JPS61121700A - Flat plate diaphragm - Google Patents

Abstract

PURPOSE:To reproduce the whole band with one flat plate by fixing a piezo-electric thin film transducer to part of the inner surface of the surface material at the side to irradiate the sound wave of the core material of the sandwiched construction body, oscillating the piezo-electric thin film transducer which is part of the surface material and reproducing the high sound area. CONSTITUTION:A ceramic piezo-electric transducer 7 fixed to part of the inner surface of a surface material 2a at the side irradiating the sound wave, is fixed on the surface of the aluminum honeycomb core material 6 side of the surface material 2a. Here, the surface materials 2a and 2b are aluminum thin films and aluminum honeycomb core materials, and 6 is an aggregate of the hexagonal cell composed of an aluminum thin film with the thickness of 20mum. By fixing and oscillating the ceramic piezo-electric transducer at part of the surface material 2a of a flat plate diaphragm 3, the high sound area of fh or above of the flat plate diaphragm which can not be reproduced by the flat plate diaphragm 3 single body, can be reproduced. Further, since the whole band from a low tone to a high tone can be reproduced by one flat plate speaker, a sound source goes to be one and an acoustic characteristic such as directional characteristics goes to be satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a flat diaphragm having a sandwich structure in which surface materials are bonded to both sides of a core material.

Conventional technology Ideally, the diaphragm of a speaker should make piston motion over the frequency band used, and if the diaphragm deforms during vibration or split vibration occurs, the sound pressure frequency characteristics, distortion rate two-phase characteristics, etc. will deteriorate. This interferes with high-fidelity playback. In order to solve these problems, in recent years flat plate diaphragms using a highly rigid sandwich structure have been adopted in place of the conventional paper cone diaphragms.

Conventional techniques include, for example, a flat plate diaphragm with a sandwich structure using alumino-nicum as a core material, as shown in Japanese Utility Model Publication No. 84-57027, and Japanese Utility Model Publication No. 59-83.
As shown in Publication No. 497, a thin plate having a large number of hollow protrusions arranged circularly and circumferentially around the center on the entire surface of the diaphragm, and the bottoms of these protrusions are punched holes. There is a sandwich structure flat plate diaphragm with a core material of

In addition, generally, such a flat plate speaker generates the first resonance by driving the inner part of the cylinder at the first resonance frequency of the imaging plate.
The high frequency limit frequency (hereinafter fh) of the speaker cancels the next resonance.
The so-called nodal drive method is used, which increases the frequency of the diaphragm to near the second resonance frequency of the diaphragm. The conventional sandwich structure flat plate diaphragm as described above will be explained below with reference to the drawings. FIG. 3 shows a cross-sectional view of a conventional flat diaphragm. In FIG. 3, 1 is a core material, 2a and 2b are surface materials bonded to both sides of the core material 1, and 3 is a flat imaging plate in which the core material 1 and surface materials 2a and 2b are bonded. 4 is a coupling cone with one opening tip fixed to the surface material 2b and the other opening tip fixed to a Poissdil bobbin (not shown); 5, an inner peripheral end is fixed to the outer peripheral end of the surface material 2a; Glue and attach the outer edge to the frame (not shown)
This is an edge that is stuck to the surface.

The operation of the conventional flat plate diaphragm configured as described above will be described below. First, by transmitting the driving force from the voice coil to the surface material 2b via the coupling cone 4, the flat diaphragm 3 vibrates and generates sound. At this time, the edges 6 support the flat diaphragm 3 and prevent the sound behind the diaphragm from leaking to the front.

Problems to be Solved by the Invention However, with the above configuration, it is impossible to reproduce the entire audible range from bass to treble using one speaker. Therefore, in general, by reducing the size of the flat diaphragm for high-frequency sound reproduction speakers,
There are speakers for bass, midrange, and treble, and these are used in appropriate combinations to reproduce the entire range.

However, there is a problem in that the use of multiple speakers causes the sound sources to be dispersed, resulting in poor directional characteristics.

In view of the above problems, the present invention provides a flat diaphragm that can reproduce the entire frequency range with one speaker.

Means for solving the problem In order to achieve this object, the flat plate diaphragm of the present invention has a piezoelectric thin film transducer fixed to a part of the inner surface of the surface material on the side of the core material of the sandwich structure that emits sound waves. The structure is as follows.

Function: With this configuration, the entire flat plate diaphragm vibrates to reproduce low to mid-range K, and the piezoelectric thin film transducer, which is a part of the surface material, vibrates to reproduce the high range. The diaphragm makes it possible to reproduce the entire range.

Embodiment Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. FIG. 1 shows a cross-sectional view of a flat diaphragm in an embodiment of the present invention, and FIG. 2 shows a top view of the main parts thereof. In FIGS. 1 and 2, 2a.

2b is a surface material, 3 is a flat plate diaphragm, 4 is a coupling cone, and 6 is an edge, which are the same as those of the conventional example. 6 is an aluminum honeycomb core material, and 7 is a ceramic piezoelectric transducer fixed to a part of the inner surface of the surface material 2a on the side that radiates the sound groove, that is, fixed to the surface of the surface material 2a on the aluminum honeycomb core material e side. There is. Here, the surface material 2a
, 2b is an aluminum thin film (30 μm thick). The aluminum honeycomb core material 6 is an assembly of hexagonal cells made of a 20 μm thick aluminum thin film.

The operation of the flat plate diaphragm configured as described above will be described below. First, by transmitting the driving force from the voice coil to the surface material 2b via the coupling coil 74, the flat imaging plate 3 vibrates and generates sound. The reproduction band at this time is from the lowest resonant frequency fo of the flat diaphragm 3 to fh, and fh is determined by the rigidity of the flat diaphragm 3, and the higher the rigidity, the higher the fh.However, sufficient bass can be reproduced. In order to achieve this, it is necessary that the area of the flat diaphragm 3 be large to some extent, but this conversely reduces the rigidity and causes fh
will also become low, resulting in insufficient high-frequency reproduction.

For this reason, high-frequency sound reproduction, which is impossible with the flat imaging plate 3 alone, is achieved by moving the ceramic piezoelectric transducer 7 and vibrating a portion of the surface material 2a fixed thereto. At this time, the edges 5 support the flat diaphragm 3 as in the conventional example and prevent the sound behind the diaphragm from leaking to the front.

As described above, according to this embodiment, by fixing the ceramic piezoelectric transducer 7 to a part of the surface material 2a of the flat diaphragm 3 and vibrating it, it is possible to create a flat plate that cannot be reproduced by the flat diaphragm 3 alone. It is also possible to reproduce treble frequencies above fh of the diaphragm 3. Furthermore, since one flat speaker can reproduce the entire range from bass to treble, there is only one sound source, and the acoustic characteristics such as directional characteristics are improved compared to the conventional method, which uses multiple flat speakers and has dispersed sound sources. It will get better.

Although aluminum honeycomb core material 6 was used in this example, the same effect can be obtained with core materials made of other materials such as a molded body of plastic film or a honeycomb core material made of paper pulp as long as the core material is hollow. It is. However, the shape of the cell is not limited to a hexagon, but may be a triangle, square, two circles, etc. depending on the desired characteristics, and the size can be arbitrarily selected. Furthermore, the piezoelectric transducer 7 is not limited to ceramic, and may also be made of polymeric piezoelectric resin (for example, polyvinylidene fluoride). In this case, the weight can be reduced compared to ceramics, and the efficiency of the speaker can be increased.

Effects of the Invention The present invention makes it possible to reproduce the entire range from bass to treble with one flat speaker by fixing a piezoelectric thin film transducer to a part of the surface material of a flat plate diaphragm with a sandwich structure and taking pictures. Furthermore, since there is only one sound source, it is possible to realize a flat plate diaphragm that can obtain excellent effects such as good directivity.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a flat diaphragm according to an embodiment of the present invention, FIG. 2 is a top view of the main part thereof, and FIG. 3 is a sectional view showing a conventional flat diaphragm. 2a, 2b...surface material, 3...flat plate diaphragm, 6...aluminum honeycomb core material, 7...
...Ceramic piezoelectric transducer. ′

Claims (1)

[Claims] A flat plate diaphragm characterized in that a piezoelectric thin film transducer is fixed to a part of the inner surface of a surface material on the side that emits sound waves of a core material of a sandwich structure.