Patent Publication Number: US-2013249337-A1

Title: Hydrodynamic bearing module and spindle motor having the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2012-0029350, filed on Mar. 22, 2013, entitled “Hydrodynamic Bearing Module and Spindle Motor Having the Same”, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a hydrodynamic bearing module and a spindle motor having the same. 
     2. Description of the Related Art 
     Generally, in a spindle motor used as a driving device of a recording disk such as a hard disk, or the like, a hydrodynamic bearing using dynamic pressure generated by a lubricating fluid such as oil, or the like, stored between a rotor part and a stator part at the time of rotation of the motor has been widely used. 
     More specifically, since the spindle motor including the hydrodynamic bearing that maintains shaft rigidity of a shaft only by movable pressure of lubricating oil by centrifugal force is based on centrifugal force, metal friction does not occur and a sense of stability increases as a rotation speed increases, such that the generation of noise and vibration is reduced and a rotating object can be more readily rotated at a high speed than a motor having a ball bearing. As a result, the spindle motor has been mainly applied to a high end optical disk device, a magnetic disk device, or the like. 
     The following Prior Art Document (Patent Document) relates to a spindle motor having a hydrodynamic bearing. However, in the spindle motor according to the prior art including the prior art document, when a hub is press-fitted into a shaft, a cover is deformed as much as a distance between the cover and the shaft, such that a coupling part such as a welding part or the like may be damaged, or a micro-crack, leakage of oil, or the like may occur. 
     PRIOR ART DOCUMENT  
     Patent Document 
     (Patent Document 1) U.S. Pat. No. 6,534,890 B 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a hydrodynamic bearing module capable of preventing leakage of oil by decreasing an interval between a shaft and a cover by a thickness of a protrusion member to thereby decrease volume change at the time of movement of the shaft in an axial direction according to external impact and preventing a micro-crack and oil leakage caused by deformation of the center part by a coupling part of the cover and a sleeve since the center part of the cover facing the shaft is deformed by the interval between the shaft and the cover and the deformed displacement is decreased by the thickness of the protrusion member in the case in which the shaft is press-fitted into a hub due to an outer peripheral surface of the cover which is secured to the sleeve, and a spindle motor having the same. 
     According to a preferred embodiment of the present invention, there is provided a hydrodynamic bearing module, including: a shaft; a sleeve having the shaft rotatably and insertedly coupled thereinto and forming a micro-interval together with the shaft; oil injected in order to form a hydrodynamic bearing part between the shaft and the sleeve; a cover coupled to a lower end portion of the sleeve and sealing the oil; and a protrusion member positioned between the shaft and the cover in an axial direction of the shaft and selectively mounted on the cover or the shaft. 
     The protrusion member may be coupled to a lower end portion of the shaft so as to face the cover. 
     The protrusion member may be coupled to one surface of the cover so as to face the shaft. 
     According to another preferred embodiment of the present invention, there is provided a hydrodynamic bearing module, including: a shaft; a sleeve having the shaft rotatably and insertedly coupled thereinto and forming a micro-interval together with the shaft; oil injected in order to form a hydrodynamic bearing part between the shaft and the sleeve; and a cover coupled to a lower end portion of the sleeve and sealing the oil, wherein the cover may face the shaft in an axial direction of the shaft so as to form a protrusion part. 
     The protrusion part may be formed by press processing of the cover. 
     According to another preferred embodiment of the present invention, there is provided a spindle motor, including: a rotor including a shaft, a hub, and a magnet; a stator including a sleeve rotatably supporting the shaft, a base having the sleeve coupled thereto, an armature coupled to the base so as to face the magnet, and a cover coupled to a lower portion of the sleeve; a hydrodynamic bearing part formed between the rotor and the stator by being filled with oil, which is working fluid; and a protrusion member positioned between the shaft and the cover in an axial direction of the shaft and selectively mounted on the cover or the shaft. 
     The protrusion member may be coupled to a lower end portion of the shaft so as to face the cover. 
     The protrusion member may be coupled to one surface of the cover so as to face the shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a partial cross-sectional view schematically showing a hydrodynamic bearing module according to a first preferred embodiment of the present invention; 
         FIG. 2  is a partial cross-sectional view schematically showing a hydrodynamic bearing module according to a second preferred embodiment of the present invention; 
         FIG. 3  is a partial cross-sectional view schematically showing a hydrodynamic bearing module according to a third preferred embodiment of the present invention; and 
         FIG. 4  is a cross-sectional view schematically showing a spindle motor having the hydrodynamic bearing module according to a preferred embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The objects, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first”, “second”, “one side”, “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted. 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
       FIG. 1  is a partial cross-sectional view schematically showing a hydrodynamic bearing module according to a first preferred embodiment of the present invention. As shown in  FIG. 1 , the hydrodynamic bearing module  10  includes a shaft  11 , a sleeve  12 , a cover  13 , and a protrusion member  14 , wherein the protrusion member  14  is coupled to a lower end portion of the shaft  11  facing the cover in an axial direction of the shaft. 
     More specifically, the shaft  11  is insertedly coupled to the sleeve  12  so as to form a micro-interval between the shaft  11  and the sleeve  12 , and the sleeve  12  rotatably supports the shaft  11 . In addition, oil is injected into the micro-interval, such that a radial bearing part (not shown) which is a hydrodynamic bearing part is formed. Further, the radial bearing part may be formed on upper and lower portions of the sleeve. 
     In addition, an oil circulation hole  12   a  connecting upper and lower surfaces of the sleeve  12  to each other in order to circulate the oil which is injected to form the hydrodynamic bearing part in a shaft system may be formed in the axial direction of the shaft  11 . 
     In addition, the cover  13 , which is to seal the oil injected in order to form the hydrodynamic bearing part between the shaft and the sleeve, is coupled onto an inner peripheral surface of a lower end portion of the sleeve  12  in the axial direction of the shaft  11 . In addition, the cover and the sleeve may be coupled to each other by a method such as welding, bonding, or the like. 
     In addition, the protrusion member  14  is coupled to the lower end portion of the shaft  11  facing the cover  13  in the axial direction of the shaft as described above. 
     According to the configuration as described above, an interval between the shaft  11  and the cover  13  is decreased by a thickness of the protrusion member  14 . This may prevent leakage of oil by decreasing volume change at the time of movement of the shaft in an axial direction according to external impact. 
     In addition, since an outer peripheral surface of the cover is secured to the sleeve, in the case in which the shaft is press-fitted into a hub, the center part of the cover facing the shaft is deformed by an interval between the shaft and the cover and the deformed displacement is decreased by the thickness of the protrusion member  14 , such that a coupling part of the cover and the sleeve may prevent a micro-crack and oil leakage caused by deformation of the center part. 
       FIG. 2  is a partial cross-sectional view schematically showing a hydrodynamic bearing module according to a second preferred embodiment of the present invention. 
     As shown in  FIG. 2 , the hydrodynamic bearing module  20  according to the second preferred embodiment of the present invention is different only in a cover from the hydrodynamic bearing module  10  according to the first preferred embodiment of the present invention. That is, the hydrodynamic bearing module according to the second preferred embodiment of the present invention deforms a shape of the cover so as not to include a separate protrusion member. 
     More specifically, the hydrodynamic bearing module  20  includes a shaft  21 , a sleeve  22 , and a cover  23 , wherein the cover  23  faces the shaft  21  in the axial direction of the shaft so as to form a protrusion part  23   a.  In addition, the protrusion part  23   a  may be easily formed by press processing. 
     In addition, the shaft  21  is insertedly coupled to the sleeve  22  so as to form a micro-interval between the shaft  21  and the sleeve  22 , and the sleeve  22  rotatably supports the shaft  21 . In addition, oil is injected into the micro-interval, such that a radial bearing part (not shown) which is a hydrodynamic bearing part is formed. Further, the radial bearing part may be formed on upper and lower portions of the sleeve. 
     In addition, an oil circulation hole  22   a  connecting upper and lower surfaces of the sleeve  22  to each other in order to circulate the oil which is injected to form the hydrodynamic bearing in a shaft system may be formed in the axial direction of the shaft  21 . 
     In addition, the cover  23 , which is to seal the oil injected in order to form the hydrodynamic bearing part between the shaft  21  and the sleeve  22 , is coupled onto an inner peripheral surface of a lower end portion of the sleeve  22  in the axial direction of the shaft  21 . In addition, the cover and the sleeve may be coupled to each other by a method such as welding, bonding, or the like. 
     According to the configuration as described above, an interval between the shaft  21  and the cover  23  is decreased by a thickness of the protrusion part  23   a.  This may prevent leakage of oil by decreasing volume change at the time of movement of the shaft in an axial direction according to external impact, and since an outer peripheral surface of the cover is secured to the sleeve, in the case in which the shaft is press-fitted into a hub, the center part of the cover facing the shaft is deformed by an interval between the shaft and the cover and the deformed displacement is decreased by the protrusion part  23   a,  such that a coupling part of the cover and the sleeve may prevent a micro-crack and oil leakage caused by deformation of the center part. 
       FIG. 3  is a partial cross-sectional view schematically showing a hydrodynamic bearing module according to a third preferred embodiment of the present invention. 
     As shown in  FIG. 3 , the hydrodynamic bearing module  30  according to the third preferred embodiment of the present invention is different only in a coupling target of the protrusion member from the hydrodynamic bearing module  10  according to the first preferred embodiment of the present invention. That is, the hydrodynamic bearing module  30  according to the third preferred embodiment of the present invention couples the protrusion member to the cover. 
     More specifically, the hydrodynamic bearing module  30  includes a shaft  31 , a sleeve  32 , a cover  33 , and a protrusion member  34 , wherein the protrusion member  34  is coupled to a lower end portion of the shaft  31  facing the cover in an axial direction of the shaft. 
     More specifically, the shaft  31  is insertedly coupled to the sleeve  32  so as to form a micro-interval between the shaft  31  and the sleeve  32 , and the sleeve  32  rotatably supports the shaft  31 . In addition, oil is injected into the micro-interval, such that a radial bearing part (not shown) which is a hydrodynamic bearing part is formed. Further, the radial bearing part may be formed on upper and lower portions of the sleeve. 
     In addition, an oil circulation hole  32   a  connecting upper and lower surfaces of the sleeve  32  to each other in order to circulate the oil which is injected to form the hydrodynamic bearing part in a shaft system may be formed in the axial direction of the shaft  31 . 
     In addition, the cover  33 , which is to seal the oil injected in order to form the hydrodynamic bearing part between the shaft and the sleeve, is coupled onto an inner peripheral surface of a lower end portion of the sleeve  32  in the axial direction of the shaft  31 . In addition, the cover and the sleeve may be coupled to each other by a method such as welding, bonding, or the like. 
     In addition, the protrusion member  34  is coupled to one surface of the cover  33  facing the shaft  31  in the axial direction of the shaft as described above. 
     According to the configuration as described above, an interval between the shaft  31  and the cover  33  is decreased by a thickness of the protrusion member  34 . This may prevent leakage of oil by decreasing volume change at the time of movement of the shaft in an axial direction according to external impact. 
     In addition, since an outer peripheral surface of the cover  33  is secured to the sleeve, in the case in which the shaft is press-fitted into a hub, the center part of the cover facing the shaft is deformed by an interval between the shaft and the cover and the deformed displacement is decreased by the thickness of the protrusion member  34 , such that a coupling part of the cover and the sleeve may prevent a micro-crack and oil leakage caused by deformation of the center part. 
       FIG. 4  is a cross-sectional view schematically showing a spindle motor having the hydrodynamic bearing module according to a preferred embodiment of the present invention. 
     As shown in  FIG. 4 , the spindle motor  100  is configured to include a rotor including a shaft  110 , a hub  120 , a magnet  130 , and a thrust plate  140 ; a stator including a sleeve  150 , a sealing member  160 , a base  170 , an armature  180 , and a cover; and a hydrodynamic bearing part formed between the rotor and the stator by being filled with oil, which is working fluid. 
     More specifically, in the rotor, the shaft  110  includes the hub  120  fixedly coupled to an outer peripheral portion thereof. 
     In addition, the hub  120  includes a cylindrical part  121  fixed to the shaft  110 , a disk part  122  extended from the cylindrical part  121  in an outer diameter direction, a sidewall part  123  extended downwardly from an end portion of the disk part  122  in the outer diameter direction in an axial direction of the shaft, and a disk mounting part  124  extended from the sidewall part  123  in the outer diameter direction. 
     In addition, the shaft  110  includes the thrust plate  140  coupled to an upper portion thereof and the thrust plate  140  is mounted on the outer peripheral portion so as to be positioned at a lower portion of the hub in the axial direction of the shaft. 
     In addition, the sidewall part  123  includes an annular ring shaped magnet  130  mounted on an inner peripheral surface thereof so as to face the armature  180  including a core  181  and a coil  182 . 
     In addition, the disk mounting part  124 , which is formed in a circumferential direction of the hub, is mounted with a disk (not shown). 
     In addition, an outer peripheral surface of the shaft  110  is mounted with the thrust plate  140  positioned below the cylindrical part  121  of the hub  120  and facing an upper surface of the sleeve. The thrust plate  140  may be provided with a thrust dynamic pressure generation groove (not shown) for forming the thrust dynamic pressure bearing together with the sleeve  150 . 
     Next, in the stator, the sleeve  150  rotatably supports the shaft  110 . In addition, an upper portion of the sleeve  150  is coupled to the sealing member  160  for forming an oil sealing part together with the thrust plate  140 . 
     In addition, a dynamic pressure generation groove (not shown) is selectively formed at upper and lower portions of an inner peripheral surface of the sleeve  150  or upper and lower portions of an outer peripheral surface of the shaft  110  in order to form the radial bearing part. 
     Further, the sleeve  150  may have an oil circulation hole  142  formed therein in the axial direction of the shaft  110  so that upper and lower surfaces of the sleeve  150  are connected to each other in order to circulate the oil injected for forming the hydrodynamic bearing part in the shaft system. 
     In addition, the sleeve  150  is fixed to an inner peripheral surface of the base  170  by press-fitting, adhesion, or the like. In addition, the base  170  includes the armature  180  fixed to an outer peripheral portion thereof by press-fitting, adhesion, or the like, so as to face the magnet  130 , wherein the armature  180  includes the core  181  and the coil  182 . 
     Further, the base  170  is mounted with a pulling plate  171  so as to face the magnet  130  in the axial direction of the shaft, wherein the pulling plate  171  prevents floating of the rotor by attractive force of the magnet  130 . 
     Further, the cover  190  is coupled to an inner peripheral surface of a lower portion of the sleeve  150  so as to seal the oil injected in order to form the hydrodynamic bearing. In addition, a protrusion member  191  is coupled to one surface of the cover  190  facing the shaft in the axial direction of the shaft. 
     According to the configuration as described above, the spindle motor having the hydrodynamic bearing module according to the preferred embodiment of the present invention may prevent leakage of oil by decreasing an interval between a shaft and a cover by a thickness of a protrusion member to thereby decrease volume change at the time of movement of the shaft in an axial direction according to external impact and prevent a micro-crack and oil leakage caused by deformation of the center part by a coupling part of the cover and the sleeve since the center part of the cover facing the shaft is deformed by the interval between the shaft and the cover and the deformed displacement is decreased by the thickness of the protrusion member in the case in which the shaft is press-fitted into a hub due to an outer peripheral surface of the cover which is secured to the sleeve. 
     In addition, the spindle motor according to the above described embodiment of the present invention has the hydrodynamic bearing module according to the third embodiment of the present invention shown in  FIG. 3  and the present invention may be implemented as the spindle motor having the hydrodynamic bearing module according to the first and second embodiments. 
     According to the configuration as described above, the spindle motor according to the preferred embodiment of the present invention may include a fixed protrusion part that the thrust plate is inserted into a bush and the disk part facing the sleeve, improve robustness and stability by coupling to the fixed protrusion part, and form the disk part having a thin thickness. Therefore, in the spindle motor according to the present invention, a span length of the bearing may become longer than the thrust plate according to the prior art as much as the thickness decreased as compared to the spindle motor according to the prior art and stress may be distributed although the rotor is un-balanceablely rotated, thereby making it possible to implement uniform pressure distribution. 
     Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. 
     Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.