Abstract:
The invention enhances a joined portion between a bearing holder and a stator core in a blower. In the blower including a stator core attached to the outer circumference of a bearing holder, a setscrew for impeding the stator core from being pulled out is interposed between the bearing holder and the stator core. The setscrew is used for fixing in place of adhesives which is used in conventional art, ensuring the joining between the bearing holder and the stator core as well as facilitating the disassembling work.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improved blower for use in a variety of OA (office automation) appliances. 
     2. Description of the Related Art 
     Each OA appliance houses many electronic circuits within its housing, so that heat generated by electronic parts constituting those electronic circuits is hard to be discharged. Because of this, there is a fear that some of the electronic parts are broken or deteriorated. Particularly in view of a recent trend towards downsizing of the OA appliance, in which the appliance is simply reduced in size despite an absence of reduction in quantity of the generated heat so much, countermeasures against the heat have come to an important technical object. Then troubles that would be caused by heat generated inside are prevented by forming a ventilation hole on a side wall of the appliance and mounting a blower around the hole to discharge internal heat to the outside of the appliance. 
     An example of the blower that has been frequently used will now be described with reference to a half-sectional view in FIG.  5 . Reference symbol  1  denotes a casing that is cylindrical and functions as a wind tunnel. A housing  2  is formed integrally with this casing  1  at the center. A bearing holder  3  is formed in the housing&#39;s central portion. Outer races of bearings  4  and  5  are supported inside the bearing holder  3  and a shaft  6  is fitted and inserted to inner races of the bearings  4  and  5 . A ring  7  is mounted at the lower end of the shaft  6  to thereby prevent the shaft  6  from being pulled out and to position the shaft  6  in the axial direction. A spring  8  is interposed between the bearings  4  and  5  in such a state where it is compressed to give the bearings  4  and  5  a force pulling them apart. 
     Reference symbol  9  denotes an impeller made of synthetic resins. This impeller  9  comprises a body  10  having in section a shape of letter L and blades  11  formed around the outer circumference of the body  10 , which are integrally formed. When forming the impeller  9 , a cup-shaped motor yoke  12  is placed inside the body  10 , a zinc die-cast-made bush  13  attached to the shaft  6  is further put in the center of the motor yoke  12 , and these are then integrated. The motor yoke  12  has a hole  12   a  with which a convex portion  10   a  of the body  10  is engaged. A ring-shaped magnet  14  is attached to the inner circumferential portion of the motor yoke  12 . The shaft  6 , the motor yoke  12 , the impeller  9  and the magnet  14  together constitute a rotary part. 
     A stator core  16  around which a stator coil  15  is wound is arranged on the outside of the bearing holder  3  and the stator core  16  is fixed to the bearing holder  3  with adhesives to form a stationary part. A printed circuit board  17  on which electronic circuits composed of electric parts are installed as a brushless motor is mounted on a lower portion of the stator core  16 . The electronic circuits incorporated into this printed circuit board  17  control electric current for rotating the rotary part relative to the stationary part. A pin-shaped connecting terminal  18  is projected downward from the stator core  16  to pierce through a part of the printed circuit board  17 , thereby electrically connecting the stator coil  15  to the circuits on the printed circuit board  17 . 
     The thus-constructed blower is used when mounted through the ventilation hole on the housing of the OA appliance. In the mounting work, the upper side of the blower in the drawing is directed to the outside of the housing of the OA appliance with the shaft  6  being directed in the horizontal direction. When a predetermined voltage is applied to a control circuit on the printed circuit board  17  under this state, the electric current controlled by the control circuit is caused to flow through the stator coil  15  so that the rotary part is rotated by a magnetic interference action between the magnetic flux generated in the stator core  16  and the magnetic flux generated by the magnet  14 . The impeller  9  is rotated so that the air in the lower part of the housing in the drawing is sucked and is discharged toward the outside in the upper part in the drawing. With this air flow operation, the interior of the housing is cooled. 
     The blower formed as the above structure has no problem when used for cooling OA appliances. However, considering this structure from the view point of preservation of environment in the future, a portion where different kinds of materials are joined should be formed in such a manner that it can be easily disassembled upon disposal. The above-described structure does not meet this requirement because the bearing holder and the stator core are fixed to each other with adhesives, making disassembling work difficult. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above, and an object of the present invention is therefore to provide a blower that is easy to be disassembled. 
     In order to attain the object above, according to a first aspect of the present invention, in a blower constructed by rotatably supporting a shaft with bearings arranged inside a bearing holder, rotatably fixing to the shaft a motor yoke, an impeller and a ring-shaped magnet to form a rotary part, arranging a stator core with a stator coil wound therearound in the inner circumferential portion of the magnet while providing a clearance which is supported by the outer circumferential portion of the bearing holder, it is characterized in that a setscrew for preventing the stator core from being pulled out is interposed between the bearing holder and the stator core. Incidentally, the “blower” referred to herein means an axial flow fan motor and a centrifugal fan motor, and the centrifugal fan motor further includes a cross-flow type and motor impellized type. 
     Also, according to a second aspect of the present invention, the blower in the first aspect of the invention is characterized in that the head of the setscrew is slotted. 
     Furthermore, according to a third aspect of the invention, the blower in the first aspect of the invention is characterized in that a hexagonal hole is formed in the head of the setscrew. 
     Furthermore, according to a fourth aspect of the present invention, the blower in the first aspect of the invention is characterized in that the setscrew is formed from a tapping screw. 
     Furthermore, according to a fifth aspect of the present invention, the blower in the first aspect of the invention is characterized in that one sheet of the stator core has a thickness of 0.35 mm to 0.5 mm, and in that the pitch of the setscrew coincides with the thickness of the stator core per sheet. 
     With the structure according to each aspect of the present invention, the stator core can be readily separated from the bearing holder by turning the setscrew and loosening the engagement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a half-sectional view of the blower according to an embodiment of the present invention, with a half thereof shown in section; 
     FIG. 2 is a half-sectional view showing only the casing and the bearing holder in FIG. 1; 
     FIG. 3 is a plan view showing the bearing holder in FIG. 1; 
     FIG. 4 is a plan view showing a stator core in FIG. 1; 
     FIG. 5 is a half sectional view of the conventional blower with a half thereof shown in section; 
     FIG. 6 is a frontal view separately showing the impeller that has a different structure; 
     FIG. 7 is a diagram showing the half-sectional view and the side elevational view of a portion taken along the line O-A in FIG. 6; and 
     FIG. 8 is a longitudinal sectional view showing an embodiment in which the impeller shown in FIG. 6 is used. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will now be described. In FIG. 1, reference symbol  1  denotes a casing that is cylindrical and functions as a wind tunnel. A housing  2  is formed integrally with this casing  1  at the center. A bearing holder  3  is formed in the housing&#39;s central portion. Outer races of bearings  4  and  5  are supported inside the bearing holder  3  and a shaft  6  is fitted and inserted to inner races of the bearings  4  and  5 . A ring  7  is mounted at the lower end of the shaft  6  to thereby prevent the shaft  6  from being pulled out and to position the shaft  6  in the axial direction. A spring  8  is interposed between the bearings  4  and  5  in such a state where it is compressed to give the bearings  4  and  5  a force pulling them apart. 
     Reference symbol  9  denotes an impeller made of synthetic resins. This impeller  9  comprises a body  10  having in section a shape of letter L and blades  11  formed around the outer circumference of the body  10 , which are integrally formed. When forming the impeller  9 , a cup-shaped motor yoke  12  is placed inside the body  10 , a zinc die-cast-made bush  13  attached to the shaft  6  is further put in the center of the motor yoke  12 , and these are then integrated. The motor yoke  12  has a hole  12   a  with which a convex portion  10   a  of the body  10  is engaged. A ring-shaped magnet  14  is attached to the inner circumferential portion of the motor yoke  12 . The shaft  6 , the motor yoke  12 , the impeller  9  and the magnet  14  together constitute a rotary part. 
     A stator core  16  around which a stator coil  15  wound is arranged on the outside of the bearing holder  3  and the stator core  16  is fixed to the bearing holder  3  with a setscrew  19  to form a stationary part. A printed circuit board  17  on which electronic circuits composed of electric parts are installed as a brushless motor is mounted on a lower portion of the stator core  16 . The electronic circuits incorporated into this printed circuit board  17  control electric current for rotating the rotary part relative to the stationary part. A pin-shaped connecting terminal  18  is projected downward from the stator core  16  to pierce through a part of the printed circuit board  17 , thereby electrically connecting the stator coil  15  to the circuits on the printed circuit board  17  as well as supporting the printed circuit board  17 . 
     FIG. 2 shows the casing  1  separately from other components shown in FIG.  1 . As shown in FIG. 2, a groove  3   a  is formed on the outer circumferential portion of the bearing holder  3  from its top end to a certain depth. The plan view of this groove  3   a  is a semicircle as shown in FIG. 3. A groove  16   a  on the stator core  16  side which is opposed to this groove  3   a  is also semicircular as shown in FIG.  4 . The setscrew  19  shown in FIG. 1 is interposed between the groove  3   a  and the groove  16   a  from above in FIG.  1 . 
     If the head of the setscrew  19  is slotted, a normal flathead screwdriver can be used to screw the setscrew  19 , making it easily to interpose the setscrew between the grooves  3   a  and  16   a . Formation of a hexagonal hole in the head of the setscrew, instead of slotting the head, allows to use an Allen wrench that is bent to form a shape of letter L. If the setscrew  19  is formed not from a normal machine screw but from a tapping screw, the setscrew  19  may be prevented from falling out after interposed. In any of those cases, one sheet of the stator core  16  has a thickness of 0.35 mm to 0.5 mm and the pitch of the set screw coincides with the thickness of the stator core per sheet. This brings the thread of the setscrew  19  into an overlapped portion of the stator core  16 , which also helps in preventing the setscrew from falling out. 
     The actual manufacture of the blower will be described. For conveniences in the manufacture, the radius of the groove  16   a  formed in the stator core  16  does not vary over its length from the uppermost portion down to the lowermost portion. On the other hand, the groove  3   a  of the bearing holder  3  is formed into a tapered shape by utilizing draft upon aluminum die-casting. With this pointed groove  3   a , the setscrew  19  is screwed gradually increasing the degree of the engagement, so that the bearing holder and the stator core are more securely fixed with the screw. Incidentally, it may not be necessary to set the same radius in both of the groove  3   a  and the groove  16   a.    
     When this axial flow fan motor is broken or to be disposed of, the stator core  16  is readily separated from the bearing holder  3  by loosening the engagement and removing the setscrew  19 . Therefore, this facilitates separation according to type of materials. 
     In an example, the radius of the groove  16   a  formed in the stator core  16  is set to 1.5 mm, and the radius of the groove  3   a  formed in the bearing holder  3   a  is set to the same value. A hexagonally-holed setscrew of M 3  (P=0.5) having a length of 10 mm is used as the setscrew, and is screwed in by about 6 kg-cm. In this condition, a shock of 1.000 G is applied at 5 times in total to the setscrew in a direction along which the screw is to be pulled out. Loosening of the engagement is not observed. 
     According to the embodiment described above, one groove is formed in each of the stator core  16  and the bearing holder  3 , i.e., the groove  16   a  for the stator core and the groove  3   a  for the bearing holder, to interpose one setscrew between the groove  16   a  and the groove  3   a . If several setscrews are used, the bearing holder and the stator core can be more securely fixed to each other. Instead of simply inserting the setscrew, the setscrew may be coated with an agent upon insertion for preventing the setscrew from being pulled out so as to enhance the effect of preventing pulling out of the screw. 
     The present invention may also be applied to a blower that uses an impeller having the structure different from the one described above. An example thereof will be described with reference to FIGS. 6 and 7. FIG. 6 shows the entirety of an impeller  9 A and FIG.7 is a half-sectional view showing a part of the impeller  9 A taken along the line O-A in FIG.  6 . This impeller  9 A is provided with a number of arcuate blades  11 A mounted radially on its body  12 A. 
     FIG. 8 shows a blower using this impeller  9 A. The same reference symbols as in FIG. 1 are used to indicate the like portions. In such an impeller also, the setscrew  19  for preventing the stator core  16  from being pulled out is interposed between the bearing holder  3  and the stator core  16 . According to the present invention, the stator core  16  is securely fixed to the bearing holder  3  also in the blower having such structure. 
     The arrangement of the blower has been described above. Therefore, according to the first aspect of the invention, the fixing of the stator core to the bearing holder is carried out more securely and less costly. Also, the present invention facilitates the disassembling work at the time of disposal, which has been difficult because the stator core is fixed to the bearing holder with adhesives in conventional art. Therefore, separation according to type of materials becomes easy. 
     In this case, adoption of the structures according to the second to fifth aspects of the present invention makes the insertion and removal work of the setscrew easy, ensuring the fixing of the stator core to the bearing holder. In addition, the setscrew is readily removed upon disassembling.