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JPH08317493

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DESCRIPTION JPH08317493
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electrodynamic speaker in which heat generation of a voice coil due to high power driving is
prevented.
[0002]
2. Description of the Related Art For large acoustic spaces such as theaters and halls, speakers
are provided which can reproduce loud sounds. In general, a horn speaker which can obtain a
large sound pressure is used for reproduction of middle and high tone ranges, but if it is intended
to use the horn speaker for the low tone range, the shape of the horn becomes too large to be
practical. Therefore, it is a general practice to reproduce sound by direct radiation from the
diaphragm using a large aperture electrodynamic speaker having a large area of the diaphragm.
Here, a conventional electrodynamic speaker that reproduces a large volume will be described
with reference to the drawings.
[0003]
FIG. 9 is a cross-sectional view showing a structural example of a conventional electrodynamic
speaker. In the drawing, the lower plate 1 is a disk-shaped magnetic metal member and
constitutes a part of a magnetic circuit. The center pole 2 is a magnetic metal member integrally
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formed with the lower plate 1 and has a cylindrical shape. The inside of the center pole 2 is a
through hole 3 opened along the central axis, and an opposing surface 2a which is a part of the
magnetic gap portion G is formed in the upper part of the outer peripheral side surface.
[0004]
The magnet 4 is an annular magnet that generates the magnetic flux of the magnetic circuit, and
is fixed to the upper surface of the lower plate 1. The upper plate 5 is a disk-shaped magnetic
metal member fixed to the upper surface of the magnet 4 and has an inner diameter smaller than
the inner diameter of the magnet 4. An inner surface of the upper plate 5 is formed with an
opposing surface 5 a which is a part of the magnetic gap portion G. As described above, the
magnetic gap portion G is an air gap that generates a high density uniform magnetic field by the
magnetic flux of the magnetic circuit including the center pole 2, the lower plate 1, the magnet 4,
and the upper plate 5.
[0005]
A voice coil 6, a voice coil bobbin 7, a diaphragm 10, a dust cap 13 and the like are provided as
movable parts of the electrodynamic speaker. The voice coil 6 is a coil wound around a portion of
the voice coil bobbin 7 located in the magnetic gap portion G, and a drive current is given by a
power amplification circuit (not shown). The diaphragm 10 is a conical diaphragm, and is formed
of paper or a lightweight, high-rigid, fiber-like resin plate or the like. The inner peripheral edge of
the diaphragm 10 is joined to the voice coil bobbin 7, and the outer peripheral edge is joined and
held to the edge 11.
[0006]
The frame 8 integrally fixes all the members constituting the electrodynamic speaker to the
cabinet, and is formed of a substantially conical frame member. An outer peripheral portion of
the frame 8 is formed with a flange portion 8a, and an inner peripheral portion is formed with a
joint surface 8c for connecting to the holding portion 8b of the damper 9 and the upper plate 5.
The damper 9 has a bellows formed concentrically, the outer peripheral portion thereof is joined
to the holding portion 8 b of the frame 8, and the inner peripheral portion is joined to the voice
coil bobbin 7. The damper 9 holds the voice coil bobbin 7 in a freely vibrating manner.
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[0007]
The outer peripheral portion of the diaphragm 10 is vibratably held by the flange portion 8 a of
the frame 8 and the gasket 12 via the edge 11. The gasket 12 is a buffer member when the
speaker body is attached to the cabinet, and prevents parasitic vibration of the frame 8 itself. The
dust cap 13 is a dome-shaped diaphragm fixed to the central portion of the diaphragm 10, and
also functions to prevent fine dust from entering the magnetic gap portion G. In the speaker body
having such a configuration, a space surrounded by the lower surface of the dust cap 13, the
inner side surface of the voice coil bobbin 7 and the upper surface of the center pole 2 is referred
to as an air chamber 14.
[0008]
When an acoustic drive current is applied to the voice coil 6, the voice coil bobbin 7 performs a
piston movement by the electromagnetic force in the magnetic gap portion G. This motion
(vibration) is transmitted to the diaphragm 10 to emit a sound into the air. In particular, when a
large drive current is applied, the temperature of the voice coil 6 rises due to Joule heat.
Depending on the diameter of the speaker, for example, a voice coil with a diameter of 100 mm
may raise the voice coil 6 up to 250 ° C. for a drive current of 650 W.
[0009]
On the other hand, with the vibration of the diaphragm 10, the air chamber 14 on the back of the
dust cap 13 compresses and expands. For this reason, without the through hole 3, the movement
of the dust cap 13 is inhibited. However, due to the presence of the through hole 3, the air in the
air chamber 14 is expelled from the lower center of the center pole 2 to the outside through the
through hole 3 as shown by the arrow a. As described above, since the air resistance of the
through hole 3 is small, the amount of air flowing into the magnetic gap portion G side becomes
very small.
[0010]
Since the driving force generated in the voice coil bobbin 7 is proportional to the current flowing
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in the voice coil 6, it is necessary to apply a large current to the voice coil 6 for reproduction of a
large volume. However, in the above-described conventional electrodynamic speaker, even if a
large current is supplied to the voice coil 6 and the voice coil 6 generates heat, this heat is hard
to escape to the outside. As a result, the temperature of the voice coil 6 rises abnormally, and
there is a problem that the electric resistance value of the voice coil itself rises.
[0011]
Therefore, when the speaker is driven with high power, the reproduction sound pressure of the
speaker does not have a value proportional to the electric input, and the sound pressure level is
limited by the temperature rise of the voice coil 6. In addition, when the temperature of the voice
coil 6 becomes high, there is a fatal problem that the voice coil 6 itself is burned and the speaker
is destroyed. Therefore, until now, a method has been used in which the heat generation of the
voice coil 6 is dissipated by the voice coil bobbin 6 itself using a metal material such as duralmin
having a large thermal conductivity as the material of the voice coil bobbin 7. In any case, the
heat radiation area is small with the voice coil bobbin 7 alone, and the cooling action of the voice
coil 6 is limited.
[0012]
The present invention has been made in view of such conventional problems, and it is possible to
suppress the temperature rise of the voice coil by an effective cooling method, and to reproduce
a large volume by a large power drive while maintaining the sound quality. The purpose is to
realize an electrodynamic speaker.
[0013]
According to a first aspect of the present invention, there is provided a diaphragm having an
opening at a central portion and generating air vibration, and a cylindrical voice coil bobbin
joined to the central portion of the diaphragm. A voice coil wound around the outer periphery of
the voice coil bobbin, a dust cap joined to the central portion of the diaphragm and covering the
voice coil bobbin, and the inside of the voice coil bobbin inserted to form a through hole along
the central axis A center pole, an annular upper plate located on the outer periphery of the voice
coil bobbin and facing the upper outer periphery of the center pole via a magnetic gap, a lower
surface of the dust cap, an inner side of the voice coil bobbin, and a center pole An air chamber
formed by the upper surface of the dust cap, and an outer peripheral portion of the lower surface
of the dust cap as a first air chamber, and a central lower surface of the dust cap as a second air
chamber An air chamber dividing means for dividing the air chamber, and the air chamber
dividing means is a central portion of the dust cap and is attached downward so as to be
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insertable into and removable from the through hole of the center pole through a fixed gap And a
fixed cylinder attached to the upper surface of the center pole and formed in a tubular shape so
as to maintain a fixed gap with the outer surface of the movable cylinder.
[0014]
The invention according to claim 2 of the present application is a diaphragm having an opening
at the center and generating air vibration, a cylindrical voice coil bobbin joined to the center of
the diaphragm, and a coil wound around the outer periphery of the voice coil bobbin. A voice
coil, a dust cap joined to the center of the diaphragm and covering the voice coil bobbin, a center
pole inserted into the voice coil bobbin and having a through hole formed along the central axis,
and an outer periphery of the voice coil bobbin And an annular upper plate facing the upper
outer peripheral portion of the center pole via a fixed magnetic gap, an air chamber formed by
the lower surface of the dust cap, the inner surface of the voice coil bobbin, and the upper
surface of the center pole An air chamber dividing means for dividing the air chamber by setting
the outer periphery of the lower surface of the dust cap as a first air chamber and setting the
center of the lower surface of the dust cap as a second air chamber; The dust cap is integrally
formed to be convex toward the center lower side, and has a bottomed cylindrical portion so as
to be insertable into and removable from the through hole of the center pole through a fixed gap,
and an air chamber The dividing means is characterized by having a cylindrical portion of the
dust cap and a fixed cylinder attached to the upper surface of the center pole and formed in a
cylindrical shape so as to maintain a fixed gap with the outer surface of the cylindrical portion. .
[0015]
The invention according to claim 3 of the present application is a diaphragm having an opening
at the center and generating air vibration, a cylindrical voice coil bobbin joined to the center of
the diaphragm, and a coil wound around the outer periphery of the voice coil bobbin. A voice
coil, a dust cap joined to the center of the diaphragm and covering the voice coil bobbin, a center
pole inserted into the voice coil bobbin and having a through hole formed along the central axis,
and an outer periphery of the voice coil bobbin And an annular upper plate facing the upper
outer peripheral portion of the center pole via a fixed magnetic gap, an air chamber formed by
the lower surface of the dust cap, the inner surface of the voice coil bobbin, and the upper
surface of the center pole And the dust cap is integrally formed to be convex toward the center
lower side, and is cylindrical so as to be insertable into and removable from the through hole of
the center pole through a fixed gap. The center pole extends in such a way that the thickness of
the gap opposing portion where the outer peripheral portion of the through hole opposes the
inner side surface of the upper plate via the magnetic gap portion and the thickness of the gap
opposing portion gradually decreases. And the tapered portion are integrally formed.
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[0016]
The invention according to claim 4 of the present application is a diaphragm having an opening
in the center and generating air vibration, a cylindrical voice coil bobbin joined to the center of
the diaphragm, and a coil wound around the outer periphery of the voice coil bobbin. A voice
coil, a dust cap joined to the center of the diaphragm and covering the voice coil bobbin, a center
pole inserted into the voice coil bobbin and having a through hole formed along the central axis,
and an outer periphery of the voice coil bobbin And an annular upper plate facing the upper
outer peripheral portion of the center pole via a fixed magnetic gap, an air chamber formed by
the lower surface of the dust cap, the inner surface of the voice coil bobbin, and the upper
surface of the center pole An air chamber dividing means for dividing the air chamber by setting
the outer periphery of the lower surface of the dust cap as a first air chamber and setting the
center of the lower surface of the dust cap as a second air chamber; The air chamber dividing
means is a central portion of the dust cap, and a cylindrical movable cylinder mounted downward
so as to be insertable into and removable from the through hole of the center pole through a
fixed gap, and the center And a fixed cylinder having an annular groove mounted on the upper
surface of the pole and having an outer cylinder for holding an air gap between the outer surface
of the movable cylinder and the inner surface of the voice coil bobbin and an outer cylinder for
holding the air gap. It is characterized by having.
[0017]
The invention according to claim 5 of the present application is a diaphragm having an opening
at the center and generating air vibration, a cylindrical voice coil bobbin joined to the center of
the diaphragm, and a coil wound around the outer periphery of the voice coil bobbin. A voice
coil, a dust cap joined to the center of the diaphragm and covering the voice coil bobbin, a center
pole inserted into the voice coil bobbin and having a through hole formed along the central axis,
and an outer periphery of the voice coil bobbin And an annular upper plate facing the upper
outer peripheral portion of the center pole via a fixed magnetic gap, an air chamber formed by
the lower surface of the dust cap, the inner surface of the voice coil bobbin, and the upper
surface of the center pole An air chamber dividing means for dividing the air chamber by setting
the outer periphery of the lower surface of the dust cap as a first air chamber and setting the
center of the lower surface of the dust cap as a second air chamber; The dust cap is integrally
formed to be convex downward in the center and has a cylindrical portion so as to be insertable
into and removable from the through hole of the center pole through a fixed gap, and the air
chamber dividing means is A fixed cylinder having an annular groove mounted on the top surface
of the center pole and having an outer cylinder for holding a fixed gap with the outer surface of
the movable cylinder and a fixed gap, and an outer cylinder for holding a fixed gap with the inner
surface of the voice coil bobbin It is characterized by having.
[0018]
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The invention according to claim 6 of the present application is a diaphragm having an opening
at the center and generating air vibration, a cylindrical voice coil bobbin joined to the center of
the diaphragm, and a coil wound around the outer periphery of the voice coil bobbin. A voice
coil, a dust cap joined to the center of the diaphragm and covering the voice coil bobbin, a center
pole inserted into the voice coil bobbin and having a through hole formed along the central axis,
and an outer periphery of the voice coil bobbin And an annular upper plate facing the upper
outer peripheral portion of the center pole via a fixed magnetic gap, an air chamber formed by
the lower surface of the dust cap, the inner surface of the voice coil bobbin, and the upper
surface of the center pole And the dust cap is integrally formed to be convex toward the center
lower side, and is cylindrical so as to be insertable into and removable from the through hole of
the center pole through a fixed gap. The center pole extends with the thickness of the gap facing
portion facing the outer surface of the through hole facing the inner surface of the upper plate
via the magnetic gap portion, and the upper portion of the gap facing portion. It is characterized
in that it is integrally formed with a tapered portion formed such that its tip end face is
substantially parallel to the inner surface of the dust cap.
[0019]
The invention according to claim 7 of the present application is a diaphragm having an opening
in the center and generating air vibration, a cylindrical voice coil bobbin joined to the center of
the diaphragm, and a coil wound around the outer periphery of the voice coil bobbin. Voice coil,
a dust cap joined to the center of the diaphragm and covering the voice coil bobbin, a center pole
inserted inside the voice coil bobbin, and the top face of the center pole attached to the center
pole. And a stationary support base, an annular upper plate located on the outer periphery of the
voice coil bobbin and facing the upper outer surface of the center pole via a magnetic gap, a
lower surface of the dust cap, and an inner surface of the voice coil bobbin And an air chamber
formed by the upper surface of the center pole and the outer surface of the fixed base, and the
dust cap has its central portion elastically joined to the fixed base It is characterized in that it has
a because of the edge.
[0020]
The invention according to claim 8 of the present application is a diaphragm having an opening
in the center and generating air vibration, a cylindrical voice coil bobbin joined to the center of
the diaphragm, and a coil wound around the outer periphery of the voice coil bobbin. A voice
coil, a dust cap joined to the center of the diaphragm and covering the voice coil bobbin, a center
pole inserted into the voice coil bobbin and having a through hole formed along the central axis,
and an outer periphery of the voice coil bobbin And an annular upper plate opposed to the upper
outer surface of the center pole through a magnetic gap portion, an air chamber formed by the
lower surface of the dust cap, the inner surface of the voice coil bobbin, and the upper surface of
the center pole The cup outer surface is opposed to the inner side surface of the voice coil
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bobbin via a constant gap, and the cup bottom surface is It is characterized in that it comprises
an air flow control unit that faces the upper surface of the upper plate via a constant air gap, the.
[0021]
According to the invention of claims 1 to 7 of the present application having such a feature, the
magnetic gap portion constituted by the center pole and the upper plate of the air of a portion of
the air chamber formed on the back surface of the dust cap The voice coil bobbin is moved along
the inner circumferential side surface of the voice coil bobbin.
In this way, even if the voice coil is driven with high power, its heat generation is cooled by the
air flow, and the electrical resistance of the voice coil is kept constant.
For this reason, the linearity between the drive current of the voice coil and the electromagnetic
force is secured.
Also, even if the diaphragm and dust cap vibrate with large amplitude, most of the air on the
back of the dust cap is easily expelled from the through hole in the center pole, so the distortion
caused by the compression and expansion of the air on the back of the dust cap is It will not
occur.
[0022]
Further, according to the invention of claim 7 of the present application, by providing the fixed
base on the top of the center pole, the volume of the air chamber on the back of the dust cap is
reduced, and all the air in that portion is the vibration of the diaphragm and the dust cap.
Sometimes it moves to the outside of the speaker body through the magnetic gap part.
Therefore, even if the voice coil is driven with high power, the electrical resistance of the voice
coil is kept constant due to the cooling effect due to the movement of the air flow.
For this reason, the linearity between the drive current of the voice coil and the electromagnetic
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force is secured.
[0023]
Furthermore, according to the invention of claim 8 of the present application, in addition to the
functions of claims 1 to 7, the air of the air chamber formed on the back surface of the dust cap
by providing the air flow control unit on the upper portion of the center pole. Can be controlled
at any rate between passing through the magnetic gap and passing through the through hole.
[0024]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dynamic loudspeaker according
to a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a cross-sectional view showing the structure of an electrodynamic speaker in the first
embodiment. The same components as in the conventional example are given the same reference
numerals, and the description thereof will be omitted.
Further, as in the prior art, an air chamber is formed on the lower surface of the dust cap 13, the
inner side surface of the voice coil bobbin 7, and the upper surface of the center pole 2.
[0025]
Unlike the conventional example, a movable cylinder 15 is provided inside the dust cap 13.
The movable cylinder 15 is a cylindrical member fixed to the central portion of the lower surface
of the dust cap 13, and the outer diameter thereof is slightly smaller than the through hole 3 of
the center pole 2.
The movable cylinder 15 integrally moves when the voice coil 6 performs a piston movement.
On the other hand, a fixed cylinder 16 is attached to the upper surface of the center pole 2. The
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fixed cylinder 16 is one in which a cylindrical portion 16 a and a collar portion 16 b are
integrally formed, and the inner diameter of the cylindrical portion 16 a is the same as the inner
diameter of the center pole 2. The fixed cylinder 16 is fixed to the center pole 2 via a collar 16 b.
[0026]
By providing the movable cylinder 15 and the fixed cylinder 16 as air chamber dividing means in
this way, the air chamber under the dust cap 13 can be divided into two. That is, a void 17
serving as a flow resistance portion of air, a first air chamber 18 as a stagnant space of air, and a
second air chamber 19 communicated with the outside are formed. The air gap 17 is a space
formed by the outer surface of the movable cylinder 15 and the inner surface of the fixed
cylinder 16. The first air chamber 18 means a space on the outer peripheral side of the back
surface of the dust cap 13 divided by the air gap 17, and the second air chamber 19 is a space of
the central portion of the back surface of the dust cap divided by the air space 17. means.
[0027]
The operation of the electrodynamic speaker thus configured will be described focusing on air
movement. When a drive current is applied to the voice coil 6, the voice coil bobbin 7 vibrates by
the electromagnetic force received from the magnetic gap portion G of the voice coil 6, and the
diaphragm 10 also vibrates integrally. At this time, the dust cap 13 and the movable cylinder 15
also vibrate vertically.
[0028]
Since the gap 17 is sufficiently narrow, the value of the acoustic impedance is large. Therefore,
the air in the first air chamber 18 can not move toward the through hole 3 due to the vertical
vibration of the dust cap 13 and the inner side surface of the voice coil bobbin 7 and the upper
plate 5 and the voice coil 6 as shown by arrow c. Move through the gap on the outer surface of
the upper part. This air further passes through the damper 9 and flows out of the speaker body.
The damper 9 is obtained by applying an elastic resin to a rough woven fabric and molding it
into a bellows shape by pressing and heating with a mold. For this reason, many fine holes
through which air passes are secured in the damper 9.
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[0029]
Also, the air in the second air chamber 19 is easily exhausted out of the speaker body through
the through hole 3 as shown by the arrow b. Since the air of the first air chamber 18 divided by
the air gap 17 rapidly flows in the vicinity of the voice coil 6, the heat of the voice coil 6 is easily
dissipated by the air cooling effect. Also, the amount of air in the first air chamber 18 is small
when viewed from the entire air chamber on the back surface of the dust cap 13 and the air in
the second air chamber 19 is directly eliminated by the large through hole 3. The back pressure
of the cap 13 does not distort the movement of the dust cap 13 and the diaphragm 10.
[0030]
FIG. 2 is a cross-sectional view showing the structure of the electrodynamic speaker in the
second embodiment. The same components as in FIG. 1 are assigned the same reference
numerals, and the description thereof will be omitted. In the first embodiment, the dust cap 13
and the fixed cylinder 15 fixed to the lower surface thereof are separate parts, but in FIG. 2, the
central portion of the dust cap 20 is integrally formed to be downwardly convex, Is a cylindrical
portion 21. Also in this case, the outer diameter of the cylindrical portion 21 is slightly smaller
than the inner diameter of the fixed cylinder 16 and the inner diameter of the through hole 3.
And let the lower space of cylinder part 21 be the 2nd air room. In this case, the air cooling effect
is the same as in the case of FIG. 1, and the air flow from the first air chamber 18 flows along the
side of the voice coil bobbin 7 as shown by the arrow e, and the temperature rise of the voice coil
6 is small. Become. On the other hand, the air from the second air chamber 22 flows as shown by
the arrow d.
[0031]
FIG. 3 is a cross-sectional view showing the structure of an electrodynamic speaker in the third
embodiment. The same components as in FIG. 2 are assigned the same reference numerals and
descriptions thereof will be omitted. As shown in FIG. 3, the center pole 23 of this embodiment
has a through hole 24 at the central axis. Further, in the center pole 23, a gap facing portion 23a
facing the inner side surface of the plate 5 via the magnetic gap portion G and a taper portion
23b extended so that the thickness of the upper portion of the gap facing portion 23a gradually
decreases Is formed. And this taper part 23b is made into the fixed cylinder which has a function
equivalent to the fixed cylinder 16 of FIG. The outer side portion of the tapered portion 23b has
an outwardly curved tapered surface to reduce the resistance of the air in the first air chamber
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27 when it moves. The air gap 26 formed by the inner side surface of the tapered portion 23 b
and the outer side surface of the cylindrical portion 21 has a large acoustic impedance value as
viewed from the first air chamber 27.
[0032]
In such a structure, the air flow around the voice coil 6 flows more smoothly through the path
shown by the arrow g as compared with the embodiment of FIG. 1 or FIG. Therefore, the
temperature rise of the voice coil 6 is reduced. Further, air in the lower space of the cylindrical
portion 21 which is the second air chamber also flows easily from the through hole 24 to the
outside of the speaker main body as shown by the arrow f.
[0033]
Next, an electrodynamic speaker according to a fourth embodiment of the present invention will
be described with reference to FIG. FIG. 4 is a cross-sectional view showing the structure of an
electrodynamic loudspeaker according to the fourth embodiment. The same components as those
in the first to third embodiments are designated by the same reference numerals, and the
description thereof will be omitted. A fixed cylinder 28 having a shape different from that of the
first embodiment is provided on the upper surface of the center pole 2.
[0034]
The fixed cylinder 28 is formed by integrally forming an inner cylinder 28a, an outer cylinder
28b, and a collar portion 28c. The inner cylinder 28 a has the same shape as the cylindrical
portion 16 a of FIG. 1 and has an inner diameter slightly larger than the outer diameter of the
movable cylinder 15. A space between the inner wall of the inner cylinder 28 a and the outer
wall of the movable cylinder 15 is a gap 29 with high acoustic impedance. The outer diameter of
the outer cylinder 28 b is equal to the outer diameter of the center pole 2 in the magnetic gap
portion G, and a constant air gap 32 is secured with the inner wall of the voice coil bobbin 7. The
fixed cylinder 28 having such a structure is fixed to the center pole 2 via a collar 28 c. The first
air chamber 30 is a space divided by the dust cap 13, the movable cylinder 15, the air gap 29,
and the air gap 32. The second air chamber 31 refers to the lower space of the movable cylinder
15.
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[0035]
The operation of the electrodynamic speaker thus configured will be described focusing on air
movement. When a drive current is applied to the voice coil 6, the dust cap 13 and the movable
cylinder 15 vibrate up and down with the vibration of the diaphragm 10. The air in the first air
chamber 30 passes from the upper inner side surface of the voice coil bobbin 7 through the air
gap 32 between the outer peripheral surface of the center pole 2 and the inner side surface of
the voice coil bobbin 7 as shown by arrow i under the voice coil bobbin 7 Fold back at. Further,
this air passes through the outer peripheral portion of the voice coil 6, passes through the
damper 9, and flows to the outside of the speaker body.
[0036]
Even when the value of the drive current is large, even if the voice coil 6 generates heat, the heat
is transmitted to the voice coil bobbin 7 and the air from the first air chamber 30 extends along
the voice coil bobbin 7 over a longer distance. Flow. For this reason, the temperature rise of the
voice coil 6 can be more effectively reduced. Further, as in the first embodiment, the amount of
air in the first air chamber 30 is small as viewed from the entire air chamber on the back surface
of the dust cap 13. Further, since the air in the second air chamber 31 is directly exhausted by
the through hole 3 as shown by the arrow h, the back pressure does not distort the movement of
the dust cap 13.
[0037]
FIG. 5 is a cross-sectional view showing the structure of an electrodynamic loudspeaker in the
fifth embodiment. The same components as in FIG. 4 are assigned the same reference numerals
and descriptions thereof will be omitted. In the fourth embodiment, the dust cap 13 and the fixed
cylinder 15 fixed to the lower surface of the dust cap 13 are separate parts, but in the present
embodiment, as in the case of FIG. It is integrally formed in the shape of a cylinder, and this
portion is a cylindrical portion 34. Also in this case, the outer diameter of the cylindrical portion
34 is slightly smaller than the inner diameter of the fixed cylinder 28 and the inner diameter of
the through hole 3.
[0038]
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13
A space covered by the fixed cylinder 28 and the dust cap 33 is referred to as a first air chamber
36, and a lower space of the cylindrical portion 34 is referred to as a second air chamber 37.
Then, the air from the first air chamber 36 flows from the tip of the voice coil bobbin 7 along the
side as indicated by the arrow k, and the temperature rise of the voice coil 6 is further reduced
by the air cooling effect. The air from the second air chamber 37 flows to the outside of the
speaker body as indicated by the arrow j.
[0039]
FIG. 6 is a cross-sectional view showing the structure of the electrodynamic speaker in the sixth
embodiment. The same components as in FIG. 5 are assigned the same reference numerals and
descriptions thereof will be omitted. As shown in FIG. 6, the center pole 38 of the present
embodiment is a cylindrical member having a through hole 39. In the middle of this cylindrical
portion, there is provided a gap facing portion 38a opposed to the inner side surface of the upper
plate 5 via the magnetic gap portion G. Then, the thickness of the cylindrical portion is held and
extended upward, and the tapered portion 38 b is integrally formed so that the tip end surface
thereof is substantially parallel to the inner surface of the dust cap 33.
[0040]
The tapered portion 38b is a fixed cylinder having the same function as the fixed cylinder 16 of
FIG. The outer portion of the tapered portion 38b has the same outer diameter as the gap facing
portion 38a, thereby securing a larger area of the air flow along the voice coil bobbin 7 and
reducing the space of the first air chamber 41. The air gap 40 formed by the inner side surface of
the tapered portion 38 b and the outer side surface of the cylindrical portion 34 has a large value
of acoustic impedance when viewed from the first air chamber 41.
[0041]
In such a structure, the air flow around the voice coil 6 flows smoothly in the path shown by the
arrow m, as compared with that in FIG. 4 or FIG. Also, air in the lower space of the movable
cylinder 34, which is the second air chamber, easily flows to the outside of the speaker main
body through the through hole 39 as shown by the arrow l.
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[0042]
Next, an electrodynamic speaker according to a seventh embodiment of the present invention
will be described with reference to FIG. FIG. 7 is a cross-sectional view showing the structure of
an electrodynamic loudspeaker according to the seventh embodiment. The same components as
those of the first embodiment are designated by the same reference numerals, and the
description thereof will be omitted.
[0043]
Unlike the previous embodiments, the lower plate 42 and the center pole 43 have no through
holes at their centers. The center pole 43 is identical to that shown in FIG. 1 except that it is not
hollow. Furthermore, unlike the speaker shown in FIG. 1, a fixing base 46 is attached to the
upper surface of the center pole 43. The fixing base 46 is a cylindrical member and serves to
support the center of the dust cap 44 at a fixed point.
[0044]
The dust cap 44 is a member in which only the outer peripheral portion is dome-shaped, the
central portion is flat, and a boundary between the outer peripheral portion and the central
portion is integrally formed with an edge 45 which is annularly convex. An inner peripheral
portion of the diaphragm 10 generating the main acoustic vibration is acoustically supported by
an edge 45, and an outer peripheral portion is vibratably supported by the edge 8 with respect to
the frame 8. A space surrounded by the voice coil bobbin 7, the dust cap 44 and the fixing base
46 forms an air chamber 47.
[0045]
The operation of the electrodynamic speaker thus configured will be described focusing on air
movement. When a drive current is applied to the voice coil 6, the voice coil hovin 7, the
diaphragm 10 and the dust cap 44 vibrate up and down. The air in the air chamber 47 is folded
back under the voice coil bobbin 7 from the upper inner side surface of the voice coil bobbin 7
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through the magnetic gap portion G as shown by the arrow n. Further, this air passes through the
outer peripheral portion of the voice coil 6, passes through the damper 9, and flows to the
outside of the speaker body.
[0046]
Also in this case, since the air rapidly passes in the vicinity of the voice coil 6, the heat of the
voice coil 6 is rapidly removed, and the temperature rise of the voice coil 6 is reduced by the air
cooling effect. Further, by providing the support 46 at the central portion of the dust cap 44, the
volume of the air chamber 47 is reduced. Therefore, the amount of air change of the air chamber
47 at the excessive amplitude of the dust cap 44 can be reduced, and the movement of the dust
cap 47 due to the back pressure can be made undistorted. Although in the embodiment shown in
FIG. 7 the support base 46 is a separate part with the center pole 43, there is no problem even if
the support pole 46 is integrally formed with the center pole 43.
[0047]
Finally, an electrodynamic speaker according to an eighth embodiment of the present invention
will be described with reference to FIG. FIG. 8 is a cross-sectional view showing the structure of
an electrodynamic loudspeaker in the eighth embodiment. The same components as those in the
first to seventh embodiments are designated by the same reference numerals, and the description
thereof will be omitted.
[0048]
In the drawing, the lower plate 48 is a disk-shaped magnetic metal member and constitutes a
part of a magnetic circuit. The center pole 49 is a member integrally formed with the lower plate
48, and its shape is substantially cylindrical. Unlike the previous embodiments, the center pole
49 has its upper end expanded in the inside diameter in a trumpet shape. The inside of the center
pole 49 is a through hole 50, and functions as an exhaust port of air moving along the wall
surface of the air flow control unit 51 described later.
[0049]
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Assuming that the lower internal space of the dust cap 13 is an air chamber 52, the air flow
control unit 51 controls the amount of air movement when air present in the air chamber 52
flows out or flows in from this portion by the piston movement of the dust cap 13. Do. The air
flow control unit 51 has, for example, a cup-like shape, and the outer diameter thereof is smaller
than the inner diameter of the voice coil bobbin 7. An air gap 54 is formed at the bottom of the
air flow control unit 51 so as to have a predetermined air resistance, and the bottom is held
slightly higher than the top surface of the center pole 49. Further, an air gap 53 is formed
between the outer peripheral side surface of the air flow control unit 51 and the inner side
surface of the voice coil bobbin 7.
[0050]
The operation of the electrodynamic speaker thus configured will be described focusing on air
movement. When a drive current is applied to the voice coil 6, the voice coil hovin 7, the
diaphragm 10 and the dust cap 13 vibrate up and down. The air in the air chamber 52 once
passes through the air gap 53 and is split into two hands. One part passes through the air gap 54
from the inner peripheral surface on the upper side of the voice coil bobbin 7 as shown by the
arrow o, and comes out to the through hole 50. The other passes through the gap between the
outer peripheral surface of the center pole 49 and the inner surface of the voice coil bobbin 7 as
shown by the arrow p, and is folded back under the voice coil bobbin 7. Furthermore, it flows
through the outer peripheral part of the voice coil 6, passes through the damper 9 and flows to
the outside of the speaker main body.
[0051]
The heat of the voice coil 6 is transmitted to the voice coil bobbin 7, but the air of the air
chamber 52 rapidly passes in the vicinity of the voice coil bobbin 7 and the voice coil 6, so the
voice coil 6 and the voice coil bobbin 7 are effectively effective from both sides. It can be cooled.
Also, the change in the air pressure of the air chamber 52 becomes large when the dust cap 13
has a large amplitude, but the air flow control unit 51 is provided to optimally set the gap
between the air gap 53 and the air gap 54, thereby making the air displacement amount
arbitrary It becomes possible to control. Therefore, the back pressure does not distort the
movement of the dust cap 13.
[0052]
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As described above, according to the present invention, by dividing the air chamber formed by
the center pole, the voice coil bobbin, and the dust cap, part of the air in the air chamber is
vibrated when the diaphragm is vibrated. It can be eliminated by passing through the magnetic
gap. Therefore, even if the voice coil is driven by a large amount of power, the heat generation of
the voice coil can be effectively cooled, and an increase in electrical resistance and burnout of the
voice coil can be prevented. Furthermore, by controlling the displacement of air at the back of
the dust cap, distortion of the movement of the dust cap due to changes in air pressure can be
lessened. In this way, it is possible to realize an electrodynamic speaker with a large input and
little deterioration in sound quality even at a large volume.
[0053]
Brief description of the drawings
[0054]
1 is a cross-sectional view showing the structure of an electrodynamic speaker in the first
embodiment of the present invention.
[0055]
2 is a cross-sectional view showing the structure of an electrodynamic speaker according to a
second embodiment of the present invention.
[0056]
3 is a cross-sectional view showing the structure of an electrodynamic speaker according to a
third embodiment of the present invention.
[0057]
4 is a cross-sectional view showing the structure of an electrodynamic speaker according to a
fourth embodiment of the present invention.
[0058]
5 is a cross-sectional view showing the structure of an electrodynamic speaker according to a
fifth embodiment of the present invention.
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[0059]
6 is a cross-sectional view showing the structure of an electrodynamic speaker according to a
sixth embodiment of the present invention.
[0060]
7 is a cross-sectional view showing the structure of an electrodynamic speaker according to a
seventh embodiment of the present invention.
[0061]
8 is a cross-sectional view showing the structure of an electrodynamic speaker according to an
eighth embodiment of the present invention.
[0062]
9 is a cross-sectional view showing an example of the structure of a conventional electrodynamic
speaker.
[0063]
Explanation of sign
[0064]
1, 42, 48 Lower plate 2, 23, 38, 43, 49 Center pole 3, 24, 39, 50 Through hole 4 Magnet 5
Upper plate 6 Voice coil 7 Voice coil bobbin 8 Frame 9 Damper 10 Diaphragm 11, 45 Edge 12
Gaskets 13, 20, 44 Dust caps 14, 47, 52 Air chambers 15 Movable cylinders 16, 28 Fixed
cylinders 16a, 21, 34 Cylindrical portion 16b Flange portions 17, 26, 32, 35, 40, 53, 54 Air gaps
18, 27 , 30, 36, 41 first air chamber 19, 22, 31, 37 second air chamber 20 dust cap 23a, 38a gap
facing portion 23b, 38b taper portion 28a inner cylinder 28b outer cylinder 28b outer cylinder
28c rim portion 46 support base 51 Air flow control unit G Magnetic gap unit
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