JPH0230960Y2 - - Google Patents

Description

[Detailed description of the invention] (1) Industrial application field This invention relates to a piezoelectric ultrasonic vibrator used, for example, as a bubble detection sensor.

(2) Prior art When using a piezoelectric ultrasonic transducer as a bubble detection sensor, two piezoelectric ultrasonic transducers are immersed in a liquid facing each other, and one piezoelectric ultrasonic transducer is immersed in a liquid. The transmitter and the other piezoelectric ultrasonic transducer serve as receivers, and the receiver receives the ultrasonic waves emitted from the transmitter. If there is a bubble between the transmitter and receiver, the bubble is detected by the attenuation of the ultrasonic signal. are doing.

(3) Problems to be solved by the invention In the conventional piezoelectric ultrasonic transducer as described above, as shown in FIG. A piezoelectric vibrator 4 is adhesively fixed on the top, and the recess 2 is casted with resin 5. However, since the wall thickness on both sides of the recess 2 of the resin case 1 is large, the vibration of the piezoelectric vibrator 4 is suppressed. Furthermore, since the base 6 made of the same material and molded integrally with the resin case 1 is attached to the device, the vibration propagated to the resin case changes depending on the degree of attachment to the device. Therefore, there were variations in sensitivity.

(4) Means for solving the problem In order to solve the above problem, this invention is such that both sides of the recessed part of the resin case are formed into a knife edge shape, and the resin case is fixed on a metal base. It is.

(5) Effect Since this device has the above structure, when used as a transmitter, for example, it becomes an ultrasonic transmitter by applying a high frequency voltage to the piezoelectric vibrator. Furthermore, if a receiving circuit is connected to the piezoelectric vibrator, it becomes an ultrasonic receiver, so it can be used as various sensors that utilize ultrasonic waves.

(6) Example In Figures 1 and 2, 11 is a resin case;
Reference numeral 12 denotes a recess provided in the resin case, on the bottom of which an ultrasonic sound absorbing material 13 such as cork is glued and fixed, and a piezoelectric vibrator 14 is glued and fixed thereon. This piezoelectric vibrator is, for example, something like a bimorph made of two piezoelectric elements glued together, and lead wires 16, 16' soldered to the electrodes of each piezoelectric element are drawn out.

As described above, by pouring the synthetic resin 15 such as epoxy resin into the recess 12 in which the ultrasonic sound absorbing material 13 and the piezoelectric vibrator 14 are fixed and curing it, the sound absorbing material 13 and the piezoelectric vibrator 14 are completely encapsulated. Ru.

Further, both sides of the recess 12 of the resin case 11 are formed as inclined surfaces 17 starting from both sides of the recess.
Both side walls of the recess 12 are shaped like sharp knife edges.

Furthermore, the resin case 11 is made of a metal base 1.
Glue and fix on 8.

(7) Effects This invention improves sensitivity by forming both sides of the recess 12 of the resin case 11 into a knife edge shape and by using the metal base 18 as described above.

That is, in the conventional example shown in FIG. 3, for example, if the thickness of both side walls of the recessed part of the resin case is considerably large and the width of the resin case is about 5 mm, the width of part a is about 0.7 mm.
becomes.

The impedance characteristics of such a piezoelectric ultrasonic transducer are shown in Figure 4, and the piezoelectric vibration is 200K.
It can be seen that vibrations near Hz are suppressed.

In the case of this invention, the part a in Fig. 3 is removed and the
By forming the knife edge shape as shown in the figure, the influence of the load on the resin case is reduced, and the characteristics as shown in FIG. 4 can be obtained.

In other words, a resonance peak occurs near 200KHz, improving sensitivity. Further, by adjusting the slope of the knife edge, for example, making it more acute, the sensitivity is further improved as shown by the dotted line in FIG.

Therefore, sensitivity can be freely adjusted by adjusting the slope of this knife edge.

If the base 6 shown in Figure 3 is also integrally molded from resin, if this base is attached to another board, the frequency will change by about 10 KHz before and after attachment due to vibration leakage from the piezoelectric vibrator, which may affect the sensitivity. There was a lot of variation.

On the other hand, in the case of this invention, by attaching the metal base to another substrate or the like, there are effects such as eliminating leakage of vibration from the piezoelectric vibrator and almost eliminating variations in sensitivity.

[Brief explanation of the drawing]

Figure 1 is a front view showing an embodiment of the piezoelectric ultrasonic transducer of this invention, Figure 2 is a perspective view of the same, and Figure 3 is a perspective view of the same.
FIG. 4 is a front view showing an example of a conventional piezoelectric ultrasonic transducer, and FIG. 4 is a graph showing frequency characteristics of the piezoelectric ultrasonic transducer of this invention and a conventional piezoelectric ultrasonic transducer. 11...resin case, 12...recess, 13...
Ultrasonic sound absorbing material, 14... Piezoelectric vibrator, 15... Synthetic resin, 17... Inclined surface, 18... Metal base.

Claims (1)

[Scope of utility model registration request] Ultrasonic sound absorbing material is glued into the recess of the resin case,
In a piezoelectric ultrasonic transducer on which a piezoelectric vibrator is adhesively fixed and a recessed part is casted with resin, both sides of the recessed part are formed into a knife edge shape, and the resin case is fixed on a metal base. A piezoelectric ultrasonic transducer characterized by: