Patent Publication Number: US-2010123361-A1

Title: Motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2008-0113634, filed with the Korean Intellectual Property Office on Nov. 14, 2008, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a motor. 
     2. Description of the Related Art 
     Currently, spindle motors are applied in various mobile products, such as mobile phones, PMPs, game players and MP3s. Accordingly, recent years have seen the reduction in the size of the spindle motor. 
     In response to a trend toward smaller spindle motors, a hydrodynamic bearing is widely used in the spindle motor. However, there are a number of difficulties in injecting a lubricant into the smaller spindle motor and implementing a sealing structure thereof. 
     Particularly, when injecting the lubricant into the spindle motor, injecting a certain amount of lubricant may cause a problem, significantly deteriorating the reliability of the spindle motor. If the amount of the lubricant injected into the spindle motor is insufficient, the life of the spindle motor can be shortened. Likewise, if the amount of the lubricant injected into the spindle motor is excessive, it may cause a breakdown of the spindle motor due to the leakage of lubricant. 
     Therefore, controlling a steady amount of the lubricant injected into the spindle motor has become one of the major tasks for improving the reliability of the spindle motor. 
     SUMMARY 
     The present invention provides a motor that can check the amount of a lubricant filled. 
     An aspect of the present invention provides a motor. The motor in accordance with an embodiment of the present invention includes: a rotor, a shaft, which is coupled to the rotor; a plate, which is coupled to an outer surface of the shaft; a bearing, which supports the shaft such that the shaft can rotate; a cap, which is coupled to the bearing such that an edge of the plate is covered; a lubricant, which is filled between the shaft and the bearing; and a sealing part, which is coupled to an inner side of the cap and in which the sealing part is made of a transparent material such that an amount of the lubricant filled can be checked. 
     An end of the sealing part can be tapered toward the shaft: A supporting protrusion can be formed on a lower surface of the sealing part, in which the supporting protrusion is protruded downward, and a flowing groove can be radially formed on a lower surface of the sealing part. 
     A supporting protrusion can be formed on a lower surface of the cap, in which the lower surface faces the plate and the supporting protrusion is protruded downward. A flowing groove can be radially formed on a lower surface of the cap, in which the lower surface faces the plate. 
     The bearing can be a hydrodynamic bearing, and a dynamic pressure groove can be formed on an inner circumference of the hydrodynamic bearing, in which the dynamic pressure groove is tilted from the axis of the shaft. Moreover, a through-hole can be formed on the bearing, in which the through-hole penetrates through the bearing vertically such that the lubricant flows. 
     Additional aspects and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating a spindle motor in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view illustrating a hydrodynamic bearing of a spindle motor in accordance with an embodiment of the present invention. 
         FIG. 3  is a bottom view illustrating a cap of a spindle motor in accordance with an embodiment of the present invention. 
         FIG. 4  is a magnified view illustrating a portion of a spindle motor in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional view illustrating a portion of a spindle motor in accordance with another embodiment of the present invention. 
         FIG. 6  is a bottom view illustrating a cap of a spindle motor in accordance with another embodiment of the present invention. 
         FIG. 7  is a cross-sectional view illustrating a portion of a spindle motor in accordance with yet another embodiment of the present invention. 
         FIG. 8  is a bottom view illustrating a cap of a spindle motor in accordance with yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The features and advantages of this invention will become apparent through the below drawings and description. 
     A spindle motor according to certain embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. Those components that are the same or are in correspondence are rendered the same reference numeral regardless of the figure number, and redundant descriptions are omitted. 
       FIG. 1  is a cross-sectional view illustrating a spindle motor  100  in accordance with an embodiment of the present invention. The spindle motor  100  in accordance with an embodiment of the present invention can include: a rotor  130 ; a shaft  120 , which is coupled to the rotor  130 ; a plate  122 , which is coupled to an outer circumference of the shaft  120 ; a bearing  150 , which supports the shaft  120  such that the shaft  120  can rotate; a cap  160 , which is coupled to the bearing  150  such that an edge of the plate  122  is covered; a lubricant, which is filled between the shaft  120  and the bearing  150 ; and a sealing part  170 , which is coupled to an inner side of the cap  160 . The sealing part  170  can be made of a transparent material such that the amount of the lubricant filled can be determined. Thus, the amount of the lubricant filled between the shaft  120  and the bearing  150  can be directly checked. 
     Coupled to the shaft  120  is the rotor  130 , which is a part to be rotated relatively with respect to a stator  140 . A hole can be formed in the middle of the rotor  130 , and the shaft  120  is inserted in the hole and thus coupled to the hole. The rotor  130  covers the stator  140 , and a part extended downward is formed on an outer circumference of the rotor  130 . Then, a magnet  132  is coupled to an inner circumference of the part extended downward. The magnet  132  faces an outer circumference of the stator  140  and can generate a driving force through an electromagnetic interaction with the stator  140 . 
     The rotor  130  is coupled to one side of the shaft  120 , and the other side of the shaft  120  is supported by the bearing  150 , which is a hydrodynamic bearing, such that the shaft  120  can rotate. An end of the shaft  120  is vertically supported by a thrust washer  112 . 
     The hydrodynamic bearing  150  supports the outer circumference of the shaft  120  such that the shaft  120  can rotate. An outer circumference of the bearing  150  is supported by a base  110 . A hole is formed in the middle of the base  110  such that the bearing  150  can be inserted in the hole, and an inner circumference of the stator  140  is coupled to an outer circumference of the hole. 
     The stator  140  is shaped like a ring surrounding the outer circumference of the bearing  150 , and a coil  142  is wound on the stator  140 . The outer circumference of the stator  140  faces a magnet  132 , and the driving force is provided to the rotor  130  through the electromagnetic interaction between the magnet  132  and the stator  140 . 
     The plate  122  is coupled to the outer circumference of the shaft  120  such that an upper side of the bearing  150  is covered. The cap  160  is coupled to the upper side of the bearing  150  such that the edge of the plate  122  is covered. The cap  160  covers the edge of the plate  122 , thereby preventing the shaft  120  from detaching. 
     Additionally, the cap  160  covers the upper side of the bearing  150  and the edge of the plate  122 , so that the lubricant filled between the shaft  120  and the bearing  150  can be prevented from leaking. It shall be evident that the cap  160  can be coupled to the base  110  in some cases such that the edge of the plate  122  is covered. 
       FIG. 2  is a cross-sectional view illustrating the hydrodynamic bearing  150  of the spindle motor  100  in accordance with an embodiment of the present invention. As illustrated in  FIG. 2 , a dynamic pressure groove  152  is formed on an inner circumference of the hydrodynamic bearing  150 , on which the dynamic pressure groove  152  is tilted from the axis of the shaft  120 . The dynamic pressure groove  152  can guide a flow of the lubricant filled between the shaft  120  and the bearing  150  in a desired direction when the shaft  120  rotates. Fluid pressure by the flow of such lubricants is called dynamic pressure, and the dynamic pressure groove  152  can provide the dynamic pressure of the lubricant more efficiently. 
     Additionally, a through-hole  154  penetrating through the bearing  150  vertically can be formed on the bearing  150  such that the lubricant can flow vertically through the bearing  150 . The through-hole  154  provides a path by which the lubricants can freely circulate through the bearing  150 , thereby reducing the pressure difference between the lubricants inside the spindle motor  100 . Likewise, the through-hole  154  can provide a path through which bobbles that may be present inside the lubricants can be discharged to the upper side of the hydrodynamic bearing  150 . 
       FIG. 3  is a bottom view illustrating the cap  160  of the spindle motor  100  in accordance with an embodiment of the present invention. As illustrated in  FIGS. 1 and 3 , the cap  160  can be shaped like a ring having a hollow part  167  formed in the middle thereof. A lower side of the cap  160  has a part extended downward  165  to be coupled to the upper side of the bearing  150 , and an upper side of the cap  160  is shaped like a circular disk extended inward to cover the edge of the plate  122 . 
     The sealing part  170  is made of a transparent material such that the amount of the lubricant filled between the bearing  150  and the shaft  120  can be checked. The sealing part  170  is coupled to an inner end of the cap  160 . The sealing part  170  can be made of a material that can transmit the light, for example, plastic resin. 
     The lubricant is filled between the bearing  150  and the shaft  120 , more particularly in a space surrounded by the bearing  150 , the shaft  120 , the plate  122  and the cap  160 . Since the sealing part  170  is made of a transparent material, the amount of the lubricant filled inside the spindle motor  100  can be seen with the naked eye. 
     Therefore, the sealing part  170  can control the amount of the lubricant filled inside the spindle motor  100  more precisely, and thus the leakage of the lubricant by an effect of excessive or insufficient lubricant in the spindle motor  100  or potential shortening of life-span of the spindle motor  100  can be solved. 
     Therefore, the amount of the lubricant filled inside the spindle motor  100  can be more directly controlled, improving the reliability of the spindle motor  100 . 
     A supporting protrusion  172 , which is protruded downward, is formed on a lower surface of the sealing part  170 . The supporting protrusion  172  can be formed in a shape of a ring in accordance with the shape of the cap  160 . The supporting protrusion  172  reduces a contact area between the plate  122  and the sealing part  170 , allowing the rotor  130  to rotate smoothly. Since the supporting protrusion  172  is formed on the lower surface of the sealing part  170  made of a plastic material, processing the cap  160  made of a hard metal material can be performed more easily. 
     A flowing groove  171  can be radially formed on the lower surface of the sealing part  170 . Each of the flowing grooves  171  can be radially extended and provide a path through which the lubricants and the bubbles can move along the circumference. 
     An end of the sealing part  170  is tapered toward the shaft  120 . Therefore, toward the shaft  120 , a lower surface of the end of the sealing part  170  can be increasingly separated from the plate  122 . 
       FIG. 4  is a magnified view illustrating a portion of the spindle motor  100  in accordance with an embodiment of the present invention. As illustrated in  FIG. 4 , the lubricant filled between the end of the sealing part  170  and the plate  122  forms a concave-shaped surface by the surface tension of the lubricant, thereby preventing the leakage of the lubricant by the self-sealing effect. Additionally, it can be determined whether a sufficient amount of lubricant is filled because the sealing part  170  is made of a transparent material, as described above. 
       FIG. 5  is a cross-sectional view illustrating a portion of a spindle motor in accordance with another embodiment of the present invention, and  FIG. 6  is a bottom view illustrating a cap  260  of a spindle motor in accordance with another embodiment of the present invention.  FIG. 5  will not be used here to describe the present embodiment, and as the same components illustrated in  FIG. 1  are not redundantly illustrated in  FIG. 5 , detailed description of the same structure described above will be omitted hereinafter. 
     As illustrated in  FIGS. 5 and 6 , a supporting protrusion  262 , which is protruded downward, is formed on a lower surface of the cap  260 , in which the lower surface of the cap faces the plate  122 . The supporting protrusion  262  can reduce a contact area between the plate  122  and the cap  260 , allowing the rotor  130  to rotate smoothly. Since the supporting protrusion  262  is a portion of the cap  260  made of a hard metal material, the wear caused by the friction with the plate  122  can be effectively controlled. 
     A fixing protrusion  263  protruded inward is formed on an end of the cap  260 . The fixing protrusion  263  is a part for structurally supporting a sealing part  270  such that the sealing part  270  can be easily coupled to the end of the cap  260 . 
     A flowing groove  261  can be radially formed from a lower surface of the sealing part  270  to the lower surface of the cap  260  facing the plate  122 . 
       FIG. 7  is a cross-sectional view illustrating a portion of a spindle motor in accordance with yet another embodiment of the present invention, and  FIG. 8  is a bottom view illustrating a cap  360  of a spindle motor in accordance with yet another embodiment of the present invention.  FIG. 7  will not be used here to describe the present embodiment, and as the same components illustrated in  FIG. 1  are not redundantly illustrated in  FIG. 7 , detailed description of the same structure described above will be omitted hereinafter. 
     As illustrated in  FIGS. 7 and 8 , if a sealing part  370  can be reliably coupled to an end of the cap  360 , all the sealing part  370  and the cap  360  can be formed in a simple structure, thereby saving the cost to manufacture the sealing part  370  and the cap  360 . Particularly, if the cap  360  is made of a hard metal material, the effectiveness of cost reduction will be maximized due to the simple structure. 
     While the spirit of the invention has been described in detail with reference to particular embodiments, the embodiments are for illustrative purposes only and shall not limit the invention. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention. As such, many embodiments other than those set forth above can be found in the appended claims.