JPS6026870Y2 - ultrasonic transducer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of an electrostrictive ultrasonic vibrator using, for example, lead titanium zirconate (abbreviated as PZT).

When putting the pz'r'' vibrator into practical use, metal is sandwiched from both sides of the vibrating element and tightened with bolts to form an integral piece.
It is well known that a so-called "Langevin type vibrator", which forms a vibrating body as a whole, is used.

Figure 1 shows a typical example of a bolted "Langevin type resonator", in which 1 is a circular metal block made using the same method, 2 is a PZT resonator, and 3 is a positive electrode placed between two pz'r resonators. A side electrode, 4 is a tightening bolt, and 5 is a vibration radiation surface. Generally, the length 1 satisfies the resonance condition for l=λ12, where λ is the wavelength of vibration.

In order to make the phases of each part of the vibration radiation surface 5 as in-phase as possible and to make the vibration mode of the vibration radiation surface uniform, the diameter a of the vibration radiation surface is usually set to a≦λc.

However, while limiting the dimensions in this way makes it possible to make the vibration mode uniform, it also increases the Q of the ultrasonic transducer, making it difficult to achieve tuning, especially when combined with a driving oscillator. Since a pull-in phenomenon occurs in automatic oscillators, separate countermeasures are required.

The present invention is intended to eliminate these drawbacks, and the Q of the ultrasonic transducer is lowered to ensure stable operation.

“When using a Langevin type vibrator in an ultrasonic cleaning device, for example, if the ultrasonic vibrator is bonded to the bottom of the bottom plate 6 of the cleaning tank as shown in Fig. 2, the Q will be high, so the Q will be lowered. Therefore, conventionally, as shown in FIG. 3, an additional metal mass 7 of arbitrary size was attached between the vibration radiation surface and the bottom plate.

However, since no dimensional consideration is given to the additional mass, although the Q can be lowered, the vibration itself is damped and the resonant frequency is significantly lowered compared to the case without the additional mass.

As a result, not only is the vibration system inefficient, but the value of the distance a between the positive electrode provided in the middle of the vibration element and the bottom plate is different from the value of 174, which is the vibration wavelength, causing nodal points to be generated. As a result, the positive electrode vibrates and there is a risk of a short circuit, which is inconvenient.

In the present invention, the dimensions of the additional mass are carefully considered to reduce Q and to prevent vibrations from causing any trouble. An embodiment thereof is shown in FIG. 4.

In Figure 4, 8 is an ultrasonic transducer, 9 is a front metal block, 1
0 is a rear metal block, 11 is a tightening screw, the overall thickness is set to λ/2, and the thickness of the front block 10 is input.
4.

This dimension is just an example, and the point is that the overall thickness is λ/2
The thicknesses of the front block 9 and the rear block 10 may be appropriately selected so that

The shape of the vibration radiation surface of the front block 9 is particularly square, and the dimensions C and d of each side are c=d-λ/2.

In this case, to be more specific, it is important to be careful to set the value as close to λ/2 as possible, since performance is affected to a large extent by being too large or too small from λ/2.

Table 1 is an example comparing the electrical characteristics in the case of c=d=λ14 and c=d=λ12. As can be seen from this table, when c=d=input 12 inlet 2, the Q decreases and the resonant frequency Values such as admittance do not change.

When combined with a self-excited oscillator, c = d = input 14 Although oscillation is impossible due to the entrainment phenomenon, it oscillates normally without any abnormality, contributing to the reduction of Q, and also contributes to the reduction of other electrical It does not have any adverse effect on various properties.

As explained above, when the present invention is applied to a Langevin type vibrator, it effectively contributes to lowering the Q without affecting the electrical properties, so it is extremely effective in practical use.

[Brief explanation of the drawing]

Figure 1 shows an example of a bolted Langevin resonator. 1...Metal, 2...PzT resonator, 3
...Positive electrode, 4...Volt, 5.
... Vibration radiation surface. Figure 2 shows an example of conventional usage. 6...Bottom plate. Figure 3 is an example of a conventional case where Q is lowered. 7...Additional mass of metal. Figure 4 shows an embodiment of the present invention. 8... Ultrasonic transducer, 9... Front metal block, 10... Rear metal block, 11.
·····bolt.

Claims (1)

[Scope of utility model registration request] It is a Langevin type vibrator constructed by sandwiching metal blocks on both sides of an ultrasonic vibrating element, and the total length of the vibrator is 172 cm, which is the vibration wavelength, and the shape of the vibration radiation surface is square. An ultrasonic transducer characterized in that the dimensions of one side of the ultrasonic transducer are configured to be 12 mm.