Source: http://www.sumobrain.com/patents/wipo/Electromechanical-generator-converting-mechanical-vibrational/WO2019185463A1.html
Timestamp: 2019-12-09 19:29:31
Document Index: 632007566

Matched Legal Cases: ['art.\n10', 'art.\n11', 'art 118', 'art 120', 'art 118', 'art 120', 'art 118']

WIPO Patent Application WO/2019/185463
An electromechanical generator for converting mechanical vibrational energy into electrical energy, the electromechanical generator comprising: a central mast, an electrically conductive coil assembly fixedly mounted to the mast, the coil assembly at least partly surrounding the mast, a mount for the coil assembly extending radially inwardly of the coil assembly and fixing the coil assembly to the mast, a magnetic core assembly movably mounted to the mast for linear vibrational motion along an axis about an equilibrium position on the axis, the magnetic core assembly at least partly surrounding the coil assembly and the mast, a biasing device mounted between the mast and the magnetic core assembly to bias the magnetic core assembly in opposed directions along the axis towards the equilibrium position, the biasing device comprising a pair of first and second plate springs, each of the first and second plate springs having an inner edge respectively fitted to first and second opposite ends of the mast and an outer edge fitted to the magnetic core assembly, the outer edge of the first plate spring being fitted to a first end part of the magnetic core assembly and the outer edge of the second plate spring being fitted to a second end part of the magnetic core assembly, wherein each of the first and second plate springs comprises a spring member comprising an inner portion, which is substantially orthogonal to the axis and includes the respective inner edge, and a cylindrical outer portion which is substantially parallel to the axis and includes the respective outer edge, the spring member being a folded sheet spring and the inner and outer portions are connected by a fold.
WASENCZUK, Adam (Unit 7 The QuadrangleAbbey Park,Abbey Insdustrial Estate, Romsey SO51 9DL, SO51 9DL, GB)
EP2019/057197
JP2002181126A 2002-06-26
a mount for the coil assembly extending radially inwardly of the coil assembly and fixing the coil assembly to the mast,
a magnetic core assembly movably mounted to the mast for linear vibrational motion along an axis about an equilibrium position on the axis, the magnetic core assembly at least partly surrounding the coil assembly and the mast,
a biasing device mounted between the mast and the magnetic core assembly to bias the magnetic core assembly in opposed directions along the axis towards the equilibrium position, the biasing device comprising a pair of first and second plate springs, each of the first and second plate springs having an inner edge respectively fitted to first and second opposite ends of the mast and an outer edge fitted to the magnetic core assembly, the outer edge of the first plate spring being fitted to a first end part of the magnetic core assembly and the outer edge of the second plate spring being fitted to a second end part of the magnetic core assembly, wherein each of the first and second plate springs comprises a spring member comprising an inner portion, which is substantially orthogonal to the axis and includes the respective inner edge, and a cylindrical outer portion which is substantially parallel to the axis and includes the respective outer edge, the spring member being a folded sheet spring and the inner and outer portions are connected by a fold.
2. An electromechanical generator according to claim 1 wherein each outer edge is fitted to an outer circumferential surface of the magnetic core assembly.
3. An electromechanical generator according to claim 2 wherein each outer edge is push-fitted onto the outer circumferential surface of the magnetic core assembly.
4. An electromechanical generator according to any foregoing claim wherein the inner edge of each of the first and second plate springs is fitted to the mast by a riveted joint between the inner edge and the mast.
5. An electromechanical generator according to any foregoing claim further comprising a pair of first and second spacers, the first spacer being fitted between the first plate spring and a first surface of the mast, and the second spacer being fitted between the second plate spring and a second surface of the mast, the first and second surfaces being located at the respective first and second opposite ends of the mast.
6. An electromechanical generator according to any foregoing claim, wherein the inner portion is substantially circular.
7. An electromechanical generator according to claim 6, wherein the inner portion has an outer circumferential part adjacent to the fold, an inner circumferential part adjacent to the inner edge, and at least three arms connecting together the outer and inner circumferential parts, the arms being mutually spaced around the axis and each pair of adjacent arms being separated by a respective opening therebetween.
8. An electromechanical generator according to claim 7, wherein the arms are equally mutually spaced around the axis.
9. An electromechanical generator according to claim 7 or claim 8, wherein each arm comprises a radial outer part connected to the outer circumferential part, a middle circumferential part connected to the radial outer part, and a radial inner part connected between the middle circumferential part and the inner circumferential part.
10. An electromechanical generator according to any one of claims 7 to 9, wherein each opening comprises an outer circumferential region adjacent to the outer circumferential part, a middle radial region connected to the outer circumferential region, and an inner circumferential region connected to the middle radial region and adjacent to the inner circumferential part.
11. An electromechanical generator according to any one of claims 7 to 10, wherein each opening extends between outer and inner opening ends, each of the opening ends having an enlarged width as compared to the adjacent portion of the opening.
12. An electromechanical generator according to any one of claims 7 to 11 , wherein there are exactly three arms and exactly three openings.
13. An electromechanical generator according to any one of claims 7 to 12, wherein the arms have the same shape and dimensions.
14. An electromechanical generator according to any one of claims 7 to 13, wherein the openings have the same shape and dimensions.
15. An electromechanical generator according to any foregoing claim further comprising a resilient device mounted between the biasing device and the magnetic core assembly, the resilient device being configured to be deformed between the biasing device and the magnetic core assembly when the magnetic core assembly has moved, by the linear vibrational motion, away from the equilibrium position by a predetermined non-zero threshold amplitude, the resilient device comprising a pair of first and second flat spring elements, each of the first and second flat spring elements having an outer edge fitted to the magnetic core assembly and a free inner edge spaced radially outwardly from the mast and spaced axially inwardly of the respective first and second plate spring, the outer edge of the first flat spring element being fitted to the first end part of the magnetic core assembly and the outer edge of the second flat spring element being fitted to the second end part of the magnetic core assembly.
16. An electromechanical generator according to claim 15, when appendant on claim 5 or any claim dependent thereon, wherein the first and second spacers extend radially outwardly of the mast and define respective first and second faces each of which is oriented inwardly towards, and spaced from, in a direction along the axis, the respective free inner edge of the respective first and second flat spring element.
17. An electromechanical generator according to claim 16 wherein the first and second faces are spaced from, in the direction along the axis, the respective free inner edge of the respective first and second flat spring elements by a respective gap having a predetermined length.
18. An electromechanical generator according to any one of claims 15 to 17 wherein only the outer edge of each of the first and second flat spring elements is in contact with any other part of the electromechanical generator.
19. An electromechanical generator according to claim 18 wherein each of the first and second flat spring elements has an inner surface which faces the magnetic core assembly, and a peripheral portion of each inner surface contacts the magnetic core assembly.
20. An electromechanical generator according to claim 19 wherein the peripheral portion of each inner surface contacts an upstanding peripheral edge of the magnetic core assembly.
21. An electromechanical generator according to any foregoing claim wherein the magnetic core assembly comprises two opposed magnetic circuits spaced along the axis.
22. An electromechanical generator according to any foregoing claim wherein the magnetic core assembly comprises a pair of magnets spaced along the axis, poles of the magnets having a first common polarity facing towards each other, and poles of the magnets facing away from each other being of a second common polarity, and a ferromagnetic body contacting and magnetically coupled to the poles of the magnets facing away from each other, the ferromagnetic body extending radially outwardly of the magnets relative to the axis.
23. An electromechanical generator according to claim 22 wherein the ferromagnetic body is tubular and has radially inwardly extending arms at each end thereof, each arm mounting a respective magnet thereon.
24. An electromechanical generator according to claim 22 or claim 23 wherein the ferromagnetic body comprises a radially outer portion, and opposite end portions, of the magnetic core assembly and the magnets comprise a radially inner portion of the magnetic core assembly.
The Applicant’s earlier US-A-7586220, US-A-8492937 and WO-A-2014/076143 disclose vibration energy harvesters in the form of an electromechanical generator in which the spring of a spring-mass combination comprises a flat spring as a linear flexure bearing. However, precise control of the spring rate (frequency) and friction is difficult to achieve.
In these prior patent specifications, the flat spring comprises thickened outer and inner circumferential edges, which localises the spring strain in a central region of the spring between the edges, thereby to control the spring rate (frequency) and friction. This means that the outer and inner circumferential edges of the spring must be made relatively stiff in relation to the remainder of the spring. This implies substantially thicker material in the ends of the spring, with a smooth transition to a thinner central portion. Also, in these prior designs, the thicker outer and inner ends of the spring are provided with helical screw threads to enable the spring to be securely fitted to the mass. This increases manufacturing complexity and cost. US-A-8492937 discloses an alternative embodiment in which the outer circumferential edge of the flat spring is received in an annular recess cut into a housing. However, such a structure can exhibit reduced performance and again also increases manufacturing complexity and cost.
US-A-7586220, US-A-8492937 and W O- A-2014/076143 also disclose that openings can be cut into the thin central‘web’ of the flat spring to help concentrate the flexural strain therein. The thin central‘web’ of the flat spring can be provided with a pair of opposed spiral arms extending between the outer and inner circumferential edges of the spring, or alternatively a pair of oppositely oriented yokes connecting the outer and inner circumferential edges of the spring. These prior structures suffer from the problem that they provide a non-uniform spring constant around the spring, and the spring has a low mechanical strength in one direction extending though the plane of the spring.
There is a need in the art to provide a spring of the spring-mass arrangement of the electromechanical generator which minimizes the manufacturing complexity and cost of such a spring, yet provides an accurate and uniform spring constant.
The present invention aims at least partially to provide an energy harvester in the form of electromechanical generator which incorporates a spring of the spring-mass arrangement of the electromechanical generator which minimizes the manufacturing complexity and cost of such a spring, yet provides an accurate and uniform spring constant.
The present invention accordingly provides an electromechanical generator electromechanical generator for converting mechanical vibrational energy into electrical energy, the electromechanical generator comprising: a central mast, an electrically conductive coil assembly fixedly mounted to the mast, the coil assembly at least partly surrounding the mast, a mount for the coil assembly extending radially inwardly of the coil assembly and fixing the coil assembly to the mast, a magnetic core assembly movably mounted to the mast for linear vibrational motion along an axis about an equilibrium position on the axis, the magnetic core assembly at least partly surrounding the coil assembly and the mast, a biasing device mounted between the mast and the magnetic core assembly to bias the magnetic core assembly in opposed directions along the axis towards the equilibrium position, the biasing device comprising a pair of first and second plate springs, each of the first and second plate springs having an inner edge respectively fitted to first and second opposite ends of the mast and an outer edge fitted to the magnetic core assembly, the outer edge of the first plate spring being fitted to a first end part of the magnetic core assembly and the outer edge of the second plate spring being fitted to a second end part of the magnetic core assembly, wherein each of the first and second plate springs comprises a spring member comprising an inner portion, which is substantially orthogonal to the axis and includes the respective inner edge, and a cylindrical outer portion which is substantially parallel to the axis and includes the respective outer edge, the spring member being a folded sheet spring and the inner and outer portions are connected by a fold.
The present invention is predicated on the finding that a flat spring having a folded edge between a central inner portion, to function as a flexural plate spring, and an outer portion for fitting to a magnetic core assembly, can achieve a high stiffness outer part of the plate spring. This structure can be readily achieved by press-moulding a sheet of spring metal having constant thickness. Thickened edges of the spring can be avoided. The outer portion can readily be fitted a magnetic core assembly of the electromechanical generator, for example by a press-fit around an outer surface of the magnetic core assembly. The inner portion can also avoid a thickened edge, since the inner portion can readily be fitted to a central fixed mast of the electromechanical generator, for example by a riveted fitting to the mast. The spring of the spring-mass arrangement can have a low manufacturing cost, is easy to manufacture and provides an accurate and uniform spring constant.
The resultant spring structure can reliably and accurately provide support for the spring structure at the centre and edge of the flexure portion of the spring without frictional losses, fretting, or looseness at the joints, without requiring any thickening of the inner and outer edges of the spring. It has been found that forming a flat sheet of the metal spring material into a folded dish is an improved technique to stiffen the outer edge, and the inner edge can be fitted to the mast in an improved technique to stiffen the inner edge of the fitted spring without thickening the constant thickness sheet.
The present invention is furthermore predicated on the finding that a flat spring having at least three arms connecting together outer and inner circumferential parts of an inner portion of the spring, the arms being mutually spaced around the axis and each pair of adjacent arms being separated by a respective opening therebetween, can provide a spring that has high stiffness and strength in the radial direction. The spring constant is substantially uniform and isotropic in any radial direction extending through the plane of the flat spring. Again, this structure can be readily achieved by press-moulding a sheet of spring metal having constant thickness.
Figure 2 is a schematic plan view of a spring in the electromechanical generator of Figure 1;
The electromechanical generator of the present invention is a resonant generator known in the art as “velocity-damped” where substantially all of the work done by the movement of the inertial mass relative to the housing is proportional to the instantaneous velocity of that movement lnevitably, a portion of that work is absorbed overcoming unwanted mechanical or electrical losses, but the remainder of the work may be used to generate an electrical current via a suitable transduction mechanism, such as the electrical coil/magnetic assembly described below.
Figures 1 and 2 illustrate an electromechanical generator 2 for converting mechanical vibrational energy into electrical energy in accordance with a first embodiment of the present invention. In operation, the electromechanical generator 2 is enclosed within a housing (not shown) and the device is provided with a fitting (not shown) for securely mounting the electromechanical generator 2 to a support (not shown) from which support mechanical vibrational energy is harvested which is converted into electrical energy by the electromechanical generator 2.
The electromechanical generator 2 comprises a central mast 4 extending along a longitudinal axis A-A. In use, the amplitude of the input mechanical vibrational energy is typically along, or has a component extending along, the longitudinal axis A-A. The opposite ends 6, 8 of the mast 4 are fitted to the housing (not shown) and one or both ends 6, 8 of the mast 4 may be provided with a fitting (not shown), for example a threaded hole, for securely mounting the electromechanic al generator 2 to a support, or to a housing.
The mount 22 comprises a conical wall 26 extending between the coil assembly 10 and the mast 4. The conical wall 26 is integral with the annular coil support 24. The annular coil support 24 includes a radially oriented inner wall 28 which connects to the conical wall 26. The conical wall 26 is a moulded body, preferably injection moulded, composed of a thermoplastic material, and the moulded body comprises the annular coil support 24 and the conical wall 26. Preferably the thermoplastic material is a very low-conductivity material, such as glass-loaded plastic.
The magnetic core assembly 40 further comprises first and second end cores 54, 56 contacting and magnetically coupled to the outer core 50 at respective opposite first and second ends 58, 60 of the outer core 50. The first and second end cores 54, 56 extend radially inwardly and enclose the respective first and second opposite edges 18, 20 of the coil assembly 10. The magnetic core assembly 40 further comprises the first and second magnets 42, 44 spaced along the axis A-A. The first and second magnets 42, 44 contact and are magnetically coupled to the respective first and second end cores 54, 56. The first and second coil portions l3a, l3b are respectively at least partly located between the outer core 50 of the common ferromagnetic body and one of the magnets 42, 44.
The first and second end cores 54, 56 comprise plates. The first and second end cores 54, 56 may be planar or may be provided with some three-dimensional shaping on the outer or inner surfaces. The first and second end cores 54, 56 are circular, each having an outer circumferential surface 74 fitted to an inner circumferential surface, which is the longitudinal mounting surface 70, of the outer core 50 and a central hole 76 surrounding the mast 4. In the illustrated embodiment the first and second end cores 54, 56 are circular discs which are fitted into the ends of the tubular body 52. The circular circumference of the first and second end cores 54, 56 may be axially fitted to shoulders, formed by the transverse and longitudinal mounting surfaces 68, 70, on the inner side 66 of the tubular body 52. The fitting may be a pressure, relaxation or elastic fit. The first and second end cores 54, 56 may be optionally bonded to the tubular body 52. The resultant structure provides a substantially C-shaped magnetic core with substantially uniform ferromagnetic properties, and an accurate axial length.
The cavity 92 has respective cavity portions between each of the first and second coil portions l3a, l3b and the central mast 4, and above or below, respectively, the conical wall 26 of the mount 22.
The resultant effect is that a single magnetic core assembly 40 comprises two separate magnets 42, 44 and each has a respective magnetic circuit in which a very high proportion of the magnetic flux is constrained to pass through the respective coil portion l3a, 13b. This in turn provides a very high degree of magnetic coupling between the magnets 42, 44 and the coil 12. Consequently, any relative movement between the magnets 42, 44 and the coil 12, in particular as described below by linear axial resonant movement of the magnetic core assembly 40 relative to the fixed coil 12, produces a very high electrical power output at the coil 12.
A biasing device 100 is mounted between the mast 4 and the magnetic core assembly 40 to bias the magnetic core assembly 40 in opposed directions along the axis A-A towards the equilibrium position. The biasing device 100 comprises a pair of first and second plate springs 102, 104. Each of the first and second plate springs 102, 104 has an inner edge 106, 108 respectively fitted to the first and second opposite ends 6, 8 of the mast 4 and an outer edge 114, 116 fitted to the magnetic core assembly 40. The outer edge 114 of the first plate spring 102 is fitted to a first end part 118 of the magnetic core assembly 40 and the outer edge 116 of the second plate spring 104 is fitted to a second end part 120 of the magnetic core assembly 40.
Each of the first and second plate springs 102, 104 comprises a spring member 122, 124 comprising an inner portion 126, 128, which is substantially orthogonal to the axis A-A and includes the respective inner edge 106, 108, and a cylindrical outer portion 130, 132 which is substantially parallel to the axis A-A and includes the respective outer edge 114, 116.
Each outer edge 114, 116 is fitted to an outer circumferential surface 138, 140 of the magnetic core assembly 40. In the illustrated embodiment, each outer edge 114, 116 is push-fitted onto the outer circumferential surface 138, 140 of the magnetic core assembly 40 and fitted thereto by an elastic fit.
The resilient device 186 comprises a pair of first and second flat spring elements 188, 190. Each of the first and second flat spring elements 188, 190 has an outer edge 192, 194 fitted to the magnetic core assembly 40 and a free inner edge 196, 198 spaced radially outwardly from the mast 4 and spaced axially inwardly of the respective first and second plate spring 102, 104. The outer edge 192 of the first flat spring element 188 is fitted to the first end part 118 of the magnetic core assembly 40 and the outer edge 194 of the second flat spring element 190 is fitted to the second end part 120 of the magnetic core assembly 40.
Typically, the outer edge 192, 194 of each of the first and second flat spring elements 188, 190 is fitted to the magnetic core assembly 40 by being urged by a spring so as to be securely retained in position against the magnetic core assembly 40. As shown schematically in Figure 1, a spring bias element 191 is provided between the outer edge 192, 194 and respective first or second plate spring 102, 104 which urges the outer edge 192, 194 firmly against the first or second end part 118, 120 of the magnetic core assembly 40. In an alternative, although less preferred, embodiment, the outer edge 192, 194 of each of the first and second flat spring elements 188, 190 may be otherwise fitted, for example directly fixed, to the magnetic core assembly 40.
However, the generator 2 is configured such that, when the oscillation amplitude exceeds the predetermined threshold amplitude, such as when it is subjected to a severe shock, the resilient device 186 is then deformed, i.e. flexed, between the biasing device 100 and the mass to act as a limiter that limits the oscillation amplitude. Accordingly, the electromechanical generator 2 according to the preferred embodiments of the present invention has particular utility in environments where it may be subjected to occasional severe shocks.
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