Patent Publication Number: US-7214033-B2

Title: Blower fan

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a blower fan, and more particularly, to a blower fan that is designed to improve the blowing efficiency by reducing airflow loss and reduce the noise generated when blades rotate. 
   2. Description of the Related Art 
   Generally, a blower fan is a device for forcedly producing air current. Particularly, a turbo fan that is one of the blower fans is designed to induce air in an axial direction, allow the induced air to make a turn by 90° and forcedly blow the same in a radial direction thereof. 
   The blower fan includes a shroud formed on an air inducing side, a hub formed on an air discharge side, and a plurality of blades fixed between the shroud and the hub. To improve the productivity of the blower fan in a molding process and increase an airflow rate, the blower fan is designed having an inner diameter less than an outer diameter of the hub. In addition, the blade is designed having an outer diameter greater than that of the hub. The hub formed on the air discharge side functions to guide airflow such that air can effectively discharged, changing its flow direction by the blades. For the production convenience, an outer end of the blade is formed perpendicular to the hub and shroud. 
   When the hub is designed having the outer diameter less than that of the blade, airflow of the air passing the blower fan cannot be sufficiently guided. That is, although the air current is forcedly formed by the blades, there may be a non-guide area where the airflow cannot be guided by the hub. Particularly, eddy current is increased in the non-guide area. This causes the noise to be increased. Furthermore, since the air guided and discharged by the hub conflicts with the air guided and discharged by the blades, intensive turbulence is created to further increase the noise. 
   In addition, the eddy current deteriorates the operating efficiency of the fan, thereby increasing the power consumption. The eddy current also causes the airflow loss. Therefore, when the fan is employed to an air conditioner, the eddy current causes the reduction in an amount of cool air. Therefore, to increase the amount of cool air, an RPM of the blower fan should be increased. This causes the increase of the power consumption. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a blower fan that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
   An object of the present invention is to provide a blower fan that can reduce the turbulence and the noise, which may be created at an air discharge side, by optimizing the designs of blades and a hub. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
   To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a blower fan including: a shroud; a hub for guiding airflow being discharged; and a plurality of blades disposed between the shroud and the hub, wherein a first outer diameter of a first portion, which is close to the hub, of the blade is different from a second outer diameter of a second portion, which is close to the shroud, of the blade, for forcedly blowing an air through a rotation of the blades. 
   In an aspect of the present invention, there is provided a blower fan including: a shroud; a hub disposed facing the shroud at a predetermined distance from the shroud; and a plurality of blades disposed between the shroud and the hub, wherein, when a first outer diameter of a first portion, which is close to the hub, of the blade is D1, a second outer diameter of a second portion, which is close to the shroud, of the blade is D2, and an outer diameter of the hub is D0, 0.5&lt;(D2−D1)/(D2−D0)&lt;0.9 is satisfied. 
   In another aspect of the present invention, there is provided a blower fan including: a shroud formed on an air intake side; a hub formed on an air discharge side to guide airflow being discharged; and a plurality of blades disposed between the shroud and the hub, wherein an outer end of each of the blades is inclined as it goes from a shroud side to a hub side, for reducing airflow noise. 
   It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
   According to the present invention, by the optimized design of the blades, eddy current that may be caused by the flow interference between the hub and the ends of the blades can be suppressed, while the airflow noise and the power consumption rate can be reduced. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
       FIG. 1  is a perspective view of a blower fan according to an embodiment of the present invention; 
       FIG. 2  is a sectional view taken along line I–I′ of  FIG. 1 ; 
       FIG. 3  is a view illustrating internal airflow of a blower fan according to the present invention; 
       FIG. 4  is a graph illustrating a noise characteristic with respect to a variation of an outer diameter of each blade of a blower fan according to the present invention; 
       FIG. 5  is a graph illustrating a frequency range of airflow noise generated by a blower fan; and 
       FIG. 6  is a sectional view of a wall mount air conditioner where a flower fan of the present invention is applied. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIG. 1  shows a blower fan according to an embodiment of the present invention. 
   The inventive blower fan includes a shroud  122  formed on an air intake side, a hub  124  formed on an air discharge side, and a plurality of blades  126  formed between the shroud  122  and the hub  124 . 
   Formed on a front surface of the shroud  122  is a bell mouth  130  (see  FIG. 6 ) for effectively guiding the airflow of intake air. 
   In this embodiment, although a turbo fan is exampled as the inventive blower fan, the concepts of the present invention are not limited to the turbo fan. The concepts of the present invention can be applied to a variety of other types of blower fan. 
   As a feature of the present invention, each of the blades  126  is designed such that an outer diameter of each blade  126  with respect to the rotation of the blades is gradually reduced as it goes from the shroud  122  to the hub  124 . That is, the outer diameter of the blade  126 , which is closer to the shroud  122 , is greater than the outer diameter of the blade  126 , which is closer to hub  124 , whereby the interference and confliction between the air discharged from the blades  126  and the air discharged from the hub  124  can be reduced to thereby reduce airflow noise and turbulence. 
   Describing in more detail, the hub  124  is formed in a truncated-funnel shape and disposed facing the shroud  122 . A central portion of the hub  124  is elevated toward the shroud  122  so as to reduce air resistance and convert the airflow direction into a circumferential direction of the fan. A motor (not shown) is installed on an inner-central portion of the hub  124 . The hub  124  is provided at the central portion with a shaft insertion portion in which a rotational shaft (not shown) of the motor is inserted. 
   Upper and lower longitudinal sides of the blade  126  are gently curved. The upper longitudinal side, which is close to the shroud  122 , extends up to an outer circumference of the shroud  122 , being longer than the lower longitudinal side, which is close to the hub  124 . A length of the lower longitudinal side of the blade  126  is preferably less than that of an outer diameter of the hub  124 . That is, as described above, each of the blades  126  is designed such that the outer diameter of each blade  126  is gradually reduced as it goes from the shroud side to the hub side. 
   The operation of the above-described blower fan will be described hereinafter. 
   Referring to  FIGS. 1 and 6 , air is induced into the blower fan while being effectively guided by the bell mouth  130 . The induced air changes its flow direction by 90° by the blades  126 . The air is then discharged out of the fan while being guided by the hub  124  and the shroud  122 . That is, the air is induced in a vertical direction of the blower fan and discharged in a central direction of the blower fan after being changed in its flow direction by 90°. Since the outer circumferential portion defined by the blades  126  is gradually inclined inward as it goes from an upper end to a lower end, i.e., from the shroud side to the hub side, a little interference between the air discharged from lower ends of the blades and the air discharged from the hub  124  is incurred. 
   At this point, the inclination of the circumferential portion may cause the reduction in a flow rate. Therefore, to compensate for this, the blades  126  are designed extending toward the central portion of the hub  124  as far as possible. That is, the hub  124  is provided at a central portion with an elevated portion  125  on which the motor is mounted. The blades  126  extend up to an outer circumference of the elevated portion. Preferably, a length of each blade  126  is greater than a half of a radius of the hub  124  to effectively compensate for a loss of the flow rate. In order to design the blades as described above, a width of the blade  126  is designed being gently reduced as it goes toward the central portion of the hub  124 . An outer end of the blade is gently formed. 
     FIG. 2  shows a sectional view taken along line I–I′ of  FIG. 1 . 
   Referring to  FIG. 2 , there are shown the shroud  122 , the hub  124  and the blade  126 . 
   An outer diameter of the blade  126  is varied as it goes from the shroud side to the hub side. That is, an outer diameter D1 of a portion of the blade  125 , which is close to the hub  124 , is less than that D2 of a portion of the blade  124 , which is close to the shroud  122 . At this point, the variation ratio (ΔD-ratio) of the outer diameter can be defined as Equation 1 below.
 
Δ D -ratio=( D 2 −D 1)/( D 2 −D 0)  (Equation 1)
 
   where, D0 is a diameter of the hub  124 . 
   It is preferable that the variation ratio is in a range of 50–90%. The diameters D0, D1 and D2 are defined with reference to a center of the blower fan. The reason why the variation ratio is preferably set in the range of 50–90% is to reduce the airflow interference between ends of the hub  124  and the blade  126  as well as to reduce eddy current that may be generated at an end of the blade  126  proximal to the hub  124 . As the generation of the eddy current is reduced, the noise can be alleviated. 
     FIG. 3  shows an internal airflow state of a blower fan according to the present invention. 
   Referring to  FIG. 3 , arrows indicate streamlines of the air. From the drawing, it can be note that the streamlines at an air discharge side are gently formed. This shows that the airflow interference and the noise caused thereby are reduced. 
     FIG. 4  shows a graph illustrating a noise characteristic with respect to the variation rate of the outer diameter of the blade of a blower fan according to the present invention. 
   As shown in the graph, the nose is lowest when the variation rate is about 72%. That is, it is noted that, when the variation rate is increased or decreased from the 72%, the noise is increased. Therefore, when the variation rate of the outer diameter of the blade  126  is set in a rage of 50–90%, it can be expected that the nose can be effectively alleviated. The variation rate can be adjusted by varying an outer diameter of a portion, which is close to the hub  124 , of the blade  126  in a state where an outer diameter of a portion, which is close to the shroud  122 , of the blade  126  is fixed to be identical to that of the shroud  122 . 
     FIG. 5  shows a graph illustrating a frequency range of airflow noise generated by a blower fan. 
   In the graph, a curve  10  shows an amount of noise generated in a case where an end of each blade is vertically formed, and a curve  20  shows an amount of noise generate in a case where a variation rate of an outer diameter of the blade is 72%. As shown by the curves  10  and  20 , the noise is alleviated in a frequency range of 1000–2000 Hz. 
   The blower fan can be applied to a wall mount air conditioner, an outdoor unit/indoor unit integrated air conditioner, or a ceiling embedded air conditioner to provide noise alleviation, reduction in power consumption, and increase in flow rate. 
     FIG. 6  shows a wall mount air conditioner where a flower fan of the present invention is applied. 
   Referring to  FIG. 6 , a wall mount air conditioner  100  includes a case  180  provided at a center with an intake hole  160 , a blower fan  120  installed in the case  180  to forcedly generate air current into the case  180 , a motor  150  for driving the blower fan  120 , a bell mouth  130  for guiding airflow induced into the blower fan  120 , and an evaporator  140  for generating cool air by heat-exchanging the indoor air, which is induced into the case by the blower fan  120 , with a refrigerant, the cool air being discharged to the indoor side by the blower fan  120  through discharge holes  170  formed on upper and lower portions of the case  180 . 
   The operation of the above-described wall mount air conditioner will be described hereinafter. 
   The refrigerant that is phase-changed into a liquid state is directed into the evaporator  140  and the indoor air is induced into the air conditioner  100  through the intake hole  160  by the blower fan  120 . The indoor air introduced into the air conditioner is changed into the cool air by being heat-exchanged with the refrigerant flowing along the evaporator  140  and is then discharged to the indoor side through the discharge holes  170  formed on the case  180  by the blower fan  120 . At this point, by the above-described inventive structure of the blower fan, the noise generating by the airflow can be remarkably reduced, thereby providing agreeable environment. 
   According to the present invention, by the optimized design of the blades, eddy current that may be caused by the flow interference between the hub and the ends of the blades can be suppressed, while the airflow noise and the power consumption rate can be reduced. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.