JPS5821857B2 - torsional vibration transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torsional vibration transducer, particularly to a torsional vibration transducer used in a mechanical filter.

Mechanical filters utilize the stable, high-selectivity resonance characteristics of mechanical oscillators to create a band P that has very steep selectivity characteristics.
Compared to a P-wave device consisting of an inductance and a capacitor, the P-wave device has the advantage of being smaller, more robust, more stable, and of higher performance.

In recent years, with the development of communication technology, devices have become smaller and smaller.
High performance is required, and mechanical filters are no exception.

Longitudinal vibration transducers and torsional vibration transducers are widely used in mechanical filters with frequencies of 100 KHz or higher, but torsional vibration transducers can be made smaller and have almost no effect of vibration loss due to air pressure. One example of a conventionally used transducer is shown in FIG. 1 because it is advantageous and commonly used.

In a conventional transducer as shown in Fig. 1, when a mechanical resonator 1 and terminals A and H of a rectangular piezoelectric ceramic plate 2 coupled to its surface are connected to conductive wires a and b as shown in the figure and a voltage is applied, a rectangular piezoelectric Tension acts on the porcelain plate as shown by arrows a and b in the figure.

This tension ayb is al, aT and bA, bT, respectively.
It can be decomposed into

Here, the forces aT and bT are in opposite directions, and this couple causes torsional vibration. However, the drawback of this conventional resonator is that the component forces aA and bl in the figure cause the resonator 1 This is to generate parasitic vibrations.

Moreover, since the resonant frequency of this parasitic vibration occurs very close to the resonant frequency of torsional vibration, it has an adverse effect on the resonant frequency characteristics of the torsional vibration transducer.

An object of the present invention is to propose a small and economical torsional vibration transducer with less such parasitic vibrations or spurious vibrations.

In order to achieve this object, the torsional transducer according to the present invention connects a rectangular plane portion formed in the longitudinal direction of a mechanical resonator and a piezoelectric ceramic plate to connect the mechanical resonator and the piezoelectric ceramic plate. In the torsional vibration transducer, the piezoelectric ceramic plate is arranged parallel to the length direction of the rectangular plane part in a torsional vibration transducer that applies an alternating current electric field between the piezoelectric ceramic plates to drive torsional vibration in the mechanical resonator by the vibration of the piezoelectric ceramic plates. It has a triangular shape consisting of a base and a side obliquely intersecting the length direction, and the direction of residual polarization is in the thickness direction of the piezoelectric ceramic plate, with the triangle being bordered by a line connecting the apex and a point on the base. It is characterized by being divided into two residual polarization parts that are the same but have opposite polarities.

Embodiments of the torsional vibration transducer according to the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of a torsional vibration transducer according to the present invention, in which a triangular piezoelectric ceramic plate 4 is bonded to the surface of a mechanical resonator 30 having a rectangular flat surface. An alternating current electric field is applied between the piezoelectric ceramic plates 4 and 4 through conducting wires 3a and 4a.

In FIG. 2, the details of the piezoelectric ceramic plate 4 are as shown in FIG. 3. The left and right sides of the piezoelectric ceramic plate 4 are bordered by the center, and the thickness direction is on one side, and the remanent polarizations 6a and 6b, which have opposite polarities, are on the top and bottom. It is formed between the electrodes Sat sb.

When an alternating current electric field is applied between the piezoelectric ceramic plate 4 and the mechanical resonator 3 of the torsional vibration transducer configured as shown in FIGS. Since it is polarized in the direction, the arrows α, −α,
As shown by β and -β, a tension force acts on one side of the triangular magnetic plate 4, and a compressive force acts on the other side.

When the tension force -α and the compression force β are decomposed, they are -α□, -α1 and β1, respectively, as shown in the figure. It can be decomposed into β.

Here, the direction of force applied by the car α and β forces is opposite, and this couple causes torsional vibration as shown in rotation directions 7a and 7b in the figure.

In the same figure, car α. β1 has no relation to this torsional vibration, and in FIG. 2, the tension force α and compressive force −β are similarly α, α1 and −β1. −β1, which is 3
Since the forces are related to one point at the apex of the rectangle, neither of them generates a couple.

The torsional vibration transducer 10 constructed as shown in FIGS. 2 and 3 is effective when used in a narrow band mechanical filter, and its features are listed below.

(a) The direction of residual polarization and the direction of applying the alternating current electric field match, making it easy to manufacture piezoelectric ceramic plates.

(b) Since the directions of the residual magnetic poles are opposite on the left and right sides from the center of the triangle, even-order vibrations of torsional vibration, odd-numbered vibrations of bending vibration, and odd-numbered vibrations of longitudinal vibration cannot be driven in principle, resulting in spurious A transformer with fewer is obtained.

FIG. 4 shows an example of its characteristics. In the present invention, according to experimental data, the conversion efficiency is maximum when the piezoelectric ceramic plate 4 is a right triangle with the apex angle being a right angle.

e→ Since a piezoelectric ceramic plate is bonded to the rectangular flat portion on the longitudinal surface of the mechanical resonator, it is mechanically strong.

2) Since the piezoelectric ceramic plate is bonded to the rectangular plane part of the mechanical resonator, the transducer is easy to manufacture and economical.

(E) The frequency of a torsional transducer is proportional to the reciprocal of the length of the mechanical resonator of the transducer, so the frequency is adjusted by adjusting the length of the mechanical resonator. It is easy to adjust the cage length and frequency adjustment is simple.

In the torsional vibration transducer of the present invention shown in FIG. 2, a case has been described in which the mechanical resonator forms a rectangular plane part in the length direction of the cylinder, but the invention is not limited to this. A similar effect can be obtained by using a square columnar mechanical resonator 8 as shown in FIG.

FIG. 6 shows an example of the configuration of a mechanical filter using a torsional vibration transducer according to the present invention. As shown in the figure, the torsional vibration transducer 10 or 11 according to the present invention is used as a torsional vibration resonator 12 and a connector 13.

As shown in FIG. 6, the connector 13 is the transformer 10 or 1
1. Since it can be directly coupled to the resonance 12 by welding or the like, a compact and economical mechanical filter can be realized.

Although the torsional vibration transducer according to the present invention has been described in detail above, the most distinctive feature of the present invention is that the structure of the piezoelectric ceramic plate is formed as shown in FIG. This is because only the vibrations are extracted, and the effect is extremely significant when it comes to configuring a mechanical filter.

In the embodiments according to the present invention, the case where the shape of the piezoelectric ceramic plate is triangular is explained, but the shape is not necessarily limited to this, and the present invention can be applied as long as the shape has sides oblique to the base. It can be easily understood from the above explanation that the invention has various effects.

[Brief explanation of the drawing]

FIG. 1 shows an example of a conventional torsional vibration transducer, FIG. 2 shows an embodiment of a torsional vibration transducer according to the present invention, and FIG.
Detailed view of the piezoelectric ceramic plate in the embodiment shown in the figure, FIG.
An example of the frequency characteristics of the torsional vibration transducer shown in the figure, FIG. 5 is another embodiment of the torsional vibration transducer according to the present invention, and FIG. An example of a constructed mechanical filter is shown. In the figure, 4 is a piezoelectric ceramic plate.

Claims (1)

[Claims] 1. A rectangular plane portion formed in the length direction of a mechanical resonator and a piezoelectric ceramic plate are joined together, and an alternating current electric field is applied between the mechanical resonator and the piezoelectric ceramic plate. In the torsional vibration transducer that drives torsional vibration in the mechanical resonator by vibration of the piezoelectric ceramic plate, the piezoelectric ceramic plate has a base parallel to the length direction of the rectangular plane portion and a base that intersects obliquely with the length direction. Two residual polarizations having a triangular shape consisting of sides, and with a line connecting the apex of the triangle and a point on the base as the boundary, the direction of residual polarization is the same as the thickness direction of the piezoelectric ceramic plate, and the polarity is opposite. A torsional vibration transducer characterized by being divided into polarized parts. 2. The piezoelectric ceramic plate has approximately right angle 2 isosceles 3 with the right angle as its apex.
2. The torsional vibration transducer according to claim 1, wherein the torsional vibration transducer is formed of a rectangular portion having residual polarizations of different polarities with a line connecting the midpoint of the apex and the base as a boundary.