JP2002300690A - Method of manufacturing diaphragm for speakers and diaphragm for speakers, using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light weight and high rigidity diaphragm for speakers. SOLUTION: The speaker diaphragm manufacturing method comprises steps of osmosing an inactive gas in an undrawn crystalline thermoplastic resin sheet under a high pressure, releasing it from the pressure, heating to foam the sheet at temperatures over the resin softening point but below its melting point and heating and pressuring the sheet into a molding of a specified shape, thereby obtaining a superior diaphragm for speakers usable in acoustic apparatus which has a uniformly foamed body, a high density, a high rigidity and a light weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a speaker diaphragm for a speaker used in audio equipment and a speaker diaphragm using the same.

[0002]

2. Description of the Related Art An example of a speaker to which a speaker diaphragm according to the present invention is applied will be described with reference to the sectional view of FIG.

As shown in FIG. 2, a loudspeaker includes a lower plate 1 provided with a center pole 1a, a ring-shaped magnet 2 adhesively bonded to the lower plate 1, and an upper portion adhesively bonded to the ring-shaped magnet 2. A magnetic circuit 4 constituted by the plate 3, a frame 5 adhesively bonded on the upper plate 3, and a speaker diaphragm 7 whose outer periphery is adhesively held on the frame 5 via an edge 6.
A voice coil 8 whose inner periphery is fitted so that the coil portion is located in the magnetic gap 4a of the magnetic circuit 4;
The outer periphery is adhered and held to the frame 5, and the inner periphery is adhesively bonded to the voice coil 8, and is constituted by a damper 9 which supports the voice coil 8 so as to be vertically movable.

Next, the operation of the speaker will be described. When an acoustic signal from the outside is input to the coil section of the voice coil 8, the voice coil 8 moves up and down in response to the acoustic signal, thereby driving the speaker diaphragm 7 to generate sound.

[0005] Therefore, since the speaker diaphragm is an important factor that affects the acoustic characteristics, various types have conventionally been proposed.

[0006] A diaphragm made of paper is most popular because it is lightweight and inexpensive, but tends to be poor in moisture resistance, poor in weather resistance in the environment, and poor in aging resistance.

[0007] Further, the metal diaphragm has a problem that it has high rigidity but is heavy and has a small internal loss, so that divided vibration is apt to occur, and mass production is poor due to poor processing.

[0008] A diaphragm made of a synthetic resin is excellent in weather resistance and heat resistance as well as moisture resistance and water resistance, and has been adopted for an in-vehicle speaker having severe environmental resistance characteristics. However, for the diaphragm made of synthetic resin, further reduction in weight and increase in rigidity are desired, and a part made of a foamed resin obtained by foaming a synthetic resin is partially used.

[0009]

A speaker diaphragm using a foamed resin is manufactured by mixing a synthetic resin with a foaming agent and foaming it at the same time as molding to produce a speaker diaphragm, or by adding a foaming agent to the resin. The speaker diaphragm is formed by a method of mixing, molding, heating and foaming, but the thickness is increased due to the foam, and the thickness and density are non-uniform due to variations in the foaming state. As the performance of acoustic equipment using a speaker cannot be suppressed due to the occurrence of split resonance, the appearance of a speaker diaphragm for a speaker having a lighter weight, higher rigidity and good frequency characteristics is desired.

The present invention relates to a speaker diaphragm made of foamed resin, which is lighter and has excellent reliability such as rigidity and other excellent moisture resistance, water resistance, weather resistance and heat resistance. Is provided.

[0011]

According to a first aspect of the present invention, there is provided a method for manufacturing a diaphragm for a speaker according to the present invention, wherein a non-reactive gas is permeated under pressure into an unstretched resin sheet made of a crystalline thermoplastic thermoplastic resin. Then, after releasing the pressure, the resin sheet is heated and foamed, and the sheet is further heated and pressed to form a predetermined shape. The foamed state is uniform, high density, high rigidity. -It is possible to provide a lightweight and excellent speaker diaphragm.

According to a second aspect of the present invention, in the method for manufacturing a speaker diaphragm according to the first aspect, polypropylene, polyethylene terephthalate, polyethylene naphthalate or polybutylene naphthalate is used as the crystalline thermoplastic thermoplastic resin. In particular, it is possible to provide a lightweight and highly rigid speaker diaphragm.

A speaker diaphragm according to a third aspect of the present invention is manufactured by the manufacturing method according to the first or second aspect, and is lightweight, has moisture resistance including rigidity, and water resistance. It is possible to provide a speaker having excellent performance such as heat resistance, weather resistance and heat resistance.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the speaker diaphragm of the present invention will be described below.

In the embodiment of the present invention, a non-reactive gas is applied to a speaker diaphragm at a room temperature by pressurizing and penetrating a non-stretched molded sheet of a crystalline thermoplastic thermoplastic resin, and then the pressure is released. The resin sheet is heated to a temperature equal to or higher than the resin softening point and equal to or lower than the melting point temperature to cause foaming, and the sheet is heated and pressed to form a predetermined shape to obtain a speaker diaphragm.

More specifically, as the crystalline thermoplastic resin sheet, polyethylene terephthalate (hereinafter referred to as PET) is used.
Or polyethylene naphthalate (hereinafter PE)
N) or polybutylene naphthalate (hereinafter PB)
N) or polypropylene (hereinafter referred to as PP)
Was used.

These unstretched resin sheets are left in a high-pressure carbon dioxide gas atmosphere, which is a non-reactive gas, to allow the carbon dioxide gas to penetrate into the unstretched resin molded sheet, and then taken out at atmospheric pressure to promptly make the resin molded sheet. About 180 ° C. to 200 ° C., which is a temperature of not less than the resin softening point and not more than the melting point (in the case of PET, about 200 ° C.)
(° C. to 240 ° C.) to form a foamed resin sheet from the unstretched resin molded sheet.

Each of these foamed resin sheets is heated at about 180 ° C. to 200
℃ (approximately 200 ℃ ~ 240 ℃ in case of PET) to make it in a soft state, then molded in a molding die with a surface temperature of about 80 ℃ to 120 ℃ for a short time and then a diaphragm for speaker Was formed.

The molding was very easy and the mass productivity was high, and the speaker diaphragm after molding was completed to the exact finished dimensions. As a result, a speaker diaphragm for a speaker having a diameter of 16 cm was obtained.

A speaker shown in FIG. 2 was produced using the speaker diaphragm of the present invention and a conventional speaker diaphragm for comparison.

Table 1 shows measurement results of various characteristics of each speaker diaphragm, and FIG. 1 is a characteristic curve diagram showing sound pressure frequency characteristics measured by operating as a speaker.

[0022]

[Table 1]

In Table 1, Sample A was a resin sheet before foaming, and a non-stretched PET sheet of 200 μm thick was processed as described above to obtain a speaker diaphragm having a diameter of 16 cm. As a resin sheet before foaming, a PEN unstretched resin sheet having a thickness of 200 μm was processed as described above to obtain a speaker diaphragm having a diameter of 16 cm.
Sample C is a 200 μm thick P as a resin sheet before foaming.
The BN unstretched resin sheet is processed as described above to obtain
The sample D is a speaker diaphragm having a diameter of 16 cm obtained by performing the above-described processing on a 200 μm-thick PP unstretched resin sheet as a resin sheet before foaming. In Example 1, a foaming agent was mixed with a polypropylene resin and foamed simultaneously with molding to obtain a conventional diaphragm for a speaker having a diameter of 16 cm. Comparative Example 2
Is a paper diaphragm in which a paper base material is impregnated with a resin and heated and pressed to form a speaker diaphragm of a conventional speaker having a diameter of 16 cm.

As is apparent from Table 1, the speaker diaphragms (samples A to D) of this embodiment are lighter (lower) than the conventional speaker diaphragms (Comparative Examples 1 and 2). Density), high rigidity (high sound velocity), and large internal loss (tanδ
Is large) and that it also has excellent environmental resistance (PEN has the best rigidity).

FIG. 1 shows a frequency characteristic (bold line) of a speaker having a diameter of 16 cm using the speaker diaphragm of the sample D of this embodiment and a speaker having a diameter of 16 cm using the speaker diaphragm of Comparative Example 1. Although it shows frequency characteristics (thin lines), the speaker diaphragm of the embodiment of the sample D is used as compared with the comparative example 1 due to the difference in the foaming process, although the same diaphragm is used for the speaker using the same polypropylene resin. In addition, it was confirmed that the loudspeaker had less peak dip in the band of 1 KHz or more and the divided vibration was suppressed, and it was confirmed that the higher frequency band was extended as compared with the conventional loudspeaker.

Next, Table 2 shows the measurement results of various characteristics of the foamed resin sheet which is the material of the speaker diaphragm of this embodiment.

[0027]

[Table 2]

As is evident from Table 2, the difference between Comparative Example 1 and Samples A to D of this embodiment is that the average bubble diameter of this embodiment is about 10 μm. In the example, it exceeded 100 μm.

In addition, measurement with an electron microscope confirmed that the sample of this embodiment had a relatively small variation in bubble diameter, and that of Comparative Example 1 had a large bubble diameter and large variation.

In this embodiment, a skin layer without air bubbles was formed on the surface of each of them. However, in the case of Comparative Example 1, a skin layer without air bubbles could not be confirmed.

From the above results, the diaphragm for a speaker according to the manufacturing method of the present invention is formed by previously forming an unstretched resin sheet made of a crystalline thermoplastic thermoplastic resin, so that carbon dioxide gas can permeate into the sheet. Then, after releasing the pressure, the resin sheet is heated to a temperature higher than the resin softening point and lower than the melting point temperature and foamed to form a foamed resin having a fine skin diameter having a thin skin layer on the surface and a small variation. Obtain a sheet, improve the rigidity as a speaker diaphragm with the skin layer on the surface, and reduce bubbles caused by foaming inside the sheet into small and small bubbles to suppress split resonance. It is presumed that a plate was obtained.

The stretched resin sheet has too high a crystallinity and is difficult for carbon dioxide gas to permeate. In addition, the strength of the stretched resin sheet is different from the strength in the longitudinal direction and the transverse direction. Sheet forming is difficult.

In order to improve rigidity and heat resistance, it is preferable to add an inorganic filler such as mica, talc, silica, and short glass fiber. By setting the blending amount to about 20% of the whole, rigidity is improved by 15 to 20% and heat resistance (thermal deformation) is improved by about 20%.

However, the above-mentioned inorganic filler is used in an amount of 20%.
If the amount exceeds the range, the resin sheet tends to become brittle. Therefore, the content of the additive is preferably set to 10% to 15%.

For smooth foaming, a crystallization agent such as talc is preferably compounded. It is also possible to add an ultraviolet absorber and a flame retardant within a range that does not impair the gist of the present invention.

By mixing two or more of these resins, the sound quality of the speaker diaphragm can be freely designed.

[0037]

As is clear from the description based on the above embodiments, the method for manufacturing a speaker diaphragm according to the present invention is characterized in that an unreacted gas is applied under pressure to an unstretched resin sheet made of a crystalline thermoplastic thermoplastic resin. By infiltrating and foaming, to obtain a foam by ultra-fine foaming with a skin layer on the surface, lightweight,
An object of the present invention is to provide a method of manufacturing a speaker diaphragm that enables provision of a speaker diaphragm excellent in high rigidity.

[Brief description of the drawings]

FIG. 1 is a diagram showing frequency and sound pressure characteristics of a speaker diaphragm according to the present invention;

FIG. 2 is a side sectional view of a conventional speaker.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lower plate 2 magnet 3 upper plate 4 magnetic circuit 5 frame 6 edge 7 speaker diaphragm 8 voice coil 9 damper

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) // B29K 23:00 B29K 67:00 67:00 C08L 101: 00 C08L 101: 00 B29C 67/22 (72 Inventor Shoji Nakajima 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture, Japan Matsushita Electric Industrial Co., Ltd. 1006 Kadoma, Matsushita Electric Industrial Co., Ltd.Matsushita Electric Industrial Co., Ltd. 2-6-1 Furukawa Electric Co., Ltd. (72) Inventor Hiroshi Ikeda 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F term in the formula company (reference) 4F074 AA00 AA24 AA66 AC32 AC34 AC36 AE04 BA32 CA29 CC04Y CC10X DA19 DA47 4F212 AA11 AA24 AA26 AE07 AG01 AG20 AH39 UA04 UA09 UB30 UG02 UW06 UW26 5D016 CA03 EC03 JA06

Claims (3)

[Claims] 1. An unreacted gas is penetrated under pressure into an unstretched resin sheet made of a crystalline thermoplastic thermoplastic resin, and then, after the pressure is released, the resin sheet is heated and foamed, and the sheet is further heated. A method for manufacturing a diaphragm for a speaker, which comprises forming a predetermined shape by applying pressure. 2. The method according to claim 1, wherein the crystalline thermoplastic thermoplastic resin is polypropylene, polyethylene terephthalate, polyethylene naphthalate, or polybutylene naphthalate. 3. A speaker diaphragm manufactured by the method for manufacturing a speaker diaphragm according to claim 1.