JPH03190499A - Ultrasonic vibrator - Google Patents

Abstract

PURPOSE:To apply electromagnetic shield to a resonator by means of a metallic cylindrical tube by disconnecting the electric connection between a negative electrode of the resonator and the metallic cylindrical tube, leading a ground lead wire from the metallic cylindrical tube and connecting a terminal to ground. CONSTITUTION:A resonator 2 formed to be a disk smaller than an outer diameter of a disk shaped matching layer 1 and bonded to the center of a rear side of the matching layer 1 and having positive and negative electrodes and a metallic cylinder tube 3 formed to be a cylinder with the same size as the outer diameter of the matching layer 1, covering the resonator 2 and provided to the rear side of the matching layer 1 are adopted for the vibrator. Then the negative electrode and the metallic cylindrical tube 3 are not electrically connected and a ground lead wire 7 is led from the metallic cylindrical tube 3. When a terminal led with the ground lead wire 7 is connected to ground, the metallic cylindrical tube 3 has a function of electromagnetic shield and even when noise such as an external electromagnetic wave is invaded in the metallic cylindrical tube 3, the noise is escaped to ground via the ground lead wire 7. Thus, the adverse effect due to external noise is not imposed onto the resonator 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic transducer used in an ultrasonic sensor or the like.

[Conventional technology]

As this type of ultrasonic transducer, one having a structure as shown in FIG. 3 is known. This ultrasonic transducer has a disc-shaped resonator 2 whose diameter is smaller than the outer diameter of the matching layer 1 bonded to the center of the back surface of an insulating disc-shaped matching layer 1 made of, for example, epoxy. A metal cylindrical tube (made of aluminum, for example) 3 having the same outer diameter as l is placed over the resonator 2, and the upper end surface of the metal cylindrical tube 3 is bonded to the back surface of the matching layer. Positive electrode lead wires 4 from the bottom surface (positive electrode) and top surface (negative electrode) of the resonator 2, respectively. The negative electrode lead wire 5 is drawn out. Further, the negative electrode is electrically connected to the metal cylindrical tube 3 through a connecting lead wire 6 to constitute a ground electrode.

[Problems to be Solved by the Invention] The ultrasonic transducer having the structure described above has the following problems. In other words, noise such as electromagnetic waves from the outside invades the metal cylindrical tube, but since the metal cylindrical tube is electrically connected to the negative electrode by the connecting lead wire, noise such as electromagnetic waves will affect the negative electrode and will cause damage to the resonator. There was a risk that the received electric signal, which is converted from the received minute reflected wave, would be disturbed.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an ultrasonic transducer having a structure in which the resonator is not affected even if the metal cylindrical tube receives noise such as electromagnetic waves from the outside.

[Means to solve the problem]

In this invention, the resonator is constructed as follows so that it is not affected by noise. That is, a resonator having a disk shape smaller than the outer diameter of the disk-shaped matching layer and having a positive electrode and a negative electrode bonded to the center of the back side of the matching layer, and a cylindrical resonator having the same size and diameter as the outer diameter of the matching layer. and a metal cylindrical tube provided on the back side of the matching layer so as to cover the resonator, and a positive electrode lead wire and a negative electrode lead wire are drawn out from the positive electrode and negative electrode of the resonator, respectively. In the sound wave vibrator, a ground lead wire was drawn out from the metal cylindrical tube and this terminal was connected to the ground. In addition, when installing an amplifier on the positive electrode of the resonator, attach the printed circuit board with the amplifier mounted on the open end of the metal cylindrical tube, electrically connect the metal cylindrical tube to the ground side of the printed circuit board, and then A positive electrode lead wire is electrically connected to the input side of the amplifier and further led out, and a negative electrode lead wire of the resonator is connected to the ground side of the printed circuit board and further led out to the outside, and the output side of the amplifier is connected. Pull out the amplifier lead wire.

[For production]

Even if the metal cylindrical tube receives external noise such as electromagnetic waves,
This noise does not affect the resonator but flows from the connecting lead wire to the ground side. That is, the metal cylindrical tube functions as an electromagnetic shield for the resonator.

[Example] Fig. 1 is a longitudinal cross-sectional view of an ultrasonic transducer which is an embodiment of the present invention, and parts that are the same as those shown in Fig. 3 are given the same reference numerals. The difference is that the negative electrode and the metal cylindrical tube 3 are not electrically connected, and the ground lead wire 7 is drawn out from the metal cylindrical tube 3. If the terminal from which this ground lead wire 7 is drawn out is connected to the ground, the metal cylindrical tube 3 has an electromagnetic shielding function, and even if noise such as electromagnetic waves from the outside enters the metal cylindrical tube 3, the ground lead wire 7
The resonator 2 is not adversely affected by external noise because the current flows to the ground through the resonator 2.

If the transmitted electrical signal due to the reflected wave received by the resonator is weak, it must be electrically amplified, so an amplifier is used. Conventionally, the amplifier was installed on the side of the ultrasonic sensor body, but in the present invention, as shown in FIG. It was electrically connected to the ground side of the board 10. And the positive electrode lead wire 4 of the resonator 2
was electrically connected to the input side of the amplifier 9, and then further drawn out to the ultrasonic sensor main body side. Further, the negative electrode lead wire 5 of the resonator 2 is electrically connected to the ground side of the printed circuit board 10 and then further led out to the ultrasonic sensor main body side. In this structure, the transmitted electrical signal from the ultrasonic sensor body is input to the resonator 2 via the positive electrode lead wire 4 and the negative electrode lead wire 5, and the delivered electrical signal is inputted to the resonator 2 via the amplifier lead wire 8 and the negative electrode lead wire 5. The ultrasonic sensor is drawn out through the ultrasonic sensor and sent to the main body of the ultrasonic sensor.

〔Effect of the invention〕

In this invention, the electrical connection between the negative electrode of the resonator of the ultrasonic transducer and the metal cylindrical tube is cut off, the ground lead wire is drawn out from the metal cylindrical tube, and this terminal is connected to the ground, so that the resonator is connected to the metal cylindrical tube. is electromagnetically shielded, and even if noise such as electromagnetic waves from the outside enters the metal cylindrical tube, it will flow to the ground via the ground lead wire, and the ultrasonic transducer will operate normally without having any negative effect on the resonator. . In addition, if an amplifier is attached to the ultrasonic transducer, the printed circuit board with the amplifier mounted on it can be attached to the open end of the metal cylindrical tube to minimize the lead wire from the positive electrode of the resonator to the input side of the amplifier. Further, since the lead wire and the amplifier are housed inside a metal cylindrical tube having an electromagnetic shielding function, the ultrasonic transducer is not affected by noise and operates normally.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of an ultrasonic transducer which is an embodiment of the present invention, Fig. 2 is a longitudinal sectional view of an ultrasonic transducer with an amplifier, and Fig. 3 is a longitudinal sectional view of a conventional ultrasonic transducer. It is. 1: Matching layer, 2: Resonator, 3: Metal cylindrical tube, 4: Piezo electrode lead wire, 5: Negative electrode lead wire, 7: Ground lead wire, 8
: Amplifier lead wire, 9: Amplifier, Drop 1 Figure 2

Claims (1)

[Scope of Claims] 1) a disc-shaped matching layer; a resonator having a disc-shaped shape smaller than the outer diameter of the matching layer and having a positive electrode and a negative electrode bonded to the center of the back side of the matching layer; A metal cylindrical tube having the same size and diameter as the outer diameter of the matching layer is provided on the back side of the matching layer so as to cover the resonator, and a positive electrode is connected to the positive electrode and the negative electrode of the resonator, respectively. An ultrasonic transducer having a lead wire and a negative electrode lead wire drawn out, the ultrasonic transducer characterized in that a ground lead wire is drawn out from a metal cylindrical tube and its terminal is connected to earth. 2) a disc-shaped matching layer, a disc-shaped resonator having a positive electrode and a negative electrode, which is bonded to the center of the back side of the matching layer and has a disc shape smaller than the outer diameter of the matching layer; A metal cylindrical tube with the same dimensions and diameter is provided on the back side of the matching layer so as to cover the resonator, and a positive electrode lead wire and a negative electrode lead are respectively connected to the positive and negative electrodes of the resonator. In the ultrasonic transducer with the wire drawn out, a printed circuit board equipped with an amplifier is attached to the open end surface of the metal cylindrical tube, and the metal cylindrical tube is electrically connected to the ground side of the printed circuit board, and the positive electrode lead wire of the resonator is is electrically connected to the input side of the amplifier and further led out, the negative electrode lead wire of the resonator is connected to the ground side of the printed circuit board, and further led out to the outside, and the amplifier lead wire is connected from the output side of the amplifier. An ultrasonic transducer characterized by drawing out.