JPH0260088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric filter in which a plurality of three-terminal piezoelectric vibrating elements are C-coupled, and a capacitor and a piezoelectric vibrating element are integrally formed of a piezoelectric body.

FIG. 1 is an explanatory diagram of a conventional piezoelectric filter in which a plurality of three-terminal piezoelectric vibrating elements are C-coupled. A piezoelectric vibrating element 4 is formed in which a dot electrode 2 and a ring electrode 3 surrounding the dot electrode 2 are provided concentrically on the main surface of a rectangular piezoelectric plate 1, and a whole surface electrode is provided on the other main surface to perform spreading vibration. 2 through capacitor C
The input/output terminals 5 and 6 are connected to the dot electrode 2, and the entire surface electrode is grounded. Then, the pass band is adjusted by changing the capacitance value of the capacitor C. However, in this type of piezoelectric filter, the size and shape of the piezoelectric vibrating element 4 are determined by the frequency, so there is little freedom in the interelectrode capacitance, and the interelectrode capacitance becomes small, making it susceptible to external capacitance. In addition, the connection of input/output terminals, etc. to the electrodes and the connection between the electrodes are made by elastically bringing a metal piece into point contact with the electrode, and a capacitor for external connection is also required, which increases the number of parts and makes assembly difficult. It's also a hassle.

The present invention aims to improve the drawbacks of such conventional piezoelectric filters.

In the piezoelectric filter of the present invention, a plurality of elongated vibrating pieces and a connecting part that connects the vibrating pieces are formed into one piece by a piezoelectric material, and inside the vibrating pieces there is a first tube extending over almost the entire surface of the vibrating pieces. One or more sets of electrodes are laminated, including a set of electrodes and second and third electrodes that face the first electrode via a piezoelectric material and extend in the length direction of the vibrating piece, Adjacent vibrating pieces are electrically C-coupled by extending at least one second and third electrode to the coupling part, and the second and third electrodes of the vibrating pieces at both ends are electrically C-coupled. Input/output terminals are formed by exposing the ends of the electrodes on one side of each vibrating piece and making a common connection, and by exposing the first electrodes of each vibrating piece near the joint and making a common connection, a grounding terminal is formed. The second electrode and the third electrode, which are not connected to the input/output terminal and are not connected to the input/output terminal, are exposed in the vicinity of the joint and are commonly connected to each other.

Embodiments of the piezoelectric filter of the present invention will be described below with reference to FIGS. 2 to 5. Fig. 2 is a perspective view of a piezoelectric filter, Fig. 3 is an enlarged sectional view taken along line A-A' in Fig. 2, Fig. 4 is a perspective view for explaining an example of a manufacturing method, and Fig. 5 is a piezoelectric filter. FIG. 3 is a plan view showing the external connection state of the device.

The piezoelectric filter 10 has two vibrating pieces 11 and 12, and a coupling part 13 formed into an H shape by a piezoelectric ceramic plate.
The body is formed. Long and thin rectangular vibrating piece 11,1
2, there are a first electrode 14 that extends over almost the entire surface in a plane, and a second electrode 15 that faces the first electrode 14 via a piezoelectric ceramic and extends in its length direction. , a third electrode 16 is provided.

The second electrode 15 and the third electrode 16 are on the same horizontal plane and are arranged in parallel. Further, the corresponding electrodes of the vibrating piece 11 and the vibrating piece 12 are on the same horizontal plane. In the embodiment, these three electrodes constitute one set, and four sets of electrodes are stacked on each of the vibrating pieces 11 and 12. Further, by extending the third electrode 16 of the third set from the top of the vibrating element 11 and the second electrode 15 of the second set from the top of the vibrating element 12 to the coupling part 13 and facing them, a parallel plate capacitor is formed. 17 is formed. The end of the third electrode 16 is exposed on the outer end surface 18 of the vibrating element 12, and is connected in common to form an input/output terminal 19. Vibration piece 11
The ends of the second electrodes 15 are exposed on the outer end surfaces of the electrodes, and similarly connected in common to form input/output terminals 20.

The ends of the first electrode 14 and the third electrode 16 are exposed on the side surface of the vibrating element 11 on the coupling part 13 side, and the first electrode 14 is also exposed on the end of the side surface 21 of the coupling part 13. ing. The first electrodes 14 are commonly connected at the end portions of the side surfaces 21 of the coupling portions 13 that are not exposed to the third electrodes 16, and the commonly connected portions form the grounding terminals 22. Only the third electrode 16 is exposed at a position corresponding to the grounding terminal 22 on the side opposite to the side 21 and is commonly connected. The first electrode 14 and the second electrode 15 of the vibrating element 12 are also exposed on the side surface on the coupling part 13 side, and the first electrode 1
4 are commonly connected at the end portion of the side surface 21 opposite to the grounding terminal 22, and that portion forms the grounding terminal. The second electrodes 15 are commonly connected at the end portions of the sides opposite to the side faces 21.

As shown in FIG. 4, the piezoelectric filter 10 is constructed by stacking a plurality of piezoelectric ceramic green sheets 30 by aligning their H-shaped outlines, which are mainly represented by dotted lines, and then stacking them.
It is best to punch out the shaped part and fire it as a piezoelectric plate.

A second electrode 15 and a third electrode 16 are formed on the first, third and fifth green sheets 30 from the top, and a first electrode 14 is formed on the second and fourth green sheets 30. It has been done. Second electrodes 15 and 5 on the right side of the third photo
The third electrode 16 on the left side of the second sheet extends to the central portion 31 that will later become the coupling portion 13. First electrode 14
When the green sheets 30 are stacked, the removed portion 32 is removed so that the first electrode 14 of this portion is not exposed to the outside, and the second electrode 15 and the third electrode that are not connected to the input/output terminals 19 and 20 are removed. The purpose is to expose the electrodes 16 and connect them in common. Further, in the removed portion 33 of the second electrode 15 and the removed portion 34 of the third electrode 16, only the first electrode 14 is exposed at these portions, so that the grounding terminal 22 can be formed. 1st, 2nd, 3rd and 4 from the top
The third electrodes later constitute the top and second set of electrodes in FIG. 3, respectively, and the fifth electrode likewise forms part of the third set of electrodes. In order to construct the four sets of electrodes shown in FIG. 3, it is necessary to stack more green sheets in the same manner as in FIG. 4, but they are not shown. Each electrode in FIG. 4 is formed by screen printing. After firing, a conductive paint is applied to the exposed portions of each electrode to connect them in common, and the input/output terminals 19 and 20 and the ground terminal 22 are formed at positions that do not inhibit vibration and are polarized to form the piezoelectric filter 10. is completed. Polarization is performed in the direction in which the electrodes are stacked, and the vibrating pieces 11 and 12 vibrate by stretching and contracting in the length direction. The coupling portion 13 is located at a vibration node.

The piezoelectric filter 10 as described above is held in a case 35 as shown in the plan view of FIG. 5, and input and output of signals is performed by, for example, external terminals 36 that come into elastic contact with each other. 37 is an external terminal for grounding. 3
8 and 39 are common connection portions of the second electrode 15 and the third electrode 16, which are not connected to the input/output terminals 19 and 20, respectively. The piezoelectric filter 10 is equivalently the sixth
The vibrating pieces 11 and 12 each constitute a three-terminal piezoelectric vibrating element consisting of four vibrators 40 connected in parallel. The inter-electrode capacitance is four times that of one vibrator 40, and if the electrodes are stacked by the method shown in FIG. 4, the distance between opposing electrodes can be made very narrow, so the inter-electrode capacitance can be dramatically increased. Also, vibrating piece 11
The capacitor C-coupling the vibrating element 12 and the capacitor is formed in the coupling part 13 as a parallel plate capacitor 17, and there is no need for lead wires connecting the capacitor or metal pieces that contact the electrodes, and everything except the external terminals is formed in one piece. has been done. Therefore, the number of parts is reduced and manufacturing becomes easier.

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

The piezoelectric filter 50 has three elongated rectangular vibrating pieces 5.
1, 52, 53 and the connecting portion 54 are integrally formed from a piezoelectric ceramic plate. vibrating piece 51,
52 and 53 are constructed in the same manner as the vibrating piece 11 and the vibrating piece 12, and are C-coupled by a parallel plate capacitor formed in the coupling part 54. 55 and 59 are input/output terminals, 56 is a grounding terminal, 57 is a common connection portion of the third electrode, and 58 is a common connection portion of the second electrode. In this way, two or more vibrating pieces can be formed into one body.

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

This piezoelectric filter 60 has a coupling portion 61 curved in a U-shape in a vertical plane, and input/output terminals 64 and 65 of vibrating pieces 62 and 63 are formed on the lower surface thereof. Just connect the piezoelectric filter 10 in FIG.
It has a curved shape at part 3. Piezoelectric filter 6
0 can be configured three-dimensionally, so it is possible to narrow the interval between the vibrating pieces 62 and 63, and it becomes smaller in plan. 66 is a ground terminal.

As described above, in the piezoelectric filter of the present invention, the vibrating piece and the coupling part are formed as one piece from a piezoelectric material, and each vibrating piece has three terminal type vibrators formed inside that are connected in parallel. It constitutes one terminal type piezoelectric vibrating element. The respective vibrating pieces are C-coupled at the coupling portion, and are formed as one piece except for the external terminals. Furthermore, as described above, the capacitance between the electrodes can be adjusted freely, and the degree of freedom in the capacitance between the electrodes is increased, so that the size can be reduced.

In the example, the C-coupling between the vibrating pieces is performed by one parallel plate capacitor, but a plurality of second parallel plate capacitors are used.
This may be performed using a plurality of parallel plate capacitors formed by extending the electrode or the third electrode. Also, the second terminal that is not connected to the ground terminal or input/output terminal
Although the location of the common connection portion of the third electrode and the third electrode is not limited to the embodiment, it is preferable to provide the common connection portion at the end of the coupling portion or at the vibrating piece near the end in view of not inhibiting vibration. Further, in the embodiment, the ends of the electrodes are exposed in areas other than the terminals and the common connection portion, but they may be exposed only at necessary locations in order to maintain good insulation between the electrodes.

In this manner, the present invention can provide a piezoelectric filter formed by C-coupling a plurality of three-terminal piezoelectric vibrating elements.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional piezoelectric filter, Fig. 2 is a perspective view showing an embodiment of the piezoelectric filter of the present invention, and Fig. 3 is an explanatory diagram of a conventional piezoelectric filter.
The figure is an enlarged sectional view taken along the line A-A' in FIG. 2, FIG. 4 is a perspective view for explaining one example of the method for manufacturing a piezoelectric filter of the present invention, and FIG. 5 is a piezoelectric filter showing the external connection state. 6 is a wiring diagram, FIG. 7 is a plan view showing another embodiment of the piezoelectric filter of the present invention, and FIG. 8 is a plan view of another embodiment of the piezoelectric filter of the present invention. FIG. 1: piezoelectric plate, 2: dot electrode, 3: ring electrode, 4: piezoelectric vibration element, 5, 6, 19, 20, 5
5, 59, 64, 65: Input/output terminal, 10, 5
0,60: piezoelectric filter, 11,12,51,5
2, 53, 62, 63: Vibration piece, 13, 54, 6
1: Coupling part, 14: First electrode, 15: Second electrode, 16: Third electrode, 17: Parallel plate capacitor, 18: Outer end surface, 21: Side surface, 22, 56: Earth terminal, 30 : Green sheet, 31: Center part, 32, 33, 34: Removed part, 36, 3
7: external terminal, 38, 39, 57, 58: common connection part, 40: vibrator.

Claims (1)

[Claims] 1 A plurality of elongated rectangular vibrating pieces and a connecting part that connects the vibrating pieces are formed into one piece by a piezoelectric material, and inside the vibrating piece there is a first electrode extending almost over the entire surface of the vibrating piece, and a first electrode extending over almost the entire surface of the vibrating piece. A second electrode and a third electrode extend in the length direction of the vibrating piece, facing the first electrode via a piezoelectric material.
One or more sets of electrodes are laminated, and adjacent vibrating pieces are electrically connected by extending at least one second and third electrode on the adjacent side to the joint part. The ends of the second and third electrodes of the vibrating piece at both ends are exposed on one side of the vibrating piece and connected in common to form input/output terminals. A grounding terminal is formed by exposing the first electrode of the vibrating element near the joint and making a common connection, and the second and third electrodes, which are not connected to the input/output terminal, are connected near the joint. A piezoelectric filter characterized in that each piezoelectric filter is exposed and commonly connected.