An electromagnetic double-degree-of-freedom vibration energy harvester based on a planar spring

Abstract

The present invention discloses an electromagnetic double-degree-of-freedom vibration energy harvester based on a planar spring, which includes a cover, a housing, a magnetic induction power generation module, and an excitation module; the housing is a hollow cylinder, with internal threads provided at both ends, and the openings at the upper and lower ends are the same size as the diameter of the planar spring. The magnetic induction module is placed at the top of the housing, and the excitation module is placed at the bottom of the housing. The two ends of the cylindrical housing are hermetically sealed by two identical covers with threads. The present invention overcomes the drawback that the output performance of a single-degree-of-freedom harvester drops sharply when the external excitation frequency deviates from the resonance frequency, and is applicable to vibration environments with a wide frequency range.

Description

Technical Field

[0001] The present invention belongs to the technical field of self - power generation, and specifically relates to an electromagnetic dual - degree - of - freedom vibration energy harvester based on a planar spring. Background Art

[0002] In the past few decades, with the rapid development of wireless sensor networks, the number of sensor nodes has increased exponentially, and people's requirements for the reliability and durability of sensor node power supply are also increasing day by day. Traditional batteries have problems such as environmental impact, limited battery life, and limited capacity, which have led many researchers to turn their research perspectives to obtaining energy from the surrounding environment where the sensor nodes are located, enabling the sensor nodes to achieve self - power supply, thereby greatly improving the service life of the entire wireless sensor network and significantly reducing the system maintenance cost.

[0003] The ways to collect energy from the surrounding environment include solar energy, thermal energy, vibration energy, etc. Compared with other environmental energies, vibration energy is more common in industry, the human body, and transportation. There are mainly three ways to collect vibration energy: electromagnetic, electrostatic, and piezoelectric. Compared with the other two vibration energy collection methods, the electromagnetic method has the advantages of simple structure and higher output power. Traditional electromagnetic vibration energy harvesters usually have a single resonance frequency, and when the external excitation frequency is equal to its resonance frequency, the maximum displacement can be achieved, and the maximum collection power can be realized. However, when the external excitation frequency deviates from the resonance frequency, the collected power drops sharply. The actual vibration in the environment always has a wide dynamic range. How to be applicable to complex vibration environments, how to improve energy collection efficiency, and how to eliminate the friction of the internal structure of the harvester during vibration have become technical difficulties in self - power supply. Summary of the Invention

[0004] In view of the above problems, the present invention provides a design of an electromagnetic dual - degree - of - freedom vibration energy harvester based on a planar spring. This harvester can overcome the problem that traditional electromagnetic single - degree - of - freedom vibration energy harvesters cannot efficiently collect vibration energy in complex and variable vibration environments, can effectively collect energy in a wider frequency range, and can also make the assembly of the harvester more convenient.

[0005] To achieve the above object, the present invention adopts the following technical solution: An electromagnetic dual - degree - of - freedom vibration energy harvester based on a planar spring, comprising a lid, a housing, a magnetic induction power generation module, and an excitation module; the housing is a hollow cylinder, with internal threads provided at both ends. The openings at the upper and lower ends are the same size as the diameter of the planar spring. The magnetic induction module is placed on the top of the housing, and the excitation module is placed at the bottom of the housing. The two ends of the cylindrical housing are hermetically sealed with two identical lids by threading.

[0006] The described magnetic induction power generation module includes: an upper bolt, an upper flat spring, a hot-melt nut, a winding bracket, and a coil winding. The hot-melt nut is embedded in the resin material of the winding bracket; the coil winding is wound in the groove of the winding bracket; the upper bolt passes through the central circular hole of the upper flat spring and is screwed into the hot-melt nut in the winding bracket, and the upper flat spring is fixed at the bottom of the internal thread at the upper end of the housing. The described excitation module includes: a nut, an upper magnet, a ferromagnetic gasket, a lower magnet, a magnet bracket, a lower flat spring, and a lower bolt. The upper magnet and the lower magnet are annular magnets of the same size and opposite polarities; a ferromagnetic gasket is used to adsorb the two annular magnets together between the two annular magnets to form an upper magnet-ferromagnetic gasket-lower magnet combination; the magnet bracket passes through the upper magnet-ferromagnetic gasket-lower magnet combination, and the central through-hole of the magnet bracket is aligned with the central circular hole of the lower flat spring. The lower bolt passes through the central circular hole of the lower flat spring and the central through-hole of the magnet bracket, and the nut is used to fix the excitation module.

[0007] Preferably, the spring used is a flat spring.

[0008] The material used for the flat spring is 65Si2Mn. The upper flat spring consists of four serpentine sectors, and the lower flat spring consists of three serpentine sectors.

[0009] The material used for the winding bracket is resin. The lower part of the winding bracket is a groove, the middle part is a hollow cylinder, and the top is a hollow cylinder with a diameter smaller than that of the middle part. The inner diameter of the winding bracket is larger than the diameter of the magnet, which is beneficial to placing the coil winding with a very small distance from the magnet to increase the magnetic induction intensity in the coil winding, so that the present invention can obtain a larger induced voltage;

[0010] Preferably, the magnet bracket is used to fix the upper magnet-ferromagnetic gasket-lower magnet combination on the lower flat spring. The bottom of the magnet bracket is a hollow cylinder to prevent the excitation module from colliding and rubbing with the lower flat spring during vibration. There is a circular through-hole in the middle of the magnet bracket for passing the bolt.

[0011] Preferably, the housing is a hollow cylinder made by cutting and setting internal threads at both ends. The openings at the upper and lower ends are the same size as the diameter of the flat spring, which is beneficial to fixing the flat spring and preventing the flat spring from having a lateral displacement. There is a small hole in the middle of the housing through which the coil can lead out the collected energy for the use of the subsequent stage. The lid can be screwed into the housing to fix the flat spring and prevent the flat spring from having a longitudinal displacement.

[0012] The present invention uses Faraday's law of electromagnetic induction. After being externally excited, the device will generate forced vibration. The permanent magnet and the coil winding move relative to each other, and the magnetic flux in the coil winding also begins to change accordingly, thereby generating an induced voltage in the coil winding. According to the principle, the greater the amplitude of the relative motion, the greater the induced voltage generated. A coil winding with a very small distance from the permanent magnet can be placed inside the structure to increase the magnetic induction intensity in the coil winding, so that the present invention can obtain a relatively large induced voltage.

[0013] The structure of the present invention is simple and easy to assemble. It only requires core components such as planar springs, coil windings, winding brackets, permanent magnets, and ferromagnetic gaskets, and is suitable for vibration energy harvesting in a wide frequency range.

[0014] Compared with other electromagnetic collectors, the present invention can adjust the two resonance frequencies of the double-degree-of-freedom collector by changing the stiffness of the upper and lower planar springs, and apply it to different scenarios to obtain the best output characteristics. Secondly, the components of the collector can all be manufactured according to 3D printing, which reduces the manufacturing cost of the device and is easy to mass-produce.

[0015] The beneficial effects of the present invention are:

[0016] 1. When the magnetic induction power generation module and the excitation module are externally excited, they have their respective resonance angular frequencies ω1 and ω2, overcoming the disadvantage that the output performance of a single-degree-of-freedom collector drops sharply when the external excitation frequency deviates from the resonance frequency, and is suitable for vibration environments in a wide frequency range.

[0017] 2. The excitation module composed of an upper magnet - ferromagnetic gasket - lower magnet is used. The mutually repulsive magnets are attached together, which is beneficial to weakening the axial magnetic field intensity and increasing the longitudinal magnetic field intensity. The ferromagnetic gasket in the middle eliminates the repulsive force between the magnets and can also increase the radial magnetic induction intensity, thereby improving the output performance of the collector.

[0018] 3. The planar spring structure ensures that the internal moving magnets and coils only move axially, avoiding collisions and frictions between internal structures. Brief Description of the Drawings

[0019] Figure 1 is an exploded schematic view of the present invention;

[0020] Figure 2 is a sectional view of the present invention;

[0021] Figure 3 is a top view of the upper planar spring;

[0022] Figure 4 is a top view of the lower planar spring;

[0023] Figure 5 is a 3D view of the planar spring;

[0024] Figure 6 Side view of the magnetic induction power generation module;

[0025] Figure 7 Side view of the winding bracket;

[0026] Figure 8 Side view of the excitation module;

[0027] Figure 9 Side view of the magnet bracket;

[0028] Figure 10 Schematic diagram of the upper magnet - ferromagnetic gasket - lower magnet combination;

[0029] Figure 11 Schematic diagram of the collector housing;

[0030] Figure 12 Schematic diagram of the collector lid;

[0031] Figure 13 Output voltage waveform diagram of the present invention. Detailed implementation manners

[0032] The following describes in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0033] As Figure 1 and Figure 2 shown, an electromagnetic double - degree - of - freedom vibration energy harvester based on a planar spring includes a lid 1, a housing 2, a magnetic induction power generation module, and an excitation module; the housing 2 is a hollow cylinder, with internal threads provided at both ends, and the openings at the upper and lower ends have the same diameter as the planar spring. The magnetic induction module is placed on the top of the housing 2, the excitation module is placed at the bottom of the housing 2, and the two ends of the cylindrical housing 2 are hermetically sealed by two identical lids 1 through threads.

[0034] The described magnetic induction power generation module includes: an upper bolt 3, an upper flat spring 4, a hot-melt nut 5, a winding bracket 6, and a coil winding 7. The hot-melt nut 5 is embedded in the resin material-made winding bracket 6; the coil winding 7 is wound in the groove of the winding bracket 6, with a total of 2500 turns; the upper bolt 3 passes through the central circular hole of the upper flat spring 4 and is screwed into the hot-melt nut 5 in the winding bracket 6, and the upper flat spring 4 is fixed at the bottom of the internal thread at the upper end of the housing 2. The described excitation module includes: a nut 8, an upper magnet 9, a ferromagnetic gasket 10, a lower magnet 11, a magnet bracket 12, a lower flat spring 13, and a lower bolt 14. The upper magnet 9 and the lower magnet 11 are annular magnets with an inner diameter of 10 mm, an outer diameter of 30 mm, a thickness of 10 mm and opposite polarities; a ferromagnetic gasket with an inner diameter of 10 mm, an outer diameter of 30 mm, and a thickness of 6 mm is used to adsorb the two annular magnets together in the middle to form an upper magnet 9-ferromagnetic gasket 10-lower magnet 11 combination; the magnet bracket 12 passes through the upper magnet 9-ferromagnetic gasket 10-lower magnet 11 combination, and the central through hole of the magnet bracket is aligned with the central circular hole of the lower flat spring 13. The lower bolt 14 is passed through the central circular hole of the lower flat spring 13 and the central through hole of the magnet bracket 12, and the nut 8 is used to fix the excitation module.

[0035] Preferably, the spring used is a flat spring.

[0036] The material used for the flat spring is 65Si2Mn. The upper flat spring 4 consists of three serpentine sectors, and the lower flat spring 13 consists of four serpentine sectors. The diameters of the two flat springs are 56 mm and the thickness is 0.8 mm.

[0037] The material used for the winding bracket 6 is resin. The lower part of the winding bracket 6 is a groove with an inner diameter of 35 mm, an outer diameter of 49 mm, and a height of 16 mm. The middle part is a hollow cylinder with a diameter of 38 mm and a height of 25 mm. The top is a hollow cylinder with an inner diameter of 8 mm, an outer diameter of 14 mm, and a height of 4 mm. The inner diameter of the winding bracket 6 is larger than the diameter of the magnet, which is beneficial to placing the coil winding 7 with a very small distance from the magnet to increase the magnetic induction intensity in the coil winding 7, so that the present invention can obtain a larger induced voltage;

[0038] Preferably, the magnet bracket 12 is used to fix the upper magnet 9-ferromagnetic gasket 10-lower magnet 11 combination on the lower flat spring 13. The bottom of the magnet bracket 12 is a hollow cylinder with an inner diameter of 6 mm, an outer diameter of 14 mm, and a height of 4 mm, to prevent the excitation module from colliding and rubbing with the lower flat spring 13 during vibration. There is a circular through hole in the middle of the magnet bracket for passing through the lower bolt 14.

[0039] Preferably, the housing 2 is made by cutting off hollow cylinders with an inner diameter of 54 mm, an outer diameter of 56 mm, and a height of 12 mm at both ends from a hollow cylinder with an inner diameter of 54 mm, an outer diameter of 64 mm, and a height of 81 mm, and then setting internal threads. The openings at the upper and lower ends have the same diameter as the flat spring, which is conducive to fixing the flat spring and preventing the flat spring from undergoing lateral displacement. There are small holes in the middle of the housing 2 through which the coil can be led out to supply the collected energy for the subsequent stage. The lid 1 can be screwed into the housing 2 to fix the flat spring and prevent the flat spring from undergoing longitudinal displacement.

[0040] Embodiment:

[0041] An electromagnetic double-degree-of-freedom vibration energy harvester based on a flat spring, as Figure 1 shown, includes a lid 1, a housing 2, a magnetic induction power generation module (including an upper bolt 3, an upper flat spring 4, a hot-melt nut 5, a winding bracket 6, and a coil winding 7), and an excitation module (including a nut 8, an upper magnet 9, a ferromagnetic gasket 10, a lower magnet 11, a magnet bracket 12, a lower flat spring 13, and a lower bolt 14); the magnetic induction power generation module is fixed to the upper flat spring 4 through the embedded hot-melt nut 5 and the upper bolt 3. The upper flat spring 4 is placed in a card slot of the same size in the housing 2 and fixed around it, and is fixed up and down by using the lid 1; the excitation module uses the magnet bracket 12, the nut 8, and the lower bolt 14 to combine and fix the upper magnet 9 - ferromagnetic gasket 10 - lower magnet 11 to the lower flat spring 13. The lower flat spring 13 is placed in a card slot of the same size in the housing 2 and fixed around it, and is fixed up and down by using the lid 1.

[0042] In this embodiment, as Figure 3 、 Figure 4 and Figure 5 shown, the flat spring is made by laser cutting 65Si2Mn. The upper flat spring 4 is designed as four serpentine cantilever beams, and the lower flat spring 13 is designed as three serpentine cantilever beams. By changing parameters such as the number, width, and length of the cantilever beams, the stiffness of the flat spring can be changed. This kind of flat spring structure can ensure the axial movement of the moving block and avoid the moving blocks from colliding and rubbing against each other.

[0043] In this embodiment, as Figure 6 、 Figure 7 and Figure 8 shown, the size of the winding bracket 6 is slightly larger than the diameter of the magnet block. When the magnetic induction power generation module and the excitation module move relative to each other, the coil winding 7 can be as close to the magnet as possible, increasing the magnetic flux density gradient, thereby improving the output performance. The winding bracket 6 is made by 3D printing with resin material, can embed the hot-melt nut 5, and is fixed to the upper flat spring 4 through the upper bolt 3.

[0044] In this embodiment, as Figure 9 and Figure 10As shown, the combination of the upper magnet 9 - ferromagnetic gasket 10 - lower magnet 11 consists of two magnets with opposite polarities and a ferromagnetic gasket. The combination of permanent magnets with opposite polarities helps to weaken the axial magnetic field intensity and increase the longitudinal magnetic field intensity. The ferromagnetic gasket is placed between the two permanent magnets, which helps to eliminate the repulsive force between them, increase the attractive force between them, and can also increase the radial magnetic induction intensity, thereby improving the output performance of the collector.

[0045] In this embodiment, as Figure 11 and Figure 12 shown, the size of the card slot on the upper part of the housing 2 is the same as the diameter of the upper planar spring 4. Place the magnetic induction power generation module in the card slot and fix it up and down with the cover 1. The size of the card slot on the lower part of the housing 2 is the same as the diameter of the lower planar spring 13. Place the excitation module in the card slot and fix it up and down with the cover 1.

[0046] The working principle and process are as follows: The upper planar spring 4, winding support 6, and coil winding 7 are the main components of the magnetic induction power generation module. According to the expression:

[0047]

[0048] The total weight of the winding support 6 and the coil winding 7 is m1, and the elastic coefficient of the upper planar spring 4 is k1. When subjected to external excitation, the resonant angular frequency of the magnetic induction power generation module is ω1. The lower planar spring 13, upper magnet 9, ferromagnetic gasket 10, lower magnet 11, and magnet support 12 are the main components of the excitation module. According to the above expression, the total weight of the upper magnet 9 - ferromagnetic gasket 10 - lower magnet 11 combination is m2, and the elastic coefficient of the lower planar spring 13 is k2. When subjected to external excitation, the resonant angular frequency of the excitation module is ω2. The resonant angular frequencies ω1 and ω2 can be adjusted by adjusting the elastic coefficients k of the upper planar spring 4 and the lower planar spring 13 according to the application environment, so as to optimize the performance of the electromagnetic double - degree - of - freedom vibration energy harvester.

[0049] The specific implementation steps of the whole structure are as follows:

[0050] Step 1: Use 3D printing technology to make the cover 1, housing 2, winding support 6, and magnet support 12.

[0051] Step 2: Use laser cutting technology to make the upper planar spring 4 and the lower planar spring 13 with different stiffnesses.

[0052] Step 3: Purchase enameled wire and wind it into a coil winding 7 on the winding support.

[0053] Step 4: Purchase the upper magnet 9, ferromagnetic gasket 10, lower magnet 11, heat - melting nuts 5, upper bolts 3, lower bolts 14, and nuts 8.

[0054] Step Five: System Assembly.

[0055] Figure 13 It is the output voltage curve of the electromagnetic double-degree-of-freedom vibration energy harvester varying with the external excitation frequency. When the external excitation frequency is equal to the two resonance frequencies ω1 and ω2 of the harvester, the output voltage of the harvester has two peaks. When the external excitation deviates from the resonance frequency, the harvester still has a high harvesting efficiency. This electromagnetic double-degree-of-freedom vibration energy harvester overcomes the defect that the output performance of a single-degree-of-freedom harvester drops sharply when the external excitation frequency deviates from the resonance frequency, can efficiently harvest vibration energy in a complex and variable vibration environment, and can effectively harvest energy in a wider frequency range.

[0056] As described above, only some specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An electromagnetic double-degree-of-freedom vibration energy harvester based on a plane spring, characterized in that: It comprises a cover (1), a housing (2), a magnetic induction power generation module and an excitation module; The shell (2) is a hollow cylinder with internal threads at both ends. The openings at the upper and lower ends are the same size as the diameter of the plane spring. The magnetic induction module is placed on the top of the shell (2), and the excitation module is placed on the bottom of the shell (2). The two ends of the cylindrical shell (2) are thread-sealed by two identical covers (1). The magnetic induction power generation module comprises: an upper bolt (3), an upper plane spring (4), a hot melt nut (5), a winding support (6) and a coil winding (7); The hot melt nut (5) is embedded in a winding support (6) made of resin material; the coil winding (7) is wound in a groove of the winding support (6); the upper bolt (3) passes through the central circular hole of the upper plane spring (4) and is screwed into the hot melt nut (5) in the winding support (6); the upper plane spring (4) is fixed to the bottom of the internal thread at the upper end of the housing (2); The excitation module comprises: a nut (8), an upper magnet (9), a ferromagnetic gasket (10), a lower magnet (11), a magnet bracket (12), a lower plane spring (13) and a lower bolt (14); the upper magnet (9) and the lower magnet (11) are annular magnets of the same size and opposite polarities; a ferromagnetic gasket is used between the two annular magnets to adsorb the two annular magnets together, and from top to bottom they are the upper magnet (9), the ferromagnetic gasket (10) and the lower magnet (11); the magnet bracket (12) passes through the combination of the upper magnet (9), the ferromagnetic gasket (10) and the lower magnet (11), the central through hole of the magnet bracket is aligned with the central circular hole of the lower plane spring (13), the lower bolt (14) passes through the central circular hole of the lower plane spring (13) and the central through hole of the magnet bracket (12), and the nut (8) is used to fix the excitation module.

2. The electromagnetic double-degree-of-freedom vibration energy harvester based on a plane spring according to claim 1 is characterized in that: The upper plane spring (4) and the lower plane spring (13) are made of 65Si2Mn. The upper plane spring (4) is composed of four serpentine sectors, and the lower plane spring (13) is composed of three serpentine sectors.

3. The electromagnetic double-degree-of-freedom vibration energy harvester based on a plane spring according to claim 2 is characterized in that: The material used for the winding bracket (6) is resin. The lower part of the winding bracket (6) has a groove, the middle part is a hollow cylinder, the top part is a hollow cylinder with a diameter smaller than the middle part, and the inner diameter of the winding bracket (6) is larger than the diameter of the magnet.

4. The electromagnetic double-degree-of-freedom vibration energy harvester based on a plane spring according to claim 3 is characterized in that: The shell (2) has a small hole in the middle, which is used to lead out the coil to obtain the collected energy.

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