Abstract:
Provided is a brushless direct current (BLDC) motor applied to a fuel pump for a motor vehicle, and more particularly, a BLDC motor of a fuel pump for a motor vehicle in which an end of a shaft of a rotor is coupled to a stator side to be rotated such that a length of the shaft is reduced.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2016-0002689, filed on Jan. 8, 2016, in the Korean Intellectual Property Office. The entire disclosure of which is incorporated herein by reference in its entirety for all purposes. 
       TECHNICAL FIELD 
       [0002]    The following disclosure relates to a brushless direct current (BLDC) motor applied to a fuel pump for a motor vehicle, and more particularly, to a BLDC motor of a fuel pump for a motor vehicle in which an end of a shaft of a rotor is coupled to a stator side to be rotated such that a length of the shaft is reduced. 
       BACKGROUND 
       [0003]      FIG. 1  is a view schematically illustrating a fuel delivery system for a motor vehicle. 
         [0004]    Referring to  FIG. 1 , the fuel delivery system for a motor vehicle delivers a fuel from a fuel tank  10  to a fuel supply line  30  using a fuel pump  20 , and supplies the fuel delivered to the fuel supply line  30  to each injector  50  of an engine at constant pressure and flow rate using a pressure regulator  40 . Further, the fuel delivery system for a motor vehicle returns the remaining fuel after being supplied to each injector  50  of the engine from the fuel supply line  30  to the fuel tank  10  through a fuel return line  60 . 
         [0005]    The above-mentioned fuel delivery system for a motor vehicle uses a general direct current (DC) motor as the fuel pump  20 . By using the DC motor as the fuel pump, the fuel pump  20  of the fuel delivery system is rotated at a designed speed to deliver the fuel having the same or varying flow rate and pressure to the fuel supply line  30 . 
         [0006]      FIG. 2  illustrates an exploded perspective view of a brushless direct current (BLDC) motor  100  of a fuel delivery system for a motor vehicle according to the related art. The general BLDC motor  100  used as the fuel pump of the fuel delivery system for a motor vehicle according to the related art includes a cylindrical outer case  110 , a stator  120  inserted into the outer case  110 , a rotor  130  rotatably inserted into the stator  120 , a shaft  135  guiding a rotation of the rotor  130 , a pump outlet  140  closing one side of the outer case  110  and including a terminal  145 , and a lower-side case  150  closing the other side of the outer case  110  and including an impeller  155  rotated by the rotation of the rotor  130 . 
         [0007]    The shaft  135  of the BLDC motor  100  according to the related art as described above has an end of one side which is rotatably coupled to the pump outlet  140 , and an end of the other side which is rotatably coupled to the lower-side case  150 . In particular, one side of the shaft  135  is extended by a significant length in one side direction from one side of the rotor  130  so as to be connected to the pump outlet  140 . Accordingly, as a length of the shaft  135  is formed to be long, a support point is apart from the center of gravity of the rotor  130 , which causes noise and vibration to be increased. 
       SUMMARY 
       [0008]    An embodiment of the present invention is directed to providing a BLDC motor of a fuel pump for a motor vehicle in which an end of one side of a shaft is coupled to one side of a stator to reduce a length of the shaft such that a support point of the shaft approaches the center of gravity of a rotor. 
         [0009]    To this end, an embodiment of the present invention is directed to providing a BLDC motor of a fuel pump for a motor vehicle in which a coupling part formed at one side of the rotor is formed by performing a secondary injection molding for the stator after performing a primary injection molding for the stator. 
         [0010]    In one general aspect, a brushless direct current (BLDC) motor of a fuel pump for a motor vehicle, including an outer case, a stator inserted into the outer case, a rotor rotatably inserted into the stator, a shaft formed on a rotation shaft of the rotor, a pump outlet closing one side of the outer case and including a terminal, and a lower-side case closing the other side of the outer case and including a driving body which is rotated by rotation of the rotor, includes: a shaft coupling part formed on one side of the stator and having an end of one side of the shaft which is rotatably coupled thereto. 
         [0011]    The shaft coupling part may include a bushing having the end of one side of the shaft which is rotatably coupled thereto; a bushing coupling part disposed at the center of one side of the stator and having the bushing which is coupled and fixed thereto; and a plurality of ribs connecting an outer circumference surface of the bushing coupling part and a circumference surface of one side of the stator. 
         [0012]    The shaft coupling part may be formed by first performing a primary injection molding for a molding part of the stator and then performing a secondary injection molding. 
         [0013]    The shaft coupling part may be formed on the same line as an end portion of one side of the stator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic view of a fuel delivery system for a motor vehicle. 
           [0015]      FIG. 2  is an exploded perspective view of a general BLDC motor. 
           [0016]      FIG. 3  is a perspective view of a BLDC motor according to an exemplary embodiment of the present invention. 
           [0017]      FIG. 4  is a cross-sectional perspective view of the BLDC motor according to an exemplary embodiment of the present invention. 
           [0018]      FIG. 5  is a coupling perspective view of a stator and a rotor according to an exemplary embodiment of the present invention. 
           [0019]      FIG. 6  is a coupling cross-sectional perspective view of the stator and the rotor according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF MAIN ELEMENTS 
       [0020]      
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 500: BLDC motor 
                   
               
               
                   
                 510: outer case 
               
               
                   
                 520: stator 
               
               
                   
                 525: shaft coupling part 
               
               
                   
                 525a: bushing coupling part 
                 525b: rib 
               
               
                   
                 530: rotor 
                 535: shaft 
               
               
                   
                 540: pump outlet 
                 545: terminal 
               
               
                   
                 550: lower-side case 
                 551: sub stator 
               
               
                   
                 552: upper case 
                 553: lower case 
               
               
                   
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]    Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
         [0022]      FIG. 3  illustrates a perspective view of a BLDC motor  500  (hereinafter, referred to as “motor”) according to an exemplary embodiment of the present invention and  FIG. 4  is a cross-sectional perspective view of the BLDC motor  500  according to an exemplary embodiment of the present invention. 
         [0023]    As illustrated, the motor  500  is configured to include an outer case  510 , a stator  520 , a rotor  530 , a pump outlet  540 , and a lower-side case  550 . 
         [0024]    The outer case  510  which is formed of a cylindrical resin material has a space into which the stator  520  and the rotor  530  are inserted, and upper and lower sides which may be formed to be opened. 
         [0025]    The stator  520  is formed in a cylindrical shape having a predetermined thickness, and has a space into which the rotor  530  is rotatably inserted in a shaft direction. The stator  520  may include a stator, a coil, a connector, and a molding part such as a stator of a typical BLDC motor. 
         [0026]    The rotor  530  is configured to be inserted into the stator  520  and be rotatable in the shaft direction by the magnetism of the stator  520 . The rotor  530  includes a core, a shaft  535 , a magnet, and a molding. 
         [0027]    The pump outlet  540  is coupled to an upper side of the outer case  510  so as to close the upper side of the outer case  510 , and has a terminal  545  electrically connected to the connector controlling the rotation of the motor  500 . 
         [0028]    The lower-side case  550  is coupled to the lower side of the outer case  510  so as to close the lower side of the outer case  510 , and includes a sub stator  551  which is rotated by receiving the rotation of the rotor  530  through an end of a lower side of the shaft  535 , an upper case  552  surrounding an upper side of the sub stator  551  and having the end of the lower side which is rotatably coupled thereto, and a lower case  553  surrounding a lower side of the sub stator  551 . The lower side of the shaft  535  may be coupled to be rotatable through a first bushing  552   a  provided to the center of the upper case  552 . 
         [0029]    In this case, an upper side of the shaft  535  according to the present invention may be coupled to the stator  520 . Hereinafter, a coupling structure between the shaft  535  and the stator  520  according to the present invention will be described in more detail with reference to the drawings. 
         [0030]      FIG. 5  illustrates a coupling perspective view of the stator  520  and the rotor  530  according to an exemplary embodiment of the present invention and  FIG. 6  is a coupling cross-sectional perspective view of the stator  520  and the rotor  530  according to an exemplary embodiment of the present invention. 
         [0031]    As illustrated, a shaft coupling part  525  may be formed on an open surface of one side of the stator  520 . The shaft coupling part  525  is configured to include a bushing coupling part  525   a  into which a second bushing B 2  is inserted so that the upper side of the shaft  535  is coupled thereto, and a plurality of ribs  525   b  connecting an outer circumference surface of the bushing coupling part  525   a  and a circumference surface of one side of the stator  520  so that the bushing coupling part  525   a  is fixed to the open surface of one side of the stator  520 . The plurality of ribs  525   b  may be radially disposed so that the bushing coupling part  525   a  is stably fixed. By the configuration of the shaft coupling part  525  as described above, the upper side of the shaft  535  which is extended from one side of the rotor  530  may be configured to be short. That is, a support point of the upper side of the shaft  535  may be configured to approach the center of gravity of the rotor  530 . 
         [0032]    In this case, the shaft coupling part  525  may be implemented by a double injection molding. 
         [0033]    After the molding part  522  of the stator  520  is first formed by performing a primary injection molding, the coil is wound and the connector is formed. Next, the shaft coupling part  525  is formed by performing a secondary injection molding, thereby making it possible to easily form the shaft coupling part  525  in the stator  520 . 
         [0034]    In the BLDC motor of the fuel pump for a motor vehicle according to the exemplary embodiment of the present invention, the shaft is coupled to the rotor, such that the support point of the shaft is configured to approach the center of gravity of the rotor, thereby making it possible to significantly reduce the vibration and noise caused by the rotation of the rotor. 
         [0035]    A technical spirit of the present invention should not be construed to being limited to the above-mentioned exemplary embodiments. The present invention may be applied to various fields and may be variously modified by those skilled in the art without departing from the scope of the present invention claimed in the claims. Therefore, it is obvious to those skilled in the art that these alterations and modifications fall within the scope of the present invention.