Abstract:
The present invention relates to a permanent magnet generator for outputting a stabilized electromotive force. More specifically, the permanent magnet generator for stabilizing an electromotive force outputs an electromotive force stably according to the rotation speed of a motor and stabilizes the wave form of the electromotive force to be close to sine waves.

Description:
TECHNICAL FIELD 
     The present invention relates to a permanent magnet generator for outputting a stabilized electromotive force, and more particularly, to a permanent generator for outputting an electromotive force stably in response to a revolution speed of a prime mover and for stabilizing the waveform of the electromotive force to be close to a sine wave. 
     BACKGROUND ART 
     A generator is axially coupled to a prime mover that converts a natural energy, such as wind power, water power and nuclear power, into a mechanical energy so as to convert the mechanical energy of the prime mover into an electric energy. The generator is configured in such a manner that rotating magnetic fluxes of a rotator, which is axially coupled to the prime mover, are linked to a stator, which is fixed to the outer circumferential surface of the rotator with a gap, thereby generating an electromotive force. 
     A small generator is configured in such a manner that permanent magnets are mounted on a rotator in place of a field winding to link rotating magnetic fluxes to an armature winding wound on a stator. Conventionally, N-pole and S-pole permanent magnets are alternately arranged along the outer circumferential surface of the rotator, so that processes of linking the armature winding to an N-pole and then to an S-pole may be repeated to generate an electromotive force close to a sine wave. 
     However, in a conventional generator, the N-poles form boundaries with the S-poles along an axial direction, and a space exists at each of the boundary parts, which causes the magnetic fluxes linked between the N-poles and S-poles to be abruptly fluctuated. As a result, an electromotive force induced thereby is distorted rather than being formed in a sine wave form. To this end, the induced electromotive force, which is not formed in a sine wave form, contains a lot of harmonic wave components, and causes a problem in that the harmonic wave components contained in the electromotive force result in copper loss in the armature winding, thereby decreasing electricity generating efficiency and adversely affecting a load device which is supplied with the induced electromotive force. That is, a part of energy, which should be converted into the electromotive force with a desired sine wave form, is converted into harmonic components that merely decrease electricity generating efficiency and have a detrimental effect. 
     In addition, when the coil of the armature winding passes while being opposed to a magnetic pole (N-pole or S-pole), it is impossible to generate an electromotive force with a sine wave form since linkage to the coil is made with uniform fluxes throughout the passage. 
     That is, when a flux distribution by magnetic poles in the conventional generator is shown along a cylindrical surface, the distribution is close to a square wave where magnetic fluxes are abruptly fluctuated at empty spaces between magnetic poles. Therefore, there is a problem in that the induced electromotive force cannot be formed in a sine wave form. 
     In order to solve this problem, the prior art obtains an electromotive force close to a sine wave form by distributing a plurality of windings around the stator and connecting the windings in serial. However, this winding method is too complicated to be applied to a small generator. 
     Meanwhile, since an induced electromotive force is fluctuated depending on the revolution speed of a rotator, the prior art employs a method for keeping the revolution speed of a prime mover axially coupled to the rotator constant in order to generate a predetermined electromotive force. 
     However, providing a control means for keeping the revolution speed of the prime mover is difficult to employ since providing such a control means in a small generator, which uses wind power or water power, is uneconomic in view of securing the costs and spaces for installing the generator. As such, the control means has not been employed, and an arrangement configured to release the axial coupling with the prime mover has been used in place of the control means in order to prevent excessive power generating. However, this makes it difficult to utilize wind power or water power properly, thereby decreasing generating efficiency. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem 
     An object of the present invention is to provide a permanent magnet generator for stabilizing an electromotive force, which is configured in such a manner that an induced electromotive force generated in an armature winding of a stator may be formed close to a sine wave form by allowing magnetic fluxes by the magnetic poles of a rotator to be continuously connected without being cut. 
     Another object of the present invention is to provide a permanent magnet generator for stabilizing an electromotive force, which is configured to generate an electromotive force in a predetermined range even when the rotating force transmitted from a prime mover is fluctuated, by adding a simple arrangement. 
     Technical Solution 
     In accordance with an aspect of the present invention, there is provided a permanent magnet generator for stabilizing an electromotive force including: a case  100  provided with a stator  110  on the inner circumferential surface thereof, the stator  110  being wound with an armature winding; and a rotator  200  provided with permanent magnets, the rotator  200  being fixed to a rotation shaft  210  rotated by a prime mover and mounted in the inside of the case  100 . The rotator includes: a fixed rotor  220  having a plurality of first one-pole permanent magnets  221  with the same polarity, wherein each of the first one-pole permanent magnets is formed to widen as approaching to the rear end from a pointed peak at the front end thereof and to have a length corresponding to the axial length of the stator  110 , and then the first one-pole permanent magnets  220  are fixedly arranged around the outer circumferential surface of the rotation shaft  210 ; and a centrifugal rotor  230  having a plurality of second one-pole permanent magnets  231  formed in the same shape as the one-pole permanent magnets  221  and with the same polarity which is different from that of the first one-pole permanent magnets  221 , wherein the second one-pole permanent magnets  231  are fixedly arranged around the outer circumferential surface of the centrifugal rotator  230  in a state in which the pointed peaks are directed rearward, so that the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231  are engaged with each other with a spacing d. The centrifugal rotator further includes a guide tube  213  configured to be fitted on the rotation shaft  210 , in which a guide protrusion  213  in a shape of an elongated protrusion extending in the axial direction is formed on the outer circumferential surface of the rotation shaft  210 , and an elongated guide recess  236  in a shape of an elongated recess extending in the axial direction is formed on the inner circumferential surface of the guide tube  233  such that the guide protrusion  213  is inserted into the elongated guide recess  236  and guided in the axial direction of the rotation shaft  210  to be capable of being moved to and fro. 
     Each of the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231  may be formed in an equilateral triangle shape when they are spread on a plane. 
     The rotation shaft  210  may be provided with a centrifugally movable unit  300 ;  300 ′ at the front end thereof which makes the rotation shaft  210  move forward as the revolution speed of the rotation shaft  210  is increased. As a result, as the revolution speed of the rotation shaft  210  is increased, the centrifugal rotator may gradually escape from the inside of the stator  110 . 
     In addition, the rotation shaft  210  may be formed in a shape of a hollow tube provided with a guide hole  211  along the axial direction, a reciprocating shaft  240 , which is provided with a compression disc  241  at the front end thereof, may be inserted into an axial bore  212  of the rotation shaft  210 , then an anchoring pin  234  may be inserted through the guide hole  211  to fix the centrifugal rotator  230  to the rear end of the reciprocating shaft  240 . The centrifugally movable unit  300 ;  300 ′ may move the compression disc  241  to and fro along the axial direction. 
     The compression disc  241  provided at the front end of the reciprocating shaft  240  may be elastically supported by a tension elastic body  242 , or the rear end of the reciprocating shaft  240  may be elastically supported at the rear side by a tension elastic body  242 A or a compression elastic body  242 B inserted into the axial bore  212  of the rotation shaft  210 . The centrifugally movable unit  300  may include: an abutment  310  fixed to the front side outer circumferential surface of the rotation shaft  210 ; and a centrifugal pivot bar  320  formed in a bent bar shape, the bent portion being hinged  322  to an end of the abutment  310  in a state in which the bent inner side is positioned to be directed to the axial direction of the rotation shaft  210  and the rear end of the centrifugal pivot bar  320  is engaged with the rear surface of the compression disc  241 . 
     The centrifugally movable unit  300 ′ may include: a revolution counter  330  configured to sense the revolution speed (RPM) of the rotation shaft ( 240 ); and a compression disc movement control unit ( 340 ) configured to move the compression disc ( 241 ) to and fro in accordance with the sensed revolution speed. 
     Advantageous Effects 
     In accordance with the present invention constructed as described above, N-pole magnets and S-pole magnets provided on a rotator are arranged to be engaged with each other with a predetermined spacing so that magnetic fluxes linked to an armature winding may be continuously connected without being cut. As a result, an electromotive force may be induced to be close to a sine wave form, thereby increasing electricity generating efficiency. 
     In addition, in accordance with the present invention, linkage magnetic fluxes by any of N-pole magnets or S-pole magnets (e.g., the second permanent magnets) may be increased or reduced depending on a magnitude of rotatory power of a prime mover to supply an electromotive force with a value of a predetermined range even if the rotatory power of the prime mover is fluctuated. As a result, it is possible to suppress the damage of the armature winding and a load device. 
     Furthermore, in accordance with the present invention, the reciprocating shaft  240  is configured to be rotated with the rotation shaft  210 , and to be inserted into the axial bore of the rotation shaft  210  to be axially guided, thereby being fixed to the centrifugal rotator  230 . As a result, an arrangement for moving the centrifugal rotator  230  can be simply mounted at an end of the reciprocating shaft  240 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a permanent magnet generator for stabilizing an electromotive force in accordance with a first exemplary embodiment of the present invention; 
         FIG. 2  shows an exploded perspective view of a rotator  200  in the first exemplary embodiment of the present invention; 
         FIG. 3  shows an exploded perspective view of the permanent magnet generator for stabilizing an electromotive force in accordance with the first exemplary embodiment of the present invention; 
         FIG. 4  shows cross-sectional side views of the permanent magnet generator for stabilizing an electromotive force in accordance with the first exemplary embodiment of the present invention; 
         FIG. 5  shows a cross-sectional side view of a permanent magnet generator for stabilizing an electromotive force in accordance with a second exemplary embodiment of the present invention; 
         FIG. 6  illustrates permanent magnets provided in a rotator in accordance with an exemplary embodiment in a state in which the permanent magnets are spread on a plane; 
         FIG. 7  illustrates permanent magnets arranged with different spacings in the exemplary embodiments in a state in which the permanent magnets are spread on a plane; and 
         FIG. 8  illustrates that an elastic body may be mounted in the rear side of a rotation shaft  210  in the first exemplary embodiment of the present invention. 
     
    
    
     REFERENCE NUMERALS FOR MAIN ELEMENTS IN THE DRAWINGS 
     
         
         
           
               100 : case  110 : stator  120 : front cover 
               121 : centrifugal rotator reception part 
               122 : bearing  123 : axial through-hole 
               124 : flange  125 : bolt  130 : back plate 
               131 : bearing  132 : axial through-hole 
               200 : rotator  210 : rotation shaft  211 : guide hole 
               212 : axial bore  213 : guide protrusion 
               220 : fixed rotator 
               221 : first one-pole permanent magnet 
               222 : first magnet holding tube 
               230 : centrifugal rotator 
               231 : second one-pole permanent magnet 
               232 : second magnet holding tube 
               233 : guide tube  234 : anchoring pin 
               235 : pin insertion hole  236 : guide recess 
               240 : reciprocating shaft  241 : compression disc 
               242 : elastic body  243 : fastening nut 
               244 : through-hole  300 : centrifugation moving unit 
               310 : abutment  311 : cylindrical tube 
               312 : deflection preventing protrusion 
               320 : centrifugal rotating bar 
               321 : hook piece  322 : hinge 
               330 : revolution counter 
               340 : compression disc movement control unit 
           
         
       
    
     MODE FOR CARRYING OUT THE INVENTION 
     Various exemplary embodiments are now described with reference to the drawings in such a manner that a person skilled in the art can readily practice the present invention. It shall be noted that the same elements will be designated by the same reference numerals if possible even if they are shown in different drawings. Further, in the following description of the present invention, a detailed description of related known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. 
       FIG. 1  is a perspective view of a permanent magnet generator for stabilizing an electromotive force in accordance with a first exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , the generator in accordance with the first exemplary embodiment of the present invention includes a case  100  configured to generate an electromotive force by electromagnetic induction caused between a stator and a rotator, and is configured such that a rotation shaft  210  of the rotator axially extends through the case  100 , a prime mover (not shown) is fixed to the rear end of the rotation shaft  210  so that rotatory power is transmitted to the rotation shaft  210 , and a centrifugally movable unit  300  is mounted at the front end of the rotation shaft  210  so that an induced electromotive force can be increased or decreased depending on the magnitude of the rotatory power. 
     Here, the prime mover (not shown) may be configured to be suitable for a method of obtaining driving force: when the present invention is applied to a wind power generator, the prime mover may be constituted with a fan blade assembly, and when the present invention is applied to a water power generator, the prime mover may be constituted with a waterwheel. 
     Now, the detailed elements in accordance with the first exemplary embodiment of the present invention will be described in detail with reference to  FIGS. 2 to 4 . 
       FIG. 2  is an exploded perspective view of a rotator  200  in the first exemplary embodiment of the present invention. 
       FIG. 3  is an exploded perspective view of the permanent magnet generator for stabilizing an electromotive force in accordance with the first exemplary embodiment of the present invention. 
       FIG. 4  shows cross-sectional side views of the permanent magnet generator for stabilizing an electromotive force in accordance with the first exemplary embodiment of the present invention, in which  FIG. 4   a  illustrates the permanent magnet generator prior to moving the centrifugal rotator  230 , and  FIG. 4   b  illustrates the permanent magnet generator after having moved the centrifugal rotator  230 . 
     Referring to  FIGS. 2 to 4 , the present invention includes: a case  100  provided with a stator  110  on the inner circumferential surface thereof; a rotator  200  including a plurality of permanent magnets  221  and  231 , and rotatably mounted in the inside of the case  100 ; and a centrifugally movable unit  300  mounted at the front end of the rotator  200 . 
     The case  100  has a cylindrical body, and the stator  110  wound with an armature winding is fixed circumferentially along the inner circumferential surface of the case  100 . The rear side of the case  100  is configured to be closed by a back plate  130  which is formed with an axial through-hole  132  at the center thereof, and the front side of the case  100  is configured to be closed by a front cover  120  which is formed with an axial through-hole  123  at the center thereof. 
     Here, the front cover  120  is provided with a cylindrical centrifugal rotator reception part  121  in order to provide a free space for allowing a centrifugal rotator  230  to be moved in the direction of rotation axis, in which the centrifugal rotator  230  will be described later. A flange  124  is formed on the rear side outer periphery of the centrifugal rotator reception part  121  and is fixed to the front side of the body of the case  100  by bolts  125 . The front side of the centrifugal rotator reception part  121  is closed by a plate formed with the axial through-hole  123  at the center thereof. 
     In addition, bearings  122  and  131  are fitted in the axial through-holes  123  and  132 , respectively, so that the rotation shaft  210  of the rotator  200  extends through the bearings  122  and  131  to be rotatably supported in the case  100 , in which the rotator  200  will be described later. 
     The stator  110  is wound with an armature coil which is arranged to link to the magnetic fluxes of permanent magnets  221  and  231 , so that when the permanent magnets  221  and  231  are rotated about the rotation shaft  210 , an electromotive force is generated by linked magnetic fluxes and supplied to the outside, in which the permanent magnets  221  and  231  will be described later. 
     The rotator  200  includes a rotation shaft  210  that serves as a rotation axis, a fixed rotator  220  fixed to the rotation shaft  210 , and a centrifugal rotator  230  mounted on the rotation shaft  210  to be capable of reciprocating in the direction of rotation axis. 
     The rotation shaft  210  is formed in a shape of hollow tube. When the rotation shaft  210  is received within the case  100 , the rear side extends through the bearing  131  of the back plate  130  of the case  100 , and the front side extends through the bearing  122  of the front cover  120  of the case  100  to be rotatably supported by the bearings  131  and  122 . In addition, on the rotation shaft  210 , an elongated guide hole  211  and an elongated guide protrusion  213  are formed along the axial direction at a portion corresponding to the moving range of the centrifugal rotator  230 , an elongated recess  214  is formed at the front portion, and male threads  215  are formed at the periphery of the front end portion. 
     The fixed rotator  220  includes: a first magnet holding tube  222  formed in a cylindrical shape having a diameter larger than the outer diameter of the rotation shaft  210  and fixed to the rotation shaft  210  in a state in which the first magnet holding tube  222  is fitted on the rotation shaft  210 ; a plurality of first one-pole permanent magnets  221  having the same polarity, each of the first one-pole permanent magnets  221  being formed to have a pointed peak at the front end thereof and to gradually widen as approaching to the rear end thereof, in which the first one-pole permanent magnets  221  are fixedly arranged around the outer periphery of the first magnet holding tube  222  like a series of saw teeth when the first one-pole permanent magnets  221  are viewed along the circumferential direction of the first magnet holding tube  222 . 
     Thus, the first one-pole permanent magnets  221  are arranged to be opposed to the stator  110  with a gap G being formed between the first one-pole permanent magnets  221  and the stator  110 . When the first one-pole permanent magnets  221  are spread on a plane, each of the first one-pole permanent magnets  221  is formed in a shape of an equilateral triangle such that a pointed peak of the equilateral triangle shape is positioned at the front end of the permanent magnet and the bottom side of the equilateral triangle shape is positioned at the rear end of the permanent magnet. At this time, the axial length of the first magnet holding tube  222  is smaller than a half of the axial length of the first one-pole permanent magnets  221  so that a plurality of second one-pole permanent magnets  231  can be positioned close to and engaged with the first one-pole magnets  221  even if a second magnet holding tube  232  approaches to the first magnet holding tube  222 , in which the second one-pole magnets  231  and the second magnet holding tube  232  will be described later. 
     Here, the axial length of the first one-pole permanent magnets  221  is determined to be suitable for the axial length of the stator. With reference to the equilateral triangle, the height of the equilateral triangle is determined to be suitable for the axial length of the stator. Thus, when the second one-pole permanent magnets  221  described later are moved forward to be further spaced away from the first one-pole permanent magnets  221 , the magnet fluxes linked by the second one-pole permanent magnets  221  are reduced. 
     The centrifugal rotator  230  includes: a second magnet holding tube  232  formed in the same shape with the first magnet holding tube  222  and fitted on the rotation shaft  210  to be biased to the front as compared to the first magnet holding tube  222 ; a plurality of second one-pole permanent magnets  231  having a polarity different from that of the first one-pole permanent magnets  221 , each of the second one-pole permanent magnets  231  is formed in a shape which is the same with that of each of the first one-pole permanent magnets  221 , in which the first one-pole permanent magnets  221  are fixedly arranged around the outer periphery of the first magnet holding tube  222  such that the pointed peaks of the second one-pole permanent magnets  232  are oriented to the rear side; and a guide tube  233  snugly fitted on the rotation shaft  210  corresponding to the inside portion of the second magnet holding tube  232  to be capable of being reciprocated by being guided along the axial direction of the rotation shaft  210 , the guide tube  233  being fixed to the second magnet holding tube  232 . 
     Specifically, when the first one-pole permanent magnets  221  are formed to have an N-pole outer circumferential surface, the second one-pole permanent magnets  231  are formed to have an S-pole circumferential surface, and when the second magnet holding tube  232  is formed to be the same with the first magnet holding tube  222  and the first and second magnet holding tubes  222  and  232  are moved adjacent to each other, the second one-pole permanent magnets  231  are engaged with the first one-pole permanent magnets  221  with a spacing d being formed therebetween, in which the spacing d is determined depending on the moving distance of the centrifugal rotator  230 . 
     Here, the centrifugal rotator  230  is configured to be rotated together with the fixed rotator  220  as the rotation shaft  210  is rotated, and to be capable of being moved along the axial direction of the rotation shaft  210 . For this purpose, the exemplary embodiment of the present invention forms an elongated guide recess  236  on the inner circumferential surface of the guide tube  233  to be fitted on the guide protrusion  213  of the rotation shaft  210  such that the centrifugal rotator  230  is guided along the rotation shaft  210  to be moved axially, and rotated in the same direction with the rotation shaft  210  when the rotation shaft  210  is rotated since the guide protrusion  213  keeps its state fitted in the elongated guide recess  236 . 
     In addition, the centrifugal rotator  230  is rigidly fixed to a reciprocating shaft  240  which is fitted in an inside bore  212  of the rotation shaft  210 . 
     The reciprocating shaft  240  is formed in a rod shape and provided with a compression disc  241  at the front end thereof and with a through-hole  244  extending vertically, in which the reciprocating shaft  240  is fitted in the inside bore  212  of the rotation shaft  210 . Here, the reciprocating shaft  240  is mounted in such a manner that even when the reciprocating shaft  240  is reciprocated, the compression disc  241  is kept in the state of being exposed to the front side, and the through-hole  244  does not get out of the range of the guide hole  211  formed in the rotation shaft  210 . That is, a pin insertion hole  235  is formed in the guide tube  232  of the centrifugal rotator  230 , and an anchoring pin  234  is inserted into the pin insertion hole  235 , the guide hole  211  and the through-hole  244  so that the centrifugal rotator  230  can be moved along the guide hole  211  in the state the centrifugal rotator  230  is fixed to the reciprocating shaft  240 . At this time, since the anchoring pin  234  is also inserted into the guide hole  211 , the centrifugal rotator  230  is movable only within the range of the guide hole  211 . 
     Meanwhile, the compression disc  241  is elastically supported to the front end of the rotation shaft  210  by a tensioned elastic body  242  to be pulled rearward. In the present exemplary embodiment, the elastic body  242  is constituted with a tension spring, one end of which is fixed to the rear surface of the compression disc  241  and the other end  241   a  of which is fixed to the front end of the rotation shaft  210  by a fastening nut  243 . Here, the fastening nut  243  is also configured to fix a cylindrical tube  311  of the centrifugally movable unit  300 , which will be described later. In addition, in order to install the centrifugally movable unit  300  to be described later at the front end of the rotation shaft  210 , the compression disc  241  is fabricated separately from the reciprocating shaft  240 , and when coupling the centrifugally movable unit  300 , the compression disc  241  is configured to be fixed to the front end of the reciprocating shaft  240  by a bolt (see reference numerals  245  and  245   a ). 
     The centrifugally movable unit  300  includes: a plurality of abutments  310  inclinedly extending from the cylindrical tube  311  in the form of plural branches, the cylindrical tube  311  being fitted on the front end portion of the rotation shaft  210 ; and a plurality of centrifugal pivot bars  320 , each of which is formed in a bent bar shape, the centrifugal pivot bars  320  being hinged to the ends of the abutments  310  (see reference numeral  322 ) at the bent parts, respectively, in the state in which the bent inner surfaces are arranged to face the axial direction of the rotation shat  210 . 
     Here, the abutments  310  are arranged along the outer circumferential surface of the cylindrical tube  311  to be gradually spread out as approaching to the front ends thereof. 
     The centrifugal pivot bars  320  are configured such that the centrifugal pivot bars  320  extend substantially toward the front side when the rotation shaft  210  is not rotated, and the rear end of each of the centrifugal pivot bars  320  is formed with a hook piece  321  bent toward the rotation shaft  210 , in which the hook pieces  321  are hooked to the rear surface of the compression disc  241 . The abutments  310  are respectively provided with deflection prevention protrusions  312  configured to be hooked to the hook pieces  321  respectively to prevent the centrifugal pivot bars  320  from being deflected downward. 
     Meanwhile, an elongated protrusion  311   a  is formed along the axial direction on the inner circumferential surface of the cylindrical tube  311 , and an elongated recess  214  is formed on the rotation shaft  210  to be fitted on the elongated protrusion  311   a , so that when the rotation shaft  210  is rotated, the centrifugally movable unit  300  can be also rotated as the elongated protrusion  311   a  and the elongated recess  214  are coupled to each other. 
     Now, the fluctuation of a generated electromotive force by the operation of the centrifugally movable unit  300  in the first exemplary embodiment of the present invention constructed as described above will be discussed. 
     When the rotation shaft  210  is rotated by the rotatory power of a prime mover (not shown), the centrifugal pivot bars  320  are also rotated to receive centrifugal force. As such, the centrifugal pivot bars  320  are spread out in such a manner that the front ends of the centrifugal pivot bars  320  are spaced away from one another. To this end, the hook pieces  321  push the compression disc  241  to the front side. 
     As a result, due to the forward movement of the compression disc  241 , the centrifugal rotator  230  is also moved toward the front side. As such, the spacing d between the first one-pole permanent magnets  211  and the second one-pole permanent magnets  231  is further increased, and the second one-pole permanent magnets  231 , which have been positioned in the form of being fitted in the stator  110 , gradually escape from the second one-pole permanent magnets  231  such that the second one-pole permanent magnets  231  fixed to the centrifugal rotator  230  escape out from the stator  110 . This will reduce the amount of magnetic fluxes linked to the stator  110  by the second one-pole permanent magnets  231 , thereby lowering the electromotive force generated by the stator. 
     That is, the present invention increases linked magnetic fluxes when the rotatory power of a prime mover (not shown) is low, and reduces linked magnetic fluxes when the rotatory power is high, so that the electromotive force generated by the stator can be maintained substantially constantly without suffering from substantial fluctuation. 
     Referring to an action of a conventional generator, when rotatory power from a prime mover is severely fluctuated as in a wind power generator although the electromotive force for operating a load device (not shown) is constant, it is unavoidable that the electromotive force generated thereby is severely fluctuated since the rotatory power is largely fluctuated depending on the intensity of wind power. As such, it may bring about a concern of damaging an electric part due to excessive power generation. However, the present invention can dispel such a concern by keeping the electromotive force constant in response to rotatory power. 
       FIG. 5  is a cross-sectional side view of a permanent magnet generator for stabilizing an electromotive force in accordance with a second exemplary embodiment of the present invention. 
     In accordance with the second exemplary embodiment illustrated in  FIG. 5 , a centrifugally movable unit  300 ′ is constituted with a revolution counter  330  and a compression disc movement control unit  340 , and is not provided with an elastic body  242  in the first exemplary embodiment  242 . 
     Here, the revolution counter  330  measures the revolution speed value of the rotation shaft  210  by sensing the revolution speed (RPM) of the compression disc  241 . 
     In addition, the compression disc movement control unit  340  moves the compression disc  241  forward or rearward in the direction of rotation axis. For this purpose, a bearing  342  is provided in front of the compression disc  241  to rotatably connect the compression disc  241  to a rod  341 , and the compression disc movement control unit  340  is configured to push or pull the rod  341  in the direction of rotation axis. 
     That is, the compression disc movement control unit  340  is configured such that when the revolution speed value is increased, the compression disc movement control unit  340  pulls the rod  341 , and when the revolution speed value is reduced, the compression disc movement control unit  340  pushes the rod  341 , thereby moving the compression disc  241  forward or rearward in the direction of rotation axis. The compression disc movement control unit  340  may be constituted with a hydraulic machine configured such that the load  341  is connected to the inside of a cylinder (not shown) to be moved forward or rearward by a hydraulic motor (not shown) or with a stepping motor (not shown) which can move the rod  341  forward or rearward. However, the present invention is not limited to the hydraulic machine or the stepping motor. 
     As constructed as described above, the second exemplary embodiment of the present invention can control the moving amount of the compression disc  241  precisely in accordance with a revolution speed value more precisely than the first exemplary embodiment that moves the compression disc  241  with the elastic body  242  and the centrifugally movable unit  300  although the second exemplary embodiment of the present invention consumes electric power since it employs the compression disc movement control unit  340  which is a power unit. 
       FIG. 6  illustrates permanent magnets provided in a rotator in accordance with the exemplary embodiments of the present invention in a state in which the permanent magnets are spread on a plane. In  FIG. 6 , the winding of the stator  110  is formed as 3-phase windings. For the convenience, one 3-phase pair (R, S, T) is illustrated. Here,  FIG. 6   a  illustrates a state in which the revolution speed of the rotation shaft  210  is low, and  FIG. 6   b  illustrates a state in which the revolution speed of the rotation shaft  210  is high. 
     Referring to  FIG. 6 , a plurality of first one-pole permanent magnets  221  are arranged on the first magnet holding tube  222  with a spacing D 1 , and a plurality of second one-pole permanent magnets  231  are arranged on the second magnet holding tube  232  with a spacing D 1 . The first one-pole permanent magnets have the same polarity and the second one-pole permanent magnets have the same polarity. The polarity of the first one-pole permanent magnets is different from that of the second one-pole magnets. Before the second magnet holding tube  232  is moved, the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231  are engaged with each other in a tooth meshing form with a spacing d 1  ( FIG. 6   a ). Here, the spacing D 1  between the permanent magnets  221  and  231  is determined to be equal to the base side of each of the permanent magnets  221  and  231 . 
     When the rotator  200  is rotated to rotate the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231 , the entire magnetic fluxes of the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231  are linked to the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231  are linked to the windings (R, S, T) of the stator  100 . At this time, for the magnetic fluxes linked when each of the winding (R, S, T) coils passes, the fluxes of the second one-pole permanent magnets  231  are reduced while the fluxes of the first one-pole permanent magnets  221  are increased, or the fluxes of the permanent magnets  231  are also reduced while the fluxes of the permanent magnets  221  are reduced. In addition, between the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231 , flux linkage by the second one-pole permanent magnets  231  is implemented simultaneously when the flux linkage by the first one-pole permanent magnets  221  is terminated. 
     In the prior art, the magnetic poles are formed in a rectangular shape. As such, since the magnetic fluxes are abruptly fluctuated at a transition from one pole to the other pole, the waveform of an electromotive force induced in the windings (R, S, T) is not formed as a sine wave. However, in accordance with the present invention, since a continuous change of magnetic fluxes is formed at the transition from a first one-pole permanent magnet  221  to a second one-pole permanent magnet  231 , the wave form of an induced electromotive force is formed close to a sine wave. To this end, the present invention can minimize the harmonic wave components as compared to the prior art, which makes it possible to reduce the power loss by the harmonic wave components. 
       FIG. 6   b  illustrates a state in which the centrifugal rotator  230  is spaced away from the fixed rotator  220  as the revolution speed of the rotation shaft  210  is increased, in which since the spacing d 2  between the magnetic poles is increased as compared to the spacing d 1  in  FIG. 6   a , and hence the linkage fluxes by the second one-pole permanent magnets  231  are reduced, an induced electromotive force is reduced. As such, even if the revolution speed is fluctuated, the magnitude of induced electromotive force can be substantially maintained. Even in this case, although a spaced part may occur between the first one-pole permanent magnets and the second one-pole permanent magnets, the magnetic fluxes linked to a coil can be maintained by the first one-pole permanent magnets  221  in a desirable waveform as compared to the prior art. 
       FIG. 7  illustrates permanent magnets arranged with a narrow spacing in the exemplary embodiments in a state in which the permanent magnets are spread on a plane. Here,  FIG. 7   a  illustrates a state in which the revolution speed of the rotation shaft  210  is low, and  FIG. 7   b  illustrates a state in which the revolution speed is high. 
     That the spacing D 2  between the first one-pole permanent magnets  221  arranged in the form of saw teeth is set to be smaller than the spacing D 1  in the exemplary embodiment in  FIG. 6 , and the spacing D 2  of the second one-pole permanent magnets  231  are set to be equal to the spacing D 2  of the first one pole magnets such that the spacing d 3  between the first one-pole permanent magnets  221  and the second one-pole permanent magnets  231  is smaller than that of the exemplary embodiment of  FIG. 6 . 
     Thus, since magnetic fluxes applied to a coil by one magnetic pole are formed in the spacing D 2  which is set further smaller than  FIG. 6 , it is possible to supply an electromotive force more stabilized than the exemplary embodiment of  FIG. 6 . Furthermore, assuming the revolution speed is increased to be the same with the state as illustrated in  FIG. 7   b , a coil is continuously connected without being cut when it crosses from a first one-pole permanent magnet  221  to a second one-pole permanent magnet  231 . 
     Meanwhile, the maximum moving distance of the second one-pole permanent magnets  231  is set to be smaller than the axial length of the second one-pole permanent magnets  231  such that flux linkage can be executed by the stator even if the second one-pole permanent magnets  231  are moved at the maximum thereof. In the present exemplary embodiment, the maxim moving distance of the second one-pole permanent magnets  231  is set to about ⅔ of the axial length of the second one-pole permanent magnets  231 , and such a moving distance may be set by adjusting the length of the guide hole  211  formed in the rotation shaft  210 . 
       FIG. 8  illustrates that an elastic body may be mounted in the rear side of a rotation shaft  210  in the first exemplary embodiment of the present invention. 
     That is, referring to the exemplary embodiment illustrated in  FIG. 8 , an elastic body is mounted in a rear side axial bore  212  of the rotation shaft  210  where a prime mover (not shown) is mounted rather than being mounted on the compression disc  241  side of the reciprocating shaft  240 . 
     Specifically, the elastic body  242 A in the exemplary embodiment of  FIG. 8   a  is fitted in the axial bore  212  of the rear side of the rotation shaft  210  in such a manner that one end of the elastic body  242 A is fixed to the rear end of the reciprocating shaft  240  (see reference numeral  245 ) and the other end is fixed to the rear end of the rotation shaft  210  (see reference numeral  250 A), in which the elastic body  242 A is constituted with a tension spring. 
     In addition, in the exemplary embodiment of  FIG. 8   b , the rear side part of the axial bore  212  of the rotation shaft  210  is formed to have a diameter larger than the front side part so that the inner circumferential surface of the axial bore  212  is stepped, and then the elastic body  242 B is mounted by being inserted into the axial bore  212  so that the front end is caught by the stepped part. In addition, a rod  246  is formed to extend rearward from the rear end of the reciprocating shaft  240 , the rod  246  is inserted into an elastic body  242 B, and then the rear end of the rod  246  is fixed to the rear end of the elastic body  242 B (see reference numerals  246 A and  246 B). At this time, the elastic body  240  is constituted with a compression spring. 
     That is, in configuring the reciprocating shaft  240  to receive elastic force directed rearward, although the present invention may provide the elastic body  242  at the front side of the reciprocating shaft  240  as illustrated in  FIGS. 1 to 4 , it can be seen that the present invention may provide an elastic body  242 A or  242 B which can be inserted into the axial bore  212  of the rotation shaft  210  as in the exemplary embodiments illustrated in  FIG. 8  and mount the elastic body at the rear side of the reciprocating shaft  240 . 
     While the present invention has been illustrated and described in connection with various specific exemplary embodiments in order to exemplify the technical ideas of the present invention, it will be understood that the present invention is not limited to the constructions and actions which are the same with the specific exemplary embodiments as described above, and various modifications can be made without departing from the scope of the present invention. Accordingly, such modifications shall be considered as belonging to the scope of the present invention, which shall be determined on the basis of the accompanying claims.