JP3557679B2

JP3557679B2 - Axial fan

Info

Publication number: JP3557679B2
Application number: JP31965194A
Authority: JP
Inventors: 憲二鎌田
Original assignee: Matsushita Electric Works Ltd
Current assignee: Panasonic Electric Works Co Ltd
Priority date: 1994-12-22
Filing date: 1994-12-22
Publication date: 2004-08-25
Anticipated expiration: 2019-08-25
Also published as: JPH08177791A

Description

【０００１】
【産業上の利用分野】
本発明は、毛髪乾燥用ドライヤー等に用いられる軸流ファンに関するものであり、特に軸流ファンの低騒音化に関するものである。
【０００２】
【従来の技術】
従来より軸流ファンにおいて、羽根車から発生する騒音を低減するために、特公平５−１４１１８号公報等に見られるように羽根車の羽根を回転方向に前進させる手法が取られてきた。
これらの軸流ファンにおいて、羽根車の羽根を回転方向に前進させることが騒音低減できる理由を図８、図９に基づいて詳述する。１１は羽根車の羽根、１１ｔは羽根外周部、１１ｐは羽根前縁部、１１ｑは羽根後縁部、６は羽根１１を取付けるための回転軸としてのボス部である。
【０００３】
ここで、軸流ファンの騒音の主な原因となる翼端渦の発生メカニズムについて説明すると軸流ファンにおける流れ２０（図８、図９中矢印）は軸方向から見た場合、羽根車後流部の抵抗物のため、羽根１１面上を回転軸と同心円でなく外周方向に向くようになる。そのため、図８、図９中においてクロスハッチングに示される領域Ａの流れが羽根外周部１１ｔから漏れることになり、この漏れた流れが翼端渦２１となって後流に流れて騒音の原因となる。
【０００４】
図８において羽根が前進していない場合、領域Ａの流れが翼端渦２１になる。しかし、図９のように羽根１１を回転方向に前進させることにより領域Ａが小さくなることが分かる。つまり、羽根１１を回転方向に前進させることにより翼端渦２１の発生を少なくし、騒音を低減していると言える。
【０００５】
【発明が解決しようとする課題】
しかしながら、回転軸付近において流れ２０が外周部に向いている場合、図８、図９において破線のクロスハッチングにて示される領域Ｂの低流量域が発生しており、この領域Ｂと、図８、図９においてハッチングにて示される領域Ｃとの間には流量差による乱れ２２が存在して騒音発生の原因となる。
【０００６】
この様に後縁部と前縁部とを同じように前進させた場合、領域Ａが減少すると同時に領域Ｂが増加することになり翼端渦２１の発生は減少するが、領域Ｂと領域Ｃの流量差による乱れ２２が増加する欠点も持っている。
本発明は上記問題点の解決を目的とするものであり、ファン外周部の翼端渦の発生を少なくするとともに、回転軸付近の低流量域を小さくし流量差による流れの乱れを抑えて低騒音の軸流ファンを提供しようとするものである。
【０００７】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明は、円筒形ケーシング内部に、羽根車とその後流側にモータ及びモータの保持と風の整流を目的とした整流翼からなる構造の軸流ファンにおいて、羽根車を回転軸方向から見て、回転軸中心を原点Ｏとし、羽根の回転方向側端面である前縁部と羽根車外周との交点をＰｔ、回転軸外周と前縁部との交点をＰｂとし、さらに直線Ｏ−Ｐｔと直線Ｏ−Ｐｂのなす角度をθｐとし、羽根の回転方向の反対側端面である後縁部と羽根車外周部との交点をＱｔ、回転軸外周と後縁部との交点をＱｂとし、さらに直線Ｏ−Ｑｔと直線Ｏ−Ｑｂのなす角度をθｑとした場合、θｐの値をθｑの値よりも大きくし、軸方向から見た羽根表面の流れが、回転方向だけでなく外周方向に向かっているとき、さらに点Ｑｔを通る流れと前縁との交点をＰｓ、点Ｐｂを通る流れと後縁との交点をＱｓとした場合、（面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔの面積）と（面Ｐｔ−Ｐｓ−Ｑｔの面積）＋（面Ｑｓ−Ｐｂ−Ｑｂの面積）の比が最大となるようにθｐとθｑを定義し、羽根車の外径を１００ｍｍ以下に形成すると共に、θｐを３５度から４５度、θｑを１５度から２５度に設定したことを特徴とするものである。
【０００９】
【作用】
しかして、ファン外周部の翼端渦の発生を少なくするとともに、回転軸付近の低流量域を小さくして流量差による流れの乱れを抑えることができる。
【００１０】
【実施例】
以下、本発明を図示された実施例に基づいて詳述する。
図３に示される軸流ファンは、円筒形のケーシング１内部に羽根車２と羽根車駆動用のモータ３、モータ３の固定と風の整流を目的とした整流翼４を配置してある。この構造において羽根車２の回転によりケーシング１内に風を発生させるようになっている。この羽根車２は、図２に示されるように羽根１１とそれを固定する回転軸としてのボス部６から形成されている。
【００１１】
羽根車２を回転軸方向から見た図１において、回転軸中心を原点Ｏとし、羽根１１の回転方向側端面である前縁部１１ｐと羽根車外周１１ｔとの交点をＰｔ、回転軸外周１１ｂと前縁部１１ｐとの交点をＰｂとし、さらに直線Ｏ−Ｐｔと直線Ｏ−Ｐｂのなす角度をθｐとし、また、回転方向反対側端面である後縁部１１ｑと羽根車外周部１１ｔとの交点をＱｔ、ボス部外周１１ｂと後縁部１１ｑとの交点をＱｂとし、さらに、直線Ｏ−Ｑｔと直線Ｏ−Ｑｂのなす角度をθｑとする。
【００１２】
羽根１１表面の流れ２０は図１に示されるように円周に沿った流れではなく、後流の抵抗物のため外周方向に向いている。このとき、点Ｑｔを通る流れ２０ａと前縁部１１ｐとの交点をＰｓ、点Ｐｂを通る流れ２０ｂと後縁部１１ｑとの交点をＱｓとすると、面Ｐｔ−Ｐｓ−Ｑｔの流れは羽根外周部１１ｔから流れ出し、翼端渦２１となって後流に流れる。その渦が騒音の原因となる。
【００１３】
また、ボス部６付近においては面Ｐｂ−Ｑｂ−Ｑｓに流れ込む風は少なく面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔとの流量に差ができて流れの乱れの原因となり騒音が発生する。つまり、面Ｐｔ−Ｐｓ−Ｑｔと面Ｐｂ−Ｑｂ−Ｑｓの面積に対して面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔの面積が大きいと騒音発生防止に有効であることが分かる。一般に面Ｐｔ−Ｐｓ−Ｑｔの面積を小さくする手段として、羽根１１を全体を回転方向に前進する形状がとられる。このとき前進形状を示す図９と、前進していない図８を比較すると明らかなように羽根１１が前進すると面Ｐｔ−Ｐｓ−Ｑｔの面積が減少することが分かる。しかし、逆に面Ｐｂ−Ｑｂ−Ｑｓは前進と共に増加し、そのために面Ｐｔ−Ｐｓ−Ｑｔの減少による騒音減少効果を最大限いかせていない。
【００１４】
そこで、図１に示される本実施例ではθｐに対してθｑを小さくすることにより面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔに対する面Ｐｂ−Ｑｂ−Ｑｓの増加の割合を少なくしている。
図７にθｐ＝θｑ及びθｐ＞θｑのときの面Ｐｂ−Ｑｂ−Ｑｓの差が分かるように、２つの場合の羽根１１を重ねた状態を示す。
【００１５】
しかしながら、点Ｑｔを基準に小さくした場合、θｑを小さくしすぎると有効に仕事をする面である面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔの面積まで狭くなる欠点がある。また、点Ｑｂを基準にθｑを小さくした場合、面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔは増加するが、面Ｐｔ−Ｐｓ−Ｑｔが増加してしまう欠点がある。
そのため（面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔ）の面積と（面Ｐｔ−Ｐｓ−Ｑｔの面積）＋（面Ｐｂ−Ｑｂ−Ｑｓの面積）の比が最大となるようにθｐとθｑを決定するのが最も良い。
【００１６】
流れ２０が図１のように羽根１１面上をきれいな円弧として流れている場合、面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔの面積と面Ｐｔ−Ｐｓ−Ｑｔ＋面Ｐｂ−Ｑｂ−Ｑｓの面積の比が最大となるのは、０．４θｐ＜θｑ＜０．６θｐの範囲であり、この範囲にてθｐ及びθｑを決めるのが良い。
本実施例の羽根車外径６０ｍｍ、採光効率点における騒音を、θｐ、θｑをパラメータにしたグラフを図４に示す。
【００１７】
θｐ＝θｑのとき３５度付近を最小値にして騒音が変化しているのが分かる。これは３５度付近までは（面Ｐｔ−Ｐｓ−Ｑｔ）の面積が減し翼端渦２１の発生の減少効果が、面Ｐｂ−Ｑｂ−Ｑｓの増加の乱れ２２による騒音増大要因よりも大きいためである。また、それ以上に前進角θｐ、θｑを大きくすると（面Ｐｂ−Ｑｂ−Ｑｓ）が大きくなる割合が大きく、逆に騒音が増加している。図５にθｐを一定にして、θｑのみ減らした場合の騒音を示す。θｐ＝４３度の時θｑが２０度前後にて騒音が最も小さくなる。θｐを３５度のままθｑを変化させた場合は、面Ｐｂ−Ｑｂ−Ｑｓがそれほど大きくならないため、騒音の変化は小さい。
【００１８】
以上の結果から、小型の軸流ファンにおいて、θｐ＝３４度から４５度、θｑ＝１５度から２５度のとき最も騒音を小さくできる。
次に本発明を毛髪乾燥用のドライヤーに応用した実施例を図６に基づき示す。ヘアードライヤーの本体ハウジング３１は円筒形をしており、本体ハウジング３１の一端の開口部を吸い込み口３２、他端の開口部を吹き出し口３３とする。本体ハウジング３１内には羽根車２と羽根車２を駆動するモータ３と、モータ３の固定と風の整流を目的とした整流翼４を配置してある。羽根車２の後流にはヒータ３４を設置し、風を温風にする働きを持つ。本体ハウジング３１からは下方にハンドル３５を一体に垂下してある。
【００１９】
本実施例における羽根車２の外径は６０ｍｍ、本体ハウジング３１と羽根車２の外周部との間の隙間は１ｍｍ以下に設定してある。
上記構造のドライヤーを動作した場合、羽根車後流側にヒータ３４等の抵抗物があるため、羽根車２の羽根１１表面の流れは図１に示されるように外周方向に向く。そのため、羽根車外周部から翼端渦２１が発生し、ボス部６付近にては流量差が大きくなることによる騒音が大きくなる。
【００２０】
そのため、本実施例においては、吸い込み側軸方向から羽根車２を見た場合、図１に示すように回転方向に羽根１１が前進しており、前進角θｐ、θｑはそれぞれ４３度及び２０度に設定してある。それにより翼端渦２１の発生を少なくし、さらにボス部付近の低流量領域Ｐｂ−Ｑｂ−Ｑｓを小さくして乱れ２２を小さくできる。
【００２１】
上記構造のドライヤーにより、θｐ、θｑとも２０度の場合と比較して約３ｄＢ（Ａ）、θｐ、θｑとも４３度の場合と比較して約１．５ｄＢ（Ａ）騒音低減効果が見られる。
【００２２】
【発明の効果】
本発明は、円筒形ケーシング内部に、羽根車とその後流側にモータ及びモータの保持と風の整流を目的とした整流翼からなる構造の軸流ファンにおいて、羽根車を回転軸方向から見て、回転軸中心を原点Ｏとし、羽根の回転方向側端面である前縁部と羽根車外周との交点をＰｔ、回転軸外周と前縁部との交点をＰｂとし、さらに直線Ｏ−Ｐｔと直線Ｏ−Ｐｂのなす角度をθｐとし、羽根の回転方向の反対側端面である後縁部と羽根車外周部との交点をＱｔ、回転軸外周と後縁部との交点をＱｂとし、さらに直線Ｏ−Ｑｔと直線Ｏ−Ｑｂのなす角度をθｑとした場合、θｐの値をθｑの値よりも大きくし、軸方向から見た羽根表面の流れが、回転方向だけでなく外周方向に向かっているとき、さらに点Ｑｔを通る流れと前縁との交点をＰｓ、点Ｐｂを通る流れと後縁との交点をＱｓとした場合、（面Ｐｓ−Ｐｂ−Ｑｓ−Ｑｔの面積）と（面Ｐｔ−Ｐｓ−Ｑｔの面積）＋（面Ｑｓ−Ｐｂ−Ｑｂの面積）の比が最大となるようにθｐとθｑを定義し、羽根車の外径を１００ｍｍ以下に形成すると共に、θｐを３５度から４５度、θｑを１５度から２５度に設定しているので、ファン外周部の翼端渦の発生を少なくするとともに、回転軸付近の低流量域を小さくし流量差による流れの乱れを抑えることができるものである。
【図面の簡単な説明】
【図１】本発明の羽根車の軸方向正面図である。
【図２】同上の斜視図である。
【図３】同上の設置状態を示す断面図である。
【図４】前縁と後縁の前進角が同じ場合の前進角の変化による騒音変化を説明する説明図である。
【図５】前縁の前進角を一定にした場合の後縁の前進角による騒音の変化を説明する説明図である。
【図６】本発明の第２実施例の断面図である。
【図７】後縁の前進角が前縁の前進角と同じ場合と、後縁の前進角が前縁の前進角より小さい場合の比較を説明する説明図である。
【図８】従来例の前進していない羽根車の説明図である。
【図９】従来例の前縁と後縁を同じ角度前進した羽根車の説明図である。
【符号の説明】
１ケーシング
２羽根車
３モータ
４整流翼
６ボス部
１１羽根
１１ｐ羽根前縁部
１１ｔ羽根外周部
１１ｑ羽根後縁部
１１ｂ回転軸外周[0001]
[Industrial applications]
The present invention relates to an axial fan used for a hair dryer or the like, and more particularly to a reduction in noise of an axial fan.
[0002]
[Prior art]
Conventionally, in order to reduce the noise generated from the impeller in an axial fan, a technique has been adopted in which the blade of the impeller is advanced in the rotational direction as disclosed in Japanese Patent Publication No. 5-14118.
The reason why advancing the blades of the impeller in the rotational direction in these axial fans can reduce noise will be described in detail with reference to FIGS. Reference numeral 11 denotes an impeller blade, 11t denotes a blade outer peripheral portion, 11p denotes a blade front edge portion, 11q denotes a blade rear edge portion, and 6 denotes a boss portion as a rotating shaft for mounting the blade 11.
[0003]
Here, the generation mechanism of the blade tip vortex, which is a main cause of the noise of the axial fan, will be described. The flow 20 (arrows in FIGS. 8 and 9) in the axial fan is a wake behind the impeller when viewed from the axial direction. Because of the resistance of the portion, the blade 11 is not concentric with the rotation axis but directed to the outer peripheral direction. Therefore, the flow in the region A indicated by cross-hatching in FIGS. 8 and 9 leaks from the outer peripheral portion 11t of the blade, and the leaked flow becomes the wing tip vortex 21 and flows to the wake, which causes noise. Become.
[0004]
In FIG. 8, when the blade is not advanced, the flow in the area A becomes the tip vortex 21. However, it can be seen that the area A is reduced by advancing the blade 11 in the rotation direction as shown in FIG. In other words, it can be said that the generation of the blade tip vortex 21 is reduced by advancing the blade 11 in the rotation direction, thereby reducing noise.
[0005]
[Problems to be solved by the invention]
However, when the flow 20 is directed to the outer periphery in the vicinity of the rotation axis, a low flow rate region of a region B indicated by a dashed cross-hatching in FIGS. 8 and 9 is generated. 9, a turbulence 22 due to a flow rate difference exists between a region C shown by hatching and causes noise.
[0006]
When the trailing edge and the leading edge are advanced in the same manner, the area A decreases and the area B increases at the same time, and the generation of the tip vortex 21 decreases. Also has the disadvantage that the turbulence 22 due to the flow rate difference increases.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems. In addition to reducing the generation of blade tip vortices on the outer periphery of the fan, the low flow rate region near the rotation axis is reduced, and the flow disturbance due to the flow rate difference is suppressed. It is intended to provide a noise axial fan.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an axial flow fan having a structure comprising an impeller, a motor and a rectifying blade for holding the motor and rectifying the wind inside the cylindrical casing. When the impeller is viewed from the rotation axis direction, the center of the rotation axis is defined as the origin O, the intersection point of the leading edge, which is the end face in the rotation direction of the blade, and the outer periphery of the impeller is Pt, and the intersection between the rotation shaft outer periphery and the front edge is defined. The intersection point is Pb, the angle between the straight line O-Pt and the straight line O-Pb is θp, the intersection point between the trailing edge, which is the end face on the opposite side in the rotation direction of the blade, and the outer periphery of the impeller is Qt, and the rotation shaft outer periphery is When the intersection with the trailing edge is Qb, and the angle between the straight line O-Qt and the straight line O-Qb is θq, the value of θp is made larger than the value of θq, and the flow on the blade surface as viewed from the axial direction. Is moving not only in the rotational direction but also in the outer peripheral direction, Area that when the intersection of the flow and the leading edge Ps, an intersection between the trailing edge and the flow through the point Pb and the Qs, and (the area of the surface Ps-Pb-Qs-Qt) ( plane Pt-Ps -qt ) + (Area of plane Qs-Pb-Qb) is defined so as to maximize the ratio, and the outer diameter of the impeller is formed to be 100 mm or less. The angle is set from 15 degrees to 25 degrees .
[0009]
[Action]
Thus, it is possible to reduce the generation of blade tip vortices on the outer periphery of the fan and to reduce the low flow rate region near the rotation axis to suppress the flow disturbance due to the flow rate difference.
[0010]
【Example】
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
The axial flow fan shown in FIG. 3 has an impeller 2, a motor 3 for driving the impeller, and a rectifying blade 4 for fixing the motor 3 and rectifying the wind inside a cylindrical casing 1. In this structure, the rotation of the impeller 2 generates wind in the casing 1. As shown in FIG. 2, the impeller 2 includes a blade 11 and a boss 6 serving as a rotating shaft for fixing the blade.
[0011]
In FIG. 1 in which the impeller 2 is viewed from the rotation axis direction, the center of the rotation axis is the origin O, the intersection point between the front edge 11p, which is the end face of the blade 11 in the rotation direction, and the outer periphery 11t of the impeller is Pt, and the outer periphery 11b of the rotation shaft. The intersection between the straight line O-Pt and the straight line O-Pb is θp, and the rear edge 11q , which is the end surface on the opposite side in the rotation direction, and the impeller outer peripheral portion 11t. The intersection is Qt, the intersection between the boss outer periphery 11b and the trailing edge 11q is Qb, and the angle between the straight line O-Qt and the straight line O-Qb is θq.
[0012]
The flow 20 on the surface of the blade 11 is not a flow along the circumference as shown in FIG. At this time, if the intersection of the flow 20a passing through the point Qt and the leading edge 11p is Ps and the intersection of the flow 20b passing through the point Pb and the trailing edge 11q is Qs, the flow of the surface Pt-Ps-Qt is It flows out from the portion 11t and becomes a wing tip vortex 21 and flows downstream. The vortex causes noise.
[0013]
In the vicinity of the boss 6, the amount of wind flowing into the surface Pb-Qb-Qs is small, and the flow rate is different from that of the surface Ps-Pb-Qs-Qt, causing flow disturbance and generating noise. That is, it can be seen that if the area of the plane Ps-Pb-Qs-Qt is larger than the area of the plane Pt-Ps-Qt and the area of the plane Pb-Qb-Qs, it is effective for preventing noise generation. Generally, as a means for reducing the area of the surface Pt-Ps-Qt, a shape in which the entire blade 11 is advanced in the rotational direction is adopted. At this time, a comparison between FIG. 9 showing the advancing shape and FIG. 8 not advancing shows that the area of the surface Pt-Ps-Qt decreases when the blade 11 advances. However, on the contrary, the plane Pb-Qb-Qs increases with the forward movement, and therefore the noise reduction effect due to the decrease of the plane Pt-Ps-Qt is not maximized.
[0014]
Thus, in the present embodiment shown in FIG. 1, the ratio of the increase of the plane Pb-Qb-Qs to the plane Ps-Pb-Qs-Qt is reduced by making θq smaller than θp.
FIG. 7 shows a state where the blades 11 in the two cases are overlapped so that the difference between the planes Pb-Qb-Qs when θp = θq and θp> θq can be seen.
[0015]
However, when the point Qt is reduced based on the point Q, if θq is too small, there is a disadvantage that the area of the surface Ps-Pb-Qs-Qt, which is a surface on which work is effectively performed, is reduced. When θq is reduced with reference to the point Qb, the plane Ps-Pb-Qs-Qt increases, but there is a disadvantage that the plane Pt-Ps-Qt increases.
Therefore, θp and θq are determined so that the ratio of the area of (plane Ps-Pb-Qs-Qt) to the area of (plane Pt-Ps- Qt ) + (area of plane Pb-Qb-Qs) is maximized. Is the best.
[0016]
If the stream 20 is flowing as a clean arc vane 11 Menjo as in FIG. 1, the ratio of the area of the surface Ps Pb- Qs-Qt area of the surface Pt-Ps-Qt + surface Pb-Qb-Qs up Is in the range of 0.4θp <θq <0.6θp, and it is better to determine θp and θq in this range.
FIG. 4 is a graph in which the noise at the impeller outer diameter of 60 mm and the lighting efficiency point of the present embodiment is set with θp and θq as parameters.
[0017]
When θp = θq, it can be seen that the noise changes with the minimum value around 35 degrees. This is because up to around 35 degrees, the area of (plane Pt-Ps-Qt) is reduced, and the effect of reducing the generation of the wing tip vortex 21 is greater than the noise increase factor due to the turbulence 22 of the increase in the plane Pb-Qb-Qs. It is. Further, when the advance angles θp and θq are further increased, the ratio of (plane Pb−Qb−Qs) increases, and noise increases. FIG. 5 shows the noise when θp is fixed and only θq is reduced. When θp = 43 degrees, the noise becomes minimum when θq is around 20 degrees. If θq is changed while θp is 35 degrees, the change in noise is small because the plane Pb-Qb-Qs does not become so large.
[0018]
From the above results, in a small axial fan, the noise can be minimized when θp = 34 ° to 45 ° and θq = 15 ° to 25 °.
Next, an embodiment in which the present invention is applied to a hair dryer is shown based on FIG. The main housing 31 of the hair dryer has a cylindrical shape, and an opening at one end of the main housing 31 is a suction port 32, and an opening at the other end is a blowout port 33. In the main body housing 31, an impeller 2 and a motor 3 for driving the impeller 2 and a rectifying blade 4 for fixing the motor 3 and rectifying the wind are arranged. A heater 34 is installed downstream of the impeller 2, and has a function of making the wind warm. A handle 35 is integrally hung downward from the main body housing 31.
[0019]
In this embodiment, the outer diameter of the impeller 2 is set to 60 mm, and the gap between the main housing 31 and the outer peripheral portion of the impeller 2 is set to 1 mm or less.
When the dryer having the above structure is operated, the flow on the surface of the blade 11 of the impeller 2 is directed to the outer peripheral direction as shown in FIG. 1 because there is a resistor such as the heater 34 on the downstream side of the impeller. For this reason, the blade tip vortex 21 is generated from the outer periphery of the impeller, and noise near the boss 6 due to a large flow difference increases.
[0020]
Therefore, in this embodiment, when the impeller 2 is viewed from the suction side axial direction, as shown in FIG. 1, the blade 11 advances in the rotation direction, and the advance angles θp and θq are 43 degrees and 20 degrees, respectively. Is set to As a result, generation of the tip vortex 21 is reduced, and the turbulence 22 can be reduced by reducing the low flow rate region Pb-Qb-Qs near the boss.
[0021]
With the dryer having the above structure, a noise reduction effect of about 3 dB (A) is obtained as compared with the case where both θp and θq are 20 degrees, and a noise reduction effect of about 1.5 dB (A) as compared with the case where both θp and θq are 43 degrees.
[0022]
【The invention's effect】
The present invention relates to an axial flow fan having a structure including a cylindrical casing, an impeller and a rectifying blade for the purpose of holding the motor and rectifying the wind on the downstream side with respect to the motor, and the impeller viewed from the rotation axis direction. , The center of the rotation axis as the origin O, the intersection of the leading edge, which is the end face on the rotation direction side of the blade, with the outer periphery of the impeller, Pb, the intersection of the periphery of the rotation shaft and the leading edge with Pb, and a straight line O-Pt. The angle formed by the straight line O-Pb is θp, the intersection of the trailing edge, which is the end face opposite to the rotation direction of the blade, and the outer periphery of the impeller is Qt, the intersection of the rotation shaft outer periphery, and the trailing edge is Qb, When the angle between the straight line O-Qt and the straight line O-Qb is θq, the value of θp is set to be larger than the value of θq, and the flow on the blade surface viewed from the axial direction is directed not only in the rotational direction but also in the outer circumferential direction. The point of intersection between the flow passing through the point Qt and the leading edge is denoted by Ps and the point P When the intersection of the trailing edge and the flows Qs through, the (surface Ps-Pb-Qs-Qt area) and (the area of the surface Pt-Ps -qt) + (area of the surface Qs-Pb-Qb) Since θp and θq are defined so that the ratio is maximized , the outer diameter of the impeller is formed to be 100 mm or less, θp is set to 35 to 45 degrees, and θq is set to 15 to 25 degrees. In addition to reducing the occurrence of tip vortices on the outer periphery, the low flow rate region near the rotation axis can be reduced to suppress flow disturbance due to the flow rate difference.
[Brief description of the drawings]
FIG. 1 is an axial front view of an impeller of the present invention.
FIG. 2 is a perspective view of the same.
FIG. 3 is a sectional view showing an installation state of the above.
FIG. 4 is an explanatory diagram illustrating a noise change due to a change in the advance angle when the leading edge and the trailing edge have the same advance angle.
FIG. 5 is an explanatory diagram illustrating a change in noise due to the advance angle of the trailing edge when the advance angle of the leading edge is constant.
FIG. 6 is a sectional view of a second embodiment of the present invention.
FIG. 7 is an explanatory diagram illustrating a comparison between a case where the advancing angle of the trailing edge is the same as the advancing angle of the leading edge and a case where the advancing angle of the trailing edge is smaller than the advancing angle of the leading edge.
FIG. 8 is an explanatory view of a non-advancing impeller of a conventional example.
FIG. 9 is an explanatory view of an impeller in which the leading edge and the trailing edge of the conventional example are advanced by the same angle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Casing 2 Impeller 3 Motor 4 Straightening vane 6 Boss part 11 Blade 11p Blade front edge 11t Blade outer periphery 11q Blade rear edge 11b Rotation shaft outer periphery

Claims

Inside the cylindrical casing, an axial fan with a structure consisting of an impeller and a motor on the downstream side thereof and a rectifying blade for the purpose of holding the motor and rectifying the wind. Is the origin O, the intersection between the leading edge, which is the end face of the blade in the rotation direction, and the outer periphery of the impeller is Pt, the intersection between the outer periphery of the rotating shaft and the leading edge is Pb, and the straight line O-Pt and the straight line O-Pb Θt, the intersection between the trailing edge, which is the end face on the opposite side in the direction of rotation of the blade, and the outer periphery of the impeller is Qt, the intersection between the rotation shaft outer periphery, and the trailing edge is Qb, and a straight line O-Qt When the angle between the straight line O-Qb and θq is θq, the value of θp is made larger than the value of θq, and when the flow on the blade surface viewed from the axial direction is not only in the rotation direction but also in the outer peripheral direction, Further, the intersection point between the flow passing through the point Qt and the leading edge is Ps, and the flow passing through the point Pb is Maximum ratio when the intersection of the trailing edge was Qs, (surface Ps-Pb-Qs-Qt area) and (the area of the surface Pt-Ps -qt) + (area of the surface Qs-Pb-Qb) and An axis characterized by defining θp and θq so that the outer diameter of the impeller is set to 100 mm or less, and setting θp from 35 degrees to 45 degrees and θq from 15 degrees to 25 degrees. Flow fan.