close

Вход

Забыли?

вход по аккаунту

?

JPH066899

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH066899
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of temperature compensation of sound pressure characteristics of an electroacoustic
transducer used as sounding means such as a buzzer for converting an electrical signal to sound.
[0002]
2. Description of the Related Art Conventionally, as shown in FIG. 6, for example, as shown in FIG.
6, a plurality of electromagnetic type electroacoustic transducers having an electromagnetic coil
as driving sources are provided on the inner wall of a cylindrical outer case 2 formed of a
synthetic resin. The rib 3 is provided in the axial direction, and the diaphragm 4 is installed on
the lower side of the rib 3 and orthogonal to the central axis of the outer case 2, and the
resonance chamber 6 and the back surface thereof are mounted on the front part of the
diaphragm 4. A drive source 8 is provided on the side to cause the diaphragm 4 to vibrate. In the
resonance chamber 6, a sound emission hole 10 having a cylindrical shape is formed in a closed
wall surface parallel to the diaphragm 4 of the outer case 2.
[0003]
The drive source 8 is a means for generating an alternating magnetic field in response to an
externally applied drive current through the terminals 12 and 14 and causing the diaphragm 4 to
03-05-2019
1
generate an acoustic vibration by the action of the alternating magnetic field. The diaphragm 4
excited by the drive source 8 is formed of a thin magnetizable thin metal plate, and a disk-shaped
magnetic piece 16 is attached to the central portion thereof. Further, the diaphragm 4 is
magnetically fixed on the edge side in a magnetized state on the upper surface of a cylindrical
magnet 18 incorporated in the exterior case 2. The magnet 18 is firmly fixed to the inside of the
exterior case 2 by a base 20 made of a magnetizable metal which closes the back surface side of
the exterior case 2. A substrate 22 on which terminals 12 and 14 are erected is fixed to the back
surface of the base 20, and an iron core 24 is erected on the central axis of the magnet 18 at the
central portion of the substrate 22 and the base 20. There is. The iron core 24 has a cylindrical
shape, and an air gap 26 is formed between the end face portion and the diaphragm 4 to form a
space allowing magnetic coupling and vibration. A coil 30 is wound around the iron core 24 via a
coil bobbin 28. Terminals 12 and 14 are connected to the coil 30, and a driving current is given
through the terminals 12 and 14 as an input current causing vibration.
[0004]
In such an electroacoustic transducer, it is known that the sound pressure characteristic is
determined mainly by the diaphragm 4 and the resonance chamber 6 due to its structure. The
vibrating plate 4 has a resonance frequency fo as a characteristic value, and the resonance
chamber 6 has a resonance frequency fv as a characteristic value. The resonance frequency fo is
a physical property such as the material and shape of the diaphragm 4, the mass of the magnetic
piece 16, the size of the air gap 26, the magnetic force of the magnet 18, the size of the back
space 32 of the diaphragm 4, and the diameter of the iron core 24. It is decided by various
factors. Also, the resonant frequency fv is
[0006]
It is determined by Equation (1) is a Helmholtz relation, where V is the volume of the resonance
chamber 6, D is the diameter of the sound emission hole 10, L is the length of the sound emission
hole 10, and C is the speed of sound (about 344000 mm / sec). . Therefore, the resonance
frequency fv is determined by the diameter of the sound emission hole 10 and the volume V of
the resonance chamber 6, but if the diameter of the sound emission hole 10 is constant, the
resonance frequency fv is only at the volume V of the resonance chamber 6 It depends on you.
[0007]
03-05-2019
2
Then, in this electro-acoustic transducer, as a countermeasure for increasing the sound pressure
of the resonance frequency fo conventionally, as shown in FIG. 7, the resonance frequency fv is
set to a value twice the resonance frequency fo (fv = 2fo) As shown in FIG. 8, a method of setting
the resonance frequency fv to a value slightly higher than the resonance frequency fo (fv> fo) has
been taken in order to achieve setting of the sound pressure characteristics and broadening of
the sound pressure characteristics. The reproduction frequency fw is set to be in the range of the
resonance frequency fo in the former case and in the range of fo to fv in the latter case.
[0008]
By the way, in this electroacoustic transducer, it is known that the sound pressure characteristic
largely changes depending on the temperature, and the following characteristic change factors
can be mentioned. a. The coil 30 forming the center of the drive source 8 is a wound copper
wire or the like, so the internal resistance increases when the temperature is high. As a result, the
current decreases and the generated magnetic field decreases, and the driving force of the
diaphragm 4 Decreases. The opposite is true at low temperatures. b. At high temperatures, the
external dimensions of the magnet 18 having a magnetic relationship with the iron core 24
wound with the coil 30 change, so that the air gap 26 forming a part of the magnetic circuit
increases and the magnetic efficiency deteriorates, particularly, The use of a plastic magnet as
the magnet 18 is significant. Conversely, at low temperatures, the magnetic efficiency is high.
c. At high temperatures, the magnetic force of the magnet 18 decreases, and at low
temperatures, the magnetic force tends to increase.
[0009]
Therefore, the resonant frequency fo decreases at high temperature, and the resonant frequency
fo increases at low temperature due to a factor opposite to that at high temperature.
[0010]
Further, at the resonance frequency fv, the shape and size of the outer case 2 change depending
on the temperature, so the resonance frequency fv also depends on the temperature, and has a
characteristic of rising at high temperature and decreasing at low temperature.
[0011]
03-05-2019
3
Looking at such temperature changes of the resonance frequencies fo and fv for the frequency
setting (fv = 2fo) shown in FIG. 7, as shown in FIG. 9, the normal temperature (TH = 85 ° C.) The
resonant frequency fo at Ts = 25 ° C. shifts to foH (<fo), and the resonant frequency fv at
normal temperature shifts to fvH (> fv).
In this case, the frequency interval fov at normal temperature is expanded to fovH (> fov), and
the sound pressure is significantly reduced due to the factors a, b and c.
At low temperature (TL = −40 ° C.), the resonance frequency fo at normal temperature shifts to
foL (> fo), and the resonance frequency fv at normal temperature shifts to fvL (<fv). In this case,
the frequency interval fov at normal temperature is reduced to fovL (<fov), and the sound
pressure significantly increases. In this case, the sound pressure at the reproduction frequency
fw causes a significant sound pressure change of 10 dB or more, which is disadvantageous in
that a necessary and sufficient sound output can not be obtained.
[0012]
Further, the temperature change of the resonance frequencies fo and fv similarly occurs in the
case of the frequency setting shown in FIG. 8, and as shown in FIG. 10, at high temperature (TH =
85.degree. C.), resonance at normal temperature Since the frequency fo shifts to foH (<fo) and the
resonance frequency fv shifts to fvH (> fv) at normal temperature (Ts = 25 ° C.), the frequency
interval fov is expanded to fovH (> fov) The pressure drops significantly. At low temperature (TL
= -40 ° C), the resonance frequency fo at normal temperature shifts to foL (> fo), and the
resonance frequency fv at normal temperature shifts to fvL (<fv), at normal temperature The
frequency interval fov of is reduced to fovL (<fov), and the sound pressure is significantly
increased. Also in this case, the sound pressure at the reproduction frequency fw has a
disadvantage that a significant sound pressure change of 10 dB or more occurs.
[0013]
FIG. 11 shows sound pressure characteristics of the conventional electroacoustic transducer,
wherein Ts is at 25 DEG C., TH is at 85 DEG C., and TL is at -40 DEG C. FIG. FIG. 12 shows coil
current characteristics in that case, where Ts is 25 ° C., TH is 85 ° C., and TL is −40 ° C. In
this case, the sound pressure fluctuation at temperature changes of −40 ° C. and 85 ° C. is
about 10 dB in the reproduction frequency range fw (2 kHz to 3 kHz).
03-05-2019
4
[0014]
As described above, in the conventional electroacoustic transducer, the sound pressure
characteristic changes with temperature, and there is a disadvantage in that it can be perceived
appreciably depending on the use environment or the season in terms of hearing.
[0015]
Therefore, it is an object of the present invention to provide a temperature compensation method
of sound pressure characteristics of an electroacoustic transducer in which temperature
variations of sound pressure characteristics are compensated by utilizing such a change tendency
of resonant frequencies fo and fv with temperature. To aim.
[0016]
In the electroacoustic transducer of the present invention, a diaphragm (4) is provided in an
outer case (2), and a resonance chamber (6) is provided on the front side of the diaphragm. In
the electroacoustic transducer, a drive source (8) is installed on the back side, the diaphragm
vibrates by the drive source, and the vibration sound of the diaphragm is emitted through the
resonance chamber, wherein the resonance frequency of the resonance chamber It is
characterized in that (fv) is set to be lower than the resonance frequency (fo) of the diaphragm
(fo> fv).
[0017]
The magnitude relation (fo> fv) of the resonance frequency fo of the diaphragm and the
resonance frequency fv of the resonance chamber is set based on the normal temperature.
The resonance frequency fv tends to rise at high temperature and fall at low temperature, and
the resonance frequency fo tends to decrease at high temperature and rise at low temperature.
When the temperature is high, the sound pressure is lowered due to the reduction of the
magnetic driving force, and when the temperature is low, the sound pressure tends to be
increased due to the improvement of the magnetic driving force.
03-05-2019
5
If the resonance frequency fv is set lower than the resonance frequency fo based on the increase
/ decrease relationship of the resonance frequency and the sound pressure due to such
temperature, the frequency interval narrows at high temperature and the sound pressure
decreases due to the decrease of the magnetic driving force The decrease and the increase in
sound pressure due to the narrowing of the frequency interval are offset to compensate for the
decrease in sound pressure. Also, at low temperatures, the frequency interval is expanded, and
the sound pressure is enhanced by the improvement of the magnetic driving force, but the
increase and the sound pressure decrease due to the expansion of the frequency interval are
offset, and the increase in sound pressure is compensated. Ru. That is, the tendency of
enlargement and reduction of the interval of the resonance frequency is opposite to that of the
conventional one, and the change of the sound pressure due to the change of the frequency
interval and the change of the sound pressure due to the increase and decrease of the magnetic
driving force cancel each other. Sound pressure characteristics small enough to ignore
temperature changes can be obtained.
[0018]
The invention will now be described in detail with reference to the embodiments shown in the
drawings.
[0019]
FIG. 1 shows an embodiment of a temperature compensation method of sound pressure
characteristics of the electroacoustic transducer of the present invention.
In this electro-acoustic transducer, a resonant frequency fo and a resonant frequency fv exist as
characteristic values, but the magnitude relationship of these is set as fo> fv as a method of
compensating the sound pressure characteristic.
[0020]
The magnitude relationship between the resonance frequencies fo and fv is set at normal
temperature, and for example, is set to a value such that the magnitude relationship between the
two does not reverse due to temperature change. The method of setting such resonance
frequencies fo and fv is as follows: material and shape of diaphragm 4, mass of magnetic piece
16, size of air gap 26, magnetic force of magnet 18, size of back space 32 of diaphragm 4, iron
03-05-2019
6
core The resonance frequency fo is determined by physical factors such as the diameter of 24
and the fact that the resonance frequency fv is determined by equation (1) is used. In particular,
the resonance frequency fv is adjusted by the volume of the resonance chamber 6.
[0021]
Thus, when the resonant frequencies fv and fo are set to fo> fv, the resonant frequency fv rises at
high temperature (= TH) to become fvH (> fv) and decreases at low temperature (= TL) fvL (<fv)
Further, the resonance frequency fo decreases at high temperature to become foH (<fo), and rises
at low temperature to become foL (> fo). Such a relationship is a characteristic of this type of
electroacoustic transducer, and changes in the resonance frequencies fv and fo are as described
with reference to FIGS. 9 and 10, and the resonance frequencies fv and fo have fo> fv Even if the
relationship is set, the relationship is established similarly.
[0022]
Then, when fo> fv, if the resonance frequency fv is fvH (> fv) and the resonance frequency fo is
foH (<fo) at high temperature (= TH), the resonance frequencies fo and fv approach each other
and the frequency interval between the two fovH is smaller than the frequency interval fov at
normal temperature.
[0023]
At this time, referring to the electro-acoustic transducer of FIG. 6, the sound pressure is lowered
due to the decrease of the magnetic driving force at high temperature due to the factors a, b and
c, but the resonance frequencies fo and fv are increased or decreased due to increase or decrease
Since the interval is fovH and the frequency interval is reduced from fov (fov> fovH), sound
pressure is enhanced in characteristics.
In other words, since the increase of the sound pressure due to the reduction of the frequency
interval and the decrease of the sound pressure due to the decrease of the magnetic driving force
offset each other, the remarkable reduction of the sound pressure as in the prior art is
suppressed.
[0024]
03-05-2019
7
When the resonant frequency fv is fvL (<fv) and the resonant frequency fo is foL (> fo) at low
temperatures (= TL), the resonant frequencies fo and fv are separated due to their increase and
decrease, and the frequency interval fovL between them is at normal temperature The frequency
interval fov of
[0025]
At this time, in the electro-acoustic transducer shown in FIG. 6, as a result of the magnetic driving
force becoming high due to the factors a, b and c, the sound pressure is increased.
By increasing or decreasing the resonance frequencies fo and fv, the frequency interval between
the two becomes fovL, and the sound pressure is reduced in terms of characteristics because it is
wider than the frequency interval fov (fov <fovL). Since the decrease in sound pressure due to the
expansion of the frequency interval and the increase in sound pressure due to the increase in
magnetic driving force offset each other, a significant increase in sound pressure as in the prior
art is suppressed.
[0026]
By setting fo> fv in this way, the temperature change of the sound pressure is compensated, and
the change of the sound pressure characteristic due to the temperature in the reproduction
frequency range can be made as small as negligible.
[0027]
Next, FIG. 2 shows an electro-acoustic transducer which is a specific embodiment of the method
of temperature compensation of sound pressure characteristics of the electro-acoustic transducer
of the present invention.
This electro-acoustic transducer has the same structure as the electro-acoustic transducer shown
in FIG. 6, and the same reference numerals are given to the same parts.
[0028]
03-05-2019
8
Comparing this electro-acoustic transducer with the shape of the conventional electro-acoustic
transducer shown in FIG. 6, as shown in FIG. 3, although the diameter (= a) of the exterior case 2
is set to be the same, The height b1 of the case 2 is small, and the volume ratio of the resonance
chamber 6 in the outer case 2, that is, the height c1 is set large. The height d1 of the magnet 18
is set low, and the inner diameter e1 thereof is set large. b2, c2, d2, and e2 indicate
corresponding portions of the conventional electroacoustic transducer, and the magnitude
relationship is b1 <b2, c1> c2, d1 <d2, e1> e2.
[0029]
As described above, by increasing the volume ratio of the resonance chamber 6 in the outer case
2, the resonance frequency fv can be significantly reduced as compared with the conventional
case, and the relationship of fo> fv can be easily set. In the electroacoustic transducer in which
such a relationship is set, the sound pressure characteristics with respect to the temperature
shown in FIG. 1 are obtained, and the temperature is set to TL = -40 ° C, Ts = 25 ° C, TH = 85
° C In the case, it was confirmed that the sound pressure fluctuation was about 1 dB which was
negligible.
[0030]
FIG. 4 shows the sound pressure characteristics of the electroacoustic transducer in which the
relationship of fo> fv is set, and FIG. 5 shows the coil current characteristics. When the
temperature is set to TL = -40 ° C, Ts = 25 ° C, TH = 85 ° C, the temperature change of the
sound pressure characteristic of the reproduction frequency band fw (= 1.7 kHz to 2.2 kHz) is
about 1 dB It can be seen that the temperature change of the sound pressure characteristic is
compensated, suppressing to a negligible change.
[0031]
As described above, according to the present invention, by setting the resonance chamber
resonance frequency lower than the diaphragm resonance frequency, the change in the sound
pressure characteristic due to the temperature is compensated, and the temperature is stabilized
regardless of the temperature. Sound pressure can be obtained, and stable sound pressure
characteristics can be realized even in the case of using a plastic magnet whose characteristic
changes significantly with temperature.
03-05-2019
9
03-05-2019
10
Документ
Категория
Без категории
Просмотров
0
Размер файла
19 Кб
Теги
jph066899
1/--страниц
Пожаловаться на содержимое документа