Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JPH0465999 [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of isolating the back of an ultrasonic sensor. 2. Description of the Related Art As shown in FIG. 3, an ultrasonic sensor uses one side of a vibrator 1 as a wave receiving surface, and the other side is a sound insulating material 2 such as sponge or cork so that it does not detect incoming waves. It is covered with However, the sound insulation effect of this type of sound insulation material 2 decreases as the frequency of the incoming sound wave decreases, and when used under high pressure, the sound insulation material 2 is compressed and the sound insulation is generated. The effect is only lost (there is a problem that this compression also leads to the destruction of the container of the ultrasonic sensor itself). The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sound insulation method which can obtain sufficient sound insulation characteristics even under high pressure. [Means for Solving the Problems] In order to solve the above problems, in the present invention, two ultrasonic sensors A and B are opposed to each other at a predetermined interval, and a detection signal from one ultrasonic sensor A is detected. By delaying and adding it to the detection signal from the other ultrasonic sensor B, the rain detection signals for the ultrasonic waves from the rear of the ultrasonic sensor B are canceled out in reverse phase, and the ultrasonic sensors from the front of the ultrasonic sensor A Only ultrasonic waves are detected. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an embodiment of a specific configuration for implementing the sound insulation method of the present invention. With the two ultrasonic sensors A and B facing each other at a distance d, the detection signal from the ultrasonic sensor A is delayed by the delay circuit C, and the delayed signal and the signal from the delay sensor B are Addition is performed by the addition circuit. Now, assuming that an ultrasonic wave of X = pa−ej2fffot (pa is a constant) is incident from the side (front) of the ultrasonic sensor A, the outputs Va and Vb of the ultrasonic 03-05-2019 1 sensors A and B are Va = Pa E′πfot Vb = Pb−ej2πfo (t−d / v) (where v is the speed of sound). A signal obtained by delaying the sensor output Va by the delay circuit C is Vc = Pa−ej2πfo (t−τ). Here, when Pa = Pb and τ = d / v, the output of the addition circuit becomes VdF−2 Pa−ej 27 rr 0 (t−r), and the signal from the front of the ultrasonic sensor A is obtained. Next, when the same ultrasonic wave X ′ is incident from the side (rear) of the ultrasonic sensor B, the ultrasonic sensor B has an output Va ′ of Va′−Pa, e ′ ′ ′ πfot. The output of 'is Vb' = Pb, ej2πfo (t + d / v). Therefore, the output of the delay circuit E is Vc ′ = Pa, ej2πro (t−τ), and also assuming that Pa = Pb, τ = d / v, the output of the adder is Vd′−Pa, e × 2πfot (E 2 2πfor +, −j2πfoτ) 2P8. ej 2π ′ ′ t, cos 27 r for. Here, when setting to become, it becomes and it becomes Vd "-〇 . Follow? When sound waves are incident on the ultrasonic sensor from the front and back, only the sound waves from the front are output and the sound waves from the back are canceled. r = d / v, λ. Is the wavelength of fo (.lambda.O-V / fo). Then Vd '= Q and f. Think of a frequency other than Vd,-2P0. ej2πrt (t−τ) Vda ′ = 2 P a−e cos 2 yr rt v, and the ultrasonic wave from the front is detected, while the output signal of the ultrasonic wave from the rear is cos 2 y rft r − cos 2 y r f − '4 f. Thus, sound is isolated when an ultrasonic wave of a satisfying frequency f satisfying 2n + 1 □ π · 2m + 1 (m = o, 1.2 ···) is received from the rear side. Also, assuming that the level ratio R of the detection signals from the front and the rear is set to, the addition outputs VdF ′ and V dB ′ of the ultrasonic waves from the front and the rear become: If the case of the case 2 is examined here, it becomes as shown in FIG. As understood from this figure, the ultrasonic waves from the rear are completely isolated. As can be understood from the above description, the distance between the two ultrasonic sensors A and B and the delay time τ may be changed according to the wavelength of the sound wave to be isolated, but both ultrasonic sensors A and B have almost the same level. Since it is necessary to make the signal incident, when one ultrasonic sensor hides the other and the signal levels of both sensors are greatly different (for example, when it is larger than the wavelength of the sensor), both ultrasonic sensors are shifted from each other Just do it. As described above, the present invention uses two ultrasonic sensors, and delays the signal detected by one ultrasonic sensor and adds it to the detection signal from the other ultrasonic sensor. Since the detection signals of the sound waves from one side are mutually offset, the sound insulation material used in the conventional ultrasonic sensor becomes unnecessary, and hence it can be used under high pressure. [0002] Brief description of the drawings [0003] 03-05-2019 2 FIG. 1 is a block diagram showing an embodiment of an ultrasonic sound insulation apparatus to which the sound insulation method of the present invention is applied, FIG. 2 is a waveform diagram showing the output of the apparatus of FIG. It is a sectional view of an ultrasonic sensor. A, B: ultrasonic sensor, C: delay circuit, D: addition circuit. Patent Assignee Furuno Electric Co., Ltd. 03-05-2019 3
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