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 JPS60212097 [0001] Industrial application Field of application This invention is a super device that is constructed by combining a parabolic horn with a piezoelectric element having a diaphragm at its central portion, an electro-acoustic conversion device including a case etc. for housing the piezoelectric element, and a paraboloid horn. The present invention relates to an acoustic transducer. The structure of the conventional example and its problems An electro-acoustic transducer (hereinafter referred to as an ultrasonic sensor) using a piezoelectric element provided with a diaphragm at the center of the conventional element as an electro-acoustic transducer (hereinafter referred to as an ultrasonic sensor) Various ultrasonic transducers are known which are combined with the paraboloid horn made. For example, ultrasonic transducers as disclosed in Japanese Patent Application Laid-Open Nos. 58-85699 and 58-88999 are known. The ultrasonic transducer disclosed in Japanese Patent Application Laid-Open No. 58-85699 has a plurality of ultrasonic transducers on the front surface of an ultrasonic sensor comprising a piezoelectric element 1, a diaphragm 2, a case 3 and the like as shown in FIG. A thin plate 4 having an opening is provided, and the ultrasonic sensor and the thin plate 4 are incorporated in the parabolic horn 6. In the figure, reference numeral 6 denotes a connecting shaft for fixing the diaphragm 2 to the central portion of the piezoelectric element 1. On the other hand, the ultrasonic transducer disclosed in Japanese Patent Application Laid-Open No. 58-88999, as shown in FIG. 1, has an elastic diaphragm 2 as the case 3 in comparison with the example shown in the same figure. The cushioning material 7 is additionally provided with a shock absorbing material 7 to be fixed thereto. The directional characteristics are improved by forming a circular opening centered on a line and various other openings arranged concentrically with this opening. In general, an ultrasonic sensor using a piezoelectric element having a diaphragm at its central portion as an electro-acoustic transducer has higher sensitivity, lower price, and excellent humidity characteristics as compared with a conventional capacitor-type ultrasonic sensor. It is known that 02-05-2019 1 the directivity characteristic is not good although it has advantages such as. The abovementioned proposal is a proposal aiming at improvement of directivity characteristics based on the above-mentioned recognition, and the cause of directivity characteristics deterioration is the finite size of the diaphragm 2 which forms a part of an ultrasonic sensor. The size can not be neglected with respect to the wavelength of the vibration frequency, so even if the end face of the diaphragm 2 is positioned at the focal point of the parabolic horn, the sound source located at the non-focal point is necessarily present By blocking the sound source of the non-focus area by the thin plate 4 as shown in the non-heating point group, and by regarding the thin plate 4 as an apparent sound source It seems that they are trying to improve the directional characteristics. Further, according to the above-mentioned proposal, it is described that the directivity characteristic shown in FIG. 3 can be improved to the characteristic shown in FIG. 3 by providing the thin plate 4. However, although the characteristics of the mouth of FIG. 3 are narrower than the characteristics of FIG. 3 and it can be recognized that the directivity characteristics are surely improved, the sound source of the non-focus portion described above is completely It can not be blocked and, as is apparent from the drawing, it still has the characteristic of having a side rope although it is small. For this reason, the ultrasonic wave transmitting and receiving operation still has a problem that a malfunction may occur. On the other hand, the practical use of the ultrasonic transducer in the above-described proposal also has the following problems. First of all, when the ultrasonic transducer based on the proposal is manufactured and the characteristics are examined, the generation of side lobes is largely different, and the ultrasonic transmission and reception having directivity characteristics as shown in FIG. It turned out that it is extremely difficult to obtain a waver stably. That is, the state of the acoustic circuit formed by the relationship between the vibration operation of the diaphragm 2 and the thin plate 4 is a change in the shape and thickness of the diaphragm 2, inclination 1 ambient temperature etc. The analysis is considered to be extremely difficult because it is considered to be greatly fluctuated, and therefore, there is a problem that the qualification at the mass production level becomes extremely difficult. In other words, any of the above-mentioned proposals is improved by improving the acoustic characteristics of the characteristic gold ultrasonic sensor itself of the ultrasonic transducer. Considering the fact that it changes extremely easily due to the deformation of 2 and the change of ambient temperature etc., it is extremely difficult to stably obtain a product with improved characteristics as an ultrasonic transducer. SUMMARY OF THE INVENTION The object of the present invention is to solve the problems as described above, and it is an ultra-high-power piezoelectric element which hardly causes side lobes of -2 s dB or more to affect the transmission and reception of ultrasonic waves. An acoustic transducer is provided. Another object of the present invention is that the ultrasonic sensor itself consisting of a piezoelectric element or the like provided with a diaphragm can be considered as a simple ultrasonic source, that is, a slight deformation, inclination or the like of the diaphragm 2 of the ultrasonic sensor It is an object of the present invention to provide a mass-productive ultrasonic 02-05-2019 2 transducer having directivity characteristics which are not greatly affected by the fluctuation of the ambient temperature or the fluctuation of the ambient temperature. The ultrasonic transducer according to the present invention comprises an electro-acoustic transducer comprising a diaphragm and a piezoelectric element provided with the diaphragm, an optional rigid wall and a cylindrical hollow portion. An acoustic tube positioned in front of the acoustic conversion element, and a position near the focal point on the horn axis on the horn axis including the focal point at the center of the hollow portion at one end not facing the electroacoustic conversion element of the acoustic tube And at least a paraboloid horn. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an ultrasonic transducer using a piezoelectric element provided with a diaphragm as an electroacoustic transducer having a significantly improved directivity characteristic, which will be described below with reference to the drawings. FIG. 4 is a cross-sectional view showing an embodiment of an ultrasonic transducer according to the present invention, in which the same reference numerals as in FIG. 1 indicate the same functional members. Reference numeral 8 denotes a support fixed to the vibration node of the piezoelectric element 1 and supporting the piezoelectric element 1; 9, a terminal for exchanging electrical energy with the piezoelectric element 1; and 1o, the piezoelectric element 1 and the terminal 9 electrically Lead wire to connect to Reference numeral 11 denotes an acoustic tube positioned in front of an electroacoustic transducer composed of an arbitrary rigid wall 11a and a cylindrical hollow portion 11b, a piezoelectric element 1 and a diaphragm 2. Although the acoustic tube 11 in the present embodiment is apparent also from the drawing, it has only one electro-acoustic transducer, and its central axis corresponds to the horn axis of the electro-acoustic transducer and the parabolic horn 6. The center of the hollow portion 11 b of the other end 11 c is on the horn axis of the paraboloid horn 5 so that the one end 11 d is located on the same plane as the top surface of the diaphragm 2 so as to be coaxial. It is arranged to be located at a position near the focal point on the horn opening side including the focal position. Furthermore, when the acoustic tube 11 shown in FIG. 4 is illustrated, it is needless to say that the plan view can be shown in FIG. 6 and the perspective view can be shown as the mouth of the same figure. Furthermore, when a forced sound pressure is applied from one end of an acoustic tube having a cylindrical hollow portion to an arbitrary rigid wall in general, the wavelength of the forced sound pressure is λ, and the radius of the hollow portion of the acoustic tube is τ. Assuming that the length is l, 2 r ≦ ˜ bow; · · · · · · · · · (1) l ζ + n λ[email protected] r · · · · · · · · ······································································································································································································· ··················· (2) (n: positive integer: constant = o, es) Considering the condition that the other end of the above-mentioned acoustic tube is centered on the hollow portion of the acoustic tube It is known that a stable spherical wave can be formed, and the acoustic tube 11 according to the present invention is also configured in consideration of the above equations (1) and (2). According to the experiments of the inventors of the present invention, r in the equation (1) is advantageously smaller than r = 4 f 6 j t s-· λ with respect to the occurrence of side lobes, (2) 02-05-2019 3 The equation 4 can not of course be strictly defined because it contains λ, which changes with temperature, and the approximation values k and n, but it is intermediate in the general operating temperature conditions of the equipment used Speed of sound 2 at a predetermined temperature of 2 For example, considering general use in the natural world, it is set to a value obtained when general 0.65 is substituted for λ and k based on the speed of sound with 25 ° C. as the predetermined temperature It has been confirmed that no significant difference occurs in the occurrence of side lobes due to temperature fluctuations and the like. As an example, assuming, for example, that the electro-acoustic transducer is transmitted to the conical diaphragm with a tip diameter of 7φ with the vibration frequency of the piezoelectric element being 76 KHz and the air temperature is 26 ° C. = = 1.74 m ++ Any value sufficiently small can be set, for example, 1 cabinet by an experiment of measuring the directivity characteristic. Further, if r = 1 mm is set, equation (2) can be expressed as 1.63 m assuming n = 1. Therefore, for example, the value 1.63 mm can be set as l. Needless to say, in order to obtain better results, it is possible to select an appropriate value by an experiment to measure the directivity characteristics for the value in the vicinity of the value of 1.63 mm. Since one embodiment of the ultrasonic transducer according to the present invention is configured as described above, when electrical energy is supplied from the terminal e, an electro-acoustic transducer comprising the piezoelectric element 1 and the diaphragm 2 Generates a sound wave, which is supplied to the one end 11d of the acoustic tube 11 as a forced sound pressure and transmitted to the outside through the hollow portion 11b. Here, when the directivity characteristics at the time of driving as described above were measured, the directivity characteristics as shown in FIG. 6 were obtained. It is needless to say that the directivity angle is the characteristic when the diameter of the parabolic horn 6 is set to be similar to that of the embodiment shown in FIG. Although it is apparent from FIG. 6, the side lobes of −25 dB or more have only a slight first side lobe, and even when compared with the directivity characteristics of the device with extremely sharp directivity characteristics, FIG. One unit of the directivity characteristic chart of FIG. 1 was 10 dB when it was actually manufactured and confirmed. It is clear that the second side rope has been generated and improved. Here, consider the reason why the directivity characteristics as described above are obtained. First, at the time of driving as described above, the vibration wave transmitted to the outside from the end of the hollow portion 11b of the other end portion 11c of the acoustic tube 11 has a configuration in which the acoustic tube 11 takes into consideration the above-described relational expression. It is needless to say that it is a spherical wave centered on the end opening center of the portion 11b. On the other hand, the end 11C side center of the hollow portion 11b of the acoustic tube 11 is positioned at a position near the focal point on the horn opening side including the focal position on the horn axis of the parabolic horn 5 as described above. Accordingly, it is considered that the spherical wave transmitted to the outside mentioned above will travel parallel to the horn axis in the paraboloid horn 5, and as a result, the opening of the paraboloid horn 6 travels to the outside It is considered that the sound waves that have been transmitted have extremely sharp directivity 02-05-2019 4 characteristics as shown in FIG. In other words, in the ultrasonic transducer according to the present invention, the spherical sound source is provided by the acoustic tube 11 in the vicinity of the focal point on the horn opening side including the focal position on the horn axis of the parabolic horn 6, It can be considered that extremely sharp directivity characteristics are obtained because the sound source clearly located in the non-focus area is largely reduced. By the way, in the embodiment of FIG. 4 mentioned above, although good results were obtained as shown in FIG. 6 with respect to directivity characteristics, it is considered to be good when examining transmission and reception sensitivity. However, when considering the use as a device, there are problems in practical use that are limited to extremely special applications. Also, as mentioned above, although r in the above equation (1) works for the side ropes as it is smaller as it is certain, it is certain that if it is too small, the transmission and reception sensitivity drops. The inventors of the present invention have also confirmed through experiments that a decrease in sensitivity is similarly observed when n is made too large for l in (2). As a result of the inventor of the present invention performing various experiments to address the above problems, if an appropriate acoustic space is provided between the acoustic tube 11 and the diaphragm 2, transmission and reception sensitivity will be remarkable. It has been confirmed that the directivity characteristic is also further improved. Furthermore, according to the experiment of the inventor of the present invention, the above-mentioned acoustic space is simply formed with respect to the directivity characteristic, so that the side rope level is further lowered and the lowering rate is a change in the size of the space and the length etc. Although the transmission and reception sensitivity can be increased by providing it as in the embodiment of FIG. 4, the transmission and reception sensitivities are greatly fluctuated by the change of the size, and conversely the size is changed. It has been confirmed that the characteristics have a property of being largely fluctuated by the change of the vibration frequency and the shape of the diaphragm 2 if fixed. From this fact, it can be considered that the change in sensitivity as described above is caused by the change in sound pressure level applied to one end 11 d of the acoustic tube 11 since there is no large change in directivity characteristics. The reduction in sensitivity in the case as described above can be achieved by suppressing the actual or apparent sound pressure level applied to the one end 11d by shortening the configuration itself or by shortening r and increasing l. It is thought that it is because it becomes a thing. It is considered that the improvement of the directivity characteristic is caused by the fact that supply of forced sound pressure in a more stable phase state to the one end portion 11 d of the acoustic tube 11 becomes possible by the acoustic space. Hereinafter, another embodiment of the ultrasonic transducer according to the present invention made based on the above fact will be described with reference to the sectional view of FIG. In FIG. 7, the same reference numerals as in FIG. 4 indicate the same functional members, and 12 is an acoustic space formed between the diaphragm 2 and the acoustic tube 11. As is apparent from 02-05-2019 5 the drawing, the configuration of the embodiment shown in FIG. 7 is the same as that of the embodiment of FIG. 4 except that the acoustic space 12 is present, and the other configuration is completely the same. By the way, the acoustic space 12 is marked in the hollow portion 11b of the one end 11d of the acoustic tube 11 by the above-mentioned experimental confirmation so that the sound pressure level that can be 77Il becomes stable and large, that is, the diaphragm 2 It is desirable to form so that the sound pressure by the vibration of can be efficiently transmitted. In the present embodiment, as a result of various experiments, for example, the shape is cylindrical and the length and diameter are the same as those of the specific numerical example described above for the conditions of the acoustic tube 11 etc. Cabinet, is set to -10 tran. That is, 1) An ultrasonic transducer having a cylindrical acoustic space with various lengths and diameters is created, and the directivity characteristics, transmission and reception sensitivity characteristics of each transducer are measured, and the results are as described above. I set it to the value. It is needless to say that it is desirable that the value of the above-mentioned acoustic space can be variously changed in consideration of the degree of influence on transmission and reception sensitivity when the expected characteristic condition or the condition of the acoustic tube 11 or the like is changed. . Now, looking at the directivity characteristics, transmission and reception sensitivity in the embodiment shown in FIG. 7 having the values as described above in the acoustic tube 11 and the acoustic space 12 etc. It can be confirmed that the above characteristics and the transmission and reception sensitivity characteristics are each increased by 8 dB as compared with the embodiment shown in FIG. As is clear from the drawing, it is clear that the directivity is improved without the side rope of -25 dB or more, and that the transmission and reception sensitivity also increase by 8 dB. In terms of output level, a signal of about six times can be obtained, and the range of use as a device can be greatly expanded. In the embodiments shown in FIG. 4 and FIG. 7, the acoustic tube 11 is described as being independent, but the length and the radius of the hollow portion are the equations (1) j (2) described above. It is needless to say that as long as it can be set in consideration, it may be integrated with a case in which the parabolic horn 6 or the piezoelectric element 1 or the like is enclosed to form a part of the ultrasonic sensor. According to the present invention, as described above, the sound wave obtained by the ultrasonic sensor comprising the piezoelectric element, the diaphragm and the like is appropriately determined in consideration of the wavelength of the sound wave obtained by this sound wave and an appropriate temperature condition. A non-focusing position is obtained because the spherical sound source is converted to a sound source via an acoustic pipe that can be set, and the obtained spherical sound source is located near the focal point on the horn opening side including the focal position on the horn axis of the parabolic horn. Since it is possible to make the sound source located at a very small amount, it is possible to stably provide an ultrasonic transducer having extremely sharp directivity characteristics. Furthermore, according to the present invention, directivity characteristics are further improved by providing an appropriate acoustic space between the above-mentioned acoustic tube and an electro- 02-05-2019 6 acoustic conversion element consisting of a piezoelectric element and a diaphragm, and in addition, transmission and reception are performed. It has the effect of being able to provide an ultrasonic transducer of extremely high practical value that has significantly increased wave sensitivity. It is a thin plate located in front of the conversion element, and therefore it is vibrated by the vibration of the diaphragm during driving, which adversely affects the transmission characteristics of ultrasonic waves, ie, to the electro-acoustic conversion element. Even if the vibration energy supply to the diaphragm 2 is stopped and the vibration of the diaphragm 2 stops, the thin plate continues to vibrate by inertia, and on the contrary, the vibration energy is supplied to the diaphragm, unnecessary vibration of the diaphragm In the ultrasonic transducer according to the present invention, the one positioned in front of the electro-acoustic transducer is an acoustic pipe having a certain length, and On the contrary, it also has the effect that vibration does not cause << deterioration of the transmission characteristics as described above. [0002] Brief description of the drawings [0003] Sectional drawing which shows one Example of a wave speed receiving device, FIG. 6 a. The mouth is a plan view and a perspective view of an example of the acoustic tube shown by the numeral 11 in FIG. 4, FIG. 6 is a directional characteristic view of the embodiment shown in FIG. 4, and FIG. FIG. 8 is a cross-sectional view showing another embodiment of the wave device, and FIG. 8 shows directivity characteristics of the embodiment shown in FIG. DESCRIPTION OF SYMBOLS 1 ···· Piezoelectric element, 2 ··················································· , 12 ... ... acoustic space. Name of agent Attorney Nakao Toshio and 1 other person Fig. 1 (Waba D Fig. 2 (λ λ [ニ 3 〔儂 儂] αS 4 Fig. R degree) Fig. 7 02-05-2019 7
© Copyright 2021 DropDoc