The present invention relates to an axial flow blower, more particularly relates to a structure of a fan blade which achieves both noise reduction and blowing performance.
An axial flow blower is required to provide both blowing performance and low noise. PTL1 discloses to provide a plurality of triangle shape projections in a sawtooth manner (below, referred to as “serrations”) in a chord line direction of a leading edge of a blade as a whole to try to reduce the noise of operation of the blower fan 1. The positive pressure surface and the negative pressure surface of a blade of the axial flow blower become as shown in
PTL1: Japanese Unexamined Patent Publication No. 2000-087898A
The present invention, in view of the above problems, provides a blower which aims at both a noise reduction effect and the inherent blowing performance of a blade by the provision of a plurality of triangle shape projections in the chord line direction of a leading edge part of the blade as a whole at just the negative pressure surface.
To solve the above problem, the aspect of the invention of claim 1 provides an axial flow blower (10) which is provided with an electric motor (300), and a blower fan (1) which has a hub (4) which is attached to said electric motor (300), and a plurality of blades (3) which are provided at said hub (4) in a radial manner, wherein in said axial flow blower, a negative pressure surface of a leading edge (6) of each said blade (3), comprised of a negative pressure surface and a positive pressure surface, is provided with a plurality of triangle shape projections which have vertexes along the leading edge (6), and the positive pressure surface of the leading edge (6) of each said blade (3) is not provided with said triangle shape projections but is a smooth continuous surface.
To solve the above problem, the aspect of the invention of claim 7 provides an axial flow blower (10) which is provided with an electric motor (300) and a blower fan (1) which has a hub (4) which is attached to said electric motor (300) and a plurality of blades (3) which are provided at said hub (4) in a radial manner, wherein in said axial flow blower, a leading edge (6) of each said blade (3), comprised of a negative pressure surface and a positive pressure surface, is provided in the negative pressure surface and the positive pressure surface with a plurality of triangle shape projections which have vertexes along the leading edge (6), and angles (φ2) formed by valleys (3-2) of said plurality of triangle shape projections at said positive pressure surface are respectively larger than angles (φ1) formed by said valleys at said negative pressure surface.
Note that the reference numerals given above are illustrations showing the correspondence with specific means described in the embodiments described later.
Below, referring to the figures, embodiments of the present invention will be explained. In the embodiments, parts of the same configuration are assigned the same reference notations and the explanations omitted. Referring to
Between the shroud ring part 210 and the rectangular shape outer circumference of the shroud 200, an air guide part 220 which expands toward the upstream side of the blower fan 1 is formed. At the center of the shroud ring part 210, a circular motor holding part 230 is formed. This motor holding part 230 is supported by a plurality of motor stays 240 which extend in a radial shape outward in the radial direction and are connected to the shroud ring part 210. At the motor holding part 230, an electric motor 300 is fastened. The shaft of the electric motor 300 and the hub 4 of the blower fan 1 (see
First, at the start, the effects of serrations which form the basis of the present invention will be explained. The simulation of
In the present embodiment, the effects of the above-mentioned serrations are utilized while reducing the rotating noise of the blower fan. The inherent objective of a blower fan, that is, the blowing performance, is kept from being impaired so as to realize both noise reduction and blowing performance (lift). As shown in
As the effect created by the serrations, flow separation is reduced near the blade surfaces of the negative pressure surfaces and disturbances near the blade surfaces are eased. Further, by keeping down pressure fluctuations at the blade surfaces, noise reduction is realized. The present embodiment not only can achieve both noise reduction and blowing performance (lift), but also can perform blowing work more efficiently than even conventional blower fans, so lower torque is realized and the power used becomes smaller, so this leads to energy saving.
The second embodiment is characterized as follows. The side surfaces 3-3 of the peaks 3-1 of the triangle shape projections are slanted like the slopes of mountains. The side surfaces 3-3 of the peaks 3-1, as shown in
The sizes “a” of the bottom sides of the peaks 3-1, the angles ψ of the vertexes, and the center directions “O” of the triangle shape projections (see
Further, in the case of an axial flow blower, the further to the outer circumference side of the blower fan 1, the faster the flow rate is. Sometimes it is effective to increase the size “a” of the bottom side or reduce the angle ψ of the vertex the further to the outer diameter side of the blades. It is possible to control the fast flow rate flow where separation easily occurs, by changing the shapes of the peaks 3-1 of the triangle shape projections.
The fourth embodiment, while not shown, provides serrations which run through the blade thickness at the trailing edge 7 of the blade 3. This is an embodiment where, in the embodiments explained above, the negative pressure surface to the positive pressure surface of the trailing edge 7 of the blade 3 is provided with a plurality of triangle shape projections along the trailing edge 7. In addition to the effects of the embodiments explained up to here, the disturbances in the back flow of the blades can be reduced, so it is possible to obtain the effects of noise reduction, reduction of the air flow, and prevention of the increase of the drive torque.
The fifth embodiment is an embodiment in the case of applying the embodiments which were explained above to a shape of blade such as shown in
In the sixth embodiment, the leading edge 6 of blade 3 in the negative pressure surface and the positive pressure surface 3 is provided with a plurality of triangle shape projections which have vertexes along the leading edge 6.
In this embodiment, the angles φ2 which are formed by the valleys 3-2 of the plurality of triangle shape projections at the positive pressure surface are all larger than the angles φ1 which are formed by the valleys of the negative pressure surface. In this case as well, the positive pressure surface can maintain the blowing performance (lift), compared with negative pressure surface. When the angles φ2=180 degrees, the result becomes included in the second embodiment. Further, when the angles φ2 are close to 180 degrees, it is possible to obtain substantially the same effects as the second embodiment. Of course, if the angles φ2 are larger than the angles φ1, the positive pressure surface can maintain the blowing performance (lift) compared with negative pressure surface.
Number | Date | Country | Kind |
---|---|---|---|
2012-124252 | May 2012 | JP | national |