JPH02243100A - ultrasonic sensor - Google Patents

Abstract

PURPOSE:To reduce the amplitude and the duration of a reverberation signal generated from a vibrator by adopting such a constitution that the outer peripheral part of a truncated conical metallic case formed through the stick piezoelectric ceramic vibrators is covered with an elastic member with plural holes made therein. CONSTITUTION:The outer peripheral part of the metallic case 2 is covered with an elastic member 3 and plural holes 3a are provided to part of the elastic member 3 corresponding to the bottom of the case 2. When a transmission signal T is applied, as shown in a waveform diagram, to a piezoelectric ceramic vibrator 1, the propagation of the vibration of the vibrator 1 to the side face of the case 2 with the elastic member 3 covering the case 2 is suppressed. Thus, the vibration to the vibrator 1 propagated from the side face of the case 2 when the application of the signal is finished is very small and the time of a reverberation signal T2 is much reduced as shown in waveform diagram. Thus, the detection of an objected at a shorter distance and stable distance measurement are attained by the ultrasonic wave sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic sensor for transmitting and receiving ultrasonic waves, which is applied to detect objects at short distances, as a proximity switch, and as a distance meter.

2. Description of the Related Art Conventionally, this type of ultrasonic sensor has had a configuration as shown in FIG. In FIG. 3, a piezoelectric ceramic vibrator 1 is firmly bonded to the center of the bottom of a truncated cone-shaped metal case 2 to form a unimorph vibrator. A resonance ring 4 is fixed to the upward side surface of the metal case 2, and a terminal plate 5 is fixed to the inner surface of the resonance ring 4 and the metal case 2 via a spacer 6 made of an elastic material. An elastic adhesive 7 is injected between the terminal plate 5 and the metal case 2, and the inside of the metal case 2 is sealed. The terminal 9A implanted in the terminal plate 5 and the electrode of the piezoelectric ceramic vibrator l are connected by a lead wire 8A, and the terminal 9B and the connecting portion of the metal case 2 and the resonance ring 4 are connected by a lead wire 8B. Each is electrically fixed by solder 10 or conductive adhesive 11.

Problems to be Solved by the Invention In the conventional configuration described above, when a tone burst signal as shown in FIG. 2(a) is applied to the piezoelectric ceramic vibrator 1, the piezoelectric ceramic vibrator 1 and The bottom surface of the metal case 2 bends and vibrates, and ultrasonic waves are emitted into the air. At the same time, the vibrations are also transmitted to parts such as the side surface of the metal case 2 and the resonance ring 4, causing them to vibrate. Even after the signal application is finished, vibrations remain in the metal case 2, resonance ring 4, and other members, so the piezoelectric ceramic vibrator 1 is excited and generates an electrical signal, and the signal between the input and output terminals is As shown in FIG. 2(b), the reverberation signal T1 appears even after the signal application ends. When distance measurement and object detection are performed using ultrasonic waves, the ultrasonic waves reach the object and the returned echo waves are compared. Therefore, if there is an echo wave within the reverberation time Tl, the comparison will not be possible. In other words, there is a problem that the longer the time of the reverberation signal T1, the more difficult it becomes to detect an object at a short distance.

The present invention is intended to solve these problems, and aims to provide an ultrasonic sensor capable of shortening the reverberation signal time and detecting short distances.

Means for Solving the Problems In order to solve the above problems, the present invention has a structure in which the outer periphery of a truncated conical metal case to which a piezoelectric ceramic vibrator is bonded is covered with an elastic material provided with a plurality of holes. It is something.

Effect: With the above configuration, when a tone burst signal is applied to the piezoelectric ceramic vibrator, the vibration of the piezoelectric ceramic vibrator is suppressed from being transmitted to the side surface of the metal case by the elastic material covering the metal case. Therefore, when the signal application is finished, the vibration transmitted to the piezoelectric ceramic vibrator from the side surface of the metal case becomes very small, and the remaining signal time can be made very short.

Example Embodiments of the present invention will be described below based on the drawings.

Note that the same components as those of the conventional ultrasonic sensor are given the same numbers and their explanations will be omitted.

FIG. 1 is a sectional view of an ultrasonic sensor showing an embodiment of the present invention. As shown in FIG. 1, the outer periphery of the metal case 2 is covered with an elastic material 3.
A plurality of holes 3a are provided in a corresponding portion of the bottom surface.

With the above configuration, when a tone burst signal as shown in FIG. transmission to the sides is suppressed. Therefore, when the signal application is finished, the vibration transmitted to the piezoelectric ceramic vibrator 1 from the side surface of the metal case 2 becomes very small.
As shown in FIG. 2(C), the time of the reverberation signal T2 can be made very short. Therefore, this ultrasonic sensor enables short-distance object detection and stable distance measurement.

Effects of the Invention As described above, according to the present invention, the outer periphery of the truncated conical metal case to which the piezoelectric ceramic vibrator is bonded is covered with an elastic material having a plurality of holes. The vibration of the metal case is less likely to be transmitted to the side of the metal case, and the metal case n! Since the vibration on one surface is reduced, the reverberation signal generated when the signal application to the piezoelectric ceramic JiA actuator is finished can be made small and short, and the reverberation is transmitted through the elastic material with multiple holes. Ultrasonic output with little signal influence can be obtained, and short-range object detection and stable distance Mi11I determination can be realized.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an ultrasonic sensor according to an embodiment of the present invention, FIG. 2(a) is a diagram of a tone burst signal applied to the ultrasonic sensor, and FIG. 2(b) is a diagram of a conventional ultrasonic sensor. Reverberation signal diagram when a tone burst signal is applied, Figure 2 (
C) is a reverberation signal diagram when a tone burst signal is applied to the ultrasonic sensor according to the present invention, and FIG. 3 is a sectional view showing a conventional ultrasonic sensor. 1... Piezoelectric ceramic vibrator, 2... Metal case, 3...
- Elastic material, 3a -- hole. Agent Yoshihiro Morimoto No. 1 Prisoner 1 - Toraiji Rakudorei 2 - Ichimetal d-2 3-1-Da chapter Surname Sai) 3a-shishi 2nd picture

Claims (1)

[Claims] 1. An ultrasonic sensor in which a piezoelectric ceramic vibrator is bonded to a truncated cone-shaped metal case to form a unimorph vibrator, and the outer periphery of the metal case is covered with an elastic material provided with a plurality of holes.