CN206041775U - A multi-frequency vibration energy recovery device - Google Patents

Abstract

The utility model belongs to the technical field of vibration energy recovery unit, specific multi -frequency vibration energy recovery unit who converts vibration energy into the electric energy that says so. This recovery unit includes magnetoelectric conversion subtotal energy collecting part, the magnetoelectric conversion part is including shell, extension spring, quality piece, inductance coils, energy collecting part includes the electrical energy storage circuit, the shell is the hollow casing of a rectangle, and inside evenly is provided with a plurality of cavitys, be provided with an extension spring in every cavity, extension spring sets up in the inside of shell, and wherein one end is fixed on the inboard upper portion of shell, and the other end links to each other with the quality piece, inductance coils sets up the outside at the quality piece, there is the permanent magnet quality piece inside, and quality piece and permanent magnet are in the inside vibration of inductance coils. The utility model relates to a can guarantee high efficiency in several kinds of typical vibration frequency of environment, solve present vibration energy and retrieved a structure multi -frequency vibration energy recovery unit to defects such as single frequency sensitivities.

Description

A multi-frequency vibration energy recovery device

technical field

The utility model belongs to the technical field of vibration energy recovery devices, in particular to a multi-frequency vibration energy recovery device which converts vibration energy into electric energy.

Background technique

With the rapid development of modern industry, environmental pollution and energy shortage are two major problems facing countries all over the world. In order to solve the impact of energy crisis on economic development and people's life, scientific and technological workers from various countries began to explore new green energy. Energy recovery refers to the process of obtaining external energy and converting it into usable electrical energy.

In the past few years, portable devices, wireless sensors and MEMS have developed rapidly. These devices or sensor systems are portable or distributed, so they need their own power supply. In most cases, these power sources are conventional batteries, but the battery power and life are limited. For these devices, battery replacement will cause a lot of inconvenience; in addition, batteries contain heavy metals, and improper disposal of waste batteries will cause serious environmental pollution. There is an urgent need for these systems to generate electrical energy for their own use. Although the energy collected in the environment is usually relatively small, with the rapid development of electronic technology, the integration of electronic products is constantly improving while the power consumption is constantly decreasing. enough.

There are mainly the following energy harvesting sources to obtain external energy: solar energy, vibration energy, noise, and temperature gradient. Among them, vibration is a common phenomenon in people's daily life. Because it has a high energy density and a functional density of 100-200 μW/cm3 for a one-year service life, it is undoubtedly the most convenient and most efficient way to recover energy from the vibration of the surrounding environment. way with potential.

At present, there are three main methods of research on vibration energy recovery technology: electrostatic electrostatic, electromagnetic electromagnetic and piezoelectric piezoelectric. The basic principle of the electromagnetic energy recovery device is Faraday's law of electromagnetic induction: when passing through a closed loop When the magnetic flux in the surrounding area changes, an induced electromotive force will be generated in the circuit. This converts the mechanical energy of the ambient vibration into electrical energy. According to the different vibrating parts, the electromagnetic vibration energy recovery device can be divided into three types: moving iron magnet vibration, moving coil coil vibration, and iron ring co-vibration magnet coil vibration.

The electromagnetic vibration power generation device 201210499462.3 developed by Zhejiang University of Technology includes a casing, a vibrator, an induction coil, a yoke and a bracket. The main advantage of this invention is that the multi-tooth structure makes the frequency of the magnetic flux change of the coil much higher than the vibration frequency of the vibrator. Improved power generation efficiency.

Jiangsu University has developed an electromagnetic vibration energy harvester with adjustable power generation 201410016971.5, including energy conversion devices, guide rails, mass blocks and magnets. By turning the knob of the adjustable platform to adjust the distance between the energy conversion device and the passive magnet, the force between the driving magnet and the passive magnet can be adjusted, and the vibration amplitude of the passive magnet can be changed, so as to achieve the purpose of adjusting the power generation. The advantage of the device is that the generating power can be adjusted, which solves the problem of single generating power of most vibration energy harvesters.

An electromagnetic vibration generator 201310444325.4 developed by Hebei University of Technology, the core components are a yoke, a vibration shaft, and a hub. Experiments show that the output voltage peak value of the generator is 6V when the frequency is 10Hz and the amplitude is 10mm.

Based on the above analysis, the vibration pickup mechanism of the existing vibration energy harvesting device only collects the vibration near the natural frequency, and the ability to acquire vibration far away from the natural frequency is weak. Environmental vibration is usually composed of a series of vibration signals with different frequencies. The utility model aims at the defect that the existing vibration energy recovery structure is only sensitive to a single frequency, etc., and provides an energy recovery structure that can make the system have excellent effects under different frequencies, and this case arises from it.

Contents of the invention

The utility model provides a multi-frequency vibration energy recovery device, which can ensure high-efficiency collection of vibration energy in several typical vibration frequencies of the environment, and solves the defects that the existing vibration energy recovery structure is only sensitive to a single frequency.

The technical solution of the utility model is described as follows in conjunction with the accompanying drawings: a multi-frequency vibration energy recovery device, the recovery device includes a magnetoelectric conversion part and an energy collection part; wherein the magnetoelectric conversion part includes a shell 1, a tension spring 2, Mass block 3, inductance coil 4; the energy collection part includes an electric energy storage circuit 5; the shell 1 is a rectangular hollow shell with a plurality of cavities evenly arranged inside; wherein each cavity is provided with A tension spring 2; the tension spring 2 is arranged inside the casing 1, one end of which is fixed on the upper part of the inside of the casing 1, and the other end is connected to the mass block 3; the inductance coil 4 is arranged in the hollow of the casing 1 In the cavity, outside the mass block 3; there is a permanent magnet 6 inside the mass block 3, and the mass block 3 and the permanent magnet 6 vibrate inside the inductance coil 4.

The inductance coil 4 includes an inductance coil bobbin 9, an inductance coil magnetic core 7 and an enameled wire 8; wherein the inductance coil bobbin 9 is fixed inside the cavity with a through hole in the middle; the inductance coil magnetic core 7 is set It is inside the inductor coil frame 9 and is in interference fit with the through hole; the enameled wire 8 is wound on the inductor coil frame 9 .

The beneficial effects of the utility model are:

1. A multi-frequency vibration energy recovery device described in the utility model adopts the method of changing the tension spring parameters of the system and changing the quality of the mass block to control the natural frequency of the system, so that the device can achieve resonance under different typical vibration frequencies of the environment, In order to solve the problem of single operating frequency of existing devices;

2. A multi-frequency vibration energy recovery device described in the utility model can be simplified into a single-degree-of-freedom spring-mass-damping vibration model, the device has a simple structure, and the analysis method is simple, and complex failures are not easy to occur during use;

3. A multi-frequency vibration energy recovery device described in this utility model mainly includes two parts: magnetoelectric conversion and electric energy collection, and the vibration energy collected by the magnetoelectric conversion part is stored in the battery, so as to solve the problem of traditional vibration when the power generation is small. The problem with energy harvesting devices not making MEMS work.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the utility model;

Fig. 2 is the front view of Fig. 1;

Fig. 3 is a schematic diagram of the utility model;

Fig. 4 is the sectional view of mass block in the utility model;

Fig. 5 is the structural representation of the inductance coil in the utility model;

Fig. 6 is a schematic diagram of the energy storage circuit in the utility model.

In the figure: 1. Shell; 2. Tension spring; 3. Mass; 4. Inductance coil; 5. Electric energy storage circuit; 6. Permanent magnet; 7. Inductance coil core; 8. Enameled wire; 9. Inductance coil skeleton .

detailed description

Referring to Fig. 1-Fig. 2, a multi-frequency vibration energy recovery device, the recovery device includes a magnetoelectric conversion part and an energy collection part; wherein the magnetoelectric conversion part includes a shell 1, an extension spring 2, a mass block 3, The inductance coil 4; the energy collection part includes an electric energy storage circuit 5; a plurality of cavities are uniformly arranged inside the housing 1; a tension spring 2 is arranged in each cavity; the tension spring 2 is arranged inside the shell 1, one end of which is fixed on the upper part inside the shell 1, and the other end is connected to the mass block 3; the inductance coil 4 is set outside the mass block 3; there is a permanent magnet inside the mass block 3 6. The mass block 3 and the permanent magnet 6 vibrate inside the induction coil 4 .

The inductance coil 4 includes an inductance coil bobbin 9, an inductance coil magnetic core 7 and an enameled wire 8; wherein the inductance coil bobbin 9 is fixed inside the cavity with a through hole in the middle; the inductance coil magnetic core 7 is set It is inside the inductor coil frame 9 and is in interference fit with the through hole; the enameled wire 8 is wound on the inductor coil frame 9 .

Described housing 1 is a hollow three-dimensional structure, and the size of housing 1 will be determined according to the number of turns of inductance coil bobbin 9, inductance coil magnetic core 7 and enameled wire 8 in inductance coil 4, and in the present embodiment, the final design overall size is 248mm×60mm×60mm. The mass block 3 is located in each cavity of the casing 1 and is connected with the casing 1 through a tension spring 2 . The number of tension springs 2 and masses 3 is equal to the number of shell cavities. The number of cavities in the casing should be determined according to the number of typical vibration frequencies of the environment in which the device is placed. In this example, it is designed as a hollow three-dimensional structure with four cavities.

A multi-frequency vibration energy recovery device described in the utility model can be simplified into a single-degree-of-freedom spring-mass-damping system vibration model, that is, the forced vibration caused by the external basic movement, the kinetic energy of the mass block 3 is transferred by electromagnetic induction converted into electricity. When the mass block 3 vibrates under external excitation, it is equivalent to that the permanent magnet 6 placed inside the mass block 3 reciprocates at a certain frequency with the vibration of the environment, that is, it moves relative to the inductance coil 4 . According to Faraday's law of electromagnetic induction: when the magnetic flux passing through the area enclosed by a closed loop (usually a coil) changes, an induced electromotive force will be generated in the loop. The induced electromotive force can be expressed as:

Among them, U _e represents the induced electromotive force, and the unit is V; _Ne represents the number of coil turns forming a closed loop; is the magnetic flux passing through each turn of the coil, the unit is Wb; B is the magnetic induction intensity, the unit is T; Is the area vector of the coil; t is the time, the unit is s.

Referring to Fig. 3, the response of the magnet when it vibrates externally can be represented by a spring-mass block-damping system. The permanent magnet 6 is placed in the mass block 3. Let the mass block be m, B is the magnetic induction intensity, and k is the stiffness coefficient of the spring , L is the inductance of the coil, the internal resistance of the coil is Rc, the length of the coil is l, and the load resistance is R _L . The vibration displacement y(t) and the vibration frequency of the housing 1 with the external environment will cause the vibration displacement x(t) of the mass block 3, thereby affecting the output voltage and power of the system. Let the vibration displacement of the spring-mass-damping system be f(t). According to Newton's law, the forced vibration differential equation of the system under any excitation is:

In the formula, x(t)=A cos(ωt+θ) is the vibration displacement function of the mass block 3 (ie, the permanent magnet 6), and c is the damping coefficient of the system.

When the initial condition is zero, it is transformed by Laplace, and its transfer function is obtained as:

According to the principle of voltage:

In the formula, I(t) is the change function of the induced current with time.

From (5), the induced voltage of the vibration device can be obtained as:

Therefore, the transfer function from the relative motion of the permanent magnet 5 to the output voltage can be expressed as:

The feedback generated by the induced current in the electromagnetic coil 4 is:

Combining (3), (4), (6), and (7), the transfer function of the system can be obtained as:

After Laplace transform, the transfer function of the oscillation link can be obtained as:

In the formula, When 0≤ζ≤1, it is an oscillation link.

The damping coefficient ζ can be decomposed into mechanical damping coefficient ζ _m and electrical damping coefficient ζ _s , where:

Therefore, the overall transfer function of the system becomes:

That is, the output voltage can be seen as a function of a sinusoidal input signal. Because the output power is:

The average power is obtained as:

It can be concluded that at the resonant frequency, ω=ω _n , the output average power and output voltage value reach the maximum:

The motion equation of the system can be described by this mathematical model, and the maximum output power of the system can be optimally designed by analyzing the given external vibration mode.

From the above analysis, it can be seen that the design of the device should ensure that the natural frequency of the device is close to the typical vibration frequency of the environment, so that the device and the environment can achieve resonance and maximize energy recovery efficiency. In the energy recovery device described in the utility model, it is necessary to ensure that the natural frequency of each spring-mass block unit is close to a typical vibration frequency of the environment, so as to ensure that in each typical vibration situation of the external environment, there is At least one unit resonates with the environment. The typical frequency of the environment can be simply measured by experiment. The natural frequency of the spring can be calculated by the following formula:

Among them, f is the natural frequency of the spring, the unit is Hz; k is the stiffness coefficient of the spring, the unit is N/m; m is the system mass, the unit is kg.

The stiffness coefficient k of the tension spring can be obtained by the following formula:

Among them, G is the rigid modulus of the wire. Common wires include carbon steel wire G=79300, stainless steel wire G= ₆₉₇₃₀₀ , phosphor bronze wire G=4500, brass wire G=350; Diameter, N _C is the number of effective coils of the spring.

Based on the above two formulas, the appropriate spring can be selected according to the vibration frequency of the external environment or the spring can be reasonably designed to meet the environmental requirements of the device.

Referring to FIG. 3 , the mass block 3 is a cubic structure made of soft magnetic material, and a permanent magnet 6 in the shape of a cylinder or a cuboid is placed inside it. Soft magnetic materials refer to magnetized materials whose magnetization occurs when the coercive force is not greater than 1000A/m, and its main performance parameters include magnetic permeability, saturation magnetic induction and coercive force. Magnetic permeability determines the ability of a material to transmit magnetic lines of force and is one of the more important parameters. In this device, the mass block 3 not only vibrates due to external excitation, but also plays the role of conducting magnetic force lines. Therefore, materials with low coercive force and high magnetic permeability are selected, while soft magnetic materials have the above two characteristics, such as pure iron (The density is 7.86g/cm3).

The magnetic field in the device of the utility model is produced by the permanent magnet 6, and the main parameters of the permanent magnet characteristics include three items of magnetic energy product, coercive force and residual magnetic induction. Among them, the magnetic energy product represents the magnetic energy density established by the permanent magnet in the air gap space, that is, the static magnetic energy per unit volume of the air gap. The larger the magnetic energy product, the greater the magnetic energy stored in the unit volume, and the better the material performance; the coercive force refers to the reverse magnetic field strength required to reduce the magnetic induction intensity of the permanent magnet magnetized to technical saturation to zero, and the coercive force The greater the force, the better the permanent magnetism; the residual magnetic induction refers to the magnetic induction retained after the permanent magnet is magnetized to technical saturation and the external magnetic field is removed. The larger the value of the parameter, the better the performance of the permanent magnet material. Permanent magnets include magnets, ferrites and rare earth permanent magnets. Among them, the advantage of magnetic steel is that it is not affected by temperature and can be used in high temperature environments. At the same time, its corrosion resistance is relatively good, so it has a long service life, and its maximum magnetic energy product is second only to rare earth permanent magnets. The performance of ferrite is relatively poor compared with the other two permanent magnets, but it is also widely used because of its low cost. Compared with the other two permanent magnet materials, rare earth permanent magnet materials are magnetic materials with high magnetic energy product, high coercive force and high residual magnetic induction intensity. Among them, the maximum magnetic energy product of NdFeB series permanent magnets can reach 398KJ/m3, and the residual magnetic induction The strength can reach 1.47T, which is the most magnetic permanent magnet material at present. Under the same volume, the rare earth permanent magnet has the highest magnetic field strength, so it is often the first choice for vibration energy devices. At the same time, because of its relatively high coercive force, it will not demagnetize due to the vibration of the device. Therefore, this device uses rare earth permanent magnets as The material of the permanent magnet 6 is determined to be NdFe35 as the permanent magnet material, and the material density is 7.5g/cm3. In this device, the size of the mass block is designed to be a cube with a side length of 10 mm, and the permanent magnet material is a cylinder with a radius of 4 mm and a length of 10 mm, which is placed inside the mass block as shown in Figure 3 .

Referring to FIG. 3 , the mass 3 and the permanent magnet 6 inside vibrate inside the inductance coil 4 , so the inductance coil 4 adopts an air-core coil structure.

Referring to the inductance coil structure in Fig. 5, both the magnetic core 7 and the skeleton 9 are hollow structures, and the outer diameter of the magnetic core 7 should match the diameter of the hollow part of the skeleton 9, so that the magnetic core 7 is placed in the skeleton 9. The enameled wire 8 is wound on the skeleton 9 as a winding.

First of all, according to the working frequency, the wire of the coil is selected: the inductance coil working in the low frequency band is generally wound with insulated wire such as enameled wire. In circuits whose operating frequency is higher than tens of thousands of hertz but lower than 2MHz, multiple insulated wires are used to wind the coil, which can effectively increase the surface area of the conductor, thereby overcoming the influence of the skin effect. In a circuit with a frequency higher than 2MHz, the inductance coil should be wound with a single thick wire, and the diameter of the wire is generally 0.3mm-1.5mm. Therefore the utility model selects enameled wire for use as the coil wire material. Among various conductors, the conductivity of copper is second only to silver, and the resistivity of soft copper is the lowest among various copper materials. The DC resistivity at 20°C is 0.017241Ω·mm2/m, and its dielectric constant ε=ε ₀ =8.85×10 ^-12 F/m, conductivity γ=5.80×10 ⁷ S/m, the larger the wire diameter and the shorter the length of the enameled wire, the smaller the DC resistance.

Selecting a high-quality skeleton can reduce the dielectric loss, such as choosing a high-frequency porcelain material as the skeleton. Putting a magnetic core inside the coil can reduce the number of turns of the coil, that is, reduce its resistance value, increase its inductance, and reduce the volume of the coil. The magnetic core material can be a high-permeability annular magnetic core MnZn, the higher the initial permeability, the higher the operating frequency. The role of the tape in the structure is to act as insulation between each layer of windings and to fix the core and wires. The size of the skeleton should ensure that the tension spring 2 can drive the movement of the mass block 3 in the magnetic core without hindrance. After determining the size of the mass block 3 in this device, you can select a skeleton with a circular diameter of 50mm for the wallboards on both sides, a hollow diameter of 20mm, and a height of 25mm. Based on this size, the size of the housing 1 can be further determined. The inductance coil 4 is placed in the cavity of the shell 1, that is, the width of the cavity should be slightly larger than the circle diameter of the wall panel of the coil frame by 50 mm, and the length of the cavity should be greater than the height of the coil frame and a gap for adjusting the position of the inductance coil 4 should be left. The width of each cavity is 52mm, the length is 50mm, and the thickness of the shell is 5mm, so the overall size of the shell 1 is 248mm×60mm×60mm.

The inductor coil 4 needs to have two windings, a primary winding and a secondary winding. The electric energy output by the primary coil is stored by the inductance in the subsequent circuit, and the electric energy output by the secondary coil provides energy for the circuit chip. The design of the number of coil turns needs to consider the voltage required by the chip in the final circuit. The inductance of the coil mainly depends on the number of coil turns, geometric shape, and coil structure size, such as winding length, diameter, thickness, etc.

From (14), (15) and (16) three formulas, it can be seen that the internal resistance of the coil directly affects the size of the output voltage and power, so the internal resistance should be minimized during design. According to the resistance calculation formula:

R=ρl/S (19)

Where ρ is the resistivity of the material in Ω·m; l _R is the length of the resistor in m; S is the cross-sectional area of the resistor in m ² .

The length and cross-sectional area of the winding coil are:

Then the resistance of the winding coil is:

Among them, d ₀ is the outer diameter of the helical coil, in m; d ₁ is the inner diameter of the helical coil, in m; W ₀ is the length of the cross-sectional area of the coil, in m; w ₁ is the thickness of the coil cross-sectional area , the unit is m; μ is the duty cycle.

Coil Turns:

The approximate engineering calculation of the inductance of the spiral coil is:

in, By changing the outer diameter d ₀ of the coil and the number of turns N of the coil, the relationship between the outer diameter of the coil and the number of turns of the coil and the inductance can be calculated.

The electric energy generated by the magnetoelectric conversion part is relatively small and cannot directly provide driving energy for most circuits, so electric power storage is required. There are two main methods of collecting electricity generated by electromagnetic vibration: collecting vibration energy generated by capacitance/inductance and using rechargeable batteries. The entire structure of the device does not rely on external energy for power supply, and only relies on the electricity generated by the magnetoelectric conversion part to drive the circuit to work normally.

Referring to Fig. 6, the switch S in the energy storage circuit is used for the power switch at the input end, Ls is the superconducting energy storage coil, the diode D plays the role of freewheeling, S2 is the inductor discharge control switch, and S3 is connected during charging and discharging. The inductance Lf and the electric capacity Cf are the filter inductances, Rl is the system load. The switch S1 has two functions: it is used to form a current path when charging and storing energy, and it is used to shunt current when discharging to realize constant current or constant voltage control. When working, the circuit has three operating states: charging state; energy storage state; discharging state. When charging, the switch S is powered on, S1 is closed, S2 is open, and S3 is open. When storing energy, S is disconnected from the power supply, S1 is still connected, S2 is disconnected, and S3 is closed.

In the above examples, the size of the mass block and the size of the inductor coil skeleton of the device of the present invention are variable parameters in practical applications. From the above description, it can be seen that the overall size of the device in this example is only 248mm×60mm×60mm, which meets the requirement of miniaturization of the structure. Due to size limitations, this device is only suitable for low frequency vibrations of 10-200Hz in recycling environments. It can be applied to various large mechanical bases or vibration components, automobile engines, mixers, washing machines, and low-frequency vibration energy recovery in various microstructures to provide electrical energy for micro-electromechanical systems or wireless sensors.

Claims (2)

1. A multi-frequency vibration energy recovery device is characterized in that the recovery device comprises a magnetoelectric conversion part and an energy collection part; wherein said magnetoelectric conversion part comprises a shell (1), an extension spring (2), a mass block (3), inductance coil (4); the energy collection part includes an electric energy storage circuit (5); the shell (1) is a rectangular hollow shell with a plurality of cavities uniformly arranged inside; wherein A tension spring (2) is arranged in each cavity; the tension spring (2) is arranged inside the shell (1), one end of which is fixed on the upper part of the inside of the shell (1), and the other end is connected to the mass block (3) connected; the inductance coil (4) is arranged in the cavity of the casing (1), outside the mass block (3); the permanent magnet (6) is arranged inside the mass block (3), and the mass block (3) and the permanent magnet (6) vibrate inside the inductance coil (4). 2. A multi-frequency vibration energy recovery device according to claim 1, characterized in that, said inductance coil (4) comprises an inductance coil bobbin (9), an inductance coil magnetic core (7) and an enameled wire (8) ; wherein said inductance coil bobbin (9) is fixed inside the cavity, with a through hole in the middle; said inductance coil magnetic core (7) is arranged inside the inductance coil bobbin (9) and is interference fit with the through hole ; The enameled wire (8) is wound on the inductor bobbin (9).