Multidirectional low-frequency piezoelectric vibration energy collector

Abstract

A multi-direction low-frequency piezoelectric vibration energy collector comprises a base, a flexible beam, an inertial mass body and a piezoelectric plate. The base is of a cylindrical hollow structure; the inertial mass body is located in the center of the base in a static state; the flexible beam is a sheet which is deformable and has a self-recovery trend during deformation, and the width direction of the flexible beam is along the axial direction of the base; the flexible beam is bent along a fold line in the width direction of the flexible beam and is divided into a piezoelectric flexible beam and an elastic connecting beam which are located on the two sides of the bend, and the included angle between the piezoelectric flexible beam and the elastic connecting beam is smaller than 90 degrees. Wherein the elastic connecting beam is connected with the inertial mass body, and the piezoelectric flexible beam is connected with the edge of the base; and the piezoelectric plate is arranged on the surface of the piezoelectric flexible beam. According to the multi-direction low-frequency piezoelectric vibration energy collector, the inherent frequency of the structure is reduced, the collection efficiency of vibration energy is further improved, and therefore multi-direction and low-frequency vibration energy collection is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration energy collectors, and in particular to a multi-directional low-frequency piezoelectric vibration energy collector. Background Art

[0002] With the rapid development of micro-electromechanical systems (MEMS) technology, various miniaturized, low-power electronic devices continue to emerge, such as wireless sensor network nodes, wearable devices, and implantable medical devices. In many application scenarios, such as remote monitoring and human health monitoring, these devices are often difficult to be powered continuously and effectively through traditional power supply methods. Therefore, it is crucial to find an energy harvesting technology that is self-powered, long-term stable, and suitable for micro-scale.

[0003] Piezoelectric materials have a unique piezoelectric effect, that is, they generate electric charges when subjected to mechanical stress. This property enables piezoelectric materials to convert vibration energy in the environment into electrical energy, providing a continuous energy supply for electronic devices. As early as the 1880s, the Curie brothers discovered the piezoelectric phenomenon, but it was not until recent years that piezoelectric vibration energy harvesting technology has developed rapidly with the continuous advancement of materials science, micromachining technology and electronics. Early piezoelectric vibration energy harvesters had a relatively simple structure and relatively low performance. However, with the continuous deepening of research, various new structural designs and material applications have continued to emerge.

[0004] Vibration energy is ubiquitous in the environment. Most vibrations in the natural environment are low-frequency vibrations. The frequencies of vibrations generated by human activities, ocean waves, large buildings and mechanical equipment are mostly concentrated below 20Hz or even 5Hz. There have always been many difficulties in efficiently collecting low-frequency vibration energy. Summary of the invention

[0005] The purpose of the present invention is to propose a multi-directional low-frequency piezoelectric vibration energy collector to reduce the natural frequency of the structure itself and further improve the collection efficiency of vibration energy, thereby realizing multi-directional, low-frequency vibration energy collection.

[0006] The technical solution adopted by the present invention is: a multi-directional low-frequency piezoelectric vibration energy collector, including a base, a flexible beam, an inertial mass body and a piezoelectric sheet; The base is a hollow structure with a cylindrical appearance; The inertial mass body is located at the center of the base when static; The flexible beam is a thin sheet that is deformable and has a self-recovery tendency when deformed, and its width direction is along the axial direction of the base; the flexible beam is bent along the fold line in its width direction, and is divided into a piezoelectric flexible beam and an elastic connecting beam on both sides of the bend, and the angle between the piezoelectric flexible beam and the elastic connecting beam is less than 90°; The two ends of the flexible beam are respectively fixedly connected to the edge of the base and the inertial mass body, wherein the elastic connecting beam is connected to the inertial mass body, and the piezoelectric flexible beam is connected to the edge of the base; The piezoelectric sheet is arranged on the surface of the piezoelectric flexible beam.

[0007] As a preferred solution, a plurality of flexible beams are distributed in the circumferential direction of the base, and the flexible beams are connected between the edge of the base and the inertial mass body in a manner that both ends of the flexible beams apply static tension to the edge of the base and the inertial mass body respectively when static.

[0008] As a preferred embodiment, the base includes two annular outer rings distributed up and down and with overlapping central axes. The two annular outer rings are fixedly connected by pillars located at the edges of the two rings, and a plurality of piezoelectric flexible beams are fixedly connected to corresponding pillars respectively.

[0009] As a preferred solution, the central axis of the column is parallel to the central axis of the base, and the free end of the piezoelectric flexible beam is centered on the column.

[0010] As a preferred solution, the end face of the inertial mass body is coplanar with the outer end face of the annular outer ring at the same side end.

[0011] As a preferred solution, there are no less than three flexible beams, which are arranged at equal angles along the circumference of the base.

[0012] As a preferred solution, the angle between the piezoelectric flexible beam and the elastic connecting beam is less than 60°.

[0013] As a preferred solution, the length of the piezoelectric flexible beam is smaller than the length of the elastic connecting beam.

[0014] As a preferred solution, the inertial mass body comprises a cylinder, and mass blocks coinciding with the central axis of the cylinder are fixed at both ends of the cylinder, and the diameter of the mass blocks is greater than the diameter of the cylinder.

[0015] As a preferred solution, a disk coinciding with the central axis of the cylinder is fixed at the center of the cylinder, and the disk is fixedly connected to the corresponding end of the flexible beam.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts a flexible parallel mechanism composed of an annular outer ring, an inertial mass body and flexible beams evenly distributed in a cross shape, which can sense the vibration energy from multiple directions in the external environment and transfer it to the piezoelectric flexible beams, triggering the piezoelectric sheet to deform, so that the energy collection device can collect vibration energy in multiple directions. Compared with the energy collection device in the prior art that can only collect energy in a single direction, the energy collection efficiency is effectively improved.

[0017] 2. A piezoelectric sheet is pasted on the piezoelectric flexible beam between the base and the bend. In this way, the axial vibration acceleration of the elastic connecting beam will produce lateral excitation on the piezoelectric flexible beam at the other end of the bend. The piezoelectric flexible beam has a small lateral stiffness, and the bending deformation of the piezoelectric flexible beam is achieved under a small vibration amplitude, thereby causing the piezoelectric sheet attached to the piezoelectric flexible beam to produce a larger deformation, thereby improving the energy collection efficiency.

[0018] 3. By applying axial static pressure to the piezoelectric flexible beam to reduce its natural frequency, the bending angle is an acute angle. The pulling force of the inertial mass body and the annular outer ring on the flexible beam will have an axial static pressure on the piezoelectric flexible beam. The greater the axial static pressure, the lower the natural frequency, thereby realizing the collection of low-frequency vibration energy that is widely present in nature.

[0019] 4. Due to the deformation recovery of the flexible beam, its two ends exert static tension on the edge of the base and the inertial mass body respectively in static state; therefore, after assembly, the elastic connecting beam increases the axial static pressure, and the piezoelectric flexible beam has a lower natural frequency when subjected to axial static pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is an overall axial side schematic diagram of the present invention; Figure 2 It is a schematic diagram of an overall top view of the present invention; Figure 3 is a schematic diagram of a flexible beam in the present invention; Figure 4 is a schematic diagram of the base in the present invention; Figure 5 is a schematic diagram of an inertial mass body in the present invention; Figure 6 It is a half-section schematic diagram of the present invention in a top view.

[0022] Reference numerals: 1. base, 101. annular outer ring, 102. column; 2. Inertial mass body, 201, cylinder, 202, mass block, 203, disk; 3. Flexible beam, 301. Piezoelectric flexible beam, 302. Elastic connecting beam; 4. Piezoelectric film. DETAILED DESCRIPTION

[0023] The present invention is described in detail below by way of exemplary embodiments. However, it should be understood that, without further description, elements, structures and features in one embodiment may also be beneficially combined in other embodiments.

[0024] It should be noted that: unless otherwise defined, the technical terms or scientific terms used in this document shall have the usual meanings understood by people with ordinary skills in the field to which the invention belongs. The words "one", "an" or "the" and the like used in the patent application specification and claims of the present invention do not express quantity restrictions, but indicate the existence of at least one; the words "first", "second" and "third" used in this document shall not be regarded as restrictions on the order of components, but are only used to distinguish different components; words such as "include" or "comprise" and the like indicate that the elements or objects appearing before "include" or "comprise" include the elements or objects listed after "include" or "comprise" and their equivalents, but do not exclude other elements or objects with the same function.

[0025] In order to more clearly describe the specific structure of the multi-directional low-frequency piezoelectric vibration energy harvester, Figure 1-6 Describe this embodiment: like Figure 1 , Figure 2 and Figure 3 As shown, a multi-directional low-frequency piezoelectric vibration energy harvester comprises: The base 1 is a hollow structure with a cylindrical shape; The inertial mass body 2 is located at the center of the base 1 when static; The flexible beam 3 is a thin sheet that is deformable and has a self-restoring tendency when deformed, and its width direction is along the axial direction of the base 1; the flexible beam 3 is bent along the fold line in its width direction, and is divided into a piezoelectric flexible beam 301 and an elastic connecting beam 302 on both sides of the bend, and the angle between the piezoelectric flexible beam 301 and the elastic connecting beam 302 is less than 90°; The two ends of the flexible beam 3 are respectively fixedly connected to the edge of the base 1 and the inertial mass body 2, wherein the elastic connecting beam 302 is connected to the inertial mass body 2, and the piezoelectric flexible beam 301 is connected to the edge of the base 1; The piezoelectric sheet 4 is disposed on the surface of the piezoelectric flexible beam 301 .

[0026] When in use, the inertial mass body 2 receives the vibration acceleration emitted by the external vibration source and generates an inertial force, which is transmitted to the piezoelectric flexible beam 301 through the elastic connecting beam 302, causing the piezoelectric flexible beam 302 to deform at a lower natural frequency, thereby causing the piezoelectric sheet 4 attached to the inner surface and / or outer surface of the piezoelectric flexible beam 301 to deform, thereby converting the environmental vibration energy into electrical energy.

[0027] The piezoelectric sheet 4 is pasted on the piezoelectric flexible beam 301 between the base 1 and the bend, so that the axial vibration acceleration of the elastic connecting beam 302 will produce lateral excitation to the piezoelectric flexible beam 301 at the other end of the bend (the axial direction of the flexible beam refers to its length direction, and the lateral direction is the thickness direction, which is perpendicular to the length direction). The piezoelectric flexible beam 301 has a small lateral stiffness, and the bending deformation of the piezoelectric flexible beam 301 is achieved at a small vibration amplitude, so that the piezoelectric sheet 4 applied to the piezoelectric flexible beam 301 produces a larger deformation, thereby improving the energy collection efficiency.

[0028] See also Figure 1 or Figure 4 Specifically, the base 1 includes two annular outer rings 101 distributed up and down with the central axes coinciding. The two annular outer rings 101 are fixedly connected by pillars 102 located at the edges of the two rings, and a plurality of piezoelectric flexible beams 301 are fixedly connected to the corresponding pillars 102 respectively.

[0029] The central axis of the column 102 is parallel to the central axis of the base 1 , and the free end of the piezoelectric flexible beam 301 is centered on the column 102 .

[0030] See also Figure 5 Specifically, the inertial mass body 2 includes a cylinder 201, and a mass block 202 coinciding with the central axis of the cylinder 201 is fixed at both ends of the cylinder 201, and the diameter of the mass block 202 is larger than the diameter of the cylinder 201. A disk 203 coinciding with the central axis of the cylinder 201 is fixed at the center, and the disk 203 is fixedly connected to the corresponding end of the flexible beam 3.

[0031] The end face of the inertial mass body 2 is coplanar with the outer end face of the annular outer ring 101 at the same side. Specifically, the upper end face of the mass block 202 on the upper side is coplanar with the upper end face of the annular outer ring 101 on the upper side, and the lower end face of the mass block 202 on the lower side is coplanar with the lower end face of the annular outer ring 101 on the lower side.

[0032] There are multiple flexible beams 3 distributed in the circumferential direction of the base 1 . In a specific configuration, it is best to have no less than three flexible beams 3 , which are arranged at equal angles along the circumferential direction of the base 1 .

[0033] In specific configuration, the angle between the piezoelectric flexible beam 301 and the elastic connecting beam 302 is preferably less than 60°, the length of the piezoelectric flexible beam 301 is less than the length of the elastic connecting beam 302 , and the elastic connecting beam 302 can be twice the length of the piezoelectric flexible beam 301 .

[0034] By applying axial static pressure to the piezoelectric flexible beam 301 to reduce its natural frequency, the bending angle is an acute angle, and the pulling force of the inertial mass body 2 and the annular outer ring 101 on the flexible beam 3 will have an axial static pressure in the axial direction of the piezoelectric flexible beam 301. The greater the axial static pressure, the lower the natural frequency, thereby realizing the collection of low-frequency vibration energy that is widely present in nature.

[0035] In the above embodiment, the piezoelectric sheet 4 is specifically a piezoelectric ceramic transducer, and the positive and negative electrodes are welded as the output of the energy collector. The piezoelectric sheet 4 is pasted on at least one side of the piezoelectric flexible beam 301.

[0036] See also Figure 6 There are multiple flexible beams 3 distributed in the circumferential direction of the base 1. The flexible beams 3 are connected between the edge of the base 1 and the inertial mass body 2 in a manner that the two ends of the flexible beams 3 respectively apply static tension to the edge of the base 1 and the inertial mass body 2 in a static state. The two ends of the flexible beams 3 are respectively fixedly connected to the inertial mass body 2 and the column 102 at the center of the base 1 in a static state. The original spacing of the flexible beams 3 before installation is smaller than the spacing between the inertial mass body 2 and the column 102, and the flexible beams 3 are respectively connected along F 1 and F 2 The flexible beam 3 is pulled in the direction to increase the distance between the two ends and then fixed to the inertial mass body 2 and the column 102 respectively; After installation, in static state, the deformation recovery effect of the flexible beam 3 applies static tension to the column 102 and the inertial mass body 2 respectively. On the contrary, the column 102 and the inertial mass body 2 generate two forces F of equal magnitude and opposite direction on the piezoelectric flexible beam 201 and the elastic connecting beam 202 respectively. 1 and F 2 , where F 1 There will be an axial force F in the axial direction of the elastic connecting beam 202. N , F 2 There is an axial force F on the piezoelectric flexible beam 201 L , F N is the axial static pressure (along the length direction of the elastic connecting beam 202), F L The piezoelectric flexible beam 201 has a relatively low natural frequency under the action of the axial static pressure, so that the low-frequency energy widely existing in nature can be collected.

[0037] The parts not described in detail in this embodiment are prior art.

[0038] It should be noted that although the present invention is described by the above embodiments, the present invention may also have other various embodiments. Without departing from the spirit and scope of the present invention, it is obvious that those skilled in the art may make various corresponding changes and deformations to the present invention, but these changes and deformations should all fall within the scope of protection of the appended claims of the present invention and their equivalents.

Claims

1. A multi-directional low-frequency piezoelectric vibration energy collector, characterized in that: It comprises a base (1), a flexible beam (3), an inertial mass body (2) and a piezoelectric sheet (4); The base (1) is a hollow structure with a cylindrical appearance; The inertial mass body (2) is located at the center of the base (1) when static; The flexible beam (3) is a thin sheet that is deformable and has a tendency to self-recover when deformed, and its width direction is along the axial direction of the base (1); the flexible beam (3) is bent along a fold line in its width direction, and is divided into a piezoelectric flexible beam (301) and an elastic connecting beam (302) located on both sides of the bend, and the angle between the piezoelectric flexible beam (301) and the elastic connecting beam (302) is less than 90°; The elastic connecting beam (302) is connected to the inertial mass body (2), and the piezoelectric flexible beam (301) is connected to the edge of the base (1); The piezoelectric sheet (4) is arranged on the surface of the piezoelectric flexible beam (301).

2. A multi-directional low-frequency piezoelectric vibration energy collector according to claim 1, characterized in that: A plurality of the flexible beams (3) are distributed in the circumferential direction of the base (1), and the plurality of flexible beams (3) are connected between the edge of the base (1) and the inertial mass body (2) in a manner such that both ends of the flexible beams (3) respectively apply static pulling forces to the edge of the base (1) and the inertial mass body (2) in a static state.

3. A multi-directional low-frequency piezoelectric vibration energy collector according to claim 2, characterized in that: The base (1) comprises two annular outer rings (101) distributed up and down and with overlapping central axes, the two annular outer rings (101) are fixedly connected via columns (102) located at the edges of the two annular outer rings, and a plurality of piezoelectric flexible beams (301) are respectively fixedly connected to corresponding columns (102).

4. The multi-directional low-frequency piezoelectric vibration energy collector according to claim 3 is characterized in that: The central axis of the column (102) is parallel to the central axis of the base (1), and the free end of the piezoelectric flexible beam (301) is centered on the column (102).

5. The multi-directional low-frequency piezoelectric vibration energy collector according to claim 3 is characterized in that: The end face of the inertial mass body (2) is coplanar with the outer end face of the annular outer ring (101) at the same side end.

6. The multi-directional low-frequency piezoelectric vibration energy collector according to claim 2, characterized in that: There are no less than three flexible beams (3), which are arranged at equal angles along the circumference of the base (1).

7. The multi-directional low-frequency piezoelectric vibration energy collector according to claim 1, characterized in that: The included angle between the piezoelectric flexible beam (301) and the elastic connecting beam (302) is less than 60°.

8. The multi-directional low-frequency piezoelectric vibration energy collector according to claim 1, characterized in that: The length of the piezoelectric flexible beam (301) is shorter than the length of the elastic connecting beam (302).

9. The multi-directional low-frequency piezoelectric vibration energy collector according to claim 1, characterized in that: The inertial mass body (2) comprises a cylinder (201), with mass blocks (202) being fixed at both ends of the cylinder (201) and coinciding with the central axis thereof, and the diameter of the mass block (202) being greater than the diameter of the cylinder (201).

10. The multi-directional low-frequency piezoelectric vibration energy collector according to claim 9, characterized in that: A disk (203) that coincides with the center axis of the cylinder (201) is fixed at the center of the cylinder (201), and the disk (203) is fixedly connected to the corresponding end of the flexible beam (3).

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