JP3129203B2 - Soundproofing equipment for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soundproof device attached to a vehicle to prevent noise generated by a vehicle engine from propagating outside the vehicle.

[0002]

2. Description of the Related Art In a vehicle equipped with an engine, a driving force for running the vehicle is obtained by exploding and combusting an air-fuel mixture in a combustion chamber. Here, various noises, such as the explosion sound of the air-fuel mixture,
Exhaust noise, gear meshing noise, etc. are generated. In recent years, since there is a tendency that quietness is required for vehicles equipped with such an engine, various techniques for reducing the engine noise as described above have been proposed.

One of such techniques is disclosed in
Japanese Patent Publication No. 124578 discloses an "engine undercover". As shown in FIG. 6, the cover 100 is provided below the engine 101, and reduces noise outside the vehicle by absorbing and insulating noise generated in the engine 101.

For this type of cover, a steel plate, a resin plate, a lead plate or the like having excellent sound insulation properties is used. In addition, a sound absorbing material such as a porous material (for example, glass wool) may be attached to a surface of a steel plate or the like in order to improve a soundproofing effect. Noise incident on such a cover is first absorbed by the sound absorbing material. Then, the noise that cannot be completely absorbed by the sound absorbing material is reflected by a steel plate or the like. Therefore, by providing the above-described cover near the engine, the propagation of noise from the engine to the outside of the cover is suppressed.

[0005]

However, in a soundproofing technique in which the propagation of engine noise to the outside of the vehicle is suppressed by a cover, the diffraction phenomenon of noise becomes a problem. That is, as shown in FIG. 7, the noise generated by the engine 200 propagates to the outer region R of the cover 201 so as to go around the peripheral portion 201a of the cover 201.
There is a problem that a large soundproofing effect cannot be expected. Therefore, in order to suppress the noise more effectively, it is necessary to reduce the noise transmitted to the outer region R of the cover 101 as much as possible, for example, by covering the engine 200 with the cover 201 over substantially the entirety.

However, when the entire engine 200 is covered by the cover 201,
Since the heat transfer from 0 to the outside is hindered by the cover 201, there is a possibility that the cooling performance is reduced. In addition, visibility below the engine deteriorates, and serviceability decreases. Further, there is a problem that mud, snow, and the like are deposited on the upper surface of the cover 201.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle soundproofing device that does not lower the engine cooling performance and improves the soundproofing performance while improving the above-mentioned problems. Is to improve.

[0008]

According to one aspect of the present invention, there is provided a soundproofing device for a vehicle equipped with an engine, wherein the soundproofing device is disposed on a side of the engine and hangs downward. The gist is that a substantially cylindrical shape is formed along the peripheral edge of the lower end of the plate, and a sound absorbing member having an air layer is provided therein .

According to the structure of the first aspect of the present invention ,
The noise generated from the engine is incident on a sound insulating plate that is disposed on the side of the engine and hangs downward. Most of the noise that has entered the sound insulation plate is reflected by the plate toward the engine.

Further, the noise diffracts near the lower edge of the sound insulating plate and tends to propagate to the outer region of the sound insulating plate. Since the sound absorbing member provided on the peripheral edge of the sound insulating plate is located on the propagation path of the diffracted noise, the noise travels along the outer peripheral surface of the sound absorbing member. At this time, the vibration energy of the diffracted wave is converted into heat energy by the sound absorbing member.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied as a soundproofing device for a cargo transport vehicle (hereinafter simply referred to as "vehicle") will be described below with reference to FIGS.
The soundproofing device in the present embodiment includes a pair of plate-like soundproofing covers (hereinafter, simply referred to as “covers”) arranged on both sides of the engine. Figure 1 shows this cover 1
1 is shown, and FIG. 4 shows a cross section taken along line 4-4 in FIG. FIGS. 2 and 3 show a state in which each cover 11 is attached to a cargo vehicle 12.

As shown in FIG. 2 and FIG.
Is located on the side of the engine 17 and is arranged to hang downward. Each cover 11 has an upper end surface corresponding to the vehicle 1.
The second deck 13 (shown in FIG. 2) is attached to the frame 14 of the vehicle 12 so as to be in close contact with the lower surface.

The cover 11 has a rectangular sound insulating plate 15.
And three pipes 16 provided on both sides and a lower peripheral portion of the sound insulating plate 15, and a protective material 23 covering the outer peripheral surface of each pipe 16. The sound insulation plate 15 is formed of a metal plate such as a steel plate in order to improve the sound insulation effect. A sound absorbing member 18 made of a glass wool sheet is attached to a side surface of the sound insulating plate 15 on the engine 17 side.

Each of the three pipes 16 is assembled with glass wool so as to form a U-shape as a whole. As shown in FIG. 4, the cross section of the pipe 16 has an annular shape, and an air space 19 is formed inside the pipe.
The peripheral portion of the sound insulating plate 15 is inserted into the pipe 16 through a cut 20 formed in the longitudinal direction of the pipe 16. In this embodiment, the pipe 16 constitutes the sound absorbing member of the present invention.

The protective member 23 is formed in a substantially cylindrical shape from iron or a resin material, and has a plurality of holes 24 formed on the surface thereof. The protection member 23 prevents damage to the pipe 16 and adhesion of water, mud, and the like. The hole 24 is
The pipe 16 has a predetermined shape and number so as not to deteriorate the sound absorbing performance. As shown in FIG.
The pipe 16 is fixed to the sound insulating plate 15 by fixing a part of 3 to both side surfaces of the sound insulating plate 15.

The air-fuel mixture explodes and burns in a combustion chamber (not shown) of the engine 17, so that the engine 17 has a driving force for running the vehicle 12. On this occasion,
Noise is generated from the engine 17 due to various factors. The arrows in FIG. 4 indicate the propagation path of the noise generated from the engine 17 in this manner. Noise (incident wave) directly incident on the cover 11 from the engine 17 is absorbed by the sound absorbing material 18. Further, the noise that has not reached the sound absorbing member 18 and reaches the sound insulating plate 15 is reflected by the plate 15 toward the engine 17. The reflected noise is again absorbed by the sound absorbing material 18.

The noise that has reached the vicinity of the lower end of the cover 11 from the engine 17 becomes a diffracted wave on the protective member 23 as shown by an arrow in FIG. 11 to the outer region R (region opposite to the engine 17). At this time, the diffracted wave passes through the hole 24 of the protection member 23 and reaches the pipe 16. The diffracted waves are absorbed by the pipe 16 made of a sound absorbing material (glass wool). In other words, the vibration energy of the diffracted wave is finally converted into thermal energy by vibrating each fiber of the glass wool. As a result, according to the present embodiment, it is possible to reduce the noise that propagates from the engine side to the outer region R due to the diffraction phenomenon of the noise.

Here, the medium and high frequency components contained in the diffracted wave are absorbed by the glass wool with a relatively high absorption rate, but the low frequency components (for example, 500 Hz or less) tend to be hardly absorbed. Therefore, part of the low-frequency component travels to the inside of the pipe 16 without being absorbed. According to the present embodiment, since the air layer 19 is formed inside the pipe 16, the diffracted wave traveling inside the pipe 16 vibrates the air in the air layer 19 as described above. As a result, vibration energy of the low frequency component of the diffracted wave is consumed as heat energy. That is, according to the present embodiment, the low frequency components included in the diffracted wave can be effectively reduced.

As a method of suppressing the engine noise, there is a method of covering the entire engine 17 with a soundproof cover. However, as described above, there is a possibility that the cooling performance of the engine 17 is reduced. Furthermore, in the above configuration example, a large amount of cover is required, and the engine 1 is installed in a limited space.
Since the cover surrounding the entirety of the cover 7 is provided, the workability is reduced when the cover is assembled, or the arrangement of various members provided around the cover needs to be changed.

On the other hand, according to the present embodiment, since the cover 11 covers only both sides of the engine 17, it is not necessary to consider the influence of the cover 11 on the cooling performance of the engine 17, and the engine There is no danger of overheating.

Further, according to the present embodiment, the engine 17
Unlike a configuration in which the whole is covered with a cover, a large amount of cover is not required, so that the soundproofing device can be reduced in cost, weight, and size, and work when assembling the cover is performed. There is no necessity of reducing the performance or changing the arrangement of various members.

In addition, according to the present embodiment, the engine 1
Unlike the configuration in which the lower side of the engine 7 is covered with a soundproof cover, the visibility below the engine 17 is not deteriorated, and the serviceability during maintenance of the engine 17 is not reduced. Further, there is no problem such as accumulation of mud, snow and the like on the upper surface of the cover provided on the lower side of the engine 17.

When the entire engine 17 is covered by the cover, the internal space surrounded by the cover may become a resonator, and the resonator may resonate due to vibrations of the vehicle or the like to generate noise. Further, when the internal space as described above is formed, the internal sound pressure increases, so that the forcible force acting on the cover increases with the increase in the sound pressure, so that the membrane resonance of the cover easily occurs. However, according to the present embodiment, engine noise can be reduced without generating noise or membrane resonance due to such a resonance phenomenon.

The present invention can be embodied as another embodiment described below in addition to the above embodiment. According to these other embodiments, substantially the same functions and effects as those of the above embodiment can be obtained.

(1) In the above embodiment, glass wool is adhered to the surface of the sound insulating plate 15 as the sound absorbing material 18. On the other hand, other sound absorbing materials 18 such as rock wool and felt 18
May be used. Further, the cost of the cover 11 may be reduced by omitting the sound absorbing material 18.

Further, for example, a perforated plate may be used as the sound absorbing material 18. That is, as shown in FIG. 5, a perforated plate 21 in which a plurality of holes 21a are formed is provided on a side surface of the sound insulating plate 15 on the engine side. In this case, by interposing the support member between the sound insulating plate 15 and the porous plate 2 1 to form an air layer 22 between the two plates 1 5, 21.

According to such a configuration, by appropriately changing the shape of each hole 21a and the thickness of the air layer 22,
It is possible to change frequency range most sound absorption coefficient increases in the porous plate 2 1 (resonance frequency range). Therefore, by setting this resonance frequency range so as to coincide with the frequency range where the level of the engine noise is highest, the noise can be surely reduced.

(2) In the above embodiment, the shape of each cover 11 is rectangular, but the cover 11 may be semicircular, triangular, or the like, and the shape is not particularly limited. (3) In the above embodiment, the sound absorbing member according to the present invention is embodied by the pipe 16 having an annular cross section. However, the shape of the cross section need not be annular as in the above embodiment. Instead, any shape may be used as long as it has a substantially cylindrical shape, such as a semicircular shape.

(4) In the above embodiment, the pipe 16 as the sound absorbing member according to the present invention is made of glass wool, but other materials can be used as long as they can exhibit a certain sound absorbing effect. You may do so.

(5) In the above embodiment, the sound insulating plate 15 is formed of a steel plate. On the other hand, the sound insulating plate 15 may be formed of lead or a synthetic resin. Further, the sound insulation plate 15 is not limited to a single material, and may be formed of, for example, a so-called damping steel plate in which a lead plate is attached to a steel plate. When the damping steel plate is used as the sound insulating plate 15 as described above, even when the area of the sound insulating plate 15 is increased, the resonance phenomenon of the sound insulating plate 15 due to vehicle vibration or the like can be prevented, and the resonance phenomenon can be prevented. Thus, it is possible to prevent noise from being generated from the sound insulating plate 15.

(6) In the above embodiment, the pipes 16 as sound absorbing members are provided on both sides of the sound insulating plate 15 and the lower peripheral portion.
Was provided. On the other hand, the pipe 16 may be provided only at the lower peripheral portion of the sound insulating plate 15.

(7) In the above embodiment, the cover 11 is provided on the vehicle 12 as a separate member. On the other hand, the sound insulating plate 15 may be configured as a member of the vehicle 12, and the sound insulating plate 15 may be provided with a pipe 16.

(8) In each of the above embodiments, the cover 11 is provided on the cargo transporting vehicle. On the other hand, the cover 11 can be provided for a passenger vehicle.

(9) In each of the above embodiments, the cover 11
Is attached to the frame 14 such that the upper end surface thereof is in close contact with the deck 13 of the vehicle 12. Cover 11
Does not have to be in close contact with the deck 13,
For example, when the cover 11 is disposed apart from the deck 13, a configuration may be adopted in which a gap between the deck 13 and the frame 14 is sealed with a rubber sheet or the like.

[0035] (10) The combined use of the engine under cover and the cover 11 of the small heat transfer is good, it is also possible to further improve the sound insulation effect.

[0036]

[0037]

[0038]

As described above in detail, according to the present invention, the sound insulating plate is disposed so as to hang downward on the side of the engine, and has a substantially cylindrical shape along the lower peripheral edge of the sound insulating plate. A sound absorbing member is provided. Therefore, the noise (diffraction wave) diffracted near the periphery of the sound insulating plate is absorbed and reduced by the sound absorbing member. As described above, according to the present invention, since the diffraction phenomenon of noise can be suppressed,
Without covering the entire engine, in other words, without lowering the cooling performance of the engine, and without lowering the serviceability during maintenance and without accumulating mud, snow, etc., the soundproofing performance of the vehicle soundproofing device Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a cover.

FIG. 2 is a front view showing a cover attached to the vehicle.

FIG. 3 is a perspective view showing a mounting position of a cover.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 1;

FIG. 5 is a partial cross-sectional view showing a cover according to another embodiment.

FIG. 6 is a cross-sectional view showing an “undercover” according to the related art.

FIG. 7 is an explanatory diagram for explaining a noise diffraction phenomenon.

[Explanation of symbols]

15 ... Sound insulation plate, 16 ... Pipe as sound absorbing member, 17 ...
engine.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-120833 (JP, U) JP-A-3-78932 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) F02B 77/13 B62D 25/20

Claims (1)

(57) [Claims] 1. A soundproofing device for a vehicle equipped with an engine, wherein the soundproofing device has a substantially cylindrical shape along a lower edge portion of a sound insulating plate disposed on a side of the engine and hanging downward, and an air layer is formed inside the sound insulating plate. A soundproofing device for a vehicle, comprising a sound-absorbing member provided.