JPH0124978Y2 - - Google Patents

Description

[Detailed description of the invention] A three-terminal device in which a center electrode and an outer electrode surrounding the center electrode are provided on one main surface of a plate piezoelectric ceramic, and a ground electrode that covers almost the entire surface of the other main surface is provided. A type piezoelectric resonator is housed in an opening of an annular insulating frame, and is provided with a contact piece that comes into contact with each electrode surface of the piezoelectric resonator, and is held by a terminal plate seated on an end face of the insulating frame. The three-terminal ceramic filter, which is integrally sealed with a synthetic resin outer shell, maintains stable filtering characteristics over a long period of time without being affected by vibrations, shocks, or external moisture. Although it is known to be easy to maintain and mass-producible, it has the following drawbacks.

That is, since the main surface of the piezoelectric resonator on the ground electrode side is entirely covered by the ground terminal plate supported by the end face of the insulating chamber, the surface is covered by the synthetic resin constituting the outer shell. Although there is no risk of contamination, the center electrode and outer electrodes provided on the opposite main surface are inward from the center terminal plate and outer terminal plate, respectively, which are arranged facing each other on the other end surface of the insulating frame. It is in contact with and supported by the contact of the protruding contact piece, and it is necessary to provide an insulating gap between the opposing terminal plates, so when forming the outer shell, some of the resin may enter through the insulating gap and cover the surface. There was a risk of contamination and deterioration of characteristics.

The present invention was devised to eliminate the above-mentioned drawbacks of this type of three-terminal ceramic filter, and an embodiment thereof will be described below with reference to the drawings.

In the figure, reference numeral 1 denotes a center electrode 12 on one main surface of a plate-shaped piezoelectric ceramic 11 made of a lead zirconate titanate-based compound, and an annular outer electrode 13 surrounding the center electrode with an insulating interval. A ground electrode 14 covering substantially the entire surface of the other main surface is formed by silver baking or the like, and is a polarized three-terminal type piezoelectric resonator, which is usually called a dot-and-ring type. 2 and 3 are a center terminal plate and an outer terminal plate arranged to face one main surface of the three-terminal piezoelectric resonator (hereinafter abbreviated as piezoelectric resonator) 1, and the center terminal plate 2 is connected to the center electrode 12. and a tongue-shaped contact piece 21 that comes into elastic contact at the center which becomes the node of vibration.
and a terminal leg 22 for connecting to an external circuit, and the outer terminal plate 3 is provided with a contact piece 21 of the center terminal plate 2.
A pair of contact pieces 31, 31 are provided on both sides so as to sandwich the annular outer electrode 13 and come into elastic contact with the annular outer electrode 13, and a terminal leg 32 is connected to an external circuit. Reference numeral 4 designates a grounding terminal plate which is disposed facing the other main surface of the piezoelectric resonator 1 and has a contact 41 that abuts the center of the grounding electrode 14 and a terminal leg 42 that connects to an external circuit. The terminal board 2, the outer terminal board 3, and the ground terminal board 4 are provided with a plurality of small holes 23, 33, and 43 that fit with the small protrusions of the insulating frame described below.
...to be drilled. 5 stores the piezoelectric resonator 1 in the opening 51, and connects the center terminal plate 2 and the outer terminal plate 3 to the first opening end surface 5 so as to sandwich the piezoelectric resonator 1.
FIG. 1A shows an insulating frame in which the ground terminal plates 4 are respectively seated on the second open end face 5b, and each of the terminal plates is seated by projecting from the four corners of the first end face 5a of the insulating frame 5. The small holes 23..., 33... of the center terminal plate 2 and the outer terminal plate 3 are formed in the small protrusions 52... provided on the ground terminal plate 4, and the small holes 23..., 33... of the ground terminal plate 4 are formed in the small protrusions 53... protruding from the four corners of the second end surface 5b. This is done by fitting the small holes 43, respectively. Next, 6 is a center terminal plate 2 and a ground terminal plate 3 connected to the center electrode and outer electrode on one main surface of the piezoelectric resonator 1 housed in the opening 51 of the insulating frame 5.
7 is an insulating thin film such as a synthetic resin coated with an adhesive on the surfaces of the insulating frame, which are seated facing each other with an insulating interval g between them, on the first end surface 5a of the insulating frame; 7 is the piezoelectric resonator 1; , center terminal plate 2, outer terminal plate 3,
The assembly consisting of the grounding terminal plate 4, the insulating frame 5, and the insulating thin film 6, such as synthetic resin, is attached to the terminal legs 22, 32 of each terminal.
and 42 are insulating outer shells covered with synthetic resin such as epoxy resin.

In this example, each terminal board is seated on both the first and second end surfaces of the annular insulating frame housing the piezoelectric resonator by means of a small protrusion provided on the annular insulating frame and a small hole drilled in each terminal board. Although the mode of fitting the holes was shown,
Directly attach each terminal plate to the corresponding end faces of the annular insulating frame.
The outer terminal plate that contacts and connects with the outer electrode of the piezoelectric resonator has a pair of tongue-shaped contact pieces protruding in parallel, but one pair is not necessarily required, and only one piece can be used. Preferably, the resonator may be provided approximately on the same line as the tongue-shaped contact piece protruding from the opposing center terminal plate, and furthermore, the piezoelectric resonator may be a disc-shaped resonator instead of a square plate-shaped resonator. can.

The three-terminal ceramic filter of the present invention is constructed as described above, and includes a center terminal plate and an outer terminal plate that are connected to the center electrode and outer electrode on one main surface of the piezoelectric resonator by tongue-like contact pieces, respectively. The piezoelectric resonator is seated on the first end surface of the annular insulating frame housing the piezoelectric resonator, with an absolute spacing between the two, and the second end surface of the insulating frame is covered with an insulating thin film made of synthetic resin or the like. Since the end face is covered with a ground terminal plate that comes into contact with the other main surface of the piezoelectric resonator, contamination of the piezoelectric resonator by the synthetic resin during the formation of the outer shell can be reliably prevented.
It has an excellent effect that does not impair the filtering characteristics in the slightest.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, in which A is a front view with main parts cut away, B is a vertical side view, and FIG. 2 is an exploded perspective view of FIG. 1 excluding the outer shell 7. 1... Three-terminal piezoelectric resonator, 11... Plate piezoelectric ceramic, 12... Center electrode, 13... Outer electrode, 1
4... Ground electrode, 2... Center terminal plate, 21... Contact piece, 22... Terminal piece, 3... Outer terminal plate, 31
... Contact piece, 32 ... Terminal piece, 4 ... Ground terminal plate, 41 ... Contact, 42 ... Terminal piece, 5 ... Insulation frame, 5a ... First end surface, 5b ... Second end surface ,
51...opening, 6...synthetic resin isoconductive thin film,
7...Outer shell.

Claims (1)

[Scope of utility model registration request] A center electrode 1 is provided on one main surface of the plate piezoelectric ceramic 11.
2, and an annular outer electrode 13 surrounding the center electrode.
A three-terminal piezoelectric resonator 1 has a ground electrode 14 formed on its other main surface to cover the entire surface thereof, and an annular insulating frame 5 that accommodates the resonator 1 in an opening 51.
and a center electrode 1 on one main surface of the piezoelectric resonator.
2 and the contact piece 2 that comes into contact with the outer electrode 13, respectively.
1, 31 and terminal legs 22, 3 connected to external circuits.
2 and are in contact with the center terminal plate 2 and the outer terminal plate 3 facing each other with an insulating interval g, g on the first end surface 5a of the insulating frame, and also with the ground electrode 14 on the other surface of the piezoelectric resonator. There is an insulation gap g between the ground terminal plate 4, which includes contacts 41 and terminal legs 42 connected to an external circuit, and is seated on the second end surface 5b of the insulating frame 5, and the first end surface 5a of the annular insulating frame 5. , g, and an insulating thin film 6 of synthetic resin or the like adhered to the surfaces of the center terminal plate 12 and the outer terminal plate 13, which are seated and facing each other via
A three-terminal type ceramic filter characterized in that it is constituted by a synthetic resin outer shell 7 covering the outer periphery of the three terminals.