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JPS5797296

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DESCRIPTION JPS5797296
Description 1, title of the invention
Small thin sound generator
3. Detailed Description of the Invention The present invention relates to the structure of a thin
sounding body, particularly a small thin sounding body, whose height is as small as possible. FIG.
1 is a side view of a conventional speaker, partially showing the appearance of its cross section. 1
is a permanent magnet, 2a is a center pole, 2b is a yoke, 2c is a yoke plate, and the magnetic
circuit 6 is constituted by the permanent magnet 1, the center pole 2a1 yoke 2b, and the yoke
plate 2c. The diaphragm 4 has a conical shape and is called a cone. ?????????????
????????????????????????????????????? In the
speaker structure shown in FIG. 1, the frame 8 is coupled to the magnetic circuit rod, the edge 4a
of the diaphragm 4 is coupled to the peripheral portion 8a of the frame 8 together with the
gasket 7, and the central portion 4b of the diaphragm 4 is coupled. The voice coil 9 is fixed to the
middle portion of the voice coil 9 by the dieper 5 so that the voice coil 9 is eccentric to the gap
6a of the magnetic circuit rod (inserted, dust cap on central upper surface of diaphragm 4) It has
a structure to stick 6. As described above, in the conventional example of FIG. 1, the EndPage: 1
shape of the diaphragm 4 has a conical shape spreading in the opposite direction with respect to
the magnetic circuit rod, so the size is increased, and a large cabinet such as a television or stereo
Although it is useful for electric devices having the above, it has a disadvantage that it can not be
used for small devices such as micro cassette recorders and micro pocket radios. FIG. 2 shows a
side view of a conventional thin speaker developed from the above, partially showing the cross
section thereof. A permanent magnet 11 and yokes 12a and 12b form a magnetic circuit 16 by
the permanent magnet 11 and the yokes 12a and 12b. 14 is a diaphragm, 14a is an edge of the
diaphragm 14, 18 is a frame made of synthetic resin, metal or the like, and 19 is a voice coil. In
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the speaker structure shown in FIG. 2, the frame 18 is fixed to the outer peripheral surface of the
yoke 12b of the magnetic circuit 16 so that the yoke 12a and the frame 18 are almost flush with
each other. The diaphragm 14 on the substantially flat plate having the projecting portion
14C114d is fixedly supported, the central portion 14bl C of the diaphragm 14 is fixed, and the
voice coil 19 is fitted into the gap 13a of the magnetic circuit 13. There is. By adopting such a
structure, the height of the speaker in FIG. 2 becomes a height that is the sum of the height of the
magnetic circuit 13 and the height of the diaphragm 14, and the thickness becomes considerably
thin, but this is also sufficient. It can not be said that it has been thinned.
Also, the diaphragm 14 has to be provided with projections such as 14C and 14d for preventing
divided vibration caused when forced vibration is made, and there is a disadvantage that the
formation of the diaphragm is difficult. The invention seeks to eliminate these drawbacks, which
will be explained below with reference to the drawings. FIG. 3 is a side view of a thin speaker that
is a thin speaker, showing an embodiment of the present invention, partially showing the
appearance of its cross section. 21 is a disk-shaped permanent magnet, which is anisotropicized
and magnetized so that a different pole is generated in the axial direction, and 7 / l / l Kunico,
barium ferrite magnets, etc. are used, but the maximum magnetic The use of a rare earth magnet
having a large energy product (generally expressed as (BT-I) max), such as SmCo, a magnet is
very effective for miniaturizing and thinning. Reference numerals 22a and 22b denote yokes
made of a high magnetic permeability material, such as magnetic soft iron, and the magnetic
circuit 26 is constituted by the permanent magnets 21 and the yokes 22a 22b. Reference
numeral 24 denotes a diaphragm having a flat outer peripheral portion 24a and a trapezoidal
sectional shape of the inner peripheral portions 24b and 24C, for example, a thin metal plate
such as titanium or beryllium, and an aromatic polyester based material having a stable Young's
modulus temperature coefficient It is composed of a molded product of polymeric material film
such as polyarylate and the like. A frame 28 is made of a synthetic resin, a metal made of a
nonmagnetic material, etc. In the embodiment of FIG. 3, the opposing surface 28b of the
diaphragm 24 has substantially the same shape as the diaphragm 24. Water pressure when
stored in the case of the watch, deformation of the diaphragm 24 when pressure is applied from
the outside due to air pressure, vibration when using the speaker in a place where external
pressure is likely to be applied We have taken preventive measures. A voice coil 29 is made of,
for example, a copper wire or an aluminum wire, and in the embodiment of FIG. 3, it is formed
into an air-cored coil to reduce a useless load. The structure of the speaker of FIG. 3 according to
the present invention has the same structure as that of FIG. 2 except that the outer peripheral
surface of the yoke 22b of the magnetic circuit 26 is fixed so that the yoke 22a and the frame 28
are substantially coplanar. The voice coil 29 is fixed to the inner bottom portion 24d of the disklike circular flat portion 24c of the diaphragm 24 fixedly supporting the diaphragm 24 at the
periphery / edge portion 28a of the frame 28 and having a trapezoidal shape. The coil 29 is
fitted in the gap 23 a of the magnetic circuit 26. As apparent from FIG. 3, since the diaphragm 24
of the speaker according to the present invention is formed into a trapezoidal shape so as to
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surround the magnetic circuit 26, it is possible to omit a useless space as compared with the
speaker of FIG. , Smaller EndPage: can be 2 type.
Furthermore, the diaphragm 24 of the present invention is characterized in that it can be thinner
than the speaker of FIG. 2 because it has no upwardly projecting portions such as 14G and 14d
of the diaphragm 14 of FIG. . Generally, among the performances required for the speaker, there
is a condition that the reproduction frequency range is wide (it has flat frequency characteristics,
but in order to satisfy this condition, the diaphragm is brought close to a rigid body to vibrate
Various attempts have been made to reduce the stiffness of the edge of the plate and to make the
diaphragm move in a piston motion. The shape of the diaphragm thus determined is, for example,
a cone shape such as 4 in FIG. 1, and in the thin speaker, it is a shape having a projecting portion
such as 14C114 d in FIG. However, the diaphragm 24 shown in the embodiment of the present
invention is a trapezoidal diaphragm having a portion in which the inner peripheral portion 24G
is planarized in order to further miniaturize and thin the diaphragm 24. The vibration is a
movement closer to a membrane vibration than a piston movement, and it is difficult to obtain
so-called divided impressions and to obtain a flat sound pressure frequency characteristic. The
present invention is intended to solve the problems as described above and to provide a smaller
and thinner speaker. FIG. 4 is a free vibration mode diagram of a circular vibrating membrane.
When the circular vibrating membrane vibrates freely, the entire membrane surface moves up
and down as shown in Fig. 4 (5) while the frequency car is low, but when the frequency becomes
high, as shown in Fig. 4 (Bl, When the central part is displaced upward, the peripheral part
vibrates downward and does not vibrate at all, so-called nodal circle at a position of 0.4356 with
respect to the outer diameter (assuming that the outer diameter of the circular diaphragm is Do,
It will occur one at the 0.4356 DO position). Fig.4 (In the frequency higher than Bl, Fig.4 (two q
as shown by two concentric nodal circles exist, there is a vibration that vibrates in the opposite
direction between the inside and the outside with these boundaries) It comes to show the
posture. Therefore, if this circular diaphragm is used as a diaphragm of a speaker, the air flow
(sound wave) at the central portion and the peripheral portion of the circular diaphragm is as
shown in FIG. In the opposite direction to each other, the sound pressure drops sharply at this
vibration frequency. In terms of sound pressure frequency characteristics, these appear as
valleys of sound pressure in the characteristics. Therefore, if the coil is attached to the position of
the nodal circle of FIG. 4 which is also theoretically calculated so as not to take the vibration
mode as shown in FIG. It can be seen from FIG. 4 (that the flat sound pressure frequency
characteristic can be obtained up to the vibration frequency at which the vibration mode
appears.
Now, in FIG. 3, although the shape of the imaging plate 24 is a trapezoidal shape, consider the
vibration mode of the diaphragm 24 of the trapezoidal shape. Since the sloped surface portion
24b having a trapezoidal shape works the same as the cone shape of the diaphragm 4 shown in
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FIG. 1, it is difficult to vibrate, and it is presumed that the circular flat surface portion 24C is
easily vibrated. However, although the sloped portion 24b of the diaphragm 24 does not vibrate
easily, it works to reduce the stiffness of the image pickup plate itself to lower the minimum
resonance frequency of the speaker and to allow the circular flat portion 24C to freely vibrate. It
can also be inferred that there is a function to support the outer circumference. That is, the
trapezoidal flat surface 24c of the diaphragm 24 is supported as if the free vibration of the
circular diaphragm of FIG. 4 can be performed as free vibration, and the sound is emitted by the
vibration of the circular flat surface 24C. Is guessed. FIG. 5 is a sound pressure frequency
characteristic diagram of the speaker when the average diameter of the voice coil 29 of the
speaker of FIG. 3 is changed, and the vertical axis represents the sound pressure, and the
horizontal axis represents the frequency. 5 (5), when the average diameter of the voice coil 29 of
FIG. 3 is d and the diameter of the inner bottom 24d of the moving plate 24 is D, the voice coil
29 of d = o, 535 D is used. Sound pressure frequency characteristics, FIG. 5 (B) shows sound
pressure frequency characteristics when the voice coil 29 of d = 0.4. 35 D is used, and FIG. 5 (C 1
shows a voice coil of d = 0. 335 D The sound pressure frequency characteristics when using 29
were shown as an example of the result of actual measurement. The voice coil diameter of d = o,
435 D and EndPage: 3 in CB1 are approximate to the positions of 0, 4356 D, which are the
positions of the nodal circle of the above-mentioned circular diaphragm, and FIG. (A), (q is ▒ 0.
???????????? In FIG. 5 (B1 and (A +, (as can be seen by comparing C1, it is assumed
that the trapezoidal flat surface 24G is vibrating) and the voice coil 29 is positioned at the nodal
circle position (0, 4356 D)). It has been proved that the fixed reproduction frequency
characteristics are broad and flat frequency characteristics. FIG. 6 shows by numerical
calculation the pattern of forced oscillation in the vicinity of the second resonance when a
uniform and vertical driving force acts on the entire circular vibrating film, where ? / ?1 is the
drive for the first resonance frequency. It represents the ratio of the angular frequency of the
force. As seen from FIG. 6, the displacement of the peripheral portion is small relative to the
displacement of the central portion until ? / ?1-2 where the angular frequency ? of the
driving force is small, but ? / ?, = 2.2 to 2.7 It can be seen that the displacement of the
peripheral portion becomes larger when.
The position of the nodal circle in this case is about 0.371). It can also be seen from FIG. 6 that
the value is .about.0.5 Do (Do is the outer diameter of the circular vibrating membrane). In the
loudspeaker shown in the embodiment of FIG. 3, the diaphragm 24 is forcibly driven by the ringshaped voice coil 29. Therefore, although the drive condition of FIG. 6 is slightly different, 0.37D
? cl. As a result of forming and measuring the voice coil 29 in the range of 40.5 D, FIG. 5 (N,
(the large sound pressure valley 61.62 as seen in C1 is eliminated, FIG. 5 (13) The sound
pressure frequency characteristics of the Thus, when the average diameter d of the voice coil 29
is set to 0.371, g (+ and 0.5 D), a small and thin diaphragm 24 having a trapezoidal shape as
shown in FIG. Also in the speaker, it is possible to prevent divided vibration, and flat sound
pressure frequency characteristics can be reduced. Although the embodiment of FIG. 3 shows an
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embodiment of the electrodynamic speaker, it is of course applicable to an electromagnetic
speaker. FIG. 7 is a plan view of an electronic wristwatch equipped with a speaker according to
an embodiment of the present invention in which the speaker of FIG. 3 is attached to the case of
the wristwatch, and FIG. Reference numeral 60 denotes the speaker shown in FIG. 3. The speaker
60 is fixed to the screw portion 41a of the bezel 41 which is a part of the watch case 40 by fixing
the ring-shaped support member 45 provided with screws on the outer periphery. The packin 46
provided between the 60 and the diaphragm 24 is compressed and fixed. Thus, the waterproof
structure of the watch case 4o is formed by compressing the packing 46. However, as the
function of the packing 46, the sound of the back of the speaker 60 (the inner side of the watch
case 40) (The sound radiated to the front of the diaphragm and the sound radiated to the back
are prevented from canceling each other), and the sound pressure, especially the low frequency
sound pressure, is also reduced. It is supposed to The fixing structure of the ring-shaped support
member 45 and the bezel 41 may be a fixing structure using bayonet, brazing, 0 ring, E ring, etc.
instead of using screws. The reference numeral 42 denotes a body, 46 denotes a back pig, and
the module support frame 44 is fixed by fitting the back pig 46 to the body 42, and the circuit
board 48 is fixed. Reference numeral 49 denotes a protective plate having a large number of
sound emission holes, and 50 a glass, which together with the bezel 41, the body 42, and the
back pig 46 constitute a watch case 40. Reference numeral 47 denotes a time display member,
for example, a liquid crystal cell, which is fixed so as to be electrically connected to the circuit
board 48, and displays the time as shown in FIG.
A coil spring 51 electrically connects the speaker 60 and the circuit board 48 together with
another coil spring not shown. 52 is a silver battery, 56 is a lithium battery, and an IC 54
mounted on the circuit board 48, electronic components such as a quartz crystal moving element
55 soldered on the circuit board 48, a time display member 4Z, and a speaker 60 Is electrically
connected to the circuit board 48 so as to drive the speaker electronic timepiece. Reference
numeral 56 denotes a sealed air chamber (hereinafter referred to as a back pressure chamber
and 1 pump) formed between the circuit board 48 and the speaker 60, and by forming the back
pressure chamber 56, the apparent lowest resonance frequency fo ' 'Omitted' is preventing it
from rising. Here, the size of the back pressure chamber 56 is briefly described EndPage: 4.
Assuming that the stiffness of the back pressure chamber 56 is sb, it is represented by S1] =
?oC2?2a '/ Vb-(1). Here ?. Is the air density, C is the speed of sound, a- is the effective
oscillation radius of the diaphragm, and vb is the volume of the back pressure chamber. Also, m
equal speaker mass. , S equivalent stiffness. ?????? 'Is fo и = 21. J8 и + 8b иииииииииииииииииии (2)
2?rrIIO. For example, when a plastic film material is used as the material of the diaphragm 24 of
the speaker 60 of FIG. 3 and the diameter of the trapezoid inner bottom 24d of the diaphragm
24 is D = 2 (cm), the effective vibration radius a is It has been experimentally confirmed that a ?
? = 0.7 (cm). Then, assuming that /1ll=1.2 (kg / m 3), C = 344 (m / S), a = 7 О 10 ?3 (m) and
vb is, for example, Vb = IX 10 ? (rn 3), the equation (1) It becomes% expression% (3). When a
plastic film is used as the material of the diaphragm 24 in the equation (2), the equivalent
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stiffness of the speaker is S. It becomes a value such as ?2 О 10 2 to 8 О 10 2 (N 7 m), which
is one digit smaller than s b in equation (3). Also, the equal image mass m of the speaker. Is
different depending on the thickness and density of the diaphragm 24 and the specifications of
the voice coil 29, but m is for D = 2 cm. It is confirmed by experiment that = 9 Qm and around 9
are the most efficient. Then, in the equation (2), for example, So = 2 О 102 (N7 m), m.
?????????????????? If we look for ', we have fo' = 1002 (IIZ)---(4). Also, So =
0 (N7 m), m. ?????????????????????????????????????
????????????
The apparent lowest resonance frequency f of the speaker 60, as can be seen by comparing the
equations (4) and (5). It can be seen that the 's' is determined by the stiffness sb of the back
pressure chamber 56. That is, when the speaker is used in a place where the back pressure
chamber 56 can not take a large size such as a watch case ?) case, the volume of the back
pressure chamber 56 is f. It can be seen that the 'is almost determined. Therefore, consider the
size of the back pressure chamber 56 when sound is output from the speaker 60 with a watch as
shown in FIG. In general, the voice is f. It is known that '? IKI (not (z is not clear)). When the
diameter of the inner bottom 24 d of the trapezoidal shape of the diaphragm 24 is D = 2 cm, as is
apparent from the equation (4), ?. 'Is about IKI (z. Therefore f. In order to reduce 'IKI (z or less, it
is necessary to reduce the stiffness sb of the back pressure chamber by providing the size of the
back pressure chamber 56 of Vb = lXIQ1m3 = 1 cm3 or more. As described above, when the
speaker is mounted in the case of the watch, it is necessary to provide a closed air chamber
called a back pressure chamber (for example, 56) inside the case, and the entire watch tends to
be thick (it tends to be thick). Also in this sense, the use of the speaker of FIG. 3, which is an
embodiment of the present invention, is very effective in making the case thin and compact. Now,
in the electronic watch with a speaker shown in FIG. 7 and FIG. 8, consider a case where an audio
clock is used to notify the time by means of voice, such as "what time is it?" FIG. 9 is an example
showing a relation between an IC and a speaker and a battery as a driving power source thereof.
As shown in FIG. 9, the IC 54 has three chips of, for example, a voice synthesis IC 61, a current
amplification IC 62 for driving a speaker, and a watch IC 66. It can be configured using C. The IC
61 for voice synthesis requires a power supply voltage of 5 * at the present technical level, and a
power supply voltage of at least 3 * is required even for an IC with a low operating voltage. The
minimum operating voltage of the voice synthesizing IC 61 of the present embodiment is 3 V.
Therefore, a lithium battery 56 capable of obtaining a battery 3 'is selected as a power supply.
The lithium battery 56 simultaneously serves as a power supply for the current amplification
capacitor C 62 and the speaker 60, and the silver battery 52 serves as a power supply for the
watch IC 66, and a 3-chip IC of EndPage: 5 is driven. 64 is a boosting circuit, 65 is a constant
voltage circuit, and the boosting circuit 64 doubles the battery voltage of the lithium battery 56,
and the constant voltage circuit 65 stabilizes the battery voltage of 3v using this battery voltage.
It is configured to supply.
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In general, in an electrodynamic speaker as shown in FIGS. 1 to 3, it is necessary to flow a large
amount of current to extract a loud sound. For this reason, as a power source of the speaker 60, a
battery which has a size that can be put in the case of a wristwatch, for example 40, and which
can take out a relatively large amount of current is necessary. Choose. Therefore, a high-rate
lithium battery is selected as the lithium battery 56 shown in FIG. 9. However, when the high-rate
lithium battery is connected to a load of 80 ? at -10 ░ C. It is confirmed that the battery voltage
is lowered. The temperature of -10 ░ C is the temperature at which the environmental test of the
wristwatch must pass, and the IC 61 for speech synthesis must not malfunction at -10 ░ C. By
the way, the constant voltage circuit 65 shown in FIG. 9 can stably supply 3 v of battery voltage
to the voice synthesizing IC 61 if the voltage of the filter battery is 4.8 v or more after being
boosted by the booster circuit 64. It has become. In other words, when the battery voltage before
being boosted by the booster circuit 64 is 2.4 v or more, the voice synthesizing IC 61 can be
stably supplied with the battery voltage 3 О. Therefore, if the direct current resistance of the
voice coil 29 of the speaker 60 is set to 80 ? or more, the drop of the battery voltage due to the
load resistance does not fall to 2.4 v or less even at -10 ░ C. The battery voltage of 3 * can be
stably supplied to the voice synthesizing IC 61, and the voice synthesizing IC 61 can be driven
without malfunction even at -10 ░ C. In the embodiment of FIG. 9, the clock r, c 63 is driven by
the silver battery 52, there is no fluctuation of the battery voltage due to the load of the speaker
60 etc., and the clock IC 65 can be driven very stably. However, two batteries of a silver battery
52 and a lithium turtle battery 56 are required, and the size of the watch is large. Now consider
the case of an individual lithium battery. In this case, in order to lower the power consumption, it
is necessary to supply a voltage obtained by dividing the battery voltage of the lithium battery 56
to the oscillator, in order to lower the power consumption of the oscillator IC (not shown) in the
watch IC 66. As the minimum operating voltage of the oscillator, it is necessary to secure 1.2 v or
more, and therefore it is necessary to secure 2.4 v or more as the battery voltage before voltage
division. When a liquid crystal cell is used as the time display member 47 and the liquid crystal
cell is matrix driven, it is necessary to secure a battery voltage of 2.4 v or more.
From the above, it is also understood that it is necessary to set the DC resistance of the voice coil
29 to 80 ? or more. Of course, it is obvious that the resistance of the sound generator is
required to be 80 ? or more even in the sound generator other than the speaker 60 of this
embodiment. That is, when the voice coil 29 whose DC resistance is set to 80 ? or more is
combined with the speaker 60 according to the present invention, a voice clock having a thin
speaker watch capable of outputting voice as shown in FIGS. Can be configured. As described
above, according to the present invention, since the shape of the diaphragm 24 is simple, the
forming process of the diaphragm 24 becomes very easy, and the position of the node circle of
the diaphragm 24 is driven. Although the efficiency is improved and the diaphragm shape is
simple and thin, a divided vibration of the diaphragm 24 can be prevented and a speaker having
flat sound pressure frequency characteristics can be configured. Also, as described above, since it
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can be made extremely small and thin, it can be housed in the case of a watch, and if the direct
current resistance of the voice coil 29 is set to 80 ? or more, the IC 66 for watch Since a battery
voltage for driving an IC such as a voice synthesis IC 61 without malfunction can be secured, it
can be used as a small thin speaker for a wristwatch. Of course, it is obvious that EndPage: 6
which can be used for small devices such as micro cassette recorders and very small pocket
radios.
4. Brief description of the drawings (1st companion) and Fig. 2 show the prior art. Fig. 1 is a side
view of the slip force, Fig. 2 is a side view of the thin speaker, Fig. 3 and 5 7, 8 and 9 show an
embodiment of the present invention, FIG. 3 is a side view of a thin speaker which is a thin
speaker, and FIG. 4 is a general example of free vibration of a circular diaphragm. FIG. 5 is a
sound pressure frequency characteristic diagram of the speaker when the average diameter of
the voice coil 29 of the speaker of FIG. 3 is changed, and FIG. 6 is a general example and uniform
and perpendicular to the whole circular diaphragm. Fig. 7 is a plan view of an electronic watch
with a speaker according to an embodiment of the present invention in which the speaker of Fig.
3 is mounted on the case of the watch, and Fig. 7 is a plan view of an electronic watch with a
speaker according to the second embodiment. FIG. 8 is a cross-sectional view of FIG. 7 taken
along the line Y-Y, FIG. 21 иииииииии Permanent magnet 22a, 22b
иииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии ? и и Voice coil Fig. 1 Fig. 2 ?
111 offense 1: ll / D Fig. 3 Fig. 4 (A) (C) Fig. 6 End Page: ?
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