Patent Publication Number: US-2007122277-A1

Title: Fan assembly for vacuum cleaner

Description:
REFERENCE TO RELATED APPLICATION  
      This application claims the benefit under 35 U.S.C. § 119(a) from Korean Patent Application No. 2005-114158 filed on Nov. 28, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a vacuum cleaner. More particularly, the present invention relates to a fan assembly for a vacuum cleaner.  
      1. Description of the Related Art  
      Generally, a vacuum cleaner is an apparatus that sucks contaminants with air by suction force, and then, separates and collects contaminants from the sucked air using a contaminants collecting apparatus. An example of the vacuum cleaner is shown in  FIG. 1 .  
      Referring to  FIG. 1 , the vacuum cleaner  1  includes a suction brush  2 , an extension pipe assembly  3 , and a main body  4 .  
      The suction brush  2  is provided with a suction port (not shown) at a bottom surface thereof, and sucks contaminants from a cleaning surface. The extension pipe assembly  3  connects the suction brush  2  with the main body  4  so as to form a pathway through which sucked contaminants are moved. The main body  4  has a contaminant collecting apparatus  6  and a fan assembly  7 . The contaminant collecting apparatus  6  separates contaminants from sucked air and collects the separated contaminants. The contaminant collecting apparatus  6  may be implemented by any of a general dust bag or a cyclone dust collecting apparatus or so on. The fan assembly  7  generates the suction force for sucking air and contaminants.  
      The fan assembly  7  includes a motor  9 , an impeller (not shown), and a diffuser  8 . The impeller is mounted on a rotation shaft of the motor  9 . The motor  9  rotates the impeller to generate suction force, sucking air and contaminants. The diffuser  8  guides air being discharged from the impeller to the motor  9  so that the air cools the motor  9  and then is discharged outside through an outlet  5  of the main body  4 .  
      However, the fan assembly  7  generates a loud noise because the impeller rotates at high speed inside the diffuser  8 . Especially, the impeller has a plurality of blades so that peak noises are generated at BPF (Blade Passing Frequency) and at integer multiply frequencies of the BPF. The peak noises are referred to as BPF noises. Here, the BPF presents the number of blades passing per second measured in cycles per second (Hz). BPF noises do not greatly affect the whole noise level of the vacuum cleaner, but they cause users to feel ill because they are high frequency noises with strong tones.  
     SUMMARY OF THE INVENTION  
      The present invention has been developed in order to overcome the above drawbacks and other problems associated with the conventional arrangement. An aspect of the present invention is to provide a fan assembly for a vacuum cleaner to reduce noise, especially BPF noises, generated by an impeller. The above aspect and/or other feature of the present invention can substantially be achieved by providing a fan assembly for a vacuum cleaner, which includes a motor; an impeller having a plurality of impeller blades, the impeller being rotated by the motor to suck air, and a diffuser disposed to wrap around an outer circumference of the impeller, the diffuser having a plurality of diffuser blades arranged in a predetermined interval. A ratio of an exit area of the diffuser to an entrance area of the diffuser is determined to reduce noise generated when the impeller rotates.  
      In one embodiment of the present invention, the ratio of an exit area of the diffuser to an entrance area of the diffuser satisfies a follow formula:  
       0.51   ≤     DI   DO     ≤   0.62       
 
      where DI is the entrance area of the diffuser, and DO is the exit area of the diffuser.  
      The diffuser is formed to satisfy the formula by controlling the number of the diffuser blades or an inclined angle of each entrance of the plurality of diffuser blades.  
      The fan assembly for the vacuum cleaner according to an embodiment of the present invention as described above can reduce the BPF noises while minimizing the decrease of suction force.  
      Furthermore, with the fan assembly for the vacuum cleaner according to an embodiment of the present invention, it is easy to control a ratio of the diffuser exit area to the diffuser entrance area by controlling the number of the diffuser blades or an inclined angle of an entrance of the diffuser blade.  
      Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
       FIG. 1  is a view illustrating a conventional vacuum cleaner,  
       FIG. 2  is a sectional view illustrating a fan assembly for a vacuum cleaner according to an embodiment of the present invention;  
       FIG. 3  is a perspective view illustrating an impeller of the fan assembly in  FIG. 2 ;  
       FIG. 4  is a perspective view illustrating a diffuser of the fan assembly in  FIG. 2 ;  
       FIG. 5  is a plain view illustrating the diffuser of  FIG. 4 ;  
       FIG. 6  is a partial perspective view illustrating a diffusing channel of the diffuser of  FIG. 5 ;  
       FIG. 7  is a partial plain view for explaining changes of a sectional area of an entrance of a diffusing channel according to changes of an inclined angle of an entrance of a diffuser blade;  
       FIG. 8  is a graph illustrating a relationship between suction force of a fan assembly and ratios of a diffuser exit area to a diffuser entrance area; and  
       FIG. 9  is a graph illustrating a relationship between BPF noises and ratios of a diffuser exit area to a diffuser entrance area. 
    
    
      Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures.  
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS  
      Hereinafter, certain exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.  
      The matters defined in the description, such as a detailed construction and elements thereof are provided to assist in a comprehensive understanding of the invention Thus, it is apparent that the present invention may be carried out without those defined matters. Also, well-known functions or constructions are omitted to provide a clear and concise description of exemplary embodiments of the present invention.  
      Referring to  FIG. 2 , a fan assembly  40  for a vacuum cleaner according to an embodiment of the present invention includes a motor  10 , an impeller  20 , and a diffuser  30 .  
      The motor  10  rotates the impeller  20 , and any of various types of motors, which are generally used in vacuum cleaners, may be used as the motor  10 . The motor  10 , in general, has a rotation speed range of 30,000˜36,000 rpm, and a capacity range of 1,000˜2,000W.  
      Referring to  FIG. 3 , the impeller  20  is rotated by the motor  10  so as to generate suction force sucking air, and includes an upper plate  22 , a lower plate  21 , and a plurality of impeller blades  23 .  
      The upper plate  22  is formed in a substantially disk shape, and an air inlet  25  is formed at a center of the upper plate  22 . The lower plate  21  is formed a disk shape corresponding to the upper plate  22  and a center of the lower plate  21  is fixed to a motor shaft  11 . The plurality of impeller blades  23  is radially arranged at a predetermined interval between the upper plate  22  and the lower plate  21 . Each of the plurality of impeller blades  23  is bent with a predetermined curvature. Therefore, air entering through the air inlet  25  is discharged outside the impeller  20  through a plurality of air channels formed by the plurality of impeller blades  23 .  
      The diffuser  30  guides air discharged from the impeller  20  to the motor  10 . Referring to  FIGS. 4 and 5 , the diffuser  30  includes a diffuser plate  32 , a plurality of diffuser blades  31 , and a plurality of guiding blades  33 .  
      The diffuser plate  32  is formed in a substantially disk shape and is disposed between the impeller  20  and the motor  10 . The diffuser plate  32  has on a center thereof a boring hole  34  through which the motor shaft  11  passes. The plurality of diffuser blades  31  is disposed on an upper surface of the diffuser plate  32  to wrap around the impeller  20 . In other words, the diffuser blades  31  are radially disposed at a predetermined interval on an outer circumference of the diffuser plate  32 . A space between neighboring diffuser blades  31  forms a diffusing channel  36 . An impeller-side end  31   b  of each of the diffuser blades  31  forms an entrance of the diffusing channel  36 . Each of the plurality of diffuser blades  31  is bent with a predetermined curvature as shown in  FIG. 5 . The plurality of guiding blades  33  is radially disposed at a predetermined interval on an under surface of the diffuser plate  32 . A space between neighboring  2  guiding blades  33  forms a guiding channel  37 . The plurality of guiding blades  33  is formed to guide air entered from the plurality of diffusing channels  36  to the motor  10 . A plurality of openings  35  is formed at each outer end of the diffusing channels  36  on the diffuser plate  32  to fluidly communicate the diffusing channels  36  and the guiding channels  37 . Each of the openings  35  covered by an upper cover  15  forms an exit of each of the diffusing channels  36 . Therefore, air passing through each of the diffusing channels  36  flows to each of the guiding channels  37  through the plurality of openings  35 , and then, is guided to the motor  10 .  
      The upper cover  15  covers upper sides of both of the impeller  20  and the diffuser  30  to form a space in which the impeller  20  rotates. The upper cover  15  prevents air discharged from the impeller  20  from leaking out a top end of the diffuser  30 .  
      The inventors have determined that noise, especially BPF noises, generated by the impeller  20  rotating inside the plurality of diffuser blades  31  may be decreased while minimizing a decrease of suction force of the fan assembly  40  if the diffuser  30  has a ratio of a diffuser exit area to a diffuser entrance area within a predetermined range. Then, the inventors have, through experimentation, determined the predetermined range of the ratio of the diffuser exit area to the diffuser entrance area that can decrease the BPF noises of the impeller  20  while minimizing the decrease of suction force of the fan assembly  40 . Here, the diffuser exit area means an exit area of the diffuser  30 , and the diffuser entrance area means an entrance area of the diffuser  30 .  
      At this time, the diffuser entrance area is computed by multiplying an entrance cross sectional area of one diffusing channel  36  by the number of the diffuser blades  31 . The entrance cross sectional area of one diffusing channel  36 , referring  FIG. 6 , is computed by multiplying a height H of the diffuser blade  31  by a length B of a vertical line from an entrance end  31   b  of the diffuser blade  31  to next diffuser blade  31 ′. In other words, the entrance cross sectional area of one diffusing channel  36  is computed by Formula 1:
 
 CI=B×H   (1)
 
      where, CI is the entrance cross sectional area of one diffusing channel  36 , B is a length of a vertical line from an entrance end of the diffuser blade  31  to next diffuser blade  31 ′, and H is a height of the diffuser blade  31 .  
      Then, the diffuser entrance area is computed by Formula 2:
 
 DI=CI×N   (2)
 
      where, DI is the diffuser entrance area, CI is the entrance cross sectional area of one diffusing channel  36 , and N is the number of the diffuser blades  31 .  
      Furthermore, the diffuser exit area is computed by multiplying an opening area forming an exit of the diffusing channel  36  by the number of the diffuser blades  31 . Referring  FIG. 5  and  7 , the opening  35  of the diffusing channel  36  is formed at an outer circumference of the diffuser plate  32  forming a bottom surface of the diffusing channel  36 .  
      Therefore, the diffuser exit area is computed by Formula 3:
 
 DO=CO×N   (3)
 
      where, DO is the diffuser exit area, CO is the opening area of the diffusing channel  36 , and N is the number of the diffuser blades  31 .  
      Here, the ratio of the diffuser exit area to the diffuser entrance area is defined as Formula 4:  
             R   =     DI   DO             (   4   )             
 
      where, R is the ratio of the diffuser exit area to the diffuser entrance area, and DI is the diffuser entrance area, and DO is the diffuser exit area.  
      The inventors have measured the changes of suction force and BPF noises corresponding to the changes of the ratio of the diffuser exit area to the diffuser entrance area of the fan assembly  40  for the vacuum cleaner. The results are shown in Table 1, and  FIGS. 8 and 9 .  
                           TABLE 1                          Area of       Peak value of           Diffuser (mm 2 )       BPF noises (dB)   Suction                                             Entrance   Exit   R   1 st     2 nd     3 rd     Total H   force (W)               330   728   0.45   64.4   68.7   55.1   65.5   549       374   728   0.51   65.9   68.1   55.5   65.5   620       435   801   0.54   66.3   68.2   59.6   65.9   643       435   697   0.62   70.9   71.2   59.8   69.5   646       519   815   0.64   74.8   68.1   63.7   71.1   657       612   728   0.84   72.7   72.5   66.2   71.3   662                  
 
      In one embodiment a motor  10  of the fan assembly  40  has a capacity of 1800 W, and operates approximately at 31,000 rpm, 230 V, and 50 Hz. In the impeller  20 , a maximum height is 17.4 mm, a minimum height is 8 mm, an inner diameter, namely, a diameter of the air inlet  25  is 35 mm, and an outer diameter is 109.6 mm (see  FIG. 3 ). In the diffuser  30 , a height is 23.5 mm, a height of the diffuser blade  31  is 10 mm, and an outer diameter is 130 mm (see  FIG. 4 ).  
      A curve shown in  FIG. 8 , and four straight lines  1 ,  2 ,  3 , and  4  shown in  FIG. 9  illustrate the data of Table 1. In  FIG. 9 , straight lines  1 ,  2 ,  3 , and  4  indicate a first, a second, a third, and a total BPF noise, respectively.  
      Referring to  FIG. 8 , suction force of the fan assembly  40  rises substantially in proportion to a rise in the ratio of the diffuser exit area to the diffuser entrance area (hereinafter, referred to as a diffuser area ratio), and then, when the diffuser area ratio becomes over a predetermined value, the suction force decreases. Therefore, referring to  FIG. 8 , a maximum suction force of the fan assembly according to this embodiment is approximately 675 W. When the diffuser area ratio is 0.51, the suction force is approximately 600 W. As a result, with the objective of minimizing the decrease in suction force of the fan assembly  40  (the rate of decrease is below 10%), it is preferable that the diffuser area ratio is approximately 0.51 land over.  
      Referring to  FIG. 9 , as the diffuser area ratio decreases, a first, a second, a third, and a total BPF noise  1 ,  2 ,  3 , and  4  decrease. Also, as the diffuser area ratio increases, a fit a second, a third and a total BPF noise  1 ,  2 ,  3 , and  4  increase. As a result, with the objective of keeping a first, a second, a third, and a total BPF noise  1 ,  2 ,  3 , and  4  of the fan assembly  40  approximately 70 dB and below, it is preferable that the diffuser area ratio is approximately 0.62 and below.  
      As a result described above, with the objective of minimizing the decrease of suction force and keeping a first, a second, a third, and a total BPF noise  1 ,  2 ,  3 , and  4  of the fan assembly 70 dB and below, it is preferable that the diffuser  30  is formed to have a range of the diffuser area ratio of 0.51˜0.62.  
      Any one or both of the diffuser exit area and the diffuser entrance area as described above may be controlled so that the diffuser  30  has the substantially same size as the conventional diffuser and the diffuser area ratio may come within the range described above.  
      For an example, the diffuser exit area may be constant and the diffuser entrance area is controlled so that the ratio of the diffuser exit area to the diffuser entrance area is controlled. For this purpose, below methods can be used.  
      First, controlling of the number of the diffuser blades  31  causes the diffuser entrance area to be controlled. At this time, when the number of the diffuser blades  31  increases, a gap between neighboring  2  diffuser blades  31  narrows thereby the diffuser area ratio decreasing. As a result, the diffuser entrance area with respect to the diffuser exit area decreases so that the diffuser area ratio decreases. Contrarily, when the number of the diffuser blades  31  decreases, a gap between neighboring  2  diffuser blades  31  widens thereby the diffuser area ratio increasing.  
      Second, controlling of an inclined angle θ of the entrance of the diffuser blade  31  causes the diffuser entrance area to be controlled. Here, the inclined angle θ of the entrance of the diffuser blade  31  means an angle that an entrance end of the diffuser blade  31  is inclined. Accordingly, the maximum inclined angle of the entrance of the diffuser blade  31  is 90°. When the inclined angle θ of the entrance of the diffuser blade  31  is 90°, the diffuser entrance area is minimum. As the inclined angle θ of the entrance of the diffuser blade  31  decreases, the diffuser entrance area increases. These are because the diffuser entrance area is defined as an area of a section  38  of the diffusing channel  36  at a point P where a top end  31   a  of the diffuser blade  31  meets the inclined entrance end  31   b  of the diffuser blade  31  (see  FIG. 6 ).  
      Because the diffusing channel  36  is formed to diffuse from the entrance to the exit, a gap between neighboring  2  diffuser blades  31  and  31 ′ becomes gradually wider from the entrance to the exit.  FIG. 7  is a plain view for explaining changes of gap dimension between neighboring  2  diffuser blades  31  and  31 ′ corresponding to changes of the inclined angle θ of the entrance of the diffuser blade  31 . P is a first point where the top end  31   a  of the diffuser blade  31  meets the inclined entrance end  31   b  of the diffuser blade  31  when the inclined angle of the entrance of the diffuser blade is θ as shown in  FIG. 6 , B is the gap dimension between the 2 diffuser blades  31  and  31 ′ of this case. P 1  is a second point where the top end  31   a  of the diffuser blade  31  meets the inclined entrance end  31   b  of the diffuser blade  31  when the inclined angle of the entrance of the diffuser blade  31  is more than θ, B 1  is the gap dimension between the 2 diffuser blades  31  and  31 ′ of this case. P 2  is a third point where the top end  31   a  of the diffuser blade  31  meets the inclined entrance end  31   b  of the diffuser blade  31  when the inclined angle of the entrance of the diffuser blade  31  is less than θ, B 2  is the gap dimension between the 2 diffuser blades  31  and  31 ′ of this case. At this time, because a gap between neighboring 2 diffuser blades  31  and  31 ′ becomes gradually wider from the entrance of the diffusing channel  36  to the exit thereof, B satisfies B 1 &lt;B&lt;B 2 . Accordingly, as the inclined angle θ of the entrance of the diffuser blade  31  decreases, the diffuser entrance area increases gradually. As a result, controlling of the inclined angle θ of the entrance of the diffuser blade  31  can cause the ratio of the diffuser exit area to the diffuser entrance area to be controlled  
      Hereinafter, operation of the fan assembly  40  for the vacuum cleaner with above-described structure will be explained in detail with reference to FIGS.  2  to  4 .  
      Upon rotating the motor  10 , the impeller  20  fixed on the motor shaft  11  is rotated. As the impeller  20  rotates, air is sucked in through the air inlet  25 , and then, is discharged to the diffuser  30  through the exit of the impeller  20 . The air discharged from the impeller  20  is entered into each entrance of the plurality of diffusing channels  36 , and then, passes through each of the diffusing channels  36  thereby being discharged to each of the guiding channels  37  through the opening  35  that is an exit of the diffusing channel  36 . At this time, the ratio of the diffuser exit area to the diffuser entrance area is a range of 0.51˜0.62 so that the BPF noises generated by impeller rotation are minimized. The air entered into the guiding channels  37  passes through the motor  10 , and then, is discharged outside the main body through an air outlet.  
      While the embodiments of the present invention have been described, additional variations and modifications of the embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims shall be construed to include both the above embodiments and all such variations and modifications that fall within the spirit and scope of the invention.