JPH06101876B2 - Vibration plate for speakers - Google Patents

Description

TECHNICAL FIELD The present invention relates to a diaphragm for a speaker used as an acoustic output device.

2. Description of the Related Art In recent years, cassette tape recorders, microcassette tape recorders, and in the hi-fi stereo industry, a speaker that is superior in output sound pressure, distortion rate, and flatness to the acoustic characteristics of a speaker as an acoustic output device is desired. The diaphragm for speakers, which influences the acoustic characteristics, is becoming more and more important.

An example of the above-described conventional speaker will be described below with reference to the drawings.

FIG. 2 shows a sectional view of a vibration system of a conventional speaker. In FIG. 2, 1 is a diaphragm, 2 is a voice coil bobbin whose tip is fixed to the diaphragm 1, and 3 is a voice coil inserted into a magnetic gap (not shown) of a magnetic circuit.

The operation of the speaker configured as above will be described below. As shown in FIG. 2, the speaker includes a vibration system such as a diaphragm 1, a voice coil bobbin 2 and a voice coil 3 and a magnetic circuit system (not shown) including a magnet, a pole, a plate and a yoke. When a voice current flows through the voice coil 3 in a uniform magnetic field, a vertical electromagnetic force is generated in the voice coil 3 and vibrates according to the current. This vibration is correctly transmitted to the vibration of the diaphragm 1 and radiated as a sound wave (for example, Toshio Hayasaka: Introduction to Acoustic Engineering, Nikkan Kogyo Shimbun).

Problems to be Solved by the Invention It is ideal that the diaphragm of the speaker makes a piston motion over the frequency band used, and if the diaphragm is deformed or divided vibration occurs during vibration, sound pressure-frequency characteristics, distortion rate,
The phase characteristics are deteriorated, which hinders high fidelity reproduction. Also.
Conventional paper cone diaphragms and plastic diaphragms have low E / ρ (E: elastic modulus, ρ: density) of the diaphragm material, so the high resonance frequency is low and the speaker cannot reproduce up to high frequencies. There was a flaw.

In view of the above problems, the present invention provides a speaker diaphragm having a high high resonance frequency, which does not cause the diaphragm to deform or generate divided vibration during vibration.

Means for Solving the Problems In order to achieve this object, the speaker diaphragm of the present invention has a three-layer structure in which polyimide prepreg sheets are laminated on both sides of a polyamide prepreg sheet by thermoforming. The molded product is used as a diaphragm.

Action In the present invention, the surface material (front surface, back surface) of the above-mentioned molded product has a large elastic modulus (6.2 × 10 ¹⁰ dyne / cm ² about 1.3 times that of paper) polyamide, and the core material has a large mechanical internal loss ( Since it has a three-layer structure composed of 0.05 times (2.5 times that of polyester film) polyamide-imide, the bending rigidity is very large due to the surface material, and the vibration plate does not deform during vibration or split resonance does not occur. Moreover, since the mechanical internal loss is large due to the core material, it is rare that there is a frequency characteristic, and a speaker having excellent sound pressure-frequency characteristic, distortion rate, and phase characteristic can be obtained. Further, since this diaphragm material is a material whose main component is polyimide, it can be plastically deformed by heat and pressure, and can be processed into an arbitrary diaphragm shape by, for example, pressing. Therefore, not only the plate-shaped diaphragm but also the dome-shaped diaphragm can be freely processed, and desired acoustic characteristics can be obtained. In addition, since the material is made of a polyimide-based material, it has a very high thermal softening temperature and thus has excellent heat resistance, and thus a speaker having a large input withstand characteristic can be obtained.

Example Hereinafter, regarding the speaker diaphragm of one example of the present invention,
A description will be given with reference to the drawings.

FIG. 1 is a sectional view of a speaker according to an embodiment of the present invention. In FIG. 1, 4 is a diaphragm formed by heat pressing a sheet of a three-layer structure in which polyimide prepreg sheets are laminated on both sides of a polyamide prepreg sheet, and 5 is a voice coil bobbin whose tip is fixed to the diaphragm 4. Is a voice coil inserted into a magnetic gap (not shown) of the magnetic circuit.

The operation of the speaker configured as above will be described below.

As shown in FIG. 1, the speaker includes a vibration system such as a diaphragm 4, a voice coil bobbin 5, and a voice coil 6 and a magnetic circuit system (not shown) including a magnet, a ball, a plate, and a yoke. When a voice current flows through the voice coil 6 in a uniform magnetic field, a vertical electromagnetic force is generated in the voice coil 6 and vibrates in accordance with the current. This vibration is correctly transmitted to the vibration of the diaphragm 4 and is emitted as a sound wave.

Hereinafter, a method for manufacturing the diaphragm 4 will be described.

First, a polyimide prepreg sheet of 20 μm was used as the surface material, and a polyamide imide prepreg sheet of 80 μm was used as the core material. This material was formed into a dome shape (dome diameter φ30 mm) under the conditions of a temperature of 250 ° C., a pressure of 50 kg / cm ² and a time of 60 min by a hot press to obtain a vibration plate.

As described above, according to this embodiment, the speaker using the diaphragm 4 formed by hot pressing a sheet having a three-layer structure in which the polyimide prepreg sheets are bonded to both surfaces of the polyamide prepreg sheet is Good acoustic characteristics are obtained without deformation and split resonance, and the distortion rate is better when compared to an aluminum dome type diaphragm of the same shape.
It is 24 dB lower. The high resonance frequency is 21KH
It rises to 28KHz from z, and the peak dip of the output sound pressure is ± 3dB, which is about ± 3dB lower than that of the aluminum diaphragm.

EFFECTS OF THE INVENTION As described above, according to the present invention, a polyimide prepreg sheet is attached to both surfaces of a polyamide prepreg sheet.
It is possible to obtain a speaker with a low distortion rate, a high high resonance frequency, and a large acoustic output by using a molded product in which a layered sheet is laminated and bonded by thermoforming such as hot pressing as a diaphragm. Therefore, an excellent speaker having good acoustic characteristics can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of a vibration system of a speaker in one embodiment of the present invention, and FIG. 2 is a sectional view of a vibration system of a conventional speaker. 4 ... Vibration plate, 5 ... Voice coil bobbin, 6 ... Voice coil.

Claims (1)

[Claims] 1. A speaker diaphragm, comprising a molded product obtained by thermoforming a laminated sheet of a three-layer structure in which a polyimide prepreg sheet is laminated on both sides of a polyamide prepreg sheet.