Ultrasonic transducer, ultrasonic sensor, object detection device, object detection method, and object detection program

Abstract

The present invention relates to an ultrasonic transducer, an ultrasonic sensor, an object detection device, an object detection method, and an object detection program. The ultrasonic transducer (4) includes a transducer housing (5) and an ultrasonic element (6). The transducer housing is formed in a bottomed cylindrical shape having a side plate portion (51) and a bottom plate portion (52). The side plate portion is formed in a cylindrical shape surrounding a central axis (DA), and the bottom plate portion closes one end side of the side plate portion in the axial direction to form a diaphragm (50). The ultrasonic element (6) is fixedly supported on the bottom plate portion so as to face an internal space (53) surrounded by the side plate portion and the bottom plate portion. The ultrasonic element is arranged at a position offset in the in-plane direction with respect to the central position (P) of the diaphragm in the in-plane direction orthogonal to the axial direction, so as to be able to generate a first transmission wave having a first directivity characteristic and a second transmission wave having a second directivity characteristic, the second directivity characteristic being a directivity characteristic different from the first directivity characteristic and reducing the sound pressure in the axial direction.

Description

Technical Field

[0001] The present disclosure relates to an ultrasonic transducer and an ultrasonic sensor including the ultrasonic transducer. Further, the present disclosure relates to an object detection device and an object detection method for detecting an object using the ultrasonic transducer, and an object detection program executed by the object detection device. Background Art

[0002] The ultrasonic transceiver described in Patent Document 1 includes two bottomed cylindrical shells having different sizes. Specifically, the ultrasonic transceiver has a structure in which the bottom surface of one bottomed cylindrical shell having a larger shape is fixed to the opening of the other bottomed cylindrical shell, and a piezoelectric element is adhered to the outside of the bottom surface of the other bottomed cylindrical shell.

[0003] According to such a structure, two different resonance frequencies can be generated by one ultrasonic transceiver. Thereby, it is possible to perform detection at a short distance and a long distance by one ultrasonic transceiver. Specifically, for example, in order to detect a long distance, the directivity is sharpened to eliminate false detection caused by the ground or the like.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-267472

[0005] In the ultrasonic transceiver described in Patent Document 1, the directivity characteristics of two different resonance frequencies each become the maximum sound pressure on the central axis and have an axisymmetric spindle shape centered on the central axis. The difference in the directivity characteristics between the two different resonance frequencies is mainly manifested as the difference in the directivity angle, that is, the sound pressure half-value angle. Therefore, for example, it is difficult to distinguish whether an object detected at a short distance is a low-height protrusion such as a wheel chock protruding from the ground or a high-height structure such as a wall existing in front of the ultrasonic transceiver. Summary of the Invention

[0006] The present disclosure has been made in view of the above-exemplified circumstances and the like. That is, the present disclosure provides, for example, an ultrasonic transducer having excellent object detection performance compared with the prior art, and an ultrasonic sensor including the ultrasonic transducer. Alternatively, the present disclosure provides, for example, an object detection device, an object detection method, and an object detection program for detecting an object using the ultrasonic transducer.

[0007] According to one aspect of the present disclosure, an ultrasonic transducer includes:

[0008] a transducer housing formed in a bottomed cylindrical shape having a side plate portion and a bottom plate portion, the side plate portion being formed in a cylindrical shape surrounding a central axis, and the bottom plate portion closing one end side of the side plate portion in an axial direction parallel to the central axis to form a diaphragm capable of ultrasonic vibration; and

[0009] An ultrasonic element is fixedly supported on the bottom plate portion so as to face the internal space surrounded by the side plate portion and the bottom plate portion, and converts an electrical signal and ultrasonic vibration.

[0010] The ultrasonic element is arranged at a position offset in the in-plane direction with respect to the center position of the diaphragm in the in-plane direction orthogonal to the axial direction, so as to be able to generate a first transmission wave having a first directivity characteristic and a second transmission wave having a second directivity characteristic, the second directivity characteristic being a directivity characteristic different from the first directivity characteristic and reducing the sound pressure in the axial direction.

[0011] According to another aspect of the present disclosure, an ultrasonic sensor includes:

[0012] The ultrasonic transducer; and

[0013] A control circuit element electrically connected to the ultrasonic transducer to switch between the first vibration mode and the second vibration mode.

[0014] The control circuit element generates the first transmission wave by driving the ultrasonic element provided at the center position and not driving the ultrasonic element provided at a position different from the center position, and generates the second transmission wave by not driving the ultrasonic element provided at the center position and driving the ultrasonic element provided at a position different from the center position.

[0015] According to still another aspect of the present disclosure, an ultrasonic sensor includes:

[0016] The ultrasonic transducer; and

[0017] A control circuit element electrically connected to the ultrasonic transducer to switch between the first vibration mode and the second vibration mode.

[0018] The control circuit element switches the driving timing of a pair of the ultrasonic elements between in-phase and anti-phase.

[0019] According to still another aspect of the present disclosure, an object detection device is configured to use the ultrasonic transducer to detect an object existing around a vehicle on which the ultrasonic transducer is mounted.

[0020] The object detection device includes:

[0021] An amplitude information acquisition unit that acquires amplitude information corresponding to the amplitude of a reflected wave obtained by reflecting a transmission wave transmitted from the ultrasonic transducer by the object;

[0022] A distance measurement information acquisition unit that acquires distance measurement information corresponding to the distance to the object based on the reflected wave; and

[0023] A determination unit determines the presence of an object, i.e., an obstacle, that becomes an obstacle to the travel of the vehicle, based on the ranging information and / or the amplitude information obtained from the reflected wave of the transmitted wave having the second directivity characteristic that is axisymmetric about the center in the vehicle height direction, i.e., the second transmitted wave.

[0024] According to another aspect of the present disclosure, an object detection method is a method of detecting an object existing around a vehicle equipped with the ultrasonic transducer using the ultrasonic transducer, and includes the following processes or steps:

[0025] Obtaining amplitude information corresponding to the amplitude of the reflected wave obtained by reflecting the transmitted wave transmitted from the ultrasonic transducer by the object;

[0026] Obtaining ranging information corresponding to the distance to the object based on the reflected wave; and

[0027] Determining the presence of an object, i.e., an obstacle, that becomes an obstacle to the travel of the vehicle, based on the ranging information and / or the amplitude information obtained from the reflected wave of the transmitted wave having the second directivity characteristic that is axisymmetric about the center in the vehicle height direction, i.e., the second transmitted wave.

[0028] According to another aspect of the present disclosure, an object detection program is a program executed by an object detection device configured to use the ultrasonic transducer to detect an object existing around a vehicle equipped with the ultrasonic transducer,

[0029] The processes executed by the object detection device include:

[0030] A process of obtaining amplitude information corresponding to the amplitude of the reflected wave obtained by reflecting the transmitted wave transmitted from the ultrasonic transducer by the object;

[0031] A process of obtaining ranging information corresponding to the distance to the object based on the reflected wave; and

[0032] A process of determining the presence of an object, i.e., an obstacle, that becomes an obstacle to the travel of the vehicle, based on the ranging information and / or the amplitude information obtained from the reflected wave of the transmitted wave having the second directivity characteristic that is axisymmetric about the center in the vehicle height direction, i.e., the second transmitted wave.

[0033] In addition, in each part of the application document, there are cases where reference numerals enclosed in parentheses are assigned to each element. However, such reference numerals merely show a simple example of the correspondence between the element and the specific unit described in the embodiments below. Therefore, the present disclosure is not limited by any of the descriptions of the above reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a perspective view showing the appearance of a vehicle equipped with the ultrasonic sensor of the first embodiment.

[0035] Figure 2 is showing Figure 1 a cross-sectional view schematically showing the device configuration of the ultrasonic sensor shown.

[0036] Figure 3 is showing Figure 2 a bottom view of a first configuration example of the ultrasonic transducer shown.

[0037] Figure 4 is showing Figure 2 a perspective view of a second configuration example of the ultrasonic transducer shown.

[0038] Figure 5A is showing the Figure 4 first vibration mode in the diaphragm of the transducer housing shown in a cross-sectional view.

[0039] Figure 5B is showing the Figure 4 first vibration mode in the diaphragm of the transducer housing shown in a perspective view.

[0040] Figure 6A is showing the Figure 4 second vibration mode in the diaphragm of the transducer housing shown in a cross-sectional view.

[0041] Figure 6B is showing the Figure 4 second vibration mode in the diaphragm of the transducer housing shown in a perspective view.

[0042] Figure 7 is showing Figure 3 and Figure 4 a diagram showing the directivity characteristics in the ultrasonic transducer shown.

[0043] Figure 8 is showing Figure 2 a perspective view of a third configuration example of the ultrasonic transducer shown.

[0044] Figure 9 is showing Figure 2 a cross-sectional view of a fourth configuration example of the ultrasonic transducer shown.

[0045] Figure 10 is Figure 9 the bottom view of the ultrasonic transducer shown

[0046] Figure 11 represents Figure 2 the perspective view of the fifth configuration example of the ultrasonic transducer shown

[0047] Figure 12 is Figure 11 the cross-sectional view of the ultrasonic transducer shown

[0048] Figure 13 represents the case of in-phase driving of a pair of ultrasonic elements of the ultrasonic transducer provided in Figure 11 and Figure 12 the diagram of the directivity characteristic in the case of in-phase driving of a pair of ultrasonic elements of the ultrasonic transducer shown

[0049] Figure 14 represents the case of anti-phase driving of a pair of ultrasonic elements of the ultrasonic transducer provided in Figure 11 and Figure 12 the diagram of the directivity characteristic in the case of anti-phase driving of a pair of ultrasonic elements of the ultrasonic transducer shown

[0050] Figure 15 represents Figure 2 the perspective view of the sixth configuration example of the ultrasonic transducer shown

[0051] Figure 16 is Figure 15 the cross-sectional view of the ultrasonic transducer shown

[0052] Figure 17 represents Figure 15 and Figure 16 the diagram of the directivity characteristic in the ultrasonic transducer shown

[0053] Figure 18 represents Figure 15 and Figure 16 the diagram of the directivity characteristic in the ultrasonic transducer shown

[0054] Figure 19 is the block diagram showing the schematic structure of the object detection device of the second embodiment

[0055] Figure 20 represents Figure 19 the schematic diagram showing the outline of the operation of the object detection device shown

[0056] Figure 21 represents Figure 19 the flowchart of the first operation example of the object detection device shown

[0057] Figure 22 representsFigure 19 Flowchart of the second operation example of the object detection device shown

[0058] Figure 23 It represents Figure 19 Diagram showing the outline of the third operation example of the object detection device shown

[0059] Figure 24 It represents Figure 19 Flowchart of the third operation example of the object detection device shown

[0060] Figure 25 It represents Figure 19 Flowchart of the fourth operation example of the object detection device shown

[0061] Figure 26 It represents Figure 19 Flowchart of the fifth operation example of the object detection device shown

[0062] Figure 27 It represents Figure 19 Flowchart of the sixth operation example of the object detection device shown

[0063] Figure 28 Block diagram showing the schematic structure of the object detection device of the third embodiment

[0064] Figure 29 It represents Figure 28 Flowchart of the operation example of the object detection device shown

[0065] Figure 30 Front view showing the appearance of a vehicle equipped with the object detection device of the fourth embodiment Detailed implementation mode

[0066] Hereinafter, embodiments of the present disclosure will be described based on the drawings. In addition, for various modification examples applicable to one embodiment, if inserted in the middle of a series of descriptions related to that embodiment, it may hinder the understanding of that embodiment. Therefore, the modification examples are not inserted in the middle of a series of descriptions related to that embodiment, but are described collectively later.

[0067] (First Embodiment: Sensor Structure)

[0068] If referring to Figure 1 , the vehicle V is a so-called four-wheel automobile and includes a box-shaped vehicle body V1. A front bumper V2 as a vehicle body component is installed at the front end of the vehicle body V1. A rear bumper V3 as a vehicle body component is installed at the rear end of the vehicle body V1.

[0069] The ultrasonic sensor 1 is a so-called in-vehicle clearance sonar, which is installed on the front bumper V2 and the rear bumper V3. Through holes, i.e., mounting holes V4, for installing the ultrasonic sensor 1 are provided on the front bumper V2 and the rear bumper V3. The mounting hole V4 provided on the front bumper V2 is formed to open forward, i.e., to the outside of the front bumper V2, on the outer surface V5 of the bumper. Hereinafter, the state in which the ultrasonic sensor 1 is mounted on the vehicle V, i.e., the state of being mounted on the front bumper V2 or the rear bumper V3, is referred to as the "in-vehicle state". In addition, the vehicle V equipped with the ultrasonic sensor 1 is sometimes referred to as "this vehicle".

[0070] (Ultrasonic sensor)

[0071] Figure 2 The overall structure of the ultrasonic sensor 1 is shown in the in-vehicle state of being mounted on the front bumper V2. For the convenience of explanation, as shown in the figure, a right-handed XYZ orthogonal coordinate system is set such that the Y-axis is parallel to the central axis DA, and the Z-axis is parallel to the vehicle height direction in the in-vehicle state. The central axis DA is a virtual straight line extending along the transmission and reception direction of ultrasonic waves in the ultrasonic sensor 1. The direction parallel to the central axis DA is referred to as the "axial direction". The vehicle height direction is the direction parallel to the direction of gravity in the state where this vehicle is stably placed on a horizontal plane. In addition, sometimes the Figure 2 upper side in, i.e., the positive Y-axis direction side, is referred to as the "front end side" of the axial direction. Similarly, sometimes the Figure 2 lower side in, i.e., the negative Y-axis direction side, is referred to as the "base end side" of the axial direction. And, any direction orthogonal to the axial direction is sometimes referred to as the "in-plane direction". That is, the "in-plane direction" is the direction parallel to the XZ plane.

[0072] If referring to Figure 2 , in the present embodiment, the ultrasonic sensor 1 is mounted on this vehicle with the central axis DA being horizontal. The ultrasonic sensor 1 includes: a sensor housing 2, an elastic holding member 3, and an ultrasonic transducer 4. The ultrasonic transducer 4 includes a transducer housing 5 and an ultrasonic element 6. Hereinafter, the structures of the respective parts constituting the ultrasonic sensor 1 will be described.

[0073] The sensor housing 2 constituting the outer shell of the ultrasonic sensor 1 is integrally formed of a hard synthetic resin such as polypropylene. The sensor housing 2 has: a housing main body portion 21, a connector portion 22, and a housing cylinder portion 23.

[0074] The housing main body portion 21 is formed in a box shape that is open at the base end side in the axial direction. The connector portion 22 is provided to electrically connect the ultrasonic sensor 1 to the ECU. ECU is the abbreviation of Electronic Control Unit. The connector portion 22 extends and is arranged outward from the side wall portion in the housing main body portion 21 away from the central axis DA.

[0075] The cylindrical portion of the sensor housing 2 that surrounds the central axis DA, i.e., the housing tube portion 23, protrudes from the housing main body portion 21 toward the front end side in the axial direction. The housing tube portion 23 is configured to hold the axial base end portion of the elastic holding member 3. The cylindrical space inside the housing tube portion 23 is provided to communicate with the space inside the housing main body portion 21. A circuit board 24, a control circuit element 25, a wiring portion 26, a shock-absorbing member 27, and a housing filling material 28 are arranged inside the sensor housing 2.

[0076] The circuit board 24 is housed in the housing main body portion 21. A control circuit element 25 that controls the operation of the ultrasonic sensor 1 is mounted on the circuit board 24. The control circuit element 25 is a so-called integrated circuit element and is configured to control the transmission and reception operations in the ultrasonic transducer 4. The wiring portion 26 is provided to electrically connect the ultrasonic transducer 4 and the circuit board 24. That is, the control circuit element 25 is electrically connected to the ultrasonic transducer 4 via a circuit (not shown) provided on the circuit board 24 and the wiring portion 26.

[0077] The shock-absorbing member 27 is provided to suppress the vibration transmission from the ultrasonic transducer 4 to the sensor housing 2. Specifically, the shock-absorbing member 27 is formed of a foamed elastomer such as foamed silicone having insulation and elasticity. The shock-absorbing member 27 is formed in a disk shape having an outer diameter corresponding to the inner diameter of the elastic holding member 3. The shock-absorbing member 27 is inserted into the cylindrical space inside the elastic holding member 3 on the base end side closer than the ultrasonic transducer 4 in the axial direction.

[0078] The space inside the sensor housing 2 is filled with the housing filling material 28. The housing filling material 28 is formed of a synthetic resin material having insulation such as silicone rubber.

[0079] The elastic holding member 3 is formed in a cylindrical shape with the central axis DA as the axis center. The elastic holding member 3 is held at the front end portion in the axial direction of the housing tube portion 23 provided in the sensor housing 2. The elastic holding member 3 is formed of a synthetic resin-based elastic material such as silicone rubber having insulation and elasticity.

[0080] The elastic holding member 3 is configured to support the ultrasonic transducer 4 in a state where the front end face in the axial direction of the ultrasonic transducer 4 is exposed and the base end side is covered. That is, the ultrasonic transducer 4 is elastically supported by the sensor housing 2 via the elastic holding member 3.

[0081] (Ultrasonic transducer)

[0082] The ultrasonic transducer 4 has the function of an ultrasonic microphone that combines transmission and reception. That is, the ultrasonic transducer 4 is configured to be able to transmit and receive ultrasonic waves. Specifically, the ultrasonic transducer 4 is configured to transmit a transmission wave as an ultrasonic wave. In addition, the ultrasonic transducer 4 is configured to receive the reflected wave of the transmission wave reflected by an object existing around the vehicle and generate a signal corresponding to the intensity and frequency of the received reflected wave.

[0083] (First configuration example)

[0084] Hereinafter, with reference to Figure 2 and Figure 3 , the details of the structure of the ultrasonic transducer 4 of the present embodiment will be described. In addition, Figure 3 the right-handed XYZ orthogonal coordinate system shown in Figure 2 is the same as the right-handed XYZ orthogonal coordinate system shown in

[0085] The transducer housing 5 is formed in a bottomed cylindrical shape surrounding the central axis DA. In the present embodiment, the transducer housing 5 has a cylindrical outer shape with the central axis DA as the axis center. In addition, the transducer housing 5 is integrally formed seamlessly from a metal such as aluminum.

[0086] The transducer housing 5 has a diaphragm 50 capable of ultrasonic vibration. The diaphragm 50 is a thin plate-like portion in the transducer housing 5 having a thickness direction parallel to the axial direction, and is provided to flexurally deform with the outer edge portion as a fixed end, that is, a node position, and vibrate at a specified frequency within the ultrasonic frequency band.

[0087] In the present embodiment, the diaphragm 50 is formed in a flat plate shape with a constant thickness. In addition, as shown in Figure 3 , the diaphragm 50 is formed in an elliptical shape having a long side direction and a short side direction that are orthogonal to each other. Specifically, the diaphragm 50 is formed in a rounded rectangular shape or an oval shape with the Z-axis direction as the long side direction and the X-axis direction as the short side direction. Thus, the ultrasonic transducer 4 is configured to have a narrower directivity angle in the Z-axis direction than in the X-axis direction. Hereinafter, the long side direction in the elliptical shape of the diaphragm 50 will be simply referred to as the "long side direction". The same applies to the "short side direction".

[0088] That is, the diaphragm 50 is formed by a region surrounded by a pair of arc portions 50a and a pair of chord portions 50b. The arc portions 50a are provided at both ends of the diaphragm 50 in the long side direction so as to open toward the central axis DA. The chord portions 50b are arranged to extend in the long side direction at both ends of the diaphragm 50 in the short side direction to connect the opposing ends of the pair of arc portions 50a to each other.

[0089] The transducer housing 5 has a side plate portion 51 and a bottom plate portion 52. The side plate portion 51 is formed in a cylindrical shape surrounding the central axis DA. The bottom plate portion 52 constituting the diaphragm 50 is provided to close one end side in the axial direction of the side plate portion 51, that is, the front end side. The bottom plate portion 52 is seamlessly integrally joined to the front end portion of the side plate portion 51 in the axial direction. The internal space 53 surrounded by the side plate portion 51 and the bottom plate portion 52 is provided to open toward the base end side in the axial direction.

[0090] The side plate portion 51 has a thin wall portion 511 and a thick wall portion 512. The thin wall portion 511 is formed in a partial cylindrical shape having a predetermined thickness in the radial direction orthogonal to the central axis DA. The "radial direction" is the direction extending radially from the central axis DA. That is, the radial direction is the radius direction of a virtual circle drawn on a plane having the central axis DA as the normal line with the intersection of the plane and the central axis DA as the center.

[0091] The thin wall portions 511 are provided at both ends in the long side direction of the elliptical diaphragm 50, that is, at positions corresponding to the arc portions 50a in the circumferential direction. The "circumferential direction" is the circumferential direction of the above-mentioned virtual circle. A pair of thin wall portions 511 are arranged to face each other across the central axis DA.

[0092] The thick wall portion 512 is formed thicker than the thin wall portion 511 in the radial direction. The thick wall portion 512 is provided at both ends in the short side direction of the elliptical diaphragm 50, that is, at positions corresponding to the chord portions 50b in the circumferential direction. A pair of thick wall portions 512 are arranged to face each other across the central axis DA. When viewed in cross section based on a cross section orthogonal to the central axis DA, the thick wall portion 512 is formed in a bow shape.

[0093] The surface of the bottom plate portion 52 facing the internal space 53, that is, the inner surface 521, is the surface constituting the bottom surface of the diaphragm 50 and is formed in an elliptical shape identical to that of the diaphragm 50. The back surface of the inner surface 521 of the bottom plate portion 52, that is, the surface on the opposite side, that is, the outer surface 522, is provided to be exposed in the exposure direction DD. The exposure direction DD is parallel to the axial direction and is a direction from the inner surface 521 toward the outer surface 522. A protective film (not shown) such as a coating film having the same color as the outer surface V5 of the bumper is formed on the outer surface 522. The front end surface of the ultrasonic transducer 4 in the axial direction is formed by the outer surface on the opposite side of the joint surface of the protective film with the outer surface 522.

[0094] The transducer housing 5 is configured to hold the ultrasonic element 6 in the internal space 53 surrounded by the side plate portion 51 and the bottom plate portion 52. That is, the ultrasonic element 6 is fixedly supported on the bottom plate portion 52 so as to face the internal space 53. Specifically, the ultrasonic element 6 is fixed to the diaphragm 50 on the inner surface 521 side.

[0095] The ultrasonic element 6 is configured to convert an electrical signal and ultrasonic vibrations. Specifically, the ultrasonic element 6 is a piezoelectric element and is formed in a thin film shape having a thickness direction in the axial direction.

[0096] In the present embodiment, only one ultrasonic element 6 is provided in the diaphragm 50. In addition, the ultrasonic element 6 is disposed at a position radially offset in the in-plane direction with respect to the center position PC of the diaphragm 50 in the in-plane direction. The center position PC is the position of the intersection of the central axis DA and the inner surface 521.

[0097] The planar shape of the ultrasonic element 6 when viewed in a line of sight parallel to the Y-axis is formed in a circular shape. The ultrasonic element 6 is provided such that the element center PP is offset upward in the vertical direction, i.e., the positive Z-axis direction, from the center position PC in the vehicle-mounted state. The element center PP is the center of the outer shape of the ultrasonic element 6 in the in-plane direction. Specifically, when the planar shape of the ultrasonic element 6 is circular or elliptical, the element center PP is the center of the circle or ellipse.

[0098] The ultrasonic transducer 4 of the present embodiment is configured such that by providing the ultrasonic element 6 as described above, a first transmission wave having a first directivity characteristic and a second transmission wave having a second directivity characteristic can be generated. The first directivity characteristic is a spindle-shaped directivity characteristic (i.e., the directivity characteristic shown by the dashed line in Figure 7 ) that becomes the maximum sound pressure on the central axis DA, and can also be referred to as a normal directivity characteristic. The second directivity characteristic is a directivity characteristic different from the first directivity characteristic and is a directivity characteristic that reduces the sound pressure in the axial direction (i.e., the directivity characteristic shown by the solid line in Figure 7 ). That is, the second directivity characteristic is a "heart"-shaped directivity characteristic that significantly reduces the sound pressure on the central axis DA in the spindle-shaped directivity characteristic like the first directivity characteristic while maintaining symmetry with respect to the central axis DA in the Z-axis direction. In addition, the "symmetry" with respect to the central axis DA in the Z-axis direction in the second directivity characteristic does not require numerical perfect symmetry, but allows a difference of a degree that can be referred to as "practical symmetry" or "substantial symmetry".

[0099] The central position PC is the antinode position in the first vibration mode of the diaphragm 50 corresponding to the first directivity characteristic and is the node position in the second vibration mode of the diaphragm 50 corresponding to the second directivity characteristic. In the present embodiment, the ultrasonic element 6 is provided at a position different from the central position PC. That is, the ultrasonic element 6 is arranged in the in-plane direction at a position not overlapping with the central position PC. In other words, when observed with a line of sight parallel to the Y-axis, that is, when the ultrasonic element 6 and the central position PC are projected onto the XZ plane, the central position PC is provided outside the outer shape of the ultrasonic element 6. Alternatively, the ultrasonic element 6 is arranged between the central position PC on the plumb line LZ and the thin wall portion 511. The plumb line LZ is the intersection line of the plane containing the central axis DA and parallel to the YZ plane and the plane containing the inner surface 521 and parallel to the XZ plane. In contrast, the intersection line of the plane containing the central axis DA and parallel to the XY plane and the plane containing the inner surface 521 and parallel to the XZ plane is referred to as the horizontal line LX.

[0100] In the present embodiment, the ultrasonic element 6 is arranged at the antinode position in the second vibration mode. Specifically, the ultrasonic element 6 is set such that the in-plane direction position of the element center PP coincides with the antinode position in the second vibration mode.

[0101] (Second configuration example)

[0102] Figure 4 The ultrasonic transducer 4 shown is an ultrasonic transducer in which the shape of the transducer housing 5 is changed from the above configuration. That is, in Figure 4 the ultrasonic transducer 4 shown, the side plate portion 51 of the transducer housing 5 has a uniform thickness and is formed in a cylindrical shape surrounding the central axis DA. In other words, Figure 4 the structure shown corresponds to the structure in Figure 3 the structure shown in which the thick wall portion 512 is changed to the thin wall portion 511.

[0103] (Effect)

[0104] Hereinafter, an outline of the operation of the structure based on the present embodiment and the effects achieved by this structure will be described with reference to the respective drawings.

[0105] In the ultrasonic sensor 1 having the above structure, when the ultrasonic element 6 housed inside the bottomed cylindrical transducer housing 5 is driven, the ultrasonic element 6 performs ultrasonic vibration. By the ultrasonic element 6 performing ultrasonic vibration, the transducer housing 5 is excited. In this way, the ultrasonic transducer 4 composed of the transducer housing 5 and the ultrasonic element 6 vibrates in a specified vibration mode. As a result, a transmission wave is emitted from the diaphragm 50 along the exposure direction DD.

[0106] Hereinafter, for simplicity of explanation, Figure 4The vibration modes in the transducer housing 5 shown explain the directivity characteristics of the ultrasonic transducer 4. Figure 5A and Figure 5B show the first vibration mode based on the resonance frequency f1. Figure 6A and Figure 6B show the second vibration mode based on the resonance frequency f2. f1 < f2. Figure 5A and Figure 6A The double-dashed line in shows the vibration of the diaphragm 50. Figure 5B and Figure 6B show the amplitude distribution of the diaphragm 50 in terms of the density of the cross-hatching.

[0107] Figure 3 and Figure 4 The structure of the transducer housing 5 shown enables the generation of the first and second vibration modes. The switching between the first vibration mode based on the resonance frequency f1 and the second vibration mode based on the resonance frequency f2 is performed by switching the drive frequency of the ultrasonic element 6 in the control circuit element 25. The "drive frequency" refers to the frequency of the alternating voltage applied to the ultrasonic element 6, i.e., the element drive voltage.

[0108] As Figure 5A and Figure 5B shown, the first vibration mode is a vibration mode in which the entire diaphragm 50 flexes and deforms in the same direction along the Y-axis. In the first vibration mode, the node position is the radially outer edge portion of the diaphragm 50, and the antinode position is the center position PC.

[0109] As Figure 6A and Figure 6B shown, the second vibration mode is a vibration mode in which one side of the diaphragm 50 on the side closer to the Z-axis direction than the horizontal line LX flexes and deforms toward the positive Y-axis side, while the other side flexes and deforms toward the negative Y-axis side. On one side and the other side, the magnitudes of the amplitudes are substantially symmetric across the horizontal line LX. In the second vibration mode, node positions are generated on the horizontal line LX including the center position PC and at the radially outer edge portion of the diaphragm 50. At two positions on the vertical line LZ at the intermediate position between the center position PC and the side plate portion 51, antinode positions are generated.

[0110] By disposing the ultrasonic element 6 at the antinode position or near it in the vibration mode, the diaphragm 50 is thus well excited. On the other hand, if the ultrasonic element 6 is disposed at the node position or near it in the vibration mode, it is difficult to well excite the diaphragm 50 to the extent that a transmission wave can be sent.

[0111] Regarding this point, the in-plane position of the ultrasonic element 6 in the diaphragm 50 that can well emit the first transmission wave based on the first vibration mode exists in a relatively wide range centered on the center position PC as the antinode position. Specifically, for example, asFigure 3 and Figure 4 As shown, there is a case where the radial dimension of the ultrasonic element 6 is about 1 / 2 to 1 / 4 of the radial dimension of the diaphragm 50. In this case, as long as the ultrasonic element 6 is arranged within the range of the diaphragm 50 in the in-plane direction, the first vibration mode can be generated well regardless of the in-plane position of the ultrasonic element 6.

[0112] In contrast, if the ultrasonic element 6 is arranged at the center position PC which is a node position, it is almost impossible to generate the second vibration mode. Regarding this point, if the element center PP of the ultrasonic element 6 is offset from the center position PC, the generation degree of the second vibration mode increases according to the offset amount. By arranging the ultrasonic element 6 at a position different from the center position PC, that is, at a position that does not overlap with the center position PC in the in-plane direction, the second transmission wave based on the second vibration mode can be transmitted with a good intensity that can receive the reflected wave from an object outside. In particular, by arranging the ultrasonic element 6 so that the in-plane direction position of the element center PP coincides with the antinode position of the second vibration mode, the excitation efficiency of the second vibration mode is improved.

[0113] Figure 7 represents the directivity along the plumb line LZ. In Figure 7 , the dotted line represents the directivity of the first transmission wave, and the solid line represents the directivity of the second transmission wave. As Figure 7 shown, the first transmission wave has a prescribed directivity from the center of the diaphragm 50, that is, a directivity angle and propagates radially. Therefore, the first transmission wave has a spindle-shaped directivity with the maximum sound pressure in the positive Y-axis direction, that is, the front surface of the ultrasonic transducer 4, which is the exposure direction DD. That is, the first transmission wave can be said to have almost no directivity as the directivity along the plumb line LZ.

[0114] Thus, the reflected wave of the first transmission wave can be received from any one of the high-height structure, the low-height protrusion, and the ceiling protrusion. The high-height structure is a relatively high-height structure such as a wall existing on the front surface of the ultrasonic transducer 4, that is, the front surface of the vehicle. The low-height protrusion is a relatively low-height protrusion such as a wheel chock protruding upward from the ground. The ceiling protrusion is a beam or a gate protruding downward from the ceiling.

[0115] In contrast, the second directivity in the second transmission wave is different from the first directivity in the first transmission wave, and the sound pressure in the axial direction is reduced. Specifically, in the second transmission wave, the sound pressure in the exposure direction DD is significantly reduced, and the maximum sound pressure is obtained in the direction at an elevation angle θ above and below the exposure direction DD. The angle θ is determined by the in-plane position of the ultrasonic element 6 and the in-plane shape of the ultrasonic element 6 in the diaphragm 50, and can be set to about 5 to 15 degrees, for example.

[0116] That is, the second transmitted wave becomes a "heart" shape that significantly reduces the sound pressure on the central axis DA while maintaining symmetry across the central axis DA, as the directivity characteristic along the plumb line LZ. Unlike the first transmitted wave, the axial sound pressure of the second transmitted wave does not reach a specified sound pressure level that can receive the reflected wave from the object well. In other words, compared with the first directivity characteristic of the first transmitted wave, the axial sound pressure of the second directivity characteristic in the second transmitted wave is reduced. Therefore, the reflected wave of the second transmitted wave reflected by the object is hardly received from the front surface of the ultrasonic transducer 4, that is, the exposure direction DD, and on the other hand, the reflected wave of the second transmitted wave reflected by the object is received well from the direction at an angle θ to the exposure direction DD.

[0117] Therefore, the ultrasonic sensor 1, that is, the ultrasonic transducer 4, is mounted on the vehicle in such a way that the directivity characteristic of the second transmitted wave is symmetric across the central axis DA in the vehicle height direction. In this way, for the reflected wave of the second transmitted wave, it is not received from the high-height structure, but from the low-height protrusion and the roof protrusion. However, the roof protrusion rarely becomes an obstacle to the travel of the vehicle, and even if it becomes an obstacle, it can be clearly identified visually.

[0118] In this way, in the first transmitted wave and the second transmitted wave with significantly different directivity characteristics, the detection area, that is, the range of existence of the reflection point in the object that can receive the reflected wave, is different. Specifically, in the present embodiment, the elevation angle range of the reflection point is different between the first transmitted wave and the second transmitted wave. Thus, by switching the first transmitted wave and the second transmitted wave by changing the drive frequency, it is easy to distinguish whether the object detected at close range is a low-height protrusion or a high-height structure.

[0119] Regarding this point, according to the present embodiment, the switching between the first transmitted wave and the second transmitted wave with significantly different directivity characteristics can be simply performed by switching the transmission frequency, that is, the drive frequency. In addition, the ultrasonic transducer 4 capable of performing such switching between the first transmitted wave and the second transmitted wave can be realized by changing the minimum specifications of the conventional configuration, such as offsetting the ultrasonic element 6 in the in-plane direction relative to the central position PC. Thus, when providing the ultrasonic transducer 4 with excellent object detection performance compared to the prior art and the ultrasonic sensor 1 including the ultrasonic transducer, it is possible to suppress the cost increase as much as possible or ensure good durability. And by arranging the ultrasonic element 6 at a position different from the central position PC in the in-plane direction, a significant difference in directivity characteristics (that is, a difference in detection area) can be set between the first transmitted wave and the second transmitted wave.

[0120] The ultrasonic sensor 1 of the present embodiment includes: the ultrasonic transducer 4 described above; and a control circuit element 25, which is electrically connected to the ultrasonic transducer 4 to switch between a first vibration mode and a second vibration mode. Therefore, according to the present embodiment, it is possible to provide an ultrasonic transducer 4 with more excellent object detection performance than in the past and an ultrasonic sensor 1 including the ultrasonic transducer.

[0121] In contrast, in the structures described in Japanese Patent Application Laid-Open No. 2009-267472 and Japanese Patent Application Laid-Open No. 2010-278913, although transmission and reception can be performed at two mutually different resonance frequencies, the difference in directivity characteristics between them is small. Therefore, according to these conventional structures, it is not possible to create a large difference in the detection area between two mutually different resonance frequencies as in the present embodiment.

[0122] (Third Configuration Example)

[0123] Figure 8 is a diagram showing a part of the structure of the transducer housing 5 of the ultrasonic transducer 4 shown in Figure 3 and Figure 4 In the following description of the configuration example, mainly the parts different from the above-described first and second configuration examples will be described. In addition, in the above-described first and second configuration examples and the configuration examples described below, the same or equivalent parts are given the same reference numerals. Therefore, in the following description of the configuration example, for the components having the same reference numerals as those in the above-described first and second configuration examples, as long as there is no technical contradiction or special additional explanation, the descriptions in the above-described first and second configuration examples can be appropriately cited.

[0124] Figure 8 The transducer housing 5 shown in

[0125] has a protrusion 523. The protrusion 523 is provided on the bottom plate portion 52 so as to protrude toward the internal space 53 side. The protrusion 523 can be arranged on the straight line connecting the connection center position PC and the element center PP. According to the above structure, the generation of the second vibration mode can be favorably promoted. The number of protrusions 523 is one or more. Figure 6B

[0126] In addition, the in-plane position, shape, and number of the protrusions 523 can be appropriately set according to the resonance frequency f2 and / or the difference between the resonance frequency f1 and the resonance frequency f2. In addition, it is preferable that the protrusion 523 is arranged on the straight line passing through the center position PC and the element center PP. Thereby, it is possible to achieve (Fourth Configuration Example)

[0127] Figure 9 andFigure 10 is a diagram of a part of the structure of the transducer housing 5 in the ultrasonic transducer 4 that has been changed Figure 3 and Figure 4 a diagram of a part of the structure of the transducer housing 5 in the ultrasonic transducer 4 shown

[0128] Figure 9 and Figure 10 the transducer housing 5 shown has a protrusion 523. The protrusion 523 is provided on the side plate portion 51 so as to protrude into the internal space 53. Specifically, in the transducer housing 5 as shown in Figure 9 and Figure 10 a pair of protrusions 523 are symmetrically arranged with respect to the central axis DA in the transducer housing 5 shown. With such a structure, the generation of the second vibration mode can be favorably promoted

[0129] In addition, the shape of the protrusion 523 can be appropriately set according to the resonance frequency f2 and / or the difference between the resonance frequency f1 and the resonance frequency f2. Further, it is preferable that the protrusion 523 is arranged on the straight line passing through the central position PC and the element center PP, that is, on the vertical line LZ. Thereby, a favorable vibration state in the second vibration mode as shown in Figure 6B can be achieved. In addition, the protrusion 523 provided on the side plate portion 51 according to this configuration example and the protrusion 523 provided on the bottom plate portion 52 according to the above third configuration example can be used in combination

[0130] (Fifth Configuration Example)

[0131] Figure 11 and Figure 12 is a diagram of a part of the structure of the ultrasonic transducer 4 that has been changed Figure 3 and Figure 4 a diagram of a part of the structure of the ultrasonic transducer 4 shown

[0132] In Figure 11 and Figure 12 in the ultrasonic transducer 4 shown, a pair of ultrasonic elements 6 are symmetrically provided with respect to the central position PC across the diaphragm 50. That is, in the diaphragm 50, two ultrasonic elements 6 are mounted at positions different from the central position PC. The pair of ultrasonic elements 6 are respectively arranged at the antinode positions in the second vibration mode

[0133] In Figure 11 and Figure 12 in the ultrasonic transducer 4 shown, the driving timing of the pair of ultrasonic elements 6 can be switched between in-phase and anti-phase. "In-phase" means that the phase difference between the alternating current voltage of a prescribed frequency applied to one of the pair of ultrasonic elements 6, that is, the first element driving voltage, and the alternating current voltage applied to the other, that is, the second element driving voltage having the same frequency as the first driving voltage, is actually zero. In contrast, "anti-phase" means that the phase difference is a half-cycle amount of the period corresponding to the above-described prescribed frequency. The above-described switching is performed byFigure 2 is performed by the control circuit element 25 shown.

[0134] Figure 13 Shows the directivity characteristics in the case of driving a pair of ultrasonic elements 6 in phase at the driving timing with the driving frequency f1. Figure 14 Shows the directivity characteristics in the case of driving a pair of ultrasonic elements 6 out of phase at the driving timing with the driving frequency f2. In Figure 13 and Figure 14 , the dotted line represents the directivity characteristics corresponding to the first vibration mode, and the solid line represents the directivity characteristics corresponding to the second vibration mode.

[0135] As Figure 13 shown, in the case of in-phase driving, the vibration based on the first vibration mode is well excited, while the vibration based on the second vibration mode is hardly excited. In contrast, as Figure 14 shown, in the case of out-of-phase driving, the vibration based on the second vibration mode is well excited, while the vibration based on the first vibration mode is very small. In addition, by arranging a pair of ultrasonic elements 6 at the antinode positions in the second vibration mode, the vibration intensity based on the second vibration mode, that is, the transmission sound pressure of the second transmitted wave, can be increased.

[0136] In this way, according to the ultrasonic transducer 4 of this structural example and the ultrasonic sensor 1 including the ultrasonic transducer, the switching between the first transmitted wave and the second transmitted wave having different directivity characteristics can be performed well. In particular, as Figure 13 and Figure 14 shown, the intensity ratio between the first vibration mode and the second vibration mode, that is, the S / N ratio, under the same driving conditions can be increased as much as possible. In addition, at the time of reception, the isolation between the two frequencies (that is, f1 and f2) can also be improved by using the first combined signal obtained by in-phase combining the reception signals in each of the pair of ultrasonic elements 6 and the second combined signal obtained by out-of-phase combining.

[0137] In Figure 11 and Figure 12 , the transducer housing 5 has a protrusion 523. Specifically, in the diaphragm 50, one protrusion 523 is provided at the center position PC. Thereby, the excitation of the second vibration mode is promoted. However, from the viewpoint of achieving the effects brought about by the switching between in-phase driving and out-of-phase driving as described above, such a protrusion 523 can be omitted.

[0138] (Sixth structural example)

[0139] Figure 15 and Figure 16 are diagrams in which a part of the structure of the ultrasonic transducer 4 shown in Figure 3 and Figure 4 is changed. InFigure 15 and Figure 16 In the ultrasonic transducer 4 shown, in the diaphragm 50, only one ultrasonic element 6 is provided at the central position PC. The ultrasonic element 6 is configured such that the element center PP coincides with the central position PC. Further, in the diaphragm 50, only one ultrasonic element 6 is provided at a position different from the central position PC.

[0140] In Figure 15 and Figure 16 the ultrasonic transducer 4 shown, the following two driving modes can be realized.

[0141] · First driving mode: Drive one of the pair of ultrasonic elements 6 provided at the central position PC, and do not drive the other provided at a position different from the central position PC.

[0142] · Second driving mode: Do not drive one of the pair of ultrasonic elements 6 provided at the central position PC, and drive the other provided at a position different from the central position PC.

[0143] By the first driving mode, a first transmission wave can be generated. On the other hand, by the second driving mode, a second transmission wave can be generated. The switching between the first driving mode and the second driving mode is performed by Figure 2 the control circuit element 25 shown.

[0144] Figure 17 Shows the directivity characteristics when the ultrasonic transducer 4 is driven in the first driving mode by the driving frequency f1. Figure 18 Shows the directivity characteristics when the ultrasonic transducer 4 is driven in the second driving mode by the driving frequency f2. In Figure 17 and Figure 18 , the dotted line shows the directivity characteristics corresponding to the first vibration mode, and the solid line shows the directivity characteristics corresponding to the second vibration mode. As Figure 17 and Figure 18 shown, in this configuration example, the same effects as those of the Figure 11 and Figure 12 shown configuration examples can also be achieved. Further, in this configuration example, the protrusion 523 in the above-described third and / or fourth configuration examples can be provided.

[0145] (Second Embodiment: Object Detection Device)

[0146] Figure 19 Shows the overall configuration of the object detection device 700 using the ultrasonic transducer 4 of the above-described first embodiment. Figure 20The figure shows the state of the object detection operation in the vehicle V equipped with the object detection device 700, that is, in the present vehicle. The object detection device 700 is configured to detect an object B existing around the present vehicle equipped with the ultrasonic sensor 1, that is, the ultrasonic transducer 4. Hereinafter, with reference to Figure 19 etc., the details of the structure of the object detection device 700 of the present embodiment will be described.

[0147] The object detection device 700 includes: a transmission unit 701, a reception unit 702, a drive signal generation unit 703, a reception signal processing unit 704, a transmission control unit 705, a determination unit 706, and a memory 707. In the present embodiment, the transmission unit 701, the reception unit 702, the drive signal generation unit 703, and the reception signal processing unit 704 are provided in the ultrasonic sensor 1, that is, Figure 2 the control circuit element 25 shown. On the other hand, the transmission control unit 705, the determination unit 706, and the memory 707 are provided in the object detection ECU 708.

[0148] The transmission unit 701 is arranged to be able to transmit a transmission wave to the outside. The reception unit 702 is arranged to be able to receive a reception wave including a reflected wave reflected by the object B from the transmission wave transmitted by the transmission unit 701.

[0149] In the present embodiment, the ultrasonic sensor 1 has a transmission / reception integrated structure. In other words, the ultrasonic sensor 1 is configured to use one ultrasonic transducer 4 to perform the transmission and reception functions through the ultrasonic transducer 4.

[0150] That is, the transmission unit 701 includes an ultrasonic transducer 4 and a transmission circuit 711. The transmission circuit 711 is configured to drive the ultrasonic transducer 4 based on an input drive signal to cause the ultrasonic transducer 4 to emit a transmission wave having a frequency corresponding to the frequency of the drive signal. Specifically, the transmission circuit 711 includes a digital / analog conversion circuit, a boost circuit, etc.

[0151] In addition, the reception unit 702 includes the ultrasonic transducer 4 shared with the transmission unit 701 and a reception circuit 721. The reception circuit 721 is configured to generate a reception signal corresponding to the reception result of the reception wave of the ultrasonic transducer 4 and output it to the reception signal processing unit 704. Specifically, the reception circuit 721 includes an amplifier circuit, a filter circuit, and an analog / digital conversion circuit, etc.

[0152] The drive signal generation unit 703 is configured to generate a drive signal based on a control signal received from the transmission control unit 705 and output the drive signal to the transmission unit 701, i.e., the transmission circuit 711. The drive signal is a signal for driving the transmission unit 701, i.e., the ultrasonic transducer 4, to transmit a transmission wave from the ultrasonic transducer 4. The control signal is a signal for controlling the output of the drive signal from the drive signal generation unit 703 to the transmission unit 701.

[0153] The received signal processing unit 704 is configured to generate and output information or a signal required for the object detection operation in the determination unit 706 by performing various signal processes on the received signal output from the reception unit 702, and output the information or signal to the determination unit 706. Specifically, the received signal processing unit 704 includes an amplitude information acquisition unit 741 and a distance measurement information acquisition unit 742.

[0154] The amplitude information acquisition unit 741 is configured to generate and output an amplitude signal corresponding to the amplitude of the received signal output from the reception circuit 721. That is, the amplitude information acquisition unit 741 acquires amplitude information corresponding to the amplitude of the reflected wave obtained by reflecting the transmission wave transmitted from the ultrasonic transducer 4 by the object B. The "amplitude information" refers to information corresponding to the amplitude of the received wave included in the amplitude signal, i.e., the reception intensity.

[0155] The distance measurement information acquisition unit 742 is configured to generate and output a distance measurement signal based on the received signal when the amplitude in the received signal exceeds a specified value. That is, the distance measurement information acquisition unit 742 acquires distance measurement information corresponding to the distance between the ultrasonic transducer 4 and the object B based on the TOF when receiving the reflected wave of the transmission wave from the object B. TOF is an abbreviation for Time of Flight, which is the time required from the transmission of the transmission wave to the reception of the reflected wave. The TOF may also be referred to as the propagation time. The "distance measurement information" is information corresponding to the distance between the ultrasonic transducer 4 and the object B included in the distance measurement signal.

[0156] The transmission control unit 705 is configured to control the emission state of the transmission wave from the transmission unit 701 by outputting a control signal to the drive signal generation unit 703. Specifically, the transmission control unit 705 sets the drive frequency and output timing of the drive signal generated and output in the drive signal generation unit 703 through the control signal. That is, the transmission control unit 705 controls the transmission timing and transmission waveform of the transmission wave.

[0157] The determination unit 706 is configured to perform an obstacle determination based on various signal processing results of the received signal by the received signal processing unit 704. The "obstacle determination" is a determination of whether the object B detected by acquiring the distance measurement information is an obstacle that hinders the progress of the vehicle. That is, the obstacle determination refers to determining the presence of obstacles around the vehicle.

[0158] The determination unit 706 is configured to determine the presence of an obstacle based on the ranging information and / or amplitude information obtained from the reflected wave of the second transmitted wave. As described above, the second transmitted wave is a transmitted wave having a second directivity characteristic that is symmetric about the central axis DA of the ultrasonic transducer 4 in the vehicle height direction of the host vehicle and reduces the sound pressure in the front direction.

[0159] In the present embodiment, the determination unit 706 performs obstacle determination based on the comparison result between the amplitude information and / or the ranging information and a determination threshold set based on the second directivity characteristic. Specifically, the determination unit 706 includes a threshold setting unit 761. A determination threshold set based on the second directivity characteristic is stored in the threshold setting unit 761. Further, the threshold setting unit 761 is configured to set the determination threshold for determining the presence or absence of an obstacle in the determination unit 706.

[0160] The memory 707 is configured to store the signal processing result of the reception signal processing unit 704 and the determination result of the determination unit 706 in time series. That is, the amplitude information, the ranging information, and the determination result of the determination unit 706 are stored in the memory 707 in time series and in correspondence with each other.

[0161] In the present embodiment, the transmission control unit 705, the determination unit 706, and the memory 707 are configured as functional components implemented by the object detection ECU 708. That is, the object detection ECU 708 has a structure as a so-called sonar ECU that controls the overall operation of the object detection device 700. The object detection ECU 708 is connected to the ultrasonic sensor 1 via an in-vehicle LAN communication line according to a predetermined communication standard (e.g., DSI3 etc.) so as to enable information communication. DSI3 is an abbreviation of Distributed System Interface 33.

[0162] The object detection ECU 708 is a microcomputer mounted on the vehicle V and includes a CPU, a ROM, a RAM, a non-volatile rewritable memory, an input / output interface, etc., which are not shown. The CPU is an abbreviation for Central Processing Unit. The ROM is an abbreviation for Read Only Memory. The RAM is an abbreviation for Random access memory. The non-volatile rewritable memory is a storage medium that can rewrite information while the power is on and, on the other hand, retains information in a non-rewritable manner when the power is off, such as an EPROM, an EEPROM, a flash memory, etc. The EPROM is an abbreviation for Erasable Programmable Read Only Memory. The EEPROM is an abbreviation for Electrically Erasable Programmable Read Only Memory. The ROM, the non-volatile rewritable memory, and the RAM are non-transitory physical storage media. The ROM and / or the non-volatile rewritable memory corresponds to the non-transitory physical storage medium storing the object detection program of the present embodiment. Hereinafter, the CPU, the ROM, the RAM, and the non-volatile rewritable memory of the object detection ECU 708 will be simply referred to as "CPU", "ROM", "RAM", and "non-volatile memory", respectively. The object detection device 700 is configured to be able to execute various operations such as object detection operations in the present vehicle and reports accompanying such operations by reading and executing a program stored in the ROM or the non-volatile memory by the object detection ECU 708.

[0163] (Operation overview)

[0164] Hereinafter, an overview of the object detection operation of the object detection device 700 of the present embodiment, that is, an overview of the object detection method or the object detection program executed by the object detection device 700 will be described.

[0165] As Figure 20 shown, the ultrasonic sensor 1 is mounted on the front bumper V2. In addition, in the present embodiment, the ultrasonic sensor 1 is mounted on the present vehicle such that the central axis DA of the ultrasonic transducer 4 is offset downward by a predetermined amount ΔH from the vehicle height center Hc. That is, the ultrasonic sensor 1 is configured such that the mounting height Hm is less than half of the vehicle height Hv. The vehicle height center Hc is the central position of the vehicle V in the vehicle height direction. The mounting height Hm is the height of the central axis DA of the ultrasonic transducer 4 from the ground, i.e., the road surface.

[0166] (First operation example)

[0167] Refer to Figures 19 - 21 , and an operation example of the object detection device 700 of the present embodiment will be described.

[0168] As Figure 7 、 Figure 14 or Figure 18 as shown by the solid line in , the ultrasonic sensor 1 can transmit a second transmission wave having a second directivity characteristic of reducing the sound pressure on the central axis DA and being symmetric with respect to the central axis DA in the vehicle height direction. The second transmission wave has a maximum sound pressure in the directions at elevation angles of ±θ from the central axis DA. Therefore, typically, as Figure 20 shown in , an object B is detected in the directions at elevation angles of ±θ from the central axis DA by the second transmission wave.

[0169] When the object B is a low-height protrusion BL, the low-height protrusion BL is detected as an obstacle when the ranging distance D is less than a lower determination threshold DL shown in the following formula (1). Further, the ranging distance D is the distance obtained by converting the ranging information into an actual distance.

[0170] [Equation 1]

[0171]

[0172] On the other hand, for the roof protrusion BS, when the ranging distance D is less than an upper determination threshold DH shown in the following formula (2), it is detected as an obstacle. Alternatively, a roof determination threshold DS shown in the following formula (3) can be used instead of the upper determination threshold DH. In the formula (3), the designed roof height Hs is the height obtained by adding a prescribed design margin value to the vehicle height Hv.

[0173] [Equation 2]

[0174]

[0175] [Equation 3]

[0176]

[0177] However, the roof protrusion BS rarely becomes an obstacle to the travel of the present vehicle, and even if it becomes an obstacle, it can be identified visually. Therefore, in this operation example, the object detection ECU 708, that is, the determination unit 706 performs an obstacle determination when the ranging distance D is less than the lower determination threshold DL. That is, the object detection ECU 708 determines the presence of an obstacle based on the comparison result between the ranging information and the lower determination threshold DL set based on the second directivity characteristic.

[0178] Figure 21 A flowchart corresponding to this operation example is shown. In the flowchart, "S" is an abbreviation for step. The CPU of the object detection ECU 708 reads out a program (i.e., an object detection program) corresponding to the Figure 21 flowchart shown in from the ROM or the non-volatile memory and executes it, thereby implementing an object detection method.Figure 22 The flowcharts in other accompanying drawings such as

[0179] If the reception timing of the reflected wave in the ultrasonic sensor 1 arrives, the CPU starts Figure 21 the routine shown. The reception timing is the timing after a prescribed standby time considering the reverberation time has elapsed since the end timing of the transmission of the transmitted wave. If this routine is started, first in step 2101, the CPU acquires the ranging distance D. That is, the CPU temporarily holds the ranging distance D corresponding to the latest ranging information obtained by the determination unit 706 from the ranging information acquisition unit 742 in a prescribed area in the RAM. Next, in step 2102, the CPU determines whether the ranging distance D is less than the lower determination threshold DL.

[0180] When the ranging distance D is less than the lower determination threshold DL (i.e., step 2102 = YES), the CPU executes the process of step 2103 and then temporarily ends this routine. In step 2103, the CPU performs an obstacle determination. That is, the CPU determines the presence of the low-height protrusion BL that becomes an obstacle to the travel of the present vehicle.

[0181] When the ranging distance D is equal to or greater than the lower determination threshold DL (i.e., step 2102 = NO), the CPU executes the process of step 2104 and then temporarily ends this routine. In step 2104, the CPU performs a non-obstacle determination. That is, the CPU determines the absence of the low-height protrusion BL that becomes an obstacle to the travel of the present vehicle.

[0182] (Second operation example)

[0183] Figure 22 is a flowchart corresponding to the second operation example in which a part of the above first operation example is changed. This operation example is also the same as the above first operation example, and determines the presence of an obstacle based on the comparison result between the ranging information and the determination threshold set based on the second directivity characteristic.

[0184] Specifically, in this operation example, the object detection ECU 708, that is, the determination unit 706 performs a road obstacle determination when the ranging distance D is less than the lower determination threshold DL. The road obstacle determination is a determination of the presence of a low-height obstacle on the road at the travel destination of the present vehicle. In addition, when the ranging distance D is equal to or greater than the lower determination threshold DL and less than the upper determination threshold DH, the object detection ECU 708 performs an overhead obstacle determination. The overhead obstacle is a determination that the ceiling protrusion BS present overhead at the travel destination of the present vehicle is an obstacle.

[0185] That is, Figure 22 the processing content of step 2201 in Figure 21 is the same as the processing content of step 2101 in Figure 22The determination content of step 2202 in Figure 21 is the same as the determination content of step 2102 in

[0186] When the ranging distance D is less than the lower determination threshold DL (i.e., step 2202 = YES), after the CPU executes the processing of step 2203, this routine is temporarily ended. In step 2203, the CPU performs an on-road obstacle determination. On the other hand, when the ranging distance D is above the lower determination threshold DL (i.e., step 2202 = NO), the CPU causes the processing to proceed to step 2204. In step 2204, the CPU determines whether the ranging distance D is less than the upper determination threshold DH.

[0187] When the ranging distance D is less than the upper determination threshold DH (i.e., step 2204 = YES), the CPU executes the processing of step 2205, and then this routine is temporarily ended. In step 2205, the CPU performs an overhead obstacle determination.

[0188] When the ranging distance D is above the upper determination threshold DH (i.e., step 2204 = NO), the CPU executes the processing of step 2206, and then this routine is temporarily ended. In step 2206, the CPU performs a non-obstacle determination. That is, the CPU determines the non-existence of the low-height protrusion BL and the ceiling protrusion BS that become obstacles to the progress of the vehicle.

[0189] (Third operation example)

[0190] Figure 23 Shows the state of change of the amplitude Am of the received signal of the reflected wave reflected by the low-height protrusion BL and the ceiling protrusion BS based on the second transmitted wave with the change of the ranging distance D. In the figure, the solid line represents the case of the low-height protrusion BL, and the dotted line represents the case of the ceiling protrusion BS.

[0191] As Figure 20 shown, it is assumed that the vehicle travels forward and the vehicle approaches an object B existing in front of it. In this case, as Figure 23 shown, at a stage where the distance, that is, the ranging distance D, is farther than the specified distance Dth, it is difficult to find a meaningful difference in the amplitude Am and its change pattern between the low-height protrusion BL and the ceiling protrusion BS. On the other hand, if the distance approaches the specified distance Dth, a large difference occurs in the amplitude Am and its change pattern between the low-height protrusion BL and the ceiling protrusion BS. That is, for the low-height protrusion BL, even if the distance changes, the amplitude Am hardly changes. In contrast, for the ceiling protrusion BS, the attenuation gradient of the amplitude Am caused by the approach of the distance is large. In addition, a large difference occurs in the amplitude Am between the low-height protrusion BL and the ceiling protrusion BS.

[0192] Thus, by using the second transmitted wave with a substantially "heart" - shaped directivity characteristic that is vertically symmetric and reduces the sound pressure in the front direction, a large difference in the amplitude Am and its variation pattern is generated between the low - height protrusion BL and the ceiling protrusion BS. Therefore, the object detection ECU708, i.e., the determination unit 706, determines the presence of an obstacle based on the variation pattern of the amplitude Am corresponding to the amplitude information, which varies with the ranging distance D corresponding to the ranging information.

[0193] Specifically, in this operation example, the object detection ECU708 determines the presence of an obstacle based on the comparison result between the amplitude variation and a determination threshold set based on the second directivity characteristic. More specifically, when the gradient dAm / dD of the variation of the amplitude Am caused by the variation of the ranging distance D in a state where the ranging distance D is less than the specified distance Dth is less than the gradient determination threshold α, the object detection ECU708 performs obstacle determination.

[0194] Figure 24 A flowchart corresponding to this operation example is shown. When the reception timing of the reflected wave arrives at the ultrasonic sensor 1, the CPU starts Figure 24 the routine shown. In addition, the counter N is a counter for counting the number of consecutive starts of this routine and is an integer of 1 or more. The counter N is reset to "1" at the first start. "At the first start" means the moment when this routine is first started after the specified object detection condition is established. Even when the object detection condition is temporarily established and then not established, and then the object detection condition is established again before the ignition switch of this vehicle is turned off, the moment when this routine is first started from the re - establishment of the object detection condition is also set as "at the first start".

[0195] If this routine is started, first, in step 2401, the CPU acquires the ranging distance D(N). The ranging distance D(N) is the ranging distance D acquired when this routine is started for the Nth time. In step 2402, the CPU acquires the amplitude Am(N). The amplitude Am(N) is the amplitude Am acquired when this routine is started for the Nth time. Then, in step 2403, the CPU stores the acquisition results of steps 2401 and 2402 in a specified area of the RAM or non - volatile memory in time series (i.e., corresponding to the counter N).

[0196] After the processing of steps 2401 to 2403, the CPU executes the processing of step 2404. In step 2404, the CPU determines whether the counter N exceeds 1.

[0197] When the counter N is 1 (i.e., step 2404 = no), the change in the amplitude Am associated with the change in the ranging distance D cannot be calculated. Therefore, in this case, the CPU skips the processing of steps 2405 to 2408, increments the value of the counter N by 1 in step 2409, and then temporarily ends this routine. In contrast, when the counter N exceeds 1 (i.e., step 2404 = yes), the CPU proceeds to step 2405.

[0198] In step 2405, the CPU determines whether the ranging distance D is less than a specified distance Dth. When the ranging distance D is greater than or equal to the specified distance Dth (i.e., step 2405 = no), the CPU skips the processing of steps 2406 to 2408, increments the value of the counter N by 1 in step 2409, and then temporarily ends this routine. In contrast, when the ranging distance D is less than the specified distance Dth (i.e., step 2405 = yes), the CPU moves the processing to step 2406. In step 2406, the CPU determines whether the gradient dAm / dD exceeds a gradient determination threshold α.

[0199] When the gradient dAm / dD is less than the gradient determination threshold α (i.e., step 2406 = yes), the CPU proceeds to step 2407. In step 2407, the CPU performs an obstacle determination. That is, the CPU determines the presence of a low-height protrusion BL that obstructs the progress of the vehicle.

[0200] When the gradient dAm / dD is greater than or equal to the gradient determination threshold α (i.e., step 2406 = no), the CPU proceeds to step 2408. In step 2408, the CPU performs a non-obstacle determination. That is, the CPU determines the absence of a low-height protrusion BL that obstructs the progress of the vehicle.

[0201] After the processing of step 2407 or step 2408 is executed, the CPU executes the processing of step 2409 and temporarily ends this routine. In step 2409, the CPU increments the value of the counter N by 1. That is, the CPU adds 1 to the value of the counter N.

[0202] (Fourth operation example)

[0203] Figure 25 It is a flowchart corresponding to the fourth operation example in which a part of the above third operation example is changed. This operation example is also the same as the above third operation example. The object detection ECU 708, that is, the determination unit 706, determines the presence of an obstacle based on Figure 23 the manner of change in the amplitude Am corresponding to the amplitude information associated with the change in the ranging distance D corresponding to the ranging information as shown.

[0204] Specifically, in this operation example, the object detection ECU 708 determines the presence of an obstacle based on the comparison result between the amplitude Am and the amplitude determination threshold β set based on the second directivity characteristic. More specifically, in a state where the ranging distance D is less than the specified distance Dth, when the amplitude Am exceeds the amplitude determination threshold β, the object detection ECU 708 performs obstacle determination.

[0205] That is, Figure 25 the processing contents of steps 2501 to 2505 in Figure 24 are the same as the processing contents of steps 2401 to 2405 in

[0206] In step 2506, the CPU determines whether the amplitude Am exceeds the amplitude determination threshold β.

[0207] When the amplitude Am exceeds the amplitude determination threshold β (i.e., step 2506 = YES), the CPU proceeds to step 2507. In step 2507, the CPU performs obstacle determination.

[0208] When the amplitude Am is below the amplitude determination threshold β (i.e., step 2506 = NO), the CPU proceeds to step 2508. In step 2508, the CPU performs non-obstacle determination.

[0208] After the processing of step 2507 or step 2508 is executed, the CPU executes the processing of step 2509, and then temporarily ends this routine. The processing content of step 2509 is the same as the processing content of step 2409 in Figure 24

[0209] (Fifth operation example)

[0210] The ultrasonic sensor 1 or the object detection device 700 can be mounted on vehicles V of multiple vehicle types. In this regard, according to Figure 20 and Equation (1) etc., it can be known that the determination thresholds such as the lower determination threshold DL are set according to the mounting conditions of the ultrasonic sensor 1, that is, the ultrasonic transducer 4, in the vehicle-mounted state.

[0211] However, the manufacturer of the ultrasonic sensor 1 or the object detection device 700 may be different from the manufacturer of the vehicle V. Therefore, the ultrasonic sensor 1 or the object detection device 700 may be "retrofit", that is, mounted on the vehicle V after the possessor of the vehicle V changes from the manufacturer to a third party (i.e., a dealer, a repair shop, a user, etc.).

[0212] In addition, there may be a situation where the mounting conditions change in the vehicle V in the possession of the user. Specifically, for example, there may be a situation where the vehicle height Hv changes due to legally modifying the vehicle V. Or, for example, there may be a situation where the vehicle V is equipped with a so-called vehicle height adjustment mechanism.

[0213] Therefore, in this operation example, the object detection ECU 708, that is, the determination unit 706 changes the determination threshold according to the change in the mounting conditions of the ultrasonic transducer 4 in the vehicle V. Figure 26 It is a flowchart showing an outline of the operation of setting or changing the determination threshold.

[0214] Execute at a specified timing Figure 26 The threshold setting program shown. The "specified timing" is, for example, the moment when a specified operation is performed at the vehicle V's manufacturer, dealer, or repair shop. Or, the "specified timing" is, for example, the moment when the ignition switch of the vehicle V is turned on, or a specified moment during the period from said moment until the object detection condition is first satisfied. Or, the "specified timing" is, for example, the moment when the vehicle height adjustment operation of the vehicle height adjustment mechanism (such as an air suspension mechanism) provided in the vehicle V ends.

[0215] If the Figure 26 shown threshold setting program is started, then first in step 2601, the CPU acquires the current vehicle height Hv. For example, the vehicle height Hv can be acquired through the operator's input, reception of vehicle height setting information from the ECU controlling the vehicle height adjustment mechanism, etc.

[0216] Next, in step 2602, the CPU acquires the current mounting height Hm. For example, the mounting height Hm can be acquired through the operator's input. Or, for example, the mounting height Hm can be calculated based on the vehicle height Hv acquired in step 2601.

[0217] Then, in step 2603, the CPU sets the determination threshold based on the acquired vehicle height Hv and mounting height Hm. For example, a table or map taking the vehicle height Hv and / or the mounting height Hm as parameters created through experiments or computer simulations can be used to set the determination threshold. If the processing of step 2603 ends, the CPU temporarily ends this routine.

[0218] (Sixth operation example)

[0219] This operation example is an operation example for determining the presence of an obstacle on the road using a first transmitted wave and a second transmitted wave. This operation example is effective, for example, in a parking support scenario. Specifically, for example, when the present vehicle is traveling towards a parking space, there is a wheel chock at the end on the traveling destination side within the parking space, and there is a wall on the traveling destination side compared to the wheel chock. In this case, even if the wheels of the present vehicle come into contact with the wheel chock and parking is completed, the wall will not collide with the present vehicle. Thus, this wall is not an obstacle.

[0220] Receive reflected waves from both the wheel chock and the wall according to the first transmitted wave having a spindle shape pointing characteristic centered on the front direction. At this time, the elevation angle position of the wheel chock is largely offset from the front direction where the highest sound pressure is achieved. Therefore, the intensity of the reflected wave from the wheel chock is low. In contrast, according to the second transmitted wave having a substantially "heart" shape pointing characteristic that is vertically symmetric and reduces the sound pressure in the front direction, mainly receive the reflected wave from the wheel chock. At this time, the wheel chock is located near the elevation angle θ direction from the central axis DA where the highest sound pressure is achieved. Therefore, the intensity of the reflected wave from the wheel chock is higher than that in the case of the first transmitted wave.

[0221] Therefore, in this operation example, the object detection ECU708, that is, the determination unit 706 determines the presence of an obstacle based on the amplitude corresponding to the reflected wave of the first transmitted wave and the amplitude corresponding to the reflected wave of the second transmitted wave. Specifically, the object detection ECU708 compares the amplitude Am1 corresponding to the reflected wave of the first transmitted wave and the amplitude Am2 corresponding to the reflected wave of the second transmitted wave with substantially the same ranging distance D. Moreover, when Am1 < Am2, the object detection ECU708 determines the detected object B as a low-height protrusion BL such as a wheel chock for obstacle determination.

[0222] Figure 27 A flowchart corresponding to this operation example is shown. Starting from the establishment time of the object detection condition, the CPU repeatedly starts Figure 27 the routine shown at a specified time interval.

[0223] If this routine is started, first in step 2701, the CPU obtains the object detection result based on the transmission frequency f1, that is, the first transmitted wave. Next, in step 2702, the CPU obtains the object detection result based on the transmission frequency f2, that is, the second transmitted wave. Then, the CPU proceeds to step 2703.

[0224] In step 2703, the CPU determines whether the object B is detected by the first transmitted wave. If the object is not detected by the first transmitted wave (i.e., step 2703 = no), the CPU skips all the subsequent processes in step 2704 and temporarily ends this routine. In contrast, if the object B is detected by the first transmitted wave (i.e., step 2703 = yes), the CPU proceeds to step 2704.

[0225] In step 2704, the CPU determines whether object B is detected by the second transmitted wave. If an object is not detected by the second transmitted wave (i.e., step 2704 = NO), the CPU skips all the processing after step 2705 and temporarily ends this routine. In contrast, if object B is detected by the second transmitted wave (i.e., step 2704 = YES), the CPU advances the processing to step 2705.

[0226] In step 2705, the CPU compares the amplitude Am1 corresponding to the reflected wave of the first transmitted wave and the amplitude Am2 corresponding to the reflected wave of the second transmitted wave, which are approximately the same in ranging distance D. If Am1 < Am2 (i.e., step 2705 = YES), the CPU executes the processing of step 2706 and then temporarily ends this routine. In step 2706, the CPU determines the presence of an obstacle on the road. In contrast, if it is not the case that Am1 < Am2 (i.e., step 2705 = NO), the CPU skips the processing of step 2706 and temporarily ends this routine.

[0227] (Third Embodiment)

[0228] In the above-described second embodiment, the object detection operation using the transmission and reception results of one ultrasonic sensor 1 has been described. However, as Figure 1 shown, a vehicle V can be equipped with multiple ultrasonic sensors 1. Specifically, multiple (e.g., three or four) ultrasonic sensors 1 can be respectively mounted at mutually different positions in the vehicle width direction on the front bumper V2. The same applies to the rear bumper V3.

[0229] Figure 28 The system configuration of an object detection device 700 that can detect an object B in front of the host vehicle by including multiple ultrasonic sensors 1 mounted on the front bumper V2 is shown. In the object detection device 700 having the above-described structure, the determination accuracy is improved by integrating the detection results of each of the multiple ultrasonic sensors 1. Therefore, in the present embodiment, the object detection ECU 708, i.e., the determination unit 706, determines the presence of an obstacle in front of the host vehicle as follows.

[0230] That is, the determination unit 706 obtains the determination result of the presence of an obstacle based on the reflected wave corresponding to the transmission wave transmitted from the first ultrasonic transducer 4. In addition, the determination unit 706 obtains the determination result of the presence of an obstacle based on the reflected wave corresponding to the transmission wave transmitted from the second ultrasonic transducer 4. The "first ultrasonic transducer 4" is provided in the first ultrasonic sensor 1 which is one of the plurality of ultrasonic sensors 1 mounted on the front bumper V2. The "second ultrasonic transducer 4" is provided in the second ultrasonic sensor 1 which is the other of the plurality of ultrasonic sensors 1 mounted on the front bumper V2. The first ultrasonic sensor 1 and the second ultrasonic sensor 1 are two adjacent ones among the plurality of ultrasonic sensors 1 mounted on the front bumper V2 and arranged in the vehicle width direction. Then, the determination unit 706 determines the presence of an obstacle in front of the vehicle based on the detection results of the first ultrasonic sensor 1 and the second ultrasonic sensor 1.

[0231] Figure 29 The flowchart corresponding to this embodiment is shown. Starting from the establishment time of the object detection condition, the program shown is repeatedly started by the CPU at a specified time interval. Figure 29 as shown.

[0232] If this routine is started, first in step 2901, the CPU obtains the object detection result of each ultrasonic sensor of the plurality of ultrasonic sensors 1 mounted on the front bumper V2. Next, in step 2902, the CPU determines whether an obstacle is detected by at least one of these ultrasonic sensors 1.

[0233] When no obstacle is detected by each of the plurality of ultrasonic sensors 1 (that is, step 2902 = NO), the CPU skips all the processes after step 2903 and temporarily ends this routine. In contrast, when an obstacle is detected by at least one of the plurality of ultrasonic sensors 1 (that is, step 2902 = YES), the CPU advances the process to step 2903. In step 2903, the CPU determines whether the same obstacle is detected by two adjacent ultrasonic sensors 1.

[0234] When the same obstacle is detected by two adjacent ultrasonic sensors 1 (that is, step 2903 = YES), the CPU executes the process of step 2904 and then temporarily ends this routine. In step 2904, the CPU makes an obstacle determination.

[0235] When the same obstacle is not detected by two adjacent ultrasonic sensors 1 (that is, step 2903 = NO), the CPU executes the process of step 2905 and then temporarily ends this routine. In step 2905, the CPU makes a non - obstacle determination.

[0236] (Fourth Embodiment)

[0237] In the third embodiment, in each of the plurality of ultrasonic sensors 1 mounted on the front bumper V2, the mounting height Hm is substantially the same. In this case, the same determination threshold can be used for each of the plurality of ultrasonic sensors 1. The same applies to the plurality of ultrasonic sensors 1 mounted on the rear bumper V3. However, as Figure 30 shown, there may be a case where the mounting height Hm is not substantially the same in each of the plurality of ultrasonic sensors 1 mounted on the front bumper V2.

[0238] Specifically, in Figure 30 the example shown, four ultrasonic sensors 1 are mounted on the front bumper V2. In the ultrasonic sensor 1 at the right end of the figure and the ultrasonic sensor 1 adjacent thereto, the mounting positions of the ultrasonic transducers 4 in the vehicle height direction are different. Similarly, in the ultrasonic sensor 1 at the left end of the figure and the ultrasonic sensor 1 adjacent thereto, the mounting positions of the ultrasonic transducers 4 in the vehicle height direction are different. In addition, the ultrasonic sensor 1 at the right end of the figure and the ultrasonic sensor 1 at the left end of the figure may have the same mounting position of the ultrasonic transducer 4 in the vehicle height direction. The same applies to the second ultrasonic sensor 1 from the right end of the figure and the second ultrasonic sensor 1 from the left end of the figure.

[0239] In this case, for the ultrasonic sensors 1 with different mounting conditions, i.e., different mounting heights Hm, different determination thresholds are used. By integrating the detection results of the plurality of ultrasonic sensors 1 with different determination thresholds due to different mounting conditions, the determination accuracy is further improved.

[0240] (Modification example)

[0241] The present disclosure is not limited to the above-described embodiments. Therefore, the above-described embodiments can be appropriately modified. Hereinafter, representative modification examples will be described. In the following description of the modification examples, mainly the differences from the above-described embodiments will be described. In addition, in the above-described embodiments and modification examples, the same reference numerals are assigned to the same or equivalent parts. Therefore, in the following description of the modification examples, for the components having the same reference numerals as those in the above-described embodiments, as long as there is no technical contradiction or special additional explanation, the descriptions in the above-described embodiments can be appropriately cited.

[0242] The ultrasonic sensor 1 is not limited to in-vehicle use. That is, the ultrasonic sensor 1 can be used for various purposes other than in-vehicle gap sonar or angle sensors.

[0243] The ultrasonic sensor 1 is not limited to a structure capable of transmitting and receiving ultrasonic waves. That is, for example, the ultrasonic sensor 1 may also have a structure capable of only transmitting ultrasonic waves. In other words, the ultrasonic transducer 4 can be either for transmission and reception or for transmission only.

[0244] The structure of each part in the ultrasonic transducer 4 is not limited to the above specific examples either. Specifically, for example, the outer shape of the transducer housing 5 of the ultrasonic transducer 4 is not limited to a substantially cylindrical shape, and can also be a substantially regular hexagonal prism shape, a substantially regular octagonal prism shape, etc. In addition, the material forming the transducer housing 5 can be a non-metal or a composite material of metal and non-metal.

[0245] The planar shape of the diaphragm 50 is not particularly limited either. That is, for example, when the diaphragm 50 is formed into an elliptical shape, the said elliptical shape can also be a rounded rectangular shape, that is, a shape combining a pair of semi-circles separated in the long side direction and a rectangle therebetween, or can also be an elliptical shape. In addition, the planar shape of the diaphragm 50 is not limited to an elliptical shape. Specifically, for example, the planar shape of the diaphragm 50 can also be a circular shape, a regular polygon, a dumbbell shape, etc.

[0246] The side plate portion 51 and the bottom plate portion 52 may not be integrally formed seamlessly either. That is, for example, the bottom plate portion 52 can also be joined to one end of the cylindrical side plate portion 51 by various joining techniques such as welding and bonding. In this case, the side plate portion 51 can also be formed of a material different from that of the bottom plate portion 52.

[0247] The ultrasonic element 6 is not limited to a piezoelectric element. That is, for example, a so-called electrostatic capacitance type element can be used as the ultrasonic element 6. The planar shape of the ultrasonic element 6 is not limited to a substantially circular shape or a substantially elliptical shape either. Specifically, for example, the ultrasonic element 6 can also be formed into a planar shape similar to the planar shape of the diaphragm 50 (for example, a similar shape).

[0248] In the object detection device 700, there may be a case where the ultrasonic transducer 4 for transmission and the ultrasonic transducer 4 for reception are separately provided. In this case, the ultrasonic transducer 4 for transmission is electrically connected to the transmission circuit 711. On the other hand, the ultrasonic transducer 4 for reception is electrically connected to the reception circuit 721. In this case, as long as at least the ultrasonic transducer 4 for transmission has the configuration shown in the above first embodiment, that is sufficient. That is, the ultrasonic transducer 4 for reception can also have a conventional structure. However, from the viewpoint of detection accuracy, it is preferable that both the ultrasonic transducer 4 for transmission and the ultrasonic transducer 4 for reception have the structure shown in the above first embodiment.

[0249] Regarding which of the elements constituting the object detection device 700 are provided in the ultrasonic sensor 1 and the object detection ECU 708, it is also possible to appropriately change from the above specific examples. That is, for example, the drive signal generation unit 703 and / or the received signal processing unit 704 can be provided in the object detection ECU 708. Or, as in the third embodiment, there is a case where a plurality of ultrasonic sensors 1 and the object detection ECU 708 are line-connected so as to be able to communicate with each other, and the detection results of the plurality of ultrasonic sensors 1 are integrated. In this case, the function of integrating the detection results of the plurality of ultrasonic sensors 1 in the function of the determination unit 706 can be provided in the object detection ECU 708, and at least a part of the other functions can be provided in the ultrasonic sensor 1.

[0250] The in-vehicle LAN communication standard applied to the line connection between the ultrasonic sensor 1 and the object detection ECU 708 is not limited to DSI. For example, it can also be Safe-by-Wire, PSI5, CAN (registered trademark), etc. PSI5 is the abbreviation of Peripheral Sensor Interface 5. CAN (registered trademark) is the abbreviation of Controller Area Network.

[0251] All or part of the object detection ECU 708 can also be configured as a digital circuit capable of performing the above-described operations, such as an ASIC or an FPGA. ASIC is the abbreviation of Application Specific Integrated Circuit. FPGA is the abbreviation of Field Programmable Gate Array. That is, in the object detection ECU 708, a microcomputer part and a digital circuit part can coexist.

[0252] The program of the present disclosure that can execute various operations, processes, or processes described in the above embodiments can be downloaded or upgraded via V2X communication. V2X is the abbreviation of Vehicle to X. Or, the program can be downloaded or upgraded via a terminal device provided in a vehicle V manufacturing factory, repair shop, sales store, etc. The storage destination of the program can also be a memory card, optical disc, magnetic disk, etc.

[0253] Thus, each of the above-described functional components and methods can also be implemented by a dedicated computer provided with a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, each of the above-described functional components and methods can also be implemented by a dedicated computer provided with a processor constituted by one or more dedicated hardware logic circuits. Alternatively, each of the above-described functional components and methods can also be implemented by one or more dedicated computers constituted by a combination of a processor and a memory programmed to execute one or more functions and a processor constituted by one or more hardware logic circuits. Additionally, the computer program can also be stored as instructions executable by a computer in a non-transitory entity storage medium readable by the computer. That is, each of the above-described functional components and methods can also be represented as a computer program including the sequence for implementing the functional components and methods or a non-transitory entity storage medium storing the program.

[0254] In the case of using the ceiling determination threshold value DS instead of the upper determination threshold value DH, the offset ΔH from the vehicle height center Hc of the mounting height Hm can also be 0.

[0255] In most cases, the ultrasonic sensor 1 is mounted on the bumper. In most cases, the bumper is mounted below the vehicle height center Hc. Therefore, the offset direction of the mounting height Hm from the vehicle height center Hc is usually downward. Using Figure 20 The above-described specific examples described use such structural features to improve the accuracy of obstacle detection, particularly the discrimination in the vertical direction.

[0256] However, the present disclosure is not limited to the above-described manner in the broadest sense. That is, for example, the ultrasonic sensor 1 may be mounted on the body panel constituting the vehicle body V1. In this case, the offset direction of the mounting height Hm from the vehicle height center Hc may be upward. Or, the offset amount ΔH may be 0. Even in such a case, the above-described embodiments can be applied as long as there is no technical contradiction.

[0257] The present disclosure is not limited to the specific operation examples shown in the above-described embodiments. Specifically, for example, in the above-described embodiments, for the sake of simplicity of explanation, the example of obstacle detection in front of the own vehicle using the ultrasonic sensor 1 mounted on the front bumper V2 has been mainly described. However, the present disclosure is not limited to such a manner. That is, for example, obstacle detection behind the own vehicle using the ultrasonic sensor 1 mounted on the rear bumper V3 can also be performed in the same manner as the above-described embodiments. The same applies to obstacle detection on the side of the own vehicle using the ultrasonic sensor 1 mounted on the side of the vehicle body V1.

[0258] Each process in the above-described operation examples can also be appropriately changed. That is, for example, in the above-described specific examples, a determination using the ranging distance D is performed. However, the present disclosure is not limited to the described manner. That is, even if the ranging information is not converted into the ranging distance D, each of the above-described operation examples can be realized. Specifically, a K-bit hexadecimal value corresponding to the ranging information can be used instead of the ranging distance D. In this case, a K-bit hexadecimal value corresponding to the determination threshold can be used instead of the determination threshold (for example, the lower determination threshold DL, etc.). K is, for example, 2 or 4.

[0259] In each of the above-described embodiments, the mounting elevation angle of the ultrasonic transducer 4, that is, the angle formed by the central axis DA in the vehicle-mounted state and the horizontal plane, is approximately 0 degrees. However, the present disclosure is not limited to the described manner. When the mounting elevation angle is not approximately 0 degrees, the angle formed by the Z-axis direction and the vehicle height direction corresponds to the mounting elevation angle. In this way, the "symmetry" of the second directivity characteristic across the central axis DA in the Z-axis direction becomes the symmetry in the direction along the vehicle height direction. In addition, when setting or changing the determination threshold corresponding to the mounting conditions of the ultrasonic transducer 4 in the vehicle V, the mounting elevation angle can also be considered. In this case, in the Figure 26 shown flowchart, a step of obtaining the mounting elevation angle can also be provided before the process of step 2603.

[0260] In each determination process, "less than the threshold" and "below the threshold" can be interchanged. Similarly, "above the threshold" and "exceeding the threshold" can be interchanged. That is, as long as there is no technical contradiction, the inequality sign "<" in each determination step can also be "≤". Similarly, as long as there is no technical contradiction, the inequality sign ">" in each determination step can also be "≥".

[0261] In the above description, a plurality of constituent elements integrally formed seamlessly with each other can also be formed by pasting mutually independent components. Similarly, a plurality of constituent elements formed by pasting mutually independent components can also be integrally formed seamlessly with each other.

[0262] In the above description, a plurality of constituent elements formed of mutually identical materials can also be formed of mutually different materials. Similarly, a plurality of constituent elements formed of mutually different materials can also be formed of mutually identical materials.

[0263] The elements constituting the above-described embodiments are not necessarily essential, except in cases where they are specifically stated as essential or are clearly considered essential in principle. In addition, when numerical values such as the number, quantity, and range of constituent elements are mentioned, the present disclosure is not limited to the specific numerical value, except in cases where it is specifically stated as essential or is clearly limited to a specific number in principle. Similarly, when the shape, direction, positional relationship, etc. of constituent elements are mentioned, the present disclosure is not limited to the shape, direction, positional relationship, etc., except in cases where it is specifically stated as essential or is clearly limited to a specific shape, direction, positional relationship, etc. in principle.

[0264] Similar expressions such as "acquire", "calculate", "estimate", "detect", "inspect", "determine", etc. can be appropriately replaced with each other within the range where there is no technical contradiction. "Detect" or "inspect" can also be appropriately replaced with "extract" within the range where there is no technical contradiction.

[0265] The modification examples are not limited to the above examples. For example, all or part of one of the multiple configuration examples or embodiments can be combined with all or part of another as long as there is no technical contradiction. The number of combinations is not particularly limited. Similarly, all or part of one of the multiple modification examples can be combined with all or part of another as long as there is no technical contradiction. Also, all or part of one of the multiple embodiments can be combined with all or part of one of the multiple modification examples as long as there is no technical contradiction.

[0266] (Method·Program)

[0267] The present disclosure shown by the above embodiments and modification examples includes the following viewpoints related to the object detection method and the object detection program. In addition, the following viewpoints can be combined and applied with each other as long as there is no technical contradiction.

[0268] The object detection method is a method of using an ultrasonic transducer (4) to detect an object existing around a vehicle (V) on which the ultrasonic transducer is mounted. The object detection program is a program executed by an object detection device (700) configured to use the ultrasonic transducer to detect an object existing around the vehicle on which the ultrasonic transducer is mounted.

[0269] The above ultrasonic transducer includes:

[0270] A transducer housing (5) is formed as a bottomed cylindrical shape having a side plate portion (51) and a bottom plate portion (52). The side plate portion is formed as a cylindrical shape surrounding a central axis (DA), and the bottom plate portion closes one end side of the side plate portion in an axial direction parallel to the central axis to form a diaphragm (50) capable of ultrasonic vibration; and

[0271] An ultrasonic element (6) is fixedly supported on the bottom plate portion so as to face an internal space (53) surrounded by the side plate portion and the bottom plate portion, and converts an electrical signal and ultrasonic vibration,

[0272] The ultrasonic element is arranged at a position offset in the in-plane direction with respect to the central position (PC) of the diaphragm in the in-plane direction orthogonal to the axial direction, so as to be able to generate a first transmission wave having a first directivity characteristic and a second transmission wave having a second directivity characteristic, and the second directivity characteristic is a directivity characteristic different from the first directivity characteristic and reduces the sound pressure in the axial direction.

[0273] According to a first aspect, the object detection method and the processing performed by the object detection device include:

[0274] An amplitude acquisition process for acquiring amplitude information corresponding to the amplitude of a reflected wave obtained by reflecting a transmission wave transmitted from the ultrasonic transducer by the object;

[0275] A distance acquisition process for acquiring ranging information corresponding to the distance to the object based on the reflected wave; and

[0276] A determination process for determining the presence of the object, that is, an obstacle, which becomes an obstacle to the travel of the vehicle, based on the ranging information and / or the amplitude information obtained from the reflected wave of the second transmission wave having the second directivity characteristic that is symmetric about the central axis in the vehicle height direction of the vehicle.

[0277] According to a second aspect, the determination process includes: a process of determining the presence of the obstacle based on a change pattern of the amplitude corresponding to the amplitude information accompanying a change in the distance corresponding to the ranging information.

[0278] According to a third aspect, the determination process includes: a process of determining the presence of the obstacle based on a comparison result between the amplitude or the change in the amplitude and a determination threshold set based on the second directivity characteristic.

[0279] According to a fourth aspect, the determination process includes: a process of determining the presence of the obstacle based on a comparison result between the ranging information and a determination threshold set based on the second directivity characteristic.

[0280] According to the fifth aspect, the above determination process includes: a process of changing the above determination threshold according to the mounting conditions of the above ultrasonic transducers in the above vehicle.

[0281] According to the sixth aspect, the above determination process includes: a process of determining the presence of the above obstacle based on the above amplitude corresponding to the above reflected wave of the above first transmitted wave and the above amplitude corresponding to the above reflected wave of the above second transmitted wave.

[0282] According to the seventh aspect, the above determination process includes: a process of determining the presence of the above obstacle based on the above determination result of the presence of the above obstacle based on the above reflected wave corresponding to the above transmitted wave transmitted from the first above ultrasonic transducer and the above determination result of the presence of the above obstacle based on the above reflected wave corresponding to the above transmitted wave transmitted from the second above ultrasonic transducer.

[0283] According to the eighth aspect, the mounting positions of the above first above ultrasonic transducer and the above second above ultrasonic transducer in the above vehicle height direction are different.

Claims

1. An ultrasonic transducer, comprising: a transducer housing formed in a bottomed cylindrical shape having a side plate portion and a bottom plate portion, the side plate portion being formed in a cylindrical shape surrounding a central axis, and the bottom plate portion closing one end side of the side plate portion in an axial direction parallel to the central axis to form a diaphragm capable of ultrasonic vibration; and an ultrasonic element fixedly supported on the bottom plate portion so as to face an internal space surrounded by the side plate portion and the bottom plate portion, and converting an electrical signal and ultrasonic vibration, the ultrasonic element is arranged at a position offset in the in-plane direction with respect to the central position of the diaphragm in the in-plane direction orthogonal to the axial direction, so as to be capable of generating a first transmission wave having a first directivity characteristic and a second transmission wave having a second directivity characteristic, the second directivity characteristic being a directivity characteristic different from the first directivity characteristic and reducing the sound pressure in the axial direction.

2. The ultrasonic transducer according to claim 1, wherein the transducer housing further has a protrusion provided on the side plate portion or the bottom plate portion so as to protrude toward the internal space side.

3. The ultrasonic transducer according to claim 1 or 2, wherein the central position is the antinode position in the first vibration mode of the diaphragm corresponding to the first directivity characteristic and is the node position in the second vibration mode of the diaphragm corresponding to the second directivity characteristic, in the in-plane direction, the ultrasonic element is arranged at a position different from the central position.

4. The ultrasonic transducer according to claim 3, wherein the ultrasonic element is arranged at the antinode position in the second vibration mode.

5. The ultrasonic transducer according to claim 3, wherein the diaphragm is formed in a flat plate shape with a constant thickness and is elliptical with a long side direction and a short side direction orthogonal to each other, the side plate portion has: a thin wall portion formed in a partial cylindrical shape having a predetermined thickness and respectively provided at both ends in the long side direction; and a thick wall portion formed thicker than the thin wall portion and respectively provided at both ends in the short side direction, only one ultrasonic element is provided on the diaphragm.

6. The ultrasonic transducer according to claim 3, wherein in the diaphragm, only one ultrasonic element is provided at the central position, and only one ultrasonic element is provided at a position different from the central position.

7. The ultrasonic transducer according to claim 3, wherein a pair of ultrasonic elements are symmetrically provided on the diaphragm with respect to the central position.

8. An ultrasonic sensor, comprising: the ultrasonic transducer according to claim 6; and a control circuit element electrically connected to the ultrasonic transducer to switch between the first vibration mode and the second vibration mode, The above control circuit element generates the first transmission wave by driving the above ultrasonic element disposed at the above central position and not driving the above ultrasonic element disposed at the above position different from the above central position, and generates the second transmission wave by not driving the above ultrasonic element disposed at the above central position and driving the above ultrasonic element disposed at the above position different from the above central position.

9. An ultrasonic sensor, comprising: the ultrasonic transducer according to claim 7; and a control circuit element electrically connected to the ultrasonic transducer to switch between the first vibration mode and the second vibration mode, the control circuit element switches the driving timing of a pair of the above ultrasonic elements in phase and antiphase.

10. An object detection device configured to use an ultrasonic transducer to detect an object existing around a vehicle equipped with the ultrasonic transducer according to any one of claims 1 to 7, comprising: an amplitude information acquisition unit that acquires amplitude information corresponding to the amplitude of a reflected wave obtained by reflecting a transmission wave transmitted from the ultrasonic transducer by the object; a distance measurement information acquisition unit that acquires distance measurement information corresponding to the distance to the object based on the reflected wave; and a determination unit that determines the presence of the object, that is, an obstacle that becomes an obstacle to the travel of the vehicle, based on the distance measurement information and / or the amplitude information obtained from the reflected wave of the second transmission wave having the second directivity characteristic that is axisymmetric with respect to the center in the vehicle height direction, that is, the second transmission wave.

11. The object detection device according to claim 10, wherein the determination unit determines the presence of the obstacle based on the change pattern of the amplitude corresponding to the amplitude information accompanying the change in the distance corresponding to the distance measurement information.

12. The object detection device according to claim 10 or 11, wherein the determination unit determines the presence of the obstacle based on the comparison result between the amplitude or the change in the amplitude and a determination threshold set based on the second directivity characteristic.

13. The object detection device according to claim 10, wherein the determination unit determines the presence of the obstacle based on the comparison result between the distance measurement information and a determination threshold set based on the second directivity characteristic.

14. The object detection device according to claim 12, wherein the determination unit changes the determination threshold according to the mounting conditions of the ultrasonic transducer in the vehicle.

15. The object detection device according to claim 10, wherein the determination unit determines the presence of the obstacle based on the amplitude corresponding to the reflected wave of the first transmission wave and the amplitude corresponding to the reflected wave of the second transmission wave.

16. The object detection device according to claim 10, wherein The above determination unit determines the presence of the obstacle based on the determination result of the presence of the obstacle based on the reflected wave corresponding to the transmitted wave transmitted from the first ultrasonic transducer and the determination result of the presence of the obstacle based on the reflected wave corresponding to the transmitted wave transmitted from the second ultrasonic transducer.

17. The object detection device according to claim 16, wherein the mounting positions of the first ultrasonic transducer and the second ultrasonic transducer in the vehicle height direction are different.

18. An object detection method is an object detection method for detecting an object existing around a vehicle on which the ultrasonic transducer according to any one of claims 1 to 7 is mounted by using the ultrasonic transducer, acquiring amplitude information corresponding to the amplitude of the reflected wave obtained by reflecting the transmitted wave transmitted from the ultrasonic transducer by the object, acquiring ranging information corresponding to the distance to the object based on the reflected wave, determining the presence of the object, that is, the obstacle that becomes an obstacle to the progress of the vehicle, based on the ranging information and / or the amplitude information obtained from the reflected wave of the transmitted wave having the second directivity characteristic that is symmetric about the center axis in the vehicle height direction, that is, the second transmitted wave.

19. A storage medium storing an object detection program, wherein, The above object detection program is executed by an object detection device configured to use the ultrasonic transducer according to any one of claims 1 to 7 to detect an object existing around a vehicle on which the ultrasonic transducer is mounted, when the above object detection program is executed by the above object detection device, the processes executed by the above object detection device include: a process of acquiring amplitude information corresponding to the amplitude of the reflected wave obtained by reflecting the transmitted wave transmitted from the ultrasonic transducer by the object; a process of acquiring ranging information corresponding to the distance to the object based on the reflected wave; and a process of determining the presence of the object, that is, the obstacle that becomes an obstacle to the progress of the vehicle, based on the ranging information and / or the amplitude information obtained from the reflected wave of the transmitted wave having the second directivity characteristic that is symmetric about the center axis in the vehicle height direction, that is, the second transmitted wave.

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