Cantilever vibration power generation device based on bistable structure

Abstract

The invention discloses a cantilever vibration power generation device based on a bistable structure, which comprises a bistable beam and a piezoelectric plate attached and fixed on the bistable beam, the piezoelectric plate is bent along with the bending of the bistable beam, the bistable beam comprises a thin-plate-shaped beam body, the end part of the beam body is provided with two branch bodies extending out, and the two branch bodies extend out of the bistable beam. And after the two forked bodies are bent oppositely and laterally, the ends of the two forked bodies are fixedly connected to form a bistable beam. The lateral buckling type bistable beam structure is convenient to manufacture through laser cutting, for example, bistable can be achieved without an additional magnet, the structure is simple, the bistable beam is a bistable beam, bistable beams with different performances can be conveniently obtained by controlling rich design parameters such as the included angle, the size and the shape of bifurcation, and the lateral buckling type bistable beam structure is suitable for large-scale popularization and application. And use under different working conditions is facilitated. The lateral buckling type bistable beam does not need an external clamping device and is simple in structure.

Description

Technical Field

[0001] The invention relates to the field of novel power generation technology, and in particular to a cantilever vibration power generation device based on a bistable structure. Background Art

[0002] The bistable structure has two natural stable configurations, corresponding to the two local minimum values ​​of the system potential energy. Under the action of external load, the potential energy barrier of the bistable structure will be broken, jumping from one stable state to another. This phenomenon is called snap-through. Since no external force is required to maintain a stable configuration, a larger displacement output can be obtained with less energy input.

[0003] Bistable structures can be found everywhere in daily life, such as metal measuring tapes, plastic straws, hairpins, curved slender rods, and spring-link mechanisms. Since no external force is needed to maintain a stable configuration, the external load only needs to do work during the steady-state transition. Therefore, the bistable structure is an energy-saving mechanism.

[0004] Traditional piezoelectric single / double crystal beams can easily convert vibration energy in the environment into electrical energy to power low-power devices such as wireless sensors. However, it is a linear energy harvester, and its optimal output power only occurs when the external excitation frequency matches its low-order natural frequency. Since the excitation frequency in the environment is often multi-frequency and time-varying, the working efficiency of linear energy harvesters in practical applications is relatively low. The main advantages of bistable energy harvesters are: (1) The large geometric deformation during the dynamic sudden jump process is conducive to increasing the strain of piezoelectric materials and improving voltage output; the nonlinear dynamic responses such as limit cycle vibration and chaotic behavior are conducive to increasing output power; (2) The two stable states of the structure can be designed to have different natural frequencies, and under large excitation, it will have a higher voltage output in a wider frequency range, which is a broadband energy harvester.

[0005] The bistable piezoelectric energy harvesters that have been studied more are: (1) bistable piezo-electromagnetic elastic beam type; a magnetic block is installed at the free end of the piezoelectric cantilever beam and a magnetic force is applied to induce the energy harvester to have two or more stable states. (2) bistable buckling beam type; for a piezoelectric beam that buckles under axial force, when the external excitation is large, the buckled beam will jump and switch back and forth between two stable states. This process belongs to geometric large deformation behavior, which is beneficial to increase output power and bandwidth. (3) bistable plate type; a composite material plate with bistable properties is prepared by using residual stress (or prestress), and the piezoelectric sheet is attached to the surface of the bistable plate to achieve broadband energy harvesting. For designs (1) and (2), additional devices need to be installed to apply mechanical force or nonlinear magnetic force, which increases the complexity of the structure and is not conducive to integration in miniature low-power electronic devices. For design (3), in order to generate sufficient thermal residual stress to cause the composite laminate to deform out of the plane, a larger structural size is required, and the structure is sensitive to ambient temperature and easily loses its steady state at high temperatures.

[0006] Therefore, it is necessary to design a new type of energy harvester with a simple structure, a bistable structure and a broadband type. Summary of the invention

[0007] The embodiment of the present application provides a cantilever vibration power generation device based on a bistable structure to solve at least one of the above-mentioned technical problems.

[0008] The technical solution adopted by the present invention is to design a cantilever vibration power generation device based on a bistable structure, including a bistable beam and a piezoelectric sheet fixed on the bistable beam, the piezoelectric sheet bends as the bistable beam bends, the bistable beam includes a thin plate-shaped beam body, the end of the beam body has two forked bodies extending therefrom, and after the two forked bodies are relatively bent laterally, the ends of the two forked bodies are fixedly connected to form a bistable beam.

[0009] In some embodiments, a mass block is disposed at the end of the fork body.

[0010] In some embodiments, the beam body is fixed on a vibration source, the forked body is suspended relative to the vibration source, and the forked body is bent up and down relative to the beam body.

[0011] In some embodiments, the mass block is a liquid storage cavity, and the liquid storage cavity is connected to a liquid supply device, and the liquid supply device controls the amount of liquid in the liquid storage cavity.

[0012] In some embodiments, a piston sliding along the liquid storage chamber is provided in the liquid storage chamber, one end of the liquid storage chamber is connected to the liquid supply pipeline of the liquid supply device and the other end is connected to the external air, and relative to the liquid storage chamber, the piston is located at the end opposite to the beam body.

[0013] In certain embodiments, the ends of the two forked bodies are connected by a telescopic mechanism.

[0014] In some embodiments, both ends of the forked bodies are provided with through holes, the telescopic mechanism includes a screw passing through the two through holes, both ends of the screw have threaded portions, both threaded portions are matched with nuts, and the two ends of the forked bodies are located between the two nuts.

[0015] In some embodiments, the telescopic mechanism includes a telescopic chamber, a piston is disposed in the telescopic chamber, the telescopic chamber is fixedly connected to the end of one of the forked bodies, the piston is fixedly connected to the end of the other forked body, the telescopic chamber is connected to a pressure control device through a pipeline, and the pressure control device drives the piston to move relative to the telescopic chamber by controlling the liquid pressure in the telescopic chamber.

[0016] In certain embodiments, the telescoping mechanism includes a shape memory alloy spring connecting two ends of the forked body.

[0017] In certain embodiments, the shape memory alloy spring is connected to a current control circuit.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The side-bending bistable beam structure of the present invention is easy to manufacture using laser cutting. For example, the structure itself does not require external magnets to achieve bistable state, and the structure is simple. The bistable beam of the present invention is a forked beam, which is convenient for obtaining bistable beams with different performances by controlling a variety of design parameters such as the angle, size, and shape of the fork, so as to facilitate use in different working conditions. The side-bending bistable beam of the present invention does not require an external clamping device, and the structure is simple. By setting an adjustable mass block or a connecting structure at the forked end, the structural parameters such as the vibration frequency of the bistable beam can be controlled, so that the resonant frequency of the bistable beam can be conveniently adjusted according to the frequency of the vibration source, thereby obtaining a greater energy conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is described in detail below in conjunction with specific embodiments and drawings. In order to show details and facilitate understanding of its principles, it is not necessarily drawn to scale, and similar reference numerals may describe similar components in different views. The drawings generally illustrate the embodiments discussed herein by way of example and not limitation. Among them:

[0021] Figure 1 It is a schematic diagram of the two forked ends of the bistable beam when no lateral force is applied.

[0022] Figure 2 It is a schematic diagram of the two forked bodies of the bistable beam after the ends are close together.

[0023] Figure 3 is a schematic diagram of a bistable beam arranged on a vibration source.

[0024] Figure 4 is a schematic diagram of the upward bending of the mass block of a bistable beam.

[0025] Figure 5 It is a schematic diagram of the second embodiment.

[0026] Figure 6 It is a schematic diagram of embodiment 3.

[0027] Figure 7 It is a schematic diagram of embodiment 3.

[0028] In the figure, 1, beam body; 2, fork body; 3, vibration source; 4, piezoelectric sheet; 5, mass block; 6, screw rod; 7, nut; 8, connecting hole; 9, liquid storage chamber; 10, liquid supply pipeline; 11, telescopic chamber; 12, piston; 13, pressure pipeline; 14, shape memory alloy spring; 15, current control circuit. DETAILED DESCRIPTION

[0029] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments, and the following embodiments do not limit the invention involved in the claims. In addition, all combinations of the features described in the embodiments are not necessarily required for the solutions of the invention.

[0030] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0031] Embodiment 1

[0032] like Figure 1 , 2 As shown, a cantilever vibration power generation device based on a bistable structure includes a bistable beam and a piezoelectric sheet 4 fixed on the bistable beam, the piezoelectric sheet 4 bends as the bistable beam bends, the bistable beam includes a thin plate-shaped beam body 1, the end of the beam body 1 has two forked bodies 2 extending therefrom, and after the two forked bodies 2 are bent laterally relative to each other, the ends of the two forked bodies 2 are fixedly connected to form a bistable beam.

[0033] The bistable beam is a thin straight beam, and the beam body 1 and the two forked bodies 2 are integrally formed as a plate body, for example, by cutting and forming on a thin metal plate by laser.

[0034] Each individual forked body 2 is also equivalent to a thin plate straight beam or a cantilever beam. In addition to the pre-compression axial buckling of the straight beam, applying a lateral load or displacement to the thin plate straight beam can also cause the thin plate straight beam to bend to two positions, resulting in a larger torsion and out-of-plane bending deformation, so that the structure exhibits a bistable characteristic. In this way, in the natural state, the ends of the two forked bodies 2 are connected together after being moved closer from a far-away state, thereby forming a bistable beam equivalent to a hairpin (or hairpin).

[0035] like Figure 3 , 4 As shown, when in use, the beam body 1 is fixed on the vibration source 3, and the forked body 2 is suspended relative to the vibration source 3, that is, one end of the bistable beam is fixed on the object that generates vibration, so that the bistable beam swings with the vibration, and then a snap-through occurs, so that the bistable beam undergoes a large bending deformation, so that the piezoelectric sheet 4 fixed thereon is deformed, so that the piezoelectric sheet 4 generates electrical energy, and realizes power generation using vibration. A mass block 5 can be provided at the end of the forked body 2, so that the end of the beam body 1 is fixedly connected to the vibration source 3, and the power generation sheet is provided at the place where the deformation is the largest when the bistable beam is deformed, for example, the piezoelectric sheet 4 is provided between the beam body 1 and the forked body.

[0036] like Figure 3 As shown, the forked body 2 is bent up and down relative to the beam body 1, that is, the plate surface of the beam body 1 is located in a roughly horizontal plane. In this way, the mass block 5 breaks the symmetry of the two potential wells of the bistable system under the action of gravity, that is, the snap-through loads required to escape the potential wells are different, so that the two stable states have two different natural frequencies. Under large excitation, the energy harvester is expected to have a snap-through in two frequency ranges, increase the output voltage, and improve the bandwidth of energy harvesting.

[0037] The advantages of the lateral buckling bistable structure over the axial buckling bistable structure are as follows: (1) Metal bifurcated beams with various planar configurations can be designed by laser cutting, and structures with multiple stable configurations can be prepared after lateral buckling occurs. (2) The angle, size, shape, etc. of the bifurcated beam can provide a wealth of design parameters. (3) The lateral buckling bistable structure does not require an external clamping device and has a simple structure. (4) If the ends of the two bifurcated bodies are connected by a controllable structure, the structural parameters such as the vibration frequency of the bistable beam can also be intelligently controlled. For example, through holes are provided at the ends of the two bifurcated bodies 2, and the telescopic mechanism includes a screw 6 passing through the two through holes, and both ends of the screw 6 have threaded portions, and the two threaded portions are matched with nuts 7. The ends of the two bifurcated bodies 2 are located between the two nuts 7. By adjusting the distance between the two nuts 7, the lateral force on the ends of the two bifurcated bodies 2 is adjusted, thereby adjusting the resonant frequency of the bistable structure. The smaller the distance between the ends of the two bifurcated bodies 2, the greater the resonant frequency.

[0038] Embodiment 2

[0039] like Figure 5 As shown, different from the above embodiment, the mass block 5 is a liquid storage chamber 9, and the liquid storage chamber 9 is connected to a liquid supply device through a liquid supply pipeline 10. The liquid supply device can be, for example, a device such as a liquid supply pump that can control the amount of liquid in the liquid storage chamber 9. The liquid supply device controls the amount of liquid in the liquid storage chamber 9, thereby adjusting the mass of the mass block 5, and then adjusting the resonance frequency of the bistable beam as needed. The larger the mass, the smaller the resonance frequency, so that the resonance frequency of the bistable beam is close to the frequency of the vibration source 3. A piston 12 that can slide along the liquid storage chamber 9 is arranged in the liquid storage chamber 9. One end of the liquid storage chamber 9 is connected to the liquid supply pipeline 10 and the other end is connected to the external air. Liquid enters and drives the piston 12 to move in the liquid storage chamber 9. Relative to the liquid storage chamber, the piston is located at the end opposite to the beam body, and the piston is located on the side close to the beam body, so that when the bifurcated body swings, the centrifugal force on the liquid in the liquid storage chamber is far away from the piston.

[0040] Embodiment 3

[0041] like Figure 6As shown, different from the above embodiment, the ends of the two forked bodies 2 are connected by a telescopic mechanism, the telescopic mechanism includes a telescopic chamber 11, a piston 12 is arranged in the telescopic chamber 11, the telescopic chamber 11 and the piston 12 are equivalent to a hydraulic cylinder, the telescopic chamber 11 is fixedly connected to the end of one of the forked bodies 2, the piston 12 is fixedly connected to the end of the other forked body 2, the telescopic chamber 11 is connected to a pressure control device through a pressure pipeline 13, the pressure control device can be, for example, a pump or other device capable of controlling the liquid pressure in the telescopic chamber 11, the pressure The control device drives the piston 12 to move relative to the telescopic chamber 11 by controlling the liquid pressure in the telescopic chamber 11, thereby controlling the distance between the two ends of the forked body 2 and adjusting the resonant frequency of the bistable beam. The telescopic chamber 11 is also equivalent to the mass block 5, so the resonant frequency of the bistable beam is adjusted by increasing the mass. The greater the pressure, the closer the distance between the two ends of the forked body 2, and the greater the mass of the mass block 5, so the resonant frequency of the bistable beam is smaller. The two parameters of mass and distance are adjusted at the same time, and the adjustment efficiency is high. A connecting hole 8 connected to the outside air is arranged at the other end of the telescopic chamber 11 opposite to the piston 12.

[0042] Embodiment 4

[0043] like Figure 7 As shown, different from the above embodiment, the telescopic mechanism can also be a shape memory alloy spring 14 connecting the two ends of the forked body 2. The shape memory alloy spring 14 can automatically and regularly expand and contract with temperature changes, so that the distance between the two ends of the forked body 2 changes with temperature changes. In this way, the resonant frequency of the bistable beam can change with temperature changes, so that it is suitable for the use of a vibration source 3 whose vibration changes with temperature changes. For example, the temperature of a water pump will increase with the increase of the vibration frequency. Further, the shape memory alloy spring 14 is connected to a current control circuit 15, which controls the temperature of the shape memory alloy spring 14 by controlling the current passing through the shape memory alloy spring 14, thereby controlling the expansion and contraction of the shape memory alloy spring 14.

[0044] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described, or replace them in similar ways, without departing from the spirit of the present invention or exceeding the scope defined by the appended claims.

Claims

1. A cantilever vibration power generation device based on a bistable structure, comprising a bistable beam and a piezoelectric sheet fixed to the bistable beam, wherein the piezoelectric sheet bends as the bistable beam bends, characterized in that: The bistable beam comprises a thin plate-shaped beam body, and two forked bodies are extended from the end of the beam body. After the two forked bodies are bent laterally relative to each other, the ends of the two forked bodies are fixedly connected to form a bistable beam.

2. The cantilever vibration power generation device based on a bistable structure according to claim 1 is characterized in that: A mass block is arranged at the end of the forked body.

3. The cantilever vibration power generation device based on the bistable structure according to claim 2 is characterized in that: The beam body is fixed on the vibration source, the forked body is suspended relative to the vibration source, and the forked body is bent up and down relative to the beam body.

4. The cantilever vibration power generation device based on a bistable structure according to claim 2 is characterized in that: The mass block is a liquid storage cavity, the liquid storage cavity is connected to a liquid supply device, and the liquid supply device controls the amount of liquid in the liquid storage cavity.

5. The cantilever vibration power generation device based on the bistable structure according to claim 4 is characterized in that: A piston sliding along the liquid storage cavity is arranged in the liquid storage cavity, one end of the liquid storage cavity is connected to the liquid supply pipeline of the liquid supply device and the other end is connected to the external air. Relative to the liquid storage cavity, the piston is located at the end opposite to the beam body.

6. The cantilever vibration power generation device based on a bistable structure according to claim 1 is characterized in that: The ends of the two forked bodies are connected through a telescopic mechanism.

7. The cantilever vibration power generation device based on a bistable structure according to claim 6 is characterized in that: The two ends of the forked bodies are both provided with through holes, the telescopic mechanism comprises a screw rod passing through the two through holes, both ends of the screw rod have threaded parts, the two threaded parts are both matched with nuts, and the two ends of the forked bodies are located between the two nuts.

8. The cantilever vibration power generation device based on a bistable structure according to claim 6 is characterized in that: The telescopic mechanism includes a telescopic chamber, a piston is arranged in the telescopic chamber, the telescopic chamber is fixedly connected to the end of one of the forked bodies, and the piston is fixedly connected to the end of the other forked body. The telescopic chamber is connected to a pressure control device through a pipeline, and the pressure control device drives the piston to move relative to the telescopic chamber by controlling the liquid pressure in the telescopic chamber.

9. The cantilever vibration power generation device based on a bistable structure according to claim 6, characterized in that: The telescopic mechanism includes a shape memory alloy spring connecting two ends of the forked body.

10. The cantilever vibration power generation device based on a bistable structure according to claim 9, characterized in that: The shape memory alloy spring is connected to a current control circuit.

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