JPH08338224A - Surrounding engine noise reduction device - Google Patents

Abstract

(57) [Summary] [Purpose] Active noise control (AN) with good accuracy and followability in response to changes in the conditions inside the enclosed engine.
Perform C). [Configuration] Optimum compensation filter B coefficient value, compensation filter C coefficient value, and adaptive filter W coefficient value are previously obtained by experiments using the rotation speed of the ventilation fan in the enclosed engine and the temperature of the ventilation part as parameters. It is stored in the memory 31. Then, based on the current temperature and rotation speed detected by the temperature sensor 32 and the rotation speed sensor 33, the CPU
30 transfers the corresponding filter coefficient value to the ANC processing unit 37, and the ANC processing unit 37 reduces the noise at the duct opening of the enclosed engine by ANC control using each transferred filter coefficient value as an initial value.

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, and more particularly to a noise reduction device for an enclosed engine which reduces noise of an engine surrounded by a soundproof wall or the like.

[0002]

2. Description of the Related Art Conventionally, as a technique for reducing noise in an engine and an exhaust duct, a passive method of providing a sound absorbing material and a vibration damping material has been proposed. On the other hand, in recent years, active noise control (active noise control, hereinafter referred to as ANC) that emits a canceling sound of the same amplitude and opposite phase to noise to reduce the noise by the interference effect of sound waves has been put to practical use. Has been actively researched in various fields. According to ANC, it is difficult to reduce with sound absorbing material near 100 Hz to 500.
Since it also has a reducing effect on low-frequency noise in the vicinity of Hz, it is used to reduce muffled noise in the passenger compartment, air conditioning duct noise, etc. (Japanese Patent Publication No. 2-503219, Japanese Patent Laid-Open No. 3-204354). etc).

FIG. 14 is a schematic block diagram of a duct silencer for reducing air conditioning duct noise 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 flow of the air. In the air conditioning duct 101, a reference noise microphone 102 on the upstream side,
A residual noise microphone 104 near the exhaust port 103 is provided,
A loudspeaker 105 that generates a canceling sound is provided between the microphones 102 and 104.

In this duct silencer, the reference sound detected by the reference noise microphone 102 interferes with the canceling sound to form a residual sound, and the residual sound signal detected by the residual noise microphone 104 minimizes the residual sound. ANC control unit 106
By sequentially updating the adaptive digital filter coefficient of, the canceling sound radiated from the loudspeaker 105 is changed and the noise is reduced. In the case of this silencer, before the actual sound is silenced, the compensation filter B for the electroacoustic characteristics between the reference noise microphone 102 and the loudspeaker 105 and the compensation filter C for the electroacoustic characteristics between the reference noise microphone 102 and the loudspeaker 105. It is necessary to perform a process called system identification, which is obtained in advance. Then, at the time of the actual muffling operation, the adaptive digital filter coefficient of the ANC control unit 106 is sequentially updated based on the compensation filter B and the compensation filter C obtained by the system identification, thereby canceling out the emission from the loudspeaker 105. Change the sound and reduce the noise.

On the other hand, in recent years, there has been a demand for the development of environmentally friendly products, and engine generators and the like in which the engine is housed in a soundproof case have been preferred in order to reduce noise. Considering the increase of the environmental problems, it is considered that the ANC is applied to the enclosed engine to reduce noise.

[0006]

However, in a closed space such as a cabin of an automobile or a cabin, there have been proposed a configuration example in which ANC is applied, a device for reducing exhaust noise of a muffler, and the like. The present situation is that no effective device configuration for applying the above to reduce noise is disclosed.

Further, in an engine used outdoors, such as an engine generator, the ambient environment such as temperature is constantly changing, and the engine load and the rotation speed of the ventilation fan are also changing. It is normal. Therefore, in the system identification, the coefficient value of the compensation filter B and the coefficient value of the compensation filter C are often greatly deviated from the optimum electroacoustic characteristics at the time of actually performing the silencing operation.

If the compensation filter coefficient value set during system identification is used in a state that is out of the reference state during system identification, the adaptive range on the adaptive filter side may be exceeded. In this case, since the adaptive filter cannot converge well, the noise reduction of the enclosed engine may be deteriorated, or the noise may be amplified in severe cases. To solve this problem, it is possible to increase the filter coefficient calculation speed as much as possible to improve the system followability, but a high-speed dedicated processor that can perform a large amount of calculation within the sampling time is required, and the device is There is a problem of becoming expensive.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an enclosed type engine which can obtain a sufficient noise reduction performance with an inexpensive device configuration even when the temperature and the engine speed change. An object is to provide a noise reduction device.

[0010]

In order to achieve the above-mentioned object, a noise reducing device for an enclosed engine according to claim 1 surrounds the engine with a soundproof wall, and an outside air intake port and a final position are provided at a predetermined position of the soundproof wall. An exhaust port is provided, and a ventilation part that takes in outside air from the outside air intake port and exhausts ventilation air from the final exhaust port is provided.In the ventilation part, a suction fan that sucks out the hot air of the engine is installed from the engine to the final exhaust side, and ventilation is provided. Reference noise detecting means for detecting noise including engine sound and fan wind noise is provided at a predetermined position of the section, residual noise detecting means is provided near the final outlet of the ventilation section, and the ventilation section position where the reference noise detecting section is provided Further on the downstream side, a canceling noise generating means is provided at a predetermined position on the upstream side of the position of the ventilation part where the residual noise detecting means is arranged, and a temperature sensor for detecting the temperature in the ventilation part and a suction fan are provided. And a fan rotation speed sensor for detecting the rotation speed of the fan, the electroacoustic characteristics of the ventilation section including at least the electroacoustic characteristics between the canceling sound generation means and the residual noise detection means, the temperature in the ventilation section, the fan rotation speed as a parameter A storage means that is obtained and stored in advance is provided, and the electroacoustic characteristics of the ventilation part stored in the storage means are selected based on the detected temperature and fan rotation speed in the silencing processing operation, and the selected electroacoustic characteristics are selected. A canceling sound to generate a canceling sound so as to reduce noise at the final discharge port based on the reference noise signal detected by the reference noise detecting means and the residual noise signal detected by the residual noise signal detecting means. An ANC control means for driving the generating means is provided.

According to another aspect of the noise reducing apparatus for an engine of the enclosed type, the storage means stores the filter coefficient value of the adaptive digital filter that finally determines the characteristics of the canceling sound using the temperature and the fan rotation speed as parameters. The electroacoustic characteristic selected by the ANC control means includes a filter coefficient value of the adaptive digital filter.

[0012]

According to the noise reduction device for an enclosed engine of claim 1, when the temperature changes, the speed at which sound is transmitted also changes, and when the rotation speed of the ventilation fan changes, the speed of the ventilation air flowing through the ventilation section also changes. Since it changes, it is necessary to consider the influence of the canceling sound, but since the ANC control means selects the electroacoustic characteristics of the ventilation part stored in the storage means based on the detected temperature and the fan rotation speed, the muffling sound is reduced. The electroacoustic characteristic corresponding to the state at the time of the attempt can be used as the initial value of the adaptive control. Therefore, it is possible to shorten the time until the filter coefficient that can be muted is converged, and it is possible to realize ANC control with good followability and accuracy.

According to the noise reducing apparatus for the enclosed engine of the second aspect, the filter coefficient value of the adaptive digital filter that finally determines the characteristics of the canceling sound can be selected according to the state when the noise is to be silenced. The tracking is more effective than the electroacoustic characteristic between the canceling sound generating means and the residual noise detecting means and the electroacoustic characteristic between the canceling sound generating means and the reference noise detecting means selected in claim 1. It is possible to realize ANC control with good performance and accuracy. When selecting the filter coefficient value of the adaptive digital filter that ultimately determines the characteristics of the canceling sound, use an evaluation function that checks the convergence of the filter coefficient of the adaptive digital filter to make that selection accurately. You can

[0014]

As described in the above operation, according to the invention of claim 1, the following unique effects are exhibited. (A) The electroacoustic characteristic corresponding to the state when the sound is about to be silenced can be used as the initial value of the adaptive control, the time until it converges to the filter coefficient that can be silenced can be shortened, and the followability is good. ANC control can be realized. (B) Since not only the temperature but also the electroacoustic characteristics in consideration of the speed of the ventilation wind generated by the ventilation fan in the enclosed engine are stored in the storage means, the noise reduction performance of the enclosed engine can be enhanced. (C) Since the electroacoustic characteristics required for system identification are stored in the storage means in advance, the system identification process at the time of engine start is unnecessary, the time required for system identification is reduced, and the enclosed engine is easy to use. Can be

According to the invention of claim 2, in addition to the effect of the invention of claim 1, the filter coefficient value of the adaptive digital filter which finally determines the characteristic of the canceling sound can be selected in accordance with the state at the time of silencing. Therefore, AN with even better followability
It has a unique effect that C control can be realized.

[0016]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 1 is a basic block diagram of a noise reduction device for an enclosed engine generator as an embodiment of a noise reduction device for an enclosed engine according to the present invention, and FIG. 2 is a schematic block diagram showing the relationship between an ANC processing unit and an enclosed engine. It is a figure.

This noise reduction device detects in the central processing unit (CPU 30) that processes the entire control, the ANC processing unit 37 that controls the ANC processing, the memory 31 (ROM) that stores each filter coefficient value, and the CPU 30. A temperature sensor 32 for inputting a temperature, a rotation speed sensor 33 for inputting the rotation speed of the suction fan to the CPU 30, a reference noise microphone 22 for inputting a reference noise signal to the ANC processing unit 37, and an ANC.
Residual noise microphone 1 for inputting a residual noise signal to the processing unit 37
9 and a loudspeaker 16 that generates a canceling sound based on the anti-noise signal from the ANC processing unit 37. In the memory 31, filter coefficient values are stored for each of the compensation filter B, the compensation filter C, and the adaptive filter W corresponding to the combination of temperature and fan rotation speed. FIG.
3A is a vertical cross-sectional view showing the configuration of an enclosed engine to which a noise reduction device is applied, and FIG. 3B is a cross-sectional view taken along the line BB of FIG. 3A.

In this enclosure type engine generator 1, a diesel engine 3 is arranged in a substantially central portion of a soundproof case 2, and a generator 4 is arranged on the right side in the figure. A partition wall 5 is provided on the upper side and the side surface of the diesel engine 3, and a radiator 6 is attached to the left side surface of the partition wall 5, so that an engine power generation chamber 7 in which the engine 3 and the generator 4 are housed in the soundproof case 2 is provided. It is divided into an exhaust passage 8 and a side surface space 9.

The exhaust passage 8 is composed of an ascending passage 8a provided so as to face the radiator 6 and an exhaust passage 8b which communicates with an exhaust port 10 provided at the upper wall 2a of the soundproof case 2. A suction type radiator fan 11 is attached to the radiator 6, and the radiator fan 11 is driven by a crankshaft of the engine 3 by a fan belt and a pulley. The drive shaft that drives the radiator fan 11 is provided with a rotation speed sensor 33 that detects the rotation speed. Since the radiator fan 11 is driven in conjunction with the crankshaft, the rotation speed sensor 33 may detect the rotation speed of the crankshaft. When an electric fan is used as the radiator fan, the fan rotation speed may be detected from the drive signal of the electric fan.

A cylindrical muffler 12 extending in the horizontal direction is provided in the ascending passage 8a facing the radiator 6, and the suction air of the radiator fan 11 passes through the side surface of the cylindrical muffler 12 to the exhaust passage 8b. is there. The exhaust port of the engine is communicated with the muffler 12 by an exhaust pipe 20a that bypasses the side space 9, and the exhaust gas from the muffler 12 is communicated with the outside through the exhaust pipe 20b through the left wall of the soundproof case.

On the upper wall 2a of the soundproof case 2, a substantially rectangular duct 13 having a base end portion on the radiator 6 side and a duct outlet 13a on the opposite side is fixed, and a duct portion above the discharge port 10 is fixed. Is provided with a shielding wall 14 that horizontally divides the duct 13 into two rooms. The outlet 10 is covered by the shielding wall 14 by about half.

A loudspeaker 16 having a directivity is disposed in an upper room (referred to as an upper duct room 15) partitioned by the shield wall 14 with its speaker surface facing the duct outlet 13a. In addition, the lower room (lower duct room 17
Has a function of guiding cooling air passing through the ascending passage 8a and the exhaust passage 8b toward the duct outlet 13a. The loudspeaker 16 is surrounded by a unit case 18 so that it can be detachably replaced, and by fitting the loudspeaker 16 with the upper duct chamber 15 without leaving a gap, the duct 1 of the loudspeaker 16 is removed.
It can be easily attached to the 3.

A residual noise microphone 19 for detecting residual noise near the duct outlet 13a is provided at a predetermined position near the duct outlet 13a. A temperature sensor 32 for detecting the temperature in the duct 13 is provided on the upper wall 2a in the duct 13. A reference noise microphone 22 is provided in the ascending passage 8a on the downstream side of the muffler 12, and the engine noise, the wind noise of the radiator fan 11, and the muffler 12 are provided.
The reference noise in a state where the noise transmitted from the chassis (hereinafter, referred to as muffler transmitted noise) is mixed is detected and input to the ANC controller 23.

On the other hand, the side wall 2 of the soundproof case 2 on the generator 4 side
An intake port 24 for sucking the outside air for ventilating the inside of the soundproof case 2 is provided at b, and a fuel tank 25 supported by the partition wall 5 is provided above the generator 4. In addition, the intake port 2
An air passage from 4 to the upper portion of the power generation chamber 7, the exhaust passage 8, and the duct 13 to the duct port 13a constitutes a ventilation portion 21.
Further, the fuel supply port 26 of the fuel tank 25 is provided in the upper part of the soundproof case 2 on the front side of the drawing in FIG. An air cleaner 27 is provided at a substantially central position of the engine power generation chamber 7, and supplies the outside air sucked from the intake port 24 to the intake port through the intake pipe.

As shown in FIG. 1, the noise reduction device comprises a reference noise microphone 22, a directional loudspeaker 16, a residual noise microphone 19, an ANC processing section 37, a CPU 30, and a memory 31. Part 37, CP
As shown in FIG. 3A, the U30 and the memory 31 are arranged at a lower position of the soundproof case 2 so as to be surrounded by the heat insulating member 28 so as not to be affected by the heat of the engine.

FIG. 2 is a block diagram showing the configuration of the ANC processing unit 37. The ANC processing unit 37 includes an adaptive digital filter 38 that generates an antiphase waveform serving as a control sound, and an LM.
The S control unit 39, a compensation filter 40 between the reference noise microphone 22 and the loudspeaker 16, and a compensation filter 41 between the residual noise microphone 19 and the loudspeaker 16 are included. The electroacoustic characteristic B determined by system identification becomes the initial value of the compensation filter 40, and the electroacoustic characteristic C becomes the initial value of the compensation filter 41. The LMS method is an algorithm operated by the mathematical formula shown in the following Expression 1.

[0027]

[Equation 1]

However, Wn: Adaptive filter coefficient (W [0], W [1], ..., W
[L]) Xn: Reference noise signal (X [n], X [n-1], ..., X
[N−L]) en: residual noise signal n: discrete time μ: convergence coefficient L: filter order. The operation of the noise reducing device for the enclosed engine will be described with reference to FIGS. 1 to 3 and the flowcharts shown below. FIG. 4 is a flow chart showing the processing performed by the CPU 30. In step SP1, the initial values of the compensation filter B, the compensation filter C, and the adaptive digital filter W due to changes in temperature and fan speed are experimentally determined for each model of the surrounding engine. When the initial value is obtained and stored in the memory, the rotation speed sensor 33 detects the rotation speed in step SP2, and if it is determined that the rotation speed is within the rotation speed in the memory 31, the temperature sensor 3 is detected in step SP3.
When it is determined that the temperature is detected from 2 and the temperature is in the memory 31, the compensation filter B, the compensation filter C, and the compensation filter C based on the rotation speed and the temperature detected in step SP4.
Select adaptive digital filter W and set compensation filter B to A
To the correction filter 40 of the NC processing unit 37, the compensation filter C
To the correction filter 41 of the ANC processing unit 37 and the adaptive digital filter W to the initial value of the adaptive digital filter 38.

Then, in step SP5, the evaluation function is calculated, and in step SP6, it is determined whether or not the filter coefficient of the adaptive digital filter W needs to be switched based on the evaluation function, and the filter coefficient of the adaptive digital filter W is switched. If it is determined that is required, step SP
In 7, the filter coefficient of the adaptive digital filter W is switched, the switched adaptive digital filter W is set as the initial value of the adaptive digital filter 38, and the process returns to step SP2.

If the rotational speed cannot be detected normally in step SP2 and the temperature cannot be detected normally in step SP3, abnormal processing is performed in step SP8 and the processing is terminated. When it is determined in step SP6 that the filter coefficient of the adaptive digital filter W does not need to be corrected, the switching process is not performed and the process returns to step SP2. 5 and 6 are flowcharts showing the interrupt processing performed by the ANC processing unit 37 separately from the CPU processing. The interrupt processing shown in FIG. 5, for example, is performed at intervals of a sampling frequency of 2.5 kHz, so-called ANC.
The adaptive control is shown.

In step SP1 of FIG. 5, the reference noise signal and the residual noise signal are taken in, and in step SP2 the filter coefficient is calculated with the coefficient value of the selected compensation filter C as an initial value, and the filter coefficient is calculated based on the LMS method. In step SP3, the filter value is corrected by using the coefficient value of the selected compensation filter B as an initial value, and the filter coefficient is corrected based on the LMS method. In step SP4, the selected adaptive digital filter coefficient value W Is calculated as an initial value, and the adaptive digital filter W is calculated.
The adaptive digital filter W is corrected based on the MS method, and anti-noise (offset sound) is generated based on the adaptive digital filter coefficient value corrected in step SP6.

The interrupt process of FIG. 6 shows, for example, a rotation speed and temperature detection operation performed at intervals of one second. The rotation speed is detected in step SP1 and the temperature is detected in step SP2. FIG. 7 is a flowchart showing an example of the evaluation function routine performed in step SP5 of FIG. In step SP1 of FIG. 7, the filter coefficient is calculated by the LMS method, and in step SP2, the sum of squares S of the filter coefficients in one loop is calculated.
(N), that is, S (n) = W ₁ ² + W ₂ ² + ... + W _n-1 ² + W _n ² is calculated, and the sum of squares S ′ (n obtained in the previous loop in step SP3 is calculated. ) Is calculated, and the deviation β is evaluated by comparing the deviation β with the reference value in step SP4, and the processing of the evaluation function ends.

Further description will be made. In an enclosed engine used outdoors, such as an engine generator, the ambient environment such as temperature changes every moment, and the wind speed of the ventilation fan also changes depending on the rotation speed of the ventilation fan. Therefore, assuming the reference temperature and the reference condition of the reference velocity of the ventilation air flowing through the ventilation section, the compensation filter B for the electroacoustic characteristics between the reference noise microphone 22 and the loudspeaker 16, and the electrical connection between the residual noise microphone 19 and the loudspeaker. Even if the compensation filter C having the acoustic characteristic is identified, the electroacoustic characteristic does not always have the optimum value.

Therefore, as shown in FIG. 1, the optimum compensation filter B coefficient value, compensation filter C coefficient value, and adaptive filter W coefficient value are previously obtained by experiments using the rotation speed of the fan and the temperature of the ventilation section as parameters. Then, it is stored in the memory 31. For example, the rotation speed of the fan is 1000r
pm, 2000 rpm, and 3000 rpm, and the temperature is divided into five types of -20 ° C, 0 ° C, 20 ° C, 40 ° C, and 60 ° C, and the filter coefficient values of these are compensated filter B, compensated filter C, and adaptive. Prepare for each filter W. In this case, a total of 3 × 5 × 3 = 45 types of filter coefficients are stored in the memory 31.

Then, which of the above-mentioned groups the detected rotational speed and temperature values are close to is determined, and each filter coefficient value of the group is transferred to the ANC processing unit 37. With this configuration, adaptive control can be performed from the coefficient value of each filter most suitable for the current condition, so that the convergence time can be shortened even with a relatively low-speed processor, and highly accurate silencing operation can be performed. Can be achieved. Next, the processing from step SP5 to step SP7 in FIG. 4 will be further described.

Step S in the flowchart of FIG.
In P4, the coefficient values of the compensation filter B, the compensation filter C, and the adaptive filter W are transferred to the ANC processing unit 37,
Adaptive control shown in is performed. Here, it is convenient to have an evaluation function that can determine whether or not the value of the adaptive digital filter 38 is actually converging so that the residual noise is minimized at the position of the residual noise microphone 19. The reason is that if the coefficient value of the adaptive filter W temporarily selected in step SP4 is inappropriate, the filter coefficient cannot be converged unless a large number of calculations are repeated in the LMS method. Rather than repeating the calculation to converge the coefficient value of the adaptive filter W to the optimum value,
This is because switching the initial value of the coefficient value of the adaptive filter W can result in shortening the time until convergence.

FIG. 8 is a diagram showing the weight value at each tap of the digital filter. The horizontal axis shows the number of taps of the digital filter and the vertical axis shows the weight value of the digital filter. The weight value takes both positive and negative values. The weight value at each tap at a certain point is shown in FIG.
, The weight value of each tap varies greatly in the first stage of adaptive control (shown by the swing width D), but the weight value of each tap hardly changes in the final stage of adaptive control ( The swing width d is shown).

In this convergence state, the sum ΣW of the filter coefficients of the digital filter becomes a certain constant value p as shown in FIG. However, since the weight value can take positive or negative values, the value fluctuates up and down around the constant value p as shown in FIG. 9 in the process of convergence. Further, when the sum of the filter coefficients is calculated, subtraction must be performed, which requires time for calculation, and when the CPU 30 having low computing ability is adopted, the convergence of the filter coefficients, that is, the followability of ANC control is also reduced. Will be done.

Therefore, considering the square value of the filter coefficient of the digital filter, each filter coefficient becomes a positive value as shown in FIG. 10, and the sum of squares of the filter coefficients also has a certain value as shown in FIG. It will converge to q. Thus, by taking the squared sum of the filter coefficients,
The degree of convergence can be made faster than simply taking the sum of the filter coefficients, and the time required for the calculation can be shortened because the subtraction does not have to be performed in the calculation of the sum.

Further, the difference β between the sum of squares S (n) of the filter coefficients of the digital filter at a certain point of time and the sum of squares S ′ (n) of the filter coefficients of the digital filters of the preceding loops is taken, and its magnitude is taken. The current state of convergence can be known by investigating. Therefore, if the difference β is large, it is determined that the selected filter coefficient W is not appropriate, and the filter coefficient W is switched in step 7 of FIG. By doing so, it is possible to suppress the occurrence of divergence of ANC control due to the inappropriate filter coefficient W becoming the initial value, and to obtain a condition with good followability in a short time.

In the calculation of the difference, in order to suppress the variation of β and obtain the integration effect, as shown in the evaluation function routine of FIG. 12, the total sum of a plurality of loops, for example, a cycle of an integer i times the filter order k is extended. A method of setting the convergence coefficient based on the difference β ′ between the sum of products Sk (n) and the sum Sk ′ (n) can also be adopted. The integer i times the filter order k is, for example, 2 if the number of filter stages is 20.
0 × i (1,2,3,4, ..., n) and 20,4
This means that the sum of the loops of 0, 60, 80, ... Is taken. In this way, it has been experimentally confirmed that the convergence is improved by taking an integer i times the filter order k.

Next, the operation of the enclosed engine shown in FIG. 3 will be described. When the engine is started, the radiator fan 11 interlocked with the crankshaft is also driven to generate cooling air indicated by the symbol M in FIG. See also noise microphone 2
A reference noise signal Xn including engine sound, muffler transmitted noise, fan wind noise, etc. is obtained from 2 and the residual noise signal en is input from the residual noise microphone 19. Then, the ANC processing section generates a canceling sound toward the inside of the duct section to reduce noise leaking from the duct outlet.

If necessary, a shielding wall 14 is provided as shown in FIG. 1, and a directional loudspeaker 16 is adopted.
By configuring the sound from the loudspeaker 16 so as not to easily enter the reference noise microphone 22, the compensation filter B is identified during system identification and the compensation filter B during ANC processing.
You can omit the calculation of
And the accuracy can be increased.

Further, since the reference noise microphone 22 is located downstream of the cylindrical muffler 12 and the radiator fan 6 in the flow of the cooling air, not only engine noise but also
The noise transmitted from the chassis surface of the muffler 12 (hereinafter referred to as muffler transmitted noise) and the wind noise of the radiator fan 11 can also be detected, and the muffler transmitted noise and the radiator fan 11 can be detected.
The wind noise can also be silenced by the loudspeaker.
Furthermore, since the cylindrical muffler 12 is provided on the downstream side of the radiator fan 11 at a position facing the suction air discharge surface, cooling air flows through the upper and lower side surfaces of the cylindrical muffler 12 to cool the muffler. . Cooling of this muffler reduces the frequency variation of muffler transmitted noise.
In the NC control, there is an advantage that the sound is easily muted. Further, since the muffler 12 is not provided in the engine power generation chamber 7 but is provided in the ascending passage 8a, the temperature rise of the engine power generation chamber 7 can be suppressed.

[0045]

[Embodiment 2] FIG. 13 is a view showing a second embodiment of the present invention, and FIG. 13 (A) is a schematic vertical sectional view showing the structure of a noise reduction device for an enclosed engine generator, and FIG. 13 (B). FIG. 13C is a left side view, and FIG. 13C is a right side view with the exhaust duct case removed. The characteristic point of the fourth embodiment as compared with the first embodiment is that the structure of the enclosed engine is changed. In this enclosure type engine generator 51, a diesel engine 3 is arranged on the right side in the figure of a soundproof case 2 composed of six rectangular parallelepiped soundproof walls, and an engine generator 4 is arranged on the left side in the figure. is there. Also, the right soundproof wall 2
The outlet 10 is opened at a substantially central position of b, and the left soundproof wall 2c
An intake port 24 is opened at a lower position of the.

An air guide plate 53 having an air outlet 52 is attached to the right soundproof wall 2b so as to cover the outlet 10 from the upper side, and an air exhaust duct case 54 is provided on the right side to accommodate the air guide plate 53. It is attached to the soundproof wall 2b. A duct outlet 55 is provided on the upper right side of the exhaust duct case 54, and a wire mesh having a predetermined exhaust area is stretched over the duct outlet 55. Inside the baffle plate 53, a cylindrical muffler 12 extending in the horizontal direction is provided.
The intake port and the muffler 12 are communicated with each other by the first exhaust pipe 20a, and the exhaust gas passing through the muffler 12 is discharged to the outside from the side surface of the exhaust duct case 34 by the second exhaust pipe 20b. A temperature sensor 32 for detecting the temperature inside the exhaust duct case is provided at a lower position of the exhaust duct case 54. A metal mesh having a predetermined exhaust area is stretched over the intake port 24.

The radiator 6 is disposed so as to face the discharge port 10, and the radiator 6 is provided with a radiator fan 11 that is driven by a fan belt in conjunction with the crankshaft. The radiator fan 11 is a fan that sucks out the air inside the soundproof case 2. Also,
Above the engine 3, an air cleaner 2 that communicates with an intake pipe
7 are provided.

Enclosed engine generator 5 according to this embodiment
1 includes an exhaust-side noise reduction device that reduces noise from the duct outlet 55. The exhaust-side noise reduction device includes a reference noise microphone 22 provided in an exhaust air guide chamber 56 that is a space surrounded by a baffle plate 53 on the downstream side of the cylindrical muffler 12.
The loudspeaker 16 provided at the upper position of the soundproof wall 2b in the exhaust duct case 54, the residual noise microphone 19 provided at the end position above the duct outlet 55, and the rotation speed of the radiator fan 11 are detected. Rotation speed sensor 33
And the temperature sensor 3 provided in the exhaust duct case 54
2, a CPU (not shown), a memory (not shown),
It is composed of an ANC processing unit (not shown).

Since the engine 3 and the generator 4 are housed in the soundproof case 2 via the antivibration rubber 57 provided at a predetermined position on the bottom wall 2d of the soundproof case 2, the engine 3
Also, the vibration of the generator 4 is reduced from being transmitted to the soundproof case 2. In addition, the air intake 2 at the upper left of the soundproof case 2
A fuel tank 25 is provided at a position where the fuel cell 4 is not closed, and fuel can be supplied from a fuel supply port 26 provided in the soundproof case upper wall 2a.

The operation of the engine generator noise reduction device configured as described above will be described. When the engine 3 of the engine generator 51 is operated and power generation is started, the radiator fan 11 that is interlocked with the crankshaft of the engine is driven to suck the outside air from the intake port 24. The sucked outside air flows through the soundproof case 2, cools the generator 4 and the engine 3, then flows through the exhaust air guide chamber 56 and the exhaust rising air passage 58 in the exhaust duct case 54, and is exhausted from the duct outlet 55. (See arrow M in the figure). It should be noted that this exhaust path constitutes the ventilation section 21.

Then, similar to the first embodiment, each filter coefficient value is selected from the memory 31 based on the temperature and the fan rotation speed, and the ANC control suitable for the environmental conditions is performed. Also in this embodiment, since the muffler 12 is provided downstream of the radiator fan 11 so as to face the radiator fan 11 and is not provided in the soundproof case 2, the muffler is canceled by the loud speaker 16. There is an advantage that the transmitted noise can be silenced, and the muffler 12 can be cooled and the temperature rise in the soundproof case 2 due to the heat of the muffler 12 can be suppressed. Further, in the structure of the first embodiment, since the duct 13 is formed on the soundproof case 2, the space in the width direction can be made compact, whereas in the structure of the second embodiment, the exhaust duct case 54 is soundproofed. Since it is provided on the side wall of the case, the space in the height direction can be made compact.

The present invention is not limited to the above-mentioned embodiments, and various design changes can be made within the scope of the present invention. Hereinafter, such an embodiment will be described. (1) It is obvious that the present invention can be widely applied to an enclosed engine device other than the engine generator. (2) In the above-mentioned embodiment, the loudspeaker 16, the reference noise microphone 22 and the residual noise microphone 19 are each one, but the loudspeaker 16, the reference noise microphone 22 and the residual noise microphone 19 are plural respectively. The present invention can be applied to the case where In this case, it is necessary to identify many electroacoustic characteristics between a plurality of microphones and loudspeakers, so that the advantage of preliminarily storing them in the ROM or the like becomes great. (3) In the above-described embodiment, the muffler transmission noise is also reduced by the ANC. However, if the exhaust gas of the muffler 12 is also discharged to the duct in the ventilation part, not only the muffler transmission noise but also the exhaust pipe 22b. Muffler sound emitted from the AN
It is possible to reduce with C.

[Brief description of drawings]

FIG. 1 is a basic block diagram of a noise reduction device for an enclosed engine generator as an embodiment of a noise reduction device for an enclosed engine according to the present invention.

FIG. 2 is a schematic block diagram showing a relationship between an ANC processing unit and an enclosed engine.

3 (A) is a vertical cross-sectional view showing the configuration of an enclosed engine to which a noise reduction device is applied, and FIG. 3 (B) is FIG.
It is a BB line cross-sectional view of (A).

FIG. 4 is a flowchart showing processing performed by a CPU.

FIG. 5 is a flowchart showing ANC control performed by an ANC processing unit.

FIG. 6 is a flowchart showing a fan rotation speed and temperature detection process.

FIG. 7 is a flowchart showing processing of an evaluation function routine.

FIG. 8 is a diagram showing weight values of a digital filter.

FIG. 9 is a diagram showing how the total sum of filter coefficients converges to a constant value.

FIG. 10 is a diagram showing a squared value of a weight value of a digital filter.

FIG. 11 is a diagram showing how the sum of squares of filter coefficients converges to a constant value.

FIG. 12 is a flowchart showing processing of another evaluation function.

13 is a diagram showing a second embodiment of the present invention, and FIG.
13A is a schematic vertical cross-sectional view showing the configuration of a noise reduction device for an enclosed engine generator, FIG. 13B is a left side view, and FIG.
(C) is a right side view of a state in which the exhaust duct case is removed.

FIG. 14 is a schematic block diagram of a conventional duct silencer that reduces air conditioning duct noise.

[Explanation of symbols]

2 ... Soundproof case, 3 ... Engine, 5 ... Compartment wall, 11 ... Radiator fan, 12 ... Cylindrical muffler, 13a ... Duct outlet, 16 ... Loud speaker, 19 ... Residual noise microphone,
21 ... Ventilation part, 22 ... Reference noise microphone, 24 ... Intake port,
31 ... Memory, 32 ... Temperature sensor, 33 ... Rotation speed sensor, 37 ... ANC processing unit, 38 ... Adaptive digital filter, 53 ... Air guide plate, 54 ... Exhaust duct case, 55 ... Duct outlet.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area G10K 11/16 G

Claims (2)

[Claims] 1. A soundproof wall (2,5) (2,53,54) surrounds the engine (3), and an outside air intake port is provided at a predetermined position of the soundproof wall (2,5,) (2,53,54). (24) and final outlets (13a) (55) are provided, and the outside air is taken in through the outside air intake (24), and the final outlets (13a) (5
A ventilation part (21) for exhausting ventilation air from the (5) is provided, and the final outlet (13a) from the engine (3) in the ventilation part (21).
A suction fan that sucks out the hot air of the engine (3) to the (55) side
(11) is provided, reference noise detection means (22) for detecting noise including engine sound and fan wind noise is provided at a predetermined position of the ventilation section, and the ventilation section (21) is located near the final discharge port (13a) (55). The residual noise detection means (19) is provided, and the ventilation part (2) provided with the residual noise detection means (19) is located downstream of the position of the ventilation part (21) provided with the reference noise detection means (22).
1) A canceling sound generation means (16) is provided at a predetermined position upstream of the position, and a temperature sensor (32) for detecting the temperature in the ventilation part (21) and a fan rotation for detecting the rotation speed of the suction fan (11) Number sensor (3
3) is provided, and at least the canceling sound generating means (16) and the residual noise detecting means (19) are provided.
The electroacoustic characteristics of the ventilation section (21) including the electroacoustic characteristics are obtained in advance by using the temperature in the ventilation section (21) and the fan rotation speed as parameters, and a storage means (31) is provided for storing the noise reduction processing operation. The electroacoustic characteristics of the ventilation part (21) stored in the storage means (31) are selected based on the detected temperature and the fan rotation speed, and the selected electroacoustic characteristics and reference noise detection means (22) are selected. Based on the reference noise signal detected from the residual noise signal detecting means (19) and the residual noise signal detected from the residual noise signal detecting means (19), a canceling sound is generated so as to reduce noise at the final outlets (13a) (55). A noise reduction device for an enclosed engine, characterized in that the ANC control means (37) for driving the canceling sound generation means (16) is provided. 2. A storage means (31) stores a filter coefficient value of an adaptive digital filter (38) that finally determines the characteristics of the canceling noise with temperature and fan rotation speed as parameters.
The noise reduction device for an enclosed engine according to claim 1, wherein the electroacoustic characteristic selected by the ANC control means (37) includes a filter coefficient value of the adaptive digital filter (38).