Magnetostrictive member and method of manufacturing the same

Abstract

To provide a magnetostrictive member and a method of manufacturing the same that can easily evaluate the device characteristics when manufacturing a magnetostrictive vibration power generation device, and that use a stable index that is not affected by the size or thickness of the magnetostrictive member, thereby achieving large device characteristics and suppressing variations in optimal magnetic field strength.SOLUTION: A plurality of magnetostrictive members are obtained from the same crystal, and are plate-shaped members made of iron-based alloy crystals having magnetostrictive properties, and having longitudinal and lateral directions, and at least one of the front and back surfaces of the plate-shaped member has multiple grooves extending in the longitudinal direction, and the plurality of magnetostrictive members has an optimal magnetic field strength that is the magnetic field strength at which the half-value frequency coupling coefficient (=kf1f2) obtained by electro-mechanical equivalent circuit analysis is maximized, and the ratio (standard deviation / average value) of the standard deviation of the optimal magnetic field strength to the average value of the optimal magnetic field strength is 0.2 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetostrictive member and a method for manufacturing a magnetostrictive member. [Background technology]

[0002] Magnetostrictive materials have been attracting attention as functional materials. For example, Fe-Ga alloys, which are iron-based alloys, exhibit magnetostrictive and inverse magnetostrictive effects, exhibiting large magnetostriction of approximately 100 to 350 ppm. Therefore, in recent years, they have attracted attention as vibration-powered energy harvesting materials in the energy harvesting field, and are expected to be applied to wearable devices, sensors, and the like. A single crystal growth method using the Czochralski method (hereinafter abbreviated as the "Cz method") is known as a method for producing Fe-Ga alloy single crystals (e.g., Patent Document 1). Other known production methods besides the Cz method include the vertical Bridgman method (VB method) and the vertical gradient freezing method (VGF method) (e.g., Patent Documents 2 and 3).

[0003] Fe-Ga alloys are crystalline <100> The magnetostrictive material of Fe-Ga alloy has an easy axis of magnetization in the direction of the magnetization, and can exhibit large magnetostriction in this direction. <100> Magnetostrictive materials are manufactured by cutting a single crystal portion oriented in a certain direction to the desired size (for example, Non-Patent Document 1). However, since the crystal orientation has a large effect on the magnetostrictive properties, the direction in which the magnetostriction of the magnetostrictive material is required and the direction in which the magnetostriction of the crystal is greatest are also important. <100> It is believed that a single crystal with the same orientation is the best material for the magnetostrictive member.

[0004] Fe-Ga alloy single crystals are <100> When a magnetic field is applied parallel to the direction, positive magnetostriction appears (hereinafter referred to as "parallel magnetostriction"). <100> When a magnetic field is applied perpendicular to the orientation, negative magnetostriction appears (hereinafter referred to as "perpendicular magnetostriction"). When the strength of the applied magnetic field is gradually increased, the parallel magnetostriction or perpendicular magnetostriction saturates. The magnetostriction constant (3 / 2λ 100) is determined by the difference between the saturated parallel magnetostriction amount and the saturated perpendicular magnetostriction amount, and is calculated by the following formula (A) (for example, Patent Document 4, Non-Patent Document 2).

[0005] 3 / 2λ 100 =ε( / / )― ε(⊥) ···Formula (A) 3 / 2λ 100 : Magnetostriction constant ε( / / ): <100> Parallel magnetostriction when saturated by applying a magnetic field parallel to the direction ε(⊥): <100> Amount of perpendicular magnetostriction when saturated by applying a magnetic field perpendicular to the direction

[0006] The magnetostrictive properties of Fe-Ga alloys are believed to affect the magnetostrictive and inverse magnetostrictive effects and the characteristics of magnetostrictive vibration power generation devices, and are an important parameter in device design (e.g., Non-Patent Document 4). In particular, the magnetostrictive constant depends on the Ga composition of the Fe-Ga alloy single crystal, and it is known that the magnetostrictive constant is maximized at Ga compositions of 18-19 at% and 27-28 at% (e.g., Non-Patent Document 2). It is considered desirable to use Fe-Ga alloys with such Ga concentrations in devices. Furthermore, in recent years, it has been reported that in addition to a large magnetostrictive constant, the greater the parallel magnetostriction, the better the device characteristics, such as output voltage, tend to be (e.g., Non-Patent Document 3).

[0007] A magnetostrictive vibration power generation device is composed of, for example, an Fe-Ga magnetostrictive member wound around a coil, a yoke, and a permanent magnet for the field magnet (for example, Patent Document 5 and Non-Patent Document 4). In this magnetostrictive vibration power generation device, when the yoke, which is the moving part of the device, is vibrated, the Fe-Ga magnetostrictive member fixed to the center of the yoke vibrates in conjunction with it, and the inverse magnetostrictive effect changes the magnetic flux density of the coil wound around the Fe-Ga magnetostrictive member, generating an electromagnetically induced electromotive force and generating electricity. In a magnetostrictive vibration power generation device, a force is applied in the longitudinal direction of the yoke, causing vibration, so the Fe-Ga magnetostrictive member used in the device must be aligned along the easy axis of magnetization. <100> It is desirable to process it so that the direction of the arrow is in the longitudinal direction. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2016-28831 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-138028 [Patent Document 3] Japanese Patent Application Publication No. 4-108699 [Patent Document 4] Special Publication No. 2015-517024 [Patent Document 5] International Publication No. 2011 / 158473 [Patent Document 6] International Publication No. 2021 / 100467 [Patent Document 7] Japanese Patent Application Publication No. 2020-63997 [Non-patent literature]

[0009] [Non-Patent Document 1] Etrema, State of the Art of Galfenol Processing. [Non-patent document 2] AE Clark et al., Appl. Phys. 93(2003)8621. [Non-patent document 3] Jung Jin Park, Suok-Min Na, Ganesh Raghunath, and Alison B. Flatau., AIP ADVANCES 6, 056221(2016). [Non-patent document 4] Toshiyuki Ueno, Journal of the Japan Society for Precision Engineering, Vol. 79, No. 4, (2013) 305-308. [Non-Patent Document 5] Journal of Marine Acoustics, Vol. 24, No. 3 (1997) Summary of the Invention [Problem to be solved by the invention]

[0010] Since the device characteristics of magnetostrictive vibration power generation devices are affected by the magnetostrictive properties of the magnetostrictive material, the magnetostrictive material is required to have high magnetostrictive properties and little variation in the magnetostrictive properties. <100> It was thought that if the Ga concentration was uniform, a magnetostrictive member with a uniform magnetostriction constant would be obtained. However, as described in Non-Patent Document 3, it is disclosed that device characteristics are affected not only by the magnetostriction constant but also by the amount of parallel magnetostriction. Therefore, Patent Document 6 discloses that by adding multiple grooves, such as grinding marks, extending in the longitudinal direction of the magnetostrictive member, it is possible to obtain a magnetostrictive member with a high magnetostriction constant and amount of parallel magnetostriction and with little variation in the magnetostriction constant and amount of parallel magnetostriction between members. When this magnetostrictive member was incorporated into the magnetostrictive vibration power generation device and the device characteristics were confirmed, it was confirmed that a predetermined device output (e.g., power generation amount such as force coefficient) was obtained and that there was little variation in the device output between devices.

[0011] However, to maximize the output (power generation) of the device, it is necessary to appropriately set the magnetic flux density of the magnet incorporated into the device. More specifically, the magnetic flux density (hereinafter referred to as the optimal magnetic field strength) must be approximately half the maximum parallel magnetostriction of the magnetostrictive material incorporated into the device.

[0012] Here, in the magnetostrictive vibration power generation device using the magnetostrictive member of Patent Document 6, there is a large variation in the optimal magnetic field strength of the magnetostrictive material, and in order to improve the output of the device, it is necessary to adjust the magnet strength (magnetic flux density) for each device, which reduces productivity.

[0013] Furthermore, in the above, the device output is evaluated using a force coefficient, but since the force coefficient depends on the size and thickness of the magnetostrictive member, it was necessary to set an appropriate value for each size and thickness of the magnetostrictive member.

[0014] Therefore, the present invention aims to provide a magnetostrictive member and a method for manufacturing a magnetostrictive member that can be easily evaluated based on the device characteristics when incorporated into the magnetostrictive vibration power generation device using a magnetostrictive member that has a high amount of parallel magnetostriction and little variation in the amount of parallel magnetostriction between members, and that uses a stable index that is not affected by the size or thickness of the magnetostrictive member, and that has large device characteristics based on this index and also suppresses variation in the optimal magnetic field strength. [Means for solving the problem]

[0015] According to an aspect of the present invention, there is provided a magnetostrictive member obtained in plurality from the same crystal, which is a plate-like member made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction and a lateral direction, and at least one of the front and rear surfaces of the plate-like member has a plurality of grooves extending in the longitudinal direction, and the plurality of magnetostrictive members have a half-value frequency coupling coefficient (=k f1f2 The strength at which the difference (standard deviation) is maximized is defined as the optimum magnetic field strength, and a magnetostrictive member is provided in which the ratio of the standard deviation of the optimum magnetic field strength to the average value of the optimum magnetic field strength (standard deviation / average value) is 0.2 or less.

[0016] Furthermore, the plurality of magnetostrictive members have a half-value frequency coupling coefficient (=k f1f2 ) is the standard deviation of the maximum value and the half-value frequency coupling coefficient (=k f1f2 ) to the average value of the maximum value (standard deviation / average value) may be 0.3 or less. The plurality of magnetostrictive members may also have a half-value frequency coupling coefficient (=k f1f2 ) is the standard deviation of the maximum value and the half-value frequency coupling coefficient (= k f1f2 ) may be configured such that the ratio of the maximum value of the standard deviation to the average value (standard deviation / average value) is 0.1 or less.

[0017] Furthermore, there are magnetostrictive members obtained in plural from the same crystal, which are made of crystals of an iron-based alloy having magnetostrictive properties, and are plate-shaped bodies having a longitudinal direction and a lateral direction, and the plural magnetostrictive members have a half-value frequency coupling coefficient (= k f1f2) is the strength at which it is maximized, and the ratio of the standard deviation of the optimum magnetic field strength to the average value of the optimum magnetic field strength (standard deviation / average value) is 0.2 or less, and the half-value frequency coupling coefficient (=k f1f2 The magnetostrictive member has a ratio (standard deviation / average value) of the standard deviation of the maximum value of the half-value frequency coupling coefficient to the average value of the maximum value of the half-value frequency coupling coefficient of 0.3 or less. The thickness of the plate-like body may be 0.3 mm or more and 5 mm or less.

[0018] According to an aspect of the present invention, there can be provided a method for manufacturing a magnetostrictive member of the above aspect, which comprises forming a plurality of grooves extending in the longitudinal direction on at least one of the front and back surfaces of a plate-shaped body made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction and a lateral direction, and heat-treating the plate-shaped body having the plurality of grooves extending in the longitudinal direction formed thereon.

[0019] The plurality of grooves may be formed by surface grinding. The heat treatment temperature may be 400°C or higher and 700°C or lower. The heat treatment holding time may be 5 hours or less. The heat treatment method may further include re-grooving the plurality of grooves extending in the longitudinal direction of the heat-treated plate-like body. The method may further include a cutting step of cutting the plate-like body with the plurality of grooves formed therein, and a chamfering step of chamfering the plate-like body cut in the cutting step. [Effects of the Invention]

[0020] According to an aspect of the present invention, it is possible to provide a magnetostrictive member and a method for manufacturing a magnetostrictive member, which have a high parallel magnetostriction amount and little variation in the parallel magnetostriction amount between members, and which can easily evaluate the device characteristics when a magnetostrictive vibration power generation device is manufactured using a magnetostrictive member that has a stable index that is not affected by the size or thickness of the magnetostrictive member, and which has high device characteristics and suppresses variation in the optimal magnetic field strength. [Brief explanation of the drawings]

[0021] [Figure 1] 1A and 1B are diagrams showing an example of a magnetostrictive member according to an embodiment. [Figure 2] FIG. 10 is a diagram showing an example of a change in a BH curve when stress is applied to a magnetostrictive member. [Figure 3] FIG. 1 illustrates an example of an impedance measuring device. [Figure 4] FIG. 2 is a diagram showing an electromechanical equivalent circuit of a measurement coil. [Figure 5] 3 is a flowchart showing an example of a method for manufacturing a magnetostrictive member according to an embodiment. [Figure 6] 1A and 1B are diagrams showing examples of single crystal and thin plate members. DETAILED DESCRIPTION OF THE INVENTION

[0022] The following description will be made with reference to the drawings. In each drawing, some or all of the components are shown in schematic form and scaled as appropriate.

[0023] [Embodiment] The magnetostrictive member and the method for manufacturing the magnetostrictive member according to this embodiment will be described below.

[0024] (Magnetostrictive material) First, the magnetostrictive member of this embodiment will be described. Fig. 1 is a diagram showing an example of the magnetostrictive member according to the embodiment.

[0025] As shown in Fig. 1, the magnetostrictive member 1 is a plate-like body having a longitudinal direction D1 and a lateral direction D2. The plate-like body is preferably rectangular in plan view. The plate-like body has a front surface 3 and a back surface 4. The front surface 3 and the back surface 4 are preferably parallel to each other, but do not have to be parallel to each other.

[0026] The magnetostrictive member 1 is made of an iron-based alloy crystal. Multiple magnetostrictive members 1 are obtained from the same crystal. The iron-based alloy is not particularly limited as long as it has magnetostrictive properties. Magnetostrictive properties refer to the property of changing shape when a magnetic field is applied. Examples of iron-based alloys include Fe-Ga, Fe-Ni, Fe-Al, Fe-Co, Tb-Fe, Tb-Dy-Fe, Sm-Fe, and Pd-Fe. The above alloys may also be alloys to which a third component has been added. For example, an Fe-Ga alloy may be alloyed to which Ba, Cu, or the like has been added. Among these iron-based alloys, Fe-Ga alloys have greater magnetostrictive properties and are easier to process than other alloys. Therefore, they are used in vibration power generation materials in the energy harvesting field, wearable devices, sensors, and the like. In the following explanation, an example of a magnetostrictive member 1 will be described in which the magnetostrictive member 1 is made of a single crystal of an Fe-Ga alloy.

[0027] The single crystal of the Fe-Ga alloy has a body-centered cubic lattice structure, and the first to third directional indices in the Miller indices <100> The basis of this is that the axes (see FIG. 6) are equivalent, and the first to third {100} planes (see FIG. 6) among the plane indices in the Miller index are equivalent (i.e., (100), (010), and (001) are equivalent). Furthermore, Fe-Ga alloys have the property of producing large magnetostriction in a specific orientation of the crystal. When this property is utilized in a magnetostrictive vibration power generation device, it is desirable to match the direction in the device where magnetostriction of the magnetostrictive member 1 is required with the orientation (direction) where the magnetostriction of the crystal is at its maximum. Specifically, as mentioned above, the direction of easy magnetization in a single crystal is <100> It is desirable to set the direction in the longitudinal direction D1 of the magnetostrictive member 1. <100> The direction can be set to the longitudinal direction D1 of the magnetostrictive member 1, for example, by calculating the crystal orientation of the single crystal using known crystal orientation analysis and cutting the single crystal based on the calculated crystal orientation of the single crystal.

[0028] The crystal that can be used for the magnetostrictive member 1 of this embodiment may be a single crystal or a polycrystal. <100> In order to increase the degree of orientation integration in the direction and improve the properties of the magnetostrictive material, it is advantageous to use a single crystal rather than a polycrystal. Although polycrystals have inferior magnetostrictive properties to single crystals, they can be produced at low cost, so polycrystals are sometimes used.

[0029] Magnetostrictive members 1 are used, for example, as materials (components) for vibration power generation devices in the energy harvesting field, and as materials (components) for wearable terminals and sensors. For example, a magnetostrictive vibration power generation device such as that shown in Patent Document 5 above is composed of a coil, a magnetostrictive member made of an Fe-Ga alloy wound around the coil, a yoke, and a permanent magnet for a field magnet. This magnetostrictive vibration power generation device has a mechanism in which, when the yoke, which is the moving part of the device, is vibrated, the magnetostrictive member fixed to the center of the yoke vibrates in conjunction with the yoke. The inverse magnetostrictive effect changes the magnetic flux density of the coil wound around the magnetostrictive member, generating electromagnetically induced electromotive force, thereby generating electricity. When used in such a mechanism, the magnetostrictive member 1 is preferably thin and rectangular in shape in a plan view. There are no particular limitations on the thickness of the magnetostrictive member 1. For example, a thickness of 0.3 mm to 5 mm is preferred. The shape and size of the magnetostrictive member 1 are appropriately determined depending on the size of the intended device. For example, the length of the long side of the magnetostrictive member 1 may be any of 10 mm or more, 30 mm or more, 60 mm or more, and 80 mm or more. For example, the size of the magnetostrictive member 1 may be such that the length (dimension) in the longitudinal direction D1 is 16 mm, the width (dimension) in the lateral direction D2 is 4 mm, and the thickness is 0.5 mm.

[0030] The shape and dimensions of the magnetostrictive member 1 are not particularly limited. For example, the magnetostrictive member 1 does not have to be rectangular in plan view. For example, the shape of the magnetostrictive member 1 may be elliptical, track-shaped, or irregular in plan view. When the shape of the magnetostrictive member 1 is other than rectangular in plan view, the longitudinal direction D1 is the major axis direction, long axis direction, etc., and the lateral direction D2 is the direction perpendicular to the longitudinal direction D1.

[0031] As described above, the inventors of the present invention confirmed that, as described in Patent Document 6, by adding multiple grooves, such as grinding marks, extending in the longitudinal direction of a magnetostrictive member, it is possible to obtain a magnetostrictive member with a high magnetostriction constant and parallel magnetostriction amount and little variation in the magnetostriction constant and parallel magnetostriction amount between members. However, in magnetostrictive vibration power generation devices using this magnetostrictive member, the optimum magnetic field strength of the magnetostrictive member varies greatly, requiring adjustment of the magnet strength for each device according to the variation in the optimum magnetic field strength, which reduces productivity. Therefore, the inventors have discovered that the variation in the optimum magnetic field strength can be reduced by heat-treating the magnetostrictive member. The present invention is based on this finding.

[0032] Since magnetostrictive materials are used in magnetostrictive vibration power generation devices, we will first explain the principles of magnetostrictive vibration power generation. The easy axis of magnetization of iron-based magnetostrictive materials is

[0100] . As shown in Figure 2, when compressive stress is applied in the

[0100] direction, the applied magnetic field strength required for magnetic saturation increases, while when tensile stress is applied in the

[0100] direction, the applied magnetic field strength required for magnetic saturation decreases. When a bias magnetic field is applied to a magnetostrictive material, generating compressive and tensile stresses continuously, the magnetic flux density, which is the difference between the BH curves, changes. Magnetostrictive vibration power generation utilizes this change in magnetic flux density to generate an AC current in a coil wrapped around the magnetostrictive material through Faraday's electromagnetic induction.

[0033] In Figure 2, when there is no magnetic field (magnetic field strength is 0 kA / m), the magnetic flux density is close to 0 T during both compression and tension, so there is no change in the magnetic flux density and no power generation occurs. As the magnetic field strength increases, a difference in magnetic flux density occurs between compression and tension, making it possible to generate power. When the magnetic field strength becomes very large, the magnetic field saturates during both compression and tension, so there is almost no difference in magnetic field strength and no power generation occurs. Therefore, in order to generate power efficiently, it is necessary to apply an optimized magnetic field strength so that the difference in magnetic flux density between compression and tension is maximized. In this specification, the magnetic field strength at this point is referred to as the optimal magnetic field strength.

[0034] Furthermore, as a method for evaluating the power generation characteristics of a magnetostrictive vibration power generation device, there is an evaluation method based on analysis (impedance measurement) using an electromechanical equivalent circuit, as disclosed in Patent Document 7 and Non-Patent Document 5 above.

[0035] Below, we will explain analysis (impedance measurement) using an electromechanical equivalent circuit. Figure 3 shows an overview of the impedance measurement device. A bias magnetic field is generated by an excitation coil using a DC (direct current) power supply, magnetizing the magnetostrictive material. The impedance of the measurement coil is measured with the magnetostrictive material placed inside the measurement coil. The equivalent circuit of the measurement coil is shown in Figure 4, and the equivalent impedance of this circuit can be expressed by equation (1) below. The force coefficient α is the degree of coupling between the mechanical system and the electrical system, and is an index of the efficiency of energy conversion from mechanical energy to electrical energy, and is positively correlated with the power generation output of the vibration power generation device.

[0036]

number

[0037] The measured impedance loop is converted into a dynamic impedance loop by removing the electric circuit component from the measured impedance loop, and the force coefficient α is calculated using the following equations (2) and (3).

number

number

[0038] The impedance measurement is performed multiple times while changing the bias magnetic field generated by the excitation coil by changing the current of the DC power supply. When the force factor α is measured while changing the magnetic field strength from 0 kA / m to the saturation magnetic field, the force factor α is maximized near half the saturation magnetic field strength and decreases elsewhere. The magnetic field strength at which the force factor α is maximized is the optimal magnetic field strength. The force factor α at the optimal magnetic field strength is defined as the force factor αmax (note that the force factor αmax may also be abbreviated to "force factor"). That is, a bias magnetic field is generated to magnetize the magnetostrictive material, and the impedance of the measurement coil is measured with the magnetostrictive material placed in the measurement coil multiple times while changing the bias magnetic field up to the saturation magnetic field strength. Based on the measurement results of the impedance of the measurement coil obtained, the optimal magnetic field strength, which is the magnetic field strength at which the force factor α is maximized, and the characteristics of the magnetostrictive member, including the force factor αmax at the optimal magnetic field strength, can be determined.

[0039] The power generation characteristics of magnetostrictive materials can be evaluated by the force coefficient αmax, but if the magnetic field strength deviates from the optimal magnetic field strength, the power generation characteristics will decrease. In other words, since the force coefficient α depends on the applied magnetic field strength, it is ideal to design a bias magnet so that the force coefficient αmax can be used within the power generation device and the magnetic field strength is the optimal magnetic field strength. Therefore, the optimal magnetic field strength is also an important performance indicator, and it is required that there is no variation between magnetostrictive materials. Furthermore, a smaller optimal magnetic field strength is preferable from the perspective of miniaturizing power generation devices, as it allows for the bias magnet to be incorporated into the power generation device to be smaller.

[0040] However, since the force coefficient depends on the size and thickness of the magnetostrictive member, it is necessary to set an appropriate value for each size and thickness of the magnetostrictive member.

[0041] Therefore, the inventors have studied and, as will be explained below, have found that the half-value frequency coupling coefficient (=k f1f2 It has been found that the above problems can be improved by using the above-mentioned property of the magnetostrictive member.

[0042] In this embodiment, the impedance is measured using an analysis (impedance measurement) using an electromechanical equivalent circuit, similar to the force coefficient, and the half-value of the resonance frequency (= f1) and the half-value of the anti-resonance frequency (= f2) obtained from the impedance measurement are used to calculate the half-value frequency coupling coefficient (= k f1f2 ) is calculated.

number

[0043] The half-frequency coupling coefficient is calculated from the impedance measurement using the method described above. The half-frequency coupling coefficient is measured multiple times by varying the excitation strength of the excitation coil. The excitation strength is set multiple times within a range from no magnetic field to magnetic field saturation. Magnetic field saturation can be defined as the state in which the half-frequency coupling coefficient reaches a peak, then drops and becomes nearly constant. The excitation strength varies depending on the material, size, and thickness of the magnetostrictive material, so it is set appropriately. For example, for an FeGa alloy with a thickness of 2 mm and an excitation coil, a magnetic field of 0.2 to 3.6 kA / m can be set. The measurement interval should be set to a current value of 5 to 10 mA flowing through the excitation coil to ensure a resolution that allows the peak position to be determined. The impedance is measured in a frequency range of, for example, 10 kHz to 200 kHz. The measurement frequency range is set to the frequency range in which resonance and antiresonance occur.

[0044] In this embodiment, the half-value of the resonance frequency (= f1) and the half-value of the anti-resonance frequency (= f2) obtained from impedance measurement are used as indicators of magnetostriction characteristics. As a result, the magnetostrictive material has the maximum energy absorption at the half-value frequency, which improves the correlation with the force coefficient. In addition, since the force coefficient is derived using the half-value frequency, the correlation with the half-value frequency coupling coefficient improves.

[0045] Like the force coefficient, the half-frequency coupling coefficient reaches a maximum value at a predetermined magnetic field strength. In the magnetostrictive member of this embodiment, the magnetic field strength at which this half-frequency coupling coefficient is maximized is defined as the optimal magnetic field strength. The force coefficient and the half-frequency coupling coefficient have a nearly positive correlation. Furthermore, the optimal magnetic field strength for the force coefficient and the optimal magnetic field strength for the half-frequency coupling coefficient were nearly identical. The force coefficient tends to increase as the size and thickness of the magnetostrictive member increase. In contrast, as shown in Examples 1 to 4, the half-frequency coupling coefficient is not affected by size and is nearly constant, with a high value and little variation, making it stable. Therefore, by using the maximum value of the half-frequency coupling coefficient as an index for a magnetostrictive member, it can be easily evaluated and can be a stable index that is not affected by the size or thickness of the magnetostrictive member.

[0046] The magnetostrictive member of this embodiment is a plate-like member made of crystals of an iron-based alloy having magnetostrictive properties, having a longitudinal direction and a lateral direction, and at least one of the front and back surfaces of the plate-like member has a plurality of grooves extending in the longitudinal direction, and the magnetic field strength at which the half-value frequency coupling coefficient of the plurality of magnetostrictive members is maximized is defined as the optimal magnetic field strength, and the ratio of the standard deviation of this optimal magnetic field strength to the average value of the optimal magnetic field strength (standard deviation / average value) is 0.2 or less, and the optimal magnetic field strength is calculated by electro-mechanical equivalent circuit analysis. This will be explained in detail below.

[0047] As shown in FIG. 1 , the magnetostrictive member 1 of this embodiment has a plurality of grooves 2 extending in the longitudinal direction D1 on at least one of the front and back surfaces 3 and 4 (sometimes collectively referred to as the “front and back surfaces”). The plurality of grooves 2 extending in the longitudinal direction D1 can be similar to those described in Patent Document 6, for example. As described in Patent Document 6, by forming a plurality of grooves 2 extending in the longitudinal direction D1 on at least one of the front and back surfaces of the magnetostrictive member, both the magnetostriction constant and the parallel magnetostriction amount can be improved to a high level with little variation between members (also referred to as “improving the magnetostriction constant and the parallel magnetostriction amount”), and the parallel magnetostriction amount in particular can be improved. In this embodiment, “the plurality of grooves 2 extending in the longitudinal direction D1” includes the plurality of grooves 2 extending in a direction parallel to the longitudinal direction D1 and the plurality of grooves 2 extending in a direction intersecting the longitudinal direction D1 at an angle of less than 40°.

[0048] It has been found that by forming multiple grooves 2 on the surface of the magnetostrictive member as described above, the magnetostriction constant and parallel magnetostriction amount are stable at high levels. When the impedance measurement described above was performed using this magnetostrictive member, it was found that the force coefficient and half-value frequency coupling coefficient were also stable at high levels. This gives the magnetostrictive member 1 of this embodiment excellent magnetostriction characteristics. Furthermore, it is presumed that by forming multiple grooves 2 on the surface of the magnetostrictive member 1, stress such as residual strain in a certain direction is applied within the crystal, and the magnetic moments are uniformly rearranged, thereby improving the parallel magnetostriction amount, force coefficient, etc. to high levels.

[0049] Furthermore, the magnetostrictive member of this embodiment is modified by heat treatment, which will be described later, so that the variation in magnetostrictive properties is suppressed. For example, from the results of Example 2 (heat treated) and Comparative Example 2 (no heat treatment), which compare magnetostrictive members of the same size that have been heat treated, it can be seen that heat treatment (i) reduces the variation (standard deviation) and the ratio of the standard deviation to the average value (standard deviation / average value) of the half-value frequency coupling coefficient, and (ii) reduces the average value, variation (standard deviation), and the ratio of the standard deviation to the average value (standard deviation / average value) of the optimal magnetic field strength.

[0050] In the magnetostrictive member of this embodiment, the half-value frequency coupling coefficient (=k f1f2 When the magnetic field strength at which the value of (1 / 2) is maximized is defined as the optimum magnetic field strength, the ratio of the standard deviation of the optimum magnetic field strength to the average value of the optimum magnetic field strength (standard deviation / average value) is 0.2 or less, and preferably 0.15 or less.

[0051] Furthermore, the standard deviation of the optimum magnetic field strength is preferably 0.6 or less, and more preferably 0.3 or less.

[0052] In addition, in the magnetostrictive member 1 of this embodiment, the half-value frequency coupling coefficient (=k f1f2 ) and the standard deviation of the maximum value of the half-value frequency coupling coefficient (=k f1f2 ) to the average value (standard deviation / average value) is preferably 0.3 or less, more preferably 0.2 or less, and even more preferably 0.1 or less.

[0053] In addition, in the magnetostrictive member 1 of this embodiment, the half-value frequency coupling coefficient (=k f1f2 ) is preferably 0.7 or more.

[0054] In addition, in the magnetostrictive member 1 of this embodiment, the half-value frequency coupling coefficient (=k f1f2 ) is preferably 0.05 or less.

[0055] In this embodiment, the force coefficient, half-value frequency coupling coefficient, and optimal magnetic field strength are values ​​calculated by electromechanical equivalent circuit analysis as described above, and can be determined, for example, by the method described in this specification.

[0056] The above average values ​​and variations (standard deviations) may be values ​​calculated from a plurality of magnetostrictive members produced from the same crystal. For example, they may be calculated from a plurality of magnetostrictive members produced under the same manufacturing conditions from a single grown crystal, or may be calculated from magnetostrictive members produced simultaneously under the same manufacturing conditions. There are no limitations on the number of magnetostrictive members produced from the same crystal, or on the number of measurements (n) for calculating the above average values ​​and variations (standard deviations). The number n is preferably 4 to 10.

[0057] As described above, the magnetostrictive member of this embodiment is a plate-like member obtained from the same crystal, made of iron-based alloy crystals having magnetostrictive properties, having a longitudinal direction and a lateral direction, at least one of the front and rear surfaces of the plate-like member has a plurality of grooves extending in the longitudinal direction, and the plurality of magnetostrictive members have a half-value frequency coupling coefficient (=k f1f2 The magnetic field strength at which the value of the standard deviation of the optimum magnetic field strength is maximized is defined as the optimum magnetic field strength, and the ratio of the standard deviation of the optimum magnetic field strength to the average value of the optimum magnetic field strength (standard deviation / average value) is 0.2 or less.

[0058] The magnetostrictive member 1 of this embodiment has the above-mentioned configuration, and when a magnetostrictive vibration power generation device is manufactured using a magnetostrictive member with a high amount of parallel magnetostriction and little variation in the amount of parallel magnetostriction between members, the device characteristics can be easily evaluated using a stable index that is not affected by the size or thickness of the magnetostrictive member, resulting in high device characteristics and reduced variation in the optimal magnetic field strength.

[0059] (Magnetostrictive member manufacturing method) Next, a method for manufacturing the magnetostrictive member of this embodiment will be described. The method for manufacturing the magnetostrictive member of this embodiment is the method for manufacturing the magnetostrictive member 1 of this embodiment described above. The method for manufacturing the magnetostrictive member of this embodiment is the method for manufacturing the magnetostrictive member 1 of this embodiment described above, and includes forming a plurality of grooves 2 extending in the longitudinal direction D1 on at least one of the front surface 3 and the back surface 4 of a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction D1 and a lateral direction D2, and heat-treating the plate-like body with the plurality of grooves extending in the longitudinal direction formed therein.

[0060] In the following description, a method for manufacturing the magnetostrictive member 1 from a single crystal ingot of an Fe-Ga alloy is described as an example, but the manufacturing method of the magnetostrictive member of this embodiment is not limited to the following description. Furthermore, any description in this specification that is applicable to the manufacturing method of the magnetostrictive member of this embodiment is also applicable to the manufacturing method of the magnetostrictive member of this embodiment. Furthermore, in the manufacturing method of the magnetostrictive member of this embodiment that is applicable to the magnetostrictive member of this embodiment described above, is also applicable to the magnetostrictive member of this embodiment.

[0061] Fig. 5 is a flowchart showing an example of a method for manufacturing a magnetostrictive member of this embodiment. Fig. 6 is a diagram showing first to third examples (a, b, c) of a single crystal (single crystal ingot) and a thin plate member. The method for manufacturing a magnetostrictive member of this embodiment includes, for example, a crystal preparation step (step S1), a crystal cutting step (step S2), a groove forming step (step S3), a cutting step (step S4), a heat treatment step (step S5), and a chamfering step (step S6).

[0062] In the manufacturing method of the magnetostrictive member of this embodiment, first, in the crystal preparation step (step S1), a crystal of an iron-based alloy having magnetostrictive properties is prepared. The prepared crystal may be a single crystal or a polycrystal. Furthermore, the prepared crystal may be a grown crystal or a commercially available crystal. For example, in the crystal preparation step, a single crystal of an Fe-Ga alloy is prepared. There are no particular limitations on the method for growing the single crystal of an Fe-Ga alloy. The method for growing the single crystal of an Fe-Ga alloy may be, for example, a pulling method or a unidirectional solidification method. For example, the Cz method can be used as the pulling method, and the VB method, VGF method, and micro-pulling-down method can be used as the unidirectional solidification method.

[0063] The magnetostriction constant of a single crystal of an Fe—Ga alloy is maximized by adjusting the gallium content to 18.5 at% or 27.5 at%. Therefore, the Fe—Ga single crystal is preferably grown so that the gallium content is 16.0 to 20.0 at% or 25.0 to 29.0 at%, and more preferably 17.0 to 19.0 at% or 26.0 to 28.0 at%. The shape of the grown single crystal is not particularly limited, and may be, for example, cylindrical or rectangular prism. The grown single crystal may be cut into a cylindrical single crystal, if necessary, by cutting the seed crystal, the diameter-increasing portion, or the shoulder portion (the portion that increases from the seed crystal to the predetermined diameter of the single crystal) with a cutting device. The size of the grown single crystal is not particularly limited, as long as the magnetostrictive member can be secured in the predetermined direction. When growing an Fe—Ga single crystal, the growth axis direction is <100> The seed crystal is grown using a seed crystal whose top or bottom surface is processed to a {100} plane so that the Fe-Ga alloy single crystal grows in a direction perpendicular to the top or bottom surface of the seed crystal, and inherits the orientation of the seed crystal.

[0064] Following the crystal preparation step (step S1), a crystal cutting step (step S2) is carried out. The crystal cutting step is a step of cutting a crystal to produce a thin plate member. The thin plate member is a member that will be the material for the magnetostrictive member 1 of this embodiment. The crystal cutting step is, for example, a step of cutting a single crystal of an Fe-Ga alloy having magnetostrictive properties using a cutting device to produce a thin plate member having a {100} plane as the main surface. The cutting device may be a wire electric discharge machine, an inner diameter blade cutting device, a wire saw, or other cutting device. Among these, it is particularly preferable to use a multi-wire saw, since it can cut multiple thin plate members simultaneously. The cutting direction of the single crystal is, in the case of an Fe-Ga single crystal, <100> The cutting is performed so that the cut surface, i.e., the main surface of the thin plate member, is the {100} plane. The cutting direction of the single crystal is not particularly limited. For example, as shown in FIG. 6, the cutting direction of the single crystal may be perpendicular or parallel to the growth direction of the single crystal (the direction in which the crystal is grown).

[0065] Following the crystal cutting step (step S2), a groove forming step (step S3) is performed. In the groove forming step, multiple grooves 2 are formed on at least one of the front and back surfaces 3 and 4 of the obtained thin plate member. The multiple grooves 2 stabilize the magnetostriction constant and parallel magnetostriction at high levels and can improve the magnetostriction constant and parallel magnetostriction. In the groove forming step, multiple grooves 2 are formed in the thin plate member so that, when the thin plate member is finally cut into the magnetostrictive member 1, multiple grooves 2 extending in the longitudinal direction D1 of the magnetostrictive member 1 are formed. The multiple grooves 2 to be formed can be similar to those described in Patent Document 6, for example. For example, multiple grooves 2 can be formed by surface grinding at least one of the front and back surfaces of the thin plate member obtained by the crystal cutting step. Below, an example of performing the groove forming step by surface grinding of the thin plate member will be described. When multiple grooves 2 are formed by surface grinding, the effects of improving the magnetostriction constant, parallel magnetostriction, force coefficient, and half-value frequency coupling coefficient can be efficiently achieved.

[0066] The surface grinding process is performed using a surface grinding machine. In order to efficiently achieve the effect of modifying the magnetostriction constant and the amount of parallel magnetostriction, it is preferable that the direction of the grinding marks formed on the thin plate member be parallel to the longitudinal direction D1 of the magnetostrictive member 1. For this reason, it is preferable that the grinding marks be linear. When making the grinding marks linear, it is preferable that the surface grinding machine be a type in which the grinding wheel or processing table moves in a linear direction, and it is preferable to use a surface grinding machine that uses a flat grinding wheel and has a processing table that moves back and forth. It is also possible to use a surface grinding machine that uses a cup grinding wheel and has a processing table that rotates, but when using such a surface grinding machine, the grinding marks will be curved, so it is preferable to set the curvature of the grinding marks to be small (the degree of curvature is small).

[0067] Furthermore, the grinding marks must be formed on the surface of the magnetostrictive member 1. For this reason, when processing a thin plate member to adjust its thickness, etc., the surface grinding process may be performed after the predetermined processing is performed using a processing machine other than a surface grinder, such as a double-sided lapping machine or a surface grinder using a cup grinding wheel. Alternatively, the surface of the thin plate member (magnetostrictive member) may be polished as in the conventional method to give a mirror finish to the surface, and then the surface grinding process may be performed. From the viewpoint of efficiently achieving the effects of improving the magnetostriction constant, parallel magnetostriction amount, force coefficient, and half-value frequency coupling coefficient, it is preferable to perform the surface grinding process on both the front and back surfaces of the thin plate member.

[0068] The grinding stone used for surface grinding preferably has a lower limit of roughness (grit) of #40 or more, more preferably #100 or more, and an upper limit of #500 or less, more preferably #400 or less. The range is preferably #40 to #500, more preferably #40 to #400, and more preferably #100 to #400. When the roughness (grit) of the grinding stone is within the above range, the effects of improving the magnetostriction constant, parallel magnetostriction, force coefficient, and half-value frequency coupling coefficient can be more reliably achieved. Note that using a grinding stone smaller than #40 may result in inconsistent grinding marks. Using a grinding stone exceeding #500 may result in the surface of the magnetostrictive member being smooth, which may prevent the effects of improving the magnetostriction constant, parallel magnetostriction, force coefficient, and half-value frequency coupling coefficient from being efficiently achieved.

[0069] In the groove forming step, for example, the grooves 2 are preferably formed so that the surface roughness Ra in the longitudinal direction D1 of the surface on which the grooves 2 are formed in the magnetostrictive member 1 is within a predetermined range. For example, the grooves 2 are preferably formed so that the lower limit of the surface roughness Ra in the longitudinal direction D1 of the surface on which the grooves 2 are formed is preferably 0.3 μm or more, and the upper limit is preferably 1.5 μm or less, ranging from 0.3 μm to 1.5 μm. Furthermore, the grooves 2 are preferably formed so that the surface roughness Ra in the lateral direction D2 of the surface on which the grooves 2 are formed in the magnetostrictive member 1 is preferably 0.6 μm or more, more preferably 0.7 μm or more, and the lower limit is preferably 4.5 μm or less, ranging from 0.6 μm to 4.5 μm. Furthermore, the grooves 2 are preferably formed so that the magnetostriction constant and parallel magnetostriction amount of the magnetostrictive member 1 and the magnetostrictive material from which the magnetostrictive member 1 is made are within predetermined ranges. For example, the plurality of grooves 2 are preferably formed so that the magnetostrictive member 1, or magnetostrictive material, has a magnetostriction constant of 200 ppm or more and a parallel magnetostriction of 200 ppm or more. The plurality of grooves 2 that fall within the above-mentioned preferred ranges of surface roughness Ra, magnetostriction constant, parallel magnetostriction, force coefficient, and half-value frequency coupling coefficient can be formed by the above-mentioned surface grinding process. The groove forming process may be performed by a method other than surface grinding, as long as it is possible to form the plurality of grooves 2 on at least one of the front surface 3 and the back surface 4 of the obtained thin plate member. For example, the thin plate member may be fabricated so that the plurality of grooves 2 are formed using a fixed abrasive wire saw. In other words, the grooves 2 may be formed when slicing a crystal to create the thin plate member using a fixed abrasive wire saw. There are two types of cutting using a wire saw: the free abrasive method, in which the workpiece is pressed against a row of multiple parallel, extremely fine wires arranged at a constant pitch, and the wires are fed in the linear direction while a machining liquid containing abrasive grains (also called a slurry) is supplied between the workpiece and the wires to cut it; and the fixed abrasive method, in which the workpiece is cut by feeding a wire in the linear direction with abrasive grains such as diamonds fixed to it by electroplating or adhesive.The cut surface produced by the free abrasive grain method has a non-directional matte finish, which does not achieve the present effect. However, when cutting with a fixed abrasive grain wire saw, grinding marks are generated in the wire feed direction, making it possible to form multiple grooves 2 similar to those formed by the surface grinding process. When cutting with a fixed abrasive grain wire saw, the crystal cutting process (step S2) and the groove forming process (step S3) can be performed simultaneously, allowing for efficient production of thin plate members. Alternatively, multiple grooves 2 may be formed by applying a certain amount of pressure using sandpaper or the like. In the groove forming process, by appropriately adjusting the configuration of the multiple grooves 2 formed in the magnetostrictive member, a magnetostrictive member material having the optimal magnetic field strength of the present embodiment can be obtained. For example, as described above, in this embodiment, the magnetostrictive properties, including the force coefficient, are affected by the width, length, and thickness of the magnetostrictive member. However, by appropriately adjusting the configuration of the multiple grooves 2 formed in the magnetostrictive member in the groove forming process according to the width, length, and thickness of the magnetostrictive member, the magnetostrictive properties can be adjusted (modified) to obtain a magnetostrictive member having the properties of this embodiment. The configuration (conditions) of the plurality of grooves 2 formed in the magnetostrictive member of this embodiment can be determined through preliminary experiments.

[0070] Following the groove forming step (step S3), a cutting step (step S4) is carried out. In the cutting step, the thin plate member in which the plurality of grooves 2 have been formed in the groove forming step is cut to obtain a magnetostrictive material. This magnetostrictive material is the material for the magnetostrictive member 1 of this embodiment. The magnetostrictive material is subjected to a heat treatment in a heat treatment step described below to obtain the magnetostrictive member 1 of this embodiment.

[0071] In the cutting process, when cutting the thin plate member having a plurality of grooves 2 formed therein, the thin plate member is cut so that a plurality of grooves 2 extending in the longitudinal direction D1 are formed in the magnetostrictive member 1 to be finally manufactured. In the cutting process, the thin plate member is cut to a predetermined size. In the cutting process, the thin plate member is cut as a magnetostrictive material so that, for example, the magnetostrictive member 1 becomes a rectangular plate-like body in a planar view. In the cutting process, the thin plate member is cut using a cutting device. The cutting device used in the cutting process is not particularly limited, and for example, a peripheral blade cutting device, a wire electric discharge machine, a wire saw, etc. can be used. The direction in which the magnetostrictive material is extracted from the thin plate member is not particularly limited, and it may be set to a direction that allows for efficient extraction depending on, for example, the size of the magnetostrictive member.

[0072] Next, a heat treatment step (step S5) is performed. The heat treatment step lowers the optimum magnetic field strength of the magnetostrictive member and reduces its variation while maintaining the force coefficient and half-value frequency coupling coefficient at high levels. This is believed to be due to the heat treatment alleviating internal stress on the front and back surfaces of the magnetostrictive member. For example, in the heat treatment step, a magnetostrictive material obtained in the cutting step has multiple grooves 2 extending in the longitudinal direction D1 formed on its front and back surfaces, and this magnetostrictive material is heat-treated at a predetermined temperature and time. This heat treatment modifies the magnetostrictive member so that the ratio (standard deviation / average value) of the standard deviation of the optimum magnetic field strength determined by electromechanical equivalent circuit analysis of the magnetostrictive member to the average value of the optimum magnetic field strength is 0.2 or less. This heat treatment allows the magnetostrictive member 1 of this embodiment to be obtained. The effect of the heat treatment, which lowers the optimum magnetic field strength of the magnetostrictive member and reduces its variation while maintaining the force coefficient and half-value frequency coupling coefficient at high levels, is also effective for materials without multiple grooves 2.

[0073] The heat treatment method is not particularly limited. For example, a box-shaped or tubular electric furnace can be used. The heating temperature is not particularly limited as long as the heat treatment exhibits the above-mentioned effects. The heat treatment conditions (temperature, time) can be determined through preliminary experiments. The heating temperature (heat treatment temperature) of the heat treatment is preferably, for example, 400°C or higher and 700°C or lower, and more preferably 600°C or higher and 650°C or lower. If the heat treatment temperature is lower than 400°C, the temperature is too low and internal stress is not alleviated by the heat treatment, so the optimal magnetic field strength may not change. Furthermore, if the heat treatment temperature exceeds 700°C, the temperature is too high and the grinding effect is weakened by the heat treatment, reducing the amount of parallel magnetostriction and, accordingly, the force coefficient and half-value frequency coupling coefficient. If the heat treatment temperature is within the above temperature range, the average optimal magnetic field strength of the magnetostrictive member can be lowered and its variation reduced.

[0074] The holding time of the heat treatment is preferably 5 hours or less, more preferably 30 minutes to 5 hours, and even more preferably 30 minutes to 1 hour. Within the above range, the effect of suppressing variations in the magnetostrictive member can be more reliably achieved.

[0075] Furthermore, it is preferable that the heat treatment be carried out in an inert gas atmosphere. For example, argon gas or nitrogen gas can be used. By using an inert gas atmosphere, oxidation of the surface of the magnetostrictive member can be prevented. The inert gas may be continuously supplied to the heat treatment furnace. The flow rate depends on the heat treatment furnace, but when the inert gas is argon gas, it is preferably 0.5 to 5 L / h.

[0076] Furthermore, when the thickness of a magnetostrictive member exceeds 2 mm, the effect of forming multiple grooves 2 extending in the longitudinal direction D1 on the front and back surfaces of the magnetostrictive member on improving the magnetostriction constant, parallel magnetostriction, force coefficient, and half-frequency coupling coefficient is smaller than when the thickness is 2 mm or less. However, it has been found that by forming multiple grooves 2 extending in the longitudinal direction D1 on the front and back surfaces of the magnetostrictive member and then performing a heat treatment, it is possible to obtain almost the same improvement effect as when the thickness is 2 mm or less. Therefore, even with a magnetostrictive member with a thickness exceeding 2 mm, a stable force coefficient and half-frequency coupling coefficient can be obtained. For example, a stable force coefficient and half-frequency coupling coefficient can be obtained even with a thickness of 3 mm or more.

[0077] If the heat treatment process (step S5) is performed without the groove formation process (step S3), the internal stress is alleviated and the variation in the optimal magnetic field strength is reduced, but the force coefficient and half-value frequency coupling coefficient do not change, and the average value remains low and the variation remains large.

[0078] In the above example, in the cutting process (step S4), the magnetostrictive member is cut into the shape before the heat treatment process (step S5). However, in the present invention, the heat treatment process (step S5) may be performed after the groove forming process (step S3), and then the cutting process (step S4) may be performed.

[0079] Next, the chamfering step (step S6) is performed. The chamfering step (step S6) is a step of chamfering the plate-shaped body (magnetostrictive member) cut in the cutting step. In the chamfering step, for example, each side of the magnetostrictive member is chamfered. The magnetostrictive member is made of an Fe-based alloy material and has high ductility. Therefore, when the magnetostrictive member is cut into a predetermined shape in the cutting step, burrs may occur on each side of the magnetostrictive member. If the magnetostrictive properties are measured while burrs remain on the magnetostrictive member, the magnetostrictive properties may change. This has been a factor in increasing the variability in the magnetostrictive properties. In this embodiment, adding the chamfering step reduces the variability in the magnetostrictive properties and stabilizes the measured values ​​of the magnetostrictive properties. In the chamfering step, the means of chamfering is not particularly limited. For example, beveling may be performed using a beveling device, or if the amount is small, processing may be performed using a file or the like. The chamfering step may be performed after the cutting step. [Example]

[0080] The present invention will be specifically explained below using examples, but the present invention is not limited to these examples.

[0081] [Example 1] The magnetostrictive member was manufactured based on the manufacturing method of this embodiment described above. The raw materials were adjusted to a stoichiometric ratio of iron and gallium of 81:19, and a cylindrical Fe-Ga alloy single crystal was prepared by growing it by the vertical Bridgman (VB) method. The growth axis direction of the single crystal was <100> The orientation of the {100} plane on the top or bottom surface of the single crystal, which was perpendicular to the crystal growth axis, was confirmed by X-ray diffraction. At this time, measurements of the top and bottom surface samples of the crystal were performed using a Shimadzu sequential plasma emission spectrometer (ICPS-8100), and the gallium content of the single crystal was found to be 17.2 to 19.8 at%.

[0082] A magnetostrictive member was manufactured from the grown single crystal as follows. First, a free abrasive grain wire saw was used to cut the single crystal in a direction parallel to the direction of growth ( <100> The single crystal was cut in a direction parallel to the {100} orientation to produce a thin plate member with a cut surface, i.e., a main surface, of {100} (crystal cutting process). Next, the obtained thin plate member was subjected to surface grinding using a #170 flat grinding wheel on a surface grinder to adjust the thickness of the thin plate member and to form multiple grooves (grinding marks) on the front and back surfaces to obtain the magnetostrictive member of the above-mentioned embodiment (groove forming process). After that, the cutting position was set so that the longitudinal direction of the magnetostrictive member was the same as the grinding direction during surface grinding, i.e., the grinding mark direction, and a peripheral blade cutting device was used to cut out magnetostrictive material (magnetostrictive member before heat treatment) measuring 16 mm in the longitudinal direction, 4 mm in the lateral direction, and 0.5 mm in thickness (cutting process). The 10 magnetostrictive material pieces cut out as described above were heat treated. A tubular electric furnace was used as the heat treatment furnace. Argon gas was flowed through the furnace at 1 L / min. Heat treatment was carried out at a temperature of 600°C for a holding time of 60 minutes (heat treatment step). After the heat treatment, chamfering was carried out on each side of the magnetostrictive member using a file (chamfering step).

[0083] Next, the magnetostrictive properties of the manufactured magnetostrictive members were measured. The magnetostrictive properties were measured using the characteristic evaluation device shown in Figure 4, and the impedance of the prepared magnetostrictive members was measured using the method described above under conditions of a magnetic field strength (applied magnetic field) of 1.1 kA / m to 8.8 kA / m and a measurement frequency of 10 kA / m to 200 kHz. The force coefficient and half-value frequency coupling coefficient were calculated from the measurement results. Ten magnetostrictive materials were manufactured, and the maximum values ​​of the force coefficient and half-value frequency coupling coefficient, as well as the optimal magnetic field strength at which the half-value frequency coupling coefficient reached its maximum value, were determined using the same method, and the average values ​​and variations (standard deviations) for each were calculated. The results are shown in Table 1.

[0084] [Example 2] In Example 2, the grinding wheel used in the grinding process was a #100 flat grinding wheel, the size of the magnetostrictive member cut out in the cutting process was 32 mm in the longitudinal direction, 8 mm in the lateral direction, and 1 mm in thickness, and the holding time for the heat treatment was 120 minutes. Other than the above, the same as in Example 1 was used. The manufacturing conditions and evaluation results are shown in Table 1.

[0085] [Example 3] In Example 2, the grinding wheel used in the grinding process was a #40 flat grinding wheel, the size of the magnetostrictive member cut out in the cutting process was 64 mm in the longitudinal direction, 16 mm in the lateral direction, and 2 mm in thickness, and the holding time for the heat treatment was 120 minutes. Other than the above, the same as in Example 1 was used. The manufacturing conditions and evaluation results are shown in Table 1.

[0086] [Example 4] In Example 2, the grinding wheel used in the grinding process was a #40 flat grinding wheel, the size of the magnetostrictive member cut out in the cutting process was 96 mm in the longitudinal direction, 24 mm in the lateral direction, and 3 mm in thickness, and the holding time for the heat treatment was 120 minutes. Other than the above, the same as in Example 1 was used. The manufacturing conditions and evaluation results are shown in Table 1.

[0087] [Comparative Example 1] In Comparative Example 1, the surface of the magnetostrictive material was a processed surface (wire-saw processed surface) cut with a wire-saw device of the free abrasive type, which cuts by supplying a processing fluid containing abrasive grains, and no heat treatment was performed. Other than that, the same as in Example 1. The manufacturing conditions and evaluation results are shown in Table 1.

[0088] Comparative Example 2 In Comparative Example 2, no heat treatment was performed. Other than that, the procedure was the same as in Example 2. The production conditions and evaluation results are shown in Table 1.

[0089] [Table 1]

[0090] [summary] The magnetostrictive members of Examples 1 to 4 showed high average values ​​for the force coefficient and half-value frequency coupling coefficient, and exhibited favorable values. Furthermore, the magnetostrictive members of Examples 1 to 4 had low values ​​for the variation (standard deviation) and the ratio of the standard deviation to the average value (standard deviation / average value) for the half-value frequency coupling coefficient, and also had low values ​​for the ratio of the standard deviation to the average value (standard deviation / average value) for the optimum magnetic field strength. Furthermore, the magnetostrictive members of Examples 1 to 4 each exhibited a force coefficient that increased with increasing size, but no such tendency was observed for the half-value frequency coupling coefficient and the optimum magnetic field strength, and the values ​​were stable.

[0091] On the other hand, the magnetostrictive member of Comparative Example 1 had lower force coefficients and half-frequency coupling coefficients, and a larger ratio of the standard deviation to the average value of the half-frequency coupling coefficients (standard deviation / average value) than the same-sized member of Example 1. The magnetostrictive member of Comparative Example 2 had a larger variation in optimal magnetic field strength, and a larger ratio of the standard deviation to the average value of the optimal magnetic field strength (standard deviation / average value) than the same-sized member of Example 2.

[0092] From the above, it is confirmed that the magnetostrictive member of this embodiment has a high parallel magnetostriction amount and little variation in the parallel magnetostriction amount between members, and when a magnetostrictive vibration power generation device is manufactured using such a magnetostrictive member, the device characteristics can be easily evaluated using a stable indicator that is not affected by the size or thickness of the magnetostrictive member, and the device characteristics are large and the variation in the optimal magnetic field strength is also suppressed.

[0093] The technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above-mentioned embodiments may be omitted. The requirements described in the above-mentioned embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated by reference into this specification.

[0094] For example, in the above description, an example of a magnetostrictive member has been described in which at least one of the front and back surfaces of the plate-like body has a plurality of grooves 2 extending in the longitudinal direction, but the plurality of grooves 2 may be omitted. For example, the magnetostrictive member is a plate-like body made of iron-based alloy crystals having magnetostrictive properties, and has a longitudinal and lateral direction, and the plurality of magnetostrictive members have a half-value frequency coupling coefficient (=k f1f2 ) is the strength at which it is maximized, and the ratio of the standard deviation of the optimum magnetic field strength to the average value of the optimum magnetic field strength (standard deviation / average value) is 0.2 or less, and the half-value frequency coupling coefficient (= k f1f2 ) and the half-value frequency coupling coefficient (= k f1f2 ) to the average value (standard deviation / average value) of 0.3 or less. This configuration also achieves the effect of the present application described above, in which when a magnetostrictive vibration power generation device is manufactured using a magnetostrictive member with a high parallel magnetostriction and little variation in the parallel magnetostriction between members, the device characteristics can be easily evaluated using a stable index that is not affected by the size or thickness of the magnetostrictive member, resulting in high device characteristics and reduced variation in the optimal magnetic field strength. This magnetostrictive member can be obtained, for example, by modifying the magnetostrictive member by the heat treatment described above to reduce the characteristics and variation. [Explanation of symbols]

[0095] 1: Magnetostrictive material 2:Groove 3: Surface 4: Back side D1: Longitudinal direction D2: Lateral direction S1: Crystal preparation process S2: Crystal cutting process S3:Groove formation process S4: Cutting process S5: Heat treatment process S6: Chamfering process

Claims

1. A magnetostrictive member obtained from the same crystal, It is made of iron-based alloy crystals with magnetostrictive properties, A plate-like body having a longitudinal direction and a lateral direction, At least one of the front and back surfaces of the plate-like body has a plurality of grooves extending in the longitudinal direction, The plurality of magnetostrictive members have a half-value frequency coupling coefficient (=k ｆ１ｆ２ ) is maximized, the magnetic field strength is defined as the optimum magnetic field strength, and the ratio of the standard deviation of the optimum magnetic field strength to the average value of the optimum magnetic field strength (standard deviation / average value) is 0.2 or less.

2. The plurality of magnetostrictive members have the half-value frequency coupling coefficient (=k ｆ１ｆ２ ) and the standard deviation of the maximum value of the half-value frequency coupling coefficient (= k ｆ１ｆ２ 2. The magnetostrictive member according to claim 1, wherein the ratio of the maximum value of the magnetostrictive coefficients (standard deviation) to the average value (standard deviation / average value) is 0.3 or less.

3. The plurality of magnetostrictive members have the half-value frequency coupling coefficient (=k ｆ１ｆ２ ) and the standard deviation of the maximum value of the half-value frequency coupling coefficient (= k ｆ１ｆ２ 2. The magnetostrictive member according to claim 1, wherein the ratio of the maximum value of said magnetostrictive coefficients to the average value (standard deviation / average value) is 0.1 or less.

4. A magnetostrictive member obtained from the same crystal, It is made of iron-based alloy crystals with magnetostrictive properties, A plate-like body having a longitudinal direction and a lateral direction, The plurality of magnetostrictive members have a half-value frequency coupling coefficient (=k ｆ１ｆ２ ) is the strength at which the optimum magnetic field strength is maximized, and the ratio of the standard deviation of the optimum magnetic field strength to the average value of the optimum magnetic field strength (standard deviation / average value) is 0.2 or less, and the half-value frequency coupling coefficient (= k ｆ１ｆ２ ) and the standard deviation of the maximum value of the half-value frequency coupling coefficient (= k ｆ１ｆ２ ) the ratio of the maximum value of the magnetostrictive coefficients to the average value (standard deviation / average value) is 0.3 or less.

5. 5. The magnetostrictive member according to claim 1, wherein the thickness of the plate-like body is 0.3 mm or more and 5 mm or less.

6. A method for manufacturing a magnetostrictive member according to any one of claims 1 to 4, forming a plurality of grooves extending in a longitudinal direction on at least one of a front surface and a back surface of a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction and a transverse direction; a heat treatment of the plate-like body having the plurality of grooves formed therein extending in the longitudinal direction.

7. The method for manufacturing a magnetostrictive member according to claim 6 , further comprising forming the plurality of grooves by surface grinding.

8. The method for manufacturing a magnetostrictive member according to claim 6, wherein the heat treatment temperature is 400°C or higher and 700°C or lower.

9. The method for manufacturing a magnetostrictive member according to claim 6, wherein the heat treatment is held for 5 hours or less.

10. a cutting step of cutting the plate-like body having the plurality of grooves formed therein; The method for manufacturing a magnetostrictive member according to claim 6 , further comprising a chamfering step of chamfering the plate-like body cut in the cutting step.

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