JP7663012B2 - Ultrasonic Sensor - Google Patents

Description

The present invention relates to an ultrasonic sensor equipped with multiple ultrasonic receiving elements.

Conventionally, ultrasonic sensors that have at least one transmitting ultrasonic element (hereinafter referred to as "transmitting element") and multiple receiving ultrasonic elements (hereinafter referred to as "receiving elements") and can detect the distance to an obstacle and its direction are known (for example, Patent Document 1). The ultrasonic sensor described in Patent Document 1 has a base material, a transmitting element, multiple receiving elements arranged at a predetermined interval within the base material, and a waveguide that is provided on the base material and guides ultrasonic waves between the outside and the outer surface of the receiving element. This ultrasonic sensor configures an object detection device that can detect the distance to an obstacle and its direction by guiding ultrasonic waves reflected outside to the receiving element through the waveguide, while balancing good appearance and impact resistance.

JP 2008-89569 A

This ultrasonic sensor transmits ultrasonic waves of a specified frequency to the outside using a transmitting element, receives the reflected waves using multiple receiving elements arranged at a specified interval, and detects the direction of external obstacles relative to the ultrasonic sensor based on the phase difference of the reflected waves.

For ease of explanation, the direction normal to the receiving surface of the receiving element will be referred to as the "reference direction (0°)", the direction of incidence of the reflected wave on the receiving surface will be referred to as the "arrival direction", and the angle between the reference direction and the arrival direction will be referred to as the "arrival angle".

Specifically, this ultrasonic sensor uses the fact that the phase difference between the reflected waves received by multiple receiving elements changes depending on the angle of arrival of the reflected waves to calculate the direction of arrival of the reflected waves.

Recently, there has been a need to further improve the accuracy of object orientation detection in object detection using this type of ultrasonic sensor. In order to improve the accuracy of orientation detection using the above method, it is possible to increase the amount of change in the phase difference of the reflected wave with respect to the angle of arrival, thereby increasing the sensitivity to the angle of arrival.

Here, the phase difference of the reflected wave with respect to the angle of arrival is uniquely determined by the distance between adjacent receiving elements and the wavelength of the ultrasound transmitted to the outside (hereinafter referred to as the "transmitted wave"). Therefore, to increase the sensitivity to the angle of arrival, it is necessary to change the distance between the receiving elements or the wavelength of the transmitted wave.

However, the ultrasonic sensor described in Patent Document 1 is configured such that the transmitting element and the receiving element are disposed within the substrate, and ultrasonic waves are transmitted and received through a waveguide disposed or formed within the substrate, making it difficult to arbitrarily change the spacing between the receiving elements. In addition, while the method of changing the wavelength of the transmitting wave, i.e., the drive frequency, improves the sensitivity to the angle of arrival, it also causes a decrease in the attenuation rate of ultrasonic waves and a decrease in the resolution of measuring the distance to an object, so there is a limit to how much the sensitivity to the angle of arrival can be improved.

In view of the above, the present invention aims to provide an ultrasonic sensor that improves the accuracy of detecting the direction of external obstacles while protecting the transmitting and receiving ultrasonic elements from the external environment.

In order to achieve the above object, the ultrasonic sensor described in claims 1 , 2, and 4 comprises an ultrasonic element (2) having a vibration part (25) capable of vibrating at a predetermined driving frequency, a mounting board (4) to which the ultrasonic element is attached via an adhesive (3) and having a through hole (41) formed at a position corresponding to the vibration part, a case material (5) having a storage space (54) in which the ultrasonic element and the mounting board are stored and a waveguide (511) communicating with the through hole and an external space, and a resonance space (6, 7) formed between the ultrasonic element and the mounting board or in at least one of the waveguides, wherein the minimum dimension of the resonance space in a plane perpendicular to the extension direction of the waveguide is greater than the diameter of the waveguide.
In the ultrasonic sensor described in claim 1, the end of the waveguide facing the external space is defined as the outer end (511a), and the end opposite the outer end is defined as the inner end, and the waveguide has a shape in which the extension direction changes at least once between the outer end and the inner end.
In the ultrasonic sensor described in claim 2, a resonance space is formed in a waveguide, and a portion of the waveguide located closer to the ultrasonic element than the resonance space is designated as a first waveguide (5111), and a portion of the waveguide located closer to the external space than the resonance space is designated as a second waveguide (5112), and the second waveguide is arranged at a position different from an extension line of the first waveguide.
In the ultrasonic sensor described in claim 4, a plurality of vibration parts and waveguides are formed at a distance from each other and are arranged along at least one direction, and the resonance space spans the plurality of vibration parts or waveguides and is a common space corresponding to at least two or more vibration parts.

In this ultrasonic sensor, in which the transmission wave from the ultrasonic element is transmitted to the outside through the waveguide and the reflected wave is received through the waveguide, there is at least one resonance space formed between the ultrasonic element and the mounting board or in the waveguide. The minimum dimension of this resonance space in a radial plane with the extension direction of the waveguide as its axis is larger than the diameter of the waveguide. By providing the above-mentioned resonance space in the ultrasonic propagation path, this ultrasonic sensor has a structure that makes it possible to adjust the phase difference of the reflected wave relative to the angle of arrival without changing the spacing between the receiving elements or the wavelength of the transmitted wave. Therefore, this ultrasonic sensor can improve the accuracy of directional detection of external obstacles, etc., while protecting the transmitting and receiving ultrasonic elements from the external environment.

The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below.

1 is a cross-sectional view showing an ultrasonic sensor according to a first embodiment. FIG. 2 is an exploded perspective view showing an ultrasonic element, an adhesive material, and a mounting substrate. 3 is a cross-sectional view showing a cross-sectional configuration taken along line III-III in FIG. 2. 4 is a plan view showing the ultrasonic element and the adhesive material as viewed from the waveguide side. FIG. FIG. 2 is an explanatory diagram for explaining the relationship between the arrival angle and the phase difference. FIG. 1 is a diagram showing an example of a cubic waveguide. FIG. 1 is a diagram showing an example of an acoustic mode generated in a cubic space. FIG. 1 is a diagram illustrating an example of a model in an acoustic simulation. FIG. 13 is a diagram showing characteristics obtained by acoustic simulation of a model having a resonant space. FIG. 11 is a cross-sectional view showing an ultrasonic sensor according to a second embodiment. FIG. 11 is a cross-sectional view showing an example of a modified example of the ultrasonic sensor of the second embodiment. FIG. 11 is a cross-sectional view showing another example of a modified example of the ultrasonic sensor of the second embodiment. 13A and 13B are diagrams illustrating an example of an arrangement at an opening of a waveguide in an ultrasonic sensor according to a third embodiment. 13A and 13B are diagrams illustrating other examples of the arrangement of the openings of the waveguide in the ultrasonic sensor of the third embodiment. 13A and 13B are explanatory diagrams for explaining a modified example of the ultrasonic sensor of the third embodiment. FIG. 13 is a cross-sectional view showing an ultrasonic sensor according to a fourth embodiment. 17 is a cross-sectional view showing a cross-sectional configuration taken along line XVII-XVII in FIG. 16 . FIG. 13 is a cross-sectional view showing an ultrasonic sensor according to a fifth embodiment. FIG. 13 is a cross-sectional view showing an ultrasonic sensor according to a sixth embodiment. FIG. 13 is a diagram showing a model in an acoustic simulation, which corresponds to the ultrasonic sensor of the sixth embodiment. FIG. 21 is a diagram showing characteristics obtained by an acoustic simulation of the analysis model of FIG. 20, in which the dimension in the thickness direction of the resonance space is changed. FIG. 21 is a diagram showing characteristics obtained by acoustic simulation of the analysis model of FIG. 20, in which the dimensions of the resonance space in the planar direction are changed. FIG. 21 is a diagram showing characteristics obtained by an acoustic simulation of the analysis model of FIG. 20, in which the distance between the resonance space and the receiving point is changed. FIG. 13 is a cross-sectional view showing a first modified example of the ultrasonic sensor of the sixth embodiment. FIG. 13 is a cross-sectional view showing a second modified example of the ultrasonic sensor of the sixth embodiment. FIG. 23 is a cross-sectional view showing a third modified example of the ultrasonic sensor of the sixth embodiment. FIG. 13 is an exploded perspective view showing an ultrasonic element, an adhesive, and a mounting substrate in an ultrasonic sensor according to a seventh embodiment. FIG. 13 is a plan view showing an ultrasonic element and an adhesive according to an ultrasonic sensor of a seventh embodiment as viewed from the waveguide side.

The following describes embodiments of the present invention with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals.

First Embodiment
An ultrasonic sensor 1 according to a first embodiment will be described with reference to Figures 1 to 4. The ultrasonic sensor 1 is preferably used in an object detection device that is mounted on a vehicle such as an automobile and detects objects such as external obstacles, but can of course also be used for other purposes.

In FIG. 1, dashed lines indicate parts of the outer contours of the ultrasonic element 2, adhesive 3, mounting substrate 4, and base material 51 in another cross section, which will be described later. In FIG. 2, dashed lines indicate the area of one surface 4a of the mounting substrate 4 that is in contact with the adhesive 3, and the outer contour of the diaphragm 25 of the ultrasonic element 2, which is not visible at the angle shown in FIG. 2, which will be described later. Also, in FIG. 2, dashed lines indicate auxiliary lines indicating the corresponding positions of the ultrasonic element 2, adhesive 3, and mounting substrate 4. In FIG. 3, dashed lines indicate the outer contour of the adhesive 3, which is not a component of the ultrasonic element 2. In FIG. 4, dashed lines indicate the outer contour of the piezoelectric film 26, which will be described later, which is not visible at the angle shown in FIG. 4.

As shown in FIG. 1, the ultrasonic sensor 1 of this embodiment includes an ultrasonic element 2 having a vibration part capable of vibrating at a predetermined drive frequency, an adhesive material 3, a mounting substrate 4 having a through hole 41 corresponding to the vibration part, a case material 5, and a waveguide 511. As shown in FIG. 1 and FIG. 2, the ultrasonic sensor 1 includes an ultrasonic element 2 attached to the mounting substrate 4 via the adhesive material 3, which is stored in a storage space 54 of the case material 5, and includes a waveguide 511 that communicates with the through hole 41 and the external space. The ultrasonic sensor 1 further includes a resonance space 6, and in this embodiment, the resonance space 6 is formed between the ultrasonic element 2 and the mounting substrate 4.

As shown in FIG. 3, the ultrasonic element 2 is configured using an SOI (abbreviation of Silicon on Insulator) substrate in which a support substrate 21, an embedded insulating film 22, and a semiconductor layer 23 are laminated in this order. The ultrasonic element 2 is provided with a recess 24 that penetrates the support substrate 21 and the embedded insulating film 22 and exposes the semiconductor layer 23, and the portion of the semiconductor layer 23 that corresponds to the recess 24 is a diaphragm 25. The ultrasonic element 2 is configured, for example, with a piezoelectric film 26 formed on the surface of the diaphragm 25 opposite the embedded insulating film 22. The piezoelectric film 26 is configured, for example, by sandwiching a piezoelectric material between a pair of electrodes and contracting or expanding in a predetermined direction by application of an electric field. The diaphragm 25 is a vibration part that can vibrate at a predetermined driving frequency (for example, but not limited to, 30 kHz to 100 kHz for vehicle use) by driving the piezoelectric film 26. The ultrasonic element 2 has four diaphragms 25 (drivers) as shown in FIG. 2, and is an array element arranged in two rows and two columns at a predetermined pitch interval P1 as shown in FIG. 3. The ultrasonic element 2 is, for example, a MEMS (abbreviation for Micro Electro Mechanical Systems) type having multiple drive units. The ultrasonic element 2 has, for example, the diaphragm 25 as a vibration unit, and functions as a transmitting element that transmits ultrasonic waves to the outside and a receiving element that receives sound waves from the outside.

For ease of explanation, hereinafter, the diaphragm 25 functioning as the drive unit may be referred to as a "cell", the diameter of the cell as the "cell diameter", and an element having multiple cells and arranged in α rows and β columns (α, β: natural numbers) as an "α×β array element". In the above example, the ultrasonic element 2 is a 2×2 array element having four cells. In addition, the transmission wave transmitted from the ultrasonic element 2 to the outside and the reception wave incident on the waveguide 511 from the outside may be collectively referred to as the "transmitted and received wave".

The adhesive 3 is a member that bonds and fixes the ultrasonic element 2 to the mounting substrate 4, and may be, for example, any adhesive resin material. As shown in, for example, Figures 2 and 4, the adhesive 3 has the same external shape as the ultrasonic element 2, and in the area located directly below the diaphragm 25 of the ultrasonic element 2, a lattice-like frame shape having multiple openings 31 with a planar size larger than the diaphragm 25. The thickness of the adhesive 3 is, for example, about 10 μm to 200 μm, but is not limited to this.

The openings 31 are provided in the same number as the cells of the ultrasonic element 2, and in this embodiment, they are independent of each other. The multiple openings 31 are arranged so that the entire area of one of the multiple diaphragms 25 corresponding thereto is accommodated in each of the multiple openings 31, as shown in FIG. 1, for example. The multiple openings 31 are arranged so that the entire area of one of the multiple waveguides 511 corresponding thereto in the base material 51 is accommodated inside the opening 31, as in the case of the diaphragm 25. In other words, the multiple openings 31 are arranged so that the minimum dimension is larger than the cell diameter of the ultrasonic element 2 and the diameter of the waveguide 511, and the multiple openings 31 are arranged to include the corresponding cells and waveguides 511 in a plan view. The multiple openings 31 become internal spaces by bonding the adhesive 3 to the ultrasonic element 2 and the mounting substrate 4, and function as propagation paths for transmitted and received waves, as well as independent resonance spaces 6, as shown in FIG. 1.

The mounting board 4 is a circuit board on which wiring and circuits (not shown) are formed on a board made of any insulating material such as glass epoxy resin or ceramic, and on which various electronic components and the like can be mounted. The mounting board 4 is electrically connected to the ultrasonic element 2 by wires or the like in an area located outside the outer periphery of the ultrasonic element 2, and is also connected to a control unit and a power supply (not shown), enabling drive control of the ultrasonic element 2 and exchange of electrical signals. As shown in FIG. 2, the mounting board 4 has a plurality of through holes 41 formed at positions corresponding to the diaphragm 25. The plurality of through holes 41 are propagation paths for transmitting and receiving waves that are independent of each other, and are, for example, circular, but are not limited to this, and can be any shape such as an elliptical shape or a polygonal shape. The plurality of through holes 41 are, for example, the same shape and dimensions as the waveguide 511 that communicates with them.

The case material 5 includes, for example, a base material 51 on which a plurality of waveguides 511 are formed, a frame body part 52 that surrounds the ultrasonic element 2, adhesive material 3, and mounting board 4 while being spaced apart from them, and a lid part 53 that is placed on the frame body part 52. The space surrounded by the base material 51, frame body part 52, and lid part 53 of the case material 5 forms a storage space 54 that stores the ultrasonic element 2, adhesive material 3, and mounting board 4. The case material 5 is made of, for example, metal, resin, ceramic, or a composite material that combines some or all of these.

As shown in FIG. 1, for example, the substrate 51 is a base member on which the mounting board 4 is mounted with an adhesive or the like (not shown), and a plurality of waveguides 511 are formed. One surface of the substrate 51 on which the opening of the waveguide 511 facing the external space is formed is the outer surface 51a, and in the case of an in-vehicle application, for example, the substrate 51 is arranged so that the outer surface 51a faces or is in contact with the exterior of the vehicle body, a bumper, etc.

The waveguides 511 are formed in the base material 51 in a plurality of through holes that serve as a propagation path for the transmitted and received waves. For example, the waveguides 511 are circular cylindrical, but are not limited thereto, and may be any shape such as an elliptical cylindrical or polygonal cylindrical shape. The plurality of waveguides 511 are independent of each other and communicate with a corresponding one of the through holes 41, the opening 31, and the cell. For example, the end (opening) of the waveguide 511 on the external space side is the outer end 511a, and the end on the opposite side is the inner end, and the outer end 511a and the inner end are connected in a straight line to form a through hole. The direction in which the waveguide 511 is extended is defined as the "extension direction", and in this embodiment, the plurality of waveguides 511 are in a state in which their extension directions are aligned. In other words, the base material 51 is configured such that the plurality of waveguides 511 extending in a straight line are arranged in parallel. The number of waveguides 511 is, for example, the same as the number of cells of the ultrasonic element 2, and when the cell arrangement of the ultrasonic element 2 is α×β, the outer end 511a is arranged in an array of α×β.

The frame portion 52 is the portion of the case material 5 that surrounds the ultrasonic element 2, adhesive material 3, and mounting board 4, and has an inner shape that follows the outer shape of the mounting board 4, for example.

The lid portion 53 is a member that is disposed at the end of the frame portion 52 opposite the base material 51 and closes the frame portion 52.

In the above, an example has been described in which the base material 51, the frame body 52, and the lid portion 53 constituting the case material 5 are separate bodies, but this is not limited thereto, and the base material 51 and the frame body 52, or the frame body 52 and the lid portion 53, may be integrated, and the configuration may be modified as appropriate.

The resonance space 6 is a space provided on the propagation path of the transmission and reception waves in order to adjust the phase difference of the reflected wave with respect to the arrival angle of the ultrasonic sensor 1, and in this embodiment, it is provided between the ultrasonic element 2 and the mounting board 4. The resonance spaces 6 are provided, for example, in the same number as the cells of the ultrasonic element 2, and are independent of each other. In the resonance space 6, one of the multiple waveguides 511 that communicates with each other is considered to be a "communicating waveguide", and the minimum dimension of the plane perpendicular to the extension direction of the communicating waveguide is larger than the perpendicular dimension of the communicating waveguide. Specifically, the size of the above-mentioned plane of the resonance space 6 is larger than the diameter of the communicating waveguide, and is in a state in which the outer hull of the communicating waveguide is included when viewed from the extension direction of the communicating waveguide. In addition, since the diameter of the waveguide 511 is approximately the same as the cell diameter, for example, the resonance space 6 is larger than the cell diameter of the ultrasonic element 2 and is in a state in which the corresponding cell is included. The positional relationship of the through hole 41 and the waveguide 511 to the resonance space 6 can be appropriately determined according to the acoustic resonance mode described below.

The above is the basic configuration of the ultrasonic sensor 1 of this embodiment. The ultrasonic sensor 1 has a structure that can increase the amount of change in phase difference with respect to the angle of arrival of the reflected wave by providing a resonance space 6 of a predetermined dimension in the propagation path of the transmitted and received waves between the ultrasonic element 2 and the external space.

In addition, in terms of improving transmission performance, it is preferable that the ultrasonic sensor 1 has a linear distance from the diaphragm 25 to the outer end 511a of the waveguide 511 of L, and a wavelength equivalent value of the drive frequency of λ, such that L is within ±10% of the value expressed by nλ/2 (n: odd number equal to or greater than 1).

[Resonant Space]
Next, the effect of the resonance space 6 will be described with reference to FIGS.

First, the arrival angle and phase difference of the reflected wave will be explained with reference to Figure 5.

For example, as shown in Fig. 5, when two linearly extending waveguides are arranged at a pitch _d0 and a reflected wave of wavelength λ is incident from the outside at an arrival angle θ, a phase difference of Δx occurs between the reflected waves incident on the two waveguides 511. In this case, the arrival angle θ is expressed by the following formula (1).

θ=sin ^-1 (Δx×λ/(2π×d ₀ ))...(1)
In addition, when the cells of the ultrasonic elements are arranged on the extension lines of the two waveguides, the pitch d ₀ of the waveguides is substantially the same as the pitch of the receiving elements. The wavelength λ [unit: mm] of the incident reflected wave depends on the wavelength of the transmission wave transmitted from the ultrasonic element 2, that is, the driving frequency of the cell. Also, as shown in FIG. 5, the pitch d ₀ is determined by the arrangement of the outer end on the receiving surface, with the plane facing the outer end of the waveguide being the receiving surface. And, when the pitch d ₀ and the wavelength λ of the reflected wave are fixed at a certain value, according to the formula (1), the phase difference Δx depends on the arrival angle θ. In other words, the relationship between the arrival angle θ and the phase difference Δx is basically uniquely determined by the interval of the pitch d ₀ on the receiving surface and the driving frequency. Therefore, in order to improve the sensitivity of the ultrasonic sensor to the arrival angle θ and to further increase the accuracy of azimuth detection, it is necessary to increase the amount of change in the phase difference Δx per 1° of arrival angle.

A conventional ultrasonic sensor that does not have a resonance space 6 (hereinafter simply referred to as a "conventional ultrasonic sensor") has a small degree of freedom in design, and it is difficult to improve the sensitivity to the arrival angle θ. Specifically, in a conventional ultrasonic sensor, it is necessary to adjust the spacing between the receiving elements of the ultrasonic element or the spacing between the waveguides on the receiving surface (i.e., the pitch d ₀ ), or the driving frequency (i.e., the wavelength λ), or both.

However, when changing the interval between receiving elements or the interval between waveguides, it is necessary to change the structure or arrangement of ultrasonic elements or waveguides, which is a major design change, and is difficult to implement in practice. In addition, the conditional expression of the interval between receiving elements d ₀ < λ/2 must be satisfied. Specifically, when d ₀ > λ/2, based on the formula (1), if the arrival angle θ falls outside a predetermined range, the sign of the phase difference Δx is inverted, and there are two or more arrival angles θ corresponding to one phase difference Δx (so-called binarization), making it difficult to estimate the arrival angle θ. Therefore, it is difficult to freely change the interval between receiving elements from the viewpoint of the constraint of d ₀ < λ/2.

In addition, when changing the drive frequency of the ultrasonic element, although there is no need to change the structure or arrangement, etc., this causes a decrease in the attenuation rate of the ultrasonic waves and a decrease in the resolution of measuring the distance to the object, so even if the sensitivity to the arrival angle can be improved, other characteristics will be degraded.

In contrast, the ultrasonic sensor 1 of this embodiment has a resonance space 6 in the propagation path of the transmitted and received waves, where a resonance mode of the reflected wave occurs.

Here, the acoustic resonance mode in a cubic waveguide will be described with reference to Fig. 6. For example, as shown in Fig. 6, in a cubic waveguide in which the dimension in one direction of the waveguide is _a0 (unit: m) and the dimension in the direction perpendicular thereto is _b0 (unit: m), the acoustic resonance mode that can exist in the waveguide is expressed by the following formula.

上記の式において、ｆ_ｍｎはモードｍ、ｎ（ｍ、ｎ：自然数）の共振周波数〔単位：ｋＨｚ〕であり、ｃは媒体（例えば空気など）の音速〔単位：ｍ／ｓ〕である。つまり、構造体により内包された空間（例えば壁に囲まれた空間など）である導波路が、空気等の気体媒体で満たされている場合、当該空間の大きさと媒体を伝搬する音波の波長に応じて、気体が音響的に共振する周波数・モードが存在する。そして、導波路を伝搬する音波の周波数ｆがｆ＞ｆ_ｍｎの場合、共振モードｍ、ｎは存在する。

In the above formula, f _mn is the resonance frequency (unit: kHz) of modes m and n (m, n: natural numbers), and c is the sound speed (unit: m/s) of the medium (e.g., air, etc.). In other words, when a waveguide, which is a space enclosed by a structure (e.g., a space surrounded by walls, etc.), is filled with a gas medium such as air, there exists a frequency/mode in which the gas acoustically resonates depending on the size of the space and the wavelength of the sound wave propagating through the medium. And, when the frequency f of the sound wave propagating through the waveguide is f>f _mn , the resonance modes m and n exist.

The dimensions of the resonant space 6 are such that acoustic modes with phase differences occur at the frequency of the propagating reflected wave, as shown in FIG. 7, for example.

The acoustic mode corresponding to the dimensions of the resonance space 6 can be calculated, for example, by simulation using acoustic analysis software that uses the finite element method (such as Ansys (registered trademark) by Ansys, Inc.). In Fig. 7, in order to make it easier to understand the regions with different phase differences in the acoustic modes generated in the space, different types of hatching are used in the regions with different phases, although a cross section is not shown.

In the example shown in FIG. 7, for example, the largest phase difference occurs at points A and B. The resonance space 6 is dimensioned to generate an acoustic mode by acoustic analysis simulation, and the waveguide 511 is connected to a location where the phase difference in the acoustic mode is largest. The ultrasonic sensor 1 has a structure in which each of the multiple waveguides 511 is connected to a different resonance space 6 that is independent of each other, and the waveguide 511 is connected to a position in the resonance space 6 where the phase difference in the acoustic mode generated at a predetermined drive frequency is maximum. For example, in the case of FIG. 7, when one waveguide 511 is connected to a position corresponding to point A in a certain resonance space 6, another waveguide 511 adjacent to the waveguide 511 is connected to a position corresponding to point B in another resonance space 6.

As a result, the phase difference generated at the outer end 511a of the waveguide 511 is Δx1, and the phase difference Δx2 in the resonance space 6 is further added to this, so that the phase difference of the reflected wave received by the ultrasonic element 2 is ultimately greater than Δx1. As a result, the phase difference Δx for a change in the arrival angle of 1° in the ultrasonic sensor 1 equipped with the resonance space 6 is greater than that of a conventional ultrasonic sensor, and the sensitivity to the arrival angle θ is improved. Note that the phase difference of the reflected wave received by the ultrasonic element 2 can be calculated by acoustic simulation, and since an interaction occurs between the waveguide 511 and the resonance space 6, it is not Δx1 + Δx2, but is at least greater than Δx1.

Next, the results of the acoustic simulation will be explained with reference to Figures 8 and 9.

The inventors designed a simulation model for acoustic analysis corresponding to the ultrasonic sensor 1 of this embodiment, as shown in FIG. 8, for example.

For ease of explanation, as shown in FIG. 8, the direction along the vertical direction of the paper is z, one direction of the plane normal to z is x, and the direction perpendicular to x on the plane is y. The size of the resonance space 6 on the plane formed by x and y is referred to as the "plane size". The dimension of the resonance space 6 in the z direction is referred to as the "thickness", and the simulation model of the acoustic analysis is simply referred to as the "analysis model". In addition, in FIG. 8, the extension line of the extension direction of the waveguide at the outer end is shown by a two-dot chain line. The angle between the direction of the sound wave incident on the waveguide shown in FIG. 8 and the extension line corresponds to the arrival angle θ, and the receiving point corresponds to the position of the cell (receiving element) of the ultrasonic element 2.

In the analytical model, the resonance space 6 is cubic, with dimensions a, b, and c in the x, y, and z directions, respectively. In the acoustic simulation, the wavelength corresponding to the drive frequency of the ultrasonic element 2 is set to λ, and a and b are fixed at 4λ/4 and 5λ/4, respectively, and the arrival angle θ and phase difference Δx for each thickness c of the resonance space 6 are calculated, resulting in the results shown in Figure 9. Here, two results are shown as representative values: c = 4 mm and c = 8 mm.

In Figure 9, the simulation results for c = 4 mm are shown by a two-dot chain line, the simulation results for c = 8 mm are shown by a solid line, and the slope of the phase difference Δx when the arrival angle θ is in the range of 0° to 20° is shown by a dashed line.

The greater the change in phase difference Δx per 1° of the arrival angle θ shown in Figure 9, i.e., the greater the slope shown by the dashed line, the greater the sensitivity to the arrival angle θ. As a result of the simulation, it was found that the slope of Δx, i.e., the sensitivity to the arrival angle θ, is greater when c = 8 mm compared to when c = 4 mm. This shows that it is possible to improve the sensitivity to the arrival angle θ by adjusting the thickness c of the resonance space 6.

Therefore, by providing the resonance space 6, the amount of change in the phase difference Δx relative to the arrival angle θ can be increased without changing the drive frequency of the ultrasonic element 2 or the pitch of the outer end 511a of the waveguide 511, thereby improving the accuracy of azimuth detection.

When multiple resonance spaces 6 are provided, the planar dimensions a, b and thickness c may all be the same, or some or all of the planar dimensions, thickness dimensions and shapes may be different. The connection positions of the waveguides 511 to each of the multiple resonance spaces 6 are changed as appropriate in accordance with the acoustic resonance modes described above, as long as the phase difference between the different waveguides 511 is large.

According to this embodiment, the ultrasonic element 2 is housed in the case material 5, and a resonance space 6 is provided in the propagation path of the transmitted and received waves connecting the ultrasonic element 2 with the external space, resulting in an ultrasonic sensor 1 with a large amount of change in phase difference Δx relative to the arrival angle θ of the reflected wave. Therefore, while protecting the ultrasonic element 2, the design has a high degree of freedom, and the accuracy of azimuth detection is improved.

Second Embodiment
The ultrasonic sensor 1 according to the second embodiment will be described with reference to FIG.

In FIG. 10, like FIG. 1, parts of the outer contours of the ultrasonic element 2, adhesive 3, mounting substrate 4, and base material 51 in another cross section are shown by dashed lines. This is also the case for FIGS. 11 and 12, which will be described later.

The ultrasonic sensor 1 of this embodiment differs from the first embodiment in that the waveguide 511 has a shape in which the diameter changes continuously, as shown in FIG. 10, for example. This difference will be mainly described in this embodiment.

In this embodiment, the waveguide 511 has an outer end 511a that is the end facing the external space and an inner end on the opposite side, with the diameter of the outer end 511a being larger than the diameter of the inner end. The waveguide 511 has a tapered shape in which the diameter increases continuously from the inner end to the outer end 511a, for example, in a cross-sectional view. In this case, the ultrasonic sensor 1 has a configuration in which the range of the transmitted wave is narrower and the directivity is sharper than in the first embodiment.

This embodiment provides the same effects as the first embodiment. In addition, the shape of the waveguide 511, in which the diameter changes continuously, provides the effect of sharpening the directionality of the transmission wave.

(Modification of the second embodiment)
11 , in the ultrasonic sensor 1 of the second embodiment, in addition to the waveguide 511, the through hole 41 of the mounting substrate 4 may also have a tapered shape having continuity with the waveguide 511 in a cross-sectional view. In this case, the diameter of the through hole 41 increases continuously from the ultrasonic element 2 side toward the waveguide 511 side, and the diameter of the opening at the end on the waveguide 511 side is approximately the same as the diameter of the inner end of the waveguide 511.

In addition, as shown in FIG. 12, the ultrasonic sensor 1 of the second embodiment may have a tapered shape in which the waveguide 511 has a diameter that increases continuously from the outer end 511a toward the inner end in a cross-sectional view. In this case, the through hole 41 of the mounting substrate 4 has a diameter at the opening on the waveguide 511 side that is substantially the same as the diameter at the inner end of the waveguide 511, and a diameter that increases continuously toward the ultrasonic element 2 side. In addition, the through hole 41 has a diameter at the opening on the ultrasonic element 2 side that is substantially the same as the diameter of the diaphragm 25. The through hole 41 may have a constant diameter. In this case, the ultrasonic sensor 1 has an effect of widening the transmission range of the transmission wave compared to the first embodiment.

This modified example also provides the same effect as the first embodiment. In the case shown in FIG. 11, directivity similar to that of the second embodiment is obtained, and in the case shown in FIG. 12, the effect of widening the transmission range of the transmission wave is obtained. In other words, in the second embodiment and its modified example, it is possible to control the transmission directivity.

In the above second embodiment and its modified example, an example was described in which the wall surfaces of the waveguide 511 and the through hole 41 are linear in cross section, but this is not limited thereto, and they may be curved, and the degree of change in shape and diameter, etc. may be changed as appropriate.

Third Embodiment
The ultrasonic sensor 1 according to the third embodiment will be described with reference to FIG.

Figure 13 shows the case material 5 as viewed from the normal direction to the outer surface 51a, and for ease of viewing, only a portion of the area near the outer end 511a of the waveguide 511 is shown, with other areas omitted.

The ultrasonic sensor 1 of this embodiment differs from the first embodiment in that the outer ends 511a of the multiple waveguides 511 are linearly arranged in one direction, as shown in FIG. 13, for example. This difference will be mainly described in this embodiment.

In this embodiment, the number of waveguides 511 is, for example, n1 or more (n1 is a natural number equal to or greater than 2), and the outer ends 511a of the waveguides 511 are arranged in one direction, forming a so-called "1D array."

According to this embodiment, the same effect as the first embodiment can be obtained. In addition, this ultrasonic sensor 1 is configured to be able to detect at least one of the directions (azimuth and altitude) of external obstacles, etc., relative to the ultrasonic sensor 1.

(Modification of the third embodiment)
The ultrasonic sensor 1 of the third embodiment may be arranged in a so-called "2D array" in which the outer ends 511a of a plurality of waveguides 511 are arranged along two directions that are perpendicular to each other, as shown in Fig. 14. In this case, the ultrasonic sensor 1 can detect two directions (azimuth and altitude) of an external obstacle relative to the ultrasonic sensor 1.

The number of outer ends 511a of the waveguides 511 in a row along the left-right direction in FIG. 14 is n1 (n1 is a natural number equal to or greater than 2), and the number of outer ends 511a of the waveguides 511 in a row along a direction perpendicular to the left-right direction is n2 (n2 is a natural number equal to or greater than 2). In this case, the numbers n1 and n2 may be changed as appropriate.

In addition, the ultrasonic sensor 1 of the third embodiment may have a structure in which the arrangement of the diaphragm 25 of the ultrasonic element 2 and the arrangement of the outer end 511a of the waveguide 511 are different, for example, as shown in FIG. 15. Specifically, for example, in a case where the ultrasonic element 2 has four cells and the waveguide 511 has four cells, the four cells of the ultrasonic element 2 may be arranged in a 1D array along one direction, while the outer end 511a of the waveguide 511 may be arranged in a 2×2 array. In this case, some or all of the multiple waveguides 511 are shaped such that the extension direction is changed at least once (for example, bent, curved, etc.) on the way from the inner end to the outer end 511a. As a result, even if the multiple cells of the ultrasonic element 2 are arranged in a 1D array, the outer end 511a is arranged along two orthogonal directions, making it possible to detect the azimuth in two directions.

In FIG. 15, the waveguides 511 connecting the cells and the outer ends 511a are shown with dashed lines to make it easier to understand the relationship between the cell arrangement of the ultrasonic elements 2 and the arrangement of the outer ends 511a of the waveguides 511. Also, in FIG. 15, an example is shown in which two of the four waveguides 511 are bent midway from the inner ends to the outer ends 511a, but this is not limited to this, and the number and shapes of the waveguides 511 whose extension direction changes can be changed as appropriate.

This modified example also provides the same effect as the third embodiment. In addition, by arranging the outer ends 511a of the multiple waveguides 511 in an n1 x n2 array, the ultrasonic sensor 1 can be structured to detect two directions of an external obstacle, etc., regardless of the cell arrangement of the ultrasonic elements 2.

Fourth Embodiment
The ultrasonic sensor 1 according to the fourth embodiment will be described with reference to FIGS.

In FIG. 16, like FIG. 1, a part of the outer contour of the ultrasonic element 2, adhesive 3, mounting substrate 4, and base material 51 in another cross section is shown by a dashed line. In FIG. 17, in order to easily understand the positional relationship between the second resonance space 7 described below and the waveguide 511 in which it is provided, the outer contour of the part of the waveguide 511 that communicates with the second resonance space 7 in another cross section is shown by a dashed line.

The ultrasonic sensor 1 of this embodiment differs from the first embodiment in that, as shown in FIG. 16, in addition to the resonance space 6 located directly below the ultrasonic element 2, the waveguide 511 also has a resonance space 7. This difference will be mainly described in this embodiment.

The multiple waveguides 511 each have a resonance space 6 directly below the ultrasonic element 2 as a "first resonance space," and a second resonance space 7 formed between the inner end and the outer end.

As shown in FIG. 17, for example, the second resonance spaces 7 are provided in the same number as the multiple waveguides 511, are mutually independent, and have a minimum dimension in the planar direction shown in FIG. 17 that is larger than the diameter of the other parts of the waveguide 511. In other words, like the first resonance space 6, the multiple second resonance spaces 7 have a planar size larger than the waveguide 511, and are arranged so that the outer periphery of the communicating part of the waveguide 511 is enclosed inside the inner periphery. Like the first resonance space 6, the multiple second resonance spaces 7 each have a planar dimension and thickness that generate an acoustic resonance mode. The second resonance space 7 is formed, for example, by configuring the substrate 51 with two members, that is, one member having a part of the waveguide 511 and a recess communicating therewith, and the other member having the remaining part of the waveguide 511, and connecting them.

While the first resonance space 6 is formed by the opening 31 of the adhesive 3 and cannot be larger than the planar size of the ultrasonic element 2, the second resonance space 7 is provided in the base material 51 and can therefore have a planar size larger than the ultrasonic element 2. Therefore, one dimension of the second resonance space 7 in the planar direction shown in FIG. 17 is a, and the other dimension perpendicular to this is b, and the dimensions a and b are not limited by the planar size of the ultrasonic element 2.

From the viewpoint of improving sensitivity to the angle of arrival, it is preferable that a and b are different dimensions, and that the shorter dimension is at least greater than 3λ/2. Also, assuming that the dimension of the second resonance space 7 in the thickness direction is c, from the same viewpoint, it is preferable that the dimension c is smaller than 0.3λ.

According to this embodiment, the ultrasonic sensor 1 has the same effect as the first embodiment. Furthermore, in addition to the phase difference at the outer end 511a of the waveguide 511 and the first resonance space 6, the ultrasonic sensor 1 further has a phase difference generated in the second resonance space 7, which results in a wider adjustment range of the sensitivity to the angle of arrival of the reflected wave. Furthermore, the planar size of the second resonance space 7 can be made larger than that of the ultrasonic element 2, resulting in a structure with greater design freedom.

Fifth Embodiment
The ultrasonic sensor 1 according to the fifth embodiment will be described with reference to FIG.

In Figure 18, like Figure 1, parts of the outer periphery of the ultrasonic element 2, adhesive 3, mounting substrate 4, and base material 51 in another cross section are shown with dashed lines.

In the ultrasonic sensor 1 of this embodiment, as shown in FIG. 18, for example, second resonance spaces 7 are formed in multiple waveguides 511. In addition, in the ultrasonic sensor 1, the portion of the waveguide 511 closer to the ultrasonic element 2 than the second resonance space 7 is the first waveguide 5111, and the portion closer to the external space than the second resonance space 7 is the second waveguide 5112, and these are arranged with their axes shifted in a cross-sectional view. The ultrasonic sensor 1 differs from the first embodiment in the above-mentioned points. The second resonance space 7, which is the former difference, is the same as in the fourth embodiment, so in this embodiment, the latter difference will be mainly described.

In this embodiment, the multiple waveguides 511 include a first waveguide 5111 and a second waveguide 5112, and in cross-sectional view, these waveguides are offset in that their axes (i.e., the center positions of the waveguides) are shifted. In this way, the multiple waveguides 511 may be configured to be arranged with the positions of the two openings connected to the second resonance space 7 shifted.

This embodiment also provides the same effect as the fourth embodiment. Furthermore, the ultrasonic sensor 1 is structured so that the pitch of the waveguides 511 on the outer surface 51a of the substrate 51 can be adjusted as desired, regardless of the cell pitch of the ultrasonic element 2.

Sixth Embodiment
The ultrasonic sensor 1 according to the sixth embodiment will be described with reference to FIGS.

In Figure 19, like Figure 1, parts of the outer periphery of the ultrasonic element 2, adhesive 3, mounting substrate 4, and base material 51 in another cross section are shown with dashed lines.

The ultrasonic sensor 1 of this embodiment differs from the first embodiment in that the resonance space 6 spans multiple waveguides 511, as shown in FIG. 19, and is a single resonance space 6 common to the multiple waveguides 511. This difference will be mainly described in this embodiment.

In this embodiment, for example, when there are four waveguides 511, the resonance space 6 spans all four waveguides 511 and is connected to all of the waveguides 511. In other words, in this embodiment, the adhesive 3 is in the shape of a frame having only one opening, and is surrounded by the ultrasonic element 2 and the mounting substrate 4 to form one common resonance space 6.

The inventors also performed acoustic analysis simulations when the resonant space 6 is a common, interconnected space to verify whether the sensitivity to the angle of arrival of the reflected wave can be improved.

Specifically, in the acoustic analysis, for example, the analytical model shown in FIG. 20 was designed. In this analytical model, two linearly extending waveguides are arranged in parallel apart from each other, and a common resonance space is provided between the receiving point of these waveguides and the external space, and the two waveguides communicate through the resonance space. In this analytical model, the dimensions of the resonance space in the x, y, and z directions are a, b, and c, respectively, and the dimension of the waveguide in the z direction between the resonance space and the receiving point is d. In this analytical model, a simulation of acoustic analysis was performed using the finite element method, as in the first embodiment, with a drive frequency of 46.4 kHz (wavelength 7.4 mm) and air as the gas medium.

Figure 21 shows the simulation results when the thickness c is changed. In Figure 21, the horizontal axis is the angle of arrival, the vertical axis is the phase difference, and the curve based on the theoretical value in the absence of a resonance space is shown by a two-dot chain line. This is also true for Figures 22 and 23 described below.

As shown in FIG. 21, the gradient of the phase difference in the range of arrival angles from 0° to 20° was similar to that of the theoretical value when c = 2 mm. The gradient of the phase difference in the range of arrival angles from 0° to 20° was smaller when c = 3 mm than when c = 2 mm and the theoretical value, whereas it was larger when c = 1 mm than when c = 2 mm and the theoretical value. This shows that by designing c = 1 mm, the sensitivity to the arrival angle of the reflected wave can be made higher than when there is no resonance space. From the viewpoint of improving the sensitivity to the arrival angle of the reflected wave, it is preferable that the thickness c of the resonance space 6 is 0.3 λ [unit: m] or less and shorter than the length of the waveguide 511.

Next, the simulation results when the planar dimensions a and b are changed are shown in Figure 22. In this simulation, a = b, and a (= b) was changed in the range of 5λ/4 to 7λ/4. As shown in Figure 22, the gradient of the phase difference in the arrival angle range of 0° to 20° was similar to that of the theoretical value when a = b = 6λ/4. The gradient of the phase difference in the arrival angle range of 0° to 20° was smaller than the theoretical value when a = b = 5λ/4, whereas it was larger than the theoretical value when a = b = 7λ/4. This shows that by designing for a = b = 7λ/4, the sensitivity to the arrival angle of the reflected wave can be made higher than in the case of no resonant space.

Next, Figure 23 shows the simulation results when the distance d between the resonant space 6 and the receiving point is changed in the range of λ/8 to λ/2. As shown in Figure 23, the slope of the phase difference in the arrival angle range of 0° to 20° is almost the same when d = λ/2 and λ/4, and is smaller than the theoretical value. The slope of the phase difference in the arrival angle range of 0° to 20° is larger than the theoretical value when d = λ/8. This shows that by designing for d = λ/8, the sensitivity to the arrival angle of the reflected wave can be made higher than in the case of no resonant space.

As described above, even when the resonant space 6 is a common space connected to multiple waveguides 511, it is possible to increase the sensitivity to the angle of arrival of the reflected wave by appropriately designing the parameters of the planar size, thickness, and distance from the receiving element of the resonant space 6.

According to this embodiment, the ultrasonic sensor 1 can achieve the same effect as the first embodiment. In addition, since one common opening 31 is provided in the adhesive 3, and the space created when the opening 31 is surrounded by the ultrasonic element 2 and the mounting substrate 4 becomes the common resonance space 6, it also has the effect of being easier to manufacture than the first embodiment.

(Modification of the sixth embodiment)
24, the ultrasonic sensor 1 of the sixth embodiment may be configured to include a common second resonance space 7 in the waveguide 511 that communicates with the multiple waveguides 511 in addition to the first resonance space 6. In this case, similar to the fourth embodiment, the effect of further increasing the sensitivity to the arrival angle of the reflected wave can be obtained.

In this case, the ultrasonic sensor 1 may have a porous member 8 that transmits sound waves disposed in the second resonance space 7, as shown in FIG. 25, for example. The porous member 8 is made of, for example, any resin or metal material, and has a porosity of about 90%, although this is not limited thereto. The porous member 8 is fixed to the second resonance space 7, for example, by an adhesive (not shown). By disposing the porous member 8 in the second resonance space 7, even if a foreign object from the outside enters the waveguide 511, the foreign object can be prevented from adhering to the ultrasonic element 2, resulting in an ultrasonic sensor 1 with improved reliability.

The porous member 8 may be any material that transmits sound waves, and the constituent materials and structure may be changed as appropriate. In addition, since the porous member 8 transmits sound waves, it has little effect on the acoustic mode in the second resonance space 7, and there is no problem in adjusting the sensitivity to the angle of arrival.

As shown in FIG. 26, for example, the ultrasonic sensor 1 may have only the second resonance space 7 without the first resonance space 6. Even in this case, the structure allows the phase difference at the outer end of the waveguide 511 to be added to the phase difference generated in the resonance space 7, so that it is possible to improve the sensitivity to the angle of arrival.

These modified examples also provide the same effects as the first embodiment. In addition, the second resonance space 7 provides an expanded range of sensitivity adjustment and the porous member 8 provides a reduced effect of foreign matter.

Seventh Embodiment
The ultrasonic sensor 1 according to the seventh embodiment will be described with reference to FIGS.

In Figure 27, as in Figure 2, the outer contour of the diaphragm 25 is shown by a dashed line, and auxiliary lines indicating the corresponding positions of the ultrasonic element 2, adhesive 3, and mounting board 4 are shown by two-dot chain lines.

The ultrasonic sensor 1 of this embodiment differs from the first embodiment in that, as shown in FIG. 27, for example, the adhesive 3 is made of two separate members, and the resonance space 6 located directly below the ultrasonic element 2 is connected to the storage space 54. This difference will be mainly described in this embodiment.

In this embodiment, the adhesive 3 is arranged in parallel along two opposing sides of the outer periphery of the ultrasonic element 2 in a plan view, as shown in FIG. 28, for example. As a result, the resonance space 6 formed by the adhesive 3 sandwiched between the ultrasonic element 2 and the mounting board 4 is configured to communicate with the storage space 54 of the case material 5 in which the ultrasonic element 2 is stored. In this ultrasonic sensor 1, the storage space 54 also functions as the resonance space 6, and the acoustic resonance mode can be changed as appropriate depending on the planar size and thickness dimensions of the storage space 54.

This embodiment also provides the same effects as the first embodiment, and allows the acoustic resonance mode to be changed by adjusting the dimensions of the storage space 54, regardless of the arrangement of the ultrasonic element 2 and the waveguide 511, resulting in an ultrasonic sensor 1 with a structure that allows for high design freedom.

Other Embodiments
The ultrasonic sensor shown in each of the above-mentioned embodiments is an example of the ultrasonic sensor of the present invention, and is not limited to the above-mentioned embodiments. For example, the ultrasonic sensor of the present invention can be modified as appropriate to various combinations and forms of the above-mentioned embodiments, and further to other combinations and forms including only one element thereof, more than one element thereof, or less than one element thereof.

For example, the above embodiments and their variations may be freely combined as appropriate within the limits of what is possible.

2: ultrasonic element, 25: vibration part (diaphragm), 3: adhesive,
4: mounting substrate, 41: through hole, 5: case material, 51: base material,
511... Waveguide, 511a... Outer end, 5111... First waveguide,
5112: second waveguide; 54: storage space; 6: (first) resonance space;
7... (Second) Resonance Space

Claims (13)

An ultrasonic element (2) having a vibration part (25) capable of vibrating at a predetermined drive frequency;
a mounting substrate (4) to which the ultrasonic element is bonded via an adhesive (3) and which has a through hole (41) formed at a position corresponding to the vibration portion;
A case material (5) having a storage space (54) in which the ultrasonic element and the mounting board are stored, and a waveguide (511) that communicates with the through hole and an external space;
A resonance space (6, 7 ) formed between the ultrasonic element and the mounting substrate or in at least one of the waveguide,
The minimum dimension of the resonance space in a plane perpendicular to the extension direction of the waveguide is greater than a diameter of the waveguide,
An ultrasonic sensor, wherein the end of the waveguide facing the external space is an outer end (511a) and the end opposite the outer end is an inner end, and the waveguide has a shape in which the extension direction changes at least once between the outer end and the inner end . An ultrasonic element (2) having a vibration part (25) capable of vibrating at a predetermined drive frequency;
a mounting substrate (4) to which the ultrasonic element is bonded via an adhesive (3) and which has a through hole (41) formed at a position corresponding to the vibration portion;
A case material (5) having a storage space (54) in which the ultrasonic element and the mounting board are stored, and a waveguide (511) that communicates with the through hole and an external space;
A resonance space (6, 7) formed between the ultrasonic element and the mounting substrate or in at least one of the waveguide,
The resonance space is formed in the waveguide, and a minimum dimension of the resonance space in a plane perpendicular to an extension direction of the waveguide is larger than a diameter of the waveguide ,
An ultrasonic sensor in which a portion of the waveguide located closer to the ultrasonic element than the resonance space is designated as a first waveguide (5111), and a portion of the waveguide located closer to the external space than the resonance space is designated as a second waveguide (5112), and the second waveguide is positioned at a position different from an extension line of the first waveguide. The ultrasonic sensor according to claim 1 , wherein the vibration portion and the waveguide are arranged in a plurality of positions spaced apart from each other and aligned in at least one direction. An ultrasonic element (2) having a vibration part (25) capable of vibrating at a predetermined drive frequency;
a mounting substrate (4) to which the ultrasonic element is bonded via an adhesive (3) and which has a through hole (41) formed at a position corresponding to the vibration portion;
A case material (5) having a storage space (54) in which the ultrasonic element and the mounting board are stored, and a waveguide (511) that communicates with the through hole and an external space;
A resonance space (6, 7) formed between the ultrasonic element and the mounting substrate or in at least one of the waveguide,
The vibration portion and the waveguide are formed in a plurality of locations spaced apart from each other and arranged along at least one direction,
An ultrasonic sensor, wherein the resonance space has a minimum dimension in a plane perpendicular to the extension direction of the waveguide that is greater than the diameter of the waveguide, spans a plurality of the vibration parts or the waveguides, and is a common space corresponding to at least two or more of the vibration parts. The resonance spaces are provided in a plurality of spaces corresponding to the plurality of vibration sections,
5. The ultrasonic sensor according to claim 3 , wherein at least one of the plurality of resonance spaces has a shape or size different from the other resonance spaces. An ultrasonic sensor according to any one of claims 1 to 5, wherein the resonance space is provided between the ultrasonic element and the mounting board and is connected to the storage space. 7. The ultrasonic sensor according to claim 1, wherein a dimension of the resonance space in a direction along the extension direction is defined as a thickness, and a wavelength corresponding to the drive frequency is defined as λ, and the thickness of the resonance space is 0.3λ or less. The ultrasonic sensor according to claim 1 , wherein the resonant space is formed in the adhesive. 8. The ultrasonic sensor according to claim 1, wherein the resonant space is formed in the waveguide. 10. The ultrasonic sensor according to claim 9, wherein a porous member (8) that transmits sound waves is disposed in the resonance space. The case material includes a base material (51) having the waveguide,
11. The ultrasonic sensor according to claim 1, wherein the substrate is a composite material made of at least one material selected from the group consisting of resin, metal, and ceramic, or a combination of two or more materials. 12. The ultrasonic sensor according to claim 1, wherein an end of the waveguide facing the external space is an outer end (511a), a wavelength corresponding to the drive frequency is λ, and a linear distance between the outer end and the vibration portion is within ±10% of a value expressed by the formula nλ/ 2 (n: odd number equal to or greater than 1). 13. The ultrasonic sensor according to claim 1, wherein the drive frequency is in the range of 30 kHz to 100 kHz.

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