Ultrasonic Sensors

Abstract

The present invention relates to an ultrasonic sensor. An ultrasonic sensor (1) comprises a first electrode (21c; 20), a second electrode (41) and a third electrode (42). The first electrode is provided on an ultrasonic microphone (2) having a vibration element (21) having a function of converting mechanical vibration into an electrical signal. The second electrode is provided outside the ultrasonic microphone in such a manner that the electrical characteristics between the second electrode and the first electrode change according to the attachment state of an attachment (S) to the ultrasonic microphone. The third electrode is provided to suppress changes in the electrical characteristics between the first electrode and the second electrode caused by reasons other than the attachment of the attachment to the ultrasonic microphone.

Description

Technical Field

[0001] The present invention relates to ultrasonic sensors. Background Art

[0002] An ultrasonic sensor is known that detects an object by transmitting and receiving ultrasonic waves. Specifically, such an ultrasonic sensor transmits ultrasonic waves by exciting a diaphragm portion through a vibrating element such as a piezoelectric element. In addition, such an ultrasonic sensor detects an object by converting the vibration of the diaphragm portion into an electrical signal when receiving a reflected wave from an object accompanying the transmitted ultrasonic wave.

[0003] In such ultrasonic sensors, if water, mud, snow, etc. adhere to the diaphragm, there are problems such as the transmission and reception of ultrasonic waves being blocked, and the object detection performance being reduced. Therefore, various structures capable of detecting the attachment of attached objects to ultrasonic sensors have been proposed in the past. For example, Patent Document 1 describes a technology that can detect attached objects by detecting the change in impedance of an ultrasonic oscillator due to attached objects.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 60-15577

[0005] Ultrasonic sensors are widely used for vehicle operation assistance, such as parking assistance. In addition, ultrasonic sensors are expected to be used for automatic driving of vehicles. In addition, ultrasonic sensors are also expected to be used for purposes other than vehicles. Specifically, ultrasonic sensors can be used in conveyors, agricultural equipment (such as tillers), small aircraft, etc., installed in factories, etc., when they are unmanned or automated.

[0006] As described above, the attachment of deposits to the ultrasonic sensor leads to a decrease in the detection performance of the ultrasonic sensor. Therefore, it is important to improve the detection accuracy of the deposits to the ultrasonic sensor in various applications of the ultrasonic sensor. The present invention is made in view of the above-mentioned exemplified situations and the like. Summary of the invention

[0007] According to one aspect of the present invention, the ultrasonic sensor has:

[0008] A first electrode is provided on an ultrasonic microphone having a vibration element, wherein the vibration element has a function of converting mechanical vibration into an electrical signal;

[0009] a second electrode disposed outside the ultrasonic microphone so that electrical characteristics between the second electrode and the first electrode vary according to a state of attachment of an attachment to the ultrasonic microphone; and

[0010] The third electrode is provided to suppress a change in the electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the ultrasonic microphone.

[0011] In the above structure, the electrical characteristics (e.g., electrostatic capacitance) between the first electrode and the second electrode change according to the attachment state of the attachment to the ultrasonic microphone. On the other hand, the electrical characteristics may also change due to reasons other than the attachment of the attachment to the ultrasonic microphone. In this regard, the above structure includes 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 reasons other than the attachment of the attachment to the ultrasonic microphone. Therefore, according to the above structure, the presence or absence of the attachment of the attachment can be detected with high accuracy based on the changes in the electrical characteristics between the first electrode and the second electrode.

[0012] In addition, in the application documents, each element is sometimes given a reference symbol with brackets. However, even in this case, the reference symbol is only an example of the correspondence between each element and a specific mechanism described in the embodiment described later. Therefore, the present invention is not limited by the description of the reference symbol. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a perspective view showing the appearance of a vehicle equipped with the ultrasonic sensor according to the embodiment.

[0014] Figure 2 It is a side cross-sectional view showing a schematic structure of an ultrasonic sensor according to an embodiment.

[0015] Figure 3 Yes means Figure 2 A front view of the appearance of the ultrasonic microphone is shown.

[0016] Figure 4 Yes means Figure 2 The block diagram of the simplified circuit structure of the ultrasonic sensor is shown.

[0017] Figure 5 It is an explanatory diagram showing conditions of a computer simulation for verifying the effects brought about by the structure of the ultrasonic sensor according to the embodiment.

[0018] Fig. 6A It is a graph showing the results of computer simulation.

[0019] Figure 6B It is a graph showing the results of computer simulation.

[0020] Figure 7 Yes means Figure 2A side sectional view showing a schematic structure of a modified example of an ultrasonic sensor shown.

[0021] Figure 8 Yes means Figure 2 A side sectional view showing a schematic structure of another modified example of the ultrasonic sensor shown.

[0022] Fig. 9 Yes means Figure 2 A side sectional view showing a schematic structure of another modified example of the ultrasonic sensor shown.

[0023] Fig.10 Yes means Figure 2 A side sectional view showing a schematic structure of another modified example of the ultrasonic sensor shown. DETAILED DESCRIPTION

[0024] (Implementation Method)

[0025] The following describes the embodiments of the present invention in conjunction with the accompanying drawings. In addition, if various modified examples that can be applied to an embodiment are inserted in the middle of a series of descriptions related to the embodiment, it may hinder the understanding of the embodiment. Therefore, the modified examples are not inserted in the middle of a series of descriptions related to the embodiment, but are collectively described thereafter.

[0026] (Vehicle-mounted structure)

[0027] Reference Figure 1 In this embodiment, the ultrasonic sensor 1 is configured as a vehicle-mounted sensor for a vehicle V. The vehicle V is a so-called four-wheeled vehicle, and has a box-shaped vehicle body V1. The vehicle body V1 is mounted with a vehicle body panel V2, a front bumper V3, and a rear bumper V4, which are vehicle body parts constituting an outer plate. The front bumper V3 is provided at the front end of the vehicle body V1. The rear bumper V4 is provided at the rear end of the vehicle body V1.

[0028] The ultrasonic sensor 1 is a so-called clearance sonar, and is provided to detect objects around the vehicle V. Specifically, a plurality of (e.g., four) ultrasonic sensors 1 are mounted on the front bumper V3. The plurality of ultrasonic sensors 1 mounted on the front bumper V3 are respectively arranged at different positions in the vehicle width direction. Similarly, a plurality of (e.g., four) ultrasonic sensors 1 are also mounted on the rear bumper V4.

[0029] Below, refer to Figure 2 to Figure 4 The structure of the ultrasonic sensor 1 according to the present embodiment will be described. Figure 2The ultrasonic sensor 1 is configured to be able to transmit and receive ultrasonic waves. That is, the ultrasonic sensor 1 is configured to transmit a detection wave as an ultrasonic wave along a directional axis DA. The "directional axis" is an imaginary semi-straight line extending from the ultrasonic sensor 1 along the direction of transmission and reception of the ultrasonic wave, and is an axis that serves as a reference for the directional angle. The "directional axis" may also be referred to as a directional center axis or a detection axis. In addition, the ultrasonic sensor 1 is configured to receive a reflected wave of a detection wave from an object in the surroundings, and to generate and output a detection signal based on the reception result.

[0030] For ease of explanation, Figure 2 In the figure, the right-handed XYZ orthogonal coordinate system is set so that the Z axis is parallel to the directional axis DA. At this time, the direction parallel to the directional axis DA is called the "directional axial direction". The "front end side of the directional axial direction" is the sending direction side of the detection wave, which is parallel to the directional axis DA. Figure 2 The upper side of the Z axis corresponds to the positive direction side of the Z axis. Figure 2 The lower side corresponds to the negative direction side of the Z axis. In addition, observing a certain component from the front end side to the base end side with a line of sight parallel to the axial direction is called the "main view", and the figure based on the main view is called the main view. The end of the base end side of a certain component pointing to the axial direction is called the "base end portion", and the end of the front end side pointing to the axial direction is called the "front end portion". In addition, any direction orthogonal to the axial direction is called the "in-plane direction". The "in-plane direction" is Figure 2 The direction parallel to the XY plane.

[0031] Figure 2 One of the plurality of ultrasonic sensors 1 mounted on the front bumper V3 is shown in a vehicle mounted state. The “vehicle mounted state” may also be referred to as a “mounted state” in which the ultrasonic sensor 1 is mounted on the front bumper V3 constituting the outer panel of the vehicle V.

[0032] Reference Figure 2 The front bumper V3 has a bumper outer surface V31 as an outer surface and a bumper back surface V32 as its back surface. In addition, the front bumper V3 has a through hole, i.e., a mounting hole V33, for mounting the ultrasonic sensor 1. The mounting hole V33 is formed to penetrate the front bumper V3 in the axial direction, i.e., in the vehicle full length direction.

[0033] The ultrasonic sensor 1 includes an ultrasonic microphone 2, an elastic support member 3, an external electrode 4, a circuit unit 5, a sensor case 6, and a buffer member 7. The ultrasonic sensor 1 is attached to the front bumper V3 via an auxiliary member 8. The configuration of each of the above components will be described below in order.

[0034] (Ultrasonic Microphone)

[0035] Below, refer to Figure 2 as well as Figure 3The structure of the ultrasonic microphone 2 will be described. In the present embodiment, the microphone case 20 constituting the frame of the ultrasonic microphone 2 has a substantially cylindrical outer shape. Specifically, the microphone case 20 has a diaphragm portion 20a and a diaphragm support portion 20b.

[0036] The diaphragm portion 20a is formed in a thin plate shape having a thickness direction in the axial direction. The diaphragm portion 20a is provided as a vibration plate that performs ultrasonic vibration in such a manner that the central portion in the in-plane direction reciprocates along the axial direction. That is, the diaphragm portion 20a is supported by the diaphragm support portion 20b at the outer edge portion 20c so as to be bent and deformed with the outer edge portion 20c in the in-plane direction as a fixed end.

[0037] The outer surface of the diaphragm 20a, namely the detection surface 20d, is formed into a smooth plane shape orthogonal to the directional axis DA. The element fixing surface 20e on the back side of the detection surface 20d is parallel to the detection surface 20d and is formed into a smooth plane shape.

[0038] The diaphragm support portion 20b is formed into a cylindrical shape with the directional axis DA along the vibration direction of the diaphragm portion 20a as the central axis. Specifically, the diaphragm support portion 20b is formed into an approximately cylindrical shape surrounding the directional axis DA. The diaphragm support portion 20b is formed so that the base end portion is open toward the base end side directional to the axial direction. On the other hand, the front end portion of the diaphragm support portion 20b is closed by the diaphragm portion 20a. That is, the microphone housing 20 is formed into a bottomed cylindrical shape with one end portion directional to the axial direction closed by the diaphragm portion 20a.

[0039] In the present embodiment, the diaphragm portion 20a is formed into a shape having a long side direction and a short side direction in a plane perpendicular to the directional axis DA. Figure 3 The diaphragm portion 20a has a rounded rectangular shape in a plane perpendicular to the directional axis DA. Corresponding to the above-mentioned in-plane shape, the diaphragm support portion 20b has a thick wall portion 20f and a thin wall portion 20g.

[0040] The thick wall portion 20f is a portion along the long side direction of the diaphragm portion 20a, i.e., the long side direction, and has a maximum thickness D1 in a direction parallel to the short side direction. The thin wall portion 20g is a portion along the short side direction of the diaphragm portion 20a, i.e., the short side direction, and has a maximum thickness D2 in a direction parallel to the long side direction. D2<D1. That is, in this embodiment, the thick wall portion 20f is provided corresponding to the long side of the rounded rectangle of the diaphragm portion 20a. In addition, the thin wall portion 20g is provided corresponding to the short side of the rounded rectangle of the diaphragm portion 20a.

[0041] The outer peripheral surface 20h of the diaphragm support portion 20b is formed into a substantially cylindrical surface parallel to the directional axis DA. An engaging groove 20k is formed on the outer peripheral surface 20h of the thick wall portion 20f. The engaging groove 20k is an angle groove used when the microphone housing 20 is supported on the sensor housing 6 via the elastic support member 3. The engaging groove 20k is arranged to extend along the long side direction of the diaphragm portion 20a, that is, the long side direction.

[0042] In this embodiment, the microphone housing 20 is seamlessly integrally formed of insulating synthetic resin. A lead portion 20n is provided on the outer peripheral surface 20h of the thick wall portion 20f. The lead portion 20n is a component constituting a power supply line for supplying power to the external electrode 4 and is formed of a good conductor film such as copper foil.

[0043] When the microphone housing 20 is mounted on the vehicle, the diaphragm portion 20a is inserted into the mounting hole V33 and the detection surface 20d is exposed toward the outside of the vehicle V. When the microphone housing 20 is mounted on the vehicle, the diaphragm support portion 20b extends from the mounting hole V33 toward the bumper back surface V32.

[0044] A substantially quadrangular column-shaped space 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.

[0045] The ultrasonic microphone 2 includes a microphone housing 20 and a vibration element 21. That is, the microphone housing 20 is configured to accommodate and support the vibration element 21 having a function of converting mechanical vibration into an electrical signal.

[0046] The vibration element 21 is fixedly supported on the diaphragm portion 20a on the element fixing surface 20e side. The vibration element 21 is attached to the element fixing surface 20e of the diaphragm portion 20a by an insulating adhesive. In this embodiment, the vibration element 21 has a structure as a so-called piezoelectric element. Specifically, the vibration element 21 includes a piezoelectric body 21a, a driving electrode 21b, and a reference electrode 21c.

[0047] The piezoelectric body 21a is a plate-shaped or film-shaped component having a thickness direction in the axial direction, and is formed of a piezoelectric material such as a piezoelectric ceramic. The piezoelectric body 21a is arranged between the drive electrode 21b and the reference electrode 21c in the axial direction. Specifically, the vibration element 21 is formed by stacking and bonding the drive electrode 21b, the piezoelectric body 21a, and the reference electrode 21c in this order in the axial direction.

[0048] The driving electrode 21b is formed of a conductive metal film. The driving electrode 21b is provided on one main surface of the piezoelectric body 21a, that is, the main surface on the lower side in the figure. The "main surface" refers to the surface of the plate-like or film-like part that is perpendicular to the thickness direction. That is, in this embodiment, the driving electrode 21b is arranged on the base end side pointing to the axial direction compared to the reference electrode 21c.

[0049] The reference electrode 21c is formed of a conductive metal film. The reference electrode 21c is provided on the other main surface of the piezoelectric body 21a, that is, the main surface on the upper side in the figure. Specifically, in the present embodiment, the reference electrode 21c is bonded to the diaphragm portion 20a via an insulating adhesive layer not shown. The reference electrode 21c, which is the "first electrode" provided on the ultrasonic microphone 2, is grounded when the ultrasonic sensor 1 is used.

[0050] The vibration element 21 is configured such that the piezoelectric body 21a is deformed according to the driving voltage applied between the driving electrode 21b and the reference electrode 21c, thereby bending and deforming the diaphragm portion 20a. In addition, the vibration element 21 is configured to generate an output voltage between the driving electrode 21b and the reference electrode 21c according to the deformation of the piezoelectric body 21a accompanying the bending and deformation of the diaphragm portion 20a.

[0051] (Elastic support member)

[0052] Reference Figure 2 The elastic support member 3 is configured to elastically support the microphone housing 20 and suppress the vibration propagation between the microphone housing 20 and the sensor housing 6. In addition, the elastic support member 3 is configured to be sandwiched between the microphone housing 20 and the front bumper V3 in the vehicle-mounted state, thereby suppressing the vibration propagation between the microphone housing 20 and the front bumper V3. Specifically, the elastic support member 3 is a substantially cylindrical member having rubber elasticity and non-conductivity, and is formed to have a central axis along the axial direction.

[0053] The elastic support member 3 includes a support cylinder 31 and a base 32. The support cylinder 31 is a portion of the elastic support member 3 pointing to the front end side in the axial direction, and is configured to accommodate and elastically support the microphone housing 20. The base 32 is a portion of the elastic support member 3 pointing to the base end side in the axial direction, and is fixed to the sensor housing 6. In the present embodiment, the elastic support member 3 is seamlessly integrally formed of silicone rubber or the like.

[0054] The front end of the support cylinder 31 is inserted into the mounting hole V33 and clamped between the inner peripheral surface of the mounting hole V33 of the front bumper V3 and the outer peripheral surface 20h of the microphone housing 20 when the support cylinder 31 is mounted on the vehicle. A snap-fitting protrusion 33 protruding radially inward is provided on the base end side of the inner peripheral surface of the support cylinder 31. The "radial direction" is a direction orthogonal to the directional axis and is a direction extending radially from the directional axis DA. The snap-fitting protrusion 33 is formed to snap-fit ​​with the snap-fitting groove 20k provided on the microphone housing 20.

[0055] A fixing protrusion 34 is provided at the base end of the outer peripheral surface of the base 32. The fixing protrusion 34 is formed to protrude outward in the radial direction. In addition, a fixing groove 35 is formed at a position of the outer peripheral surface of the base 32 adjacent to the fixing protrusion 34 in the axial direction. That is, the fixing groove 35 is provided at the front end side of the axial direction compared with the fixing protrusion 34. The fixing protrusion 34 and the fixing groove 35 are arranged to extend in the circumferential direction. The "circumferential direction" is a circumferential direction of a circle within an imaginary plane orthogonal to the axial direction, with the intersection of the directional axis DA and the imaginary plane as the center.

[0056] (Detection electrode / guard electrode)

[0057] The external electrode 4 is provided outside the ultrasonic microphone 2. In 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 of a conductor, specifically, a good conductor metal. The detection electrode 41 and the guard electrode 42 are provided at a position different from the reference electrode 21c in the in-plane direction.

[0058] The detection electrode 41 as the "second electrode" is provided so that the electrical characteristics between it and the reference electrode 21c change according to the attachment state of the attachment S to the detection surface 20d of the ultrasonic microphone 2. Specifically, the "electrical characteristics" mentioned here are, for example, impedance, current, and electrostatic capacitance. In this embodiment, it is usually electrostatic capacitance. More specifically, the detection electrode 41 is provided near the microphone housing 20 in a manner close to the detection surface 20d of the ultrasonic microphone 2 in the axial direction and radial direction when mounted on the vehicle.

[0059] In the present embodiment, the detection electrode 41 is formed into a flat thin plate or film having a thickness direction in the axial direction. The detection electrode 41 is arranged along the bumper back surface V32 of the front bumper V3. That is, the detection electrode 41 is closely opposed to the bumper back surface V32 and is arranged close to the mounting hole V33 when it is mounted on the vehicle. In addition, the detection electrode 41 is arranged on the radially outer side of the microphone housing 20. Specifically, when the detection electrode 41 is observed from the front when it is mounted on the vehicle, it is formed into a ring shape surrounding the mounting hole V33.

[0060] The protection electrode 42 as the "third electrode" is provided to suppress changes in the electrical characteristics between the reference electrode 21c and the detection electrode 41 caused by reasons other than the attachment of the attachment S to the detection surface 20d. The "electrical characteristics" mentioned here are specifically, for example, impedance, current, and electrostatic capacitance, and in this embodiment, it is usually electrostatic capacitance.

[0061] The guard electrode 42 is provided on the outer side of the microphone housing 20 in the radial direction. In addition, the guard electrode 42 is arranged to extend in the axial direction along the diaphragm support portion 20b. Specifically, in the present embodiment, the guard electrode 42 is a thin plate-like or film-like member having a thickness direction in the radial direction, and is formed into a cylindrical or partially cylindrical shape extending in the axial direction surrounding the directional axis DA. The guard electrode 42 is arranged to face the outer peripheral surface 20h of the microphone housing 20 via the elastic support member 3.

[0062] The protective electrode 42 is configured to be sandwiched between the reference electrode 21c and the detection electrode 41. Specifically, the protective electrode 42 is arranged on the radially outer side compared to the reference electrode 21c. In addition, the protective electrode 42 is arranged on the radially inner side compared to the detection electrode 41. That is, in the present embodiment, the protective electrode 42 is arranged between the reference electrode 21c and the detection electrode 41 in the radial direction. In addition, in the present embodiment, the protective electrode 42 is arranged on the base end side pointing in the axial direction compared to the detection electrode 41. In this way, the protective electrode 42 is arranged in an area closer to the base end side pointing in the axial direction than the outer surface V31 of the bumper in such a manner as to play the function of a protective electrode between the reference electrode 21c and the detection electrode 41. Furthermore, the protective electrode 42 is isolated and configured from the radial inner edge of the detection electrode 41 in such a manner as not to directly contact or short-circuit with the detection electrode 41.

[0063] (Circuit Structure)

[0064] The circuit unit 5 includes a circuit substrate 50, a drive wiring 51, a detection wiring 52, and a protection wiring 53. The circuit substrate 50 and the drive wiring 51 are housed in the sensor housing 6. The base end side portions of the detection wiring 52 and the protection wiring 53 are housed in the sensor housing 6. In order to avoid complication of the illustration, the illustration of the drive wiring 51, the detection wiring 52, and the protection wiring 53 is partially omitted.

[0065] One end of the driving wire 51 is electrically connected to the circuit board 50 via the first connector C1. The other end of the driving wire 51 is electrically connected to the vibration element 21. That is, the driving wire 51 is provided to apply a driving voltage to the vibration element 21.

[0066] One end of the detection wiring 52 constituting a power supply line for supplying power to the detection electrode 41 is electrically connected to the circuit substrate 50 via the second connector C2. The other end of the detection wiring 52 is electrically connected to the detection electrode 41. In the present embodiment, the detection wiring 52 is configured so that a portion thereof includes Figure 3 The wire portion 20n is shown.

[0067] One end of the protection wiring 53 constituting a power supply line for supplying power to the protection electrode 42 is electrically connected to the circuit board 50 via the third connector C3. The other end of the protection wiring 53 is electrically connected to the protection electrode 42.

[0068] A control circuit device 54 is mounted on the circuit board 50. The control circuit device 54 is a so-called one-chip microcomputer including a CPU, an A / D converter, a D / A converter, etc., and is provided to control the operation of the ultrasonic sensor 1. CPU is an abbreviation of Central Processing Unit.

[0069] Figure 4 The schematic circuit structure of the ultrasonic sensor 1 of this embodiment is shown together with the functional structure realized in the control circuit device 54 which is a one-chip microcomputer. Figure 4 As shown, the control circuit device 54 includes a control unit 54a, a signal transceiver unit 54b, and an impedance acquisition unit 54c.

[0070] The control unit 54a is configured to execute an object detection operation to detect an object around the ultrasonic sensor 1 when a predetermined object detection condition is satisfied. The object detection condition includes, for example, that the gear position of the vehicle V equipped with the ultrasonic sensor 1 is a drivable position and the vehicle speed of the vehicle V is less than a predetermined value.

[0071] Specifically, the control unit 54 a is provided so as to be able to transmit and receive signals with the signal transmitting and receiving unit 54 b . That is, the control unit 54 a controls the operation of the signal transmitting and receiving unit 54 b , thereby controlling the transmission and reception operation of the ultrasonic wave microphone 2 .

[0072] The signal transceiver 54b is electrically connected to the vibration element 21 so as to transmit and receive an electrical signal including a drive signal and an output voltage signal between the signal transceiver 54b and the vibration element 21. That is, the signal transceiver 54b is configured to input a drive signal to the vibration element 21 and receive an output voltage signal from the vibration element 21.

[0073] The signal transceiver 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 input a driving signal to the vibration element 21, thereby causing the vibration element 21 to transmit a detection wave in the ultrasonic frequency band.

[0074] The reception wave processing circuit 54e is electrically connected to the vibration element 21. The reception wave processing circuit 54e is configured to perform signal processing such as amplification on the output voltage signal generated by the vibration element 21 by exciting the diaphragm portion 20a. The specific circuit structures of the transmission circuit 54d and the reception wave processing circuit 54e are well known. Therefore, in this specification, further description of the transmission circuit 54d and the reception wave processing circuit 54e is omitted.

[0075] The control unit 54a is configured to detect the presence of the attached object S using the impedance acquisition unit 54c when the object detection operation is not performed. Specifically, the control unit 54a is configured to be able to transmit and receive signals between it and the impedance acquisition unit 54c. The impedance acquisition unit 54c includes a drive circuit 54f, a protection voltage application unit 54g, and a receiving circuit 54h.

[0076] The non-grounded output terminal of the driving circuit 54f is electrically connected to the detection electrode 41 via the detection wiring 52. That is, the driving circuit 54f is provided so as to output a power supply voltage for obtaining impedance between the reference electrode 21c and the detection electrode 41.

[0077] The non-grounded output terminal of the driving circuit 54f is electrically connected to the protection electrode 42 via the protection wiring 53 and the protection voltage applying unit 54g. The protection wiring 53 is provided between the protection electrode 42 and the protection voltage applying unit 54g to electrically connect the protection electrode 42 and the protection voltage applying unit 54g.

[0078] The protection voltage applying unit 54g is configured to separate the protection electrode 42 from the driving circuit 54f and to supply power to the protection electrode 42. Specifically, in the present embodiment, the protection voltage applying unit 54g is configured by a voltage follower. Thus, the impedance acquiring unit 54c is configured so that when power is supplied to the detection electrode 41 and the protection electrode 42, the detection electrode 41 and the protection electrode 42 have the same potential.

[0079] In addition, the non-grounded output terminal of the driving circuit 54f is electrically connected to the receiving circuit 54h. The receiving circuit 54h is configured to have a known integrating circuit, etc., and generates an output corresponding to the impedance between the reference electrode 21c and the detection electrode 41. The principle of obtaining or measuring the impedance and the specific circuit structures of the driving circuit 54f and the receiving circuit 54h are well known. Therefore, in this specification, further description thereof is omitted.

[0080] As described above, the impedance acquisition unit 54c is configured to acquire the impedance between the reference electrode 21c and the detection electrode 41. In addition, the control unit 54a is configured to obtain the change in the acquired impedance and detect the attachment of the attached object S to the detection surface 20d based on the change. That is, the ultrasonic sensor 1 of this embodiment is configured to be able to detect the attachment of the attached object S to the detection surface 20d based on the electrical characteristic between the reference electrode 21c and the detection electrode 41, that is, the electrostatic capacitance.

[0081] (Frame)

[0082] Refer again Figure 2 The sensor housing 6 constituting the frame of the ultrasonic sensor 1 is integrally formed of a hard insulating synthetic resin such as polybutylene terephthalate. Specifically, the housing body 61, which is the main part of the sensor housing 6, has a substrate storage portion 62 and a protrusion 63. The substrate storage portion 62 and the protrusion 63 are integrally formed without a joint.

[0083] The substrate storage portion 62 is formed in a bathtub shape, that is, a box shape that is open toward the base end side in the axial direction. The protrusion 63 is a substantially cylindrical portion having a central axis parallel to the axial direction, and is provided to protrude from the substrate storage portion 62 toward the front end side in the axial direction. The housing body 61 is formed so that the space inside the substrate storage portion 62 and the space inside the protrusion 63 are communicated with each other.

[0084] The circuit board 50 is stored in the board storage portion 62. The space inside the board storage portion 62 and the protruding portion 63 is filled with a sealing resin 64. The sealing resin 64 is formed of a synthetic resin such as silicone rubber having high insulation, low dielectric constant, chemical stability and durability.

[0085] The protrusion 63 is configured to hold the elastic support member 3 at the front end portion pointing in the axial direction. Specifically, a support groove 65 and a support protrusion 66 are provided at the front end portion of the inner peripheral surface of the protrusion 63. The support groove 65 is formed to engage with the fixing protrusion 34 of the elastic support member 3. The support protrusion 66 is formed to engage with the fixing groove 35 of the elastic support member 3.

[0086] The buffer member 7 is a disc-shaped member having an outer diameter corresponding to the inner diameter of the elastic support member 3. That is, the buffer member 7 is embedded in the cylindrical space inside the elastic support member 3 on the base end side of the portion elastically supporting the ultrasonic sensor 1 in the axial direction. The buffer member 7 is formed of a foamed elastic body such as foamed silicone having insulating properties and elasticity, so as to suppress the transmission of vibration from the ultrasonic sensor 1 to the sensor housing 6.

[0087] (Mounting parts)

[0088] The auxiliary component 8 is formed of a hard insulating synthetic resin such as polybutylene terephthalate. The auxiliary component 8 is a component for mounting the ultrasonic sensor 1 on the vehicle V, and is formed as a component independent of the sensor housing 6. That is, the auxiliary component 8 is configured to be fixed to the front bumper V3 and the sensor housing 6 in the vehicle-mounted state, thereby holding the ultrasonic sensor 1 on the front bumper V3. Specifically, the auxiliary component 8 has a holding portion 81 and a flange portion 82.

[0089] The holding portion 81 is formed into a substantially cylindrical shape surrounding the protrusion 63 of the sensor housing 6 and the elastic support member 3. That is, the holding portion 81 is provided to hold the protrusion 63 of the sensor housing 6 and the elastic support member 3. The flange portion 82 is extended from the front end portion of the holding portion 81 toward the radially outer side. The flange portion 82 is formed as a portion on the radially outer side and is fixed to the bumper back surface V32 by an adhesive layer (not shown) such as a double-sided tape.

[0090] In this embodiment, the auxiliary component 8 is provided with a detection electrode 41. Specifically, the detection electrode 41 is fixed to the bumper facing surface 83 side in a manner coplanar with the surface of the flange portion 82 that faces the bumper back surface V32 in the vehicle-mounted state, that is, the bumper facing surface 83. That is, the detection electrode 41 is accommodated or buried in the shallow groove, that is, the annular recessed portion 84 formed on the bumper facing surface 83. In addition, the detection electrode 41 is arranged at a position close to the inner side of the flange portion 82 in the radial direction.

[0091] In addition, in the present embodiment, the auxiliary member 8 is provided with a protective electrode 42. Specifically, the protective electrode 42 is fixed to the inner peripheral surface 85 side of the cylindrical surface-shaped inner peripheral surface 85 of the holding portion 81 in a coplanar manner. That is, the protective electrode 42 is accommodated or buried in a shallow groove, that is, a cylindrical recessed portion 86 formed in the inner peripheral surface 85. In addition, the protective electrode 42 is arranged at a position close to the front end portion of the holding portion 81 in the axial direction.

[0092] (Action Summary)

[0093] Hereinafter, the outline of the operation of the structure of this embodiment and the effect of the structure will be described with reference to each of the drawings. In addition, the following operation examples are simple exemplary operation examples for briefly describing this embodiment.

[0094] At time t0, after the ignition switch of the vehicle V is turned on, the ultrasonic sensor 1 does not transmit the detection wave, nor does it receive the reflected wave until the object detection condition is satisfied at time t1. If the object detection condition is satisfied at time t1, the ultrasonic sensor 1 transmits the detection wave and receives the reflected wave, thereby performing the object detection operation. Then, the vehicle speed increases, and if the object detection condition is not satisfied at time t2, the object detection operation is stopped. Further, if the vehicle speed decreases to stop the vehicle, the object detection condition is satisfied again at time t3, and the transmission of the detection wave and the reception of the reflected wave are restarted.

[0095] In this embodiment, the attachment detection action is not performed during the time period from t1 to t2 when the object detection condition is satisfied and the object detection action is performed. The attachment detection action is an action to detect whether the attachment S is attached to the ultrasonic sensor 1. Similarly, the attachment detection action is not performed after time t3 until the object detection condition is not satisfied again.

[0096] On the other hand, the attachment detection operation is performed when the object detection operation is not performed, that is, during the time period t0 to t1 and / or during the time period t2 to t3. That is, in this embodiment, the attachment detection operation is performed when the detection wave is not sent and the reflected wave is not received. In this way, good object detection accuracy can be maintained and attachment detection can be performed.

[0097] Reference Figure 1 as well as Figure 2 The ultrasonic sensor 1 is usually mounted on the front bumper V3 so that the axial direction is substantially perpendicular to the vehicle height direction. Therefore, the gravity of the attachment S attached to the detection surface 20d of the microphone housing 20 has almost no component parallel to the vibration direction of the diaphragm 20a.

[0098] Therefore, the impedance of the equivalent circuit of the mechanical vibration of the ultrasonic microphone 2 hardly changes depending on the presence or absence of the attachment S. In particular, when the attachment S is a light object such as snow or water, the impedance of the equivalent circuit of the mechanical vibration may not change at all depending on the presence or absence of the attachment S. Therefore, it is difficult to detect the attachment of light objects such as snow or water based on the impedance of the equivalent circuit of the mechanical vibration. In addition, in the conventionally known method of detecting the attachment of the attachment S to the ultrasonic sensor 1 using the reverberation time, it is difficult to detect the attachment of light objects such as snow or water.

[0099] In this point, in the structure of this embodiment, the electrical characteristics, specifically, the electrostatic capacitance, between the reference electrode 21c and the detection electrode 41 changes according to the attachment state of the attached object S to the detection surface 20d. Therefore, the control unit 54a obtains the impedance between the reference electrode 21c and the detection electrode 41. Thus, the change in the electrostatic capacitance between the reference electrode 21c and the detection electrode 41 is obtained. Therefore, according to the above structure, the presence or absence of the attached object S can be detected based on the change in the electrical characteristics, that is, the electrostatic capacitance, between the reference electrode 21c and the detection electrode 41.

[0100] According to the structure of this embodiment, even if there is almost no component parallel to the vibration direction of the diaphragm portion 20a that acts on the gravity of the attachment S attached to the detection surface 20d, it is possible to detect with high accuracy whether the attachment S is attached. In addition, according to the above structure, even if the attachment S is a light object such as snow or water, it is possible to detect with high accuracy whether the attachment S is attached.

[0101] However, as a method for detecting the attachment S to the ultrasonic sensor 1, a technique using the resistance value between electrodes is considered. However, the above method is difficult to adopt due to oxidation of the electrodes, prevention of electric shock to people around, design problems, etc. In practice, as in this embodiment, an insulating film is usually formed on the surface of the microphone housing 20 to prevent corrosion, etc.

[0102] In this regard, according to the structure of this embodiment, the presence of the attached matter S can be detected based on the change in the electrostatic capacitance between the reference electrode 21c and the detection electrode 41. Therefore, according to the above structure, even when an insulating film is formed on the surface of the microphone housing 20, the presence of the attached matter S can be detected with high accuracy.

[0103] As described above, according to the attachment detection method based on the change of the electrostatic capacitance, which is the electrical characteristic between the reference electrode 21c and the detection electrode 41, as in the present embodiment, the presence or absence of the attachment of the attachment S can be detected with high accuracy compared with other methods. However, the electrical characteristic between the reference electrode 21c and the detection electrode 41 may also change due to reasons other than the attachment of the attachment S to the detection surface 20d. Therefore, the following problem is considered.

[0104] For example, when the attached matter S is water, the attached state of the detection surface 20d may be eliminated in a relatively short time due to gravity or evaporation, etc. On the other hand, when the attached matter S is snow, the attached state lasts for a relatively long time. Therefore, it is more important to detect the attachment of snow than the attachment of water.

[0105] In this regard, the relative dielectric constant of water is about 80. On the other hand, the relative dielectric constant of snow is about 3. Therefore, in a structure without the protective electrode 42, for example, when condensation occurs on the side of the bumper back surface V32, the change in the electrostatic capacitance between the reference electrode 21c and the detection electrode 41 is large compared to the case where snow adheres to the detection surface 20d. Similarly, there are two places where water may penetrate into the gap between the retaining portion 81 of the auxiliary component 8 and the microphone housing 20. Specifically, water may penetrate between the outer peripheral surface 20h of the microphone housing 20 and the elastic support component 3. In addition, water may penetrate between the elastic support component 3 and the retaining portion 81. In the case where water penetrates into these gaps, the change in the electrostatic capacitance between the reference electrode 21c and the detection electrode 41 is large compared to the case where snow adheres to the detection surface 20d.

[0106] In addition, there may be a harness inside the components constituting the outer panel of the vehicle body V1 including the front bumper V3. The harness may move or vibrate irregularly during the running of the vehicle V. With the movement or vibration, the parasitic capacitance between the reference electrode 21c and the detection electrode 41 may change.

[0107] In contrast, in the structure of the present embodiment, a protective electrode 42 is provided together with the detection electrode 41. The protective 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 reasons other than the attachment of the attachment S to the detection surface 20d. That is, the protective electrode 42 is provided to be clamped between the reference electrode 21c and the detection electrode 41. In addition, the "clamping" mentioned here means electrostatically clamping in a manner to suppress changes in the electrical characteristics between the reference electrode 21c and the detection electrode 41 caused by reasons such as water or wiring harness on the inner side of the components constituting the outer panel of the vehicle body V1. Therefore, as long as the protective electrode 42 is clamped in a manner to realize the protective electrode function between the reference electrode 21c and the detection electrode 41, it is not necessary to be arranged on the imaginary straight line connecting the reference electrode 21c and the detection electrode 41 in the side cross-sectional view.

[0108] Figure 5 The simulation conditions used to verify the effect of the structure of the present embodiment by computer simulation are shown. In this simulation, in order to simplify the calculation conditions, the above-mentioned structure is modified as follows. First, as in the modified example described later, the entire microphone housing 20 made of a good conductor metal such as aluminum is used as the reference electrode 21c. In addition, the detection electrode 41 is exposed to the outer surface of the vehicle V. And the entire side of the reference electrode 21c is covered by the protective electrode 42.

[0109] exist Figure 5In the calculation model shown, the entire approximately cylindrical region of the microphone housing 20 constituting the reference electrode 21c is set to 0 V. In addition, the detection electrode 41 and the guard electrode 42 are set to 1 V. Then, the electrostatic capacitance between the reference electrode 21c and the detection electrode 41 is calculated for the following three states.

[0110] State 1: No attachments

[0111] State 2: Snow S1 adheres to the detection surface 20d

[0112] State 3: Water S2 adheres to the back side of the auxiliary component 8

[0113] Fig. 6A The simulation results are shown in the case where the guard electrode 42 is not provided. Figure 6B 4 shows the simulation results when the guard electrode 42 is provided. Fig. 6A as well as Figure 6B In FIG. 1 , “SIT1” indicates state 1, “SIT2” indicates state 2, and “SIT3” indicates state 3. In addition, the vertical axis CA indicates electrostatic capacitance.

[0114] like Fig. 6A As shown in FIG. 1 , when there is no guard electrode 42, the change in electrostatic capacitance is greater when the snow S1 is attached to the detection surface 20d than when the water S2 is attached to the back side of the auxiliary component 8. Figure 6B As shown, in the case where the guard electrode 42 is present, the change in electrostatic capacitance is greater when the snow S1 adheres to the detection surface 20 d than when the water S2 adheres to the back side of the auxiliary member 8 .

[0115] As described above, according to the structure of this embodiment, the change of the electrical characteristics between the reference electrode 21c and the detection electrode 41 caused by water in the case of condensation on the back side V32 of the bumper can be well suppressed. In addition, according to the above structure, the influence of the parasitic capacitance caused by the wiring harness can be well suppressed. Therefore, according to the above structure, the attachment detection using the change of the electrical characteristics between the reference electrode 21c and the detection electrode 41, that is, the electrostatic capacitance, can be performed with better accuracy.

[0116] In the structure of this embodiment, the guard electrode 42 is set to the same potential as the detection electrode 41. Therefore, it is easy to supply power to the detection electrode 41 and the guard electrode 42. In addition, the reference electrode 21c is set to the same potential as the ground of the vehicle body V1, so that the electrical characteristic, that is, the electrostatic capacitance, can be stably obtained.

[0117] In the structure of the present embodiment, the detection electrode 41 and the protection electrode 42 are provided in the auxiliary component 8 which is a component for mounting the ultrasonic sensor 1 on the vehicle V. Therefore, a special operation process for mounting the detection electrode 41 and the protection electrode 42 is not required. Therefore, according to the above structure, a structure for detecting the attached object S is realized by the same mounting process as the conventional ultrasonic sensor 1. In addition, the positional relationship among the reference electrode 21c, the detection electrode 41, and the protection electrode 42 can be stabilized. Therefore, the attached object detection using the change of the electrical characteristics between the reference electrode 21c and the detection electrode 41 can be performed with better accuracy.

[0118] In the structure of the present embodiment, the detection electrode 41 is provided along the back surface V32 of the bumper. In addition, the protection electrode 42 is provided along the diaphragm support portion 20b. In the above-mentioned structure, even if condensation occurs along the back surface V32 of the bumper, the influence of the change in electrostatic capacitance accompanying the condensation can be well suppressed by the protection electrode 42. In addition, even if condensation occurs along the diaphragm support portion 20b, the influence of the change in electrostatic capacitance accompanying the condensation can be well suppressed by the protection electrode 42. Furthermore, the influence of the change in electrostatic capacitance accompanying the penetration of water into the space between the retaining portion 81 of the auxiliary component 8 and the microphone housing 20 can be well suppressed by the protection electrode 42.

[0119] In the structure of this embodiment, the diaphragm portion 20a is formed into a shape having a long side direction and a short side direction in a plane orthogonal to the directional axis DA. In addition, a lead portion 20n constituting a power supply line for supplying power to the detection electrode 41 is provided in the thick wall portion 20f along the long side direction of the diaphragm support portion 20b.

[0120] The thick-walled portion 20f has a groove or an additional object provided in comparison with the thin-walled portion 20g, thereby reducing the influence on the vibration characteristics of the diaphragm portion 20a. Therefore, the engaging groove 20k is provided in the thick-walled portion 20f instead of the thin-walled portion 20g. Similarly, the lead portion 20n constituting the power supply line for supplying power to the detection electrode 41 is also provided in the thick-walled portion 20f instead of the thin-walled portion 20g. Therefore, according to the above-mentioned structure, the influence on the vibration characteristics of the diaphragm portion 20a can be suppressed as much as possible, and the manufacturing cost when providing the power supply line for supplying power to the detection electrode 41 can be well reduced.

[0121] (Variation Example)

[0122] The present invention is not limited to the above-mentioned embodiment. Therefore, the above-mentioned embodiment can be appropriately changed. Below, representative modified examples are described. In the following description of the modified examples, the differences from the above-mentioned embodiment are mainly described. In addition, in the above-mentioned embodiment and the modified examples, the same or equivalent parts are marked with the same figure marks. Therefore, in the description of the following modified examples, with respect to the structural elements with the same figure marks as those in the above-mentioned embodiment, as long as there is no technical contradiction or special additional description, the description in the above-mentioned embodiment can be appropriately cited.

[0123] The member of the vehicle body V1 to which the ultrasonic sensor 1 is mounted is not limited to the front bumper V3 and the rear bumper V4. That is, for example, the ultrasonic sensor 1 may be mounted on the vehicle body panel V2. In this case, the detection electrode 41 may be provided along the vehicle body panel V2.

[0124] The object to which the ultrasonic sensor 1 is mounted is not limited to the vehicle V. That is, for example, the ultrasonic sensor 1 may be mounted on a conveyor installed in a factory or the like, agricultural equipment (for example, a tiller), an aircraft, or the like.

[0125] The ultrasonic sensor 1 is not limited to the so-called transmission and reception configuration. That is, an ultrasonic sensor 1 dedicated to transmission of detection waves and an ultrasonic sensor 1 dedicated to reception of reflected waves may be separately mounted on the vehicle V. The present invention is also well applicable to such a case.

[0126] In the above embodiment, the microphone housing 20 is seamlessly integrally formed of an insulating synthetic resin. However, the present invention is not limited to the above embodiment. That is, for example, the microphone housing 20 may be formed by joining the diaphragm portion 20a and the diaphragm support portion 20b, which are formed independently of each other. In this case, the diaphragm portion 20a and the diaphragm support portion 20b may be formed of the same material or different materials.

[0127] The whole or a part of the microphone housing 20 may also be formed of a conductive or semi-conductive material. Specifically, for example, at least the diaphragm portion 20a in the microphone housing 20 may be formed of a good conductor metal such as aluminum. In this case, the reference electrode 21c in the above embodiment, which serves as the "first electrode", may be integrated with the microphone housing 20. The "integration" here is not limited to the case where two structural elements are joined to each other. That is, fusing two structural elements, in other words, making one component serve as two structural elements is also included in "integration".

[0128] Specifically, for example, the reference electrode 21c is bonded to the diaphragm portion 20a via a conductive adhesive, thereby being integrated with the microphone housing 20. That is, the reference electrode 21c is electrically connected to the diaphragm portion 20a via a conductive adhesive, thereby being grounded. In the above structure, the bonded body of the reference electrode 21c and the diaphragm portion 20a can function as a "first electrode".

[0129] Alternatively, the diaphragm portion 20a can be used as both the ground side electrode of the vibration element 21 and the "first electrode" for detecting deposits. That is, the diaphragm portion 20a, which is regarded as 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 by an adhesive.

[0130] An example in which the entire microphone housing 20 is formed of a good conductor metal such as aluminum will be described. Figure 7 As shown, the microphone housing 20 is a member constituting the reference electrode 21 c and is integrated with the reference electrode 21 c .

[0131] Reference Figure 7 In this modification, the microphone housing 20 is made of a good conductor metal such as aluminum and is seamlessly integrally formed. In this case, the piezoelectric body 21a can be attached to the element fixing surface 20e of the diaphragm 20a by a conductive adhesive.

[0132] According to the above structure, the microphone housing 20 can be used as the "first electrode". Therefore, the electrical characteristics between the microphone housing 20 as the "first electrode" and the detection electrode 41, that is, the electrostatic capacitance can be stably obtained. In addition, the microphone housing 20 can be used as a component that serves as both the "first electrode" and the ground side electrode of the vibration element 21. Therefore, the manufacturing cost can be reduced by reducing the number of components.

[0133] The vibration element 21 is not limited to a piezoelectric element. That is, for example, the ultrasonic microphone 2 may have a structure of an electrostatic capacitance microphone.

[0134] The structure of the detection electrode 41 is also not limited to the above-mentioned specific example. That is, for example, the shape of the detection electrode 41 is not limited to a plate or a film, and may be a mesh, a rod, or a spiral shape. In addition, the detection electrode 41 may be arranged at the approximate center of the flange portion 82 in the thickness direction, so as to be buried inside the flange portion 82. In other words, the detection electrode 41 may also be arranged to be separated from the bumper-facing surface 83 of the flange portion 82 in the axial direction.

[0135] The plurality of detection electrodes 41 may also be arranged in a predetermined direction (e.g., in-plane direction). Specifically, for example, the plurality of detection electrodes 41 arranged in the radial direction and / or the circumferential direction may also be arranged so as not to pass through each other. In this case, the control unit 54a can detect the presence and attachment position of the attachment S based on the change in the electrical characteristics (i.e., electrostatic capacitance) between each of the plurality of detection electrodes 41 and the reference electrode 21c.

[0136] In the above embodiment, both the detection electrode 41 and the protection electrode 42 are provided in the auxiliary member 8. However, the present invention is not limited to the above embodiment. That is, for example, only one of the detection electrode 41 and the protection electrode 42 may be provided in the auxiliary member 8.

[0137] The detection electrode 41 may not be provided on the auxiliary component 8. That is, for example, the detection electrode 41 may be fixed to the back surface V32 of the bumper. 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 part of the front bumper V3 formed by adding a conductive filler to the portion facing the mounting hole V33 of the front bumper V3.

[0138] The detection electrode 41 may also be provided on the elastic support member 3. That is, for example, the ring-shaped detection electrode 41 may be embedded in the front end portion of the elastic support member 3 that points in the axial direction. Or, for example, the entire elastic support member 3 or at least the front end portion that points in the axial direction may be made conductive so that it can be used as the detection electrode 41. In addition, as described above, the shape of the detection electrode 41 is not limited to a specific shape, and any shape other than a ring shape may be used.

[0139] In the above specific example, the situation where the guard electrode 42 is set to the same potential as the detection electrode 41 does not mean that the potentials of the two are completely consistent as a result. That is, for example, as long as the two are electrically connected to a common power supply via wiring and powered, a slight potential difference may be generated between the two. In addition, the guard electrode 42 may also be set to the same potential as the reference electrode 21c or the microphone housing 20 as the "first electrode". In this case, the guard electrode 42 can be grounded. The "same potential" in this case does not mean that the potentials of the two are completely consistent as a result. Therefore, "same potential" can also be referred to as "actually the same potential".

[0140] The structure of the protective electrode 42 is also not limited to the above specific examples. For example, the shape of the protective electrode 42 is not limited to a plate or a film, and may be a mesh, a rod, or a spiral, etc. In addition, a plurality of protective electrodes 42 may be arranged in a predetermined direction, such as in the axial direction and / or the circumferential direction.

[0141] The protection electrode 42 may not be provided on the auxiliary member 8. That is, for example, the protection electrode 42 may be fixed to the outer peripheral surface 20h of the diaphragm support part 20b formed of an insulating material. Or, for example, the protection electrode 42 may be bonded to the outer peripheral surface 20h of the diaphragm support part 20b formed of a conductive material via an insulating layer.

[0142] The guard electrode 42 may also be provided on the elastic support member 3. In the above structure, a special operation process for providing the guard electrode 42 is also not required. Specifically, for example, the guard electrode 42 having a ring shape or a cylindrical shape along the central axis pointing in the axial direction may be embedded in the elastic support member 3 made of insulating synthetic resin. Or, for example, the elastic support member 3 may be formed entirely or partially of conductive rubber, so that it can be used as the guard electrode 42.

[0143] The protection electrode 42 may also be provided along the detection electrode 41. Figure 8 as well as Fig. 9 As shown in FIG. 8 , the protection electrode 42 may be stacked with the detection electrode 41 via the insulating layer 87. Figure 8 as well as Fig. 9 In the example, Figure 7 Similar to the example of FIG. 1 , the entire microphone housing 20 is formed of a good conductor metal such as aluminum.

[0144] exist Figure 8 In the example of FIG. 4 , the detection electrode 41 is formed into a flat thin plate or film having a thickness direction in the axial direction. That is, the detection electrode 41 is provided along the bumper back surface V32 of the front bumper V3. Specifically, the detection electrode 41 is provided so as to be in close contact with the bumper back surface V32 and close to the mounting hole V33 when mounted on the vehicle.

[0145] The guard electrode 42 is formed in a thin plate or film shape. In a cross-sectional view based on a plane including the directional axis DA, the guard electrode 42 has a substantially U-shaped shape surrounding the detection electrode 41 from the base end side in the directional axis direction. Specifically, the guard electrode 42 has a ring electrode portion 421, an inner protrusion portion 422, and an outer protrusion portion 423.

[0146] The ring electrode portion 421 is a thin plate-like or film-like portion having a thickness direction in the axial direction, and is arranged in parallel with the detection electrode 41. The inner protrusion 422 is provided to protrude from the radial inner edge of the ring electrode portion 421 to the front end side in the axial direction. The front end of the inner protrusion 422 in the axial direction is arranged to be coplanar with the bumper-facing surface 83, on the radial inner side of the detection electrode 41. The outer protrusion 423 is provided to protrude from the radial outer edge of the ring electrode portion 421 to the front end side in the axial direction. The front end of the outer protrusion 423 in the axial direction is extended to be coplanar with the bumper-facing surface 83, on the radial outer side of the detection electrode 41.

[0147] The insulating layer 87 is provided between the detection electrode 41 and the protection electrode 42. That is, the insulating layer 87 has a substantially U-shaped shape covering the detection electrode 41 from the base end side in the axial direction in a cross-sectional view based on a plane including the directional axis DA. The insulating layer 87 is formed of an insulating synthetic resin constituting the auxiliary component 8.

[0148] In the above structure, the guard electrode 42 is fixedly stacked with the detection electrode 41 via the insulating layer 87, so that the positional relationship between the detection electrode 41 and the guard electrode 42 can be fixed. In addition, the assembly 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. Therefore, according to the above structure, the detection error caused by the assembly error can be well suppressed.

[0149] Fig. 9 Indicates that Figure 8 The example shown is that the assembly of the detection electrode 41, the insulating layer 87, and the protection electrode 42 is fixedly supported by the holding portion 81 of the auxiliary member 8. That is, Fig. 9 An example is Figure 8 The partial modification of the structure and also Figure 7 Partial modification of the structure.

[0150] exist Fig. 9 In the example of , the detection electrode 41 is a thin plate or film-like member having a thickness direction in the radial direction, and is formed into a cylindrical or partially cylindrical shape that surrounds the directional axis DA and extends in the directional axis direction. The detection electrode 41 is arranged radially outside the protection electrode 42. That is, the detection electrode 41 is buried inside the holding portion 81 in a manner that it is arranged at a middle position in the thickness direction of the holding portion 81 having a thickness direction in the radial direction.

[0151] The guard electrode 42 is a thin plate or film-like component having a thickness direction in the radial direction, and is formed into a cylindrical or partially cylindrical shape that surrounds the directional axis DA and extends in the directional 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 to the inner peripheral surface 85 side of the cylindrical surface of the holding portion 81 in a manner that is coplanar with the inner peripheral surface 85 of the holding portion 81.

[0152] The insulating layer 87 is a thin plate or film-like portion having a thickness direction in the radial direction, and is formed into a cylindrical or partially cylindrical shape that surrounds the directional axis DA and extends in the directional axis direction. The protective electrode 42, the insulating layer 87, and the detection electrode 41 are arranged concentrically in this order toward the radially outer side. The insulating layer 87 is formed of an insulating synthetic resin constituting the auxiliary component 8.

[0153] In the above structure, the guard electrode 42 is fixedly stacked with the detection electrode 41 via the insulating layer 87, so that the positional relationship between the detection electrode 41 and the guard electrode 42 can be fixed. In addition, the assembly 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. Therefore, according to the above structure, the detection error caused by the assembly error can be well suppressed.

[0154] exist Fig. 9 In the structure shown, the protective electrode 42 may be fixed to the outer peripheral surface 20h of the diaphragm support part 20b formed of an insulating material. Alternatively, for example, the protective electrode 42 may be bonded to the outer peripheral surface 20h of the diaphragm support part 20b formed of a conductive material via an insulating layer. Alternatively, for example, the protective electrode 42 may be provided on the elastic support member 3.

[0155] exist Figure 8 as well as Fig. 9 In, with Figure 7 The microphone housing 20 is formed entirely of a good conductor metal such as aluminum. However, the present invention is not limited to the above-mentioned embodiment. Figure 8 as well as Fig. 9 In the structure shown, the whole or a part of the microphone housing 20 may have insulating properties.

[0156] In the above embodiment, Figure 3 The conductor portion 20n shown is provided to constitute a part of the detection wiring 52. However, the present invention is not limited to the above embodiment. That is, for example, the conductor portion 20n may also be provided to constitute a part of the protection wiring 53. Or, for example, the conductor portion 20n may also be provided to constitute a part of the detection wiring 52 and a part of the protection wiring 53.

[0157] The control circuit device 54 can be configured in the form of hardware such as ASIC. ASIC is an abbreviation of Application Specific Integrated Circuit.

[0158] The guard electrode 42 can be used to detect water infiltration or condensation. For example, water infiltration may occur between the holding portion 81 of the auxiliary component 8 and the microphone housing 20. Or condensation may occur along the back surface V32 of the bumper. The electrical characteristics between the reference electrode 21c and the guard electrode 42, that is, the electrostatic capacitance, changes due to the occurrence of these changes. Therefore, by detecting the changes in the above electrical characteristics, the occurrence of these changes can be well detected.

[0159] As described above, the movement of the harness, water penetration, condensation, etc. in the area inside the front bumper V3 may cause errors or noise components when detecting the attached matter S on the detection surface 20 d. The above-mentioned error factors or noise components can be measured using the guard electrode 42 .

[0160] Therefore, the control unit 54a may also detect the attached matter by taking into account the change 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 detect the attachment of the attached matter S 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.

[0161] According to the above configuration, the control unit 54a obtains the change in the electrostatic capacitance, which is the electrical characteristic, between the reference electrode 21c and the detection electrode 41. In addition, the control unit 54a obtains the change in the electrostatic capacitance, which is the electrical characteristic, between the detection electrode 41 and the protection electrode 42. And, based on the obtained results, the control unit 54a detects the attachment of the attached object S to the detection surface 20d. Thus, the attached object detection using the change in the electrical characteristic between the reference electrode 21c and the detection electrode 41 can be performed with better accuracy.

[0162] like Fig.10 As shown, the protective electrode 42 as the "third electrode" may be stacked with the microphone housing 20 as the "first electrode" via the insulating layer 97. Fig.10 The protective electrode 42 is provided along the diaphragm support portion 20b. In addition, the protective electrode 42 is provided to cover approximately half of the base end side of the diaphragm support portion 20b pointing in the axial direction. The insulating layer 97 is provided between the protective electrode 42 and the diaphragm support portion 20b. The insulating layer 97 is formed of, for example, an insulating adhesive or the like.

[0163] In the above structure, the positional relationship between the protective electrode 42 as the "third electrode" and the microphone housing 20 constituting the "first electrode" can be well fixed. Therefore, the protective effect of the protective electrode 42 can be stably achieved. In addition, the protective electrode 42 covers approximately half of the base end side of the microphone housing 20 constituting the "first electrode" pointing to the axial direction, so that changes in electrical characteristics caused by reasons other than the attachment of the attachment S to the ultrasonic microphone 2 are well suppressed. Therefore, the attachment detection can be performed with better accuracy.

[0164] In addition, the structure in which the "first electrode" and the "third electrode" are stacked with the insulating layer 97 interposed therebetween is not limited to Fig.10 The specific example shown. That is, for example, Figure 2 In the illustrated structure, a stack of the insulating layer 97 and the protective electrode 42 may be provided so as to surround the stack of the piezoelectric body 21 a and the driving electrode 21 b .

[0165] In the above specific example, the attachment detection action is performed by the control circuit device 54, i.e., the control unit 54a. Therefore, the control circuit device 54, i.e., the control unit 54a, can be evaluated as a "detection unit that detects the attachment state of the attachment S based on the electrical characteristics between the first electrode and the second electrode". However, the present invention is not limited to the above embodiment. That is, for example, the attachment detection action can be performed by the ECU on the vehicle to which the ultrasonic sensor 1 is electrically connected. ECU is the abbreviation of Electronic Control Unit.

[0166] The protection voltage applying unit 54g is not limited to the voltage follower, and a so-called isolation amplifier can be used as the protection voltage applying unit 54g, for example.

[0167] There is no particular limitation on the structure of the auxiliary component 8. That is, the shape and structure of the auxiliary component 8 of the above-mentioned specific example are simplified to avoid complicating the description. Therefore, the present invention is not limited to the shape and structure of the auxiliary component 8 of the above-mentioned specific example. Therefore, for example, the auxiliary component 8 may be a component called a "retainer" or a component called a "frame". In addition, the entirety or a portion of the auxiliary component 8 may be integrated with the sensor housing 6.

[0168] In the above description, a plurality of components that are seamlessly integrated may be formed by bonding independent components together. Similarly, a plurality of components that are formed by bonding independent components together may be seamlessly integrated.

[0169] In the above description, a plurality of components formed of the same material may be formed of different materials. Similarly, a plurality of components formed of different materials may be formed of the same material.

[0170] Of course, the elements constituting the above-mentioned embodiments are not necessarily required, except for the cases that are specifically indicated as required and the cases that are obviously considered to be required in principle. In addition, when referring to the number, value, amount, range and other numerical values ​​of the structural elements, the present invention is not limited to the specific number, except for the cases that are specifically indicated as required and the cases that are obviously limited to a specific number in principle. Similarly, when referring to the shape, direction, positional relationship and the like of the structural elements, the present invention is not limited to the shape, direction, positional relationship and the like, except for the cases that are specifically indicated as required and the cases that are limited to a specific shape, direction, positional relationship and the like in principle.

[0171] The modification examples are not limited to the above examples. In addition, a plurality of modification examples can be combined with each other. Moreover, all or part of the above embodiment can be combined with all or part of any modification examples.

Claims

1. An ultrasonic sensor comprising: A first electrode is provided on an ultrasonic microphone having a vibration element, wherein the vibration element has a function of converting mechanical vibration into an electrical signal; a second electrode disposed outside the ultrasonic microphone so that an electrical characteristic between the second electrode and the first electrode changes according to an attachment state of an attachment object to the ultrasonic microphone; and a third electrode provided to suppress a change in electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the ultrasonic microphone, The third electrode is provided so as to be sandwiched between the first electrode and the second electrode.

2. The ultrasonic sensor according to claim 1, wherein: The ultrasonic microphone is provided with a microphone shell, which has: a diaphragm portion formed in a thin plate shape for ultrasonic vibration; and a diaphragm supporting portion formed in a cylindrical shape with a directional axis along the vibration direction of the diaphragm portion as a central axis and arranged to support the diaphragm portion at the outer edge portion of the diaphragm portion, and the vibration element is fixedly supported on the diaphragm portion.

3. The ultrasonic sensor according to claim 2, wherein: The microphone housing is formed of a conductive material, and the first electrode is integrated with the microphone housing.

4. The ultrasonic sensor according to claim 1, wherein: The above-mentioned electrical characteristic is electrostatic capacitance.

5. An ultrasonic sensor comprising: A first electrode is provided on an ultrasonic microphone having a vibration element, wherein the vibration element has a function of converting mechanical vibration into an electrical signal; a second electrode disposed outside the ultrasonic microphone so that an electrical characteristic between the second electrode and the first electrode changes according to an attachment state of an attachment object to the ultrasonic microphone; and a third electrode provided to suppress a change in electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the ultrasonic microphone, The third electrode is set to have the same potential as the first electrode or the second electrode.

6. An ultrasonic sensor comprising: A first electrode is provided on an ultrasonic microphone having a vibration element, wherein the vibration element has a function of converting mechanical vibration into an electrical signal; a second electrode disposed outside the ultrasonic microphone so that an electrical characteristic between the second electrode and the first electrode changes according to an attachment state of an attachment object to the ultrasonic microphone; and a third electrode provided to suppress a change in electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the ultrasonic microphone, The second electrode or the third electrode is provided on an auxiliary member which is a member for attaching the ultrasonic sensor to an attachment object.

7. An ultrasonic sensor comprising: A first electrode is provided on an ultrasonic microphone having a vibration element, wherein the vibration element has a function of converting mechanical vibration into an electrical signal; a second electrode disposed outside the ultrasonic microphone so that an electrical characteristic between the second electrode and the first electrode changes according to an attachment state of an attachment object to the ultrasonic microphone; and a third electrode provided to suppress a change in electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the ultrasonic microphone, The third electrode is stacked on the first electrode or the second electrode via an insulating layer.

8. An ultrasonic sensor comprising: A first electrode is provided on an ultrasonic microphone having a vibration element, wherein the vibration element has a function of converting mechanical vibration into an electrical signal; a second electrode disposed outside the ultrasonic microphone so that an electrical characteristic between the second electrode and the first electrode changes according to an attachment state of an attachment object to the ultrasonic microphone; and a third electrode provided to suppress a change in electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the ultrasonic microphone, The ultrasonic microphone comprises a microphone housing, the microphone housing comprising: a diaphragm portion formed in a thin plate shape for ultrasonic vibration; and a diaphragm support portion formed in a cylindrical shape with a directional axis along the vibration direction of the diaphragm portion as a central axis and arranged to support the diaphragm portion at the outer edge portion of the diaphragm portion. The vibration element is fixedly supported by the diaphragm portion. The third electrode is provided to suppress changes in the electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the outer surface of the diaphragm portion and the detection surface exposed toward the outside of the installation object when the ultrasonic sensor is mounted on the outer plate of the installation object, The device is configured to be capable of detecting attachment of the attached matter to the detection surface based on electrical characteristics between the first electrode and the second electrode.

9. The ultrasonic sensor according to claim 8, wherein: The second electrode is disposed along the back surface of the outer plate.

10. The ultrasonic sensor according to claim 8, wherein: The third electrode is provided along the diaphragm support portion.

11. The ultrasonic sensor according to claim 8, wherein: The device is configured to be capable of detecting attachment of the attached matter to the detection surface based on electrical characteristics between the first electrode and the second electrode and electrical characteristics between the second electrode and the third electrode.

12. An ultrasonic sensor comprising: A first electrode is provided on an ultrasonic microphone having a vibration element, wherein the vibration element has a function of converting mechanical vibration into an electrical signal; a second electrode disposed outside the ultrasonic microphone so that an electrical characteristic between the second electrode and the first electrode changes according to an attachment state of an attachment object to the ultrasonic microphone; and a third electrode provided to suppress a change in electrical characteristics between the first electrode and the second electrode caused by reasons other than attachment of the attachment to the ultrasonic microphone, The ultrasonic microphone comprises a microphone housing, the microphone housing comprising: a diaphragm portion formed in a thin plate shape for ultrasonic vibration; and a diaphragm support portion formed in a cylindrical shape with a directional axis along the vibration direction of the diaphragm portion as a central axis and arranged to support the diaphragm portion at the outer edge portion of the diaphragm portion. The vibration element is fixedly supported by the diaphragm portion. The diaphragm portion is formed into a shape having a long side direction and a short side direction in a plane perpendicular to the directional axis. A lead portion constituting a power supply path for supplying power to the second electrode or the third electrode is provided in a thick portion that is a portion of the diaphragm support portion along the longitudinal direction.

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