JP2017187315A - Detection device and detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection device capable of detecting electric noise.SOLUTION: A detection device 10 includes: a piezoelectric element 20 for outputting a received ultrasonic wave as an electric signal; a signal processing unit 40 connected with the piezoelectric element 20, for acquiring the electric signal output by the piezoelectric element 20; a switching unit 50 for switching between an electric connection state and a disconnection state of the piezoelectric element 20 and the signal processing unit 40; and a determination unit 62 for detecting electric noise, if the signal processing unit 40 acquires an electric signal when the switching unit 50 is in the disconnection state, on the basis of the acquired electric signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a detection device that detects ambient vibration and a detection system including the detection device.

  Conventionally, an exploration wave that is an ultrasonic wave is transmitted from a transmission unit, a reflected wave reflected by a surrounding object is received by a receiving unit, and a time between the transmission and reception is obtained, thereby obtaining A detection device for detecting a distance is realized.

  As such a detection device, there is a detection device described in Patent Document 1. In the detection apparatus described in Patent Document 1, the electrical connection between the wave receiving unit and the signal processing unit is interrupted when the exploration wave is transmitted. Thereby, in the detection apparatus of patent document 1, it can prevent that a drive signal is input into a signal processing part at the time of transmission of an exploration wave.

JP 7-325146 A

  By the way, in the detection device as described in Patent Document 1, electrical noise may enter the signal processing unit from a device or the like provided around the detection device. When electrical noise enters the signal processing unit, if the electrical noise cannot be distinguished from the signal generated based on the reflected wave, there is a risk of erroneous detection of the position of the object.

  The present invention has been made to solve the above problems, and a main object thereof is to provide a detection device capable of detecting electrical noise.

  The present invention is a detection device, a piezoelectric element that outputs received ultrasonic waves as an electrical signal, a signal processing unit that is connected to the piezoelectric element and acquires an electrical signal output from the piezoelectric element, a piezoelectric element, and a signal A switching unit that switches between an electrical connection state and a cutoff state with the processing unit, and a determination that performs detection of electrical noise based on the electrical signal if the signal processing unit acquires when the switching unit is in the cutoff state A section.

  When detecting an ultrasonic wave using a piezoelectric element, the ultrasonic wave is acquired as an electric signal. Therefore, when there is an influence of electric noise from surrounding devices, the acquisition accuracy of the value of the electric signal is lowered. However, since the piezoelectric element outputs an electrical signal based on the ultrasonic noise even when the surrounding ultrasonic noise is acquired, is the noise acquired by the signal processing unit the ultrasonic noise acquired by the piezoelectric element? It is difficult to distinguish between electrical noises generated from surrounding devices and the like.

  In this regard, in the above configuration, since the piezoelectric element and the signal processing unit are connected via the switching unit, if the switching unit is in a cut-off state, the electrical signal generated by the ultrasonic wave received by the piezoelectric element is It is not input to the department. Therefore, if an electrical signal is detected when the switching unit is in the shut-off state, it can be said that the electrical signal is electrical noise generated from surrounding equipment or the like. Therefore, with the above configuration, it is possible to accurately detect the electrical noise input to the signal processing unit.

It is a block diagram of the ultrasonic sensor which concerns on 1st Embodiment. It is a flowchart which shows control of the ultrasonic sensor which concerns on 1st Embodiment. It is a time chart which shows control of the ultrasonic sensor concerning a 1st embodiment. It is a block diagram of the ultrasonic sensor which concerns on 2nd Embodiment. It is a flowchart which shows control of the ultrasonic sensor which concerns on 2nd Embodiment. It is a time chart which shows control of the ultrasonic sensor concerning a 2nd embodiment. It is a block diagram of the ultrasonic sensor which concerns on 3rd Embodiment.

  Hereinafter, each embodiment will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

<First Embodiment>
The detection device according to the present embodiment is an ultrasonic sensor and is mounted on a moving body such as a vehicle. The ultrasonic sensor transmits ultrasonic waves to the surroundings of the moving body, receives the reflected waves reflected by the objects existing in the surroundings, and measures the time from transmission to reception, thereby measuring the distance between the moving body and the objects. Ask for.

  FIG. 1 is a configuration diagram of an ultrasonic sensor 10 according to the present embodiment. The ultrasonic sensor 10 transmits ultrasonic waves by applying a voltage to the piezoelectric element 20. The piezoelectric element 20 converts the received ultrasonic energy into a voltage.

  Application of a voltage to the piezoelectric element 20 is performed by controlling the drive unit 30. The drive unit 30 includes a first power supply 31 that applies a positive constant voltage and a second power supply 32 that applies a negative constant voltage. The first power supply 31 is connected to the first side of the piezoelectric element 20 via the first switch Q1, and the second power supply 32 is connected to the first side of the piezoelectric element 20 via the second switch Q2. Yes. The second side of the piezoelectric element 20 is grounded. The first switch Q1 and the second switch Q2 are, for example, MOSFETs.

  Since the drive unit 30 is configured in this way, the control of turning on the first switch Q1 and turning off the second switch Q2 and the control of turning off the first switch Q1 and turning on the second switch Q2 are alternated. By repeating the above, a positive voltage and a negative voltage are alternately applied to the piezoelectric element 20. By applying this voltage, the piezoelectric element 20 oscillates and ultrasonic waves are transmitted. The frequency of this ultrasonic wave is equal to the control cycle in which the first switch Q1 and the second switch Q2 are alternately turned on.

  On the other hand, the ultrasonic energy received by the piezoelectric element 20 is converted by the piezoelectric element 20 into an electrical signal having a voltage based on the ultrasonic energy. This electrical signal is input to an input terminal which is an input unit of the signal processing unit 40. In the signal processing unit 40, the electrical signal is first input to the amplification unit 41. The amplifying unit 41 is configured so that the gain can be variably set. Specifically, a high gain and a low gain that is lower than the high gain can be set. The amplifying unit 41 amplifies the input electrical signal with a predetermined gain, and inputs the amplified electrical signal to the bandpass filter 42.

  The band pass filter 42 includes a pass band including the frequency of the ultrasonic wave at the time of transmission. This is because the frequency of the reflected wave reflected by the object surrounding the object is close to the frequency of the transmitted ultrasonic wave. Since the pass band is set in this way, the band-pass filter 42 removes an electrical signal having a frequency that deviates from the frequency of the ultrasonic wave transmitted from the piezoelectric element 20. The electrical signal that has passed through the bandpass filter 42 is input to the comparison unit 43. The comparison unit 43 compares the voltage value of the electrical signal with a threshold value that is a predetermined value, and outputs the comparison result.

  Note that the reference value setting unit 45 inputs the potential difference 44 from the grounded portion to the amplification unit 41, the band pass filter 42, and the comparison unit 43. By doing so, it becomes possible to control the input electrical signal according to the amount of deviation from the reference potential difference.

  The signal processing unit 40 and the piezoelectric element 20 are connected via a switching unit 50. The switching unit 50 includes a third switch Q3 that switches an electrical connection state between the input terminal of the signal processing unit 40 and the first side of the piezoelectric element 20, and an electrical connection between the input terminal of the signal processing unit 40 and the ground portion. And a fourth switch Q4 for switching the connection state. The third switch Q3 and the fourth switch Q4 are, for example, MOSFETs. If the third switch Q3 is ON and the fourth switch Q4 is OFF, the signal processing unit 40 and the piezoelectric element 20 are electrically connected, and an electric signal output from the piezoelectric element 20 is sent to the signal processing unit 40. Entered. On the other hand, if the third switch Q3 is OFF and the fourth switch Q4 is ON, the signal processing unit 40 and the piezoelectric element 20 are electrically disconnected, and the electric signal output from the piezoelectric element 20 is the signal processing unit. 40 is not input. If the third switch Q3 is OFF and the fourth switch Q4 is ON, the input terminal of the signal processing unit 40 is grounded.

  The above-described open / closed states of the first to fourth switches Q1 to Q4 and the gain of the amplifying unit 41 are controlled by a command from the control unit 61 provided in the control device 60. Specifically, first, in order to determine whether or not there is ultrasonic noise around the ultrasonic sensor 10, the third switch Q3 is turned on and the fourth switch Q4 is turned off based on the ultrasonic noise. An electrical signal generated from the piezoelectric element 20 is input to the signal processing unit 40. At this time, the gain of the amplification unit 41 of the signal processing unit 40 is set to a high gain. In addition, the period which performs control which detects ultrasonic noise is called a 1st detection period.

  Following the first detection period, control is performed to alternately turn on the first switch Q1 and the second switch Q2 in order to generate ultrasonic waves from the piezoelectric element 20. The control states of the third switch Q3 and the fourth switch Q4 are maintained in the same state as the first detection period. That is, the third switch Q3 is turned on and the fourth switch Q4 is turned off. At this time, since the voltage of the drive unit 30 is also input to the signal processing unit 40, the gain of the amplification unit 41 is set to a low gain so that the voltage is not excessively amplified. Note that a period in which the driving circuit is controlled to generate ultrasonic waves is referred to as a driving period.

  Following the driving period, the state where the third switch Q3 is turned on and the fourth switch Q4 is turned off is maintained, and when the ultrasonic wave transmitted in the driving period is reflected by a surrounding object, the reflected wave is Enable reception. At this time, the gain of the amplifying unit 41 is set to a high gain in order to amplify and detect the electric signal generated by the received wave. The period for waiting for reception of the reflected wave is referred to as a reception waiting period.

  Based on the ultrasonic noise, the third switch Q3 is turned off and the fourth switch Q4 is turned on to detect electric noise generated from the electric devices mounted around the ultrasonic sensor 10 following the reception standby period. The electrical signal generated from the piezoelectric element 20 is prevented from being input to the signal processing unit 40. At this time, if the surrounding electrical equipment is the noise source 70 and generates electrical noise, an electrical signal based on the electrical noise passes through the amplification unit 41, the bandpass filter 42, and the comparison unit 43. Become. Therefore, it can be determined that the electrical signal generated in the signal processing unit 40 is due to electrical noise. At this time, the gain of the amplification unit 41 of the signal processing unit 40 is set to a high gain. In addition, the period which performs control which detects an electrical noise is called a 2nd detection period.

  In the present embodiment, the period from the start of the first detection period to the end of the second detection period is defined as one exploration cycle. When one exploration period is completed, the next exploration period is subsequently started. The Note that it is possible to arbitrarily set which period the start point of the search cycle is set to.

  The comparison result output from the comparison unit 43 of the signal processing unit 40 is input to the determination unit 62 of the control device 60. If the determination unit 62 acquires an electrical signal that exceeds the threshold during the reception standby period, the electrical signal is likely to be generated by a reflected wave, and therefore transmits the detection result to the ECU 100 as an object detection result. If an electrical signal exceeding the threshold is acquired in the first detection period, the electrical signal is determined as ultrasonic noise, and the determination result is transmitted to ECU 100. In addition, if an electric signal exceeding the threshold is acquired in the second detection period, the electric signal is determined as electric noise, and the determination result is transmitted to the ECU 100.

  When ECU 100 receives the detection result of the object from determination unit 62, ECU 100 calculates the position of the object based on the detection result, and performs processing according to the position of the object. Specifically, the vehicle driver is notified of the presence of the object. This notification may be performed using a speaker mounted on the vehicle, or may be performed using a lamp, a display device, or the like. Further, when the distance to the object is small and the vehicle is moving in the direction in which the object exists, control for operating a brake device provided in the vehicle may be performed.

  On the other hand, if the ECU 100 obtains a determination result indicating that ultrasonic noise or electrical noise exists, the ECU 100 accumulates the determination result of the noise for a predetermined period, and determines whether the noise is generated periodically or continuously. judge. This is because if the noise is generated only once, the influence is temporary and the influence on the detection result of the object is limited. In addition, the case where electric noise is generated in a single shot includes, for example, electric noise generated when an electric device is started.

  If noise is periodically generated, processing for suppressing the influence of the noise on object detection is performed. Specifically, an instruction is given to the comparison unit 43 provided in the signal processing unit 40 of the ultrasonic sensor 10 to increase the threshold value. Thereby, if the electrical signal based on noise is relatively smaller than the electrical signal based on the reflected wave, erroneous detection of an object based on the noise can be suppressed. On the other hand, when the electrical signal based on noise is about the same size as the electrical signal due to the reflected wave, or when the electrical signal based on the reflected wave is larger than the electrical signal due to the reflected wave, the process of removing the influence of the noise due to the change of the threshold is: Have difficulty. Therefore, in this case, after notifying the vehicle driver that the object cannot be detected, not performing the notification of the detection result of the object or the control for avoiding the collision with the object. And In this case, although detection of the detection result of the object and control for avoiding collision with the object are not performed, detection of the object and detection of noise are continuously performed. This is to enable control based on the position of the object to be resumed when noise is no longer detected.

  When ECU 100 determines that there is electrical noise that occurs periodically or continuously, ECU 100 accumulates the determination result. By doing so, it is easy to specify the noise source 70 that generates electrical noise by reading out the determination result when the vehicle is inspected.

  Next, processing executed in the ultrasonic sensor 10 will be described with reference to the flowchart of FIG. The flowchart of FIG. 2 is repeatedly executed every predetermined search cycle.

  First, in step S101, the third switch Q3 is turned on and the fourth switch Q4 is turned off, so that the electrical signal output from the piezoelectric element 20 is input to the signal processing unit 40. At this time, if the piezoelectric element 20 receives ultrasonic noise generated around the ultrasonic sensor 10, an electrical signal based on the ultrasonic noise is generated from the piezoelectric element 20 and input to the signal processing unit 40. The period for detecting the ultrasonic noise is referred to as a first detection period. Subsequently, in step S102, it is determined whether or not the first detection period has ended. The process in step S102 is repeatedly performed until an affirmative determination is made, that is, until the first detection period ends.

  If an affirmative determination is made in step S102, that is, if the first detection period ends, the process proceeds to step S103, and it is determined whether ultrasonic noise is detected in the first detection period. In the process of S103, as a result of the comparison process with the threshold value in the comparison unit 43, it is determined whether there is ultrasonic noise exceeding the threshold value. If an affirmative determination is made in step S103, that is, if ultrasonic noise is detected in the first detection period, the detection result is transmitted to ECU 100 in step S104, and the process proceeds to step S105.

  On the other hand, if a negative determination is made in step S103, that is, if no ultrasonic noise is detected in the first detection period, the process proceeds to step S105 as it is. When a negative determination is made in step S103, that is, when it is determined that no ultrasonic noise is detected in the first detection period, a result indicating that no ultrasonic noise is detected is transmitted to the ECU 100. Also good. Further, instead of transmitting the ultrasonic noise detection result when the first detection period ends, the detection result may be transmitted to the ECU 100 each time ultrasonic noise is detected.

  In step S105, the gain of the amplifying unit 41 is switched to a low gain so that the electrical signal when driving the piezoelectric element 20 input to the signal processing unit 40 does not become excessively large. In subsequent step S106, drive control in the drive unit 30 is started. That is, as described above, the drive control that alternately turns on the control to turn on the first switch Q1 and turn off the second switch Q2 and the control to turn off the first switch Q1 and turn on the second switch Q2 is started. .

  Subsequently, in step S107, it is determined whether or not the drive period, which is a period during which drive control is performed, has ended. The process in step S107 is repeated until an affirmative determination is made, that is, until the drive period ends.

  If an affirmative determination is made in step S107, that is, if the drive period ends, the process proceeds to step S108, and the drive control ends. That is, both the first switch Q1 and the second switch Q2 are turned off. In subsequent step S109, the gain of the amplifying unit 41 is switched to a high gain, and the process proceeds to step S110.

  In step S110, it is determined whether or not the reception standby period has ended. The process in step S110 is repeatedly performed until an affirmative determination is made, that is, until the reception standby period ends.

  If an affirmative determination is made in step S110, that is, if the reception standby period ends, the process proceeds to step S111, and the reception result of the reflected wave is transmitted to the ECU 100. If the reflected wave is not received, the reception result need not be transmitted. Alternatively, instead of transmitting the reception result of the reflected wave when the reception standby period ends, the reception result may be transmitted to the ECU 100 each time the reflected wave is received.

  Subsequently, the process proceeds to step S112, where the third switch Q3 is turned off and the fourth switch Q4 is turned on. That is, the piezoelectric element 20 and the signal processing unit 40 are electrically disconnected so that an electric signal output from the piezoelectric element 20 is not input to the signal processing unit 40, and the input terminal of the signal processing unit 40 is grounded. In the signal processing unit 40, a closed circuit is formed. If an electrical signal is detected by the signal processing unit 40 after the processing of step S112 is performed, the electrical signal is highly likely to be electrical noise generated from another electrical device. This period for detecting the electric noise is referred to as a second detection period.

  Subsequently, in step S113, it is determined whether or not the second detection period has ended. The process of step S113 is repeatedly performed until an affirmative determination is made, that is, until the second detection period ends.

  If an affirmative determination is made in step S113, that is, if the second detection period ends, the process proceeds to step S114 to determine whether or not electrical noise is detected in the second detection period. In the process of S <b> 114, it is determined whether there is electrical noise exceeding the threshold as a result of the comparison process with the threshold in the comparison unit 43. If an affirmative determination is made in step S114, that is, if electrical noise is detected in the second detection period, the detection result is transmitted to ECU 100 in step S115, and the series of processing ends.

  On the other hand, if a negative determination is made in step S114, that is, if no electrical noise is detected in the second detection period, the series of processing ends. If a negative determination is made in step S114, a result indicating that no electrical noise is detected may be transmitted to the ECU 100 as in the case of the first detection period. Further, instead of transmitting the electrical noise detection result when the second detection period ends, the detection result may be transmitted to the ECU 100 each time electrical noise is detected.

  The control state of the first to fourth switches Q1 to Q4 and the gain of the amplifying unit 41 when the processing performed in the ultrasonic sensor 10 is performed as described above will be described with reference to the time chart of FIG. .

  First, at time t1, control is performed to turn on the third switch Q3 and turn off the fourth switch Q4 in step S101. A period from time t1 to time t2 is a first detection period in which the piezoelectric element 20 and the signal processing unit 40 are electrically connected to detect ultrasonic noise.

  At time t2, control for switching the gain of the amplifying unit 41 to a low gain in step S105 is performed, and driving control in the driving unit 30 in step S106 is started. From time t2 to time t3 is a drive period in which drive control in the drive unit 30 is performed and ultrasonic waves are generated from the piezoelectric element 20.

  At time t3, control for ending the drive control in step S108 is performed, and control for switching the gain in step S109 to a high gain is performed. From time t3 to time t4 is a reception standby period in which reception of reflected waves reflected by surrounding objects is waited. The detection range of the ultrasonic sensor 10 is determined by the length of the reception standby period. That is, it is possible to detect the distance to an object located at a distance obtained by multiplying half the length of the reception standby period by the speed of sound.

  At time t4, control is performed to turn off the third switch Q3 and turn on the fourth switch Q4 in step S112. That is, at time t4, the piezoelectric element 20 and the signal processing unit 40 are electrically disconnected. From time t4 to time t5 is a second detection period in which the signal processing unit 40 is used as a closed circuit to determine the influence of electrical noise. At time t5, similarly to time t1, control is performed to turn on the third switch Q3 and turn off the fourth switch Q4 in step S101. At subsequent time t6 and time t7, the same control as that at time t2 and time t3 is performed, respectively.

  With the above configuration, the ultrasonic sensor 10 according to the present embodiment has the following effects.

  Since the piezoelectric element 20 and the signal processing unit 40 are connected via the switching unit 50, if the switching unit 50 is in the cut-off state, an electrical signal generated by the ultrasonic wave received by the piezoelectric element 20 is transmitted to the signal processing unit. 40 is not entered. Therefore, if an electrical signal is detected when the switching unit 50 is in the shut-off state, it can be said that the voltage is electrical noise generated from surrounding equipment or the like. Therefore, the electrical noise input to the signal processing unit 40 can be detected with high accuracy.

  -At the time of manufacture of a vehicle, arrangement | positioning of an electric equipment etc. is performed so that the influence of the electrical noise with respect to the ultrasonic sensor 10 may become small. On the other hand, when an electric device or the like is added after the vehicle is sold, electric noise generated from the electric device may affect the ultrasonic sensor 10. In the present embodiment, when there is a noise source 70 that may affect the detection result of the ultrasonic sensor 10, the influence is not excluded, or control using the detection result affected by the influence is not performed. Therefore, it is possible to suppress the influence of electrical noise generated from the added electrical equipment.

  Even if electrical noise occurs, it can be ignored because the effect is limited if it is temporarily generated, such as when it is generated at the start-up of an electrical device. On the other hand, if electrical noise continues to occur, there is a high possibility that an erroneous object detection will occur in the ultrasonic sensor 10 due to the electrical noise. In this embodiment, since the 2nd detection period which detects an electrical noise for every search period is provided, it can be determined whether it is the electrical noise which arises continuously.

  -Since the gain in the reception standby period, the first detection period, and the second detection period is larger than the gain in the drive period, the reception standby period is suppressed while suppressing excessive amplification of the signal in the drive period. In addition, it is possible to improve the detection accuracy of received waves and the detection accuracy of noise in the first detection period and the second detection period.

  Since the gains in the reception standby period, the first detection period, and the second detection period are equal, it is easy to determine the relative magnitude of noise with respect to the received wave. Therefore, it is possible to easily determine whether or not noise can be ignored in detecting the received wave, and in the process of changing the threshold value when noise is detected, the threshold value is influenced by the noise. Can be set to a value that does not receive.

  -Immediately after the reception standby period, a reflected wave reflected by an object outside the detection range may be received. Although the reflected wave in this case is not actually ultrasonic noise, if the first detection period is provided after the reception standby period, the reflected wave reflected by the object existing outside the detection range is erroneously determined as ultrasonic noise. There are things to do. In this embodiment, since the second detection period for detecting electrical noise is provided following the reception standby period, and the first detection period for detecting ultrasonic noise is provided subsequent to the second detection period, the detection range is provided. A situation in which a reflected wave reflected by an object outside the detection range outside is erroneously determined as ultrasonic noise can be suppressed.

  In the second detection period in which the piezoelectric element 20 and the signal processing unit 40 are shut off by the switching unit 50, the detected electrical signal is based on electrical noise. On the other hand, in the first detection period in which the piezoelectric element 20 and the signal processing unit 40 are electrically connected by the switching unit 50, the detected electrical signal is a mixture of ultrasonic noise and electrical noise. If it can be detected that electrical noise is generated periodically or continuously in the second detection period, it can be determined that the noise excluding the electrical noise is ultrasonic noise in the first detection period. . Therefore, in addition to detecting electrical noise, ultrasonic noise can be detected with high accuracy.

  Since the input unit of the signal processing unit 40 is grounded when the piezoelectric element 20 and the signal processing unit 40 are electrically cut off by the switching unit 50, the signal processing unit 40 and the switching unit 50 are formed. The closed circuit is a circuit in which the piezoelectric element 20 is separated from the closed circuit formed by the signal processing unit 40, the switching unit 50, and the piezoelectric element 20. As a result, the closed circuit when detecting electrical noise has a circuit configuration that approximates the closed circuit when ultrasonic waves are detected by the piezoelectric element 20. Therefore, it is possible to detect electrical noise that is likely to affect the detection of an object using the piezoelectric element 20.

Second Embodiment
The ultrasonic sensor 110 according to the present embodiment is partly different from the first embodiment in circuit configuration. Further, since a part of the circuit configuration is different from that of the first embodiment, the control to be performed is also partially different.

  The configuration of the ultrasonic sensor 110 according to this embodiment will be described with reference to FIG. The ultrasonic sensor 110 is disposed in the vicinity of the ultrasonic sensor 10 according to the first embodiment, and receives the reflected wave when the ultrasonic wave transmitted by the ultrasonic sensor 10 is reflected by a surrounding object. . And the position of an object is pinpointed by using the transmission time of the ultrasonic wave by the ultrasonic sensor 10, and the reception time of the reflected wave of the ultrasonic sensor 10 and the ultrasonic sensor 110.

  The piezoelectric element 120 included in the ultrasonic sensor 110 converts the received ultrasonic wave into an electric signal having a voltage and outputs the electric signal. This electrical signal is input to an input terminal which is an input unit of the signal processing unit 140. In the signal processing unit 140, the electrical signal is first input to the amplification unit 141. The amplification unit 141 has a constant gain value. The electric signal amplified by the amplification unit 141 is input to the comparison unit 143 after passing through the band pass filter 142. Since the band pass filter 142 and the comparison unit 143 are the same as those in the first embodiment, a detailed description thereof will be omitted. Note that the reference value setting unit 145 inputs the potential difference 144 from the grounded portion to the amplification unit 141, the band pass filter 142, and the comparison unit 143.

  The signal processing unit 140 and the piezoelectric element 120 are connected via a switching unit 150. Since the configuration of the switching unit 150 is the same as that of the first embodiment, description thereof is omitted.

  Opening and closing states of the third and fourth switches Q3 and Q4 provided in the switching unit 150 are controlled by a command from the control unit 161 provided in the control device 160. Specifically, first, in order to determine whether or not ultrasonic noise exists around the ultrasonic sensor 110, the third switch Q3 is turned on and the fourth switch Q4 is turned off based on the ultrasonic noise. An electrical signal generated from the piezoelectric element 120 is input to the signal processing unit 140. That is, similarly to the first embodiment, a first detection period that is a period for performing control for detecting ultrasonic noise is provided.

  Subsequent to the first detection period, a period of waiting without processing is provided while ultrasonic transmission is performed by another ultrasonic sensor 10. This period is referred to as a transmission standby period. Following the transmission standby period, a reception standby period for waiting for reception of the reflected wave is provided. A second detection period is provided following this reception standby period. The reception standby period and the second detection period are the same as those in the first embodiment, and thus description thereof is omitted.

  The comparison result output from the comparison unit 143 of the signal processing unit 140 is input to the determination unit 162 of the control device 160. If the determination unit 162 acquires an electrical signal that exceeds the threshold during the reception standby period, the electrical signal is highly likely to be generated by a reflected wave, and therefore transmits the detection result to the ECU 100 as an object detection result. If an electrical signal exceeding the threshold is acquired in the first detection period, the electrical signal is determined as ultrasonic noise, and the determination result is transmitted to ECU 100. In addition, if an electric signal exceeding the threshold is acquired in the second detection period, the electric signal is determined as electric noise, and the determination result is transmitted to the ECU 100.

  Subsequently, processing executed in the ultrasonic sensor 110 will be described with reference to a flowchart of FIG. The flowchart of FIG. 5 is repeatedly executed every predetermined search cycle.

  First, the process of a 1st detection period is performed by step S201-step S204. Since the processing in the first detection period is the same as the processing in steps S101 to S104 in the first embodiment, description thereof is omitted.

  In subsequent step S205, a transmission standby period is started, and by repeating the determination of whether or not the transmission standby period in step S206 has ended, standby is performed until the transmission standby period elapses.

  If the transmission standby period has elapsed and an affirmative determination is made in step S206, the process proceeds to step S207 to start the reception standby period. Note that the processing from step S208 to step S213 after the start of the reception standby period is the same as the processing from step S110 to step S115 of the first embodiment, and thus description thereof is omitted.

  Subsequently, the control states of the third switch Q3 and the fourth switch Q4 when the processing according to the present embodiment is performed will be described with reference to FIG.

  First, at time t11, control is performed to turn on the third switch Q3 and turn off the fourth switch Q4 in step S201. A period from time t11 to time t12 is a first detection period in which the piezoelectric element 120 and the signal processing unit 140 are electrically connected to detect ultrasonic noise. From time t12 to time t13 is a transmission standby period in which the ultrasonic sensors 10 wait for transmission of ultrasonic waves. A period from time t13 to time t14 following the transmission standby period is a reception standby period. In these first detection period, transmission standby period, and reception standby period, the third switch Q3 is turned on and the fourth switch Q4 is turned off. That is, the state in which the electric signal generated from the piezoelectric element 20 is input to the signal processing unit 140 is maintained.

  At time t14, control is performed to turn off the third switch Q3 and turn on the fourth switch Q4 in step S210. That is, at time t14, the piezoelectric element 120 and the signal processing unit 140 are electrically disconnected. From time t14 to time t15 is a second detection period in which the signal processing unit 140 is used as a closed circuit to determine the influence of electrical noise. At time t15, similarly to time t11, control is performed to turn on the third switch Q3 and turn off the fourth switch Q4 in step S201. At subsequent time t16 and time t17, the same control as that at time t12 and time t13 is performed, respectively.

  With the above configuration, the ultrasonic sensor 110 according to the present embodiment has an effect similar to the effect exhibited by the ultrasonic sensor 10 according to the first embodiment.

<Third Embodiment>
In the present embodiment, a plurality of ultrasonic sensors 10 according to the first embodiment and the ECU 100 constitute a detection system. This detection system will be described with reference to FIG.

  The plurality of ultrasonic sensors 10 are attached to the front bumper of the vehicle 200 at intervals. When any of the ultrasonic sensors 10 transmits ultrasonic waves, the ultrasonic sensor 10 adjacent to the ultrasonic sensor 10 does not transmit ultrasonic waves and performs reception processing of reflected waves. That is, processing equivalent to that performed by the ultrasonic sensor 110 according to the second embodiment is performed. By doing so, the position of the object can be calculated using the transmission / reception time of the ultrasonic sensor 10 that transmitted the ultrasonic wave and the reception time of the ultrasonic sensor 10 adjacent to the ultrasonic sensor 10. .

  If ECU100 acquires the detection result of the electrical noise from any ultrasonic sensor 10, in that ultrasonic sensor 10, the process which reduces the influence of the electrical noise according to 1st Embodiment will be performed. In addition, the ultrasonic sensor 10 that has detected the electrical noise is specified and stored in a built-in memory. By doing so, the ultrasonic sensor 10 located in the vicinity of the noise source 70 can be specified, and the position of the noise source 70 can be estimated. At this time, the ECU 100 can be said to function as an estimation unit that estimates the position of the noise source 70.

  With the above configuration, the detection system according to the present embodiment has the following effects in addition to the effects exhibited by the ultrasonic sensor 10 according to the first embodiment.

  The electric noise generally affects the surroundings of the electric device that is the noise source 70, and the influence decreases as the distance increases. In the present embodiment, since the plurality of ultrasonic sensors 10 are respectively attached to predetermined positions of the vehicle 200, the noise source 70 exists in the vicinity of the ultrasonic sensor 10 that has detected the detection of electrical noise. Can be estimated. Therefore, it becomes easy to remove the electrical device that is the noise source 70 or to take measures to prevent electrical noise from being generated.

<Modification>
The circuit configuration of the switching unit 50 is not limited to that shown in the embodiment. The switching unit 50 only needs to have at least a function of switching between an electrical connection state and a cutoff state of the piezoelectric element 20 and the signal processing unit 40, and a specific circuit configuration can be arbitrarily designed. it can.

  In each embodiment, when electric noise or ultrasonic noise is detected and the frequency deviates from the transmission frequency of the exploration wave, the pass band of the bandpass filters 42 and 142 may be narrowed. . In this way, the noise that has passed through the bandpass filters 42 and 142 is removed or sufficiently attenuated, and the possibility that the comparison units 43 and 143 exceed the threshold value is reduced. Further, this control may be performed in combination with control for increasing the threshold values of the comparison units 43 and 143.

  In the driving period of the first embodiment, the third switch Q3 may be turned off and the fourth switch Q4 may be turned on so that electrical noise can be detected. In this case, since the electric signal is not input to the signal processing circuit during the driving period, the gain of the amplifying unit 41 may not be variable.

  In the transmission waiting period of the second embodiment, the third switch Q3 may be turned off and the fourth switch Q4 may be turned on so that electrical noise can be detected.

  In the first embodiment, the first to fourth switches Q1 to Q4 are MOSFETs, but other switches may be employed. The same applies to the third switch Q3 and the fourth switch Q4 of the second embodiment.

  In the third embodiment, a plurality of ultrasonic sensors 10 according to the first embodiment are provided. However, the ultrasonic sensors 10 according to the first embodiment and the ultrasonic sensors 110 according to the second embodiment are mixed. It may be provided. In this case, if the ultrasonic sensor 10 according to the first embodiment is installed next to the ultrasonic sensor 110 according to the second embodiment, the ultrasonic wave transmitted from the ultrasonic sensor 10 according to the first embodiment will be described. The ultrasonic wave sensor 110 which concerns on 2nd Embodiment can receive the reflected wave based on a sound wave.

  In the third embodiment, when electrical noise is detected in any of the ultrasonic sensors 10, the noise source 70 exists in the vicinity of the ultrasonic sensor 10, and the influence on the ultrasonic sensor 10 is great. On the other hand, the noise source 70 may also affect the adjacent ultrasonic sensor 10. Therefore, the ultrasonic sensor 10 adjacent to the ultrasonic sensor 10 that has detected the electrical noise may be controlled to suppress the influence of the electrical noise.

  In the embodiment, the ultrasonic sensor 10 is mounted on the vehicle 200, but may be mounted on a moving body other than the vehicle. Further, the mounting target is not limited to a moving body, but may be mounted on a stationary object and used for detecting a distance from a surrounding object.

  DESCRIPTION OF SYMBOLS 10 ... Ultrasonic sensor, 20 ... Piezoelectric element, 30 ... Drive part, 40 ... Signal processing part, 41 ... Amplification part, 50 ... Switching part, 62 ... Determination part, 70 ... Noise source, 110 ... Ultrasonic sensor, 120 ... Piezoelectric element, 140 ... signal processing unit, 141 ... amplifying unit, 150 ... switching unit, 162 ... determination unit.

Claims (10)

A piezoelectric element (20, 120) for outputting the received ultrasonic wave as an electrical signal;
A signal processing unit (40, 140) connected to the piezoelectric element and acquiring an electrical signal output from the piezoelectric element;
A switching unit (50, 150) for switching between an electrical connection state and a cutoff state between the piezoelectric element and the signal processing unit;
If the signal processing unit acquires an electrical signal when the switching unit is in a cut-off state, the detection device includes a determination unit (62, 162) that detects electrical noise based on the acquired electrical signal. . A standby period for waiting to receive the ultrasonic waves is provided for each predetermined period,
Between the end of the standby period and the start of the standby period of the next cycle, a detection period including a period of performing the detection with the switching unit (50, 150) being in a shut-off state is provided. The detection device according to claim 1. A drive unit (30) for supplying drive power for generating ultrasonic waves from the piezoelectric element;
The detection device (10) according to claim 2, wherein the standby period is provided after a driving period in which the driving power is supplied in each cycle. The detection period is provided between the end of the standby period and the start of the driving period of the next cycle,
The signal processing unit (40) includes an amplification unit (41) that amplifies the input electric signal,
The detection device according to claim 3, wherein the amplification unit makes the gain in the standby period and the gain in the detection period larger than the gain in the drive period.   The detection device according to claim 4, wherein the amplification unit equalizes the gain in the standby period and the gain in the detection period. The signal processing unit includes an amplification unit (41, 141) for amplifying the input electric signal,
The detection device according to claim 2, wherein the amplification unit equalizes the gain in the standby period and the gain in the detection period. The determination unit further detects noise based on the electrical signal acquired by the signal processing unit when the switching unit is in a connected state,
The detection period includes a first detection period in which the detection is performed with the switching unit in a connected state, and a second detection period in which the detection is performed with the switching unit in a cut-off state. The detection device according to any one of claims.   The detection device according to claim 7, wherein the second detection period is provided subsequent to the standby period, and the first detection period is provided subsequent to the second detection period.   The switching unit includes a state where the piezoelectric element and the input unit of the signal processing unit are electrically connected, and the piezoelectric element and the input unit of the signal processing unit are electrically disconnected, and signal processing is performed. The detection apparatus of any one of Claims 1-8 which switches the state by which the input part of a part is earth | grounded. A detection system comprising a plurality of the detection devices according to any one of claims 1 to 9,
Each detection device is provided at a predetermined position,
A detection system comprising an estimation unit (100) that estimates a position of a noise source (70) based on a position of the detection device including the determination unit that has detected the presence of noise.

Images