JPS61113310A - Ceramic tuning fork vibrator - Google Patents

Abstract

PURPOSE:To obtain a tuning fork vibrator with a low capacitance ratio by forming an internal electrode and an outer electrode to both arms of the tuning fork vibrator made of a laminated piezoelectric material. CONSTITUTION:The arm 5 is made of a piezoelectric laminated material. The plural inner electrodes 1 are laminated to both the arms 5 at a prescribed internal in the lengthwise direction of the arms 5. Further, one end of the inner electrodes 1 is exposed to the surface of the arms 5. Then the adjacent piezoelectric material layer clipped by the internal electrodes 1 is polarized in opposite direction, and the inner electrodes 1 are connected to the outer electrodes 2 at the two different surfaces of the arms 5 at an interval of a layer. Since the coupling factor of the longitudinal effect is several times larger than that of the lateral effect through the forming above, a small capacitance ratio is obtained. Thus, the tuning fork vibrator with the low capacitance ratio is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field of the Invention) The present invention relates to a tuning fork vibrator made of laminated piezoelectric materials used in filter oscillators and the like.

(Prior Art and its Problems) FIG. 5 shows a plan view of a tuning fork using a conventionally known piezoelectric element. In the figure, 6 is a piezoelectric ceramic plate, and electrodes 7 made of Ag-Pd or the like are formed on the front and back surfaces of the plate to form a piezoelectric vibrator. The vibrator is fixed to the side surface of a tuning fork arm 5 made of a constant elastic metal such as Erinba via a conductive adhesive or the like.

The operation of the tuning fork is as follows: [When an alternating current electric field is applied from the pole IJ-do 8, the piezoelectric vibrator undergoes expansion and contraction motion due to the piezoelectric transverse effect, and the arm 5 is excited by this and vibrates in-plane in the same phase. be. Note that the arrow in Figure @5 indicates the polarization direction.

However, in a tuning fork vibrator having such a structure, the capacitance ratio of its electrical equivalent circuit is at least about 100,
Therefore, when used as a filter, the bandwidth will be relatively narrow.

(Object of the invention) The present invention provides a tuning fork with a low capacity ratio that eliminates the drawbacks of the conventional tuning fork.
Therefore, it is an object of the present invention to provide a tuning fork vibrator that has a wide bandwidth when used as a filter, and has a small resonance resistance when used as an oscillator.

(Structure of the Invention) The present invention is a U-shaped tuning fork vibrator made of a piezoelectric material,
A plurality of internal electrodes are stacked on both arm parts of the cough tuning fork vibrator at predetermined intervals in the length direction of the arm so that one end part of the internal electrode is exposed on the right end or left end surface of the arm, Adjacent piezoelectric material layers sandwiched between internal electrodes are polarized in opposite directions to each other, and every other internal electrode is connected to an external electrode at two different surface portions of the arm portion. This is a ceramic tuning fork vibrator featuring:

(Detailed explanation of the structure) The ceramic tuning fork vibrator of the present invention includes a slurry-like sheet made of a piezoelectric material with internal electrodes 1 printed on its surface, and an i
As shown in Figure 2, a dummy layer 3 with no printed L pole is molded so that internal electrodes are partially laminated and sintered. To finish the laminate into a U-shaped shape as shown in the figure, cut off the dashed line → in Figure 3 on the base of the knife.

This can also be done before sintering. After this, a layer of internal electrode 1 is placed on the front and back surfaces of the tuning fork arm section (this is connected to external electrode 2).This is done by placing a layer of internal electrode 1 on top of the exposed internal electrode 1 and covering it with an insulator 4 as shown in Fig. 4. A method of forming an outer conductive layer is also conceivable.

The fork vibrator of the present invention can use a three-component piezoelectric ceramic such as lead titanate, barium titanate, or lead zirconium titanate.

Further, it is desirable that the width of the internal electrode is less than half the width of the tuning fork arm.

FIGS. 1(a) and 1(b) show examples of oval shaped tuning forks according to the present invention. In the figure, 5 is an arm of a tuning fork made of a laminate of piezoelectric ceramic plates made of zirconate lead titanate, etc., and 1 is an internal electrode 2 is an external electrode.

The piezoelectric material layers sandwiched between the internal electrodes are arranged such that the polarization directions of each layer are opposite to each other, that is, the internal electrodes are alternately polarized in the positive direction.
They are connected in parallel to become the E and negative electrodes.

When an electric field E is applied between the inside 'N and pole 1 in parallel to the polarization direction, the piezoelectric ceramic plate sandwiched between the electrodes is displaced (elongated) in parallel to the electric field direction due to the piezoelectric longitudinal effect. On the other hand, adjacent parts within the same arm part to which no electric field is applied have the same length as before, so the parts become traversed in a state equivalent to being subjected to a bending moment in the direction of the arrow in the figure. Therefore, the tip size of the U-shaped arm is induced to be displaced in a direction that reduces the distance between the opposing arms.

For simplicity, if the bending moment generated at this time is +M, the displacement at the tip of the arm is given by the following equation.

Here, 1 is the arm length, E is the Young's modulus of the piezoelectric ceramic plate. That is, the internal electrode layer portion becomes a vibration source, and is excited by this to cause the tuning fork arm to move in-plane. (
However, the external leads of the left and right arms are connected so that they move symmetrically with respect to the center line of symmetry of the U-shape. ) The tuning fork vibrator configured in this way has a change in electrical and mechanical energy through the coupling coefficient of longitudinal vibration of 3s, which is approximately 3 times as large as the coupling coefficient of transverse effect of 1cs+. Because of its large size (PbTiO3 system has a capacitance ratio of 0 to 10 k), it is possible to achieve a smaller capacity ratio than the conventional one.

Therefore, the bandwidth expressed using the resonant and anti-resonant frequencies is wider than that of the conventional method.

Furthermore, because of its laminated structure, it is possible to achieve the same electric field at a lower voltage than a tuning fork vibrator using a conventional male plate or bimorph type piezoelectric ceramic plate. In other words, there is also the advantage that it becomes possible to drive with a low voltage.

As shown in FIG. 6, it goes without saying that a tuning fork vibrator can be obtained even if the internal electrodes are printed on the inside of the tuning fork arm.

(Example) FIGS. 1(a) and 1(b) show an example of a tuning fork according to the present invention.

First, a calcined powder of ceramics based on lead zirconate titanate is prepared and dispersed in an organic solvent together with a small amount of an organic binder and a plasticizer to form a slurry. Put this in a doctor blade container and cast it on an organic film to a thickness of 3.
A green sheet of about 0 to 100 μm is obtained. This green sheet is peeled off from the organic film and cut into appropriate sizes. An Ag--Pd paste film is printed on one side of a portion of this. As shown in FIG. 2, the desired number of sheets are stacked in the order of one dummy layer, one internal electrode layer, and one dummy layer, and are hot pressed at about 100° C. to make them adhere, and then sintered. After sintering, the #F1i four-body blotter block is cut into a tuning fork shape by removing unnecessary portions (broken line in FIG. 3) and cutting the block to a desired thickness. Here, the internal electrodes are exposed in a linear manner on the surface of the arm part of the tuning fork, so they are lined up every other layer. Apply insulation paste to the internal electrodes every other layer.1111 on the opposite side
Insulating paste is applied to the internal electrodes of I'frJ so as to be alternated with the above. A film of Ag is formed on top of this paste.

The ceramic electric machine used in the tuning fork camera obtained in this way has a high directivity coefficient of 70, a limiting capacitance of 0.1 μF, and a capacitance ratio of 10 μF. degree.

The value of this capacitance ratio was less than one-tenth of that of the conventional tuning fork.

(Effects of the Invention) As described above, according to the present invention, a tuning fork vibrator that can be driven at low voltage and has an extremely small ratio of 88 can be obtained.

[Brief explanation of drawings]

Figures 1(a) and (bl are diagrams showing an example of a ceramic tuning fork holder of the present invention, Figure 2 is a diagram showing a method of manufacturing a ceramic tuning fork vibrator, and Figure 3 is a diagram showing a process in the middle of the manufacturing process of the present invention. FIG. 4 is a schematic diagram showing the state of connection between internal and external electrodes; FIG. 5 is a diagram showing an example of a conventional tuning fork vibrator; FIGS. 6(a) and (b) are A diagram showing another example of the present invention. In the diagram, 1 is an internal electrode, 2 is an external electrode, 3 is a dummy layer, 4 is an insulating layer, 5 is an arm, 6 is a piezoelectric ceramic plate, 7 is an electrode, 8 is w,
This is Rei Reed.・Te: 2, -1 ,,',IJ,'-+ Proxy valve 7 Tsuchiuchi Hara Susumu Kame'1,・Fig. 1 (a) (b) Fig. 2 Fig. 3 Fig. 4 Fig. 5 Figure 6 Figure 2 External conduction procedure amendment form (voluntary) Showa year, month, day

Claims (2)

[Claims] (1) A U-shaped tuning fork vibrator made of piezoelectric material, in which a plurality of internal electrodes are arranged at one end of the internal electrodes at predetermined intervals in the length direction of the arms on both arms of the tuning fork vibrator. are stacked so that they are exposed on the right or left end surface of the arm, and adjacent piezoelectric material layers sandwiched between internal electrodes are polarized in opposite directions, and the internal electrodes are stacked so that they are exposed on the right or left end surface of the arm. A ceramic tuning fork vibrator characterized by having a structure in which two surface parts are connected to external electrodes. (2) The ceramic tuning fork vibrator according to claim 1, wherein the width of the internal electrode is less than half the width of the arm.