Object detection device

Abstract

To provide an object detection device capable of determining the height of an object with good accuracy. [Solution] The object detection device (1) comprises a transmitting unit (50A) that transmits ultrasonic waves, a receiving unit (50B) that receives ultrasonic waves, and a determination unit (8) that performs object detection determination based on the received signal of the reflected wave in the receiving unit. The transmitting unit is configured to transmit ultrasonic waves in a frequency band that vibrates in a vibration mode of a higher order than a first resonant frequency and ultrasonic waves in a frequency band that vibrates in a vibration mode of a higher order than a first resonant frequency, wherein the ultrasonic waves in the frequency band of the vibration mode of a higher order than the ultrasonic waves in the first frequency band have directional characteristics in which the sound pressure in the direction of the directional center axis (DL) is reduced, and the determination unit detects an object based on a comparison of the amplitudes of multiple received signals in the first frequency band and the frequency band of the higher order vibration mode.

Description

Technical Field

[0001] The present disclosure relates to an object detection device configured to detect an object by transmitting ultrasonic waves and receiving reflected waves from the object.

Background Art

[0002] In an object detection device that detects an object by transmitting and receiving ultrasonic waves, it is required to further improve the determination accuracy of the object. Specifically, for example, assume the case of an in-vehicle object detection device. In this case, an object such as a wall with a relatively large protruding height from the road surface has a high possibility of contacting the vehicle body. Therefore, such an object needs to be appropriately recognized as an obstacle. On the other hand, an object such as a wheel stopper with a sufficiently small protruding height from the road surface has an extremely low possibility of contacting the vehicle body. Therefore, such an object is not substantially evaluated as an obstacle. The same applies to a beam that protrudes slightly downward from the ceiling. Therefore, in the case of an in-vehicle object detection device, it is required to accurately distinguish an object that has a high possibility of contacting the vehicle body and becomes an obstacle from other objects.

[0003] In this regard, the object detection device described in Patent Document 1 includes a signal generation unit that generates a drive signal, a transmission unit that transmits ultrasonic waves as a detection wave in response to the input drive signal, a reception unit that receives the ultrasonic waves and generates a reception signal, and a determination unit that performs object detection determination based on the reception signal. In such an object detection device, the drive signal has at least two frequencies. Then, the determination unit extracts at least two amplitudes corresponding to at least two frequencies from the reception signal, and makes a determination based on the relationship between the at least two amplitudes.

[0004] Ultrasound changes its directivity depending on its frequency. Therefore, the amplitude of the received signal of a reflected wave from an object, for at least two types of ultrasound with different directivity, changes depending on the positional relationship between the object and the directivity range corresponding to the directivity. Specifically, for example, an object may be located within the directivity range of a wide-directivity ultrasound but outside the directivity range of a narrow-directivity ultrasound. In this case, there will be a significant difference in the amplitude of the received signal between the reflected wave of the wide-directivity ultrasound and the reflected wave of the narrow-directivity ultrasound. Conversely, an object may be located in a region where the directivity ranges of the wide-directivity ultrasound and the narrow-directivity ultrasound overlap. In this case, there will be no significant difference in the amplitude of the received signal between the reflected wave of the wide-directivity ultrasound and the reflected wave of the narrow-directivity ultrasound.

[0005] Therefore, the object detection device having the above configuration transmits ultrasonic waves having at least two frequencies as search waves, extracts amplitudes for each frequency from the received signal, and performs object detection and determination based on the relationship between the at least two amplitudes. Specifically, for example, the determination unit compares the at least two extracted amplitudes. This makes it possible to detect and determine objects with high accuracy. Specifically, it becomes possible to distinguish between obstacle objects and other objects with good accuracy. For example, it is possible to distinguish between objects that may come into contact with the vehicle body and other objects. Furthermore, by performing object detection and determination based on the amplitudes in the received signal corresponding to multiple frequencies, the effects of changes in amplitude levels due to air turbulence and the like can be mitigated. Therefore, with the above configuration, the accuracy of object determination can be further improved compared to conventional methods. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-98157 [Patent Document 2] Patent No. 3628480 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the object detection device described in Patent Document 1, it is assumed that at least two frequencies are used, one lower and one higher than the fundamental resonant frequency. In this configuration, when attempting to obtain a larger difference in directivity, at least two frequencies are transmitted and received using frequencies outside the inefficient resonant frequency, raising concerns that it may be difficult to obtain sufficient reflection intensity.

[0008] Therefore, in this disclosure, at least two frequencies are used: a resonant frequency for a low-order vibration mode (typically first-order) and a spurious frequency which is the resonant frequency for a higher-order vibration mode. By using at least two frequencies that are resonant frequencies with good transmission and reception efficiency, the intensity of the reflected wave is improved. Furthermore, the large difference in directivity between the at least two frequencies resulting from the difference in vibration modes makes it possible to improve the accuracy of object identification compared to conventional methods.

[0009] However, the ultrasonic sensor shown in Patent Document 2 has weak resonance in higher-order vibration modes (generally referred to as having a low Q), and there is a concern that if the resonant frequency (spurious frequency) becomes high (for example, exceeding 100 kHz), distance attenuation will increase, making it difficult to obtain sufficient reflection intensity.

[0010] This disclosure has been made in view of the circumstances exemplified above. Specifically, this disclosure provides, for example, an object detection device that can determine the height of an object with better accuracy than conventional devices. [Means for solving the problem]

[0011] The object detection device (1) is configured to detect an object (B) by transmitting ultrasonic waves and receiving the reflected waves from the object. According to one aspect of this disclosure, this object detection device is A transmitting unit (50A) that transmits ultrasonic waves, A receiving unit (50B) that receives ultrasonic waves, A determination unit (8) performs object detection determination based on the received signal of the reflected wave in the receiving unit, Equipped with, The transmitting unit uses a transmitting / receiving element (4) having a resonant frequency that vibrates in a higher-order vibration mode than the first resonant frequency. The system is configured to transmit ultrasonic waves in a frequency band that constitute the vibration mode of the first resonant frequency and ultrasonic waves in a frequency band that constitute the higher-order vibration mode. Ultrasound in frequency bands of higher-order vibration modes than the first frequency band has directional characteristics in which sound pressure in the direction of the directional center axis (DL) is reduced. The determination unit detects the object based on a comparison of the amplitudes of multiple received signals in the first frequency band and the frequency band of the higher-order vibration mode.

[0012] With an object detection device having such a configuration, by switching between transmitting ultrasound at a first resonant frequency (low-order vibration mode) and ultrasound at a spurious frequency (high-order vibration mode), the difference in directivity between at least two frequencies can be increased, making it possible to detect and determine objects using ultrasound at at least two frequencies with a simple configuration.

[0013] In this object detection device, the transmitting and receiving elements in the transmitting and receiving section have a structure that increases or decreases the resonance frequency at the spurious frequency. Therefore, it is possible to improve transmission and reception at the spurious frequency, or to suppress distance attenuation as much as possible. Consequently, with this object detection device, it is possible to determine the height of an object with better accuracy than conventional methods.

[0014] In addition, each element in the application documents may be denoted by a reference numeral in parentheses. However, such reference numerals merely indicate one example of the correspondence between the element and the specific means described in the embodiments described later. Therefore, this disclosure is not limited in any way by the notation of the above reference numerals. [Brief explanation of the drawing]

[0015] [Figure 1] It is a plan view showing a schematic configuration of a vehicle equipped with an in-vehicle system constituting an object detection device according to an embodiment of the present disclosure. [Figure 2A] It is a block diagram showing a schematic functional configuration in an embodiment of the in-vehicle system shown in FIG. 1. [Figure 2B] It is a block diagram showing a schematic functional configuration in the sensor control unit shown in FIG. 2A. [Figure 3] It is a front view showing a schematic configuration of the transmitting and receiving element shown in FIG. 2A. [Figure 4] It is a side view showing a schematic configuration of the microphone case shown in FIG. 3. [Figure 5] It is a schematic diagram showing an overview of vibration modes in the structure of a conventional transmitting and receiving element without the slit shown in FIGS. 3 and 4. [Figure 6] It is a graph showing the relationship between the resonance frequency, vibration mode, and bandwidth. [Figure 7] It is a graph showing the directivity characteristics of the probing wave of the first resonance frequency and spurious frequency in the embodiment. [Figure 8] It is a conceptual diagram showing the first directivity characteristic corresponding to the first resonance frequency in the embodiment. [Figure 9] It is a conceptual diagram showing the second directivity characteristic corresponding to the spurious frequency in the embodiment. [Figure 10] It is a graph showing the detection state of the wall constituting an obstacle according to the embodiment. [Figure 11] It is a graph showing the detection state of a step that does not constitute an obstacle according to the embodiment. [Figure 12] It is a graph showing a method of discriminating whether an object is a high-back object or a low-back object using sound pressure directivity. [Figure 13] It is a diagram schematically showing the vibration state due to the spurious frequency of the diaphragm in the microphone case of the comparative example. [Figure 14]Figure 4 schematically shows the vibration state of the diaphragm in the microphone case due to its spurious frequency. [Figure 15] Figures 3 and 4 show graphs illustrating the sound pressure directivity in the primary vibration mode, which is the main resonance, of the microphone case. [Figure 16] Figures 3 and 4 show graphs illustrating the sound pressure directivity in the third vibration mode, which is the second resonance, of the microphone case. [Figure 17] This graph shows the change in spurious frequency between the embodiment and the comparative example. [Figure 18] This block diagram shows a schematic functional configuration in another embodiment of the in-vehicle system shown in Figure 1. [Figure 19] Figure 19 is a time chart showing one mode of drive control in an ultrasonic sensor. [Figure 20] This block diagram shows a schematic functional configuration in yet another embodiment of the in-vehicle system shown in Figure 1. [Figure 21] Figure 20 is a block diagram showing an example of filter band switching in an ultrasonic sensor. [Figure 22] This block diagram shows a schematic functional configuration in yet another embodiment of the in-vehicle system shown in Figure 1. [Figure 23] This block diagram shows a schematic functional configuration in yet another embodiment of the in-vehicle system shown in Figure 1. [Figure 24] This is a schematic diagram showing a comparative example of a measurement schedule when one of a pair of ultrasonic sensors is designated as Sensor 1 and the other as Sensor 2. [Figure 25] This is a schematic diagram illustrating a specific example of a measurement schedule when one of a pair of ultrasonic sensors is designated as Sensor 1 and the other as Sensor 2. [Figure 26] This is a schematic diagram showing another specific example of a measurement schedule when one of a pair of ultrasonic sensors is designated as Sensor 1 and the other as Sensor 2. [Modes for carrying out the invention]

[0016] (Embodiment) The embodiments of this disclosure will be described below with reference to the drawings. The following embodiments, their modifications, and the drawings relating thereto are schematic or simplified for the purpose of concisely explaining the contents of this disclosure, and do not limit the contents of this disclosure in any way. Therefore, it goes without saying that the descriptions in the drawings do not necessarily correspond to the specific device configurations actually manufactured and sold. In other words, unless explicitly limited by the applicant in the application history, this disclosure should not be interpreted restrictively by the descriptions in the drawings and the corresponding descriptions of the device configurations, functions, or operations described below.

[0017] (In-vehicle system configuration) Referring to Figure 1, the on-board system 1 is mounted on a vehicle C, which is a mobile vehicle. Vehicle C is a so-called four-wheeled automobile and has a box-shaped body C1 that is formed in a roughly rectangular shape in plan view. The shape of each part of vehicle C in "plan view" refers to the shape when the vehicle C is stably placed on a horizontal surface in a manner that allows it to move, and that part is viewed from a line of sight in the same direction as the direction of gravity. The vehicle C on which the on-board system 1 according to this embodiment is mounted will be referred to as "the vehicle" below.

[0018] Hereinafter, in a plan view, the imaginary straight line passing through the center of the vehicle in the width direction and parallel to the vehicle's overall length direction will be referred to as the vehicle centerline CL. The vehicle's overall length direction is perpendicular to both the vehicle width direction and the vehicle height direction. The vehicle height direction is the direction that defines the vehicle's height and is parallel to the direction of gravity acting when the vehicle is stably placed on a horizontal surface in a drivable position. Furthermore, "front," "rear," "left," "right," and "up" are defined as shown by the arrows in Figure 1. That is, the vehicle's overall length direction is synonymous with the front-rear direction. Also, the vehicle width direction is synonymous with the left-right direction.

[0019] The in-vehicle system 1 comprises an electronic control unit 2 and an ultrasonic sensor 3. The electronic control unit 2 is an in-vehicle microcomputer, which may also be called an ECU, and includes a CPU, ROM, RAM, non-volatile rewritable memory, etc. (not shown). ECU is an abbreviation for Electronic Control Unit. Non-volatile rewritable memory is a storage device that allows information to be rewritten when the power is on, but retains information in a non-rewritable state when the power is off, such as flash ROM. ROM, RAM, and non-volatile rewritable memory are non-transitional physical storage media. The electronic control unit 2 is mounted inside the vehicle body C1.

[0020] The electronic control unit 2 is connected to the ultrasonic sensor 3 via an in-vehicle information communication line, enabling information exchange. In this embodiment, the vehicle is equipped with multiple ultrasonic sensors 3. The electronic control unit 2 is configured to control the entire operation of the in-vehicle system 1, including the timing of ultrasonic transmission and reception operations at each of the multiple ultrasonic sensors 3, by reading and executing a control program stored in ROM or non-volatile rewritable memory. In other words, the in-vehicle system 1, which constitutes the object detection device according to this embodiment, is configured to detect objects B around the vehicle based on the ultrasonic transmission and reception results at the ultrasonic sensors 3 while mounted on the vehicle.

[0021] The front bumper of the vehicle, specifically the front bumper C2 of the vehicle body C1, is equipped with ultrasonic sensors 3: a first front sensor 3A, a second front sensor 3B, a third front sensor 3C, and a fourth front sensor 3D. Similarly, the rear bumper of the vehicle, specifically the rear bumper C2 of the vehicle body C1, is equipped with ultrasonic sensors 3: a first rear sensor 3E, a second rear sensor 3F, a third rear sensor 3G, and a fourth rear sensor 3H.

[0022] The first front sensor 3A is located at the right end of the front bumper to transmit a probe wave, which is a transmitted wave, to the right front of the vehicle. The second front sensor 3B is located between the first front sensor 3A and the vehicle centerline CL in the vehicle width direction to transmit a probe wave approximately in front of the vehicle. The third front sensor 3C is located approximately symmetrically to the second front sensor 3B with respect to the vehicle centerline CL. The third front sensor 3C is located between the vehicle centerline CL and the fourth front sensor 3D in the vehicle width direction to transmit a probe wave approximately in front of the vehicle. The fourth front sensor 3D is located approximately symmetrically to the first front sensor 3A with respect to the vehicle centerline CL. The fourth front sensor 3D is located at the left end of the front bumper to transmit a probe wave to the left front of the vehicle.

[0023] The first rear sensor 3E is located at the right end of the rear bumper to transmit a probe wave to the right rear of the vehicle. The second rear sensor 3F is positioned between the first rear sensor 3E and the vehicle centerline CL in the vehicle width direction to transmit a probe wave approximately behind the vehicle. The third rear sensor 3G is positioned approximately symmetrically to the second rear sensor 3F with respect to the vehicle centerline CL. The third rear sensor 3G is positioned between the vehicle centerline CL and the fourth rear sensor 3H in the vehicle width direction to transmit a probe wave approximately behind the vehicle. The fourth rear sensor 3H is positioned approximately symmetrically to the first rear sensor 3E with respect to the vehicle centerline CL. The fourth rear sensor 3H is located at the left end of the rear bumper to transmit a probe wave to the left rear of the vehicle.

[0024] (First Embodiment) The first embodiment of this disclosure will be described below.

[0025] (Ultrasonic sensor) The following describes the general configuration of the ultrasonic sensor 3 with reference to Figure 2A. Note that in Figure 2A, for the sake of simplicity, only one of the multiple ultrasonic sensors 3 connected to the electronic control unit 2 is shown; the others are omitted from the illustration.

[0026] The ultrasonic sensor 3 is configured to transmit ultrasonic probe waves toward the outside of the vehicle. The ultrasonic sensor 3 is also configured to detect the object B in the surroundings and obtain the distance to the object B based on the received signal corresponding to the reception result of the received wave, which includes the reflected wave from the probe wave by object B.

[0027] Specifically, the ultrasonic sensor 3 comprises a transmitting / receiving unit 5 including a transmitting / receiving element 4, a drive signal generation unit 6, a received signal processing unit 7, and a sensor control unit 8. In this embodiment, the transmitting / receiving unit 5, the drive signal generation unit 6, the received signal processing unit 7, and the sensor control unit 8 are supported by a single sensor housing made of synthetic resin or the like.

[0028] The transmitting / receiving element 4 is configured to function as a transmitter that transmits probe waves outwards, or as a receiver that receives reflected waves. The transmitting / receiving element 4 has the configuration of a so-called resonant ultrasonic microphone and is mounted in a through hole C3 formed in the bumper C2 such that the transmitting / receiving surface 40, which is the outer surface, faces the external space of the vehicle when mounted on the vehicle. Specifically, the transmitting / receiving element 4 comprises an electromechanical conversion element 41 such as a piezoelectric element that has an electromechanical energy conversion function, and a microphone case 42 that holds it. Details of the configuration of the transmitting / receiving element 4 will be described later.

[0029] In this embodiment, one ultrasonic sensor 3 is equipped with only one transmitting / receiving unit 5, and this single transmitting / receiving unit 5 is configured to perform the transmitting and receiving functions. That is, the transmitting / receiving unit 5 has the function of a transmitting unit 50A that transmits a probe wave to the outside, and the function of a receiving unit 50B that receives a received wave. Specifically, one transmitting / receiving unit 5 has one transmitting / receiving element 4. The transmitting unit 50A and the receiving unit 50B are configured to realize the transmitting and receiving functions, respectively, using a common transmitting / receiving element 4.

[0030] The transmitting / receiving unit 5 comprises a transmitting / receiving element 4, a transmitting circuit 51, and a receiving circuit 52. Specifically, the transmitting unit 50A comprises the transmitting / receiving element 4 and the transmitting circuit 51. The receiving unit 50B also comprises the transmitting / receiving element 4 and the receiving circuit 52. The transmitting / receiving element 4 is electrically connected to the transmitting circuit 51 and the receiving circuit 52.

[0031] The transmitting circuit 51 is configured to drive the transmitting and receiving elements 4 based on the input drive signal, thereby causing the transmitting and receiving elements 4 to emit probe waves in the ultrasonic band. Specifically, the transmitting circuit 51 includes a digital / analog conversion circuit, etc. That is, the transmitting circuit 51 is configured to perform processing such as digital / analog conversion on the drive signal output from the drive signal generation unit 6, and to apply the resulting AC voltage to the transmitting and receiving elements 4.

[0032] The receiving circuit 52 is configured to generate a received signal corresponding to the ultrasonic reception result at the transmitting / receiving element 4, and to output the generated received signal to the receiving signal processing unit 7. Specifically, the receiving circuit 52 includes an amplification circuit and an analog / digital conversion circuit. In other words, the receiving circuit 52 is configured to generate and output a received signal corresponding to the frequency, phase, and amplitude of the received ultrasonic signal by performing signal processing such as amplification and analog / digital conversion on the voltage signal input from the transmitting / receiving element 4.

[0033] The drive signal generation unit 6 is provided to generate a drive signal to drive the transmission unit 50A based on a control signal input from the sensor control unit 8. The drive signal is a signal that drives the transmission unit 50A to transmit a probe wave from the transmitting / receiving element 4. The control signal includes the output timing of the drive signal and the driving conditions of the transmitting / receiving element 4. The driving conditions include, for example, at least one of the following: drive current or drive voltage, drive pulse duty cycle, number of drive pulses, drive frequency, etc.

[0034] The received signal processing unit 7 is configured to perform various signal processing, such as filtering and quadrature detection, on the received signal output from the receiving circuit 52. Furthermore, the received signal processing unit 7 is configured to output the processed signal, which is the result of these signal processing operations, to the sensor control unit 8.

[0035] The sensor control unit 8 is connected to the electronic control unit 2 in a communication manner so as to control the operation of the ultrasonic sensor 3 in cooperation with the electronic control unit 2. Specifically, the sensor control unit 8 is configured to control the output of a drive signal from the drive signal generation unit 6 to the transmission unit 50A, and to detect object B based on a processing signal output from the reception signal processing unit 7. In other words, the sensor control unit 8, as the determination unit of this disclosure, performs object detection determination based on the reception state of the reflected wave in the transmission / reception unit 5. The object detection determination includes determining the presence or absence of object B in a predetermined range around the vehicle and obtaining the distance, as well as determining the height of object B if it is present.

[0036] The sensor control unit 8 has the configuration of an in-vehicle microcomputer, which includes a CPU, ROM, RAM, non-volatile rewritable memory, etc. (not shown). In other words, the sensor control unit 8 is configured to control the operation of the ultrasonic sensor 3 by reading and executing a control program stored in the ROM or non-volatile rewritable memory.

[0037] Specifically, the sensor control unit 8 drives the transmitting and receiving elements 4 by switching between the primary resonant frequency and a spurious frequency, which is a higher-order resonant frequency. The sensor control unit 8 then determines the height of object B based on the difference in the received amplitude between the primary resonant frequency and the spurious frequency. More specifically, as shown in Figure 2B, the sensor control unit 8 includes a control information acquisition unit 8a, a frequency determination unit 8b, a control signal output unit 8c, a processing signal acquisition unit 8d, a detection information generation unit 8e, and a detection information output unit 8f.

[0038] The control information acquisition unit 8a acquires, or receives, control information from the electronic control unit 2 for controlling the operation of the ultrasonic sensor 3. The control information includes information regarding the start / end of transmission and reception operations by the ultrasonic sensor 3 and the operating mode. The operating modes include, for example, an obstacle detection mode during low-speed driving and a parking space detection mode. The operating modes also include, for example, a short-range detection mode and a long-range detection mode.

[0039] The frequency determination unit 8b determines the drive frequency based on the control information acquired by the control information acquisition unit 8a. In other words, the switching of the above frequency is achieved by the function of the frequency determination unit 8b. The technology related to the switching of the frequency itself is the same as the prior art prior to the filing of this application, so no further detailed explanation is provided in this specification. The control signal output unit 8c generates a control signal based on the drive frequency determined by the frequency determination unit 8b and outputs this control signal to the drive signal generation unit 6.

[0040] The processing signal acquisition unit 8d acquires, i.e., receives, the processing signal output from the receiving signal processing unit 7. The detection information generation unit 8e generates object detection information based on the processing signal acquired by the processing signal acquisition unit 8d. The detection information output unit 8f outputs the object detection information generated by the detection information generation unit 8e to the electronic control unit 2. The processing signal acquisition unit 8d, the detection information generation unit 8e, and the detection information output unit 8f are the same as those in the prior art prior to the filing of this application, so no further detailed description is provided in this specification.

[0041] (Transmitting / receiving element) The details of the configuration of the transmitting / receiving element 4 according to this embodiment will be described with reference to Figures 3 and 4. For the sake of explanation, a right-handed XYZ coordinate system will be set as shown in Figures 3 and 4.

[0042] The transmitting / receiving element 4 has a configuration in which an electromechanical conversion element 41 is bonded to a diaphragm 421 that constitutes the bottom plate of a microphone case 42, which is a substantially bottomed cylindrical casing with the microphone central axis LC parallel to the Z axis in the figure. Specifically, the electromechanical conversion element 41 is bonded to the inner surface of the diaphragm 421, that is, the back surface opposite to the transmitting / receiving surface 40. The diaphragm 421 is formed in a thin plate or thin film shape with a thickness direction along the axial direction so that it vibrates ultrasonically in the axial direction along the microphone central axis LC when transmitting and receiving ultrasonic waves.

[0043] In this embodiment, as shown in Figure 3, the electromechanical conversion element 41 is positioned at the center position PC of the diaphragm 421. The center position PC is the position where the microphone central axis LC and the diaphragm 421 intersect in the in-plane direction. The "in-plane direction" is the direction along the plane perpendicular to the microphone central axis LC. That is, the in-plane direction is any direction in the XY plane in the figure. The center position PC is the intersection of the first center line LX, which is parallel to the X axis in the figure, and the second center line LY, which is parallel to the Y axis in the figure. The diaphragm 421 is formed in an oval shape with a longitudinal direction in the Y axis direction in the figure and a short direction in the X axis direction in the figure. An "oval" is a shape formed by connecting two opposing semicircles with a pair of line segments of the same length, and is different from an "ellipse".

[0044] The outer edge of the diaphragm 421 in the in-plane direction is supported by a cylindrical diaphragm support 422. That is, the diaphragm 421 is positioned to close one end of the diaphragm support 422 in the axial direction. The diaphragm 421 and the diaphragm support 422 are formed integrally and seamlessly from the same material (e.g., an aluminum alloy).

[0045] A slit 425 is formed in the diaphragm support 422 so as to penetrate the inner internal space 423 and the outer surface, which is the side surface 424, of the diaphragm support 422. The slit 425 is located adjacent to the diaphragm 421 in the axial direction. Specifically, the end face of the slit 425 on the positive Z-axis side in the figure is formed to be substantially flush with the inner surface of the diaphragm 421, i.e., the surface on the internal space 423 side. In other words, in this embodiment, the transmitting and receiving element 4 has a structure that reduces spurious frequencies by providing a slit 425 on the side surface 424 of the cylindrical diaphragm support 422.

[0046] Furthermore, the slit 425 is filled with a sealing material, such as silicone rubber, which has a lower density and Young's modulus than the material of the microphone case 42 (e.g., aluminum alloy), for waterproofing purposes. The shape of the slit 425 (length, width) and the physical properties of the sealing material (density, Young's modulus, Poisson's ratio) are used to set the resonance strength (Q value) of the second resonant frequency (spurious frequency) to a desired value.

[0047] In this embodiment, the slits 425 extend along the X-axis in the figure at positions corresponding to both ends in the longitudinal direction of the diaphragm 421. That is, a pair of identical slits 425 are provided symmetrically on either side of the microphone central axis LC and the first center line LX. The slits 425 are formed such that their length, i.e., their width in the X-axis direction in the figure, is approximately the same as or slightly narrower than the width of the diaphragm 421 in the short direction (for example, about 80-90%). In other words, the slits 425 are provided at positions corresponding to the thin-walled portion of the diaphragm support 422 in the circumferential direction surrounding the microphone central axis LC.

[0048] (Operation overview) In the following description, the in-vehicle system 1 as an object detection device according to this embodiment, and the object detection method and object detection program executed thereunder, will be simply referred to as "this embodiment." Below, an overview of the operation of this embodiment will be described along with the effects achieved by this embodiment.

[0049] Referring to Figure 2A, the sensor control unit 8 outputs a control signal to the drive signal generation unit 6. The drive signal generation unit 6 then generates a drive signal based on the control signal and outputs the generated drive signal to the transmitter unit 50A. The transmitter unit 50A is driven by this drive signal. That is, the transmission circuit 51 excites the transmitting and receiving element 4 based on the input drive signal. As a result, the transmitting and receiving element 4, which functions as a transmitter, transmits a search wave to the outside of the vehicle.

[0050] When the received wave, which includes the reflected wave generated when the probe wave is reflected by object B, reaches the transmitting / receiving element 4, the transmitting / receiving element 4 is excited. In other words, the received wave is received by the transmitting / receiving element 4. Then, a voltage signal corresponding to the excitation state, i.e., the receiving state, is output from the transmitting / receiving element 4. The receiving circuit 52 generates a received signal by performing signal processing such as amplification and analog / digital conversion on this voltage signal, and outputs this received signal to the receiving signal processing unit 7.

[0051] The received signal processing unit 7 generates processed signals, including frequency signals and amplitude signals, by performing various signal processing such as filtering and quadrature detection on the received signal, and outputs them to the sensor control unit 8. The frequency signal is a signal corresponding to the frequency of the received wave. The amplitude signal is a signal corresponding to the amplitude of the received wave. Specifically, for example, the received signal processing unit 7 generates and outputs phase signals and amplitude signals by quadrature detection. Based on the processed signals such as the amplitude signal output from the received signal processing unit 7, the sensor control unit 8 detects whether object B is present or not, and if object B is present, the distance and height of object B.

[0052] Furthermore, the details of the signal processing in the receiving signal processing unit 7 and the outline of the object detection determination by the sensor control unit 8 were already publicly known or well-known at the time of filing this application (see, for example, Patent Document 1), and it is possible to utilize such publicly known or well-known technologies in this embodiment as well. For this reason, further details regarding these will not be described in this specification.

[0053] In this embodiment, the sensor control unit 8 drives the transmitting and receiving element 4 by switching the drive frequency between a first resonant frequency having a first-order vibration mode and a spurious frequency, which is a second resonant frequency having a higher-order vibration mode, using a control signal. The sensor control unit 8 then determines the height of object B based on the relationship, or difference, of the received amplitude between the first resonant frequency and the spurious frequency.

[0054] Figure 5 shows an overview of the first, second, and third vibration modes using the structure of a conventional transmitting / receiving element 4 without the slit 425 shown in Figures 3 and 4. In Figure 5, the vibration state of the vibrating surface is shown by a dashed curve, and the fixed end is indicated by a circle. The vibrating surface is the plane passing through the center in the thickness direction of the diaphragm 421. The displacement is shown in an exaggerated manner. Filling materials such as foam are omitted from the illustration. Figure 6 shows the relationship between the resonant frequency, vibration mode, and bandwidth. The relatively large resonances observed are referred to as the primary resonance (first resonance) and the second resonance, respectively.

[0055] As shown in Figure 5, in the conventional structure, both ends of the diaphragm 421 coincide with both ends of the internal space 423. That is, both ends of the diaphragm 421 are radially inward from the outer surface 424 of the microphone case 42 by the thickness of the diaphragm support 422. In other words, both ends of the diaphragm 421 are on the inside of the cylindrical shape of the diaphragm support 422. These ends of the diaphragm 421 become fixed ends and therefore act as vibration nodes.

[0056] Here, the second vibration mode is hardly observed because its resonance is weak. Therefore, as shown in Figure 6, the first vibration mode is the primary resonance, and the third vibration mode is the second resonance. The spurious frequencies are the resonance frequencies other than the resonance frequency of the first vibration mode (f1 in the figure), which is the primary resonance. Figure 6 shows the resonance frequency of the second resonance (f2 in the figure) as a spurious frequency.

[0057] Figure 7 shows the sound pressure directivity. In Figure 7, the dotted line shows the directivity characteristics at the resonant frequency with the first vibration mode, and the solid line shows the directivity characteristics at the spurious frequency, which is the resonant frequency with the third vibration mode. As shown in Figure 6, in the band of the primary resonant frequency, which is the first vibration mode, the sound pressure in the front direction, i.e., 0°, is greater than the sound pressure in the θ2 direction shown in Figure 7. Conversely, in the band of the second resonant frequency, which is the third vibration mode, the sound pressure in the θ2 direction is greater.

[0058] Figure 8 shows the case when a probe wave with a first directional characteristic corresponding to a first resonant frequency having a first vibration mode is radiated toward a high-backed object BH such as a wall and a low-backed object BL such as a wheel stop or step. Figure 9 shows the case when a probe wave with a second directional characteristic corresponding to a spurious frequency is radiated toward a high-backed object BH such as a wall and a low-backed object BL such as a wheel stop or step. The directional center axis DL in Figures 8 and 9 is a virtual straight line indicating the center of directivity, and in this embodiment it substantially coincides with the microphone center axis LC shown in Figure 4.

[0059] Figure 10 shows the received amplitude for a wall, which is an example of a high-backed structure (BH). Figure 11 shows the received amplitude for a step, which is an example of a low-backed structure (BL). In Figures 10 and 11, the dotted line represents the case of the first resonant frequency of the first vibration mode, and the solid line represents the spurious frequency of the second resonant frequency of the third vibration mode. In these examples, the low-backed structure (BL) is assumed to be in the -θ2 direction.

[0060] As shown in Figures 7 to 9, in this embodiment, the transmitting and receiving element 4 has a symmetrical directivity characteristic with respect to the directivity center axis DL, which coincides with the microphone central axis LC. Furthermore, the probe wave at the spurious frequency has a directivity characteristic in which the sound pressure in the direction of the directivity center axis DL is reduced compared to the directivity characteristic of the probe wave at the first resonant frequency of the primary vibration mode. Specifically, in the case of the first resonant frequency of the primary vibration mode, the sound pressure in the direction of the directivity center axis DL is not reduced, and the directivity center axis DL is the direction of maximum sound pressure. In contrast, in the case of the spurious frequency, the sound pressure in the direction of the directivity center axis DL is greatly reduced.

[0061] Therefore, as shown in Figures 9 and 10, in the case of tall objects such as walls (BH), a large difference occurs between the received amplitude at the primary resonant frequency and the received amplitude at the spurious frequency. That is, as shown in Figure 10, the ratio Vf2 / Vf1 of the reflected wave voltage in the received signal when the frequency is f1 versus f2 becomes less than 1. In contrast, as shown in Figures 8 and 11, in the case of low objects such as wheel stops or steps (BL), no large difference occurs between the received amplitude at the primary resonant frequency and the received amplitude at the spurious frequency. That is, as shown in Figure 11, the value of Vf2 / Vf1 becomes greater than 1.

[0062] Therefore, this embodiment allows switching between transmitting a search wave at the primary resonant frequency and a search wave at the spurious frequency. This makes it possible to accurately determine whether object B is a high-backed object BH or a low-backed object BL based on the difference (i.e., difference or ratio) of the received amplitude between the primary resonant frequency and the spurious frequency. Specifically, for example, as shown in Figure 12, when the determination threshold is set to 1, the direction of the obstacle's presence is ±θ depending on the value of Vf2 / Vf1. cross It is possible to determine whether or not it is within the range of ±θ. cross This is the angle corresponding to the intersection of the two sound pressure directivity lines in Figure 12.

[0063] Here, the lower the frequency, the smaller the distance attenuation, making it possible to ensure good reflection intensity. Therefore, in this embodiment, the transmitting and receiving elements 4 that constitute the transmitting and receiving unit 5 have a structure that lowers the frequency of the spurious frequencies. Specifically, a slit 425 is formed on the side surface 424 of the cylindrical diaphragm support 422 that supports the outer edge of the diaphragm 421 in order to widen the effective vibration surface of the diaphragm 421.

[0064] Figures 13 and 14 show a comparison of the change in vibration state at spurious frequencies with and without the slit 425. Specifically, Figure 14 shows the case with the slit 425, while Figure 13 shows a comparative example without the slit 425, i.e., a conventional example. Note that the right-handed XYZ coordinate system in Figures 13 and 14 is drawn to be consistent with the right-handed XYZ coordinate system shown in Figures 3 and 4.

[0065] As shown in Figure 13, in the comparative example, i.e., the conventional configuration, the spurious frequencies with higher-order vibration modes have nodes at the outer edge of the diaphragm 421. Specifically, both ends of the diaphragm 421 are fixed ends. Therefore, by making the outer edge of the diaphragm 421 more susceptible to vibration, it is possible to increase the width of the vibration surface and reduce the frequency.

[0066] In this regard, as shown in Figure 14, the effective vibration amplitude WD1 of the diaphragm 421 in the embodiment having the slit 425 is larger than the effective vibration amplitude WD2 in the comparative example. That is, both ends of the diaphragm 421 extend to the outer circumference of the microphone case 42. Furthermore, since both ends of the diaphragm 421 are semi-fixed ends, they do not become vibration nodes. For this reason, in the embodiment, the wavelength of vibration at the spurious frequency becomes longer than in the comparative example, and thus the vibration frequency becomes lower.

[0067] Figure 15 shows the sound pressure directivity in the primary vibration mode, which is the main resonance, in an embodiment with a slit 425, and Figure 16 shows the sound pressure directivity in the third vibration mode, which is the second resonance. As shown in Figure 15, even in the configuration with a slit 425, the primary vibration mode achieves normal directivity with one antinode. Also, as shown in Figure 16, the third vibration mode achieves directivity with three antinodes and a concave direction in the 0° direction. Figure 17 shows how, in contrast to the comparative example shown by a dotted line, the frequency of the third resonance mode, i.e., the spurious frequency, is shifted significantly to the lower frequency side in the embodiment shown by a solid line.

[0068] Thus, in this embodiment, by lowering the frequency at the spurious frequency (i.e., shifting it to a lower frequency), it is possible to suppress distance attenuation during transmission and reception at the spurious frequency as much as possible. Therefore, according to this embodiment, it is possible to determine the height of object B with better accuracy than in the conventional method.

[0069] (Second embodiment) The following describes a second embodiment of this disclosure. In the following description of the second embodiment, the differences from the first embodiment described above will be mainly explained. In addition, parts that are the same or equivalent to each other in the first and second embodiments are denoted by the same reference numerals. Therefore, in the following description of the second embodiment, with respect to components that have the same reference numerals as in the first embodiment, the description in the first embodiment may be appropriately referenced unless there is a technical inconsistency or additional explanation to be provided. The same applies to other embodiments described later.

[0070] To more effectively suppress distance attenuation at spurious frequencies, for example, when transmitting a search wave at a spurious frequency, it is effective to increase the drive energy compared to when transmitting a search wave at a first resonant frequency having a first-order vibration mode, by increasing the drive current, drive voltage, or duty cycle of the drive pulse, or by increasing the number of drive pulses.

[0071] Therefore, as shown in Figure 18, the in-vehicle system 1 according to this embodiment further includes a drive power supply unit 9. The drive power supply unit 9 is configured to supply drive current and drive voltage to the transmission unit 50A based on command values ​​of current and voltage received from the sensor control unit 8. In addition, the control signal output from the sensor control unit 8 to the drive signal generation unit 6 includes command values ​​such as the drive frequency, number of pulses, and duty cycle.

[0072] Figure 19 is a time chart showing one aspect of drive control in this configuration. While Figure 19 is a time chart for drive current control, changing the time chart for the current setting value at the bottom to a time chart for the voltage setting value will provide an example of drive voltage control. The same applies to the control of pulse count and duty cycle.

[0073] (Third embodiment) A third embodiment of this disclosure will be described below. For example, it is effective to switch the filter bandwidth in the received signal processing unit 7 when transmitting a search wave at a spurious frequency and when transmitting a search wave at a first resonant frequency. This embodiment corresponds to that.

[0074] Figures 20 and 21 show examples of filter bandwidth switching. Figure 20 shows an example of measurement using the main resonant frequency f1 corresponding to the first vibration mode. Figure 21 shows an example of measurement using the spurious frequency f2 corresponding to the third vibration mode.

[0075] The receiving signal processing unit 7 includes a filter 701 and an amplitude generation unit 702. The filter 701 can be a bandpass filter, a correlation filter, or the like. Since the configuration of the receiving signal processing unit 7 having such a filter 701 and amplitude generation unit 702 is already well known at the time of filing this application, further details, including the circuit configuration, will be omitted.

[0076] The filter characteristics of filter 701 are variable based on the input signal from the sensor control unit 8. Therefore, as shown in Figure 20, when the drive frequency is f1, the corresponding filter characteristics are set. Similarly, when the drive frequency is f2, the corresponding filter characteristics are set. In this way, it is possible to switch the filter bandwidth according to the drive frequency.

[0077] (Fourth embodiment) A fourth embodiment of the present disclosure will be described below with reference to Figures 22 and 23. This embodiment corresponds to a modification of the third embodiment described above, and specifically, the filter 701 and the amplitude generation unit 702 are provided in parallel. That is, in this embodiment, a set of filter 701 and amplitude generation unit 702 corresponding to the drive frequency f1 and a set of filter 701 and amplitude generation unit 702 corresponding to the drive frequency f2 are provided in parallel.

[0078] In this case, as shown in Figure 22, when ultrasonic waves of frequencies f1 and f2 are transmitted and received by one ultrasonic sensor 3, it becomes possible to process the received signals corresponding to both frequencies simultaneously. Also, as shown in Figure 23, when ultrasonic waves of frequency f1 are transmitted by one of the two ultrasonic sensors 3 and ultrasonic waves of frequency f2 are transmitted by the other, it becomes possible to process the received signals corresponding to both frequencies simultaneously.

[0079] (Fifth embodiment) It is preferable for the transmitting / receiving unit 5 to have pre-adjusted measurement parameters such as the driving energy (current or voltage, or duty cycle) and receiving sensitivity (amplifier gain, etc.) at the spurious frequency, so that the reflected wave amplitude at a specified obstacle remains constant.

[0080] (Sixth Embodiment) In this embodiment, one ultrasonic sensor 3 switches between a first resonant frequency and a second resonant frequency (spurious frequency) for the driving frequency. In this case, for example, if the second front sensor 3B and the third front sensor 3C, which are adjacent ultrasonic sensors 3 in the vehicle width direction, have one driving frequency at the first resonant frequency and the other driving frequency at the second resonant frequency (spurious frequency), the received signals of the two frequencies can be easily separated by a bandpass filter or the like.

[0081] Figures 24 to 26 show examples of measurement schedules when one of the pair of ultrasonic sensors 3 is designated as sensor 1 and the other as sensor 2.

[0082] Figure 24 shows an example, as a comparative example, in which only the main resonant frequency, i.e., the first resonant frequency corresponding to the main resonance, is used, and a time difference is introduced between the transmission and reception operations of both. In this example, Section 1, in which sensor 1 is driven at the main resonant frequency to perform transmission and reception operations while sensor 2 only performs reception operations, and Section 2, in which sensor 2 is driven at the main resonant frequency to perform transmission and reception operations while sensor 1 only performs reception operations, are repeatedly executed alternately.

[0083] Figure 25 shows an example of applying the operation mode of Figure 24 to a form using the principal resonant frequency and spurious frequency. In this example, sections 1-1, 1-2, 2-1, 2-2, ... are executed alternately and repeatedly.

[0084] In Section 1-1, sensor 1 is driven at the main resonant frequency to perform transmission and reception operations, while sensor 2 is configured to perform reception operations only. In Section 1-2, sensor 1 is driven at the spurious frequency to perform transmission and reception operations, while sensor 2 is configured to perform reception operations only. In Section 2-1, sensor 2 is driven at the main resonant frequency to perform transmission and reception operations, while sensor 1 is configured to perform reception operations only. In Section 2-2, sensor 2 is driven at the spurious frequency to perform transmission and reception operations, while sensor 1 is configured to perform reception operations only.

[0085] Figure 26 shows an example in which Section 1 and Section 2 are repeatedly executed alternately, but it differs from the operation mode in Figure 24. Specifically, in Section 1, Sensor 1 is driven at the main resonant frequency to perform transmission and reception operations, and Sensor 2 is driven at the spurious frequency to perform transmission and reception operations. In Section 2, Sensor 1 is driven at the spurious frequency to perform transmission and reception operations, and Sensor 2 is driven at the main resonant frequency to perform transmission and reception operations.

[0086] In sections 1 and 2, as shown in Figure 23, the filter 701 and amplitude generation unit 702 for the main resonant frequency and the filter 701 and amplitude generation unit 702 for the spurious frequency are provided in parallel. Therefore, there is no need to set a time difference between the transmission and reception operations of both sensor 1 and sensor 2. In other words, multiple ultrasonic sensors 3 with different drive frequencies can be operated simultaneously for transmission and reception.

[0087] Therefore, according to this embodiment, for the multiple ultrasonic sensors 3 mounted on the front bumper, namely the first front sensor 3A, the second front sensor 3B, the third front sensor 3C, and the fourth front sensor 3D, it is possible to increase the transmission period compared to setting the transmission timing cyclically. The same applies to the multiple ultrasonic sensors 3 mounted on the rear bumper, namely the first rear sensor 3E, the second rear sensor 3F, the third rear sensor 3G, and the fourth rear sensor 3H. Furthermore, by continuously switching between the first and second resonant frequencies during transmission, amplitude information of two frequencies used for object identification can be obtained in a single measurement.

[0088] (modified version) This disclosure is not limited to the embodiments described above. Therefore, the embodiments can be modified as appropriate. Representative modifications are described below. In the following description of modifications, the differences from the embodiments will be mainly described. In addition, parts that are the same or equivalent to each other in the embodiments and modifications are denoted by the same reference numerals. Therefore, in the following description of modifications, with respect to components that have the same reference numerals as in the embodiments, the descriptions in the embodiments can be appropriately referenced unless there is a technical inconsistency or additional explanation to be provided.

[0089] This disclosure is not limited to the specific uses shown in the embodiments described above. In other words, vehicle C may not only travel on public roads, but also travel within specific areas such as private land like golf courses, factories, warehouses, or exhibition venues. There are no particular limitations on the shape of the vehicle body C1 or the number of wheels in vehicle C. Furthermore, the object detection device according to this disclosure is not limited to the configuration mounted on vehicle C.

[0090] This disclosure is not limited to the specific device configuration shown in the embodiments described above. That is, for example, all or part of the electronic control unit 2 may be configured to include a digital circuit, such as an ASIC or FPGA, configured to enable the above-described operation. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. In other words, the in-vehicle microcomputer portion and the digital circuit portion can coexist in the electronic control unit 2.

[0091] The ultrasonic sensor 3 is not limited to a configuration that allows ultrasonic waves to be transmitted and received by a single transmitting / receiving element 4, as shown in Figure 2A. That is, for example, a transmitting / receiving element 4 for probe wave transmission, electrically connected to a transmitting circuit 51, and a transmitting / receiving element 4 for receiving, electrically connected to a receiving circuit 52, may be provided in parallel. Alternatively, for example, an ultrasonic sensor 3 for probe wave transmission and an ultrasonic sensor 3 for receiving may be provided.

[0092] The configuration and function of the transmitting / receiving element 4 can also be modified as appropriate. For example, the transmitting / receiving element 4 may have so-called polarized directivity. Such polarized directivity can be easily achieved, for example, by offsetting the arrangement of the electromechanical conversion element 41 by a predetermined amount from the center position PC of the diaphragm 421.

[0093] There are no particular limitations on the structure of the microphone case 42. For example, the shape of the diaphragm 421 is not limited to an oval, but may be a perfect circle, ellipse, polygon, etc., and the thickness of the diaphragm 421 does not have to be uniform. The shape of the diaphragm support 422 may be an elliptical cylinder or a polygonal cylinder. It is also possible to adopt a configuration in which an elastic material such as silicone rubber is interposed between the plate-shaped diaphragm 421 that constitutes the top plate of the microphone case 42 and the diaphragm support 422.

[0094] There are no particular limitations on the position, number, or shape of the slits 425. For example, the slits 425 may be formed as grooves (with a thin diaphragm) that open toward the microphone central axis LC at the upper end of the internal space 423, or they may form recessed portions that do not penetrate, or convex portions (with a thicker diaphragm in some areas). The slits 425 do not have to penetrate.

[0095] The configuration of each part, such as the transmitting circuit 51 and the receiving circuit 52, is not limited to the specific examples shown in the above embodiment. That is, for example, the digital / analog conversion circuit may be provided in the drive signal generation unit 6 instead of the transmitting circuit 51. Also, the transmitting circuit 51 may be integrated with the drive signal generation unit 6. Similarly, the receiving circuit 52 may be integrated with the receiving signal processing unit 7. The receiving signal processing unit 7 may be provided in the sensor control unit 8.

[0096] All or part of the functional configurations in the sensor control unit 8 may be provided in the receiving signal processing unit 7 and / or the electronic control unit 2, insofar as it does not conflict with the technical standards. That is, the object detection device according to this disclosure may be composed of at least one of the electronic control unit 2 and the ultrasonic sensor 3.

[0097] The sensor control unit 8 may be configured with all or part of a digital circuit, such as an ASIC or FPGA, that is configured to enable the above-described operation. In other words, the in-vehicle microcomputer portion and the digital circuit portion can coexist in the sensor control unit 8. To put it another way, each process in this disclosure may be a hardware process or a software process.

[0098] The program relating to this disclosure, which enables the execution of various operations, procedures, or processes described in the above embodiments, can be downloaded or upgraded via V2X communication. V2X stands for Vehicle to X. Alternatively, such a program can be downloaded or upgraded via terminal equipment installed at a manufacturing plant, repair shop, dealership, etc., of vehicle C. The storage location of such a program may be a memory card, optical disk, magnetic disk, etc.

[0099] Thus, each of the above functional configurations and methods may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, each of the above functional configurations and methods may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, each of the above functional configurations and methods may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits.

[0100] Furthermore, the computer program may be stored in a computer-readable, non-transitional, substantial storage medium as instructions executed by the computer. In other words, each of the above functional configurations and methods can also be represented as a computer program including the procedures for realizing it, or as a non-transitional, substantial storage medium storing said program.

[0101] As is clear from the above, the functional configuration blocks shown in Figure 2A are merely functional configuration blocks set up for convenience to facilitate understanding of the contents of this disclosure. Therefore, even if these functional configuration blocks are not actually implemented as subroutines or hardware, the requirements of this disclosure may be satisfied as long as the functions or processes specified in this disclosure are implemented.

[0102] This disclosure is not limited to the specific examples of operation or processing shown in the embodiments described above. That is, for example, there are no particular limitations on the order of the vibration mode at the spurious frequency, as long as object detection is possible.

[0103] In the above description, multiple components that were formed as a single, seamless unit may be formed by bonding together separate components. Similarly, multiple components that were formed by bonding together separate components may be formed as a single, seamless unit. Furthermore, in the above description, multiple components that were formed from the same material may be formed from different materials. Similarly, multiple components that were formed from different materials may be formed from the same material.

[0104] It goes without saying that the elements constituting the above embodiments are not necessarily essential unless explicitly stated to be particularly essential or considered to be fundamentally essential. Furthermore, when numerical values ​​such as the number, quantity, or range of components are mentioned, this disclosure is not limited to those specific numerical values ​​unless explicitly stated to be particularly essential or considered to be fundamentally limited to those specific numerical values. Similarly, when the shape, orientation, positional relationship, etc., of components are mentioned, this disclosure is not limited to those shape, orientation, positional relationship, etc., unless explicitly stated to be particularly essential or considered to be fundamentally limited to those specific shape, orientation, positional relationship, etc.

[0105] Modifications are not limited to the examples given above. That is, parts of one embodiment may be combined with parts of another embodiment. Multiple modifications may also be combined with each other. Furthermore, all or part of the above embodiments may be combined with all or part of the modifications. [Explanation of Symbols]

[0106] 1. In-vehicle system (object detection device) 2. Electronic control unit 3. Ultrasonic Sensor 4 Transceiver elements 421 Diaphragm 422 Diaphragm support 425 Slit 5 Transmitter / Receiver 8. Sensor Control Unit (Determination Unit) DL Directional center axis

Claims

1. An object detection device (1) is configured to detect an object (B) by transmitting ultrasonic waves and receiving the reflected waves from the object (B), A transmitting unit (50A) that transmits ultrasonic waves, A receiving unit (50B) that receives ultrasonic waves, A determination unit (8) performs object detection determination based on the received signal of the reflected wave in the receiving unit, Equipped with, The transmitting unit uses a transmitting / receiving element (4) having a resonant frequency that vibrates in a higher-order vibration mode than the first resonant frequency, The system is configured to transmit ultrasonic waves in a frequency band that constitute the vibration mode of the first resonant frequency and ultrasonic waves in a frequency band that constitute the higher-order vibration mode. Ultrasound in frequency bands of higher-order vibration modes than the ultrasound in the first frequency band has directional characteristics in which the sound pressure in the direction of the directional central axis (DL) is reduced. The determination unit detects the object based on a comparison of the amplitudes of multiple received signals in the first frequency band and the frequency band of the higher-order vibration mode. Object detection device.

2. The aforementioned transmitting and receiving element is A diaphragm (421) formed in the shape of a thin plate or thin film to vibrate ultrasonically during the transmission and reception of ultrasonic waves, A cylindrical diaphragm support (422) that supports the outer edge of the diaphragm, It has, The diaphragm support has a slit (425) on its side (423). The object detection device according to claim 1.

3. When transmitting ultrasonic waves in the frequency band of the higher-order vibration mode, the drive current, or the drive voltage, or both, is increased to increase the drive power compared to when transmitting ultrasonic waves in the frequency band of the first resonant frequency vibration mode. The object detection device according to claim 1.

4. When transmitting ultrasonic waves in the frequency band of the higher-order vibration mode, the number of drive pulses is increased compared to when transmitting ultrasonic waves in the frequency band of the first resonant frequency vibration mode. The object detection device according to claim 1.

5. A filter that extracts the received ultrasonic signal in the frequency band of the higher-order vibration mode and a filter that switches the filter band when outputting the received ultrasonic signal in the frequency band of the first resonant frequency vibration mode, or has multiple filters. The object detection device according to claim 1.

6. The matching circuit is switched when transmitting and receiving ultrasonic waves at the aforementioned spurious frequency and when transmitting and receiving ultrasonic waves at the aforementioned first resonant frequency. The object detection device according to claim 1.

7. The transmitting and receiving unit has its current and sensitivity adjusted in advance to the spurious frequency. The object detection device according to claim 1.

8. Multiple ultrasonic sensors (3) having the aforementioned transmitting and receiving units are provided. The first ultrasonic sensor, which transmits and receives ultrasonic waves in the frequency band of the vibration mode of the first resonant frequency, and the second ultrasonic sensor, which transmits and receives ultrasonic waves in the frequency band of the higher-order vibration mode, are operated simultaneously for transmitting and receiving. The object detection device according to claim 1.

Images