JPH11161283A - Engine room internal noise absorption structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine room internal noise absorption structure capable of uniformly absorbing the wide frequency band sounds within an engine room contributing to the improvement in heat balance. SOLUTION: In an engine room internal noise absorption structure provided with a sound absorbing body 2 within an engine room 1 to absorb the sound within the engine room 1 by the sound absorbing body 2, the sound absorbing body 2 comprises a plate air permeable member 2a having an end part fixed to either one or the both of the inner wall of the engine room 1 and a device 6 within the engine room 1, and sound absorbing materials 2b fixed to both sides of the plate air permeable member 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing structure in an engine room which is provided in an engine room and which can uniformly and efficiently absorb a wide frequency band sound and contribute to improvement of heat balance.

[0002]

2. Description of the Related Art In recent years, construction machines (for example, power shovels and wheel loaders, hereinafter simply referred to as "example machines") even in towns.
Works. An example machine is required to have a high output at all times and receives a large load change. For this reason, unlike a gasoline engine, a diesel engine that can obtain high torque even at low speeds is installed. By the way, because high output is always required,
For heat balance, it is necessary to increase the heat exchange capacity of the radiator. For this reason, the cooling air volume is increased by increasing the radiator or the outer diameter and the rotation speed of the cooling fan. Therefore, a large fan noise is generated. In addition, because of the high torque, not only the intake and exhaust sounds but also the exhaust sounds are emitted to the outside while being muffled by the muffler. Auxiliary noise of hydraulic pumps and gears rotating with engine output is also large. The fact that the load fluctuation is large means that the fluctuation of the engine speed is also drastic. Therefore, in the example machine, not only the fan noise and the engine noise, but also the auxiliary device noise becomes a wide frequency band sound. Therefore, as shown in FIG. 7, for example, it is known to attach a sound absorber 2 to an inner wall of an engine room 1.

That is, a radiator 4, a suction-type cooling fan 5, and an engine 6 are arranged on a base 3 in this order, and these are surrounded by a side wall 1S, a rear wall 1R, and an engine hood 1H. That is, the engine room 1 is constituted by the base 3, the side wall 1S, the rear wall 1R, and the engine hood 1H.
The radiator 4 has a front surface (left side in the figure) that is open to the outside air, and both side walls 1S have ventilation holes 7 that communicate with the outside air. Therefore, when the cooling fan 5 is rotated by the engine 6, the outside air is sucked from the front surface of the radiator 4 as the cooling air X, and the radiator 4 absorbs the heat generated by the engine.
After passing through the cooling fan 5 and the periphery of the engine 6 in this order, the air is discharged from the ventilation hole 7 to the outside air. However, at this time, fan noise, engine noise, and accessory noise are generated in a wide frequency band in the engine room 1 and are released from the ventilation holes 7 to the outside air together with the cooling air X, thereby causing noise pollution. Therefore, the sound absorber 2 is mounted on the inner wall surface of the engine room 1 so that the fan sound and the engine sound are absorbed as much as possible in the engine room 1.

[0004] As the sound absorbing material, a porous material, a perforated material, a film material and the like are known. The porous material is glass wool, felt, foamed resin (urethane foam, etc.), the perforated material is perforated gypsum board, perforated asbestos cement, etc., and the film material is vinyl film, leather, canvas, metal foil, etc. . In addition, there is a resonator and the like. It is known that the porous material has a high sound absorption coefficient for middle and high frequency band sounds, the perforated material has a high sound absorption coefficient for low and medium frequency band sounds, and the film material has a high sound absorption coefficient for medium frequency band sounds. And among these sound absorbing materials, the sound absorbing body 2
Is appropriately selected. As the sound absorber 7 in the engine room 1, a porous material such as urethane foam is frequently used.

[0005]

However, the above prior art has the following problems. (1) The example machine increases the cooling air flow rate by increasing the outer diameter and the number of rotations of the cooling fan 5 on the heat balance. However, as the outer diameter and the number of rotations of the cooling fan 5 are increased, the fan noise is significantly increased. Also, the output of the engine for heat exchange is increased. Therefore, as shown in FIG. 7, a fan shroud 8 is provided between the outer circumference of the radiator 4 and the cooling fan 5.
a, and a bell mouth 8b whose opening area gradually increases from the opening of the fan shroud 8a toward the engine 6 is provided. Thereby, the ventilation resistance of the cooling air X is reduced. As a result, an increase in the outer diameter and the number of revolutions of the cooling fan 5 is suppressed (therefore, fan noise is also reduced), and an increase corresponding to the engine output for heat exchange is also suppressed. However, even if such efforts are made, the flow of the cooling air X is obstructed depending on the unevenness and piping of the engine 6 in the engine room 1 and the shape and arrangement of the sound absorber 2, so that the ventilation resistance in the entire engine room 1 is reduced. It can be seen that it is increasing. It is presumed that a vortex is generated locally, and even a vortex sound is generated.

(2) As shown in FIGS. 7 and 3 (b), the sound absorber 2 is attached to the wall of the engine room 1 so that it is so-called single-sided. Therefore, there is a limit to the sound absorbing effect.

The present invention has been made in view of the above-mentioned problems of the prior art,
An object of the present invention is to provide a sound absorbing structure in an engine room that is provided in an engine room and can uniformly absorb a wide frequency band sound and contribute to improvement of a heat balance.

[0008]

In order to achieve the above object, a first sound absorbing structure for an engine room according to the present invention has a sound absorbing body 2 in an engine room 1 and a sound absorbing body 2.
In the sound absorbing structure in the engine room, which absorbs the sound in the engine room 1, the sound absorber 2 is connected to (a) one or both of the inner wall of the engine room 1 and the device 6 in the engine room 1. Fixed plate-shaped air-permeable member 2a
And (b) a sound absorbing material 2 fixed to both sides of a plate-shaped permeable member 2a.
b.

According to the first configuration, the following operation and effect can be obtained. Although the sound absorbing material 2b depends on the material, if it is a porous material, it has a high sound absorption coefficient for middle and high frequency band sounds. Also, if the sound absorbing material 2b is a perforated material, the sound absorbing rate for low and middle frequency band sounds is high. Further, if the sound absorbing material 2b is a film material, the sound absorbing coefficient for the middle frequency band sound is high. Such a sound absorbing material 2
b, the first configuration has a sound absorbing material 2b on both surfaces of a plate-shaped permeable member 2a. That is, the first configuration shown in FIG.
In comparison with the prior art shown in FIG. 3B, when the total thickness T is the same, the thickness of the sound absorbing material 2b is “2”.
Although the sound wave incident from one surface is absorbed by the sound absorbing material on the incident side, passes through the plate-shaped permeable member 2a, and is further absorbed by the sound absorbing material 2b on the opposite surface. It acts as a sound absorbing material of the same thickness T. Furthermore, since the same effect is provided for the sound incident from both sides, the sound absorbing power is improved. Furthermore, the sound absorption by the resonance in the ventilation hole is improved. Then, these sound absorbing effects are superimposed, and sound can be uniformly absorbed at a very high sound absorbing rate with respect to a wide frequency band sound in the engine room 1.

Second, in the first configuration, the sound absorber 2
The sound absorber 2 is arranged so that either one of the surfaces of the sound absorber 2 follows the flow of the cooling air X in the engine room 1.

According to the second configuration, the following operation and effect can be obtained. In the second configuration, the sound absorber is arranged so as to follow the flow of the cooling air X. For this reason, there is no fear that the ventilation resistance in the engine room 1 will increase. Rather, the vortex and turbulence of the cooling air X generated by the unevenness due to the engine 6 and its piping can be rectified, and the laminar flow is obtained. Of course, it is possible to prevent the generation of a new swirling sound. That is, the second configuration is a configuration in which the ventilation resistance in the engine room 1 is hard to increase. For this reason, in addition to the function and effect of the first configuration, it contributes to the improvement of the heat balance.

Third, in the second configuration, the sound absorber 2
Characterized by having a plurality of

According to the third configuration, the following operation and effect can be obtained. The space in the engine room 1 has a complicated shape. Therefore, according to the third configuration, a more reliable sound absorbing effect and a heat balance improving effect can be obtained by providing the sound absorbers in accordance with the shape in the engine room 1.

Fourth, in the first, second or third configuration, the sound absorber 2 is provided on a detachable or openable / closable member 1H provided on a wall surface of the engine room 1. I do.

According to the fourth configuration, the following operation and effect can be obtained. The “detachable or openable / closable member provided on the wall surface of the engine room 1” in the fourth configuration is, for example, the engine hood 1H. A sound absorber is arranged on such a member 1H. Thus, when the engine hood 1H is removed or opened, the sound absorbing body is separated from the engine 6 integrally with the engine hood 1H. Therefore, the maintenance and inspection of the sound absorbing body itself as well as the maintenance and inspection of the engine 6 and its peripheral devices become easy.

[0016]

Embodiments and examples of the present invention will be described with reference to FIGS. The example machine is a power shovel, and most of the elements in FIG. 1 are the same as the elements in FIG. Therefore, FIG.
The same elements as those described above are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 1, the engine room 1 has a ventilation hole 7 communicating with the side wall 1S and the engine hood 1H inside and outside. The rear end of the sound absorber 2A is fixed to the rear end of the ventilation hole 7. The sound absorber 2 </ b> A is a curved member that extends in the engine room 1 with its tip toward the cooling fan 5. The upper and side surfaces (not shown) of the engine 6 also have a flat sound absorber 2A having a front or rear end fixed to the engine 6 and a front end extending toward the cooling fan 5. It should be noted that the sound absorbing body 2A has a surface that follows the flow of the cooling air X, whether it is curved or flat, as is clear from the description that the tip is extended toward the cooling fan 5. It will be located in. Details of the sound absorber 2A are shown in FIGS. 2 and 3 (a).

FIG. 2 is a perspective view, partially in section, of a flat sound absorber 2A, and FIG. 3A is a sectional view. In addition, the curved sound absorber 2
A has a configuration in which the flat sound absorbing body 2A is curved two-dimensionally or three-dimensionally along the flow of the cooling air X, and thus details thereof are omitted.

As shown in FIGS. 2 and 3A, the sound absorber 2A
Is composed of a plate-shaped gas-permeable member 2a and a sound-absorbing material 2b attached to both sides of the plate-shaped gas-permeable member 2a. And FIG.
As shown, the tip (cooling fan 5 side) is sharpened. As shown in FIG. 1, the front or rear end of the plate-shaped permeable member 2a is fixed to the inner wall of the engine room 1, the engine 6, or the like. The plate-shaped air-permeable member 2a itself was made of so-called punching metal.

The operation and effect of the first embodiment will be described below. (1) First, the effects on the improvement of the sound absorption coefficient will be described below with reference to the test results of the reverberation room method sound absorption efficiency in FIG. (1) As shown in FIG. 3 (b), which is a conventional technique, the sound absorption coefficient characteristic P1 of a single flat sound absorbing material 2b (thickness 2t) when there is no unevenness on the surface of the non-breathable plate material 2c. This is the characteristic when pasting on only one surface. (2) The sound absorption coefficient characteristic P2 is a characteristic when one flat sound absorbing material 2b (plate thickness t) having irregularities on the surface is attached to the non-breathable plate 2c. That is, the sound absorption area for the high frequency band sound is improved by increasing the sound absorption area due to the unevenness of the surface, but the sound absorption coefficient in the low frequency band is deteriorated by the decrease in the effective thickness. (3) The sound absorption coefficient characteristic P3 is a characteristic of the first embodiment, and is a characteristic when two flat sound absorbing materials 2b (thickness t) with no irregularities on the surface are stacked with a punching metal interposed therebetween. is there. That is, the sound absorption coefficient is improved because the sound is very effective for the sound incident from both sides. (4) The sound absorbing characteristic P4 is a characteristic when two flat sound absorbing members 2b (plate thickness t) having irregularities on the surface are stacked with a punching metal interposed therebetween. That is, the sound absorption area for the high frequency band sound is improved by increasing the sound absorbing area due to the unevenness of the surface, and the sound absorbing material 2b is sandwiched by the air permeable plate material.
By increasing the thickness of the substantial sound absorbing material 2b by stacking the sheets, the sound absorbing coefficient for low frequency band sound is also improved. Since the total thickness is the thickness between the convex and concave ends, the effective thickness is smaller than that of the first embodiment. For this reason, the sound absorption coefficient for the low frequency band sound is lower than the sound absorption coefficient characteristic P3. In addition, since the plate-shaped air-permeable member 2a made of punched metal with the sound absorbing properties P3 and P4 has the sound absorbing material 2b on both surfaces, a Helmholtz resonator or the like is generated in the punching, and the sound absorbing coefficient for low frequency band sound is generated. Is estimated to have further improved. In addition, a sound deadening effect due to diffusion when passing through punching is estimated.

(2) Second, the effect on the airflow resistance is that the sound absorber 2A is curved two-dimensionally or two-dimensionally along the flow of the cooling air X as described above. Therefore, the ventilation resistance is clearly low. Further, since the tip of the sound absorbing body 2A (on the side of the cooling fan 5) is sharpened, this also contributes to a reduction in ventilation resistance. Rather, the vortex and turbulence of the cooling air X generated by the unevenness of the engine 6 are rectified, and even the function of laminarizing the cooling air X is generated. Therefore, new generation of swirling noise can be prevented.

(3) The side wall 1S of the engine room 1 and the engine hood 1H (particularly, the engine hood 1H) are usually detachable or openable and closable. That is, when they are removed or opened, the sound absorber 2A is separated from the engine 6 integrally therewith. Therefore, maintenance and inspection of the cooling fan 5 and the engine 6 as well as maintenance and inspection of the sound absorbing body 2A itself become easy. Although not described in the first embodiment, the rear wall 1R of the engine room 1 and the engine 6
The sound absorber 2 is provided on the wall surface of the lower cover provided in the base 3 below the base.
A may be provided. Also in this case, the above-described maintenance and inspection easiness effect can be obtained when the lower cover is attached or detached or opened and closed.

According to the above, a wide frequency band sound of the fan noise, the engine noise and the auxiliary device noise in the engine room 1 can be absorbed uniformly, which can contribute to the improvement of the heat balance, and the engine 6 and the sound absorber 2A itself can be absorbed. Maintenance and inspection can be performed without any trouble.

Hereinafter, other embodiments will be described.

(1) As shown in FIG. 5, the plate-shaped air-permeable member 2a may be a net-like material provided in a frame. In this case, the plate-shaped air-permeable member 2a serves as a support member for the sound absorbing material 2b, and the sound absorbing and silencing effects of the Helmholtz resonator can be obtained to some extent.

(2) As shown in FIG. 6, the plate-shaped permeable member 2a may be a honeycomb-shaped member provided in a frame. In this case, the sound absorption effect by the Helmholtz resonator is significantly generated. Of course, it is not necessary to limit the shape to a honeycomb shape, and it may be a triangle, a quadrangle, or a polygon.

(3) Although the cooling fan 5 of the first embodiment is of the suction type, it may be of the discharge type. In the discharge type, the same effect as described above can be obtained by disposing the sound absorber 2A outside the radiator 4.

(4) In the example of the above embodiment, the radiator 4, the cooling fan 5 and the engine 6 are arranged in this order on the base 3, but the engine room 1 in which the cooling fan 5, the radiator 4 and the engine 6 are arranged in this order. In this case, when the above embodiment is applied, the same operation and effect as described above can be obtained.

(5) Although the example of the above embodiment is a power shovel equipped with a diesel engine, the above embodiment may be applied to the engine room 1 of another vehicle. Of course, the present invention may be applied to the engine room 1 of a vehicle equipped with a gasoline engine.

[Brief description of the drawings]

FIG. 1 is a sectional view of an engine room in which a sound absorber according to a first embodiment is mounted.

FIG. 2 is a partial sectional perspective view of the sound absorber according to the first embodiment.

3A and 3B are cross-sectional views of a sound absorber, wherein FIG. 3A is a sound absorber of the first embodiment, and FIG. 3B is a conventional sound absorber.

FIG. 4 is a graph showing a comparison between the sound absorbing member according to the first embodiment and another sound absorbing member.

FIG. 5 is a partial cross-sectional perspective view of a sound absorber according to a second embodiment.

FIG. 6 is a partial sectional perspective view of a sound absorber according to a third embodiment.

FIG. 7 is a sectional view of an engine room in which a conventional sound absorbing body is mounted.

[Explanation of symbols]

1: engine room, 1S: side wall, 1R: rear wall, 1H ...
Engine hood, 2 and 2A: sound absorbing body, 2a: plate-shaped air-permeable member, 2b: sound absorbing material, 3: base, 4 ... radiator, 5 ...
Cooling fan, 6 engine, 7 vent.

Claims (4)

[Claims] 1. An engine room having a sound absorbing body in an engine room.
In the sound absorbing structure in the engine room, in which the sound in the engine room 1 is absorbed by the sound absorbing body 2, the sound absorbing body 2 is composed of (a) an inner wall of the engine room 1 and a device 6 in the engine room 1.
And (b) sound absorbing members 2b fixed on both sides of the plate-shaped permeable member 2a. The sound absorbing structure in the engine room. 2. One side or both sides of the sound absorber 2 are arranged so as to follow the flow of the cooling air X in the engine room 1.
The sound absorbing structure in an engine room according to claim 1, wherein a sound absorbing body (2) is arranged. 3. The sound absorbing structure in an engine room according to claim 2, comprising a plurality of sound absorbing bodies. 4. The engine room according to claim 1, wherein the sound absorbing body is provided on a detachable or openable / closable member provided on a wall surface of the engine room. Sound absorbing structure.