JPH06317179A - Device for reducing engine noise of vehicle - Google Patents

Abstract

PURPOSE:To provide a device capable of reducing the engine noise of a vehicle with a simple structure. CONSTITUTION:A device for reducing the noise generated from the engine 12 of a vehicle has a noise separation means disposed below the engine 12. The separation means comprises two reflecting plates 14, separating the noise into a component to be transmitted directly to the outside of the transverse direction of the vehicle and a component to be reflected on the ground 20 and transmitted indirectly to the outside of the transverse direction of the vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing engine noise of a vehicle, and more particularly to a device for reducing engine noise exerted on a person outside the vehicle.

[0002]

2. Description of the Related Art A multilayer slit-shaped curved passage is formed in a bumper of a vehicle, and a sound wave traveling without passing through these curved passages and a sound wave refracted through the curved passage are interfered with each other, thereby causing noise. A device for reducing the noise has been proposed (Japanese Utility Model Laid-Open No. 62-162152).

[0003]

In order to change the traveling direction of a sound by refracting it, it is necessary to make the shape of each bent passage match the wavelength. Since the sound generated from the vehicle engine, muffler, etc. is a combination of sound waves in several wavelength ranges, at least the number of wavelength ranges is required for refraction as a pretreatment for attenuation by the device according to the above proposal. A curved passage is required, which complicates the structure.

By the way, in the sound field analysis of vehicle exterior noise using the boundary element method, the radiated sound from the oil pan, which is the largest noise source of the engine, directly propagates in the lateral direction of the engine (direct wave) and the ground. It is separated into a component (reflected wave) that is reflected and arrives at, and as a result of vector analysis, the direct wave and the reflected wave are close to the same phase near the ground, but shift to an antiphase relationship at a position higher than the ground, and It was confirmed that there is an overdamped region caused by the interference between the waves and the reflected waves.

The object of the present invention is based on the above confirmation facts.
An object of the present invention is to provide a device capable of reducing engine noise of a vehicle with a simple structure.

[0006]

SUMMARY OF THE INVENTION The present invention is a device for reducing noise generated from an engine of a vehicle, the device comprising noise separating means arranged below the engine, the separating means comprising: Is separated into a component that directly propagates outward in the lateral direction of the vehicle and a component that reflects on the ground and indirectly propagates outward in the lateral direction of the vehicle.

The present invention is also a device for reducing noise generated from a vehicle engine, comprising two reflectors arranged on both sides of the vehicle so as to sandwich the engine,
Each of the reflectors has a first guide surface with a sound absorbing material that guides the noise outward in the lateral direction of the vehicle, and a second guide surface with a sound absorbing material that guides the noise to the ground so as to reflect the noise on the ground. Have
The first guide surface and the second guide surface are formed in a wedge shape that widens toward the outside from the inside in the lateral direction of the vehicle.

The present invention is also a device for reducing noise generated from a vehicle engine, wherein two reflectors are arranged below the engine in the lateral direction of the vehicle and are spaced apart from each other. A sound absorbing member provided at edges facing each other, wherein the reflecting plate and the sound absorbing member directly guide the noise outward in the lateral direction of the vehicle, and reflect the noise on the ground surface of the vehicle. It is formed so as to indirectly guide outward in the lateral direction.

[0009]

[Operation and effect] The noise or sound wave propagated from the engine of the vehicle becomes, on the one hand, a direct wave directly propagating outward in the lateral direction of the vehicle, and on the other hand, it is reflected on the ground and is reflected outside the lateral direction of the vehicle. It becomes a reflected wave that propagates indirectly to one side, and interference between the direct wave and the reflected wave occurs. This reduces the sound pressure level.

Noise can be reduced simply by disposing the separating means below the engine, by disposing a wedge-shaped reflector, or by disposing a reflector with a sound absorbing material, which is a simple structure. Further, interference between the cover and the suspension system and deterioration of engine cooling performance, which are problems in reducing noise by covering the engine with the cover, do not occur.

When the reflection plate having the sound absorbing material attached to the edge is arranged, the sound absorbing material reduces the diffracted sound that wraps around the lower side of the reflection plate, so that the interference between the direct wave and the reflected wave is promoted. This makes it possible to reduce the size of the entire device,
The noise reduction effect can be enhanced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a reduction device 10 is for reducing noise generated from an engine 12 of a vehicle, and is a noise separating means arranged below the engine 12.
In the illustrated embodiment, two reflectors 14 are provided on both sides of the vehicle so as to sandwich the engine 12.

Although the engine 12 is arranged in the engine room 16, since no cover is provided below the engine room 16, the engine 12 exhibits a noise emission characteristic with a virtual sound source particularly at a position below the oil pan. .

Each of the reflectors 14 is based on the above-mentioned confirmed facts, that is, a component that directly propagates the sound emitted from the engine in the lateral direction of the engine (direct wave) and a component that is reflected and reaches the ground (reflected wave). The first guide surface with a sound-absorbing material that separates the noise into the vehicle and causes the interference of the direct wave and the reflected wave at a higher position from the ground to reduce the noise. 18 and a second guide surface 22 with a sound-absorbing material that guides noise to the ground so that it reflects on the ground 20.
The first guide surface 18 and the second guide surface 22 are formed in a wedge shape that widens toward the outside from the inside in the lateral direction of the vehicle.

In the embodiment shown in FIGS. 1 and 2, the reflector 14 is a triangular prism whose cross-sectional shape is an isosceles triangle, and the two reflectors 14 are sandwiched between the two guide surfaces 18 and 22. The apex edges 24 are opposed to each other and are arranged on both sides of the vehicle at a distance from the engine room 16 so as to extend parallel to the front-rear direction of the vehicle. A sound absorbing material (not shown) known per se, such as sheet-shaped glass wool, rock wool or urethane, is attached to the guide surfaces 18 and 22 by bonding, spraying or the like to adjust the sound absorbing characteristics of the sound absorbing material.
The reflector 14 is attached to the engine compartment 16 by a plurality of attachment plates 26 that are spaced in the front-rear direction of the vehicle.

As shown in FIG. 6, by providing the reflection plate 14, the noise from the engine 12 travels outwardly in the lateral direction of the vehicle via the first guide surface 18, and
It can be separated into reflected waves B which are reflected on the ground 20 and travel outward in the lateral direction of the vehicle. The size of the reflection plate 14 is determined so that the direct wave A and the reflected wave B thus separated interfere with each other at the location of a person laterally outside the vehicle to reduce the noise level.

Now, from the sound source of the engine 12 to the reflector 14
Is the distance to the vertical surface 25 of the
Let b be the distance from the vehicle to a person outside the vehicle, and c be the length of the vertical surface 25 of the reflector 14, the path length of the reflected wave B is approximately (a ² + c ² ) ^1/2 + ( It is given by b ² + c ² ) ^1/2 . On the other hand, since the path length of the direct wave A is (a + b), the path difference between the reflected wave B and the direct wave A is (a ² + c ² ) ^1/2 + (b ² + c ² ) ¹ If the height c of the vertical surface 25 of the reflector 14 is set so that ^{/ 2-} (a + b) is 1/4 to 1/2 of the wavelength of the sound wave to be interfered, the reflected wave directly The phase difference with the wave is 90-180 °, causing interference.

The reflecting plate may be formed so that the two guide surfaces form a wedge shape that widens from the inner side to the outer side in the lateral direction of the vehicle, and the dimensions may be determined so as to satisfy the above relationship.
The shape shown in FIG. 3 can also be used. The reflection plate 34 of FIG. 10A has a right-angled triangular cross-section, the first guide surface 36 is formed horizontally, and the second guide surface 37 is formed to be inclined downward, and the reflection plate 34 of FIG. 38 has a cross-sectional shape of a right triangle, the first guide surface 40 is inclined upward, and the second guide surface 41 is horizontally formed. Further, the reflection plate 42 of FIG. The shape is substantially triangular or polygonal, and the first guide surface 44 is formed with two slopes having different upward slopes and the second guide surface 45 is formed with two slopes having different downward slopes.

The shape of the reflector in the front-rear direction of the vehicle is such that a uniform cross section is provided over its entire length as shown in FIG. 2 and the first guide surface 56 and the second guide surface 56 are provided as in the reflector 54 shown in FIG.
A portion having a first guide surface 58 and a second guide surface 59 having different lengths, respectively, is connected to the portion having the guide surface 57, and like the reflection plate 60 shown in FIG.
The first guide surface 62 and the second guide surface 63 can be narrowed in a triangular pyramid shape. In the embodiments of FIGS. 4 and 5, it is possible to adjust the path difference of sound waves in a plurality of wavelength bands.

A reduction device 7 of the embodiment shown in FIGS. 7 and 8.
At 0, the separating means located below the engine 12 is
It is composed of two reflectors 72 which are arranged below the engine 12 in the lateral direction of the vehicle at a distance from each other, and a sound absorbing material 74 which is provided on edges of the reflectors 72 facing each other. The reflector 72 and the sound absorbing material 74 guide the engine noise directly to the outside in the lateral direction of the vehicle via the gap 76, while guiding the noise to the ground 20 via the gap 78, where it is reflected and reflected. It is formed so as to indirectly guide outward in the lateral direction.

In the illustrated embodiment, the reflection plate 72 is a flat plate, and the sound absorbing material 74 is attached to the edge part of the reflection plate 72 on the three sides of the upper surface, the end surface and the lower surface. The reflector 72 and the sound absorbing material 74 extend in the front-rear direction of the vehicle by substantially the same length as the engine room 16. The reflector 72 is on the ground 20.
Mounted parallel to, or with the lateral outer edge of the body raised relative to the lateral inner edge of the vehicle and slightly inclined to the ground. The reflection plate 72 may be attached to the vehicle body according to the above-described embodiment.

The reflection plate 72 is formed of a metal plate or a resin plate having a thickness sufficient to block sound waves passing therethrough, but it is not always necessary to have a sound absorbing structure. On the other hand, the sound absorbing material 74 is made of a material having a sound absorbing effect, such as glass wool or rock wool, and reduces the diffraction of sound waves that go around the lower side of the reflection plate 72 as much as possible. As a result, it is possible to prevent the sound reduction effect from decreasing due to the presence of a sound wave having a small path difference from the direct wave as a diffracted sound. Dimensions such as thickness and width of the sound absorbing material 74, the sound absorbing material 74
Since the degree of diffraction differs depending on the sound absorption characteristics of the above, the upper surface, the end surface, and the lower surface of the edge portion to which the sound absorbing material 74 is attached and other factors, it is preferable to experimentally determine the above factors.

The sound wave from the virtual sound source 80 of the engine propagates as a direct wave A as shown in FIG.
And is propagated as a reflected wave B. At this time, since there is no wave like the diffracted wave C due to the diffraction suppressing effect of the sound absorbing material 74 arranged at the edge of the reflection plate 72, the direct wave A
The interference phenomenon between the reflected wave B and the reflected wave B appears more clearly.

As is apparent from FIG. 8, the reflector 72
Need only have a size and arrangement in which a sound wave from the virtual sound source 80 is reflected at the point D on the ground 20, and since there is no thickness corresponding to c in FIG. 6, the overall size of the device can be reduced. Incidentally, in FIG. 8 as well, by defining a, b, and c as shown in the figure, the path difference between the direct wave A and the reflected wave B can be defined by the above mathematical formula.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a vehicle engine noise reduction device according to the present invention.

FIG. 2 is a perspective view of the reflector of FIG.

FIG. 3 shows a reflector that can be used in the present invention.
b and c are cross-sectional views of different embodiments.

FIG. 4 is a perspective view of yet another embodiment of a reflection plate that can be used in the present invention.

FIG. 5 is a perspective view of yet another embodiment of a reflection plate that can be used in the present invention.

FIG. 6 is a sectional view schematically showing the noise reduction principle of the embodiment of FIG.

FIG. 7 is a cross-sectional view of another embodiment of the vehicle engine noise reduction device according to the present invention.

8 is a cross-sectional view schematically showing the noise reduction principle of the embodiment of FIG.

[Explanation of symbols]

10, 70 Reduction device 12 Engine 14, 34, 38, 42, 54, 60 Reflector 18, 36, 40, 44, 56, 58, 62 First guide surface 22, 37, 41, 45, 57, 59, 63 Second guide surface 72 Reflector plate 74 Sound absorbing material

Claims (3)

[Claims] 1. A device for reducing noise generated from an engine of a vehicle, the device comprising noise separating means arranged below the engine, wherein the separating means separates the noise laterally outward of the vehicle. A device for reducing engine noise of a vehicle that separates into a component that directly propagates to the vehicle and a component that reflects on the ground and indirectly propagates outward in the lateral direction of the vehicle. 2. A device for reducing noise generated from an engine of a vehicle, comprising two reflectors arranged on both sides of the vehicle so as to sandwich the engine, and each reflector has a function of reducing the noise. The first guide surface is provided with a sound absorbing material, which guides outward in the lateral direction of the vehicle, and the second guide surface with a sound absorbing material, which guides the noise to the ground so that the noise is reflected on the ground. The surface and the second guide surface are formed as a wedge-shaped device that reduces the width of the vehicle from the inner side to the outer side in the lateral direction of the vehicle in a wedge shape. 3. A device for reducing noise generated from an engine of a vehicle, comprising: two reflectors arranged below the engine in the lateral direction of the vehicle and spaced from each other; and the reflectors facing each other. With a sound absorbing material provided at the edge,
The reflection plate and the sound absorbing member are formed so as to directly guide the noise outward in the lateral direction of the vehicle, and indirectly reflect the noise on the ground to indirectly outward in the lateral direction of the vehicle. Was
Vehicle engine noise reduction device.