Abstract:
An axial gap type generator which is shorter in axial length and lightweight is provided. An axial gap type engine driven generator in an axial gap type generator formed by an armature and a field magnet disposed in a housing along an axial direction of a drive shaft  100  includes a coreless armature  110  which is fixedly supported in the housing and to which an armature coil is mounted, and a pair of rotating field magnets  120  which have a pair of rotary disks to which permanent magnets  122  are mounted respectively, and are mounted to a drive shaft to sandwich the armature from both sides in a thickness direction of the armature.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a generator using a permanent magnet for a field magnet, and more particularly, to an axial gap type engine driven generator in which an armature and a field magnet are disposed in an axial direction of a drive shaft. 
         [0003]    2. Related Art 
         [0004]    In recent years, an engine driven generator using a permanent magnet for a field magnet has come into widespread use, and for example, the one disclosed in Japanese Patent No. 2679758 is provided. This generator uses a neodymium-iron-boron rare earth magnet for the field magnet and has an axial length substantially shorter than that of a former generator. 
         [0005]    Since the generator disclosed in Japanese Patent No. 2679758 has a radial gap structure, the field magnet and the armature are arranged in the radial direction to form a magnetic gap between them. Therefore, the equipment dimension in the axial direction is required due to the arrangement of the field magnet and the armature for forming the magnetic gap, and the generator protrudes further from the drive shaft of the engine. The protruded length is significantly large. 
         [0006]    This is a problem in the respect that it becomes difficult to meet the demand for compactness and high output of the generator. Thus, an axial gap type engine driven generator is required. 
         [0007]    However, in order to construct a compact and lightweight axial gap type generator, various kinds of problems need to be solved. There are the basic problems: first, which one of an armature and a field magnet is made a stator side while the other one is made a movable side; next, how the armature and the field magnet are constructed; further, how the internal heat generation due to reduction in size is dissipated, and the like. 
         [0008]    Cores (iron cores) are generally used for an armature and a field in the viewpoint of the magnetic efficiency, but use of cores increases the weight, and inhibits reduction in weight. 
         [0009]    The present invention is made in consideration of the above described respects, and has an object to provide an axial gap type engine driven generator which is shorter in axial length and lightweight. 
       SUMMARY OF THE INVENTION 
       [0010]    In order to attain the above-described object, the present invention provides an axial gap type engine driven generator in an axial gap type generator that is an engine driven generator driven by an engine and forming at least one of output for welding and output for an alternating current power supply, and is formed by an armature and a field magnet disposed in a housing along an axial direction of a drive shaft, characterized by including 
         [0011]    a coreless armature which is fixedly supported in the aforesaid housing and to which an armature coil is mounted, and 
         [0012]    a pair of rotating field magnets which have a pair of rotary disks to which permanent magnets are mounted respectively, and are mounted to the aforesaid drive shaft to sandwich the aforesaid armature from both sides in a thickness direction of the armature. 
         [0013]    In the present invention, the planar coreless armature is fixed to the housing, and a pair of rotating field magnets by permanent magnets are disposed at both sides in the axial direction, of the armature, and therefore, the generator which is short in the axial length and lightweight can be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a vertical sectional view showing the constitution of an emobodiment of the present invention; 
           [0015]      FIGS. 2A and 2B  show structures of an armature and a rotating field magnet in the embodiment shown in  FIG. 1 ,  FIG. 2A  is a partially vertical sectional view, and  FIG. 2B  is a side view; 
           [0016]      FIG. 3  is an exploded perspective view showing a structure of the embodiment shown in  FIG. 1 ; and 
           [0017]      FIG. 4  is an explanatory view showing the flow of cooling air in the embodiment shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    An embodiment of the present invention will now be described with reference to the attached drawings. 
       Embodiment 1 
       [0019]      FIG. 1  shows a vertical sectional structure of an emobodiment of the present invention.  FIG. 1  shows an engine E that is a drive source at the right side in the drawing (phantom line), and an emobodiment of the present invention is mounted to a drive shaft  100  extended in the left direction in the drawing from the engine E. 
         [0020]    Namely, a cylindrical coupling pipe  101  with a key groove is fitted on the drive shaft  100  of the engine E. A pair of field magnets  120 - 1  and  120 - 2  disposed to sandwich an armature  110  from both sides in an axial direction are axially positioned and fixed onto a full-flighted outer periphery of the coupling pipe  101  by a pair of large-sized nuts  102   a  and  102   b  and a spacer  103 . 
         [0021]    A key groove of the coupling pipe  101  is positioned with respect to the drive shaft  100  of the engine E, a key is driven into the key groove to perform fixation in the rotational direction, and the coupling pipe  101  is fixed to an end surface of the drive shaft  100  by an end plate  104  and a fastening bolt  105 . 
         [0022]    The armature  110  is stationary, and is fixed to substantially a center in the axial direction in a housing  130 . In a rotating field magnet  120 , permanent magnets  122  formed by a rare earth material are bonded to surfaces, which are opposed to the armature  110 , of field magnet disks  121  fixed to the coupling pipe  101 , and cooling fans  123  are disposed on a rear surface of the field magnet disks  121 . 
         [0023]    A holding ring  124 , which holds an outer peripheral surface of the permanent magnet  122 , is fitted on an outer peripheral surface of the field magnet disk  121 , and the holding ring  124  holds the permanent magnet  122  against a centrifugal force. The cooling fan  123  is a centrifugal (radial) fan in which blades  123   a  formed by plate-shaped bent members are mounted to an independent flat disk, and is mounted to an opposite side from the magnet of the field magnet disk. 
         [0024]    In order to hold the armature  110  and contain a pair of rotating field  120  inside, a housing  130  constituted of an engine side cover  131 , an outer cover  132  with an exhaust port, and an end cover  133  with an intake port is provided. The housing  130  is mounted by the engine side cover  131  being fixed to a casing of the engine E. 
         [0025]    Then, the armature  110  is held at a predetermined position on the coupling pipe  101  by a through-bolt  134   a , a nut  134   b  and a collar  135 , and an internal space for containing the armature  110  and the rotating field  120  is formed in the housing  130 . 
         [0026]    This internal space communicates with an outside by the intake port with a wire net provided in a center in the radial direction of the end cover  133 , and the outer cover  132  with the exhaust port (not shown), and is constituted so that ventilation for dissipating the heat generated mainly from the armature  110  to the outside by the operation of the cooling fan  123  is performed. 
         [0027]      FIGS. 2A and 2B  are explanatory views showing the constitution of each of the parts around the armature  110  and the rotating field  120  shown in  FIG. 1 .  FIG. 2B  shows the state of the armature  110  and the rotating field  120  seen from the same direction from  FIG. 1 . As shown in  FIG. 2B , the cooling fan  123  is provided at an outer side in the radial direction of the field magnet disk  121  in the rotating field magnet  120 - 2  at the right side in the drawing, while the cooling fan  123  is provided at an inner side in the radial direction of the field magnet disk  121  in the rotating field magnet  120 - 1  at the left side in the drawing with the armature  110  therebetween. 
         [0028]    Thereby, the cooling fan  123  at the side opposite to the engine changes the flow of the cooling air which the cooling fan  123  takes in from the intake port with the wire net provided at the center of the end cover  133  to the flow toward the outside in the radial direction to take the air inside the housing  130 , and the cooling fan  123  at the side of the engine creates a draft which flows toward the outer side in the radial direction in the housing  130  and flows to the outside along the both surfaces of the armature  110 . 
         [0029]      FIG. 2A  shows the state of  FIG. 2B  seen from the left side direction of  FIG. 2B , the upper half of  FIG. 2A  shows the armature  110 , and the lower half of it shows a rear surface of the rotating field  120 .  FIG. 2A  shows a coil constitution of the armature, and  18  coils are disposed in the entire periphery. 
         [0030]    In the armature  110  drawn in the upper part of  FIG. 2A , nine coreless sector coils  112  formed in a plane shape are disposed in the range of 180 degrees in the surface of a support plate  111  of the armature  110 . This is adapted to the fact that the field magnet not shown is constituted of 18 poles. In order to fix the coils  112  to the support plate  111 , the coils  112  are molded with the support plate  111  with a resin, for example. 
         [0031]    Next, the blades  123   a  and ventilation holes  123   b  of the cooling fan  123  are provided on the rear surface of the rotating field  120  drawn in the lower half of  FIG. 2A , and ventilation passages to the direction orthogonal to the plane of the rotating field  120  are formed. 
         [0032]      FIG. 3  shows an exploded view of the armature  110  and the rotating field  120  which are main components of the embodiment 1, and the engine side cover  131 , the outer cover  132  with the exhaust port and the end cover  133  which constitute the housing  130  that contains these components, and the drive shaft and the components around the drive shaft are omitted in the drawing. 
         [0033]    As is understood from the relation in the drawing of the armature and the two rotating field magnets  120 - 1  and  120 - 2 , the rotating field magnets  120 - 1  and  120 - 2  are symmetrically disposed on the drive shaft (not shown) with the armature  110  therebetween, and magnetically, the magnetic fields by the two rotating field magnets  120 - 1  and  120 - 2  are similarly caused to act on the armature  110 . 
         [0034]    Heat generated by the electromagnetic action at the time of this electric generation is released outside from an exhaust port  132 A (shown by the phantom line) formed by a part of the outer cover  132  being opened by cooling air as a radial flow which is formed by the cooling fan  123  provided at the rear surface of the rotating field  120 . The exhaust port  132 A is formed as two openings separated by the armature  110 , and is constituted to exhaust heat from both surfaces of the armature  110 . 
         [0035]      FIG. 4  is a view showing the flow of cooling air inside and outside the housing. As shown by the lines with arrows, the cooling air taken in from the intake port with the wire net provided at the central portion of the end cover  133  first flows toward the end portion of the drive shaft  100 , then is changed to the flow outward in the radial direction by the cooling fan  123  at the side opposite to the engine, and becomes the flow in the axial direction through the ventilation holes  123   b.    
         [0036]    This flow passes along each of the surfaces at the side opposite to the engine and at the side of the engine of the armature  110  and goes outward in the radial direction, and is divided into the flow which deprives both the surfaces of the armature  110  of heat and reaches the exhaust port  132 A, and the flow which further passes through the ventilation holes  123   b  of the rotating field magnet  120 - 1  at the side of the engine and along the inner wall of the cover  131  at the side of the engine, and goes outward in the radial direction to reach the exhaust port  132 A. This flow also cools the surfaces of the two rotating field magnets  120 - 1  and  120 - 2  and reaches the exhaust port  132 A. 
         [0037]    Thereby, the heat generated by the armature  110  and the rotating field magnets  120 - 1  and  120 - 2  is effectively discharged outside. 
       (Concrete Constitution) 
       [0038]    In the above described embodiment, the magnet is explained generally as the permanent magnet, but in concrete, it is suitable to use, for example, a neodymium-iron-boron rare earth magnet in consideration of the temperature-demagnetizing factor characteristics and the like. 
         [0039]    As for the constitution of the ventilation passage, especially the exhaust port, the example in which one exhaust port is provided in the outer cover is shown, but the exhaust ports may be provided at a plurality of spots. 
         [0040]    Further, in the above described embodiment, the example of the field magnet constituted of 18 poles is shown, but the number of poles with the maximum efficiency is suitably selected in accordance with the number of phases, the rotational frequency and the like of the generator.