Patent Publication Number: US-2006002640-A1

Title: Composite dynamic bearing assembly and manufacturing method thereof

Description:
BACKGROUND  
      The invention relates to a dynamic bearing, and in particular to a composite dynamic bearing assembly and manufacturing method thereof.  
      In recent years, most electronic devices and elements such as motors or fans are miniature so that the sizes of internal components thereof are reduced accordingly. Moreover, high rotational accuracy of the bearing is also required.  
      A dynamic bearing is a compact and highly accurate bearing device. As shown in  FIGS. 1A and 1B , the dynamic bearing comprises a bearing bracket  11  and a bearing  12 . The bearing bracket  11  comprises an internal space containing the bearing  12 . The bearing  12  is a cylinder with an external surface, contacting the bearing bracket  11  and an internal surface with a plurality of grooves  13  formed thereon. A lubricant is disposed in the grooves  13 . When the shaft (not shown) rotates, lubricant flows due to shearing stress and dynamic pressure is generated to support and lubricate the shaft.  
      When manufacturing a dynamic bearing, initially, a bearing is provided. The grooves are then formed on an inner surface of the bearing by engraving. Since minute marking of the grooves is necessary and requires precise measurements within a tiny hollow space, the procedure is difficult. Moreover, the grooves cannot be formed simultaneously with the bearing, thus an additional manufacturing step is required. Hence the cost of manufacturing dynamic bearings is higher than other types of bearings, and manufacturing completely results in reduced yield.  
      Thus, an improved design is necessary to solve the above-mentioned problem.  
     SUMMARY  
      Embodiments of the invention provide a composite dynamic bearing assembly comprising a bearing bracket and a bearing. The bearing bracket comprises an internal space. The bearing, disposed in the internal space of the bearing bracket, comprises a plurality of bearing blocks. Each bearing block comprises a surface and a plurality of grooves. The surfaces of adjacent bearing blocks are shaped corresponding to each other and fit together tightly such that an interior side of the bearing bracket closely holds the bearing blocks together through contact therebetween. The bearing blocks are provided with the grooves for accommodating lubricant on an inner surface of the bearing after the bearing blocks are combined.  
      Embodiments of the invention further provide a method of manufacturing a composite dynamic bearing assembly. The method includes the following steps. A bearing bracket comprising an internal space is provided. A plurality of bearing blocks of the identical shape and size are formed. The bearing blocks are then combined to form a bearing. The bearing is disposed in an internal space of the bearing bracket. When combining the bearing blocks, surfaces of adjacent bearing blocks fit together tightly and fix the bearing blocks. When the bearing is disposed in the internal space of the bearing bracket, an external surface of the bearing closely contacts the bearing bracket, holding the bearing blocks together. That is, an interior side of the bearing bracket closely holds the bearing blocks together through contact therebetween. The bearing blocks comprise a plurality of grooves. When combined, the grooves of the bearing blocks accommodate lubricant on the inner surface of the bearing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Embodiments of the invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
       FIG. 1A  is a schematic perspective view of a conventional dynamic bearing;  
       FIG. 1B  is an unfolded view of the interior side of the dynamic bearing of  FIG. 1A ;  
       FIG. 2A  is a perspective view of a composite dynamic bearing assembly of a first embodiment of the invention after assembly;  
       FIG. 2B  is an unfolded view of the interior side of individual bearing blocks of the composite dynamic bearing assembly in  FIG. 2A ;  
       FIG. 3A  is a perspective view of a composite dynamic bearing assembly of a second embodiment of the invention after assembly;  
       FIG. 3B  is an unfolded view of the interior side of individual bearing blocks of the composite dynamic bearing assembly in  FIG. 3A ; and  
       FIG. 4  is a flowchart showing a manufacturing method of a composite dynamic bearing assembly of embodiments of the invention. 
    
    
     DETAILED DESCRIPTION  
       FIG. 2A  is a perspective view of a composite dynamic bearing assembly of a first embodiment of the invention after assembly. Common elements described in embodiments subsequent to the first embodiment share the same symbols. Bearing bracket  11 , shown in  FIG. 1A , is common to all described embodiments of the invention. Note that depiction of a bearing bracket is omitted in  FIG. 2A  to clearly illustrate a bearing of the first embodiment.  
       FIG. 2B  is an unfolded view of the interior side of individual bearing blocks of the composite dynamic bearing assembly in  FIG. 2A . Note that in  FIG. 2B , the bearing  22  is cut open and unfolded to show the grooves  23  on an interior side thereof. As shown in  FIGS. 2A and 2B , the bearing  22  comprises three curved bearing blocks  22   a ,  22   b ,  22   c  of the identical shape and size. Connecting surfaces  24 ,  25  of the bearing blocks  22   a ,  22   b , and  22   c  correspond to each other and tightly connected. For example, the connecting surface  24  of the bearing block  22   b  and the connecting surface  25  of the bearing block  22   c  are complementary. In this case, connecting surfaces  24 ,  25  have a toothed shape or chevron pattern. The bearing blocks  22   a ,  22   b ,  22   c  are combined to form a cylindrical bearing  22  and disposed in an internal space of the bearing bracket (not shown). When the bearing  22  is disposed in the internal space of the bearing bracket, an external surface of the bearing  22  closely contacts the bearing bracket, holding the bearing blocks  22   a ,  22   b , and  22   c  together. That is, an interior side of the bearing bracket closely holds the bearing blocks  22   a ,  22   b , and  22   c  together through contact therebetween.  
      A plurality of grooves  23  with identical patterns are defined on an internal surface of each bearing block  22   a ,  22   b , and  22   c . The pattern of the grooves  23  can be identical to or different from the shapes of the connecting surfaces  24 ,  25 . Thus, after combination of the bearing blocks  22   a ,  22   b ,  22   c , grooves  23  can accommodate lubricant on the inner surface of the bearing  22 .  
      The quantity, size, and shape of bearing blocks and groove patterns, and combination thereof are given here as an example of one possible arrangement. Embodiments can be varied according to demands. For example, as shown in  FIGS. 3A and 3B , the bearing  32  comprises three bearing blocks  32   a ,  32   b , and  32   c  with similar shapes but different sizes. The connecting surfaces  34  and  35  and the grooves  33  of the bearing blocks  32   a ,  32   b ,  32   c  are both curved.  
      Alternatively, the connecting surfaces  34  and  35  of the bearing blocks  32   a ,  32   b ,  32   c  are curved, but the grooves  33  can have a chevron pattern (not shown). Although not mentioned here other combinations are possible.  
       FIG. 4  is a flowchart showing a manufacturing method of a composite dynamic bearing assembly of embodiments of the invention. In step  41 , a bearing bracket comprising an internal space is provided. In step  42 , a plurality of bearing blocks are formed. The shape and size of the bearing blocks are designed such that they can be combined to form a bearing (step  43 ). When the bearing blocks are combined, surfaces of adjacent bearing blocks fit together tightly and fix the bearing blocks. The bearing is disposed in an internal space of the bearing bracket. When the bearing is disposed in the internal space of the bearing bracket, contact from an external surface of the bearing holds the bearing blocks. During formation of the bearing blocks, a plurality of grooves can be simultaneously formed on an internal surface of each bearing block. Thus, after combination of the bearing blocks, the grooves can accommodate lubricant on the inner surface of the bearing.  
      Furthermore, as mentioned, in step  43 , the bearing blocks are combined to form the bearing. In step  44 , the bearing formed by bearing blocks is placed in the internal space of the bearing bracket, thereby producing a composite dynamic bearing assembly. The contact between the external surface of the bearing and the bearing bracket securely hold the bearing blocks together. Thus, an additional step of gluing or engaging the bearing blocks is unnecessary.  
      In step  42 , the bearing blocks can be formed by casting, molding, or similar methods. The number, size, shape, combination type, patterns of the grooves depend on practical demands. If the bearing is required to be cylindrical, the bearing blocks can be curved blocks and combined in a radial direction of the bearing. Furthermore, to increase production capacity, the shapes and sizes of the bearing blocks can be identical, and formed by the same mold. The shape of the grooves, depends on the requirements of the grooves. In one embodiment, the shapes of the grooves and each connecting surface of each bearing block are identical.  
      In conclusion, the bearing of embodiments of the invention is formed by a plurality of bearing blocks. When manufacturing each bearing block, the grooves are formed thereon simultaneously. Compared with conventional designs, the manufacturing method of the invention is simpler. Furthermore, the grooves are formed in an open space, rather than in a narrow, confined space. Thus, manufacturing the grooves is easier.  
      While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.