Background technology
The unify common feature of micro electromechanical systems such as individual mobile device of
radio sensing network, micro-electro-mechanical systems is: energy consumption is very low; From a few μ W to hundreds of mW; But require service time very long, very crucial is because the limiting them and generally can not carry out the energy supply with power line of service condition.There are shortcomings such as volume is big, the life-span is short in present battery-powered mode, adopts solar energy, thermal gradient homenergic to supply power and then need in the environment that corresponding sunlight or thermal gradient are arranged, carry out, and this has limited their application.
The energy that has abundant vibration mode in
environment, these collection of energy are got up becomes a kind of good selection for the power supply of above-mentioned micro electromechanical system.Piezoelectric is a kind of intellectual material that can realize that electromechanical energy exchanges, when receiving alternate stress, just can produce electric energy endlessly, and it can be an electric energy with the power conversion of vibration.Piezoelectric commonly used now has piezoelectric ceramic and piezopolymer and their compound etc., and wherein the electromechanical conversion efficiency of piezoelectric ceramic is higher, is the preferred material that carries out collection of energy.(piezoelectric constant is d to the commonly used generating mode of vibration of piezoelectric ceramic perpendicular to the telescopic mould of length in order to adopt electric field 31 ), electric field is parallel to the flexible mould of thickness of direction of wave travel (piezoelectric constant is d 33 ) and electric field is parallel to the thickness shear mode of direction of wave travel, and (piezoelectric constant is d 15 ), wherein: d 33 Be about d 31 2 ~ 3 times, and d 15 Be about d 31 3 ~ 4 times.Adopt suitable mode of operation can improve the efficient of the electromechanics conversion of piezoelectric ceramic according to the application scenario.Under specific mode of operation, will make piezoelectric produce many electric weight will apply big stress or make piezoelectric produce big deformation.Piezoelectric stack is the structure multi-disc piezoelectric patches is stacked together and that on circuit, carry out perhaps part series connection of serial or parallel connection, part parallel connection, and it mainly utilizes the higher d of piezoelectric constant 33 , series connection can improve output voltage on the piezoelectric patches circuit, and parallel connection can improve output current; Can carry out the series and parallel design to the requirement of electric current and voltage according to actual collecting circuit; Under onesize external force effect, for onesize piezoelectric patches, the more voluminous electric weight of giving birth to of range upon range of sheet number is just big more; But the sheet number has too much increased volume and cost, need between actual power consumption demand, application space requirement and deployment cost require, weigh.Through the connection in series-parallel on the piezoelectric patches circuit in the piezoelectric stack is designed, the internal driving when making it when increasing piezoelectric length and lifting surface area, make piezoelectric material to generate electricity does not increase or increases very little, so that the impedance matching of realization and external circuit.At present, the method for carrying out collection of energy with piezoelectric stack mainly is that it is embedded in the vibrating elements, make the pressure (drawing) that its two sides is equal to thus power produces electric energy.If just piezoelectric stack is pasted on the vibrating elements surface; The length of PZT (piezoelectric transducer) will equal quarter-wave multiple; This can make piezoelectric size under lower frequency long; Such as at the nearly 21cm of 5kHz lower piezoelectric material require, thereby this mode only is applicable to tens kilo hertzs to up to a hundred kilo hertzs frequency range.Additional certain quality piece is pasted on and can constitutes the spring proton structure with certain resonance frequency on the vibrating elements on piezoelectric stack; Energy conversion efficiency is very high near this resonance frequency; But because piezoelectric ceramic very hard (rigidity is high); Just need up to a hundred kilograms mass for the vibration of hundreds of hertz, more be difficult to be applied to the frequency range below the 50Hz, and piezoelectric ceramic receive bigger static compression force after piezoelectric modulus have certain decline; Make electromechanical conversion efficiency become very low, thereby this structure also is difficult to use.
are found through the retrieval to prior art; Chinese invention patent notification number: CN1258866; Title: piezoelectric generating apparatus, this device comprise the piezoelectric ceramic plate that the piezo ceramic element by two plate shapes forms, they be layering and be engaged with each other with contrapolarization; Wherein by the one or both sides of patting piezoelectric ceramic plate with hard beater, thereby the bending vibration that is activated in the piezoelectric ceramic plate produces.Because it is of short duration that beater is once patted the time of generating; The beating that needs beater to continue could produce stable electric energy; But situation, particularly beater that it generally only is suitable for low-frequency vibration need bigger amplitude ability starting of oscillation, and these have all limited its application.
Summary of the invention
the objective of the invention is to overcome the deficiency of prior art; A kind of multiband piezoelectric vibration energy gatherer is provided; Adopt dynamic absorber structure commonly used in the vibration control; It is additional on the piezoelectric, utilizes the strong resonance effect of dynamic vibration absorber to make piezoelectric obtain enough stress, thereby under the small size vibration of vibrating elements, produce more electric energy.Because the resonance frequency of dynamic vibration absorber can design in the frequency domain from several hertz to several KHzs, thereby the operating frequency of energy collecting device can be selected in the frequency domain of broad.In addition; Can realize the energy collecting device of small size, little quality through design; And the structure that adopts piezoelectric stack and piezoelectric cantilever simultaneously can be widened the working band of energy collecting device; Improve the energy density of energy collecting device, thereby obtain to be easy to use, energy gathering apparatus efficiently.
the present invention realize through following technical scheme; The present invention includes: piezoelectric element, cover plate, dynamic vibration absorber and energy acquisition circuit; Wherein: securing cover plate on the piezoelectric element, cover plate links to each other with dynamic vibration absorber, and the energy acquisition circuit links to each other with piezoelectric element.
described dynamic vibration absorber comprises: mass and flexible member, and wherein: flexible member links to each other with cover plate, and mass links to each other with flexible member.
The damping ratio of
described flexible member is less than 0.3.
described piezoelectric element is piezoelectric stack or piezoelectricity overarm arm configuration.
described piezoelectric stack adopts flexible mould of thickness or thickness shear mode.
described collection of energy circuit adopts full-bridge rectification filter circuit.
course of work of the present invention: piezoelectric element receives the excitation of extraneous vibration element to produce forced vibration; In the working band of energy acquisition circuit; Because the damping ratio of flexible member is less than 0.3; Thereby dynamic vibration absorber generation strong resonance effect drive pressure electric device produces the electric current of alternation, and alternating current has obtained than galvanic current behind energy acquisition circuit rectifying and wave-filtering, thereby stores or directly utilization.
the present invention compare prior art and have the following advantages: owing to adopted the dynamic vibration absorber structure; Piezoelectric element need not embed the inside of extraneous vibration element among the present invention; Do not need bigger amplitude yet; Collect the vibrational energy of little amplitude on the surface that can be arranged in vibrating elements easily, and can the operating frequency of this device be designed in a plurality of frequency ranges realization is easy to use, the collection of vibrational energy efficiently.
Embodiment
elaborate in the face of embodiments of the invention down; Present embodiment is being to implement under the prerequisite with technical scheme of the present invention; Provided detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.
Embodiment 1
are as shown in Figure 1; Present embodiment comprises: vibrating elements 1, piezoelectric element 2, cover plate 3, dynamic vibration absorber 4 and energy acquisition circuit 5; Wherein: vibrating elements 1 links to each other with piezoelectric element 2; Securing cover plate 3 on the piezoelectric element 2, and cover plate 3 links to each other with dynamic vibration absorber 4, and energy acquisition circuit 5 links to each other with piezoelectric element 2.
described dynamic vibration absorber 4 comprises: mass 6 and flexible member 7, and wherein: flexible member 7 links to each other with cover plate 3, and mass 6 links to each other with flexible member 7.
The damping ratio of
described flexible member 7 is less than 0.3.
The piezoelectric element 2 of present embodiment adopts the flexible mould of thickness, and its piezoelectric constant is d
33
described energy acquisition circuit 5 is full-bridge rectification filter circuits; Comprise: rectifier bridge 8, filter capacitor 9 and load 10; Wherein: piezoelectric element 2 links to each other with rectifier bridge 8, and rectifier bridge 8 links to each other with filter capacitor 9, load 10 and filter capacitor 9 parallel connections.
Piezoelectric element 2 is piezoelectric stacks in
present embodiment, and flexible member 7 is springs.
The effect of
cover plate 3 is whole surfaces that protection piezoelectric element 2 and the power that makes flexible member 7 can be evenly distributed to piezoelectric element 2.Because receiving to stretch, piezoelectric is easy to damage; And the intensity by compression the time is higher; Thereby need carry out pretension to piezoelectric stack when being applied in the strong occasion of vibration, and can adopt two structure of cover plate, promptly all arrange cover plate 3 on the piezoelectric stack both sides; Pass piezoelectric with screw and carry out pretension, just need perforation like this in the middle of the piezoelectric.
The most energy that the vibrational system that
vibrating elements 1, piezoelectric element 2 and dynamic vibration absorber 4 are formed produces when resonance takes place, this moment, piezoelectric element 2 was stressed greater than outside exciting force; The piezoelectric element 2 stressed exciting forces that equal when excited frequency equals the natural frequency of dynamic vibration absorber 4, the energy that this moment, whole device produced is also more; When the natural frequency of dynamic vibration absorber 4 equaled the natural frequency of vibrating elements 1, the resonance bands of this device was the wideest, and the mass ratio that increases mass 6 and vibrating elements 1 this moment can be widened the resonance bands of this device.
Embodiment 2
are as shown in Figure 2, and the dynamic vibration absorber 4 of present embodiment is the stack of two flexible members 7 and mass 6, has constituted double-deck dynamic absorber structure.Dynamic vibration absorber 4 comprises first spring 11, first mass 12, second spring 13 and second mass 14, and wherein: first spring 11 links to each other with cover plate 3, and first spring 11, first mass 12, second spring 13 link to each other with second mass 14 successively.Be that flexible member 7 comprises: first spring 11 and second spring 13, mass 6 comprises: first mass 12 and second mass 14.
Other execution modes of
present embodiment are identical with embodiment 1.
this embodiment adopts two springs and mass 6 to form the Three Degree Of Freedom vibrational system with vibrating elements 1, has increased formant number and resonance bands width, thereby has widened the bandwidth of operation of whole device.
Embodiment 3
are as shown in Figure 3; The flexible member 7 of present embodiment comprises: first support 15, second support 16, the 3rd spring 17 and first lever 18; Mass 6 comprises: the 3rd mass 19 and the 4th mass 20; Wherein: first support 15 and the 4th mass 20 lay respectively at the two ends of first lever 18, and second support 16 links to each other with cover plate 3 with first lever 18 respectively, and first support 15 links to each other with the 3rd mass 19; The 3rd mass 19 links to each other with the 3rd spring 17, and the 3rd spring 17 links to each other with cover plate 3.
Other execution modes of
present embodiment are identical with embodiment 1.
this structure is fit to be applied in to the conditional occasion of weight.
Embodiment 4
are as shown in Figure 4; The flexible member 7 of present embodiment comprises: the 3rd support 21, the 4th support 22 and overarm arm 23, and wherein: an end and the 4th support 22 of overarm arm 23 are fixedly linked, and the other end is provided with mass 6; The 4th support 22 is fixedly linked with cover plate 3; The 3rd support 21 flexibly connects with overarm arm 23, and the both sides of overarm arm 23 adhere to piezoelectric patches 24 respectively, and the damping ratio of whole elastic element 7 is less than 0.3.
Starting of oscillation element 1 is provided with vertical sidewall 25 in
present embodiment; Adhere to first piezoelectric stack 26 on the sidewall 25; First piezoelectric stack 26 is provided with cover plate 3, piezoelectric patches 24 and the piezoelectricity overarm arm configuration of arm 23 compositions of hanging oneself from a beam and the piezoelectric element 2 that first piezoelectric stack 26 has constituted present embodiment.One end of the 3rd support 21 is movably connected with overarm arm 23, and the other end and sidewall 25 are fixedly linked.
The contact-making surface of
sidewall 25 and first piezoelectric stack 26 is provided with the angle of 10 ~ 15 degree, and this makes the piezoelectric stack 26 of winning mainly be parallel to the stretching and the compression stress of polarized electric field.
Being provided with two rectifier bridges 8 in
energy acquisition circuit 5 links to each other with first piezoelectric stack 26 with piezoelectric patches 24 respectively; The alternating current that piezoelectricity is exported becomes the direct current of unidirectional output; Reduced the couplings of two kinds of structure output electric weight, the numerical value of appropriate design filter capacitor 9 can provide more stable voltage to load 10.
Other execution modes of
present embodiment are identical with embodiment 1.
In
present embodiment: when vibrating elements 1 vibration; Dynamic vibration absorber 4 just can resonate at certain band frequency; Because cantilever beam 23 is to lean on the 3rd support 21 and the 4th support 22 to fix, and so just can on two piezoelectric stacks, produce the stress of alternation, and because the free partial-length of cantilever beam 23 is longer; The stress that mass 6 up-down vibration produce can produce the lever amplification on the 4th support 22, this will increase the generating capacity of piezoelectric stack greatly.The length direction of first piezoelectric stack 26 is arranged along the Width of cantilever beam 23, can reduce the length of cantilever beam 23 standing parts like this, increases the amplification of lever.In fact, owing to adopt cantilever beam 23, the resonance frequency of dynamic vibration absorber 4 is more, can in a plurality of frequency ranges, carry out vibrational energy collection efficiently.
Embodiment 5
As shown in Figure 5, present embodiment adopts the big (d of piezoelectric constant
15
) thickness shear mode, second piezoelectric stack 27 is pasted on upright side walls 25, the contact-making surface of the sidewall 25 and second piezoelectric stack 27 does not have angle.In the present embodiment; Flexible member 7 comprises: cantilever beam 23, the 5th support 28 and the 6th support 29, and wherein: the 5th support 28 1 ends are fixed on the sidewall 25, and an end links to each other with cantilever beam 23; The 6th support 29 1 ends are fixed on the cover plate 3, and an end links to each other with cantilever beam 23.The both sides of cantilever beam 23 are provided with piezoelectric patches 24.
Other execution modes of
present embodiment are identical with embodiment 4.