JP2002332659A - Noise reducing device for construction machinery and construction machinery equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce noise in a prescribed frequency band. SOLUTION: A plurality of passages 12 are formed via bulkheads 11 in a dust 10, which is mounted on a cover 20 forming an engine compartment 4, and a sound absorbing material 13 is stuck on the bulkhead 11. In that case, a cross-sectional length b of the passage 12 is set to be taken as half or the whole of a wavelength at a frequency f of the noise to be absorbed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction machine noise reduction device for reducing noise from an engine room and a construction machine provided with the noise reduction device.

[0002]

2. Description of the Related Art Generally, in a construction machine such as a hydraulic shovel, an engine room is covered with a cover, and a heat exchanger such as an engine, a hydraulic pump, a radiator, etc.
A cooling fan, a muffler, and the like are housed. The cover is provided with an air intake port and an air exhaust port, and the cooling air flowing in from the intake port passes through the engine room to cool each component and is discharged from the exhaust port. In such construction machinery,
Noise is generated by driving the engine, the hydraulic pump, the cooling fan, and the like, and the noise is emitted outside the engine room through the intake port and the exhaust port of the cover. In particular, in a large-sized construction machine, the engine capacity is increased, the noise in the engine room is increased, and the opening area of the intake port needs to be increased in order to inhale much cooling air. For this reason, fan noise and the like emitted through the intake port to the outside of the engine room tend to increase.

In recent years, noise given to the surrounding environment such as a residential area has become a social problem, and a low-noise construction machine has been demanded. In particular, European countries have their own noise regulations, and it is desired to develop construction machinery that meets these noise regulations. As an example of noise regulation, when the body of a construction machine is in a dynamic state,
At the time of a simulated work load including a turning operation, etc., a plurality of hemispherical locations surrounding the vehicle body (4 locations in the horizontal direction and 2 locations above the vehicle body)
The noise must be measured, and the measured value must satisfy a predetermined reference value.

[0004] Under such circumstances, various noise reduction devices have been conventionally proposed. For example, JP-A-5-139
Japanese Patent Publication No. 166 discloses an apparatus in which a plurality of sound absorbing plates are arranged at a radiator outlet along the flow direction, and a sound absorbing material is attached to an inclined surface facing the radiator outlet, thereby absorbing noise. Is disclosed. Japanese Utility Model Application Laid-Open No. 62-167810 discloses that a plurality of partition plates are attached to an exhaust port provided in a counterweight at a rearward position so that noise flowing out of an engine room is absorbed by repeated collisions between the partition plates. An apparatus is disclosed.

[0005]

However, the above-mentioned Japanese Patent Application Laid-Open No. 5-139166 and Japanese Utility Model Application Laid-Open No. 61-167 have been disclosed.
The device described in Japanese Patent Publication No. 810 does not specifically address the characteristics of noise flowing out of the engine room. Therefore, it is difficult for the devices described in these publications to effectively reduce noise in a specific frequency band, for example, a low frequency band such as fan noise.

An object of the present invention is to provide a noise reduction device for a construction machine capable of effectively reducing noise in a predetermined frequency band and a construction machine provided with the noise reduction device.

[0007]

The present invention will be described with reference to the drawings of the embodiments. (1) The invention according to claim 1 is a device for reducing noise leaking from the engine room 4 covered with the cover 20 to the outside, and has a duct 10 having at least one passage 12 and penetrating the cover 20. The cross section size b of the passage 12 in the duct 10 is set to at least 1/1 of the predetermined frequency band f so that the sound in the predetermined frequency band is absorbed in the duct 10.
The above-mentioned object is achieved by forming the light emitting element having a wavelength larger than two wavelengths (λ / 2) and smaller than one wavelength λ. (2) According to a second aspect of the present invention, in the noise reduction device for a construction machine according to the first aspect, the duct 10 is an intake duct that takes air from outside the engine room 4 into the engine room 4. (3) According to a third aspect of the present invention, in the noise reduction device for a construction machine according to the first or second aspect, the sound absorbing material 13 is attached to an inner peripheral surface of the passage 12. (4) The invention of claim 4 is the noise reduction device for a construction machine according to any one of claims 1 to 3, wherein
Are provided in the duct 10 via the partition 11. (5) A construction machine equipped with the noise reduction device according to the fifth aspect of the present invention is a noise reduction device according to any one of the first to fourth aspects, the work machine main body 2, and the work machine main body 2. The above-mentioned object is achieved by having the working device 6 provided.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an external structure of a hydraulic shovel to which the present invention is applied. The hydraulic shovel is provided on a traveling body 1, a revolving body 2 rotatably provided on the traveling body 1, a cab 3 mounted on the left side of the revolving body 2, and a rear side of the cab 3. The engine compartment 4 includes a counterweight 5 attached to the rear of the engine compartment 4, and an articulated front device 6 including a boom 6a, an arm 6b, and a bucket 6c attached to the right side of the cab 3. I have.

The traveling body 1 has a pair of left and right crawler tracks 1a,
The crawler belt 1a is driven by a traveling motor 1b. Revolving superstructure 2
Is turned with respect to the traveling body 1 by a turning motor (not shown) provided at the center thereof. Boom 6a, arm 6
b and the bucket 6c are rotated by expansion and contraction of the boom cylinder 7a, the arm cylinder 7b, and the bucket cylinder 7c, respectively. These motor 1a and cylinders 7a to 7c
Is driven by pressure oil from a hydraulic pump 45 (FIG. 2) provided in the engine room 4.

The engine compartment 4 is covered with a cover 20, and an exhaust port 21 is opened at the right side of the upper surface of the cover 20.
A duct 10 for intake, which will be described later, is welded to the left side surface of 0. In addition, the duct 10 covers the cover 2 with bolts.
0 may be attached. FIG. 2 is a diagram (a cross-sectional view taken along line II-II in FIG. 1) illustrating an internal configuration of the engine room 4. In the engine room 4, an oil cooler 41, a radiator 42, a cooling fan 43, an engine 44, and a hydraulic pump 4
5 are arranged in this order in the vehicle width direction. The cooling fan 43 and the hydraulic pump 45 are connected to an output shaft of the engine 44 and are driven by the engine 44. Cooling fan 4
When the motor 3 is driven, air is sucked into the engine room 4 through the duct 10, and the sucked air passes through the oil cooler 41 and the radiator 42 to be heat-exchanged. Then, they pass around the engine 44 and the hydraulic pump 45 to cool them, and are discharged from the exhaust port 21.

Here, the structure of the duct 10 will be described. FIG. 3 is a perspective view of the duct 10. A plurality of passages 12 having a rectangular cross section are formed in the duct 10 by partition walls 11 from the entrance end surface to the exit end surface.
Have the same shape. A sound absorbing material 13 made of a material such as urethane foam, glass wool, or felt is adhered to the partition 11. That is, passage 1
2 is covered with a sound absorbing material 13. The opening area of the duct 10 is determined according to the amount of suction of the cooling air, and the size of the passage 12 is determined as follows.

(1) Length of passage If the length of the passage 12 is L and the lengths of the short side and the long side of the cross section of the passage are a and b (a ≦ b), the sound propagating in the passage 12 The transmission loss TL (absorption volume) is generally obtained by the following equation (I). TL = 1.05α1.4P / S × L ≒ (α−0.1) × P / S × L (I) where α: sound absorption coefficient of the sound absorbing material 13 P: circumferential length of the passage 12 (= 2a + 2b) S : Cross-sectional area of passage 12 (= a × b) From the above equation (I), transmission loss TL increases in proportion to passage length L. Therefore, the passage length L is set to the longest possible value (for example, 40 cm) in consideration of the balance between the vehicle width limit value and the design of the construction machine.

(2) Cross-sectional shape of passage Assuming that the frequency of a sound wave is f and the wavelength is λ (= c / f, where c is the speed of sound), as shown in FIG. At λ, the vibration of the air on the wall surface increases. Therefore, as shown in FIG.
At c / b (= λ / 2 to λ), the transmission loss TL increases. Therefore, the length b of the long side is set so as to satisfy the following equation (II) for the frequency f to be absorbed. c / 2f <b <c / f (II) This point will be further described with a specific example.

For example, when reducing the rotational noise of the fan 43, the frequency f corresponding to the noise (here, f
= 290 Hz) and the sound velocity c (= 340 m / s) are substituted into the above equation (II). Accordingly, the condition that b satisfies is 0.58 <b <1.18. Therefore, the length b of the long side
Was set to 0.6 m, for example, and the effect of noise reduction was confirmed. FIG. 5 is a perspective view of the duct 10 set to b = 0.6 m, and FIG. 6 is a measured value of noise using the duct 10 (with duct) and a measured value of noise not using the duct 10 ( It is a figure which shows an example of the comparison of "no duct". In addition, the total opening area of the passage is set substantially equal with or without a duct. As shown by 101 in the figure, frequency f = 290H
At z, the noise with the duct is greatly reduced as compared with the case without the duct. To reduce noise other than fan noise (for example, noise of the engine 44 and the hydraulic pump 45), the length b of the long side may be determined according to the noise characteristics.

On the other hand, the unsteady wind noise is a noise in a wide range where the frequency f is 600 Hz to 2000 Hz. In this case, when f = 600 Hz is substituted into the above equation (II), 0.28 <b <0.57, and f = 2000 Hz
Is substituted, 0.08 <b <0.17. Therefore, the length b of the long side was set to, for example, b = 0.17 m, and the effect of noise reduction was confirmed. FIG. 7 is a diagram illustrating an example of a comparison between the measured value and the calculated value of the noise using the duct 10 of b = 0.17 m, and the measured value of the noise without using the duct 10. Here, urethane foam is used as the sound absorbing material 13, and the duct length L is set to 0.4 m. Also,
Since the sound absorbing performance (sound absorbing coefficient) of the sound absorbing material 13 increases with an increase in frequency, the calculated sound absorbing coefficient α is set to 0.54 (600
Hz), 0.76 (1000 Hz), 0.94 (150
0 Hz) and 0.96 (2000 Hz). As shown in FIG.
In the range of Hz, the noise with the duct is greatly reduced as compared with the case without the duct. In addition, the calculated value with duct and the measured value are almost the same. Thereby, the sound absorbing effect of the duct 10 was confirmed.

In the above description, the dimensions of the passages 12 in the duct 10 are set equal to each other, but may be set differently. Thereby, the sound absorption characteristics in each passage 12 are different, and the noise from low frequency to high frequency can be effectively reduced. In this case, when a noise distribution occurs at the opening of the duct 10, the size of each passage 12 may be determined according to the noise distribution. Further, the passage 12 has a rectangular shape, but may have a circular shape. In that case, the diameter d of the passage 12 may be set so as to satisfy λ / 2 <d <λ. Further, a plurality of passages 12 are provided in the duct 10, but one passage 12 may be provided as long as a necessary amount of air can be secured. Furthermore, duct 10
Rather than providing a plurality of passages 12 in one passage 1
The cover 20 may be provided with a plurality of ducts each having 2. 3 and 5, the vertical length a of the passage 12
Is shorter than the horizontal length b, but may be reversed or square.

(3) Thickness of the sound absorbing material In the duct structure in which the sound absorbing material 13 is lined, the sound absorbing material 1
The sound absorbing characteristic changes according to the thickness of the sound absorbing member 3. However, the thicker the sound absorbing material 13 is, the smaller the passage area is, and there is a possibility that the amount of cooling air taken into the engine room 4 may be reduced. In order to avoid this, the shape of the duct 10 may be increased accordingly, but this may be difficult due to space restrictions. Therefore, the relationship between the reduction rate of the passage area (the intake opening rate) and the reduction rate of the cooling air volume will be examined. FIG. 8 is a diagram showing the relationship between the air flow rate reduction rate (%) and the intake opening rate (%). As shown in the figure, as the intake opening ratio decreases, the cooling air volume also decreases. However, when the intake opening ratio is 60%, the air flow reduction ratio is less than 2%, and the reduction amount at this time is not so large. Thus, in the present embodiment, for example, the intake opening ratio is limited to 60%, and the thickness of the sound absorbing material 13 is set within this range.

As described above, in the present embodiment, the duct 10 is mounted on the cover 20 forming the engine compartment 4 and the size (long side b) of the passage 12 of the duct 10 is set to 波長 wavelength of the predetermined frequency f. Since the setting is made within the range of ~ 1 wavelength, noise in a predetermined frequency band can be effectively reduced. Further, since the sound absorbing material 13 is stuck around the passage 12, the noise reduction effect is increased. Furthermore, since the duct 10 is used as an intake duct, fan noise from the intake duct 10 can be reduced satisfactorily, and it is particularly suitable for use in large construction machines having a large intake opening area. Furthermore, since the duct 10 is formed by providing a plurality of passages 12 each having a predetermined length b, a required amount of cooling air can be taken into the engine room 4 while enhancing the sound absorbing effect. Further, by simply attaching the duct 10 to the cover 20, the current construction machine can be easily improved to a low-noise construction machine.

In the above embodiment, the sound absorbing material 13 is adhered to the partition 11, but it is not always necessary to adhere.
In this case, the partition 11 may be formed of a material having a different sound absorption coefficient, such as a metal, a plastic, or a resin, to adjust the sound absorption characteristics. In addition, although the duct 10 is used as an intake duct, the duct 10 may be used as an exhaust duct. Further, a plurality of ducts 10 may be mounted on the cover 20. Furthermore, in the above embodiment,
Although applied to a hydraulic excavator, it may be applied to other construction machines.

[0020]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first aspect of the invention, the size of the cross section of the passage in the duct attached to the cover of the engine compartment is formed to be at least larger than 1/2 wavelength of the predetermined frequency band and smaller than 1 wavelength. The duct can effectively reduce noise in a predetermined frequency band. (2) According to the second aspect of the present invention, since the duct is an intake duct, fan noise can be reduced satisfactorily. (3) According to the third aspect of the present invention, since the sound absorbing material is stuck around the passage, the effect of reducing noise is increased. (4) According to the invention of claim 4, since a plurality of passages suitable for noise reduction are provided in the duct, a required amount of cooling air can be taken into the engine room while reducing noise. (5) According to the fifth aspect of the present invention, since the construction machine is provided with a duct suitable for noise reduction, the construction machine can be easily changed to a low noise type construction machine.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external structure of a hydraulic shovel to which the present invention is applied.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a perspective view of a duct included in the noise reduction device according to the embodiment.

FIG. 4 is a view for explaining a method of setting the size of a passage.

FIG. 5 is a diagram showing a modified example of the duct according to the embodiment.

FIG. 6 is a diagram showing an example of the effect of the present invention.

FIG. 7 is a diagram showing another example of the effect of the present invention.

FIG. 8 is a diagram showing a relationship between an intake opening ratio and an air flow reduction ratio.

[Description of Signs] 2 Revolving unit 4 Engine room 6 Front device 10 Duct 11 Partition wall 12 Passage 13 Sound absorbing material 20 Cover 43 Cooling fan 44 Engine

Claims (5)

[Claims] 1. An apparatus for reducing noise leaking from an engine room covered by a cover to the outside, comprising: a duct having at least one passage and penetrating the cover; Like absorbing sound,
A noise reduction device for a construction machine, wherein a size of a cross section of the passage in the duct is larger than at least a half wavelength of the predetermined frequency band and smaller than one wavelength. 2. The noise reduction device for a construction machine according to claim 1, wherein the duct is an intake duct that takes air from outside the engine room into the engine room. 3. The noise reduction device for a construction machine according to claim 1, wherein a sound absorbing material is attached to an inner peripheral surface of the passage. 4. The noise reduction device for a construction machine according to claim 1, wherein a plurality of the passages are provided in the duct via a partition. Reduction device. 5. A noise reduction device comprising: the noise reduction device according to claim 1; a work machine main body; and a work device attached to the work machine main body. Construction machinery.