JP6915367B2 - Power generation device - Google Patents

Description

The present invention relates to a power generation device.

Vibration power generation using vibration energy is being studied as a method of power generation. Vibration power generation is a power generation method that utilizes the piezoelectric effect of a piezoelectric material in which a voltage is generated according to strain according to applied pressure. Ceramics and the like are known as materials constituting the piezoelectric body. Further, Patent Document 1 discloses a piezoelectric film using a piezoelectric film made of a polymer electret (a polymer electret).

Japanese Unexamined Patent Publication No. 2014-207391

In vibration power generation, power generation efficiency can be improved by using resonance. The power generation efficiency is greatly improved at the resonance frequency. On the other hand, most of the vibrations in a general environment (environmental vibrations) are low-frequency vibrations. In order to efficiently perform vibration power generation using low-frequency environmental vibration, a power generation device having a sufficiently low resonance frequency is required. Further, as such a power generation device, it is desired to develop a power generation device using a piezoelectric film made of a polymer having high workability and flexibility.

Therefore, one of the purposes of the present invention is to provide a power generation device including a piezoelectric film made of a polymer electret, which can efficiently generate power by utilizing low-frequency environmental vibration.

A power generation device according to the present invention includes a piezoelectric unit and a weight. The piezoelectric unit is a piezoelectric element including a piezoelectric film made of a polymer electlet, a first electrode and a second electrode sandwiching the piezoelectric film in the thickness direction, and the first electrode opposite to the side of the first electrode in contact with the piezoelectric film. It includes an elastic member arranged on the side that adjusts the resonance frequency of the power generation device to 200 Hz or less. The weight is arranged so as to apply a load to the piezoelectric element and the elastic member.

According to the present invention, it is possible to provide a power generation device including a piezoelectric film made of a polymer electret, which can efficiently generate power by utilizing low-frequency environmental vibration.

It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 1. FIG. It is a schematic cross-sectional view of a piezoelectric element. It is a block diagram for demonstrating the power generation system provided with the power generation device. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 2. FIG. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 3. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 4. FIG. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 5. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 6. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 7. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 8. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 9. It is a schematic diagram which shows an example of the power generation device which concerns on Embodiment 10.

[Explanation of Embodiments of the Invention]
First, embodiments of the present invention will be listed and described. The power generation device of the present application includes a piezoelectric unit and a weight. The piezoelectric unit is a piezoelectric element including a piezoelectric film made of a polymer electlet, a first electrode and a second electrode sandwiching the piezoelectric film in the thickness direction, and the first electrode opposite to the side of the first electrode in contact with the piezoelectric film. It includes an elastic member arranged on the side that adjusts the resonance frequency of the power generation device to 200 Hz or less. The weight is arranged so as to apply a load to the piezoelectric element and the elastic member.

The power generation device is a device that generates power by the piezoelectric effect of a piezoelectric film made of a polymer electret. Resonance occurs in the presence of weights, and the Q value of the power generation device rises. The Q value is also called a quality coefficient, and in vibration, the larger this value is, the more stable the vibration is. In addition, the amount of power generated by a power generation device that uses vibration power generation increases as the Q value increases. This is because the amount of power generation is proportional to the square of the Q value. That is, by using a weight, the Q value of the power generation device can be increased and the power generation efficiency can be improved, but the resonance frequency is in the high frequency range exceeding 1000 Hz only by mounting a weight of a practical size. The resonance of low frequency environmental vibration cannot be utilized. For example, in the plane dimension of 40 mm × 40 mm, a weight having a plane direction of 40 mm × 40 mm and having a density of 7.7 g / cm ^{3 made of SUS440 is placed on a piezoelectric element having a thickness of 1.01 mm.} Explaining the case, the thicker the weight, the smaller the resonance frequency. However, even if the thickness of the weight is 100 mm, it is not practically sufficient because it is on the order of k (kilo) Hz or more. The present invention is characterized in that the resonance frequency of the power generation device is controlled to be within the frequency range corresponding to the environmental vibration by including an elastic member for adjusting the resonance frequency of the power generation device to 200 Hz or less. With the above-mentioned power generation device having these configurations, it is possible to efficiently generate power by utilizing environmental vibration. The generated electric energy can be taken out to the outside through the first electrode and the second electrode.

In the power generation device, the weight may be arranged so as to be in contact with the piezoelectric unit. By arranging the weight in contact with the piezoelectric unit, vibration is efficiently transmitted to the piezoelectric element, and power generation efficiency is improved.

In the power generation device, the elastic member may include a first elastic member made of an elastomer. By including the first elastic member made of an elastomer, a load is uniformly applied to the piezoelectric element, and the output electricity can be easily taken out as electricity close to a sine wave with less turbulence.

In the power generation device, the Young's modulus of the first elastic member may be 1 MPa or less. When the Young's modulus of the elastomer elastic member is 1 MPa or less, the resonance frequency of the power generation device can be reduced more reliably.

Here, an elastic member having a Young's modulus of 500 k (kilo) Pa (0.5 MPa) will be described as follows. The Poisson's ratio of the elastic member is 0.49, and the density is 1.1 g / cm ³ . A piezoelectric element having a plane dimension of 40 mm × 40 mm and a thickness of 1 mm is placed on an elastic member having a thickness of 6 mm in a plane direction of 40 mm × 40 mm. It is assumed that a weight having a plane dimension of 40 mm × 40 mm and having a density of 7.7 g / cm ³ made of SUS440, for example, is placed on the weight. Here, when the thickness of the weight is 50 mm and the displacement of the weight in the XY direction is fixed, the resonance frequency is 169 Hz. When the thickness of the weight is 75 mm and the displacement of the weight in the XY direction is fixed, the resonance frequency is 139 Hz. Further, when the thickness of the elastic member is 12 mm, the thickness of the weight is 50 mm, and the displacement of the weight in the XY direction is fixed, the resonance frequency is 82 Hz. When the thickness of the elastic member is 12 mm, the thickness of the weight is 75 mm, and the displacement of the weight in the XY direction is fixed, the resonance frequency is 67 Hz. When the target of the resonance frequency is 100 Hz or less, the Young's modulus needs to be about 0.5 MPa or less.

In the power generation device, the loss coefficient η of the first elastic member may be 0.5 or less. The smaller the loss coefficient η is, the more the power generation amount can be improved, and if the loss coefficient η is 0.5 or less, it becomes easy to secure a sufficient power generation amount.

In the power generation device, the elastomer may be silicone rubber. The elastomer may be urethane, silicone rubber, or one having an elastomeric property due to a foamed structure. Among them, silicone rubber is desirable because it can achieve both a small loss coefficient and low elasticity.

In the power generation device, the elastic member may include a second elastic member made of a diaphragm. By including the second elastic member made of a diaphragm in the elastic member, the resonance frequency can be sufficiently reduced.

In the above power generation device, the piezoelectric film may be made of a porous body. This is because the presence of pores in the polymer electret causes the thickness to fluctuate during pressure sensitivity, resulting in piezoelectricity.

In the above power generation device, the piezoelectric film may be made of a fluorine-containing resin. By adopting a piezoelectric film made of a fluorine-containing resin, it is possible to exhibit suitable piezoelectric characteristics, suitable heat resistance, and environmental resistance.

The thickness of the piezoelectric film is preferably 1 μm or more. This is because if it is too thin, the handleability will deteriorate. If it is 5 μm or more, it is still preferable. It is desirable to laminate the piezoelectric film because the amount of power generation increases by laminating the piezoelectric film sandwiched between the electrodes. The thickness of the piezoelectric film is preferably 100 μm or less, and more preferably 50 μm or less. For example, in the case of a structure in which a piezoelectric film having a thickness of 30 μm is sandwiched between aluminum foils of 50 μm, the resonance point changes only from 81.9 Hz to 82.0 Hz even if the number of layers is changed from 12 to 4.

The power generation device may further include a first support including a support magnet portion, which is arranged on the side opposite to the weight when viewed from the piezoelectric unit. The weight may include a weight ferromagnet portion made of a ferromagnet, which is magnetically attracted by the support magnet portion. By allowing a magnetic attraction force to act between the weight and the attractive support, the gravitational acceleration applied to the weight is increased in a pseudo manner, and as a result, the Q value becomes large. That is, the degree of deformation of the piezoelectric film can be improved, and the power generation efficiency can be improved.

The power generation device may further include a second support arranged on the side opposite to the weight when viewed from the piezoelectric unit. The weight may include a weight magnet portion made of a magnet. The second support is magnetically attracted by the weight magnet portion of the weight. The second support includes, for example, a ferromagnet or an attractive magnet on which a magnetic attractive force acts with the weight magnet portion. By allowing a magnetic attraction force to act between the weight and the support, the movement of the power generation device in the direction parallel to the surface of the piezoelectric film is suppressed, and vibration in the thickness direction of the piezoelectric film is suppressed. Can be larger.

The power generation device may further include a third support including a support repulsion magnet portion, which is arranged on the side opposite to the weight when viewed from the piezoelectric unit. The weight may include a weight magnet portion made of a magnet. The third support and the weight may be magnetically repelled. When the initial load of the piezoelectric film made of a porous body is large during non-vibration, the pores are crushed and the amount of power generation tends to decrease (the piezoelectric strain constant d value decreases). Therefore, the power generation efficiency can be improved by reducing the initial load applied to the piezoelectric film by utilizing the repulsive force of the magnet.

The power generation device includes a piezoelectric unit, a housing surrounding the weight, and a first load adjusting member inside the housing, which is provided between the weight and the housing and adjusts a load applied to the piezoelectric unit of the weight. May be further provided. The first load adjusting member reduces the initial load applied to the piezoelectric film. Thereby, the power generation efficiency of the power generation device can be improved. Further, when the weight is urged toward the piezoelectric unit side by the first load adjusting member, the resonance frequency can be adjusted to the lower frequency side.

The power generation device is located between a fourth support arranged on the side opposite to the weight when viewed from the piezoelectric unit, and a position between the weight and the fourth support, avoiding the position where the piezoelectric unit is provided. A second load adjusting member for adjusting the load applied to the piezoelectric unit of the weight may be further provided. The second load adjusting member reduces the initial load applied to the piezoelectric film. Thereby, the power generation efficiency of the power generation device can be improved. Further, when the weight is urged toward the piezoelectric unit side by the second load adjusting member, the resonance frequency can be adjusted to the lower frequency side.

In the above power generation device, the load application by the magnet can be dealt with by using a spring as well as a magnet or the like. Further, an electrostatic suction chuck or an electromagnet can be used. In the case of an electromagnet, a current is required, but the load and thus the resonance frequency can be adjusted by changing the magnitude of the current.

[Details of Embodiments of the present invention]
Next, an embodiment of the power generation device of the present application will be described with reference to FIGS. 1 to 12. In the drawings below, the same or corresponding parts are given the same reference number and the explanation is not repeated.

(Embodiment 1)
[Structure of power generation device]
The power generation device according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic view showing an example of a power generation device. With reference to FIG. 1, the power generation device 10 includes a weight 12 and a piezoelectric unit 20. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member 16 which is a first elastic member. In FIG. 1, the negative direction of the z-axis is the direction in which gravity acts. That is, the weight 12 applies a load to the piezoelectric element 14 and the rubber member 16.

The weight 12 is arranged on the main surface 14A side of the piezoelectric element 14 so as to be in contact with the piezoelectric unit 20. The rubber member 16 is arranged on the main surface 14B side of the piezoelectric element 14. The piezoelectric element 14 is electrically connected to an electric circuit 50 for extracting the generated electricity. The rubber member 16, the piezoelectric element 14, and the weight 12 are stacked in this order so that the rubber member 16 is on the lower side in the vertical direction.

The power generation device 10 is installed so that the piezoelectric element 14 and the rubber member 16 are vertically downward with respect to the weight 12 so that the load of the weight 12 is appropriately applied to the piezoelectric element 14 and the rubber member 16. Used.

In the present embodiment, the width W of the power generation device 10 in the x-axis direction is 40 mm. _{The height h 1} of the weight 12 in the z-axis direction is 50 mm or 75 mm. _{The height h 2} of the piezoelectric element 14 in the z-axis direction is 1 mm. _{The height h 3} of the rubber member 16 in the z-axis direction is 5 mm to 12 mm. However, these are examples, and the sizes of the power generation device 10 and each member are not particularly limited to these. Although not shown, the width in the direction perpendicular to the x-axis (y-direction) in the cross section perpendicular to the z-axis direction may be set to be about the same as the width W in the x-axis direction.

Next, the members constituting the power generation device 10 will be described. The weight 12 applies a load to the piezoelectric element 14 and the rubber member 16 which is the first elastic member. The material of the weight 12 is not particularly limited, but a metal having a high specific density or a resin filled with a filler of a metal having a high specific density is preferable. Examples of the metal having a high specific density include stainless steel, lead, and tungsten.

In the present embodiment, the rubber member 16 made of silicone rubber is used as the elastic member (first elastic member). The rubber member 16 adjusts the resonance frequency of the power generation device 10 to 200 Hz or less. The silicone rubber constituting the rubber member 16 is a kind of elastomer. By using an elastic member made of an elastomer, a load is uniformly applied to the piezoelectric element 14, and the output electricity can be taken out as electricity close to a sine wave with less turbulence.

The Young's modulus of the first elastic member is preferably 1 MPa or less, and more preferably 0.7 MPa or less. By using an elastic member having such Young's modulus, it is possible to more reliably reduce the resonance frequency of the power generation device 10. The Young's modulus was measured as follows. It was derived from the relationship between the pressure and the sample thickness when gradually applying a load to a sample having a diameter of 20 mm and a thickness of 18 mm using a precision universal testing machine AG-250 kNI M1 (manufactured by Shimadzu Corporation). Specifically, the "sample compressibility (%)" derived by dividing the difference between the sample thickness under a 2N (0.0064 MPa) load and the sample thickness under a 5N (0.015 MPa) load by the original sample thickness (18 mm). ) ”, The pressure difference between 2N load and 5N load: 0.0095 MPa was divided.

Further, the loss coefficient η of the first elastic member is preferably 0.5 or less, and more preferably 0.45 or less. The loss coefficient η is one of the evaluation indexes of the vibration damping characteristics of the material, and is also called the loss tangent (tan δ). The loss factor η of the first elastic member can be measured by a dynamic viscoelasticity measuring device. The larger the loss coefficient η is, the more energy is absorbed and the higher the damping characteristic is. The loss coefficient (tan δ) of the elastic member in the usage environment can be measured by DMS. Specifically, a strip-shaped sample having a width of 10 mm and a thickness of 1 mm can be held between chucks at a distance of 20 mm, and a strain of 5 μm can be applied for measurement.

Here, it is known that the amount of power generated by the power generation device 10 using the piezoelectric element 14 is proportional to the square of the Q value described above. As the loss coefficient η becomes smaller, this Q value becomes larger and the amount of power generation is improved. Therefore, in order to secure a sufficient Q value and thereby secure a sufficient amount of power generation, the loss coefficient η of the first elastic member is preferably 0.5 or less.

The elastic member preferably has a low Young's modulus and a low loss coefficient, and the elastomer is a relatively suitable material. Elastomers are usually resilient structures, but lowering Young's modulus makes the structure easier to move, making it difficult to lower the loss factor η. As a result of various studies, the present inventors have found that silicone rubber is suitable for the purpose of making the structure easy to move and lowering the loss coefficient η. Silicone rubber is obtained by cross-linking a silicone resin, and desired properties can be obtained by mixing a silicone polymer and a cross-linking agent.

An example of the above-mentioned silicone rubber is a silicone rubber obtained from DOWN CORNING TORAY SILPOT 184 W / C manufactured by Toray Dow Corning Co., Ltd. Here, by setting the composition of the main agent: curing agent at the time of forming the silicone rubber to 19: 1, it is possible to obtain a film made of silicone rubber having a Young's modulus of 0.5 MPa, a room temperature, and a loss coefficient of 0.35 at 100 Hz. ..

With reference to FIGS. 1 and 2, the piezoelectric element 14 includes a piezoelectric film 30 made of a polymer electret, a first electrode 32 and a second electrode 34 that sandwich the piezoelectric film 30 in the thickness direction (z-axis direction). Includes protective layers 36, 38. The electret is a dielectric (insulator) that holds an electric charge semi-permanently.

The piezoelectric film 30 is made of a layered porous body having pores 40 in the layer. The presence of the pores 40 in the layer allows the charge to be properly captured. Therefore, by adopting a porous polymer electret as the piezoelectric film 30, suitable piezoelectric characteristics can be exhibited. Due to the porous body, non-uniform deformation occurs with respect to pressure. Due to this deformation, the relative position of the electric charge becomes non-uniform, polarization is promoted, and piezoelectricity is exhibited.

The porosity of the piezoelectric film 30 is not particularly limited as long as it can appropriately capture electric charges during piezoelectric treatment such as corona discharge. The porosity is preferably 10% or more, more preferably 15% or more. The porosity is preferably 40% or less, more preferably 35% or less. If the porosity is too large, the durability against a load repeatedly applied becomes low, and the piezoelectric characteristics may change due to deformation over time. On the other hand, if the porosity is too small, the amount of deformation with respect to the load becomes small, and there is a possibility that sufficient piezoelectric characteristics cannot be exhibited. The porosity refers to, for example, the ratio of the pore volume (V ₀ ) to the apparent volume (V) of the piezoelectric film 30, and is calculated by the following formula.

Porosity (%) = (V ₀ / V) x 100

The piezoelectric film 30 is made of a fluorine-containing resin. By applying a polymer electret made of a fluorine-containing resin as the piezoelectric film 30, suitable piezoelectric characteristics can be exhibited.

Examples of the fluorine-containing resin include a fluoroethylene polymer containing fluoroethylene as a monomer unit. Examples of the fluoroethylene polymer include polytetrafluoroethylene (PTFE: Polytetrafluoroethylene), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA: Tetrafluorooilene-perfluoroalkylvinylester copolymer), and tetrafluoroethylene / hexafluoropropylene copolymer. : Tetrafluorooilerene-hexafluoropropylene copolymer), tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether (EPA: Tetrafluorooilerene-hexafluoropropyrene-perfluoreyletermerethylene) Fluoroethylene, chlorotrifluoroethylene / ethylene copolymer and the like can be mentioned. Among these, PTFE is preferable. The porous material of PTFE is preferable because it has an excellent ability to trap charges. PTFE can also be used as a mixture with one or more other fluoroethylene polymers. The tetrafluoroethylene copolymer such as PFA, FEP, and EPA may be any of a random copolymer, a block copolymer, and a pendant type copolymer.

By performing a piezoelectric treatment on a layered porous body made of a fluorine-containing resin by corona discharge or the like, the porous body has a piezoelectric property, and a piezoelectric film 30 which is a polymer electret is formed.

The first electrode 32 and the second electrode 34 are arranged so as to sandwich the piezoelectric film 30. By connecting the first electrode 32 and the second electrode 34 to the external electric circuit 50, the electric energy generated in the piezoelectric film 30 can be taken out to the outside.

The first electrode 32 and the second electrode 34 can be obtained, for example, by forming a metal film on the surface of the piezoelectric film 30 by vapor deposition or the like. It is preferable that the surfaces of the first electrode 32 and the second electrode 34 and the surface of the piezoelectric film 30 can move individually. Since the surfaces of the first electrode 32 and the second electrode 34 and the surface of the piezoelectric film 30 are not adhered or only partially adhered, the deformation of the piezoelectric film 30 may be hindered by the electrodes. This is because high piezoelectricity can be obtained because there is no such material. Further, the amount of charge on the electrode surface induced by the surface charge of the piezoelectric film 30 fluctuates due to the change in the positional relationship between the surface of the electrode and the surface of the piezoelectric film 30 facing the electrode. That is, it can contribute to power generation. The first electrode 32 and the second electrode 34 are preferably made of copper foil or aluminum foil, and particularly preferably made of aluminum foil, because of their electrical characteristics, price, availability, and thin film processing.

If the thickness of the aluminum foil is too thin, there is a high risk of breakage, so 1 μm or more is preferable, and 10 μm or more is more preferable. The thickness is preferably 50 μm or less, and more preferably 20 μm or less so that the thickness does not become too thick when the amount of power generation by stacking is increased and the degree of freedom in designing the power generation device 10 can be secured. According to the study results of the present inventors, when comparing the power generation amount of the power generation device 10 using the aluminum foil with a thickness of 50 μm and the power generation device 10 using the aluminum foil with a thickness of 18 μm, the aluminum foil with a thickness of 18 μm was used. It has actually been confirmed that the power generation device 10 has a significantly larger amount of power generation than the power generation device 10 using the aluminum foil having a thickness of 50 μm.

The piezoelectric element 14 may include protective layers 36 and 38 for protecting the first electrode 32 and the second electrode 34. The protective layers 36 and 38 impart moisture resistance, impact resistance, and the like to the surface of the piezoelectric film 30. These protective layers 36 and 38 can be formed by attaching a resin film such as a polyethylene terephthalate film or a polypropylene film with an adhesive. The protective layers 36 and 38 are not essential and can be omitted.

The power generation by the power generation device 10 utilizes the piezoelectric effect of the piezoelectric film 30 made of a polymer electret. When vibration is transmitted to the piezoelectric film 30 of the piezoelectric element 14, polarization occurs in the piezoelectric film 30 due to fluctuations in the relative positions of electric charges, and power is generated. The power generation efficiency is greatly improved at the resonance frequency. Further, the presence of the weight 12 improves the Q value of the power generation device 10. Further, the rubber member 16 adjusts the resonance frequency of the power generation device 10. As a result, it becomes possible to provide a power generation device 10 capable of efficiently utilizing environmental vibration and generating power with sufficient power generation efficiency.

[Power generation system]
By electrically connecting the external electric circuit 50 to the power generation device 10, electric energy can be extracted from the power generation device 10 to the outside. FIG. 3 is a block diagram for explaining a power generation system including the power generation device 10. With reference to FIGS. 1 and 3, the electric circuit 50 is configured as a power storage circuit including a rectifier 51 and a secondary battery 52. The electric circuit 50 is connected to the first electrode 32 and the second electrode 34 of the power generation device 10. The electric circuit 50 extracts electric energy from the power generation device 10 via the first electrode 32 and the second electrode 34.

The rectifier 51 converts the AC voltage output from the power generation device 10 into a DC voltage. The secondary battery 52 stores the electric energy output from the power generation device 10. By connecting an external electric component or the like to the secondary battery 52, the electric energy stored in the secondary battery 52 is released. A DC-DC converter for step-up / step-down for controlling the charging voltage may be included between the rectifier 51 and the secondary battery 52. Further, the secondary battery 52 may be a capacitor.

The above is the content of the first embodiment. The power generation device 10 according to the first embodiment includes a piezoelectric film 30 made of a polymer electret. Since the polymer electret made of resin has flexibility, it has an advantage that it is not easily cracked by impact. Moreover, a large-area piezoelectric material can be easily manufactured. Further, the power efficiency can be further improved by laminating layered polymer electrets to form a multilayer body. Therefore, the power generation device 10 can be applied to a wide range of applications.

Further, the polymer electlet itself has a problem that the power generation efficiency per unit volume is smaller than that of a piezoelectric ceramic such as PZT (lead zirconate titanate Piezoelectric Transducer). Sufficient power generation efficiency can be achieved as the power generation device 10. In particular, by providing the rubber member 16 as an elastic member for adjusting the resonance frequency of the power generation device 10 to 200 Hz or less, and the weight 12 for applying a load to the piezoelectric element 14 and the rubber member 16, it is efficient from low-frequency environmental vibration. Can provide a power generation device 10 capable of generating electricity.

(Embodiment 2)
Next, the power generation device 10 according to the second embodiment will be described with reference to FIG. FIG. 4 is a schematic view showing an example of the power generation device 10 according to the second embodiment.

With reference to FIG. 4, the power generation device 10 according to the second embodiment includes a weight 12 and a piezoelectric unit 20 like the power generation device 10 according to the first embodiment. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member 16 which is a first elastic member. However, the arrangement positions of the rubber member 16 and the piezoelectric element 14 are different from those of the power generation device 10 in the first embodiment. Specifically, the piezoelectric element 14, the rubber member 16, and the weight 12 are stacked in this order so that the piezoelectric element 14 is on the lower side in the vertical direction. In this case, both the weight 12 and the rubber member 16 are arranged on the main surface 14A side when viewed from the piezoelectric element 14. The weight 12 is arranged in the positive direction (upper side) along the z-axis with respect to the piezoelectric element 14 and the rubber member 16. By arranging in this way, a load by the weight 12 is applied to both the piezoelectric element 14 and the rubber member 16.

The power generation device 10 according to the second embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Therefore, the power generation device 10 according to the second embodiment can also efficiently generate power by utilizing the low frequency environmental vibration as in the first embodiment. Further, other advantageous effects are also exhibited in the same manner as in the first embodiment.

(Embodiment 3)
Next, the power generation device 10 according to the third embodiment will be described with reference to FIG. FIG. 5 is a schematic view showing an example of the power generation device 10 according to the third embodiment.

With reference to FIG. 5, the power generation device 10 in the third embodiment includes a weight 12 and a piezoelectric unit 20 in the same manner as the power generation device 10 in the first embodiment. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member which is a first elastic member. However, the power generation device 10 in the third embodiment is different from the first embodiment in that it includes a plurality of rubber members. The plurality of rubber members 16a and 16b are arranged so as to sandwich the piezoelectric element 14 from above and below in the thickness direction. The rubber member 16a is arranged on the main surface 14A side of the piezoelectric element 14. The rubber member 16b is arranged on the main surface 14B side of the piezoelectric element 14. The vertical thickness of each of the rubber member 16a and the rubber member 16b is about half the thickness of the rubber member 16 in the first embodiment.

In the power generation device 10 according to the third embodiment, the rubber member 16b, the piezoelectric element 14, the rubber member 16a, and the weight 12 are stacked in this order so that the rubber member 16b is on the lower side in the vertical direction. The weight 12 is arranged in the positive direction (upper side) along the z-axis with respect to the rubber member 16b, the piezoelectric element 14, and the rubber member 16a. By arranging in this way, the load by the weight 12 is applied to the rubber member 16b, the piezoelectric element 14, and the rubber member 16a.

The power generation device 10 according to the third embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Therefore, the power generation device 10 according to the second embodiment can also efficiently generate power by utilizing the low frequency environmental vibration as in the first embodiment. Further, other advantageous effects are also exhibited in the same manner as in the first embodiment.

(Embodiment 4)
Next, the power generation device 10 according to the fourth embodiment will be described with reference to FIG. FIG. 6 is a schematic view showing an example of the power generation device 10 according to the fourth embodiment.

With reference to FIG. 6, the power generation device 10 according to the fourth embodiment includes a weight 12 and a piezoelectric unit 20 like the power generation device 10 according to the first embodiment. However, the piezoelectric unit 20 includes a piezoelectric element 14 and, as an elastic member, a diaphragm member 18 which is a second elastic member instead of the rubber member 16 which is the first elastic member. The diaphragm member 18, the piezoelectric element 14, and the weight 12 are stacked in this order so that the diaphragm member 18 is on the lower side in the vertical direction. By arranging in this way, the load by the weight 12 is applied to both the diaphragm member 18 and the piezoelectric element 14.

The diaphragm constituting the diaphragm member 18 is a metal or non-metal thin film that is displaced in response to the action of pressure. The diaphragm member 18 has a support having a shape that opens at the top surface of the columnar body and has a hollow recess in a cross section along the vertical direction, and a diaphragm whose outer periphery is fixed by the support so as to close the top surface. And. The thickness of the diaphragm used in this embodiment is 0.2 mm.

Like the rubber member 16, the diaphragm member 18 has the effect of lowering the resonance frequency of the power generation device 10 to 200 Hz or less. The power generation device 10 according to the fourth embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Therefore, even in the power generation device 10 according to the fourth embodiment, it is possible to efficiently generate power by utilizing low-frequency environmental vibration. Further, other advantageous effects are also exhibited in the same manner as in the first embodiment.

(Embodiment 5)
Next, the power generation device 10 according to the fifth embodiment will be described with reference to FIG. 7. FIG. 7 is a schematic view showing an example of the power generation device 10 according to the fifth embodiment.

With reference to FIG. 7, the power generation device 10 according to the fifth embodiment includes a weight 12 and a piezoelectric unit 20. The piezoelectric unit 20 includes both a piezoelectric element 14 and, as elastic members, a rubber member 16 (first elastic member) and a diaphragm member 18 (second elastic member). The diaphragm member 18, the rubber member 16, the piezoelectric element 14, and the weight 12 are stacked in this order so that the diaphragm member 18 is on the lower side in the vertical direction. In FIG. 7, the position of the piezoelectric element 14 and the position of the rubber member 16 can be interchanged.

The power generation device 10 according to the fifth embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Further, when the rubber member 16 is used alone (the first embodiment and the second embodiment) by using the rubber member 16 and the diaphragm member 18 together as the elastic member, or when the diaphragm member 18 is used alone. Compared with (Embodiment 4), the resonance frequency can be further reduced by the synergistic effect. As a result, the power generation device 10 according to the fifth embodiment can exhibit higher power generation performance as compared with the case where the rubber member 16 or the diaphragm member 18 is used alone.

(Embodiment 6)
Next, the power generation device 10 according to the sixth embodiment will be described with reference to FIG. FIG. 8 is a schematic view showing an example of the power generation device 10 according to the sixth embodiment.

With reference to FIG. 8, the power generation device 10 according to the sixth embodiment includes a weight 12, a piezoelectric unit 20, and a first support 22. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member 16 which is a first elastic member. The first support 22, the rubber member 16, the piezoelectric element 14, and the weight 12 are stacked in this order so that the first support 22 is on the lower side in the vertical direction. By arranging in this way, the load due to the weight 12 is applied to both the piezoelectric element 14 and the rubber member 16. The first support 22 and the weight 12 are arranged so as to sandwich the piezoelectric unit 20.

The first support 22 includes a support magnet portion made of a magnet. The entire first support 22 may be made of a magnet. In the example shown in FIG. 8, the entire first support 22 is made of a magnet.

The weight 12 includes a weight ferromagnetic portion made of a ferromagnetic material, which is magnetically attracted by the support magnet portion. Preferably, the entire weight 12 is made of a ferromagnetic material. In the example shown in FIG. 8, the entire weight 12 is made of a ferromagnetic material.

The power generation device 10 according to the sixth embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Further, in the present embodiment, the weight 12 is magnetically attracted by the first support 22 including the support magnet portion in the negative direction of the z-axis. Due to this magnetic attraction, movement in the plane perpendicular to the z-axis of the power generation device 10 (movement in a direction parallel to the surface of the piezoelectric film 30) is suppressed. As a result, vibration in the z-axis direction can be efficiently transmitted to the piezoelectric film 30. Further, as a result of increasing the gravitational acceleration applied to the weight in a pseudo manner, the Q value becomes large. That is, the degree of deformation of the piezoelectric film 30 can be improved, and the power generation efficiency can be improved.

(Embodiment 7)
Next, the power generation device 10 according to the seventh embodiment will be described with reference to FIG. FIG. 9 is a schematic view showing an example of the power generation device 10 according to the seventh embodiment.

With reference to FIG. 9, the power generation device 10 according to the seventh embodiment includes a weight 12, a piezoelectric unit 20, and a second support 24. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member 16 which is a first elastic member. The second support 24, the rubber member 16, the piezoelectric element 14, and the weight 12 are stacked in this order so that the second support 24 is on the lower side in the vertical direction. By arranging in this way, a load by the weight 12 is applied to both the piezoelectric element 14 and the rubber member 16. The second support 24 and the weight 12 are arranged so as to sandwich the piezoelectric unit 20.

The weight 12 includes a weight magnet portion made of a magnet. The entire weight 12 may be made of a magnet. In the example shown in FIG. 9, the entire weight 12 is composed of a magnet.

The second support 24 includes a portion made of a material that is magnetically attracted by the weight magnet portion. As an example, the second support 24 includes a ferromagnet, or includes a ferromagnet portion made of a ferromagnet. As another example, the second support 24 includes a magnet portion made of an attractive magnet on which a magnetic attractive force acts with the weight magnet portion.

The power generation device 10 according to the seventh embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Further, in the present embodiment, when the second support 24 includes a ferromagnetic part, the second support 24 magnetically moves in the positive direction of the z-axis due to the magnetic force of the weight 12. Is sucked into. Further, when the second support 24 includes an attractive magnet portion that exerts a magnetic attraction force between the weight magnet portion and the weight magnet portion, the weight 12 and the second support 24 are magnetically attracted along the z-axis. Mutually. Due to this magnetic attraction, movement in the plane perpendicular to the z-axis of the power generation device 10 (movement in a direction parallel to the surface of the piezoelectric film 30) is suppressed. As a result, vibration in the z-axis direction can be efficiently transmitted to the piezoelectric film 30. Further, as a result of increasing the gravitational acceleration applied to the weight in a pseudo manner, the Q value becomes large. That is, the degree of deformation of the piezoelectric film 30 can be improved, and the power generation efficiency can be improved.

(Embodiment 8)
Next, the power generation device 10 according to the eighth embodiment will be described with reference to FIG. FIG. 10 is a schematic view showing an example of the power generation device 10 according to the eighth embodiment.

With reference to FIG. 10, the power generation device 10 according to the eighth embodiment includes a weight 12, a piezoelectric unit 20, and a third support 26. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member 16 which is a first elastic member. The third support 26, the rubber member 16, the piezoelectric element 14, and the weight 12 are stacked in this order so that the third support 26 is on the lower side in the vertical direction. By arranging in this way, a load by the weight 12 is applied to both the piezoelectric element 14 and the rubber member 16. The third support 26 and the weight 12 are arranged so as to sandwich the piezoelectric unit 20.

In the eighth embodiment, the weight 12 includes a weight magnet portion made of a magnet. The entire weight 12 may be made of a magnet. In the example shown in FIG. 10, the entire weight 12 is composed of a magnet.

The third support 26 is a support that is magnetically repelled by the weight. The third support 26 includes a support repulsive magnet portion made of a magnet having resilience to the weight 12. The entire third support 26 may be made of a magnet having resilience to the weight 12. In the example shown in FIG. 10, the entire third support 26 is composed of a magnet having resilience to the weight 12.

The power generation device 10 according to the eighth embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration.

In the piezoelectric film 30 made of a porous body, if the initial load applied in a state without vibration is large, the holes tend to be crushed and the amount of power generation tends to decrease. This is because the piezoelectric strain constant d decreases when the initial load is large. If the piezoelectric strain constant d is small, the power generation efficiency is lowered. Therefore, it is desirable that the initial load applied to the piezoelectric film 30 is low. In this case, it is conceivable to omit the weight 12, but in a state where vibration is generated, a larger load is applied to the piezoelectric film 30 due to the acceleration of the weight 12, and the piezoelectric film 30 is greatly deformed by the vibration. It has the effect of becoming. Therefore, while making the weight 12 an essential component, in order to reduce the initial load applied to the piezoelectric film 30, a repulsive force is applied between the weight 12 and the third support 26, and the magnetic repulsive force is used. do. As a result, the power generation efficiency of the power generation device 10 can be improved.

(Embodiment 9)
Next, the power generation device 10 according to the ninth embodiment will be described with reference to FIG. FIG. 11 is a schematic view showing an example of the power generation device 10 according to the ninth embodiment.

With reference to FIG. 11, the power generation device 10 according to the ninth embodiment includes a weight 12, a piezoelectric unit 20, a housing 54, and a spring 56 as a first load adjusting member. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member 16 which is a first elastic member. The housing 54 is configured to surround the weight 12, the piezoelectric unit 20, and the spring 56. The spring 56 is provided in the housing 54 between the weight 12 and the housing 54. Specifically, the spring 56 is provided between the upper surface 12A of the weight 12 and the wall surface 54A on the inner side of the housing 54 facing the upper surface 12A. The spring 56 is a load adjusting member that adjusts the load applied to the piezoelectric unit 20 of the weight 12.

The power generation device 10 according to the ninth embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Further, in the present embodiment, the initial load applied to the piezoelectric film 30 is reduced by the spring 56 which is the first load adjusting member. As a result, the power generation efficiency of the power generation device 10 is improved. Further, when the weight 12 is urged to the piezoelectric unit 20 side by the spring 56, the resonance frequency can be adjusted to the lower frequency side.

(Embodiment 10)
Next, the power generation device 10 according to the tenth embodiment will be described with reference to FIG. FIG. 12 is a schematic view showing an example of the power generation device 10 according to the tenth embodiment.

With reference to FIG. 12, the power generation device 10 according to the tenth embodiment includes a weight 12, a piezoelectric unit 20, a fourth support 58, and a plurality of springs 60 and 62 as a second load adjusting member. Be prepared. In the example of FIG. 12, two springs 60 and 62 are shown. The piezoelectric unit 20 includes a piezoelectric element 14 and a rubber member 16 which is a first elastic member.

The fourth support 58 is arranged on the side opposite to the weight when viewed from the piezoelectric unit 20. Both ends of the springs 60 and 62 are attached to the lower surface 12B of the weight 12 and the upper surface 58A of the fourth support 58, respectively. The springs 60 and 62 are provided between the weight 20 and the fourth support 58, respectively, at positions avoiding the position where the piezoelectric unit 20 is provided, specifically, on the side portion of the piezoelectric unit 20. ing.

The power generation device 10 according to the tenth embodiment has a sufficiently low (specifically, 200 Hz or less) resonance frequency suitable for low frequency environmental vibration. Further, in the present embodiment, the initial load applied to the piezoelectric film 30 is reduced by the springs 60 and 62 which are the second load adjusting members. Thereby, the power generation efficiency of the power generation device 10 can be improved. Further, when the weight 12 is urged to the piezoelectric unit 20 side by the springs 60 and 62, the resonance frequency can be adjusted to the lower frequency side.

The above is the contents of the power generation device 10 of each embodiment. As described above, according to the power generation device according to the above embodiment, there is provided a power generation device including a piezoelectric film made of a polymer electret, which can efficiently generate power by utilizing low frequency environmental vibration. It becomes possible.

Except for the third embodiment (FIG. 5) having a plurality of rubber members 16a and 16b, an example of the power generation device 10 including a single rubber member 16 is shown in each elastic member, but in other examples. May also be provided with a plurality of elastic members. Further, not only the elastic member but also other members such as the piezoelectric element 14 have a single number of members as long as the weight 12 is arranged so as to apply a load to the piezoelectric element 14 and the elastic members 16 and 18. The present invention is not limited to the above, and a plurality of members may be provided for each.

It should be understood that the embodiments disclosed here are exemplary in all respects and are not restrictive in any way. The scope of the present invention is not defined as described above, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The power generation device of the present application may be particularly advantageously applied to vibration power generation utilizing low frequency environmental vibration.

10 Power generation device 12 Weight 12A Top surface 12B Bottom surface 14 Piezoelectric element 14A Main surface 14B Main surface 16 Rubber member 16a Rubber member 16b Rubber member 18 Diaphragm member 20 Piezoelectric unit 22 First support 24 Second support 26 Third support Body 30 Piezoelectric film 32 First electrode 34 Second electrode 36 Protective layer 38 Protective layer 40 Pore 50 Electric circuit 51 Rectifier 52 Secondary battery 54 Housing 54A Wall surface 56, 60, 62 Spring 58 Fourth support 58A Top surface

Claims (13)

Piezoelectric unit and
With weights,
The piezoelectric unit is
A piezoelectric film made of a polymer electret, a piezoelectric element including a first electrode and a second electrode sandwiching the piezoelectric film in the thickness direction, and a piezoelectric element.
An elastic member including a first elastic member made of an elastomer , which is arranged on the side of the first electrode opposite to the side in contact with the piezoelectric film and which adjusts the resonance frequency of the power generation device to 200 Hz or less. Stacked and
The weight is a power generation device arranged so as to load a load on the piezoelectric element and the elastic member. The power generation device according to claim 1, wherein the weight is arranged so as to be in contact with the piezoelectric unit. The power generation device according to claim 1 , wherein the Young's modulus of the first elastic member is 1 MPa or less. The power generation device according to any one of claims 1 to 3, wherein the loss coefficient η of the first elastic member is 0.5 or less. The power generation device according to any one of claims 1 to 4 , wherein the elastomer is a silicone rubber. The power generation device according to any one of claims 1 to 5 , wherein the elastic member includes a second elastic member made of a diaphragm. The power generation device according to any one of claims 1 to 6 , wherein the piezoelectric film is made of a porous body. The power generation device according to claim 7 , wherein the piezoelectric film is made of a fluorine-containing resin. A first support including a support magnet portion, which is arranged on the side opposite to the weight when viewed from the piezoelectric unit, is further provided.
The power generation device according to any one of claims 1 to 8 , wherein the weight includes a weight ferromagnetic portion made of a ferromagnetic material, which is magnetically attracted by the support magnet portion. A second support arranged on the side opposite to the weight when viewed from the piezoelectric unit is further provided.
The weight includes a weight magnet portion made of a magnet, and includes a weight magnet portion.
The power generation device according to any one of claims 1 to 8 , wherein the second support is magnetically attracted by the weight. A third support including a support repulsion magnet portion, which is arranged on the side opposite to the weight when viewed from the piezoelectric unit, is further provided.
The weight includes a weight magnet portion made of a magnet, and includes a weight magnet portion.
The power generation device according to any one of claims 1 to 8 , wherein the third support and the weight magnetically repel each other. A housing that surrounds the piezoelectric unit and the weight,
Claims 1 to 11 further include a first load adjusting member provided between the weight and the housing in the housing and for adjusting a load applied to the piezoelectric unit of the weight. The power generation device according to any one of the above. A fourth support arranged on the side opposite to the weight when viewed from the piezoelectric unit,
A second load adjusting member which is provided between the weight and the fourth support at a position avoiding the position where the piezoelectric unit is provided and which adjusts the load applied to the piezoelectric unit of the weight. The power generation device according to any one of claims 1 to 11 , further comprising.

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