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JPH07327296

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH07327296
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer for converting an input electric signal into sound by electromagnetic
conversion.
[0002]
2. Description of the Related Art FIGS. 11 to 14 show the internal structure of a conventional
electromagnetic acoustic transducer. These electromagnetic acoustic transducers include a
housing 102, a vibrating body 104, a magnetic drive unit 106, and the like. The vibrating body
104 is constituted by the resonance plate 108 and the magnetic piece 110, and the magnetic
piece 110 is a means for enhancing the substantial vibration mass of the resonance plate 108,
and constitutes a magnetic path together with the magnetic drive unit 106. The magnetic drive
unit 106 includes a pole piece 112, a coil 114 and a magnet 116. A resonance chamber 118
enclosed by the housing 102 is formed on the upper surface side of the vibrating body 104, and
a sound emission hole 120 is formed in the housing 102 as a means for emitting the resonance
sound generated in the resonance chamber 118 to the outside. It is done.
[0003]
A substrate 122 is attached to the back side of the housing 102, and a pair of terminals 124 and
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126 are attached to the back side of the substrate 122. When an alternating current signal is
applied between the terminals 124 and 126, an alternating magnetic field is generated in the
magnetic drive unit 106 in accordance with the level of the alternating current signal, and the
vibrating body 104 is vibrated by the magnetic field action by the alternating magnetic field. In
response to the vibration, the resonance chamber 118 resonates, and the resonance sound is
emitted from the sound emission hole 120 to the outside. Such an operation is fundamental as an
electroacoustic transducer.
[0004]
By the way, looking at the form of the housing 102 employed in these electromagnetic acoustic
transducers, in the electromagnetic acoustic transducer shown in FIG. 11, the housing 102 is
integrally molded with a synthetic resin. The housing 102 forms, on the front side of the
vibrating body 104, a resonance chamber 118 which forms a relatively large space. Further, in
the electromagnetic acoustic transducer shown in FIGS. 12 and 13, the housing 102 is
configured as two separate housing pieces, that is, an upper housing 102A and a lower housing
102B made of synthetic resin. Then, in the electromagnetic acoustic transducer shown in FIG. 13,
the space of the resonance chamber 118 is set narrow because of its flattening. Further, the
housing 102 of the electromagnetic acoustic transducer shown in FIG. 14 is formed by
processing a metal plate. As described above, the housing 102 of the conventional
electromagnetic acoustic transducer is made of various materials such as synthetic resin or metal
as the constituent material, single structure or plural structures, wide and narrow resonance
chambers 118, etc. There is
[0005]
By the way, although such an electroacoustic transducer is widely used for the generation means
of ringing tone of mobile communication such as a mobile telephone etc., mass production,
miniaturization, high performance, price reduction etc. are requested. In order to meet these
requirements, conventionally, a housing 102 having a synthetic resin molded thereon has often
been used.
[0006]
However, in the case of the housing 102 (FIG. 11) integrally formed of a synthetic resin, it is
technically difficult to reduce the thickness to, for example, 0.5 mm or less because the container
structure is formed. And prevent the miniaturization or flattening of the electromagnetic acoustic
transducer as a product.
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[0007]
Further, as shown in FIG. 13, as the thinning of the electromagnetic acoustic transducer due to
the narrowing of the resonance chamber 118, the resonance operation of the resonant chamber
118 is suppressed by that much, and the operating characteristics of the electromagnetic
acoustic transducer are degraded. It becomes a problem.
[0008]
And, in the electromagnetic acoustic transducer shown in FIG. 14, the drawing process of the
metal plate is inferior in processability as compared to the molding process of the synthetic resin,
is unsuitable for mass production, and difficult to reduce the price.
[0009]
Therefore, it is a first object of the present invention to provide an electroacoustic transducer
which is easy to mass-produce and which can be miniaturized and thinned.
[0010]
The second object of the present invention is to provide an electroacoustic transducer in which
stabilization of frequency characteristics is realized together with improvement of acoustic
efficiency.
[0011]
The third object of the present invention is to provide an electroacoustic transducer in which the
protective function of the vibrator is enhanced.
[0012]
SUMMARY OF THE INVENTION In order to achieve the first object, an electromagnetic acoustic
transducer according to the present invention comprises a cylindrical housing body (2) as
illustrated in FIGS. 1 and 2. The vibration body (4) supported and vibrated by the housing main
body is formed of a thin plate formed of a separate member from the housing main body, the
opening of the housing main body is closed, and a resonance space is formed on the front side of
the resonance plate And a magnetic drive unit (6) disposed on the back side of the vibrating body
to vibrate the resonance plate.
[0013]
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Further, in the electromagnetic acoustic transducer of the present invention, the cover plate is
formed of a magnetic material in order to achieve the second object.
[0014]
Further, in the electromagnetic acoustic transducer of the present invention, in order to achieve
the third object, the cover plate is used as the means for controlling the movement range of the
vibrator.
[0015]
And in the electromagnetic acoustic transducer of the present invention, although the formation
position of the sound emission hole (42) formed in the cover plate (8) is arbitrary, it was
displaced from the magnetic piece (12) of the vibrating body in the cover plate. A sound release
hole may be formed at the position.
[0016]
In the electromagnetic acoustic transducer of the present invention, the housing main body is a
cylindrical body, and the opening of the cylindrical housing main body is closed by a cover plate
forming a thin plate with a separate member from the housing main body. It is.
The lid plate is made of various materials such as a synthetic resin plate and a metal plate.
As for the molding accuracy of the synthetic resin, if it is a coin-shaped thin plate, it is possible to
realize a molding accuracy of 0.5 mm or less as compared to the conventional container molding
in housing shape.
As described above, when the housing main body is set as the strength maintaining means and
the closing means of the opening is used as the cover plate, the cover plate can be thinned, and
the electroacoustic transducer can be made thinner, smaller, lighter Can be implemented.
Further, by thinning the cover plate, a resonance chamber having a necessary volume can be
formed between the vibrator and the cover plate, and the resonance effect can be enhanced.
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[0017]
In the electromagnetic acoustic transducer of the present invention, the cover plate is formed of
a magnetic material such as permalloy.
When the cover plate is formed of such a magnetic material, the cover plate is included in the
closed magnetic path of the vibrator.
That is, since the cover plate is installed on the outer surface side of the vibrating body, the
vibrating body is sandwiched between the magnetic drive unit and the cover plate, and magnetic
leakage from the vibrating body can be reduced.
[0018]
Moreover, in the electromagnetic acoustic transducer, it is known that the gap between the
vibrating body and the iron core of the magnetic drive part greatly affects the frequency
characteristics, and the influence is known to be sharp. The influence of the gap becomes minor,
and stabilization of frequency characteristics can be achieved.
[0019]
In addition, when the vibrating body receives falling or excessive input of the transfer input, it
may be bounced apart from the vibration in the steady state, and may receive mechanical impact
to cause mechanical displacement.
In the present invention, the mounting position of the cover plate with respect to the housing
main body is set within the movement allowable range of the vibrator to prevent the vibrator
from moving more than necessary, thereby protecting the vibrator from breakage.
[0020]
And also in such an electromagnetic acoustic transducer, a resonance sound can be emitted
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outside by forming a sound emission hole in the arbitrary positions of the lid plate which has
been thinned.
In particular, when the sound emission hole is formed at a position displaced from the center
position of the vibrator, the distance between the vibration center of the vibrator and the sound
emission hole becomes longer, and the resonance space of the resonance chamber can be
effectively used by that amount. , The resonance effect is obtained.
[0021]
The invention will now be described in detail with reference to the embodiments shown in the
drawings.
[0022]
1 and 2 show an embodiment of the electromagnetic acoustic transducer of the present
invention, FIG. 1 is a plan view thereof, and FIG. 2 is a cross-sectional view taken along the line IIII of FIG.
[0023]
The housing body 2 which comprises a cylindrical body as an exterior means is used for this
electromagnetic sound transducer.
Although various cylindrical bodies, such as a rectangular cylinder, etc. can be considered for the
form of the housing main body 2, as a form corresponding to the vibration mode of the vibrating
body 4, a cylindrical body is suitable.
Further, in the case of this embodiment, the housing main body 2 is integrally molded of
synthetic resin.
The housing body 2 has the vibrator 4 supported at its middle portion, the magnetic drive unit 6
installed on the back side, and the front opening side formed of a magnetic material plate or a
synthetic resin plate It is closed by a cover plate 8 made of a thin plate.
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The thinning of the substrate 8 is one feature.
[0024]
The vibrating body 4 has a small-diameter magnetic piece 12 attached to the center of a
resonance plate 10 made of a magnetic material.
The magnetic piece 12 is a means for enhancing the vibrating mass of the resonance plate 10,
and forms a closed magnetic path with the magnetic drive unit 6 together with the resonance
plate 10.
[0025]
The magnetic drive unit 6 is an electric-magnetic field conversion unit, and applies an alternating
magnetic field corresponding to an input signal to the vibrator 4.
The magnetic drive unit 6 is provided with a pole piece unit 14. The pole piece portion 14 is a
disc-shaped base 16 made of a magnetic material, and a columnar magnetic core 18 is provided
upright. In this embodiment, the magnetic core 18 has the base end side as a small diameter
portion 20, and the small diameter portion 20 is inserted into the base 16 and the substrate 22,
and the end is crimped to be fixed to the base 16 . In this embodiment, a magnetic core 18 is
used as a fixing means of the base 16 and the substrate 22. A coil 24 is wound around the
magnetic core 18, and the coil end is connected to the terminals 26 and 28 erected on the
substrate 22. In addition, an annular magnet 30 is provided on the outer peripheral portion of
the coil 24. The magnet 30 forms a closed magnetic circuit together with the base 16, the
vibrating body 4 and the magnetic core 18, and causes the vibrating body 4 to act a fixed
magnetic field, which is a bias magnetic field.
[0026]
The end of the magnetic core 18 is slightly exposed from the end face of the coil 24, but a gap
32 is provided between the end face and the vibrator 4. The gap 32 forms a vibration allowance
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space of the vibrating body 4 and prevents the vibrating body 4 from colliding with the end face
of the magnetic core 18 during vibration. In the electromagnetic acoustic transducer of this
embodiment, the vibrating body 4 is supported by the housing main body 2, and a first support
step portion 34 is formed as the support means. The support step 34 is formed at a position
where an optimum gap 32 can be formed between the support step 34 and the tip of the
magnetic core 18 of the pole piece 14. The support step portion 34 is formed to be larger than
the inner diameter of the housing body 2, and the upper surface portion thereof is a flat surface
in order to stabilize the support of the vibrating body 4. Then, the holding of the vibrating body 4
installed in the support step portion 34 utilizes the magnetic force of the magnet 30. In some
cases, the support step 34 may be formed on the magnet 30 side to support the vibrating body 4.
[0027]
Further, a second support step 36 for supporting the lid plate 8 is formed at the opening of the
housing body 2. The inner diameter of the wall 38 surrounding the support step 36 is set larger
than that of the support step 36. The cover plate 8 is formed in a circular shape which is shaped
to match the inner diameter of the support shoulder 36 of the housing body 2, and the
peripheral edge thereof is supported on the support shoulder 36 of the housing 2, and the
support shoulder The portion 36 is fitted in and fixed to the wall of the housing body 2. The
cover plate 8 can be formed of a magnetic material plate such as a resin plate or permalloy. That
is, the cover plate 8 forms closing means for closing the opening of the housing body 2 and
forms a resonance chamber 40 as a resonance space on the upper surface side of the vibrating
body 4. The supporting step 36 is closely related to the size of the resonance chamber 40 to be
formed on the front side of the vibrating body 4, and the vibration supported by the supporting
step 34 when the inside diameter of the housing body 2 is constant. The distance between the
upper surface of the body 4 and the inner surface of the lid plate 8 supported by the support
step 36 determines the volume of the resonance chamber 40.
[0028]
A sound emission hole 42 is formed in the cover plate 8 as a means for emitting the resonance
sound of the resonance chamber 40 to the outside. The sound release hole 42 may be formed at
any position, and in the case of this embodiment, it is set at a position displaced from the center
of the vibrating body 4, that is, the position of the magnetic piece 12. Further, although the shape
and size of the sound release hole 42 are arbitrary, in the case of this embodiment, it is circular
and the size thereof is substantially the same as the magnetic piece 12 of the vibrating body 4.
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That is, there is a distance L1 between the vibration center of the vibrator 4 and the center of the
sound emission hole 42, and the distance L1 and the diameter L2 of the sound emission hole 42
are related to the utilization of the resonance space of the resonance chamber 40. .
[0029]
Further, in the electromagnetic acoustic transducer of this embodiment, the cover plate 8
constitutes a means for restricting the moving range of the vibrating body 4 in the vertical
direction, and the distance L3 between the magnetic piece 12 of the vibrating body 4 and the
cover plate 8 is narrow. It has been In addition, since the sound release hole 42 is displaced from
the position of the magnetic piece 12, the portion of the magnetic piece 12 of the vibrating body
4, that is, the center of gravity is received at the central portion of the cover plate 8.
[0030]
The function of each part will be described together with the operation of the electromagnetic
acoustic transducer configured as described above.
[0031]
When an alternating current signal is applied between the terminals 26, 28, the alternating
current signal excites the coil 24.
As a result, an alternating magnetic field is generated in the pole piece portion 14 opposite to the
bias magnetic field of the magnet 30, and the alternating magnetic field acts on the vibrating
body 4 through the magnetic core 18. As a result, the vibrator 4 repeatedly vibrates in the
vertical direction in the drawing, and the vibration causes the resonance chamber 40 to resonate.
As a result, the resonance sound is emitted from the sound emission hole 42 to the outside.
[0032]
In such an electroacoustic transducer, the cover plate 8 is formed of a thin plate, and the
electroacoustic transducer is intended to be flattened, reduced in size and reduced in weight. In
this embodiment, although the thin plate 8 is formed of a permalloy plate, the resin plate can be
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made thinner as compared to the case of forming a conventional container-like housing. In the
case of a permalloy board, its thickness is extremely thin, for example, it can be set to a thickness
of about 0.2 mm, so that the housing can be thinned.
[0033]
When the cover plate 8 is made of a magnetic material, particularly permalloy, the cover plate 8
functions as a shield plate covering the front side of the vibrating body 4. Moreover, the cover
plate 8 forms a closed magnetic path together with the vibrating body 4 and the magnetic drive
unit 6 side, so that magnetic leakage can be suppressed. In particular, since the vibrating body 4
is disposed between the lid plate 8 made of a magnetic plate and the magnetic core 18, the
influence of the gap 32 between the vibrating body 4 and the magnetic core 18 on the center
frequency Fo value is blunted. Characteristics can be stabilized.
[0034]
The distance between the cover plate 8 and the vibrating body 4 is set to a width slightly
exceeding the allowable range of vibration during normal operation of the vibrating body 4, that
is, since the two are brought close to each other Function as a means to control Moreover, since
the position of the sound release hole 42 is displaced from the center position of the vibrating
body 4, the magnetic piece 12 abuts on the cover plate 8, and the movement regulating function
of the vibrating body 4 is achieved. Can be prevented.
[0035]
In the electromagnetic acoustic transducer of this embodiment, the resonance chamber 40 is
narrowed in order to flatten the electromagnetic acoustic transducer. However, by displacing the
position of the sound release hole 42 from the center position of the vibrator 4, a distance L1 is
generated between the vibration center of the vibrator 4 and the sound release hole 42, and this
distance L1 is a resonance chamber. This can lead to the expansion of the 40 substantial
resonance spaces to enhance the resonance sound.
[0036]
Further, since the housing main body 2 has a relatively simple shape in which the support
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stepped portions 34 and 36 are formed in the cylindrical body, the molding accuracy by the
synthetic resin is high, and uniformization and miniaturization of the product can be achieved. It
becomes unnecessary to set the thickness by the bent portion, and the manufacturing can be
simplified.
[0037]
Next, experimental results of the electromagnetic acoustic transducer of the present invention
will be described.
[0038]
3 and 4 show operating characteristics of the cover plate, and FIG. 3 shows sound pressure
characteristics at an input frequency of 1 kHz to 3 kHz, and FIG. 4 shows current consumption
characteristics at an input frequency of 1 kHz to 3 kHz.
In FIG. 3 and FIG. 4, the characteristic A is the case where permalloy is used as the magnetic
material, the characteristic B is the case where brass is used as the cover plate 8 as the
nonmagnetic material, and the characteristic C is the case where plastic is used as the
nonmagnetic material. .
When measuring the characteristics A to C, the applied voltage uses a pulse voltage with an
amplitude of 1.5 V with 0 V as a reference. When the characteristics A, B and C are compared,
the peak point of the sound pressure level of the characteristic A is higher than the
characteristics B and C, and the frequency is shifted to 2.2 kHz. a shows the difference in sound
pressure level. Further, in the comparison of the overall sound pressure level, the sound pressure
level of characteristics B and C reaches the peak point near 2 kHz, but the sound pressure level
of characteristic A is generally high. b represents the difference between sound pressure levels of
the characteristic A and the characteristics B and C, and indicates an increase of the sound
pressure level of 5 dB or more. Also, in the comparison of the consumption current, the
characteristic A is reduced in the entire frequency range compared to the characteristics B and C,
the rise of the internal resistance of the resonance portion is remarkable, and the consumption
current is reduced. c shows the difference, and a decrease in the current value far exceeding 5
mA has occurred. As described above, when a magnetic material is used for the cover plate 8, it is
possible to suppress the magnetic leakage, and as a result, it is understood that the sound
pressure level can be enhanced and the consumption current can be reduced, and the efficiency
can be improved.
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[0039]
Next, FIG. 5 and FIG. 6 show operating characteristics according to the position of the sound
release hole 42, FIG. 5 shows sound pressure characteristics at an input frequency of 1 kHz to 3
kHz, and FIG. 6 shows current consumption characteristics at an input frequency of 1 kHz to 3
kHz. There is. In FIGS. 5 and 6, the characteristic A is an eccentric position (the embodiment of
FIG. 2), and the characteristic B is a characteristic at the center position. The measurement
conditions are the same as the operation characteristics of FIGS. 3 and 4. As apparent from the
characteristics A and B, when the sound release hole 42 is decentered, the resonance frequency
is lowered and the sound pressure level is increased by the level difference g, and it is recognized
that the consumption current is reduced. This is because the sound emission hole 42 is
decentered, and the resonance effect by the resonance chamber 40 improves the efficiency as
well as the sound pressure level.
[0040]
Next, FIG. 7, FIG. 8, FIG. 9 and FIG. 10 show the operating characteristics of the input frequency
of 1 kHz to 3 kHz by the applied voltage, and FIG. 7 shows the lid plate 8 when the lid plate 8 is
made of brass. 9 shows the current consumption characteristics when the cover plate 8 is made
of permalloy, and FIG. 10 shows the current consumption characteristics when the cover plate 8
is made of permalloy. In each drawing, the characteristic A is an applied voltage of 1.0 V, the
characteristic B is 1.5 V, and the characteristic B is 2.0 V. Such a change in applied voltage
equivalently changes the size of the gap 32 of the vibrating body 4 and the magnetic core 18 of
the magnetic drive unit 6, and how the gap 32 affects the frequency characteristics. In order to
see if the magnetic encircling effect by. As a result of such an experiment, when brass, that is, a
nonmagnetic material, is used for the cover plate 8, the frequency of the peak point of the sound
pressure level decreases as the applied voltage increases, as is apparent from FIG. There is. As
apparent from FIG. 8, such a relationship also occurs in the consumption current, and the lowest
resonance frequency Fo of the vibrator 4 has a remarkable frequency change e as the applied
voltage becomes higher. On the other hand, when permalloy, ie, a magnetic material, is used for
the cover plate 8, as apparent from FIG. 9, even if the applied voltage changes, the frequency at
which the peak point of the sound pressure level changes Absent. That is, only the sound
pressure level is similarly changed according to the applied voltage. As is clear from FIG. 10, such
a relationship is the same for the consumption current, and the lowest resonance frequency Fo of
the vibrator 4 has a small frequency change f even if the applied voltage changes. As described
above, when a nonmagnetic material is used for the cover plate 8, the fluctuation of the lowest
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resonance frequency Fo, which is a representative value of the frequency characteristics, is
remarkable and reacts sharply to the change of the gap 32. In the case where a magnetic
material is used, it can be seen that only the frequency fluctuation is observed, and the influence
of the change of the gap 32 is small. And, as is apparent from these operating characteristics,
when the cover plate 8 is made of a magnetic material, there is no magnetic leakage, the
magnetic efficiency is improved, the operating characteristics are stable, and the excellent
acoustic conversion characteristics are obtained. It is obtained.
[0041]
As described above, according to the present invention, the following effects can be obtained.
a. The housing is composed of the housing main body and the cover plate, and by thinning the
cover plate, mass production is facilitated, and downsizing, flattening, and weight reduction of
the electroacoustic transducer can be achieved. b. The cover plate can be set as a movement
control means of the vibrating body, and displacement of the vibrating body due to an impact or
excessive input during transportation can be prevented, and the vibrating body can be protected
from breakage. c. When the thin body is formed of a magnetic material, the front side of the
vibrating body can be shielded by a cover plate, magnetic leakage can be prevented, and
stabilization of the center frequency can be achieved, so that stable operation can be realized.
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