JP2003116198A - Device for detecting disconnection of transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more surely detect disconnection of a transducer in an ultrasonic transmitter provided with a transducer for transmitting ultrasonic waves in such a manner that a voltage signal is applied. SOLUTION: In an ultrasonic type obstacle detecting device 1 in this example, a second envelope detection circuit 19 detects a voltage signal applied to the transducer 5 through an attenuation circuit 17 while a drive circuit 9 outputs a drive signal, and if the voltage signal is larger than a prescribed threshold, the transducer 5 is decided to be in a disconnected state. Since the change of the voltage signal between before and after disconnection is clearer than the change of reverberation time, the disconnection of the transducer 5 can be detected more accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire breakage detecting device for detecting wire breakage of a transducer that emits ultrasonic waves when a predetermined voltage signal is applied.

[0002]

2. Description of the Related Art Conventionally, a transducer which emits an ultrasonic wave when a predetermined voltage signal is applied is used, for example, in an obstacle detection device for a vehicle. The obstacle detection device drives a transducer for a predetermined time by a voltage signal, emits an ultrasonic wave from its ultrasonic transducer, and detects the reflected wave of the ultrasonic wave to detect the presence or absence of an obstacle and the presence of an obstacle. It is to detect the distance.

In such an obstacle detecting device, an obstacle cannot be accurately detected unless ultrasonic waves are normally transmitted from the transducer. Therefore, based on the presence or absence of reverberation after the drive of the transducer is stopped, the length of reverberation time, and the like. It is configured to determine whether or not the operating state of the transducer is normal and notify the user of the determination result.

[0004]

However, since the reverberation time of the transducer is not stable due to mechanical or electrical factors, its change is not clear before and after the disconnection, and strict judgment is not easy. Such a problem can occur not only in the obstacle detection device but also in the ultrasonic wave generation device in which ultrasonic waves are transmitted by the transducer.

The present invention has been made in view of these problems, and an object thereof is to make it possible to more reliably detect disconnection of a transducer which emits ultrasonic waves when a voltage signal is applied.

[0006]

Means for Solving the Problems and Effects of the Invention In the disconnection detecting device of the present invention (claim 1) made in order to solve the above-mentioned problems, the voltage signal detecting means detects the drive signal from the driving means. During output (that is, while the transducer is being driven), the magnitude of the voltage signal applied to this transducer is detected, and the disconnection detection means detects the disconnection of the transducer based on the detection result.

In the state where the transducer is disconnected, the voltage signal applied to the transducer during driving of the transducer becomes larger than that in the normal state. The change in the magnitude of the voltage signal before and after the disconnection is clearer than the change in the reverberation time. Therefore, by detecting the magnitude of the voltage signal applied during the driving of the transducer and detecting the disconnection of the transducer based on the detection result, the disconnection of the transducer can be detected more accurately than before.

As a method for detecting the voltage signal, for example, as described in claim 2, envelope voltage detection of the voltage signal can be considered. Since the magnitude of the voltage signal is obtained by the envelope detection, the disconnection of the transducer can be detected based on this result. Also, as a voltage signal detection method,
It is also conceivable to integrate the voltage signal applied to the transducer, for example as defined in claim 3. Since the magnitude of the voltage signal is reflected in the integration result, the disconnection of the transducer can be detected based on this. Further, since the voltage signal is integrated, noise is unlikely to affect the detection result, and it is considered that more accurate disconnection detection can be realized.

When the integration is used in this way, for example, if the voltage signal larger than a predetermined threshold value is integrated and the voltage signal in the normal state of the transducer is not integrated, the integrated value in the normal state is obtained. Since the difference from the integrated value at the time of disconnection failure becomes clear, more accurate disconnection detection can be realized. The threshold value may be a fixed value or may be set according to conditions such as individual differences of transducers and usage conditions.

By the way, the absolute value of the result of detecting the voltage signal may fluctuate even in a normal state due to the usage state of the transducer, individual difference, and the like. Therefore, as described in claim 4, the disconnection detecting means may be configured to detect that the transducer is in the disconnection state when the change amount of the detection result by the voltage signal detecting means is larger than the reference value.

With this configuration, it is possible to reduce the influence of the transducer usage condition, individual difference, etc., on the disconnection detection. A fixed value may be used as the reference value to be compared with the amount of change, or may be set according to the past detection result, for example, a predetermined ratio of the previous detection result is used as the reference value. You may do it.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a block diagram showing a configuration of an ultrasonic obstacle detection device 1 incorporating a failure detection device of the present invention as a first embodiment. As shown in this figure, the ultrasonic obstacle detection device 1 is a microcomputer (hereinafter referred to as "microcomputer") that performs a predetermined control process.
3, a transducer 5 for transmitting and receiving ultrasonic waves, a transformer 7 for applying a high-voltage voltage signal to the transducer 5, which is composed of an ultrasonic transducer 5a and a capacitor 5b connected in parallel, and a microcomputer 3 Drive circuit 9 which receives a control signal (ultrasonic signal) of the transformer 7 to input a voltage to the primary coil of the transformer 7, a resistor 11 connected in parallel to the transducer 5, and both ends of the transducer 5 after the transducer 5 is stopped. An amplifier circuit 13 that detects a voltage signal between the slaves, amplifies and outputs the voltage signal, a first envelope detection circuit 15 that envelope-detects the signal amplified by the amplifier circuit 13, and a transducer 5 is being driven. An attenuator circuit 17 that detects a voltage signal between both terminals of the transducer 5, attenuates the voltage signal, and outputs the attenuated signal.
And a second envelope detection circuit 19 for performing envelope detection of the voltage signal attenuated by.

The microcomputer 3 is shown in FIG.
As shown in (b), the control signal in the ultrasonic band (for example, 40 kHz) is repeatedly output for a predetermined transmission period (a period corresponding to 10 pulses) at a predetermined time interval (for example, several tens ms). When the control signal is transmitted to the drive circuit 9,
A drive signal corresponding to this is sent from the drive circuit 9 to the transformer 1
It is input to the secondary coil 7a. The winding ratio of the transformer 7 is 1: n (n> 1), and a voltage that is n times the voltage applied to the primary coil 7a is output from the secondary coil 7b. That is, the drive signal output from the drive circuit 9 is
It is amplified n times by the transformer 7 and applied between both terminals of the resistor 11 and the transducer 5, and as a result, ultrasonic waves are emitted from the transducer 5.

When the ultrasonic waves thus transmitted reach the transducer 5 while the driving of the transducer 5 is stopped by being reflected by an obstacle, the ultrasonic transducer 5a
Vibrates, and a voltage signal appears between both terminals of the transducer 5. This voltage signal is amplified by the amplifier circuit 13, then enveloped by the first envelope detection circuit 15, and is input to the first A / D converter 3a of the microcomputer 3 as the detection result.

The microcomputer 3 determines that an obstacle is present when the detection signal exceeds a predetermined threshold value, and determines the time from the transmission of ultrasonic waves to the reception of reflected waves. Based on this, a process of calculating the distance to the obstacle (obstacle detection process) is performed. By the way, when the drive signal is output from the drive circuit 9, the voltage on the secondary side of the transformer 7 (that is, the voltage signal appearing between both terminals of the transducer 5).
As shown in FIG. 2, when the transducer 5 is disconnected, it becomes larger than in the normal case. It is considered that this is because the load impedance seen from the secondary side of the transformer 7 increases due to the disconnection of the transducer 5.

Therefore, in the ultrasonic obstacle detecting apparatus 1 of this embodiment, the microcomputer 3 operates as shown in the flow chart of FIG. The process shown in FIG. 3 is performed at a predetermined time interval, and first the transmission of the control signal is started (S1
0), while continuing to transmit the control signal thereafter (that is, during the current transmission period), the voltage signal generated between both terminals of the transducer 5 is detected by envelope detection,
The maximum value is stored (S20). When the control signal is transmitted to the drive circuit 9, a predetermined voltage signal is generated between both terminals of the transducer 5, and this voltage signal is detected by the second envelope detection circuit 19 via the attenuation circuit 17, so this detection is performed. The result is detected by the second A / D conversion unit 3b and stored in a predetermined storage unit.

Next, a fixed reference value is added to the detection result (previous detection result) detected and stored during the previous transmission period, and a disconnection judgment value for comparison with the present detection result is set ( S30). Then, it is determined whether or not the current detection result is larger than the disconnection determination value (S40), and if it is not larger than the disconnection determination value (S40: NO), the obstacle detection process is executed (S50). On the other hand, when the current detection result is larger than the disconnection determination value (S40: YES), it is determined that the transducer 5 is in the disconnection state, and predetermined disconnection handling processing is performed (S60). In the disconnection handling process, an alarm sound is generated to notify the outside that the disconnection of the transducer 5 has been detected.

As described above, in the ultrasonic obstacle detecting device 1 of this embodiment, while the drive signal is being output from the drive circuit 9, the second envelope detection circuit 1 is passed through the attenuation circuit 17.
The voltage signal applied to the transducer 5 is detected by 9 (S20), and when this is larger than the predetermined disconnection determination value (S40: YES), it is determined that the transducer 5 is disconnected. Since the change in the voltage signal before and after the disconnection is clear compared with the change in the reverberation time, the disconnection of the transducer 5 can be detected more accurately.

Further, in this embodiment, as the "disconnection judgment value" to be compared with the current detection result, a value obtained by adding a predetermined reference value to the previous detection result is used. That is, when the change amount of the detection result is larger than the reference value, it is configured to detect the disconnection state of the transducer. Therefore, there is an effect that the accuracy of wire break detection is less likely to be affected by the usage state of the transducer, individual difference, and the like.

In this embodiment, the attenuation circuit 1
7, second envelope detection circuit 19, second A / D converter 3b
The processing of S20 and S20 constitutes the "voltage signal detecting means" of the claims. Further, the processing in S30 and S40 constitutes "a disconnection detecting means" in the claims. Further, the processing of S10 and the driving circuit 9 constitute the "driving means" in the claims, and the microcomputer 3, the transducer 5, the transformer 7 and the driving circuit 9 constitute the "ultrasonic wave transmitting device" in the claims. ing.

Next, a second embodiment will be described. Figure 4
FIG. 7 is a block diagram showing a configuration of an ultrasonic obstacle detection device 21 incorporating a failure detection device of the present invention as a second embodiment. In this ultrasonic obstacle detecting device 21, an integrating circuit 29 is provided in place of the second envelope detecting circuit 19, but in other respects, the ultrasonic obstacle detecting device 1 of the first embodiment. The description is omitted because it is substantially the same as.

The integrating circuit 29 detects the voltage signal by integrating the voltage signal appearing between both terminals of the transducer 5. The signal attenuated by the attenuation circuit 17 is input to the integration circuit 29.
9 is configured to integrate only signals larger than a predetermined threshold. That is, as shown in FIG. 5, the small signal when the transducer 5 is in the normal state is not integrated, and the integration is performed when the transducer 5 is in the disconnection state. Then, the microcomputer 3 sets the disconnection determination value by performing the same processing as the processing shown in the flowchart of FIG. 3 (S3
0), if the detection result (output of the integrating circuit 29) is larger than the disconnection determination value (S40: YES), it is determined that disconnection has occurred, and the disconnection handling process (S5) corresponding thereto is performed.
0) is performed.

As described above, in the ultrasonic obstacle detecting apparatus 21 of this embodiment, since the detection is performed by integrating the voltage signal applied to the transducer 5, noise influences the detection result. It is difficult and more accurate disconnection detection can be realized. Further, since it is configured to integrate only the voltage signal larger than the predetermined threshold value, the difference between the normal state and the disconnection failure becomes clear, so that more accurate disconnection detection can be realized.

In this embodiment, the attenuation circuit 1
7, integrating circuit 29, second A / D converter 3b and S20
The "voltage signal detecting means" in the claims is constituted by the processing of. Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modes can be adopted.

For example, in the above embodiment, in addition to the previous detection result, the reference value for setting the disconnection judgment value is
Although it has been described that the value is a constant value, the value is not limited to this. For example, a predetermined ratio (for example, a value for 10%) of the previous detection result may be used as the reference value.

In the above-described embodiment, the disconnection determination value is set by adding the reference value to the previous detection result, but the present invention is not limited to this. For example, a fixed value may be used as the disconnection determination value.

[Brief description of drawings]

FIG. 1A is a block diagram showing a configuration of an ultrasonic obstacle detecting device as a first embodiment, and FIG. 1B is a diagram showing a control signal output from a microcomputer to a drive circuit. .

FIG. 2 is a diagram showing how a voltage signal between both terminals of a transducer increases when the transducer is disconnected.

FIG. 3 is a flowchart showing processing performed by a microcomputer.

FIG. 4 is a block diagram showing a configuration of an ultrasonic obstacle detection device as a second embodiment.

FIG. 5 is a diagram showing an output signal and the like from an integrating circuit.

[Explanation of symbols]

1,21 ... Ultrasonic obstacle detection device 3 ... Microcomputer 5 ... Transducer 5a ... Ultrasonic transducer 5b ... Capacitor 7 ... Transformer 9 ... Drive circuit 13 ... Amplifying circuit 15 ... First envelope detection circuit 17 ... Attenuation circuit 19 ... Second envelope detection circuit 29 ... Integrator circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takekazu Mawa             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F-term (reference) 5D019 AA00 GG00                 5J083 AA02 AB13 AC17 AC27 AD04                       BA01 BE23 BE38

Claims (4)

[Claims] 1. A transducer for transmitting ultrasonic waves,
A device for detecting a disconnection fault of the transducer in an ultrasonic wave transmission device comprising a drive means for transmitting an ultrasonic wave from the transducer by outputting a drive signal to the transducer. Voltage signal detecting means for detecting the magnitude of the voltage signal applied to the transducer during the output of the drive signal from the transducer, and disconnection detection for detecting the disconnection of the transducer based on the detection result by the voltage signal detecting means. A disconnection detection device for a transducer, comprising: 2. The transducer according to claim 1, wherein the voltage signal detecting means performs envelope detection on the voltage signal, and outputs the detection result to the voltage signal detecting means as the detection result. Disconnection detector. 3. The disconnection of the transducer according to claim 1, wherein the voltage signal detecting means integrates the voltage signal and outputs the integration result to the voltage signal detecting means as the detection result. Detection device. 4. The disconnection detecting means detects that the transducer is in a disconnection state when the amount of change in the detection result of the voltage signal detecting means is larger than a reference value. A disconnection detection device for a transducer according to any one of 1.