Patent Publication Number: US-2007116576-A1

Title: Fan blade unit in a centrifugal fan

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention is related to a fan blade unit in a centrifugal fan and particularly to fan structure for a centrifugal fan capable of dissipating heat.  
      2. Brief Description of the Related Art  
      Due to the semiconductor and information industry developing rapidly in the recent years, products gradually approaches a trend with high performance, high frequency, high speed, lightness and thinness gradually and the chips is designed being minimized gradually in size. As a result, intensity of heat generation provided by the electronic components is getting higher and it easily leads to the electronic component running unstably. Thus, if heat is capable of being removed properly is one of key points for successful product development.  
      Less heat was generated from the computer in the past so that requirement of heat dissipation system was less strict. The current computer provides faster operation speed with more powerful functions and in order to solve problem of heat dissipation for the electronic component and bring the heat generated by the electronic component outside the host unit, usually, some heat dissipation devices such as the thermosyphon, the heat pipe and the heat sink are mounted in the host unit of the computer to assist removing heat from the electronic component and the entire computer system. Nevertheless, the heat dissipation system composed of a fan associated with the heat sink is more acceptable by the users while the economic effect is considered with the heat dissipation function. The fan blade wheel is driven by a prime mover to transform electric power to mechanical energy and energy transmitted with the fan blade wheel forces the air to flow for increasing coefficient of convection in a space. Flow movement resulted from pressure change and velocity increase carries heat from the heat sink directly to attain purpose of heat dissipation. Hence, in order to increase amount of heat removal in a limited space, design of fan becomes a vital subject of research.  
      Conventionally, there are two kinds of fans, the axial flow fan and the centrifugal fan. The centrifugal fan induces the air flowing radially or perpendicular to the shaft. When the blade wheel rotates, the air inters along the center of the blade wheel and energy is obtained due to centrifugal force of the air itself. The air flows outward radially along the fan blades such that configuration of the respective fan blade significantly affects performance of the entire fan. Hence, the respective fan blade provides three different types: (a) back bending type; (b) radial type; and (c) front bending type. The air pressure is higher for the centrifugal fan such that the centrifugal fan is used in a system with greater resistance. Further, the flow field of the centrifugal fan is extremely complicated due to the air turning into radial direction via rotation of the blade wheel. Under this circumference, air in the fan wheel occurs phenomena such as recirculation, reversed flow and separation. Hence, how to improve these problems for promoting effect of heat removal is a subject worth us to investigate.  
      Referring to  FIGS. 1 and 2 , a conventional centrifugal fan provides a blade wheel, which has a hub  11  and a plurality of fan blades  12  surrounding the hub  11  and extending outward from the hub  11 . The fan blades  12  are radially disposed at the periphery of the hub  11  and the fan blades are changed at the radial parts thereof such as the respective fan blade  12  near the hub being flat as shown in  FIG. 1  or the respective fan blade being bending radially from the end at the hub to the end at the outer side as shown in  FIG. 2 .  
      Referring to  FIGS. 3 and 4 , the fan being joined in a case is illustrated. The case includes an upper case member  13  and a lower case member  14 . The upper case member  13  has a first hole.  131  at the surface thereof and the lower case member  14  has a second hole  141  at the surface thereof. The upper case member  13  is integrally joined to the lower case member  14  to define a spiral flow passage  15  to receive the hub  11  and the fan blades  12 . An outlet  16  is formed with the upper case member  13  and the lower case member  14  at a lateral side thereof respectively. When the hub  11  rotates with the fan blades  12  to suck fluid, the fluid enters via the first hole  131  and the second hole  141  and rotational force urges the fluid ejecting outward along the fan blades  12  before blowing toward along the spiral flow passage  15 .  
      The preceding fan blades  12  is straight in the axial direction and air pressure at the first hole  131  is supposed to be equal to that at the second hole  141 . However, the problem in the practical application resides in that due to conditions of flowing in at the first hole  131  is different from those at the second hole  141 , for instance, a plurality of support ribs being disposed at the second hole  141 , fluid is unable to discharge via the outlet  16  completely once the resistance is slightly higher and then the fluid left in the fan flows reversely outward via the first hole  131  or the second hole  141  to decrease flow rate of incoming fluid through the first hole  131  or the second hole  141 . Further, louder noise is generated at the time of the reversed flow impacting the incoming flow.  
     SUMMARY OF THE INVENTION  
      A main object of the present invention is to provide a fan blade unit in a centrifugal fan in which each of the fan blades extends at least a baffle part from at least an end edge thereof to prevent from the fluid being reversed flow.  
      In order to achieve the preceding object, the fan blade unit in a centrifugal fan according to the present invention includes a hub and a plurality of fan blades connected to the periphery of the hub and each of the fan blades at least has an end edge with at least a baffle part being joined to the end edge and extending toward another one of the fan blades next to it. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The detail structure, the applied principle, the function and the effectiveness of the present invention can be more fully understood with reference to the following description and accompanying drawings, in which:  
       FIG. 1  is a perspective view of the first type of the conventional centrifugal fan;  
       FIG. 2  is a perspective view of the second type of the conventional centrifugal fan;  
       FIG. 3  is a disassembled perspective view of the conventional centrifugal fan being received in an upper and a lower case member parts;  
       FIG. 4  is an assembled perspective view of the conventional centrifugal fan being received in an upper and a lower case member parts;  
       FIG. 5  is a sectional view of  FIG. 4 ;  
       FIG. 6  is a perspective view of the preferred embodiment of a centrifugal fan according to the present invention;  
       FIG. 7  is a sectional view of the fan blade on the centrifugal fan according to the present invention;  
       FIG. 8  is a disassembled perspective view illustrating the centrifugal fan being joined with an upper and lower cover parts according to the present invention;  
       FIG. 9  is an assembled perspective view illustrating the centrifugal fan being joined with an upper and lower cover parts according to the present invention;  
       FIG. 10  is a sectional view illustrating the centrifugal fan being joined with an upper and lower cover parts according to the present invention;  
       FIG. 11  is a sectional view illustrating another type of the fan blade on the centrifugal fan according to the present invention;  
       FIG. 12  is a sectional view illustrating a further type of the fan blade on the centrifugal fan according to the present invention;  
       FIG. 13  is a sectional view illustrating a still further type of the fan blade on the centrifugal fan according to the present invention;  
       FIG. 14  is a sectional view illustrating a still further type of the fan blade on the centrifugal fan according to the present invention;  
       FIG. 15  is a sectional view illustrating a still further type of the fan blade on the centrifugal fan according to the present invention; and  
       FIG. 16  is a sectional view illustrating a still further type of the fan blade on the centrifugal fan according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIGS. 6 and 7 , the first preferred embodiment of a fan blade unit in a centrifugal fan includes a hub  21  and a plurality of fan blades  22  surrounding the hub  21 . Each of the fan blades  22  has a blade root  221  attached to the circumference of the hub  21  with two lateral sides thereof providing a first end edge  222  and a second end edge  223  opposite to first end edge  222 . At least a baffle part  224  is provided at one of the end edges of each fan blade  22  and it is preferable that the baffle part  224  is disposed at the first end edge  222  and extends toward another fan blade next to it along the same direction respectively with the width of the baffle part  224  being less than the space between any two of the fan blades. Further, an angle is formed between the baffle part  224  and the fan blade  22 , that is, the baffle part  224  is perpendicular to the fan blade  22  or slant to the fan blade  22 .  
      Referring to  FIGS. 8, 9  and  10 , the fan blade unit of the present invention is joined between an upper case member  23  and a lower case member  24 . The upper case member  23  has a first hole  231  at the surface thereof and the lower case member  24  has a second hole  241  at the surface thereof. The upper case member  23  and the lower case member  24  are assembled as a single piece to define a spiral flow passage  25  to receive the hub  21  and the fan blades  22  and the upper and the lower case members  23 ,  24  form an outlet  26  at a lateral side thereof to communicate with the spiral flow passage  25 . When the hub  21  rotates with the fan blades  22  to suck fluid, the fluid enters the case members  23 ,  24  via the first hole  231  and the second hole  241  and passes through passages between the fan blades  22  before the fluid is radiated outward along the fan blades by means of the dynamic force resulting from rotation. Then, the fluid is blown toward the outlet  26  along the spiral flow passage  25 . When the fluid moves into passages between the fan blades  22  via the first hole  231  and the second hole  241  and resistance of the outlet  26  increases, part of the sucked fluid, which tends to flow reversely, is resisted to flow backward by the baffle part  224  and ejected outward radially along the fan blades  22 . In this way, reversed flow is reduced to increase the sucked flow rate largely and noise resulting from the inflow impacting the reverse flow is diminished.  
      Besides, the angle between the baffle part  224  and the fan blades  22  at the first end edge  222  can be changed to an inclined angle instead of a right angle as shown in  FIG. 11 . The baffle part  224  can extend outward to cover another fan blade next to it or extend outward to exceed position of another fan blade next to it as shown in  FIG. 12  for providing a function of shading. The baffle part  224  can be arranged at the second end edge  223  as shown in  FIG. 13 . The baffle part  224  can be provided at the first end edge  222  and the second end edge  224  respectively as shown in  FIG. 14 . The baffle part  224  at the second end edge  224  extends in a direction different from the baffle part  224  at the first end edge  222  as shown in  FIG. 15 . The baffle part  224  either at the first end edge  222  or at the second end edge  224  extends in two opposite directions as shown in  FIG. 16 . In addition, the baffle part  224  at the first end edge  222  provides either the same width as or different from the baffle part  224  at the second end edge  224 .  
      While the invention has been described with referencing to preferred embodiments thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention, which is defined by the appended claims.