Abstract:
A bearing includes an axial hole and a plurality of first grooves. The first grooves are disposed formed on the inner wall of the bearing, and extends through the top surface and to the outer wall of the bearing. The lubricant oil originally hold in the bearing can be guided to flow around the whole bearing effectively.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 095111465 filed in Taiwan, Republic of China on Mar. 31, 2006, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The invention relates to a fan, a bearing and a sleeve thereof, and in particular, to a fan, a bearing and a sleeve thereof with reduced consumption and volatilization of lubrication fluid. 
         [0004]    2. Related Art 
         [0005]    Motors have been widely used in vehicles, fans, pumps and computer peripherals, such as printers and scanners, and the bearing structure of a motor directly influences the quality of the motor. In order to enhance the self-lubrication of the bearing and prevent impact, a bearing is usually adopted. The conventional bearing is made of a porous material, has a plurality of micro voids and contains lubrication oil. When the bearing is rotated, the bearing allows the lubrication oil to fill into a gap between a shaft and the bearing to achieve the function of lubrication according to the capillary action of the micro voids. 
         [0006]    Referring to  FIG. 1 , a conventional bearing  10  has an axial hole  101  for accommodating a shaft  11 . The bearing  10  is disposed in a sleeve  12  of a stator base. Because a top surface  102  of the bearing  10  is in direct contact with the outside, the lubrication oil volatilizes from the top surface  102  of the bearing  10 . In addition, the lubrication oil leaks from a gap between the bearing  10  and the shaft  11 , and a gap between the bearing  10  and the sleeve  12 . More particularly, when the bearing  10  is placed upended, such leakage become more serious that the lifetime of the bearing  10  is shortened, or the overall operation becomes rough due to insufficient lubrication oil and the resultant excessive frictional force between the bearing and the shaft  11  or the sleeve  12 . 
         [0007]    In order to solve this problem, as shown in  FIG. 2 , a baffle  13  is disposed on the top surface  102  of the bearing  10  to block the leaking path of the lubrication oil. However, the effect is limited because the lubrication oil may still leak to the outside through the gap between the bearing  10  and the shaft  11  and the gap between the bearing  10  and the sleeve  12 . 
         [0008]    In view of this, it is therefore an important subject of the invention to provide a bearing structure capable of effectively reducing the consumption and volatilization of lubrication fluid while providing a circulating lubrication loop to reduce the friction between the sleeve and the bearing, thus lengthening the lifetime of the bearing. 
       SUMMARY OF THE INVENTION 
       [0009]    In view of the foregoing, the invention is to provide a bearing structure capable of effectively reducing the lubrication fluid consumption and volatilization, providing a circulating lubrication loop to reduce the friction between a sleeve and a bearing, and thereby lengthening the lifetime of the bearing. 
         [0010]    To achieve the above, the invention discloses a bearing including an axial hole and a plurality of first grooves. The first grooves are formed on an inner surface of the axial hole and extend to a top surface of the bearing. 
         [0011]    To achieve the above, the invention also discloses a bearing structure, which is used in conjunction with a shaft and disposed in a sleeve. The bearing has an axial hole and a plurality of first grooves. The shaft passes through the axial hole. The first grooves are formed on a first wall of the bearing and extend to a top surface of the bearing. 
         [0012]    In addition, the invention further discloses a fan including an impeller, a stator structure and a rotor structure. The impeller has a hub and a plurality of blades mounted around a periphery of the hub. The stator structure has a magnetic element and a sleeve. The rotor structure is disposed corresponding to the stator structure and has a shaft and a bearing structure. The shaft is connected to the hub. The bearing is disposed in the sleeve. The bearing includes an axial hole and a plurality of first grooves. The shaft passes through the axial hole. The first grooves are formed on a first wall of the bearing and extend to the top surface of the bearing. 
         [0013]    As mentioned hereinabove, in the fan, the bearing according to the invention is used in conjunction with a shaft and a sleeve, and the shaft passes through the bearing, which is disposed in a chamber of the sleeve. The bearing is constituted by the axial hole, the first grooves, a plurality of chamfers and at least one cut side. Compared with the prior art, when the bearing is rotating, the first grooves, the plurality of chamfers and the cut side can mix the oil gas of the lubrication fluid sufficiently, to form a circulating lubrication loop and to generate oil gas hydrodynamic pressure on the top surface and the periphery of the bearing. Thus, the thrust functions in the axial and radial directions can be generated in order to prevent the bearing from rubbing against the top surface and the inner wall of the sleeve, and to reduce the up and down vibrations of the bearing and the pneumatic hammer phenomenon without using the conventional resisting washer. In addition, the invention forms the circulating loop of the lubrication fluid in the closed chamber. Thus, the consumption and volatilization of the lubrication fluid can be reduced, the lifetime of the bearing can be lengthened, and the manufacturing cost can be decreased because the machining precision of the bearing does not have to be very high. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein: 
           [0015]      FIG. 1  is a schematic illustration showing a conventional bearing; 
           [0016]      FIG. 2  is a schematic illustration showing another conventional bearing; 
           [0017]      FIG. 3  is a schematic illustration showing a bearing according to an embodiment of the invention; 
           [0018]      FIG. 4  is a schematic illustration showing another bearing according to the embodiment of the invention; 
           [0019]      FIG. 5  is a schematic illustration showing a bearing structure according to another embodiment of the invention; 
           [0020]      FIG. 6  is a schematic illustration showing a gap formed between a rotating bearing structure and a sleeve according to the embodiment of the invention; and 
           [0021]      FIG. 7  is a schematic illustration showing a fan according to the embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
         [0023]    Referring to  FIG. 3 , a bearing  1  according to the embodiment of the invention includes an axial hole  11  and a plurality of first grooves  12 . In this embodiment, the first grooves  12  are disposed on an inner surface  111  of the axial hole  11  and extend to a top surface  13  of the bearing  1 . The first grooves  12  extend in a direction parallel to the axial direction of the axial hole  11 , or extend helically (not shown) on the inner surface  111  of the axial hole  11 . 
         [0024]    A plurality of second grooves  15  can be formed on a periphery  14  of the bearing  1 . The second grooves  15  respectively correspond to the first grooves  12 , or are correspondingly formed between the first grooves  12  (not shown). When the bearing  1  is rotating, the lubrication fluid flows up to the top surface  13  of the bearing  1  along the first grooves  12 , and then flows down along the second grooves  15  to form a circulating lubrication loop. The circulating lubrication loop can lubricate the top surface  13  of the bearing  1  and prevent the lubrication fluid from over volatilizing and being over consumed on the top surface  13 . 
         [0025]      FIG. 4  is a schematic illustration showing another bearing  1 A according to the embodiment of the invention. Referring to  FIG. 4 , the difference between another bearing  1 A and the bearing  1  shown in  FIG. 3  is that the periphery  14  of the bearing  1 A is formed with the second grooves  15 , which do not correspond to the first grooves  12 . Instead, the first grooves  12  on the inner surface  111  of the axial hole  11  directly extend through the top surface  13  to the periphery  14  of the bearing  1 A. The bearing  1 A further includes chamfers  16  correspondingly formed at connection portions between the first grooves  12  and the top surface  13  of the bearing  1 A. In this embodiment, the shape of the chamfer  16  is not particularly limited, and the chamfer  16  may have a sloped surface shown in  FIG. 4  or an arc surface (not shown). The chamfers  16  aid the flow of lubrication fluid to the top surface  13 . 
         [0026]    The bearing  1 A further includes at least one cut side  17  formed on the periphery  14  of the bearing  1 A. The number of cut sides  17  is not particularly limited. If a plurality of cut sides  17  is formed, the cut sides  17  can be disposed symmetrically and have the same size. According to the structure designs of the first grooves  12 , the chamfers  16  and the cut sides  17 , the lubrication fluid can be smoothly guided to the top surface  13  and the cut side  17  when the bearing  1 A is rotating. Thus, the mixing of the oil gas of the lubrication fluid can be enhanced to prevent pneumatic hammer phenomena. 
         [0027]    As shown in  FIG. 5 , a bearing structure  2  of this embodiment is used in conjunction with a shaft  3  and is disposed in a sleeve  4 . The bearing structure  2  has at least one bearing having the same structure and function as that of the bearing  1  shown in  FIG. 3  or the bearing  1 A shown in  FIG. 4 . The bearing structure  2  can be applied to a rotor structure of a motor or a fan. Illustrations will be made by taking the bearing structure  2 , having two bearings  1 A, as an example. 
         [0028]    The inner wall  41  of the sleeve  4  has a positioning part  42 , through which the shaft  3  passes so that a chamber  43  is formed between the positioning part  42  and the top of the sleeve  4 , and the bearing  1 A is accommodated in the chamber  43 . In this embodiment, the positioning part  42  has a positioning element  421 , and the positioning part  42  can rest against the bearing  1 A through the positioning element  421 . In addition, the positioning part  42  and the sleeve  4  can also be formed as a monolithic piece. 
         [0029]    The top of the sleeve  4  is formed with an opening  44  sealed by a cover  45 . The shaft  3  passes through a through hole  451  at the middle of the cover  45 . The cover  45  and the sleeve  4  can also be formed as a monolithic piece. 
         [0030]    In addition, the bottom of the sleeve  4  of this embodiment is formed with an opening  46  sealed by a sealing element  47 . The sealing element  47  and the sleeve  4  can also be formed as a monolithic piece. 
         [0031]      FIG. 6  is a schematic illustration showing a gap formed between a rotating bearing structure and a sleeve according to the embodiment of the invention. Referring to  FIGS. 5 and 6 , when the shaft  3  rotates with the bearing structure  2 , the bearing  1 A of the bearing structure  2  releases the lubrication oil, which is mixed with the air sufficiently to form the oil gas O. The oil gas O is guided into the outer wall of the cut side  17  along the first grooves  12 . When the bearing structure  2  is rotating to gradually enlarge or reduce a gap S between the cut side  17  and the chamber  43 , the bearing structure  2  presses the oil gas O to mix the oil gas O evenly. Meanwhile, the oil gas O also flows to the top surface  13  of the bearing  1 A along the first groove  12  and the chamfer  16 , and flows to the cut side  17  on the periphery  14  of the bearing  1 A along the first groove  12 , then filling into the gap S. When the gap S is filled with the oil gas O, the excess oil gas O is gathered to the chamber  43  on the outer portion of the bearing  1 A, and the lubrication fluid O accumulates as the rotating speed of the rotor structure increases. The gathered oil gas O can fill the gap between the bearing  1 A and the shaft  3  and the first grooves via capillary action to form a circulating lubrication loop. 
         [0032]    The oil gas O of the circulating lubrication loop can flow to the top surface  13  of the bearing  1 A smoothly and can generate oil gas hydrodynamic pressure between the bearing  1 A and the cover  45 . Thus, the bearing structure  2  has an axial thrust function that prevents the bearing  1 A from rubbing against the cover  45  without the use of a resisting washer. In addition, the oil gas O in the circulating lubrication loop can generate hydrodynamic pressure between the bearing  1 A and the sleeve  4  according to the dimensional change of the gap S, and radial thrust can be generated. 
         [0033]    Referring to  FIG. 7 , a fan  5  includes an impeller  51 , a stator structure  52  and a rotor structure  53 . In this embodiment, the impeller  51  has a hub  511  and a plurality of blades  512 . The blades  512  are mounted around the periphery of the hub  511 . The stator structure  52  has a sleeve  521  and a magnetic element  522 . 
         [0034]    The rotor structure  53  is disposed corresponding to the stator structure  52  and has a shaft  531  and a bearing structure  532 . The shaft  531  is connected to the hub  511 . The bearing structure  532  is disposed in the sleeve  521 . The bearing structure  532  includes at least one bearing  5321 . 
         [0035]    Since the bearing  5321 , the bearing structure  532 , the shaft  531  and the sleeve  521  of this embodiment have the same structures and functions as those of the bearing  1  or  1 A, the bearing structure  2 , the shaft  3  and the sleeve  4  of the above-mentioned embodiment, detailed descriptions thereof will be omitted. 
         [0036]    In summary, a bearing is used in conjunction with a shaft and a sleeve. The shaft passes through the bearing, which is disposed in a chamber of the sleeve in the fan, the bearing structure and the bearing thereof according to the invention. The bearing has an axial hole, a plurality of first grooves (and second grooves), a plurality of chamfers and at least one cut side. Compared with the prior art, when the bearing is rotating, the invention utilizes the first grooves (and second grooves), the chamfers and the cut side to sufficiently mix the lubrication fluid oil gas to form a circulating lubrication loop. In addition, the gap between the bearing and the sleeve contains oil gas such that the oil gas hydrodynamic pressure is generated on the top surface and the periphery of the bearing. Thus, the thrust functions in the axial and radial directions can be generated in order to prevent the bearing from rubbing against the top surface and the inner wall of the sleeve, and to reduce up and down vibrations of the bearing and the pneumatic hammer phenomena without the use of a conventional resisting washer. In addition, the invention forms the circulating loop of the lubrication fluid in the closed chamber. Thus, the consumption and volatilization of the lubrication fluid can be reduced, the lifetime of the bearing can be lengthened, and the manufacturing cost can be decreased because the machining precision of the bearing does not have to be very high. 
         [0037]    Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.