JPH0545455A - Ultrasonic detector - Google Patents

Abstract

PURPOSE:To prevent erroneous operation by monitoring a plurality of continuous reverberation-ending times, storing the times when the amount of change is within a specified range, comparing the time with the next reverberation-ending time, and judging that there is the received wave when the amount of change is larger than the specified amount. CONSTITUTION:Ultrasonic pulses are transmitted from a transmitting-wave-pulse generating part 17 in a control part through a wave transmitting part 15 and an ultrasonic piezoelectric transducer 14. The reflected wave from a body is received with the piezoelectric transducer 14. The received waveform of the output is shaped with a detecting part 19 and a wave-shaping part 20 through an amplifier part 18. A reverberation-ending-time detecting part 21 and a reverberation-time-changing-amount judging part 22 are provided in the control part 16. The changing amounts of the N times of the continuous reverberation ending times are monitored with the detecting part 21 and the judging part 22. When the amounts are within the specified value, the amounts are stored. The stored ending times and the changing amount at the next time are detected. It can be judged that there is the received wave when the changing amount is larger than the specified amount and that there is no received wave when the amount is smaller. Thus, the continuous received wave in the reverberation can be detected without erroneous operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic detector which transmits an ultrasonic pulse and detects a reflected wave from an object to measure the distance to the object.

[0002]

2. Description of the Related Art An ultrasonic wave pulse is transmitted from an ultrasonic wave detector, propagates in the air, and hits an object, and a reflected wave 2 is received by the same detector. Distance L from the following equation to the object from the time T required from the start of ultrasonic wave transmission to the reception of ultrasonic pulse
Find (m). L = (C · T) / 2 where L is the distance between the detector and the object (m) C is the speed of sound (m / s) However, the ultrasonic transducers that transmit and receive ultrasonic pulses are the same. Therefore, as shown in FIG. 3, the attenuation waveform 1 (hereinafter referred to as reverberation) exists even after the ultrasonic pulse transmission. FIG. 3B shows the reverberation 3 and the received wave 4 which are obtained by shaping FIG. 3A.
Is shown. The fact that the reverberation 1 and the received wave (reflected waveform) 2 are continuous is detected by the reverberation 5 end time T shown in FIG.
By storing 0 (6 is received) and comparing with the end time T of reverberation 7 shown in FIG. 7B, if T−T0 ≧ Tth, there is received wave, and if T−T0 <Tth. , There was no reception. Here, Tth is a set value of the set change amount. By the way, FIG. 5A shows the reverberation 8 and the reflected waveform (received wave) 9 after the normal shaping. However, depending on the overlapping condition of the reverberation and the received wave, as shown in A of FIG. 5B. , Reverberation 1
A value that is shorter than the reverberation end time when the received wave 11 interferes with 0 and the received wave 11 does not overlap with the reverberation 10 (see FIG. 5).
(B) T2) is stored, and compared with the reverberation end time (T3 in FIG. 5C) when the receiving wave 12 does not interfere with the reverberation 13, if T3−T2 ≧ Tth, then Since it is determined that there is a wave, there is a problem that even if the received wave 13 in FIG. 5C is outside the detection area, it remains detected (malfunction).

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic detector that does not malfunction by monitoring the reverberation end time.

[0004]

The present invention according to claim 1, which is proposed to achieve the above object, transmits an ultrasonic pulse and receives a reflected wave from an object to detect the distance to the object. The reverberation end time is stored in the ultrasonic detector for measuring. The present invention according to claim 2 is characterized in that the amount of change in the reverberation end time is monitored a plurality of times consecutively, and if the amount of change is within a preset value range, the reverberation end time is stored. To do. According to the present invention of claim 3, the amount of change between the stored reverberation end time and the next reverberation end time is detected. If the amount of change is larger than a preset value, the wave is received, and if it is smaller, the wave is received. It is characterized by determining that there is no.

[0005]

According to the present invention as set forth in claims 1, 2 and 3, as described above, the change amount of the reverberation end time is continuously set a plurality of times. If it is within the range, by storing the reverberation end time and comparing the stored reverberation end time with the next reverberation end time,
If the amount of change in the reverberation end time is larger than a preset value, it is possible to determine that there is wave reception, and if it is small, it can be determined that there is no wave reception.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram of an ultrasonic detector, FIG. 2A is a diagram showing a change in reverberation end time for each transmission, and FIG. 2B is a reverberation end time for each transmission. It is a figure showing the amount of change of. As shown in FIG.
The ultrasonic transducer 14 transmits an ultrasonic pulse from the transmitting pulse generator 17 in the inside through the transmitting unit 15.
Further, the detection unit 1 receives the reflected wave from the object by the ultrasonic transducer 14 and adjusts the output of the output wave via the amplification unit 18.
9 and a shaping unit 20 for shaping, and further, a reverberation end time detection unit 21 and a reverberation end time change amount determination unit 22 are provided in the control unit 16 to measure a distance to an object. In the reverberation end time detection unit 21 and the remaining amount end time change amount determination unit 22 in the control unit 16, as shown in FIGS. 2A and 2B, N consecutive reverberations (for example, N = 10) are performed. The change amount of the end time is monitored, and if the change amount is within a preset value (x in FIG. 2B), the reverberation end time is stored.

The preset value is larger than, for example, a gradual change amount such as temperature change, and is larger than a large change amount when the reverberation and the received wave interfere with each other. Also a small value. Then, the amount of change between the stored reverberation end time and the next reverberation end time is detected, and if the amount of change is larger than a preset value, it is determined that there is reception, and if it is small, it is determined that there is no reception. You can

[0008]

As described above, the present invention according to claims 1, 2 and 3 is an ultrasonic wave for measuring the distance to an object by transmitting an ultrasonic pulse and receiving a reflected wave from the object. The detector monitors the amount of change in the reverberation end time that occurs multiple times in succession, and if the amount of change is within the preset value range, the function that stores the reverberation end time and the stored reverberation end time and the next time There is a function to detect the amount of change in the reverberation end time and to judge that there is a received wave when the changed amount is larger than a preset value and to judge that there is no received wave when the changed amount is small. The advantage is that it is possible to detect received waves that are continuous with reverberation.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2A is a diagram showing a change in reverberation end time for each transmission wave, and FIG. 2B is a diagram showing a change amount in the reverberation end time for each transmission wave.

3A and 3B are explanatory diagrams of distance measurement.

4A and 4B are explanatory views of a conventional technique.

5A, 5B, and 5C are explanatory diagrams of reflected waveforms.

[Explanation of symbols]

 1 ... Reverberation waveform 2 ... Reflection waveform 3, 5, 7, 8, 10, 12 ... Reverberation waveform (after shaping) 4, 6, 9, 11, 13 ... Reflection waveform (after shaping) 14 ... Ultrasonic transducer 15 ... Transmitting unit 16 ... Control unit 17 ... Transmitting pulse generating unit 18 ... Amplifying unit 19 ... Detection unit 20 ... Shaping unit 21. ..Reverberation end time detection unit 22 ... Reverberation end time change amount determination unit

Claims (3)

[Claims] 1. An ultrasonic wave detecting device, characterized in that an ultrasonic wave detector that measures the distance to an object by transmitting an ultrasonic wave pulse and receiving a reflected wave from the object stores the reverberation end time. vessel. 2. A reverberation end time is stored when the amount of change in the reverberation end time is monitored a plurality of times consecutively and if the amount of change is within a preset value range. 1. The ultrasonic detector according to 1. 3. A change amount between the stored reverberation end time and the next reverberation end time is detected. If the change amount is larger than a preset value, there is reception, and if it is small, there is no reception. The ultrasonic detector according to claim 1, wherein the ultrasonic detector is judged.