JPS635357Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ultrasonic ceramic microphone used for transmitting and receiving ultrasonic waves.

A conventional ultrasonic ceramic microphone will be explained with reference to FIG. A conventional ultrasonic ceramic microphone has a bimorph oscillator 1 made by bonding two piezoelectric ceramic oscillators 1a with their polarization directions facing each other, a coupling shaft 2 is provided in the center, and a conical resonator 3 is attached The bimorph resonator 1 was attached to a central support portion of a terminal plate 5 via an elastic adhesive 4, and these were housed in a case 6. According to such a conventional configuration, the vibrations of the bimorph resonator 1 and the resonator 3 have free end vibrations and have a high Q, so they have high sensitivity and excellent narrow band selectivity. However, due to the high Q of the resonator 3, the pulse response was poor. In addition, since the conical resonator 3 is made of a thin material such as aluminum, which has a low inherent acoustic impedance and high electro-acoustic conversion efficiency, high-order resonance is likely to occur, and the high-order resonance affects the resonance, and as mentioned above, The pulse response was extremely slow.

In view of the above points, the purpose of this invention is to obtain an ultrasonic ceramic microphone with excellent narrow directivity and pulse response, which is ideal for communication applications in which data signals are oscillated, and the signals are received and reproduced. shall be.

In other words, the present invention includes a cylindrical case, a vibration isolator made of an elastic material fixed to the inner surface of the case, a resonator whose enlarged diameter end outer peripheral surface is adhesively fixed to the vibration isolator, and a central part. a bimorph resonator disposed such that the enlarged diameter end of the resonator faces one end of the case, a sound absorbing material disposed at the other end of the case, and a blockage with the other end of the case. The top of a conical or truncated conical resonator is attached to the terminal plate, and the outer peripheral surface of the enlarged diameter end of this resonator is adhesively fixed to a vibration isolating material made of an elastic material with a high vibration damping effect. A vibration isolating material is fitted into a cylindrical case from one open end, a sound absorbing material is inserted from the other open end, and the other end of the case is closed with a terminal plate.The resonator is made of an elastic material. Because the resonator is supported and fixed with vibration isolating material made of It becomes stable and the pulse response improves. Also, unlike conventional structures, the structure does not utilize standing wave resonance within the case, but rather generates ultrasonic waves through the vibration of a resonator, so there is no interference of sound waves and the radiation conditions remain constant, resulting in sharper directivity.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 2, 7 is a bimorph vibrator made by bonding two piezoelectric ceramic vibrators 7a together. The shape of the piezoelectric ceramic vibrator 7a may be a circular plate, a square plate, an elliptical plate, or the like. The bimorph vibrator 7 may be made of a single piezoelectric ceramic vibrator 7a, or may be made by bonding the piezoelectric ceramic vibrator 7a and a metal diaphragm together. 8
is a cone-shaped resonator made of metal or resin, and is attached to the center of the bimorph vibrator 7,
A composite vibrator is formed. The resonator 8 may be in the shape of a truncated cone. In order to increase the strength of the connection between the resonator 8 and the bimorph vibrator 7, a joint 8a is provided integrally with the top of the resonator 8, and the joint 8a is inserted and fixed in a joint hole formed in the center of the bimorph vibrator 7, thereby improving the vibration resistance. 9 is made of cork, silicone rubber,
This is a vibration-proof material made of an elastic material such as butyl rubber.
The outer peripheral surface of the enlarged end of the resonator 8 is fixed to the inclined surface 9a formed on one end surface of the vibration-proof material 9. The support area of the resonator 8 is optimally 20% to 50% of the entire inclined surface because the vibration amplitude is significantly attenuated if the entire surface is fixed, and conversely, if the support area is small, the Q becomes high and the pulse response is deteriorated. Reference numeral 10 denotes a cylindrical case having openings at both ends, and the enlarged end of the resonator 8 to which the vibration-proof material 9 is fixed is housed so as to face the one end opening side of the case 10. The other end opening is closed by a terminal plate 11. A sound absorbing material 12 is housed in the space within the case 10 surrounded by the vibration-proof material 9, the resonator 8, and the terminal plate 11 to prevent fluctuations in characteristics due to diffuse reflection of sound waves. Reference numerals 13a and 13b denote lead wires, and external terminals 14a and 14b are attached to the terminal plate 11.
14b and the upper and lower electrodes 1 of the bimorph vibrator 7
The lead wires 13a and 13b are electrically connected to each other. A vibration isolating rubber 16 is provided to reduce vibration interference between the lead wires 13a and 13b.

According to the above configuration, the Q of resonance is reduced because the resonator 8 is supported and fixed by the vibration isolating material 9 made of an elastic material. Further, since the space inside the case 10 is filled with the vibration isolating material 9 and the sound absorbing material 12, interference due to diffuse reflection of sound waves and sound leakage can be eliminated, and stable characteristics and pulse response are improved. Also, unlike the conventional structure, the structure does not utilize the standing wave resonance within the case 10, but instead generates ultrasonic waves by the vibration of the resonator 8, so there is no interference of sound waves and the radiation conditions are constant, so the directivity can be improved. Sexuality becomes sharper. Furthermore, by adjusting the thickness and outer diameter of the bimorph resonator 7 and the outer diameter dimensions of the resonator 8, high sensitivity and broadband acoustic performance can be obtained.

As described above, according to the present invention, it is possible to provide an ultrasonic ceramic microphone with excellent pulse response and narrow directivity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional ultrasonic ceramic microphone, and FIG. 2 is a sectional view of an ultrasonic ceramic microphone according to an embodiment of the present invention. 7...bimorph oscillator, 8...resonator, 9...
...Vibration isolation material, 10...Case, 11...Terminal board, 1
2...Sound absorbing material.

Claims (1)

[Scope of utility model registration request] A cylindrical case, a vibration isolator made of an elastic material fixed to the inner surface of the case, and a resonator in the center whose enlarged diameter end outer peripheral surface is adhesively fixed to the vibration isolator, a bimorph resonator arranged such that an enlarged diameter end of the resonator faces one end of the case;
An ultrasonic ceramic microphone comprising a sound absorbing material disposed at the other end of the case, and a terminal plate closing the other end of the case.