FR2838885A1 - Electrical generator using human energy comprises piezoelectric transducer struck repeatedly to generate electricity in response to hand movement - Google Patents

Abstract

The electrical generator produces small quantities of electricity for portable devices. A rotating cam mechanism provides repetitive impacts on a piezoelectric transducer in order to generate electricity. The piezoelectric transducer is mounted to resonate under these conditions. The device for generating electricity includes a piezoelectric element (100) supported within a frame which transfers human mechanical movement to movement of the piezo element. The piezo element is mounted in order to vibrate in resonance, and a mechanical system is provided to drive this resonant oscillation. The mechanical system may comprise a rotating cam, with a radius which varies, increasing progressively to four maximum points, before dropping back to a lower radius value. Rotation of the cam by moving a rack and pinion linkage causes a repetitive series of impacts on the piezoelectric element. This causes resonant oscillation of the element to generate electricity.

Description

as an electric motor.

  The invention relates to a device transforming human mechanical actions into electrical energy by piezoelectric effect, in

  especially for the supply of autonomous electronic devices.

  With the proliferation of portable electronic devices, the question of the autonomy of these devices on the energy level arises

crucially.

  The idea of converting the mechanical energy produced by man in his daily activities into electrical energy stored in an organ of

  storage (capacity or accumulator) is attractive.

  Providing a generator with sufficient overall conversion efficiency to be able to supply conventional electronic devices, for example devices consuming several Waffs, constitutes a

central goal these days.

  In practice, there is a clear interest in making an integrable energy transformer with an overall conversion efficiency equal to or greater than 1%. Considering for example the market as an initial source of energy (power supplied in the order of 70 Waffs), the usable electrical power decreases 1 Waff for an overall yield of 1.4%. This power is sufficient to operate many electronic devices

portable.

  In this perspective, the conversion by piezoelectric effect is particularly interesting because it combines compactness and robustness of the

  in particular that it requires little or no moving parts.

  The conversion of mechanical energy into electrical energy by piezoelectric effect has been known for a very long time. However, in the case where the energy source is the action of the members of the human body, the devices proposed so far do not have a sufficient overall conversion efficiency (ratio of the electrical energy available at output by

  the mechanical energy available at the input).

  In general, the physical principles which have been proposed to transform the mechanical energy produced by the members into energy

  electric wind multiple. We can filth them in trots categories.

  Inertial devices transform the kinetic energy of a mass in electrical form, by electromagnetic induction. This proven principle has been the subject of industrial achievements, the most famous of which is the Seiko "Kinetic" watch (registered trademark). The conversion efficiency of such devices is low and the available powers are on the order of a microwatt. Dynamo-type devices have been used in shoe prototypes developed at the Media Lab of MIT (Massachussets Institute of Technology) (rbf. [1]) and by the Electric Shoe

  Company (ref. [2]). The available power can reach several Watts.

  <Dynamo >> type devices pose integration problems and

  reliability because they have many moving parts.

  Finally, piezoelectric conversion has notably been used in the production of shoes, also at the Media Lab of MIT (ref [1]) (based on PZT type ceramics or polymers known under the acronym PVDF) and by the Electric Shoe Company (ref [2]). PZT is a generic term meaning Titano Lead Zirconate describing the most common piezoelectric ceramics since the early 1960s.

  wind ceramics manufactured by many companies in the world.

  Means inherent in this piezoelectric conversion have also been

described in FR 2 745 476.

  In the case of the MIT shoe, the conversion is produced by static deformation in flexion of a piezoelectric plate. The overall conversion yield is typically 0.005%. The energies produced

wind of the order of a milliwatt.

  Document FR 2 745 476 proposes a leverage effect to deform, in a quasi-static manner, a multilayer piezoelectric stack. An evaluation of the mechanical constraints involved only suggests that there is insufficient power for many applications (in particular

practical, in the order of a milliwatt).

  The object of the invention is a mechanical energy transformer

  human with improved yield and compactness.

  This object is achieved according to the invention thanks to a device for producing electricity from human movement, the device comprising a piezoelectric organ and a set of mechanical transformation of an initial human movement into a mechanical solicitation of the piezoelectric organ. , characterized in that the piezoelectric organ is designed to be able to vibrate in resonance, and the mechanical transformation assembly is designed to transform the initial human movement into a series of impacts on the piezoelectric organ so that the latter enters

  then in resonance under the effect of this series of impacts.

  Other features, objects and advantages of the invention

  will appear on reading the description which follows, made with reference

  to the appended figures in which: - Figure 1 is an electrical diagram which models the energy roles of a human user and mechanical means and

electrics according to the invention.

  - Figures 2 and 3 are side and perspective views of a piezoelectric member used in the context of the invention; - Figure 3bis represents this same piezoelectric member in a deformed position; - Figure 4 is a sectional perspective of an impact production assembly according to the invention; - Figure 5 is a side view of a movement transforming device according to another variant; - Figure 6 is a sectional perspective view of another assembly

impact production.

  - Figure 7 is a sectional view of a shoe equipped with means of producing electricity according to the invention; The electricity production device described here is made up of three main elements (fig. 1): - a piezoelectric transducer 100, in the form of a bending plate, whose role is to constitute the energy conversion point electrical energy mechanics; - a mechanism 200 whose role is to transform an initial movement produced by a human member into another movement more suitable for the stress of the piezoelectric transducer; - an electronic circuit 300 whose role is to recover the electrical energy at the terminals of the piezoelectric transducer and to charge a

  storage capacity under a few tens of volts.

  The piezoelectric transducer 100 here has a high coupling coefficient (ratio of electrical energy transformed from

mechanical energy input).

  For this, the transducer 100 is a plate whose piezoelectric matbrioux constituting wind piezoelectric ceramics of the PZT type, very rigid and very fragile by nature. These ceramics present

  high intrinsic coupling coefficients.

  In addition, a conversion method known as "type 33" is used, which corresponds to orientations of mechanical constraints and

  induced electric fields parallel to the polarization of ceramic.

  This conversion mode is also suitable for obtaining a

high coupling coefficient.

  The deformation energy that can be stored in the piezoelectric plate 100 is limited, due to a maximum allowable limit

  constraints beyond which the rupture of the plate occurs.

  This mechanical limit corresponds to an energy concentration limit of around 6mJ per cm3 of active piezoelectric material. This value, which is detrimental to obtaining compact devices in the prior art, is no longer a concern here thanks to the transformation of movement.

which is proposed below.

  Thus, the human mechanical energy is transmitted on the piezoelectric plate 100, by the mechanism 200, according to a transformation

  particularly advantageous in terms of overall performance.

  The mechanical energy of a human movement considered is not transmitted on the transducer 100 at once, but it passes through

successive pulses.

  The mechanism 200 transforms the displacement initially produced by the human movement considered, into a series of impacts. Thus, a single movement of the human limb alone generates a series of successive impacts, used for a solicitation

  jerk of the piezoelectric transducer 100.

  Under the effect of this series of impacts, the transducer 100 enters

vibration on a resonance mode.

  A sinusofdale voltage is then induced at the output terminals of the transducer 100, output modeled in FIG. 1 by a capacity 110 representing the intrinsic aptitude of the transducer 100 to store and supply

  electrical energy at its output.

  This intrinsic capacity 110 for recovering and storing electricity is connected to the primary of a transformer 400 which amplifies

the flow.

  The circuit 300, which is placed at the secondary of the transformer 400, is itself constituted by a rectifying diode 310 and the storage member constituted by the capacity Cs previously mentioned. According to a variant, the circuit 300 is constituted by an assembly comprising a diode bridge and a capacitance, or else it is constituted by a switching circuit. The loading of the intrinsic capacity 110 of the piezoelectric plate 100 is carried out at each of the multiple abrupt variations of application or withdrawal of force, and not in a single bending of the organ

piezoelectric 100.

  The principle associating the excitation of the transducer 100 by successive impacts (sudden application and release of the force) and the resonance of the transducer 100 allows the energy to transit

  gradually through the piezoelectric material.

  This principle removes the limitation linked to the maximum energy of deformation storable in the piezoelectric material, inherent in all

  static or quasi-static devices.

  In other words, this device promotes compactness because the maximum stress limit only applies for each impact. The piezoelectric transducer 100 has, at its input, a mechanical impedance which must be adapted to the impedance of the source (namely the human limb) to optimize the transfer of the mechanical energy produced by the limb in deformation energy of the

transducer 100.

  The transducer adopts here is. as indicated above, a

plate 100 subjected to bending.

  This plate 100 (fig. 2) is formed by multi-layer ceramic blades 120 and 130 mounted on both sides of a central blade 140. The polarization of the multi-layer blades 120 and 130 is alternated and

parallel to blade 140.

  The size of such mechanical devices is of the order of

2cm3 (40x1 Ox5mm).

  The layers forming the plates 120 and 130 wind referenced 125 and 135 in Figure 2, they succeed one another along the plate, according to a polarization parallel to the large dimension of the plate. The reverse wind polarizations on the upper and lower faces of the central blade 140. This choice makes it possible to guarantee a good mechanical adaptation to the input (plate in bending), a high coupling coefficient (operation in mode 33) and an electrical adaptation. improved output (capacity 1 10 of the transducer increased by the use of

multilayer ceramics).

  This results in a higher overall conversion yield and a

  acceleration of energy transfer to capacity 110.

  The use of polarized ceramics perpendicular to the plane

  of the plate 100 is also possible (operation in mode 13).

  This variant, however, has the disadvantage of degrading the coefficient

  coupling and reduce the capacity 110.

  The electrical output impedance of the transducer 100 must

  preferably be adapted to the impedance of the storage member Cs.

  The device having to be compact because portable, the capacity 110 of the piezoelectric transducer considered is naturally of several orders of magnitude smaller than the storage member Cs. The electrical adaptation using the 400 transformer at the output proposed here, responds to

this concern.

  The current transformer 400 connected at the output of the transducer is also advantageous because it improves the transfer of energy to the organ of

storage Cs.

  In addition, the primary of the transformer 400 constitutes, with the capacity 110 of the transducer, a plug circuit which optimizes the transfer of energy. The transformation ratio can be adjusted so as to adapt the value of the storage member Cs which is seen in the primary of the

  transformer 400 to optimize energy transfer.

  The duration of each charge depends on the coupling coefficient of the device. This duration is typically a few vibration periods (ie a few milliseconds), if the electromechanical coupling coefficient is greater than 50%. Many loads

  successive can therefore be applied in a very short time.

  The association of a resonant transducer 100 and the adaptation transformer 400 which plays both the role of plug circuit and adapter

  electric with respect to storage means, is very advantageous.

  This combination improves overall conversion efficiency and

  consequence accelerates the transfer of energy to the storage member Cs.

  The capacitance 110 of the transducer 100, associated with the inductance at the primary of the transformer, at the output of the transducer, provides preferential means for constituting a plug circuit which stores the energy of

  very temporary (a few periods) before transfer.

  Before describing a set of impact production, we will describe (Figures 2, 3, 3bis) a set of assistance to mechanical stress according to

a preferred variant.

  11 has two levers 150 and 160 pairs each at one end

from plate 100.

  Each of the two levers extends from one end of the plate

  , to come overhang a central part of it.

  Above this central part of the plate 100, the levers are opposite by their free end. The levers for this have a shape substantially at right angles to come overhang the central part of the plate 100. They can, as a variant, be straight. When moved closer to the blade, each of the levers produces a bending of one

  end of the blade with the same curvature.

  The use of these levers 150 and 160 thus makes it possible to apply a

  bending moment and thus homogenize the stress.

  This geometric produces in the plate 100 a constant bending moment which tends to standardize the stress field and therefore the energy of deformation along the length of the plate. This standardization guarantees optimal use of the volume available for a functioning device

in flexion.

  The levers 150, 160 also contribute to the mechanical adaptation at the input by amplification of the force, and their effect is advantageously combined with the impact stress, exerted preferentially on the free end of these levers in the direction of the plate, thus favoring

a resonant movement of the blade.

  We will now describe several variants of means of

impact production.

  We can, as proposed above, use the device to replace the batteries in electronic keys, more precisely in keys comprising both a mechanical key and an electronic transmitter

unlocking.

  In such keys, the mechanical part is closed by the user in a housing according to a movement of rotation or translation against

a spring recall.

  The energy supplied by the user, when storing the key in the box, or the same energy released when the spring is released, is

  advantageously used as a movement for producing electricity.

  For this, use is made of a movement transformation device 200 of the type of that of FIG. 4, which transforms the rotation of a disc 210, subject to the rotary part of the key, into a series of impacts on a

plate 100.

  This device works on the principle of a peripheral notching

  212 of the disc 210, on which repeating stop a vibrating finger 230.

  This finger 230 is held by a link having a certain

  elasticity of movement, to allow the vibration of the finger.

  This loose and elastic connection is constituted by a block 240 surrounding the finger 230. This block 240 is held in place by a shaft which crosses the block with a sliding freedom in a transverse direction

to this tree.

  This sliding freedom is authorized by a light which extends in the longitudinal direction of the block, and in which the holding shaft is located. A helical spring in the same direction as the light of the block 240 retains the movements of the block. Thus, the vibration of finger 230 is authorized by short back and forth movements of the transverse shaft in the light of the

  block, against the deformation of the spring.

  In addition, in its middle part located between the toothed wheel 210 and the block 240, the finger 230 is in contact with a wall 235. This wall 235 therefore constitutes a support which allows the finger to operate as a lever. Lever operation allows efficient transmission of back and forth

on block 240.

  This block 240, brought into contact with the levers 150 and 160 previously described of the plate 100, forms a hammer which applies the

  desired impacts directly on these levers.

  Only half of the plate 100 is shown in FIG. 4,

  for greater clarity of the illustration.

  For the transformation of an initial movement of human translation, there is shown in FIG. 4, by way of illustration, a straight rack 250 which engages the disc 210 by means of a second notch

peripheral, lateral to the disc.

  This type of device adapts for example to a key which can be stored

  in its sheath by a rectilinear sliding movement.

  According to yet another variant, the straight rack 250 is used directly to transmit the series of successive stops on the finger 230. In this variant, represented in FIG. 5, the rack 250 is mounted to slide on a guide, and recalled by a spring according to

direction of this guide.

  This type of device with transformation of rectilinear movement applies for example to the transformation of the crushing energy transmitted on shoe soles. In this case (FIG. 7), the rectilinear rack 250 is placed vertically in the sole under the

eVou heel under the sole of the foot.

  According to yet another variant, a disc 215 is brought into contact directly with the upper part of a lever 150 of the plate 100, by the periphery of this disc. The periphery is then preferably provided with notches 217 of progressive diameter, each notch 217 ending in a

abrupt break in its slope.

  Each lever 150 and 160, being supported by its elasticity against the periphery of such a notched disc 215, is therefore abutted against the disc 215 each time such a notch is crossed. The size of such

  mechanical devices is around 2cm3 (40x1 Ox5mm).

  Thanks to the set of provisions described above, the measurement has shown that the conversion efficiency of the devices obtained is

greater than 1%.

  Thanks to such devices, it is possible to partially recover the mechanical energy produced during extraction and retraction actions by rotation or translation of the key in a rigid sheath, so as to produce the electrical energy necessary for the operation of the transmitter of

the key.

  In this type of application in particular, it is typical that the assembly for mechanical transformation of the human movement in deformation action of the piezoelectric organ includes an elastic or loving element and means for maintaining [ elastic or magnet element in a position biased against the direction of the recall (deformation for elastic element, distance for the attractive magnet), as well as means for transforming a release of the recall into a stress

  mechanics of the piezoelectric organ.

  In other words, it is possible to provide means for storing potential mechanical energy, actuated initially by a movement

  human, and which, when released, activate the piezoelectric organ.

  The devices described constitute autonomous sources of energy

  or complementary for any type of portable electronic equipment.

  The implementation of these devices improves the overall yield

  known piezoelectric transducers by a factor of around 100.

  The field of activity envisaged is extremely wide since it concerns the supply of energy to all portable electronic devices consuming powers lower than a few Watts. The potential users of the invention are the industries of

  electronics, IT and telecommunications.

  More generally, the invention can be adapted to give energetic autonomy to electronic or electric devices having an external mechanical energy source (swell, wind, vibration ...). On the military level, the question of energy autonomy is part of a broader reflection on the "fighter of the future". The DARPA (US Army) also organized a seminar on this subject, entitled "human powered systems" << systems powered by human energy >>

Washington in November 1997.

  [1] J. Kymissis, C. Kendall, J. Paradiso, N. Gershenfeld, "Parasitic power harvesting in shoes" presented at the 2nd IEEE International

  Conference on Wearable Computing, (1998).

  [2] The works of Trevor Bayliss have been the subject of numerous "general public" articles that lion can find on the site http.//www. theelectricshoeco.com.

Claims (10)

  1. Device for producing electricity from human movement, the device comprising a piezoelectric organ (100) and a mechanical transformation assembly (200) from an initial human movement into a mechanical stress on the piezoelectric organ ( 100), characterized in that the piezoelectric organ (100) is designed to be able to vibrate in resonance, and the mechanical transformation assembly (200) is designed to transform the initial human movement into a series of impacts on the piezoelectric organ ( 100) so that the latter enters   resonance under the effect of this series of impacts.   2. Device according to claim 1, characterized in that the mechanical movement transformation assembly (200) comprises a movable element (210, 215, 250), having an edge carrying a series of successive teeth, and a finger (230 ) movable mount with elastic return which is in contact against this dense edge of the movable element, so that the finger (230) is urged by successive stops against the teeth of this edge during the movement of the movable element (210 , 215, 250), the mechanical transformation assembly further comprising an impacting element (240) placed opposite the piezoelectric member (100) and mechanically couples to the movable finger (230) so that successive finger stops (230) result in repetitive impacts of the element   impact against the piezoelectric organ (100).   3. Device according to claim 1 or claim 2, characterized in that the piezoelectric organ is a piezoelectric blade (100) mounted in flexion.   4. Device according to claim 3, characterized in that the mechanical movement transformation assembly (200) comprises an elongated element (150, 160), having a first end integral with the blade (100) and a second movable end, The movement transformation assembly comprising means for applying impacts to the mobile end of this elongated element (150, 160) so that these impacts are transformed by this elongated element (150, 160) into   corresponding flexions of the blade (100).   5. Device according to the preceding claim, characterized in that the blade (100) is in lateral support by its two ends and in that ['movement transformation assembly (200) has two elongated elements (150, 160) each having an end integral with the blade (100) at a respective end thereof, the two elongated elements (150, 160) further having their free end substantially at the right of   the central part of the blade (100).   6. Device according to claim 5, characterized in that the movement transformation assembly is provided for applying the   impacts on the free end of each of the elongated elements (150, 160).   7. Device according to any one of the preceding claims,   characterized in that it includes a circuit (300) comprising an electrical energy storage element (Cs), the circuit further comprising means for collecting electrical energy at the outlet of the piezo member   electric (130) and store this energy in this storage element (Cs).   8. Device according to the preceding claim, characterized in that the circuit comprises a rectifying diode (310) mounted in series with ['storage element (Cs).   9. Device for producing electricity according to any one of   previous claims, characterized in that the set of   mechanical transformation of human movement into deformation action of the piezoelectric organ includes a mechanical recall assembly and means for maintaining this recall assembly in a position urged against the recall, as well as means for transforming a release of the booster assembly in mechanical stress on the piezoelectric organ. 10. Electronic key including an electronic unlocking transmitter and a mechanical unlocking member, as well as a sleeve coupled to the mechanical unlocking member by a link authorizing an introduction and an extraction of this member in and out of the sleeve, the key being characterized in that it includes a device for   power generation Solon any of the claims   precedents, of which the movement transformation assembly (200) is provided for transforming the movement of the mechanical unlocking member with respect to the sheath into the series of impacts on the piezoelectric element (100), and the device for electricity production being related to   the electronic transmitter so as to power it.