VIBRATION ENERGY CONVERTER

Description

Domain

[0001] This description applies generally to energy harvesters and, more specifically, to vibration energy harvesting devices adapted to produce electricity from mechanical vibrations. This description is particularly relevant to the production of electricity by equipment capable of vibrating, such as building air conditioning ducts, operating computers, industrial machinery, motors, vehicles, transport infrastructure, etc. Prior state of the art

[0002] It has long been known that it is possible to harvest electricity from the vibrations of a mechanical system. Some mechano-electric converters or vibration energy harvesters use piezoelectric elements to convert mechanical energy from vibrations into electricity.

[0003] An example of an electric generator with mechanical vibration energy recovery is described in document WO A 2011 / 073591 (B9966PCT).

[0004] The US-A-2008 / 0100181 document describes a system and method for a nonlinear piezoelectric mechano-electric generator.

[0005] The US-A-2012 / 0119620 document describes a multistage force amplification apparatus and method for piezoelectric stacks.

[0006] Document WO-A-2002 / 029965 describes a piezoelectric energy collector.

[0007] Document EP 3 107 202 A1 describes a piezoelectric energy collector without a sliding connection at a wall of the frame with the conversion device located inside the frame. Summary

[0008] There is a need for improvement of mechano-electric converters in terms of industrialization.

[0009] There is also a need to improve the reliability of mechanical vibration energy recovery electric generators.

[0010] One embodiment overcomes all or part of the drawbacks of conventional vibrational energy harvesters.

[0011] One embodiment provides a device for recovering vibratory mechanical energy as defined by claim 1.

[0012] According to one embodiment, said sliding connection is obtained by a sliding element in said wall and connecting said structure to said conversion device.

[0013] According to one embodiment, said sliding connection is obtained by a deformation of said wall between said structure and said conversion device.

[0014] According to one embodiment, the conversion device is connected to a fixed point relative to the frame.

[0015] According to one embodiment, at least one mass is fixed in the central part of the blade structure.

[0016] According to one embodiment, the blade structure is put into buckling between the frame and said sliding joint.

[0017] According to one embodiment, the conversion device includes a piezoelectric element in a direction approximately perpendicular to the direction of the blade structure.

[0018] According to one embodiment, the conversion device comprises a double-arched frame, the midpoints of the arches being connected respectively to the sliding joint and the fixed point.

[0019] One embodiment provides for an electricity production system comprising equipment subjected to mechanical vibrations and a device for recovering vibratory mechanical energy.

[0020] According to one embodiment, the device is attached to the equipment. Brief description of the drawings

[0021] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the attached figures, among which: there figure 1 is a very schematic view illustrating the operating principle of a bistable-type electrical generator for recovering mechanical vibration energy; the figure 2 is a very schematic plan view of one embodiment of a device for recovering vibrational energy and converting it into electrical energy; the figure 3 is a schematic and partial perspective view of one embodiment of a sliding connection between a blade structure and a mechano-electrical conversion device; the figure 4is a very schematic plan view of another embodiment of a device for recovering vibrational energy and converting it into electrical energy; the figure 5 is a schematic and partial perspective view of another embodiment of a sliding connection from a blade structure to a mechano-electrical conversion device; and the figure 6 is an enlarged view of an embodiment of an energy conversion device adapted to the embodiments of energy recovery systems described. Detailed description

[0022] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0023] For the sake of clarity, only the steps and elements necessary for understanding the described embodiments have been shown and detailed. In particular, the system, equipment, device, or environment providing the vibrational energy (vibrations) has not been detailed, as the described embodiments are compatible with common vibration sources in electrical energy conversion applications. Furthermore, the use of the recovered electrical energy has also not been detailed, as the described embodiments are, again, compatible with common applications of energy harvesters and electrical energy conversion.

[0024] Unless otherwise specified, when referring to two elements connected or fixed together, this means directly connected without any intermediate element other than a binder such as glue, welding or screwing, and when referring to two elements associated or coupled together, this means that these two elements can be directly connected or connected via one or more other elements.

[0025] In the description that follows, when referring to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative positional qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientational qualifiers, such as the terms "horizontal", "vertical", etc., unless otherwise specified, it refers to the orientation of the figures.

[0026] Unless otherwise specified, the expressions "approximately", "roughly", "about", and "on the order of" mean within 10%, preferably within 5%.

[0027] There figure 1 is a very schematic view illustrating the operating principle of a bistable type electrical generator for the recovery of mechanical vibration energy.

[0028] The generator comprises a support and protection housing 2', generally parallelepiped in shape, adapted for mounting on a vibrating surface 6' of equipment capable of vibrating. In this example, external vibrations are likely to exert an excitation on the housing 2', the effect of which can be schematically represented by a directional force Fext. The housing 2' contains a spring blade 3' whose two ends bear, in compression, on two opposite lateral faces of the housing. The two points of contact of the blade 3' on the housing 2' are positioned along an axis substantially orthogonal to the direction Fext of the vibrations. A mass 4' is fixed to the blade 3', substantially at its midpoint.The blade 3', compressed between its two ends, and the mass 4', define a nonlinear, or bistable, system which, under the influence of external vibrations, can move from one to the other of two stable equilibrium positions (represented respectively by solid and dashed lines in the figure). This system can also oscillate around each of the two equilibrium positions. A piezoelectric-type mechano-electric converter (not shown) is provided to convert the motion of the blade 3' and the mass 4' into electrical energy.

[0029] There figure 2 is a very schematic plan view of an embodiment of a device 1 for recovering vibrational energy and converting it into electrical energy.

[0030] According to the described embodiments, the energy recovery device 1 comprises a support housing provided with a rigid frame 2, formed of walls 22, 24, 26, 28. The housing is for example closed by two plates (not shown), on either side of the frame 2, in order to protect the interior from dust or other.

[0031] A bistable leaf spring structure 3, associated with at least one mass 4, constitutes the vibrational energy recovery mechanism. According to the embodiments described, the leaf spring structure is a structure comprising two parallel leaves, for example of the type described later in relation to the figure 3 .

[0032] One end of the blade structure 3 is fixed to one side 22 of the frame (point 23). The other end of the structure 3 is connected to an element 8, mounted in translation through the opposite wall 24 of the frame 2. This element 8 is intended to slide through the wall 24 in a direction approximately parallel to the median direction of the bistable structure 3.

[0033] Element 8 rigidly connects the blade structure 3 to a mechano-electrical energy conversion device 5. Device 5 comprises a piezoelectric element 52 constrained, in the example shown, by a armature, generally referred to as a flex-tensor, here in the form of a double arch 54, 56, or a rhombus. On the side opposite element 8, device 5 is connected to a fixed point 72, for example, on a frame 7, relative to the wall 22 of the frame 2. In other words, the distance between the end of the blade structure 3 and point 72 is constant. This ensures the bistable operation of the recuperator despite the sliding connection through the wall 24. For example, the frame 7 is part of a second frame rigidly connected to the frame 2.

[0034] Thus, the conversion device 5, based on a piezoelectric element, is planned to be placed outside the frame housing 2. One advantage is that this avoids the passage of conductive wires 58 through the walls of the frame.

[0035] There figure 3 is a schematic and partial perspective view of one embodiment of a sliding element 8 connecting a blade structure 3 to a device 5. The figure 3 also illustrates one embodiment of the blade structure 3.

[0036] According to this embodiment, structure 3 consists of two parallel blades 32 and 34. Mass 4 is fixed to the two blades at their midpoint. One advantage of a double-blade structure is that it prevents torsion of the blade structure and constrains the direction of oscillation.

[0037] Preferably, the space between the two blades 32 and 34 is kept constant. In the example of the figure 3, this space is kept constant by the respective fixings of the blades to the mass 4, to the frame (point 23) for one end of the structure and to the element 8 for the other end.

[0038] According to the embodiment shown in figure 3 , element 8 has the form of a plate arranged perpendicularly to blades 32 and 34. Element 8 is slidably mounted in a slot 242 in the edge 24 of the frame to be connected to device 5.

[0039] One advantage of this method of implementation is that it avoids twisting the system.

[0040] According to another embodiment, the element 8 is a cylindrical rod mounted to slide in the wall 24. Preferably, to avoid any twisting of the blade structure 3, an oval section rod is preferred to a round section rod.

[0041] Any other type of sliding joint from a kinematic point of view (in translation in the axis of the blade structure 3) without rotation (in order to avoid a twisting of the bistable structure 3) may be suitable.

[0042] There figure 4 is a very schematic plan view of another embodiment of a device 1 for recovering vibrational energy and converting it into electrical energy.

[0043] It should be noted that, as with the figure 2 The two-parallel-blade structure is not detailed in figure 4 for the sake of simplifying the design. However, whether in the method of implementation of the figure 2 or in that of the figure 4 A structure with two parallel blades is planned.

[0044] In relation to the method of implementation of the figure 2The sliding connection between the blade structure 3 and the electrical energy conversion device 5 is not sliding, but is achieved by a flexible wall 24' between the blade structure 3 and the device 5. In the example of the figure 4 This is schematically represented by a wall 24' that is thinner than the other walls 22, 26, and 28 of the housing frame 2. However, the same effect can, for example, be achieved with a wall 24' made of a different material. In this embodiment, the blade structure 3 on one side and a connecting element 8' of the device 8 to the wall 24' bear directly against the wall 24'.

[0045] One advantage of such a sliding connection without sliding is that friction is avoided, which optimizes the transmission of forces axially.

[0046] There figure 5 is a schematic and partial perspective view of a non-sliding sliding connection of a blade structure 3 to a device 5.

[0047] According to this example, the two blades 32 and 34 bear directly against the wall 24' at their respective ends on the device side 5. Similarly, the element 8' bears directly against the wall 24'.

[0048] The buckling of the blade structure, in order to give it a bistable character, is achieved, for example, by constraining sides 26 and 28 of frame 2 (the two long sides in the example of the figure 2 ) outwards, that is, by moving them apart. This causes a shortening between walls 22 and 24 ( figure 2 ), respectively 22 and 24' ( figure 4 ) and, since the distance between points 23 and 7 is fixed, a buckling of the structure.

[0049] Other solutions could be considered to place the blade structure in a buckling position, for example, by causing an elongation of the blade structure 3.

[0050] Preferably, the two support points 23 and 7 of the resulting system are placed along an axis substantially orthogonal to the expected Fext orientation of the vibrations.

[0051] There figure 6 is an enlarged view of an embodiment of an energy conversion device 5 adapted to the embodiments of energy recovery systems described.

[0052] A structure with two parallel blades and a mass, preferably central in the length of the structure, has many advantages.

[0053] The two blades and the fact that their gap is fixed prevent any rotation of the structure around an axis perpendicular to the plane of the system, particularly at the level of mass 4 (or masses in the case where several masses are planned).

[0054] Furthermore, this limits any rotational movement at the sliding joint, regardless of whether it is implemented according to the embodiment of the figure 3or according to that of the figure 5 Indeed, the median position of the structure, in unstable equilibrium between its two stable positions, is planar (in a fictitious plane parallel to the planes in which the blades are inscribed), which forces the deformation of the sliding joint in the axis (the longitudinal median direction) of the blades.

[0055] Therefore, the presence of two parallel blades facilitates the connection with the slide by limiting mechanical movement on it. The midpoints of the hoops 54 and 56 are connected, for one, to element 8 and, for the other, to the frame 7, preferably via a rigid arm 37. The ends of the hoops 54 and 56 are fixed to the ends of the piezoelectric element 52 (for example, a stack of interlocking piezoelectric plates, a piezoelectric bar, or any other suitable piezoelectric structure). The connections 545 and 565 of the midpoints of the hoops 54 and 56 to element 8 and frame 7 are, for example, rigid (bonded or welded), or made via pivot joints. The end electrodes of the piezoelectric element 52 are connected, by conductive wires 58, to electrical / electronic circuits (not shown) for shaping the recovered electrical signal.

[0056] The piezoelectric effect is obtained by deforming (crushing, releasing) the hoops 54 and 56 from their mid-sections (connections 545 and 565), which causes stress (extension, compression) on the piezoelectric element 52 and generates electricity. figure 6 Arrows illustrate the stresses during the passage of the system through the median (unstable) position. The piezoelectric element 52 is constrained in tension by the approach of points 545 and 565 towards each other, which causes an elongation of the armature.

[0057] It is noted that the active direction of the piezoelectric element 52 is approximately perpendicular to the direction of the blade structure 3, therefore approximately parallel to the direction of the vibrations.

[0058] One might have considered inserting a piezoelectric element in line with a spring blade. However, this would generate excessive torsional stresses on the element. An advantage of the described conversion devices is that the piezoelectric element 52 is protected, as the hoops 54 and 56 form a non-square, diamond-shaped frame in one diagonal of which the piezoelectric element 52 is fixed.

[0059] The kinematics of device 1 in operation are as follows. Starting from one of the two stable positions, for example the one illustrated in solid line in figure 2 , a displacement of the blade assembly 3 / mass 4 towards the other stable position (dotted line in figure 2) causes the hoops 54 and 56 of the conversion device 5 to compress in order to pass the median position, hence an elongation of the piezoelectric element 52, which causes the generation of electricity. The system relaxes upon reaching the other stable position. The frame 2 and the chassis 7 are rigidly fixed, for example screwed or glued to the vibrating equipment (6', figure 1 ). The vibrations cause the system to oscillate between the two stable positions, thus generating electricity.

[0060] Although we have shown an embodiment with a single conversion device, we can foresee two devices 5 (or even more) one after the other between the element 8 and the fixed point 72.

[0061] One advantage of the described embodiments is that it is now possible to design, fabricate, and assemble the bistable oscillator 3-4 and the energy converter 5 separately, thus offering greater flexibility in terms of design and implementation. The system is also thereby made modular.

[0062] Another advantage of the described embodiments is that the robustness of the resulting device is improved by reducing stress on the electrical connections of converter 5. Indeed, it is no longer subjected to oscillations about the axis, due to buckling as would be the case if placed inside frame 2, but thanks to the presence of a bimetallic strip (or multiple parallel strips), it is only subjected to axial displacements. Thus, the connections (welds) of the electrical connections are preserved.

[0063] For example, the blade(s) can be formed from a steel strip approximately 5 to 50 mm wide, for example, approximately 20 mm, and approximately 100 to 500 µm thick, for example, approximately 200 µm. The blade structure 3 can be 5 to 20 cm long, for example, approximately 10 cm. The mass 4 can weigh approximately 10 to 250 g, for example, approximately 50 g. The mass 4 can be attached to the blade(s) by gluing, welding, screwing, or any other suitable method. Of course, the dimensions above are given only as examples. In practice, the system dimensions can range from a few tenths of a millimeter to a few tens of centimeters.

[0064] Various embodiments and variations have been described. These various embodiments and variations are combinable, and other variations will become apparent to those skilled in the art. In particular, other frame geometries 2 may be considered. Furthermore, although a bi-blade system is a preferred embodiment due to its simplicity, more than two parallel blades may be used to form the blade structure 3. Finally, the practical implementation of the described embodiments is within the grasp of those skilled in the art, based on the functional specifications given above, particularly regarding the dimensions of the various elements according to the application.

Claims

1. A mechanical vibration energy harvesting device (1) including a bistable spring blade structure (3) in a frame (2), and a sliding joint (8, 24') at the level of a wall (24, 24') of the frame between said structure and at least one mechanical-to-electrical conversion device (5) external to the frame, characterised in that the blade structure (3) comprises at least two blades (32, 34) parallel to each other and in that a mass (4) is attached in a central portion of the blade structure (3), the mass (4) connecting the at least deux blades (32, 34).

2. The device according to claim 1, wherein said sliding joint is obtained by an element (8) sliding in said wall (24) and coupling said blade structure (3) to said mechanical-to-electrical conversion device (5).

3. The device according to claim 1, wherein said sliding joint is obtained by a deformation of said wall (24') between said blade structure (3) and said mechanical-to-electrical conversion device (5).

4. The device according to any of claims 1 to 3, wherein the mechanical-to-electrical conversion device (5) is coupled to a fixed point (72) with respect to the frame (2).

5. The device according to any of claims 1 to 4, wherein the blade structure (3) is buckled between the frame (2) and said sliding joint (8, 24').

6. The device according to any of claims 1 to 5, wherein the mechanical-to-electrical conversion device (5) comprises a piezoelectric element (52) in a direction approximately perpendicular to the direction of the blade structure (3).

7. The device according to claim 6, wherein the mechanical-to-electrical conversion device (5) comprises a frame in the form of a double arch (54, 56), the middles (545, 565) of the arches being respectively coupled to the sliding joint (8, 24') and to the fixed point (72).

8. An electric power generation system comprising: - an equipment (6') submitted to mechanical vibrations; and - a device (1) according to any of claims 1 to 7.

9. The system according to claim 8, wherein the device (1) is attached to the equipment (6').