JP2007298999A - Vibration/noise reduction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration/noise reduction device which can efficiently convert a wide frequency range of vibrations or noises over a widest possible area into electric energy, and enables the mounting position of the vibration/noise reduction device to be easily changed or transferred when the change, transfer and addition of the mounting position are required. <P>SOLUTION: (a) In the vibration/noise reduction device comprising an energy conversion system for converting vibrations and noises into electricity and an energy consumption means for consuming the converted electric energy as thermal energy, (b) the energy conversion system is configured of two or more sheets of piezoelectric loudspeakers 2 in each of which a vibrating plate 21 constituted of piezoelectric ceramics or the like is supported on an elastic support 22, and an electrode is connected to the vibrating plate 21, and (c) those piezoelectric loudspeakers are attached to a sheet-like magnet 6, and the magnet is attached to a suppression object 1 of a magnetic substance by magnetic attraction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a vibration / noise reduction device that suppresses vibration or noise generation of a relatively lightweight object such as a vehicle wall surface, a building wall surface, a machine itself, or a machine housing.
In this specification, an object for suppressing vibration or noise generation is referred to as an object to be suppressed.
The present invention is particularly suitable for reducing the vibration and noise of an object to be suppressed that exists in an environment where the frequency band is susceptible to vibration or noise in the audible range.

  Generation of vibration or noise due to external vibrations such as railway vehicles, wall surfaces of other vehicles, and wall surfaces of buildings, or the generation of vibrations due to external sounds deprives the quiet life of vehicle passengers or building residents, etc. Impairs stability and may impair health. In addition, the generation of noise due to external vibration or self-vibration of the machine itself or its casing, or the generation of vibration due to external sound not only impedes the performance of the original functions of the machine, but also the mental stability of machine operators and operators. Threaten and increase the risk of accidents. For this reason, there is a need for a technique that effectively suppresses the generation of vibrations or noise of relatively light objects such as walls of vehicles and buildings, machines, or housings thereof.

  Among conventional vibration / noise reduction devices, energy conversion in a system composed of an energy conversion system for converting vibration or noise into electricity and an energy consuming means for consuming the converted electricity as heat energy In the system, a microphone is generally used as a noise-electric converter and a piezoelectric material is recently used as a vibration-electric converter. As the energy consuming means, a shunt circuit including a coil and a resistor is used, and a resonance circuit is constituted by the capacitance C of the piezoelectric material, the coil inductance L of the shunt circuit, and the resistor R. Energy is consumed by causing a current to flow through the resistor of the shunt circuit to release Joule heat (for example, see Non-Patent Document 1).

Journal of Sound & Vibration Vol.146 No.2 p24,52,68 1991

The conventional vibration / noise reduction device has the following problems in the energy conversion system and the energy consumption means.
(1) Problems with the energy conversion system The energy conversion system using a microphone only converts the sound pressure in a very small space near the position where the microphone is installed into an electrical signal, and the acoustic energy of the intrusion sound. Cannot be efficiently converted into electrical energy. That is, the regional range where energy can be converted is narrow, and the conversion efficiency is low.
When a piezoelectric material such as piezoelectric ceramics is used as a converter from vibration energy to electric energy, the frequency range that can be converted is narrow due to the characteristics of the piezoelectric material itself. That is, the piezoelectric material has high frequency dependence on the energy conversion performance. The frequency and level of vibration or noise transmitted to the vehicle or the wall of the building, the prime mover, the casing thereof, or the like, or the acoustic environment is varied. Therefore, in practice, it cannot be expected that the conversion performance of wideband vibration or noise in the field remains in the wide frequency range.

(2) Problems of Energy Consumption Means Conventional resonance circuits constituting energy consumption means are generally composed of an inductance L of a coil and a capacitance C of a piezoelectric element, and 1 / (2π√ (LC)) resonance occurs at the frequency. That is, in the vicinity of the resonance frequency determined by L and C, it is possible to effectively dissipate power with a resistor for energy consumption, but at other frequencies, power dissipation is small (resonant circuit current). Frequency dependence on amplification). The frequency band of vibration or noise transmitted to the object to be suppressed may be in a wide range depending on the environment. Therefore, the vibration / noise reduction device using the conventional shunt circuit constituting the resonance circuit cannot exhibit a sufficient energy consumption effect with respect to broadband vibration or noise.

(3) Necessity of using individual signal converters Since conventional signal or energy converters are single converters for noise-electricity and vibration-electricity, noise and vibration are converted into electricity. Need to use their own dedicated converter.

(4) Problems related to mounting method Generally, when a vibration / noise reduction device is attached to an object to be suppressed, the device is generally attached to the object to be suppressed or mechanically attached with a screw or the like. Depending on the object to be suppressed or the use environment thereof, the intensity of vibration or sound or the direction of entry may change. In such a case, it is desired to change or move the attachment position of the vibration / noise reduction device. However, conventionally, it has been difficult to remove the device once it has been attached, or it has been troublesome to loosen or remove a screw.

(5) Problems related to vibration suppression effects The vibration damping materials and various ANC systems (Active Noise Control System) that are already on the market are used for each narrow band, and only the vibration suppression effect of a single system is exhibited. . In general, the damping material is effective only in the high frequency region, and the ANC system is effective in the low frequency region. Therefore, when a wall surface of a vehicle, a wall surface of a building in the vicinity such as a highway, a railroad track, or a public notification speaker receives vibration or noise in a wide frequency band, a satisfactory vibration suppression effect or soundproof effect can be obtained. In order to achieve this, it is necessary to install a plurality of types of vibration / noise reduction devices, which increases the cost and is difficult to realize.

  The present invention has been made in view of the above problems, and the problem to be solved is to solve the problems of the energy conversion system and to solve the problems related to the mounting method. When it is possible to efficiently convert vibration or noise in a wide frequency range to electrical energy over a wide area, and it is necessary to change, move, or add the installation position of the vibration / noise reduction device It is another object of the present invention to provide a vibration / noise reduction device that can easily change or move the mounting position. (Expansion of the area where energy can be converted, improvement of conversion efficiency, and ease of changing or moving the mounting position)

  In order to solve the above-mentioned problems, the present invention provides a vibration / noise reduction apparatus comprising: (a) an energy conversion system for converting vibration or noise into electricity; and energy consuming means for consuming the converted electricity as thermal energy. (B) the energy conversion system is constituted by a piezoelectric speaker in which a diaphragm made of piezoelectric ceramics or the like is supported on an elastic support and an electrode is connected to the diaphragm, and (c) them. The piezoelectric speaker is attached to a sheet-like magnet, and the magnet is attached to an object to be suppressed, which is a magnetic body, by magnetic adsorption (claim 1).

  When attaching a piezoelectric speaker to a sheet-like magnet, it is desirable to attach a plurality of piezoelectric speakers in an overlapping manner (claim 2).

  In the vibration / noise reduction apparatus, when the object to be suppressed is an acoustic piezoelectric speaker, a piezoelectric speaker as an acoustic-electric converter is attached to a sheet-like magnet on the back side of the acoustic piezoelectric speaker. It is desirable to suppress unnecessary noise generated on the back side of the acoustic piezoelectric speaker.

  According to the first aspect of the present invention, first, the energy conversion system includes a plurality of piezoelectric systems in which a vibration plate made of piezoelectric ceramics or the like is supported on an elastic support, and electrodes are connected to the vibration plate. Since it is constituted by a speaker, the energy conversion system can efficiently convert into electric energy over a wider area and in a wider frequency band than conventionally used piezoelectric elements. Therefore, it is possible to exhibit a vibration damping or sound absorbing effect in a wide frequency band. Secondly, unlike conventional energy conversion systems, piezoelectric speakers are thin-walled, so that vibrations or noises of relatively lightweight objects such as vehicle wall surfaces, building wall surfaces, machines themselves, or machine housings are not generated. It is useful as a vibration and noise reduction device to suppress. Thirdly, the piezoelectric speaker is attached to the sheet-shaped magnet in advance, and the magnet is easily fixed to the object to be suppressed, which is a magnetic body, by magnetic attraction. This saves mounting effort and enables easy removal. It can be easily moved or added as needed.

  According to the second aspect of the present invention, when the amount of noise to be input to the object to be suppressed is large, the plurality of piezoelectric speakers sequentially convert the noise that has passed through the previous piezoelectric speaker into electric energy, and the previous speaker is Since the transmitted noise is further converted into electric energy by a later speaker, the energy conversion efficiency is further improved.

  According to the invention of claim 3, unnecessary noise generated on the back side of the acoustic piezoelectric speaker can be suppressed by attaching a piezoelectric speaker as an acoustic-electric converter to the back side of the acoustic piezoelectric speaker. Therefore, a clear sound that is not affected by noise can be produced on the front side of the acoustic piezoelectric speaker.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a basic configuration of the first embodiment, FIG. 2 is a circuit diagram showing an example of a piezoelectric speaker and energy consuming means, and FIG. 3 is a circuit diagram showing an equivalent circuit of the piezoelectric speaker and energy consuming means. 4 is a circuit diagram showing one implementation example of the negative capacitance, FIG. 5 is a circuit diagram showing another implementation example of the negative capacitance, and FIG. 6 is an electric circuit diagram showing an example of the storage means, 7A and 7B are diagrams showing an example of a mounting structure of a piezoelectric speaker. FIG. 7A is a front view, FIG. 7B is a cross-sectional view, FIG. 8 is a graph showing a vibration reduction effect together with a comparative example, and FIG. It is a figure which shows the attachment structure at the time of attaching in a pile, (a) is a conceptual diagram at the time of attaching a piezoelectric speaker simply in piles, (b) is a conceptual diagram at the time of providing the support | pillar in the first piezoelectric speaker, Figure 10 shows the frequency dependence of the piezoelectric performance of piezoelectric elements and piezoelectric speakers. It is a graph (energy conversion characteristic graph of the piezoelectric element and the piezoelectric speaker).

  In FIG. 1, reference numeral 1 denotes an object to be suppressed, 2 is a piezoelectric speaker that is attached to the object 1 to be controlled, and converts sound or vibration into electric energy, and 3 is an electric that is taken out by the piezoelectric speaker 2. It is an energy consuming means that consumes energy.

  The object 1 to be suppressed is a relatively lightweight object or member such as a railroad vehicle or other vehicle wall, a building wall, the machine itself, or a machine casing, and it is these that effectively exert the effects of the present invention. This is a case where the suppression object 1 exists in an environment that is susceptible to vibration or noise of a relatively wide frequency band.

  The piezoelectric speaker 2 is configured by supporting a vibration plate 21 made of piezoelectric ceramics or the like on an elastic support 22 and connecting an electrode to the vibration plate. When a sound signal is received, it vibrates at a predetermined frequency to generate a sound wave. In the present invention, the piezoelectric effect of the diaphragm 21 of the piezoelectric speaker (a phenomenon that generates a charge when subjected to mechanical vibration) is used. Thus, it is used as a kind of energy conversion system that converts the distortion caused by the received vibration or noise into electric energy.

FIG. 10 is a graph showing the frequency characteristics of the output of the piezoelectric element and the piezoelectric speaker, where the thin line is the output of the piezoelectric element and the thick line is the output of the piezoelectric speaker. As shown in the figure, the piezoelectric element has a low output level in the vicinity of 500 Hz and 1000 to 2000 Hz, while the piezoelectric speaker has a slightly low output level in the narrow range of 750 to 1100 Hz and 1700 to 2000 Hz. It can be seen that good output can be obtained in a wide range.
Therefore, in the above configuration, basically the piezoelectric speaker is laid flat on the object to be suppressed or in the space, and external or self-generated vibration or noise is efficiently converted into electric energy in a wide frequency band and output. To do. The electric energy is converted into heat energy by the energy consuming means 3 and consumed.

One of the methods for attaching the piezoelectric speaker 2 to the suppression target 1 is a method of directly attaching the elastic support plate 22 or the housing of the piezoelectric speaker 2 to a wall or the like, or a method of fixing using an adhesive tape or the like. Alternatively, there may be a method of fixing using a fixing tool such as a screw.
Conventionally, it has been proposed to use a piezoelectric element to convert acoustic energy or vibration energy into electric energy. As shown in FIG. 10, this piezoelectric element generally has a natural frequency (100 to 300 Hz) determined by its shape. ) Energy conversion is performed efficiently in the vicinity, but energy conversion efficiency is much lower at other frequencies.

  On the other hand, the piezoelectric speaker 2 is manufactured on the assumption that it is used as an acoustic speaker, and is designed to widen the frequency band of acoustic radiation. Even when this piezoelectric speaker 2 is used as a strain-electric converter, as shown in FIG. 10, there is a feature that distortion due to vibration or noise in a wide frequency band of 50 to 1700 Hz can be converted into electricity. According to the present invention, a piezoelectric speaker having a wide frequency band is used as an energy converter, so that acoustic energy and vibration energy can be converted into electric energy in a wide band.

  When the intensity of vibration or noise applied to the suppression target 1 is large, a plurality of piezoelectric speakers are used, and the positive and negative electrodes of each piezoelectric speaker are coupled in parallel or in series.

As illustrated in FIG. 2, the electric energy consuming means 3 is a known shunt circuit S <b> 1 including a coil 31 and a resistor 32 connected in series between both electrodes connected to the diaphragm 21 of the piezoelectric speaker 2. Can be configured. By connecting the shunt circuit S1 to the piezoelectric speaker 2, an LCR resonance circuit is configured by the capacitance (C) of the diaphragm 21, the inductance (L) of the coil 31, and the resistance (R) of the resistor 32. ing.
With the above configuration, when an external vibration or noise enters the object 1 to be suppressed, the vibration or noise is transmitted to the diaphragm 21 of the piezoelectric speaker 2, and the distortion generated in the diaphragm is converted into an electric charge, A resonance current flows through the shunt circuit S1, and the current is converted into Joule heat in the resistor 32 and released into the atmosphere, thereby consuming energy.

  As described above, when the shunt circuit S1 constituting the resonance circuit is used, when the suppression target 1 vibrates at the same frequency as the resonance frequency, the maximum current flows from the piezoelectric speaker 2 to the shunt circuit S1. A good vibration attenuating effect can be obtained, but the vibration attenuating effect becomes low when vibrations of other frequencies are received.

FIG. 3 shows an embodiment in which the above difficulties are eliminated. That is, in this embodiment, the shunt circuit S2 has a negative capacitance (-C) substantially equivalent to the capacitance C possessed by the piezoelectric speaker 2, and a resistance Re in series with the negative capacitance. Connected and configured.
For example, as shown in FIG. 4, the negative electrostatic capacitance (−C) can be generated by an inverting circuit 33 formed of an operational amplifier and an integrating circuit 34 that integrates the output of the inverting circuit. It can also be generated using a circuit as shown in FIG.
When the electrostatic capacity (C) of the piezoelectric speaker 2 and the negative electrostatic capacity (-C) substantially equivalent to the electrostatic capacity are combined, the combined impedance becomes 0 in all frequency bands. Therefore, the frequency characteristic is lost, and the current can be efficiently passed from the piezoelectric speaker 2 to the resistor 32. Therefore, according to this embodiment, a damping effect or a silencing effect that is greater than the mass rule can be expected.

  In addition, when using a plurality of piezoelectric speakers, such as when covering the required area or mounting by overlapping, by connecting a negative capacitance that matches the combined capacitance of the piezoelectric speakers, One or a minimum number of shunt circuits can be used.

In the above embodiment, the electric energy extracted from the piezoelectric speaker is converted into heat energy by the resistor 32 (Re) and consumed. As shown in FIG. 6, the electric energy is not consumed. In addition, it is possible to store power by connecting the power storage means 4 to the shunt circuit S3. The power storage means 4 includes a second coil 41, a rectifier 42, and a storage battery 43. The primary coil and the secondary coil of the transformer 44 are respectively connected to the first coil 31 and the second coil 41 of the shunt circuit S3. Is forming.
When the power storage unit 4 is provided, the power storage unit 4 can be used as a power source for driving a circuit that generates a negative capacitance. That is, a plurality of piezoelectric speakers are used, and a shunt circuit S2 including a negative capacitance and a resistor substantially equivalent to the capacitance of the entire piezoelectric speaker in FIG. 6 is connected to the shunt circuit S1 and the power storage unit 4 in FIG. 6 to generate a negative capacitance from the battery 43 of the power storage unit, for example, the inverting circuit 33 and the integration circuit 34 in FIG. Can be supplied with drive power.

When a piezoelectric speaker is used as an energy conversion system, the quality of vibration transmission from the object to be suppressed to the diaphragm of the piezoelectric speaker determines the damping effect or the sound absorbing effect. In the preferred embodiment, as shown in FIG. 7, a support column 5 is preferably provided between the center of the diaphragm 21 and the object to be suppressed, and the vibration of the object 1 to be suppressed is applied to the diaphragm 21 of the piezoelectric speaker 2. I try to communicate directly. The strut 5 may be a rigid body such as metal or an elastic body such as rubber.
In the piezoelectric speaker alone, basically only the applied acoustic energy is converted into electric energy. However, by connecting the diaphragm 21 of the piezoelectric speaker 2 and the suppression object 1 with the support column 5, Since vibration energy can be directly transmitted to the diaphragm 21 of the piezoelectric speaker 2, an improvement in energy conversion efficiency is expected. Furthermore, not only the component excited by the acoustic energy to which the vibration of the object to be suppressed is applied, but also the solid-propagation vibration caused by other factors can be converted into electric energy together.
As shown in FIG. 8, the output when the support column 5 is not provided between the vibration plate 21 and the suppression target plate 1 (FIG. 8A) is compared with the output when it is provided (FIG. 8B). It can be seen that an output that faithfully follows the vibration of the suppression target plate can be obtained in the case of the support column.

  When a plurality of piezoelectric speakers 2 are used, not only are the two-dimensionally attached to the target surface of the object 1 to be suppressed, but the piezoelectric speakers 2a, 2b, and 2c are overlapped as illustrated in FIG. 9A. It is possible to use. In order to increase the energy conversion efficiency, it is possible to convert vibration or noise into electrical energy in multiple stages in the sound incident direction by attaching piezoelectric speakers on the same surface, and the overall energy conversion efficiency can be improved. improves.

As described above, when the piezoelectric speakers are used in an overlapping manner, as shown in FIG. 9B, the support 5 is attached to the piezoelectric speaker 2 a that is directly attached to the suppression target 1, and the piezoelectric material that is attached thereto is attached. The type speaker 2b is preferably used without a support.
By attaching the column 5 to the piezoelectric speaker 2a that is directly attached to the suppression object 1, the vibration energy of the suppression object 1 is converted into electrical energy mainly by the piezoelectric speaker 2a, and the column is mounted on the piezoelectric speaker 2b thereon. By not attaching, it becomes possible to convert acoustic energy into electrical energy, and it is possible to convert different energy into electrical energy.

Regarding the mounting structure of the piezoelectric speaker 2, all of the above examples are directly attached to the suppression target 1. However, depending on the object to be suppressed or the use environment thereof, the intensity of vibration or sound or the direction of entry may change. In such a case, it is desirable to change or move the mounting position of the vibration / noise reduction device. However, with the mounting structure as described above, it cannot be removed once it has been attached, or it may be time consuming to remove it by loosening screws etc. It takes.
Therefore, in the present invention, the following mounting structure is adopted. This mounting structure can be employed when the object 1 to be suppressed is a magnetic body such as an iron plate. As shown in FIGS. 1 and 8, the piezoelectric speaker 2 is attached to a sheet-like magnet 6. The magnet 6 is stuck and magnetically attracted to the object 1 to be fixed. Since the piezoelectric speaker 2 is attached to the sheet-like magnet 6 and is magnetically attracted to the object 1 to be suppressed, it can be easily attached without using a dedicated attachment tool (screw or the like). Further, there is an advantage that the placement position of the piezoelectric speaker 2 can be easily moved or increased or decreased according to the movement or increase or decrease of the vibration source or the sound source.

  In the above description, a device for suppressing vibration and reducing noise when the suppression target 1 vibrates or generates sound due to external noise has been considered. Since the basic principle is to perform vibration damping and soundproofing using conversion or vibration-electrical conversion (piezoelectric effect), it goes without saying that the present invention can also be applied to the case where the suppression object 1 itself generates vibration or noise. If the technical idea of the present invention is further developed, when applied to the case where the suppression object 1 is a piezoelectric speaker that is used for original sound generation, the function of the sound generation piezoelectric speaker is further improved. Improvements can be made. In other words, a sheet-like magnet with a noise-suppressing piezoelectric speaker attached is provided on the back side of the acoustic-generating piezoelectric speaker corresponding to the object to be suppressed, and energy is consumed via electrodes on the diaphragm of the latter noise-suppressing speaker. By connecting the means and / or the power storage means, it is possible to reduce the reverse phase sound radiated to the back side of the sound generating speaker, that is, noise. Provides a clear, clear sound. Instead of the energy consuming means and / or the power storage means, a control circuit for adjusting the reactance (L) or the resistance value (R) for setting the resonance frequency corresponding to the frequency to be reduced is connected, so that the sound generating speaker Noise other than the necessary range radiated from the back side can be suppressed or eliminated.

The conceptual diagram which shows the basic composition of 1st Embodiment. The circuit diagram which shows an example of a piezoelectric speaker and an energy consumption means. The circuit diagram which shows the equivalent circuit of a piezoelectric speaker and an energy consumption means. The circuit diagram which shows one implementation example of negative electrostatic capacitance. The circuit diagram which shows the other implementation example of a negative electrostatic capacitance. The electric circuit diagram which shows an example of an electrical storage means. It is a figure which shows an example of the attachment structure with respect to the suppression target object of a piezoelectric speaker, (a) is a front view, (b) is sectional drawing. The measurement graph which shows the difference of the output when not providing a support | pillar between a diaphragm and a suppression object board (a) and when it provides (b). It is a figure which shows the attachment structure at the time of attaching a piezoelectric speaker in piles, (a) is a conceptual diagram at the time of attaching a piezoelectric speaker simply, and (b) is the case where a support | pillar is provided in the first piezoelectric speaker. Conceptual diagram. The output comparison figure of a piezoelectric element and a piezoelectric speaker.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control object 2 Piezoelectric speaker 3 Energy consumption means S1, S2 Shunt circuit 31 Coil 32 Resistor C Capacitance -C Negative electrostatic capacity 4 Power storage means 42 Rectifier 43 Power storage 44 Transformer 31 1st coil 41 2nd Coil 5 Post 6 Magnetic sheet

Claims (3)

In a vibration / noise reduction device comprising an energy conversion system for converting vibration or noise into electricity and an energy consuming means for consuming the converted electricity as heat energy,
The energy conversion system is configured by a piezoelectric speaker in which a diaphragm made of piezoelectric ceramics or the like is supported on an elastic support and an electrode is connected to the diaphragm.
Attach those piezoelectric speakers to a sheet-like magnet,
A vibration / noise reduction device characterized in that the magnet is attached to an object to be suppressed, which is a magnetic body, by magnetic adsorption.   2. The vibration / noise reduction device according to claim 1, wherein when the piezoelectric speaker is attached, a plurality of piezoelectric speakers are attached in an overlapping manner.   3. The vibration / noise reduction device according to claim 1, wherein the object to be suppressed is a piezoelectric piezoelectric speaker, and a piezoelectric speaker as an acoustic-electric converter is attached to the back side of the acoustic piezoelectric speaker. A vibration / noise reduction device that suppresses unnecessary noise generated on the back side of the acoustic piezoelectric speaker.

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