JPH0483193A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To surely make a judgement as to whether or not there is some abnormality in an ultrasonic vibrator by comparing the period of time required for the level of a signal sampled from an ultrasonic-wave transmitting portion to fall from first to second threshold value to a predetermined period of time. CONSTITUTION:A first comparing portion 10 compares the level of a signal sampled from a wave transmitting portion 2 with a first threshold value and a second comparing portion 11 compares the level of the signal with a second threshold value and the result of each comparison is input to a control portion 7. Next, a period detecting portion 72 detects the period of time required for the signal level being less than the first threshold value to fall to below the second threshold value. A period comparing portion 73 judges when the detected period of time is longer than a predetermined period of time that there is no abnormality and otherwise the portion 73 judges that there is some abnormality. The first and second threshold values are properly set so as to surely detect whether or not there is some abnormality in an ultrasonic vibrator 1 such as adhesion of foreign material to the vibration face of the vibrator 1, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic sensor that determines the presence or absence of an object by transmitting ultrasonic pulses and detecting reflected waves from the object.

[Prior Art] Conventionally, ultrasonic sensors that detect objects using reflections of ultrasonic pulses have been widely used. In this type of ultrasonic sensor, if a foreign object adheres to the vibrating surface of the ultrasonic vibrator or a wire is broken, even if an object is present,
This cannot be detected. Therefore, it is conceivable to detect abnormalities such as foreign matter adhering to the vibrating surface or wire breakage using the principle shown in FIG. 2.

Figures 2 (a) and (b) are waveform diagrams of the signal S taken out from the ultrasonic wave transmitter, and the figures (,) indicate abnormalities such as foreign matter adhering to the vibration surface of the ultrasonic transducer or wire breakage. If there is no
FIG. 6(b) shows a case where such an abnormality exists. As is clear from the above figures, when there is no abnormality, the duration of the signal S is long, and when it decays, it decays over time.On the other hand, when there is an abnormality, the duration of the signal S is long. is short, and when it does decay, it decays quickly.

The state of this signal attenuation is shown in FIG. 2(e), in which the vertical axis is the level of the envelope of the signal S, and the horizontal axis is time.

Further, the attenuation waveform a shows the level change of the signal S in the case of Fig. 2(a), and the attenuation waveform a shows the level change of the signal S in the case of Fig. 2(b). Figure 2 (a
) to (e), if the time at which the level of the signal S falls below the predetermined value vth is later than time T0, it can be determined that there is no abnormality, and if it is earlier than time T0, it can be determined that there is an abnormality.

[Problems to be Solved by the Invention] In the method shown in FIG. In the initial state after the end of wave transmission, the level of the signal S taken out from the ultrasonic wave transmitter may suddenly attenuate as shown in attenuation waveforms a and b in Fig. 3(e). In some cases, even when there is no abnormality such as foreign matter adhering to the vibration surface of the ultrasonic vibrator or wire breakage,
Sometimes it was mistakenly determined that there was an abnormality.

The present invention was made in view of these points, and its purpose is to provide an ultrasonic sensor that determines the presence or absence of an object by transmitting ultrasonic pulses and detecting reflected waves from the object. An object of the present invention is to make it possible to reliably determine the presence or absence of abnormalities such as foreign matter adhering to the vibrating surface of an ultrasonic transducer or wire breakage.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, in an ultrasonic sensor that detects the presence or absence of an object by transmitting ultrasonic pulses and receiving reflected waves from the object, the level of the signal S extracted from the ultrasonic wave transmitter 2 is First and second comparators 10. determine the times at which they fall below first and second threshold values V, , V2, respectively.
11, and a time width detection unit 72 that calculates the difference between the times determined by the first and second comparison units 10.11 and determines whether there is an abnormality by comparing the detected time width with a predetermined time 7th. The present invention is characterized in that a time width comparison section 73 is provided.

[Function] In the ultrasonic sensor of the present invention, as described above, the level of the signal S taken out from the ultrasonic wave transmitter 2 is equal to the first and second levels.
Since the difference in the time when the threshold values V, V2 of By appropriately setting the values V,,V,, it is possible to detect the time width that changes depending on the presence or absence of an abnormality, and by comparing this with the predetermined time 7th, it is possible to reliably determine the presence or absence of an abnormality. be able to.

[Example] FIG. 1 is a block diagram of one embodiment of the present invention.

The configuration will be explained below. Reference numeral 1 denotes an ultrasonic transducer, which has the function of transmitting ultrasonic pulses and receiving reflected waves from objects. 2 is a wave transmitting unit, which amplifies the transmitting pulse outputted from the control unit 7 and sends it to the ultrasonic transducer 1.
to drive. Reference numeral 3 denotes a transfer amplification section, which amplifies the transfer signal obtained by the ultrasonic transducer 1. 4 is a delivery detection section;
A transfer comparison unit 5 detects the transfer signal and extracts its amplitude component, and compares the amplitude component of the transfer signal with a predetermined value vth. When the amplitude component of the transfer signal exceeds the predetermined value vth, a high level signal is input to the control section 7. 6
is a notification unit, and when the control unit 7 determines that an object is growing, it performs a notification operation using sound or light. If an abnormality such as the following is detected, a notification operation is also performed.

In addition to the above configuration, the circuit shown in FIG. 1 includes an amplifying section 8, a detecting section 9, and a first and second comparing section 10. It is equipped with 11. The amplifying section 8 amplifies the signal S extracted from the wave transmitting section 2. The detection section 9 detects the output of the amplification section 8 to detect the level of the envelope of the signal S. The first comparator 10 sets the level of the signal S to a first threshold value V1.
Compare with. The second comparator 11 compares the level of the signal S with a second threshold value V2 (<Vl).

The comparison output of the first and second comparison sections 10.11 is the control section 7.
are input respectively.

Next, the control section 7 will be explained. The control section 7 includes an oscillation section 71, a time width detection section 72, a time width comparison section 73, and a reception determining section 74.

The oscillation unit 71 generates a transmission pulse at a predetermined period, and the zero time width detection unit 72 that supplies it to the wave transmission unit 2 detects that the level of the signal S extracted from the wave transmission unit 2 is below a first threshold value V. The time width from when the voltage falls below the second threshold value V2 (<Vl>) is detected.

In the time width comparison unit 73, when the detected time width is longer than the predetermined time 7th, it is determined that there is no abnormality.
When it is shorter than th, it is determined that there is an abnormality. If it is determined that there is an abnormality, the notification unit 6
Performs the first notification operation to notify that there is an abnormality.
If it is determined that there is no abnormality, the delivery determination unit 74 determines whether or not a wave is received, and if a reflected wave from an object is received, the notification unit 6 sends a message to notify that there is an object. A second notification operation is performed.

The first notification operation and the second notification operation may be performed using a sound or light that is different from the identification number.

FIG. 3 is an explanatory diagram of the operation of this embodiment. Figure 3(a)
, (b) is a waveform diagram of the signal S extracted from the ultrasonic wave transmitting unit 2, and (a) of the same figure shows the case where there is no abnormality such as foreign matter adhering to the vibration surface of the ultrasonic vibrator 1 or wire breakage. , same figure (b)
is a case where such an abnormality exists.

As is clear from the above countries, when there is no abnormality, the signal S attenuates over time, and when there is an abnormality, the signal S attenuates quickly. This signal attenuation is shown in Figure 3 (c
), the vertical axis is the level of the signal S, and the horizontal axis is time. Further, the attenuation waveform a shows the level change of the signal S in the case of FIG. 3(a), and the attenuation waveform a shows the level change of the signal S in the case of FIG. 3(b).

Here, assuming that the driving frequency and the resonant frequency of the ultrasonic transducer 1 are different from each other, the attenuation waveforms a and b both drop rapidly in the initial state after the end of the transmission pulse. After that,
The attenuation waveform a when there is no abnormality falls gently, and on the contrary, the attenuation waveform a when there is an abnormality falls sharply. Therefore, if the time Ta required for the level of the signal S to fall below the first threshold value ■1 and then fall below the second threshold value ■ is longer than the predetermined time Tth, it is determined that there is no abnormality. Also, the signal S
The time Tb required for the level to fall below the second threshold value v2 after the level falls below the first threshold value V,
is shorter than the predetermined time 7th, “abnormality exists”
It can be determined that

Note that if the driving frequency of the ultrasonic transducer 1 and the resonance frequency of the ultrasonic transducer match, the attenuation waveforms a and b as shown in FIG. 2(e) will be obtained. The attenuation waveform a in the abnormal state and the attenuation waveform in the normal state can be reliably distinguished by comparing the time width required for the attenuation from the threshold value v1 to V2.

[Effects of the Invention] As described above, the present invention provides an ultrasonic sensor that detects the presence or absence of an object by transmitting ultrasonic pulses and receiving reflected waves from the object. Since the presence or absence of an abnormality is determined based on whether the time width required for the level of the extracted signal to drop from the first threshold value to the second threshold value is shorter than a predetermined time, the ultrasonic transducer Even when the driving frequency and the resonant frequency do not match, by appropriately setting the first and second threshold values, it is possible to reliably distinguish between cases where there is an abnormality and cases where there is no abnormality. This has the advantage that it is possible to reliably detect the presence or absence of an abnormality that is accompanied by a change in signal decay time, such as foreign matter adhering to the vibrating surface or wire breakage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of a conventional example, and FIG. 3 is an explanatory diagram of the operation of the present invention. 1 is an ultrasonic transducer, 2 is a wave transmitting section, 3 is a receiving amplification section, 4 is a delivery detection section, 5 is a delivery comparison section, 6 is a notification section, 7 is a control section, 8 is an amplification section, 9 is a detection section part, 10 is the first comparison part, 11
71 is a second comparison section, 71 is an oscillation section, 72 is a time width detection section,
73 is a time width comparison section, and 74 is a delivery judgment section.

Claims (1)

[Claims] (1) In an ultrasonic sensor that detects the presence or absence of an object by transmitting ultrasonic pulses and receiving reflected waves from the object, the levels of the signals extracted from the ultrasonic wave transmitting section are the first and second levels. a first and second comparison section that respectively determines when the time falls below a threshold value; a time width detection section that determines the difference between the times determined by the first and second comparison sections; An ultrasonic sensor comprising: a time width comparison section that determines the presence or absence of an abnormality by comparing it with time.