Abstract:
A magnetically driven reciprocating power output system including: at least one first electromagnet having a direction of elongation defining an axial direction, having a first end and a second end, and having an elongated opened core extending from the first end to the second end, the core having an axis of symmetry substantially coaxial with the axial direction; a control unit adapted to provide a first power input to the first electromagnet and adapted to cause the electromagnet to have a time-varying first magnetic field with a first polarity directed in substantially the axial direction; at least one stationary body having a second magnetic field with a second polarity directed in substantially the axial direction and configured substantially coaxially with the core region at the first end; at least one reciprocating ferromagnetic body configured substantially coaxially with the core, and not extending completely outside of the core at the second end, adapted to have a second magnetic field in response to the first magnetic field, the body displaceable axially in response to the first and second magnetic fields; and a transducer unit mechanically connected to the reciprocating body and adapted to convert a displacement of the reciprocating body to a power output.

Description:
[0001]    The current application claims the benefit of U.S. Provisional Patent Application No. 60/822,237, filed Aug. 13 2006, whose disclosure is incorporated herein by reference. 
     
     FIELD AND BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a magnetically driven reciprocating system and method and, in particular, it concerns a magnetically driven reciprocating system and method that provide output power. 
         [0003]    Conventional rotary electric motor or actuator systems typically convert electrical energy into mechanical energy. Examples of electric motors are those found in household appliances such as: fans: exhaust fans: fridges: washing machines: pool pump; and fan-forced ovens-to name a very few. 
         [0004]    Most rotary electric motors work by electromagnetism (although there are motors based on other electromechanical phenomena, such as electrostatic forces and piezoelectric effect). The fundamental principle upon which electromagnetic motors are based is that there is a mechanical force on any current-carrying wire contained within a magnetic field. The force, described by the Lorentz force law, is normal to both the conductor and the magnetic field. Rotary motors as known in the art are configured to take advantage of this effect. 
         [0005]    A linear motor is essentially a multi-phase AC electric motor that has had its stator (i.e. the stationary part of the motor) “unrolled” so that instead of producing a torque (rotation), it produces a linear force along its length The most common mode of operation is as a Lorenz-type actuator, in which the applied force is linearly proportional to the current and the magnetic field, according to the aforementioned Lorentz force law. 
         [0006]    Many conventional electromagnetic motors, such as those mentioned hereinabove, function with limited efficiencies as a result of various factors including, but not limited to structure, operating speed and conditions, torque, and material composition. Very few, if any, of the devices mentioned hereinabove are typified by reciprocating motion. 
         [0007]    There is therefore a need for a scalable magnetic reciprocating system which can operate with high efficiency and/or can generate power. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is a magnetic reciprocating system and method that provide output power. According to the teachings of the present invention there is provided, a magnetically driven reciprocating power output system including: at least one first electromagnet having a direction of elongation defining an axial direction, having a first end and a second end, and having an elongated opened core extending from the first end to the second end, the core having an axis of symmetry substantially coaxial with the axial direction; a control unit adapted to provide a first power input to the first electromagnet and adapted to cause the electromagnet to have a time-varying first magnetic field with a first polarity directed in substantially the axial direction; at least one stationary body having a second magnetic field with a second polarity directed in substantially the axial direction and configured substantially coaxially with the core region at the first end; at least one reciprocating ferromagnetic body configured substantially coaxially with the core, and not extending completely outside of the core at the second end, adapted to have a second magnetic field in response to the first magnetic field, the body displaceable axially in response to the first and second magnetic fields; and a transducer unit mechanically connected to the reciprocating body and adapted to convert a displacement of the reciprocating body to a power output Preferably, the power output is not less than the first power input Most preferably, the transducer unit further includes a mechanical energy buffer adapted to non-simultaneously store the power output and to return a second power input. 
         [0009]    Typically, the transducer unit is further adapted to sense the power output, displacement, and velocity of the reciprocating body. Most typically, the control unit is further adapted to control a plurality of time-varying electrical pulses to provide the first power input based on data indicative from the transducer unit of the sensed power output, displacement, and velocity of the reciprocating body. Most preferably, the control unit is further adapted to control the first power input to maximize the power output. 
         [0010]    Most preferably, the stationary body is substantially permanently magnetic. Typically, the stationary body is ferromagnetic and the second magnetic field is present in response to the first magnetic field. Most typically, the stationary body is a non-powered electromagnet. 
         [0011]    Preferably, the stationary body is a powered electromagnet electromagnetic and the second field is maintained substantially constant or second field is varied in coordination with variations of the first magnetic field. Most preferably, the first electromagnet and the reciprocating ferromagnetic body are fixed in a common housing, and wherein the housing is displaceable axially in response to the first and second magnetic fields. 
         [0012]    According to the teachings of the present invention there is further provided a method of operating a magnetic reciprocating generating system including the steps of taking at least one first electromagnet having a direction of elongation defining an axial direction, having a first end and a second end, and having an elongated opened core extending from the first end to the second end, the core having an axis of symmetry substantially coaxial with the axial direction; providing a first power input to the first electromagnet with a control unit and causing the electromagnet to have a time-varying first magnetic field with a first polarity directed in substantially the axial direction; configuring at least one stationary body substantially coaxially with the core region at the first end, the stationary body having a second magnetic field with a second polarity directed in substantially the axial; configuring at least one reciprocating ferromagnetic body substantially coaxially with the core, and not extending completely outside of the core at the second end, having a second magnetic field in response to the first magnetic field, the body displaced axially in response to the first and second magnetic fields; and connecting a transducer unit mechanically to the reciprocating body, the transducer unit converting a displacement of the reciprocating body to a power output. 
         [0013]    Most preferably, the transducer unit further includes a mechanical energy buffer unit which non-simultaneously stores power output and to return a second power input. Preferably, the transducer unit further senses the power output, displacement, and velocity of the reciprocating body. Typically, a plurality of time-varying electrical pulses is controlled by the control unit to provide the first power input based on data indicative from the transducer unit of the sensed power output, displacement, and velocity of the reciprocating body. Most typically, the power output is maximized by the control unit controlling the first power input 
         [0014]    Preferably, the stationary body is substantially permanently magnetic. Most preferably, the stationary body is ferromagnetic and the second magnetic field is present in response to the first magnetic field. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
           [0016]      FIGS. 1A and 1B  are schematic representations of a magnetically driven reciprocating power output system including a housing, a toroidal shaped electromagnet configured within the housing, and a ferromagnetic body positioned within the open space of electromagnet, in accordance with an embodiment of the present invention; 
           [0017]      FIGS. 2A and 2B  are schematic representations of a magnetically driven reciprocating power output system similar to the system shown in  FIGS. 1A and 1B , in accordance with an embodiment of the present invention; 
           [0018]      FIGS. 3A and 3B  schematic representations of a magnetically driven reciprocating power output system similar to the system shown in  FIGS. 1A and 1B , in accordance with an embodiment of the present invention; 
           [0019]      FIG. 4  is a graph showing force versus displacement for a series of experiments; and 
           [0020]      FIGS. 5 and 6  are output of an oscilloscope and a schematic diagram, respectively, of an additional experimental setup. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0021]    The present invention includes a magnetic reciprocating system and method that provides output power. 
         [0022]    Reference is now made to  FIGS. 1A and 1B , which are schematic representations of a magnetically driven reciprocating power output system  10  including a housing  15 , a toroidal shaped electromagnet  18  configured within the housing, and a ferromagnetic body  20  positioned within an open core  21  of electromagnet  18 , in accordance with an embodiment of the present invention. The term “electromagnet” noted hereinbelow in the specification and in the claims which follow refers to any inductor that creates a magnetic field and subsequent magnetic force due to an electric current. Electromagnet  18  is typically an “open core” electromagnet of any suitable construction; however a solid core electromagnet that may be bored or otherwise modified to allow the ferromagnetic body to be configured substantially in open core  21  is also suitable. Open core  21  typically has an axis of symmetry (not shown in the figure) defining an axial direction of the system. Electromagnet  18  is fixed within the housing and ferromagnetic body  20  may translate axially within the open core. The magnetic polarities of electromagnet  18  and of ferromagnetic body  20  are aligned axially, as shown in the figures and as are further described hereinbelow. Optionally or alternatively, electromagnet  18  may represent more than one electromagnets having a similar configuration as described hereinabove and arranged substantially coaxially (not shown in the figure) to allow ferromagnetic body  20  to translate within the open cores. 
         [0023]    A stationary body  22  is configured coaxially with the open core, in close proximity to electromagnetic  18 , but outside of the housing and outside of core  21 . In embodiments of the present invention, stationary body is alternatively or optionally: ferromagnetic with ideally no remanence, meaning that it retains no magnetization when the driving magnetic field of electromagnet  18  ceases; permanently magnetized (with high remanence); or electromagnetic—either activated or not activated when electromagnet  18  is activated. The magnetic polarity of stationary body  22  is aligned axially and is non-varying when stationary body is not an activated electromagnet (no electric current is flowing in the electromagnet) as shown by the non-varying “+” and “−” notations in the figures. 
         [0024]    In the case where stationary body  22  is an electromagnet, the overall function and configuration of stationary body  22  is similar to that of electromagnet  18 , and only the core of stationary body  22  is represented in the figure. When stationary body  22  is an activated electromagnet, its polarity and may be time-varying in a manner similar to that described for electromagnet  18  hereinbelow. Alternatively or optionally, stationary body  22  may be an electromagnet which is not activated, in which case the core of the stationary body functions essentially similarly to that of the ferromagnetic body as described hereinabove. 
         [0025]    A control unit  24  controls the power input to electromagnet  18 , and causes the magnetic polarity to change with time. The terms “power input” and “power output” noted hereinbelow in the specification and in the claims which follow refer to electrical or mechanical power, typically expressed in watts. In an embodiment of the current invention, the control unit controls power pulses to the electromagnet by controlling the pulse frequency (number of power pulses per second, for example) and pulse duration (measured in milliseconds, for example) of power pulses. In one embodiment, control unit  24  supplies time-variable power pulses, as known in the art (such as, but not limited to, Pulse Wave Modulation methods) to alternately change the direction of magnetic polarity of the electromagnet, as shown by the alternate “+” and “−” notations in  FIGS. 1A and 1B . Alternatively or optionally, control unit  24  supplies time-variable power pulses, as known in the art (such as but not limited to Pulse Wave Modulation methods) to alternately power and de-energize the electromagnet, thereby creating and ceasing a magnetic polarity in only one direction (not shown in the figures). As noted previously and as further noted hereinbelow, the magnetic polarity of ferromagnetic body  20  reacts to that of the electromagnet. 
         [0026]    In the case where stationary body  22  is an activated electromagnet, as noted hereinabove, control unit  24  may additionally control the power input to the stationary body to enhance reciprocation of ferromagnetic body  20 , as described hereinbelow. 
         [0027]    In  FIG. 1A , it can be seen that when the magnetic polarities of the ferromagnetic body and the stationary body are of opposing signs, ferromagnetic body  20  is attracted to the stationary body and moves a displacement “s” towards stationary body  22 . In  FIG. 1B , it can be seen that when the magnetic polarities of the ferromagnetic body and the stationary body are of matching signs, ferromagnetic body  20  is repelled and moves a displacement “s” away from stationary body  22 . Controller unit  24  controls and varies the power input to electromagnet  18  (and of stationary body  22 , when applicable) as described hereinabove so that ferromagnetic body  20  reciprocates axially a displacement “s” towards and away from stationary body  22 . In addition to variations in polarities of magnetic fields within the system, reciprocating movement of the ferromagnetic body may be enhanced and/or aided by means of mechanical energy, as described hereinbelow. 
         [0028]    A transducer unit  26 , having a mechanical connection to ferromagnetic body  20 , as shown, serves to transduce mechanical energy from ferromagnetic body  20  as it reciprocates within the open core, as described hereinbelow. In one embodiment of the current invention, transducer unit  26  takes the form of a crank connected to a flywheel mounted on a shaft, which in turn drives an additional element, such as an electric generator (not shown in the figure). The flywheel serves to alternately store and return mechanical energy from and back to the ferromagnetic body, with excess mechanical energy transduced to electricity in the generator. Movement of the shaft in the transducing unit may be sensed, as known in the art, using encoders, for example, and information indicative of movement of the ferromagnetic body is fed back to the controller unit (as indicated by the dotted line in  FIGS. 1A and 1B ). In this way, controller unit  24  controls time variations of power input to the electromagnet to optimize movement of the ferromagnetic body and/or optimize output power of the system. In other embodiments of the current invention, transducer unit  26  may include other components, such as, but not limited to mechanical, electrical, thermal, chemical, and hydraulic components, which may all similarly store and/or transduce energy, while providing feedback to controller unit  24 . 
         [0029]    In embodiments of the current invention, electromagnet  18  ideally exhibits no hysteresis, meaning that the magnetic field of the electromagnet instantaneously develops and ceases when power is applied and stopped, respectively. Similarly, ferromagnetic body  20  ideally exhibits no remanence, meaning that body  20  retains no magnetization when the driving magnetic field of electromagnet  18  ceases. In one embodiment of the current invention, body  20  is made from steel; however other materials that exhibit mechanical stability and that can acquire a magnetic field and exhibit low magnetic hysteresis, as described hereinabove, are suitable. 
         [0030]    Exemplary electromagnets suitable to operated as electromagnet  18  are seen at the website http://www.mannel-magnet.info/en_round.php of Mannel Magnet Technik GbR, Tente 3, 42859 Remscheid, Germany, whose disclosure is incorporated herein by reference. 
         [0031]    Experiments, described hereinbelow, were performed to determine and to demonstrate various levels of operation, including input and output work of magnetically driven reciprocating power output system  10 . 
         [0032]    Reference is now made to  FIGS. 2A and 2B , which are schematic representations of a magnetically driven reciprocating power output system  110  similar to the system shown in  FIGS. 1A and 1B , in accordance with an embodiment of the present invention. Apart from differences described below, magnetically driven reciprocating power output system  110  is generally similar to operation of magnetically driven reciprocating power output system  10  as shown in  FIGS. 1A and 1B , so that elements indicated by the same reference numerals are generally identical in configuration and operation. In system  110 , the electromagnet and ferromagnetic body are fixed within housing  15  and the housing reciprocates by a displacement “s” to and from stationary body  22 . Transducer unit  26  is connected to the housing and functions in similar fashion as described hereinabove. 
         [0033]    Reference is now made to  FIGS. 3A and 3B , which are schematic representations of a magnetically driven reciprocating power output system  120  similar to the system shown in  FIGS. 1A and 1B , in accordance with an embodiment of the present invention. Apart from differences described below, magnetically driven reciprocating power output system  120  is generally similar in operation to magnetically driven reciprocating power output system  10  as shown in  FIGS. 1A and 1B , so that elements indicated by the same reference numerals are generally identical in configuration and operation. In system  120 , a second stationary body  27  is configured coaxially with the open core, in close proximity to electromagnetic  18 , but outside of the housing and outside of core  21  and in opposition to stationary body  22 . 
         [0034]    In embodiments of the present invention, stationary bodies  22  and  27  are alternatively or optionally: ferromagnetic with ideally no remanence, meaning that they retain no magnetization when the driving magnetic field of electromagnet  18  ceases; permanently magnetized (with high remanence); or electromagnetic. When not an electromagnet that is activated, the magnetic polarity of stationary body  27  is aligned axially and is non-varying, as shown by the non-varying “+” and “−” notations in the figures. Furthermore, stationary body  27  may be an electromagnetic and may be operated similarly to the operation described hereinabove for stationary body  22 , when stationary body  22  is an activated electromagnet. Although not shown in  FIGS. 3A and 3B , system  120  includes transducer unit  26  which functions as described in  FIGS. 2A and 2B  for system  110 , hereinabove. 
         [0035]    Another embodiment of system  120  of the current invention includes a configuration with the electromagnet and ferromagnetic body fixed inside the housing  15  and the entire housing reciprocating, similarly to that described in  FIGS. 2A and 2B  for system  110 , hereinabove. 
         [0036]    Another embodiment of systems  10  and  120  additionally or optionally includes ferromagnetic body comprising two pieces (not shown in the figures), with one piece being maintained stationary substantially within the core and the second piece reciprocating, as described hereinabove. 
         [0037]    Experimental Work and Results 
         [0038]    Measurements and calculations of the forces, work, timing, and power were made from experimental setups modeling system  10  (as described hereinabove in  FIGS. 1A and 1B ]. Characteristics of components of system  10  and other components used for the experiment were:
       Electromagnet: Industrial celluloid magnet having input of 45 W, length=80 mm, core diameter=25 mm, rated magnetic force of 60 kg.   Two Paramagnetic bodies: each with diameter=22 mm, length=80 mm, material: soft steel, ST37. The two bodies served to model the reciprocating body of system  10 . Relative displacements of one or both of the paramagnetic bodies were measured, as described hereinbelow.   Calibrated springs to measure force: length approximately 200 mm, with spring constant of k=1.1 kg/mm   Strain gauge, manufacturer: Vishay, max. rated 350 kg   Control unit: Power supply 12 VDC, max 4 A, typical operation at 2 A.   Oscilloscope: Gould 475       
 
         [0045]    Note: Had a ferromagnetic material been used in the experiments—instead of the paramagnetic material noted above—it is very reasonable to assume that results would have been substantially improved, as noted hereinbelow. 
         [0046]    Objectives of experimental work were to: 
         [0047]    1. Determine the maximum forces operating on the paramagnetic material; 
         [0048]    2. Provide a measurement of the system&#39;s mechanical output work; and 
         [0049]    3. Measure of the electrical energy input to obtain the work output. Each of the three objectives and specific experimentation are described in greater detail hereinbelow. 
         [0050]    Maximum Forces
       1. The two steel paramagnetic bodies were inserted, touching each other at the center point within the electromagnetic core.   2. Each body was fitted with a spring which was attached to a displacement-measurable fixture. The electromagnet was powered at 12 VDC and 2 A and the two bodies were attracted to each other by magnetic force, with the springs having no elongation.   3. The two bodies were then separated by controllably pulling the springs The spring elongation was recorded, yielding a value of the force necessary to counteract and pull the bodies away from one another while they were in the magnetic field of the electromagnet.   4. The measured elongation of the springs was approximately 12 cm. Applying the spring constant of the springs, as noted above, the attractive force was calculated as approximately 60 kg.       
 
         [0055]    Output Work
       1. The springs were detached from the bodies and the bodies were again inserted, touching and centered into the core of the magnet, as in step one hereinabove One body was fixed. The second body could move freely axially out of the core. A strain gauge was connected to the end of the second body and a the strain gauge was mechanically connected with an apparatus, which could apply a controlled pulling force acting to separate the bodies.   2. The electromagnet was activated and the apparatus was activated to pull the second body. A separation force was measured based on the strain gague output. The second body moved a given displacement “s” from the other stationary body. Force values were recorded for various “s” values.       
 
         [0058]    Reference is now made to  FIG. 4 , which is a graph  200  showing force (in kgF) versus displacement “s” (mm) for the series of experiments as described in step 2, hereinabove. The area under line  204  represents the integral of the force-versus-displacement function, evaluated from the maximum force (60 kg) to minimum force (4 kg). The integral may also be expressed as the mechanical work of the ferromagnetic body. Representative chord  206  on the graph, connecting the values of 60 kg and 7 mm on the respective axes, gives a reasonable linear approximation of line  204 , with the areas under chord  206  and under line  204  being approximating equal. The work was calculated as approximately 2.35 Joules. 
         [0059]    An additional series of experiments was performed with one body fixed and the second body mechanically connected to a crank arm, which in turn was connected to a shaft upon which a flywheel was mounted. The flywheel had a mass of approximately 10 kg. The work output of the flywheel was measured at one rotation equal to 1.3 Joule. It was further measured that one pulse of the electromagnet yielded a movement of the second body, causing 3 revolutions of the flywheel. The work output of the body was therefore calculated at 1.3×3=4.2 Joule, not taking into account any friction. 
         [0060]    Electrical Energy Input 
         [0061]    Experimental measurements were made using the bodies and setup as described hereinabove. Reference is now made to  FIGS. 5 and 6  which are output of an oscilloscope and a schematic diagram, respectively, of an experimental setup used for the electrical energy input determination. The experimental setup allowed the integrated energy input of an electrical pulse to the electromagnet to be measured for body displacements of 30 mm and 10 mm with respective sets of voltage and current response curves  310  and  320 , as indicated in  FIG. 5 . Response curve set  320 , reflecting a typical body displacement of 10 mm was of primary interest. The time scale is indicated in milliseconds from 0, 10, 20, . . . , 50 milliseconds in a horizontal axis in  FIG. 5 . 
         [0062]    Oscilloscope  345  was connected to the electromagnet, indicated as “coil” in  FIG. 6 . The stationary body was located with its end centered within the electromagnetic core and the moving body was positioned 10 mm away from the center point. The oscilloscope was configured to measure the time response of the electromagnet and the time the moving body contacted the stationary body. A time response was measured as approximately 30 milliseconds. 
         [0063]    The input energy may be calculated by taking the 45 W nominal power input and dividing it by 30 milliseconds, yielding 1.5 Joule. 
         [0064]    Intermediate Conclusion 
         [0065]    Using the values obtained hereinabove: an energy input of 1.5 Joule and a work output of 4.2 Joule, and not taking any other losses into account, there appears to be a significant energy margin “created” by the system. No other losses were measured in the experimental work. An assumption was made of an energy loss due to friction, reducing the work output to approximately 2.3 Joule. 
         [0066]    As a result, an intermediate conclusion from the experimental work was that the system, having an approximate energy input of 1.5 Joule and an approximate work output (including friction losses) of 2.3 Joule was, at the least, highly energy efficient, as no other explanation could be made regarding the aforementioned energy margin. 
         [0067]    Future Experimentation 
         [0068]    Additional experiments are planned using a much larger scaled electromagnet, having approximately 1,000 kg magnetic force, based on an input power of approximately only 37 W. Additional experiments will utilize ferromagnetic bodies, and not paramagnetic bodies as used in previous experiments described hereinabove. Therefore, it is anticipated that the additional experiments will yield even better results regarding energy efficiency. 
         [0069]    It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.