JPH0427299A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To suppress the occurrence of split oscillation in a thin part and to obtain a stable acoustic pressure frequency characteristic by making the part, which is made thin by forming a recessed part, in a resin foam plate of a material which has a high resin density and is superior in rigidity. CONSTITUTION:Recessed parts 40 and 50 are formed on the sides of less resin density of resin foam plates 4 and 5, namely, sticking faces of resin foam plates 4 and 5. Therefore, thin parts A where recessed parts 40 and 50 are formed have a high resin density and are superior in rigidity. With respect to production of these resin foam plates 4 and 5, a mold to form rein foam plates is used, and a resin having a high resin density (small air bubbles) is charged to one side of this mold, and a resin having a low resin density (large air bubbles) is charged to the other side. At this time, the resin is so charged that the resin having a high resin density passes round to the part of a projection 41 supporting a piezoelectric driver 6, and the piezoelectric driver 6 is firmly supported.

Description

[Detailed Description of the Invention] The production is complete! The present invention relates to a piezoelectric speaker in which a piezoelectric driver is provided in a recess formed in a foamed resin plate constituting a diaphragm so as to drive the diaphragm.

As an example of the conventional structure of the piezoelectric speaker described above, the one shown in FIG. 3 is known. This piezoelectric speaker has a diaphragm 3 formed by two foamed resin plates 4.5, and a recess 40 provided in the center of the opposing surfaces of both foamed resin plates 4.5.
．． The piezoelectric driver 6 is housed in the recess 40.50, and the piezoelectric driver 6 is sandwiched and supported between projections 41.51 provided at the center of the recess 40.50.

Therefore, in this type of piezoelectric speaker, since the above-mentioned recesses 40,50 are provided in the foam resin plate 4.5, the portion of the foam resin plate in which the recesses 40, 50 are formed,
It is thinner than other portions B, and the thinner portion A lacks rigidity. For this reason, when the vibration from the piezoelectric driver 6 is transmitted to the diaphragm 3, split vibration is likely to occur in the thin portion A, and this causes the sound pressure frequency characteristics to have peaks and valleys, resulting in poor sound quality. There was a problem.

The solution to the above problem is to create a foamed resin board with a higher resin density by making the bubbles smaller or fewer than before.
In other words, it is possible by using something with high rigidity,
This results in an increase in the weight of the foamed resin board, which lowers the sound pressure, which is undesirable.

The present invention has been made in view of the current situation, and provides a piezoelectric speaker that minimizes the increase in weight to make it difficult to reduce sound pressure, and that can improve sound quality by suppressing the occurrence of split vibration in the diaphragm. It is intended to.

i ° The present invention provides a piezoelectric speaker in which a piezoelectric driver is provided in a recess formed in a foamed resin plate constituting a diaphragm in a state in which the diaphragm is driven, in which the foamed resin plate increases the resin density in the thickness direction. It is characterized in that the concave portion is formed on the side with lower resin density.

According to the above configuration, the thin part of the foamed resin board is made of a material with high resin density and excellent rigidity, and the resin density is not high in the entire foamed resin board, and a part of the foamed resin board is made of a light resin. Materials with low density are present.

Sue” L-First Doctor Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a piezoelectric speaker according to the present invention, and FIG. 2 is a front view of the piezoelectric speaker.

3 in the figure is a diaphragm having a rectangular shape when viewed from the front, and is driven by a piezoelectric driver 6 provided inside to generate sound. A frame 1 having the same (rectangular shape in front view) is attached to the peripheral edge of the diaphragm 3, and an elongated tape-shaped elastic support piece 2 is provided between the rear surface of the diaphragm 3 and the frame 1.
It is interposed around the entire circumference of the diaphragm. The diaphragm 3 is formed by adhering two large and small rectangular foam resin plates 4 and 5 made of foamed polystyrene, foamed polyethylene, etc., facing each other. The foamed resin board 5 protrudes from the end face around the entire circumference, and is used with the larger foamed resin board 4 on the front side and the foamed resin board 5 on the rear side.

An annular recess 40 is provided in the center of the opposing surfaces of the foamed resin plates 4 and 5.
, 50 are provided in an abutting manner, and the piezoelectric driver 6 is housed between these recesses 40 and 50, and the piezoelectric driver 6 is bonded between circular protrusions 41 and 51 provided at the center of the recesses 40 and 50. It is attached using adhesive, etc. The height of the projections 41.degree. 51 is slightly shorter than the depth of the recesses 40 and 50.

The piezoelectric driver 6 has a structure in which piezoelectric bodies 61 and 61 made of, for example, PZT are adhered concentrically to both sides of a circular metal plate 60, and receives electrical signals from an amplifier (not shown). is applied, the piezoelectric driver 6 drives the diaphragm 3. This drives the diaphragm 3 to emit sound. In addition, it is preferable to use a material having appropriate elasticity for the elastic support piece 2 so as not to interfere with the vibration of the diaphragm 3. Further, the cross-sectional shape of the frame 1 is U-shaped, as shown in the first part, so that the inside is not visible from the outside.

By the way, the internal structure of the foamed resin plate 4.5 constituting the diaphragm 1 that vibrates and generates sound as described above is such that the resin density is varied in the thickness direction. Specifically, in each of the foamed resin plates 4.5, the size of the air bubbles C shown in FIG. . Here, the resin density refers to the proportion of resin per unit volume of the foamed resin plates 4 and 5.

The recesses 40, 50 in the foamed resin plates 4, 5 are formed on the side where the resin density is low, that is, on the side where both the foamed resin plates 4.5 are attached. For this reason, the recesses 40, 5
The thin portion A in which 0 is formed has a high resin density and high rigidity.

In addition, regarding the creation of such a foamed resin board 4.5,
You can do it as follows. Using a mold for forming a foamed resin board, first inject resin with high resin density (small air bubbles) to one side of the mold, then pour resin with low resin density (large air bubbles) to the remaining side. inject. At this time, it is preferable to inject resin with a high resin density so as to wrap around the portion of the projection 41 that supports the piezoelectric driver 6. This makes it possible to firmly support the piezoelectric driver 6.

In addition, in the above example, a foamed resin board 4.5 made using two types of resins with different sizes of bubbles C is used, but the present invention is not limited to this, and the size of bubbles C is the same. However, it is also possible to use a foamed resin board with a different number of resins and a different resin density.

Further, in the above embodiment, the recesses 40, 50 and the projections 41.
Although the foamed resin plates 4.5 on which 51 are formed are integrally molded using a mold, the present invention is not limited to this, and flat foamed resin plates 4, 5 having different resin densities in the thickness direction may be molded. After that, the recesses 40 and 50 may be formed on the sides of the foamed resin plates 4 and 5 where the resin density is lower.

Further, in the above embodiment, the foamed resin board 4.5 was created using two types of resins having different resin densities, but each foamed resin board may be created using three or more types of resin.

4. Furthermore, in the above embodiment, the case where the diaphragm is formed by two foamed resin plates has been described, but the present invention is also suitable for a piezoelectric speaker having a configuration in which the diaphragm is formed by one foamed resin plate. Needless to say, it can be implemented.

As described above, according to the present invention, the portion of the foamed resin plate that becomes thin due to the formation of the concave portion can be made of a material with high resin density and excellent rigidity, and the split vibration in the thin portion can be It is possible to obtain stable sound pressure frequency characteristics by suppressing the occurrence of noise, and to improve the sound quality.Also, since the resin density does not increase in the entire foamed resin board and there are some low resin density parts, The overall weight increase is small, and a reduction in sound pressure due to weight increase can be prevented, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a piezoelectric speaker according to the present invention, and FIG.
The figure is a front view thereof, and FIG. 3 is a sectional view showing a conventional piezoelectric speaker. 3...Diaphragm, 4°5...Foamed resin plate, C...Cubble, 6...Piezoelectric driver, 40°0...Concave portion, A...Thin wall portion.

Claims (1)

[Claims] (1) A piezoelectric speaker in which a piezoelectric driver is provided in a recess formed in a foamed resin plate constituting a diaphragm to drive the diaphragm, in which the foamed resin plate has a resin density that varies in the thickness direction. . A piezoelectric speaker, characterized in that the recess is formed on the side with lower resin density.