JPH03289299A - Dust cap for speaker - Google Patents

Abstract

PURPOSE:To provide a high internal loss over a wide temperature range especially by using two kinds of thermoplastic resin fibers or over whose glass transposition temperature differs. CONSTITUTION:The dust cap is made of two kinds of thermoplastic resin fibers or over whose glass transposition temperature differs and the thermoplastic resin fibers having a higher glass transposition temperature (Tg1) are linked and made composite with the molten thermoplastic resin fibers having a lower glass transposition temperature (Tg2) at heat molding. Thus, the glass transposition temperature of the composite takes a value between the temperatures (Tg1) and (Tg2) and in comparison with the case where two kinds of synthetic resins are completely mixed, the internal loss is increased over a wide temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a dust cap for a cone-type speaker.

[Prior Art] As is well known, the dust cap of a cone-shaped speaker is located near the center of the diaphragm and has the function of blocking out foreign matter such as dust. Since it affects the vibration mode of the diaphragm,
It is required to have a certain degree of rigidity and a relatively large vibration absorption force to suppress abnormal resonance of the diaphragm.

Typical structures of conventional dust caps include (1) molded from a single material such as pulp, metal, or synthetic resin, and (2) thermoformed carbon fiber fabric impregnated with thermosetting resin. and (3) those made by laminating a carbon fiber woven fabric or the like and a thermoplastic synthetic resin sheet and heat-molding them have been put into practical use.

[Problems to be solved] Conventional dust caps with such a structure have (1)
It is difficult for dust caps belonging to category (2) to have both rigidity and vibration absorption power due to the properties of the material, and dust caps belonging to category (2) have low impact resistance and water resistance because the fiber binding material is thermosetting resin. properties and long-term stability. Furthermore,
The molding cycle during production is long, and the prepreg used as a molding raw material has poor shelf life. Further, when a dust cap belonging to (3) is used, for example, polypropylene resin as a thermoplastic synthetic resin sheet, the drape during molding is poor and high-pressure pressing is required, which is a problem to be solved.

Therefore, the present invention uses two or more types of thermoplastic synthetic resin fibers with different glass transition temperatures (Tg) to solve the above-mentioned problems of the conventional example, and also to achieve high internal loss (hereinafter referred to as tIIlδ) in a particularly wide range. It is an object of the present invention to provide a dust cap for a speaker having the following abbreviation).

[Means for Solving the Problems] A speaker dust cap according to the present invention for achieving the above object is made of two or more types of thermoplastic synthetic resin fibers having different glass transition temperatures, and has a high glass transition temperature ( A dust cap for a speaker, characterized in that thermoplastic synthetic resin fibers having a low glass transition temperature (Tg2) are bonded and composited by thermoplastic synthetic resin fibers having a low glass transition temperature (Tg2) that are melted during heat molding. It is.

[Function] In general, when two types of synthetic resins with different glass transition temperatures (Tf1) and (Tg2) are completely mixed down to the molecular order, the temperature characteristic of [lδ] of the mixture is as shown by the dotted line in Figure 1. takes a value between the respective glass transition temperatures of both synthetic resins, and the maximum value of lxnδ appears only at one point (dotted line). ) is melt-bonded and composited with thermoplastic synthetic resin fibers having a low glass transition temperature (Tg2), the glass transition temperature of the composite is (Tit) and (T
g2), and the internal loss can be increased over a wider temperature range than when the two types of synthetic resins are completely mixed (solid line). In the same figure, the temperature characteristics of Innδ of two types of thermoplastic synthetic resin fibers having different glass transition temperatures (Tg1) and (Tg21) are shown by a dashed line and a dashed double dotted line, respectively.

Therefore, by using thermoplastic synthetic resin fibers that have a glass transition temperature near room temperature,
Mechanical internal losses increase over a wide temperature range. Furthermore, if a high modulus resin fiber is used as the thermoplastic synthetic resin fiber having a high glass transition temperature, the value of (Young's modulus)/(density) will increase.

Furthermore, since both fibers are thermoplastic synthetic resin fibers, they have excellent impact resistance and storage stability, and in particular, molding eliminates the drawbacks of conventional examples using sheet-like thermoplastic synthetic resin composites that belong to (3) above. It can save time.

Furthermore, it has better drape and wettability than conventional examples, so there are no voids and the quality is stable.

[Example] Polyvinyl alcohol (abbreviated as PVA) was used as a thermoplastic synthetic resin fiber having a high glass transition temperature (Tg1).
...Tgl=85℃, melting point 240℃) fiber, polypropylene (P, abbreviated as P...T12=0) as a thermoplastic synthetic resin fiber with a low glass transition temperature (Tg2)
℃, melting point 170℃) Two sheets of commingled yarn plain woven fabric mixed with fibers are laminated with the folds shifted by 45 degrees, and then press-molded for 2 minutes at 130℃ in a dome-shaped mold to make a dust cap for a speaker. I got it.

The temperature characteristics of tan δ of the dust cap are shown in FIG. 2 (solid line). At the same time, the temperature characteristics of tan δ of each of the two types of thermoplastic synthetic resin fibers are shown by the one-dot chain line and the two-dot chain line. From this temperature characteristic table, the composite dust cap of the present invention shows a larger tan δ in a wider temperature range than the raw material.

As a means for obtaining the composite of the present invention, as a modification 1 of the above embodiment, a thermoplastic synthetic resin fiber having a high glass transition temperature (Tg1) is wrapped with a thermoplastic synthetic resin fiber having a low glass transition temperature (Tg2). A single layer or multiple layers of woven fabric made of the braided matrix may be stacked and molded. Alternatively, as a second modification, a method of using a woven fabric made by interweaving two types of fibers, or as a third modification, a method of laminating and forming woven fabrics of the respective fibers may be considered.

The dust cap for the speaker according to the present invention has been described in detail based on the representative embodiments, but the embodiment of the dust cap according to the present invention differs from the structure of the above embodiment in terms of the material of the resin material, etc. However, as long as the invention is not limited to the following, as long as it has the constituent features described in the claims described above, exhibits the functions described in the present invention, and has the effects described below,
It can be implemented with appropriate modifications.

[Effects] The speaker dust cap according to the present invention is a composite of thermoplastic synthetic resin fibers having a high glass transition temperature and thermoplastic synthetic resin fibers having a low glass transition temperature, which are fused and bonded. As shown in FIG. 2, the tIIlδ of the composite maintains a high value over a wide temperature range between the respective glass transition temperatures of the two synthetic resins. Therefore, stable characteristics can be obtained over this wide temperature range.

Furthermore, if a high modulus resin fiber is used as the thermoplastic synthetic resin fiber having a high glass transition temperature, the value of (Young's modulus)/(density) will increase. Furthermore, since both fibers are thermoplastic synthetic resin fibers, they have excellent impact resistance and storage stability, and the molding time can be shortened. Furthermore, compared to conventional sheet-shaped thermoplastic synthetic resin composites, it has excellent drapability and wettability, so it has the effect of being free of voids and having stable quality.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the temperature characteristics of the material 11116 of the present invention,
FIG. 2 is a temperature characteristic diagram of internal loss in the embodiment of the present invention.

Claims (2)

[Claims] (1) Consists of two or more types of thermoplastic synthetic resin fibers with different glass transition temperatures, and has a high glass transition temperature (Tg1
) is bonded and composited with thermoplastic synthetic resin fibers having a low glass transition temperature (Tg2) melted during heat molding. (2) Glass transition temperature (T
2. The dust cap for a speaker according to claim 1, wherein g) is 0°C±30°C, and the glass transition temperature (Tg) of the thermoplastic synthetic resin fiber is 50°C±30°C.