JPS6264199A - Manufacture of speaker diapharagm - Google Patents

Abstract

PURPOSE:To prevent discrete vibration from occurring and to flatten the frequency characteristic by depositing a powder resin for powder coating reinforced chiefly by a carbon fiber on the surface of a diaphragm substrate of pulp material by means of electrostatic powder blasting, fluidized immersion, or electrostatic immersion. CONSTITUTION:The diaphragm substrate is made by dispersing a pulp material in water and paper making it, on whose surface a thermo-setting liquid acryl resin mixed with 20 percent by weight of carbon fiber and 10 percent by weight of graphite is sprayed and dried, and made as paint for powder coating. Then this powder paint is charged with a high voltage, and attracted and adhered on the surface of the substrate. If the temperature of the substrate is higher than the melting point of the powder resin, the paint attached o the surface melts and is fused and adhered. When a speaker is assembled using the diaphragm made of the substrate which is powder- coated on both surfaces, its sound-pressure frequency characteristic is made as a curve 2. The reproduction band of the curve 2 extends wider than a curve 1, and the rigidity goes to large, preventing the discrete vibration of the diaphragm from occurring. I.e. the sound pressure frequency characteristic is made flat and the diaphragm is provided with excellent features.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing an electrodynamic speaker diaphragm, and in particular to a method for manufacturing an electrodynamic speaker diaphragm, in particular, a method of manufacturing an electrodynamic speaker diaphragm, in which a carbon fiber-reinforced powder coating powder is applied to the surface of a diaphragm substrate made of pulp material. The present invention relates to a method of manufacturing a speaker diaphragm plate, in which a body resin is powder-coated on the surface of the base material of the diaphragm.

Conventional technology The conditions generally required for a diaphragm are (1) Young's modulus■
is large, (2) density (ρ) is small, (3)
One example is that the internal loss (tan δ) is appropriately large.

One of the important characteristics that determines the performance of a speaker is the sound pressure frequency characteristic.

The reproduction limit of this characteristic is determined by the low resonance frequency (0) and the high resonance frequency (h), and it is desirable that the frequency characteristic be flat within this range.

This can be lowered by reducing the stiffness of the diaphragm support or by using a heavier diaphragm, but there is a limit to the weight because making the diaphragm heavier will reduce the output sound pressure level, that is, the efficiency. .

Further, Jh is related to the stiffness of the base of the diaphragm and is proportional to the Young's modulus of the diaphragm. Internal loss determines the magnitude of resonance of the diaphragm and affects the flatness of the sound pressure frequency characteristics, so an appropriate internal loss is required.

Conventional diaphragm materials were made by mixing pulp-based natural fibers with bast, animal fibers, or reinforcing fibers, dispersing the mixture in water, and making it into a diaphragm shape. The material made is E=1~2.5X1010dyne 7cm
2. p (apparent) = 0.4 to 0.8 tan δ =
0.02-0.05 cannot be said to have a satisfactory value. Therefore, recently, carbon fiber, polyamide fiber reinforced composite resin, honeycomb diaphragm, foam resin sandwich diaphragm, various filler reinforced synthetic resin diaphragm, or medium.

A wide variety of diaphragm materials have been developed for high-frequency use, including berylum diaphragms, hardened titanium, and aluminum, each offering their own unique features.

Problems to be solved by the invention However, the carbon fiber and polyamide fiber composite resins mainly used for low frequencies are heavy and expensive, the honeycomb diaphragm has a complicated process and is expensive, and the foamed resin sandwich diaphragm has poor frequency characteristics. Various filler-reinforced synthetic resins are heavy.

Means for Solving the Problems In order to solve these drawbacks, the present invention improves the mechanical characteristics required of a diaphragm and provides a method for manufacturing a speaker diaphragm. The feature is that the powder resin for powder coating, which is mainly reinforced with carbon fiber, is attached to the surface of the pulp material diaphragm base material having the desired shape by electrostatic powder spraying, fluid dipping, electrostatic dipping, etc. The resin film is formed only on the surface of the substrate without penetrating it into the substrate through a controlled steady-state treatment after drying.It has excellent effects that cannot be obtained with methods other than powder coating, such as solution impregnation and solution coating. It has the following.

Example Examples of the present invention will be described.

Example 1 The diaphragm base material made by dispersing pulp material in water is similar to a normal paper cone, and its characteristics are E=L5XIQ
"dyne/am2. ρ=0.3. jan=0.0
It is 3.

The sound pressure frequency characteristic of a speaker with the same diameter IQcm assembled using this diaphragm base material is curve 1 in FIG. carbon fiber 20
A thermosetting solution acrylic resin mixed with 10% by weight of graphite is spray-dried to obtain a paint for powder coating. The powder coating charged with a high voltage is attracted and adhered to the surface of the diaphragm base material, and this base material may be at room temperature or heated. If the temperature of the base material is higher than the melting point of the powder coating resin, the paint will adhere to the surface and melt and fuse, but in order to further melt and harden,
It is preferable to heat at ~200°C for about 5 to 20 minutes.

In this way, both sides of the diaphragm base material are powder coated to a thickness of approximately 30μ, and the weight of the constant loss dynamic plate increases by approximately 0.5g compared to the original diaphragm base material, but E = s, 5x10" dyne/am”
Since the powder coating resin hardly permeated into the diaphragm base material, it was found that tan δ = 0.03, which is a good diaphragm material.

The sound pressure frequency characteristic of a companion diaphragm created using this method and assembled into a speaker with a diameter of 10 crn like the above speaker is curve 2 in Figure 1. Compared to curve 1, fh shifts to a higher range, so the reproduction band is wider. Since the rigidity of the diaphragm is increased, split vibration is prevented and a flat frequency characteristic can be obtained.

In this example, an acrylic resin was used as the powder coating, but resins such as vinyl, thermoplastic polyester, nylon, and epoxy resins also exhibit substantially the same effect. For comparison, the characteristics of a diaphragm material coated with a solution-type acrylic resin mixed with 20% by weight of carbon fiber and 10% by weight of graphite as in the example are E=4.5X 10"dyne/am2゜ρ=1.2. tan δ = 0.015.The sound pressure frequency characteristic of the speaker assembled with the diaphragm made according to this comparative example has an even larger peak of fh than curve 1.
Peaks and valleys appear intensely over the entire reproduction band, making it unusable.

As explained above, the diaphragm obtained by the method of the present invention has excellent features, and since it is powder coated, it is easy to mass produce and is inexpensive.

[Brief explanation of drawings]

Figure 1 is a diagram showing how the sound pressure frequency characteristics of a loudspeaker change when a speaker diaphragm according to the method of the present invention is used. is a comparison diagram of the sound pressure frequency characteristics of speakers using the diaphragm produced according to the present invention.

Claims (1)

[Claims] A method for manufacturing a speaker diaphragm, which comprises powder coating a powder resin containing carbon fiber on the surface of a pulp diaphragm base material.