JPS5834820Y2 - Three-terminal piezoelectric device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a three-terminal piezoelectric device, and particularly to a three-terminal piezoelectric device with excellent characteristics.

Conventionally, there have been all-ceramic filters for AM radio, such as those shown in FIGS. 1 and 2, which utilize the radial vibration of a disk or the contour vibration of a square plate.

In FIG. 1, 1 is a square plate-shaped piezoelectric substrate, 2 and 3 are dot electrodes provided concentrically on one surface of the piezoelectric substrate 1,
A ring electrode 4 is a ground electrode provided on the ground surface of the piezoelectric substrate 1.

In addition, in FIG. 2, 1a is a disc-shaped piezoelectric substrate, 2a
and 3a are a dot electrode and a ring electrode provided concentrically on one surface of the piezoelectric substrate 1a, and 4a is a ground electrode provided on the ground surface of the piezoelectric substrate 1a.

Among these, the one shown in FIG. 1 has a structure as shown in Japanese Utility Model Publication No. 44-24888 as a conventional example.

That is, the scope of the utility model registration claim states, ``On the split pole side of the split electrode type three-terminal porcelain piezoelectric element 1, there is a metal plate 5 for an input terminal having a tongue piece 6 in the center and tongue pieces 9 on both sides. The provided U-shaped metal plates 8 for output terminals are stacked one on top of the other with an insulating plate 7 having a central portion cut out interposed therebetween, and the tongue piece 6 and the input electrode 2 are brought into contact with each other, and the tongue piece 9 and the output electrode 3 are brought into contact with each other, On the entire surface electrode side, a common terminal metal plate 10 having a tongue piece 11 is disposed in the center, and the tongue piece 11 and the whole surface electrode 4 are brought into contact with each other to form a porcelain piezoelectric element 1.
"A small porcelain piezoelectric wave device which is housed in an inner case 14 and an outer case 13 so as to hold the porcelain piezoelectric elements, and which is selected so that the pressure on the porcelain piezoelectric element of each metal plate is balanced."

(See FIGS. 3 to 11) Conventionally, this type of three-terminal piezoelectric device has been manufactured one by one by assembling components such as a piezoelectric element, a terminal, and a case.

Generally, these parts are small and have a structure that makes assembly work difficult, so automatic assembly is difficult and requires skill, and the product price is high.

Various structural improvements have been made to make assembly easier, but nothing definitive enough to allow automatic assembly has been achieved, and there are limits to cost reduction.

In recent years, various types of radios have been put on the market to suit specific purposes, and the number of units sold is quite large.

On the other hand, interference is becoming more and more severe, and users are demanding radios with high selectivity, values that are becoming difficult to achieve with conventional IFTs, and conventional IFTs are compatible with miniaturization and C. It was difficult.

For these reasons, there is a need for a piezoelectric filter that is comparable in price to or lower than conventional IFTs and that is superior to conventional IFTs in selectivity.

Therefore, a method for manufacturing a three-terminal piezoelectric device is provided in which a dot electrode and a ring electrode are provided on one surface of a piezoelectric element plate, and a ground electrode is provided on the other surface to perform contour vibration or radial vibration. In each partial case of the first partial case group, which is formed by connecting and molding a plurality of divided piezoelectric device cases on one side, two terminals are provided from the connecting part, and one is a dot at the tip of each terminal. A plurality of terminal rows of a first terminal group are formed by integrally connecting and molding a plurality of rows of terminals, one of which has a portion to be pressed against the electrode and the other has a portion to be pressed against the ring electrode, and the plurality of piezoelectric Place the element board on each terminal row and connect the electrodes and terminals electrically (
Each terminal of the second terminal group, which is formed by integrally connecting and molding a plurality of terminals having a portion at the tip that is to be pressed into contact with the ground electrode from the connecting portion, is placed on each I of the piezoelectric element plate. The other side of the divided piezoelectric device case is connected to the ground electrode of the piezoelectric element plate, and each partial case of the second partial case group is connected to the first partial case group. The inventors of the present invention have devised an invention that enables automatic assembly and reduces the cost of the product by attaching the terminal to each partial case to integrate the two and cutting off the connecting parts of the terminal and the case.

First, an example in which the present invention is implemented in a three-terminal piezoelectric filter will be described with reference to the drawings.

In the figure, 20 is a first partial case group, 21 is a first terminal group, 22 is a piezoelectric element plate, 23 is a second terminal group, 24
is the second subcase group.

The first partial case group 20 is made of thermoplastic synthetic resin, and the filter case is a so-called hollow rectangular parallelepiped in the direction of the terminal surface (partial case 2 can be considered as one side of the shape divided into two parts).
It is formed by connecting and molding a plurality of pieces 0a with connecting portions 20b.

Connecting portion 2 of the four sides of recess 20C of partial case 20a
20f planar protrusions on the sides other than the 0b & hard sides
, 20g.

20h is provided.

201 is a hole provided near the planar projection 20f.

20j is a leg necessary for positioning during manufacturing.

The height of the side surface 20 where the planar projections 20g and 20h are provided is lower than the other three sides.

On the other hand, the second partial case group 24 is paired with the first partial case group 20, and is made of thermoplastic synthetic resin and has a shape in which a hollow rectangular parallelepiped filter case is divided into two in the terminal surface direction. It is formed by molding a plurality of partial cases 24a, which can be considered as sides, connected by connecting portions 24b.

A flat plate-shaped protrusion 24C is provided on one surface side of the partial case 24a (excluding the peripheral part), and a pin-shaped protrusion 24C that fits into the hole 20i of the first partial case 20a is provided, and further a first partial case 2 is provided.
A wall-like protrusion 24e is provided which comes into contact with the side surface 20kt of 0a.

24f is a leg necessary for positioning during manufacturing.

The first terminal group 21 is made of metal, and has terminals 21a and 21b which are pressed into contact with the dot electrodes 22a and the ring electrodes 22b of the piezoelectric element plate 22, and are integrally spaced from the connecting portion 21c by a distance of I.

The terminal 21a has a leg portion 21 extending at a right angle from the connecting portion 21c.
Two arms 21e and 21f are spaced apart from the tip of d.
The arms 21e and 21f are each bent into an arch shape (vertices 21g and 21h) to provide elasticity.

A partial case 2 is provided below the arm 21f in the leg portion 21d.
A stepped portion 21i is provided which engages the inner side of the side surface 20 of 0a.

In the terminal 21b, a terminal plate 211 protrudes between the arms 21e and 21f from the tip of the leg 21 extending perpendicularly from the connecting portion 21C, and a conical truncated projection 21m is provided at the center of the terminal plate 217. ing.

In the leg portion 21k, a lower portion I of the terminal plate 211 is provided with a stepped portion 21rt that engages with the inner side of the side surface 20 of the partial case 20a.

The second terminal group 23 is made of metal, and has a terminal 23a whose tip is pressed into contact with a ground electrode (not shown) of the piezoelectric element plate 22, and is provided integrally with a connecting portion 23b at a distance.

The terminal 23a has a leg portion 23c extending perpendicularly from the connecting portion 23b.
Arms 23d, 23e, 23 expanded in a cross shape at the tips of
f.

This arm has a weight of 23g and is bent and made elastic.

The center of each arm 23d to 23g is a conical truncated projection 23h.
is provided.

A piezoelectric filter is manufactured using these components as follows.

The first partial case group 20 is kept in place, and each terminal 2 of the first terminal group 21 is inserted into the recess 20C of each partial case 20a.
Attach 1a and 21b.

More specifically, the stepped portion 21i of the terminal 21a and the stepped portion 21n of the terminal 21b each engage inside the side surface 20 of the partial case 20a.

The piezoelectric element plate 22 is connected to the terminals so that the dot electrode 22a of the piezoelectric element plate 22 and the conical truncated protrusion 21m of the terminal 21b are in contact with each other, and the ring electrode 22b is in contact with the vertices 21g and 21h of the arms 21e and 21f of the terminal 21a. 21a, 2ib
Above.

At this time, it goes without saying that the terminals should be brought into contact at nodes of vibration of the piezoelectric element plate.

Trapezoidal conical protrusion 23 of each terminal 23a of the second terminal group 23
The terminal 23a is placed on the piezoelectric element plate 22 so that h contacts the ground electrode at its vibration node.

The second partial case group 24 and the first partial case group 20 are joined by ultrasonic welding, and the connection parts 20b, 21c, 23b, and 24b of the terminals and cases are connected from the dotted chain lines in the figure. Excise.

The first partial case group 20 and the second partial case group 24 may be bonded together with an adhesive, or may be structured such that one fits into the other, or they may be fitted together in other ways. You may also use a method of integrating.

A cross-sectional view of the completed three-terminal piezoelectric filter is shown in FIG.

In this type of filter, it is common for the dot terminal 21b and the ring terminal 21a to have different contact pressure ratios to their corresponding electrodes.

This is because when the square plate type vibrator is performing contour vibration, the tip 21m of the dot terminal 21b is brought into contact with the node of complete vibration, so from the viewpoint of stability, it may be brought into contact with strong pressure, but the ring terminal 21a Since the tips 21g and 21h have no choice but to come into contact with nodes of incomplete vibration, if they are brought into contact with strong pressure, it will have a negative effect on the vibration.

This is also clear from Figures 20 and 21.

In this embodiment, the terminal 23a has strong elasticity, while the dot terminal 21b has no elasticity.

The ring terminal 21a has an elasticity higher than that of the terminal 23a, for example, about ⅓ in the embodiment.

In this way, even if different contact pressures are applied from both sides of the piezoelectric element plate 22, the dot terminal 2 does not have elasticity.
1b acts as a spacer so that the ring terminal 21a is not crushed.

Furthermore, when the tip 21p of the terminal 21a is floating in the space inside the case, the vibration of the piezoelectric element plate 22 is transmitted to generate parasitic vibration, and this vibration is transmitted to the piezoelectric element plate 12c, which adversely affects the selectivity characteristics. There are times when this happens.

In this case, for example, a protrusion 24g is provided at the corresponding location of the partial case 24a, and when the partial cases 20a and 24a are joined, the terminal tip 21p is connected to the terminal tip 21p by the protrusion 24g.
It is preferable to press it against the inner surface of 0a.

Then, parasitic vibration does not occur at the terminal tip 21p, and therefore the selectivity characteristics are not adversely affected.

In addition, it is possible to prevent the elasticity of the ring terminal 21a from decreasing due to external impact, and therefore the contact pressure to the electrode can be kept constant, resulting in a longer life.

As is clear from the above examples (this invention
A terminal group in which a plurality of terminals are connected and molded and a piezoelectric element plate are assembled into a partial case group in which a plurality of partial cases made of an insulating material and which can be said to be one of the divided cases are connected and molded. This involves integrating the partial cases and cutting out the connected parts of each case.

As described above, this method is completely different from the conventional manufacturing method of this type of piezoelectric device, and an automatic assembly system can be introduced, which greatly contributes to reducing the cost of the product.

Although this invention is very useful, it has the following drawbacks when explained using the drawings of the embodiments.

In other words, the side surface of the piezoelectric element plate 22 comes into contact with the inner surface of the partial case 20a, which impedes vibration, particularly at the four corners, and deteriorates the characteristics.

This invention was made in order to eliminate such drawbacks, and is a three-terminal type piezoelectric device as described above, in which a protrusion is provided on the inner surface of the case, and a portion of the piezoelectric element plate having a relatively small vibration amplitude is provided with a protrusion. This is because a gap is created between the inner surface of the case and the piezoelectric element plate.

An embodiment of this invention will be described below.

Figures 22 and 23 (herein, the above invention and A-'s)
These are given the same numbers and the explanation will be omitted.

Connecting portion 2 of the four sides of recess 20C of partial case 20a
Curved protrusions 20d and 20e are provided on the side surface connected to 0b.

Further, the arm 21 at the leg portion 21d of the first terminal group 21
A curved protrusion 2 of the partial case 20a is located between e and 21f.
A curved notch 21j into which Oa fits is provided.

Furthermore, the center l of the terminal plate 211 is located on the leg 2ikl (this part is the curved protrusion 20e of the case 20a).
A curved notch 210 into which the material fits is provided.

When the first terminal group 21 is attached to the first partial case group 20, the curved protrusion 20d of the partial case 20a fits into the curved notch 21j of the terminal 21a, and the curved notch 210 of the terminal 21b fits into the curved notch 21j of the terminal 21a. The curved protrusion 20e of the partial case 20a is fitted into the portion.

This causes the terminal 21a. There is no longer any displacement in the length direction of 21b.

When the piezoelectric element plate 22 is placed on this first terminal group 21, the left and right side parts of the piezoelectric element plate 22 in the drawing are moved to the partial case 20 by the curved protrusions 20d and 20e of the partial case 20a.
It is held with a gap from the inner surface of a.

Therefore, the vibrations of the piezoelectric element plate 22, especially the vibrations at the four corners, are prevented and the characteristics do not deteriorate.

Moreover, since the curved protrusions 20d and 20e are brought into contact with the piezoelectric element plate 22 at the center of the side where the vibration amplitude is relatively small, the effect of this on the vibration is relatively small and there is no problem in practical use.

Of course, this invention is not limited to the above illustrated embodiment,
In short, if a projection is provided on the inner surface of the case and brought into contact with a portion of the piezoelectric element plate where the vibration amplitude is relatively small, thereby creating a gap between the inner surface of the Kegos and the piezoelectric element plate, it is included in this idea. .

[Brief explanation of drawings]

Figure 1 is a perspective view showing the principle structure of a square plate type three-terminal piezoelectric filter, Figure 2 is a perspective view showing the principle structure of a disc type three terminal piezoelectric filter, and Figures 3 to 11 are conventional square plate type piezoelectric filters. An example of the structure of a type three-terminal piezoelectric filter is shown in which FIG. 3 is a front view of the input terminal metal plate 5, FIG. 4 is a side view of the same, FIG. 5 is a front view of the insulating plate 7, and FIG. 7 is a front view of the output terminal metal plate 8, FIG. 7 is a front side view of the common terminal metal plate 10, FIG. 9 is a front view of the common terminal metal plate 10, FIG. 10 is a sectional view, and
The drawing is a bottom view, and Fig. 12 to Fig. 21 show an embodiment of the invention for explaining the invention. Fig. 12 is a front view showing the first partial case group 20, and Fig. 13 is the same. 14 is a front view showing the first terminal group 21, FIG. 15 is a front view showing the piezoelectric element plate 22, and FIG. 16 is a front view showing the second terminal group 2.
3, FIG. 17 is a front view showing the second partial case group 24, FIG. 18 is a side view of the same, and FIG. 19 is a sectional view.
Figure 20 shows (ring terminal/dot terminal contact pressure ratio) -
(insertion loss); 21 is a selected sound characteristic curve; 22 and 23 are for explaining an embodiment of this invention; and 22 is a diagram showing the first partial case group 20. FIG. 23 is a front view showing the first terminal group 21. FIG. 20 is a first partial case group, 20d and 20e are curved projections, 21 is a first terminal group, 21a is a ring terminal, 21b
are dot terminals, 21j and 21o are curved notches, 22 is a piezoelectric element plate, 23 is a second terminal group, 23a is a terminal, 24
is the second subcase group.

Claims (1)

[Scope of utility model registration request] This is a three-terminal piezoelectric device in which a dot electrode and a ring electrode are provided at the center of gravity on one surface of a piezoelectric element plate, and a ground electrode is provided on the other surface to perform contour vibration or radial vibration, and a projection is provided on the inner surface of the case. A three-terminal piezoelectric device in which a gap is provided between the inner surface of the case and the piezoelectric element plate by bringing the piezoelectric element plate into contact with a portion of the piezoelectric element plate whose vibration amplitude is relatively small.