Abstract:
A motor bearing preload mechanism is a modulized object composed of a screw, a resilient pad and a connecting pad to be fixed in a motor housing of a motor so as to apply a pre-pressure to a motor shaft of the motor.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to motors, and more particularly, to a motor bearing preload mechanism applying a pre-pressure to a motor bearing so as to remedy or improve internal clearance of the motor bearing. 
         [0003]    2. Description of Related Art 
         [0004]    A motor bearing has been known as one of the critical factors that determine stability of a motor. Generally, a plurality of balls is settled in the bearing and circle inside a housing of the bearing when the bearing rotates. However, the conventional motor bearing tends to have internal clearance that impairs the operational efficiency of the motor and causes vibration, noise, heat and power waste during operation of the motor. Besides, as the balls vibrate in the housing of the bearing, a ball-contacting surface is subject to fretting wear. Thus, a pre-pressure has to be applied to the bearing so as to remedy or improve internal clearance of the bearing. 
         [0005]    A conventional preload mechanism for a motor bearing, as shown in  FIGS. 1 and 2 , comprises a motor housing  10 , a motor shaft  11  settled in the motor housing  10 , a bearing  12  settled between the motor housing  10  and the motor shaft  11 , a packing  13  arranged in the motor shaft  11 , a positioning ring  14  deposited in the motor housing  10  and a preload mechanism  15  provided on the motor housing  10 . The bearing  12  has an outer ring  121  connected with the motor housing  10 , an inner ring  122  connected with the motor shaft  11  and a plurality of balls  123  settled between the inner ring  122  and the outer ring  121 . The packing  13  abuts the inner ring  122  of the bearing  12  and the positioning ring  14  abuts the outer ring  121  of the bearing  12 . The preload mechanism  15  includes a screw  151 , and a spring  152  having an end connected with the screw  151  while having an opposite end connected with a metal pad  153 . The preload mechanism  15  is screwed into a threaded hole  101  formed on the motor housing  10  so that the pad  153  abuts a shaft end  111  of the motor shaft  11  and presses against the spring  152 , thereby a resilience of the spring  152  acting on the motor shaft  11 . At this time, the packing  13  presses against the inner ring  122  of the bearing  12  along the motor shaft  11  so as to push the bearing  12  toward the positioning ring  14  and in turn make the positioning ring  14  press against the outer ring  121  of the bearing  12 , thereby eliminating internal clearance among the inner ring  122 , the outer ring  121  and the balls  123  of the bearing  12 . 
         [0006]    Though the prior art device accomplishes preload of the bearing  12  by using the preload mechanism  15 , following drawbacks nevertheless happen in assembling and use of the aforementioned prior art device: 
         [0007]    For performing particular resilience, the spring  152  must have a particular length and diameter, and, for accommodating such spring  152 , the motor housing  10  must have a relatively large volume. 
         [0008]    When the motor shaft  11  rotates, the spring coils of the spring  152  tend to shake and vertically impact the motor housing  10  and incur vibration and noise during operation of the motor. 
         [0009]    While the motor shaft  11  and the connector  153  simply contact mutually without a fixed positioning point, when the motor shaft  11  has its worm  112  combined and operating with a worm gear to rotate, the worm  112  tends to be affected by a lateral pressure from the worm gear. 
         [0010]    Additional assembling procedures and time are required by a wear-resistant material necessarily to be provided at the shaft end  111  of the motor shaft  11 . 
       SUMMARY OF THE INVENTION 
       [0011]    One object of the present invention is to provide a motor bearing preload mechanism, which is a modulized object composed of a screw, a resilient pad and a connecting pad so that the motor bearing preload mechanism has a reduced volume thereby saving space the motor bearing preload mechanism takes in a motor housing and simplifying assembling procedures of the motor bearing preload mechanism. 
         [0012]    Another object of the present invention is to provide a motor bearing preload mechanism, which is composed of a screw, a resilient pad and a connecting pad, wherein the resilient pad applies a pre-pressure to a motor bearing with its resilience so that when the motor shaft rotates, the bearing is secured from giving vibration and noise. 
         [0013]    To achieve the above objectives of the present invention, the disclosed motor bearing preload mechanism comprises: 
         [0014]    a main body, having a first end and a second end opposite mutually along an axis of the main body, and settled in a motor housing wherein the second end corresponds to a shaft end of a motor shaft in the motor housing; 
         [0015]    an axial hole, preformed inside the main body and leading to the second end of the main body so as to provide an opening at the second end of the main body; 
         [0016]    a resilient pad settled in the axial hole, having a first end abutting an extreme of the axial hole; and 
         [0017]    a connecting pad, having a first end abutting a second end of the resilient pad so that the shaft end of the motor shaft presses against the connecting pad and receives a resilience from the resilient pad. 
         [0018]    Another object of the present invention is to provide a motor bearing preload mechanism, which serves to support a shaft end of a motor shaft so as to enable the motor shaft to withstand a lateral pressure to a predetermined extent. 
         [0019]    To achieve the above objective of the present invention, the disclosed motor bearing preload mechanism further comprises a supporting portion in the main body so as to support the shaft end of the motor shaft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0021]      FIG. 1  is a disassembled sectional view of a conventional motor bearing preload mechanism and a motor; 
           [0022]      FIG. 2  is an assembled sectional view of the conventional motor bearing preload mechanism and the motor; 
           [0023]      FIG. 3  is a disassembled sectional view of a motor bearing preload mechanism in a form of a set screw and a motor according to the present invention; 
           [0024]      FIG. 4  is an assembled sectional view of the motor bearing preload mechanism in the form of a set screw and the motor according to the present invention; 
           [0025]      FIG. 5  is an exploded sectional view of a motor bearing preload mechanism in a form of a raised head screw and a motor according to the present invention; and 
           [0026]      FIG. 6  is an assembled sectional view of the motor bearing preload mechanism in the form of the raised head screw and the motor according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    While a preferred embodiment is provided herein for illustrating the concept of the present invention as described above, it is to be understood that the components in these drawings are made for better explanation and need not to be made in scale. 
         [0028]    Referring to  FIGS. 3 to 6 , a motor bearing preload mechanism  20  of the present invention comprises a main body  21 , an operational portion  22 , an axial hole  23 , a resilient pad  25 , a connecting pad  26 , and a supporting portion  27 . 
         [0029]    The main body  21  has a first end  211  and a second end  212  opposite mutually along an axis of the main body  21 . Furthermore, the main body  21  is formed with external threads. 
         [0030]    The operational portion  22  is formed at the first end  211  of the main body  21 . 
         [0031]    The axial hole  23  is preformed inside the main body  21  and leads to the second end  212  of the main body  21  so as to provide an opening  24  at the second end  212  of the main body  21 . 
         [0032]    The resilient pad  25  is put from the opening  24  and fixed in the axial hole  23 . The resilient pad  25  has a first end  251  abutting an extreme of the axial hole  23 . In the present embodiment, the resilient pad  25  is substantially a pad made of rubber. 
         [0033]    The connecting pad  26  is also put from the opening  24  and fixed in the axial hole  23 . The connecting pad  26  has a first end  261  abutting a second end  252  of the resilient pad  25 . The connecting pad  26  may be integrally made of a wear-resistant material or coated by a wear-resistant material, or may have received a surface wear-resistant process, so as to be imparted with a wear-resistant characteristic. 
         [0034]    The supporting portion  27  is formed by a peripheral wall of the axial hole  23  and adjacent to the second end  212  of the main body  21 . 
         [0035]    As shown in  FIGS. 3 and 4 , the main body  21  is realized by a set screw. Alternatively, as shown in  FIGS. 5 and 6 , the main body  21  is realized by a raised head screw. 
         [0036]    The bearing preload mechanism  20  is then combined with a threaded hole  301  preformed on a motor housing  30 . A user may use a hand tool to drive the operational portion  22  of the main body  21  so as to screw the bearing preload mechanism  20  into the threaded hole  301 . As can be seen in the drawings, the motor housing  30  encloses a motor shaft  31 , a bearing  32  settled between the motor housing  30  and the motor shaft  31 , a packing  33  arranged on the motor shaft  31  and a positioning ring  34  settled in the motor housing  30 . The bearing  32  has an outer ring  321  connected with the motor housing  30 , an inner ring  322  connected with the motor shaft  31  and a plurality of balls  323  settled between the inner ring  322  and the outer ring  321 . The packing  33  presses against the inner ring  322  of the bearing  32  and the positioning ring  34  abuts the outer ring  321  of the bearing  32 . 
         [0037]    After the bearing preload mechanism  20  has the opening  24  facing a shaft end  311  of the motor shaft  31  and then has the main body  21  screwed to the threaded hole  301 , the shaft end  311  of the motor shaft  31  pierces into the axial hole  23  through the opening  24  while an outer periphery of the shaft end  311  contacts the supporting portion  27 . As a result, the motor shaft  31  is supported by the bearing preload mechanism  20  and enabled to withstand a lateral pressure to a predetermined extent. As mentioned herewith, the lateral pressure is referred to a lateral pressure produced as a worm  312  of the motor shaft  31  is combined and operates with a worm gear. 
         [0038]    The motor shaft  31  pushes a second end  262  of the connecting pad  26  that in turn pushes the resilient pad  25  so that the resilience of the resilient pad  25  acts on the motor shaft  31  to make the packing  33  push the inner ring  322  of the bearing  32  along the motor shaft  31 , thereby forcing the bearing  32  to press against the positioning ring  34  and then making the positioning ring  34  press against the outer ring  321  of the bearing  32 , resulting in eliminating internal clearance among the inner ring  322 , the outer ring  321  and the balls  323  of the bearing  32 . 
         [0039]    Although the particular embodiment of the invention has been described in detail for purposes of illustration, it will be understood by one of ordinary skill in the art that numerous variations will be possible to the disclosed embodiments without going outside the scope of the invention as disclosed in the claims.