Magnetostrictive element for power generation and magnetostrictive power generation device

Abstract

To provide a magnetostriction power generation device which reduces cost, improves durability and is capable of achieving a power generation amount equal to or more than those of conventional magnetostriction power generation devices.SOLUTION: A magnetostriction element for power generation is formed from a laminate including at least one electromagnetic steel sheet layer including at least one electromagnetic steel sheet and satisfies at least one of a condition A and a condition B, wherein the condition A: the at least one electromagnetic steel sheet layer includes two or more electromagnetic steel sheets and the two or more electromagnetic steel sheets are bonded with each other via a brazing material part, and the condition B: the laminate further includes at least one elastic material layer and the at least one electromagnetic steel sheet layer is bonded to the elastic material layer via a brazing material part.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a magnetostrictive element for power generation and a magnetostrictive power generation device. [Background technology]

[0002] In the use of the Internet of Things (IoT), which has been developing in recent years, wireless sensor modules that integrate sensors, power sources, wireless communication devices, etc. are used to connect things to the Internet. There is a demand for the development of power generation devices that can generate electricity from energy generated in the environment where the device is installed, as a power source for such wireless sensor modules, without the need for regular manual maintenance such as battery replacement or charging.

[0003] One example of such a power generator is a magnetostrictive vibration power generator that uses inverse magnetostriction, which is the opposite effect of magnetostriction. Inverse magnetostriction is a phenomenon in which the magnetization of a magnetostrictive material changes when strain is applied to the material due to vibration or other causes. Magnetostrictive vibration power generators apply strain to the magnetostrictive material through vibration, and the change in magnetization caused by the inverse magnetostrictive effect generates an electromotive force in a coil wound around the magnetostrictive element according to the law of electromagnetic induction.

[0004] Conventionally, attempts have been made to increase the magnetostriction of magnetostrictive materials in order to improve their power generation performance. This is because the larger the magnetostriction, the larger the change in magnetic flux density (ΔB) due to inverse magnetostriction when the magnetostrictive material is subjected to alternating tensile and compressive strains, and the larger the power generation output. From this perspective, FeGa alloys, FeCo alloys, FeAl alloys, etc. have been developed as materials with large magnetostriction, and power generation devices using these magnetostrictive materials have also been developed (Patent Documents 1 to 6).

[0005] For example, in the power generation device described in Patent Document 1, a magnetostrictive material and a soft magnetic material are bonded together to improve power generation performance and reduce quality variations, and the magnetization of the soft magnetic material is changed by the magnetization of the magnetostrictive material. In this way, in addition to the voltage caused by the change in magnetization of the magnetostrictive material, a voltage caused by the change in magnetization of the soft magnetic material is also induced in the detection coil. Examples of magnetostrictive materials used include FeCo, FeAl, Ni, NiFe, and NiCo, while examples of soft magnetic materials include Fe, FeNi, FeSi, and electromagnetic stainless steel. Furthermore, methods for bonding the magnetostrictive material and the soft magnetic material include thermal diffusion bonding, hot rolling, hot drawing, adhesive bonding, welding, clad rolling, and explosive bonding.

[0006] Patent Document 2 discloses a power generation device that uses a parallel beam structure combining a magnetostrictive material and a magnetic material to increase electromotive force, reduce manufacturing costs, and improve mass productivity. The actuator is designed to use the magnetic material in a state of magnetic saturation due to a bias magnetic field. In this actuator, the back yoke is U-shaped, the neutral plane is located outside the magnetostrictive material, and the electromotive force is increased by superimposing changes in the bias magnetic field caused by vibration on changes in the magnetization of the magnetostrictive material. Examples of magnetostrictive materials listed include FeGa, FeCo, FeAl, FeSiB, and amorphous materials. Examples of magnetic materials listed include SPCC, carbon steel (SS400, SC, SK, SK2), and ferritic stainless steel (SUS430). Patent Document 2 also describes fixing the ends of the magnetostrictive material and magnetic material together using soldering, welding, brazing, resistance welding, laser welding, ultrasonic bonding, adhesives, etc., when fabricating the parallel beam structure.

[0007] Patent Document 3 discloses a power generating element in which a magnetostrictive material is bonded to a non-magnetic material as a reinforcing material to improve power generation efficiency and distribute stress uniformly, and the cross-sectional area ratio of the magnetostrictive material to the reinforcing material is specified to be reinforcing material / magnetostrictive material > 0.8. Examples of magnetostrictive materials described include FeGa, FeCo, and FeNi, and examples of reinforcing materials include filler-containing resin, Al, Mg, Zn, and Cu. Furthermore, methods of bonding the magnetostrictive material and the non-magnetic material include ultrasonic bonding, solid-phase diffusion bonding, liquid-phase diffusion bonding, bonding with a resin-based adhesive, and bonding with a metal brazing material.

[0008] The power generation device of Patent Document 4 employs a structure that allows for a larger number of coil turns in order to improve power generation output. Specifically, a structure is fabricated in which a magnetostrictive plate and a non-magnetic structure are surface-bonded, and a magnetic field is returned from the magnetostrictive plate to a U-shaped yoke around which a coil is wound. FeGa and FeCo are described as magnetostrictive plates, and stainless steel (SUS304, etc.) is described as the non-magnetic structure. Furthermore, bonding using an adhesive or an adhesive sheet (photocurable resin, thermosetting resin) is described as a method for surface-bonding the magnetostrictive plate and the non-magnetic structure.

[0009] In the power generation device of Patent Document 5, a structure is fabricated by bonding a magnetostrictive material and a non-magnetic material (reinforcement material) together to improve power generation efficiency and to apply a uniform stress load, and this structure is used as two parallel beams. Examples of magnetostrictive materials described include FeGa, FeCo, FeCo-based amorphous, Fe-based amorphous, Ni-based amorphous, metamagnetic shape memory alloy, and ferromagnetic shape memory alloy. Examples of non-magnetic materials described include silicon oxide, alumina, polyimide, polycarbonate, fiber-reinforced plastic, and non-magnetic metals (Al, Cu). However, there is no description of a method for bonding the magnetostrictive material and the non-magnetic material together.

[0010] The power generation device of Patent Document 6 uses a parallel beam structure in which the magnetostrictive material and the magnetic material are separated to improve power generation output. This structure allows the magnetic material to be used without magnetic saturation, and the magnetic flux of the magnetic material is changed by changing the magnetic flux of the magnetostrictive material, allowing a voltage to be extracted that is the sum of the induced voltage by the magnetostrictive material and the induced voltage by the magnetic material. Examples of magnetostrictive materials listed include FeGa, FeCo, FeNi, and FeDyTe, and examples of magnetic materials listed include ferritic stainless steel, FeSi, NiFe, CoFe, SmCo, NdFeB, CoCr, and CoPt. Patent Document 6 also discloses bonding the magnetostrictive material to a soft magnetic material or a non-magnetic material, but the bonding is performed using a resin adhesive. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2018 / 230154 [Patent Document 2] Japanese Patent Application Publication No. 2018-148791 [Patent Document 3] International Publication No. 2014 / 021197 [Patent Document 4] International Publication No. 2013 / 038682 [Patent Document 5] International Publication No. 2013 / 186876 [Patent Document 6] Japanese Patent Application Laid-Open No. 2015-70741 Summary of the Invention [Problem to be solved by the invention]

[0012] As is clear from the descriptions in Patent Documents 1 to 6, various magnetostrictive materials are used together with other materials in magnetostrictive power generation elements and magnetostrictive power generation devices. Patent Documents 2 to 6 describe FeGa alloys, which are known to have the greatest magnetostriction. However, FeGa alloys are very expensive because they are manufactured by a single crystal pulling method (CZ method). The FeCo alloys described in Patent Documents 1 to 6 are manufactured by a rolling method, but they are also expensive because they contain Co. Furthermore, the FeAl alloys described in Patent Documents 1 and 2 are less expensive than FeGa alloys and FeCo alloys, but are still expensive. Furthermore, they have low toughness, making them difficult to manufacture into plate shapes by ordinary rolling methods.

[0013] As described above, the conventionally used magnetostrictive materials, FeGa alloy, FeCo alloy, and FeAl alloy, <100> Because the magnetostriction in the direction, λ100, is large at 80 ppm or more, it has been described in many patent documents as a magnetostrictive material for use in magnetostrictive elements for power generation. However, these magnetostrictive materials have problems such as high manufacturing costs and limitations in molding.

[0014] In consideration of these problems, when manufacturing a magnetostrictive power generation device using the above-mentioned high-cost magnetostrictive material, a magnetostrictive element for power generation is manufactured, which is composed of the magnetostrictive material and a mating material to be bonded thereto, and a structure is adopted in which the magnetostrictive element for power generation is fixed to a frame or the like made of a lower-cost material. Patent Documents 1 and 6 describe FeSi alloys (electromagnetic steel sheets) as soft magnetic materials, but in both cases they are used as a mating material to be bonded to the magnetostrictive material, not as the magnetostrictive material itself. This use of FeSi alloys is a common method of using FeSi alloys in conventional magnetic circuits.

[0015] Although ultrasonic bonding, solid-phase diffusion bonding, liquid-phase diffusion bonding, and bonding using a resin-based adhesive or adhesive sheet have been disclosed as bonding methods for bonding magnetostrictive materials to other materials, the main bonding method has been bonding using a resin-based adhesive or adhesive sheet, which has the problem of difficulty in maintaining bonding strength and reduced durability.

[0016] Furthermore, Patent Documents 2 and 3 also describe joining using a brazing material as a joining method, but do not include any working examples in which a brazing material is used. [Means for solving the problem]

[0017] In view of the above problems, a first aspect of the present invention is the following magnetostrictive element for power generation. [1] A magnetostrictive element for power generation formed of a laminate including at least one electromagnetic steel sheet layer, wherein the electromagnetic steel sheet layer includes at least one electromagnetic steel sheet, and the laminate satisfies at least one of the following conditions A and B: Condition A: The at least one electromagnetic steel sheet layer includes two or more electromagnetic steel sheets, and the two or more electromagnetic steel sheets are joined to each other via a brazing material portion; and Condition B: The laminate further includes at least one elastic material layer, and the at least one electromagnetic steel sheet layer is joined to the elastic material layer via a brazing material portion. [2] The magnetostrictive element for power generation according to [1], wherein the laminate satisfies only the condition A. [3] The magnetostrictive element for power generation according to [2], wherein the laminate further includes at least one elastic material layer, and the elastic material layer is bonded to the electromagnetic steel sheet layer. [4] The magnetostrictive element for power generation according to [1], wherein the laminate satisfies the conditions A and B. [5] The magnetostrictive element for power generation according to [1], wherein the at least one electromagnetic steel sheet layer is made of one electromagnetic steel sheet, and the laminate satisfies only the condition B. [6] The magnetostrictive element for power generation according to any one of [1] to [5], wherein at least one of the electromagnetic steel sheets included in the electromagnetic steel sheet layer is a grain-oriented electromagnetic steel sheet. [7] The magnetostrictive element for power generation according to any one of [1] to [5], wherein at least one of the electromagnetic steel sheets included in the electromagnetic steel sheet layer is a non-oriented electromagnetic steel sheet. [8] The magnetostrictive element for power generation according to any one of [1] to [7], wherein the elastic material layer is made of a non-magnetic material. [9] A magnetostrictive element for power generation according to any one of [1] to [8], wherein the brazing material portion contains Ni as a main element and at least one element selected from the group consisting of Cr, Si, Fe, B, P, C, Cu, and Mo, and further contains at least one oxide selected from the group consisting of Mg oxide, Cr oxide, and Si oxide.

[10] A magnetostrictive element for power generation described in [9], wherein at least one of the contact surfaces between the electromagnetic steel sheet and the brazing material portion present in the magnetostrictive element for power generation has a region in which Fe derived from the electromagnetic steel sheet and Ni derived from the brazing material portion are alloyed, and in an elemental analysis of a cross section in the thickness direction of the magnetostrictive element for power generation, the alloyed region is present over a width of 2 μm or more.

[11] A magnetostrictive element for power generation according to any one of [1] to [8], wherein the brazing material portion contains Fe as a main element, at least one element selected from the group consisting of Cr, Ni, Si, B, P, C, Cu, and Mo, and further contains at least one oxide selected from the group consisting of Mg oxide, Cr oxide, and Si oxide.

[12] The magnetostrictive element for power generation according to any one of [9] to

[11] , wherein the at least one oxide in the brazing material portion is in the form of a block.

[0018] A second aspect of the present invention is the following magnetostrictive power generating device.

[13] A magnetostrictive power generation device comprising the magnetostrictive element for power generation according to any one of [1] to

[12] and a frame coupled to the magnetostrictive element for power generation.

[14] A magnetostrictive power generation device according to

[13] , wherein the magnetostrictive element for power generation and the frame are continuous, and at least a portion of the frame is composed of a laminate that forms the magnetostrictive element for power generation.

[15] The magnetostrictive power generation device according to

[14] , wherein the entire frame is integral with an electromagnetic steel plate extending from a laminate that forms the magnetostrictive element for power generation.

[16] A magnetostrictive power generation device according to

[14] , wherein the laminate contains an elastic material, and the entire frame is integrally formed with the elastic material extending from the laminate that forms the magnetostrictive element for power generation.

[17] The magnetostrictive power generation device according to

[14] , wherein the entire frame is integral with the magnetostrictive element for power generation. [Effects of the Invention]

[0019] According to the present invention, a magnetostrictive element for power generation and a magnetostrictive power generation device are provided which are lower in cost than FeGa alloys, FeCo alloys, and FeAl alloys used as magnetostrictive materials for magnetostrictive elements for power generation, yet can achieve magnetostrictive power generation amounts equal to or exceeding those of conventional technology, while also achieving high durability. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows a displacement-load curve of a laminate including magnetic steel sheets and elastic material. [Figure 2] FIG. 2 is a schematic diagram of an apparatus for testing the durability of a magnetostrictive element. [Figure 3] 1 is a schematic diagram of a unit for applying bending strain to a magnetostrictive element of the present invention and measuring a change in magnetic flux density ΔB. [Figure 4] 1 shows the results of observing the cross-sectional structure of the magnetostrictive element of the present invention using SEM-EDS. [Figure 5] 10 shows the results of SEM-EDS observation of the cross-sectional structure of another magnetostrictive element of the present invention. [Figure 6] 1 is a schematic diagram showing the structure of a magnetostrictive generating device of the present invention. [Figure 7] FIG. 2 is another schematic diagram showing the structure of the magnetostrictive generating device of the present invention. [Figure 8] FIG. 10 is still another schematic diagram showing the structure of the magnetostrictive generating device of the present invention. [Figure 9]13 shows the results of elemental analysis of the cross-sectional structure of the magnetostrictive element of Example 14. DETAILED DESCRIPTION OF THE INVENTION

[0021] As described above, in conventional magnetostrictive power generation devices, a magnetostrictive element for power generation is manufactured using a laminate in which a magnetostrictive material is bonded to another material, and the magnetostrictive element for power generation is then fixed to a frame or the like made of a lower-cost material. Resin-based adhesives have primarily been used to bond magnetostrictive materials to other materials. However, resins have a low Young's modulus, and even epoxy-based adhesives with a relatively high Young's modulus are only about 2000 MPa (2 GPa), which is several tenths of that of metals. Therefore, the inventors have discovered that when magnetic steel sheets are bonded with an adhesive in a laminate containing magnetic steel sheets as the magnetostrictive material, the resin layer, which is made of the adhesive between the layers, has a low Young's modulus. Therefore, when bending strain due to vibration is applied to the laminate, the resin layer relieves the strain, reducing the strain applied to the entire laminate. Furthermore, this reduction in strain leads to a reduction in the amount of power generated by the magnetostrictive element for power generation.

[0022] Furthermore, when a magnetostrictive power generation device equipped with a magnetostrictive element for power generation including the above-mentioned laminate is operated, i.e., when the magnetostrictive element is vibrated, the strength of the joint made of adhesive is low, so delamination can cause a problem of reduced durability of the magnetostrictive power generation device.

[0023] Although the use of brazing filler metals in metal-to-metal joining methods is known, brazing filler metals have not been used in the past when laminating electrical steel sheets. This is because commercially available electrical steel sheets are provided with oxide-based coatings as insulating coatings or tensile coatings to reduce iron loss, and there is a concern that joining using brazing filler metals may damage these coatings. Therefore, when laminating electrical steel sheets for use as transformer cores or motor core materials, the electrical steel sheets have been joined by mechanical crimping or resin bonding.

[0024] In light of this situation, the inventors have discovered that if an electromagnetic steel sheet is used as the magnetostrictive material and multiple electromagnetic steel sheets, or an electromagnetic steel sheet and another material (e.g., an elastic material) are joined together to form a laminate using a brazing material, the aforementioned problems of reduced power generation due to reduced distortion and durability can be resolved. Because metal brazing material has a higher Young's modulus than adhesives, if the electromagnetic steel sheets in the laminate included in the magnetostrictive element for power generation are joined together using a brazing material, relaxation of strain between the laminated layers can be suppressed when bending strain due to vibration is applied to the magnetostrictive element for power generation. Therefore, a decrease in the power generation capacity of the magnetostrictive element for power generation can be suppressed.

[0025] Furthermore, brazing filler metals have higher bonding strength than resin-based adhesives and are less susceptible to environmental factors such as ultraviolet light and humidity, making it possible to improve the durability of magnetostrictive power generation devices.

[0026] The present invention will be described below with reference to exemplary embodiments, but the present invention is not limited to the following embodiments.

[0027] 1. Magnetostrictive elements for power generation The present invention relates to a magnetostrictive element for power generation formed of a laminate including at least one electromagnetic steel sheet layer, wherein the electromagnetic steel sheet layer includes at least one electromagnetic steel sheet, and the laminate satisfies at least one of the following conditions A and B: Condition A: At least one electromagnetic steel sheet layer includes two or more electromagnetic steel sheets, and the two or more electromagnetic steel sheets are joined to each other via a brazing material portion; and Condition B: The laminate further includes at least one elastic material layer, and at least one magnetic steel sheet layer is joined to the elastic material layer via a brazing material portion.

[0028] In the present invention, a "magnetostrictive element for power generation" (hereinafter often abbreviated as "magnetostrictive element") means an element that has a magnetostrictive part formed from a magnetic material that exhibits magnetostrictive properties, i.e., a change in shape (i.e., distortion) when a magnetic field is applied, and is capable of generating power based on the inverse magnetostriction of the magnetostrictive part.

[0029] The laminate forming the magnetostrictive element for power generation of the present invention includes at least one electromagnetic steel sheet layer, and the electromagnetic steel sheet layer includes at least one electromagnetic steel sheet as the magnetostrictive material. In the present invention, "electromagnetic steel sheet" refers to a functional material, sometimes called a "silicon steel sheet," in which silicon (Si) is added to iron (Fe) to improve the magnetic properties of iron. The electromagnetic steel sheet in the present invention is an electromagnetic steel sheet with a silicon content of 0.5% to 4%. Electromagnetic steel sheets with a silicon content of 0.5% to 4% are suitable for use in magnetostrictive parts because the increased electrical resistance due to the addition of silicon can suppress the generation of eddy currents that interfere with magnetization changes during AC vibration.

[0030] The electrical steel sheet in the present invention may or may not be provided with an oxide-based coating. As will be described later, an oxide-based coating is preferably provided as the electrical steel sheet, since this forms a stronger metal bond between the electrical steel sheet and the brazing filler metal. The oxide-based coating may be an insulating coating or a tension coating that is provided on commercially available electrical steel sheets for the purpose of reducing iron loss.

[0031] Furthermore, at least one of the electromagnetic steel sheets included in the electromagnetic steel sheet layer may be either a grain-oriented electromagnetic steel sheet or a non-oriented electromagnetic steel sheet. The electromagnetic steel sheet layer may be composed of only one of grain-oriented electromagnetic steel sheets and non-oriented electromagnetic steel sheets, or may include both. A grain-oriented electromagnetic steel sheet is one in which the crystal orientation of the metal crystals is aligned in the rolling direction of the steel sheet. Specifically, <001> The direction was aligned, and the rolling surface was oriented in the {110} direction. <001> It is an electrical steel sheet with a GOSS texture. On the other hand, non-oriented electrical steel sheet has a relatively random crystal orientation, where the crystal orientation of the metal crystals is not aligned in a specific direction. Both oriented and non-oriented electrical steel sheets have a lower saturation magnetostriction than FeGa alloys and FeCo alloys, but are capable of generating electricity equivalent to or exceeding that of conventional magnetostrictive materials. The reason for this is not clear, but it is presumed as follows.

[0032] As mentioned above, grain-oriented electrical steel sheets have a <001> The direction was aligned, and the rolling surface was oriented in the {110} direction. <001> It has a GOSS texture. <001> When compressive strain is applied with a bias magnetic field applied in the direction, the magnetic flux density of the grain-oriented electrical steel sheet changes significantly. <001> When a magnetic field is applied in a specific direction, <001> It is thought that the ratio of 180° magnetic domains and 90° magnetic domains parallel to the direction is the ratio at which the two interact well, and when strain is applied to grain-oriented electrical steel sheet, the 180° magnetic domains tend to convert to 90° magnetic domains, or vice versa. Specifically, when the 180° magnetic domains are parallel to the magnetization direction (i.e., <001> When compressive strain is applied in the direction of the magnetic field, the 180° magnetic domains decrease and the 90° magnetic domains increase. <001> When tensile strain is applied in the direction, the 90° domains decrease and the 180° domains increase. <110> When compressive strain is applied in the direction of the magnetic field, the 90° magnetic domains decrease and the 180° magnetic domains increase. <110> When tensile strain is applied in the direction, the 180° magnetic domains decrease and the 90° magnetic domains increase. These changes in magnetic domains change the magnetization of the grain-oriented electrical steel sheet, causing it to function as a magnetostrictive element. In a magnetostrictive power generation device, this change in magnetization induces a voltage in the detection coil wound around the magnetostrictive element.

[0033] Furthermore, while non-oriented electrical steel sheets do not have the same crystal orientation as oriented electrical steel sheets, when strain is applied while a bias magnetic field is applied, the magnetic flux density changes significantly. Because the crystal orientation of non-oriented electrical steel sheets is relatively random, the magnetic domains are smaller than those of oriented electrical steel sheets. Therefore, when strain is applied, the magnetic domains that are easiest to move among the many magnetic domains are the ones that move first, which is thought to result in a large change in magnetic flux density when used as a magnetostrictive element.

[0034] In the present invention, grain-oriented electrical steel sheets are more likely to induce a larger change in magnetization than non-oriented electrical steel sheets, and therefore grain-oriented electrical steel sheets are preferred as the electrical steel sheets contained in the magnetostrictive element.

[0035] Specific examples of grain-oriented electrical steel sheets include Nippon Steel Corporation's Orient Core, Orient Core Hi-B (for example, 27ZH100), Orient Core Hi-B Laser, and Orient Core Hi-B Permanent.

[0036] Specific examples of non-oriented electrical steel sheets include Highlight Core (for example, 35H210) and Home Core manufactured by Nippon Steel Corporation.

[0037] There is no particular limit to the number of electromagnetic steel sheets contained in the electromagnetic steel sheet layer, and it may be one sheet or two or more sheets, but the number of electromagnetic steel sheets is preferably one to 100 sheets, and more preferably two to 20 sheets. Since the generated voltage is proportional to the cross-sectional area of ​​the magnetostrictive element, it is possible to increase the generated voltage by stacking multiple electromagnetic steel sheets to increase the cross-sectional area. Furthermore, vibration generates AC magnetization in the electromagnetic steel sheets according to the vibration frequency, and when AC magnetization occurs in electromagnetic steel sheets, which are magnetic bodies, eddy currents that interfere with the magnetization are generated. In this case, eddy currents are less likely to occur when the electromagnetic steel sheets are thin than when they are thick, so using thin electromagnetic steel sheets is advantageous in terms of the amount of power generated.

[0038] Since the dimensions of the magnetostrictive element for power generation vary depending on the dimensions of the magnetostrictive power generation device in which it is incorporated, there are no particular limitations on the dimensions of the electromagnetic steel sheet layer that forms the magnetostrictive portion in the magnetostrictive element for power generation of the present invention. The larger the dimensions of the electromagnetic steel sheet layer, the more coil turns can be made in the power generation device, allowing for a higher voltage to be obtained, making it preferable. There are also no particular limitations on the thickness of the electromagnetic steel sheet layer that forms the magnetostrictive portion, but it is typically between 0.2 mm and 10 mm. A magnetostrictive portion thickness of 0.2 mm or more is advantageous because it allows for a larger change in magnetic flux and therefore a larger generated voltage, while a thickness of 10 mm or less is advantageous because it facilitates the design of rigidity suitable for vibration.

[0039] When an electromagnetic steel sheet layer includes two or more electromagnetic steel sheets, the electromagnetic steel sheets are joined to each other via a brazing filler metal portion, which is a joint formed with a brazing filler metal, and the details of which will be described later in relation to the layer structure of the laminate.

[0040] The laminate forming the magnetostrictive element for power generation of the present invention may further include at least one elastic material layer. In the magnetostrictive element of the present invention, the elastic material layer functions as a stress control section. The "stress control section" in the magnetostrictive element of the present invention is a section for controlling stress in order to achieve either a compressive or tensile stress load on the entire magnetostrictive section when bending strain or the like is applied to the magnetostrictive element. The material forming the stress control section is not particularly limited as long as it is an elastic material that can achieve the above purpose, and both non-magnetic and magnetic materials can be used.

[0041] Using a nonmagnetic material for the elastic material that functions as the stress control section is preferable because the magnetic field flows preferentially only through the magnetostrictive portion of the magnetostrictive element, making it easier to adjust the bias magnetic field of the magnetostrictive portion. Furthermore, when a magnetostrictive portion is formed of a grain-oriented electromagnetic steel sheet and a stress control section is formed of a nonmagnetic material, a larger change in magnetic flux density occurs compared to other combinations when bending strain is applied to a magnetostrictive element. This is thought to be because, when a magnetic material is used as the elastic material, magnetic interaction occurs between the elastic material and the electromagnetic steel sheet, which can hinder the conversion between 90° and 180° magnetic domains. However, when the elastic material is a nonmagnetic material, such magnetic interaction does not occur, making it easier for the electromagnetic steel sheet to convert between 90° and 180° magnetic domains.

[0042] Examples of non-magnetic elastic materials include, but are not limited to, fiber-reinforced plastics (e.g., glass fiber-reinforced plastic (GFRP), carbon fiber-reinforced plastic (CFRP)), austenitic stainless steel (e.g., SUS304, SUS316, etc.), copper alloys (e.g., brass, phosphor bronze), aluminum alloys (e.g., duralumin), and titanium alloys (e.g., Ti-6Al-4V). Among these, fiber-reinforced plastics and austenitic stainless steel are preferred because they have a relatively high Young's modulus and it is easy to position the neutral plane outside the magnetostrictive portion when a bending strain is applied.

[0043] Using a magnetic material as the elastic material is effective in reducing costs. When the magnetostrictive portion of a magnetostrictive element is made of a grain-oriented or non-oriented electromagnetic steel sheet and the elastic material functioning as the stress control portion is made of a magnetic steel sheet, applying a bias magnetic field causes the bias magnetic field to flow through both the magnetostrictive portion and the stress control portion. However, because the grain-oriented or non-oriented electromagnetic steel sheet forming the magnetostrictive portion is a high-permeability material, a large bias magnetic field flows through the magnetostrictive portion, which is thought to result in sufficient magnetic domain change for power generation. However, compared to when the stress control portion is made of a non-magnetic material, the magnetic force applied to the magnetostrictive portion is reduced by the amount of magnetic flux flowing through the stress control portion made of a magnetic material. To compensate for this reduction in magnetic force, the strength of the magnets included in the magnetostrictive power generation device can be increased.

[0044] Examples of elastic materials that are magnetic materials include, but are not limited to, general structural rolled steel (e.g., SS400), general structural carbon steel (e.g., S45C), high-tensile steel (e.g., HT80), ferritic stainless steel (e.g., SUS430), and martensitic stainless steel (e.g., SUS410).

[0045] The number of elastic materials contained in the elastic material layer is not particularly limited, and may be one or more. When multiple elastic materials are contained, they may include multiple sheets of the same elastic material or several different elastic materials, but the elastic materials are bonded to each other. There are no particular limitations on the method for bonding the elastic materials in the elastic material layer, but typical examples include lamination using an adhesive or adhesive sheet, brazing bonding, liquid phase diffusion bonding, etc.

[0046] There are no particular limitations on the dimensions of the elastic material layer that functions as a stress control section, but from the viewpoint of achieving either a compressive or tensile stress load on the entire electromagnetic steel sheet layer that forms the magnetostrictive section, it is desirable that the elastic material layer be the same as or larger than the electromagnetic steel sheet layer. There are also no particular limitations on the thickness of the elastic material layer that functions as a stress control section, but it is usually 0.02 mm to 50 mm, preferably 0.1 mm to 10 mm, and more preferably 0.2 mm to 5 mm. If the thickness of the elastic material layer is 0.02 mm or more, it is advantageous for achieving either a compressive or tensile stress load on the entire magnetostrictive section, and if it is 50 mm or less, interference with the vibration of the magnetostrictive element can be suppressed.

[0047] As described above, the laminate forming the magnetostrictive element for power generation of the present invention has an electromagnetic steel sheet layer containing at least one electromagnetic steel sheet, and optionally also has at least one elastic material layer. There is no limit to the number of electromagnetic steel sheet layers and elastic material layers, and examples include a laminate consisting only of electromagnetic steel sheet layers, a laminate having one electromagnetic steel sheet layer and one elastic material layer, a laminate having multiple electromagnetic steel sheet layers and one elastic material layer, and a laminate having multiple electromagnetic steel sheet layers and multiple elastic material layers. Various layer configurations are possible for the laminate forming the magnetostrictive element for power generation of the present invention, but in any case, at least one of the following conditions A and B must be satisfied. Condition A: At least one electromagnetic steel sheet layer includes two or more electromagnetic steel sheets, and the two or more electromagnetic steel sheets are joined to each other via a brazing material portion; and Condition B: The laminate further includes at least one elastic material layer, and at least one magnetic steel sheet layer is joined to the elastic material layer via a brazing material portion.

[0048] The brazing filler metal portions present between the electromagnetic steel sheets and / or between the electromagnetic steel sheet layer and the elastic material layer are joints formed by a metallic brazing filler metal that can be joined to the electromagnetic steel sheets.

[0049] When two or more electromagnetic steel sheets are included in the electromagnetic steel sheet layer of the laminate forming the magnetostrictive element for power generation of the present invention, the laminate satisfies condition A. Specifically, the multiple electromagnetic steel sheets included in the electromagnetic steel sheet layer are joined to each other via brazing material. When multiple electromagnetic steel sheets are joined to each other via brazing material, when bending strain due to vibration is applied to the laminate during operation of the magnetostrictive power generation device, the brazing material (the joint made of brazing material between the electromagnetic steel sheets) can suppress the reduction of strain applied to the entire laminate. Furthermore, suppressing this reduction in strain can suppress the reduction in the amount of power generated by the magnetostrictive element for power generation.

[0050] Furthermore, the brazing material that constitutes the brazing material portion has higher bonding strength than resin-based adhesives and is less susceptible to environmental factors such as ultraviolet light and humidity, making it possible to improve the durability of the magnetostrictive element.

[0051] When the laminate forming the magnetostrictive element for power generation of the present invention satisfies the above-mentioned condition A and includes an elastic material layer, there are no particular limitations on the method for joining the electromagnetic steel sheet layer and the elastic material layer. The elastic material layer may be joined by a common joining method, such as lamination with an adhesive or adhesive sheet interposed therebetween, or liquid phase diffusion bonding, or may be joined via a brazing filler metal. However, when the electromagnetic steel sheet layer of the laminate of the present invention does not satisfy condition A, for example, when it is made of a single electromagnetic steel sheet, the laminate necessarily satisfies condition B. That is, the electromagnetic steel sheet layer and the elastic material layer are joined via a brazing filler metal. Joining the electromagnetic steel sheet via a brazing filler metal suppresses the reduction in strain applied to the entire laminate, suppressing the reduction in power generation and further enabling the durability of the magnetostrictive power generation device to be improved.

[0052] Furthermore, the laminate forming the magnetostrictive element for power generation of the present invention may simultaneously satisfy condition A and condition B. From the viewpoint of the strength of the laminate and the durability of the device, it is preferable that all layers included in the laminate are joined via brazing material parts.

[0053] Examples of the laminate structure of the laminate that satisfies at least one of the above conditions A and B include, but are not limited to, the following structures (1) to (8). In the structures below, the portions shown as "adhesive portions" for convenience can be changed to joints formed by other joining means than adhesive and brazing material. (1) Electromagnetic steel sheet / brazing material / electromagnetic steel sheet (2) Electromagnetic steel sheet / brazing material / elastic material (3) Electromagnetic steel sheet / brazing material / electromagnetic steel sheet / adhesive / elastic material (4) Electromagnetic steel sheet / brazing material / electromagnetic steel sheet / brazing material / elastic material (5) Electromagnetic steel sheet / brazing material / electromagnetic steel sheet / brazing material / electromagnetic steel sheet / brazing material / elastic material (6) Electromagnetic steel sheet / brazing material / elastic material / brazing material / electromagnetic steel sheet (7) Electromagnetic steel sheet / brazing material / electromagnetic steel sheet / adhesive material / elastic material / adhesive material / electromagnetic steel sheet / brazing material / electromagnetic steel sheet (8) Electromagnetic steel sheet / brazing material part / electromagnetic steel sheet / brazing material part / elastic material / brazing material part / electromagnetic steel sheet / brazing material part / electromagnetic steel sheet

[0054] The laminate of structure (1) has an electromagnetic steel sheet layer including two or more electromagnetic steel sheets and satisfies only condition A. The laminate of structure (2) has an electromagnetic steel sheet layer made of one electromagnetic steel sheet, has an elastic material layer, and satisfies only condition B. The laminate of structure (3) has an electromagnetic steel sheet layer including two or more electromagnetic steel sheets, has an elastic material layer, and satisfies only condition A. The laminates of structures (4) and (5) have an electromagnetic steel sheet layer containing two or more electromagnetic steel sheets, have an elastic material layer, and satisfy conditions A and B. The laminate of structure (6) has a plurality of electromagnetic steel sheet layers each made of a single electromagnetic steel sheet, has an elastic material layer, and satisfies only condition B. The laminate of structure (7) has a plurality of electromagnetic steel sheet layers each including two or more electromagnetic steel sheets, has an elastic material layer, and satisfies only condition A. The laminate of the structure (8) has a plurality of electromagnetic steel plate layers each including two or more electromagnetic steel plates, has an elastic material layer, and satisfies the conditions A and B.

[0055] In a laminate satisfying the above condition A and / or condition B, the brazing filler metal constituting the brazing filler metal portion present between two or more electromagnetic steel sheets or between an electromagnetic steel sheet layer and an elastic material layer is not particularly limited as long as it can form a metallic bond with the electromagnetic steel sheets, and examples include many types of brazing filler metals such as silver brazing filler metal, copper brazing filler metal, nickel brazing filler metal, iron brazing filler metal, gold brazing filler metal, aluminum brazing filler metal, titanium brazing filler metal, etc. Among various brazing filler metals, a brazing filler metal containing nickel (Ni) as the main element (hereinafter often abbreviated as "Ni-based brazing filler metal") or a brazing filler metal containing iron (Fe) as the main element (hereinafter often abbreviated as "Fe-based brazing filler metal") is preferred in the present invention.

[0056] In the present invention, the brazing filler metal portion made of a Ni-based brazing filler metal preferably contains Ni as a primary element and at least one element selected from the group consisting of Cr, Si, Fe, B, P, C, Cu, and Mo. Brazing filler metals capable of forming such brazing filler metal portions include brazing filler metals having compositions such as BNi-1, BNi-1A, BNi-2, BNi-3, BNi-4, BNi-5, BNi-6, and BNi-7, as described in JIS Z 3265. Brazing filler metals containing Ni as a primary element are generally used for metal-to-metal brazing, and as mentioned above, have been considered unsuitable for brazing commercially available electrical steel sheets coated with an oxide-based coating. However, the present inventors have joined electrical steel sheets using a brazing filler metal containing Ni as a primary element and at least one element selected from the group consisting of Cr, Si, Fe, B, P, C, Cu, and Mo, and have surprisingly been able to form strong bonds. Although the reason for this is unclear, it was found that a strong metallic bond was formed between the electrical steel sheet and the brazing filler metal, i.e., a region where the Fe derived from the electrical steel sheet and the Ni derived from the brazing filler metal were alloyed.

[0057] The alloyed region can be confirmed by elemental analysis of a cross section in the thickness direction of the magnetostrictive element for power generation. There are no particular limitations on the method for elemental analysis of the cross section of the magnetostrictive element for power generation, but elemental analysis of the cross section can be performed using a scanning electron microscope (SEM) (sometimes abbreviated as "SEM-EDS") equipped with an energy dispersive X-ray analyzer (EDS), or line analysis using an electron probe microanalyzer (EPMA). In the present invention, the alloyed region is confirmed and measured by elemental analysis of the cross section of the magnetostrictive power generation element using SEM-EDS. An example of an SEM-EDS device is the JSM-7000F (EDS is JED-2300) manufactured by JEOL.

[0058] As an example of the results of elemental analysis by SEM-EDS, the analysis results of the magnetostrictive element for power generation produced in Example 14 of the present application are shown in Figure 9. In Figure 9, the Fe concentration profile is high inside the electrical steel sheet and very low in the center of the brazing filler metal. On the other hand, the Ni concentration profile is high within the brazing filler metal and very low in the center of the electrical steel sheet. This is because the Ni-based brazing filler metal used contains only a small amount of Fe (3 mass%), and the electrical steel sheet does not contain Ni.

[0059] The concentrations of Fe and Ni can be determined by performing point analysis using EDS at multiple locations along the analysis line in Figure 9 and quantifying the composition of those locations. In Figure 9, the circle indicates the area where Fe originating from the electrical steel sheet and Ni originating from the Ni-based brazing filler metal are alloyed.

[0060] Furthermore, in the region where the Fe derived from the electrical steel sheet and the Ni derived from the Ni-based brazing filler metal are alloyed, there is a region on the brazing filler metal side where the Fe concentration is higher than the Fe concentration in the brazing filler metal used. In this case, the increase in the Fe concentration on the brazing filler metal side is due to the diffusion of Fe from the electrical steel sheet side to the brazing filler metal. The diffusion of 0.2 mass% or more of Fe into the brazing filler metal results in alloying of the diffused Fe and the Ni in the brazing filler metal. Therefore, the region where the Fe concentration is [Fe concentration contained in the brazing filler metal used] + 0.2 mass% or more is the region where the Fe derived from the electrical steel sheet and the Ni derived from the brazing filler metal are alloyed. It is more preferable that the amount of Fe diffusing from the electrical steel sheet side to the brazing filler metal is 0.5 mass% or more. It is believed that the greater the diffusion amount, the larger the alloyed region and the stronger the joint.

[0061] Similarly, there is a region on the electrical steel sheet side where the Ni concentration is higher than the Ni concentration contained in the electrical steel sheet. The increase in the Ni concentration on the electrical steel sheet side is due to the diffusion of Ni from the brazing filler metal side to the electrical steel sheet, and it is preferable that 0.2 mass% or more of Ni diffuses into the electrical steel sheet, causing the diffused Ni and the Fe of the electrical steel sheet to alloy with each other. Therefore, on the electrical steel sheet side, the region where the Ni concentration is [the Ni concentration of the electrical steel sheet used] + 0.2 mass% or more is the region where the Fe derived from the electrical steel sheet and the Ni derived from the brazing filler metal are alloyed. It is more preferable that the amount of Ni diffusing from the brazing filler metal side to the electrical steel sheet is 0.5 mass% or more. It is thought that the greater the diffusion amount, the greater the alloyed region and the stronger the joint.

[0062] In the present invention, the width L of the alloyed region is preferably 2 μm or more. A width L of 2 μm or more is sufficient to achieve high joint strength. Since a larger width L increases joint strength, a width L of 4 μm or more is more preferable. The width L of the alloyed region can be determined by performing point analysis using EDS at multiple locations on the contact surface between the electrical steel sheet and the Ni-based brazing filler metal, quantifying the elemental composition, and determining the alloyed region (i.e., the region where the Fe concentration on the brazing filler metal side is [the Fe concentration contained in the brazing filler metal used] + 0.2 mass% or more, and the region where the Ni concentration on the electrical steel sheet side is [the Ni concentration of the electrical steel sheet used] + 0.2 mass% or more) based on the obtained Fe and Ni concentrations. Whether the width L of the alloyed region is 2 μm or more can also be confirmed by selecting any region of 2 μm or more from within the contact surface, including a region where the Fe concentration and Ni concentration are close to each other, based on the concentration profiles of Fe and Ni, and quantifying the elemental composition of the selected region.

[0063] Furthermore, when an alloyed region exists on both the electrical steel sheet side and the Ni-based brazing filler metal side, the alloyed region on the Ni-based brazing filler metal side and the alloyed region on the electrical steel sheet side are continuous, and a sum of the width L1 of the alloyed region on the Ni-based brazing filler metal side and the width L2 of the alloyed region on the electrical steel sheet side of 2 μm or more is sufficient to achieve high joint strength. Furthermore, it is more preferable that width L1 and width L2 are each 1 μm or more, and even more preferable that they are 2 μm or more. This is because the larger widths L1 and L2 are, the higher the joint strength. Note that, because the brazing filler metal becomes liquid during brazing, Fe from the electrical steel sheet easily diffuses into the liquid brazing filler metal, and therefore width L1 tends to be wider than width L2.

[0064] When the magnetostrictive element for power generation of the present invention has multiple contact surfaces between the electrical steel sheets and the brazing filler metal parts formed with Ni-based brazing filler metal, it is preferable that an alloyed region is formed on at least one of the contact surfaces, more preferably 70% or more of the total contact surfaces have an alloyed region, and most preferably all of the contact surfaces have an alloyed region.

[0065] Furthermore, brazing filler metals containing Ni as a primary element have excellent corrosion resistance, which contributes to the durability of magnetostrictive power generation devices.

[0066] In the present invention, the brazing filler metal part made of an Fe-based brazing filler metal preferably contains Fe as a main element, at least one element selected from the group consisting of Cr, Ni, Si, B, P, C, Cu, and Mo, and further contains at least one oxide selected from the group consisting of Mg oxide, Cr oxide, and Si oxide. Brazing filler metals that can be used to form such a brazing filler metal part include Fe-Cr-Ni-Si-P-Mo-based, Fe-Ni-BC-based, and Fe-B-Si-based brazing filler metals. Specific examples of compositions include the following: Fe-20%Cr-30%Ni-5.0%Si-8.0%P-2.0%Mo Fe-20%Cr-20%Ni-5.0%Si-8.0%P-2.0%Mo Fe-20%Cr-15%Ni-5.0%Si-8.0%P-2.0%Mo Fe-32%Ni-13%B-1.0%C Fe-14%B-2.5%Si-1.0%C-1.2%P

[0067] When the inventors joined electrical steel sheets using the above-mentioned brazing filler metal containing Fe as a primary element, they were surprised to find that a strong bond was formed. The reason for this is unclear, but it is thought to be as follows: Typically, the Fe content of an electrical steel sheet is higher than the Fe content of the brazing filler metal. After joining an electrical steel sheet and an Fe-based brazing filler metal by brazing heat treatment, if the Fe concentration profile is measured in the sheet thickness direction at the joint cross section by elemental analysis as described above, the Fe concentration profile changes continuously from the electrical steel sheet to the Fe-based brazing filler metal near the joint interface. When the Fe concentration changes continuously in this way, the Fe of the electrical steel sheet and the Fe of the brazing filler metal mix at the joint site, resulting in sufficient joint strength.

[0068] The brazing filler metal portion using the Ni-based brazing filler metal and the Fe-based brazing filler metal, which are preferred brazing filler metals in the present invention, preferably further contains at least one oxide selected from the group consisting of Mg oxide, Cr oxide, and Si oxide. These oxides originate from the oxide coating that was present on the surface of the electrical steel sheet and are removed by the brazing filler metal and incorporated into the brazing filler metal. It is believed that the incorporation of oxides from the oxide coating of the electrical steel sheet into the brazing filler metal forms a strong metallic bond between the electrical steel sheet and the brazing filler metal. While it is sufficient to contain any one of Mg oxide, Cr oxide, and Si oxide, two or three types may also be contained. These oxides are less likely to deform than metals. Therefore, a magnetostrictive element including a brazing filler metal portion containing these oxides is less likely to deform when subjected to bending strain due to vibration than a magnetostrictive element including a brazing filler metal portion that does not contain these oxides. As a result, the relaxation of strain between the layers of the laminate is further suppressed, improving power generation. The oxides in the brazing filler metal portion may exist alone or as a composite oxide containing at least one of these oxides.

[0069] Furthermore, the oxides in the brazing filler metal are preferably lumpy. The presence of lumpy oxides in the brazing filler metal makes deformation of the brazing filler metal less likely to occur. There are no particular limitations on the method for confirming the presence of lumpy oxides in the brazing filler metal. For example, the laminate can be cut perpendicular to the plate surface and the brazing filler metal in the cross section can be observed using a scanning electron microscope (SEM). The maximum diameter of the oxides present in the observed field can be measured and used as the size of the lumpy oxides. The size of the lumpy oxides is preferably 90 μm or less, more preferably 70 μm or less. A lumpy oxide size of 90 μm or less is preferable because it is difficult for the oxide to separate from the brazing filler metal matrix. Furthermore, the size of the oxide measured in the plate thickness direction of the laminate is preferably 95% or less, more preferably 70% or less, of the thickness of the brazing filler metal. A lumpy oxide size of 95% or less of the thickness of the brazing filler metal is preferable because it is difficult for the oxide to separate from the brazing filler metal matrix.

[0070] Furthermore, the brazing filler metal may contain Cu or Mo to improve the strength of the brazing filler metal itself.

[0071] Furthermore, when the magnetostrictive element has a plurality of brazing filler metal portions, the plurality of brazing filler metal portions may be formed from the same brazing filler metal, or brazing filler metal portions formed from different brazing filler metals may be mixed.

[0072] The thickness of the brazing filler metal is not particularly limited as long as it can join the electromagnetic steel sheets, but is preferably 5 to 100 μm. If the thickness of the brazing filler metal is less than 5 μm, the metallurgical bond between the brazing filler metal and the electromagnetic steel sheets may be insufficient. In particular, if the electromagnetic steel sheets have an oxide coating on their surfaces, if the thickness of the brazing filler metal is less than 5 μm, the effect of peeling the oxide coating from the electromagnetic steel sheets and incorporating it into the brazing filler metal will be reduced, resulting in insufficient metallurgical bond between the brazing filler metal and the electromagnetic steel sheets and reduced joint strength. Note that even if the thickness of the brazing filler metal exceeds 100 μm, no further effects will be observed in terms of joint strength and durability.

[0073] Furthermore, the brazing material may have voids of 50% or less in volume fraction. The voids have the effect of alleviating distortion, and if the volume fraction is 50% or less, durability is further improved. Even if the volume fraction of the voids is 0%, there are no problems with durability. Furthermore, the voids in the brazing material alleviate distortion between the layers of the laminate, but if the volume fraction of the voids is 50% or less, the impact on power generation can be minimized. This is thought to be because more than 50% of the volume fraction between the layers is occupied by metallic brazing material with high rigidity, which is firmly bonded to the electromagnetic steel sheet.

[0074] A method for manufacturing a magnetostrictive element will now be briefly described. First, only the portions to be joined with the brazing material are prepared. The electromagnetic steel sheets (and elastic material) are sheared and cut to the required size to prepare the required number of electromagnetic steel sheets (and elastic material). Next, the desired number of electromagnetic steel sheets (and elastic material) are stacked in the desired order with the brazing material sandwiched between them. Brazing material can be, for example, foil-shaped with a thickness of approximately 25 μm to 75 μm, or powder brazing material with a particle size of 150 μm or less. When using foil-shaped brazing material, it is also cut to the same size as the electromagnetic steel sheets (and elastic material) and laminated with the electromagnetic steel sheets (and elastic material). When powder brazing material is used, the powder brazing material is applied to the electromagnetic steel sheets and / or elastic material and then laminated. An electromagnetic steel sheet layer containing two or more electromagnetic steel sheets can be produced by stacking the brazing material and electromagnetic steel sheets in the following order: electromagnetic steel sheet, brazing material, electromagnetic steel sheet. Furthermore, by laminating an electromagnetic steel sheet, a brazing material, and an elastic material, a laminate including an electromagnetic steel sheet layer and an elastic material layer can be produced.

[0075] The above stacked materials are subjected to heat treatment for brazing. Heat treatment can be performed on a single laminate, or multiple laminates can be stacked together. For example, multiple stacks of magnetic steel sheets, brazing filler metal, and magnetic steel sheets can be stacked together in the following order: magnetic steel sheet / brazing filler metal / magnetic steel sheet / magnetic steel sheet / brazing filler metal / magnetic steel sheet / ...magnetic steel sheet / brazing filler metal / magnetic steel sheet; or multiple stacks of magnetic steel sheets, brazing filler metal, and elastic material can be stacked together in the following order: magnetic steel sheet / brazing filler metal / magnetic steel sheet / brazing filler metal / elastic material / ...magnetic steel sheet / brazing filler metal / magnetic steel sheet / brazing filler metal / elastic material. Because an oxide film exists on the surface of the magnetic steel sheets, the brazed laminates can be easily separated after brazing, even if they are subjected to heat treatment while in contact with each other or with a magnetic material. However, to facilitate easier separation, a release agent can be sprayed on the surface of the magnetic steel sheets before stacking them.

[0076] Heat treatment for brazing is performed in an inert gas atmosphere such as Ar or in a vacuum, preferably using a furnace capable of heating in a vacuum. The brazing temperature varies depending on the brazing material used, but is preferably within 70°C of the melting point of the brazing material. Brazing temperatures exceeding 70°C of the melting point of the brazing material do not improve the strength or durability of the brazed portion. The heat treatment time is preferably approximately 5 to 120 minutes. When the number of layers in the laminate is large, the interior of the laminate may not reach the predetermined temperature even after the furnace temperature has risen to the predetermined temperature, so time is required for the temperature of the laminate to become uniform. Therefore, by maintaining the treatment temperature for a longer period, for example, 120 minutes, the interior of the laminate can be heated uniformly.

[0077] Furthermore, during the heat treatment for brazing, a load is applied to the laminate. There is no particular limitation on the load per unit area of ​​the laminate, but it is usually 0.1 g / mm 2 ~5g / mm 2 The load is preferably 0.1 g / mm 2 If it is less than 5g / mm, the porosity in the brazing material will exceed 50%, which is not preferable as it may reduce the strength of the joint. 2 Even if a load of over 1000kJ is applied, no significant change occurs in the brazing material. To apply a load to the laminate, a hot press can be used, which can be used in a vacuum or in an inert gas atmosphere such as Ar.

[0078] A laminate in which all layers are bonded via brazing filler metal parts can be produced by the above method. When layers are bonded using a material other than brazing filler metal, the layer having the brazing filler metal part produced by the above method and another layer (for example, a plate of an elastic material or a laminate in which multiple layers are bonded with an adhesive) are bonded by a method other than brazing, for example, by using an adhesive.

[0079] The change in magnetic flux density ΔB that occurs when an external stress is applied to a magnetostrictive element can be used as an index for evaluating the performance of the element. ΔB (unit: mT or T) can be calculated using the following method.

[0080] A magnetostrictive element with a cross-sectional area of ​​S is inserted into a coil with N turns and an external stress is applied. At this time, if a change in magnetic flux density ΔB occurs over time Δt, a voltage of V = -N(S ΔB / Δt) is generated in the coil. Therefore, ΔB can be calculated as the time integral of the voltage signal generated in the coil. The performance index of a magnetostrictive vibration power generator can be evaluated as the total voltage generated over Δt. In other words, it can be evaluated as the change in magnetic flux density ΔB, which is the time integral of the voltage. ΔB can be measured by connecting the voltage generated in the coil to a flux meter. The detailed method and apparatus for measuring ΔB (unit: mT or T) will be explained in the examples below.

[0081] 2. Magnetostrictive power generation device The present invention relates to a magnetostrictive power generation device comprising the magnetostrictive element for power generation of the present invention described above and a frame connected to the magnetostrictive element for power generation.

[0082] The magnetostrictive power generation device of the present invention is formed from the magnetostrictive element of the present invention described above, i.e., a laminate including at least one electromagnetic steel sheet layer, the electromagnetic steel sheet layer including at least one electromagnetic steel sheet, and there are no particular limitations on its structure as long as the laminate includes a magnetostrictive element that satisfies at least one of the above-mentioned conditions A and B. Therefore, it can have the same structure as a power generation device using the inverse magnetostriction effect, in which a conventional magnetostrictive material (such as an FeGa alloy, an FeCo alloy, or an FeAl alloy) is used in the magnetostrictive portion.

[0083] The magnetostrictive generating device of the present invention further comprises a frame connected to the magnetostrictive element. In the present invention, the "frame" of the magnetostrictive generating device refers to the part that is joined to the magnetostrictive element, the weight, and the magnet, respectively, and that constitutes the main body of the magnetostrictive generating device. Furthermore, in the present invention, it is preferable that the frame is continuous with the magnetostrictive element, and that at least a part of the frame is composed of a laminate that forms the magnetostrictive element. This means that at least the part of the frame adjacent to the magnetostrictive element (the part near the coil where the coil is not wound) is integral with the magnetostrictive element; it is not necessary that the entire frame be integral with the magnetostrictive element.

[0084] Hereinafter, a magnetostrictive power generating device will be described in which at least a part of the frame is constructed of a laminate that forms the magnetostrictive element.

[0085] The magnetostrictive element in the device of the present invention refers to an element that includes a magnetostrictive portion formed from an electromagnetic steel sheet and a stress control portion formed from an elastic material, and that is capable of generating electricity based on the inverse magnetostriction of the magnetostrictive portion (i.e., the generation of a magnetic field associated with a change in shape (distortion) of the magnetostrictive portion). Structurally, it is a region that contributes to power generation, with a detection coil wound around a laminate including the magnetostrictive portion and stress control portion. In an actual power generation device, the adjacent portion outside the region around which the coil is wound also contributes to power generation, but in this specification, the region around which the coil is wound is defined as the magnetostrictive power generation element.

[0086] In the frame of a magnetostrictive power generation device, there is a region on each end of the magnetostrictive element (extending beyond the coil) that is composed of a laminate (i.e., a laminate including electromagnetic steel sheets and, if desired, an elastic material) that forms the magnetostrictive element. The length of this region is at least 50% of the length of the coil, preferably at least the length of the coil. In such a magnetostrictive power generation device, the joint between the power-generating magnetostrictive element and the frame is not located within or near the magnetostrictive element, so stress concentration is less likely to occur at the joint when continuous bending strain is applied to the magnetostrictive element for power generation, improving the durability of the device. Furthermore, it is preferable that the laminate including electromagnetic steel sheets (and an elastic material) extending from the magnetostrictive element extend to the joint position of the weight that applies bending strain to the magnetostrictive part, so that bending strain caused by the vibration of the weight is efficiently transmitted to the magnetostrictive element.

[0087] Furthermore, the portion of the frame composed of the laminates that form the magnetostrictive element preferably accounts for 20% or more of the overall length of the frame, and more preferably 40% or more. By having 20% ​​or more of the overall length of the frame composed of the laminates, it is possible to expand the bonding surface between the two or more electromagnetic steel sheets included in the electromagnetic steel sheet layer and / or between the electromagnetic steel sheets and the elastic material. As a result, the continuity within the components that make up the magnetic circuit is improved, reducing the occurrence of magnetic gaps, making it easier to adjust the bias magnetic field using magnets and stabilizing the voltage.

[0088] When only a portion of the frame is composed of the laminate that forms the magnetostrictive element, there are no particular limitations on the material of the remaining portion of the frame; the frame can be completed by joining other steel plates or elastic materials. However, from the standpoint of device durability and ease of manufacturing, it is preferable that the entire frame be integrally composed of electromagnetic steel plates extending from the laminate that forms the magnetostrictive element. In particular, when the laminate that forms the magnetostrictive element includes an electromagnetic steel plate layer and an elastic material layer, a structure in which the electromagnetic steel plate is present in the portion corresponding to the magnetostrictive element and the entire frame, and an elastic material is laminated in the portion corresponding to the magnetostrictive element and the entire frame, or a structure in which an elastic material is present in the portion corresponding to the magnetostrictive element and the entire frame, and an electromagnetic steel plate is laminated in the portion corresponding to the magnetostrictive element and the entire frame, is preferable. In such a structure in which the electromagnetic steel plate or elastic material that forms the magnetostrictive element extends throughout the entire frame, both the magnetostrictive element and the frame can be manufactured by fabricating a laminate including the electromagnetic steel plate and the elastic material. This simplifies the manufacturing process. Furthermore, it is particularly preferable that at least a portion of the electromagnetic steel plate and elastic material constituting the magnetostrictive element extend to the fixing portion for fixing the magnetostrictive power generation device to a vibration source, etc., since this enables vibrations from the vibration source, etc. to be efficiently transmitted to the magnetostrictive element portion.

[0089] Furthermore, the entire frame may be composed of a laminate that forms the magnetostrictive element. In particular, when the laminate that forms the magnetostrictive element includes an electromagnetic steel sheet layer and an elastic material layer, this configuration is preferable from the standpoint of durability, since the laminate including the electromagnetic steel sheet and the elastic material continuously forms both the magnetostrictive element and the frame, and there are no joints between the magnetostrictive element and the frame. Furthermore, since the continuity within the components that make up the magnetic circuit is increased, the occurrence of magnetic gaps is reduced, making it easier to adjust the bias magnetic field using magnets and further stabilizing the voltage.

[0090] Although there are no particular limitations on the dimensions of the frame containing the magnetostrictive element, the length of the frame containing the magnetostrictive element is generally 30 mm to 700 mm, preferably 60 mm to 500 mm, and more preferably 120 mm to 300 mm. The width of a typical frame is 4 mm to 70 mm, preferably 6 mm to 50 mm, and more preferably 8 mm to 30 mm. The frame dimensions can be reflected in the design according to the amount of power required to operate the device.

[0091] The shape of the frame is not particularly limited, and it can be a plate shape or a shape with a curved portion such as a U-shape, a V-shape, etc. In the present invention, since a highly tough electromagnetic steel sheet is used for the magnetostrictive element, not only a plate shape but also a U-shaped frame with a curved portion can be manufactured from the magnetostrictive material that forms the magnetostrictive element.

[0092] The larger the dimensions of the magnetostrictive element for power generation in the magnetostrictive power generation device of the present invention, the more the number of coil turns can be increased in the power generation device, and the greater the voltage that can be obtained. Therefore, there are no particular restrictions on the dimensions of the magnetostrictive element (the length of the region around which the coil is wound), but it is usually 5 mm or more and 150 mm or less, preferably 10 mm or more and 100 mm or less, and more preferably 20 mm or more and 70 mm or less.

[0093] There are no particular limitations on the thickness of the electromagnetic steel sheet layers of the magnetostrictive element and the electromagnetic steel sheet layers forming the frame, but they are typically between 0.2 mm and 10 mm. A thickness of 0.2 mm or more for the part corresponding to the magnetostrictive element is advantageous because it allows for a large change in magnetic flux and therefore a large generated voltage, while a thickness of 10 mm or less is advantageous because it makes it easier to design rigidity suitable for vibration. The thickness of the electromagnetic steel sheet layers in the laminate forming the magnetostrictive element and in the laminate forming the frame may be the same or different.

[0094] The thickness of the elastic material layer of the magnetostrictive element and the elastic material layer forming the frame is not particularly limited, but is typically 0.02 mm to 50 mm, preferably 0.1 mm to 10 mm, and more preferably 0.2 mm to 5 mm. If the thickness of the portion corresponding to the magnetostrictive element is 0.02 mm or more, it is advantageous for achieving either a compressive or tensile stress load on the entire magnetostrictive portion, and if it is 50 mm or less, it is possible to suppress interference with the vibration of the magnetostrictive element. The thickness of the elastic material layer in the laminate forming the magnetostrictive element and in the laminate forming the frame may be the same or different.

[0095] As long as the magnetostrictive power generating device of the present invention includes the magnetostrictive element and the frame, there are no particular limitations on the other configurations, and it can be configured similarly to conventional magnetostrictive power generating devices. Specifically, the device includes a coil mounted around the magnetostrictive element, a frame, a weight attached to the frame, and a magnet. In such a device, the magnetic field lines of the magnet pass through the magnetostrictive element and apply a bias magnetic field to the magnetostrictive portion. Vibration of the weight then vibrates the frame, applying tensile and compressive forces to the magnetostrictive element. At this time, the direction of applying bending strain to the magnetostrictive element and the direction of applying the bias magnetic field to the magnetostrictive element are parallel, and the magnetization of the magnetostrictive element is changed by the inverse magnetostriction effect, generating an induced current (or induced voltage) in the coil.

[0096] When the magnetostrictive element is made of grain-oriented electromagnetic steel sheet, <001> It is preferable to configure the device so that a bias magnetic field is applied in the direction of the magnetization direction, since this allows for a larger voltage to be obtained.

[0097] There are no particular limitations on the size or number of magnets in a magnetostrictive power generation device, and they can be selected according to the device configuration. It is preferable to use a permanent magnet to generate the bias magnetic field, because permanent magnets can be miniaturized and the bias magnetic field is easy to control. Furthermore, NdFeB magnets are preferred as permanent magnets because they can generate a larger bias magnetic field.

[0098] Next, the basic configuration of the magnetostrictive generating device of the present invention will be described with reference to FIGS. 6 to 8, which are schematic diagrams of the devices produced in Examples 11 to 13, but the device of the present invention is not limited to these.

[0099] 6 is a schematic diagram of a magnetostrictive generating device 200 in which the entire U-shaped frame is integral with an elastic material extending from a stress control section. The magnetostrictive element 210 included in the magnetostrictive generating device 200 is composed of a laminate 220 in which an electromagnetic steel sheet layer 221 and an elastic material layer 222 (in Example 11, a grain-oriented electromagnetic steel sheet and a non-magnetic material, SUS304) are joined via a brazing material (not shown). In the magnetostrictive element 210, the electromagnetic steel sheet layer 221 forms the magnetostrictive section 211, the elastic material layer 222 forms the stress control section 212, and a detection coil 260 is mounted around the magnetostrictive element 210. Furthermore, the entire frame 230 is integral with the elastic material layer 222 extending from the stress control section 212, and a portion of the frame (approximately 71%) is composed of the laminate 220. The device 200 further has a weight 240 for applying a strain to the magnetostrictive portion 211 and a magnet 250 for applying a bias magnetic field, and can be fixed on a vibration source or the like by a fixing portion 270 .

[0100] 7 is a schematic diagram of a magnetostrictive generating device 300 in which the entire U-shaped frame is integral with an elastic material extending from a stress control section. The magnetostrictive element 310 included in the magnetostrictive generating device 300 is composed of a laminate 320 in which an electromagnetic steel sheet layer 321 and an elastic material layer 322 (in Example 12, a grain-oriented electromagnetic steel sheet and a magnetic material, SUS430) are joined via a brazing material (not shown). In the magnetostrictive element 310, the electromagnetic steel sheet layer 321 forms the magnetostrictive section 311, the elastic material layer 322 forms the stress control section 312, and a detection coil 360 is mounted around the magnetostrictive element 310. Furthermore, the entire frame 330 is integral with the elastic material layer 322 extending from the stress control section 312, and a portion of the frame (approximately 71%) is composed of the laminate 320. The device 300 further includes a weight 340 for applying a strain to the magnetostrictive portion 311 and a magnet 350 for applying a bias magnetic field, and can be fixed onto a vibration source or the like by a fixing portion 370 .

[0101] 8 is a schematic diagram of a magnetostrictive power generation device 400 in which a magnetostrictive element and a portion of a U-shaped frame are formed of a laminate having a laminated structure of electromagnetic steel sheet / brazing material portion / elastic material / brazing material portion / electromagnetic steel sheet. The magnetostrictive power generation device 400 includes a magnetostrictive element 410. The magnetostrictive element 410 is formed of a laminated body 420 having a laminated structure of electromagnetic steel sheet / brazing material portion / elastic material / brazing material portion / electromagnetic steel sheet, in which two electromagnetic steel sheet layers 421 and an elastic material layer 422 (a grain-oriented electromagnetic steel sheet and a non-magnetic material, SUS304, in Example 13) are joined via a brazing material portion (not shown). In the magnetostrictive element 410, the electromagnetic steel sheet layer 421 serves as the magnetostrictive portion 411, the elastic material layer 422 serves as the stress control portion 412, and a detection coil 460 is mounted around the magnetostrictive element 410. The device 400 further includes a weight 440 for applying a strain to the magnetostrictive portion 411 and a magnet 450 for applying a bias magnetic field. Furthermore, the frame 430 of the device 400 is mostly composed of a laminate 420 extending from the magnetostrictive element 410, and the outer electromagnetic steel sheet layer 421 of the U-shaped frame 430 contacts the other electromagnetic steel sheet layer 421 arranged inside through a hole opened in the elastic material layer 422 at the fixing portion 470. Furthermore, the outer and inner electromagnetic steel sheet layers 421 of the U-shaped frame 430 are also in contact at the tip on the side where the weight 440 is arranged. In this way, by bringing the outer and inner electromagnetic steel sheets into contact, it is possible to efficiently magnetize the electromagnetic steel sheets using a magnet. In addition, the device 400 has a support 480 at the U-shaped portion of the frame 430 to facilitate vibration of the magnetostrictive element 410 in the detection coil 460. Furthermore, the device 400 can be fixed onto a vibration source or the like using the fixing portion 470, and a height adjustment plate 490 made of SUS304 stainless steel with the same thickness as the electromagnetic steel sheets is adhered to this plate.

[0102] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Example]

[0103] In the following examples, "%" means "% by mass" unless otherwise specified.

[0104] Example 1 Comparison of bonding strength The electrical steel sheet used was a coated grain-oriented electrical steel sheet 35ZH115 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.35 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared to a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain grain-oriented electrical steel sheets for the magnetostrictive portion.

[0105] To produce a laminate (test piece) for a tensile test to measure the joint strength, two grain-oriented electrical steel sheets, each 40 mm long and 6.0 mm wide, were stacked with a 20 mm offset in the longitudinal direction so that the joint was 20 mm long and 6.0 mm wide.

[0106] For the joining, a 25 μm thick amorphous foil of BNi-2 composition or an activated Ag brazing foil (AgCuTi system, 50 μm thick) was used as the brazing material. The composition of each brazing material is as follows: BNi-2 composition: Ni-7.0%Cr-4.5%Si-3.0%B-3.0%Fe, Active Ag brazing composition: Ag-28%Cu-2%Ti-5%Sn

[0107] Each brazing foil was cut to a length of 20 mm and a width of 6.0 mm, and each foil was sandwiched between two grain-oriented electrical steel sheets. Brazing was performed under the following conditions to obtain a laminate satisfying condition A. For BNi-2 foil, brazing is performed at 1050°C for 10 minutes in a vacuum. In the case of activated Ag brazing foil, brazing is performed in a vacuum at 1000°C for 10 minutes.

[0108] For comparison, two grain-oriented electrical steel sheets similar to those described above were prepared and bonded together at room temperature using an epoxy adhesive instead of brazing foil to obtain a laminate (test piece).

[0109] In addition, a grain-oriented electrical steel sheet measuring 40 mm in length and 6.0 mm in width was also prepared as a test piece.

[0110] A tensile test was carried out on each of the test pieces prepared above. Specifically, both ends of the test piece were clamped and the displacement-load curve was measured. The displacement rate was 1 mm / min, and measurements were taken until fracture. The results are shown as displacement-load curves in Figure 1.

[0111] In the laminate bonded with BNi-2 foil, fracture did not occur at the joint, but occurred in the base material. In addition, in the laminate bonded with activated Ag brazing foil, fracture occurred at the joint, and the fracture strength was 50 N or less, which was lower than that of the BNi-2 foil bonded laminate. On the other hand, fracture occurred at the joint in the laminate bonded with epoxy adhesive. The fracture strength was close to that of the base material, but there was almost no elongation compared to BNi-2 foil. From the above results, it can be seen that the BNi-2 foil bond, which fractured in the base material, is superior to bonding with adhesive.

[0112] Example 2 Durability of magnetostrictive elements made of magnetic steel sheet / brazing material (Ni-based) / magnetic steel sheet The magnetostrictive material used was a coated grain-oriented electrical steel sheet 35ZH115 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.35 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared to a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain grain-oriented electrical steel sheets for the magnetostrictive portion.

[0113] A BNi-2 amorphous foil measuring 40 mm in length, 6.0 mm in width, and 25 μm in thickness was sandwiched between the two grain-oriented electrical steel sheets as a brazing material, and brazing was performed in a vacuum at 1050°C for 10 minutes to obtain a magnetostrictive element that satisfies condition A of the present invention. Two sets of the magnetostrictive element were produced.

[0114] For comparison, two magnetostrictive elements were fabricated by bonding two of the same grain-oriented electromagnetic steel sheets as above with an epoxy adhesive.

[0115] Each set of magnetostrictive elements thus fabricated was subjected to vibration as shown in Fig. 2. Specifically, one longitudinal end of magnetostrictive element 1 was fixed by fixing part 2, and the other free end was repeatedly vibrated up and down. The element was vibrated 100,000 times at an amplitude of ±1.0 mm and a vibration frequency of 30 Hz.

[0116] Next, to measure ΔB when bending strain was applied, a 0.5 mm thick piece of carbon fiber reinforced plastic (CFRP) was cut into a length of 40 mm and a width of 6.3 mm, with the carbon fiber direction as the longitudinal direction, and these were attached to the magnetostrictive elements (before vibration and after 100,000 vibrations) prepared above using an epoxy adhesive at room temperature. The magnetic flux density change ΔB was measured using the magnetostrictive elements with the obtained CFRP.

[0117] To measure the magnetic flux density change ΔB, a measurement unit 100 for applying bending strain to a magnetostrictive element was used, as shown in Fig. 3. As an example, Fig. 3 shows a unit in which the left end of a magnetostrictive element 110 having a magnetostrictive portion 111 and a stress control portion 112 is fixed to a fixed support base 150, and the right end is pressed downward to apply bending strain.

[0118] In the unit 100, downward pressure 170 is applied (i.e., pressed) to the right end of the magnetostrictive element 110. At this time, the magnetostrictive portion 111 (magnetostrictive material) is subjected to compressive strain, and the longer the movement distance 171 of the magnetostrictive portion 111 when pressed, the greater the compressive strain. Pressing was performed using a micrometer cylinder head, and the pressing depth Δh (movement distance 171) was set to 0.5 mm.

[0119] Furthermore, in the measurement unit of Figure 3, a Helmholtz-type coil was used as the bias magnetic field coil 120, and a current was passed through it to apply a magnetic field to the magnetostrictive element 110. The magnitude of the magnetic field was adjusted by the magnitude of the DC power supply 140, and the magnitude of the magnetic field was previously calibrated using a Gauss meter. At this time, the magnetic field applied to the magnetostrictive element 110 was evaluated as 8000 A / m (1000 e). The change in magnetic flux of the magnetostrictive element 110 was detected as an induced voltage by the detection coil 130 (number of turns: 3500), and this induced voltage was measured as a change in magnetic flux by the flux meter 160. Furthermore, the change in magnetic flux density ΔB was calculated by dividing the change in magnetic flux by the number of turns of the detection coil and the cross-sectional area of ​​the magnetostrictive material based on the following formula I. The results are shown in Table 1.

[0120]

number

[0121] The magnetic flux density change ΔB obtained by this measurement method is the time integral value of the voltage change, and therefore does not depend on the speed at which the strain is applied.

[0122] [Table 1]

[0123] As is clear from the results in Table 1, the magnetostrictive element of Example 1, which is made by brazing two electromagnetic steel plates and satisfies condition A, has a smaller decrease in ΔB and improved durability compared to the magnetostrictive element of Comparative Example 1, which is joined with an adhesive.

[0124] Example 3 Cross-sectional structure of the brazing material: Magnetostrictive element consisting of electromagnetic steel sheet / brazing material / electromagnetic steel sheet The magnetostrictive material used was a coated grain-oriented electrical steel sheet 35ZH115 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.35 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared and cut into a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0125] A BNi-2 amorphous foil measuring 40 mm in length, 6.0 mm in width, and 50 μm in thickness was sandwiched between the two grain-oriented magnetic steel sheets as a brazing material, and brazing treatment was performed in a vacuum at 1050°C for 10 minutes to obtain a magnetostrictive element that satisfied condition A (i.e., had a brazing material portion between the two magnetic steel sheets).

[0126] The magnetostrictive element thus obtained was cut in the width direction, and the cross-sectional structure was observed using a SEM-EDS (JEOL JSM-7000F). The results are shown in Figure 4.

[0127] As is clear from Figure 4, when electrical steel sheets with oxide films are brazed with a brazing filler metal containing Ni as the main element, no oxide layer is visible on the cross section. It is believed that the oxide film is removed by the brazing filler metal and incorporated into the brazing filler metal. As a result, a metallic bond consisting mainly of Fe and Ni is formed between the electrical steel sheets and the brazing filler metal.

[0128] Furthermore, when the maximum diameter of the oxides observed in the brazing filler metal part in Fig. 4 was measured, it was found that there were aggregates of Mg oxides with sizes of about 0.3 μm to about 63 μm, aggregates of Cr oxides with sizes of about 0.3 μm to about 20 μm, and aggregates of Si oxides with sizes of about 0.3 μm to about 20 μm. Furthermore, a composite oxide of Si oxide and Mg oxide was also present.

[0129] Example 4 Cross-sectional structure of the brazing material: Magnetostrictive element consisting of electromagnetic steel sheet / brazing material / elastic material The magnetostrictive material used was a coated grain-oriented electrical steel sheet 35ZH115 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.35 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared to a length of 40 mm and a width of 6.1 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0130] The elastic material was a 0.5 mm thick cold-rolled sheet of non-magnetic SUS304. After cutting it into a length of 40 mm and a width of 6.1 mm, it was held in a vacuum at 1050°C for 1 minute and then gas quenched for solution treatment to remove the effects of cutting distortion, yielding a non-magnetic material for the stress control section.

[0131] A BNi-2 amorphous foil measuring 40 mm in length, 6.1 mm in width, and 38 μm in thickness was sandwiched between one of the above-mentioned grain-oriented electromagnetic steel sheets and SUS304 as a brazing material, and brazing was performed in a vacuum at 1050°C for 10 minutes to obtain a magnetostrictive element that satisfies condition B (i.e., has a brazing material portion between the electromagnetic steel sheet and the elastic material).

[0132] The magnetostrictive element thus obtained was cut in the width direction, and the cross-sectional structure was observed using a SEM-EDS (JEOL JSM-7000F). The results are shown in FIG.

[0133] As is clear from Figure 5, when electrical steel sheets with oxide films are brazed with a brazing filler metal containing Ni as the main element, no oxide layer is visible on the cross section. It is believed that the oxide film is removed by the brazing filler metal and incorporated into the brazing filler metal. As a result, a metallic bond consisting mainly of Fe and Ni is formed between the electrical steel sheets and the brazing filler metal.

[0134] Furthermore, when the maximum diameter of the oxides observed in the brazing filler metal in Figure 5 was measured, it was found that there were clumps of Mg oxide and Cr oxide measuring approximately 0.3 μm to 20 μm in size. A composite oxide of Si oxide and Mg oxide was also present. Furthermore, the SUS304 and brazing filler metal formed a metallic bond primarily composed of Fe and Ni.

[0135] Example 5 ΔB of magnetostrictive element consisting of grain-oriented electrical steel sheet / brazing material / SUS304 The magnetostrictive material used was a coated grain-oriented electrical steel sheet 27ZH100 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared in the direction of the arrow to a length of 40 mm and a width of 5.9 mm. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0136] The elastic material was a 0.5 mm thick cold-rolled sheet of non-magnetic SUS304. After cutting it into a length of 40 mm and a width of 6.3 mm, it was held in a vacuum at 1050°C for 1 minute and then gas quenched to remove the effects of cutting distortion, yielding an elastic material for magnetostrictive elements.

[0137] The brazing filler metal used was a 25 μm thick amorphous foil of BNi-2 composition, a Ni brazing filler metal, or activated Ag brazing foil (AgCuTi system, 50 μm thick). The foil was cut to a length of 40 mm and a width of 5.9 mm, and one piece was sandwiched between a grain-oriented electrical steel sheet and SUS304. Brazing was performed under the following conditions to obtain a magnetostrictive element that satisfied condition B. The conditions for brazing are as follows: BNi-2 brazing foil: in vacuum, 1050℃ for 10 minutes Activated Ag brazing foil: 10 minutes at 1000°C in vacuum

[0138] As a comparative example, a magnetostrictive element was fabricated by bonding the above-mentioned grain-oriented electrical steel sheet 27ZH100 and SUS304 together at room temperature with an epoxy adhesive.

[0139] The ΔB of the fabricated magnetostrictive element was measured in the same manner as in Example 2 using the measurement unit 100 shown in FIG. 3, which applies bending strain to the magnetostrictive element. However, in this example, taking into account one vibration cycle, ΔB was measured when a downward pressure 170 was applied to the right end of the magnetostrictive element 110, pushing it in 1 mm, and when it was pulled up 1 mm, and the sum of these values ​​was used as the ΔB value. The pushing was performed using the cylinder head of a micrometer. Furthermore, since the cylinder head of a micrometer cannot pull up the end of the magnetostrictive element, the magnetostrictive element was installed upside down and a downward pressure 170 was applied to the right end of the magnetostrictive element 110, pushing it in 1 mm, thereby reproducing the same state as when the end of the magnetostrictive element 110 was pulled up. In addition, the magnetic field applied to the magnetostrictive element 110 was 2800 A / m (350 e) for evaluation. The results are shown in Table 2.

[0140] [Table 2]

[0141] As is clear from the results in Table 2, the magnetostrictive elements of invention examples 2 and 3, which satisfy condition B and are made by brazing electromagnetic steel sheets to SUS304, an elastic material, have ΔB improved by approximately 1.6 times for invention example 2 and 1.5 times for invention example 3, compared to the magnetostrictive element of comparison example 2, which is bonded with an adhesive. This is thought to be because by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between laminations when bending strain is applied is suppressed, improving ΔB.

[0142] Furthermore, in Example 1, the joint strength of the magnetostrictive element in which two electromagnetic steel sheets were joined with an active Ag brazing material was 50 N or less, but in Invention Example 3 in which an electromagnetic steel sheet and SUS304 were joined with an active Ag brazing material, it is thought that a stronger joint was obtained than with two electromagnetic steel sheets. Therefore, it is thought that peeling is less likely to occur at the joint when the cantilever type bending is performed by pushing the sheet downward by about 1 mm, and ΔB is improved compared to joining using an adhesive.

[0143] Example 6 ΔB of a magnetostrictive element made of grain-oriented electrical steel sheet / brazing material / SUS430 The magnetostrictive material used was a coated grain-oriented electrical steel sheet 27ZH100 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared to a length of 40 mm and a width of 6.1 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0144] The elastic material was a 0.5 mm thick magnetic ferritic stainless steel (SUS430). After cutting it into a length of 40 mm and a width of 6.5 mm, it was held in a vacuum at 1050°C for 1 minute and then gas quenched to remove the effects of cutting distortion, yielding an elastic material for magnetostrictive elements.

[0145] A 25 μm thick amorphous foil with a BNi-2 composition was used as the brazing material. The foil was cut to a length of 40 mm and a width of 6.1 mm, and one piece was sandwiched between a grain-oriented electrical steel sheet and SUS430. Brazing was performed in a vacuum at 1050°C for 10 minutes to obtain a magnetostrictive element that satisfied condition B.

[0146] As a comparative example, the above-mentioned grain-oriented electrical steel sheet 27ZH100 and SUS430 were bonded together at room temperature with an epoxy adhesive to obtain a magnetostrictive element.

[0147] Except for changing the applied bias magnetic field to 3600 A / m (450 e), ΔB was measured in the same manner as in Example 5. The results are shown in Table 3.

[0148] [Table 3]

[0149] As is clear from the results in Table 3, the magnetostrictive element of Example 4, which satisfies condition B and which is made by brazing an electromagnetic steel sheet to SUS430, a magnetic material used as an elastic material, has an improved ΔB of about 1.5 times that of the magnetostrictive element of Comparative Example 3, which is bonded with an adhesive. This is thought to be because by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between laminations when bending strain is applied is suppressed, improving ΔB.

[0150] Example 7 ΔB of a magnetostrictive element consisting of non-oriented electrical steel sheet / brazing material / SUS304 The magnetostrictive material used was a non-oriented electrical steel sheet (35H210, manufactured by Nippon Steel Corporation) with a coating. The thickness of the electrical steel sheet was 0.35 mm. The non-oriented electrical steel sheet was sheared to a length of 40 mm and a width of 6.1 mm, with the rolling direction of the non-oriented electrical steel sheet as the longitudinal direction, and then annealed in a vacuum at 740°C for 2 hours to remove distortion caused by cutting, to obtain a non-oriented electrical steel sheet for the magnetostrictive element.

[0151] The elastic material was a 0.5 mm thick cold-rolled sheet of non-magnetic SUS304. After cutting it into a length of 40 mm and a width of 6.5 mm, it was held in a vacuum at 1050°C for 1 minute and then gas quenched to remove the effects of cutting distortion, yielding an elastic material for magnetostrictive elements.

[0152] A 25 μm thick amorphous foil with a BNi-2 composition was used as the brazing material. The foil was cut to a length of 40 mm and a width of 6.1 mm, and one piece was sandwiched between a non-oriented electrical steel sheet and a SUS304 sheet. Brazing was performed in a vacuum at 1050°C for 10 minutes to obtain a magnetostrictive element that satisfied condition B.

[0153] As a comparative example, the above-mentioned grain-oriented electrical steel sheet 35H210 and SUS304 were bonded together at room temperature with an epoxy adhesive to obtain a magnetostrictive element.

[0154] Except for changing the applied bias magnetic field to 3200 A / m (400 e), ΔB was measured in the same manner as in Example 5. The results are shown in Table 4.

[0155] [Table 4]

[0156] As is clear from the results in Table 4, the magnetostrictive element of Example 5, which satisfies condition B and which is made by brazing non-oriented electrical steel sheet to SUS304 as an elastic material, has an improved ΔB of approximately 1.4 times compared to the magnetostrictive element of Comparative Example 4, which is bonded with an adhesive. This is thought to be because by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between laminations when bending strain is applied is suppressed, thereby improving ΔB.

[0157] Example 8 ΔB of a magnetostrictive element consisting of grain-oriented electrical steel sheet / brazing material / grain-oriented electrical steel sheet / adhesive / CFRP The magnetostrictive material used was a coated grain-oriented electrical steel sheet 35ZH115 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.35 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared and cut into a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to produce four grain-oriented electrical steel sheets for use in magnetostrictive elements.

[0158] A 25 μm thick amorphous foil with a BNi-2 composition was used as the brazing filler metal. The foil was cut to a length of 40 mm and a width of 6.0 mm and sandwiched between two grain-oriented electrical steel sheets. The two grain-oriented electrical steel sheets were brazed together by a brazing process in a vacuum at 1050°C for 10 minutes to obtain an electrical steel sheet layer.

[0159] The elastic material was a non-magnetic carbon fiber reinforced plastic (CFRP) with a thickness of 0.5 mm. The carbon fiber was cut into a length of 40 mm and a width of 6.4 mm, with the direction of the carbon fiber being the longitudinal direction, to obtain an elastic material for the magnetostrictive element.

[0160] A magnetostrictive element satisfying condition A was obtained by bonding an elastic material (CFRP) to an electromagnetic steel sheet layer formed by brazing two grain-oriented electromagnetic steel sheets together using an epoxy adhesive at room temperature.

[0161] As a comparative example, two of the above-mentioned grain-oriented electrical steel sheets 35ZH115 were bonded together at room temperature with an epoxy adhesive, and then a CFRP was bonded thereto at room temperature with an epoxy adhesive to obtain a magnetostrictive element.

[0162] Except for changing the indentation depth of the cylinder head of the micrometer to 0.5 mm and the applied bias magnetic field to 8000 A / m (1000 e), ΔB was measured in the same manner as in Example 5. The results are shown in Table 5.

[0163] [Table 5]

[0164] As is clear from the results in Table 5, the magnetostrictive element of Example 6, which satisfied condition A but not condition B, had an improvement in ΔB of approximately 1.2 times compared to the magnetostrictive element of Comparative Example 5, which did not include a brazing material portion. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing material made of a metal with a large Young's modulus, relaxation of strain between laminations when bending strain is applied is suppressed, thereby improving ΔB.

[0165] Example 9 ΔB of a magnetostrictive element consisting of grain-oriented electrical steel sheet / brazing material / grain-oriented electrical steel sheet / brazing material / SUS304 The magnetostrictive material used was a coated grain-oriented electrical steel sheet 35ZH115 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.35 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared and cut into a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0166] The elastic material was a cold-rolled sheet of SUS304, a non-magnetic material, with a thickness of 0.83 mm. After cutting it into a length of 40 mm and a width of 6.0 mm, it was held in a vacuum at 1050°C for 1 minute and then gas quenched to remove the effects of cutting distortion, yielding an elastic material for magnetostrictive elements.

[0167] A 25 μm thick amorphous foil with a BNi-2 composition was cut to a length of 40 mm and a width of 6.0 mm for the brazing filler metal. To laminate two magnetic steel sheets and one SUS304 sheet, the layers were stacked in the following order: magnetic steel sheet / brazing filler metal / magnetic steel sheet / brazing filler metal / SUS304. The two grain-oriented magnetic steel sheets and the SUS304 sheet were brazed together by vacuum brazing at 1050°C for 10 minutes, resulting in a magnetostrictive element that satisfied both conditions A and B.

[0168] The ΔB of the obtained magnetostrictive element was measured in the same manner as in Example 8. The results are shown in Table 6.

[0169] [Table 6]

[0170] As is clear from Table 6, the magnetostrictive element of Example 7, which satisfies conditions A and B and in which all joints are brazed, exhibited a ΔB improvement of approximately 1.4 times compared to the magnetostrictive element of Comparative Example 5, in which all joints are bonded. Furthermore, the magnetostrictive element of Example 7 exhibited a ΔB improvement of approximately 1.2 times compared to the magnetostrictive element of Example 6, which satisfies only condition A and in which the elastic material layer is bonded. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between laminations when bending strain is applied is suppressed, resulting in an improvement in ΔB.

[0171] Example 10 ΔB of magnetostrictive element consisting of grain-oriented electrical steel sheet / brazing material / SUS304 The magnetostrictive material used was a coated grain-oriented electrical steel sheet 27ZH100 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared and cut into a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0172] The elastic material was a 0.5 mm thick cold-rolled sheet of non-magnetic SUS304. After cutting it into a length of 40 mm and a width of 6.3 mm, it was held in a vacuum at 1050°C for 1 minute and then gas quenched to remove the effects of cutting distortion, yielding an elastic material for magnetostrictive elements.

[0173] The brazing filler metal used was a 35 μm thick amorphous foil of BNi-1 or BNi-3 composition. The brazing filler metal composition is as follows: BNi-1 composition: Ni-14%Cr-4.0%Si-3.5%B-4.5%Fe (mass%), melting point: 1040℃ BNi-3 composition: Ni-4.5%Si-3.2%B, (mass%), melting point: 1040℃ Each foil was cut to a length of 40 mm and a width of 6.0 mm, and one piece was sandwiched between a grain-oriented electrical steel sheet and SUS304. Brazing was performed in a vacuum at 1100°C for 10 minutes to obtain a magnetostrictive element that satisfied condition B.

[0174] The ΔB of the obtained magnetostrictive element was measured in the same manner as in Example 5. The results are shown in Table 7.

[0175] [Table 7]

[0176] As is clear from Table 7, the magnetostrictive elements of Examples 8 and 9, which satisfy condition B and in which electromagnetic steel sheets and an elastic material, SUS304, are brazed together, have a ΔB that is approximately 1.5 to 1.6 times higher than the magnetostrictive element of Comparative Example 2, in which the same electromagnetic steel sheets and an elastic material are bonded together with an adhesive. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between laminations when bending strain is applied is suppressed, improving ΔB.

[0177] Example 11 Magnetostrictive power generation device equipped with a magnetostrictive element consisting of grain-oriented electrical steel sheet / brazing material (Ni-based) / SUS304 In Example 11, a magnetostrictive power generating device 200 having the structure shown in FIG. 6 was fabricated using grain-oriented electrical steel sheets as the electrical steel sheet layers 221 and SUS304 as the elastic material layers 222.

[0178] The electrical steel sheet layer 221 was a coated grain-oriented electrical steel sheet 27ZH100 manufactured by Nippon Steel Corporation. The thickness was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The piece was sheared and cut to a length of 100 mm and a width of 6.0 mm in the direction indicated by the arrows. The piece was then bent into a U-shape as shown in Fig. 6. The length corresponding to the lower fixing part 270 was approximately 40 mm, and the length of the upper part where the detection coil 260 and weight 240 were attached was approximately 40 mm. After bending the grain-oriented electrical steel sheet into a U-shape, it was annealed in a vacuum at 800° C. for 2 hours to remove distortion.

[0179] A non-magnetic material, SUS304, with a thickness of 0.5 mm and a width of 6.0 mm was used for the elastic material layer 222. It was cut to a length of 140 mm so that it could be integrated with the U-shaped electromagnetic steel plate, and then molded into a U-shape to adjust the shape. The SUS304 was molded into a U-shape and held at 1050°C for 1 minute in a vacuum, after which it was subjected to solution treatment by gas quenching to remove the effects of cutting distortion.

[0180] A 35 μm thick amorphous foil with a BNi-2 composition was used as the brazing material. The foil was cut to a length of 100 mm and a width of 6.0 mm. One foil was sandwiched between a grain-oriented electrical steel sheet bent into a U-shape and a SUS304 steel sheet, aligning it with the grain-oriented electrical steel sheet and fixing it in place. A brazing process was performed in a vacuum at 1050°C for 10 minutes to form a laminate. A portion of the frame (100 mm / 140 mm = approximately 71%) was composed of the above-mentioned laminate 220, and an integrated structure was obtained in which the elastic material layer 222 extending from the stress control unit 212 of the magnetostrictive element 210 and the entire frame 230 were integrated.

[0181] For comparison, an integrated structure was prepared by bonding grain-oriented electrical steel sheets bent into a U-shape of the same size as above and SUS304 at room temperature using an epoxy adhesive.

[0182] A 5000-turn detection coil 260 was loaded into the portion of the obtained integrated structure corresponding to the magnetostrictive element. The length of the coil was 15 mm. Next, a 7 g tungsten weight 240 was adhesively fixed next to the magnetostrictive element 210. Furthermore, an NdFeB magnet 250 was attached to the electromagnetic steel plate side of the fixed portion on the lower side of the U-shape, thereby obtaining a magnetostrictive power generation device 200 in which the entire frame is integrated with the magnetostrictive element.

[0183] The AC voltage induced in the detection coil of the fabricated magnetostrictive power generation device 200 was captured using a digital oscilloscope and measured. The performance of the magnetostrictive power generation device was evaluated based on the peak voltage of the measured voltage waveform. Specifically, the U-shaped lower fixing part 270 of the magnetostrictive power generation device was fixed onto a vibrator with adhesive. Next, a bias magnetic field was applied using an NdFeB magnet. The strength (size) of the magnet was changed and the magnet that maximized the peak voltage was used. The strength of the magnetic field applied to the magnetostrictor was estimated to be about 2800 A / m (350 e) for grain-oriented electrical steel sheets. The vibrator was vibrated at 0.5 G, and the frequency was changed to measure the peak voltage at the resonance frequency with an oscilloscope.

[0184] The measured resonant frequencies were 105 Hz for the brazed joint and 97 Hz for the bonded joint. The peak voltages are shown in Table 8.

[0185] [Table 8]

[0186] As is clear from Table 8, the device of Example 10, which includes a magnetostrictive element that satisfies condition B (i.e., an electromagnetic steel sheet and an elastic material, SUS304, brazed together), had a peak voltage that was approximately 1.4 times higher than the device of Comparative Example 6, which includes a magnetostrictive element in which an electromagnetic steel sheet and an elastic material were bonded together with an adhesive. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between lamination layers that occurs when bending strain is applied is suppressed, thereby improving the peak voltage.

[0187] Example 12 Magnetostrictive power generation device equipped with a magnetostrictive element made of grain-oriented electrical steel sheet / brazing material / SUS430 In Example 12, a magnetostrictive power generating device 300 having the structure shown in FIG. 7 was fabricated using grain-oriented electrical steel sheets as the electrical steel sheet layers 321 and SUS430, a magnetic material, as the elastic material layers 322.

[0188] The electrical steel sheet layer 321 was a 27ZH100 grain-oriented electrical steel sheet with a coating manufactured by Nippon Steel Corporation. The thickness was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The piece was sheared and cut to a length of 100 mm and a width of 6.0 mm in the direction indicated by the arrows. The piece was then bent into a U-shape as shown in Fig. 7. The length corresponding to the lower fixing part 370 was approximately 40 mm, and the length of the upper part where the detection coil 360 and weight 340 were attached was approximately 40 mm. After bending the grain-oriented electrical steel sheet into a U-shape, it was annealed in a vacuum at 800° C. for 2 hours to remove distortion.

[0189] A magnetic material, SUS430, with a thickness of 0.5 mm and a width of 6.0 mm was used for the elastic material layer 322. It was cut to a length of 140 mm so that it could be integrated with the U-shaped electromagnetic steel plate, and then molded into a U-shape to adjust the shape. The SUS430 molded into a U-shape was held at 1050°C for 1 minute in a vacuum, and then subjected to solution treatment by gas quenching to remove the effects of cutting distortion.

[0190] A 35 μm thick amorphous foil with a BNi-2 composition was used as the brazing material. The foil was cut to a length of 100 mm and a width of 6.0 mm. One foil was sandwiched between a grain-oriented electrical steel sheet bent into a U-shape and a SUS430 sheet, aligned with the grain-oriented silicon steel sheet, and fixed to prevent misalignment. A brazing process was performed in a vacuum at 1050°C for 10 minutes to form a laminate. A portion of the frame (100 mm / 140 mm = approximately 71%) was composed of the above-mentioned laminate 320, and an integrated structure was obtained in which the elastic material layer 322 extending from the stress control unit 312 of the magnetostrictive element 310 and the entire frame 330 were integrated.

[0191] For comparison, an integrated structure was prepared by bonding grain-oriented electrical steel sheets bent into a U-shape of the same size as above and SUS430 at room temperature using an epoxy adhesive.

[0192] A 5000-turn detection coil 360 was mounted in the position of the resulting integrated structure corresponding to the magnetostrictive element. The length of the coil was 15 mm. Next, a 7 g tungsten weight 340 was glued and fixed next to the magnetostrictive element 310. Furthermore, an NdFeB magnet 350 was attached to the electromagnetic steel plate side of the lower fixing part of the U-shape, thereby obtaining a magnetostrictive power generation device 300 in which the entire frame is integrated with the magnetostrictive element.

[0193] The voltage of the magnetostrictive generating device 300 was measured in the same manner as in Example 11, and the performance of the magnetostrictive generating device was evaluated based on the peak voltage of the measured voltage waveform. The strength of the magnetic field applied to the magnetostrictor was estimated to be approximately 3600 A / m (450 e) for grain-oriented electrical steel sheets.

[0194] The measured resonant frequencies were 109 Hz for the brazed joint and 101 Hz for the bonded joint. The peak voltages are shown in Table 9.

[0195] [Table 9]

[0196] As is clear from Table 9, the device of Example 11, which is equipped with a magnetostrictive element that satisfies condition B (i.e., the electromagnetic steel sheet and the elastic material SUS430 are brazed together), has a peak voltage that is approximately 1.3 times higher than the device of Comparative Example 7, in which the electromagnetic steel sheet and the elastic material are bonded together with an adhesive. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between the lamination layers that occurs when bending strain is applied is suppressed, thereby improving the peak voltage.

[0197] Example 13 A magnetostrictive power generation device equipped with a magnetostrictive element consisting of electromagnetic steel sheet / brazing material / SUS304 / brazing material / electromagnetic steel sheet In Example 13, a magnetostrictive power generating device 400 having the structure shown in FIG. 8 was fabricated using grain-oriented electrical steel sheets as the electrical steel sheet layers 421 and SUS304 as the elastic material layers 422.

[0198] The electrical steel sheet layer 421 was a coated grain-oriented electrical steel sheet 27ZH100 manufactured by Nippon Steel Corporation. The thickness was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The piece was sheared and cut into two pieces, one with a length of 120 mm and a width of 6.0 mm, and the other with a length of 125 mm and a width of 6.0 mm. These were then bent into a U-shape as shown in Fig. 8. The length corresponding to the lower fixing part 470 was approximately 80 mm, and the length of the upper part where the detection coil 460 and weight 440 were attached was approximately 50 mm. After bending the grain-oriented electrical steel sheet into a U-shape, it was annealed in a vacuum at 800° C. for 2 hours to remove distortion.

[0199] SUS304, a non-magnetic material, was used for elastic material layer 422. The thickness was 0.5 mm, the length was approximately 140 mm, the width of the portion excluding fixed portion 470 was 6.0 mm, and the width of the portion including fixed portion 470 was 12 mm. A hole was drilled in part of fixed portion 470 so that grain-oriented electromagnetic steel sheet layer 421 could pass through.

[0200] As shown in Figure 8, grain-oriented electromagnetic steel plates were placed on both sides of the SUS304. At the fixed part, the outer magnetostrictive material passes through a hole opened in the SUS304 and comes into contact with the electromagnetic steel plate placed on the inside. The outer and inner electromagnetic steel plates are also in contact at the tip on the side where the weight 440 is placed. In this way, by bringing the outer and inner electromagnetic steel plates into contact, it becomes possible to efficiently magnetize the electromagnetic steel plates using a magnet. Furthermore, a height adjustment plate 490 made of SUS304 of the same thickness as the electromagnetic steel plate was adhered to the fixed part. The SUS304 molded into a U-shape was subjected to solution treatment by holding it at 1050°C for 1 minute in a vacuum and then gas quenching to remove the effects of cutting distortion.

[0201] A 35 μm thick amorphous foil with a BNi-2 composition was used as the brazing filler metal, and the foil was cut to a length of 100 mm and a width of 6.0 mm. The brazing filler metal was sandwiched between the outer and inner grain-oriented electrical steel sheets, which were bent into a U-shape, and the elastic material (SUS304) at the contact points, and the foil was fixed in place to prevent misalignment. The laminate 420 was then brazed in a vacuum at 1050°C for 10 minutes. A portion of the frame (100 mm / 140 mm = approximately 71%) was composed of the laminate 420, and the elastic material layer 422 extending from the stress control unit 412 of the magnetostrictive element 410 and the entire frame 430 were integrated into one body. Furthermore, a block of SUS304 was attached to the grain-oriented electrical steel sheet as a support 480 using an epoxy adhesive.

[0202] For comparison, an integrated structure was prepared by bonding grain-oriented electrical steel sheets bent into a U-shape of the same size as above and SUS304 at room temperature using an epoxy adhesive.

[0203] A 5000-turn detection coil 460 was loaded into the portion of the obtained integrated structure corresponding to the magnetostrictive element. The length of the coil was 15 mm. Next, a 7 g tungsten weight 440 was glued and fixed next to the magnetostrictive element 410. Furthermore, an NdFeB magnet 450 was attached to the electromagnetic steel plate side of the lower fixing part of the U-shape, thereby obtaining a magnetostrictive power generation device 400 in which the entire frame is integrated with the magnetostrictive element.

[0204] The voltage of the magnetostrictive generating device 400 was measured in the same manner as in Example 11, and the performance of the magnetostrictive generating device was evaluated based on the peak voltage of the measured voltage waveform. The strength of the magnetic field applied to the magnetostrictive element was estimated to be approximately 2800 A / m (350 e) for each of the inner and outer grain-oriented electrical steel sheets.

[0205] The measured resonant frequencies were 221 Hz for the brazed joint and 205 Hz for the bonded joint. The peak voltages are shown in Table 10.

[0206] [Table 10]

[0207] As is clear from Table 10, in the device of Example 12, which has two electromagnetic steel sheet layers and is equipped with a magnetostrictive element that satisfies condition B (i.e., the electromagnetic steel sheet and the elastic material SUS304 are brazed together), the peak voltage was improved by about 1.3 times compared to the device of Comparative Example 8, which has a magnetostrictive element in which the electromagnetic steel sheet and the elastic material are bonded together with an adhesive. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between the lamination layers that occurs when bending strain is applied is suppressed, thereby improving the peak voltage.

[0208] Example 14 Cross-sectional structure of the brazing material: Magnetostrictive element consisting of electromagnetic steel sheet / brazing material / electromagnetic steel sheet The magnetostrictive material used was a coated grain-oriented electrical steel sheet 35ZH115 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.35 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared and cut into a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0209] A BNi-2 amorphous foil, a Ni brazing filler metal with a length of 40 mm, a width of 6.0 mm and a thickness of 59 μm, was sandwiched between the two grain-oriented electrical steel sheets and brazed in a vacuum at 1050°C for 60 minutes to obtain a magnetostrictive element that satisfied condition A (i.e., had a brazing filler metal portion between the two electrical steel sheets). The composition of the brazing filler metal was as follows: BNi-2 composition: Ni-7.0%Cr-4.5%Si-3.0%B-3.0%Fe

[0210] The magnetostrictive element thus obtained was cut in the width direction, and the cross-sectional structure was subjected to elemental analysis along the lamination thickness direction using a SEM-EDS (JEOL JSM-7000F). The cross-sectional structure and the results of the elemental analysis are shown in Figure 9.

[0211] Elemental analysis was performed along the analysis line shown in Figure 9. The Fe concentration profile was high inside the electrical steel sheet and very low at the center of the brazing filler metal. On the other hand, the Ni concentration profile was high within the brazing filler metal and very low at the center of the electrical steel sheet. However, at the contact surface between the electrical steel sheet and the brazing filler metal and its vicinity, as indicated by the circle in the figure, there was an alloyed region where Fe from the electrical steel sheet and Ni from the Ni-based brazing filler metal were alloyed. The concentrations of Fe and Ni were determined by performing point analysis using EDS at multiple locations along the analysis line shown in Figure 9 and quantifying the composition of each location. At a position 1 μm toward the brazing filler metal from the contact surface between the electrical steel sheet and the Ni-based brazing filler metal on the left side of Figure 9, the Fe concentration was approximately 64 mass%, which was more than [Fe concentration of the brazing filler metal used: 3 mass%] + 0.2 mass%. Furthermore, at a position 1 μm toward the electrical steel sheet from the contact surface between the electrical steel sheet and the Ni-based brazing filler metal, the Ni concentration was approximately 1.1 mass%, which was a value equal to or greater than [Ni concentration of the electrical steel sheet used: 0 mass%] + 0.2 mass%. Therefore, at the contact surface between the electrical steel sheet and the Ni-based brazing filler metal, there was an alloyed region of Fe and Ni with a width of 1 μm or more on both the electrical steel sheet side and the brazing filler metal side, i.e., a total of 2 μm or more.

[0212] Example 15 ΔB of magnetostrictive element consisting of grain-oriented electrical steel sheet / brazing material (Fe-based) / SUS304 The magnetostrictive material used was a coated grain-oriented electrical steel sheet 27ZH100 manufactured by Nippon Steel Corporation. The thickness of the electrical steel sheet was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The sheet was sheared and cut into a length of 40 mm and a width of 6.0 mm in the direction perpendicular to the sheet. To remove distortion caused by cutting, the sheet was annealed in a vacuum at 800°C for 2 hours to obtain a grain-oriented electrical steel sheet for a magnetostrictive element.

[0213] The elastic material was a 0.5 mm thick cold-rolled sheet of non-magnetic SUS304. After cutting it into a length of 40 mm and a width of 6.3 mm, it was held in a vacuum at 1050°C for 1 minute and then gas quenched to remove the effects of cutting distortion, yielding an elastic material for magnetostrictive elements.

[0214] The brazing filler metal used was a powdered Fe brazing filler metal with the following composition: The powder size was 150 μm or less, and the brazing filler metal had the following composition. Fe-based brazing filler metal composition: Fe-20%Cr-20%Ni-5.0%Si-8.0%P-2.0%Mo

[0215] Powdered brazing filler metal was mixed with an organic binder and applied to one side of SUS304. An electromagnetic steel sheet was then placed on the applied surface and brazed in a vacuum at 1100°C for 30 minutes to obtain a magnetostrictive element that satisfied condition B. The thickness of the brazing filler metal was 23 μm. The organic binder was volatilized and removed during the brazing temperature rise.

[0216] ΔB of the produced magnetostrictive element was measured in the same manner as in Example 5. The results are shown in Table 11, along with the measurement results of the magnetostrictive element of Comparative Example 2 produced in Example 5 using an adhesive instead of a brazing material.

[0217] [Table 11]

[0218] As is clear from the results in Table 11, the magnetostrictive element of Example 13, which satisfies condition B and is made by brazing an electromagnetic steel sheet to an elastic material such as SUS304, has an improved ΔB of approximately 1.5 times that of the magnetostrictive element of Comparative Example 2, which is bonded with an adhesive. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between laminations when bending strain is applied is suppressed, thereby improving ΔB.

[0219] Example 16 Magnetostrictive power generation device equipped with a magnetostrictive element consisting of electrical steel sheet / brazing material (Fe-based) / SUS304 A magnetostrictive generating device having the same structure as the magnetostrictive generating device 200 shown in Fig. 6 was fabricated in the same manner as in Example 11. However, the Ni-based brazing filler metal used in Example 11 was changed to the same Fe-based brazing filler metal used in Example 15. A grain-oriented electrical steel sheet was used as the electrical steel sheet layer 221, and SUS304 was used as the elastic material layer 222, in the same manner as in Example 11 except for the change in the brazing filler metal.

[0220] The electrical steel sheet layer 221 was a coated grain-oriented electrical steel sheet 27ZH100 manufactured by Nippon Steel Corporation. The thickness was 0.27 mm and the crystal orientation was {110} <001> The longitudinal direction of the grain-oriented electrical steel sheet is the GOSS texture. <001> The piece was sheared and cut to a length of 100 mm and a width of 6.1 mm in the direction indicated by the arrows. The piece was then bent into a U-shape as shown in Fig. 6. The length corresponding to the lower fixing part 270 was approximately 40 mm, and the length of the upper part where the detection coil 260 and weight 240 were attached was approximately 40 mm. After bending the grain-oriented electrical steel sheet into a U-shape, it was annealed in a vacuum at 800° C. for 2 hours to remove distortion.

[0221] A non-magnetic material, SUS304, with a thickness of 0.5 mm and a width of 6.1 mm was used for the elastic material layer 222. It was cut to a length of 140 mm so that it could be integrated with the U-shaped electromagnetic steel plate, and then molded into a U-shape to adjust the shape. The SUS304 was molded into a U-shape and held at 1050°C for 1 minute in a vacuum, after which it was subjected to solution treatment by gas quenching to remove the effects of cutting distortion.

[0222] The brazing filler metal used was an Fe-based brazing filler metal mixed with the same organic binder as in Example 15. The brazing filler metal was applied between a grain-oriented electrical steel sheet bent into a U-shape and a SUS304 steel sheet, and they were fixed to prevent misalignment. A brazing process was performed in a vacuum at 1100°C for 30 minutes to form a laminate. A portion of the frame (100 mm / 140 mm = approximately 71%) was composed of the laminate 220, and the elastic material layer 222 extending from the stress control section 212 of the magnetostrictive element 210 and the entire frame 230 were integrated to obtain an integrated structure of Example 14. The brazing filler metal had a thickness of 33 μm. The organic binder was volatilized and removed during the brazing temperature rise.

[0223] The peak voltage of the obtained magnetostrictive element of the integral structure was measured in the same manner as in Example 11. The results are shown in Table 12 together with the measurement results of the magnetostrictive element of Comparative Example 6, which was produced in Example 11 and used an adhesive instead of a brazing material. The measured resonant frequency was 107 Hz.

[0224] [Table 12]

[0225] As is clear from Table 12, the device of Example 14, which includes a magnetostrictive element that satisfies condition B (i.e., an electromagnetic steel sheet and an elastic material, SUS304, brazed together), had a peak voltage that was approximately 1.4 times higher than the device of Comparative Example 6, which includes a magnetostrictive element in which an electromagnetic steel sheet and an elastic material were bonded together with an adhesive. This is thought to be because, by changing from lamination using an adhesive such as resin to lamination using a brazing metal with a large Young's modulus, relaxation of strain between the lamination layers that occurs when bending strain is applied is suppressed, thereby improving the peak voltage.

[0226] Example 17 Bonding strength of Fe-based brazing filler metal A laminate (test piece) for a tensile test to measure the bonding strength was prepared in the same manner as in Example 1, except that the brazing filler metal was changed to the Fe-based brazing filler metal used in Example 15. As the brazing material, a powdered Fe brazing material having the following composition was used. Fe-based brazing filler metal composition: Fe-20%Cr-20%Ni-5.0%Si-8.0%P-2.0%Mo

[0227] Powdered brazing filler metal was mixed with an organic binder and applied to one side of one electrical steel sheet. Another electrical steel sheet was then placed on top of the applied surface, and brazing was performed in a vacuum at 1100°C for 30 minutes to obtain a laminate satisfying condition A. The thickness of the brazing filler metal was 26 μm. The organic binder was volatilized and removed during the brazing temperature rise.

[0228] The obtained test piece was subjected to a tensile test in the same manner as in Example 1. As a result, no fracture occurred at the joint, but fracture occurred in the base material.

[0229] Example 18 Durability of magnetostrictive elements consisting of electromagnetic steel sheet / brazing material (Fe-based) / electromagnetic steel sheet A laminate for measuring durability was produced in the same manner as in Example 2, except that the brazing filler metal was changed to the Fe-based brazing filler metal used in Example 15. As the brazing material, a powdered Fe brazing material having the following composition was used. Fe-based brazing filler metal composition: Fe-20%Cr-20%Ni-5.0%Si-8.0%P-2.0%Mo

[0230] Powdered brazing filler metal was mixed with an organic binder and applied to one side of one electrical steel sheet. Another electrical steel sheet was then placed on top of the applied surface, and brazing was performed in a vacuum at 1100°C for 30 minutes to obtain a laminate satisfying condition A. The thickness of the brazing filler metal was 25 μm. The organic binder was volatilized and removed during the brazing temperature rise.

[0231] The rate of decrease in ΔB after the durability test was measured in the same manner as in Example 2. The results are shown in Table 13, along with the measurement results of the magnetostrictive element of Comparative Example 1, which was produced in Example 2 and used an adhesive instead of a brazing material.

[0232] [Table 13]

[0233] As is clear from the results in Table 13, the magnetostrictive element of Example 15 of the invention, which satisfies condition A and is made by brazing two electromagnetic steel plates together with an Fe-based brazing filler metal, has a smaller decrease in ΔB and improved durability compared to the magnetostrictive element of Comparative Example 1, which is joined with an adhesive. [Industrial Applicability]

[0234] The present invention provides a magnetostrictive power generation element and a magnetostrictive power generation device that are lower in cost than the FeGa alloys, FeCo alloys, and FeAl alloys used as magnetostrictive materials for magnetostrictive power generation elements, while achieving high durability and magnetostrictive power generation equivalent to or exceeding that of conventional technologies.The magnetostrictive power generation element of the present invention is lower in cost than conventional magnetostrictive elements, yet is capable of achieving equivalent to or exceeding that of conventional magnetostrictive elements, and is therefore useful as a power source for various devices, including wireless sensor modules in IoT and the like. [Explanation of symbols]

[0235] 1 Magnetostrictive element 2 Fixed part 100 Magnetic flux density change ΔB measurement unit 110 Magnetostrictive element 111 Magnetostrictive part 112 Stress control section 120 Bias magnetic field coil 130 detection coil 140 DC power supply 150 Fixed support base 160 Flux Meter 170 Pressure 171 Distance traveled 200, 300, 400 Magnetostrictive power generation device 210, 310, 410 Magnetostrictive elements for power generation 211, 311, 411 Magnetostrictive part (magnetic steel sheet layer) 212, 312, 412 Stress control section (elastic material layer) 220, 320, 420 laminate 221, 321, 421 electrical steel sheet layer 222, 322, 422 Elastic material layer 230, 330, 430 frames 240, 340, 440 weight 250, 350, 450 magnets 260, 360, 460 detection coil 270, 370, 470 Fixed part 480 Post 490 Height Adjustment Board

Claims

1. A magnetostrictive element for power generation formed of a laminate including at least one electromagnetic steel sheet layer, the magnetic steel sheet layer includes at least one magnetic steel sheet, The laminate satisfies at least one of the following conditions A and B: Condition A: The at least one electromagnetic steel sheet layer includes two or more electromagnetic steel sheets, and the two or more electromagnetic steel sheets are joined to each other via a brazing filler metal portion; and Condition B: The laminate further includes at least one elastic material layer, and the at least one electromagnetic steel sheet layer is joined to the elastic material layer via a brazing material portion. The brazing filler metal portion is a brazing filler metal portion containing Ni as a main element or a brazing filler metal portion containing Fe as a main element, the brazing filler metal portion containing Ni as a main element contains at least one element selected from the group consisting of Cr, Si, Fe, B, P, C, Cu, and Mo, and further contains at least one oxide selected from the group consisting of Mg oxide, Cr oxide, and Si oxide; A magnetostrictive element for power generation, wherein the brazing filler metal portion containing Fe as a main element contains at least one element selected from the group consisting of Cr, Ni, Si, B, P, C, Cu, and Mo, and further contains at least one oxide selected from the group consisting of Mg oxide, Cr oxide, and Si oxide.

2. 2. The magnetostrictive element for power generation according to claim 1, wherein said laminate satisfies only said condition A.

3. 3. The magnetostrictive element for power generation according to claim 2, wherein the laminate further includes at least one elastic material layer, the elastic material layer being bonded to the magnetic steel sheet layer.

4. 2. The magnetostrictive element for power generation according to claim 1, wherein the laminate satisfies the conditions A and B.

5. the at least one electromagnetic steel sheet layer is made of one electromagnetic steel sheet, 2. The magnetostrictive element for power generation according to claim 1, wherein said laminate satisfies only said condition B.

6. 6. The magnetostrictive element for power generation according to claim 1, wherein at least one of the electromagnetic steel sheets included in the electromagnetic steel sheet layer is a grain-oriented electromagnetic steel sheet.

7. 6. The magnetostrictive element for power generation according to claim 1, wherein at least one of the electromagnetic steel sheets included in the electromagnetic steel sheet layer is a non-oriented electromagnetic steel sheet.

8. 8. The magnetostrictive element for power generation according to claim 1, wherein the elastic material layer is made of a non-magnetic material.

9. 9. The magnetostrictive element for power generation according to claim 1, wherein the brazing filler metal portion contains Ni as a main element.

10. a region in which Fe derived from the electromagnetic steel sheet and Ni derived from the brazing filler metal portion are alloyed is present in at least one contact surface between the electromagnetic steel sheet and the brazing filler metal portion present in the magnetostrictive element for power generation, 10. The magnetostrictive element for power generation according to claim 9, wherein, in an elemental analysis of a cross section in the thickness direction of the magnetostrictive element for power generation, the alloyed region exists over a width of 2 [mu]m or more.

11. 9. The magnetostrictive element for power generation according to claim 1, wherein the brazing filler metal portion contains Fe as a main element.

12. 12. The magnetostrictive element for power generation according to claim 9, wherein the at least one oxide in the brazing material portion is in the form of a block.

13. The magnetostrictive element for power generation according to any one of claims 1 to 12, a frame coupled to the magnetostrictive element for power generation; A magnetostrictive power generation device comprising:

14. The magnetostrictive power generation device according to claim 13 , wherein the magnetostrictive element for power generation and the frame are continuous, and at least a portion of the frame is configured by a laminate that forms the magnetostrictive element for power generation.

15. The magnetostrictive power generation device according to claim 14 , wherein the entire frame is integral with an electromagnetic steel plate extending from a laminate that forms the magnetostrictive element for power generation.

16. 15. The magnetostrictive power generating device according to claim 14, wherein the laminated bodies include an elastic material, and the entire frame is integral with the elastic material extending from the laminated bodies that form the magnetostrictive element for power generation.

17. The magnetostrictive power generation device according to claim 14 , wherein the entire frame is integral with the magnetostrictive element for power generation.

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