Broadband piezoelectric vibration energy harvesting device

Abstract

The application provides a wide-frequency piezoelectric vibration energy harvesting device, and relates to the field of vibration energy harvesting.The wide-frequency piezoelectric vibration energy harvesting device comprises a base, an arched cantilever beam and an arched piezoelectric element, the arched cantilever beam is installed on the base in a cantilevered state, the arched piezoelectric element is connected to the surface of the arched cantilever beam, and the profile of the arched piezoelectric element is adapted to the profile of the arched cantilever beam, the overhanging end of the arched cantilever beam is provided with an end mass structure, the lower side of the arched cantilever beam is provided with a lower mass structure, and a spring member is connected between the lower mass structure and the arched cantilever beam.The arched cantilever beam has a lower vibration frequency and is closer to low-frequency vibration in an actual environment, the polarization directions of each part of the arched piezoelectric element are all directed to the center of the arch, has the advantage of balanced polarization effect, can respond to vibration excitation in the horizontal direction and other arbitrary directions, realizes the effect of harvesting vibration energy in multiple directions, and improves the conversion efficiency from vibration energy to electric energy.

Description

Technical Field

[0001] This invention relates to the field of vibration energy harvesting technology, and in particular to a broadband piezoelectric vibration energy harvesting device. Background Technology

[0002] Due to the limitations of chemical battery applications, technologies using piezoelectric structures to harvest vibrational energy from the environment have gradually been developed. These piezoelectric vibration harvesting devices convert environmental vibrational energy into electrical energy, enabling self-powered microelectronic devices.

[0003] Currently, piezoelectric vibration energy harvesting devices generally adopt the design of cantilever beam piezoelectric energy harvesting, utilizing the up-and-down swing of the cantilever beam and the deformation of the piezoelectric element to output electrical energy. Research shows that when the cantilever beam resonates under environmental vibration, the piezoelectric element generates a large voltage output. However, when the environmental vibration frequency is far from the cantilever beam's resonant frequency, the output voltage of the piezoelectric element decreases significantly. Because the operating bandwidth of the environmental vibration frequency is very wide, while the operating bandwidth of current cantilever beam piezoelectric systems is narrow, this results in low energy harvesting efficiency.

[0004] For example, Chinese invention patent CN109039156B, with an authorization announcement date of June 2, 2020, discloses a piezoelectric energy harvester with a dual-beam bending-torsional coupled vibration mode. Specifically, it includes a fixed base, two piezoelectric cantilever beams with one end connected to the fixed base, piezoelectric layers bonded to the piezoelectric cantilever main beams with conductive adhesive, and a piezoelectric cantilever crossbeam placed perpendicular to the two piezoelectric cantilever beams in the same horizontal plane and connected to them. Two mass blocks of different sizes are placed at each end of the piezoelectric cantilever crossbeam. Under external excitation, the placement of the two offset mass blocks on the piezoelectric cantilever crossbeam causes the two piezoelectric cantilever main beams to undergo torsional motion simultaneously with bending vibration.

[0005] However, existing piezoelectric energy harvesters are mainly used to harvest vibration energy in the vertical direction, and cannot respond to vibration excitation in other directions. Therefore, existing energy harvesters cannot effectively capture vibration energy from multiple directions in the external environment, and cannot further improve energy harvesting efficiency. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a broadband piezoelectric vibration energy harvesting device to solve the problem that existing energy harvesters cannot effectively capture vibration energy from multiple directions in the external environment, thus failing to further improve energy harvesting efficiency.

[0007] The technical solution of the broadband piezoelectric vibration energy harvesting device of the present invention is as follows:

[0008] The broadband piezoelectric vibration energy harvesting device includes a base, an arched cantilever beam, and an arched piezoelectric element, wherein the arched cantilever beam is mounted on the base in a cantilevered state;

[0009] The arched piezoelectric element is attached to the surface of the arched cantilever beam, and the outline of the arched piezoelectric element is adapted to the outline of the arched cantilever beam.

[0010] The cantilever beam has an end mass structure at its cantilever end and a lower mass structure on its lower side. A spring is connected between the lower mass structure and the cantilever beam.

[0011] Furthermore, the arched cantilever beam is shaped like an upward-arching semicircular arc, with the cantilever end of the arched cantilever beam extending along the diameter of the semicircular arc, and the lower mass structure connected directly below the top of the arched cantilever beam.

[0012] Furthermore, at least two arched cantilever beams are provided, including a first arched cantilever beam and a second arched cantilever beam, with the cantilever ends of the first arched cantilever beam and the cantilever ends of the second arched cantilever beam arranged opposite to each other.

[0013] The first arched cantilever beam has a first end mass structure at its cantilever end, and the second arched cantilever beam has a second end mass structure at its cantilever end. The lower side of both the first arched cantilever beam and the second arched cantilever beam is provided with the lower mass structure and the spring member.

[0014] Furthermore, the first end mass structure is a first end magnet, the second end mass structure is a second end magnet, the first end magnet and the second end magnet are spaced apart, and the first end magnet and the second end magnet are arranged with the same pole facing each other.

[0015] Furthermore, the base is a concave base, and the first arched cantilever beam and the second arched cantilever beam are respectively installed inside the concave base.

[0016] Furthermore, the concave base includes a base plate, a first side wall, and a second side wall, the first side wall and the second side wall being arranged at intervals relative to each other, and the first side wall and the second side wall being fixedly connected to the edge of the base plate respectively;

[0017] A first power amplifier is provided on the inner side of the first sidewall, and a second power amplifier is provided on the inner side of the second sidewall. The first arched cantilever beam is connected to the first power amplifier, and the second arched cantilever beam is connected to the second power amplifier.

[0018] Furthermore, the structure of the first power amplifier is the same as that of the second power amplifier. The first power amplifier includes a main spring, a floating support, and an adjusting rod. The main spring is connected between the floating support and the base plate.

[0019] The adjustment direction of the adjusting rod is set along the elastic force direction of the main spring. The adjusting rod is limited to the floating support, and the arched cantilever beam is fixedly connected to the floating support.

[0020] Furthermore, the upper part of the first sidewall and the upper part of the second sidewall are respectively provided with an inner flange, and a threaded hole is opened on the inner flange. The adjusting rod is an adjusting screw, which is threadedly engaged with the threaded hole, and the lower end of the adjusting screw is limitedly engaged with the floating support.

[0021] Furthermore, it also includes an elastic clamping structure and a straight piezoelectric element, the straight piezoelectric element being stretched and connected to the elastic clamping structure, the elastic clamping structure being disposed on the lower side of the arched cantilever beam, and an upper mass structure being installed on the upper part of the elastic clamping structure.

[0022] Furthermore, the lower mass structure is a lower magnet, the upper mass structure is an upper magnet, the lower magnet and the upper magnet are distributed vertically at intervals, and the upper magnet and the lower magnet are arranged with the same pole facing each other.

[0023] Beneficial effects: This broadband piezoelectric vibration energy harvesting device adopts a design of a base, an arched cantilever beam, and arched piezoelectric elements. The arched cantilever beam is installed on the base in a cantilevered state, and the cantilever end of the arched cantilever beam is equipped with an end mass structure. Under the same parameter conditions, finite element analysis shows that the arched cantilever beam has a lower vibration frequency. Compared with existing cantilever beams, this arched cantilever beam is closer to the low-frequency vibration in the actual environment, making up for the defect that existing cantilever beams cannot effectively match the environmental vibration.

[0024] Because the arched piezoelectric element is attached to the surface of the arched cantilever beam, and its profile conforms to the profile of the cantilever beam, the polarization direction of each part of the arched piezoelectric element points towards the center of the arch, exhibiting the advantage of a balanced polarization effect. Under external vibration excitation, the arched cantilever beam vibrates, causing the arched piezoelectric element to deform. Electrical energy is generated through the positive piezoelectric effect of the arched piezoelectric element, and this energy is output to an external energy harvesting device through the conductors attached to the arched piezoelectric element. The arched piezoelectric element can harvest vibration energy not only in the vertical direction but also respond to vibration excitation in the horizontal direction and any other arbitrary direction, achieving the effect of capturing vibration energy in multiple directions and improving the conversion efficiency from vibration energy to electrical energy.

[0025] Based on the end mass structure at the cantilever end, a lower mass structure is also provided on the underside of the arched cantilever beam. A spring is connected between the lower mass structure and the arched cantilever beam, which increases the vibration amplitude of the arched cantilever beam. Furthermore, the arched cantilever beam, the end mass structure, the spring, and the lower mass structure form an arch-spring mass system. This arch-spring mass system is a nonlinear dynamic system. Under the action of environmental vibration, this system can produce internal resonances in the form of 1:2, 1:3, or 1:5, which expands the operating frequency band of the system and thus significantly improves the energy harvesting efficiency. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the broadband piezoelectric vibration energy harvesting device in a specific embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the elastic clip structure in a specific embodiment of the broadband piezoelectric vibration energy harvesting device of the present invention.

[0028] In the figure: 1 - base, 10 - bottom plate, 11 - first side wall, 12 - second side wall, 13 - inner flange;

[0029] 2 – First arched cantilever beam, 20 – Arched piezoelectric element, 21 – First end mass structure, 22 – Lower mass structure, 23 – Spring element;

[0030] 3 - Second arched cantilever beam, 31 - Second end mass structure, 4 - Elastic clamping structure, 40 - Straight piezoelectric element, 41 - Upper mass structure, 42 - Top edge, 43 - Bottom edge, 44 - Hydrated edge;

[0031] 5 - First power amplifier, 50 - Main spring, 51 - Floating support, 52 - Adjusting rod, 6 - Second power amplifier. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0033] A specific embodiment 1 of the broadband piezoelectric vibration energy harvesting device of the present invention is as follows: Figure 1 , Figure 2 As shown, the broadband piezoelectric vibration energy harvesting device includes a base 1, an arched cantilever beam, and an arched piezoelectric element 20. The arched cantilever beam is mounted on the base 1 in a cantilevered state. The arched piezoelectric element 20 is attached to the surface of the arched cantilever beam, and the outline of the arched piezoelectric element 20 is adapted to the outline of the arched cantilever beam. The cantilever end of the arched cantilever beam is provided with an end mass structure, and the lower side of the arched cantilever beam is provided with a lower mass structure 22. A spring 23 is connected between the lower mass structure 22 and the arched cantilever beam.

[0034] This broadband piezoelectric vibration energy harvesting device adopts a design of base 1, arched cantilever beam and arched piezoelectric element 20. The arched cantilever beam is installed on base 1 in a cantilevered state, and the cantilever end of the arched cantilever beam is provided with an end mass structure. Under the same parameter conditions, finite element analysis shows that the arched cantilever beam has a lower vibration frequency. Compared with existing cantilever beams, this arched cantilever beam is closer to the low-frequency vibration in the actual environment, making up for the defect that existing cantilever beams cannot effectively match the environmental vibration.

[0035] Because the arched piezoelectric element 20 is attached to the surface of the arched cantilever beam, and its contour matches that of the beam, the polarization direction of each part of the element points towards the center of the arch, exhibiting the advantage of a balanced polarization effect. Under external vibration excitation, the arched cantilever beam vibrates, causing the piezoelectric element 20 to deform. Electrical energy is generated through the positive piezoelectric effect of the element, and this energy is output to an external energy harvesting device via its built-in wire. The arched piezoelectric element 20 can harvest vibration energy not only vertically but also horizontally and in any other direction, achieving multi-directional vibration energy capture and improving the conversion efficiency from vibration energy to electrical energy.

[0036] Based on the end mass structure at the cantilever end, a lower mass structure 22 is also provided on the lower side of the arched cantilever beam. A spring member 23 connects the lower mass structure 22 to the arched cantilever beam, which increases the vibration amplitude of the arched cantilever beam. Furthermore, the arched cantilever beam, the end mass structure, the spring member 23, and the lower mass structure 22 form an arch-spring mass system. This arch-spring mass system is a nonlinear dynamic system. Under the action of environmental vibration, this system can generate internal resonances in the form of 1:2, 1:3, or 1:5, which expands the operating frequency band of the system and thus significantly improves the energy capture efficiency.

[0037] In this embodiment, the arched cantilever beam is shaped like an upward-arching semicircular arc. The cantilever end of the arched cantilever beam extends along the diameter of the semicircular arc, and the lower mass structure 22 is connected directly below the top of the arched cantilever beam. The semicircular arc shape of the arched cantilever beam is matched by the semicircular arc shape of the arched piezoelectric element 20, ensuring that the polarization direction of each part of the arched piezoelectric element 20 points towards the center of the arch, achieving a balanced polarization effect.

[0038] The arched cantilever beam consists of two beams: a first arched cantilever beam 2 and a second arched cantilever beam 3. The cantilever ends of the first arched cantilever beam 2 and the second arched cantilever beam 3 are arranged opposite each other. The cantilever end of the first arched cantilever beam 2 is provided with a first end mass structure 21, and the cantilever end of the second arched cantilever beam 3 is provided with a second end mass structure 31. The lower sides of both the first arched cantilever beam 2 and the second arched cantilever beam 3 are provided with a lower mass structure 22 and a spring member 23.

[0039] Two arched cantilever beams constitute a double-arch, double-spring mass-coupled nonlinear dynamic system. Compared with a single-arch structure, the double-arch structure is more likely to enter a bistable state and can undergo large-amplitude vibrations to capture more vibrational energy. Moreover, the first arched cantilever beam 2 and its lower mass structure 22 and spring 23, and the second arched cantilever beam 3 and its lower mass structure and spring 23 respectively constitute an arch-spring mass system. By adjusting the stiffness of the spring 23, the arch-spring mass system can achieve internal resonance under environmental vibration, further improving the energy capture efficiency.

[0040] Furthermore, the first end mass structure 21 is a first end magnet, and the second end mass structure 31 is a second end magnet. The first end magnet and the second end magnet are spaced apart and arranged with their same poles facing each other. During the vibration of the arched cantilever beam, the permanent magnets at the ends of the two arched cantilever beams generate a repulsive force due to their identical magnetic poles, which changes the equilibrium position of the two arched cantilever beams, increases the vibration amplitude of the arched cantilever beam, and causes it to produce a bistable or even multistable vibration effect.

[0041] In this embodiment, the base 1 is a concave base, and the first arched cantilever beam 2 and the second arched cantilever beam 3 are respectively installed inside the concave base. Specifically, the concave base includes a base plate 10, a first side wall 11, and a second side wall 12. The first side wall 11 and the second side wall 12 are arranged at intervals relative to each other, and the first side wall 11 and the second side wall 12 are respectively fixedly connected to the edge of the base plate 10. A first power amplifier 5 is provided on the inner side of the first side wall 11, and a second power amplifier 6 is provided on the inner side of the second side wall 12. The first arched cantilever beam 2 is connected to the first power amplifier 5, and the second arched cantilever beam 3 is connected to the second power amplifier 6. Connecting the arched cantilever beams to the corresponding power amplifiers gives the arch-spring mass system a lower system frequency and amplifies the vibration amplitude, thereby improving the energy capture efficiency.

[0042] The structure of the first power amplifier 5 is the same as that of the second power amplifier 6. In this embodiment, the structure of the first power amplifier 5 will be specifically described. The first power amplifier 5 includes a main spring 51, a floating support 50, and an adjusting rod 52. The main spring 51 is connected between the floating support 50 and the base plate 10. The adjusting rod 52 is set along the elastic force direction of the main spring 51. The adjusting rod 52 is in a limiting fit with the floating support 50. The arched cantilever beam is fixedly connected to the floating support 50. The upper part of the first side wall 11 and the upper part of the second side wall 12 are respectively provided with an inner flange 13. The inner flange 13 is provided with a threaded hole. The adjusting rod 52 is an adjusting screw. The adjusting screw is threadedly fitted with the threaded hole of the inner flange 13. The lower end of the adjusting screw is in a limiting fit with the floating support 50.

[0043] The main spring 51 can be squeezed or released by adjusting the screw up and down, thereby changing the overall stiffness of the arch-spring mass system. Furthermore, by lowering the height of the arch-spring mass system formed by the first arched cantilever beam 2 and raising the height of the arch-spring mass system formed by the second arched cantilever beam 3, the operating frequencies of the two arch-spring mass systems are placed in different ranges, significantly improving the operating frequency band of the entire energy harvesting device. In engineering environments with wide vibration frequency bands, it can capture vibration energy with rapidly changing frequencies and has good environmental adaptability.

[0044] In addition, the broadband piezoelectric vibration energy harvesting device also includes an elastic clamp structure 4 and a straight piezoelectric element 40. The straight piezoelectric element 40 is stretched and connected to the elastic clamp structure 4. The elastic clamp structure 4 is located on the lower side of the arched cantilever beam, and an upper mass structure 41 is installed on the upper part of the elastic clamp structure 4. Furthermore, the lower mass structure 22 of the arched cantilever beam is a lower magnet, and the upper mass structure 41 of the elastic clamp structure 4 is an upper magnet. The lower magnet and the upper magnet are distributed vertically at intervals, and the upper magnet and the lower magnet are arranged with the same pole facing each other.

[0045] Specifically, the elastic clamping structure 4 has a hexagonal outline and includes a top edge 42, a bottom edge 43, and four inclined edges 44. The two upper inclined edges 44 are connected to the two ends of the top edge 42 to form an upper clamping opening, and the two lower inclined edges 44 are connected to the two ends of the bottom edge 43 to form a lower clamping opening. The upper and lower clamping openings are arranged with their openings facing each other. The straight piezoelectric element 40 is clamped between the upper and lower clamping openings. When the elastic clamping structure 4 is subjected to vertical compression, the inclined edges 44 cause the elastic clamping structure 4 to undergo tensile deformation. When the arched cantilever beam undergoes vertical bistable vibration, the magnetic force between the lower mass structure 22 and the upper mass structure 41 causes the lower elastic clamping structure 4 to undergo compression deformation, which in turn causes the straight piezoelectric element 40 to undergo tensile deformation, thereby capturing more vibration energy.

[0046] Other specific embodiments of the broadband piezoelectric vibration energy harvesting device of the present invention can be flexibly designed with respect to different application requirements. For example, the number of arched cantilever beams is not limited to two; it can be designed as one, three, or more. Furthermore, the end mass structure and lower mass structure are not limited to magnets; they can be replaced with traditional mass blocks, which can also increase the amplitude. In addition, the specific structures such as the base, power amplifier, and elastic clamp structure can be adaptively adjusted or replaced.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A broadband piezoelectric vibration energy harvesting device, characterized in that, It includes a base, an arched cantilever beam, and an arched piezoelectric element, wherein the arched cantilever beam is mounted on the base in a cantilevered state; The arched piezoelectric element is attached to the surface of the arched cantilever beam, and the outline of the arched piezoelectric element is adapted to the outline of the arched cantilever beam. The cantilever beam has an end mass structure at its cantilever end and a lower mass structure on its lower side. A spring is connected between the lower mass structure and the cantilever beam. The arched cantilever beam is in the shape of an upward-arching semicircular arc, with the cantilever end of the arched cantilever beam extending along the diameter of the semicircular arc, and the lower mass structure connected directly below the top of the arched cantilever beam. The arched cantilever beam is provided in at least two parts, including a first arched cantilever beam and a second arched cantilever beam, with the cantilever ends of the first arched cantilever beam and the second arched cantilever beam arranged opposite to each other. The first arched cantilever beam has a first end mass structure at its cantilever end, and the second arched cantilever beam has a second end mass structure at its cantilever end. The lower side of both the first arched cantilever beam and the second arched cantilever beam is provided with the lower mass structure and the spring member.

2. The broadband piezoelectric vibration energy harvesting device according to claim 1, characterized in that, The first end mass structure is a first end magnet, and the second end mass structure is a second end magnet. The first end magnet and the second end magnet are spaced apart and arranged with the same pole facing each other.

3. The broadband piezoelectric vibration energy harvesting device according to claim 1 or 2, characterized in that, The base is a concave base, and the first arched cantilever beam and the second arched cantilever beam are respectively installed inside the concave base.

4. The broadband piezoelectric vibration energy harvesting device according to claim 3, characterized in that, The concave base includes a base plate, a first side wall and a second side wall, the first side wall and the second side wall are arranged at intervals relative to each other, and the first side wall and the second side wall are respectively fixedly connected to the edge of the base plate; A first power amplifier is provided on the inner side of the first sidewall, and a second power amplifier is provided on the inner side of the second sidewall. The first arched cantilever beam is connected to the first power amplifier, and the second arched cantilever beam is connected to the second power amplifier.

5. The broadband piezoelectric vibration energy harvesting device according to claim 4, characterized in that, The structure of the first power amplifier is the same as that of the second power amplifier. The first power amplifier includes a main spring, a floating support and an adjusting rod. The main spring is connected between the floating support and the base plate. The adjustment direction of the adjusting rod is set along the elastic force direction of the main spring. The adjusting rod is limited to the floating support, and the arched cantilever beam is fixedly connected to the floating support.

6. The broadband piezoelectric vibration energy harvesting device according to claim 5, characterized in that, The upper part of the first sidewall and the upper part of the second sidewall are respectively provided with an inner flange, and a threaded hole is provided on the inner flange. The adjusting rod is an adjusting screw, which is threadedly engaged with the threaded hole. The lower end of the adjusting screw is limitedly engaged with the floating support.

7. The broadband piezoelectric vibration energy harvesting device according to claim 1 or 2, characterized in that, It also includes an elastic clamping structure and a straight piezoelectric element, the straight piezoelectric element being stretched and connected to the elastic clamping structure, the elastic clamping structure being disposed on the lower side of the arched cantilever beam, and an upper mass structure being installed on the upper part of the elastic clamping structure.

8. The broadband piezoelectric vibration energy harvesting device according to claim 7, characterized in that, The lower mass structure is a lower magnet, and the upper mass structure is an upper magnet. The lower magnet and the upper magnet are distributed vertically at intervals, and the upper magnet and the lower magnet are arranged with the same pole facing each other.

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