JPH0233395Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a piezoelectric filter in which an elongated vibrating piece and a coupling piece for coupling the vibrating pieces are integrally formed with a piezoelectric plate.

An example of a conventional piezoelectric filter using an elongated vibrating element is shown in plan view in FIG. An input conductor pattern and an output conductor pattern are provided on one side of a flat insulating frame 1 provided with a punched portion 2, and a grounding conductor pattern 3 is provided on the other side. Two strip-shaped vibrating pieces 4 made of piezoelectric ceramic are placed side by side, and one electrode of each vibrating piece 4 is connected to an input conductor pattern and an output conductor pattern by a lead wire 5. The other electrodes 6 of 4 are fixed to each other and connected to a connector wire 7 which crosses the punched portion 2 and is connected to the grounding conductor pattern 3. The input conductor pattern and the output conductor pattern are provided on the back surface of the frame 1 in FIG. Further, the vibrating piece 4 is of a two-terminal type, and electrodes 6 are provided on the front and back surfaces to perform stretching vibration in the length direction. Further, the coupler wire 7 serves to fix the vibrating piece 4 and transmit its vibration. Since such a piezoelectric filter connects the vibrating piece 4, connector wire 7, and lead wire 5 made of different materials, there are inconveniences in connection work and in making each part separately.

FIG. 2 is a plan view of a piezoelectric filter in which a vibrating piece 9 is formed by punching out an H-shaped metal plate of Elinvar, which is a constant elastic member, and fixing piezoelectric ceramics 8 to both ends. In this way, the vibration transmitting portion 10 and the vibrating piece 9 are formed as one unit, so there is no need for the connection work as in the piezoelectric filter shown in FIG. It is still necessary to make them separately and fix them both together. In addition, the length direction of the vibrating elements of the piezoelectric filters shown in Figures 1 and 2 is approximately determined by the resonant frequency and material, and the spacing between the vibrating elements is determined by the passband width, etc., so the piezoelectric filter can be made smaller in plan view. In this case, the width W of the vibrating element was narrowed. However, if the width W is made narrower, the interelectrode capacitance becomes smaller, and the input impedance and output impedance become larger, making them more susceptible to the influence of external capacitance, so there is a natural limit to this.

The present invention solves various conventional technical problems and provides a piezoelectric filter that can be downsized and easily manufactured.

In the piezoelectric filter of the present invention, a plurality of elongated rectangular vibrating pieces and a coupling piece that connects the vibrating pieces are integrally formed of a piezoelectric plate, and inside the endmost vibrating piece extends to the coupling plate. a first electrode exposed on the side surface of the connector piece; and a second electrode located parallel to at least one above and below the first electrode; The second electrode of the vibrating piece is exposed on the surface of the vibrating piece as an input/output terminal, and the first electrode exposed on the side surface of the coupling piece is used as a grounding terminal. do.

Embodiments of the piezoelectric filter of the present invention will be described below with reference to FIGS. 3 to 6. Fig. 3 is a perspective view of the piezoelectric filter, Fig. 4 is a sectional view taken along line A-A' in Fig. 3, Fig. 5 is a wiring diagram equivalent to Fig. 3, and Fig. 6 is a piezoelectric filter shown in Fig. 3. It is a perspective view for explaining an example of the manufacturing method of a filter.

The piezoelectric filter 20 is made of an H-shaped piezoelectric ceramic plate, and includes two vibrating pieces 21 and 22 and a coupling piece 23. Two first electrodes 24 are formed inside the elongated rectangular vibrating pieces 21 and 22, extending in common to the connector piece 23 and exposed on the side surface of the connector piece 23. Furthermore, vibrating piece 2
1, two second electrodes 25 are formed parallel to the first electrode 24 above and below it. Further, another second electrode 26 is formed on the vibrating piece 22 in the same manner as the second electrode 25. The ends of the second electrodes 25 and 26 are exposed on the side surface of the vibrating piece opposite to the connector piece 23. and a first electrode 24,
The exposed ends of the second electrodes 25 and 26 are connected in common, the first electrode 24 has a ground terminal 27, and the second electrodes 25 and 26 have input/output terminals 28 and 29, respectively. It is formed.

The piezoelectric filter 20 is preferably made by stacking a plurality of green sheets 30 of piezoelectric ceramic with the dotted line portions aligned, as shown in FIG. 6, and then punching out the dotted line portions and firing them as a single piezoelectric plate. Although no electrodes are formed on the first green sheet 30 from the top,
Second electrodes 25 and 26 are formed on the surface of the second green sheet 30 by screen printing. On the third green sheet 30, an H-shaped first electrode 24 is formed at the same position on the front and back sides by screen printing. There are 3 green sheets corresponding to the 2nd and 1st green sheets 30.
The green sheets 30 are stacked symmetrically under the green sheet 30, but are not shown. After firing,
The piezoelectric filter 20 is completed by applying conductive paint to the exposed portion of each electrode, forming the grounding terminal 27 and input/output terminals 28 and 29 at positions that do not inhibit vibration, and polarizing them. Polarization is performed in the direction in which the electrodes are stacked, and the vibrating pieces 21 and 22 extend and contract in the longitudinal direction. Such a piezoelectric filter 20 is held within a case, and input and output of signals is performed by, for example, external terminals that elastically contact each terminal.

The piezoelectric filter 20 is equivalently constructed as shown in FIG. 5, and the vibrating pieces 21 and 22 each consist of two vibrators 31 connected in parallel. The inter-electrode capacitance can be doubled if the facing area of the electrodes and the distance between the electrodes are the same as those of a conventional vibrating element. Of course, if the electrodes are stacked by the method shown in FIG. 6, the distance between the electrodes can be made very narrow, and the capacitance between the electrodes can be dramatically increased. Therefore, the width of the vibrating pieces 21 and 22 and the piezoelectric filter 2
The overall shape of 0 becomes smaller. Moreover, the second electrode 25,
No. 26 was laminated one each on the top and bottom of the first electrode, but
There may be a plurality of them, or they may be stacked one above the other.

FIG. 7 is a plan view showing another embodiment of the piezoelectric filter of the present invention.

The piezoelectric filter 40 has three elongated rectangular vibrating pieces 4.
1, 42, 43 and the connector piece 44 are integrally formed from a piezoelectric ceramic plate. Input/output terminals 45 and 46 are formed on the endmost vibrating pieces 41 and 43, and a grounding terminal 47 is formed on the connector piece 44. The vibrating piece 42 is located at the center of the coupling piece 44 and resonates. A first electrode and a second electrode are laminated on each vibrating piece or coupling piece 44 in a similar relationship to that of the piezoelectric filter 20, but the second electrode of the vibrating piece 42 is exposed on its side surface. do not have to. Note that the vibrating piece 42 does not have the role of a transducer like the vibrating pieces 41 and 43, so the first
The electrode and the second electrode may not be provided. However, only the first electrode that connects the vibrating pieces 41 and 43 must be provided inside.

FIG. 8 is a perspective view showing still another embodiment of the piezoelectric filter of the present invention.

This piezoelectric filter 50 has a coupling piece 51 curved in a U-shape in a vertical plane, and input/output terminals 54 and 55 of vibrating pieces 52 and 53 are formed on the lower surface thereof. The piezoelectric filter 20 shown in FIG. 3 is just curved at the connector piece 23. Since the piezoelectric filter 50 can be configured three-dimensionally, the interval between the vibrating pieces 52 and 53 can be narrowed, and the piezoelectric filter 50 can be made smaller in plan view. 56 is a grounding terminal. When trying to obtain a desired bandwidth by adjusting the coupling between the vibrating pieces 52 and 53 by mechanically cutting the width of the coupler piece 51 to narrow it, a three-dimensional configuration is convenient for work. It's easy.

As described above, in the piezoelectric filter of the present invention, the vibrating piece and the coupling piece are integrally formed of a piezoelectric plate, and electrodes are laminated inside. Therefore, there is no need to connect the vibrating piece and the coupling piece, and manufacturing is easy. Further, as described above, since the capacitance between the electrodes can be freely adjusted, the size can be easily reduced. Of course, the electromechanical conversion efficiency is also improved. In the embodiment, the end of each electrode is exposed only on the surface forming the input/output terminal and the ground terminal, but it may be exposed on other surfaces. However, in order to maintain insulation between the electrodes, it is better to have as little exposed portion as possible. Therefore, even on the same surface, the ends of the electrodes may be exposed only in the portions forming the terminals. Furthermore, although the case where each vibrating piece vibrates by stretching and contracting in the length direction has been described, it may be in another vibration mode such as bending vibration. Further, there may be a plurality of coupling pieces depending on the vibration mode. In this way, the present invention can provide a highly practical piezoelectric filter.

[Brief explanation of the drawing]

Figures 1 and 2: Plan view of a conventional piezoelectric filter,
Figure 3: A perspective view showing an embodiment of the piezoelectric filter of the present invention, Figure 4: A sectional view taken along line AA' in Figure 3, Figure 5:
A wiring diagram equivalently representing the piezoelectric filter in Fig. 3, Fig. 6
Figures: A perspective view for explaining the manufacturing method of the piezoelectric filter of Figure 3, Figure 7: A plan view showing another embodiment of the piezoelectric filter of the present invention, Figure 8: Piezoelectric filter of the present invention FIG. 7 is a perspective view showing yet another embodiment of the invention. 1: Frame body, 2: Punching part, 3: Grounding conductor pattern, 4, 9, 21, 22, 40, 42, 4
3, 52, 53: vibrating piece, 5: lead wire, 6: electrode, 7: coupling wire, 8: piezoelectric ceramic, 20,
40, 50: Piezoelectric filter, 23, 44, 51: Coupler piece, 24: First electrode, 25, 26: Second electrode, 27, 47, 56: Earth terminal, 28,
29, 45, 46, 54, 55: input/output terminals,
30: green sheet, 31: vibrator.

Claims (1)

[Scope of utility model registration request] A plurality of elongated rectangular vibrating pieces and a coupler piece that connects the vibrating pieces are integrally formed of a piezoelectric plate, and inside the endmost vibrating piece extends to the coupler piece, A first electrode exposed on the side surface and a second electrode located parallel to at least one above and below the first electrode are formed, and a second electrode of the most end vibrating element is formed. A piezoelectric filter characterized in that a first electrode exposed on the surface of the vibrating element is used as an input/output terminal, and a first electrode exposed on the side surface of the coupling element is used as a grounding terminal.