JPH0360176A - Magnetostriction element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to magnetostrictive elements such as magnetostrictive vibrators, magnetostrictive actuators, and magnetostrictive sensors.

<Prior art> Magnetostrictive materials are materials that generate displacement when a magnetic field is applied.
Furthermore, it is a material that has inverse magnetostriction (Hillary effect) in which a magnetic field is generated by applying displacement.

Utilizing such properties of magnetostrictive materials, various active elements and passive elements such as magnetostrictive vibrators, magnetostrictive actuators, and magnetostrictive sensors have been proposed.

In particular, magnetostrictive materials containing rare metal elements such as Tb--Fe and iron have a large amount of magnetostriction, so magnetostrictive elements using such magnetostrictive materials have attracted attention in recent years.

The structure and operation of these magnetostrictive elements are usually as follows.

(Magnetostrictive sensor) A magnetostrictive sensor is usually constructed by arranging a magnetostrictive material and a permanent magnet for generating a bias in series so as to be in contact with each other, and winding a coil around them.

When a force that deforms the magnetostrictive material, such as external vibration or impact, is applied to such a magnetostrictive sensor, a current is induced in the coil due to the Hillary effect. By measuring this current or end voltage, the applied force can be determined.

(Magnetostrictive vibrator, magnetostrictive actuator) A magnetostrictive material, a permanent magnet, and a coil are arranged in the same manner as in the magnetostrictive sensor, and an alternating current, pulsed current, direct current, etc. is applied to the coil to generate a magnetic field. It is used as a vibrator or actuator by utilizing vibrations, displacements, etc. caused by this magnetic field. In addition, a magnetostrictive element with such a configuration,
It can also be used as a sounding body.

Further, in these magnetostrictive elements, by inserting a magnetic material in series so as to make contact with the magnetostrictive material or the permanent magnet, the closed magnetic circuit can be formed into an arbitrary shape.

In a magnetostrictive material, when the applied magnetic field intensity changes, the amount of magnetostriction changes accordingly, but the amount of displacement at this time is not necessarily proportional to the applied magnetic field intensity. For this reason, in magnetostrictive vibrators and magnetostrictive actuators, the displacement of the magnetostrictive material is linear in response to changes in the applied magnetic field strength, and in magnetostrictive sensors, the displacement of the magnetostrictive material is linear in response to changes in the applied magnetic field strength. Typically, a DC bias magnetic field is applied to change the current.

The strength of the DC bias magnetic field may be fixed in magnetostrictive vibrators, etc., but in magnetostrictive actuators and magnetostrictive sensors, it is particularly important in applications where the absolute amount of displacement and the linearity of displacement with respect to changes in applied magnetic field strength are issues. is preferably changeable.

That is, magnetostrictive materials have different optimal bias magnetic field strengths depending on their characteristics, but if the characteristics vary during manufacturing, it is necessary to adjust the bias magnetic field strength to the optimal bias magnetic field strength when incorporating it into an element.

In addition, in elements that use both alternating current and direct current as the driving current, such as some magnetostrictive actuators,
This is because, in order to increase the maximum displacement when using direct current, it may be necessary to set the bias magnetic field strength smaller than when using alternating current.

<Problems to be Solved by the Invention> Methods of applying a DC bias magnetic field include a method of applying a DC current to a coil and a method of using a permanent magnet.

In the method of applying a direct current to the coil, the bias magnetic field strength can be easily changed by changing the current strength. However, when direct current is superimposed on a coil through which alternating current flows to drive the magnetostrictive material, chokes and capacitors are required to avoid interference between the alternating current and direct current power supplies, making the element configuration complex and large. . Furthermore, when the bias magnetic field coil is provided separately from the magnetostrictive material drive coil, the element becomes more complicated and larger.

On the other hand, when a permanent magnet is used to generate the bias magnetic field, the element configuration becomes simple and a compact magnetostrictive element can be realized, but the bias magnetic field strength cannot be changed.

In addition, when using permanent magnets, the permanent magnets are placed in series in the direction of displacement in contact with the magnetostrictive material, so the displacement of the magnetostrictive material is absorbed at the interface between the two, making it difficult to obtain an accurate amount of displacement. Become.

The present invention was developed under these circumstances, and because it uses a permanent magnet as a bias magnetic field generation source, the structure is simple and compact, and the bias magnetic field strength can be changed, and accurate displacement can be achieved. The purpose is to realize a magnetostrictive element that can obtain a large amount of energy.

Means for Solving the Problems> Such objects are achieved by the present invention as described in (1) to (3) below.

(1) A magnetostrictive material containing a rare earth metal element and iron, a permanent magnet for generating a bias magnetic field, and a coil, the permanent magnet having a cylindrical shape with at least one end open, and the magnetostrictive material and the permanent magnet are arranged coaxially, and the bias magnetic field strength within the magnetostrictive material can be changed by relatively moving the permanent magnet and the magnetostrictive material. magnetostrictive element.

(2) The magnetostrictive element according to (1) above, wherein the magnetostrictive material and the permanent magnet are not in contact with each other.

(3) The magnetostrictive element according to (1) or (2) above, wherein the permanent magnet is a laminate of a ring-shaped permanent magnet and a ring-shaped nonmagnetic material.

<Example> Hereinafter, the present invention will be described in detail based on a preferred example shown in the drawings.

FIG. 1 shows a preferred embodiment of the magnetostrictive element of the present invention.

The magnetostrictive element 1 shown in FIG. 1 includes a magnetostrictive material 2 and a magnetostrictive material 2.
a coil 3 wound through an insulating material 6, a cylindrical permanent magnet 4 disposed coaxially with the magnetostrictive material 2, and a permanent magnet 4.
It has an inner cylinder 7 adhered to the outer circumferential side of the cylinder, and an outer cylinder 5 which is screwed into the inner cylinder 7. The magnetostrictive material 2 and the coil 3 are fixed or fixedly arranged with respect to the outer cylinder 5 by a connecting member (not shown) or the like, and the permanent magnet 4 and the inner cylinder 7 are rotated by a driving means (not shown). It is configured.

Note that the axis of the magnetostrictive material 2 refers to the longitudinal direction in FIG. 1, that is, the axis in the direction of displacement due to magnetostriction.

When such a magnetostrictive element 1 is used as an active element such as a magnetostrictive actuator or a magnetostrictive vibrator, the coil 3 is connected to an AC power source and/or a DC power source.

Further, when the magnetostrictive element 1 is used as a passive element such as a magnetostrictive sensor, various measuring instruments for detecting current, voltage, etc. induced in the coil 3 are connected to the coil 3.

Permanent magnet 4 is provided to apply a DC bias magnetic field to magnetostrictive material 2 . A certain amount of magnetostriction is generated in advance in the magnetostrictive material 2 by the bias magnetic field applied by the permanent magnet 4.

Then, when the permanent magnet 4 is rotated by the driving means, the permanent magnet 4 moves in the axial direction with respect to the magnetostrictive material 2.

As the permanent magnet 4 moves away from the magnetostrictive material 2, the intensity of the bias magnetic field applied to the magnetostrictive material 2 decreases, and conversely, as the permanent magnet 4 approaches the magnetostrictive material 2, the intensity of the bias magnetic field applied to the magnetostrictive material 2 decreases. To increase. In this way, the initial magnetostriction value of the magnetostrictive material 2 can be changed.

In addition, in FIG. 1, the magnetostrictive material 2 is fixed within the element and the permanent magnet 4 is moved relative to it, but the effect of the present invention will be improved if the magnetostrictive material 2 and the permanent magnet 4 move relative to each other. Realize.

Therefore, the magnetostrictive material 2 may be configured to be movable, or both the permanent magnet 4 and the magnetostrictive material 2 may be configured to be movable.

In any of the above cases, it is preferable that the permanent magnet 4 and/or the magnetostrictive material 2 be configured to move in the axial direction of the cylindrical permanent magnet 4. This allows the moving mechanism to have a simple configuration. Furthermore, the change profile of the applied magnetic field strength due to movement can be made relatively simple. Furthermore, since the magnet and the magnetostrictive material can be placed close to each other, the magnet can be used efficiently and the element can be miniaturized.

Note that the permanent magnet 4 may be composed of a plurality of ring-shaped permanent magnets, and at least one ring-shaped permanent magnet may be configured to be movable. Even with such a configuration, it is possible to change the magnetic field strength applied to the magnetostrictive material 2.

In the magnetostrictive element of the present invention, the permanent magnet 4 may have a cylindrical shape with at least one end open, and other than that, the shape is not particularly limited.

For example, the outer surface and/or the inner surface may be polyhedral, or may be pot-shaped with one end closed.

However, among these, a cylindrical magnet with both ends open as shown in FIG. 1 is preferred because it is easy to manufacture and easy to magnetize.

In addition, the reason why the magnetostrictive material 2 and the permanent magnet 4 are provided coaxially is as follows.
This is to efficiently utilize the magnetic flux from the permanent magnet 4,
This is also to reduce the size of the element.

The coil 3 is provided between the permanent magnet 4 and the magnetostrictive material 2 as shown in FIG. 1 because it facilitates the movement of the permanent magnet 4 and allows efficient application of a magnetic field to the magnetostrictive material 2. is preferable, but it may be provided outside the permanent magnet 4.

It is preferable that the magnetostrictive material 2 and the permanent magnet 4 are arranged so as not to come into contact with each other. This is because when the magnetostrictive material 2 and the permanent magnet 4 are in contact with each other and are connected in series in the displacement direction of the magnetostrictive material 2, the displacement is caused by the roughness of the contact surfaces of the magnetostrictive material 2 and the permanent magnet 4. This is because it gets absorbed.

In the present invention, the permanent magnet 4 is preferably a laminate of a ring-shaped permanent magnet 41 and a ring-shaped nonmagnetic material 42, as shown in FIG.

When the permanent magnet 4 is composed of a single permanent magnet, the second b
As shown in the figure, the magnetic field becomes strong near both ends of the permanent magnet 4, that is, near the magnetic poles, and becomes weak in the middle. However, if the permanent magnet 4 is made of a laminate of a ring-shaped permanent magnet 41 and a ring-shaped non-magnetic material 42, a plurality of magnetic poles will exist in the axial direction of the permanent magnet 4, which is not shown in FIG. 2a. Thus, a magnetic field of relatively uniform strength can be applied to the magnetostrictive material. In addition,
The variation of the magnetic field shown in the graphs of FIGS. 2a and 2b is on the axis of the permanent magnet 4.

In such a configuration, if the permanent magnet 4 is long, for example, 20
It is extremely effective when the thickness is 30 mm or more, especially 30 mm or more.

There is no limit to the composition of the permanent magnet used in the present invention, and various ferrite magnets, metal magnets, etc. may be used.

Further, the material of the ring-shaped nonmagnetic body 42 is not particularly limited as long as it is nonmagnetic, and various resins such as nylon, various nonmagnetic metals such as stainless steel, etc. can be used.

Although there is no particular restriction on the ratio of the lengths of the ring-shaped permanent magnet 41 and the ring-shaped nonmagnetic body 42, it is possible to achieve the above effects,
In order to minimize the non-magnetic portion of the permanent magnet 4, the length of the ring-shaped non-magnetic body 42 is preferably about 0.5 to 1 times the length of the ring-shaped permanent magnet 41. Further, there is no particular restriction on the length of the ring-shaped permanent magnet, and it may be set to an appropriate length depending on the dimensions of the magnetostrictive material, but it is usually about 3 to 10 mm.

Although there is no particular restriction on the dimensions of the permanent magnet 4, it is preferable that the total length in the axial direction be equal to or longer than the length of the magnetostrictive material.

There is no particular restriction on the shape of the magnetostrictive material 2, and it may be a normal shape such as a rod, annular, or cylindrical shape.

In addition, the magnetostrictive material 2 may be formed by laminating and adhering thin plates, or may be formed by bundling and adhering wire rods.

Further, there is no particular restriction on the dimensions of the magnetostrictive material 2, and it may be set to an appropriate dimension depending on the intended element, but usually the length is 1.
It is about 0 to 70 mm.

There is no particular restriction on the length of the coil 3, but it is preferably about 0.8 times or more the length of the magnetostrictive material in order to effectively apply the magnetic field. The dimensions may be such that it is not difficult to extract the displacement to the outside of the element.

Note that the effect of the present invention is achieved when the magnetostrictive material 2 and the permanent magnet 4 move relative to each other, so the moving means is not limited to a means using a screw as shown in FIG. Any object may be used as long as it can be moved.

Further, there is no particular restriction on the driving means for these movements, and various automatic means using various motors, transmission gears, etc. can be suitably used. Moreover, various manual means can also be used.

Note that the resonance frequency of a magnetostrictive material containing a rare earth metal element and iron changes according to changes in the applied magnetic field strength. Therefore, when driving with an alternating magnetic field, it is preferable to change the frequency in conjunction with a change in the resonant frequency of the magnetostrictive material 2 that corresponds to a change in the bias magnetic field strength. In order to apply such an alternating magnetic field, it is preferable to use an automatic tracking frequency oscillator. Thereby, it is possible to automatically track changes in the resonant frequency corresponding to changes in the bias magnetic field strength, and to always apply an alternating current magnetic field with a frequency equal to the resonant frequency.

When applying the present invention to active elements such as actuators and vibrators, by applying a driving magnetic field from the coil 3,
The amount of magnetostriction is superimposed according to the magnetic field strength. Note that when the magnetic field applied from the coil 3 is alternating current, the magnetostrictive material vibrates at a frequency equal to the applied alternating magnetic field.

Furthermore, when applied to a passive element, external vibrations or shocks received by the magnetostrictive material 2 induce current and voltage in the coil 3 due to the Hillary effect.

For active elements such as magnetostrictive actuators and magnetostrictive vibrators, the intensity of the bias magnetic field applied to the magnetostrictive material 2 is preferably set to a magnetic field intensity that provides the highest rate of change in the amount of magnetostriction. Note that when the drive magnetic field is a direct current, it is not necessary to set the bias magnetic field strength to such a value, and it is also possible to set the bias magnetic field strength to a lower value to increase the amount of displacement.

Further, in the magnetostrictive sensor, it is preferable that the magnetic field intensity is such that the applied magnetic field intensity and the amount of magnetostriction are in a substantially proportional relationship.

In the magnetostrictive element of the present invention, the strength of the bias magnetic field to be applied may be determined according to the characteristics of the magnetostrictive material so as to satisfy the above-mentioned conditions, and its range is not particularly limited, but is usually about 6000e or less. . Further, there is no particular limit to the range of change in the bias magnetic field strength, and it may be determined depending on the purpose, but it is usually about 2000e or less.

When the magnetostrictive element of the present invention is used as an active element, the strength of the alternating current magnetic field or direct current magnetic field superimposed on the bias magnetic field is usually 1
It is about 5000e or less, and its frequency is usually determined according to the resonant frequency of the magnetostrictive material described above. In addition,
The number of turns of the coil of the alternating current magnetic field generating means may be appropriately determined depending on the strength of the applied magnetic field.

Note that the present invention is not limited to a configuration in which the permanent magnet 4 and the magnetostrictive material 2 move relative to each other in the axial direction, but may also be configured so that the permanent magnet 4 moves in a direction perpendicular to the axis.

In this case, the permanent magnet 4 is composed of a plurality of small pieces obtained by dividing a cylindrical body at least in the radial direction, and at least one small piece is configured to be movable in a direction perpendicular to the axis of the magnetostrictive material 2.

Even with such a configuration, the effects of the present invention can be achieved, and it is useful when applied to an element whose configuration is difficult to move in the axial direction.

The magnetostrictive material 2 used in the present invention contains a rare earth metal element and iron. Since such magnetostrictive materials have a large amount of magnetostriction,
It is suitable for both active elements such as magnetostrictive actuators and passive elements such as magnetostrictive sensors.

Although there are no particular limitations on rare earth elements and rare earth elements containing iron, it is preferable that the magnetostriction amount ΔI2/flooding under a DC magnetic field of 1 kOe is 400 ppm or more. In particular, when those having the following compositions are used, better magnetostrictive elements can be obtained.

[Formula■] RT.

Here, R represents one or more rare earth elements including yttrium (Y), and T represents one or more of Fe, Ni, and Co.

In the above composition, 1.5≦X≦2.5, especially 1.85
It is preferable that ≦X≦2.00.

When X is outside the above range, the amount of magnetostriction in a high magnetic field and the amount of change in magnetostriction dλ/dH per unit magnetic field strength decrease.

Rare earth elements include La, Nd, Pm, Sm, Gd%
Tb%Eu%Dy, Ho%Er.

Lanthanide elements of Yb%Lu%Tm are preferred, and combinations of one or more elements selected from these include Sm
, Tb, Dy%Ho%Er and Tm alone, TbGd,
TbDy, TbHo%TbHoDy%SmTb.

Combinations of two or more of SmDy, SmHo, SmEr1 5mHoDy, HoEr and HosE r and Dy are preferred, and among these, Tb is particularly preferred since it has excellent magnetostriction in high and low magnetic fields at room temperature. alone, part of Tb is Dy and/
Or substituted with Ho, Sm alone, part of Sm replaced with D
Those substituted with y and/or Ho are preferred.

Note that those containing Tb exhibit positive magnetostriction, and those containing Sm exhibit negative magnetostriction.

In addition, in such a composition, 30 at% of the total
A transition metal element, Zn, etc. may be contained within the range.

As transition metal elements, 5c1Ti, V, Cr%Mn%
Fe%Co%Ni%Cu%Y.

Zr%Nb%Mo, Tc%Ru, Rh%Pd.

Ag%Cd, Hf, Ta, W, Re, Os.

Ir%pt%Au%Hg can be used.

Such magnetostrictive materials are described in US Pat. No. 4,375,372, US Pat. No. 4,152,178, and US Pat.
Specification No. 1, Specification No. 4308474, Specification No. 437
Specification No. 8258, etc., Japanese Patent Application Laid-open No. 53-64798,
Japanese Patent Application No. 62-172376 filed by the present applicant, No. 62-
No. 227962, No. 62-227963, No. 63-2
No. 84133, No. 63-284134, Patent Application No. 1-4
No. 1171, etc.

Such magnetostrictive materials can be manufactured by - simple alloy manufacturing methods, e.g.
It is manufactured by an arc melt method, a unidirectional solidification method, a zone melt method, a high frequency melting method, a powder metallurgy method, etc., is molded into a predetermined shape and size, and is used as a magnetostrictive material for a magnetostrictive element.

<Operations and Effects of the Invention> The magnetostrictive element of the present invention uses a permanent magnet to generate a bias magnetic field.

Therefore, unlike the case where alternating current is used to generate the bias magnetic field, there is no need for chokes, capacitors, etc., and the structure is simple and can be made smaller.

Furthermore, in the present invention, since the permanent magnet and the magnetostrictive material are configured to be relatively movable, it is possible to change the bias magnetic field strength within the magnetostrictive material even though the permanent magnet is used to generate the bias magnetic field. be.

Therefore, even if the properties of the magnetostrictive material vary, the strength of the bias magnetic field can be easily adjusted to the optimum bias field strength after being incorporated into an element, resulting in good productivity.

In addition, since any initial magnetostriction value can be obtained by changing the bias magnetic field strength, it is extremely suitable for applications such as magnetostrictive actuators and magnetostrictive sensors, where the absolute amount of displacement and the linearity of displacement with respect to changes in magnetic field strength are issues. Useful.

Furthermore, in conventional magnetostrictive elements, the permanent magnet is placed in series in the displacement direction in contact with the magnetostrictive material, so the displacement of the magnetostrictive material is absorbed at the interface between the two, making it difficult to obtain an accurate amount of displacement. However, in the present invention, since the magnetostrictive material and the permanent magnet are configured in a non-contact manner, an accurate amount of displacement can be obtained.

When a permanent magnet is constructed by laminating a ring-shaped permanent magnet and a ring-shaped nonmagnetic material, a bias magnetic field can be strongly and uniformly applied to the magnetostrictive material.

4,

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a preferred embodiment of the magnetostrictive element of the present invention. FIG. 2a is a graph showing the magnetic field strength on the axis of a cylindrical permanent magnet which is a laminate of a ring-shaped permanent magnet and a ring-shaped nonmagnetic material. FIG. 2b is a graph showing the magnetic field strength on the axis of a cylindrical permanent magnet made of a single material. Explanation of symbols 1...Magnetostrictive element 2...Magnetostrictive material 3...Coil 4...Permanent magnet 41...Ring-shaped permanent magnet 42...Ring-shaped nonmagnetic material 5...Outer tube 6 ...Insulator 7...Inner cylinder Applicant: TDT-K Co., Ltd., agent Patent attorney Seika Ishii, patent attorney
Increase 1) Tatsuya FIG, 1 FIG, 20 1-IG, 2b

Claims (3)

[Claims] (1) A magnetostrictive material containing a rare earth metal element and iron, a permanent magnet for generating a bias magnetic field, and a coil, the permanent magnet having a cylindrical shape with at least one end open, and the magnetostrictive material and the permanent magnet are arranged coaxially, and the bias magnetic field strength within the magnetostrictive material can be changed by relatively moving the permanent magnet and the magnetostrictive material. magnetostrictive element. (2) The magnetostrictive element according to claim 1, wherein the magnetostrictive material and the permanent magnet are not in contact with each other. (3) The magnetostrictive element according to claim 1 or 2, wherein the permanent magnet is a laminate of a ring-shaped permanent magnet and a ring-shaped nonmagnetic material.