JP2000177643A - Engine room - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently absorb standing waves to efficiently reduce the internal noise of an engine room by arranging a resonance sound absorber having a sound absorption resonance frequency matched to the frequency of standing wave noise in opposition to the lateral center where the loop of standing wave noise is present. SOLUTION: Resonance sound absorbers 18C, 18R, 18L having a resonance frequency matched to the frequency of the lateral directional standing wave of an engine room 11 are arranged in the lateral center M of the engine room 11 corresponding to the loop of the standing wave, or the center part M and both end parts R, L so that the opening of the neck part of the resonance sound absorber 18C is opposite thereto to form the engine room 11. In the engine room 11, the resonance sound absorber 18C is set within a cowl 12 opposite to the lateral center M of the engine room 11, and the resonance sound absorber 18R and the resonance sound absorber 18L are provided within cowls opposite to the lateral ends R, L of the engine room in order to enhance the sound absorbing effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art The noise of automobiles such as passenger cars, trucks, and buses can be roughly classified into interior noise felt by drivers and occupants and exterior noise felt by people outside the vehicle. From the viewpoint, each noise countermeasure has been taken. The main sources of noise inside and outside the vehicle are:
This is engine noise generated in the engine room. This engine noise includes intake system noise and cooling fan noise in addition to mechanical noise generated from the engine body.

[0003] Then, quietness in the cabin is ensured,
In order to reduce outside noise, it is important to reduce engine noise, which is the main sound source of automobiles. However, since this engine noise is transmitted to the interior of the vehicle via the engine room and radiated outside the vehicle, Regarding the propagation of this noise,
The acoustic characteristics of the engine room, which corresponds to the propagation path, have a great effect.

As schematically shown in FIG. 9, the structure of an engine room 1 of a general automobile has an engine hood 3 at an upper portion.
The hood ridge 4 and the fender 5 on the side and the body part such as the cowl 2 having both ends connected to the vehicle body structural member 7 and the dash panel 6 which is a partition from the vehicle interior, Siege. A shield 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 Measures have been taken to prevent propagation and reduce outside noise.

However, in general, vehicle interior noise is 5%.
The problem is the sound of relatively low frequency components of 00 Hz or less. In particular, the main components that are perceived as engine noise are:
The band is from 200 Hz to 500 Hz.

On the other hand, in a passenger car class vehicle in which quietness is particularly important, the width B of the engine room in the left-right direction is approximately 1200 mm to 14 mm in view of the overall width of the vehicle.
Since it is about 00 mm, noise in a frequency range that is a problem in vehicle interior noise causes resonance in the left and right directions of the engine room, and becomes a standing wave (standing wave). Then, since the noise of the frequency amplified as the standing wave propagates inside and outside the vehicle, there is a problem that the indoor noise and the noise outside the vehicle increase.

[0007] As an example of such a silencer in an engine room, Japanese Utility Model Laid-Open Publication No. 62-023129 discloses that a resonance box for reducing intake noise is provided inside a cowl panel so as to face an intake passage and to enter a passenger compartment. In order to prevent noise propagation, this resonance box is supported with vibration isolation and a sound absorbing material is packed between the cowl panel. In this engine room structure, it is necessary to reduce the intake noise in the intake passage. Therefore, the contribution to the reduction of the standing wave in the engine room is small, and the effect of reducing the standing wave, which is the subject of the present invention, is small.

As another example of a muffler in an engine room, Japanese Patent Application Laid-Open No. 7-329828 discloses a partition plate in which an absorber is fixed in an engine room to reduce the resonance mode to a high frequency by setting a small space area. There has been proposed an engine room structure in which a Helmholtz-type resonance space is formed in a right rear corner portion and a left front corner portion while being moved to a region to reduce noise of a specific frequency.

In this engine room, the central portion of the engine is intended to reduce the noise and vibration in the one-node mode in which the amplitude of the sound pressure becomes a "node" where the amplitude of the sound pressure is minimal. Is located in the center of the engine room, so that even if the standing wave in the single mode is generated by the engine serving as the sound source, the noise is not so large, and the contribution to the noise in the vehicle compartment is small.

Further, in this engine room, since the interior of the engine room is partitioned into a resonance space, the actual volume of the engine room is reduced, and even a small vibration generates a large noise, and the substantial effect is small. There is a problem that it becomes. This is because the noise pressure (sound pressure) is P, where P is pressure, Vr is volume, and γ is specific heat ratio.
This is because there is a relation of × V × γ = constant, and the larger the volume change rate, the higher the pressure noise.

[0011]

The standing wave in the engine room, which is a problem, is a two-node mode standing wave in the left-right direction of the engine room 1 as shown in FIG. In other words, the standing wave is applied to the center M of the engine room 1 and the hood ridge 4 corresponding to the right end R and the left end L of the engine room 1. That is, since the "antinode" of the acoustic mode in which the amplitude of the sound pressure is maximized comes to a portion related to the propagation into the vehicle interior and the radiation of noise to the outside of the vehicle, this is a major problem in noise control.

An engine 10, which is a sound source, is present in the center of the engine room 1 to generate noise.
Parts that are likely to generate large noise, such as the gap between the dash panel 6 and the engine 10 and the gap between the engine hood 3 and the engine 10, are concentrated, and measures for these noises are important. In particular, in the engine room of the vertical layout in which the engine is placed in the center, the noise in the left and right two-node mode is located at the antinode of this sound mode because the engine that is the sound source part is located on the antinode of this sound mode. This is an important issue.

In particular, the problem of standing waves in the left-right direction is that reflection of sound waves at the boundary surface is a problem as a condition for generating cavity resonance. In the front-back direction and the up-down direction, a radiator, There is a gap in the lower gap, and it is difficult for cavity resonance, that is, a standing wave, to cause a problem because sound pressure leaks to the outside in the process of causing resonance. This is because a standing wave is easily generated because the sound wave is reflected at the hood ridge portion.

[0014] Regarding the standing wave in the left and right 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, while the noise level is high near the rear dash panel. . The present invention
The purpose of the present invention is to solve the above-mentioned problem. The object is to efficiently absorb the sound of the two-node resonance mode having antinodes of the acoustic mode at the center and both ends in the left-right direction of the engine room, While reducing the noise inside
An object of the present invention is to provide an engine room capable of reducing vehicle interior noise and vehicle exterior noise.

[0015]

In order to achieve the above object, an engine room is defined as a two-node mode having an acoustic mode antinode at the lateral center of the engine room and at the left and right ends of the engine room. In order to reduce the standing wave noise, a resonance type sound absorber in which the resonance frequency of the sound absorption is adjusted to the frequency of the standing wave noise is provided facing the center of the standing wave noise antinode in the left-right direction. It is composed.

Alternatively, the antinode of the standing wave noise is provided at the lateral center of the engine room and at the left and right ends of the engine room in order to reduce the standing wave noise of the two-node mode having the antinode of the acoustic mode. Resonance-type sound absorbers in which the resonance frequency of the sound absorption is adjusted to the frequency of the standing wave noise are provided to face the central portion and the left and right ends in the left-right direction. The resonance type sound absorbers at the center can be provided inside the cowl or above the engine hood, and the resonance type sound absorbers at the left and right ends can be mounted on the hood ridge and fender surrounding the side of the engine room. It can be provided between them.

The locations of the resonance type sound absorbers at the center and the locations of the resonance type sound absorbers at the left and right ends can be appropriately combined and arranged. As a resonance type sound absorber, a well-known Helmholtz is used. Other well-known resonance-type sound absorbers can be used, including a resonance-type sound absorber of the type described above.

According to these constructions, the antinodes of the standing wave mode are used to reduce the absorption of the two-node standing wave in the left and right direction of the engine room, which is the main factor of the noise in the engine room. In the center of the engine room, or
Since the resonance type sound absorber (resonator) is arranged facing the center and both ends, the standing wave of the two-node mode can be efficiently absorbed at the part where the sound pressure level becomes maximum, so that the sound absorption efficiency is improved. Good silence in the engine room can be significantly improved.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Engine room 1 of the present invention
As shown in FIGS. 1 to 6, 1, 21 and 31 have engine hoods 13, 23 and 33 on the upper side and hood ridges 14, 24 and 24 on the side. 34, fenders 15, 25, 35, and the rear part of which is connected to body structural members (front pillars) 17, 27, 37 at both ends to form cowls 12, 22, 32 and a cabin forming a lower part of front window 8. Body parts such as dash panels 16, 26, and 36, which are partitions, surround the periphery of the engine 10.

The resonance-type sound absorber (resonator) 18 whose resonance frequency is matched (tuned) in accordance with the frequency of the standing wave in the left-right direction of the engine rooms 11, 21, 31.
The resonance of C, 18R, 18L to 38C, 38R, 38L is made to the center part M or the center part M and both ends R, L in the left-right direction of the engine rooms 11, 21, 31 at the part corresponding to the antinode of the standing wave. The sound absorbers 18C to 38L are arranged facing the opening of the neck 82,
The engine rooms 11, 21, 31 are formed.

As shown in FIGS. 1 and 2, an engine room 11 according to the first embodiment of the present invention has a cowl facing a central portion M of the engine room 11 in a lateral direction.
12, a resonance type sound absorber 18C is installed. Further, in order to enhance the sound absorption effect, the resonance type sound absorber 18R and the resonance type sound absorber 18L are installed in the cowl 2 facing the right and left ends R, L of the engine room 1. Provided.

An engine room 21 according to a second embodiment of the present invention has a structure as shown in FIGS.
Above the engine hood 23 facing the lateral center M of the engine room 21A, a resonance type sound absorber 28C is installed.
In order to enhance the sound absorbing effect, a resonance type sound absorber is provided above the engine hood 23 facing the right and left ends R and L of the engine room 1.
28R and a resonance type sound absorber 28L.

Further, an engine room 31 according to a third embodiment of the present invention has a structure as shown in FIGS.
A cowl 32 facing the center M in the lateral direction of the engine room 31A.
Inside, a resonance type sound absorber 18C is installed. Further, in order to enhance the sound absorption effect, a resonance type sound absorber 38R is provided outside the hood ridge 34 facing the left and right ends R and L of the engine room 31 and inside the fender 33. It is configured by providing a resonance type sound absorber 38L.

Although not shown, a resonance type sound absorber 28C provided above the engine hood 23 facing the lateral center M of the engine room 21A shown in FIGS. 3 and 4, and FIG. 5 and FIG. The resonance type sound absorber 38R and the resonance type sound absorber 38L provided in the fender 33 facing the left and right ends R and L of the engine room 31 may be combined, or another combination may be used.

Further, these resonance type sound absorbers 18C to 38L
In the front and rear direction of the engine compartments 11, 21, 31
Since the sound pressure level is higher at the rear dash panels 16, 26, and 36 than at the front radiator, it is provided as desired at this high portion.

And, the resonance type sound absorber 18C according to the present invention.
Well-known sound absorbers such as Helmholtz-type resonance sound absorbers can be used as ~ 38L, and have a diameter and a length of a volume chamber 81 having a predetermined volume corresponding to the frequency of noise to be sound-absorbed and a neck 82. Then, a neck portion communicating with the volume chamber is formed to open to the engine room.

The resonance frequency f of this Helmholtz type resonance type sound absorber is such that c is the speed of sound, d is the diameter of the introduction hole, k is the number of the introduction holes, V is the volume, and tc is the thickness of the introduction hole. To
f = (c / 2π) × SQRT (C0 / V) Here, β = π / 2, C0 = kπ (2d) ² / (tc + β ×
d / 2).

According to the engine room having the above-described structure, the resonance type sound absorber 18C and the resonance type sound absorber 28C facing the center M in the horizontal direction of the engine rooms 11, 21, and 31 use the engine to be subjected to sound absorption as a sound source. Since the standing wave faces the antinode of the standing wave in the left and right two-node mode in the engine room, this standing wave is efficiently absorbed by these resonance type sound absorbers 18C and 28C, and the sound pressure rises. Is suppressed. Therefore, noise in the engine room can be efficiently reduced.

The resonance type sound absorbers 18C and 28 facing the central portion M
In C, since the sound can be absorbed at the center of the acoustic mode where the acoustic energy is concentrated in the central portion M, which is a major factor in the propagation into the passenger compartment where the occupant is present, a significant effect can be achieved in reducing the noise in the passenger compartment. Also, the engine room
Resonance-type sound absorbers 18R and 18L facing the right and left ends R and L of 11, 21, 31 and resonance-type sound absorbers 28R and 28R and resonance-type sound absorbers 28
Since L and the resonance-type sound absorber 38R and the resonance-type sound absorber 38L are arranged facing the antinode of the standing wave in the two-node mode to be sound-absorbed, noise can be reduced more efficiently.

In particular, by reducing the noise at the side portions R and L, the noise can be reduced at the boundaries between the engine rooms 11, 21, and 31, so that the noise radiated outside the vehicle can be significantly reduced.

Accordingly, these engine rooms 11, 21,
According to 31, the engine rooms 11, 21, 31, which are the main factors of the noise in the engine rooms 11, 21, 31, and the engine rooms 11, 21, 31, which are the antinode positions of the standing waves in the left-right two-node mode of the engine rooms 11, 21, 31,
The resonance type sound absorbers 18R, 18L, 28R, 28L, and 38 face the central portion M and both end portions R and L in the lateral direction (left and right direction) of 31.
Since the R and 38L are installed, the standing wave in the two-node mode can be efficiently absorbed and the quietness in the engine rooms 11, 21, and 31 can be improved.

By reducing the noise in the engine rooms 11, 21, and 31, the noise radiated outside the vehicle from the engine rooms 11, 21, and 31 can be reduced, so that the noise outside the vehicle can be reduced.

FIGS. 7 and 8 show measurement examples of the noise reduction effect in the engine room 11 shown in FIGS. 1 and 2. FIG. In this measurement example, as shown in FIG.
In the case of 200 Hz to 500 HZ around 300 Hz which is the resonance frequency of 18 C, 18 R, and 18 L, when the resonance sound absorber is arranged with respect to the C1 line when the resonance type sound absorbers 18 C, 18 R, and 18 L are not arranged. , A line D1 is obtained, and it can be seen that the noise reduction effect of the portion E1 indicated by oblique lines is obtained over the entire range of the engine speed indicated by the horizontal axis.

FIG. 8 shows a sixth-order engine rotation component obtained by extracting only a frequency component six times the fundamental frequency of the engine rotation.
With respect to the engine room resonance near z, the noise reduction effect of the portion E2 is obtained.

[0035]

As described above, according to the engine room of the present invention, the resonance type sound absorber that faces the center of the engine room in the lateral direction, the two-way mode in the left and right directions generated in the engine room using the engine as a sound source. In the antinode part of the standing wave, this standing wave can be efficiently absorbed,
Noise in the engine room can be reduced efficiently.

As a result, acoustic energy can be absorbed in the central portion, which has a large factor in the propagation into the passenger compartment where the occupant is located, so that it is possible to significantly reduce the noise in the passenger compartment and enhance the quietness of the passenger compartment. be able to.

Further, since the resonance-type sound absorbers facing the left and right ends of the engine room are arranged facing the antinodes of the standing wave of the two-node mode to be sound-absorbed, noise can be reduced more efficiently. In particular, since noise can be reduced at the boundary between the side portion and the outside of the engine room, the noise radiated outside the vehicle can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing an engine room according to a first embodiment of the present invention.

FIG. 2 is a schematic side view of FIG.

FIG. 3 is a schematic front view showing an engine room according to a second embodiment of the present invention.

FIG. 4 is a schematic side view of FIG. 3;

FIG. 5 is a schematic front view showing an engine room according to a third embodiment of the present invention.

FIG. 6 is a schematic side view of FIG.

FIG. 7: 200 Hz to 5 in the engine room of FIG.
It is a figure of the noise level which shows the noise reduction effect in the range of 00Hz.

FIG. 8 is a diagram of a noise level showing a noise reduction effect of a sixth-order component in the engine room of FIG. 1;

FIG. 9 is a front view schematically showing a structure of an engine room.

FIG. 10 is a diagram schematically illustrating standing waves in a two-bar mode generated in an engine room.

[Explanation of symbols]

 1, 11, 21, 31 engine room 2, 12, 22, 32 cowl 3, 13, 23, 33 engine hood 4, 14, 24, 34 hood ridge 5, 15, 25, 35 fender 10 engine 18C, 28C, 38C Resonance type sound absorber (center) 18R, 28R, 38R Resonance type sound absorber (right end) 18L, 28L, 38L Resonance type sound absorber (left end) 81 Resonance room 82 Neck M Center part L Left end R Right end

Claims (5)

[Claims] An antinode of a standing wave noise is provided at a lateral center portion of an engine room and at left and right ends of the engine room in order to reduce standing wave noise of a two-node mode having an antinode of an acoustic mode. An engine room, wherein a resonance type sound absorber in which a resonance frequency of sound absorption is adjusted to a frequency of the standing wave noise is provided facing a central portion in the left-right direction. 2. The antinode of the standing wave noise is provided at the lateral center of the engine room and at the left and right ends of the engine room in order to reduce the standing wave noise of the two-node mode having the antinode of the acoustic mode. An engine room in which resonance-type sound absorbers are provided to face a central portion in the left-right direction and left and right ends, respectively, in which a resonance frequency of sound absorption is adjusted to a frequency of the standing wave noise. 3. The engine room according to claim 1, wherein the resonance type sound absorber is provided in a cowl. 4. The engine room according to claim 1, wherein the resonance type sound absorber is disposed above an engine hood. 5. The engine room according to claim 2, wherein the resonance sound absorbers at the left and right ends are disposed between a hood ridge and a fender.