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FIELD OF THE INVENTION The present invention relates to acoustic diaphragms. [Conventional
art and its problems] Carbon fibers are conventionally used as one of the constituent materials of
acoustic diaphragms. For example, a diaphragm for an electroacoustic apparatus has been
proposed in which carbon fibers having a Young's modulus of 15000 kg / m "or more are mixed
with pulp having a freeness of 300 cc or less and freeness (Japanese Patent Publication No. 5433130). The pulp fiber and the carbon fiber having a D Young's modulus of 3000 to 15000 KV /
mm (the proportion of the weight ratio between the former pulp fiber and the latter carbon fiber
is 10 to 40% for the former and 90 for the latter). A speaker diaphragm of 60 to 60 q6 has also
been proposed (Japanese Patent Publication No. 56-47757). However, these diaphragms have
weak bonds between carbon fibers because the material used as a binder is pulp, which leaves
problems in terms of strength, rigidity and internal loss. It can not be said that the frequency
characteristic is relatively large and sufficiently good. [Means for Solving the Problems] The
acoustic diaphragm is mainly composed of carbon fibers and a binder having no fiber structure.
A water-soluble organic non-fibrous binder, such as a water-soluble acrylamide resin (molecular
weight 800,000 to 1,000,000 as an anionic resin), is dispersed in water to disperse 100 parts by
weight of the elementary fiber in water. Add 50 to 100 parts by weight and stir. Next, a sulfuric
acid band is added to adjust the pH to 4 to 6, about 1 to 10 parts by weight of a sizing agent is
added thereto, the mixture is stirred, and immediately thereafter, it is formed into a sheet with a
desired diaphragm shape. Then, the wet carbon fiber mat removed from the web was subjected
to a mold temperature of 140 to 200 ° C. 1. It heat-press dries on conditions of press time 3 to
15 minutes, and comprises the acoustic diaphragm which becomes this invention. The acoustic
diaphragm thus configured has a composition of about 30 to 50 parts by weight of a binder
having no fiber structure with respect to 100 parts by weight of carbon fibers. An acoustic
diaphragm composed of such a carbon fiber and a binder not having a fiber structure has a high
propagation speed desirable for the characteristic of the carbon fiber as a diaphragm, and a fiber
used as the binder is a fiber. Since it does not have a structure, it does not cause defects such as
little bonding in the cross-linked portion of the carbon fiber, and a sufficiently homogeneous
strength as a whole is obtained, the rigidity is high, and further, The strain characteristics are
also reduced and show desirable characteristics. For example, as shown in the drawing, the
frequency characteristic of the speaker using the acoustic diaphragm of the present embodiment
is shown by a solid line, and the frequency characteristic of the speaker using an acoustic
diaphragm by mixing pulp and carbon fiber in the related art is shown by a dotted line. The high
frequency limit frequency is 10 KHz in the case of this, while the high frequency band limit is
greatly extended to 18 KHz in the case of this embodiment, and the second harmonic distortion
in the middle frequency is also about 6 dB on average It is extremely good as it is declining and
Furthermore, this acoustic diaphragm can be manufactured by the same manufacturing process
as when using conventional natural pulp, and has features such as being excellent in moldability
and mass productivity, and being flame retardant. There is. [Effects] With appropriate internal
loss, high rigidity, and sufficient strength, high frequency limit frequency is significantly larger
than that of the conventional one, and distortion is also large. The sound quality is reduced and
the sound quality is extremely excellent. In addition, the conventional method can be adopted as
it is, and it can be obtained extremely easily and at low cost.
Brief description of the drawings
The drawing is a graph of frequency characteristics of the speaker.
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