Patent Publication Number: US-2009230786-A1

Title: Linear Power-Generating Apparatus

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a power-generating apparatus, and more specifically to a power-generating apparatus by using the linear relative motion between permanent magnetic field and the coil. 
     BACKGROUND OF THE INVENTION 
     The conventional power-generating apparatus relies on the relative motion between the permanent magnetic field and the coil to induce the electromotive force in the coil to generate power. The permanent magnetic field is usually generated by arranging the permanent magnets in a ring, and the electromotive force induction is accomplished by rotating the coil inside the permanent magnets ring. This type of conventional power-generating apparatus is widely used in the daily, and various improvements in power generation efficiency are disclosed. However, one remaining major disadvantage of this type of power-generating apparatus is the bulky size, and another disadvantage is the power generated is usually alternating current (AC). 
     SUMMARY OF THE INVENTION 
     The present invention has been made to overcome the above-mentioned drawback of conventional power-generating apparatus of bulky size and AC-only power generation. The primary object of the present invention is to provide a power-generating apparatus that is small in size and able to generate direct current (DC). The present invention provides a power-generating apparatus by using a linear, instead of rotation, relative motion to generate power. 
     The linear power-generating apparatus of the present invention includes a column element having permanent magnetic field, and a coil set surrounding the column element. The column element includes a plurality of magnetic segments, with one end as N and the other as S, and a plurality of yokes placed between two neighboring magnetic segments. The magnetic segments are arranged in the manner that the same polar ends are facing each other; in other words, N to N, and S to S. The coil set includes a plurality of coils. The winding directions of two neighboring coils are opposite. The linear power-generating apparatus of the present invention can induce electromotive force in the coil set to generate power by using the linear back-and-forth relative motion between the column element and the coil set. In the constant speed relative motion, the linear power-generating apparatus of the present invention can generate a near-constant direct current (DC) voltage. 
     As the linear power-generating apparatus of the present invention uses linear relative motion, the size of the apparatus can be minimized. In addition, the reverse magnetic arrange of the permanent magnets, i.e., S-S and N-N, allow the full segment of every coil of the coil set to generate power; therefore, the power generation efficiency is high. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be understood in more detail by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein: 
         FIG. 1   a  shows a perspective view of an embodiment of the linear power-generating apparatus of the present invention; 
         FIG. 1   b  shows an exploded view of the embodiment of  FIG. 1   a;    
         FIGS. 2   a,    2   b  show a side perspective view of the relative motion between column element and coil set of  FIG. 1   a;    
         FIG. 3   a  shows the relation between magnetic flux Φ BL  of permanent magnet versus axis distance L; 
         FIG. 3   b  shows the relation between total magnetic flux Φ B  of permanent magnet versus axis distance L; 
         FIG. 3   c  shows the relation between differential 
       
         
           
             
               
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       of total magnetic flux Φ B  in regard of axis distance L of permanent magnet versus axis distance L; and 
         FIG. 3   d  shows the relation between induced electromotive force ε of coil at constant speed relative motion versus axis distance L. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1   a  and  1   b  show a perspective view and an exploded view of an embodiment of the linear power-generating apparatus of the present invention. As shown in the figures, the present embodiment includes a column element  10  and a coil set  20 . Column element  10  provides the permanent magnetic field, and the linear back-and-froth relative motion between column element  10  and coil set  2 —along the axis of column element  10 , shown as the arrow in  FIG. 1   a,  will induce the electromotive force in coil set  20 , and generate power. 
     Column element  10  includes at least two segments of permanent magnets  11  and at least a segment of yoke  12 , arranged linearly in an end to end manner. A yoke  12  is placed between any two neighboring permanent magnets  11 . It is worth noting that one end of permanent magnet is N pole, and the other end is S pole. In addition, any two permanent magnets  11  of column element  10  are arranged to have the same pole facing each other; that is, the two ends of yoke  12  between any two neighboring permanent magnets  11  will have the same pole, either S pole or N pole. This type of arrangement is usually called reverse magnetic arrangement. In the present embodiment, column element  10  is housed inside a tube sheath  100 . 
     Coil set  20  is winding around a tube sheath  200 . Tube sheaths  100 ,  200  can be made of any appropriate material that will not shield the magnetic field of permanent magnets  11 . Also, tube sheath  200  should be made of insulative material, and has a diameter that is slightly larger than the diameter of tube sheath  100  so that tube sheath  100  can be inserted inside tube sheath  200 , and the linear back-and-forth relative motion along the axis of the tube sheaths is allowed. 
     Coil set  20  includes at least two coils  21 ,  22  connected in series. It is worth noting that the winding directions of any two neighboring coils  21 ,  22  are the opposite of each other, as shown by the arrows in  FIG. 1   b.  In addition, each coil  21 ,  22  can be divided into two coil segments  211 ,  212 , or  221 ,  222 . In the present embodiment, coil segments  211 ,  212 ,  221 ,  222  have approximately the same axis length l, which is also approximately the same length of the axis length of permanent magnets  11  and yoke  12 , as shown in  FIGS. 2   a,    2   b.  In other words, the axis length of each coil  21 ,  22  is approximately twice the axis length of permanent magnet  11 . 
       FIGS. 2   a,    2   b  show a side perspective view of relative motion between column element  10  and coil set  20  of an embodiment of the present invention. It is worth noting that motion direction indicated by the arrows in the figures are for column element  10  to be stationary while for coil set  20  to move linearly in the direction. The similar linear relative motion can be accomplished by having coil set  20  to be stationary while having column element  10  to move in the reverse direction indicated by the arrows. 
     The theory behind the present invention is explained as follows. First, when no relative motion exists, magnetic flux Φ BL  generated by two permanent magnets  11  and a yoke  12  versus axis distance L is shown in  FIG. 3   a.    FIG. 3   b  shows total magnetic flux Φ B  from the center of a permanent magnet  11  to the center of neighboring permanent magnet  11  versus axis distance L. The relation between magnetic flux Φ BL  and total magnetic flux Φ B  is as follows: 
       Φ B =∫Φ BL dL 
     When relative motion between column element  1  and coil set  20  occurs, coil set  20  is induced with an electromotive force ε, which has a relation with total magnetic flux Φ B  that can be derived by the following equation (where N is a constant): 
     
       
         
           
             
               
                 
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     In other words, the relation between electromotive force ε, speed v of the relative motion and differential 
     
       
         
           
             
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     of total magnetic flux Φ B  in regard of axis distance L is proportional. Differential 
     
       
         
           
             
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     of total magnetic flux Φ B  in regard of axis distance L can be derived from  FIG. 3   b,  as shown in  FIG. 3   c.    
     Assuming that speed v of the relative motion is constant, i.e., the relative motion between column element  10  and coil set  20  is at a constant speed. According to the above equation, electromotive forces ε 211 , ε 212  generated by coil segments  211 ,  212  and electromotive force ε 21 =ε 211 +ε 212  generated by coil  21  can be derived as in  FIG. 3   d.  As shown in  FIG. 3   d,  electromotive force ε 21  generated by coil  21  is almost a constant. Similarly, electromotive force ε 22  generated by coil  22  is almost a constant. Therefore, electromotive force ε=ε 21 +ε 22  generated by coil set  20  is almost a constant. Hence, the generated voltage is a near constant DC voltage. 
     In summary, because the linear power-generating apparatus of the present invention uses linear relative motion, the size of the power-generating apparatus of the present invention can be much smaller than the size of a conventional rotating power-generating apparatus. Also, the reverse magnetic arrangement of the permanent magnets allows the entire coil segment of any coil to generate power. So, the power generation efficiency is high. Finally, when the relative motion is at a constant speed, the generated voltage is a near-constant DC voltage. 
     Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.