JPH07108039B2 - Square plate vibrator driving method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of driving a vibrator provided with arc-shaped interdigital electrodes on a square piezoelectric plate, and more specifically, oblique symmetry-oblique symmetry (AA). ) It relates to a method for driving a square plate vibrator that efficiently vibrates in a mode.

(Prior Art) Conventionally, a vibrator having a comb-shaped electrode provided on one surface of a rectangular piezoelectric plate has been considered and used as a bandpass filter. Further, when it is used as this band pass filter, it is said that the piezoelectric plate is preferably square.

(Problems to be Solved by the Invention) However, in a square plate oscillator, a number of modes exist simultaneously, and it is difficult to operate in a single mode as compared with the case of a rectangular plate, and there is a problem that efficiency is poor. is there.

The present invention aims to solve the above problems.

(Means and Actions for Solving Problems) The present invention performs a vibration mode analysis of a square piezoelectric plate having arched interdigital transducers, and a square plate oscillator (in-plane oscillator) that vibrates most efficiently in the AA mode. ) To realize the driving method.

From this point of view, the present invention is configured as follows.

That is, according to the present invention, on one surface of a square piezoelectric plate in an unpolarized state, the square piezoelectric plates are arranged in concentric circles centered on the intersections of the diagonals of the square piezoelectric plates and are alternately combined and vibrate in each diagonal direction. Four sets of arch-shaped interdigital electrodes, which are comb-shaped electrodes in the propagation direction, are provided, and DC voltage is increased so that each electrode terminal, which is a common terminal of each arch-shaped interdigital electrode, becomes positive or negative sequentially and alternately in the circumferential direction. A vibrator that is polarized by applying a voltage for a predetermined time, and positively connects two sets of arched interdigital electrodes facing each other with respect to the center of a square piezoelectric plate for an AC signal, and A characteristic is a square plate vibrator driving method in which two sets of opposing arch-shaped interdigital electrodes are connected in reverse and driven in an oblique symmetry-oblique symmetry mode.

(Example) Hereinafter, one example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, on one surface of a thin piezoelectric plate 10 having a square shape, comb electrodes arranged in concentric circles centered on an intersection of square diagonal lines are alternately combined, and each diagonal direction is a vibration propagation direction. 4 sets of arched interdigital transducers 9a-9d
Is provided. These arch-shaped interdigital electrodes are attached to the unpolarized piezoelectric plate 10 by vacuum-depositing a metal such as aluminum. The piezoelectric plate 10 applies a high DC voltage to the electrode terminals 1-8 of the arched interdigital transducers 9a-9d for a predetermined time (electrode terminals 1, 3, 5, 7 are positive, 2, 4, 6, 8 are negative). Then, the arcuate interdigital electrodes 9a to 9d are polarized in a direction perpendicular to the arched electrode fingers. As a result, the four sets of arched interdigital transducers 9a to 9d function as vibrators that expand and contract in the polarization axis direction. in this case,
The vibration mode of the square piezoelectric plate 10 is selected by the combination of the connection of the electrode terminals during driving. In particular, when an AC signal is applied with the same polarity as when polarized, the four sets of arched interdigital transducers 9a-9d expand and contract with the same polarity, but the reversely connected interdigital transducers 9a-9d operate with opposite polarities. To do.
That is, the electrode terminals 1 and 2 and the electrode terminals 5 and 6 are positively connected, and the electrode terminals
When driving by connecting 3 and 4 and electrode terminals 7 and 8 in reverse,
At the moment when the displacement of the arch-shaped interdigital electrode 9d composed of 1, 2 and the arch-shaped interdigital electrode 9b composed of the electrode terminals 5 and 6 extends, the arch-shaped interdigital electrode 9a composed of the electrode terminals 3 and 4 and the electrode terminal 7 The arch-shaped interdigital transducer electrode 9c composed of 8 and 8 contracts. That is, it can be understood that the connection makes the most efficient vibration in the oblique symmetry-oblique symmetry (AA) mode, which is a symmetric vibration mode. This is also clear from the characteristics shown in FIG. 3 described later.

2 (a) to (c) classify vibration modes based on the symmetry of displacement. The same figure (a) has symmetry-symmetry (S which has two symmetry axes (the said symmetry axis is shown by the dotted straight line in the figure).
S) mode, the same figure (b) shows a symmetrical-oblique symmetrical (SA) mode having one axis of symmetry, and the same figure (c) shows an oblique symmetrical-oblique symmetrical (AA) mode without a symmetrical axis. Is. Here, in order to realize the SS mode oscillator, the four corners need to expand and contract at the same time, so the electrode terminals may be connected to the same polarity as that at the time of polarization. Further, the SA mode and the AA mode can be realized by connecting the electrode terminals so that a part of the polarities is inverted, as shown in an experimental example described later.

Next, examples will be described. The pitch of the arched interdigital transducers 9a to 9d shown in FIG. 1 is 0.4 mm (gap 0.25 mm).
The logarithm is 6, and a high DC voltage of 2 kV / mm was applied to this for 3 hours for polarization treatment. Piezoelectric plate 10 made by TDK Corporation 1
01A material (19 × 19 × 0.23 mm) was used. FIG. 3 is a diagram showing the frequency characteristics (phase change amount) of the electrode terminal corresponding to each mode of FIG. 2 obtained by using the vibrator thus formed. In the figure, the black electrode terminals of the schematically drawn vibrator are positive, and the other electrode terminals are negative.

As can be seen from FIG. 3, in the figure (a), the SS mode of SS4 vibrates more efficiently than other AA1, SA1 and SA2.
In the same figure (b), SA1, SA2, and SA3 vibrate most efficiently than other SS4 in SA mode. In the figure (c), AA1 and AA4
It vibrates most efficiently in AA mode than other SS4. In this case, the type (c) AA mode oscillator is most effective, and FIG. 4 is a diagram showing frequency characteristics of its impedance. The resonance frequencies of AA1, SS4, AA4 are 65.51, 145.5 respectively.
At 5,147.58kHz, high-order AA mode resonance is also observed at 256.02kHz.

As described above, we performed a mode analysis of a square plate oscillator with arched interdigital electrodes, and combined the vibration polarities of four sets of arched interdigital electrodes to realize a square plate oscillator that efficiently vibrates in AA mode. I do.

(Effects of the Invention) As described above, according to the present invention, the vibration polarities of the four sets of arched interdigital transducers are combined to obtain the oblique symmetry-
A method of driving a square plate oscillator that efficiently vibrates in the oblique symmetry (AA) mode can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a vibration mode of this embodiment, FIG. 3 is a diagram showing frequency characteristics of this embodiment, and FIG. 4 is a diagram showing this embodiment. It is a figure which shows the frequency characteristic of impedance. 1 to 8 ... Electrode terminals, 9a to 9d ... Arch-shaped interdigital electrodes, 10 ... Piezoelectric plate.

Claims (1)

[Claims] 1. A surface of an unpolarized square piezoelectric plate,
Four sets of arched interdigital electrodes are provided which are arranged in concentric circles centering on the intersections of the diagonal lines of the square piezoelectric plate and are alternately combined, and which are comb-shaped electrodes whose vibration propagation direction is in each diagonal direction. A vibrator that is polarized by applying a DC high voltage for a predetermined time so that it becomes positive or negative sequentially and alternately in the circumferential direction to each electrode terminal that is a common terminal of the arched interdigital transducer, For signals, two sets of arch-shaped interdigital electrodes facing each other with respect to the center of the square piezoelectric plate are positively connected, and two sets of the other interdigitated interdigital electrodes facing each other are reversely connected to each other to obtain a diagonal symmetry- A square plate vibrator driving method characterized by driving in a diagonally symmetric mode.