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JP2002044781

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DESCRIPTION JP2002044781
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm of a speaker mounted on a portable terminal.
[0002]
2. Description of the Related Art In recent years, the spread of mobile terminals represented by
mobile phones and PHSs has been remarkable, and their functions have been developing rapidly.
Above all, the function related to the speaker is important, and it is necessary to have a higher
reproduction quality, assuming that it is used in a noisy place such as the outdoors or a place
where the radio sensitivity is poor. Recently, there is also a demand for a speaker that can
faithfully reproduce a wide variety of sounds, such as the widespread use of products that
express ring tones called ringtones with high sound effects such as popular songs. At present, it
is common that a speaker dedicated to a ringing tone is provided separately from the speaker
used at the time of a call.
[0003]
However, due to the characteristics of being a portable terminal, in order to realize size reduction
and weight reduction that are convenient for carrying around, each component is similarly
reduced in size, weight reduction, and further, Integration of multiple parts is required.
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1
[0004]
The technology of the speaker has been known for a long time, and an audio signal vibrates a
thin diaphragm (diaphragm) through a magnetic field, converts it into sound, and makes it feel to
the human ear.
The material and shape of the diaphragm included in the speaker greatly contribute to the
influence on the reproduced sound, and in particular, the shape near the contour of the
diaphragm called an edge portion plays an important role.
[0005]
The edge portion on the outer peripheral side of the diaphragm is required to have a large
amplitude vibration in order to increase the sound pressure in the low range, and it is desirable
that the edge portion be a material with high elasticity. On the other hand, a cone portion from
the inner peripheral side to the central portion of the diaphragm needs a material having high
rigidity and a low elongation rate because it requires fine vibrations with small amplitude to
increase the sound pressure in the high region. Low-rigidity materials cause rolling and
distortion of sound called rolling, so good quality sound effects can not be expected. If the
rigidity is too high, the diaphragm itself is likely to be broken by an external impact or the like,
which causes a problem in terms of durability.
[0006]
As described above, since the edge portion and the cone portion of the diaphragm are required to
have mutually contradictory properties, different materials are used for the edge portion and the
cone portion in a large speaker etc. It is common. However, in the case of a small speaker, it is
difficult to process in the case of formability and integration, and it is required to realize high
quality with one type of material.
[0007]
The frequency characteristic of the conventional loudspeaker is that the sound pressure in the
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low band (near 300 Hz) is low. Generally, a characteristic required for a good speaker is that a
sound pressure of a constant value of 55 dB or more can always be obtained for a section of
about 300 Hz to 3500 Hz which is a frequency band usually used in daily life. However,
conventional speakers do not satisfy the above conditions, and the common tendency is that the
sound pressure at low frequencies is very low, about 35 dB to 45 dB. The main object of the
present invention is to provide a loudspeaker diaphragm that can obtain high sound pressure at
low frequencies.
[0008]
SUMMARY OF THE INVENTION According to the speaker diaphragm of the present invention,
the diaphragm body is made of polycarbonate. Therefore, a sound pressure of 55 dB or more can
be obtained even in the low frequency range, and the condition which is a characteristic required
for a good speaker can be satisfied.
[0009]
According to the speaker diaphragm of the second aspect of the present invention, the edge
portion has a shape including a convex portion having an arc-shaped cross section in the radial
direction, and the cone portion has an arc-shaped cross section in the radial direction It has a
shape that includes a recessed portion. Therefore, a sound pressure of 55 dB or more can be
obtained even in the low frequency range, and the condition which is a characteristic required for
a good speaker can be satisfied.
[0010]
According to the method of manufacturing a diaphragm for a speaker of the present invention,
the method includes the steps of rolling a material and cutting the material formed by the rolling.
Therefore, the thickness is formed to be equal to or less than a predetermined value, and the
manufacture of a diaphragm for a speaker excellent in formability with a thin film is realized.
[0011]
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According to the speaker of claim 4 of the present invention or the portable terminal of claim 5,
the speaker diaphragm of claim 1 or 2 is provided. Accordingly, an excellent sound pressure can
be obtained even in the low frequency range, and the condition which is a characteristic required
for a good speaker can be satisfied.
[0012]
According to the speaker diaphragm of the present invention, the edge portion and the cone
portion have a wall thickness of 30 μm or less. Therefore, a diaphragm for a speaker which is
thin and excellent in formability is realized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings. A speaker diaphragm according to an
embodiment of the present invention is provided as one of the components of the speaker. A
speaker provided with this speaker diaphragm is mounted on a portable terminal.
[0014]
As shown in FIGS. 1 and 2, the edge 21 of the diaphragm 20 forms a curved surface 211. The
radius of curvature of the curved surface portion 211 greatly affects the sound pressure at the
frequency of 300 Hz to 1000 Hz, which is the low to mid range. Empirically, it is known that the
best quality frequency characteristics can be obtained when the radius of curvature of the curved
surface portion 211 has a predetermined value. In addition, the curved surface portion 221 of
the cone portion 22 greatly affects the sound pressure at the frequency higher than 1000 Hz.
The larger the radius of curvature, the higher the sound pressure. However, if the radius of
curvature is made too large to be nearly flat, noise may occur. It is known that the best quality
frequency characteristics can be obtained when the radius of curvature of the curved surface
portion 221 has a predetermined range of values.
[0015]
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As shown in FIGS. 3 and 4, one hundred and several dozens of groove lines 24 are radially
formed on the surface of the diaphragm 20. As shown in FIG. This groove line 24 is usually called
tangential. The presence or absence of the groove line 24 greatly affects the sound pressure at
the frequency of 300 Hz to 700 Hz which is the low to middle frequency range. When vibration
occurs in the diaphragm 20, the vibration wave moves outward from the center of the diaphragm
20 and returns to the center again. At this time, since the vibration wave moves along the groove
line 24, resonance and noise are prevented, and comfortable sound reproduction is realized.
[0016]
5 and 6 show the construction of a loudspeaker provided with a diaphragm 20. FIG. First, a
circular container-like yoke 11 is provided as a base, and a disk-shaped magnet 12 is disposed
concentrically with the yoke 11 on the bottom surface of the yoke 11. Similarly, a disc-shaped
pole piece 13 is disposed on the upper part of the magnet 12 concentrically with the yoke 11.
That is, the magnet 12 and the pole piece 13 are housed in the yoke 11. Next, there is a gap
between the circular tube portion of the outer edge of the yoke 11 and the cylindrical portion
formed by the magnet 12 and the pole piece 13, and the voice coil 14 of a circular tubular shape
is inserted into this gap. Subsequently, a case 15 is installed so as to surround the outer edge of
the yoke 11. The case 15 is in the form of a circular container slightly wider than the yoke 11,
and the bottom surface has a cylindrical shape in which the center is hollowed out, and the yoke
11 completely fits into the hollow portion.
[0017]
Further, a disk-shaped diaphragm 20 is provided so as to be surrounded by a circular pipe
portion at the inner edge of the case 15. The diaphragm 20 is formed with an edge portion 21
which is an outer peripheral portion and a cone portion 22 which is an inner peripheral portion,
and a connection portion 23 is formed between the edge portion 21 and the cone portion 22. A
stepped portion 16 is formed on the bottom surface of the case 15, and the upper surface of the
stepped portion 16 is in contact with the lower surface of the outermost peripheral portion of the
edge portion 21 to support the diaphragm 20. The upper surface of the voice coil 14 is
connected to the connecting portion 23 only, and the lower surface is not in contact with any
part. A protective cover 17 is provided to cover the diaphragm 20 from above. The external
dimensions of the speaker 10 configured in this way are 13 mm or less in diameter and 2 mm or
less in thickness, and realize the world's smallest miniaturization.
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[0018]
The speaker 10 can be mounted on various portable terminals.
[0019]
The diaphragm 20 is manufactured by a manufacturing method called an extrusion method.
This method comprises the steps of rolling the material and cutting the material formed by
rolling. The thickness of the diaphragm 20 thus formed is formed to be equal to or less than a
predetermined value, and a thin film is realized.
[0020]
FIG. 7 is a graph showing the frequency characteristics of the speaker diaphragm according to
one embodiment of the present invention. In the case of the embodiment of the present
invention, a sound pressure of a constant value of approximately 55 dB or more is obtained for a
section of about 300 Hz to 3500 Hz which is a frequency band usually used in daily life. On the
other hand, in the case of the conventional example, only a sound pressure of 55 dB or less is
obtained for the low to mid range of about 300 Hz to 1000 Hz. As a result, it can be said that the
present invention significantly improves the sound pressure at low frequencies.
[0021]
Brief description of the drawings
[0022]
1 is a perspective view showing a speaker diaphragm according to an embodiment of the present
invention.
[0023]
2 is a cross-sectional view showing a speaker diaphragm according to an embodiment of the
present invention.
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[0024]
FIG. 3 is a schematic view showing that the speaker diaphragm according to the embodiment of
the present invention is tangentially applied.
[0025]
4 is a cross-sectional view taken along the line AA 'in FIG.
[0026]
5 is a perspective view showing a speaker according to an embodiment of the present invention.
[0027]
6 is a partial cross-sectional view showing a speaker according to an embodiment of the present
invention.
[0028]
7 is a diagram showing the frequency characteristics of the speaker diaphragm according to an
embodiment of the present invention.
[0029]
Explanation of sign
[0030]
DESCRIPTION OF REFERENCE NUMERALS 10 speaker 11 yoke 12 magnet 13 pole piece 14
voice coil 15 case 16 stepped portion 17 protective cover 20 diaphragm 21 edge portion 22
cone portion 23 connection portion 24 groove line 211 curved surface portion 221 curved
surface portion
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