JPH07193891A - Diaphragm for speaker and its manufacture - Google Patents

Abstract

PURPOSE:To provide the diaphragm for speaker small in distortion factor and high in input resistance by impregnating a polyethylene terephthalate oxyethylene copolymer polyester into paper pulp. CONSTITUTION:A polyethylene terephthalate oxyethylene copolymer polyester resin is obtained by reacting a telephthalic acid dimethyle, ethylene glycol, polyoxyethyleneglycol in a ratio of 1:2:1 for the synthesis. The resin is impregnated to a craft pulp at a rate of 20% of conversion and dried and only the surface layer is heated and molten ion a metallic die and then cooled and solidified to be a prescribed form as the diaphragm. The speaker using the diaphragm having a sandwich structure the surface layer of which is heated, molten and then cooled and solidified has an excellent acoustic characteristic without deformation of the diaphragm and split resonance. That is, the distortion factor is small and a high resonance frequency is set higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm for a speaker used in a sound output device or the like.

[0002]

2. Description of the Related Art Recently, in the audio industry,
With the digitization of reproduced music sources, speakers as acoustic output devices are required to have output sound pressure, distortion rate, and flatness that are better than before in terms of their characteristics, and it is desired to improve the reproduced sound quality. Therefore, speaker diaphragms, which influence the acoustic characteristics, are becoming more and more important.

In addition, especially for PA, studio monitor,
In-vehicle speakers are used under severe conditions, and particularly when a large input is applied, appropriate strength for the diaphragm is required according to the amplitude amount of the vibration system.

From the viewpoint of the acoustic characteristics of the speaker, it is ideal that the diaphragm for the speaker makes a piston motion over the frequency band to be used, but if the diaphragm is deformed during vibration or divided vibration occurs, the sound pressure is reduced. -Frequency characteristics, distortion factor,
The phase characteristics are deteriorated, which hinders high fidelity reproduction.

From the viewpoint of input resistance, the speaker diaphragm has sufficient strength against bending stress applied when the vibration system vibrates and peeling force applied to the joint between the diaphragm and other parts. If it is not done, it will be destroyed especially at large amplitude.

[0006]

The conventional paper-pulp diaphragms that have been widely used are: (1) Since the material has a small E / ρ (E: elastic modulus, ρ: density), it has a high resonance frequency. The speaker is too low to play at high frequencies. (2) Since the elastic modulus is low and the strength against bending stress is low, buckling occurs at the time of large input. (3) Since the binding force between pulp fibers constituting the material is weak and the peel strength in the surface thickness direction is weak, peel failure occurs in layers at the bonding site. There was a drawback.

In view of the above problems, the present invention provides a speaker diaphragm having a high high resonance frequency without the diaphragm being deformed or divided vibration during vibration.

[0008]

In order to achieve this object, a speaker diaphragm of the present invention comprises a kraft pulp impregnated with polyethylene terephthalate / oxyethylene copolymerized polyester, and only the surface portion is heated and melted and then cooled and solidified. Also, a material having a sandwich structure is used as the diaphragm.

[0009]

With this structure, the polymer chains of the copolyester, which is the impregnating resin, intersects with the cellulose, which is the constituent unit of the pulp, and the hydrogen bonds between them physically reinforce each other, so that the pulp fibers The binding force between them and the bending rigidity can be improved. Further, in the structure of the above-mentioned material, since an ethylene chain is introduced, a higher internal loss is obtained as compared with a polyethylene terephthalate resin or paper pulp alone, and the sound pressure-frequency characteristic peak dip is improved. It

Further, by heating, melting and cooling and solidifying only the surface layer after the impregnation, a more uniform and dense resin layer can be re-formed on the surface, and a material having a sandwich structure can be easily obtained. Therefore, when the above-mentioned resin is impregnated into paper pulp and molded to have a predetermined structure and used as a vibration plate, the drawback of delamination failure of the paper pulp vibration plate is improved, and the vibration due to the improvement of bending rigidity is improved. Of deformation of diaphragm and generation of split resonance, specific elastic modulus E
/ Ρ (however, E: elastic modulus, ρ: density) increases,
Since the high frequency resonance frequency is improved and the internal loss is improved, a speaker having excellent flatness and distortion rate in sound pressure-frequency characteristics can be obtained.

[0011]

EXAMPLE A speaker diaphragm according to an example of the present invention will be described below.

The speaker diaphragm according to the embodiment of the present invention is formed into a predetermined shape by impregnating kraft pulp with polyethylene terephthalate / oxyethylene copolymerized polyester, heating and melting only the surface layer in a mold, and cooling and solidifying. It is molded. This speaker diaphragm is fixed to a voice coil bobbin, and a voice coil provided at the tip of the voice coil bobbin is inserted into a magnetic gap of a magnetic circuit.

The operation of the speaker configured as described above will be described below. The speaker includes a vibration system such as a diaphragm, a voice coil bobbin, and a voice coil, and a magnetic circuit system including a magnet, a pole, a plate, and a yoke. When a voice current flows through the voice coil in a uniform magnetic field, a vertical electromagnetic force is generated in the voice coil and vibrates according to the current. This vibration is correctly transmitted to the diaphragm and is emitted as a sound wave.

Next, a method of manufacturing the speaker diaphragm will be described. Polyethylene terephthalate / oxyethylene copolymerized polyester synthesized by reacting dimethyl terephthalate, ethylene glycol and polyoxyethylene glycol at a ratio of 1: 2: 1. The resin was impregnated with kraft pulp in a weight ratio of 20%, dried, and then, only the surface layer was heated and melted in the mold, cooled and solidified, and molded into a predetermined shape to obtain a vibration plate.

As in this embodiment, a speaker using a diaphragm having a sandwich structure in which kraft pulp is impregnated with polyethylene terephthalate / oxyethylene copolymerized polyester resin, and only the surface layer is heated and melted and then cooled and solidified is Deformation and split resonance did not occur, good acoustic characteristics were obtained, and the distortion rate could be reduced by 20 dB as compared with the paper cone diaphragm of the same shape. Further, the high frequency resonance frequency could be increased from 8 kHz to 11 kHz. In addition, the improvement of the internal loss enabled the peak dip of the output sound pressure to be reduced by about ± 3 dB as compared with the conventional paper cone diaphragm.

[0016]

As described above, in the speaker diaphragm according to the present invention, kraft pulp is impregnated with polyethylene terephthalate / oxyethylene copolymerized polyester resin,
A material having a sandwich structure in which only the surface layer is heated and melted and then cooled and solidified is used as a diaphragm, and the molding process is simple, and at the same time, the strain rate is small and the high resonance frequency can be increased. Further, it is possible to obtain a speaker having high input resistance, and to realize a speaker having good acoustic characteristics, sound quality, and high reliability.

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Claims (2)

[Claims] 1. A speaker diaphragm, wherein paper pulp is impregnated with polyethylene terephthalate / oxyethylene copolymerized polyester. 2. A speaker diaphragm manufactured by impregnating a paper pulp with a thermoplastic resin, heating and melting only a surface layer, and cooling and solidifying the paper to have a shape having a sandwich structure. Method.