Patent Publication Number: US-2005140231-A1

Title: Power generator and torque amplifier

Description:
TECHNICAL FIELD  
      The present invention relates to a power generator using a permanent magnet, and a torque amplifier suitable for use in driving-the power generator.  
     BACKGROUND ART  
      There has been known a torque multiplier or amplifier adapted, particularly, to obtain an output power greater than an external input power by means of a permanent magnet, such as a magnetic rotation apparatus disclosed in Japanese Patent Laid-Open Publication No. 09-285103. This magnetic rotation apparatus utilizes a repulsion force between a permanent magnet and an electromagnet or a repulsion force between a plurality of permanent magnets. There has also been known a power generator using a neodymium-based (Nd—Fe-Bo) magnet, such as a power generator disclosed in Japanese Patent Laid-Open Publication No. 10-191623, which is designed to lead a magnetic flux from respective poles of a rod-shaped neodymium-based magnet to a plurality of ferromagnetic members disposed in opposed relation to each other to form a plurality of magnetic gaps intermittently in the circumferential direction of the magnet, and obtain an electrical power from a terminal of a stator coil disposed across the magnetic gaps.  
      While the aforementioned magnetic rotation apparatus can purportedly provide an output power greater than an input power, it has poor practicality because the difference between the output and input powers or a torque amplification coefficient is too small for an increased size of the apparatus caused by the need for intricately combining a member of permanent magnets. Moreover, the magnetic rotation apparatus is not designed to generate electrical power from an electromagnet, and thereby a power generator has to be connected to a driven rotor of the magnetic rotation apparatus to generate electrical power.  
      The aforementioned power generator using a neodymium-based magnet is designed to lead a magnetic flux through the ferromagnetic members. This structure inevitably causes deterioration in magnetic force at the magnetic gaps for receiving the coil therein, and involves the risk of leakage of the magnetic flux from the ferromagnetic members if another magnetic member is located adjacent to the ferromagnetic members. Moreover, the power generator utilizing a magnetic flux from a single rod-shaped magnet has limitations in amplifying an output power.  
     DISCLOSURE OF INVENTION  
      In view of the above conventional problems, it is therefore an object of the present invention to provide a torque amplifier having a simple structure and a large torque amplification coefficient. It is another object of the present invention to provide a power generator capable of efficiently obtaining an output power relative to an input power.  
      In order to achieve the above objects, the present invention provides a power generator having a rotatable rotor adapted to be rotatively driven by an external force; a plurality of permanent magnets disposed on the rotor, along an annular zone formed parallel to either the rotational plane or the rotational axis of the rotor and around the rotational axis, at constant intervals in the circumferential direction to form an annular array, the polarities of the permanent magnets being oriented in the same direction which is orthogonal to the annular zone; and a plurality of coreless coils supported by a stationary member and disposed along the annular zone to form an annular array such that the axes of said coils intersect with the annular zone, wherein the annular zone in said rotor is formed of a nonmagnetic material; and each of the coreless coils consists of a pair of shunt coils disposed such that the pair of shunt coils sandwich the orbital plane of the permanent magnets formed by the rotation of the rotor therebetween, from the both sides of the polar direction with a gap, the pair of shunt coils having the same turn direction.  
      Further, in order to achieve the above objects, the present invention provides a torque amplifier having a rotatably driven rotor; a plurality of driven permanent magnets disposed on the driven rotor, along an annular zone formed parallel to either the rotational plane or the rotational axis of the rotor and around the rotational axis, at constant intervals in the circumferential direction to form an annular array, the polarities of the permanent magnets being oriented in the same direction which is orthogonal to the annular zone; a group of magnet wheels including a plurality sets of magnet wheels disposed along the circumferential direction of the driven rotor, each of the sets of magnet wheels is a pair of magnet wheels rotatable in the rotation direction of the driven permanent magnets and disposed such that the pair of magnet wheels sandwich the orbital plane of the driven permanent magnets formed by the rotation of the driven rotor therebetween, from the both sides of the polar direction with a gap; and a driving source for rotatively driving the magnet wheels of the magnet wheel group in a synchronous manner, wherein: the annular zone in the driven rotor is formed of a nonmagnetic material; and the magnet wheel includes a rotating member rotatable around a rotational axis parallel to the annular zone of the driven rotor and orthogonal to the circumferential direction of the annular zone, and a plurality of driving permanent magnets attached to the outer periphery of the rotating member at even intervals in the rotation direction of the rotating member and such that the polarities thereof have the same direction relative to the rotational axis of the rotating member, and the magnet wheel is disposed such that the driving permanent magnets and the driven permanent magnets have the same polarity at the opposing surfaces.  
      Furthermore, in order to achieve the above objects, the present invention provides a power generator comprising an input power shaft provided integrally and coaxially with the aforementioned rotor, and coupled to an output power shaft rotatable coaxially with the driven rotor of the aforementioned torque amplifier. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is an exploded perspective view showing a power generator according to a first embodiment of the present invention.  
       FIG. 2  is an enlarged sectional view taken along the line II-II in  FIG. 1 .  
       FIG. 3  is a block diagram showing an electrical system of the power generator.  
       FIG. 4  is an enlarged sectional view taken along the line IV-IV in  FIG. 1 .  
       FIG. 5  is a schematic sectional view showing a power generator according to a second embodiment of the present invention.  
       FIG. 6  is an exploded perspective view showing a power generator according to a third embodiment of the present invention.  
       FIG. 7  is a block diagram showing an electrical system of a power generator according to a fourth embodiment of the present invention.  
       FIG. 8  is a diagram showing an output waveform of the power generator according to the fourth embodiment.  
       FIG. 9  is a perspective view showing a power generator according to a fifth embodiment of the present invention.  
       FIG. 10  is a perspective view showing the substantial part of a power generator according to a sixth embodiment of the present invention.  
       FIG. 11  is an enlarged sectional view taken along the line XI-XI in  FIG. 10 .  
       FIG. 12  is a perspective view showing the substantial part of a power generator according to a seventh embodiment of the present invention.  
       FIG. 13  is a perspective view showing the substantial part of a power generator according to an eighth embodiment of the present invention.  
       FIG. 14  is a perspective view showing a power generator according to a ninth embodiment of the present invention.  
       FIG. 15  is a fragmentary perspective view showing the substantial part of a power generator according to a tenth embodiment of the present invention.  
       FIG. 16  is a block diagram showing another connection mode of shunt coils in a power generator of the present invention.  
      FIGS.  17 (A) and  17 (B) are schematic fragmentary top plan views showing other examples of the shapes of a permanent magnet and a coreless coil. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      With reference to the drawings, an embodiment of the present invention will now be described in detail.  
      As shown in  FIG. 1 , a power generator  10  according to a first embodiment of the present invention comprises a rotor  12  rotatably supported by a stationary member  11  (see  FIG. 2 ) in such a manner as to be rotatively driven by an external force, a plurality of permanent magnets  19  disposed along an annular zone  14 , which is defined on a surface of the rotor  12  and around the rotational axis  13  of the rotor  12 , at constant intervals in the circumferential direction of the rotor  12  to form an annular array, while uniformly orienting their polarities in a direction orthogonal to said annular zone or in the thickness direction of the rotor  12 , and a plurality of coreless coils  18  supported by the stationary member  11  and disposed along the annular zone  14  to form an annular array, while allowing the respective axes  19  of the coils  18  to intersect with the annular zone  14 . The permanent magnets  16  are moved along the coreless coils  18  in conjunction with the rotation of the rotor  12  induced by a rotational force supplied through a center shaft  22  from a torque amplifier  20  disposed below the rotor  12 , so as to obtain an output power from the coreless coils  18 .  
      The permanent magnets  16  has a disc shape, and the pitch Pm of the permanent magnets  16  along the circumferential direction of the annular zone  14  is set to satisfy the following relation with the outer diameter Dm of each of the permanent magnets  16  along the circumferential direction (Dm is substantially equal to the diameter of the disc): Pm≧2 Dm. Each of the coreless coils  12  has a circular ring shape, and the outer diameter Dc of each of the coreless coils  18  along the circumferential direction of the annular zone  14  is set to be equal to the outer diameter Dm of each of the permanent magnets  16 . Further, the pitch Pc of the coreless coils  18  along the circumferential direction is set at a value of 1 to 1.4 times of the outer diameter Dc, preferably 1.1 to 1.3 times of the outer diameter Dc, more preferably 1.2 times of the outer diameter Dc.  
      In the rotor  12 , at least the annular zone  14  is formed of a nonmagnetic material, such as aluminum plate. Each of the coreless coils  18  is composed of a pair of shunt coils  18 A,  18 B. The pair of shunt coils  18 A,  18 B have the same winding or turn direction. Further, as shown in  FIG. 2 , the pair of shunt coils  18 A,  18 B are aligned along the polar direction of the permanent magnets  16  in such a manner as to sandwich therebetween the orbital plane of the permanent magnets  16  rotated in conjunction with the rotation of the rotor  12 , from the opposite sides of the orbital plane while leaving a gap between the orbital plane and each of the shunt coils  18 A,  18 B.  
      The shunt coils  18 A,  18 B in each of the coreless coils  18  are connected in series with one another, and the coreless coils  18  are connected in series with each other as shown in  FIGS. 1 and 3 .  
      The output terminal of the coreless coils  18  is connected to a rectifier  26  through a transformer  24 . An alternating current output from the coreless coils  18  is transformed into an optimal voltage through the transformer  24 , and then rectified to a direct current through the rectifier  26 .  
      The rectifier  26  is connected in parallel with a battery  28 , a load  30  and a motor  42  (described in detail later). The motor  42  is connected to the rectifier  26  through a switch  41 .  
      As enlargedly shown in  FIG. 2 , each of the permanent magnets  16  is composed of two superimposed magnets  17 ,  17  having a circular plate shape with the same size. The permanent magnet  16  is fixedly attached to the rotor  12  by press-fitting it into a through-hole  32  which is formed in the annular zone  14  of the rotor  12  in advance to penetrate the rotor  12  in its thickness direction, and then caulking the outer peripheral edge of the through-hole  32 .  
      The pair of shunt coils  18 A,  18 B in each of the coreless coils  18  are fixedly fastened, respectively, to the upper inner and lower inner surfaces of an annular-shaped frame  34  having an outer peripheral wall with a reverse C-shaped section, using bolts  35  as shown in  FIG. 2 , while leaving a gap between the shunt coils  18 A,  18 B so as to allow the annular zone  14  of the rotor  12  to be rotatively passed therethrough.  
      The term “coreless coil” herein means a coil devoid of a core formed of a magnetic material, such as an iron core. Thus, as shown in  FIG. 4 , a nonmagnetic core  19  made, for example, of hard resin, may be attached to the coreless coil  18  to stabilize the winding shape of the coreless coil  18 .  
      The annular-shaped frame  34  is fixedly attached to the stationary member  11  serving as a part of a frame. The reference numeral  22  in  FIG. 1  indicates a center shaft integrally attached to the rotor  12  in such a manner as to be aligned with the rotational axis  13  of the rotor  12 .  
      The torque amplifier  20  for rotatively driving the rotor  12  through the center shaft  22  will be described below.  
      The torque amplifier  20  comprises a circular driven rotor  36  coupled to the center shaft  22  and adapted to be rotatively driven coaxially and integrally with the rotor  12 , and a magnet wheel group  38  for rotatively driving the driven rotor  36  by means of a repulsion force of a permanent magnet, and eight motors  42  for synchronously driving eight magnetic wheels  40  comprising the magnet wheel group  38 .  
      The driven rotor  36  has a surface including an annular zone  44  formed along the outer periphery of the driven rotor  36  and around the rotational axis of the driven rotor  36  (center shaft  22 ), and a plurality of driven permanent magnets  46  disposed along the annular zone at constant intervals in the circumferential direction of the driven rotor  36  to form an annular array, while uniformly orienting their polarities in a direction orthogonal to the annular zone  44  or in the thickness direction of the driven rotor  36 .  
      The driven permanent magnets  46  has a plate shape with the same size as that of each of after-mentioned driving permanent magnets  58 . In the annular zone  44 , the interval or pitch between the adjacent driven permanent magnets  46  along the circumferential direction of the driven rotor  36  is set at a value of 1.0 to 1.4 times, preferably 1.1 to 1.3 times, more preferably 1.2 times, of the outer diameter of each of the driven permanent magnets  46  along the circumferential direction.  
      The annular zone  44  in the driven rotor  36  is formed of a nonmagnetic material. For example, the entire driven rotor  36  or only the annular zone  44  may be formed of an aluminum plate to allow the annular zone  44  to be nonmagnetic.  
      The magnet wheel group  38  is comprised of four pairs of upper and lower magnetic wheels  48 A,  48 B;  50 A,  50 B;  52 A,  52 B;  54 A,  54 B, and the four magnet wheel pairs are disposed along the outer periphery and the circumferential direction of the driven rotor  36  at equiangular intervals. Each of the magnet wheel pairs or sets are designed to be rotatable in the rotation direction of the driven permanent magnets  46  and aligned along the polar direction of the driven permanent magnets  46  in such a manner as to sandwich therebetween the orbital plane of the driven permanent magnets  46  rotated in conjunction with the rotation of the driven rotor  36 , from the opposite sides of the orbital plane while leaving a gap between the orbital plane and each of the magnet wheels (see  FIG. 4 ). The motors  42  are coupled, respectively, to the eight magnet wheels to rotate the magnet wheels in the above rotation direction.  
      The magnet wheels  48 A to  54 B includes a rotating member  56  parallel to the annular zone  44  of the driven rotor  36  and rotatable around a rotational axis  56 A orthogonal to the circumferential direction of the annular zone  44 , and four driving permanent magnets  58  attached to the outer periphery of the rotating member  56  at even intervals in the rotation direction of the rotating member  56  while uniformly orienting their polarities relative to the rotational axis of the rotating member  56 . Each of the driving permanent magnets  58  is arranged to have the same polarity as that of each of the driven permanent magnets  46  to be opposed thereto.  
      As particularly shown in  FIG. 4 , each of the driving permanent magnets  58  is formed of a plate-shaped magnet disposed in the outer periphery of the rotating member  56  point-symmetrically around the rotational axis  56 A of the rotating member  56 , and the plate-shaped magnet is attached to the rotating member  56  in such a manner that the closest distance d 1  between the leading edge of the plate-shaped magnet in the rotation direction of the rotating member  56  and the orbital plane of the driven permanent magnets  46  is greater than the closest distance d 2  between the trailing edge of the plate-shaped magnet in the rotation direction and the orbital plane.  
      As with the permanent magnet  16  attached to the rotor  12 , each of the driven permanent magnets  46  and the driving permanent magnets  58  is composed of two circular plate-shaped magnets  46 A,  46 B;  58 A,  58 B, which are magnetically attached together in a superimposed manner.  
      A power generation process using the above power generator  10  will be described below.  
      The battery  28  is charged in advance. When the switch  41  is turned on to activate the motors  42 , the motors  42  rotatively drive the corresponding magnet wheels  48 A to  54 B in respective directions as indicated by the arrows in  FIG. 1 .  
      This operation will be described in more detail by taking the magnet wheels  48 A,  48   b  as an example. As shown in  FIG. 4 , each of the driving permanent magnets  58  of the magnet wheel  48 A disposed above the driven rotor  36  is arranged to have the N-pole located outside, and each of the driving permanent magnets  58  of the magnet wheel  48 B disposed below the driven rotor  36  is arranged to have the S-pole located outside. On the other hand, each of the driven permanent magnets  46  of the driven rotor  36  is arranged to have the N-pole on the upper side and the S-pole on the lower side.  
      Thus, when the upper magnet wheel  48 A and the lower magnet wheel  48 B are rotated clockwise and counterclockwise, respectively, as indicated by the arrows in  FIG. 4 , the driven permanent magnet  46  is pushed leftward in  FIG. 4  by the repulsion force between the N-pole of the driven permanent magnet  46  and the N-pole of the driving permanent magnet  58  in the upper magnet wheel  48 A getting close to the driven permanent magnet  46 .  
      In the same manner, the driven permanent magnet  46  is also pushed leftward in  FIG. 4  by the repulsion force between the S-pole of the driven permanent magnet  46  and the S-pole of the driving permanent magnet  58  in the lower magnet wheel  48 B.  
      As mentioned above, each of the driving permanent magnets  58  in the magnet wheels  48 A,  48 B is arranged such that the closest distance d 1  between the leading edge of the driving permanent magnet  58  in the rotation direction and the surface of the driven permanent magnet  46  is greater than the closest distance d 2  between the trailing edge of the driving permanent magnet  58  and the surface of the driven permanent magnet  46 . Thus, during the above operation, the repulsion force is increased on the side of the trailing edge of the driving permanent magnet  58  in the rotation direction to prevent the driven permanent magnet  46  from being moved rightward in  FIG. 4  by the repulsion force between the permanent magnets induced by the rotations of the magnet wheels  48 A and  48 B.  
      The driven rotor  36  is integrally coupled to the rotor  12  through the center shaft  22 . Thus, even if it is attempted to drive the driven rotor  36  in conjunction with the rotations of the magnet wheels  48 A to  54 B, the driven rotor  36  cannot follow the rotations of the magnet wheels  48 A to  54 B immediately after startup of the motors  42  due to an insufficient magnetic repulsion force relative to a large rotational resistance of the rotor  12  and the driven rotor  36 .  
      However, the rotation speed of the driven rotor  36  is gradually increased by the repulsion force from the driving permanent magnets  58  in conjunction with the rotations of the magnet wheels  48 A to  54 B, and the rotation speed of the magnet wheels is synchronized with the rotation speed of the driven rotor  36  after a given time from the startup of the motors  42 .  
      During this process, when the driving permanent magnet  58  located closest to the driven rotor  36  is further rotated away from the driven rotor  36 , and the subsequent driving permanent magnet  58  is moved closer to the driven rotor  36 , it is likely that the driven rotor  36  is undesirably driven in the opposite direction or rightward in  FIG. 4  by a magnetic repulsion force to the driven permanent magnet  46 .  
      In the torque amplifier  20  according to this embodiment, the interval or pitch between the adjacent driven permanent magnets  46  along the circumferential direction of the driven rotor  36  is set at a value of 1.0 to 1.4 times, preferably 1.1 to 1.3 times, more preferably 1.2 times, of the outer diameter of each of the driven permanent magnets  46  along the circumferential direction. Thus, almost no repulsion force causing the reverse rotation of the driven rotor  36  is generated between the subsequent driven permanent magnet  46  and the driving permanent magnet  58 .  
      In this manner, according to the driving permanent magnets  58  driven by the eight motors  42 , the driven rotor  36  is rotated at a constant speed through the driven permanent magnets  46 . As above, the driven rotor  36  is driven by the magnetic repulsion force to the driven permanent magnets. Simultaneously, this repulsion force also acts to the driving permanent magnets  56 , and each of the magnet wheels  48 A to  54 B receives the repulsion force in a direction accelerating the rotation thereof. Thus, after the driven rotor  36  gets into the constant-speed rotation, a required driving power for the motors  12  will be reduced as compared to that before the constant-speed rotation.  
      When the rotor  12  is rotated through the driven rotor  36  and the center shaft  22 , the permanent magnets  11  are passed between the shunt coils  18 A,  18 B in the coreless coils  18  intermittently at a constant speed.  
      Thus, an alternating current having a frequency corresponding to the number of times that the permanent magnets  16  are passed between the pair of shunt coils  18 A,  18 B per second is generated at each of the shunt coil sets.  
      The pair of shunt coils  18 A,  18 B connected in series with one another and the entire coreless coils  18  connected in series with each other can provide a higher voltage in proportion to the total number of the shunt coils.  
      Further, the adjacent coreless coils  18  are spaced apart from one another at the interval as shown in  FIG. 1 , the interval or pitch is set at a value of 1.0 to 1.4 times, preferably 1.1 to 1.3 times, more preferably 1.2 times, of the outer diameter of each of the coreless coils along the circumferential direction of the annular zone  14 . This prevents the permanent magnet  16  passed through one of the coreless coils  18  from receiving a rotational resistance due to a magnetic attraction and/or repulsion force arising from the change in magnetic flux caused by the adjacent coreless coil  18 . The number of turns in the coreless coil may be adjusted to conform an output voltage to a target voltage, for example, of 100 V or 200 V, so as to eliminate the need for providing any transformer.  
      The coreless coils  18  literally devoid of a magnetic core, such as iron core, can prevent the occurrence of rotational resistance due to the magnetic attraction between such a magnetic core and each of the permanent magnets  16 . In addition, any heat due to an eddy-current loss in the inside of the iron core or the like is never generated.  
      Generally, the performance of a neodymium-based magnet is sharply deteriorated at a temperature of 80° C. or more. Thus, despite various countermeasures against heat, the deterioration in the neodymium-based magnet has not been suppressed because it is often the case that an electromagnetic coil for a motor or the like is rapidly heated up to a temperature greater than 0° C. after startup of the motor.  
      While the driven rotor  36  in the torque amplifier  20  substantially corresponds to a rotor of a motor, no heat is generated in an electromagnetic coil because the driven rotor  36  is rotated only by the repulsion force between the permanent magnets, and the heat generation in the motors  42  has no adverse affect on the permanent magnets because the motors  42  are located away from the permanent magnets. Thus, the driven permanent magnets  46  and the driving permanent magnets  58  have no deterioration due to heat.  
      The alternating current generated in the above way is reduced to a given voltage through the transformer  24 . Then the alternating current is rectified to a direct current through the rectifier  26 , and the obtained direct current is supplied to the battery  28 , the load  30  and the motors  42 .  
      Under conditions in the after-mentioned Example, the output power obtained from the coreless coils  18  was 3 KW, and the power consumption in the motors  42  was 0.75 KW. Thus, a net power of 2.25 KW could be obtained.  
      The battery  28  is designed to store therein an excessive power when there is a power enough to spare for the motors  42  and the load  30 , and discharge the stored power when the power is insufficient.  
      A voltage to be usually applied to the battery  28  is set at a floating charge voltage, and a small current to the extent compensating for a self-discharge is supplied to the battery  28  in the steady state.  
      With reference to  FIG. 5 , a second embodiment of the present invention will be described below.  
      In a power generator  60  according to the second embodiment, two sets of the combinational structures, each of which includes the rotor  12  and the plurality of coreless coils  18  surrounding the rotor  12  as described in the first embodiment, are attached to the center shaft  22 .  
      According to this structure, without excessively increasing the volume of the power generator, the two-fold increase of output power can be achieved by increasing the power or the number of the motors  42  in the torque amplifier  20 .  
      In  FIG. 5 , the reference numerals  62 A,  62 B indicate a pair of bearings for rotatably supporting the upper and lower ends of the center shaft  22 , respectively. The remaining structure is the same as that in the first embodiment illustrated in FIGS.  1  to  4 . Thus, in  FIG. 5 , the same component or element as that in the first embodiment is defined by the same reference numeral, and its description will be omitted.  
      With reference to  FIG. 6 , a power generator  70  according to a third embodiment of the present invention will be described below.  
      In this power generator  70 , a plurality of second coreless coils  72  are disposed, respectively, in the intervals or spaces between the coreless coils  18  in the power generator  10  according to the first embodiment. Each of the second coreless coils  72  is designed to have a turn direction opposite to that of the coreless coil  18 , and to be connected in series to the adjacent permanent magnet  16 .  
      As with the coreless coils  18 , each of the second coreless coils  72  comprises a pair of shunt coils  72 A,  72 B which are disposed, respectively, on the upper and lower sides of the rotor  12 , and connected in series with one another.  
      According to the power generator  70  in which the permanent magnet  16  and the second coreless coils  72  having a turn direction opposite to that of permanent magnet  16  are disposed in an alternate arrangement, when the permanent magnet  16  is passed between the shunt coils  18 A,  18 B of the coreless coil  18  and between the shunt coils  72 A,  72 B of the second coreless coil  72 , the magnetic flux from the permanent magnet  16  first passing through the shunt coils  18 A,  18 B is increased from zero to a maximum value and then returned to zero, and the magnetic flux from the permanent magnet  16  subsequently passing through the adjacent shunt coils  72 A,  72 B is increased from zero to a maximum value and then reduced to zero in the opposite direction because the shunt coils  72 A,  72 B have a turn direction opposite to that of the shunt coils  18 A,  18 B.  
      Thus, the dose/alternate arrangement of the coreless coils  18  and the second coreless coils  72  having opposite turn directions can provide a doubled output voltage.  
      It should be noted that when the permanent magnet  16  in this embodiment is moved from the position of the coreless coil  18  to the adjacent second coreless coil  72  or from the second coreless coil  72  to the adjacent coreless coil  18 , the respective coils  18 ,  72  have an electromagnetic force generated in opposite directions relative to the change in magnetic flux, and thereby the electromagnetic force acts to pull the permanent magnet  16  so as to increase the rotational resistance of the rotor  12 .  
      With reference to  FIG. 7 , a power generator  80  (its overall view is omitted) according to a third embodiment of the present invention will be described below.  
      While  FIG. 7  shows only coreless coils, a battery and a motor, the remaining structure is the same as that of the aforementioned power generator  10  or  60 , and its illustration and description will be omitted.  
      This power generator  80  is a DC type in which a plurality of DC coreless coils  82  are disposed, respectively, in the intervals and spaces between the coreless coils  18  in the power generator  10  illustrated in  FIG. 1 , and each of the DC coreless coils  82  is designed to have the same turn direction as that of the coreless coils  18 , and to be connected in series to the adjacent coreless coils  18 .  
      Thus, as seen in  FIG. 7 , the power generator  80  does not include any transformer and rectifier.  
      According to the arrangement in which the coreless coils  18  and the DC coreless coils  82  having the same turn direction as that of the coreless coils  18  are alternately connected in series with each other and arranged to form an annular array without any gap or space therebetween, when the permanent magnets  16  disposed intermittently in the annular zone  14  of the rotor  12  are passed through these coils, the coreless coil  18  and the DC coreless coil  82  have sine wave outputs different in phase by 180° degrees, respectively, as indicated by the one-dot chain line and two-dot chain line in  FIG. 8 . Thus, while a peak voltage slightly fluctuates, a pseudo-direct current as indicated by the solid line in  FIG. 8  is obtained as the sum of the above two outputs.  
      In this embodiment, each of the permanent magnets  16  may be designed to have a size greater than that of each of the coils  18 ,  82 , or each of the coreless coils  18  and the DC coreless coils  82  may be designed to have an outer diameter along the circumferential direction of the annular zone  14 , less than that of each of the permanent magnets  16 . In this case, the phase lag can be reduced to provide a DC voltage having a peak value with smaller fluctuation.  
      With reference to  FIG. 9 , a power generator  90  according to a fifth embodiment of the present invention will be described below.  
      In this power generator  90 , each of the magnet wheel sets of the magnet wheel group  38  in the first embodiment is disposed along the periphery of the rotor  12  and between the adjacent coreless coils  18  to allow the rotor  12  to additionally serve as a driven rotor in a torque ampler.  
      More specifically, the magnet wheel sets  48 A,  48 B;  50 A,  50 B;  52 A,  52 B;  54 A,  54 B of the magnet wheel group  38  are arranged such that the permanent magnets  16  attached to the annular zone  14  of the rotor  12  are sandwiched between their driving permanent magnets  58  from the opposite sides in the thickness direction of the rotor  12 .  
      Thus, in the power generator  90 , the permanent magnets  16  is rotatively driven in one direction by the driving permanent magnets  58  attached to the magnet wheels  48 A to  54 B, and moved between the shunt coils  18 A,  18 B in each of the coreless coils  18  so as to generate an electrical power in the shunt coils  18 A,  18 B.  
      While the number of the coreless coils  18  in this power generator  90  is reduced as compared with the power generator  10  in  FIG. 1 , the rotor  12  additionally serving as the driven rotor allows the volume of the power generator to be reduced as a whole.  
      Further, the permanent magnets  16  can be used for both the torque amplifier and the power generator.  
      In the above case where a single rotor additionally serves as a driven rotor for a torque amplifier, and a set of permanent magnets are used for both a torque amplifier and a power generator, an annular-shaped rotor  96  including an annular zone  94  and having a shape analogous to the annular zone  94  may be used as illustrated in  FIG. 10  showing a power generator  92 .  
      In this case, as shown in  FIG. 11 , an annular-shaped frame  98  corresponding to the annular-shaped frame  34  in  FIG. 2  for supporting the shunt coils  18 A,  18 B can be formed to have a closed space  99  allowing the annular-shaped rotor  96  to penetrate therethrough.  
      Thus, while each of the shunt coils  18 A,  18 B in  FIG. 2  is supported in a cantilevered manner, the annular-shaped frame  98  in  FIG. 11  allows each of the shunt coils  18 A,  18 B to be supported at both ends thereof in the closed space  99 .  
      Further, in the annular-shaped frame  34  in  FIG. 2 , it is required to set the gap between each of the shunt coils  18 A,  18 B and the rotor  12  at a relatively large value, because the magnetic attraction between the circular plate-shaped magnets  17  and the shunt coils  18 A,  18 B is likely to cause the displacement of the shunt coils  18 A,  18 B in a direction getting closer to the rotor  12 . As a result, the magnetic flux from the circular plate-shaped magnets  17  could leak out of the shunt coils  18 A,  18 B.  
      In contrast, according to the structure in  FIGS. 10 and 11  where each of the shunt coils  18 A,  18 B is supported at both ends thereof by the annular-shaped frame  98  having the closed space  99 , the displacement of the shunt coils  18 A,  18 B toward the annular-shaped rotor  96  can be suppressed Thus, the gap between each of the shunt coils  18 A,  18 B and the rotor  12  can be reduced to suppress the leakage of the magnetic flux.  
      In addition, according to the power generator  92 , the annular-shaped rotor  96  can be supported in a floating manner by means of the repulsion force between the driving permanent magnets  58  of the magnet wheels and the permanent magnets  16 .  
      Thus, the annular-shaped rotor  96  is rotatively driven almost without contact with surrounding members to achieve suppressed wearing, longer operating life and significantly reduced maintenance cost.  
      The reference numeral  97  in  FIG. 11  indicates a roller bearing for preventing the annular-shaped roller  96  from being displaced in the thickness and radial directions beyond a given value. At least three of the roller bearings  97  are disposed along the inward periphery of the annular-shaped rotor  96  and in contact with the respective inward corners of the annular-shaped rotor  96  from an oblique direction.  
      While the annular zone  14  in the first to sixth embodiments is a part of the rotor  12 , and formed parallel to the rotational plane of the rotor  12 , the present invention is not limited to such an annular zone  14 . For example, as illustrated in  FIG. 12  showing a power generator  110  according to a seventh embodiment of the present invention, the annular zone for attaching the permanent magnets thereto may be a pair of annular zones  102 A,  102 B formed in a rotor  102  to extend vertically relative to the rotational plane of the rotor  102 .  
      In this case, the annular zones  102 A,  102 B are formed as a pair of flanges extending from the outer periphery of a disc-shaped portion of the rotor  102  at a right angle with or in the thickness direction of the disc-shaped portion in opposite directions. As with the annular zone  14  in the aforementioned power generator  10 , the permanent magnets  16  are fixedly embedded in the annular zones  102 A,  102 B.  
      A plurality of coreless coils  104  ( FIG. 12  shows only a part of the coreless coils) are disposed relative to the annular zones  102 A,  102 B and the permanent magnets  16  perpendicular to the rotational plane, in such a manner that each of the annular zones  102 A,  102 B is sandwiched between plural pairs of shunt coils constituting the coreless coils  104 , from the inside and outside, and the pairs of shunt coils are arranged to extend radially from the rotational axis  103  of the rotor  102 .  
      As compared with the power generator  10  in  FIG. 1 , the power generator  100  allows a doubled number of the permanent magnets  16  to be attached to a rotor having substantially the same size. Thus, an electrical power to be obtained is naturally doubled. Further, as compared with the power generator  60  in  FIG. 5 , while an electrical power to be obtained is substantially the same, the volume of the power generator can be reduced.  
      Further, the number of the annular zones perpendicular to the rotational plane of the rotor may be increased in the radial direction to provide an increased electrical power to be obtained from a rotor having the same size.  
      For example, as illustrated in  FIG. 13  showing a power generator  110  according to an eighth embodiment of the present invention, a first pair of annular zones  112 A,  112 B and a second pair of annular zones  114 A,  114 B having a different radius from that of the first pair are formed in a rotor  112  around the rotational axis of the rotor  112 .  
      As compared with the power generator  100  in  FIG. 12 , the power generator  110  allows a power generation capacity per rotor to be approximately doubled.  
      As with  FIG. 12 ,  FIG. 13  shows only a part of coreless coils for the power generator  110 . Further, in  FIGS. 12 and 13 , the illustration of a torque amplifier for the power generators  100 ,  110  is omitted.  
      If the coreless coils and the magnet wheels are disposed relative to a common rotor as in the power generators  90 ,  92  illustrated in  FIGS. 9 and 10 , a pair of magnet wheels  106 A,  106 B may be disposed in such a manner as to sandwich therebetween the annular zone  102 A extending vertically upward or the annular zone  102 B extending vertically downward in the thickness direction thereof, as indicated by the two-dot chains line in  FIG. 12 . In  FIG. 12 , the illustration of the remaining magnet wheels is omitted.  
      In cases where a plurality of rotors are disposed in a superimposed manner as in the power generator  60  illustrated in  FIG. 5 , or a plurality of annular zones are disposed in a multistage manner as in the power generator  110  illustrated in  FIG. 13 , the permanent magnets and the coreless coils to be disposed adjacent to each other in the thickness direction of the rotor may be matched with each other in terms of pitch and phase to further effectively utilize the magnetic flux of the permanent magnets so as to provide enhanced power generation efficiency.  
      In  FIG. 14  showing a power generator  120 , a plurality (two in this embodiment) of rotors  122 ,  124  are integrally coupled together coaxially and parallel to each other. The rotors  122 ,  124  have annular zones  123 ,  125 , respectively. The annular zones  123 ,  125  are formed to extend parallel to at least the rotational plane of each of the rotor  122 ,  124  and have the same radius from the rotational axis  126  of the rotors. The coreless coils  18  are disposed along the circumferential direction of the respective annular zones  123 ,  125  of the adjacent rotors  122 ,  124  at the same pitch in the same phase. The respective annular zones  123 ,  125  of the adjacent rotors  122 ,  124  are spaced apart from one another along the rotational axis by a distance slightly greater than the axial length of each of the coreless coils  18  or the sum of the respective axial lengths of the shunt coils  18 A,  18 B.  
      In  FIG. 15  showing a power generator  130 , two annular zones  134 ,  136  are formed in a rotor  132  to extend parallel to the rotational axis  133  of the rotor  132  around the rotational axis  133  at respective positions different in radius from the rotational axis  133 . The permanent magnets  16  are disposed along the respective annular zones  134 ,  136  adjacent to one another in the radial direction of the rotor  132 , at equiangular intervals and in the same phase in the circumferential direction of the respective annular zones  134 ,  136  around the rotational axis  133 . The coreless coils  18  opposed to the respective annular zones  134 ,  136  are disposed along the circumferential direction of the respective annular zones  134 ,  136  at equiangular intervals and in the same phase in the circumferential direction. The adjacent annular zones  134 ,  136  are spaced apart from one another by a distance slightly greater than the axial length of each of the coreless coils  18 .  
      In each of the above power generators  120 ,  130 , the coreless coils disposed adjacent to each other in the direction of the axis of the coreless coil are arranged at the same pitch and in the same phase relative to each of the permanent magnets  16 . Thus, the magnetic flux of the permanent magnet  16  can pass through not only the coreless coil directly opposed to the permanent magnet  16  but also the coreless coil adjacent thereto, to provide further enhanced power generation efficiency.  
      While the shunt coils in the first to tenth embodiments are designed such that the pair of shunt coils sandwiching the annular zone are connected in series with one another, the present invention is not limited to such a connection. For example, as shown in  FIG. 16 , a plurality of shunt coils  118 A disposed on one of the sides of an annular zone is connected in series with each other, and a plurality of shunt coils  118 B disposed on the other side of the annular zone is connected in series with each other. Then, an output power may be picked up parallel or serially. In this case, the need for serially connecting the pairs of shunt coils individually can be eliminated to facilitate the arrangement of the coreless coil.  
      Alternatively, a plurality of shunt coils may be divided into an appropriate number of groups. Then, the shunt coils in each of the groups may be connected in series with each other, and the groups may be connected in parallel with each other to obtain an output power.  
      Further, while each of the permanent magnet  16 , the driven permanent magnet  46  and the driving permanent magnet  58  in the above embodiments is composed of two superimposed magnets and formed in a circular shape, the present invention is not limited to such a structure or shape, but the permanent magnet may be composed of a single magnet or three or more superimposed magnets, or formed in any suitable shape, such as a rectangular or square shape or a trapezoidal shape. In particular, when the rotor has a relatively small diameter, it is preferable to use a sector-shaped permanent magnet  140  an as shown in  FIG. 17 (A) which is similar to a trapezoidal shape having a lower base greater than an upper base on the side of the rotational axis of the rotor. In this case, it is understood that a coreless coil  142  has a shape approximately identical to that of the permanent magnet  140 . Otherwise, when the rotor has a relatively large diameter or the annular zone is formed as a flange as in  FIGS. 12 and 13 , a rectangular-shaped permanent magnet  144  and a rectangular-shaped coreless coil  146  as shown in  FIG. 17 (B) are preferably used.  
      Furthermore, while the power generators in the above embodiments are designed to drive the rotor through the motor-driven magnetic wheels, the present invention is not limited to such a driving mechanism. For example, each of the magnet wheels may be connected to and driven by an output shaft of any other suitable driving source, such as a wind turbine, a water turbine or an engine.  
     EXAMPLE  
      Two disc-shaped aluminum rotors having a diameter of 120 cm and a thickness of 20 mm were prepared. A driven rotor for a torque amplifier was formed of an aluminum disc-shaped plate having a diameter of 120 cm and a thickness of 20 mm. Each of a plurality of permanent magnets to be attached to the rotors, the driven rotor and a plurality of magnet wheels was formed by superimposing three doughnut-shaped neodymium-based (Nd—Fe-Bo) magnets (NEOMAX available from Sumitomo Special Metals Co., Ltd.) having an outer diameter of 76 mm, an inner diameter of 42 mm and a thickness of 6 mm. The permanent magnet had magnetic characteristics including a magnetic flux density KG of 3.5 and a magnetic force of 55 Kg. An annular zone was defined in each of the rotors in such a manner that the center of the width thereof along the outer periphery of the rotor has a radius of 55 cm from the rotational axis of the rotor  72  of the permanent magnets and  60  of permanent magnets were attached, respectively, to the annular zones in the rotor and the driven rotor, at even intervals. As with the magnet wheels in  FIG. 1 , eight cubic magnet wheels were prepared. Three of the doughnut-shaped permanent magnets were superimposed, and the superimposed permanent magnet set was attached to each of the four side surfaces of the cubic magnet wheel, or total 12 (3×4) of the permanent magnets were attached to each of the magnet wheels.  
      A plurality of coreless coils each having a pair of shunt coils were prepared. Each of the shunt coils had a wire diameter of 1 mm, a turn number of 1000, a coil outer diameter of 75 Φ, and a coil axial length of 30 mm. The gap between the shunt coil and the surface of the rotor was set at 10 mm. A DC motor (available from Japan Servo Co., Ltd.) having an operating voltage of 24V, a current of 3.2 A, a power consumption of 50 W and a speed of 2000 rpm was used as each of eight motors for the magnet wheels.  
      The rotor and the driven rotor of the torque amplifier constructed as above were rotatively driven at a speed of 3000 rpm. As a result, an AC power output of 2 KW could be obtained from the output terminal of the coreless coils. That is, a net power output of 1.6 KW=2 KW (power output)−8×50 W (power consumption of the motors) could be obtained.  
      In this example, the gap between the shunt coil and the surface of the rotor was set at 10 mm, because a frame supporting the coreless coils had a low rigidity, and thereby there was the risk of the collision between the shunt coil and the rotor due to vibrations in conjunction with the switching of the magnetic attraction between the coreless coils and the permanent magnets. Thus, if the rigidity of the support frame is increased to reduce the gap, a larger output power can be obtained.  
     INDUSTRIAL APPLICABILITY  
      The power generator and the torque amplifier according to the present invention have an excellent effect of providing an output power far greater than an input power using a permanent magnet.