JP2022082718A - Vibration power generation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide is a vibration power generation element which increases power generation electromotive force without increasing a size of a vibration power generation element.

SOLUTION: A vibration power generation element includes: a first electrode; a second electrode that moves in a predetermined direction with respect to the first electrode; a third electrode; a fourth electrode that moves in a predetermined direction with respect to the third electrode; and a support part that supports the second electrode and the fourth electrode so as to be movable in the predetermined direction, in which the first electrode and the third electrode are arranged in a predetermined direction, at least one of facing surfaces of the first electrode and the second electrode and at least one of facing surfaces of the third electrode and the fourth electrode are charged, and the support part supports the second electrode and the fourth electrode in a state of keeping a balance of an electrostatic force by the first electrode and the second electrode and an electrostatic force by the third electrode and the fourth electrode in a predetermined direction.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a vibration power generation element.

In recent years, as one of the energy harvesting techniques for harvesting energy from the environment, a method of generating power from environmental vibration using a vibration power generation element (vibration power generation device) has attracted attention. It has been proposed to utilize the electrostatic force of the electlet in the vibration power generation element for such an application in order to obtain a small size and high power generation efficiency. For example, Patent Document 1 discloses an electrostatic induction type conversion element in which an electret is formed on a vertical surface of a comb tooth electrode formed on a movable portion and a fixed portion by using soft X-rays.

Japanese Patent No. 5551914

The electrostatic induction conversion element described in Patent Document 1 generates electricity by vibrating a movable portion in a predetermined direction by environmental vibration. At this time, by changing the overlapping area of the electlet surfaces of the opposing comb tooth electrodes, the mechanical work is converted into electrostatic energy by the electrostatic force acting between the comb tooth electrodes, and an electromotive force can be generated. However, in order to obtain a larger electromotive force, an extra space is required in the vibration direction of the moving portion, and there is a problem that the electrostatic induction conversion element becomes large.

According to the first aspect of the present invention, the vibration power generation element includes a first electrode, a second electrode that moves along a predetermined direction with respect to the first electrode, and a third electrode. A support portion that movably supports a fourth electrode that moves along the predetermined direction with respect to the third electrode, and the second electrode and the fourth electrode that move along the predetermined direction. The first electrode and the third electrode are arranged along the predetermined direction, and at least one of the facing surfaces of the first electrode and the second electrode and the above. At least one of the facing surfaces of the third electrode and the fourth electrode is charged with a predetermined charging voltage, whereby the support portion is subjected to the electrostatic force of the first electrode and the second electrode. The second electrode and the fourth electrode are supported in a state where the electrostatic force of the third electrode and the fourth electrode is balanced along the predetermined direction, and the predetermined electrode is supported. The charging voltage is a charging voltage that positions the vibration center position of the vibration due to the movement between the second electrode and the fourth electrode at the stable point position of the support portion, and the force coefficient is the first electrode or the first electrode or The number n of the second electrodes, the dielectric constant ε ₀ of the vacuum, the thickness b of the first electrode or the second electrode, the charging voltage V ₀ , the first electrode and the first electrode. The distance g between the two electrodes and the electrode is a value A satisfying the following equation (1).
A = 2nε ₀ bV ₀ / g ... (1)
The value A of the force coefficient is 13.5 [μC / m] or more.

According to the present invention, it is possible to increase the generated electromotive force without increasing the size of the vibration power generation element.

It is a top view which shows the schematic structure of the vibration power generation element by one Embodiment of this invention. It is a figure which shows typically the structure of the elastic support part of the vibration power generation element by embodiment. It is a figure which shows the equivalent circuit of the vibration power generation element of this embodiment shown in FIG. It is a figure which shows the result of the simulation. It is a top view which shows the structure of the vibration power generation element in the modification. It is a figure which shows typically the structure of the elastic support part of the vibration power generation element in the modification.

A mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a plan view showing a schematic configuration of a vibration power generation element 1 according to an embodiment of the present invention.
The vibration power generation element 1 is formed by a general MEMS processing technique using, for example, an SOI (Silicon On Insulator) substrate. The SOI substrate is composed of, for example, a lower Si layer on which a handle layer is formed, a SiO ₂ layer on which a BOX layer is formed, and an upper Si layer on which a device layer is formed.
The vibration power generation element 1 includes a base 2, fixed electrodes 3a and 3b, movable electrodes 4a and 4b, a movable portion 5, and an elastic support portion 6. A load 9 is connected to the vibration power generation element 1.
In the following description, it is assumed that an orthogonal coordinate system consisting of an X-axis, a Y-axis, and a Z-axis set as shown in FIG. 1 is used.

The movable portion 5 is movably supported by an elastic support portion 6 described later. The movable portion 5 has a movable electrode 4a at the end on the X direction − side and a movable electrode 4b at the end on the X direction + side.
The fixed electrodes 3a and 3b and the movable electrodes 4a and 4b each have a comb tooth structure. A plurality of comb teeth 30a are formed on the fixed electrode 3a, and a plurality of comb teeth 40a are formed on the movable electrode 4a. The fixed electrode 3a and the movable electrode 4a are arranged so that the comb teeth 30a and the comb teeth 40a mesh with each other on the X-direction-side of the vibration power generation element 1. Similarly, a plurality of comb teeth 30b are formed on the fixed electrode 3b, and a plurality of comb teeth 40b are formed on the movable electrode 4b. The fixed electrode 3b and the movable electrode 4b are arranged so that the comb teeth 30b and the comb teeth 40b mesh with each other on the X direction + side of the vibration power generation element 1.

As described above, the fixed electrodes 3a and 3b form a fixed comb tooth electrode, and the movable electrodes 4a and 4b form a movable comb tooth electrode. The comb tooth electrode is a device in which a plurality of comb teeth are arranged in parallel, such as the fixed electrodes 3a and 3b and the movable electrodes 4a and 4b in FIG. The number of comb teeth in the present invention is not limited to that shown in FIG. When the number of comb teeth is the minimum, the comb tooth electrode has two comb teeth formed on one of the fixed comb tooth electrode and the movable comb tooth electrode, and is inserted between the two comb teeth. One comb tooth is formed on the other electrode. With the comb tooth electrode having such a basic configuration, a vibration power generation element having the functions as described below can be configured regardless of the number of comb teeth.

The movable portion 5 elastically supported by the base 2 by the elastic support portion 6 can slide and move in the X direction integrally with the movable electrodes 4a and 4b. Since the movable portion 5 is slid and moved in the X direction, the elastic support portion 6 has a small spring constant k in the X direction and a large spring constant in the Y direction and the Z direction.

FIG. 2 is a diagram schematically showing a structure included in the region 100 surrounded by a broken line in FIG. 1. In the example shown in FIG. 2, the elastic support portion 6 has a flat plate shape extending along the Y direction. The elastic support portion 6 is connected to the base 2 on one end side in the Y direction of the flat plate shape, and is connected to the movable portion 5 on the other end side. In the flat plate-shaped elastic support portion 6, the thickness (length) in the X direction is shorter than the thickness (length) in the Z direction. The length of the elastic support portion 6 in the Y direction is longer than the thickness (length) in the X direction. That is, the rigidity of the elastic support portion 6 in the X direction is smaller than the rigidity in the Y direction and the Z direction. Therefore, since the support rigidity of the elastic support portion 6 in the X direction with respect to the movable portion 5 is smaller than the support rigidity in the Y direction and the Z direction, the movable portion 5 slides in the X direction.
As shown in FIG. 2, the elastic support portion 6 is not limited to that formed by one flat plate-shaped member, and may be formed by a plurality of flat plate-shaped members. As the elastic support portion 6, for example, the structure described in Japanese Patent No. 5551914 can be applied.
Further, the elastic support portion 6 is not limited to a flat plate shape, that is, a shape having a rectangular cross section in the ZX plane, and may be an elliptical shape or a polygonal shape. In this case, the support rigidity in the X direction is made smaller than the support rigidity in the other direction by forming the elastic support portion 6 so that the maximum length in the X direction of the cross section is smaller than the length in the Z direction. Can be done.

At least one of the comb teeth 30a of the fixed electrode 3a and the comb teeth 40a of the movable electrode 4a that are in mesh with each other, and at least one of the comb teeth 30b of the fixed electrode 3b and the comb teeth 40b of the movable electrode 4b are opposed to each other. An electlet is formed near the surface of the surface. As a result, at least one of the facing surfaces of the fixed electrode 3a and the movable electrode 4a and at least one of the facing surfaces of the fixed electrode 3b and the movable electrode 4b are charged. In the present embodiment, electrets are formed on at least one of the facing surfaces of the fixed electrode 3a and the movable electrode 4a and at least one of the facing surfaces of the fixed electrode 3b and the movable electrode 4b at substantially the same charging voltage. Has been done. As a result, the electrostatic force of the electret acting on the X-direction-side end portion of the movable portion 5 and the electrostatic force of the electret acting on the X-direction + side end portion are in a balanced state and are supported by the elastic support portion 6. That is, when the movable portion 5 vibrates in the X direction, the vibration center position thereof is located at the stable point position of the elastic support portion 6. The vibration center position may be located within a predetermined allowable range set by the result of a test or the like with reference to the stable point position of the elastic support portion 6.
The charging voltage is not limited to exactly the same, and as described above, the electrostatic force acting on the movable portion 5 may be balanced, that is, the vibration center position may be located at the stable point position of the elastic support portion 6. Any charging power that can be realized is sufficient. Further, as an example of the method for forming the electret, for example, as described in Japanese Patent Application Laid-Open No. 2016-149914, a method of forming an oxide film on the surface of the comb tooth structure and applying a high temperature bias treatment is used. Can be done. Of course, the method is not limited to the above method, and various methods disclosed in, for example, Japanese Patent No. 5551914 can be applied.

The load 9 is, for example, the input impedance of a power supply controller that adjusts the voltage and the code, and consumes the electric power supplied from the vibration power generation element 1 to perform a predetermined operation. The positive electrode side of the load 9 is connected to the fixed electrode 3a, and the negative electrode side is electrically connected to the fixed electrode 3b. The negative electrode side of the load 9 may be connected to the fixed electrode 3a, and the positive electrode side may be electrically connected to the fixed electrode 3b.

When the vibration power generation element 1 is shaken in a direction including the X direction due to vibration in the environment, the movable electrodes 4a and 4b vibrate in the X direction with respect to the fixed electrodes 3a and 3b and are displaced. For example, when the movable electrodes 4a and 4b are displaced toward the + side in the X direction, the facing area between the fixed electrode 3a and the movable electrode 4a decreases, and the facing area between the fixed electrode 3b and the movable electrode 4b increases. .. Such a change in the facing area changes the induced charge of the electret. As a result, the voltage between the fixed electrodes 3a and 3b and the movable electrodes 4a and 4b changes to generate an electromotive force, so that the vibration power generation element 1 is generated. The electromotive force obtained by the power generation of the vibration power generation element 1 is applied to the load 9 via the above-mentioned electrical connection, and the load 9 is driven.

なお、ｍは可動部５の質量、Ｘは振動発電素子１内における可動部５の固定部（たとえば固定電極３ａ、３ｂ）に対する相対変位、Ｘ_outは振動発電素子１の外部振動の変位、ｒ_fは空気や機械の摩擦によるダンピング係数、Ｖ_LおよびＶ_Rは固定電極３ａ、３ｂで発生する電圧、Ｖ₀は固定電極３ａ、３ｂでのエレクトレット帯電電圧である。また、Ａはエレクトレットによる強さの量を示す力係数であり、以下の式（２）により表すことができる。 The movement of the movable electrodes 4a and 4b of the vibration power generation element 1 having the above configuration will be described.
FIG. 3 is an equivalent circuit diagram corresponding to the configuration of the vibration power generation element 1 shown in FIG. By using this equivalent circuit, the equation of motion of the movable portion 5 when the movable portion 5 vibrates along the X direction can be expressed as the following equation (1).

Note that m is the mass of the movable portion 5, X is the relative displacement of the movable portion 5 with respect to the fixed portion (for example, the fixed electrodes 3a and 3b) in the vibration power generation element 1, and X _out is the displacement of the external vibration of the vibration power generation element 1. _f is a damping coefficient due to friction of air or a machine, _VL and V _R are voltages generated at fixed electrodes 3a and 3b, and V ₀ is an electlet charging voltage at fixed electrodes 3a and 3b. Further, A is a force coefficient indicating the amount of strength due to the electret, and can be expressed by the following equation (2).

A = 2nε ₀ bV ₀ / g ... (2)
Note that n is the number of teeth of the comb teeth 30a or 40a, ε ₀ is the dielectric constant of the vacuum, b is the thickness of the comb teeth 30a and 40a (length in the Z direction), V ₀ is the electlet charging voltage, and g is the comb tooth. The distance between 30a and the comb teeth 40a. In order to change the value of the force coefficient A, that is, to change the strength of the effect of the electret, at least one of the interval g between the comb teeth 30a and 40a and the electret charging voltage V ₀ shown in the equation (2). Should be changed. For example, the force coefficient A can be changed to a large value by reducing the interval g, increasing the charging voltage V ₀ , or both.

The first term on the right side of the equation (1) is the force that the external vibration of the vibration power generation element 1 acts on the movable portion 5, the second term is the elastic force that acts on the movable portion 5 by the elastic support portion 6, and the third term is air. It represents the force exerted on the movable portion 5 by mechanical friction and the like. The fourth term represents the electrostatic force acting on the movable electrode 4a, and the fifth term represents the electrostatic force acting on the movable electrode 4b. This equation (1) is set under the condition that the value of the load 9 is set to the optimum value R shown by the following equation (3), the external vibration is a sine wave, and the frequency is close to the resonance frequency of the movable portion 5. Eq. (4) can be obtained by approximating and transforming with.

なお、Ｃ₀は可動電極４ａまたは４ｂの静電容量であり、ω₀は可動部５の共振角振動数、すなわち可動電極４ａまたは４ｂの共振角振動数である。静電容量Ｃ₀は、固定電極と可動電極とが対向するときのＸ方向の長さをｗとし、浮遊容量をＣ₁として、Ｃ₀＝Ｃ₁＋（２ｎε₀ｂｗ／ｇ）のように表され、共振角振動数ω₀は、ω₀＝｛（ｋ＋Ａ²／Ｃ₀）／ｍ｝^1/2のように表される。式（３）は、固定電極および可動電極の静電容量と負荷９による放電との時定数が、可動部５の振動の時定数と一致する場合に、負荷９が有し得る抵抗値を最適値Ｒとして設定されていることを表す。 R = 2 / (C ₀ ω ₀ )… (3)

Note that C ₀ is the capacitance of the movable electrode 4a or 4b, and ω ₀ is the resonance angular frequency of the movable portion 5, that is, the resonance angular frequency of the movable electrode 4a or 4b. Capacitance C ₀ is such that C ₀ = C ₁ + (2nε ₀ bw / g), where w is the length in the X direction when the fixed electrode and the movable electrode face each other, and C ₁ is the floating capacitance. The resonance angle frequency ω ₀ is expressed as ω ₀ = {(k + A ² / C ₀ ) / m} ^1/2 . Equation (3) optimizes the resistance value that the load 9 can have when the time constant between the capacitance of the fixed electrode and the movable electrode and the discharge due to the load 9 matches the time constant of the vibration of the movable portion 5. Indicates that the value R is set.

As shown on the right side of the equation (4), the force acting on the movable part 5 is the force from the external vibration and the force due to the hard spring effect by the electric of the second term on the right side (hereinafter referred to as the hard spring term). It can be classified into the force due to the electrical damping effect of the third term on the right side (hereinafter referred to as the electrical damping term). When the force coefficient A shown in the equation (2) is changed, the value of the hard spring term (k + A ² / C ₀ ) and the value of the electrical damping term ( _rf + A ² / (C ₀ ω ₀ )) are changed. It is possible. As described above, the force coefficient A can be changed by changing at least one of the distance g between the comb teeth 30a and 40a and the electret charging voltage V ₀ . Therefore, the value of the hard spring term and the value of the electrical damping term can be changed by changing at least one of the distance g between the comb teeth 30a and 40a and the electret charging voltage V ₀ .

式（５）に示すように、力係数Ａを大きな値に設定すると、Ｑ値を低い値に下げることが可能になる。Ｑ値が低い値であるほど共振のピークがなだらかとなり、可動部５の共振周波数と外部振動の周波数のマッチングを容易にすることができる。すなわち、振動発電素子１内部を高真空にしなくても、広い帯域において、加わった外部振動に対して可動部５が共振をして発電が行われ、固定電極３ａ、３ｂから電力が出力される。 The electrical damping term included in equation (4) depends on the vibration bandwidth of the movable portion 5. By changing the force coefficient A and changing the electrical damping term, the resonance Q value of the vibration frequency response of the movable portion 5 can be set to an arbitrary value. The total Q value is expressed by the following equation (5), where the Q value due to mechanical damping is Q _M and the Q value due to electrical damping is Q _e .

As shown in the equation (5), when the force coefficient A is set to a large value, the Q value can be lowered to a low value. The lower the Q value, the smoother the peak of resonance, and it is possible to facilitate matching between the resonance frequency of the movable portion 5 and the frequency of external vibration. That is, even if the inside of the vibration power generation element 1 is not made into a high vacuum, the movable portion 5 resonates with the applied external vibration to generate electric power in a wide band, and the electric power is output from the fixed electrodes 3a and 3b. ..

力係数Ａの値を大きくする程、上記式（６）のうち発電効率Ｅ_Hである｛１／（１＋Ｃ₀ｋ／（Ａ²Ｑ_M））｝の値は１に近い値になり、機械的ダンピングの影響を無視することが可能となる。すなわち、力係数Ａの値を大きな値に設定することにより、機械的ダンピングを増加させることなくＱ値を低い値に設定でき、機械的ダンピングの増加による損失を抑制して発電特性を向上させることができる。本実施の形態の場合では、力係数Ａの値を大きく設定することにより、電気的ダンピングによる効果を機械的ダンピングによる効果に対して上回る構成とすることができるので、振動発電素子１による発電効率を大きくさせることができる。 In this case, the output power P from the fixed electrodes 3a and 3b is expressed by the following equation (6).

As the value of the force coefficient A increases, the value of {1 / (1 + C ₀ k / (A ² Q _M ))}, which is the power generation efficiency E _H in the above equation (6), becomes closer to 1, and the machine It is possible to ignore the effect of target damping. That is, by setting the value of the force coefficient A to a large value, the Q value can be set to a low value without increasing the mechanical damping, and the loss due to the increase in the mechanical damping can be suppressed to improve the power generation characteristics. Can be done. In the case of the present embodiment, by setting a large value of the force coefficient A, the effect of the electric damping can be exceeded by the effect of the mechanical damping, so that the power generation efficiency by the vibration power generation element 1 can be obtained. Can be increased.

The hard spring term in equation (4) depends on the resonance frequency. By changing the force coefficient A and changing the hard spring term, the resonance frequency of the movable portion 5 can be changed. Generally, the resonance frequency of the movable portion 5 is determined by the mechanical mass and the spring constant k of the elastic support portion 6. On the other hand, in the vibration power generation element 1 of the present embodiment, since the hard spring effect is generated by the electrostatic force of the electlet, the force coefficient A is adjusted by adjusting the charging voltage V ₀ to change the resonance frequency. can do. This makes it possible to manufacture the vibration power generation element 1 that can be changed to a resonance frequency suitable for the frequency of external vibration.

FIG. 4 is a diagram showing the results of simulation for the vibration power generation element 1. In the simulation, it is assumed that there is no mechanical damping (that is, r _f = 0), the value of the load 9 is set to the optimum value R shown in the equation (3), the vibration power generation element 1 is subjected to sinusoidal vibration, and the movable portion 5 is subjected to the sinusoidal vibration. The maximum amplitude was set to 200 [μm]. In FIG. 4, the vertical axis is the output power [μW] and the horizontal axis is the frequency [Hz], and the relationship between the frequency and the output power under the first condition described later is shown by the graph L1 and the frequency under the second condition described later. The relationship between the frequency and the output power is shown by graph L2.

The first condition is as follows.
Electret charging voltage V ₀ = 300 [V].
Force coefficient A = 13.5 [μC / m].
Optimal value of load 9 R = 18.37 [MΩ].
Acceleration 24.6 [m / s ² ].
Q value = 7.9.

The second condition is as follows.
Electret charging voltage V ₀ = 50 [V].
Force coefficient A = 2.25 [μC / m].
Optimal value of load 9 R = 19.62 [MΩ].
Acceleration 0.685 [m / s ² ].
Q value = 250.

In the first condition described above, the value of the force coefficient A is set to a large value, that is, the Q value shown in the equation (5) is set to a small value as compared with the second condition. As shown in FIG. 4, in the graph L2 under the second condition where the Q value is large, the peak of resonance is sharp. As shown in graph L2, at the resonance frequency, the movable portion 5 reaches the maximum amplitude even if it receives a small external vibration, but the output power becomes small. On the other hand, in the graph L1 of the first condition where the Q value is low, the peak of resonance is gentle as described above. As shown in graph L1, when a relatively large external vibration is received, the movable portion 5 reaches the maximum amplitude and the output power also increases. Further, the graph L1 shows that the fixed electrodes 3a and 3b can generate electricity in a wider frequency band as compared with the graph L2. Further, the resonance frequencies are different between the graphs L1 and L2 having different force coefficients A, and the resonance frequency in the graph L1 is increased due to the above-mentioned hard spring effect. That is, as described above, by adjusting the force coefficient A, it is possible to change to a resonance frequency suitable for the frequency of external vibration.

According to the above-described embodiment, the following effects can be obtained.
(1) At least one of the facing surfaces of the fixed electrode 3a and the movable electrode 4a and at least one of the facing surfaces of the fixed electrode 3b and the movable electrode 4b are charged. The elastic support portion 6 supports the movable electrodes 4a and 4b in a state where the electrostatic force of the fixed electrode 3a and the movable electrode 4a and the electrostatic force of the fixed electrode 3b and the movable electrode 4b are balanced along the X direction. ..
In the present embodiment, the force coefficient A is set to a large value as in the case of the first condition of the simulation described above. That is, the vibration power generation element 1 is created so that the electlet charging voltage V ₀ in the equation (2) is set to a large value and the distance g between the comb teeth 30a and the comb teeth 40a is small.

Generally, when the electret charging voltage V ₀ is set to a large value, the electrostatic force also increases. For example, in a vibrating element having a configuration as disclosed in Japanese Patent Application Laid-Open No. 2016-149914, the amount of movement of the movable comb tooth electrode in the X direction increases as the electrostatic force increases. Therefore, a space is required in the X direction for the movement of the movable comb tooth electrode. Further, since the amount of bending of the elastic support portion becomes large and the elastic support portion may be damaged, a configuration for preventing the large bending elastic support portion from being damaged is required. Therefore, it is necessary to make the shape of the vibrating element large in the Y direction as well.

On the other hand, in the vibration power generation element 1 of the present embodiment, the movable portion 5 is supported by the elastic support portion 6 in a state where the electrostatic forces are balanced. That is, even if the movable portion 5 is vibrating, the vibration center position is located at the stable point position, so that it is not necessary to provide a space in the X direction and a configuration for preventing damage to the elastic support portion 6 is not required. .. As a result, the value of the force coefficient A can be increased to increase the amount of power generation without increasing the size of the vibration power generation element 1. In other words, it is possible to obtain a vibration power generation element 1 having a large amount of power generation as compared with a conventional vibration element of the same size.
Further, when the movable portion 5 is supported by the elastic support portion 6 in a state where the electrostatic force is balanced, the force acting on the movable portion 5 by vibration does not exceed a predetermined force according to the electrostatic force of the electlet. However, the movable portion 5 can start vibration by a minute external vibration at the vibration center position. In particular, when the external vibration matches the resonance frequency, the movable portion 5 can be vibrated greatly by resonance. That is, it is possible to generate power even when the external vibration applied to the vibration power generation element 1 is minute.
Further, while the conventional power generation element corresponds to the impulse-like environmental vibration, the vibration power generation element 1 of the present embodiment has a weak sinusoidal environmental vibration, for example, a weak vibration of a pump, a fan, or the like. Can also be detected. Since the frequency in this case fluctuates depending on the load, the vibration power generation element 1 of the present embodiment having wide band characteristics can be preferably used.

Further, since the movable portion 5 is supported by the elastic support portion 6 in a state where the electrostatic force is balanced, the electlet charging voltage V ₀ can be made a large value, thereby changing from mechanical energy to electrical energy. It becomes possible to manufacture the vibration power generation element 1 having a high conversion speed. By increasing the electret charging voltage V ₀ , it is possible to set the force coefficient A shown in the above equation (2) as a large value and decrease the Q value as shown in the equation (5) without increasing the mechanical damping. Will be. As a result, the vibration power generation element 1 having wide band characteristics as shown in the graph L1 of FIG. 4 can be realized, so that the matching of the resonance frequency of the vibration power generation element 1 and the frequency of the external vibration can be facilitated, and the power generation efficiency can be improved. Can be done.
Further, by adjusting the electlet charging voltage V ₀ and changing the value of the force coefficient A, it is possible to manufacture the vibration power generation element 1 having a resonance frequency matched to the frequency of the external vibration.

(2) Of the support rigidity of the elastic support portion 6 that supports the movable electrodes 4a and 4b, the support rigidity along the X direction is higher than the support rigidity along the direction different from the X direction (for example, the Y direction and the Z direction). Is also small. As a result, the elastic support portion 6 can slide the movable portion 5 in the X direction and vibrately support the movable portion 5 without moving the vibration center position of the movable portion 5 at the stable point position of the spring.

(3) The load 9 is connected to the fixed electrodes 3a and 3b, and power generation due to the capacitance changed by the relative displacement between the fixed electrode 3a and the movable electrode 4a and the relative of the fixed electrode 3b and the movable electrode 4b. It is driven by the power obtained from the power generation due to the capacitance changed by the displacement. As a result, the vibration power generation element 1 of the present embodiment receives twice as much electric power in total from the fixed electrodes 3a and 3b as compared with the case where the vibration power generation element 1 of the present embodiment has a configuration such as the power generation element of JP-A-2016-149914. can get. Therefore, the amount of power generated to the load 9 can be increased without increasing the size of the vibration power generation element 1. In other words, it is possible to obtain a vibration power generation element 1 having a large amount of power generation as compared with a conventional vibration element of the same size.

The structure of the vibration power generation element according to the present invention is not limited to that described in the above-described embodiment. For example, in FIG. 1, each of the plurality of comb teeth 30a of the fixed electrode 3a and each of the plurality of comb teeth 30b of the fixed electrode 3b are formed along the X direction as an example. Not limited to.

Further, in the vibration power generation element 1 described in the embodiment shown in FIG. 1, the elastic support portion 6 supports the movable portion 5 at two locations, the Y direction + side and the Y direction − side, but at three or more locations. It may be supported by the elastic support portion 6. For example, in the XY plane of FIG. 5, the case where the movable portion 5 is supported by the elastic support portion 6 at four points is shown as an example. In this case, the movable portion 5 is supported by the first elastic support portion 61 from the Y direction + side and is supported by the second elastic support portion 62 from the Y direction − side near the end portion on the X direction + side. To. The movable portion 5 is supported by the third elastic support portion 63 from the Y direction + side and is supported by the fourth elastic support portion 64 from the Y direction − side in the vicinity of the end portion on the X direction − side.

Further, in the vibration power generation element 1 described in the embodiment, the one in which the support rigidity in the X direction is reduced by the cross-sectional shape of the elastic support portion 6 is given as an example, but the present invention is not limited to this. For example, the vibration power generation element 1 may be configured such that a plurality of elastic support portions 6 extending along the Y direction are arranged along the Z direction. An example of the structure in this case is shown in FIG. FIG. 6 is a diagram schematically showing a structure included in the region 100 in FIG. 1, similarly to FIG. 2. In the example shown in FIG. 6, the vibration power generation element 1 includes two plate-shaped elastic support portions 6 (hereinafter referred to as upper elastic support portion 611 and lower elastic support portion 612) extending along the Y direction. .. The upper elastic support portion 611 and the lower elastic support portion 612 are connected to the base 2 on one end side in the Y direction and to the movable portion 5 on the other end side. In this case, the upper elastic support portion 611 and the lower elastic support portion 612 are arranged along the Z direction. As a result, the rigidity of the two elastic support portions 6 acts in the Z direction. Therefore, in the vibration power generation element 1, the support rigidity in the X direction can be made smaller than the support rigidity in the other directions. The vibration power generation element 1 is not limited to having two elastic support portions 6 of an upper elastic support portion 611 and a lower elastic support portion 612, and may have three or more elastic support portions 6.

Further, the case is not limited to the case where the elastic support portion 6 is composed of a plate-shaped member. For example, the movable portion 5 may be supported by a coil spring. At this time, the movable portion 5 is connected to the base 2 via a coil spring in each of the X direction, the Y direction, and the Z direction. At this time, by making the spring constant of the coil spring connected in the Y direction and the Z direction larger than the spring constant of the coil spring connected in the X direction, the support rigidity of the movable portion 5 in the X direction can be reduced. can. In this case, for example, the number of coil springs connected in the Y direction and the Z direction of the movable portion 5 may be larger than the number of coil springs connected in the X direction.

The present invention is not limited to the above-described embodiment as long as the features of the present invention are not impaired, and other embodiments considered within the scope of the technical idea of the present invention are also included within the scope of the present invention. ..

1 ... Vibration power generation element, 2 ... Base, 3a, 3b ... Fixed electrode,
4a, 4b ... Movable electrode, 5 ... Movable part, 6 ... Elastic support part,
9 ... Load, 30a, 30b ... Comb teeth, 40a, 40b ... Comb teeth

Claims (4)

With the first electrode
A second electrode that moves in a predetermined direction with respect to the first electrode, and a second electrode.
With the third electrode
A fourth electrode that moves along the predetermined direction with respect to the third electrode, and a fourth electrode.
A support portion for movably supporting the second electrode and the fourth electrode along the predetermined direction is provided.
The first electrode and the third electrode are arranged along the predetermined direction.
At least one of the facing surfaces of the first electrode and the second electrode and at least one of the facing surfaces of the third electrode and the fourth electrode are charged with a predetermined charging voltage. As a result, the support portion is in a state where the electrostatic force of the first electrode and the second electrode and the electrostatic force of the third electrode and the fourth electrode are balanced along the predetermined direction. , Supporting the second electrode and the fourth electrode,
The predetermined charging voltage is a charging voltage that positions the vibration center position of the vibration due to the movement between the second electrode and the fourth electrode at the stable point position of the support portion.
The force coefficient includes the number n of the first electrode or the second electrode, the dielectric constant ε ₀ of the vacuum, the thickness b of the first electrode or the second electrode, and the charging voltage V ₀ . And the distance g between the first electrode and the second electrode are values A satisfying the following equation (1).
A = 2nε ₀ bV ₀ / g ... (1)
A vibration power generation element having a force coefficient value A of 13.5 [μC / m] or more. In the vibration power generation element according to claim 1,
Of the support rigidity of the support portion that supports the second electrode and the fourth electrode, the support rigidity along the predetermined direction is higher than the support rigidity along a direction different from the predetermined direction. Small vibration power generation element. In the vibration power generation element according to claim 1 or 2,
Further comprising a load connected to the first electrode and the third electrode.
The load changes due to the power generation due to the capacitance changed by the relative displacement between the first electrode and the second electrode and the relative displacement between the third electrode and the fourth electrode. A vibration power generation element driven by the electric power obtained from the electric power generated by the generated electrostatic capacity. In the vibration power generation element according to claim 3,
The load is a value in which the capacitance C ₀ in the second electrode or the fourth electrode and the resonance angular frequency ω ₀ of the second electrode or the fourth electrode satisfy the following equation (2). Vibration power generation element having R.
R = 2 / (C ₀ ω ₀ )… (2)

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