JPH11161278A - Piezoelectric buzzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small piezoelectric buzzer providing stably an announcing sound of 2 KHz. SOLUTION: This piezoelectric buzzer 50 has a cylindrical lower case 58 comprising a bottom wall 53 with external connecting terminals 51, 52 and a side wall 55 provided with a diaphragm locking part 59 and a recess 57 in its inner circumferential surface 55a and opened in its upper side, a cylindrical upper case 60 comprising a side wall 62 provided in its outer surface with a protrusion 61 engaged with the recess 57 and an upper wall 64, a piezoelectric element 71 fixed with a piezoelectric element provided with an electrode in a main face of a piezoelectric ceramic 72 2-50 μm thick in the central part of one of main faces of a metal diaphragm 2-50 μm thick and 8-14 mm diagonally, and insulation-covered conductors 77, 78 connected conductively to the matal diaphragm 71 and the electrode 73 of the piezoelectric element and connected in the other end to the external connecting terminals 51, 52 respectively with deflection. The peripheral part of the metal diaphragm 71 is constituted to be nipped between the diaphragm locking part 59 of the lower case 58 and the lower edge 65 of the side wall of the upper case 60 not to impede free vibration as well as to be locked to the diaphragm locking part 59.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric buzzer used at a single frequency for notification, which is frequently used in personal computers and other electric appliances, and in particular, listens to a conventional 4 kHz piezoelectric buzzer. The present invention relates to a structure of a piezoelectric buzzer which is gentle to a human ear and provides a more stable tone of 2 kHz and realizes the same level of size as a 4 kHz piezoelectric buzzer.

[0002]

2. Description of the Related Art A piezoelectric buzzer used as a sound source for confirmation and notification in electric products such as a personal computer and an electric rice cooker generally has a cylindrical shape in which a vertically divided case is fitted by fitting portions on the sides thereof. A ferroelectric material such as a thin piezoelectric ceramic (PZT (lead zirconate titanate)) is provided on one main surface of a thin metal vibrating plate (brass or iron-Ni alloy) called a piezoelectric vibrator or a piezoelectric element inside a plastic case. (A body ceramic, which has an electrostrictive effect that generates mechanical stress when an electric field is applied). A piezoelectric element provided with electrodes such as silver is fixed on the main surface with an adhesive or the like. This is a structure in which an external connection terminal electrically conductively connected to the electrode of the piezoelectric element is drawn out of the case.

The piezoelectric buzzer is required to be miniaturized and have a high sound pressure with diversifying applications.

A piezoelectric buzzer which emits at a single frequency used as a sound source for the above-mentioned confirmation and notification is measured by applying a rectangular wave input voltage of 5.0 Vp-p at an input frequency of 4 kHz in sound pressure-frequency characteristics, for example. 70dB at a distance of 10cm
A so-called 4 kHz product that can obtain the above sound pressure is currently common, and has a relatively unpleasant tone that sounds relatively high-pitched "Pe".

FIG. 6 shows an example of the sound pressure-frequency characteristics of the above 4 kHz piezoelectric buzzer. As you can see from the figure, frequency 4k
The first sound pressure peak appears near Hz, and its value exceeds 80 dB. Conversely, at frequencies below 3.5 kHz, it is less than 70 dB.

In general, the first large sound pressure peak (fundamental vibration mode) in the sound pressure-frequency characteristics of a piezoelectric element is such that the thinner the metal diaphragm and the piezoelectric ceramic, the larger the diameter of the piezoelectric element, and the peripheral portion thereof. Appear at a lower frequency as they are free rather than fixed.

Therefore, the diameter of a 4 kHz product used at a relatively high frequency can be reduced relatively easily. That is, the peripheral portion of a metal diaphragm of a piezoelectric element having a thickness of several tens of μm (for example, 50 μm) and a diameter of about 10 mm is provided on the inner wall surface of a cylindrical case with a relatively soft adhesive such as a silicon adhesive. This is realized by a structure that is adhered and fixed to the part.

The piezoelectric buzzer 10 shown in the perspective view of FIG. 5B is a 4 kHz piezoelectric buzzer having the above-described structure, and the smallest one has a case thickness D1 of 6 m.
m, and the diameter Φ1 is about 12 mm. Reference numeral 1 denotes a sound emission hole, 2 denotes a cylindrical upper case, 3 denotes a cylindrical lower case, and 4 and 5 denote external connection terminals implanted in the lower case 3. The lower case 3, which is entirely open at the top, is covered by a cover so that the upper case 2 having a larger dimension covers the upper case 2 in a direction in which they are bonded to each other by locking means (not shown) provided on both side surfaces. Only a pressing force is applied and it is firmly assembled. At this time, the metal vibrating plate of the piezoelectric element is placed on a step provided on the side surface or the upper end surface of the lower case and fixed with an adhesive, or pressed from the upper case to the step of the lower case. Adhesively fixed.

By the way, as a result of the frequent use of a 4 kHz piezoelectric buzzer for various electric appliances, a somewhat harsh and jarring electronic sound is frequently heard from here and there. From this point, it is considered that the use of a piezoelectric buzzer that is gentle to the listener's ear and vibrates at a low tone of about 2 kHz with a more stable feeling will increase in the future.

[0010]

However, a 2 kHz product piezoelectric buzzer 20 shown in the perspective view of FIG. 5A currently has a case Φ2 of about 25 mm in diameter and the same scale. 4 kh of FIG. 5 (b) drawn
As apparent from comparison with the z-type piezoelectric buzzer 10, about 2
It is twice the size. This means that in order to obtain a high sound pressure at a low frequency of 2 kHz, the diameters of the piezoelectric element 12 and the metal diaphragm 11 of the piezoelectric element having a predetermined thickness must be increased, and As can be seen, the external connection terminals 13, 14 serve as conductive connection means between the external connection terminals 13, 14 and the electrodes of the metal diaphragm 11 and the piezoelectric element 12.
(14) that frame leads 15 and 16 are used, each of which is integral with the component 14, and that connection portions (soldering portions) 17 and 18 are pressed by the frame leads to prevent free vibration of the piezoelectric element. The fact that the peripheral portion of the metal diaphragm 11 is fixed to the inner periphery of the case 19 with an adhesive over almost the entire periphery and the vibration of the peripheral portion is suppressed is three points for obtaining a sufficient sound pressure at 2 kHz. It is an impeding factor, and the size increase compensates for these impeding factors.

The present invention has been made in view of the above circumstances, and provides a piezoelectric buzzer capable of stably obtaining a 2 kHz sound pressure and having a size reduced to the same level as that of a conventional 4 kHz piezoelectric buzzer. To provide.

[0012]

According to the present invention, there are provided: (1) a bottom wall on which a plurality of external connection terminals are planted; And a side wall provided with a first case fitting means. The lower case has an upper opening, and a sound emission hole is formed. An upper case having an upper wall to be closed, and a side wall erected around the upper wall, and an outer surface provided with second fitting means fitted to the first case fitting means on an outer surface thereof; , Thickness 2μm ~ 5
A piezoelectric element in which a piezoelectric element having an electrode on a main surface of a piezoelectric ceramic having a thickness of 2 to 50 μm is fixed to a central portion of one main surface of a metal vibrating plate having a thickness of 0 μm and a diameter of 8 mm to 14 mm; One end is electrically conductively connected to the plate and the electrode of the piezoelectric element, and the other end is connected to the external connection terminal by bending each of the external connection terminals.
A peripheral portion of the metal diaphragm is locked to a diaphragm locking portion of a side wall of the lower case, and a gap between the diaphragm locking portion and a lower edge of the side wall of the upper case fitted to the lower case. The above object is attained by providing a piezoelectric buzzer characterized by being sandwiched by.

(2) The above object is achieved by providing the piezoelectric buzzer according to (1), wherein the lower edge of the side wall of the upper case is pointed.

(3) The piezoelectric buzzer according to the above (1) or (2), wherein the insulated conductor is an insulated conductor having lower rigidity than the external connection terminal. The above purpose is achieved by providing.

(4) In the piezoelectric buzzer according to any one of the above (1) to (3), the insulation-coated conductor has a wire diameter of 10 μm to 5 μm.
The object is achieved by providing a piezoelectric buzzer characterized by a twisted wire in which a plurality of 0 μm thin wires are twisted.

(5) In the piezoelectric buzzer according to any one of (1) to (4), the fitting position between the lower case and the upper case is higher than the diaphragm locking portion of the lower case. The above object is achieved by providing a piezoelectric buzzer characterized by the following.

(6) In the piezoelectric buzzer according to any one of the above (1) to (5), the length of the insulated conductor is longer than two thirds of the diameter of the metal diaphragm and not more than three times the diameter. The above object is achieved by providing a piezoelectric buzzer characterized in that:

(7) Further, in the piezoelectric buzzer according to any one of the above (1) to (6), the depth d is h / 6 ≦ in relation to the height h of the lower case in the upper part of the side wall of the lower case.
The above object is attained by providing a piezoelectric buzzer having a plurality of cutouts in the range of d ≦ h / 2.

In the present invention, the lower case having the external connection terminal of the above (1) is provided with a diaphragm locking portion, and a thin piezoelectric element is sandwiched by a fitting structure of the upper case and the lower case. Due to the synergistic effect of using the conductive connecting means with the insulated conductive wire connected with a flexure, the diaphragm can be vibrated efficiently, and a 2 kHz piezoelectric material having a dimension approximately half that of the conventional product can be obtained. A buzzer can be realized.

In the above (2), since the lower edge of the side wall of the upper case, which is one of the sides for holding the metal diaphragm, is sharp, the contact portion with the metal diaphragm becomes a very small line,
More free vibration is ensured.

Further, in the above (3), since the insulation-covered conductive wire has a lower rigidity than the external connection terminals, free vibration is ensured, so that a higher sound pressure can be obtained.

Further, in the above (4), since the insulated wire is a twisted thin wire, the influence on the vibration of the piezoelectric element can be reduced as compared with a single insulated wire and the sound pressure can be improved. In addition, the piezoelectric element can be easily incorporated into the case without damaging the thin piezoelectric element.

Further, in the above (5), since the fitting position of the lower case and the upper case is at a position higher than the holding portion (away from the surface of the substrate), the vapor of the flux flows through a slight gap of the fitting portion. And the like hardly penetrate, and the reliability of the piezoelectric buzzer is further improved.

In the above (6), as is apparent from the structure of the piezoelectric buzzer of the present invention,
After connecting the insulated conductor wire to the piezoelectric element first by soldering or the like, it is necessary to turn the piezoelectric element upside down and place it with the main surface of the piezoelectric ceramic fixed to the locking part of the lower case with the main surface facing down. The coated conductor must have a certain length, which must be at least longer than 2/3 of the diameter of the metal diaphragm. On the other hand, since the insulation-covered conductor is housed in the closed space on the bottom side of the lower case, if it is too long, the middle part thereof contacts the piezoelectric element and hinders vibration, so that the diameter may be three times or less the diameter of the diaphragm. It is preferred.

Further, in the above (7), the depth dimensions of the plurality of cutouts provided on the opening side end face of the larger lower case are specified. The upper case and the lower case can be fitted together, and the thin piezoelectric element is less likely to be damaged during work.

[0026]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view for explaining the structure of a piezoelectric buzzer according to the present invention.

FIG. 2 is a sectional view for explaining the internal structure of the piezoelectric buzzer according to the present invention.

FIG. 3 is an enlarged partial sectional view of a fitting portion between the lower case and the upper case of the piezoelectric buzzer according to the present invention.

FIG. 4 is a diagram showing a sound pressure-frequency characteristic of a 4 kHz piezoelectric buzzer according to the present invention.

In FIG. 1 and FIG.
Is a bottom wall 5 on which two external connection terminals 51 and 52 are planted.
And a side wall 55 which is provided upright from the outer peripheral edge of the bottom wall 53 and has a diaphragm locking portion 59 and a concave portion 57 as a first case fitting means provided around the inner peripheral surface 55a. And
A lower case 58 having a cylindrical shape whose upper part is entirely open; an upper wall 64 having a sound emission hole 63 formed therein and facing the bottom wall 53 of the lower case 58 to close the opening; The recess 5 of the first case fitting means of the side wall 55
7, a cylindrical upper case 60 composed of a side wall 62 provided on the outer surface with a convex portion 61 as a second fitting means fitted with each other, a thickness of 2 μm to 50 μm, and a diameter of 8 mm
At the center of one main surface of the metal diaphragm 71 of ~ 14 mm,
One end is provided for each of a piezoelectric element 70 in which a piezoelectric element having electrodes 73 on both sides of a piezoelectric ceramic 72 having a thickness of 2 μm to 50 μm is fixed with an adhesive or the like, the metal vibration plate 71 and the electrode 73 of the piezoelectric element. Are electrically connected, and the other end is connected to the two external connection terminals 51 and 52 with flexures, respectively, with insulated conductors 77 and 78. The peripheral portion of the metal diaphragm 71 is Side wall 5 of the lower case 58
5 is locked (placed) on the diaphragm locking portion 59 inside the diaphragm 5, and between the diaphragm locking portion 59 and the lower edge 65 of the side wall of the upper case 60 fitted to the lower case 58. The first feature is to be sandwiched. Reference numeral 81 is a standoff.

Here, in the holding means obtained by the fitting structure of the concave portion 57 and the convex portion 61, the upper surface 57a of the concave portion 57 presses the upper surface 61a of the convex portion 61 downward, so that it serves as a clamping pressure applying means. I have.

In addition to the above structure, as shown in FIG. 3, the diaphragm locking portion 59 of the side wall 55 of the lower case 58 and the side wall 6 of the upper case 60 fitted to the lower case 58.
2 is in the range of t−20 ≦ w ≦ t (μm) in relation to the thickness t of the peripheral portion of the metal diaphragm 71, and the metal diaphragm 71 is held without play. Is preferably performed.

A third feature is that the lower edge of the side wall 62 of the upper case 60 is sharp. As shown in FIG. 3, the lower edge 65 of the side wall 62 of the upper case 60 has a triangular cross section with a pointed lower portion, and is in point contact (the metal diaphragm 71).
(Line contact along the periphery of the line). Therefore, compared to the surface contact, the metal diaphragm 71
Free vibration is ensured.

The third characteristic is that a single wire or a double wire having a lower rigidity than the external connection terminal is used as the insulated conductor used in the piezoelectric buzzer 50. As a result, the sound pressure is improved.

Further, as shown in FIG. 2, the insulation covered conductors 77 and 78 are preferably twisted plural wires (preferably 4 to 12 wires) having a wire diameter of 10 to 50 μm. With this, the influence on the vibration of the piezoelectric element 70 can be reduced as compared with the case of a single insulated conductor, and the sound pressure can be improved, and the incorporation of the piezoelectric element into the case may damage the thin piezoelectric element. Can be easily performed without the need.

The fitting position of the concave and convex portions of the lower case 58 and the upper case 60 (the positions of the concave portions 57 and the convex portions 61 in FIG. 3) is a diaphragm locking portion of the lower case which is a holding portion of the piezoelectric element 70. A fifth feature is that the device is disposed at a position higher than 59. In this regard, in the conventional product, as shown in FIG. 5B, the size relationship of the fitting of the upper case 2 and the lower case 3 is reversed, and the fitting portion has a height close to the bottom surface (near the notch portion 7). )It is in.

With the configuration in which the fitting position is higher than the holding portion (away from the substrate surface), it becomes difficult for flux vapor or the like due to solder bonding to enter the inside from the gap between the fitting portions, so that the piezoelectric buzzer 50 Is considered to be more reliable.

A sixth feature is that the length of the insulated conductors 77 and 78 is longer than two thirds of the diameter of the metal diaphragm 71 and three times or less.

This is inevitably due to the shape of the case during the manufacturing process.
8 are connected by soldering or the like, the piezoelectric element 70 is turned over, and the piezoelectric ceramic 73 is fixed to the locking portion 59 of the lower case 58 with the main surface thereof facing down. , 78 must have a certain length, which must be at least longer than 2/3 of the diameter of the metal diaphragm. On the other hand, the insulated conductors 77, 7
8 is not more than three times the diameter of the diaphragm, because if it is too long, the intermediate portion thereof will contact the piezoelectric element 70 and hinder free vibration because it is housed in the closed space on the bottom wall side of the lower case 58. Is preferred.

Further, a plurality of cutouts whose depth d is in the range of h / 6 ≦ d ≦ h / 2 in relation to the height h of the lower case 58 are provided above the side wall surface 55 of the lower case 58. The seventh feature is that 80 (optimally, 6 to 12 dimensional widths of 1/5 to 1/10 of the case diameter) are provided.

When the upper case 60 and the lower case 58 are fitted to each other, the fitting can be performed with a smaller force so that the workability is improved and the thin piezoelectric element is hardly damaged. An appropriate elasticity of the resin is given to the convex portion of the unevenness formed by the notch portion 80, so that the fitting is easy. In this regard, the depth d of the notch 80 is in the range of h / 6 ≦ d ≦ h / 2 in consideration of the strength of the case itself while considering that the fitting position is at a high position of the lower case 58. Was found to be appropriate.

The assembly of the piezoelectric buzzer 50 is as follows.
(A) Implanting the external connection terminals 51 and 52 in the lower case 58; (b) conducting connection between the piezoelectric element 70 and the external connection terminals 51 and 52 by insulating coating wires 77 and 78; Is placed (locked) on the diaphragm locking portion 59 of the lower case 58, and (d) the upper case 60 is fitted to the lower case 58 to close the case.

According to the prototype of the inventor, as can be seen from the sound pressure-frequency characteristics of the piezoelectric buzzer 50 shown in FIG. 4, the first large sound pressure level peak is obtained in a frequency band of about 2 kHz. The sound pressure exceeds 70 dB (measurement conditions are as follows: at an ambient temperature of 25 ° C., an input voltage of 5.0 Vp-p is changed from a frequency of around 1.5 kHz to over 20 kHz, and the sound pressure is changed at a distance of 10 cm. It was measured).

The dimensions of the piezoelectric buzzer 50 are approximately 7 mm in height of the whole case and 14 mm in diameter, which is almost the same level as the smallest 4 kHz product.

[0046]

The piezoelectric buzzer according to the present invention is configured as described above. (1) The piezoelectric element has a piezoelectric element with a diameter of about 12 mm and a size of 2 kHz.
The product has a piezoelectric buzzer with an input frequency of 2.0 kHz,
A sound pressure of 70 dB or more can be obtained with a rectangular wave input voltage of 5.0 Vp-p.

(2) 2k of the same tone size as the conventional minimum 4 kHz piezoelectric buzzer and gentler than the conventional 4 kHz
Hz piezoelectric buzzer is obtained.

(3) Assembly is easy without damaging the piezoelectric element.

(4) A highly reliable 2 kHz piezoelectric buzzer is less affected by flux vapors on the substrate.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view for explaining a structure of a piezoelectric buzzer according to the present invention.

FIG. 2 is a cross-sectional view illustrating an internal structure of a piezoelectric buzzer according to the present invention.

FIG. 3 is an enlarged partial sectional view of a fitting portion between a lower case and an upper case of the piezoelectric buzzer according to the present invention.

FIG. 4 is a diagram showing a sound pressure-frequency characteristic of a 4 kHz piezoelectric buzzer according to the present invention.

5A and 5B are perspective views of a conventional piezoelectric buzzer, in which FIG. 5A is a perspective view of a 2 kHz piezoelectric buzzer with one case removed, and FIG. 5B is a view showing the appearance of a 4 kHz piezoelectric buzzer. is there.

FIG. 6 is a diagram showing an example of a sound pressure-frequency characteristic of a conventional 4 kHz piezoelectric buzzer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sound emission hole 2 Upper case 3 Lower case 4, 5, 13, 14, 51, 52 External connection terminal 7, 80 Notch 10, 20, 50 Piezoelectric buzzer 11 Metal diaphragm 12 Piezoelectric element 15, 16 Frame lead 17, Reference Signs List 18 connection portion (soldering portion) 19 case 53 bottom wall 55, 62 side wall 55a inner peripheral surface 57 concave portion 57a upper surface of concave portion 58 lower case 59 diaphragm locking portion 60 upper case 61 convex portion 61a upper surface of convex portion 63 Sound emission hole 64 Upper wall 65 Lower edge 70 Piezoelectric element 71 Metal vibration plate 72 Piezoelectric ceramic 73 Electrode 77, 78 Insulated wire (twisted wire) 81 Standoff D1 Case thickness Φ1 Case diameter w Gap t Metal vibration plate Thickness h Height dimension d Depth Φ1, Φ2 Case diameter

Claims (7)

[Claims] 1. A bottom wall on which a plurality of external connection terminals are planted, and a diaphragm locking portion and first case fitting means are provided on an inner peripheral surface of the bottom wall, the standing wall standing from an outer peripheral edge of the bottom wall. With side walls,
A lower case having an upper opening, a sound emitting hole being drilled, an upper wall opposing a bottom wall of the lower case, closing the opening, and being erected around the upper wall. Side walls,
An upper case provided on the outer surface thereof with a second fitting means fitted to the first case fitting means, and a metal diaphragm having a thickness of 2 μm to 50 μm and a diameter of 8 mm to 14 mm. One end of each of a piezoelectric element in which a piezoelectric element having an electrode is fixed to a main surface of a piezoelectric ceramic having a thickness of 2 μm to 50 μm and a metal diaphragm and an electrode of the piezoelectric element are provided at the center of one main surface. An insulating-coated conductive wire that is conductively connected and the other end of which is connected to the external connection terminal so as to bend, wherein a peripheral portion of the metal diaphragm is a diaphragm locking portion on a side wall of the lower case. And a piezoelectric buzzer that is sandwiched between the diaphragm locking portion and a lower edge of a side wall of the upper case fitted to the lower case. 2. The piezoelectric buzzer according to claim 1, wherein
A piezoelectric buzzer wherein the lower edge of the side wall of the upper case is sharp. 3. The piezoelectric buzzer according to claim 1, wherein the insulated conductor is an insulated conductor having lower rigidity than the external connection terminal. 4. The method according to claim 1, 2 or 3.
2. The piezoelectric buzzer according to item 1, wherein the insulated conductor has a wire diameter of 10
A piezoelectric buzzer comprising a twisted wire formed by twisting a plurality of thin wires of μm to 50 μm. 5. The method according to claim 1, 2 or 3.
5. The piezoelectric buzzer according to claim 4, wherein a fitting position of the lower case and the upper case is arranged at a position higher than a diaphragm locking portion of the lower case. 6. 6. The method according to claim 1, wherein said first and second means are different from each other.
In the piezoelectric buzzer according to claim 4 or 5, the length of the insulated conductor is 2/3 of the diameter of the metal diaphragm.
A piezoelectric buzzer, which is longer than three times the diameter. 7. The method according to claim 1, 2 or 3.
Alternatively, in the piezoelectric buzzer according to claim 4 or claim 5 or claim 6, the depth d
Is h / 6 ≦ d in relation to the height h of the lower case.
A piezoelectric buzzer having a plurality of cutouts in a range of ≦ h / 2.