1. Field of the Invention
The present invention relates to an impeller for an axial flow fan, and an axial flow fan using the impeller, and more particularly, to an impeller which maintains an air flow characteristic in a normal rotation direction without a significant deterioration in the air flow characteristic even in a case of rotating in a reverse direction, and an axial flow fan using the impeller.
2. Description of the Related Art
Axial flow fans have been used for blowing or cooling of electronic devices such as home appliances and information devices.
Electronic devices such as personal computers and copy machines include a number of electronic components accommodated in a relatively small casing. Therefore, heat generated from the electronic components stays in the casing, possibly resulting in destroying the electronic components. Thermal destruction causes a big problem for the device. For this reason, a ventilation hole is provided on the side wall or ceiling of the casing of the electronic device. The heat generated in the casing is discharged from the ventilation hole to the outside. Also, axial flow fans have been used as cooling means for electronic devices.
The axial flow fan is disclosed in JP-A-H8-303391, and
Some axial flow fan is rotatable in a reverse direction to change an air flow direction such that the axial flow fan can be used not only for blowing but also for exhaust. Since the related-art axial flow fan as shown in
Meanwhile, there is a known bi-directional axial blower which is rotatable in a normal direction and a reverse direction and is called as a jet fan for air ventilation of a tunnel or the like (see JP-A-2009-097430, for example). The jet fan is configured to have the same air flow characteristic even if an air flow direction is changed between the normal direction and the reverse direction. Therefore, it is possible to send air forward or backward in a tunnel according to the internal environment situation of the tunnel.
As shown in
As in the axial blower disclosed in JP-2009-097430, if a blade shape is S-shaped and has a point symmetrical shape, even if the rotation direction is changed, the same air flow characteristic can be achieved. However, in this case, the air flow characteristic in the normal rotation direction is deteriorated as compared to the axial flow fan disclosed in JP-A-H8-303391. For this reason, in a case where a high air flow characteristic in the normal rotation direction is required, a blower as disclosed in JP-A-2009-097430 may not satisfy that requirement.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an impeller which can maintain an air flow characteristic in a normal rotation direction of an axial flow fan while suppressing a significant deterioration in the air flow characteristic even in a case of rotating in a reverse direction by designing the shape of the impeller, and an axial flow fan using the impeller.
According to an aspect of the present invention, there is provided an impeller for an axial flow fan, comprising: a plurality of blades arranged in a circumferential direction. In each of the blades, with respect to a center point of a chord length of the blade, a leading edge side shape of the blade and a trailing edge side shape of the blade are line-symmetric, and a shape of the blade at one face side is different from a shape of the blade at the other face side.
In the above impeller, the shape of the blade at the one face side may be defined by a concave shape having an arc shape with a predetermined radius of curvature, and the shape of the blade at the other face side may be defined by a convex shape having an arc shape with a predetermined radius of curvature.
In the above impeller, the one face side may be a pressure face side during a normal rotation of the impeller.
According to another aspect of the present invention, there is provided an axial flow fan comprising: the above impeller; a motor configured to rotate the impeller; and a casing which accommodates the impeller, and includes a base portion supporting the motor.
According to the above configuration, it is possible to provide an impeller which can maintain an air flow characteristic in a normal rotation direction of an axial flow fan while suppressing a significant deterioration in the air flow characteristic even in a case of rotating the axial flow fan in a reverse direction, and an axial flow fan using the impeller.
In the accompanying drawings:
Hereinafter, an illustrative embodiment of the present invention will be described with reference to the accompanying drawings.
An axial flow fan 1 includes an impeller 3 having a plurality of blades 4 arranged in a circumferential direction, a motor 2 configured to rotate the impeller 3, and a casing 6 which accommodates the impeller 3 and has a base portion 7 supporting the motor 2.
The base portion 7 is fixed to the casing 6 by a plurality of spokes 8. If the impeller 3 rotates according to rotation of the motor 2, air is suctioned from an inlet of the casing 6, passes through the gaps between the blades 4 and the inside of the casing 6, and is discharged from an outlet of the casing 6.
The impeller 3 includes a cylindrical hub 5, and the plurality of blades 4 arranged on an outer circumferential surface of the hub 5. The blades 4 (five blades in an example shown in
The blades 4 are forward swept blades in which the leading edges 10 of the blades 4 moves more forward than the roots of the blades 4 when normally rotating in a rotation direction of an arrow 9 in
In
The center portion of the surface of the pressure surface 13 of the blade 4 is formed in an arc having a predetermined radius of curvature R2, and the center of the radius of curvature R2 is provided at a side of the pressure surface 13 of the blade 4. In other words, the center portion of the surface of the pressure surface 13 of the blade 4 has a concave shape (a shape where the center portion of the pressure surface 13 becomes convex toward a side of the suction surface 14).
Both ends of the pressure surface 13 of the blade 4 are formed in an arc having a predetermined radius of curvature R1 (
That is, the surface of the pressure surface 13 of the blade 4 is formed by a curved surface where the arcs having the radius of curvature R1 and the arc having the radius of curvature R2 are connected (a curved surface whose end portions are convex and whose center portion is concave). One of the connection positions of the arcs are shown by a point A in
Meanwhile, the center portion of the surface of the suction surface 14 of the blade 4 is formed in an arc having a predetermined radius of curvature R4, and both end sides of the suction surface 14 of the blade 4 are formed in arcs having a predetermined radius of curvature R3 (
That is, the surface of the suction surface 14 of the blade 4 is formed from a curved surface where the arcs having the radius of curvature R3 and the arc having the radius of curvature R4 are connected. One of the connected positions of the arcs is shown by a point B in
As the values of R1 to R4 with respect to the length L of the blade chord line 12, the following values are preferable.
As shown in the cross-sectional view of
Also, as shown in
An attachment angle of the blade 4 represents an angle which is formed by the blade chord line 12 which is a straight line connecting the leading edge 10 of the blade 4 and the trailing edge 11 of the blade 4, and a plane perpendicular to a rotation axis line. The attachment angle of the blade 4 generally depends on the position of the blade 4 in a radial direction. An attachment angle at the root side (portion which is attached to the hub 5) of the blade 4 is 33°, and an attachment angle at the tip end side of the blade 4 is smaller than the attachment angle at the root side of the blade 4. For example, the attachment angle at the tip end side is 75% to 80% of the attachment angle at the root side (portion which is attached to the hub 5) of the blade 4.
The axial flow fan of the comparative example has a blade shape bent with respect to a rotation direction for increasing an air flow such that a pressure surface side is convex, as shown in
In
As shown in
The axial flow fan of the comparative example represents a characteristic in which the maximum air flow rate during reverse rotation is about 79% of that during normal rotation, whereas the axial flow fan of the present illustrative embodiment represents a characteristic in which the maximum air flow rate during reverse rotation is about 90% of that during normal rotation. That is, as compared to the axial flow fan of the comparative example, the axial flow fan of the present illustrative embodiment is slightly worse in the maximum static pressure, but shows an increase in the maximum air flow rate, and has the characteristic in which the maximum air flow rate during reverse rotation is about 90% of that during normal rotation.
Accordingly, the axial flow fan of the present illustrative embodiment has an optimized blade shape, and thus can maintain an air flow characteristic in a normal rotation direction while suppressing a significant deterioration in the air flow characteristic even in a case of rotating in a reverse direction.
Herein, in the above-described illustrative embodiment, although the number of blades is five, the present invention is not limited thereto. Further, the values of the shape and size of the blade are merely preferable examples, and can be variously changed within the scope of the claims.
The shape of each blade may be a forward swept blade or a sweptback blade.
Further, the blades may have any shape as long as a shape at one face side is different from a shape at the other (opposite) face side, and its variation is not limited to that shown in
It should be understood that the illustrative embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
Number | Date | Country | Kind |
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2011-278590 | Dec 2011 | JP | national |