ULTRASCHALLSENSOR

Abstract

Ultrasonic sensor (1), comprising: a first electrode (21c; 20) provided in an ultrasonic microphone (2) including a vibration element (21) providing a function for converting between mechanical vibrations and electrical signals; a second electrode (41) external to the ultrasonic microphone (2) such that an electrical characteristic between the second electrode (41) and the first electrode (21c; 20) changes based on an adhesion state of substances (S) adhering to the ultrasonic microphone (2); and a third electrode (42) provided to suppress changes in the electrical characteristics between the first electrode (21c; 20) and the second electrode (41) caused by factors other than the adhesion of substances (S) adhering to the ultrasonic microphone (2).

Description

[Technical field]

[0001] The present disclosure relates to an ultrasonic sensor. [State of the art]

[0002] An ultrasonic sensor that detects an object by transmitting and receiving ultrasonic waves is known. Specifically, this type of ultrasonic sensor transmits ultrasonic waves by exciting a diaphragm portion with a vibrating element such as a piezoelectric element. Furthermore, this type of ultrasonic sensor detects an object by converting vibrations of the diaphragm portion into electrical signals, which accompany the reception of reflected waves of the transmitted ultrasonic waves from an object.

[0003] In this type of ultrasonic sensor, when water, mud, snow, or the like adhere to the diaphragm portion, a problem arises in that the transmission and reception of ultrasonic waves is hindered and object detection performance decreases. Therefore, various configurations have been conventionally proposed to detect the adhesion of substances adhering to the ultrasonic sensor. For example, JP S60-015577 A describes that since an impedance of an ultrasonic vibration element changes as a result of adhering substances, detection of the adhering substances can be performed by detecting this impedance change.

[0004] Reference is also made to DE 10 2010 028 009 A1, which was identified as state of the art.

[0005] DE 10 2010 028 009 A1 describes an ultrasonic sensor comprising a first electrode provided in an ultrasonic microphone including a vibration element providing a function for converting between mechanical vibrations and electrical signals, and a second electrode. [Overview of the invention]

[0006] Ultrasonic sensors are widely used in driving assistance applications such as vehicle parking assistance. Furthermore, the use of ultrasonic sensors in automated driving and the like is expected. Furthermore, the use of ultrasonic sensors in applications other than vehicles is also expected. Specifically, for example, ultrasonic sensors can be used for unmanning or automating conveyors used in factories and the like, agricultural equipment (such as cultivators), small aircraft, and the like.

[0007] As described above, adhesion of substances adhering to the ultrasonic sensor causes a decrease in the detection performance of the ultrasonic sensor. Therefore, improving the detection accuracy of substances adhering to the ultrasonic sensor is important in various applications of the ultrasonic sensor. The present disclosure has been achieved in light of the problems exemplified above, and the like.

[0008] According to one aspect of the present disclosure, an ultrasonic sensor includes: a first electrode provided in the ultrasonic microphone including a vibration element that provides a function of converting between mechanical vibrations and electrical signals; a second electrode arranged externally to the ultrasonic microphone such that an electrical characteristic between the second electrode and the first electrode changes based on an adhesion state of substances adhering to the ultrasonic microphone; and a third electrode provided to suppress changes in the electrical characteristic between the first electrode and the second electrode caused by factors other than the adhesion of substances adhering to the ultrasonic microphone.

[0009] In the above-described configuration, the electrical characteristics (such as electrostatic capacitance) between the first electrode and the second electrode change based on the adhesion state of substances adhering to the ultrasonic microphone. However, these electrical characteristics may also change due to factors other than the adhesion of substances adhering to the ultrasonic microphone. In this regard, the above-described configuration provides the third electrode. The third electrode is provided to suppress changes in the electrical characteristics between the first electrode and the second electrode caused by factors other than the adhesion of substances adhering to the ultrasonic microphone.Accordingly, as a result of the above-described configuration, a presence / absence of adhesion of adhering substances can be accurately detected based on the changes in electrical characteristics between the first electrode and the second electrode.

[0010] Reference numerals in parentheses may be appended to elements in the application documents. However, even in such cases, the reference numerals merely indicate examples of corresponding relationships between the elements and specific means described in accordance with embodiments described below. Therefore, the present disclosure is in no way limited by the reference numerals described above. [Brief description of the drawings] Fig. 1 is a perspective view of an external appearance of a vehicle in which an ultrasonic sensor according to an embodiment is mounted; Fig. 2 is a cross-sectional side view of an overall configuration of the ultrasonic sensor according to the embodiment; Fig. 3 is a front view of an external appearance of an ultrasonic microphone used in Fig. 2 is shown; Fig. 4 is a block diagram of a schematic circuit configuration of the ultrasonic sensor used in Fig. 2 is shown; Fig. 5 is an explanatory diagram of computer simulation conditions for verifying effects of the configuration of the ultrasonic sensor according to the embodiment; Fig. 6A a graph of computer simulation results; Fig. 6B is a graph of computer simulation results; Fig. 7 is a cross-sectional side view of an overall configuration of a modification of the ultrasonic sensor used in Fig. 2 is shown; Fig. 8 is a cross-sectional side view of an overall configuration of another modification of the ultrasonic sensor used in Fig. 2 is shown; Fig. 9 is a cross-sectional side view of an overall configuration of another modification of the ultrasonic sensor used in Fig. 2 is shown; and Fig. 10 is a cross-sectional side view of an overall configuration of another modification of the ultrasonic sensor used in Fig. 2 is shown. [Description of Embodiments](Embodiments)

[0011] Hereinafter, a first embodiment of the present disclosure will be described according to the drawings. Since understanding of the embodiment may be hindered as a result of inserting modifications in the middle of a series of descriptions regarding the embodiment, various modifications applicable to the embodiment will be collectively described following the descriptions of the embodiment. (Onboard configuration)

[0012] According to Fig. 1, according to the present embodiment, an ultrasonic sensor 1 is configured as an on-board sensor, of which a vehicle V is a mounting target. The vehicle V is a so-called four-wheeled automobile and includes a box-shaped vehicle body V1. A vehicle body panel V2, a front bumper V3, and a rear bumper V4, which are vehicle body components that configure an outer shell, are mounted on the vehicle body V1. The front bumper V3 is provided at a front end portion of the vehicle body V1. The rear bumper V4 is provided at a rear end portion of the vehicle body V1.

[0013] The ultrasonic sensor 1 is a so-called proximity sonar and is provided for detecting an object in the vicinity of the vehicle V. Specifically, a plurality of ultrasonic sensors 1 (such as four) are mounted on the front bumper V3. The plurality of ultrasonic sensors 1 mounted on the front bumper V3 are each arranged at different positions in a vehicle width direction. Similarly, a plurality of ultrasonic sensors 1 (such as four) are mounted on the rear bumper V4.

[0014] A configuration of the ultrasonic sensor 1 according to the present embodiment will be described below according to Fig. 2 to Fig. 4. According to Fig. 2, the ultrasonic sensor 1 is configured to transmit and receive ultrasonic waves. That is, the ultrasonic sensor 1 is configured to transmit a probe wave, which is an ultrasonic wave, along a directivity axis DA. The directivity axis is a virtual half-line extending along a transmission / reception direction of the ultrasonic wave from the ultrasonic sensor 1 and serves as a reference for the directivity angle. The "directivity axis" may also be referred to as a directional center axis or a detection axis. Further, the ultrasonic sensor 1 is configured to receive a reflection wave of the probe wave from an object present nearby and generate and output a detection signal based on a reception result.

[0015] To simplify the description, Fig. 2, as shown in the drawing, a right-handed Cartesian XYZ coordinate system is set such that a Z axis is parallel to the directivity axis DA. At this time, a direction parallel to the directivity axis DA is referred to as a directivity axis direction. A tip end side in the directivity axis direction is a transmission direction side of the test wave and corresponds to a top side in Fig. 2, that is, a positive Z-axis direction.

[0016] In contrast, a base end side in the directivity axis direction corresponds to a lower side in Fig. 2, that is, a negative Z-axis direction. Furthermore, a specific component viewed from the tip end side toward the base end side in a line of sight parallel to the directivity axis direction is called a front view. A diagram of a front view is called a front view. An end portion on the base end side in the directivity axis direction of a specific component is called a base end portion, and an end portion on the tip end side in the directivity axis direction is called a tip end portion. Furthermore, any direction orthogonal to the directivity axis direction is called an in-plane direction. The in-plane direction is a direction parallel to an XY plane in Fig. 2 is.

[0017] Fig. 2 shows one of the plurality of ultrasonic sensors 1 mounted on the front bumper V3 in a mounted state. The mounted state may also be referred to as a mounted state in which the ultrasonic sensor 1 is mounted on the front bumper V3, which configures the outer shell of the vehicle V, which is the mounting target.

[0018] According to Fig. 2, the front bumper V3 includes a bumper outer surface V31, which is an outer surface, and a bumper rear surface V32, which is a rear surface thereof. Furthermore, the front bumper V3 has a mounting hole V33, which is a through hole for mounting the ultrasonic sensor 1. The mounting hole V33 is formed to pass through the front bumper V3 in the directivity axis direction, that is, a vehicle's entire longitudinal direction.

[0019] The ultrasonic sensor 1 includes an ultrasonic microphone 2, an elastic support member 3, an external electrode 4, an electrical circuit unit 5, a sensor housing 6, and a damping element 7. Furthermore, the ultrasonic sensor 1 is mounted on the front bumper V3 via an auxiliary component 8. Configurations of these parts will be described successively below. (Ultrasonic microphone)

[0020] A configuration of the ultrasonic microphone 2 is shown below according to Fig. 2 and Fig. 3. According to the present embodiment, a microphone housing 20, which configures a housing of the ultrasonic microphone 2, has an outer shape that is a substantially circular columnar shape. Specifically, the microphone housing 20 has a diaphragm portion 20a and a diaphragm support portion 20b.

[0021] The diaphragm portion 20a is formed into a thin film having a thickness direction in the directivity axis direction. The diaphragm portion 20a is provided as a vibration plate that vibrates ultrasonically such that the center portion in the in-plane direction moves reciprocally along the directivity axis direction. That is, the diaphragm portion 20a is supported by the diaphragm support portion 20b at an outer edge portion 20c such that it bends and deforms in the in-plane direction with the outer edge portion 20c constituting a fixed end.

[0022] A detection surface 20d, which is an outer surface of the diaphragm portion 20a, is formed in a uniform planar shape orthogonal to the directivity axis DA. An element fixing surface 20e on a back side of the detection surface 20d is formed in a uniform planar shape parallel to the detection surface 20d.

[0023] The diaphragm support portion 20b is formed in a cylindrical shape in which the directivity axis DA along a vibration direction of the diaphragm portion 20a is a central axis. Specifically, the diaphragm support portion 20b is formed in a substantially circular cylindrical shape surrounding the directivity axis DA. The diaphragm support portion 20b is formed such that a base end portion is open toward the base end side in the directivity axis direction. Meanwhile, a tip end portion of the diaphragm support portion 20b is closed by the diaphragm portion 20a. That is, the microphone housing 20 is formed in a bottomed cylindrical shape, one end portion of which in the directivity axis direction is closed by the diaphragm portion 20a.

[0024] According to the present embodiment, the diaphragm portion 20a is formed in a shape having a long direction or long side and a short direction or short side in a plane orthogonal to the directivity axis DA. In particular, according to Fig. 3, the diaphragm section 20a has a rectangular shape with rounded corners in a plane orthogonal to the directivity axis DA. The diaphragm support section 20b has a thick section 20f and a thin section 20g corresponding to this in-plane shape.

[0025] The thick portion 20f is a portion along the long direction, that is, a long side direction, of the diaphragm portion 20a, and has a maximum thickness D1 in a direction parallel to a short side direction. The thin portion 20g is a portion along the short direction, that is, the short side direction of the diaphragm portion 20a, and has a maximum thickness D2 in a direction parallel to the long side direction. D2 < D1. That is, according to the present embodiment, the thick portion 20f is provided with rounded corners in correspondence with the long side of the rectangular shape of the diaphragm portion 20a. Further, the thin portion 20g is provided with rounded corners in correspondence with the short side of the rectangular shape of the diaphragm portion 20a.

[0026] An outer peripheral surface 20h of the diaphragm support portion 20b is formed in a substantially circular columnar shape parallel to the directivity axis DA. An engagement groove 20k is formed in the outer peripheral surface 20h in the thick portion 20f. The engagement groove 20k is a square groove used for supporting the microphone housing 20 to the sensor housing 6 by means of the elastic support member 3. The engagement groove 20k extends along the long direction, that is, the long side direction, of the diaphragm portion 20a.

[0027] According to the present embodiment, the microphone housing 20 is seamlessly and integrally formed from an insulating resin. Furthermore, a conductor portion 20n is provided on the outer peripheral surface 20h in the thick portion 20f. The conductor portion 20n configures a power supply path to the external electrode 4 and is formed from a highly conductive film such as a copper foil.

[0028] In the assembled state, the microphone housing 20 is provided such that the diaphragm portion 20a is inserted into the mounting hole V33 and the detection surface 20d is exposed to the outside of the vehicle V. Further, in the assembled state, the microphone housing 20 is provided such that the diaphragm support portion 20b extends toward the bumper rear surface V32 side from the mounting hole V33.

[0029] A space having a substantially quadrangular column shape and surrounded by the diaphragm portion 20a and the diaphragm support portion 20b is formed inside the microphone housing 20. The space is filled with a vibration-proof material 20p made of silicone rubber or the like.

[0030] The ultrasonic microphone 2 includes the microphone housing 20 and a vibrating element 21. That is, the microphone housing 20 is configured to support the vibrating element 21, which provides a function of converting between mechanical vibrations and electrical signals while receiving the vibrating element 21.

[0031] The vibrating element 21 is fixedly supported by the diaphragm portion 20a on the element fixing surface 20e side. The vibrating element 21 is attached to the element fixing surface 20e of the diaphragm portion 20a by an insulating adhesive. According to the present embodiment, the vibrating element 21 is configured as a so-called piezoelectric element. Specifically, the vibrating element 21 includes a piezoelectric body 21a, a driving electrode 21b, and a reference electrode 21c.

[0032] The piezoelectric body 21a is a sheet- or film-like element with a thickness direction in the directivity axis direction and is formed from a piezoelectric material such as piezoelectric ceramic. The piezoelectric body 21a is arranged between the driving electrode 21b and the reference electrode 21c in the directivity axis direction. Specifically, the vibration element 21 is formed by bonding the driving electrode 21b, the piezoelectric body 21a, and the reference electrode 21c while laminating them in this order in the directivity axis direction.

[0033] The driving electrode 21b is formed by a conductive metal film. The driving electrode 21b is provided on a main surface of the piezoelectric body 21a, that is, a main surface on the bottom side in the drawing. The main surface refers to a surface orthogonal to the thickness direction in the foil or film-like portion. That is, according to the present embodiment, the driving electrode 21b is arranged farther toward the base end side in the directivity axis direction than the reference electrode 21c.

[0034] The reference electrode 21c is formed by a conductive metal film. The reference electrode 21c is provided on another main surface of the piezoelectric body 21a, that is, a main surface on the upper side in the drawing. Specifically, according to the present embodiment, the reference electrode 21c is bonded to the diaphragm portion 20a by means of an insulating adhesive layer (not shown). The reference electrode 21c, which serves as a first electrode provided in the ultrasonic microphone 2, is grounded using the ultrasonic sensor 1.

[0035] The vibration element 21 is configured to bend and deform the diaphragm portion 20a as a result of the deformation of the piezoelectric body 21a based on a drive voltage applied between the drive electrode 21b and the reference electrode 21c. Furthermore, the vibration element 21 is configured to generate an output voltage between the drive electrode 21b and the reference electrode 21c based on the deformation of the piezoelectric body 21a that accompanies the bending and deformation of the diaphragm portion 20a. (Elastic support element)

[0036] According to Fig. 2, the elastic support member 3 is provided to elastically support the microphone housing 20 and suppress vibration propagation between the microphone housing 20 and the sensor housing 6. Furthermore, the elastic support member 3 is provided to suppress vibration propagation between the microphone housing 20 and the front bumper V3 by being disposed between the microphone housing 20 and the front bumper V3 in the assembled state. Specifically, the elastic support member 3 is a member having a substantially circular cylindrical shape and exhibiting rubber elasticity and non-conductivity. The elastic support member 3 is formed to have a central axis along the directivity axis direction.

[0037] The elastic support member 3 includes a cylindrical support portion 31 and a base portion 32. The cylindrical support portion 31 is a portion on the tip end side in the directivity axis direction of the elastic support member 3 and is configured to elastically support the microphone housing 20 while accommodating the microphone housing 20. The base portion 32 is a portion on the base end side in the directivity axis direction of the elastic support member 3 and is fixed to the sensor housing 6. According to the present embodiment, the elastic support member 3 is seamlessly integrally formed by silicone rubber or the like.

[0038] In the assembled state, a tip end portion of the cylindrical support portion 31 is sandwiched between an inner peripheral surface of the mounting hole V33 in the front bumper V3 and the outer peripheral surface 20h of the microphone housing 20 while being inserted into the mounting hole V33. An engaging protrusion 33, which protrudes toward an inner side in a radial direction, is provided on the base end side on an inner peripheral surface of the cylindrical support portion 31. The radial direction is a direction orthogonal to the directivity axis direction and is a direction extending radially from the directivity axis DA. The engaging protrusion 33 is formed to engage with the engaging groove 20k provided in the microphone housing 20.

[0039] A fixing protrusion 34 is provided in a base end portion on an outer peripheral surface of the base portion 32. The fixing protrusion 34 is formed to protrude toward the outside in the radial direction. Further, a fixing groove 35 is formed at a position adjacent to the fixing protrusion 34 in the directivity axis direction on the outer peripheral surface of the base portion 32. That is, the fixing groove 35 is provided farther toward the tip end side in the directivity axis direction than the fixing protrusion 34. The fixing protrusion 34 and the fixing groove 35 extend in the circumferential direction. The circumferential direction is a circumferential direction of a circle within a virtual plane, a center of which is an intersection point between the virtual plane orthogonal to the directivity axis direction and the directivity axis DA. (Detection electrode and protective electrode)

[0040] The external electrode 4 is external to the ultrasonic microphone 2. According to the present embodiment, a detection electrode 41 and a guard electrode 42 are provided as the external electrode 4. The detection electrode 41 and the guard electrode 42 are formed from a conductor, or more specifically, from a highly conductive metal. The detection electrode 41 and the guard electrode 42 are provided in positions different from that of the reference electrode 21c in the in-plane direction.

[0041] The detection electrode 41, which serves as a second electrode, is provided so that an electrical characteristic between the detection electrode 41 and the reference electrode 21C changes based on an adhesion state of substances S adhering to the detection surface 20d of the ultrasonic microphone 2. Here, the electrical characteristic may be, specifically, an impedance, a current, or an electrostatic capacitance. According to the present embodiment, the electrical characteristic is typically the electrostatic capacitance. Specifically, in the assembled state, the detection electrode 41 is provided near the microphone housing 20 so as to be close to the detection surface 20d of the ultrasonic microphone 2 in the directivity axis direction and the radial direction.

[0042] According to the present embodiment, the detection electrode 41 is formed as a thin sheet or film that is flat and has a thickness direction in the directivity axis direction. The detection electrode 41 is provided along the bumper rear surface V32 of the front bumper V3. That is, in the assembled state, the detection electrode 41 is arranged near the mounting hole V33 while facing the bumper rear surface V32 in a closely adhering state. Further, the detection electrode 41 is provided on an outer side of the microphone housing 20 in the radial direction. Specifically, the detection electrode 41 is formed in a ring shape surrounding the mounting hole V33 from a front view in the assembled state.

[0043] The protective electrode 42, which serves as a third electrode, is provided to suppress changes in the electrical characteristics between the reference electrode 21c and the detection electrode 41 caused by factors other than the adhesion of substances S to the detection surface 20d. The electrical characteristics may also be, for example, impedance, current, or electrostatic capacitance. According to the present embodiment, the electrical characteristic is typically electrostatic capacitance.

[0044] The guard electrode 42 is provided on the outside in the radial direction of the microphone housing 20. Further, the guard electrode 42 extends in the directivity axis direction along the diaphragm support portion 20b. Specifically, according to the present embodiment, the guard electrode 42 is a thin foil or thin film member having a thickness direction in the radial direction. The guard electrode 42 is formed in a cylindrical shape or a partially circular cylindrical shape surrounding the directivity axis DA and extending in the directivity axis direction. The guard electrode 42 is arranged to face the outer peripheral surface 20h of the microphone housing 20 via the elastic support member 3.

[0045] The guard electrode 42 is provided to be located between the reference electrode 21c and the detection electrode 41. Specifically, the guard electrode 42 is arranged farther outward in the radial direction than the reference electrode 21c. Further, the guard electrode 42 is arranged farther inward in the radial direction than the detection electrode 41. That is, according to the present embodiment, the guard electrode 42 is provided between the reference electrode 21c and the detection electrode 41 in the radial direction. Further, according to the present embodiment, the guard electrode 42 is arranged farther toward the base end side than the detection electrode 41 in the directivity axis direction.In this way, the guard electrode 42 is provided in a region farther toward the base end side than the bumper outer surface V31 in the directivity axis direction to provide a guard electrode function between the reference electrode 21c and the detection electrode 41. Furthermore, the guard electrode 42 is arranged to be separated from an inner edge in the radial direction of the detection electrode 41 so as not to be in direct contact with or short-circuited by the detection electrode 41. (circuit configuration)

[0046] The electrical circuit unit 5 includes a circuit board 50, a driver wiring 51, a detection wiring 52, and a protection wiring 53. The circuit board 50 and the driver wiring 51 are housed within the sensor housing 6. Portions on the base end side of the detection wiring 52 and the protection wiring 53 are housed within the sensor housing 6. Here, to prevent the drawings from becoming complicated, the illustration of the driver wiring 51, the detection wiring 52, and the protection wiring 53 is partially omitted.

[0047] One end of the driver wiring 51 is electrically connected to the circuit board 50 through a first connector C1. Another end of the driver wiring 51 is electrically connected to the vibrating element 21. That is, the driver wiring 51 is provided to apply a drive voltage to the vibrating element 21.

[0048] One end of the detection wiring 52, which configures a power supply path to the detection electrode 41, is electrically connected to the circuit board 50 through a second connector C2. Another end of the detection wiring 52 is electrically connected to the detection electrode 41. According to the present embodiment, the detection wiring 52 is provided to connect the conductor portion 20n, as shown in Fig. 3 is shown, in a section thereof.

[0049] One end of the protective wiring 53, which configures a power supply path to the protective electrode 42, is electrically connected to the circuit board 50 through a third connector C3. Another end of the protective wiring 53 is electrically connected to the protective electrode 42.

[0050] A control circuit device 54 is mounted in the circuit board 50. The control circuit device 54 is a so-called single-chip microcomputer that includes a CPU, an analog-to-digital converter (A / D converter), a digital-to-analog converter (D / A converter), and the like. The control circuit device 54 is provided to control operations of the ultrasonic sensor 1. CPU is an abbreviation for Central Processing Unit.

[0051] Fig. Fig. 4 shows a schematic circuit configuration of the ultrasonic sensor 1 according to the present embodiment, along with a functional configuration implemented in the control circuit device 54, which is the single-chip microcomputer. As shown in Fig. 4, the control circuit device 54 includes a control unit 54a, a signal transmission / reception unit 54b, and an impedance acquisition unit 54c.

[0052] The control unit 54a is provided to perform an object detection operation for detecting an object in the vicinity of the ultrasonic sensor 1 when a predetermined object detection condition is met. For example, the object detection condition may include a gear position of the vehicle V in which the ultrasonic sensor 1 is mounted being a travel-enabled position, a vehicle speed of the same vehicle V being less than a predetermined value, and the like.

[0053] Specifically, the control unit 54a is provided to transmit and receive signals to and from the signal transceiver unit 54b. That is, the control unit 54a controls a transmission / reception operation of ultrasonic waves in the ultrasonic microphone 2 by controlling the operation of the signal transceiver unit 54b.

[0054] The signal transceiver unit 54b is electrically connected to the vibrating element 21 to transmit and receive electrical signals including a drive signal and an output voltage signal to and from the vibrating element 21. That is, the signal transceiver unit 54b is provided to input the drive signal to the vibrating element 21 and receive the output voltage signal from the vibrating element 21.

[0055] The signal transmission-reception unit 54b includes a transmission circuit 54d and a reception wave processing circuit 54e. The transmission circuit 54d is electrically connected to the vibration element 21. The transmission circuit 54d is configured to cause the vibration element 21 to perform a transmission operation of an ultrasonic band test wave by inputting the drive signal to the vibration element 21.

[0056] The received wave processing circuit 54e is electrically connected to the vibrating element 21. The received wave processing circuit 54e is configured to perform signal processing such as amplifying the output voltage signal generated by the vibrating element 21 as a result of the diaphragm portion 20a being excited. Specific circuit configurations of the transmitting circuit 54d and the received wave processing circuit 54e are well known. Therefore, further descriptions of the transmitting circuit 54d and the received wave processing circuit 54e are omitted in this specification.

[0057] The control unit 54a is provided to detect the presence / absence of adhering substances S using the impedance acquisition unit 54c at a time when the object detection operation is not being performed. Specifically, the control unit 54a is provided to be able to send and receive signals to and from the impedance acquisition unit 54c. The impedance acquisition unit 54c includes a driver circuit 54f, a protective voltage application unit 54g, and a receiver circuit 54h.

[0058] An ungrounded output terminal of the driver circuit 54f is electrically connected to the detection electrode 41 through the detection wiring 52. That is, the driver circuit 54f is provided to output a power supply voltage for obtaining an impedance between the reference electrode 21c and the detection electrode 41.

[0059] Furthermore, the ungrounded output terminal of the driver circuit 54f is electrically connected to the protective electrode 42 through the protective wiring 53 and the protective voltage application unit 54g. The protective wiring 53 is provided between the protective electrode 42 and the protective voltage application unit 54g to electrically connect the protective electrode 42 and the protective voltage application unit 54g.

[0060] The protective voltage application unit 54g is provided to supply power to the protective electrode 42 while performing circuit isolation between the protective electrode 42 and the driver circuit 54f. Specifically, according to the present embodiment, the protective voltage application unit 54g is configured by a voltage follower. Thus, the impedance acquisition unit 54c is configured such that the detection electrode 41 and the protective electrode 42 have the same potential when power is supplied to the detection electrode 41 and the protective electrode 42.

[0061] Furthermore, the ungrounded output terminal of the driver circuit 54f is electrically connected to the receiver circuit 54h. The receiver circuit 54h includes a known integration circuit or the like and is configured to generate an output corresponding to the impedance between the reference electrode 21c and the detection electrode 41. An acquisition principle, that is, measurement of the impedance, and specific circuit configurations of the driver circuit 54f and the receiver circuit 54h are known. Therefore, further descriptions are omitted in the present specification.

[0062] As described above, the impedance acquisition unit 54c is provided to acquire the impedance between the reference electrode 21c and the detection electrode 41. Further, the control unit 54a is provided to acquire changes in the acquired impedance and detect the adhesion of substances S adhering to the detection surface 20d based on the changes. That is, the ultrasonic sensor 1 according to the present embodiment is configured to detect the adhesion of substances S adhering to the detection surface 20d based on the electrical characteristic, that is, the electrostatic capacitance, between the reference electrode 21c and the detection electrode 41. (Housing)

[0063] Again according to Fig. 2, the sensor housing 6, which configures a housing of the ultrasonic sensor 1, is integrally formed of a hard insulating resin such as polybutylene terephthalate. Specifically, a housing main body 61, which forms a main portion of the sensor housing 6, includes a plate receiving portion 62 and a protrusion portion 63. The plate receiving portion 62 and the protrusion portion 63 are seamlessly formed integrally.

[0064] The disk receiving portion 62 is formed in a bathtub-like shape, that is, a box shape open toward the base end side in the directivity axis direction. The protrusion portion 63 is a substantially circular cylindrical portion having a center axis parallel to the directivity axis direction and protruding toward the tip end side in the directivity axis direction from the disk receiving portion 62. The housing main body 61 is formed such that a space on an inner side of the disk receiving portion 62 and a space on an inner side of the protrusion portion 63 communicate with each other.

[0065] The circuit board 50 is housed in the board receiving portion 62. The spaces within the board receiving portion 62 and the protrusion portion 63 are filled with a sealing resin 64. The sealing resin 64 is formed from a silicone rubber resin, which has high insulating properties, a low dielectric constant, chemical stability, and weather resistance.

[0066] The protrusion portion 63 is configured to retain the elastic support member 3 at a tip end portion in the direction of the directivity axis. Specifically, a support groove 65 and a support projection 66 are provided in the tip end portion on an inner peripheral surface of the protrusion portion 63. The support groove 65 is configured to engage with the fixing projection 34 of the elastic support member 3. The support projection 66 is configured to engage with the fixing groove 35 of the elastic support member 3.

[0067] The damping member 7 is a disc-shaped member and has an outer diameter corresponding to an inner diameter of the elastic support member 3. That is, the damping member 7 is fitted into a cylindrical space on the inner side of the elastic support member 3 in the directivity axis direction further toward the base end side as a portion that elastically supports the ultrasonic sensor 1. The damping member 7 is formed by a foamed elastic body, such as foamed silicone, which has insulating properties and elasticity to suppress vibration transmission from the ultrasonic sensor 1 to the sensor case 6. (assembly components)

[0068] The auxiliary component 8 is formed of a hard insulating resin such as polybutylene terephthalate. The auxiliary component 8 is a component used to mount the ultrasonic sensor 1 to the vehicle V and is formed as a component separate from the sensor housing 6. That is, the auxiliary component 8 is configured to hold the ultrasonic sensor 1 to the front bumper V3 by being fixed to the front bumper V3 and the sensor housing 6 in the mounted state. Specifically, the auxiliary component 8 includes a holding portion 81 and a flange portion 82.

[0069] The holding portion 81 is formed in a substantially circular cylindrical shape surrounding the protrusion portion 63 of the sensor housing 6 and the elastic support member 3. That is, the holding portion 81 is provided to hold the protrusion portion 63 of the sensor housing 6 and the elastic support member 3. The flange portion 82 extends toward the outside in the radial direction from the tip end portion of the holding portion 81. The flange portion 82 is fixed to the bumper rear surface V32 by an adhesive layer (not shown) such as a double-sided adhesive tape in a portion that is on the outside in the radial direction.

[0070] According to the present embodiment, the detection electrode 41 is provided in the auxiliary component 8. Specifically, the detection electrode 41 is fixed on one side of the bumper counter surface 83 of the flange portion 82 so as to be flush with the bumper counter surface 83, which is a surface of the flange portion 82 opposite the bumper rear surface V32 in the assembled state. That is, the detection electrode 41 is received or embedded in an annular recessed portion 84, which is a shallow groove formed in the bumper counter surface 83. Further, the detection electrode 41 is arranged in a position toward the inside in the radial direction of the flange portion 82.

[0071] Furthermore, according to the present embodiment, the protective electrode 42 is provided in the auxiliary component 8. Specifically, the protective electrode 42 is fixed on one side of an inner peripheral surface 85 so as to be flush with the inner peripheral surface 85, which is a circular cylindrical surface of the holding portion 81. That is, the protective electrode 42 is housed or embedded in a cylindrical recessed portion 86, which is a shallow groove formed in the inner peripheral surface 85. Further, the protective electrode 42 is arranged at a position toward the tip end side in the directivity axis direction of the holding portion 81. (Operation overview)

[0072] An overview of operations of the configuration according to the present embodiment will be described below according to the drawings, along with effects achieved by the configuration. Here, the following operation examples are merely examples for briefly describing the present embodiment.

[0073] After an ignition switch of the vehicle V is turned on at time t0, until the object detection condition at time t1 is satisfied, neither transmission of a test wave from the ultrasonic sensor 1 nor reception of a reflection wave by the ultrasonic sensor 1 is performed. When the object detection condition is satisfied at time t1, the object detection operation is performed by the ultrasonic sensor 1, which performs transmission of the test wave and reception of the reflection wave. Subsequently, when the object detection condition is no longer satisfied at time t2 as a result of the vehicle speed increasing, the object detection operation is stopped. Then, when the object detection condition is satisfied again at time t3 as a result of the vehicle speed decreasing for parking, transmission of a test wave and reception of a reflection wave are restarted.

[0074] According to the present embodiment, an adherent substance detection operation is not performed during time t1 to t2, which is a time when the object detection condition is satisfied and the object detection operation is performed. The adherent substance detection operation is an operation for detecting the presence / absence of substances S adhering to the ultrasonic sensor 1. Similarly, at time t3 and thereafter, the adherent substance detection operation is not performed until the object detection condition is no longer satisfied again.

[0075] Meanwhile, the adherent substance detection operation is performed from time t0 to t1 and / or from t2 to t3, which are periods during which the object detection operation is not performed. That is, according to the present embodiment, the adherent substance detection operation is performed during a period during which the transmission of a probe wave and the reception of a reflection wave are not performed. Accordingly, the adherent substance detection can be performed while maintaining a favorable object detection accuracy.

[0076] According to Fig. 1 and Fig. 2, the ultrasonic sensor 1 is typically mounted on the front bumper V3 such that the directivity axis direction is substantially orthogonal to a vehicle height direction. Therefore, a component parallel to the vibration direction of the diaphragm portion 20a is hardly generated in a gravitational force acting on the substances S adhering to the sensing surface 20d of the microphone housing 20.

[0077] Therefore, in the ultrasonic microphone 2, the impedance of an equivalent circuit for mechanical vibrations hardly changes depending on the presence / absence of the adhering substances S. Particularly, in cases where the adhering substances S are lightweight substances such as snow or water, the impedance of the equivalent circuit for mechanical vibrations changes very little depending on the presence / absence of the adhering substances S. Therefore, adhesion of lightweight substances such as snow and water is difficult to detect by the equivalent circuit for mechanical vibrations. Furthermore, adhesion of lightweight substances such as snow and water is difficult to detect by a conventionally known method for detecting an adherent substance for substances adhering to the ultrasonic sensor 1 using a reverberation time.

[0078] In this regard, in the configuration according to the present embodiment, the electrical characteristics, or specifically, the electrostatic capacitance, between the reference electrode 21c and the detection electrode 41 changes based on the adhesion state of substances S adhering to the detection surface 20d. Thus, the control unit 54a acquires the impedance between the reference electrode 21c and the detection electrode 41. Consequently, the changes in the electrostatic capacitance between the reference electrode 21c and the detection electrode 41 are acquired. Consequently, as a result of this configuration, the presence / absence of adhering substances S can be detected based on the changes in the electrical characteristics, that is, the electrostatic capacitance, between the reference electrode 21c and the detection electrode 41.

[0079] As a result of the configuration according to the present embodiment, the presence / absence of adhesion of adhering substances S can be accurately detected even when a component parallel to the vibration direction of the diaphragm portion 20a is hardly generated in the gravitational force acting on the substances S adhering to the detection surface 20d. Furthermore, as a result of this configuration, even when the adhering substances S are lightweight substances such as snow or water, the presence / absence of adhesion of adhering substances S can be accurately detected.

[0080] Here, as the method for detecting an adhered substance, for substances S adhering to the ultrasonic sensor 1, a method using a resistance value between electrodes can be considered. However, this method is difficult to apply due to oxidation of the electrodes, preventing electric shock to nearby persons, design issues, and the like. In fact, an insulating film is usually formed on the surface of the microphone housing 20 as in the present embodiment to prevent corrosion and the like.

[0081] In this regard, as a result of this configuration, according to the present embodiment, the presence / absence of adhering substances S can be detected based on the changes in electrostatic capacitance between the reference electrode 21c and the detection electrode 41. Therefore, as a result of this configuration, even when the insulating film is formed on the surface of the microphone housing 20, the presence / absence of the adhesion of adhering substances S can be accurately detected.

[0082] As described above, as a result of the method of detecting an adhered substance based on the changes in the electrical characteristic, that is, the electrostatic capacitance between the reference electrode 21c and the detection electrode 41 according to the present embodiment, the presence / absence of the adhesion of adhered substances S can be detected more accurately than by other methods. However, the electrical characteristic between the reference electrode 21c and the detection electrode 41 may change as a result of factors other than the adhesion of substances S adhering to the detection surface 20d. Therefore, the following problem can be considered.

[0083] For example, when the adhering substance S is water, the adhesion state on the sensing surface 20d can be released in a relatively short amount of time by gravitational force, evaporation, or the like. In contrast, when the adhering substance S is snow, the duration of the adhesion state is relatively long. Therefore, detecting the adhesion of snow is more important than detecting the adhesion of water.

[0084] In this regard, a relative dielectric constant of water is about 80. Meanwhile, the relative dielectric constant of snow is about 3. Therefore, for example, in a configuration where the protective electrode 42 is not present, the changes in electrostatic capacitance between the reference electrode 21c and the detection electrode 41 are larger when condensation forms on the bumper rear surface V32 side than when snow adheres to the detection surface 20d.

[0085] Similarly, gaps into which water can penetrate exist at two locations between the holding portion 81 of the auxiliary component 8 and the microphone housing 20. Specifically, water can penetrate between the outer peripheral surface 20h of the microphone housing 20 and the elastic support member 3. Furthermore, water can penetrate between the elastic support member 3 and the holding portion 81. The changes in electrostatic capacitance between the reference electrode 21c and the detection electrode 41 are greater when water penetrates these gaps than when snow adheres to the detection surface 20d.

[0086] Furthermore, a wiring harness may be present inside the components that configure the exterior of the vehicle V, including the front bumper V3. The wiring harness may move and vibrate irregularly during travel of the vehicle V. A parasitic capacitance between the reference electrode 21c and the detection electrode 41 may change along with the movement or vibration.

[0087] In this regard, in the configuration according to the present embodiment, the guard electrode 42 is provided together with the detection electrode 41. The guard electrode 42 is provided to suppress changes in the electrical characteristics (i.e., electrostatic capacitance) between the reference electrode 21c and the detection electrode 41 caused by factors other than the adhesion of substances S to the detection surface 20d. That is, the guard electrode 42 is provided to be located between the reference electrode 21c and the detection electrode 41.

[0088] Here, "located between" refers to the protection electrode 42 being electrostatically interposed to suppress changes in electrical characteristics between the reference electrode 21c and the detection electrode 41 caused by factors such as water or the wiring harness on the inside of the components that configure the outer shell of the vehicle V. Therefore, the protection electrode 42 does not necessarily need to be arranged on a virtual line connecting the reference electrode 21c and the detection electrode 41 from a cross-sectional side view, as long as the protection electrode 42 is located between the reference electrode 21c and the detection electrode 41 to achieve the protection electrode function.

[0089] Fig. 5 shows simulation conditions for verifying the effects achieved by the configuration according to the present embodiment through computer simulation. In the present simulation, the following changes are made to the above-described configuration to simplify calculation conditions. First, as in a modification described below, the entire microphone housing 20, made of a highly conductive metal such as aluminum, serves as the reference electrode 21c. Further, the detection electrode 41 is exposed on the outer surface of the vehicle V. Furthermore, the entire side of the reference electrode 21c is covered with the protective electrode 42.

[0090] In a Fig. 5, an entire region having a substantially circular columnar shape configuring the microphone housing 20 was set, that is, the reference electrode 21c was set to 0 V. Further, the detection electrode 41 and the guard electrode 42 were set to 1 V. Further, the electrostatic capacitance between the reference electrode 21c and the detection electrode 41 was calculated for the following three situations. Situation 1: no adhering substance; Situation 2: Snow S1 adheres to the detection surface 20d; and Situation 3: Water S2 adheres to the auxiliary component 8.

[0091] Fig. Figure 6A shows simulation results when the protective electrode 42 is not present. Fig. Figure 6AB shows simulation results when the protective electrode 42 is present. In Fig. 6A and Fig. 6B, SIT1 indicates situation 1, SIT2 indicates situation 2, and SIT3 indicates situation 3. Furthermore, a vertical axis CA indicates the electrostatic capacity.

[0092] As in Fig. 6A, when the protective electrode 42 is not present, the changes in the electrostatic capacity with respect to the adhesion of water S2 on the back of the auxiliary component 8 are larger than with respect to the adhesion of snow S1 on the detection surface 20d. In contrast, as shown in Fig. 6B, when the protective electrode 42 is present, the changes in electrostatic capacity are larger with respect to the adhesion of snow S1 to the sensing surface 20d than the adhesion of water S2 to the back of the auxiliary component 8.

[0093] As described above, in the configuration according to the present embodiment, the changes in the electrical characteristics between the reference electrode 21c and the detection electrode 41 caused by water in the event of condensation and the like occurring on the bumper rear surface V32 can be advantageously suppressed. Furthermore, as a result of this configuration, effects on the parasitic capacitance through the wire harness can be advantageously suppressed. Therefore, as a result of this configuration, detection of an adhered substance can be performed with even more advantageous accuracy using the changes in the electrical characteristics, that is, the electrostatic capacitance, between the reference electrode 21c and the detection electrode 41.

[0094] In the configuration according to the present embodiment, the guard electrode 42 is provided to have the same potential as the detection electrode 41. Therefore, the power supply to the detection electrode 41 and the guard electrode 42 can be simplified. Furthermore, as a result of the reference electrode 21c having the same potential as the ground of the vehicle body V1, acquisition of the electrical characteristic, that is, the electrostatic capacity, can be stably performed.

[0095] In the configuration according to the present embodiment, the detection electrode 41 and the guard electrode 42 are provided in the auxiliary component 8, which is a component used to mount the ultrasonic sensor 1 on the vehicle V. Therefore, special processing for attaching the detection electrode 41 and the guard electrode 42 is not required. Therefore, as a result of this configuration, the configuration for detecting the adhered substances S is realized through mounting processing similar to that of the conventional ultrasonic sensor 1. Furthermore, positional relationships between the reference electrode 21c, the detection electrode 41, and the guard electrode 42 can be stabilized.Accordingly, the detection of an adhered substance can be carried out with even more advantageous accuracy by using the changes in the electrical characteristic between the reference electrode 21c and the detection electrode 41.

[0096] In the configuration according to the present embodiment, the detection electrode 41 is provided along the bumper back surface V32. Further, the guard electrode 42 is provided along the diaphragm support portion 20b. In this configuration, even when condensation occurs along the bumper back surface V32, the effects of changes in electrostatic capacitance associated with the condensation can be advantageously suppressed by the guard electrode 42. Furthermore, even when condensation occurs along the diaphragm support portion 20b, the effects of changes in electrostatic capacitance associated with the condensation can be advantageously suppressed by the guard electrode 42.Furthermore, effects on the changes in electrostatic capacity associated with the penetration of water between the holding portion 81 of the auxiliary component 8 and the microphone housing 20 can advantageously be suppressed by the protective electrode 42.

[0097] In the configuration according to the present embodiment, the diaphragm portion 20a is formed in a shape having the long direction (long side) and the short direction (short side) on a plane orthogonal to the directivity axis DA. Furthermore, the conductor portion 20n, which configures the power supply path to the detection electrode 41, is provided in the thick portion 20f, which is the portion along the long direction (long side) of the diaphragm support portion 20b.

[0098] The thick portion 20f has less impact on the vibration characteristics of the diaphragm portion 20a as a result of providing a groove or an add-on than the thin portion 20g. Therefore, the engagement groove 20k is provided in the thick portion 20f rather than the thin portion 20g. Similarly, the conductor portion 20n that configures the power supply path to the detection electrode 41 is also provided in the thick portion 20f rather than the thin portion 20g. Consequently, as a result of this configuration, manufacturing costs for providing the power supply path to the detection electrode 41 can be advantageously reduced while suppressing the effects on the vibration characteristics of the diaphragm portion 20a as much as possible. (Modifications)

[0099] The present disclosure is not limited to the above-described embodiment. Therefore, appropriate modifications can be made to the above-described embodiment. Typical modifications will be described below. In the following descriptions of the modifications, differences from the above-described embodiment will be mainly described. In addition, portions according to the above-described embodiment and in the modifications that are identical or equivalent to each other are denoted by the same reference numerals. Therefore, in the descriptions of the following modifications, with respect to the constituent elements whose reference numerals are the same as those in the above-described embodiment, the descriptions according to the above-described embodiment apply unless there are technical inconsistencies or additional descriptions are particularly given.

[0100] The components of the vehicle body V1 on which the ultrasonic sensor 1 is mounted are not limited to the front bumper V3 and the rear bumper V4. For example, the ultrasonic sensor 1 can also be mounted on the vehicle body panel V2. In this case, the detection electrode 41 can be provided along the vehicle body panel V2.

[0101] The mounting target of the ultrasonic sensor 1 is not limited to the vehicle V. That is, the ultrasonic sensor 1 can be mounted, for example, on conveyor equipment provided in factories and the like, on agricultural equipment (such as cultivators), on aircraft, and the like.

[0102] The ultrasonic sensor 1 is not limited to a so-called transmit / receive configuration. That is, the ultrasonic sensor 1 designed to transmit probe waves and the ultrasonic sensor 1 designed to receive reflected waves can be mounted separately on the vehicle V. The present disclosure can be preferably applied to cases such as these.

[0103] According to the above-described embodiment, the microphone housing 20 is seamlessly and integrally formed from an insulating resin. However, the present disclosure is not limited to this mode. For example, the microphone housing 20 may be configured such that the diaphragm portion 20a and the diaphragm support portion 20b, which are formed as separate parts, are joined. In this case, the diaphragm portion 20a and the diaphragm support portion 20b may be formed of the same material or different materials.

[0104] The entire microphone housing 20 or a portion thereof may be formed of a conductive or semiconductive material. Specifically, for example, at least the diaphragm portion 20a of the microphone housing 20 may be formed of a highly conductive metal such as aluminum. In this case, the reference electrode 21c according to the above-described embodiment, which serves as the first electrode, may be integrated with the microphone housing 20. "Integrated" in this case is not limited to two components being joined together. That is, "integrated" also includes two components being fused together, or in other words, a single element being used as two components.

[0105] Specifically, for example, the reference electrode 21c can be integrated with the microphone housing 20 by connecting it to the diaphragm portion 20a with a conductive adhesive. That is, the reference electrode 21c can be grounded by electrically connecting it to the diaphragm portion 20a with a conductive adhesive. In this configuration, a joined body of the reference electrode 21c and the diaphragm portion 20a can function as the first electrode.

[0106] Alternatively, the diaphragm portion 20a can be used as both the ground-side electrode of the vibrating element 21 and the first electrode for detecting an adhered substance. That is, the diaphragm portion 20a, which is considered the same as the reference electrode 21c, can function as the first electrode. In this case, the piezoelectric body 21a can be attached to the element fixing surface 20e of the diaphragm portion 20a with an adhesive.

[0107] An example in which the entire microphone housing 20 is formed by a highly conductive metal such as aluminum will be described. In this example, as in Fig. 7, the microphone housing 2 is integrated with the reference electrode 21c as the one that configures the reference electrode 21c.

[0108] That is, according to Fig. 7, in the present modification, the microphone housing 20 is seamlessly and integrally formed from a highly conductive metal such as aluminum. In this case, the piezoelectric body 21a can be attached to the element fixing surface 20e of the diaphragm portion 20a using a conductive adhesive.

[0109] As a result of this configuration, the microphone housing 20 can be used as the first electrode. Therefore, the electrical characteristics, that is, the electrostatic capacitance, between the microphone housing 20, which serves as the first electrode, and the detection electrode 41 can be stably obtained. Furthermore, the microphone housing 20 can be used as both the first electrode and the ground-side electrode of the vibration element 21. Consequently, a reduction in manufacturing costs is achieved by reducing the number of components.

[0110] The vibration element 21 is not limited to the piezoelectric element. For example, the ultrasonic microphone 2 may have an electrostatic capacitance type microphone configuration.

[0111] The configuration of the detection electrode 41 is also not limited to the specific example described above. That is, for example, the shape of the detection electrode 41 is not limited to the foil shape or the film shape, and may be a mesh shape, a rod shape, a coil shape, or the like. Further, as a result of the detection electrode 41 being arranged in a substantially central portion in the thickness direction of the flange portion 82, the detection electrode 41 may be embedded within the flange portion 82. In other words, the detection electrode 41 may be arranged so as to be separated from the bumper opposing surface 83 of the flange portion 82 in the directivity axis direction.

[0112] A plurality of detection electrodes 41 may be arranged or lined up in a predetermined direction (such as the in-plane direction). Specifically, for example, a plurality of detection electrodes 41 arranged or lined up in the radial direction and / or the circumferential direction may be provided so that they are not conductive with each other. In this case, the control unit 54a can detect the presence / absence of adhering substances S and adhesion positions based on changes in the electrical characteristics (i.e., the electrostatic capacitance) between each of the plurality of detection electrodes 41 and the reference electrode 21c.

[0113] According to the above-described embodiment, both the detection electrode 41 and the guard electrode 42 are provided in the auxiliary component 8. However, the present disclosure is not limited to this mode. For example, only one of the detection electrode 41 and the guard electrode 42 may be provided in the auxiliary component 8.

[0114] The detection electrode 41 does not need to be provided in the auxiliary component 8. For example, the detection electrode 41 may be fixed to the bumper rear surface V32. Specifically, for example, the detection electrode 41 may be embedded around the mounting hole V33 of the front bumper V3. Alternatively, the detection electrode 41 may be a portion of the front bumper V3 formed by a conductive filler added to a portion of the front bumper V3 facing the mounting hole V33.

[0115] The detection electrode 41 may be provided in the elastic support member 3. That is, for example, the annular detection electrode 41 may be embedded in the tip end portion in the directivity axis direction of the elastic support member 3. Alternatively, for example, as a result of the entire elastic support member 3 or at least the tip end portion in the directivity axis direction being conductive, the entire elastic support member 3 or at least the tip end portion in the directivity axis direction may be used as the detection electrode 41. As described above, the shape of the detection electrode 41 is not limited to a specific shape. Any shape other than the annular shape may be used.

[0116] In the specific example described above, the fact that the guard electrode 42 is provided to have the same potential as the detection electrode 41 does not mean that the potentials of both are the same as a result. That is, for example, as long as both are powered by being electrically connected to a common power source through wiring, a slight potential difference may exist between them. Further, the guard electrode 42 may be provided to have the same potential as the reference electrode 21c or the microphone housing 20 serving as the first electrode. In this case, the guard electrode 42 may be grounded. Even in this case, the same potential does not mean that the potentials are completely the same. Accordingly, the same potential may also be referred to as substantially the same potential.

[0117] The configuration of the protective electrode 42 is also not limited to the specific example described above. For example, the shape of the protective electrode 42 is not limited to a foil or film shape, and may be a mesh shape, a rod shape, a coil shape, or the like. Furthermore, a plurality of protective electrodes 42 may be arranged or lined up in a predetermined direction, such as the directivity axis direction and / or the circumferential direction.

[0118] The protective electrode 42 does not need to be provided in the auxiliary component 8. For example, the protective electrode 42 may be fixed to the outer peripheral surface 20h of the diaphragm support portion 20b, which is formed of an insulating material. Alternatively, the protective electrode 42 may be connected to the outer peripheral surface 20h of the diaphragm portion 20b, which is formed of a conductive material, via an insulating layer.

[0119] The protective electrode 42 can be provided in the elastic support member 3. Even with this configuration, no special processing is required for setting the protective electrode 42. Specifically, for example, the annular or circular-cylindrical protective electrode 42 having a central axis along the directivity axis direction can be embedded in the elastic support member 3 made of an insulating synthetic resin. Alternatively, for example, as a result of the elastic support member 3 or a portion thereof being formed of a conductive rubber, the entire elastic support member 3 or a portion thereof can be used as the protective electrode 42.

[0120] The guard electrode 42 may be provided along the detection electrode 41. That is, as shown in Fig. 8 and Fig. 9, the protective electrode 42 may be laminated to the detection electrode 41 by means of an insulating layer 87. Here, in the examples in Fig. 8 and Fig. 9 the entire microphone housing 20 by a highly conductive metal such as aluminum in a similar manner to that in the example of Fig. 7 trained.

[0121] In the example of Fig. 8, the detection electrode 41 is formed as a thin plate or a thin film that is flat and has a thickness direction in the direction of the directivity axis. That is, the detection electrode 41 is provided along the bumper rear surface V32 of the front bumper V3. Specifically, in the mounted state, the detection electrode 41 is arranged near the mounting hole V33 while facing the bumper rear surface V32 in a closely adhering state.

[0122] The protective electrode 42 is formed as a thin foil or film. The protective electrode 42 has a substantially U-shaped configuration that surrounds the detection electrode 41 from the base end side in the directivity axis direction when viewed in a cross-sectional view on a plane including the directivity axis DA. Specifically, the protective electrode 42 includes a ring electrode portion 421, an inner protrusion portion 422, and an outer protrusion portion 423.

[0123] The ring electrode portion 421 is a thin foil or thin film portion having a thickness direction in the directivity axis direction and is arranged parallel to the detection electrode 41. The inner protrusion portion 422 protrudes toward the tip end side in the directivity axis direction from an inner edge in the radial direction of the ring electrode portion 42. The inner protrusion portion 422 is provided such that a tip end in the directivity axis direction extends to a position flush with the bumper counter surface 83, further toward the inside in the radial direction than the detection electrode 41. The outer protrusion portion 423 protrudes toward the tip end side in the directivity axis direction from an outer edge in the radial direction of the ring electrode portion 421.The outer protrusion portion 423 is provided such that a tip end in the directivity axis direction extends to a position flush with the bumper counter surface 83, further outward in the radial direction than the detection electrode 41.

[0124] The insulating layer 87 is provided between the detection electrode 41 and the guard electrode 42. That is, the insulating layer 87 has a substantially U-shaped form, covering the detection electrode 41 from the base end side in the directivity axis direction from a cross-sectional view on a plane including the directivity axis DA. The insulating layer 87 is formed by an insulating resin constituting the auxiliary component 8.

[0125] In this configuration, the positional relationship between the detection electrode 41 and the guard electrode 42 can be fixed as a result of the guard electrode 42 being firmly laminated to the detection electrode 41 by means of the insulating layer 87. Furthermore, a joined body of the detection electrode 41, the insulating layer 87, and the guard electrode 42 is fixedly supported by the flange portion 82 of the auxiliary component 8. Accordingly, as a result of this configuration, a detection error caused by an assembly error and the like can be advantageously suppressed.

[0126] Fig. 9 shows an example in which the connected body of the detection electrode 41, the insulating layer 87 and the protective electrode 42, the in Fig. 8 is supported in a fixed manner by the holding portion 81 of the auxiliary component 8. That is, the example in Fig. 9 is a partial modification of the configuration in Fig. 8 and a partial modification of the configuration in Fig. 7.

[0127] In the example in Fig. 9, the detection electrode 41 is a thin foil or thin film member having a thickness direction in the radial direction. The detection electrode 41 is formed in a cylindrical shape or a partially circular cylindrical shape surrounding the directivity axis DA and extending in the directivity axis direction. The detection electrode 41 is arranged farther outward in the radial direction than the guard electrode 42. That is, the detection electrode 41 is embedded within the holding portion 81 so as to be arranged at an intermediate position in the thickness direction of the holding portion 81 having a thickness direction in the radial direction.

[0128] The guard electrode 42 is a thin foil or thin film member having a thickness direction in the radial direction. The guard electrode 42 is formed in a cylindrical shape or a partially circular cylindrical shape surrounding the directivity axis DA and extending in the directivity axis direction. The guard electrode 42 is arranged between the microphone housing 20 and the detection electrode 41. Specifically, the guard electrode 42 is fixed on the inner peripheral surface 85 side so as to be flush with the inner peripheral surface 85, which is a circular cylindrical surface of the holding portion 81.

[0129] The insulating layer 87 is a thin foil or thin film portion having a thickness direction in the radial direction. The insulating layer 87 is formed in a cylindrical shape or a partially circular cylindrical shape surrounding the directivity axis DA and extending in the directivity axis direction. The guard electrode 42, the insulating layer 87, and the detection electrode 41 are concentrically arranged or lined up to be in a line toward the outside in the radial direction, in this order. The insulating layer 87 is formed by an insulating resin constituting the auxiliary component 8.

[0130] In this configuration, the positional relationship between the detection electrode 41 and the guard electrode 42 can be fixed as a result of the guard electrode 42 being firmly laminated to the detection electrode 41 by means of the insulating layer 87. Furthermore, a joined body of the detection electrode 41, the insulating layer 87, and the guard electrode 42 is fixedly supported by the holding portion 81 of the auxiliary component 8. Accordingly, as a result of this configuration, a detection error caused by an assembly error and the like can be advantageously suppressed.

[0131] In the configuration shown in Fig. As shown in Figure 9, the protective electrode 42 may be fixed to the outer peripheral surface 20h of the diaphragm portion 20b, which is formed of an insulating material. Alternatively, for example, the protective electrode 42 may be connected to the outer peripheral surface 20h of the diaphragm support portion 20b, which is formed of a conductive material, via an insulating layer. Alternatively, for example, the protective electrode 42 may be provided in the elastic support member 3.

[0132] In Fig. 8 and Fig. 9, the entire microphone housing 20 is covered by a highly conductive metal such as aluminum in a similar manner to that in the example of Fig. 7. However, the present disclosure is not limited to this mode. That is, in the configurations shown in Fig. 8 and Fig. 9, the entire microphone housing 20 or a portion thereof may have isolating properties.

[0133] According to the embodiment described above, the conductor section 20n which is in Fig. 3, is provided to configure a portion of the detection wiring 52. However, the present disclosure is not limited to this mode. That is, for example, the conductor portion 20n may be provided to configure a portion of the protection wiring 53. Alternatively, for example, the conductor portion 20n may be provided to configure a portion of the detection wiring 52 and a portion of the protection wiring 53.

[0134] The control circuit device 54 may be configured by hardware such as an ASIC. ASIC is an abbreviation for Application Specific Integrated Circuit.

[0135] The protective electrode 42 can be used to detect water intrusion or condensation. For example, water intrusion may occur between the support portion 81 of the auxiliary component 8 and the microphone housing 20. Alternatively, condensation may occur along the bumper rear surface V32. As a result of these events, an electrical characteristic, i.e., an electrostatic capacitance, changes between the reference electrode 21c and the protective electrode 42. Here, these events can be advantageously detected as a result of the detected changes in the electrical characteristic.

[0136] As described above, the movement of the wire harness, water intrusion, occurrence of condensation, and the like in an area inside the front bumper V3 become an error factor or a noise component during detection of substances S adhering to the detection surface 20d. The error factor or noise component can be measured using the guard electrode 42.

[0137] Here, the control unit 54a can perform detection of an adhering substance taking into account the changes in the electrical characteristic, that is, the electrostatic capacitance between the reference electrode 21c and the guard electrode 42. That is, the ultrasonic sensor 1 is configured to be able to detect the adhesion of substances S adhering to the detection surface 20d based on the electrical characteristic between the reference electrode 21c and the detection electrode 41 and the electrical characteristic between the detection electrode 41 and the guard electrode 42.

[0138] As a result of this configuration, the control unit 54a acquires the changes in the electrical characteristic, that is, the electrostatic capacitance, between the reference electrode 21c and the detection electrode 41. Furthermore, the control unit 54a acquires the changes in the electrical characteristic, that is, the electrostatic capacitance, between the detection electrode 41 and the guard electrode 42. Then, the control unit 54a detects the adhesion of substances S adhering to the detection surface 20d based on these acquisition results. Consequently, detection of an adhering substance can be performed with even more advantageous accuracy using the changes in the electrical characteristic between the reference electrode 21c and the detection electrode 41.

[0139] As in Fig. 10, the protective electrode 42 serving as the third electrode may be laminated to the microphone housing 20 serving as the first electrode by means of the insulating layer 97. In particular, for example, according to Fig. 10, the protective electrode 42 may be provided along the diaphragm support portion 20b. Furthermore, the protective electrode 42 is provided to cover substantially half of the diaphragm support portion 20b on the base end side in the directivity axis direction. The insulating layer 97 is provided between the protective electrode 42 and the diaphragm support portion 20b. For example, the insulating layer 97 may be formed by an insulating adhesive or the like.

[0140] In this configuration, the positional relationship between the guard electrode 42 serving as the third electrode and the microphone housing 20 configuring the first electrode can preferably be fixed. Thus, a protective effect of the guard electrode 42 can be stably achieved. In addition, since the guard electrode 42 covers substantially half of the microphone housing 20 configuring the first electrode on the base end side in the directivity axis direction, changes in the electrical characteristic due to factors other than the adhesion of substances S adhering to the ultrasonic microphone 2 can be advantageously suppressed. Thus, detection of an adhering substance can be performed with even more advantageous accuracy.

[0141] Here, the configuration in which the first electrode and the third electrode are laminated by means of the insulating layer 97 is not limited to the specific example shown in Fig. 10. This means, for example, in the configuration shown in Fig. 2, a laminated body of the insulating layer 97 and the protective electrode 42 may be provided so as to surround the periphery of the laminated body of the piezoelectric body 21a and the driving electrode 21b.

[0142] In the specific example described above, the adherent substance detection operation is performed by the control circuit device 54, that is, the control unit 54a. Therefore, the control circuit device 54, that is, the control unit 54a, can be evaluated as a detection unit that detects an adhesion state of adherent substances S based on an electrical characteristic between the first electrode and the second electrode. However, the present disclosure is not limited to this mode. That is, for example, the adherent substance detection operation can be performed by an on-board ECU electrically connected to the ultrasonic sensor 1. ECU is an abbreviation for Electronic Control Unit.

[0143] The protective voltage application unit 54g is not limited to the voltage follower. For example, a so-called buffer amplifier can be used as the protective voltage application unit 54g.

[0144] The configuration of the auxiliary component 8 is not particularly limited. That is, the shape and structure of the auxiliary component 8 in the specific example described above are simplified to avoid complexity in description. Accordingly, the present disclosure is not limited to the shape and structure of the auxiliary component 8 in the specific example described above. Thus, for example, the auxiliary component 8 may be a component called a holder or a component called a bezel. Further, the auxiliary component 8 or a portion thereof may be integrated with the sensor housing 6.

[0145] In the above description, a plurality of seamlessly integrated components may be formed by separate components that are attached to one another. Similarly, a plurality of components that are formed by separate components that are attached to one another may be seamlessly integrated with one another.

[0146] In the above description, several components formed of the same material may be formed of different materials. Similarly, several components formed of different materials may be formed of the same material.

[0147] It goes without saying that an element configuring the above-described embodiment is not mandatory unless it is explicitly specified as required, is obviously required, or the like. Furthermore, in cases where a numerical value such as an amount, a numerical value, an amount, or a range of a constituent is mentioned, the present disclosure is not limited to the specific number unless it is explicitly specified as a requirement, is limited in principle to the specific number, or the like.Similarly, in cases where a shape, direction, positional relationship, or the like of a constituent part or the like is mentioned, the present disclosure is not limited to the shape, direction, positional relationship, or the like unless particularly specified as a requirement, in principle limited to a certain shape, direction, positional relationship, or the like.

[0148] The modifications are not limited to the examples described above. Furthermore, multiple modifications may be combined. Furthermore, the above-described embodiment and any modification may be combined in whole or in part.

Claims

[1] Ultrasonic sensor (1), comprising: a first electrode (21c; 20) provided in an ultrasonic microphone (2) including a vibration element (21) providing a function for converting between mechanical vibrations and electrical signals; a second electrode (41) external to the ultrasonic microphone (2) such that an electrical characteristic between the second electrode (41) and the first electrode (21c; 20) changes based on an adhesion state of substances (S) adhering to the ultrasonic microphone (2); and a third electrode (42) provided to suppress changes in the electrical characteristics between the first electrode (21c; 20) and the second electrode (41) caused by factors other than the adhesion of substances (S) adhering to the ultrasonic microphone (2). [2] Ultrasonic sensor (1) according to claim 1, wherein: the third electrode (42) is provided so that it is located between the first electrode (21c; 20) and the second electrode (41). [3] Ultrasonic sensor (1) according to claim 1 or 2, wherein the third electrode (42) is provided to have the same potential as the first electrode (21c; 20) or the second electrode (41). [4] Ultrasonic sensor (1) according to one of claims 1 to 3, wherein: the second electrode (41) or the third electrode (42) is provided in an auxiliary component (8), which is a component used to mount the ultrasonic sensor (1) to a mounting target object (V). [5] Ultrasonic sensor (1) according to one of claims 1 to 4, wherein: the third electrode (42) is laminated to the first electrode (21c; 20) or the second electrode (41) by means of an insulating layer (87; 97). [6] Ultrasonic sensor (1) according to one of claims 1 to 5, wherein: the ultrasonic microphone (2) contains a microphone housing (20) including a diaphragm portion (20a) formed as a thin film to vibrate with ultrasound, and a diaphragm support portion (20b) formed in a cylindrical shape in which a directivity axis (X) along a vibration direction of the diaphragm portion (20a) is a central axis, and provided to support the diaphragm portion (20a) in an outer edge portion (20c) of the diaphragm portion (20a); and the vibration element (21) is firmly supported by the diaphragm portion (20a). [7] Ultrasonic sensor (1) according to claim 6, wherein: the microphone housing (20) is formed by a conductive material; and the first electrode (21c; 20) is integrated with the microphone housing (20). [8] Ultrasonic sensor (1) according to claim 6 or 7, wherein: the third electrode (42) is provided so as to suppress changes in the electrical characteristics between the first electrode (21c; 20) and the second electrode (41) caused by factors other than the adhesion of substances (S) adhering to a detection surface (20d) which is an outer surface of the diaphragm portion (20a) and is exposed to an outside of a mounting target object (V) in a state in which the ultrasonic sensor (1) is mounted on an outer shell (V3) of the mounting target object (V); and the adhesion of substances (S) adhering to the detection surface (20d) can be detected based on the electrical characteristic between the first electrode (21c; 20) and the second electrode (41). [9] Ultrasonic sensor (1) according to claim 8, wherein: the second electrode (41) is provided along a back surface (V32) of the outer shell (V3). [10] Ultrasonic sensor (1) according to claim 8 or 9, wherein: the third electrode (42) is provided along the membrane support portion (20b). [11] Ultrasonic sensor (1) according to one of claims 8 to 10, wherein: the adhesion of substances (S) adhering to the detection surface (20d) can be detected based on the electrical characteristic between the first electrode (21c; 20) and the second electrode (41) and an electrical characteristic between the second electrode (41) and the third electrode (42). [12] Ultrasonic sensor (1) according to one of claims 6 to 11, wherein: the diaphragm portion (20a) is formed in a shape having a long side and a short side in a plane orthogonal to the directivity axis (X); and a conductor portion (20n) configuring a power supply path to the second electrode (41) or third electrode (42) is provided in a thick portion (20f) which is a portion along the long side of the diaphragm support portion (20b). [13] Ultrasonic sensor (1) according to one of claims 1 to 12, wherein: the electrical characteristic is an electrostatic capacitance.

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