Electromagnetic device for converting mechanical energy into electrical energy

Description

Technical field of the invention

[0001] The present invention relates to an electromagnetic device for converting mechanical energy into electrical energy. State of the art

[0002] The conversion of mechanical energy into electrical energy has been a subject of study for many years. Different types of devices exist. For example, some use the piezoelectric effect, while others use an electromagnetic principle.

[0003] Currently, such devices are used in residential switches and industrial push buttons, which are known to be wireless and battery-free. When the button is pressed, the mechanical energy exerted is converted into electrical energy capable of powering a radio transmitter. The radio transmitter sends a message to a receiver designed to control an application (lamp, appliance, machine, etc.).

[0004] Numerous patent applications have already been filed for devices operating on the electromagnetic principle. Examples include patent applications WO2007 / 060072A1, WO2009 / 109449A1, and EP1611662A1.

[0005] These known devices operate on the basic principle originally described in patent application GB1312927.

[0006] This basic principle involves creating a reversal of magnetic flux through the casing of a coil wound around a magnetic circuit by pivoting a magnet. Depending on the position of the permanent magnet, the magnetic flux flows in one direction and then the other. The change in magnetic flux observed by the coil allows for the creation, by induction, of a voltage across the coil's terminals. This voltage can then be used to power the radio transmitter. The devices are monostable or bistable and are suitable, for example, for integration into the mechanism of a switch.

[0007] To achieve a significant change in flux through the coil and maximize the electrical energy obtained, the resulting mechanical motion must be rapid and of high amplitude. Therefore, these previous solutions are not necessarily suitable for use in space-constrained applications where a small amplitude mechanical motion is required.

[0008] For devices requiring a small actuation amplitude, a vibratory type mechanical movement can be used.

[0009] The principle of recovering electrical energy from a vibratory type mechanical movement is described in patent US8080906B2, as well as in patent applications WO2005 / 062443A1 and WO2009 / 003799A1.

[0010] There figure 1This schematically illustrates a conversion device, according to the prior art, that generates electrical energy from vibrational mechanical energy. The device comprises a magnetic circuit with several branches, in which a permanent magnet is inserted to create a magnetic flux within the circuit. The magnetic circuit passes through the casing of an electromagnetic coil. The magnetic circuit includes a variable air gap created by the bending motion of a beam partially embedded within the magnetic circuit. The beam is fixed at one end, allowing it to be actuated in its bending motion, and its free end carries a mass to facilitate its vibrational movement.

[0011] This solution is unsatisfactory because it does not allow for a sufficiently large flux variation through the coil. Indeed, the permanent magnet inserted in the magnetic circuit behaves like a fixed air gap, which is added to the variable air gap. In practice, we observe that, regardless of the beam's position, and therefore the value of the variable air gap, the majority of the magnet's magnetic flux always passes through the variable air gap. Consequently, the coil experiences little or no magnetic flux variation, which prevents it from obtaining a sufficient output voltage.

[0012] Patent application JP2020078237 describes an electrical power generator using a vibrating beam.

[0013] The aim of the invention is therefore to propose a conversion device that is capable of maximizing the electrical energy obtained from vibratory mechanical energy, that is to say with a low amplitude of movement, for example less than 1mm and / or less than five times the length of the magnet in the direction of its polarization. Description of the invention

[0014] This goal is achieved by an electromagnetic device for converting input mechanical energy into output electrical energy, comprising: A moving element capable of moving in a vibratory mechanical motion, A vibration source configured to actuate the moving element in its vibratory mechanical motion, A coil, A magnetic circuit passing through said coil, said coil being configured to generate the output electrical energy when said moving element is actuated in its vibratory mechanical motion, A permanent magnet arranged in the magnetic circuit and capable of generating a so-called total magnetic flux in the magnetic circuit, The magnetic circuit comprising a first air gap and a second air gap, said first air gap being substantially fixed and said second air gap being variable according to the position taken by the moving element in its vibratory mechanical motion,The permanent magnet is arranged in the magnetic circuit so that the total magnetic flux is split into a first magnetic flux through a first part of the magnetic circuit comprising the fixed air gap and a second magnetic flux through a second part of the magnetic circuit comprising the variable air gap. The coil is traversed by only one part of the magnetic circuit, chosen from the first part of the magnetic circuit and the second part of the magnetic circuit. The ratio between the first magnetic flux and the second magnetic flux varies according to the position of the moving element.

[0015] According to one particular feature, the moving element has at least one first branch integrated into the magnetic circuit.

[0016] According to another feature, the magnetic circuit has a second branch and the device has a link joining the first branch to the second branch.

[0017] According to another peculiarity, the link is inserted into the magnetic circuit and the first air gap is integrated into said link.

[0018] According to another peculiarity, the first air gap is arranged in a connecting branch joining said first branch to said second branch, arranged in parallel with said connection.

[0019] According to a particular embodiment, the link is a spring link capable of allowing the vibratory mechanical movement of the moving element.

[0020] According to another particular embodiment, said link is a rigid link and the first branch and / or the second branch is configured to flex in order to permit vibratory mechanical movement.

[0021] According to a particular feature, the said first branch is in the form of a beam fixed to the said connection by a first end part and which includes a second opposite end part which is free.

[0022] According to another particular embodiment, the magnetic circuit includes a third air gap which is variable and said moving element is arranged to oscillate between said second air gap and said third air gap.

[0023] According to another particular embodiment, said first branch is held in support by a first end part against a part of non-ferromagnetic material forming the first air gap, by at least one spring mounted between the first branch and the second branch.

[0024] According to another particular embodiment, the first branch is formed of a deformable membrane, and the connection includes an annular part forming a connection with the second branch.

[0025] One particular feature of the device is that it includes a seismic mass carried by the moving element.

[0026] According to a particular embodiment, the seismic mass is made of a ferromagnetic material and the second air gap is arranged between said seismic mass and the second branch of the magnetic circuit.

[0027] According to one particular feature, the vibration source includes a vibrating support to which the second branch is connected by a fixing point.

[0028] According to another particularity, the fixing point is positioned along an axis passing through the center of gravity of the seismic mass when the moving element is at rest.

[0029] According to a particular embodiment, the coil is positioned around the first branch of the magnetic circuit.

[0030] According to another particular embodiment, the coil is positioned around the second branch of the magnetic circuit. Brief description of the figures

[0031] Other features and advantages will appear in the detailed description that follows, in conjunction with the attached drawings, in which: There figure 1 schematically represents a device for converting mechanical energy into electrical energy, according to the state of the art; The figure 2 illustrates the operating principle of the conversion device according to the invention; The figures 3 to 12 represent different embodiments of the conversion device of the invention; Detailed description of at least one embodiment

[0032] The conversion device of the invention is intended to convert mechanical energy into electrical energy. The input mechanical energy is supplied in the form of vibrations. The output electrical energy is generated from the input mechanical energy using electromagnetic means.

[0033] The device is intended to exploit vibrations of relatively low amplitudes, typically less than 1 m / s² at 50Hz, i.e. often less than 10µm in amplitude, which can go up to a maximum of 1mm if the vibration frequency of the vibration source corresponds to the resonance frequency.

[0034] The source of vibration can be a vibrating support 70 to which the device is attached. This vibrating support can be subjected to an external mechanical force causing it to vibrate.

[0035] The system mainly comprises: A magnetic circuit; An electromagnetic coil 50 comprising a support and a winding formed around its support, said winding being positioned around the magnetic circuit; A permanent magnet 40 arranged to generate a magnetic flux through the magnetic circuit; A moving element 100 actuated in a vibratory mechanical motion. The moving element 100 comprises at least one part made of ferromagnetic material, inserted into the magnetic circuit. A magnetic flux is therefore capable of flowing through this part of the moving element; A vibration source enabling the vibratory mechanical motion to be imparted to the moving element 100;

[0036] The magnetic circuit comprises several branches made of ferromagnetic material which are assembled together and which define between them a path followed by the magnetic flux, said path comprising at least a first air gap E1 and a second air gap E2, the second air gap E2 being distinct from the first air gap E1.

[0037] A branch of a magnetic circuit is defined as an element of any shape whose cross-section is sufficient to allow the flow of magnetic flux. A branch may be elongated, straight, or angled. Other shapes are also possible.

[0038] The first air gap E1 is always fixed, that is to say that the non-zero distance which separates the two parts of the magnetic circuit forming this first air gap E1 always remains substantially the same, regardless of the position of the moving element 100.

[0039] The second air gap E2 is variable, that is to say that the distance which separates the two parts of the magnetic circuit forming this second air gap varies over time, depending on the position taken by the moving element 100.

[0040] With reference to the figure 2 , unlike the state-of-the-art solution shown on the figure 1In the invention, the permanent magnet 40 is arranged relative to the magnetic circuit so as to generate a first magnetic flux Fm_1 in a first part of the magnetic circuit comprising the first fixed air gap E1 and a second magnetic flux Fm_2 in a second part of the magnetic circuit comprising the second variable air gap E2. In other words, the permanent magnet 40 generates a total magnetic flux Fm_T which is divided between the first magnetic flux Fm_1 and the second magnetic flux Fm_2, the ratio between the first magnetic flux and the second magnetic flux then depending on the value of the variable air gap, and therefore on the position of the moving element 100.

[0041] Coil 50 is positioned in the part of the magnetic circuit likely to experience the greatest variation in magnetic flux. It may be traversed by the first part of the magnetic circuit or by the second part of the magnetic circuit defined above.

[0042] We will see below that in certain embodiments, some portions of the magnetic circuit may be common to its first and second parts. The two parts are thus distributed across the different branches that make up the magnetic circuit.

[0043] The magnetic circuit mainly comprises a first branch 10, a second branch 20 and a link 30 between the first branch and the second branch.

[0044] The mobile element 100 is, for example, integrated into the first branch 10.

[0045] The moving element 100 can be formed from a deformable beam.

[0046] In the latter case, it should be noted that to build a resonator that operates at low frequencies (<150Hz), it is useful to have a beam with a relatively high length-to-thickness ratio (for example, greater than 20). However, for manufacturing and robustness reasons, the beam's thickness cannot be too small, and its length must be relatively large compared to the other dimensions of the device.

[0047] The beam can be fixed at one end and free at a second end.

[0048] The second end part of the beam can carry a seismic mass 60, allowing it to be promoted through vibration and increasing the recoverable power.

[0049] In its first end section, the beam can be attached to a second branch of the magnetic circuit via the link 30. The link 30 can have a spring effect, allowing the vibratory movement of the moving element. Alternatively, the link 30 can also be rigid, the spring effect enabling the vibratory movement then being provided by at least one of the two branches 10, 20 of the device, which has sufficient mechanical properties to deform in bending.

[0050] Link 30 can be integrated into the magnetic circuit and used to carry the first magnetic flux Fm_1 or the second magnetic flux Fm_2. But link 30 can also be used to fulfill only a mechanical function of the spring type, allowing the beam to bend during its vibratory movement.

[0051] In its first end section, the beam can bear against a support attached to the second branch of the magnetic circuit. The link 30 is then replaced by a first spring 90 mounted between the moving element and the second branch. A second spring 91 can be mounted and configured to limit the movement of the seismic mass 60 relative to the second branch 20.

[0052] The first air gap can be inserted into the magnetic circuit, in the connection between the first branch and the second branch.

[0053] The first air gap E1 can be inserted between the beam and said block.

[0054] The first air gap E1 can be formed from a layer or piece of non-ferromagnetic material.

[0055] The second branch 20 has a free end relative to which the moving element 100 creates the second air gap E2.

[0056] The second air gap E2 can be formed between the seismic mass 60 carried by the beam and the free end of the second branch 20.

[0057] The second air gap E2 can be split, defined by two distinct spaces between the moving element 100 and the free end of the second branch 20.

[0058] The second air gap E2 varies with the movement of the moving element relative to the second arm 20. A stop can be provided to limit the stroke of the mechanical movement of the moving element 100, without the second air gap E2 becoming zero. This can be useful if the electromagnetic force becomes too strong at very small air gaps and risks inducing electromagnetic sticking, typically when this electromagnetic force becomes greater than the elastic restoring force exerted on the moving element 100.

[0059] Without limitation, the first air gap E1 and the second air gap E2 can be chosen to be almost identical when the moving element 100 is at rest.

[0060] The permanent magnet 40 can be attached to the first arm 10 and / or the second arm 20 of the magnetic circuit. It is oriented so as to generate the total magnetic flux Fm_T in the magnetic circuit, this total magnetic flux Fm_T being divided between the first magnetic flux Fm_1 which passes through the first air gap E1 and the second magnetic flux Fm_2 which passes through the second air gap E2. The permanent magnet 40 can, of course, be magnetically oriented in either direction between the two arms of the magnetic circuit, in order to polarize the magnetic field generated in the magnetic circuit in the desired direction.

[0061] The vibration source can be a vibrating support 70 to which the device is attached, in order to generate and maintain the vibratory movement of the moving element 100.

[0062] By way of example, the second arm 20 can be fixed to the vibrating support 70. Depending on the device configuration, where possible, the point of attachment of the device to the vibrating support 70 can ideally be aligned with the center of gravity of the seismic mass in the direction of vibration (see figure 4 with the center of gravity G of the seismic mass 60), to limit the torsional moments at the anchorage when the seismic mass is in motion.

[0063] Any additional mass can be added to the moving element 100 to promote its vibratory motion and increase the convertible mechanical energy.

[0064] Note that increasing the seismic mass (mass m) at the end of a beam does not necessarily result in a greater relative displacement. In fact, increasing this mass stiffens the beam so that the resonant frequency (Fr) remains close to the frequency of the vibration source, Fr = 1 / (2π)*√(k / m). The amplitude of the relative motion between the support and the seismic mass will remain approximately equal to the vibration amplitude multiplied by the quality factor Q. The recoverable power will be proportional to Q*m. Therefore, the greater the mass, the more energy can be recovered at a constant input vibration amplitude.

[0065] The coil 50 can be crossed by the first branch 10 of the magnetic circuit or by the second branch 20 of the magnetic circuit.

[0066] The device may have a symmetrical structure, with respect to a vertical plane or of revolution around an axis (A).

[0067] In a version with rotational symmetry, the moving element 100 can be in the form of a membrane capable of deforming during its vibratory mechanical movement.

[0068] The two branches 10, 20 can also be made in the form of plates, assembled together.

[0069] It should be noted that the permanent magnet 40 does not necessarily completely fill the space between the two arms 10 and 20 of the magnetic circuit. In practice, since the permeability of the permanent magnet 40 is close to that of a free space, it is not necessary to achieve mechanical contact between the two arms to induce a magnetic field in the magnetic circuit, at least as long as this space does not become significant compared to the length of the magnet. This characteristic allows the use of magnets whose dimensional characteristics are not critical, thus reducing their cost. Furthermore, the space between the free end of the permanent magnet and the opposite arm (first or second arm, as the case may be) can be used to adjust, without requiring high dimensional precision, the level of induction in the magnetic circuit relative to the intrinsic induction of the permanent magnet.

[0070] It should be noted that some of the features listed above can be combined. The general principles below should be taken into account in the various possible configurations: The bending that allows the vibratory movement can be made at the level of the first branch 10, the second branch 20 and / or the link 30. The link 30 can be a simple continuation of the second branch 20 or of the first branch 10, the first air gap E1 then being positioned as the case may be between the link 30 and the first branch 10 or between the link 30 and the second branch 20. The air gaps E1 and E2 are advantageously chosen to be small compared to the length of the permanent magnet 40 (the length of the magnet in its polarization direction can be 3 to 10 times greater than that of each air gap).

[0071] Based on these different characteristics, various embodiments of the device are described below in relation to the figures 3 to 12 .

[0072] In the description below of each variant, only the most significant features are highlighted. It should be understood that various other arrangements can be made in each case, for example, regarding the position of the coil 50, the permanent magnet 40, the shape of each branch 10, 20 of the circuit, the function of the link 30, the operating principle always remaining consistent with that described above in connection with the figure 2 . Figure 3

[0073] On this figure 3 This is the simplest architecture of the device. It corresponds to that of the figure 2 already mentioned above.

[0074] It comprises a first branch 10 and a second branch 20, each formed by two parallel beams. A link 30 connects one end of each branch and is configured to create a spring effect. The second branch is bent at its free end. A movable element 100 is integrated into the first branch 10. At its free end, the movable element 100 carries a seismic mass 60 designed to increase the mechanical input power.

[0075] The first air gap E1 is formed of a part of non-ferromagnetic material inserted in the connection between the first branch 10 and the second branch 20.

[0076] The second air gap E2 is inserted between the free end of the second branch 20 and the first branch 10, integrating the moving element.

[0077] The permanent magnet 40 is fixed to the second branch 20 and oriented to generate a total magnetic flux, dividing into a first magnetic flux Fm_1 through the first air gap E1 and a second magnetic flux Fm_2 through the second air gap E2.

[0078] Coil 50 is positioned around the second branch 20.

[0079] As an alternative to this configuration, as described above, the joint 30 can be made rigid, with the first branch 10 then being deformable in bending and acting as a spring. In this configuration, the joint 30 is included within the second branch 20 and simply extends it. It should be noted that the bending deformability can also be attributed to the second branch 20.

[0080] In this variant embodiment, the second branch 20 is anchored on the vibrating support 70, enabling the vibratory movement of the moving element 100 to be generated. Figure 4

[0081] This variant of the implementation of the figure 4 differs from that of the figure 3 in that the moving element 100 is integrated into the magnetic circuit and is therefore coincident with the first branch 10. The seismic mass 60 is made of a ferromagnetic material, this forming the second air gap E2 with the second branch 20. The second magnetic flux Fm_2 is therefore able to pass through the entire moving element 100 as well as the seismic mass 60 to circulate through the second air gap E2. Figure 5

[0082] This variant of the implementation of the figure 5 differs from that of the figure 4in that the coil 50 is positioned around the first arm 10 and the permanent magnet 40 is fixed to the first arm. This arrangement increases the mass of the moving element 100 and therefore increases the available mechanical energy. This principle can be applied generally to other embodiments. Figure 6

[0083] In this variant of the figure 6 , in order to transmit the movement of the vibrating support 70 to the moving element, the second branch 20 and the link 30 are made in the form of flexible parts.

[0084] The coil 50 is carried by the first branch 10 and an additional mass 80 is added to the seismic mass 60. Figure 7

[0085] In this variant of the figure 7The first air gap E1 is separated from the mechanical connection between the first branch 10 and the second branch 20. This connection is used only to mechanically link the two branches and is either not made of ferromagnetic material or, if it is, has an insufficient cross-section to allow the magnetic flux to pass through. The first air gap E1 is arranged between the first branch 10 and an additional branch attached to the second branch 20. Alternatively, the first air gap E1 can be arranged between the second branch 20 and the additional branch attached to the first branch 10. This additional branch is sized to allow the magnetic flux to pass between the two branches 10 and 20 via the first air gap E1. Figure 8

[0086] In this variant of the figure 8The second air gap E2 is split. This results in two variable air gaps E2, E3 created between the first branch 10 and the second branch 20. When one of the two air gaps is maximal, the other is minimal and vice versa.

[0087] This solution allows the frequency of the reluctance variation to be doubled compared to the vibration frequency. Figure 9

[0088] In this variant of the figure 9 The link 30 between the two branches 10 and 20, as well as the first air gap E1, are doubled. This solution allows the permanent magnet 40 to be placed in the space cleared between the two parts of the link thus formed. Figure 10

[0089] In this variant of the Figure 10, the moving element 100 is held against the link 30 by two springs 90, 91 each mounted between the second arm 20 and the first arm 10. The first air gap E1 is made by a layer of non-ferromagnetic material inserted between the moving element 100 and the link 30 at the level of the support area.

[0090] Note that for the figures 1 to 10It is possible to have the mechanical chain composed of the first branch 10, the first air gap E1, the link 30, and the second branch 20 attached to the same seismic mass 60 multiple times. For example, to ensure left-right symmetry. Or, to block all rotational movements of the seismic mass 60, for example, by using three arms placed at 120° intervals in the plane. These symmetries allow, for example, limiting the rotational moments of the seismic mass 60, or aligning, along the axis of displacement, the center of gravity of the overall mass of the device with the center of gravity of the portion of the mass that is in relative motion. This makes it possible to limit the rotational moments on the vibration support regardless of the amplitude of the relative motion, provided that the vibrating support 70 is itself fixed in alignment with the centers of gravity, in the direction of motion. Figure 11

[0091] According to the figure 11The device can be in a symmetrical form of revolution. It can thus take the form of a cylinder made using two nested parallel discs (the first disc forming branch 10 and the second disc forming branch 20). An annular space is provided between the two discs to form the first air gap E1. For example, the first disc 10 has a central stud onto which the coil is inserted. This central stud extends axially towards the second disc, and the second air gap E2 is formed between this stud and the second disc. The permanent magnet 40, made in an annular shape, is fixed to one of the two discs, arranged concentrically around the central stud. The second disc can be anchored to a vibrating support 70. The first disc can carry a mass 60 and be made in the form of a membrane capable of deforming during its vibratory motion.Alternatively, the second disc 20 can also behave as a deformable membrane.

[0092] In both versions, the membrane can be solid, but also optionally structured for flexibility, for example with a spiral pattern or a corrugation. The permanent magnet 40 can be ring-shaped, or composed of discrete magnets evenly distributed around its circumference. Figure 12

[0093] In this variant of the figure 12 The second branch 20 and the link 30 are each made in the form of a ferromagnetic plate. The two plates are joined on either side of a layer made of non-ferromagnetic material forming the first fixed air gap E1.

[0094] Each of the two plates can have an extension. The first arm 10 incorporates at least part of the moving element 100. The moving element 100 is positioned to extend between the two extensions, thus defining the second air gap E2. The permanent magnet 40 is, for example, held between two ferromagnetic elements, each fixed respectively to the first and second plates to create the magnetic circuit. The moving element 100 can be mounted on a support (not shown), and a spring solution can be used to allow relative movement of the moving element 100 with respect to the vibrating support 70.

[0095] Below is an example of sizing to better understand the principle of the invention. At rest, the two air gaps E1 and E2 are identical: the total magnetic flux Fm_T of the permanent magnet is thus divided approximately equally between the first and second parts of the magnetic circuit, passing respectively through the first air gap E1 and the second air gap E2. The magnetic permeability of the magnetic circuit is considered to be much greater than that of the air gaps; therefore, the air gaps are predominant in determining the reluctance values. In the lower position of the moving element (at the maximum of its relative displacement), the second air gap E2 is considered, for example, to be equal to half the size of the first air gap (E2 = 1 / 2 × E1). In this position, two-thirds of the total magnetic flux Fm_T passes through the second part of the magnetic circuit, via the second air gap E2, and one-third of the total magnetic flux Fm_T passes through the first part of the magnetic circuit, via the first air gap E1.In the upper position (at the maximum of relative displacement), the second air gap E2 is considered, for example, to be equal to 1.5 times the first air gap (E2 = 3 / 2 x E1). In this position, 2 / 5 of the total magnetic flux Fm_T passes through the second part of the magnetic circuit via the second air gap E2, and 3 / 5 of the total magnetic flux passes through the first part of the magnetic circuit, via the first air gap E1. Between the lower and upper positions, the coil 50 experiences a flux variation ranging from 2 / 3 to 2 / 5 of the total magnetic flux Fm_T.

[0096] For example, if we consider that the total magnetic flux Fm_T produces a magnetic field of 1T, at the level of the second air gap E2 in the lower position, the magnetic field passing through the second part of the magnetic circuit will then vary from 0.6 to 1T and the magnetic field passing through the first part of the magnetic circuit will vary from 0.5T to 0.9T. Coil 50 will see a variation of 0.4T.

[0097] Furthermore, it is possible to determine the magnetic energy that the device can generate, as well as the air gap cross-section required to generate this magnetic energy. To do this, the following data can be taken into account: A seismic mass m=20g; A vibration frequency of F=50Hz; The second air gap E2 located at 2 / 3 of the center of gravity of the seismic mass; A maximum acceleration vibration of A=0.2 m / s² and a maximum mechanical amplification of 100; A maximum beam end displacement of 203µm and at the level of the second air gap of 135µm in one direction or the other; The second air gap at rest, for example, equal to twice this displacement, i.e., 270µm; With a desired effective coupling k² of 0.6, a maximum mechanical deformation energy which is then E meca-max =ke*x² = 1608*(135µm)² = 29.3µJ. With a coupling loss of 0.2 due to copper losses, a change in magnetic energy required is (0.6+0.2)*E mecha-max =0.8*29.3pJ=23.5µJ; From the minimum air gap to the maximum air gap, then, during this change, it is necessary to transform twice this energy, i.e. 47µJ.The magnetic energy in each of the air gaps is E mag = B 2< / (2µ0)*V air gap with V air gap the volume of the air gap; A determined air gap section of 0.73 mm 2< ; .

[0098] The solution of the invention thus offers numerous advantages, including: It allows for a significant flux variation in the coil, from a relatively low amplitude vibratory movement; It allows the device to be used in systems with limited space; It remains of a relatively simple design, using means commonly employed in the electromagnetic field; It can be made according to different embodiment variants, while keeping a principle of operation always identical; It allows the use of magnets whose dimensional characteristics are not essential, reducing their cost.

Claims

1. Electromagnetic device for converting input mechanical energy into output electrical energy, comprising: - a movable element (100) that is able to make a vibratory mechanical movement, - a vibration source configured to actuate the vibratory mechanical movement of the movable element, - a coil (50), - a magnetic circuit passing through said coil (50), said coil being configured to generate the output electrical energy when said movable element (100) is making its vibratory mechanical movement, - a permanent magnet (40) arranged in the magnetic circuit and able to generate a magnetic flux, referred to as the total magnetic flux (Fm_T), in the magnetic circuit, - the magnetic circuit comprising a first gap (E1) and a second gap (E2), - characterized in that: - said first gap (E1) remains substantially constant and said second gap (E2) is variable as a function of the position taken by the movable element during its vibratory mechanical movement, - the permanent magnet (40) is arranged in the magnetic circuit so that the total magnetic flux (Fm_T) is split into a first magnetic flux (Fm_1) through a first portion of the magnetic circuit comprising the constant gap and a second magnetic flux (Fm_2) through a second portion of the magnetic circuit comprising the variable gap, - the coil (50) is passed through by a single portion of the magnetic circuit, which portion is chosen from the first portion of the magnetic circuit and the second portion of the magnetic circuit, and in that - the ratio between the first magnetic flux and the second magnetic flux varies as a function of the position of the movable element (100).

2. Device according to Claim 1, characterized in that the movable element (100) comprises at least one first leg (10) integrated into the magnetic circuit.

3. Device according to Claim 2, characterized in that the magnetic circuit comprises a second leg (20) and in that the device comprises a link (30) joining the first leg to the second leg.

4. Device according to Claim 3, characterized in that the link is inserted in the magnetic circuit and in that the first gap (E1) is integrated into said link.

5. Device according to Claim 4, characterized in that the first gap (E1) is arranged in a junction leg joining said first leg (10) to said second leg (20), which leg is arranged parallel to said link.

6. Device according to one of Claims 3 to 5, characterized in that the link (30) is a spring link apt to permit the vibratory mechanical movement of the movable element (100).

7. Device according to one of Claims 3 to 6, characterized in that said link (30) is a stiff link and in that the first leg and / or the second leg is configured to flex with a view to permitting the vibratory mechanical movement.

8. Device according to one of Claims 3 to 7, characterized in that said first leg (10) takes the form of a beam fastened to said link by a first end portion and that comprises a second end portion opposite that is free.

9. Device according to one of Claims 3 to 7, characterized in that the magnetic circuit comprises a third gap (E3) that is variable and in that said movable element (100) is arranged to oscillate between said second gap (E2) and said third gap (E3).

10. Device according to one of Claims 3 to 7, characterized in that a first end portion of said first leg (10) is held in abutment, against a portion made of non-ferromagnetic material forming the first gap (E1), by at least one spring (90) mounted between the first leg (10) and the second leg (20).

11. Device according to Claim 3, characterized in that the first leg (10) is formed from a deformable membrane, and in that the link (30) comprises an annular portion forming a link with the second leg (20).

12. Device according to one of Claims 3 to 11, characterized in that it comprises a seismic mass (60) borne by the movable element (100).

13. Device according to Claim 12, characterized in that the seismic mass (60) is made of a ferromagnetic material and in that the second gap (E2) is arranged between said seismic mass and the second leg of the magnetic circuit.

14. Device according to Claim 12 or 13, characterized in that the vibration source comprises a vibrating carrier (70) to which said second leg is connected at a fastening point.

15. Device according to Claim 14, characterized in that the fastening point is positioned along an axis passing through the centre of gravity of the seismic mass (60) when the movable element is at rest.

16. Device according to one of Claims 3 to 12, characterized in that the coil (50) is positioned around the first leg (10) of the magnetic circuit.

17. Device according to one of Claims 3 to 12, characterized in that the coil (50) is positioned around the second leg (20) of the magnetic circuit.