Patent Abstract:
A propeller fan molded by injection molding using a resin material containing a continuous fiber, includes a hub having an end surface wall and a peripheral wall; and a plurality of blades on an outer periphery of the hub, the propeller fan being molded by providing a plurality of injection positions for injecting the resin material containing the continuous fiber in a part of the end surface wall corresponding to a root portion of one of the blades of the hub.

Full Description:
RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2011/065895, filed on Jul. 12, 2011, which in turn claims the benefit of Japanese Application No. 2010-160959, filed on Jul. 15, 2010, the disclosures of which Applications are incorporated by reference herein. 
     FIELD 
     The present invention relates to a propeller fan manufactured by injection molding of a resin material and a manufacturing method thereof, and more specifically, to a propeller fan with high durability, and a manufacturing method thereof. 
     BACKGROUND 
     In the related art, as a propeller fan that is included in an outdoor unit of an air conditioner, an air cleaner, a ventilator or the like and is used for fluid feeding of air or the like, it has been known a propeller fan formed, using a fiber reinforced plastic (FRP) in which a glass fiber or the like is mixed with a thermoplastic resin such as an acryl resin at a predetermined rate (for example, 30 weight %), through an injection molding by setting molding conditions such as an injection pressure and a metal mold temperature to predetermined values. 
       FIG. 5  illustrates a general injection molding machine  110  that is used for the injection molding of the above-mentioned propeller fan. The injection molding machine  110  includes an injection unit  111  that melts a resin material serving as a material in order to inject the resin material, a metal mold  112  that molds the molten resin from the injection unit  111 , a mold opening and closing mechanism  113  that closes the metal mold  112  after molding, and a projection mechanism  114  that projects the molded article to release the molded article from the mold after opening the mold. 
     Next, a molding machining sequence using the metal mold  112  will be described based on  FIGS. 6 to 8 . As illustrated in  FIG. 6 , the metal mold  112  is a three piece type metal mold including a stationary mold  121 , a mobile mold  122 , and an intermediate metal mold  123  located between both of them, and a plurality of projection pins  124  driven by the projection mechanism  114  is placed on a back side of the mobile mold  122 . 
     Moreover, in a state of joining the stationary mold  121 , the mobile mold  122  and the intermediate metal mold  123  at a predetermined clamping pressure, the molten resin is injected from the injection unit  111  into a cavity, not illustrated, formed between the mobile mold  122  and the intermediate metal mold  123  through a runner, not illustrated, formed throughout the stationary mold  121  and the intermediate metal mold  123 , and thereby a molded article corresponding to an internal surface shape of the cavity is formed. 
       FIG. 7  illustrates a state of mutually separating the stationary mold  121 , the mobile mold  122  and the intermediate metal mold  123  after molding to open the mold. Due to the opening of the mold, a molded article  116  molded in the cavity remains in a state of being attached to a molding surface of the mobile mold  122 , and a runner portion  117  solidified in the runner remains in a state of being attached to the stationary mold  121  side. 
     In a state of opening the metal mold  112 , as illustrated in  FIG. 8 , the projection pins  124  are caused to advance, the molded article  116  is separated from the mobile mold  122  by the projection pins  124 , and the runner portion  117  is separated from the stationary mold  121 . The molded article  116  manufactured in this manner is a propeller fan  101  serving as a molding object illustrated in  FIG. 3 . Furthermore, the injection molding state of the propeller fan  101  in the metal mold  112  is illustrated in  FIG. 4 . 
     As illustrated in  FIG. 3 , the propeller fan  101  has a peripheral wall  105  and an end surface wall  106 , and includes a hub  102  which is approximately cylindrical with a bottom provided with a boss  104  for inserting a driving shaft of a motor, not illustrated, configured to rotate the propeller fan  101  in a central portion of the end surface wall  106 , and three blades  103  having the same shape integrally attached onto the peripheral wall  105  of the hub  102 . As mentioned above, the propeller fan  101  is manufactured by the injection molding using the injection molding machine  110  including the metal mold  112  illustrated in  FIG. 4 . 
     As illustrated in  FIG. 4 , when joining the mobile mold  122  with the intermediate metal mold  123 , a cavity  127  is formed between the mobile mold  122  and the intermediate metal mold  123 . Furthermore, when joining the stationary mold  121  with the intermediate metal mold  123 , a runner  128  for supplying the molten resin injected from an injection nozzle  111   a  of the injection unit  111  to the cavity  127  is formed between the stationary mold  121  and the intermediate metal mold  123 . 
     Furthermore, the shape of the cavity  127  is set so that a molding surface  125  of the mobile mold  122  side forms a positive pressure surface  103   a  of the blade  103 , and a molding surface  126  of the intermediate metal mold  123  forms a negative pressure surface  103   b  of the blade  103  in consideration of mold release characteristics of the hub  102 . Furthermore, as illustrated in  FIG. 3 , the runner  128  forms a three-pronged branched road shape corresponding to the number of the blades  103  of the propeller fan  101 , and a downstream end of each branched road of the runner  128  is a gate  129  serving as an injection hole of the molten resin into the cavity  127 . 
     Thus, the molten resin is injected into the cavity  127  through the runner  128  from the injection nozzle  111   a  at a predetermined injection pressure, the cavity  127  is filled with the molten resin, and thereby the propeller fan  101  having a shape corresponding to the inner surface shape of the cavity  127  is molded. 
     At this time, the runner portion  117  having a shape corresponding to the inner surface shape of the runner  128  is molded in the runner  128  by the molten resin supplied thereto, and the runner portion  117  is integrally connected to the propeller fan  101  by each gate  129 . The propeller fan  101  and the runner portion  117  are cut and separated by each gate  129  when the metal mold  112  is opened. Thus, as illustrated in  FIG. 3 , cutting traces in the runner portion  117 , that is, three gate marks  118  remain on the end surface wall  106  of the propeller fan  101  after the molding. 
     However, in general, since the shape of the blade of the propeller fan greatly affects the blowing performance, the shape is designed under extremely exact calculations, and thus there is a need to pay a close attention so as to obtain the shape of the blade corresponding to the design shape, particularly when manufacturing the propeller fan. 
     For example, when setting the gate  129  of the runner  128  to a position corresponding to a blade surface (the negative pressure surface  103   b  illustrated in  FIG. 4 ) of the blade  103  of the cavity  127 , the gate marks  118  remain on the blade surface of each blade  103  of the molded propeller fan  101 , the blade surface becomes uneven due to the presence of the gate marks  118 , the blade surface shape is different from the design shape, and thus the blowing performance may decline. 
     Thus, in the related art, generally, as illustrated in  FIGS. 3 and 4 , each gate  129  is set to a position corresponding to a root of the blade  103  of the peripheral wall  105  on the end surface wall  106  of the hub  102  while avoiding the provision thereof on the blade  103  side. 
     Furthermore, the shape of the propeller fan of the related art and the manufacturing method thereof mentioned above is, for example, described in the description of the related art in Patent Literature 1. 
     However, in the propeller fan of the related art mentioned above, the number of the gates  129  at the time of the injection molding is one with respect to each blade  103 , as illustrated in  FIG. 9 , the molten resin that flowed into the cavity  127  from the gate  129  flows like the flow of the resin indicated by reference numeral  400 . 
     Specifically, the molten resin that flowed into the cavity  127  from the gate  129  flows so as to spread in the cavity  127  from the gate  129 , and flows like the flow  400  ( 400   a  to  400   f ) of the resin illustrated in  FIG. 9 . Although the blade  103  is jointed to the peripheral wall  105  of the hub  102  by a root portion  200 , as illustrated in  FIG. 4 , a thickness from a root portion  200  to the leading end portion of the blade  103  becomes thinner toward the leading end portion of the blade  103  from the root portion  200 . 
     The molten resin that flowed from the gate  129  initially reaches the root portion  200  just below the gate  129  (the gate mark  118 ). The molten resin that reaches this then flows in a direction along the root portion  200 , that is, like the flows  400   a  and  400   b  of the resin illustrated in  FIG. 9  before flowing in the direction of the blade  103  for a difference in thicknesses from the above-mentioned root portion  200  to the leading end portion of the blade  103 . Moreover, the molten resin that reached the root portion  200  by other courses is pressed into the flows  400   a  and  400   b  of the resin, and flows in a direction along the root portion  200  like the flows  400   c  to  400   f  of the resin illustrated in  FIG. 9 . 
     The molten resin is a fiber reinforced plastic, and includes a continuous fiber  300 . However, since the orientation direction of the continuous fiber  300  is parallel to the flow of the resin, the orientation direction thereof is oriented in a direction along the root portion  200  by the above-mentioned flows  400   a  to  400   f  of the resin. There is concern that cracks may occur in the root portion  200  in the direction along the root portion  200  due to force applied to the root portion  200  when rotating the propeller fan  101 . However, when the occurrence direction of the cracks is equal to the orientation direction of the continuous fiber  300 , strength of the force applied to the root portion  200  is degraded. Thus, when rotating the propeller fan  101 , the blade  103  might break in the root portion  200  at a relatively low revolution number (for example, 2,500 rpm). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent No. 3928380 (pages 2 to 3, FIGS. 3 to 8) 
     SUMMARY 
     Technical Problem 
     The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a propeller fan in which a root portion of a blade does not break even if strength of the root portion of the blade is raised so as to rotate the root portion at a higher revolution number, and a manufacturing method thereof. 
     Solution To Problem 
     In order to solve the afore-mentioned problems, a propeller fan molded by injection molding using a resin material containing a continuous fiber includes, a hub having an end surface wall and a peripheral wall, and a plurality of blades on an outer periphery of the hub. The propeller fan is molded by providing a plurality of injection positions for injecting the resin material containing the continuous fiber in a part of the end surface wall corresponding to a root portion of one of the blades of the hub. A flow direction of the resin material containing the continuous fiber is regulated by the flow of the resin material from the injection positions adjacent to each other, and is in a direction perpendicular to a width direction of the root portion of the blade. 
     The plurality of injection positions is dispersed and placed in a circumferential direction around a rotation center of the propeller fan. The plurality of injection positions is dispersed and placed on the same circumference around the rotation center of the propeller fan. 
     In order to solve the afore-mentioned problems, a method of manufacturing a propeller fan includes molding the propeller fan containing a hub having an end surface wall and a peripheral wall, and a plurality of blades on an outer periphery of the hub, and using a metal mold containing a cavity and a runner connected to the cavity via a gate and serving as an injection passage of a molten resin having a continuous fiber, by injecting the molten resin into the cavity through the runner. The plurality of gates is set at a part of the end surface wall corresponding to a root portion of the blade of the propeller fan in the cavity. 
     Advantageous Effects of Invention 
     According to the propeller fan and the manufacturing method thereof of the present invention, a plurality of gates is set into a metal mold so that a plurality of injection positions is included for one blade, and the propeller fan is manufactured by the injection molding. Accordingly, the molten resin flows in a direction perpendicular to the width direction of the root portion in the root portion of the blade, and an orientation direction of a continuous fiber contained in the molten resin is also perpendicular to the width direction of the root portion. Thus, it is possible to provide a propeller fan in which strength of the root portion of the blade is improved, and durability is further increased. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a perspective view of a propeller fan manufactured by a manufacturing method according to the present invention. 
         FIG. 1B  is a view taken in a direction of an arrow A of the propeller fan in  FIG. 1A . 
         FIG. 2  is a view that illustrates a state of a root portion of a blade of the propeller fan according to the manufacturing method of the present invention. 
         FIG. 3  is a perspective view of the propeller fan manufactured by the manufacturing method of the related art. 
         FIG. 4  is a cross-sectional view that illustrates an injection molding state of the propeller fan according to the manufacturing method of the related art. 
         FIG. 5  is a general view of an injection molding machine. 
         FIG. 6  is a view that illustrates an injection molding state of a metal mold. 
         FIG. 7  is a view that illustrates a mold opening state of the metal mold. 
         FIG. 8  is a view that illustrates a mold release state of a molded article from the metal mold. 
         FIG. 9  is a view that illustrates a state of the root portion of the blade of the propeller fan according to the manufacturing method of the related art. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described in detail based on the accompanying drawings. Furthermore, in the embodiment, a propeller fan provided in an outdoor unit of an air conditioner will be described as an example. Furthermore, the present invention is not limited to the embodiment mentioned below and can be variously modified within a scope that does not depart from the gist of the present invention. 
     EXAMPLE 
       FIG. 1A  is a perspective view of a propeller fan manufactured by a manufacturing method related to the present invention, and  FIG. 1B  is a view taken in a direction of an arrow A of the propeller fan in  FIG. 1A . A propeller fan  1  is formed, using a fiber reinforced plastic (FRP) in which a thermoplastic resin such as an acryl resin and a polystyrene resin is mixed with a continuous fiber (length of 0.2 to 0.5 mm) having a needle-like shape and a strip-like shape such as a glass fiber, a carbon fiber and talc at a predetermined ratio (for example, 10 to 40 weight %), through the injection molding by setting molding conditions such as an injection pressure and a metal mold temperature to predetermined values. Furthermore, the continuous fiber is an additive for improving strength of the propeller fan  1 , and may be oriented approximately parallel to a flow direction of the thermoplastic resin becoming to a molten state at the time of the injection molding. 
     As illustrated in  FIG. 1A , the propeller fan  1  has a peripheral wall  5  and an end surface wall  6 . A hub  2  which is approximately cylindrical with a bottom provided with a boss  4  for inserting a driving shaft of a motor, not illustrated, driving the propeller fan  1 , and three blades  3  having the same shape integrally attached onto the peripheral wall  5  of the hub  2  are included in the central portion of the end surface wall  6 . Furthermore, since the metal mold for manufacturing the propeller fan  1  is the same as a metal mold of the related art illustrated in  FIG. 4  except for a runner shape and an injection position described later, the detailed description thereof will be omitted. Furthermore, since the injection molding machine used for the injection molding of the propeller fan  1 , and the molding machining sequence using the metal mold are the same as the injection molding machine and the molding machining sequence of the related art illustrated in  FIGS. 5 to 8 , the detailed descriptions thereof will be omitted. 
     Between a stationary mold and an intermediate metal mold, not illustrated, of the metal mold for manufacturing the propeller fan  1 , a runner  8  for supplying the molten resin injected from the injection molding machine illustrated in  FIG. 1A  into a cavity is formed. The runner  8  has a three-pronged branched road shape corresponding to the number (three) of the blades  3  of the propeller fan  1 , a downstream end of each branched road is further branched into three branched roads, and a leading end thereof becomes a gate  9  (a center thereof is  9   a , a leading edge  3   c  side of the blade  3  is  9   b , and a trailing edge  3   d  side of the blade  3  is  9   c ). 
     A runner portion, not illustrated, formed by the molten resin supplied to the runner  8  is integrally connected to the propeller fan  1  by each gate  9 . As illustrated in  FIGS. 1A and 1B , the cutting trace with the runner portion, that is, a gate marks  7  serving as the injection positions of three locations with respect to one blade  3  remains on the end surface wall  6  of the propeller fan  1  after the molding. 
     As illustrated in  FIG. 1B , the gate marks  7  of three locations are located at positions (on a straight line L passing through a central portion of the root portion  20  in the width direction from a rotation center of the propeller fan  1 ) of each size H from a right end (the trailing edge  3   d  side) and a left end (the leading edge  3   c  side) of the root portion  20  with respect to the width direction of the root portion  20  in the peripheral wall  5  of the blade  3  so that a central gate mark  7   a  is placed on a circumference C around the rotation center of the propeller fan  1 , and left and right gate marks  7   b  and  7   c  are each placed at positions each rotated by 20° to the left side and the right side around the rotation center of the propeller fan  1  from the gate mark  7   a , and on the circumference C around the rotation center of the propeller fan  1 . Furthermore, the root portion  20  may be provided with a curve surface having a predetermined radius of curvature (for example, 3 mm) at the positive pressure surface side and/or the negative pressure surface side of the blade  3  so as to cause the molten resin to easily flow, and so as to increase strength. 
     Furthermore, as illustrated in  FIG. 1B , since the blade  3  is configured so that an angle between the adjacent blades  3  is placed at an interval of 120° around the rotation center of the propeller fan  1 , the gate marks  7  ( 7   a ,  7   b  and  7   c ) of three locations corresponding to each blade  3  are also each placed at an interval of 120° as in the blade  3 . Furthermore, the respective gates  9   a ,  9   b  and  9   c  are provided in the metal mold so as to be located at positions each corresponding to the gate marks  7   a ,  7   b  and  7   c.    
     Next, effects of the propeller fan  1  manufactured by the manufacturing method related to the present invention will be described using  FIGS. 1A, 1B and 2 . As mentioned above, on the end surface wall  6  of the propeller fan  1 , three gates  9  are provided for one blade  3 . The gate  9  is a joining portion with a runner portion, not illustrated, and when performing the injection molding of the propeller fan  1 , the molten resin flows into the cavity of a metal mold, not illustrated, of the propeller fan  1  from the gate  9 . 
     In the manufacturing method of the propeller fan of the related art, as mentioned above using  FIGS. 3 and 9 , since there is one gate for each blade, the continuous fiber contained in the molten resin in the root portion of the blade is oriented parallel to the root portion, and thus the root portion might break at a relatively low revolution number (for example, 2500 rpm) due to strength of the root portion declining. 
     On the contrary, in the manufacturing method of the propeller fan of the present invention, since three gates  9  are provided for each blade  3 , as illustrated in  FIG. 2 , the molten resin flows toward the root portion  20  along the peripheral wall  5  (cavity corresponding thereto) from the gates  9  of the three locations in the same course as the flow of the resin indicated by reference numeral  40 . 
     Specifically, the molten resin that flowed in the cavity from the three gates  9  flows so as to radially spread from each gate  9 , and flows like the flows  40  ( 40   a  to  40   i ) of the resin illustrated in  FIG. 2 . Although the blade  3  is joined to the peripheral wall  5  of the hub  2  by the root portion  20 , the thickness from the root portion  20  to the leading end portion of the blade  3  becomes thinner toward the leading end portion of the blade  3  from the root portion  20 . 
     The molten resin that flowed from the gate  9  (the gate mark  7 ) and reached the root portion  20  tries to flow in a direction along the root portion  20  having a wide cross-sectional area before flowing in a direction of the blade  3  having a narrow cross-sectional area. However, since the molten resin that flowed into the cavity from the respective gates  9   a  to  9   c  (the gate marks  7   a  to  7   c ) and reached the root portion  20 , in order to reach the root portion  20  at almost the same timing, the flows  40   a  to  40   i  of the resin each regulate the flow direction thereof, and thus the flows  40   a  to  40   i  of the resin becomes directions perpendicular to the root portion  20 . 
     Since the molten resin is a fiber reinforced plastic, the molten resin contains a continuous fiber  30 . However, since the orientation direction of the continuous fiber  30  is parallel to the flow of the resin, as illustrated in  FIG. 2 , the continuous fiber  30  is oriented in a direction perpendicular to the width direction of the root portion  20  along the flow of the molten resin. Although there is concern that cracks may occur in the root portion  20  in a direction along the root portion  20  due to force applied to the root portion  20  when rotating the propeller fan  1 , in the present embodiment, the direction of the crack is perpendicular to the orientation direction of the continuous fiber  30 . Thus, strength of the force applied to the root portion  20  is improved, and even when rotating the propeller fan  1  at a higher revolution number (for example, 3500 rpm), the root portion  20  does not break. 
     Although a case of providing the three gates  9  has been described in the above-mentioned embodiment, the number of the gate may be two or greater than or equal to four. However, when describing a position of the corresponding gate mark, there is a need to disperse and place the plurality of gates on left and right sides on the boundary of the straight line L (the central portion of the root portion  20 ) of  FIG. 1B . Furthermore, a case has been described where three gates  9  are dispersed and placed on the same circumference around the rotation center of the propeller fan  1 . However, if another gate is not placed on the straight line that connects one gate (the gate mark corresponding thereto) with the rotation center, as illustrated in  FIG. 1B , for example, the gate mark  7   a  may be placed with a gate mark  7   d  located at a position close to the rotation center with respect to the gate mark  7   c , and the gate mark  7   b  may be placed with a gate mark  7   e  located at a position close to the rotation center with respect to the gate mark  7   d.    
     As mentioned above, according to the propeller fan and the manufacturing method thereof of the present invention, since a plurality of gates is set into the metal mold so as to include a plurality of injection positions in one blade, and the propeller fan is manufactured by the injection molding, the molten resin flows in a direction perpendicular to the width direction of the root portion in the root portion of the blade, and the orientation direction of the continuous fiber contained in the molten resin is also perpendicular to the width direction of the root portion. Thus, it is possible to provide a propeller fan in which strength of the root portion of the blade is improved, and durability is further improved. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  propeller fan 
               2  hub 
               3  blade 
               3   c  leading edge 
               3   d  trailing edge 
               4  boss 
               5  peripheral wall 
               6  end surface wall 
               7 ,  7   a  to  7   e  gate mark 
               8  runner portion 
               8   a  distribution portion 
               9 ,  9   a  to  9   c  gate 
               20  root portion 
               30  continuous fiber 
               40 ,  40   a  to  40   i  flow of the resin

Technology Classification (CPC): 5