JP2019097052A - Supersonic wave projection device - Google Patents

Abstract

To improve a sound pressure in a supersonic wave projection device capable of projecting a supersonic wave with high directivity.SOLUTION: A supersonic wave projection device 1 projecting a supersonic wave, comprises: a vibration part generating a vibration in accordance with the supersonic wave to be projected; a columnar support 5 extended from a tip end surface of the vibration part; a vibration plate 6 that executes flexural vibration by being fixed to the tip of the columnar support 5 and transferring the vibration, and in which an outer edge is projected and positioned at a radial direction outer side of the columnar support to the circumference surface of the columnar support 5. In the vibration plate 6, a shortest distance dimension from the outer edge to the columnar support 5 in a whole periphery of the outer edge is equal to 1/4 of a wavelength of the flexural vibration. In the columnar support 5, a length dimension in an extension direction is equal to 1/4 of the wavelength of a longitudinal vibration in the columnar support 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic projection apparatus.

  2. Description of the Related Art In recent years, small-sized ultrasonic projection devices have been used as ultrasonic sensors for vehicles and parametric speakers that project sound waves with directivity. For example, an ultrasonic sensor for a vehicle projects an ultrasonic wave, receives a reflected ultrasonic wave, and outputs a signal indicating the distance to an obstacle. In addition, the parametric speaker includes a plurality of ultrasonic projection devices arranged in an array, and projects a strong sound wave in a predetermined direction. For example, Patent Document 1 discloses an ultrasonic sensor including a piezoelectric member that emits ultrasonic waves. According to the ultrasonic sensor shown in such Patent Document 1, ultrasonic waves can be projected to the outside by the ultrasonic vibration generated by the piezoelectric member.

JP, 2010-243414, A

  Generally, in the case of an ultrasonic sensor that projects ultrasonic waves to a further distance, a horn that resonates with the ultrasonic vibration generated by the piezoelectric member is provided. Such horns are usually in the form of solid rods. However, even with an ultrasonic projection apparatus provided with such a horn, the sound pressure of the ultrasonic waves that can be generated is small. For this reason, the ultrasonic sensor as disclosed in Patent Document 1 can project effective ultrasonic waves only at a very short distance.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to improve sound pressure in an ultrasonic projection apparatus capable of projecting an ultrasonic wave with high directivity.

  The present invention adopts the following configuration as means for solving the above-mentioned problems.

  A first aspect of the present invention is an ultrasonic projection apparatus for projecting an ultrasonic wave, comprising: a vibration unit for generating a vibration according to the ultrasonic wave to be projected; a support extending from a tip surface of the vibration unit; A vibrating plate fixed to the tip end to be flexed and vibrated by the transmission of the vibration, and an outer edge of the diaphragm is positioned so as to protrude radially outward of the pillar with respect to the circumferential surface of the pillar; The shortest distance dimension from the outer edge to the support column over the entire periphery of the outer edge is equal to or less than a quarter of the wavelength of the flexural vibration, and the length dimension of the support column in the extension direction is the wavelength of the longitudinal vibration in the support column Adopt a configuration that is less than a quarter.

  According to a second aspect of the present invention, in the first aspect, the diaphragm has a configuration in which the outer edge is a circular disc.

  According to a third aspect of the present invention, in the second aspect, the diaphragm is arranged such that the center position thereof is overlapped with the axis when viewed from the direction along the axis of the support.

  According to the present invention, the diaphragm is connected to the tip end surface of the vibrating portion through the support column, and the shortest distance dimension from the outer edge to the support column over the entire periphery of the outer edge is 1/4 or less of the wavelength of the flexural vibration. The length dimension of the support in the extending direction is not more than a quarter of the wavelength of the longitudinal vibration in the support. According to such an embodiment of the present invention, the diaphragm flexes and vibrates without joints. That is, according to the present invention, the entire area of the diaphragm is swayed and oscillated so as to be repeatedly displaced in the same direction. As a result, when the diaphragm projects the ultrasonic wave forward, the sound wave of the component directed backward can not be generated, and the sound pressure of the ultrasonic wave projected from the diaphragm can be improved. Therefore, according to the present invention, it is possible to improve the sound pressure in an ultrasonic projection apparatus capable of projecting ultrasonic waves with high directivity.

It is an outline view showing a schematic structure of an ultrasonic projection device in one embodiment of the present invention. It is a front view of a diaphragm and a support with which an ultrasonic projection device in one embodiment of the present invention is provided. It is a graph which shows the admittance characteristic of the ultrasonic projection device in one embodiment of the present invention, and the ultrasonic projection device for comparison, and is a graph which shows the admittance characteristic of the ultrasonic projection device in one embodiment of the present invention. (B) is a graph which shows the admittance characteristic of the ultrasonic projection apparatus for comparison. It is a graph which shows the vibration distribution of the ultrasonic projection apparatus in one Embodiment of this invention, and the ultrasonic projection apparatus for comparison. It is a graph which shows sound pressure distribution of the ultrasonic projection apparatus in one Embodiment of this invention, and the ultrasonic projection apparatus for comparison.

  Hereinafter, an embodiment of an ultrasonic projection apparatus according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

  FIG. 1 is an external view showing a schematic configuration of the ultrasonic projection apparatus 1 of the present embodiment. As shown in this figure, the ultrasonic projection apparatus 1 of the present embodiment includes a vibrator 2, a vibration transmission unit 3, a horn 4, a support 5, and a diaphragm 6.

  The vibrator 2 is a unit that generates vibration (ultrasonic vibration), and includes a plurality of piezoelectric elements 2a that vibrate when power is supplied, and a holder 2b that supports the piezoelectric elements 2a. Instead of the piezoelectric element 2a, an electromechanical transducer such as a magnetostrictive element or an electrostrictive element can be used. As such a vibrator 2, for example, a bolt-clamped Langevin type Transducer (BLT) that generates strong ultrasonic waves can be suitably used. Such a vibrator 2 is driven by power supplied from a power supply circuit (power supply) not shown.

  The vibration transfer unit 3 is disposed between the vibrator 2 and the horn 4 and transmits the ultrasonic vibration generated by the vibrator 2 to the horn 4. The vibration transmitting unit 3 includes a rod portion 3a having a uniform solid cross section, and a flange 3b connected to the circumferential surface of the rod portion 3a. One end of the rod portion 3 a is connected to the vibrator 2, and the other end is connected to the horn 4. The flange 3b is connected to a node of the rod portion 3a (a portion not displaced when ultrasonic vibration is transmitted), and a mounting portion in the case of mounting the ultrasonic projection apparatus 1 of the present embodiment to an external member Site to be

  The horn 4 is a portion for amplifying ultrasonic vibration by resonating with ultrasonic vibration transmitted from the vibrator 2 via the vibration transmitting unit 3 and transmitting the ultrasonic vibration to the support 5 and the diaphragm 6. In the ultrasonic projection apparatus 1 of the present embodiment, the vibrator 2, the vibration transfer unit 3 and the horn 4 function as a vibration unit that generates a vibration according to the ultrasonic wave to be projected.

  The support 5 is a cylindrical or cylindrical portion extending from the end surface of the horn 4 (that is, the end surface of the vibrating portion), and is disposed concentrically with the horn 4. The support 5 supports the diaphragm 6 and transmits the vibration transmitted from the horn 4 to the diaphragm 6. The column 5 has a diameter smaller than that of the horn 4 and the diaphragm 6 when viewed from the direction along the axis. In addition, the length dimension in the extension direction of the support 5 is set to one fourth or less of the wavelength of the longitudinal vibration in the support 5 and is sufficiently smaller than one quarter of the wavelength of the flexural vibration of the diaphragm 6 Is desirable.

  The diaphragm 6 is a portion where the outer edge 6 a is positioned so as to protrude outward in the radial direction of the support 5 with respect to the circumferential surface of the support 5 and is integrally fixed to the tip of the support 5. The vibrating plate 6 is bent and vibrated by the longitudinal vibration transmitted from the support 5. FIG. 2 is a front view of the diaphragm 6 as viewed from the direction along the axial center of the support 5 (the direction along the extension direction from the horn 4). As shown in this figure, the diaphragm 6 is a disc whose outer edge 6 a has a circular shape, and the center position of the diaphragm 6 is arranged on the axis of the support 5. When this diaphragm 6 is viewed from the direction along the axis of the column 5, the distance dimension d to the outer peripheral surface of the column 5 is set to 1/4 or less of the wavelength of the flexural vibration of the diaphragm 6 . In such a diaphragm 6, the shortest distance dimension from the outer edge 6a to the support 5 is equal to or less than a quarter of the wavelength of the flexural vibration all around the outer edge 6a.

  Such a diaphragm 6 vibrates in the same phase in the entire region in the radial direction. For example, when the portion on the central side in the radial direction of the diaphragm 6 is displaced in the projection direction of the ultrasonic wave, the other regions excluding the portion on the central side in the radial direction are also displaced in the projection direction of the ultrasonic wave When the central side portion of the direction is displaced to the opposite side to the projection direction of the ultrasonic wave, the other regions except the central side portion in the radial direction are also vibrated to be displaced to the opposite side to the projection direction of the ultrasonic wave . That is, the frequency of the ultrasonic vibration generated by the vibrator 2 is a frequency at which no node occurs in the direction along the surface of the diaphragm 6. The diaphragm 6 vibrates in a flexural manner by resonating with the ultrasonic vibration as in the horn 4 and thereby emits a strong sound wave having high directivity.

  The support 5 and the diaphragm 6 can be made of, for example, the same material as the horn 4. In such a case, it is possible to integrally form, for example, the horn 4, the support 5, and the diaphragm 6 by cutting out, and the diaphragm 6 can transmit the vibration well.

  In the ultrasonic projection apparatus 1 of the present embodiment, when power is supplied from the external power supply circuit (power supply) to the piezoelectric element 2a of the vibrator 2, the piezoelectric element 2a vibrates to generate ultrasonic vibration. Ru. The ultrasonic vibration is transmitted from the vibration transmitter 3 to the diaphragm 6 via the horn 4 and the support 5. As a result, strong ultrasonic waves are emitted from the diaphragm 6 with directivity.

Then, basic examination using the ultrasonic projection device 1 of this embodiment is explained.
In this study, a 60 kHz bolt-clamped Langevin type vibrator was used as the vibrator 2. The vibrator 2 had a diameter of 15 mm and a length of 39 mm. Moreover, in the vibration transmission part 3, the diameter dimension of the rod part 3a was 15 mm, and the length dimension of the rod part 3a was 42.5 mm. Further, in the vibration transfer unit 3, the flange 3b had a diameter of 25 mm and a thickness of 1 mm, and was installed at a position of 19.5 mm from the end of the rod 3a on the vibrator 2 side.

  The horn 4 had a diameter of 15 mm and a length of 60 mm. The support 5 has a diameter of 4 mm and a length of 5 mm. The diaphragm 6 had a diameter of 10 mm and a thickness of 0.8 mm.

  Moreover, in this examination, in order to compare with the ultrasonic projection apparatus 1 of this embodiment, the ultrasonic projection apparatus (comparative ultrasonic projection apparatus) which is not provided with the support | pillar 5 and the diaphragm 6 was also examined. .

  First, in order to obtain the resonance frequency and the sharpness of the ultrasonic projection apparatus 1 of the present embodiment and the ultrasonic projection apparatus for comparison, the admittance characteristics were measured using an impedance analyzer. FIG. 3 is a graph showing the admittance characteristics of the ultrasonic projection device 1 of the present embodiment and the ultrasonic projection device for comparison, and (a) is a graph showing the admittance characteristics of the ultrasonic projection device 1 of the present embodiment. (B) is a graph which shows the admittance characteristic of the ultrasonic projection apparatus for comparison. In FIG. 3, the horizontal axis represents conductance, and the vertical axis represents susceptance.

  The resonance frequency of the ultrasonic projection device 1 of the present embodiment was 61.4 kHz, and the sharpness was 1661. The conductance maximum of the ultrasonic projection device 1 of the present embodiment was 12.2 mS, as shown in FIG. 3 (a). In addition, the resonance frequency of the comparative ultrasonic projection apparatus was 57.8 kHz, and the sharpness was 615. The conductance maximum of the comparative ultrasonic projection device was 31.8 mS, as shown in FIG. 3 (b).

  Subsequently, in order to examine the vibration displacement of the diaphragm 6, the vibration distribution was measured using a laser Doppler vibrometer. Moreover, it measured also about the case of the ultrasonic projection apparatus for comparison as comparison as a case where there is no diaphragm 6. FIG. The measurement was made in the range of 15 mm in the radial direction passing through the center, and was performed at 0.5 mm intervals. The drive condition of the ultrasonic projection apparatus 1 of the present embodiment and the ultrasonic projection apparatus for comparison is a constant input power of 0.1 W, and the drive frequency is a value shown for the resonance frequency in the description of FIG.

  FIG. 4 is a graph showing the vibration distribution of the ultrasonic projection device 1 of the present embodiment and the ultrasonic projection device for comparison. In FIG. 4, the horizontal axis represents the distance from the center of the diaphragm 6 (horn tip surface), and the vertical axis represents vibration displacement (effective value). Further, in FIG. 4, a line connecting black circles indicates the vibration distribution of the ultrasonic projection apparatus 1 of the present embodiment, and a line connecting white circles indicates the vibration distribution of the comparative ultrasonic projection apparatus.

  As shown in FIG. 4, it can be seen that the vibration displacement of the ultrasonic projection device 1 of the present embodiment is relatively small near the center, and becomes larger as the end of the diaphragm 6 is approached. On the other hand, it can be seen that the comparative ultrasonic projection apparatus has uniform vibration displacement over the entire surface. Moreover, when both results are compared, it turns out that the largest vibration displacement of the ultrasonic projection apparatus 1 of this embodiment is about 22 times larger than the largest vibration displacement of the ultrasonic projection apparatus for comparison.

  Subsequently, in order to examine the sound pressure distribution of the diaphragm 6, the sound pressure was measured using a microphone with a probe (ACO, TYPE-7118) and a rotary stage. Moreover, the ultrasonic projection apparatus for comparison was also measured as a comparison. In the measurement, the distance between the ultrasonic projection apparatus 1 of this embodiment and the ultrasonic projection apparatus for comparison and the measurement point is 300 mm, and the ultrasonic projection apparatus 1 of this embodiment and the ultrasonic projection apparatus for comparison are on the central axis. The angle was 0 °, and the angle was changed by 1 ° in the range of -90 ° to 90 °. The driving conditions of the ultrasonic projection apparatus 1 of the present embodiment and the comparative ultrasonic projection apparatus are the same as the conditions in the description of FIG. 4 described above.

  FIG. 5 is a graph showing sound pressure distributions of the ultrasonic projection device 1 of the present embodiment and the comparative ultrasonic projection device. In FIG. 5, the horizontal axis represents the angle of the ultrasonic projection apparatus 1 of the present embodiment or the ultrasonic projection apparatus for comparison, and the vertical axis represents the sound pressure. Further, in FIG. 4, a line connecting black circles indicates the sound pressure distribution of the ultrasonic projection apparatus 1 of the present embodiment, and a line connecting white circles indicates the sound pressure distribution of the comparative ultrasonic projection apparatus.

  As shown in FIG. 5, it can be seen that the sound pressure of the ultrasonic projection device 1 of the present embodiment and the ultrasonic projection device for comparison both have a maximum at the direction of 0 °. In addition, it was found that the maximum sound pressure in the case of the ultrasonic projection device 1 of the present embodiment is 45 Pa, and the sound pressure is about 6 times as high as the maximum sound pressure 8 Pa of the comparative ultrasonic projection device. .

  Thus, as a result of examining the sound pressure distribution and the vibration distribution of the ultrasonic projection apparatus 1 of the present embodiment, the sound pressure and the vibration displacement of the ultrasonic projection apparatus 1 of the present embodiment are compared with the ultrasonic projection apparatus for comparison. It turned out that it becomes large compared with. That is, the ultrasonic projection apparatus 1 of the present embodiment can improve the sound pressure in an ultrasonic projection apparatus capable of projecting an ultrasonic wave with high directivity.

  According to the ultrasonic projection apparatus 1 of the present embodiment as described above, the diaphragm 6 is connected to the tip end surface of the horn 4 via the support 5, and the vibration plate 6 is the shortest from the outer edge to the support around the entire outer edge. The distance dimension is equal to or less than a quarter of the wavelength of the flexural vibration, and the length dimension of the support 5 in the extending direction is equal to or less than a quarter of the wavelength of the longitudinal vibration of the support 5. According to the ultrasonic projection device 1 of the present embodiment, the diaphragm 6 bends and vibrates without joints. That is, according to the ultrasonic projection apparatus 1 of the present embodiment, the entire area of the diaphragm 6 is flexurally vibrated so as to be repeatedly displaced in the same direction. As a result, when the diaphragm 6 projects the ultrasonic wave forward, the sound wave of the component directed backward can not be generated, and the sound pressure of the ultrasonic wave projected from the diaphragm 6 can be improved.

  Further, in the ultrasonic projection apparatus 1 of the present embodiment, the diaphragm 6 is a disc whose outer edge 6a has a circular shape. Therefore, no bent portion exists in the outer edge 6 a of the diaphragm 6, and it is possible to suppress that a large stress locally acts on the outer edge 6 a of the diaphragm 6 by vibration.

  Furthermore, in the ultrasonic projection apparatus 1 of the present embodiment, the center of the disk-shaped diaphragm 6 is disposed so as to overlap the axis of the support 5 as viewed from the direction along the axis of the support 5. For this reason, the diaphragm 6 vibrates while being deformed uniformly in the radial direction centering on the axial center of the support 5. For this reason, the spread of the ultrasonic wave emitted from the diaphragm 6 becomes uniform, and the directivity of the ultrasonic wave can be further enhanced.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the above embodiments. The shapes, combinations, and the like of the constituent members shown in the above-described embodiment are merely examples, and various changes can be made based on design requirements and the like without departing from the spirit of the present invention.

  For example, in the above embodiment, the configuration in which the support 5 and the diaphragm 6 are formed of the same material as the horn 4 has been described. However, the present invention is not limited to this. It is also possible to form the diaphragm 6 of a material different from that of the horn 4 and the support 5. Further, it is also possible to form the horn 4, the support 5 and the diaphragm 6 by a resin material or the like. Furthermore, the diaphragm 6 is divided into a surface layer portion exposed and disposed on the side where ultrasonic waves are projected and a bottom layer portion formed of a material different from the surface layer portion and located on the horn 4 side. It is also possible to adopt. For example, it is also possible to adopt a configuration in which the bottom layer portion is formed of a metal for enhancing the rigidity and the surface layer portion is formed of a resin material of the same color as the paint of the vehicle.

  Moreover, in the said embodiment, the support | pillar 5 demonstrated the structure which is a cylinder type or cylindrical shape extended from the front end surface (namely, front end surface of a vibration part) of the horn 4. FIG. However, the present invention is not limited to this. For example, it is also possible to adopt a configuration provided with a polygonal pillar-shaped or polygonal cylindrical support.

  Also, the diaphragm 6 may not be a disk but may be a plate member having another shape such as a polygonal shape or an elliptical shape. Further, the center of the diaphragm 6 does not necessarily have to be arranged to coincide with the axis of the support 5. For example, there is a possibility that the projection direction of the ultrasonic wave can be changed by eccentrically attaching the diaphragm 6 to the axial center of the support 5.

  Moreover, in the said embodiment, the structure provided with the horn 4 was employ | adopted. However, the present invention is not limited to this. For example, without providing the horn 4, it is also possible to adopt a configuration in which the support 5 is provided to the vibration transfer unit 3 and the support 5 is directly connected to the vibration transfer unit 3. In addition, it is also possible to adopt a configuration in which the support 5 is provided to the vibrator 2 and the support 5 is directly connected to the vibrator 2 without the horn 4 and the vibration transfer unit 3.

DESCRIPTION OF SYMBOLS 1 ...... Ultrasonic wave projection apparatus 2 ...... Vibrator 2a ...... Piezoelectric element 2b ...... Holder 3 ...... Vibration transmission part 3a ...... Bar part 3b ...... Flange 4 ホ ー ン Horn 5 支柱 Support 6 振動 Diaphragm 6a ...... Outer edge

Claims (3)

An ultrasonic projection apparatus for projecting ultrasonic waves, wherein
A vibration unit that generates a vibration according to the projected ultrasonic wave;
A post extending from the end face of the vibrating portion;
The vibrator is fixed to the tip of the column and vibrates by transmitting the vibration, and an outer edge of the diaphragm is positioned to project radially outward of the column with respect to the circumferential surface of the column.
In the diaphragm, the shortest distance dimension from the outer edge to the support column is less than or equal to a quarter of the wavelength of the flexural vibration all around the outer edge,
The ultrasonic projection device according to claim 1, wherein a length dimension of the support in the extending direction is equal to or less than a quarter of a wavelength of longitudinal vibration in the support.   The ultrasonic projection apparatus according to claim 1, wherein the diaphragm is a circular disc having a shape of the outer edge.   3. The ultrasonic projection apparatus according to claim 2, wherein the diaphragm is disposed such that a center position of the diaphragm is superimposed on the axis when viewed from a direction along the axis of the support.

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