Abstract:
A multipolar magnetogenerator, which is operable under sufficient performance of its capability, permitting simultaneous extraction of various voltage outputs and is excellent in spatial efficiency, includes a magnet rotor ( 3 ) as an outer rotor and a multipolar stator ( 10 ) opposed to the radially inner surface of the magnet rotor ( 3 ) to permit extraction of an output of generated power from output windings ( 30 ) wound around the stator core  10 . A transformer core ( 21 ) has a primary winding ( 31 ) and secondary windings ( 32, 33 ) wound therearound and is located adjacent the radially inner circumferential surface of the stator ( 10 ), which is remote from the magnet rotor ( 3 ), and the output windings ( 30 ) are connected to the primary wiring ( 32 ) such that transformed outputs are extracted from the secondary windings ( 32, 33 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a multipolar magnetogenerator having a magnetic rotor and an opposed multipolar stator to permit extraction of generated power from output windings wrapping the stator core. 
   2. Description of the Related Art 
   Multipolar magnetogenerators are compact and light but can nevertheless generate relatively large energy. Recently, therefore, they are widely used as power sources of engine-driven portable generators, such as power-generating portions of inverter-controlled generators. 
   In case of extracting different independent outputs, like different voltage outputs, from such a multipolar magnetogenerator, it was a typical way to wrap multiple generating portions of the stator with windings adjusted for required outputs independently as disclosed in Japanese Examined Utility Model Publication hei 7-13405. 
     FIG. 9  shows the stator  01  of an outer rotor type generator that is the multipolar magnetogenerator disclosed by that publication. In  FIG. 9 , a stator core  02  has 23 salient poles  02   a  projecting radially outwardly. Among these salient poles  02   a,  15 salient poles are wrapped with power-generating armature coils C 1 , six salient poles with coils C 2  for battery-charging electric power, one salient pole with a single-phase ignition power coil C 3 , and the last one salient pole with a single-phase power source generating coil C 4 . The power-generating armature coils C 1  and the coils C 2  for battery-charging electric power are connected in three phase to generate three-phase alternating-current power, respectively. As such, coils C 1 , C 2 , C 3  and C 4  are wound in a role-sharing manner on 23 salient poles to permit extraction of different voltage outputs. 
   Although the conventional multipolar magnetogenerator is available for high-output drive, since it uses salient poles independently in a role-sharing manner as power generating portions different in output characteristics, its total output of generated power does not reach the output that should be obtained when making the best use of the true capability of power generation. 
   It is therefore an object of the invention to provide a multipolar magnetogenerator operable under sufficient performance of its capability of power generation, nevertheless permitting simultaneous extraction of various voltage outputs, and excellent in spatial efficiency. 
   SUMMARY OF THE INVENTION 
   To accomplish the object, a multipolar magnetogenerator according to the invention having a magnet rotor, and a multipolar stator including a stator core oppposed to the magnet rotor and output windings wound around the stator core to extract, an output of generated power from the output windings characterized by; a transformer having a core located on a circumferential surface opposite from the circumferential surface facing the magnet rotor of the stator; a primary winding wound around the core of the transformer; and connected to the output windings; and secondary windings wound around the core of the transformer to extract outputs of the transformer. 
   With the multipolar magnetogenerator according to the invention, having the above-summarized configuration, outputs of identical output characteristics can be obtained from output windings on all salient poles of the stator core. Therefore, a high output can be obtained by driving the multipolar magnetogenerator in a high-efficiency range. Additionally, by connecting the output windings to the primary winding on the transformer portion and extracting only necessary quantities of outputs of various voltages from the secondary windings, it is possible not only to extract high output under sufficient performance of the original capability of power generation as a multipolar magnetogenerator but also to simultaneously extract outputs of various voltages. 
   Additionally, since the transformer core is located adjacent to the circumferential surface of the stator, which is opposite from the circumferential surface thereof opposed to the magnet rotor, it is possible to use one side of the stator substantially in no use as the path of the stator core and to thereby prevent upsizing of the stator. Furthermore, since the transformer portion is integral with the stator, it can be cooled simultaneously with the output windings of the stator. 
   The transformer core preferably is associated with the stator core to form a closed magnetic circuit. By using the stator core, the closed magnetic circuit of the transformer portion can be made easily, and a portion of the stator core opposite from a portion used as a magnetic path for power generation can be effectively used as a magnetic path for the transformer. 
   The magnet rotor is preferably an outer rotor located around the stator such that a space is formed radially inward of the stator core and the transformer core is formed to extend in the space radially inwardly from the stator core. The magnet rotor made configured as an outer rotor makes it possible to effectively use the transformer portion in the inner space of the stator core that has been difficult to use in the conventional generator and to reliably prevent upsizing of the multipolar magnetogenerator. 
   The radially inward end portion of the transformer may be extended in circumferential directions to form arm portions and to use these arm portions to make a transformer&#39;s magnetic path passing through the transformer core. Such extension of the arm portions in the circumferential directions form the inner circumferential end of the transformer core makes it easy to form a closed magnetic circuit in cooperation with the stator core. 
   Support projections for fixing wiring terminals may be formed as radially inward projections of the stator core, and these support projections may be used to form a transformer&#39;s magnetic path passing through the transformer core. By forming such support portions for fixture of wiring terminals to project radially inwardly, it is possible not only to support the wiring terminals inside the stator core and for making the effective use of the space but also to use the same support portions to make a closed magnetic circuit together with the transformer core. 
   A rotary axis of the rotor may extend through the space radially inward of the transformer core such that the portion including the rotary shaft makes a transformer&#39;s magnetic path passing through the transformer core. By employing this configuration positioning the rotary shaft of the rotor to extend through the space inside the inner circumferential surface of the transformer, the rotary shaft can be directly, effectively used as the transformer&#39;s magnetic path. 
   The transformer core may have a multi-layered structure of steel plates and a separate element from the stator core such that it can be wrapped with the primary and secondary coils before it is assembled to the stator core. In this case, the transformer core can be made by punching from stacked steel plates with a press die simultaneously with the stator core. Thus the transformer can be manufactured efficiently, and the production yield of expensive electromagnetic steel plates is improved. Further, since the transformer core is manufactured as a separate member from the stator core, the work of wrapping the transformer core with windings is easier. 
   It is preferable to extend the radially inward end of the transformer core in the circumferential directions to form the arm portions and form support projections as radially inward extensions of the stator core so as to support the transformer core between two adjacent arm portions. With this structure, the transformer core can be reliably assembled inside the stator core. 
   A plurality of support projections may be formed as radially inward extensions of the stator core to support a wiring terminal holder between two adjacent support projections. With this structure, the wiring terminal holder can be reliably assembled inside the stator core. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front elevational view of a multipolar magnetogenerator according to an embodiment of the invention; 
       FIG. 2  is a back view of the same multipolar magnetogenerator; 
       FIG. 3  is a sectional view taken along the III—III line of  FIG. 1 ; 
       FIG. 4  is a front elevation showing a stator core and a transformer core assembled together; 
       FIG. 5  is a front elevational view of the transformer core; 
       FIG. 6  is a diagram showing an exemplary circuit for outputting generated power in the same multipolar magnetogenerator; and 
       FIG. 7  is an enlarged view of an essential part of a transformer-contained multipolar magnetogenerator modified from the foregoing embodiment; 
       FIG. 8  is a back view of a multipolar magnetogenerator according to another embodiment; and 
       FIG. 9  is a front elevational view of an example of a stator of a known multipolar magnetogenerator. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the invention will now be described below with reference to  FIGS. 1 through 6 . A multipolar magnetogenerator according to the embodiment is shown in its front elevational view in FIG.  1  and in its back view in FIG.  2 . In addition, a sectional view taken along the line III—III of  FIG. 1  is shown in FIG.  3 . The multipolar magnetogenerator according to the invention is of an outer rotor type placing an annular magnet rotor  3  around a stator  10  (FIG.  2 ). 
   The magnet rotor  3  constitutes an outer rotor commonly used as a flywheel. As best shown in  FIG. 3 , the magnet rotor  3  has a disk-shaped bottom wall  4  and a cylindrical outer wall  5  that form a bottomed cylinder or a cup. The magnet rotor  3  is fitted on a rotary shaft  2  extending through the bottom wall  4  via a sleeve  7 , and supported by the rotary shaft  2  to rotate together with the rotary shaft  2 . The bottom wall  4  of the cylindrical magnet rotor  3  has a circular bore receiving the central sleeve  7  therein, and has formed cooling air openings  4   a , which may be four openings, for example, at equal intervals around the circular bore. 
   On the inner circumferential surface of the cylindrical outer wall  5 , magnets  6 , which may be 20 magnets, are arranged annularly in the circumferential direction. Each magnet  6  is polarized in N and S poles in radial directions of the generator  1 , and radially outer and inner ends of adjacent magnets  6  confront with opposite polarities. 
   A stator  10  is contained in the inner space facing the annularly aligned magnets  6 . As shown in  FIG. 2 , the stator  10  is disposed around the sleeve  7  and has a stator core  11  fixed at its central part. The stator includes  30  salient poles  13 , for example, that radially outwardly project in its outer circumferential region. The salient poles  13  are wrapped with output windings  30 . The salient poles  13  are radially opposed to the magnets  6  with a small gap therebetween. 
   The stator core  11  is made by punching of electromagnetic steel plates with a press die and stacking the punched members.  FIG. 4  shows the stator core  11  obtained by press punching. From the stator core base portion  12 , 30 salient poles  13 , for example, extend radially outwardly, and four support projections  14 , for example, extend at equal intervals radially inwardly toward the center. 
   Between adjacent support projections  14 ,  14 , a sectorial space  15  is formed, and a transformer  20  and wiring terminal holders  34  and  35  are disposed therein. The transformer  20  has a transformer core  21 , and it can be punched out simultaneously when each core plate that forms the stator core  11  is punched out from an electromagnetic steel plate as shown in FIG.  4 . The transformer core  21  is formed such that its winding-wrapped core portion  22  to be wrapped with windings extends in the radially outward direction while passing the center of one of the sectorial spaces  15 , and the inner circumferential end portion of the winding-wrapped core portion  22  is extended in opposite directions along the circumferential direction to form arm portions  23 . The arm portions  23  are configured to contact under pressure with distal ends of the support projections  14  of the stator core  11 , respectively. The stator core base portion  12  has a groove  15   a  having a trapezoidal cross section at an outer circumferential section aligned with the sectorial space  15  in which the transformer core  21  is formed, and the transformer core  21  has a projection  22   a  at the distal end of the winding-wrapped core portion  22  for engagement with the groove  15   a.    
   Thus, the transformer core  21  having the shape shown in  FIG. 5  is formed as a separate body from the stator core  11 . However, as shown in  FIG. 4 , the transformer core  21  is held in position by pressure contact of its arm portions  23 ,  23  press-fitted and sandwiched by support projections  14 ,  14  of the stator core  11  from opposite sides and by press fitting of the projection  22   a  at the distal end of the winding-wrapped core  22  in the groove  15   a . The transformer core  21  can be made by punching out stacked steel plates with a press die simultaneously with the stator core  11 , and therefore, it can be manufactured efficiently while improving the production yield of expensive electromagnetic steel plates. 
   As shown in  FIG. 2 , one primary winding  31  and two secondary windings  32  and  33  are wound around the core portion  22  of the transformer core  21 . The primary winding  31  is wound around the radially outer portion of the core portion  22  while one of the secondary windings  32  is wound around the radially inner portion of the core portion  22  and the other secondary winding  33  is wound around the former secondary winding  32 . As such, since the transformer core  21  is formed separately from the stator core  11 , the work of winding the primary winding  31  and the secondary windings  32  and  33  is easier, and the transformer  20  completed with necessary windings can be inserted in the predetermined sectorial space  15 . This totally makes the manufacturing process of the generator easier. 
   Further, since the generator is of the outer rotor type, the transformer portion can be placed in the inner space of the stator core, which was difficult to utilize in the conventional multipolar magnetogenerator, and the efficient use of the space prevents upsizing of the transformer-contained multipolar magnetogenerator. Once the transformer  20  is assembled to the stator  10 , the winding-wrapped core portion  22  and the arm portions  23  of the transformer core  22  and the support projections  14  of the stator core base portion  12  makes a magnetic path and form a closed magnetic circuit  25  (FIG.  2 ). 
   Therefore, the closed magnetic circuit  25  of the transformer  20  can be readily formed by using the stator core  11 , and simultaneously, the portion of the stator core  11  in the opposite side (nearer to the support projection  14 ) from the portion used as the magnetic path for generating electric power (nearer to the salient pole  13 ) can be used as the magnetic path for the transformer. 
   In the transformer  20 , the arm portions  23  may be shorter to be more distant from the support projections  14  as shown in FIG.  7 . In case the arm portions  23  are shorter, the rotary shaft portion (rotary shaft  2  and sleeve  7 ) of the magnet rotor  3  extending along the inner side of the inner wall surface of the transformer core  21  can be used as the magnetic path to form the closed magnetic circuit  55 . 
   Since the transformer  20  is made integrally with the stator  10 , the output windings  30  of the stator  10  and the transformer  20  can be cooled simultaneously and easily. 
   In two other sectorial spaces  15  of the stator core  11 , the wiring terminal holders  34 ,  35  are received as shown in  FIG. 2 , and the support projections  14  of the stator core  11  at opposite sides of the wiring terminal holder  34  and those at opposite sides of the wiring terminal holder  35  sandwich and hold them respectively. Therefore, the wiring terminal holders  34  and  35  can be placed and held efficiently in space. 
   When the multipolar magnetogenerator  1  having the above-described construction is driven, an engine-driven generator is formed. An engine-driven generator of this type will be described with reference to FIG.  6 . 
   The rotary shaft  2  of the multipolar magnetogenerator  1  is connected to the crankshaft of an engine, not shown. When the engine is driven, a three-phase alternating-current power is output from the three-phase output windings  30  wound around the multipolar stator core  11 . Output terminals of the three-phase output windings  30  wound around the multiplolar stator core  11  are connected to an input end of an inverter unit  41 . The three-phase alternating-current power introduced into the inverter unit  41  is rectified and smoothed, thereafter converted to alternating-current power of the commercial frequency (50 Hz or 60 Hz), and output as a 100V alternating-current voltage from the outlet  42 . 
   Two-phase part of the output of the three-phase output windings  30  is connected to the primary winding  31  of the transformer  20 . The secondary wirings  32  and  33  of the transformer are connected as an igniter power source of the engine to an ignition unit  43  and as a power source for controlling the drive of the entire system to a direct-current power source unit  47 . 
   In response to a control signal from a drive control unit  40 , explained later, the ignition unit  43  drives an ignition coil  44  with a direct-current voltage of 52V to fire up an ignition plug  45  or activate an engine stop switch  46 . 
   The direct-current power source unit  47  is connected to the drive control unit  40 , battery  49  and engine-starting electric motor  51  via a backflow-preventing diode  48  to operate as their 14V direct-current supply source. 
   The drive control unit  40  supervises the drive of the entire system to start the engine by driving the starting electric motor  51  via a starting electromagnetic switch  50 , controls the ignition unit  43  and the engine stop switch  46  as stated before, or controls the function of the inverter unit  41 . 
   Revolution of the engine is controlled in accordance with the load connected to the outlet  42 , i.e. the demanded quantity of power, and the output voltage of the three-phase output windings  30  varies as well with the change of the revolution. For example, if the revolution of the engine varies in the range of 2,300 to 4,000 rpm, output voltage of the three-phase output windings  30  changes in the range of 119 to 248V (line-to-line voltage; effective value), output voltage of the transformer&#39;s secondary winding  32  of the transformer  20  changes in the range of 19.8 to 41.4V, and output voltage of the secondary winding  33  of the transformer  20  changes in the range of 8.5 to 17.7V. 
   However, since only an actually required quantity of the output power from the three-phase output windings is supplied to the ignition unit  43  and the direct-current power source unit  47  from the secondary windings  32  and  33  of the transformer  20 , the remainder power can be extracted from the outlet  42  without failing to use it. Therefore, the multipolar magnetogenerator  1  may be adjusted to be driven with high efficiency, taking account of the output characteristics of the three-phase windings  30 , and it is possible to drive it under a condition making the best use of its capability of generating electric power and to extract respective voltage outputs efficiently. 
   The multipolar generator  1  described above is configured to insert a single transformer  20  inside the stator  10 . However, one or more transformers can be added.  FIG. 8  shows a modification of the foregoing embodiment by adding a transformer  60 . 
   In two of the four sectorial spaces  15  of the stator core  11  opposed in the diametric direction, the above-described transformer  20  and the additional transformer  60  are received, respectively. In the other two opposed sectorial spaces  15 , wiring terminal holders  61  and  62  are received. The transformer  60  is identical in shape to the transformer  20 , and received in the sectorial spaces  15  identical in shape. 
   By using the additional transformer in this manner, more various voltage outputs can be obtained easily. Simultaneously, since the transformers  20  and  60  can be placed by making use of the inner space of the stator  10 , the multipolar magnetogenerator need not be upsized. 
   Although there have been described what are the present embodiments of the invention, it will be understood that variations and modifications may be made thereto without departing from the spirit or essence of the invention.