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JP2002066457

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DESCRIPTION JP2002066457
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
Langevin-type vibrator using a giant magnetostrictive element composed of a giant
magnetostrictive material which is displaced by a magnetic field.
[0002]
2. Description of the Related Art In general, in a Langevin type vibrator, a plate made of metal or
the like with an appropriate thickness is bonded or bonded with a bolt or the like to both sides of
a plate of piezoelectric strain material such as a piezoelectric ceramic material. It is a transducer
of the attached structure, and is utilized for generation or reception of an ultrasonic wave.
[0003]
A Langevin type vibrator in which a plate made of metal or the like is pressure-bonded to a
piezoelectric ceramic material or the like by a bolt is called a bolt-clamped type, and the
piezoelectric ceramic material is generally weak to tensile stress but strong to compressive stress.
Focusing on the point, it is added in advance to the piezoelectric ceramic material by tightening
the compressive load that overcomes the maximum stress at the time of excitation with a bolt so
that it does not break due to the tensile stress due to the vibration even at the maximum
vibration. It is characterized in that the vibration breaking strength is large.
[0004]
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1
On the other hand, the giant magnetostrictive material is generally an alloy of a rare earth
element and iron, and the composition thereof is 1: 2 (RFe 2) in atomic ratio of rare earth
element R to iron Fe, for example, TbFe 2, DyFe 2, HoFe 2, ErFe 2 Etc.
These alloys have good controllability because of their large mechanical internal loss, and their
shape change rate is several thousand ppm, which is one or more orders of magnitude greater
than that of ordinary magnetostrictive materials, and can be greatly deformed. It is used as an
actuator that realizes large displacement.
However, on the other hand, since the giant magnetostrictive material has a small tensile stress
that can be mechanically tolerated and strength can not be secured, it is suitable for dynamic
applications such as a vibrator that constantly vibrates or keeps rapid motion. Application is
difficult.
[0005]
In the case where a giant magnetostrictive material is used as an actuator, in order to improve
the linearity and sensitivity of the magnetic field-distortion characteristics, a compressive preload
is applied to the giant magnetostrictive material using a disc spring or the like. However, there is
no disclosure about applying compressive stress to compensate for the tensile stress property of
the giant magnetostrictive material.
[0006]
By the nature of the piezoelectric ceramic material currently used generally for Langevin type
vibrators, the mechanical internal loss is small and the amount of deformation is also relatively
small.
For this reason, in order to generate ultrasonic oscillation of large amplitude with the
conventional Langevin-type transducer, it is necessary to use resonance, and for this reason, the
conventional Langevin-type transducer is a narrow band transducer. That is, the large-amplitude
ultrasonic vibrations that can be generated by these transducers are limited to vibrations with a
frequency equal to the mechanical resonance frequency determined by the material, shape, and
dimensions of the transducers.
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[0007]
However, the practical application of these vibrators, for example, control of powder particles,
bonding of plastics, promotion of chemical reactions such as dissociation and polymerization of
polymer materials, and optimum vibration frequency in machining etc. It does not necessarily
coincide with the resonant frequency of the transducer, which makes it difficult to efficiently
obtain the effect of ultrasonic vibration.
[0008]
For this reason, there is a demand for development of a transducer capable of obtaining
ultrasonic vibration of large amplitude in a wide frequency band.
[0009]
In addition, with respect to the giant magnetostrictive material, as described above, in spite of the
advantages of good controllability and a large amount of deformation due to the mechanical
characteristics of being weak to the tensile stress, the movement of the vibrator etc. Application
to various applications has not progressed.
[0010]
From the above, the object of the present invention is to overcome the defect that the giant
magnetostrictive material is vulnerable to tensile stress and to apply the giant magnetostrictive
material having a large mechanical internal loss and a large amount of deformation to a Langevin
type vibrator. Thus, it is an object of the present invention to provide a vibrator which can
generate ultrasonic vibration of large amplitude in a wide frequency band with a large generated
stress (generated vibration stress).
[0011]
Another object of the present invention is to provide a method of manufacturing a ring-shaped
giant magnetostrictive element suitable for use in the above-described vibrator.
[0012]
SUMMARY OF THE INVENTION In order to achieve the above object, the invention according to
claim 1 is a ring-shaped giant magnetostrictive element made of a giant magnetostrictive
material, and a ring-shaped giant magnetostrictive element. A hollow bolt having a threaded
portion provided on the outer surface of at least both end portions through the hole of the
element, and a threaded portion of the hollow bolt so as to sandwich the ring-shaped giant
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magnetostrictive element Provided is a bolted Langevin type vibrator having a pair of metal rings
tightened so as to apply a compressive force, and a coil for vibration excitation wound radially
outward of a giant magnetostrictive element.
[0013]
According to a second aspect of the present invention, in the bolt-clamped Langevin-type vibrator
according to the first aspect, the ring-shaped super magnetostrictive element is formed by
bonding a plurality of small pieces of super magnetostrictive material in the circumferential
direction. To provide a bolted Langevin type vibrator.
[0014]
According to a third aspect of the present invention, there is provided a bolted Langevin type
vibration according to the first or second aspect, wherein the hollow bolt and the pair of metal
rings constitute a differential screw. Provide a child.
[0015]
According to a fourth aspect of the present invention, in the bolt-clamped Langevin type vibrator
according to any one of the first to third aspects, each of the pair of metal rings has a radius as it
approaches the ring-shaped giant magnetostrictive element. A bolt-clamped Langevin type
vibrator is provided which has a portion with a narrow direction width, thereby uniformly
applying a compressive force to the giant magnetostrictive element.
[0016]
According to a fifth aspect of the present invention, in the bolt-clamped Langevin type vibrator
according to any one of the first to fourth aspects, the vibration excitation coil comprises a
hollow tube, and the hollow portion is A bolted Langevin type vibrator characterized by passing a
cooling fluid is provided.
[0017]
According to a sixth aspect of the present invention, there is provided a bolted Langevin type
vibrator according to any one of the first to fifth aspects, wherein a cooling fluid is passed
through the hollow portion of the hollow bolt. Provided is a Langevin type vibrator.
[0018]
According to a seventh aspect of the present invention, there is provided a bolted Langevin type
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vibration according to any one of the first to sixth aspects, wherein the hollow bolt is made of a
low magnetic permeability material. Provide a child.
[0019]
According to an eighth aspect of the present invention, in the bolt-clamped Langevin type
oscillator according to any one of the first to seventh aspects, a ring for a magnetic bias disposed
so as to surround the outer periphery of the vibration excitation coil. A bolt-clamped Langevin
vibrator having a ring-shaped permanent magnet, a ring-shaped permanent magnet, and a pair of
rings made of a high magnetic permeability material disposed so as to sandwich a vibration
excitation coil.
[0020]
The invention according to claim 9 is a method of manufacturing a ring-shaped giant
magnetostrictive element used for a bolt-clamped Langevin type vibrator, which comprises the
steps of fabricating a plurality of small pieces of giant magnetostrictive material; Bonding the
plurality of small pieces in the circumferential direction to form a ring, and providing a method
of manufacturing a ring-shaped giant magnetostrictive element.
The ring-shaped giant magnetostrictive element manufactured in this manner can obtain high
amplitude even in a high frequency band as compared with the integral type ring-shaped giant
magnetostrictive element of the same size.
[0021]
According to a tenth aspect of the present invention, in the method for manufacturing a ringshaped super magnetostrictive device according to the ninth aspect, in the step of manufacturing
a plurality of small pieces of super magnetostrictive material, the small pieces of super
magnetostrictive material are truncated. A method is provided for manufacturing a ring-shaped
giant magnetostrictive element fabricated to have a fan-shaped or trapezoidal cross-section.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described in detail with reference to the accompanying drawings.
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[0023]
FIG. 1 is a perspective view in which a portion of a vibrating portion 10 of a bolt-clamped
Langevin-type vibrator using a magnetostrictive element formed of the magnetostrictive material
of the present invention is cut away.
The vibrating portion 10 includes a ring-shaped giant magnetostrictive element 1 formed of a
giant magnetostrictive material, a pair of metal rings 2a and 2b sandwiching the giant
magnetostrictive element 1 in a sandwich, and the ring-shaped giant magnetostrictive element 1
A hollow bolt 3 is provided, which is provided with a screw thread on the outer surface of its
both side end parts, which penetrates the respective holes of the metal rings 2a and 2b.
The inner surface of the hole of the metal ring 2a, 2b is provided with a screw thread to be
screwed with the screw thread provided on the outer surface of the both end portion of the
hollow bolt 3 and the two metal rings 2a, 2b are hollow bolt 3 Can be applied to the giant
magnetostrictive element 1 from both ends by attaching and tightening it.
[0024]
On the other hand, FIG. 2 is a cross-sectional view showing an outline of a vibration system
including the vibration portion 10 shown in FIG. 1, and a vibration excitation coil composed of a
hollow tube wound on the outside of the giant magnetostrictive element 1. 4 and a pair of rings
5a and 5b made of a high permeability material sandwiching the coil 4 in a sandwich, and
between the rings 5a and 5b made of two high permeability materials outside the coil 4 Ring
permanent magnet 6 is shown.
[0025]
The ring-shaped giant magnetostrictive element 1 of the present embodiment is formed by
bonding small magnetostrictive material pieces 1 '.
By doing this, a high amplitude can be obtained even in a high frequency band as compared with
the integral ring-shaped super magnetostrictive element of the same size due to the frequency
characteristic of the magnetostrictive amplitude depending on the material size of the giant
magnetostrictive material. Become.
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An example of a ring-shaped giant magnetostrictive element having an inner diameter of 66 mm,
an outer diameter of 90 mm and a height of 20 mm is shown in FIG.
In the case of manufacturing the ring-shaped giant magnetostrictive element 1 of this example,
first, the shape or the cross-sectional shape seen from above as shown in FIG. As shown in FIG. 3,
80 pieces of truncated fan-shaped or trapezoidal pieces 1 'having a pair of sides formed at an
angle of 4.5 ° are manufactured by bonding such pieces 1' in the circumferential direction with
epoxy resin. Manufactured by constructing a ring as shown in (b).
The adhesive for bonding the small pieces 1 'may be any suitable adhesive other than epoxy
resin.
Further, the shape of the small pieces 1 'may be a shape other than the shape of the present
embodiment, as long as a desired ring shape is formed by combination.
For example, the small piece 1 'shown in FIG. 3 (a) may be configured by bonding two smaller
pieces together.
[0026]
The giant magnetostrictive material used for the ring-like giant magnetostrictive element 1 is, for
example, an alloy of iron and a suitable rare earth-iron alloy having an element ratio of 1: 2
(RFe2) such as TbFe2, DyFe2, HoFe2, ErFe2. It is good.
Since the giant magnetostrictive element made of these alloys has a much higher rate of change
in shape compared to elements fabricated of conventional magnetostrictive materials and
piezoelectric materials, the vibrator of the present invention using this giant magnetostrictive
element is As in the case of using a conventional element, it is not necessary to use resonance to
increase the amount of deformation of the element, and thus it is not necessary to limit the use to
the resonance frequency specific to the element, for example, as shown in FIG. When the ringshaped giant magnetostrictive element with an inner diameter of 66 mm, an outer diameter of 90
mm, and a height of 20 mm shown in 3 (c) is used, it can be used in a wide frequency band of 13
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kHz or less, which is its primary resonance frequency. It is possible to freely change the
frequency according to
[0027]
As described above, the compression pressure is applied to the giant magnetostrictive element 1
by the metal rings 2a and 2b.
This is because the giant magnetostrictive material constituting the giant magnetostrictive
element 1 is weak to the tensile stress, and is easily broken when the tensile stress is applied.
The giant magnetostrictive element 1 expands and contracts in response to changes in the
magnetic field, but since tensile stress is applied to the element at the time of extension, it is
necessary to apply a compressive force in advance to prevent breakage.
[0028]
In general, there are two types of magnetostrictive materials, one extending only in proportion to
the absolute value of the magnetic field regardless of the direction of the magnetic field, and the
other only reducing. The giant magnetostrictive element 1 of the present invention Use one that
only extends in proportion to the absolute value of the magnetic field.
[0029]
As described above, the hollow bolt 3 has screw threads on the outer surfaces of both ends
thereof, and the metal rings 2a and 2b are screwed into and tightened with the screw parts,
thereby being held between the metal rings 2a and 2b. Compressive force can be applied to the
giant magnetostrictive element 1.
At this time, assuming that the metal rings 2a and 2b are differential screws, the compression
surface, ie, the contact surface between the giant magnetostrictive element 1 and the respective
metal rings 2a and 2b is compressed relative to the giant magnetostrictive element 1 without
slipping relatively. You can add power.
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Further, on the inner surface of the hollow bolt 3, a flange portion 7 projecting radially inward is
provided near the center in the longitudinal direction, and is used for fixing the vibrator.
[0030]
The hollow bolt 3 is preferably made of a material with low permeability such as duralumin,
ceramics and the like.
This is because, when the magnetic circuit surrounding the vibration excitation coil 4 described
later is configured, most of the magnetic flux passes through the giant magnetostrictive element.
Further, as described above, since the giant magnetostrictive element 1 has a large mechanical
internal loss, heat is easily generated in the vibrating portion 10, so cooling water is allowed to
flow through the hollow portion of the bolt to promote the dissipation of the heat generated in
the vibrating portion. You may do so.
Duralmin is also preferable from the viewpoint of heat dissipation because it has a high thermal
conductivity.
[0031]
Each of the pair of metal rings 2a and 2b sandwiching the giant magnetostrictive element 1
becomes smaller as the outer diameter approaches from the vicinity of the center in the
longitudinal direction to the giant magnetostrictive element 1, and the width in the radial
direction becomes narrower gradually It is shaped. This shape makes the finite element analysis
system such that the contact stress distribution at the interface between the giant
magnetostrictive element 1 and the metal rings 2a and 2b approaches an optimal one in order to
apply uniform compressive pressure to the entire giant magnetostrictive element 1 It is a shape
found by using. The optimum shape changes depending on the outer diameter and the inner
diameter of the metal rings 2a and 2b, or the length of the threaded portion of the metal rings 2a
and 2b coupled to the hollow bolt 3. When the metal ring of the rectangular cross section whose
inner diameter and outer diameter are constant is used without using the metal ring 2a, 2b of
such an optimal shape, a strong compressive pressure is exerted only on the inner peripheral
04-05-2019
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portion of the giant magnetostrictive element. In addition, since the distribution is biased, it is
more difficult to compensate for the weakness of the giant magnetostrictive element against
tensile stress. The metal rings 2a and 2b are made of, for example, stainless steel.
[0032]
The vibration excitation coil 4 as a wire wound around the outside in the radial direction of the
giant magnetostrictive element 1 is preferably made of, for example, a hollow tube such as a
copper pipe, in which case cooling water is passed through the hollow portion. It is possible to
dissipate the heat. A tape or the like is wound on the surface of a hollow tube or the like
constituting the coil 4, and silicone rubber or the like is further filled between the hollow tubes to
insulate them from each other.
[0033]
A pair of rings 5a, 5b are arranged sandwiching the coil 4 and receiving the vibrating portion 10
in its central hole. The rings 5a and 5b are preferably made of a high magnetic permeability
material such as ferrite, and become a part of a magnetic circuit described later.
[0034]
The ring-shaped permanent magnet 6 is disposed radially outside the coil 4 so as to be
sandwiched between the pair of rings 5a and 5b, and applies a bias magnetic field to the giant
magnetostrictive element 1. Since the giant magnetostrictive element 1 used in the present
invention has a property of extending with respect to the absolute value of the magnetic field as
described above, the giant magnetostrictive element 1 is always stretched by the bias magnetic
field of the ring-shaped permanent magnet 6. By superimposing the AC magnetic field by the coil
4 in this state, the giant magnetostrictive element 1 can be expanded and contracted to obtain
the behavior of vibration. At this time, by adjusting the bias magnetic field, it is possible to use a
portion with high linearity of hysteresis of the giant magnetostrictive element 1. Furthermore,
not only mechanical compression force but also magnetic compression force can be applied by
stretching the giant magnetostrictive element 1 against the clamping force of the metal rings 2a
and 2b by applying a bias magnetic field. This means that although the magnetostrictive element
1 is responsive at high speed and can cope with the change of the high frequency magnetic field
if it is only mechanical compression force, the metal rings 2a and 2b can not follow this
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displacement speed. When there is a possibility that peeling occurs at the interface between the
giant magnetostrictive element 1 and the metal rings 2a and 2b when the element 1 shrinks, and
time may not be applied to the compressive force, the compressive force is always applied to the
giant magnetostrictive element 1. It is necessary to add.
[0035]
Referring to FIG. 2, the ring-shaped permanent magnet 6 and one highly magnetically permeable
material ring 5a, one metal ring 2a, the giant magnetostrictive element 1, and the other metal
ring 2b surround the vibration excitation coil 4. It can be seen that the other high magnetic
permeability material ring 5b is followed by a magnetic circuit that returns to the ring-shaped
permanent magnet 6. This magnetic circuit is divided into an outer portion consisting of the high
magnetic permeability material rings 5a and 5b and the ring-shaped permanent magnet 6, and a
vibrating portion side consisting of the giant magnetostrictive element 1 and the metal rings 2a
and 2b. The parts are in close proximity via a very narrow gap, so that they form a magnetically
integrated circuit and are not visibly coupled to one another.
[0036]
The magnetic flux generated by the ring-shaped permanent magnet 6 flows through the abovedescribed magnetic circuit, and the magnetic flux generated by the vibration excitation coil 4
flows to the super magnetostrictive element 1 through the metal rings 2a and 2b. Transform the.
Therefore, by passing an alternating current having a frequency equal to the desired frequency
through the vibration excitation coil 4, the vibrator can be vibrated at the desired frequency, and
vibration of the desired frequency can be obtained. Since the hollow bolt 3 is made of a material
of low magnetic permeability, almost no magnetic flux passes through, so efficient excitation is
possible.
[0037]
As apparent from the above description, according to the present invention, there is provided a
vibrator which has large generated stress (generated vibrational stress) and can obtain ultrasonic
vibration with a large amplitude in a wide frequency band. Be done.
[0038]
Brief description of the drawings
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[0039]
1 is a perspective view in which a portion of the vibration portion of one embodiment of a boltclamped Langevin type vibrator using a giant magnetostrictive element formed using the giant
magnetostrictive material of the present invention is cut away.
[0040]
2 is a cross-sectional view of one embodiment of a bolted Langevin-type vibrator of the present
invention including a permanent magnet for magnetic bias.
[0041]
FIG. 3 is a detailed view of a ring-shaped super magnetostrictive element used in an embodiment
of the bolt-clamped Langevin type vibrator according to the present invention, wherein (a) a
small piece of super magnetostrictive material constituting the ring-shaped super
magnetostrictive element; b) A top view of the ring-shaped giant magnetostrictive element, and
(c) a cross-sectional view of the ring-shaped giant magnetostrictive element.
[0042]
Explanation of sign
[0043]
1 ': super magnetostrictive material small piece 1: super magnetostrictive element 2a, 2b: metal
ring 3: hollow bolt 4: coil for vibration excitation 5a, 5b: high magnetic permeability material ring
6: ring-shaped permanent magnet 7: flange portion 10: vibration portion
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