Ultrasonic Sensor

Abstract

To realize an ultrasonic sensor that protects an ultrasonic element for transmission and reception from an external environment while improving the accuracy of direction detection of an external obstacle.SOLUTION: In an ultrasonic sensor 1, an ultrasonic element 2 is adhered to a mounting substrate 4 by an adhesive 3, and these are housed in a housing space 54 of a case material 5. A diaphragm 25 that functions as a vibrating portion of the ultrasonic element 2 communicates with an external space through a waveguide 511 of the case material 5. Between the ultrasonic element 2 and the mounting substrate 4 or in the waveguide 511 or both the ultrasonic element 2 and the mounting substrate 4, a resonance space 6 having a planar size larger than the diameter of the waveguide 511 is formed. In the ultrasonic sensor 1, the ultrasonic element 2 receives a sound wave in which a phase difference due to an acoustic resonance mode generated in the resonance space 6 is added to the phase difference with respect to the arrival angle of the reflected wave generated at the outer end of the waveguide 511.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic sensor having a plurality of ultrasonic receiving elements. [Background technology]

[0002] Conventionally, there is known an ultrasonic sensor that includes at least one ultrasonic element for transmission (hereinafter referred to as a "transmitting element") and multiple ultrasonic elements for reception (hereinafter referred to as "receiving elements") and is capable of detecting the distance to an obstacle and its direction (for example, Patent Document 1). The ultrasonic sensor described in Patent Document 1 includes 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 achieving both good appearance and impact resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-89569 A Summary of the Invention [Problem to be solved by the invention]

[0004] This ultrasonic sensor transmits ultrasonic waves of a predetermined frequency to the outside using a transmitting element, and receives the reflected waves using multiple receiving elements arranged at predetermined intervals. Based on the phase difference of the reflected waves, the sensor detects the direction of external obstacles, etc. relative to the ultrasonic sensor.

[0005] 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 incident direction of the reflected wave to 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".

[0006] Specifically, this ultrasonic sensor calculates the direction of arrival of the reflected wave by utilizing the fact that the phase difference between the reflected waves received by a plurality of receiving elements changes depending on the angle of arrival of the reflected wave.

[0007] In recent years, there has been a need to further improve the accuracy of object direction detection in object detection using this type of ultrasonic sensor. In order to improve the accuracy of direction 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 arrival angle and to increase the sensitivity with respect to the arrival angle.

[0008] Here, the phase difference of the reflected wave with respect to the arrival angle is uniquely determined by the interval between adjacent receiving elements and the wavelength of the ultrasonic wave (hereinafter referred to as the "transmission wave") transmitted to the outside. Therefore, in order to increase the sensitivity to the arrival angle, it is necessary to change the interval between the receiving elements or the wavelength of the transmission wave.

[0009] However, the ultrasonic sensor described in Patent Document 1 has a configuration in which the transmitting element and the receiving element are disposed within a substrate, and ultrasonic waves are transmitted and received through a waveguide disposed or formed within the substrate, making it difficult to arbitrarily change the distance between the receiving elements. In addition, while the method of changing the wavelength of the transmitting wave, i.e., the driving frequency, improves the sensitivity to the arrival angle, it causes a decrease in the attenuation rate of the ultrasonic waves and a decrease in the resolution of the distance measurement to the object, so there is a limit to the improvement in sensitivity to the arrival angle.

[0010] In view of the above, an object of the present invention is to provide an ultrasonic sensor that protects transmitting and receiving ultrasonic elements from the external environment while improving the accuracy of detecting the direction of external obstacles, etc. [Means for solving the problem]

[0011] In order to achieve the above object, claim 1 、2、4The ultrasonic sensor described in the above includes an ultrasonic element (2) having a vibration portion (25) capable of vibrating at a predetermined drive frequency, a mounting board (4) to which the ultrasonic element is bonded via an adhesive material (3) and having 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, and a space between the ultrasonic element and the mounting board or the waveguide. At least one of Resonant space formed in (6, 7) and , and the minimum dimension of the resonant 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 is a common space that spans the plurality of vibration parts or waveguides and corresponds to at least two or more vibration parts.

[0012] As a result, the ultrasonic sensor transmits a transmission wave from the ultrasonic element to the outside through the waveguide and receives the reflected wave through the waveguide, and has at least one of a resonance space between the ultrasonic element and the mounting board or a resonance space formed in the waveguide. The minimum dimension of this resonance space in a radial plane with the extension direction of the waveguide as an axis is larger than the diameter of the waveguide. This ultrasonic sensor has a structure in which the above-mentioned resonance space is provided in the propagation path of the ultrasonic wave, making it possible to adjust the phase difference of the reflected wave with respect to the arrival angle without changing the interval between the receiving elements or the wavelength of the transmission 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.

[0013] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing an ultrasonic sensor according to a first embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing an ultrasonic element, an adhesive material, and a mounting substrate. [Diagram 3] 3 is a cross-sectional view showing a cross-sectional configuration taken along line III-III in FIG. 2. [Figure 4] 4 is a plan view showing the ultrasonic element and the adhesive material as viewed from the waveguide side. FIG. [Diagram 5] FIG. 2 is an explanatory diagram for explaining the relationship between the arrival angle and the phase difference. [Figure 6] FIG. 1 is a diagram showing an example of a cubic waveguide. [Figure 7] FIG. 1 is a diagram showing an example of an acoustic mode generated in a cubic space. [Figure 8] FIG. 1 is a diagram illustrating an example of a model in an acoustic simulation. [Figure 9] FIG. 13 is a diagram showing characteristics obtained by acoustic simulation of a model having a resonant space. [Figure 10] FIG. 11 is a cross-sectional view showing an ultrasonic sensor according to a second embodiment. [Figure 11] FIG. 11 is a cross-sectional view showing an example of a modified example of the ultrasonic sensor of the second embodiment. [Figure 12] FIG. 11 is a cross-sectional view showing another example of a modified example of the ultrasonic sensor of the second embodiment. [Figure 13] 13A to 13C are diagrams illustrating an example of arrangement at an opening of a waveguide in an ultrasonic sensor according to a third embodiment. [Figure 14] 13A to 13C are diagrams illustrating other examples of the arrangement of the openings of the waveguide in the ultrasonic sensor of the third embodiment. [Figure 15] 13 is an explanatory diagram for explaining a modified example of the ultrasonic sensor of the third embodiment. FIG. [Figure 16] FIG. 11 is a cross-sectional view showing an ultrasonic sensor according to a fourth embodiment. [Figure 17] 17 is a cross-sectional view showing a cross-sectional configuration taken along line XVII-XVII in FIG. 16. [Figure 18] FIG. 13 is a cross-sectional view showing an ultrasonic sensor according to a fifth embodiment. [Figure 19] FIG. 13 is a cross-sectional view showing an ultrasonic sensor according to a sixth embodiment. [Figure 20] FIG. 13 is a diagram showing a model in an acoustic simulation, which corresponds to the ultrasonic sensor of the sixth embodiment. [Figure 21] 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. [Figure 22] FIG. 21 is a diagram showing characteristics obtained by acoustic simulation of the analysis model of FIG. 20, in which the dimensions in the planar direction of the resonance space are changed. [Figure 23] FIG. 21 is a diagram showing characteristics obtained by acoustic simulation of the analysis model of FIG. 20, in which the distance between the resonance space and the receiving point is changed. [Figure 24] FIG. 13 is a cross-sectional view showing a first modified example of the ultrasonic sensor of the sixth embodiment. [Diagram 25] FIG. 13 is a cross-sectional view showing a second modified example of the ultrasonic sensor of the sixth embodiment. [Figure 26] FIG. 13 is a cross-sectional view showing a third modified example of the ultrasonic sensor of the sixth embodiment. [Figure 27] 13 is an exploded perspective view showing an ultrasonic element, an adhesive material, and a mounting substrate in an ultrasonic sensor according to a seventh embodiment. FIG. [Figure 28] FIG. 13 is a plan view showing an ultrasonic element and an adhesive material according to an ultrasonic sensor of a seventh embodiment as viewed from the waveguide side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0016] (First embodiment) An ultrasonic sensor 1 according to a first embodiment will be described with reference to Fig. 1 to Fig. 4. The ultrasonic sensor 1 is preferably used in an object detection device mounted on a vehicle such as an automobile and detecting objects such as external obstacles, but can of course also be used for other purposes.

[0017] In Fig. 1, parts of the outer contours of the ultrasonic element 2, adhesive 3, mounting board 4, and base material 51, which will be described later, in another cross section are shown by dashed lines. In Fig. 2, the area of ​​one surface 4a of the mounting board 4 that contacts the adhesive 3, and the outer contour of a diaphragm 25, which will be described later and is not visible at the angle shown in Fig. 2, of the ultrasonic element 2 are shown by dashed lines. In Fig. 2, auxiliary lines indicating the corresponding positions of the ultrasonic element 2, adhesive 3, and mounting board 4 are shown by two-dot chain lines. In Fig. 3, the outer contour of the adhesive 3, which is not a component of the ultrasonic element 2, is shown by a two-dot chain line. In Fig. 4, the outer contour of a piezoelectric film 26, which will be described later and is not visible at the angle shown in Fig. 4, is shown by a dashed line.

[0018] 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 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 the ultrasonic element 2 attached to the mounting substrate 4 via the adhesive 3, which is stored in a storage space 54 of the case material 5, and includes a waveguide 511 communicating with the through hole 41 and an 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.

[0019] The ultrasonic element 2 is configured, for example, as shown in FIG. 3, using an SOI (abbreviation of Silicon on Insulator) substrate in which a support substrate 21, a buried 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 buried insulating film 22 and exposes the semiconductor layer 23, and a portion of the semiconductor layer 23 corresponding to the recess 24 is a diaphragm 25. The ultrasonic element 2 is configured, for example, to have a piezoelectric film 26 formed on the surface of the diaphragm 25 opposite to the buried insulating film 22. The piezoelectric film 26 is configured, for example, to be sandwiched between a pair of electrodes made of a piezoelectric material and to contract or expand 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 (drive units) 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 of Micro Electro Mechanical Systems) type having a plurality of drive units. The ultrasonic element 2 has, for example, a diaphragm 25 as a vibration unit, and functions as a transmission element that transmits ultrasonic waves to the outside and a reception element that receives sound waves from the outside.

[0020] For ease of explanation, hereinafter, the diaphragm 25 functioning as the driving unit may be referred to as a "cell", the diameter of the cell as a "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 a "transmitted / received wave".

[0021] The adhesive 3 is a member that bonds and fixes the ultrasonic element 2 to the mounting board 4, and may be, for example, any adhesive resin material. As shown in Fig. 2 and Fig. 4, the adhesive 3 has the same outer shape as the ultrasonic element 2, and is in the form of a lattice-like frame having a plurality of openings 31 in a planar size larger than the diaphragm 25 in a region located directly below the diaphragm 25 of the ultrasonic element 2. The thickness of the adhesive 3 is, for example, about 10 µm to 200 µm, but is not limited thereto.

[0022] The openings 31 are provided in the same number as the cells of the ultrasonic element 2, and are independent of each other in this embodiment. 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 include the corresponding cell and waveguide 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 board 4, and function as propagation paths for transmission and reception waves, as well as independent resonance spaces 6, as shown in FIG. 1.

[0023] 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 a region located outside the outer periphery of the ultrasonic element 2, and is 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 a position corresponding to the diaphragm 25. The plurality of through holes 41 are propagation paths for transmitting and receiving waves independent of each other, and are, for example, circular, but are not limited thereto, and may 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 communicating therewith.

[0024] 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, the adhesive material 3, and the mounting board 4 while being spaced apart from these, and a lid part 53 that is placed on the frame body part 52. In the case material 5, the space surrounded by the base material 51, the frame body part 52, and the lid part 53 forms a storage space 54 that stores the ultrasonic element 2, the adhesive material 3, and the mounting board 4. The case material 5 is made of, for example, metal, resin, ceramic, or a composite material that combines part or all of these.

[0025] 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 has a plurality of waveguides 511 formed thereon. One surface of the substrate 51 on which the opening of the waveguide 511 facing the external space is formed is defined as an outer surface 51a, and in the case of an in-vehicle application, for example, the substrate 51 is disposed such that the outer surface 51a faces or is in contact with the exterior of the vehicle body, a bumper, or the like.

[0026] The waveguides 511 are formed in the base material 51 in a plurality of through holes that serve as a propagation path for transmitting and receiving waves, and are, for example, circular cylindrical, but are not limited thereto, and may be any shape such as an elliptical cylindrical shape or a polygonal cylindrical shape. The plurality of waveguides 511 are independent of each other and communicate with one corresponding through hole 41, opening 31, and cell. The plurality of waveguides 511 are, for example, through holes in which the end (opening) of the waveguide 511 on the external space side is the outer end 511a and the opposite end is the inner end, and the outer end 511a and the inner end are linearly connected. The direction in which the waveguide 511 is extended is defined as the "extension direction", and the plurality of waveguides 511 are in a state in which their extension directions are aligned in this embodiment. In other words, the base material 51 is configured such that the plurality of waveguides 511 that are linearly extended are arranged in parallel. The number of the multiple waveguides 511 is, for example, the same as the number of cells of the ultrasonic element 2. When the cell arrangement of the ultrasonic element 2 is α×β, the outer ends 511a are arranged in an array of α×β.

[0027] The frame portion 52 is a portion of the case material 5 that surrounds the ultrasonic element 2, the adhesive material 3, and the mounting board 4, and has an inner contour that follows the outer shape of the mounting board 4, for example.

[0028] 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 .

[0029] In the above, an example has been described in which the base material 51, the frame body portion 52 and the lid portion 53 constituting the case material 5 are separate bodies, but this is not limited to this, and the base material 51 and the frame body portion 52, or the frame body portion 52 and the lid portion 53 may be integrated, and the configuration may be changed as appropriate.

[0030] 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 is provided between the ultrasonic element 2 and the mounting board 4 in this embodiment. 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. The resonance space 6 has a size in which the minimum dimension of a plane perpendicular to the extension direction of the communicating waveguide, with one of the multiple waveguides 511 communicating with each other being a "communicating waveguide", is larger than the perpendicular dimension of the communicating waveguide. Specifically, the size of the plane of the resonance space 6 is larger than the diameter of the communicating waveguide, and the resonance space 6 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, the diameter of the waveguide 511 is, for example, approximately the same as the cell diameter, so that 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 with respect to the resonance space 6 can be appropriately determined according to the acoustic resonance mode described later.

[0031] 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 arrival angle of the reflected wave by providing a resonance space 6 with a predetermined dimension in the propagation path of the transmitted and received wave between the ultrasonic element 2 and the external space.

[0032] In addition, in the ultrasonic sensor 1, the linear distance from the diaphragm 25 to the outer end 511a of the waveguide 511 is defined as L, and the wavelength equivalent value of the drive frequency is defined as λ. From the viewpoint of improving the transmission performance, it is preferable that L is within ±10% of the value expressed by nλ / 2 (n: an odd number equal to or greater than 1).

[0033] [Resonance space] Next, the effect of the resonance space 6 will be described with reference to FIGS.

[0034] First, the arrival angle and phase difference of the reflected wave will be described with reference to FIG.

[0035] For example, as shown in Fig. 5, when two linearly extending waveguides are arranged with a pitch of 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).

[0036] θ=sin -1 (Δx×λ / (2π×d0)) (1) In addition, when the cells of the ultrasonic elements are arranged on the extension lines of the two waveguides, the pitch d0 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 d0 is determined by the arrangement of the outer ends of the waveguides on the receiving surface, with the plane facing the outer ends being the receiving surface. When the pitch d0 and the wavelength λ of the reflected wave are fixed at a certain value, according to 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 d0 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 the arrival angle.

[0037] Conventional ultrasonic sensors that do not have a resonance space 6 (hereinafter simply referred to as "conventional ultrasonic sensors") have a small degree of freedom in design, and it is difficult to improve the sensitivity to the arrival angle θ. Specifically, in conventional ultrasonic sensors, 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., pitch d0), or the driving frequency (i.e., wavelength λ), or both.

[0038] However, when changing the interval between receiving elements or the interval between waveguides, it is necessary to change the structure or arrangement of the ultrasonic elements or the 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 d0<λ / 2 must be satisfied. Specifically, when d0>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, resulting in a state in which 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, from the viewpoint of the constraint of d0<λ / 2, it is difficult to freely change the interval between receiving elements.

[0039] Furthermore, when changing the drive frequency of the ultrasonic element, although there is no need to change the structure, arrangement, etc., a decrease in the attenuation rate of ultrasonic waves and a decrease in the resolution of measuring the distance to an object occur, so even if the sensitivity to the arrival angle can be improved, other characteristics are degraded.

[0040] In contrast, the ultrasonic sensor 1 of this embodiment is provided with a resonance space 6 in which a resonance mode of a reflected wave occurs in the propagation path of a transmitted and received wave.

[0041] 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 to this is b0 (unit: m), the acoustic resonance mode that can exist in the waveguide is expressed by the following formula.

[0042]

number

[0043] The dimensions of the resonance space 6 are such that an acoustic mode with a phase difference occurs at the frequency of the propagating reflected wave, as shown in FIG.

[0044] The acoustic mode corresponding to the dimensions of the resonance space 6 can be calculated by, for example, a simulation using acoustic analysis software (such as Ansys (registered trademark) by Ansys, Inc.) that uses the finite element method. 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.

[0045] In the example shown in FIG. 7, for example, the largest phase difference occurs at points A and B. The resonance space 6 is sized to generate an acoustic mode by simulation of acoustic analysis or the like, 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 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 driving frequency is largest. 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.

[0046] As a result, the phase difference generated at the outer end 511a of the waveguide 511 is taken as Δx1, and the phase difference Δx2 in the resonance space 6 is further added to this, and finally, the phase difference of the reflected wave received by the ultrasonic element 2 becomes larger than Δx1. As a result, the phase difference Δx for a change in the arrival angle of 1° in the ultrasonic sensor 1 having the resonance space 6 becomes larger 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 larger than Δx1.

[0047] Next, the results of the acoustic simulation will be described with reference to FIGS.

[0048] The present inventors have designed a simulation model for acoustic analysis corresponding to the ultrasonic sensor 1 of this embodiment, as shown in FIG.

[0049] For convenience 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, and 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.

[0050] In the analytical model, the resonance space 6 is cubic, with dimensions in the x, y, and z directions being a, b, and c, 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 for c=4 mm and c=8 mm are shown as representative values.

[0051] In FIG. 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 gradient of the phase difference Δx in the range of the arrival angle θ from 0° to 20° is shown by a dashed line.

[0052] The change in phase difference Δx per 1° of the arrival angle θ shown in Fig. 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.

[0053] Therefore, by providing the resonance space 6, the amount of change in the phase difference Δx with respect to the arrival angle θ can be increased without changing the drive frequency of the ultrasonic element 2 and the pitch of the outer end 511a of the waveguide 511, thereby improving the accuracy of azimuth detection.

[0054] When a plurality of 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 plurality of resonance spaces 6 may be appropriately changed in accordance with the above-mentioned acoustic resonance mode as long as the phase difference between the different waveguides 511 is large.

[0055] 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 transmission and reception waves connecting the ultrasonic element 2 and the external space, resulting in an ultrasonic sensor 1 with a large amount of change in phase difference Δx with respect to the arrival angle θ of the reflected wave. Therefore, while protecting the ultrasonic element 2, the degree of freedom in design is high, and the effect of further improving the accuracy of azimuth detection is obtained.

[0056] Second embodiment The ultrasonic sensor 1 according to the second embodiment will be described with reference to FIG.

[0057] 10, like Fig. 1, parts of the outlines of the ultrasonic element 2, adhesive 3, mounting board 4, and base material 51 in another cross section are indicated by dashed lines. This also applies to Figs. 11 and 12 described below.

[0058] 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. In this embodiment, this difference will be mainly described.

[0059] In this embodiment, the waveguide 511 has an outer end 511a that is on the outer space side 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 continuously increases from the inner end to the outer end 511a in a cross-sectional view, for example. In this case, the ultrasonic sensor 1 has a configuration in which the range of the transmission wave is narrower and the directivity is sharper than in the first embodiment.

[0060] According to this embodiment, it is possible to obtain the same effects as those of the above-described embodiment 1. In addition, since the diameter of the waveguide 511 is continuously changed, it is possible to obtain an effect of sharpening the directivity of the transmission wave.

[0061] (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.

[0062] In addition, in the ultrasonic sensor 1 of the second embodiment, as shown in FIG. 12, the waveguide 511 may have a tapered shape in which the diameter 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 board 4 has a shape in which the diameter at the opening on the waveguide 511 side is substantially the same as the diameter at the inner end of the waveguide 511, and the diameter increases continuously toward the ultrasonic element 2 side. In addition, the diameter of the through hole 41 at the opening on the ultrasonic element 2 side is substantially the same as the diameter of the diaphragm 25. The through hole 41 may have a shape with 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.

[0063] This modification 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 modification, the transmission directivity can be controlled.

[0064] In the above second embodiment and its modified example, an example has been described in which the wall surfaces of the waveguide 511 and the through hole 41 are linear in cross-sectional view, but this is not limited to this and may be curved, and the degree of change in shape and diameter, etc. may be changed as appropriate.

[0065] Third embodiment The ultrasonic sensor 1 according to the third embodiment will be described with reference to FIG.

[0066] FIG. 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 being omitted.

[0067] The ultrasonic sensor 1 of this embodiment differs from the first embodiment in that outer ends 511a of a plurality of waveguides 511 are linearly arranged in one direction, as shown in Fig. 13. This difference will be mainly described in this embodiment.

[0068] In this embodiment, the number of waveguides 511 is, for example, n1 or more (n1: a natural number equal to or greater than 2), and their outer ends 511a are arranged in one direction, that is, in a so-called “1D array.”

[0069] According to this embodiment, the same effects as those of the first embodiment can be obtained. In addition, the ultrasonic sensor 1 is configured to be able to detect at least one of the directions (azimuth and altitude) of an external obstacle relative to the ultrasonic sensor 1.

[0070] (Modification of the third embodiment) The ultrasonic sensor 1 of the third embodiment may be arranged in a so-called "2D array" in which outer ends 511a of a plurality of waveguides 511 are arranged along two directions 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.

[0071] 14, the number of outer ends 511a of the waveguides 511 in one row along the left-right direction is n1 (n1: a natural number of 2 or more), and the number of outer ends 511a of the waveguides 511 in one row along a direction perpendicular to the left-right direction is n2 (n2: a natural number of 2 or more). In this case, the numbers n1 and n2 may be changed as appropriate.

[0072] 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 waveguides, the four cells of the ultrasonic element 2 may be arranged in a 1D array along one direction, whereas 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, so that azimuth detection in two directions is possible.

[0073] In Fig. 15, the waveguides 511 connecting the cells and the outer ends 511a are shown by dashed lines in order to easily understand the relationship between the cell arrangement of the ultrasonic elements 2 and the arrangement of the outer ends 511a of the waveguides 511. In addition, Fig. 15 shows an example 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 thereto, and the number and shapes of the waveguides 511 whose extension direction changes can be changed as appropriate.

[0074] This modification also provides the same effects as those of the third embodiment. In addition, by arranging the outer ends 511a of the multiple waveguides 511 in an n1×n2 array, the ultrasonic sensor 1 can detect two directions of an external obstacle, regardless of the cell arrangement of the ultrasonic elements 2.

[0075] (Fourth embodiment) The ultrasonic sensor 1 according to the fourth embodiment will be described with reference to FIGS.

[0076] 16, like Fig. 1, parts of the contours of the ultrasonic element 2, adhesive 3, mounting board 4, and base material 51 in another cross section are indicated by dashed lines. In Fig. 17, in order to make it easier to understand the positional relationship between a second resonance space 7 (described later) and a waveguide 511 in which the second resonance space 7 is provided, the contours of the part of the waveguide 511 that communicates with the second resonance space 7 in another cross section are indicated by dashed lines.

[0077] 16, the ultrasonic sensor 1 of this embodiment differs from the above-described first embodiment in that in addition to the resonance space 6 located directly below the ultrasonic element 2, a resonance space 7 is also provided in the waveguide 511. In this embodiment, this difference will be mainly described.

[0078] The plurality of 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.

[0079] As shown in FIG. 17, the second resonance spaces 7 are provided in the same number as the plurality of waveguides 511, are independent of each other, 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, the plurality of second resonance spaces 7 are arranged such that, like the first resonance space 6, the planar size is larger than the waveguide 511, and the outer periphery of the communicating part of the waveguide 511 is enclosed inside the inner periphery. Like the first resonance space 6, the plurality of 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 forming the base material 51 from 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.

[0080] 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 have a planar size larger than the ultrasonic element 2. Therefore, when one dimension of the second resonance space 7 in the planar direction shown in FIG. 17 is a and the other dimension perpendicular to the same is b, the dimensions a and b are not limited to the planar size of the ultrasonic element 2.

[0081] From the viewpoint of improving the sensitivity to the arrival angle, 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.

[0082] According to this embodiment, the ultrasonic sensor 1 can obtain the effects of the first embodiment. Moreover, in this ultrasonic sensor 1, in addition to the phase difference at the outer end 511a of the waveguide 511 and the first resonance space 6, the phase difference generated in the second resonance space 7 is further added, so that the effect of widening the adjustment range of the sensitivity to the arrival angle of the reflected wave is obtained. Moreover, since the planar size of the second resonance space 7 can be made larger than that of the ultrasonic element 2, the structure has a higher degree of freedom in design.

[0083] Fifth embodiment The ultrasonic sensor 1 according to the fifth embodiment will be described with reference to FIG.

[0084] 18, 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 indicated by dashed lines.

[0085] In the ultrasonic sensor 1 of this embodiment, as shown in FIG. 18, for example, the second resonance space 7 is formed in a plurality of 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 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.

[0086] In this embodiment, the multiple waveguides 511 include a first waveguide 5111 and a second waveguide 5112, and in a cross-sectional view, these waveguides are configured to be offset in a sense, with their axes (i.e., the center positions of the waveguides) shifted. In this manner, 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.

[0087] This embodiment also provides the same effects as those of the above-described embodiment 4. Moreover, the ultrasonic sensor 1 has a structure in which the pitch of the waveguides 511 on the outer surface 51a of the base material 51 can be arbitrarily adjusted, regardless of the pitch of the cells of the ultrasonic elements 2.

[0088] Sixth embodiment The ultrasonic sensor 1 of the sixth embodiment will be described with reference to FIGS.

[0089] 19, 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 indicated by dashed lines.

[0090] 19, the ultrasonic sensor 1 of this embodiment differs from the first embodiment in that the resonance space 6 spans a plurality of waveguides 511, forming one resonance space 6 common to the plurality of waveguides 511. In this embodiment, this difference will be mainly described.

[0091] In this embodiment, for example, when the number of the waveguides 511 is four, the resonance space 6 spans all four waveguides 511 and communicates with all the waveguides 511. That is, in this embodiment, the adhesive 3 is formed in a frame shape having only one opening, and is surrounded by the ultrasonic element 2 and the mounting board 4 to form one common resonance space 6.

[0092] The present inventors also performed simulations of acoustic analysis in the case where the resonant spaces 6 are connected to each other as a common space, and verified whether the sensitivity to the arrival angle of the reflected wave can be improved.

[0093] Specifically, in the acoustic analysis, for example, an 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 an external space, and the two waveguides communicate with each other 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 driving frequency of 46.4 kHz (wavelength 7.4 mm) and air as the gas medium.

[0094] The simulation results when the thickness c is changed are shown in Fig. 21. In Fig. 21, the horizontal axis is the arrival angle, the vertical axis is the phase difference, and the curve based on the theoretical value in the case where there is no resonance space is shown by a two-dot chain line. This is the same for Figs. 22 and 23 described later.

[0095] As shown in FIG. 21, the gradient of the phase difference in the range of the arrival angle of 0° to 20° was almost the same as that of the theoretical value when c=2 mm. The gradient of the phase difference in the range of the arrival angle of 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 that without the 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 0.3λ [unit: m] or less and shorter than the length of the waveguide 511.

[0096] Next, the simulation results when the planar dimensions a and b are changed are shown in FIG. 22. In this simulation, a=b was set, and a(=b) was changed in the range of 5λ / 4 to 7λ / 4. As shown in FIG. 22, the gradient of the phase difference in the arrival angle range of 0° to 20° was almost the same as 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 it to a=b=7λ / 4, the sensitivity to the arrival angle of the reflected wave can be made higher than the case without the resonant space.

[0097] Next, Fig. 23 shows the simulation results when the distance d between the resonance space 6 and the receiving point is changed in the range of λ / 8 to λ / 2. As shown in Fig. 23, the gradient 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 gradient 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 when there is no resonance space.

[0098] As described above, even when the resonance space 6 is a single common space connected to multiple waveguides 511, it is possible to increase the sensitivity to the arrival angle of the reflected wave by appropriately designing the parameters of the resonance space 6, namely, its planar size, thickness, and distance from the receiving element.

[0099] According to this embodiment, the ultrasonic sensor 1 can obtain the same effect as the first embodiment. In addition, since one common opening 31 is provided in the adhesive 3, and the space generated when the opening 31 is surrounded by the ultrasonic element 2 and the mounting substrate 4 serves as the common resonance space 6, an effect is obtained that the structure is easier to manufacture than the first embodiment.

[0100] (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 a plurality of 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.

[0101] 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.

[0102] The porous member 8 may be any member that transmits sound waves, and the constituent material and structure may be appropriately changed. 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 arrival angle.

[0103] 26, 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 generated in the resonance space 7 to be added to the phase difference at the outer end of the waveguide 511, so that the sensitivity to the angle of arrival can be improved.

[0104] These modifications also provide the same effects as the first embodiment, and 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.

[0105] Seventh embodiment The ultrasonic sensor 1 of the seventh embodiment will be described with reference to FIGS.

[0106] 27, similarly to FIG. 2, the outline of the diaphragm 25 is indicated by a dashed line, and auxiliary lines indicating the corresponding positions of the ultrasonic element 2, adhesive material 3, and mounting board 4 are indicated by two-dot chain lines.

[0107] 27, the ultrasonic sensor 1 of this embodiment is different from the first embodiment in that the adhesive 3 is composed of two separate members, and the resonance space 6 located directly below the ultrasonic element 2 communicates with the storage space 54. In this embodiment, this difference will be mainly described.

[0108] In this embodiment, the adhesive material 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, a resonance space 6 formed by the adhesive material 3 sandwiched between the ultrasonic element 2 and the mounting board 4 is configured to communicate with a 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 appropriately changed depending on the planar size and thickness dimension of the storage space 54.

[0109] 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.

[0110] (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.

[0111] For example, the above-described embodiments and their modified examples may be freely combined as appropriate within the possible range. [Explanation of symbols]

[0112] 2 ultrasonic element, 25 vibration part (diaphragm), 3 adhesive material, 4 mounting board, 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

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 6. The ultrasonic sensor according to claim 1, wherein the resonance space is provided between the ultrasonic element and the mounting board, and communicates with the storage space.

7. 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.

8. An ultrasonic sensor described in any one of claims 1 to 7, wherein the resonant space is formed in the adhesive.

9. An ultrasonic sensor described in any one of claims 1 to 7, wherein the resonant space is formed in the waveguide.

10. An ultrasonic sensor as described in claim 9, wherein a porous member (8) that is transparent to sound waves is arranged in the resonant space.

11. 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. 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. 13. The ultrasonic sensor according to claim 1, wherein the drive frequency is within a range of 30 kHz to 100 kHz.

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