JPH02301400A - Ultrasonic ceramic microphone - Google Patents

Abstract

PURPOSE:To absorb the undesired vibration transmitted to a bimorph vibrator and to reduce the echo time by providing a vibration proof member and a buffer block to absorb the needless vibration, arranging the vibration proof member to a radiation face of a conical resonator and radiating an ultrasonic wave output transmitted from the conical resonator into air through the vibration proof member. CONSTITUTION:A piezoelectric vibrator 11 forms a bimorph vibrator while being stuck with a 2nd piezoelectric vibrator 12 and a conical resonator 13 is fixed to the middle of the bimorph vibrator with adhesives 14. A vibration proof member 15 of net shape made of a resin is arranged to a radiation face of the conical resonator 13 through an adhesives 16 to constitute a composite resonator. A buffer block 17 is formed by using a foamed buffer member to improve the vibration absorption efficiency. Then the bimorph vibrator is fixed to the buffer block 17 through the elastic adhesives 18 and the buffer block 17 is assembled to a mount hole of a terminal board 19. Thus, the undesired vibration generated from the conical resonator 13 is absorbed and the interference of the ultrasonic wave generated from the inside of the case is relaxed to reduce the vibration interference between the terminal board and the case.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic ceramic microphone for transmitting and receiving ultrasonic waves used in devices such as ultrasonic proximity switches.

Conventional technology Conventionally, this type of ultrasonic ceramic microphone has a second
The configuration was as shown in the figure. In FIG. 2, l denotes a piezoelectric vibrator, which is bonded to a metal diaphragm 2 to form a bimorph vibrator. A coupling shaft 3 is fixed to a through hole provided in the center of this bimorph resonator, and a conical resonator 4 is fixed to the root of the coupling shaft 3 to form a composite resonator.

This composite resonator is adhesively fixed to a convex portion 6a provided at the center of a terminal plate 6 via an elastic adhesive 5, and the composite resonator and terminal plate 5 are housed in a cylindrical case 7. Ta.

Problems to be Solved by the Invention In such a conventional configuration, when the bimorph oscillator is driven, the vibrations are caused by the vibrations of the surrounding components of the bimorph oscillator, such as the conical resonator, the lead wire, and the coupling shaft.

When transmitted to the terminal plate and case, it becomes a reflected vibration that is transmitted to the bimorph resonator and interferes with it, causing reverberation, which poses a problem of reducing pulse response.

The present invention is intended to solve these problems, and aims to absorb unnecessary vibrations transmitted to the bimorph resonator and shorten the reverberation time for pulse signals.

Means for Solving the Problem In order to solve this problem, the present invention provides a piezoelectric vibrator and a second
A conical resonator is fixed to the center of a bimorph vibrator made of a piezoelectric vibrator or a metal diaphragm laminated together, and a vibration isolating material is placed on the radiation surface of the conical resonator to create a composite resonator. , the composite resonator is fixed to a buffer block via an elastic adhesive, the buffer block is incorporated into a terminal plate, and the composite resonator, buffer block, and terminal plate are housed in an exterior case. This is what I did.

Effect: With this configuration, unnecessary vibrations generated from the conical resonator are absorbed by the vibration isolating material, and interference of ultrasonic waves generated within the case is alleviated. Further, by fixing the bimorph vibrator on the terminal plate via the buffer block, vibration interference with the terminal plate and the case can be reduced.

Embodiment FIG. 1 is a sectional view of an ultrasonic ceramic microphone according to an embodiment of the present invention. In FIG. 1, numeral 11 is a piezoelectric sensor, and a second piezoelectric sensor 12 is attached to form a bimorph transducer. It consists of Reference numeral 13 denotes a conical resonator made of metal or resin, which is fixed to the center of the bimorph resonator with an adhesive 14 interposed therebetween. The conical resonator 13
A mesh-like anti-vibration material 15 made of resin is placed on the radiation surface of the adhesive 1.
6 to form a composite resonator. In order to prevent a decrease in sensitivity, this vibration isolating material 15 is required to have sufficient air ventilation and a lightweight structure. m) of 100
I used mesh board. Reference numeral 17 denotes a buffer block, which is made of foamed buffer material to increase vibration absorption efficiency. The bimorph vibrator is fixed to the buffer block 17 via an elastic adhesive 18, and the buffer block 17 is assembled into the mounting hole of the terminal plate 19.

Reference numeral 20 denotes an exterior case, which houses the composite resonator and the buffer block 1.
7. The structure is such that the terminal board 19 is accommodated. 21 and 2
2 is a lead wire, and 23 and 24 are terminals. Reference numeral 25 denotes an elastic adhesive for dampening vibrations of the lead wires 21 and 22. 26 is a metal base for shielding.

Effects of the Invention As described above, according to the present invention, the reverberation time in pulse response can be shortened by providing a vibration isolating material and a buffer block for absorbing unnecessary vibrations transmitted to the bimorph vibrator. In addition, since the vibration isolating material is placed on the radiation surface of the conical resonator, the ultrasonic output converted from the conical resonator into the air is radiated through the vibration isolating material without being attenuated. It is possible to provide high sensitivity while suppressing reverberation. Furthermore, since it absorbs the interference of ultrasonic waves generated within the case, there is no pull-in phenomenon that occurs during standing wave resonance when used for transmitting, and stable driving is achieved.

The present invention enables use as a transducer for both transmitting and receiving ultrasonic waves.

Note that in the present invention, a bimorph vibrator may be constructed by laminating a piezoelectric vibrator and a metal diaphragm.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an ultrasonic ceramic microphone according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional ultrasonic ceramic microphone. 11... Piezoelectric vibrator, 12... Second piezoelectric vibrator, 13... Conical resonator, 14...
...Adhesive, 15...Vibration-proofing material, 16...
...Adhesive, 17...Buffer block, 18
...Elastic adhesive, 19...Terminal board, 2
0...Exterior case, 21.22...Lead wire, 23.24...Terminal, 25...
・Elastic adhesive, 26...Metal base.

Claims (1)

[Claims] A conical resonator is fixed to the center of a bimov vibrator formed by laminating a piezoelectric vibrator and a second piezoelectric vibrator or a metal diaphragm, and a vibration-proofing material is provided on the radiation surface of the conical resonator. This composite resonator is fixed to a buffer block via an elastic adhesive, the buffer block is assembled into a terminal plate, and the composite resonator, buffer block, and terminal plate are placed in an exterior case. A housed ultrasonic ceramic microphone.