JP3323386B2 - Noise reduction device for enclosed engine - Google Patents

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 for reducing the noise of an engine surrounded by an enclosure such as a soundproof case, and more particularly to a noise reduction device for an enclosed engine.
The present invention relates to a noise reduction device for an enclosed engine employing a microphone device capable of improving the / N ratio.

[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. Has been studied. According to ANC, around 100 Hz-50
It has an effect of reducing even low-frequency noise near 0 Hz, and is used to reduce the muffled noise of the passenger compartment, the noise of air-conditioning ducts, and the like (Japanese Patent Publication No. 2-503219,
JP-A-3-204354 and the like).

FIG. 13 is a schematic block diagram of a duct silencer for reducing the noise of an air conditioning duct as an example of the ANC. In the figure, the air conditioning duct 101 is configured so that air flows from the left side to the right side, and noise also propagates through the air conditioning duct 101 according to the air flow. The air conditioning duct 101 is provided with an upstream microphone 102 (primary noise microphone) and a downstream microphone 104 (residual noise microphone) near the exhaust port 103, and a loudspeaker 105 that generates a canceling sound between the microphones 102 and 104. Is provided.

In this duct silencer, the upstream microphone 1
The secondary sound (remaining sound) interferes with the primary sound detected at step 02 in the ANC control unit 106 so that the secondary sound is minimized by the error signal detected from the downstream microphone 104. By successively updating the coefficients, the cancellation sound radiated from the loudspeaker 105 is changed, and the noise is reduced. In such ANC control, an anti-vibration microphone device for detecting a reference signal and a residual signal while reducing the influence of vibration is required. FIG. 14A is a cross-sectional view of a vibration-proof microphone device disclosed in Japanese Utility Model Laid-Open No. 1-126682, and FIG. 14B is a longitudinal sectional view thereof. In this anti-vibration microphone device 128, the rear end of the microphone device is formed of an anti-vibration elastic body 123, and the shield case 125 having the sound wave introduction port 124 is formed in a substantially cylindrical shape and held inside the shield case 125. The microphone unit 127 is accommodated via the member 126.

[0005]

However, in order to apply the ANC to an enclosed engine such as an enclosed engine generator, if the above-described anti-vibration microphone device 128 is employed as it is, the following problems arise. Occurs. (1) As shown in FIG. 15, the noise of an enclosed engine is composed of a fundamental frequency and its harmonics caused by the rotation speed of a crankshaft, a cooling fan shaft, and the like, a wind noise of a fan, vibration of an enclosure, and the like. Spectrum. Therefore, unlike the case of reducing the periodic noise, in order to increase the noise reduction level, it is necessary to reliably convert only the noise to be reduced into an electric signal. FIG.
In the case of the anti-vibration microphone device 128 as shown in FIG. 4, all of low-frequency noise to high-frequency noise are detected. Therefore, it is necessary to pass through a low-pass filter to extract a signal of 500 Hz or less. A processing delay occurs, which is not preferable for ANC control.

(2) It is essential for the enclosed engine to generate cooling air in order to cool the inside of the enclosure, and the influence of the cooling air must be considered separately from the vibration of the engine. In the case of the anti-vibration microphone device 128 as shown in FIG. 14, there is a problem that the airflow of the cooling air is disturbed by the sound wave introduction port 124 and the vibration and noise of the microphone device increase. (3) Since the surrounding type engine is in a state in which the surroundings of the engine are surrounded by the surrounding body, the temperature inside the surrounding body becomes high and contaminants such as oil content increase. The vibration-proof microphone device 128 as shown in FIG.
4, there is a problem that the heat insulating effect is low, and the contaminants enter through the sound wave introduction port 124, so that the life of the microphone device is shortened.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a noise detection microphone device which can detect a high S / N of a noise even in a bad environment with a simple and inexpensive configuration. The purpose is to: Another object of the present invention is to provide a noise detection microphone device that can detect a high S / N ratio without being affected by an airflow in an environment having a strong airflow. Another object of the present invention is to provide a noise reduction device for an enclosed engine that can improve noise reduction by using the noise detection microphone device.

[0008]

According to a first aspect of the present invention, there is provided a noise reduction device for an enclosed engine, wherein the engine is housed in an enclosure, at least an intake port and an exhaust port are provided at predetermined positions of the enclosure, and outside air is supplied from the intake port. In order to reduce the noise of the enclosed engine that takes in and exhausts from the exhaust port, at least an exhaust side duct communicating with the exhaust port is formed around the enclosure, and a primary noise detection microphone that detects noise near the exhaust port, A residual noise detection microphone that detects noise near the duct opening of the side duct, a canceling sound generating means arranged in the exhaust side duct, and a canceling sound that cancels the noise at the duct opening based on the primary noise signal and the residual noise signal ANC control means for driving the canceling sound generating means so as to generate noise, the primary noise microphone and the residual noise detection microphone are provided inside the outer case and the outer case. And a microphone unit supported at the center of the outer case. The outer case uses a low-frequency noise of less than 500 Hz to be reduced by the ANC control means. No sound wave inlet is provided at all, and low-frequency noise transmitted through the outer case is detected by an internal microphone unit.

According to another aspect of the present invention, the primary noise microphone and the residual noise detection microphone are provided with a damping member inside an outer case, and the shock absorbing material is provided inside the damping member. 700 Hz at least around the microphone unit of the residual noise microphone.
The above high frequency noise is surrounded by a sound absorbing material for preventing the noise from entering the microphone unit. In addition, the periphery of the microphone unit of the primary noise microphone may be surrounded by the sound absorbing material. According to a third aspect of the present invention, the material of the outer case is made of metal. According to a fourth aspect of the present invention, there is provided a noise reduction device for an enclosed engine, wherein a rod-shaped support member is fixed to the exhaust-side duct in a direction parallel to an extending direction of an air passage in the duct, and a primary noise microphone is attached to the exhaust port side of the rod-shaped support member. The residual noise microphone is attached to the duct opening side of the rod-shaped support member, and the noise canceling means is disposed at a predetermined position in the air passage in the duct.

According to a fifth aspect of the present invention, there is provided a noise reduction device for an enclosed engine, wherein the engine is housed in an enclosure, at least an intake port and an exhaust port are provided at predetermined positions of the enclosure, external air is taken in from the intake port and exhausted from the exhaust port. In order to reduce the noise of the enclosed engine, at least an exhaust duct communicating with the exhaust port is formed around the enclosure, and a primary noise detection microphone that detects noise close to the exhaust port, and a duct opening of the exhaust duct. A residual noise detecting microphone for detecting near noise, a canceling sound generating means disposed in the exhaust duct, and a canceling sound for canceling noise at the duct opening based on the primary noise signal and the residual noise signal. ANC control means for driving the sound generation means, the exhaust duct is a bag-shaped air guide plate having an exhaust port on the lower side to cover the exhaust port from above,
A rectangular bowl-shaped exhaust duct case with an opening on the upper wall provided to accommodate the air guide plate on the wall of the enclosure with the exhaust port, and an exhaust duct case defined on the upper wall An exhaust air guide chamber, which is composed of a horizontal duct that communicates and extends in the horizontal direction, and the cooling air that comes out of the exhaust port is surrounded by a wind guide plate, and an exhaust-side rising wind formed by the wind guide plate and the exhaust duct case The primary noise microphone is fixed to the lower end area of the air guide plate facing the exhaust side ascending wind path, and the primary noise microphone is fixed near the duct opening of the horizontal duct. A residual noise microphone is fixed, and a canceling sound generating means is provided at a predetermined position on an upper wall of the exhaust duct case.

[0011]

According to the first aspect of the present invention, the noise in the enclosure is detected by the primary noise detection microphone, and is based on the primary noise signal from the primary noise microphone and the residual noise signal from the residual noise detection microphone. ANC
By the ANC control of the control means, a canceling sound having the opposite phase and the same amplitude as the noise is generated from the canceling sound generating means, and the noise at the duct opening is reduced. In this ANC silencing operation, the primary noise detection microphone and the residual noise detection microphone do not have any sound wave introduction ports in the outer case. it can. In addition, since the microphone unit has a structure in which the microphone unit is hermetically sealed, there is no possibility that the microphone main body is contaminated with oil or the like, and a high-sensitivity detection state can be stably maintained for a long period of time. In addition, the cooling air flowing through the exhaust duct is hot, but without an acoustic wave inlet, the outer case and elastic members can function completely as heat insulating members, solving the problem of thermal damage to microphones. can do.

[0012] The external case uses a low-frequency noise of less than 500 Hz to be reduced by the ANC control means and transmits the low-frequency noise transmitted through the external case to the internal microphone unit. , So that the ANC control is targeted for 5
For a sound in a low frequency range of less than 00 Hz, noise can be detected with high sensitivity, and there is no problem in ANC control. Further, the material of the outer case and the material of the shock absorbing material can fulfill the function of absorbing high frequency noise that is unnecessary for ANC control.

According to the noise reduction device for an enclosed engine of the present invention, the vibration of the primary noise microphone and the residual noise detection microphone can be suppressed by providing the vibration damping member, and at least the microphone unit of the residual noise microphone is provided. Surrounding the surroundings with a sound absorbing material, it is possible to mechanically remove high frequency noise entering the residual noise microphone, which is more advantageous for ANC control than removing high frequency sound electrically with a low-pass filter. Can be. Claim 3
In the case of the noise reduction device for an enclosed engine, the rigidity can be increased by making the material of the outer case metal, and the noise is detected without causing vibration even at the duct position where strong cooling air blows. be able to. Further, the configuration can be made durable against heat, oil, and the like.

According to a fourth aspect of the present invention, there is provided a noise reduction device for an enclosed engine, wherein the rod-shaped support member is fixed to the rod-shaped support member in parallel to the direction in which the air duct in the exhaust duct extends. By fixing the primary noise detection microphone on the exhaust port side and fixing the residual noise detection microphone on the duct opening side of the rod-shaped support member, the characteristics of vibration transmitted to the exhaust side duct are the same for the primary noise detection microphone and the residual noise detection microphone. Therefore, the correlation of sound between the primary noise detection microphone and the residual noise detection microphone can be improved. In addition, the strength and direction of the cooling air may vary depending on the position of the air passage in the duct, but the rod-shaped support member is fixed in parallel with the extending direction of the air passage in the duct, so that the cooling air flows through the air passage in the duct. Since the rod-shaped support member is arranged in parallel with the direction of the cooling air, the influence of the cooling air is almost the same in the primary noise detection microphone and the residual noise detection microphone. Between the sounds can be increased.

In the noise reduction device for an enclosed engine according to the fifth aspect, the cooling air flowing out of the exhaust port bypasses the baffle plate, rises in the exhaust-side ascending air path, exits the opening, and exits the horizontal air path. From the duct outlet. Here, noise is also emitted to the outside on the cooling wind, but since the exhaust side duct has three curved passages in the air guide plate, the exhaust side ascending air passage, and the horizontal air passage, the overall Noise level can be reduced. Although the detailed reason is unknown, the arrangement of the exhaust-side duct, the canceling sound generating means, the primary noise detection microphone, and the residual noise detection microphone is as described in claim 5, so that the primary noise detection microphone can be used. And the residual noise detection microphone can be improved, and the noise reduction level by ANC can be improved. In addition, the performance of noise reduction can be further enhanced by configuring the primary noise detection microphone and the residual noise detection microphone as the microphone configuration according to the first aspect.

[0016]

As described above, according to the first aspect of the present invention, the following specific effects can be obtained. (A) The primary noise detection microphone and the residual noise detection microphone do not have any sound wave introduction port in the outer case, so that noise generation can be eliminated, a high S / N can be obtained, and the microphone unit has an internal microphone unit. Since the microphone body is hermetically sealed, it is possible to achieve stable noise detection over a long period of time without inconveniences such as thermal damage to the microphone body and a decrease in detection sensitivity due to contaminants. (B) Since the low-frequency sound transmitted through the external case is detected by the internal microphone unit, the ANC
Low frequency noise to be controlled can be detected well. (C) Due to the presence of the outer case and the shock absorbing material, high-frequency noise that is not to be controlled by ANC can be mechanically cut. (D) Since the structure is simple and the number of necessary parts is small, the cost is low, and the unit price of a general-purpose engine generator can be reduced. According to the second aspect of the present invention, the vibration of the microphone can be suppressed by providing the vibration damping member, and the high frequency noise can be prevented from entering the residual noise microphone by the sound absorbing material. It works.

According to the third aspect of the present invention, since the material of the outer case is made of metal, the rigidity can be improved, and the outer case can be made durable against heat and oil. It has the unique effect of being able to. According to the fourth aspect of the present invention, it is possible to increase the correlation between sounds between the primary noise detection microphone and the residual noise detection microphone, and to achieve a unique effect of improving the noise reduction of the noise reduction system. According to the fifth aspect of the present invention, it is possible to reduce the overall noise level, improve the coherence between the primary noise detection microphone and the residual noise detection microphone, and increase the noise reduction amount. To play.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a diagram showing a configuration of a noise reduction device for an enclosed engine generator as one embodiment of the noise reduction device for an enclosed engine according to the present invention.
1A is a longitudinal sectional view, and FIG. 1B is a plan view of a duct. The enclosed engine generator 1 has a diesel engine 3 disposed substantially at the center of a soundproof case 2,
The engine generator 4 is arranged on the right side in the figure. A partition wall 5 is provided above the diesel engine 3, and a radiator 6 is attached to the left side surface of the partition wall 5, so that the soundproof case 2 has an engine power generation chamber 7 in which an engine and a generator are housed, and an exhaust passage. 8

The exhaust passage 8 comprises an ascending passage 8a provided facing the radiator 6, and an exhaust passage 8b communicating with an outlet 10 provided in the upper wall 2a of the soundproof case 2.
A muffler 12 is provided on the partition wall 5 in the exhaust passage 8b. The exhaust port 12a of the muffler 12 is provided on the upper side of the soundproof case 2 on the near side in FIG. A radiator fan 20 is attached to the radiator 6, and the radiator fan 20 is driven in conjunction with a crankshaft of the engine 3 by a fan belt and a pulley. Soundproof case 2
A substantially rectangular duct 1 having a base end on the radiator 6 side and a duct outlet 13a on the opposite side on the upper wall 2a.
3 is fixed, and a shielding wall 14 that partitions the duct 13 into two rooms in the horizontal direction is provided in a duct portion above the outlet 10. The outlet 10 is covered by the shielding wall 14.

A loudspeaker 16 having directivity with a loudspeaker surface facing the duct outlet 13a is provided in an upper room (referred to as an upper duct chamber 15) defined by the shielding wall 14. A primary noise microphone 18 is provided at a predetermined position in a lower room (referred to as a lower duct room 17). The speaker 16 is surrounded by a unit case 28 which can be detachably exchanged, and is fitted into the upper duct chamber 15 without any gap, so that the duct 1
3 can be easily mounted. At a predetermined position near the duct outlet 13a, a residual noise microphone 19 for detecting residual noise near the duct outlet 13a is provided. Note that the detailed configurations of the primary noise microphone 18 and the residual noise microphone 19 will be described in detail with reference to FIGS. 7, 8, and 11 described later.

On the other hand, an intake port 21 for ventilating the inside of the soundproof case 2 is provided on a side surface of the soundproof case 2 on the generator 4 side, and a fuel tank 22 supported by the partition wall 5 is provided above the generator 4. Is provided. The fuel supply port 23 of the fuel tank 22 is provided in the upper part of the soundproof case 2 on the near side in FIG. An air cleaner 24 is provided at a substantially central position of the engine power generation chamber 7, and supplies outside air sucked from the intake port 21 to the combustion chamber via an intake pipe. A sound deadening material is attached to the inner wall of the soundproof case 2, the inner wall of the exhaust passage 8, and the inner wall of the duct 13 to prevent high-frequency sound of 1 kHz or more from leaking to the outside.

The noise reduction device includes the primary noise microphone 1
8, directional speaker 16, residual noise microphone 19,
And the ANC controller 25.
The ANC controller 25 is disposed at a lower position of the soundproof case 2 and surrounded by a heat insulating member 26 so as not to be affected by the heat of the engine. The detailed configuration of the ANC controller 25 will be described in a later-described seventh embodiment.
The operation of the noise reduction device for an engine generator having the above configuration will be described. When the engine 3 of the engine generator 1 is operated and power generation is started, the radiator fan 20 linked to the crankshaft of the engine 3 is driven. Cooling air flows inside the engine generator 1 by driving the radiator fan 20. That is, the outside air sucked from the intake port 21 by driving the radiator fan 20 is supplied to the engine 3 and the generator 4.
After cooling, the ascending passage 8a of the exhaust passage 8 and the exhaust passage 8
The air flows through the duct 13 from the exhaust port 10 through the outlet b, and is discharged outside from the duct outlet 13a (see the arrow H in the figure).

When the operation of the engine 3 starts, the ANC controller 25 detects the noise in the lower duct chamber 17 by the primary noise microphone 18. The lower duct chamber 17 is a rising passage 8
a, noise transmitted through the partition wall 5 and noise transmitted through the chassis surface of the muffler 12 are mixed, and the primary noise microphone 18
Will detect that noise. Also, duct outlet 1
3a, the residual noise microphone 19 detects residual noise near the duct outlet 13a, and the ANC controller 2
5 generates a canceling sound from the speaker 16 to minimize noise near the duct outlet 13a.

In this embodiment, in this ANC operation, the speaker 16 and the primary noise microphone 1
8 is spatially partitioned, so that the amount of canceling sound generated by the speaker 16 entering the primary noise microphone 18 can be greatly reduced. This effect can be further enhanced by using a speaker 16 having directivity. Therefore, the correction of the electrical and acoustic characteristics of the speaker 16 and the primary noise microphone 18 at the time of system identification can be omitted, and the speaker 16
It is no longer necessary to perform howling correction between the ANC controller 18 and the primary noise microphone 18, so that the amount of calculation in the ANC controller 25 can be reduced.

Further, since the transmitted noise transmitted through the chassis surface of the muffler 12 is emitted to the lower duct chamber 17, the canceling sound generated from the speaker 16 also corresponds to the transmitted noise of the muffler 12, and the engine power is generated. The sound deadening performance of the entire machine can be improved.

[0026]

[Embodiment 2] Fig. 2 is a view showing the structure of a duct according to a second embodiment of the present invention. Fig. 2 (A) is a longitudinal sectional view, and Fig. 2 (B) is a view as seen from the duct outlet direction. is there. This second
The second embodiment is different from the first embodiment only in that the shielding wall is not provided in parallel in the horizontal direction, but is a bag-shaped shielding wall 14 surrounding the speaker 16. In this embodiment, the same operation and effect as those of the first embodiment can be obtained.

[0027]

Third Embodiment FIG. 3 is a view showing a third embodiment of the present invention, and FIG. 3 (A) is a schematic longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator, and FIG. 3 (B). FIG. 3C is a left side view in a state where the air intake duct case is removed, and FIG. 3C is a right side view in a state where the exhaust air duct case is removed. This enclosed engine generator 31 has a diesel engine 3 disposed on the right side in the figure of a soundproof case 2 formed of six soundproof walls of a rectangular parallelepiped shape, and an engine generator 4 disposed on the left side in the figure. is there. The outlet 10 is opened at a substantially central position of the right soundproof wall 2b, and the intake port 21 is opened at a lower position of the left soundproof wall 2c.

An air guide plate 33 having an air outlet 32 is attached to the right soundproof wall 2b so as to cover the outlet 10 from above, and an air exhaust duct case 34 is provided on the right side to accommodate the air guide plate 33. It is attached to the soundproof wall 2b. A duct outlet 35 is provided on the upper right side of the exhaust duct case 34, and a wire mesh having a predetermined exhaust area is stretched at the duct outlet 35.

On the other hand, the left soundproof wall 2c is provided with a wind guide plate 38 provided with an air outlet 37 so as to cover the air inlet 21 from below, and further, an air intake duct case is provided so as to accommodate the wind guide plate 38. 40 is attached to the left soundproof wall 2c.
A duct inlet 41 is located at a lower position of the air intake duct case 40.
Is provided, and a wire mesh having a predetermined exhaust area is stretched at the duct entrance 41. Radiator 6 has outlet 10
The radiator 6 is provided with a radiator fan 20 which is driven in conjunction with a crankshaft by a fan belt. Above the engine 3, an air cleaner 24 communicating with the intake pipe and a primary muffler 42 communicating with the exhaust pipe are provided. The primary muffler 42 communicates with a secondary muffler 43 provided in the exhaust duct case 34, and a muffler port 43 a of the secondary muffler 43 is provided outside through the front wall of the exhaust duct case 34.

The enclosed engine generator 31 according to this embodiment includes an exhaust-side noise reduction device for reducing noise from the duct outlet 35 and an intake-side noise reduction device for reducing noise from the duct entrance 41. Have. The exhaust-side noise reduction device includes an exhaust-side primary noise microphone 4 provided in an exhaust-air guiding chamber 45 surrounded by the exhaust port 10 and the baffle plate 33.
6 and a duct outlet 35 on the right side wall of the exhaust duct case 34
The exhaust speaker 47 provided on the lower side and the duct outlet 3
5 Exhaust-side residual noise microphone 4 provided at the upper end position
8 and an exhaust-side ANC controller (not shown).

The intake-side noise reduction device includes an intake-side primary noise microphone 51 provided in an intake air-guiding chamber 50 surrounded by an intake port 21 and a baffle plate 38, and an intake duct case 40.
Intake speaker 52 provided at an upper position on the left side wall of the vehicle.
And an intake-side residual noise microphone 53 provided at an end portion of the duct entrance 41, and an intake-side ANC controller (not shown). The speakers 47, 52
Is canceled out by the baffle plates 33, 38, so that they are not directly input to the primary noise microphones 46, 51. The primary noise microphone 46,
The detailed configuration of 51 and the residual noise microphones 48 and 53 will be described in detail in an embodiment described later.

The engine 3 and the generator 4 are housed in the soundproof case 2 via the vibration isolating rubber 55 provided at a predetermined position on the bottom wall 2d of the soundproof case 2;
In addition, the transmission of the vibration of the generator 4 to the soundproof case 2 is reduced. In addition, the intake port 2 at the upper left in the soundproof case 2
The fuel tank 22 is disposed at a position where the fuel tank 1 is not closed, so that fuel can be supplied from a fuel pouring port 56 provided on the soundproof case upper wall 2a.

The operation of the engine generator noise reduction device having the above configuration will be described. Engine generator engine 3
Is driven to start power generation, the radiator fan 20 linked to the crankshaft of the engine is driven. The external air sucked from the duct inlet 41 by the driving of the radiator fan 20 is guided into the soundproof case 2 through the intake-side rising air passage 61 in the air intake duct case 40 and the intake air guide chamber 50, and After cooling the engine 3, the exhaust air guide chamber 45 in the exhaust duct case 34 and the exhaust-side rising air path 62
And is exhausted from the duct outlet 35 (see arrow H in the figure).

When the operation of the engine 3 is started, the intake and exhaust ANC controllers control the primary noise microphones 51 and 4 respectively.
6, the noise in the intake air guide chamber 50 and the noise in the exhaust air guide chamber 45 are detected, and based on the residual signals of the residual noise microphones 53 and 48, the speakers are set so that the noise at the duct entrance 41 and the duct exit 35 is minimized. By driving 52 and 47, a canceling sound is generated. In this ANC operation, in this embodiment, the speaker 52 and the primary noise microphone 51 and the speaker 47 and the primary noise microphone 46 are spatially partitioned by the air guide plates 38 and 33 functioning as shielding walls, respectively. , 47 cancel the primary noise microphones 51, 4
6 can be greatly reduced.

An air inlet 2 opened in the soundproof case 2
1. By providing an intake duct and an exhaust duct at the exhaust port 10 and forming wind guide chambers 50, 45 and rising air paths 61, 62, a space for detecting primary noise on the ANC so as to have a high noise reduction effect. In this case, a space is created in which the cancellation sound is radiated from the speaker. In addition, since the speakers 47 and 52 have directivity such that noise is canceled out on the side of the residual noise microphones 48 and 53, noise at the duct outlet 35 and the duct entrance 41 can be efficiently reduced, and the speakers 47 and 52 can be efficiently reduced. Can be prevented from entering the primary noise microphones 46 and 51.

FIG. 4 is a schematic vertical sectional view showing a modification of the third embodiment. This engine generator is different from the engine generator shown in FIG. 3 in that the upper wall of the exhaust duct case 34 is extended to the upper wall 2a of the soundproof case 2, and the engine generator is disposed in a horizontal air passage 65 formed by the extension. Residual noise microphone 48,
The only difference is that the speaker 47 is provided. According to this embodiment, since the exhaust duct case 34 is extended, noise from the engine 3, the generator 4, noise from the radiator fan 20, and noise from the muffler 42 are reduced by the exhaust air guide chamber 45,
Since the air is finally discharged from the duct outlet 35 through the rising air path 62 and the horizontal air path 65, the noise energy is attenuated in each air path and the simple acoustic characteristics in the horizontal air path 65 There is an advantage that the noise frequency component is selected and the effect of noise reduction is enhanced.

[0037]

Embodiment 4 FIG. 5 is a view showing a fourth embodiment of the present invention, and FIG. 5 (A) is a schematic longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator, and FIG. 5 (B). FIG. 5C is a left side view with the air intake duct case removed, and FIG. 5C is a right side view with the exhaust air duct case removed.
FIG. 5D is a cross-sectional view taken along the line DD in FIG. 5A. FIG. 6A is a perspective view for explaining how to arrange the primary noise microphone and the residual noise microphone in the exhaust duct case, and FIG. 6B is an enlarged view of a main part thereof.

In the fourth embodiment, as in the first to third embodiments, a silencer is attached to the inner wall of the soundproof case 2 and the inner wall of the duct to prevent high-frequency sounds of 1 kHz or more from leaking to the outside. ing. As such a silencing material, a known lightweight and inexpensive silencing material such as glass wool is used. The difference between this embodiment and the enclosed engine generator of the embodiment shown in FIG. 3 is as follows. First, in the third embodiment, the air intake duct case 4
0, the noise reduction device by ANC is provided in both of the exhaust duct case 34. In the fourth embodiment, the noise reduction device by ANC is provided only on the exhaust side.

Second, the shape of the air intake duct case 67 is changed from a square shape to a curved shape having a predetermined radius.
The lower wall 68a also serves as the lower wall of the air intake duct case 67, and a wire net 69 for preventing foreign matter from entering is installed at a position above the duct entrance 41 of the air intake duct case 67. Third, the configuration of the exhaust duct case 71 is different.

The exhaust duct case 71 of the fourth embodiment
The configuration inside the exhaust duct case 71 is as follows. A bag-shaped air guide plate 73 having an air outlet 72 is attached so as to cover the outlet 10 of the right soundproof wall 2b from above. The air guide plate 73 employs an upper wall having a curved surface portion 73a having a predetermined radius. On the upper side of the air guide plate 73, two exhaust-side speakers 47, 47 are provided side by side. The right wall 2b of the soundproof case has an opening 7 of a predetermined size in the upper wall 71a.
A substantially rectangular bowl-shaped exhaust duct case 71 having an inner wall 4 is attached, and a horizontal duct 75 is attached to an upper wall 71a so as to cover an opening 74 thereof. Exhaust air duct case 7
The corner connecting the lower wall 71c and the right wall 71b and the corner connecting the upper wall 75a and the right wall 75b of the horizontal duct 75 are smooth curved surfaces 71d and 75c having a predetermined radius, respectively. At the duct outlet 35 of the horizontal duct 75, a wire mesh 76 for preventing foreign matter from entering is stretched.

In the third embodiment, the soundproof case 2
Although the secondary muffler 43 is provided in the exhaust duct case 34 in communication with the primary muffler 42 provided therein to discharge exhaust gas to the outside, in the fourth embodiment, the secondary muffler 43 is directly connected to the primary muffler 42. An exhaust gas discharge pipe 77 communicates with the external exhaust pipe 78 and is connected to the secondary muffler 4.
3 is not provided in the exhaust duct case 71. As shown by an arrow H in FIG. 5, the cooling air discharged from the exhaust port 72 of the exhaust air guide chamber 79 in the air guide plate 73
Exhaust-side rising air passage 81, opening 74, horizontal air passage 8 in horizontal duct 75, which is composed of
After passing through 2, the wire mesh 76 is discharged to the outside from the duct outlet 35 where the wire mesh 76 is stretched.

Further, a rod-shaped microphone support member 83 having an L-shaped cross section extending from the lower wall 71c to the upper wall 71a of the exhaust duct case is fixed in a vertical direction in the exhaust-side rising air passage 81. As shown in FIG. 6A, the microphone support member 83 is attached from the lower side in the order of the primary noise microphone 46 and the residual noise microphone 48.
3 is firmly fixed with an adhesive or the like via a shock absorbing material 84. As the shock absorbing material 84, a hard vibration isolating sponge can be exemplified. The position of the primary noise microphone 46 is slightly above the lowermost position of the right wall of the baffle plate 73. At this position, the canceling sound generated from the speaker 47 is canceled out by the curved surface 73 a of the baffle plate 73. It is shielded from entering directly.

Note that the lower end of the microphone support member 83 is implanted in the lower wall 71c of the air discharge tact case, and the microphone support member 83 is
Of the exhaust duct case upper wall 71 via a support plate 85.
a. As shown in FIG. 5D, the microphone support member 83 is provided at a central position in the exhaust-side ascending air passage 81 that is symmetrical in the left-right direction. According to the fourth embodiment, since the microphones 46 and 48 are attached to the single microphone support member 83 using the L-shaped steel which is difficult to deform, the individual microphones 46 and 48 do not vibrate independently. The correlation coefficient of the sound between the primary noise microphone 46 and the residual noise microphone 48 can be improved. Further, the microphone support member 83 is provided via the shock absorber 84.
, The vibration of the microphone support member 83 caused by the vibration of the engine and the exhaust wind causes the primary noise microphone 4
6. The direct transmission to the residual noise microphone 48 can be suppressed, and the correlation between sounds between the two microphones 46 and 48 can be improved.

Further, the microphone support member 83 is disposed along the extending direction S of the exhaust-side ascending air passage 81 through which the exhaust air flows, and is provided at a position symmetrical in the exhaust-side ascending air passage 81 in the left-right direction. Therefore, noise flowing on the cooling wind can be detected without bias in all regions, and as a result, noise reduction performance can be improved. Further, by providing the horizontal duct 75, the level of the noise can be reduced as compared with a mode in which the noise is directly emitted to the outside from the opening 74 of the exhaust duct case 71. This is because, by providing the horizontal duct 75 substantially perpendicular to the extending direction of the exhaust rising air passage 81, it is possible to prevent the generation of a standing wave mainly having the opening 74 in the exhaust rising air passage 81 with the antinode of the acoustic vibration. Because.

The configuration of the horizontal duct 75 is not necessarily limited to the curved surface portion 75c having a predetermined radius, but is a duct having a wall surface inclined at an angle to the extending direction of the exhaust-side ascending air passage 81. I just need. Note that the inclination angle of the wall surface may be appropriately set in consideration of the effect of suppressing the standing wave and the amount of the noise component returning to the exhaust-side ascending air passage 81 after colliding with the inclined wall surface. In an experiment using a microphone described later, the sound absorbing material provided on the inner wall and A
With the configuration of this embodiment in which the NC control is combined, the noise level on the side of the exhaust port 10 when no measure is taken is 8
It was confirmed by actual equipment that the reduction from 5 dB to 75 dB after the countermeasure was taken.

[0046]

Fifth Embodiment FIG. 7A is a longitudinal sectional view showing a detailed configuration of a primary noise microphone and a residual noise microphone used in the fourth embodiment, and FIG. 7B is a vertical sectional view of FIG. FIG. 8 is an exploded perspective view taken along a line B-B. The microphone 94 used in the reduction device of the enclosed engine includes a rectangular external case 87 made of various plastics and a shock absorbing material 88 such as a hard vibration-proof sponge housed inside the external case 87.
And a microphone unit 89 supported at the center of the outer case 87 with the side surface pressed against the shock absorber 88.

The outer case 87 is formed of a rectangular bowl-shaped housing case 90 and a lid 91 of the housing case 90. A cut-out portion 93 through which the microphone cord 92 of the microphone unit 89 is inserted is provided on the rear wall of the housing case 90. Is provided. The front wall 90a and the side wall 90b of the storage case 90 have a predetermined thickness (1 m).
m), and these walls 90a and 90b are not provided with any sound wave introduction ports. The microphone unit 89 detects sound transmitted through the front wall 90a of the housing case 90 and the outer case side wall 90b in front of the position where the microphone unit 89 is housed.

As shown in FIG. 8, the shock absorbing member 88 is formed in a substantially cylindrical shape having a hole 95 into which the microphone unit 89 is inserted, and the housing case is provided with the microphone unit 89 inserted into the hole 95. 90 and fixed by the lid 91. The thickness of the shock absorbing material 88 is set so as to receive an elastic force pressing from the side when the lid 91 is attached, and the microphone unit 89 is held at a predetermined position by the elastic force. This shock absorbing material 88 also has an effect of absorbing high-frequency noise of 1 kHz or more. As described above, the noise reduction by the ANC of the surrounding engine generator is intended for a low-frequency sound of 500 Hz or less (a muffled sound resounding on the belly) which cannot be reduced by the sound absorbing material. Therefore,
Unlike a conventional general microphone, there is no need to detect a wide range from low-frequency sound of 500 Hz or less to high-frequency sound of several kHz or more.

According to the microphone of this embodiment, by transmitting through the plastic surface, the sound of 1 kHz or more is absorbed by the latch, and only the sound of 1 kHz or less can be detected by the microphone unit. In the case of a conventional anti-vibration microphone having a sound wave inlet, a turbulence of strong cooling fan wind flowing through the exhaust duct case 71 adversely affects noise detection. Although a problem such as adhesion occurs, the microphone 94 according to the present embodiment can solve the problem and improve the signal S / N ratio. In this way, by taking measures against turbulence of the microphone 94 and measures against vibration of the microphone, and by setting the position of the microphone support member to the appropriate position described in the fourth embodiment, the position of the primary noise microphone and the residual noise microphone can be reduced. Correlation can be increased.
As shown in FIG. 6B, the microphone arrangement direction of the primary noise microphone and the residual noise microphone is relative to the flow T of the cooling air (substantially equal to the extending direction S of the exhaust-side rising wind path 81). A configuration in which the surface 90a faces upstream, a configuration in which the microphone surface 90a faces downstream with respect to the flow T of cooling air, and a configuration in which the microphone surface 90a is parallel to the flow T of cooling air In the case of a microphone having a rectangular external case, a configuration in which the microphone surface 90a faces the downstream with respect to the flow T of the cooling air, the flow S of the cooling air can be adopted.
It has been confirmed that the configuration in which the microphone surface 90a is parallel to the above has good coherence. In addition, in order to reduce the resistance of the outer case due to the flow of cooling air, it was confirmed that the outer case was streamlined to suppress vibration and improve coherence.

FIG. 9A shows a case in which the microphone 94 having the turbulence countermeasures of the present embodiment is used, and the microphone support member 83 is disposed in a symmetrical manner in the direction parallel to the extending direction of the exhaust-side rising wind path 81. FIG. 9B shows the correlation coefficient of the two microphones 46 and 48 in the vertical axis and the horizontal axis shows the frequency. FIG. 9B shows a case where a microphone having a normal sound wave introduction port is used, and the microphone support member 83 is attached. FIG. 8 is a diagram illustrating a relationship between a correlation coefficient and a frequency of two microphones 46 and 48 in a case where the microphones are arranged obliquely with respect to an extending direction of an exhaust-side ascending air passage 81. In FIG. 9A corresponding to the present embodiment, the correlation coefficient has a good value close to about 1.0 for noise of 500 Hz or less to be reduced, whereas FIG. In the conventional configuration shown in FIG.
Even when the NC control is performed, the value is a bad value of about 0.5 at which the sound can hardly be reduced.

[0051]

Sixth Embodiment FIG. 10 is a view showing a sixth embodiment of the present invention, and FIG. 10 (A) is a schematic longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator, and FIG. 10 (B). FIG. 6A is a diagram corresponding to FIG. FIG. 11 is a longitudinal sectional view showing a detailed configuration of a microphone used in the sixth embodiment, and FIG. 11B is a transverse sectional view taken along line BB of FIG. 11A. The differences between the sixth embodiment and the fourth embodiment are as follows.
First, the microphone support member 83 is not provided in the exhaust duct case 71, the primary noise microphone 46 is provided at the lower end of the baffle plate 73, and the residual noise microphone 48 is provided outside the duct outlet 35 of the horizontal duct 75. This is a point provided at the upper end.
FIG. 10 shows a case where the residual noise microphone 48 is provided at the outer upper end.
As shown in (B), the microphone surface is set so as to be parallel to the extending direction of the horizontal duct 75 and not to protrude from the extension of the horizontal duct 75. With this configuration, it is possible to prevent the cooling air discharged from the duct outlet 35 from directly hitting, prevent the residual noise microphone 48 from vibrating, and perform good noise detection.

Second, as shown in FIG.
Forty-eight external case 87 is replaced with metal,
The inside of the microphone unit 89 is lined with a vibration damping material 108 such as a vibration damping rubber, and then a shock absorbing material 88 such as a hard vibration damping sponge is accommodated. This is the point covered by 107. The outer periphery of the microphone unit 89 of the primary noise microphone 46 may be covered with the sound absorbing material 107 as necessary. With this configuration, it has been confirmed that the vibrations of the microphones 46 and 48 can be suppressed and the noise detection characteristics of both microphones can be improved with respect to the target low-frequency noise.

Third, the arrangement position of the exhaust-side speaker 47 is set on the upper wall 71a of the exhaust duct case 71, and the speaker surface of the speaker 47 is directed toward the curved surface portion 75c. In the configuration in which the residual noise microphone 48 is disposed outside the duct outlet 35 as shown in FIG. 10, the upper wall 71a is larger than the configuration in which the speaker 47 is disposed above the wind guide plate 73 (see FIG. 5). It has been confirmed that the noise reduction performance of the ANC is improved when the speaker 47 is provided above. Note that the microphones 46 and 48 are attached to the wind guide plate 73 and the outer upper end of the horizontal duct 75 via the shock absorbing material 84. Further, the length L in the depth direction of the exhaust duct case 71 and the horizontal duct 75 in which the primary noise microphone 46 and the residual noise microphone 48 are disposed are the same, and both are disposed at symmetrical positions. ing. This configuration is necessary to increase the coherence of the sounds of the microphones 46 and 48. According to the sixth embodiment, even if the microphone support member 83 is not provided unlike the fourth embodiment shown in FIG. 5, the noise level on the exhaust port 10 side is similarly reduced from 85 dB to 75 dB in the experiment.
It was confirmed that it could be reduced by

[0054]

Embodiment 7 Next, an example of the configuration of an ANC controller applicable to the present invention will be described. FIG.
FIG. 16 is a block diagram illustrating a schematic configuration of an ANC controller used in the sixth to sixth embodiments. 12, the ANC controller 25 is roughly classified into an adder 117, a compensation digital filter 118, and a compensation digital filter 11.
9. Adaptive digital filter 120, LMS control unit 121
It is composed of The noise detected from the primary noise microphone 46 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 primary noise signal _Xn to the compensating digital filter 119 and the adaptive digital filter. 120
Output to The output signal Y _n of the adaptive digital filter 120 is the drive signal of the exhaust-side speaker 47.

The compensating digital filter 118 is a filter for compensating electroacoustic characteristics <B> between the exhaust speaker 47 and the primary noise microphone 46, and the compensating digital filter 119 is a filter for compensating the exhaust speaker 47 and the residual noise microphone 4.
This is a filter for compensating the electroacoustic characteristics <C> between the eight.
LMS control unit 121, so canceling sound issued from the exhaust side speaker 47 to reduce the noise of the surrounding engine, the residual based on the residual noise signal e _n from the residual noise microphone and the reference input signal X _n noise signal e _n to update the filter coefficients of the adaptive digital filter 120 so as to minimize. 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 coefficient of the adaptive digital filter 120 is recursively updated by the following equation. _{W n + 1 = W n +} 2μe n · X n ...... However, W _n: adaptive digital filter coefficient (W [0], W
[1],..., W [L-1]) _Xn : Primary 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.

Here, by providing the shielding wall 14 shown in FIG. 1, the baffle plate 33 in FIGS. 3 and 4, and the baffle plate 73 in FIG. 5, the value of the compensation digital filter 118 is determined at the time of system identification. Can be omitted or simplified. In the ANC operation, it is unnecessary or reduced to perform the howling correction between the exhaust speaker 47 and the primary noise microphone 46 in the ANC control calculation. The amount of calculation in the LMS control unit 121 can be reduced. Further, by making the configuration of the microphone as described above, it is not necessary to provide an analog filter for cutting off high-frequency sound from the microphones 46 and 48 in the circuit shown in FIG. 12, and it is possible to prevent an electrical delay from occurring. . 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 third embodiment, the air intake duct case 40 and the air exhaust duct case 3
Although the configuration adopting both of Nos. 4 and 4 has been described, noise reduction by ANC can be performed for only one of them. For example, A
When only the noise countermeasures on the exhaust side by the NC are performed, the air intake duct case 40 and the noise reduction device on the intake side are omitted, and a wire mesh is directly provided on the intake port 21 of the soundproof case 2.
The outside air may be sucked through the air inlet 21. In a configuration in which outside air is taken in from the intake port and exhausted from the exhaust port, the wind noise of the engine and the fan rides on the flow of the wind, so the exhaust port is louder than the intake port. Therefore, even with a configuration in which the ANC noise reduction device is provided only on the exhaust port side, a sufficient noise reduction effect can be achieved.

(2) In the third embodiment, the soundproof case 2 accommodating the engine 3 and the generator 4 as noise sources is taken as an example of the enclosure, but the enclosure is not necessarily the engine 3 and the generator. It is not limited to the one that completely accommodates the engine 4, but may be a member that surrounds a part of the engine 3 and the generator 4 with a soundproof wall or the like. For example, the soundproof case 2 of the engine 3 and the generator 4
May be covered by a predetermined area with a partition wall, a sound deadening duct portion made of ANC may be formed outside the partition wall, and a sound deadening case may be provided so as to surround these sound deadening ducts. (3) The shape of the microphone support member 83 is not limited to an L-shaped cross section, and any material such as a square tube steel material, a U-shaped steel material, an H-shaped steel material, etc., which does not easily deform due to vibration can be used as appropriate.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a noise reduction device of an enclosed engine generator as one embodiment of a noise reduction device of an enclosed engine according to the present invention, and FIG.
(B) is a plan view of the duct.

FIGS. 2A and 2B are diagrams showing a configuration of a duct showing a second embodiment of the present invention, wherein FIG. 2A is a longitudinal sectional view, and FIG. 2B is a view seen from a duct outlet direction.

FIG. 3 is a diagram showing a third embodiment of the present invention, and FIG.
(A) is a schematic longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator, FIG. 3 (B) is a left side view of a state where a ventilation duct case is removed, and FIG. 3 (C) is an exhaust duct. It is a right side view in the state where the case was removed.

FIG. 4 is a schematic longitudinal sectional view showing a modification of the third embodiment.

FIG. 5 is a view showing a fourth embodiment of the present invention, FIG. 5 (A) is a schematic longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator, and FIG. FIG. 5 (C) is a right side view of a state where the exhaust duct case is removed, and FIG. 5 (D) is a cross-section in the direction of line DD in FIG. 5 (A). FIG.

FIG. 6A is a perspective view for explaining how to arrange a primary noise microphone and a residual noise microphone in an exhaust duct case, and FIG. 6B is an enlarged view of a main part thereof.

7A is a longitudinal sectional view showing a detailed configuration of a primary noise microphone and a residual noise microphone, and FIG. 7B is a transverse sectional view taken along line BB of FIG. 7A.

FIG. 8 is an exploded perspective view of the microphone according to the embodiment.

FIG. 9A is a diagram illustrating a relationship between a correlation coefficient and a frequency according to the present embodiment, and FIG. 9B is a diagram illustrating a relationship between a correlation coefficient and a frequency in a comparative example.

FIG. 10 is a view showing a sixth embodiment of the present invention. FIG. 10 (A) is a schematic longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator, and FIG. FIG.
(A) It is an equivalent figure.

FIG. 11 is a longitudinal sectional view showing a detailed configuration of a microphone used in a sixth embodiment, and FIG. 11 (B) is FIG. 11 (A).
FIG. 7 is a cross-sectional view taken along line BB of FIG.

FIG. 12 shows A used in the first to sixth embodiments.
FIG. 2 is a block diagram illustrating a schematic configuration of an NC controller.

FIG. 13 is a block diagram showing an example of a conventional noise control device.

FIG. 14A is a cross-sectional view of a vibration-proof microphone device disclosed in Japanese Utility Model Laid-Open Publication No. 1-126682, and FIG. 14B is a longitudinal sectional view thereof.

FIG. 15 is a diagram illustrating an example of a noise spectrum characteristic of the enclosed engine.

[Explanation of symbols]

2 ... Soundproof case, 3 ... Engine, 10 ... Exhaust port, 13 ...
Duct, 13a duct outlet, 16 speaker, 18 ...
Primary noise microphone, 19: residual noise microphone, 21: intake port, 25: ANC controller, 34: exhaust duct case, 35: duct outlet, 41: duct entrance, 46: exhaust primary noise microphone, 47: exhaust speaker 48, an exhaust side residual noise microphone, 50, an intake air guide chamber, 71, an exhaust duct case, 71a, an upper wall, 73, a wind guide plate, 74, an opening,
75 ... horizontal duct, 79 ... exhaust air guide chamber, 81 ... exhaust side rising air path, 82 ... horizontal air path, 83 ... microphone support member, 87
... External case, 88 ... Shock absorber, 89 ... Microphone unit, 97 ... Exhaust duct case, 98 ... Exhaust side descending air path,
107: sound absorbing material, 108: damping material.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02B 77/13 B60R 11/02 F01N 1/00 G10K 11/16 G10K 11/178

Claims (5)

(57) [Claims] An engine (3) is housed in an enclosure (2), and at least a suction port (2) is provided at a predetermined position of the enclosure (2).
1) and an exhaust port (10), at least the exhaust port (10) in order to reduce the noise of an enclosed engine that takes in outside air from the intake port (21) and exhausts it through the exhaust port (10).
Exhaust duct (13) (34) (71, 7)
A primary noise detection microphone (18) (4) is formed around the enclosure (2) and detects noise near the exhaust port (10).
6) and the exhaust side duct (13) (34) (71, 75)
Noise detection microphones (19) and (48) for detecting noise near the duct openings (13a) and (35), and canceling noise generation disposed in the exhaust ducts (13) (34) (71, 75). The canceling sound generating means (16) (47) is driven to generate a canceling sound for canceling the noise at the duct openings (13a) (35) based on the means (16) (47) and the primary noise signal and the residual noise signal. ANC control means (2
5), the primary noise microphones (18) and (46) and the residual noise detection microphones (19) and (48) are provided with an outer case (87) and a shock absorbing material housed inside the outer case (87). (8
8) and a microphone unit (89) supported at the center of the outer case (87).
C means that transmits low-frequency noise of less than 500 Hz to be reduced by the control means (25) is used, and no sound inlet is provided in the outer case (87).
7) A noise reduction device for an enclosed engine, wherein low-frequency noise transmitted through 7) is detected by an internal microphone unit (89). 2. The primary noise microphones (18) and (46) and the residual noise detection microphones (19) and (48) are provided with a vibration damping member (108) inside an outer case (87), and the vibration damping member (108) is provided. 108), the shock absorbing material (88) is provided inside, and at least the residual noise microphone (1) is provided.
9) 700 around the microphone unit (89) of (48)
Microphone unit (89)
2. The noise reduction device for an enclosed engine according to claim 1, wherein the noise reduction device is surrounded by a sound absorbing material (107) for preventing intrusion into the vehicle. 3. 3. The noise reduction device for an enclosed engine according to claim 1, wherein the material forming the outer case (87) is made of metal. 4. A rod-shaped support member (8) extending parallel to the direction in which the duct air passage (81) extends in the exhaust duct (71, 75).
3) is fixed, and the exhaust port (10) of the rod-shaped support member (83) is provided.
The primary noise microphone (46) is mounted on the side of the main body, and the residual noise microphone (1) is mounted on the side of the duct opening (35) of the rod-shaped support member (83).
9) The noise reduction device for an enclosed engine according to claim 1, wherein (48) is attached, and a canceling sound generating means (47) is provided at a predetermined position in the air duct (81) in the duct. 5. An engine (3) is housed in an enclosure (2), and at least a suction port (2) is provided at a predetermined position of the enclosure (2).
1) and an exhaust port (10), at least the exhaust port (10) in order to reduce the noise of an enclosed engine that takes in outside air from the intake port (21) and exhausts it through the exhaust port (10).
The exhaust-side duct (71, 75) communicating with the enclosure (2)
A primary noise detection microphone (46) which is formed in the periphery and detects noise close to the exhaust port (10);
75) a residual noise detecting microphone (48) for detecting noise near the duct opening (35), and an exhaust duct (71, 75).
And a canceling sound generating means (47) disposed therein, and driving the canceling sound generating means (47) so as to generate a canceling sound for canceling noise at the duct opening (35) based on the primary noise signal and the residual noise signal. The exhaust-side duct (71, 75) includes a bag-shaped air guide plate (73) having an exhaust port (72) on the lower side so as to cover the exhaust port (10) from above. ), And a rectangular body having an opening (74) in an upper wall (71a) provided on a wall surface (2b) of an enclosure (2) having an exhaust port (10) to accommodate a baffle plate (73). A bowl-shaped exhaust duct case (71), and a horizontal duct (75) partitioned from the exhaust duct case (71) by the upper wall (71a) and communicating with the opening (74) and extending in the horizontal direction, The cooling air coming out of the exhaust port (10) is a baffle plate (73)
The exhaust-side ascending air path (8) formed by the exhaust air guide chamber (79), the air guide plate (73), and the exhaust duct case (71) surrounded by
1) The lower end of the air guide plate (73) configured to be discharged from the duct opening (35) through the horizontal air passage (82) in the horizontal duct (75), and faces the exhaust-side ascending air passage (81). The primary noise microphone (46) is fixed in the area and the horizontal duct (7)
5) Residual noise microphone (48) near duct opening (35)
The upper wall (71a) of the exhaust duct case (71).
A noise reduction device for an enclosed engine, wherein a noise canceling means (47) is provided at a predetermined position.