JPS6340911Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a piezoelectric ceramic filter that is small and suppresses unnecessary frequency response by using a plurality of rectangular piezoelectric resonant elements having unevenness on the side surface.

As shown in Fig _. 1 _{, a} piezoelectric ceramic filter is constructed by connecting piezoelectric ceramic resonant elements in series with S _{1 ,} S ₂ . It consists of Generally, piezoelectric ceramic resonant elements used in this filter utilize circular or square contour vibration, and when these piezoelectric ceramic resonant elements are used, there is a limit to the shape of the filter body, and miniaturization is not possible.

For example, in the case of a filter for a radio's intermediate frequency of 455 kHz, the shape of the piezoelectric ceramic resonant element whose resonance frequency is around 455 kHz is approximately 5 mm square on each side or circular with a diameter of 5 mm, and the thickness is approximately 0.8 mm for those connected in series.
Those connected in parallel are approximately 0.4 mm thick, and if a filter is constructed by stacking, for example, nine piezoelectric ceramic resonant elements in the thickness direction, the external dimensions of this filter will be a rectangular parallelepiped of approximately 8 mm x 10 mm x 20 mm. was. On the other hand, in order to achieve a smaller size, some devices have been designed to have a rectangular element shape, but vibrations in the length direction and vibrations in the width direction are close to each other, resulting in unnecessary vibrations and leaving problems with filter performance.

Therefore, the purpose of the present invention is to provide a filter that eliminates the above-mentioned drawbacks of the conventional filter.As shown in FIG. After determining that the vibration frequencies in the direction and width direction are far apart, unevenness 3 is provided on the side surface 2 as shown in FIG. By doing this, it is possible to reduce the width vibration as shown by the solid line due to the irregular vibration of the contour due to the unevenness of the side surface, instead of the characteristic where the width vibration was large as shown by the dotted line in Figure 3. The influence of unnecessary vibrations on filter performance can be reduced.

In the case of the present invention, by providing unevenness on the side surface of the rectangular piezoelectric ceramic resonant element 1, vibrations in the width direction are canceled out in the length direction so that the filter performance is not affected, and the vibrations are arranged in a line in the thickness direction. When stacked and assembled, the external shape can be reduced to approximately 3 x 10 x 20 mm (in the case of 9 sheets).

As shown in FIGS. 4 and 5, such piezoelectric resonant elements 1 are placed in a case 4 made of resin or the like and stored in an overlapping manner. The electrode plate 5, connecting piece 6, ground wire 7, and spacer or insulating elastic material 8 are used to connect the electrode plate 9 on the ground side and the input/output side to form a predetermined ladder shape as shown in FIG. Connect to the circuit. In addition, a protrusion 10 is provided on the part of the electrode plate 5 that connects with the element 1, and as shown in FIG. It is preferable that the ground is connected to the electrode plate 9, which serves as a lead wire, at the end surface, and a lid or resin is placed in the case 4.

As described above, according to the present invention, it is possible to reduce the size of the piezoelectric ceramic filter, and also to improve the characteristics, which has great practical effects.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a piezoelectric ceramic filter, Figures 2 a and b are perspective views of elements used in the piezoelectric filter in an embodiment of the present invention, Figure 3 is its characteristic diagram, and Figures 4 and 5. are a sectional front view and a plan view thereof. 1...Piezoelectric ceramic element, 2...Side surface, 3...Irregularities, 4...Case.

Claims (1)

[Scope of utility model registration request] A piezoelectric ceramic filter in which rectangular piezoelectric ceramic resonant elements having irregularities on the side surfaces are used as piezoelectric resonant elements connected in series and parallel, and a plurality of the resonant elements are stacked on a case and connected in a ladder shape.