LT6963B - Piezoelectric generator excited by accelerated magnets - Google Patents

Abstract

The invention relates to micro-power generators using a piezoelectric effect. It is a piezoelectric vibration energy harvester, having an increased harvesting efficiency and stability under low frequency (<10 Hz) oscillations. The generator comprises a housing (1), a cantilever-type piezoelectric transducer (2) with a magnetic mass (3), and a special system of accelerated magnets. The accelerating magnets (13), under external vibrations and inertial forces, move in special beds (12) of the housing (1), and via magnetic interaction accelerate the driving magnets (9) in a non-contact manner. The array (9) comprises at least 2 magnets (10) separated by nonferromagnetic gaskets (11). Due to the accelerating magnets, the array (9) slides at nearly constant speed, interacts with the magnetic mass (3), deforms the transducer (2) thereby initiating its free high-frequency oscillations. The generator is applicable and efficient under low-frequency excitations such as biomechanical oscillations, e.g. generated by limbs of an actively moving person.

Description

FIELD OF THE INVENTION

The invention is attributed to electric power generation devices using the direct piezoelectric effect. More specifically, it is a piezoelectric generator excited by accelerated magnets, which efficiently converts low-frequency, for example, biomechanical vibrations into electrical energy.

STATE OF THE ART

Various devices are known in this technical field, in which electricity is generated by exciting a piezoelectric transducer with mechanical vibrations.

US patent application US2011/0074162A1 and patent US8350394B2 (priority date 2009-09-30) describe a piezoelectric generator consisting of two wedge-type piezoelectric transducers with concentrated masses of different sizes attached at the ends, which, when excited by mechanical vibrations, collide with each other and acquire high deformation rate. In this way, the piezoelectric layers of the transducers, which are deformed at a higher speed, produce a higher amount of electricity. However, this device uses piezoelectric transducers hitting each other, the constant collisions of which lead to noisy operation and wear of contacting materials, so such a generator does not fully meet ergonomic, reliability and durability requirements.

Another US patent application US2012/0267982A1 (priority date 200612-22) describes a piezoelectric generator consisting of a number of bell-type piezoelectric transducers, with magnetic masses attached at their ends and an array of driving magnets sliding below them, where the magnetic interactions between the driving and transducer magnetic masses are continuous. thanks to which the transducer is periodically deformed, and in this way electricity is produced in the piezoelectric layers. In this device, an array of driving magnets anchored by springs at the edges deforms one of the piezoelectric transducers with continuous magnetic interaction forces. Therefore, the deformation of the converter is dynamically constrained by magnetic forces, and the vibration frequency of the converters is directly determined by the speed of movement of the array of driving magnets. Therefore, the amount of electricity produced by such a generator is not stable enough under changing conditions of external vibration excitation. Also, intense high-frequency bending oscillations are not induced under low-frequency excitation. In this case, due to the excessively low deformation speed and low amplitude of the piezoelectric layers, the amount of electricity produced by this piezoelectric generator drops significantly.

This invention solves the shortcomings observed in the aforementioned analogues, and realizes non-contact, stabilized and higher efficiency piezoelectric conversion of mechanical energy in the low frequency range.

ESSENCE OF THE INVENTION

A piezoelectric generator is a "vibration energy harvesting" device, which usually efficiently generates electricity by operating with vibrations of a frequency of about 100 Hz and higher. The purpose of this invention is to increase and stabilize the amount of electricity produced by a piezoelectric generator over time, when the generator relatively low-frequency (<10 Hz) high-amplitude vibrations operate (for example, biomechanical vibrations in the form of human body movements). For this, special non-contact magnetic interaction means are used, which amplify and equalize the high-frequency bending vibrations of the piezoelectric transducer. When generators operate at low frequencies (<10 Hz), large amplitude oscillations, thanks to the movement and interaction of the magnets installed in it, amplified high-frequency (>100 Hz) bending oscillations are excited in the piezoelectric transducer, which deform the piezoelectric layers and thus generate electricity.

The construction of the generator includes a housing, a piezoelectric transducer installed in it, consisting of a rod with a magnetic mass, and a special system of (accelerating and driving magnets, (accelerating magnets, under the influence of external low-frequency vibrations, move in the generator body and, thanks to their magnetic interaction, push the array of driving magnets. the magnet array is composed of at least 2 magnets, separated from each other by non-magnetic spacers, and this array, under the influence of (accelerating magnets, moves at a relatively high and constant speed. This array, moving slidingly below the piezoelectric transducer arm, acts at certain moments of time with its magnetic forces the magnetic mass of the rod, deforms the rod and, accordingly, generates high-frequency amplified vibrations of the piezoelectric transducer.

ή = 0.5 7t and t _P = Tt, where ή - duration of interaction of one driving magnet with the magnetic mass of the converter, Tt - period of free oscillations of the converter with the magnetic mass, t _P - time interval between two adjacent deformation moments of the converter caused by the driving magnets.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the drawings. The accompanying diagrams and drawings are an integral part of the description of the invention and are provided by way of reference to the possible implementation of the invention, but are not intended to limit the scope of the invention.

Fig. (principle diagram for converting low-frequency biomechanical vibrations of a piezoelectric generator excited by accelerated magnets into electrical energy.

Fig. (schematic representation of a typical transient voltage signal generated by a piezoelectric generator excited by accelerated magnets.

DETAILED DESCRIPTION OF THE INVENTION

Device construction. The design of the generator is shown in Figure 1. The piezoelectric generator consists of a bell-type high-frequency piezoelectric transducer 2 fixed in the body 1, which is rigidly connected to the magnetic mass 3 at the free end. The piezoelectric transducer 2 consists of a rectangular base 4, which is covered with a piezoelectric layer 5 with electrodes 6, 7. Below the magnetic mass 3, an array of driving magnets 9 with at least two driving magnets 10, which are separated from each other by a non-ferromagnetic spacer 11, is attached to the axis 8. On the edges 9 of the array of driving magnets 10, the side beds 12 of the body 1 are placed (accelerating magnets 13.

Device operation. Inertia forces caused by vertical (or partially vertical) low-frequency (<10 Hz) high-amplitude oscillations act on (accelerating magnets 13, which begin to slide alternately vertically in the beds 12 of the housing 1. Due to magnetic interaction, the moving (accelerating magnets 13 horizontally push the array of driving magnets 9 ( in which the number of driving magnets is >1).As the first driving magnet 10 moves past the magnetic mass 3 of the piezoelectric transducer 2, the bending forces caused by the magnetic interaction deform the piezoelectric transducer 2 to the first extreme position I. The first driving magnet 10 moves further away from the magnetic mass 3. When the transducer 2 is no longer affected by the magnetic force of the first driving magnet 10, its further deformation process takes place in the mode of free oscillations until the second extreme position II is reached. In this position II, the transducer 2 begins to be deformed by the second driving magnet 10, and it deforms until the transducer 2 reaches the other extreme position III. When the second driving magnet moves away from the magnetic mass 3, the piezoelectric transducer 2 continues to periodically deform itself, in the mode of high-frequency high-amplitude free oscillations (1/Tt >100 Hz). In this way, electric charges are created in the piezoelectric layer 5 of the deformable transducer 2, which accumulate on the electrodes

6, 7, from which they are transmitted to the external electrical circuit connected to the generator.

During one cycle of the piezoelectric generator (in which the drive magnets 10 array 9 is pushed once through the magnetic mass 3 of the piezoelectric transducer 2), a periodic voltage signal proportional to the deformation rate of the piezoelectric layers 5 is generated. This signal is composed of two vibrational stages, shown in Figure 2:

1) the stage of forced oscillations, when the piezoelectric transducer 2 is subjected to the bending forces caused by the magnetic interaction (shown by the thicker curved line), and

2) free-oscillation stage, when converter 2 is allowed to oscillate freely with a frequency of 1/Tt >100 Hz (shown by a thinner curve line).

The time instants O and II indicate the starting instants of the first and subsequent stages of forced oscillations caused by the driving magnets 10, respectively. Time instants I and III indicate the end of the phases of forced oscillations and the corresponding maximum voltage amplitudes.

The durations of the generated voltage signal characterizing the operation of the generator are as follows:

η - the duration of the interaction of the driving magnet 10 with the magnetic mass 3 of the piezoelectric transducer 2, when the driving magnet 10 deforms the transducer and a voltage signal is generated, t _P - the time interval between two adjacent moments of deformation and voltage generation of the transducer 2 caused by the array of driving magnets 10 - this time interval is determined by the width of the non-ferromagnetic gap 11.

Industrial application. This set of structural elements, with properly selected magnetic, non-ferromagnetic and piezoelectric elements, allows the energy of low-frequency (<10 Hz) high-amplitude oscillations (for example, biomechanical oscillations such as human body movements) to be efficiently converted into electrical energy. The effect of external low-frequency vibrations, through the accelerating magnets 13, gives the array 9 of the driving magnets 10 a relatively high and constant speed of movement. This speed depends little (changes rather insignificantly) when the conditions of external (biomechanical) excitation are variable. In this way, the high-frequency bending vibrations of the piezoelectric transducer 2 are intensified and stabilized, and a larger and more uniform amount of electricity produced by the generator is obtained in real operating conditions.

For example, such a generator can be effectively used by attaching it to a person's limbs, the amplitude and frequency of which are constantly changing in time, depending on the level of intensity of the person's movement.

Also, the generator without limitations can be effectively used in various other applications where relatively low-frequency (<10 Hz) high-amplitude oscillations, which are significantly lower than the free-oscillation frequency of the piezoelectric transducer 2, operate.

Claims (2)

Piezoelectric generator for converting low-frequency mechanical vibrations into electrical energy, comprising at least - a body (1), - a bell-type high-frequency piezoelectric transducer (2) fixed in the body (1), with a magnetic mass (3) attached to its end, differing in that additionally includes: - accelerating magnets (13) capable of moving in the cradles (12) of the generator body (1) from inertia when the generator is affected by mechanical vibrations of the external environment, - an array of driving magnets (10) installed in the body (1) comprising more than one driving magnet (10), where the array (9) is arranged in such a way that: - the accelerating magnets (13), while moving in the beds (12), provide a relatively high and constant speed of movement to the array (9) of the driving magnets (10) in a non-contact manner, - the magnets (10) of the array (9) are shaped so that one driving magnet (10) of the moving array (9), interacting with the magnetic mass (3), deforms the converter (2), thus causing its free vibrations esius, and the subsequent driving magnet (10) additionally strengthens the free oscillations of the converter (2). The generator according to point 1, differing in that - the speed of movement of the driving magnets (10) is constructively selected such that the duration ti of the interaction of the moving driving magnet (10) with the magnetic mass (3) of the converter (2) is equal to or close to the free time of the converter (2) for the half of the oscillation period Tt, and - in the structure of the array (9) of the driving magnets (10), no less than two driving magnets (10) are installed, which are separated by non-ferromagnetic spacers (11), the width of which ensures the amplification of the vibrations of the converter (2), after it is additionally excited by a subsequent by the driving magnet (10), where the time interval tp between the deformation events of the converter (2) caused by the adjacent driving magnets (10) is equal to or close to the period of free oscillations of the converter (2) Tt.