Patent Publication Number: US-2007098571-A1

Title: Centrifugal fan

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a electrically operated centrifugal fan used in air blasting.  
      2. Description of the Related Art  
      Conventionally, an impeller with a plurality of blades arranged in the circumferential direction with the rotating axis as the center is arranged in the centrifugal fan for taking air in the axis direction and exhausting air in the radial direction, and various modifications are made on the impeller to achieve a quieter sound, to improve air volume property, and to suppress lowering in performance involved in the temperature rise of the motor.  
      For example, a multi-blade fan in which an inducer section is coupled to the inner side of the blade is disclosed. Furthermore, an impeller is disclosed in which the fan efficiency is enhanced compared to the sirocco fan of general shape of the same size by having the shape of the blade as a combination of a turbo fan and a sirocco fan.  
      The technique is disclosed in which the impeller configuration includes an air current guiding means of a plate shape perpendicular to the rotating shaft on the inner side of the blade, and which air current guiding means is arranged on the movement path of the air current to change the pattern of the air current thereby reducing the noise, and a technique is disclosed of forming an opening communicating to the air hole between the blades at the lower part of the impeller thereby reducing the noise or the current value of when the impeller rotates.  
      In the centrifugal fan where the impeller including a cup part for accommodating a motor at the central part is used, turbulent flow of air tends to produce near the outer surface of the cup part, and the noise of the centrifugal fan increases when such turbulent flow moves away from the cup part towards the outer side and flows into the blades arranged in the circumferential direction. Furthermore, since air is less likely to be supplied to the inside of the cup part, the heat generated at the stator accommodated in the cup part tends to remain therein, and thus becomes essential to suppress the temperature rise of the stator.  
     BRIEF SUMMARY OF THE INVENTION  
      In the present invention, the production of the turbulent flow caused by the air flowing near the outer surface of the cup part is efficiently suppressed, and the noise of the centrifugal fan is reduced by arranging the auxiliary blades. Air is also supplied to the stator by the auxiliary blades, and thus the temperature rise of the stator is also suppressed.  
      The present invention relates to a centrifugal fan comprising: a cup part of substantially bottomed cylindrical shape with a cylindrical yoke portion having a predetermined center axis as center; a field magnet fixed on an inner surface of the cup part; an impeller, including a blade assembly connected to the cup part and arranged radially in an annular region on the outer side of the cup part, taking in air from the bottom side of the cup part and exhausting air in a direction away from the center axis when rotating with the cup part, the blade assembly including: a plurality of main blades arranged along the periphery of the impeller; and a plurality of auxiliary blades connected to the outer surface of the cup part and directly or indirectly connected with the plurality of main blades at an opening side of the cup part between the outer surface of the cup part and the plurality of main blades; a housing including a side wall part for covering the periphery of the impeller, a base part for covering the opening side of the cup part, and a cover part formed with an air intake port facing the bottom of the cup part, a width of a flow path between the side wall part and the impeller gradually widening towards an air exhaust port; a bearing mechanism for rotatably supporting the cup part with respect to the base part with the center axis as the center; and a stator, fixed to the base part and having at least one part positioned in the cup part, for generating a torque having the center axis as the center between the field magnet.  
      Other features, elements, steps, advantages and characteristics of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a cross sectional view showing a configuration of a centrifugal fan of one embodiment of the present invention;  
       FIG. 2  is a plan view showing the centrifugal fan;  
       FIG. 3  is a perspective view showing an impeller;  
       FIG. 4  is a plan view showing another example of the impeller;  
       FIG. 5  is a plan view showing another example of the impeller;  
       FIG. 6  is a cross sectional view showing another example of the impeller;  
       FIG. 7  is a cross sectional view showing another example of the impeller;  
       FIG. 8  is a plan view showing another example of the impeller;  
       FIG. 9  is a plan view showing another example of the impeller;  
       FIG. 10  is a cross sectional view showing another example of an auxiliary blade;  
       FIG. 11  is a cross sectional view showing another example of an auxiliary blade;  
       FIG. 12  is a cross sectional view showing another example of an auxiliary blade;  
       FIG. 13  is a cross sectional view showing another example of an auxiliary blade;  
       FIG. 14  is a cross sectional view showing another example of an auxiliary blade;  
       FIG. 15  is a cross sectional view showing another example of an auxiliary blade;  
       FIG. 16  is a cross sectional view showing another example of an auxiliary blade; and  
       FIG. 17  is a cross sectional view showing another example of an auxiliary blade. 
    
    
     DETAILED DESCRIPTION OF INVENTION  
      The centrifugal fan according to the present invention will now be described for each embodiment with reference to the drawings. The present invention is not limited to the examples described below.  
       FIG. 1  is a view showing a configuration of a centrifugal fan  1  according to one embodiment of the present invention, and shows a longitudinal cross section cut along a plane including a center axis J 1 .  FIG. 2  is a plan view showing the centrifugal fan  1 . The illustration of the end portions of a housing  10  on both left and right sides are omitted in  FIG. 1 , and a state in which a cover part (denoted with reference character  111  in  FIG. 1 ) of the upper surface of the housing  10  is removed is shown in  FIG. 2 . As shown in  FIGS. 1 and 2 , the centrifugal fan  1  includes an impeller  2  for generating the flow of air by rotating, and a motor  3 , connected to the impeller  2 , for rotating the impeller  2  about a predetermined center axis J 1 , where the impeller  2  and the motor  3  are housed in the housing  10 . The centrifugal fan  1  is used as a power operated fan for air cooling the electrical products and electronic equipments.  
      As shown in  FIG. 1 , the housing  10  includes a cover part  111  formed with an air intake port  12 , and a base part  112  attached with a stator section  31  to be hereinafter described, and further includes a side wall part  113  that covers the outer periphery of the impeller  2 , as shown in  FIG. 2 . The housing  10  is assembled by attaching the cover part  111  to a housing main body  11  including the base part  112  and the side wall part  113  shown in  FIG. 2 , and a flow path of the air is formed (i.e., flow of air generated by rotation of impeller  2  is adjusted and fed by housing  10 ) as the housing  10  surrounds the impeller  2 . The width of the flow path between the side wall part  113  and the impeller  2  has a shape that gradually widens towards an air exhaust port  13  (see  FIG. 2 ), and the space between the base part  112  and the side wall part  113  in the housing  10  is blocked.  
      The motor  3  is an outer rotor type motor, as shown in  FIG. 1 , and includes a stator section  31  which is a fixed assembly, and a rotor section  32  which is a rotating assembly, where the rotor section  32  is rotatably supported with respect to the stator section  31  with the center axis J 1  as the center by a bearing mechanism to be hereinafter described. The following description is made with the rotor section  32  side as the upper side and the stator section  31  side as the lower side along the center axis J 1  for the sake of convenience, but the center axis J 1  does not necessarily need to coincide with the direction of gravitational force.  
      The stator section  31  is fixed to a base part  112  which is the lower surface of the housing  10 , and a bearing holding part  311  of a substantially cylindrical shape having the center axis J 1  as the center and projecting upward (i.e., rotor section  32  side) from the base part  112  is attached at a cylindrical region formed at the center part of the base part  112 . On the inner side of the bearing holding section  311 , ball bearings  312 ,  313  serving as bearing mechanism are arranged on the upper and lower sections in the center axis J 1  direction and a pre-load spring  314  is arranged on the lower side of the ball bearing  313 .  
      The stator section  31  further includes a stator  315  fixed on the periphery of the bearing holding part  311  (i.e., fixed to the base part  112  at the periphery of the bearing holding part  311 ), and a circuit substrate  316  electrically connected to the stator  315  between the stator  315  and the base part  112  and mounted with electronic components for current control to the stator  315 .  
      The rotor section  32  includes a cup part  321  of a substantially bottomed cylindrical shape having the center axis J 1  as the center and having an opening  3211  facing downward (i.e., opening  3211  facing the base part  112 ), a substantially cylindrical field magnet  322  fixed to the inner surface of the cup part  321  and facing the stator  315 , and a shaft  323  projecting downward from the bottom of the cup part  321  (i.e., region of substantially circular disc shape at the upper end of the cup part  321 ).  
      The shaft  323  is attached to the cup part  321  by being press fit and fixed to the bush  324  fixed at the bottom of the cup part  321 , and inserted to the bearing holding part  311  and rotatably supported by the ball bearings  312 ,  313 . An engagement member  3231  for engaging the spring  314  is attached to the vicinity of the lower end of the shaft  323 , where the shaft  323  and the ball bearings  312 ,  313  are held at the appropriate positions when preload is applied to the ball bearing  313  by the spring  314 .  
      In the centrifugal fan  1 , the ball bearings  312 ,  313  serve as the bearing mechanism for rotatably supporting the cup part  321  with respect to the base part  112  with the center axis J 1  as the center. When the drive current supplied to the stator  315  via the circuit substrate  316  is controlled and a torque (i.e. rotational force) having the center axis J 1  as the center is generated between the stator  315  and the field magnet  322 , the shaft  323  as well as the impeller  2  including the blade assembly  22  connected to the cup part  321  rotate with the cup part  321  with the center axis J 1  as the center. The shaft  323  may be directly attached to the cup part  321  without the bush  324  in between.  
      In the centrifugal fan  1 , the opening  3211  side of the cup part  321  is covered by the base part  112 , and the inner side of the cup part  321  is arranged with a yoke member  3212  of a substantially bottomed cylindrical shape including a cylindrical yoke portion  321   a  having the center axis J 1  as the center. The yoke member  3212  is made of metal having magnetism, the field magnet  322  is attached to the inner surface of the yoke part  321   a , and the bush  324  is attached to the center of the bottom thereof. The outer side of the cup part  321  is arranged with an outer side cup part  3213  of substantially bottomed cylindrical shape made of resin, which is integrally molded with the entire impeller  2 , and is press fit and fixed with the yoke member  3212 . The configuration of the cup part  321  is not limited to the configuration of  FIG. 1 , and for example, the yoke member  3212  may be a cylindrical shape, the outer side cup part  3213  may be connected to the shaft  323  or the bush  324 , or the outer side cup part  3213  may be omitted and the impeller  2  may be directly connected to the opening of the yoke member  3212 .  
       FIG. 3  is a perspective view showing the impeller  2  and the outer side cup part  3213  integrally molded with the impeller  2 . The impeller  2  includes the blade assembly  22  arranged radially in the annular region (having center axis J 1  as center) on the outer side of the cup part  321 , as shown in FIGS.  1  to  3 . In the centrifugal fan  1 , the air is taken in from the air intake port  12  facing the upper side (i.e., bottom side of the cup part  321 ) of the impeller  2  and the air is exhausted in a direction away from the center axis J 1 , when the impeller  2  rotates with the cup part  321 , whereby the air is introduced to the air exhaust port  13  along the side wall part  113  as described above.  
      The blade assembly  22  includes a plurality of main blades  221  arranged along the periphery of the impeller  2  at a distance from the outer surface  321   b  of the cup part  321  (outer cup part  3213 ), and a plurality of auxiliary blades  222  arranged between the cup part  321  and the plurality of main blades  221  along the outer surface  321   b  of the cup part  321 . In  FIG. 2 , the distal end of the main blade  221  is hidden except for one section, but each of the plurality of main blades  221  are formed as forward blades inclined in the rotating direction  51  of the impeller  2  while being directed to the outer side. The plurality of main blades  221  have the lower ends on the base part  112  side perpendicular to the center axis J 1  and coupled by an annular plate  23  having the center axis J 1  as the center, and the upper ends coupled by an annular coupling part  24 , which are integrally molded. In  FIG. 2 , one section of the coupling part  24  is omitted to show the shape of the main blade  221  (same as in FIGS.  4  to  7 ).  
      Each of the plurality of auxiliary blades  222  is a backward blade inclined to the side opposite the rotating direction  51  of the impeller  2  while being directed to the outer side as shown in  FIG. 2 , and is connected to the outer surface  321   b  of the outer side cup part  3213  of the cup part  321 , and also has the outermost region of the auxiliary blades  222  connected to the region on the inner side of the annular plate  23 . The auxiliary blade  222  is directly connected to one main blade  221  for every two main blades  221  on the base part  112  side, and each of the plurality of auxiliary blades  222  is continued to one of the plurality of main blades  221 , as shown in  FIGS. 1 and 2 . Thus, the region between the main blade  221  and the auxiliary blade  222  functions as a rib, and the auxiliary blades  222  itself also function as the rib, whereby the rigidity of the impeller  2  is enhanced.  
      In particular, when the impeller  2  is molded by resin, the molding (resin injection, take out from die etc.) of the impeller  2  is facilitated by connecting the main blade  221  and the auxiliary blade  222  using the annular plate  23  on the base part  112  side. If problems do not arise in terms of rigidity and molding of the impeller  2 , the main blade  221  and the auxiliary blade  222  may obviously be separated, and the plurality of auxiliary blades  222  may be indirectly connected to the plurality of main blades  221  by way of the annular plate  23 . The auxiliary blade  222  may be connected to the outer surface of the yoke member  3212  (see  FIG. 1 ) through insert molding and the like.  
      In the blade assembly  22 , the main blade  221  and the auxiliary blade  222  are preferably continued in terms of smoothly flowing the air in from the auxiliary blade  222  to the main blade  221 . On the other hand, the flow-in efficiency of the air to the main blade  221  enhances if an obstacle is not arranged between the cup part  321  and the main blade  221 . The main blade  221  and the auxiliary blade  222  are designed so as to be continued in the centrifugal fan  1  and the width in the center axis J 1  direction of the impeller  2  between the main blade  221  and the auxiliary blade  222  (i.e., boundary) is made small, and thus the turbulent flow suppressing effect by the auxiliary blade  222  is obtained, and the influence of the auxiliary blade  222  on the property (e.g., static pressure-air volume property) of the centrifugal fan  1  caused by the air flow generated at the main blade  221  is reduced. A specific preferable designing condition includes having the width (denoted with reference character W in  FIG. 1 ) in the center axis J 1  direction of the impeller  2  between the plurality of main blades  221  and the plurality of auxiliary blades  222  to be less than or equal to ⅓ of the length (denoted with reference character L) in the center axis J 1  direction of the plurality of main blades  221 . Since the turbulent flow region becomes wider at the vicinity of the lower part of the outer surface by the air flowing along the outer surface of the cup part  321 , the edge  2222  on the side away from the base part  112  of the auxiliary blade  222  is inclined towards the base part  112  while extending towards the outer side from the outer surface  321   b  of the cup part  321 , and the width of the auxiliary blade  222  with respect to the center axis J 1  direction is gradually increased from the peripheral side of the impeller  2  towards the cup part  321  in the centrifugal fan  1 , as shown in  FIG. 1 . As a result, the production of turbulent flow is efficiently suppressed without lowering the fan property. The width in the center axis J 1  direction of the impeller  2  between the main blade  221  and the auxiliary blade  222  is a minimum width in the up and down direction between one main blade  221  and one auxiliary blade  222  when the main blade  221  and the auxiliary blade  222  are directly connected (i.e., width in the up and down direction of a rib shaped region the annular region when focusing only on a substantially concave region of annular shape having the center axis J 1  as the center between the plurality of main blades  221  and the plurality of auxiliary blades  222 ), and is the thickness of the annular plate  23  when the main blade  221  and the auxiliary blade  222  are indirectly connected by way of the annular plate  23 .  
      A plurality of openings  25  passing through with respect to the center axis J 1  direction between the plurality of auxiliary blades  222  are further arranged in the impeller  2 , as shown in FIGS.  1  to  3 . As shown in FIG.  1 , the opening ends of the base part  112  side of the plurality of openings  25  include an edge  2221  on the base part  112  side of the plurality of auxiliary blades  222 , and the region  251  (i.e., region on the inner side of the annular plate  23 ) on the plurality of main blades  221  side of the opening end is brought closer to the base part  112  than the region  252  (i.e., region on the opening  3211  side of the cup part  321 ) on the center axis J 1  side.  
      Therefore, the opening end inclines towards a gap between the stator  315  and the circuit substrate  316 . In order to incline the opening end, the edge  2221  on the base part  112  side of the auxiliary blade  222  is inclined towards the base part  112  while extending towards the outer side from the opening  3211  of the cup part  321 .  
      The configuration of the centrifugal fan  1  has been described, where a plurality of auxiliary blades connected to the outer surface  321   b  and directly connected to the main blade  221  on the base part  112  side (may be indirectly connected by way of the annular plate  23 ) are arranged between the outer surface  321   b  of the cup part  321  and the main blade  221  in the centrifugal fan  1 , whereby the air flowing near the outer surface  321   b  of the cup part  321  is taken in by the auxiliary blade  222  and thus the air is smoothly introduced into the main blade  221  without stagnating. As a result, the production of the turbulent flow at the vicinity of the outer surface  321   b  of the cup part  321  is suppressed, the air is smoothly flowed to the main blade  221 , and noise of the centrifugal fan  1  is reduced.  
      In the centrifugal fan  1 , heat generated in the stator  315  tends to remain when the motor  3  rotates since at least one part of the stator  315  is positioned in the cup part  321 , but since the opening  25  passing through with respect to the center axis J 1  direction is arranged between two adjacent auxiliary blades  222 , some air flowing along the outer surface  321   b  of the cup part  321  flows into the inside of the cup part  321  (region where air flows out from the cup part  321  is also formed on the air exhaust port  13  side), and furthermore, the air is efficiently sent to the cup part  321  as the air current is produced in the vicinity of the opening  25  by the auxiliary blade  222 , whereby the temperature rise of the stator  315  is suppressed by supplying air to the stator  315 . Although it depends on the designing condition, if the temperature of the stator  315  is about 115° C. in the impeller in which the opening  25  is not formed, the temperature lowers to about 47° C. by arranging the opening  25 .  
      The supply efficiency of the air flowing towards the stator  315  can be enhanced, and cooling of the circuit substrate  316  can be performed by inclining the opening ends on the base part  112  side of the plurality of openings  25  toward the stator  315  or the circuit substrate  316  (in particular, toward the gap between the stator  315  and the circuit substrate  316 ).  
      Various other shapes for the main blade  221  and the auxiliary blade  222  of the impeller  2  will now be described. FIGS.  4  to  9  are views showing other examples of the impeller. Each auxiliary blade  222  is a backward blade in the impeller  2  shown in  FIG. 2 , but the shape of the auxiliary blade is not limited to the backward blade, and each auxiliary blade  222   a  may be a forward blade as in the impeller  2   a  shown in  FIG. 4 , or each auxiliary blade  222   b  may be a radial blade extending linearly in the radial direction from the cup part  321  as in the impeller  2   b  shown in  FIG. 5 . The main blade  221  of the impeller  2   a  and the impeller  2   b  is a forward blade, similar to in the impeller  2 .  
      A comparison experiment in the noise value of the impellers  2 ,  2   a ,  2   b  and the impeller (not shown) arranged only with the main blade  221  was performed, which result was 54.1 dB(A), 55.2 dB(A), 54.8 dB(A), and 55.8 dB(A). Therefore, the noise value is apparently reduced the most by having the auxiliary blade  222  as the backward blade when the main blade  221  is formed as the forward blade to enhance the static pressure of the fan. The noise is still reduced by arranging the auxiliary blade even if the auxiliary blade is not the backward blade.  
      The main blade is not limited to the forward blade as in the impeller  2  of  FIG. 2 , and for example, may be the main blade  221   a , which is the radial blade, as in the impeller  2   c  shown in  FIG. 6  or the main blade  221   b , which is the backward blade, as in the impeller  2   d  shown in  FIG. 7 .  
      In the blade assembly  22  of the impeller  2 , one main blade  221  and one auxiliary blade  222  may be connected for every three or more main blades  221 , or the auxiliary blade  222  may be continuously formed to all the main blades  221  as in the impeller  2   e  shown in  FIG. 8 . The shape of the auxiliary blade is not limited to a flat plate shape, and each auxiliary blade  222   c  may be curved while extending to the peripheral side of the impeller  2   f  from the cup part  321  when looking at the impeller  2   f  from the upper side, as shown in  FIG. 9 .  
      Furthermore, the connecting range of the auxiliary blade  222  and the cup part  321  is not only the range from the middle to the lower end of the outer surface  321   b  of the cup part  321  with respect to the center axis J 1  direction, as shown in  FIG. 1 , and may be the range from the upper end to the lower end of the cup part  321  as shown in  FIG. 10 , the range from the middle to the middle of the outer surface  321   b  with respect to the center axis J 1  direction, as shown in  FIG. 11 , or may be the range from the upper end to lower than the lower end of the cup part  321 , as shown in  FIG. 12 . Furthermore, the edges  2221 ,  2222  of the lower side and the upper side of the auxiliary blade  222  may be curved, as shown in  FIG. 13 , or the edge  2222  of the upper side and the edge  2223  parallel to the center axis J 1  may be continued, as shown in  FIGS. 14 and 15 .  
      Therefore, the shape, number, and size of the blade may be changed in variety of ways, and the shape etc. of the main blade  221  and the auxiliary blade  222  are determined based on the equipment on which the centrifugal fan  1  is mounted, the air volume property that is required etc. The production of turbulent flow at the vicinity of the outer surface  321   b  of the cup part  321  is suppressed and the noise is reduced for any type of main blade  221  and auxiliary blade  222 .  
      The embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and various modifications are possible.  
      For example, the shape of the edge  2222  on the upper side of the auxiliary blade  222  may be a shape in which a step is formed in the middle, as shown in  FIG. 16 . Alternatively, the edges  2221  of the plurality of auxiliary blades  222   d  may be extended horizontally from the opening  3211  of the cup part  321  to the outer side so that the shape of the plurality of auxiliary blades  222   d  is substantially triangular, and the outermost region of the plurality of auxiliary blades  222   d  may be connected only to the region on the inner side of the annular plate  23 , as shown in  FIG. 17 . In this case as well, the production of the turbulent flow at the outer surface  321   b  of the cup part  321  is suppressed and the noise is reduced, and moreover, the temperature rise of the stator  315  is suppressed since the opening  25  is arranged between two adjacent auxiliary blades  222   d  and the air is supplied to the inside of the cup part  321  by the action of the auxiliary blade  222 d and the opening  25 .  
      The entire stator  315  is substantially accommodated in the cup part  321  in the above embodiment, but only one part of the stator  315  may be positioned in the cup part  321  when the stator  315  is arranged in the concave part formed around the center axis J 1  of the base part  112 . Furthermore, a sleeve bearing and the like may be used for the bearing mechanism other than the ball bearing.  
      The annular plate  23  does not need to be a plate perpendicular to the center axis J 1 , and the cross section at the plane including the center axis J 1  may be inclined from the direction perpendicular to the center axis J 1  as in the inclined surface of a frustum of circular cone. Moreover, air is supplied from the opening  25  to the stator  315  in the embodiment, but the opening  25  does not need to be arranged if the opening  25  does not need to be arranged due to reasons that the temperature rise of the stator  315  is within the tolerable range.  
      While the present invention has been described with respect to preferred embodiments, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically set out and described above. Accordingly, it is intended by the appended claims to cover all modifications of the present invention which fall within the true spirit and scope of the invention.