Vibratory power generator, low-load device, and power storage system

Abstract

A vibratory power generator 1 uses vibration that is transmitted from the outside to generate power. The vibratory power generator 1 includes a housing 10 that receives the vibration, a beam 21 that is formed from a flexible, non-magnetic material, is fixed to the housing at one end, and extends in the longitudinal direction at another, free end, a core 22 that is provided to the free end side of the beam, a coil 23 that is wound around the core, a permanent magnet 31 that is fixed at a position that is opposite the core, and a back yoke 32 that is formed from a magnetic material, is provided so as to cover the permanent magnet except a surface that is opposite the core, and has the opposite polarity of the permanent magnet. The vibratory power generator outputs induced voltage that is generated in the coil as a result of the vibration received by the housing being transmitted to the beam and the core vibrating relative to the permanent magnet.

Description

Vibration power generator, low load device and power storage system

[0001] The present invention relates to a vibration-generated power generator that generates power by utilizing vibrations transmitted from the outside, and to a low-load device and a power storage system that include the vibration-generated power generator.

[0002] The movement to automate maintenance using sensors is accelerating in various fields. For example, sensors are being installed on bridges and roads to diagnose deterioration. Sensors that detect and record the environment of such objects, preferably automatically, are called environmental sensors. It is desirable to install multiple environmental sensors in locations that require monitoring. They are positioned as low-load devices requiring approximately 3 W to measure and transmit data such as displacement, acceleration, temperature, and humidity. Therefore, the development of low-cost, mass-producible energy-harvesting power sources to power these sensors is desirable. In the following descriptions, units are also enclosed in square brackets [ ]. Solar power generation is an example of an energy-harvesting power source, but its power generation efficiency depends on sunlight conditions, making it unsuitable for installation in locations where sunlight cannot be ensured.

[0003] Vibration power generation, a type of energy harvesting, converts kinetic energy from vibrations generated by people or objects moving, the rotation of doors or wheels, or the flow of water into electrical energy. It can operate autonomously even in environments where solar cells cannot be used, and is expected to be applied to bridge piers, roads, and other areas where periodic vibrations occur. The main types of vibration power generation include inverse magnetostriction and electromagnetic induction as current sources, and piezoelectric and electrostatic induction as voltage sources. Even inverse magnetostriction and electromagnetic induction types, which have a power generation output of over 100 mW, there are issues such as the inability to generate sufficient power from weak vibrations, or the inability to mass-produce them due to their complex and expensive structure. Therefore, they are currently being applied to devices with limited sensor functions to reduce power consumption.

[0004] The principle of inverse magnetostrictive vibration power generation is that when a highly magnetostrictive material is subjected to strain by vibration, the magnetic flux density increases or decreases, generating an induced voltage in a coil. Methods for increasing the induced voltage include increasing the number of turns N of the coil, increasing the cross-sectional area of ​​the coil, and selecting a highly magnetostrictive material for the power generation element.

[0005] As an example of an inverse magnetostrictive type, Patent Document 1 discloses a power generating element that combines an inverse magnetostrictive element with a U-shaped frame yoke and a permanent magnet. A magnetic circuit including a permanent magnet increases the excitation and magnetization of the magnetostrictive element, thereby increasing the fluctuation of magnetic flux density and thereby increasing the amount of power generated. The induced voltage of an inverse magnetostrictive element is on the order of a few volts. In order to increase the induced voltage, the number of coil turns N (N≧3000) and the coil cross-sectional area must be increased, which inevitably leads to an increase in the size of the device. Furthermore, the material of the magnetostrictive element contains expensive rare earth elements (Tb, Dy), which poses a problem of increased manufacturing costs for mass production.

[0006] The principle of electromagnetic induction vibration power generation is to move a magnet in and out of an air-core coil, increasing or decreasing the magnetic field lines in the coil, thereby generating an induced voltage in the coil. It has a simple structure and can be constructed using only inexpensive materials, but it requires large vibrations to move the magnet, and like the inverse magnetostrictive type, it has the problem of increasing in size to increase the induced voltage.

[0007] As another example of the electromagnetic induction type, Patent Document 2 discloses a method that uses a core made of amorphous alloy foil, which has a higher magnetic permeability than an air-core coil (relative magnetic permeability of up to 1). Power is generated when the core, which flexes and deforms due to external vibration, shifts from a magnet placed opposite the core, and because the increase and decrease in magnetic flux density within the coil can be made greater than with the air-core coil, effective power can reach milliwatt levels.

[0008] JP 2023-081696 A JP 2017-225261 A

[0009] Borozoth.Ferromagnetizm. pp.845-849 (2003 edition). Wiley-IEEE Press(1978)Li, H., Tian, ​​C., & Deng, ZD (2014). Energy harvesting from low frequency applications using piezoelectric materials. Applied physics reviews, 1(4). "Elucidation of the impact force generation mechanism due to wheel flats using FEM analysis." Saito, R., Sakai, H., Journal of Railway Engineering, August 1, 2024

[0010] The above-mentioned conventional methods all use weak vibrations of a few Hz to a few tens of Hz (less than 1 G; G is the gravitational acceleration of 9.8 [m / s 2 ]), making it difficult to obtain sufficient output from the sensor, and providing a stable power supply to the environmental sensor.

[0011] The generated voltage V (also called induced voltage) is expressed by the following equation: where N is the number of turns in the coil and δφ / δt is the change in magnetic flux density.

[0012]

[0013] The vibration power generation device described in Patent Document 1 uses an inverse magnetostrictive element, and it is necessary to increase the number of turns in the coil to increase the power generation output. Since an increase in the number of turns directly leads to an increase in the weight and size of the device, as well as an increase in the number of processes required for mass production, reducing the number of turns is an issue. According to the above-mentioned Equation 1 for induced voltage, it is expected that the number of turns in the coil can be reduced by increasing the change in magnetic flux density.

[0014] The reason why the inventions described in Patent Documents 1 and 2 fail to obtain sufficient power generation output is due to the small increase and decrease in magnetic flux density. In both cases, maximum output is obtained at the natural frequency of the cantilever, i.e., the resonance point where maximum amplitude is obtained. The magnetic flux density φ induced in the core by magnetostriction in Patent Document 1 changes gradually (δφ / δt) in synchronization with the displacement of the free end of the yoke. In the electromagnetic induction method described in Patent Document 2, the magnet has only one magnetic pole, and no magnetic pole reversal (from north pole to south pole or vice versa) occurs, so the rate of change in magnetic flux density is small. In other words, the timing of the maximum coil movement speed due to vibration does not coincide with the timing of the maximum change in magnetic flux density, resulting in a configuration that cannot maximize power generation output.

[0015] As shown in Non-Patent Document 1, environmental vibrations in suburban areas without power sources that require monitoring exist at frequencies below 50 Hz. Current vibration power generation technologies target frequencies in the hundreds of Hz range generated by mechanical vibrations, and the issue is that there are very few vibration power generation technologies that can handle environmental vibrations in the low-frequency range of a few Hz to a few tens of Hz.

[0016] Furthermore, the inverse magnetostrictive type of Patent Document 1 uses a magnetostrictive alloy containing expensive rare earths (Tb, Dy) to increase the magnetic flux density change, which poses a problem for mass production. Therefore, with a view to mass production, it is desirable to use an apparatus configuration that uses an Fe-based soft magnetic alloy that is low in cost and has a low environmental impact, or in some locations, resin, etc.

[0017] In order to apply vibration-based power generators to low-load devices such as environmental sensors described in the background art, as well as to power storage systems, it is essential that they operate at low frequencies with weak vibrations and have high output. To reduce manufacturing and maintenance costs, they are also required to have a small and simple device configuration.

[0018] The present invention was devised in light of these problems, and aims to provide a vibration-based power generator that generates electricity with weaker vibrations and has a higher output than conventional inverse magnetostrictive vibration-based power generators by configuring it so that magnetic pole reversal occurs at the point where the physical displacement of the coil that moves due to vibration is greatest, thereby maximizing the induced voltage. Another aim is to provide a power generator with a simple structure that can be mass-produced and at a low price.

[0019] (1) The vibration generator disclosed herein generates electricity by utilizing vibrations transmitted from the outside and includes a housing that receives the vibrations, a beam formed of a flexible non-magnetic material and extending in the longitudinal direction with one end fixed to the housing and the other end being a free end, a core provided on the free end side of the beam, a coil wound around the core, a permanent magnet fixed in a position facing the core, and a back yoke formed of a magnetic material that is provided to cover the permanent magnet except for the surface facing the core and that has an opposite magnetic polarity to the permanent magnet, and outputs an induced voltage that is generated in the coil when the vibrations received by the housing are transmitted to the beam and the core vibrates relative to the permanent magnet.

[0020] (2) In the above (1), it is preferable that the core is configured as a flat magnetic material that satisfies a / t≧5 and b / t≧5, where a is the longitudinal length of the core, b is the width of the core, and t is the thickness of the core.

[0021] (3) In the above (2), it is preferable that the permanent magnet satisfies t≦h≦20*t and w≧b, where h is the height of the permanent magnet and w is the width of the permanent magnet.

[0022] (4) In the above (1), it is preferable that the core and the surface of the permanent magnet facing the core face each other with a predetermined distance therebetween when the beam is stationary.

[0023] (5) In (4) above, it is preferable that the predetermined distance has a lower limit value of the distance at which the core does not adhere to the surface of the permanent magnet when the core vibrates relative to the permanent magnet, and an upper limit value of the distance at which the core does not deviate from the magnetic field in space from the permanent magnet.

[0024] (6) In any one of the above (1) to (5), it is preferable that the beam has a lead wire electrically connected to the coil.

[0025] (7) In the above (1), it is preferable that the beams are resonant with vibrations received by the housing.

[0026] (8) In the above (1), it is preferable that the beams are provided in plurality, and each of the beams has a different length in the longitudinal direction.

[0027] (9) In the above (1), it is preferable that there are multiple beams, the multiple beams have the same longitudinal length, and the masses of the core and the coil provided at the free end of each of the multiple beams are different.

[0028] (10) In the above (1), it is preferable that the beams are provided in plurality, and each of the beams has the same length in the longitudinal direction but different thicknesses.

[0029] (11) It is preferable that the low-load device includes the vibration-generator described above in (1).

[0030] (12) The power storage system preferably includes the vibration-driven power generator described above in (1).

[0031] The disclosed vibration-based power generator can generate electricity in response to weak vibrations in a lower frequency band than conventional inverse magnetostrictive vibration-based power generators, and has a large output. Furthermore, because it has a simple structure that can be mass-produced, it can be provided at an affordable price.

[0032] 1 is a schematic perspective view illustrating the overall configuration of a vibration-generating power generator according to an embodiment. It is a schematic plan view of the vibration-generating power generator of FIG. 1 as viewed from above. It is a schematic side view of the vibration-generating power generator of FIG. 1 as viewed from the side. It is a schematic enlarged side view for explaining the configurations of the vibration unit and magnetic unit of FIG. 1. It is a table showing the conditions for configurations a to g of vibration-generating power generators. FIGS. 6A, 6B, and 6C are diagrams showing configurations a to c of vibration-generating power generators based on the conditions in Table 1 of FIG. 5. FIGS. 7A, 7B, and 7C are graphs of induced voltages for configurations a to c of the vibration-generating power generator shown in FIG. 6. FIGS. 8A, 8B, and 8C are graphs of time waveforms of the power generation output of configurations a to c of the vibration-generating power generator shown in FIG. 6. FIG. 9 is a diagram showing the relationship between the maximum induced voltage at the open end and the vibration frequency when a back yoke is applied to the magnetic unit and when it is not applied. FIG. 9A is a graph showing the results for configuration b of the magnetic unit shown in FIG. 6, and FIG. 9B is a graph showing the results for configuration c of the magnetic unit shown in FIG. 6. FIG. 10A is a graph showing the relationship between open-end power generation output and acceleration with and without a back yoke applied to the magnetic unit, and the relationship between the effective value (effective power) of power generation output and acceleration. FIG. 10B is a graph showing the results for magnetic unit configuration b shown in FIG. 6, and FIG. 10B is a graph showing the results for magnetic unit configuration c shown in FIG. 6. FIG. 11 is a graph showing the relationship between maximum effective power output and load resistance. It is a graph showing the results for a load maximum power evaluation circuit in which load resistance R is connected to the vibration-generator configuration b shown in FIG. 6. FIGS. 12A, 12B, 12C, and 12D are graphs of induced voltage for vibration-generator configurations d to g shown in FIG. 5. FIGS. 13A, 13B, 13C, and 13D are graphs of the time waveforms of power generation output for vibration-generator configurations d to g shown in FIG. 5. FIGS. 14A and 14B are graphs showing the relationship between induced voltage in the coil and time when the free end of the beam is flicked with a finger in the vibration-generator configurations b and c shown in FIG. 5 without using a vibration tester. Fig. 15A is a graph showing the relationship between the maximum induced voltage and the distance Gap for the vibration-generated power generators of configurations b and c shown in Fig. 5, and Fig. 15B is a graph showing the relationship between the damping constant β approximated by Equation 2 and the distance Gap for the vibration-generated power generators of configurations b and c shown in Fig. 5. Figs. 16A and 16C are mapping results of measurements of the magnetic field in space from the permanent magnets for the vibration-generated power generators of configurations b and c shown in Fig. 5.16B and 16D are graphs showing the relationship between the distance and the partial differential of the magnetic flux in the vertical direction in configurations b and c.

[0044] FIG. 18A, 18B, and 18C are schematic plan views showing, from above, various different configurations i to iii for obtaining the frequency characteristics of the induced voltage shown in FIG. 17.

[0033] A vibration-driven power generator according to an embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or applications of techniques not explicitly described in the following embodiments. The configurations of the embodiments can be modified in various ways without departing from the spirit of the embodiments. Furthermore, they can be selected or combined as needed.

[0034] In this specification, the direction of the double-headed arrow X in each drawing is the left-right direction, the direction of the double-headed arrow Y is the up-down direction, and the direction of the double-headed arrow Z, which is perpendicular to the left-right and up-down directions, is the depth direction (front-back direction; see FIG. 1 ). In the embodiments described below, an example will be given in which the vibration power generator 1 is fixed to a horizontal, flat surface (for example, a floor or a road), and therefore the up-down direction coincides with the vertical direction.

[0035] 1 to 4, the vibration power generator 1 of this embodiment is composed of a housing 10, a vibration unit 20 and a magnetic unit 30 provided in the housing 10, and is fixed to a vibration source (not shown). When vibrations are transmitted to the vibration power generator 1 fixed to the vibration source, the housing 10 is subjected to vibration, and the vibration unit 20 vibrates relative to the magnetic unit 30 inside the housing 10, thereby generating electric power. The magnetic unit 30 in FIGS. 1 to 4 is described using the configuration a in FIGS. 5 and 6A as an example, but configurations b, d to g having other back yokes shown in FIG. 5 may also be applied, and the principle is the same for all of them.

[0036] The housing 10 is a base for receiving vibrations transmitted from the outside and is made of, for example, stainless steel or resin. The housing 10 is open upward and in the front-to-rear directions. That is, the housing 10 is shaped (U-shaped when viewed from the front-to-rear direction) surrounded by left and right side surfaces and a bottom surface, with the vibration unit 20 disposed inside one of the left and right side surfaces, and the magnetic unit 30 disposed inside the other side surface so as to face the vibration unit 20. For the sake of explanation, FIGS. 1 to 4 show the fixed end of the beam 21 and the magnetic unit 30, which are integrated with the housing 10, by dashed lines.

[0037] The vibration unit 20 is composed of a beam 21, a core 22 made of a magnetic material, and a coil 23 wound around the core 22. The beam 21 is a member that temporarily deforms due to vibrations transmitted from a vibration source and periodically fluctuates around a rest position depending on the direction in which the housing 10 vibrates (e.g., the Y direction in FIG. 4 ). The beam 21 has one end fixed to the housing 10 and the other end as a free end, and is fixedly supported by the housing 10 in a so-called cantilever state. The longitudinal length of the beam 21 is determined depending on the vertical length of the housing 10, and is desirably set to a length that prevents the free end from colliding with the bottom surface of the housing 10 when the beam 21 vibrates up and down to its maximum extent. Similarly, the position at which the beam 21 is fixed within the housing 10 is desirably set to a position suitable for the vertical vibration of the beam 21.

[0038] The beam 21 extends in the longitudinal direction and has, for example, a long plate shape (a flat plate shape extending in the X direction). The beam 21 is made of a flexible non-magnetic material. Examples of non-magnetic materials include non-magnetic steel (such as spring steel), carbon fiber, and resin materials (such as hard polyvinyl chloride plates, low-foam PVC plates, PET resin plates, and polystyrene plates). Spring steel and resin materials have excellent rigidity, transmit force easily, and are inexpensive.

[0039] The beam 21 preferably resonates at a resonant frequency of 50 Hz or less, and more preferably at a wide frequency band between 0.1 and 30 Hz. Note that the configuration of the vibration power generator 1 can be adapted to different resonant frequency bands (for example, resonant frequencies of 100 to 500 Hz) by changing the length of the beam 21. In this way, the configuration of the vibration power generator 1 makes it possible to obtain a wide range of resonant frequencies, both low and high.

[0040] The core 22 is provided on the free end side of the beam 21. The longitudinal end face of the core 22 (the free end side of the beam 21) faces one side of the permanent magnet 31. A gap (the distance Gap described below) is provided between the opposing core 22 and permanent magnet 31. This gap refers to the distance between the core and the permanent magnet, and may be simply referred to as the distance or gap below. The range of the gap that allows the core 22 to be fully magnetized and saturated in a short time and does not interfere with the vibration of the beam 21 is preferably 0.5 mm≦Gap≦10 mm. It was confirmed that this range of the gap is also desirable in Example 7 described below.

[0041] The core 22 is formed of a soft magnetic material with high magnetic permeability. The use of a soft magnetic material allows for rapid absorption of surrounding magnetic flux, thereby increasing the magnetic flux and the rate of change of the magnetic flux, thereby increasing the induced electromotive force (induced voltage) generated. Examples of soft magnetic materials include amorphous metals, specifically amorphous ribbons (amorphous foils) and electromagnetic steel sheets. The core 22 may be formed in any shape as long as it can be attached to the free end of the beam 21; for example, a flat plate shape is preferable. A flat core 22 can be firmly coupled to the beam 21, which is formed in a long plate shape. The core 22, around which the coil 23 is wound, can be coupled to the beam 21 by, for example, adhesive bonding, joining (welding, fusion welding, etc.), or fastening.

[0042] The core 22 is desirably configured as a flat magnetic body that satisfies a / t≧5 and b / t≧≧5, where a is the longitudinal length of the core 22, b is the width (see FIG. 2), and t is the thickness (see FIG. 3). The thinner t is, the more the demagnetizing field of the mechanism that suppresses the magnetization of the core is suppressed, and the shape magnetic anisotropy of the thin plate shape can increase the magnetization reversal speed in the in-plane direction of the plate.

[0043] To explain the relationship between the shape of the core 22 and the demagnetizing factor N, the effective magnetic field Heff in a direction parallel to the longitudinal length a of the core 22 (the side of the flat plate) is expressed as Heff = Hex-NM (Hex is the external magnetic field, N is the demagnetizing factor, and M is the magnetization). For example, as described in the Demagnetization Factor section of Borozot's Ferromagnetizm, Wiley-IEEE Press (Non-Patent Document 1), for a flat plate with a / t > 5, the demagnetizing factor N when magnetized in the a direction is 0.01 or less. In terms of ease of magnetization, soft magnetic materials with low saturation magnetization inherently have a small demagnetizing field, so a size of approximately a > 5t is considered. While thinner materials are indeed more easily magnetized, the absolute value of magnetization decreases as they become thinner, whereas the demagnetizing factor depends only on the shape, so it is not necessary to set absolute upper limits for a and b. In practice, upper limits are set according to the size of the device.

[0044] A coil 23 is wound around the core 22. For the sake of explanation, Figures 1 to 3 show the coil 23 roughly wound around the core 22, but as shown in Figure 4, it is desirable for the coil 23 to be wound so as to cover the entire core 22. The coil is wound as shown in Figure 1, and is wound around the core 22 so that the magnetic flux of the permanent magnet 31 interlinks within the coil 23. The material of the coil 23 is formed from a conducting wire, such as enameled copper wire. The core 22 around which the coil 23 is wound is fixed to the beam 21 by an existing method.

[0045] A lead wire 41 is electrically connected to the coil 23. The lead wire 41 is connected to an external device. Examples of the external device include a sensor, a communication device, a measuring device (such as an oscilloscope, a voltmeter, or a wattmeter), and a capacitor (not shown) connected via a storage circuit including a rectifier circuit and a capacitor. Other devices will be described in [4. Application Examples] below.

[0046] 1 and 4, the magnetic unit 30 is composed of a permanent magnet 31 and a back yoke 32, which is a magnetic body arranged around the permanent magnet. Hereinafter, the back yoke may be simply referred to as BY in the text or drawings.

[0047] 4, the north pole of permanent magnet 31 and the south pole induced above and below back yoke 32 by the magnetic pole on the opposite side face the end of core 22. In this way, magnetic unit 30, in which permanent magnet 31 and back yoke 32 are integrated, is provided so that the surface facing core 22 is exposed on the surface of housing 10.

[0048] The permanent magnet 31 is fixed at a position facing the core 22. In the examples shown in Figures 1 and 4, the polarity of the permanent magnet 31 is such that the side facing the core 22 is a north pole and the opposite side is a south pole, but the polarity may be reversed.

[0049] The size of the surface of the permanent magnet 31 exposed on the surface of the housing 10 preferably satisfies t≦h≦20*t and w≧b (where b is the core width; see FIG. 2), where t is the core thickness, h is the height of the permanent magnet 31, and w is the width of the permanent magnet 31 (see FIG. 1). This thickness range is one that fully saturates the core in a short time and does not interfere with the vibration of the beam. In this case, the central magnetic flux density is preferably greater than 4 kOe (0.4 T). The length of the permanent magnet 31 in the depth direction is not important as long as it can generate a magnetic field of 0.4 T or more that interlinks with the coil 23 of the core 22. t≦h≦20*t is a range that prevents the core 22 from being attracted to the permanent magnet 31 and attenuating when the beam 21 vibrates. It is also a range that allows the movement of the beam 21 to cause a large change in magnetic flux when the magnetic poles of the multiple permanent magnets 31 are changed. w≧b is necessary to fully saturate the entire width of the core.

[0050] Note that if b (the width of the core 22) and the widthwise length of the beam 21 (the width of the beam 21) b' (the length in the Z direction in FIG. 1; see FIG. 2) are approximately the same length, b can be replaced with b'. In this case, it is desirable that the size of the surface of the permanent magnet 31 exposed on the surface of the housing 10 satisfy t≦h≦20*t and w≧b'. As described below, the entire permanent magnet 31 except for the surface facing the core 22 is covered by the back yoke 32, so that the magnetic flux generated by the permanent magnet 31 can be concentrated toward the core 22. In other words, this prevents magnetic flux leakage in the amplitude direction of the free end of the beam, increases the rate of change of the magnetic flux of the core 22, and minimizes the attenuation of the beam vibration. The effect of the back yoke will be described later with reference to FIG. 16.

[0051] The back yoke 32 is provided so as to cover the entire permanent magnet 31 except for the surface facing the core 22. The exposed portion of the back yoke 32 has an opposite magnetic polarity to that of the exposed portion of the permanent magnet 31. As shown in FIG. 4 , the polarity of the back yoke 32 on the north pole side of the permanent magnet 31 is an south pole, and the polarity of the back yoke 32 on the south pole side of the permanent magnet 31 is an north pole. When the polarity of the permanent magnet 31 is opposite to that in the example of FIG. 4 , the polarity of the back yoke 32 is also opposite. The back yoke 32 is formed of a magnetic material, such as ferritic stainless steel, soft magnetic iron-based amorphous alloy, electromagnetic steel sheet, pure iron, or steel with a low carbon concentration (low-carbon steel).

[0052] [2. Operation] The operation of the vibration power generator 1 according to the embodiment will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the housing 10 vibrates in response to vibration transmitted from the outside (vibration source), and this vibration is transmitted to the beam 21. The beam 21 vibrates in the vertical direction, and the core 22 provided at the free end of the beam 21 vibrates relative to the permanent magnet 31. Here, "vibrate relative to" means that both the beam 21 and the permanent magnet 31 vibrate relative to each other. This is because while the beam 21 vibrates, the permanent magnet 31 also vibrates integrally with the housing 10. This includes cases where the amplitudes of the vibrations of the beam 21 and the permanent magnet 31 are the same or different. When vibrations having a period matching the natural frequency of the beam 21 are applied from the outside, a resonance phenomenon occurs in the beam 21, generating harmonic vibrations of n times the external frequency (fundamental wave) and n times the external frequency (n≧2, where n is an integer).

[0053] The natural frequency of a typical plate-shaped cantilever beam is expressed by the following formula.

[0054] where λ １ is the constant of the first resonance, λ １ =1.875, l is the length of the cantilever, A is the cross-sectional area of ​​the cantilever, I is the second moment of area of ​​the cantilever, E is Young's modulus, and ρ is the density. Therefore, the natural frequency f of the beam 21 is r can be controlled by the length of the beam 21 and the weight of the core 22 and coil 23 provided at the free end of the beam 21.

[0055] The core 22 is instantaneously magnetized by the opposing permanent magnet 31. In the example shown in FIG. 4 , when the beam 21 is stationary, the core 22 is magnetized to the south pole. However, when the beam 21 flexes and vibrates in response to vibration of the housing 10, the core 22 moves to a position facing the back yoke 32, and the south pole of the back yoke 32 changes the magnetic pole of the core 22 to the north pole. In this way, the magnetic pole of the core 22 switches to the north pole or south pole depending on the opposing magnetic pole due to vibration. Because the core 22 vibrates in the magnetic field generated by the magnetic unit 30, the magnetic field penetrating the coil 23 constantly changes. The instantaneous change in magnetic flux density of the core 22 causes a current to flow through the coil 23. As a result, an induced voltage V is generated between both ends (lead wires 41) of the coil 23 (see FIG. 1 ). In other words, when both ends (lead wires 41) are open, an open-end induced voltage is output from the coil 23.

[0056] [3. Actions and Effects] <Actions and Effects Obtained from the Configuration> (1) The vibration power generator 1 described above is composed of a housing 10 that receives vibrations, a vibration unit 20 fixed to the housing 10, and a magnetic unit 30. The vibration unit 20 is made of a flexible, non-magnetic material and includes a beam 21 that extends in the longitudinal direction and has one end fixed to the housing 10 and the other end as a free end, a core 22 provided on the free end side of the beam 21, and a coil 23 wound around the core 22. The magnetic unit 30 also includes a permanent magnet 31 fixed in a position facing the core 22, and a back yoke 32 made of a magnetic material that is provided to cover the permanent magnet 31 except for the surface facing the core 22, and the surface facing the core 22 has an opposite magnetic polarity to that of the permanent magnet 31. Vibrations received by the housing 10 are transmitted to the beam 21, causing the core 22 to vibrate relative to the permanent magnet 31, causing the vibration power generator 1 to output an induced voltage in the coil 23.

[0057] First, the vibration-driven power generator 1 has a small number of parts, and the beam 21 and magnetic unit 30 are fixed to the housing 10, so it is structurally robust and simple. Because it has a simple structure that can be mass-produced, costs can be reduced.

[0058] Furthermore, because the material forming the beam 21 is flexible, it has a low elastic modulus (modulus of longitudinal elasticity, Young's modulus) and is easily deformed, so it easily vibrates even when external vibrations are small. Also, because the beam 21 is formed of a non-magnetic material, the beam 21 can vibrate without being attracted by the permanent magnet 31. As described above, the beam 21 according to this embodiment is formed of a flexible non-magnetic material and is not attracted to the magnet. It is lightweight, easy to process, and strong, so it is less likely to deteriorate or break. The beam 21 can increase acceleration at the resonance point and increase the rate of change of magnetic flux, thereby obtaining a high power generation output.

[0059] The spring constant k of a plate-shaped cantilever beam is expressed by the following equation: (E is Young's modulus, I is the moment of inertia of the cantilever, and l is the length of the cantilever.)

[0060] Furthermore, by providing the core 22 on the free end side of the beam 21, the mass of the core 22 (and the mass of the coil 23 wound around the core 22) acts as a weight, making the beam 21 more likely to vibrate. Furthermore, because the beam 21 is made of a flexible non-magnetic material, the beam 21 can vibrate more strongly than the housing 10. When the housing 10 vibrates, the magnetic unit 30 contained therein also vibrates simultaneously. However, if the phase of the vibration of the beam 21 is the same as the phase of the vibration of the magnetic unit 30, the core 22 continues to face the permanent magnet 31. In this case, the core 22 remains magnetized with a magnetic pole (south pole) opposite the polarity (north pole) of the opposing permanent magnet 31, so no change in magnetic flux occurs and no induced voltage is generated. In contrast, in the beam 21 according to the embodiment, the core 22 moves near the magnetic unit 30 at a speed faster than the speed at which the magnetic unit 30 moves up and down. As a result, the core 22 can alternately face the polarity (north pole) of the permanent magnet 31 and the polarity (south pole) of the back yoke 32 above and below it, causing a change in the magnetic flux of the core 22 and generating an induced voltage.

[0061] Furthermore, by making the beam 21 long and the core 22 flat, assembly efficiency is improved. When the beam 21 is long and plate-shaped, the amplitude in the direction perpendicular to the plate surface can be increased during resonance, resulting in a larger amplitude than when the beam 21 is rod-shaped. The thickness t of the long plate of the beam 21 may be increased from near the center to the fixed end. In this case, stress during resonance will not be concentrated at the fixed end of the beam 21, which will contribute to an increase in the lifespan of the beam 21 and ultimately the lifespan of the entire device.

[0062] By covering the permanent magnet 31 with the back yoke 32 as described above, the magnetic flux of the magnetic unit 30 is not dispersed, and the leakage magnetic field can be efficiently used for power generation. Specifically, the leakage magnetic flux from the permanent magnet 31 can be concentrated near the center of the amplitude of the vibrating core 22, which is provided at the free end of the beam 21, thereby increasing the strength of the magnetic field near the core 22. If only the permanent magnet 31 were used, the core 22 would continue to be attracted to the permanent magnet 31 while vibrating, resulting in small vibrations and not reaching resonance unless large vibrations are applied. In contrast, the presence of the back yoke 32 prevents the magnetic flux of the permanent magnet 31 from dissipating into space, allowing the core 22 to resonate at a position away from the magnetic unit 30 without being affected by the magnetic field, even with weak vibrations. This increases the rate of change of the magnetic flux, even with weak vibrations. This will be explained later with reference to FIG. 16 .

[0063] The above-described configuration and arrangement of the vibration unit 20 and magnetic unit 30 results in a configuration in which magnetic pole reversal occurs at the point where the physical displacement of the coil 23 moving in response to vibration is greatest (i.e., the maximum moving speed). Furthermore, the influence of the leakage magnetic field of the permanent magnet 31 in the amplitude direction of the coil 23 can be eliminated, maximizing the rate of change of the magnetic flux linking the coil 23, thereby obtaining a high-output generated voltage.

[0064] (2) The core 22 is configured as a flat plate such that a / t≧5 and b / t≧5 are satisfied, where a is the length of the core 22 relative to the longitudinal direction of the beam, b is the width of the core 22, and t is the thickness of the core 22. A flat core 22 is more likely to be magnetized in the in-plane direction of the plate. This allows for instantaneous magnetic flux changes. The basis for the above numerical values ​​is that the demagnetizing factor N, an index of shape magnetic anisotropy that makes a magnetic material more likely to be magnetized in that direction, is N to 0 in the in-plane direction for a shape ratio of approximately 20 for a flat plate. Within the above range, the in-plane direction becomes the easy axis of magnetization, allowing for instantaneous induction of positive and negative magnetic flux densities of 1 T or more along the magnetic field (>0.4 T) generated by the permanent magnet 31.

[0065] (3) The permanent magnet 31 is configured to satisfy t≦h≦20*t and w≧b, where h is the height of the permanent magnet 31 and w is the width of the permanent magnet 31. In this way, the size of the permanent magnet 31 can be easily calculated from the thickness t and width b of the core 22, and the device can be made smaller and lighter within this range.

[0066] (4) The core 22 and the surface of the permanent magnet 31 facing the core 22 face each other with a predetermined gap when the beam 21 is stationary. (5) The predetermined gap has a lower limit value of the distance at which the core 22 does not adhere to the surface of the permanent magnet 31 when the core 22 vibrates relative to the permanent magnet 31, and an upper limit value of the distance at which the core 22 does not deviate from the magnetic field in space from the permanent magnet 331. By appropriately setting the predetermined gap, the core can be fully magnetized and saturated in a short time, and the vibration of the beam is not hindered.

[0067] (6) The beam 21 has a core 22 around which a coil 23 is wound at its free end. Two lead wires 41 are electrically connected to the coil 23. When an induced voltage V that periodically swings between positive and negative is generated in the coil 23 wound around the core 22, the induced voltage V is supplied to an external device via the lead wires 41. Note that a constant voltage can be output by connecting a constant voltage circuit to the lead wires 41.

[0068] (7) The beam 21 resonates when vibrations received by the housing 10 are transmitted and satisfy the resonance condition. The resonance condition is a condition in which the frequency of the external vibration matches the natural frequency determined by the physical elements (length, weight, etc.) of the beam 21 and the core 22, and Equation 2 is satisfied. When the beam 21 resonates, higher power output can be generated compared to when it is not resonating. Higher power output can be generated compared to conventional inverse magnetostrictive vibration power generation (Patent Document 1).

[0069] FIG. 5 is a table showing the conditions for configurations a to g of the vibration-generating power generator 1. FIGS. 6A, 6B, and 6C in FIG. 6 are diagrams showing configurations a to c of the vibration-generating power generator based on the conditions in Table 1 in FIG. 5. Configuration a has one permanent magnet and a back yoke, configuration b has two permanent magnets and a back yoke, and configuration c (comparison example) has two permanent magnets and no back yoke. The differences between the configurations are as shown in the table in FIG. 5. In Example 1, a vibration testing machine was used, and the fixing function of the vibration testing machine corresponds to the housing 10 in the above-described embodiment. Both ends of the coil 23 were connected to a digital oscilloscope, and the power generation waveform displayed on the oscilloscope was observed.

[0070] Example 1 was carried out under the following conditions. =Common conditions= -Vibration unit 20- Core 22: 50 layers of Fe-based amorphous ribbon (0.025 [um], MADC-A (registered trademark) by PROTERIAL) Coil 23: Enameled copper wire (diameter 0.1 [mm], coil window area 1.5 × 18 [mm], number of turns N = 1000, resistance 90 [Ω]) Mass of core 22 and coil 23 combined: 6.35 g, thickness 1 [mm] Excitation acceleration: 0.5 and 1.0 [G] (9.8 m / s 2 ) Maximum displacement: ±20[mm] Vibration testing machine: 0.5 and 1.0[G], 10-40[Hz] (Tabletop vibration testing machine model number CV-101Ma) =Individual conditions= (Also shown in Figures 5 and 6) >Configuration a -Vibration unit 20- Beam 21: Hard polyvinyl chloride plate (longitudinal length 61[mm], width 2[cm], thickness 1[mm], Young's modulus 2.5-4.1[GPa], general-purpose product) -Magnetic unit 30- Exposed area of ​​permanent magnet 31: 2.5 x 15[mm] (N pole only) Maximum magnetic flux of exposed part of permanent magnet 31: 0.43 (T) Back yoke: SUS430 Configuration: One permanent magnet 31 is covered with a back yoke 32 except for the N pole surface facing the core 22, and the back yoke 32 has the opposite polarity to the permanent magnet. Distance between the core 22 and the permanent magnet 31: Gap: 2 [mm] -Other- Frequency: 21 [Hz] Effective power P rms (a = 1G): 9.6 [mW] (maximum 200 [mW]) Effective power P rms(a=0.5G): None >Configuration b -Vibration unit 20- Beam 21: Hard vinyl chloride plate (longitudinal length 84[mm], width 2[cm], thickness 1[mm], Young's modulus 2.5-4.1[GPa], general-purpose product) -Magnetic unit 30- Exposed area of ​​permanent magnet 31: 7 x 30[mm] (S / N poles arranged above and below) Maximum magnetic flux of exposed part of permanent magnet 31: 0.52(T) Back yoke: SUS430 Structure: Two permanent magnets 31 are stacked so that they have opposite magnetic poles, and are covered with a back yoke 32 except for the N and S pole faces facing the core 22. The back yoke 32 has opposite polarity to adjacent permanent magnets. Distance Gap between core 22 and permanent magnet 31: 4[mm] -Other- Frequency: 14[Hz] Effective power P rms (a = 1G): 21.2 [mW] (maximum 235 [mW]) Effective power P rms (a = 0.5G): 16.9 [mW] (maximum 140 [mW]) >Configuration c -Vibration unit 20- Beam 21: Hard vinyl chloride plate (longitudinal length 81 [mm], width 2 [cm], thickness 1 [mm], Young's modulus 2.5-4.1 [GPa], general-purpose product) -Magnetic unit 30- Exposed area of ​​permanent magnet 31: 7 x 30 [mm] (S / N poles arranged above and below) Maximum magnetic flux of exposed part of permanent magnet 31: 0.54 (T) Fixing device: SUS304 Structure: The magnetic unit 30 is configured by stacking two permanent magnets 31 so that they have opposite magnetic poles, and the permanent magnets 31 are fixed to the housing 10 with non-magnetic stainless steel material without being covered by a back yoke 32. Distance Gap between core 22 and permanent magnet 31: 7 [mm] -Other- Frequency: 14 [Hz] Effective power P rms (a = 1G): 11.6 [mW] (maximum 74 [mW]) Effective power P rms (a=0.5G): 7.5[mW] (maximum 34[mW])

[0071] FIG. 6 shows multiple configurations of the vibration-generating power generator 1 based on the conditions in Table 1 of FIG. 5 . FIG. 6A shows configuration a, FIG. 6B shows configuration b, and FIG. 6C shows configuration c. FIG. 7 is a graph of the induced voltage for different configurations of the vibration-generating power generator 1 shown in FIG. 6 , with FIG. 7A showing the induced voltage for configuration a, FIG. 7B showing the induced voltage for configuration b, and FIG. 7C showing the induced voltage for configuration c. FIG. 8 is a graph of the power generation output and time waveform for different configurations of the vibration-generating power generator 1 shown in FIG. 6 , with FIG. 8A showing the power generation output and time waveform for configuration a, FIG. 8B showing the power generation output and time waveform for configuration b, and FIG. 8C showing the power generation output and time waveform for configuration c. The dashed lines in each graph indicate one period [ms] of the movement of the beam 21. If the position at which the vibration unit 20 is stationary is defined as point 0 (also referred to as the zero point), one period is the time it takes for the beam 21 to bend downward under the influence of an external force F, return to point 0, pass through point 0, bend upward, and then return to point 0 again. In this case, one period is 48 [ms]. The graphs shown in Figures 7 and 8 are based on an excitation acceleration of 1.0 G [m / s 2 ] is the result.

[0072] The graph in Figure 7 shows the relationship between induced voltage [V] and time [ms]. In the graph for configuration a in Figure 7A, peaks of approximately -4 [V] and approximately 2 [V] alternate. The peaks are sharp. The line from the peak at approximately -4 [V] to the adjacent peak at approximately 2 [V] represents the induced voltage in coil 23 when the free end of beam 21 moves from bottom to top or from top to bottom. The peak at approximately -4 [V] represents the induced voltage generated when coil 23 leaves the magnetic field, i.e., when coil 23 moves away from the center of permanent magnet 31. The peak at approximately 2 [V] represents the induced voltage generated when coil 23 enters the magnetic field, i.e., when coil 23 approaches the center of permanent magnet 31. It was confirmed that applying configuration a resulted in a peak-to-peak induced voltage of approximately 6 [V].

[0073] In contrast, the graph for configuration b in Figure 7B shows peak values ​​of approximately -4.5 [V] and approximately 4.5 [V], as well as peak values ​​of approximately -1.5 [V] and approximately 1.5 [V] around them, but the peak shapes are broader. The peaks at approximately -4.5 [V] and approximately 4.5 [V] are induced voltages generated when the coil 23 crosses the exposed surfaces of the permanent magnets with different magnetic poles near the center, while the peaks around approximately -1.5 [V] and approximately 1.5 [V] are induced voltages generated when the coil 23 crosses the exposed surfaces of the permanent magnets and the magnetic poles at the ends of the back yoke. Furthermore, the graph for configuration c in Figure 7C shows the same frequency as configuration b, but the peak values ​​are reduced to approximately -3 [V] and approximately 2.2 [V], and the peak shapes are broader.

[0074] The graph in Figure 8 shows the relationship between power output [mW] and time [ms]. Looking at the graph of configuration a in Figure 8A, P max = 200 [mW]. Converting this to an effective value gives P rms = 9.6 [mW], and it was confirmed that an output of approximately 10 [mW] could be obtained.

[0075] In the graphs of Figures 8A and 8B for the configurations a and b in which the back yoke is installed, the peak value is about 200 mW, and the peak shape is sharp. rms In contrast, in the graph of the configuration c without a back yoke in FIG. 8C, the peak shape is broad and the effective power P rms This translates to 11.6 mW.

[0076] According to the vibration-driven power generator 1 of the first embodiment, the polarity of the magnetic flux in the core 22 is instantly reversed at the point where the excitation speed is maximized, thereby maximizing the output. In addition, a stable high output can be obtained continuously.

[0077] FIG. 9 shows the maximum value of the induced voltage (V max) [V] and excitation frequency [Hz]. In Example 2, the excitation acceleration was constant at 0.5G and 1G, and the excitation frequency was swept from 10 to 56 [Hz], with the other conditions being the same as in Example 1. In each graph, V max indicates the peak.

[0078] Looking at the graph in Figure 9A (configuration b), V max In the case of the configuration c in FIG. 9B, the frequency at which the voltage was 13-16 Hz at 1 G and 13-14 Hz at 0.5 G was 1 V or more.

[0079] According to this second embodiment, the presence of the back yoke 32 prevents the leakage magnetic field of the magnetic pole on the side of the permanent magnet 31 that does not face the core 22 from being released into space, and the magnetic field can be concentrated in the magnetic pole on the side of the back yoke 32 that faces the core 22, thereby widening the frequency band in which induced voltage can be obtained.

[0080] FIG. 10 shows the effective power [mW] (P rms ) and excitation acceleration [m / s 2 10A is a graph showing the relationship between the excitation acceleration [m / s2] and the power output [W] at a resonance frequency of 14 [Hz]. Example 3 was performed under the same conditions as Example 1, except for the resonant frequency and the excitation acceleration. In Example 3, the setting of the distance Gap [mm] (see FIG. 2) between the core 22 and the permanent magnet 31 when the beam 21 is stationary was changed, and the dependence of the power output [W] on the excitation acceleration [m / s2] at a resonant frequency of 14 [Hz] was observed. The graph in FIG. 10A shows the results for configuration b, and the graph in FIG. 10B shows the results for configuration c.

[0081] Looking at the graph in Figure 10A, the gap is 4 mm and the excitation acceleration is 0.5 m / s 2 ], output 17 [mW] (P rms ) is obtained, and the excitation acceleration is 1.0 [m / s 2 ], output 21 [mW] (P rms ) was obtained. Note that when the gap was 2 mm or less, the core 22 stuck to the permanent magnet 31, so it was set to 3 mm or more, and stable results were obtained when the gap was 4 mm or more.

[0082] In contrast, looking at the graph in Figure 10B, when Gap = 7 [mm] and the excitation acceleration is 0.5 G [m / s 2 ], output 8 [mW] (P rms ) is obtained, and the excitation acceleration is 1.0G [m / s 2 ], the output is 11.6 [mW] (P rms ) was obtained. Compared to configuration a, more than twice the gap was required, and the output was about half.

[0083] According to the third embodiment, the presence of the back yoke 32 prevents leakage magnetic fields from the magnetic pole of the permanent magnet 31 on the side not facing the core 22 from escaping into space, and the magnetic field can be concentrated at the magnetic pole of the back yoke 32 on the side facing the core 22, thereby achieving large resonance even with weak excitation. This indicates that the distance Gap [mm] between the core 22 and the permanent magnet 31 when the beam 21 is stationary should desirably have a lower limit value that prevents the core 22 from adhering to the permanent magnet 31, and that the upper limit value should desirably be a distance that allows the core 22 to exist within the range where the magnetic field is concentrated. In the third embodiment, the lower limit value was 4 [mm] and the upper limit value was 7 [mm], but these values ​​vary depending on the configuration.

[0084] Figure 11 shows the effective power [mW] (P rms 10 is a graph showing the relationship between the load resistance [Ω] and the vibration acceleration [Ω]. In Example 4, the test was carried out under the same conditions as in Example 1, except for the excitation acceleration (1.0 G only in Example 1, and both 0.5 G and 1.0 G in Example 4).

[0085] A load maximum power curve was obtained with a broad peak near 90 Ω, which is the resistance of the core 22. The maximum power was 3.0 mW and 3.8 mW at 0.5 G and 1.0 G, respectively.

[0086] 5 shows configurations d to g in which the number of turns of the coil 23 in the configuration b of the vibration power generator 1 is set to N = 1000, 2000, 3000, and 4000. The core is made of an electromagnetic steel sheet (JFE Steel, JGH TM CORE, 35JGH135) was used.

[0087] Example 5 was carried out under the following conditions. =Common conditions= Beam 21: polyethylene terephthalate (longitudinal length 87.5 mm, width 1.5 cm, thickness 1.5 mm, Young's modulus 2.0-4.1 GPa, general-purpose product) -Vibration unit 20- Core 22: electromagnetic steel plate (0.35 μm, JFE Steel, JGH TM Coil 23: Enameled copper wire (diameter 0.09 mm, coil window area 1.5 x 16 mm) Excitation acceleration: 0.5 and 1.0 G (9.8 m / s 2 ) Maximum displacement: ±30 [mm] Vibration testing machine: 0.5 and 1.0 [G], 10-40 [Hz] (Tabletop vibration testing machine model number CV-101Ma) - Magnetic unit 30 - Exposed area of ​​permanent magnet 31: 7 x 30 [mm] (S / N poles arranged above and below) Maximum magnetic flux of exposed part of permanent magnet 31: 0.52 (T) Back yoke: SUS430 Structure: Two permanent magnets 31 are stacked so that they have opposite magnetic poles, and are covered with a back yoke 32 except for the N and S pole faces facing the core 22, and the back yoke 32 has the opposite polarity to the adjacent permanent magnets. Distance Gap between core 22 and permanent magnet 31: 5 [mm] = Individual conditions = (also shown in Figures 5 and 12) > Configuration d - Vibration unit 20 - Number of turns N = 1000, resistance 98 [Ω], weight 2.53 [g] ("Weight" is the combined weight of core 22 and coil 23. The same applies below.) - Other - Frequency: 19 [Hz] Effective power P rms (a = 1G): 16.5 [mW] (maximum 197 [mW]) Effective power P rms (a = 0.5G): 5.0 [mW] (maximum 24 [mW]) > Configuration e - Vibration unit 20 - Number of turns N = 2000, Resistance 215 [Ω], Weight 4.96 [g] - Other - Frequency: 15 [Hz] Effective power P rms (a = 1G): 16.3 [mW] (maximum 220 [mW]) Effective power P rms(a = 0.5G): 4.7 [mW] (maximum 25 [mW]) > Configuration f - Vibration unit 20 - Number of turns N = 3000, Resistance 365 [Ω], Weight 7.83 [g] - Other - Frequency: 13 [Hz] Effective power P rms (a = 1G): 28.7 [mW] (maximum 521 [mW]) Effective power P rms (a = 0.5G): 18.4 [mW] (maximum 274 [mW]) > Configuration g - Vibration unit 20 - Number of turns N = 4000, Resistance 518 [Ω], Weight 11.2 [g] - Other - Frequency: 11 [Hz] Effective power P rms (a = 1G): 25.9 [mW] (maximum 446 [mW]) Effective power P rms (a=0.5G): 21.3[mW] (maximum 316[mW])

[0088] The graphs in Figure 12 show the relationship between induced voltage [V] and time [ms]. The graphs for configurations d and e in Figures 12A and 12B show the induced voltage in coil 23, with broad peaks of approximately -5 V and approximately 5 V appearing alternately. The graphs for configurations f and g in Figures 12C and 12D show peaks of approximately -15 V and approximately 15 V appearing alternately.

[0089] The graph in Figure 13 shows the relationship between power output [mW] and time [ms]. Looking at the graphs in Figures 13A and 13B for configurations d and e, P max ~200 [mW]. Converting this to an effective value is P rms The output power was ~16.5 mW, and it was confirmed that an output power of 10 mW or more could be obtained. max ~500 [mW], P at 0.5G vibration max ~300 [mW]. Converting these into effective values, we can see that the effective power obtained is approximately 26~28 [mW] and 18~21 [mW].

[0090] =Individual conditions= >Configurations h to l In configuration b of the vibration power generator 1, the distance Gap between the coil 23 and the permanent magnet 31: 2-6 mm, in 1 mm increments >Configurations m to q In configuration c of the vibration power generator 1, the distance Gap between the coil 23 and the permanent magnet 31: 5-9 mm, in 1 mm increments

[0091] The graph in Figure 14 shows the relationship between the induced voltage [V] of the coil 23 and time [ms] when the free end of the beam is flicked with a finger without using a vibration tester for configurations b and c. Figure 14A shows the results (a) to (e) when the gap is changed for configuration b, and Figure 14B shows the results (f) to (j) when the gap is changed for configuration c. The small graph in the lower right of each graph is an enlarged view of the initial vibration in the figure over a range of 500 [ms]. This confirms that the frequency (period) is the same as the forced vibration waveforms shown in Figures 7B and 7C of Example 1.

[0092] The graph in Figure 14 shows how the damping effect on the beam weakens as the gap increases. In other words, the closer the core and permanent magnet are, the stronger the damping effect, and the farther they are, the weaker the damping effect. The degree of damping depends on the beam's damping constant β. The free vibration (damped vibration) waveform (shown by the solid line) at the free end of the beam, as shown in [Equation 4], and the induced voltage waveform of the vibration generator during free vibration can be fitted with [Equation 5] to estimate the beam's β. u(t): Vertical displacement of the free end of the beam ω0: Resonant frequency of the beam β: Damping constant d max : Maximum displacement of the free end φ: Phase delay from the initial position

[0093] Under the conditions shown in (a) and (b) of Figure 14A and (f) and (g) of Figure 14B, the beam does not vibrate unless the force exceeds 1 G, and is therefore considered unsuitable for vibration power generation. In contrast, the graphs shown in (c) of Figure 14A and (h) of Figure 14B are considered suitable for vibration power generation because the beam resonates stably with forced vibration of 1 G at the resonant frequency, generating a high induced voltage. Therefore, it was confirmed that the conditions shown in (c) of Figure 14A and (h) of Figure 14B, a 4 mm gap in configuration b, and a 7 mm gap in configuration c are suitable. This corresponds to the results shown in Figures 10A and 10B.

[0094] FIG. 15A shows the maximum induced voltage V max and Gap, and FIG. 15B shows the relationship between β and Gap approximated by Equation 2. Maximum induced voltage V maxdecreases quadratically as the gap increases. This is because the magnetic field in space from the permanent magnet 31 of the magnetic unit 30 decreases as the square of the distance. On the other hand, an approximation of the damping constant β of the vibration of the free end of the beam in free vibration shows a rapid increase as the gap decreases. When β is large in the configurations h to q of [Example 6], the resonance of the beam subjected to external vibration does not continue. Therefore, even when the gap is small, the configurations h to l with small β have better performance as a vibration generator (V max The value of the damping constant β differs depending on the configuration of the vibration generator. The "stable beam resonance" in Figure 15B is the range in which power generation output can be obtained with forced vibration of 1 G.

[0095] 16A and 16C show the magnetic field (magnetic pole direction) in space from the permanent magnets 31 in configurations b and c, measured with a Gaussian probe (LakeShore, 425 type) at a resolution of 1 mm, mapped onto a plane that is symmetrical in the depth direction and includes the length and height of the generator. It can be seen that configuration b, which uses high-permeability BY (SUS430), suppresses the leakage magnetic field in space more than configuration c, which does not use BY (SUS304). This suggests that the use of BY can suppress the damping of vertical vibrations caused by the leakage magnetic field, which is consistent with the results of Example 6.

[0096] 16B and 16D show the relationship between the vertical magnetic field partial differential (partial differential of magnetic flux) [Oe / mm] and distance [mm] for configurations b and c under the same conditions as configurations b and c in the individual conditions of Example 1. This can be approximated to dΦ / dt in the law of electromagnetic induction, Equation 1 in paragraph 0012, when the core at the free end of the beam periodically moves in the vertical direction under resonant conditions. The waveforms of the lower peaks in FIGS. 16B and 7B and those in FIGS. 16D and 7C have the same shape.

[0097] From Example 7, it was also found that it is desirable to set the lower limit to the distance at which the core 22 does not adhere to the permanent magnet 31, and furthermore, from Figures 16C and 16D, it was found that it is desirable to set the upper limit to the distance at which the core 22 does not deviate from the magnetic field in space from the permanent magnet 31.

[0098] [4. Application Examples] One possible application of the vibration power generator 1 is as a vibration-powered power source for a low-load device (Application Example 1). Low load refers to a maximum current consumption of approximately 100 mA, or in other words, a low-power device. For example, this generator full-wave rectifies and smooths the sinusoidal voltage induced across both terminals of the core coil 23 and supplies it as a DC power source. An example of a possible application scenario is to install the generator in a fixed-frequency vibration source and supply power to a low-load device such as a sensor (e.g., an environmental sensor) or a light source. In other words, this is a low-load device that uses the vibration power generator 1 as a power source. The vibration power generator 1 may be connected to the low-load device separately, either wired or wirelessly (via wireless power supply), or integrated with the device.

[0099] Another potential application is battery-less vibration measurement (Application Example 2). By building a circuit with power generation elements with different resonant frequencies and sending a signal when each element generates power, the circuit can be used as an environmental monitor capable of detecting noise and vibration frequency without a power source. Examples of applications include detecting abnormalities in vibrating vehicles (automobiles and trains) and understanding the usage frequency of industrial equipment that vibrates during operation. Examples of environmental vibration frequencies include 13 Hz (car panels) and 4 to 14 Hz (vibrations caused by train movement). (Source: H. Li et al., Appl. Phys. Rev. (2014) https: / / pubs.aip.org / aip / apr / article / 1 / 4 / 041301 / 123585 (Non-Patent Document 2); "Elucidating the Mechanism of Impact Force Generation Due to Wheel Flats Using FEM Analysis," Risa Saito and Hirotaka Sakai, Journal of Railway Technology, published August 1, 2024 (Non-Patent Document 3))

[0100] Another possible application example is use in a power storage system having a storage battery and a power conversion device (DC / AC). Electricity generated by the vibration power generator 1 is sent to the power storage system and stored in the storage battery, and the stored electricity is output as DC or AC, making it usable for general electrical appliances. A converter (power conversion device) that increases or decreases the voltage to the required level for DC output may be provided, or an inverter (power conversion device) that controls the frequency, waveform, etc. for AC output may be provided. In other words, a power storage system that includes the vibration power generator 1 for power supply is conceivable. The vibration power generator 1 may be connected to the power storage system separately by wire or wirelessly, or may be integrated with the power storage system.

[0101] FIG. 17 is a graph showing the relationship between induced voltage and frequency for each beam in Application Example 2 of the vibration-generating power generator 1 according to the embodiment. FIG. 18 is a schematic plan view showing, from a top view, various different configurations for obtaining the frequency characteristics of the induced voltage shown in FIG. 17. The configuration shown in FIG. 18 is basically the same as that of the above-described embodiment, and although each coil 23 has two lead wires extending therefrom, these two lead wires are depicted as one for simplicity. As shown in FIG. 18, the difference between the configuration of Application Example 2 and the above-described embodiment is that the vibration-generating power generator 1 is provided with multiple vibration units 20 (beams 21 and cores 22 wound with coils 23) having different conditions, which are arranged to face a single common magnetic unit 30 (permanent magnet 31 with back yoke 32). The different conditions include, for example, a case where each of the multiple beams 21 has a different longitudinal length (configuration i; FIG. 18A), a case where each of the multiple beams 21 has the same longitudinal length but the masses of the cores 22 and coils 23 provided at the free ends of the beams 21 are different (configuration ii; FIG. 18B), a case where each of the multiple beams 21 has the same longitudinal length but different thicknesses (configuration iii; FIG. 18C), etc. Beams 21A to 21C in FIG. 17 correspond to beams 21A to 21C in FIG. 18, and their resonant frequencies differ depending on the conditions shown in FIG. 18. In the example of FIG. 17, the resonant frequencies of beams 21A to 21C are 11 Hz, 15 Hz, and 25 Hz, respectively. Since each beam of structures i to iii resonates at a different frequency, according to application example 2 of the vibration generator 1, by sharing the magnetic unit 30 in the housing 10 and providing multiple vibration units 20 with different conditions, different resonant frequencies can be detected with a simple structure with a small number of parts.

[0102] As described above, the vibration power generator 1 has a simple structure and can be applied to a variety of devices, making it possible to realize mass-produced, inexpensive devices that generate electricity using weak vibrations and have high output.

[0103] [5. Other] The configuration of the vibration-driven power generator 1 described above is an example and is not limited to the above. For example, the shape of the housing 10 may be a box shape with sides in the front-to-rear direction. Furthermore, the vibration-driven power generator 1 described above may be fixed to any vibration source as long as the surface is perpendicular to the vibration direction.

[0104] According to the above-described first to fifth examples, good results were obtained with the vibration power generator 1, but there is still room for improvement in the optimal structure, which depends on small parameters. Possible parameters include the material, the distance Gap between the vibration unit 20 and the magnetic unit 30, the degree of influence of the back yoke 32 on the nearby magnetic field, and the number of permanent magnets 31. By clarifying the combinations and optimal values ​​of such various parameters and applying them to the vibration power generator 1, it becomes possible to generate power with a higher output.

[0105] In the above-described embodiment, as shown in FIGS. 1 to 4, the beam 21 of the vibration unit 20 and the magnetic unit 30 are fixed to the housing 10. Alternatively, the beam 21 and the magnetic unit 30 may be fixed to separate objects. Although the gap (distance Gap) between the core 22 and the permanent magnet 31 shown in FIG. 2 must be kept constant, the same effect as in the above-described embodiment can be obtained. Furthermore, since the beam 21 and the magnetic unit 30 may be fixed to separate objects, the degree of freedom in the configuration is increased.

[0106] In the above-described embodiment, as shown in Figures 1 to 4, the lead wire 41 is configured to be separated from the beam 21 near the portion where it is connected to the coil 23, i.e., near the end of the core 22. Instead of this configuration, the lead wire 41 may be configured to run along the longitudinal direction of the beam 21 or to be built into the beam 21. This configuration provides the same effects as the above-described embodiment. Furthermore, since the lead wire 41 is synchronized with the deflection of the beam 21, metal fatigue, particularly near the connection portion, can be reduced, and loss of induced voltage output can be reduced.

[0107] In the above-described embodiment, as shown in Figures 1 to 3, the coil 23 and the lead wire 41 are formed separately and electrically connected. Instead of this configuration, the coil 23 may be extended to form the lead wire 41. This configuration provides the same effects as the above-described embodiment. In addition, it is possible to eliminate the time and effort required to electrically connect the coil 23 and the lead wire 41.

[0108] [6. Supplementary Notes] (Supplementary Note 1) A vibration power generator that generates power by utilizing vibrations transmitted from the outside, comprising: a housing that receives the vibrations; a beam that is formed from a flexible non-magnetic material and extends in the longitudinal direction, with one end fixed to the housing and the other end being a free end; a core that is provided on the free end side of the beam; a coil that is wound around the core; a permanent magnet that is fixed in a position facing the core; and a back yoke that is formed from a magnetic material and is provided so as to cover the permanent magnet except for a surface that faces the core and has an opposite magnetic polarity to that of the permanent magnet, wherein the vibrations received by the housing are transmitted to the beam, and the core vibrates relative to the permanent magnet, thereby outputting an induced voltage that is generated in the coil.

[0109] (Appendix 2) The vibration-generating power generator described in Appendix 1, characterized in that the core is configured as a flat magnetic body that satisfies a / t≧5 and b / t≧5, where a is the longitudinal length of the core, b is the width of the core, and t is the thickness of the core.

[0110] (Supplementary Note 3) The vibration-driven power generator according to Supplementary Note 1 or 2, wherein the permanent magnet satisfies t≦h≦20*t and w≧b, where h is the height of the permanent magnet and w is the width of the permanent magnet.

[0111] (Supplementary Note 4) The vibration power generator according to any one of Supplementary Notes 1 to 3, wherein the core and a surface of the permanent magnet facing the core face each other with a predetermined distance therebetween when the beam is stationary.

[0112] (Appendix 5) A vibration generator as described in any one of Appendices 1 to 4, characterized in that the predetermined distance has a lower limit value of the distance at which the core does not adhere to the surface of the permanent magnet when the core vibrates relative to the permanent magnet, and an upper limit value of the distance at which the core does not deviate from the magnetic field in space from the permanent magnet.

[0113] (Supplementary Note 6) The vibration-based power generator according to any one of Supplementary Notes 1 to 5, wherein the beam has a lead wire electrically connected to the coil.

[0114] (Supplementary Note 7) The vibration power generator according to any one of Supplementary Notes 1 to 6, wherein the beams resonate when vibrations received by the housing are transmitted to the beams.

[0115] (Supplementary Note 8) The vibration power generator according to any one of Supplementary Notes 1 to 7, wherein the beam resonates at a resonance frequency of 50 Hz or less.

[0116] (Supplementary Note 9) The vibration power generator according to any one of Supplementary Notes 1 to 8, wherein the beam preferably resonates in a frequency band between 0.1 and 30 Hz.

[0117] (Supplementary Note 10) The vibration power generator according to any one of Supplementary Notes 1 to 7, wherein the beam preferably resonates in a frequency band between 100 and 500 Hz.

[0118] (Supplementary Note 11) The vibration power generator according to any one of Supplementary Notes 1 to 10, characterized in that it has a plurality of beams, and each of the plurality of beams has a different length in the longitudinal direction.

[0119] (Appendix 12) A vibration power generator as described in any one of Appendices 1 to 10, characterized in that it has a plurality of beams, each of the plurality of beams has the same longitudinal length, and each of the plurality of beams has a different mass of the core and the coil provided at the free end.

[0120] (Supplementary Note 13) The vibration power generator according to any one of Supplementary Notes 1 to 10, comprising a plurality of beams, each of the plurality of beams having the same length in the longitudinal direction and each of the plurality of beams having a different thickness.

[0121] (Supplementary Note 14) A low-load device comprising the vibration-based power generator according to any one of Supplementary Notes 1 to 13.

[0122] (Supplementary Note 15) A power storage system comprising the vibration-based power generator according to any one of Supplementary Notes 1 to 13.

[0123] REFERENCE SIGNS LIST 1 vibration generator 10 housing 20 vibration unit 21, 21A, 21B, 21C beam 22 core 23 coil 30 magnetic unit 31 permanent magnet 32 ​​back yoke 41 lead wire a longitudinal length of core b width of core b' width of beam h height of permanent magnet t thickness of core w width of permanent magnet

Claims

In a vibration generator that generates electricity using vibrations transmitted from outside, a housing that receives the vibration; a beam formed of a flexible non-magnetic material, one end of which is fixed to the housing and the other end of which is a free end, and extending in a longitudinal direction; a core provided on the free end side of the beam; a coil wound around the core; a permanent magnet fixed to a position facing the core; a back yoke formed of a magnetic material, arranged to cover the permanent magnet except for a surface facing the core, and having an opposite magnetic polarity to that of the permanent magnet; Vibrations received by the housing are transmitted to the beam, and the core vibrates relative to the permanent magnet, generating an induced voltage in the coil, which outputs the voltage. A vibration power generator characterized by: 　 The core is configured as a flat magnetic body that satisfies a / t≧5 and b / t≧5, where a is the length in the longitudinal direction of the core, b is the width of the core, and t is the thickness of the core.

2. The vibration power generator according to claim 1. 　 The permanent magnet satisfies t≦h≦20*t and w≧b, where h is the height of the permanent magnet and w is the width of the permanent magnet. fulfill 3. The vibration power generator according to claim 2. 　 The core and a surface of the permanent magnet facing the core are opposed to each other with a predetermined distance therebetween when the beam is stationary.

2. The vibration power generator according to claim 1. 　 The predetermined distance has a lower limit value of a distance at which the core does not adhere to the surface of the permanent magnet when the core vibrates relative to the permanent magnet, and an upper limit value of a distance at which the core does not deviate from the magnetic field in space from the permanent magnet.

5. The vibration power generator according to claim 4. 　 The beam has a lead wire electrically connected to the coil. The vibration power generator according to any one of claims 1 to 5. 　 The beam resonates when vibrations received by the housing are transmitted.

2. The vibration power generator according to claim 1 . 　 The beams are provided in a plurality of positions, Each of the plurality of beams has a different longitudinal length.

2. The vibration power generator according to claim 1 . 　 The beams are provided in a plurality of positions, Each of the plurality of beams has the same length in the longitudinal direction, The plurality of beams each have a different mass of the core and the coil provided at the free end.

2. The vibration power generator according to claim 1 . 　 The beams are provided in a plurality of positions, Each of the beams has the same length in the longitudinal direction and different thicknesses.

2. The vibration power generator according to claim 1 . 　 A vibration power generator according to claim 1 is provided. A low load device characterized by: 　 A vibration power generator according to claim 1 is provided. A power storage system characterized by:

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