JPS5834819Y2 - 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 having a characteristic terminal structure.

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 and a ring electrode provided concentrically on one surface of the piezoelectric substrate 1, and 4 is a dot electrode provided on the ground surface of the piezoelectric substrate 1. This is the ground electrode provided.

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 divided electrode side of the divided 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 together with an insulating plate I cut out in the center interposed therebetween, so that the tongue piece 6 and the input electrode 2,
The tongue piece 9 and the output electrode 3 are brought into contact with each other, and the common terminal metal plate 10 having a tongue piece 11 in the center is arranged on the whole electrode side, and the tongue piece 11 and the whole surface electrode 4 are brought into contact with each other. A small porcelain filter which is housed in an inner case 14 and an outer case 13 to hold a piezoelectric element 1, and which is selected so that the pressure of each metal plate on the porcelain piezoelectric element is balanced.

(See FIGS. 3 to 11) As described above, conventional three-terminal piezoelectric devices of this type have been manufactured one by one by assembling components such as piezoelectric elements, terminals, and cases.

In general, these parts are small and have a structure that is difficult to assemble, so automatic assembly is difficult and requires skill and skill, resulting in high product prices.

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 cost to conventional IFTs or lower in price and that is superior to conventional IFTs in selectivity.

Therefore, a method for manufacturing a three-terminal piezoelectric device is provided in which dot electrodes and ring electrodes are arranged 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. Two terminals are provided from the connecting part in each partial case group of the first partial case group, which is formed by connecting and molding a plurality of piezoelectric device cases on one side, and one is a dot at the tip of each terminal. Each row of terminals of a first terminal group is accommodated in a plurality of rows of terminals integrally molded together, one row having a portion to be pressed against the electrode and the other having a portion to be pressed against the ring electrode. A piezoelectric element plate is placed on each terminal row, and the electrodes and terminals are connected electrically (
Each terminal of the second terminal group, which is made up of a plurality of integrally connected and molded terminals each having a portion at the tip that is to be brought into contact with the ground electrode from the connecting portion, is placed on each of the piezoelectric element plates. Each partial case group of the second partial case group, which is formed by connecting and molding a plurality of divided piezoelectric device cases on the other side, is electrically connected to the ground electrode of the piezoelectric element plate, and is connected to each partial case group of the first partial case group. The present inventors have devised an invention that attempts to reduce the cost of the product by attaching it to a partial case and integrating the two, and cutting off the connecting parts of the terminal and the case to enable automatic assembly and reduce the cost of the product.

First, an example in which the present invention is applied to 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 can be regarded as one side of a hollow rectangular parallelepiped filter case divided into two in the terminal surface direction.
A is formed by connecting and molding a plurality of pieces A by a connecting part 20b.

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, and planar protrusions 20f and 20g are provided on the remaining side surfaces.
.

20h is provided.

20i 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 the same as the first partial case group 20, and is made of thermoplastic synthetic resin.
A partial case 24a that can be regarded as the other side of a hollow rectangular parallelepiped filter case divided into two in the terminal surface direction.
A plurality of solid connecting parts 24b are used to connect and mold a plurality of parts.

A flat plate-like projection 24c is provided on one surface side of the partial case 24a except for the peripheral part, and a pin-like projection 24d that fits into the hole 20i of the first partial case 20a is provided in a part of the peripheral part. This is the first partial case 20.
A wall-like protrusion 24e that abuts on the side surface 20k of a is provided.

24f is a leg necessary for positioning during manufacturing.

The first terminal group 21 is made of metal, and the terminals 21a and 21b, which are pressed into contact with the dot electrodes 22a1 and the ring electrodes 22bf of the piezoelectric element plate 22, are integrally formed with the connecting portion 21c (with a space provided therebetween).

The terminal 21a has a leg portion 21d extending at right angles from the connecting portion 21c.
Two arms 21e and 21f protrude from the tip at a distance, and these arms 21e and 21f are respectively
It is bent into an arch shape (vertices 21g, 21h) to provide elasticity.

A step portion 21i that engages inside the side surface 20 of the partial case 20a is provided below the leg portion 21d (here, the arm 21f).

Further, in the leg portion 21d, a curved cutout 21j into which the curved protrusion 20d of the partial case 20a fits is provided between the arms 21e and 21f.

The terminal 21b extends from the tip of the leg 21 extending perpendicularly from the connecting portion 21c to between the arms 21e and 21f (this terminal plate 211
The terminal board 211 has a conical truncated projection 21m provided at its center.

A step portion 21n is provided below the terminal plate 211 at the leg portion 21k and engages with the inner side of the side surface 20 of the partial case 20a.

Further, a curved cutout 21o into which the curved protrusion 20e of the partial case 20a fits is provided at the center of the terminal plate 211 in the leg portion 21.

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 at right angles from the connecting portion 23b.
Arms 23d and 23e are expanded in a cross shape at their tips.

23f and 23g, and this arm is bent and has elasticity.

A truncated conical projection 23 is provided at the center of each arm 23d to 23g.
h 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 component case 20a.
Attach 1a and 21b.

To be more specific, the curved notch 2 of the terminal 21a
The curved protrusion 20d of the partial case 20a fits into the curved notch 21o of the terminal 21b.
The curved protrusion 20e of the terminal 20a fits in, and the stepped portion 21i of the terminal 21a and the stepped portion 21n of the terminal 21b engage with the inside of the side surface 20 of the partial case 20a, respectively.

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 and the apex 21g of the arms 21e and 21f of the terminal 21a.

The piezoelectric element plate 22 is connected to the terminal 21a so that it is in contact with the terminal 21h.
, 21b.

Needless to say, at this time, the terminals should be brought into contact at the vibration nodes 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 the terminal 23a contacts the ground electrode at its vibration node.

The second partial case group 24 and the first partial case group 20 are joined together by ultrasonic welding, and the connection parts 20b, 21c, 23b and 24 of the terminals and cases
b is cut out from the point indicated by the dashed-dotted line in the figure.

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.

By the way, the partial case 20a has curved protrusions 20d, 2.
0e is provided.

This is to regulate the position of the terminals 21a and 21b, and if it were not present, the side surface of the piezoelectric element plate 22 would come into contact with the inner surface of the partial case 20a, preventing vibration, especially at the four corners, and deteriorating the characteristics. In order to prevent this, the piezoelectric element plate 22 is supported at the center of the side and a gap is created between it and the case because the vibration amplitude is relatively small in the center of the side and there is little effect even if other objects come into contact with it. It is.

Note that 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 22, adversely affecting the selectivity characteristics. Sometimes.

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 243 bolts are joined, the protrusion 24g connects the terminal tip 21p to the partial case 2.
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 f, and therefore the contact pressure to the electrode can be kept constant, resulting in a longer service life.

As is clear from the above embodiments, the present invention provides terminals in a group of partial cases made of an insulating material and formed by connecting and molding a plurality of partial cases, which can be said to be one of the divided cases. A plurality of connected and molded terminal groups and a piezoelectric element plate are assembled, the partial cases are integrated, and the connected portions of each case are cut out.

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.

In this way, this invention is extremely useful.

This invention was made in conjunction with this invention, but of course the scope of the rights is not limited to the scope of this invention.

This invention will be explained below with reference to the drawings of the embodiments of the invention. 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 of the tips have no choice but to come into contact with nodes of incomplete vibration, if they come into contact with strong pressure, the vibration E will have an adverse effect.

This is also clear from FIGS. 20 and 21.

In this embodiment, the terminal 23a is provided with strong elasticity, while the dot terminal 21b is not provided with elasticity.

The ring terminal 21a has an elasticity higher than that of the terminal 23a, for example, in the embodiment, about 1/3 to 2/3 of the elasticity of dust.

In this way, even if different contact pressures are applied from both sides of the piezoelectric element plate 22, the dot terminal 21b, which has no elasticity, acts as a spacer, and the ring terminal 21a
will not be crushed.

Of course, this invention is not limited to the above-described embodiment shown in the drawings, but the essence is a ground terminal plate that is ferroelastically pressed against the ground electrode,
If a dot electrode (a dot terminal plate that presses against the ring electrode in an inelastic manner and a ring terminal plate that presses against the ring electrode in a weakly elastic manner) are enclosed in a case, it is included in this invention.

[Brief explanation of the drawing]

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 side view, FIG. 8 is a front view of the common terminal metal plate 10, FIG. 9 is a side view, FIG. 10 is a sectional view, and
The drawing is a bottom view, and Fig. 12 to Fig. 19 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.
Figures 20 and 21 are diagrams showing the effects of an embodiment of this invention, Figure 20 is a curve diagram showing (ring terminal/dot terminal contact pressure ratio) - (insertion loss), and Figure 21 is a curve diagram showing the selection 20 is a first partial case group, 21 is a first terminal group, 21
a is a ring terminal, 21b is a dot terminal, 22 is a piezoelectric element plate, 23 is a second terminal group, 23a is a ground terminal, and 24 is a second partial case group.

Claims (1)

[Claims for Utility Model Registration] CI) A three-terminal piezoelectric device in which a dot electrode and a ring electrode are provided concentrically 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. a ground terminal plate that is in ferroelastic pressure contact with the ground electrode;
A three-terminal piezoelectric device in which a dot terminal plate that is inelastically pressed against a dot electrode and a ring terminal plate that is weakly elastically pressed against a ring electrode are enclosed in a case. ] Utility model registration claim No. (D
A three-terminal piezoelectric device described in IJj.