JP2015027214A - Vibration power generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration power generation device which is capable of generating relatively large power by vibration and has high resistance to breakdown and high reliability over a long period.SOLUTION: The vibration power generation device 10 includes: vibration curved sections 11a, 11b curved by vibration; a magnetic field application section 15 which applies a magnetic field to the vibration curved sections 11a, 11b; and coils 12a, 12b wound around peripheries of the vibration curved sections 11a, 11b. The vibration curved sections 11a, 11b are formed from vibration-damping alloy.

Description

  The present invention relates to a vibration power generation device.

  In recent years, development of low power consumption short-range wireless communication technology such as ZigBee has progressed, and a wireless sensor network using such short-range wireless communication technology has been constructed. However, when a battery is used as the power source of the wireless sensor network, problems such as battery life and environmental load at the time of disposal occur. Therefore, an energy harvesting technique that harvests various energy existing around us, such as heat, vibration, light, or radio waves, and converts it into electric power has attracted attention.

  As one of energy harvesting techniques, a power generation device having a pair of beams formed of a magnetostrictive material, a coil wound around the beam, and a magnet that generates magnetic flux has been proposed. In this type of power generation device, the beam bends due to vibration, the density of magnetic flux passing through the beam changes, and a current flows through the coil. This current can be extracted from the coil and used as electric power for driving the electronic device.

  In the present application, a power generation device that generates power by this type of vibration is called a vibration power generation device. Conventionally, in order to improve the power generation capability of the vibration power generation device, it has been preferable to form the beam with a material having a large magnetostriction amount. An Fe (iron) -Ga (gallium) alloy called Galfenol has been developed as a magnetostrictive material suitable for a vibration power generation device. The magnetostriction amount of Galfenol is about 300 ppm.

WO2011 / 158473 Special table 2012-514710 gazette JP 2001-59139 A

  An object of the present invention is to provide a vibration power generation device that can generate relatively large electric power by vibration, is not easily damaged, and has high reliability over a long period of time.

  According to one aspect of the disclosed technology, a vibration bending portion that is formed of a damping alloy and is bent by vibration, a magnetic field application portion that applies a magnetic field to the vibration bending portion, and a winding around the vibration bending portion. A vibration power generation device having a coil is provided.

  According to the vibration power generation device according to the above aspect, since the vibration bending portion is formed of the vibration damping alloy, it is difficult to break and can maintain high reliability over a long period of time.

FIG. 1A is a front view showing an example of the vibration power generation device according to the embodiment, FIG. 1B is a side view thereof, and FIG. 1C is shown by a line I-I in FIG. It is sectional drawing in a position. FIG. 2 is a schematic view showing a power generation device attached to a support. FIG. 3 is a diagram showing the results of examining the power generation capabilities of two vibration power generation devices. 4A is a micrograph of the surface of the Fe—Al alloy having a magnetostriction amount of 60 ppm, and FIG. 4B is a micrograph of the surface of the Fe—Al alloy having a magnetostriction amount of 80 ppm. FIGS. 5A to 5C are schematic views showing changes in magnetic flux density in a member made of a single crystal magnetic material such as Galfenol. FIGS. 6A to 6C are schematic diagrams showing changes in magnetic flux density in a member made of a magnetic material in which the internal magnetic flux density changes greatly due to the movement of the domain wall. FIG. 7 is a diagram showing the results of examining the electromotive force of a vibration power generation device in which a beam is formed of Galfenol, Fe—Al alloy, SUS430, or Fe—Cr—Al alloy.

  Hereinafter, before describing the embodiment, a preliminary matter for facilitating understanding of the embodiment will be described.

  As described above, by using Galfenol as a beam material, a vibration power generation device having a large power generation capability can be manufactured. However, although Galfenol is a single crystal and can be machined, it has poor ductility and malleability. Therefore, when processing into a beam, a fine crack and a chip | tip are easy to generate | occur | produce, and there exists a possibility that a crack and a chip | tip may be expanded by repeatedly receiving a vibration and a beam may be damaged finally. For this reason, the vibration power generation device using Galfenol as the material of the beam is not sufficiently reliable over a long period of time.

  In the following embodiments, a vibration power generation device that can generate relatively large electric power by vibration, is not easily damaged, and has high reliability over a long period of time will be described.

(Embodiment)
FIG. 1A is a front view showing an example of the vibration power generation device according to the embodiment, FIG. 1B is a side view thereof, and FIG. 1C is shown by a line I-I in FIG. It is sectional drawing in a position.

  As shown in FIGS. 1A to 1C, the vibration power generation device 10 according to this embodiment includes beams 11a and 11b, coils 12a and 12b, connecting yokes 13a and 13b, and permanent magnets 14a and 14b. And a back yoke 15.

  The beams 11a and 11b are examples of vibration bending portions. The permanent magnets 14a and 14b are an example of a magnetic field application unit that applies a magnetic field to the beam.

  Each of the beams 11a and 11b is formed in a thin and thin plate shape by a magnetic material whose domain wall moves when stress is applied. In this embodiment, the beams 11a and 11b are formed of an Fe (iron) -Al (aluminum) alloy. The size of the beams 11a and 11b is, for example, 8.2 mm (length) × 1 mm (width) × 0.2 mm (thickness).

  The beams 11a and 11b may be formed of ferritic stainless steel such as SUS430 and SUS405, or an Fe—Cr—Al alloy.

  The beams 11a and 11b are arranged to face each other, and coils 12a and 12b are wound around the beams 11a and 11b, respectively. The upper portions of the beams 11a and 11b are connected by a connecting yoke 13a, and the lower portions of the beams 11a and 11b are connected by a connecting yoke 13b.

  The N pole of the magnet 14a is connected to the ends of the beams 11a and 11b on the connecting yoke 13a side, and the S pole of the magnet 14b is connected to the end of the connecting yoke 13b side. The back yoke 15 is made of a magnetic material containing iron as a main component, and magnetically connects the south pole of the magnet 14a and the north pole of the magnet 14b. Thereby, the magnetic path which passes the magnet 14a, the beams 11a and 11b, the magnet 14b, and the back yoke 15 in order is formed.

  One of the connecting yokes 13a and 13b of the vibration power generation device 10 is fixed to the support. Here, as shown in FIG. 2, it is assumed that the connecting yoke 13a is fixed to the support 19, and the connecting yoke 13b side is free. In general, the side fixed to the support is called a fixed end, and the opposite side is called a movable end.

  When vibration is applied to the vibration power generation device 10, the beams 11a and 11b are curved according to the vibration, and the density of magnetic flux passing through the beams 11a and 11b changes. Thereby, the current according to the change of the magnetic flux density flows through the coils 12a and 12b. This current can be extracted from the coils 12a and 12b and used as electric power for driving the electronic device.

  Conventionally, it has been considered that the power generation capability of the vibration power generation device increases as the amount of magnetostriction of the beam increases. However, it has been found from experiments and research conducted by the inventors of the present application that a beam having a small magnetostriction amount may have a larger power generation capacity than a beam having a large magnetostriction amount.

  FIG. 3 is a diagram showing the results of examining the power generation capabilities of two vibration power generation devices under conditions where time is taken on the horizontal axis, and electromotive force is taken on the vertical axis, with an acceleration of 1 G and a vibration frequency of 150 Hz.

  As can be seen from FIG. 3, a vibration power generation device using a beam made of a Fe—Al alloy having a magnetostriction amount of 60 ppm is more powerful than a vibration power generation device using a beam made of a Fe—Al alloy having a magnetostriction amount of 80 ppm. Great ability.

  4A is a micrograph of the surface of the Fe—Al alloy having a magnetostriction amount of 60 ppm, and FIG. 4B is a micrograph of the surface of the Fe—Al alloy having a magnetostriction amount of 80 ppm. 4A and 4B, the average grain size of the Fe—Al alloy crystal having a magnetostriction amount of 60 ppm is about 100 μm, and the average grain size of the Fe—Al alloy crystal having a magnetostriction amount of 80 ppm is 200 μm. It turns out that it is a grade.

  In general, it is considered that the grain boundary in the polycrystalline metal is a hindrance when the domain wall moves, so it is considered that the larger the crystal grain size, the larger the magnetostriction amount and the higher the internal friction. . Therefore, conventionally, in order to improve the power generation capability of the vibration power generation device, the beam is formed of a magnetic metal having a large crystal grain size.

  As shown in FIG. 3, it is not clear why a vibration power generation device with a small amount of magnetostriction of a beam has a larger power generation capacity than a vibration power generation device with a large amount of magnetostriction of a beam. However, in the case of the Fe—Al alloy, it is considered that the change in the magnetic flux due to the movement of the domain wall has a greater influence on the power generation capacity than the amount of magnetostriction.

  FIGS. 5A to 5C are schematic views showing changes in magnetic flux density in a member made of a single crystal magnetic material such as Galfenol. 5A shows a state when there is no external magnetic field, FIG. 5B shows a state where an external magnetic field is applied, and FIG. 5C shows an external force applied with the external magnetic field applied. Shows the state.

  As shown in FIG. 5A, in the absence of an external magnetic field, the magnetic moment in the member 21 is in a random direction, and the internal magnetic flux density B is zero.

  When an external magnetic field H is applied to the member 21 as shown in FIG. 5B, the magnetic moment in the member 21 is affected by the external magnetic field and aligned in a certain direction, and the internal magnetic flux density B increases.

  When an external force is applied in this state, as shown in FIG. 5C, the magnetic moment in the member 21 changes its direction and becomes stable, and the internal magnetic flux density B changes.

  On the other hand, FIGS. 6A to 6C are schematic diagrams showing changes in magnetic flux density in a member made of a magnetic material in which the internal magnetic flux density greatly changes due to movement of the domain wall. 6A shows a state when there is no external magnetic field, FIG. 6B shows a state where an external magnetic field is applied, and FIG. 6C shows an external force applied while the external magnetic field is applied. Shows the state.

  As shown in FIG. 6A, in the state where there is no external magnetic field, the magnetic domains in the member 22 are kept in a balanced state, and the internal magnetic flux density is zero.

  When an external magnetic field H is applied to the member 22 as shown in FIG. 6B, the domain wall moves in the member 22 due to the influence of the external magnetic field H, and the internal magnetic flux density B increases.

  When an external force is applied in this state, the domain wall in the member 22 moves according to the stress as shown in FIG. 6C, and the internal magnetic flux density B changes.

  As a magnetic metal whose internal magnetic flux density greatly changes due to the movement of the domain wall, there is a damping alloy that converts vibration energy into heat energy. As this type of damping alloy, there are known Fe-Al alloys, ferritic stainless steels such as SUS430 and SUS405, and Fe-Cr-Al alloys (Silentaroy: manufactured by Toshiba). These vibration-damping alloys are polycrystalline, have relatively good workability, and are less likely to have defects such as cracks and chips during processing.

  The inventors of the present application have found that when these damping alloys are used as the beam material, a vibration power generation device having a relatively large power generation capability and capable of maintaining high reliability over a long period of time can be obtained.

  Hereinafter, a damping alloy suitable as a beam material for a vibration power generation device will be described.

(Fe-Al alloy)
The Fe—Al alloy used as the damping alloy has an Al content of 6 wt% to 10 wt%, and the balance is made of Fe and inevitable impurities. When the Al content is less than 6 wt% and when the Al content exceeds 10 wt%, the internal friction is reduced and the vibration damping properties are reduced. As a result, sufficient power generation capacity cannot be obtained.

  Moreover, when Al content is less than 6 wt%, it becomes difficult to obtain sufficient strength, and when the Al content exceeds 10 wt%, ductility and malleability are lowered.

  From these facts, the Al content in the Fe—Al alloy forming the beam is preferably 6 wt% to 10 wt%.

  When the average crystal grain size of the Fe—Al alloy is less than 100 μm, the magnetic domain becomes too small and the average magnetic field is easily canceled. On the other hand, if the average crystal grain size of the Fe—Al alloy exceeds 250 μm, the domain wall becomes difficult to move, and the vibration damping property is lowered. For this reason, the average crystal grain size of the Fe—Al alloy is preferably 100 μm or more and 250 μm or less.

(Stainless steel)
The composition of SUS430 used as a vibration damping alloy has a Cr content of 16 wt% to 18 wt%, the balance being Fe and inevitable impurities. When the Cr content is out of the above range, sufficient vibration damping cannot be obtained.

  The composition of SUS405 used as a damping alloy is that the Cr content is 11.5 wt% to 14.5 wt%, the Al content is 0.1 wt% to 0.3 wt%, the balance is Fe and inevitable impurities. is there. When the Cr content and the Al content are out of the above ranges, sufficient vibration damping cannot be obtained.

(Fe-Cr-Al alloy)
The composition of the Fe—Cr—Al alloy (Silentalo) used as the damping alloy is 12 wt% Fe content, 1.36 wt% Cr content, the balance being Al and inevitable impurities.

  FIG. 7 shows the electromotive force of a vibration power generation device in which a beam is formed of Galfenol, Fe—Al alloy, SUS430, or Fe—Cr—Al alloy with time on the horizontal axis and electromotive force on the vertical axis. It is a figure which shows a result. However, the acceleration is 1 G, and the vibration frequency is 140 Hz to 157 Hz.

  As shown in FIG. 7, the vibration power generation device in which the beam is formed of Fe—Al alloy, SUS430, or Fe—Cr—Al alloy is not as much as the vibration power generation device in which the beam is formed of Galfenol. A large electromotive force was obtained.

  As described above, the vibration power generation device according to the present embodiment uses the vibration-damping alloy whose domain wall greatly moves by vibration as the material of the beams 11a and 11b. Therefore, the processability is good, good reliability can be secured over a long period of time, and the power generation capacity is relatively high.

  The following additional notes are disclosed with respect to the above embodiments.

(Supplementary Note 1) A vibration bending portion formed of a damping alloy and curved by vibration;
A magnetic field application unit for applying a magnetic field to the vibration bending unit;
A vibration power generation device comprising a coil wound around the vibration bending portion.

  (Additional remark 2) The said vibration bending part has the plate-shaped 1st beam and 2nd beam arrange | positioned facing each other, The vibration power generation device of Additional remark 1 characterized by the above-mentioned.

  (Supplementary note 3) The vibration power generation device according to supplementary note 1 or 2, wherein the damping alloy has a property that when a stress is applied, a domain wall moves to change an internal magnetic flux density.

  (Supplementary note 4) The vibration according to any one of Supplementary notes 1 to 3, wherein the damping alloy is any one of an Fe-Al alloy, a ferritic stainless steel, and an Fe-Cr-Al alloy. Power generation device.

  (Supplementary note 5) The vibration power generation according to any one of supplementary notes 1 to 3, wherein the vibration damping alloy has an Al content of 6 wt% to 10 wt%, and the balance is Fe and inevitable impurities. device.

  (Supplementary note 6) The vibration power generation device according to any one of supplementary notes 1 to 3, wherein an average crystal grain size of the damping alloy is 100 μm or more and 250 μm or less.

  (Additional remark 7) Said damping alloy is stainless steel which Cr content is 16 wt%-18 wt%, and remainder consists of Fe and an unavoidable impurity, The any one of additional remark 1 thru | or 3 characterized by the above-mentioned. Vibration power generation device.

  (Supplementary note 8) The damping alloy is a stainless steel having a Cr content of 11.5 wt% to 14.5 wt%, an Al content of 0.1 wt% to 0.3 wt%, and the balance being Fe and inevitable impurities. The vibration power generation device according to any one of appendices 1 to 3, wherein the vibration power generation device is provided.

  (Supplementary note 9) In any one of supplementary notes 1 to 3, wherein the vibration damping alloy has an Fe content of 12 wt%, a Cr content of 1.36 wt%, and the balance consisting of Al and inevitable impurities. The vibration power generation device described.

  DESCRIPTION OF SYMBOLS 10 ... Vibration power generation device, 11a, 11b ... Beam, 12a, 12b ... Coil, 13a, 13b ... Connection yoke, 14a, 14b ... Permanent magnet, 15 ... Back yoke, 19 ... Support body.

Claims (5)

A vibration bending portion that is formed of a damping alloy and is bent by vibration;
A magnetic field application unit for applying a magnetic field to the vibration bending unit;
A vibration power generation device comprising: a coil wound around the vibration bending portion.   2. The vibration power generation device according to claim 1, wherein the vibration bending portion includes a plate-like first beam and a second beam arranged to face each other.   3. The vibration power generation device according to claim 1, wherein the damping alloy has a property that when a stress is applied, a domain wall moves to change an internal magnetic flux density. 4.   The vibration power generation device according to any one of claims 1 to 3, wherein the damping alloy is any one of an Fe-Al alloy, a ferritic stainless steel, and an Fe-Cr-Al alloy.   4. The vibration power generation device according to claim 1, wherein an average crystal grain size of the vibration damping alloy is 100 μm or more and 250 μm or less. 5.

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