JPH07274299A - Manufacture of piezoelectric sounder - Google Patents

Abstract

PURPOSE:To provide an inexpensive piezoelectric sounder with stable frequency characteristics by placing a circumferential ridge of a diaphragm onto a step difference face of a sidewall inside a resin case whose sprint terminal is subjected to insert-molding, a part of the sidewall is melted while an outermost circumferential ridge of the diaphragm is floated due to a recessed part and applying thermal caulking to the circumferential ridge of the diaphragm. CONSTITUTION:A resin case 12 having a flat part 12a and a sidewall 12b with a margin of a melt part 28 is subjected to insert molding together with a terminal board 18. A step difference face 32 having a recessed part 30 in its inside is formed to the inside of the side wall 12b. A circumferential ridge of a diaphragm 22 is placed on the step difference face 32 so that the piezoelectric body 24 fixed to the diaphragm 22 is in press contact with a spring terminal 18b and in close contact onto the step difference face 32 in this state. However, the outermost circumferential ridge of the diaphragm 22 is floated by the recessed part 30. While the circumferential ridge is in close contact, the melt part 28 is heated and the material of the softened melt part 28 is used to fix the diaphragm 22. Since the recessed part 30 is provided, no caulking stress is exerted and deformation such as bent is not caused to the diaphragm 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a piezoelectric sounder, and more particularly to a method for manufacturing a piezoelectric sounder in which a vibration plate having a piezoelectric material fixed thereto is attached to a resin case.

[0002]

2. Description of the Related Art An example of a conventional piezoelectric sounder is shown in FIGS. 4 and 5, for example. In the piezoelectric sounder shown in FIG. 4, which is the first conventional technique, the vibration plate 2 is fixed to the side wall of the resin case 1 with the silicone adhesive 3. And
The tip of the terminal 5 is connected to the piezoelectric body 4 fixed to the vibration plate 2 by solder 6. The terminal 5 is fixed to the resin case 1 by the heat staking portion 7.

The piezoelectric sounder shown in FIG. 5, which is the second conventional technique, is disclosed in, for example, Japanese Utility Model Laid-Open No. 59-157394, and in the second conventional technique, the diaphragm 2 includes the side wall of the resin case 1 and the resin cover. It is supported by 8 and pressure contact. The resin cover 8 also has a function of holding the contact state of the terminal 5 with the piezoelectric body 4.

[0004]

According to the first conventional technique, the diaphragm 2 must be fixed to the resin case 1 by the silicone adhesive 3 and the terminals 5 must be heat-staked to the resin case 1. Further, the piezoelectric body 4 and the terminal 5 are solder 6
Have to connect by. Therefore, the piezoelectric sounder shown in FIG. 4 has a drawback that its assembly becomes complicated.

On the other hand, in the second conventional technique, the silicone adhesive 3 and the solder 6 are not required, but the resin cover 8 is required. Therefore, another mold is required, and there is a drawback that the cost increases. Furthermore, in the third prior art, for example, Japanese Utility Model Laid-Open No. 52-55278, there is disclosed a piezoelectric sounding body in which a bimorph type piezoelectric vibrator is heat-welded or ultrasonic-welded to the case opening without using such a resin cover. Has been done.

However, in the third prior art, although the vibrator is directly welded to the opening of the resin case, the cost is low. However, when the vibrator is welded to the opening, the molten resin causes stress on the diaphragm. However, there is a problem that, for example, the frequency characteristic is not as designed. Therefore, a main object of the present invention is to provide a manufacturing method capable of manufacturing a piezoelectric sounder having stable frequency characteristics at low cost.

[0007]

The present invention provides (a) air holes
A spring terminal (1) including a flat surface portion (12a) formed with (16) and a side wall (12b) rising from the peripheral edge of the flat surface portion and insert-molded in the flat surface portion and having its tip exposed above the flat surface portion.
8b), a resin case having a step surface (32) formed at a position corresponding to the tip position of the spring terminal on the inner surface of the upper end of the side wall, and a recess (30) formed in the step surface is prepared (b) Piezoelectric body
Prepare a diaphragm (22) to which (24) is fixed, (c) place the peripheral edge of the diaphragm on the step surface so that the tip of the spring terminal contacts the piezoelectric body, and (d) peripheral edge of the diaphragm. Is a method for manufacturing a piezoelectric sounder, in which a part of the side wall is melted in a state of being floated due to the concave portion and the peripheral edge of the diaphragm is caulked.

[0008]

First, the peripheral edge of the diaphragm is placed on the step surface inside the side wall of the resin case in which the spring terminal is insert-molded. After that, the diaphragm is fixed to the resin case by melting a part of the side wall and performing heat caulking. When performing heat staking, the resin on the melted side wall wraps around the recess. Therefore, the resin is prevented from exerting an excessive stress on the diaphragm.

[0009]

According to the present invention, since the step of soldering the terminals to the piezoelectric body can be omitted without using another resin cover, the assembly can be simplified and the cost can be reduced. Moreover, since the spring terminal is insert-molded in the resin case, it is mechanically stable as compared with the conventional fixing method by heat staking.

Further, since the stepped surface is formed with a concave portion for floating the peripheral edge of the mounted vibration plate, it is possible to prevent stress due to heat staking from being applied to portions other than the fixed portion of the vibration plate.
No deformation such as “warp” occurs in the diaphragm, and thus the frequency characteristics of the piezoelectric sounder are stable. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0011]

Referring to FIG. 2, a piezoelectric sounder 10 of this embodiment includes a resin case 12 having a disk shape and having a flat surface portion 12a and a side wall 12b, and the inside of the resin case 12 is a circular surface flat surface. Cavity 14 is formed. An air hole 16 for communicating between the cavity 14 and the outside is formed in a substantially central portion of the flat surface portion 12a of the case 12. The air holes 16 are for assisting the flow of air generated by the vibration when the diaphragm 22 described later vibrates.

Two terminal plates 18 arranged side by side are insert-molded on the flat surface portion 12a of the resin case 12. From one end (the left end in FIG. 2) of each terminal board 18 to the connection terminal 1
8a extends, and the connection terminal 18a is exposed from one side surface (left side in FIG. 2) of the flat surface portion 12a of the resin case 12. Further, one end of the spring terminal 18b is fixed to the upper surface of each terminal plate 18. The other end (free end) of the spring terminal 18b
Project into the cavity 14. The spring terminal 18b is
For example, it is made of an elastic metal such as phosphor bronze, and due to its elasticity, its tip is press-contacted to a piezoelectric body 24 described later.

An exposure hole 20 for exposing a part of the terminal plate 18 is formed on the lower surface of the flat surface portion 12a of the resin case 12. When the piezoelectric sounder 10 is mounted, the exposed hole 20 is for connecting with a lead wire (not shown) without using the connection terminal 18a. In this case, since the lead wire is soldered to the terminal plate 18 through the exposed hole 20, the connection terminal 18a is unnecessary, and the connection terminal 18a may be cut flush with the outer surface of the resin case 12.

A peripheral edge of a disk-shaped vibrating plate 22 is fixed to the side wall 12b of the resin case 12 so as to seal the cavity 14. The diaphragm 22 is fixed by so-called "heat staking" in which a part of the side wall 12b is melted and solidified.
A disk-shaped piezoelectric body 24 having a diameter slightly smaller than the diameter of the cavity 14 is fixed to the lower surface of the diaphragm 22.
Although not shown, on the lower surface of the piezoelectric body 24, two electrodes to which the tips of the above-mentioned spring terminals 18b are pressure-connected are formed, and a voltage is applied thereto through the spring terminals 18b.

It should be noted that, as is apparent from FIG. 2, a void 26 remains inside the side wall 12b without being filled with the resin of the melted side wall 12b even after the vibrating plate 22 is heat caulked. That is, this void 26 is the result of the recess 30 described later being left as it is without being filled with the softened melting portion 28 (FIG. 1). Such a piezoelectric sounder 10 can be manufactured as follows.

First, as shown in FIG. 1, a resin case 12 having a flat surface portion 12a and a side wall 12b having a size that allows for the fusion portion 28 is insert-molded together with a terminal plate 18. At this time, the air holes 16 and the exposed holes 20 are formed in the flat surface portion 12a, and the inside of the side wall 12b is
A step surface 32 having a recess 30 is formed inside thereof.
The peripheral edge of the diaphragm 22 is placed on the step surface 32,
In this state, the peripheral edge of the diaphragm 22 is in close contact with the step surface 30, but the outermost peripheral edge thereof remains floating because of the recess 30.

Since the fusion zone 28 must be softened as described later, a thermoplastic resin (such as PBT or PET) is used as the material of the resin case 12. When the diaphragm 22 is positioned in the resin case 12, the outermost peripheral edge of the diaphragm 22 is placed above the recess 30 so as to float, and the peripheral edge of the diaphragm 22 is brought into close contact with the step surface 32 of the resin case 12. After that, the melted portion 28 is heated with the peripheral edge kept in close contact with the step surface 32, and the vibration plate 22 is fixed by the softened material of the melted portion 28. In this way, the piezoelectric sounder 10 as shown in FIG. 2 is completed.

At this time, since the softened material of the melted portion 28 wraps around the recess 30, the caulking stress is prevented from acting on portions other than the fixed portion of the diaphragm 22. If the recess 30 is not provided, caulking stress is applied to the vibrating plate 22 by pushing up the peripheral edge of the vibrating plate 22 by the resin melted during the heat caulking, but the recess 30 is provided as in this embodiment. For example, since the resin enters the concave portion 30, such caulking stress is not applied, so that the diaphragm 22 is “warped”.
Deformation does not occur.

If the vibrating plate 22 is deformed, as shown in FIG.
The sound pressure level varies as indicated by the alternate long and short dash line in the frequency characteristic of. However, in this embodiment, the recess 3
0 effectively prevents such deformation due to the stress of thermal staking, so that the sound pressure level does not vary as shown by the solid line in FIG.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a diaphragm is locked to a resin case when the piezoelectric sounder shown in FIG. 2 is manufactured.

FIG. 2 is a schematic sectional view showing a piezoelectric sounder manufactured according to the present invention.

FIG. 3 is a graph showing a sound pressure level with respect to frequency of a conventional piezoelectric sounder and a piezoelectric sounder manufactured according to the present invention.

FIG. 4 is a schematic sectional view showing an example of a conventional piezoelectric sounder.

FIG. 5 is a schematic sectional view showing an example of a conventional piezoelectric sounder.

[Explanation of symbols]

 10 ... Piezoelectric sounder 12 ... Resin case 12a ... Plane part 12b ... Side wall 14 ... Cavity 18 ... Terminal plate 18a ... Connection terminal 18b ... Spring terminal 20 ... Exposed hole 22 ... Vibration plate 24 ... Piezoelectric body 26 ... Void 28 ... Melting part 30 ... Recessed portion 32 ... Step surface

Claims (1)

[Claims] 1. A flat portion (12a) having an air hole (16) formed therein.
And a spring terminal (18b) including a side wall (12b) rising from the peripheral edge of the flat surface portion, the tip of which is insert-molded in the flat surface portion and the tip of which is exposed above the flat surface portion, the inner surface of the upper end portion of the side wall. A resin case having a step surface (32) formed at a position corresponding to the tip position of the spring terminal and a recess (30) formed in the step surface is prepared, and (b) the piezoelectric body (24) is fixed. A vibrating plate (22) is provided, (c) the peripheral edge of the vibrating plate is placed on the step surface so that the tip of the spring terminal contacts the piezoelectric body, and (d) the vibrating plate has a peripheral edge. A method of manufacturing a piezoelectric sounder, wherein a part of the side wall is melted while being floated due to the recess, and the periphery of the vibrating plate is heat caulked.