JPS54170126

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DESCRIPTION JPS54170126
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front sectional view showing a conventional
magnetic circuit. FIG. 2 is a front sectional view showing an embodiment of the present
invention. FIG. 3 is an external perspective view of a pole piece used in the above embodiment.
FIG. 4 is a front sectional view showing another embodiment of the present invention. FIG. 5 is an
external perspective view of a bow-piece used in the other embodiment. FIG. 6 is a characteristic
diagram showing measurement results of output sound pressure and frequency characteristics of
an embodiment of the present invention and a conventional example. 11 ····· Magnetic circuit, 12-·
························································································
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· · · · · · · · · · · · · · · 15 ··· Diaphragm, 15a ···························································· · · · · · · · · · · · · · · · · · · · · · · · · · ·
first communication hole, 21 · · · ----- inner space formed by the diaphragm and the pole piece, 22
...... second communicating hole, 23------ through holes, 24a, 24b, 24c. 24d・・・・・・スリッ
ト。 (す(79
DETAILED DESCRIPTION OF THE INVENTION In the present invention, air is trapped between
the rear surface of the diaphragm and the magnetic circuit portion in an electroacoustic
transducer such as a dynamic type speaker or microphone, and the air is taken from the outside
space 1-4-72 / ( The lowest resonance frequency of the vibration system (hereinafter simply
referred to as f). ,, and resonance sharpness (hereinafter simply referred to as a). An electroacoustic transducer configured to perform the adjustment of. It has been known that this god's
magnetic circuit, for example, has a configuration as shown in FIG. 1 (also referred to as "") in
order to adjust f, value and threshold value in small loudspeakers and microphones to
appropriate values. ing. That is, in FIG. 1, an inner magnetic type magnetic circuit 4 configured
by combining the yaw 1, the magnet 2 and the hole piece 3 is provided with one through hole 5
with its central axis as an axis. And in the magnetic gear knob 9 formed between the abovementioned magnetic circuit 40 hole piece 3 and the peripheral edge of the yaw 10-the above-
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mentioned magnetic coil 40 of the vibration system comprising the diaphragm 6, the coil hobin 7
and the voice coil 8 etc. The occupation position is arranged to constitute a small speaker. . The
through hole 5 provided in the magnetic circuit 4 is a dome-shaped internal space 110 formed
between the rear surface 6 a of the diaphragm 6 and the surface 3 a of the pole piece 3, and the
external space of the magnetic circuit −2 = 4. Are connected, and by setting their length,
capacity, etc., f of the above-mentioned vibration system. It serves to adjust the value and d value
appropriately. By the way, since it is extremely difficult to form the through hole 5a by
processing the existing magnet 2 usually, it is desirable to magnetize the magnetic material in
which the through hole 5a is shaped and distorted in advance. The link shape is used. Therefore,
according to the through hole 5 a of the magnet 2, the through hole 5 b is also formed in the
pole piece 3, and the through hole 5 C is formed in the yoke 1 to make the tono, shape internal
space 110 an external space. The through holes 5 to be communicated are formed by the
respective through holes 5a, 5b and 5C. However, the ring-shaped magnet described above is
freely selected from the method 1 etc. of the existing product. The large number of types that can
be obtained are not commercially available, which is a factor that greatly limits the design
freedom of the conventional magnetic circuit as described above. However, the ring-shaped
magnet described above is generally expensive and extremely uneconomical compared to a
cylindrical magnet. Therefore, the present invention is for an electro-acoustic transducer in
which a pole piece is fixed on a magnet disposed at the center of a yoke and integrally formed
with a diaphragm: a magnetic kanoff in which a Heus coil taking a picture moves is formed. In
the magnetic circuit, a first communication hole communicating the internal space of the Lclosed magnetic circuit and the external space is formed in the yoke, and a dome space formed
by the rear surface of the diaphragm and the pole piece surface is the magnetic A second
communication hole communicating with the internal space of the circuit is formed in the pole
piece, and the external space and the dome space are communicated through the first and second
communication holes, thereby forming a cylindrical shape. The new configuration has been
designed so that the f, value and d values of the vibration system can be adjusted even with the
use of the madai-noto, and that the design freedom of the magnetic circuit can be expanded and
the cost can be reduced. It is intended to provide a magnetic circuit of the gas-acoustic
transducer.
Hereinafter, an embodiment of the present invention will be described in detail with reference to
the drawings. 4-Fig. 2 is a front sectional view showing an embodiment of the present invention.
In this embodiment, the magnetic circuit 11 comprises a cylindrical magnet 12, a trapezoidal
yawing member 13 fixed to the central portion of the magnet 12, and a pole piece 14 fixed to the
magnet 12 above. , Is of the external magnet type. In FIG. 2, 15 is a dome-shaped diaphragm, 16
is a coil coil, 17 is a voice coil, and a voice coil 17 constitutes a vibration system, and the voice
coil 17 constitutes a yaw 130 peripheral edge of the magnetic circuit 11 and a pole. In the
magnetic gap 18 between the piece 14 and the flange portion 14A, a small speaker is configured.
Further, in the yoke 13, a first communication hole 20 is provided at a position other than the
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fixing portion of the magnet 12 so as to communicate the internal space 19 of the magnetic
circuit 11 with the external space. The pole piece 14 communicates the dome-shaped internal
space 21 formed by the surface 14 a of the pole piece 14 and the rear surface 15 a of the
diaphragm 15 with the internal space 19 of the magnetic circuit 5-11. In order to form the two
communication holes 22, five through holes 23 along the central axis and five slits 24a, 24b,
24c, 24d in the cross shape are provided on the joint surface 14bIII with the magnet 12,
respectively. An external perspective view of the pole piece 14 is shown in FIG. As shown in FIGS.
4 and 5, the magnetic circuit 11 has a plate 13 'disposed on the wedge-shaped yoke 13, a pole
piece 14 having a fixing portion 14b having a truncated cone shape, and the plate 13'. Even if the
magnetic gear knob 18 is formed between them, the through hole 23 and the slits 24a, 24b, 24C,
24d are provided in the hole piece 14 in the same manner as in the above embodiment. It is
better to form the holes 22. Further, in this example, a conical notch 22 ′ is provided on the
surface side of the pole piece 14 of the through hole 22 provided in the pole piece 14 so as to
adjust the flow of air passing through the second communication hole 22. is there. Furthermore,
an acoustic element such as a sound absorbing material may be provided in the notch 22 'and
the like to adjust the strain 6 on the surface of the material. FIG. 6 shows the measurement
results of the output sound pressure and frequency characteristics of the embodiment of the
present invention and the conventional example. In FIG. 6, a characteristic line X indicated by a
solid line indicates a result of measurement of an embodiment of the configuration as shown in
FIG. 3 and FIG.
In the figure, characteristics shown by alternate long and short dash lines in the figure, 1jijY
show the measurement results of the conventional example using the ring magnet of FIG.
Further, a characteristic line Z indicated by a chain line in the drawing shows a measurement
result of the conventional example in a state in which the dome-shaped internal space is sealed
without providing the pole piece with an opening. The actual measurement results are obtained
when the same vibration system is driven by each magnetic circuit. As is clear from FIG. 6,
according to the embodiment of the present invention, the effect of adjusting the fo value and the
a value can be obtained as well as the conventional example using the ring magnet. As described
above, in the embodiment as described above, the dome-shaped internal space 7-21 formed by
the diaphragm 15, the rear surface 15a, and the surface 14a of the pole piece 14 is a through
hole 23 provided in the pole piece 14. The first communication is provided in the inner space 19
of the magnetic circuit 11 or in the yoke 13 in communication with the inner space 19 of the
magnetic circuit 11 through the second communication holes 22 formed by the individual slits
24a 24b 24c 24d. Since the air is communicated with the external space through the hole 20, the
air confined in the dome-shaped internal space 21 is circulated through the first and second
communication holes 22 and 20 to the external space. By appropriately setting the length,
volume, and the like of the air flow passage passing through 22 and 20, it is possible to adjust
the f, value, and a values of the vibration system to optimal values. Furthermore, since the
magnet 12 has a general cylindrical shape, many types of commercially available magnets are
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commercially available, and the degree of freedom in designing the magnetic circuit 11 is not
limited. In addition, since the magnet is a cylindrical shape, the cost does not increase much even
if it is custom-made. Furthermore, since the magnet 12 has a cylindrical shape, it can reduce the
leakage of the same cross-sectional area with a smaller outer diameter, compared to the
conventionally used ring-shaped one 8. Improve their performance. Furthermore, since the first
and second communication holes 20 and 22 are provided not on the processing difficult like the
magnet 12 but on the yaw 13 and the pole piece 14, the processing operation is also easy. It can
be carried out. As apparent from the description of the above-described embodiment, according
to the present invention, since the first communication hole is provided in the yoke and the
second communication hole is provided in the pole piece, even if a cylindrical magnet is used The
vibration system's / value and a value can be adjusted to the optimum value.
Therefore, according to the present invention, compared to the use of the conventional ringshaped magnet, it is possible to obtain the same performance with a magnet having a small outer
diameter, and to miniaturize the magnetic circuit and improve the performance. I have a good
idea. Moreover, the cost can be reduced. The present invention is not limited to the abovedescribed embodiment, and changes the shape and arrangement position of the first and second
communication holes formed in the yoke and the pole piece, and modifies the magnetic circuit
itself. It includes many modifications, such as
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