JPS5841038B2 - acoustic diaphragm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acoustic diaphragm for an electrodynamic speaker, and particularly relates to an acoustic diaphragm for an electrodynamic speaker, in which a paper cone is used as a substrate, at least one surface of the substrate is smooth, and a predetermined electroless nickel plating layer is applied to the smooth surface. By using a thin layer that is adhered to the thickness, it is possible to suppress peaks and dips caused by high-frequency resonance to a minimum, and to achieve an acoustic diaphragm that can increase the reproduction frequency and improve distortion characteristics. The purpose is to provide.

Conventionally, a paper cone made from vegetable fibers has been used as a diaphragm for an electrodynamic speaker.

Recently, with the development of peripheral equipment, speakers have become wider and wider.
In particular, the demand for higher frequencies has increased rapidly.

Therefore, various attempts have been made to change paper-making conditions, etc., but the current situation is that paper itself cannot cover sufficiently high frequencies.

Furthermore, instead of using paper as a speaker, there are speakers using a diaphragm made of a single metal plate, or a diaphragm having a structure in which a thin plastic plate or a thin metal plate is bonded to the surface of a honeycomb structure.

A diaphragm with this structure (in this case, the longitudinal wave velocity is large and the high-frequency resonance frequency can be extended, but the internal loss is too small, so the peak dip due to high-frequency resonance cannot be sufficiently suppressed) There was a drawback that it was not possible.

The present invention eliminates the above-mentioned drawbacks and provides an acoustic diaphragm that takes advantage of the favorable acoustic properties of paper and has good acoustic properties as a whole, combining the excellent acoustic properties of a metal plate. An embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a cross section of an embodiment of an acoustic diaphragm according to the present invention.

This acoustic diaphragm 1 for an electrodynamic speaker uses a base paper 2 made from vegetable fibers as a substrate, and forms smooth surfaces on the front and back surfaces of the base paper 2 by sealing exposed pores. Smooth layers 3a and 3b made of resin etc. are formed, and an electroless nickel plating layer 4a is further formed on the surface of the smooth layers 3a+3b.
, 4b are adhered to a predetermined thickness to form a sandwich structure.

In this S, the smooth layers 3a, 3b are for forming the electroless nickel plating layers 4a, 4b evenly and uniformly on the surface without penetrating into the inside of the base paper. It is not intended to change the properties of the base paper 2, and the resin etc. only needs to be applied to the front and back surfaces of the base paper 2, and does not necessarily have to penetrate into the inside of the base paper.
Furthermore, the properties of the resin used are not limited.

In addition, without forming the smooth layers 3a and 3b, the base paper 2
It is also possible to form an electroless nickel plating layer directly on the front and back surfaces of the base paper 2, but in this case, due to the porosity of the base paper 2, the nickel plating layer is not formed uniformly and becomes uneven, as described below. Therefore, good characteristics as an acoustic diaphragm cannot be obtained.

In this section, various physical properties and acoustic characteristics of general acoustic diaphragms will be explained.

The high frequency limit of an electrodynamic speaker is determined by the longitudinal wave velocity of the acoustic diaphragm, and the higher the longitudinal wave velocity, the higher the high frequency limit.

In particular, in the case of a diaphragm with a sandwich-inch structure, the maximum high frequency of the speaker is determined by the longitudinal wave velocity of the outer layer.

Also, in order to prevent steep and large amplitude peaks and dips from appearing in the output level frequency characteristics of the speaker,
The internal loss of the acoustic diaphragm is approximately 0.015 or more (this is approximately twice the internal loss of the metal plate itself, 0.007 to 0.0085).
(equivalent to this).

Furthermore, increasing the rigidity of the acoustic diaphragm reduces harmonic distortion of the speaker.

The above is known. Next, various physical properties of the acoustic diaphragm 1 having the above structure will be explained.

First, tweeter cone paper (belongs to the hardest category)
The physical properties of nickel and electroless nickel are shown in the table below.

In this table, the ratio of longitudinal wave velocities of tweeter cone paper and electroless nickel is 3.5/2.3=1.5, so
A speaker with a sandwich structure acoustic diaphragm 1 coated with electroless nickel has a high limit frequency that extends in a higher direction than a speaker using a paper cone (see FIG. 4).

Further, regarding the Young's modulus of both, electroless nickel is considerably larger than cone paper, and therefore, the Young's modulus (rigidity) of the acoustic diaphragm 1 is considered to be greater than that of paper cone.

Therefore, it is thought that the harmonic distortion of the speaker is reduced in the speaker using the acoustic diaphragm 1 shown in FIG. 1 compared to the speaker using the paper cone (see FIG. 5).

FIGS. 2 and 3 show the longitudinal wave velocity and internal loss of the acoustic diaphragm 1 having the structure shown in FIG. Indicates a state of change.

In both figures, the horizontal axis is the thickness hl of the electroless nickel plating layer.
)/represents 1/2 (h2) of the thickness of the base paper.

The measurement results are based on a test piece (length 50m x width 10mm)
) was obtained by conducting vibration lead method tests and tensile tests.

In FIG. 2, a graph line 1 indicates the thickness of the base paper 2 (with respect to the electroless nickel plating layer 4a) in the structure of the acoustic diaphragm 1.
, 4b are sequentially increased in thickness.

In the figure, the graph line ■ indicates the plating layer of an acoustic diaphragm obtained by applying electroless nickel directly to the base paper 2 (hereinafter referred to as a diaphragm without pretreatment), omitting the pretreatment to form the smooth layers 3a and 3b. This shows the change in longitudinal wave velocity when the thickness of the wave is changed.

The following can be seen from Figure 2.

(2) There is a difference in the longitudinal wave velocity depending on whether or not the cone paper has been pretreated, and this difference becomes especially significant when h2/h1 is less than 0.1.

In other words, an acoustic diaphragm with a structure in which nickel is precipitated and laminated on cone paper that has been treated to have a smooth surface is better than a diaphragm without pretreatment (in this case, the surface of the nickel plating layer is not smooth, and (It is thought that it has penetrated into the base paper as well) The larger the size, the higher the high frequency limit of the speaker.

Therefore, the pre-treated diaphragm 1 having the structure shown in FIG. 1 is more effective in raising the upper limit frequency than the diaphragm without pre-treatment.

Note that the above-mentioned effect of the pretreatment is thought to be due to the fact that the pores on the surface of the cone paper were closed by the resin and the surface became smooth, as observed from surface observation using an electron microscope.

■ When the thickness of the nickel plating layer is thin, it is smaller than the original longitudinal wave velocity of electroless nickel, but as the thickness of electroless nickel increases, it approaches the final value.

■ When h2/h1 is about 0.03, even if the surface of the base paper 2 is smoothed, the acoustic effect as an electroless nickel plating layer can be fully exhibited, and the absolute longitudinal wave velocity is The value is small.

Therefore, when used as an acoustic diaphragm for a speaker, h2
It is desirable that /h1 is 0.03 or more.

From the above (1), (2), and (2), in order to increase the high limit frequency, the speaker diaphragm should have a structure that has undergone the pretreatment shown in Figure 1, and must have the electroless nickel plating layer 4a.
, 4b preferably has a thickness h2/h1 of 0.03 or more.

The graph line ■ in FIG. 3 shows the internal curve of the pretreated acoustic diaphragm 1 shown in FIG. Indicates the state of change in loss.

From graph line ■, electroless nickel plating layer 4 a +4
It can be seen that by increasing the thickness of the acoustic diaphragm 1, the internal loss of the acoustic diaphragm 1 becomes smaller.

The peak dip (metal peak) that occurs when using a diaphragm made of a single metal plate has an internal loss of approximately 2 that of a metal plate.
If it is only a moderate amount, it will be considerably suppressed and become small.

Since the internal loss of a single metal plate is 0.007 to 0.0085, it considerably reduces the "metal shank" (in this case, the internal loss only needs to be about 0.015 or more).

From the graph line ■, the internal loss is 0.015 h2/h1
When calculating the value of h2/h1, it becomes about 0.3.

Therefore, in order to reduce the "metal shank" and suppress peaks and dips, in other words, to eliminate the disadvantages of metal veneers and take advantage of the advantages of paper, the speaker diaphragm shown in Figure 1 should be used as a speaker diaphragm. It can be seen that it is preferable to have a structure in which the value of h2/h1 is about 0.3 or less.

From the above considerations, in the pretreated sandwich-type acoustic diaphragm 1 shown in FIG.
2/hl) is set within the range of about 0.03 to 0.3, the speaker has characteristics that combine the advantages of a paper cone and the advantages of a metal plate cone, and eliminate the disadvantages of both. That is, it can be seen that a speaker is provided in which the peak dip due to resonance resonance is suppressed to a low level, the reproduction limit frequency is raised to a high range, and the distortion characteristics are improved.

Next, an acoustic diaphragm 1 having the structure shown in FIG.
The characteristics of a speaker actually incorporating a diaphragm in which the value of /h1 is 0.1 will be described.

FIG. 4 shows the frequency characteristics of the speaker.

The solid graph line ■ in the figure indicates the acoustic diaphragm 1 according to the present invention.
The graph line V, which is a one-dot chain line, shows the frequency characteristics of a speaker incorporating a paper cone made only of base paper.

From this, it can be seen that in the speaker incorporating the diaphragm 1 of the present invention, the high limit frequency is high and the peak/dip is not large.

FIG. 5 shows the distortion characteristics of the speaker.

In the figure, the solid graph line ■ indicates the acoustic diaphragm 1 according to the present invention.
The distortion characteristics of a speaker incorporating a paper cone (particularly secondary distortion characteristics), and the dashed-dotted graph line ■ indicates the distortion characteristics of a speaker incorporating a paper cone made only of base paper.

From this, it can be seen that the distortion level of the speaker incorporating the diaphragm of the present invention is lower than the distortion level of the paper cone speaker, and the former speaker is also superior to the latter speaker in terms of distortion characteristics.

Further, due to the characteristics of the diaphragm 1 described above, the diaphragm 1 exhibits particularly excellent effects when incorporated into a tweeter.

Next, a method for manufacturing the diaphragm 1 will be explained.

The smooth layers 3a and 3b are formed by impregnating the base paper 2 with vinyl acetate.

Note that the resin used at this time may be any resin that can close the pores on the surface of the base paper 2 and make the surface smooth, and it does not matter whether it has other properties, such as high elasticity.

Therefore, in addition to the above-mentioned vinyl acetate, a wide range of resins such as acrylic, phenol, urethane, etc. can be used.

Furthermore, the smoothing material for the surface of the base paper is not limited to resin, but also materials other than resin, such as water glass, clay, etc.
Talc, calcium carbonate, etc. can also be used.

Furthermore, the smooth layers 3a and 3b are formed not only by immersing the base paper 1 in a resin, but also by coating the surface with a resin or the like.

After smoothing the surface of the base paper 2, as a hydrophilic treatment,
A solution of 10 f/l of stannous chloride and 30 cc/l of hydrochloric acid (
It is soaked until it loses its water repellency, and then added with 0.5% palladium chloride to make it active. /l1 hydrochloric acid 2.5cc
/l solution for 15-90 seconds.

Next, nickel is deposited and deposited on the surfaces of the smooth layers 3a and 3b under standard conditions using a commercially available electroless nickel plating solution to form electroless nickel plating layers 4a and 4b of desired thickness.

Through the series of steps described above, the acoustic diaphragm 1 shown in FIG. 1 is obtained.

Note that the above-mentioned diaphragm without pretreatment is one manufactured by omitting the smooth layer forming step in the series of steps described above.

In addition, the above-mentioned electroless plating can be done with copper in addition to nickel, but in terms of acoustic characteristics as an acoustic diaphragm,
Good results were not obtained with metals other than nickel.

Furthermore, instead of making the entire plating layer an electroless nickel plating layer, it is also possible to form a thin electroless nickel plating layer and then layer a nickel plating layer on this surface by electroplating. The nickel plating layer and the electrolytic nickel plating layer have different physical properties, and the diaphragm with the double plating layer structure described above did not provide satisfactory acoustic results.

In the above embodiment, the smooth layers 3a+3b are formed on the front and back surfaces of the base paper 1, but the smooth layer may be formed on either one of the front and back surfaces of the base paper 1. You can also do this and have almost the same effect.

As described above, the acoustic diaphragm of the present invention uses a base paper made from vegetable fiber as a substrate, and after smoothing at least one surface of this substrate, electroless nickel of a predetermined thickness is coated on two smooth surfaces. By forming a plating layer and creating a structure, the acoustic characteristics that take advantage of the advantages of base paper and metal plates are effectively suppressed, in other words, peak and dip are effectively suppressed, and the high limit frequency is It is possible to achieve acoustic characteristics in which the area is effectively divided and the distortion level is reduced, and it is particularly effective when applied to tweeters. The ratio to this is 0.03
By forming it to a thickness of ~0.3, the above-described acoustic characteristics can be effectively achieved, and it has excellent features such as being able to realize an electrodynamic speaker that can respond to the development of peripheral audio equipment.

[Brief explanation of the drawing]

Fig. 1 is an enlarged cross-sectional view showing the structure of an embodiment of the acoustic diaphragm according to the present invention, and Fig. 2 shows cases in which the thickness of the electroless nickel plating layer of the acoustic diaphragm of Fig. 1 is varied. Figure 3 shows the acoustic diaphragm in Figure 1 with various thicknesses of the electroless nickel plating layer. Fig. 4 is a diagram showing the frequency characteristics of a speaker incorporating the acoustic diaphragm of Fig. 1 in comparison with that of a speaker incorporating a paper cone, and Fig. 5 is a diagram showing changes in internal loss. FIG. 2 is a diagram showing the distortion characteristics of a speaker incorporating the acoustic diaphragm of FIG. 1 in comparison with that of a speaker incorporating a paper cone. 1...Acoustic diaphragm, 2...Base paper, 3
a t 3 b...Smooth layer, 4a+4b...
...Electroless nickel plating layer.

Claims (1)

[Scope of Claims] 1. A base paper made from vegetable fibers, a smooth layer that smoothes at least one surface of the base paper, and an electroless nickel plating layer of a predetermined thickness formed on the surface of the smooth layer. An acoustic diaphragm characterized by: 2. The electroless nickel plating layer has a thickness such that the ratio to half the thickness of the base paper is within the range of 0.03 to 0.3. acoustic diaphragm.