JPS603246B2 - piezoelectric vibrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric vibrator, and particularly to a piezoelectric vibrator that utilizes spreading vibration.

FIGS. 1 to 3 are illustrative views showing different examples of conventional square plate type vibrators using spreading vibration, which are the background of the present invention.

Such a piezoelectric vibrator 1 has an electrode 12 formed on one main surface of a pressure plate 11 such as PZT, and an electrode 13 formed on the other main surface. The vibrator 1 shown in FIG. 2 shows an example in which the electrode 14 formed on the other main surface of the piezoelectric plate 11 is a partial electrode. What is shown in FIG. 3 is a so-called terminal type vibrator in which the electrode 15 formed on the other main surface of the piezoelectric plate 11 is a dot electrode, and the electrode 16 is a ring electrode. The principles of operation of these piezoelectric vibrators are already well known, and their explanation will be omitted here. FIG. 4 is a graph showing the frequency characteristics of the vibrator shown in FIG. 3, which is used in an intermediate frequency circuit of an AM band radio receiver, for example, as an example of a conventional square plate type pressure-turtle vibrator that utilizes spreading vibration. .

As can be seen from this graph, in the conventional device, spurious waves such as the third harmonic or the fifth harmonic of the fundamental vibration frequency are extremely large, which has been a problem. For example, third harmonics are generated as shown in FIG.
That is, it is generated when a standing wave with a frequency three times that of the fundamental vibration is placed in the direction in which the piezoelectric plate 11 spreads.
Therefore, as a method of suppressing such spurious noise, the fly poles are replaced with partial light poles 12a, 12a,
13a, it is known to take measures to prevent such standing waves from appearing. In other words, if partial electrodes 12a and 13a are used as shown in FIG. 6, the surface charge in the shaded area in the surface charge distribution in FIG. S is canceled out, and the oscillation of the third harmonic is suppressed. . By appropriately changing the dimensions and shape of the partial electrodes,
It is also possible to suppress fifth-order harmonics, seventh-order harmonics, contour vibration spurious, etc. However, with this method, only a single targeted spurious (for example, only the third harmonic) is suppressed, and many spurious cannot be suppressed at the same time. Furthermore, due to other characteristic requirements, it may not be possible to arrange the electrodes in consideration only of spurious suppression. Therefore, a primary objective of the present invention is to provide an improved piezoelectric vibrator that utilizes spreading vibrations and is effective against all spurious components.

To summarize, this invention has a piezoelectric plate of a piezoelectric vibrator having a rhombus shape, and one of the angles formed by the two sides of the rhombus is 750 to 89 degrees.
The piezoelectric vibrator was selected to FIG. 7, FIG. 8, and FIG. 9 are plan views showing different embodiments of the present invention, and simply show the shape of the piezoelectric plate.

7 corresponds to FIG. 1, FIG. 8 corresponds to FIG. 2, and FIG. 9 corresponds to FIG. 3. In this invention, the shape of the main surface of the piezoelectric plate is not square as in the prior art, but is rhombic. Then, 1 of the angle formed by the two sides of the rhombus
Select angle 0 from 75o to 89o. FIG. 10 is a graph in which the angle 8 is taken as the axis and the ratio between the anti-resonant resistance and the resonant resistance is taken as the vertical axis. Line A in this figure 10
indicates the fundamental vibration frequency, for example, 455 kHz. Then, line B is the third harmonic, for example 1. Shows Ogawa z,
Line C is its fifth harmonic, for example 2. Indicates Hz, line D
indicates a contour vibration of, for example, 650 kHz, and line E indicates a bending vibration of, for example, 300 kHz. As can be seen from Fig. 10, the shape of the piezoelectric plate is rhombus, and the angle between the two sides is 1
It can be seen that almost all spurious vibrations can be effectively suppressed by setting the angle of 8 to approximately 750 to 890. FIG. 11 shows the frequency characteristics when the present invention is applied to, for example, the three-terminal pressure box vibrator shown in FIG. 9, and the angle 8 is set to, for example, 87.5 degrees. Looking at FIG. 1, it can be seen that the present invention can suppress all harmonics more effectively than the conventional one (FIG. 4). The same is true for contour vibration (Figure 10), and what kind of electrode structure (
For example, FIG. 7, FIG. 8, or FIG. 9) has the same effect of suppressing spurious vibrations. Furthermore, as can be seen in Fig. 10, there is also an effect of suppressing spurious vibrations when the angle 0 is less than 750, but
If this angle 8 is too small, the workability will become poor.
The structure to be incorporated into the case becomes complicated.

At the same time, a resonance splitting phenomenon occurs, which is not preferable. Therefore, in this invention, the angle 8 was selected from 750 to 890. Note that the present invention can be used in a resonator, a three-terminal filter, a ladder type filter, and the like.

As described above, according to the present invention, the shape of the main surface of the piezoelectric plate is rhombus, and one of the angles a formed by the two sides of the rhombus is
By selecting 750 and 890, all harmonics can be effectively suppressed.

It should be noted that the electrode structure formed on the pressure slope may have any other shape other than the shapes shown in FIGS. 7 to 9 of the embodiment, and the point is that The shape of the main surface of the indentation plate is selected as described above. Traditionally,
The reason why such a piezoelectric vibrator has a square shape is that vibration occurs more easily when the piezoelectric vibrator is symmetrical when viewed from the vibration mode point and the material is uniform. Therefore, if the outer shape and dimensions of the pressure fin plate are changed as in this invention, it will also affect the fundamental vibration and spurious, but in any case, for the fundamental vibration, the minimum dimension on which the wavelength can ride is It is fine if there is one, and changing the external shape or dimensions does not have much effect on the fundamental vibration. On the other hand, spurious vibrations such as third-order harmonics and fifth-order harmonics naturally have shorter wavelengths than fundamental vibrations, and the effects of changing the shape and dimensions appear more strongly than on fundamental vibrations. A feature of the present invention is that the optimum external dimensions are selected based on the balance between the basic vibration and the spurious vibration.

[Brief explanation of drawings]

1 to 3 are illustrative views showing different examples of conventional square piezoelectric vibrators using spreading vibration, which are the background of the present invention. FIG. 4 is a graph showing an example of frequency characteristics when the three-terminal piezoelectric vibrator shown in FIG. 3 is used in an AM band intermediate frequency circuit. FIG. 5 is a diagram showing an example of third harmonics. FIG. 6 is a diagram showing an example for suppressing the third harmonic. 7 to 9 are planar illustrative views showing different embodiments of the present invention, respectively. FIG. 10 is a graph showing the characteristics of antiresonance resistance/resonance resistance at an angle of 8'. For example, FIG. 11 shows the embodiment of FIG.
12 is a graph showing frequency characteristics when used in an intermediate frequency circuit of a semiconductor. In the figure, 1 is a Shoelectric vibrator, 11' is a piezoelectric plate, 13' is a full-surface electrode, 14' is a partial electrode, and 15' is a piezoelectric plate.
indicates a dot electrode, and 16' indicates a ring electrode. Hair' figure, 2 figures, fishing figure, 5 figures, 7 figures, 8 figures? Illustration of Atsun o Zuko

Claims (1)

[Claims] 1 A piezoelectric vibrator that utilizes the spreading vibration of a piezoelectric plate whose main surface has a rhombic shape, characterized in that one of the angles formed by the two sides of the rhombus is 75° to 89°. , piezoelectric vibrator.