JPS5927155B2 - Manufacturing method of speaker diaphragm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a cone-shaped diaphragm for a speaker, and an object of the present invention is to improve the elastic modulus of the base of the cone and increase the high frequency limit of the speaker.

In a cone-shaped speaker diaphragm, if the elastic modulus of the base of the cone is improved, the high frequency limit of a speaker using this diaphragm will be increased, and the reproducible band will be expanded.

Conventionally, the base of a paper cone was impregnated with thermoplastic resin or thermosetting resin to increase its strength.

However, the conventional manufacturing method described above requires a resin impregnation process in addition to a papermaking process and a molding process, and has many manufacturing steps and is complicated.

The present invention eliminates the above-mentioned conventional drawbacks, and embodiments of the present invention will be described below.

A composite sheet made of a mixture of high-density polyethylene synthetic pulp (85wt%) and carbon fiber (15wt%) (basis weight 100
y/m').

After preheating this composite sheet at 180°C, it is cold pressed using the mold shown in Figure 1.The composite sheet softened by the preheating is cold pressed into a cone shape, and at the same time This improves the elastic modulus of the base.

FIG. 1 shows a cross section of a lower mold used in the manufacturing method of the present invention.

The diameter of the lower mold 1 is 10 CrrL, and the upper pressing surface is cone-shaped.

A hole 2 is formed in the center of the lower mold 1, and a movable mold 3 is supported in the hole 2 so as to be vertically slidable.

Reference numeral 4 denotes a spring that urges the movable mold 3 in the direction of the press surface.

The movable mold 3 serves as a lower mold corresponding to the root of the cone-shaped diaphragm, and is normally pushed upward by a spring 4 by about ICrrL, as shown in FIG.

Generally, in the method of pressing a sheet using an upper die and a lower die, during press forming, the convex part of the upper die and the sheet, and the outer periphery (edge part) of the concave part of the lower die are first After contact, the sheet is pressed, but the sheet stretches from the part that will become the base of the cone.

This is because the force F that acts during molding is constant over the entire surface of the cone, but the mold that supports it is less at the root of the cone and more at the outer periphery, so the sheet stretches from the root side where the pressure is applied.

For this reason, the root portion of the cone becomes thinner and thinner and the elastic modulus decreases.

However, according to the manufacturing method of the present invention, in order to prevent the cone base from becoming thinner during molding, the movable mold 3 that comes into contact with the cone base is floated.

In FIG. 1, a preheated composite sheet is fed above the lower mold, and the stopper mold 5 is lowered from above the composite sheet, and as shown in FIG. Lower mold 1,
The composite sheet 6 is held between the movable mold 3 and formed into a cone shape (pressing pressure 10 kg/crtt). During this pressing, the part of the composite sheet 6 that comes into contact with the movable mold 3 The root part is movable mold 3 at an early stage.
By holding the composite sheet 6, the expansion of the base part is suppressed, and after the composite sheet 6 comes into contact with the movable mold 3, the parts that are not in contact with the movable mold 3 mainly expand, and the composite sheet 6, the movable mold 3 is thinner near its outer periphery.

Although a slight step appears on the back surface of the molded composite sheet 6 (diaphragm), no step appears on the front surface.

Furthermore, since the film thickness at this part is thicker than the film thickness at the base of the conventional cone, it is superior in strength to the conventional method.

In this way, the press pressure at the root portion is increased, and the elastic modulus of this root portion is improved.

Further, as expressed by the following equation, the reproduction limit frequency fh in the high range has a large elastic modulus E at the base, and the thicker the thickness T, the longer the reproduction limit frequency can be extended.

After forming a portion of the composite sheet 6 into a cone shape as described above, the outer circumferential portion of the cone portion is cut and the central flat portion of the root portion is cut off to complete the diaphragm.

A coil bobbin is fixed to a hole formed in the center of this diaphragm.

In addition, the elastic modulus of the base of the diaphragm in the above example is 3
．． The elastic modulus of other parts was 3.Ox 101 Odyn/i.

Note that the present invention is not limited to the above-mentioned embodiments, but can be used when manufacturing a diaphragm made of a fiber aggregate.

The above-mentioned fiber aggregate is a paper made of natural pulp, a fiber aggregate made of a thermoplastic resin, or a mixed paper of a fiber aggregate made of a thermoplastic resin and an inorganic fiber.

Further, thermoplastic resin fibers are fibers such as polyethylene, polypropylene, nylon, polyester, etc., and inorganic fibers are carbon fibers, glass fibers, etc.

As described above, the present invention increases the press pressure at the root portion during press forming to improve the elastic modulus of the root portion, and simultaneously increases the elastic modulus of the root portion during press forming without increasing the number of steps. This has the advantage that improvements can be made.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a lower mold used in a method for manufacturing a speaker diaphragm according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view during press molding in a method for manufacturing a speaker diaphragm according to an embodiment of the present invention. 1... Lower mold, 2... Hole, 3...
... Movable mold, 4 ... Spring, 5 ... Upper mold, 6 ... Composite sheet.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a speaker diaphragm in which a fiber aggregate is pressed and formed into a cone shape, characterized in that the press pressure at the root of the cone during press molding is increased. Method of manufacturing the board. 2. In the method for manufacturing a speaker diaphragm according to claim 1, an elastic body slidably supports a movable mold in the central hole and urges the movable mold in the direction of the pressing surface. 1. A method for manufacturing a speaker diaphragm, which comprises using a lower mold having a lower mold and pressing a fiber aggregate between the lower mold and the upper mold.