JPH08291703A - Noise reduction device for engine room of construction machine - Google Patents

Abstract

PURPOSE: To reduce noises generated in an engine room of a construction machine without affecting taking-in of cooling wind. CONSTITUTION: Stacked ducts 30, 32 are arranged on a take-in port and a discharge port 16 for cooling wind. A total amount of the cooling wind is taken in through the stacked ducts 30, 32, or discharged therefrom. The stacked ducts 30, 32 are divided into four small ducts 30a to 30d. The longest small duct 30a and the shortest small duct 30d have the length ratio such that a phase difference of λ0/2 is formed where λ0 is wavelength of frequency of noise to be reduced. Adjacent small ducts have lengths differentiated from each other by λ0/20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing noise generated in an engine room of a construction machine.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 4 and 5, the construction around the engine room of a construction machine such as a hydraulic excavator has a counterweight 2 at the rear end of the machine and an oil cooler ( The radiator 4, the cooling fan 6, the engine 8, the pump 10 and the like are arranged in a line in the lateral direction. The cooling air enters the engine room 14 from the air intake 12, passes through the oil cooler (and radiator) 4, and is discharged from the air discharge port 16.

[0003]

However, since the parts other than the air intake port 12 and the air exhaust port 16 are usually surrounded by the iron plate, the noise in the engine room 14 is hard to leak to the outside, but the opening part There is a problem that noise in the engine room largely leaks from the air intake port 12 and the air exhaust port 16.

In this regard, noise leakage can be reduced to some extent by reducing the sizes of the air intake port 12 and the air exhaust port 16, but it is no longer possible to take in sufficient cooling air. A new problem occurs.

The present invention has been made in view of the above-mentioned problems of the prior art, and allows sufficient air movement without reducing the size of the air intake port or the air exhaust port. The object is to significantly reduce the noise in a specific frequency region that is particularly audible, and thus reduce the noise felt by a person as a whole.

[0006]

According to a first aspect of the present invention, there is provided a noise reducing device for an engine room of a construction machine for reducing noise generated in the engine room of the construction machine. At least one of the air intake port and the air exhaust port has a different length n.
Arranging integrated ducts having n (n is an integer of 2 or more) small ducts, and noise passing through each of the small ducts in the integrated ducts is interfered by a difference in length of the small ducts,
The problem is solved by reducing noise in a specific frequency range.

Further, in the invention according to claim 2, among the small ducts, the longest small duct and the shortest small duct are:
If the wavelength of the noise frequency to be reduced is λ0, λ0
The length ratio is such that a phase difference of / 2 is formed, and the lengths of adjacent small ducts are set to differ from each other by λ0 / 2n, thereby similarly solving the above problem.

Further, the invention according to claim 3 is the same as the above-mentioned problem, wherein the length of at least one of the small ducts is variable.

[0009]

In the present invention, the integrated duct is arranged at either one or both of the air intake port and the air exhaust port provided in the engine room. This integrated duct consists of n small ducts (n is an integer of 2 or more) of different lengths, and the cooling air to the engine room or the cooling air from the engine room passes through each small duct in this integrated duct. I am trying to let you.

As a result, the noises passing through the respective small ducts interfere with each other due to the difference in the length of the small ducts,
Noise in a specific frequency range is reduced.

For example, assuming that the wavelength of the noise frequency to be reduced is λ0, a phase difference of exactly λ0 / 2 is formed in the length ratio of a specific pair of small ducts among the small ducts. By setting the loudness, the sound near the frequency is greatly reduced by the interference.

As a conventional technique configured to reduce noise by using a plurality of ducts having slightly different duct lengths, the following soundproof device has been proposed (Catalog of Bridgestone Corporation: trade name Calmson). ).

This soundproof device captures a part of noise (including a wide range of frequency components) at the uppermost part of the soundproof wall and passes it through a plurality of ducts having slightly different duct lengths to obtain the original noise. By generating a delayed wave in several stages, a phase difference with the original noise that does not pass through the plurality of ducts is formed, and the noise with the phase difference formed (passing through the duct) is The sound pressure of the original noise in the resonance region is lowered by interfering with the original noise that does not pass through the duct directly over the soundproof wall.

However, this soundproof device is for reducing the noise that gets over the upper part of the soundproof wall in a place where a large amount of noise is generated over a wide frequency band such as noise of a factory. The fields of application are different.

Further, even if it is attempted to apply this to noise reduction in the engine room of a construction machine, the basic technical idea is to pass some of the original noise as it is and form a phase difference (duct. Since the noise was to interfere with the original noise (which did not pass through the duct), there was a problem that the interference was not always good and a sufficient noise reduction effect could not be obtained. It is thought that.

In the present invention, as described above, the cooling air to the engine room or the cooling air from the engine room is passed through the "all" duct, while this duct causes interference in a specific frequency range. Since the sound passing through the duct is delayed in several stages so as to occur and they are directly interfered with each other, a very large reduction effect can be obtained in the specific frequency region.

That is, in general, the noise of the engine or the cooling fan or the noise caused by the cooling air forms a peak in a specific frequency range, and the peak tends to be very audible. By reducing the noise in the frequency range of, it is possible to obtain a large noise reduction effect in terms of sensation.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing the vicinity of an engine room of a hydraulic excavator to which the present invention is applied.

As is apparent from FIG. 1, in this embodiment, the integrated ducts 30 and 32 are arranged at both the air intake 12 and the air exhaust 16 of the engine room 14.
The two accumulation ducts 30 and 32 are symmetrical with each other. Here, the integrated duct 30 on the air intake 12 side is shown in FIG.

As is apparent from FIG. 2, the integrated duct 30 is divided into n (4 in the illustrated example) small ducts 30a to 30d in the inside thereof, and the lengths of adjacent small ducts are ( It is set so that a phase difference is generated by λ0 / 2n) = λ0 / 8. That is, the longest small duct 30a and the shortest small duct 30d differ in length by .lambda.0 / 2. Here, .lambda.0 is the wavelength corresponding to the frequency fo that is most desired to be reduced.

The accumulating ducts 30 and 32 are mounted so as to completely close the air intake 12 and the air exhaust 16 as shown in the figure, so that all the cooling air flows through the accumulating duct 30 in the engine room. 14 and is discharged from the engine room 4 via the total accumulation duct 32.

Next, the operation will be described.

The sound generated from the engine 8 as the sound source, the cooling fan 6 or the like leaks to the outside through the integrated duct 30 or 32. The basic technical idea for noise reduction does not differ between the air intake 12 and the air exhaust 16, so the description will focus on the air intake 12 side.

The noise enters the small ducts 30a to 30d almost evenly, and when it is emitted to the outside, the small ducts 30a to 30d.
The phase difference due to the different length of 0d is
It occurs in a to 40d. If the frequency of the noise to be reduced is fo and the speed of sound is C, then λ0 = C / fo. The phase difference between the longest duct 30a and the shortest duct 30d is exactly λ 0/2, and the sound passing through them is in a state of being out of phase with each other by half a wavelength due to the delay due to the duct length. , The sounds of frequency fo are largely interfered with each other, and the sound of frequency fo is greatly reduced.

For the same reason, the small ducts 30b and 30c are
2 × (λ0 / 2n) = λ0 / 4 and 3 × (λ0 /
Since there is a phase difference of 2n) = 3λ0 / 8, n / 2
This contributes to the reduction of noise (frequency component noise) having a frequency of × fo = 2fo and n / 3 × fo = 4 / 3fo.

Incidentally, the length is generally a × (λ / 2n).
The different ducts will reduce the sound of the frequency of n / a × fo. Here, a is an integer larger than 1 and smaller than n.

In this way, the four small ducts 30a ...
By the integrated duct 30 divided into 30d, it is possible to greatly reduce the noise near the frequency fo and its high-frequency components. Therefore, by matching this frequency with the frequency of the noise that peaks in the hydraulic excavator. , Will be able to obtain a very large sound reduction effect.

The same effect can be obtained in the integrated duct 32 provided on the air discharge port 16 side. In this case, if the duct lengths of the integrated ducts 30 and 32 are made different, noise can be reduced in two frequency regions.

Further, these collecting ducts 30 (or 3)
2), for example, as shown in FIG. 3, the sliding members 50a to 50d are provided near the outlets of the small ducts 30a to 30d.
Is provided so that the effective lengths of the small ducts 30a to 30d can be changed (for example, L0 → L1), the frequency band to be reduced to the most audible frequency band at the actual site can be easily set. To be able to match,
In each site, it becomes possible to easily match the frequency to be attenuated with the frequency that currently has the largest peak due to the engine speed, air flow, and other influences at that time. As a result, the effect of the present invention can always be maximized.

In this case, it is not always necessary that all the small ducts have variable lengths.

The number of small ducts in the integrated duct must be at least two for the purpose of the present invention, but the number is not particularly limited.

[0033]

As described above, according to the present invention,
It is possible to effectively reduce the noise of the most audible frequency without reducing the area through which the cooling air passes, so that it is possible to greatly reduce the noise experienced by the user. That is an excellent effect.

[Brief description of drawings]

FIG. 1 is a perspective view showing the vicinity of an engine room of a hydraulic excavator to which the present invention is applied.

FIG. 2 is a perspective view showing an example of a collecting duct arranged at an air intake.

FIG. 3 is a vertical sectional view showing an example of an integrated duct having a variable duct length.

FIG. 4 is a schematic plan view of an inside of an engine room of a conventional hydraulic excavator.

[Fig. 5] Similarly, an oblique view around the engine room

[Explanation of symbols]

 6 ... Cooling fan 8 ... Engine 12 ... Air intake 14 ... Engine room 16 ... Air discharge port 30, 32 ... Integrated duct 30a-30d ... Small duct 50a-50d ... Sliding member

Claims (3)

[Claims] 1. A noise reduction device for an engine room of a construction machine for reducing noise generated in the engine room of the construction machine, comprising: at least one of an air intake port and an air exhaust port provided in the engine room. , Arranging integrated ducts having n small ducts (n is an integer of 2 or more) of different lengths, and noises passing through the respective small ducts in this integrated duct are
A noise reduction device for an engine room of a construction machine, characterized in that interference is caused by a difference in length of the small duct to reduce noise in a specific frequency range. 2. The small duct according to claim 1, wherein
The longest small duct and the shortest small duct have a length ratio such that a phase difference of λ0 / 2 is formed when the wavelength of the noise frequency to be reduced is λ0. The noise reduction device for the engine room of a construction machine is characterized in that the lengths are set to differ by λ0 / 2n. 3. The small duct according to claim 1, wherein
A noise reduction device for an engine room of a construction machine, at least one of which has a variable length.