JPH0127357Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a speaker diaphragm having a flat acoustic radiation surface, and in particular provides a speaker diaphragm that can increase the divided resonance frequency. A conventional speaker diaphragm (hereinafter simply referred to as a diaphragm) with a flat acoustic projection surface has a disk shape or a truncated cone shape, as shown in Fig. 1 a, b and Fig. 2 a, b. are doing. In the disk-shaped diaphragm shown in Figure 1 a and b, its divided resonance frequency is
₁₀₀ is given by the following formula. Here, E is the Young's modulus of the diaphragm, ρ is the density of the diaphragm, σ is Poisson's ratio, a is the radius of the diaphragm, t is the thickness of the diaphragm, and _a10 is a frequency constant that varies depending on Poisson's ratio σ. is usually a ₁₀ =3.018. In this way, for the diaphragm, once the dimensions and material are determined, the divided resonant frequency ₁₀₀ is determined. Furthermore, _the resonant frequency ' ₁₀₀ of the truncated cone-shaped diaphragm _shown in FIG.
1.27 ₁₀₀ ) can be made higher (however, the thickness of the disc part can be
This is a case where d _i /d _p =4.0, where d _i is the thickness of the entire d _p , and the truncated cone-shaped diaphragm and the disc-shaped diaphragm have the same weight). That is, it can be seen that once the material of the speaker's diaphragm is determined, its divided resonant frequency changes depending on its shape. The present invention has been made in consideration of the above points, and provides a diaphragm having a shape in which a disk with a small radius is arranged coaxially with a disk with a large radius on a disk with a large radius. By adopting such a shape, the divided resonant frequency is higher than that of a conventional diaphragm, and the sound pressure reproduction band of the speaker is expanded. Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 3 is an exploded perspective view of a diaphragm of a speaker according to an embodiment of the present invention, and FIG. 4 is a perspective view of the diaphragm. The configuration of the diaphragm 1 of this speaker is the diameter r _p
A large-diameter (diameter r _p ) disk 5 is formed by sandwiching both sides of a thick core material 4 with a diameter r _p between the two thin surface materials 2 and 3 . A small diameter disc 8 formed from a surface material 6 with a diameter r _i (r _i < r _p ) and a core material 7 with a diameter r _i is laminated on one plane of a disc 5 with a large diameter. The circular plate 5 and the small diameter circular plate 8 are arranged in a coaxial relationship, and their diameter ratio r _i /r _p is in the range of 0.7 to 0.85. The core materials 4 and 7 are made of a honeycomb shape (the shape of a honeycomb) made by continuously forming a large number of hexagonal cylinders from lightweight and rigid metal such as aluminum, paper, polymer film, etc., or they are made of foamed resin, A disk-shaped piece of foamed metal is used. Further, the surface materials 2, 3, and 6 are made of lightweight and rigid metal such as aluminum, paper, film, or the like. When a honeycomb-shaped body is used for the diaphragm 1, the space occupied by the diaphragm 1 is increased, so that the diaphragm has the advantage of being lightweight. Furthermore, the use of foamed resin or foamed metal has the advantage that the diaphragm can be manufactured at low cost. FIG. 5 shows the results of theoretical calculation of the characteristics of the diaphragm of the speaker of the above embodiment. The figure shows the diameter ratio r i /r _p versus _split resonance using the thickness ratio d _i /d _p between the overall thickness d _i of the diaphragm 1 and the thickness d _p of the large-diameter disk 5 as a parameter. Relationship of frequency ratio _10/100 and diameter ratio r _i /r _p to weight _ratio M
This is a calculation of the relationship _D /M _DO . Here, the relationship between the diameter ratio r _i /r _p and the divided resonance frequency ratio _10/100 was determined by deriving the vibration equation of _the diaphragm and inserting the following two as boundary conditions. (i) Assume that the step, displacement, moment of inertia, and shear force are equal at the joint of the two discs 5 and 8. (ii) The periphery shall be a free edge. Further, the relationship between the diameter ratio r _i /r _p and the weight ratio M _D /M _DO was determined by simple geometric calculation assuming that the density of the diaphragm 1 is uniform. Note that ₁₀₀ , M _DO is the thickness d _p and diameter shown in Figure 1.
r _p indicates the primary resonance frequency and weight of the disk-shaped diaphragm, and ₁₀ and M _D indicate the diameter and thickness of the diaphragm 1 (large diameter disk 5) in this embodiment shown in FIG. are respectively r _p and d _p , and the diameter of the small diameter disk 8 is
r _i and the thickness of the diaphragm 1 is d _i ), the first resonance frequency and weight are shown, respectively. Looking at the case where the thickness ratio d _i /d _p =3.0 in Fig. 5, as the diameter ratio r _i /r _p increases from 0.4 → 0.6 → 0.8 → 1.0, the weight ratio M _D /M _DO increases from 1.3 → 1.7 → 2.3 → 3.0 (curve 9). On the other hand, the split resonant frequency ratio _10/100 increases from 1.3 → 2.2 → 3.3 → 3.0 until the radius ratio r _i /r _p reaches around 0.8 (curve 10), and the _radius ratio r _i /r _p increases from 0.5 to 1.0. In this range _, the split resonance frequency ratio of _10/100 exceeds the weight ratio M _D /M _DO . In this range, the diaphragm 1 of this embodiment can increase the resonance frequency ₁₀ compared to the disk _- shaped diaphragm of equal weight shown in FIG _. It can be seen that when the value is set to 0.7 to 0.85, the resonance frequency ₁₀ can be increased most relative to the weight. For example, when the thickness ratio d _i /d _p = 3.0 and the diameter ratio r _i /r _p = 0.8, from Fig. 5, the weight ratio M _D /M _DO = 2.3, the divided resonance frequency ratio ₁₀ / ₁₀₀ = 3.3, etc. Compared to the weight of a disc-shaped diaphragm, ( _10/100 )/(M _D /M _DO ) = 3.3/2.3 = 1 _.
The resonant frequency can be increased by 4 times and divided _{by 10} . Note that the same thing can be said for the case of d _i /d _p =2.0 as for the case of d _i /d _p =3.0. Table 1 shows _{the shape effect ratio (10/100 )} /(M _D /M _DO )
The figure shows the calculated value.

[Table] From Table 1, when the thickness ratio d _i /d _p =2.0, the shape effect ratio becomes the largest around r _i /r _p =0.65 to 0.75. Further, when the thickness ratio d _i /d _p =3.0, the shape effect ratio becomes the largest when r _i /r _p =0.7 to 0.85. Incidentally, if the thickness ratio becomes larger than 3.0, the range of r _i /r _p in which the shape effect ratio becomes larger moves higher and approaches 1.
(The range shown in Table 1 indicates the range in which the shape effect ratio for each thickness ratio is approximately 90% or more of the maximum value.) Therefore, as a speaker diaphragm, r _i /r _p = 3 or more. Considering the case where r _i /r _p is defined as 0.7 to 0.85, this indicates the range in which the shape effect ratio is the largest. As described above, the diaphragm of this embodiment can increase the resonance frequency and expand the sound pressure reproduction area of the speaker compared to a disc-shaped diaphragm of equal weight. FIG. 6 shows another embodiment of the present invention, in which surface materials 12, 13, and 14 are bonded to both flat surfaces of a core material 11 with a stepped cross section to form a large-diameter disk 1.
5 and a small diameter disc 16 is formed. When the diaphragm is formed in this way, it has the advantage of reducing the number of manufacturing steps because the number of core materials can be reduced. Figure 7 shows that using the speaker diaphragm of the present invention,
An example of a speaker configured with a flat acoustic radiation surface is shown. To explain its structure, a ring-shaped magnet 19 and a ring-shaped top plate 20 are arranged on a plate 18 having a hollow center pole 17 to form a magnetic circuit 21, and a frame 22 is placed on this magnetic circuit 21. is arranged, and the peripheral edge of the damper 23 is fixed to the lower part of the frame 22. Furthermore, the voice coil 24 is fitted into the central part of the damper 23, and the voice coil 24 is
A diaphragm 27 whose lower portion is held in a magnetic gap 25 and whose peripheral portion is fixed to the upper surface of the frame 22 via a free edge 26 is disposed at the upper end of the voice coil 24. The speaker with the above configuration using the diaphragm according to the present invention can obtain a high divided resonance frequency that is almost the same as the calculation result shown in Fig. 5, and the sound pressure reproduction band of the speaker can be approximately
We were able to increase it to 1.4 times. As explained above, the present invention has the advantage that by devising the shape and structure, a speaker diaphragm with a high divided resonant frequency can be obtained, and the sound pressure reproduction band of the speaker can be expanded.

[Brief explanation of the drawing]

1a and b are a plan view and a front view of a conventional disc-shaped speaker diaphragm, and FIGS. 2 a and 2b are a plan view and a front view of a conventional truncated cone-shaped speaker diaphragm, Fig. 3 is an exploded perspective view of a flat speaker according to an embodiment of the present invention, Fig. 4 is a perspective view of the diaphragm, and Fig. 5 is a diagram showing the results of calculating the frequency characteristics of the diaphragm. , FIG. 6 is an exploded perspective view of a speaker diaphragm according to another embodiment of the present invention, and FIG. 7 is a diagram showing an embodiment of a speaker equipped with a speaker diaphragm according to the present invention. 5, 15... Large diameter disc, 8, 16... Small diameter disc.

Claims (1)

[Claims for Utility Model Registration] (1) A speaker diaphragm having a shape in which a small-diameter disc is bonded coaxially with the large-diameter disc on one plane of a large-diameter disc. A diaphragm for a speaker, wherein the ratio of the diameter of the small-diameter disk to the diameter of the large-diameter disk is 0.7 to 0.85. (2) The speaker diaphragm according to claim 1, wherein the core material constituting the large-diameter disk and the core material constituting the small-diameter disk are honeycomb-shaped bodies. (3) The speaker diaphragm according to claim 1, wherein the core material constituting the large-diameter disk and the core material constituting the small-diameter disk are foamed resins. (4) The speaker diaphragm according to claim 1, wherein the core material constituting the large-diameter disk and the core material constituting the small-diameter disk are foam metal.