JPH0733099U - Broadband ultrasonic generator - Google Patents

Abstract

(57) [Summary] [Purpose] Efficiently emit sound waves other than the resonance frequency. [Structure] A damping material 8 is fixed to a radiation plate 2, and a constraining plate 9 for constraining the deformation of the damping material 8 is attached to the damping material 8.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a wide band ultrasonic wave generator suitable for use in a sound producing section of a super directional speaker.

[0002]

[Prior art]

 Conventionally, an ultrasonic wave generator, for example, a drip-proof ultrasonic wave generator has a structure as shown in FIG. In FIG. 4, reference numeral 1 is a case of the ultrasonic generator. An insulating plate 4 is provided at the lower end of the case 1, and the lower surface thereof, that is, the lower surface of the ultrasonic generator is sealed with silicone rubber 7 for the purpose of drip-proofing.

A pair of terminals 5 are fixed to the insulating plate 4. Each terminal 5 is connected to a piezoelectric vibrator 3 attached to the radiation plate 2 at the upper end of the case 1 via a lead wire 6, respectively. The sizes of the radiation plate 2 and the piezoelectric vibrator 3 are determined so that their natural frequencies match the frequency fo of the transmitted signal.

When an AC voltage having a frequency fo is applied to the terminal 5 from the outside, the voltage is applied to the piezoelectric vibrator 3 via the lead wire 6. Then, the piezoelectric vibrator 3 excites the radiation plate 2 at the frequency fo. Thereby, the sound wave is radiated from the radiation plate 2. The radiation sound pressure frequency characteristic of such a drip-proof ultrasonic generator is as shown in FIG.

[0005]

[Problems to be solved by the device]

 In the conventional ultrasonic wave generator having the structure as shown in FIG. 4, since the attenuation of the ultrasonic wave at the radiation plate (radiation surface) 2 is small, the resonance peak of the radiated sound pressure frequency characteristic is clear as shown in FIG. sharp. Therefore, sound waves other than the resonance frequency cannot be efficiently radiated.

The present invention has been made in view of the above circumstances, and an object thereof is not only a sound wave having only a resonance frequency component but also a sound wave having a wide frequency component including a resonance frequency can be efficiently radiated. It is to provide an ultrasonic generator.

[0007]

[Means for Solving the Problems]

 The present invention is characterized in that an attenuating material is fixed to a sound wave emitting surface of an ultrasonic generator, and a constraining layer for constraining deformation of the attenuating material is formed on the attenuating material.

[0008]

[Action]

 In the above configuration, when generating a sound wave, the sound wave emitting surface vibrates. Then, the vibration amplitude of the radiation surface is attenuated by the bending deformation of the damping material fixed to the radiation surface. Further, since the damping material is provided with a constraining layer that constrains the deformation, shear deformation occurs in the damping material, and the vibration amplitude of the radiation surface is further damped. Therefore, since the resonance peak of the radiation sound pressure frequency characteristic of the radiation surface becomes gentle, it is possible to efficiently radiate sound waves in a wide frequency band including the resonance frequency.

[0009]

【Example】

 An embodiment in which the present invention is applied to a drip-proof ultrasonic generator will be described below with reference to the drawings. FIG. 1 is a plan view of the drip-proof ultrasonic generator, and FIG. 2 is a sectional view taken along the line AA of FIG.

As shown in FIG. 2, a cylindrical case 1 and a radiation plate (radiation surface) 2 that forms the upper end (upper end surface) of the case 1 and generates sound waves are integrally formed of an aluminum thin plate. Is formed in A plate-shaped piezoelectric vibrator 3 is attached to the surface of the radiation plate 2 inside the case 1 with an adhesive. The diameter and thickness of the radiation plate 2 and the dimensions of the piezoelectric vibrator 3 are tuned (adjusted) so that their eigenvalues match the frequency (natural frequency) fo of the sound wave to be generated.

Further, both surfaces of the radiation plate 2 to which the piezoelectric vibrator 3 is attached are covered with the damping material 8. The damping material 8 is made of a material having large internal damping, such as rubber or resin.

A restraint plate 9 is attached on the damping material 8 on the outside of the case 1. The restraint plate 9 is for restraining the deformation of the damping member 8, and is, for example, a thin metal plate. On the other hand, the lower end of the case 1 is closed by the insulating plate 4. The insulating plate 4 is made of, for example, bakelite. A pair of terminals 5 are attached to the insulating plate 4 so as to penetrate the insulating plate 4. Each terminal 5 is connected to an electrode (not shown) on both sides of the piezoelectric vibrator 3 attached to the radiation plate 2 via a lead wire 6.

Further, the lower end of the case 1 closed by the insulating plate 4 is sealed with a silicon rubber 7 for the purpose of drip-proof. Next, the operation of the ultrasonic generator configured as described above will be described.

First, an AC voltage having a frequency f is applied to the terminal 5 from the outside. Then, the piezoelectric vibrator 3 and the radiation plate 2 vibrate at the frequency f of the applied voltage to generate a sound wave. At this time, it is assumed that the frequency f of the voltage is changed from the frequency f1 = 30 KHZ to the frequency f2 = 50 KHZ. Here, it is assumed that f1 <fo and f2> fo. The radiated sound pressure frequency characteristics at this time are shown in FIG.

When the frequency f = fo, the vibration amplitude of the radiation plate 2 becomes maximum, so that the generated sound pressure also becomes maximum. On the other hand, both sides of the radiation plate 2 are covered with a damping material 8, and a constraining plate 9 is attached to the upper surface of the damping material 8 outside the case 1. Therefore, when the radiation plate 2 vibrates, the damping member 8 is bent and deformed in the vertical direction (direction perpendicular to the upper surface of the damping member 8). Further, since the deformation of the upper surface of the damping member 8 is restricted by the restraint plate 9, the amount of deformation of the upper surface and the lower surface of the damping member 8 during vibration is different (the upper surface has a smaller amount of deformation), and the damping member 8 is sheared. Deformation occurs. Since the vibration energy is consumed by the bending deformation and shear deformation of the damping member 8, the vibration amplitude of the radiation plate 2 is reduced.

Therefore, the resonance peak of the sound pressure of the sound wave radiated from the radiation plate 2 does not become sharp as shown in FIG. 5, but becomes gentle as shown in FIG. Therefore, not only the sound wave whose frequency component is only the natural frequency fo of the radiation plate 2 but also the sound wave of a relatively wide band frequency component including this natural frequency fo can be emitted.

It should be noted that by attaching the damping material 8 to the radiation plate 2, there is a defect that the amplitude of the resonance peak is reduced, but this can be compensated by increasing the applied voltage. Further, the drip-proof ultrasonic wave generator can be applied to a sounding section of a superdirective speaker, a transmitting section of an object recognition device, and the like.

[0018]

[Effect of device]

 According to the present invention, an attenuating material is fixed to the sound wave emitting surface of the ultrasonic wave generator, and a constraining layer is formed on the attenuating material to restrain the deformation of the attenuating material. Since the vibration energy is consumed by the bending deformation and the shear deformation of the damping material, the vibration amplitude of the radiation surface is damped. Therefore, since the resonance peaks of the radiation surface when the sound wave is generated become gentle, not only the sound wave of the resonance frequency but also the sound wave of the wide frequency band including the resonance frequency can be efficiently generated.

[Brief description of drawings]

FIG. 1 is a plan view of a drip-proof ultrasonic generator according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing radiated sound pressure frequency characteristics in the example.

FIG. 4 is a diagram showing a structure of a conventional drip-proof ultrasonic generator.

FIG. 5 is a diagram showing a radiation sound pressure frequency characteristic of a conventional drip-proof ultrasonic generator.

[Explanation of symbols]

1 ... case, 2 ... radiation plate (radiation surface),
3 ... Piezoelectric vibrator, 4 ... Insulation plate, 5 ...
Terminals, 6 ... Lead wire, 7 ... Silicon rubber for sealing, 8 ... Damping material, 9 ... Restraint plate (restraint layer).

Continued Front Page (72) Inventor Hiroshi Hata 1 717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Nagahishi Engineering Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A broadband ultrasonic generator, wherein an attenuating material is fixed to a sound wave emitting surface of the ultrasonic generator, and a constraining layer for constraining deformation of the attenuating material is formed on the attenuating material.