Ultrasonic sensor and object detection device

Abstract

To provide a configuration capable of more stably achieving desired directivity and further improving transmission / reception characteristics in an ultrasonic sensor.SOLUTION: An ultrasonic sensor (1) mounted on a mobile object (V) includes a fixing portion (3) and a conversion element (4). The conversion element has a proximal end (41), which is one end, and a distal end (42), which is the other end, in an axial direction along a directional axis (DA), and has a conversion function between an ultrasonic vibration and an electrical signal. The fixing portion is provided closer to the proximal end than the distal end of the conversion element, and supports the conversion element in a fixed manner. The ultrasonic sensor has a transmitting function and / or a receiving function. In the transmitting function, a drive signal is applied to the conversion element, and an ultrasonic wave is transmitted from the conversion element in a transmission direction from the proximal end toward the distal end. In the receiving function, an ultrasonic vibration transmitted from an external space to the conversion element is converted into a reception signal by the conversion element.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an ultrasonic sensor mounted on a moving object, and an object detection device equipped with such an ultrasonic sensor. [Background technology]

[0002] Various techniques for detecting obstacles around a moving body such as a vehicle using an ultrasonic sensor have been disclosed in the past. In this type of ultrasonic sensor, a predetermined directivity may be set. Specifically, for example, when an ultrasonic sensor is used in a vehicle, it is desirable not to detect the road surface or a parking curb on the road surface as an obstacle or to issue a warning. Therefore, in this case, it is preferable to have a directivity such that the transmission and reception range of ultrasonic waves in the horizontal direction is wide while the transmission and reception range of ultrasonic waves in the vertical direction is narrow, that is, to narrow the vertical directivity relative to the horizontal directivity.

[0003] In this regard, the ultrasonic sensor described in Patent Document 1 includes a sensor housing and a piezoelectric vibrator. The sensor housing has a substantially circular cross-sectional shape, a hollow portion is formed inside, and one side is open. The piezoelectric vibrator is fixed to the center position on the bottom surface of the sensor housing by adhesive or the like. The vibration surface is provided by a part of the bottom surface of the sensor housing to which the piezoelectric vibrator is fixed. The left and right sides of the open side of the sensor housing are cut off in an arc shape, and the cross-sectional shape is an oval shape. In addition, the hollow portion is formed in a shape that follows the oval outline of the open side of the sensor housing, and the cross-sectional shape is also oval. As a result, the vibration surface of the ultrasonic sensor provided by a part of the bottom surface of the sensor housing is formed in a shape that follows the outline of the open side of the sensor housing. In addition, the outline of the open side of the sensor housing has a curvature, and the outline of the vibration surface has the same curvature. In addition, the outline of the vibration surface on the side of the vehicle that contributes to the road surface perpendicular direction has the same curvature as the outline of the vibration surface side of the sensor housing. In addition, the outline of the thinnest part of the vibration surface on the side of the vehicle that contributes to the road surface perpendicular direction is formed along the outline of the vibration surface side of the sensor housing, and the outline of the thinnest part of the vibration surface and the outline of the vibration surface side of the sensor housing have the same curvature. This makes it possible to narrow the directivity of the ultrasonic waves. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4274679 Summary of the Invention [Problem to be solved by the invention]

[0005] In this type of ultrasonic sensor, attempts have been made to more stably realize the desired directivity and further improve the transmission and reception characteristics. Specifically, for example, in the ultrasonic sensor described in Patent Document 1, the efficiency drops extremely at vibration frequencies other than the resonance frequency determined by the joint structure between the piezoelectric vibrator and the vibration surface. Therefore, in such a configuration, it is difficult to widen the bandwidth. In addition, the vibration mode changes with the change in vibration frequency. Furthermore, the vibration mode also changes with temperature change. When the vibration mode changes, the directivity also changes.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, etc. That is, the present invention provides a configuration that can more stably achieve a desired directivity and further improve transmission and reception characteristics in, for example, an ultrasonic sensor. [Means for solving the problem]

[0007] The ultrasonic sensor (1) according to claim 1 comprises: A conversion element (4) having a base end (41) which is one end in an axial direction along a directional axis (DA) and a tip end (42) which is the other end, and performing a conversion function between ultrasonic vibration and an electrical signal; a fixing portion (3) provided closer to the base end portion of the conversion element than to the tip end portion and fixedly supporting the conversion element; a vibration converter (5) connected to the tip of the conversion element so as to be capable of transmitting vibration and configured to convert the vibration unit into a primary vibration mode; Equipped with The driving signal which is the electric signal is applied to the conversion element. When the ultrasonic vibration generated in the conversion element is applied, the ultrasonic vibration is transmitted from the conversion element to the vibration conversion unit, and the vibration conversion unit vibrates ultrasonically. A transmission function of transmitting a transmission wave, which is an ultrasonic wave, to an external space (SG) existing in a transmission direction from the base end toward the tip end beyond the conversion element. and / or From the external space The vibration converter is excited by receiving the ultrasonic wave. A receiving function of converting the ultrasonic vibration transmitted to the conversion element into the received signal, which is an electrical signal, at the conversion element. It is configured to R, The vibration converter is made of a conductive material and is set to a predetermined potential. There are.

[0008] In addition, in each section of the application documents, each element may be given a reference symbol in parentheses. In this case, the reference symbol merely indicates an example of the correspondence between the element and the specific configuration described in the embodiment described later. Therefore, the present invention is not limited in any way by the description of the reference symbol. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the appearance of a vehicle equipped with an ultrasonic sensor according to a first embodiment. [Diagram 2] 2 is a cross-sectional view showing a schematic configuration of the ultrasonic sensor shown in FIG. [Diagram 3] 3 is a cross-sectional view showing an outline of the operation of the ultrasonic sensor shown in FIG. 2. [Figure 4] 3 is a cross-sectional view showing an outline of the operation of the ultrasonic sensor shown in FIG. 2. [Diagram 5] FIG. 11 is a perspective view showing the appearance of a vehicle equipped with an ultrasonic sensor according to a second embodiment. [Figure 6A] 6 is a cross-sectional view showing an example of a schematic configuration of the ultrasonic sensor shown in FIG. 5. [Figure 6B] 6 is a cross-sectional view showing another example of the schematic configuration of the ultrasonic sensor shown in FIG. 5. [Figure 7] 5 is a cross-sectional view showing an outline of the operation of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 8] 8 is a cross-sectional view showing a schematic configuration and an outline of operation of a modified example of the ultrasonic sensor shown in FIG. 7. [Figure 9] 8 is a cross-sectional view showing a schematic configuration and an outline of operation of another modified example of the ultrasonic sensor shown in FIG. 7. FIG. [Figure 10] 8 is a cross-sectional view showing a schematic configuration and an outline of operation of still another modified example of the ultrasonic sensor shown in FIG. 7. FIG. [Figure 11] FIG. 7 is a cross-sectional view showing a schematic configuration of a modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 12]FIG. 7 is a cross-sectional view showing a schematic configuration of another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 13] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 14] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 15] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 16] 2, 6A or 6B. FIG. 7 is a rear view showing a configuration example of a sensor housing and a vibration converter in still another modified example of the ultrasonic sensor shown in FIG. [Figure 17] 17 is a cross-sectional view showing an outline of the operation of the ultrasonic sensor including the sensor housing and the vibration converter shown in FIG. 16. [Figure 18] 17 is a cross-sectional view showing an outline of the operation of the ultrasonic sensor including the sensor housing and the vibration converter shown in FIG. 16. [Figure 19] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 20] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 21] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 22] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Diagram 23] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Figure 24] FIG. 7 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 2, FIG. 6A or FIG. 6B. [Diagram 25]FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a third embodiment. [Figure 26] 26 is a cross-sectional view showing a schematic configuration of a modified example of the ultrasonic sensor shown in FIG. 25. [Figure 27] FIG. 13 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a fourth embodiment. [Figure 28] FIG. 13 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a fifth embodiment. [Figure 29] 29 is a cross-sectional view showing a schematic configuration of a modified example of the ultrasonic sensor shown in FIG. 28. [Diagram 30] FIG. 13 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a sixth embodiment. [Diagram 31] 31 is a cross-sectional view showing a schematic configuration of a modified example of the ultrasonic sensor shown in FIG. 30. [Diagram 32] 31 is a cross-sectional view showing a schematic configuration of another modified example of the ultrasonic sensor shown in FIG. 30. [Diagram 33] 31 is a cross-sectional view showing a schematic configuration of still another modified example of the ultrasonic sensor shown in FIG. 30. [Diagram 34] FIG. 13 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a seventh embodiment. [Diagram 35] 1 is a functional block diagram showing an example configuration of an object detection device using an ultrasonic sensor according to the present disclosure. FIG. [Diagram 36] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Figure 37] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Figure 38] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Figure 39] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Diagram 40] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Diagram 41] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Diagram 42]FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Diagram 43] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Diagram 44] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Diagram 45] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Diagram 46] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Figure 47] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. [Figure 48] FIG. 11 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (First embodiment: vehicle mounting structure) Hereinafter, a schematic configuration of an ultrasonic sensor 1 according to a first embodiment will be described with reference to Fig. 1 and Fig. 2. First, referring to Fig. 1, the ultrasonic sensor 1 is configured to be mounted on a vehicle V as a moving body, and to generate and output a detection signal corresponding to the presence state of an object (e.g., an obstacle) present in an external space SG around the vehicle V. That is, the ultrasonic sensor 1 has a configuration as an on-board clearance sonar to which the vehicle V is attached.

[0011] The vehicle V is typically a so-called four-wheeled automobile, and includes a box-shaped vehicle body V1. The vehicle body V1 includes a vehicle body panel V2 and a bumper V3, which are plate-shaped body components constituting an outer panel. The bumper V3 is provided at each of the front end and rear end of the vehicle body V1. In this embodiment, the ultrasonic sensor 1 is configured to be attached to the bumper V3. The state in which the ultrasonic sensor 1 is mounted on the vehicle V by being attached to the bumper V3 is hereinafter referred to as the "mounted state."

[0012] Specifically, in an installed state, a plurality of (e.g., four) ultrasonic sensors 1 are attached to the front bumper, i.e., the bumper V3 on the front side of the vehicle body V1. The plurality of ultrasonic sensors 1 attached to the front bumper are disposed at different positions at least in the vehicle width direction. Similarly, in an installed state, a plurality of (e.g., four) ultrasonic sensors 1 are attached to the rear bumper, i.e., the bumper V3 on the rear side of the vehicle body V1. In this embodiment, the bumper V3 is provided with a mounting hole V4 which is a through hole for mounting the ultrasonic sensor 1.

[0013] Fig. 2 shows one of the ultrasonic sensors 1 mounted on the bumper V3. For the sake of simplicity, in Fig. 2, bonding layers (e.g., adhesive layers such as adhesive layers or welding layers) or fasteners (e.g., bolts, tapes, etc.) for fixedly connecting adjacent components that are in a bonded state to each other are omitted unless otherwise specified. Here, the "bonding layer" includes not only the adhesive layer (i.e., a synthetic resin layer formed by solidifying the adhesive) but also a double-sided tape layer (i.e., an adhesive layer that appears when the release paper is peeled off from both the front and back sides of the double-sided tape) and the like.

[0014] Referring to FIG. 2, the ultrasonic sensor 1 is configured to be capable of transmitting and / or receiving ultrasonic waves. That is, the ultrasonic sensor 1 is configured to perform a transmission function of transmitting a transmission wave, which is an ultrasonic wave, to the external space SG along a directional axis DA, and / or a reception function of receiving a reflected wave of the transmission wave by an object from the external space SG. The "directional axis" is a virtual straight line extending from the ultrasonic sensor 1 along the traveling direction of the transmission wave, and serves as a reference for the directional angle. The "directional axis" may also be called the "directional central axis" or the "detection axis." The "directional angle" may also be called the "half-value angle." The ultrasonic sensor 1 is configured to receive a reception wave, including a reflected wave of the transmission wave by an object present around the vehicle V, from the external space SG, and generate and output a detection signal according to the reception result of the reception wave.

[0015] Here, a direction along the traveling direction of the transmission wave, specifically, a direction parallel to the directional axis DA, is referred to as the "axial direction". More specifically, the axial direction includes the transmission direction DT and the reception direction DR. The transmission direction DT is parallel to the axial direction and is a direction from the ultrasonic sensor 1 to the external space SG. That is, the transmission direction DT is the direction in which the transmission wave travels on the directional axis DA. On the other hand, the reception direction DR is a direction opposite to the transmission direction DT, parallel to the axial direction, and is a direction from the external space SG to the ultrasonic sensor 1. That is, the reception direction DR is the direction in which the reception wave travels on the directional axis DA. In addition, the "tip in the axial direction" of a certain component refers to the end of the component on the transmission direction DT side. In contrast, the "base end in the axial direction" of a certain component refers to the end of the component on the reception direction DR side. In addition, any direction perpendicular to the axial direction is referred to as the "in-plane direction". The "in-plane direction" is a direction parallel to a virtual plane having the directional axis DA as a normal line. Moreover, the shape of a certain component projected onto the virtual plane is referred to as the "in-plane shape." The in-plane direction includes the "radial direction." The "radial direction" is the direction in which a half-line is drawn in the virtual plane with the intersection of the virtual plane and the pointing axis DA as the starting point. In other words, the "radial direction" is the radial direction of a circle drawn in the virtual plane with the intersection of the virtual plane and the pointing axis DA as the center.

[0016] 2, the bumper V3 has a bumper outer surface V5 and a bumper inner surface V6. The bumper outer surface V5 is provided so as to face the external space SG, which is the space outside the vehicle V. The bumper inner surface V6 is the reverse side of the bumper outer surface V5. The mounting hole V4 is provided so as to open on the bumper outer surface V5 and the bumper inner surface V6. The mounting hole V4 is formed as a circular hole with the directional axis DA as the central axis.

[0017] (First embodiment: sensor structure) The ultrasonic sensor 1 according to this embodiment includes a sensor housing 2, a fixed portion 3, a conversion element 4, and a vibration conversion portion 5. Below, specific configuration examples of each portion of the ultrasonic sensor 1 according to this embodiment will be described.

[0018] The sensor housing 2 is formed in a bottomed cylindrical shape, with the tip of the cylindrical side wall in the axial direction closed by a bottom wall, while the base end is open. The sensor housing 2 can be made of, for example, metal materials such as aluminum and aluminum alloys, synthetic resin materials such as polypropylene, polyacetal (i.e., POM) and acrylic resin, composite materials such as CFRP, etc. POM is an abbreviation for Polyoxymethylene. CFRP is an abbreviation for Carbon Fiber Reinforced Plastics.

[0019] (diaphragm) In this embodiment, the sensor housing 2 has a diaphragm 21. The diaphragm 21 is formed in a plate shape having a plate thickness direction along the directional axis DA. That is, the diaphragm 21 is formed by a bottom wall of the bottomed cylindrical sensor housing 2 that intersects with the directional axis DA. The diaphragm 21 has any in-plane shape, such as a circle, an ellipse, a polygon, or the like. The diaphragm 21 has an outer surface 21a that is exposed to the external space SG in a mounted state, and an inner surface 21b that is the back surface of the outer surface 21a. In FIG. 2, in order to briefly explain the contents of this disclosure, the diaphragm 21 is assumed to have a flat plate shape having a certain plate thickness as a typical configuration example. Therefore, in this specific example, the outer surface 21a and the inner surface 21b are provided as a pair of main surfaces of the diaphragm 21. The "main surface" is a surface of a plate-shaped part or member having a plate thickness direction as a normal direction. That is, the outer surface 21a and the inner surface 21b are provided so as to be perpendicular to the directional axis DA. However, it will be apparent from the description of each modified example below that the present disclosure is not limited to such a configuration.

[0020] Diaphragm 21 may be formed with non-connected portion 22 and connected portion 23. Non-connected portion 22 is a portion on the outer edge side in the radial direction of diaphragm 21, where inner surface 21b of diaphragm 21 does not face vibration converter 5. In contrast, connected portion 23 is a portion on the inner side of non-connected portion 22 in the radial direction of diaphragm 21, where inner surface 21b faces vibration converter 5.

[0021] The vibration plate 21 is provided so that the center 24 in the in-plane direction can be ultrasonically vibrated in a manner that moves along the directional axis DA. Specifically, the sensor housing 2 has a support portion 26 that supports an outer edge portion 25 in the in-plane direction of the vibration plate 21. That is, the support portion 26 is formed by a side wall surrounding the directional axis DA in the bottomed cylindrical sensor housing 2. The vibration plate 21 has a plate thickness smaller than the dimension in the axial direction of the support portion 26. The vibration plate 21 can be formed of a material softer than the support portion 26. The outer edge portion 25 of the vibration plate 21 is connected to the tip portion in the axial direction of the support portion 26. Note that, when the vibration plate 21 and the support portion 26 are formed of the same material, the sensor housing 2 can be molded integrally without a seam, but as described later, the present invention is not limited to such an embodiment. The vibration plate 21 is provided so that it can be ultrasonically vibrated in a primary vibration mode with the outer edge portion 25 in the in-plane direction as a node and the center portion 24 as an antinode. The support portion 26 has an outer peripheral surface 27 and an inner peripheral surface 28. The outer peripheral surface 27 is formed into a cylindrical surface. At least the tip portion in the axial direction of the outer peripheral surface 27 is accommodated inside the mounting hole V4 in the mounted state. When the diaphragm 21 has a circular shape, the inner peripheral surface 28 is formed into a cylindrical inner surface facing the pointing axis DA.

[0022] (fixed part) The fixed part 3 is provided so as to close the opening on the base end side in the axial direction of the sensor housing 2. The fixed part 3 can be formed of a metal material, a synthetic resin material, a composite material, or the like. The fixed part 3 has a fixed surface 31 and a back surface 32. The fixed surface 31 is provided so as to face the inner surface 21b of the vibration plate 21. The fixed surface 31 is bonded to the base end of the support part 26 in the axial direction via a bonding layer such as an adhesive. The bonding layer is formed to a thickness sufficiently smaller than the wavelength of the transmission / reception wave (for example, 100 μm or less or less than one-eighth of the wavelength). The back surface 32 is provided on the back side of the fixed surface 31. In FIG. 2, in order to briefly explain the contents of the present disclosure, the fixed part 3 is assumed to have a flat plate shape having a certain plate thickness as a typical configuration example. Therefore, in this specific example, the fixed surface 31 and the back surface 32 are provided as a pair of main surfaces in the fixed part 3 that intersect (i.e., specifically, are perpendicular to) the directional axis DA. However, it will be apparent from the description of each modified example described later that the present disclosure is not limited to such a configuration. In addition, a circuit board (not shown) electrically connected to the vibration conversion unit 5 is provided on the rear surface 32 side.

[0023] The base end of the support 26 in the axial direction is joined to the fixed surface 31, and the space enclosed by the sensor housing 2 and the fixed part 3 contains the conversion element 4 and the vibration conversion part 5. The conversion element 4 and the vibration conversion part 5 are disposed adjacent to each other on the directional axis DA. Specifically, the fixed part 3, the conversion element 4, and the vibration conversion part 5 are arranged in this order along the transmission direction DT. The sensor housing 2, the fixed part 3, the conversion element 4, and the vibration conversion part 5 form a so-called ultrasonic transducer as an ultrasonic speaker and / or an ultrasonic microphone.

[0024] (Conversion element) The conversion element 4 is composed of an electromechanical energy conversion element that performs a conversion function between ultrasonic vibration along the axial direction and an electric signal. Specifically, a piezoelectric element, a monomorph or bimorph type transducer, a Langevin type transducer, or the like can be used as the conversion element 4. A monomorph or bimorph type transducer has a configuration in which a piezoelectric element is bonded to a plate material. A Langevin type transducer has a configuration in which a piezoelectric element formed in a plate shape having a thickness direction in the axial direction is sandwiched between a pair of blocks.

[0025] The conversion element 4 has a base end 41, which is one end in the axial direction, and a tip end 42, which is the other end. The base end 41 is fixed to the fixing surface 31 of the fixing part 3 via a bonding layer such as an adhesive layer. The bonding layer is formed to a thickness sufficiently smaller than the wavelength of the transmission and reception waves (for example, 100 μm or less or less than one-eighth of the wavelength). The tip end 42 protrudes from the fixing part 3 toward the tip side in the axial direction, i.e., toward the transmission direction DT. In this way, the fixing part 3 is disposed so as to be closer to the base end 41 than the tip end 42 of the conversion element 4, and is provided to support the conversion element 4 in a fixed manner. The ultrasonic sensor 1 is configured to perform a transmission function of transmitting a transmission wave to an external space SG that is present on the side of the conversion element 4 in the transmission direction DT (i.e., the direction from the base end 41 toward the tip end 42) by applying a drive signal, which is an electric signal, to the conversion element 4. Alternatively, the ultrasonic sensor 1 is configured to perform a receiving function of converting ultrasonic vibrations transmitted from the external space SG to the conversion element 4 by receiving a reception wave into a reception signal, which is an electrical signal, in the conversion element 4.

[0026] (Vibration conversion part) The vibration converter 5 is provided between the diaphragm 21 and the conversion element 4. The vibration converter 5 is connected to the tip 42 of the conversion element 4 so as to be able to transmit vibration. The vibration converter 5 is also connected to the diaphragm 21 so as to be able to transmit vibration. That is, the vibration converter 5 is provided so as to perform a vibration conversion function from one of the ultrasonic vibrations in the conversion element 4 (for example, stretching vibrations along the axial direction) and the ultrasonic vibrations in the diaphragm 21 (for example, membrane vibrations) to the other. The ultrasonic sensor 1 is configured to perform a transmission function in which ultrasonic vibrations generated in the conversion element 4 by application of a drive signal are transmitted from the conversion element 4 to the diaphragm 21 via the vibration converter 5, and the diaphragm 21 vibrates ultrasonically, thereby transmitting a transmission wave from the diaphragm 21 to the external space SG. Alternatively, the ultrasonic sensor 1 is configured to perform a reception function in which the ultrasonic vibrations transmitted to the conversion element 4 via the vibration converter 5 from the diaphragm 21 excited by receiving a reception wave from the external space SG are converted into a reception signal by the conversion element 4.

[0027] The vibration conversion unit 5 has a first opposing surface 51 close to the tip 42 of the conversion element 4, and a second opposing surface 52 that is the back side of the first opposing surface 51 and close to the diaphragm 21. In this specific example, the first opposing surface 51 and the second opposing surface 52 are formed in a plane that intersects with the directional axis DA (specifically, perpendicular to it). That is, the first opposing surface 51 and the second opposing surface 52 are provided approximately parallel to each other. The first opposing surface 51 is bonded to the tip 42 of the conversion element 4 via a bonding layer such as an adhesive layer. The second opposing surface 52 is bonded to the inner surface 21b of the connection portion 23 of the diaphragm 21 via a bonding layer such as an adhesive layer. These bonding layers are formed to a thickness that is sufficiently smaller than the wavelength of the transmission / reception wave (for example, 100 μm or less or less than one-eighth of the wavelength).

[0028] In this embodiment, the vibration converter 5 is formed so as to perform an area conversion function of the vibration surface by having the first opposing surface 51 and the second opposing surface 52 have different areas. Specifically, as shown in Fig. 2, in this specific example, the vibration converter 5 is formed so that the second opposing surface 52 has a larger area than the first opposing surface 51. For this reason, the end surface 53 provided between the first opposing surface 51 and the second opposing surface 52 is formed in a partial pyramidal surface shape having a linear generatrix and an in-plane shape that becomes larger toward the transmission direction DT.

[0029] The ultrasonic sensor 1 has a configuration in which the vibration mode of the diaphragm 21 is limited to the above-mentioned primary vibration mode by the vibration conversion unit 5. Specifically, the vibration conversion unit 5 has a hardness equal to or greater than that of the diaphragm 21 so that the connection portion 23 of the diaphragm 21 can be efficiently pushed in the transmission direction DT when the vibration conversion unit 5 is biased in the transmission direction DT by the conversion element 4 in the transmission function. Here, "hard" refers to a high density and / or Young's modulus. In general, when the density is high and the Young's modulus is high, the acoustic impedance is high. That is, the vibration conversion unit 5 is configured to behave like a rigid body when transmitting vibration between the diaphragm 21 and the conversion element 4. In other words, the vibration conversion unit 5 is provided so as to ultrasonically vibrate in such a manner that the second opposing surface 52 moves parallel to the axial direction with almost no bending (i.e., almost no change in the in-plane shape) in association with the ultrasonic vibration of the conversion element 4.

[0030] The vibration conversion unit 5 is configured to increase the vibration transmission efficiency between the diaphragm 21 and the conversion element 4. Specifically, the vibration conversion unit 5 is formed of a material whose acoustic impedance is equal to or greater than that of the diaphragm 21 and equal to or less than that of the conversion element 4. However, the acoustic impedance of the conversion element 4 is greater than that of the diaphragm 21. For example, the vibration conversion unit 5 may be made of a metal material such as aluminum, an aluminum alloy, or a magnesium alloy, a synthetic resin material such as PBT or a glass epoxy resin, or a composite material such as CFRP. PBT is an abbreviation for polybutylene terephthalate. When the vibration conversion unit 5 is made of a conductive material such as a metal, it may be set to a predetermined potential (for example, a reference potential such as a ground potential).

[0031] Moreover, the vibration converter 5 is formed so that the second opposing surface 52 has an area corresponding to the area of ​​the vibration plate 21 (i.e., the inner surface 21b) to suppress spurious vibrations in the vibration plate 21. That is, the vibration converter 5 has a shape in which the outer diameter of the second opposing surface 52 is equal to or smaller than the outer diameter of the inner surface 21b, and the difference between the two is as small as possible. The vibration converter 5 is joined to the vibration plate 21 so that the radial width of the non-connected portion 22, i.e., half the difference between the outer diameter of the inner surface 21b and the outer diameter of the second opposing surface 52, is less than half the wavelength of the transmitted and received waves.

[0032] (effect) An outline of the operation of the ultrasonic sensor 1 according to this embodiment having the above-mentioned configuration will be described below with reference to Figs. 2 to 4, along with the effects achieved by the configuration. For the sake of simplicity, in the following outline of the operation, it is assumed that the ultrasonic sensor 1 has at least a transmission function, and the conversion element 4 has a configuration of a type that ultrasonically vibrates in a manner that expands and contracts in the axial direction. The following mainly describes the operation when the transmission function is activated, that is, when the ultrasonic sensor 1 transmits a transmission wave to the external space SG.

[0033] At the time of transmission, a drive signal is applied to the conversion element 4. As a result, the conversion element 4 ultrasonically vibrates in such a manner that it expands and contracts in the axial direction. Specifically, at the time of application of a positive voltage, the conversion element 4 is extended in the axial direction from the state shown in FIG. 2. Here, the base end 41 of the conversion element 4 is fixed to the fixing part 3 fixedly supported by the bumper V3. Therefore, as shown in FIG. 3, as the conversion element 4 is extended in the axial direction, the tip part 42 of the conversion element 4 moves in the transmission direction DT. Then, the vibration conversion unit 5 is biased in the transmission direction DT by the tip part 42 of the conversion element 4. At this time, the vibration conversion unit 5 moves in the transmission direction DT while maintaining the planar state of the second opposing surface 52 joined to the vibration plate 21. As a result, the connection part 23 of the vibration plate 21 is pushed out in the transmission direction DT while maintaining the shape of the joint surface with the second opposing surface 52.

[0034] On the other hand, when a negative voltage is applied, the conversion element 4 is compressed in the axial direction more than in the state shown in FIG. 2. Here, the base end 41 of the conversion element 4 is fixed to the fixed part 3 fixedly supported by the bumper V3. Therefore, as shown in FIG. 4, when the conversion element 4 is compressed in the axial direction, the tip part 42 of the conversion element 4 moves in the receiving direction DR. Then, the vibration conversion unit 5 is urged in the receiving direction DR by the tip part 42 of the conversion element 4. At this time, the vibration conversion unit 5 moves in the transmitting direction DT while maintaining the planar state of the second opposing surface 52 joined to the diaphragm 21. As a result, the connection part 23 of the diaphragm 21 is drawn in the receiving direction DR while maintaining the shape of the joining surface with the second opposing surface 52.

[0035] In this way, by applying a drive signal to the conversion element 4, the diaphragm 21 ultrasonically vibrates in a primary vibration mode with the outer edge 25 as a node and the central portion 24 as an antinode. The vibration mode of the diaphragm 21 is limited to the above-mentioned primary vibration mode by the vibration conversion unit 5. This makes it possible to effectively suppress the loss of directivity due to the occurrence of a vibration mode of a higher order than the primary vibration mode. In particular, by forming the diaphragm 21 to a plate thickness smaller than the dimension in the axial direction of the support portion 26 or by forming it from a material softer than the support portion 26, it is possible to vibrate substantially only the diaphragm 21 in the sensor housing 2 consisting of the diaphragm 21 and the support portion 26. This makes it possible to achieve good transmission and reception characteristics, i.e., high output and / or high sensitivity.

[0036] Moreover, the vibration of the above-mentioned mode in the diaphragm 21 can be realized without resonance. Therefore, it is possible to realize any transmission and reception frequency. That is, for example, it is possible to adjust the directivity by making the transmission frequency variable. Specifically, in the case of the primary vibration mode, it is known that the proportional relationship of the directivity angle ∝ wavelength / vibration length approximately holds. Therefore, by increasing the frequency, narrow directivity is realized. On the other hand, by decreasing the frequency, wide directivity is realized. Alternatively, it is possible to effectively suppress the influence of the fluctuation of the directivity due to the temperature change. In particular, even if the sensor housing 2, i.e., the diaphragm 21 and the support part 26, are made of a synthetic resin material whose physical properties are likely to change due to temperature change, it is possible to more stably realize the desired directivity.

[0037] In addition, in the conventional technology, there is a trade-off between narrow directivity and wide band. That is, for example, when the outer diameter of the diaphragm 21 is increased, the directivity becomes narrow and the resonant frequency becomes low. On the other hand, when the outer diameter of the diaphragm 21 is decreased, the directivity becomes wide and the resonant frequency becomes high. The frequency band that can be transmitted and received depends on the electrical-mechanical energy conversion characteristics of the joint between the sensor housing 2 including the diaphragm 21 and the piezoelectric element. In contrast, according to the present embodiment, the conversion element 4 as the vibration generating part and the diaphragm 21 as the directivity design part are separated, so that the trade-off relationship between the directivity and the band is eliminated and the degree of design freedom is improved. Specifically, for example, it is possible to realize an ultrasonic sensor 1 with narrow directivity and wide band. It is also clear that an ultrasonic sensor 1 with wide directivity and wide band can be realized.

[0038] Furthermore, by forming the vibration conversion unit 5 from a conductive material such as metal and setting it to a predetermined potential (for example, a reference potential such as a ground potential), the conversion element 4 can be electromagnetically shielded well. This makes it possible to achieve excellent EMC characteristics in the ultrasonic sensor 1 that is exposed to various noise environments by being attached to the bumper V3. EMC stands for Electromagnetic Compatibility. In particular, when the sensor housing 2 is integrally formed from a non-conductive material (for example, synthetic resin), suitable EMC measures can be achieved.

[0039] In this way, this embodiment employs a configuration in which the diaphragm 21 is ultrasonically vibrated in a manner that pushes and pulls in the surface. This makes it possible to more stably achieve the desired directivity and further improve the transmission and reception characteristics. Note that it is not necessarily required to pull in, and "pushing and returning" may also be used.

[0040] Second Embodiment The second embodiment will be described below with reference to FIG. 5, FIG. 6A, and FIG. 6B. In the following description of the second embodiment, the differences from the first embodiment will be mainly described. In addition, the same reference numerals are used for the same or equivalent parts in the first and second embodiments. Therefore, in the following description of the second embodiment, the description of the first embodiment may be appropriately used for the components having the same reference numerals as those in the first embodiment, unless there is a technical contradiction or a special additional description. The same applies to the other embodiments from the third embodiment onward described below.

[0041] As shown in FIG. 5, in this embodiment, the bumper V3 is not provided with the mounting hole V4 shown in FIG. 1. That is, the ultrasonic sensor 1 according to this embodiment can be attached to the bumper V3 without forming the mounting hole V4 in the bumper V3. In other words, the ultrasonic sensor 1 can be easily "retrofitted" to the bumper V3 of a non-mounted vehicle, which is a vehicle V that has been shipped from the factory without the ultrasonic sensor 1 mounted thereon. The ultrasonic sensor 1 according to this embodiment having such a configuration is covered from the outside by the bumper V3 that does not have the mounting hole V4 when mounted. Therefore, such a configuration may be referred to hereinafter as an "invisible sonar configuration."

[0042] Specifically, the ultrasonic sensor 1 according to this embodiment is configured to transmit and / or receive ultrasonic waves using ultrasonic vibrations in a vibration plate 21 that is a part of a bumper V3. FIG. 6A shows an example of such a configuration. As shown in FIG. 6A, the vibration plate 21 is configured by a vibration section V7 that is a part of the bumper V3. Specifically, the vibration plate 21, i.e., the vibration section V7, is formed by bonding a vibration-damping section V8, which is a cylindrical, ring-shaped, fence-shaped, or wall-shaped part arranged to surround the directional axis DA, to the bumper inner surface V6 via a bonding layer such as an adhesive layer. That is, the vibration-damping section V8 is provided integrally or divided into a plurality of parts in the circumferential direction surrounding the directional axis DA so as to surround the directional axis DA. The "circumferential direction" surrounding the directional axis DA is the direction of a locus in which a point on the single closed curve moves on the single closed curve when a single closed curve surrounding the directional axis DA is drawn on a virtual plane that intersects with the directional axis DA (i.e., typically perpendicular to the directional axis DA). A "single closed curve" is a closed curve that does not intersect with itself in a three-dimensional Euclidean space, and may also be called a simple closed curve or a Jordan curve. A "single closed curve" includes polygons such as a rectangle. In other words, the vibration-damping portion V8 is composed of at least one part arranged to surround the directional axis DA. As described later, when the vibration-damping portion V8 is composed of a plurality of parts arranged in the circumferential direction, a slit or gap may be provided between adjacent parts. In this way, the vibration-damping portion V8 may be provided to surround the directional axis DA intermittently or discontinuously in the circumferential direction. Similarly, when the vibration-damping portion V8 is formed in a cylindrical shape that continuously surrounds the directional axis DA in the circumferential direction, one or more slits or openings may be provided in the circumferential direction. The vibration portion V7 is the inner part of the vibration-damping portion V8 when the bumper V3 and the vibration-damping portion V8 are joined together. Such a bonding layer is formed to a thickness sufficiently smaller than the wavelength of the transmitted and received waves (for example, 100 μm or less or less than one-eighth of the wavelength). In the mounted state, the ultrasonic sensor 1 has a sensor housing 2, which is composed of a vibration damping part V8 corresponding to a support part 26 described later and shown in FIG. 6B, a vibration converter 5, a conversion element 4, and a fixing part 3, fixed to the bumper inner surface V6 within a holding surface V9, which is the inner peripheral surface of the vibration damping part V8. In this embodiment, the vibration converter 5 is connected to the diaphragm 21, which is a part of the bumper V3, so as to be able to transmit vibration. Specifically, the second opposing surface 52, which is the outer surface of the vibration converter 5, and the bumper inner surface V6 of the diaphragm 21 are abutted or joined together so as not to create a gap, i.e., an air layer. In this case, the vibration converter 5 also serves as an acoustic matching layer 61, which will be described later, shown in FIG. 6B. Note that the above-mentioned acoustic matching layer 61 may be provided between the second opposing surface 52, which is the outer surface of the vibration converter 5, and the bumper inner surface V6 of the diaphragm 21 so as not to create a gap, i.e., an air layer. In this case, the acoustic matching layer 61 is sandwiched between the vibration converter 5 and the diaphragm 21. Specifically, for example, the acoustic matching layer 61 is fixed to one of the vibration converter 5 and the diaphragm 21. The acoustic matching layer 61 interposed between the vibration converter 5 and the bumper V3, i.e., the diaphragm 21, is provided to increase the vibration transmission efficiency between them. That is, the acoustic matching layer 61 is configured to increase the vibration transmission efficiency between the vibration converter 5 and the diaphragm 21 as much as possible. Specifically, the acoustic matching layer 61 is formed of a material whose acoustic impedance is equal to or greater than the diaphragm 21, i.e., the bumper V3, and equal to or less than the vibration converter 5. However, the acoustic impedance of the vibration converter 5 is greater than the acoustic impedance of the diaphragm 21, i.e., the bumper V3. The acoustic matching layer 61 may be formed of a curing type synthetic resin such as an epoxy resin. Alternatively, the acoustic matching layer 61 may be formed to a thickness of 50 μm or less. The ultrasonic sensor 1 of this embodiment having such a configuration transmits a transmission wave by vibrating a part of the bumper V3 as the diaphragm 21 during transmission. Also, during reception when the receiving function is realized, the vibration of the diaphragm 21 excited by the received wave is converted into an electric signal to generate a received signal. And, in this embodiment, the same effect as the first embodiment can be obtained. Note that the configuration example shown in FIG. 6A is a simplified configuration example shown in FIG. 6B described below. Specifically, in the configuration example shown in FIG. 6A, the diaphragm 21 and the bumper V3 in the sensor housing 2 provided in the configuration example shown in FIG. 6B are integrated, and the support part 26 and the vibration damping part V8 are integrated. FIG. 6B shows another example of the configuration shown in FIG. 6A. Specifically, the ultrasonic sensor 1 according to this embodiment is configured to transmit and / or receive ultrasonic waves using ultrasonic vibrations in a vibration part V7 that is a part of a bumper V3. As shown in FIG. 6B, the vibration part V7 is formed by joining a vibration-damping part V8, which is a cylindrical, ring-shaped, fence-shaped, or wall-shaped part that surrounds the directional axis DA, to the bumper inner surface V6 via a bonding layer such as an adhesive layer. That is, the vibration-damping part V8 is provided integrally or divided into a plurality of parts in the circumferential direction surrounding the directional axis DA so as to surround the directional axis DA. In other words, the vibration-damping part V8 is composed of at least one part that is arranged to surround the directional axis DA. The vibration part V7 is the inner part of the vibration-damping part V8 when the bumper V3 and the vibration-damping part V8 are joined together. The bonding layer is formed to a thickness sufficiently smaller than the wavelength of the transmitted and received waves (for example, 100 μm or less or less than one-eighth of the wavelength). In the mounted state, the ultrasonic sensor 1 is fixed to the bumper inner surface V6 while the sensor housing 2 is housed within a holding surface V9, which is the inner peripheral surface of the vibration damping portion V8.

[0043] In this embodiment, the diaphragm 21 is connected to the vibrating part V7 so as to be capable of transmitting vibration. Specifically, an acoustic matching layer 61 is provided between the outer surface 21a of the diaphragm 21 and the bumper inner surface V6 of the vibrating part V7 so as to prevent a gap, i.e., an air layer, from being generated. That is, the acoustic matching layer 61 is sandwiched between the diaphragm 21 and the vibrating part V7. The acoustic matching layer 61 is fixed to one of the diaphragm 21 and the vibrating part V7.

[0044] The acoustic matching layer 61 interposed between the diaphragm 21 and the bumper V3, i.e., the vibrating part V7, is provided to increase the vibration transmission efficiency between them. That is, the acoustic matching layer 61 is configured to increase the vibration transmission efficiency between the diaphragm 21 and the vibrating part V7 as much as possible. Specifically, the acoustic matching layer 61 is formed of a material whose acoustic impedance is equal to or greater than the vibrating part V7 and equal to or less than the diaphragm 21. However, the acoustic impedance of the diaphragm 21 is greater than the acoustic impedance of the vibrating part V7, i.e., the bumper V3. The acoustic matching layer 61 may be formed of a curing type synthetic resin such as an epoxy resin. Alternatively, the acoustic matching layer 61 may be formed to a thickness of 50 μm or less.

[0045] The ultrasonic sensor 1 of this embodiment having such a configuration transmits a transmission wave by vibrating a part of the bumper V3 as the vibration part V7 during transmission. Also, during reception when the receiving function is exerted, the vibration of the vibration part V7 excited by the received wave is converted into an electric signal to generate a received signal. Thus, in this embodiment as well, the same effects as those of the first embodiment can be achieved.

[0046] (Structure of vibration conversion part) 7 to 10 show how the directivity of the ultrasonic sensor 1 changes when the structure of the vibration conversion unit 5 is changed. In each figure, the vibration displacement of the outer surface 21a of the vibration plate 21 and the propagation of the transmission wave caused by the vibration displacement are shown by dotted lines. The directivity is also shown by a two-dot chain line. In the examples of FIGS. 7 to 10, the area of ​​the second opposing surface 52 is larger than the area of ​​the first opposing surface 51, that is, the outer diameter of the second opposing surface 52 is larger than the outer diameter of the first opposing surface 51. In the examples of FIGS. 7 to 10, the configurations of the fixed portion 3 and the conversion element 4 are the same, the in-plane shapes, i.e., the outer diameters, of the vibration plate 21 and the vibration conversion unit 5 are the same, and the plate thickness of the vibration plate 21 at the outer edge portion 25 is also the same.

[0047] In the example of Fig. 7, similarly to the configurations shown in Fig. 2, Fig. 6A, etc., the diaphragm 21 is formed in a flat plate shape having a constant plate thickness. The first opposing surface 51 and the second opposing surface 52 are formed in planar shapes parallel to each other. Furthermore, the end surface 53 is formed in a partial pyramidal surface shape having a linear generatrix and an in-plane shape that becomes larger toward the transmission direction DT. In this example, as shown in Fig. 7, a depression occurs in the traveling wave near the center, i.e., the directional axis DA, and a side lobe is generated.

[0048] In the example of Fig. 8, the shape of the end face 53 of the vibration converter 5 in the example of Fig. 7 is changed to a convex shape. In this example, as shown in Fig. 8, the concave of the traveling wave near the center, i.e., the directional axis DA, is eliminated, and a plane wave is radiated. In addition, the side lobes are well suppressed.

[0049] In addition, by making the planar first opposing surface 51 and the second opposing surface 52 parallel to each other, the efficiency of vibration transmission from the conversion element 4 to the diaphragm 21 can be improved. However, these parallelism and flatness can be changed as appropriate within a range in which desired directivity and transmission / reception characteristics are obtained. In other words, the parallelism and flatness can vary to a predetermined extent within the range of manufacturing errors and tolerances. Alternatively, these parallelism and flatness may be intentionally adjusted to achieve desired directivity and transmission / reception characteristics.

[0050] In the example of Fig. 9, the shape of the second opposing surface 52 of the vibration converter 5 in the example of Fig. 8 is changed to a convex shape, that is, a curved shape that is convex toward the transmission direction DT. In this example, as shown in Fig. 9, the concave of the traveling wave near the center, i.e., the directional axis DA, is eliminated, and a convex spherical wave is radiated toward the transmission direction DT. The directivity is wider than that of the example of Fig. 8. Also, the side lobes are suppressed more effectively than in the example of Fig. 8.

[0051] In the example of Fig. 10, the shape of the second opposing surface 52 of the vibration converter 5 in the example of Fig. 8 is changed to a concave shape, that is, a curved shape that is concave toward the transmission direction DT, opposite to the example of Fig. 9. In this example, as shown in Fig. 10, a relatively large concave occurs in the traveling wave near the center, i.e., the directional axis DA. Then, the sound pressure of the transmission wave in the front direction, i.e., around the directional axis DA, is reduced by interference. Such directivity makes it possible to detect road bumps and ceiling protrusions well.

[0052] (Lower costs) 11 and 12 show a configuration in which the ultrasonic sensor 1 shown in FIG. 2, FIG. 6A, etc. has been reduced in cost. As shown in FIG. 11, the vibration conversion unit 5 is integrally formed with the diaphragm 21, thereby enabling a reduction in cost. Specifically, for example, the vibration conversion unit 5 can be seamlessly formed integrally with the diaphragm 21 using the same material. Moreover, as shown in FIG. 12, the conversion element 4 is a thin plate-like piezoelectric element, thereby enabling a reduction in cost.

[0053] (Transmission and reception characteristics) As described above, increasing the outer diameter of the diaphragm 21 results in narrow directivity, whereas decreasing the outer diameter of the diaphragm 21 results in wide directivity. Therefore, the directivity can be adjusted by the outer diameter of the diaphragm 21.

[0054] Also, as in each of the above specific examples, by forming the vibration converter 5 so that the area, i.e., the outer diameter, of the second opposing surface 52 is larger than that of the first opposing surface 51, it is possible to reduce the radial size of the conversion element 4, and costs can be reduced. Also, during reception, i.e., during vibration transmission in the reception direction DR, the vibration converter 5 performs an area conversion function in a manner of reducing the area. Therefore, according to Pascal's theorem that the product of area and pressure is constant, the reduction in area causes an increase in pressure, and this can improve the reception sensitivity. Conversely, by forming the vibration converter 5 so that the area, i.e., the outer diameter, of the second opposing surface 52 is smaller than that of the first opposing surface 51, during transmission, i.e., during vibration transmission in the transmission direction DT, the vibration converter 5 performs an area conversion function in a manner of reducing the area. This can improve the output, i.e., the sound pressure, during transmission.

[0055] In this way, by adjusting the outer diameter of the diaphragm 21 and the shape of the vibration converter 5, the desired directivity and transmission / reception characteristics can be achieved. Specifically, for example, the configurations shown in Figs. 2 and 6A correspond to high reception sensitivity and narrow directivity. That is, such configurations are suitable for application to narrow-directivity receiving sensors. A "receiving sensor" refers to an ultrasonic sensor 1 that has a receiving function but not a transmitting function. In contrast, an ultrasonic sensor 1 that has a transmitting function but not a receiving function is called a "transmitting sensor." Also, an ultrasonic sensor 1 that has both a transmitting function and a receiving function is called an "integrated transmitting / receiving sensor."

[0056] In contrast, in the configuration shown in FIG. 13, the outer diameter of the diaphragm 21 is reduced, and the vibration converter 5 is formed so that the area, i.e., the outer diameter, of the second opposing surface 52 is larger than that of the first opposing surface 51. Such a configuration is suitable for application to a wide-directivity receiving sensor. In this configuration, in order to suppress spurious vibrations while maintaining a small radial size of the conversion element 4, the support 26 may be formed so that the thickness, i.e., the radial dimension, increases toward the tip side in the axial direction, i.e., the transmission direction DT. Specifically, in FIG. 13, the support 26 has an outer peripheral surface 27 formed in a cylindrical shape, while an inner peripheral surface 28 formed in a truncated cone shape having a linear generatrix and a diameter that decreases toward the transmission direction DT.

[0057] In the configuration shown in FIG. 14, the outer diameter of the diaphragm 21 is increased, and the vibration converter 5 is formed so that the area, i.e., the outer diameter, of the second opposing surface 52 is smaller than that of the first opposing surface 51. This configuration corresponds to high transmission output and narrow directivity. In other words, this configuration is suitable for application to a narrow-directivity transmitting sensor. In this configuration, a tapered portion 261 may be provided at the axial tip of the support portion 26 in order to suppress spurious vibrations. The tapered portion 261 is formed so that the thickness, i.e., the radial dimension, increases toward the tip side in the axial direction, i.e., toward the transmission direction DT.

[0058] In the configuration shown in Fig. 15, the outer diameter of the diaphragm 21 is reduced, and the vibration converter 5 is formed so that the area, i.e., the outer diameter, of the second opposing surface 52 is smaller than that of the first opposing surface 51. This configuration corresponds to high transmission output and wide directivity. In other words, this configuration is suitable for application to a transmitting sensor with wide directivity. Note that, even in this configuration, a tapered portion 261 may be provided at the tip of the support portion 26 in the axial direction in order to suppress spurious vibrations.

[0059] (biased directivity) 16 to 18 show a configuration for realizing a so-called "biased directivity" in which the directivity differs between the horizontal direction and the vertical direction. As shown in FIG. 16, the diaphragm 21 has an in-plane shape (e.g., elliptical, oval, rectangular, etc.) having a longitudinal direction in a first in-plane direction (i.e., left-right direction in the figure) and a lateral direction in a second in-plane direction (i.e., up-down direction in the figure). The first in-plane direction and the second in-plane direction are in-plane directions perpendicular to each other. The vibration converter 5 is also formed to have an in-plane shape corresponding to the in-plane shape of the diaphragm 21.

[0060] According to this configuration, as shown in Fig. 17 and Fig. 18, different directivities are realized in the longitudinal direction and the lateral direction. That is, it is possible to design the horizontal directivity and the vertical directivity by the in-plane shape of the diaphragm 21 and the vibration converter 5 without changing the shape or structure of the conversion element 4. When the frequency, i.e., the wavelength, is fixed, if the vibration length of the diaphragm 21 is large, the directivity becomes narrow. Also, when the vibration length is fixed, if the frequency is high, i.e., the wavelength is short, the directivity becomes narrow. In the opposite case, the directivity becomes wide.

[0061] (Sensor housing structure) As shown in Figures 19 and 20, the diaphragm 21 may be supported by a so-called "float structure". Specifically, in such a configuration, the support portion 26 has a rigid portion 262 and an elastic portion 263. The rigid portion 262 is a portion of the support portion 26 that is closer to the base end than the elastic portion 263 in the axial direction, and is made of a rigid material such as metal. The elastic portion 263 is a tip portion of the support portion 26 in the axial direction, and is made of an elastomer material such as silicone rubber. The rigid portion 262 and the elastic portion 263 can be joined by a joining layer such as an adhesive.

[0062] The vibration plate 21, which is a plate-like member, is joined at its outer end in the radial direction to the elastic portion 263 by a joining layer such as an adhesive. That is, the vibration plate 21 is elastically supported by the rigid portion 262 via the elastic portion 263. With this configuration, ultrasonic vibration that pushes and pulls the vibration plate 21 on a surface can be satisfactorily realized. As shown in FIG. 20, the rigid portion 262 may have a recess 264 that accommodates the outer end of the vibration plate 21 in the radial direction.

[0063] As shown in Figs. 21 to 23, the sensor housing 2 may be provided with a slit 265. This can improve the transmission and reception characteristics, i.e., the transmission output and the reception sensitivity. Specifically, for example, as shown in Fig. 21, the slit 265 can be provided at the tip end of the support part 26 in the axial direction so as to open toward the directional axis DA on the inner circumferential surface 28 of the support part 26. Alternatively, for example, as shown in Fig. 22, the slit 265 can be provided at the end of the diaphragm 21 in the radial direction so as to open in the receiving direction DR on the inner surface 21b of the diaphragm 21. Alternatively, for example, as shown in Fig. 23, the slit 265 can be provided along the directional axis DA so as to open in the receiving direction DR on the base end surface of the support part 26 in the axial direction.

[0064] As shown in FIG. 24, the sensor housing 2 and the fixed part 3 may be fastened with a fastening bolt 266 so that an initial load is applied in a direction that urges the conversion element 4 toward the vibration conversion part 5. With this configuration, the amount of displacement of the diaphragm 21 during transmission is increased, thereby improving the transmission output. Also, the bonding layer may be omitted. Furthermore, when a negative voltage is applied, the diaphragm 21 is displaced to a position where the initial load is canceled, and then is further displaced in the receiving direction DR by the momentum of the elastic energy of the diaphragm 21. Therefore, the voltage when a negative voltage is applied can be satisfactorily reduced. Alternatively, good driving can be achieved even without applying a negative voltage.

[0065] (Conversion element structure) As described above, various types of electromechanical energy conversion elements can be used as the conversion element 4. For example, in each of the above specific examples, for the sake of simplicity of explanation, the conversion element 4 is of a type that vibrates in an expanding and contracting manner along the axial direction. However, the present invention is not limited to such an embodiment.

[0066] 25 shows an example in which a plate-shaped piezoelectric element that flexurally vibrates is used as the conversion element 4. Such conversion element 4 is supported by a protruding portion 331 that protrudes in the transmission direction DT from the fixed surface 31 of the fixed portion 3. Specifically, the protruding portion 331 formed in a block shape is provided with a support protrusion 332. The support protrusion 332 protrudes in the transmission direction DT from the tip surface of the protruding portion 331 in the axial direction. The support protrusion 332 is also provided at the outer end of the protruding portion 331 in the radial direction.

[0067] The conversion element 4 has a configuration as a monomorph type piezoelectric element formed in a plate shape having a thickness direction in the axial direction. Specifically, the conversion element 4 has a support plate 401 and a piezoelectric thin plate 402. The support plate 401 is a plate-like member having a thickness direction in the axial direction, and is formed of metal or the like. The support plate 401 is provided so as to have a configuration as a so-called doubly supported beam, in which both ends in the in-plane direction are supported by the support protrusions 332 in a cross-sectional view. The piezoelectric thin plate 402 is a piezoelectric element plate formed in approximately the same in-plane shape as the support plate 401, and is joined to the support plate 401.

[0068] The conversion element 4 is provided so as to ultrasonically vibrate in a bending vibration mode with the central portion 431 in the in-plane direction as a node or antinode. That is, the fixed portion 3 is configured to fixedly support the fixed end portion 432 which is the end portion in the in-plane direction of the conversion element 4. With this configuration, it is possible to obtain a high transmission output or high reception sensitivity by the resonant design of the conversion element 4.

[0069] FIG. 26 also shows an example in which a plate-shaped piezoelectric element that vibrates flexibly is used as the conversion element 4, similar to FIG. 25. In this example, the protruding portion 331 is formed in a cylindrical shape. The conversion element 4 has a configuration as a monomorph type or bimorph type piezoelectric element formed in a plate shape having a thickness direction in the axial direction. In FIG. 26, for the sake of simplicity, the conversion element 4 is shown as a single plate. In the configuration shown in FIG. 26, the size of the conversion element 4 in the in-plane direction is made larger than that of the configuration shown in FIG. 25 in order to achieve even higher output or higher sensitivity.

[0070] According to this configuration, an amount of displacement in the axial direction of the vibration converter 5, i.e., the second opposing surface 52, occurs in response to an amount of bending of the conversion element 4. That is, the vibration caused by the bending motion of the conversion element 4 is converted by the vibration converter 5 into an axial vibration caused by the translation of the second opposing surface 52.

[0071] (Integrated transmitter and receiver structure) As the conversion element 4 provided in the transmitting sensor, for example, a laminated piezoelectric element, a monomorph transducer, a bimorph transducer, a Langevin transducer, etc. can be preferably used. On the other hand, as the conversion element 4 provided in the receiving sensor, for example, a single-layered piezoelectric element, a monomorph transducer, a bimorph transducer, etc. can be preferably used.

[0072] 2, 6A, etc., when using a type of conversion element 4 that vibrates in an axial direction, stacking, i.e., multi-layering, is preferable from the viewpoint of transmission output, and single-layering is preferable from the viewpoint of reception sensitivity. Therefore, in this case, when realizing an integrated transmission / reception sensor, it is expected that there will be a trade-off between transmission output and reception sensitivity.

[0073] 27 shows a configuration in which the function of one conversion element 4 can be switched between a stacked type piezoelectric element and a single-layer type piezoelectric element to avoid such a trade-off. That is, as shown in FIG. 27, the conversion element 4 has a plurality of piezoelectric layers 441, at least one insulating layer 442, one reference electrode layer 443, one driving electrode layer 444, at least one internal reference electrode layer 445, and at least one internal driving electrode layer 446.

[0074] The piezoelectric layer 441 is formed of a piezoelectric material such as lead zirconate titanate (i.e., PZT). The piezoelectric layers 441 are arranged in the axial direction. The insulating layer 442 is formed of an insulating non-piezoelectric material (e.g., alumina ceramics, etc.) and is disposed between two piezoelectric layers 441 adjacent to each other in the axial direction. The piezoelectric layer 441 and the insulating layer 442 are formed in a layer or film shape having a thickness direction in the axial direction.

[0075] The reference electrode layer 443 is provided on the tip surface in the axial direction of the conversion element 4, that is, on the tip surface in the axial direction of the one of the plurality of piezoelectric layers 441 arranged at the tip end side in the axial direction. The driving electrode layer 444 is provided on the base end surface in the axial direction of the conversion element 4, that is, on the base end surface in the axial direction of the one of the plurality of piezoelectric layers 441 arranged at the base end side in the axial direction. The internal reference electrode layer 445 is provided so as to be sandwiched between the tip surface in the axial direction of the one of the plurality of piezoelectric layers 441 other than the one arranged at the tip end side in the axial direction and the insulating layer 442. The internal driving electrode layer 446 is provided so as to be sandwiched between the base end surface in the axial direction of the one of the plurality of piezoelectric layers 441 other than the one arranged at the base end side in the axial direction and the insulating layer 442. The reference electrode layer 443, the driving electrode layer 444, the internal reference electrode layer 445, and the internal driving electrode layer 446 are formed in a layer or film shape having a thickness direction in the axial direction, for example, using silver paste or the like.

[0076] According to this configuration, the reference electrode layer 443 and the internal reference electrode layer 445 are set to a reference potential. During transmission, a high-frequency drive voltage is applied between the reference electrode layer 443 and the internal drive electrode layer 446, between the internal reference electrode layer 445 and the internal drive electrode layer 446, or between the internal reference electrode layer 445 and the drive electrode layer 444. This causes the conversion element 4 to operate as a stacked piezoelectric element. On the other hand, during reception, a reception signal is generated based on the voltage between the reference electrode layer 443 and the internal drive electrode layer 446 provided on both sides of the one of the multiple piezoelectric layers 441 that is arranged at the most distal end side in the axial direction. On the other hand, the other internal drive electrode layers 446 and drive electrode layers 444 are set to a reference potential. This causes the conversion element 4 to operate as a single-layer piezoelectric element.

[0077] In this manner, with this configuration, the function of one conversion element 4 can be switched between a multi-layer piezoelectric element and a single-layer piezoelectric element by a switching operation in a control circuit (not shown) electrically connected to the conversion element 4. Therefore, it is possible to realize an integrated transmission / reception sensor that can achieve both high transmission output and high reception sensitivity with a simple configuration.

[0078] (Separate transmitting and receiving elements) 28 shows a configuration in which a transmitting element 451 having a transmitting function and a receiving element 452 having a receiving function are separately provided as the conversion element 4. That is, the conversion element 4 includes the transmitting element 451, the receiving element 452, and a connecting portion 453.

[0079] As the transmitting element 451, for example, a laminated piezoelectric element, a monomorph transducer, a bimorph transducer, a Langevin transducer, etc. can be used. As the receiving element 452, for example, a single-layer piezoelectric element, a monomorph transducer, a bimorph transducer, etc. can be used. The connecting portion 453 is sandwiched between the transmitting element 451 and the receiving element 452. The transmitting element 451, the connecting portion 453, and the receiving element 452 are arranged in this order on the directional axis DA. In this example, the transmitting element 451 is provided on the base end portion 41 side of the conversion element 4. Moreover, the receiving element 452 is provided on the tip end portion 42 side of the conversion element 4.

[0080] The connecting portion 453 has a transmitting element facing surface 454 which is a main surface facing the transmitting element 451, and a receiving element facing surface 455 which is a main surface facing the receiving element 452. The transmitting element facing surface 454 and the receiving element facing surface 455 are formed in planes parallel to each other and substantially perpendicular to the directional axis DA. The connecting portion 453 is joined to the transmitting element 451 at the transmitting element facing surface 454 via a bonding layer such as an adhesive layer. The connecting portion 453 is joined to the transmitting element 451 at the receiving element facing surface 455 via a bonding layer such as an adhesive layer. These bonding layers are formed to a thickness sufficiently smaller than the wavelength of the transmitted and received waves (for example, 100 μm or less or less than one-eighth of the wavelength).

[0081] In this example, the receiving element 452 is formed with an area smaller than that of the transmitting element 451. Correspondingly, the connecting portion 453 is formed in a substantially frustum shape so that the receiving element facing surface 455 has an area, i.e., an outer diameter, smaller than that of the transmitting element facing surface 454. The connecting portion 453 is configured to behave like a rigid body when transmitting vibration between the transmitting element 451 and the receiving element 452, similar to the vibration converter 5. That is, the connecting portion 453 is provided so as to ultrasonically vibrate in such a manner that the transmitting element facing surface 454 and the receiving element facing surface 455 move in parallel in the axial direction with almost no bending in association with ultrasonic vibration of the transmitting element 451 or the receiving element 452.

[0082] The transmitting element 451 has an improved transmission output by increasing its area, i.e., its outer diameter. In contrast, the receiving element 452 has an improved reception sensitivity by decreasing its area, i.e., its outer diameter. In this respect, in this configuration, for example, as shown in FIG. 28, the transmitting element 451 can be a large-diameter laminated piezoelectric element, and the receiving element 452 can be a small-diameter single-layer piezoelectric element. This makes it possible to realize a transmission / reception integrated sensor that can achieve both high transmission output and high reception sensitivity with a simple configuration. In addition, the transmitting element 451 and the receiving element 452, which have different in-plane shapes, can be well connected by the connecting portion 453, so that vibration transmission loss between the transmitting element 451 and the receiving element 452 can be well avoided.

[0083] Here, Fig. 28 shows a configuration for narrow directivity in which the outer diameter of diaphragm 21 is large. That is, such a configuration corresponds to high transmission / reception characteristics and narrow directivity. In contrast, Fig. 29 shows a configuration for wide directivity in which the outer diameter of diaphragm 21 is small. That is, such a configuration corresponds to high transmission / reception characteristics and wide directivity. In this configuration, in order to suppress spurious vibrations, as shown in Fig. 29, support portion 26 may be formed in a stepped shape having a first side plate portion 267, a second side plate portion 268, and a step portion 269.

[0084] The first side plate 267 is a portion on the base end side in the axial direction of the support 26, and has a large inner diameter corresponding to the large diameter transmitting element 451. The second side plate 268 is a portion on the tip end side in the axial direction of the support 26, and has a small inner diameter corresponding to the small diameter receiving element 452. The step portion 269 is provided so as to connect the large inner diameter of the first side plate 267 and the small inner diameter of the second side plate 268. The first side plate 267, the second side plate 268, and the step portion 269 have the same outer shape. That is, the support 26 is formed in a substantially cylindrical shape whose inner diameter changes in the axial direction.

[0085] Third embodiment Hereinafter, the third embodiment will be described with reference to Fig. 30 to Fig. 33. This embodiment shows a configuration which omits the vibration converter 5 in each of the above embodiments shown in Fig. 2 etc., but which can provide the same effects as those embodiments.

[0086] As shown in FIG. 30, in this embodiment, the ultrasonic sensor 1 includes a sensor housing 2, a fixed portion 3, and a conversion element 4. The sensor housing 2 has a diaphragm 21. The diaphragm 21 has a plate thickness direction along the directional axis DA, and is supported by a support portion 26 so that the diaphragm 21 can ultrasonically vibrate in a manner in which a center portion 24 in an in-plane direction intersecting with the directional axis DA moves along the directional axis DA. The conversion element 4 is provided so that a tip portion 42 abuts against the inner surface 21b of the diaphragm 21 directly or via the above-mentioned bonding layer. That is, the conversion element 4 is sandwiched between the fixed portion 3 and the diaphragm 21. The conversion element 4 is provided so as to ultrasonically vibrate the diaphragm 21 in a manner in which the diaphragm 21 is pushed out or pulled in on the surface.

[0087] In this way, the ultrasonic sensor 1 according to this embodiment is configured to perform a transmission function of transmitting a transmission wave from the diaphragm 21 to the external space SG by ultrasonic vibrations generated in the conversion element 4 by application of a drive signal and transmitted from the conversion element 4 to the diaphragm 21, causing the diaphragm 21 to ultrasonically vibrate. Alternatively, the ultrasonic sensor 1 is configured to perform a reception function of converting the ultrasonic vibrations transmitted from the diaphragm 21 excited by receiving ultrasonic waves from the external space SG to the conversion element 4 into a reception signal in the conversion element 4.

[0088] Below, an overview of the operation of the ultrasonic sensor 1 according to this embodiment having the above configuration will be described with reference to Fig. 30, along with the effects achieved by the configuration. For the sake of simplicity, in the following overview of the operation, it is assumed that the ultrasonic sensor 1 has at least a transmission function, and the conversion element 4 has a configuration of a type that ultrasonically vibrates in a manner that expands and contracts in the axial direction. Then, the operation when the transmission function is activated, that is, when the ultrasonic sensor 1 transmits a transmission wave to the external space SG, will be mainly described.

[0089] At the time of transmission, a drive signal is applied to the conversion element 4. As a result, the conversion element 4 ultrasonically vibrates in such a manner that it expands and contracts in the axial direction. Specifically, at the time of application of a positive voltage, the conversion element 4 is expanded in the axial direction more than the state shown in FIG. 30. Here, the base end 41 of the conversion element 4 is fixed to the fixing portion 3 fixedly supported by the bumper V3. Therefore, as the conversion element 4 expands in the axial direction, the tip portion 42 of the conversion element 4 moves in the transmission direction DT. Then, the vibration plate 21 is urged in the transmission direction DT by the tip portion 42 of the conversion element 4. At this time, the vibration plate 21 moves in the transmission direction DT while maintaining the flat state at the joint with the tip portion 42 of the conversion element 4. As a result, the vibration plate 21 is pushed out in the transmission direction DT while maintaining the shape of the joint surface with the tip portion 42 of the conversion element 4.

[0090] On the other hand, when a negative voltage is applied, the conversion element 4 is compressed in the axial direction more than the state shown in FIG. 30. Here, the base end 41 of the conversion element 4 is fixed to the fixed portion 3 fixedly supported by the bumper V3. Therefore, when the conversion element 4 is compressed in the axial direction, the tip portion 42 of the conversion element 4 moves in the receiving direction DR. Then, the diaphragm 21 is urged in the receiving direction DR by the tip portion 42 of the conversion element 4. At this time, the diaphragm 21 moves in the transmitting direction DT while maintaining the planar state at the joint with the tip portion 42 of the conversion element 4. As a result, the diaphragm 21 is drawn in the receiving direction DR while maintaining the shape of the joint surface with the tip portion 42 of the conversion element 4.

[0091] In this way, application of a drive signal to the conversion element 4 causes the diaphragm 21 to ultrasonically vibrate in a primary vibration mode with the outer edge 25 as a node and the center 24 as an antinode. The vibration mode of the diaphragm 21 is limited to this primary vibration mode. This makes it possible to effectively suppress loss of directivity due to the occurrence of a vibration mode of a higher order than the primary vibration mode.

[0092] In this configuration, in order to suppress spurious vibrations, a tapered portion 261 may be provided at the axial tip of the support portion 26 as shown in Fig. 31. Also, as shown in Fig. 32, an acoustic matching layer 61 may be provided between the conversion element 4 and the diaphragm 21. The acoustic matching layer 61 may be formed in a thin plate shape, or may be formed to be relatively thick.

[0093] 33, the conversion element 4 may include a transmitting element 451, a receiving element 452, and a connecting portion 453. In this example, similar to the example of FIG. 28, the receiving element 452 is formed with an area smaller than that of the transmitting element 451. Meanwhile, in this example, unlike the example of FIG. 28, the arrangement order of the transmitting element 451, the receiving element 452, and the connecting portion 453 is reversed. That is, the receiving element 452, the connecting portion 453, and the transmitting element 451 are arranged in this order in the transmission direction DT.

[0094] According to this configuration, by pushing out the diaphragm 21 with a surface using the transmitting element 451, which is a large-diameter laminated piezoelectric element, the diaphragm 21 ultrasonically vibrates in a primary vibration mode with the outer edge portion 25 as a node and the center portion 24 as an antinode. The vibration mode of the diaphragm 21 is limited to this primary vibration mode. This makes it possible to effectively suppress the loss of directivity caused by the occurrence of a vibration mode of a higher order than the primary vibration mode. Furthermore, ultrasonic vibration of this type can be realized without resonance. Therefore, it is possible to realize any transmission and reception frequency. Furthermore, changes in the transmission and reception characteristics due to temperature changes can be effectively suppressed. Therefore, it is possible to realize an integrated transmission and reception sensor that can achieve both high transmission output and high reception sensitivity with a simple configuration.

[0095] (Fourth embodiment) Hereinafter, the fourth embodiment will be described with reference to Fig. 34. This embodiment shows a configuration which can obtain the same effects as those of the first and second embodiments shown in Fig. 2 and the like, while omitting the diaphragm 21 of these embodiments.

[0096] As shown in FIG. 30, in this embodiment, the ultrasonic sensor 1 includes a sensor housing 2, a fixing portion 3, a conversion element 4, and a vibration conversion portion 5. The sensor housing 2 is formed in a cylindrical shape without a bottom, which does not have the diaphragm 21 shown in FIG. 2 and the like. The vibration conversion portion 5 is fixed to the tip portion 42 of the conversion element 4, and is connected to the tip portion 42 so as to be able to transmit vibrations. Specifically, the vibration conversion portion 5 has a first opposing surface 51 close to the tip portion 42 of the conversion element 4, and a second opposing surface 52 which is the back surface of the first opposing surface 51. The first opposing surface 51 is joined to the tip portion 42 of the conversion element 4 via a joining layer such as an adhesive layer. The second opposing surface 52 is provided so as to face the external space SG in the mounted state.

[0097] In this example, the vibration converter 5 is formed so that the second opposing surface 52 has a larger area than the first opposing surface 51. The second opposing surface 52 is formed so that the outer diameter is slightly smaller than the inner diameter of the inner circumferential surface 28 of the support portion 26. A sealant 621 is provided so as to fill a gap between the tip end of the vibration converter 5 in the axial direction and the support portion 26. The sealant 621 may be formed of an elastomer material such as silicone rubber so as not to impede the reciprocating vibration of the vibration converter 5 in the axial direction.

[0098] In this way, the ultrasonic sensor 1 according to this embodiment is configured to perform a transmission function of transmitting a transmission wave from the vibration conversion unit 5 to the external space SG by ultrasonic vibrations generated in the conversion element 4 by application of a drive signal and transmitted from the conversion element 4 to the vibration conversion unit 5, causing the vibration conversion unit 5 to vibrate ultrasonically. Alternatively, the ultrasonic sensor 1 is configured to perform a reception function of converting ultrasonic vibrations transmitted from the vibration conversion unit 5 excited by reception of ultrasonic waves from the external space SG to the conversion element 4 into a reception signal in the conversion element 4.

[0099] In the ultrasonic sensor 1 having such a configuration, the vibration converter 5 ultrasonically vibrates in a manner that moves back and forth in the axial direction while maintaining the planar state of the first opposing surface 51 and the second opposing surface 52. Therefore, with such a configuration, it is possible to always transmit and receive in the primary vibration mode. Ultrasonic vibration in such a manner can be realized without resonance. Therefore, it is possible to realize any transmission and reception frequency. In addition, changes in the transmission and reception characteristics due to temperature changes can be effectively suppressed.

[0100] (Object detection device) An object detection device 700 including an ultrasonic sensor 1 having the above configuration will be described below mainly with reference to Fig. 35. The object detection device 700 includes a plurality of ultrasonic sensors 1. The object detection device 700 also includes a transmission circuit 701, a reception circuit 702, a drive signal generation unit 703, a reception signal processing unit 704, and a control unit 705.

[0101] The transmission circuit 701 is electrically connected to the ultrasonic sensor 1 so as to input a drive signal to the ultrasonic sensor 1. Specifically, the transmission circuit 701 has a digital / analog conversion circuit and the like. That is, the transmission circuit 701 is configured to perform processing such as digital / analog conversion on the drive signal output from the drive signal generation unit 703, and apply the AC voltage generated thereby to the conversion element 4 in the ultrasonic sensor 1. The reception circuit 702 is provided to perform signal processing such as amplification and analog / digital conversion on the reception signal generated by the conversion element 4 corresponding to the reception result of the ultrasonic wave in the ultrasonic sensor 1, and output it to the reception signal processing unit 704. Specifically, the reception circuit 702 has an amplifier circuit, an analog / digital conversion circuit, and the like. The transmission circuit 701 and the reception circuit 702 can be provided corresponding to each of the multiple ultrasonic sensors 1.

[0102] The drive signal generating unit 703 is provided to generate a drive signal for outputting a transmission wave of a predetermined frequency from the ultrasonic sensor 1 and input the drive signal to the transmission circuit 701. Specifically, the drive signal generating unit 703 is configured to be able to change the frequency of the drive signal based on a control signal output from the control unit 705. The received signal processing unit 704 is provided to perform various signal processing such as filtering on the received signal output from the receiving circuit 702. The received signal processing unit 704 is also provided to output a processed signal resulting from the various signal processing to the control unit 705. The drive signal generating unit 703 and the received signal processing unit 704 may be provided in common to a plurality of ultrasonic sensors 1.

[0103] The control unit 705 is provided in common to the multiple ultrasonic sensors 1. The control unit 705 has a configuration as an in-vehicle microcomputer equipped with a CPU, a ROM, a RAM, a non-volatile rewritable memory, etc. (not shown). That is, the control unit 705 is configured to control the operation of the object detection device 700, including the transmission and reception operation of each of the multiple ultrasonic sensors 1, by reading and executing a control program stored in the ROM or the non-volatile rewritable memory. The control unit 705 is configured to generate a detection signal corresponding to the presence state of an object (e.g., an obstacle) existing in the external space SG based on the reception signal of each of the multiple ultrasonic sensors 1, and output the detection signal to an external device. Specifically, the control unit 705 has a parameter acquisition unit 751, a frequency adjustment unit 752, and an object measurement unit 753 as functional configurations realized on the in-vehicle microcomputer.

[0104] The parameter acquisition unit 751 is adapted to acquire parameters relating to physical quantities that affect the transmission and reception operation of the ultrasonic sensor 1. Such parameters include structural parameters and environmental parameters. The structural parameters are parameters relating to the structure of the ultrasonic sensor 1 including the diaphragm 21, such as the thickness, outer diameter, and temperature characteristics of physical properties (Young's modulus, etc.) of the diaphragm 21. The environmental parameters are parameters relating to the environment of the ultrasonic sensor 1 including the diaphragm 21, such as temperature, etc.

[0105] The frequency adjustment unit 752 adjusts the frequency of the drive signal to set the frequency of the transmission wave to a predetermined frequency. That is, the frequency adjustment unit 752 adjusts the frequency of the transmission wave to obtain a predetermined directivity in the ultrasonic sensor 1. The frequency adjustment unit 752 also adjusts, i.e. corrects, the drive signal frequency based on at least one of the structural parameters and the environmental parameters. Furthermore, the frequency adjustment unit 752 adjusts the frequency of the transmission wave so that the frequencies of the transmission waves in two adjacent ultrasonic sensors 1 are different, thereby suppressing the occurrence of interference. The object measurement unit 753 measures the shape of an object present around the vehicle V based on the reception result of the reflected wave of the transmission wave by the object.

[0106] In the object detection device 700 having such a configuration, the frequency of the drive signal is corrected based on the structural parameters and the environmental parameters, so that the transmission and reception characteristics such as the directivity, the sound pressure, and the sensitivity can be adjusted within the specified values. In addition, the desired directivity can be obtained by changing the frequency according to the application and the mounting position. In particular, in the configuration shown in FIG. 5, FIG. 6A, etc., in which a part of the bumper V3 is used as the vibration part V7, calibration is required depending on the mounting position, so this is very effective. Furthermore, it is possible to obtain the height information of the object based on the object measurement results with different directivities.

[0107] In addition, simultaneous and high-frequency measurements can be achieved by taking measures against interference. From this viewpoint, it is preferable to modulate the transmission wave. Specifically, by transmitting a transmission wave whose frequency changes over time and detecting the correlation between a reference signal corresponding to the modulation mode of the transmission wave and the received signal, it is possible to take good measures against interference. It is also preferable to use a transmission wave having at least one of frequency shift keying and phase shift keying. According to this configuration, false detection due to interference can be more effectively avoided, and the S / N ratio and distance resolution can be improved.

[0108] (Other variations) The present invention is not limited to the above embodiment. Therefore, the above embodiment can be modified as appropriate. Representative modified examples will be described below. In the following description of the modified examples, differences from the above embodiment will be mainly described. In addition, the same reference numerals are used for parts that are the same or equivalent to each other in the above embodiment and the modified examples. Therefore, in the following description of the modified examples, the description of the above embodiment can be appropriately used for components having the same reference numerals as the above embodiment, unless there is a technical contradiction or special additional explanation.

[0109] The present invention is not limited to the specific device configurations shown in the above embodiments. That is, for example, the vehicle V to which the present invention is applied is not limited to a four-wheeled vehicle. Specifically, the vehicle V may be a three-wheeled vehicle, or a six- or eight-wheeled vehicle such as a cargo truck. The type of the vehicle V may be a vehicle equipped with only an internal combustion engine, an electric vehicle or a fuel cell vehicle without an internal combustion engine, or a so-called hybrid vehicle. The shape and structure of the vehicle body V1 are also not limited to a box shape, i.e., a substantially rectangular shape in a plan view. Furthermore, the moving body to which the present invention is applied is not limited to the vehicle V, and may be, for example, a ship or an aircraft.

[0110] The object to which the ultrasonic sensor 1 is attached is not limited to the bumper V3. Specifically, for example, the ultrasonic sensor 1 may be attached to a vehicle body panel V2. There is also no particular limitation on the material constituting the vehicle body panel V2 and / or the bumper V3 to which the ultrasonic sensor 1 is attached. That is, for example, such a material may be FRP, CFRP, a steel plate, etc. FRP is an abbreviation for Fiber Reinforced Plastics. CFRP is an abbreviation for Carbon Fiber Reinforced Plastics.

[0111] Alternatively, for example, the ultrasonic sensor 1 may be applied to an input device in a human-machine interface device such as a car navigation device or a center information display device, etc. In this case, the ultrasonic sensor 1 may be attached inside the vehicle, that is, on the dashboard, the center console, the vehicle ceiling, etc.

[0112] The present invention is not limited to a configuration in which the ultrasonic sensor 1 is mounted on a moving object such as a vehicle V. Specifically, for example, the ultrasonic sensor 1 can also be used as an input device in a mobile phone, a personal computer, an electrical appliance, a machine tool, etc. Alternatively, for example, the ultrasonic sensor 1 can also be used as a human detection sensor in an automatic door, a security camera, etc.

[0113] As described above, the ultrasonic sensor 1 is not limited to a configuration that is integrated with transmission and reception. That is, for example, the ultrasonic sensor 1 may have a configuration that is capable of only transmitting ultrasonic waves. Alternatively, the ultrasonic sensor 1 may have only a function of receiving a transmission wave, which is an ultrasonic wave transmitted from another ultrasonic transmitter, reflected by an object present in the vicinity.

[0114] The configuration of each part of the ultrasonic sensor 1 is not limited to the above specific example. For example, the in-plane shape of each part is not limited to a circle, and may be an ellipse, a rectangle, a hexagon, an octagon, or the like. Specifically, for example, the sensor housing 2 may have an outer shape formed in a polygonal column. Furthermore, the components formed in a cylindrical shape surrounding the directional axis DA may be formed in an elliptical cylinder or a polygonal cylinder (for example, a rectangular cylinder) in addition to a cylindrical shape. Alternatively, the components formed in a cylindrical shape surrounding the directional axis DA may be realized by arranging a plurality of components having any shape, such as a columnar shape, a block shape, a cone shape, a wall shape, or the like, around the directional axis DA. There is also no particular limitation on the materials constituting each part, and they may be selected for a specific purpose.

[0115] Specifically, Fig. 36 shows a case where the vibration-damping portion V8 is formed in a cylindrical shape or a circular ring shape. Fig. 37 shows a case where the vibration-damping portion V8 is formed in a square tube shape. The in-plane shape of the vibration-damping portion V8 is not limited to these examples, and may be, for example, an elliptical tube shape or a polygonal tube shape (e.g., a square tube shape).

[0116] FIG. 38 shows a case where the vibration-damping portion V8 shown in FIG. 37 is divided into a plurality of parts in the circumferential direction. The division manner of the vibration-damping portion V8 is not limited to the manner shown in FIG. 38. Similarly, the cylindrical or circular ring-shaped vibration-damping portion V8 shown in FIG. 36 can also be divided into a plurality of parts in the circumferential direction. The same applies to the case of an elliptical cylinder or a polygonal cylinder. When the vibration-damping portion V8 is divided into a plurality of parts, the shape of each vibration-damping portion V8 is not particularly limited, and it can be formed into any shape, such as a circular cylinder, an elliptical cylinder, a flat plate, a polygonal cylinder, a cylinder, an elliptical cylinder, a polygonal cylinder, a truncated cone, a truncated polygonal pyramid, or the like.

[0117] FIG. 39 shows an example in which the vibration-damping part V8 is bonded to the bumper V3 via a bonding layer 801 in the configuration shown in FIG. 6A. The bonding layer 801 is formed of an adhesive layer, a double-sided tape layer, or the like. In contrast, FIG. 40 shows an example in which the vibration-damping part V8 is integrally formed with the bumper V3 without using such a bonding layer 801. FIG. 41 shows an example in which an acoustic matching layer 61 is provided between the vibration converter 5 and the diaphragm 21, i.e., the bumper V3, in the configuration shown in FIG. 39. FIG. 42 shows an example in which an acoustic matching layer 61 is provided between the vibration converter 5 and the diaphragm 21, i.e., the bumper V3, in the configuration shown in FIG. 40. In these examples, the same effect as that of the configuration shown in FIG. 6A can be achieved.

[0118] FIG. 43 is a diagram for supplementary explanation of the bonding layer and the fastener, which are omitted as appropriate in the explanation of the configuration shown in FIG. 6A of the first embodiment. In FIG. 43, the fixing part 3 is fixed to the vibration-damping part V8 at a first fixing part F1 facing the holding surface V9, which is the inner peripheral surface of the vibration-damping part V8. At the first fixing part F1, a screw or a fitting structure (for example, an engagement structure between an engagement hole and an engagement claw) or the like can be used. In addition, the vibration-damping part V8 is fixed to the bumper V3 at a second fixing part F2 facing the bumper inner surface V6. At the second fixing part F2, a joining means such as the bonding layer 801 or welding shown in FIG. 39 or the like, or a fastening means using a fastener such as a screw can be used.

[0119] A joining means such as an adhesive or an acoustic matching material for filling the gap may be used at the third fixing point F3 for fixing the conversion element 4 to the fixed part 3. The same applies to the fourth fixing point F4 between the conversion element 4 and the vibration converter 5. A joining means such as an adhesive or an acoustic matching material for filling the gap may be used at the fifth fixing point F5 between the vibration part V7 of the bumper V3 constituting the diaphragm 21 and the vibration converter 5. The same applies when the acoustic matching layer 61 is provided between the vibration part V7 of the bumper V3 and the vibration converter 5.

[0120] FIG. 45 shows a modified example of the configuration in which the mounting hole V4 is provided in the bumper V3 shown in FIG. 1 and FIG. 2. In this example, a synthetic resin diaphragm portion 901 is accommodated in the mounting hole V4 so that its outer surface is substantially flush with the bumper outer surface V5. The diaphragm portion 901 is supported at its outer portion in the in-plane direction so as to be ultrasonically vibrated by a vibration-damping support portion 902 that is provided integrally or divided into a plurality of portions in the circumferential direction surrounding the directional axis DA so as to surround the directional axis DA. That is, the vibration-damping support portion 902 has the same configuration and function as the support portion 26 shown in FIG. 2 or the vibration-damping portion V8 shown in FIG. 6A. Note that a sensor holder that fixes the ultrasonic sensor 1 to the bumper V3 to keep the diaphragm portion 901 flush with the bumper outer surface V5 is omitted from the illustration.

[0121] The vibration-damping support part 902 has a tip surface 903 and a base end surface 904 in the axial direction. The tip surface 903 and the base end surface 904 are formed in a plane perpendicular to the axial direction. The vibration-damping support part 902 is bonded to the diaphragm part 901 at the tip surface 903 via a bonding layer 801. The fixing part 3 is fixed to the vibration-damping support part 902 at an inner wall surface 905 that is a side surface of the vibration-damping support part 902 and faces the directional axis DA. FIG. 46 shows an example in which the diaphragm part 901 and the vibration-damping support part 902 are integrally configured without using the bonding layer 801, as compared to the configuration shown in FIG. 45.

[0122] Fig. 47 shows an example in which an acoustic matching layer 61 is provided between the vibration converter section 5 and the diaphragm section 901 in the configuration shown in Fig. 45. Fig. 48 shows an example in which an acoustic matching layer 61 is provided between the vibration converter section 5 and the diaphragm section 901 in the configuration shown in Fig. 46.

[0123] 1 to 48 show a simplified device configuration in order to briefly explain the contents of the present invention. Therefore, the detailed configuration when the present invention is actually realized as a specific product does not necessarily match the configuration shown in Fig. 1 to 48. In other words, when the present invention is actually realized as a specific product, the details of the specific configuration of each part of the ultrasonic sensor 1 may differ from the configuration shown in Fig. 1 to 48.

[0124] In the above description, a plurality of components that are formed seamlessly and integrally with each other may be formed by bonding separate members together. Similarly, a plurality of components that are formed by bonding separate members together may be formed seamlessly and integrally with each other.

[0125] In the above description, a plurality of components that are made of the same material may be made of different materials. Similarly, a plurality of components that are made of different materials may be made of the same material.

[0126] Needless to say, the elements constituting the above-mentioned embodiment are not necessarily essential, except when expressly stated as essential or when considered to be obviously essential in principle. Furthermore, when the numbers, amounts, ranges, etc. of the components are mentioned, the present invention is not limited to the specific values, except when expressly stated as essential or when clearly limited to a specific value in principle. Similarly, when the shapes, directions, positional relationships, etc. of the components are mentioned, the present invention is not limited to the shapes, directions, positional relationships, etc., except when expressly stated as essential or when clearly limited to a specific shape, direction, positional relationship, etc. in principle.

[0127] The modified examples are not limited to the above examples. For example, all or part of one of the multiple embodiments and all or part of the other may be combined with each other as long as there is no technical contradiction. There is no particular limit to the number of combinations. Similarly, all or part of one of the multiple modified examples and all or part of the other may be combined with each other as long as there is no technical contradiction. Furthermore, all or part of one of the multiple embodiments and all or part of one of the multiple modified examples may be combined with each other as long as there is no technical contradiction. Specifically, for example, the invisible sonar configuration shown in FIG. 6A or FIG. 6B may also be realized in the configurations shown in FIG. 11 to FIG. 34. More specifically, for example, in the configurations shown in FIG. 30 to FIG. 32, the bumper V3 and the vibration damping unit V8 shown in FIG. 6A may be used instead of the diaphragm 21 and the support unit 26. [Explanation of symbols]

[0128] 1 Ultrasonic sensor 2 Sensor housing 21 Vibration plate 3 Fixed part 4. Conversion element 41 Proximal end 42 Tip 5 Vibration conversion unit SG external space V Vehicle (moving object)

Claims

1. An ultrasonic sensor (1), A conversion element (4) having a base end (41) which is one end in an axial direction along a directional axis (DA) and a tip end (42) which is the other end, and performing a conversion function between ultrasonic vibration and an electrical signal; A fixing portion (3) that is provided closer to the base end portion of the conversion element than the tip end portion and fixedly supports the conversion element; A vibration converter (5) connected to the tip of the conversion element so as to be capable of transmitting vibration and configured to convert the vibration unit into a primary vibration mode; Equipped with A transmission function in which ultrasonic vibration generated in the conversion element by application of the drive signal, which is the electrical signal, to the conversion element is transmitted from the conversion element to the vibration conversion unit, causing the vibration conversion unit to vibrate ultrasonically, thereby transmitting a transmission wave, which is an ultrasonic wave, from the vibration conversion unit to an external space (SG) existing in a transmission direction from the base end toward the tip end, further than the conversion element. and / or A receiving function of converting ultrasonic vibrations excited by receiving ultrasonic waves from the external space and transmitted from the vibration conversion unit to the conversion element into a received signal, which is an electrical signal, by the conversion element. The present invention is configured to The vibration converter is made of a conductive material and is set to a predetermined potential. Ultrasonic sensor.

2. The vibration converter has a truncated cone shape. The ultrasonic sensor of claim 1 .

3. The ultrasonic transducer further includes a vibration plate (21) having a plate thickness direction along the directional axis, and a center portion (24) in an in-plane direction intersecting the directional axis being arranged to be ultrasonically vibrated in a manner that moves along the directional axis, The diaphragm has an outer surface (21a) that faces the external space and an inner surface (21b) that faces the outer surface (21a), The vibration converter is joined to the inner surface such that a half value of the difference in outer diameter between a joining surface (52) joined to the inner surface of the vibration plate and the inner surface is less than a half value of the wavelength of the transmission wave or the ultrasonic vibration.

3. The ultrasonic sensor according to claim 1 or 2.

4. The ultrasonic transducer further includes a vibration plate (21) having a plate thickness direction along the directional axis, and a center portion (24) in an in-plane direction intersecting the directional axis being arranged to be ultrasonically vibrated in a manner that moves along the directional axis, a transmission function in which ultrasonic vibrations generated in the conversion element by application of the drive signal are transmitted from the conversion element to the vibration plate via the vibration conversion unit, causing the vibration plate to vibrate ultrasonically, thereby transmitting the transmission wave from the vibration plate to the external space; and / or a receiving function of converting ultrasonic vibrations transmitted from the diaphragm excited by receiving ultrasonic waves from the external space to the conversion element via the vibration conversion unit into a received signal by the conversion element; The present invention is configured to The ultrasonic sensor of claim 1 .

5. The vibration converter has a hardness equal to or greater than the hardness of the diaphragm.

5. The ultrasonic sensor according to claim 4.

6. The vibration conversion unit has a first opposing surface (51) adjacent to the tip of the conversion element, and a second opposing surface (52) on the back side of the first opposing surface adjacent to the vibration plate.

6. The ultrasonic sensor according to claim 4 or 5.

7. The vibration converter is formed so that the second opposing surface has a larger area than the first opposing surface.

7. The ultrasonic sensor according to claim 6.

8. The vibration converter is formed so that the second opposing surface has an area corresponding to an area of ​​the diaphragm, thereby suppressing spurious vibrations in the diaphragm.

8. The ultrasonic sensor according to claim 6 or 7.

9. A support portion (26) is provided to support an outer edge portion (25) of the diaphragm in an in-plane direction intersecting the directional axis, The diaphragm has a plate thickness smaller than a dimension of the support portion in the axial direction. The ultrasonic sensor according to any one of claims 4 to 8.

10. The diaphragm is made of a material softer than the support portion.

10. The ultrasonic sensor of claim 9.

11. The diaphragm is a part of the outer plate (V3) of the moving body (V), The diaphragm is an inner part of a vibration damping part (V8) that is integrally or divided into a plurality of parts in a circumferential direction surrounding the directional axis so as to surround the directional axis when the vibration damping part and the outer plate are joined together. The ultrasonic sensor according to any one of claims 4 to 10.

12. The vibration plate is connected to the vibration part (V7) which is a part of the outer plate (V3) of the moving body (V) so as to be capable of transmitting vibration. The vibration part is an inner part of the vibration damping part (V8) that is integrally or divided into a plurality of parts in a circumferential direction surrounding the directional axis so as to surround the directional axis when the outer plate is joined to the vibration damping part (V8). The ultrasonic sensor according to any one of claims 4 to 10.

13. The frequency of the transmission wave is adjusted based on at least one of a structural parameter, which is information about a structure of the diaphragm, and an environmental parameter, which is information about an environment of the diaphragm. The ultrasonic sensor according to any one of claims 4 to 12.

14. As the conversion element, a transmitting element (451) performing the transmitting function and a receiving element (452) performing the receiving function are provided. The ultrasonic sensor according to any one of claims 1 to 13.

15. The transmitting element is a laminated piezoelectric element.

15. The ultrasonic sensor of claim 14.

16. The receiving element is a single-layer piezoelectric element.

16. The ultrasonic sensor according to claim 14 or 15.

17. The receiving element is formed with an area smaller than that of the transmitting element. The ultrasonic sensor according to any one of claims 14 to 16.

18. The transmitting element, a connecting portion (453) sandwiched between the transmitting element and the receiving element, and the receiving element are arranged in this order on the directional axis. The ultrasonic sensor according to any one of claims 14 to 17.

19. The conversion element has a configuration as a piezoelectric element formed in a plate shape having a thickness direction in the axial direction, The fixed portion fixedly supports a fixed end portion (432) which is an end portion of the conversion element in an in-plane direction intersecting the directional axis so that the conversion element ultrasonically vibrates in a bending vibration mode with a central portion (431) in the in-plane direction intersecting the directional axis as a node or antinode. The ultrasonic sensor according to any one of claims 1 to 13.

20. The conversion element has a configuration as a monomorph type or bimorph type piezoelectric element.

20. The ultrasonic sensor of claim 19.

21. The transducer element is configured as a Langevin transducer having a piezoelectric element formed in a plate shape having a thickness direction in the axial direction. The ultrasonic sensor according to any one of claims 1 to 13.

22. At least one of the transmitting element and the receiving element is configured as a Langevin type transducer having a piezoelectric element formed in a plate shape having a thickness direction in the axial direction. The ultrasonic sensor according to any one of claims 14 to 18.

23. By adjusting the frequency of the transmission wave, a desired directivity is obtained. The ultrasonic sensor according to any one of claims 1 to 22.

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