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JP2013187893

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DESCRIPTION JP2013187893
Abstract: The present invention provides a resonator element capable of obtaining pulse
responses such as rise and fall without delay in a resonant vibrator. SOLUTION: A vibrator such
as a diaphragm is provided on the surface of a substrate, an electromagnetic coil is formed on at
least one main surface of the vibrator, and a driving magnet is formed by bonding via an elastic
body on the upper or lower part of the electromagnetic coil. Vibrating element to be installed.
[Selected figure] Figure 3
Vibrating element and method of manufacturing vibrating element
[0001]
The present invention relates to the structure of a vibrator composed of an electromagnetic coil
and a magnet.
[0002]
Active devices configured by transducers, such as thin speakers, ultrasonic elements, balanced
armature devices, are used in various applications.
The most used piezoelectric vibrator is one that vibrates by utilizing a property such as PZT or
quartz that deforms when a voltage is applied.
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[0003]
As a piezoelectric vibrator for exciting from the audible sound band to the ultrasonic region, one
based on ceramic is generally used. For example, in the case of measuring the distance by
ultrasonic waves, this can be realized by oscillating the ultrasonic waves by the vibrator and
receiving them by the receiver. This depends on, for example, a method of measuring a delay
time between transmission and reception, a method of using a phase difference, a method of
using a resonant frequency, and the like. Similar vibrators include those driven by
electromagnetic drive.
[0004]
Patent Document 1: JP-A-2010-35348 Electromagnetic Drive Type Actuator and Method of
Manufacturing Electromagnetic Drive Type Actuator JP2009-166016 Reciprocal vibration
generator JP2010-204337 A light scanner and an image forming apparatus JP2005-12694 A
flat speaker
[0005]
"Micromachine and material technology", supervised by Akira Hayashi, p. 57-64 CMC "Ultrasonic
wave and how to use it", by Takuya Takuji, p. Journal of the journal E, Volume 130, No. 4, 2010,
P113-P117 "Application to three-dimensional shape measurement using electromagnetically
driven two-axis movable MEMS grating and near infrared low coherence interferometry", Journal
of the Institute of Electrical Engineers of Japan 132, No. 2, 2012, P31-P36.
[0006]
FIG. 1 (b) shows a pulse output waveform of a general piezoelectric vibrator.
The pulse output waveform diagram 1 (b) of the piezoelectric vibrator to which the drive input
waveform of FIG. 1 (a) is added is such a waveform that its rising gradually rises even when the
input voltage is applied, and the input is turned off However, the vibration does not show a sharp
convergence like a stringed instrument, and gradually attenuates, resulting in the generation of
an ultrasonic wave that is substantially longer than the actual input time.
Therefore, even if the drive is a clean input pulse, the acoustic vibration outputted therefrom
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draws a gentle waveform, and there is a possibility that false detection may be performed only by
performing simple signal processing.
[0007]
Such an output waveform is a phenomenon not only found in piezoelectric vibrators, but also in
all elements such as electromagnetically driven actuators that are trying to obtain an amplitude
using resonant vibration. In addition, in such an electromagnetic drive type actuator, as disclosed
in the patent document, the driving magnet and the coil are separately disposed, and a moving
magnet (MM) or a moving coil (MC) in which one of them is vibrated ) The structure is common.
[0008]
When it is intended to obtain various information such as distance and temperature by ultrasonic
waves, the drive input signal of the vibrator needs to be a pulse signal such as an on / off
rectangular waveform, but in the conventional piezoelectric element, Due to such rising and
falling pulse characteristics, the waveform actually output is in the form of a gentle envelope.
Therefore, the signal obtained on the receiver side does not necessarily accurately reflect the
information from the object, and if the rise and fall characteristics can be improved, accurate
measurement in ultrasonic waves can be realized. It will be possible.
[0009]
As a vibrator which oscillates an ultrasonic wave, in addition to a piezoelectric vibrator, an
electromagnetic drive vibration element constituted by an electromagnetic coil and a magnet can
be considered. As shown in FIG. 2, the element is constituted by a coil and a magnet, and by
inputting an AC drive current of a desired oscillation frequency to the coil, vibration occurs due
to the interaction between the magnetic field formed by the coil and the magnet. Occurs. Here, in
general, the electromagnetic coil is integrally formed with a vibrator structure such as a thin
plate or a diaphragm to be vibrated.
[0010]
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Although such an electromagnetic drive vibration element is suitable for miniaturization as
compared with a piezoelectric element, the driving force is reduced in proportion to the cube of
the size, so a strong magnetic field is required to obtain a large oscillation output. It is necessary
to drive at the mechanical resonance frequency of the vibrator in which the coil is formed.
However, in this case, the oscillation output waveform has the same rise and fall characteristics
as the piezoelectric element.
[0011]
SUMMARY OF THE INVENTION An object of the present invention is to provide a structure for
realizing steep rise and fall characteristics in an electromagnetic drive element that can be
miniaturized.
[0012]
Therefore, the present invention realizes an electromagnetic drive element structure capable of
obtaining an oscillation output waveform closer to the drive input waveform.
[0013]
The inventors have found that, in a vibrator in which an electromagnetic coil formed on a silicon
element is disposed, the above object can be achieved by providing a driving magnet on the
vibrator via an elastic body. The present invention has been completed.
[0014]
FIG. 1A shows a transducer drive input signal waveform, and FIG. 1B shows a pulse response
output waveform of a general piezoelectric vibration element.
Fig. 2 shows the principle of electromagnetic drive by an electromagnetic coil and a magnet.
FIG. 3 shows a cross-sectional view of an example of the vibration element of the present
invention.
FIG. 4 shows an application example of the present invention. FIG. 5 shows an example of the
manufacturing method of the first embodiment. FIG. 6 shows an output waveform of a
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conventional vibrating element and a vibrating element output waveform according to the
present invention. FIG. 7 shows the effect of inserting an elastic body between the diaphragm
and the drive magnet. FIG. 8 shows an example in which the transducer elements according to
the present invention are arranged on an array. FIG. 9 shows an example in which the control
magnet is disposed below the vibration element according to the present invention.
[0015]
The vibrator according to the present invention has a vibrator on at least one of the main
surfaces, and an electromagnetic coil is formed on at least one of the main surfaces of the
vibrator, and is driven via an elastic body in the upper or lower portion of the electromagnetic
coil. A magnet is installed.
[0016]
The vibrator of the present invention is made of metal, resin, oxide, preferably silicon.
[0017]
The electromagnetic coil of the present invention preferably comprises a thin film coil.
[0018]
An elastic resin is applied to the surface of the vibrator, and the driving magnet is adhered via
the elastic resin.
The elastic resin is, for example, silicone, polydimethylsiloxane (PDMS), rubber or the like.
[0019]
The magnet of the present invention is made of ferrite, samarium cobalt, neodymium, alnico or
the like and can be selected appropriately, but neodymium is preferably selected.
[0020]
The magnet of the present invention is made of bulk or thin film.
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[0021]
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
[0022]
For example, a circular or polygonal diaphragm structure 3d is provided at the center of an
element formed of silicon 3a.
[0023]
The size of the diaphragm is such that resonant oscillations occur at the desired oscillation
frequency.
In the case of, for example, a circular diaphragm, its dimensions are derived from the following
equation.
<img class = "EMIRef" id = "399038459-00003" /> where r is a radius, E is a Young's modulus,
ν is a Poisson's ratio, and ρ is a density.
As is apparent from this equation, the value of the resonant frequency f can be lowered by
decreasing the plate thickness t or increasing the radius r.
[0024]
JP 7-174651 "pressure sensor"
[0025]
On the diaphragm, an electromagnetic coil made of a thin film electrode, for example, a metal
film such as aluminum, chromium, nickel, gold, silver, copper or the like, or a transparent
electrode material such as ITO is provided via the insulating film 3b.
[0026]
The surface of the diaphragm 3d is provided with a resin layer 3e having a thickness of 0.01 to 2
mm, preferably 0.01 to 1 mm, by a resin which is an elastic body.
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[0027]
Furthermore, a drive magnet 3f is adhered on the resin layer 3e, and for example, ferrite,
samarium cobalt, neodymium, alnico, etc. can be used, and its shape is a cylinder, a rectangular
parallelepiped, a polygonal weight, a cone, a thin film, etc. Has an outer diameter of 0.1 to 5
times, preferably 0.1 to 2 times the outer diameter of the electromagnetic coil and a height of
0.01 to 5 mm, preferably 0.01 to 2 mm.
[0028]
A permanent magnet or a thin film magnetic film can be appropriately selected as the drive
magnet 3 f, and the shape thereof can be cylindrical, cylindrical, rectangular parallelepiped, or
the like.
[0029]
An example of a method of manufacturing the vibration element of the present invention will be
described with reference to the element configuration shown in FIG.
(1) An oxide film 3b is formed on a silicon substrate 3a, and an electromagnetic coil material
such as aluminum is deposited on one surface of the substrate.
(2) A photosensitive resin such as positive resist OFPR-800 manufactured by Tokyo Ohka Kogyo
Co., Ltd. is applied by spin coating or the like on the electromagnetic coil material using
photolithography technology.
(3) The photosensitive resin is exposed through a photo mask on which a coil pattern is drawn,
and an electromagnetic coil pattern is transferred through steps such as development.
(4) Using the transferred photosensitive resin pattern as a mask, the electromagnetic coil
material is etched to obtain an electromagnetic coil 3c.
(5) From the back side of the substrate, a diaphragm 3d having a desired film thickness is formed
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by etching, for example, silicon deep etching by the Bosch process.
(6) The surface of the electromagnetic coil 3c is coated with a resin 3e such as
polydimethylsiloxane (PDMS).
(7) A samarium-cobalt magnet 3f having a diameter of, for example, 0.8 mm and a height of 1
mm is adhered onto the central portion of the electronic coil pattern.
Effect of the invention
[0030]
In the vibration element manufactured according to the present invention, the rise time was 1/6
or less of the conventional one, and the natural vibration suppression effect resulted in the fall
time of 1/7 or less of the conventional one.
In addition to the diaphragm shape shown in FIG. 4A, for example, the vibration element
manufactured according to the present invention has a weight attached shape shown in FIG. 4B
or a mirror shape shown in FIG. 4C. To realize high resolution of sensors, optical switches, etc.
[0031]
Hereinafter, the present invention will be described in more detail by way of examples.
[0032]
Example 1 FIG. 5 shows an example of a method of manufacturing a vibration element according
to the present invention.
(1) An insulating film 5b, for example, a silicon oxide film is formed on a substrate, for example, a
silicon substrate 5a. (2) The electromagnetic coil material 5c such as aluminum is vapor
deposited so as to sandwich the insulating film 5b on one main surface of the substrate 5a. As
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the electromagnetic coil material 5c, a material having good adhesion to the insulating film 5b is
selected, and when using a material having poor adhesion such as gold, a metal chromium layer
or the like is inserted as an intermediate layer. (3) Using a photolithographic technique, a
photosensitive resin 5d such as OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd. is
applied by spin coating or the like. (4) The photosensitive resin 5d is exposed through a
photomask on which an electromagnetic coil pattern is drawn, and the electromagnetic coil
pattern is transferred onto the electromagnetic coil material 5c through steps such as
development. (5) The electromagnetic coil material 5c is etched using the transferred
photosensitive resin 5d pattern as a mask, and the photosensitive resin 5d is peeled off after the
etching. (6) From the back side of the substrate, a diaphragm 5e having a desired film thickness
is formed by etching, for example, silicon deep etching by the Bosch process. Here, a convex
weight may be formed on, for example, the central portion of the diaphragm without partially
etching. (7) The surface of the electromagnetic coil pattern 5c is coated with a resin 5f, for
example, polydimethylsiloxane (PDMS) to a thickness of about 0.5 mm. (8) A samarium-cobalt
magnet 5g having a diameter of 0.8 mm and a height of 1 mm, for example, is bonded to the
center of the electromagnetic coil pattern 5c.
[0033]
Confirmation of the effect of the present invention according to the present example The
confirmation of the effect according to the present invention was performed using the vibration
element manufactured according to the present example. The vibration element used for
confirmation has an outer diameter of 5 mm × 5 mm × 0.45 mm, a diaphragm thickness of 20
μm, and a radius of 1.3 mm. The electromagnetic coil was formed on the diaphragm with 10
turns. Further, the surface magnetic flux density of the drive magnet (φ 0.8 mm × 2 mm) is
about 1200 gauss. Generally, in the case of an actuator driven by an electromagnetic drive, since
the driving force decreases in proportion to the cube of the size when the actuator is
miniaturized, it is necessary to increase the magnetic field. On the diaphragm, PDMS (Toray Dow
Corning, Sylgard 184) was applied. In addition, in this confirmation, what installed the magnet
for control in the lower part of the element was also evaluated.
[0034]
(1) Resonant frequency A trigger output created by a function generator (model 166 made by
Wavetek) is input to a digital function generator made by nf to a diaphragm designed at a
resonant frequency of about 40 kHz to form an excitation signal to generate an excitation signal.
The resonant frequency of the device was evaluated by scanning the frequency. The ultrasonic
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wave output from the vibration element was detected by a silicon microphone SPM0404UD5
manufactured by Knowles Electronics, and a detection waveform was observed by a digital
storage oscilloscope GDS1062A manufactured by nf. As a result, resonance was confirmed at
about 39 kHz, and resonance was observed at about 54 kHz for the element in which the control
magnet was disposed at the lower part.
[0035]
(2) Verification of characteristics The rise was performed by evaluating the wave number until
the oscillation of the element reaches a steady state, and the wave number until the fall becomes
1/2 and 1/4 of the amplitude from the input OFF. In the evaluation system described above, an
AC output with an amplitude of 5-10 V was appropriately selected and input to the vibrating
element. The output of the vibrating element detected by the silicon microphone was amplified
by a self-made amplifier, and the waveform was observed with an oscilloscope.
[0036]
FIG. 6 shows the results when 20 pulses are input to the vibration element according to the
present invention. FIG. 6 (a) shows an output waveform of a conventional vibration element. FIG.
6 (b) is a waveform of the vibration element manufactured according to this example. The
conventional vibrator has a typical pulse response waveform, and the rise does not stand up at
the input of 20 waves, and even when a pulse of 30 waves or more is injected, the steady state is
not reached. Also, the mechanical vibration of about 19 waves remained until the amplitude was
halved, and about 36 waves before the amplitude became 1/4. On the other hand, in the case of
the vibration element manufactured according to the present invention, the rise is about 5 waves
and the steady state is reached, and the fall is about 3 waves before the amplitude is 1⁄2 and
about 5 waves before the amplitude is 1⁄4. Met. In the fall, the vibration continues for a long time
after the amplitude is halved in the conventional vibrator, and it takes 36 or more waves before
the amplitude attenuates to 1⁄4 or less, but the vibration according to the present invention In a
child, it attenuates sharply with 5 waves and a convergence time of about 1/7.
[0037]
FIG. 7 is a comparison of output waveforms when a resin (PDMS) to be an elastic body is
sandwiched between the drive magnet and the diaphragm. In FIG. 7A, the drive magnet is
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installed on the surface of the diaphragm without the resin. Although the convergence of the
waveform can be confirmed, no effect was found in the rising. FIG. 7 (b) shows the same element
as in FIG. 7 (a) in which the drive magnet is installed via the resin, but improvement in the rising
characteristic has been confirmed.
[0038]
From the above, it can be confirmed that the vibration element manufactured according to the
present invention is significantly improved in the pulse response to the input as compared with
the conventional vibration element, and an ultrasonic vibration element, vibration type gyro
utilizing such vibration It has been found that application to optical scanners, optical switches,
etc. is also possible.
[0039]
Example 2 A production example is shown in FIG.
In this embodiment, at least two or more of the transducer elements manufactured according to
the first embodiment are arranged in an array on one substrate. For example, by arranging a
plurality of transducers in an array at a half wavelength pitch, it is possible to enhance
directivity, or to move the traveling direction to the left or right.
[0040]
Example 3 A production example is shown in FIG. In the present embodiment, a control magnet
9f is provided in the lower part of the vibration element manufactured according to the first
embodiment. This vibrating element is composed of the insulating film 9b, the drive coil 9c, the
elastic body 9e, and the drive magnet 9g on the diaphragm 9d formed on the silicon substrate 9a
as in the first embodiment, and the control magnet 9f is provided below it. Is installed. The
magnet 9 f may be a permanent magnet, such as ferrite, samarium cobalt, neodymium, alnico or
the like, and may be an electromagnet. By installing the magnet 9f capable of changing the
magnetic force and the magnetic pole, it is possible to control the behavior of the vibrator, for
example, the convergence time of the vibration, the resonance frequency, etc. It is feasible.
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