JPH0212797Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a diaphragm for an electroacoustic transducer that provides a large bending rigidity E/I.

[Conventional technology]

Generally, a diaphragm used in an electroacoustic transducer is required to have a large specific Young's modulus E/ρ, a large bending rigidity E/I, and an appropriately large internal loss η (E is Young's modulus, ρ is Density, I is cross section 2
second moment). That is, the larger the specific Young's modulus E/ρ, the higher the resonant frequency, the wider the piston vibration region, and the wider the usable frequency band. In addition, the speed of sound is generally used to simply express the vibration characteristics of a diaphragm, but this is expressed as √ of the 1/2 power of the specific Young's modulus E/ρ, and the higher the speed of sound, the longer the frequency characteristics. Because it will be done,
From this, it can be said that the larger the specific Young's modulus E/ρ, the better. In addition, the larger the bending rigidity E/I is, the more distortion is reduced, and the larger the internal loss η is, the lower the Q value of the divided resonance of the diaphragm is, flattening the characteristics and obtaining good frequency characteristics. .

FIGS. 2a to 2d show diaphragms with various configurations that have been conventionally used to increase bending rigidity E/I. In FIG. 2a, a bent portion 12 is formed near the edge of the diaphragm 10. This configuration had the disadvantage that the richness of the low range was insufficient and the connection with the middle and high ranges deteriorated. The reason is that the flatness of the radiation surface A of the diaphragm 10
2 (that is, it does not form a correct conical surface) and despite the reinforcement by the bent portion 12, the radial direction α of the diaphragm 10 is still
This is considered to be because the bending rigidity E·I in the circumferential direction β is small.

In FIG. 2b, the diaphragm 14 has a honeycomb sandwich structure. However, since the honeycomb sandwich structure is thick, when it is formed into a cone shape, the end faces 14a and 14b are cut diagonally, which makes processing troublesome.If processed roughly, the honeycomb core formed body etc. may become loose. It was affecting the playback sound. Further, in general, the honeycomb sandwich structure has a complicated vibration transmission path, including a back side skin material, a honeycomb core material, and a front side skin material, and the sound quality cannot necessarily be said to be good.

In FIG. 2c, a circumferential groove 18 is formed in the diaphragm 16. With this configuration, although the bending rigidity E·I in the circumferential direction α becomes large, the bending rigidity E·I in the radial direction β becomes smaller because it functions in a substantially bellows-like manner in the radial direction β. Moreover, the non-flatness of the radiation surface A also had a negative effect on the sound quality.

In FIG. 2d, circumferential ribs 22 are formed on the back surface of the diaphragm 20 using the same material as the diaphragm 20 or a different material. With this configuration, the ribs 16 increase the weight, which reduces efficiency, and furthermore, there is a problem that the design is restricted by the balance between weight and bending rigidity E/I, efficiency and cost, etc.

As described above, all of the conventional techniques have the drawback that the efforts to increase the bending rigidity E/I have a negative effect on others.

[Problem that the invention attempts to solve]

This invention aims to solve the drawbacks of the conventional techniques and realize a diaphragm for electroacoustic transducers that can increase the bending rigidity E/I and improve the sound quality without adversely affecting others. It is.

[Means for solving problems]

This invention provides a diaphragm for an electroacoustic transducer in which ribs are formed in the circumferential direction on the plate surface of a cone-shaped diaphragm base, and the ribs include a protrusion for forming a hollow in the center in the width direction and an adhesive attachment on both sides of the protrusion. a strip-shaped rib member consisting of a piece is bonded to the back surface of the diaphragm base via the adhesive mounting piece;
The diaphragm base portion other than the portion to which the rib member is bonded has a single-layer structure.

[Effect]

According to the solution of this invention, the ribs formed in the circumferential direction particularly increase the bending rigidity E/I in the circumferential direction, and since the ribs are hollow, the weight is reduced as in the one in FIG. 2d. It is possible to obtain good sound quality without becoming heavy and deteriorating efficiency.

In addition, according to the solution of this invention, the rib member is band-shaped and there are only the minimum necessary parts for forming the rib, so the diaphragm basically has a single-layer structure, and the mass increases due to the formation of the rib. can be kept to a minimum, and deterioration of efficiency can be prevented.

[Example 1] An example of this invention is shown in FIG. In FIG. 1, ribs 2 are provided on the back surface of the cone-shaped diaphragm 24.
6 are formed in upper and lower directions along the circumferential direction α of the diaphragm 24. The inside of this circumferential rib 26 is a hollow portion 28 . For example, as shown in the enlarged view in the figure, the circumferential rib 26 is formed on the diaphragm base 24.
It can be formed by adhering a rib member 26a having a concave cross section to the back surface of a. Rib member 26a
consists of a hollow part forming protrusion 26a-1 and adhesive attachment pieces 26a-2 on both sides thereof, and is formed in a band shape. The rib member 26 and the diaphragm base 24a are bonded together at an adhesive attachment piece 26a-2.
The portion of the diaphragm base 24a other than the portion bonded to the adhesive mounting piece 26a-2 has a single-layer structure. The rib member 26a can be made of the same material as the diaphragm base 24a, or can be made of a different material. If it is made of a highly elastic material such as carbon prepreg like the diaphragm base 24a, particularly excellent characteristics can be obtained. The individual characteristics of carbon prepreg are as follows. For comparison, the properties of paper alone are shown in the box.

Density ρ: 1.77×10 ³ Kg/m ³ (0.5 to 0.8× ^{10 3} Kg/m ³ ) Young's modulus E: 1.43×10 ¹¹ N/m ² (2 to 5×10 ⁹ N/m ² ) Young's modulus Rate E/ρ: 8.1×10 ⁷ m ² /S ² (4 to 7×10 ⁶ m ² /S ² ) Sound velocity √ : 9.0×10 ³ m/S (2 to 2.6×10 ³ m/S) Rib 26 The dimensions of the rib member 26a are preferably about 5 mm or less in width and about 3 to 4 mm in height, and the thickness of the rib member 26a is about 0.25 mm like the diaphragm base 24a.
When the two are glued together, the overall thickness should be about 0.5mm.

According to the above configuration, the diaphragm 24 has a large bending rigidity E·I in the circumferential direction α due to the circumferential ribs 26. In addition, the sound velocity √ in the circumferential direction is 1/3 of the value of the material alone (9.0×10 ³ m/S as mentioned above in the case of carbon prepreg) due to the conical shape when there is no rib 26. However, the ribs 26 can prevent this deterioration. Furthermore, since there is no bent portion 12 as shown in FIG. 2a, the radiation surface A has good flatness (that is, it is a correct conical surface), and the sound quality is improved. In addition, unlike the honeycomb sandwich structure shown in FIG. It is easy as in the case of a diaphragm. Further, unlike the case in which grooves 18 as shown in FIG. 2c are formed, the bending rigidity E/I in the radial direction β does not decrease, but is rather increased to some extent by the presence of the ribs 26. Also,
Since the ribs 26 are hollow, they are lighter than the ribs 22 whose insides are closed as shown in FIG. 2d. Further, since the portion of the diaphragm base 24a other than the portion bonded to the adhesive mounting piece 26a-2 has a single layer structure, the increase in mass due to the formation of the ribs is small, and deterioration of efficiency can be prevented.

[Embodiment 2] Another embodiment of this invention is shown in FIG. In this case, the hollow portion 28 of the rib 26 shown in FIG. 1 is filled with a lightweight damping material 30 such as urethane foam. According to this, it is possible to improve the internal loss η and lower the Q value.

[Embodiment 3] Still another embodiment of this invention is shown in FIG. In this embodiment, the hollow portion 28 in the embodiment shown in FIG. 1 is filled with a honeycomb core material 32 such as aluminum. According to this, the bending rigidity E・I
can be made larger. In this case, since the honeycomb core material 32 is light, the increase in weight due to filling it therein is minimal, and there is no deterioration in efficiency as shown in FIG. 2d.

[Example of change]

In the embodiment described above, the rib 26 has a rectangular cross-sectional shape, but it may also have a triangular or other polygonal shape as shown in FIG. 5a, or a circular shape as shown in FIG. 5b.

〔effect〕

As explained above, according to this invention, since hollow ribs are formed in the circumferential direction on the back surface of the cone-shaped diaphragm, the bending rigidity E/I in the circumferential direction is increased.
Sound quality can be improved. Furthermore, since the circumferential ribs are hollow, there is only a slight increase in weight and no deterioration in efficiency occurs.

Further, according to this invention, the rib member is strip-shaped,
Since there are only the minimum necessary locations for rib formation, the diaphragm is basically a single-layer structure, which can minimize the increase in mass due to rib formation and prevent deterioration of efficiency. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of this invention. FIG. 2 is a sectional view showing a conventional diaphragm. FIG. 3 is a sectional view showing another embodiment of this invention. FIG. 4 is a sectional view showing still another embodiment of this invention. FIG. 5 is a sectional view showing an example of a change in the cross-sectional shape of the rib 26. 24... diaphragm, 24a... diaphragm base, 26
...Circumferential rib, 26a...Rib member, 28...
Hollow part, 30... dump material, 32... honeycomb core material.

Claims (1)

[Scope of utility model registration request] In a diaphragm for an electroacoustic transducer in which circumferential ribs are formed on the plate surface of a cone-shaped diaphragm base,
The rib is formed by bonding a band-shaped rib member consisting of a hollow part forming protrusion at the center in the width direction and adhesive mounting pieces on both sides thereof to the back surface of the diaphragm base via the adhesive mounting pieces. A diaphragm for an electroacoustic transducer, characterized in that a diaphragm base portion other than the portion to which the rib member is bonded has a single-layer structure.