CN110445417B - Low-frequency broadband vibration energy harvesting device - Google Patents

Abstract

Translated fromChinese

本发明公开了一种低频宽频带震动俘能装置，包括基座，两个分别与基座固定连接、上下设置的呈等腰梯形的悬臂梁，悬臂梁的上下表面分别连有压电片，两个悬臂梁远离基座的一端通过两个弹簧和一个永磁铁连接，永磁铁的上下两端分别固定连接在两个弹簧上，两个弹簧上分别套设有连接在悬臂梁上的感应线圈。本发明两个平行设置的悬臂梁可以使压电装置在低频范围内存在多阶谐振频率，且各阶谐振频率之间的差值较小，拓宽了频带，对低频环境的适用性更广；两个悬臂梁存在不同的谐振频率，通过弹簧相连使能量在不同频率振动下可以互相传递，宽频适用性更广；两个悬臂梁自由端用弹簧连接永磁铁，永磁铁可以降低悬臂梁的谐振频率，对低频环境的适应性更强。

The invention discloses a low-frequency broadband vibration energy capturing device, comprising a base, two isosceles trapezoidal cantilever beams fixedly connected to the base and arranged up and down respectively, and piezoelectric sheets are respectively connected to the upper and lower surfaces of the cantilever beams. One end of the two cantilever beams away from the base is connected by two springs and a permanent magnet, the upper and lower ends of the permanent magnet are respectively fixedly connected to the two springs, and the two springs are respectively sleeved with induction coils connected to the cantilever beams . The two parallel cantilever beams of the present invention can make the piezoelectric device have multi-order resonance frequencies in the low frequency range, and the difference between the resonance frequencies of each order is small, the frequency band is widened, and the applicability to the low-frequency environment is wider; The two cantilever beams have different resonant frequencies, and the energy can be transferred to each other under different frequencies of vibration through the connection of springs, and the broadband applicability is wider; the free ends of the two cantilever beams are connected with permanent magnets by springs, which can reduce the resonance of the cantilever beams. The frequency is more adaptable to the low frequency environment.

Description

Low-frequency broadband vibration energy harvesting device

Technical Field

The invention relates to a piezoelectric-electromagnetic composite energy harvesting device in the technical field of new energy, in particular to a low-frequency broadband vibration energy harvesting device.

Background

In recent years, portable electronic devices, micro-electro-mechanical systems (MEMS), and wireless sensor networks have been widely used in civilian, military, medical, and industrial applications. Most of the present microelectronic products use chemical batteries to provide electric energy, but the conventional batteries have the problems of low energy density, need of regular replacement or charging, environmental pollution and the like, so that the demand of high-speed development of the microelectronic products is difficult to meet. In the environment of our living environment, there are various kinds of waste energy, such as solar energy, pressure energy, vibration energy, etc., and capturing energy in the environment to power microelectronic products becomes a promising technology and attracts researchers' attention. Solar energy and pressure energy, although having relatively high energy density, are difficult to be widely used in life due to limitations of energy collection and supply technologies. Vibration energy widely exists in daily life and engineering practice, is not easily influenced by factors such as position and weather, and has high energy density, so more and more scholars and experts are dedicated to research on capturing and converting vibration energy in the environment into electric energy to serve as an alternative energy source for supplying energy to microelectronic products. The piezoelectric material has the characteristics of low energy consumption, easy miniaturization and the like, and the piezoelectric ceramic vibration generator is a novel durable, clean and maintenance-free power generation device, so that the research on the piezoelectric ceramic power generation technology has been widely regarded, and the piezoelectric ceramic vibration generator has a wide application prospect in the aspect of self-power supply of a wireless sensor network.

The two-dimensional piezoelectric-electromagnetic hybrid energy harvester disclosed in the chinese patent CN201711122064.9 and the two-degree-of-freedom piezoelectric-electromagnetic hybrid energy harvester disclosed in the chinese patent CN201711121543.9 use a spring to generate elastic amplification in order to induce low-frequency vibration, so that the application is wide, but the use is single, and the induced vibration effect is not uniform. The chinese patent CN201710454532.6 discloses a piezoelectric-electromagnetic combined type vibration energy-harvesting button cell, in which a spring is used to transmit pressure to deform a piezoelectric plate to generate energy, but this method affects the service life of the piezoelectric plate.

The existing piezoelectric vibration power generation device has the problems of poor environmental adaptability, low power generation efficiency, poor low-frequency adaptability and small power generation amount in unit time.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems, the invention provides a low-frequency broadband vibration energy harvesting device which can be suitable for random, broadband, low-frequency, large-amplitude and high-intensity vibration energy recovery in the environment.

The technical scheme is as follows: the low-frequency broadband vibration energy harvesting device comprises a base, two cantilever beams which are fixedly connected with the base respectively and are in an isosceles trapezoid shape, wherein the two cantilever beams are arranged in parallel, the upper surface and the lower surface of each cantilever beam are respectively connected with a piezoelectric sheet, one ends of the two cantilever beams, far away from the base, are connected with a permanent magnet through two springs, the upper end and the lower end of the permanent magnet are respectively and fixedly connected to the two springs, and induction coils connected to the cantilever beams are respectively sleeved on the two springs. Wherein the diameter of the induction coil is slightly larger than the diameter of the spring and the permanent magnet.

For the structure of the cantilever beam, compared with a rectangular structure, the stress distribution of the isosceles trapezoid is more uniform and the stress is larger; the cantilever beam has the structure that under the condition that the cantilever beam can normally work, the length of the cantilever beam needs to be long, and the resonant frequency of the cantilever beam can be reduced.

Preferably, the piezoelectric sheets on the upper surface and the piezoelectric sheets on the lower surface of the cantilever beam are in a series or parallel structure. If a series structure is adopted, a larger output voltage can be obtained; if a parallel structure is adopted, larger output current can be obtained.

Preferably, the center of the induction coil is over against the permanent magnet.

Preferably, the piezoelectric sheet has the same shape as the cantilever beam, and is attached to the surface of the cantilever beam by a conductive adhesive.

Preferably, the base is made of an acrylic glass material.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: (1) the isosceles trapezoid cantilever beams adopted by the invention can obtain more uniform stress distribution and larger stress value, the two cantilever beams can enable the piezoelectric device to have multi-order resonance frequency in a low-frequency range, and the difference value between the resonance frequencies of all orders is smaller, so that the frequency band is widened, and the applicability of the piezoelectric device to a low-frequency environment is wider; (2) the two cantilever beams have different resonant frequencies and are connected through the spring, so that energy can be mutually transmitted under the vibration of different frequencies, and the broadband applicability of the cantilever beams is wider; (3) the free ends of the two cantilever beams are connected with the permanent magnets through springs, and the permanent magnets can be used as mass blocks, so that the resonance frequency of the cantilever beams is reduced, and the adaptability of the cantilever beams to a low-frequency environment is stronger; (4) the coupling effect of the piezoelectric and the electromagnetism makes up the defects of small output current of the piezoelectric device and small output voltage of the electromagnetic device, so that the output voltage is higher and the current is larger.

Drawings

FIG. 1 is a schematic view of the apparatus of the present invention;

FIG. 2 is a front view of the apparatus of the present invention;

FIG. 3 is a top view of the apparatus of the present invention;

FIG. 4 is a schematic view of the apparatus of the present invention without the induction coil;

FIG. 5 is a graph of piezoelectric simulation data for the device of the present invention;

FIG. 6 is a graph of simulation data for the upper half-coil of the apparatus of the present invention;

FIG. 7 is a graph of lower half-coil simulation data for the apparatus of the present invention.

Detailed Description

The invention is further described below with reference to the figures and examples.

As shown in fig. 1 and 2, the low-frequency broadband vibration energy harvesting device of the invention comprises abase 1 made of acrylic glass material, two cantilever beams 2 (fig. 3) which are fixedly connected with thebase 1 and are in isosceles trapezoid shape, the twocantilever beams 2 are arranged in parallel, the upper and lower surfaces of thecantilever beams 2 are respectively connected with apiezoelectric plate 3, thepiezoelectric plate 3 has the same shape as thecantilever beams 2 and is adhered to the surfaces of thecantilever beams 2 through conductive adhesive, one ends of the twocantilever beams 2 far away from thebase 1 are connected with apermanent magnet 5 through two springs 4, the upper and lower ends of thepermanent magnet 5 are respectively fixedly connected with the two springs 4, one end of each spring 4 is connected with the free end of thecantilever beam 2, the other end of each spring is connected with the permanent magnet 5 (fig. 4), the two springs 4 are respectively sleeved with aninduction coil 6 connected with thecantilever beams 2, wherein the diameter of theinduction coil 6 is slightly larger than the diameter of the spring 4 and the diameter of thepermanent magnet 5, theinduction coil 6 is ensured to be close to thepermanent magnet 5, the electromagnetic energy harvesting effect is enhanced, and the circle center of theinduction coil 6 is over against thepermanent magnet 5.

For the structure of thecantilever beam 2, compared with a rectangular structure, the stress distribution of the isosceles trapezoid is more uniform and the stress is larger; the structure of thecantilever beam 2 is that under the condition that thecantilever beam 2 can work normally, the length of thecantilever beam 2 needs to be long, and the resonant frequency of thecantilever beam 2 can be reduced.

Thepiezoelectric sheets 3 positioned on the upper surface and the lower surface of thecantilever beam 2 adopt a series connection or parallel connection structure. If a series structure is adopted, a larger output voltage can be obtained; if a parallel structure is adopted, larger output current can be obtained.

The free ends of theupper cantilever beam 2 and thelower cantilever beam 2 are connected with thepermanent magnet 5 through the spring 4, the spring 4 is used for fixing thepermanent magnet 5 and restraining the movement direction of thepermanent magnet 5, and the vibration direction of thepermanent magnet 5 is ensured to be the vertical direction as much as possible, so that the energy loss is reduced, and the electromagnetic energy harvesting efficiency is improved; twocantilever beams 2 have different resonant frequency, and twocantilever beams 2 are connected to spring 4, can let it influence each other when vibrations to makecantilever beam 2 multistage resonant frequency can appear in the low frequency range, when the system is in vibrations, spring 4 andpermanent magnet 5 can absorb some vibrations energy, and feed backcantilever beam 2, thereby reach the purpose of widening the frequency band.

The respective resonant frequencies of theupper cantilever beam 2 and thelower cantilever beam 2 can be adjusted by adjusting the thickness ratio of thepiezoelectric sheet 3 to thecantilever beams 2, the mass ratio of thepermanent magnet 5 to thepiezoelectric sheet 3 and the position ratio of thepermanent magnet 5 to thecantilever beams 2, so that the cantilever beams are more suitable for the low-frequency environment.

The working process of the device is as follows: when an external force acts on thebase 1, thebase 1 transmits vibration energy to theupper cantilever beam 2 and thelower cantilever beam 2, thecantilever beams 2 vibrate and bend to generate deformation, thepiezoelectric sheet 3 adhered to the upper surface and the lower surface of thecantilever beams 2 also generates deformation, and thepiezoelectric sheet 3 is a piezoelectric material with piezoelectric effect, so that charged particles on the surface of thepiezoelectric sheet 3 deviate from a balance position when thepiezoelectric sheet 3 generates deformation, and further the upper surface and the lower surface of thepiezoelectric sheet 3 generate potential difference; in addition, the vibration of thecantilever beam 2 can drive thepermanent magnet 5 at the free end to move up and down, the phase difference can be generated when thepermanent magnet 5 and theinduction coil 6 move, the magnetic flux passing through theinduction coil 6 is changed due to the relative movement of thepermanent magnet 5 and theinduction coil 6, and the closedinduction coil 6 can generate induced electromotive force according to Faraday electromagnetic induction; because the twocantilever beams 2 are connected through the spring 4, the energy between the twocantilever beams 2 can be mutually transmitted, so that the broadband applicability of the energy harvesting device is wider, and compared with a common energy harvesting device relying on a single-resonant-frequency cantilever beam structure, the electromagnetic power generation capability of the energy harvesting device is improved, the number of resonant frequency points is increased, the broadband adaptability is better, and the comprehensive power generation capability is excellent.

Fig. 5 is a graph of piezoelectric simulation data of the device of the present invention, and it can be seen that the simulation result has three peaks in the low frequency range, and the frequency band is wide and the adaptability is good. Fig. 6 is a graph of simulation data for the upper half coil of the apparatus of the present invention, taken from the magnet movement at the resonant peak point, showing a peak-to-peak voltage of about 2.5V, calculated from the load resistance, for a power of about 1.25 mw. Fig. 7 is a plot of simulated data for the lower half coil of the device of the present invention, taken from the magnet motion at the resonant peak point, showing a peak-to-peak voltage of about 3V, calculated from the load resistance, at a power of about 1.5 mw.

Claims (4)

1. A low-frequency broadband vibration energy harvesting device comprises a base (1), two cantilever beams (2) which are fixedly connected with the base (1) and are in an isosceles trapezoid shape and arranged up and down, wherein the upper surface and the lower surface of each cantilever beam (2) are respectively connected with a piezoelectric sheet (3), and the low-frequency broadband vibration energy harvesting device is characterized in that one ends of the two cantilever beams (2) far away from the base (1) are connected with a permanent magnet (5) through two springs (4), the upper end and the lower end of the permanent magnet (5) are respectively and fixedly connected to the two springs (4), and induction coils (6) connected to the cantilever beams (2) are respectively sleeved on the two springs (4);

the circle center of the induction coil (6) is over against the permanent magnet (5);

the diameter of the induction coil (6) is larger than that of the permanent magnet (5).

2. The low-frequency broadband vibration energy harvesting device according to claim 1, wherein the piezoelectric sheets (3) on the upper and lower surfaces of the cantilever beam (2) are in a series or parallel connection structure.

3. The low-frequency broadband vibration energy harvesting device is characterized in that the piezoelectric sheet (3) is the same as the cantilever beam (2) in shape and is adhered to the surface of the cantilever beam (2) through conductive adhesive.

4. The low-frequency broadband vibration energy harvesting device according to claim 1, wherein the base (1) is made of acrylic glass material.

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