second sound absorbing tube having the resonance frequency is arranged at approximately one third and two thirds of the engine room in the left-right direction.

When the standing waves in the two-bar mode and the three-bar mode, which are the main causes of engine noise, are to be silenced,
Since the antinode of the two-node mode is generated in the center part in the left-right direction of the engine room, the opening of the first resonance sound absorbing tube having the first resonance frequency of the standing wave of the two-node mode is arranged in this part, Approximately one-third of the engine room in the left-right direction and 3
Since the antinode of the three-node mode occurs in the second half, the second node having the second resonance frequency of the standing wave of the three-node mode in this portion.
By arranging the opening of the resonance sound absorbing tube, it is possible to very efficiently absorb the acoustic energy of the standing waves in the two-node mode and the three-node mode, and reduce noise due to cavity resonance due to each standing wave.

4) In the soundproof type engine hood having the above-described configuration, the resonance sound absorbing tube is formed to have rigidity, and is configured to also serve as a reinforcing member of the engine hood in which the resonance sound absorbing tube is provided.

Since the resonance sound absorbing tube has an elongated tube shape, when the resonance sound absorbing tube is provided with rigidity and has a reinforcing function, the reinforcement of the engine hood provided with the resonance sound absorbing tube is enhanced. It can also serve as a member, and can reduce the thickness of other reinforcing members and panels. Therefore, the increase in weight due to the installation of the resonance sound absorbing tube can be partially offset by the decrease in weight due to the decrease in the thickness of the reinforcing member and the panel, and the increase in the weight of the engine room as a whole can be suppressed.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 to 5, an engine room 1 of a general passenger car having a soundproof type engine hood 3A according to the embodiment of the present invention has an engine hood 3A in which an upper part of an engine 10 is placed. , The side with food ridge 4,
The rear portion is formed of vehicle body components such as the dash panel 6, and surrounds the engine 10 in the center.

Further, the intercooler 9 is disposed between the engine 10 and the engine hood 3A, and an outside air inlet 30a for the intercooler 9 is provided in front of the vehicle.
The air passage 30 is provided on the lower surface side of the engine hood 3A.

As shown in FIGS. 1 to 3, open-ended resonance sound absorbing tubes 41 to 43 having the resonance frequency of the standing wave in the left and right direction generated by the cavity resonance of the engine room 1 as their own resonance frequency. Is provided in the air passage 30 for the intercooler 9.

Then, as shown in FIG. 3, the openings 41a, 42a, 43 on the dash panel 6 side of the resonance sound absorbing tubes 41-43.
a in the left and right directions of the engine room 1 at the sites M, M ′, M ′ where antinodes of the acoustic mode of the standing wave occur.
Arrange and configure.

That is, the first resonance sound absorbing tube 41 having the first resonance frequency of the standing wave in the two-node mode generated in the left and right direction of the engine room 1 is opened.
Provided so as to be disposed substantially at the center M in the left-right direction,
The second resonance sound absorbing tubes 42 and 43 having the second resonance frequency of the standing wave of the three-bar mode are formed by opening the opening portions 42a and 43a of the engine room 1 with a substantially one-third part M ′ in the left-right direction and a third part. 2 so as to be arranged in the portion M ′.

The resonance in the engine room 1 is mainly dominated by left and right (lateral) modes, and the frequency is determined by the width of both ends inside the engine room (if there is a relatively large reflector such as a battery). . In a typical vehicle, the resonance width B is a little over 1 m. If the resonance width B is 1.14 m, the wavelength λn of the standing wave is also λ2 = 1.14 in the two-node mode.
m, the frequency is around 300 Hz. In the three-bar mode, .lambda.3 = 0.76 m, and the frequency is around 450 Hz.

Therefore, the length Lr of the resonance sound absorbing tube having both ends opened.
If the wavelength of the target frequency is assumed to be λn, the aperture end correction is strictly necessary, but if this is omitted, Lrn = m (λn
/ 2), m = 1, 2, 3,..., Lr2 = 0.57 m, 1.14 m, 1.71 in the case of the two-bar mode.
m. In the case of the three-bar mode, Lr
3 = 0.38m, 0.76m, 1.14m ...

The larger the cross-sectional area of the resonance sound absorbing tubes 41 to 43 is, the better the sound absorbing efficiency is. However, the resonance sound absorbing tubes 41 to 43 have a higher sound absorption efficiency because of the storage in the air passage 30 and the position of the antinode of the standing wave acoustic mode.
The cross-sectional shapes of 41 to 43 are formed in appropriate sizes and shapes.

When the sound absorption target is expanded to a resonance mode different from that of the second and third bars, the wavelength λ of the sound absorption target is further increased.
A resonance sound absorbing tube having a length corresponding to n is arranged so that the opening is located at the antinode of the mode of the resonance sound.

The openings 41a to 43a are arranged near the dash panel 6 where the sound pressure level becomes high in the front-back direction of the engine room 1. Further, since the resonance sound absorbing tubes 41 to 43 also serve as an air passage for the intercooler 9, the resonance sound absorbing tubes 41 to 43 may be provided to be inclined with respect to the air passage 30 due to the length of the resonance sound absorbing tubes 41 to 43. It is preferable to arrange it in parallel with the air passage 30 so that it can be performed.

Further, these resonance sound absorbing tubes 41 to 43 are formed to have rigidity, and are configured to also serve as reinforcing members of the engine hood 3.

According to the above soundproof type engine hood 3A, the following effects can be obtained.

Outside air inlet 30a for intercooler 9
Is provided in front of the vehicle at a position distant from the engine 10 to avoid forming an opening in the vicinity of the engine 10, so that noise radiation to the outside of the vehicle can be reduced.

Since the resonance sound absorbing tubes 41 to 43 are housed in the engine hood 3A, it is easy to secure an installation space and can be arranged while avoiding interference with other components in the engine room 1A.

The sound absorbing action of the resonance sound absorbing tubes 41 to 43 in the engine hood 3A causes the left and right (horizontal) two-bar and three-bar modes to be generated in resonance with the engine 10 using the engine 10 as a sound source. Waves can be absorbed, reducing acoustic energy and reducing noise.

Further, the openings 41a to 41a of the resonance sound absorbing tubes 41 to 43 are provided.
43a is a portion where antinodes of standing waves in the two- and three-node modes are generated in the left-right direction of the engine room 1, substantially at the center M, a third portion M 'and a two-thirds portion M'. '
, It is possible to very efficiently absorb the standing waves in the two- and three-bar modes and lower the sound pressure level.

In particular, the portions M and M 'facing the openings 41a to 43a occupy a large factor in the propagation into the passenger compartment where the occupant is present. Since the sound can be absorbed at the antinode of the mode, a remarkable effect can be achieved in reducing the noise in the vehicle interior.

Further, in the soundproof type engine hood 3A having these configurations, the sound absorbing tubes 41, 42, 43 are formed to have rigidity, and the sound absorbing tubes 41, 42, 43 are provided with the engine hood 3A. In this case, the weight increase due to the installation of the sound absorbing tubes 41, 42, and 43 can be offset by the decrease in the reinforcement member and the decrease in the thickness of the panel in this case. Therefore, it is possible to suppress an increase in the weight of the engine hood 3A and the engine room 1 due to the provision of the sound absorber and the muffler.

[0050]

As described above, according to the soundproof engine hood of the present invention, the following effects can be obtained.

By providing the outside air introduction port for the intercooler in front of the vehicle, it is possible to avoid the formation of the outside air introduction port leading to the outside in the vicinity of the engine, so that noise radiation to the outside of the vehicle can be reduced.

Further, since the resonance sound absorbing tube is housed in the engine hood, it can be easily installed while avoiding interference with other components in the engine room.

By the sound absorbing function of the resonance sound absorbing tube, the left and right (horizontal) sides of the engine room are generated by using the engine as a sound source.
The acoustic energy of the standing waves in the two- and three-bar modes generated in resonance in the direction can be absorbed to reduce noise.

In addition, the opening of the resonance sound absorbing tube is positioned at the center and one-third of the left and right directions of the engine room where antinodes of standing waves in the two- and three-node modes are generated.
And two-thirds of the part, it is a part that occupies a large factor in the propagation into the passenger compartment where the occupant is, and absorbs standing waves in the two- and three-bar modes very efficiently, The sound pressure level can be reduced, and a remarkable effect can be achieved in reducing vehicle interior noise.

Furthermore, in the soundproof type engine hood having these structures, the resonance sound absorbing tube can be formed to have rigidity and can also be configured as a reinforcing member. Can be offset by a decrease in weight due to a decrease in the thickness of the panel or panel, and an increase in the weight of the engine hood due to the provision of the sound absorber and the silencer can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a soundproof engine hood according to the present invention.

FIG. 2 is a schematic side view showing the soundproof type engine hood of FIG. 2 according to the present invention.

FIG. 3 is a schematic plan view showing an arrangement of resonance sound absorbing tubes in the soundproof engine hood according to the embodiment of the present invention.

FIG. 4 is an enlarged view as viewed from the direction of arrows UU in FIG. 3;

FIG. 5 is a schematic front view showing a conventional engine hood.

6 is a schematic side view showing the conventional soundproof engine hood of FIG. 5;

FIG. 7 is a schematic plan view showing the conventional soundproof engine hood of FIG. 5;

FIG. 8 is a front view schematically showing a structure of an engine room.

FIG. 9 is a front view schematically showing the structure of an engine room provided with a Helmholtz-type resonance sound absorber of the related art.

FIG. 10 is a side view schematically showing the structure of the engine room in FIG.

FIG. 11 is a front view schematically showing the structure of another engine room provided with a Helmholtz type resonance type sound absorber of the related art.

FIG. 12 is a side view schematically showing the structure of the engine room in FIG.

[Explanation of symbols]

 Reference Signs List 1 engine room 2, 12, 22 cowl 3A, 3 engine hood 4, 14, 24 hood ridge 5, 15, 25 fender 10 engine 41, 42, 43 resonance sound absorbing tube 41a, 41b, 42a, 42b, 43a, 43b opening M Central part M '1/3, 2/3 L Left end R Right end

Claims (4)

[Claims] 1. An engine hood provided with an air passage from an outside air introduction port provided in front of a vehicle to an intercooler on a lower surface side, wherein the air passage is provided in a left and right direction caused by cavity resonance of an engine room. A soundproof engine hood having a resonance sound absorbing tube having a resonance frequency of a wave and having openings on both sides. 2. The resonance sound absorbing tube is arranged such that a position of an opening of the resonance sound absorbing tube in the left-right direction of an engine room is a portion where an antinode of the acoustic mode of the standing wave is generated. The soundproof engine hood according to claim 1. 3. A first resonance sound absorbing tube and a second resonance having a first resonance frequency of a standing wave of a two-node mode and a second resonance frequency of a standing wave of a three-node mode, respectively, which are generated in a left-right direction of the engine room. A sound absorbing tube is disposed in the air passage, an opening of the first resonance sound absorbing tube is disposed substantially at the center of the engine room in the left-right direction, and a second resonance sound absorbing tube of the second resonance frequency is provided. The soundproof engine hood according to claim 1 or 2, wherein the openings are arranged in approximately one-third and two-thirds of the engine room in the left-right direction. 4. The soundproof engine hood according to claim 1, wherein the resonance sound absorbing tube is formed to have rigidity and also serves as a reinforcing member of the engine hood.