Abstract:
An electromechanical energy converter ( 1 ) is provided that can convert mechanical vibration energy into electrical energy. For this purpose, the energy converter ( 1 ) has a housing ( 2 ) in which a coil ( 12 ) and a permanent magnet ( 15 ) are disposed moveable with respect to each other, the coil ( 12 ) lying within the magnetic field of the magnet ( 15 ). To fully utilize the entire field intensity of the magnet ( 15 ), flux guides ( 18 ) are disposed at the poles of the magnet ( 15 ) that divert the magnetic flux lines ( 17 ) substantially in the direction of the coil ( 12 ).

Description:
CROSS-SECTION TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of German Patent Application No. DE 2010 045 063.4, filed Sep. 10, 2010, and a second German Patent Application having the same title and the same inventors as the first German Patent Application noted above which has not been assigned an application number as of the time for filing this application, both of which are incorporated herein by reference as if fully set forth. 
       BACKGROUND 
       [0002]    The invention is directed to an electromechanical energy converter for converting mechanical vibration energy into electrical energy having a housing with at least one coil and at least one permanent magnet, the coil and the magnet being so disposed in the housing that on movement of the housing a relative movement between the magnet and coil takes place, thus causing a current to be induced in the coil. 
         [0003]    These kinds of energy converters are also called energy harvesters because they can absorb energy from their surroundings, “harvest” it, and convert it into electrical energy. In the described energy converter, mechanical kinetic energy as created, for example, during the operation of a motor or a machine or by people using mobile devices such as watches, mobile telephones, MP3 players, and various remote controls etc., is converted into electrical energy. Aside from this, there are also energy converters that are able to convert such variables as heat, differences in temperature or light into electrical energy. 
         [0004]    The energy converter is thus suitable for a decentralized and autarkic supply of energy, for example, for sensors, handheld devices or other energy consumers. These kinds of energy converters are gaining in importance because they allow such applications as monitoring systems, sensors or remote controls to be independently supplied with electrical energy. Complex and expensive wiring of individual systems is thus no longer necessary. 
         [0005]    Alongside the price, the crucial factors for any application are, in particular, the dimensions and the efficiency of such energy converters. 
       SUMMARY 
       [0006]    The object of the invention is thus to provide an energy converter of the type described above that has compact dimensions and an improved energy yield compared to known systems. 
         [0007]    This object has been achieved according to the invention in that a flux guide is disposed on each of the magnetic poles of the permanent magnet, the flux guide concentrates the magnetic flux substantially in the direction of the coil. 
         [0008]    To enable an energy converter as described above to serve a wide range of applications, it should be made as compact as possible. As a rule, the dimensions of the coil are made to conform to the dimensions of the magnet. The magnetic flux lines enclose the entire magnet and reach far into the surrounding area. Consequently, many flux lines pass by the coil and are thus not available for inducing a current in the coil and, moreover, cause undesirable magnetic leakage flux. 
         [0009]    The flux guides according to the invention now collect the flux lines at the magnetic poles and focus them in the direction of the coil. This means that the natural flux paths are diverted by the plates and they now run mainly in the plate rather than in the surrounding area. The concentrated flux lines then emerge from the short sides of the plates that are preferably located directly opposite the coil. This goes to minimize the magnetic leakage field, resulting in an increase in the field intensity in the coil. For the same movement of the magnet, a greater electromagnetic force (EMF) is thereby induced and consequently a larger current in the coil. Using this simple measure, it is possible to approximately triple the current yield. 
         [0010]    In a preferred embodiment of the invention, the at least one coil is fixedly disposed on the housing and the at least one permanent magnet is disposed on a vibrating arm. The vibrating arm ensures that a movement of the housing is transformed into a one-dimensional vibrational movement of the magnet, provided that a component of the housing movement is in the direction of the vibration direction of the vibrating arm. 
         [0011]    The coil is preferably designed as a flat coil being substantially oblong or cylindrical in shape. It is advantageous if the magnet is also made substantially oblong in shape. 
         [0012]    It is clear that the flat coil could also be given a different form, such as a circular or oval shape, the shape of the magnet being made to conform accordingly. 
         [0013]    The vibrating arm preferably has at least two fingers, a magnet being disposed on each finger and a coil being disposed between the fingers. Each coil is thus enclosed by two magnets whose magnetic field passes through the coils. 
         [0014]    The flux guides are preferably disposed at the end faces of the magnets. The magnets may also be made up of a plurality of part magnets, flux guides being disposed only on the outer poles. 
         [0015]    It is advantageous if the flux guides are aligned such that when the vibrating arm is at a standstill, the magnetic flux is substantially concentrated at the centre of the coils. 
         [0016]    A further advantageous embodiment of the invention provides for the vibrating arm to have more than two fingers, a magnet being disposed on each finger and a coil being disposed on the housing between all fingers. By connecting the coils, the current yield can be easily multiplied. 
         [0017]    To make the vibrating arm readily responsive to a vibration, it is advantageous if it is given a substantially tongue-like shape and one end is firmly fixed to the housing. The thickness of the vibrating arm is thereby substantially smaller than its width and its length. 
         [0018]    It is advantageous if the vibrating arm is made at least partially of spring steel that preferably has low mechanical damping. 
         [0019]    Another embodiment of the invention provides for a magnet to be moved between two coils. So as to additionally concentrate the magnetic flux on the coil, a magnetic back yoke can be disposed on the side of the coil facing away from the magnet, the magnetic back yoke closing the flux lines behind the coil. This has the added advantage that the magnetic field does not escape as an interference field out of the housing towards the outside. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0020]    The invention is described in more detail below on the basis of several embodiments with reference to the enclosed drawings. 
           [0021]    In the drawings: 
           [0022]      FIG. 1  is an oblique view of a first embodiment of the invention having a coil and two or four magnets, 
           [0023]      FIG. 2  is a sectional view of  FIG. 1 , 
           [0024]      FIG. 3  is a view of a second embodiment of the invention having three coils and four or eight magnets, 
           [0025]      FIG. 4  is a detailed view of the vibrating arm of  FIG. 3 , 
           [0026]      FIG. 5  is a view of a preferred embodiment of the invention having a magnet and two coils each having a magnetic back yoke, 
           [0027]      FIG. 6  is a view of a further embodiment of the invention having two coils that are disposed on a common coil core which also acts as a magnetic back yoke for the magnet, 
           [0028]      FIG. 7  is a view of a further embodiment of the invention having one coil that is disposed on a coil core which also acts as a magnetic back yoke for the magnet, 
           [0029]      FIG. 8  is an oblique view of a preferred embodiment of the invention according to  FIG. 5 , 
           [0030]      FIG. 9  is a cross-sectional view of the embodiment of  FIG. 8  through the vibrating arm, 
           [0031]      FIG. 10  is an exploded view of the embodiment of  FIG. 8 , 
           [0032]      FIG. 11  is a block diagram of a voltage supply having an energy converter according to the invention, 
           [0033]      FIG. 12  is a block diagram of an electric device having an energy converter according to the invention, 
           [0034]      FIG. 13  is a block diagram of a further electric device having an energy converter according to the invention, and 
           [0035]      FIG. 14  is a block diagram of a further electric device having an energy converter according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]      FIG. 1  shows an electromechanical energy converter according to the invention which, in its entirety, is designated by  1 . The energy converter  1  is disposed in a two-piece, cuboid-shaped housing  2  that is made up of a lower housing half  3  and a removable, upper ( FIG. 2 ) housing half  4 . 
         [0037]    A tongue-shaped vibrating arm  5  is fixed to the housing  2 . For this purpose, the lower housing half  3  has a flat supporting surface  6  on which one end  7  of the vibrating arm  5  rests. The vibrating arm end  7  is fixed from above using a mounting block  8  that is fastened to the supporting surface  6  by two screws  9 . 
         [0038]    The other end  10  of the vibrating arm  5  is free. The vibrating arm  5  is made from flat sheet metal of spring steel, such that it can vibrate within the housing  2  in a vibration direction  11 . 
         [0039]    Moreover, a coil  12  is fixed to the lower housing half  3 . The coil  12  is formed as a flat coil that is aligned parallel to the vibration direction  11  ( FIG. 2 ). In the example, the coil  12  is substantially oblong in shape, the two long coil sides  13  lying parallel to the vibrating arm  5  in its non-deflected position. 
         [0040]    At its free end  10 , the vibrating arm  5  has two fingers  14  on each of which at least one permanent magnet  15  is disposed. In the example, the magnets  15  are cuboid in shape and magnetized in the vibration direction  11 . This means that in the illustration, the top is, for example, the north pole and the bottom is the south pole. In the illustrated embodiment, the magnets  15  are formed from two part magnets  16  that are fixed on the fingers  14 , above and below the sheet metal respectively. The magnets  15  may, however, also be integrally formed as one piece and fixed elsewhere on the fingers  14  or on the vibrating arm  5 . 
         [0041]    The fingers  14  are spaced only so far apart from each other that the coil  12  is disposed with the smallest possible air gap between the fingers  14 , and thus between the magnets  15 . 
         [0042]    The magnets  15  simultaneously form the vibratory mass for the vibrating arm  5 . When there is a movement of the housing  2 , the vibrating arm  5  is incited to vibrate due to the inertia of the vibratory mass. The magnets  15  thereby move parallel to the coil  12  causing the magnetic field within the coil  12  to change. According to the law of induction, a current is thereby induced in the coil  12 . 
         [0043]    The coil  12  and/or the magnet  15  may have other shapes differing from the illustrated example, such as a cylindrical shape. 
         [0044]    On a permanent magnet  15 , the flux lines flow between the two magnetic poles N and S generally on closed paths that reach far into the surrounding area. This means that in the energy converter  1 , a significant portion of the flux lines pass by the coil  12 . These flux lines are thus not available for inducing a current. 
         [0045]    To increase the current yield compared to the prior art, according to the invention flux guides  18  are disposed at the magnetic poles  15 , the flux guides  18  concentrating the flux lines substantially in the direction of the coil  12 . The flux guides  18  are preferably made of a ferromagnetic material so that the magnetic flux can be guided unhindered as far as possible. The flux guides  18  are made, for example, from soft magnetic iron. 
         [0046]    The flux guides  18  now ensure that as many flux lines as possible are collected and diverted in the direction of the coil  12 . This makes the magnetic field within the coil  12  significantly stronger, which in turn allows a larger current to be induced in the coil  12 . 
         [0047]    The flux guides  18  are preferably disposed on the outer magnetic poles of the part magnets  16 . 
         [0048]    Stop buffers  19  are additionally fixed to the flux guides  18 , which, on strong vibrations of the vibrating arm  5 , hit against the housing base  20  or cover  21  and prevent any damage to the magnets  15  and the housing  2 . These buffers  19  are made, for example, of plastics or rubber or any other damping material. 
         [0049]    The flux guides  18  are aligned on the magnet  15  such that when the vibrating arm  5  is at a standstill, the flux lines are substantially guided to the long sides of the coil  13 . For this purpose, the magnets  15  are dimensioned such that the flux guides  18  are disposed substantially opposite the coil sides  13 . 
         [0050]    Thanks to the flux guides  18  according to the invention, the current yield of the energy converter  1  according to the invention is up to three times higher than for the prior art. 
         [0051]    As an alternative to the embodiment illustrated here, the coil  12  could also be disposed on the vibrating arm  5  and the magnets  15  fixedly disposed on the housing  2 . 
         [0052]    To achieve an even greater current yield, a plurality of coils  12  could also be connected in the energy converter  1  in series or in parallel. In  FIG. 3 , such an alternative energy converter  1  having three coils  12  is shown. The construction corresponds substantially to the energy converter of  FIG. 1 . The vibrating arm  5 , however, has four fingers  14 , where between every two adjacent fingers  14 , a coil  12  fixedly attached to the housing  2  is disposed. Compared to the outer magnets  15 , the two middle magnets  22  are made almost double as wide since they are dimensioned for two coils  12 . 
         [0053]      FIG. 4  once again shows the construction of the vibrating arm  5  having four fingers  14 . Here, the construction of the magnets  15  made up of two part magnets  16  can be seen more clearly. Except for the number of fingers, the vibrating arm of  FIG. 1  is identical. It is clear that the vibrating arm may, for example, have three fingers or any arbitrary number of fingers. 
         [0054]    A further, preferred embodiment of the invention is schematically shown in  FIG. 5 . Only one single magnet  15  having flux guides  18  is disposed here on the vibrating arm  5 . In the drawing, a coil  12  fixedly attached to the housing  2  is disposed respectively to the right and left of the magnet  15 , the flux guides  18  of the magnet  15  here again being disposed opposite the long sides of the coils  13 . On each side of the coils  12  facing away from the magnet  15 , a magnetic back yoke  23  is disposed, which is made of a ferromagnetic material and by which the flux lines of the magnet  15  are largely closed and do not stray into the surrounding area. In the example, the back yoke takes the form of a U-core  23  and is made of a soft magnetic material. This goes to improve the yield since additional flux lines can be used to generate a current in the coils. In addition, the magnetic interference field of the generator towards the outside is reduced. 
         [0055]    The back yoke  23  may thereby be fixedly attached to the housing or moveably attached to the magnet  15 . Moreover, it is also possible, alongside the single magnet  15 , to provide only a single coil  12 . 
         [0056]    A further embodiment of the invention according to  FIG. 6  provides that the magnetic back yoke simultaneously acts as a coil core for the coil  12 . In the illustrated example, the magnetic back yoke takes the form of an E-core  24  that can be stacked, for example, from individual iron laminations. Two coils  12  are disposed on the core  24 , each coil  12  being wound around the back  25  of the core  24 . The effective magnetic field in this embodiment is conducted solely in the core  24 . 
         [0057]    On vibration of the magnet  15  with respect to the core  24 , the flux guides  18 , which in this embodiment project laterally from the magnet  15 , sweep by the limbs  26  of the E-core  25 . Depending on the position of the magnet  15 , a flux reversal is thereby produced in the core  24 , thus inducing a particularly large current. This embodiment consequently goes to produce an even greater yield which is why even extremely small-scale constructions have a large energy yield. 
         [0058]    For the sake of symmetry, it is advantageous in this embodiment if another core having coils is disposed on the other side of the magnet  15  (not illustrated). 
         [0059]    A further variant of the embodiment, illustrated in  FIG. 7 , provides a permanent magnet  15 , unchanged with respect to  FIG. 6  and likewise having flux guides  18  disposed at the end faces, that is located opposite an E-core  24 . In this arrangement only one single coil  12  is provided that is wound around the middle core limb  26  of the E-core  24 . An important advantage of the embodiments according to  FIGS. 6 and 7  is that the air gap between the permanent magnet  15  and the coil core  24  can be kept comparatively small. 
         [0060]      FIGS. 8 to 10  show a preferred realization of the embodiment according to  FIG. 5 . The energy converter is constructed in substantially the same way as the energy converter of  FIG. 1 . 
         [0061]    Here, however, the vibrating arm  5  has three fingers  14 , the middle finger being wider than the two outer fingers. A permanent magnet  15  is disposed on the middle finger that is magnetized in the vibration direction and that has a flux guide plate  18  at each of the upper and lower end faces. A U-shaped back yoke  23  ( FIG. 10 ) is further disposed on the vibrating arm  5 , the limbs of the back yoke  23  being disposed on the outer fingers. The limbs of the back yoke  23  themselves are U-shaped, these limbs  26  being aligned opposite the flux guides  18  when the vibrating arm  5  is in a non-deflected state. Two ring coils  12  fixedly attached to the housing are disposed between the fingers  14 . 
         [0062]    In the illustrated embodiment, the magnet  15  and the back yoke  23  are disposed on the underside of the vibrating arm  5 . 
         [0063]    The housing cover  21  in this embodiment is screwed onto the housing base  20  using two separate screws  9 ′ ( FIG. 10 ). 
         [0064]    It is clear that the invention is in no way limited to the illustrated embodiments. Wherever a stationary coil and a moving magnet are described, it is also basically possible to have the magnet stationary and the coil moving. Likewise, almost any desired number of coils and magnets can be chosen. Thus, for example, a plurality of magnets can be stacked with a flux guide being disposed between each magnet. 
         [0065]    In particular, the magnetic back yoke according to  FIG. 5  or according to  FIG. 7  may form a part of the housing or the housing may act as a magnetic back yoke. Moreover, the arrangement of the magnet  15  and the back yokes  18  may be interchanged in that in the position of the permanent magnet  15 , a ferromagnetic back yoke is disposed, and in that instead of the back yokes  18 , magnetized permanent magnets are disposed at the end faces of the back yoke perpendicular to the vibration plane  11 . 
         [0066]    An energy converter  1  according to the invention may, for example, be installed in a voltage supply  27  for supplying an electric device. The advantage here is that, due to the energy converter  1 , the voltage supply  27  is autarkic and there is no need for connection to a mains power supply. 
         [0067]      FIG. 11  shows a block diagram of this kind of voltage supply  27  having an energy converter  1  and an energy storage unit  28  for the intermediate storage of the converted energy. 
         [0068]    Depending on the conversion principle, the energy converter  1  delivers either an AC voltage or a DC voltage. In order to adjust this conversion voltage to the operating or charging voltage of the energy storage unit  28 , a voltage converter  29  is provided. In accordance with the conversion voltage of the energy converter, this converter takes the form of an AC/DC inverter or a DC/DC converter. The conversion voltage of the energy converter  1  may thereby be higher or lower than the charging voltage of the energy storage unit  28 . The voltage converter  29  is accordingly designed as an up and/or down converter. 
         [0069]    The voltage supply  27  has an output for a supply voltage V_out, at which a regulated DC voltage is available to supply any desired electric device. In addition, the voltage supply provides a control signal that shows the availability of the supply voltage. 
         [0070]    In  FIG. 12  an electric device  31  is schematically shown that has an energy converter  1  according to the invention having a voltage supply  27  according to  FIG. 11 . The electric device  31  has optionally a supply voltage output V_out and a control signal that can be used for the voltage supply of any other electric devices with or without their own energy converter. 
         [0071]    In the example, the electric device  31  additionally has a sensor module  32  and a transmitter module  33 . 
         [0072]    The sensor module  32  comprises at least one sensor and an evaluation circuit for the sensor values that may, for example, be realized by a microcontroller. The sensor may, for example, be a temperature, pressure and/or humidity sensor. 
         [0073]    The sensor values can be transmitted via the transmitter module  33  to a remote receiver  34  where they can be further processed and analyzed. 
         [0074]    Such an electric device  31  can, for example, be used in a production plant for monitoring critical process variables. Here, the advantage is that the electric device  31  according to the invention can function without any wiring whatsoever and can thus be easily mounted and used everywhere. 
         [0075]    The variant of the electric device of  FIG. 12  shown in  FIG. 13  does not have a sensor of its own. Here instead, there is only an interface  35  for connecting one or more external sensors  36 . 
         [0076]    It is clear that the device of  FIG. 12  may also have in addition to its own built-in sensor module  32 , an interface  35  for connecting external sensors  36  as is shown in  FIG. 14 . 
         [0077]    Alongside its transmitting capacity, the transmitter module  33  may be additionally or alternatively designed to also receive sensor values from adjacent equivalent devices, control signals or other signals. 
         [0078]    The illustrated electric devices  31  are not restricted to the use of a mechanical energy converter  1 . Alternatively or additionally, other kinds of energy can be used to produce the supply voltage. 
       REFERENCE NUMBERS 
       [0079]      1  Electromechanical energy converter 
         [0080]      2  Housing 
         [0081]      3  Lower housing half 
         [0082]      4  Upper housing half 
         [0083]      5  Vibrating arm 
         [0084]      6  Supporting surface 
         [0085]      7  Fixed end (vibrating arm) 
         [0086]      8  Mounting block 
         [0087]      9 , 9 ′ Screws 
         [0088]      10  Free end (vibrating arm) 
         [0089]      11  Plane of vibration 
         [0090]      12  Coil 
         [0091]      13  Long coil side 
         [0092]      14  Fingers 
         [0093]      15  Magnet 
         [0094]      16  Part magnets 
         [0095]      18  Flux guide 
         [0096]      19  Stop buffer 
         [0097]      20  Housing base 
         [0098]      21  Housing cover 
         [0099]      22  Middle magnets 
         [0100]      23  U-core 
         [0101]      24  E-core 
         [0102]      25  Core back 
         [0103]      26  Core limb 
         [0104]      27  Voltage supply 
         [0105]      28  Energy storage unit 
         [0106]      29  Voltage converter 
         [0107]      31  Electric device 
         [0108]      32  Sensor module 
         [0109]      33  Transmitter module 
         [0110]      34  Receiver 
         [0111]      35  Sensor interface 
         [0112]      36  Sensor 
         [0113]    V_out Supply voltage output