Piezoelectric energy collection device based on negative Poisson's ratio structure

Abstract

The invention belongs to the technical field of energy collection, and discloses a piezoelectric energy collection device based on a negative Poisson's ratio structure, a negative Poisson's ratio structure hole is arranged on the surface of a negative Poisson's ratio structure beam, an epoxy resin layer is adhered to the top of the negative Poisson's ratio structure hole, and the epoxy resin layer and the negative Poisson's ratio structure hole are conformally combined. A piezoelectric plate is bonded to the top of the epoxy resin layer, a mass block is fixed to the front end of the negative Poisson's ratio structural beam, a fixing base is arranged at the root of the negative Poisson's ratio structural beam, negative Poisson's ratio structural holes are distributed in the surface of the beam, and the piezoelectric plate can be driven to synchronously stretch or contract in the length direction and the width direction. The negative Poisson's ratio structural beam is a trapezoidal beam of which the sectional area is linearly increased from the front end to the root part, stress is not concentrated on the root part of a cantilever beam, but is distributed at the position of the whole piezoelectric patch, so that the stress of the piezoelectric patch is more uniform, and the piezoelectric patch is more stable in performance. And the service life of the energy collector is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy harvesting, and particularly relates to an energy harvester based on a negative Poisson's ratio structure. Background Art

[0002] With the continuous progress of human science and technology, the Internet of Things (IoT), as an important revolution in information industry technology, has been widely popularized in fields such as industry and infrastructure. The key to realizing IoT technology is the continuous operation of a large number of information sensing devices, and currently these sensors usually use batteries for power supply. The battery capacity is limited, and when the battery runs out of power, the sensors cannot work, and the batteries need to be replaced frequently or recharged. Therefore, related sensors have problems such as difficult power supply and short working hours. At the same time, frequent maintenance of the power supply system will further increase the working cost of the IoT. Energy harvesters can continuously collect the ever-present energy from the surrounding environment, such as magnetic fields, vibrations, etc., and have the advantages of simple assembly, high energy harvesting density, and easy integration. Moreover, there are a large number of vibration sources in the IoT working environment, which can continuously provide mechanical vibration energy. Therefore, using a vibration energy harvester as the power supply device for sensors has become one of the optimal solutions to solve the battery life problem of IoT sensing devices currently.

[0003] Currently, piezoelectric energy harvesting devices generally adopt the design of traditional cantilever beam structures, which essentially belong to the positive Poisson's ratio structure system. In such structures, the mechanical deformation of the cantilever beam will cause a bidirectional strain coupling effect: when the beam undergoes longitudinal tension, it is accompanied by transverse contraction, and when it undergoes longitudinal compression, it produces transverse expansion. It should be noted that the transverse piezoelectric coefficient of piezoelectric ceramic materials has isotropy in the plane. This characteristic leads to the formation of charge distributions with opposite polarities on the surface of the piezoelectric element when the structure is subjected to stress with alternating directions. Specifically, under the action of bidirectional strain coupling, the heteropolar charges generated in different regions of the piezoelectric material will form a current loop through the surface electrodes, resulting in a charge neutralization phenomenon. This intrinsic charge cancellation mechanism directly leads to a significant attenuation of the effective output charge quantity. At the same time, the stress of the traditional cantilever beam is concentrated at the fixed part of the root of the piezoelectric sheet, which has a great impact on the use of the piezoelectric sheet during operation and greatly shortens the working life of the energy harvester. Summary of the Invention

[0004] The present invention provides a piezoelectric energy harvesting device based on a negative Poisson's ratio structure, which solves the problem that the stress of the traditional cantilever beam is concentrated at the fixed part of the root of the piezoelectric sheet, has a great impact on the use of the piezoelectric sheet during operation, and greatly shortens the working life of the energy harvester.

[0005] To achieve the above object, the present invention provides the following technical solutions: A piezoelectric energy harvesting device based on a negative Poisson's ratio structure, comprising a negative Poisson's ratio structure beam. The negative Poisson's ratio structure beam is a trapezoidal beam with a linearly increasing cross-sectional area from the front end to the root. Negative Poisson's ratio structure holes are provided on the surface of the negative Poisson's ratio structure beam. An epoxy resin layer is bonded to the top of the negative Poisson's ratio structure holes. The epoxy resin layer is conformally combined with the negative Poisson's ratio structure holes. A piezoelectric sheet is bonded to the top of the epoxy resin layer. A mass block is fixed at the front end of the negative Poisson's ratio structure beam, and a fixed base is provided at the root of the negative Poisson's ratio structure beam.

[0006] Preferably, two electrode layers are provided on the upper and lower surfaces of the piezoelectric sheet, namely an electrode surface and a ground plane.

[0007] Preferably, the electrode surface is connected to the positive electrode for output, and the ground plane is grounded to output signals.

[0008] Preferably, the piezoelectric sheet is in a vibration mode that expands and contracts along the length direction or a vibration mode that deforms along the shear direction.

[0009] Preferably, the negative Poisson's ratio structure holes are uniformly distributed on the surface of the negative Poisson's ratio structure beam.

[0010] Preferably, the negative Poisson's ratio structure holes are structure holes that will synchronously expand and contract in the width direction when expanding and contracting in the length direction.

[0011] Preferably, the negative Poisson's ratio structure beam and the fixed base are fixed by fixing bolts.

[0012] Preferably, the piezoelectric sheet material includes lead zirconate titanate piezoelectric ceramics, bismuth scandate-lead titanate piezoelectric ceramics, barium titanate piezoelectric ceramics, potassium sodium niobate piezoelectric ceramics, lead magnesium niobate-lead titanate piezoelectric single crystals, lead zinc niobate-lead titanate piezoelectric single crystals, and piezoelectric fiber composites.

[0013] Preferably, the negative Poisson's ratio structure beam material includes resin, rubber, plastic, nylon, polylactic acid or metal.

[0014] Preferably, the mass block and the fixed base are made of aluminum alloy, brass, cast iron or stainless steel.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a piezoelectric energy harvesting device based on a negative Poisson's ratio structure, a negative Poisson's ratio structural hole is arranged on the surface of a negative Poisson's ratio structural beam, an epoxy resin layer is bonded to the top of the negative Poisson's ratio structural hole, the epoxy resin layer is conformally combined with the negative Poisson's ratio structural hole, a piezoelectric sheet is bonded to the top of the epoxy resin layer, a mass block is fixed to the front end of the negative Poisson's ratio structural beam, a fixed base is provided at the root of the negative Poisson's ratio structural beam, and the negative Poisson's ratio structural holes are distributed on the surface of the beam, which can drive the piezoelectric sheet to synchronously extend or contract in the length and width directions, greatly reducing the generation and offset of heterogeneous charges on the electrode surface of the piezoelectric sheet, and further improving the performance of the energy collector. The negative Poisson's ratio structural beam is a trapezoidal beam with a linearly increasing cross-sectional area from the front end to the root. Compared with the traditional cantilever beam type energy collector, the stress will not be concentrated on the root of the cantilever beam, but the stress will be distributed to the entire piezoelectric sheet position, so that the piezoelectric sheet is more evenly stressed and the service life of the energy collector is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a schematic diagram of the assembly of a piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to the present invention.

[0017] FIG2 is a schematic diagram of the structure of a piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to the present invention.

[0018] FIG. 3 is a schematic diagram showing an example of a negative Poisson's ratio structural hole according to the present invention.

[0019] FIG. 4 is a schematic diagram of a vibration mode of a piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to the present invention.

[0020] Figure 5 It is a schematic diagram of the expanded structure of the negative Poisson's ratio structural pore structure of the present invention.

[0021] Figure 6 It is a schematic diagram of the structure of the matrix form energy collection of the present invention.

[0022] Among them, 101 is a mass block, 102 is a negative Poisson's ratio structural beam, 103 is a piezoelectric sheet, 104 is an epoxy resin layer, 105 is a fixing bolt, 106 is a fixing base, 201 is an electrode surface, and 202 is a grounding surface. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Accordingly, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0025] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0026] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements.

[0027] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] As Figure 1 shown, the present invention provides a piezoelectric energy harvesting device based on a negative Poisson's ratio structure, including a negative Poisson's ratio structure beam 102. The negative Poisson's ratio structure beam 102 is a trapezoidal beam with a linearly increasing cross-sectional area from the front end to the root. Negative Poisson's ratio structure holes are provided on the surface of the negative Poisson's ratio structure beam 102. An epoxy resin layer 104 is bonded to the top of the negative Poisson's ratio structure holes. The epoxy resin layer 104 is conformally combined with the negative Poisson's ratio structure holes. A piezoelectric sheet 103 is bonded to the top of the epoxy resin layer 104. A mass block 101 is fixed at the front end of the negative Poisson's ratio structure beam 102, and a fixed base 106 is provided at the root of the negative Poisson's ratio structure beam 102.

[0029] The negative Poisson's ratio structural beam 102 is a trapezoidal variable cross-sectional area beam, whose cross-sectional area gradually linearly increases as it moves away from the front end. Negative Poisson's ratio holes are evenly distributed on the surface, which can distribute the concentrated stress at the root of the beam to the piezoelectric sheet 103, further enhancing the energy harvesting output performance of the piezoelectric sheet 103. The negative Poisson's ratio structural beam 102 is connected to the end of the fixed base 106 through the fixing bolt 105.

[0030] The materials of the piezoelectric sheet 103 include but are not limited to lead zirconate titanate piezoelectric ceramics, bismuth scandate-lead titanate piezoelectric ceramics, barium titanate piezoelectric ceramics, potassium sodium niobate piezoelectric ceramics, as well as lead magnesium niobate-lead titanate piezoelectric single crystals, lead zinc niobate-lead titanate piezoelectric single crystals, and piezoelectric fiber composite materials, etc.

[0031] The materials of the negative Poisson's ratio structural beam 102 include but are not limited to resin, rubber, plastic, nylon, polylactic acid, metal, etc.

[0032] The mass block 101, the fixing bolt 105, and the fixed base 106 include but are not limited to materials such as aluminum alloy, brass, cast iron, and stainless steel.

[0033] The energy harvester can work in the form of a multi-unit matrix, which contains multiple independent negative Poisson's ratio structural energy harvesters. The working performance of the entire matrix can be adjusted according to actual service requirements, featuring high-efficiency integration, which is particularly suitable for environments with narrow working spaces. At the same time, the later expansion of the module matrix and maintenance and upgrade are also very convenient.

[0034] As Figure 2 shown, two electrode layers are provided on the upper and lower surfaces of the piezoelectric sheet 103, namely the electrode surface 201 and the ground surface 202. The piezoelectric sheet 103 is in a vibration mode of longitudinal expansion and contraction or a vibration mode of deformation in the shear direction. A structural schematic diagram of the negative Poisson's ratio structure provided in this embodiment is as Figure 3 shown, which is a double-arrow-shaped structure.

[0035] When the energy harvester is excited by vibration, it will generate a vibration mode as Figure 4 shown, transfer the externally excited vibration received to the piezoelectric sheet 103, causing it to generate longitudinal expansion and contraction deformation and generating charges on the electrode surface 201 and the ground surface 202.

[0036] The negative Poisson's ratio structural holes are not limited to a certain structure, but refer to all structural holes with a negative Poisson's ratio and a dilatational effect, that is, structures that will synchronously expand and contract in the width direction when expanding and contracting in the length direction. The extended structure of the negative Poisson's ratio structure of the energy harvester is as Figure 5As shown. From left to right, there are concave hexagonal, dumbbell-shaped, rotated square, star-shaped concave Poisson's ratio structures. These and other negative Poisson's ratio structures mentioned in the present invention can be applied to the energy collector to prevent the piezoelectric sheet 103 from generating heterogeneous charges, and can be designed to meet different service requirements according to the characteristics of different negative Poisson's ratio structures.

[0037] Energy harvester matrix energy harvesting specific structure such as Figure 6 As shown. The multi-unit matrix form includes multiple independent energy collectors, each of which performs energy collection according to different external vibration excitations. Based on the small volume advantage of the negative Poisson's ratio structure, the space occupied by the independent polymer-based energy collector is significantly reduced, making it more suitable for integrated energy collection in the form of a matrix. In addition, this matrix form design can be modularly replaced and expanded, making the actual work scope of application wider.

[0038] The energy harvesting performance of the energy harvester under vibration excitation will be described in detail in the following two implementation cases.

[0039] Embodiment 1 This embodiment has built an experimental environment for testing the energy collection performance of vibration excitation. The experimental platform consists of a signal generator, a power amplifier, a vibration table, a vibration sensor, a charge amplifier, an oscilloscope, a variable resistance box and an energy collector sample. First, set the parameters of the signal generator and adjust the output signal of the power amplifier. The power amplifier is connected to the vibration table to drive the vibration table to output the simple harmonic vibration signal set by the signal generator. Query relevant information to determine the vibration frequency and acceleration of each vibration source in the Internet of Things. After that, the signal generator is used to perform a sweep test in the approximate range of the vibration frequency to find the resonant frequency of the energy collector sample itself. Thereafter, continue to use the power amplifier to drive the vibration platform to output a simple harmonic signal, fasten the vibration sensor on the surface of the vibration table, and amplify the sensor signal with a charge amplifier. The amplified signal is observed with an oscilloscope, and the conversion between acceleration and sensor voltage can be calculated to obtain the magnitude of the real-time acceleration output by the vibration table. The root of the energy collector is clamped on the top of the fixed base 106 by the fixing bolt 105, and then the fixed base 106 is fastened to the surface of the vibration table. The positive electrode surface 201 of the piezoelectric sheet 103 and the grounding surface 202 are connected with the wire using conductive silver paste. At the same time, the other end of the wire is connected to the oscilloscope, and the frequency, size, etc. of the electrical signal collected by the energy collector in the vibration field can be observed from the oscilloscope. Finally, keep the acceleration unchanged and test the peak-to-peak value of the output voltage corresponding to the energy collector at different frequencies. Keep the resonant frequency unchanged and use the variable resistance box to test the impedance of the energy collector and the energy collection power density.

[0040] The specific operation is as follows: starting from the minimum input frequency, observe the peak-to-peak value of the voltage output by the energy harvester every 1 Hz, and determine the approximate range of the resonant frequency based on the size. Then, observe again every 0.1 Hz between the two adjacent frequencies where the resonant frequency is most likely to appear, and finally take the frequency at which the voltage peak appears as the resonant frequency. By arranging the observed data, the relationship between the peak-to-peak value of the output voltage and the input frequency of the energy harvester based on the negative Poisson's ratio structure under vibration excitation can be obtained. Then, keeping the resonant frequency and the size of the external excitation vibration acceleration unchanged, the variable resistance box and the oscilloscope are connected in parallel. Scan the parallel resistors from small to large to measure the peak-to-peak value of the voltage corresponding to each resistor. According to the size of the piezoelectric sheet 103, the power density corresponding to each resistor can be calculated, and the impedance appears at the maximum power density. By arranging the above data, the relationship between the output power and impedance of the energy harvester based on the negative Poisson's ratio structure under vibration excitation can be formed. Embodiment 2 This embodiment has built a test environment for the impact of different structures on the performance of the energy collector. First, the stress distribution and deformation of the traditional rectangular cantilever beam, the rectangular negative Poisson's ratio structure cantilever beam and the trapezoidal negative Poisson's ratio structure beam 102 are simulated using simulation software. It is found that when the rectangular negative Poisson's ratio structure cantilever beam and the trapezoidal negative Poisson's ratio structure beam 102 undergo expansion and contraction deformation in the length direction, synchronous deformation will also occur in the width direction, while the traditional rectangular cantilever beam undergoes expansion and contraction changes in the width direction when the expansion and contraction changes in the length direction. And the average degree of stress distribution of the trapezoidal negative Poisson's ratio structure beam 102 is higher than that of the traditional rectangular cantilever beam and the rectangular negative Poisson's ratio structure cantilever beam.

[0041] Then, control samples were prepared, namely, conventional rectangular cantilever beam samples, rectangular negative Poisson's ratio cantilever beam samples, and trapezoidal negative Poisson's ratio structure beam samples 102. Mass blocks 101 and piezoelectric sheets 103 of the same material and size were fastened to the surfaces of the three samples, and performance tests were performed on the three samples.

[0042] Similar to Example 1, the relationship between the peak-to-peak voltage and frequency of the three samples under vibration excitation and the relationship between the output power and impedance of the energy harvester based on the negative Poisson's ratio structure under external magnetic field excitation are formed. It is found that the peak-to-peak voltage and output power of the trapezoidal negative Poisson's ratio structural beam 102 in the resonant state are higher than those of the other two samples.

[0043] In summary, it can be seen that the energy collector based on the negative Poisson's ratio structure proposed in the present invention combines the tensile expansion effect of the negative Poisson's ratio structure to reduce the generation of heterogeneous charges on the electrode surface 201; adopts a trapezoidal and open hole design to distribute the stress on the piezoelectric sheet 103, effectively increasing the output performance of the energy collector and broadening the application scenarios of the energy collector.

[0044] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Under the inspiration of the specification, those of ordinary skill in the art can also make many forms without departing from the scope protected by the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A piezoelectric energy harvesting device based on a negative Poisson's ratio structure, characterized in that It includes a negative Poisson's ratio structural beam (102). The negative Poisson's ratio structural beam (102) is a trapezoidal beam with a linearly increasing cross-sectional area from the front end to the root. Negative Poisson's ratio structural holes are provided on the surface of the negative Poisson's ratio structural beam (102). An epoxy resin layer (104) is bonded to the top of the negative Poisson's ratio structural holes. The epoxy resin layer (104) is conformally combined with the negative Poisson's ratio structural holes. A piezoelectric sheet (103) is bonded to the top of the epoxy resin layer (104). A mass block (101) is fixed at the front end of the negative Poisson's ratio structural beam (102), and a fixed base (106) is provided at the root of the negative Poisson's ratio structural beam (102).

2. The piezoelectric energy harvesting device based on the negative Poisson's ratio structure according to claim 1, wherein, Two electrode layers are provided on the upper and lower surfaces of the piezoelectric sheet (103), namely an electrode surface (201) and a ground plane (202).

3. The piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, wherein The electrode surface (201) is connected to the positive output, and the ground plane (202) is grounded to output a signal.

4. A piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, characterized in that The piezoelectric sheet (103) is in a vibration mode of expanding and contracting along the length direction or a vibration mode of deforming along the shear direction.

5. A piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, characterized in that, The negative Poisson's ratio structural holes are uniformly distributed on the surface of the negative Poisson's ratio structural beam (102).

6. The piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, wherein The negative Poisson's ratio structural holes are structural holes that will synchronously expand and contract in the width direction when expanding and contracting in the length direction.

7. A piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, characterized in that, The negative Poisson's ratio structural beam (102) and the fixed base (106) are fixed by a fixing bolt (105).

8. A piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, characterized in that, The material of the piezoelectric sheet (103) includes lead zirconate titanate piezoelectric ceramics, bismuth scandate-lead titanate piezoelectric ceramics, barium titanate piezoelectric ceramics, potassium sodium niobate piezoelectric ceramics, lead magnesium niobate-lead titanate piezoelectric single crystals, lead zinc niobate-lead titanate piezoelectric single crystals, and piezoelectric fiber composites.

9. A piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, characterized in that, The material of the negative Poisson's ratio structural beam (102) includes resin, rubber, plastic, nylon, polylactic acid, or metal.

10. A piezoelectric energy harvesting device based on a negative Poisson's ratio structure according to claim 1, characterized in that, The materials of the mass block (101) and the fixed base (106) include aluminum alloy, brass, cast iron, or stainless steel.

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