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Description 1, title of the invention
3. Detailed Description of the Invention The present invention relates to a loudspeaker, and in
particular to its constituent materials. The speaker diaphragm should ideally perform complete
piston movement in the frequency band to be used, and if the diaphragm is deformed or split
vibration occurs during vibration, the sound pressure frequency characteristics, distortion factor
2 phase characteristics, etc. will be degraded and high I can not expect fidelity reproduction. In
order to solve these problems, flat diaphragms using a honeycomb sand-inch structure or the like
have recently been adopted. If the voice coil is bonded to the inner portion of the flat diaphragm
at the first resonance resonant frequency and driven, the first resonance is canceled and fh (high
frequency limit frequency) can be greatly increased. However, since the diameter of the nodal
circle is usually about 65 of the diaphragm outer diameter, the voice coil has a large diameter
compared to the conventional one. Therefore, the weight of the voice coil is increased, which
reduces the efficiency of the speaker. The magnetic circuit that drives the very large-diameter
voice coil also becomes a special large-sized one, resulting in high cost. In order to solve these
problems, a method has been proposed in which a 71-inch coil of conventional size and an intranodal part EndPage: 1 of a plane diaphragm are connected by a cone-shaped coupling material
(referred to as a coupling cone). Is adopted by However, in the above-mentioned method, if the
material of the coupling cone is not sufficiently light weight and high in bending rigidity, it
causes not only the decrease of the efficiency but also the peak of the sound pressure frequency
characteristic due to the resonance of the coupling cone, Problems such as increase in distortion
occur. In the speaker using the above-described high rigidity flat diaphragm, the internal loss of
the diaphragm is small and the amplitude at the resonance frequency is large. Therefore, the
resonance peak at fh is higher than that of the conventional speaker using the paper cone
diaphragm. There is a phenomenon that gets extremely high. This peak makes the speaker
system design difficult, and even a flat speaker with high fh has to be leveled down from a
considerably low frequency in order to attenuate it if the peak level is high, which limits the
frequency band used It will be In order to reduce this resonance peak, it is known that an effect
can be obtained by providing a damping layer having a large internal loss between the
diaphragm and the voice coil to give an internal loss to the vibration system, but at the same time
fh It is also lacking in practicality because it decreases. Although aluminum alloy sheet and paper
etc. are actually used as a material of a coupling cone from these things, in the former, although
the fall of fh is small, since the internal loss is small, the resonance peak becomes large and the
latter is fh However, there is a merit and demerit that the resonance peak becomes smaller
because the internal loss is thick.
The present invention seeks to obtain a flat loudspeaker with a small resonance peak without
reducing fh by using a material having high rigidity and large internal loss for the coupling cone
in order to solve these problems. Hereinafter, an embodiment of the present invention will be
shown and described. FIG. 1 shows the appearance of a flat diaphragm used in the speaker of the
present invention and the shape of a core material with a part of the surface material cut away.
Figure 1 shows a 19-inch diameter, 1-cm, 6-height structure in which a 40 μm-thick aluminum
foil 2 is bonded to both sides of June 1 of a car-weight-symmetrical no-Nickam core made of 20
μm-thick aluminum-foil. It is a flat diaphragm for bass of the torso. FIG. 2 is a cross-sectional
view showing the structure of the loudspeaker of this embodiment. In FIG. 2, reference numeral 3
denotes the flat diaphragm shown in FIG. 1, which is adhesively held on the frame 6 via the edge
4. The upper end of the coupling cone 6 is bonded to the inside of the cylinder of the flat
diaphragm 3 and the lower end is bonded to the upper end of the voice coil bobbin 8 in the
magnetic circuit 7. The cross-sectional structure of the coupling cone 6 is shown in the circle by
the lead wire, 9 is a foamed polyethylene, 1 ° is a high density polyethylene sheet reinforced by
carbon fiber reinforcement, and the sheet 10 is covered with the foamed polyethylene 9 It has a
sand inch structure. Next, the method for producing the campling cone will be described with
reference to FIG. In FIG. 2, the fiber length of high density polyethylene fiber is 6 brains, 15 wt%
of carbon fiber of fiber g of 10 pm is added, and papermaking is carried out with a weight ig 17
m. This paper-made sheet is disposed on both sides of a sheet having an area density of 80 to 7
m 2 (foaming ratio: about 5 times) obtained by adding a foaming agent to polyethylene, and after
heat lamination, this laminate sheet is heated at 200 ° C. for several seconds Immediately after
that, it is press-molded to obtain a coupling cone used in the present embodiment. In the heating
step, the high density polyethylene of the above-mentioned sheet is melted and the surface of the
carbon fiber is covered to form a high modulus elastic polyethylene sheet. Meanwhile, the
foamed polyethylene sheet is also foamed at the same time. Then, "the polyethylene of one
person melts and adheres to form a sand-inch structure having a core of foamed polyethylene.
Because this sheet is a structural body, it is ideal to have a high flexural rigidity, a light weight,
and a large internal loss as a tumbling cone material. The physical properties of this sheet are
shown in the following table. Physical properties of aluminum and paper conventionally used for
comparison, and carbon C? The physical properties of only the fiber reinforced polyethylene
sheet were combined.
EndPage: 2 According to this embodiment, an ideal coupling cone can be obtained in which the
bending stiffness and internal loss are overwhelmingly larger than those using other materials.
Next, a speaker was prepared as shown in FIG. 2 using the above-mentioned coupling cone, and
the sound pressure frequency characteristic IW '71 m was measured with a JIS standard box. The
result is shown in FIG. 4 a (dashed line). Also, the characteristics when a coupling cone of
aluminum is used to similarly form a speaker are shown in FIG. 4C (solid line) and the
characteristics when a carbon fiber reinforced polyethylene sheet is used are shown in FIG. 4b
(broken line). As apparent from the results of FIG. 4, by using the campling cone according to the
present embodiment, a speaker having excellent characteristics with significantly reduced
resonance peak and little decrease in fh is obtained compared to the case of using aluminum. It is
In addition, it can be seen that in the speaker using the carbon fiber reinforced polyethylene
sheet, although the fh is slightly reduced, the resonance peak can be reduced, and the speaker
has considerably good characteristics. As apparent from the above-described embodiments,
according to the present invention, the high-frequency resonance peak is significantly reduced
and the decrease in fh is small in the planar speaker of the joint circle drive system using the
coupling cone, which is very excellent. It is possible to provide a speaker of various
4. Brief description of the drawings. FIG. 1 is a partially cutaway top view of the flat diaphragm
used in the present invention, FIG. 2 is a cross sectional view showing an embodiment of the
speaker of the present invention, and FIG. FIG. 4 is a diagram of sound pressure frequency
characteristics of the present embodiment and a conventional speaker. 3 · · · Flat diaphragm, 6 · ·
· · · · · Coupling cone, 7 · · · · Magnetic circuit, 8 · · · · · Voice coil, 9 · · · · · · Polyethylene, 1 o ..... High
density polyethylene sheet. Name of agent Attorney Nakao et al. 1 person Fig. 1 Fig. 2 End Page:
3113 Fig. 4 Fig. 4 Fig. 4 * tnz] EndPage: 4
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