JPS5921541Y2 - ceramic filter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a ceramic filter in which a piezoelectric ceramic resonator is housed in a case, lead terminals are drawn out from the case opening, and the case opening is sealed with epoxy resin. The purpose is to prevent the sealing resin from flowing into the case.

A ladder-type ceramic filter will be explained below as an example.

A conventional ladder-type ceramic filter using a square piezoelectric ceramic resonator is shown in FIG. 1a.

The structure was as shown in b.

That is, as shown in FIGS. 1a and 1b, a plurality of piezoelectric ceramic resonators 2 are housed in a bottomed cylindrical case 1, and a lead terminal 3 whose one end is connected to the electrode of the piezoelectric ceramic resonator 2 is provided. is pulled out from the case opening, and a sealing plate 5 having a through hole 4 through which the lead terminal 3 passes is inserted into the case 1 opening, and a resin 6 such as epoxy resin is filled from above the sealing plate 5. However, the opening of the case 1 was sealed.

In addition, those using round piezoelectric ceramic resonators are shown in Figure 2a,
As shown in Figure 1), the piezoelectric ceramic resonator 2 is housed in a holder 8 having a window 7 through which the lead terminal 3 passes, and then housed in the case 1 and placed in the square shape shown in Figures 1a and 1). The structure was such that a sealing plate 5 was inserted into the opening of the case 1 and sealed with resin 6, as in the case of using a piezoelectric ceramic resonator.

By the way, as shown in FIGS. 1 and 2, in the conventional ladder-type ceramic filter, a sealing plate 5 is used with a low-viscosity liquid resin to seal the opening of the case 1 housing the piezoelectric ceramic resonator 2. However, in the structure of the conventional ladder-type ceramic filter, the gap between the sealing plate 5 and the lead terminal 3 and the sealing plate 5 are uniformly covered.
Due to the capillary phenomenon, the liquid resin filled on the sealing plate 5 enters the interior of the piezoelectric ceramic resonator 2 as shown by the arrow A in FIGS.
The problem has been that it adheres to the filter and adversely affects its properties as a filter.

Therefore, in order to prevent this, in the past, the gap through which liquid resin enters the interior is closed with silicone rubber, the entire piezoelectric ceramic resonator 2 is wrapped with a thin film of tape, or the sealing plate 5 is covered with resin. The method used was to cover the gap by pasting a thin film tape to prevent intrusion, but this method had the drawback of increasing the price due to lower workability due to increased material costs and manufacturing steps, and was not a very desirable method.

This invention was developed in view of these conventional problems.
The ceramic filter of the present invention will be explained below with reference to the drawings of FIGS. 3 to 5 showing this embodiment.

In addition, in the drawings of Figures 3 to 5, Figures 1 and 2 are
The same parts as those of the conventional ladder-type ceramic filter shown in the figure are given the same numbers, and the explanation will be omitted.

Fig. 3 shows a ladder type ceramic filter according to one embodiment of the present invention, Fig. 4 shows a ladder type ceramic filter according to another embodiment of the invention, and Figs. 4 shows the main components of the ladder-type ceramic filter shown in FIG.

Furthermore, the embodiment shown in FIG. 3 uses a rectangular piezoelectric resonator 2 corresponding to the conventional one shown in FIGS. 1a and 1), and the embodiment shown in FIG. Figure a, l)
This example uses a round piezoelectric resonator 2 corresponding to the conventional one shown in FIG.

In FIGS. 3 to 5, 9 is a sealing plate made of a rigid body such as a baking plate, and 10 is a viscoelastic plate such as silicone attached to the inner surface of the case 1 of this sealing plate 9. 10 is provided with a through hole 9a and a through hole 10a, which is smaller than the lead terminal 3, at a position corresponding to the through hole 9a of the sealing plate 9 through which the lead terminal 3 passes. It protrudes and is in close contact with the peripheral wall surface of the opening of the case 1.

That is, in the ceramic filter according to the present invention, by inserting the sealing plate 9 and the viscoelastic plate 10 into the opening of the case 1, the peripheral part of the viscoelastic plate 10 is brought into close contact with the peripheral wall surface of the opening of the case 1. Further, the periphery of the through hole 10a of the viscoelastic plate 10 is brought into close contact with the lead terminal 3 passing through the through hole 9a of the sealing plate 9, and the opening of the case 1 is filled with resin 6.
If the opening is sealed, it is possible to completely prevent the liquid resin from entering the inside.

As described above, in the ceramic filter according to the present invention, a viscoelastic plate is pasted on the sealing plate that is inserted into the opening of the case, and the viscoelastic plate creates a gap between the case and the sealing plate and a gap between the sealing plate and the lead terminal. Since it prevents gaps, it can completely prevent the liquid resin used to seal the opening of the case from entering the inside, and the characteristics of the ceramic filter will not deteriorate. Since it can be assembled in exactly the same process as the previous one, the price will not be high and it has a very high practical value.

[Brief explanation of the drawing]

Figures 1a and 1) are perspective views and cross-sectional views of conventional ladder-type ceramic filters that use square piezoelectric ceramic resonators, and Figure 2 a and 1) show conventional ladder-type ceramic filters that use round piezoelectric ceramic resonators. FIG. 3 is a sectional view showing a ladder-type ceramic filter which is an embodiment of the ceramic filter of the present invention, and FIG. 4 is a perspective view and a sectional view showing a conventional ladder-type ceramic filter. FIG. 5a is a cross-sectional view showing a ladder-type ceramic filter according to an embodiment of the present invention, and FIG. 5a is a front view of the main parts of the filter shown in FIGS. It is a sectional view when the same filter is cut along the line '. 1... Case, 2... Piezoelectric ceramic resonator, 3... Lead terminal, 6... Resin, 9
... Sealing plate, 10 ... Viscoelastic board, 9a
, 10a...through hole.

Claims (1)

[Scope of utility model registration request] A piezoelectric ceramic resonator having a lead terminal, a case in which the piezoelectric ceramic resonator is housed, a sealing plate inserted into an opening of the case and having a through hole through which the lead terminal passes, and the sealing plate. a resin filled in a case opening on the outside of the plate to seal the case opening, and the sealing plate has a through hole smaller than the lead terminal at a position opposite to the through hole. and a ceramic filter having a viscoelastic plate attached thereto that is larger than the opening of the case.