Patent Publication Number: US-2011050027-A1

Title: Motor Rotor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a motor rotor and, more particularly, to a motor rotor suitable to be formed by injection molding. 
     2. Description of the Related Art 
       FIGS. 1 and 2  show a conventional motor rotor  8  including a hub  81 , a metal ring  82 , and an annular magnet  83 . The metal ring  82  is formed by bending a metal strip having a length equal to or slightly smaller than a circumference of an inner periphery of the hub  81 . The metal ring  82  is mounted to and presses against the inner periphery of the hub  81  with two ends of the metal ring  82  in contact with or slightly spaced from each other. The annular magnet  83  is force-fitted to an inner periphery of the metal ring  82 . An example of such a motor rotor is disclosed in Taiwan Publication No. 490912. Since the metal ring  82  only presses against the inner periphery of the hub  81  in a radial direction and since the ends of the metal ring  82  are not positioned, the engagement between the hub  81  and the metal ring  82  is not reliable. 
       FIG. 3  shows another conventional motor rotor  9  including a hub  91 , a metal ring  92 , and a permanent magnet  93 . The hub  91  includes an opening  911  and is formed by injection molding to embrace the metal ring  92 . The metal ring  92  includes a first end  921  facing the opening  911  and a second end  922  spaced from the first end  921  along an axis about which the motor rotor  9  rotates. The permanent magnet  93  is coupled to the inner periphery of the metal ring  92  that provides magnetically conducting effect for the permanent magnet  93 . By such an arrangement, the hub  91  embraces and engages with the metal ring  92  to provide enhanced engaging effect. However, the metal ring  92  is liable to deform when it is fixed by a jig in a cavity of a mold for injection molding of the hub  91  in which the metal ring  92  is embedded. This is because the first end  921  of the metal ring  92  is not reinforced. The metal ring  92  can not maintain a true circle due to deformation of the first end  921 , adversely affecting the quality of the motor rotor  9  formed after injection molding and reducing rotational stability of the motor rotor  9 . Furthermore, the structure of the first end  921  of the metal ring  92  does not allow the first end  921  and the whole metal ring  92  to be easily placed in the cavity of the mold. Embedding of the metal ring  92  becomes more difficult if the metal ring  92  deforms during placing of the metal ring  92  in the cavity of the mold. Further, the first end  921  of the metal ring  92  does not provide any structure for guiding the permanent magnet  93  when coupling the permanent magnet  93  with the metal ring  92 . Thus, assembly of the permanent magnet  93  and the metal ring  92  is not easy, and deformation may occur during assembly. Further, if the metal ring  92  deforms during the injection molding process, the permanent magnet  93  will not be in intimate contact with the metal ring  92  or even unable to couple with the metal ring  92 . 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a motor rotor including a magnetically conducting member with improved structural strength for injection molding. 
     Another objective of the present invention is to provide a motor rotor including a magnetically conducting member that is less likely to deform during injection molding. 
     A further objective of the present invention is to provide a motor rotor including a magnetically conducting member allowing easy assembly. 
     Still another objective of the present invention is to provide a motor rotor with a magnetically conducting member to increase rotational stability of a motor utilizing the motor rotor. 
     A motor rotor according to the preferred teachings of the present invention includes a magnetically conducting member having an inner periphery and an outer periphery spaced from the inner periphery in a radial direction. The magnetically conducting member further includes first and second ends spaced along an axis perpendicular to the radial direction. The magnetically conducting member includes a reinforcing portion extending from the first end in the radial direction. A rotatable member is formed by injection molding and embraces and engages the outer periphery of the magnetically conducting member. The rotatable member includes an opening receiving the first end of the magnetically conducting member. The rotatable member is adapted to rotate about the axis. A permanent magnet is coupled to the inner periphery of the magnetically conducting member. 
     The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The illustrative embodiments may best be described by reference to the accompanying drawings where: 
         FIG. 1  shows an exploded, perspective view of a conventional motor rotor. 
         FIG. 2  shows another exploded, perspective view of the motor rotor of  FIG. 1  with a metal ring mounted in a hub and with portions broken away. 
         FIG. 3  shows a cross sectional view of another conventional motor rotor. 
         FIG. 4  shows a cross sectional view of a motor rotor of a first embodiment according to the preferred teachings of the present invention. 
         FIG. 5  shows a perspective view of a magnetically conducting member of the motor rotor of  FIG. 4  with portions broken away. 
         FIG. 6  shows a cross sectional view of a motor rotor of a second embodiment according to the preferred teachings of the present invention. 
         FIG. 7  shows an exploded, cross sectional view illustrating assembly of the motor rotor of  FIG. 4 . 
         FIG. 8  shows a cross sectional view of a motor utilizing the motor rotor of  FIG. 4 . 
     
    
    
     All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiments will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood. 
     Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms “first”, “second”, “inner”, “outer”, “end”, “portion”, “section”, “radial”, “circumferential”, “annular”, “outward”, “inward”, and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A motor rotor according to the preferred teachings of the present invention is shown in  FIGS. 4-7  and includes a magnetically conducting member  1 , a rotatable member  2 , and a permanent magnet  3 . The magnetically conducting member  1  is made from metal capable of providing magnetically conducting effect. The rotatable member  2  embraces the magnetically conducting member  1  to which the permanent magnet  3  is engaged. The magnetically conducting member  1  is intermediate the rotatable member  2  and the permanent magnet  3  to provide the magnetically conducting effect for the permanent magnet  2 . 
     The magnetically conducting member  1  is an annular ring including an inner periphery  11  and an outer periphery  12  spaced from the inner periphery  11  in a radial direction perpendicular to an axis about which the rotatable member  2  rotates. The annular ring further includes first and second ends  13  and  14  spaced along the axis. The magnetically conducting member  1  further includes a reinforcing portion  15  extending in the radial direction to reinforce the first end  13  for avoiding deformation of the magnetically conducting member  1 . 
     The rotatable member  2  is formed by injection molding to embrace and engage the magnetically conducting member  1  as a single piece, so that the rotatable member  2  firmly and intimately engages with the outer periphery  12  of the magnetically conducting member  1 . The rotatable member  2  includes an opening  21  receiving the first end  13  of the magnetically conducting member  1 . 
     The permanent magnet  3  can be an annular magnet formed of a plastic magnet, a rubber magnet, or a magnet made of other suitable material. The permanent magnet  3  is coupled to the inner periphery  11  of the magnetically conducting member  1 . 
     In the preferred forms shown in  FIGS. 4-6 , the reinforcing portion  15  includes an annular flange  15   a  extending outward from the outer periphery  12  of the magnetically conducting member  1  in the radial direction. The annular flange  15   a  includes inner and outer annular faces  15   c  spaced along the axis and a circumferential end face  15   b  extending between the inner and outer annular faces  15   c.  When the rotatable member  2  integrally embraces the magnetically conducting member  1 , the rotatable member  2  can firmly and intimately engage with the outer periphery  12  and the annular flange  15   a.  The engaging strength between the magnetically conducting member  1  and the rotatable member  2  is, thus, enhanced. The rotatable member  2  also embraces and firmly engages with the circumferential end face  15   b,  the outer annular face  15   c,  and a portion of the inner periphery  11  at the second end  14  of the magnetically conducting member  1  in the preferred form shown in  FIGS. 4 and 5 . In the preferred form shown in  FIG. 6 , the second end  14  of the magnetically conducting member  1  includes an extension  16  extending inward from the inner periphery  11  in the radial direction and spaced from the annular flange  15   a  along the axis. The extension  16  includes inner and outer surfaces  16   a  and  16   b  spaced along the axis. The inner surface  16   b  is intermediate the outer surface  16   a  and the reinforcing portion  15  of the magnetically conducting member  1 . The rotatable member  2  also embraces and firmly engages with the outer surface  16   a  and the outer annular face  15   c  to enhance the engaging strength between the rotatable member  2  and the magnetically conducting member  1 . 
     In the preferred forms shown in  FIGS. 4-6 , the rotating member  2  includes an annular wall  22  and a sealing portion  23  formed on and sealing an end of the annular wall  22 . The opening  21  is formed in the other end of the annular wall  22 . A hub is, thus, formed. The sealing portion  23  includes a shaft coupling portion  24  located in a central portion of the sealing portion  23 . The opening  21  and the shaft coupling portion  24  are located at two sides of the rotatable member  2  with the opening  21  spaced from the shaft coupling portion  24  along the axis. 
     The rotatable member  2  can further include a plurality of blades formed on the outer periphery of the rotatable member  2 , so that the rotatable member  2  can be utilized as an impeller of a heat dissipating fan. 
     In the preferred forms shown in  FIGS. 4-6 , a guiding section  17  is formed at an intersection of the reinforcing portion  15  and the first end  13  of the magnetically conducting member  1 . The guiding section  17  can be a rounded corner or a beveled face in cross section or any other suitable provisions for guiding the permanent magnet  3 . When coupling the permanent magnet  3  with the magnetically conducting member  1 , the guiding section  17  guides the permanent magnet  3 , allowing easy engagement between the permanent magnet  3  and the magnetically conducting member  1 , as shown in  FIG. 7 . In the preferred form shown in  FIGS. 4 and 5 , the permanent magnet  3  engages with the inner periphery  11  of the magnetically conducting member  1  and abuts a portion of the rotatable member  2  embracing the portion of the inner periphery  11  at the second end  14  of the magnetically conducting member  1 . In the preferred form shown in  FIG. 6 , the permanent magnet  3  engages with the inner periphery  11  of the magnetically conducting member  1  and abuts the inner face  16   b  of the extension  16 . 
     With reference to  FIG. 8 , in use, a shaft  4  is coupled to the shaft coupling portion  24  of the rotatable member  2  and engaged with a shaft tube  51  on a base  5  to which a stator  52  is mounted. The rotatable member  2  is rotatably coupled with the shaft tube  51  by the shaft  4  with the permanent magnet  3  aligned with the stator  52 . The stator  52  magnetically interacts with the permanent magnet  3  to drive the rotatable member  2  to rotate. 
     The first end  13  of the magnetically conducting member  1  according to the preferred teachings of the present invention is reinforced due to provision of the reinforcing portion  15 , allowing easy and smooth injection molding of the rotatable member  2 . Specifically, when the magnetically conducting member  1  is fixed by a jig in a cavity of a mold for injection molding of the rotatable member  2 , deformation of the first end  13  of the magnetically conducting member  1  can be avoided. This is because the magnetically conducting member  1  with the reinforcing portion  15  can be fixed in the predetermined location in the cavity of the mold. The reinforcing portion  15  also prevents deformation of the motor rotor according to the preferred teachings of the present invention during transport. Furthermore, the magnetically conducting member  1  can maintain a true circle, allowing easy, firm, and intimate engagement between the permanent magnet  3  and the magnetically conducting member  1 . Assembling convenience is, thus, enhanced. Further, a motor utilizing the motor rotor according to the preferred teachings of the present invention capable of maintaining a true circle has enhanced rotational stability. 
     Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.