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DESCRIPTION JP2004080198

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DESCRIPTION JP2004080198
An electro-acoustic transducer for driving a piezoelectric diaphragm with an audio signal or a
music signal, transmitting vibration to the head of a listener by a vibration transmitting member
attached to the piezoelectric diaphragm, and making the listener listen as sound. We propose a
structure that is prone to low frequency vibration. An outer edge of a piezoelectric diaphragm 2
is sandwiched by a polymer gel material having a Young's modulus of 10 kPa to 10 kPa and
mounted in a cylindrical casing 1 and at the center of at least one vibration surface of the
piezoelectric diaphragm 2. The vibration transmitting member is mounted, and the elastic
vibration area of the piezoelectric diaphragm is expanded by the elastic deformation of the
polymer gel material 5 to make it possible to vibrate even a low frequency. [Selected figure]
Figure 1
Electro-acoustic transducer
FIELD OF THE INVENTION The present invention relates to an electroacoustic transducer
intended to vibrate the skull and to generate sound waves. 2. Description of the Related Art A
bone conduction type electroacoustic transducer which converts a voice signal or a music signal
into a vibration and vibrates a skull to hear the signal as a sound is used for the hearing impaired
and for the elderly. It is put to practical use for the disabled. In addition, there is an example that
is practically used for hearing people. Conventional electro-acoustic transducers of this type used
a large number of parts and were large in size and used magnets, while electro-dynamic type
consisting of magnets and electric coils was often used as a drive system. At present, an electroacoustic transducer using a piezoelectric element is widely used because of the disadvantage that
the weight is increased. FIG. 7 shows the structure of a conventional bone-conduction type
electroacoustic transducer using a piezoelectric element. In the figure, 1 is a cylindrical casing
whose one end is closed, 2 is a piezoelectric diaphragm, 3 is a holder for mounting the
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piezoelectric diaphragm 2 inside the casing 1, and 4 is a vibration of the piezoelectric diaphragm
2. And a vibration transmitting member for transmitting the sound to the listener's head. The
housing 1 is formed of a cylindrical cylindrical body whose one opening surface is closed by the
bottom plate 1A, and the piezoelectric diaphragm 2 is mounted inside. The outer peripheral edge
of the piezoelectric diaphragm 2 is held by a ring-shaped holding member 3 formed of hard
plastic, and a housing is formed by a pressure contact force of the lid 1B (the lid 1B is fixed to the
housing 1 with an adhesive or the like). It is fixed in 1 and supported so that the central part can
vibrate freely. The vibration transmitting member 4 is attached to the central portion of the
piezoelectric diaphragm 2, and the vibration transmitting member 4 is inserted into the housing
1 through a circular hole 1 B-1 formed in the lid 1 B closing the opening surface of the housing
1. It is projected outside. An enlarged portion 4A having a large diameter is formed at the end of
the vibration transfer member 4, and the end side of the expanded portion 4A is an arc surface
4B, and this arc surface 4B is pressed against the head of the listener. The vibration of the
piezoelectric diaphragm 2 is shown in FIG. Conventionally, since the outer peripheral edge of the
piezoelectric diaphragm 2 is sandwiched and fixed by the holder 3 formed of hard plastic, the
piezoelectric diaphragm 2 vibrates with the peripheral edge fixed. SUMMARY OF THE
INVENTION In the conventional bone conduction type electroacoustic transducer using the
piezoelectric diaphragm, the edge of the piezoelectric diaphragm 2 is fixed because the edge of
the piezoelectric diaphragm 2 is fixed. It does not move. As a result, the effective vibration area of
the piezoelectric diaphragm 2 becomes narrow, and there is a first problem that it is difficult to
output low frequency vibrations. In the conventional bone conduction type electroacoustic
transducer using a voltage diaphragm, there is a second problem that a single piezoelectric
diaphragm does not produce a sufficient output to produce vibration.
A first object of the present invention is to provide an electroacoustic transducer capable of
sufficiently reproducing low frequency sound in a bone conduction type electroacoustic
transducer using a piezoelectric diaphragm. A second object of the present invention is to
provide a high-power electroacoustic transducer. According to the present invention, there is
provided a piezoelectric diaphragm having an outer edge thereof sandwiched by a polymer gel
material having a Young's modulus of 10 kPa to 10 <3> kPa in a housing, and a piezoelectric
diaphragm of the piezoelectric diaphragm. An electroacoustic transducer is proposed having a
vibration transfer member at the center of at least one vibration plane. In the present invention,
the second piezoelectric diaphragm is further sandwiched between the first piezoelectric
diaphragm and a polymer gel material having a Young's modulus of 10 kPa to 10 <3> kPa as in
the case of the first piezoelectric diaphragm. A connecting member is sandwiched between the
central portion of the other vibration surface of the diaphragm and the central portion of the one
vibration surface of the second piezoelectric diaphragm, and the plurality of piezoelectric
diaphragms excite the common vibration transmitting member. We propose an acoustic
transducer. According to the electro-acoustic transducer of the present invention, since the
piezoelectric diaphragm is used as the excitation system, it can be constituted only by the
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piezoelectric diaphragm and its holding parts. This makes it possible to reduce the size and
weight. In particular, according to the present invention, since the outer edge of the piezoelectric
diaphragm is sandwiched by a polymer gel material having a Young's modulus of 10 kPa to 10
<3> kPa, the portion of the piezoelectric diaphragm sandwiched by the polymer gel material is
also deformed It can vibrate. As a result, the effective vibration area of the diaphragm is
increased, the output of low frequency is increased, and the first problem can be solved.
Furthermore, according to the present invention, since a plurality of piezoelectric vibration plates
are connected by the connecting member to excite the common vibration transmitting member,
high output can be achieved. This can solve the second problem. DESCRIPTION OF THE
PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an electroacoustic transducer
according to the present invention. FIG. 1A shows a cross section along the YY line shown in FIG.
1B, and FIG. 1B shows a cross section along the XX line shown in FIG. 1A. The housing 1 can be
made of, for example, a hard plastic, and is formed in a tubular shape having an inner diameter of
about 15 to 25 mm. One opening surface of the housing 1 is closed by the bottom plate 1A, and
the lid 1B is bonded and closed with an adhesive on the other opening surface. The cylindrical
portion of the housing 1 and the bottom plate 1A are integrally formed of hard plastic such as
ABS resin. The cylindrical portion and the bottom plate 1A are selected to have a thickness that
does not resonate with the sound waves generated by the drive of the piezoelectric diaphragm 2
stored inside, for example, a thickness of about 3 to 5 mm to obtain strength as a housing Be
done.
Similarly, the lid 1B is selected to have a strength as a housing and a thickness not to resonate
with a sound wave generated by the drive of the piezoelectric diaphragm 2, about 2 to 3 mm.
Further, the lid 1B is bonded to the open end face of the cylindrical portion constituting the
housing 1 with an adhesive that generates strength of the housing and an adhesive strength that
does not resonate with sound waves generated by the drive of the piezoelectric diaphragm 2. Ru.
The piezoelectric diaphragm 2 is formed of a ceramic disk having a diameter of about 15 to 25
mm and a thickness of about 2 to 3 mm. In the present invention, the polymer gel material 5
having a Young's modulus of 10 kPa to 10 <3> kPa is applied to both surfaces of the outer edge
of the piezoelectric diaphragm 2, and the outer edge of the piezoelectric diaphragm 2 is held by
the polymer gel material 5. For example, silicone gel can be used as the polymer gel material 5,
and the polymer gel material 5 is applied from the outer edge of the piezoelectric diaphragm 2 to
a width of about 2 to 5 mm. The thickness is set to about 2 to 4 mm, and the thickness of the
polymer gel material 5 is set such that the sum of the thicknesses of the piezoelectric diaphragm
2 and the polymer gel material 5 is slightly larger than the dimension H in the depth direction of
the housing 1 Do. The vibration transfer member 4 is mounted at a substantially central position
of the surface of the piezoelectric diaphragm 2 facing the lid 1 B. The vibration transfer member
4 can be made of a hard plastic such as ABS resin as in the case 1 and has a total length of about
10 to 20 mm and a cylindrical shape of about 5 to 9 mm in diameter. An adhesive is applied to
one end face of the vibration transfer member 4, and the vibration transfer member 4 is bonded
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to the central portion of the piezoelectric diaphragm 2 with this adhesive. The adhesive used
here is firmly connected between the piezoelectric diaphragm 2 and the vibration transmitting
member 4 in a cured state, but the piezoelectric diaphragm 2 has a characteristic that it can be
deformed following the deformation. For example, use is made of a pressure-sensitive rubberbased adhesive that increases adhesion by compressive force. A circular hole 1B-1 having a
diameter of, for example, about 10 to 15 mm larger than the diameter of the vibration
transmitting member 4 is formed in a central portion of the lid 1B for closing one end side of the
housing 1 through the circular hole 1B-1. The tip of the vibration transfer member 4 is projected
to the outside of the housing 1. At the tip of the vibration transfer member 4, an enlarged portion
4 </ b> A having a diameter about 2 to 3 times larger than the diameter of the vibration transfer
member 4 is formed. An arc surface 4B is formed on the tip end side of the enlarged portion 4A,
and this arc surface 4B is brought into contact with the head of the listener. FIG. 2 shows an
example of a state in which the electro-acoustic transducer according to the present invention is
mounted on the head of the listener. For example, a headband 6 formed of an elastic resin is
attached between the side portions of the listener. The head band 6 resiliently applies pressure to
both side heads of the listener due to its spring property.
The electroacoustic transducer 10 according to the present invention is attached to one end or
both ends of the headband 6. On the side shown in FIG. 2, for example, a support rod 7 having a
diameter of about 7 to 10 mm and a length of about 10 to 20 mm is integrally formed integrally
with the same material as the housing 1 on the peripheral surface of the housing 1 The
electroacoustic transducer 10 is attached to the headband 6 by connecting the connecting lever
8 to the end of the headband 6 with the connecting lever 8. The electroacoustic transducer 10 is
in pressure contact with the side of the listener by the elasticity of the headband 6, and the
pressure of the pressure contact causes the tip of the vibration transfer member 4 to be in
pressure contact with the side of the listener. By exciting the piezoelectric diaphragm 2 in this
state, the vibration is transmitted to the skull of the listener through the vibration transfer
member 4, and the listener can hear the vibration as a sound. FIG. 3 shows a modified
embodiment of the present invention. In the embodiment shown in FIG. 3, a shock absorbing
material having high vibration absorbing property is provided along a lid 1B closing one opening
face of the housing 1. A sealing elastic material 9 made of rubber and having a thickness of about
1 to 3 mm is adhered with an adhesive, and the sealing elastic material 9 is used to close the gap
G generated between the lid 1B and the vibration transmitting member 4 In addition, four
grooves 11 are formed in the longitudinal direction on the inner circumferential surface of the
housing 1, for example, at intervals of 90.degree. In the circumferential direction, and the nonadhered surface of the polymer gel material 5 is aligned with each position of the grooves 11. 12,
a chamber RO1 formed between the front side of the piezoelectric diaphragm 2 and the lid 1B, a
chamber RO2 formed between the back side of the piezoelectric diaphragm 2 and the bottom
plate 1B, the groove 11 and the polymer The case where it is set as the structure made to
connect by the space | gap formed of the non-adhesion surface 12 of the gel material 5 is shown.
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The sealing elastic member 9 is in contact with the peripheral surface of the vibration
transmitting member 4 and the contact portion is displaced following the vibration of the
vibration transmitting member 4 by the contact frictional resistance, and the vibration
transmitting member 4 and the sealing elastic member 9 It has a structure in which no friction
occurs. By blocking the gap G formed between the vibration transmitting member 4 and the edge
of the circular hole 1B-1 formed in the lid 1B with the sealing elastic material 9, the sound is
prevented from leaking to the outside Can. Furthermore, in this embodiment, the chambers RO1
and RO2 formed on the front and back sides of the piezoelectric diaphragm 2 are communicated
by the gaps formed by the grooves 11 and the non-adhered surface 12 of the polymer gel
material 5, Since air can flow between the two chambers RO1 and RO2 formed in the housing 1
when the piezoelectric diaphragm 2 vibrates, the pressure of the air in the two chambers is kept
constant and the piezoelectric diaphragm It is possible to prevent disturbing the vibration of 2.
That is, in this embodiment, since the gap G existing between the lid 1 B and the vibration
transmitting member 4 is closed by the sealing elastic material 9, the inside of the case 1 is
sealed.
For this reason, when one of the two air pressures formed inside the housing 1 decreases while
the piezoelectric diaphragm 2 vibrates, the other repeatedly repeats a rising change, so that the
piezoelectric diaphragm 2 vibrates due to air resistance. There is the disadvantage of being
blocked and causing a drop in power. Therefore, by connecting the two chambers RO1 and RO2
in the case 1 by the gap formed by the groove 11 and the non-adhered surface of the polymer
gel material 5 as in this embodiment, the air resistance is reduced, It can be vibrated at high
output. FIG. 4 shows how the piezoelectric diaphragm 2 used in the electroacoustic transducer
according to the present invention vibrates. As shown in FIG. 4, according to the present
invention, since the piezoelectric diaphragm 2 is sandwiched by the polymer gel material 5
having a Young's modulus of 10 kPa to 10 <3> kPa, the piezoelectric diaphragm 2 is sandwiched
by the polymer gel material 5 Can also vibrate. As a result, the effective vibration area is
increased, and low frequency vibrations can be output more efficiently. When the polymer gel
material 5 is too hard, the vibration of the piezoelectric diaphragm 2 is hindered. When it is too
soft, when the vibration transmitting member 4 is pressed against the human body, it collapses
and the piezoelectric diaphragm 2 is pressed against the bottom plate 1A. Vibration may not be
possible. For this reason, it is desirable that the polymer gel material 5 have a Young's modulus
of 10 kPa to 10 <3> kPa. FIG. 5 shows still another modified embodiment of the present
invention. In this embodiment, two piezoelectric diaphragms 2 are disposed in the case 1 and the
two piezoelectric diaphragms 2 are connected to each other by the connecting member 13 to
excite the common vibration transmitting member 4. Show. The connection member 13 can be
made of a hard plastic or the like such as ABS resin as the vibration transfer member 4. The two
piezoelectric diaphragms 2 are held and held by the polymer gel material 5 at an interval of, for
example, about 2 to 4 mm, and stored in the housing 1. The connecting member 13 is cut to the
same length as the facing distance between the two piezoelectric diaphragms 2 and both end
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surfaces thereof are bonded to the other surface and one surface of the piezoelectric diaphragm
2 by an adhesive. With this structure, by driving the two piezoelectric diaphragms 2 in phase, the
excitation force of the vibration transfer member 4 is doubled, and a strong excitation force can
be obtained. 6 shows a structure in which the sealing elastic material 9 is attached to the
embodiment shown in FIG. 5, and as shown in FIG. 6A and FIG. An embodiment is shown in
which the three chambers RO1 and RO2 and RO3 which are partitioned by the piezoelectric
diaphragm 2 having the non-adhered surface 12 of the polymer gel material 5 communicate with
each other.
By these structures, it is possible to prevent the leakage of sound, and it is possible to eliminate
the reduction of the output generated by the air resistance in the housing 1. In the embodiment
shown in FIGS. 5 and 6, an example in which two piezoelectric diaphragms 2 are provided in the
housing 1 has been described, but it is further connected to the first piezoelectric diaphragm of
the second piezoelectric diaphragm. A third piezoelectric diaphragm can be provided by
sandwiching the connecting member on the opposite surface. As described above, according to
the present invention, since the supporting portion of the piezoelectric diaphragm 2 can also be
vibrated, it is possible to produce low frequency vibration, and it is possible to obtain a wide
band bone conduction. An earphone can be realized. Further, according to the present invention,
by employing a structure in which a plurality of piezoelectric diaphragms are connected and
driven, higher output vibration can be obtained even when driven with the same input level as
compared with the case of one piezoelectric diaphragm. Can. BRIEF DESCRIPTION OF THE
DRAWINGS FIG. 1A is an enlarged cross-sectional view taken along the line Y-Y shown in FIG. B
for describing an embodiment of the present invention, and B is an XX shown in FIG. The
expanded sectional view on a line. FIG. 2 is a perspective view for explaining a situation where
the electro-acoustic transducer according to the present invention is attached to a listener. 3A is
an enlarged cross-sectional view taken along the line Y-Y shown in FIG. 3B, and FIG. 3B is an
enlarged cross-sectional view taken along the line X-X shown in FIG. FIG. 4 is an enlarged crosssectional view for explaining the operation of the piezoelectric diaphragm used in the present
invention. FIG. 5 is an enlarged sectional view for explaining still another modified embodiment
of the present invention. 6A is an enlarged cross-sectional view taken along the line YY shown in
FIG. 6B showing another embodiment of the embodiment shown in FIG. 5; B is the expanded
sectional view on the XX line shown to the figure A. FIG. 7 is an enlarged cross-sectional view for
explaining the prior art. FIG. 8 is an enlarged cross-sectional view for explaining a conventional
electroacoustic transducer. [Description of the code] 1 case 5 polymer gel material 1A bottom
plate 6 headband 1B lid 7 support rod 2 piezoelectric diaphragm 8 connecting rod 3 holder 10
electroacoustic transducer 4 vibration transmitting member 11 groove 4A enlarged portion 13
connected Member 4B Arc face
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