Abstract:
A magneto-generator includes: a plurality of magnets disposed being bonded to an inner circumferential surface of a flywheel; and a magneto coil that is disposed in the flywheel being opposed to the magnets and coaxial with the flywheel, and that generates an electric power by the action of electromagnetic induction with the magnets. The magneto coil is cooled with a cooling medium to be supplied from the opening side of the flywheel. A gap is formed in an axial direction of the flywheel between the mentioned adjacent magnets, and an annular magnet holder is bonded to an inner circumferential surface on the opening side of the flywheel and to the opening side of the flywheel of each magnet to close the opening side of the gap between the magnets. As a result, the magneto-generator is capable of suppressing the fluctuation in temperature of the magneto coil, and further reducing a coil temperature.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a magneto-generator that generates an electric power by the action of electromagnetic induction between a magnet and a magneto coil due to the rotation of a flywheel.  
         [0003]     2. Description of the Related Art  
         [0004]      FIGS. 12 and 13  show a rotor of a conventional flywheel-shaped magneto-generator disclosed in the Japanese Patent Publication (unexamined) No, 101630/2002.  FIG. 12  is a cross sectional view of the magneto-generator, and  FIG. 13  is a longitudinal section view taken along the line A-A of  FIG. 12 . In the drawings, reference numeral  1  designates a bowl-shaped flywheel formed of a circumferential wall  1   c , a sidewall  1   d  on the side of one end of the circumferential wall  1   c , and an opening  1   e  on the other end side. Numeral  2  designates a plurality of magnets mounted onto the circumferential wall  1   c  of the flywheel  1 . These magnets  2  engage with protrusions  1   a  provided circumferentially on the inside of the circumferential wall  1   c . Numeral  3  designates a tubular guard ring that is annularly mounted in close contact with the inside of the magnet  2 . This guard ring  3  is formed by drawing of a metal plate, and includes a flange part  3   a  that is formed by bending at one end.  
         [0005]     Numeral  4  designates a resin that fixes the magnet  2  and the guard ring  3  to the flywheel  1 , thus forming an integral whole. This resin  4  is filled in between both sides of the magnet  2  and between ends of each magnet  2 . Numeral  5  designates a boss part for mounting onto a rotary shaft (not shown). This rotary shaft  5  is fixed to a central portion of the sidewall  1   d  of the flywheel  1 . Numeral  4   a  designates fins provided on the inside of the sidewall  1   d  of the flywheel  1 . Numeral  1   b  designates a shoulder that is formed by extrusion molding on the inside of the circumferential wall  1   c  at several points of the entire circumference of the flywheel  1 .  
         [0006]     Describing the operations of the aforementioned conventional flywheel-shaped magneto-generator, by the rotation of the rotary shaft, the boss part  5  and the flywheel  1  that are attached to the rotary shaft rotate. Then, the fins  4   a  that are provided on the inside of the sidewall  1   d  of the flywheel  1  agitate gas in an air gap between a magneto coil and the sidewall  1   d  of the flywheel  1 , thereby cooling the magneto coil.  
         [0007]     In the field of a magneto-generator, it is a recent trend that further downsizing and higher power are needed. As an effective way to meet such needs, the air gap between the magneto coil and the flywheel  1  is made to be smaller so that magnetic flux from the magnet  2  is efficiently transmitted to the magneto coil.  
       SUMMARY OF THE INVENTION  
       [0008]     Accordingly, it is an object of the present invention to suppress the fluctuation in magneto coil temperature, and further to reduce the coil temperature. More specifically, the invention intends to provide a magneto-generator in which a guard ring of a magnet is eliminated thereby achieving improvement in power output, and furthermore a cooling medium of a magneto coil is efficiently sprinkled over the magneto coil thereby preventing a magneto coil temperature from rising and enabling to prevent the reduction in generated current.  
         [0009]     A magneto-generator according to the present invention includes: a bowl-shaped flywheel that is formed of a circumferential wall, a sidewall on the side of one end of the mentioned circumferential wall, and an opening on the other side of the mentioned circumferential wall, and that is fixed to a rotary shaft to rotate; a plurality of magnets that are disposed being bonded to an inner circumferential surface of the mentioned flywheel; and a magneto coil that is disposed in the mentioned flywheel being opposed to the mentioned magnets and coaxial with the mentioned flywheel, and that is caused to generate an electric power by the action of electromagnetic induction with the mentioned magnets. In this magneto-generator, the mentioned magneto coil is cooled with a cooling medium to be supplied from the opening side of the mentioned flywheel. In this magneto-generator, a gap is formed in an axial direction of the mentioned flywheel between the mentioned adjacent magnets, and an annular magnet holder is provided in such a manner as to have an annular part that is bonded to an inner circumferential surface on the opening side of the mentioned flywheel and to the opening side of the mentioned flywheel of each magnet to close the mentioned opening side of the mentioned gap between the mentioned magnets.  
         [0010]     As a result, in the magneto-generator of above construction according to the invention, a space between the magneto coil and the sidewall of the flywheel and a gap between the adjacent magnets are both filled with a cooling medium of the magneto coil. The annular magnet holder bonds and holds the magnet, and closes the opening side of the gap between the magnets, so that a part of the above-mentioned cooling medium having been filled is dammed. Due to the fact that the flywheel rotates in the peripheral portion of the magneto coil, the cooling medium having been filled and partially dammed is efficiently sprinkled over the magneto coil. Furthermore, since the gap between the magnets possesses the effect of agitating the cooling medium, thus making it possible to efficiently cool the magneto coil.  
         [0011]     In the magneto-generator according to the invention, the mentioned annular magneto-holder preferably includes: an annular part that is bonded to an inner circumferential surface on the opening side of the mentioned flywheel, and bonded to the opening side of the mentioned flywheel of each magnet to close the mentioned opening side of the mentioned gap between the mentioned magnets; and a columnar part that is embedded in a part of the mentioned gap between the mentioned magnets, and that is bonded to the mentioned magnets.  
         [0012]     As a result, in the magneto-generator of above construction according to the invention, with the annular part and columnar part of the magnet holder, it is possible for the magnet to be bonded and fixed reliably and rigidly, and positioned.  
         [0013]     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent the following detailed description of the present invention when taken in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a cross sectional view of a rotor according to a first preferred embodiment of the present invention.  
         [0015]      FIG. 2  is a longitudinal sectional view taken along the line C-C of  FIG. 1   
         [0016]     FIGS.  3 ( a ) and ( b ) are perspective views each showing a part of an annular magnet holder according to the first embodiment.  
         [0017]      FIG. 4  is a cross sectional explanatory view of the magneto-generator showing the cooling with cooling oil according to the first embodiment.  
         [0018]      FIG. 5  is a graphic diagram indicating results of measuring a coil temperature of the magneto-generator according to the first embodiment.  
         [0019]      FIG. 6  is a perspective view of a flywheel sowing a state of the magnet holder being mounted according to the first embodiment.  
         [0020]      FIG. 7  is a cross sectional view of a rotor according to a prototype magneto-generator.  
         [0021]      FIG. 8  is a longitudinal sectional view taken along the line B-B of  FIG. 7 .  
         [0022]      FIG. 9  is a graphic diagram indicating results of measuring a coil temperature of the prototype magneto-generator.  
         [0023]      FIG. 10  is an explanatory view of a side face showing points of measuring a coil temperature of the prototype magneto-generator.  
         [0024]      FIG. 11  is a cross sectional explanatory view of showing oil cooling with a magneto coil of the prototype magneto-generator.  
         [0025]      FIG. 12  is a cross sectional view of a rotor of the conventional flywheel-type magneto-generator.  
         [0026]      FIG. 13  is a longitudinal section view taken along the line A-A of  FIG. 12 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]      FIGS. 7 and 8  show a rotor of a magneto-generator made as a prototype.  FIG. 7  is a cross sectional view thereof, and  FIG. 8  is a longitudinal section view taken along the line B-B of  FIG. 7 . Referring to the drawings, a flywheel  11  designates a bowl-shaped flywheel consisting of a circumferential wall  11   c , a sidewall part  11   d  on one end side of the circumferential wall  11   c , and an opening  11   e  on the other side. Numeral  12  designates a plurality of magnets that are disposed being bonded to an inner circumferential surface of the circumferential wall  11   c  of the flywheel  11 . These magnets  12  are arranged so that be N poles and S poles are disposed alternately at even intervals. A central portion at the sidewall  11   d  of the flywheel  11  is mounted and fixed onto a rotary shaft  13 , for example, a shaft of an internal combustion engine. The flywheel  11  rotates in synchronization with the rotation of the rotary shaft  13 .  
         [0028]     To make small a gap between a magneto coil  14  ( FIG. 10 ) and the flywheel  11 , in the structure of this prototype magneto-generator, note that there is disposed neither guard ring for the magnet  12  nor resin for making the magnet  12  integral with the flywheel  11 . As a method of making the magnet  12  integral with the flywheel  11 , a bonding with the use of an adhesive  15  is employed. Numeral  16  designates a fan intended to cool the magneto coil  14  and agitate oil (electrical insulating cooling medium). It is certain that higher power can be obtained with such a structure, but means for solving the problem of high temperature of the magneto coil  14  still remains. This problem of high temperature of the magneto coil  14  also induces the reduction in generated current due to rise in resistance value. Hence, a structure of high cooling effect for the magneto coil  14  is still needed.  
         [0029]     In this regard,  FIG. 9  shows results of measuring a coil temperature of the aforementioned magneto-generator having been prototyped. Points of measuring a coil temperature are taken at U phase, V phase, and W phase.  FIG. 10  is an explanatory view of the side face of the magneto generator. Numeral  20  designates a holding hole for fixing and holding a rotor that includes the magneto coil  14  on the side of a car body. A rotational speed of the magneto generator when measuring a coil temperature is 7000 r/min, and the cooling method of the magneto coil  14  is oil cooling (engine oil is used as a cooling medium). As a result of measuring a coil temperature of the prototype magneto-generator, U phase is 198° C., V phase is 256° C., and W phase is 231° C. Further reduction in the coil temperature as well as suppression of fluctuation in coil temperatures are needed.  
         [0030]     It is presumed that the presence of a gap  17  between the magnets  12  that are fixed by bonding to an inner circumferential surface of the flywheel  11  (refer to  FIG. 7 ) is a cause of the mentioned fluctuation in the coil temperatures. This problem of fluctuation in temperature is caused by such a construction of the prototype magneto-generator that the magnet  12  is fixed to the flywheel  11  by bonding.  FIG. 11  is a cross sectional explanatory view showing oil cooling of the magneto coil  14  of the prototype magneto-generator. For example, engine oil is injected from the side of the opening  11   e  of the flywheel  11 . The engine oil having been injected flows from, e.g., the gap between the magnetic poles  18  and reaches the side of the sidewall  11   d  of the flywheel  11 . In addition, numeral  21  designates a holding shaft acting to fix and hold a rotor including the magneto coil  14  onto the car body side, and one of these three holding shafts is shown in  FIG. 11 .  
         [0031]     By the rotation of the flywheel  11 , the cooling oil is agitated with the fan  16  and sprinkled over each phase of the magneto coil  14  to absorb heat. However, since there is a gap  17  between the magnets  12 , the cooling oil will soon flow out. Therefore, the flywheel  11  is not sufficiently filled with the necessary amount of cooling oil, thus being incapable of efficiently cooling the magneto coil  14 . Consequently, a coil temperature is low at U phase where oil is likely to be retained, while a coil temperature at V phase and W phase where oil is unlikely to be sprinkled tends to be higher.  
         [0032]     Hence, the invention intends to suppress the fluctuation in temperature of a magneto coil and, further, to reduce a coil temperature.  
       Embodiment 1  
       [0033]     A magneto-generator according to a first preferred embodiment of the present invention is described with reference to FIGS.  1  to  6 .  FIGS. 1 and 2  show a rotor of the magneto-generator according to the first embodiment, and in which  FIG. 1  is a cross sectional view thereof and  FIG. 2  is a longitudinal section view taken along the line C-C of  FIG. 1 . FIGS.  3 ( a ) and ( b ) are perspective views showing a part of an annular magnet holder, and  FIG. 4  is a cross sectional explanatory view of the magneto-generator showing the cooling with cooling oil.  FIG. 5  is a graphic diagram indicating results of measuring a coil temperature of the magneto-generator, and  FIG. 6  is a perspective view of a flywheel showing a state of the magnet holder being mounted. In the drawings, same reference numerals indicate the same or like parts, and repetition of a part or the whole of descriptions may be omitted.  
         [0034]     As compared with the prototype magneto-generator shown in  FIGS. 7 and 8 , the magneto-generator according to the first embodiment is provided with an annular magnet holder  19  for the purpose of closing the opening  11   e  of the flywheel  11  of the axial gap  17  between the adjacent magnets  12 , as well as bonding and fixing each magnet  12 . The magnet holder  19  is made, for example, of a heat-resistant resin of non-magnetic substance. The annular non-magnetic magnet holder  19  is bonded to an inner circumferential surface on the opening  11   e  side of the flywheel  11 , and is disposed in the opening  11   e  side of the gap  17  between the adjacent magnets  12  in such a manner as being bonded to each magnet  12 . An adhesive is used for the purpose of bonding between each magnet  12  and the magnet holder  19  and bonding of each magnet  12  and the magnet holder  19  to an inner circumferential surface of the flywheel  11 .  
         [0035]     Although the annular magnet holder  19  can be formed solely of an annular part  19   a  shown in  FIG. 3 ( b ), it is preferred to employ the one that is provided with columnar parts  19   b  extending from the above-mentioned annular part  19   a  and being embedded in a part of each gap  17  between the adjacent magnets  12  as shown in  FIG. 3 ( b ). The columnar part  19   b  of the magnet holder  19  is embedded in a part of each gap  17  between the adjacent magnets  12  as shown in  FIGS. 1, 2  and  4 .  
         [0036]     The columnar part  19   b  of the magnet holder  19  possesses preferably 40% to 60% as long as a shaft length of the magnet  12  (length of the magnet  12  in an axial direction of the above-mentioned flywheel  11 ).  FIG. 6  shows a state of the magnet holder  19  being mounted. Since the columnar part  19   b  having 40% to 60% as long as a shaft length of the magnet  12  is mounted, a part of the gap  17  between the adjacent magnets can be left.  
         [0037]     The reason why the columnar part  19   b  of the magnet holder  19  possesses 40% to 60% as long as a shaft length of the magnet  12  is as follows. Supposing that the columnar part  19   a  becomes shorter than 40% of a shaft length of the magnet  12 , the magnet  12  is likely to be dislodged, resulting in lower effectiveness of preventing the magnets from falling. On the contrary, supposing that the columnar part  19   b  becomes longer than 60% of a shaft length of the magnet  12 , an amount of coil cooling oil to be filled in the gap  17  (concave-shaped) comes to be smaller.  
         [0038]     The flywheel  11  rotates on the peripheral portion of the stationary side magneto coil  14  in the state that the gap  17  is filled with oil acting as a cooling medium of the magneto coil  14 , thereby enabling to cool the magneto coil  14  efficiently. The magnet holder  19  functions not only to fill a part of the gap  17  between the magnets  12 , but also to achieve improved positioning and improved power of the magnet  12  being fixed.  
         [0039]     In the magneto-generator according to the first embodiment, a cólumnar part  19   b  of the magnet holder  19  is disposed at a part of the gap  17  formed between the adjacent magnets  12 . As shown in  FIG. 4 , a part of the gap  17  between the magnets  12  is filled with this columnar part  19   b  and, as a result, the oil acting as a cooling medium of the magneto coil  14  existing in the flywheel is less likely to leak out. Thus, the oil is dammed within the flywheel  11 , and a necessary amount of oil is filled and maintained, thereby enabling to efficiently cool the magneto coil  14 . It is preferable that any gas or air is employed as a cooling medium of the magneto coil  14  other than oil. In such a case, the gas or air that filled within the flywheel  11  is also agitated, making it possible to obtain a cooling effect of the magneto coil  14 .  
         [0040]      FIG. 5  shows results of measuring a coil temperature of the magneto-generator according to the first embodiment with the use of a magnet holder shown in  FIG. 3 ( a ) as the magnet holder  19 . Coil temperatures are measured at each of U phase, V phase, and W phase of the coil. Points of measuring a coil temperature are the same as those shown in  FIG. 10 . A rotational speed of the magneto-generator when measuring a coil temperature is 7000 r/min. U phase is 149° C., V phase is 141° C., and W phase is 149° C. As compared with results of measuring a coil temperature of the prototype magneto-generator shown in  FIG. 9 , the coil temperatures are enormously lowered and the fluctuation in coil temperature come to be smaller.  
         [0041]     It is understood from the above-mentioned results of measuring a coil temperature that, as a result of embedding the annular magnet holder  19  in a part of the gap  17  between the adjacent magnets  12 , it is possible to fill sufficiently the flywheel  11  of the magneto coil  14  with the cooling oil. Consequently, the smaller fluctuation in coil temperature is achieved, thus enabling to considerably reduce a coil temperature.  
       Embodiment 2  
       [0042]     As described above and shown in  FIG. 3 ( a ), the magnet holder  19  is provided at equal intervals with the annular part  19   a  and the columnar parts  19   b  extending from the annular part  19   a  and located in the flywheel  11  in order to partially fill the gap  17  between the magnets  12 . The number of columnar parts is n in the same manner as the number of magnets is n. The annular part  19   a  is located on an inner circumferential surface on the opening  11   e  side of the flywheel  11 . To make it smooth to insert the magnet holder  19  into the flywheel  11 , a chamfer part  19   c  is formed at the tip end of the columnar part  19   b.    
         [0043]     In the magneto-generator, in addition to the gap (concave-shaped) between the adjacent magnets  12 , the sidewall  11   d  on the side of one end of the circumferential wall  11   c  is formed into a fan shape by forging. This fan  16  intends to cool the magneto coil  14  and to agitate oil. Specifically, it is possible to efficiently cool the magneto coil  14  by the effect of agitating a cooling medium with both of the fan  16  and the gap  17  (concave-shaped).  
         [0044]     Furthermore, in the magneto-generator according to a second preferred embodiment, the magnet and the magnet holder  19  are bonded, and then they are fixed to an inner circumferential surface of the flywheel  11  with an adhesive  15  as described above. At this time, a very narrow gap between the magnet  12  and the magnet holder  19  may cause the adhesive  15  to get out of the gap. However, as a result of forming a chamfer part  19   d  at the annular part  19   a  and the columnar part  19   b  where the magnet holder  19  and the magnet  12  are in contact, any extra adhesive  15  gets into the chamfer parts  19   d  and does not get out to the side of the magneto coil  14  of the fly wheel  11 . It is preferable that the chamfer parts  19   d  of the annular part  19   a  and the columnar part  19   b  is formed on the side opposite to an inner circumference of the flywheel  11  (see  FIG. 3 ).  
         [0045]     This magneto-generator according to the invention is applicable to, for example, a three-phase magneto-generator to be driven by an internal combustion engine.  
         [0046]     While the presently preferred embodiments of the present invention have been shown and described. It is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.