Abstract:
Provided is an electric waste gate actuator for a turbocharger, which includes a return spring for assisting a retention force of a final output gear, and a stopper for adjusting a rotation angle of the final output gear, thereby reducing an amount of a current consumed for maintaining the final output gear at a constant position. The electric waste gate actuator for a turbocharger includes: a housing having an installation space formed by a body and a cover; a driving motor installed within the installation space; a decelerator including gear trains provided with a plurality of gears, such that the decelerator is coupled to a lever installed outside the housing and transmits power of the driving motor; and an elastic member cooperating with the driving motor so as to maintain a rotation angle of a final output gear for finally transmitting power to the lever among the gear trains.

Description:
CROSS-REFERENCE(S) TO RELATED APPLICATION 
       [0001]    This application claims priority of Korean Patent Application No. 10-2010-0123922, filed on Dec. 7, 2010, in the Korean Intellectual Property Office, which is hereby incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an electric waste gate actuator for a turbocharger, and more particularly, to an electric waste gate actuator for a turbocharger, which includes a return spring for assisting a retention force of a final output gear, and a stopper for adjusting a rotation angle of the final output gear, thereby reducing an amount of a current consumed for maintaining the final output gear at a constant position. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, power generated by an internal combustion engine is dependent on a mass of air and an amount of fuel that may be supplied to the internal combustion engine. In order to increase the power of the internal combustion engine, it is necessary to supply a larger amount of combustion air and fuel. The increase in the power of the internal combustion engine may be achieved by increasing a cubic capacity or rotational speed of an intake engine. However, the increase in the cubic capacity leads to an expensive internal combustion engine having a relatively heavy weight and a large size. In particular, the increase in the rotational speed accompanies serious problems and disadvantages in a relatively large internal combustion engine. 
         [0006]    Supercharging has been often adopted as a technical solution to increasing the power of the internal combustion engine. Supercharging refers to precompressing combustion air using an exhaust gas turbocharger or a compressor mechanically driven by an engine. The exhaust gas turbocharger basically includes a turbine and a compressor connected to a common shaft and rotating at a constant rotational speed. The turbine converts uselessly exhausted energy into rotational energy through exhaust gas. The turbine drives the compressor. The compressor sucks new air and supplies precompressed air to individual cylinders of an engine. An increased amount of fuel is supplied to a relatively large amount of air in the cylinder. As a result, the internal combustion engine outputs higher power. Therefore, a combustion process is additionally influenced preferably, and the internal combustion engine has a higher total efficiency level. In addition, a torque profile of the internal combustion engine, which is supercharged by the turbocharger, may be formed very preferably. 
         [0007]    Since a series induction motor from a vehicle manufacturer uses an exhaust gas turbocharger, it may be considerably optimized without a structural interference with an internal combustion engine over a wide range. Generally, the supercharged internal combustion engine has a relatively low specific fuel consumption and a lower pollutant emission rate. Furthermore, since the exhaust gas turbocharger itself acts as an additional silencer, the turbo engine is silent at the same power level as compared to a typical intake engine. 
         [0008]    In an internal combustion engine having a wide rotational speed range (for example, an internal combustion engine for a car), a high charging pressure is required at a low rotational speed of an engine. To this end, a charging pressure control valve, called a waste gate valve, has been applied to a turbocharger. By selecting a relevant turbine casing, a high charging pressure is formed at a low rotational speed of an engine. The waste gate valve limits a charging pressure to a predetermined level according to the increase in the rotational speed of an engine. 
         [0009]    In the conventional electric waste gate actuator having the above-described functions, power for rotating a final output gear is derived from only a driving force of a motor. Therefore, a large amount of a current is consumed so as to maintain the final output gear at a constant position. 
       SUMMARY OF THE INVENTION 
       [0010]    An aspect of the present invention is directed to an electric waste gate actuator for a turbocharger, which includes a return spring for assisting a retention force of a final output gear, and a stopper for adjusting a rotation angle of the final output gear, thereby reducing an amount of a current consumed for maintaining the final output gear at a constant position. 
         [0011]    According to an embodiment of the present invention, an electric waste gate actuator for a turbocharger includes: a housing having an installation space formed by a body and a cover; a driving motor installed within the installation space; a decelerator including gear trains provided with a plurality of gears, such that the decelerator is coupled to a lever installed outside the housing and transmits power of the driving motor; and an elastic member cooperating with the driving motor so as to maintain a rotation angle of a final output gear for finally transmitting power to the lever among the gear trains. 
         [0012]    The cover may include: an insertion hole into which a rotational shaft of the final output gear is inserted; and a groove portion formed around the insertion hole, such that the elastic member is disposed at the groove portion. 
         [0013]    The elastic member may be a coil spring, one end of which is disposed within a concave portion formed at one side of the groove portion, and the other end of which is fixed the final output gear, such that the coil spring generates a restoring force when the final output gear is rotated. 
         [0014]    The cover may include a stopper protruding on a rear surface thereof around an insertion hole in which a rotational shaft of the final output gear is inserted. The final output gear may include a protrusion portion. Accordingly, the rotation of the final output gear may be restricted by a contact between the protrusion portion and the stopper. 
         [0015]    The electric waste gate actuator may further include: a magnet installed at one end of a rotational shaft of the final output gear within the housing; a sensor installed in installation space under the magnet within the housing and measuring the rotation angle of the final output gear by sensing a variation in a flux of the magnet; and an electronic control unit (ECU) installed in the housing outside the installation space. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is an exploded perspective view showing an electric waste gate actuator for a turbocharger according to an embodiment of the present invention. 
           [0017]      FIG. 2  is a partial cut-away cross-sectional view schematically showing the electric waste gate actuator for a turbocharger according to the embodiment of the present invention. 
           [0018]      FIG. 3A  is a perspective view showing a bottom of a cover, in which a return spring is disposed, in the electric waste gate actuator for a turbocharger according to the embodiment of the present invention. 
           [0019]      FIG. 3B  is a perspective view showing the bottom of the cover, in which a final output gear is disposed, in the electric waste gate actuator for a turbocharger according to the embodiment of the present invention. 
       
    
    
       [0020]      
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 &lt;Reference Numerals&gt; 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10: housing 
                 11: cover 
               
               
                 11b: concave portion 
                 11c: stopper 
               
               
                 20: blocking plate 
                 30: driving motor 
               
               
                 40: sensor unit 
                 50: decelerator 
               
               
                 55: return spring 
                 55a: one end of return spring 
               
               
                 55b: the other end of return spring 
                 60: ECU 
               
               
                 G: final output gear 
                 S: rotational shaft of final output gear 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0021]    Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. However, the present invention should not be construed as being limited to the exemplary embodiments set forth herein. Throughout the disclosure, like reference numerals refer to like parts throughout the drawings and embodiments of the present invention. 
         [0022]      FIG. 1  is an exploded perspective view showing an electric waste gate actuator for a turbocharger according to an embodiment of the present invention.  FIG. 2  is a partial cut-away cross-sectional view schematically showing the electric waste gate actuator for a turbocharger according to the embodiment of the present invention.  FIG. 3A  is a perspective view showing a bottom of a cover, in which a return spring is disposed, in the electric waste gate actuator for a turbocharger according to the embodiment of the present invention.  FIG. 3B  is a perspective view showing the bottom of the cover, in which a final output gear is disposed, in the electric waste gate actuator for a turbocharger according to the embodiment of the present invention. 
         [0023]    For reference, it should be noted that  FIG. 2  is a partial cut-away view of an electric waste gate actuator for a turbocharger according to an embodiment of the present invention, and thus, a part of a decelerator is not shown herein. 
         [0024]    In addition, it should be noted that the following description will be made with reference to  FIG. 2 , focusing on installation directions of elements. 
         [0025]    Referring to  FIGS. 1 and 2 , an electric waste gate actuator for a turbocharger according to an embodiment of the present invention includes a housing  10  having an installation space  13  inside. A decelerator  50  is installed in an upper portion of the installation space  13 . A lever  70  is installed in the exterior such that the lever  70  is coupled to an upper end of the decelerator  50 . A driving motor  30  is installed in a lower portion of the installation space  13 . A blocking plate  20  divides the installation space into the upper portion and the lower portion. An electronic control unit (ECU)  60  is installed at the outer periphery of the housing  10 . 
         [0026]    The housing  10  includes a cylindrical body  12  and a cover  11 . The body  12  has an opened upper end and forms the installation space  13 . The cover  11  closes the opened upper end of the body  12 . The cover  11  has a plate shape, and an insertion hole  11   a  is formed at one side of the cover  11 . 
         [0027]    The driving motor  30  is installed in the lower portion of the installation space  13  and generates a torque. A sealing member  15  is disposed between the cover  11  and the body  12  and seals a gap between the cover  11  and the body  12 . 
         [0028]    In  FIGS. 1 and 2 , although reference numerals are assigned to a final output gear a rotational shaft S of the final output gear and a return spring  55  as an elastic member, the decelerator  50  includes a plurality of gears forming gear trains, a plurality of rotational shafts forming shafts of the gears, and a return spring  55 . A motor shaft  31  extends toward the upper portion of the installation space  13 , and is organically coupled to the gear located in a lower portion among the gears of the decelerator  50 . The decelerator  50  coupled to the motor shaft  31  generates a relatively higher torque than that generated by the driving motor  30 . Meanwhile, the rotational shaft S disposed at the upper portion passes through the insertion hole  11   a  and is exposed to the exterior, and the upper portion of the exposed rotational shaft S is coupled to the lever  70 . Therefore, the decelerator  50  may transmit a torque to the turbocharger (not shown) through a load  71 . 
         [0029]    The blocking plate  20  includes a motor terminal  23  and a plate  21 . The motor terminal  23  has a plate shape in which a first through-hole  23   a  is drilled. The motor terminal  23  is closely installed at the upper end of the driving motor  30 , such that the motor terminal  23  fixes the position of the driving motor  30  and the plate  21  is closely installed on the top surface of the motor terminal  23 . The plate  21  has a plate shape in which a second through-hole  21   a  is drilled. The plate  21  is closely installed on the top surface of the motor terminal  23 . The first through-hole  23   a  and the second through-hole  21   a  are vertically connected to each other. Therefore, the motor shaft  31  protruding vertically from the upper end of the driving motor  30  passes through the first and second through-holes  23   a  and  21   a  and is coupled to the upper portion of the installation space  13 . The installation space  13  is divided into the upper portion and the lower portion by the blocking plate  20 . 
         [0030]    In addition, the rotational shaft S of the final output gear G of the decelerator  50  passes through a portion of the blocking plate  20 , and the lower end of the rotational shaft S is coupled to the lower portion of the installation space  13 . A magnet  41  is installed at the lower end of the rotational shaft S, which is coupled to the lower portion of the installation space  13 . A sensor  43  is installed in the lower portion of the installation space  13  under the magnet  41 . The magnet  41  and the sensor  43  installed as above constitute a sensor unit  40 . 
         [0031]    The sensor  43  is a contactless type and is installed under the magnet  41 . The sensor  43  measures a rotation angle by sensing a variation of a flux which is generated when the magnet  41  is rotated with the rotation of the rotational shaft S. 
         [0032]    The ECU  60  is disposed at the outer periphery of the housing  10 . In particular, the ECU  60  is disposed at one side of the driving motor  30  under the sensor  43 . 
         [0033]    Since the blocking plate  20  divides the installation space  13  into the upper portion and the lower portion as described above, the decelerator  50  is separated from the driving motor  30 , the sensor unit  40 , and the ECU  60 . Therefore, it is possible to prevent malfunction or performance degradation, which may be caused when foreign particles generated by the abrasion of the gear G and grease used in the gear G are introduced into the driving motor  30 , the sensor unit  40 , and the ECU  60 . Moreover, since the sensor  43  has a contactless structure, the spatial limitation of the installation space  13  is structurally reduced. Therefore, it is easy to support both ends of the rotational shaft included in the decelerator  50 . That is, it may be preferable that the rotational shaft S of the decelerator  50  is supported to the blocking plate  20 . 
         [0034]    Meanwhile, since the ECU  60  is separately installed at the outer periphery of the housing  10 , water does not directly infiltrate into the ECU  60 . Also, brush powder generated in the driving motor  30  does not adhere to grease used in the gear. 
         [0035]    Referring to  FIGS. 3A and 3B , a groove portion having an approximately ring shape is formed on the rear surface of the cover  11 , such that the return spring  55  is inserted into and located at the groove portion. The groove portion is formed around the insertion hole  11   a . A concave portion  11   b  is formed at one side of the groove portion. A stopper  11   c  protruding from the rear surface of the cover  11  is formed at the outer side of the groove portion. 
         [0036]    One end  55   a  of the return spring  55  is disposed within the concave portion  11   b  to prevent the return spring  55  from being freely rotated. As shown in  FIG. 3B , the other end  55   b  of the return spring  55  is fixed to a fixing portion Gb formed in the final output gear G. Accordingly, when seen in  FIG. 3   b , a restoring force is generated in the return spring  55  if the final output gear G rotates in a counterclockwise direction. 
         [0037]    The final output gear G includes a protruding portion Ga having an approximately semicircular or fan shape. The rotation of the final output gear G may be restricted by the contact between the protrusion portion Ga and the stopper  11   c.    
         [0038]    According to the embodiments of the present invention, since the return spring  55  capable of assisting the retention force of the final output gear G is installed, an amount of a current consumed by the motor may be reduced, as compared to a case in which the rotation angle of the final output gear G is maintained by only the driving force of the motor. In addition, due to the interaction between the stopper  11   c  and the protrusion portion Ga of the final output gear which are formed on the rear surface of the cover  11 , the final output gear G is not unnecessarily rotated by the elastic force of the return spring  55 . Therefore, the rotation angle of the final output gear G may be restricted. 
         [0039]    As described above, according to the embodiments of the present invention, the electric waste gate actuator includes the return spring for assisting the retention force of the final output gear, and the stopper for adjusting the rotation angle of the final output gear. 
         [0040]    Accordingly, the electric waste gate actuator may reduce an amount of a current consumed for maintaining the final output gear at the constant position. 
         [0041]    While the embodiments of the present invention has been described with reference to the specific embodiments, it will be apparent to 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.