JP2019082115A - Centrifugal fan - Google Patents

Abstract

To provide a centrifugal fan which has excellent static pressure characteristics and air volume characteristics and is small in noise.SOLUTION: A centrifugal fan includes a motor having a rotor, an impeller that is fixed to the rotor and rotates with the rotor, a circuit board electrically connected to the motor, and a casing that accommodates the motor, the impeller, and the circuit board. The impeller includes a cylindrical boss portion fixed to the rotor, a plurality of blade portions that are arranged radially outside of the boss portion at intervals in a circumferential direction and extend radially outward, an annular upper shroud connecting axially-upper sides of the plurality of blade portions, and an annular lower shroud connecting axially-lower sides of the plurality of blade portions. The casing has a lower casing disposed axially below the impeller. The lower casing has a board accommodation portion accommodating the circuit board, and a cover member axially facing a lower end face of the blade portions and an upper face of the circuit board.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a centrifugal fan.

  The centrifugal fan is disclosed by Unexamined-Japanese-Patent No. 2016-106197. The centrifugal fan has a structure in which an impeller having a plurality of blades circumferentially arranged between an upper casing and a lower casing in which an air suction port is formed is housed. The centrifugal fan discharges the air introduced through the opening to the side of the impeller as the impeller rotates. The lower casing is made of a metal plate and has a recess that is recessed downward. A motor is attached to the bottom of the recess. A portion of the motor stator and the circuit board on which the motor drive circuit is mounted are housed inside the recess. The recess is provided with a hole through which means for supplying power to rotate the motor pass.

JP, 2016-106197, A

  In the configuration in which the impeller blade portion is sandwiched between the upper shroud and the lower shroud, when the impeller is formed by a single member, a lateral slide mechanism of the mold is required, and the structure of the mold is complicated. There is a restriction that the undercut portion can not be provided in the vicinity of the intake port. On the other hand, when the impeller is made of two parts, it is possible to solve the geometrical problem that is a problem when molding with a single part. However, since two molds are required and a construction method such as welding for fastening two members is required, the degree of difficulty of manufacture becomes high. Therefore, it is preferable to mold the structure of the impeller with a single member as a structure that allows the mold to be pulled up and down.

  On the other hand, there is a demand to enlarge the circuit board in accordance with the increase in size of the electronic components in order to increase the size of the electronic components to be used in the high output motor. When enlarging a circuit board by the structure of Unexamined-Japanese-Patent No. 2016-106197, it is necessary to enlarge the recessed part which accommodates a circuit board. As a result, a space is created between the peripheral portion of the recess and the impeller, and the air guiding function of the lower casing is lost. As described above, when the circuit board is enlarged, the static pressure characteristic, the air volume characteristic, and the noise characteristic may be deteriorated.

  As a countermeasure for this, it is also conceivable to fill the space between the peripheral portion of the recess and the impeller by extending the lower shroud of the impeller radially outward. However, this method has a problem that undercuts occur in the upper and lower shrouds, and the mold structure becomes complicated. In addition, the height of the blade portion may be shortened, and the air volume may be reduced in the thin centrifugal fan.

  An object of the present invention is to provide a centrifugal fan excellent in static pressure characteristics and air volume characteristics when the circuit board is enlarged and having a small noise with a configuration suitable for thinning.

  An exemplary centrifugal fan according to the present invention comprises a motor having a rotor rotating about a vertically extending central axis, an impeller fixed to the rotor and rotating with the rotor, and a circuit electrically connected to the motor It has a substrate and a casing that accommodates the motor, the impeller, and the circuit board. The impeller has a cylindrical boss fixed to the rotor, and a plurality of vanes circumferentially spaced on the radially outer side of the boss and extending radially outward, and a plurality of blades. It has an annular upper shroud which connects at least one copy of an axial upper part of the above-mentioned blade part, and an annular lower shroud which connects at least one copy of an axial lower side of a plurality of above-mentioned blade parts. The casing has a lower casing disposed axially below the impeller. The lower casing is recessed axially downward, and axially faces at least a portion of a lower end surface of a lower end surface of the blade portion and a substrate accommodating portion for accommodating the circuit substrate, and at least a portion of an upper surface of the circuit substrate. And a cover member.

  According to the present invention, it is possible to provide a technique suitable for thinning the centrifugal fan.

FIG. 1 is an external perspective view showing an entire configuration of a centrifugal fan according to an embodiment of the present invention. FIG. 2 is a vertical sectional view of a centrifugal fan according to an embodiment of the present invention. FIG. 3 is a perspective view showing the centrifugal fan with the upper casing, the impeller, and the cover member removed. FIG. 4 is a schematic plan view of the cover member as viewed from above. FIG. 5 is a perspective view of the impeller as viewed from above. FIG. 6 is a perspective view of the impeller as viewed from below. FIG. 7 is a partial cross-sectional view around the exhaust port of the centrifugal fan according to the embodiment of the present invention. FIG. 8 is an enlarged view of the upper and lower shrouds of the impeller in FIG. 7. FIG. 9 is a view for explaining a centrifugal fan according to a modification.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In this specification, the direction parallel to the central axis P of the motor 30 of the centrifugal fan 100 shown in FIG. 2 is “axial direction”, the direction orthogonal to the central axis P is “radial direction”, and the central axis P is central The direction along the arc of the circle is referred to as "circumferential direction". Further, in the present specification, the axial direction is the vertical direction, the impeller 10 side is upward, and the motor 30 side is downward. However, there is no intention to limit the use direction of the centrifugal fan 100 according to the present invention based on the definition in the vertical direction.

  Further, in the present application, the “parallel direction” also includes a substantially parallel direction. Further, in the present application, the “orthogonal direction” also includes a substantially orthogonal direction.

<1. Configuration of centrifugal fan>
FIG. 1 is an external perspective view showing an entire configuration of a centrifugal fan 100 according to an embodiment of the present invention. FIG. 2 is a vertical sectional view of a centrifugal fan 100 according to an embodiment of the present invention. FIG. 3 is a perspective view showing the centrifugal fan 100 from which the upper casing 2, the impeller 10 and the cover member 6 are removed. As shown in FIGS. 1 and 2, the centrifugal fan 100 has a casing 1, an impeller 10, a motor 30, and a circuit board 40.

  The casing 1 accommodates the impeller 10, the motor 30, and the circuit board 40. The casing 1 has an upper casing 2 and a lower casing 3. The upper casing 2 and the lower casing 3 are made of, for example, resin. However, the upper casing 2 and the lower casing 3 may be made of materials other than resin, such as metal. The upper casing 2 and the lower casing 3 may be made of the same material, or may be made of different materials. In addition, the centrifugal fan 100 may have a configuration without the upper casing 2.

  The upper casing 2 is disposed axially above the impeller 10. The upper casing 2 has an air inlet 2 a facing the central portion in the radial direction of the impeller 10. Specifically, the upper casing 2 has a rectangular cylindrical shape in which four corners are combined on the outer periphery of the cylindrical portion. The intake port 2a is circular. However, the upper casing 2 may have another shape such as a cylindrical shape. The shape of the intake port 2a may also be other than circular. By providing the upper casing 2, generation of turbulent flow around the upper shroud 15 described later can be suppressed, and the centrifugal fan 100 can efficiently deliver air in the centrifugal direction.

  The lower casing 3 is disposed axially below the impeller 10. The lower casing 3 is rectangular in plan view in the axial direction, and has substantially the same size as the upper casing 2. The lower casing 3 has a substrate housing portion 4 and a cover member 6. Lower casing 3 further includes a flange portion 5.

  The board accommodation portion 4 is recessed downward in the axial direction, and accommodates the circuit board 40. In the present embodiment, the board accommodation portion 4 has the same shape as the circuit board 40 and is slightly larger in the radial direction than the circuit board 40. However, the shape of the board housing portion 4 may not be the same as the shape of the circuit board 40. The motor 30 is positioned at the radial direction central portion of the substrate accommodation portion 4, and a part of the circuit board 40 protrudes radially outward with respect to the motor 30.

  The flange portion 5 extends radially outward from the outer peripheral edge of the substrate accommodation portion 4. A part of the cover member 6 is fixed to the flange portion 5. FIG. 4 is a schematic plan view of the cover member 6 as viewed from the upper side. As shown in FIGS. 2 and 4, the cover member 6 is in the form of a rectangular plate and has a circular opening 6a at its center. The shape of the opening 6a is not limited to a circle, and may be another shape such as a rectangle. Further, in the present embodiment, the cover member 6 has the step portion 6b in which the thickness in the axial direction changes, and the thickness on the inner side in the radial direction from the step portion 6b is thinner than the thickness on the outer side in the radial direction It has become. The cover member 6 is disposed on the flange portion 5. A portion radially outside the step portion 6 b of the cover member 6 contacts the flange portion 5, and the portion is fixed to the flange portion 5. A region for fixing the cover member 6 can be sufficiently secured by the flange portion 5, and the cover member 6 can be firmly fixed.

  In addition, the fixing method with respect to the flange part 5 of the cover member 6 is not specifically limited. The cover member 6 may be fixed to the flange portion 5 using, for example, a screw or an adhesive. In the present embodiment, the cover member 6 is fixed to the flange portion 5 by a screw (not shown) together with the upper casing 2. However, the cover member 6 may be fixed to the flange 5 by a screw separately from the upper casing 2. Further, the cover member 6 may have a flat plate shape without the step portion 6 b. The cover member 6 is made of, for example, a resin or a metal. The cover member 6 may be made of the same material as the substrate housing portion 4 and the flange portion 5. Furthermore, in the present embodiment, the radially outer end of the cover member 6 is at the same position as the radially outer end of the flange portion 5. However, the radially outer end of the cover member 6 may be positioned radially inward of the radially outer end of the flange portion 5 or may be positioned radially outward of the radially outer end of the flange portion 5 .

  The motor 30 has a rotor 32. The motor 30 further includes a stator 31, a shaft 33, a bearing 34, and a bearing holder 35.

  The rotor 32 rotates about a central axis P extending in the vertical direction. The rotor 32 is disposed above the stator 31 and radially outward. The rotor 32 is in the form of a cup that opens downward. The impeller 10 is disposed radially outside the rotor 32, and the impeller 10 is fixed to the rotor 32. A shaft 33 is disposed radially inward of the rotor 32, and the shaft 33 is fixed to the rotor 32. A rotor magnet 36 is fixed to the inner circumferential surface of the rotor 32. In the present embodiment, the rotor magnet 36 is a single annular magnet. An N pole and an S pole are alternately magnetized in the circumferential direction on the radially inner surface of the rotor magnet 36. A plurality of magnets may be disposed on the inner circumferential surface of the rotor 32 instead of a single annular magnet.

  The shaft 33 is a columnar member disposed along the central axis P. As a material of the shaft 33, for example, a metal such as stainless steel is used. The upper end portion of the shaft 33 is located above the upper bearing portion 34. An upper end portion of the shaft 33 is passed through a rotor hole axially penetrating along a central axis P of the rotor 32 and fixed to the rotor 32.

  The bearing portion 34 rotatably supports the shaft 33 about the central axis P. In the present embodiment, the number of bearing portions 34 is two, and the two bearing portions 34 are vertically arranged. The two bearings 34 are ball bearings. The number and type of bearings 34 may be changed as appropriate.

  The bearing holder 35 supports the stator 31 radially outward and supports the bearing 34 radially inward. As a material of the bearing holding portion 35, for example, a metal such as stainless steel or brass is used. However, the material of the bearing holding portion 35 is not limited to metal, and may be resin. The bearing holding portion 35 axially extends in a cylindrical shape around the central axis P. The lower end portion of the bearing holding portion 35 is inserted into a circular hole centered on a central axis P provided in the lower casing 3 and fixed to the lower casing 3.

  The stator 31 is an armature that generates a magnetic flux according to the drive current. The stator 31 has a stator core, an insulator, and a coil.

  The stator core is a magnetic body. The stator core is formed, for example, by laminating electromagnetic steel sheets. The stator core has an annular core back and a plurality of teeth. The core back is fixed to the outer peripheral surface of the bearing holder 35. The plurality of teeth project radially outward from the core back. The insulator is an insulator. For example, resin is used as a material of the insulator. The insulator covers at least a part of the stator core. A coil is configured by winding a wire around teeth via an insulator.

  By supplying a drive current to the stator 31, a rotational torque is generated between the rotor magnet 36 and the stator 31. Thereby, the rotor 32 rotates with respect to the stator 31, and the impeller 10 fixed to the rotor 32 also rotates around the central axis P. The motor 30 illustrated in FIG. 2 is an outer rotor type motor in which the rotor 32 is disposed radially outside the stator 31. However, the motor 30 may be an inner rotor type motor in which the rotor 32 is disposed radially inward of the stator 31.

  The circuit board 40 is electrically connected to the motor 30. The circuit board 40 is supported on the lower side of the motor 30. The circuit board 40 is disposed in the board housing portion 4 of the lower casing 3. The circuit board 40 is disposed substantially perpendicularly to the central axis P on the upper side of the lower casing 3 and the lower side of the stator 31. The circuit board 40 is fixed to, for example, an insulator. On the circuit board 40, an electric circuit for supplying a drive current to the coil is mounted. The ends of the conductive wires constituting the coil are electrically connected to the terminals provided on the circuit board 40.

  FIG. 5 is a perspective view of the impeller 10 as viewed from above. FIG. 6 is a perspective view of the impeller 10 as viewed from below. The impeller 10 is fixed to the rotor 32 and rotates with the rotor 32. As shown in FIGS. 5 and 6, the impeller 10 has a boss 11, a plurality of blades 13, an upper shroud 15, and a lower shroud 17. In the present embodiment, the boss portion 11, the plurality of blade portions 13, the upper shroud 15, and the lower shroud 17 are single members formed of the same resin material.

  The boss portion 11 is cylindrical and fixed to the rotor 32. In the present embodiment, the boss portion 11 is cylindrical, and is fixed to the outer peripheral surface of the rotor 32 on the upper side of the motor 30. The boss portion 11 is fixed to the rotor 32 by, for example, press fitting or bonding. More specifically, the boss portion 11 has an annular projecting portion that protrudes radially inward at the upper end in the axial direction. The projection is located above the rotor 32. The protrusion may not be provided. The projecting portion is provided, for example, to enable placement of a weight member that performs balance adjustment.

  The plurality of blade portions 13 are disposed radially outward of the boss portion 11 at intervals in the circumferential direction, and extend outward in the radial direction. In the present embodiment, the blade portion 13 faces the boss portion 11 via a gap in the radial direction. However, the blade portion 13 may be in contact with the boss portion 11. The vanes 13 radially extend outward in the radial direction while being inclined in a direction opposite to the rotational direction of the centrifugal fan 100 in a plan view. The direction in which the vanes 13 extend radially outward is not limited to this. A part of the vanes 13 may extend in the same direction as the rotational direction, or may extend orthogonal to the rotational direction. Moreover, in this embodiment, although the some blade part 13 is arrange | positioned at equal intervals in the circumferential direction, it is not necessary to necessarily arrange at equal intervals.

  The upper shroud 15 is annular. In the present embodiment, the upper shroud 15 is annular. The upper shroud 15 connects at least a part of the upper axial sides of the plurality of vanes 13. In the present embodiment, the upper shroud 15 connects a part of the radially outer side of the plurality of vanes 13.

  The lower shroud 17 is annular. In the present embodiment, the lower shroud 17 has a cylindrical shape that tapers from the axially lower side to the upper side. The lower shroud 17 connects at least a portion of the plurality of vanes 13 on the lower side in the axial direction. In the present embodiment, the lower shroud 15 connects a part of the radially inner side of the plurality of vanes 13. The radially inner end of the lower shroud 17 is connected to the boss 11. The upper shroud 15 and the lower shroud 17 are connected by the plurality of vanes 13.

  The air taken in from the intake port 2a of the upper casing 2 is circumferentially swirled in the casing 1 by the rotation of the impeller 10, and then exhausted from the exhaust port 2b provided between the upper casing 2 and the lower casing 3 Ru. The upper shroud 15 and the lower shroud 17 improve the fan efficiency of the centrifugal fan 100 by efficiently guiding the air drawn into the casing 1 from the air inlet 2a to the air outlet 2b. In the present embodiment, the exhaust port 2 b is provided in the entire circumferential direction of the casing 1. However, the exhaust port 2 b may be provided only in a part of the casing 1 in the circumferential direction.

<2. Configuration around the exhaust port of centrifugal fan>
Next, the configuration around the exhaust port 2b, which is a characteristic part of the centrifugal fan 100 according to the present embodiment, will be described in detail. FIG. 7 is a partial cross-sectional view of the vicinity of the exhaust port 2 b of the centrifugal fan 100 according to the embodiment of the present invention. FIG. 8 is an enlarged view around the upper shroud 15 and the lower shroud 17 of the impeller 10 in FIG.

  As shown in FIG. 7, the rotor 32, the boss 11 of the impeller 10, and the blades 13 are arranged to overlap in the radial direction. The lower end surface of the rotor 32 and the lower end surface of the boss portion 11 are located axially above the lower end surface 13 a of the blade portion 13. Furthermore, the axial height of the boss portion 11 is accommodated within the axial height of the impeller 10. By these, the centrifugal fan 100 is configured to be thin. Further, in the present embodiment, the blade portion 13 extends to a position where a part thereof overlaps with the flange portion 5 in a plan view from the axial direction. For this reason, the volume of air generated by the rotation of the impeller 10 can be increased.

  As shown in FIG. 8, the radially outer end 17a of the lower shroud 17 is at the same position in the radial direction as the radially inner end 15a of the upper shroud 15a. As a result, when the impeller 10 is injection-molded from resin, the mold can be removed in one direction such as the vertical direction. Therefore, there is no need to split the mold or to provide the mold with a slide mechanism, and the structure or manufacturing process of the mold can be simplified. The radially outer end 17 a of the lower shroud 17 may be located radially inward of the radially inner end 15 a of the upper shroud 15. That is, if the radially outer end 17 a of the lower shroud 17 is located at the same position in the radial direction as the radially inner end 15 a of the upper shroud 15 or radially inward of the radially inner end 15 a of the upper shroud 15 , The mold can be pulled out in one direction, such as up and down.

  As shown in FIG. 7, the cover member 6 axially faces at least a portion of the lower end surface 13 a of the blade portion 13 and at least a portion of the upper surface 40 a of the circuit board 40. In the present embodiment, the upper surface 6 c of the cover member 6 axially faces a portion of the lower end surface 13 a of the blade portion 13 which is located radially outward of the lower shroud 17. The lower surface 6 d of the cover member 6 axially faces the radially outer portion of the upper surface 40 a of the circuit board 40. Thereby, the air which has flowed in the axial direction from the gap between the outer peripheral surface of the intake port 2 a and the boss portion 11 and the inner peripheral surface of the upper shroud 15 can be guided in the centrifugal direction along the upper surface 6 c of the cover member 6 it can. In the present embodiment, although the radial outer end 17 a of the lower shroud 17 and the inner circumferential surface 4 a of the substrate housing portion 4 are separated in the radial direction due to the enlargement of the circuit board 40, the cover member 6 causes centrifugal Air can be efficiently introduced in the direction. In other words, according to the present embodiment, the radial length of the lower shroud 17 can be shortened by providing the air guiding function to the cover member 6, and the mold structure or manufacturing process of the impeller 10 is simplified. can do.

  As shown in FIGS. 7 and 8, the radially inner end 6 e of the cover member 6 is located radially inward of the radially outer end 17 a of the lower shroud 17. The upper surface 6 c of the cover member 6 axially faces the lower surface 17 b of the lower shroud 17. That is, the cover member 6 and the lower shroud 17 overlap in the axial direction. According to this, it is possible to make it difficult for the air flowing from the air inlet 2a to the cover member 6 along the lower shroud 17 to pass through the radially inner end 6e of the cover member 6. That is, according to this configuration, it is possible to suppress air flowing from the lower shroud 17 to the cover member 6 from flowing into the motor side (radially inward).

  The upper surface 6 c of the cover member 6 is preferably opposed to the lower surface 17 b of the lower shroud 17 with a gap. Thereby, the impeller 10 can be rotated smoothly.

  In the present embodiment, as shown in FIG. 8, the inner circumferential surface 4 a of the substrate housing portion 4 and the radial outer end 40 b of the circuit board 40 face each other with a first gap 50 therebetween. Further, the lower surface 6 d of the cover member 6 and the upper surface 40 a of the circuit board 40 face each other at a second interval 51. A space on the upper side in the axial direction of the cover member 6 communicates with a space in the board accommodation portion 4 located on the lower side in the axial direction of the circuit board 40 via the first gap 50 and the second space 51. Thereby, heat can be prevented from remaining in the space located below the circuit board 40 in the axial direction. That is, the electronic component can be easily disposed on the lower surface of the circuit board 40. In the present embodiment, the inner circumferential surface 4 a of the substrate housing portion 4 and the radially outer end 40 b of the circuit board 40 are opposed in the radial direction. The lower surface 6 d of the cover member 6 and the upper surface 40 a of the circuit board 40 face each other in the axial direction. Further, the lower surface 6 d of the cover member 6 may be in contact with the upper surface 40 a of the circuit board 40. That is, the second gap 51 may not be provided.

  As shown in FIG. 8, the lower shroud 17 has an inclined portion 171. The inclined portion 171 is inclined downward in the axial direction from the radially inner side toward the outer side. In detail, the radially inner end of the inclined portion 171 is connected to the outer peripheral surface of the boss portion 11. From this connection point, the inclined portion 171 extends obliquely downward. The inclined portion 171 may be linear in a cross sectional view, but is curved in the present embodiment. In detail, the inclined portion 171 is concavely curved. By providing the inclined portion 171, it is possible to efficiently change the flow direction of the air flowing in in the axial direction from the intake port 2a to the direction along the upper surface 6c of the cover member 6.

  As shown in FIG. 8, the lower shroud 17 has a flat portion 172. The flat portion 172 is continuous with the radially outer side of the inclined portion 171. The flat portion 172 extends along a plane perpendicular to the axial direction. In detail, the flat portion 172 is parallel to the upper surface 6 c of the cover member 6. By providing the flat portion 172 continuous with the inclined portion 171, the direction in which the air flows can be smoothly changed to the direction along the upper surface 6c of the cover member 6. The flat portion 172 may not be provided.

<3. Modified example>
FIG. 9 is a view for explaining a centrifugal fan 100A according to a modification. FIG. 9 is an enlarged cross-sectional view similar to FIG. The centrifugal fan 100A of the modified example is different from the configuration of the embodiment described above and in the relationship between the cover member 6A and the impeller 10A. The cover member 6A is fixed to the flange portion 5A of the lower casing 3A. The circuit board 40A is accommodated in the board accommodation portion 4A.

  Similar to the embodiment described above, the cover member 6A axially faces a portion of the lower end surface 13aA of the blade portion 13A and a portion of the top surface 40aA of the circuit board 40A. However, in the present modification, the cover member 6A does not axially face the lower surface 17bA of the lower shroud 17A. In the present modification, the radially inner end surface 6eA of the cover member 6A radially faces the radially outer end surface 17aA of the lower shroud 17A. Also in the present modification, the lower shroud 17A has an inclined portion 171A and a flat portion 172A. The radially outer end surface 17aA of the lower shroud 17A is a radially outer end surface of the flat portion 172A.

  It is preferable that the radial inner end surface 6eA of the cover member 6A and the radial outer end surface 17aA of the lower shroud 17A not be in contact with each other, and further that the radial interval be small. By avoiding the contact, the impeller 10A can be rotated smoothly. By narrowing the spacing, the amount of air directed in a direction different from the centrifugal direction can be reduced. The radial inner end face 6eA of the cover member 6A and the radial outer end face 17aA of the lower shroud 17A are flat in this modification, but may be curved. When the end face 6eA, 17aA is a plane, the plane may be parallel to the axial direction or may be inclined.

  Also in this modification, the air flowing in the axial direction from the gap between the outer peripheral surface of the boss portion 11A and the inner peripheral surface of the upper shroud 15A can be guided in the centrifugal direction along the upper surface 6cA of the cover member 6A. In this modification, although the radial outer end 17aA of the lower shroud 17A and the inner peripheral surface 4aA of the substrate accommodation portion 4A are separated in the radial direction due to the enlargement of the circuit board 40A, the cover member 6A Air can be efficiently introduced in the direction. In other words, according to the present modification, the radial length of the lower shroud 17A can be shortened by providing the air guiding function to the cover member 6A, and the mold structure or manufacturing process of the impeller 10A is simplified. can do. Furthermore, in the present modification, since the cover member 6A and the lower shroud 17A do not overlap in the axial direction, the thickness of the centrifugal fan 100A can be reduced.

<4. Points to keep in mind>
Various technical features disclosed in the present specification can be variously modified without departing from the spirit of the technical creation. In addition, the plurality of embodiments and modifications shown in the present specification may be implemented in combination as far as possible.

  The present invention can be used, for example, for a range hood fan, a ventilation fan for a duct, a heat exchange unit, and a centrifugal fan used for sheet adsorption of a printing apparatus.

DESCRIPTION OF SYMBOLS 1 ... Casing 2 ... Upper casing 2a ... Air intake 3 ... Lower casing 4 ... Board | substrate accommodating part 5 ... Flange part 6 ... Cover member 10 ... Impeller 11 ... · Boss portion 13 · · · Blade portion 15 · · · upper shroud 17 · · · lower shroud 30 · · · · · · · · · motor 32 · · · · · · · · · · · circuit board 50 first gap 51 second Gap 100: Centrifugal fan 171: Inclined part 172: Flat part P: Central axis

Claims (9)

A motor having a rotor rotating about a central axis extending up and down;
An impeller fixed to the rotor and rotating with the rotor;
A circuit board electrically connected to the motor;
A casing for housing the motor, the impeller, and the circuit board;
A centrifugal fan having
The impeller is
A cylindrical boss fixed to the rotor;
A plurality of vanes which are disposed at intervals in the circumferential direction on the radially outer side of the boss portion and extend radially outward;
An annular upper shroud connecting at least a portion of the plurality of axially upper portions of the blades;
An annular lower shroud that connects at least a portion of the plurality of axially lower portions of the blades;
Have
The casing has a lower casing disposed axially below the impeller,
The lower casing is
A substrate accommodating portion which is recessed downward in the axial direction and which accommodates the circuit board;
A cover member axially facing at least a portion of the lower end surface of the blade portion and at least a portion of the upper surface of the circuit board;
Have a centrifugal fan. The lower casing has a flange portion extending radially outward from the outer peripheral edge of the substrate accommodation portion,
The centrifugal fan according to claim 1, wherein a part of the cover member is fixed to the flange portion. The radially inner end of the cover member is located radially inward of the radially outer end of the lower shroud,
The centrifugal fan according to claim 1, wherein an upper surface of the cover member is axially opposed to a lower surface of the lower shroud.   The centrifugal fan according to claim 1, wherein a radial inner end surface of the cover member is radially opposed to a radial outer end surface of the lower shroud.   The centrifugal fan according to any one of claims 1 to 4, wherein the lower shroud has an inclined portion which inclines axially downward from the radially inner side to the outer side.   The centrifugal fan according to claim 5, wherein the lower shroud has a flat portion which is continuous with a radial outer side of the inclined portion and extends along a plane perpendicular to the axial direction.   The radial outer end of the lower shroud is located at the same position in the radial direction as the radial inner end of the upper shroud, or radially inward of the radial inner end of the upper shroud. Centrifugal fan as described in 1 or 2. The inner circumferential surface of the substrate accommodation portion and the radial outer end of the circuit board are opposed to each other with a first gap,
The lower surface of the cover member and the upper surface of the circuit board face each other at a second distance,
The space in the axial direction of the cover member is in communication with the space in the substrate accommodation portion located in the axial direction of the circuit board via the first gap and the second gap. The centrifugal fan according to any one of the above. The casing has an upper casing disposed axially above the impeller,
The centrifugal fan according to any one of claims 1 to 8, wherein the upper casing has an air inlet opposed to a radial center of the impeller.

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