JP3250001B2 - 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, 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 of 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 (hereinafter referred to as ANC) has been put to practical use in which noise is emitted by canceling out noises having the same amplitude and opposite phase to each other to reduce noise by an interference effect of sound waves. It has been actively researched in various fields. According to ANC, around 100 Hz-500
Since it has an effect of reducing low-frequency noise in the vicinity of Hz, it is used to reduce the muffled sound of a passenger compartment, the noise of an air-conditioning duct, and the like (Japanese Patent Publication Nos. 2-503219 and 3-204354). etc).

FIG. 14 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 has 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 become a residual sound, and the residual sound is detected by the residual noise microphone 104 so that the residual sound is minimized. ANC control unit 106
By sequentially updating the adaptive digital filter coefficients of the above, 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, a compensation filter B for the electroacoustic characteristics between the reference noise microphone 102 and the loudspeaker 105 and a compensation filter C for the electroacoustic characteristics between the reference noise microphone 102 and the loudspeaker 105 Is required in advance, a process called system identification is required. Then, at the time of the actual silencing operation, the adaptive digital filter coefficients of the ANC control unit 106 are sequentially updated based on the compensation filters B and C obtained by the system identification, thereby canceling out the radiated sound from the loudspeaker 105. Changes sound and reduces noise.

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

[0006]

However, in a closed space such as a car or a cabin of a cabin, a configuration example in which ANC is applied, a device for reducing exhaust noise of a muffler, and the like have been proposed. At present, there is no disclosure of an effective device configuration for reducing noise by applying the present invention.

In an engine used outdoors, such as an engine generator, the surrounding environment such as temperature changes every moment, and the load of the engine and the rotation speed of the ventilation fan also change. Normal. Therefore, the coefficient value of the compensation filter B and the coefficient value of the compensation filter C at the time of system identification often deviate significantly from the optimal electroacoustic characteristics at the time of actually performing the silencing operation.

If the compensation filter coefficient value set at the time of system identification is used in a state outside the reference state at the time of system identification, the value may exceed the adaptive range of the adaptive filter. In this case, since the adaptive filter cannot converge well, the noise reduction of the enclosed engine is reduced, and in severe cases, the noise is amplified. To solve this problem, it is conceivable to increase the calculation speed of the filter coefficient as much as possible to improve the followability of the system.However, a high-speed dedicated processor capable of performing a large amount of operations within the sampling time is required, and the There is a problem that becomes expensive.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-mentioned problems. It is intended to provide a noise reduction device.

[0010]

According to a first aspect of the present invention, there is provided a noise reduction device for an enclosed engine, wherein the engine is surrounded by a soundproof wall, and an outside air intake is provided at a predetermined position on the soundproof wall. An exhaust port is provided, a ventilator is provided to take in outside air from the outside air intake port, and exhausts ventilation air from the final exhaust port.A draft fan is provided inside the ventilator to draw the engine's hot air from the engine to the final exhaust port side. A reference noise microphone for detecting noise including engine noise and fan wind noise is provided at a predetermined position, a residual noise microphone is provided near the final exhaust port of the ventilation unit, and a downstream side from the ventilation unit position where the reference noise microphone is provided. The loud speed at a predetermined position upstream of the ventilation section where the residual noise microphone is located .
Mosquitoes provided, a temperature sensor for detecting the temperature in the ventilation part, and the fan speed sensor for detecting the rotational speed of the suction fan, and a central processing unit for processing the entire control, the ANC processing
ANC control means for controlling and storing each filter coefficient value
Storage means, and the ANC control means serves as a control sound.
An adaptive digital filter that generates antiphase waveforms and a residual
Includes compensation filter between noise microphone and loudspeaker
The storage means stores the number of rotations of the fan,
Optimal compensation filter coefficients with temperature as a parameter
Values and coefficient values of the adaptive digital filter
The central processing unit detects the detected rotation.
Of the compensation filter in the storage means based on the number and temperature.
Numbers, select the coefficient values of the adaptive digital filter, ANC
The control means controls the coefficient value of the selected compensation filter,
The initial value is the coefficient value of the digital filter,
Based on those coefficient values, the reference noise signal detected from the reference noise detection microphone , and the residual noise signal detected from the residual noise microphone , a canceling sound is generated so as to reduce the noise at the final outlet. It characterized the Turkey to drive the loudspeaker.

According to a second aspect of the present invention, the central processing unit detects the number of revolutions and temperature during operation.
And the number of rotations and temperature detected.
The coefficient value of the compensation filter in the
Step of selecting the filter coefficient value and setting it to the initial value
And the value of the selected adaptive desilter filter actually remains
Converge to minimize residual noise at the noise microphone position
A function that calculates an evaluation function that can determine whether
Adaptive digital filter based on Tep and its evaluation function
Step to determine whether the filter coefficient of the
And turn off the filter coefficients of the adaptive digital filter.
If it is determined that replacement is necessary,
Switch the filter coefficients of the
Digital filter as initial value of adaptive digital filter
Set the filter coefficient of the adaptive digital filter to
If it is determined that it is not necessary, the switching process is not performed and the
The method is characterized by returning to the step of detecting the number of turns and the temperature . The noise reduction device for an enclosed engine according to claim 3 is configured as described above.
The evaluation function is the filter coefficient 2 of the adaptive digital filter.
The sum of the powers S (n) and the filter of the digital filter of the previous loop
The difference is the difference β of the square sum S ′ (n) of the Lutha coefficients.
And The noise reduction device for an enclosed engine according to claim 4 is:
The evaluation function has a period equal to an integer i times the filter order k.
Difference β ′ between the sum of product sum Sk (n) and sum Sk ′ (n)
It is characterized by being.

[0012]

According to the noise reduction device for an enclosed engine of the first aspect, if the temperature changes, the speed at which sound is transmitted also changes, and if the rotation speed of the ventilation fan changes, the speed of the ventilation wind flowing through the ventilation section also increases. It is necessary to consider the effect of the canceling noise as well, but the storage means stores the fan speed,
The optimal compensation filter
The coefficient value and the coefficient value of the adaptive digital filter are
The central processing unit detects
Of the compensation filter in the storage means based on the number of turns and the temperature.
Select the coefficient value and the coefficient value of the adaptive digital filter, and
C control means: the coefficient value of the selected compensation filter;
Since the coefficient values of the adaptive digital filter and the initial value may be the initial value of the adaptive control filter coefficient values corresponding to the state when to be muted. Therefore, ene
Inexpensive even if temperature and engine speed change during gin operation
Sufficient noise reduction performance can be obtained with a simple device configuration.

According to the second aspect of the present invention, when selecting the filter coefficient value of the adaptive digital filter which finally determines the characteristic of the canceling sound, the convergence of the filter coefficient of the adaptive digital filter is determined. The selection can be performed accurately by employing the evaluation function to be checked. A noise reduction device for an enclosed engine according to claim 3,
According to the noise reduction device for an enclosed engine of claim 4,
ANC due to non-initial filter coefficients
Suppress the occurrence of control divergence and set conditions with good tracking
You can ask in the meantime.

[0014]

As described above, according to the first aspect of the present invention, the following specific effects can be obtained. (B) Filter staff corresponding to the state when trying to mute sound
A numerical value can be used as the initial value of the adaptive control, the time required for convergence to a filter coefficient capable of silencing can be reduced, and ANC control with good tracking performance can be realized. (B) Not only the temperature but also the filter coefficient value in consideration of the speed of the ventilation wind generated by the ventilation fan in the enclosed engine is stored in the storage means, so that the noise reduction performance of the enclosed engine is enhanced. be able to. (C) Since the filter coefficient values required for system identification are stored in the storage means in advance, the system identification process at the time of engine start is not required, and the time required for system identification is reduced, and the easy-to-use surrounding engine is used. It can be.

According to a second aspect of the present invention, in addition to the effects of the first aspect of the invention, an adaptive digital signal that finally determines the characteristic of the canceling sound is provided.
When selecting the filter coefficient value of the filter,
Evaluation function for checking the convergence of filter coefficients of digital filters
By adopting, the selection can be made accurately
It has a unique effect that it can be cut. Claim 3 of the invention, claim
The invention of claim 4 has the effect of the invention of claim 2,
A due to an inappropriate filter coefficient being the initial value
Suppress the occurrence of divergence in NC control,
It has a unique effect that it can be obtained in a short time
You.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a basic block diagram of a noise reduction device of an enclosed engine generator as one embodiment of the noise reduction device of the enclosed engine according to the present invention, and FIG. 2 is a schematic block diagram showing a relationship between the ANC processing unit and the enclosed engine. FIG.

The noise reduction device includes a central processing unit (CPU 30) for processing the entire control, an ANC processing unit 37 for controlling the ANC processing, a memory 31 (ROM) storing each filter coefficient value, and a CPU 30 for detecting the noise. 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 residual noise signal to processing unit 37
9 and a loudspeaker 16 for generating a cancellation sound based on an anti-noise signal from the ANC processing unit 37. In the memory 31, a filter coefficient value is stored for each of the compensation filter B, the compensation filter C, and the adaptive filter W corresponding to the combination of the temperature and the fan rotation speed. FIG.
(A) is a longitudinal sectional view showing a configuration of an enclosed engine to which the noise reduction device is applied, and FIG. 3 (B) is a transverse sectional view taken along the line BB of FIG. 3 (A).

The enclosed engine generator 1 has a diesel engine 3 disposed substantially at the center of a soundproof case 2 and a generator 4 disposed 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 a left side surface of the partition wall 5. It is partitioned into an exhaust passage 8 and a side space 9.

The exhaust passage 8 comprises an upward 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 radiator fan 11 of a suction type is attached to the radiator 6, and the radiator fan 11 is driven in conjunction with a crankshaft of the engine 3 by a fan belt and a pulley. The drive shaft for driving the radiator fan 11 is provided with a rotation speed sensor 33 for detecting 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 speed may be detected from a 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, so that the draft of the radiator fan 11 flows through the side surface of the cylindrical muffler 12 to the exhaust passage 8b. is there. An exhaust port of the engine is communicated with the muffler 12 by an exhaust pipe 20a bypassing the side space 9, and exhaust gas from the muffler 12 is communicated to the outside through an exhaust pipe 20b through a 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 on the radiator 6 side and a duct outlet 13a on the opposite side is fixed. Is provided with a shielding wall 14 that partitions the duct 13 into two rooms in the horizontal direction. The discharge port 10 is covered by the shielding wall 14 about halfway.

A loudspeaker 16 having directivity with a loudspeaker surface facing the duct outlet 13a is disposed in an upper room (referred to as an upper duct chamber 15) defined by the shielding wall 14. The lower room (lower duct room 17)
) Has a function of guiding the cooling air passing through the rising passage 8a and the exhaust passage 8b toward the duct outlet 13a. The loudspeaker 16 is surrounded by a unit case 18 so that the loudspeaker 16 can be detachably exchanged.
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. 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 downstream of the muffler 12, and the engine noise, the wind noise of the radiator fan 11, the muffler 12
(Hereinafter referred to as muffler transmitted noise) is detected and input to the ANC controller 23.

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

The noise reduction device comprises a reference noise microphone 22, a directional loudspeaker 16, a residual noise microphone 19, an ANC processing unit 37, a CPU 30, and a memory 31, as shown in FIG. Part 37, CP
As shown in FIG. 3A, the U30 and the memory 31 are disposed at a lower position of the soundproof case 2 so as to be surrounded by a 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
It is configured to include an 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. The electroacoustic characteristic B determined by the 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 calculated by the following mathematical formula 1.

[0027]

(Equation 1)

Where Wn: adaptive filter coefficients (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 reduction device for the enclosed engine will be described with reference to FIGS. 1 to 3 and a flowchart shown below. FIG. 4 is a flowchart 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 according to changes in the temperature and the fan speed are determined by experiments for each model of the enclosed engine. Initial setting for obtaining and storing it in the memory is performed, and the rotational speed is detected from the rotational speed sensor 33 in step SP2. If it is determined that the rotational speed is within the rotational speed in the memory 31, the temperature sensor 3 is determined in step SP3.
2, the temperature is detected within the memory 31. If it is determined that the temperature is within the temperature in the memory 31, the compensation filter B, the compensation filter C,
Select adaptive digital filter W and set compensation filter B to A
The correction filter 40 of the NC processing unit 37 and the compensation filter C
Is set to the correction filter 41 of the ANC processing unit 37, and the adaptive digital filter W is set to the initial value of the adaptive digital filter 38.

At step SP5, an evaluation function is calculated. At 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. If it is determined that is necessary, step SP
At 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 rotation speed cannot be detected normally in step SP2 and the temperature cannot be detected normally in step SP3, an abnormal process is performed in step SP8 and the process ends. If it is determined in step SP6 that the correction of the filter coefficient of the adaptive digital filter W is not necessary, the process returns to step SP2 without performing the switching process. FIGS. 5 and 6 are flowcharts showing interrupt processing performed by the ANC processing unit 37 separately from the CPU processing. The interrupt processing shown in FIG. 5 is performed at intervals of a sampling frequency of 2.5 kHz, for example, so-called ANC.
4 illustrates adaptive control.

In step SP1 of FIG. 5, the reference noise signal and the residual noise signal are fetched. In step SP2, the filter coefficient is calculated using 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 coefficient is calculated 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 used as an initial value to calculate the adaptive digital filter W, and at step SP5, L
The adaptive digital filter W is corrected based on the MS method, and anti-noise (cancellation sound) is generated based on the adaptive digital filter coefficient value corrected in step SP6.

The interrupt processing in 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 coefficients are calculated by the LMS method, and in step SP2, the square sum 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, and the sum of squares S ′ (n ) Is calculated, and by comparing the deviation β with a reference value in step SP4, the deviation β is evaluated, and the processing of the evaluation function ends.

Further description will be given. In an enclosed engine used outdoors, such as an engine generator, the surrounding environment such as temperature changes every moment, and the wind speed of the ventilation fan also changes according to the rotation speed of the ventilation fan. Therefore, assuming the reference conditions of the reference temperature and the reference speed of the ventilation wind flowing through the ventilation section, the compensation filter B of the electroacoustic characteristics between the reference noise microphone 22 and the loudspeaker 16 and the electric filter between the residual noise microphone 19 and the loudspeaker are used. Even if the compensation filter C having the acoustic characteristic is identified, the electric acoustic characteristic does not always have an optimum value.

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

Then, it is determined which of the above set the values of the detected rotation speed and temperature are close to, and the filter coefficient values of the close set are transferred to the ANC processing unit 37. With this configuration, adaptive control can be performed from the coefficient value of each filter that is most suitable for the current conditions, so that the convergence time can be shortened even with a relatively low-speed processor, and a highly accurate noise reduction 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,
Is performed. Here, it is convenient if there is an evaluation function that can determine whether the value of the adaptive digital filter 38 is actually converging so as to minimize the residual noise 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 coefficients cannot be converged unless a large number of calculations are repeated in the LMS method. Rather than repeating the operation to converge the coefficient value of the adaptive filter W to the optimal one,
This is because switching the initial value of the coefficient value of the adaptive filter W can shorten the time until convergence as a result.

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. FIG. 8 shows the weight value of each tap at a certain point in time.
, The weight value of each tap greatly varies at the first stage of the adaptive control (denoted by the swing width D), but the weight value of each tap hardly changes at the final stage of the adaptive control ( (Indicated by the swing width d).

In this convergence state, as shown in FIG. 9, the sum ΣW of the filter coefficients of the digital filter becomes a certain constant value p. However, since the weight value can take a plus or minus value, the value fluctuates up and down around the fixed value p as shown in FIG. 9 in the process of convergence. Further, when calculating the total sum of the filter coefficients, the subtraction must be performed, so that it takes a long time to perform the calculation. Will do.

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 is also a certain value as shown in FIG. will converge to q. Thus, by taking the sum of the squares 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 reduced since no subtraction is required 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 in time and the sum of squares S ′ (n) of the filter coefficients of the digital filter of the previous loop is taken, and the magnitude is calculated. By examining it, the current convergence state can be known. 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. In this way, it is possible to suppress the occurrence of the divergence of the ANC control due to the inappropriate filter coefficient W becoming the initial value, and it is possible 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 an integration effect, as shown in the evaluation function routine of FIG. 12, the sum of a plurality of loops, for example, over a period of an integer i times the filter order k. A method of setting a 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
.. Means the sum of loops of 0, 60, 80,... It has been experimentally confirmed that the convergence is improved by taking the 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 linked to the crankshaft is also driven to generate cooling air indicated by a reference symbol M in FIG. Reference noise microphone 2
2, a reference noise signal Xn including an engine sound, a muffler transmitted noise, a wind noise of a fan, etc. is obtained, and a residual noise signal en is input from the residual noise microphone 19. Then, the ANC processing unit generates a canceling sound toward the inside of the duct unit 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 employed.
By configuring so that the sound from the loudspeaker 16 does not easily enter the reference noise microphone 22, identification of the compensation filter B at the time of system identification and compensation filter B at the time of ANC processing are performed.
Can be omitted, the adaptive speed in silencing,
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 the engine noise but also the noise is reduced.
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.
Wind noise can also be silenced by the loudspeaker.
Further, 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, the cooling air flows on the upper and lower side surfaces of the cylindrical muffler 12, and the muffler can be cooled. . By cooling the muffler, the frequency change width of the muffler transmitted noise is reduced, and A
There is an advantage that noise can be easily eliminated in the NC control. Furthermore, since the muffler 12 is not provided in the engine power generation chamber 7 but is provided in the rising 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 longitudinal sectional view showing a configuration of a noise reduction device of an enclosed engine generator, and FIG. 13 (B). Is a left side view, and FIG. 13 (C) is a right side view with the exhaust duct case removed. The feature of the fourth embodiment compared to the first embodiment is that the structure of the enclosed engine is changed. The enclosed engine generator 51 is configured such that the diesel engine 3 is disposed on the right side in the figure of the soundproof case 2 including six soundproof walls of a rectangular parallelepiped shape, and the engine generator 4 is disposed on the left side in the figure. is there. Also, the right soundproof wall 2
b, the discharge port 10 is opened at a substantially central position, and the left soundproof wall 2c is opened.
The intake port 24 is opened at the lower position of.

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 above, 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 at the upper right side of the exhaust duct case 54, and a wire mesh having a predetermined exhaust area is stretched at the duct outlet 55. A cylindrical muffler 12 extending in the horizontal direction is provided in the air guide plate 53, and the engine 3
And the muffler 12 are communicated with each other by a 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 a 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. Note that a wire 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. The radiator 6 is provided with a radiator fan 11 which is driven by a fan belt in conjunction with a crankshaft. The radiator fan 11 is a fan that sucks air from the soundproof case 2. Also,
Above the engine 3, an air cleaner 2 communicating with the intake pipe
7 are provided.

The 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 downstream of the cylindrical muffler 12 and in an exhaust wind guide chamber 56 which is a space surrounded by a wind guide plate 53.
And a loudspeaker 16 provided at an upper position of the soundproof wall 2b in the exhaust duct case 54, a residual noise microphone 19 provided at an end position above the duct outlet 55, and a rotation speed of the radiator fan 11 are detected. Rotating speed sensor 33
And the temperature sensor 3 provided in the exhaust duct case 54.
2, a CPU (not shown), a memory (not shown),
And an ANC processing unit (not shown).

Since the engine 3 and the generator 4 are accommodated in the soundproof case 2 via the vibration isolating rubber 57 provided at a predetermined position on the bottom wall 2d of the soundproof case 2, the engine 3
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
A fuel tank 25 is provided at a position where the fuel tank 4 is not closed, and fuel can be supplied from a fuel supply port 26 provided in the upper wall 2a of the soundproof case.

The operation of the engine generator noise reduction device having the above configuration will be described. When the engine 3 of the engine generator 51 is operated and power generation is started, the radiator fan 11 linked to the crankshaft of the engine is driven, and outside air is sucked from the intake port 24. The inhaled outside air flows through the soundproof case 2, cools the generator 4 and the engine 3, and 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). Note that this exhaust path constitutes the ventilation section 21.

Then, in the same manner as in the first embodiment, each filter coefficient value is selected from the memory 31 based on the temperature and the number of rotations of the fan, and ANC control suitable for 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 12 is canceled out by the loudspeaker 16. There is an advantage that the transmitted noise can be reduced, and the temperature of the muffler 12 can be prevented from rising due to the cooling of the muffler 12 and the heat of the muffler 12. Further, in the configuration 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. On the other hand, in the configuration of the second embodiment, the exhaust duct case 54 is soundproof. 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 embodiment, and various design changes can be made without departing from the scope of the present invention. Hereinafter, such an embodiment will be described. (1) It is clear that the present invention can be widely applied to an enclosed engine device other than the engine generator. (2) In the above embodiment, the loudspeaker 16, the reference noise microphone 22, and the residual noise microphone 19 are each one. However, the loudspeaker 16, the reference noise microphone 22, and the residual noise microphone 19 are each provided in a plurality. The present invention can also 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 storing the characteristics in a ROM or the like in advance increases. (3) In the above-described embodiment, the muffler transmission noise is configured to be reduced by the ANC. However, if the exhaust gas of the muffler 12 is also output to the duct in the ventilation section, not only the muffler transmission noise but also the exhaust pipe 22b is provided. Muffler sound emitted from
C can reduce it.

[Brief description of the drawings]

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

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

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

FIG. 4 is a flowchart illustrating a process performed by a CPU.

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

FIG. 6 is a flowchart showing a process of detecting a fan speed and a temperature.

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

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

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

FIG. 10 is a diagram illustrating a square 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 illustrating processing of another evaluation function.

FIG. 13 is a diagram showing a second embodiment of the present invention, and FIG.
13A is a schematic longitudinal 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 in a state where the exhaust duct case is removed.

FIG. 14 is a schematic block diagram of a conventional duct silencer for reducing air conditioning duct noise.

[Explanation of symbols]

Reference numeral 2 denotes a soundproof case, 3 denotes an engine, 5 denotes a partition wall, 11 denotes a radiator fan, 12 denotes a cylindrical muffler, 13a denotes a duct outlet, 16 denotes a loudspeaker, and 19 denotes a residual noise microphone.
21: ventilation section, 22: reference noise microphone, 24: intake port,
30 central processing unit (CPU) 31 memory 32
Temperature sensor, 33: rotation speed sensor, 37: ANC processing unit, 38: adaptive digital filter, 41: compensation filter
C , 53: air guide plate, 54: exhaust duct case, 55: duct outlet.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FIG10K 11/16 G (58) Investigated field (Int.Cl. ⁷ , DB name) F01N 1/00 F01P 5/06 511 F02B 77 / 13 G10K 11/16 G10K 11/178

Claims (4)

(57) [Claims] The engine (3) is surrounded by a soundproof wall (2,5) (2,53,54), and an outside air intake is provided at a predetermined position of the soundproof wall (2,5,) (2,53,54). (24) and a final discharge port (13a) (55), and outside air is taken in from the outside air intake port (24), and the final discharge port (13a) (5
A ventilation section (21) for exhausting ventilation air from 5) is provided, and the final exhaust port (13a) from the engine (3) in the ventilation section (21)
A suction fan that sucks the heat of the engine (3) on the (55) side
(11), and a reference noise microphone (22) for detecting noise including engine noise and fan wind noise at a predetermined position in the ventilation section, which remains near the final outlet (13a) (55) of the ventilation section (21) Noise My
A microphone (19) is provided downstream of the position of the ventilation unit (21) where the reference noise microphone (22) is located, and upstream of the position of the ventilation unit (21) where the residual noise microphone (19) is located. the loudspeaker (16) provided at a predetermined position, a temperature sensor for detecting the temperature in the ventilation part (21) (32), a fan speed sensor for detecting the rotational speed of the suction fan (11)
(33) , a central processing unit (30) for processing the entire control, and AN
ANC control means (37) for controlling the C processing,
Storage means (31) for storing numerical values; and an ANC control means (37) for generating an antiphase waveform serving as a control sound.
Adaptive digital filter (38) and a residual noise microphone (1
9) and a compensation filter (41) between the loudspeakers (16)
The storage means (31) stores the number of rotations of the fan and the temperature of the ventilation section.
As the parameters, the optimal coefficient value of the compensation filter (41),
The coefficient value of the adaptive digital filter (38) is determined in advance by experiments.
The central processing unit (30) operates based on the detected rotation speed and temperature.
Coefficient value of the compensation filter (41) in the storage means (31).
ANC control means (37) selects the coefficient value of the digital filter (38), and the ANC control means (37) selects the selected compensation filter (4).
Initialize the coefficient value of 1) and the coefficient value of the adaptive digital filter (38).
Values, their coefficient values, and the reference noise detection
Reference noise signal is detected from the click (22), and the residual noise Ma
On the basis of the detected residual noise signal from the microphone (19), Turkey to drive the loudspeaker (16) as the final discharge port (13a) (55) to generate canceling sound to reduce noise < A noise reduction device for an enclosed engine. 2. The central processing unit (30) rotates during operation.
Detecting the number of revolutions and temperature, and detecting the number of revolutions and temperature.
Coefficient of the compensation filter (41) in the storage means based on the degree
Value and coefficient value of the adaptive digital filter (38).
Setting the value and the selected adaptive digil
Filter (38) actually remains at the position of the residual noise microphone (19)
Determine whether you are heading for convergence to minimize noise.
A step of calculating a distinguishable evaluation function, and the evaluation function
Based on the filter coefficients of the adaptive digital filter (38)
Determining whether switching is necessary or not, and
It is necessary to switch the filter coefficient of the digital filter (38)
Is determined, the filter of the adaptive digital filter (38) is
Switch the adaptive digital filter
Filter (38) as the initial value of the adaptive digital filter (38).
Correction of the filter coefficient of the adaptive digital filter (38)
If it is determined that is not necessary, the switching process is not performed,
The noise reduction device for an enclosed engine according to claim 1 , wherein the process returns to the step of detecting the number of revolutions and the temperature . 3. The adaptive digital filter according to claim 2, wherein the evaluation function is an adaptive digital filter.
The sum of squares S (n) of the filter coefficients of (38) and the sum of squares S '(n) of the filter coefficients of the digital filter of the previous loop
The noise reduction device for an enclosed engine according to claim 2, wherein the difference β is: 4. The method according to claim 1, wherein the evaluation function is a sum of product sum Sk (n) and a sum Sk ′ over an integer i times cycle of the filter order k.
The noise reduction device for an enclosed engine according to claim 2, wherein the difference is β 'from (n).