JP3524952B2 - Noise control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects noise from a noise source with a microphone, creates a signal having an approximately opposite phase and equal sound pressure to the noise, and outputs the signal as an electrical signal from a speaker or the like.
The present invention relates to a noise control device that reduces noise by outputting a sound wave using a sound wave converter.

[0002]

2. Description of the Related Art Conventionally, a passive muffler such as a muffler has been used for noise generated from an internal combustion engine or the like, but improvements have been desired from the viewpoints of exhaust efficiency, size, muffling characteristics and the like. On the other hand, conventionally, the speaker outputs the noise generated from the noise generation source and the compensation sound of approximately the opposite phase and equal sound pressure,
An active noise control device that cancels noise has been proposed.

In recent years, a signal processing technique using a digital circuit has been developed, the signal processing speed has been dramatically improved, and the frequency range that can be handled has been expanded.
Many practical noise control devices have been proposed. FIG. 4 shows an example of the configuration of the noise control device which is the premise of the present invention, which has been already proposed by the present applicant in Japanese Patent Application No. 3-195449.

The noise control device outputs a speaker 3 for eliminating the noise transmitted from the engine of the automobile, which is the noise source 100, through the exhaust pipe near the muffling point P (in the figure), and the output to the speaker 3. An amplifier 201 for amplification and a D / A converter (Digital To Analo) for converting a digital signal into an analog signal in order to supply the analog signal to the amplifier 201.
g Converter) 202.

A microphone 101 installed in a lower part of a rear bumper or the like for converting a residual sound of the noise generated by canceling the noise emitted from the noise generating source 100 with the sound wave from the speaker 3 into an electric signal, and the microphone 101 of the microphone 101. An amplifier 301 for amplifying an electric signal and an A / A for converting an analog signal of the amplifier 301 into a digital signal
A D converter (Analog To Digital Converter) 302.

Based on this digital signal, adaptive filtering means 103 for controlling a filter coefficient to form a compensating signal for canceling noise to the speaker 3, and ignition timing from the engine of the automobile which is the noise generating source, A timing signal from the rotation timing (rotation speed) is input, and a noise signal from the microphone 102 or the like, or
Input the noise reproduction signal from the difference signal calculation means 105,
The noise cycle is detected and the cycle change is predicted.

The noise detection source 10 and the cycle detection control means 104 for controlling the adaptive filtering means 103 according to the cycle prediction change so as to follow a steep change.
A microphone 102 installed near 0, an amplifier 601 for amplifying the output of the microphone 102, an A / D converter 602 for converting an analog output signal of the amplifier 601 into a digital signal, and the adaptive filtering means 103. The difference signal calculating means 10 is connected to the output, and from the output point via the speaker 3 and the microphone 101.
Transfer characteristic simulation means 1 for simulating the transfer characteristic up to the input of 5
06, the output of the transfer characteristic simulating means 106 and the A / D
It includes a difference signal calculation means 105 for calculating a difference signal with the output of the converter 302, and a switch means 107 for selectively selecting the input means of the adaptive filtering means 103. Here, the adaptive filtering means 103, the cycle detection control means 104, etc. are a DSP (Digital Signal Processor).
It is composed of.

With this configuration, when the engine speed fluctuates significantly during acceleration / deceleration, etc., in response to a shift signal from a transmission (not shown) and an accelerator / brake signal linked with accelerator pedals and brake pedals (not shown). , A noise signal from the microphone 102 is selected as an input signal of the adaptive filtering means 103, and when there is almost no change in the engine speed during constant speed traveling, the noise reproduction signal from the difference signal calculating means 105 is adaptive filtering means. The switching means 107 is controlled so as to be selected as the input signal of 103.

Then, the adaptive filtering means 103
A compensating signal having a substantially equal sound pressure is generated in a phase substantially opposite to that of the noise from the noise generating source, is reproduced as a sound wave by the speaker 3, and the noise is erased at the sound deadening point P. Further, by inputting the residual sound of noise and sequentially controlling the filter coefficient of the adaptive filtering means 103 according to the residual sound, the residual sound can be further reduced, that is, the noise can be more completely eliminated. A compensation signal is created and output as a sound wave from the speaker 3.

Next, the applicant of the present invention has filed Japanese Patent Application No. 5-222671.
Fig. 5 shows the structure near the outlet of the exhaust pipe in the noise control device already proposed in No. As shown in FIG. 5, a duct 2 having a speaker box 4 in which the speaker 3 in the noise control device of FIG. 4 described above is installed is provided in parallel near the outlet of the exhaust pipe 1 of the automobile. In the exhaust pipe 1 in this case, a catalytic converter and a sub-muffler are provided in the middle of the exhaust pipe as in the conventional case, but the main muffler is eliminated and the sub-muffler makes it difficult to follow noise control. Is muted, and the noise control device mainly mutes the low-pitched portion of the noise that is easy to follow. By eliminating this main muffler, the back pressure is lowered and the exhaust efficiency is improved, which is also effective in terms of the power performance of the vehicle. Further, by using the exhaust pipe 1 and the duct 2 of the noise control device as separate systems, there is an advantage that the exhaust gas does not damage the speaker 3 of the noise control device and the exhaust control does not cause exhaust interference. there were.

At least one of the opening and the inside of the duct 2 is provided with a lid 5 for blocking the inside and the outside of the duct 2. By controlling the opening and closing of the lid 5 by the motor 6, foreign matter such as water is prevented from entering the noise control device, and the speaker 3 and the duct 2 are protected from corrosion caused by the adhesion of the foreign matter and have the same noise control performance. There was a noise control device to maintain.

[0012]

However, when a noise control device is installed to control the exhaust noise of an automobile, the microphone 101 is conventionally installed outside the vehicle rear bumper 7 near the exhaust port. Was there. For this reason, the microphone 101 is exposed to dust and raindrops, and water during car washing, which causes deterioration due to breakage, corrosion, etc., and has a problem in durability. Further, even if the microphone 101 having excellent waterproof performance and corrosion resistance is used, foreign matter may adhere to the surface of the microphone 101 to deteriorate the signal detection capability, and accurate noise control may not be possible. was there. Furthermore, the microphone 101
It may be possible to separately provide a protective means against water and corrosion, but there is a problem that the cost becomes high.

It is an object of the present invention to protect a noise control device and improve its durability with a simple structure.

[0014]

In order to solve the above-mentioned problems, the present invention creates a compensation signal having substantially the opposite phase and equal sound pressure to the noise from a noise source, and incorporates an electric signal / sound wave converter. In a noise control device that reduces the noise by outputting a compensation sound that reproduces the compensation signal from an opening of a duct arranged near the noise generation source, in the opening of the duct, inside the duct. In addition to providing a shut-off means that is controlled to open and close to shut off from the outside,
Characterized in that mounted microphone for detecting noise on.

Further, the noise generated from the noise source has a phase substantially opposite to that of the noise.
By creating a compensating signal of equal sound pressure and outputting a compensating sound that reproduces the compensating signal from the opening of the duct that is built in the electric signal / sound wave converter and is located near the noise source, In a noise control device to reduce, a resonance box having one end opened so as to cover both the opening of the duct and the outlet of noise from a noise generation source, and the resonance box at the opening of the resonance box. It is characterized in that it comprises a shut-off means for controlling the opening and closing to shut off the inside and the outside, and a noise detecting microphone is attached inside the shut-off means.

[0016]

[Function] A duct is arranged near the exit of the noise from the noise source as a transmission path of the compensation sound having a phase opposite to that of the noise and equal sound pressure, and the inside and the outside of the duct are cut off at the opening of the duct. And a microphone for noise detection is mounted inside the blocking means.

By controlling the opening and closing of the shut-off means, foreign matter such as water is prevented from entering the noise control device to protect the duct and the speaker, and the microphone is housed in the duct, and the microphone is also foreign matter. It is possible to prevent the performance deterioration due to the adhesion and corrosion of the noise and maintain the noise control performance. In particular, it is possible to improve the durability of the noise control device in a vehicle used outdoors or in a factory where dust is generated.

Next, when a resonance box having at least one open end is provided so as to cover both the open portion of the duct for outputting the compensation sound and the noise outlet, the noise and the compensation sound diverge in the resonance box. Resonated without. A blocking unit for blocking the inside and the outside of the resonance box is provided at the opening of the resonance box, and a noise detecting microphone is attached to a part of the inside of the blocking unit or inside the resonance box.

By controlling the opening / closing of the shut-off means, the noise control device and the noise generation source are shut off from the outside, the noise control device and the noise generation source are protected from corrosion due to the intrusion of foreign matter, and the microphone is also Since the cutoff means cuts off the outside of the resonance box, it is possible to prevent performance deterioration due to adhesion of foreign matter to the microphone or corrosion.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a noise control device according to an embodiment of the present invention, and FIG. 2 is a perspective view thereof, showing an example adapted to silencing exhaust noise of an automobile. As shown in the figure, the exhaust pipe 1 of the automobile and the duct 2 of the noise control device are separate parallel systems, and the duct 2 is installed near the outlet of the exhaust pipe 1 of the automobile.

With the configuration of the noise control device shown in FIG. 4, for example, the speaker 3 outputs a compensating sound for noise control having a phase and an equal sound pressure substantially opposite in phase to the noise detected by the noise detecting microphone 8. The noise control noise is transmitted through the duct 2 and is emitted from the opening. This makes the exhaust pipe 1
Noise control is performed by canceling out the noise from the exit and the compensation sound.

The noise control device in this embodiment is provided with a lid 5 which is rotated by a motor 6 at the opening of the duct 2 of the noise control device. The control of the motor 6 that controls the opening degree of the lid 5 is performed according to the on / off state of the engine key 11 connected to the battery power source + B. When the engine key 11 is turned on, the motor driving means 10 applies a voltage in the positive direction to the motor 6 for a predetermined time to rotate the motor 6 in the direction in which the lid 5 opens. When the engine key 11 is turned off, the motor driving means 10 applies a negative voltage to the motor 6 for a predetermined time to rotate the motor 6 in the direction in which the lid 5 closes. As a result, when the engine is driven, the opening of the duct 2 is fully opened, and when the engine is stopped, the opening of the duct 2 is fully closed by the lid 5 (dotted line in FIG. 1). ).

A microphone 8 for noise detection is attached to the inside of the lid 5. As a result, by closing the opening of the duct 2 when the noise control device is not used, it is possible to prevent dust, water, insects, etc. from entering the noise control device through the duct 2 when parking or washing the vehicle. Since the microphone 8 is also housed in the duct 2 by closing the lid 5, the microphone 8 is protected from the adhesion and corrosion of foreign matter, the noise detection performance is prevented from lowering, and the noise control performance is maintained.

The lid 5 or the opening of the duct 2 preferably has a waterproof structure provided with rubber packing or the like. Further, when performing noise control, by fully opening the lid 5 to which the microphone 8 is attached, the residual sound of the noise canceled by the noise and the compensating sound is input by the microphone 8 at an appropriate position near the muffling point. It

Next, FIG. 3 is a plan view of a noise control device provided with a resonance box which is partially opened so as to cover the opening of the duct 2 and the outlet of the exhaust pipe 1 of the noise control device. The noise control device is installed by bringing the outlet of the exhaust pipe 1 and the opening of the duct 2 of the noise control device close to each other, so that both the outlet of the exhaust pipe 1 and the opening of the duct 2 of the noise control device are covered. A muffler cutter 9 is provided as an open resonance box. This muffler cutter 9 can prevent the noise and the compensation sound of the noise control from diverging and resonate.

The muffler cutter 9 is installed in the same manner as when the lid 5 is installed in the open portion of the duct 2 of the noise control device.
The opening 5 is provided with a rotatable lid 5 for shutting off from the outside. With this, foreign matter can be prevented from entering and the exhaust pipe 1 can be protected together with the noise control device, as described above. Furthermore, the lid 5
By attaching the microphone 8 for noise detection inside of the microphone 8, the microphone 8 is housed in the muffler cutter 9 when the lid 5 is closed, and the microphone 8 is also protected from foreign matter adhesion and corrosion.

Further, the microphone 8 is not attached to the lid 5, but is attached to the muffler cutter 9 at a position A, for example. Also in this case, since the noise control device, the exhaust pipe 1, and the microphone 8 are shut off from the outside by closing the lid 5, foreign matter can be prevented from entering and protected in the same manner as described above, so that the durability of the noise control device can be improved. .

[0028]

According to the present invention, the durability can be improved by protecting the microphone for noise detection together with the duct and the speaker with a simple structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a noise control device of the present invention.

FIG. 2 is a perspective view showing an embodiment of a noise control device of the present invention.

FIG. 3 is a plan view showing a second embodiment of the noise control device of the invention.

FIG. 4 is a block diagram showing the configuration of a noise control device.

FIG. 5 is a cross-sectional view showing a configuration near an outlet of an exhaust pipe of a conventional noise control device.

[Explanation of symbols]

1 ... Exhaust pipe 2 ... duct 3 ... speaker 4 ... Speaker box 5 ... Lid 6 ... Motor 10 ... Motor driving means 8: Microphone 9 ... Muffler cutter

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Ishikawa 1-2-2 Gosho-dori, Hyogo-ku, Kobe-shi, Hyogo Prefecture Fujitsu Ten Limited (72) Inventor Shinichi Iwamoto 1-chome, Gosho-dori, Hyogo-ku, Hyogo Prefecture No. 2 to 28 in Fujitsu Ten Limited (56) Reference JP-A-59-133595 (JP, A) JP-A-2-108329 (JP, A) JP-A-6-58123 (JP, A) JP-A-6-58123 1-117472 (JP, A) JP 5-296020 (JP, A) JP 7-77993 (JP, A) Actually opened 63-119816 (JP, U) Actually opened 55-110721 (JP, U) Actual development 53-21218 (JP, U) Actual development 60-155088 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G10K 11/178 B60K 13/04 F01N 1 / 00

Claims (2)

(57) [Claims] 1. A compensating signal having a phase substantially opposite to that of a noise from a noise source and an equal sound pressure is created, and an electric signal / sonic wave converter is built-in from an opening of a duct arranged near the noise source. by outputting a compensating sound obtained by reproducing the compensation signal, the noise control apparatus for reducing the noise, the opening of the duct, Ru provided blocking means which is opening and closing control for blocking the interior of the duct and the outside At the same time , a noise control device is characterized in that a noise detecting microphone is attached inside the blocking means. 2. A compensating signal having substantially the opposite phase and equal sound pressure from the noise from the noise source is created, and an electric signal / sound wave converter is built-in from the opening of the duct arranged near the noise source. In a noise control device that reduces the noise by outputting a compensation sound that reproduces a compensation signal, one end provided so as to cover both the opening of the duct and the outlet of noise from the noise source is open. a resonance box that, a shut-off means to be opened and closed controlled to block the inside and the outside of the co-sounding box into the opening of the co-sounding box, take the microphone for detecting noise in the inside of the shut-off means
A noise control device characterized by being attached .