JPS5826240B2 - Goseijyuushisen Ioriyoshitaspicano Shindoban - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speaker diaphragm, and more specifically, to a speaker diaphragm using polypropylene/fiber.

A speaker diaphragm is required to have a small mass, a large Young's modulus (that is, a large specific Young's modulus), and a moderately large internal loss.Furthermore, the larger the bending rigidity, the better the vibration. characteristics can be obtained.

The materials used in conventional speaker diaphragms are natural fibers, such as plant fibers such as pine and hemp, or animal fibers such as wool, but when forming these natural fibers into cone paper, For example, there are so-called pressed paper cones, which are dried at the same time as press-forming with a heated mold while still containing some moisture after fiber paper is made, and so-called non-press paper cones, which are dry-formed without being pressed after paper dehydration. Young's modulus E1 ratio Young's modulus E/p of cone paper formed by each of these methods,
The internal loss tan δ is approximately as shown in Table 1.

As is clear from this, the specific Young's modulus E/p is relatively large in the pressed paper cone, but the internal loss tan δ is small;
Conversely, in the case of a non-pressed paper cone, the internal loss tan δ is large, but the specific Young's modulus E/p is small.

Therefore, when only these natural fibers are used, it is quite difficult to achieve both a large specific Young's modulus and a large internal loss using any molding method, and there is a limit to the final characteristic values that can be obtained. Therefore, it has been extremely difficult to obtain desired good frequency characteristics.

The characteristics shown in FIG.
0.5kg/c of kneaded 0% and 40% kapok
The material is made of a plate-shaped material that has been pressed with a press pressure of
The absolute value of the level difference between valleys B is as large as 25 dB, which causes distortion and other problems in the reproduced speaker sound, resulting in poor sound quality such as noisy or tiring sound. , resulting in unfavorable results such as a timbre.

Also, from the point of view of the internal loss tan δ, as shown by the dotted line curve in Figure 2, the value is quite small, and the resonance sharpness Q is large, which is one of the causes of the various auditory disturbances mentioned above. was.

Incidentally, FIG. 3 shows a microscopic photograph of Manila hemp as an example of natural fiber used in a speaker diaphragm.

In addition, when the diaphragm of a speaker is constructed only from conventional synthetic resin fibers (for example, polyethylene, polyethylene terephthalate, polypropylene, etc.), the cross section of these synthetic resin fibers is circular or close to it, and when viewed microscopically, it is axial. Because it has properties such as being straight in the direction and having a smooth surface, overall there is very little entanglement between the fibers, so the bending stiffness D (Young's modulus is E, the moment of inertia of area is Letting I, D=E −I.

), and as a result, it is not possible to perform motion that follows the input signal frequency, causing harmonic distortion to occur easily, and the frequency range in which split vibration occurs to be lowered.

Furthermore, as mentioned above, since the surface of the fibers is smooth, the frictional resistance between the fibers is small, and the level difference between peaks and troughs in the frequency characteristics becomes noticeable in the divided vibration region.

However, these synthetic resin fibers generally have a sufficiently satisfactory specific Young's modulus E/ and internal loss tan.
Since it has δ, if it is used in combination with the natural fibers mentioned above, it can successfully compensate for the conflicting characteristic values of a corn made only of natural fibers, whether it is a pressed corn or a non-pressed corn. It is expected that a speaker diaphragm having a specific Young's modulus E/p and an internal loss tan δ that are sufficiently satisfactory in terms of characteristics can be realized.

However, even if synthetic resin fibers are simply mixed with natural fibers to form a paper, there are the following disadvantages, and a speaker diaphragm with good characteristics cannot be obtained.

In other words, in the case of natural fibers, the surface is branched to some extent during the normal processing process, but synthetic resin fibers originally have extremely smooth surfaces, and their cross sections are circular or close to it. , and there are almost no branched fiber pieces on the surface.

Therefore, the surface area of synthetic resin fibers is small, and the bonding area with natural fibers is also small.

Furthermore, the meat fibers are not placed in a very close state, and the bonding force between them is weak, and the diaphragm as a whole is also weak, and it is not possible to realize a very good specific Young's modulus E/p and internal loss tan δ.

This invention solves the drawbacks of the conventional diaphragms made of only natural fibers, synthetic resin fibers, or a simple mixture of these, and improves the specific Young's modulus E/p.
, provides a speaker diaphragm with better internal loss tan δ and bending rigidity, and is characterized by a large number of branched branches on the surface of the main fiber, which has an irregular cross-sectional shape and surface roughness. The fiber is made by mixing polypropylene fiber and natural fiber.

Hereinafter, a detailed description will be given based on one embodiment of the present invention.

The speaker diaphragm of the present invention is made of polypropylene as a synthetic resin fiber. A stretching force is applied to this polypropylene resin to align the crystal directions to form a thin film. By scraping with a regularly roughened linear blade, the cross-sectional shape and surface roughness of the main fiber are irregular, and many branched fiber pieces are formed on the surface of the main fiber, and the crystals are forms polypropylene fibers that are not straight in the axial direction, and this polypropylene fiber is coated with NUKP, which is a natural fiber.
For example, 60% NUKP and 40% polypropylene are kneaded, and then a sticky water-soluble substance such as polyvinyl alcohol or a thin condensed resin liquid is used as an auxiliary to form a paper sheet of 0.5 kg/cr? Press with a certain amount of press pressure to make a press cone diaphragm.

FIG. 4 shows polypropylene/fibers used in the diaphragm of the present invention, and 3a to 3c in the figure are branched fiber pieces formed on the main fiber 2.

In this way, by using polypropylene fibers as synthetic resin fibers, subjecting the polypropylene fibers to the processing steps described above, and then mixing them with natural fibers, the following types of speaker diaphragms can be produced. Effects can be obtained.

First, polypropylene has a specific Young's modulus E/p of 1.65
This is a sufficient value of about 1010i/8ee2, and the internal loss tan δ is extremely large at 0.091, both of which are good.

In addition, its density is the smallest among most synthetic resins and has excellent stretchability, so the specific Young's modulus of the entire diaphragm obtained by mixing it with natural fibers, E/2, and internal loss tanδ. In addition, the processability of the fibers also improves.

In addition, this polypropylene/fiber has an irregular cross-sectional shape and surface roughness of its main fiber, and a large number of branched fiber pieces are formed on the surface of the main fiber, so that the appearance of polypropylene fiber is The volume of the diaphragm can be increased, the bonding area with natural fibers can be increased, and both fibers can be intertwined in a very close state, making the bond between both fibers strong and improving the specific Young's modulus, E/p, etc. of the diaphragm as a whole. In addition, the entire diaphragm made in this way can be made bulky with low density, so in other words, to obtain a diaphragm with the same mass, the thickness t of the diaphragm must be increased. Therefore, it is the product of I (the second moment of area, which is proportional to the cube of the thickness t of the diaphragm) (which is based on the shape and is one of the factors that determines the strength of that shape), and Young's modulus E. Of course, the bending stiffness can also be increased,
As a result, such a diaphragm is less likely to cause split vibration,
Good piston movement can be achieved up to a high frequency range.

When we actually measured the characteristics of the diaphragm of the speaker formed in this way, we found that the internal loss tan δ was as shown by the solid line curve in Figure 2, compared to the conventional one (the dotted line curve in the figure). It can be seen that the damping characteristics are better than those shown in Figure 1).

This is because the internal loss tan δ of the polypropylene fiber itself is extremely large at 0.091 as mentioned above, and the entanglement between the fibers is dense due to the branched fiber pieces 3a to 3c formed in the main fiber 2 of this polypropylene/fiber. This is due to the fact that the frictional resistance between fibers increases.

Next, regarding the frequency characteristics, as shown in Figure 5, the frequency range of the piston movement has expanded compared to the conventional one (shown in Figure 1), and extreme changes in the level between peaks and valleys are within the usage band. no longer appears.

This is because, as mentioned above, the internal loss tan δ has increased moderately, improving the damping characteristics, and the bending rigidity of the diaphragm itself has increased, making it difficult for the diaphragm as a whole to cause split vibration. .

Further, according to experiments, the diaphragm of the present invention has excellent properties such as high tensile strength, high diaphragm paper (cone paper) bursting strength, and the ability to withstand large inputs.

In addition, in the above-mentioned example, in order to make the cross-sectional shape and surface roughness of the main fiber of the polypropylene fiber irregular, and to form a large number of branched fiber pieces on the surface of the main fiber, a stretching force was applied. In addition, we have shown a thin film of polypropylene fibers with the crystal orientation aligned, scraped off with an irregularly roughened linear blade. By collecting the strips cut at right angles and then mechanically kneading them for a long time, the surface becomes irregular due to mechanical friction or abrasion, and branched fiber pieces are also formed. The same effect can be obtained.

As described above, the speaker diaphragm of the present invention is made by mixing polypropylene fibers, in which a large number of branched fibers are formed on the surface of a main fiber with an irregular cross-sectional shape and surface roughness, and natural fibers. Therefore, it was possible to create a speaker diaphragm with a sufficiently large specific Young's modulus E/p, a large internal loss tanδ, and a large bending rigidity, and the damping characteristics and frequency range of piston motion were expanded to the high frequency side. Not only can it be made into a good speaker diaphragm, but it also has the effect of increasing tensile strength, increasing bursting strength, being able to withstand large input levels, and obtaining a speaker diaphragm with good tone quality.

[Brief explanation of the drawing]

Fig. 1 is a characteristic curve diagram of a speaker using a conventional speaker diaphragm made mainly of natural fibers, Fig. 2 is a frequency characteristic diagram of internal loss tan δ of the diaphragm of a conventional speaker and a speaker according to the present invention, and Fig. 3 4 is a microscopic photograph showing an example of natural fiber, FIG. 4 is a microscopic photograph showing polypropylene/fiber used in the present invention, and FIG. 5 is a characteristic curve diagram of a speaker using the speaker diaphragm according to the present invention. . 1... Natural fibers, 2... Main fibers of polypropylene fibers, 3a to 3c... Branched fiber pieces of polypropylene fibers.

Claims (1)

[Claims] 1. A speaker characterized in that a polypropylene fiber having an irregular cross-sectional shape and surface roughness, in which a large number of branched fibers are formed on the surface of the main fiber, and a natural fiber are mixed and made. diaphragm. *