JPH0627785Y2 - Active canceller system for intake and exhaust pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an active canceller system for intake / exhaust pipes, which is used for silencing intake / exhaust noise of an automobile engine or the like.

(Prior Art) As a conventional active canceller system for intake / exhaust pipes, for example, one described in JP-A-57-6897 is known (FIG. 2). This conventional active canceller system for intake and exhaust pipes has an exhaust pipe 01 whose one end is connected to an engine, and a cancel speaker 03 which is connected to the exhaust pipe 01 through a branch pipe 02.
A microphone 04 provided in the exhaust pipe 01; and an active cancel control means 06 for monitoring exhaust noise based on a signal from the microphone 04 and outputting a predetermined control signal to the cancel speaker 03. Speaker 03 for canceling compressional and pressure waves having a phase opposite to that of noise
By outputting from, the sound was silenced by the canceling action of both pressure waves.

(Problems to be solved by the invention) However, in such a conventional active canceller system for intake and exhaust pipes, since a normal type speaker that vibrates cone paper is used as the cancel speaker, There was a problem to do.

Since the speaker cone paper is exposed to high temperature exhaust gas, it has low heat resistance and durability. In addition, weather resistance is poor due to the use of cone paper.

The vibration of the speaker magnet and coil deteriorates due to heat.

Since a speaker normally disperses an oscillating sound on the front side, a large amount of power consumption is required to obtain a strong sound in a noise path.

(Means for Solving Problems) The present invention solves the problems described above, is excellent in heat resistance, durability, and weather resistance, and is capable of producing a stronger sound with less power consumption. It is intended to provide an active canceller system for pipes.

In order to achieve this object, in the present invention, it is possible to superimpose a pressure wave on the noise of the intake and exhaust pipes, one end of which is connected to the engine that is the noise source and in which the intake or exhaust flow path is formed. A cancel speaker provided in the intake and exhaust pipe system, and active cancel control means for monitoring noise based on a signal input from a microphone provided in the intake and exhaust pipe system and outputting a predetermined control signal to the cancel speaker. In the active canceller system for intake and exhaust pipes, which outputs a compression and compression pressure wave having a phase opposite to that of the noise from the cancellation speaker by the canceling action of both pressure waves to the intake and exhaust flow paths, A piezoelectric speaker whose exposed surface is made of ceramic or metal is used. And a means which is formed on the focusing geometry to be focused to the airflow path side.

(Operation) In the active canceller system for intake and exhaust pipes of the present invention, a pressure wave having a phase opposite to that of the noise transmitted through the intake pipe or the exhaust pipe of the engine is output from the piezoelectric speaker, and the noise is canceled by both. Be erased.

At this time, since the piezoelectric speaker is formed in a focusing shape, the oscillating sound is focused on the intake / exhaust flow path side.

Therefore, a strong sound can be obtained with less power consumption than the noise of the intake and exhaust pipes.

Also, although a piezoelectric speaker is used as the cancel speaker, this piezoelectric speaker has a property that it is more compact than an ordinary electromagnetic speaker, but that it is easy to obtain low-frequency sound and that it is not easily affected by heat. .

Therefore, it is advantageous to be mounted on a vehicle, is effective in silencing low-frequency sound that is a problem with engine noise, and is also excellent in heat resistance.

Further, since the exposed surface of the piezoelectric speaker to the intake / exhaust pipe is made of ceramic or metal, it is not easily affected by heat and climate, and has excellent heat resistance and weather resistance.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

In describing this embodiment, an exhaust pipe active canceller system used to muffle the exhaust noise of an automobile will be taken as an example.

First, the structure of the embodiment shown in FIG. 1 will be described.

Exhaust pipe active canceller system A of the embodiment
As shown in FIG. 1, the main components are the exhaust pipe 1 and the active cancellation control means 6.

One end of the exhaust pipe 1 is connected to an engine 7 that is a noise source, an exhaust flow path a is formed inside, and a muffler is provided in a portion not shown.

The active cancellation control means 6 is a control means for monitoring the exhaust sound from the engine 7 and outputting a predetermined silencing pressure wave generation signal (1) (actually a minute current) to the piezoelectric speaker 3. The noise detection microphone 4 and the error detection microphone 8 are provided as input means, and the control unit 5 is provided as output means.

The piezoelectric speaker 3 includes a ceramic plate 31 and a metal plate 32.
And the focus point c of the oscillating sound b.
Is formed in a hemispherical converging shape so as to be positioned on the axis of the exhaust flow path a, and is elastically supported by the support member 35 in the casing 33. Further, glass wool 34 is provided between the casing 33 and the piezoelectric speaker for noise reduction.

When the muffling pressure wave generation signal (l) from the active cancellation control means 6 is input to the piezoelectric speaker 3, the piezoelectric speaker 3 has a phase opposite to the pressure wave of exhaust sound (hereinafter referred to as noise pressure wave). The dense and dense pressure wave (hereinafter referred to as a muffling pressure wave = oscillation sound b) is output.

The noise detection microphone 4 detects a noise pressure wave and outputs a noise signal (m) to the control unit 5.

The error detection microphone 8 is provided on the outlet side of the exhaust pipe 1, and the error detection microphone 8 outputs a monitor signal (n) of a silencing pressure wave.

The control unit 5 includes the noise detection microphone 4
The control unit 5 is an apparatus for outputting a silencing pressure wave having a phase opposite to that of the noise pressure wave from the piezoelectric speaker 3 based on the noise signal (m) from the A / D converter 5
1, a memory 52, a CPU 53, a D / A converter 54, graphic equalizers 55 and 56, and a power amplifier 57.

The A / D converter 51 is a converter that converts the noise signal (m) from the noise detection microphone 4 and the waveform from the graphic equalizer 56 into a digital signal that can be processed by the CPU 53.

The memory 52 is a writable and readable memory in which noise pressure wave information is written based on the noise signal from the noise detection microphone 4 and information is written in the middle of calculation in the CPU 53, and calculation processing in the CPU 53 is performed. Necessary information is stored in advance, and if necessary, CP
It is read to U53.

The CPU 53 is a device that performs arithmetic processing on various input information according to predetermined processing conditions.

The D / A converter 54 is a converter that converts a digital signal, which is a calculation result signal from the CPU 53, into an analog signal.

The graphic equalizer 55 includes a D / A converter 54.
It is a pressure wave generator that forms an arbitrary waveform based on an analog signal from.

One graphic equalizer 56 is a pressure wave generator that forms an arbitrary waveform based on the monitor signal (n) from the error detection microphone 8.

The power amplifier 57 is an amplifier that amplifies the pressure wave from the graphic equalizer 55 and outputs a silencing pressure wave generation signal (1) to the piezoelectric speaker 3.

Next, the operation of the embodiment will be described.

First, when the frequency of the noise pressure wave in the exhaust pipe 1 is detected by the noise detection microphone 4 and input to the control unit 5, the piezoelectric speaker 3 is output from the control unit 5.
Then, a muffling pressure wave generation signal (l) for generating a muffling pressure wave having a phase opposite to the detected noise pressure wave is output.

When this silencing pressure wave generation signal (l) is input to the piezoelectric speaker 3, a silencing pressure wave (= oscillation sound b) having a phase opposite to that of the noise pressure wave is output from the piezoelectric speaker 3, and the pressure waves cancel each other. That is, the noise pressure wave in the exhaust pipe 1 disappears due to the active canceling action, and the exhaust sound is silenced.

At this time, since the piezoelectric speaker 3 is formed in a hemispherical focusing shape, the oscillating sound b is focused on the center of the exhaust flow path a which is the center of the noise of the intake / exhaust pipe 1.

Therefore, the density of the muffling pressure wave with respect to the noise pressure wave is increased, and a powerful noise pressure wave can be obtained with less power consumption than the noise pressure wave of the intake / exhaust pipe 1. .

Moreover, although the piezoelectric speaker 3 is used as the cancel speaker, the piezoelectric speaker 3 has a property that it is more compact than an ordinary electromagnetic speaker, yet it is easy to obtain a low-frequency sound, and that it is not easily affected by heat. ing.

Therefore, in addition to being advantageous for vehicle mounting, it is effective in silencing low-frequency noise that is a problem with engine noise, and in addition, it has excellent heat resistance, and has the effect of improving reliability against performance deterioration, failure due to heat, and durability. can get.

Further, since the exposed surface of the piezoelectric speaker 3 to the intake / exhaust flow path a is the metal plate 32, it is difficult to be affected by exhaust heat and climate, and excellent heat resistance and weather resistance can be obtained.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and the present invention can be applied even if there is a design change or the like within a range not departing from the gist of the present invention. included.

For example, although an example in which the invention is applied to the exhaust pipe is shown in the embodiment, it may be applied to the intake pipe of the engine.

In addition, although an automobile engine is shown as the engine in the embodiments, it can be applied to any other engine.

Further, in the embodiment, the focus position of the oscillating sound of the piezoelectric speaker is the center position of the exhaust flow path, but the focus position is preferably set appropriately by experiments or the like according to the noise characteristics, etc. However, it does not necessarily have to be in the exhaust passage. Further, although the piezoelectric speaker has a hemispherical shape as a focusing shape, it is not limited to this shape such as a multifaceted shape.

(Effect of device) As described above, in the active canceller system for intake and exhaust pipes of the present invention, the cancel speaker is
By using a piezoelectric speaker whose exposed surface to the intake / exhaust flow path is made of ceramic or metal, and forming the piezoelectric speaker in a focusing shape in which oscillation sound is focused on the intake / exhaust flow path side, the effects listed below can be obtained. It is also obtained.

Since the oscillating sound is focused on the intake / exhaust flow passage, a powerful sound can be obtained with less power consumption than the noise of the intake / exhaust pipe.

Piezoelectric speakers are more compact than ordinary electromagnetic speakers, but have the property of easily obtaining low-frequency sound and the property of being less susceptible to heat. It is effective in silencing low frequency sound, and in addition, has excellent heat resistance.

The exposed surface of the intake / exhaust flow path of the piezoelectric speaker is not easily affected by heat and climate, and has excellent heat resistance and weather resistance.

[Brief description of drawings]

FIG. 1 is an overall view showing an exhaust pipe active canceller system of an embodiment of the present invention, and FIG. 2 is an overall view showing a conventional example. 1 ... Exhaust pipe 3 ... Piezoelectric speaker 4 ... Noise detection microphone 6 ... Active cancellation control means 7 ... Engine 8 ... Error detection microphone a ... Exhaust flow path

Claims (1)

[Scope of utility model registration request] 1. An engine, one end of which is connected to a noise source,
An intake / exhaust pipe in which an intake or exhaust flow path is formed, a cancel speaker provided so that a pressure wave can be superimposed on noise of the intake / exhaust pipe, and a signal input from a microphone provided in the intake / exhaust pipe system And a cancellation control speaker that outputs a predetermined control signal to the cancellation speaker based on the above, and outputs a compression pressure wave having a phase opposite to the pressure wave of the intake and exhaust pipe noise from the cancellation speaker. Then, in the active canceller system for intake and exhaust pipes, which silences by the canceling action of both pressure waves, the cancel speaker uses a piezoelectric speaker whose exposed surface to the intake and exhaust passages is formed of ceramic or metal,
An active canceller system for intake / exhaust pipes, characterized in that the piezoelectric speaker is formed in a focusing shape in which oscillation sound is focused on the intake / exhaust flow path side.