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DESCRIPTION JPH03185999

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DESCRIPTION JPH03185999
[0001]
FIELD OF THE INVENTION The present invention relates to electroacoustic transducers, and in
particular to its central support. 2. Description of the Related Art In recent years, with the advent
of compact disks and the miniaturization of products, a compact speaker system capable of bass
reproduction is also desired. FIG. 6 is a cross-sectional view of this conventional speaker. In this
figure, 1 is a pole piece, 2 is a magnet, 3 is a plate, 4 is a frame, 5 is a diaphragm, 6 is a support
edge, 7 is a suspension, 8 is a voice coil, and 9 is a bobbin. The audio signal is supplied to the
voice coil 6, and the voice coil 6 vibrates relative to the magnet 2 due to the change of the
generated magnetic field accompanying the change of the audio signal, and the vibration is
transmitted to the diaphragm 5 The sound is emitted by The diaphragm 5 is supported by the
edge 6 on the frame 4 and the voice coil 8 is centered by the suspension 7 so that the friction
with the pole piece 1 is prevented. In the prior art, in order to lower the first resonance
frequency so as to enable bass reproduction, the compliance of the vibration supporting portion
of the edge 6 and the suspension 7 is increased. As a result, the degree of freedom of the
diaphragm 5 is increased, and a large amplitude can be obtained to enable bass reproduction.
[Problem to be Solved by the Invention] However, in the above-mentioned conventional
apparatus, when the compliance of the suspension 7 is increased, the freedom degree of the
voice coil 8 in the thrust direction is increased, but the radial vibration is also allowed. There was
a dilemma that the role of maintaining the original center would be neglected. The present
invention has been made in view of the above-mentioned problems of the prior art, and the
object of the present invention is to ensure that the centering is performed even if the degree of
freedom in the thrust direction of the voice coil is increased. Providing an electro-acoustic
transducer. [Means for Solving the Problems] The electro-acoustic transducer according to the
present invention comprises a transducer main body in which a vibrating portion and a magnetic
circuit portion are attached to a frame, and an audio relative to the magnetic circuit portion of
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the vibrating portion and audio. An electro-acoustic transducer for generating sound by
mechanical vibration according to a signal, wherein a cylinder member is attached to the inside
of the transducer main body so as to vibrate integrally with the diaphragm, and the cylinder
member is mounted on the magnetic circuit A gap is inserted between the outer peripheral
surface of the pole piece and the inner peripheral surface of the cylinder member at the inserted
portion, and a vent hole communicating the inside and the outside of the converter main body is
provided. It is characterized in that air is made to pass through the air gap in accordance with the
vibration of the vibrating plate, and the dimension thereof is set so that the air gap is maintained
by the air flow.
[Operation] If a cylindrical member is loosely inserted in a cylindrical member and air pressure is
applied from the outside to air existing between the peripheral surfaces of both members, this air
pressure releases the cylindrical member and the cylindrical member by this air pressure. A
uniform pressure acts on the entire circumference in the direction, so to say, an air bearing is
formed between the inner peripheral surface of the cylindrical member and the outer peripheral
surface of the cylindrical member. According to the present invention, utilizing this phenomenon,
air is allowed to pass through the air gap provided by inserting the cylinder member into the
pole piece located at the center of the magnetic circuit portion by vibration of the diaphragm,
and the air flow is maintained by the air flow. Since the voice coil is centered by using the action,
even if the degree of freedom in the thrust direction of the voice coil is increased, the centering
can be reliably performed. Further, since the damping is determined by the size of the vent
communicating the inside and the outside of the transducer body, the compliance can be
adjusted by adjusting the size of the vent. Embodiments of the present invention will be
described below with reference to the drawings. FIG. 1 is a cross-sectional view of an
electroacoustic transducer according to an embodiment of the present invention, and FIG. 2 is an
enlarged view of the main part thereof. In FIG. 1, 10 is a pole piece, 10a is a back plate, 10b is a
center pole, 11 is a magnet, 12 is a front plate, 13 is a frame, 14 is a diaphragm, 15 is an edge,
16 is a voice coil, Reference numeral 17 denotes a voice coil bobbin. The pole piece 10, the
magnet 11, and the plate 12 constitute a magnetic circuit portion, and the diaphragm 14, the
edge 15, the voice coil 16, and the bobbin 17 constitute a vibration portion. The bobbin 17
functions as a cylinder member, and one end of the bobbin 17 is attached to the center of the
conical cone of the diaphragm 15. The other end side of the bobbin 17 is fitted into the center
ball portion 10b, and the inner peripheral surface of the bobbin 17 faces the outer peripheral
surface of the center ball portion 10b. The inner peripheral diameter of the bobbin 17 is slightly
larger than the outer peripheral diameter of the center pole portion 10b, and an air gap 18 is
formed between the both as shown in FIG. The center pole portion 10b is formed with one vent
hole for communicating the internal space defined by the pole piece 10, the magnet 11, the front
plate 12, the frame 13, the diaphragm 14, the edge 15 and the like with the outside. The
vibration of the air 14 allows air to flow in and out through this one vent. Along with this, air also
passes through the air gap 18. The dimension of the air gap 18 is a phenomenon that uniform
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pressure is applied to the inner peripheral surface of the bobbin 17 and the outer peripheral
surface of the center ball portion 10b in the direction in which they are separated along the
entire circumference by passing the air. Is specifically set to 10 to 50 μm.
As a result, when the voice coil 6 vibrates, the air gap holding function causes centering. Further,
since the size of the diameter φ 19 of the vent 19 affects the damping, the compliance can be
adjusted by adjusting the size of the vent 19. The center ball portion 10 b protrudes from the
front plate 12 and corresponds to the stroke of the bobbin 17. A digging portion 20 is formed in
the protruding portion of the center pole portion 10b from the tip to the base direction, and the
bottom surface thereof is flush with the surface of the front plate 12 on the side of the
diaphragm 14. Thereby, the reduction of the air-gap magnetic flux density due to the protrusion
of the center pole portion 10b from the magnetic circuit is prevented. The thinner the thickness
T of the peripheral wall of the digging portion 20, the more effective. According to the
experiment, the size of the back plate portion 10a is an outer diameter? -75, thickness Tlo, -5
mm. Oa Size of center ball portion 10b, outer diameter φ10b. -251111% of the size of the recess
20, inner diameter φ 2 o-23 vbya. Depth D = 10 mm. The size of the magnet 11 is: outer
diameter φ1 o -80, inner diameter φ -40 mm, thickness Tll "151111 ms11 Front plate 12 size:
outer diameter φ12 ° m 75 mm, inner diameter φ121-28 mm, thickness T t When the size of
the vent hole 19 of 2′′5 Ilm s is inner diameter φt g ′ ′ 7 lll 5%, the void density is 7.910
Gauss without the digging portion 20, and 8,150 Gauss in some cases. In the case where the
digging portion 20 is present, a rise in air gap magnetic flux density of 2.9% is obtained as
compared with the case where the digging portion 20 is absent. Further, since the air gap 18 is
on the order of several tens of μm, by forming the cylinder member 17 with metal, the heat
generated from the voice coil 16 is released to the outside through the pole piece 10, and the
heat radiation effect is achieved. Is advantageous in that That is, there is a problem of heat
generation due to the need to input a large current to the voice coil 16 to obtain a large
amplitude in small bass reproduction. Conventionally, heat generation from the voice coil was
dealt with by using a heat-resistant wire for the voice coil, but there was a limit in itself. In that
respect, according to the present embodiment, the heat itself can be dissipated by forming the
cylinder member 17 of metal, which is advantageous. In addition, when there is no problem of
the heat generation, the cylinder member 17 can also be made of a lightweight plastic with good
sliding.
And as a method of use, it is generally used in such a way that the central axis of the
electroacoustic transducer is horizontal. Therefore, as shown by a two-dot chain line in FIG. 1, by
mounting the bellows type suspension 21, it is possible to define the initial position in the axial
direction and the radial direction of the vibrating portion and the limit of the amplitude. The
bellows type suspension 21 has been developed by the inventor of the present invention and has
already been filed by the applicant of the present application (Application: January 31, 1991,
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Application No .: Utility model, Showa 64) Registration No. 10542, Name of the Invention
"Supporting member of diaphragm in speaker". It is also possible to omit the suspension 21 by
giving the edge 15 a strength equivalent to that of the suspension 21. Furthermore, by closing
one air vent with a screw or the like, the internal space can be sealed and the vibrating part can
be prevented from moving. Therefore, during transportation, etc., conversion is achieved by
closing one air vent. Can be protected from impact. FIG. 3 is a cross-sectional view of an electroacoustic transducer according to a second embodiment of the present invention, in which the
vent holes 22 are provided in the back plate portion 10b. Also in this embodiment, the same
function and effect as those in the first embodiment can be obtained. FIG. 4 is a cross-sectional
view of an electro-acoustic transducer according to a third embodiment of the present invention,
and FIG. 5 is a conceptual view showing the operation thereof. What is shown in these drawings
is characterized in that another cylinder member such as a voice coil bobbin is disposed. In FIG.
4, the voice coil 23 and the bobbin 24 have the same configuration as the voice coil 8 and the
bobbin 9 shown in FIG. 6, and their pole pieces 10 ° magnet 11 and front plate 12 The
positional relationship in the radial direction is also similar to that of FIG. 6, and a magnetic gap
similar to that of the prior art is provided. By the way, a cylinder portion U ′ 25 having a
diameter smaller than that of the bobbin 24 is attached to the cone cap of the diaphragm 14. A
fitting insertion hole 26 is bored at the center of the center ball portion 10 b, and the cylinder
member 25 is loosely inserted in the fitting insertion hole 26, and between the outer peripheral
surface of the cylinder member 25 and the peripheral surface of the insertion hole 26. The air
gap 27 is formed in the The bottom surface of the insertion hole 26 is flush with the back plate
portion 10a on the magnet 11 side, and the vent hole 28 is formed to come out of the bottom
surface to the outside. In such a configuration, the air flow as shown in FIG. 5 is generated by the
vibration of the vibrating portion, and the cylinder member 25 is held at the central position.
Also in this embodiment, the same function and effect as the above-described embodiment can be
obtained. Furthermore, since it is possible to hold the center with a small diameter cylinder
member, restrictions such as its thickness are relaxed. [Effects of the Invention] As described
above, according to the present invention, utilizing this phenomenon, the gap formed by
inserting the cylinder member in the pole piece located at the center of the magnetic circuit unit
is accompanied by the vibration of the diaphragm. Since the air is allowed to pass and the voice
coil is held at the center by using the air gap holding action by the air flow, the centering can be
surely performed even if the degree of freedom in the thrust direction of the voice coil is
increased. In addition, since the damping is determined by the size of the vent that communicates
the inside and the outside of the converter body, the compliance can be adjusted by adjusting the
size of the vent.
[0002]
Brief description of the drawings
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[0003]
FIG. 1 is a cross-sectional view of the electro-acoustic transducer according to the first
embodiment of the present invention, FIG. 2 is an enlarged view of the main part thereof, and
FIG. 3 is a cross-section of the electro-acoustic transducer according to the second embodiment
of the present invention FIG. 4 is a cross-sectional view of an electro-acoustic transducer
according to a third embodiment of the present invention, FIG. 5 is an operation explanatory view
thereof, and FIG. 6 is a cross-sectional view of a conventional electro-acoustic transducer.
DESCRIPTION OF SYMBOLS 10 ... pole piece, 11 ... magnet, 12 ... front plate, 13 ... flame | frame,
14 ... diaphragm, 15 ... end, 16 ... voice coil, 17 ... Bobbin (cylinder member), 18.27: Air gap, 19,
22.28: Air hole, 25: Cylinder member, 26: Insertion hole.
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