JPS585560B2 - Shindoban no Seihou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a diaphragm using a carbon fiber cloth or thin plate as a base material.

Generally speaking, thin plates used as speaker diaphragms must have high efficiency and good transient characteristics.In addition, in order to extend the treble range as a treble speaker diaphragm, the thin plates must have a small mass and a Young's modulus. In addition, the thin plate is required to be strong.

The present invention focuses on carbon and its compound materials as materials that satisfy such requirements, and provides a novel method for manufacturing a speaker diaphragm.

Therefore, the method for manufacturing the diaphragm of the present invention is to apply a compound capable of liberating carbide by thermal decomposition onto a substrate made of a cloth-like body made of carbon fibers or a carbon thin plate material having a predetermined shape, if necessary, in the presence of an inert atmosphere. It is characterized by thermally decomposing the carbide to precipitate carbide, and depositing it on a substrate, such as filling the grains of this cloth-like body.

The diaphragm manufactured by the method of the present invention exhibits better frequency characteristics and is superior in durability compared to diaphragms manufactured from conventionally used titanium Ti or aluminum AI alloys.

Furthermore, since the mechanical properties of the crystalline carbide, such as Young's modulus, can be controlled by the thermal decomposition temperature, it is possible to produce a distinctive diaphragm with desired acoustic properties by changing the speed of sound that propagates in the thickness direction of the diaphragm.

This invention will be described in more detail.

The carbon fiber of the base material used in this invention is low grade carbon fiber or high grade carbon fiber (strength 1
09N/m" or more, Young's modulus 13.7X10"N/m2
Either of the above) may be used, but in consideration of Young's modulus, it is preferable to use high-grade carbon fiber as a treble speaker diaphragm.

This carbon fiber material is a synthetic or semi-synthetic fiber used for manufacturing carbon fibers.

Examples of carbon fiber materials include synthetic fibers such as polyacrylonitrile and rayon, vinyl chloride, crude oil pyrolysis pitch, petroleum sludge, etc., but are not limited to these. You can use anything you can find.

The cloth-like body made of carbon fibers preferably has a mesh size of about 50 to 300 mesh.

If it is more than 300 mesh, the cloth material will be too thin and the strength of the product will decrease, and if it is less than 50 mesh, if carbon is precipitated until it fills the grains of the cloth material, the product will be too thick and the performance of the diaphragm will deteriorate. This is because it decreases.

The thickness of this cloth-like body or thin plate is preferably 10 to 200 μm, preferably 20 to 100 μm.

In particular, about 40 to 70 μm is desirable.

If it is 10 μm or less, it is not suitable as a diaphragm in terms of strength, and if it is 200 μm or more, it becomes heavy in terms of weight.

In this specification (including the claims), the term cloth-like body refers to all cloth-shaped fibers, including woven cloth as well as
It also includes nonwoven fabrics.

The woven fabric is generally woven from strands obtained by bundling carbon fibers having a diameter of about 10 μm, and the weaving method is not particularly limited, such as plain weave or satin weave.

A carbon thin plate can be obtained by depositing carbon or graphite on a predetermined removable substrate by thermal decomposition, or by molding a resin into a predetermined shape and then carbonizing it in an inert atmosphere.

The method for manufacturing a diaphragm of the present invention is to thermally decompose a compound capable of liberating carbon or carbide by thermal decomposition onto the substrate of this cloth-like body or thin plate in an inert atmosphere.

In this specification (including the claims), an inert atmosphere means that it does not contain any active compounds other than compounds that can liberate carbon or carbide by thermal decomposition. This includes not only cases where the compound contains a compound capable of releasing a carbide and an inert gas, but also a case where nothing other than a compound capable of liberating a carbide by thermal decomposition is contained.

The purpose of depositing carbon or carbide on a cloth or thin plate substrate in an inert atmosphere is to control the rate of carbide deposition on the substrate.

The inert gas introduced into the reaction system to create this inert atmosphere is, for example, argon, helium, or nitrogen.

Compounds that generate carbides include all compounds or mixtures that liberate carbon or carbides by thermal decomposition and precipitate on the substrate, and further precipitate elemental carbon or other substances (metals, metal compounds, etc.) along with carbides. It shall include all compounds or mixtures that

That is, it includes not only carbides but also carbides and elemental carbon, carbides and elemental carbon and other substances (e.g. metals, metal compounds, etc.), or carbides and all compounds that precipitate other substances, such as methane, ethyl alcohol. , butane, etc. and TtClt, WC14
Examples include mixtures with one or more metal compounds such as.

The amount of the inert gas can be increased or decreased in order to adjust the gas concentration in the reaction system of the compound capable of liberating carbides through thermal decomposition.

The sum of the partial pressures of the inert gas and this gaseous compound is preferably normal pressure.

This is because no special seals are required to operate the device.

On the other hand, under a reduced pressure atmosphere, the decomposition temperature can be lowered, although the equipment becomes more complicated.

If the partial pressure of this gaseous compound is too high, the rate of carbide precipitation on the substrate will be high, resulting in the precipitation of low-density and porous carbides; if the partial pressure is too low, the rate of carbide precipitation will be slow. That would be too much.

Therefore, the partial pressure of the gaseous compound can be determined functionally taking into account the above facts.

In order to manufacture a good product as the diaphragm of this invention, there are three steps.
It is preferably in the range of 0 to 200 mmHg, and 100 m
Particularly preferred is around mHl.

Inert gas is added to adjust the gaseous compound, and the entire reaction system is maintained at, for example, 1 atm, the partial pressure of the gaseous compound is kept constant, and the inert gas is added to the reaction system. By introducing carbides, it is possible to continuously deposit carbides onto the substrate at a constant deposition rate.

It can be for diluting the gas to reduce the rate of deposition.

Pyrolysis to precipitate carbides on the substrate is 500-1
It is carried out at 500°C.

This is to cause carbide to precipitate on the base layer.

When the base material is a cloth-like material, this carbide grows along the grain of the fabric up to about 2 μm, but beyond that, it tends to grow in the direction of filling the grain with carbon.

The reason why the mesh of the cloth-like body is filled with carbon or carbide in this way is to eliminate air permeability and manufacture a diaphragm.

According to the present invention, carbides with metals precipitated by thermal decomposition on the substrate are not particularly limited, but include TiC, WC2W2C2
BeC and the like are preferably used.

The thickness of the carbide layer on this base material is preferably about 2 to 70 μm.

This is because if the thickness is less than 2 μm, the strength of the diaphragm decreases and desired frequency characteristics cannot be obtained.

If the thickness is 70 μm or more, the strength is sufficient, but the mass increases too much, resulting in disadvantages such as not being able to produce a sharp sound.

In order to obtain desired frequency characteristics, especially for a high-pitched speaker diaphragm, the thickness of the carbide layer is preferably approximately 10 to 30 μm. The density ρ of this carbide is 2 to 7 (x103ky/m3), Young's modulus E is about 1 to 12 [×1O11N/d2].

Therefore, titanium Ti (ρ4.54 (X103kg/
m3], E11.9 (X1010N/m2l) and aluminum (p2.7 (X10"kg/m", E7.0
5 (X1010N/m')), E/ρ can be large.

Therefore, it is an excellent material for diaphragms, especially high-pitched speakers.

A woven or non-woven fabric or a thin plate of carbon fiber is used as the base material in this invention, but a woven or non-woven fabric of a carbon fiber material may also be used.

This is because in the process of carbide precipitation due to gas phase decomposition,
This is because the carbon fiber material is carbonized and turned into carbon fiber.

After the carbide is precipitated on the base material, it is desirable to perform heat treatment to increase the density.

Such heat treatment increases the strength and durability of the diaphragm, and also improves the frequency characteristics.

However, this heat treatment is not essential in this invention.

Examples will be described below to make the invention easier to understand.

This embodiment shows one embodiment of the present invention, and can be arbitrarily modified within the scope of the present invention.

Example 1 A 200-mesh cloth (thickness: 40 μm) obtained by plain weaving strands obtained by bundling carbon fibers with a diameter of 8 μm is placed on a precipitation base of a predetermined shape (diaphragm shape) in a cylindrical furnace.

This precipitation base is made of graphite.

This is because heat-resistant materials must be used in consideration of the temperature in the furnace.

For example, common metals melt at temperatures of 1800 to 3000°C, and tungsten W does not melt, but since tungsten carbide WC is produced, a carbide-based precipitation base is optimal.

Moreover, this cloth-like body had 200 mesh.

After the carbon fiber cloth was placed on the carbide precipitation base, TiCI4, methane and argon were introduced into the furnace.

The partial pressure of methane was about 40 mmHg, and the sum of the partial pressures of argon, methane, and T+CI4 (ie, the atmospheric pressure inside the furnace) was 1 atm.

The temperature in this furnace was raised to 1000℃ using a high-frequency plasma flame.
and maintained at that temperature for approximately 15 minutes.

After precipitating carbide on the substrate by vapor phase decomposition for about 15 minutes, methane gas and waste gas were discharged from the furnace, and heat treatment was performed at 3000° C. for 1 hour in the same furnace.

The thickness of the carbide layer of the diaphragm manufactured in this way is approximately 1
It was 0 μm.

The density ρ of this carbide is 4.4 (X103kg/m'
), and Young's modulus E is 7.0 (XIO11N/m")
Met.

Further, the frequency of this diaphragm was as shown as curve 1 in the drawing.

Example 2 A carbon block processed to specified dimensions was placed in argon for 20 minutes.
The mixture was heated to 00°C, the argon gas was turned off, and then methane gas was introduced to deposit pyrolytic carbon on the surface of the carbon block for about 1 hour.

Afterwards, the inside of the furnace was replaced with argon, the temperature was lowered to 1200℃, and a mixed gas (total pressure of 1 atm) of 415 ml/min of Txcl, 5 mA/min of methane, and 3 liters of hydrogen was flowed, and the temperature was maintained for 1 hour. After stopping the reaction gas and purging the inside of the furnace with argon, the temperature was rapidly lowered to 400°C at a rate of 10C/min.
Thereafter, the temperature was lowered to room temperature by furnace cooling.

Electron microscopic observation of the produced diaphragm revealed that the carbon substrate thickness was approximately 0.2 mm, and on its surface there was a TiC layer with very good crystallinity (according to X-ray diffraction) with a thickness ranging from a minimum of 7 to a maximum of 30 μm. was formed.

The Young's modulus E of this diaphragm is 3.4 to 3.8 (X101
1N/m2), and its frequency characteristic curve almost matched curve 1 in the drawing.

Example 3 (Comparative Example) In Example 2 above, after pyrolytic carbon deposition, argon substitution was performed, and the temperature was increased to 400°C at 10°C/10°C without TiC deposition.
By cooling at a rate of 1 minute and then furnace cooling, the thickness is approximately 0.
．． A 2 mm carbon diaphragm was obtained.

The Young's modulus E of this diaphragm is 0.9 to 1.2 (XIO11
N/m2l, and its frequency characteristic curve was as shown as curve 2 in the drawing.

Note that the frequency characteristics of an AI diaphragm having a similar thickness are shown as curve 3 in the same drawing.

[Brief explanation of the drawing]

The drawings show frequency characteristic curves of diaphragms according to examples of the present invention and comparative examples. 1...Example (Example 1 and Example 2), 2...
...Carbon diaphragm (comparative example, example 3), 3...A1
diaphragm.

Claims (1)

[Claims] 1. A method for manufacturing a diaphragm in which a compound is thermally decomposed on a base material made of a cloth-like material made of carbon fiber or a thin plate material made of carbon to precipitate carbide, and the diaphragm is integrated with the base material.