WO2010026986A1

WO2010026986A1 - Axial fan

Info

Publication number: WO2010026986A1
Application number: PCT/JP2009/065330
Authority: WO
Inventors: 裕亮吉田; 英伸竹下; 仁明大熊
Original assignee: 日本電産株式会社
Priority date: 2008-09-02
Filing date: 2009-09-02
Publication date: 2010-03-11

Abstract

An axial fan comprising a motor section, an impeller having a plurality of blades which extend radially outward from the center axis of the motor section and which are disposed at generally equal pitches in the circumferential direction, and a housing surrounding the outer periphery of the impeller. The angle between the chord of each blade on a virtual cylindrical surface having a certain radius with the center axis as the center and the plane of rotation of the impeller is gradually increased radially outward. The circumferential width of each blade between the leading edge and the trailing edge at a certain radius of each blade is substantially increased radially outward.

Description

Axial fan

The present invention relates to an axial fan.

Conventionally, in an electronic device such as a PC (personal computer) or a server, a cooling fan is provided to cool electronic components inside the casing. In particular, a relatively large electronic device such as a server requires a cooling fan having a high static pressure.

The angle of attack in the fan blade of an axial fan is generally smaller as it goes from the root to the tip. This is for collecting the air flow while suppressing the swirl component as much as possible in the air flow discharged from the axial fan.

By the way, in the axial fan disclosed in Japanese Patent Application Laid-Open No. 2004-251179, in order to obtain a high air volume, the blade is a swept blade, and the angle of attack of the blade taper tip receding portion is determined from the angle of attack of the root portion of the fan blade. The corner is enlarged.
JP 2004-251179 A

In general, with an axial fan, the work of the impeller is maximized at the radially outer portion of the blade. In a general axial fan, as the load increases, surging occurs and a region where the static pressure decreases is generated.

On the other hand, in the axial fan disclosed in Japanese Patent Application Laid-Open No. 2004-251179, the angle of attack of the blade taper tip receding portion is larger than the angle of attack of the root portion of the fan blade, so that air can be sent effectively. Can do. However, the blade is tapered at a radially outer portion, and its area is reduced. For this reason, it was not efficient as an axial fan.

An object of the present invention is to provide an axial fan that can improve static pressure-air flow characteristics. More specifically, the present invention provides an axial fan that can have a static pressure higher than that of a conventional axial fan in a surging region.

An exemplary axial fan according to the present invention includes a motor unit and an impeller having a plurality of blades extending radially outward about the central axis of the motor unit and arranged at substantially equal pitches in the circumferential direction. And a housing surrounding the outer periphery of the impeller, and an angle formed by a chord of each blade on a virtual cylindrical surface having a certain radius with the central axis as a center and a rotation surface of the impeller is a diameter. The width in the circumferential direction at the leading edge and the trailing edge at a certain radius of each wing increases substantially as it goes outward in the radial direction.

According to the exemplary axial fan of the present invention, the static pressure can be increased even in the surging region as compared with the conventional axial fan.

1 is a partial cross-sectional view of an exemplary axial fan of the present invention. It is a top view of an example of an impeller. It is a bottom view of an example of an impeller. It is a figure explaining the angle | corner which a chord and the rotating surface of an impeller make. It is a figure which shows the cross section of an example of an impeller. 6 is a graph showing a trend of static pressure-air flow characteristics in an axial fan according to the present invention and a conventional axial fan. It is a conceptual diagram explaining the difference in the low load area | region of a static pressure-air volume characteristic about the axial fan by this invention, and the conventional axial fan. Similarly, it is a conceptual diagram illustrating the difference in the surge region of the static pressure-air flow characteristics. Similarly, it is a conceptual diagram illustrating the difference in the high load region of the static pressure-air flow characteristics. It is a figure explaining the parameter of an impeller. It is a schematic diagram showing a mode that the parameter of an impeller is changed. It is a top view of the impeller of another example. It is a side view of the impeller of another example. It is a perspective view of the impeller of another example. It is a fragmentary sectional view of the series type axial flow fan comprised using the axial flow fan by this invention.

FIG. 1 is a cross-sectional view of an exemplary axial fan of the present invention.
The axial fan 1 includes an impeller 2, a motor unit 3 that rotates the impeller about the central axis J1, a housing 4 that surrounds the outer periphery of the impeller, a base unit 5 that supports the motor unit, a base unit 5 and a housing 4 And a plurality of support ribs 6 for connecting the two. The housing 4, the base portion 5, and the support rib 6 are formed as one member by resin injection molding.

The impeller 2 has a plurality of blades 21 formed on an impeller cup 22 having a cup shape. The motor unit 3 includes a stator 31 and a rotor magnet 32. The stator 31 includes a core 311 and a coil 312. A bearing housing 81 is fixed to the base portion 5. A bearing 82 is fixed inside the bearing housing 81. The shaft 7, the bearing housing 81 and the bearing 82 constitute a bearing portion 8. The shaft 7 is fitted in the center of the impeller cup 22. In the exemplary axial fan of the present invention, the bearing 82 is a ball bearing. However, the bearing 82 is not limited to this, and various bearing structures such as a sliding bearing and a fluid dynamic pressure bearing can be employed.

In FIG. 1, the support rib 6 that connects the base portion that supports the motor portion and the housing is provided on the discharge side of the axial fan, and has a wing shape. Therefore, the support rib 6 functions as a stationary blade that suppresses the swirling component of the air flow. The shape of the support rib 6 is not limited to a wing shape, and may be various shapes such as a rod shape and a plate shape.

FIG. 2 is a plan view of the impeller 2 and FIG. 3 is a bottom view of the impeller 2. In this example, the impeller 2 has five wings. The five blades 21 of the impeller 2 extend radially outward from the outer surface of the impeller cup 22 around the central axis J1 and are arranged at a substantially equal pitch in the circumferential direction. The impeller 2 rotates counterclockwise in FIG. 2 and 3, reference numeral 211 is attached to the leading edge of each blade in the rotational direction, and reference numeral 212 is attached to the trailing edge.

FIG. 4 is a diagram for explaining the angle formed between the chord and the rotating surface of the impeller. Here, the chord is defined as follows. That is, in the impeller 2 shown in FIG. 2, a cylindrical surface (for example, A1) having a certain radius around the central axis J1 is assumed, and the impeller blades are cut by the cylindrical surface. A straight line connecting the leading edge and the trailing edge of the blade when the cylindrical surface which is the cut surface 21C of the blade is developed into a plane is called a chord L. An angle formed by the chord L and the impeller rotating surface P is defined as θ. In the axial fan according to the present invention, first, this θ increases as it goes radially outward. Hereinafter, this angle may be referred to as an angle of attack. This angle is also called a pitch angle. The impeller blades rotate in the direction of the arrow in FIG.

The angle formed between the chord of each blade and the rotating surface of the impeller increases toward the radially outward direction. The angle formed between the chord of each blade and the central axis increases toward the radially outward direction. It may be understood that it becomes smaller.

FIG. 5 is a diagram in which the outline of the blade cutting surface 21C is overlapped by a virtual cylindrical surface centered on the central axis J1 at the positions indicated by reference signs A1 to A4 in FIG. It shows. The up-down direction in FIG. 5 is a direction parallel to the central axis J1, and the left-right (horizontal) direction is parallel to the rotating surface of the impeller. The right direction in FIG. 5 is the direction in which the blade rotates as viewed from the outside in the radial direction. A straight line connecting the leading edge and the trailing edge in each cross section is indicated by an alternate long and short dash line, and the chords corresponding to the positions of the reference signs A1 to A4 are respectively given reference signs L1 to L4.

As shown in FIG. 5, the angle formed between the chord of each wing and the rotating surface of the impeller gradually increases from the chord L1 toward the chord L4. That is, in each wing, the wing stands as it goes radially outward, that is, toward the tip of the wing.

In the axial fan according to the present invention, the lengths of the chords L1 to L4 are also increased toward the outer side in the radial direction. Further, the width in the direction parallel to the central axis J1 between the leading edge and the trailing edge of the blade, that is, the height in the direction of the central axis J1, is also increased toward the outer side in the radial direction.

Furthermore, as shown in FIGS. 2 and 3, the blades are directed radially outward so that the circumferential width between the leading edge and the trailing edge of each blade increases in the radially outward direction. The chord is getting bigger. The circumferential width between the leading edge and the trailing edge of each blade may be understood as the circumferential width when the blade is projected onto a plane perpendicular to the central axis J1.
As a result, the ratio of work to electric power in the blade can be increased. When the chord of the wing is increased radially outward, the radially inner portion is made thicker than the radially outer portion of the wing in order to keep the attachment strength of the wing better. .

”In each of the blades in the conventional axial fan, there are many examples in which the chords become larger outward in the radial direction. However, the angle of attack of each wing is smaller outward in the radial direction, that is, toward the tip. This is to collect the air flow while suppressing the swirl component as much as possible in the air flow discharged from the axial fan. Further, the width (height) of the blade in the direction of the central axis J1 is not increased.

In the axial flow fan of the present invention, each chord has a chord that increases radially outward. For this reason, the area of the wing | blade in the site | part of a radial direction outer side is large. This is equivalent to a large projected area when the wing is projected onto a plane perpendicular to the rotation axis. For this reason, it is efficient as an axial fan and has a high exhaust capacity.

In addition, as shown in FIGS. 2 and 3, the tip of each blade may be rounded for reasons of molding. Also in this case, it does not depart from the gist of the present invention. According to the present invention, also in this case, the circumferential width between the leading edge and the trailing edge of each blade is substantially increased toward the outer side in the radial direction.

In the axial flow fan 1, since the angle of attack of each blade is increased radially outward, the air velocity generated from the blade increases the wind speed in the axial direction at the radially outer periphery of each blade. In the region where surging occurs, a backflow of air is generated from the root portion of the blade, and the pressure in the radially outer peripheral portion is lowered by increasing the axial wind speed. Thereby, a pressure gradient is generated in the radial direction, and the flow of the wind moves outward in the radial direction. Therefore, even in the maximum air volume region, the wind flow is directed radially outward, so the characteristic deterioration due to the backflow of air at the root of the blade in the surging region can be reduced, and the characteristics in the surging region are more than those of conventional axial fans. Can be improved.

FIG. 6 is a conceptual graph showing a trend of static pressure-air flow characteristics in the axial fan according to the present invention and the conventional axial fan. FIG. 7 is a conceptual diagram illustrating the difference in static pressure-air flow characteristics in various load regions between the axial fan according to the present invention and the conventional axial fan.

FIG. 7A conceptually shows the speed of the air flow in the low load region by the length of the arrow. That is, in the conventional axial fan, there is no technical idea that the air flow velocity is positively varied depending on the radial position of the blade. On the other hand, in the axial fan according to the present invention, the angle of attack of each blade increases toward the outer side in the radial direction, so the air flow becomes faster toward the outer side in the radial direction.

FIG. 7B shows the state of airflow in the surging area. In the surging region, the influence of centrifugal force increases, so the air flow moves outward. If it does so, a backflow will come to arise in the root part of the trailing edge side of a wing. In the axial fan of the present invention, the characteristics of the surging region are particularly improved as compared with the conventional axial fan.

FIG. 7C shows the state of air flow in the high load region. In the high load region, a reverse flow also occurs at the tip portion on the leading edge side of the blade.

In the above explanation, the number of wings was five. The number is not limited to five, and may be other than five, for example, three, four, six, seven, and the like.

Next, parameters of each blade of the impeller will be described with reference to FIG.
In each blade of the impeller, the radius of the tip portion of the width in the direction parallel to the central axis between the leading edge and the trailing edge of each blade is set as R and the radius of the root portion is r. And A is the width of the tip in the radial direction.

FIG. 9 is a diagram schematically showing how the parameters of the impeller blades are changed. In FIG. 9, (1) is a reference wing, (2) is an example in which the mounting position (height) of the leading edge at the root of the wing is lowered, and (3) is the same mounting position (height). ). Further, (4) is an example in which the radius r of the root part of the blade is reduced with reference to A, and (5) is an example in which the radius r of the root part of the blade is also increased.
In this way, the static pressure-air volume characteristics were examined by changing r / R, A / B, and B / R, respectively.

First, r / R was changed in each impeller blade, and the static pressure-air flow characteristics of the axial fan were examined. As a result, it was found that the static pressure-air flow characteristics were particularly excellent in the range of 0.45 ≦ r / R ≦ 0.8.
When r / R is set to 0.45 or more, the blade length (Rr) becomes relatively long, the radially outer wind speed is increased, and the characteristics in the surging region can be effectively improved. Is preferred. When r / R is 0.8 or less, it is suitable for securing the angle of attack of the tip of the blade and the projected area of the blade. In consideration of such points, r / R may be appropriately adjusted according to the application.

Next, the static pressure-air flow characteristics of the axial fan were examined by changing A / B in each impeller blade. As a result, it was found that the static pressure-air flow characteristics were particularly excellent in the range of 0.3 ≦ A / B ≦ 0.8.
If A / B is 0.3 or more, the width of the root portion is sufficient, the work amount of the root portion is secured, the characteristics in the surging region are further improved, and the mechanical strength can be sufficiently secured. Is preferable. When A / B is 0.8 or less, the angle of attack at the tip of the blade and the projected area of the blade can be sufficiently secured, which is preferable. In consideration of such points, A / B may be appropriately adjusted according to the application.

Further, the static pressure-air flow characteristics of the axial fan 1 were examined by changing the B / R in each impeller blade. As a result, it was found that the static pressure-air flow characteristics were particularly excellent in the range of 0.56 ≦ B / R ≦ 1.4.
When B / R is set to 0.56 or more, it is preferable because a sufficient projected area of the blade can be secured and characteristics in the surging region can be further improved. When B / R is 1.4 or less, the relationship between the impeller diameter and the angle of attack of the tip of the blade becomes appropriate, which is preferable because the characteristics can be further improved. In consideration of such points, B / R may be appropriately adjusted according to the application.

FIG. 10A to FIG. 10C show another example of the impeller. 10A is a plan view, FIG. 10B is a side view, and FIG. 10C is a perspective view.

The exemplary embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made.

(Application example)
FIG. 11 shows an example in which an axial flow fan 100 is configured using the axial flow fan according to the present invention. The serial axial fan 100 is a so-called counter-rotating axial fan, used as a cooling fan for air-cooling electronic equipment such as a server, and the first axial fan 11 disposed on the upper side in FIG. The second axial fan 12 connected to the lower side of the first axial fan 11 along the central axis J1 of the first axial fan 11 is provided.

In the serial axial fan 100 shown in FIG. 11, air flows in the direction of the central axis J1 so that air is taken in from the upper side and sent out to the lower side.

The first axial fan 11 includes a first impeller 112, a first motor unit 113 that rotates the first impeller 112 around the central axis J1, a first housing 114 that surrounds the outer periphery of the first impeller 112, A first base portion 115 that supports the motor portion 113 and a plurality of first support ribs 116 are provided. The first impeller 112 has a plurality of blades extending radially outward from the outer surface of the impeller cup. The plurality of first support ribs 116 connect the first base portion 115 and the first housing 114. In this example, four first support ribs 116 are provided. The first housing 114, the first base portion 115, and the first support rib 116 are formed as one member by resin injection molding.

The structure of the second axial fan 12 is basically the structure of the motor section of the first axial fan 11 turned upside down to reduce the width of the first impeller in the rotational axis direction, and the rotational direction is reversed. It can be understood that the pitch angle of each blade is reversed.

The second axial fan 12 includes a second impeller 122, a second motor portion 123 that rotates the second impeller 122 around the central axis J1, a second housing 124 that surrounds the outer periphery of the second impeller 122, and a second A second base portion 125 that supports the motor portion 123 and a plurality of second support ribs 126 are provided. The plurality of second support ribs 126 connect the second base portion 125 and the second housing 124. In this example, four second support ribs 126 are provided. The second housing 124, the second base portion 125, and the second support rib 126 are formed as one member by resin injection molding.

In the serial axial fan 100, the first motor unit 113 rotates in the direction of the right arrow in the drawing, and the second motor unit 123 rotates in the direction of the left arrow in the drawing to send air downward.

The present invention can be used not only as a single axial fan but also as a series axial fan in combination with other axial fans.

1: Axial fan, 2: Impeller,
21: Wing, 211: Leading edge of the wing, 212: Trailing edge of the wing, 22: Impeller cup,
3: Motor part, 31: Stator, 311: Core,
312: Coil, 32: Rotor magnet,
4: Housing, 5: Base part,
6: support rib, 7: shaft,
8: bearing part, 81: bearing housing, 82: bearing,
J1: central axis, L1-L4: chord,
100: Inline axial fan,
11: 1st axial fan, 12: 2nd axial fan,
112: First impeller, 122: Second impeller,
113: 1st motor part, 123: 2nd motor part,
114: first housing, 124: second housing,
115: 1st base part, 125: 2nd base part,
116: first support rib, 126: second support rib,

Claims

An axial fan,
A motor section;
An impeller having a plurality of wings extending radially outward about the central axis of the motor portion and arranged at a substantially equal pitch in the circumferential direction;
A housing surrounding the outer periphery of the impeller;
With
The angle formed between the chord of each wing on the virtual cylindrical surface having a certain radius with the central axis as the center and the rotation surface of the impeller increases as it goes radially outward,
An axial fan in which a circumferential width between a front edge and a rear edge at a certain radius of each blade is substantially increased toward the outer side in the radial direction.
The axial fan according to claim 1,
An axial fan in which a width in a direction parallel to the central axis between a leading edge and a trailing edge at a radius of each blade is increased toward a radially outward direction.
The axial fan according to claim 1,
In each of the wings, when the radius of the radial tip is R and the radius of the root is r,
r / R is
0.45 ≦ r / R ≦ 0.8
An axial fan in the range of
The axial fan according to claim 1,
Of the widths in the direction parallel to the central axis between the leading edge and the trailing edge of each wing, when the width of the root portion is A and the width of the radial tip is B,
A / B is
0.3 ≦ A / B ≦ 0.8
An axial fan in the range of
The axial fan according to claim 1,
In each of the wings, let R be the radius of the radial tip.
Of the widths in the direction parallel to the central axis between the leading edge and the trailing edge of each wing, when the width of the radial tip is B,
B / R is
0.56 ≦ B / R ≦ 1.4
An axial fan in the range of
The axial fan according to claim 1,
Furthermore, the axial fan provided with the stationary blade in the discharge | emission side of the said axial fan.
The axial fan according to claim 6,
The stationary blade is an axial fan in which a base portion supporting a motor portion and a housing are connected.