JP2516993Y2 - Piezoelectric vibration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a piezoelectric vibrating device that fixes a piezoelectric vibrating plate in which a piezoelectric ceramic and a metal plate are joined to each other in an outer case to generate various acoustic signals. .

[Prior Art] A conventional piezoelectric vibrating device has a piezoelectric ceramics 12 in which electrodes such as silver and nickel are provided on both surfaces of a thin metal disk 10 as shown in FIGS. 6 and 7, for example. However, they are concentrically attached with an adhesive to form a piezoelectric vibrating plate 14, and the piezoelectric vibrating plate 14 is housed in an outer case 16 made of synthetic resin. The piezoelectric vibration plate 14 is fixed by mounting the piezoelectric vibration plate 14 on an acute-angled step portion 18 formed on the inner wall surface of the outer case 16, and further by mounting a bottom plate 22 having a ring-shaped protrusion 20 on the stepped portion 18.
Attached so as to cover the bottom side opening of the outer case 16, the projection 20 holds the piezoelectric vibrating plate 14 between the step portion 18,
It is fixed with an elastic adhesive.

A sound emitting hole 24 is formed in the center of the upper surface closed portion of the outer case 16, and a pair of mounting seats 26 facing each other are formed at the side edges of the bottom opening, and a mounting hole 28 is formed in the mounting seat 26. Has been formed.

When an alternating electric field is applied to the piezoelectric vibrating plate 14 from the outside, the bending vibration is excited in the piezoelectric vibrating plate 14 and the oscillating sound is emitted from the sound emitting hole 24 in the piezoelectric vibrating device having the above configuration.

[Problems to be Solved by the Invention] In the case of the above conventional technique, the mounting seat 26 of the outer case 16 is used.
Therefore, when mounted on a printed circuit board or a column of the mounted device, the resonance frequency fluctuates to a value different from that measured by the standard measurement method performed by mounting on a thick plate, and the sound pressure also decreases. There is. In particular, in the case of a so-called self-exciting type piezoelectric vibrating device, there is a problem that the oscillation frequency varies greatly depending on the mounting state.

This is because when a bending vibration is excited in the piezoelectric diaphragm 14, the peripheral portion of the piezoelectric diaphragm 14 also vibrates with a slight amplitude, and the vibration propagates to the outer case 16 and is applied to the piezoelectric diaphragm 14. This is because the load will be different.

The present invention has been made in view of the above-mentioned problems of the conventional technique, and an object thereof is to provide a piezoelectric vibrating device having a simple structure in which the output does not change depending on the mounting state.

[Means for Solving the Problem] The present invention has a piezoelectric case in which a piezoelectric vibrating plate to which a piezoelectric body is adhered is housed, and a piezoelectric body having a mounting seat protruding from the side of the external case. In the vibrating device, the piezoelectric vibrating plate in the outer case is fixed in the outer case by a protrusion protruding from a bottom plate provided on the bottom of the outer case on the mounting seat side, and the piezoelectric vibrating plate is fixed in the outer case. It is held slightly inward from the peripheral edge of the piezoelectric vibrating plate by the stepped portion inside and the protrusion of the bottom plate, and the bottom plate is elastically caused by the outer case or the engagement surface of the inclined surface of the peripheral surface of the bottom plate. When the thickness from the mounting surface of the mounting seat is T, and the distance from the bottom surface of the bottom plate to the mounting surface of the mounting seat is t, , T / T 0.3 More than 0.
The piezoelectric vibrating device is characterized by being formed to 7 or less.

[Operation] In the piezoelectric vibrating device of the present invention, the bottom surface of the outer case is separated from the mounting surface of the mounting seat by a predetermined distance so that the load applied to the piezoelectric vibrating plate during oscillation is constant.
The output does not fluctuate depending on the mounting condition.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 to 4 show an embodiment of the present invention, in which a piezoelectric ceramic 32 provided with electrodes such as silver or nickel is concentrically attached to the surface of a thin metal plate 30 with an adhesive. Thus, the piezoelectric vibrating plate 34 is formed, and the piezoelectric vibrating plate 34 is housed in an outer case 36 made of synthetic resin. The electrodes of the piezoelectric vibrating plate 34, as shown in FIG.
The piezoelectric vibrating device of this embodiment, which is composed of the small electrodes 33, is of a so-called self-excitation type.

The piezoelectric vibrating plate 34 is fixed by mounting the piezoelectric vibrating plate 34 on an acute-angled step portion 38 formed on the inner wall surface of the outer case 36, and further by mounting a bottom plate 42 having a ring-shaped protrusion 40 on the outer surface. Case
It is attached so as to cover the bottom side opening of 36, and the protrusion 40 is formed by holding the inner peripheral side of the peripheral edge of the piezoelectric vibrating plate 34 slightly between the step 40 and the elastic member and fixing it. ing.
Therefore, the bottom plate 42 forms the bottom portion of the outer case 36.

In addition, the sound output hole 44 is provided at the center of the upper surface closed portion of the outer case 36.
Is formed, and a pair of mounting seats are provided on both side edges of the bottom opening.
46 is formed, and a mounting hole 48 is formed in this mounting seat 46. Further, the outer case 36 includes the mounting surface of the mounting seat 46 and the surface of the bottom plate 42, that is, the outer case 36.
The mounting surface of the mounting seat 46 is formed in a shape protruding downward by a step t from the surface of the bottom plate 42 so as to be slightly separated from the bottom surface portion by a distance t.

The bottom plate 42 is attached by engaging the peripheral portion of the bottom plate 42 with the notch groove 41 formed on the entire periphery of the bottom opening of the outer case 36. Here, the peripheral surfaces of the notch groove 41 and the bottom plate 42 are formed in a sloped shape. Due to this slope, the bottom plate 42
By engaging with the notch groove 41, the outer case 36 is elastically expanded and the bottom plate 42 is mounted, so a force in the contracting direction acts on the outer peripheral surface of the bottom plate 42, and the bottom plate 42 is moved by the slope. The piezoelectric vibrating plate 34 is sandwiched and is biased upward.

In the oscillation circuit of the piezoelectric vibrating device of the present invention, as shown in FIG. 4, a power supply voltage of + V is applied to the large electrode 31 of the piezoelectric vibrating device 34 via the resistor R ₁ , and the small electrode 33 also has a voltage of + V. A voltage is applied from the power supply voltage via resistors R ₁ and R ₂ . A transistor Q is provided in parallel with the piezoelectric vibrating plate 34, and the base of the transistor Q is grounded via the diode D and is also connected to the small electrode 33 via the resistor R ₃ .

The results of measurement experiments of the piezoelectric vibration device according to this example are shown.
Shown in 1,2,3. Here, the thick plate used was 100 × 100 × 300 mm square material, the printed circuit board used was 1.2 mm thick and 70 × 90 mm, and the support pillar used was 5 mmφ and 5 mm high. The outer case 36 has an outer diameter of 24 mmφ, and the piezoelectric diaphragm 34 has a diameter of 21 mm.
mmφ. Then, the thickness T of the mounting seat 46 is made constant, the interval t between the mounting surface of the mounting seat 46 and the bottom surface of the outer case 36 is changed, and the oscillation frequency and the sound pressure level are set for each of the three types of applied voltages. Was measured.

Table 1 shows the experimental results for T = 1.5 mm, t = 0, that is, no step, and t = 0.3 mm.
Is the same as T = 1.5mm, t is 0.45, and t is 0.6mm. Table 3 shows T = 1.5m.
The experimental results are for m and t of 0.9 and t of 1.05 mm.

In the piezoelectric vibrating device of this example, as shown in the above tables, when t / T is 0.2 or less, it is understood that the oscillation characteristics change depending on the mounting state. Further, in the structure of the outer case 36 of this embodiment, when t / T exceeds 0.7, the mechanical strength of the mounting seat 46 becomes weak and it is not practical, so t / T was expected to be in the range of 0.3 to 0.7. It can be said that the result is obtained.

The piezoelectric vibrating device of the present invention has electrodes 50 and 52 formed on both surfaces of a piezoelectric ceramic 32 as shown in FIG.
This can be applied to a so-called separately excited type in which this is attached to the metal plate 30 and an external alternating electric field is applied to the electrodes 50 and 52 to oscillate, and the same effect can be obtained.

[Effect of the Invention] In the piezoelectric vibration device of the present invention, the mounting seat of the exterior case accommodating the piezoelectric vibration plate is projected downward in a predetermined range,
Since the bottom surface of the bottom plate of the outer case is mounted so that it is spaced from the mounting surface by a predetermined distance, the characteristics of the oscillating sound do not change depending on the mounting condition of the mounted device, and stable resonance frequency and sound pressure can be obtained. To be

Further, the piezoelectric vibrating device of the present invention can obtain a desired effect only by changing the shape of the outer case, does not require a change in the assembling process, and is extremely convenient in terms of manufacturing control.

Further, since the bottom plate holding the piezoelectric vibrating plate elastically contacts and holds the piezoelectric vibrating plate, the holding is reliable and there is no adverse effect on vibration. Further, since the piezoelectric vibrating plate is sandwiched slightly inside the peripheral edge portion, it is possible to reliably and stably hold the piezoelectric vibrating plate over the entire circumference.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the piezoelectric vibration device of the present invention, FIG. 2 is a bottom view of the piezoelectric vibration device of this embodiment, and FIG.
FIG. 4 is a plan view of the piezoelectric vibrating plate of this embodiment, FIG. 4 is a circuit diagram of an oscillation circuit of the piezoelectric vibrating device of this embodiment, and FIG. 5 is another piezoelectric vibrating plate used in the piezoelectric vibrating device of the present invention. FIG. 6 is a vertical sectional view of a conventional piezoelectric vibration device,
FIG. 7 is a bottom view of a conventional piezoelectric vibration device. 30 …… Metal plate, 32 …… Piezoelectric ceramics, 31,33,50,52
...... Electrode, 36 …… External case, 42 …… Bottom plate, 46 …… Mounting seat

Claims (1)

(57) [Scope of utility model registration request] 1. A piezoelectric vibrating device having an outer case that houses a piezoelectric vibrating plate to which a piezoelectric body is attached, and a mounting seat protruding from a side of the outer case.
The piezoelectric vibrating plate in the outer case is fixed in the outer case by a protrusion protruding from a bottom plate provided on the bottom of the mounting case side of the outer case, and the piezoelectric vibrating plate is a stepped portion in the outer case. And the projection of the bottom plate holds the piezoelectric vibrating plate on the inner peripheral side slightly from the peripheral edge of the piezoelectric vibrating plate, and the bottom plate elastically resiliently moves by the outer case or the slanting engagement surface of the peripheral surface of the bottom plate. When the thickness of the mounting seat from the mounting surface is T, and the distance from the bottom surface of the bottom plate to the mounting surface of the mounting seat is t, then t / T 0.3 to 0.7
A piezoelectric vibrating device formed as follows.