Resin-molded component and method for manufacturing thereof as well as diaphragm for loudspeaker

Abstract

A resin-molded component such as a loudspeaker diaphragm, in which rigidity is enhanced while light weight and high specific modulus of elasticity are maintained, is formed by applying carbon dioxide gas with a predetermined pressure to a thermoplastic resin in which crystallization is facilitated in the resin flowing direction to fill a mold. After the resin is filled, injection molding is performed by somewhat moving the mold to form five layers of: oriented minute-foaming layers, having approximately cylindrical foams, the length of which is twice the diameter thereof in the resin flowing direction in the mold, an unfoamed core layer positioned between both the foaming layers, and unfoamed skin layers formed on the front and rear surfaces.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. application Ser. No. 10 / 860,739, filed on Jun. 3, 2004, the disclosure of which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention related to a resin-molded component, a method for manufacturing thereof, and a resin-molded diaphragm used in a loudspeaker. [0004] 2. Description of the Related Art [0005] Conventionally, there has been known a diaphragm for a loudspeaker, which is composed of a resin-molded component. Hereupon, in order to expand the piston movement area, a diaphragm is required to have a large specific modulus E / ρ (E: elasticity modulus, ρ: density) and a large internal loss to obtain a flat frequency characteristic. Therefore, in the case of a diaphragm composed of a resin-molded component, in order to improve an elasticity modulus, a material in which high-modulus fiber or filler is highly filled in thermo...

AI Technical Summary

Benefits of technology

[0017] Accordingly, specific modulus and rigidity are maintained at higher levels to form a resin-molded component in light weight, having preferable characteristics when for example used as a diaphragm of a loud speaker.

Problems solved by technology

However, due to the increase in the amount of those additives relative density of materials increases, which causes the rising of the specific modulus and reduces a resin streak length in injection molding to makes it difficult to be thinly loaded.

Accordingly, the above described characteristics of large specific modulus and large internal loss have been limited in improvement thereof.

As a result of foaming, light weight can be realized; however, the diameter of foams becomes large to considerably decline Young's modulus and improvement in specific modulus can not be obtained.

Moreover, foamed shape is not uniform so that outer appearance may be unattractive, which is one of problems.

However, each of the foamed cells has a large diameter such as several hundred μm due to chemical foaming, so that it is extremely difficult to control the size thereof and to obtain the state in which the whole plane is uniformly foamed.

In order to compensate the above situation, a reinforcing fiber is also employed; however, the fiber does not act to reinforce the inside foaming cells and there remains limits on improvement in the specific modulus.

However, since a sheet made of a single material such as polyester resin is used as an unfoamed crystalline resin, elastic modulus thereof is low compared to materials used for conventional diaphragms and the elastic modulus is further deteriorated after foaming.

Accordingly, although specific gravity is small, elastic modulus is greatly declined, which becomes a problem when used as a diaphragm.

However, when for example a thin diaphragm is injection-molded, resin tends to solidify rapidly, so that it becomes extremely difficult to form a uniformly-foamed body on injection molding as proposed.

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