Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JPS4939693 ■ Directive air acoustic transformer for ultrasonic waves ◎ Japanese Patent Application No. 453881 [Phase] Application No. 45 (1970) January 16 @ inventor Fukuda Naomi Machida Shigefahara-cho 100 Applicants International Electric Co., Ltd. Tokyo Minato-ku Shibishi Kubo Sakuragawacho 9 ■ 代理人 Attorney Attorney Toshio Shiramizu 1 outside BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of an ultrasonic directed air acoustic transformer according to the present invention, and FIGS. 2 and 3 are side views of another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an air microphone or speaker with high efficiency or high sensitivity and excellent directivity for ultrasound. In the conventional ultrasonic airborne microphones (one used in air for an underwater microphone is referred to as an airborne microphone), the alignment is generally a diaphragm to improve the acoustic transmission efficiency between the diaphragm and air. The characteristic impedance ρC (ρ is the density of the diaphragm material and C is the speed of sound propagation in it) due to the material of the material is extremely low and transmission efficiency is extremely low. For this reason, it is common to use an acoustic transformer such as a wrapper attached to a diaphragm as a countermeasure for improvement. In order to reduce the directivity angle in order to improve the directivity of the microphone, it is effective to increase the thickness of the diaphragm vibrating in the same phase or to use a wrapper, but as ultrasonic waves, When using several tens of KHz, the dimensions of the diaphragm become too large compared to the wavelength, making it difficult to perform the same phase oscillation, and there are various limitations such as the dimensions of the wrapper can not be made too large. It is also practical to use a reflector, but it is a drawback that it is troublesome in production [111111]. Next, when the ultrasonic aerial microphone is used for distance measurement etc., 05-05-2019 1 excellent distance resolution can be obtained unless the duration of the pulse wave of the emitted ultrasonic wave and the received pulse wave, ie, the pulse width is not shortened as much as possible. The measurement can not be made accurately. This is related to the damping characteristics of the speaker and microphone. If these damping characteristics are not improved, the rise of the pulse wave is bad and it takes time to reach steady vibration. It will be too much. For this reason, in general, the Q of the speaker or the microphone is lowered (for example, several tens or less), while lowering the Q brings with it the disadvantage that the sensitivity is degraded. The present invention overcomes these drawbacks and realizes a microphone and a speaker with good directivity, high efficiency and high sensitivity, which will be described in detail with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the ultrasonic air acoustic transformer according to the present invention, where a is a cross sectional view and b is a front view. In the figure, A is a disk-type electrostrictive vibrator using a thin electrostrictive material for causing vibration in a radial mode (radial direction), and its characteristic characteristic impedance is ocooco. Such a disk vibrator vibrates at any of thickness vibration (high frequency, a few hundred KHz) and radial mode vibration (low frequency, for example 10, TG (z), among which radials resonating at low frequencies. Use mode vibration. B and C are also disks, but B has a smaller ρC than the electrostrictive vibrator (hereinafter referred to as a transducer) A (ρC of the B disk is ρ, cl). And a disk made of a material that lowers the Q of the ABC composite, for example, a plastic with a small value of ρC, a light weight and a large loss, ie, nylon, whose thickness tB is that of the oscillator A to cause thickness vibration. With respect to the resonance frequency fA, the speed of sound in B is set to a value close to 1/4 wavelength. Also, the diameter DB is made equal to or larger than the diameter DA of the transducer A. In the latter case, there is a limit to performing [111111] EndPage: 1 with the same phase oscillation in the radiation plane 1. Next, for the C disk, ρC is thicker than the oscillator A (ρC of the C disk is ρ2C2), and a material with a high Q, for example, a mild steel disk, is used. And the diameter Dc is made equal to DA to facilitate processing. Thus, the vibration as a whole of the combined vibrator consisting of A, B and C, that is, the acoustic transformer becomes an axial thickness vibration regulated by the radial vibration of the vibrator disc A. As an actual structure of the acoustic transformer according to the present invention, both surfaces 2 and 3 of the vibrator A are formed by electrode plating or the like, and the lead wires 4 and 5 are drawn from the both electrodes to vibrate the disks B and C. It is bonded to the child A to form a composite resonator. If a voltage of synthetic resonance frequency is applied from the lead wires 4 and 5, a speaker having 1 as a radiation surface becomes a speaker, and conversely, a high performance microphone as an ultrasonic detection microphone of a resonance frequency received from the surface 1 can get. The thickness of the B and C disks is adjusted so that the resonance frequency of this composite resonator is a frequency close to the resonance frequency fh of the radial mode of only the vibrator A. For example, fA = 42 KHz In the case, the combined resonant frequency was about 50 KHz. In addition, the surface of the ultrasonic wave is only the 05-05-2019 2 surface 1 of the eight disks, and in order to prevent the radiation from the surface 6 of the C disk from interfering with the radiation from the surface 1, Although a sound absorber is arranged, it is omitted in the drawing. Here, the characteristics of the acoustic transformer of the present invention will be described. First, since the resonance frequencies of the three vibrators of A, B and C are similar, the composite resonator is easily vibrated and the amplitude becomes large. The sensitivity is good for both transmission and reception. The radiation efficiency at the radiation surface (or received wave) 1 of B is 関係 □ C, where the characteristic characteristic impedance relationship is ρ. C。 Therefore, the radiation efficiency is significantly better than when using the electrostrictive oscillator A as a single unit (this is easily confirmed by experiments, but has a low impedance, so the matching with the air as the radiation medium is improved. It is the biggest advantage that is). Since the Q of the disk B is low, even if the Q of the disk C is high, the Q of the ABC composite vibrator is low, the damping is completed, the rise of the vibration is fast, and the disappearance of the vibration is also fast. Since the disk C has a high Q, the internal loss is small [111111] and its ρ 2 G 2 is ρ of the oscillator A. Since the value is larger than co, the amount of radiation of reactive acoustic energy in the direction of C is smaller than in the case of the transducer A alone. As for the diameter of the radiation surface 1 of the disc B, the resonant frequency of the disc resonator is inversely proportional to rV / に 対 し て with respect to its radius r1 density ρ. Therefore, the diameter of the eight disks can be increased to such an extent that the equal phase vibration condition of the radiation surface is not lost, so that the directivity is improved. In addition, since a large combined transducer can be used at such a ratio of frequencies and transmission efficiency is good, power larger than that of the conventional one can be sent in, and a good S wave can be obtained as an ultrasonic wave transmission / reception system. There are many outstanding advantages such as practical use. FIG. 2 is a side view of another embodiment of the present invention, A. FIG. B and C are the same as those in FIG. 1, but the radiation angle is made narrower than that in FIG. FIG. 3 is a side view of still another embodiment of the present invention, in which A, B and C are the same as FIG. On the contrary, as a countermeasure for the case where the directivity shown in FIG. 1 is too good, it is used to widen only the directivity without losing its advantage. In the above, the case where the 8-disc is a synthetic resin and the C-disc is a metal has been described, but it is also used when both the B and C discs are synthetic resins, in which case the conversion efficiency is somewhat reduced. The synthetic Q is further lowered to provide a feature that transient damping is improved. 05-05-2019 3
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