JP2015086721A - Centrifugal fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal fan capable of reducing the generation of noise.SOLUTION: A centrifugal fan has impellers stored in a casing. The impeller has an annular shroud 31, a hub 41, and a blade 51 disposed between those. The centrifugal fan discharges air introduced from a suction port opening above the impeller, to a side part of the impeller. A pressure surface 53 side of the blade 51 has a first inclined surface 53a inclining so as to approach to a negative pressure surface side of the blade 51 from the annular shroud 31 toward a lower casing, and a second inclined surface 53b provided near the lower casing as compared with the first inclined surface 53a, and inclining so as to approach to the negative pressure surface side at a sharp angle as compared with the first inclined surface 53a. The generation of a separation flow from the pressure surface 53 near a blow-off port is prevented.

Description

  The present invention relates to a centrifugal fan, and more particularly, to a thin and low-noise centrifugal fan.

  Centrifugal fans (sometimes referred to as “centrifugal fans”) are widely used for various appliances such as home appliances, OA equipment, and industrial equipment, such as cooling, ventilation, and air conditioning, and for vehicle blowers. It has been.

  A centrifugal fan is a fan that blows air in a centrifugal direction by rotating an impeller having a plurality of blades. A centrifugal fan generally has a casing having a suction port and a blowout port, and an impeller having a plurality of blades housed in the casing. The centrifugal fan rotates the impeller together with the rotation of the motor, so that air or the like flows in between the blades from the suction port, and is ejected toward the outer diameter of the impeller by the centrifugal action accompanying the rotation of the impeller. . Thereby, high-pressure air is blown out from the outlet of the casing.

  Patent Document 1 listed below discloses a centrifugal fan having such a structure, which is designed to reduce noise and reduce the size of noise generated by the turbulence of the air flow in the vicinity of the inner wall surface and the outlet of the casing. Yes. The centrifugal fan described in Patent Document 1 has a structure in which an impeller is housed in a casing including an upper plate, a lower plate, and a plurality of support columns interposed between the upper plate and the lower plate. It is what you have. An opening serving as an air outlet is formed on the side surface of the casing. The lower plate of the casing is a motor base on which a motor is mounted, and the lower part of the impeller blades is arranged to face the motor base via a predetermined gap. The blades are rearward blades having a blade shape curved and inclined rearward with respect to the rotation direction, and constitute a turbofan.

JP 2013-47483 A

  In the centrifugal fan described in Patent Document 1, the side wall of the casing is abolished to form an opening, and noise generated due to the turbulence of the air flow in the vicinity of the inner wall surface and the outlet of the casing is reduced. is there. However, with the progress of downsizing, thinning, high density mounting, and energy saving of equipment, further reduction of noise is required for centrifugal fans mounted on such equipment.

  The present invention has been made to solve such problems, and an object thereof is to provide a centrifugal fan that can reduce the generation of noise.

  In order to achieve the above object, according to one aspect of the present invention, an impeller includes a lower casing positioned below the impeller, and the impeller includes an annular annular shroud whose inner upper portion serves as a suction port, and an annular shroud. An impeller having a plurality of blades disposed between the annular shroud and the lower casing so as to protrude downward from the lower casing, and a hub joined to each of the plurality of blades inside each blade. The centrifugal fan that blows out the fluid introduced from the suction port of the annular shroud to the side of the impeller in accordance with the rotation of the annular shroud is such that the upper surface of the lower casing faces the impeller and guides the fluid introduced from the suction port Each of the plurality of blades is inclined while curving backward in the rotational direction of the impeller as it approaches the outside of the impeller, and the pressure surface side of each of the plurality of blades is an annular shim. A first inclined surface that inclines so as to approach the suction surface side of the blade as it approaches the lower casing from the loudspeaker, and a portion closer to the lower casing than the first inclined surface, and is steeper than the first inclined surface. And a second inclined surface that is inclined so as to approach the suction surface side at a certain angle.

  Preferably, the angle between the second inclined surface and the plane perpendicular to the rotation axis of the impeller is greater than 0 degree and less than 45 degrees.

  Preferably, the angle between the second inclined surface and the plane perpendicular to the rotation axis of the impeller is not less than 25 degrees and not more than 35 degrees.

  Preferably, the angle between the first inclined surface and the rotating shaft of the impeller is not less than 4 degrees and not more than 8 degrees.

  Preferably, the first inclined surface and the second inclined surface are joined via a round chamfered curved surface.

  Preferably, the centrifugal fan further includes a motor attached to the lower casing and rotating the impeller.

  According to these inventions, each of the plurality of blades is inclined while curving backward in the rotational direction of the impeller as it approaches the outside of the impeller, and the pressure surface side of each of the plurality of blades is lowered from the annular shroud. A first inclined surface that inclines so as to approach the suction surface side of the blade as it approaches the casing, and a portion closer to the lower casing than the first inclined surface, at a steeper angle than the first inclined surface And a second inclined surface inclined so as to approach the suction surface side. Therefore, it is possible to provide a centrifugal fan that can reduce the generation of noise.

It is a perspective view which shows the centrifugal fan in one of the embodiment of this invention. It is sectional drawing in the AA of FIG. FIG. 3 is a partially enlarged view of FIG. 2. It is a bottom view of an impeller. It is a sectional side view of an impeller. It is a figure which shows typically the cross section of a blade | wing. It is a graph which shows the relationship between the magnitude | size of angle (beta), and the noise level at the time of rotation of an impeller.

  Hereinafter, a centrifugal fan according to one embodiment of the present invention will be described.

  FIG. 1 is a perspective view showing a centrifugal fan according to one embodiment of the present invention. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a partially enlarged view of FIG.

  With reference to FIGS. 1 to 3, the centrifugal fan 1 includes a casing 10, an impeller 30, and a motor 60. The centrifugal fan 1 is configured in a substantially square rectangular parallelepiped shape in plan view as a whole, except for a portion where the motor 60 is attached. The centrifugal fan 1 is thin and has a relatively small vertical dimension (height). The impeller 30 is attached to the rotor 62 of the motor 60 and rotates with the rotation of the rotor 62. The centrifugal fan 1 discharges air introduced from the suction port 33 to the side of the impeller 30 as the impeller 30 rotates. That is, the air introduced from the suction port 33 passes between the blades 51 of the impeller 30 and is blown toward the outside of the impeller 30 by a fluid force due to the centrifugal action accompanying the rotation of the impeller 30. The Air is exhausted from a blow-out port (opening) 19 of the casing 10 on the side of the impeller 30.

  The motor 60 is, for example, an outer rotor type brushless motor. The motor 60 is attached to a central portion of a motor base (an example of a lower casing) 21 with a fastening member such as a screw or a bolt. The rotor 62 includes a cup-shaped rotor yoke 63 that opens downward, a shaft 61, and a magnet 65. An annular magnet 65 is attached to the inner surface of the side peripheral portion of the rotor yoke 63. A shaft 61 is fixed to the central portion of the rotor yoke 63.

  The shaft 61 is rotatably supported by a pair of bearings 66 a attached to the bearing holder 66. The bearing holder 66 is attached to the motor base 21. A stator 67 is provided on the outer periphery of the bearing holder 66. The stator 67 is configured by a laminated stator core, an insulator wound around a coil attached to the stator core, and the like. The stator core is arranged to face the magnet 65 with a predetermined gap in the radial direction (left and right direction in FIG. 2). A circuit board 69 is attached to the stator 67. The circuit board 69 is, for example, a printed wiring board. Electronic components and the like for controlling the motor 60 are mounted on the circuit board 69, a drive circuit for the motor 60 is mounted, and the drive circuit and the coil are electrically connected.

  The casing 10 is configured by combining an upper casing 11 and a motor base 21. Specifically, the upper casing 11 and the motor base 21 are assembled to each other using screws 14 positioned at the four corners in plan view to constitute the casing 10. For example, the upper casing 11 and the motor base 21 are assembled to each other so as to sandwich a substantially cylindrical column 14b at a portion where the screw 14 is disposed. Of each side surface of the casing 10, a portion surrounded by the columns 14 b adjacent to each other, the upper casing 11, and the motor base 21 is an opening, and this opening becomes a blowout port 19. In other words, the blowout port 19 is a side portion of the casing 10 excluding a fastening portion between the upper casing 11 and the motor base 21 where the support column 14 b is disposed, and is provided between the upper casing 11 and the motor base 21. It has been.

  The screw 14 is, for example, a bolt inserted from the motor base 21 side. Instead of the screw 14, other types of screws or other types of connecting materials such as rivets may be used.

  The support column 14 b may be configured integrally with either the upper casing 11 or the motor base 21. For example, the column 14b may be formed by integral molding with the upper casing 11, and the column 14b and the motor base 21 may be coupled by a screw 14 or the like. Moreover, the support | pillar 14b is formed by sheet metal processing etc. with the motor base 21, and the structure which couple | bonded the support | pillar 14b and the upper casing 11 with the screw | thread 14 etc. may be sufficient.

  The impeller 30 is disposed so as to be stored in the casing 10. The upper casing 11 is located above the impeller 30, and the motor base 21 is located below the impeller 30. That is, the centrifugal fan 1 is configured such that the impeller 30 is disposed between the upper casing 11 and the motor base 21 such that the impeller 30 is sandwiched between the upper casing 11 and the motor base 21.

  The impeller 30 roughly includes an upper annular shroud 31, a lower hub 41, and a plurality of blades 51. A suction port 33 that opens upward is formed at the center of the impeller 30. The suction port 33 is configured by being surrounded by an upper end portion 35 inside the annular shroud 31. The plurality of blades 51 are arranged on the circumference at appropriate intervals. Each blade 51 is disposed between the annular shroud 31 and the hub 41, that is, between the annular shroud 41 and the motor base 21 so as to protrude downward from the annular shroud 31. Each blade 51 is joined to the hub 41 at a part inside the blade 51.

  Each blade 51 has the same curved shape. That is, the blades 51 have a shape that is curved and inclined backward with respect to the rotation direction. More specifically, the blades 51 are inclined while curving backward in the rotational direction of the impeller 30 as they approach the outside of the impeller 30. In FIG. 1 to FIG. 3, the shape of the blade 51 is shown in a simplified manner. The specific shape of the blades 51 will be described later. The annular shroud 31, the hub 41, and the blades 51 are integrally formed using a resin such as engineering plastic.

  A cylindrical portion 43 is provided at the center of the hub 41, and the rotor 62 is fitted into the cylindrical portion 43 to hold the impeller 30.

  The upper casing 11 is formed using a resin such as an engineering plastic. An opening 13 is formed at the center of the upper casing 11. The opening 13 is circular in plan view. The opening 13 is formed so that air is introduced into a suction port 33 provided in the impeller 30. The opening 13 has an inner diameter slightly larger than the suction port 33 constituted by the annular shroud 31. A return portion that protrudes downward is formed at the periphery of the opening 13, and the inner surface of the return portion and the outer peripheral surface in the vicinity of the upper end portion 35 of the annular shroud 31 are arranged with a slight gap therebetween.

  On the upper surface of the upper casing 11, a plurality of recesses 11b serving as meat stealing portions are formed, and ribs 11a are formed between the recesses 11b adjacent to each other. Thus, since the rib 11a and the recessed part 11b are formed, the upper casing 11 is comparatively lightweight and has sufficient rigidity.

  The motor base 21 is formed using, for example, a metal plate such as iron. The motor base 21 has a quadrangular shape like the casing 10. A concave portion 23 that is recessed downward is formed in the central portion of the motor base 21. The recess 23 is formed in a bowl shape. As shown in FIG. 2, in the present embodiment, a motor 60 and a drive circuit for the motor 60 such as a circuit board 69 are mounted in the recess 23. The motor 60 is mounted on the motor base 21 with a fastening member such as a screw or a bolt. However, the lower portion of the bearing holder 66 is caulked and fixed to the recess 23 instead of the fastening member. Also good.

  The outer peripheral portion of the motor base 21 is a side plate bent in the axial direction (vertical direction in FIG. 2). By providing the side plate, the rigidity of the motor base 21 is enhanced.

  Of the upper surface of the motor base 21, the portion around the recess 23 is a partition wall 29 that faces the lower surface of the impeller 30. The partition wall 29 is formed in a flat shape so as to be close to the lower surface of the impeller 30.

  As shown in FIG. 2, the hub 41 of the impeller 30 is close to the shaft (rotary axis of the impeller 30) 61 so that at least the outer peripheral side portion of each blade 51 faces the partition wall portion 29. It is provided only in the part. In other words, each blade 51 faces the portion of the impeller 30 that faces the partition wall 29. The portion of the motor base 21 that faces the impeller 30 is a part of the wall surface that guides the air introduced from the suction port 33 to the side. The blades 51 are arranged opposite to the partition wall 29 with a predetermined gap in the axial direction. In addition, at least a part of the lower part of each blade 51 may face the partition wall part 29, or the entire part may face the partition wall part 29.

  As shown in FIG. 3, a part of the upper surface of the hub 41 is a curved surface 49 that forms a downward arcuate curved line in a side cross section. The outer peripheral end 45 of the hub 41 is located in the vicinity of the vertically lower end of the upper end 35 of the annular shroud 31. Further, the inner peripheral end portion 47 of the hub 41 is located in the vicinity of the outer peripheral upper end portion 63 a of the rotor 63. The curved surface 49 is formed between the outer peripheral end portion 45 and the inner peripheral end portion 47. Of the curved surface 49, the outermost end 45 is at the lowermost position.

  The outer diameter of the impeller 30 housed in the casing 10 is set to be smaller than the dimension of one side of the casing 10. Thereby, the rotating impeller 30 does not protrude from the outer edge of the casing 10, and contact with other members of the impeller 30, damage due to contact, and the like are prevented.

  The motor base 21 has a function as a main plate for guiding air in the impeller 30 and also has a function as a substrate of the casing 10. For this reason, the setting of the gap formed between the impeller 30 and the partition wall 29 is important. When the gap is too large, the air sucked from the suction port 33 passes between the blades 51 and also flows into the gap. As a result, the pressure of the air blown out from the impeller 30 is reduced, and the blowing characteristics are deteriorated. On the other hand, when the gap is too small, there are the following problems. That is, if the dimensional accuracy of each part varies, the blades 51 may come into contact with the partition wall 29. In order to prevent such contact, it is necessary to manage the dimensional accuracy of each component with high accuracy, and the manufacturing cost of the centrifugal fan 1 increases. In view of such problems, the gap between the impeller 30 and the partition wall 29 is appropriately set.

  Next, the structure of the impeller 30 will be described more specifically.

  FIG. 4 is a bottom view of the impeller 30. FIG. 5 is a side sectional view of the impeller 30.

  4 and 5, the impeller 30 is thin and has a disk shape as a whole. Thereby, the centrifugal fan 1 can be configured to be thin. As shown in FIG. 4, for example, seven blades 51 are arranged in the impeller 30. The inner diameter D1 of the upper end portion 35 of the annular shroud 31 is larger than the outer diameter D2 of the hub 41. For this reason, the metal mold | die spaced apart up and down can be used for manufacture of the impeller 30. FIG. Therefore, the plurality of blades 51, the annular shroud 31, and the hub 41 can be formed as a single part by integral molding, for example, by injection molding using a resin such as engineering plastic.

  Each blade 51 has a pressure surface 53 and a negative pressure surface 54. The pressure surface 53 faces the front side of the rotation direction of the impeller 30 (the direction opposite to the clockwise direction in FIG. 4: the direction indicated by the arrow R). The negative pressure surface 54 faces away from the pressure surface 53.

  The blade 51 is a backward blade and is a so-called turbo type. The blades 51 have a shape that is curved and inclined backward with respect to the rotation direction. The specific shape of each blade 51 is, for example, as follows. That is, when the pressure surface 53 is viewed from the direction in which the rotating shaft of the impeller 30 extends (when viewed from the bottom), the shape is roughly a shape in which three types of arcs are connected. These arcs are connected such that adjacent arcs are tangent. As a result, the flow rate, static pressure, and noise of the centrifugal fan 1 can be increased. The negative pressure surface 54 has a curved shape roughly along the pressure surface 53 so that the distance from the pressure surface 53 decreases as the distance from the rotation shaft of the impeller 30 decreases as viewed from the bottom. The shape of the blade 51 as viewed from the bottom is not limited to this.

  As for the blade | wing 51, the rotating shaft side, ie, the suction inlet 33 side, of the impeller 30 becomes a front edge, and the side peripheral surface side of the impeller 30 becomes a rear edge. As shown in FIG. 5, the leading edge of each blade 51 is configured in a tapered shape so as to approach the rotation axis of the impeller 30 as it approaches the hub 41 from the annular shroud 31. The trailing edge of the blade 51 has a shape substantially perpendicular to the rotation axis of the impeller 30.

  FIG. 6 is a diagram schematically showing a cross section of the blade 51.

  The cross section shown in FIG. 6 is a cross section perpendicular to the horizontal plane perpendicular to the rotation axis and substantially perpendicular to the pressure surface 53 in a bottom view. That is, the cross section shown in FIG. 6 corresponds to that taken along the line CC of FIG. In FIG. 6, hatching is omitted. An arrow Z indicates a direction (upward) parallel to the rotation axis of the impeller 30.

  In the present embodiment, as shown in FIG. 6, the thickness of each blade 51, that is, the distance between the pressure surface 53 and the negative pressure surface 54 of each blade 51 increases from the annular shroud 31 in a direction parallel to the rotation axis. It ’s getting smaller. In other words, the blades 51 are formed so as to become thinner as they approach the partition wall 29. As a result, the distance between the pressure surface 53 of the blade 51 and the negative pressure surface 54 of the blade 51 adjacent to the blade 51 increases as the partition wall 29 is approached.

  The negative pressure surface 54 is substantially parallel to the rotation axis of the impeller 30. That is, strictly speaking, the suction surface 54 is provided with a draft and is not completely parallel to the rotation axis. However, this draft is a small angle, even compared to the inclination of the pressure surface 53. It is getting smaller.

  On the other hand, the pressure surface 53 includes a first inclined surface 53a, a second inclined surface 53b, and a chamfered surface 53c. Note that the entire pressure surface 53 of one blade 51 may be constituted by these three surfaces 53a, 53b, and 53c, and may further include these other surfaces.

  The upper surface of the first inclined surface 53 a is joined to the annular shroud 31 and is inclined so as to approach the negative pressure surface 54 side of the blade 51 as it approaches the motor base 21 from the annular shroud 31.

  The second inclined surface 53b is provided in a portion closer to the motor base 21 than the first inclined surface 53a. In the present embodiment, the second inclined surface 53b is provided up to the lower end portion of the pressure surface 53, that is, the lower end portion of the blade 51, following the first inclined surface 53a via the chamfered surface 53c. The second inclined surface 53b is provided over the entire region of all the blades 51 from the inside to the outside (from the hub 41 side to the tip portion).

  Here, the second inclined surface 53b is inclined so as to approach the negative pressure surface 54 side at a steeper angle than the first inclined surface 53a. That is, in the cross section of FIG. 6, the angle between the first inclined surface 53 a and the rotation axis of the impeller 30 is α, and a plane perpendicular to the second inclined surface 53 b and the rotation axis of the impeller 30 ( That is, if β is an angle with respect to the horizontal plane), the angle β is smaller than an angle obtained by subtracting the angle α from 90 degrees.

  The chamfered surface 53c is formed between the first inclined surface 53a and the second inclined surface 53b so as to round a ridge line formed by these two surfaces 53a and 53b. In the present embodiment, the chamfered surface 53c is a rounded chamfered curved surface (for example, a curved surface having a substantially elliptical arc shape or an arcuate cross section), for example, a curved surface having a predetermined curvature.

  The angle α is set in a range of 4 degrees to 8 degrees. Thereby, noise can be reduced efficiently without significantly reducing the air flow characteristics.

  The angle β is set larger than 0 degree and smaller than 45 degrees. More preferably, the angle β is set to 25 degrees or more and 35 degrees or less.

  FIG. 7 is a graph showing the relationship between the magnitude of the angle β and the noise level when the impeller 30 rotates.

  In FIG. 7, the horizontal axis corresponds to the angle β, and the vertical axis corresponds to the noise level. FIG. 7 shows noise in the case where the angle α is a predetermined angle (in the range of 4 to 8 degrees) and the angle β is 0 degree, 15 degrees, 25 degrees, 35 degrees, 45 degrees, and 55 degrees. The result of measuring the value of the rotation sound (nz sound) as the magnitude of is shown. The rotational sound (nz sound) is an abnormal sound depending on the product of the fan rotational speed (the rotational speed of the impeller 30) n (rpm) and the number of blades z, and is generated according to the rotational speed of the impeller 30. Therefore, the sound pressure (dB) at the frequency (nz / 60) Hz of the rotating sound was measured and compared. At the time of measurement in each case, the rotational speed of the impeller 30 was set so that a predetermined static pressure was obtained.

  As shown in FIG. 7, when the angle β is 0 degree (when there is no angle β and only the angle α is formed; that is, when there is no second inclined surface 53b and only the first inclined surface 53a). In comparison, it can be seen that the rotation sound (nz sound) can be effectively reduced by setting the angle β to less than 45 degrees. In addition, the rotation sound (kn sound, k = 2, 3,...) That is a harmonic of the rotation sound (nz sound) can be reduced. In particular, when the angle β is set to 25 degrees or more and 35 degrees or less, it can be seen that the effect of reducing the rotation sound (nz sound) can be further obtained.

  Note that when the angle β is larger than 45 degrees, the effect of reducing the rotational sound (nz sound) is hardly seen.

  As described above, in the present embodiment, the pressure surface 53 of the blade 51 is provided with the first inclined surface 53a and the second inclined surface 53b such that the angle β is less than 45 degrees. While securing a high static pressure, it is possible to reduce the harmonics accompanying the reduction of the rotational sound (nz sound). This is considered to be because the generation of the separation flow from the pressure surface 53 in the vicinity of the blowout port 19 where the wind speed becomes high can be prevented.

  [Others]

  The pressure surface may not be provided with a chamfered surface. For example, a first inclined surface that gradually inclines toward the suction surface side of the blade as the pressure surface side of the blade moves from the annular shroud toward the motor base, and an angle larger than the first inclined surface from the middle of the first inclined surface And a second inclined surface inclined toward the suction surface side.

  One or a plurality of inclined surfaces having an inclination angle different from the inclination angle of the first inclined surface and the inclination angle of the second inclined surface are provided between the first inclined surface and the second inclined surface. May be.

  In only a part of the region from the inside to the outside of the blade, the pressure surface may be configured to have an inclined surface as described above. Also, at the lower end of the blade (part on the partition wall side), the pressure surface is substantially perpendicular to the horizontal surface, just like the suction surface, and only the portion of the pressure surface close to the upper shroud is tapered. May be. Moreover, you may be comprised so that a pressure surface may become a taper shape only in the some blade | wings among several blades.

  The pressure surface of the blade is not limited to a tapered shape as shown linearly in the cross section as shown in FIG. For example, the first inclined surface or the second inclined surface may be formed so as to approach the negative pressure surface as it approaches the partition wall while slightly curving in the cross section as described above.

  The rough shape of the pressure surface of the blade in the bottom view may not be a shape in which the three arcs are connected as described above, or may not be a combination of higher order functions passing through three points. The blades may be formed as appropriate so as to have a shape that satisfies the desired requirements.

  The shape of the casing is not limited to a substantially regular square in plan view. The casing may have any arbitrary shape including a polygon, a circle, and an asymmetric shape. The fastening location between the upper casing and the motor base is not limited to the inside of the four corners of the upper casing in plan view. For example, a screw or a column for connecting the upper casing and the motor base to a place connected to the upper casing so as to protrude outward from an outer peripheral edge that is substantially square in a plan view of the upper casing. May be provided.

  In addition, in the location which fastens an upper casing and a motor base, when providing a support | pillar between an upper casing and a lower casing, the shape of a support | pillar should just be as follows, for example. That is, the support column may have a substantially cylindrical shape having a size that allows a screw for connecting the upper casing and the motor base to pass therethrough. By using the struts having such a shape, the air blown from the impeller is blown outward from the side surface of the casing with almost no resistance, so that the noise of the centrifugal fan can be reduced. it can.

  The motor base may be configured using a material other than a metal plate such as a resin material. The upper casing and the motor base may be formed integrally. Instead of the motor base, a lower casing that does not have a space for mounting the motor may be used, and the upper casing and the lower casing may constitute the casing. That is, the centrifugal fan is not limited to the one in which the motor is attached to the lower casing.

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Centrifugal fan 10 Casing 11 Upper casing 19 Outlet 21 Motor base (an example of lower casing)
30 impeller 31 annular shroud 33 suction port 35 upper end 41 hub 51 blade 53 pressure surface 53a first inclined surface 53b second inclined surface 53c chamfered surface 54 negative pressure surface 60 motor

In order to achieve the above object, according to one aspect of the present invention, an impeller, an upper casing located above the impeller, a lower casing located below the impeller, and an upper casing and a lower casing are interposed. The impeller includes an annular shroud, a hub, and a plurality of blades arranged circumferentially between the annular shroud and the hub, each of the plurality of blades being in a rotational direction. The centrifugal fan that forms a backward-facing blade that is curved and inclined backward and discharges the fluid introduced from the suction port at the top of the annular shroud to the side of the impeller as the impeller rotates is provided with an upper casing and a lower casing. Is assembled by a support column to form a casing, and the fluid introduced from the suction port is provided between the upper casing and the lower casing, except for the support column. Blown out from the can out mouth to the outside of the casing, the surface facing the impeller of the lower casing, becomes part of the wall to induce a fluid introduced from the mouth narrowing have intake, blades, an annular shroud impeller has a thinner shape as the distance in a direction parallel to the rotation axis, the pressure side of the blade, in the rotation axis direction of the impeller, to approach the suction side of the blade toward the lower casing from the annular shroud A first inclined surface that is inclined in the direction and a second inclined surface that follows the first inclined surface are formed, and the annular shroud, the hub, and the plurality of blades are formed by integral molding .

Claims (6)

Impeller,
A lower casing located below the impeller,
The impeller is
An annular shroud with an inner upper part serving as a suction port,
A plurality of blades respectively disposed between the annular shroud and the lower casing so as to protrude downward from the annular shroud;
A hub joined to each of the plurality of blades inside each blade;
A centrifugal fan that blows out the fluid introduced from the suction port of the annular shroud to the side of the impeller as the impeller rotates,
The upper surface of the lower casing is opposed to the impeller and becomes a part of a wall surface for guiding the fluid introduced from the suction port,
Each of the plurality of blades is inclined while curving backward in the rotational direction of the impeller as it approaches the outside of the impeller,
The pressure surface side of each of the plurality of blades is
A first inclined surface that is inclined so as to approach the suction surface side of the blade as it approaches the lower casing from the annular shroud;
A second inclined surface provided at a portion closer to the lower casing than the first inclined surface, and inclined to approach the suction surface side at a steeper angle than the first inclined surface. Expression fan.   The centrifugal fan according to claim 1, wherein an angle between the second inclined surface and a plane perpendicular to the rotation axis of the impeller is greater than 0 degrees and less than 45 degrees.   The centrifugal fan according to claim 1 or 2, wherein an angle between the second inclined surface and a plane perpendicular to the rotation axis of the impeller is 25 degrees or more and 35 degrees or less.   The centrifugal fan according to any one of claims 1 to 3, wherein an angle between the first inclined surface and a rotation shaft of the impeller is 4 degrees or more and 8 degrees or less.   5. The centrifugal fan according to claim 1, wherein the first inclined surface and the second inclined surface are joined via a round chamfered curved surface.   The centrifugal fan according to any one of claims 1 to 5, further comprising a motor that is attached to the lower casing and rotates the impeller.

Images