JPH1039878A - Noise reduction device of enclosed engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the noise of an engine by burying at least one of a reference noise microphone, a residual noise microphone and a canceling sound generating means in the muffling material which is pasted and constituting at least one of the bending sections of the exhaust side duct by a curved surface wall. SOLUTION: When noise reduction is conducted by an active noise control(ANC) for the engine generator enclosed by a sound proof case, an exhaust side duct 33 is provided, a muffling material 10 is pasted on the inner wall surface of the duct 33 and a reference noise microphone 37 is buried in the material 10. Moreover, curved surface walls 20, 29 and 31 are provided to constitute the bending sections of the duct 33 to make the flow of cooling air smooth. By constituting the duct as indicated above, the flow of cooling air in the duct 33 is made uniform, the generation of vortexes and turbulences is prevented and the noise reduction performance is enhanced.

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 an enclosed engine which reduces noise of an engine surrounded by an enclosure such as a soundproof case.

[0002]

2. Description of the Related Art Conventionally, as a technique for reducing noise of an engine and an exhaust duct, a passive method of providing a sound absorbing material and a vibration damping material has been proposed. In contrast, in recent years,
Active noise control (active noise control, hereinafter referred to as ANC) has been put to practical use in which noise is emitted by canceling out noise with the same amplitude and opposite phase, thereby reducing the noise by the interference effect of sound waves. (JP-A-2-503219, JP-A-3-204354, JP-A-4-350314, etc.).

[0003] For example, Japanese Patent Application Laid-Open No.
In the engine exhaust noise reduction device disclosed in JP-A-350314, a ring-shaped large-diameter portion is provided around the end of the engine exhaust pipe, a speaker is disposed in the large-diameter portion, and sound emitted from the engine exhaust pipe is provided. This is to reduce the noise by generating an opposite phase canceling sound. There is no description about the method of detecting the reference signal and the residual signal in the ANC control. However, since the sound of the engine explosion can be predicted to some extent accurately on the basis of the rotation signal of the crankshaft, it is considered that the noise can be reduced relatively easily. Seem.

On the other hand, in recent years, there has been a demand for the development of environmentally friendly products, and in engine generators and the like, a type in which an engine is housed in a soundproof case to reduce noise has been preferred. Considering the increase in the environmental problem, it is conceivable to apply the ANC to an enclosed engine to reduce noise.

[0005]

However, as shown in FIG. 10, the noise of an enclosed engine such as an engine generator is a fundamental frequency and its harmonics caused by the rotation speed of a crankshaft, a cooling fan shaft, and the like, and the noise of the fan. It is composed of wind noise, vibration of the enclosure, transmitted noise of the muffler chassis, etc., and has a complex spectrum, so it generates a reference signal based on a reference periodic signal such as a crankshaft rotation signal. It is difficult to generate cancellation noise. In this case, a speaker is arranged between the reference noise microphone and the residual noise microphone, and the residual noise is determined by a predetermined ANC algorithm based on the reference noise signal from the reference noise microphone and the residual noise signal from the residual noise microphone. In this case, a method of sequentially changing the canceling sound generated by the speaker so as to minimize the energy of the loudspeaker is adopted.

When such a method is adopted, the following two problems must be solved in order to apply the ANC to the surrounding engine and reduce the noise in a practically effective manner. (1) It is essential for an enclosed engine to generate cooling air in order to cool the inside of the enclosed body. In order to cool the inside of the enclosure, it is preferable to blow the cooling air strongly.However, if the cooling air of the cooling fan is directly blown to the silencing duct, the cooling wind collides with the reference noise microphone, the residual noise microphone, and the loudspeaker. As a result, noises due to the vibration of the microphones are collected, and irregular vibration sounds due to the generation of the turbulence are generated.
There is a problem that the noise reduction performance by C cannot be improved. (2) If strong cooling air is blown to cool the inside of the enclosure, simply applying a normal silencing duct
A vortex and a turbulent flow occur, making it difficult to reduce noise by ANC control. In particular, since there are many noise sources in an enclosed engine as described above, when applying the ANC technology, it is necessary to make the flow of cooling air in the duct for noise reduction as simple and uniform as possible. It is difficult to secure practically sufficient noise reduction performance by using the method.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a noise reduction device for an enclosed engine which can ensure practically sufficient noise reduction performance with a simple and inexpensive configuration. And Another object of the present invention is to provide a noise reduction device for an enclosed engine that can exhibit high noise reduction performance without being affected by airflow in an enclosed engine that generates relatively strong cooling air by a cooling fan. .

[0008]

According to a first aspect of the present invention, a noise reduction device for an enclosed engine is described with reference to, for example, FIG. 1 and FIG. At least at a predetermined location, an intake port 6 and an exhaust port 5 are provided, a fan 12 for ventilating the air in the enclosure 2 is provided, and the noise of an enclosed engine that takes in outside air from the intake port 6 and exhausts it from the exhaust port 5 is reduced. For this purpose, at least an exhaust-side duct 33 communicating with the exhaust port 5 is formed around the enclosure 2, and a reference noise detecting microphone 37 for detecting noise near the exhaust port 5, and a noise near the duct outlet 21 of the exhaust-side duct 33. Noise detecting microphone 38 for detecting the noise, a canceling sound generating means 41 disposed in the exhaust side duct 33, and generating a canceling sound for canceling the noise at the duct outlet 21 based on the reference noise signal and the residual noise signal. And a ANC controller 65 for driving the canceling sound generating means 41 to cause the exhaust duct 33
The sound deadening material 10 is adhered to the inner wall surface of the air conditioner, and at least one of the reference noise microphone 37, the residual noise microphone 38, and the canceling sound generating means 41 is embedded in the sound deadening material 10 and the exhaust side duct 33 is bent. At least one of the parts is constituted by curved walls 29, 31, and 20. The position of the bent part on the exhaust side duct to be formed by a curved wall is determined by detecting a place where eddy currents and turbulent flows are likely to occur unless it is formed on a curved wall according to the configuration of each exhaust side duct. As needed. Also, reference noise microphone,
The number of residual noise microphones and canceling sound generating means to be embedded in the sound deadening material depends on the shape of the vortex,
This is performed by detecting a place where turbulence is likely to occur.

According to a second aspect of the present invention, in the noise reduction device for an enclosed engine, the exhaust-side duct 33 partitions the inclined plate 22 provided to cover the exhaust port 5 from the upper side and the inside of the exhaust-side duct 33 in a substantially vertical direction. A partition plate 23, which is attached to the wall 2 b of the enclosure 2 having the exhaust port 5, and an exhaust duct case 7 having an opening 18 in the upper wall 17, and the exhaust duct case 7 is partitioned by the upper wall 17 into the opening 18. And a horizontal duct 9 extending in a substantially horizontal direction, and a cooling air flowing out of the exhaust port 5 is formed in an exhaust air guide chamber 35 surrounded by the inclined plate 2 and a lower portion of the exhaust duct case 7. It is configured to be discharged from the duct outlet 21 through the exhaust bent portion 27, the exhaust-side ascending air passage 25 formed by the partition plate 23 and the exhaust duct case 7, and the horizontal air passage 55 in the horizontal duct 9, and from the exhaust side. Ascending wind path 2
5, a reference noise microphone 37 is fixed in the lower area, a residual noise microphone 38 is fixed near the duct outlet 21 of the horizontal duct 9, and a canceling sound is generated at the upper wall 17 of the exhaust duct case 7 or a predetermined position of the horizontal duct 9. A means 41 is provided.

The noise reduction device for an enclosed engine according to claim 3 will be described with reference to, for example, FIGS. 1 and 6. The engine 3 is enclosed by enclosures 2, 7, and 8.
In a surrounding engine provided with at least a cooling air inlet 51 and a cooling air outlet 21 at predetermined positions 8 and provided with a fan 12 for ventilating the air in the enclosures 2, 7, and 8, noise in the enclosure 2 is detected. A reference noise detection microphone 37; a residual noise detection microphone 38 for detecting noise close to the cooling air inlet 51 or the cooling air outlet 21; a canceling sound generating means 41 disposed at a predetermined position in the duct 33; And an ANC control means 65 for driving the canceling sound generating means 41 so as to generate a canceling sound for canceling the noise at the cooling air inlet 51 or the cooling air outlet 21 based on the residual noise signal. The sound-absorbing material 10 is attached to the inner wall of the vehicle, and the reference noise microphone 37 and the residual noise microphone 3
8. It is characterized in that at least one of the canceling sound generating means 41 is embedded in the muffling material 10 to which it is attached.

[0011]

According to the first aspect of the present invention, the noise in the enclosure 2 is controlled by the reference noise microphone 37.
The ANC control of the ANC control means 65 based on the reference noise signal from the reference noise microphone 37 and the residual noise signal from the residual noise detection microphone 38 causes the canceling sound generation means 41 to output the opposite phase and the same amplitude as the noise. Is generated, and the noise at the duct outlet 21 is reduced. This AN
In the C noise reduction operation, since at least one of the bent portions of the exhaust-side duct 33 is formed by the curved walls 29, 31, and 20, the flow of the cooling air becomes smooth, and the flow of the cooling air is preferable in the ANC control. be able to. Further, since the silencer 10 is attached to the inner wall surface of the exhaust duct 33, high-frequency noise that cannot be reduced by the ANC can be reduced. Furthermore, the reference noise microphone 3
7. Since at least one of the residual noise microphone 38 and the canceling sound generating means 41 is embedded in the muffling material 10, vortices and turbulent flows are generated due to the collision of the cooling wind with the microphones 37 and 38 and the canceling sound generating means 41. Can be suppressed,
The coherence between the two microphones 37 and 38 can be improved, and as a result, the noise reduction performance by ANC control can be improved.

According to the second aspect of the present invention, the inclined plate 22 and the partition plate 2 are provided in the exhaust side duct 33.
By providing the exhaust duct 3, the exhaust duct 33 is provided with the exhaust air guide chamber 35, the exhaust bent portion 27, and the exhaust-side rising air passage 25, and the cooling air discharged into the exhaust duct 33 by the fan 12 is inclined. Exhaust bent portion 27 by plate 22
The cooling air once descends,
After flowing upward, the air flows upward from the bottom in the exhaust-side rising air passage 25, and after being changed in the horizontal direction in the horizontal duct 9, is discharged from the duct outlet 21.

In this case, the engine noise, the muffler transmission noise, and the wind noise of the fan are mixed by the inclined plate 22 and the partition plate 23, so that the noise can be made as if it came from one sound source. The mixed noise can be detected by the reference noise microphone 37 at the lower position of the rising wind path 25. In other words, in a case where a plurality of sound sources exist in different locations in the surrounding engine,
Although it is difficult to apply the C control in terms of control, according to the present invention, the noise of the surrounding engine and the duct configuration can be extremely simplified, and the noise reduction performance in the ANC control can be enhanced. Furthermore, by directing the cooling air downward once, the length from the exhaust-side ascending air passage 25 to the horizontal air passage 55 can be used as a muffling duct, and the distance from the reference noise microphone 37 to the canceling sound generating means 41 is reduced. Therefore, there is an advantage that the operation time of the adaptive digital filter can be sufficiently taken and a processor (such as a DSP) having a relatively low operation speed can be used. Further, the configuration of the exhaust duct 33 has an advantage that the correlation between the reference noise microphone 37 and the residual noise microphone 38 is enhanced.

According to the third aspect of the present invention, the enclosures 2, 7, 8 are controlled by the reference noise detection microphone 37.
The remaining noise detection microphone 38 detects noise near the cooling air inlet 51 or the cooling air outlet 21.
Then, the ANC control means 65 drives the canceling sound generating means 41 so as to generate a canceling sound for canceling the noise at the cooling air inlet 51 or the cooling air outlet 21 based on the reference noise signal and the residual noise signal, and cancels the sound to the sound deadening space. Generate a sound. In such ANC control, the enclosure 2,
The noise reduction material 10 is attached to the inner wall surfaces of the noise reduction materials 7 and 8, and at least one of the reference noise microphone 37, the residual noise microphone 38, and the canceling sound generation means 41 is embedded in the noise reduction material 10, so that the flow of the cooling air is smooth. Thus, eddy currents and turbulent flows can be suppressed, and noise reduction performance by ANC control can be enhanced.

[0015]

As described in the above operation, according to the first aspect of the present invention, by attaching the silencing material,
Noise can be prevented from leaking, and at the same time, the generation of eddies and turbulent flow due to the collision of the cooling wind with the microphone and the canceling sound generating means can be suppressed.
There is a specific effect that the noise reduction performance by the C control can be enhanced. According to the second aspect of the invention, the noise of the enclosed engine and the duct configuration can be extremely simplified, the noise reduction performance in ANC control can be enhanced, and the operation time of the adaptive digital filter can be sufficiently taken. This makes it possible to use a processor having a relatively low operation speed, and has a unique effect that an ANC noise reduction device can be configured at low cost.

According to the third aspect of the present invention, since at least one of the reference noise microphone, the residual noise microphone, and the canceling sound generating means is embedded in the sound deadening material, the flow of the cooling air is smoothed to make the vortex flow and the turbulent flow. And the noise reduction performance by the ANC control can be enhanced.

[0017]

FIG. 1 is a view showing a first embodiment of the present invention. FIG. 1 is a schematic longitudinal sectional view showing the structure of an enclosed engine generator, and FIGS. FIG. 3A is a plan view of an exhaust duct case with a horizontal duct removed, and FIG. 3B is a partially cutaway perspective view of the exhaust duct case.

This enclosed engine generator is shown in FIGS.
As shown in the figure, inside a soundproof case 2 configured by attaching six soundproof walls to a rectangular parallelepiped frame,
The diesel engine 3 is arranged on the right side in FIG. 1, and the engine generator 4 is arranged on the left side in FIG. The discharge port 5 is opened at a substantially central position of the right soundproof wall 2b of the soundproof case 2, and the intake port 6 is opened at a lower position of the left soundproof wall 2c. An exhaust duct case 7 is provided so as to cover the exhaust port 5, and an air intake duct case 8 is provided so as to cover the intake port 6. Inner wall of soundproof case 2, air intake duct case 8, exhaust air duct case 7, horizontal duct 9 described later
A silencer 10 is attached to one side of the inner wall to prevent noise in the middle and high wavelength ranges from leaking to the outside. As such a sound deadening material 10, a known lightweight and inexpensive sound deadening material such as glass wool or hard sponge is used alone or in combination. In FIG. 3B, the silencer 10 is omitted for simplicity.

A radiator 11 is provided in the soundproof case 2 facing the discharge port 5, and a radiator fan 12 is provided close to the radiator 11, and is driven by a fan belt 13 in conjunction with a crankshaft. ing.
After cooling the radiator 11, the cooling air generated by the radiator fan 12 is released from the exhaust port 5 into the exhaust duct case 7. An air cleaner 14 and a muffler 15 are provided above the engine in the soundproof case 2. After the muffler 15 silences the sound of the exhaust pipe of the engine 3, the muffler 15 discharges the exhaust gas to the outside of the soundproof case 2 via the exhaust gas discharge pipe 16.

As described above, the right side wall 2b of the soundproof case 2
A substantially rectangular bowl-shaped exhaust duct case 7 having an opening 18 of a predetermined size is attached to an upper wall 17, and a horizontal duct 9 is horizontally attached to the exhaust duct case upper wall 17 so as to cover the opening 18. Attached to. The horizontal duct 9 is a fan-shaped duct having a pair of side walls 19 and a quarter-cylindrical curved wall 20 as shown in FIG. 2, and the direction of the duct opening 21 is as shown in FIG. It is configured to be able to select between the case of facing the wind duct case 8 and the case of facing the direction opposite to the wind duct case 8 as shown in FIG.

As shown in FIG. 1, an inclined plate 22 is provided in the exhaust duct case 7 so as to be inclined so as to cover the outlet 5 of the right soundproof wall 2b from above, and a partition plate extending in a substantially vertical direction. 23 are provided. The inclined plate 22 and the partition plate 23 are shown in FIG.
As shown in (B), the air duct unit 7 is fixedly connected to both side walls 24 without any gap so as to partition the inside of the exhaust duct case 7 into a substantially J-shaped air path. The upper part of the partition plate 23 is connected to the upper wall 17 of the exhaust air duct case 7, and forms an exhaust air rising air passage 25 in the exhaust air duct case 7. By attaching the inclined plate 22 so as to cover the outlet 5, the cooling air that has flowed out from the outlet 5 is once passed through the outlet 26 (see FIG. 3B) that is guided obliquely downward, and the exhaust bent portion 27. After that, the air flows upward from the lower part in the exhaust air rising path 25.

As shown in FIG. 1, a portion connecting the right soundproof wall 2b and the lower wall 28 of the exhaust duct case 7 is a substantially quarter cylindrical curved wall 29, and the lower wall of the exhaust duct case 7 is formed. 2
The corner connecting 8 and right wall 30 is also a similar curved wall 31,
The horizontal duct 9 also has a curved wall 20. Further, the connecting portion between the inclined plate 22 and the partition plate 23 is chamfered in a curved shape. Making the connection of the air passage in the exhaust duct case 7 into a curved surface in this way prevents the generation of eddies and turbulence and also causes a problem in ANC control by making the flow of the cooling air smooth. This is for suppressing irregular vibration. Further, the sound absorbing material 10 is attached to all surfaces of the inclined plate 22, the partition plate 23, which is the exhaust-side duct 33, the inner surface of the exhaust duct case 7, and the inner surface of the horizontal duct 9.
3 to prevent noise from leaking,
The surface is smoothly processed to suppress eddy and turbulence.

Further, in this embodiment, the cooling air blown out from the exhaust port 5 is supplied to the exhaust air guide chamber 3 surrounded by the inclined plate 22.
5, in a region including at least one of the exhaust bent portion 27 and the exhaust-side ascending air passage 25, a rectifying plate 36 for suppressing the flow of the cooling air from flowing in a direction different from the extending direction of the air passage.
Is provided. As shown in FIG. 3 (B), the current plate 36 is formed of a substantially gutter-shaped plate material on which a sound deadening material (omitted in FIG. 3 (B)) is attached. The cooling air that flows is split into two, and merges in the lower region of the exhaust-side ascending air passage 25.

As shown in FIGS. 1 and 3B, a reference noise microphone 37 is embedded in the sound deadening material 10 attached to a predetermined position below the partition plate 23 facing the exhaust-side rising air passage 25. The noise is detected via the sound deadening material 10. Therefore, it is possible to prevent the reference noise microphone 37 from receiving vibration and noise due to the cooling air coming from the cooling air. In addition, the residual noise microphone 3
Numeral 8 is covered with a sound deadening material 10 and disposed on an upper wall portion 39 of the duct opening 21 of the horizontal duct 9 with the microphone sound collecting surface parallel to the inner circumferential surface of the duct and in the same plane as the inner circumferential surface. It is installed so that the cooling air does not hit the microphone body. If necessary, the residual noise microphone 38 may be embedded in the sound deadening material 10 of the horizontal duct 9 similarly to the reference noise microphone 37.

The upper wall 17 of the exhaust duct case 7 has a structure shown in FIG.
As shown in FIG. 3 (B), a rectangular shielding plate 40 for regulating the position and size of the duct opening 21 of the horizontal duct 9 is provided.
A pair of loudspeakers 41 are provided so as to face each other while being in contact with the side walls 24, 24. Each loudspeaker 4
As shown in FIG. 3 (B), the speaker surface 41a is provided to be inclined toward the center of the duct opening 21 as shown in FIG. 3 (B) so that the speaker sound can be supplied into the muffling space in the horizontal duct 9.

The position of the loudspeaker 41 is set on the upper wall 17 of the exhaust duct case 7 and the loudspeaker 41 is inclined so that the cooling air flowing up the exhaust-side rising air passage 25 is cooled. This is for preventing the turbulent flow of the cooling air from colliding with the speaker end surface. Further, it is preferable that the partition plate 23 be configured so that the unevenness of the surface extending from the muffling material 10 to the upper part of the shielding plate 40 is eliminated, the surface becomes a smooth curved surface, and the speaker surface 41a is arranged as a part of the curved surface. is there. Note that the speaker surface 41 a of the loudspeaker 41 may be covered with the muffler 10. The ANC noise reduction device includes a reference noise microphone 37, a loudspeaker 41,
It comprises a residual noise microphone 38 and an ANC controller (not shown). The detailed configuration of the ANC controller will be described later.

As shown in FIG. 1, the engine 3 and the generator 4 are connected to a vibration damping member 4 laid on a bottom wall 2 d of the soundproof case 2.
2 is provided with a known anti-vibration receiver 43, and the engine 3 and the generator 4
Is suppressed, and the vibration is prevented from being transmitted to each wall of the soundproof case 2 and the exhaust duct case 7. A control device 44 for controlling the engine generator 4 is provided in an upper left area in the soundproof case 2, and a fuel tank (not shown) is provided behind the control device 44.

The air intake duct case 8 provided on the left soundproof wall 2c is provided with a wind guide plate 46 having a curved wall at its lower part.
Is mounted so as to cover from below, and the air guide plate 46 is covered so as to be accommodated in a substantially rectangular bowl-shaped air-absorbing duct case 8 having an open lower side, thereby forming a substantially inverted U-shaped intake air path. It is formed. A suction fan 48 inside the generator 4 is disposed at the intake port 6 so as to be located close to the suction port 48.
The inside of the generator 4 is cooled by discharging the cooling air sucked from the suction port 49 of the generator 4 through an outlet 50 provided on the engine side.

The operation of the engine generator noise reduction device having the above configuration will be described. When the engine 3 of the engine generator 4 is operated and power generation is started, the radiator fan 12 linked to the crankshaft of the engine 3 is driven. By driving the radiator fan 12, the inside of the soundproof case 2 becomes a negative pressure, and the outside air sucked from the duct inlet 51 of the suction duct case 8 is supplied to the intake side rising air passage 52 in the suction duct case 8 and the intake bent portion 53. The air is guided from the intake port 6 into the soundproof case 2 through the intake air guide chamber 54. The cooling air flowing through the soundproof case 2 cools the generator 4 and the engine 3,
After being discharged from the exhaust port 5 into the exhaust air guide chamber 35 in the exhaust duct case 7 and flowing into the two cooling air flows by the rectifying plate 36, the cooling air flows through the exhaust bent portion 27 and at the lower part of the exhaust-side rising air passage 25. It merges and flows upward, and is exhausted from the duct outlet 21 through the opening 18 and the horizontal air passage 55 of the horizontal duct 9 (see arrow H in the figure).

When the operation of the engine 3 is started, the ANC controller detects the reference noise in the lower part of the exhaust-side ascending air passage 25 through the sound absorbing material 10 by the reference noise microphone 37, and distributes the reference noise signal to the duct outlet 21. The loudspeaker 41 is driven based on the residual noise signal of the installed residual noise microphone 38 so that the noise at the duct outlet 21 is minimized to generate a canceling sound. In this series of ANC control, it is most preferable that the cooling air flowing through the duct that performs the noise reduction operation by the ANC control has a uniform velocity in the duct and is in a laminar state without eddies and turbulent flows. However, in the configuration of the exhaust side duct 33 of this embodiment, the ANC
It is preferable to increase the distance between the reference noise microphone 37 and the loudspeaker 41 in order to secure the calculation time for the control, and since the noise level coming out of the duct outlet 21 can be reduced by increasing the length of the exhaust side duct 33, The inner air passage has a meandering configuration at the exhaust bending portion 27.

In the meandering duct structure, for example, if the connection between the right soundproof wall 2b and the lower wall 28 of the exhaust duct case 7 is a corner 34, as shown in FIG. Most of the cooling air blown out strongly by the radiator fan 12 is controlled by the inclined plate 22 in the direction of the outline arrow 56, and as shown in FIG. As a result, a vortex 45 is generated in the corner area 34 of the exhaust duct case 7, causing the reference noise microphone 37 to collect irregular noise. Also, a part of the cooling air reflected by the inclined plate 22 becomes a flow 58 in the direction of the arrow, so that irregular turbulence
This may cause eddy currents.

On the other hand, as shown in FIG. 4B, in the configuration in which the curved wall 29 is provided in the corner portion 34 and the rectifying plate 36 is provided, two white air flows in the exhaust air guide chamber 35. Arrow 5
As shown by 9, the cooling air is divided into two cooling air flows, the inner cooling flow flows along the inner air passage 60, and the outer cooling flow flows along the outer air passage 61, and the cooling air flows The direction flows according to the shape of the air path in the exhaust duct case 7. In addition, since the flow reflected by the inclined plate 22 is also regulated by the rectifying plate 36, it is unlikely that the flow 58 crosses the air path as shown in FIG. Further, by providing the curved wall 29, there is no corner portion 34 in which turbulence is likely to occur, and the flow of the cooling air in the outer air passage 61 becomes extremely smooth. Therefore, the reference noise signal detected by the reference noise microphone 37 can also be reduced by the influence of irregular noise caused by the eddy current. The curved wall is not only a corner (bent portion) of the exhaust duct case 7 and the horizontal duct 9 shown in the cross-sectional view of FIG. It is preferable to provide a curved wall also in the portion. In other words, the cross section of the air path in the exhaust duct to the duct outlet 21 is a curved cross-sectional shape (for example, circular, elliptical) symmetrical in the vertical direction and the width direction (U, D directions, R, L directions in FIG. 3). , Or a square with rounded corners).

The operation of the current plate 36 is described with reference to FIG.
Considering a duct bent at 90 ° smaller than the bent portion of the exhaust bent portion 27 of the present embodiment as shown in FIG.
In the configuration provided with the rectifying plate 36 shown in FIG. 2B, the wind speed distributions 71 and 72 are symmetrical for each of the inner air passage 60 and the outer air passage 61 divided by the rectifying plate 36, so that the entire duct is formed. 5A, the wind speed distributions around the inner wall and the outer wall are almost uniform, but when the current plate is not provided as shown in FIG. The wind speed distribution 73 having the shape is changed to the wind speed distribution 7 in which the wind speed around the outer wall of the duct is increased at the bent portion position 63.
4 and the difference 64 between the wind speed around the inner wall and the wind speed on the outlet side at the position 64 near the outlet becomes a wind speed distribution 75, so that eddies and the like are easily generated, and noise and vibration in the duct are reduced. As a result, the coherence (correlation) between the reference noise microphone and the residual noise microphone decreases. Providing the rectifying plate 36 in this way has an advantage that an adverse effect due to strong cooling air can be suppressed.

Next, an example of the configuration of an ANC controller applicable to the present invention will be described. The circuit configuration and ANC algorithm of the ANC controller applicable to the present invention are not limited to the configuration shown in FIG. FIG. 6 is a block diagram showing a schematic configuration of the ANC controller used in the embodiment. 6, the ANC controller 65 is roughly composed of an adder 117, a compensating digital filter 118, a compensating digital filter 119, an adaptive digital filter 120, and an LMS control unit 121. The noise detected from the reference noise microphone 37 is converted into a digital signal by an A / D converter (not shown), and then added to the adder 117. The output signal from the compensating digital filter 118 is also added to the adder 117. The adder 117 adds these input signals, and outputs the added reference noise signal _Xn to the compensating digital filter 119 and the adaptive digital filter. Output to 120. Also, the output signal Y of the adaptive digital filter 120
_n is a drive signal of the loudspeaker 41.

The compensating digital filter 118 is a filter for compensating the electroacoustic characteristic <B> between the loudspeaker 41 and the reference noise microphone 37, and the compensating digital filter 119 is a loudspeaker 41 and the residual noise microphone 3
This is a filter for compensating the electroacoustic characteristics <C> between the eight.
LMS control unit 121, so canceling sound issued from the loudspeaker 41 to reduce the noise of the surrounding engine, remaining noise based on the residual noise signal e _n from the residual noise microphone and the reference input signal X _n The filter coefficient of the adaptive digital filter 120 is updated so that the signal e _n is minimized. Residual noise signal e _n so as to minimize as a method for the optimum value of the filter coefficient of the adaptive digital filter 120, for example, B. "Fi" proposed by Widrow et al.
The "litered-x LMS algorithm" is well known.

In this algorithm, the filter coefficients of the adaptive digital filter 120 are recursively updated by, for example, the following equation (1). _{W n + 1 = W n +} 2μe n · X n ...... (1) However, W _n: adaptive digital filter coefficient (W [0], W
[1],..., W [L-1]) _Xn : Reference noise signal (X [n], X [n-1],.
_{[N-L]) e n} : residual noise signal n: discrete time mu: convergence coefficient L: is the filter order.

[0037]

Second Embodiment FIG. 7 is a view for explaining a second embodiment of the present invention, and is a longitudinal sectional view of an exhaust side duct.
The second embodiment is characterized in that the first embodiment is characterized in that the inclination of the inclined plate 22 is changed from a linear one to a cylindrical one, and secondly, the inclined plate 22 is inclined. The point that the shape of the rectifying plate 36 is configured to have a tip portion 66 that divides the exhaust air guide chamber 35 up and down in accordance with the change in the inclination of the loudspeaker 22, and thirdly, the speaker surface 41a of the loudspeaker 41
Is covered with the sound deadening material 10. Also in this embodiment, the cooling air blown out from the radiator fan 12 is divided into two in the exhaust air guide chamber 35 and flows through the inner air passage 60 and the outer air passage 61, respectively.
Generation of turbulence can be suppressed.

The speaker surface 4 of the loudspeaker 12
1a is covered with the sound deadening material 10, so that the exhaust side ascending air passage 2 extending from the partition plate 23 to the upper wall 17 of the exhaust duct case 7 is formed.
5 and the horizontal air path 55 are smoothly connected, and the flow of airflow in the sound deadening space can be reduced.

[0039]

Third Embodiment FIGS. 8A to 8D are views for explaining a third embodiment of the present invention. FIG.
(A)-(C) are loudspeakers 41 in the horizontal duct 9.
8D is an embodiment in which the horizontal duct 9 is extended to a position reaching the upper wall 2e of the soundproof case 2 in FIG. 8D. FIG. 8A shows a configuration in which the speaker surface 41a is disposed facing the duct outlet 21 side. FIG.
(B) shows a configuration in which the loudspeaker 41 is embedded in the fan-shaped side wall 19 of the horizontal duct 9, and the speaker surface 41 a is directed into the horizontal air passage 55. FIG. 8C shows a configuration in which the loudspeaker 41 is embedded in the wall surface of the horizontal duct 9 facing the duct outlet 21, and the speaker surface 41 a is arranged toward the duct outlet 21. In the configuration of FIGS. 8B and 8C, the speaker surface 41a of the loudspeaker 41 is provided so as to substantially coincide with the peripheral wall surface of the air passage, so that the cooling air flowing through the exhaust-side ascending air passage 25 can be cooled. No more disrupting the flow, ANC
Noise reduction performance can be improved.

In the configuration of FIG. 8A, the speaker surface 41a
The opposite side of the loudspeaker 41 constitutes a part of the horizontal air passage 55 and the part is covered with the sound deadening material 10.
The projection itself does not protrude into the horizontal air passage 55, and in this case also, good sound deadening performance can be exhibited. 8D, the residual noise microphone 38, the loudspeaker 41, and the reference noise microphone 37 are all embedded in the muffler 10 from the duct outlet 21 side.
8, the presence of the loudspeaker 41 and the reference noise microphone 37 does not disturb the flow of the airflow, and the coherence between the microphones 37 and 38 does not decrease. In addition, the air passage from the exhaust-side ascending air passage 25 to the horizontal air passage 55 can be a smooth curved duct, and a noise reduction effect can be expected by extending the duct.

[0041]

[Embodiment] The LMS method shown in the above equation (1) is adopted as an ANC algorithm, and a 16-bit A / D converter and a 14-bit D
/ A converter, sampling frequency fs = 2.5k
Hz, the correction frequency is fc = 1.0 kHz, and the microphone and the speaker are of a commercial level, and are shown in FIGS. 1 and 2 (A).
In an experiment with a real machine adopting the configuration shown in FIG. 1, the configuration of the present embodiment in which the sound absorbing material 10 provided on the inner wall is combined with the ANC control, the front side, the rear side, and the intake side at a distance of 1 m from the engine generator. It was confirmed that the average noise level at the four noise detection positions on the side and the exhaust side could be reduced to 75.0 dB. In addition, the average noise level in the state where there was no countermeasure of the noise reduction material 10 and ANC was 85 db. This 7
The average noise level of 5.0 dB (A) is 1
Equivalent to 63.3 dB (A) when converted to the noise level of low-noise construction machinery (in four directions at a distance of 7 m from the machine), which was institutionalized in 983, which is less than 75 horsepower It is a quiet machine that falls into the ultra-low noise category.

FIG. 9 is a diagram comparing the noise spectrum 67 before performing the ANC control and the noise spectrum 68 after performing the ANC control in the frequency range of 0 Hz to 1000 Hz in the noise measured near the duct outlet. The vertical axis represents noise level (dB) and the horizontal axis represents frequency (Hz). As can be seen from FIG. 9, the peak noise 69 such as the wind noise of the fan, which is determined by the engine speed, the number of blades of the fan, and the speed of the fan, can be reduced well, and the noise reduction particularly from 0 to 500 Hz has been achieved. It can be seen that the unpleasant noise that resounds the belly can be reduced. The present invention is not limited to the above embodiment, and various design changes can be made without departing from the spirit of the present invention. Hereinafter, such an embodiment will be described.

(1) In the above embodiment, the exhaust side duct 3
Although the embodiment in which the noise is reduced by the ANC is described only in the example No. 3, for example, it is also possible to perform the noise countermeasure by the ANC in the intake side duct. In this case, the reference noise microphone 37, the loudspeaker 41, and the residual noise microphone 38 may be provided at predetermined locations in the air intake duct case 8, respectively. However, in a configuration in which outside air is taken in from the intake port 6 and exhausted from the exhaust port 5, the wind noise of the engine and the fan rides on the flow of the wind, so that the exhaust port 5 is larger than the intake port 6. Therefore, even with a configuration in which the noise reduction device using the ANC is provided only on the exhaust port 5 side and only the intake side duct is provided on the intake port 6 side, a sufficient noise reduction effect can be achieved. (2) In the above-described embodiment, the shape of the exhaust-side duct 33 is configured by the combination of the exhaust duct case 7 and the horizontal duct 9. However, the exhaust-side duct 33 is formed by integrating the exhaust duct case 7 and the horizontal duct 9. You may.

(3) Although the flow straightening plate 36 of the above-described embodiment has a substantially gutter-like shape that divides the inside of the exhaust duct case 7 in the vertical direction (U direction and D direction in FIG. 3B). It may be provided so as to be divided into a plurality in the width direction (the R direction and the L direction in FIG. 3B). The cooling air of the ventilation fan that ventilates the inside of the enclosed engine is not uniform in air volume and air velocity in the width direction, and the air velocity distribution is also different in the width direction. Correspondingly, a rectifying plate having a shape that suppresses generation of eddies and turbulent flow in the exhaust-side duct may be provided. (4) When at least one of the reference noise microphone, the residual noise microphone, and the canceling sound generating means is embedded in the sound deadening material in order to suppress the generation of the vortex and the turbulent flow in the duct, the reference noise microphone and the Since it has an effect of improving coherence with the residual noise microphone, it is apparent that the present invention can be applied not only to the shape of the exhaust side duct 33 described in the above embodiment, but also to an enclosure of an ANC noise reduction device used in an enclosed engine. is there.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator.

FIGS. 2A and 2B are external perspective views of an enclosed engine generator.

FIG. 3A is a plan view of an exhaust duct case with a horizontal duct removed, and FIG. 3B is a partially cutaway perspective view of the exhaust duct case.

4A is a configuration diagram of an exhaust-side duct without a current plate, and FIG. 4B is a configuration diagram of an exhaust-side duct with a current plate.

5A is a diagram of a wind speed distribution of a duct without a straightening plate, and FIG. 5B is a diagram of a wind speed distribution of a duct with a straightening plate.

FIG. 6 is a configuration diagram illustrating an example of an ANC controller according to the present embodiment.

FIG. 7 is a longitudinal sectional view of an exhaust side duct for explaining a configuration of a second embodiment of the present invention.

FIGS. 8A to 8D are diagrams for explaining the configuration of a third embodiment of the present invention.

FIG. 9 is a diagram for comparing a noise spectrum before a noise measure and a noise spectrum after the noise measure.

FIG. 10 is a diagram showing an example of a noise spectrum characteristic of an enclosed engine.

[Explanation of symbols]

2 ... Soundproof case, 2b ... Right soundproof wall, 3 ... Diesel engine, 5 ... Exhaust port, 6 ... Intake port, 7 ... Exhaust air duct case, 8 ... Air intake duct case, 9 ... Horizontal duct, 10 ... Sound damping material, 12 radiator fan, 17 upper wall, 18 opening, 21 duct outlet, 22 inclined plate, 23 partition plate,
25: exhaust side ascending wind path, 27: exhaust bent part, 29, 3
1, 20: curved wall, 33: exhaust duct, 35: exhaust air guide chamber, 37: reference noise microphone, 38: residual noise microphone,
41: loudspeaker, 51: duct entrance, 55: horizontal air path, 65: ANC controller.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G10K 11/16 G10K 11/16 BG

Claims (3)

[Claims] An engine (3) is housed in an enclosure (2),
At least a suction port (6) and an exhaust port at predetermined locations on the enclosure (2).
(5), and a fan (1) for ventilating the air inside the enclosure (2)
2) is installed, and the outside air is taken in from the intake port (6).
Exhaust duct (33) communicating at least with the exhaust port (5) to reduce noise of the enclosed engine exhausting from (5)
A reference noise detection microphone (37) formed around the enclosure (2) to detect noise near the exhaust port (5), and an exhaust side duct
(33) a residual noise detecting microphone (38) for detecting noise close to the duct outlet (21), a canceling sound generating means (41) disposed in the exhaust side duct (33), and a reference noise signal and residual noise. Canceling sound generating means (41) for generating a canceling sound for canceling noise at the duct outlet (21) based on the noise signal
And an ANC control means (65) for driving the air conditioner. A muffling material (10) is attached to the inner wall surface of the exhaust duct (33), and a reference noise microphone (37), a residual noise microphone (38), and a canceling sound. At least one of the generating means (41) is embedded in the sound deadening material (10) attached thereto, and at least one of the bent portions of the exhaust-side duct (33) is connected to the curved wall (29,
31, 20) A noise reduction device for an enclosed engine. 2. An exhaust duct (33) includes an inclined plate (22) provided so as to cover the exhaust port (5) from above, and a partition plate for partitioning the exhaust duct (33) in a substantially vertical direction. (23)
An exhaust duct case attached to the wall (2b) of the enclosure (2) having an exhaust port (5) and having an opening (18) in the upper wall (17)
(7) and a horizontal duct (9) partitioned by the upper wall (17) from the exhaust duct case (7), communicating with the opening (18), and extending in a substantially horizontal direction, from the exhaust port (5). The discharged cooling air is surrounded by the inclined plate (2), the exhaust air guide chamber (35), the exhaust bent portion (27) formed at the lower part of the exhaust duct case (7), the partition plate (23) and the exhaust air. It is configured to be discharged from the duct outlet (21) through the exhaust side ascending air passage (25) formed by the duct case (7) and the horizontal air passage (55) in the horizontal duct (9). Reference noise microphone (37) in the lower area of the wind path (25)
And the residual noise microphone (38) is fixed near the duct outlet (21) of the horizontal duct (9), and is fixed at a predetermined position on the upper wall (17) of the exhaust duct case (7) or the horizontal duct (9). The noise reduction device for an enclosed engine according to claim 1, further comprising a cancellation sound generating means (41). 3. An engine (3) is surrounded by an enclosure (2, 7, 8), and at least a cooling air inlet (51) and a cooling air outlet (21) are provided at predetermined positions of the enclosure (2, 7, 8). The surrounding body
In an enclosed engine provided with a fan (12) for ventilating the air in (2, 7, 8), a reference noise detection microphone (3) for detecting noise in the enclosure (2)
7), a residual noise detecting microphone (38) for detecting noise near the cooling air inlet (51) or the cooling air outlet (21), and a canceling sound generating means (35) disposed at a predetermined position in the duct (33). 4
1) and canceling sound generating means for generating a canceling sound for canceling noise at the cooling air inlet (51) or the cooling air outlet (21) based on the reference noise signal and the residual noise signal.
An ANC control means (65) for driving the (41) is provided, a muffler (10) is attached to the inner wall surface of the enclosure (2, 7, 8), and a reference noise microphone (37) and a residual noise microphone ( 3
8) A noise reduction device for an enclosed engine, wherein at least one of the canceling sound generating means (41) is embedded in a sound deadening material (10) attached thereto.