JP2008175158A - Axial flow fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mount more electronic components by expanding an area of a circuit board of an axial flow fan. <P>SOLUTION: An axial flow fan 1 includes a housing 11, a plurality of rotatable blades 21 that rotates inside of the housing 11, and a plurality of sheet-like fixed blades 4 provided below the plurality of the rotatable blades 21 and fixed in the housing 11. The axial flow fan 1 includes a motor 3 connected to the plurality of the rotatable blades 21 for rotating the plurality of the rotatable blades 21 about a central axis J1. Each fixed blade 4 includes a protruded portion 43 upwardly protruding from the side-wall portion 3112 of a base portion 311 in the axial direction. The protruded portion 43 of each fixed blade 4 has an inner circumferential surface 431 on a side of the center axis J1. When a stator 31 is attached to the housing 11, the outer circumferential surface of a circuit board 316 and the inner circumferential surface 431 contact with each other in the axial direction. The circuit board 316 contacts an axially upper end surface of the side wall portion 3112 of the base portion 311 in the axial direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric axial fan used for blowing air.

  Conventionally, in order to suppress the temperature rise of an electronic device or the like, an axial fan that blows air inside the electronic device to cool each device has been used. In such an axial fan, air is blown by rotating a plurality of moving blades with an electric motor, and the motor rotates at a high speed in order to cope with an increase in the amount of heat generated along with the performance improvement of electronic equipment. It is requested.

  On the other hand, in order to rotate the motor at high speed, it is necessary to increase the drive current. For this reason, the temperature rise of the electronic component on the circuit board in the motor or the coil of the armature becomes large, which may affect the performance of the electronic component or the operation of the motor. To increase the rotational speed of the motor, increase the number of electronic components to suppress heat generation, or use a motor current limit circuit (a circuit that prevents a current exceeding a predetermined current value from flowing in the circuit). There is a method of constructing a circuit for reducing the current value on the circuit board. Further, when the rotation speed of the motor becomes high, a large restraint current (current that flows in the circuit and coil when the motor is locked) flows when the motor is locked. Therefore, there is a current reduction method that constitutes a lock protection circuit (a circuit that reduces the current value flowing through the coil by increasing the ON / OFF ratio of energization at the time of locking) in order to reduce the constraint current value.

  In recent years, axial fans often require higher output than before. Two-phase unipolar or single-phase bipolar is the mainstream motor used in conventional axial fans. However, with the increase in motor output, the use of three-phase bipolar drive motors has increased, and the number of electronic components mounted on circuit boards has increased. In the three-phase bipolar drive, since the number of mounted Hall elements and FETs (field effect transistors) is large, the number of electronic components to be mounted is inevitably larger than that of the single-phase bipolar or two-phase unipolar drive.

  Further, in recent motors, complicated rotation control (PWM circuit, temperature sensor, etc.) of the motor, which has been conventionally performed outside the motor, is built in the motor. Along with this, the number of electronic components mounted on the circuit board of the motor increases.

  Due to these factors, more electronic components are mounted on the circuit board configured in the motor than in the past.

  However, since the space for mounting electronic components is small with the size of the conventional circuit board, it is not possible to secure an electronic component mounting space for meeting future requirements. Therefore, it is necessary to increase the electronic component mounting area of the circuit board. In view of this, a technique for expanding the electronic component mounting area of the motor circuit board in the axial fan has been proposed.

  For example, a conventional circuit board is held such that a clearance hole (through hole) of the circuit board is fitted to an outer peripheral side surface of a bearing box (bearing housing) in which the bearing is held, but the bearing box (bearing) The circuit board is arranged outside the housing in the axial direction, and the escape hole (through hole) formed in the circuit board is eliminated or reduced. Thus, a technique for expanding the mounting area of the electronic component by the area of the through hole is disclosed. (See Patent Document 1)

Japanese Patent Laid-Open No. 11-257280

  By the way, when the motor bearing and the circuit board are arranged at different positions in the axial direction as in Patent Document 1, the ratio of the bearing span to the overall axial height of the motor is reduced. Considering the motor life and rotational accuracy, it is advantageous to have a larger bearing span. That is, when designing the motor, it is preferable that the ratio of the bearing span to the axial height of the entire motor is as large as possible. However, in the configuration of Patent Document 1, since the bearing span is small with respect to the height of the entire motor in the axial direction, the life of the motor cannot be improved.

  The present invention has been made in view of the above problems, and an object thereof is to increase the number of electronic components mounted by increasing the area of the circuit board of the axial fan.

  An axial fan according to a first aspect of the present invention is an electric axial fan, and has a substantially bottomed cylindrical base portion centering on a central axis, and is opposed to the base portion in the axial direction. An attached circuit board; an armature disposed above the circuit board; and an impeller cup portion having a substantially covered cylindrical shape centering on the central axis, the opening portion facing the opening portion of the base portion; A field magnet that is fixed to an inner surface of the impeller cup portion and generates a torque centered on the central axis with the armature; and the impeller cup portion about the central axis is the base portion. A plurality of rotor blades that radially extend from an outer surface of the impeller cup portion and generate an axial air flow by rotating in a predetermined rotation direction together with the impeller cup portion. And outside of the base A plurality of stationary blades extending radially from the surface while being inclined in a direction opposite to the rotation direction, and the stationary blades include a protruding portion that protrudes toward the moving blade side from the upper surface of the side wall of the base portion. The circuit board is housed in an envelope surface formed by the inner peripheral surfaces of the plurality of projecting portions.

  An axial fan according to a second aspect of the present invention is the axial fan according to the first aspect, wherein the circuit board and the upper surface of the side wall of the base portion are in contact in the axial direction. And

  The axial fan according to claim 3 of the present invention is the axial fan according to claim 1 or 2, wherein the envelope surface and the outer peripheral surface of the circuit board are in contact in the radial direction. Features.

  An axial fan according to a fourth aspect of the present invention is the axial fan according to any one of the first to third aspects, wherein a plurality of locking portions are arranged on the upper surface of the side wall of the base portion in the circumferential direction. The outer peripheral end of the circuit board is locked by the plurality of locking portions.

  The axial fan according to claim 5 of the present invention is the axial fan according to claim 4, wherein the locking portion is disposed between the adjacent stationary blades. .

  An axial fan according to a sixth aspect of the present invention is the axial fan according to any one of the first to third aspects, wherein at least two of the inner peripheral surfaces of the plurality of protrusions are locking portions. The outer peripheral end of the circuit board is locked by the plurality of locking portions.

  In the axial fan according to claim 1 of the present invention, it is possible to expand the area of the circuit board to the envelope surface constituted by the inner peripheral surface of the stationary blade. As a result, the number of electronic component mounting points can be increased. Further, since the inner peripheral surface of the stationary blade and the circuit board face each other in the radial direction, the cooling air is supplied to the electronic components mounted on the circuit board through the stationary blade. Thereby, an electronic component can be cooled efficiently.

  In the axial fan according to claim 2 of the present invention, since the circuit board and the base portion are in contact with each other in the axial direction, the circuit board can be fixed to the base. Thereby, it is possible to suppress the occurrence of problems such as damage to electronic components due to vibration of the circuit board.

  In the axial fan according to claim 3 of the present invention, since the outer peripheral surface of the circuit board and the envelope surface constituted by the inner peripheral surface of the stationary blade are in contact in the radial direction, the circuit board is more firmly fixed to the housing. Is possible. Further, since the outer diameter of the circuit board can be expanded to the inner diameter of the envelope surface constituted by the inner peripheral surface of the stationary blade, more electronic components can be mounted.

  In the axial fans according to claims 4, 5 and 6 of the present invention, since the circuit board is fixed to the base portion by being locked, the movement in the axial direction is restricted and the circuit board can be fixed more firmly. Is possible. Thereby, it is possible to suppress the occurrence of problems such as damage to electronic components due to vibration of the circuit board.

  FIG. 1 is a cross-sectional view showing an axial fan according to a first embodiment of the present invention. FIG. 2 is a perspective view showing the axial fan according to the first embodiment of the present invention. FIG. 3 is a perspective view showing the positional relationship between the stationary blade and the moving blade. As shown in FIGS. 1, 2, and 3, the axial fan 1 includes a housing 11, a plurality (seven in this embodiment) of moving blades 21 rotating inside the housing 11, and a plurality of moving blades. 21 is provided with a plurality of (9 in this embodiment) stationary blades 4 which are provided on the lower side in FIG. 2 and are fixed to the housing 11. As shown in FIG. 2, the axial fan 1 includes a motor 3 that is connected to the plurality of moving blades 21 and rotates the plurality of moving blades 21 about the central axis J1. The axial fan 1 is used, for example, as an electric fan for air-cooling electrical products and electronic devices.

  The motor 3 is an outer rotor type motor, and includes a stator part 31 that is a fixed assembly and a rotor part 32 that is a rotary assembly. The rotor part 32 receives a central axis J1 via a bearing mechanism described later. The stator part 31 is supported at the center so as to be rotatable. In the following description, for convenience, the rotor part 32 side is described as the upper side and the stator part 31 side is the lower side along the central axis J1, but the central axis J1 does not necessarily coincide with the direction of gravity.

  The stator portion 31 includes a substantially bottomed cylindrical base portion 311 centering on the central axis J1, and the base portion 311 is fixed to the housing 11 via a plurality of stationary blades 4 and holds each portion of the stator portion 31. To do. The base portion 311 is made of resin, and is formed continuously by injection molding together with a plurality of the stationary blades 4 and the housing 11 that are also made of resin. The base portion 311 has a substantially cylindrical shape centered on the central axis J1 and includes a bearing holding portion 312 that protrudes upward (that is, on the rotor portion 32 side) from the bottom portion 3111 of the base portion 311. Inside the bearing holding portion 312, ball bearings 313 and 314 that are part of the bearing mechanism are provided at the upper and lower portions in the direction of the central axis J <b> 1.

  The stator portion 31 is also attached to the outer periphery of the bearing holding portion 312 (that is, attached to the base portion 311 around the bearing holding portion 312), and the base portion below the armature 315. A circuit board 316 having a substantially annular plate shape that is attached to the inside of the side wall portion 3112 of 311 and is electrically connected to the armature 315 and controls the armature 315 is further provided. In other words, in the stator portion 31, the armature 315 is disposed above the circuit board 316 while facing the circuit board 316 in the direction of the central axis J1. An electronic component 3161 is mounted on the lower surface of the circuit board 316 (that is, the surface facing the bottom surface in the base portion 311).

  The rotor portion 32 is a substantially cylindrical cup portion 321 centered on the central axis J1 and a substantially cylindrical shape that is fixed to the inner side (that is, the inner side surface) of the side wall portion 3212 of the cup portion 321 and faces the armature 315. A field magnet 322 and a shaft 323 projecting downward from the lid portion 3211 of the cup portion 321 are provided. The cup portion 321 includes a metal yoke 3214 having a substantially covered cylindrical shape and magnetism, and a resin hub 3215 having a substantially covered cylindrical shape and covering the outside of the yoke 3214. The cup portion 321 has an opening. The part 3213 is arranged to face the opening 3113 of the base part 311.

  The shaft 323 is attached to the lid portion of the yoke 3214 of the cup portion 321, inserted into the bearing holding portion 312, and rotatably supported by the ball bearings 313 and 314. In the axial fan 1, the shaft 323 and the ball bearings 313 and 314 serve as a bearing mechanism that supports the cup portion 321 rotatably with respect to the base portion 311 around the central axis J1. The driving current supplied to the armature 315 via the circuit board 316 is controlled to generate a rotational torque about the central axis J1 between the armature 315 and the field magnet 322. The plurality of moving blades 21 extending radially from the outside of the side wall portion 3212 of the cup portion 321 together with the portion 321 (that is, the outer surface of the hub 3215) rotate around the central axis J1.

  In the axial fan 1, the plurality of moving blades 21 rotate counterclockwise in FIG. 2 together with the rotor portion 32 of the motor 3, so that the upper side in FIG. 1 (that is, the lid portion 3211 side of the cup portion 321). Air is taken in and delivered to the lower side (that is, the base portion 311 and the stationary blade 4 side). That is, in the axial fan 1, the upper side in FIG. 1 is the intake side, and the lower side is the delivery side. In the following description, the rotation direction of the plurality of moving blades 21 is also referred to as “motor rotation direction”.

  As shown in FIG. 3, the plurality of stationary blades 4 are arranged on the lower side of the plurality of moving blades 21 (that is, on the delivery side) from the outer surface of the side wall portion 3112 of the base portion 311 in the direction opposite to the motor rotation direction ( That is, it extends in a radial direction while inclining in the direction opposite to the rotation direction of the moving blade 21 and in the clockwise direction in FIG. The end of each stationary blade 4 on the center axis J1 side (that is, the inner side) is connected to the side wall portion 3112 of the base portion 311, and the end opposite to the center axis J1 (that is, the outer side) is connected to the housing 11. The In the present embodiment, each stationary blade 4 is curved so that a surface 41 facing in the motor rotation direction (that is, a surface in which the direction of the normal line is substantially opposite to the motor rotation direction) is concave. Yes. The surface 41 of the stationary blade 4 facing the motor rotation direction is a surface that mainly receives the wind from the moving blade 21 and is hereinafter referred to as “wind receiving surface 41”. The surface 42 opposite to the wind receiving surface 41 of the stationary blade 4 is hereinafter referred to as a “back surface 42”.

  FIG. 4 is a perspective view of the housing 11, the base portion 311, and the plurality of stationary blades as viewed obliquely from above. FIG. 5 is a perspective view showing a state in which the stator portion 31 is attached to the housing 11. As shown in FIG. 4, each stationary blade 4 includes a protruding portion 43 that protrudes upward in the axial direction from the side wall portion 3112 of the base portion 311. In other words, each stationary blade 4 is higher in the axial direction than the side wall portion 3112 of the base portion 311. The protrusion 43 of each stationary blade 4 has an inner peripheral surface 431 on the central axis J1 side (that is, the inner side). A constant curved surface, that is, an envelope surface (virtual surface connecting the inner peripheral surfaces 431) is formed so as to be in contact with almost all of the inner peripheral surfaces 431. As shown in FIG. 5, when the stator portion 31 is attached to the housing 11, the outer peripheral surface of the circuit board 316 and the envelope surface abut on each other in the radial direction. Further, as shown in FIG. 1, the circuit board 316 is in contact with the upper end surface in the axial direction of the side wall portion 3112 of the base portion 311 in the axial direction.

  With these configurations, it is possible to extend the outer diameter of the circuit board 316, which has conventionally been accommodated in the inner peripheral surface of the side wall portion 3112 of the base portion 311, to the position of the inner peripheral surface 431 of the protruding portion 43 of each stationary blade 4. . Therefore, the area of the circuit board 316 can be enlarged. That is, the number of electronic components 3161 that can be mounted on the circuit board 316 can be increased. In addition, since the outer diameter of the circuit board 316 and the inner peripheral surface 431 of the protruding portion 43 of each stationary blade 4 are in contact with each other, the circuit board 316 has no backlash with respect to each stationary blade 4. Fixed. Since the circuit board 316 is in contact with the upper end surface in the axial direction of the side wall part 3112 of the base part 311 in the axial direction, the circuit board 316 is also fixed without rattling in the axial direction of the circuit board 316.

The air flow generated by the rotation of the plurality of moving blades 21 collides with the wind receiving surface 41 of each stationary blade 4, and the air flow that diffuses radially outward is vector-converted radially inward. Therefore, the air flow is guided along the respective stationary blades 4 to the radially inward side. As shown in FIG. 5, the protruding portion 43 of each stationary blade 4 protrudes above the upper surface of the circuit board 316 in the axial direction. Thus, the air flow guided radially inward by each stationary blade 4 is supplied to the armature 315 from between the circuit board 316 and the opening 3213 of the cup portion 321 through each stationary blade 4, The armature 315 is cooled by the air flow. Since the flow rate of air passing around the circuit board 316 is larger than that of the conventional axial fan, the circuit board 316 may be vibrated due to the passage of air flow when the circuit board 316 is unstable. . However, since the circuit board 316 is fixed to each stationary blade 4 by the above-described configuration, vibration of the circuit board 316 is suppressed.

  In addition, since the protrusions 43 are formed on each stationary blade 4, the axial interval between each moving blade 21 and each stationary blade 4 can be reduced. The smaller the distance between the moving blade and the stationary blade in the axial direction, the more the original effect of the stationary blade (wind collecting effect, rectifying effect, etc.) can be exhibited. There is also a method of bringing each moving blade 21 closer to each stationary blade 4. However, since the moving blade 21 has a higher airflow characteristic when it is arranged as close to the intake port as possible, it is necessary to increase the axial height of the moving blade 21 in order to bring the moving blade 21 closer to the stationary blade. There is. However, when the axial height of the moving blade 21 is increased, the projected area in the rotating circumferential direction of the moving blade 21 when rotating is increased. As a result, the air resistance increases, causing a current value to increase. Therefore, in order to reduce the axial distance between the moving blade 21 and the stationary blade 4, it is better to bring the stationary blade 4 closer to the moving blade 21.

  FIG. 6 is a cross-sectional view showing a modification of the axial fan according to the first embodiment of the present invention. The axial fan 1 has a wide range of applications and may be used in a bad environment with a lot of dust and high humidity. In such a case, it is necessary to prevent airflow from entering the stator portion 31 and the circuit board 316 electronic component mounting surface as a dustproof measure. In such a case, as shown in FIG. 6, the circuit board 316 and the axially upper end surface of the side wall 3112 of the base 311 are arranged so as to contact each other, and then the protruding of each stationary blade 4 What is necessary is just to comprise so that the axial direction upper end of the part 43 may be located in the same or lower side with the upper surface of the circuit board 316.

  With the above configuration, the air flow generated by the rotation of the plurality of moving blades 21 collides with the wind receiving surface 41 of each stationary blade 4, and the air flow diffused radially outward is radially inward. Vector converted. However, the air flow vector-converted radially inward collides with the outer peripheral side surface of the circuit board 316 or the side wall portion 3112 of the base portion 311 and is exhausted downward in the axial direction. Therefore, it is possible to suppress the air flow from entering the circuit board 316, particularly the mounting surface side and the stator portion 31.

  FIG. 7 is a cross-sectional view showing a modification of the axial fan according to the first embodiment of the present invention. In the embodiment shown in FIG. 1, the protruding portion 43 of each stationary blade 4 is formed in the entire region of the connecting portion of the stationary blade 4 from the housing 11 connecting portion to the base portion 311. However, as shown in FIG. 7, a region where the protrusion 43 of each stationary blade 4 is not formed on the radially inner side may be provided. According to this configuration, the protrusion 43 has the inner peripheral surface 431 on the central axis J1 side (that is, the inner side), and the size of the circuit board 316 can be increased to a size that contacts the inner peripheral surface 431. it can. That is, an area for mounting the electronic component 3161 on the circuit board 316 can be enlarged.

  Further, as shown in FIG. 8, the configuration is such that the circuit board 316 and the axially upper end surface of the side wall part 3112 of the base part 311 do not come into contact with each other. The area for mounting can be expanded. In this configuration, for example, the axial height of the side wall portion 3112 of the base portion 311 may be lowered. In this modification, a notch 432 is formed on the center axis J1 side (that is, the inside) of each stationary blade 4 as shown in FIG. At this time, the outer peripheral end lower surface of the circuit board 316 is brought into contact with the axial end surface of the notch 432 formed in the protruding portion 43 of each stationary blade 4. In this case, an airflow enters and exits through a gap between the circuit board 316 and the axially upper end surface of the side wall 3112 of the base part 311, and the electronic components mounted on the lower surface side of the circuit board 316 can be cooled. .

  Therefore, an essential feature of the present invention is that in the conventional axial fan, the outer diameter of the circuit board 316 can be increased to a region where the base portion or the stationary blade is disposed, and the electronic component on the circuit board 316 is obtained. The area where 3161 is mounted can be expanded.

  Next, an axial fan according to a second embodiment of the present invention will be described. FIG. 9 is a cross-sectional view showing an axial fan according to the second embodiment. FIG. 10 is a perspective view showing a modification of the axial fan according to the second embodiment. Other configurations are the same as those in FIGS. 1 to 7 and are denoted by the same reference numerals in the following description.

  In the axial fan according to the second embodiment, as shown in FIG. 9, circuit boards 316 are engaged at least at four locations in the circumferential direction at the upper end in the axial direction of the side wall portion 3112 of the base portion 311. A locking portion 3113 to be stopped is formed. The places where the locking portions 3113 are formed are not limited to four, and may be formed at any number as long as there are at least a plurality of places. The plurality of locking portions 3113 protrude from the axially upper end of the side wall portion 3112 of the base portion 311 toward the axially upper side. In addition, a locking hook portion projects from the distal end of the locking portion 3113 toward the central axis J1 side (that is, the inner side).

  When the circuit board 316 is brought close to be fixed to the base portion 311, the outer peripheral end of the circuit board 316 and the locking portion 3113 first come into contact with each other. When the circuit board 316 is further inserted toward the base 311 side, the locking portion 3113 is elastically bent outward in the radial direction. When the circuit board 316 is further inserted toward the base portion 311 side, the locking portion 3113 is moved to the center axis by the elastic force of the locking portion 3113 when the locking hook portion is positioned above the circuit board 316 in the axial direction. Restored toward the J1 side (ie, the inside). Therefore, the locking hook portion is locked to the upper surface of the outer peripheral end of the circuit board 316, and the movement of the circuit board 316 in the axial direction is restricted.

  In 2nd Embodiment, the latching | locking part 3113 is formed in the position which does not overlap with the stationary blade 4 in radial direction. That is, the locking portion 3113 is formed between the adjacent stationary blades 4. When the locking portion 3113 overlaps the stationary blade 4 in the radial direction, it is difficult to secure a space for elastic deformation of the locking portion 3113 when the circuit board 316 is attached. An object of the present invention is to increase the outer diameter (area) of the circuit board 316. However, when the stationary blade 4 and the locking portion 3113 overlap, the area of the circuit board 316 is reduced accordingly. .

  In the case where the locking portion 3113 and the stationary blade 4 are disposed at the overlapping position, it is necessary to prevent the area of the circuit board 316 from being reduced as much as possible. For that purpose, it is necessary to enlarge until the outer peripheral surface of the circuit board 316 contacts the inner peripheral surface 431 of the protrusion 43 of the stationary blade 4. In order to contact the outer peripheral surface of the circuit board 316 and the inner peripheral surface 431 of the protruding portion 43, as shown in FIG. 10, the locking portion 3113a is provided on the inner peripheral surface 431 of the protruding portion 43 as the central axis J1. What is necessary is just to project toward the side (namely, inner side). In this way, the outer peripheral surface of the circuit board 43 and the inner peripheral surface 431 of the protrusion 43 are in contact with each other, and the upper surface of the outer peripheral end of the circuit board 43 is locked by the locking portion 3113a. Thereby, the movement of the circuit board 43 in the axial direction is restricted.

It is sectional drawing of the axial-flow fan concerning 1st Embodiment. It is a perspective view of the axial fan concerning a 1st embodiment. It is a perspective view which shows the positional relationship of the moving blade of the axial flow fan concerning 1st Embodiment, and a stationary blade. It is a perspective view of a housing, a base part, and a stationary blade of an axial fan concerning a 1st embodiment. It is a perspective view of a housing, a stator part, and a stationary blade of an axial fan concerning a 1st embodiment. It is sectional drawing which shows the other modification of the axial fan concerning 1st Embodiment. It is sectional drawing which shows the other modification of the axial fan concerning 1st Embodiment. It is sectional drawing which shows the other modification of the axial fan concerning 1st Embodiment. It is sectional drawing of the axial-flow fan concerning 2nd Embodiment. It is sectional drawing which shows the other modification of the axial fan concerning 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Axial fan 4 Stator blade 21 Rotor blade 41 Wind receiving surface 311 Base part 313,314 Ball bearing 315 Armature 316 Circuit board 321 Cup part 322 Field magnet 323 Shaft 3111 Bottom part 3112 Side wall part 3113 Open part 3114 Side wall part opening 3161 Electronic component 3211 Lid 3213 Opening J1 Central axis

Claims (6)

An electric axial fan,
A substantially bottomed cylindrical base centered on the central axis;
A circuit board attached opposite to the base portion in the axial direction;
An armature disposed above the circuit board;
An impeller cup portion having a substantially covered cylindrical shape centering on the central axis, the opening portion facing the opening portion of the base portion;
A field magnet that is fixed to the inner surface of the impeller cup portion and generates torque centered on the central axis with the armature;
A bearing mechanism that rotatably supports the impeller cup portion with respect to the base portion around the central axis;
A plurality of blades extending radially from the outer surface of the impeller cup portion and generating an axial air flow by rotating in a predetermined rotational direction together with the impeller cup portion;
A plurality of stationary blades extending radially from the outer surface of the base portion while being inclined in a direction opposite to the rotation direction;
With
The stationary blade includes a protruding portion that protrudes toward the moving blade side from the upper surface of the side wall of the base portion, and the circuit board is accommodated in an envelope surface formed by inner peripheral surfaces of the plurality of protruding portions. An axial fan characterized by that.   The axial fan according to claim 1, wherein the circuit board and the upper surface of the side wall of the base portion are in contact with each other in the axial direction.   The axial fan according to claim 1 or 2, wherein the envelope surface and the outer peripheral surface of the circuit board are in contact with each other in a radial direction.   2. A plurality of engaging portions are disposed in a circumferential direction on the upper surface of the side wall of the base portion, and an outer peripheral end of the circuit board is engaged by the plurality of engaging portions. The axial flow fan in any one of thru | or 3.   The axial fan according to claim 4, wherein the locking portion is disposed between the adjacent stationary blades.   The locking portion is formed on at least two or more of the inner peripheral surfaces of the plurality of protruding portions, and an outer peripheral end of the circuit board is locked by the plurality of locking portions. The axial fan according to any one of 1 to 3.

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