Patent Publication Number: US-2007114865-A1

Title: Oilless bearing type motor with function of preventing oil leakage

Description:
FIELD OF THE INVENTION  
      The present invention relates to an oilless bearing type motor with a function of preventing oil leakage, and more particularly, to an oilless bearing type motor with a function of preventing oil leakage so as to improve durability and reliability of the motor.  
     BACKGROUND OF THE INVENTION  
      In general, a motor is a device that converts electrical energy into mechanical energy to provide a rotational force. Motors are being widely applied to various industrial fields including electric home appliances and industrial machines. For instance, motors can be applied to compressors, which are installed inside cooling appliances such as air conditioners and refrigerators to restore a refrigerant to a liquid, washing machines, vacuum cleaners, optical disk players, and hard disk drivers of computers.  
      Such a motor, particularly, a small-sized motor is installed with a self-lubricant oilless bearing to smoothly rotate a rotational shaft. A conventional oilless bearing type motor will be described with reference to  FIG. 1  hereinafter.  
       FIG. 1  illustrates a sectional view of main parts of a conventional oilless bearing type motor  10 . The oilless bearing type motor  10  includes a holder  11 , a casing (not shown), a stator (not shown), a rotor  12 , and a rotational shaft  13 . The holder  11  is attached to the casing (not shown) on both upper and lower sides. Although not illustrated, the stator is affixed to the inside of the casing. The rotor  12  is inserted into the stator (not shown) to be rotatable by having a gap inside the stator (not shown). The rotational shaft  13  passes through a central region of the rotor  12  and is affixed thereto. The rotational shaft  13  is inserted into the holder  11  to be rotatable by means of the oilless bearing  14 .  
      The holder  11  includes a bearing installation unit  11   a  in a central region of the holder  11 , and the oilless bearing  14  is installed on the bearing installation unit  11   a.    
      The oilless bearing  14  is formed of a sintered metal with multiple pores, and does not include oil but do include lubricating oil inside the pores of the sintered metal material, so that the oilless bearing  14  can be self-lubricant. One portion of the oilless bearing  14  exposed by the bearing installed unit  11   a  is elastically supported by a plate spring  15  so as to prevent separation of the oilless bearing  14  from the bearing installation unit  11   a.    
      The plate spring  15  is attached to an exterior portion of the bearing installation unit  11   a  of the holder  11 , and a bearing cover  16  that shields an inflow of foreign materials firmly fixes the plate spring  15 .  
      Around the oilless bearing  14 , the holder  11  provides a space that a permawick  17  having oil can fill.  
      The permawick  17  supplies the oil to those portions where friction occurs, for instance, a contact region between the oilless bearing  14  and the rotational shaft  13 .  
      In the conventional motor  10 , the rotational shaft  13  supported to be rotatable by the oilless bearing  14  rotates with the rotor  12  due to magnetic flux generated between the stator (not shown) and the rotor  12  by the power supplied to the motor  10 . At this time, the oil provided from the oilless bearing  14  and the permawick  17  is supplied to those parts where friction is induced, so that the rotational shaft  13  can rotate smoothly.  
      However, as the rotational shaft  13  rotates, the rotational shaft  13  and the oilless bearing  14  are likely to produce frictional heat. Thus, the temperature around the permawick  17  and the oilless bearing  14  tends to increase. This temperature increase causes the oil that the oilless bearing  14  and the permawick  17  contain is mixed into a gel-type fibroid material to thereby decrease the viscosity of the oil. As a result, the oil is likely to leak along the rotational shaft  13  and scatter due to a rotational force of the rotor  12 . Accordingly, those injection molding materials composing the interior parts of the motor  10  often deteriorate, and the deteriorated parts are easily broken, resulting in degradation of durability and reliability of the motor  10 .  
     SUMMARY OF THE INVENTION  
      It is, therefore, an object of the present invention to provide an oilless bearing type motor with a function of preventing oil leakage so as to prevent deterioration and breakage of injection molding materials composing parts of the motor and thus to improve durability and reliability of the motor.  
      In accordance with a preferred embodiment of the present invention, there is provided an oilless bearing type motor with a function of preventing oil leakage, wherein the motor includes an oilless bearing supporting a rotational shaft to be rotatable, the oilless bearing type motor including a rotor to which the rotational shaft is affixed in a central region, including an oil collecting indentation around the rotational shaft to collect oil leaked from an oilless bearing side, and formed by pressing soft magnetic powder, and an oil absorption ring including a material capable of absorbing a liquid to allow the oil moving by a centrifugal force at the oil collection indentation and installed in the oil collecting indentation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:  
       FIG. 1  illustrates a sectional view of main parts of a conventional oilless bearing type motor;  
       FIGS. 2A and 2B  illustrate a sectional view of main parts of an oilless bearing type motor with an oil leakage prevention function in accordance with an embodiment of the present invention; and  
       FIG. 3  is a perspective view illustrating how an absorption ring of the oilless bearing type motor is attached to a target in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that they can be readily implemented by those skilled in the art.  
       FIGS. 2A and 2B  illustrate a sectional view of an oilless bearing type motor with a function of preventing oil leakage in accordance with an embodiment of the present invention. The oilless bearing type motor  100  with the oil leakage prevention function includes an oilless bearing  110 , a rotational shaft  120 , a rotor  130 , an oil collecting indentation  131 , and an oil absorption ring  140 . The rotational shaft  120  is supported to be rotatable by the oilless bearing  110 . The rotor  130  is affixed to a central region of the rotational shaft  120  and formed by pressing soft magnetic powder so as to form the oil collecting indentation  131 . The oil absorption ring  140  is installed in the oil collecting indentation  131  of the rotor  130 .  
      Although not illustrated, the oilless bearing  110  is installed on a holder  150  attached to a casing on both upper and lower sides. The oilless bearing  110  supplies lubricating oil contained in pores of a sintered material to an attached region to the rotational shaft  120  so as to support the rotational shaft  120  to be rotatable.  
      A bearing installation unit  151  is disposed in an interior central region of the holder  150  to install the oilless bearing  110  thereon. A plate spring  152  is placed on one portion of the oilless bearing  110  exposed by the bearing installation unit  151 , and thus, the plate spring  152  can elastically support the oilless bearing  110 . A bearing cover  153  is attached to an exterior portion of the bearing installation unit  151 , and firmly fixes the plate spring  152 .  
      A permawick  154  having oil fills the holder  150  around the oilless bearing  110  to supply the oil to those regions where friction occurs, e.g., a contact region between the rotational shaft  120  and the oilless bearing  110 .  
      The rotational shaft  120  is affixed to a central region of the rotor  130  so as to rotate with the rotor  130 .  
      The rotor  130  is placed inside a stator (not shown), which is affixed to the inner surface of the casing (not shown), by having a gap inside the stator (not shown), and rotates due to an electron induction event generated by the stator (not shown). The rotor  130  includes the oil collecting indentation  131  formed around a certain region of the rotational shaft  120  to collect the oil leaked from the oil bearing  110 .  
      As mentioned above, the rotor  130  is molded by pressing the soft magnetic powder. The soft magnetic powder includes iron-based particles, each coated with a certain material to be electrically insulated from each other.  
      In detail of the formation of the oil collection indentation  131 , a press molding apparatus includes a molding space formed in a shape substantially the same as the rotor  130 , and the soft magnetic powder is filled into the molding space. A pressing member such as a punch presses the soft magnetic powder to form the oil collecting indentation  131  in the rotor  130 . A lubricant and/or a binder may be added to the soft magnetic powder and pressed together.  
      The rotor  130  includes a three-dimensional soft magnetic composite (SMC) by pressing the soft magnetic powder, and usually has a higher degree of freedom as compared with the conventional rotor  12  (see  FIG. 1 ) obtained by stacking silicon steel sheets over each other. As a result of this high degree of structural freedom, different from the conventional stack structure of the rotor  12 , the oil collecting indentation  131  can be formed in the rotor  130 .  
      The oil absorption ring  140  includes a felt-based material or a material that can absorbs a liquid, e.g., porous synthetic resin. The oil absorption ring  140  is installed inside the oil collecting indentation  131  such that the rotational shaft  120  is allocated at an interior central region of the oil absorption ring  140 . The oil moving due to a centrifugal force is absorbed at the oil collecting indentation  131 .  
      The oil absorption ring  140  can be forcefully inserted into the oil collecting indentation  131 . Preferably, as illustrated in  FIG. 3 , the oil absorption ring  140  can be fit into a ring installation groove  132  formed along the inner surface of the oil collection indentation  131 . As a result, the oil absorption ring  140  does not come off.  
      The oil collecting indentation  131  is preferably formed to be curved from the rotational shaft  120  to the oil absorption ring  140  to guide the oil collected along the rotational shaft  120  to smoothly move to the oil absorption ring  140  and be rapidly absorbed. Reference label ‘C’ in  FIG. 2B  denotes the curved shape of the oil collecting indentation  131 .  
      Although  FIG. 2B  illustrates the oil collecting indentation  131  and the oil absorption ring  140  disposed on only one side of the rotor  130 , the oil collecting indentation  131  and the oil absorption ring  140  can be formed and installed on both sides of the rotor  130 .  
      The above oilless bearing type motor operates as follows.  
      In the oilless bearing type motor  100  with oil leakage prevention function, when the temperature of the permawick  154  and the oilless bearing  110  increases due to frictional heat generated between the rotational shaft  120  and the oilless bearing  110  as the rotational shaft  120  rotates, the oil of the permawick  154  and the oilless bearing  110  is often mixed into a gel-type fibroid material, thereby reducing the viscosity of the oil that the permawick  154  and the oilless bearing  110  contain. As a result, the oil is likely to leak along the rotational shaft  120 , and collected at the oil collecting indentation  131 .  
      The oil collected at the oil collecting indentation  131  moves to the direction of a centrifugal force generated by the rotation of the rotor  130  and reaches the oil absorption ring  140  to be absorbed. Therefore, the oil leaked from the oilless bearing  110  is not likely to scatter inside the motor  100 .  
      The oil absorption ring  140  is fixed into the ring installation groove  132  of the oil collection indentation  131 , and thus, even though the rotor  130  rotates, the oil absorption ring  140  is firmly affixed thereto. Also, due to the curved portion of the oil collection indentation  131  extending from the rotational shaft  120  to the oil absorption ring  140  inside the oil collection indentation  131 , the oil leaked from the rotational shaft  120  can smoothly move to the oil absorption ring  140 . Thus, the oil absorption ring  140  can effectively absorb the moving oil.  
      Different from the conventional rotor  12  (see  FIG. 1 ) obtained by stacking the identically shaped silicon steel sheets over each other, the oil collecting indentation  131  of the rotor  130  can be formed by the press molding of the soft magnetic material.  
      According to various embodiments of the present invention, the oilless bearing type motor can prevent the oil leakage, and thus, further can prevent deterioration and breakage of injection molding materials composing the parts of the motor, usually caused by the oil leakage. As a result, durability and reliability of the motor can be improved.  
      While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.