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JPS5453989

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DESCRIPTION JPS5453989
Specification 1 and title of the invention Amorphous magnetostrictive transducer The ratio of
thickness t of the amorphous magnetostrictive elastic thin plate to the width α of the thin filmlike conductor is approximately t / a ≦ 1. The invention is characterized in that the alternately
folded serpentine conductive structure and the bias magnetic field applying means are provided
on the surface of the amorphous magnetostrictive elastic thin film, in which the folding intervals
of the conductor are changed and the folding width is also changed. Amorphous field type
transducer.
2, the scope of claims
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amorphous
magnetostrictive transducer for exciting a desired bulk longitudinal wave. In recent years,
research on amorphous magnetic materials has progressed, and results of various developments
have been published in the Journal of the Metals Society. 3C in these amorphous magnetic
materials! Some have a large magnetostriction constant of X1O-fl and a large electromechanical
coupling coefficient of 0, 6 which has not been used in the past. This property is included in the
variable delay line in the paper published in The Application of Amorphous Ferromagnetic
Materials by the papers of the Telecommunications Research Society of the
Telecommunications Research Institute of Tohoku University, Dr. Tsuya and Arai and the 13th
Symposium Proceedings hosted by the research institute. It is applied to the input and output
CADrs of resonator devices. These transducers are obtained by winding a solenoid coil 5 around
an amorphous magnetostrictive elastic thin plate 1 as shown in FIG. 1, or as shown in FIG. The
coil or magnetic head generates a substantially uniform magnetic field in the longitudinal
direction of the amorphous magnetostrictive elastic thin plate as shown in FIG. 3, and the Joule
effect of this magnetic field causes the amorphous thin plate to be elastic. Distortion is obtained
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to excite an elastic wave corresponding to an input electrical signal. However, these transducers
are not suitable for use in exciting the magnetostrictive thin plate with elastic waves having a
plurality of, and each in a desired positional relationship with respect to one electrical input
signal. The first reason is that the EndPage: 1 magnetic field generated by the solenoid coil 5 or
the magnetic head 6 of these transducers is substantially uniform in the longitudinal direction as
shown in FIG. Only one elastic wave can be excited for one solenoid coil 5 or magnetic head 6 in
one. For this reason, if it is intended to excite a plurality of elastic waves having a desired
positional relationship, as shown in FIGS. 4 and 5, a plurality of solenoid coils 5 'or magnetic
heads 6' are formed on the amorphous magnetostrictive thin plate 1. There was the
inconvenience of having to be placed in the desired positional relationship. The second reason is
that it is difficult to realize a solenoid coil or magnetic head of 1 W or less in length even if it is
realized after the inconvenience described above, and excites multiple elastic waves at intervals
of 1 鱈 or less It is difficult. Also, as a similar technique for exciting elastic waves in a plurality of
desired positional relationships, as shown in FIG. 6, a comb-pole 8 is installed on a piezoelectric
elastic plate 7 such as Retaem Niobe (Li1V03) or quartz. Surface acoustic wave transducers have
been developed at present, in which a serpentine coil 2 is installed on a magnetostrictive elastic
plate 9 such as YIG or YAG as shown in FIG. This technology is intended for surface acoustic
waves, and is an essentially different technology from those using bulk longitudinal wave
phenomena.
The inventors have already proposed a method of exciting a plurality of bulk longitudinal waves
having a desired positional relationship in the amorphous magnetostrictive elastic thin plate 1.
As an example, FIG. 8 shows a conventional serpentine type amorphous magnetostrictive
transducer for exciting an elastic wave in a desired positional relationship, as shown in FIG. 9,
and the folding width W of the serpentine coil 2 is constant. Because of this, the magnitudes of
elastic strain under the serpentine coil are equal as shown in FIG. 11, and excitation can not be
performed so that the ratio of each elastic strain has a desired relationship. Here, the bias
magnetic field magnet 4 is used to increase the electromechanical coupling coefficient. Further,
as shown in FIG. 10, when the folded width W of the serpentine coil is larger than the width of
the amorphous magnetostrictive elastic thin plate, the magnitude of each elastic strain is the
width 6 ··· of the amorphous magnetostrictive elastic thin plate. The same applies in this case as
well. The object of the present invention is to eliminate the above-mentioned disadvantages of
the prior art, and to obtain the desired positional relationship in the amorphous magnetic thin
plate without using a plurality of coils or magnetic heads, and the ratio of the amount of each
elastic strain Is to provide a magnetostrictive transducer for exciting a plurality of bulk mode
longitudinal waves in a desired relationship. The present invention is characterized in that 1;
using an amorphous magnetostrictive material which is a thin plate having a large
magnetostriction constant and a high coupling coefficient as an rjB strain material; and 2 a
magnetic field generating portion for elastic wave excitation of the magnetostrictive material.
Using a serpentine-type conductive structure formed by alternately turning back at different
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turn-back intervals, and changing its turn-back width to the traveling direction of the elastic
wave; It installed and provided the bias magnetic field application means. The following briefly
explains the principle. る。 FIG. 12 shows a magnetic field distribution applied to the amorphous
magnetostrictive thin plate 1 when a current is supplied to the conductive structure 2. In this
case, the folding interval p = 1, the thickness of the amorphous magnetostrictive thin plate t = o,
i, the conductive structure width α = 0.5. The number of folded backs N = 11. Curves indicated
by numerical values of 100, 200, and 300 are equal magnetic field lines for longitudinal
components of the amorphous magnetostrictive thin plate 1. The unevenness in the thickness
direction of the amorphous magnetostrictive thin plate 1 of the magnetic field distribution is
largest at the center of the width of one path of the conductive structure 2. The unevenness of
the magnetic field distribution in the thickness direction of the amorphous magnetostrictive thin
plate 1 causes the generation of a bending strain component in addition to the volume strain in
the longitudinal direction of the amorphous magnetostrictive thin plate 1. At the center of the
above width, the ratio of the magnetic field unevenness (Hmin / Hma) in the thickness direction
of the amorphous magnetostrictive thin plate 1 to the width α of the path of the conductive
structure 2 and the thickness t of the amorphous magnetostrictive thin plate 1 The relationship
with t / a complements that shown in FIG.
The present invention is EndPage: 2 configured in consideration of the above, and taking
advantage of the fact that the thickness of the amorphous magnetostrictive thin plate 1 is as thin
as several tens of microns, the path of the thickness t and the conductive structure 2 Assuming
that the ratio (t / a) to the width a is t / ′ α ≦ 1, and H ′ ′ ′ / ′ Hmax ≧ 0.1, strain energy
is not concentrated on the surface layer of the amorphous magnetostrictive thin plate 1 in the
thickness direction Is used as a uniformly distributed volume distortion wave. By the way, it is
essentially different from a surface wave element in which strain energy is concentrated on the
surface layer as t / a> 5. Next, an embodiment of the present invention will be described using
the drawings. FIG. 14 is a top view of an amorphous magnetostrictive transducer according to
the present invention. The structure is provided with a serpentine type conductive structure
(hereinafter referred to as a meander type coil 2) on the amorphous magnetostrictive elastic thin
plate 1, and as a means for applying a bias magnetic field in the longitudinal direction of the
amorphous magnetostrictive thin plate 1. , The solenoid coil 3 is installed. It is to be noted that
even if permanent magnets are used as the glue of the solenoid coil 3, the same effect can be
obtained. Here, the serpentine coil 2 is closely placed on the surface of the amorphous
magnetostrictive elastic thin plate 1 by close contact or another support C (not shown), and the
interval P and the width W thereof are changed along the longitudinal direction. It is. However,
the width W is smaller than the width of the amorphous magnetostrictive elastic thin plate 1.
2, the scope of claims
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Next, the present invention will be described in detail. A signal magnetic field by the bending coil
2 and a bias magnetic field by the solenoid coil 5 are applied to the amorphous magnetostrictive
elastic thin plate 1 in the longitudinal direction, and an elastic strain proportional to the
magnetostriction constant is excited. The bias magnetic field is effective in improving the
transducer conversion efficiency and controlling the propagation speed of the acoustoelastic
strain. FIG. 15 shows the signal elastic wave due to the serpentine coil 2. The rightward and
leftward directions of the arrow represent the direction of the applied magnetic field, and the
elastic wave of the bulk mode expanded and contracted according to this is excited. The
excitation position and width of the wave are determined by the spacing p and the width W of
the serpentine coil 2. By the way, although the distortion amplitude is also equal because the
magnetic field immediately below the coil is the same at each excitation position, the widths are
different, so the overall signal distortion amount is proportional to the width. FIG. 16 shows @W
and distortion of the serpentine coil 2; Is shown to be proportional to. From this, it is effective to
change the width of the serpentine coil corresponding to this ratio in order to make the ratio of
the distortion amount of the elastic wave at each excitation position a desired relationship.
Although the above description of the operation shows the case of electrical signal → elastic
strain conversion, conversely, the same effect is obtained also in the case of elastic strain →
electric signal conversion. As described above, by using the amorphous magnetostrictive
transducer according to the present invention, 1 and the amorphous magnetostrictive material
itself is a thin plate of about several tens of microns, so there is no need to roll like Ni etc.
Amorphous magnetostrictive material, which can reduce man-hours greatly and is inexpensive 2,
has a magnetic permeability as large as about 1000 compared to conventional magnetostrictive
materials such as NL and Alferro, and it has a plurality of solenoid coils and magnetic heads It is
possible to excite bulk mode longitudinal waves in which each elastic wave is in a desired
positional relationship and each elastic strain has a desired ratio, using a serpentine coil.
Moreover, since the serpentine coil is small in size and can easily be fine-sized 8. The frequency
range of elastic waves can be expanded, and so the contribution to this technical field is large.
4. Brief description of the drawings FIGS. 1 to 13 show the configuration and operation of a
conventional amorphous magnetostrictive transducer and a transducer similar thereto, and FIG.
A top view showing an embodiment of the amorphous magnetostrictive transducer, and FIGS. 15
and 16 are diagrams for explaining the operation thereof. 1: Amorphous magnetostrictive elastic
thin plate 2: Twisted coil 3; Solenoid coil agent for bias magnetic field Attorney Attorney Thin 1)
Toshiyuki EndPage: 3f 3 layer '1' now figure 5 5 years old 6 figure "2" r figure- i '? IfJfto 長 ′ f
point! Lz Figure Hif 13fli] squeezed EndPage: 4
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