Patent Publication Number: US-11022141-B2

Title: Fan assembly

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fan assembly. 
     2. Description of the Related Art 
     A cooling fan that discharges air for cooling the inside of a refrigerator is installed in the refrigerator. For example, Japanese Laid-open Patent Application Publication 2004-101088 exists. Japanese Laid-open Patent Application Publication 2004-101088 discloses a refrigerator in which thought is put into the disposition of the cooling fan and the form of a fan casing in which the cooling fan is installed, and noise caused by the existence of a space whose pressure is locally high is reduced. 
     However, the sizes of fan assemblies in which a fan is installed vary for refrigerators, and in recent market trends, there is a further increasing demand for a reduction in noise. 
     An object of the present invention is to provide a new structure that can reduce noise in a refrigerator by using a flow straightening member provided in a fan assembly in which a fan is installed. 
     SUMMARY OF THE INVENTION 
     An exemplary embodiment of the present invention is a fan assembly for a refrigerator interior and includes a lower housing where a fan that rotates around a rotation axis as a center is installed, the rotation axis extending in an up-down direction; an upper housing that includes an inlet that sucks air from the refrigerator interior; and a side housing that covers a surrounding portion of the fan, wherein any one of the upper housing, the lower housing, and the side housing includes a flow straightening member that straightens a flow of air that is discharged from the fan, and wherein any one of the upper housing, the lower housing, and the side housing includes a discharge port. 
     According to the exemplary embodiment of the present disclosure, noise is reduced by increasing the blowing efficiency in the inside of the fan assembly as a result of designing the flow straightening member as appropriate in the fan assembly. 
     The above and other elements, features, steps, characteristics and advantages of the present discloser will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual view of a refrigerator including a fan assembly of a first embodiment. 
         FIG. 2  is a cross sectional view of the fan assembly of the first embodiment. 
         FIG. 3  is a vertical sectional view of the fan assembly of the first embodiment. 
         FIG. 4  is an enlarged view of the cross sectional view of the fan assembly of the first embodiment. 
         FIG. 5  is a cross sectional view of a fan assembly of a second embodiment. 
         FIG. 6  is a cross sectional view of a fan assembly of a third embodiment. 
         FIG. 7  is a cross sectional view of a fan assembly of a fourth embodiment. 
         FIG. 8  is a sectional view along A-A′ according to the fan assembly of the fourth embodiment. 
         FIG. 9  is a partial enlarged view of the vicinity of discharge ports of the fan assembly of the fourth embodiment. 
         FIG. 10  is a cross sectional view of a fan assembly of a fifth embodiment. 
         FIG. 11  shows air volume characteristics of the fan assembly of the fifth embodiment. 
         FIG. 12  is a cross sectional view of a fan assembly of a sixth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the present description, a direction parallel to a rotation axis of a fan is simply called “axial direction”, a radial direction around the rotation axis as a center is simply called “radial direction”, and a peripheral direction around the rotation axis as the center is simply called “peripheral direction”. A direction in which a fan  21  is disposed is called “upstream side”, and a direction in which air is discharged from the fan  21  is called “downstream side”. However, the definitions of these directions are not intended to limit the orientation of a fan assembly that is installed in a refrigerator. 
       FIG. 1  is a conceptual view of a refrigerator  1  including a fan assembly  20  according to an exemplary embodiment of embodiments. The refrigerator  1  includes a refrigerator interior  10 , the fan assembly  20 , and a cooling device  12 . Air that has been cooled by the cooling device  12  passes through refrigerator interior through holes  11  via the fan assembly  20 , and is guided to the refrigerator interior  10 . 
       FIG. 2  is a cross sectional view of the fan assembly  20  of an exemplary first embodiment of the present disclosure.  FIG. 3  is a vertical sectional view of the fan assembly  20  of the exemplary first embodiment of the present disclosure. In the embodiment, the fan assembly  20  includes the fan  21  that rotates around a rotation axis J as a center, and a plurality of discharge ports  22 . The fan  21  is desirably a so-called centrifugal blower, but may be, for example, an axial flow fan or a diagonal flow fan. 
     The fan assembly  20  includes a lower housing  3  where the fan  21  that rotates around the rotation axis J as the center is installed, the rotation axis J extending in an up-down direction; an upper housing  4  that includes an inlet  41  that sucks air into the fan assembly  20  from the refrigerator interior  10 ; and a side housing  5  that covers a surround portion of the fan  21 . 
     Any one of the upper housing  4 , the lower housing  3 , and the side housing  5  includes a flow straightening member that straightens the flow of air that is discharged from the fan  21 . Any one of the upper housing  4 , the lower housing  3 , and the side housing  5  includes the plurality of discharge ports  22  and a plurality of ventilation ports  28  ( 281 ,  282 ,  283 ) that discharge air to the outside of the fan assembly  20 . The flow straightening member includes a first flow straightening portion that is provided at the lower housing  3 , a second flow straightening portion that is provided at the upper housing  4 , and a third flow straightening portion that is provided at the side housing  5 . However, the lower housing  3 , the upper housing  4 , and the side housing  5  need not be separate members. For example, the lower housing  3  and the side housing  5  may partly be a single member, or the side housing  5  and the upper housing  4  may partly be a single member. 
     The first flow straightening portion includes at least one of a plurality of first flow straightening plates  23 , a coupling portion  24 , and a guiding portion  25 . The plurality of first flow straightening plates  23 , the coupling portion  24 , and the guiding portion  25  are members extending in the axial direction from the lower housing  3 . The third flow straightening portion includes a partition plate  26  and guide walls  27 . The partition plate  26  and the guide walls  27  are parts of the side housing  5 . The plurality of first flow straightening plates  23 , the coupling portion  24 , the guiding portion  25 , the partition plate  26 , and the guide walls  27  desirably couple the lower housing  3  and the upper housing  4 . 
     However, part of the first flow straightening portion may be provided at the upper housing  4  or the side housing  5 . For example, any one of the plurality of flow straightening plates  23 , the coupling portion  24 , and the guiding portion  25  may be provided at the upper housing  4 , and any one of the partition plate  26  and the guide walls  27  may be provided at the lower housing  3  or the upper housing  4 . The plurality of discharge ports  22  may be provided in any of the lower housing  3 , the upper housing  4 , and the side housing  5 . In  FIG. 2 , the discharge ports  22  include a plurality of first discharge ports  221  that are disposed above the fan  21 , and a second discharge port  222  that is disposed below the fan  21 . 
     The second flow straightening portion includes at least one of a first curved portion, a second curved portion, and a connecting portion, which are described later. 
     The first flow straightening portion is in detail described below. First, in  FIG. 2 , the plurality of first flow straightening plates  23 , the coupling portion  24 , the plurality of first discharge ports  221 , and the plurality of first ventilation ports  281  are formed above the fan  21 . At a portion between the fan  21  and the plurality of first discharge ports  221 , the plurality of first flow straightening plates  23  extend from the upstream side, where the fan  21  is disposed, towards the downstream side, where the plurality of first discharge ports  221  are disposed. The plurality of first flow straightening plates  23  each include an upstream side end portion  231  and a downstream side end portion  232 . The plurality of first flow straightening plates  23  that are adjacent to each other are spaced apart from each other with gaps therebetween. Gaps between the upstream side end portions  232  that are adjacent to each other are smaller than gaps between the downstream side end portions  231  that are adjacent to each other. That is, the widths of the gaps between the first flow straightening plates  23  that are adjacent to each other increase towards the downstream side, where the plurality of first discharge ports  221  are disposed, from the upstream side, where the fan  21  is disposed. 
     This causes the air volume characteristics to improve, the blowing efficiency in the inside of the fan assembly  20  to increase, and the cooling efficiency of the refrigerator  1  to increase. Since the widths of the gaps between the first flow straightening plates  23  that are adjacent to each other become larger, it is possible to suppress an increase in the pressures in the gaps and also to reduce noise. 
     At a portion between the fan  21  and the plurality of first flow straightening plates  23 , the plurality of first ventilation ports  281  are formed. The plurality of first ventilation ports  281  are through holes provided in the lower housing  3  and extending therethrough in the axial direction. Part of air discharged from the fan  21  passes through the plurality of first ventilation ports  281 , and is discharged to the outside of the fan assembly  20 . 
     The plurality of first discharge ports  221  are through holes having a longitudinal direction in the axial direction. Part of the air discharged from the fan  21  passes through the gaps between the plurality of first flow straightening plates  23  that are adjacent to each other and gaps between the plurality of first flow straightening plates  23  and the coupling portion  24  (described later), and flows towards the plurality of first discharge ports  221 , and is discharged to the outside of the fan assembly  20  via the plurality of first discharge ports  221 . 
     In  FIG. 2 , the plurality of second ventilation ports  282  and the plurality of third ventilation ports  283  are formed below the fan  21 . The plurality of second ventilation ports  282  and the plurality of third ventilation ports  283  are through holes that are formed in the lower housing  3  and that extend therethrough in the axial direction. Part of the air discharged from the fan  21  passes through the plurality of second ventilation ports  282  and the third ventilation ports  283 , and is discharged to the outside of the fan assembly  20 . 
     An inner surface of the fan assembly  20  includes a plurality of guide walls  27 . The plurality of guide walls  27  include at least one of a first guide wall  271 , a second guide wall  272 , a third guide wall  273 , and a fourth guide wall  274 . In  FIG. 2 , the first guide wall  271  is disposed in a region on the upper right of the fan  21 . Part of the air discharged from the fan  21  passes between the rightmost first flow straightening plate  23  in  FIG. 2  among the plurality of first flow straightening plates  23  and the plurality of first guide walls  271 , and flows towards the plurality of first discharge ports  221 . 
     In this way, when part of the air moving towards the plurality of first discharge ports  221  from the fan  21  flows along the first guide wall  271 , the occurrence of turbulence is reduced, so that the blowing efficiency is increased, and noise that is produced in the inside of the fan assembly  20  is also reduced. 
     In  FIG. 2 , the guiding portion  25 , the second guide wall  272 , and the second discharge port  222  are formed in a region on the right of the fan  21 . Part of the air discharged from the fan  21  flows towards the second guide wall  272 , is guided along the second guide wall  272  to the second discharge port  222 , and is discharged to the outside of the fan assembly  20  from the second discharge port  222 . 
     The guiding portion  25  is provided between the fan  21  and the second guide wall  272 . Part of the air discharged from the fan  21  flows along a surface of the guiding portion  25  that is near the fan  21 , and is guided towards the second discharge port  222 . Therefore, compared to a case in which the guiding portion  25  is not provided, the air discharged from the fan  21  can be more efficiently guided towards the second discharge port  222 . Part of the air discharged from the fan  21  is guided to the second discharge port  222  without the occurrence of turbulence, so that the blowing efficiency in the inside of the fan assembly  20  is increased and noise that is produced in the inside of the fan assembly  20  is reduced. 
     In  FIG. 2 , the partition plate  26  is provided below the guiding portion  25 . The partition plate  26  separates air that is guided to the second discharge port  222  by the guiding portion  25  and the second guide wall  272  and air that flows towards the plurality of third ventilation ports  283  that are adjacent to the partition plate  26 . That is, by disposing the partition plate  26 , a channel for the air moving towards the second discharge port  222  and a channel for the air moving towards the third ventilation ports  283  are formed. 
     The third guide wall  273  is provided in a region on the left of the fan  21 . Part of the air discharged from the fan  21  flows along the third guide wall  273 , passes between the leftmost first flow straightening plate  23  in  FIG. 2  among the plurality of first flow straightening plates  23  and the third guide wall  273 , and is guided to the plurality of first discharge ports  221 . Therefore, the blowing efficiency in the inside of the fan assembly  20  is increased and noise that is produced in the inside of the fan assembly  20  is reduced. 
     In  FIG. 2 , the fourth guide wall  274  and the plurality of ventilation ports  282  that are adjacent to the fourth guide wall  274  are formed in a region on the lower left of the fan  21 . Therefore, part of the air discharged from the fan  21  flows along the fourth guide wall  274  and is efficiently guided to the plurality of second ventilation ports  282 . 
     In  FIG. 2 , the coupling portion  24  is formed above the fan  21  at the lower housing  3 . The coupling portion  24  is adjacent to the plurality of first flow straightening plates  23 . That is, the distance from the rotation axis J to a particular first flow straightening plate  23  and the distance from the rotation axis J to the coupling portion  24  are substantially the same. 
       FIG. 3  is a vertical sectional view of the fan assembly  20  of the exemplary first embodiment of the present disclosure. The upper housing  4  includes the inlet  41 , a first curved portion  42 , a second curved portion  43 , and a connecting portion  44 . In the upper housing  4 , the inlet  41  is formed above the fan  21  in the axial direction, and opens in a substantially circular shape around the rotation axis J as the center. Part of air that exists above the upper housing  4  in the axial direction passes through the inlet  41  and is sucked by the fan  21 , and, in the inside of the fan assembly  20 , is discharged from the upstream side to the downward side. In the embodiment, the air discharged from the fan  21  includes a swirling component that swirls around the rotation axis J as the center due to the rotation of the fan  21 . 
     An inlet upper end  411  and an inlet lower end  412  are smoothly connected to each other. More specifically, the inlet upper end  411  and the inlet lower end  412  are connected to each other at a curved surface such that the opening diameter of the inlet  41  is gradually decreased towards a lower side in the axial direction from the inlet upper end  411 . The curved surface has a shape whose upper side in the axial direction and inner side in the radial direction widen. The curved surface desirably has a catenary curve. This causes the flow of air sucked in from the inlet  41  to be efficiently guided to the fan  21  without being hampered. Therefore, the blowing efficiency of the fan  21  is increased, as a result of which the blowing efficiency in the inside of the fan assembly  20  is increased, and the cooling efficiency of the refrigerator  1  is increased. The curved surface may have other shapes. For example, the curved surface may have a shape that is substantially the same as part of an ellipse, or a shape that is substantially the same as part of a parabola. 
     An upper surface of the upper housing  4  has a planar surface  45  extending in a direction substantially orthogonal to the rotation axis J. The inlet lower end  412  is disposed above the planar surface  45  in the axial direction. In the inside of the fan assembly  20 , a space in which the fan  21  is disposed can be made wide, and even the large fan  21  whose dimension in the axial direction is large can be installed. 
     The second flow straightening portion is hereunder described in detail. As mentioned above, the upper housing  4  includes the second flow straightening portion. The second flow straightening portion includes the first curved portion  42 , the second curved portion  43 , and the connecting portion  44 , which protrude downward in the axial direction from a lower surface of the upper housing  4 . The first curved portion  42  is disposed on an outer side of the inlet lower end  412  in the radial direction, and the second curved portion  43  is disposed on an outer side of the first curved portion  42  in the radial direction. The first curved portion  42  is a portion whose thickness in the axial direction increases from the upstream side, where the fan  21  is disposed, towards the downstream side, where the discharge ports  221  are disposed. The second curved portion  43  is a portion whose thickness in the axial direction decreases from the upstream side towards the downstream side at a location that is situated closer to the downstream side than the first curved portion  42 . 
     On the other hand, an upper surface of the lower housing  3  has a planar surface extending in a direction substantially orthogonal to the axial direction. Therefore, at a region in the radial direction where the first curved portion  42  is formed, the size of a gap in the axial direction between the upper surface of the lower housing  3  and the lower surface of the upper housing  4  becomes smaller towards the outer side from the inner side in the radial direction, and static pressure is increased. That is, air that flows in the gap flows smoothly along the upper surface of the lower housing  3  and the lower surface of the upper housing  4  without being separated from the upper surface of the lower housing  3  and the lower surface of the upper housing  4 . This reduces the occurrence of turbulence in the inside of the fan assembly  20 , and increases the blowing efficiency in the inside of the fan assembly  20 . 
     The first curved portion  42  may extend outward in the radial direction from the inlet lower end  412 . That is, the first curved portion  42  may extend from the inlet lower end  412  towards the downstream side, where the discharge ports  221  are disposed. This can reduce the occurrence of turbulence below the inlet lower end  412 . 
     At a region in the radial direction where the second curved portion  43  is formed, the size of the gap in the axial direction between the upper surface of the lower housing  3  and the lower surface of the upper housing  4  becomes larger towards the outer side from the inner side in the radial direction, and the resistance force that the air receives is reduced. That is, a reduction in the air flow speed is reduced. Consequently, the air discharged from the fan  21  flows smoothly towards the outer side in the radial direction, and the blowing efficiency in the inside of the fan assembly  20  is increased. 
     The outer side of the first curved portion  42  in the radial direction and an inner side of the second curved portion  43  in the radial direction are smoothly connected to each other by the connecting portion  44 . The connecting portion  44  is a portion in which the thickness of the upper housing  4  in the axial direction is substantially constant regardless of the disposition in the radial direction. That is, at a region in the radial direction where the connecting portion  44  is disposed, the gap in the axial direction between the upper surface of the lower housing  3  and the lower surface of the upper housing  4  is substantially constant. In other words, the gap in the axial direction between the upper surface of the lower housing  3  and the lower surface of the upper housing  4  is smaller at the region where the connecting portion  44  is formed than at the region where the first curved portion  42  is disposed and the region where the second curved portion  43  is disposed. 
     In the radial direction, part of the region where the connecting portion  44  is disposed and part of a region where the plurality of first flow straightening plates  23  and the coupling portion  24  are disposed overlap each other. In other words, in a channel in the inside of the fan assembly  20 , the plurality of first flow straightening plates  23  and the coupling portion  24  are formed in a region where the static pressure is locally high. Therefore, the occurrence of turbulence is reduced and the blowing efficiency is increased. By reducing turbulence, noise that is produced in the inside of the fan assembly  20  is also reduced. Further, since the plurality of first flow straightening plates  23  and the coupling portion  24  are disposed at a region where the gap in the axial direction between the upper surface of the lower housing  3  and the lower surface of the upper housing  4  becomes small, the lengths of the plurality of first flow straightening plates  23  and the coupling portion  24  in the axial direction can be made small. Therefore, the rigidities of the plurality of first flow straightening plates  23  and the coupling portion  24  are increased, and the amount of material required to form the plurality of first flow straightening plates  23  and the connecting portion  44  can also be reduced, so that costs can be reduced. However, the plurality of first flow straightening plates  23  need not be provided at the region where the connecting portion  44  is disposed. By disposing the plurality of first flow straightening plates  23  at a region where a channel for the air discharged from the fan  21  is small, the same operation effects can be obtained. 
       FIG. 4  is an enlarged view of the cross sectional view of the coupling portion  24  of the fan assembly  20  of the first embodiment. The coupling portion  24  has a through hole  241  extending in the axial direction. That is, the coupling portion is a hollow portion having the through hole  241 . In the embodiment, by inserting a screw into the through hole  241  via the upper housing  4 , and securing the screw to a side of the refrigerator interior  10  via the lower housing  3 , the fan assembly  20  is secured to the refrigerator interior  10 . However, the member that secures the upper housing  4 , the lower housing  3 , and the refrigerator interior  10  need not be a screw. A fastening member may be selected as appropriate in accordance with a desired fastening strength and size of, for example, the fan assembly  20 . 
     In the embodiment, outer edges of the connecting portion are asymmetrical with reference to a through hole center  242 . That is, the coupling portion  24  is not circular. More specifically, an upstream-side outer edge  243  that is disposed closer to the upstream side, where the fan  21  is disposed, than the through hole center  242  has a substantially arc shape. On the other hand, at least one edge portion of a downstream-side outer edge  244  that is disposed closer to the downstream side, where the plurality of first discharge ports  221  are disposed, than the through hole center  242  is substantially parallel to the adjacent first flow straightening plate  23 . The coupling portion  24  is formed such that, from the upstream side towards the downstream side, a width d in a direction that is orthogonal to the direction from the upstream side to the downstream side becomes smaller. Further, the distance from the through-hole center  242  to a downstream-side outer edge end  245 , which is a downstream end of the downstream-side outer edge  244 , is larger than the distance from the through-hole center  242  to an upstream-side outer edge end  246 , which is an upstream-side end of the upstream-side outer edge  243 . 
     On the other hand, when the outer edges of the coupling portion are substantially circular, the downstream-side outer edge and the upstream-side outer edge have substantially arc shapes, as a result of which a gap between the adjacent first flow straightening plate  23  and each outer edge is drastically increased. Therefore turbulence tends to occur near the downstream-side outer edge and the upstream-side outer edge. In comparison, the coupling portion  24  of the embodiment is such that only the upstream-side outer edge  243  has a substantially arc shape. Therefore, turbulence that occurs in the air discharged from the fan  21  is reduced, and the blowing efficiency in the inside of the fan assembly  20  is increased. The outer edges of the coupling portion  24  need not have the aforementioned shapes. The coupling portion  24  may have an elliptical shape having a long axis in a direction towards the downstream side with reference to the through hole center  242 . For example, the downstream-side outer edge  244  may have a substantially arc shape, and the upstream-side outer edge  243  may extend so as to be substantially parallel to the adjacent first flow straightening plate  23 . 
       FIG. 5  is a cross sectional view of a fan assembly  20 A of a second embodiment. In  FIG. 5 , for convenience sake, the first guide wall  271 , the second guide wall  272 , the third guide wall  273 , the fourth guide wall  274 , the guiding portion  25 , and the partition plate  26 , which are shown in the fan assembly  20  of the first embodiment, are not shown. 
     A plurality of first flow straightening plates  23 A are disposed closer to the downstream side than a fan  21 A. The first flow straightening plates  23 A each include a flat-plate-shaped portion  233 A and an arc-shaped portion  234 A that is connected to the corresponding flat-plate-shaped portion  233 A and that is curved from the downstream side, where a plurality of first discharge ports  221 A are disposed, towards the upstream side, where the fan  21 A is disposed. This causes part of air discharged from the fan  21 A to flow towards the downstream side, to flow along the arc-shaped portions  234 A and the flat-plate-shaped portions  233 A, and to be guided to the plurality of first discharge ports  221 A. Therefore, the blowing efficiency of air discharged from the fan  21 A and moving towards the plurality of first discharge ports  221 A is increased, and noise that is produced in the inside of the fan assembly  20 A is reduced. 
     A coupling portion  24 A has an elliptical shape having a long axis that is substantially parallel to a line connecting a rotation axis JA of the fan  21 A and a through hole center  242 A of a through hole  241 A of the coupling portion  24 A. By this, when part of the air discharged from the fan  21 A passes near the coupling portion  24 A, the resistance force that the air receives from the coupling portion  24 A is reduced, and the air flows smoothly along an outer edge of the coupling portion  24 A towards the plurality of first discharge ports  221 A. Therefore, the blowing efficiency in the inside of the fan assembly  20 A is increased, and noise that is produced in the inside of the fan assembly  20 A is reduced. 
       FIG. 6  is a cross sectional view of a fan assembly  20 B of a third embodiment. In  FIG. 6 , for convenience sake, the first guide wall  271 , the fourth guide wall  274 , the first flow straightening plates  23 , and the guiding portion  25 , which are shown in the fan assembly  20  of the first embodiment, are not shown. 
     In  FIG. 6 , a plurality of ventilation ports  281 B, a coupling portion  24 B, and a plurality of first discharge ports  221 B are disposed above a fan  21 B. In  FIG. 6 , a second guide wall  272 B is disposed from above a fan  21 B towards the right of a rotation axis JB. 
     A coupling portion  24 B includes a left curved portion  247 B and a right curved portion  248 B. With reference to a through hole center  242 B, the left curved portion  247 B is curved towards the upstream side while forming an arc whose curvature radius center is disposed to the right of the rotation axis JB in  FIG. 6 . From the downstream side towards the upstream side, the width of the left curved portion  247 B in a direction orthogonal to a direction from the downstream side to the upstream side becomes smaller. That is, an upstream-side end portion of the left curved portion  247 B is pointed towards the upstream side. 
     Therefore, when part of air discharged from the fan  21 B passes through a gap between the left curved portion  247 B and the second guide wall  272 B, it flows smoothly without being separated from the left curved portion  247 B. Consequently, the blowing efficiency in the inside of the fan assembly  20 B is increased, and noise is also reduced. When part of the air discharged from the fan  21 B passes through a gap between a third guide wall  273 B and the left curved portion  247 B, it flows smoothly without being separated from the left curved portion  247 B. Consequently, the blowing efficiency in the inside of the fan assembly  20 B is increased, and noise is also reduced. Further, when part of the air discharged from the fan  21 B collides with the upstream-side end portion of the left curved portion  247 B, it does not receive a large resistance force. Therefore, the blowing efficiency in the inside of the fan assembly  20 B is increased, and noise is also reduced. 
     In the embodiment, part of the plurality of first ventilation ports  281 B is disposed between the through hole center  242 B and the upstream-side end portion of the left curved portion  247 B. Therefore, part of the air discharged from the fan  21 B is discharged to the outside of the fan assembly  20 B via the plurality of first ventilation ports  281 B. 
     With reference to the through hole center  242 B, the right curved portion  248 B is curved towards the downstream side while forming an arc whose curvature radius center is disposed on the left of the rotation axis JB in  FIG. 6 . From the upstream side towards the downstream side, the width of the right curved portion  248 B in a direction orthogonal to a direction from the upstream side to the downstream side becomes smaller. That is, a downstream-side end portion of the right curved portion  248 B is pointed towards the downstream side. 
     This causes part of the air discharged from the fan  21 B to pass through a gap between the right curved portion  248 B and the second guide wall  272 B, and to flow smoothly towards the plurality of first discharge ports  221 B without being separated up to the downstream-side end portion of the right curved portion  248 B. Therefore, it is possible to increase the blowing efficiency in the inside of the fan assembly  20 B, and also to reduce noise. 
     The shape of the coupling portion  24 B is not limited to that characterized by the left curved portion  247 B and the right curved portion  248 B as that described above. For example, the coupling portion  24 B may be a portion in which the left curved portion  247 B and the right curved portion  248 B have a plurality of inflection points and curved shapes that are characterized by a plurality of curvature radii are connected to each other. 
       FIG. 7  is a cross sectional view of a fan assembly  20 C of a fourth embodiment.  FIG. 8  is a sectional view along A-A′ in  FIG. 7 . This embodiment differs from the first embodiment in guide portions  25 C, a plurality of guide walls  27 C, a first curved portion  42 C, and a second curved portion  43 C. The plurality of guide walls  27 C include guide walls  271 C,  272 C,  273 C,  274 C,  275 C,  276 C, and  277 C. The guide portions  25 C and the guide walls  27 C are distinguished from each other in that the guide portions  25 C are part of a first flow straightening portion that is provided at a lower housing  3 , whereas the guide walls  27 C are part of a third flow straightening portion that is provided at a side housing  5 . However, in the embodiment, the guide portion may be part of a second flow straightening portion that is provided at an upper housing  4 , and the guide walls may be a single member with respect to the upper housing  4  or the lower housing  3 . 
     At an outer side in the radial direction with reference to the fan  21 C, the first guide wall  271 C, the second guide wall  272 C, the third guide wall  273 C, the fourth guide wall  274 C, the guide portions  25 C, a plurality of discharge ports  22 C, a plurality of first ventilation ports  281 C, and a second ventilation port  282 C are formed. The first flow straightening portion that is provided at the lower housing  3  extends in the axial direction between the fan  21 C and the discharge ports  22 C, and includes the guide portions  25 C that protrude towards the inside of the fan assembly  20 C. The third flow straightening portion that is provided at the side housing  5  includes the plurality of guide walls  27 C that protrude towards the inside of the fan assembly  20 C. Any one of gaps formed by the plurality of guide walls  27 C that are adjacent to each other and gaps formed by the guide walls  27 C and the guide portions  25 C that are adjacent to each other increases in size from the upstream side, where the fan  21 C is disposed, towards the downstream side, where the plurality of discharge ports  22 C are disposed. 
     This causes air discharged from the fan  21 C to be smoothly guided to the plurality of discharge ports  22 C, the plurality of first ventilation ports  281 C, and the second ventilation port  282 C while reducing turbulence that is produced in the air discharged from the fan  21 C. Therefore, the blowing efficiency in the inside of the fan assembly  20 C is increased, and the cooling efficiency of the refrigerator  1  is also increased. At the same time, since the air in the inside of the fan assembly  20 C flows smoothly, noise that is produced in the inside of the fan assembly  20 C is reduced. Further, outer end portions of the plurality of guide portions  25 C in the radial direction are adjacent to the plurality of discharge ports  22 C, the plurality of first ventilation ports  281 C, and the second ventilation port  282 C. Therefore, part of air that is discharged from the fan  21 C is smoothly guided to the plurality of discharge ports  22 C, the plurality of first ventilation ports  281 C, and the second ventilation port  282 C. As a result, the blowing efficiency in the inside of the fan assembly  20 C is increased, and the cooling efficiency of the refrigerator  1  is increased. 
     Broken lines in  FIG. 7  indicate a boundary between the first curved portion  42 C and the connecting portion  44  indicated in  FIG. 3  and a boundary between the second curved portion and the connecting portion  44 . In the embodiment, at least one of the boundary between the first curved portion  42 C and the connecting portion  44  and the boundary between the second curved portion and the connecting portion  44  is substantially concentrically disposed around a rotation axis JC as a center. Therefore, even if the fan assembly  20 C is relatively small compared to the fan  21 C, air can be discharged with variations in the air volume towards the discharge ports  22 C or the first ventilation ports  281 C being reduced. Consequently, the blowing efficiency can be increased. 
       FIG. 8  is a sectional view along A-A′ in  FIG. 7 . A channel  6  is formed by an inner surface of the fourth guide wall  274 C, an inner surface of the guide portion  25 C, the lower housing  3 C, and the upper housing  4 C. A lower surface of the upper housing  4 C gradually inclines downward from the center of the channel  6  towards the fourth guide wall  274 C and the guide portion  25 C. That is, a gap in the axial direction between the lower surface of the upper housing  4 C and an upper surface of the lower housing  3 C is largest near the center of the channel  6 . In other words, the upper housing  4 , the lower housing  3 , and the side housing  5 , or the upper housing  4  and the lower housing  3  form part of the channel  6 . In a section where the channel  6  is viewed from the upstream side, where the fan  21 C is disposed, towards the downstream side, where the plurality of discharge ports  22 C are disposed, a gap d 1  in the axial direction at the center of the channel  6  is the largest. 
     Here, fluids including air have viscosity. Fluid at the center of the channel flows easily, whereas fluid at the corners of the channel have difficulty flowing. When there are portions in the channel where fluid has difficulty flowing, this may cause turbulence. Therefore, in the embodiment, a gap in the axial direction near the center of the channel where the fluid flows easily is large, and a gap in the axial direction near the corners of the channel where the fluid has difficulty flowing is small. Therefore, turbulence is less likely to occur, and the air can flow efficiently. Consequently, the blowing efficiency can be increased. 
       FIG. 9  is a partial enlarged view of the vicinity of the plurality of discharge ports  22 C when viewed from the outside of the fan assembly  20 C. The side housing  5 C includes a wall portion  51  that extends downward in the axial direction from an outer edge of a planar surface  45 , which is an upper surface of the upper housing  4 C in the axial direction. The plurality of discharge ports  22 C are formed by the wall portion  51 , the upper housing  4 C, and the lower housing  3 C. At the center of the plurality of discharge ports  22 C in the axial direction, the wall portion  51  of the side housing  5 C includes a plate-shaped second flow straightening plate  511  extending from the inside to the outside of the fan assembly  20 C. The second flow straightening plate  511  is part of the third flow straightening portion that is provided at the side housing  5 C. This causes part of air that is discharged from the discharge ports  22 C to be discharged along the second flow straightening plate  511 . Therefore, it is possible to reduce a case in which part of the air that is discharged from the discharge ports  22 C is discharged by being veered upward and downward in the axial direction from the fan assembly  20 C. That is, since part of the air that is discharged from the discharge ports  22 C is smoothly guided to an outer side in the radial direction, the blowing efficiency and the discharge air volume to the outer side in the radial direction are increased. Since the second curved portion  43  of the upper housing  4  is curved upward in the axial direction towards the outer side in the radial direction, part of the air that is discharged from the discharge ports  22 C has a high tendency to be discharged by being veered upward in the axial direction from the fan assembly  20 C. Therefore, when the second flow straightening plate  511  is disposed on an upper side in the axial direction from the center of the fan assembly  20 C in the axial direction, it is possible to reduce the amount of air that is veered to the upper side in the axial direction and to further increase blowing efficiency. The number of second flow straightening plates  511  need not be one, and may be two or more. 
       FIG. 10  is a cross sectional view of a fan assembly  20 D of a fifth embodiment. A lower housing  3 D includes a plurality of discharge ports  22 D that open downward in the axial direction. In this embodiment, there are eight discharge ports  22 D. 
     A base portion  31 D of the lower housing  3 D includes a plurality of inclined surfaces  32 D. Each inclined surface  32 D is a portion that extends obliquely rightward and downward and that is hatched. At the vicinity of a plurality of discharge ports  22 D, the inclined surfaces  32 D are surfaces that are inclined downward in the axial direction from the base portion  31 D of the lower housing  3 D towards the discharge ports  22 D. This causes air that is discharged from a fan  21 D to be smoothly discharged to the outside of the fan assembly  20 D. Each inclined surface  32 D may be an inclined surface that extends linearly, or may be a protruding curved surface that protrudes towards a channel in the inside of the fan assembly  20 D. 
     A first flow straightening portion that is provided at the lower housing  3 D extends in the axial direction between the fan  21 D and the plurality of discharge ports  22 D and includes a guide portion  25 D that protrudes towards the inside of the fan assembly  20 D. A third flow straightening portion that is provided at a side housing  5 D includes a plurality of guide walls  27 D that protrude towards the inside of the fan assembly  20 D. The plurality of guide walls  27 D include protruding portions  27 D 1 ,  27 D 2 ,  27 D 3 , and  27 D 4  that protrude towards the fan  21 D. An end of each of the plurality of protruding portions  27 D 1 ,  27 D 2 ,  27 D 3 , and  27 D 4  has a substantially arc shape. This causes the air that is discharged from the fan  21 D to be smoothly guided without be being separated at each of the protruding portions  27 D 1 ,  27 D 2 ,  27 D 3 , and  27 D 4 . 
     A front surface in a rotation direction of the fan  21 D of each of the guide portion  25 D and the protruding portions  27 D 1 ,  27 D 2 ,  27 D 3 , and  27 D 4  that are adjacent to the fan  21 D is a protruding curved surface that protrudes towards the front in the rotation direction of the fan  21 D. Part of each curved surface contacts part of a tangent to the fan  21 D. For convenience sake, only a tangent Y where part of the fan  21 D and the curved surface of the protruding portion  27 D 2  contact each other is shown by a broken line. This causes part of the air that is discharged from the fan  21 D to be smoothly guided along the curved surfaces towards the plurality of discharge ports  22 D, and the blowing efficiency to be increased. 
     Further, in a channel that is formed by an upper housing  4 , the lower housing  3 D, the guide portion  25 D, and the plurality of guide walls  27 D, the sectional area of a portion of the channel that is connected to the discharge ports  22 D whose distance from the fan  21 D is large is larger than the sectional area of a portion of the channel that is connected to the discharge ports  22 D whose distance from the fan  21 D is small. Therefore, it is possible to discharge air uniformly to the plurality of discharge ports  22 D and to reduce variations in the air volume that is discharged from the plurality of discharge ports  22 D. Consequently, it is possible to reduce noise that is produced from the fan assembly  20 D. 
       FIG. 11  shows air volume characteristics of the fan assembly  20 D of this embodiment. The vertical axis indicates air volumes. The vertical axis only indicates the air volume at the discharge port  22 D where the air volume is the largest and the air volume at the discharge port  22 D where the air volume is the smallest among the air volumes of eight discharge ports  22 D. The horizontal axis indicates a fan assembly before an improvement A and the fan assembly  20 D after the improvement B. The fan assembly before the improvement A and the fan assembly  20 D after the improvement B are the same in the dispositions of the fan and the plurality of discharge ports; and differ, as described above, in terms of the improvements that are made as appropriate on the shapes of the lower housing, the upper housing, and the side housing. Accordingly, the air volume of the fan assembly before the improvement A is such that the difference between the maximum air volume and the minimum air volume is approximately 0.175 (m 3 /min), whereas the air volume of the fan assembly  20 D after the improvement B is such that the difference between the maximum air volume and the minimum air volume is reduced to approximately 0.075 (m 3 /min). Accordingly, the numerical data shows the effects of the embodiment in which the shapes of the lower housing, the upper housing, and the side housing are improved as appropriate. 
       FIG. 12  is a cross sectional view of a fan assembly  20 E of a sixth embodiment. A lower housing  3 E includes a substantially circular base portion  31 E and a plurality of discharge ports  22 E that are disposed outward in the radial direction from an outer edge of the base portion  31 E. A fan  21 E is disposed on the base portion  31 E. An outer side of the fan  21 E in the radial direction is covered by a wall portion  51 E of a side housing  5  and a side wall portion  235  of the lower housing  3 E described below. The base portion  31 E may be elliptical instead of being circular. 
     The discharge ports  22 E include a plurality of third discharge ports. The plurality of third discharge ports include three third discharge ports  223 E 1 ,  223 E 2 , and  223 E 3  in that order from the left of  FIG. 11 . The central angles of the plurality of third discharge ports  223 E 1 ,  223 E 2 , and  223 E 3  with reference to a center  3 DJ of the base portion  31 E are substantially the same. More specifically, the central angle of the third discharge port  223 E 1  and the central angle of the third discharge port  223 E 3  are equal to each other, and are less than the central angle of the third discharge port  223 E 2 . However, the central angles can be changed as appropriate in accordance with the structure of the inside of the refrigerator  1 . 
     In the embodiment, the air volumes that are discharged from the plurality of discharge ports  22 E are such that the air volume that is discharged from the third discharge port  223 E 2  is the largest, and the air volume that is discharged from the third discharge port  223 E 1  is the smallest. More specifically, the ratio of the air volumes of the third discharge port  223 E 1 , the third discharge port  223 E 2 , and the third discharge port  223 E 3  is approximately 2:5:3. However, the ratio of the air volumes can be changed as appropriate in accordance with the structure of the inside of the refrigerator  1 . 
     Here, when the fan  21 E is disposed such that a rotation axis JE of the fan  21 E and a center  3 EJ of the base portion  31 E simply overlap each other, the aforementioned air volume ratio cannot be satisfied. This is because the air volume ratio is calculated based on various parameters, such as the rotation direction of the fan  21 E, the relationship between the dispositions of the fan  21 E and the plurality of discharge ports  22 E, and the shape of the base portion  31 E, which influence each other. 
     Here, in the embodiment, the rotation axis JE of the fan  21 E is displaced from the center  3 EJ of the base portion  31 E. More specifically, the rotation axis JE of the fan  21 E is disposed within a region D 1  among four regions D 1 , D 2 , D 3 , and D 4  that are on the base portion  31 E and that are separated by a line connecting the center  3 EJ of the base portion  31 E and the center of the discharge ports  22 E in the peripheral direction and by a perpendicular line to the line passing through the center of the base portion  31 E. The region D 1  is adjacent to the third discharge port  223 E 3  disposed on a frontmost side in the rotation direction of the fan  21 E. The rotation direction of the fan  21 E is clockwise in  FIG. 11 . In this way, in this embodiment, since the rotation direction of the fan  21 E and the relationship between the dispositions of the fan  21 E and the plurality of discharge ports  22 E are considered, it is easy to realize the air volume ratio that is desired. 
     The base portion  31 E includes a plurality of third flow straightening plates  52  that, on the base portion  31 E, extend from portions of the outer edge of the base portion  31 E that are between adjacent ones of the plurality of discharge ports  22 E to a side in a direction opposite to the rotation direction of the fan  21 E. More specifically, the plurality of third flow straightening plates  52  include a third flow straightening plate  521  that extends from a portion between the third discharge port  223 E 1  and the third discharge port  223 E 2  to a side in a direction opposite to the rotation direction of the fan  21 E and a third flow straightening plate  522  that extends from a portion between the third discharge port  223 E 2  and the third discharge port  223 E 3  to a side in a direction opposite to the rotation direction of the fan  21 E. Therefore, the rotation direction of the fan  21 E, the relationship between the dispositions of the fan  21 E and the plurality of discharge ports  22 E, and further the shape of the base portion  31 E are considered, so that the air volume ratio that is desired is more easily realized. At the outer edge of the base portion  31 E, angles θ 1  and θ 2  between tangents to the plurality of third flow straightening plates  52  and directions of extensions of the plurality of third flow straightening plates  52  are acute angles. The extending directions and the lengths of the plurality of third flow straightening plates  52  can be changed as appropriate in accordance with the desired air volume ratio. That is, it is possible to provide a general-purpose product. 
     The base portion  31 E further includes the substantially arc-shaped side wall portion  235  that protrudes in the axial direction. A portion of the side wall portion  235  that is thickest in the radial direction is disposed in the region D 3 . In other words, the thickest portion of the side wall portion  235  in the radial direction is disposed in the region D 3  that is opposite to the region D 1 , where the rotation axis JE of the fan  21 E is disposed, with reference to the center  3 EJ of the base portion  31 E. Here, among the regions D 1 , D 2 , D 3 , and D 4 , the region D 3 , which is a space that is farthest from the fan  21 E, includes a lot of space portions that have difficulty contributing to an increase the air volume. Therefore, in order to increase the air volume of air that is discharged from the plurality of discharge ports  22 E, the space of the region D 3  needs to be small. In the embodiment, since the thickest portion of the side wall portion  235  in the radial direction is disposed in the region D 3 , the space of the region D 3  can be made small. Therefore, it is possible to increase the air volume of the air that is discharged from the plurality of discharge ports  22 E. The region in which the side wall portion  235  is disposed and the thickness of the side wall portion  235  can be changed as appropriate in accordance with the size of the fan  21 E and the size of the base portion  31 E. That is, it is possible to provide a general-purpose product. 
     Further, it is desirable to set the curvature of the wall portion  51 E of the side housing  5  and the curvature of the side wall portion  235  of the lower housing  3 E as appropriate such that a gap between the fan  21 E and the side wall  51 E of the side housing  5  and that between the fan  21 E and the side wall portion  235  of the lower housing  3 E become gradually larger at a certain ratio from a smallest gap d 2 . This causes the static pressure in the inside of the fan assembly  20 E to change smoothly, so that the blowing efficiency in the inside of the fan assembly  20 E is increased, and the cooling efficiency of the refrigerator  1  is increased. 
     The fan assemblies of the first embodiment to the sixth embodiment described above may be used in any devices. For example, although they are used for refrigerator fan assemblies, the use thereof is not limited thereto. They may be used in, for example, freezers, ovens, microwave ovens, and other cooking appliances; and televisions, desktop personal computers, notebook-size personal computers, and other home appliances. 
     The structures described in the above-described first embodiment to the sixth embodiment may be combined as appropriate within a scope that does not cause mutual contradiction. 
     Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.