GB2463919A

GB2463919A - Portable electronic device charger

Info

Publication number: GB2463919A
Application number: GB0817903A
Authority: GB
Inventors: Michael John Tudor; Neil Maurice White; Stephen Paul Beeby; Nicholas Robert Harris
Original assignee: D4 TECHNOLOGY Ltd
Current assignee: D4 TECHNOLOGY Ltd
Priority date: 2008-09-30
Filing date: 2008-09-30
Publication date: 2010-03-31
Also published as: WO2010037708A3; WO2010037708A2; GB0817903D0; GB2463919A8

Abstract

A system for harvesting electrical energy from the vibration or movement of a portable electronic device 1, the portable electronic device 1 is attached to a spring 2 anchored to a supporting housing 3. This forms a spring-mass energy harvesting system with the portable device 1 acting as the majority of the mass of the energy harvester and oscillating with respect to the housing 3. The oscillation is coupled to an electrical energy transduction mechanism including a coil 4 and a magnet 5 which harvests some of the kinetic energy of the oscillation. The object of the invention is to provide maximum harvested energy without adding additional mass to the portable device other than the spring 2, supporting housing 3, energy transduction mechanism 4, 5 and any associated electronics. The spring 2 may also act as the energy transduction mechanism by way of a strip of piezoelectric material 9.

Description

Portable electronic device charger

Background of the Invention

This invention relates to a generator for generating electrical energy or power for any electronic device when a suitable source of mains electricity is not available for charging. The method is to be applied to convert kinetic energy present in the environment into electrical energy. This approach is well known to those skilled in the art as energy harvesting or scavenging. The disclosed generator is equally suitable for use with any portable device.

The field of kinetic energy harvesting is well known and many device examples (termed generators) exist in the prior art aimed at providing a method of converting the available kinetic energy in the environment into useful electrical energy which is ultimately used to power the electronic device. This avoids the need to connect the device to a mains power supply and therefore utilises otherwise wasted energy.

Many prior art devices do not attempt to maximise the mass of the generator in order to maximise power generated. They therefore produce a very low level of efficiency in converting kinetic energy into electrical energy and hence low electrical power levels.

This is because the maximum harvested electrical energy cannot exceed the kinetic energy stored in the spring-mass system which forms the generator. The maximum level of power which can be harvested from a spring-mass inertial generator is given by: ma2 equation (1) 8 co Where m is the inertial mass of the generator a is the acceleration Q0t is the open circuit quality factor of the generator C)res is the angular resonant frequency of the generator It can be seen by those skilled in the art that maximising the inertial mass of the generator maximises the useful electrical energy harvested. Previous devices aim at self contained generator which provides its own internal mass in addition to that of the portable device. Such prior art devices maximise the useful electrical energy harvested by maximising the mass. However the extent to which the mass of the generator can be increased is limited by the need to keep the overall mass of the portable device (including the generator) at an acceptably low level to facilitate portability. There is thus a design conflict between the need to keep the mass of the portable device as low as possible to ensure portability and the need to maximise the mass of the generator which adds to the overall mass of the portable device. This invention solves this conflict. Prior art generators therefore produce insufficient electrical energy for portable devices such as mobile phone or laptop computers since they have insufficient mass in the generator to produce sufficient kinetic energy (and hence electrical energy) to make a significant energy contribution when compared with the energy stored typically in the battery of the

portable device.

The background prior art is characterised in:

W02007121367: Power generator unit for a portable device having a motion based power converter. This discloses a stand alone generator consisting of coils and magnets contained within a housing. An attachment unit, such as a belt clip, can attach the housing to an external body.

CN2896547 Portable power-supply-free mobile phone charger: This invention reveals a portable mobile phone charger which consist of a housing with magnets and coils inside the housing. Its principle is that, when worn on body, there will be relative displacement between coils and magnets due to the body movement.

CN101075773: Portable vibration generator: The invention comprises a magnet and coils arrangement, which, when the oscillation is generated outside, kinetic energy is induced in the generator and harvested by the transduction mechanism.

EP1363380: Generator for supplying a battery for portable device such as a mobile phone: This provides a magnet and coil based generator which is mounted within the

portable device.

GotWind and Orange have developed a dance charge unit in a strap attached over the wearer's bicep. A specially designed system of weights and magnets, similar to that found in kinetic energy watches, creates an electrical current which provides a top-up of charge to a storage battery.

Prior art disclosures do not maximise the generated energy for a given total mass of generator plus portable device. They seek to provide a method of kinetic to electrical energy transduction and a means to provide kinetic energy in the generator from movement. Prior art generators do not include the mass of the portable device within the generator's spring mass system.

Summary of the Invention

The present invention provides a mass and spring generator in which the mass of the portable device is utilised as the effective mass of the generator, thereby avoiding the need to add additional mass to the generator.

The mass of the portable device is utilised as the mass of the spring mass generator avoiding the need to add additional mass aimed at maximising the mass of the generator.

The resonant frequency may be tuned by adjustment of the cantilever, dimensions, stiffness or mass.

The generator may additionally include a surrounding housing which provides for displacement limiting of the oscillating generator hence providing over range protection.

In one arrangement, two or more electrically conductive springs are used to conduct energy from the generator to the stationary support.

The spring may be made of piezoelectric material providing for energy transduction.

The generator may provide electromagnetic energy transduction incorporating coil(s) and magnet(s).

The resonant frequency may be tuned by adjustment of the electrical load attached to any energy transduction mechanism.

In one embodiment, at least one moving magnet may be mounted on the generator and at least one stationary coil may be mounted on the housing.

In another embodiment, at least one moving coil may be mounted on the generator and at least one stationary magnet may be mounted on the housing.

Optionally, the magnet(s) are spaced away from generator to allow more efficient energy generation andlor the coil(s) is spaced away from generator to allow more efficient energy generation.

The energy transduction may be provided on both sides of the spring(s).

The present invention further provides a portable electrical device comprising at least one element adapted to provide one or more functions for the device and an energy transducting mechanism adapted to generate electrical power to be utilised by the device resulting from mechanical movement of the device, wherein the energy transducting mechanism is disposed between first and second mechanical parts of the device which are arranged for relative vibrational movement therebetween, and at least one said element is mounted on a vibrationally movable portion of at least one of the first and second mechanical parts.

Preferably, the element comprises one or more of one or more of: a display, a data processor, a telecommunications device, a memory device, an image recording andlor displaying device, a sensor, a battery for receiving and storing electrical charge from the generator, and electronic circuitry.

In some embodiments, the energy transducting mechanism comprises at least one magnet and at least one coil respectively mounted to the first and second mechanical parts. In other embodiments, the energy transducting mechanism comprises a piezoelectric material mounted between the first and second mechanical parts. Such a magnet/coil mechanism may be combined with a piezoelectric mechanism. In other embodiments, the energy transducting mechanism comprises first and second electrostatic conducting layers respectively mounted to the first and second mechanical parts.

Optionally, at least one of the first and second mechanical parts is at least a portion of a housing for the device.

The first and second mechanical parts may be interconnected by a spring. The spring is preferably a cantilever spring with the first and second mechanical parts mounted sat opposed ends thereof.

Preferably, the vibrationally movable portion is adapted to vibrate at a resonant frequency when the device is subjected to mechanical movement during use.

The device may be a mobile telephone, a personal digital assistant or a portable computer, or adapted to be connected to a mobile telephone, a personal digital assistant or a portable computer.

The present invention utilises the mass of the portable electronic device as the majority of the mass of the spring mass generator. This avoids the need to add extra mass to act as the inertial mass of the generator to maximise efficiency and therefore maximises electrical energy generator without significantly adding to the mass of the portable device. The only mass which may be added is that of the energy transduction mechanism and mechanical mechanism to allow the portable device to move in response to the vibrations. What is disclosed is the use of the mass of the portable device as the mass of the spring mass generator without the need to add additional mass aimed at maximising the mass of the generator.

The difference between the prior art discussed above and the present invention is illustrated by considering an automatic watch which uses body movement to generate power thus avoiding the need for winding or battery or solar power. In prior art automatic watches the generator is a self contained generator housed with the watch; the mass of the watch plays no part in the energy generation system other than to couple movement to the generator. In the present mvention the mass of the watch is an integral part of the spring mass system of the generator Potential transduction mechanisms are well known in the prior art with many specific embodiments. Such energy transduction mechanisms and mechanical mechanisms are well known to those skilled in the art and do not form the basis of this invention. The most common are electromagnetic, piezoelectric and electrostatic. Specific realisations of these transduction mechanisms can be utilised in the present invention.

This invention addresses the limitations of the prior art by providing an efficient generator whilst minimising the additional mass added to the portable device by the generator.

The present invention therefore relates to a system for harvesting electrical energy from the vibration or movement of a portable electronic device. The portable electronic device is attached to a spring anchored to a supporting housing. This forms a spring-mass system with the portable device acting as the majority of the mass of the energy harvester and oscillating with respect to the housing. The oscillation is coupled to an electrical energy transduction mechanism which harvests some of the kinetic energy of the oscillation. The object of the invention is to provide maximum harvested energy without adding additional mass to the portable device other than the spring, supporting housing, energy transduction mechanism and any associated electronics.

In operation the portable device would be attached or clipped into the housing to which is added the spring arid the energy transduction mechanism. The entire assembly would them attach or clip to the external body to provide a means of coupling the kinetic energy to the entire assembly. Associated electronics may be included within the assembly in order to directly charge the portable device. In some instances it may be more convenient to directly charge the battery of the portable device by mounting in the generator assembly instead of the entire portable device. In other instances it may be preferred to charge an auxiliary storage device such as a supercapacitor which may be subsequently used to charge the portable device.

The object of the invention is to provide maximum harvested energy without adding additional mass to the portable device other than the spring, supporting housing, energy transduction mechanism and associated electronics. This provides to the user a convenient method of carrying the portable device in the case of such devices as mobile phone and personal digital assistants or for laptop computers where the assembly may be clipped inside a brief case.

Brief Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a cross section of a generator in accordance with a first embodiment of the present invention showing a portable device in a housing attached to a spring with an example of an electromagnetic energy transduction mechanism; Figure 2 is a cross section of a generator in accordance with a second embodiment of the present invention showing a portable device in a housing attached to a spring with an example piezoelectric energy transduction mechanism; Figure 3 is a cross section of a generator in accordance with a third embodiment of the present invention showing a portable device in a housing attached to a spring with an example electrostatic energy transduction mechanism; Figure 4 is a cross section of a generator in accordance with a fourth embodiment of the present invention showing a portable device in a housing attached to a spring with a dual energy transduction mechanism; Figure 5 is a cross section of a generator in accordance with a fifth embodiment of the present invention showing a portable device in a housing attached to a spring with an over range protection; Figure 6 is a cross section of a generator in accordance with a sixth embodiment of the present invention showing direct battery charging; Figure 7 is a cross section of a generator in accordance with a seventh embodiment of the present invention showing electrical energy storage; and Figure 8 is a cross section of a generator in accordance with an eighth embodiment of the present invention where the vibrations are coupled to angular displacement and energy is extracted by a rotation based generator e.g. dynamo.

Detailed Description of the Preferred Embodiments

The following reference numerals are used to indicate the parts and environment of the invention on the drawings

1. Portable device

2. Spring 3. Housing andlor attachment 4, Coil 5. Magnet 6. Spacer 7. Movement of surroundings 8. Movement of device 9, Piezoelectric material 10. Conductive layer 11. Over range protection 12. Battery 13. Connecting wires 14. Electronic signal conditioning circuit 15. Electronic signal conditioning circuit incorporating storage device for example storage capacitor 16. Torsion spring + rotation based transduction mechanism 17. Angular motion Figure 8 is a cross section of a generator in accordance with a first embodiment of the present invention which incorporates one example of an electromagnetic energy transduction mechanism. The drawing is highly schematic and shows the principles of the structure and operation of a device in accordance with the present invention. The generator includes a portable device 1 which is mounted in, on or to in a first part of a housing or attachment 3 for the portable device. The portable device is adapted to provide a particular function or plurality of functions.

For example, the portable device could include (in a non-exhaustive list of examples) one or more of: a display, a data processor, a telecommunications device, a memory device, an image recording and/or displaying device, a sensor, a battery for receiving arid storing electrical charge from the generator, electronic circuitry, etc..

The first part of the housing or attachment 3 is attached to a spring 2, in this embodiment a cantilever spring 2, The electromagnetic energy transduction mechanism includes at least one coil 4 mounted on a first spacer 6 that in turn is mounted on the portable device 1. The first part of the housing or attachment 3 is attached to a spring 2, in this embodiment a cantilever spring 2, The electromagnetic energy transduction mechanism also includes at least one magnet 4 mounted on a second spacer 6 that in turn is mounted on a second part of the housing or attachment 3 which is also attached to the spring 2.

In use of the device, the entire device may be subject to movement in the direction of the arrows 7. This in turn may cause relative vibrational movement, in the direction of the arrows 8, between the at least one coil 4 and the at least one magnet 4. This causes electrical energy to be generated in the coil, which can be used to power an electrical device, and optionally stored in a storage device such as a battery or capacitor.

The vibrational movement in the direction of the arrows 8 is preferably movement of the portable device 1 against the bias of the spring 2 which biases the portable device 1 to a central position. The additional mass of the portable device, which includes components that are not present to generate electrical power in the electromagnetic energy transduction mechanism but are present to provide other functions as described above, causes a greater power output according to equation (1) above. Most preferably, the vibrational movement in the direction of the arrows 8 is at a resonant frequency, and the device is tuned to a resonant frequency by selection of the spring characteristics and the mass of the vibrating portion of the device.

In the electromagnetic energy transduction mechanism, the electromagnetic energy coils and magnets can be interchanged or an alternative magnetic arrangement can be employed.

In the embodiment of Figure 2, the spring incorporates piezoelectric material 9 as the energy transduction mechanism which generates electrical energy during vibrational movement in the direction of the arrows 8 of the portable device 1 relative to the second part of the housing or attachment 3.

In the embodiment of Figure 3, first and second conductive layers 10 are applied, in a spaced opposing configuration, to the portable device I and to the second part of the housing or attachment 3. The layers 10 comprise an electrostatic energy transduction mechanism which generates electrical energy during vibrational movement in the direction of the arrows 8 of the portable device 1 relative to the second art of the housing or attachment 3.

In the embodiment of Figure 4, the housing or attachment 3 comprises three parts arranged as a series and mutually connected by one or more springs, such as cantilever springs 2. The device further includes, as compared to the embodiment of Figure 1, a further coil 4/magnet 5 arrangement respectively mounted on an opposite face of the first part and a further, third, part of the housing or attachment 3. This provides a composite electromagnetic energy transduction mechanism, composed of two coil 4/magnet 5 arrangements, which are electrically and mechanically coupled together via the common central housing part on which is mounted the portable device 1.

In the embodiment of Figure 5, the device further includes, as compared to the embodiment of Figure 1, an over range protection part 11.

In the embodiment of Figure 6, as compared to the embodiment of Figure 1, the portable device comprises a battery 12 and wires 13 connect both the battery 12 and the coil 4 to an electronic signal conditioning circuit 14. This embodiment employs direct battery charging.

In the embodiment of Figure 7, as compared to the embodiment of Figure 1, the portable device comprises a battery 12 and wires 13 connect the coil 4 to an electronic signal conditioning circuit 15 which incorporates a electrical charge storage device, such as a storage capacitor.

In the embodiment of Figure 8, as compared to the embodiment of Figure 1, the spring comprises a torsion spring 16, and the transduction mechanism is adapted to be rotation bases, when subjected to angular motion along the direction of arrows 17. Tn this generator, the vibrations are coupled to angular displacement and energy extracted by a rotation based generator e.g. dynamo.

It is to be understood that the above-described embodiments are merely illustrative of numerous and varied other arrangements which form applications of the principles of the invention. Other embodiments may readily by devised by those skilled in the art without departing from the spirit and scope of the invention.

Claims

CLAIMS: 1. A mass and spring generator in which the mass of the portable device is utilised as the effective mass of the generator, thereby avoiding the need to add additional mass to the generator.
2. A mass and spring generator in which the mass of the portable device is utilised as the mass of the spring mass generator avoiding the need to add additional mass aimed at maximising the mass of the generator.
3. A generator according to claim 1 or claim 2 of which the resonant frequency may be tuned by adjustment of the cantilever, dimensions, stiffness or mass.
4. A generator according to any one of claims 1 to 3 which additionally includes a surrounding housing which provides for displacement limiting of the oscillating generator hence providing over range protection.
5. A generator according to any foregoing claim in which two or more electrically conductive springs are used to conduct energy from the generator to the stationary support.
6. A generator according to any foregoing claim in which the spring is made of piezoelectric material providing for energy transduction.
7. A generator according to any foregoing claim of which the resonant frequency may be tuned by adjustment of the electrical load attached to any energy transduction mechanism.
8. A generator according to any foregoing claim providing for electromagnetic energy transduction incorporating coil(s) and magnet(s).
9. A generator according to claim 8 with moving magnet(s) mounted on the generator and stationary coil(s) on the housing.
10. A generator according to claim 8 with a moving coil(s) mounted on the generator and a stationary magnets(s) on the housing.
11. A generator according to claim 9 or claim 10 in which the magnet(s) are spaced away from generator to allow more efficient energy generation.
12. A generator according to claim 9 or claim 10 in which the coil(s) is spaced away from generator to allow more efficient energy generation.
13. A generator according to any one of claims 8 to 12 in which energy transduction is provided on both sides of the spring(s).
14. A portable electrical device comprising at least one element adapted to provide one or more functions for the device and an energy transducting mechanism adapted to generate electrical power to be utilised by the device resulting from mechanical movement of the device, wherein the energy trarisducting mechanism is disposed between first and second mechanical parts of the device which are arranged for relative vibrational movement therebetween, and at least one said element is mounted on a vibrationally movable portion of at least one of the first and second mechanical parts.
15. A device according to claim 14 wherein the element comprises one or more of one or more of: a display, a data processor, a telecommunications device, a memory device, an image recording and/or displaying device, a sensor, a battery for receiving and storing electrical charge from the generator, and electronic circuitry.
16. A device according to claim 14 or claim 15 wherein the energy transducting mechanism comprises at least one magnet and at least one coil respectively mounted to the first and second mechanical parts.
17. A device according to claim 14 or claim 15 wherein the energy transducting mechanism comprises a piezoelectric material monnted between the first and second mechanical parts.
18. A device according to claim 14 or claim 15 wherein the energy transducting mechanism comprises first and second electrostatic conducting layers respectively mounted to the first and second mechanical parts.
19. A device according to any one of claims 14 to 18 wherein at least one of the first and second mechanical parts is at least a portion of a housing for the device.
20. A device according to any one of claims 14 to 19 wherein the first and second mechanical parts are interconnected by a spring.
21. A device according to claim 20 wherein the spring is a cantilever spring with the first and second mechanical parts mounted sat opposed ends thereof.
22. A device according to any one of claims 14 to 21 wherein the vibrationally movable portion is adapted to vibrate at a resonant frequency when the device is subjected to mechanical movement during use.
23. A device according to any one of claims 14 to 22 wherein the device is a mobile telephone, a personal digital assistant or a portable computer, or adapted to be connected to a mobile telephone, a personal digital assistant or a portable computer.
24. A portable electrical device substantially as hereinbefore described with reference to any one of Figures 1 to 8 of the accompanying drawings.