JPH0454440B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a highly rigid speaker diaphragm having a Sanderch structure.

Conventional configurations and their problems Conventionally, cone-shaped diaphragms have often been used as speaker diaphragms, but in recent years, planar diaphragms with excellent phase characteristics and flat sound pressure frequency characteristics have come to be used frequently. Ta. This flat diaphragm needs to be lightweight and highly rigid in order to widen the reproduction band and increase efficiency when used as a speaker. Therefore, a planar diaphragm having a side German trench structure in which surface materials are provided on both sides of the core material has been considered, but it is difficult to make the diaphragm lighter than conventional cone paper or the like.
In order to reduce the weight of the diaphragm, it is necessary to use a material with a high specific elastic modulus E/ρ (E: elastic modulus, ρ: density) as a constituent material. As the surface material of the diaphragm, an aluminum alloy is used which has good workability and a relatively large E/ρ. In order to reduce the weight of planar diaphragms, there is a demand for surface materials with even higher E/ρ.

OBJECT OF THE INVENTION An object of the present invention is to reduce the weight of the surface material of a planar diaphragm made of a sandwich structure.
It is an object of the present invention to provide a speaker diaphragm capable of obtaining a high-efficiency, wide-band speaker.

Structure of the Invention The speaker diaphragm of the present invention has a sandwich structure in which a sheet made of aluminum oxide is bonded to at least one side of a core material as a surface material. The surface material of a planar diaphragm made of a sand-deutsch structure must have a thickness of approximately several tens of micrometers. The doctor blade method, chemical vapor deposition (CVD) method, etc. can be considered to obtain sheet-like materials using aluminum oxide as a surface material, but the former produces materials with a diameter of 100 μm or less, and the latter produces materials with a diameter of 10 μm or more. is difficult. Therefore, aluminum oxide sheets are manufactured by firing a prepreg sheet obtained by casting a mixture of aluminum oxide sol and polyvinyl alcohol aqueous solution, and the sheet made of aluminum oxide is used as a surface material on at least one side of the core material. It is used as a diaphragm for a flat loudspeaker which is bonded to have a sanderch structure. By manufacturing in this way, aluminum oxide, which has conventionally been difficult to form into a thin layer, can be processed into a thickness of several tens of micrometers. By using this aluminum oxide sheet with a large E/ρ as the surface material of the Sanderch structure, the weight of the diaphragm can be reduced because the E/ρ is larger than when an aluminum alloy is used as the surface material. Furthermore, if the diaphragm has the same weight, it has the advantage of widening the reproduction band when used as a speaker.

DESCRIPTION OF EMBODIMENTS Figure 1 shows an embodiment of the present invention with a diameter of 2.8 cm.
FIG. 2 shows a top view with a portion of the surface material of a diaphragm for a treble flat speaker having a thickness of 0.9 mm cut away.
In FIG. 1, 1 is a surface material made of aluminum oxide with a thickness of 20 μm, and 2 is a core material made of an aluminum alloy ribbon with a thickness of 20 μm. Here, surface material 1
A prepreg sheet with a thickness of 50 μm obtained by casting a mixture of aluminum oxide sol and polyvinyl alcohol aqueous solution containing 1% by weight of aluminum oxide and 3% by weight of polyvinyl alcohol on a polyethylene plate and drying it naturally It was produced by firing at ℃. The aluminum oxide sheet prepared using this method is porous and has a density of ρ
was 1.5 g/cm ³ , Young's modulus E was 6×10 ¹¹ dgn/cm ² , and specific elastic modulus E/ρ was 4×10 ¹¹ cm ² /sec ² . In contrast, for conventional aluminum alloys, ρ=2.7g/
cm ³ , E=7×10 ¹¹ dgn/cm ² , E/ρ=2.6×10 ¹¹
cm ² /sec ² , and the weight of a diaphragm using 20 μm thick aluminum alloy foil as both surface materials is 0.147 g if the core material is the same as in this example. The weight of the diaphragm in this example is 0.107g, so 0.04
g I feel lighter.

FIG. 2 shows the results of measuring the sound pressure frequency characteristics (1W/1m) using the JIS standard box using the diaphragm of this example as a high-pitched speaker using the nodal drive method. Second
In the figure, A is the sound pressure frequency characteristic according to this embodiment, and B is the sound pressure frequency characteristic of a conventionally used high-pitched speaker whose surface material is a 20 μm thick aluminum alloy. As can be seen from Figure 2, the reduction in the weight of the diaphragm improves efficiency by approximately 1 dB. Also, if the thickness of the surface material is the same, E/ρ
3kHzfh is higher than the high-frequency limit frequency fh of conventional aluminum alloy surface materials.

Note that the core material of the diaphragm is not limited to the structure of this embodiment. Also for bass,
Needless to say, the present invention can also be applied to diaphragms for flat speakers for mid-range sounds and for all bands.

Effects of the Invention As detailed above, according to the present invention, a high efficiency, broadband speaker can be obtained by using an aluminum oxide sheet with a higher specific elastic modulus E/ρ than an aluminum alloy as a surface material. . Furthermore, since the aluminum oxide sheet was made by firing a prepreg sheet of a mixture of aluminum oxide sol and polyvinyl alcohol aqueous solution, several aluminum oxide sheets with a large E/ρ were used.
It can be processed to a thickness of 10μm. Therefore, it is possible to obtain a surface material made of aluminum oxide with a thickness suitable for a flat diaphragm, and an excellent diaphragm for a flat speaker can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view showing an embodiment of the diaphragm for a flat speaker according to the present invention, and FIG. 2 is a comparison characteristic diagram of the sound pressure frequency of the diaphragm and a conventional diaphragm. 1...Surface material, 2...Heartwood.

Claims (1)

[Claims] 1. A speaker diaphragm having a sandwich arch structure in which a sheet made of aluminum oxide obtained by baking a prepreg sheet obtained by casting a mixture of aluminum oxide sol and an aqueous polyvinyl alcohol solution is bonded as a surface material on at least one side of a core material.