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JP2009105532

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DESCRIPTION JP2009105532
An object of the present invention is to reduce wear of an acoustic diaphragm, and to maintain
stable sound quality and volume even if sound is reproduced for a long time. A shock-absorbing
member 35 is cap-shaped on a tip of a drive rod 31 of a magnetostrictive actuator 30 by a
material having a durometer D in the range of 30 to 75, such as ETFE (tetrafluoroethyleneethylene copolymer). Is loaded to drive the magnetostrictive actuator 30, and the displacement of
the drive rod 31 is transmitted to the acoustic diaphragm 10 to vibrate the acoustic diaphragm
10 to reproduce the sound. [Selected figure] Figure 1
スピーカシステム
[0001]
The present invention relates to a speaker system that reproduces sound by applying vibration to
an acoustic diaphragm by a drive rod of an actuator such as a magnetostrictive actuator.
[0002]
As disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-166027),
for example, a cylindrical acoustic diaphragm made of acrylic is vertically erected and attached to
a base casing, and the lower end of the acoustic diaphragm in the base casing Arrange the
actuator driven by the audio signal on the side, bring the tip of the drive rod of the actuator into
contact with the lower end face of the acoustic diaphragm, and reproduce the sound by applying
the vibration in the plate surface direction to the acoustic diaphragm Speaker systems are
considered.
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1
[0003]
In this speaker system, the lower end face of the acoustic diaphragm is excited by a longitudinal
wave, but the vibrational elastic wave propagates in the direction of the plate surface of the
acoustic diaphragm and becomes a wave in which the longitudinal wave and the transverse wave
are mixed Sound waves are emitted by the transverse waves in the direction perpendicular to the
plate surface of the plate, and a sound field with a sense of spreading can be obtained.
[0004]
Also, as an actuator in this case, a magnetostrictive actuator using a magnetostrictive element
whose shape changes when an external magnetic field is applied can be used. And the
magnetostrictive element generates a large stress when the shape changes, so even with a small
magnetostrictive actuator, the acoustic diaphragm can be made to sound relatively loudly, and a
hard acoustic diaphragm such as an iron plate You can even sound.
[0005]
Furthermore, the magnetostrictive actuator is also excellent in response speed, and the response
speed of the single magnetostrictive element is on the order of nanoseconds.
[0006]
Non-Patent Document 1 below shows the “softness” of a material called Hytrel (registered
trademark), which is a type of rubber elastic body (elastomer).
[0007]
The prior art documents mentioned above are as follows.
JP, 2007-166027, A Toray Du Pont Co., Ltd., product information, Hytrel, What is Hytrel?
Comparison with rubber and plastic, [September 12, 2007 search], Internet <URL: http://www.tdnet.co.jp/hytrel/about/comparison.html>
[0008]
However, in the above speaker system, when the acoustic diaphragm is vibrated for a long time
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by the actuator, the portion of the acoustic diaphragm where the drive rod of the actuator abuts
is worn away, and the sound quality and the volume change.
[0009]
The test results are shown in FIG.
The tip of the driving rod made of iron of the magnetostrictive actuator is brought into contact
with the lower end surface 12 of the acoustic diaphragm 10 made of acrylic, and a music signal
having a peak voltage of 6 to 7 Vrms is input to the magnetostrictive actuator as a driving signal.
The part which the drive rod of the lower end surface 12 of the acoustic diaphragm 10 contact |
abutted at the time of vibrating the acoustic diaphragm 10 for 1000 hours was image |
photographed.
[0010]
The black circular portion 12a at the central portion was a recess worn away by being pushed up
by the drive rod on the lower end surface 12 of the acoustic diaphragm 10, and the depth, ie, the
amount of wear was about 10 μm.
[0011]
Therefore, the present invention can reduce the wear of the acoustic diaphragm and maintain
stable sound quality and volume even if the sound is reproduced for a long time.
[0012]
A speaker system according to the present invention comprises an acoustic diaphragm and an
actuator for applying vibration to the acoustic diaphragm by a drive rod, and a buffer member is
provided at a tip of the drive rod in contact with the acoustic diaphragm. It is characterized by
[0013]
According to the present invention, wear of the acoustic diaphragm can be reduced, and stable
sound quality and volume can be maintained even if the sound is reproduced for a long time.
[0014]
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3
[1.
Embodiment of Speaker System: FIGS. 1 to 5] (1-1.
Configuration of Speaker System: FIGS. 1 to 3) FIG. 1 shows an example of a speaker system
according to the present invention, and FIG. 1 (A) is a top view (view from above) and FIG. 1 (B) is
a base It is the side view which made the part of line BB of FIG. 1 (A) the cross section about the
housing | casing.
[0015]
The speaker system of this example includes an acoustic diaphragm 10, a base housing 20, and a
magnetostrictive actuator 30.
[0016]
The acoustic diaphragm 10 is formed of, for example, acrylic and has a cylindrical shape with
both ends open, and has a thickness of 2 mm, a diameter of 10 cm, and a length (height) of 100
cm.
[0017]
The base housing 20 is formed, for example, of a synthetic resin in a disk shape having a certain
height (thickness) with an outer diameter larger than the outer diameter of the acoustic
diaphragm 10, and on the bottom side, The legs 21 are formed at three positions.
[0018]
The acoustic diaphragm 10 has the ring-shaped end face on one end side as the upper end face
11 and the ring-shaped end face on the other end side as the lower end face 12 with the axial
direction as the vertical direction. It is attached to the upper surface of the base housing 20 so as
to align with the central axis.
[0019]
Specifically, one end of the L-shaped angle 41 is made to interpose the damping material 42
made of silicon rubber between the base housing 20 and the four positions of the equiangular
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interval on the upper surface of the base housing 20. And the damping members 44 and 45
made of silicone rubber are respectively interposed on the inside and the outside of the acoustic
diaphragm 10, and the other end of the L-shaped angle 41 is screwed It is attached to the lower
end of the acoustic diaphragm 10 by a nut 47.
[0020]
By attaching the acoustic diaphragm 10 to the base casing 20 via the damping members 44, 45
and 42 in this manner, the vibration of the acoustic diaphragm 10 is transmitted to the base
casing 20 and a sound image is formed on the base casing 20 side. It is possible to prevent
localization.
[0021]
Furthermore, in the base housing 20, storage holes 23 penetrating in the vertical direction are
formed at four equiangularly spaced positions between the attachment positions of the L-shaped
angle 41, and magnetostriction is generated in each storage hole 23. The actuator 30 is inserted
from the lower side with the drive rod 31 upward, and the plate spring 32 at the lower end is
attached to the base casing 20 by the screws 33 and 34 to fix the magnetostrictive actuator 30
to the base casing 20.
[0022]
In the magnetostrictive actuator 30, a solenoid coil for applying a control magnetic field is
disposed around a rod-like magnetostrictive element, and a drive rod 31 made of, for example,
iron is connected to one end of the magnetostrictive element, and a control current flows in the
solenoid coil. As a result, a control magnetic field is generated, and the control magnetic field is
applied to the magnetostrictive element to displace the magnetostrictive element in the vertical
direction, thereby displacing the drive rod 31 in the vertical direction.
[0023]
Then, buffer members 35 are provided at the tip of the drive rod 31 of the magnetostrictive
actuator 30, which contacts the lower end surface 12 of the acoustic diaphragm 10.
[0024]
The buffer member 35 is formed of a material as described later, for example, in a cap shape as
shown in FIG. 2 and loaded on the tip of the drive rod 31 or in a sheet shape as shown in FIG. It
forms and it sticks on the front end surface of the drive rod 31 with the adhesive agent 36. As
shown in FIG.
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[0025]
As compared with the case where it is formed in a cap shape as shown in FIG. 2 and loaded in the
drive rod 31 and the case where it is formed in a sheet shape as shown in FIG. 3 and attached to
the drive rod 31, mounting on the drive rod 31 is easy. It is more desirable to form it like a cap
and load it on the drive rod 31 in that it can be easily removed from the drive rod 31.
[0026]
If the thickness of the buffer member 35 is large, the sound quality changes because the buffer
member 35 abuts on the lower end surface 12 of the acoustic diaphragm 10. Therefore, the
thickness of the buffer member 35 is several commas or less.
[0027]
As shown in FIG. 1B, between the lower end surface 12 of the acoustic diaphragm 10 and the
upper surface of the base housing 20, a damping material 13 made of silicon rubber or the like is
removed from the position of the storage hole 23. To intervene.
[0028]
As a result, the degree of sealing between the acoustic diaphragm 10 and the base housing 20
can be enhanced, and the acoustic diaphragm 10 can be made to function well as a resonance
tube, and the vibration of the acoustic diaphragm 10 is transmitted to the base housing 20.
Propagation can be prevented.
[0029]
In the speaker system having the above configuration, when an audio signal is supplied to the
solenoid coil of the magnetostrictive actuator 30 as a control current, the magnetostrictive
element constituting the magnetostrictive actuator 30 is displaced vertically according to the
audio signal, and the drive rod 31 is vertically moved. The vibration is applied to the lower end
surface 12 of the acoustic diaphragm 10 while being displaced in the direction.
[0030]
The lower end face 12 of the acoustic diaphragm 10 is excited by the longitudinal wave, but the
vibrational elastic wave propagates in the direction of the plate surface of the acoustic
diaphragm 10 to become a wave in which the longitudinal wave and the transverse wave are
mixed, and the acoustic diaphragm 10 The sound wave is emitted by the transverse wave in the
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direction perpendicular to the surface of the plate, and a sound field with a sense of spreading is
obtained.
[0031]
By driving each magnetostrictive actuator 30 with the same audio signal, it is possible to obtain
nondirectionality, but each magnetostrictive actuator 30 is obtained from audio signals of
different channels or from the same audio signal. By driving with audio signals having different
levels, delay times, or frequency characteristics, it is possible to obtain a more extensive sound
field.
[0032]
As shown in FIG. 1A, the central portion of the base housing 20 is an opening 25, and the
speaker unit of the dynamic speaker is attached to the opening 25, for example, with the front of
the speaker facing downward. The diaphragm 10 and the magnetostrictive actuator 30 can
function as tweeters that handle the high frequency side of the audio frequency band, and the
dynamic speaker can also function as a woofer that handles the low frequency side of the audio
frequency band.
[0033]
(1−2.
Material of Buffer Member: FIGS. 4 and 5) The buffer member 35 is basically softer than the
material of the drive rod 31 and the acoustic diaphragm 10 as a member for relieving the impact
on the acoustic diaphragm 10 by the drive rod 31. It may be formed of a material of material.
[0034]
However, if the buffer member 35 is too soft, the deflection of compression becomes large, the
transmission force of the excitation to the acoustic diaphragm 10 decreases, and the sound
pressure decreases.
[0035]
On the contrary, even if the material of the drive rod 31 and the acoustic diaphragm 10 is softer,
if the buffer member 35 is harder than a certain value, the adhesion deteriorates and the
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transmission force of the excitation to the acoustic diaphragm 10 decreases. Sound pressure falls.
[0036]
Considering the above points, as the material of the cushioning member 35, as shown by the
arrow in FIG. 4, the durometer D, which is one of the scales of softness (hardness), has a softness
in the range of 30 to 75. Materials of (hardness) are preferred.
[0037]
A common polypropylene has a durometer D of 75 to 80 and is relatively hard and has a small
compression deflection but poor adhesion, a reduction in the transmission force of vibration to
the acoustic diaphragm 10, and a sound pressure Is not suitable as the material of the shock
absorbing member 35.
[0038]
Styrene butadiene rubber (SBR) has a durometer D of 20 to 30, and is relatively soft and has
good adhesion, but the deflection of compression is large, and the transmission force of the
excitation to the acoustic diaphragm 10 is reduced, Since the sound pressure is reduced, it is not
suitable as the material of the buffer member 35.
[0039]
On the other hand, when the durometer D is in the range of 30 to 75, the deflection of the
compression is small and the adhesion is good.
[0040]
As materials having a durometer D in the range of 30 to 75, impact-resistant polypropylene,
ETFE (tetrafluoroethylene-ethylene copolymer) which is one of fluorine resins, and the like exist.
[0041]
Impact-resistant polypropylene has a durometer D of 50 to 60, and is suitable as a material of
the buffer member 35 in terms of softness.
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However, impact-resistant polypropylene has poor heat resistance.
[0042]
On the other hand, ETFE has a durometer D of 50 to 60, has a certain degree of elasticity, is
excellent in adhesion, is not brittle, and has a heat resistance temperature of about 300 ° C. Are
better.
Therefore, ETFE is more suitable and optimal as a material of the buffer member 35.
[0043]
Note that Hytrel (registered trademark) of Toray Dupont Co., Ltd., which is shown in Non-Patent
Document 1, has a durometer D of 30 to 75, and thus is suitable as a material of the buffer
member 35.
[0044]
The test results are shown in FIG.
The buffer member 35 is formed of ETFE in a cap shape of 0.2 mm in thickness, loaded on the
iron drive rod 31 of the magnetostrictive actuator 30, and abutted on the lower end surface 12
of the acoustic diaphragm 10 made of acrylic. Acoustic vibration plate in the case of vibrating the
acoustic diaphragm 10 for 1000 hours by inputting a music signal having a peak voltage of 6 to
7 Vrms as a drive signal to the magnetostrictive actuator 30 in the same manner as in the test of
FIG. A portion of the lower end face 12 of the lower end face 12 in contact with the buffer
member 35 is photographed.
[0045]
As shown in FIG. 5, in the lower end face 12 of the acoustic diaphragm 10, no dent was observed
at the portion where the shock absorbing member 35 abutted, and no wear was observed.
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Also, no change in sound quality was seen.
[0046]
[2.
Other Embodiments] Although the above-described example is a case where both ends of the
acoustic diaphragm 10 are opened, the upper end side of the acoustic diaphragm may be a
bottomed one.
In the case where the upper end side is a bottomed one, sound waves are emitted also from the
bottom portion on the upper end side, and it is possible to further enhance the sense of the
spread of the sound image.
[0047]
Further, the acoustic diaphragm is not limited to a cylindrical shape, and can be formed in a
cylindrical shape such as a quadrangle or a hexagonal shape, a flat shape, a spherical shape, a
conical shape, or the like.
[0048]
Furthermore, as a material of the acoustic diaphragm, not only acrylic but also glass can be used.
[0049]
The actuator is not limited to a magnetostrictive actuator using a magnetostrictive element, but
may be another element.
[0050]
It is a figure showing an example of the speaker system of this invention.
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It is a figure which shows the case where a buffer member is made into a cap shape.
It is a figure which shows the case where a buffer member is made into a sheet form.
It is a figure which shows the range of the softness | suitability suitable as a buffer member.
It is a figure which shows the test result of an example of the speaker system of this invention.
It is a figure which shows the test result of an example of the conventional speaker system.
Explanation of sign
[0051]
The main parts are all described in the figure, so they are omitted here.
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