Ultrasonic projection device

Abstract

To provide an ultrasonic projection device with high sound pressure and wide directivity, which can be stably manufactured.SOLUTION: An ultrasonic projection device 100 includes: a base part 20 including a vibration generator 4 and generating vibrations in an axis O direction; a vibrating part 13 provided on a tip side of the base part to project an ultrasonic wave; and a connecting part 15 connecting the vibrating part and the base part. The vibrating part has a polygonal shape, a circular shape, or an elliptical shape as viewed from the axis direction. When the vibrating part has a polygonal shape with n angles, the connecting part is provided at least at n×7 / 8 or more (decimal numbers are rounded up) vertices among vertices of the polygonal shape. When the vibrating part has a circular shape, the connecting part is provided at least in 7 / 8 or more (decimal numbers are rounded up) of 3 or more positions with equally spaced central angles on an outer peripheral edge of the circular shape. When the vibrating part has an elliptical shape, the connecting part is provided at least in four positions, has a space between the base part and the connecting part while being not provided in the central part of the vibrating part in a surface direction, and has one or more holes through which the space is connected to the outside.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic projection device. [Background technology]

[0002] An example of an ultrasonic source that generates strong vibrations is a bolt-clamped Langevin type transducer (see Patent Documents 1, 2 and 3). Ultrasonic projection devices that utilize such vibration sources mainly generate plane waves with narrow directionality, as in the technology of Patent Document 1 mentioned above, in order to obtain a strong output from a single unit, and are being studied mainly in the field of underwater acoustics. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5338294 [Patent Document 2] JP 2023-122410 A [Patent Document 3] JP 2019-42712 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, technology that uses powerful ultrasonic waves even in the air has been attracting attention, and technology that uses flexural vibration, such as Patent Documents 2 and 3, which can easily obtain energy even in the air where there is a lot of loss, has been proposed. Patent Document 2 uses flexural vibration with the center of the diaphragm fixed as the vibration source, so the displacement at both ends is large, and a beam is formed in which the sound pressure is highly dependent on the angular direction, that is, the directivity is narrow. On the other hand, Patent Document 3 has a structure in which the outer periphery is fixed as the vibration source, and the center has the largest amplitude. In such a case, a sound field close to a spherical wave is formed, and the directivity is wide.

[0005] Phased arrays have been attracting attention as a technology for obtaining strong ultrasonic waves at any position. Phased arrays are devices that use multiple elements to project ultrasound, and by applying a phase difference to each element, the direction of the beam can be changed as desired. This type of technology is attracting attention in the fields of measurement technology, including obstacle detection, and haptics technology. Currently, open-type ultrasonic sensors are mainly used in ultrasonic projection devices, but there is a demand for higher sound pressure per unit area. However, when using ultrasonic elements with narrow directivity as in the techniques described in Patent Documents 1 and 2, there is a problem in that output reduction occurs depending on the positional relationship between the beam direction and the element.

[0006] The technology described in Patent Document 3 places emphasis on the efficiency of vibration transmission, and forms a completely sealed hollow structure by the connection part from the vibration source and the vibrating part, but there is room for improvement in terms of manufacturing and performance. In terms of performance, when vibration occurs, sound waves are emitted into the enclosed space, which can cause a complex sound field to form due to reflected waves, and pressure to rise due to an increase in air temperature caused by the absorption and attenuation of sound waves. These can cause a load to be placed on the radiating part made of a thin plate, reducing the efficiency of the desired ultrasonic radiation. That is, an object of the present invention is to provide an ultrasonic projection device that can be stably manufactured, has strong sound pressure, and has wide directivity. [Means for solving the problem]

[0007] In order to solve the above problems, the ultrasonic projection device of the present invention is an ultrasonic projection device including: a base portion having a vibration generating portion and generating vibrations in an axial direction; a vibration portion provided at a tip end of the base portion in the axial direction and projecting ultrasonic waves; and a connection portion connecting the vibration portion and the base portion, wherein the vibration portion has a polygonal, circular, or elliptical shape when viewed from the axial direction, and when the vibration portion is a polygon with n sides, the connection portion has at least n×7 / 8 (however, the decimal point is rounded up) of the vertices of the polygon. The connection parts are provided at least at the top vertices of the vibration part, and when the vibration part is circular, the connection parts are provided at least at 7 / 8 or more locations (rounded up to the nearest integer) of three or more positions on the outer periphery of the circle that are equally spaced apart in central angle, and when the vibration part is elliptical, the connection parts are provided at least at four locations on the outer periphery of the ellipse that intersect with the major and minor axes, and the connection parts are not provided in the center of the surface direction of the vibration part, and there is a space between the base part and the vibration part that is connected to the outside at one or more locations.

[0008] With this ultrasonic projection device, most of the outer peripheral edge of the vibration part, such as the apex, is connected (restrained) to the connection part, and the central part of the vibration part in the planar direction is not restrained by the connection part, so that the vertical (axial) vibration from the base part can be converted into a bending vibration in which the central part vibrates greatly, and ultrasonic waves with a wide directionality can be projected. In addition, since a powerful vibration source utilizing the vertical direction (axial direction) can be used for the original vibration, the sound pressure can be increased. However, it is necessary to design the thickness, connection parts, and outer width of the vibrating part so that at the intended operating frequency, the vibration mode is a flexural vibration mode without nodes, with maximum displacement at the center of the vibrating part. Furthermore, if the fixation of the outer periphery is too small or uneven, unnecessary strong amplitudes on the outer periphery may be generated, narrowing the directivity or causing unintended complex changes in the rotational direction, so care must be taken. Furthermore, by having a part of the space formed by the base part and the vibrating part communicate with the outside, it is possible to avoid forming a completely sealed structure, which is a concern in terms of production and performance.

[0009] In the ultrasonic projection device of the present invention, the connection portion may be provided so as to be connected to the entire outer periphery of the vibration portion. According to this ultrasonic projection device, since the entire outer periphery of the vibration portion is connected to the connection portion, it is possible to provide wide directivity in all directions.

[0010] In the ultrasonic projection device of the present invention, the connection portion may be provided as one or more through holes that penetrate the base portion in a radial direction on the rear end side of the vibration portion. According to this ultrasonic projection device, the vibration section can be formed by simple processing such as drilling holes, so processing is easy even for ultrasonic element sizes on the order of several mm.

[0011] In the ultrasonic projection device of the present invention, the vibration section and the base section may be separate bodies. According to this ultrasonic projection device, it is possible to easily form a structure in which the connection portion is connected to the entire outer periphery of the vibration portion.

[0012] In the ultrasonic projection device of the present invention, the vibration section may be in the shape of a regular polygon or a circle when viewed from the axial direction. According to this ultrasonic projection device, all outer peripheral edges of the vibrating part are equidistant from the center of gravity of the vibrating part, thereby preventing complex bending vibration modes that would occur if the outer peripheral edges were not equidistant from the center of gravity, and ensuring wide directivity.

[0013] In the ultrasonic projection device of the present invention, a boundary portion between the connection portion and the base portion may be tapered in a radial direction toward the vibration portion. According to this ultrasonic projection device, the reflection of the longitudinal vibration occurring at the boundary portion is reduced, thereby improving the transmission efficiency of the vibration.

[0014] In the ultrasonic projection device of the present invention, a boundary portion between the connection portion and the vibration portion may be configured to become thicker in a radial direction toward the vibration portion. According to this ultrasonic projection device, the stress acting on the fixing portion can be dispersed, improving the strength. Effect of the Invention

[0015] According to the present invention, an ultrasonic projection device that can be stably manufactured, has strong sound pressure, and has wide directivity can be obtained. [Brief description of the drawings]

[0016] [Figure 1] 1 is a perspective view showing an appearance of an ultrasonic projection device according to an embodiment of the present invention. [Diagram 2] 1 is a front view of an ultrasonic projection device according to an embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view taken along an axial direction of an ultrasonic projection device according to an embodiment of the present invention. [Figure 4] FIG. 4 is a plan view of the vibration part as viewed from the axial direction. [Diagram 5] 10 is a diagram showing a schematic diagram of a change in directivity when a distance d in a radial direction Y from a center of a vibration part of an embodiment of the present invention is changed. FIG. [Figure 6] 10 is a diagram showing a schematic diagram of a change in directivity when a distance d from a center portion of a conventional vibration section is changed. FIG. [Figure 7] 10 is a diagram showing a schematic diagram of a change in directivity when a distance d from a center of a vibration part in a radial direction X is changed in an embodiment of the present invention. FIG. [Figure 8] FIG. 13 is an exploded perspective view showing a modified example of a vibrating section in which all four sides (outer periphery) are connected to the connecting section. [Figure 9] FIG. 9 is a cross-sectional view taken along line AA in FIG. [Figure 10] 13 is an exploded perspective view showing yet another modified example of a vibrating portion in which the entire outer circumferential edge is connected to the connecting portion. FIG. [Figure 11] FIG. 11 is a plan view showing the connection portion in FIG. [Figure 12] 11 is a diagram showing the results of a simulation analysis of the relationship between the connection (restraint) mode of the vibration part and directivity. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an oblique view showing the appearance of an ultrasonic projection device 100 according to an embodiment of the present invention, FIG. 2 is a front view of the ultrasonic projection device 100, FIG. 3 is a cross-sectional view along the axis O direction of the ultrasonic projection device 100, and FIG. 4 is a plan view of a vibration section 13 as viewed from the axis O direction. The ultrasonic projection device 100 is suitable for use as a source of high-intensity ultrasonic waves in the air for haptics, ultrasonic levitation, ultrasonic atomization, intraocular pressure testing, non-destructive testing, defoaming, insect repellent, parametric speakers, and the like.

[0018] As shown in FIG. 1, the ultrasonic projection device 100 has a base portion 20 that is elongated and cylindrical extending in the direction of axis O, a vibration portion 13 that is provided at the tip of the base portion 20 in the direction of axis O and projects ultrasonic waves, and a connection portion 15 that connects the vibration portion 13 and the base portion 20. More specifically, the base portion 20 is formed by coaxially assembling a cylindrical first block body 2, a cylindrical piezoelectric unit 4, a cylindrical second block body 3, and a rectangular third block body 10 in this order from the rear end side along the axis O direction.

[0019] Further, a single elliptical through-hole 10h is provided slightly toward the tip side from the center in the axis O direction of the third block body 10, penetrating two opposing side surfaces (penetrating in the radial direction X). In the third block body 10, the rear end side (second block body 3 side) of the through hole 10h constitutes a part of the base portion 20, and the tip side of the through hole 10h constitutes the vibration portion 13. Furthermore, in the third block body 10, a portion overlapping the through hole 10h in the axis O direction constitutes a connection portion 15 that connects the vibration portion 13 and the base portion 20 (11).

[0020] The piezoelectric unit 4 vibrates in the direction of the axis O, and generates vibration in the direction of the axis O via a base portion 20 connected to the piezoelectric unit 4. Then, the vibration from the base portion 20 (11) is transmitted to the vibration portion 13 via the connection portion 15, and the vibration portion 13 projects ultrasonic waves. The piezoelectric unit 4 corresponds to the "vibration generating section" in the claims.

[0021] Each component of the ultrasonic projection device 100 will be described in further detail with reference to FIGS. In the base portion 20, the first block body 2, the piezoelectric unit 4, and the second block body 3 have the same structure as those in the ultrasonic projection device of the above-mentioned Patent Document 1, but other structures may also be adopted. 3, the first block body 2 and the second block body 3 are fixed by a bolt 5, and the piezoelectric unit 4 is sandwiched between the first block body 2 and the second block body 3 by the fastening force of the bolt 5. This allows vibration of the piezoelectric unit 4 to be transmitted to the base portion 20.

[0022] A hole 2h extending in the direction of the axis O is provided in the center of the first block body 2, and a female thread is formed on the inner surface of the hole 2h for screwing in the bolt 5. The hole 2h is a blind hole, and the rear end side of the first block body 2 forms the bottom surface. In this embodiment, the hole 2h is a blind hole, but the present invention is not limited to this, and the hole 2h may be a through hole. On the other hand, a hole 3h is provided in the center of the second block body 3, forming a through hole extending in the direction of the axis O, and a female thread is formed on the inner surface of the hole 3h for screwing in the bolt 5 and the third block body 10.

[0023] The piezoelectric unit 4 vibrates when power is supplied from a driving unit (not shown). The piezoelectric unit 4 includes, for example, a plurality of stacked annular piezoelectric ceramic elements, and a bolt 5 passes through a central opening of the piezoelectric unit 4. In this example, the outer diameter of the piezoelectric unit 4 is slightly smaller than the diameters of the first block body 2 and the second block body 3, but is not limited to this. In this example, two piezoelectric units 4 are disposed adjacent to each other in the direction of the axis O. However, the number of piezoelectric units 4 can be changed.

[0024] The third block body 10 is attached to the tip side of the second block body 3. The rear end side of the third block body 10 is stepped and reduced in diameter to form a shaft portion 6d. The shaft portion 6d has an outer surface formed with a male screw for screwing into the hole portion 3h. On the other hand, the bolt 5 is also formed on its outer surface with male threads for screwing into the holes 2h and 3h.

[0025] The first block body 2, the second block body 3 and the third block body 10 may be made of a metal, such as aluminum, an aluminum alloy, titanium, a titanium alloy, stainless steel, or iron.

[0026] Next, the characteristic features of the present invention will be described with reference to FIG. 4, when viewed from the direction of axis O, vibration section 13 has a polygonal shape (square) and has four vertices A1 to A4. In vibration section 13, one side connecting vertices A1 and A2 forms first outer peripheral edge 13s1, and one side connecting vertices A3 and A4 forms second outer peripheral edge 13s2. The first outer peripheral edge 13s1 and the second outer peripheral edge 13s2 face each other. On the other hand, the connection portion 15 is formed in a rectangular shape so as to include the first outer periphery 13s1 side and the second outer periphery 13s2 side.

[0027] Among the four sides (outer peripheries) of the vibrating portion 13, a first outer periphery 13s1 and a second outer periphery 13s2 are connected (restrained) to a connecting portion 15 that is integral with the vibrating portion 13. In this case, the vibrating portion 13 is a polygon with n=4 corners, and the connecting portions 15 are provided (connected) to n×7 / 8=3.5=4 (rounded up) vertices of the polygon A1 to A4. Here, n×7 / 8 is provided for all vertices if the polygon is a triangle to a hexagon, and for a polygon of heptagon or more, some of the vertices are missing (six vertices in the case of a heptagon). This provides (connects) connections 15 to most of the vertices of the polygon.

[0028] On the other hand, no connection portion 15 is provided in the center of the vibration portion 13 in the planar direction, and a space 10v is formed between the vibration portion 13 and the base portion 20(11) 4. In this example, this space 10v also serves as a through hole 10h.

[0029] As described above, the first outer peripheral edge 13s1 and the second outer peripheral edge 13s2 of the vibration part 13 are connected (restrained) to the connection part 15, and the central part of the vibration part 13 in the planar direction is not restrained by the connection part 15. Therefore, the vibration in the vertical direction (direction of the axis O) from the base part 20 can be converted into a bending vibration in which the central part vibrates greatly, and ultrasonic waves with a wide directionality can be projected. In addition, since a powerful vibration source utilizing the vertical direction (axis O direction) can be used for the original vibration, the sound pressure can be increased.

[0030] 5 and 6 show schematic diagrams of the relationship between the connection (restraint) mode of the vibration part and the directivity. As shown in FIG. 5, in the case of the present invention, the central part in the planar direction of the vibrating part 13 is not restrained by the connecting part 15, so the sound pressure is stronger, and this central part functions as a single point sound source SS, so the directionality of the radiated sound waves is wider. For example, as shown in the lower graph of Fig. 5, the vibration amplitude VA is stronger at the center of the vibrating part 13. Since the sound pressure is higher in the area where the vibration amplitude VA is larger, this indicates that the center part of the vibrating part 13 functions as a single sound source.

[0031] 6, in the case of the conventional technology (for example, Patent Document 1), the central part in the planar direction of the vibration part 130 is constrained by the connection part 150, so that the sound pressure at both ends of the vibration part 130 becomes strong. Therefore, dual sound sources SS, SS are virtually formed, and the directivity becomes narrow. For example, as shown in the lower graph of FIG. 6, the vibration amplitude VA at both ends of the vibrating portion 13 is large and the sound pressure is high.

[0032] In this example, the through holes 10h penetrate in the radial direction X, and FIG. 5 shows the directivity when the distance d in the radial direction Y perpendicular to the radial direction X is changed. On the other hand, FIG. 7 shows the directivity when the distance d in the radial direction X is changed. 7, all the faces of the vibration part 13 are constrained by the connection parts 15 along the radial direction X, so that the vibration part 13 has the same vibration amount in the radial direction X (equal phase surface), and all the faces of the vibration part 13 function as the sound source SS. Therefore, the directivity becomes like a plane wave, and the directivity is narrower than that along the radial direction Y. For example, as shown in the lower graph of FIG. 7, even if the distance d from the center in the planar direction of the vibrating part 13 changes, the vibration amplitude VA of the surface (sound radiation surface) of the vibrating part 13 does not change.

[0033] In addition, for sonars for automobiles and robots, there is a demand for reducing reflections in a specific direction, such as from the floor, etc. Therefore, by narrowing the vertical directivity, noise can be reduced, and for such applications, it is advantageous to provide anisotropy. On the other hand, when the objective is to freely form a sound field in the field of haptics, etc., it is preferable that the sound field is uniform and has no anisotropy.

[0034] In this example, the through hole 10h is provided in the base portion 20 (11) to form the vibration portion 13 whose center is not restricted. In this way, the vibration portion 13 can be formed by a simple process such as drilling, so that even if the ultrasonic element size is on the order of several mm, the processing is easy and the strength is improved. In addition, in the conventional technology such as Patent Document 3, a method of forming a hollow structure is considered in which the vibration surface is prepared as a separate body and bonded with adhesive, etc., but in this case, even a slight change in temperature of the element can change the internal air pressure, which may cause defects in the bonded portion. In contrast, in this example, since there is one or more holes that connect to the outside, it can be manufactured without the problems of the conventional technology.

[0035] 3, in this example, since the through hole 10h is elliptical, the boundary between the connection part 15 and the base part 20 (11) has a cross-sectional area in a cross section perpendicular to the axis that decreases toward the vibration part 13. Specifically, the width W1 of this boundary becomes narrower toward the vibration part 13. In this way, the reflection of the longitudinal vibration occurring at the boundary portion is reduced, thereby improving the vibration transmission efficiency.

[0036] In this example, since the through hole 10h is elliptical, the boundary between the connection portion 15 and the vibration portion 13 has a cross-sectional area in a cross section perpendicular to the axis that increases toward the vibration portion 13. Specifically, the width W2 of this boundary increases toward the vibration portion 13. In this way, the stress acting on the fixing portion can be dispersed, improving the strength.

[0037] It goes without saying that the present invention is not limited to the above-described embodiment, but covers various modifications and equivalents within the spirit and scope of the present invention.

[0038] For example, as shown in Figures 8 and 9, all four sides (outer peripheral edges) of vibrating portion 33 may be connected (restrained) to connecting portion 35, that is, connecting portion 35 may be provided so as to be connected to all of the outer peripheral edges of vibrating portion 33. In the case of FIG. 8 as well, the vibrating portion 33 is a polygon with n=4 corners, and the connecting portions 35 are provided (connected) to n×7 / 8=3.5=4 vertices among the vertices A1 to A4 of the polygon. Furthermore, no connection portion 35 is provided in the center of the vibrating portion 33 in the planar direction, and a space 30v is formed between the vibrating portion 33 and the base portion 30. In this example, the space 30v is a recess that is recessed in a square shape in the center of the frame-shaped connection portion 35. The vibration section 33 is separate from the base section 30 (connection section 35), and can be fixed to the base section 30 (connection section 35) by adhering, for example, an aluminum sheet of the vibration section 33 with an adhesive or the like. Also, the vibration section 33 and the connection section 35 may be integrated and separated from the base section 30.

[0039] In the vibrating part 33 of FIG. 8 as well, while the outer periphery of the vibrating part 33 is restrained by the connecting part 35, the central part in the planar direction of the vibrating part 33 is not restrained by the connecting part 35, so the sound pressure is stronger, and this central part functions as a single point sound source SS, resulting in wider directivity. Furthermore, since the entire outer periphery of the vibration portion 33 is connected to the connection portion 35, it is possible to provide wide directivity in all directions.

[0040] 10 and 11, the vibration part 43 may be circular when viewed from the direction of the axis O. In this example, the entire outer periphery of the vibration part 43 is connected (restrained) to the connection part 45, that is, the connection part 45 is provided so as to be connected to the entire outer periphery of the vibration part 33. In the case of FIG. 10, vibrating portion 43 is circular, and connecting portions 45 are provided (connected) at 7 / 8 or more (7 locations) of eight positions P1 to P8 on the outer periphery of the circle that are equally spaced apart from each other in terms of central angle. Furthermore, no connecting portion 45 is provided in the center of the vibrating portion 43 in the planar direction, and a space 40v is formed between the vibrating portion 43 and the base portion 40. In this example, the space 40v is a circular recess in the center of the arc-shaped connecting portion 45. In this example, a notch 45s is provided between the positions P4 and P5, and the connection portion 45 forms an interrupted arc between P4 and P5. Like the vibration section 33, the vibration section 43 is separate from the base section 40 (connection section 45).

[0041] In the vibrating part 43 of FIG. 10 as well, while the outer peripheral edge of the vibrating part 43 is restrained by the connecting part 45, the central part in the planar direction of the vibrating part 43 is not restrained by the connecting part 45, so the sound pressure is stronger, and this central part functions as a single point sound source SS, resulting in wider directivity.

[0042] The vibrating portion may be elliptical. In the case of an elliptical shape, it is necessary to provide at least four connection portions at the outer periphery of the ellipse where the major axis and the minor axis intersect. Furthermore, when the vibrating portion is circular, it is preferable that there are four or more positions with equally spaced central angles.

[0043] The vertices (eg, A1 to A4 above) when the vibrating part is polygonal, and the positions of equiangular central angles (eg, P1 to P8 above) when the vibrating part is circular, are preferably on the outer periphery farthest from the center of gravity of the vibrating part. If a connection portion is provided on the outer peripheral edge close to the center of gravity of the vibrating portion, a complex bending vibration mode will result, and there is a possibility that wide directivity will not be obtained (control of the mode itself will become difficult). If the vibrating portion is made into a regular polygon or a circle when viewed from the axial direction, all outer peripheral edges are equidistant from the center of gravity of the vibrating portion, and the above problem does not occur. EXAMPLES

[0044] A two-dimensional acoustic-structural coupling analysis was performed using the finite element method (COMSOL Multiphysics). Example 1 (directivity when the distance d in the radial direction Y corresponding to FIG. 5 is changed), Example 2 (directivity when the distance d in the radial direction X corresponding to FIG. 7 is changed), and Comparative Example (directivity when the center of the vibrating part is constrained and the distance d is changed corresponding to FIG. 6) were analyzed. The evaluation was performed by determining the relative value of the sound pressure at a position 300 mm away from the sound source SS. The direction directly in front of the sound source was set to 0 degrees, and the sound pressure at 0 degrees was set to 0 dB.

[0045] The results obtained are shown in FIG. In Example 1, the outer circumference of the vibrating part is constrained by the connection part, and only the vibration amplitude in the center is large, resulting in a wide directivity without side lobes. In contrast, Example 2, which has the same amplitude over the entire range, and the comparative example, which has two places with large amplitude, resulted in a narrower directivity than Example 1. [Explanation of symbols]

[0046] 4. Vibration generating section 13, 33, 43 Vibration section 15, 35, 45 Connection 20, 30, 40 Base 10h through hole 10v, 30v, 40v space 100 Ultrasonic projection device O axis

Claims

1. A base portion having a vibration generating portion for generating vibration in an axial direction; a vibration unit provided on a tip side of the base unit in the axial direction and configured to project ultrasonic waves; a connection portion that connects the vibration portion and the base portion; An ultrasonic projection device comprising: When viewed from the axial direction, the vibration portion has a polygonal, circular, or elliptical shape, When the vibration portion is a polygon having n corners, the connection portion is provided at least at n×7 / 8 (rounded up to the nearest whole number) or more vertices of the polygon, When the vibrating portion is circular, the connecting portion is provided at least at 7 / 8 or more of three or more positions on the outer periphery of the circle that are equally spaced apart from each other by a central angle (rounded up to the nearest whole number), When the vibration part is elliptical, the connection part is provided at least at four points on the outer periphery of the ellipse where the connection part intersects with a major axis and a minor axis, Furthermore, the connection portion is not provided at a center portion in a planar direction of the vibration portion, and a space is formed between the connection portion and the base portion, An ultrasonic projection device, characterized in that the space has one or more holes connecting to the outside.

2. The ultrasonic projection device according to claim 1 , wherein the connection portion is provided so as to be connected to an entire outer periphery of the vibration portion.

3. The ultrasonic projection device according to claim 1 , wherein the connection portion is provided as one or more through holes that penetrate the base portion in a radial direction on a rear end side of the vibration portion.

4. 3. The ultrasonic projection device according to claim 1, wherein the vibration section and the base section are separate bodies.

5. 3. The ultrasonic projection device according to claim 1, wherein the vibration portion has a regular polygonal shape or a circular shape when viewed from the axial direction.

6. 3. The ultrasonic projection device according to claim 1, wherein a boundary between the connection portion and the base portion is tapered in a radial direction toward the vibration portion.

7. 3. The ultrasonic projection device according to claim 1, wherein a boundary between the connection portion and the vibration portion is configured to become thicker in a radial direction toward the vibration portion.

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