JPH0442699A - Diaphragm for speaker - Google Patents

Abstract

PURPOSE:To realize a diaphragm for speaker having a high internal loss over a wide range by melting and composing a thermoplastic synthetic resin fiber having a high glass transition temperature and a thermoplastic synthetic resin fiber having a low glass transition temperature so as to make them composite. CONSTITUTION:A diaphragm for speaker is made of a composite material being composition of a thermoplastic synthetic resin fiber having a high glass transition temperature Tg1 with a thermoplastic synthetic resin fiber having a low glass transition temperature Tg2 being raw materials of two kinds of thermoplastic synthetic resin fibers having different glass transition temperatures heated at the forming. That is, the glass transition temperature of the composite takes a value between the temperatures Tg1 and Tg2 and a large internal loss is obtained with a wider temperature range in comparison with the case with complete mixture of the two kinds of synthetic resins. Moreover, since both fibers are the thermoplastic synthetic resin fibers, high impact resistance and storage performance are attained. Thus, the diaphragm for the speaker making high rigidity and large internal loss compatible is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diaphragm for a speaker, particularly a diaphragm for a dynamic speaker.

[Prior Art] As is well known, the diaphragm of a speaker emits sound waves by driving a voice coil to a localized part of the diaphragm, such as the center or the periphery. Since it is not a rigid body, it is difficult to vibrate the piston except in a very low frequency band, and normally it becomes a high-order split vibration mode and the frequency characteristics deteriorate, so it is necessary to expand the piston vibration band to as high a frequency band as possible and In order to suppress the resulting split vibrations, the material constituting the diaphragm is required to have as much rigidity as possible and a relatively high ability to absorb vibration energy.

Typical structures of conventional diaphragms include (1) those molded from a single material such as pulp, metal, or synthetic resin;
2) Carbon fiber woven fabric etc. impregnated with thermosetting resin and heat molded, (3) Carbon fiber woven fabric etc. and thermoplastic synthetic resin sheet laminated and heat molded etc. have been put into practical use. .

[Problem to be solved] Conventional diaphragms with such a structure have difficulty achieving both rigidity and vibration absorption power due to the properties of the material, and diaphragms belonging to (2) belong to (1). Since the fiber binding material of the diaphragm is a thermosetting resin, it has low impact resistance, low water resistance, and low long-term stability. Furthermore, the molding cycle during production is long, and the prepreg used as a molding raw material has poor storage stability. or,
For example, when a polypropylene resin is used as a thermoplastic synthetic resin sheet for a diaphragm belonging to category (3), 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 tan δ) in a particularly wide range. The purpose of the present invention is to provide a speaker diaphragm having the following:

[Means for Solving the Problems] A speaker diaphragm 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 ( Tg1
) is a diaphragm for a speaker, characterized in that it is made of a composite material in which thermoplastic synthetic resin fibers A are bonded by thermoplastic synthetic resin fibers B having a low glass transition temperature (Tg2) that are melted during heat molding. .

[Function] In general, when two types of synthetic resins with different glass transition temperatures (Tg1) and (Tg2) are completely mixed down to the molecular order, the temperature characteristics of tan δ of the mixture will be as shown by the dotted line in Figure 1. The value is taken between the respective glass transition temperatures of both synthetic resins, and the maximum value of tan δ appears only at one point (dotted line), but it has a high glass transition temperature (Tg1) like the diaphragm with the above structure of the present invention. Thermoplastic synthetic resin fiber A having
is melt-bonded and composited with thermoplastic synthetic resin fiber B (also indicated by a two-dot chain line) having a low glass transition temperature (Tg2), the glass transition temperature of the composite is (
By taking a value in the range between Tg1) and (Tg2), the internal loss can be increased over a wide temperature range compared to when the two types of synthetic resins are completely mixed (solid line).
.

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 1] Polyvinyl alcohol (abbreviated as pvA) was used as a thermoplastic synthetic resin fiber having a high glass transition temperature (Tg1).
...Tgl=85℃, melting point 2400C) fiber, polypropylene (P, abbreviated as P...Tg2= as thermoplastic synthetic resin fiber with low glass transition temperature (Tg2)
0℃, melting point 170℃) Two sheets of commingled yarn plain woven fabric mixed with fibers were laminated with the folds shifted by 45 degrees, and press-molded for 2 minutes at 130℃ in a dome-shaped mold to produce vibration for a speaker. Got the board.

The temperature characteristics of tan δ of the diaphragm are shown in FIG. 2 (solid line). At the same time, each eye of two types of thermoplastic synthetic resin fibers
The temperature characteristics of δ are shown by the one-dot chain line and the two-dot chain line. From this temperature characteristic table, the composite diaphragm of the present invention shows a larger ian 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). It is also possible to form a single layer or a plurality of layers of a woven fabric made of the braided matrix. 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.

Furthermore, the glass transition temperatures Tgl and Tg2 of the above two types of thermoplastic synthetic resin fibers are Tg2>-30°C, Tgl<10(1°C), and (Tgl-T
g2) It is appropriate that the temperature is ≧20°C. This numerical limitation is data obtained as a result of selecting a material that can be easily manufactured and processed from among actual thermoplastic synthetic resin fibers and that can obtain the desired tan δ in the temperature range required for a speaker cabinet.

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

[Effects] The diaphragm of the speaker 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 [IIIδ] of the composite maintains a high value over a wide temperature range between the respective glass transition temperatures of the two synthetic resins. Therefore, a stable cabinet vibration suppression effect 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 drawings]

FIG. 1 is an explanatory diagram of the temperature characteristics of tan δ of the diaphragm material of the present invention, and FIG. 2 is a diagram of the temperature characteristics of internal loss of the embodiment of the present invention. Patent applicant Onkyo Corporation

Claims (2)

[Claims] (1) It is made of a composite material in which thermoplastic synthetic resin fibers A having a high glass transition temperature (Tg1) are bonded by thermoplastic synthetic resin fibers B having a low glass transition temperature (Tg2) that are melted during heat molding. Features speaker diaphragm. (2) Glass transition temperature of the thermoplastic synthetic resin fiber B (
Tg2) is Tg2>-30°C, and the glass transition temperature (Tg1) of the thermoplastic synthetic resin fiber A is Tg1<100
2. The speaker diaphragm according to claim 1, wherein (Tg1-Tg2)≧20°C.