The present application claims priority under 35 U.S.C. § 119 to Japanese Application No. 2017-208441 filed on Oct. 27, 2017 the entire content of which is incorporated herein by reference.
The present disclosure relates to a centrifugal fan.
A centrifugal fan has a structure in which an impeller having a plurality of blades arranged on the circumference thereof is accommodated between an upper casing in which an air intake port is formed and a lower casing. As the impeller rotates, the centrifugal fan discharges air, introduced through an opening portion, to a side of the impeller. The lower casing is made of a metal plate and has a recessed portion recessed downward. A motor is attached to a bottom surface of the recessed portion. A portion of a stator of the motor and a circuit board on which a drive circuit of the motor is mounted are accommodated in the recessed portion. The recessed portion is provided with a hole portion through which a supplier that supplies electric power for rotating the motor passes.
With a configuration in which the blade portion of an impeller is sandwiched between an upper shroud and a lower shroud, in the case where the impeller is formed as a single member, a lateral slide mechanism is required for the mold and the mold structure becomes complicated. There is a restriction that an undercut portion cannot be provided in the vicinity of the air intake port. On the other hand, in the case where the impeller is formed of two members, the geometrical problem that arises when the impeller is formed as a single member is reduced. However, the difficulty of manufacturing becomes high because two molds and a method such as welding for fastening the two members is used.
On the other hand, in high-output motors, as larger electronic components are used, the size of the circuit board has increased in accordance with an increase in the size of the electronic components. In the case where a circuit board is made larger with the configuration of the existing centrifugal fan, the recessed portion for accommodating the circuit board is enlarged. As a result, a space is generated between the peripheral edge of the recessed portion and the impeller, and the wind guiding function of the lower casing is lost. Thus, there is a possibility that static pressure characteristics, air volume characteristics, and noise characteristics deteriorate when the circuit board is increased in size.
As a countermeasure against this deterioration, the space between the peripheral portion of the recessed portion and the impeller is filled by extending the lower shroud of the impeller radially outward. However, in this method, an undercut portion is generated in the upper shroud and the lower shroud, which causes a problem that the mold structure becomes complicated. In addition, the height of the blade portion is shortened and there is a concern that the airflow rate in a thin centrifugal fan decreases.
A centrifugal fan according to at least one embodiment of the present disclosure includes a motor having a rotor that rotates about a center axis extending vertically. The centrifugal fan further includes an impeller that is fixed to the rotor and rotates together with the rotor. The centrifugal fan further includes a circuit board electrically connected to the motor. The centrifugal fan further includes 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 at intervals in a circumferential direction on a radially outer side of the boss portion and extend radially outward, an upper shroud having an annular shape and connecting at least portions on an axially upper side of the blade portions, and a lower shroud having an annular shape and connecting at least portions on an axially lower side of the blade portions. The casing has a lower casing disposed axially below the impeller. The lower casing includes a board accommodating portion that is recessed axially downward and accommodates the circuit board, and a cover member that faces at least a portion of a lower end surface of the blade portion and at least a portion of an upper surface of the circuit board in an axial direction.
The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of some embodiments with reference to the attached drawings.
Hereinafter, at least one embodiment of the present disclosure will be described in detail with reference to the drawings. Further, in this specification, a direction parallel to the center axis P of a motor 30 provided to a centrifugal fan 100 in
In the present disclosure, a “parallel direction” includes a substantially parallel direction. In addition, in the present disclosure, a “perpendicular direction” includes a substantially perpendicular direction.
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 include a resin, for example. However, the upper casing 2 and the lower casing 3 may include materials other than a resin, such as a metal. The upper casing 2 and the lower casing 3 may include the same material or different materials. Further, the centrifugal fan 100 may be configured not to have the upper casing 2.
The upper casing 2 is disposed axially above the impeller 10. The upper casing 2 has an air intake port 2a facing a radially central portion of the impeller 10. In detail, the upper casing 2 has a rectangular tubular shape in which four corner portions are combined with the outer periphery of a cylindrical portion. The air intake port 2a is circular. However, the upper casing 2 may have another shape such as a cylindrical shape. The shape of the air intake port 2a may be other than circular. By providing the upper casing 2, the occurrence of a turbulent flow around the upper shroud 15 described below can be suppressed. Moreover, the centrifugal fan 100 can efficiently send air in the centrifugal direction.
The lower casing 3 is disposed axially below the impeller 10. The lower casing 3 has a rectangular shape in a plan view from the axial direction, and has substantially the same size as that of the upper casing 2. In at least one embodiment, the lower casing 3 has a shape other than rectangular. The lower casing 3 has a board accommodating portion 4 and a cover member 6. The lower casing 3 further has a flange portion 5.
The board accommodating portion 4 is recessed downward axially, and accommodates the circuit board 40. In at least one embodiment, the board accommodating portion 4 has the same shape as that of the circuit board 40, and is slightly larger in the radial direction than the circuit board 40. However, the shape of the board accommodating portion 4 may not be the same as the shape of the circuit board 40. The motor 30 is positioned at a radially center portion of the board accommodating portion 4, and a portion of the circuit board 40 protrudes radially outward with respect to the motor 30.
A flange portion 5 extends radially outward from the outer peripheral edge of the board accommodating portion 4. A portion of the cover member 6 is fixed to the flange portion 5.
A method of fixing the cover member 6 to the flange portion 5 is not particularly limited. The cover member 6 may be fixed to the flange portion 5 using, for example, screws, or may be fixed with an adhesive. In at least one embodiment, the cover member 6 is fixed to the flange portion 5 by screws (not illustrated) together with the upper casing 2. However, the cover member 6 may be fixed to the flange portion 5 by screws, separately from the upper casing 2. In addition, the cover member 6 may have a flat plate shape not having the stepped portion 6b. Further, the cover member 6 includes a resin or a metal, for example. The cover member 6 may include the same material as the material constituting the board accommodating portion 4 and the flange portion 5. Furthermore, in at least one embodiment, the radially outer edge of the cover member 6 is at the same position as that of the radially outer edge of the flange portion 5. However, the radially outer edge of the cover member 6 may be positioned radially inside the radially outer edge of the flange portion 5, or may be positioned radially outside the radially outer edge of the flange portion 5.
The motor 30 has a rotor 32. The motor 30 also has a stator 31, a shaft 33, a bearing portion 34, and a bearing holding portion 35.
The rotor 32 rotates about the center axis P extending vertically. The rotor 32 is disposed above the stator 31 on the radially outer side. The rotor 32 has a cup shape opening downward. In at least one embodiment, the rotor 32 has a shape other than a cup shape. The impeller 10 is disposed radially outside the rotor 32, and the impeller 10 is fixed to the rotor 32. The shaft 33 is disposed radially inside the rotor 32, and the shaft 33 is fixed to the rotor 32. A rotor magnet 36 is fixed to the inner peripheral surface of the rotor 32. In at least one embodiment, the rotor magnet 36 is a single annular magnet. N poles and S poles are alternately magnetized in the circumferential direction on the radially inner surface of the rotor magnet 36. Instead of a single annular magnet, a plurality of magnets may be arranged on the inner peripheral surface of the rotor 32.
The shaft 33 is a columnar member disposed along the center axis P. As the material of the shaft 33, for example, a metal such as stainless steel may be used. An upper end portion of the shaft 33 is located above the bearing portion 34 on the upper side. The upper end portion of the shaft 33 passes through a rotor hole axially penetrating along the center axis P of the rotor 32, and is fixed to the rotor 32.
The bearing portion 34 rotatably supports the shaft 33 around the center axis P. In at least one embodiment, the number of the bearing portions 34 is two, and the two bearing portions 34 are lined up and down. The two bearing portions 34 are composed of ball bearings. The number and type of the bearing portions 34 may be appropriately changed.
The bearing holding portion 35 supports the stator 31 radially outside, and supports the bearing portion 34 radially inside. As the material of the bearing holding portion 35, for example, a metal such as stainless steel, brass or the like may be used. However, the material of the bearing holding portion 35 is not limited to a metal and may be a resin. The bearing holding portion 35 extends axially in a cylindrical shape around the center axis P. The lower end portion of the bearing holding portion 35 is inserted into a circular hole around the center axis P provided to the lower casing 3, and is 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 by laminating electromagnetic steel plates, for example. 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 holding portion 35. The plurality of teeth protrude radially outside from the core back. The insulator is an insulating body. As a material of the insulator, for example, a resin may be used. The insulator covers at least a portion of the stator core. The coil is formed by winding a conductive wire around the teeth via the insulator.
By supplying a drive current to the stator 31, a rotational torque is generated between the rotor magnet 36 and the stator 31. As a result, the rotor 32 rotates with respect to the stator 31, and the impeller 10 fixed to the rotor 32 also rotates about the center axis P. The motor 30 in
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 accommodating portion 4 of the lower casing 3. The circuit board 40 is disposed substantially perpendicular to the center axis P on the upper side of the lower casing 3 and on the lower side of the stator 31. The circuit board 40 is, for example, fixed to the insulator. An electric circuit that supplies a drive current to the coil is mounted on the circuit board 40. End portions of the conductor forming the coil are electrically connected to terminals provided on the circuit board 40.
The boss portion 11 is tubular, and is fixed to the rotor 32. In at least one embodiment, the boss portion 11 is cylindrical, and is fixed to the outer peripheral surface of the rotor 32 above the motor 30. The boss portion 11 is fixed to the rotor 32 by, for example, press fitting or adhesion. In detail, the boss portion 11 has an annular protruding portion protruding radially inward at the axially upper end. The protruding portion is located above the rotor 32. The protruding portion may not be provided. The protruding portion is provided to enable, for example, a weight member for performing balance adjustment to be arranged.
The blade portions 13 are disposed at intervals in the circumferential direction on the radially outer side of the boss portion 11, and extend radially outward. In at least one embodiment, the blade portions 13 face the boss portion 11 in the radial direction via a gap. However, the blade portions 13 may be in contact with the boss portion 11. In a plan view, the blade portions 13 are inclined in the opposite direction of the rotation direction of the centrifugal fan 100, and extend radially outward. The direction in which the blade portions 13 extend is not limited to radially outward. A portion of the blade portions 13 may extend in the same direction as the rotation direction or may extend perpendicularly to the rotation direction. Further, in at least one embodiment, the blade portions 13 are arranged at equal intervals in the circumferential direction. However, in at least one embodiment, the blade portions 13 are at varying intervals.
The upper shroud 15 is annular. In at least one embodiment, the upper shroud 15 is in a ring shape. The upper shroud 15 connects at least axially upper portions of the blade portions 13. In at least one embodiment, the upper shroud 15 connects radially outer portions of the blade portions 13.
The lower shroud 17 is annular. In at least one embodiment, the lower shroud 17 has a cylindrical shape tapered from the axially lower side to the upper side. The lower shroud 17 connects at least axially lower portions of the blade portions 13. In the present embodiment, the lower shroud 17 connects radially inner portions of the blade portions 13. The radially inner edge of the lower shroud 17 is connected to the boss portion 11. The upper shroud 15 and the lower shroud 17 are connected by the blade portions 13.
The air sucked from the air intake port 2a of the upper casing 2 is spun in the casing 1 in the circumferential direction by the rotation of the impeller 10, and is discharged from an exhaust port 2b provided between the upper casing 2 and the lower casing 3. The upper shroud 15 and the lower shroud 17 efficiently guide the air taken into the casing 1 from the air intake port 2a to the exhaust port 2b, thereby improving the fan efficiency of the centrifugal fan 100. In at least one embodiment, the exhaust port 2b is provided on the entire circumference of the casing 1. However, the exhaust port 2b may be provided only in a part of the circumferential portion of the casing 1.
Next, a configuration around the exhaust port 2b, which is a characteristic part of the centrifugal fan 100 according to at least one embodiment, will be described in detail.
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In at least one embodiment, the upper surface 6c of the cover member 6 face the lower surface 17b of the lower shroud 17 via a gap. Thereby, the impeller 10 can be rotated smoothly.
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In at least one embodiment, the radially inner end surface 6eA of the cover member 6A and the radial outer end surface 17aA of the lower shroud 17A do not come into contact with each other, i.e., there is a gap between radially inner end surface 6eA and radial outer end surface 17aA. In at least one embodiment, the gap in the radial direction between radially inner end surface 6eA and radial outer end surface 17aA is small. By avoiding contact between the radially inner end surface 6eA and radial outer end surface 17aA, the impeller 10A can be smoothly rotated. By narrowing the interval, the amount of air flowing in a direction different from the centrifugal direction can be reduced. The radially inner end surface 6eA of the cover member 6A and the radially outer end surface 17aA of the lower shroud 17A are flat. In at least one embodiment, at least one of the radially inner end surface 6eA of the cover member 6A or the radially outer end surface 17aA of the lower shroud 17A may be curved. In the case where the end faces 6eA and 17aA are planar, the planes may be parallel to the axial direction or inclined with respect to one another.
In at least one embodiment, the air flowing axially 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 at least one embodiment, regardless of the fact that the radially outer edge 17aA of the lower shroud 17A and the inner circumferential surface 4aA of the board accommodating portion 4A are separated radially due to enlargement of the circuit board 40A, the air can be guided efficiently in the centrifugal direction by the cover member 6A. In other words, according to at least one embodiment, by providing a wind guiding function to the cover member 6A, the radial length of the lower shroud 17A is shortened, and the mold structure or the manufacturing process of the impeller 10A is simplified. Furthermore, in at least one embodiment, as the cover member 6A and the lower shroud 17A do not overlap axially, the thickness of the centrifugal fan 100A can be reduced.
Various modifications can be made to the various technical features disclosed in this specification within the scope not deviating from the gist of the technical creation. Also, embodiments and modifications described herein may be implemented in combination as far as possible.
The present disclosure can be used for a centrifugal fan used for a range hood fan, a ventilating fan for a duct, a heat exchanging unit, paper adsorption for a printing apparatus, or the like.
Number | Date | Country | Kind |
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2017-208441 | Oct 2017 | JP | national |