Vibration power generation element

Abstract

The present application provides a kind of vibration power generation element, can substantially reduce the parasitic capacitance possibly generated in vibration power generation element, thereby can expand the frequency band that can be generated.A kind of vibration power generation element, characterized in that, with: fixed electrode, it has multiple comb-shaped electrodes;Movable electrode, it has multiple comb-shaped electrodes with the fixed electrode interlock;And elastic support part, it makes the movable electrode relative to the fixed electrode in the same plane on the predetermined direction relative movement, in the state of at least one of the fixed electrode and the movable electrode is electrified, the fixed electrode and the engagement length of the movable electrode and the deflection of the elastic support part are same, or the fixed electrode and the engagement length of the movable electrode is less than the deflection of the elastic support part.

Description

Technical Field

[0001] This disclosure relates to a vibration power generation element, and more specifically, to a technique for reducing parasitic capacitance in the vibration power generation element. Background Technology

[0002] Previously, as one of the energy harvesting technologies for extracting energy from environmental vibrations, vibration power generation devices with vibration power generation elements were known. Vibration power generation devices can obtain a large output when the resonant frequency of the vibration power generation element is synchronized with the environmental vibration, but the output decreases significantly when the environmental vibration deviates from the resonant frequency.

[0003] Such output reduction can be mitigated by decreasing the parasitic capacitance in the vibratory power generation element and expanding the frequency band in which the vibratory power generation element can generate electricity.

[0004] Based on this viewpoint, Patent Document 1 discloses a vibration power generation element that reduces parasitic capacitance by removing at least a portion of the comb tooth connection portion of a base whose length is entirely opposed to the direction of the fixed comb tooth arrangement.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-136704 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Here, the inventors are not limited to the structure disclosed in Patent Document 1, and have investigated whether there is a structure for reducing parasitic capacitance. That is, in conventional vibration power generation elements, the opposing comb electrodes of the vibration power generation element are in a state of mutual meshing over a constant length in the uncharged state before the electret is formed, but it is not possible to sufficiently reduce the parasitic capacitance between the comb electrodes.

[0010] This disclosure was made in view of the problem that the object is to provide a vibration power generation element that can significantly reduce the parasitic capacitance that may be generated in the vibration power generation element, thereby expanding the power generation frequency band.

[0011] Solution for solving the problem

[0012] A vibration-generating element according to one embodiment of the present disclosure is characterized by comprising: a fixed electrode having a plurality of comb-shaped electrodes; a movable electrode having a plurality of comb-shaped electrodes that mesh with the comb teeth of the fixed electrode; and an elastic support portion that allows the movable electrode to move relative to the fixed electrode in a predetermined direction on the same plane, wherein, when at least one of the fixed electrode and the movable electrode is energized, the engagement length between the fixed electrode and the movable electrode and the deflection of the elastic support portion are the same, or the engagement length between the fixed electrode and the movable electrode is smaller than the deflection of the elastic support portion.

[0013] Furthermore, one aspect of the vibration power generation element disclosed herein is characterized by comprising: a fixed electrode having a plurality of comb-shaped electrodes; a movable electrode having a plurality of comb-shaped electrodes that engage with the comb teeth of the fixed electrode; and an elastic support portion that allows the movable electrode to move relative to the fixed electrode in a predetermined direction on the same plane, wherein when the fixed electrode and the movable electrode change from an uncharged state to a charged state, the fixed electrode moves closer to the movable electrode, and the elastic support portion is approximately symmetrical in the direction of relative movement.

[0014] Furthermore, according to one aspect of this disclosure, the distance between the front end faces of the fixed electrode and the movable electrode when the fixed electrode and the movable electrode are not energized is the distance between the fixed electrode and the movable electrode when at least one of the fixed electrode and the movable electrode is energized, and the fixed electrode and the movable electrode have an engagement length.

[0015] Furthermore, according to one aspect of this disclosure, it is characterized by comprising a plurality of the fixed electrodes and a plurality of the movable electrodes.

[0016] Furthermore, according to one aspect of this disclosure, an electret is formed on at least one of the fixed electrode and the movable electrode.

[0017] Furthermore, according to one aspect of this disclosure, the fixed electrode and the movable electrode are not engaged when the fixed electrode and the movable electrode are not energized; if at least one of the fixed electrode and the movable electrode is energized, the movable electrode moves in the extension direction of the comb teeth of the movable electrode and has a length that engages with the fixed electrode.

[0018] Invention Effects

[0019] According to this disclosure, a vibration power generation element can be provided that can sufficiently reduce the parasitic capacitance that may be generated in the vibration power generation element, thereby expanding the frequency band of power generation. Attached Figure Description

[0020] Figure 1 (a) is a schematic diagram of an existing vibration power generation element. Figure 1 (b) is magnified. Figure 1 (a) is an enlarged view of region A, representing the engagement length of the comb electrode.

[0021] Figure 2 (a) is a schematic diagram of a vibration power generation element according to one embodiment of the present invention. Figure 2 (b) is magnified. Figure 2 (a) is an enlarged view of region B, representing the engagement length of the comb electrode. Figure 2 (c) is a schematic diagram of a fixed electrode or movable electrode in a charged state according to an embodiment of the present invention.

[0022] Figure 3 (a) is a schematic diagram showing the deflection of the elastic support portion of a vibration power generation element according to one embodiment of the present invention. Figure 3 (b) is a schematic diagram showing the flexural state of the elastic support when the fixed electrode or the movable electrode is charged. Figure 3 (c) is magnified. Figure 3 (b) is a magnified view of region C, representing the amount of deflection.

[0023] Figure 4 (a) is a schematic diagram of a vibration power generation element according to one embodiment of the present invention. Figure 4 (b) is magnified. Figure 4 (a) is an enlarged view of region D, representing the engagement length of the comb electrode.

[0024] Figure 5 (a) is a schematic diagram showing the state of the vibration power generation element before it is energized according to another embodiment of the present invention. Figure 5 (b) is a schematic diagram showing the energized state of a vibration power generation element according to another embodiment of the present invention. Detailed Implementation

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the drawings, the same elements are labeled with the same reference numerals, and repeated descriptions are omitted.

[0026] Figure 1 Images (a) and (b) show the structure of a vibration-generating element of a comparative example of the invention of this application. Figure 1 (a) is a diagram showing the schematic structure of the vibration power generation element of the comparative example. Figure 1The vibration power generation element 10 shown in (a) is connected to an environmental vibration source (not shown), such as a bridge, to transmit the vibrations of a vehicle passing over the bridge. Furthermore, the vibration power generation element 10 is electrically connected to an external load device (not shown), such as a bridge inspection device, to supply power generated by the vibrations transmitted from the environmental vibration source. Thus, the inspection device can use the supplied power to perform necessary bridge-related inspections, reports, etc. In this specification, "vibration power generation device" means "an assembly including a vibration power generation element and a resistor R (not shown) connected to the vibration power generation element."

[0027] The vibration power generation element 10 is an electrostatic capacitor-type vibration power generation element equipped with electret electrodes. Based on the vibration of an environmental vibration source, the movable electrode 11 vibrates relative to the fixed electrode 12, thereby generating electricity. An electret is formed near the surface of the movable electrode 11 and the fixed electrode 12 facing each other. In this embodiment, a negative electret is formed near the surface of the fixed electrode 12 facing the movable electrode 11. For example, the movable electrode 11 is a comb-shaped electrode with six movable comb teeth 13, and the fixed electrode 12 is a comb-shaped electrode with seven fixed comb teeth 14. The plurality of fixed comb teeth 14 formed on the fixed electrode 12 and the plurality of movable comb teeth 13 of the movable electrode 11 corresponding to the fixed electrode 12 have a predetermined engagement length in the X-axis direction in a static (neutral) state, and are arranged to mesh with each other with a gap. Furthermore, in this specification, the comb teeth of the movable electrode extend only in a specific positional direction. The direction in which the comb teeth extend is defined as the positive direction of the X-axis, and the direction in which the comb teeth do not extend in the coaxial direction is defined as the negative direction of the X-axis. In addition, the direction of the axis orthogonal to two adjacent comb teeth among the plurality of comb teeth of the movable electrode is defined as the Y-axis.

[0028] The movable comb teeth 13 of the movable electrode 11 and the fixed comb teeth 14 of the fixed electrode 12 have a predetermined thickness in the Z-axis direction shown in the figure, and their meshing portions are opposite to each other. The movable electrode 11 and the fixed electrode 12 can be manufactured, for example, into a MEMS structure based on silicon. Furthermore, in this specification, the direction of the axis orthogonal to the aforementioned X-axis and Y-axis directions is defined as the Z-axis direction.

[0029] The fixed electrode 12 is fixedly held by an insulating base 15. On the other hand, the movable electrode 11 is elastically supported by elastic supports 16a and 16b so that it vibrates relative to the base 15 in the X-axis direction in the figure on the same plane as the fixed electrode 12 (moves relative to the fixed electrode 12).

[0030] like Figure 1As shown in (a), the elastic support portion is provided with two sets of elastic support portions 16a and 16b. The end of the movable electrode 11 in the positive X-axis direction is supported by one set of elastic support portions 16b, and the end of the movable electrode 11 in the negative X-axis direction is supported by one set of elastic support portions 16a. Each elastic support portion 16a and 16b has two sets of rectangular beam structures 51a, 51b and 51c, 51d. The ends of the four sets of rectangular beam structures 51a to 51d in the negative X-axis direction of the elastic support portion 16 are connected to the connecting portion 52, and the ends in the positive X-axis direction are connected to the connecting portion 53.

[0031] like Figure 1 As shown in (a), the positive X-axis end of the rectangular beam structure 51b is connected to the movable electrode 11, and the negative X-axis end of the rectangular beam structure 51a is connected to the joint 52. That is, the movable electrode 11 is displaced in the X-axis direction relative to the joint 52 connected via the rectangular beam structure 51a. Furthermore, as... Figure 1 As shown in (a), the negative X-axis end of the rectangular beam structure 51c is connected to the movable electrode 11, and the positive X-axis end of the rectangular beam structure 51d is connected to the joint 53.

[0032] As described above, an electret is formed on at least one of the fixed comb teeth 14 and the movable comb teeth 13. Vibration of the movable electrode 11 causes changes in the meshing length and overlapping area of ​​the fixed comb teeth 14 and the movable comb teeth 13, thereby causing charge to move between the fixed electrode 12 and the movable electrode 11 to generate electricity. The movable electrode 11 and the base 15 are connected by an elastic support 16 that functions as a spring, forming a spring / mass resonant system. If external environmental vibrations are applied to the vibration-generating element 10, the movable electrode 11... Figure 1 Vibration in the X-axis direction of (a). If the movable comb tooth 13 vibrates relative to the fixed comb tooth 14, an induced current is generated, which can be used as a vibration power generation device by removing it from the electrode pads 61 and 71 to the outside.

[0033] The output power of the vibration power generation element 10 is maximized when the vibration frequency of the environmental vibration source is consistent with the resonant frequency of the vibration power generation element 10, which is determined by the elastic spring constant of the elastic support portion 16 in the vibration power generation element 10. The output power decreases when the vibration frequency of the environmental vibration source deviates from the resonant frequency.

[0034] Figure 1 (b) is a diagram illustrating the engagement length of the fixed comb teeth 14 and the movable comb teeth 13 in the comparative example. As shown in the figure, the plurality of fixed comb teeth 14 formed on the fixed electrode 12 and the plurality of movable comb teeth 13 of the movable electrode 11 corresponding to the fixed electrode 12 overlap with an engagement length w when no vibration is applied to the vibration power generation element. Figure 1(b) indicates the positional relationship between the fixed comb teeth 14 and the movable comb teeth 13 when the electret is not formed on the electrode (comb teeth). Furthermore, the state where the electret is not formed on the electrode (comb teeth) will be referred to below as the uncharged state. And, the state where the electret is formed on the electrode (comb teeth) will be referred to below as the charged state. Figure 1 In the comparative example shown in (b), the power generation element is configured to have a constant engagement length w in the uncharged state. Hereinafter, this engagement length w in the uncharged state will be defined as w1 (w = w1). Here, "engagement length" refers to the portion of the fixed comb teeth and the movable comb teeth that overlap. Figure 1 The length along the X-axis shown in (a).

[0035] In the uncharged state described above, when an electret is formed on the comb teeth and they become charged, an electrostatic attraction is generated between the comb teeth, and the comb teeth attract each other with a length w2. As a result, the meshing length w is w = w1 + w2.

[0036] Among them, w2 is represented by Equation 1 and Equation 2.

[0037] (Equation 1)

[0038]

[0039] (Equation 2)

[0040]

[0041] Wherein, k represents the spring constant in the X-axis direction of the elastic support, w2 represents the length of the movable part attracted by electrostatic attraction after the electret is charged, B represents the coefficient of parasitic capacitance of the comb teeth (comb tooth coefficient), and V represents the coefficient of parasitic capacitance of the comb teeth. o : Electret voltage, n: Number of comb teeth, ε o : Vacuum dielectric constant, b: Thickness of the active layer, g: Length of the gap between the comb teeth. Furthermore, in this specification, for convenience, regarding the cases where the engagement length of the comb electrodes is 0 in the uncharged state and the cases where the comb electrodes are separated in the uncharged state, the engagement length when the comb electrodes are engaged is set to a positive length, and the engagement length when separated is set to a negative length, denoted as w1≤0. Moreover, the movable part refers to the portion that combines the movable electrode and the elastic support part. Additionally, the active layer refers to the Si layer of the SOI (Silicon On Insulator) wafer. Furthermore, the length of the gap between the comb teeth g refers to the length of the gap in the Y-axis direction between the fixed comb teeth and the movable comb teeth extending along the X-axis direction.

[0042] If the average stable capacitance of the parasitic capacitance of the power generation element, which is constant and independent of the relative vibration displacement between the comb electrodes, is C3, then C3 can be expressed by Equations 3 and 4 through Equation 5. Furthermore, according to Equations 3-5, the parasitic capacitance C1 of the power generation element is expressed by Equation 6.

[0043] (Equation 3)

[0044]

[0045] (Equation 4)

[0046]

[0047] (Equation 5)

[0048]

[0049] (Equation 6)

[0050]

[0051] (Equation 7)

[0052]

[0053] Where w represents the meshing length of the comb teeth, w1 represents the meshing length of the comb teeth when the electret is not charged, x represents the vibration displacement of the movable part, C1 represents the parasitic capacitance of the entire power generation element, C2 represents the parasitic capacitance from the wiring part and pad part of the power generation element, Bw represents the parasitic capacitance from the overlapping part of the comb teeth (the product of B and w), Bx represents the parasitic capacitance from the vibration displacement of the movable part (the product of B and x), R1 represents the resistance value of the impedance matching, ω1 represents the resonant angular frequency of the power generation element, and Q1 represents the Q value at the resonant point of the power generation element (when R = R1).

[0054] The vibratory power generation element 10 is a resonant system based on the mass m of the movable part and the spring constant k in the X-axis direction of the elastic support. Therefore, the frequency characteristic of the generated voltage peaks at the resonant point. The resonant frequency of the vibratory power generation element coincides with the dominant frequency of the ambient vibration source. However, if the Q value is too high, the generated voltage decreases when the frequency of the ambient vibration source changes. Therefore, a power generation element with a low Q value is required. Here, the Q value is obtained by dividing ω1 by the half-width of the resonant angular frequency, so a lower Q value indicates a wider bandwidth of the resonant frequency of the vibratory power generation element. Moreover, in order to reduce the Q value, according to Equation 7, it is necessary to reduce the portion of the parasitic capacitance of the power generation element that is constant regardless of the vibration displacement x, namely the average parasitic capacitance C3.

[0055] Here, in Figure 1In the comparative example shown in (b), the plurality of fixed comb teeth 14 formed on the fixed electrode 12 and the plurality of movable comb teeth 13 of the movable electrode 11 corresponding to the fixed electrode 12, when the electret is charged, maintain a constant engagement length w = w1 + w2 to balance the elastic support portions 16a, 16b, etc., and remain stationary. Moreover, if environmental vibration is applied, the movable comb teeth 13 vibrate around the position of this stationary state.

[0056] In this vibration-generating element, in order to reduce C3, which is the average parasitic capacitance, it is known from Equation 5 that w1+w2 needs to be reduced. The following describes an implementation method for reducing w1+w2.

[0057] (Implementation Method 1)

[0058] Figure 2 Figures (a) to (c) are diagrams illustrating the structure of a vibration-generating element according to one embodiment of the present invention. Figure 2 (a) shows a schematic structure of the vibration power generation element. Figure 2 The vibration power generation element 20 of this embodiment shown in (a) has a structure that is substantially the same as the vibration power generation element 10 of the comparative example described above, except for the engagement length of the comb electrode. Therefore, the description of the same structure is omitted.

[0059] Figure 2 Figure (b) shows the engagement length of the fixed comb teeth and the movable comb teeth in the non-energized state of this embodiment. As shown in the figure, the engagement length w1 of the plurality of fixed comb teeth 24 formed on the fixed electrode 22 and the plurality of movable comb teeth 23 of the movable electrode 21 corresponding to the fixed electrode 22 is 0 (zero).

[0060] Even if the meshing length w = w1 = 0, when an electret is formed on the comb teeth, the electric field (edge ​​electric field) is exposed at the front end of the comb teeth due to the edge effect, and therefore the comb teeth attract each other through electrostatic attraction. Therefore, when transitioning from the uncharged state without an electret to the charged state with an electret, the movable comb teeth 23 and the fixed comb teeth 24 attract each other through electrostatic attraction and coincide at a distance w2. Moreover, the comb teeth are stationary in a mutually balanced position. Thus, the comb teeth are balanced with each other with the meshing length w = w1(0) + w2 as the center.

[0061] Since the engagement length w1 = 0, the engagement length w in the charged state is w = w2, that is, only the overlap w2 caused by the electrostatic attraction between the comb teeth due to the electret being charged. As a result, C3 expressed by Equation 5 can be reduced. Moreover, as shown in Equation 7, the Q value can be reduced, the bandwidth of the resonant frequency of the vibrating power generation element 20 can be expanded, and the power generation of the vibrating power generation element 20 can be maximized.

[0062] Furthermore, this structure is also advantageous in MEMS fabrication for processing comb teeth. In DRIE fabrication using gas etching of the main body, if the ratio of the depth drilled along the Z-axis to the comb tooth gap length g at the narrowest etch width (processing aspect ratio) is large, processing time is increased and costs rise. However, compared to the comparative example (w1>0), this structure (w1=0) allows the gas to easily reach the narrowest etch width, even though the processing aspect ratio remains the same, thus reducing processing time. Moreover, since there is no minimum machinable size limiting the comb tooth gap length g, it is possible to design a smaller gap length g.

[0063] Figure 2 (c) indicates that in this embodiment, the fixed comb teeth 24 and the movable comb teeth 23 overlap with a certain engagement length in the energized state. Thus, in the non-energized state, the front ends of the fixed comb teeth 24 and the movable comb teeth 23, which are not meshing with each other, mesh with each other in the energized state. In addition, the elastic support portion 16 deforms in the X-axis direction by the amount of deflection described later.

[0064] Figure 3 (a) to (c) are enlarged schematic diagrams of the elastic support portion 16a of the vibration power generation element according to Embodiment 1 of the present invention. Figure 3 (a) shows the shape of the elastic support 16a in the uncharged state of the electret. Figure 3 (b) is a schematic diagram showing the deflection of the elastic support 16a in the state of the electret being charged. Figure 3 (c) is shown Figure 3 An enlarged view of region C in (b).

[0065] like Figure 3 As shown in (a), in the uncharged state, the elastic support 16a becomes a rectangular structure before the deformation of the set of rectangular beam structures 51a and 51b. Therefore, when the fixed comb teeth 24 electret is charged, the movable electrode 21 and the fixed electrode 22 attract each other and have a certain meshing length. Thus, as Figure 3 As shown in (b), the elastic support 16a becomes a state where the rectangular beam structures 51a and 51b flex in the X-axis direction. At this time, as... Figure 3 As shown in (c), the elastic support 16a has a deflection y. Here, the deflection y refers to the displacement in the X-axis direction of the point symmetry center O of a set of rectangular beam structures 51a and 51b in the top view, with the position of the rectangular beam structures 51a and 51b before deflection as a reference.

[0066] Furthermore, referring to Figure 3In embodiments (b) and (c), in this first embodiment, the movable electrode 21 and the fixed electrode 22 attract each other when energized, and the engagement length w and the deflection y are the same when there is a certain engagement length. Furthermore, the deflection y is the same not only in embodiment 1 but also in embodiment 2 described below. However, in embodiment 2 described below, the engagement length w is smaller than the deflection y when energized.

[0067] (Implementation Method 2)

[0068] then, Figure 4 Figures (a) and (b) are diagrams illustrating the structure of a vibration-generating element according to one embodiment of the present invention. Figure 4 (a) shows a schematic structure of the vibration power generation element. Figure 4 The vibration power generation element 30 of this embodiment shown in (a) has a structure that is substantially the same as the vibration power generation element 10 of the comparative example described above, except for the engagement length of the comb-tooth electrodes. Therefore, the description of the same structure is omitted. Hereinafter, refer to Figure 4 (a) and (b) illustrate the case where the comb electrodes are separated from each other when w1 < 0.

[0069] Figure 4 (b) represents the engagement length between the fixed comb teeth and the movable comb teeth in the non-charged state of this embodiment. As shown in the figure, for convenience, the engagement length w1 of the plurality of fixed comb teeth 34 formed on the fixed electrode 32 and the plurality of movable comb teeth 33 of the movable electrode 31 corresponding to the fixed electrode 32 is set to negative. As a result, the engagement length w in the charged state becomes w = w1 + w2, which reduces C3 as expressed by Equation 5.

[0070] Thus, even when the comb electrodes are separated, the comb teeth do not mesh with each other, similar to Embodiment 1. Therefore, the parasitic capacitance caused by w1 in the average parasitic capacitance C3 in Equation 6 above is less than 0. That is, the average parasitic capacitance C3 can be reduced to the product of B and w1 (negative). As a result, as shown in Equation 7, the Q value can be reduced, the bandwidth of the resonant frequency of the vibration power generation element 30 can be expanded, and the power generation of the vibration power generation element 30 can be maximized.

[0071] The distance at which the comb electrodes are separated from each other includes the distance reached by the edge electric field and the distance that cannot be reached. In the distance where the edge electric field cannot reach, even if electrets are formed on the comb teeth and they become charged as described above, the comb teeth will still attract each other due to electrostatic attraction and cannot overlap with a positive engagement length w. Therefore, if a pulse-like acceleration is applied to the entire vibratory power generation element 30 (e.g., applying pulse excitation by gently tapping), the movable part (movable electrode and elastic support part) swings, and when the tips of the comb electrodes approach each other, electrostatic attraction takes effect, and the comb teeth directly engage. As a result, the engagement length becomes w = w1 + w2 as designed. Alternatively, the same result can be obtained by exciting at the resonant frequency of the vibratory power generation element instead of pulse excitation. Furthermore, in the distance where the edge electric field reaches, if the comb becomes charged, the comb electrodes will attract each other through electrostatic attraction and can overlap with an engagement length w.

[0072] Thus, the distance h in the X-axis direction between the front end faces of the fixed electrode 32 and the movable electrode 31 in the unenergized state (refer to...) Figure 4 (b) refers to a situation where, with at least one of the fixed electrode 32 and the movable electrode 31 charged, the fixed electrode 32 and the movable electrode 31 have a meshing length w = w1 + w2. That is, in the uncharged state, the distance between the comb electrodes is such that they can attract each other through electrostatic attraction, or the distance at which the comb teeth directly mesh when the movable part swings due to the application of pulse excitation or the like, and the electrostatic attraction comes into play when the tips of the comb electrodes approach each other.

[0073] In this embodiment, as described above, it is consistent with the embodiment shown in embodiment 1. Figure 2 (c) and Figure 3 Similar to the cases shown in (a) to (c), in the charged state, the comb electrodes mesh with each other, and the elastic support 16 deforms with a deflection y. However, at this time, the comb electrodes mesh from a state of separation, so the meshing length w of the comb electrodes is smaller than the deflection y.

[0074] Furthermore, this structure reduces the machining aspect ratio of the comb tooth region, thus offering advantages in terms of machining time. Moreover, it enables operation at a machining aspect ratio smaller than the limitation during machining (which reduces g in Equation 2), further improving the comb tooth coefficient B and enabling broadband operation of the vibration power generation element.

[0075] In the embodiments described above, by making the movable and fixed electrodes shorter than in the conventional examples, it is possible to achieve a meshing length w = w1 ≤ 0 between the comb teeth in each embodiment. Furthermore, in the method described below, it is also possible to achieve a meshing length w = w1 ≤ 0 between the comb teeth.

[0076] (Implementation Method 3)

[0077] Figure 5 (a) is a schematic diagram showing the elastic support portions 46a and 46b of the vibration power generation element 40 before it is energized according to this embodiment. Figure 5 (b) is a schematic diagram showing the elastic support portions 46a and 46b of the vibration power generation element 40 after it is energized according to this embodiment.

[0078] To make the meshing length w = w1 = 0, firstly as follows Figure 5 As shown in (a), the elastic support portions 46a and 46b connected to the movable electrode 41 are manufactured in a shape that causes the rectangular beam structures 81a-81d to bend towards the front ends of the movable comb teeth of the fixed electrode 42 and the movable electrode 41 to separate from each other in the uncharged state where the electrodes are not charged. Thus, in the uncharged state, the comb tooth electrodes are stationary at the position where the meshing length w = w1 = 0. Then, an electret is formed on the comb tooth electrodes, thus becoming charged. Therefore, as... Figure 5 As shown in (b), the comb electrodes coincide with each other around the point where they are attracted by electrostatic attraction to w2, and remain stationary. At this time, the elastic support 46 deforms from the flexed state of the rectangular beam structures 81a to 81d, and its shape is the same as that of the rectangular beam structures 51a to 51d in the uncharged state of Embodiment 1 described above. In this embodiment, the same effect as in Embodiment 1 can also be obtained. In addition, this embodiment is not limited to the illustrated arrangement, and like Embodiment 2, it also includes the case where the distance between the front end faces of the fixed electrode 42 and the movable electrode 41 in the uncharged state is h. In this case, by applying pulse excitation or the like in Embodiment 2, the comb electrodes have an engagement length w2. In addition, the same effect as in Embodiment 2 can be obtained.

[0079] Furthermore, a symmetrical shape refers to a shape in which the components constituting the elastic support extend along either the direction of relative movement, i.e., the X direction, or its orthogonal direction, i.e., the Y direction. In this embodiment, in Figure 5 In the symmetrically shaped elastic support portion 46 shown in (b), each of the rectangular beam structures 81a-81d has a portion extending along the X direction and a portion extending along the Y direction. In contrast, in Figure 5 In the elastic support portion 46 of the shape shown in (a), each of the rectangular beam structures 81a to 81d has a portion extending along the X direction and a portion extending obliquely relative to the Y direction.

[0080] In the above embodiments, when the fixed electrodes 12, 22, 32, 42 and the movable electrodes 11, 21, 31, 41 are not energized, the fixed electrodes 12, 22, 32, 42 and the movable electrodes 11, 21, 31, 41 are not engaged. When at least one of the fixed electrodes 12, 22, 32, 42 and the movable electrodes 11, 21, 31, 41 is energized, the movable electrodes 11, 21, 31, 41 move in the positive direction of the X-axis and have a length that engages with the fixed electrodes 12, 22, 32, 42. That is, as... Figures 1-5 As shown, the vibration power generation elements 10, 20, 30, and 40 have movable electrodes 11, 21, 31, and 41 and fixed electrodes 12, 22, 32, and 42, such that when they are energized, the movable electrodes 11, 21, 31, and 41 and the fixed electrodes 12, 22, 32, and 42 coincide with each other in the positive direction of the X-axis.

[0081] Furthermore, the structure of the movable and fixed electrodes is not limited to the structure shown in the figure. In this embodiment, a two-terminal structure is used, but for example, it could also be shown in a top view. Figure 2 The movable electrode 21, the fixed electrode 22, and the elastic support portions 16a and 16b in (a) are arranged in a four-terminal structure with two of them arranged in the same direction as the direction in which the movable electrode 21 is displaced due to electrostatic attraction on the plane where the multiple comb teeth of the movable electrode extend. Alternatively, it can be a multi-terminal structure. That is, the vibration power generation element of this application can also have multiple movable electrodes and multiple fixed electrodes.

[0082] In the embodiments described above, a negative electret is formed on the fixed electrode side, but this is not a limitation; a negative electret may also be formed on the movable electrode side. Furthermore, if a potential difference is generated between the comb teeth of the movable electrode and the comb teeth of the fixed electrode in a charged state, an electret may also be formed on both the movable electrode and the fixed electrode.

[0083] Furthermore, in the above embodiments, the vibration power generation element is made of SOI wafer, but it is not limited to this and can be manufactured by any method.

[0084] The implementation method described above achieves the following effects.

[0085] (1) Even if the frequency of the environmental vibration source changes, the bandwidth of the frequency that becomes the resonance state is wide, which can maintain the resonance state, thus maximizing the output of the vibration power generation element.

[0086] (2) In addition, it can avoid the significant reduction in power output caused by the resonant offset, so that when compared with conventional vibration power generation elements in the same period, it can obtain a greater power generation. That is, it can improve the power generation efficiency of vibration power generation elements.

[0087] Symbol Explanation

[0088] 10—Vibration power generation element; 11—Modible electrode; 12—Fixed electrode; 13—Modible comb teeth; 14—Fixed comb teeth; 15—Base; 16a, 16b—Elastic support parts; 51a, 51b, 51c, 51d—Rectangular beam structure; 20—Vibration power generation element; 21—Modible electrode; 22—Fixed electrode; 23—Modible comb teeth; 24—Fixed comb teeth; 30—Vibration power generation element; 31—Modible electrode; 32—Fixed electrode; 33—Modible comb teeth; 34—Fixed comb teeth; 40—Vibration power generation element; 41—Modible electrode; 42—Fixed electrode; 43—Modible comb teeth; 44—Fixed comb teeth; 46a, 46b—Elastic support parts; 81a, 81b, 81c, 81d—Rectangular beam structure; h—Distance between the front end faces of the fixed electrode and the movable electrode.

Claims

1. A vibration-generating element, characterized in that, have: A fixed electrode having multiple comb-shaped electrodes; A movable electrode having a plurality of comb-shaped electrodes that engage with the comb teeth of the fixed electrode; as well as An elastic support portion allows the movable electrode to move relative to the fixed electrode in a predetermined direction on the same plane. When at least one of the fixed electrode and the movable electrode is energized, the engagement length of the fixed electrode and the movable electrode is the same as the deflection of the elastic support, or the engagement length of the fixed electrode and the movable electrode is smaller than the deflection of the elastic support.

2. A vibration-generating element, characterized in that, have: A fixed electrode having multiple comb-shaped electrodes; A movable electrode having a plurality of comb-shaped electrodes that engage with the comb teeth of the fixed electrode; as well as An elastic support portion allows the movable electrode to move relative to the fixed electrode in a predetermined direction on the same plane. When the fixed electrode and the movable electrode change from an uncharged state to a charged state, the fixed electrode moves closer to the movable electrode, and the elastic support portion approaches a symmetrical shape in the direction of relative movement.

3. The vibration power generation element according to claim 1 or 2, characterized in that, The distance between the front end faces of the fixed electrode and the movable electrode when the fixed electrode and the movable electrode are not energized is the distance between the fixed electrode and the movable electrode when at least one of the fixed electrode and the movable electrode is energized, and the fixed electrode and the movable electrode have an engagement length.

4. The vibration power generation element according to claim 1 or 2, characterized in that, It has multiple fixed electrodes and multiple movable electrodes.

5. The vibration power generation element according to claim 1 or 2, characterized in that, An electret is formed on at least one of the fixed electrode and the movable electrode.

6. The vibration power generation element according to claim 1 or 2, characterized in that, When the fixed electrode and the movable electrode are not energized, the fixed electrode and the movable electrode are not engaged. If at least one of the fixed electrode and the movable electrode is energized, the movable electrode moves in the extension direction of the comb teeth of the movable electrode and has a length that engages with the fixed electrode.

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