JP2017137871A - Blower fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blower fan which optimizes a shape and an arrangement structure of a reinforcement rib formed at a motor base part, and which can reduce an influence of vibration transmitted to a casing via a motor base even in the case where the maximum rotational frequency of the blower fan is enhanced close to 20,000 rpm.SOLUTION: A blower fan includes a motor base part 18 formed in a discoid shape by providing a plurality of reinforcement ribs 21 extending from an outer peripheral side of a hollow cylindrical boss part 18a radially outward, and a plurality of spokes 20 for connecting the motor base part 18 and the casing 11, and both of them are formed integrally with the casing 11. The blower fan is constituted so that the number of the plurality of reinforcement ribs 21 is formed to be at least the same number as or greater than the number of the spokes 20, and the natural frequency of the casing 11 is set to be higher than the frequency transmitted to the casing 11 from a motor 15 when the motor 15 is rotated at 20,000 rpm.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a blower fan, and more particularly, to a blower fan used for cooling inside a device such as an electronic device.

  Generally, a blower fan includes a casing having a hollow portion (opening) in the center, a rotating shaft, an impeller that has a plurality of blades and rotates integrally with the rotating shaft, a motor that rotates the rotating shaft, and a motor. The motor base part to hold | maintain is provided, and the impeller, the motor, and the motor base part are accommodated in the cavity part of the casing.

  The motor base portion is integrally formed with a boss portion to which a hollow cylindrical bearing housing having a bearing for supporting the rotating shaft is fitted and attached at the center. The bearing housing attached to the boss portion has a motor stator mounted on the outer side, and a rotary shaft mounted rotatably on the inner side via a bearing. The motor base is connected to the casing by a plurality of spokes.

  Then, when the motor is driven, the rotating shaft rotates together with the impeller, and fluid (air) is sucked into the impeller from one end side of the cavity portion of the casing, that is, the suction port, by the rotation of the impeller and passes through the inside of the casing. The other end of the cavity of the casing, that is, the outlet is blown out of the casing. At this time, when it is necessary to increase the pressure of the fluid blown out of the casing, a fixed wing may be provided near the outlet of the casing, and the spoke may also serve as the fixed wing. The casing, the motor base, and the spoke are formed by integral molding with resin, metal, or the like.

  By the way, such a blower fan is mounted on an electronic device, and is used to efficiently discharge heat generated from an electronic component inside the electronic device to the outside of the electronic device to cool the electronic component. Therefore, a high air volume of the blower fan (the amount of air sent out by the fan per unit time) is required. In addition, in electronic equipment such as servers, the space through which air flows is becoming smaller due to the high-density mounting inside the housing, and the air blowing fan that cools the inside of the housing has a high static pressure (the fan is air Is also required.

  In order to obtain the high air volume and high static pressure of the blower fan, it is necessary to rotate the motor that rotates the impeller at high speed. However, when the motor is rotated at a high speed, the vibration accompanying the high-speed rotation of the motor is transmitted to the casing via the bearing, and the vibration is also transmitted to the electronic device equipped with the blower fan, and the electronic device is also vibrated. There's a problem. In particular, when the vibration associated with the rotation of the motor resonates with the natural frequency of the casing, the vibration increases, and as a result, abnormal vibration may occur in the electronic device, which may be a serious problem.

  In response to such a problem, there has been proposed a blower fan in which a plurality of reinforcing reinforcing ribs are formed in the motor base portion to reinforce the structure of the housing and suppress the occurrence of vibration (for example, Patent Document 1). reference).

JP 2006-57631 A.

  However, the technique described in Patent Document 1 is a blower fan that has a housing structure that is reinforced by forming a plurality of reinforcing reinforcing ribs in the motor base portion. However, the shape of the reinforcing reinforcing ribs formed in the motor base portion is The structure is not fully disclosed. In addition, in an electronic device such as a server, the maximum rotational speed of the blower fan may be rotated to 20000 rpm by high-density mounting inside the housing. When rotating at such a high speed, there is a problem that the effect of reducing vibration transmitted to the casing via the motor base portion is not always sufficient.

  Therefore, the present invention has been made in view of the above problems, and even when the shape and arrangement structure of the reinforcing rib formed on the motor base portion is optimized and the maximum rotational speed of the blower fan is increased to nearly 20000 rpm. It aims at providing the ventilation fan which can reduce the influence of the vibration transmitted to a casing via a motor base.

  The present invention has been proposed to achieve the above object, and a blower fan according to the present invention includes an impeller having a plurality of wings, a motor for rotating the impeller, a casing for housing the impeller and the motor. A blower fan comprising: a motor base portion for mounting the motor; and a plurality of spokes connecting the casing and the motor base portion, wherein the motor base portion forms a plurality of reinforcing ribs. When the number of the reinforcing ribs is the same as or more than the number of the spokes and the rotational speed of the motor is rotated to 20000 rpm, the natural frequency of the casing is the rotational speed of the motor. Is set higher than the frequency transmitted to the casing (claim 1).

  According to this configuration, a plurality of reinforcing ribs are provided radially between the boss portion and the outer periphery of the motor base portion on the motor base portion formed in a disk shape in plan view, and between the motor base portion and the casing, A plurality of spokes for connecting the motor base portion and the casing are provided to strengthen the structure of the housing. In addition, when the number of the plurality of reinforcing ribs is the same as or more than the number of spokes and the natural frequency of the casing is rotated at 20000 rpm, the casing is accompanied with the rotation of the motor. It is set to be higher than the transmitted frequency. Therefore, even if the motor is rotated at 20000 rpm, the motor and the housing do not resonate, and as a result, the housing can be prevented from causing abnormal vibration.

  The number of the plurality of spokes is preferably at least 7 or more (Claim 2).

  According to this configuration, when at least seven spokes are formed, if seven or more reinforcing ribs are formed on the motor base, the natural frequency of the casing depends on the rotation of the motor when the maximum rotation number of the motor is 20000 rpm. It becomes higher than a frequency, and it can prevent that a casing and a motor resonate and a casing causes abnormal vibration.

  Further, it is preferable that the plurality of spokes are inclined at a predetermined angle with respect to a plane orthogonal to a rotation axis that rotates integrally with the impeller.

  According to this configuration, each spoke functions as a fixed wing that increases the pressure of air blown out of the casing and rectifies the discharged air.

  Further, it is preferable that the plurality of reinforcing ribs are formed with the same width from the outer peripheral side of the boss portion to the outer periphery of the motor base portion.

  According to this configuration, by setting the width of the reinforcing rib to the same width up to the outer periphery, the motor base portion can be uniformly reinforced and abnormal vibration can be prevented.

  Preferably, the plurality of reinforcing ribs are formed so that the width gradually decreases as they extend from the outer peripheral side of the boss portion to the outer peripheral side of the motor base portion.

    According to this configuration, the width of the reinforcing rib is wide at the boss portion, and the width is gradually reduced as it extends toward the outer periphery of the motor base, thereby effectively reinforcing the boss portion and suppressing excess reinforcement, thereby reducing the weight of the casing. Can be achieved.

  Further, when the number of the plurality of reinforcing ribs is the same as that of the spokes, the reinforcing ribs are preferably formed to extend toward a portion where the spokes are joined to the motor base portion. 6).

  According to this configuration, by providing the reinforcing rib extending toward the portion where the spoke and the motor base portion are joined, the strength of the joined portion is increased and the overall structure of the casing can be further strengthened.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the largest rotation speed of a ventilation fan rotates to 20000 rpm, the ventilation fan which does not raise | generate an abnormal vibration can be provided.

It is sectional drawing of the ventilation fan shown as one Embodiment of this invention. It is a perspective view which shows the casing of the ventilation fan shown in FIG. The casing of FIG. 2 is shown, (a) is the top view, (b) is the AA line expanded sectional view of (a). It is the graph which showed the value of the number of reinforcement ribs formed in the motor base part, and the natural frequency value of a housing.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the accompanying drawings. In the following description, the expression indicating the up and down direction is not absolute and is appropriate when the posture of each part of the blower fan of the present invention is depicted, but when the posture changes Should be interpreted according to changes in posture.

  As shown in FIG. 1, the blower fan 10 in an example of the embodiment of the present invention is an axial fan, and includes a casing 11, a rotating shaft 12, and a plurality of blades 13 on the outer periphery, and the rotating shaft 12. An impeller 14 that rotates integrally, a motor 15 that rotates the rotating shaft 12, a hollow cylindrical bearing housing 17 in which a pair of upper and lower bearings 16 a and 16 b that support the rotating shaft 12 are mounted, and the bearing housing 17 are supported. The rotating shaft 12, the impeller 14, the motor 15, the bearing housing 17, and the motor base 18 are disposed in the casing 11.

  More specifically, as shown in FIGS. 1 to 3, the casing 11 is formed as a quadrangular frame body in a plan view by providing a circular ventilation cavity portion 19 penetrating forward and backward in the center. ing. The casing 11 has the motor base 18 disposed in the center of the cavity 19, and a plurality of spokes 20 (seven in the embodiment) are provided between the inner peripheral surface of the cavity 19 and the outer peripheral surface of the motor base 18. ) Are integrally molded with the motor base 18 and the spoke 20. And as shown in FIG. 1, the suction inlet 19a and the discharge outlet 19b are formed in the upper and lower ends of the cavity part 19, respectively.

  As shown in FIG. 1, the plurality of spokes 20 are disposed on the outlet 19 b side of the casing 11, and as shown in FIG. 3A, the motor base portion 18 is formed at equal angles in the circumferential direction. Is formed radially from the outer peripheral surface toward the inner peripheral surface of the cavity 19. Each of the plurality of spokes 20 is inclined at a predetermined angle with respect to a plane orthogonal to the rotating shaft 12 so as to increase the pressure of the air blown out of the casing 11 and to rectify the discharged air. It also functions as a fixed wing.

  The motor base portion 18 supported by the casing 20 by the spoke 20 is provided on the discharge port 19 b side of the casing 11 together with the spoke 20. Further, as shown in FIGS. 2 and 3, a hollow cylindrical boss portion 18a protruding toward the suction port 19a side is integrally provided at the center, and is formed in a disk shape in plan view. One end side of the bearing housing 17 is fitted and inserted into the boss portion 18a and fixed concentrically. An adhesive is used to fix the bearing housing 17.

  Further, the surface of the motor base portion 18 from which the boss portion 18a protrudes, that is, the surface facing the suction port 19a, corresponds to the spoke 20, respectively, from the outer peripheral surface of the boss portion 18a to the outer periphery of the motor base portion 18. A plurality of reinforcing ribs 21 (seven in the embodiment) extending in the direction and radially extending toward the joint C between the motor base 18 and the spoke 20 are provided. As shown in FIG. 3 (b), each reinforcing rib 21 protrudes outward from the back surface of the motor base 18 in a cross-sectional mountain shape as shown in FIG. 3 (a). It is integrally formed. The cross-sectional shape of the reinforcing rib 21 is not limited to the shape shown in FIG. 3B, but may be formed in other triangles, squares, trapezoids, or the like.

  As shown in FIGS. 3 (a) and 3 (b), each reinforcing rib 21 has an equal angle in the circumferential direction, and all have the same shape, and the distance from the outer peripheral surface of the boss portion 18a to the joint location C is as follows. They are formed with the same width (circumferential direction) W and the same height (axial direction) H. In addition, by providing the plurality of reinforcing ribs 21 in this way, the strength of the joint portion C is increased, and at the same time, the casing 11 as a whole is reinforced. As will be described in detail later, when the rotation of the motor 15 is rotated at 20000 rpm, the natural frequency of the casing 11 is set to be higher than the frequency at which the rotation of the motor 15 is transmitted to the casing 11.

  The casing 11, the motor base 18, the spoke 20, and the reinforcing rib 21 are integrally formed of resin, but may be integrally formed of metal or the like. Further, the bearing housing 17 may be resin-molded integrally with the boss portion 18 a of the motor base portion 18.

  As shown in FIG. 1, the rotary shaft 12 passes through a pair of bearings 16 a and 16 b mounted on the inner periphery of the bearing housing 17 and is supported so as to be rotatable. Are integrally attached.

  In the present embodiment, the bearing housing 17 is a separate component, but may be integrated with the boss portion 18a.

  The impeller 14 has a hub 22 that rotates integrally with the rotary shaft 12, and the plurality of blades 13 are provided on the outer peripheral surface of the hub 22.

  The hub 22 is formed by injection molding a general resin material (synthetic resin such as PBT and ABS), and at the time of molding, one end (upper end) side is closed in a molding die (not shown). An end (lower end) side is opened, a magnetic yoke 24 formed in a substantially cup shape with a circular cross section formed by attaching the rotor magnet 23 of the motor 15 to the inner peripheral surface, and the rotary shaft 12 are disposed, and thereafter molded. By injecting a resin material into the mold, as shown in FIG. 1, there is provided a disk-like ceiling portion 22a connected to and supported by the rotary shaft 12 and a cylindrical portion 22b extending in the axial direction. The upper end side is closed and the lower end side is opened. At the same time, the plurality of blades 13 are integrally formed on the outer peripheral surface of the cylindrical portion 22 b of the hub 22.

  As shown in FIG. 1, the motor 15 includes a rotor 15a composed of a magnetic yoke 24 on the impeller 14 side and a rotor magnet 23 attached to the inner peripheral surface of the magnetic yoke 24, and a bearing housing 17 on the casing 11 side. The stator 15b is fixedly attached to the outer periphery, and the impeller 14 and the rotary shaft 12 are rotated integrally by rotating the rotor 15a with respect to the stator 15b.

  As shown in FIG. 1, the stator 15 b is attached to the outer peripheral surface of the bearing housing 17 from the suction port 19 a side. The stator 15 b includes an iron core 25 fitted and attached to the outer periphery of the bearing housing 17, and a driving coil 27 wound around the iron core 25 via an insulator 26. A motor drive circuit board 28 on which electronic components for controlling the drive current supplied to the coil 27 are mounted is fixedly attached to the insulator 26 below the stator 15b. Also, it is electrically connected to an external power source (not shown) via a lead wire (not shown).

  In the blower fan 10 configured as described above, when a drive current is supplied from the circuit board 28 to the coil 27 of the motor 15, the rotor 15a moves and the rotary shaft 12 and the impeller 14 rotate integrally. When the impeller 14 rotates, fluid air is sucked into the blade 13 of the impeller 14 from the suction port 19 a of the casing 11, passes through the inside of the casing 11, and passes through the discharge port 19 b of the casing 11 to the outside of the casing 11. Is blown out. At this time, the plurality of spokes 20 provided on the discharge port 19b side of the casing 11 rectifies the air blown out of the casing 11 and increases the pressure of the air. As a result, in an electronic device such as a server to which the blower fan 10 is attached, ventilation (or air circulation) is performed and internal cooling is performed.

  By the way, in an electronic device such as a server, the space through which air flows becomes smaller due to high-density mounting inside the housing, and a high air volume and high static pressure are required for the blower fan 10 that cools the inside of the housing. For this reason, in order to obtain the high air volume and high static pressure of the blower fan 10, the maximum rotational speed of the motor 15 that rotates the impeller 14 may be rotated to 20000 rpm. When the motor 15 is rotated at high speed, the vibration associated therewith is transmitted to the casing 11 via the bearings 16a and 16b, and is also transmitted to the electronic device on which the blower fan 10 is mounted. As a result, the electronic device is also vibrated. Occurs. In this case, when the vibration accompanying the rotation of the motor 15 resonates with the natural frequency of the casing 11, the vibration is further increased, and as a result, abnormal vibration may occur in the electronic device.

  Table 1 shows, as parameters, the number of reinforcing ribs 21 formed on the motor base portion 18 of the casing 11 and the number of spokes 20, and the estimated natural frequency (Hz) of the casing 11 in that case. The resonance rotational speed of the motor 15 is shown. Details of the estimation method by analysis are omitted.

  In Table 1, Comparative Example 1 is a casing 11 in which four spokes 20 and four reinforcing ribs 21 are formed. Comparative Example 2 is a casing 11 in which six spokes 20 and six reinforcing ribs 21 are formed. Example 1 uses the casing 11 shown in FIGS. 1 to 3, which is an embodiment of the present invention, and has seven spokes 20 and seven reinforcing ribs 21. The comparative example 1, the comparative example 2, and the example 1 have the same casing 11 shape, and the reinforcing ribs 21 are formed so as to match the locations C where the spokes 20 are joined to the motor base 18.

  As shown in Table 1, the natural frequency of the casing estimated by the analysis is about 252 Hz in Comparative Example 1, about 275 Hz in Comparative Example 2, and about 365 Hz in Example 1. From this, it is understood that when the number of the spokes 20 and the reinforcing ribs 21 is the same, the natural frequency of the casing 11 increases when the number of the spokes 20 and the reinforcing ribs 21 is increased. Here, in Example 1, X (referred to as the vibration frequency) when the maximum rotational speed of the motor 15 that rotates the impeller 14 of the blower fan 10 is 20000 rpm is represented by a rotational speed ratio (365: X = 221910: 20000). ), It can be seen that X = 334, that is, the vibration frequency in the vibration excitation of the motor 15 is about 334 Hz.

  For this reason, when the natural frequency of the casing 11 obtained by analysis in advance is lower than the vibration frequency of 334 Hz, the vibration frequency of the casing 11 and the natural frequency of the casing 11 can resonate with the rotation of the motor 15. There is sex. As a result, abnormal vibration may occur in the electronic device or the like.

  From this, as shown in Table 1, in the casings 11 of the comparative example 1 and the comparative example 2, since the natural frequencies of the casing 11 are 252 Hz and 275 Hz, respectively, both values are lower than 334 Hz. For this reason, when the maximum rotation speed of the motor 15 that rotates the impeller 14 of the blower fan 10 is set to 20000 rpm, the vibration frequency of the casing 11 that accompanies this may resonate with the natural frequency of the casing 11. .

  On the other hand, in Example 1 shown in FIGS. 1 to 3, the natural frequency of the casing 11 shows a value higher than 334 Hz (365 Hz). As a result, even if the maximum rotational speed of the motor 15 that rotates the impeller 14 of the blower fan 10 is 20000 rpm, the resonance point is not reached, and abnormal vibrations that occur in an electronic device equipped with the blower fan 10 can be prevented. .

  Table 2 shows the reinforcing rib 21 formed on the motor base 18 by setting the number of spokes 20 to 7 in the casing 11 of the blower fan 10 (Example 1) which is the embodiment shown in FIGS. 1 to 3. As a parameter, a value obtained by analyzing the natural frequency of the casing 11 in that case and a resonance rotational speed of the motor 15 based on the value are shown. FIG. 4 is a graph showing values obtained by estimating the natural frequency of the casing 11 when the number of reinforcing ribs 21 shown in Table 2 is changed.

  In Table 2, the casing A is a casing in which the number of spokes 20 is seven and the reinforcing ribs 21 are not formed. The casing B is a casing in which the number of spokes 20 is seven and the number of reinforcing ribs 21 is four. The casing C is a casing in which the number of spokes 20 is seven and the number of reinforcing ribs 21 is five. The casing D is a casing in which the number of spokes 20 is seven and the number of reinforcing ribs 21 is six. The casing E is a casing in which the number of spokes 20 is seven and the number of reinforcing ribs 21 is also seven, which is the embodiment of the present invention shown in FIGS. 1 to 3 (Example 1). It is. The casing F is a casing in which the number of spokes 20 is seven and the number of reinforcing ribs 21 is nine. All the casings have the same shape, and only in the casing E of Example 1 which is an embodiment of the present invention, the reinforcing ribs 21 are formed so as to match the locations C where the spokes 20 are joined to the motor base 18.

  As shown in Table 2 and FIG. 4, when the spokes 20 of the casing 11 are formed into seven, the impeller 14 of the blower fan 10 is formed by forming six or more reinforcing ribs 22 formed in the motor base portion 18. Even when the maximum rotational speed of the motor 15 to be rotated is 20000 rpm, the natural frequency of the casing 11 can be higher (337 Hz) than the value estimated by analysis.

  However, when the number of the reinforcing ribs 21 formed on the motor base 18 is six, the value is slightly higher than the vibration frequency 334 Hz of the blower fan 10, and it cannot be said that there is a sufficient margin. For this reason, the number of reinforcing ribs 21 formed on the motor base 18 is equal to or more than seven, which is the same as that of the spokes 20, so that the natural frequency of the casing 11 is more than the vibration frequency 334Hz of the blower fan 10. A high value (365 Hz) with can be obtained. As a result, when the number of reinforcing ribs 21 formed on the motor base portion 18 is at least 6 or more, more preferably 7 or more, the maximum rotational speed of the motor 15 that rotates the impeller 14 of the blower fan 10 is 20000 rpm. However, the influence of vibration transmitted to the casing 11 via the motor base 18 can be reduced, and abnormal vibration generated in an electronic device or the like equipped with the blower fan 10 can be prevented.

  When the number of reinforcing ribs 21 formed on the motor base portion 18 is the same as the number of the spokes 20, it is desirable that the reinforcing ribs 21 be formed so as to match the locations where the spokes 20 are joined to the motor base portion 18.

  In addition, although the Example demonstrated the case where the number of the spokes 20 was seven, it should just be seven or more. When at least seven spokes 20 are formed, if seven or more reinforcing ribs 21 are formed in the motor base portion 18, when the maximum rotational speed of the motor 15 that rotates the impeller 14 is 20000 rpm, the natural frequency of the casing 11 is increased. Therefore, the frequency becomes higher than the vibration frequency due to the rotation of the motor 15, and abnormal vibration can be prevented.

  Further, a configuration is disclosed in which the plurality of reinforcing ribs 21 extend with the same width (circumferential direction) W and the same height (axial direction) H from the outer peripheral side of the boss portion 18 a to the outer peripheral side surface of the motor base portion 18. However, the width W may gradually decrease as it extends from the outer peripheral side of the boss portion 18a to the outer peripheral side of the motor base portion 18 and may be extended so that the height H gradually decreases. As described above, the width of the plurality of reinforcing ribs 21 is wide at the boss portion 18a, and the width is gradually reduced as it extends toward the outer periphery of the motor base portion 18, thereby efficiently reinforcing the boss portion 18a and providing extra reinforcement. The weight of the presser and casing 11 can be reduced.

  Furthermore, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 10 Blower fan 11 Casing 12 Rotating shaft 13 Blade 14 Impeller 15 Motor 15a Rotor 15b Stator 16a, 16b Bearing 17 Bearing housing 18 Motor base part 19 Cavity part 19a Suction port 19b Suction port 20 Spoke 21 Reinforcement rib

  However, the technique described in Patent Document 1 is a blower fan that has a housing structure that is reinforced by forming a plurality of reinforcing reinforcing ribs in the motor base portion. However, the shape of the reinforcing reinforcing ribs formed in the motor base portion is The structure is not fully disclosed.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a blower fan that can reduce the influence of vibration transmitted to a casing via a motor base.

The configuration of the present invention is as follows.
(1) a rotating shaft;
An impeller that rotates integrally with the rotating shaft;
A motor for rotating the rotating shaft;
A casing,
A motor base,
A spoke connecting the casing and the motor base,
The motor base portion includes a cylindrical boss portion, an outer peripheral side surface, and a plurality of reinforcing ribs connecting the boss portion and the outer peripheral side surface,
The boss portion supports the rotating shaft,
The rotating shaft includes an end portion on the boss portion side,
The blower fan, wherein the end on the boss portion side is disposed outside the reinforcing rib in the rotation axis direction.
(2) a rotating shaft;
An impeller that rotates integrally with the rotating shaft;
A motor for rotating the rotating shaft;
A casing,
A motor base,
A spoke connecting the casing and the motor base,
The motor base portion includes a cylindrical boss portion, an outer peripheral side surface, and a plurality of reinforcing ribs connecting the boss portion and the outer peripheral side surface,
The boss portion supports the rotating shaft and the motor,
The rotating shaft includes an end portion on the boss portion side,
In the radial direction, the blower fan has an end on the boss side facing the reinforcing rib.
(3) In the blower fan, the plurality of reinforcing ribs may be provided on a surface of the disk-shaped motor base portion.
(4) In any one of the above (1) to (3), the spoke is bonded to the outer peripheral surface of the motor base portion, and the plurality of reinforcing ribs are bonded to the outer peripheral side surface of the motor base portion. Also good.
(5) In any one of the above (1) to (4), the number of the plurality of reinforcing ribs may be the same as or more than the number of the spokes.
(6) In any one of the above (1) to (5), the plurality of reinforcing ribs are formed so that the width gradually decreases as they extend from the outer peripheral side of the boss portion to the outer peripheral side of the motor base portion. May be.
(7) In any one of the above (1) or (3) to (6), in the rotational axis direction, the boss portion side end portion is connected to the boss portion and a part of the reinforcing rib. You may arrange | position outside with respect to a position.

  ADVANTAGE OF THE INVENTION According to this invention, the ventilation fan which does not raise | generate an abnormal vibration can be provided.

Claims (6)

An impeller having a plurality of wings;
A motor for rotating the impeller;
A casing for housing the impeller and the motor;
A motor base for mounting the motor;
A plurality of spokes connecting between the casing and the motor base portion;
A blower fan comprising:
Forming a plurality of reinforcing ribs on the motor base;
The number of the reinforcing ribs is the same as or more than the number of the spokes,
When the rotational speed of the motor is rotated to 20000 rpm,
A blower fan, wherein the natural frequency of the casing is set to be higher than the frequency at which the rotation speed of the motor is transmitted to the casing.   The blower fan according to claim 1, wherein the number of the plurality of spokes is at least seven.   The blower fan according to claim 1 or 2, wherein the plurality of spokes are inclined at a predetermined angle with respect to a plane orthogonal to a rotation axis that rotates integrally with the impeller.   4. The air blower according to claim 1, wherein the plurality of reinforcing ribs are formed with the same width from an outer peripheral side of the boss portion to an outer periphery of the motor base portion. fan.   The plurality of reinforcing ribs are formed so as to gradually decrease in width as they extend from the outer peripheral side of the boss portion to the outer peripheral side of the motor base portion. The blower fan as described in.   The said reinforcing rib is extended | stretched and formed toward the location where the said spoke joins with the said motor base part, when the number of these reinforcing ribs is the same as the said spoke, The 1st characterized by the above-mentioned. The blower fan according to claim 5.

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