Magnetostrictive member and method for manufacturing magnetostrictive member

Abstract

[Problem] To provide: a magnetostrictive member in which the fluctuation of magnetostrictive characteristics caused by burrs generated at the time of cutting or the like is suppressed; and a method for manufacturing the magnetostrictive member. [Solution] This magnetostrictive member is composed of a crystal of an iron-based alloy having magnetostrictive characteristics, and is a plate-like body having a longitudinal direction and a lateral direction. At least some side portions of the plate-like body are chamfered surfaces.

Description

Magnetostrictive member and method of manufacturing the same

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

[0002] Magnetostrictive materials have been attracting attention as functional materials. For example, Fe-Ga alloys, which are iron-based alloys, exhibit magnetostriction and inverse magnetostriction, exhibiting large magnetostriction of approximately 100 to 350 ppm. For this reason, they have recently attracted attention as vibration-powered energy harvesting materials, and are expected to be applied to wearable devices and sensors.

[0003] A magnetostrictive vibration power generation device (sometimes abbreviated as "device") is composed of a magnetostrictive member, such as an Fe—Ga alloy wound around a coil, a yoke, and a permanent magnet for a field magnet (see, for example, Patent Document 2 and Non-Patent Document 1). In this magnetostrictive vibration power generation device, 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. This causes the magnetic flux density of the coil wound around the magnetostrictive member to change due to the inverse magnetostrictive effect, generating an electromagnetically induced electromotive force and generating electricity. In a magnetostrictive vibration power generation device, vibration occurs when a force is applied in the longitudinal direction of the yoke. Therefore, it is desirable to process the magnetostrictive member, such as an Fe—Ga alloy, used in the device so that the easy axis of magnetization, <100>, is aligned longitudinally.

[0004] The magnetostrictive properties of Fe—Ga alloys are believed to affect the magnetostrictive and inverse magnetostrictive effects and the characteristics of magnetostrictive vibration-based power generation devices, making them an important parameter in device design (Non-Patent Document 1). 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% (Non-Patent Document 2). It is therefore 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 amount of parallel magnetostriction, the better the device characteristics, such as output voltage, tend to be (Non-Patent Document 3).

[0005] International Publication No. 2021 / 100467 International Publication No. 2011 / 158473 Patent No. 7084620

[0006] Toshiyuki Ueno, Journal of the Japan Society of Precision Engineering Vol. 79, No.4, (2013) 305-308. AE Clark et al., Appl. Phys. 93(2003)8621.Jung Jin Park, Suok-Min Na, Ganesh Raghunath, and Alison B. Flatau., AIP ADVANCES 6, 056221(2016).

[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, magnetostrictive members are required to have high magnetostrictive properties and little variation in magnetostrictive properties. Under these circumstances, it was thought that if the crystal orientation of an Fe—Ga alloy single crystal was <100> and 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 amount of parallel magnetostriction. Therefore, 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 high magnetostrictive constant and amount of parallel magnetostriction and little variation in the magnetostrictive constant and amount of 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 confirmed that a predetermined device output (e.g., power generation amount such as force coefficient) was obtained and that there was little variation in device output between devices.

[0008] To measure the parallel magnetostriction of a magnetostrictive member, a strain gauge must be attached to the magnetostrictive material, which is a destructive test. On the other hand, when evaluating the force coefficient, impedance measurement can be performed by inserting and removing a measuring coil, which is a non-destructive test, so impedance measurement is preferable for product inspection.

[0009] Furthermore, prior to the present invention, the present inventors discovered that the parallel magnetostriction of a magnetostrictive member is positively correlated with the force coefficient calculated from impedance measurements. Furthermore, the force coefficient is positively correlated with device output (Patent Document 2). Prior to the present invention, the present inventors discovered that increasing device output increases not only the parallel magnetostriction but also the force coefficient (Japanese Patent Application No. 2023-037128, International Patent Application No. PCT / JP2024 / 4133).

[0010] However, it was discovered that some magnetostrictive members had a defect that reduced device output, and upon investigation, it was confirmed that this was due to tiny burrs that were difficult to see and were generated when the magnetostrictive members were cut.

[0011] Magnetostrictive members are made by processing a single crystal grown by the Cz method, VB method, or the like into a thin plate member by discharge wire cutting, etc., and then cutting the thin plate member into a predetermined shape using a cutting device, etc., to produce individual magnetostrictive members. When the magnetostrictive members that have been cut into individual pieces are examined under a microscope, it has been confirmed that burrs of various sizes have occurred at the cut portions.

[0012] It was found that if there are burrs on the magnetostrictive material, the magnetostrictive characteristics fluctuate 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 leads to a decrease in the device output, as mentioned above, which is a major problem. It was also found that during impedance measurement, when the magnetostrictive material is inserted into the measurement coil, the burrs can cause problems, such as the breakage of the enameled wire inside the measurement coil. Furthermore, it was found that when the magnetostrictive material is bonded to the frame during device fabrication, gaps can occur between the magnetostrictive material and the frame, which can reduce the device output.

[0013] Therefore, an object of the present invention is to provide a magnetostrictive member and a method for manufacturing the same, in which fluctuations in magnetostrictive properties caused by burrs generated during cutting or the like are suppressed.

[0014] According to an aspect of the present invention, there is provided a magnetostrictive member which is a plate-shaped body made of crystals of an iron-based alloy having magnetostrictive properties, having a longitudinal direction and a lateral direction, and at least some of the edges of each side of the plate-shaped body are chamfered surfaces.

[0015] The chamfered surface may be a curved or rounded surface, and the size of the curved or rounded 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 chamfered surface may be 250 μm or less. The chamfered width of the chamfered surface may be 20 μm or more and 70 μm or less.

[0016] According to another aspect of the present invention, there is provided a method for manufacturing a magnetostrictive member, the method comprising the steps of preparing a magnetostrictive member cut into individual pieces, and chamfering the prepared magnetostrictive member. The chamfering may be performed by barrel polishing.

[0017] According to the present invention, it is possible 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 the like are suppressed.

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

[0019] Specific embodiments of the present invention will be described in detail below. The present invention is not limited to the following embodiments, and can be modified as appropriate without departing from the spirit and scope of the present invention. In the drawings, some or all of the drawings are shown schematically and scaled accordingly. In the following description, the term "A to B" means "A or greater and B or less." The directions in the drawings may be explained using an XYZ coordinate system. In this XYZ coordinate system, the direction perpendicular to the XY plane is referred to as the Z direction. The X, Y, and Z directions will be explained assuming that the direction of the arrow in the drawing is the + direction and the direction opposite to the arrow is the - direction.

[0020] [Embodiment] Hereinafter, a magnetostrictive member and a method for manufacturing a magnetostrictive member according to this embodiment will be described.

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

[0022] 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. Furthermore, 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 portion 5 of the plate-like body is a chamfered surface 6 (chamfered portion). The side portions 5 and the chamfered surfaces 6 will be described in further detail later. The magnetostrictive member 1 may optionally have a plurality of grooves 2 extending in the longitudinal direction D1, as described in Patent Document 1, for example.

[0023] The magnetostrictive member 1 is made of a crystal of an iron-based alloy. For example, multiple magnetostrictive members 1 can be 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 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. 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, and therefore are used in vibration-generated energy harvesting materials, 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. FIG. 2 is a diagram showing an example of a single crystal and a thin plate member.

[0024] A single crystal of an Fe—Ga alloy has a body-centered cubic lattice structure, and is based on the principle that the first to third <100> axes (see FIG. 2) among the directional indices in the Miller indices are equivalent, and the first to third {100} planes (see FIG. 2) among the plane indices in the Miller indices are equivalent (i.e., (100), (010), and (001) are equivalent). However, these do not have to be completely equivalent. Furthermore, an Fe—Ga alloy has the property of exhibiting large magnetostriction in a specific orientation of the crystal. When utilizing this property in a magnetostrictive vibration power generation device, it is desirable to align the direction in the device requiring magnetostriction of the magnetostrictive member 1 with the orientation (direction) in which the magnetostriction of the crystal is maximized. Specifically, as described above, it is desirable to set the <100> direction, which is the easy magnetization direction in the single crystal, to the longitudinal direction D1 of the magnetostrictive member 1. The <100> direction, which is the direction of easy magnetization in a single crystal, can be made 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.

[0025] The crystal that can be used for the magnetostrictive member 1 of this embodiment may be a single crystal or a polycrystal. In order to increase the degree of orientation integration in the <100> direction and improve the properties as a magnetostrictive material, it is more advantageous to use a single crystal than a polycrystal. Although polycrystals have inferior magnetostrictive properties to single crystals, they can be produced at low cost, so polycrystals may also be used.

[0026] The magnetostrictive member 1 is used, for example, as a material (component) for vibration power generation devices in the energy harvesting field, and as a material (component) for wearable terminals and sensors. For example, a magnetostrictive vibration power generation device such as that shown in Patent Document 2 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 coil. 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 set depending on the size of the intended device. For example, the magnetostrictive member 1 may have a side length of 5 mm or more, 10 mm or more, 20 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 examples, and specifically, the length (dimension) in the longitudinal direction D1 may be 25 mm, the width (dimension) in the lateral direction D2 may be 4 mm, and the thickness may be 0.5 mm. Furthermore, the dimensions of the magnetostrictive member 1 (long side (long side), lateral side (short side), thickness) may be in a range between two values ​​selected from the group consisting of any of the above upper limit values, any of the above lower limit values, and any of the values ​​described in the examples, or one value selected from this group may be the lower limit value, or one value selected from this group may be the upper limit value.

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

[0028] As mentioned 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 little variation in the magnetostrictive properties. 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 high magnetostriction constant and parallel magnetostriction and little variation in the magnetostriction 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 confirmed that the specified power generation characteristics, such as the device output or force coefficient, were obtained and that there was little variation in the device output between devices. However, it was found that some magnetostrictive members had a defect that reduced the device output. Investigation revealed 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 subjected to chamfering processing so that a part of each side portion 5 becomes a chamfered surface 6 .

[0030] Magnetostrictive members are produced by, for example, cutting a single crystal grown by the Cz method or VB method into a thin plate-like member by discharge wire cutting or other methods. The thin plate member is then cut into a predetermined shape using a cutting device or other device to produce individual magnetostrictive members. For example, the thin plate member can be diced into individual pieces using a peripheral blade cutting device or a dicing device. It has been found that when a thin plate member is diced using the above device, burrs of up to approximately 60 μm in size are generated on the cutting exit side (burr surface side). While it is possible to reduce the size of the burrs by appropriately changing the processing conditions in the above device, burrs are usually generated. Burrs of various sizes occur on the side of the cutting exit side of a magnetostrictive member when it is cut into individual pieces. Figure 3 shows an example of a burr in a magnetostrictive member. In Figure 3, the black portion represents the magnetostrictive material, and the edge of the magnetostrictive material is shown enlarged under a microscope.

[0031] In one aspect of the present invention, burrs that occur in a magnetostrictive member when it is cut into individual pieces are removed by chamfering. Note that the magnetostrictive member 1 of one aspect of the present invention 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 some of the edges of each side of the plate-like body are chamfered surfaces (chamfered portions). In other words, the magnetostrictive member 1 is a plate-like body, and at least some of the edges of each side of the plate-like body are provided with chamfered surfaces 6. In the example shown in FIG. 1 , the edge portions include the portions of each side (12 sides in total) of the rectangular parallelepiped and the portions near the edges. Note that in this specification, "edge portions" may also be abbreviated as "sides."

[0032] Regarding the location of burrs, for example, when the magnetostrictive member is cut into individual pieces, large and small burrs are generated particularly on the side surface at the exit side of the cutting direction. FIG. 4 is a diagram showing an example of a cutting direction and burrs. For example, as shown in FIG. 4, if the cutting direction of the magnetostrictive member is the -Z direction on the +X side of the material (the workpiece), the cutting exit side is the -Z side on the +X side of the material. In this specification, this surface on the exit side of the cutting direction (the XY plane on the -Z side in the example of FIG. 4) may also be referred to as the "burr surface." Therefore, it is preferable that the chamfered surface 6 have four sides in total, two sides parallel to (extending) the longitudinal direction D1 and two sides parallel to (extending) the lateral direction D2 on the cutting exit side (burr surface) of the side surface of the magnetostrictive member (in the example of FIG. 4, it is preferable that the four sides on the XY plane on the -Z side). Note that the size of the burrs is, for example, 0.01 mm to 0.06 mm, and since it is difficult to visually identify the burred surface (burred surface side), the chamfered surface 6 may have a total of eight sides, including two sides parallel to (extending in) the longitudinal direction D1 on the side facing the burred surface and two sides parallel to (extending in) the short direction D2 (in the example of FIG. 4 , a total of eight sides may be provided, including four sides in the XY plane on the -Z side and four sides in the XY plane on the +Z side). In the case where the shape (size) of the magnetostrictive member 1 is large, for example, such as a magnetostrictive member whose length in the longitudinal direction D1 exceeds 30 mm, and the burred surface side can be reliably identified, the magnetostrictive member 1 may have a total of four sides, including two sides parallel to (extending in) the longitudinal direction D1 and two sides parallel to (extending in) the short direction D2. Furthermore, in the case of a magnetostrictive member 1 having a small shape (size), for example, a longitudinal length of less than 30 mm, it is possible to improve productivity by using barrel polishing or the like, which will be described later, to chamfer multiple materials together in a single operation, rather than chamfering each individual material. In barrel polishing or other processing, all sides can be made into chamfered surfaces 6. In an embodiment of the present invention, all sides (all side portions) may be made into chamfered surfaces 6. In the example of FIG. 1, all sides refer to 12 sides (the 12 sides and their neighboring portions). When all sides (all side portions) are made into chamfered surfaces 6, burrs can be removed more reliably.

[0033] The shape of the chamfered surface 6 may be any of various chamfered shapes. The shape of the chamfered surface 6 may be, for example, a C-surface, a curved surface (e.g., an R-surface or a barrel-polished surface), or a lightly chamfered surface. When the shape of the chamfered surface 6 is a C-surface, the processing method is not limited as long as the burrs are removed and the C-surface is processed. For example, a bevel polishing device using a grinding stone (a grinding stone tilted at 45 degrees) that produces a C-surface may be used. The C-surface may also be processed using a cutter, grinder, abrasive paper, or the like. It is preferable to select a grinding stone with a grit size greater than #400, such as #600 or #1000, to avoid the influence of processing distortion. The angle of the C-surface is generally 45 degrees, but is not particularly limited as long as the burrs during cutting can be removed. The size of the C-surface is not limited as long as it is large enough to remove the burrs. The lower limit of the size of the C-surface is, for example, 0.02 mm (20 μm) or more. The upper limit of the size of the C-plane is, for example, 0.25 mm (250 μm) or less, 0.15 mm (150 μm) or less, 0.1 mm (100 μm) or less, or 0.08 mm (80 μm) or less. The range of the size of the C-plane may be, for example, a range between the above-mentioned lower limit and upper limit, or a range between the above-mentioned upper limit and upper limit. Furthermore, the range may be between two values ​​selected from the group consisting of any of the above-mentioned upper limit values, any of the lower limit values, and any of the values ​​described in the examples, or one value selected from this group may be the lower limit, or one value selected from this group may be the upper limit.

[0034] C-face machining is performed, for example, on each side of the magnetostrictive member 1. Therefore, when the shape of the magnetostrictive member is large and the length in the longitudinal direction D1 exceeds 30 mm, for example, a magnetostrictive member with a length in the longitudinal direction D1 of 80 mm or the like, and the burr side can be determined reliably, the edges to be chamfered can be limited to the four edges on the burr side, allowing for efficient machining.

[0035] When the chamfered surface 6 is a curved surface, a bevel polishing device using a grindstone shaped to form a curved surface may be used. The size of the curved surface of the chamfered surface 6 is not particularly limited as long as it can be processed into a curved surface by removing burrs. For example, the curved surface may be processed using a bevel polishing device using a grindstone that forms an R-surface (e.g., a concave grindstone with an R of 0.1 mm). The chamfered surface 6 may be a curved surface or a bevel-processed surface. Other processing may be similar to, for example, C-surface processing. 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. When 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, or 0.07 mm (70 μm) or less. The chamfer width range may be, for example, a range between the lower limit and upper limit values ​​described above, or a range between upper limits and upper limits. It may also be a range between two values ​​selected from a group consisting of any of the upper limit values ​​and any of the lower limit values ​​and any of the values ​​described in the examples, or one value selected from this group may be the lower limit or the upper limit. The chamfer width is the length (width) of the portion that is curved relative to the outer shape when viewed from the front (e.g., the portion shown in FIG. 5). The measurement points for the chamfer width are near the center of each side (each side portion) in the longitudinal direction (for example, the portion indicated by the arrow in FIG. 5).

[0036] When the chamfered surface 6 is a rounded surface, the size of the rounded surface is not limited as long as it is large enough to remove burrs. When the chamfered surface 6 is a rounded surface, the lower limit of the rounded surface is, for example, R 0.02 mm (20 μm) or more. When the chamfered surface 6 is a rounded surface, the upper limit of the rounded surface is, for example, R 0.25 mm (250 μm) or less, R 0.15 mm (150 μm) or less, R 0.1 mm (100 μm) or less, or R 0.08 mm (80 μm) or less. The range of the rounded surface may be, for example, a range between the lower limit and upper limit values ​​described above, or a range between upper limit values ​​and upper limit values. Furthermore, it may be a range between two values ​​selected from a group consisting of any of the upper limit values ​​described above, any of the lower limit values, and any of the values ​​described in the examples, or one value selected from this group may be the lower limit or the upper limit.

[0037] Furthermore, when the chamfered surface 6 is to be a curved surface, each side may be chamfered by barrel polishing (sometimes abbreviated as barrel polishing) using a barrel polishing machine or the like. That is, 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, abrasive stones, compound, and water are added, and the container is moved or vibrated, causing the abrasive stones to come into contact with the magnetostrictive member (workpiece) in the container and polish it. As a result, all sides of the magnetostrictive member become curved chamfered surfaces. Barrel polishing is preferable because it provides good production efficiency when the magnetostrictive member is relatively small, for example, when the magnetostrictive member is a magnetostrictive member with a longitudinal length of less than 30 mm, multiple magnetostrictive members can be placed in a container and chamfered in a single process.

[0038] In barrel polishing, the magnetostrictive member is polished while rotating or otherwise moving simultaneously with the polishing stone placed in the container, so differences in the polishing state of each side of the magnetostrictive member may occur depending on the magnitude of contact, but the conditions for barrel polishing to manufacture the magnetostrictive member 1 of this embodiment can be appropriately set through preliminary experiments. An explanation will be given with reference to Example 2 described below.

[0039] Example 2 is an example of barrel polishing using a magnetic benchtop 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 changing the barrel rotation speed and processing time. Figure 5 is a photograph of the magnetostrictive member after barrel polishing in Example 2-1. Note that Figure 5 is a photograph of a magnified portion of the magnetostrictive member observed under 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 under the microscope. In Figure 5, the black portion indicates the chamfered surface (chamfered shape).

[0040] The outer shape of the chamfered portion 6 on the side parallel to the short direction was R66.8 μm, and the chamfer width (at the center of the side parallel to the long direction (central portion)) was 44.7 μm on the upper side and 43.6 μm on the lower side. Note that "R" indicates the size of the R-processing. The outer shape of the cut portion (chamfered portion on the side parallel to the long direction) of the center of the magnetostrictive member was R30 μm. Table 1 also shows the results of Examples 2-2 and 2-3. The size and width of the chamfered shape tend to increase as the rotation speed increases and the processing time increases. In the barrel polishing process of this example, the corners of the magnetostrictive member, the sides parallel to the short direction D2, and the sides parallel to the long direction D1 are polished in this order. The amount of polishing near the center of the long direction D1 is smallest. 5 and Table 1, the chamfer size (radius, width) tends to increase as the rotation speed increases and the barrel polishing time increases. Furthermore, the chamfer width (the center of the side parallel to the longitudinal direction D1) correlates with the outer shape of the portion obtained by cutting the center of the magnetostrictive member (the chamfered portion of the side parallel to the longitudinal direction D1), and tends to increase by 10 μm to 20 μm. These results suggest that in barrel polishing, burr removal can be controlled by controlling the chamfer width of the center in the longitudinal direction D1, where the amount of polishing in barrel polishing is small.

[0041] Next, the magnetostriction characteristics in barrel polishing will be described. As the magnetostriction characteristics, the maximum value of the force coefficient (force coefficient) and the maximum value of the optimum magnetic field strength (optimum magnetic field strength) were evaluated using the same method as that described in Japanese Patent Application No. 2023-037128 and International Patent Application No. PCT / JP2024 / 4133. Details will be described in the Examples.

[0042] The difference in the force coefficient before and after and the difference in the optimum magnetic field strength before and after shown in Table 1 were compared based on the average values ​​of the force coefficient and the optimum magnetic field strength at that time of 10 magnetostrictive members that were equivalent but not chamfered and had burrs of 20 μm or less when cut. As a result, in Example 2-1, the force coefficient and optimum magnetic field strength were within ±5% of the standard, and there was no change in the magnetostriction characteristics, which was good.

[0043] In Example 2-2, the force coefficient was within ±5%, but the optimal magnetic field strength was within -20% to 0% of the reference, 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 -0% of the reference, showing a tendency to decrease. It was observed that if the chamfer width was too large, the force coefficient after barrel polishing decreased and the optimal magnetic field strength also changed. This is because barrel polishing also polishes the main surfaces of the magnetostrictive member, albeit to a small extent. As shown in Patent Document 1, by adding multiple grooves extending in the longitudinal direction of the magnetostrictive member, such as grinding marks, a magnetostrictive member with high magnetostriction constant and parallel magnetostriction amount and little variation in magnetostriction constant and parallel magnetostriction amount between members can be obtained. It is presumed that the magnetostrictive properties were affected by polishing the main surfaces by barrel polishing.

[0044] As shown in Table 1, the magnetostrictive properties tend to decrease as the processing time increases. When chamfering is performed by barrel polishing, it is preferable to polish to a degree that does not decrease 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). Within this range, the decrease in magnetostrictive properties can be more reliably suppressed. Note that the barrel polishing conditions vary depending on the apparatus, but the conditions can be appropriately set, for example, 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 some of the sides of the plate-like body have chamfered surfaces (chamfered portions). That is, the magnetostrictive member 1 is a plate-like body, and at least some of the sides of the plate-like body have chamfered surfaces. The magnetostrictive member according to this embodiment suppresses fluctuations in magnetostrictive properties caused by burrs generated during cutting.

[0046] (Method for manufacturing a magnetostrictive member) Next, a method for manufacturing a magnetostrictive member of this embodiment will be described. The method for manufacturing a magnetostrictive member of this embodiment is the method for manufacturing the magnetostrictive member 1 of this embodiment described above. In the following description, a method for manufacturing the magnetostrictive member 1 from a single crystal ingot of an 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 description in this specification that is applicable to the method for manufacturing the magnetostrictive member of this embodiment will also be applied to the method for manufacturing the magnetostrictive member of this embodiment. Furthermore, in the method for manufacturing a magnetostrictive member of this embodiment described below, any description that is applicable to the magnetostrictive member of the above embodiment will also be applied to the magnetostrictive member of this embodiment.

[0047] The method for manufacturing a magnetostrictive member of the present invention includes the steps of preparing a magnetostrictive member cut into individual pieces (singulated) and chamfering the individual magnetostrictive member. One aspect of the method for manufacturing a magnetostrictive member of the present invention includes removing at least a portion of burrs that are generated during cutting (singulating) into individual pieces by chamfering.

[0048] In the process of preparing the singulated magnetostrictive members, for example, singulated magnetostrictive members manufactured by a conventional method are prepared. Magnetostrictive members are generally produced by processing a single crystal grown by a Cz method, VB method, or the like into a thin plate-like member (e.g., FIG. 2) by discharge wire cutting or the like, and then cutting the thin plate into a predetermined shape using a cutting device or the like to produce the individual magnetostrictive members. Furthermore, as shown in Patent Document 1, a magnetostrictive member may have grinding marks (ground surfaces) added by adding multiple grooves 2 extending in the longitudinal direction D1 of the magnetostrictive member, such as grinding marks (e.g., grinding marks obtained by surface grinding), to obtain a magnetostrictive member with a high magnetostriction constant and parallel magnetostriction and low variation in the magnetostriction constant and parallel magnetostriction between members. "Extending in the longitudinal direction D1" includes an angle of 45° or less between the magnetostrictive member and the longitudinal direction D1. Note that the magnetostrictive member does not necessarily have the grooves 2.

[0049] Next, the magnetostrictive member is subjected to a chamfering process. As described above, large and small burrs are generated at the cut portions of the magnetostrictive member cut into individual pieces. The chamfering process is a process for removing burrs. As described above, the chamfering process involves chamfering at least some of the edges of the plate-like body. The edges (edges) of the plate-like body on which the chamfering process is performed are as described above. Furthermore, in the chamfering process, the shape of the chamfered surface 6 may be any of various chamfered shapes, as described above. In the chamfering process, the shape of the chamfered surface 6 may be, for example, a C-surface, a curved surface (e.g., an R-surface or a barrel-polished surface), or a lightly chamfered surface. In the chamfering process, the C-surface may be processed using a bevel polishing device or jig with a grinding stone (a grinding stone tilted at 45 degrees) to produce a C-surface, using a cutter, grinder, abrasive paper, or the like, or barrel polishing may be performed using a barrel polishing machine or the like. When barrel polishing is performed in the chamfering process, as described above, multiple materials can be chamfered together in a single operation, improving productivity, and all sides can be chamfered to form chamfered surfaces 6, making it possible to more reliably remove burrs. In the chamfering process, the size of the chamfered surfaces 6 is as described above. The method for manufacturing a magnetostrictive member of this embodiment may include processes other than the process of preparing the magnetostrictive member and the chamfering process.

[0050] EXAMPLES The present invention will be specifically explained below using examples, but the present invention is not limited to these examples in any way.

[0051] Example 1 A magnetostrictive member was manufactured based on the manufacturing method of the present embodiment described above. The magnetostrictive member was prepared by processing and dividing a cylindrical Fe—Ga alloy single crystal grown by the vertical Bridgman (VB) method and having a gallium content of 17.2 to 19.8 at%.

[0052] The single crystal was processed into individual pieces using the following procedure. First, a loose abrasive wire saw was used to cut the single crystal parallel to the single crystal growth direction to produce a thin plate member. Next, the resulting thin plate member was subjected to surface grinding using a #100 flat grinding wheel on a surface grinder to adjust the thickness of the thin plate member and form multiple grooves (grinding marks) on the front and back surfaces. The cutting position was then set so that the longitudinal direction of the magnetostrictive member was the same as the grinding direction during the surface grinding process, i.e., the grinding mark direction, and a magnetostrictive material measuring 32 mm in the longitudinal direction, 8 mm in the lateral direction, and 1 mm in thickness was cut out (segmented) using a peripheral blade cutting device.

[0053] Next, chamfering was performed. The chamfering was performed using a bevel polishing machine, with the C surface at 45° and a #600 grinding stone, with a chamfer width set to 50 μm. The chamfering was performed on each side in the longitudinal and lateral directions of the main surface and back surface, a total of eight locations. The above process was performed on 10 magnetostrictive members.

[0054] The chamfering condition of the magnetostrictive member was confirmed by the following method. The center of the longitudinal side 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 on the image obtained from the optical microscope observation.

[0055] The manufacturing conditions and results of Example 1 are listed in Table 1. The chamfer width was stable, ranging from 40 μm to 60 μm. Furthermore, the maximum force coefficient (force coefficient) and the maximum optimum magnetic field strength (optimum magnetic field strength) were evaluated for magnetostriction properties using methods similar to those described in Japanese Patent Application No. 2023-037128 and International Patent Application No. PCT / JP2024 / 4133. For comparison, the force coefficients of 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less at the time of cutting were compared with the average values ​​of the optimum magnetic field strength at that time. The force coefficients and optimum magnetic field strength were within ±5% of the reference, indicating little change in magnetostriction properties and favorable results.

[0056] The following describes the evaluation of the maximum force coefficient (force factor) and the maximum optimal magnetic field strength (optimum magnetic field strength), using a method similar to that described in Japanese Patent Application No. 2023-037128 and International Patent Application No. PCT / JP2024 / 4133. The maximum force coefficient (force factor) and the maximum optimal magnetic field strength (optimum magnetic field strength) were evaluated using an evaluation method based on analysis (impedance measurement) using an electromechanical equivalent circuit. Analysis (impedance measurement) using an electromechanical equivalent circuit is described below. Figure 6 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 7, and the equivalent impedance of this circuit can be expressed by the following equation (1). The force factor α is the degree of coupling between the mechanical system and the electrical system, is an index of the energy conversion efficiency from mechanical energy to electrical energy, and is positively correlated with the power generation output of the vibration power generation device.

[0057]

[0058] 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).

[0059] 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 as 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.

[0060] In each example of this example and this comparative example, the magnetostrictive properties were measured using an impedance measurement device as shown in FIG. 6 , and the force factor and optimal magnetic field strength were determined. The impedance measurement was performed as follows. A measurement coil was created so that the manufactured magnetostrictive member would fit inside, and impedance measurements equivalent to those described in Patent Document 3 (Japanese Patent Publication No. 7084620) were performed. The excitation current was 10 to 70 mA, and current was applied at 5 mA intervals. Converted 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 to 5.488 kA / m. An impedance analyzer was used to perform impedance measurements at frequencies of 50 to 150 kHz, and the force factor α at each magnetic field strength was calculated. The optimal magnetic field strength at which the force factor α was maximized and the force factor αmax at that time were calculated.

[0061] Example 2 As in Example 1, a magnetostrictive member was prepared by processing and dividing a cylindrical Fe—Ga alloy single crystal having a gallium content of 17.2 to 19.8 at% grown by the vertical Bridgman (VB) method into individual pieces. The size of the magnetostrictive member was 25 mm in the longitudinal direction, 4 mm in the lateral direction, and 0.5 mm in thickness.

[0062] For the chamfering, each side was chamfered by barrel polishing using a barrel polishing machine or the like. A magnetic tabletop barrel polishing machine was used for the barrel polishing. A stainless steel pin was used as the polishing stone, and liquid compound and pure water were added. The rotation speed and processing time for the 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 sampled and evaluated. 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 the magnetostrictive member subjected to barrel polishing in Example 2-1. The shape of the chamfered portion of the short side was R66.8 μm, and the chamfer width was within the range of 30 μm to 50 μm. In addition, the center of the magnetostrictive member was cut and the chamfered shape of that part was measured. It was R30 μm.

[0064] As can be seen from the results of Examples 2-2 and 2-3 shown in Table 1, the size of the chamfered shape and the chamfered width tend to increase as the rotation speed increases and the processing time increases.

[0065] As in Example 1, the maximum force coefficient (force coefficient) and the maximum optimum magnetic field strength (optimum magnetic field strength) were measured as magnetostriction characteristics and compared with the standard. As a result, in Example 2-1, the force coefficient and optimum magnetic field strength were within ±5% of the standard, and the change in magnetostriction characteristics was small and favorable. In Example 2-2, the force coefficient was within ±5%, but the optimum 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 optimum magnetic field strength was within -40% to -20% of the standard, showing a tendency to decrease.

[0066] [Example 3] In Example 3, a magnetostrictive member was manufactured using the same magnetostrictive member and barrel finishing machine as in Example 2. The barrel finishing conditions in Example 3 were a rotation speed of 350 rpm, and a processing time of 15 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 between 30 μm and 50 μm in Examples 3-1 and 3-2, but between 40 μm and 60 μm in Example 3-3, which was larger. In Example 3-4, the chamfer width was between 40 μm and 60 μm, which was larger.

[0067] As in Example 1, the maximum force coefficient (force coefficient) and the maximum optimum magnetic field strength (optimum magnetic field strength) were measured as magnetostriction characteristics and compared with the standard. As a result, in Examples 3-1 and 3-2, the force coefficient and optimum magnetic field strength were within ±5% of the standard, and there was little change in magnetostriction characteristics, which was good. In Examples 3-3 and 3-4, the force coefficient was within ±5% of the standard, but the optimum magnetic field strength was within -20% to 0% of the standard, showing a tendency for decline.

[0068] In Example 4, magnetostrictive members were prepared by processing and dividing an Fe—Ga alloy single crystal grown by the vertical Bridgman (VB) method in the same manner as in Example 1. The size of the divided magnetostrictive members was 8 mm in the longitudinal direction, 2 mm in the lateral direction, and 0.3 mm in thickness. The grit size of the grinding stone used for surface grinding was #400.

[0069] The barrel polishing machine was used in the same manner as in Example 2, with the rotation speed set to 350 rpm and the treatment time set to 15 minutes. Ten pieces were subjected to barrel polishing, and three pieces were sampled and evaluated. Table 1 shows the production conditions and results of Example 4.

[0070] As a result, the chamfer width was within 30 μm to 50 μm. The force coefficient and optimal magnetic field strength of the magnetostrictive properties were evaluated in the same manner as in Example 1. For comparison, the force coefficients of 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less when cut were compared to the standard, and the average values ​​of the optimal magnetic field strength at that time were used as the standard. The force coefficient and optimal magnetic field strength were within ±5% of the standard, and there was little change in the magnetostrictive properties, which was good. As a result, in Example 4, the force coefficient and optimal magnetic field strength were both within ±5% of the standard, and there was little change in the magnetostrictive properties, which was good.

[0071] Example 5 The same procedure as in Example 4 was carried out except that the grit size of the grinding stone used in surface grinding was #170. Table 1 shows the manufacturing conditions and results of Example 5.

[0072] The chamfer width was within the range of 30 μm to 50 μm. The magnetostriction properties were evaluated by the force coefficient and optimal magnetic field strength in the same manner as in Example 1. For comparison, the force coefficients of 10 magnetostrictive members that were not chamfered and had cutting burrs of 20 μm or less and the average values ​​of the optimal magnetic field strength at that time were compared as the standard. The force coefficients and optimal magnetic field strengths were within ±5% of the standard, and the magnetostriction properties showed little change and were good. Evaluation was performed in the same manner as in Example 1. As a result, in Example 5, the applied force coefficient and optimal magnetic field strength were both within ±5% of the standard, and the magnetostriction properties showed little change and were good. Evaluation was performed in the same manner as in Example 1.

[0073] [Example 6] The magnetostrictive member was the same as Example 1, except that it was sized to have a longitudinal dimension of 25 mm, a lateral dimension of 4 mm, and a thickness of 0.5 mm, and was subjected to C-chamfering with a chamfer width of 100 μm. Table 1 shows the manufacturing conditions and results of Example 6.

[0074] The chamfer width was within the range of 80 μm to 120 μm. The magnetostriction properties were evaluated by the force coefficient and optimal magnetic field strength in the same manner as in Example 1. For comparison, the force coefficients of 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less when cut were compared to the standard, and the average values ​​of the optimal magnetic field strength at that time were used as the standard. The force coefficients and optimal magnetic field strengths were within ±5% of the standard, and the magnetostriction properties showed little change and were good. Evaluation was performed in the same manner as in Example 1. As a result, in Example 6, the execution force coefficient and optimal magnetic field strength were both within ±5% of the standard, and the magnetostriction properties showed little change and were good.

[0075] Example 7 The magnetostrictive member was the same as Example 1, except that it was sized to have a longitudinal dimension of 25 mm, a lateral dimension of 4 mm, and a thickness of 0.5 mm, and was subjected to C-chamfering with a chamfer width of 200 μm. Table 1 shows the manufacturing conditions and results of Example 7.

[0076] The chamfer width was between 180 μm and 230 μm. The magnetostriction characteristics were evaluated by force coefficient and optimum magnetic field strength in the same manner as in Example 1. For comparison, the force coefficients of 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less when cut were compared to the standard, and the average values ​​of the optimum magnetic field strength at that time. As a result, in Example 7, the optimum magnetic field strength was within ±5%, but the force coefficient was within -10% to +5% of the standard, showing a slight tendency for it to decrease.

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

[0078] [Comparative Example 1] A magnetostrictive member similar to that of Example 4 was prepared. No chamfering was performed. Observation of the prepared, non-chamfered magnetostrictive member with burrs of 10 μm to 50 μm was found to have such burrs. Magnetostrictive properties were evaluated by the force coefficient and optimal magnetic field strength in the same manner as in Example 1. For comparison, the force coefficients of 10 magnetostrictive members that were not chamfered and had burrs of 20 μm or less when cut were compared with the average values ​​of the optimal magnetic field strength at that time. A decrease in the force coefficient was observed, ranging from -40% to +5%. The optimal magnetic field strength also varied widely, being unstable, ranging from -10 to +200%.

[0079]

[0080] [Summary] The magnetostrictive members of Examples 1 to 7 had significantly more stable force coefficients and optimal magnetic field strengths than 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. The results of Examples 1 to 7 and Comparative Example 1 confirm that the magnetostrictive member of this embodiment suppresses fluctuations in magnetostrictive properties caused by burrs generated during cutting. As shown in the examples, fluctuations in magnetostrictive properties can be suppressed, and when compared to a reference value, the force coefficient can be within ±5%, -10% to 0%, -10% to +5%, and preferably within ±5%. Furthermore, the optimal magnetic field strength can vary within ±5%, -20% to 0%, or -40% to -20%, and preferably within ±5%. Furthermore, the force coefficient and optimal magnetic field strength can be within the scope of the present invention, and can be a range between two values ​​selected from the group consisting of any of the above values, ranges, any of the upper limit values, any of the lower limit values, and any of the values ​​(ranges) described in the examples, and one value selected from this group can be the lower limit value, and one value selected from this group can be the upper limit value.

[0081] 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. Furthermore, the requirements described in the above-mentioned embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of Japanese Patent Application No. 2024-153100 and all documents cited in the above-mentioned embodiments are incorporated by reference into this specification.

[0082] 1: Magnetostrictive member 2: Groove 3: Surface 4: Back surface 5: Side (side portion) 6: Chamfered surface (chamfered portion) D1: Longitudinal direction D2: Shortitudinal direction

Claims

1. A magnetostrictive member that is a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties, has a longitudinal direction and a lateral direction, and at least some of the sides of the plate-like body are chamfered surfaces.

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

3. The magnetostrictive member according to claim 1, wherein the chamfered surface is a curved surface, and 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, comprising the steps of: preparing a magnetostrictive member cut into individual pieces; and chamfering the prepared magnetostrictive member.

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

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