JP2000192506A - Noise reducing device for construction machine and cover for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise reducing device for construction machine capable of setting a sound absorption target frequency in low frequency band by providing a resonance sound absorbing means utilizing resonance action within a cover. SOLUTION: Sound absorbing bodies 31, 32, 33, 34 are provided in respective positions corresponding to an engine 8, a cooling fan 11, a hydraulic pump 25, and a muffler 26 within an engine room 4. The sound absorbing bodies 31, 32, 33, 34 are formed of a sound absorbing panel 37 having a plurality of resonance chambers 36 partitioned by partitioning plates 35, an inlet port 38 provided on each resonance chamber 36 to introduce a sound into the resonance chamber 36, and a guide 39 for guiding the sound to the inlet port 38, and a sound absorbing material 40 affixed to, for example, surface of the sound absorbing panel 37. The noise generated from each apparatus is partially introduced to the through-hole 40a of the sound absorbing material 40, and further introduced to each resonance chamber 36 through the inlet port 38. According to this, noise of a low frequency band close to a sound absorption target frequency is eliminated within the resonance chamber 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reduction device for a construction machine and a cover for the construction machine used for the device.

[0002]

2. Description of the Related Art Generally, operating members such as a boom, an arm, a bucket, a revolving unit, and a traveling unit that constitute a construction machine are hydraulically operated by a hydraulic cylinder (for example, a hydraulic cylinder, the same applies hereinafter), a hydraulic motor or the like. Driven by motive. The construction machine is provided with a hydraulic pump as a hydraulic pressure source of the hydraulic actuator, and the hydraulic pump is driven by a prime mover such as an engine. Generally, these hydraulic pumps and the prime mover are mounted on a revolving body constituting a construction machine together with accessories such as a radiator and a muffler connected to the prime mover, and are covered with a cover. Further, in order to cool the engine and the auxiliary equipment, the air introduced through an intake hole provided on one side of the cover is passed through a heat exchanger such as a radiator by a cooling fan, and then the engine and the auxiliary equipment are cooled. The fluid passes through the side of the hydraulic pump and is discharged to the outside through an exhaust hole provided on the other side of the cover.

[0003] By the way, the hydraulic pump, the prime mover,
Auxiliary equipment and cooling fans generate noise during operation,
Various measures have conventionally been taken to reduce this noise. The measures are broadly divided into measures for reducing the sound generated from each device itself and measures for absorbing or insulating the generated sound. Among these measures, a measure for absorbing the generated sound is generally used. Specifically, for example, the following three methods have been conventionally proposed.

[0004] First, there is a type in which a sound absorbing material such as a urethane foam type or a glass wool type is attached to the inner surface of the above-mentioned cover to absorb the generated sound. At this time,
Generally, sound absorbing material has a unique frequency band with the best sound absorption performance determined by its material and dimensions, so the material and size of the sound absorbing material can be freely set according to the target frequency to be targeted for sound absorption. By doing so, sound can be absorbed most effectively. Further, as described in, for example, Japanese Utility Model Laid-Open No. 1-80577, at least one panel forming a space between the cover and the cover is fixed inside the cover, and a number of ventilation holes are formed in the panel. There is a configuration to provide. According to this conventional technique, a sound absorbing effect is obtained by the space between the cover and the panel, and the sound is attenuated and reflected by a large number of ventilation holes. Further, as described in, for example, Japanese Utility Model Application Laid-Open No. 64-29230,
There is a structure in which the engine cover has a double structure, a large number of ventilation holes are provided in each of the double covers, and the positions of the ventilation holes are shifted from each other in the double cover. According to this conventional technique, the sound generated from the engine or the like passes through the ventilation holes of the inner cover of the double cover, and then, in the space between the outer cover and the inner cover, the outer and inner covers. After the reflection is repeatedly attenuated on the non-porous wall surface of the cover, the light is finally emitted to the outside through the vent hole of the outer cover. At this time, the sound can be absorbed most effectively by freely setting the distance between the outer cover and the inner cover according to the target frequency as the sound absorption target.

[0005]

In recent years, there has been a strong demand for reduction of noise from construction equipment to the surroundings based on changes in the working environment and requirements for preservation of the surrounding environment, and has a noise standard that meets the European noise regulations. There is an urgent need to develop construction machinery. Normally, the operating noise of the prime mover and hydraulic pump, which are the main noise sources in construction machinery, and the pitch noise of the cooling fan (sound generated by the passage of the fan blades) are low frequencies of about 100 Hz to 500 Hz.
It is important to reduce the noise in the low frequency band from the viewpoint of reducing the overall noise of the construction machine. Furthermore, the frequency band of such construction machinery depends on the type and specification of the prime mover, hydraulic pump, etc. of each construction machinery, and their combination, and also depending on the arrangement state of each equipment, the frequency band of each construction machinery. Individually different. Therefore, in order to reliably reduce the overall noise of a construction machine, it is necessary to be able to freely set the target sound absorption frequency in a low frequency band according to the noise characteristic of the construction machine of interest.

In the prior art using the urethane foam type or glass wool type sound absorbing material, the target frequency as the sound absorbing target can be set freely by adjusting the material and size of the sound absorbing material. In order to increase the sound absorption coefficient in the frequency band, for example, it is necessary to increase the thickness of the sound absorbing material. However, the thickness is practically limited due to the space in the cover of the construction machine, and it is difficult to absorb sound in a low frequency band. Further, in the structure described in Japanese Utility Model Laid-Open No. 1-80577, no consideration is given to the fact that the target frequency as the sound absorption target can be set as appropriate. The sound absorption target frequency cannot be set. Further, in the structure described in Japanese Utility Model Laid-Open Publication No. 64-29230, the target frequency as the sound absorption target can be set freely by adjusting the distance between the outer cover and the inner cover.
To increase the sound absorption coefficient in the low frequency band, it is necessary to increase the thickness of the cover. The space inside the cover of construction equipment is limited, and as the cover becomes thicker, the weight also increases, so in practice the thickness of the cover is limited and it is difficult to absorb sound in the low frequency band. . As described above, in the above-described related art, the sound absorption target frequency cannot be freely set in the low frequency band, and the overall noise of the construction machine cannot be sufficiently reduced.

The present invention has been made on the basis of the above-mentioned matters, and has a construction capable of freely setting a target sound absorption frequency in accordance with the noise characteristics of a target construction machine in a low frequency band which is particularly problematic for the construction machine. An object of the present invention is to provide a machine noise reduction device and a cover of a construction machine used for the device.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a construction machine provided on a construction machine having a plurality of devices including a hydraulic pump, a prime mover, and auxiliary machinery of the prime mover covered with a cover. A noise reduction device for a machine, wherein a resonance sound absorbing means for absorbing sound in a band near a desired sound absorption target frequency by using a resonance effect at a position corresponding to each device in the cover is provided. Machine noise reduction equipment. In the present invention, sound is absorbed by a resonance sound absorbing unit having, for example, a plurality of resonance chambers partitioned by partition walls and an introduction hole for introducing sound into the plurality of resonance chambers. At this time, by performing sound absorption using the resonance action, in the above example, by appropriately adjusting the hole diameter of the introduction hole, the air layer thickness of the resonance chamber, and the like, the sound absorption target frequency can be easily set in a wide range. be able to. Therefore, even in the case where there is a limited space inside the cover, unlike the conventional structure in which the thickness of the sound absorbing material is changed or the distance between the double-structured covers is changed, even in the low frequency band which is a particular problem for construction machinery, The sound absorption target frequency can be set freely according to the noise characteristics of the target construction machine, and the noise in the low frequency band can be reliably reduced. This makes it possible to sufficiently reduce the overall noise of the construction machine.

Preferably, the resonance sound absorbing means includes a plurality of resonance chambers separated from each other by partition walls, and an introduction hole provided in each of the plurality of resonance chambers for introducing sound into the resonance chamber. The feature is a noise reduction device for construction machinery.

[0010] More preferably, the hole diameter of the introduction hole and the air layer thickness of the resonance chamber are determined according to the target sound absorption frequency and the sound velocity, respectively. .

[0011] Preferably, there is provided a noise reduction device for a construction machine, wherein a guide member for guiding sound to the introduction hole is provided. Depending on the positional relationship between the resonance sound absorbing means and the noise source, the sound does not always come from the front of the introduction hole and may come from an oblique direction, but by providing a guide member, in such a case, However, sound can be positively introduced into the introduction hole and can be absorbed in the resonance chamber, so that sound can be reliably absorbed.

Preferably, there is provided a noise reduction device for a construction machine, further comprising a sound absorbing material. Normal,
The sound absorbing material is capable of absorbing sound in a wide frequency band to a certain extent, but has a property that the sound absorbing characteristic particularly in a low frequency band improves as the thickness increases. However, when it is used in a cover of a construction machine, the thickness is practically limited due to space restrictions, so that it is often used to exhibit sound absorbing performance mainly in a relatively high frequency band. Therefore, the whole sound of the construction machine is absorbed by the resonance sound absorbing means absorbing the sound near the desired sound absorption target frequency in the low frequency band and the sound absorbing material to absorb the sound in the relatively wide frequency band centered on the high frequency band. Noise can be more reliably reduced.

According to another aspect of the present invention, there is provided a construction machine provided with a plurality of devices including a hydraulic pump, a prime mover, and auxiliary machines for the prime mover, the construction covering the plurality of devices. A cover of a construction machine is provided with a resonance sound absorbing means for absorbing a sound in a band near a desired sound absorption target frequency by utilizing a resonance action in the cover of the machine.

Preferably, the resonance sound absorbing means includes a plurality of resonance chambers separated from each other by partition walls, and an introduction hole provided in each of the plurality of resonance chambers for introducing sound into the resonance chamber, and , A sound absorbing material and a guide member for guiding sound to the introduction hole.

More preferably, the guide member is fixed to an edge of an introduction hole of the resonance sound absorbing means, and the sound absorbing member is provided with the guide member in a through hole provided at a position corresponding to the guide member. A cover for a construction machine, wherein the cover is engaged with the resonance sound absorbing means by being inserted. By making the sound absorbing member and the resonance sound absorbing means an engaging structure, their attaching and detaching work during maintenance,
The work of attaching them to the existing cover can be performed easily and smoothly.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a noise reduction device for a construction machine according to the present invention. This embodiment is an embodiment in which the present invention is applied to a hydraulic shovel as an example of a construction machine.

FIG. 1 is a perspective view showing an overall external structure of a hydraulic shovel to which a noise reduction device according to the present embodiment is applied. In general, the hydraulic shovel includes a traveling body 1 and a traveling body 1. A revolving body 2 provided to be revolvable on the body 1,
A driver's cab 3 provided on the front left side of the revolving unit 2 and a revolving unit 2
A multi-joint type of engine device 4 disposed horizontally on the top, a counterweight 5 provided at the rear of the revolving superstructure 2, and a boom 6a, an arm 6b and a bucket 6c provided at the front of the revolving superstructure 2. And a front device 6.

The traveling body 1 is provided with an endless track 1
a. The crawler track 1a is driven by a driving force of a traveling motor 1b. The revolving unit 2 including the cab 3, the engine room 4, the counterweight 5, the articulated front device 6, and the like is driven by a revolving motor (not shown) provided at the center of the revolving unit 2. The vehicle is turned with respect to the traveling body 1. The boom 6a, the arm 6b, and the bucket 6c that constitute the multi-joint type front device 6 are provided with a boom cylinder 7a, an arm cylinder 7b, and a bucket cylinder 7, respectively.
The driving operation is performed by c.

The driving devices such as the cylinders 7a, 7b, 7c, the turning motor, and the traveling motor 1b are hydraulic actuators (for example, hydraulic actuators, the same applies hereinafter), and are operated by an operator in the cab 3. The control valve device controls the hydraulic oil from a hydraulic pump (same) that is driven by an engine (not shown, see FIG. 3 described later) in the engine device 4 in response to the operation from the operating lever that is operated. (Not shown).

FIG. 2 is an enlarged perspective view showing an external structure of an engine room 4 to which the noise reduction device according to the embodiment is applied. FIG. 3 is an engine device provided with the noise reduction device according to the embodiment. It is a side view which shows the detailed structure of 4 by a partial cross section. In FIGS. 2 and 3, FIG.
Those having the same reference numerals are the same parts.

2 and 3, an engine cooling device for cooling the engine 8 is provided in the engine device 4.
A radiator 9 that is a heat exchanger that cools the cooling water of the engine 8 and a cooling fan 11 that generates a cooling wind P that cools the radiator 9 by driving the auxiliary rotation shaft 10 are provided.

The outer shell of the engine device 4 is constituted by an engine cover 13 made of, for example, a thin steel plate. The engine cover 13 allows the engine 8, the cooling fan 11, the radiator 9, the hydraulic pump (described later), and the muffler (the same). ) Etc. are covered. The engine cover 13 includes a lower cover 13a, a suction side (left side) side cover 13b, a discharge side (right side) side cover 13c, an upper cover 13d, a front cover 13e, and a rear cover 13f. I have.

The upper cover 13d has a hinge 1 at one end.
4 is attached to the discharge side lateral cover 13c so as to be openable and closable, and the other end thereof is connected to the suction side lateral cover 13b
There is provided a locking member 15 for hooking the lock. The radiator 9 side and the suction side horizontal cover 13b of the upper cover 13d are provided with suction ports 16 for taking in an air flow (cooling air) P from the outside and introducing it to the cooling fan 11. The upper cover 13d and the discharge side lateral cover 13c are respectively provided with discharge ports 17 and 18 for discharging the airflow (cooling air) P flowing out of the cooling fan 11 to the outside. Further, a discharge port 19 is provided also on the side of the hydraulic pump (described later) of the lower cover 13a.

The engine 8 is installed via a vibration damping device 21 on a frame 20 which is provided below the revolving superstructure 2 and forms a foundation lower structure of the revolving superstructure 2. The driving force of the engine 8 from a crankshaft 8a is provided. Is transmitted to the auxiliary rotation shaft 10 via the pulley 22, the fan belt 23, and the pulley 24. A water pump (not shown) that circulates engine cooling water to the radiator 9 is connected to the auxiliary rotation shaft 10 on the side opposite to the cooling fan 11. The hydraulic pump 25 described above is provided on the discharge side lateral cover 13c side of the engine 8, and the hydraulic pump 25 is connected to the engine 8 via a gear mechanism (not shown). A plate (not shown) is driven. Further, exhaust gas from the engine 8 is emitted to the outside of the engine device 4 through an exhaust gas pipe 27 after being muffled by a muffler 26. A muffler cover 28 is fixed to an upper portion of the engine 8 to prevent oil from scattering from the hydraulic pump 25 to the engine 8 side.

The cooling fan 11 is usually an axial fan, and has an impeller 11 a composed of a plurality of moving blades fixed to the auxiliary rotating shaft 10. That is, the auxiliary rotating shaft 10
Constitutes a fan rotation shaft of the cooling fan 11. Further, a shroud 29 for introducing the cooling air P to the suction side of the cooling fan 11 is fixed downstream of the radiator 9. The space between the radiator 9 and the upper cover 13d is sealed by a partition member 30.

The radiator 9 is a minimum example of a heat exchanger cooled by the cooling air P, and is not limited to this. That is, other heat exchangers such as an oil cooler that cools hydraulic oil that drives the hydraulic actuators 7a to 7c, an intercooler that pre-cools combustion intake air of the engine 8, or a condenser of an air conditioner as necessary. If provided, they and the radiator 9 are arranged together and cooled by the cooling air P.

A noise reduction device according to an embodiment of the present invention is provided in the engine room 4 as described above. 2 and 3, the noise reduction device includes a sound absorbing body 31 (partly not shown) provided at a position corresponding to the engine 8 among the front cover 13e, the rear cover 13f, the upper cover 13d, and the lower cover 13a. , The front cover 13e, the rear cover 13f, and the lower cover 13a, corresponding to the cooling fan 11, and the front cover 13e, the rear cover 13f, the upper cover 13d, and the discharge side lateral cover 13c. And a sound absorber 33 (same) provided at a position corresponding to the hydraulic pump 25 in the lower cover 13a, and a sound absorber 34 provided at a portion corresponding to the muffler 26 of the muffler cover 28.

FIG. 4 is a perspective view showing the basic structure of a sound absorber provided in an embodiment of the noise reduction device of the present invention.
4 is a sectional view taken along the line V-V in FIG. 4, and FIG. 6 is a view schematically showing a structure related to one resonance chamber 36. In FIGS. Reference numerals indicate the same parts. 4 to 6, the above-described sound absorber 3
1, 32, 33, and 34 have basically the same structure, and include a sound absorbing panel 37 provided with a plurality of resonance chambers 36 separated from each other by a partition plate 35, and a sound absorption panel provided in each resonance chamber 36 to resonate. The sound absorbing panel 37 includes a guide hole 38 for guiding the sound into the chamber 36, a guide 39 for guiding sound to the guide hole 38, and a sound absorbing material 40 affixed to the surface of the sound absorbing panel 37.

The sound absorbing panel 37 is made of, for example, metal.
Alternatively, it may be made of plastic from the viewpoint of weight reduction and ease of handling. In the case of metal, for example, the cover 13a
In the case of plastic, for example, a fixing flange is provided integrally with the sound absorbing panel 37, and this flange is fixed to the covers 13a to 13f via bolts.

The guide 39 has a semi-cylindrical shape, and its root is fixed to the edge of the corresponding introduction hole 38, and its tip is a sound absorbing material 40.
Protruding from the surface. The sound absorbing material 40 is, for example,
It is usually composed of urethane foam or glass wool-based material often used as this kind of sound absorbing material,
The guide 39 is inserted into the through hole 40 a provided at a position corresponding to the guide 39, thereby engaging with the sound absorbing panel 37. With such an engagement structure, the sound absorbing material 49 and the sound absorbing panel 37 during maintenance are provided.
, And the work of attaching the sound absorbing material 49 and the sound absorbing panel 37 to the existing cover can be performed easily and smoothly. The sound absorbers 31, 32, 33,
34 have basically the same structure, but the structure of the sound absorbing panel 37, the selection of the sound absorbing material 40, the structure of the guide 39, and the like are mutually changed in accordance with the difference in required sound absorbing characteristics due to the difference in the attachment site. It goes without saying that they may be different.

In the above description, the engine 8 constitutes the prime mover, the radiator 9 and the muffler 26 constitute the auxiliary parts of the prime mover, and these, the cooling fan 11 and the hydraulic pump 25 constitute the equipment inside the cover. Also, the partition plate 35
Constitutes a partition wall, and the sound absorbing panel 37 constitutes a resonance sound absorbing means for absorbing sound in a band near a desired sound absorption target frequency by utilizing a resonance action. The guide 39 forms a guide member for guiding sound to the introduction hole.

Next, the operation of one embodiment of the above-described noise reduction device of the present invention will be described. When the engine 8 is driven to start the operation by the hydraulic shovel, the driving force is transmitted to the hydraulic pump 25 via the gear mechanism, and the swash plate rotates, and the volume corresponding to the tilt angle of the swash plate is rotated. Is discharged to the driving device via the control valve device. At this time, the rotation of the crankshaft 8a of the engine 8 is transmitted to the auxiliary rotation shaft 10 via the fan belt 23, and the auxiliary rotation shaft 10 rotates to rotate the cooling fan 11. By the rotation of the cooling fan 11, the air outside the engine cover 13 is introduced into the engine device 4 from the intake hole 16 and becomes the cooling air P to cool the radiator 9.
The flow is throttled at 9 and flows into the cooling fan 11. Further, the cooling air P blown from the cooling fan 11 cools the engine 8, the muffler 26, the hydraulic pump 25, and the like.
The gas is discharged from the engine device 4 to the outside of the engine device 4. Further, at this time, the exhaust gas from the engine 8 flows into the muffler 26 via an exhaust manifold (not shown) of the engine 8 and an exhaust pipe (the same) connected thereto. After the exhaust gas flowing into the muffler 26 is silenced by the muffler 26, the exhaust gas is discharged from the exhaust gas pipe 27 into the atmosphere.

In the above operating conditions, various noises are generated from the engine 8, the hydraulic pump 25, the muffler 27, the cooling fan 11, the radiator 9, and the like. Cooling fan 11,
100Hz generated from hydraulic pump 25, muffler 27, etc.
This is noise in a low frequency band of about 500 Hz to 500 Hz. In the present embodiment, these low frequency components are reduced by providing the sound absorbers 31 to 34 at positions corresponding to the respective devices on the covers 13a to 13f. In addition, high-frequency components higher than those are also reduced, so that the overall noise of the excavator can be sufficiently reduced.
Hereinafter, the details will be described.

(1) Reduction of Specific Frequency Component (Low Frequency Component) in Sound Absorbing Panel In FIGS. 4 to 6, a part of noise generated from each device is indicated by an arrow a in FIG. 5 or an arrow in FIG. As shown by C, the sound is introduced into the through hole 40a of the sound absorbing material 40, and is further introduced from the through hole 40a into each resonance chamber 36 through the introduction hole 38. Then, in the resonance chamber 36, a sound in a frequency band near a predetermined sound absorption target frequency (described later) is silenced by utilizing a resonance effect.

The principle of the resonance action will be specifically described below with reference to FIGS.

FIG. 7 schematically shows the structure of the resonance chamber 36 of the sound absorbing panel 37 according to the embodiment of the present invention described above. In FIG. 7, the diameter of the introduction hole 38 of the sound absorbing panel 37 is d, the thickness of the upper plate 41 in which the introduction hole 38 is provided (= the length of the introduction hole 38 in the axial direction) is t, and one introduction hole 3 is provided.
The length L and L2 of the upper plate 41 corresponding to 8 and the resonance chamber 3
Assuming that the thickness of the air layer in L.6 is L3, the resonance frequency fo of the resonance chamber 36 can be determined in a simple manner as described in, for example, the Noise and Vibration Countermeasure Handbook (edited by the Society of Acoustical Materials of Japan, 1989, published by Gihodo). It is known that the following equation is used.

Fo = (c / 2π) × {(p / t ′) × L} ^1/2 (Equation 1) where c: sound velocity p: aperture ratio of hole (= s / S; see below) s : Opening area of introduction hole 38 (= π (1/4) d ² ) S: Area of upper plate corresponding to one introduction hole 38 (= L1 ×
L2) t ': Effective plate thickness in consideration of correction of the opening end of the introduction hole 38 (= t + 0.8d) That is, by changing the above d, t, L1, L2, and L3, the resonance frequency Fo can be freely set. You can see that it can be set.

On the other hand, FIG. 8 shows a resonance chamber 3 having the above-described structure disclosed in the above-mentioned noise and vibration countermeasure handbook.
FIG. 6 is a diagram illustrating an example of a sound absorbing characteristic in No. 6; As shown in FIG. 8, the resonance chamber 36 may have a characteristic capable of absorbing a sound in a frequency band in the vicinity of the resonance frequency fo which is structurally determined based on the dimensions of each part according to the above equation (1). Are known.

As described above, d, t, and
If L1, L2, and L3 are appropriately changed and the resonance frequency Fo is set to the frequency of the sound to be reduced (sound absorption target frequency), it can be understood that the sound can be effectively silenced in the resonance chamber 36 using the resonance action. This effect will be specifically described with reference to FIG.

FIG. 9 shows sound absorbers 31 to 34 according to an embodiment of the present invention (that is, a case where both sound absorbing panel 37 and sound absorbing material 40 are provided) and sound absorbing material 4 corresponding to the prior art.
This is a comparison between the sound absorption characteristics when only 0 is provided and the sound absorption characteristics. However, the sound absorbing target frequency of the sound absorbing panel 37 is set to the frequency fp in the figure. In FIG. 9, since the arrangement of the sound absorbing members 40 is common, the difference in the sound absorbing behavior between the two indicates the sound absorbing effect due to the resonance of the sound absorbing panel 37. When the sound absorbing panel 37 is provided, the sound absorbing performance at the sound absorbing target frequency fp is remarkably improved and the noise level is greatly reduced as compared with the case where the sound absorbing panel 37 is not provided. That is, it is understood that the use of the sound absorbing panel 37 can reduce a desired specific frequency component of the noise.

Here, as described above, it is usually important from the viewpoint of reducing the overall noise of construction machinery that 100
It is a low frequency band from about Hz to 500 Hz. However, in the case of a sound absorbing material such as urethane foam or glass wool which is generally used, the sound absorbing target frequency can be freely set by adjusting the material and dimensions, but due to the space in the cover of the construction machine, it is practical. Has a limit in thickness, and it is difficult to absorb sound in a low frequency band. On the other hand, by using the sound absorbing panel 37 according to the embodiment of the present invention, the dimensions of each part of the sound absorbing panel 37 are appropriately set even when there is a restriction of a limited space in the engine device 4. Thus, the target sound absorption frequency can be set in the low frequency band. Therefore, noise in the low frequency band can be reliably reduced.

As described above, the frequency band of the noise from the construction machine is different for each construction machine depending on the type and specification of the prime mover, hydraulic pump, etc. of each construction machine. In order to reliably reduce the typical noise,
It is necessary that the sound absorption target frequency can be set freely in the low frequency band. By using the sound absorbing panel 37 of the embodiment of the present invention described above, it is possible to freely set the dimensions of each part of the sound absorbing panel 37 and freely set the sound absorbing target frequency, and therefore, according to the noise characteristics of each construction machine. The sound absorption target frequency can be set freely in the low frequency band, and low frequency components can be reliably reduced with any structure.

A guide 39 whose root is fixed to the edge of the introduction hole 38 and whose tip protrudes from the surface of the sound absorbing material 40.
Performs the following functions. That is, the noise radiated from the noise source in the engine cover 13 may have a specific direction (radiation direction) depending on its nature. In such a case, the guide 39 can promote sound incidence. For example, as shown by an arrow A in FIG. 5 and an arrow C in FIG. 6, when there is a sound flow that is obliquely incident on the axial direction of the through hole 40a, the guide 39
The sound can be guided smoothly from the through-hole 40a to the resonance chamber 36 along this. As described above, by smoothly causing the sound to enter the air layer in the resonance chamber 36, the resonance action can be more effectively exerted.

(2) Reduction of High Frequency Components in Sound Absorbing Material On the other hand, in FIGS. 4 to 6, mainly high frequency components of the noise generated from each device are reduced by the sound absorbing material 40 as shown by an arrow A in FIG. Incident inside. At this time, as described above, the sound absorbing material 40 has a different frequency band in which the sound absorbing characteristics are good according to the material, dimensions, and the like. However, as shown in FIG. Even in the case of the sound absorbing material 40 which is arranged in a space and necessarily has a limited thickness, the high frequency component that has entered can be converted into heat energy and annihilated, and noise in this high frequency band can be reduced.

(3) Overall Noise Reduction As described in (1) and (2) above, the sound absorbing action of the low frequency component due to the resonance in the resonance chamber 36 of the sound absorbing panel 37 and the high frequency component inside the sound absorbing material 40 Of the above-mentioned sound absorbing functions simultaneously act, thereby making it possible to sufficiently and reliably reduce the noise of the entire hydraulic excavator. This will be described more specifically with reference to FIG.

FIG. 10 shows a case where only the sound absorbing panel 37 according to an embodiment of the present invention is provided (however, the sound absorbing target frequency is set to a low frequency band), and only a sound absorbing material 40 corresponding to the prior art is provided. This is a comparison between the sound absorption characteristics of the two cases. As can be seen from FIG. 10, the sound absorbing material 40 has relatively good sound absorbing characteristics in a high frequency band and the noise level is lowered in a relatively wide range due to the above-described space restrictions. In a very low frequency band, the sound absorption performance is low and the noise level remains relatively high. On the other hand, in the sound absorbing panel 37 in which the target sound absorption frequency is set in the low frequency band, the noise level in the low frequency band is reduced according to the principle described in the above (1), indicating that the sound absorbing performance is good. .

However, as described above with reference to FIG. 8, the sound absorption rate of the sound absorption panel 37 utilizing the resonance action gradually decreases as the distance from the sound absorption target frequency set by the resonance frequency fo increases. Therefore, as shown in FIG. 10, when the target sound absorption frequency is set in the low frequency band, the sound absorption performance in the high frequency band is low, and
The noise level is higher than when only 0 is used.

Therefore, in one embodiment of the present invention,
A sound absorbing panel 37 in which a particularly remarkable sound absorbing performance is obtained in a relatively narrow range of a low frequency band by setting a target sound absorbing frequency in a low frequency band, and a relatively good sound absorbing performance in a relatively wide range of a high frequency band. Sound absorbing material 4 with high performance
Use with 0. This makes it possible to sufficiently reduce the overall noise of the hydraulic shovel in the high frequency band and the low frequency band. Moreover, at this time, the above (1)
As described above, since low-frequency components can be reliably reduced according to the noise characteristics of each hydraulic excavator,
According to the noise characteristics of each hydraulic excavator, the overall noise in the high frequency band and the low frequency band can be sufficiently reduced regardless of the structure.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Hereinafter, these modifications will be sequentially described.

A structure for providing a difference in the protrusion height of the guide 39. That is, as shown in FIG. 11, a case in which the height of the protrusion from the sound absorbing material 40 is made different by changing the length of the plurality of guides 39. . In the illustrated example, the protrusion height from the sound absorbing material 40 is increased in the order of the guide 39a, the guide 39b, and the guide 39c far from the noise source. In this case, even when the sound propagates from a direction substantially perpendicular to the axial direction of the guide 39 as shown by arrows d, o, and f in FIG. 11, the sound is uniformly introduced into each resonance chamber 36. This has the effect of improving the sound absorption effect due to resonance.

A structure in which the guide 39 is tilted. That is, as shown in FIG. 12, each guide 39A is tilted, and the through hole 40a of the sound absorbing material 40 is also tilted accordingly. In the illustrated example, the guide 39A is inclined according to the propagation direction of the noise from the noise source. In this case, as shown by the arrow in FIG. 12, the sound enters in a direction substantially equal to the axial direction of the guide 39A, so that the sound can be introduced more smoothly, thereby improving the sound absorbing effect by resonance. This has the effect.

In the case of a structure in which the guide 39 is inclined to the side where the guide 39 is installed (left side in FIG. 12),
After inserting the sound absorbing material 40 as shown in FIG.
Is bent to the left in FIG.
There is also a method in which a wall around 0a is pressed to forcibly form an oblique hole.

Adhesion of guide 39 to sound absorbing material, shape other than cylinder, etc. That is, in one embodiment of the present invention, guide 39
In FIG. 5, the root portion is fixed to the edge of the introduction hole 38 and the front end portion is projected outside the sound absorbing material 40 as shown in FIG. It may be fixed with an adhesive or the like. Further, the guide 39 is not limited to a semi-cylindrical shape, and may be a (1/4) cylindrical shape, a (2/3) cylindrical shape, or a particularly rectangular shape, a plate shape, or the like. Not even a thing. Further, the guide 39 may not be provided for each through hole 40a of the sound absorbing material 40, but one guide 39 may be provided for each of the plurality of through holes 40a. FIG. 13 shows an example in which one plate-shaped guide 39B is provided for each of two through holes 40a of the sound absorbing material 40 by bonding to the surface of the sound absorbing material 40, and the guide 39B is further provided like the above guide 39A. It is an example in which it is provided at an angle.

A structure in which a plurality of types of resonance chambers 36 are provided in one sound absorbing panel 37. That is, as shown in FIG. 14, the diameter of the introduction hole 38 is d and the length and width of the upper plate 41 corresponding to the introduction hole 38 are L1 and L1. ,
The longitudinal and lateral dimensions of the resonance chamber 36 of L2 and the diameter of the introduction hole 38A are d 'and the upper plate 41 corresponding to the introduction hole 38A has L1' and L1 '.
In this case, a 2 'resonance chamber 36A is provided.

In this case, the following effects are obtained. That is, as described above, in the engine device 4, noise having different characteristics may be radiated from a relatively close portion. In such a case, if one sound absorbing panel 37 can absorb a plurality of types of frequency components, More effective. FIG.
As shown in FIG.
By providing 36A, a plurality of absorption target frequencies can be set in one sound absorbing panel 37, and it becomes possible to simultaneously absorb a plurality of types of frequency components.

In the above description of the embodiment of the present invention, the case where the present invention is applied to a hydraulic excavator has been described as an example. However, the present invention can be applied to other construction machines such as a crawler crane and a bulldozer. Needless to say, in this case, the same effect is obtained.

[0057]

According to the present invention, since the sound is absorbed by the resonance sound absorbing means using the resonance action, the target sound absorption frequency can be easily set in a wide range. Therefore, unlike the conventional structure, the target sound absorption frequency can be set freely according to the noise characteristics of the target construction machine even in the low frequency band, which is a particular problem for construction machinery, to reliably reduce the noise in the low frequency band. Can be. This makes it possible to sufficiently reduce the overall noise of the construction machine.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an overall external structure of a hydraulic shovel to which a noise reduction device according to an embodiment of the present invention is applied.

FIG. 2 is an enlarged perspective view showing an external structure of an engine room to which the noise reduction device according to the embodiment of the present invention is applied.

FIG. 3 is a side view partially showing a detailed structure of an engine device provided with the noise reduction device according to the embodiment of the present invention.

FIG. 4 is a perspective view showing a basic structure of a sound absorber provided in the noise reduction device according to one embodiment of the present invention.

FIG. 5 is a sectional view taken along the line VV in FIG. 4;

FIG. 6 is a diagram schematically showing a structure related to one resonance chamber provided in the noise reduction device according to one embodiment of the present invention.

FIG. 7 is a diagram schematically showing a structure of a resonance chamber of the sound absorbing panel provided in the noise reduction device according to one embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of a sound absorption characteristic in a resonance chamber.

FIG. 9 is a diagram showing a comparison between sound absorbing characteristics of a sound absorbing body provided in a noise reduction device according to an embodiment of the present invention and a case where only a sound absorbing material corresponding to the related art is provided.

FIG. 10 is a diagram showing a comparison between a case where only a sound absorbing panel provided in a noise reduction device according to an embodiment of the present invention and a case where only a sound absorbing material corresponding to the prior art are provided. It is.

FIG. 11 is a diagram showing a modified example in which the protrusion height of the guide is different.

FIG. 12 is a view showing a modification in which a guide is installed at an angle.

FIG. 13 is a view showing a modified example in which one plate shape is provided for each of two through holes of the sound absorbing material by being adhered to the surface of the sound absorbing material, and a modified example in which the guide is further provided at an angle.

FIG. 14 is a diagram showing a modified example in which a plurality of types of resonance chambers having different dimensions of each part are provided.

[Explanation of symbols]

Reference Signs List 8 engine (motor and equipment in cover) 11 cooling fan (equipment in cover) 13 engine cover (cover) 25 hydraulic pump (equipment in cover) 26 muffler (auxiliary equipment of motor and equipment in cover) 31-31 34 sound absorber 35 partition plate (partition wall) 36 resonance chamber 37 sound absorbing panel (resonant sound absorbing means) 38 introduction hole 39 guide (guide member) 40 sound absorbing material

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[Procedure amendment]

[Submission Date] December 13, 1999 (1999.12.
13)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

Fo = (c / 2π) × ｛ p / (t ′ × L3) ｝ ^1/2 (Equation 1) where c: sound velocity p: aperture ratio of hole (= s / S; see below) s : Opening area of introduction hole 38 (= π (1/4) d ² ) S: Area of upper plate corresponding to one introduction hole 38 (= L1 ×
L2) t ': Effective plate thickness in consideration of correction of the opening end of the introduction hole 38 (= t + 0.8d) That is, by changing the above d, t, L1, L2, and L3, the resonance frequency Fo can be freely set. You can see that it can be set.

Claims (8)

[Claims] An apparatus for reducing noise of a construction machine provided on a construction machine in which a plurality of devices including a hydraulic pump, a prime mover, and auxiliary machinery of the prime mover are covered with a cover, the apparatus corresponding to each device in the cover A noise reduction device for a construction machine, wherein a resonance sound absorbing means for absorbing sound in a band near a desired sound absorption target frequency using a resonance action is provided at a position. 2. The noise reduction device for a construction machine according to claim 1, wherein said resonance sound absorbing means is provided in a plurality of resonance chambers separated from each other by a partition wall, and is provided in each of the plurality of resonance chambers to transmit sound. A noise reduction device for a construction machine, comprising: 3. The noise reduction device for a construction machine according to claim 2, wherein the diameter of the introduction hole and the thickness of the air layer of the resonance chamber are determined in accordance with the target sound absorption frequency and the sound speed, respectively. Characteristic noise reduction device for construction machinery. 4. A noise reduction device for a construction machine according to claim 2, further comprising a guide member for guiding sound to said introduction hole. 5. The noise reduction device for a construction machine according to claim 1, further comprising a sound absorbing material. 6. A construction machine provided with a plurality of devices including a hydraulic pump, a prime mover, and an auxiliary machine of the prime mover, wherein the cover of the construction machine covers the plurality of devices by utilizing a resonance effect. A cover for a construction machine provided with resonance sound absorbing means for absorbing sound in a band near a desired sound absorbing target frequency. 7. The construction machine cover according to claim 6, wherein said resonance sound absorbing means includes a plurality of resonance chambers separated from each other by partition walls, and each of said plurality of resonance chambers introduces sound into said resonance chamber. And an introduction hole, and
A cover for a construction machine, comprising: a sound absorbing material; and a guide member for guiding sound to the introduction hole. 8. A cover for a construction machine according to claim 7, wherein said guide member is fixed to an edge of an introduction hole of said resonance sound absorbing means, and said sound absorbing material is located at a position corresponding to said guide member. A cover for a construction machine, wherein the cover is engaged with the resonance sound absorbing means by inserting the guide member into the provided through hole.