JPH0612081A - Soundproof panel - Google Patents

Abstract

PURPOSE:To obtain good soundproofing performance by decreasing the vibrations by sound waves, on the surface of a second panel by the force of a piezoelectric element to nearly zero by the signal from a controller. CONSTITUTION:The first and second panels 1, 2 are adhered by holding the piezoelectric element 5 and the respective panels 1, 2 are constituted of plates having an electrical conductivity. The piezoelectric element 5 is notched in the corner part of the panels. Pezoelectric type acceleration meters (sensors) 11, 12 which are first and second vibration detecting means are mounted to the inside surfaces of the first and second panels 1, 2. Further, the outputs of the respective sensors 11, 12 are sent to a controller 6. The output of the controller 6 is sent to the first and second panels 1, 2. Namely, the signal for controlling the vibration of the second panel 2 is outputted from the input signal in the controller 6 and is impressed via the first and second panels 1, 2 to the piezoelectric element 5. The piezoelectric element 5 is then vibrated according to the impressed voltage and the vibrations of the second panel are suppressed to zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soundproof panel for vehicles such as aircraft, helicopters and vehicles.

[0002]

2. Description of the Related Art A first example of a conventional soundproof panel is a panel of a single plate 3 made of metal or reinforced plastic as shown in FIG. The soundproofing effect of this is not so good. In a second example improved on this, as shown in FIG. 11, the vibration damping material 7 is attached to the single plate 3. This provides a greater soundproofing effect than that of FIG.

Further, in the third example, as shown in FIG. 12, a vibration damping material 7 is attached to both sides of a single plate 3. This generally provides a larger soundproofing effect than that of FIG.

In a further improved fourth example, as shown in FIG. 13, two single-panel panels 1 and 2 are connected by a connecting member 4 with a gap therebetween, and a sound absorbing material 9 such as glass wool is inserted therebetween. Is. This is because the sound absorbing material absorbs the sound wave that is transmitted through the first panel 1 and is reflected by the second panel 2, and the mass and the rigidity of the sound wave in the transmission direction change abruptly.
Sound waves are less likely to penetrate, and generally, a relatively better soundproofing effect than that shown in FIGS. 10 to 13 is obtained.

[0005]

In each of the conventional soundproof panels described above, the vibration of the panel caused by the incident sound wave cannot be sufficiently reduced, and as a result, the sound wave is transmitted and the radiation from the panel due to the vibration of the panel is generated. Sound is produced,
It was difficult to raise the soundproofing effect beyond a certain limit.

Further, since most of the sound wave energy is replaced and absorbed by the kinetic energy of the soundproof panel to enhance the soundproof effect, the soundproof panel is unavoidably large in mass, resulting in a heavy panel. It had drawbacks.

In addition, there is a characteristic that the soundproof performance is extremely deteriorated at a specific frequency determined by the material, shape and configuration of the soundproof panel.

[0008]

The present invention takes the following means in order to solve the above problems.

That is, as a soundproof panel, (1) first and second conductive panels sandwiching a piezoelectric element, and first and second vibration detection means attached to the first and second panels, respectively. And a controller that receives the outputs of the first and second vibration detection means and sends a signal for suppressing the vibration of the second panel to the first and second panels. (2) In Claim 1, a vibration damping material and / or a sound absorbing material provided between the first and second panels is provided. (3) In the first and second aspects, an electrode provided on the piezoelectric element and connected to the output of the controller, and conductive or non-conductive first and second panels are provided.

[0010]

[Action]

(1) In the means of (1) above, it is assumed that sound waves are incident from the first panel side. The incident sound waves cause the first and second panels to vibrate. This vibration is detected by the vibration detecting means and input to the controller. The controller outputs a signal for suppressing the vibration of the second panel from the input signal and applies the signal to the piezoelectric element via the first and second panels. Then, the piezoelectric element vibrates according to the applied voltage, and the vibration of the second panel is suppressed to zero.

In this way, over a wide range of frequencies,
Vibration does not occur on the second panel side. That is, the incident sound wave is greatly attenuated in a wide band. (2) In the means of the above (2), the operation of the second panel is suppressed by operating in substantially the same manner as the operation of the above (1). At this time, the vibration-damping material and / or the sound-absorbing material between the panels act in the same manner as the conventional one to improve the soundproof effect. (3) In the means of (3) above, the output signal of the controller is directly applied to the electrode of the piezoelectric element. Therefore, the panel need not be limited to be conductive. The operation is almost the same as the above (1) and (2).

[0012]

【Example】

(1) An embodiment of the invention of claim 1 will be described with reference to FIGS.

The parts described in the conventional example are given the same reference numerals and the description thereof will be omitted, and the parts relating to the present invention will be mainly described.

In FIG. 1, the first and second panels 1 and 2 are shown.
Are bonded by sandwiching a piezoelectric element 5 such as polyvinylidene fluoride (for example, piezo manufactured by Daikin Industries, piezoplastics manufactured by Mitsubishi Petrochemical Co., Ltd.). The panels 1 and 2 are plates having conductivity. The piezoelectric element 5 is cut out at the corner portion of the panel, and as shown in FIG. 2, the piezoelectric accelerometers (sensors) 11 and 12 which are the first and second vibration detecting means are provided in the first and second panels. It is attached to the inner surface of 1, 2. The outputs of the sensors 11 and 12 are sent to the controller 6, and the controller 6
Output is sent to the first and second panels 1, 2.

Examples of the piezoelectric accelerometers 11 and 12 are shown in FIG.
Shown in (a), (b), (c) and (d). In the figure, 30 is a case, 31 is a weight, 32 is a piezoelectric element, 33 is a mounting base, 34 is a lead wire, 35 is an impedance conversion / output amplifier circuit element, and 36 is an electrode.

These piezoelectric accelerometers 11 and 12 have the following features. (A) A wide frequency range and acceleration measurement range that can be handled can be taken. (B) It is lightweight and compact, and is durable. (C) No power source is required.

In the above, the sound wave is assumed to be incident on the panel 1. When a sound wave is incident on the panel 1, the sensor 1 senses the vibration generated in the panel 1 by the sound wave. Sound waves are transmitted from panel 1 through piezoelectric element 5 to panel 2
And the panel 2 is vibrated. The vibration is detected by the sensor 2. These signals are input to the controller 6. The controller 6 calculates a control signal for suppressing the vibration of the panel 2 which is determined by the vibrations sensed by the sensors 1 and 2 and the characteristic constants of the panel 1, the piezoelectric element 5 and the panel 2, and the piezoelectric elements 5 are connected to the panels 1 and 2. Apply through. The piezoelectric element 5 expands and contracts in the thickness direction of the soundproof panel in response to a signal to suppress the vibration of the panel 2.

This control principle will be described in detail below. The soundproof panel is modeled as shown in FIG.

[0019] Here, x _1: Panel 1 of the displacement x _2: Panel 2 displacement m _1: Panel 1 Mass c _1: damping coefficient such as a piezoelectric element k _1: the piezoelectric element spring constant m _2: Panel 2 Mass c ₂ : Damping coefficient of panel 2 k ₂ : Spring constant of panel 2 f: Force acting on panel 1 by sound wave u: Force generated by piezoelectric element The equations of motion of panels 1 and 2 are expressed by equations (1), (2 ).

M ₁ D ² x ₁ + c ₁ (Dx ₁ −Dx ₂ ) + k ₁ (x ₁ −x ₂ ) = f−u (1) m ₂ D ² x ₂ + (c ₁ + c ₂ ) Dx ₂ + (k ₁ + k ₂ ) x ₂ = k ₁ x ₁ + c ₁ Dx ₁ + u (2) where D = d / dt where k ₁ x ₁ + c ₁ Dx ₁ + u = 0 then x ₂ The steady solution is x ₂ = 0. Therefore, the force generated in the piezoelectric element is u = -k ₁ x ₁ -c
The vibration of the panel 2 is suppressed by controlling it to be ₁ Dx ₁ .

Specific numerical examples will be shown below.

In FIG. 5, the panel 1 is made of aluminum alloy and its natural frequency is 1,000 Hz. The mass / spring constant / damping coefficient of panel 1 was calculated as m ₁ = 2.7 × 10 ³ × 0.8 × 10 ^-3 × 0.4 ² /9.8 = 0.0353 kgf ・ s ² / m k ₁ = m ₁ × (2πf _m ). ² = 0.0353 × (2π × 1,000) ² = 1.39 × 10 ⁶ kgf / m c ₁ = 2ζ × 2πf _m × m ₁ = 2 × 0.01 × 2π × 1,000 × 0.0353 = 4.44 kgf ・ s ² / m Sound pressure of 100 dB is Since the pressure is almost 2 × 10 ^-5 kgf / m ² , the acting force f of the panel 1 is f = 2 × 10 ^-5 × 0.16 = 0.32 × 10 ^-5 kgf Since the displacement and speed of the panel 1 are simple, Assuming that the acting force f and the inertial force of the mass m ₁ of the panel 1 are balanced, x ₁ = −f / (2πf _m ) ² m ₁ = −0.32 × 10 ⁻⁵ / (2π × 1,000) ² × 0.0353 = -0.23 × 10 ^-11 m ｜ Dx ₁ ｜ = f / (2πf _m m ₁ ) = 0.32 × 10 ^-5 /2π×1,000×0.0353=0.144×10 ^-7 m / s Therefore, the piezoelectric element required for control Force u is u = u ₁ + u ₂ u ₁ = -k ₁ x ₁ = -1.39 x 10 ⁶ x (-0.23 x 10 ^-11 ) = 0.32 x 10 ^-5 kgf u ₂ = -c ₁ | Dx ₁ | = −4.44 × 0.144 × 10 ⁻⁷ = −0.639 × 10 ⁻⁷ kgf The stress σ of the piezoelectric element when the control force u ₁ is generated is σ = 0.32 × 10 ⁻⁵ /0.16=2×10 ⁻⁵ kgf / m ² The piezoelectric constant g of the piezoelectric element currently on the market is generally g = 0.255 v · m / kgf The plate thickness of the piezoelectric element is t = 10 ⁻³ m, and the force u ₁ required for control is
The voltage E ₁ required to obtain E ₁ = gtσ = 0.255 × 10 ^-3 × 2 × 10 ^-5 = 0.51 × 10 ^-8 v In this way, the vibration due to the sound wave is almost zero on the surface of the panel 2. Therefore, the sound wave can be blocked almost completely, and extremely good soundproofing performance can be exhibited. Further, the conventional soundproof panel had a characteristic that the soundproof performance is extremely deteriorated at a specific frequency, but the soundproof panel of the present embodiment is automatically and actively controlled by the controller, so that the piezoelectric element can be output. In the range of force, there is no such weak point, and stable performance can be given over a wide frequency range. In addition, the above results imply that the weight of the soundproof panel for exhibiting a certain level of soundproof performance can be made significantly lighter than the conventional one, from a different viewpoint, and the soundproof panel can be significantly reduced in weight. It becomes possible to do. (2) The first embodiment of the invention of claim 2 will be described with reference to FIG.

A plurality of piezoelectric elements 5 are arranged at predetermined intervals. The panels 1 and 2 are bonded with each piezoelectric element 5 sandwiched therebetween.
Further, the sensors 1 and 2 are attached to the inner surfaces of the panels 1 and 2. Further, the vibration damping material 7 is bonded to the inner surface of the panel 1. Others are the same as those in the embodiment (1).

In the above, the operation is almost the same as that of the embodiment (1). Further, since there is a lot of space between the panels 1 and 2, the lightweight effect is great.

The second embodiment will be described with reference to FIG. Panels 1 and 2 are provided with a plurality of piezoelectric elements 5 sandwiched therebetween. A class wool 8 as a sound absorbing material is inserted between the panels 1 and 2. Others are almost the same as the first embodiment.

The operation is almost the same as that of the first embodiment. (3) A first embodiment of the invention of claim 3 will be described with reference to FIG.

The first and second piezoelectric elements 5 are formed on both sides of the plate-shaped piezoelectric element 5.
Electrodes 21 and 22 are deposited. A conductive substance such as silver is used for the electrodes 21 and 22. Further, the first and second panels 1 and 2 are bonded with the electrodes 21 and 22 sandwiched therebetween. First
The non-conductive carbon fiber reinforced plastic plate is used for the panel 1, and the non-conductive single molded plastic sheet, vinyl sheet, or cloth is used for the second panel 2.

The first and second sensors 11 and 12 are attached to the corner surfaces of the first and second panels 1 and 2, respectively. The output end of the controller 6 is connected to the electrodes 21 and 22, and the input end thereof is connected to the sensors 11 and 12, respectively.

In the above, the operation is almost the same as that of the above-mentioned embodiment, so that the explanation will be omitted.

The second embodiment will be described with reference to FIG.

The arrangement of the panels 1 and 2, the piezoelectric elements 5 and the glass wool 8 is almost the same as that of the second embodiment of the invention of claim 2. However, the side surface of each piezoelectric element 5 (panel 1,
Electrodes 21 and 22 are provided on the surface (perpendicular to 2). Further, the polarization direction of the piezoelectric element 5 is changed so that the expansion / contraction direction due to electrostriction is orthogonal to the panels 1 and 2.

In the above, the operation is almost the same as above.

Although the panels 1 and 2 are made non-conductive in the above, they may be made conductive. However, in the second embodiment, it is necessary to perform processing so that the electrodes 21 and 22 do not short-circuit.

[0034]

As described above, according to the present invention,
With the signal from the controller, the vibration of the sound wave can be made almost zero on the surface of the second panel by the force of the piezoelectric element, so that the sound wave can be almost completely blocked, and the sound insulation performance is extremely good. Can be demonstrated.

Since the controller is automatically and actively controlled, stable soundproofing performance can be obtained over a wide frequency range.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the invention of claim 1;

FIG. 2 is a detailed view of a portion A in FIG. 1 of the same embodiment.

FIG. 3 shows various types of vibration sensors of the same embodiment.

FIG. 4 is an explanatory view of the operation of the embodiment.

FIG. 5 is an explanatory view of the operation of the embodiment.

FIG. 6 is a configuration diagram of a first embodiment of the invention of claim 2;

FIG. 7 is a configuration diagram of a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a first embodiment of the invention according to claim 3;

FIG. 9 is a configuration diagram of a second embodiment of the present invention.

FIG. 10 is a first configuration diagram of a conventional example.

FIG. 11 is a second configuration diagram of the conventional example.

FIG. 12 is a third configuration diagram of the conventional example.

FIG. 13 is a fourth configuration diagram of the conventional example.

[Explanation of symbols]

 1 1st panel 2 2nd panel 3 Panel body 4 Coupling member 5 Piezoelectric element 6 Controller 7 Vibration damping material 8 Glass wool 9 Sound absorbing material 11 First sensor 12 Second sensor 21 First electrode 22 Second electrode

Claims (3)

[Claims] 1. A conductive first and second element sandwiching a piezoelectric element.
Panel, first and second vibration detecting means attached to the first and second panels, respectively, and the first
And a controller that receives the output of the second vibration detection means and sends a signal for suppressing the vibration of the second panel to the first and second panels. 2. The soundproof panel according to claim 1, further comprising a vibration damping material and / or a sound absorbing material provided between the first and second panels. 3. The piezoelectric device according to claim 1, further comprising electrodes provided on the piezoelectric element and connected to an output of the controller, and first and second conductive or non-conductive panels. Characteristic soundproof panel.