Abstract:
The present invention relates to the fluid dynamic bearing motor. The fluid dynamic bearing motor having a ring-shaped housing having a coil joined to an edge thereof, a sleeve including a protruded part joined to a central part of the housing and a ring-shaped contact part formed as a single body with the protruded part, a ring-shaped hub having an inner perimeter joined to the contact part and having a magnet attached to an edge thereof, the magnet facing the coil, a stopper positioned between the housing and the contact part and joined to the hub such that the sleeve is not detached from the hub, a storing part formed as a space between the stopper and the sleeve and filled with fluid, for supplying and maintaining the fluid in a gap formed between the contact part and the inner perimeter of the hub, and a penetration hole formed from a center of the sleeve to an edge of the sleeve, the penetration hole being spatially separated from the storing part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2006-0017189 filed with the Korean Intellectual Property Office on Feb. 22, 2006, the disclosure of which is incorporated herein by reference in its entirety.  
       BACKGROUND  
       [0002]     1. Technical Field  
         [0003]     The present invention relates to the fluid dynamic bearing motor.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, the motor used for a precise machinery like a hard disk driver requires not only high-speed driving force but also precision control. The motor, which has this character, has to support the force of the rotation load and the rotation axis, a fluid dynamic bearing motor is a recent trend to support the force instead of a metal bearing or a ball bearing.  
         [0006]     The fluid dynamic bearing motor needs fluid for supporting rotary body, and the rotation axis of the fluid dynamic bearing motor must be positioned at the center of the sleeve for minimizing the frictional force.  
         [0007]     The fluid dynamic bearing motor minimizes the frictional force by forming a thin oil film between the rotary body and fixed body, and that makes pressure to support the rotary body. In order to form the pressure for forming the oil film, it is good to form a groove of herring bone shape in the rotary body or the fixed body.  
         [0008]     A dynamic pressure becomes high while the fluid dynamic bearing motor rotates at high speed. Therefore, in case of the low speed rotation, the possibility is high to rub between the rotary body and fixed body. Therefore, it is necessary to have the structure of generating a dynamic pressure in a low speed rotation. Moreover, wrap around and maintenance of the fluid are important to spread the dynamic pressure around the fluid dynamic bearing motor. And it need to reduce the size in correspondence to the miniaturization of an instrument.  
       SUMMARY  
       [0009]     The object of the present invention is to provide the fluid dynamic bearing motor which generates the dynamic pressure supporting the rotary body in the low speed rotation, and in which the wrap around maintenance and miniaturization of the fluid are possible.  
         [0010]     Additional aspects and advantages of the present invention will become apparent and more readily appreciated from the following description, including the appended drawings and claims, or may be learned by practice of the invention.  
         [0011]     One aspect of the present invention provides a fluid dynamic bearing motor having a ring-shaped housing having a coil joined to an edge thereof, a sleeve including a protruded part joined to a central part of the housing and a ring-shaped contact part formed as a single body with the protruded part, a ring-shaped hub having an inner perimeter joined to the contact part and having a magnet attached to an edge thereof, the magnet facing the coil, a stopper positioned between the housing and the contact part and joined to the hub such that the sleeve is not detached from the hub, a storing part formed as a space between the stopper and the sleeve and filled with fluid, for supplying and maintaining the fluid in a gap formed between the contact part and the inner perimeter of the hub, and a penetration hole formed from a center of the sleeve to an edge of the sleeve, the penetration hole being spatially separated from the storing part.  
         [0012]     It may be preferable that the longitudinal direction of the storing part is formed perpendicularly to a rotation axis of the hub. It may be preferable that the stopper is a circular flat board having a central part perforated. It may be preferable that a groove is formed in the inner perimeter of the hub or in the contact part. It may be preferable that a groove is formed in the inner perimeter of the hub or in the stopper in correspondence to the inner perimeter of the hub such that induces the dynamic pressure of the fluid and pumps the fluid to the direction of centrifugal force. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a cross-sectional view of a fluid dynamic bearing motor according to the first embodiment.  
         [0014]      FIG. 2  is a cross-sectional view showing the flow of a fluid of the fluid dynamic bearing motor according to the first embodiment of the present invention.  
         [0015]      FIG. 3  is a graph showing the extent of a dynamic pressure according to the dynamic part according to the first embodiment of the present invention.  
         [0016]      FIG. 4  is a cross-sectional view of a fluid dynamic bearing motor according to the second embodiment 
     
    
     DETAILED DESCRIPTION  
       [0017]     Hereinafter, an embodiment of the fluid dynamic bearing motor according to the present invention will be described in more detail with reference to the accompanying drawings.  
         [0018]     Embodiments of the fluid dynamic bearing motor according to the invention will be described below in more detail with reference to the accompanying drawings. In the description with reference to the accompanying drawings, those components are rendered the same reference number that are the same or are in correspondence regardless of the figure number, and redundant explanations are omitted. Also, the basic principles will first be described before discussing the preferred embodiments of the invention.  
         [0019]      FIG. 1  is a cross-sectional view of the fluid dynamic bearing motor according to the first embodiment. Referring to  FIG. 1 , housing  11 , sleeve  12 , protruded part  121 , contact part  122 , coil  13 , hub  14 , inner perimeter  141 , magnet  15 , stopper  16 , penetration hole  17 , storing part  18 , fluid  19 , rotation axis  100  are illustrated.  
         [0020]     Ring-shaped housing  11  plays the role of fixing the sleeve  12 . Coil  13  is coupled with the edge of the housing  11 , and the magnetic field is formed when the electric current is applied to coil  13 . This housing  11  can be coupled with different component for facilitation of manufacturing.  
         [0021]     The central part of the housing  11  is coupled with sleeve  12 . It is preferable that sleeve  12  is made of protruded part  121  and contact part  122 . It is general that protruded part  121  directly jointed to housing  11  is coupled with a hole or a groove formed in housing  11 . Protruded part  121  is formed with the contact part  122  as one body. Contact part  122  is the part interposing the fluid and jointing with hub inner perimeter  141 . Contact part  122  is bigger than the protruded part  121 , and a circular shape, and it maintains the distance from housing  11 .  
         [0022]     Hub  14  is a rotary body, and fluid  19  is injected between contact part  122  of sleeve  12  and hub inner perimeter  141 . It is preferable that hub  14  is symmetrically formed around rotation axis  100 . If hub  14  is deflected, vibration will be created. Magnet  15  is coupled with the edge of hub  14 , and it is preferable that magnet  15  is faced with coil  13 . The magnetic field of coil  13  makes mutual repulsion with the one of magnet  15  so that hub  14  smoothly rotates. Magnet  15  is arranged at the inner side comparing with coil  13  around rotary shaft  100  as shown in  FIG. 1 . But coil  13  may be positioned at the inner side comparing with magnet  15 .  
         [0023]     Stopper  16  is positioned between housing  11  and contact part  122 . Stopper  16  is coupled with inner perimeter  141  of hub  14 . Stopper  16  serves as a fixing element preventing that hub  14  leaves away from sleeve  12 . In the meantime, a space is formed between stopper  16  and sleeve  12 , fluid  19  is filled in the space. This space is storing part  18 . It is necessary that storing part  18  must have not only a space filling fluid but also more available space not to leave the fluid to outside. That is, as shown in the enlarged view of  FIG. 1 , fluid interface  181   a  perpendicularly faces with the gravity direction at normal times. But fluid interface  181   a  is inclined to the stopper  16  while rotating by centrifugal force. Therefore, as shown in  FIG. 1 , the stopper  16  is protruded to the direction of housing  11 . Moreover, it is preferable that storing part  18  which is near the housing  11  is declined to the direction of rotation axis  100 , This prevent flowing out fluid  19  as a result of centrifugal force generated while rotating of hub  14 .  
         [0024]     Penetration hole  17  is formed inside of contact part  122  of sleeve  12 . Hole entry  172  of penetration hole  17  is formed near rotation axis  100 , and hole exit  171  of penetration hole  17  is formed to the direction of the edge of contact part  122 . Particularly, it is preferable that hole exit  171  is formed in order not to be spatially connected to fluid inlet  182  of storing part  18 . This is the reason that the inside of penetration hole  17  do not form same dynamic pressure comparing with fluid inlet  182  by oil film. Hole entry  172  can be formed at the various location. In  FIG. 1 , penetration hole  17  is formed with the oblique direction. But penetration holes  17  can be formed various angle depending on the location of hole exit  172  and hole entry  172 .  
         [0025]     The  FIG. 2  is a cross-sectional view showing the flow of the fluid of the fluid dynamic bearing motor according to the first embodiment of the present invention.  FIG. 3  is a graph showing the extent of the dynamic according to the dynamic part according to the first embodiment. Referring to  FIG. 2  and  3 , ( a )˜( f ) is the location of the dynamic part, sleeve  12 , contact part  122 , hub  14 , inner perimeter  141 , stopper  16 , storing part  18 , fluid  19  are illustrated.  
         [0026]     Hub  14  rotates while the electric current is applied to coil  13 . At this time, the fluid is injected between contact part  122  of sleeve  12  and inner perimeter  141  of the hub  14 . A groove (not illustrated) is formed at inner perimeter  141  of contact part  122  or hub  14 . Therefore, the fluid dynamic is generated by the rotation of hub  14 . The groove may be formed so that the fluid circulates to the arrow direction of  FIG. 2 . And the form of the groove is various such as herring bone or spiral type.  
         [0027]     Explaining the extent of the dynamic part and the location of the dynamic part while rotating of hub  14 . firstly, the (a) of the  FIG. 2  does not create dynamic pressure because the a of the  FIG. 2  is the store part  18  and opened to the outside although the hub  14  rotates, but the partial fluid acts pressure to the (b) by the centrifugal force.  
         [0028]     The (b) spot is spatially seperated from (a) spot because the gap of contact part  141  of hub  14  is blocked tightly with stopper  16  by the oil film. Therefore, the (b) spot maintains the high dynamic pressure. This is because the centrifugal force works at the (a) spot and a groove is formed on the route of (a) and (b) in stopper  16  or hub  14 . In the meantime, the dynamic pressure of the (b) spot more rises by work of rotating of the fluid.  
         [0029]     With this kind of mode, the dynamic pressure of the (c) spot to the (f) spot t is higher than the (a) spot. This is because the dynamic part of the (a) spot to the (f) spot is shut tightly from the outside. In the meantime, the (g) spot is formed a dynamic pressure because it was also shut tightly from the out side. In the meantime, it is preferable that the groove is formed to the arrow direction of  FIG. 2  in order to smoothly circulate.  
         [0030]     In this kind of system, the centrifugal force strongly works, and the dynamic pressure formed at the groove is increasing. Sleeve  12  supports hub  14  with stable, because the spots( from the (a) spot to the (f) spot) where the dynamic pressure must be formed is higher that the (a) spot.  
         [0031]      FIG. 4  is a cross-sectional view of the fluid dynamic bearing motor according to the e second embodiment. Referring to  FIG. 4 , housing  41 , sleeve  42 , protruded part  421 , contact part  422 , coil  43 , hub  44 , hub inner perimeter  441 , magnet  45 , stopper  46 , penetration hole  47 , hole exit  471 , storing part  48 , fluid inlet  482 , fluid  49 , rotation axis  100  are illustrated.  
         [0032]      FIG. 4  shows that stopper  46  is formed by punching the center of circular flat board. That is possible because storing part  48  filled with fluid  49  is formed to the vertical direction from the rotation axis  100 . A part of contact part  422  of sleeve  42  or stopper  46  must be removed to form storing part  48 . As shown in the enlarged sectional view in the embodiment of  FIG. 4 , Storing part  48  filled with fluid  49  is formed by removing a part of contact part  422 . The gap is perpendicular from the rotation axis  100  toward longitudinal direction. In the meantime, fluid inlet  48  should not be spatially connected with hole exit  471 . The space which can store enough fluid  49  is attained by taking the form of this kind of storing part  48 . Stopper  46  is not always protruded form in direction of housing  41 .  
         [0033]     Although fluid interface  481  a is inclined while hub  44  rotates, stopper  46  prevents outward flowing of fluid  49  like the enlarged sectional view of  FIG. 4 . Furthermore, the form of this storing part  48  increases the dynamic pressure by directing the pressure of fluid  49  to hole exit  471  while hub  44  rotates.  
         [0034]     The form of the housing can be changed as the vertical length of stopper  46  is shortened. And the whole thickness of the bearing is shortened like the embodiment of  FIG. 1 . Moreover, it is not necessary to incline the form of storing part  48 , consequently the diameter of the protruded part  421  of the sleeve  42  is attained, and the coherence with the housing  42  increases at the same time.  
         [0035]      FIG. 5   a  is the groove of a herring bone type according to the third embodiment of the present invention.  FIG. 5   b  is a groove of a spiral type according to the fourth embodiment.  
         [0036]     It is preferable that grooves ( 50   a ,  50   b ) of  FIG. 5   b  and  5   a  may be formed in the contact surface of stoppers ( 16 ,  46 ) or hubs ( 14 ,  44 ) of the first and the second embodiment.  FIG. 5   a  is general groove  50   a  of herring bone type, and the  FIG. 5   b  is general groove  50   b  of spiral bone type. The grooves ( 50   a ,  50   b ) may be formed to pump the oil toward the direction of the centrifugal force. This kind of the pumping direction increases the dynamic pressure of the whole bearing. In order to determine the pumping direction of the oil, The grooves ( 50   a ,  50   b ) must be formed according to the rotational direction of hubs ( 14 ,  44 ). The grooves ( 50   a ,  50   b ) can have various forms including the herring bone type of the  FIG. 5   a  and the spiral type of the  FIG. 5   b.    
         [0037]     In the meantime, another groove can be formed at the part (like one side of the contact part of the hubs ( 14 ,  44 ) and sleeves ( 12 ,  42 ) generating the dynamic pressure  
         [0038]     As described in the above, the penetration hole of the fluid dynamic motor according to the preferred embodiment is formed on the space separated from the storing part, and this increases the dynamic pressure of the fluid dynamic bearing motor. The retention of the fluid gets better by changing the forming location of the storing part. In addition, the deformation of a stopper is possible and it reduces the size of the whole fluid dynamic bearing motor.  
         [0039]     While the above description has pointed out novel features of the invention as applied to various embodiments, the skilled person will understand that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made without departing from the scope of the invention. Therefore, the scope of the invention is defined by the appended claims rather than by the foregoing description. All variations coming within the meaning and range of equivalency of the claims are embraced within their scope