JPH05289677A - Active type noise controller - Google Patents

Abstract

PURPOSE:To perform excellent noise reduction control by obtaining high coherence between a noise transmitted from an air blower and a reference signal required for active control. CONSTITUTION:A microphone 21 which detects the noise generated by the fan blades of the air blower 20 and supplies it as a reference signal (x) to a controller is provided inside the rotary shaft 31 of an electric motor 30 which drives and rotates the fan blades 23. The rotary shaft 31 is hollow, and a cord shaft 35 is arranged inside it relatively rotatably on the rotary shaft 31 through bearings 36 and 37, and the microphone 21 is fixed to the tip part of the cord shaft 35. The output of the microphone 21 is supplied to the controller through the cord in the cord shaft 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control device for reducing noise by interfering control noise generated from a control sound source with noise generated from a blower,
In particular, in a device that generates a control sound based on a reference signal representing the noise generation state of a blower, a reference signal with a large coherence with the noise generation state is detected, and good noise reduction control can be performed. is there.

[0002]

2. Description of the Related Art Like an air conditioner applied to a vehicle, it is used not only for stable heat load, but also for transient conditions such as rapid cooling from hot summer in the summer and rapid heating without warming up in winter. In an air conditioner that requires consideration of the defroster function and the like in an extremely cold region, a large load is required for the blower, which is a large noise source.

As a conventional active noise control device for reducing the noise emitted from a blower, Japanese Patent Laid-Open No. 61-
Japanese Unexamined Patent Publication No. 247509 (first conventional example), Japanese Patent Laid-Open No. 62-56
Japanese Patent Laid-Open No. 995 (second conventional example) and the like, and these conventional active noise control devices generate a control sound for canceling the noise based on a reference signal representing the noise generation state of the blower. Is configured to generate.

[0004]

However, in the above-mentioned conventional active noise control device, the device for detecting the noise generation state of the blower in order to generate the reference signal is the first one.
In the conventional example, since it was arranged in the inner wall of the duct in the vicinity of the blower, and in the second conventional example, it was arranged in the vicinity of the inside air intake, which is one of the noise sources, the coherence between the actual noise generation state and the generated reference signal. However, there is a problem in that the noise reduction control cannot be performed with high accuracy.

That is, since the noise generated by the blower is distributed over the entire area of the rotating blades, even if the sound pressure is measured at one point as in the first conventional example or the second conventional example, the noise characteristics of the entire noise source are increased. Is not detected, and the noise component increases as the distance from the noise source increases. Further, the detection device simply arranged in the casing detects a signal with many errors under the influence of the pulsating flow of air, and the detection device is arranged on the inner wall of the duct as in the first conventional example. If this happens, the frequency characteristics of the wall forming the duct whose main component is low-frequency vibration will be affected.

The present invention has been made by paying attention to the unsolved problem of the conventional technique as described above, and by generating a reference signal having high coherence, active noise reduction control can be performed with high accuracy. It is an object of the present invention to provide a type noise control device.

[0007]

In order to achieve the above object, the invention according to claim 1 is a control sound source capable of generating a control sound in a space where noise is transmitted from a blower, and a noise generation state of the blower. Noise detection state detecting means for detecting the noise and outputting it as a reference signal, residual noise detecting means for detecting residual noise at a predetermined position in the space, and noise in the space is reduced based on the reference signal and the residual noise. In the active noise control device including the active control means for driving the control sound source as described above, the noise generation state detection means is provided on the rotary shaft of the motor for driving the blower.

According to a second aspect of the present invention, in the above-mentioned first aspect of the invention, the rotating shaft of the motor for driving the blower is hollow, and the noise generating state detecting means is provided inside the hollow rotating shaft. did. According to a third aspect of the present invention, in the above-mentioned second aspect of the invention, an end of the rotary shaft of the motor for driving the blower is raised in the axial direction from the end and is continuous in the circumferential direction. Surrounded by a section.

Further, in the invention described in claim 4, in the invention described in claim 2, a streamline type cap is attached to an end portion of a rotary shaft of a motor for driving the blower.

[0010]

Since the noise generated by the blower as a noise source is generated in the entire circumferential direction of the blades of the blower, the noise generation state detecting means is provided on the shaft of the motor for driving the blower as in the invention of claim 1. When provided, the noise generation state detection means,
The noise characteristics of the entire noise source can be detected without causing a significant increase in the noise component because the noise source is located equidistant from the entire noise source spreading in the circumferential direction and is located at a short distance from the noise source.

Particularly, if the rotating shaft of the motor is hollow and the noise generating state detecting means is arranged inside the rotating shaft as in the second aspect of the invention, the noise source spreading in the circumferential direction is further expanded. They will be located exactly equidistant and will be less susceptible to the pulsating flow of air. Then, like the invention described in claim 3, in the invention described in claim 2, the end portion of the rotation shaft of the motor is surrounded by an annular ridge portion that is axially raised from the end portion and continuous in the circumferential direction. Then, the inside surrounded by the raised portion becomes a so-called dead water region in which the movement of air does not occur, so that the noise generation state detection means is less susceptible to the pulsating flow of air.

Further, according to the invention of claim 4, the streamlined cap attached to the end of the rotary shaft of the motor has a small resistance to the pulsating flow of air, and therefore is disposed inside the rotary shaft of the motor. The noise generation state detection means installed is
It becomes less susceptible to the pulsating flow of air.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views showing a first embodiment of the present invention, in which the active noise control device according to the present invention is transmitted from a blower of an air conditioning system for a vehicle to a vehicle interior. It is applied to a device for reducing noise.

First, the structure will be described. FIG. 1 is a block diagram showing the overall configuration of the active noise control device 1. In a vehicle interior 2 as a space where noise is transmitted from a blower 20, M loudspeakers LS as control sound sources are provided.
₁ , LS ₂ , ..., LS _M and L microphones MP ₁ , MP ₂ , ..., MP _L as residual noise detecting means are arranged at predetermined positions, respectively, and the microphones MP ₁ , MP ₂ are arranged. , ..., residual noise signals e ₁ , e ₂ , ..., e _L detected as sound pressure by MP _L are supplied to a controller 10 as an active control means composed of a microcomputer, necessary interface circuits, memories and the like. Has been done.

Further, the controller 10 includes a blower 20.
As a noise generation state detection means for detecting noise generated in
The reference signal x, which is the output of the microphone 21 of
Has been. Then, the controller 10 outputs the reference signal x
Fold and loudspeaker LS₁~ LS_MTo drive
Drive signal y₁~ Y_MGenerate a variable filter coefficient
M adaptive digital filters W_m(M = 1, 2, ...,
M) and each loudspeaker LS₁~ LS_MAnd micro
Phone MP₁~ MP_LThe transfer function between
L × M transfer function filters modeled in the form of answer function
C ^_lm(L = 1, 2, ..., L) and each microphone M
P₁~ MP_LResidual noise signal e supplied from ₁~ E_LOver
And the reference signal x for each transfer function filter C ^_lmValue processed by
r_lmAdapted to reduce the noise in the passenger compartment 2
Digital filter W_mEach filter coefficient W of_mi(I = 0,
1, ..., I-1: I is an adaptive digital filter W_mThe
It is the number of hops. ) Updating filter coefficient updating unit 11
And have.

Here, if the reference signal at the sampling time n is x (n), the adaptive digital filter W _m
The drive signal y _m (n) generated in (1) is expressed by the following equation (1). Then, in this embodiment, the filter coefficient W _mi of the adaptive digital filter W _m is set to the least mean square algorithm (LMS algorithm: specifically, one of the steepest descent methods).
Filtered-X LMS algorithm).

That is, the noise (primary sound) transmitted from the blower 20 into the vehicle interior 2 is d (n), and the transfer function filter C ^ _lm.
Each filter coefficient of C ^ _lmj (j = 0, 1, ..., J−
1: J is the number of taps of the digital filter C ^ _lm . ), The following equation (2) is established. Then, the evaluation function Je is And

The LMS algorithm finds the filter coefficient W _mi that minimizes the evaluation function Je. Specifically, the filter coefficient W _mi is updated with a value obtained by partially differentiating the evaluation function Je with respect to each filter coefficient W _mi. To do. Therefore, from the above equation (3), From the above formula (2), Since the right side of the equation (5) is the value r _lm (n) obtained by convolving the reference signal x (n) with the transfer function filter C ^ _lm , the filter coefficient W _mi is updated by the following (6 ) It becomes like a formula.

[0019] Note that α is a coefficient called a convergence coefficient and is involved in the speed at which the filter converges optimally and its stability.

That is, the filter coefficient updating unit 11 updates the filter coefficient W _mi of the adaptive digital filter W _m based on the above equation (6). FIG. 2 is a cross-sectional view showing the configuration of the blower 20 included in the vehicle air conditioning system. That is, the blower 20 is a known centrifugal blower, and a fan blade 23 that rotates around an axis extending in the vertical direction in the drawing is provided in the casing 22 thereof.

An air discharge port 24 is formed in the casing 22 so as to face the outer peripheral surface of the fan blade 23 on the air discharge side. A heater unit (not shown) or a downstream side of the air discharge port 24 is provided. An air conditioner such as a cooler unit is arranged, and the downstream side of the air conditioner communicates with a nozzle that supplies conditioned air into the vehicle interior 2 through a duct or the like not shown.

An air guide plate 22a is formed on the inner surface of the casing 22 to guide the air toward the upper end surface of the fan blade 23, which is the air intake side. further,
The casing 22 on the upstream side of the air guide plate 22a is formed with an outside air introduction port 25 for introducing air from the outside of the vehicle and an inside air introduction port 26 for introducing air from the inside of the passenger compartment 2 to the outside air introduction port 25. A damper 27 that adjusts the rate of introduction of outside air is provided inside.

On the other hand, below the fan blade 23, an electric motor 3 for rotating the fan blade 23 is provided.
0 is arranged in a state of being housed in a motor casing 22b fixed to the outer surface of the casing 22, and a rotary shaft 31 of the electric motor 30 is coupled to a boss 23A of a fan blade 23. The central portion of the boss 23A penetrates in the vertical direction.

Therefore, when a drive current is supplied to the electric motor 30 and a rotational drive force is generated on the rotary shaft 31, the fan blade 23 rotates, the air sucked from the upper end surface side thereof is pressurized, and air is discharged. Pressurized air is supplied from the outlet 24 to the air conditioner. Furthermore, the boss 2 of the fan blade 23
3A has an axial direction (upper in FIG. 2) than the end of the rotary shaft 31.
An annular ridge 2 that rises up and is continuous in the circumferential direction
3B is formed so as to surround the tip of the rotary shaft 31, and a concave portion 23C that is inclined toward the tip of the rotary shaft 31 is formed inside the raised portion 23B.

On the other hand, the rotary shaft 31 of the electric motor 30 is a hollow cylindrical shaft, the tip end portion of which is connected to the boss 23A of the fan blade 23, and the middle portion of which forms the radial bearing 32 and the support member 33. It is rotatably supported by the casing 22 via the. Further, the rotary shaft 31 projects from the lower side of the electric motor 30 to the outside of the motor, and the other end of the rotary shaft 31 projecting to the outside of the motor is rotatably supported by a motor casing 22 a covering the electric motor 30 via a thrust bearing 34. Has been done.

The recess 23C and the inner side of the rotary shaft 31 are separated by a thin metal film 23D such as an aluminum foil which has no effect on frequencies below 1 kHz. A code shaft 35 having a code for transmitting a reference signal is disposed inside the hollow rotary shaft 31 so as to be rotatable relative to the rotary shaft 31 via bearings 36 and 37. The microphone 21 that outputs the reference signal x is fixed to the tip of the cord shaft 35 so as to be located at the tip of the rotary shaft 31. The other end of the cord shaft 35 extends from the other end of the rotary shaft 31 to the outside of the motor casing 22b.

Next, the operation of this embodiment will be described. When the drive current is supplied to the electric motor 30 to rotate the fan blades 23 and the pressurized air is discharged from the air discharge port 24,
Noise is generated on the entire outer peripheral surface of the fan blade 23,
This is transmitted to the vehicle interior 2. On the other hand, when noise is generated in the fan blade 23 of the blower 20, the noise is detected by the microphone 21 and supplied to the controller 10 as the reference signal x, and the adaptive digital filter W _m in the controller 10 and the reference signal x are convoluted. or is the drive signal y ₁ ~y _M and is generated, the drive signal y ₁ that is generated
~y _M is supplied to the loudspeaker LS ₁ ~LS _M.

Then, control sounds are generated in the passenger compartment 2 from the loudspeakers LS _{1 to} LS _M, but immediately after the control is started, each filter coefficient W _mi of the adaptive digital filter W _m is converged to an optimum value. However, the noise transmitted to the vehicle interior 2 is not necessarily reduced. But,
The reference signal x and the transfer function filter C ^ _lm and processed is generated by convoluting a signal r _lm, when the remaining noise signal e ₁ to e _l is supplied to the filter coefficient updating unit 11, the filter coefficient updating unit 11 is a filter coefficient W _mi of the adaptive digital filter W _m based on the LMS algorithm described above.
Is updated as appropriate, each filter coefficient W _mi converges toward an optimum value.

As a result, the noise transmitted from the blower 20 into the passenger compartment 2 is canceled by the control sound emitted from the loudspeakers LS _{1 to} LS _M , so that the noise in the passenger compartment 2 can be reduced. In this embodiment, the reference signal x
The microphone 21 for generating the fan blade 23
Since it is arranged inside the rotary shaft 31 of the electric motor 30 for rotating the fan, noise is detected at a position equidistant from the entire outer peripheral surface of the fan blade 23, which is the main noise source in the blower 20. Moreover, the rotating shaft 3
If it is inside 1, since it is a short distance from the outer peripheral surface of the fan blade 23 as a noise source, the characteristics of the entire noise generated on the outer peripheral surface of the fan blade 23 can be detected without significantly increasing the noise component.

In other words, according to the configuration of this embodiment, a high coherence can be obtained between the noise actually generated by the blower 20 and the reference signal x output by the microphone 21, so that good noise reduction control can be performed. Further, since the microphone 21 is disposed inside the rotating shaft 31 and the tip of the rotating shaft 31 is located inside the recessed portion 23C of the boss 23A, the fan blade 23 is driven to rotate. However, the inside of the recessed portion 23C is in the flow of air and becomes a dead water region, the microphone 21 is not directly affected by the pulsating flow of air, and the reference signal x with a small noise component can be generated. .. Moreover, in this embodiment,
Since the tip portion of the rotating shaft 31 is covered with the metal film 23D, the influence of the pulsating flow of air can be eliminated, and the reference signal x with extremely small noise components can be generated, and highly accurate noise reduction. You can control.

The microphone 21 is connected to the rotary shaft 31.
If it is arranged inside, there will be no influence of the frequency characteristics of the wall that constitutes the casing 22 whose main component is low frequency vibration. FIG. 3 is a view showing a second embodiment of the present invention, and is a cross-sectional view showing a configuration of a blower 20 included in an air conditioning system for a vehicle, similar to FIG. 2 of the first embodiment.

That is, in the first embodiment, the boss 23A of the fan blade 23 is formed with the annular raised portion 23B to form the recessed portion 23C which is the dead water region, and the influence of the pulsating flow of air on the microphone 21. However, in the present embodiment, the annular raised portion 23B is reduced.
Instead of forming the above, the shell-shaped noise cone 40 as a streamlined cap is attached to the tip of the rotary shaft 31.

On the side surface of the noise cone 40, there is formed a through hole 40a consisting of a band-shaped slit or a mesh-shaped small hole having a size sufficient for passing the sound pressure signal of the noise generated by the fan blade 23. Has been done. With such a configuration, the noise cone 40, which is in the flow of air and in which airflow noise is unlikely to be generated, can minimize the airflow noise due to the pulsating flow of air.
It is possible to reduce the influence of the pulsating flow of air on the microphone 21 without processing into a special shape as in the first embodiment.

Further, in this embodiment as well, as in the first embodiment, the through hole 40a or the tip of the rotary shaft 31 is provided with a thin metal film such as an aluminum foil which has no effect on frequencies of 1 kHz or less. The effect of the pulsating flow can be made extremely small by covering with, and the reference signal x with less noise components
Can be generated. Other functions and effects are similar to those of the first embodiment.

In each of the above embodiments, the case where the present invention is applied to the device for reducing the noise transmitted from the blower of the air conditioning system for a vehicle to the passenger compartment has been described. The space is not limited to this, and may be another space in which noise is transmitted from the blower.

[0036]

As described above, according to the present invention,
Since the means for detecting the noise generation state of the blower is provided on the rotary shaft of the motor that drives the blower, a high coherence can be obtained between the noise actually generated by the blower and the generated reference signal. There is an effect that noise reduction control can be performed.

In particular, according to the third or fourth aspect of the invention, the influence of the pulsating flow of air on the noise generation state detecting means can be made extremely small, so that a reference signal with less noise components is generated. The effect that can be obtained is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the blower in the first embodiment.

FIG. 3 is a cross-sectional view showing a configuration of a blower according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Active noise control device 2 Vehicle compartment (space) 10 Controller (active control means) 11 Filter coefficient update part 20 Blower 21 Microphone (noise generation state detection means) 23 Fan blade 23A Boss 23B Annular ridge 23C Recessed part 30 Electric Motor 31 Rotation axis 40 Noise cone (streamline type cap) LS _{1 to} LS _M Loudspeaker (control sound source) MP _{1 to} MP _L Microphone (residual noise detection means) W _m Adaptive digital filter C ^ _lm Transfer function filter

Claims (4)

[Claims] 1. A control sound source capable of generating a control sound in a space where noise is transmitted from a blower, noise generation state detection means for detecting a noise generation state of the blower and outputting it as a reference signal, and a predetermined unit in the space. Active noise including residual noise detecting means for detecting residual noise at a position, and active control means for driving the control sound source so as to reduce noise in the space based on the reference signal and the residual noise. In the control device, the noise generation state detecting means is provided on a rotary shaft of a motor for driving the blower, and an active noise control device. 2. The active noise control device according to claim 1, wherein a rotating shaft of a motor for driving the blower is hollow, and the noise generation state detecting means is arranged inside the hollow rotating shaft. 3. The active noise control device according to claim 2, wherein an end of the rotary shaft of the motor for driving the blower is surrounded by an annular ridge that is axially raised and continuous in the circumferential direction from the end. .. 4. The active noise control device according to claim 2, wherein a streamlined cap is attached to an end of a rotary shaft of a motor for driving the blower.