Abstract:
A retaining structure for motor elements includes an axial tube and a cap. The cap includes a stop and a coupling portion. At lease one motor element is received in the axial tube. The coupling portion of the cap is engaged with a coupling section of the axial tube for securely mounting the cap to the axial tube, with the stop of the cap covering an end of the axial tube to prevent the motor element from disengaging from the axial tube. In another example, the coupling portion of the cap engages with a coupling section on a stator.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a retaining structure for motor elements and, more particularly, to a retaining structure with a cap providing with a coupling portion and a stop for preventing at least one motor element from disengaging from an axial tube of the motor. 
         [0003]    2. Description of Related Art 
         [0004]      FIG. 1  of the drawings illustrates a conventional motor  1  comprising a base  11 , a stator  12 , a supporting member  13 , a bearing  14 , a positioning member  15 , and a rotor  16 . The base  11  includes an axial tube  111  for receiving the bearing  14 . The stator  12  includes a winding  121 . The supporting member  13  is fixed in an end of the axial tube  111  by force-fitting. An abrasion-resisting member  131  is mounted in a lower end of the supporting member  13 . A restraining member  132  is placed on top of the supporting member  13  and includes a through-hole (not labeled) for retaining a shaft  161  of the rotor  16 . The positioning member  15  is mounted on top of the bearing  14  to prevent the bearing  14  from moving relative to the axial tube  111  of the base  11 , thereby assuring reliable assembly. 
         [0005]    Still referring to  FIG. 1 , in assembly, the supporting member  13 , the bearing  14 , and the positioning member  15  are mounted into the axial tube  111  of the base  11  in sequence, with the supporting member  13  and the positioning member  15  respectively fixed in two ends of the axial tube  11   1  by force-fitting, thereby positioning the bearing  14  in the axial tube  111 . The shaft  161  is rotatably extended through an axial hole (not labeled) formed by a through-hole in each of the bearing  14  and the positioning member  15  and a hole (not labeled) in the supporting member  13 . 
         [0006]    Still referring to  FIG. 1 , when the motor  1  turns, since the diameter of the through-hole of the retaining member  132  on top of the supporting member  13  is smaller than an end of the shaft  161  and since the retaining member  132  is engaged in a necked portion (not labeled) of the shaft  161 , the rotor  16  is prevented from disengaging from the bearing  14 . Further, the bearing  14  is prevented from moving in the axial tube  111 , as the positioning member  15  is force-fitted in an end of the axial tube  111  of the base  11 , with a bottom of the positioning member  15  pressing against a top of the bearing  14 . Hence, the bearing  14  and the shaft  16  are reliably coupled to the base  11 . 
         [0007]    However, the above conventional bearing positioning structure for a motor has some drawbacks. First, the axial tube  111  easily deforms after a period of time due to heat expansion and cold shrinkage as well as stress generated during operation of the motor  1  such that the supporting member  13  and the positioning member  15  cannot be fixed in the axial tube  111 . Hence, the bearing  14  is liable to disengage from the axial tube  111 . Further, the dusts or impurities may enter the gap between the shaft  161  and the bearing  14  when the rotor  16  turns and creates air currents. The life of the motor  1  is thus shortened. Improvement in the bearing positioning structure for a motor is thus required. 
       OBJECTS OF THE INVENTION 
       [0008]    An object of the present invention is to provide a retaining structure for motor elements with improved assembling reliability and prolonged motor life by preventing at least one motor element from disengaging from the axial tube. 
         [0009]    Another object of the present invention is to provide a retaining structure for motor elements preventing dusts or impurities from entering the gap between the shaft and the bearing, thereby prolonging the life of the motor and improving assembling reliability. 
       SUMMARY OF THE INVENTION 
       [0010]    In accordance with an aspect of the present invention, a retaining structure for motor elements comprises an axial tube and a cap. The axial tube includes a coupling section, and at least one motor element is received in the axial tube. The cap includes a stop and a coupling portion. The coupling portion of the cap is engaged with the coupling section of the axial tube for securely mounting the cap to the axial tube, with the stop of the cap covering an end ofthe axial tube to prevent the at least one motor element from disengaging from the axial tube. 
         [0011]    Preferably, the coupling portion is formed on a bottom of the cap. 
         [0012]    Preferably, the coupling portion of the cap is a hook or an engaging groove. 
         [0013]    Preferably, a restraining member is mounted in the axial tube for limiting axial movement of a shaft of a rotor. 
         [0014]    Preferably, the coupling section of the axial tube is a flange. 
         [0015]    Preferably, the flange of the axial tube includes an inclined guiding face for guiding the coupling portion of the cap to engage with the flange of the axial tube. 
         [0016]    Preferably, the cap further includes an annular wall projecting from an outer face of the stop and having an end edge close to an inner face of a rotor. 
         [0017]    Preferably, a positioning ring is mounted in the axial tube and located between the motor element and the cap to preventing the motor element from becoming loosened and from shifting in the axial tube. 
         [0018]    Preferably, the at least one motor element includes at least one of a restraining member, a bearing, and a positioning member. 
         [0019]    In accordance with another aspect of the present invention, a retaining structure for motor elements comprises an axial tube, a stator, and a cap. At least one motor element is received in the axial tube. The stator includes a first coupling section. The cap includes a stop and a coupling portion. The first coupling section of the stator is engaged with the coupling portion of the cap for securely mounting the cap to an end of the axial tube, with the stop of the cap covering an end of the axial tube to prevent the at least one motor element from disengaging from the axial tube. 
         [0020]    Preferably, the coupling portion is formed on a top portion of the cap. 
         [0021]    Preferably, the coupling portion of the cap is a hook or an engaging groove. 
         [0022]    Preferably, a restraining member is mounted in the axial tube for limiting axial movement of a shaft of a rotor. 
         [0023]    Preferably, the cap further includes an annular wall projecting from an outer face of the stop and having an end edge close to an inner face of a rotor. 
         [0024]    Preferably, the stator further includes a second coupling section and wherein the axial tube includes an engaging portion for engaging with the second coupling section of the stator, thereby securely mounting the stator to the axial tube. 
         [0025]    Preferably, a positioning ring is mounted in the axial tube and located between the motor element and the cap to preventing the motor element from becoming loosened and from shifting in the axial tube. 
         [0026]    Preferably, the at least one motor element includes at least one of a restraining member, a bearing, and a positioning member. 
         [0027]    Preferably, the first coupling section is a hook. 
         [0028]    Other objects, advantages and novel features of this invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a sectional view of a conventional motor; 
           [0030]      FIG. 2  is an exploded perspective view, party cutaway, of a first embodiment of a retaining structure for motor elements in accordance with the present invention; 
           [0031]      FIG. 3  is a sectional view of the first embodiment of the retaining structure for motor elements in accordance with the present invention; 
           [0032]      FIG. 4  is an exploded perspective view, party cutaway, of a second embodiment of the retaining structure for motor elements in accordance with the present invention; and 
           [0033]      FIG. 5  is sectional view of the second embodiment of the retaining structure for motor elements in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Referring to  FIGS. 2 and 3 , a first embodiment of a retaining structure for motor elements in accordance with the present invention comprises a base  2 , a restraining member  3 , a bearing  4 , a cap  5 , a rotor  6 , and a positioning ring  7 . Mounted to the base  2  is an axial tube  21  and a stator  22 , wherein the axial tube  21  may be assembled to or integrally formed with the base  2  for receiving motor elements including the restraining member  3 , the bearing  4 , the cap  5 , and the positioning ring  7 . The stator  22  may be of radial winding type or axial winding type. The restraining member  3  restrains axial movement of a shaft  61  of the rotor  6  relative to the axial tube  21 . The bearing  4  may be an oily bearing, a ball bearing, a fluid dynamic bearing, etc. The shaft  61  is rotatably extended through the bearing  4 . The cap  5  is engaged with the axial tube  21  to prevent the motor elements from disengaging from the axial tube  21 . Preferably, the positioning ring  7  is mounted in the axial tube  21  by force-fitting and located between the bearing  4  and the cap  5  to prevent the bearing  4  from becoming loosened and from shifting in the axial tube  21 . 
         [0035]    Still referring to  FIGS. 2 and 3 , the axial tube  21  of the first embodiment in accordance with the present invention includes a coupling section  211  that extends radially and annularly on an end edge of the axial tube  21 . Preferably, the coupling section  211  is a flange and includes an inclined guiding face (not labeled) for guiding the cap  5  to a position securely engaged with the coupling section  211 . 
         [0036]    Still referring to  FIGS. 2 and 3 , the restraining member  3  of the first embodiment in accordance with the present invention includes a plurality of protrusions  31 , a plurality of slits  32 , and a through-hole  33 . The protrusions  31  extend radially inward form an inner circumference of the restraining member  3  to the through-hole  33  for restraining axial movement ofthe shaft  61 , with one of the slit  32  formed between the two adjacent protrusions  31  so as to provide the protrusions  31  with improved deforming capacity. The through-hole  33  is defined by the protrusions  31  and in a center of the restraining member  3 , with the shaft  61  extending through the through-hole  33  of the restraining member  3 . 
         [0037]    Still referring to  FIGS. 2 and 3 , the cap  5  of the first embodiment in accordance with the present invention is preferably a ring member corresponding to the axial tube  21  and includes a through-hole  50 , a stop  51 , a coupling portion  52 , and an annular wall  53 . The through-hole  50  is defined in a center of the cap  5 , allowing the shaft  61  to extend therethrough. The stop  51  is a top portion of the cap  5  for preventing the motor elements in the axial tube  21  from disengaging from the axial tube  21 . The coupling portion  52  may be a hook or an engaging groove. In this example, the coupling portion  52  is a hook formed on a bottom of the cap  5  for engaging with the coupling section  211  of the axial tube  21 . The annular wall  53  extends axially outward from an outer face ofthe stop  51  and includes an end edge close to an inner face of the rotor  6 . 
         [0038]    Still referring to  FIGS. 2 and 3 , in assembly of the motor elements of the first embodiment in accordance with the present invention, the restraining member  3  is placed into the axial tube  21 , with an abrasion-resistant member “a” sandwiched between the restraining member  3  and the bottom end of the axial tube  21  for preventing damage to the base  2  due to friction resulting from rotation of the shaft  61  of the rotor  6 . Then, the bearing  4  is mounted into the axial tube  21 , with an end face of the bearing  4  abutting against the top of the restraining member  3 . The positioning ring  7  is then mounted in the axial tube  21  by force-fitting and abuts against the other end face of the bearing  4 . Finally, the cap  5  is mounted to the axial tube  21  by moving the coupling portion  52  of the cap  5  along the inclined guiding face of the coupling section  211 . Hence, the cap  5  is reliably coupled to the upper end of the axial tube  2 . 
         [0039]    Still referring to  FIGS. 2 and 3 , the shaft  61  is extended through an axial hole formed by a through-hole (not labeled) of the positioning ring  7 , the through-hole  50  of the positioning member  5 , and the through-holes  40  and  33  of the bearing  4  and the restraining member  3 . Since the diameter of the through-hole  33  of the restraining member  3  is slightly smaller than the diameter of an end  611  of the shaft  61 , a force is applied to forcibly pass the end  611  of the shaft  61  through the through-hole  33  that expands due to deformation of the protrusions  31 . After the end  611  of the shaft  61  passes through the through-hole  33  and a necked portion  612  reaches the through-hole  33 , the protrusions  31  return to their original position and engage with the necked portion  612 , thereby limiting axial movement of the shaft  61  relative to the axial tube  21 . 
         [0040]    Still referring to  FIGS. 2 and 3 , the shaft  61  rotates in the axial hole formed by the restraining member  3 , the bearing  4  and the cap  5  when the rotor  6  turns. Since the coupling portion  52  of the cap  5  reliably engages with the coupling section  211  of the axial tube  21  and since the stop  51  covers an end of the axial tube  21 , the bearing  4  and the positioning ring  7  are reliably retained in the axial tube  21  without the risk of disengagement, even under heat expansion and cold shrinkage, thereby enhancing assembling reliability and prolonging the life of the motor. 
         [0041]    Still referring to  FIGS. 2 and 3 , since the diameter of the through-hole  50  of the cap  5  is slightly greater than the diameter of the shaft  61  and since the outer edge of the annular wall  53  of the cap  5  is close to the inner face of the rotor  6 , air currents generated during rotation of the rotor  6  will not carry the dusts or impurities into the gap between the shaft  61  and the shaft  4 . This avoids non-smooth operation of the rotor  6  and damage to the bearing  4  or other elements. Further, in a case that the bearing  4  is an oily bearing, the cap  5  prevents leakage of the lubricating oil in the bearing  4 , prolonging the life of the motor. 
         [0042]      FIGS. 4 and 5  illustrate a second embodiment of the retaining structure for motor elements in accordance with the present invention. As compared to the second embodiment, the stator  22  ofthe second embodiment includes a first coupling section  221  on top of the stator  22  for engaging with the coupling portion  52  of the cap  5 . Hence, the cap  5  is reliably mounted to the end of the axial tube  21  through the stator  22 . Preferably, the coupling portion  52  is an engaging groove for engaging with the first coupling section  221 . Preferably, the coupling portion  52  is annularly formed along a circumference of the stop  51 . 
         [0043]    Still referring to  FIGS. 4 and 5 , the stator  22  of the second embodiment is engaged with the axial tube  21  by providing a second coupling section  222  on a bottom portion of the stator  22  for engaging with an engaging portion  212  of the axial tube  21 . Hence, the stator  22  is reliably fixed to the axial tube  21 . Preferably, the engaging portion  212  is formed on an outer circumference ofthe axial tube  21  and corresponding to the second coupling section  222 . Preferably, the first and second coupling sections  221  and  222  are hooks. 
         [0044]    Still referring to  FIGS. 4 and 5 , in assembly of the motor elements of the second embodiment, the restraining member  3 , the bearing  4 , the positioning ring  7 , and the cap  5  are mounted into the axial tube  21  in sequence. Next, the first coupling section  221  and the second coupling section  222  of the stator  22  are respectively engaged with the coupling portion  52  of the cap  5  and the engaging portion  212  of the axial tube  22  such that the stator  22  is reliably fixed to the axial tube  21 . Hence, the stator  22  and the cap  5  are reliably engaged, the stop  51  of the cap  5  covers an end of the axial tube  21 , and the cap  5  is reliably coupled to the axial tube  21 . The motor elements in the axial tube  21  are reliably retained in the axial tube  21  without the risk of disengagement, even under heat expansion and cold shrinkage, thereby enhancing assembling reliability and prolonging the life of the motor. 
         [0045]    As mentioned above, in the conventional bearing positioning structure has the drawback of easy deformation in the axial tube  111  due to heat expansion and cold shrinkage as well as stress generated during operation of the motor such that the supporting member  13 , the axial tube  14  and the positioning member  15  cannot be fixed in the axial tube  111 , leading to unreliable positioning of the bearing  14 . Namely, the bearing  14  is liable to become loosened and, thus, disengages from the axial tube  111 . 
         [0046]    In the present invention, the above drawback is eliminated by providing a cap  5  including a stop  51  and a coupling portion  52 , wherein the coupling portion  52  engages with a coupling section  211  on the axial tube  21  or a first coupling portion  221  on the stator  22  and wherein the stop  51  forms the through-hole  50  in the center and covers an end of the axial tube  21  to prevent the motor elements from disengaging from the axial tube  21  while preventing dusts or impurities from entering the gap between the shaft  61  and the bearing  4  by the annular wall  53  on the stop  51 . The assembling reliability is enhanced and the life of the motor is prolonged. 
         [0047]    While the principles of this invention have been disclosed in connection with specific embodiments, it should be understood by those skilled in the art that these descriptions are not intended to limit the scope of the invention, and that any modification and variation without departing the spirit of the invention is intended to be covered by the scope of this invention defined only by the appended claims.