JPS5830387Y2 - Ultrasonic transducer - Google Patents

Description

[Detailed description of the invention] The present invention relates to the improvement of an ultrasonic transducer for transmitting or receiving ultrasonic signals suitable for use in remote control devices of television receivers, alarms, etc. ,
The present invention relates to a transducer having a relatively high center frequency and achieving high transmitting and receiving sensitivity over a wide frequency band.

This type of ultrasonic transducer is equipped with an aluminum watering can-shaped additional resonator (hereinafter referred to as a watering can resonator) or a resin-made additional resonator with a trapezoidal cross section (hereinafter referred to as a trapezoidal resonator) in the center of a ceramic bimorph transducer. ) is known.

The former, which uses an aluminum watering can resonator, is
There is a very wide interval between the frequency point where the first sensitivity (main sensitivity) occurs and the 25th frequency point, which has a small sensitivity but does not cause the second sensitivity (sub-sensitivity), and is practically used in the frequency region between them. However, it is extremely difficult to obtain high sensitivity over a wide frequency band because it is not possible to obtain the desired sensitivity.

On the other hand, the latter transducer equipped with a resin trapezoidal resonator has a structure as shown in FIG.

In FIG. 1, reference numeral 1 denotes a composite resonator, which is constructed by fixing a resin trapezoidal resonator 3 near the center of one side of a ceramic bimorph resonator 2.

This composite vibrator 1 is fixed on a substrate 4 with a support member 5 formed integrally with the substrate 4 interposed between the substrate 4 and the bimorph vibrator 2.

6 is a shield plate, and 7 is an external case.

When viewed from the impedance characteristics shown in Figure 4a, such a transducer has a first resonance in the low frequency range where the first sensitivity should occur, and a second resonance in the high frequency range where the second sensitivity should occur. Excite resonance.

However, as is clear from Figure 4, the level of the first sensitivity that should be generated in response to the first resonance is extremely low, and with such a low level of sensitivity, it is difficult to transmit and receive ultrasonic waves in this band. It is.

Therefore, this type of transducer can only obtain narrow band characteristics only in the high frequency range where the second sensitivity occurs.

If the practically usable sensitivity level is around 73 dB (indicated by A), waves can be transmitted and received only in a narrow frequency range shown by B.

The reason why the level of the first sensitivity becomes low in this way is presumed to be due to the following reason.

In other words, according to the results of an experiment in which powder was placed on the additional resonator 3, which serves as the ultrasonic wave transmitting/receiving surface, and the first resonance and second resonance were excited respectively, the first resonance was caused by the powder vibrating vertically over the entire surface. It is thought that this is causing blow-up vibration, and the second resonance is thought to be caused by bending vibration because the powder concentrates on the node line.And since the composite vibrator 1 is fixed to the substrate 4, blow-up vibration is caused. It is estimated that the vibration due to the mode is suppressed and the first sensitivity becomes low, resulting in a bell.

Therefore, the present invention focuses on the fact that the first sensitivity is caused by the vibration caused by the blow-up mode, and uses simple means to make the vibration due to the blow-up mode smooth, and the first sensitivity affects the Q of resonance. It is an object of the present invention to provide an ultrasonic transducer in which the second sensitivity is further improved by lowering the Q of the second resonance by a simple means.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIGS. 2 and 3, reference numeral 10 denotes a composite resonator, which is made up of a square plate-shaped piezoelectric ceramic bimorph resonator 11 and an additional resin resonator 12 fixed to the center of one side with adhesive.

The bimorph resonator 11 has two piezoelectric ceramic plates bonded together, and a lead 1 is placed near the node line on both outer electrodes.
1a and 11b are connected by solder.

The additional resonator 12 is composed of a trapezoidal main body 12a having a trapezoidal vertical section and a circular cross section, and a cylindrical projection 12b integrally formed on this main body, and the short side surface of the trapezoidal main body 12a is The surface with the protrusion 12b that is brought into contact with the bimorph vibrator 11 functions together with the protrusion 12b as a surface for transmitting (receiving) ultrasonic waves.

Reference numeral 13 denotes an insulating case with an open end and integrally formed with a support 14 .

The support body 14 is constituted by a cylinder formed inside the case 13 so as to extend in the axial direction from the center of the bottom portion.

A concentric projection 15 having a smaller diameter than the outer diameter of the support 14 is provided on the end surface of the cylindrical support 14 on the case opening side.

The thickness of the peripheral wall 16 of the case 13 is gradually reduced from the bottom toward the opening on the inner peripheral side, and a plurality of steps are provided on the inner peripheral surface of the case.

That is, the inner diameter of the case 13 is largest at the open end and becomes smaller toward the bottom.

The case peripheral wall 16 is provided with a step only near the opening end on the outer peripheral side.

Reference numerals 19 and 20 indicate external lead-out pins, which are implanted in the case peripheral wall 16.

A cutout 17.18 is provided in the case peripheral wall 16 opposite the tip of the pin 19.20 protruding into the case 13.

21 is a split ring-shaped elastic body made of silicone rubber, for example, and is fitted into the protrusion 15 .

The thickness of the elastic body 21 is greater than the height of the protrusion 15, and when the elastic body 21 is fitted into the protrusion 15, a gap is formed between its upper surface and the upper surface of the protrusion 15.

Further, a circumferential wall may be provided around the protrusion 15 on the end surface of the support body 14, and the elastic body 21 may be fitted into a circumferential groove formed between the circumferential wall and the protrusion 15. It is preferable that silicone adhesive is filled between 21 and the support 14 to fix it.

A composite vibrator 10 is fixed onto the elastic body 21 with a silicone adhesive with its wave transmitting and receiving surface facing the case opening.

To install the vibrator 10, connect the solder connection part of the lead 11b on the bottom side of the bimorph vibrator 11 to the divided part 2 of the elastic body 21.
1 Place it in position a.

It is preferable that the divided portion 21a is sufficiently filled with silicone adhesive to seal the gap between the bimorph vibrator 11 and the support 14.

Lead 11a is connected to pin 19, lead 11b is connected to pin 2
It is preferable that each solder connection portion be soldered and that a silicone adhesive be applied to each solder connection portion.

22 is a shield plate that is brought into contact with the bottom of the case 13, is soldered to one pin 20, and is electrically insulated from the other pin 19.

Reference numeral 23 denotes a mesh window member that covers the opening end of the case, and its periphery extends to the outer step of the case peripheral wall 16.

The metal cover 24 is placed over the case 13 from the case opening and fixed to the case 13 by suitable means, and the window member 23 is fixed by the cover 24 and the case 13.

According to this embodiment, since the composite vibrator 10 is supported via the elastic body 21, the vibration due to the blow-up mode is efficiently generated, and as shown in FIG. May we have a great level of first sensitivity,
In combination with the second sensitivity, which originally has a high level, a transducer with good sensitivity over a wide band can be obtained.

The frequency bandwidth in which sensitivity can be obtained is significantly wider than that of the conventional example, as shown by C in FIG.

The solid and broken lines plotted in FIGS. 5a and 5b are diagrams showing changes in characteristics with respect to the formation of the protrusion 12b, the broken line is the characteristic of the transducer without the protrusion 12b on the additional resonator 12, and the solid line is These are the characteristics obtained in this example in which the protrusion 12b is provided.

As is clear from the broken line in the figure, when there is no protrusion 12b, the Q of the second resonance is large and the second sensitivity is relatively small.

Providing the protrusion 12b increases the Q of the first resonance and decreases the Q of the second resonance, as shown by the solid line.

It is presumed that this is because the protrusion 12b increases the Q of the first resonance due to the blow-up mode, and correspondingly pushes down the Q of the second resonance.

Looking at the sensitivity characteristics in the figure, it can be seen that the second sensitivity increases as the Q of the second resonance decreases.

On the other hand, the first sensitivity does not decrease despite the increase in the Q of the first resonance, and this is presumed to be because the first resonance is caused by the blow-up mode.

Furthermore, since the elastic body 21 only needs to be fitted into the protrusion 15, it can be positioned reliably, and the composite vibrator 10 can be easily attached to a predetermined position.

Moreover, the lead 11b is attached to the divided portion of the ring-shaped elastic body 21.
Since the solder portion is located, the composite vibrator 10 is not tilted by the solder portion, and a predetermined directivity can be reliably obtained.

Furthermore, the sensitivity can be changed by changing the shape of the circumferential groove between the support body 14 and the case peripheral wall 16 or the step on the inner peripheral surface of the case peripheral wall 16. You can set it to .

The present invention is not limited to the above-mentioned embodiment, and it is possible to use an elastic body in the form of a tongue or an insulating case in other shapes.

As explained above, in the present invention, a composite vibrator in which a piezoelectric bimorph vibrator and a resin additional resonator having protrusions on the wave transmitting/receiving surface are fixed is attached to a support via an elastic body. The vibration due to the bending mode operates smoothly, the first sensitivity corresponding to the vibration increases, and when combined with the second sensitivity corresponding to the vibration due to the bending mode, the sensitivity becomes good over a wide frequency band, and the additional resonator The second sensitivity is further increased by the formation of a protrusion on the
As a result, by using the present invention, a highly sensitive broadband ultrasonic transducer can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional ultrasonic transducer, and FIGS. 2 and 3 show an embodiment of the ultrasonic transducer according to the present invention.
Figure 2 is a sectional view, Figure 3 a, l), c. d shows the main parts, FIGS. 4a and 4b are resonance characteristic diagrams and sensitivity characteristic diagrams of the conventional example, and FIGS. 5a and 5b are resonance characteristic diagrams and sensitivity characteristic diagrams of the present embodiment. 10...Composite resonator, 11...Bimorph resonator, 12...Additional resonator, 12b...
...Protrusion, 13...Insulation case, 14...
...Support, 15...Protrusion, 21...
...Elastic body.

Claims (1)

[Claims for Utility Model Registration] A composite vibrator comprising a bimorph vibrator with an additional resin resonator having a trapezoidal cross section in the center, and a support body to which this composite vibrator is attached via an elastic body. In an ultrasonic transducer in which a composite vibrator causes resonance in a blow-up mode at a lower frequency side and resonance in a bending mode at a higher frequency side than a center frequency, an ultrasonic wave transmitting/receiving wave surface of the additional resonator is provided. An ultrasonic transducer characterized in that the Q of resonance due to the bending mode is reduced by providing a protrusion.