JPS59135000A - Composite diaphragm for speaker - Google Patents

Abstract

PURPOSE:To obtain a highly rigid diaphragm having proper internal loss by laminating a fibrous sheet material and a damping film on the base of a diaphragm contaning short fiber reinforcing material and sticking them together. CONSTITUTION:A damping material film 2, for instance a thermoplastic urethane sheet, and a fibrous sheet 3, for instance cotton cloth or silk cloth, are superposed on the base 1 of a conical diaphragm in this order, and heated and compressed by upper and lower dies 4, 5 to form a diaphragm 6. Highly rigid material containing short fiber reinforcing material such as POM whisker etc. is used as the base 1 of the diaphragm. When superposing the base of the diaphragm 1, damping material film 2 and fibrous sheet 3 and sticking them together by heating and forming, an edge part 7 is formed in a body with the diaphragm part 6. Accordingly, it can be manufactured as easily as fixed edge though it has structure resembling to free edge.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a composite diaphragm for speakers.

BACKGROUND ART AND PROBLEMS A speaker diaphragm must satisfy the conflicting physical properties of being lightweight, having high rigidity, and having a moderate internal loss.

In general, it is not easy to achieve these properties with a single material, and the reality is that composite materials are used to obtain the required physical properties.

In recent years, high stiffness (high Young's modulus) short fiber materials (e.g. carbon fibers, alumina fibers, glass fibers, POM whiskers, etc.) have been combined with suitable binders (e.g. polyethylene).
Attempts have been made to mold a speaker diaphragm by incorporating it into Although such a diaphragm has high rigidity, it has a high Q(
They tend to have high resonance sharpness) and low internal loss. Therefore, it is preferable to use it in combination with a suitable damping material.

Incidentally, the edges of speaker diaphragms are generally divided into free edges and fixed edges.

Free edge is made by attaching a separate edge to the diaphragm base material (cone), and has excellent vibration resistance and durability, but it requires a process of forming the edge and bonding the cone and edge. The cost will be high.

Furthermore, since the connection between the cone and the edge is a bond of different materials, there is a problem in that smooth vibration characteristics with little distortion cannot be obtained.

On the other hand, fixed edges have edges on the outer periphery of the diaphragm base material itself, and can be manufactured relatively cheaply.
The vibration resistance and durability are somewhat inferior, and a process of applying a damping material is required to suppress resonance.

Purpose of the Invention The present invention solves the above-mentioned problem 1 by combining a diaphragm substrate containing the above-mentioned short fiber reinforcement and a suitable damping material,
The main purpose is to obtain a diaphragm with excellent physical properties and sound quality, and in this case, by incorporating the advantages of both the free edge and fixed edge diaphragms mentioned above, a diaphragm with excellent vibration resistance and durability, easy to manufacture, and low cost. The aim is to obtain a low cost composite diaphragm.

Summary of the Invention The composite diaphragm of the present invention is produced by laminating a fibrous sheet material and a thermoplastic film on a diaphragm base containing short fiber reinforcement, and forming an edge portion at the same time by heat-forming and laminating them. This is what I did.

This configuration improves sound quality, physical characteristics, and mechanical characteristics, and allows for low-cost manufacturing.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2%1 is a vertical cross-sectional view showing a method of manufacturing a composite diaphragm for a speaker according to a first embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of the manufactured diaphragm. As shown in Figure 1,
A damping material film (2) is placed on the cone-shaped diaphragm base (1).
) (e.g. thermoplastic urethane sheet) and fibrous sheet +
31 (for example, cotton cloth or silk cloth) are overlapped in this order and heat compression molded using upper and lower molds (4) 151 to form a diaphragm (6) as shown in FIG. As the diaphragm base (11), a highly rigid material containing short fiber reinforcement such as POM whiskers as described later is used.

A ring-shaped uneven portion (4a) r5a for forming the edge portion of the diaphragm is formed in the mold (41+51).

Then, when the diaphragm base (1), the damping material film (2), and the fibrous sheet (3) are laminated, heat-formed, and bonded together, the edge portion (7) is attached to the diaphragm as shown in Figure 2. It is formed integrally with the section (6). Therefore, although it has a structure similar to a free edge, it can be easily manufactured like a fixed edge, and costs can be reduced.

The edge part (71 is a damping material film (2) and a fibrous sheet 13) has a double structure, and has vibration resistance and durability as well as appropriate flexibility. The diaphragm section (6) has a three-layer structure consisting of a substrate (1) containing short fiber reinforcement, a damping material film (2), and a fibrous sheet (3), and has a high Young's modulus E and a resonance sharpness Q. It exhibits ideal characteristics with low and moderate internal loss. Vibration plate part (61 (!: Edge part (7
) refers to the braking material film (2) and the fibrous sheet (31
The continuously connected force 1 can produce very smooth vibrations, with little distortion in sound quality or frequency characteristics.

As the diaphragm substrate (11), a material containing short fiber reinforcing material such as carbon fiber or glass fiber in a suitable binder can be used, but in this example, as mentioned above, POM (polyoxy (methylene) single crystal whiskers are used as reinforcement. The diaphragm substrate (1) can be produced, for example, by paper forming. The diaphragm substrate (11) can be obtained by adding the mixture and polyethylene synthetic pulp as a binder, stirring and mixing, and forming a cone-shaped paper through a mesh.

By laminating the damping material film (2) and the fibrous sheet (3) as shown in FIG. 1 on the diaphragm base material (11) produced in this way and heat compression molding, the diaphragm shown in FIG. 2 is obtained. The heating temperature during molding is the softening point of the whiskers (180°~
190°) or less, at which the polyethylene-based synthetic pulp as a binder melts (130' to 150"). In this case, as a damping material film (2), the melting temperature should be approximately equal to the heating temperature for compression molding. If a material such as The damping material film (2) penetrates into the fiber layer and mechanically connects the two.

FIGS. 3 and 4 are longitudinal sectional views similar to FIG. 1, showing embodiments on each side.

In FIG. 3, pneumatic molding is used as the heating compression molding method. As shown in Figure 6, a cone-shaped diaphragm base (1) reinforced with POM whiskers is placed on a mold 18), a damping material film (2) and a fibrous sheet 3) are laminated, and air pressure is applied from above. A diaphragm having a three-layer structure similar to that shown in FIG. 2 can be obtained by applying and heating the same. If a ring-shaped recess (8a) corresponding to the edge part is formed in the mold (8),
As shown in FIG. 2, the edge portion (7) can be formed at the same time.

As the damping material film (2) and the fibrous sheet 131, the same ones as shown in FIG. A non-woven fabric is used as the fibrous sheet (31). Polypropylene film is modified to reduce its melting point by about 150 degrees.The advantage of using non-woven fabric is that the diaphragm has no directionality. Good vibration and propagation characteristics without distortion can be obtained over the entire surface, and there is little variation in the braking effect at the outer periphery (edge).

The embodiment shown in FIG. 4 uses the pneumatic molding method as in FIG. 6, but in this example, the order of lamination is changed. That is, a nonwoven fabric as a fibrous sheet (3) is placed on a diaphragm substrate (11) containing 20M whiskers, a modified polypropylene film as a damping material film (2) is placed on top of the diaphragm substrate (11), and then heated and compressed. A diaphragm similar to that shown in Fig. 2 was obtained by molding.

By interposing the nonwoven fabric as an intermediate layer, special effects not obtained in FIGS. 1 and 3 can be obtained. That is,
When heated and pressure molded in the laminated state shown in Figure 4, the first 20M
Polyethylene synthetic pulp (
(melting point 165°) is melted, then the damping material sheet (2)
As the polypropylene modified film is melted. Then, it penetrates into the two molten outer layers or the middle nonwoven fabric layer, and after cooling, they are bonded together as three layers. 2
When the polyethylene synthetic pulp as the binder of the 0M whiskers and the polypropylene film as the damping material are melted, the 20M whiskers with a softening point of 180° to 190° remain unsoftened, but the nonwoven fabric of the intermediate layer acts as a filter and the diffusion of whiskers towards the damping layer and the edges 5 (7) is effectively prevented.

Therefore, the damping ability is not reduced due to whiskers being mixed into the damping layer and the edge portions, so that excellent physical properties can be obtained as a composite diaphragm.

The physical characteristics of the diaphragm manufactured as described above are expressed as m4
The results of measurements using the vibration lead method for the material combinations and structures shown in the examples shown in the figures are as follows.

■ Resonance sharpness (Q) 13.0 Young's modulus (VnL2) 3 x 10' density CWm
' ) 850 Longitudinal wave propagation speed Cm/S)
1880 On the other hand, the characteristics of a diaphragm made of polyepropylene synthetic resin, which is a general diaphragm material, are as follows.

■ Resonance sharpness (Q) 16.0 Young's modulus (
N/fn2) 1.6X10'density CWm'
) 900 Longitudinal wave propagation velocity (+71/s) 1330 Furthermore, a free edge type diaphragm containing polyethylene synthetic pulp as a binder and 20M whiskers as a reinforcing material (
The properties of the product (which was formed by heating and pressure molding without lamination as in the example) are as follows.

■ Resonance sharpness (Q) 21 Young's modulus (N
, 42)! +, 5X10? Density OW'm')
850 Longitudinal wave propagation velocity (m/S) 2030 Comparing these, G) is slightly inferior (higher) in resonance sharpness Q compared to ■, but all other points are improved, especially Young's modulus is twice as high. As a result, it has become a reinforced diaphragm, and the longitudinal wave propagation velocity (-
y79'*/If) also has greatly improved characteristics. In contrast to these ■■, the diaphragm according to the present invention has a Young's modulus that is slightly lower than ■, as shown by the characteristics ■■, but is much larger than ■■, and the resonance sharpness Q is There has been a significant decline in the In other words, it exhibits ideal characteristics as a diaphragm, with high rigidity and moderate internal loss. Note that the decrease in Q is due to the polypropylene film as the braking material film (2) and the fibrous sheet (3).
) and the nonwoven fabric.

Next, FIG. 5 shows a case where the laminated diaphragm ■ of the embodiment shown in FIG. It is a graph showing the output sound pressure characteristics of , where the solid line is the diaphragm of ■ and the dotted line is the diaphragm of ■. As can be seen from FIG. 5, the diaphragm ``■'' exhibits almost uniform frequency characteristics with fewer peaks and valleys than the diaphragm ``■''. Therefore, the sound quality is straightforward with little distortion.

In each of the embodiments described above, the edge portion (7) may be formed at the time of heat compression molding, and an outer ring (made of metal, paper, etc.) for fixing the diaphragm may be attached to the outer periphery of the edge portion (7). Further, as the braking material sheet to be laminated, a thermoplastic resin such as EVA (ethylene vinyl acetate copolymer) or soft vinyl chloride can be used in addition to the polypropylene film as described above.

Further, as a binder for incorporating short fiber reinforcing materials such as POM whiskers, carbon fibers, and glass fibers into the diaphragm, thermoplastic resins such as polypropylene, EEA, and EVA can be used.

Effects of the Invention As described above, the present invention has a fibrous sheet material and a damping material film laminated and bonded to a diaphragm base containing short fiber reinforcement, so that vibrations with high rigidity and moderate internal loss can be achieved. You can get a board.

In addition, since the edge portions are formed when the laminate is heat-formed, the manufacturing process is simplified and can be manufactured at lower cost, and the vibrating portion and the edge portions are continuously connected using the same material. Not only can vibration characteristics with less distortion be obtained, but also an edge portion with excellent vibration resistance and durability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of the method for manufacturing a composite diaphragm of the present invention, FIG. 2 is a longitudinal sectional view of the manufactured diaphragm, and FIGS. 6 and 4 show different embodiments. A vertical cross-sectional view similar to FIG. 1, and FIG. 5 are graphs showing the output sound pressure characteristics of the diaphragm of the present invention and a conventional diaphragm. In addition, in the symbols used in the drawings, (1)...... diaphragm base (2
)・・・・・・・・・・・・・・・ Braking material film (3
)・・・・・・・・・・・・Fibrous sheet (6)
・・・・・・・・・・・・Diaphragm part (7)...
・・・・・・・・・・・・This is the edge part. Agents Masaru Doyo I Yoshio Tsuneko I Toshiki Sugiura

Claims (1)

[Claims] A composite diaphragm for a speaker, in which a fibrous sheet material and a thermoplastic film are laminated on a diaphragm base containing short fiber reinforcement, and these are heat-formed and laminated to form an edge portion at the same time.