Ultrasonic sensor and vehicle

Abstract

The present disclosure relates to an ultrasonic sensor and a vehicle. The ultrasonic sensor of the present disclosure is provided with: an ultrasonic transducer having a plurality of resonance frequencies; and a matching circuit including a plurality of LC parallel resonance circuits connected in series with each other, the plurality of LC parallel resonance circuits having resonance frequencies smaller than a maximum value among the plurality of resonance frequencies of the ultrasonic transducer and larger than a minimum value among the plurality of resonance frequencies.

Description

Technical Field

[0001] This disclosure relates to ultrasonic sensors and vehicles that detect surrounding objects based on the reflected waves of transmitted ultrasonic waves. Background Technology

[0002] Ultrasonic sensors, which emit ultrasonic waves and detect objects through reflected waves from surrounding objects, are now widespread.

[0003] For example, Patent Document 1 discloses an ultrasonic sensor in which, when the resonant frequency of the equivalent series capacitor and the equivalent series inductor is set to F0, and the resonant frequency determined based on the equivalent parallel capacitor and the inductor connected in series between the ultrasonic transducer and the driving circuit is Fp, the driving frequency is switched to a value that is the same as one of the resonant frequencies F0 and Fp to drive the ultrasonic transducer.

[0004] Patent document 2 discloses an ultrasonic sensor that senses the reverberation time of the output of a piezoelectric vibrator and controls the opening and closing of multiple switches based on the reverberation time to keep the reverberation time of the received output of the piezoelectric vibrator within an appropriate range.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 5195587

[0008] Patent Document 2: Japanese Patent No. 4192672 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] In existing circuits, good characteristics are achieved by designing the susceptance component to approach zero. However, in the ultrasonic sensor of Patent Document 1, while the susceptance component at one of the two resonant frequencies is brought closer to zero, it is difficult to bring the susceptance component at the other frequency closer to zero. Therefore, in the ultrasonic sensor of Patent Document 1, it is difficult to obtain good characteristics at both resonant frequencies.

[0011] Patent document 2 discloses a technique for improving the performance of an ultrasonic sensor at a frequency by setting the reverberation time within an appropriate range, but does not consider the case of receiving signals at multiple frequencies simultaneously.

[0012] This disclosure contributes to providing an ultrasonic sensor and vehicle capable of transmitting and receiving at multiple frequencies and achieving good characteristics at each of the multiple frequencies.

[0013] Solution to the problem

[0014] One aspect of the ultrasonic sensor disclosed herein includes: an ultrasonic transducer having a plurality of resonant frequencies; and a matching circuit comprising a plurality of LC parallel resonant circuits connected in series, wherein the resonant frequency of the plurality of LC parallel resonant circuits is less than the maximum value among the plurality of resonant frequencies of the ultrasonic transducer and greater than the minimum value among the plurality of resonant frequencies.

[0015] One embodiment of the vehicle disclosed herein includes: the aforementioned ultrasonic sensor; and a detection circuit that detects obstacles based on information relating to transmitted and received waves acquired from the ultrasonic sensor, respectively.

[0016] Solution to the problem

[0017] According to this disclosure, it is possible to transmit and receive at multiple frequencies and obtain good characteristics at each of the multiple frequencies. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing a vehicle equipped with ultrasonic sensors.

[0019] Figure 2 This is a graph illustrating the frequency characteristics of the ultrasonic sensor in each embodiment.

[0020] Figure 3 This is a diagram illustrating an example of a functional structure in a vehicle that includes an ultrasonic sensor.

[0021] Figure 4 This is a diagram illustrating an example of the structure of the ultrasonic sensor according to the first embodiment.

[0022] Figure 5 This is a diagram illustrating an example of the structure of the matching circuit in the first embodiment.

[0023] Figure 6 This is a cross-sectional schematic diagram illustrating an example of the structure of an ultrasonic transducer.

[0024] Figure 7 This is a diagram showing the equivalent circuit of an ultrasonic transducer.

[0025] Figure 8 This is a diagram illustrating an example of the structure of the ultrasonic sensor according to the second embodiment.

[0026] Figure 9 This is a diagram illustrating an example of the structure of the matching circuit in the second embodiment.

[0027] Figure 10 It is a graph used to illustrate the effects obtained by the ultrasonic sensor of the first embodiment and the ultrasonic sensor of the second embodiment.

[0028] Figure 11 This is a diagram used to illustrate the structure of an ultrasonic sensor used as a comparative example.

[0029] Figure 12A This is a graph showing the frequency characteristics of the ultrasonic sensor in the comparative example.

[0030] Figure 12B This is a graph representing the reverberation time of the ultrasonic sensor in the comparative example.

[0031] Figure 12C This is a graph representing the reverberation time of the ultrasonic sensor in the comparative example.

[0032] Figure 13A This is a graph showing the frequency characteristics of the ultrasonic sensor according to the first embodiment.

[0033] Figure 13B This is a graph representing the reverberation time of the ultrasonic sensor according to the first embodiment.

[0034] Figure 13C This is a graph representing the reverberation time of the ultrasonic sensor according to the first embodiment.

[0035] Figure 14A This is a graph representing the frequency characteristics of the ultrasonic sensor according to the second embodiment.

[0036] Figure 14B This is a graph representing the reverberation time of the ultrasonic sensor according to the second embodiment.

[0037] Figure 14C This is a graph representing the reverberation time of the ultrasonic sensor according to the second embodiment. Detailed Implementation

[0038] Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, sometimes overly detailed descriptions may be omitted (e.g., detailed descriptions of well-known matters or repeated descriptions of substantially the same structures).

[0039] <Overview>

[0040] The following will describe various embodiments of the ultrasonic sensor of this disclosure. The ultrasonic sensor of this disclosure is capable of transmitting ultrasonic waves at multiple frequencies. In the following embodiments, a method in which the ultrasonic sensor can transmit ultrasonic waves at two frequencies f1 and f2 will be described.

[0041] Figure 1 This is a schematic diagram showing a vehicle 20 equipped with an ultrasonic sensor 10. Figure 1 An example of an ultrasonic sensor 10 being mounted on the rear bumper of vehicle 20 is shown. Figure 1In the example shown, the vertical directivity (sound wave propagation) of frequency f1 is 35 degrees, and the vertical directivity of frequency f2 is 16 degrees. By changing the vertical directivity according to the transmission frequency, it is easier to achieve... Figure 1 Obstacles of lower height, such as obstacle O shown, (e.g., curb stones) are distinguished from other obstacles.

[0042] Figure 2 This is a graph illustrating the frequency characteristics of the ultrasonic sensor 10 in each embodiment. Figure 2 The horizontal axis represents frequency, and the vertical axis represents voltage. Figure 2 In the example shown, f1 is set to 40 kHz and f2 is set to 70 kHz. Furthermore, in this disclosure, the ultrasonic sensor 10 can transmit ultrasonic waves at multiple frequencies, not limited to 40 kHz and 70 kHz, and can be set to any value by the designer of the ultrasonic sensor, etc.

[0043] Figure 3 This diagram illustrates an example of the functional structure of a vehicle 20 that includes an ultrasonic sensor 10. Figure 3 In the example shown, vehicle 20 includes ultrasonic sensor 10, ECU 21, display 22, buzzer 23 and brake 24.

[0044] The ECU (Engine Control Unit or Electronic Control Unit) 21 is a control unit that performs various controls on the vehicle 20. The ECU 21 operates at least as a detection unit, which detects obstacles around the vehicle 20 based on information related to transmitted and received waves acquired from the ultrasonic sensor 10. The ECU 21 can also perform driving control of the vehicle 20, etc.

[0045] Display 22, for example, is a display device installed inside the vehicle, which, based on the control of ECU 21, displays obstacles and the like around the vehicle 20. Buzzer 23, for example, is an audible alarm device installed inside or outside the vehicle, which, based on the control of ECU 21, sounds an alarm when the vehicle 20 approaches an obstacle. Brake 24 is the stopping mechanism and control mechanism of the vehicle 20, which, based on the control of ECU 21, slows down or stops the vehicle 20 when it approaches an obstacle.

[0046] The ultrasonic sensor 10 in the first embodiment and the second embodiment will be described in detail below. The ultrasonic sensor 10 in the first embodiment will be referred to as ultrasonic sensor 10A, and the ultrasonic sensor 10 in the second embodiment will be referred to as ultrasonic sensor 10B.

[0047] <First Implementation Method>

[0048] The ultrasonic sensor 10A according to the first embodiment of this disclosure will be described below. Among the structures described in the first embodiment, structures with "A" at the end of the reference numerals are unique to the first embodiment, while structures without "A" are structures that have the same features and properties as those in the first and second embodiments.

[0049] Figure 4 This is a diagram illustrating an example of the structure of the ultrasonic sensor 10A according to the first embodiment. Figure 4 As shown, the ultrasonic sensor 10A includes a control unit 11A, a first drive circuit 12A, a second drive circuit 13A, a matching circuit 14A, an ultrasonic transducer 15, and a signal processing unit 16. In the first embodiment, the ultrasonic transducer 15 has two resonant frequencies f1 and f2, and the ultrasonic sensor 10A is capable of transmitting ultrasonic waves at one of the two frequencies f1 and f2. Let f1 be an example frequency. <f2。

[0050] The control unit 11A controls the operation of the ultrasonic sensor 10A based on the control of the ECU 21. Specifically, when the control unit 11A receives a command from the ECU 21 to send ultrasonic waves at frequency f1, it outputs a pulse signal at frequency f1 to the first drive circuit 12A. When the control unit 11A receives a command from the ECU 21 to send ultrasonic waves at frequency f2, it outputs a pulse signal at frequency f2 to the second drive circuit 13A.

[0051] The first drive circuit 12A drives the ultrasonic transducer 15 at frequency f1 based on a pulse signal of frequency f1 input from the control unit 11A. The second drive circuit 13A drives the ultrasonic transducer 15 at frequency f2 based on a pulse signal of frequency f2 input from the control unit 11A. Thus, in the ultrasonic sensor 10A of the first embodiment, since it has two drive circuits, it is possible to transmit ultrasonic waves at two frequencies simultaneously.

[0052] Matching circuit 14A is a circuit that performs impedance matching between ultrasonic transducer 15 and other structures of ultrasonic sensor 10A. For example, in the first embodiment, matching circuit 14A can improve the overall output characteristics of ultrasonic sensor 10A by canceling (making close to 0) the susceptance component of ultrasonic transducer 15 at two resonant frequencies f1 and f2.

[0053] Figure 5This is a diagram illustrating an example of the structure of the matching circuit 14A according to the first embodiment. The matching circuit 14A has two LC parallel resonant circuits 141A and 142A connected in series. The LC parallel resonant circuit 141A has a structure in which a parallel inductor L1A and a parallel capacitor C1 are connected in parallel. The LC parallel resonant circuit 142A has a structure in which a parallel inductor L2A and a parallel capacitor C2 are connected in parallel.

[0054] like Figure 4 and Figure 5 As shown, the parallel inductor L1A of the LC parallel resonant circuit 141A and the inductor L connected to the first drive circuit 12A are... D1 Together, they constitute transformer TR1. The parallel inductor L1A of the LC parallel resonant circuit 141A forms the secondary side (output side) of transformer TR1. Furthermore, as... Figure 4 and Figure 5 As shown, the parallel inductor L2A of the LC parallel resonant circuit 142A and the inductor L connected to the second drive circuit 13A are... D2 Together, they constitute transformer TR2. The parallel inductor L2A of the LC parallel resonant circuit 142A forms the secondary side (output side) of transformer TR2. Parallel inductors L1A and L2A are an example of the first parallel inductors disclosed herein. Transformers TR1 and TR2 can easily convert the input voltage to a large voltage amplitude, and because the primary side has high impedance when viewed from the secondary side, influences from the primary side are not transmitted to the secondary side, making them suitable as input circuits to the ultrasonic transducer 15.

[0055] The two LC parallel resonant circuits 141A and 142A are designed to have a resonant frequency f1 greater than the smaller of the two resonant frequencies f1 and f2 of the ultrasonic transducer 15 and less than the larger of the two resonant frequencies f2. s Therefore, the susceptance components at the two resonant frequencies f1 and f2 of the ultrasonic transducer 15 can be appropriately canceled out.

[0056] When the capacitance of parallel capacitor C1 is denoted as C1, the inductance of parallel inductor L1A as L1, the capacitance of parallel capacitor C2 as C2, and the inductance of parallel inductor L2A as L2, the resonant frequency (resonant frequency of matching circuit 14A) of the LC parallel resonant circuits 141A and 142A is f. s It can be represented by the following formula (1).

[0057] [Formula 1]

[0058]

[0059] The principle by which the matching circuit 14A can appropriately cancel out the susceptance components at the two resonant frequencies f1 and f2 of the ultrasonic transducer 15 will be explained later.

[0060] As described above, the ultrasonic transducer 15 has two resonant frequencies f1 and f2. The ultrasonic transducer 15 transmits ultrasonic waves at one of frequencies f1 and f2 based on a pulse signal input from the first drive circuit 12A or the second drive circuit 13A. The ultrasonic transducer 15 is, for example, an ultrasonic microphone.

[0061] Figure 6 This is a cross-sectional schematic diagram showing an example of the structure of the ultrasonic transducer 15. The ultrasonic transducer 15 consists of a piezoelectric element attached to the inside of a cylindrical housing (such as aluminum) and a filler. The piezoelectric element is connected to the first drive circuit 12A, the second drive circuit 13A, and the signal processing unit 16 via leads. The housing is grounded.

[0062] Although Figure 6 Although not shown in the figure, slits, holes, protrusions, etc. are provided on the housing, thereby enabling the ultrasonic transducer 15 to have multiple frequency vibration modes.

[0063] When a signal from the drive circuit is applied to the piezoelectric element through the leads, the piezoelectric element will generate compressive or tensile strain, causing the housing to vibrate. Thus, the ultrasonic transducer 15 can transmit ultrasonic waves.

[0064] When the ultrasonic transducer 15 receives ultrasonic waves, the piezoelectric element generates a received signal in response to the vibration of the housing. The signal processing unit 16 amplifies and detects the received signal, and the control unit 11A detects obstacles around the vehicle 20 based on the intensity of the received signal.

[0065] Figure 7 This is a diagram showing the equivalent circuit of the ultrasonic transducer 15. Figure 7 In the example shown, the equivalent parallel capacitor C of the ultrasonic transducer 15 m0 It is connected in parallel with two RLC series circuits SC1 and SC2.

[0066] The RLC series circuit SC1 includes an equivalent series inductor L. m1 Equivalent series capacitor C m1 and equivalent series resistance R m1 The RLC series circuit SC2 includes an equivalent series inductor L. m2 Equivalent series capacitor C m2 and equivalent series resistance R m2 .

[0067] In the equivalent series inductor L m1 The inductance is denoted as L m1Equivalent series capacitor C m1 The capacitance is denoted as C. m1 Equivalent series inductor L m2 The inductance is denoted as L m2 Equivalent series capacitor C m2 The capacitance is denoted as C. m2 At that time, the two resonant frequencies f1 and f2 of the ultrasonic transducer 15 can be expressed by the following formulas (2) and (3).

[0068] [Equation 2]

[0069]

[0070] [Formula 3]

[0071]

[0072] As described above, so that the resonant frequency of the RLC series circuits SC1 and SC2 and the matching circuit 14A (the resonant frequency of the LC parallel resonant circuits 141A and 142A) is f s Based on the relationship between the following equation (4), an ultrasonic sensor 10A is designed.

[0073] [Formula 4]

[0074]

[0075] Specifically, when designing the ultrasonic sensor 10A, as long as equations (1) to (4) are satisfied, the parallel inductors L1A and L2A and the parallel capacitors C1 and C2 included in the matching circuit 14A, and the equivalent series inductor L1A included in the ultrasonic transducer 15 are connected in the same manner. m1 L m2 and equivalent series capacitor C m1 C m2 The inductance and capacitance can be set to appropriate values.

[0076] By equipping the ultrasonic sensor 10A with such a structure, the matching circuit 14A can cancel out the susceptance components at both resonant frequencies f1 and f2 of the ultrasonic transducer 15, thereby improving the performance of the ultrasonic sensor 10A. Specifically, it is possible to simultaneously increase the output of the ultrasonic sensor 10A and reduce the reverberation time.

[0077] <Second Implementation Method>

[0078] The second embodiment of this disclosure will now be described. In the various structures described in the second embodiment, structures ending with "B" are unique to the second embodiment, while structures without "B" are structures that have the same features and properties as those in the first and second embodiments.

[0079] Figure 8 This is a diagram illustrating an example of the structure of the ultrasonic sensor 10B according to the second embodiment. Figure 8 As shown, the ultrasonic sensor 10B includes a control unit 11B, a matching circuit 14B, an ultrasonic transducer 15, a signal processing unit 16, and a drive circuit 17B. In the second embodiment, similar to the first embodiment, the ultrasonic transducer 15 has two resonant frequencies f1 and f2, and the ultrasonic sensor 10B can transmit ultrasonic waves at one of the two frequencies f1 and f2. Let f1 be... <f2。

[0080] The control unit 11B controls the operation of the ultrasonic sensor 10B according to the control of the ECU 21. Specifically, when the control unit 11B receives a command from the ECU 21 to send ultrasonic waves at frequency f1, it outputs a pulse signal at frequency f1 to the drive circuit 17B. When the control unit 11B receives a command from the ECU 21 to send ultrasonic waves at frequency f2, it outputs a pulse signal at frequency f2 to the drive circuit 17B.

[0081] When a pulse signal of frequency f1 is input from the control unit 11B, the drive circuit 17B drives the ultrasonic transducer 15 at frequency f1. When a pulse signal of frequency f2 is input from the control unit 11B, the drive circuit 17B drives the ultrasonic transducer 15 at frequency f2.

[0082] Thus, the ultrasonic sensor 10B in the second embodiment has only one driving circuit, so it can have a simpler structure than the ultrasonic sensor 10A in the first embodiment.

[0083] Matching circuit 14B is a circuit that performs impedance matching between the ultrasonic transducer 15 and other structures of the ultrasonic sensor 10B. For example, similar to matching circuit 14A in the first embodiment, matching circuit 14B in the second embodiment can improve the overall output characteristics of the ultrasonic sensor 10B by canceling out the susceptance component of the ultrasonic transducer 15 (making it approach 0). It should be noted that, as Figure 8 and Figure 9 As shown, the circuit structure of the matching circuit 14B in the second embodiment is different from that of the matching circuit 14A in the first embodiment.

[0084] Figure 9This is a diagram illustrating an example of the structure of the matching circuit 14B according to the second embodiment. The matching circuit 14B has two LC parallel resonant circuits 141B and 142B connected in series. The LC parallel resonant circuit 141B has a structure in which a parallel inductor L1B and a parallel capacitor C1 are connected in parallel. The LC parallel resonant circuit 142B has a structure in which a parallel inductor L2B and a parallel capacitor C2 are connected in parallel.

[0085] Similar to the first embodiment, the two LC parallel resonant circuits 141B and 142B are designed to have a resonant frequency f1 greater than f1 and f2 of the two resonant frequencies f1 and f2 of the ultrasonic transducer 15, but less than f2. s Therefore, the susceptance components at the two resonant frequencies f1 and f2 of the ultrasonic transducer 15 can be appropriately canceled out.

[0086] When the capacitance of parallel capacitor C1 is denoted as C1, the inductance of parallel inductor L1B as L1, the capacitance of parallel capacitor C2 as C2, and the inductance of parallel inductor L2B as L2, the resonant frequency (resonant frequency of matching circuit 14B) of the LC parallel resonant circuits 141B and 142B is f. s It can be represented by the above formula (1).

[0087] In the ultrasonic sensor 10B of the second embodiment, the parallel inductors L1B and L2B and the parallel capacitors C1 and C2 included in the matching circuit 14B, and the equivalent series inductor L1B included in the ultrasonic transducer 15 are connected in a manner that satisfies equations (1) to (4) described in the first embodiment. m1 L m2 and equivalent series capacitor C m1 C m2 The inductance and capacitance are set to appropriate values. By equipping the ultrasonic sensor 10B with such a structure, the matching circuit 14B can cancel out the susceptance component at both resonant frequencies f1 and f2 of the ultrasonic transducer 15, thereby improving the performance of the ultrasonic sensor 10B. Specifically, it is possible to simultaneously increase the output of the ultrasonic sensor 10B and reduce the reverberation time.

[0088] Unlike the ultrasonic sensor 10A in the first embodiment, in the ultrasonic sensor 10B of the second embodiment, the parallel inductors L1B and L2B of the matching circuit 14B do not constitute a transformer.

[0089] like Figure 8 As shown, in the ultrasonic sensor 10B of the second embodiment, a parallel inductor L3 is configured in parallel with the matching circuit 14B and the ultrasonic transducer 15. The parallel inductor L3 is an example of the second parallel inductor of this disclosure.

[0090] Parallel inductor L3 and inductor L connected to drive circuit 17B D Together they form the transformer TR connected to the drive circuit 17B.

[0091] The parallel inductor L3 and the equivalent parallel capacitor C contained in the ultrasonic transducer 15 m0 The resonant frequency f a It is designed to satisfy the following equation (5).

[0092] [Formula 5]

[0093]

[0094] Because the susceptance component of the ultrasonic transducer 15 is at the resonant frequency f a The value is 0 near the resonant frequency f. a Setting the value to satisfy equation (5) can make the susceptance component of the ultrasonic transducer 15 at resonant frequencies f1 and f2 smaller, which has the effect of making the susceptance component easier to cancel.

[0095] (principle)

[0096] The specific effects and principles of the ultrasonic sensor 10A of the first embodiment and the ultrasonic sensor 10B of the second embodiment described above will be explained below.

[0097] Figure 10 It is a graph used to illustrate the effects and principles that can be obtained by the ultrasonic sensor 10A of the first embodiment and the ultrasonic sensor 10B of the second embodiment.

[0098] Figure 10 The relationship between frequency and susceptance component is shown when ultrasonic sensors 10A and 10B are capable of transmitting ultrasonic waves at two frequencies, 40 kHz and 70 kHz. Figure 10 In the diagram, the dotted line represents the susceptance component of the ultrasonic transducer 15, the dashed line represents the susceptance components of the matching circuits 14A and 14B, and the solid line represents the component obtained by adding the susceptance components of the ultrasonic transducer 15 and the susceptance components of the matching circuits 14A and 14B.

[0099] Based on experience, in the existing structure of ultrasonic sensors, without a resonant frequency, the waveform generally shows an increase in susceptance component with increasing frequency. On the other hand, as... Figure 10 As illustrated, the susceptance component decreases significantly near the resonant frequency.

[0100] As described above, the ultrasonic transducer 15 has two resonant frequencies: 40 kHz and 70 kHz. The susceptance components at these resonant frequencies have non-zero values. Figure 10In the example shown, the susceptance component at 40 kHz is smaller than the susceptance component at 70 kHz. Figure 10 In the example shown, the susceptance component of the ultrasonic transducer 15 at 40 kHz is 488 μS, and the susceptance component of the ultrasonic transducer 15 at 70 kHz is 805 μS.

[0101] As described in the first and second embodiments above, the resonant frequencies of the matching circuits 14A and 14B are designed to be greater than the smaller of the two resonant frequencies of the ultrasonic transducer 15, and less than the larger of the two resonant frequencies. Figure 10 In the example shown, the resonant frequency of matching circuits 14A and 14B is designed to be 53.5 kHz. Therefore, the susceptance component of matching circuits 14A and 14B at 40 kHz is -489 μS, and the susceptance component at 70 kHz is -806 μS.

[0102] As described above, in the existing structure of an ultrasonic sensor, except at the resonant frequency, the waveform generally shows an increase in susceptance as the frequency increases. However, by designing the matching circuits 14A and 14B so that their resonant frequencies are greater than the minimum of the two resonant frequencies of the ultrasonic transducer 15 and less than the maximum of those two resonant frequencies, it is possible to make the susceptance component of the matching circuits 14A and 14B at the minimum resonant frequency of the ultrasonic transducer 15 greater than the susceptance component of the matching circuits 14A and 14B at the maximum resonant frequency of the ultrasonic transducer 15.

[0103] By designing the matching circuits 14A and 14B in this way, the susceptance components of the matching circuits 14A and 14B at 40kHz and 70kHz can be made to cancel out the susceptance components of the ultrasonic transducer 15 at 40kHz and 70kHz, respectively.

[0104] Therefore, as Figure 10 As shown by the solid line, at the two resonant frequencies of 40kHz and 70kHz of the ultrasonic transducer 15, the susceptance component of the ultrasonic transducer 15 is appropriately canceled out by the susceptance components of the matching circuits 14A and 14B. This allows for the simultaneous increase in the output of the ultrasonic sensors 10A and 10B and the reduction in their reverberation time.

[0105] in addition, Figure 10 The diagram shows an example where the susceptance component of the ultrasonic transducer 15 is canceled out by the susceptance components of matching circuits 14A and 14B at two resonant frequencies of 40 kHz and 70 kHz, reducing it to almost zero at both locations. Figure 10The example shown is a preferred embodiment of this disclosure. This disclosure does not necessarily require that, at each of the multiple resonant frequencies at which the ultrasonic sensor can transmit ultrasonic waves, the susceptance component of the ultrasonic transducer be reduced to almost zero using the susceptance component of the matching circuit.

[0106] As explained above, by setting the resonant frequency of the matching circuit to be greater than the minimum value f among the multiple resonant frequencies possessed by the ultrasonic transducer. min And less than the maximum value f among these multiple resonant frequencies. max The value that minimizes f min The susceptance component of the matching circuit at the point is greater than the maximum value f. max The susceptance component of the matching circuit at the point. Due to the minimum value f min The susceptance component of the ultrasonic transducer at that location is less than the maximum value f. max The susceptance component of the ultrasonic transducer at that location can be minimized by such a matching circuit. min and maximum value f max In both of these locations, the susceptance component of the ultrasonic transducer is brought closer to 0 through the susceptance component of the matching circuit.

[0107] <Example>

[0108] Hereinafter, embodiments of the first and second embodiments will be compared with comparative examples and explained.

[0109] (Frequency characteristics and reverberation time of the comparative example)

[0110] As a comparative example, imagine having Figure 11 The circuit structure shown is for an ultrasonic sensor. Figure 11 This is a diagram showing the structure of an ultrasonic sensor used as a comparative example. (Example) Figure 11 As shown, in the ultrasonic sensor used as a comparative example, the ultrasonic transducer does not have multiple RLC series circuits, and the matching circuit does not have multiple parallel resonant circuits. The ultrasonic sensor used as a comparative example is configured such that the ultrasonic transducer is driven at different driving frequencies by a driving circuit, thereby enabling the transmission of ultrasonic waves at multiple frequencies.

[0111] Figures 12A-12C This is a graph showing the frequency characteristics and reverberation time of the ultrasonic sensor in the comparative example. Figures 12A-12C It was generated through simulation.

[0112] Figure 12A The frequency characteristics of the ultrasonic sensor in the comparative example when receiving waves are shown. For example... Figure 12A As shown, the comparative example ultrasonic sensor can transmit ultrasonic waves at two frequencies: 40 kHz and 70 kHz. The output at 40 kHz is -6.7 dB, and the output at 70 kHz is -9.2 dB.

[0113] Figure 12B The residual time of the comparative example ultrasonic sensor at 40 kHz is shown in the figure. Figure 12B As shown, the ultrasonic sensor in the comparative example has a reverberation time of 2.81 ms at 40 kHz.

[0114] Figure 12C The residual time of the comparative example ultrasonic sensor at 70 kHz is shown in the figure. Figure 12C As shown, the ultrasonic sensor in the comparative example has a reverberation time of 2.20 ms at 70 kHz.

[0115] (Frequency characteristics and reverberation time of the ultrasonic sensor 10A in the first embodiment)

[0116] Figures 13A-13C This is a graph showing the frequency characteristics and reverberation time of the ultrasonic sensor 10A according to the first embodiment. Figures 13A-13C It was generated through simulation.

[0117] Figure 13A The frequency characteristics of the ultrasonic sensor 10A according to the first embodiment when receiving waves are shown. In the ultrasonic sensor 10A of the first embodiment, the output at 40 kHz is -3.5 dB and the output at 70 kHz is -3.5 dB. Thus, compared with the ultrasonic sensor of the comparative example, the ultrasonic sensor 10A of the first embodiment can obtain a larger output.

[0118] Figure 13B The image shows the reverberation time of the ultrasonic sensor of the first embodiment at 40 kHz. (See image for details.) Figure 13B As shown, the ultrasonic sensor of the first embodiment has a reverberation time of 1.47 ms at 40 kHz.

[0119] Figure 13C The image shows the reverberation time of the ultrasonic sensor of the first embodiment at 70 kHz. (See image for details.) Figure 13C As shown, the ultrasonic sensor of the first embodiment has a reverberation time of 1.57 ms at 70 kHz.

[0120] Thus, in the ultrasonic sensor 10A of the first embodiment, the reverberation time can be reduced to a shorter value compared to the ultrasonic sensor of the comparative example.

[0121] (Frequency characteristics and reverberation time of the ultrasonic sensor 10B in the second embodiment)

[0122] Figures 14A to 14C This is a graph showing the frequency characteristics and reverberation time of the ultrasonic sensor 10B according to the second embodiment. Figures 14A to 14CIt is generated by simulation.

[0123] Figure 14A Fig. 4 shows the frequency characteristics of the ultrasonic sensor 10B in the second embodiment when receiving waves. In the ultrasonic sensor 10B of the second embodiment, the output at 40 kHz is -4.8 dB, and the output at 70 kHz is -5.0 dB. Thus, a larger output can be obtained in the ultrasonic sensor 10B of the second embodiment compared to the ultrasonic sensor of the comparative example.

[0124] Figure 14B Fig. 5 shows the reverberation time of the ultrasonic sensor in the second embodiment at 40 kHz. As Figure 14B shown, the reverberation time of the ultrasonic sensor in the second embodiment at 40 kHz is 1.19 ms.

[0125] Figure 14C Fig. 6 shows the reverberation time of the ultrasonic sensor in the second embodiment at 70 kHz. As Figure 14C shown, the reverberation time of the ultrasonic sensor in the second embodiment at 70 kHz is 1.32 ms.

[0126] Thus, in the ultrasonic sensor 10B of the second embodiment, the reverberation time can be reduced to a shorter value compared to the ultrasonic sensor of the comparative example.

[0127] As described in the above embodiments, it can be seen that good characteristics can be obtained in the ultrasonic sensors 10A and 10B of the first and second embodiments of the present disclosure compared to the comparative example in which the matching circuit does not have a plurality of parallel resonance circuits.

[0128] <Variant Example>

[0129] Each of the above-described embodiments is an example of a preferred mode of the present disclosure, and the present disclosure is not limited to these embodiments, and various variant examples can be adopted.

[0130] In each of the above-described embodiments, the ultrasonic oscillator 15 has two resonance frequencies f1 and f2, and the matching circuits 14A and 14B are designed such that their resonance frequency f s satisfies f1 < f s < f2. However, the number of resonance frequencies possessed by the ultrasonic oscillator in the present disclosure is not limited to two, and may also be three or more.

[0131] In this case, it is only necessary to design the resonance frequency of the matching circuit to be a value greater than the minimum value of the plurality of resonance frequencies possessed by the ultrasonic oscillator and less than the maximum value of the plurality of resonance frequencies. By doing so, similarly to the above embodiments, the performance of the ultrasonic sensor can be appropriately improved.

[0132] The various embodiments have been described above, but it should be understood that various changes may be made to the embodiments and details without departing from the spirit and scope of the present or future claims of the present invention.

[0133] The entire contents of the specification, drawings and abstract of the specification contained in Japanese Patent Application No. 2025-016719, filed on February 4, 2025, are incorporated herein by reference.

[0134] Industrial applicability

[0135] This disclosure is useful for ultrasonic sensors that detect objects by transmitting and receiving ultrasonic waves.

Claims

1. An ultrasonic sensor, characterized in that, have: An ultrasonic transducer with multiple resonant frequencies; and The matching circuit includes multiple LC parallel resonant circuits connected in series, wherein the resonant frequency of the multiple LC parallel resonant circuits is less than the maximum value among the multiple resonant frequencies of the ultrasonic transducer and greater than the minimum value among the multiple resonant frequencies.

2. The ultrasonic sensor as described in claim 1, wherein, It also has: The driving circuit that drives the ultrasonic transducer; and The transformer connected to the drive circuit, The secondary side of the transformer is composed of the first parallel inductor included in the LC parallel resonant circuit.

3. The ultrasonic sensor as described in claim 2, wherein, The drive circuit has the same number of frequencies as the plurality of resonant frequencies of the ultrasonic transducer.

4. The ultrasonic sensor as described in claim 3, wherein, Each of the plurality of driving circuits drives the ultrasonic transducer at one of the plurality of resonant frequencies.

5. The ultrasonic sensor as described in claim 1, wherein, It also has: The driving circuit that drives the ultrasonic transducer; and The transformer connected to the drive circuit, The secondary side of the transformer is composed of a second parallel inductor configured in parallel with the plurality of LC parallel resonant circuits.

6. The ultrasonic sensor as described in claim 5, wherein, The driving circuit drives the ultrasonic transducer at a frequency that is the same as one of the plurality of resonant frequencies.

7. The ultrasonic sensor as described in claim 5, wherein, The resonant frequency of the equivalent parallel capacitor and the second parallel inductor contained in the ultrasonic transducer is less than the maximum value among the multiple resonant frequencies of the ultrasonic transducer and greater than the minimum value among the multiple resonant frequencies.

8. A vehicle, characterized in that, have: The ultrasonic sensor according to any one of claims 1 to 7; and The detection circuit detects obstacles based on information related to the transmitted and received waves acquired from the ultrasonic sensor, respectively.

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