JPH08205275

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DESCRIPTION JPH08205275
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sealed acoustic transducer for use in, for example, a swimming pool, a hot water bath or
underwater water.
[0002]
2. Description of the Related Art FIG. 3 shows a speaker as a conventional sealed acoustic
transducer. The diaphragm 2 is formed in a part of the container 1. This is configured by
bonding and sealing a diaphragm to a cup-shaped container. A voice coil cylinder 30 made of
synthetic resin and constituting the voice coil portion 3 is attached to the center of the
diaphragm 2 with an adhesive. A voice coil 31 is wound around the voice coil cylinder 30. A
permanent magnet 4 includes a central magnetic pole 40, a ring-shaped permanent magnet 41,
and a ring-shaped magnetic pole 42. The central magnetic pole 40 is attached to the bottom of
the container 1 by the attachment 10 and is inserted into the cylinder 30. The permanent magnet
41 is mounted on the central magnetic pole 40 outside the cylinder 30. A closed magnetic circuit
is formed in the magnetic pole 42 so that the magnetic flux generated from the permanent
magnet 41 intersects the voice coil 31 via the central magnetic pole 40 and the magnetic pole
42. Therefore, when a signal current is supplied to the voice coil 31, the voice coil unit 3 is
displaced according to the magnitude of the signal current, and the diaphragm 2 is vibrated.
[0003]
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However, as shown in FIG. 4, the diaphragm 2 is flexed inward by water pressure, for example,
when used in water. Therefore, the cylinder 30 abnormally approaches or separates from the
distortion permanent magnet portion 4 and the gap between the permanent magnet portion 4
and the distortion changes significantly. As a result, the conversion efficiency particularly in the
low band is degraded, and a speaker device having a desired frequency characteristic can not be
obtained. In addition, the deterioration of the conversion efficiency generates heat, which distorts
the cylinder 30 and the like not only to deteriorate the conversion efficiency but also to
deteriorate the adhesive. Since this water pressure changes with water depth, waves, etc., it is
impossible to predict and design in advance.
[0004]
Therefore, it is an object of the present invention to provide a sealed acoustic transducer in
which the conversion efficiency is not affected even if the external pressure changes, and the
frequency characteristics are maintained well. SUMMARY OF THE INVENTION The present
invention for achieving the above object is a sealed container having a diaphragm formed in part,
and a diaphragm disposed opposite to a voice coil portion attached to the diaphragm. The
present invention relates to a sealed acoustic transducer characterized by comprising a
permanent magnet portion elastically attached to the
[0005]
In the sealed acoustic transducer according to the present invention, since the permanent magnet
portion is attached to the diaphragm, the relative position to the voice coil portion does not
change even when the diaphragm is bent by the external pressure.
[0006]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A loudspeaker of a sealed acoustic
transducer according to an embodiment of the present invention will be described with reference
to FIG.
The same parts as those of the conventional apparatus are denoted by the same reference
numerals, and the description thereof is omitted.
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[0007]
The permanent magnet 4 is attached to the diaphragm 2 by a ring-shaped elastic member 5
outside the voice coil cylinder 30. A first space 6 is formed by the permanent magnet 4, the
diaphragm 2, the elastic member 5 and the cylinder 30. Reference numeral 7 denotes a second
space formed by the central magnetic pole 40, the diaphragm 2 and the cylinder 30. Reference
numeral 43 denotes a through hole formed in the central magnetic pole 40 so that the second
space 7 communicates with the third space 8 of the entire container 1. A plurality of air vents 32
are formed at the base of the cylinder 30 to connect the first space 6 and the second space 7.
[0008]
The elastic member 5 mounts and supports the permanent magnet portion 4 on the diaphragm
2, and does not cause the permanent magnet portion 4 to resonate with the audio signal
frequency of the diaphragm 2. At the same time, it has an elastic force to displace the permanent
magnet portion 4 inward simultaneously. The elastic force is formed in the elastic member 5 and
a predetermined value can be obtained by the slit 51.
[0009]
Next, the operation of the embodiment of the present invention will be described. When an audio
current is supplied to the voice coil 31, a relative displacement force is generated between the
voice coil unit 3 and the permanent magnet unit 4. Since the permanent magnet 4 is heavy, it is
not displaced substantially, and the voice coil 3 is displaced so as to vibrate the diaphragm 2. On
the other hand, the permanent magnet unit 4 does not vibrate due to the vibration of the
diaphragm 2. This is because the permanent magnet portion 4 does not resonate with the sound
frequency due to the support of the predetermined elastic member 5.
[0010]
Therefore, for the audio signal, only the diaphragm 2 vibrates without the permanent magnet
portion 4 being substantially displaced. When the water pressure is large, the diaphragm 2 tries
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to bend inward, but the ring-shaped elastic member 5 acts to prevent its deflection. Because of
that, I can't feel big. However, some deflection occurs. At that time, the permanent magnet 4 is
similarly displaced inwardly, and no change occurs in the relative position with the voice coil 3.
Of course, also in an environment lower than the external pressure internal pressure, the
permanent magnet portion 3 is similarly displaced.
[0011]
On the other hand, since the voice coil unit 3 is not directly exposed to the outside air, it is
difficult to dissipate the heat generated from now on. In particular, the temperature rise of the
first space in contact with the voice coil portion 3 becomes remarkable, but this is the third space
of the entire container 1 having a large volume by the hole 32, the second space 7, and the
through hole 43 of the cylinder 30. Since it is connected to the space 8, air convection with this
space is made smooth. The through holes 43 communicate with the third space 8 to provide a
busless effect.
[0012]
In the present invention, the space on the back side of the permanent magnet 4 is used in
combination for the purpose of preventing the resonance of the sound signal of the permanent
magnet 4 and for smoothly following the deflection of the diaphragm 2 due to the water
pressure. It is also possible to fill silicone rubber or the like having appropriate elasticity.
Moreover, the contact type acoustic converter of the present invention can also be used for
outdoor use to withstand rain and humidity. Furthermore, the sealed acoustic device of the
present invention can be applied not only to speakers but also to microphones.
[0013]
According to the present invention, since the permanent magnet portion is attached to the
diaphragm, the relative position with the voice coil portion does not change even when the
diaphragm is flexed by external pressure, and a predetermined gap is maintained at all times.
Thus, it is possible to provide a sealed acoustic transducer which does not cause deterioration or
fluctuation in sound quality even in a state where a large external pressure is applied, or a state
in which the external pressure fluctuates during use.
[0014]
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Further, although the periphery of the voice coil portion is separated from the space of the entire
container by the elastic member for attaching the permanent magnet portion to the diaphragm,
the convection of the heat generated from the voice coil portion is caused by the hole formed in
the voice coil cylinder. It is smooth and has an effect of improving the heat radiation effect.
[0015]
Brief description of the drawings
[0016]
1 is a cross-sectional view of a sealed acoustic device sinker showing an embodiment of the
present invention.
[0017]
2 is a perspective view showing the voice coil portion of FIG.
[0018]
3 is a cross-sectional view of a conventional sealed speaker device.
[0019]
4 is a cross-sectional view showing a state in which a large water pressure is applied in FIG.
[0020]
Explanation of sign
[0021]
Reference Signs List 1 container 2 diaphragm 3 voice coil portion 30 cylinder for voice coil 31
voice coil 32 air vent 4 permanent magnet portion 43 through hole
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