JP2017005413

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DESCRIPTION JP2017005413
PROBLEM TO BE SOLVED: To use a headphone for driving a voice coil so as to interfere each
other signal without using a buffer structure when mechanically coupling a headphone unit to a
housing and requiring two signal inputs. Provide a diaphragm that can SOLUTION: The
diaphragm 100 is provided with a main dome 101 and a sub dome 102 integrally connected
around the main dome 101, and the piezoelectric film 120 is formed on at least one surface side
of the sub dome 102. . [Selected figure] Figure 1
Diaphragm, dynamic speaker, headphone unit and headphones
[0001]
The present invention relates to a diaphragm, an electrodynamic speaker including the
diaphragm, a headphone unit, and a headphone.
[0002]
Noise-cancelled headphones are known that allow the user to hear only the music by canceling
the noise that tries to enter the user's ear listening to the music.
According to the noise cancellation method conventionally known, a microphone attached to a
headphone detects ambient noise and generates and outputs a signal in reverse phase. The signal
of the opposite phase is a signal for canceling noise and is called a noise cancellation signal. A
general headphone is provided with a pair of headphone units, but the same is true for the noise
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cancellation method.
[0003]
The conventional noise cancellation type headphone unit inputs a signal obtained by combining a
music signal (audio signal) and a noise cancellation signal to the voice coil of the speaker unit.
Two power amplifiers are connected in parallel to one voice coil if power amplifiers for an audio
signal and a noise cancellation signal are separately arranged at the previous stage of inputting a
composite signal of two signals to the voice coil. It will be. In this configuration, the power
amplifiers may load each other, adversely affect sound quality, and so on. In addition, in the
configuration in which the voice coil is driven through one power amplifier after combining the
audio signal and the noise cancellation signal, the sound quality may be degraded because the
two signals are combined (MIX). .
[0004]
A structure for reducing the mechanical load of the diaphragm is known as one for improving the
characteristics of the speaker unit mounted on the headphone unit (see, for example, Patent
Document 1). In addition, in the noise cancellation type headphone unit, the electrical coupling
relationship including the magnetic coupling between the noise cancellation signal and the audio
signal and the electrostatic coupling is made as shallow as possible to reduce the influence of the
noise cancellation signal on the audio signal. A headphone unit is known (see, for example,
Patent Document 2).
[0005]
Japanese Patent Application Laid-Open No. 51-151121 Japanese Patent Application Laid-Open
No. 2008-99127
[0006]
The configuration described in Patent Document 1 or Patent Document 2 requires a buffer
structure that reduces the mechanical coupling between the diaphragm of the speaker unit and
the structure for fixing the diaphragm.
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In addition, since the diaphragm is driven using a signal obtained by combining two electrical
signals, mutual interference between the audio signal and the noise cancellation signal may
occur, which may lead to the deterioration of the sound quality.
[0007]
When providing a buffer structure, it is necessary to use an elastic body that does not pass sound
waves around the headphone unit in order to maintain mechanical coupling between the
headphone unit and the headphone case. Further, a structure that interferes with the audio signal
path of the headphone unit is not desirable, and it is desirable that a driving force for driving the
diaphragm by the noise cancellation signal can be applied without causing the interference.
[0008]
The present invention combines independent signals in the diaphragm without providing a
structure that affects the sound quality around the headphone unit and including an independent
input system so that the audio signal and the noise cancellation signal do not interfere with each
other, An object of the present invention is to provide a diaphragm that can output sound waves.
[0009]
The present invention is a diaphragm including a main dome and a sub dome continuing around
the main dome, and is characterized mainly in that a piezoelectric film is formed on at least one
surface side of the sub dome.
[0010]
According to the present invention, an independent input system is provided so that an audio
signal and a noise cancel signal do not interfere with each other without providing a structure
that affects the sound quality around the headphone unit, and different signals are combined in
the diaphragm. Can be output as sound waves.
[0011]
It is a longitudinal cross-sectional view which shows the example of the headphone unit which
concerns on this invention.
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It is a top view which shows the example of the diaphragm with which the said headphone unit is
equipped.
It is a longitudinal cross-sectional view which shows the example of a part of diaphragm provided
in the said headphone unit.
It is a longitudinal cross-sectional view which shows the example of the diaphragm with which
the said headphone unit is equipped.
[0012]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. In the drawings used for the following description, the headphone housing for fixing
the baffle plate included in the headphone unit 200 and the ear pads fixed to the peripheral edge
on the front side of the baffle plate are omitted. The headphone unit 200 shown in FIG. 1 outputs
a sound wave in the left direction on the paper surface. When the user uses headphones
provided with a pair of left and right headphone units 200, the outer end face of the ear pad is in
contact with the side of the head of the user, and the user's ear is positioned in the space
surrounded by the ear pad.
[0013]
The headphone unit 200 includes a diaphragm 100 having a characteristic structure, a voice coil
201 fixed to the diaphragm 100, a magnetic circuit having a gap into which the voice coil 201
enters, and a frame 205 for holding the magnetic circuit. And a speaker unit. This speaker unit is
a so-called electrodynamic speaker unit, which causes a current to flow through a voice signal to
a voice coil 201 disposed in a magnetic field produced by a magnetic circuit having a permanent
magnet, and the diaphragm 100 is directed in a predetermined direction. The tone signal is
changed to a sound wave. The magnetic circuit is configured by the pole piece 202, the magnet
203, and the yoke 204. The detailed structure of the diaphragm 100 will be described later.
[0014]
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The voice coil 201 is a coil formed by winding a wire through which an audio signal input from
the sound source device 301 flows in a cylindrical shape. A signal input wiring 302 is connected
to the voice coil 201. An audio signal from the sound source device 301 is input to the voice coil
201 via the signal input wiring 302.
[0015]
A gap (magnetic gap) of the magnetic circuit in which the voice coil 201 is disposed is formed by
the pole piece 202 and the flat petri dish yoke 204. A flat magnet 203 is fixed to the center of
the inner bottom of the yoke 204, and a plate-like pole piece 202 is fixed to the end face of the
magnet 203 fixed to the yoke 204.
[0016]
The open end face of the yoke 204 and the end face of the pole piece 202 are substantially in the
same plane, and a ring-shaped magnetic gap is formed between the outer peripheral surface of
the pole piece 202 and the open end inner peripheral surface of the yoke 204. It is done. The
voice coil 201 is adapted to be held in a state of entering into the magnetic gap. Since a magnetic
field originating from the magnet 203 is generated in the magnetic gap, the voice coil 201 is
present in the magnetic field.
[0017]
The frame 205 is a flat petri dish shaped member having a function of holding the diaphragm
100 and the magnetic circuit, and the yoke 204 is fitted and fixed in a hole formed in the central
portion. Thereby, the magnetic circuit is fixed to the central portion of the frame 205. The outer
peripheral end of the diaphragm 100 is fixed to the outer peripheral edge of the frame 205 as
described later. The frame 205 is attached to a baffle plate (not shown).
[0018]
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The diaphragm 100 includes a main dome 101 and a sub dome 102 which is a peripheral
portion surrounding the main dome 101 and has an arched cross section. The outer periphery of
the sub dome 102 is fixed to the frame 205. As a result, the voice coil 201 is held at a
predetermined position in the state shown above, and the diaphragm 100 is supported so as to
be able to vibrate in the front-rear direction (in the left-right direction in the drawing). One end of
the voice coil 201 is fixed in a cantilever manner to the boundary between the main dome 101
and the sub dome 102 of the diaphragm 100, and the voice coil 201 supports the voice coil 201
so as not to contact the yoke 204 or the pole piece 202. It is done.
[0019]
When an audio signal is input from the external sound source device 301 (for example, a music
player) to the voice coil 201 via the signal input wiring 302, the voice coil 201 vibrates in the
front-rear direction according to the audio signal, and voice corresponding to this vibration Is
output.
[0020]
Here, the diaphragm 100 will be described in more detail.
As shown in FIG. 2, the diaphragm 100 has a circular planar shape when viewed from the front
direction. The front direction refers to a direction in which the voice coil 201 is driven to emit a
sound wave when an electric signal is input to the voice coil 201 of the diaphragm 100. As
shown in FIG. 2, the diaphragm 100 has a main dome 101 at the central portion, and a
doughnut-shaped sub dome 102 is formed to surround the main dome 101. The voice coil 201 is
disposed at the boundary between the main dome 101 and the sub dome 102.
[0021]
FIG. 3 is a view showing an example of the longitudinal sectional shape when the diaphragm 100
is viewed from the direction orthogonal to the vibration direction. The diaphragm 100 is
obtained by processing a thin film-like member into a predetermined form. The diaphragm 100
is formed by heating and pressing a film having a thickness of about 25 μm to form the main
dome 101 and the sub dome 102. Each of the main dome 101 and the sub dome 102 has an
arch shape raised in the front direction.
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[0022]
FIG. 4 is a view showing a state in which the piezoelectric film 120 is formed on the diaphragm
100. As shown in FIG. 4, a piezoelectric film 120 is formed on the front surface of the sub dome
102. The piezoelectric film 120 is a kind of piezoelectric element that is displaced when an
electric field is applied, and is a thin film formed on the surface of the film-like diaphragm 100,
and constitutes a piezoelectric acting portion in the diaphragm 100. Metal deposition is
performed on both sides of the piezoelectric film 120 to form two electrodes, and a wire for
applying a noise cancellation signal is connected to the electrodes.
[0023]
When an electric field is applied to the piezoelectric film 120, it expands and contracts in the
area direction according to the electric field. When an electric field is applied to the piezoelectric
film 120, a force is applied to the surface of the sub dome 102 in accordance with the expansion
and contraction of the piezoelectric film 120. In the diaphragm 100 shown in FIG. 4, the
piezoelectric film 120 is formed only on the front side of the sub dome 102, but may be formed
on the back side or may be formed on both sides of the sub dome 102.
[0024]
Return to FIG. The material of the diaphragm 100 is made of a material that does not easily
expand and contract. Since the peripheral portion of the diaphragm 100 (peripheral portion of
the sub dome 102) is fixed to the frame 205, when displacement by the piezoelectric film 120 is
applied to the sub dome 102, the sub dome 102 conforms to the expansion and contraction of
the piezoelectric film 120. It will vibrate in the back and forth direction. That is, in accordance
with the electric field applied to the piezoelectric film 120, a driving force in the front-rear
direction is applied to the sub dome 102. The sub dome 102 vibrates by this driving force, and a
noise cancellation signal is output.
[0025]
The headphone unit 200 includes a noise cancellation signal wiring 305, a noise cancellation
signal generation unit 304, and a microphone 303 as a configuration for applying an electric
field to the piezoelectric film 120 of the sub dome 102.
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[0026]
The microphone 303 detects external noise in the usage environment of the headphone unit 200,
converts it into a noise signal, and inputs the noise signal to the noise cancellation signal
generation unit 304.
The external noise is a sound other than the target sound that the user is trying to hear. The
noise cancellation signal generation unit 304 generates and outputs a noise cancellation signal,
which is a signal for canceling the noise, based on the external noise detected by the microphone
303. The noise cancellation signal is a signal whose phase is reversed from the external noise.
The noise cancellation signal wiring 305 is a wiring for applying the noise cancellation signal
output from the noise cancellation signal generation unit 304 to the piezoelectric film 120. As
described above, since two signals of plus and minus are applied to the piezoelectric film 120 on
both the front and back sides, there are at least two noise cancellation signal wirings 305.
However, in FIG. 1, the noise cancellation signal wiring 305 is simplified and represented as one
signal line.
[0027]
As described above, when a noise cancellation signal is applied to the piezoelectric film 120, an
expansion / contraction force is applied to the surface of the sub dome 102 in the radial
direction of the diaphragm 100 according to the noise cancellation signal. The outer peripheral
end of the sub dome 102 is fixed to the frame 205, and the other end is connected to the main
dome 101, and an arch is formed between these ends. With such a structure, the expansion and
contraction force by the piezoelectric film 120 is converted into a force that causes the sub dome
102 to vibrate in the same direction as the vibration direction of the main dome 101 (the
vibration direction of the voice coil 201).
[0028]
Therefore, diaphragm 100 has an input system in which an audio signal output from sound
source device 301 is input to voice coil 201 via signal input wiring 302 and an input system in
which a noise cancellation signal is input to piezoelectric film 120. , Has two input systems. The
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former is a first input system, and the latter is a second input system.
[0029]
The first input system is a current drive system that mainly drives the main dome 101 of the
diaphragm 100 by current (the sub dome 102 is also current driven). That is, the diaphragm 100
outputs music by vibrating by current drive based on an audio signal. The second input system is
an electric field drive system that drives the sub dome 102 of the diaphragm 100 by an electric
field. That is, the diaphragm 100 vibrates due to electric field vibration based on the noise
cancellation signal to output noise cancellation sound.
[0030]
As described above, the diaphragm 100 is an electro-acoustic conversion mechanism
corresponding to 2 inputs and 2 outputs, and the signal for electric current driving and the signal
for electric field driving are combined by the diaphragm 100 and converted into sound waves.
Output. Since the current and the electric field do not interfere with each other, the diaphragm
100 having the configuration shown above does not cause mutual interference between signals
generated when signal processing such as adding an audio signal and a noise cancellation signal
is performed There is no adverse effect of signal interference.
[0031]
In addition, in the mechanical coupling structure for fixing the headphone unit 200, there is no
special structure, and it is not necessary to use a structure that does not allow sound waves to
pass around the headphone unit 200.
[0032]
In addition, since it is not necessary to connect in parallel to the voice coil 201 the signal
processing circuit required for each of the audio signal and the noise cancellation signal, it is
possible to prevent each other's signal processing circuits from becoming a load. It can be
avoided.
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In addition, since signal synthesis processing that causes an audio signal and a noise cancellation
signal to interfere with each other is unnecessary, high-quality musical tones are reproduced, and
the effect of canceling external noise is also enhanced.
[0033]
100 diaphragm 101 main dome 102 sub dome 120 piezoelectric film 200 headphone unit 201
voice coil 202 pole piece 203 magnet 204 yoke 205 frame 301 sound source device 302 signal
input wiring 303 microphone 304 noise cancellation signal generation unit 305 noise
cancellation signal wiring
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