KR20150131699A - Cantilevered piezoelectric energy harvesting apparatus using vortex shedding - Google Patents

Abstract

A cantilevered piezoelectric energy harvesting apparatus according to an embodiment of the present invention includes: a cantilevered energy generating part which is arranged in the first position of the outside of a moving body, and has a piezoelectric material; and a vortex generation part which is arranged in the second position of the outside of the moving body separated from the energy generation part, and periodically generates vortex shedding in the movement of the moving body. The first position is set in the back of the second position with respect to the moving direction of the moving body. The energy generation part receives vortex shedding generated by the vertex generation part and produces electric energy due to the deformation of the piezoelectric material at a resonance frequency.

Description

TECHNICAL FIELD [0001] The present invention relates to a piezoelectric cantilever generator using a vortex vibration,

The present invention relates to a piezoelectric cantilever generator for arranging a vortex generating part and a piezoelectric cantilever on a moving body and displacing a piezoelectric cantilever by a vortex vibration generated in a vortex generating part to harvest electrical energy .

Electrical energy is being obtained by hydropower, thermal power, and nuclear power, and interest in energy harvesting, which can be used cleanly and indefinitely recently, is increasing.

In order to convert mechanical vibration energy into electric energy, an energy conversion method using a piezoelectric effect capable of a large conversion efficiency and light weight is widely used.

A piezoelectric effect is a phenomenon in which electric polarization occurs on the surface of a crystal when a force is applied to a solid, which is also referred to as a piezoresistive effect. In other words, when a force is applied to a material, deformation occurs, and when the deformation is applied, an electric energy is generated.

Generally, the maximum displacement occurs at a resonant frequency where the frequency of the oscillating source coincides with the natural frequency of the member. Therefore, it is important to lower the resonance frequency. For this reason, a cantilever beam which is easy to lower the resonance frequency has been used as the length adjustment.

A number of papers have been published in which a cantilever beam is attached to a vibrating mechanism to produce electricity, a nano generator to generate energy from a rotating tire, and a self-generating pressure / velocity sensor.

However, these techniques were not easy to match the natural frequencies, and even if they were fitted, they were applied to the instruments that were used temporarily and the electricity production was small, and it was not easy to produce electricity on a relatively large area.

In Japanese Patent (Japanese Patent Registration No. 3951438), there was a technique of producing electricity by connecting a diaphragm for vortex vibration caused by wind with a piezoelectric material. However, the above-described invention has a characteristic of generating electricity by using the vibration of the diaphragm due to wind, but it is impossible to continuously produce high efficiency electricity in accordance with the natural frequency of the piezoelectric material due to the direction and speed of the wind.

In order to solve the above problems, a piezoelectric cantilever generator is attached to a moving object such as a vehicle, and a periodic vortex vibration (Karman vortex street), which occurs when passing through a vortex generating part according to the moving speed of the moving object, And the natural frequencies of the piezoelectric cantilevered generators at distant distances are matched to continuously produce the maximum power.

According to an aspect of the present invention, there is provided a cantilever-type energy generating device comprising: a cantilevered energy generating unit disposed at a first position outside a moving body and having a piezoelectric material; And a vortex generating unit disposed at a second position outside the moving member and spaced apart from the energy generating unit and generating a periodical vortex vibration upon movement of the moving member, And the energy generating unit receives the vortex vibration generated by the vortex generating unit to produce electric energy by deformation of the piezoelectric material at a resonance frequency.

The virtual line connecting the first position and the second position may be parallel to the direction of the moving object.

The vortex generators may include first and second surfaces opposed to each other with the same angle with respect to the imaginary line, and the vortex generators may have a shape of an equilateral triangle or an equilateral triangle,

The vortex generators may be formed such that the first surface and the second surface are concave or the first surface and the second surface are convex.

The vortex generators include first and second plates which are opposed to each other at the same angle with respect to the imaginary line and are hinged to each other,

The hinge may be located at an edge of the vortex generating part where the fluid first contacts.

The vortex generating unit may further include an angle adjusting unit for turning the first and second plates about the hinge at the same angle,

Wherein the angle adjusting portion includes an actuator and a pusher connected to the actuator, wherein the pusher is moved in the hinge direction with respect to the virtual line by receiving the driving force of the actuator, or by moving in the actuator direction, It is possible to pivot about the hinge,

The angle adjusting unit includes a rotation cam and a rotation shaft, and the rotation cam can rotate the first and second plates about the hinge while rotating about the rotation axis.

Wherein the vortex generating section further includes a first flow path forming member and a second flow path forming member formed so that the flow path becomes gradually narrower toward the downstream side, and the flow path is formed between the first flow path forming member and the first surface, The flow path may be divided between the forming member and the second surface.

Wherein the vortex generating section includes a first member and a second member that form a flow path gradually becoming narrower toward the downstream side, wherein the first and second members are each configured to generate a vortex vibration at a position corresponding to a portion where the flow path ends A guide member may be formed,

The first and second members may be arranged so that any one member is ahead of the remaining members with respect to the moving direction of the moving body.

The piezoelectric cantilever-type power generation apparatus may further include a support portion that supports the energy generation portion and the vortex generation portion and is coupled to the moving body.

The supporting portion may be formed with a slot into which the energy generating portion is slidably inserted to vary the distance between the vortex generating portion and the energy generating portion according to the speed of the moving body.

1 is a schematic view showing a piezoelectric cantilever generator fixed to a moving body according to a first embodiment of the present invention.
2 is a schematic view showing that a vortex is generated by the vortex generating unit to apply periodic vibration to the energy generating unit.
3 is a view showing a vortex generating part having an equilateral triangular cross section.
Fig. 4 is a view showing a vortex generating portion having an isosceles triangular cross section. Fig.
5 is a view showing a shape in which both surfaces of a vortex generating portion are convex.
6 is a view showing a concave shape of both sides of the vortex generating part.
FIGS. 7A and 7B are views showing a vortex generating unit in which the angle between the first surface and the second surface is changed by the first angle adjusting apparatus according to the speed of the wind according to the second embodiment of the present invention.
8A and 8B are views showing a vortex generating unit in which the angle between the first surface and the second surface is changed by the second angle adjusting device according to the wind speed according to the second embodiment of the present invention.
9A to 9B are views showing vortex generators which can be applied in an open channel according to a third embodiment of the present invention when the wind speed is small.
10A and 10B are views showing a vortex generating unit according to a fourth embodiment of the present invention.
11 is a view showing the vortex generating unit and the energy generating unit according to the fifth embodiment of the present invention combined by the support unit.
12 is a view showing that a distance adjusting unit is additionally provided so that the vortex generating unit and the energy generating unit according to the sixth embodiment of the present invention can relatively move.

Hereinafter, a configuration of a piezoelectric cantilever generator according to the present invention will be described in detail with reference to the accompanying drawings.

These and other objects and features of the present invention will become more apparent by describing in detail exemplary embodiments of the present invention with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a perspective view showing that a piezoelectric cantilever generator according to a first embodiment of the present invention is disposed on a moving body 100;

The moving body 100 can be an automobile, a motorcycle, a ship, an airplane, a military moving body, a quick board, an inline skate, or a bicycle

The piezoelectric cantilever generator includes a vortex generator 200 and a cantilevered energy generator 300.

The vortex generators 200 are disposed outside the moving object and transmit the vortex vibration due to the abrupt fluctuation of the fluid flow to the rear as the moving object moves.

An imaginary line B connecting the vortex generating unit 200 and the energy generating unit 300 can be arranged in parallel to the direction A of the moving body. In the present invention, the vortex generators 200 may be composed of a first surface and a second surface opposed to each other with the same angle with respect to the virtual line B. Accordingly, the vortex generators 200 may have an equilateral triangle, an isosceles triangle, a first surface and a second surface concave or convex in cross section, and a polygonal cross section. Further, the surface facing the edge at which the fluid initially contacts can be omitted.

The vortex generating part 200 may have a cylindrical shape and a vortex may be generated by the guide member at the end of the open passage.

The energy generating unit 300 has a cantilever shape of a rectangular parallelepiped, and is provided with a piezoelectric material for converting strain energy into electrical energy, and is formed of a tip mass and a base material.

The base material may have a cantilever shape and may have a rectangular parallelepiped shape. The cross section may be formed to be long in the traveling direction of the vortex vibration, and may be configured to be relatively short in a direction perpendicular to the traveling direction of the vortex vibration. In this case, the base material can be bent by vortex oscillation with respect to the central axis of the cross section parallel to the traveling direction of the vortex vibration at the cross section of the rectangular parallelepiped.

Piezoelectric materials convert strain energy into electrical energy using the piezoelectric effect that causes electrical polarization in the crystal surface when a force is applied to the solid. In order to obtain much electricity by periodic vortex vibration, it is necessary to induce resonance. In this case, the maximum displacement may occur, and the base material or the piezoelectric material may be destroyed. Therefore, in order to continuously obtain a large amount of electricity in a given vibration, the piezoelectric material can be made of a material which is resistant to large deformation and has a high electro-mechanical coupling coefficient.

The piezoelectric material may be coated on both sides parallel to the imaginary line B in the cantilevered energy generating part 300 or formed integrally with the base material.

The energy generating unit 300 may transfer the mechanical energy from the piezoelectric material to the piezoelectric material, convert the mechanical energy into electric energy, and store the converted electric energy or use it in real time.

A natural frequency is formed by a combination of the rigidity of the cantilever base material and the rigidity of the end mass, and the combination of the mass and the end mass of the base material. The natural frequency of the energy generating unit 300 is mainly controlled by the end mass. In addition, a cantilever type energy generating device which can easily adjust the length of the beam to easily adjust or lower the resonance frequency can be used.

It is necessary to generate the resonance by matching the frequency of the vortex generated in the vortex generator 200 with the intrinsic frequency of the energy generator 300 in order for the piezoelectric cantilever generator according to the present invention to generate the maximum power. At the resonant frequency, the maximum displacement of the member occurs, and if it deviates from the resonant frequency, the displacement decreases and the amount of electric energy decreases sharply. A large amount of electric energy can be produced by adjusting the position and shape of the vortex generator 200 and the speed of the moving body 100 within the range of the resonance frequency.

Therefore, in order to match the natural frequency of the energy generator 300 as described later, the velocity of the moving body 100, the angle between the first surface of the vortex generator 200 and the second surface of the vortex generator 200, And a distance between the energy generating unit 300 and the vortex generating unit 200 by the distance adjusting unit 500 can be adjusted according to the bandwidth of the resonant frequency by a control unit (not shown).

On the other hand, according to the experiment, it has been found that the best power is generated when the energy generating unit 300 is located at the center of the traveling direction of the vortex vibration that oscillates in the left and right direction. The imaginary line B connecting the vortex generating unit 200 and the energy generating unit 300 can be arranged parallel to the direction A of the moving body.

2 is a view for explaining the shape of vortex waves and the arrangement relationship of the vortex generators 200 and the energy generators 300. FIG.

When the fluid coming from the front passes through both surfaces 201, 203 of the vortex generator 200, a vortex vortex occurs. A vortex street is formed as shown in FIG. 2, and the vortex is vibrated transversely laterally with respect to the imaginary line B as shown in FIG.

In the case of an ideal flow that exhibits such properties as incompressibility and non-viscosity, vortex is not generated by a cylinder such as a vortex generation (200) portion. However, since the fluid has viscosity, energy is lost due to friction between the fluid and the vortex generator 200, thereby causing a sudden change in fluid flow such as a change in velocity when the fluid passes through the vortex generator 200 Which causes vortexes. In a general air flow, a karman vortex oscillating periodically from left to right behind the vortex generator 200 may occur.

FIG. 3 is a view showing the shape of the vortex generating unit 200, which is a typical triangular cross-section of the present invention. The fluid moves in a direction opposite to the direction of the moving object and is divided into a first surface 201 and a second surface 203 opposed to each other at an angle equal to each other with respect to a virtual line at the edge of the vortex generating portion 200, Flows through the first surface (201) and the second surface (203) and generates a swirling vortex.

Experiments show that the vortex is best formed and its strength is relatively great in triangular shapes with sharp edges on the sides.

4 is a view showing a vortex generating part 210 having an isosceles triangle in cross section at an angle of 60 degrees between the first surface 211 and the second surface 213 at the edge where the fluid initially contacts. The angle of the vortex generators 200 according to the speed of the moving object can be selected and mounted to the moving object in advance when the running mode is different according to the speed, such as driving in the city or traveling on the expressway. Even in this case, the fluid moves in the direction opposite to the direction of the moving body and passes through the first surface 211 and the second surface 213 opposed to each other at the same angle with respect to the imaginary line at the corners, Vortex oscillation occurs.

5 shows a state in which the first surface 221 and the second surface 223 of the vortex generating section 220 are convex toward the first surface 221 and the second surface 223 about the imaginary line B And the center of curvature of each surface is a shape located opposite to the direction in which each surface protrudes. In this case, the surface opposed to the first contact edge of the fluid may be omitted, and the curvatures of the first surface 221 and the second surface 223 may be constant or various combinations.

6 shows a state in which the first surface 231 and the second surface 233 of the vortex generating section 230 are opposed to each other about the imaginary line B and the center of curvature of the first surface 231 and the second surface 233 of the vortex generating section 230 231 and the second surface 233 and the shape thereof is concave. In this case as well, as in Fig. 5, the surface facing the edge at which the fluid initially contacts may be omitted, and the curvatures of the first surface 231 and the second surface 233 may be constant or combinations of various curvatures.

FIGS. 7A and 7B are views showing a first plate 241 and a second plate 242, the vortex generators 240 according to the second embodiment of the present invention facing the imaginary line B at the same angle, 2 plate 243, and the hinge 245 is located at the corner where the fluid first comes into contact with the vortex generator 240. [ At this time, the vortex generating unit 240 further includes a first angle adjusting unit 280 for turning the first plate 241 and the second plate 243 about the hinge 245 at the same angle have.

The angle adjusting portion 280 is composed of a connecting member 283 connected to the actuator 281 and the actuator 281 and configured to push or pull the pusher 285.

When the actuator 281 pushes the pusher 285, the driving force of the driving motor (not shown) is transmitted to the actuator 281 so that the first plate 241 and the second plate 243 The angle between the first surface 241 and the second surface 243 opposed to each other about the imaginary line B is increased so that the first plate 241 and the second plate 243 Is rotated about the hinge 245 so that the angle between the first surface 241 and the second surface 243 opposed to the imaginary line B becomes small.

In this case, both plates 241 and 243 are resiliently connected by a torsion spring (not shown) at the hinge 245, and a torsion spring (not shown) is provided between the first plate 241 and the second plate 243 Direction. When the pusher 285 pushes the first plate 241 and the second plate 243, the plates 241 and 243 are elastically opened and when the pusher 285 is pulled by the actuator 281, The angle between the first surface 241 and the second surface 243 facing the imaginary line B about the second surface 245 becomes gradually smaller. The upper surface of the vortex generating unit 240 that surrounds the vortex generating unit 240 on the first plate 241 and the second plate 243 may be formed in a rubber material having elasticity and may be omitted.

7B is a state in which the angle between the first surface 241 and the second surface 243 opposed to each other about the imaginary line B is large and FIG. And the angle between the first surface 241 and the second surface 243 is reduced.

FIGS. 8A and 8B are views showing a first plate 251 and a second plate 252, the vortex generators 250 according to the second embodiment of the present invention facing the imaginary line B at the same angle, 2 plate 253, and the hinge 255 is positioned at a corner where the fluid first comes into contact with the vortex generating part 250. [ At this time, the vortex generating unit 250 further includes a second angle adjusting unit 290 for swinging the plates 251 and 253 about the hinge 255 at the same angle.

The cam 291 rotates about the rotary shaft 293 by a drive motor (not shown) so that the angles of the plates 251 and 253 can be increased or decreased. 8A is a view showing a case where the angle between the first surface 251 and the second surface 253 at which the cam 291 faces the imaginary line B at an edge is small and FIG. Of the first surface 251 and the second surface 253 facing each other on the axis of the imaginary line B about the rotation axis 293 is large.

In this case, the plates 251 and 253 are elastically connected by a torsion spring (not shown) at the hinge 255, and the torsion springs (not shown) are engaged with the first plate 251 and the second plate 253 Direction. When the cam 291 pushes the first plate 251 and the second plate 253, the plates 251 and 253 are elastically opened and when the cam 291 rotates, the restoring force of the spring causes the hinge 255 to rotate around the hinge 255 The angle between the first surface 251 and the second surface 253 facing the imaginary line B becomes gradually smaller.

The upper surface of the vortex generating unit 250 that surrounds the vortex generating unit 250 on the first plate 251 and the second plate 253 may be formed in a rubber material having elasticity and may be omitted.

FIGS. 9A and 9B are views showing the vortex generating section 260 using the principle of increasing the velocity of the fluid when the width of the flow passage becomes narrower according to the third embodiment. The fluid is gradually increased in speed as it passes through the flow path 264 between the first flow path surface 265 of the first flow path forming member 261 and the second flow path surface 267 of the second flow path forming member 263, The flow path is formed by dividing the flow path surfaces 265 and 267 into the flow paths 266 and 268 between the first surface and the second surface of the vortex generation section 200 and causing the fluid to generate a vortex after passing through the flow paths 266 and 268 do.

When the speed of the moving body 100 is very small in a traffic-congested city driving, a sufficient fluid velocity is required to generate vortex oscillation. When the speed of the moving body is small, the flow path forming members 261 and 263 are further disposed to secure the velocity of the fluid, thereby obtaining desired vortex vibration.

10A and 10B are views showing the shape of the vortex generating unit 270 according to the fourth embodiment. The fluid is gradually increased in speed as it passes through the flow path 279 between the third flow path surface 275 of the first member 271 and the fourth flow path surface 277 of the second member 273, 271 and the second member 273 are further formed with guide members 276, 278 for generating vortex vibration at positions corresponding to the end portions of the flow paths, respectively.

The first member 271 and the second member 273 can be arranged so that any one member is ahead of the remaining member with respect to the moving direction A of the moving body 100. [

11 shows that the vortex generating unit 200 and the energy generating unit 300 according to the fifth embodiment are fixed by the supporter 400. FIG. If there is such a support part 400, it can be easily fixed to the applicable surface of the moving body 100 by using at least one piezoelectric cantilever generator. A large amount of electric energy can be produced by installing a large number of piezoelectric cantilever generators mounted on the supporting part 400 on the upper or side of the vehicle.

12 is a view showing that the vortex generating unit 200 and the energy generating unit 300 according to the sixth embodiment are relatively moved by the support unit 400. [ In this case, the distance adjusting unit 500 may further include a distance adjusting unit 500 that varies the distance between the vortex generating unit 200 and the energy generating unit 300 according to the velocity of the fluid.

In the case of the vortex generating unit 200, since the angle adjusting devices 280 and 290 can be incorporated, the distance adjusting unit 500 can be positioned below the energy generating unit 300 for smooth operation. The driving means for operating the distance adjusting portion 500 includes a pinion (not shown) which engages with a lever (not shown), a servo motor (not shown) for driving the pinion, a control portion ).

Experiments show that a large fluid velocity does not produce the maximum power. The frequency of vortex oscillation depending on the shape (angle, height) of the vortex generators 200 and the velocity of the fluid and the frequency of the vortex oscillations due to the distance between the vortex generators 200 and the energy generators 300 And the natural frequency of the energy generating unit 300 are required.

The controller (not shown) stores experimental data on these variables and controls the shape and spacing of the vortex generator 200 according to the stored values. When an error occurs between the experimental data and the actual electrical energy, the control unit (not shown) automatically controls the angles and the separation distances for producing the maximum electrical energy.

The invention has been described in an illustrative manner. The terms used herein are for the purpose of description and should not be construed as limiting. Various modifications and variations of the present invention are possible in light of the above teachings. Therefore, unless otherwise indicated, the present invention may be freely carried out within the scope of the claims.

100: moving body 200: vortex generating part
270: a vortex generating part 280 formed with a guide member 280:
290: second angle regulating unit 300: energy generating unit
400: Support part 500: Distance adjustment part

Claims (14)

A cantilever type energy generating unit disposed at a first position outside the moving body and having a piezoelectric material; And
And a vortex generator disposed at a second position outside the moving body that is spaced apart from the energy generating unit and generates periodical vortex vibration when the moving body moves,
The first position is set to the rear of the second position with respect to the moving direction of the moving body,
Wherein the energy generating unit receives the vortex vibration generated by the vortex generating unit to produce electric energy by deformation of the piezoelectric material at a resonance frequency. The method according to claim 1,
And a virtual line connecting the first position and the second position is parallel to a direction of the moving body. 3. The method of claim 2,
Wherein the vortex generators are constituted by first and second surfaces opposed to each other at the same angle with respect to the imaginary line. The method of claim 3,
Wherein the vortex generating section has a shape of an equilateral triangle or an isosceles triangle in cross section. The method of claim 3,
Wherein the vortex generators are formed such that the first surface and the second surface are concave or the first surface and the second surface are convex. 3. The method of claim 2,
The vortex generators include first and second plates which are opposed to each other at the same angle with respect to the imaginary line and are hinged to each other,
Wherein the hinge is located at an edge of the vortex generating section where the fluid initially contacts. The method according to claim 6,
Wherein the vortex generating unit further comprises an angle adjusting unit for turning the first and second plates about the hinge at the same angle with each other. 8. The method of claim 7,
Wherein the angle adjusting portion includes an actuator and a pusher connected to the actuator,
Wherein the pusher receives the driving force of the actuator and moves in the direction of the hinge with respect to the imaginary line or in the direction of the vortex generating unit so as to pivot the first and second plates around the hinge. Cantilever power generation equipment. 8. The method of claim 7,
Wherein the angle adjusting portion includes a rotation cam and a rotation axis,
Wherein the rotation cam is rotated about the rotation axis to rotate the first and second plates about the hinge. The method of claim 3,
Wherein the vortex generating unit further includes a first flow path forming member and a second flow path forming member formed so that the flow path becomes gradually narrower toward the downstream side,
Wherein the flow path is divided between the first flow path forming member and the first surface, and between the second flow path forming member and the second surface. 3. The method of claim 2,
Wherein the vortex generating unit includes a first member and a second member that form a flow path that becomes gradually narrower toward the downstream,
Wherein the first and second members are each formed with a guide member for generating vortex vibration at a position corresponding to the end portion of the flow path. 12. The method of claim 11,
Wherein the first and second members are arranged so that any one member is ahead of the remaining member with respect to the moving direction of the moving body. 3. The method according to claim 1 or 2,
Further comprising: a supporting portion supporting the energy generating portion and the vortex generating portion and coupled to the moving body. 13. The method of claim 12,
Wherein the support portion is formed with a slot into which the energy generating portion is slidably inserted to vary the distance between the vortex generating portion and the energy generating portion according to the speed of the moving body.

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