Magnetostrictive member and method for manufacturing a magnetostrictive member

Abstract

To provide a magnetostrictive member and a method for manufacturing a magnetostrictive member in which fluctuations in magnetostrictive properties caused by burrs generated during cutting or other processes are suppressed. [Solution] The magnetostrictive member is a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties, and having a longitudinal direction and a transverse direction, wherein at least a portion of each edge of the plate-like body is a chamfered surface.

Description

Technical Field

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

Background Art

[0002] Magnetostrictive materials have attracted attention as functional materials. For example, an Fe-Ga alloy, which is an iron-based alloy, is a material that exhibits a magnetostrictive effect and an inverse magnetostrictive effect, and shows a large magnetostriction of about 100 to 350 ppm. Therefore, in recent years, it has attracted attention as a material for vibration power generation in the field of energy harvesting, and applications to wearable terminals and sensors are expected.

[0003] A magnetostrictive vibration power generation device (sometimes abbreviated as a device) is composed of, for example, a magnetostrictive member such as an Fe-Ga alloy wound around a coil, a yoke, and a permanent magnet for bias magnetic field (for example, Patent Document 2, Non-Patent Document 1). In this magnetostrictive vibration power generation device, when the yoke of the movable part of the device is vibrated, the magnetostrictive member fixed to the center of the yoke vibrates in conjunction, and the magnetic flux density of the coil wound around the magnetostrictive member changes due to the inverse magnetostrictive effect, generating an electromagnetic induction electromotive force and generating electricity. In a magnetostrictive vibration power generation device, since a force is applied in the longitudinal direction of the yoke to cause vibration, for example, it is desirable to process a magnetostrictive member such as an Fe-Ga alloy used for the device so that <100>, which is the easy magnetization axis, is in the longitudinal direction.

[0004] The magnetostrictive characteristics of the Fe-Ga alloy are considered to affect the magnetostrictive / inverse magnetostrictive effect and the characteristics of the magnetostrictive vibration power generation device, and are important parameters in device design (Non-Patent Document 1). In particular, the magnetostriction constant depends on the Ga composition of the Fe-Ga alloy single crystal, and it is known that the magnetostriction constant becomes maximum when the Ga composition is 18 to 19 at% and 27 to 28 at% (Non-Patent Document 2), and it is considered desirable to use an Fe-Ga alloy having such a Ga concentration for the device. Furthermore, in recent years, in addition to a large magnetostriction constant, it has been reported that the larger the parallel magnetostriction amount, the higher the device characteristics such as the output voltage tend to be (Non-Patent Document 3).

Prior Art Documents

[0005] [Patent Document 1] International Publication No. 2021 / 100467 [Patent Document 2] International Publication No. 2011 / 158473 [Patent Document 3] Patent No. 7084620 [Non-patent literature]

[0006] [Non-Patent Document 1] Toshiyuki Ueno, Journal of the Japan Society for Precision Engineering, Vol. 79, No. 4, (2013) 305-308. [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). [Overview of the project] [Problems that the invention aims to solve]

[0007] As described above, the device characteristics of magnetostrictive vibration power generation devices and the like are affected by the magnetostrictive properties of the magnetostrictive member. Therefore, the magnetostrictive member is required to have high magnetostrictive properties and low variation in magnetostrictive properties. In this context, the crystal orientation of the Fe-Ga alloy single crystal is <100> It was previously thought that if the Ga concentration was uniform, a magnetostrictive member with a uniform magnetostrictive constant could be obtained. However, device characteristics are affected not only by the magnetostrictive constant but also by the parallel magnetostriction. Patent Document 1 discloses that by adding multiple grooves, such as grinding marks, extending in the longitudinal direction of the magnetostrictive member, a magnetostrictive member with a high magnetostrictive constant and parallel magnetostriction, and with little variation in magnetostrictive constant and parallel magnetostriction between members, can be obtained. When this magnetostrictive member was incorporated into the magnetostrictive vibration power generation device and the device characteristics were confirmed, it was found that a predetermined device output (e.g., power generation amount such as force coefficient) could be obtained, and that there was little variation in device output between devices.

[0008] Measuring the parallel magnetostriction of a magnetostrictive component requires attaching strain gauges to the magnetostrictive material, which constitutes destructive testing. In contrast, evaluating the force coefficient can be done by measuring impedance by inserting and removing a measuring coil, making it a non-destructive test. Therefore, impedance measurement is preferred for product inspection.

[0009] Furthermore, prior to the present invention, the inventors of this invention discovered that the amount of parallel magnetostriction of a magnetostrictive member is positively correlated with the force coefficient calculated from impedance measurements. The force coefficient is also positively correlated with the device output (Patent Document 2). Prior to the present invention, the inventors of this invention also discovered that increasing the device output increases not only the amount of parallel magnetostriction but also the force coefficient (Japanese Patent Application: JP 2023-037128, International Patent Application: PCT / JP2024 / 4133).

[0010] However, it was discovered that some magnetostrictive components exhibited a defect that reduced device output. Investigations revealed that this was due to minute burrs, difficult to see, generated during the cutting of the magnetostrictive components.

[0011] Magnetostrictive members are produced by processing single crystals grown using methods such as the Cz method or VB method into thin plates using methods such as electrical discharge wire cutting. These thin plates are then cut into predetermined shapes using a cutting device to produce individual pieces of magnetostrictive member. Microscopic examination of the cut pieces of magnetostrictive member revealed the presence of burrs of varying sizes at the cut edges.

[0012] It was found that the presence of burrs on the magnetostrictive material causes fluctuations in the magnetostrictive properties during impedance measurement, depending on the size of the burrs. In particular, it was found that larger burrs tend to decrease the force coefficient and increase the maximum value of the optimal magnetic field strength. A decrease in the force coefficient is a major problem as it reduces the device output as described above. It was also found that during impedance measurement, when the magnetostrictive material is placed into the measurement coil, burrs can cause the enamel wire inside the measurement coil to break, which is a problem. Furthermore, it was found that during device fabrication, gaps can form between the magnetostrictive material and the frame during bonding, which can reduce the device output.

[0013] Therefore, the present invention aims to provide a magnetostrictive member and a method for manufacturing a magnetostrictive member in which fluctuations in magnetostrictive properties caused by burrs generated during cutting or other processes are suppressed. [Means for solving the problem]

[0014] According to an aspect of the present invention, a magnetostrictive member is provided, which is a plate-like body having longitudinal and transverse directions, and is made of crystals of an iron-based alloy having magnetostrictive properties, wherein at least a portion of each edge of the plate-like body is a chamfered surface.

[0015] Furthermore, the chamfered surface may be a C-surface or an R-surface, and the size of the C-surface or R-surface may be 0.02 mm or more and 0.25 mm or less. The chamfered surface may be a curved surface, and the chamfer width of the curved surface may be 250 μm or less. Furthermore, the chamfer width of the chamfered surface may be 20 μm or more and 70 μm or less.

[0016] Also, according to an aspect of the present invention, there is provided a method for manufacturing a magnetostrictive member, comprising: a step of preparing a magnetostrictive member cut into individual pieces; and a step of chamfering the prepared magnetostrictive member. Further, the chamfering may be barrel polishing.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a magnetostrictive member and a method for manufacturing a magnetostrictive member in which variations in magnetostrictive characteristics caused by burrs generated during cutting or the like are suppressed.

Brief Description of the Drawings

[0018] [Figure 1] It is a diagram showing an example of a magnetostrictive member according to an embodiment. [Figure 2] It is a diagram showing examples of a single crystal and a thin plate member. [Figure 3] It is a diagram showing an example of a burr in a magnetostrictive member. [Figure 4] It is a diagram showing an example of a cutting direction and a burr. [Figure 5] It is a diagram and a photograph for explaining an example of a magnetostrictive member subjected to barrel polishing. [Figure 6] It is a diagram showing an example of an impedance measuring device. [Figure 7] It is a diagram showing an electrical-mechanical equivalent circuit of a measurement coil.

Embodiments for Carrying Out the Invention

[0019] The following describes specific embodiments of the present invention in detail. However, the present invention is not limited to the following embodiments and can be modified as appropriate without altering the essence of the invention. In the drawings, some or all of the invention may be depicted schematically, and the scale may be changed as appropriate. Furthermore, in the following description, "A~B" means "A or greater and B or less." In the drawings, directions may be explained using the XYZ coordinate system. In this XYZ coordinate system, the direction perpendicular to the XY plane is denoted as the Z direction. The X, Y, and Z directions are described as follows: the direction of the arrow in the drawing is the + direction, and the direction opposite to the direction of the arrow is the - direction.

[0020] [Embodiment] The magnetostrictive member and the method for manufacturing the magnetostrictive member according to this embodiment will be described below.

[0021] (Magnetostrictive member) First, the magnetostrictive member of this embodiment will be described. Figure 1 is a diagram showing an example of a magnetostrictive member according to this embodiment.

[0022] As shown in Figure 1, the magnetostrictive member 1 is a plate-like body having a longitudinal direction D1 and a transverse 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 they do not have to be parallel. In addition, a portion of each side 5 of the magnetostrictive member 1 is a chamfered surface 6. In the magnetostrictive member 1, at least a portion of each side 5 of the plate-like body is a chamfered surface 6 (chamfered portion). The side 5 and the chamfered surface 6 will be described in more detail later. The magnetostrictive member 1 may optionally have a plurality of grooves 2 extending in the longitudinal direction D1, for example, as described in Patent Document 1.

[0023] The magnetostrictive member 1 is made of a crystal of an iron-based alloy. Multiple magnetostrictive members 1 can be obtained, for example, 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 undergoing a change in 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 alloys. Alternatively, an alloy may be one in which a third component has been added to the above alloys. For example, an alloy may be an Fe-Ga alloy in which Ba, Cu, etc. have been added. Among these iron-based alloys, Fe-Ga alloy has high magnetostrictive properties and is easy to process compared to other alloys, and is therefore applied to materials for vibration power generation in the energy harvesting field, as well as wearable terminals and sensors. In the following description, as an example of a magnetostrictive member 1, an example in which the magnetostrictive member 1 is made of a single crystal of Fe-Ga alloy will be described. Figure 2 shows examples of single crystals and thin plate members.

[0024] Fe-Ga alloy single crystals have a body-centered cubic lattice structure, and among the directional indices in Miller indices, the first to third... <100> This is based on the principle that the axes (see Figure 2) are equivalent, and the first to third {100} planes (see Figure 2) among the plane indices in Miller indices are equivalent (i.e., (100), (010), and (001) are equivalent). Furthermore, Fe-Ga alloys have the property of exhibiting large magnetic strain in specific crystal orientations. When utilizing this property in a magnetostrictive vibration power generation device, it is desirable to match the direction in which magnetostrictive member 1 is required in the device with the orientation (direction) in which the magnetic strain of the crystal is maximum. Specifically, as described above, this is the easy magnetization direction in a single crystal. <100> It is desirable to set the direction to the longitudinal direction D1 of the magnetostrictive member 1. This is the easy magnetization direction in a single crystal. <100> Setting the direction to the longitudinal direction D1 of the magnetostrictive member 1 can be achieved, for example, by calculating the crystal orientation of the single crystal using a known crystal orientation analysis and cutting the single crystal based on the calculated crystal orientation.

[0025] The crystal that can be used in the magnetostrictive member 1 of this embodiment may be a single crystal or a polycrystalline crystal. <100> To increase the degree of orientation concentration and improve the properties of the material as a magnetostrictive material, the use of single crystals is more advantageous than that of polycrystalline materials. However, although polycrystalline materials have lower magnetostrictive properties than single crystals, they can be produced at a lower cost, so polycrystalline materials are sometimes used.

[0026] The magnetostrictive member 1 is used, for example, as a material (component) for vibration power generation devices in the energy harvesting field, or as a material (component) for wearable terminals and sensors. For example, the magnetostrictive vibration power generation device shown in the above-mentioned Patent Document 2 is composed of a coil, a magnetostrictive member made of Fe-Ga alloy wound around the coil, a yoke, and a permanent magnet for the field. In this magnetostrictive vibration power generation device, when the yoke, which is the movable part of the device, is vibrated, the magnetostrictive member fixed to the center of the yoke vibrates in conjunction, and the magnetic flux density of the coil wound around the magnetostrictive member changes due to the inverse magnetostrictive effect, generating an electromagnetic induction electromotive force and thus generating electricity. When used in such a mechanism, the shape of the magnetostrictive member 1 is preferably a thin plate, and preferably set to an elongated rectangular shape in plan view. There are no particular limitations on the thickness of the magnetostrictive member 1. For example, 0.3 mm to 5 mm is preferred. The shape and size of the magnetostrictive member 1 are appropriately set according to the size of the target device. For example, the length of one side of the magnetostrictive member 1 may be 5 mm or more, 10 mm or more, or 30 mm or more. For example, the size of the magnetostrictive member 1 can be within the range of dimensions described in the embodiment. Specifically, the length (dimension) in the longitudinal direction D1 may be 25 mm, the width (dimension) in the short direction D2 may be 4 mm, and the thickness may be 0.5 mm.

[0027] 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 direction of the major axis, the direction of the major axis, etc., and the short direction D2 is the direction perpendicular to the longitudinal direction D1.

[0028] As described above, the device characteristics of magnetostrictive vibration power generation devices are affected by the magnetostrictive properties of the magnetostrictive member. Therefore, the magnetostrictive member is required to have high magnetostrictive properties and low variation in magnetostrictive properties. Patent Document 1 discloses that by adding multiple grooves extending in the longitudinal direction of the magnetostrictive member, such as grinding marks, a magnetostrictive member with high magnetostrictive constant and parallel magnetostriction, and low variation in magnetostrictive constant and parallel magnetostriction between members can be obtained. When this magnetostrictive member was incorporated into the magnetostrictive vibration power generation device and the device characteristics were confirmed, it was found that a predetermined power generation amount characteristic such as device output or force coefficient could be obtained, and that there was little variation in device output between devices. However, it was found that some magnetostrictive members had a problem in which the device output decreased, and as a result of investigation, it was confirmed that the device output was affected by burrs generated when the magnetostrictive member was cut.

[0029] Therefore, in one aspect of the present invention, the cut magnetostrictive member is chamfered so that a portion of each side 5 becomes a chamfered surface 6.

[0030] Magnetostrictive members are produced by processing single crystals grown using methods such as the Cz method or VB method into thin plate-like members by cutting the crystal using methods such as electrical discharge wire cutting. Subsequently, these thin plate members are cut into predetermined shapes using a cutting device to produce individual pieces of magnetostrictive member material. For example, thin plate members can be diced by using an outer blade cutting device or a dicing device. When thin plate members are diced using the above devices, it has been found that burrs of up to 60 μm in size are generated on the cut exit side (burr side). It is possible to reduce the size of the burrs by appropriately changing the processing conditions in the above devices, but burrs are usually always generated. In magnetostrictive members, burrs of various sizes are generated on the cut exit side of the side when the material is cut into individual pieces. Figure 3 shows an example of burrs in a magnetostrictive member. In Figure 3, the black area is the magnetostrictive material, and the edge of the magnetostrictive material is shown magnified under a microscope.

[0031] In one aspect of the present invention, the magnetostrictive member includes removing burrs generated when it is cut into individual pieces by chamfering. In one aspect of the present invention, the magnetostrictive member 1 includes removing at least a portion of the burrs. In one aspect of the present invention, the magnetostrictive member 1 is a plate-like body, and at least a portion of each edge of the plate-like body is a chamfered surface (chamfered portion). That is, the magnetostrictive member 1 is a plate-like body, and at least a portion of each edge of the plate-like body is provided with a chamfered surface 6. In the example shown in Figure 1, the edge portion includes the portion of each edge (12 edges in total) of the rectangular parallelepiped shape and the portion near the edge. In this specification, "edge portion" may be abbreviated as "edge".

[0032] Regarding the location of burr generation, for example, when the material is cut into individual pieces, burrs of various sizes are generated, particularly on the side facing the cutting direction exit. Figure 4 shows an example of the cutting direction and burrs. For example, as shown in Figure 4, in a magnetostrictive member, if the cutting direction is the -Z direction on the +X side of the material (object to be cut), the cutting exit side is the -Z side on the +X side of the material. In this specification, this cutting direction exit side surface (the -Z side XY plane in the example of Figure 4) is sometimes referred to as the "burr surface". Therefore, it is preferable that the chamfered surface 6 consists of a total of four sides: two sides parallel (extending) to the longitudinal direction D1 and two sides parallel (extending) to the short direction D2 on the cutting exit side of the side surface of the magnetostrictive member (in the example of Figure 4, it is preferable that it consists of four sides on the -Z side XY plane). Note that the size of the burr is, for example, 0.01 mm to 0.06 mm, and it is difficult to visually distinguish the burr surface (burr side), so the chamfered surface 6 may be made into a total of 8 sides by adding 4 sides: 2 sides parallel to the longitudinal direction D1 and 2 sides parallel to the short direction D2 on the side facing the burr side (in the example in Figure 4, it may be a total of 8 sides: 4 sides on the XY plane on the -Z side and 4 sides on the XY plane on the +Z side). In the case of the magnetostrictive member 1, if the shape (size) of the magnetostrictive member is large, for example, a magnetostrictive member where the length of the longitudinal direction D1 exceeds 30 mm, and the burr side can be reliably identified, then it may be made into a total of 4 sides: 2 sides parallel to the longitudinal direction D1 and 2 sides parallel to the short direction D2. Furthermore, if the shape (size) of the magnetostrictive member 1 is small, for example, if the length in the longitudinal direction of the magnetostrictive member is less than 30 mm, productivity can be improved by using barrel polishing or the like described later, which allows multiple materials to be chamfered together in a single operation, rather than chamfering each material individually. With barrel polishing or the like, all sides can be made into chamfered surfaces 6. In the embodiment of the present invention, all sides (all sides) may be chamfered surfaces 6. In the example of Figure 1, the all sides refer to the 12 sides (the 12 sides and their vicinity). When all sides (all sides) are chamfered surfaces 6, burrs can be removed more reliably from the viewpoint of burr removal.

[0033] The shape of the chamfered surface 6 can be any type of chamfered shape. The shape of the chamfered surface 6 can be, for example, a C-chamfer, a curved surface (e.g., R-chamfer, barrel-polished surface), or a fine chamfer. If the shape of the chamfered surface 6 is a C-chamfer, the processing method is not limited as long as the burrs are removed and it is processed into a C-chamfer, but for example, a bevel polishing device using a grinding wheel that forms a C-chamfer (a grinding wheel tilted at 45 degrees) may be used. Alternatively, it may be processed into a C-chamfer using a cutter, grinder, abrasive paper, etc. For the grinding wheel, it is preferable to select a grit size greater than #400, such as #600 or #1000, so as not to be affected by processing distortion. The angle of the C-chamfer is generally 45 degrees, but there is no particular limitation as long as the burrs from cutting are removed. The size of the C-chamfer is not limited as long as it is large enough to remove the burrs. For example, the lower limit of the size of the C-chamfer is 0.02 mm (20 μm) or more. The size of the chamfer (C-plane) can be, for example, limited to 0.25 mm (250 μm) or less, 0.15 mm (150 μm) or less, 0.1 mm (100 μm) or less, and 0.08 mm (80 μm) or less. The range of the chamfer size can be, for example, the range between the lower and upper limits mentioned above, or the range between the upper limits.

[0034] Chamfering is performed, for example, on each side of the magnetostrictive member 1. Therefore, if the shape of the magnetostrictive member is large and the length D1 in the longitudinal direction exceeds 30 mm, for example, a magnetostrictive member with a longitudinal length of 80 mm, and the burr side can be reliably identified, the chamfering can be limited to the four burr sides, allowing for efficient processing.

[0035] When the chamfered surface 6 is a curved surface, a bevel polishing device using a grinding wheel with a curved shape may be used. The size of the curved surface on the chamfered surface 6 is not particularly limited as long as burrs are removed and it is processed into a curved surface. For example, a bevel polishing device using a grinding wheel that produces an R surface (e.g., a concave grinding wheel with R0.1 mm) may be used for curved surface processing. The chamfered surface 6 may be a curved surface or a beveled surface. Other aspects may be the same as for chamfering, for example. When the chamfered surface 6 is a curved surface, the chamfer width is not limited as long as it is large enough to remove burrs. When the chamfered surface 6 is a curved surface, the lower limit of the chamfer width is, for example, 0.02 mm (20 μm) or more. If the chamfered surface 6 is a curved surface, the upper limit of the chamfer width is 0.25 mm (250 μm) or less, 0.15 mm (150 μm) or less, 0.10 mm (100 μm) or less, 0.09 mm (90 μm) or less, 0.08 mm (80 μm) or less, and 0.07 mm (70 μm) or less. The above range of chamfer width may be, for example, the range between the lower limit and the upper limit, or the range between the upper limit and the upper limit. The chamfer width is the length (width) of the part that is curved from the outer shape when viewed from the front (e.g., the part shown in Figure 5). The measurement point for the chamfer width is near the center of each side (each side) in the longitudinal direction (e.g., the part indicated by the arrow in Figure 5).

[0036] If the chamfered surface 6 is an R-shaped surface, the size of the R-shaped surface is not limited as long as it is large enough to remove burrs. If the chamfered surface 6 is an R-shaped surface, for example, the lower limit of the R-shaped surface is R0.02 mm (20 μm) or more. If the chamfered surface 6 is an R-shaped surface, for example, the upper limit of the R-shaped surface is R0.25 mm (250 μm) or less, R0.15 mm (150 μm) or less, R0.1 mm (100 μm) or less, and 0.08 mm (80 μm) or less. The above range of the R-shaped surface may be, for example, the range between the lower limit and the upper limit, or the range between the upper limit and the upper limit.

[0037] Furthermore, if the chamfered surface 6 is to be curved, each side may be chamfered by barrel polishing (sometimes abbreviated as barrel polishing) using a barrel polishing machine or the like. In other words, the chamfered surface 6 may be a barrel polished surface. Barrel polishing is a method in which, for example, a magnetostrictive member (workpiece) is placed in a container called a barrel, polishing stones, compound, and water are added, and the container is moved or vibrated so that the magnetostrictive member (workpiece) inside the container comes into contact with the polishing stones and is polished. As a result, all sides of the magnetostrictive member become curved chamfered surfaces. Barrel polishing is preferable because, when the shape of the magnetostrictive member is relatively small, for example, a magnetostrictive member with a longitudinal length of less than 30 mm, a large number of magnetostrictive members can be placed in the container and the chamfering of a large number of magnetostrictive members can be performed in one go, resulting in good production efficiency.

[0038] In barrel polishing, the magnetostrictive member is polished simultaneously with the polishing stones in the container while rotating, so differences in the degree of contact may result in differences in the polishing condition of each side of the magnetostrictive member's shape. However, the barrel polishing conditions for manufacturing the magnetostrictive member 1 of this embodiment can be appropriately set through preliminary experiments. This will be explained with reference to the example of Embodiment 2 described later.

[0039] Example 2 describes a barrel polishing process using a magnetic tabletop barrel polishing machine. The barrel rotation speed and processing time were 350 rpm and 30 minutes for Example 2-1, 700 rpm and 15 minutes for Example 2-2, and 700 rpm and 30 minutes for Example 2-3. Tests were conducted by varying the barrel rotation speed and processing time. Figure 5 is a photograph of the magnetostrictive member after barrel polishing in Example 2-1. Figure 5 is a photograph of a magnified view of a portion of the magnetostrictive member using a microscope. In Figure 5, the arrows in the schematic diagram at the top of the photograph indicate the observed portion of the magnetostrictive member and the direction of observation with the microscope. Also, in Figure 5, the parts shown in black indicate chamfered surfaces (chamfered shapes).

[0040] The outer shape of the chamfered portion 6 on the edge parallel to the short side was R66.8μm, and the chamfer width (center of the edge parallel to the long side) was 44.7μm on the upper side and 43.6μm on the lower side. "R" represents the size of the radius. Furthermore, the outer shape of the portion where the central part of the magnetostrictive member was cut (chamfered portion on the edge parallel to the long side) was R30μm. Table 1 shows the results for Examples 2-2 and 2-3. As the rotational speed increases and the processing time increases, the size of the chamfer and the chamfer width tend to increase. In this example of barrel polishing, the corners of the magnetostrictive member, the edges parallel to the short side D2, and the edges parallel to the long side D1 are polished in that order. The amount of polishing is smallest near the center of the long side D1. As shown in Figure 5 and Table 1, the chamfer size (radius and width) tends to increase as the rotational speed and barrel polishing time increase. Furthermore, the chamfer width (the center of the edge parallel to the longitudinal direction D1) correlates with the outer shape of the central part of the magnetostrictive material when it is cut (the chamfered part of the edge parallel to the longitudinal direction D1), and tends to increase by 10 μm to 20 μm. Based on these results, in barrel polishing, for example, burr removal can be controlled by controlling the chamfer width of the central part in the longitudinal direction D1 where the amount of polishing during barrel polishing is small.

[0041] Next, we will explain the magnetostrictive properties in barrel polishing. For the magnetostrictive properties, the maximum force coefficient and the maximum optimal magnetic field strength were evaluated using the same method as described in Japanese Patent Application No. 2023-037128 and International Patent Application No. PCT / JP2024 / 4133. Details are described in the examples.

[0042] The differences in force coefficient and optimal magnetic field strength shown in Table 1 were compared against the average values ​​of the force coefficient and optimal magnetic field strength for 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less at the time of cutting. As a result, in Example 2-1, the force coefficient and optimal magnetic field strength were within ±5% of the standard, and there was no change in the magnetostrictive properties, indicating good performance.

[0043] In Example 2-2, the force coefficient was within ±5%, but the optimal magnetic field strength tended to decrease, being within -20% to 0% of the standard. In Example 2-3, the force coefficient was within -10% to 0%, but the optimal magnetic field strength tended to decrease, being within -40% to -0% of the standard. It was observed that when the chamfer width was too large, the force coefficient decreased after barrel polishing, and the optimal magnetic field strength also changed. This is because the main surface of the magnetostrictive member is polished, albeit to a small extent, during barrel polishing. In magnetostrictive members, as shown in Patent Document 1, 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 magnetostrictive constant and parallel magnetostriction, and with little variation in magnetostrictive constant and parallel magnetostriction between members. It is presumed that the polishing of the main surface by barrel polishing affected the magnetostrictive properties.

[0044] As shown in Table 1, the magnetostrictive properties tend to decrease as the processing time increases. When chamfering by barrel polishing, it is preferable to polish to an extent that does not reduce the magnetostrictive properties. For example, as shown in the results in Table 1, the chamfer width can be set to 0.09 mm (90 μm) or less, preferably 0.02 mm (20 μm) to 0.06 mm (60 μm), and within this range, the reduction in magnetostrictive properties described above can be suppressed more reliably. Note that the conditions for barrel polishing vary depending on the equipment, but for example, the conditions can be appropriately set through preliminary experiments so that the chamfer width falls within the above range.

[0045] As described above, the magnetostrictive member according to this embodiment is a plate-like body, and at least a portion of each edge of the plate-like body is a chamfered surface (chamfered portion). That is, the magnetostrictive member 1 is a plate-like body, and at least a portion of each edge of the plate-like body is provided with a chamfered surface. According to the magnetostrictive member according to this embodiment, fluctuations in magnetostrictive properties caused by burrs generated during cutting are suppressed.

[0046] (Manufacturing method for magnetostrictive members) Next, the 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. In the following description, the method for manufacturing the magnetostrictive member 1 from a single crystal ingot of Fe-Ga alloy will be described as an example, but the method for manufacturing the magnetostrictive member of this embodiment is not limited to the following description. Furthermore, any descriptions in this specification that are applicable to the method for manufacturing the magnetostrictive member of this embodiment will also be applicable to the method for manufacturing the magnetostrictive member of this embodiment. Furthermore, in the method for manufacturing the magnetostrictive member of this embodiment described below, any descriptions that are applicable to the magnetostrictive member of this embodiment described above will also be applicable to the magnetostrictive member of this embodiment.

[0047] The present invention provides a method for manufacturing a magnetostrictive member, comprising the steps of preparing a magnetostrictive member cut into individual pieces (fragmented) and chamfering the individual pieces of the magnetostrictive member. One embodiment of the present invention provides a method for manufacturing a magnetostrictive member that includes removing at least a portion of the burrs generated when the member is cut into individual pieces (fragmented) by chamfering.

[0048] In the process of preparing individual magnetostrictive members, for example, magnetostrictive members are prepared by manufacturing them using a conventional method and then preparing individual pieces. Generally, magnetostrictive members are made by processing single crystals grown by methods such as the Cz method or VB method into thin plate-shaped members (e.g., Figure 2) using electrical discharge wire cutting, and then cutting the thin plate members into predetermined shapes using a cutting device to produce individual magnetostrictive members. Alternatively, as shown in Patent Document 1, a magnetostrictive member may have a grinding surface, with multiple grooves 2 extending in the longitudinal direction D1 of the magnetostrictive member, such as grinding marks (e.g., grinding marks from surface grinding), to obtain a magnetostrictive member with a high magnetostrictive constant and parallel magnetostriction, and with little variation in magnetostrictive constant and parallel magnetostriction between members. Extending in the longitudinal direction D1 includes the angle of intersection with the longitudinal direction D1 being within 45°. Note that the magnetostrictive member does not necessarily have the above-mentioned grooves 2.

[0049] Next is the process of chamfering the individual pieces of magnetostrictive material. As described above, the magnetostrictive material cut into individual pieces will have burrs of varying sizes at the cut edges. The chamfering process is the process of removing these burrs. As described above, the chamfering process chamfers at least a portion of the edges of the plate-like material. The edges of the plate-like material on which the chamfering process is performed are as described above. In the chamfering process, the shape of the chamfered surface 6 can be any of the various chamfered shapes described above. In the chamfering process, the shape of the chamfered surface 6 can be, for example, a chamfered surface, a curved surface (e.g., a rounded surface, a barrel-polished surface), or a fine chamfered surface. The chamfering process can be carried out by using a bevel polishing device or jig with a chamfering wheel (a grinding wheel tilted at 45 degrees) to process the surface into a chamfered shape using a cutter, grinder, abrasive paper, etc., or by using a barrel polishing machine, etc. In the chamfering process, when barrel polishing is performed, as described above, productivity can be improved because multiple materials can be chamfered together in a single operation, and because all sides can be chamfered, burrs can be removed more reliably. The size of the chamfered surface 6 in the chamfering process is as described above. The manufacturing method of the magnetostrictive member in this embodiment may include steps other than the steps of preparing the magnetostrictive member and the chamfering process. [Examples]

[0050] The present invention will be described in detail below using examples, but the present invention is not limited in any way by these examples.

[0051] [Example 1] The magnetostrictive members were manufactured based on the manufacturing method of this embodiment described above. Magnetostrictive members were prepared by processing and cutting individual pieces from cylindrical Fe-Ga alloy single crystals grown by the vertical Bridgman (VB) method, which had a gallium content of 17.2 to 19.8 at%.

[0052] The fragmentation from the single crystal was performed using the following procedure. First, a thin plate was prepared by cutting the single crystal parallel to the crystal growth direction using a free abrasive wire saw. Next, the obtained thin plate was subjected to surface grinding using a #100 flat grinding wheel on a surface grinding machine to adjust the thickness of the thin plate and to form multiple grooves (grinding marks) on the front and back surfaces. Subsequently, the cutting position was set so that the longitudinal direction of the magnetostrictive material was the same as the grinding direction during surface grinding, i.e., the direction of the grinding marks, and a magnetostrictive material with dimensions of 32 mm in the longitudinal direction × 8 mm in the transverse direction × 1 mm in thickness was cut out (fragmented) using an outer blade cutting device.

[0053] Next, chamfering was performed. Chamfering was carried out using a bevel grinding machine with a 45° chamfer angle and a #600 grit grinding wheel, with a chamfer width set to 50 μm. Chamfering was performed on a total of 8 locations on each side of the main surface and the back surface in both the longitudinal and transverse directions. The above procedure was performed on 10 magnetostrictive members.

[0054] The chamfering characteristics of the magnetostrictive member were confirmed using the following method. The central part of the longitudinal side surface of the magnetostrictive member was observed with an optical microscope, and the characteristics of the chamfered portion of each side (chamfer width, chamfer shape, etc.) were measured. The chamfer width and chamfer shape were determined by measuring five arbitrary points in the image obtained from the optical microscope observation.

[0055] The manufacturing conditions and results for Example 1 are shown in Table 1. The chamfer width was stable, ranging from 40 μm to 60 μm. Furthermore, the maximum force coefficient and the maximum optimal magnetic field strength were evaluated as magnetostrictive properties using the same method as described in Japanese Patent Application No. 2023-037128 and International Patent Application No. PCT / JP2024 / 4133. For comparison, the average values ​​of the force coefficient and optimal magnetic field strength for 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less at the time of cutting were used as a baseline. The force coefficient and optimal magnetic field strength were within ±5% of the baseline, indicating little change in magnetostrictive properties and good performance.

[0056] Regarding the evaluation of the maximum force coefficient and the maximum optimal magnetic field strength, the same method as described in Japanese Patent Application No. 2023-037128 and International Patent Application No. PCT / JP2024 / 4133 will be described below. The evaluation of the maximum force coefficient and the maximum optimal magnetic field strength was performed using an evaluation method based on electromechanical equivalent circuit analysis (impedance measurement). The electromechanical equivalent circuit analysis (impedance measurement) will be described below. Figure 6 shows an overview of the impedance measurement device. A bias magnetic field is generated in the excitation coil using a DC (direct current) power supply, and the magnetostrictive material is magnetized. With the magnetostrictive material placed inside the measurement coil, the impedance of the measurement coil is measured. The equivalent circuit of the measurement coil is shown in Figure 7, and the equivalent impedance of this circuit can be expressed by the following equation (1). The force coefficient α is the degree of coupling between the mechanical system and the electrical system, and is an indicator of the energy conversion efficiency from mechanical energy to electrical energy, and has a positive correlation with the power output of the vibration power generation device.

[0057]

number

[0058] The measured impedance loop is converted to a dynamic impedance loop by subtracting the component obtained by removing the electrical circuit component, and the force coefficient α is calculated from equations (2) and (3) below.

number

number

[0059] The impedance measurement described above is performed multiple times while changing the bias magnetic field generated by the excitation coil by varying the current of the DC power supply. When the force coefficient α is measured while the magnetic field strength is varied from 0 kA / m to the saturation magnetic field, the force coefficient α is maximized at around half the saturation magnetic field strength, and decreases elsewhere. The magnetic field strength at which the force coefficient α is maximized is the optimal magnetic field strength. The force coefficient α at the optimal magnetic field strength is defined as the force coefficient αmax (note that the force coefficient αmax is sometimes abbreviated as force coefficient). In other words, by generating a bias magnetic field to magnetize the magnetostrictive material, and placing the magnetostrictive material inside the measuring coil, the impedance of the measuring coil is measured multiple times while varying the bias magnetic field strength up to the saturation magnetic field strength. Based on the obtained measurement results of the impedance of the measuring coil, the optimal magnetic field strength, which is the magnetic field strength at which the force coefficient α is maximized, and the characteristics of the magnetostrictive member, including the force coefficient αmax at the optimal magnetic field strength, can be determined.

[0060] In this example, the magnetostrictive properties were measured using an impedance measuring device as shown in Figure 6 to determine the force coefficient and optimal magnetic field strength. The impedance measurement was performed as follows: A measuring coil was fabricated so that the manufactured magnetostrictive member would fit perfectly inside, and impedance measurements equivalent to those described in Patent Document 3 (Patent No. 7084620) were performed. The excitation current was set to 10-70 mA, and the current was applied at 5 mA intervals. Converting this to magnetic field strength, 1 mA = 78.4 A / m, and a bias magnetic field was applied at 0.392 kA / m intervals in the range of 0.784-5.488 kA / m. An impedance analyzer was used to perform impedance measurements at frequencies of 50-150 kHz, and the force coefficient α was calculated for each magnetic field strength. The optimal magnetic field strength at which the force coefficient α was maximized and the force coefficient αmax at that point were calculated.

[0061] [Example 2] Similar to Example 1, magnetostrictive members were prepared by processing and fragmenting cylindrical Fe-Ga alloy single crystals with a gallium content of 17.2-19.8 at%, grown using the vertical Bridgman (VB) method. The dimensions of the magnetostrictive members were 25 mm in the longitudinal direction × 4 mm in the transverse direction × 0.5 mm in thickness.

[0062] Chamfering was performed by barrel polishing using a barrel polishing machine. A magnetic tabletop barrel polishing machine was used for barrel polishing. Stainless steel pins were used as polishing stones, and liquid compound and pure water were added. The rotation speed and processing time for barrel polishing were 350 rpm and 30 minutes for Example 2-1, 700 rpm and 15 minutes for Example 2-2, and 700 rpm and 30 minutes for Example 2-3. In each of Examples 2-1 to 2-3, barrel polishing was performed on 10 pieces, and 3 pieces were randomly selected for evaluation. Table 1 shows the manufacturing conditions and results for Examples 2-1 to 2-3.

[0063] Figure 5 shows a photograph of a representative example of a magnetostrictive member that underwent barrel polishing in Example 2-1. The chamfered shape of the short side was R66.8 μm, and the chamfer width was between 30 μm and 50 μm. The central part of the magnetostrictive member was also cut, and the chamfered shape of that portion was measured. It was R30 μm.

[0064] As shown in the results for Examples 2-2 and 2-3 in Table 1, the size and width of the chamfer shape tend to increase as the rotational speed increases and the processing time increases.

[0065] Similar to Example 1, the maximum value of the force coefficient and the maximum value of the optimal magnetic field strength were measured as magnetostrictive properties and compared with the standard. As a result, in Example 2-1, the force coefficient and optimal magnetic field strength were within ±5% of the standard, indicating little change in magnetostrictive properties and good performance. In Example 2-2, the force coefficient was within ±5%, but the optimal magnetic field strength was within -20% to 0% of the standard, showing a tendency to decrease. In Example 2-3, the force coefficient was within -10% to 0%, but the optimal magnetic field strength was within -40% to -20% of the standard, showing a tendency to decrease.

[0066] [Example 3] In Example 3, the magnetostrictive member was manufactured using the same magnetostrictive member and barrel polishing machine as in Example 2. In Example 3, the barrel polishing conditions were a rotation speed of 350 rpm, and the processing time was 15 minutes to 60 minutes in Examples 3-1 to 3-4. Table 1 shows the manufacturing conditions and results for Examples 3-1 to 3-4. The chamfer width was within 30 μm to 50 μm in Examples 3-1 and 3-2, but in Example 3-3 it was within 40 μm to 60 μm, indicating a larger chamfer width. In Example 3-4 it was within 40 μm to 60 μm, indicating a larger chamfer width.

[0067] Similar to Example 1, the maximum value of the force coefficient and the maximum value of the optimal magnetic field strength were measured as magnetostrictive characteristics and compared with the standard. As a result, in Examples 3-1 and 3-2, the force coefficient and optimal magnetic field strength were within ±5% of the standard, indicating little change in magnetostrictive characteristics and good performance. In Examples 3-3 and 3-4, the force coefficient was within ±5% of the standard, but the optimal magnetic field strength was within -20% to 0% of the standard, showing a tendency to decrease.

[0068] [Example 4] In Example 4, magnetostrictive members were prepared by processing and fragmenting a single crystal of Fe-Ga alloy grown using the vertical Bridgman (VB) method, similar to Example 1. The size of the fragmented magnetostrictive members was 8 mm in the longitudinal direction × 2 mm in the transverse direction × 0.3 mm in thickness. The grinding wheel grit was #400 during surface grinding.

[0069] Similar to Example 2, a barrel polishing machine was used with a rotation speed of 350 rpm and a processing time of 15 minutes. Ten pieces were subjected to barrel polishing, and three were selected for evaluation. Table 1 shows the manufacturing conditions and results for Example 4.

[0070] As a result, the chamfer width was within 30 μm to 50 μm. Magnetostrictive properties were evaluated in the same way as in Example 1, using the force coefficient and optimal magnetic field strength. For comparison, the average values ​​of the force coefficient and optimal magnetic field strength at the time of cutting were used as a baseline for 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less. The force coefficient and optimal magnetic field strength were within ±5% of the baseline, indicating little change in magnetostrictive properties and good performance. In addition, as a result, in Example 4, both the force coefficient and optimal magnetic field strength were within ±5% of the baseline, indicating little change in magnetostrictive properties and good performance.

[0071] [Example 5] Except for using a #170 grit grinding wheel during surface grinding, the process was the same as in Example 4. Table 1 shows the manufacturing conditions and results for Example 5.

[0072] The chamfer width was within 30 μm to 50 μm. Magnetostrictive properties were evaluated in the same way as in Example 1, by assessing the force coefficient and optimal magnetic field strength. For comparison, the average values ​​of the force coefficient and optimal magnetic field strength at the time of cutting were used as a baseline for 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less. The force coefficient and optimal magnetic field strength were within ±5% of the baseline, indicating little change in magnetostrictive properties, which was good. The evaluation was the same as in Example 1. As a result, in Example 5, both the actual force coefficient and optimal magnetic field strength were within ±5% of the baseline, indicating little change in magnetostrictive properties, which was good. The evaluation was the same as in Example 1.

[0073] [Example 6] The size of the magnetostrictive member was set to 25 mm in the longitudinal direction × 4 mm in the transverse direction × 0.5 mm in thickness, and chamfering was performed with a chamfer width of 100 μm, except that the process was the same as in Example 1. Table 1 shows the manufacturing conditions and results for Example 6.

[0074] The chamfer width was within 80 μm to 120 μm. Magnetostrictive properties were evaluated in the same way as in Example 1, by assessing the force coefficient and optimal magnetic field strength. For comparison, the average values ​​of the force coefficient and optimal magnetic field strength for 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less at the time of cutting were used as a baseline. The force coefficient and optimal magnetic field strength were within ±5% of the baseline, indicating little change in magnetostrictive properties and good performance. The evaluation was performed in the same way as in Example 1. As a result, in Example 6, both the actual force coefficient and optimal magnetic field strength were within ±5% of the baseline, indicating little change in magnetostrictive properties and good performance.

[0075] [Example 7] The size of the magnetostrictive member was set to 25 mm in the longitudinal direction × 4 mm in the transverse direction × 0.5 mm in thickness, and chamfering was performed with a chamfer width of 200 μm, except that it was the same as in Example 1. Table 1 shows the manufacturing conditions and results for Example 7.

[0076] The chamfer width was within 180 μm to 230 μm. Magnetostrictive properties were evaluated in the same way as in Example 1, with a force coefficient and optimal magnetic field strength being assessed. For comparison, the force coefficient and the average value of the optimal magnetic field strength at the time of cutting were compared to 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less. As a result, in Example 7, the optimal magnetic field strength was within ±5%, but the force coefficient was within -10% to +5% of the standard, showing a slight downward trend.

[0077] In beveling with a chamfered shape, the main surface is preserved because polishing is not performed on areas other than the chamfered portion. However, due to the effects of machining distortion in the beveled portion and the reduction in volume caused by beveling, it is thought that the force coefficient decreases when the bevel width is large.

[0078] [Comparative Example 1] A magnetostrictive member similar to that in Example 4 was prepared. Chamfering was not performed. Observation of the prepared unchamfered magnetostrictive member using an optical microscope revealed the presence of burrs ranging from 10 μm to 50 μm. The magnetostrictive properties were evaluated in the same way as in Example 1, with a force coefficient and optimal magnetic field strength being assessed. For comparison, the force coefficient and the average value of the optimal magnetic field strength at the time of cutting were compared to those of 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less. A decrease in the force coefficient was observed, ranging from -40% to +5%. The optimal magnetic field strength also showed large variability, ranging from -10% to +200%, indicating instability.

[0079] [Table 1]

[0080] [summary] The magnetostrictive members of Examples 1 to 7 exhibited significantly more stable force coefficients and optimal magnetic field strengths compared to the magnetostrictive member of Comparative Example 1. This is thought to be due to fluctuations in magnetostrictive properties caused by burrs in the magnetostrictive member of Comparative Example 1. From the results of Examples 1 to 7 and Comparative Example 1, it is confirmed that the magnetostrictive members according to this embodiment suppress fluctuations in magnetostrictive properties caused by burrs generated during cutting.

[0081] Furthermore, the technical scope of the present invention is not limited to the embodiments described above. One or more of the requirements described above may be omitted. Also, the requirements described above may be combined as appropriate. In addition, to the extent permitted by law, all disclosures of the documents cited above shall be incorporated as part of the description herein. [Explanation of symbols]

[0082] 1: Magnetostrictive member 2:Groove 3: Surface 4: Back side 5: Edge (edge ​​part) 6: Chamfered surface (chamfered part) D1: Longitudinal direction D2: Lateral direction

Claims

1. A magnetostrictive member is a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties, and having longitudinal and transverse directions, A magnetostrictive member in which at least a portion of each edge of the plate-like body is a chamfered surface.

2. The aforementioned chamfered surface is either a C-surface or an R-surface. The magnetostrictive member according to claim 1, wherein the size of the C-surface or R-surface is 0.02 mm or more and 0.25 mm or less.

3. The aforementioned chamfered surface is a curved surface, The magnetostrictive member according to claim 1, wherein the chamfer width of the chamfered surface is 250 μm or less.

4. The magnetostrictive member according to claim 3, wherein the chamfer width of the chamfered surface is 20 μm or more and 70 μm or less.

5. A method for manufacturing a magnetostrictive member, The process of preparing magnetostrictive members cut into individual pieces, A method for manufacturing a magnetostrictive member, comprising the step of performing a chamfering process on the prepared magnetostrictive member.

6. The method for manufacturing a magnetostrictive member according to claim 5, wherein the chamfering process is barrel polishing.

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