Abstract:
Provided is a method of manufacturing an impeller, the method including: providing a disc comprising a plurality of blades; casting a shroud to a first state in a mold; providing a mounting space in the mold; mounting the disc in the mounting space and casting the shroud to a second state with the mounted disc.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims priority from Patent Application No. 10-2012-0039969, filed on Apr. 17, 2012, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Apparatuses and methods consistent with exemplary embodiments relate to an impeller used in a rotational apparatus such as a compressor or a pump and a method of manufacturing the impeller, and more particularly to, an impeller including a shroud and a method of manufacturing the impeller. 
         [0004]    2. Description of the Related Art 
         [0005]    In the related art, a compressor or a pump that compresses fluid includes an impeller that generates turning force. 
         [0006]    The impeller transfers rotational motion energy to fluid and increases pressure of the fluid. The impeller includes a plurality of blades on one surface of a disc to move the fluid and transfer the rotational motion energy to the fluid. A shroud for covering the blades on an opposite surface to the disc is installed. The shroud and the blades serve as a moving path of the fluid through the impeller. 
         [0007]    When the impeller is manufactured, a method of separately producing the disc including the blades and the shroud and coupling the separately produced disc and the shroud by welding has been used in the related art. 
         [0008]    However, such a method incorporating welding and coupling may cause undesirable deformation of the shroud or the blades during the welding process, and such deformation may cause an adverse effect on the quality of the impeller. Further, the welding and coupling method makes it difficult to weld an entire contact part of the shroud and the blades, and the method may cause a problem in a coupling force. 
         [0009]    Accordingly, to solve such disadvantages, a new method of manufacturing the impeller is required. 
       SUMMARY 
       [0010]    One or more exemplary embodiments provide an improved impeller having a stably coupled disc including blades and shroud and a method of manufacturing the improved impeller. 
         [0011]    According to an aspect of an exemplary embodiment, there is provided a method of manufacturing an impeller, the method including: providing a disc including a plurality of blades; casting a shroud to a first state in a mold; providing a mounting space in the mold; mounting the disc in the mounting space; and casting the shroud to a second state with the mounted disc. 
         [0012]    The first state may be a semi-solid state and the second state may be a completely solidified state. 
         [0013]    The plurality of blades and the shroud may be coupled to each other after the casting of the shroud to the second state. 
         [0014]    The casting of the shroud to the second state comprises cooling the shroud to the completely solidified state. 
         [0015]    The mold may include an outer cast and a center cast that form a space corresponding to a shape of the shroud, wherein the casting of the shroud to the first state includes: injecting a melted metal into the space; and cooling the melted metal to a semi-solid state. 
         [0016]    The providing of the mounting space may include preparing the mounting space of the disc by removing the center cast. 
         [0017]    The method may further include removing the outer cast. 
         [0018]    The method may further include polishing a surface of the shroud. 
         [0019]    The providing of the disc includes filling a filling material between the plurality of blades. 
         [0020]    The filling material may include molding sand. 
         [0021]    The method may further include removing the molding sand by beating and breaking the molding sand. 
         [0022]    The filling material may include paraffin. 
         [0023]    The method may further include removing the paraffin by thermally melting the paraffin. 
         [0024]    According to an aspect of another exemplary embodiment, there is provided an impeller including: a disc including a plurality of blades and a shroud contacting and coupled to the plurality of blades, wherein a bonding portion of the plurality of blades and the shroud may include an entire area of a contact surface between the plurality of blades and the shroud. 
         [0025]    The bonding portion between the plurality of blades and the shroud may form a round corner. 
         [0026]    Ends of the plurality of blades may include a portion embedded into the shroud. 
         [0027]    A part of the shroud that contacts the ends of the plurality of blades may protrude toward the plurality of blades. 
         [0028]    The part of the shroud that contacts the ends of the plurality of blades may include a round exterior surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The above and/or other features and advantages will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0030]      FIG. 1  is a perspective view of a structure of an impeller manufactured by using a method according to an exemplary embodiment; 
           [0031]      FIG. 2  is a cross-sectional view of the impeller of  FIG. 1 ; 
           [0032]      FIGS. 3A through 3H  are diagrams for sequentially describing a process of manufacturing an impeller according to an exemplary embodiment; and 
           [0033]      FIGS. 4A through 4H  are diagrams for sequentially describing a process of manufacturing an impeller according to another exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    The present disclosure will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. Like reference numerals in the drawings denote like elements, and thus their description will be omitted. 
         [0035]      FIG. 1  is a perspective view of a structure of an impeller  100  manufactured by using a method according to an exemplary embodiment.  FIG. 2  is a cross-sectional view of the impeller  100  of  FIG. 1 .  FIGS. 3A through 3H  are diagrams for sequentially describing a process of manufacturing the impeller  100  according to an exemplary embodiment. 
         [0036]    The impeller  100  according to an exemplary embodiment may be used in a rotational machine such as a compressor, a pump, or an air blower, and includes, as shown in  FIGS. 1 and 2 , a disc  110  that is a main body and a shroud  120  that functions as a cover. 
         [0037]    The disc  110  includes an inner core  111 , a base unit  112 , and a plurality of blades  113 . 
         [0038]    The inner core  111  is configured to have a circular shape. A mounting hole  111   a  is formed in the center of the inner core  111 . An axis of rotation (not shown) is inserted into the mounting hole  111   a  during assembly of the impeller  100  so that the inner core  111  transfers power of the axis of rotation to the impeller  100 . 
         [0039]    The base unit  112  is positioned at an outer side of the inner core  111 . A surface  112   a  of the base unit  112  is configured to have an inclined curve so that the base unit  112  provides a smooth floor surface of a fluid path for a flow of fluid as well as transfers energy to the fluid at the maximum. 
         [0040]    The blades  113  are formed on the surface  112   a  of the base unit  112 . The blades  113  guide movement of the fluid and transfer a kinetic energy of the impeller  100  to the fluid. 
         [0041]    The shroud  120  is bonded to upper portions of the blades  113  and has an umbrella shape having an open center portion and covers the upper portions of the blades  113 . 
         [0042]    The shroud  120  forms a ceiling surface of the fluid path so that the shroud  120 , the base unit  112 , and the blades  113  together constitute the moving path of the fluid. 
         [0043]    A process of transferring energy to the fluid by using a rotational motion of the above-described impeller  100  will now be described below. 
         [0044]    If the axis of rotation rotates, the disc  110  and the shroud  120  of the impeller  100  rotate together. 
         [0045]    Accordingly, the fluid is injected into an inlet  100   a  of the impeller  100  in a direction of an arrow of  FIG. 2 , receives the rotational motion energy, and is ejected to an outlet  100   b  in a high pressure state. Thereafter, the velocity of the fluid which passes through a diffuser (not shown) decreases, and the pressure of the fluid increases to a desired level. 
         [0046]    The method of manufacturing the impeller  100  according to an exemplary embodiment will now be described with reference to  FIGS. 3A through 3G . 
         [0047]    A disc  110  including blades  113  is prepared as shown in  FIG. 3A . The disc  110  including the blades  113  may be produced through mechanical processing in the same manner as the related art manufacturing process. The disc  110  and the blades  113  may made from a ferrous metal such as carbon steel or a nonferrous metal such as aluminum. 
         [0048]    Thereafter, as shown in  FIG. 3B , molding sand  114  is filled in areas between the blades  113  of the disc  110  as a filling material. 
         [0049]    Then, as shown in  FIG. 3C , a mold  200  which includes an empty space  201  and corresponds to a shape of a shroud  120  is prepared. The mold  200  includes a center cast  220  and an outer cast  210 . The empty space  201  between the center cast  220  and the outer cast  210  corresponds to the shape of the shroud  120 . 
         [0050]    After the mold  200  is prepared, as shown in  FIG. 3D , a melted metal is injected into the empty space  201  to proceed with a first casting operation of casting the shroud  120 . The melted metal may comprise the ferrous metal such as carbon steel or the nonferrous metal such as aluminum as described above. Then, the melting metal filled in the empty space  201  is cooled down and thus the shroud  120  is slowly casted. In this process, the cooling down process is not performed to a point where the melting metal is completely solidified but rather only to a point where the melting metal is halfway solidified in such a way that the shape of the shroud  120  is not crumbled during the first casting operation. 
         [0051]    Then, as shown in  FIG. 3E , the center cast  220  of the mold  200  is removed, and the disc  110  including the blades  113  is mounted in the mold  200  from which the center cast  220  is removed. 
         [0052]    Accordingly, the blades  113  of the disc  110  are tightly adhered to the shroud  120  in a semi-solid state as shown in  FIG. 3F . The molding sand  114  that is the filling material is filled between the blades  113  so that the shroud  120  in the semi-solid state may not invade therebetween. Then, a second casting operation of cooling the shroud  120  is performed until the shroud  120  is completely solidified, and the blades  113  and the shroud  120  that contact each other are firmly bonded to each other as the shroud  120  is solidified. 
         [0053]    Finally, if the outer cast  210  is removed and the molding sand  114  filled between the blades  113  is removed, as shown in  FIG. 3G , the impeller  100  in which the blades  113  and the shroud  120  are firmly bonded to each other is manufactured. Subsequently, a process of polishing a surface of the shroud  120  may be additionally performed. 
         [0054]    Therefore, if the impeller  100  is manufactured by using the above-described method, the blades  113  and the shroud  120  in the semi-solid state contact each other and the blades  113  and the shroud  120  are bonded to each other as the shroud  120  is solidified. This exemplary method reduces undesirable deformation during a manufacturing process compared to a welding and bonding method of the related art, and thus the impeller  100  having very stable quality is manufactured. 
         [0055]    Further, the welding and bonding method of the related art may have a weak bonding force since bonding occurs only in a part on which welding is actually performed, whereas a casting method according to the present exemplary embodiment tightly bonds an entire contacting part between the blades  113  and the shroud  120  by embedding ends of the blades  113  into the shroud  120 , and thus the impeller  100  having a very excellent bonding strength may be manufactured compared to a impeller of the related art. In particular, as shown in  FIG. 3H , a bonding part A between the blades  113  and the shroud  120  having a round corner shape is advantageous to obtaining a stable coupling force. A part of the shroud  120  that contacts both sides of the ends of the plurality of blades  113  protrudes toward the plurality of blades and the part of the shroud  120  that contacts both sides of the ends of the plurality of blades has a round exterior surface. 
         [0056]    If the molding sand  114  is appropriately filled in an area between the blades  113 , the method according to the present exemplary embodiment easily forms the round corner. Thus, the above-described method provides a very advantageous effect in obtaining the bonding force between the blades  113  and the shroud  120 . 
         [0057]    Although the first casting operation performed on the shroud  120  is performed after the disc  110  is prepared in the present exemplary embodiment, to the contrary, the disc  110  may be prepared during the half solidifying process of the first casting operation. That is, the disc  110  is not necessarily prepared before the first casting operation is performed, and the disc  110  may well be prepared before the second casting operation is performed. 
         [0058]    A method of manufacturing the impeller  100  according to another exemplary embodiment will now be described with reference to  FIGS. 4A through 4G . The same reference numerals denote the same elements between the previous exemplary embodiment and the present exemplary embodiment. 
         [0059]    As shown in  FIG. 4A , a disc  110  including blades  113  is prepared. The disc  110  and the blades  113  may use a ferrous metal such as carbon steel or a nonferrous metal such as aluminum. 
         [0060]    Thereafter, as shown in  FIG. 4B , a filling material is filled between areas between the blades  113  of the disc  110 . Paraffin  115  is used as the filling material. That is, although sand ( 114 , see  FIG. 3B ) is used as the filling material in the previous embodiment, the paraffin  115  that may be thermally melted and removed is used as the filling material in the present exemplary embodiment. 
         [0061]    Thereafter, as shown in  FIG. 4C , a mold  200  including an empty space  201  corresponding to a shape of the shroud  120  is prepared. The mold  200  includes a center cast  220  and an outer cast  210 . The empty space  201  between the center cast  220  and the outer cast  210  corresponds to the shape of the shroud  120 . 
         [0062]    If the mold  200  is prepared, as shown in  FIG. 4D , a melted metal is injected into the empty space  201  to proceed with a first casting operation of casting the shroud  120 . The melted metal may use the ferrous metal such as carbon steel or the nonferrous metal such as aluminum. Then, the melted metal filled in the empty space  201  is cooled and thus the shroud  120  is slowly casted. In this process, cooling is not performed to a point where the melted metal is completely solidified but rather only to a point where the melted metal is halfway solidified in such a way that the shape of the shroud  120  is not crumbled during the first casting operation. 
         [0063]    Then, as shown in  FIG. 4E , the center cast  220  of the mold  200  is removed, and the disc  110  is mounted in the mold  200  from which the center cast  220  is removed. 
         [0064]    Accordingly, the blades  113  of the disc  110  are tightly adhered to the shroud  120  in a semi-solid state as shown in  FIG. 4F . Here, the paraffin  115  that is the filling material is filled between the blades  113  so that the shroud  120  in the semi-solid state may not invade therebetween. A second casting operation of cooling the shroud  120  is performed until the shroud  120  is completely solidified. Then, the blades  113  and the shroud  120  that contact each other are firmly bonded to each other as the shroud  120  is solidified. 
         [0065]    Finally, if the outer cast  210  is removed and the paraffin  115  filled between the blades  113  is removed, as shown in  FIG. 4G , the impeller  100  in which the blades  113  and the shroud  120  are firmly bonded to each other is manufactured, and then, a process of polishing a surface of the shroud  120  may be additionally performed. The paraffin  115  may be thermally melted and removed. That is, the molding sand  114  is used as the filling material in the previous exemplary embodiment and thus the filing material may be beaten lightly, broken, and removed, whereas the paraffin  115  is used as the filling material in the present embodiment and thus the filing material may be thermally melted and removed. 
         [0066]    If the impeller  100  is manufactured by using the above-described method, the blades  113  and the shroud  120  in the semi-solid state contact each other and are bonded to each other as the shroud  120  is solidified. This method reduces a unwanted deformation during the manufacturing process compared to a conventional welding and bonding method, and thus the impeller  100  having very stable quality is manufactured. 
         [0067]    Further, a welding and bonding method of the related art causes a weak bonding force since bonding is carried out only in a part in which welding is actually performed, whereas a casting method according to the present exemplary embodiment tightly bonds an entire bonding part between the blades  113  and the shroud  120  by embedding ends of the blades  113  into the shroud  120 , and thus the impeller  100  having a very excellent bonding strength may be manufactured compared to an impeller of the related art. In particular, as shown in  FIG. 4H , the bonding part A between the blades  113  and the shroud  120  in a round corner shape is advantageous to obtaining a stable coupling force. As shown  FIG. 4H , a part of the shroud  120  that contacts both sides of the ends of the plurality of blades  113  protrudes toward the plurality of blades and the part of the shroud  120  that contacts both sides of the ends of the plurality of blades has a round exterior surface. If the paraffin  115  is appropriately formed, the method according to the present exemplary embodiment is very advantageous in forming the round corner. Thus, the above-described method provides a very advantageous effect in obtaining a stronger bonding force. 
         [0068]    Although the first casting operation performed on the shroud  120  is performed after the disc  110  is prepared in the present exemplary embodiment, to the contrary, the disc  110  may be prepared during the halfway solidifying process of the first casting operation. That is, the disc  110  is not necessarily prepared before the first casting operation is performed and the disc  110  may well be prepared before the second casting operation is performed. 
         [0069]    According to an impeller and a method of manufacturing the impeller of exemplary embodiments, an undesirable deformation of a bonding part of blades and a shroud may be minimized, and a bonding strength therebetween may be increased. 
         [0070]    While exemplary embodiments have been particularly shown and described above, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventive concept as defined by the following claims.