JP6320843B2 - Power generator - Google Patents

Description

  The present invention is manufactured using a power generation device that performs power generation (energy conversion from kinetic energy (vibration energy) to electrical energy) by changing the distance between a dielectric and an electret, particularly using MEMS [Micro Electromechanical System] technology. The present invention relates to a vibration drive type capacitive power generator.

  FIG. 46 is a schematic diagram showing a conventional example of a vibration power generation apparatus. 46, reference numeral 201 indicates an upper substrate, reference numeral 202 indicates a lower substrate, reference numeral 203 indicates an electret, reference numeral 204 indicates a counter electrode, reference numeral 205 indicates a base electrode, and reference numeral 206 indicates a spring. The upper substrate 201 is a movable body that is elastically supported so as to be displaceable in a biaxial plane direction (X direction, Y direction) with respect to the lower substrate 202.

  The principle of operation of the vibration power generation apparatus having the above-described configuration is that the overlapping area of the electret 203 and the counter electrode 204 is changed by vibration in the biaxial plane direction (X direction, Y direction) while maintaining a predetermined gap distance. In this method, a change in charge induced in the counter electrode 204 is extracted as a current (so-called electrostatic induction method).

  In addition, as a related technique of the vibration power generation device manufactured using the MEMS technique, for example, Patent Document 1 and Non-Patent Documents 1 and 2 can be cited.

JP 2007-31551 A

Y.Naruse, N.Matsubara, K.Mabuchi, M.Izumi, K.Honma, "ELECTROSTATIC MICRO POWER GENERATOR FROM LOW FREQUENCY VIBRATION SUCH AS HUMAN MOTION", Proceedings of PowerMEMS 2008+ microEMS 2008, Sendai, Japan, November 9- 12, (2008) M.Edamoto, Y.Suzuki, N.Kasagi, K.Kashiwagi, Y.Morizawa, T.Yokoyama, T.Seki, and M.Oba, "LOW-RESONANT-FREQUENCY MICRO ELECTRET GENERATOR FOR ENERGY HARVESTING APPLICATION", Proc. IEEE Int. Conf. MEMS 2009, Sorrento, (2009), pp.1059-1062

  However, the above-described conventional vibration power generation device has a μW order even if the generated power is large, and its application is limited.

  Moreover, since the above-described conventional vibration power generation apparatus has a structure in which the electret 203 and the counter electrode 204 face each other, if the gap distance between the electret 203 and the counter electrode 204 is designed too small, the electret 203 and the counter electrode There is a possibility that electrostatic attraction works between the contact 204 and the two, or the injected charge of the electret 203 is discharged. For this reason, the gap distance between the electret 203 and the counter electrode 204 must be designed to be large to some extent. However, in order to increase the capacitance change due to vibration while increasing the gap distance, the electret 203 and the counter electrode 204 are also increased. As a result, a vicious circle has arisen in which the gap distance must be further increased. Due to such a vicious circle, it has been difficult for the above-described conventional vibration power generation apparatus to achieve miniaturization and narrowing of the apparatus while increasing the generated power.

  In view of the above problems, an object of the present invention is to provide a small-sized and large-output power generator.

  In order to achieve the above object, a power generation device according to the present invention has a dielectric serving as a movable mass and an electret that retains electric charge, and generates power by changing a distance between the dielectric and the electret. The power generation apparatus is configured to further include an electret support member that elastically supports the electret (first configuration).

  In the power generation device having the first configuration, the electret support member may be configured to include a repulsion member having a predetermined restitution coefficient (second configuration).

  Moreover, in the electric power generating apparatus which consists of the said 2nd structure, it is good to set it as the structure (3rd structure) whose said coefficient of restitution is 0.3 or more.

  Further, in the power generation device having the third configuration, the repulsion member may have a configuration (fourth configuration) formed of gel or a high repulsion material having a higher restitution coefficient.

  The power generation device having any one of the first to fourth configurations may further include a configuration (fifth configuration) further including magnets that repel each other so as to separate the dielectric and the electret.

  In the power generation device having the fifth configuration, the magnet may have a configuration (sixth configuration) in which the surface thereof is flush with the surfaces of the dielectric and the electret. .

  Further, in the power generation device having any one of the first to sixth configurations, the electret support member may be configured to include a spring member having a predetermined spring constant (seventh configuration).

  Further, in the power generation device having the seventh configuration, the spring constant may be configured to be 0.5 to 50 N / mm (eighth configuration).

  The power generation device having any one of the first to eighth configurations may further include a mass support member (9th configuration) that elastically supports the movable mass.

  The power generation device having any one of the first to ninth configurations may have a configuration (tenth configuration) further including a package for storing the dielectric and the electret.

  According to the present invention, since the vibration of the Z-axis component of the vibrator is picked up to generate electric power, fine patterning of the electret and the electrode is not required, and even when the dielectric and the electret come into contact, no discharge occurs. There is no need to avoid contact. Therefore, it becomes possible to provide a power generation device with a small size and a high output, which in turn can free the user from the annoyance of worrying about battery life.

Schematic diagram showing a first configuration example of the power generation device Equivalent circuit diagram of power generator Schematic diagram of measurement system Explanation of corona discharge device Table showing the relationship between variable resistance, output voltage and generated power Graph showing the relationship between variable resistance and output voltage Graph showing the relationship between variable resistance and generated power Oscilloscope waveform diagram at maximum power output Simulation waveform of output voltage Vm with respect to gap distance G Comparison of power generation by electrical connection on the back side of dielectric Schematic diagram showing a second configuration example of the power generation device Schematic diagram showing a third configuration example of the power generation device Schematic diagram showing a first packaging example of a power generation device Schematic diagram showing a second packaging example of the power generation device Schematic diagram showing a third packaging example of the power generation device Schematic diagram showing a fourth packaging example of the power generation device Schematic diagram showing a fifth packaging example of the power generation device Schematic diagram showing a sixth packaging example of the power generation device Schematic diagram showing a seventh packaging example of the power generation device Schematic diagram showing an eighth packaging example of the power generation device Schematic diagram showing a first example of dielectric guide Schematic diagram showing a second guide example of dielectric Schematic diagram showing a first application example of a ground ring Schematic diagram showing a second application example of the ground ring Schematic diagram showing examples of combinations of dielectric shape and lower electrode shape Schematic diagram showing a first shape example of the lower electrode Schematic diagram showing a second shape example of the lower electrode Schematic diagram showing a third shape example of the lower electrode Schematic diagram showing the first structure to achieve triaxialization Schematic diagram showing the second structure for realizing three axes Schematic diagram showing the third structure to achieve triaxialization Schematic diagram showing a fourth structure for realizing three axes A graph showing the relationship between the dielectric constant of a dielectric and the amount of power generated The schematic diagram which shows the 1st modification of an electric power generating apparatus. Correlation diagram between coefficient of restitution and maximum power generation Schematic diagram showing a second modification of the power generation device Correlation diagram between number of collisions and maximum power generation (with / without magnet) Schematic diagram showing a third modification of the power generation device Diagram showing time change of output voltage (spring / gel) Diagram showing time variation of instantaneous power (spring / gel) Table (spring / gel) showing measurement results of power generation and resistance Diagram showing time variation of output voltage (experiment / analysis) The figure which shows the time change of output voltage, mass displacement, and electret displacement Correlation diagram between spring constant and power generation Correlation diagram between acceleration and total amplitude Schematic diagram showing a fourth modification of the power generator Schematic diagram showing a conventional example of a vibration power generator

<First configuration example>
FIG. 1 is a schematic diagram (a cross-sectional view seen from the lateral direction) illustrating a first configuration example of the power generation device. The power generation device 10 of the first configuration example includes a dielectric 11, an electret 12, a lower electrode 13, a resistor 14, an upper electrode 15, a substrate 16, and a gap layer 17. In addition, the 1st state (state in which the dielectric material 11 and the electret 12 were spaced apart) of the electric power generating apparatus 10 is drawn on the upper stage of FIG. 1, and the 2nd state (the electric generator 10 is shown in the lower stage of FIG. A state in which the dielectric 11 and the electret 12 are close to each other is depicted.

  In the following, for convenience of explanation, unless otherwise specified, the upper end side of the paper surface is defined as the vertical upward direction, and the description is made on the assumption that the dielectric 11 vibrates in the vertical direction (vertical direction). The vibration direction of 11 is not limited to this. For example, it is naturally possible to adopt a configuration in which the dielectric vibrates in the left-right direction (horizontal direction) by rotating the paper surface by 90 degrees.

  The dielectric 11 is a movable body whose relative position with respect to the electret 12 changes due to vibration applied to the power generation device 10. The lower surface of the dielectric 11 is opposed to the upper surface of the electret 12 with the gap layer 17 in between. As the dielectric 11, lead zirconate titanate (PZT), barium titanate (BTO), or the like can be used. This will be described later. The dielectric 11 may be formed in a plate shape or a film shape. For example, the substrate itself may be formed of a dielectric, a dielectric film may be formed on the substrate by a thin film printing technique, or a plate-like dielectric formed in a separate process may be used. You may affix on a board | substrate.

The electret 12 is a member that holds a charge semipermanently. As the electret 12, an organic electret in which a charge is held in a polymer compound such as Cytop [registered trademark] may be used, or a substrate such as silicon oxide (SiO ₂ ) or silicon nitride (SiN) may be used. You may use the inorganic electret which hold | maintained the electric charge. The electret 12 is formed so as to cover the entire surface of the lower electrode 13. In this way, by adopting a configuration in which the lower electrode 13 is not exposed, it is possible to prevent the outflow of electric charge to the exposed lower electrode 13 when injecting electric charge to the electret 12, thereby increasing the efficiency of charge injection to the electret 12. It becomes possible.

  The lower electrode 13 corresponds to a first electrode connected to the lower surface side of the electret 12 (side not facing the dielectric 11). The lower electrode 13 is connected to the ground terminal via the resistor 14. As the lower electrode 13, an aluminum electrode or the like can be used.

  The resistor 14 is a load for taking out a current flowing between the lower electrode 13 and the ground terminal as a voltage due to the vibration of the power generation device 10.

  The upper electrode 15 corresponds to a second electrode connected to the upper surface of the dielectric 11 (the side not facing the electret 12). The upper electrode 15 is directly connected to the ground terminal. As the upper electrode 15, an aluminum electrode or the like can be used.

  The substrate 16 is a plate-like member for supporting the electret 12 and the lower electrode 13. As the substrate 16, a quartz substrate, a silicon wafer with an oxide film, or the like can be used. However, from the viewpoint of suppressing parasitic capacitance, it is preferable to use a quartz substrate or the like rather than a silicon wafer with an oxide film.

The gap layer 17 is a space sandwiched between the dielectric 11 and the electret 12. The thickness of the air gap layer 17 (gap distance separating the dielectric 11 and the electret 12) varies depending on the displacement of the dielectric 11 due to vibration. The gap layer 17 may be in a low vacuum state (a state that is not a high vacuum state or an ultra-high vacuum state), or air, an inert gas (such as N ₂ ), or a gas that has an effect of preventing discharge (for example, a main vacuum layer). A gas containing SF ₆ as a component) may be filled. When the gap layer 17 is in a low vacuum state, a deaeration process may be used, or a phenomenon in which gas is released from the gap layer 17 during some high-temperature treatment and naturally becomes a low vacuum state may be used. The reason why it is preferable not to place the gap layer 17 in a high vacuum state or an ultrahigh vacuum state is to avoid discharge of the electret 12. In this specification, “low vacuum state” refers to a state of atmospheric pressure to 10 ⁻¹ Pa, “high vacuum state” refers to a state of 10 ⁻¹ to 10 ⁻⁵ Pa, “Vacuum state” refers to a state of 10 ⁻⁵ or less. In addition, if the void layer 17 contains moisture, water molecules adhere to the surface of the electret 12 and the charge is easily released. Therefore, the moisture contained in the void layer 17 is sufficiently removed to reduce the humidity. It is desirable to keep it.

  As described above, the power generation device 10 of the first configuration example includes at least a pair of dielectrics 11 and electrets 12, and is configured to generate power by changing the gap distance between the dielectrics 11 and the electrets 12. Yes. Hereinafter, the principle of power generation will be described.

  As shown in the upper part of FIG. 1, in the first state of the power generation apparatus 10 (the state where the dielectric 11 and the electret 12 are separated), the negative fixed charge held by the electret 12 (in FIG. 1, white square marks). Drawn on the surface of the lower electrode 13 (interface with the electret 12) and drawn as a symbol with a plus sign on a white circle in FIG. ) Is induced. The positive charge in the metal has a property as a positive charge due to a potential difference from the free electrons existing in the periphery as a result of the elimination of the free electrons from a certain position in the lower electrode 13 (metal). Therefore, with respect to the physical phenomenon described above, it is better to say that the free electrons in the lower electrode 13 are moved away than the positive charges in the lower electrode 13 are attracted by the negative fixed charges held in the electret 12. correct. Note that the positive charge in the metal in the lower electrode 13 is supplied from the ground terminal (the free electrons in the lower electrode 13 move to the ground terminal), so the potential of the lower electrode 13 remains 0V.

  On the other hand, as shown in the lower part of FIG. 1, when the power generation apparatus 10 transitions from the first state to the second state (the state in which the dielectric 11 and the electret 12 approach each other), the negative fixed held by the electret 12 The inside of the dielectric 11 is polarized by the charge, and a positive polarization charge (depicted as a symbol in which a plus sign is added to a black circle in FIG. 1) is localized on the lower surface of the dielectric 11. At this time, the correspondence relationship (a part) between the negative charge in the electret 12 and the positive charge in the lower electrode 13 that has occurred in the first state is eliminated. Due to this phenomenon, excessive positive charges are temporarily generated in the lower electrode 13. However, since the lower electrode 13 is connected to the ground terminal via the resistor 14, the excess positive charge from the lower electrode 13 toward the ground terminal until the potential of the temporarily raised lower electrode 13 becomes 0V. Movement (current) occurs. In the lower part of FIG. 1, a state after a part of the positive charge has moved from the lower electrode 13 is shown. The remaining charge that did not flow out from the lower electrode 13 is Q1.

  Contrary to the above, when the power generation device 10 transitions from the second state to the first state, a positive charge movement (that is, current) from the ground end toward the lower electrode 13 occurs. Can be taken out as.

  In the second state of the power generation apparatus 10, negative polarization charges (depicted as symbols with a black circle plus a minus sign) are localized on the upper surface of the dielectric 11 due to internal polarization of the dielectric 11. Turn into. Therefore, on the upper surface of the upper electrode 15 (interface with the dielectric 11), a positive charge in the metal is induced by being attracted by the negative polarization charge described above. However, since the positive charge in the metal in the upper electrode 15 is supplied from the ground end, the potential of the upper electrode 15 remains 0V.

  When viewed electromagnetically, the second state of the power generation apparatus 10 is a state in which the electrostatic potential energy is lower than that in the first state (a stable state in which the distance between the positive charge and the negative charge is closer than in the first state). Therefore, if kinetic energy (vibration) is applied from the outside to cause the power generation device 10 to transition between the first state and the second state, the kinetic energy can be converted into electric energy.

  In particular, the power generation device 10 of the first configuration example is configured such that the upper electrode 15 is provided on the upper surface of the dielectric 11 and the upper electrode 15 is connected to the ground terminal. By adopting such a configuration, in the second state of the power generation apparatus 10, there is no potential difference in the upper electrode 15, so that the potential energy in the second state can be lowered to increase the power generation efficiency. Become.

<Equivalent circuit diagram>
FIG. 2 is an equivalent circuit diagram of the power generation apparatus 10. In addition, the code | symbol C1 has shown the electrostatic capacitance (fixed value) of the electret 12, the code | symbol C2 has shown the electrostatic capacitance (fixed value) of the dielectric material 11, and the code | symbol C3 has shown the electrostatic capacitance (capacitance of the space | gap layer 17 (fixed value). Variable C), and symbol C4 indicates a series combined capacitance of the dielectric 11 and the gap layer 17 (C4 = C2 × C3 / (C2 + C3)). The symbol R indicates the resistance value (fixed value) of the resistor 14.

  The most notable point in this equivalent circuit is that the electret 12 serving as a power source should be called a “constant charge source” that holds a constant charge Q.

  When the power generation device 10 is transitioned from the first state (upper stage in FIG. 1) to the second state (lower stage in FIG. 1), charges are also distributed to the dielectric 11 side. If the capacitance of the capacitor that distributes to a certain charge increases, the potential of the capacitor decreases. The phenomenon is the same as when a capacitor is charged and then disconnected from the power source and connected to another capacitor.

At this time, the charge remaining in the capacitor between the electret 12 and the lower electrode 13 is Q1, the charge paired with the induced charge in the dielectric 11 is Q2, and the potential difference between the contacts AA ′ is V. In this case, the following equations (1) and (2) are established.
Q = Q1 + Q2 (1)
V = Q1 / C1 = Q2 / C4 (2)

Further, according to the above formulas (1) and (2), the charge Q1 is expressed by the following formula (3).
Q1 = Q × C1 / (C1 + C4) (3)

  In the equation (3), the charge Q and the electrostatic capacitance C1 of the electret 12 are fixed values, and the series composite capacitance C4 of the dielectric 11 and the void layer 17 is the thickness of the void layer 17 (and thus the void layer 17 It is a variable value that changes according to the capacitance C3). Accordingly, when the series composite capacitance C4 changes according to the displacement of the dielectric 11 due to vibration, the ratio between the charge Q1 and the charge Q2 changes. In the power generation apparatus 10, the charge redistribution accompanying the change in capacity is taken out as a current.

In the following, the power generation amount is formulated. A current i flowing in the circuit at a certain time t is given as a time derivative of the charge Q1. When a time derivative of a function f is expressed as f ′, the current i is expressed by the following equation (4) based on the above equation (3).
i = Q1 ′ = {Q × C1 × (C1 + C4) ⁻¹ )} ′
= Q × C1 × {(C1 + C4) ⁻¹ } ′
= Q × C1 × {− (C1 + C4) ⁻² } × C4 ′ (4)

Further, the series composite capacitance C4 of the gap layer 17 is expressed by the following equation (5) using the capacitance C2 of the dielectric 11 and the capacitance C3 of the gap layer 17.
C4 = (C2 ⁻¹ + C3 ⁻¹ ) ⁻¹ (5)

From the above equation (5), the time differential C4 ′ of the series composite capacitor C4 is expressed by the following equation (6).
C4 ′ = {(C2 ⁻¹ + C3 ⁻¹ ) ⁻¹ } ′
= {(C3 / C2 + 1) ⁻² } × C3 ′ (6)

When the gap distance between the dielectric 11 and the electret 12 changes with time, the capacitance C3 of the gap layer 17 also changes at the same time. Here, when the gap distance between the dielectric 11 and the electret 12 in the initial state is X0, and the dielectric 11 is oscillating simply at an amplitude A and an angular velocity ω, the capacitance C3 of the gap layer 17 and its time The differential C3 ′ is expressed by the following equations (7) and (8). In addition, the code | symbol (epsilon) 0 in a type | formula is a dielectric constant (8.85 * 10 < ^-12 > F / m) of a vacuum.
C3 = ε0 × εr × S × {X0 + A × sin (ω × t)} ⁻¹ (7)
C3 ′ = − ε0 × εr × S × A × ω × cos (ω × t)
× {X0 + A × sin (ω × t)} ⁻² (8)

When the current i flows, the voltage V2 output from both ends of the resistor 14 provided in the power generation device 10 is expressed by the following equation (9) using the resistance value R of the resistor 14.
V2 = i × R (9)

The electric power P taken out from the resistor 14 is expressed by the following equation (10) using the average value I of the current i and the resistance value R of the resistor 14. In addition, the code | symbol T in a type | formula is a vibration period of the dielectric material 11, and is given by T = 2 * (pi) / (omega).
P = I ² × R = T ⁻¹ × ∫ ₀ ^T i ² dt × R (10)

  The simulation value of the output voltage waveform based on the above equation (9) is shown in FIG. 8B. The output waveform based on the formulation is not a sine wave but a theoretically distorted waveform from the sine wave (details will be described later).

  A useful role here is the void layer 17 that exists between the dielectric 11 and the electret 12. As the capacitance C3 of the gap layer 17 increases, that is, as the thickness (gap distance) of the gap layer 17 decreases, the amount of polarization charge in the dielectric 11 increases, and the amount of power generation increases accordingly.

  As described above, the power generation apparatus 10 of the first configuration example has the dielectric 11 and the electret 12 facing each other, unlike the conventional configuration in which the electret and the counter electrode face each other (see FIG. 46). Therefore, even if the dielectric 11 and the electret 12 are brought close (or contacted), the electret 12 is not basically discharged.

  Therefore, in the power generation device 10 of the first configuration example, when power generation is performed in accordance with the change in the gap distance separating the dielectric 11 and the electret 12, the dielectric 11 and the electret 12 until the gap distance becomes zero at the minimum. Therefore, it is possible to obtain a very large power generation amount (mW order).

<Power generation experiment>
[Measurement system]
FIG. 3 is a schematic diagram of the measurement system used in the power generation experiment. The measurement system X used in this power generation experiment includes a dielectric X1, an aluminum plate X2, an electromagnetic vibrator X3, a sample X4, an aluminum plate X5, a three-axis stage X6, a base X7, A coaxial cable X8, a coaxial cable X9, a shield case X10, a coaxial cable X11, a low-pass filter X12, a coaxial cable X13, and an oscilloscope X14 are included.

  The dielectric X1 (corresponding to the dielectric 11 in FIG. 1) has an upper surface facing the lower surface of the sample X4, and a lower surface connected to the aluminum plate X2. As the dielectric X1, lead zirconate titanate (PZT) is used (the dielectric constant of PZT used in this experiment is 2,600).

  An aluminum plate X2 (corresponding to the upper electrode 15 in FIG. 1) has a dielectric X1 connected to the upper surface thereof. The aluminum plate X2 is directly connected to the ground terminal of the measurement system X.

  The electromagnetic vibrator X3 applies vertical vibration (frequency: 40 Hz) to the dielectric X1 connected to the upper surface of the aluminum plate X2.

  In the sample X4 (equivalent to the electret 12, the lower electrode 13, and the substrate 16 in FIG. 1), a quartz substrate (thickness: 1.0 mm) on the upper surface side is connected to an aluminum plate X5, and an electret on the lower surface side ( (Thickness: 5.6 μm) is opposed to the upper surface of the dielectric X1. Cytop [registered trademark] is used as the electret. The electret is not patterned. On the other hand, the lower electrode covered with the electret is subjected to comb-like patterning (width: 30 μm, pitch: 60 μm). The lower electrode is connected to the first end of the coaxial cable X8.

  The aluminum plate X5 supports the sample X4.

  The triaxial stage X6 moves the sample X4 carried on the aluminum plate X5 in the triaxial direction.

  The base X7 supports the three-axis stage X6.

  The coaxial cable X8 has a first end connected to the lower electrode of the sample X4 and a second end connected to the first end of the coaxial cable X9.

  The coaxial cable X9 has a first end connected to the second end of the coaxial cable X8 and a second end connected to the first connector X10a of the shield case X10.

  The shield case X10 stores load resistances Rv and R (the resistance 14 in FIG. 1 corresponds to a series combined resistance of Rv and R). The main body of the shield case X10 is connected to the ground terminal of the measurement system X. The first connector X10a of the shield case X10 is connected to the ground terminal of the measurement system X via load resistors Rv and R. As described above, in the measurement system X, the sample X4 and the load resistors Rv and R are connected not by the lead wire but by the coaxial wire. A connection node of the load resistors Rv and R is connected to the second connector X10b of the shield case X10 as a measurement node of the output voltage Vm. The ground line of the second connector X10b is connected to the ground terminal of the measurement system X. Of the load resistances Rv and R, a resistance Rv (a resistance whose voltage is not measured at both ends) connected between the first connector X10a and the second connector X10b is a variable resistance (potentiometer). A resistor R connected between X10b and the ground terminal (a resistance whose voltage is measured as the output voltage Vm) is a fixed resistor (100 kΩ).

  The coaxial cable X11 connects between the second connector X10b of the shield case X10 and the input end of the low-pass filter X12.

  The low-pass filter X12 removes noise superimposed on the output voltage Vm. The cut-off frequency fc of the low-pass filter X12 is set to 200 Hz.

  The coaxial cable X13 connects between the output end of the low-pass filter X12 and the input end of the oscilloscope X14.

  The oscilloscope X14 displays the waveform of the output voltage Vm (temporal change in electrical signal) as a graph. In the graph displayed on the oscilloscope X14, the vertical axis represents the voltage value and the horizontal axis represents the time. The ground terminal of the oscilloscope X14 is connected to the ground terminal of the measurement system X.

[Experimental procedure]
The experimental procedure using the measurement system X is as follows. In step S1, charges are injected into the electret of the sample X4 using the corona discharge device Y shown in FIG. 4 under predetermined conditions (corona discharge voltage: 10 kV, 0.1 mA, grid voltage 1.5 kV). In FIG. 4, reference numerals X41, X42, and X43 denote components (electret, lower electrode, and substrate) that form the sample X, respectively. Moreover, the code | symbol Y1-Y4 has each shown the component (A grid, the discharge electrode needle | hook, the power supply for grids, DC high voltage power supply) which forms the corona discharge apparatus Y. In step S2, the surface potential of the sample X4 is measured. In step S3, the sample X4 is connected to the measurement system X. In step S4, the dielectric X1 is vibrated by the electromagnetic vibrator X3. In step S5, the waveform of the output voltage Vm generated according to the approach / separation between the dielectric X1 and the sample X4 is observed with an oscilloscope. In step S6, steps S4 to S6 are repeated while changing the resistance value of the variable resistor Rv. In step S7, the generated power P of the power generator 10 is calculated based on the obtained output voltage Vm.

First, the average value Vms of the output voltage Vm is calculated by the following (11).
Vms = T ⁻¹ × ∫ ₀ ^T Vmdt (11)

  However, when the waveform of the output voltage Vm is close to a sine wave, by measuring the maximum amplitude Vpp (peak-to-peak value) of the output voltage Vm, an approximate value of the average value Vms is obtained by the equation Vms≈0.354 × Vpp. Can be obtained.

Next, the voltage VL generated in the load resistance (R + Rv) is calculated by the following equation (12).
VL = Vms × (R + Rv) / R (12)

Then, the generated power P can be calculated from the voltage VL using the following equation (13).
P = VL ² / (R + Rv) (13)

[Experimental result]
First, the measurement result of the surface potential of the sample X4 will be described. The average potential on the surface of the sample X4 after the charge injection in step S1 was about −525V.

  Next, the result of the vibration power generation experiment performed while changing the resistance value of the variable resistor Rv will be described. FIG. 5 is a table showing the relationship between the variable resistor Rv [MΩ], the maximum amplitude Vpp [V] of the output voltage Vm, and the generated power Pm [μW]. FIG. 6 is a graph showing the relationship between the variable resistor Rv [MΩ] and the maximum amplitude Vpp [V] of the output voltage Vm. FIG. 7 is a graph showing the relationship between the variable resistance Rv [MΩ] and the generated power Pm [μW]. When the variable resistance Rv was 10 MΩ, it was confirmed that the generated power Pm was the maximum value (975 [μW] = 0.97 [mW]). Thus, in the vibration power generation experiment using the measurement system X, an extremely large power generation amount (mW order) could be obtained.

  FIG. 8A is an oscilloscope waveform diagram at the time of maximum power output. The drive waveform of the vibration simulator is depicted in the upper part of FIG. 8A, and since the drive signal is a sine wave, it can be seen that the dielectric X4 installed in the electromagnetic exciter X3 performs a single vibration. On the other hand, the output waveform of the output voltage Vm is depicted in the lower part of FIG. 8A. The output waveform of the output voltage Vm has a different shape from the sine wave. However, this waveform is not a sine wave distorted by a disturbance element such as noise, but is a theoretically correct waveform. This will be explained in the next section.

  FIG. 8B is a simulation waveform of the output voltage Vm with respect to the gap distance G. The upper part of FIG. 8B depicts the gap distance between the sample X1 and the dielectric X4, and the lower part of FIG. 8B shows the measurement system theoretically calculated using the above equations (3) to (9). The output voltage Vm of X is depicted. As parameters used for the calculation, the same numerical values as those of the sample X1, the dielectric X4, and the resistors R and Rv used in the measurement system X in the actual power generation experiment were input. However, the initial value of the gap distance G between the sample X1 and the dielectric X4 (that is, X0 in the equation (7)) and the amplitude of the vibration applied to the dielectric X4 by the electromagnetic exciter X3 (that is, (7) For A) in the formula, an accurate numerical value could not be measured. Therefore, the calculation was performed on the assumption that the gap distance G between the sample X1 and the dielectric X4 changed like the waveform depicted in the upper part of FIG. 8B. The waveforms in FIG. 8A and FIG. 8B agree very well, and it can be said that it was proved that the measured output voltage Vm was output as a result of power generation based on the proposed principle.

  Next, the relationship between the electrical connection of the aluminum plate X2 on the back surface of the dielectric X1 and the amount of power generation will be described. With the aluminum plate X2 separated from the grounding end of the measurement system X, the same vibration power generation experiment as that described above was performed. FIG. 9 is a comparison diagram of the amount of power generation according to the electrical connection state of the back surface of the dielectric X1. As shown in FIG. 9, the maximum amplitude Vpp of the output voltage Vm and the power generation when the aluminum plate X2 is connected to the ground terminal of the measurement system X (black bar graph) and when it is not connected (hatched bar graph). It was confirmed that there was a difference in both power Pm. This phenomenon will be described in detail with reference to the following second configuration example and third configuration example.

<Second configuration example>
FIG. 10 is a schematic diagram illustrating a second configuration example of the power generation device. The power generation device 10 of the second configuration example has substantially the same configuration as the first configuration example, and is characterized in that the upper electrode 15 provided on the upper surface side of the dielectric 11 is removed. That is, it can be said that the power generation device 10 of the second configuration example has a configuration in which no electrode is connected to the dielectric 11. From another viewpoint, the power generation device 10 of the second configuration example is configured such that the entire movable portion including the dielectric 11 is in an electrically floating state (not connected to any potential point). I can say that. In addition, the whole movable part including the dielectric 11 is good to hold | maintain with an insulator (insulating spring etc.), for example.

  Unlike the first configuration example described above, in the power generation device 10 of the second configuration example, the electrostatic potential energy is high (unstable) in the second state (lower stage in FIG. 10) in which the dielectric 11 and the electret 12 are brought close to each other. Therefore, the amount of power generation is reduced compared to the first configuration example. However, in the power generation device 10 of the second configuration example, it is not necessary to connect a wiring to the vibrating dielectric body 11, and therefore, it is more advantageous than the first configuration example in terms of ease of device fabrication and power generation operation stability. is there.

<Third configuration example>
FIG. 11 is a schematic diagram illustrating a third configuration example of the power generation device. The power generation device 10 of the third configuration example has substantially the same configuration as the first configuration example, and is characterized in that an electrically floating metal body 18 is formed on the upper surface side of the dielectric 11. Yes. Unlike the upper electrode 15 intended to be connected to some potential point (grounding end), the metal body 18 is a metal member that is in an electrically floating state. Therefore, the power generation apparatus 10 of the third configuration example is common to the previous second configuration example in that the entire movable portion including the dielectric 11 is in an electrically floating state. The metal body 18 may be plate-shaped or film-shaped.

  In the power generation device 10 of the third configuration example, in the second state (lower stage in FIG. 11) in which the dielectric 11 and the electret 12 are brought close to each other, negative polarization charges are locally generated on the upper surface of the dielectric 11 due to internal polarization of the dielectric 11. It becomes natural. Therefore, on the lower surface of the metal body 18 (interface with the dielectric 11), the above-described negative polarization charge is attracted to induce a positive charge in the metal.

  Unlike the first configuration example described above, in the power generation device 10 of the third configuration example, the metal body 18 is not connected to the ground end, and therefore, positive charges cannot be drawn from the ground end to the metal body 18. However, since the metal body 18 has a large number of free electrons (illustrated as a symbol in which a minus sign is added to a white circle in FIG. 11), the free electrons are present at the interface between the metal body 18 and the dielectric 11. By moving away from the ground, the same effect as when a positive charge is attracted to the metal body 18 from the ground end can be obtained.

  Due to the above effects, the power generation apparatus 10 of the third configuration example can obtain a higher power generation amount than the second configuration example in which the upper electrode 15 is completely eliminated. However, in the power generation device 10 of the third configuration example, the above-described effect is hindered by the charge bias (potential difference) generated in the metal body 18. Therefore, the power generation device 10 of the third configuration example has a lower power generation amount than the first configuration example in which the upper electrode 15 is connected to the ground terminal. However, in the power generation device 10 of the third configuration example, it is not necessary to connect a wiring to the vibrating dielectric body 11 as in the above-described second configuration example, so that in terms of ease of device fabrication and stability of power generation operation, This is more advantageous than the first configuration example.

  Thus, in terms of the amount of power generation, the first configuration example> the third configuration example> the second configuration example has superiority and inferiority, and in terms of the ease of device fabrication and the stability of the power generation operation, the second configuration example. = Third configuration example> The first configuration example is superior or inferior. Therefore, it cannot be said that any one of the configurations of the power generation apparatus 10 is always the best, and adopt any one of the first to third configuration examples depending on the use and required characteristics. Is desirable.

<Packaging>
FIG. 12 is a schematic diagram (cross-sectional view seen from the lateral direction) illustrating a first packaging example of the power generation device. The power generation device 20 of the first packaging example includes a substrate 21, a lower electrode 22, an electret 23, a dielectric 24 (a combination of a dielectric, an electrode, and a weight), a package 25, and an adhesive 26 and a wire 27. In the following description, it does not matter whether there is an upper electrode connected to the dielectric 24.

  The lower electrode 22 is formed on the upper surface of the substrate 21. The electret 23 is formed so as to cover the lower electrode 22. However, one end of the lower electrode 22 is exposed from the electret 23 and extends to the end of the substrate 21, and is connected to the wire 27 at the end. The wire 27 is connected to the ground terminal via a resistor (not shown). The package 25 is a cover member (cylindrical, columnar, hemispherical, etc.) provided with an opening on one surface, and the opening is bonded to the substrate 21 and the adhesive 26 so as to accommodate the electret 23 and the dielectric 24 inside. Has been. The package 25 may be made of resin such as resin or acrylic.

  In the power generation device 20 of the first packaging example, the dielectric 24 is accommodated so as to be displaceable (movable up and down) along the inner wall of the package 24 without being supported at all. When the power generation device 20 is in a stationary state, the dielectric 24 is in a state of being close to the electret 23 by electrostatic attraction (corresponding to the second state in the lower part of FIG. 1). Therefore, if the dielectric 24 is separated from the electret 23 by applying kinetic energy (vibration) from the outside, the kinetic energy can be converted into electric energy.

  FIG. 13 is a schematic diagram illustrating a second packaging example of the power generation device. The second packaging example has substantially the same configuration as the first packaging example, and is characterized in that it has an elastic member 31 that supports the dielectric 24 in a suspended manner inside the package 25. As the elastic member 31, a coil spring or a bellows spring (meander shape) may be used. By adopting such a configuration, the kinetic energy for separating the dielectric 24 from the electret 23 can be lowered, so that it is possible to generate electric power with smaller vibrations. It is also possible to prevent contact between the top surface of the package 25 and the dielectric 24.

  FIG. 14 is a schematic diagram illustrating a third packaging example of the power generation device. The third packaging example has substantially the same configuration as the first packaging example, and is characterized in that it has an elastic member 32 that supports both ends of the dielectric 24 inside the package 25. As the elastic member 32, a coil spring or a bellows spring (a meander shape) may be used. With this configuration, it is possible to prevent contact between the inner surface of the package 25 and the dielectric 24 without hindering the vertical movement of the dielectric 24.

  FIG. 15 is a schematic diagram illustrating a fourth packaging example of the power generation device. The fourth packaging example has substantially the same configuration as the first packaging example, and is characterized in that it has an elastic member 33 that repels the dielectric 24 on the top surface of the package 25. A plate spring may be used as the elastic member 33. With such a configuration, it is possible to prevent contact between the top surface of the package 25 and the dielectric 24 without hindering the vertical movement of the dielectric 24.

  FIG. 16 is a schematic diagram (cross-sectional view seen from above) showing a fifth packaging example of the power generation device. The fifth packaging example has substantially the same configuration as the first packaging example, and is characterized in that it has an elastic member 34 that supports vertical movement while suppressing horizontal movement of the dielectric 24 inside the package 25. doing. In the vibration device 20 of the fifth packaging example, the dielectric 24 and the package 25 are formed so that a cross section when viewed from above is rectangular. As the elastic member 34, a combination of four leaf springs that cantilever-support the four side surfaces of the dielectric 24 from the support surfaces (inner side surfaces of the package 25) orthogonal to each other may be used. With this configuration, it is possible to prevent contact between the inner surface of the package 25 and the dielectric 24 without hindering the vertical movement of the dielectric 24.

  FIG. 17 is a schematic diagram illustrating a sixth packaging example of the power generation device. The sixth packaging example has substantially the same configuration as the first packaging example, and is characterized by having magnets 35a and 35b (magnetic springs) repelling the dielectric 24 and the package 25, respectively. With such a configuration, it is possible to prevent contact between the top surface of the package 25 and the dielectric 24 without hindering the vertical movement of the dielectric 24.

  FIG. 18 is a schematic diagram illustrating a seventh packaging example of the power generation device. The seventh packaging example has substantially the same configuration as the first packaging example, and is characterized by having magnets 36a and 36b (magnetic springs) repelling the dielectric 24 and the electret 23, respectively. By adopting such a configuration, the kinetic energy for separating the dielectric 24 from the electret 23 can be lowered, so that it is possible to generate electric power with smaller vibrations. Further, the contact between the electret 23 and the dielectric 24 can be prevented.

  FIG. 19 is a schematic diagram illustrating an eighth packaging example of the power generation device. The eighth packaging example has substantially the same configuration as the first packaging example, and is characterized by having a stopper 37 protruding from the surface of the electret 23. The stopper 37 may be provided on the surface of the dielectric 24. By adopting such a configuration, the kinetic energy for separating the dielectric 24 from the electret 23 can be lowered, so that it is possible to generate electric power with smaller vibrations. Further, the contact between the electret 23 and the dielectric 24 can be prevented.

  In addition, about the structure demonstrated separately in said 1st-8th packaging example, arbitrary combinations are possible. Further, in the configuration in which the spring is provided, it is desirable to design the spring constant so that the frequency of vibration applied to the power generation device 20 matches the resonance frequency unique to the spring. On the other hand, when the frequency of vibration applied to the power generation device 20 is indefinite, it is desirable to adopt a configuration in which no spring is provided or to use a soft spring (a spring having a small spring constant).

<Dielectric guide mechanism>
FIG. 20 is a schematic diagram (a top view and a cross-sectional view from the lateral direction) showing a first guide example of a dielectric. In the vibration device 20 of the first guide example, the dielectric 24 and the package 25 are formed so that each outer edge or inner edge has a circular shape when the power generation device 20 is viewed in plan. The dielectric 24 is accommodated in a form in which a ball member 38 (steel ball) is sandwiched between the inner wall of the package 25. The ball members 38 are respectively provided at positions that divide the outer periphery of the dielectric 24 (the inner periphery of the package 25) into four equal parts when the power generation device 20 is viewed in plan. In the dielectric 24, vertical rail grooves 24 a are formed at the contact positions of the ball members 38. On the other hand, a concave ball receiving portion 25 a is formed on the inner wall of the package 25 at the contact position of the ball member 38. With such a configuration, contact between the inner surface of the package 25 and the dielectric 24 can be prevented without inhibiting the vertical movement of the dielectric 24.

  FIG. 21 is a schematic diagram (a top view and a cross-sectional view from the lateral direction) showing a second guide example of a dielectric. Similar to the first guide example, in the vibration device 20 of the second guide example, the dielectric 24 and the package 25 are formed so that each outer edge or inner edge has a circular shape when the power generation device 20 is viewed in plan. Yes. The dielectric 24 is stored in a form in which a rail member 39 is in contact with the inner wall of the package 25. The rail members 39 are respectively provided at positions that divide the outer periphery of the dielectric 24 (the inner periphery of the package 25) into four equal parts when the power generation device 20 is viewed in plan. In the inner wall of the package 25, vertical rail grooves 25 b are formed at the contact positions of the rail members 39. With such a configuration, contact between the inner surface of the package 25 and the dielectric 24 can be prevented without inhibiting the vertical movement of the dielectric 24. The rail member 39 may be integrally formed by processing the dielectric 24, or may be separately formed of a material having good slidability (fluorine resin or the like) different from the dielectric 24.

<Grand ring>
Next, a description will be given of a ground ring that is beneficial in adopting a configuration in which no electrode is provided on the dielectric side (see the second configuration example in FIG. 10). FIG. 22 is a schematic diagram (cross-sectional view from the lateral direction) showing a first application example of the ground ring. In addition, the arrow in a figure has shown the electric force line. The power generation device 40 of the first application example includes a dielectric 41, an electret 42, a lower electrode 43, a resistor 44, and a ground ring 45. The ground ring 45 is a conductive member (for example, aluminum) formed so as to surround the electret 42 and the lower electrode 43 with a predetermined distance therebetween. The ground ring 45 is directly connected to the ground end.

  In the power generation device 40, when the dielectric 41 and the electret 42 are brought close to each other, negative polarization charges are localized on the upper surface of the dielectric 41 due to the internal polarization of the dielectric 41. Here, in the power generation device 40 of the first application example, the electric lines of force can be released from the negative charge of the dielectric 41 toward the positive charge of the ground ring 45, and thus the negative charge of the dielectric 41 and the electret 42. It is possible to suppress the repulsion with the negative charge, and it is possible to increase the power generation efficiency.

  FIG. 23 is a schematic diagram (cross-sectional view from the lateral direction) showing a second application example of the ground ring. In addition, the arrow in FIG. 23 has shown the electric force line. As shown in this figure, the ground rings 45 are not necessarily formed so as to surround the electret 42 and the lower electrode 43, and the electrets 42 and the ground rings 45 may be alternately arranged adjacent to each other. . With such a configuration, the electric lines of force can be released from the negative charge of the dielectric 41 toward the positive charge of the ground ring 45 when horizontal polarization occurs in the dielectric 41. It is possible to suppress the repulsion between the negative charge of the body 41 and the negative charge of the electret 42, and thus it is possible to increase the power generation efficiency.

<Shapes of dielectric and lower electrode>
FIG. 24 is a schematic diagram showing a combination example of the shape of the dielectric and the shape of the lower electrode. The power generation device 50 of this example includes a dielectric 51, an electret 52, a lower electrode 53, and a substrate 54.

  The dielectric 51 may have a configuration in which the lower surface facing the electret 52 is flattened (see the left side in FIG. 24) or a configuration in which the lower surface is patterned (see the right side in FIG. 24). In the former configuration, the gap distance between the dielectric 51 and the electret 52 can be made uniform. In the latter configuration, the lines of electric force are likely to gather at locations sharpened by patterning, so that it is possible to expect improvement in power generation efficiency depending on the optimization of patterning.

  Further, the lower electrode 53 may be formed in a planar shape (FIG. 25) without patterning, or may be formed in a comb-like shape (FIG. 26) or a spiral shape (FIG. 27) by patterning. Also good. However, in view of power generation efficiency, it is desirable to adopt the former configuration.

  The combination of the shape of the dielectric 51 (with / without patterning) and the shape of the lower electrode (with / without patterning) is arbitrary.

<Three axes>
FIG. 28 is a schematic diagram showing a first structure for realizing triaxialization. The power generator 60 having the first structure includes a dielectric 61, an electret 62, and a lower electrode 63. The dielectric 61 is formed with a plurality of convex portions 61a, and the electret 62 is formed with a plurality of concave portions 62a into which the convex portions 61a are fitted with a predetermined gap. Although not depicted in FIG. 28, the power generation device 60 has a similar structure in the depth direction of the paper surface. By adopting such a structure, even when the dielectric 61 vibrates in the vertical direction of the paper, even when the dielectric 61 vibrates in the horizontal direction of the paper, Even in the case of vibrating in the depth direction of the paper, the gap distance between the dielectric 61 and the electret 62 changes, so that it is possible to efficiently generate power.

  Moreover, in the power generator 60 having the first structure, the electrets 62 are disposed on both sides of the dielectric 61, respectively. With such a configuration, it is possible to further increase the power generation efficiency. Further, although not depicted in FIG. 28, further improvement in power generation efficiency can be expected if dielectrics 61 are provided in multiple stages and electrets 62 are arranged on both sides. Note that such a multilayer structure can naturally be applied to the above-described basic configuration (such as FIG. 1) that does not include the convex portions 61a and the concave portions 62a.

  FIG. 29 is a schematic diagram showing a second structure for realizing triaxialization. In the power generator 70 having the second structure, the electret 72 is formed on the inner wall of the sealed container, and the dielectric 71 is made into particles and enclosed inside the sealed container. The lower electrode 73 is formed so as to surround the outer peripheral side of the electret 72, and is connected to the ground terminal via the resistor 74. By adopting such a structure, the gap distance between the dielectric 71 and the electret 72 changes even when vibration is applied to the power generation apparatus 70 in any direction, so that power generation is performed efficiently. It becomes possible.

  FIG. 30 is a schematic diagram showing a third structure for realizing triaxialization. In the power generator 80 having the third structure, the electret 82 is formed on the inner wall of the sealed sphere, and the dielectric 81 is formed into a sphere and enclosed inside the sealed sphere. The lower electrode 83 is formed so as to surround the outer peripheral side of the electret 82, and is connected to the ground terminal via the resistor 84. By adopting such a structure, the gap distance between the dielectric 81 and the electret 82 changes regardless of the direction of vibration applied to the power generation device 80, so that power generation is performed efficiently. It becomes possible.

  FIG. 31 is a schematic diagram showing a fourth structure for realizing triaxialization. In the power generation device 90 having the fourth structure, the dielectric 91 is a sphere, and a plurality of electrets 92 are formed so as to surround the dielectric 91. The lower electrode 93 is formed for each of the plurality of electrets 92 and is connected to the ground terminal via a resistor 94. By adopting such a structure, the gap distance between the dielectric 91 and the electret 92 changes even when vibration is applied to the power generation device 90 in any direction. It becomes possible.

<Relative permittivity of dielectric and power generation>
FIG. 32 is a graph showing the relationship between the relative dielectric constant of the dielectric and the amount of power generation. The horizontal axis of FIG. 32 indicates the relative permittivity εr of the dielectric, and the vertical axis of FIG. 32 indicates the power generation amount P [%] (normalized by the power generation amount when the relative permittivity εr is infinite). ing. This graph shows that the dielectric constant of the electret is 2, the film thickness of the electret is 5 μm, the amplitude of vibration of the dielectric is 20 μm, and the thickness of the void layer (air layer) when the dielectric is closest to the electret (gap) The calculation results obtained using the above equations (3) to (9) under the assumption that the distance) is 1 μm are shown. However, each generated power in the figure is normalized with the amount of power generated when the relative dielectric constant εr of the dielectric is infinite as 100%. In addition, the circle symbol, the square symbol, and the rhombus symbol in FIG. 32 indicate calculation results when the thicknesses of the dielectrics are 0.01 mm, 0.1 mm, and 1 mm, respectively.

  As can be seen from FIG. 32, the calculation result varies depending on the thickness of the dielectric. When the thickness of the dielectric is 0.01 mm, 90% of the maximum power generation amount is obtained when the relative dielectric constant εr is about 30. On the other hand, when the thickness of the dielectric is 1 mm, a relative dielectric constant εr of about 3000 is required to obtain 90% of the maximum power generation amount. Therefore, in order to increase the power generation amount, it is desirable to make the dielectric as thin as possible.

  However, if the dielectric is made too thin, there is a risk of discharging the charge in the electret when it comes into contact with the electret. Therefore, in view of both the increase in the amount of power generation and prevention of discharge, it is considered appropriate to use a dielectric having a thickness of 0.1 mm and a relative dielectric constant εr of 300 or more, for example. However, the numerical values of the thickness and the relative dielectric constant here are examples, and other values may be used. Considering comprehensively the charge retention characteristics, power generation amount, device size, manufacturing cost, etc., as a practical design range, the dielectric has a thickness of 0.01 to 1.0 mm (more preferably 0.01 mm). It is appropriate to use a material that can obtain a power generation amount of 80% or more of the maximum power generation amount.

  As a method for manufacturing the dielectric, various methods can be employed depending on the thickness of the dielectric. For example, a dielectric having a thickness of 1 μm or less to several μm can be manufactured by sputtering or electron beam evaporation. A dielectric having a thickness of 1 μm or less to several tens of μm can be produced by a hydrothermal synthesis method including a sol-gel method + spin coating + firing. In addition, a dielectric having a thickness of several tens of μm or more can be produced by adjusting the thickness by molding powder such as firing + pressure molding + slicing, cutting, polishing, or the like.

<Dielectric material>
The most promising material is barium titanate (BaTiO ₃ , BTO). The relative dielectric constant at the operating temperature (assuming about 0 to 100 ° C.) is about 1000, which satisfies the above conditions. Since it is relatively inexpensive and lead-free, its environmental impact is small, which is advantageous for commercialization. The relative dielectric constant decreases in an environment of 120 ° C. or higher. Further, the relative dielectric constant also decreases when the operating frequency is 100 kHz or higher. However, since the assumed operating frequency is 1 to several hundreds of Hz, the above characteristics are not a drawback for this device. The only problem is that there is hysteresis in the dielectric characteristics because it is a ferroelectric.

  The next most promising material is lead zirconate titanate (PZT). Since the relative dielectric constant is very large (2000 to 3000), it is effective when it is desired to increase the power generation amount as much as possible. However, the disadvantage is that it is relatively expensive and contains a high environmental load because it contains lead. In addition, since it is a ferroelectric material like barium titanate, it should be noted that it has hysteresis in characteristics.

  Further, a material obtained by adding an alkaline earth metal such as potassium (K), calcium (Ca), or strontium (Sr) or a rare earth metal such as yttrium (Y) or neodymium (Nd) to barium titanate is also promising. . In general, the addition of these lowers the relative permittivity of barium titanate, but the following effects are expected.

  The first effect is to lower the Curie temperature. Ferroelectrics have a temperature that is a singular point called the Curie temperature, and the dielectric constant has a maximum value near this temperature. Therefore, the dielectric constant at the operating temperature can be made larger than that of pure barium titanate by setting the Curie temperature of the dielectric to be near the operating temperature of the power generation device. However, there is a drawback that a change in dielectric constant due to a temperature change becomes large, leading to instability of power generation efficiency.

  The second effect is that the property changes from ferroelectricity to paraelectricity as the addition amount is increased. A paraelectric material has a small change in dielectric constant due to a temperature change and has no hysteresis, so that stable power generation is expected. Since the dielectric constant is higher among paraelectric materials, it is possible to secure a certain amount of power generation.

  Next, strontium titanate is mentioned. Strontium titanate is obtained by replacing barium in barium titanate with strontium. Although it is a paraelectric material, it has an advantage of having a relative dielectric constant of about 300 and satisfying the above conditions. However, the dielectric constant is small compared to barium titanate. Further, strontium is a rare metal, and there is a disadvantage that the cost is increased.

Next, as lead-free piezoelectric high dielectrics, lanthanum iron oxide (LaFeO ₃ ), potassium niobate (KNbO ₃ ), lanthanum titanate (LaTiO ₃ ), magnesium silicate (MgSiO ₃ ), and zirconate titanate Barium (Ba (Ti, Zr) O ₃ ) may be mentioned.

A feature of iron lanthanum oxide (LaFeO ₃ ) is that the single dielectric layer has a relative dielectric constant of 1000 or more, and a high dielectric constant of tens of thousands or more at high temperatures. By adding a small amount of iron lanthanum oxide (LaFeO ₃ ) to potassium niobate (KNbO ₃ ), there is an effect of increasing the dielectric constant. For example, by adding 0.2% of iron lanthanum oxide (LaFeO ₃ ), the relative dielectric constant of potassium niobate (KNbO ₃ ) at room temperature increases from 500 to 1250.

The crystal structure of potassium niobate (KNbO ₃ ) is a perovskite structure. It becomes rhombohedral at −10 ° C. or lower, orthorhombic at normal temperature, tetragonal at 225 to 435 ° C., and cubic at 435 ° C. (Curie temperature) or higher. Advantages include (1) a ferroelectric material that exhibits large piezoelectricity, (2) a ferroelectric material having a bismuth layer structure and a lead-free piezoelectric ceramic, and (3) easy polarization (150 ° C., 5 (4) having a relative dielectric constant (800 to 1000) equivalent to that of lead zirconate titanate (PZT), and (5) from room temperature to 200 It has a relative dielectric constant curve that is relatively flat up to about ° C. Conversely, as disadvantages, (1) difficult to sinter as ceramics, (2) when unreacted potassium oxide remains, moisture resistance deteriorates due to its deliquescence, and (3) rare metal. Since niobium is the main component, the cost is high.

Barium zirconate titanate (Ba (Ti, Zr) O ₃ ) can have a Curie temperature lower than 120 ° C. In Ti: Zr = 8: 2, the Curie temperature is 40 ° C. and the relative dielectric constant is 4000.

  Next, examples of the polymer ferroelectric include polylactic acid and polyurea acid. Polymer-based ferroelectrics are flexible and have a relatively high dielectric constant, and are expected to be applied to protective films on contact surfaces. The relative dielectric constant of polylactic acid is about 22. Polyureaic acid is an organic piezoelectric material and has a dielectric constant of 3.6 to 11.8.

  Next, a relaxor ferroelectric is mentioned. Features common to relaxor ferroelectrics are (1) large piezoelectric effect, (2) very large dielectric constant and small temperature change, and (3) huge relative dielectric constant of several tens of thousands, (4 (1) having a broad dielectric constant peak and frequency dispersion, and (5) having a spontaneous polarization characteristic showing a slow change up to a high temperature.

Many relaxor ferroelectrics have a complex perovskite type compound structure of A (B ′, B ″) O _3. A divalent ion enters the A site and a tetravalent charge on the B site on average. Two types of ions are included: a type (A (B ′ _1/3 B ″ _2/3 ) O ₃ ) in which +2 and +5 valence ions enter at a ratio of 1: 2, and +3 and +5 valence ions. Alternatively, it can be broadly classified into a type (A (B ′ _1/2 B ″ _1/2 ) O ₃ ) in which +2 and +6 valent ions are contained at a ratio of 1: 1. Many relaxers are mixed with the ferroelectric PbTiO _3. Form crystals and cause interesting phenomena.

Examples of relaxor materials include (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ .xPbTiO ₃ , (1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ .xPbTiO ₃ Or (1-x) Pb (In _1/2 Nb _1/2 ) O ₃ .xPbTiO ₃ .

The characteristics of the solid solution (PZN / xPT) of Pb (Zn _1/3 Nb _2/3 ) O ₃ and PbTiO ₃ are (1) ferroelectric and piezoelectric, and (2) PZN / 9PT The piezoelectric constant d33 is about 2500 pC / N. The composition ratio of PZN and PT is just in the region called the morphotropic phase boundary (commonly called MPB) that divides trigonal and tetragonal crystals, and it has high piezoelectric effect by using various experimental methods from the viewpoint of decreasing symmetry in MPB. The cause is being sought.

A feature of (Ba, La) (Ti, Cr) O ₃ is that it is a lead-free relaxor ferroelectric. The exact composition is the composition of (Ba _1-x La _x ) (Ti _1-x Cr _x ) O ₃ (where 0 ≦ x <1). When x = 0.035, the relative dielectric constant becomes 2000, and the dielectric constant is stable near room temperature.

<Modification for improving power generation>
FIG. 33 is a schematic diagram illustrating a first modification of the power generation device described so far. The power generation device 100 of the first modified example includes a movable mass 101, a spring member 102, a dielectric 103, an electret 104, a glass substrate 105, a repulsive member 106a, and a package 110. The dielectric 103 And the electret 104 is a vibration type power generation device that generates power by changing.

  The movable mass 101 is formed by integrating a dielectric 103 and a weight, and is housed inside the package 110 so as to vibrate up and down.

  The spring member 102 is an example of a mass support member that elastically supports the movable mass 101. In this figure, the configuration in which the movable mass 101 is supported at both ends by the inner side surface of the package 110 is illustrated, but the support form of the movable mass 101 is not limited to this. For example, the movable mass 101 is mounted from the ceiling of the package 110. It does not matter even if it is the structure which supports by suspension. In this way, by using the spring member 102 to elastically support the movable mass 101, the kinetic energy for separating the dielectric 103 from the electret 104 can be reduced, so that power generation can be performed with smaller vibrations. Can be performed. As the spring member 102, a coil spring or a bellows spring (a meander shape) may be used.

  The dielectric 103 becomes a movable body (a part of the movable mass 101) whose relative position with respect to the electret 104 is changed by vibration applied to the power generation apparatus 100. As the dielectric 103, as described above, lead zirconate titanate (PZT), barium titanate (BTO), or the like can be preferably used.

  The electret 104 is a member that holds a charge semipermanently. As the electret 12, either an organic electret or an inorganic electret may be used.

  The glass substrate 105 is a plate-like member for supporting the electret 104.

  The repulsion member 106 a is an example of an electret support member that elastically supports the electret 104. In this figure, a repulsive member 106 a is inserted between the lower surface of the glass substrate 105 and the bottom surface of the package 110. Accordingly, the electret 104 is supported by the repulsive member 106 a on the lower surface side that does not face the dielectric 103.

  The package 110 is a cover member (cylinder, column tube, hemisphere, etc.) that houses the movable mass 101, the spring member 102, the dielectric 103, the electret 104, the glass substrate 105, and the repulsion member 106a. The package 110 may be made of resin such as resin or acrylic.

  FIG. 34 is a correlation diagram between the restitution coefficient of the repulsion member 106a and the maximum power generation amount. This figure is the result of a power generation test using a large device (see FIG. 3 above). As the material of the repulsive member 106a, gel (0.53), nitrile rubber (0.42-0.52) , Fluoro rubber (0.34 to 0.38), and low elasticity rubber (0.33) were used (the coefficient of restitution in parentheses). Note that each of the above restitution coefficients is a value uniquely measured by the present inventors.

  As shown in this figure, it can be seen that the higher the restitution coefficient of the repulsion member 106a that supports the electret 104, the less the energy loss of the movable mass 101, and the greater the maximum power generation amount.

  If any one of the gel, nitrile rubber, fluororubber, and low-elastic rubber used in this experiment is selected as the material of the repulsion member 106a, it is desirable to select the gel having the largest restitution coefficient. I can say that. However, it is also possible to use a high repulsion material having a higher restitution coefficient than that of gel (for example, a high repulsion material used for a highly elastic rubber ball toy) in anticipation of further improvement in power generation amount.

  FIG. 35 is a schematic diagram illustrating a second modification of the power generation device. The second modified example is basically the same as the first modified example, and is characterized in that it further includes magnets 107 that repel each other so as to separate the dielectric 103 and the electret 104. Therefore, the same components as those in the first modification are denoted by the same reference numerals as those in FIG. 33, and redundant description is omitted. In the following, the characteristic parts of the second modification will be mainly described.

  The power generation amount of the power generation apparatus 100 increases as the surface potential of the electret 104 increases. However, the higher the surface potential of the electret 104, the easier it is for the dielectric 103 and the electret 104 to stick due to electrostatic attraction, which increases the risk that the movable mass 101 will not vibrate.

  On the other hand, in the power generation device 100 of the second modified example, the newly added magnet 107 repels each other so as to separate the dielectric 103 and the electret 104, so that the dielectric 103 and the electret 104 due to electrostatic attraction It is possible to prevent the sticking of the battery, and it is possible to expect a higher power generation amount.

  The power supply device 100 of the second modified example has basically the same configuration as that shown in FIG. 18, but the magnet 107 is formed so that the surfaces thereof are flush with the surfaces of the dielectric 103 and the electret 104, respectively. ing. With such a configuration, the gap distance between the dielectric 103 and the electret 104 can be changed as much as possible, and the power generation amount can be increased.

  FIG. 36 is a correlation diagram between the number of collisions between the dielectric 103 and the electret 104 and the maximum power generation amount of the power generation apparatus 100. The rhombus marks indicate the behavior with magnets (second modification example in FIG. 35), and the triangular marks indicate the behavior without magnets (first modification example in FIG. 33).

  In the collision up to about 500,000 times, there is a difference in the maximum power generation amount depending on the presence or absence of the magnet 107. That is, without the magnet, the dielectric 103 and the electret 104 are stuck together, so that a high power generation amount cannot be obtained, but without the magnet, the dielectric 103 and the electret 104 can be prevented from sticking. A higher power generation amount can be obtained.

  However, when the number of collisions exceeds 100,000, the difference in the amount of power generation due to the presence or absence of the magnet 107 starts to decrease, and in the range where the number of collisions exceeds 500,000, the maximum power generation is possible with or without the magnet 107. The amount is almost unchanged. As the cause, there is a possibility that metal fatigue is caused in the spring member 102. Therefore, if the design of the spring member 102 is devised, it is considered possible to improve the decrease in the maximum power generation amount.

  FIG. 37 is a schematic diagram illustrating a third modification of the power generation device. The third modified example is basically the same as the first modified example, and is characterized in that the electret 104 is supported using the spring member 106b instead of the repulsive member 106a. Therefore, the same components as those in the first modification are denoted by the same reference numerals as those in FIG. 33, and redundant descriptions are omitted. In the following, the characteristic portions of the third modification will be mainly described.

  The spring member 106 b is an example of an electret support member that elastically supports the electret 104. In this figure, a spring member 106 b is formed so as to support both ends of the glass substrate 105 on the inner side surface of the package 110. Accordingly, the electret 104 is supported by the spring member 106b on the lower surface side that does not face the dielectric 103. However, the support form by the spring member 106 b is not limited to this, and for example, the spring member 106 b may be inserted between the lower surface of the glass substrate 105 and the bottom surface of the package 110. As the spring member 106b, a coil spring or a bellows spring (a meander shape) may be used similarly to the spring member 102.

  38 and 39 are diagrams showing temporal changes in the output voltage and the instantaneous power, respectively. In addition, the solid line of both figures has shown the behavior of the structure (3rd modification of FIG. 37) using the spring member 106b as an electret support member, and a broken line uses the repulsion member 106a (gel) as an electret support member. The behavior of (first modification of FIG. 33) is shown. FIG. 40 is a table showing measurement results of the power generation amount and the resistance value.

As can be seen from each figure, when the spring member 106b is used as the electret support member, the contact time between the dielectric 103 and the electret 104 is shorter than when the repulsion member 106a (gel) is used, so the maximum value of the output voltage is Get higher. Further, if the spring member 106b is used as the electret support member, the output voltage cycle becomes shorter (frequency becomes higher) than when the repulsion member 106a (gel) is used, so that the resistance value that maximizes the amount of power generation becomes lower. (R = 1 / 2πfC). From the above, if the spring member 106b is used as the electret support member, the power generation amount of the power generation apparatus 100 can be improved (P = V ² / R).

  FIG. 41 is a diagram showing a time change of the output voltage in the third modification. In addition, the continuous line in FIG. 41 has shown the experimental result, and the broken line has shown the analysis result. FIG. 42 is a diagram showing temporal changes in output voltage, mass displacement, and electret displacement in the third modification. 42 indicates the output voltage analysis result (corresponding to the broken line in FIG. 41), the broken line indicates the displacement of the movable mass 101 (dielectric 103), and the alternate long and short dash line indicates the displacement of the electret 104. Is shown.

  If the spring member 106b is well designed, when the movable mass 101 (dielectric 103) and the electret 104 approach each other, they can collide with each other multiple times, which is expected to contribute to an improvement in power generation. .

  FIG. 43 is a correlation diagram between the spring constant of the spring member 106b and the power generation amount. As a result of conducting a power generation test while changing the spring constant, it has been found that the amount of power generation can be improved by appropriately adjusting the spring constant of the spring member 106b. From this figure, it can be seen that the spring constant of the spring member 106b may be 0.5 to 50 N / mm (more preferably 1.0 to 10 N / mm).

  FIG. 44 is a correlation diagram between the acceleration and the total amplitude of the movable mass 101 (dielectric 103). In addition, the round mark in a figure has shown the behavior of the structure (The 3rd modification of FIG. 37) which used the spring member 106b as an electret support member, and the triangular mark used the repulsion member 106a (gel) as an electret support member The behavior of the configuration (first modification of FIG. 33) is shown.

  As shown in the figure, in the configuration in which the electret 104 is supported by the spring member 106b, the total amplitude of the movable mass 101 (dielectric 103) is larger than the configuration in which the electret 104 is supported by the repelling member 106a (gel). . In view of this, the spring member 106b can be regarded as a repulsion member 106a formed of a high repulsion material having a restitution coefficient larger than that of the gel, and therefore agrees with the experimental result shown in FIG.

  FIG. 45 is a schematic diagram illustrating a fourth modification of the power generation device. The fourth modification is a combination of the first to third modifications described so far, and includes both the repulsion member 106a and the spring member 106b as the electret support member, and also the dielectric 103 and the electret. A magnet 107 is also provided for separating the magnet 104.

  In the fourth modification, a predetermined displacement margin is provided between the two members so that the repulsive member 106a does not unnecessarily hinder the vibration of the spring member 106b. Therefore, the repulsion member 106a functions as a stopper that pushes back the spring member 106b when the acceleration is applied to the power generation apparatus 100 and the spring member 106b is displaced to a position where it contacts the repulsion member 106a.

  Also in the power generation device 100 of the fourth modification, the amount of power generation is improved by appropriately adjusting the spring constant of the spring member 102, the restitution coefficient of the repulsion member 106a, the spring constant of the spring member 106b, and the magnetic strength of the magnet 107. Can be achieved.

<Application>
As a power source for various sensors and wireless devices (for example, ZigBee [registered trademark] 300 MHz band specific low-power wireless devices), a ubiquitous environment based on wireless sensors and wireless sensor networks is constructed by applying the above power generator. Can do. That is, since various types of sensors and wireless devices need no power supply wiring, it is possible to realize information linkage in the network by distributing each device.

  In addition to application to the tire pressure monitoring system (TPMS [Tire Pressure Monitoring System]) that has been put into practical use in some cases, examples of usage scenes of the ubiquitous environment using the above power generator include, for example, the medical / health field (Health management and safety confirmation), structure monitoring (wire disconnection and bolt looseness monitoring), plant monitoring (equipment abnormality monitoring), logistics management (distribution status and quality monitoring), and the like. In addition, since an electric motor such as a motor vibrates at a power supply frequency (50 Hz or 60 Hz), if the resonance condition of the spring system incorporated in the power generation device is adjusted to the above power supply frequency, a larger power generation amount is expected. It is conceivable to use the generated power as a power source for a data processing device or the like. Furthermore, an application for generating power by attaching the above power generation device to a human body, an application for generating power by mounting the above power generation device on a mobile device such as a mobile phone, and the like are also assumed.

<Other variations>
It should be noted that the configuration of the present invention can be variously modified within the scope of the gist of the invention in addition to the above-described embodiment or modification. That is, the above-described embodiment is an example in all respects and should not be considered as limiting, and the technical scope of the present invention is not the description of the above-described embodiment, but the claims. It should be understood that all modifications that come within the meaning and range of equivalents of the claims are included.

  The power generator according to the present invention is a technology that can be suitably used as a power source used for various sensors and wireless devices (wireless sensor network, health monitoring, etc.).

DESCRIPTION OF SYMBOLS 10 Power generation device 11 Dielectric 12 Electret 13 Lower electrode 14 Resistance 15 Upper electrode 16 Substrate 17 Gap layer 18 Metal body 20 Power generation device 21 Substrate 22 Lower electrode 23 Electret 24 Dielectric (dielectric, electrode, weight integrated) thing)
24a Rail groove 25 Package 25a Ball receiving portion 25b Rail groove 26 Adhesive 27 Wire 31-34 Elastic member 35a, 35b, 36a, 36b Magnet 37 Stopper 38 Ball member 39 Rail member 40 Power generating device 41 Dielectric 42 Electret 43 Lower electrode 44 Resistance 45 Ground ring 50 Power generation device 51 Dielectric 52 Electret 53 Lower electrode 54 Substrate 60 Power generation device 61 Dielectric 61a Protrusion 62 Electret 62a Recess 63 Lower electrode 70, 80, 90 Power generation devices 71, 81, 91 Dielectric 72, 82 , 92 Electret 73, 83, 93 Lower electrode 74, 84, 94 Resistance 100 Power generation device 101 Movable mass 102 Spring member (mass support member)
103 dielectric 104 electret 105 glass substrate 106a repulsion member (electret support member)
106b Spring member (electret support member)
107 Magnet 110 Package X1 Dielectric X2 Aluminum plate X3 Electromagnetic exciter X4 Sample X41 Electret X42 Lower electrode X43 Substrate X5 Aluminum plate X6 Triaxial stage X7 Foundation X8 Coaxial cable X9 Coaxial cable X10 Shield case X10b First connector X10b Connector X11 Coaxial cable X12 Low pass filter X13 Coaxial cable X14 Oscilloscope Rv, R Load resistance Y Corona discharge device Y1 Grid Y2 Discharge electrode needle Y3 Grid power supply Y4 DC high voltage power supply

Claims (7)

A power generation device that includes a dielectric serving as a movable mass, and an electret that holds electric charge, and generates power by changing a distance between the dielectric and the electret,
An electret support member that elastically supports the electret ;
Magnets repelling each other so as to separate the dielectric and the electret;
Further we have a,
The electret support member includes a rebound member having a predetermined restitution coefficient, and a spring member having a predetermined spring constant,
The repulsion member and the spring member are both provided on the side of the electret that does not face the dielectric, and a predetermined displacement is provided between the members . The power generation apparatus according to claim 1 , wherein the coefficient of restitution is 0.3 or more. The power generation device according to claim 2 , wherein the repulsion member is formed of a gel or a high repulsion material having a higher restitution coefficient. The power generator according to any one of claims 1 to 3, wherein the magnet is formed so that a surface thereof is flush with a surface of the dielectric and the electret. The said spring constant is 0.5-50 N / mm, The electric power generating apparatus as described in any one of Claims 1-4 characterized by the above-mentioned. The power generation device according to any one of claims 1 to 5 , further comprising a mass support member that elastically supports the movable mass. The power generator according to any one of claims 1 to 6 , further comprising a package for housing the dielectric and the electret.