201109532 六、發明說明： 【發明戶斤屬之技術領域】 發明領域 本發明係有關於一種將空氣吹出至離心方向之送風扇 及使用其之送風機。 I：先前技術3 發明背景 將空氣吹出至離心方向之送風扇、即所謂之離心風扇 係以曰本專利公開公報2007-170331號記載之離心風扇來 說明。第12圖係專利文獻1記載之習知離心風扇之立體圖。 第13圖係習知離心風扇之部份上面圖。此外，在第12圖及 第13圖，以箭號R顯示離心風扇之旋轉方向。 如第12圖所示，離心風扇包含有轂板21、與轂板21相 對而設之環狀覆板22、配設於轂板21與覆板22間之複數個 葉片23。轂板21之外形部21a為圓形，於中心具有孔21b。 於孔21b可固定馬達（圖中未示）之旋轉軸。覆板22之外形部 22a為圓形，於中央具有開口22b。葉片23之表面呈3維形 狀。又，葉片23配設成為内周側端部之前緣24比為外周側 端部之後緣25還靠近旋轉方向側。 離心風扇20可藉馬達之驅動而旋轉。藉離心風扇20之 旋轉，從覆板22之開口 22b吸入空氣。所吸入之空氣從葉片 23之前緣24往後緣25引導，而往離心風扇20之外側吹出。 第13圖之部份上面圖係從覆板2 2側觀看離心風扇2 0之 一部份。C係旋轉之中心。在此，以葉片23之後緣25之轂板 201109532 21側作為轂板側後緣25a，以葉片23之後緣25之覆板22側作 為覆板側後緣25b。葉片23呈轂板側後緣25a比覆板22側後 緣25b還靠近旋轉方向側之形狀。亦即，葉片23之後緣乃呈 相對於旋轉轴方向傾斜之形狀。離心風扇2〇將從覆板22之 開口22b所吸入之空氣做約略直角之流向改變，而吹出至外 側。在此，當葉片23不具如上述之3維形狀時，通過離心風 扇20之内部之空氣偏於轂板21之側。如上述，藉令葉片23 呈使穀板側後緣2 5 a比覆板側後緣2 5 b還靠近旋轉方向側之 形狀，所吸入之空氣在從前緣24往後緣25引導之期間，可 從轂板21側往覆板22側引導。藉此，可將為離心風扇2〇之 吹出部份之葉片23的後緣25之空氣風速分佈可均一化。 在此，以葉片23之前緣24之轂板21側為轂板側前緣 24a，以葉片23之前緣24之覆板22側為覆板侧前緣24b。如 第13圖所示’葉片23呈轂板側前緣之入口角/3 h大於覆板側 前緣24b之入口角召s的形狀。即，葉片23呈前緣24之入口 角呈從轂板21側朝覆板22側逐漸減少之形狀。此外，關於 葉片23之後緣25，誠如上述，呈出口角從轂板21側朝覆板 22側逐漸變化之形狀。 亦即，習知離心風扇20之葉片23呈入口角及出口角從 轂板21側朝覆板22側逐漸變化的3維形狀。又，葉片23呈厚 度逐漸變化之3維形狀。藉此，可將吹出之空氣之風速分佈 均一化’而可在不使離心風扇20之性能降低下，減低噪音。 然而，離心風扇2〇之葉片23通常以金屬板製作。由於 以金屬板所製作之葉片23為薄板，故不易呈如上述之3維形 201109532 狀。，特別是不以厚度逐漸變化之3_狀。為獲得此種3 維形狀，當將以金屬板構成之薄板2片合在一起，製作葉片 23時’不僅耗費成本，而錢離心風扇2G旋轉時之平衡差。 =者’不㈣金屬板製作，心娜製作時，雖可 主3維·^狀，但耗費製作成本。因而，為謀求因風速分佈均 :化所致之離心風扇20之性能維持及噪音減低，當使用3維 形狀之葉片23時，不易以低成本製作離心風扇2〇。 【發明内容】 發明概要 本發明可以低價提供達成了因將風速分佈均一化所致 之性能維持及噪音減低之送風扇。 本發明之送風扇包含有可固定馬達之旋轉軸之轂、與 轂相對而設之覆板、及配設於轂與覆板間之複數個葉片； 並於葉片之後緣與覆板間形成有間隙。藉使風流至此間 隙，可維持性能，並使在送風扇最外周之風速降低，而可 減低風切頻率噪音。又，藉此簡單之結構，可以低價製作 送風扇。 圖式間單說明 第1圖係本發明第1實施形態之送風扇之立體圖。 第2圖係第1實施形態之送風扇之上面圖。 第3圖係第1實施形態之送風扇之截面圖 第4圖係第1實施形態之另一送風扇之截面圖。 第5圖係第1實施形態之又另一送風扇之截面圖。 第6A圖係搭載有第1實施形態之送風扇之送風機的上 201109532 面圖。 第6B圖係第6A圖之6B-6B線之截面圖。 第7A圖係顯示第1實施形態之風扇殼體内部之覆板側 的空氣流動之說明圖。 第7B圖係顯示第1實施形態之風扇殼體内部之轂側的 空氣流動之說明圖。 第8圖係顯示不形成間隙之送風扇之噪音特性的說明 圖。 第9圖係顯示第2結構之送風扇之噪音特性的說明圖。 第10圖係顯示第1結構之送風扇之噪音特性的說明圖。 第11圖係顯示第3結構之送風扇之噪音特性的說明圖。 第12圖係習知離心風扇之立體圖。 第13圖係習知離心風扇之部份上面圖。 I：實施方式3 較佳實施例之詳細說明 (實施形態1) 第1圖係本發明第1實施形態之送風扇之立體圖。第2圖 係本實施形態之送風扇之上面圖。此外，第2圖係顯示卸除 送風扇之之狀態。第3圖係本實施形態之送風扇之截面圖。 第4圖係本實施形態之另一送風扇之截面圖。第5圖係本實 施形態之又另一送風扇之截面圖。此外，第3圖〜第5圖係顯 示安裝送風扇之覆板之狀態。又，第3圖〜第5圖係模式地顯 示葉片之配設狀態者，係包含送風扇之旋轉軸之截面圖。 第6A圖係搭載有本實施形態之送風扇之送風機的上面圖。 201109532 第圖係第6A圖之6B_6B線之截面圖。 首先’就第6A圖及第6B圖所示之送風機作說明。送風 機5〇係於以蜗牛形狀風扇殼體5形成之空氣流路之内部具 有适風扇1及用以使送風扇1旋轉之馬達6。當送風扇1以馬 達6之驅動旋轉時，空氣從殼體5之吸入口 8吸入，而從吹出 口 9吹出。此種送風機5〇藉搭載於衣類洗衣烘衣機或衣類烘 衣機（皆未以圖顯示）之空氣循環路徑，吹出空氣，而使含有 水分之衣類乾燥。此外’亦可依需要，於空氣循環路徑裝 入加熱裝置或除濕裝置。 如第1圖及第2圖所示，送風扇1包含有轂4、與轂4相對 而設之覆板2、配設於轂4與覆板2間之複數個葉片3。轂4呈 中央附近於覆板2侧隆起成吊鐘狀之約略圓盤之形狀。覆板 2呈具有開口之圓環形狀。 又，毂4於中央具有孔4a。如第6B圖所示，轂4利用孔 4a及螺絲7,固定於馬達6之旋轉軸6a。當使馬達6逆時鐘旋 轉時，穀4、覆板2及葉片3形成一體，而逆時鐘旋轉。藉此， 可從殼體5之吸入口 8將空氣吸入至覆板2之開口。所吸入之 空氣隨著葉片3之旋轉’朝為葉片3端部之後緣3a以放射狀 吹出。以放射狀吹出之空氣從吹出口 9吹出。 在此，如第3圖所示’葉片3於後緣3a之覆板2側具有切 D部30。藉葉片3具有切口部30，而於葉片3與覆板2間形成 間隙11a。以下，將此結構記載為第1結構。當使送風扇1旋 轉時，空氟流入至間隙11a。藉此，在風扇殼體5 ’可使為 風速最快之部份之舌狀體1 〇 (參照第6 A圖）附近之風速減 201109532 少。古狀體1G賴扇殼體5與送_1之_最窄之部份 結果，可使風扇殼體5之風速分佈均一化 _使於以金屬板製作葉 片3時，亦可輕易且以低價形成。又，因間隙Ua，風扇殼 體5之最大風速減少，風切頻率„桑音減低。此外，形成間隙 lla之=片3之旋翼性能低之處。因此，即使形成間隙 Ua’送風機1之送風性能亦幾乎不降低。因而，可维持送 風機50之性能’且可減低送風弟〇之噪音。此外，即使以 樹脂製作葉片3時，藉形成因切口部30而形成 可不需下部切割形狀。亦即’可以低成本製作送風扇卜 在此，就用以於葉片3與覆板2間形成間隙之另— (以Γ記載為第2結構)作說明。如第4圖所示，藉將緣部2a 構:成將覆板2n緣形成為相對於覆板2之傾斜面2b擴 展空氣之出口的方向，而可形成間隙lib。藉此，由於空氣 流入至葉片3與覆板2間之間隙11b，故可具有與形成切口部 3〇之間隙11a時同樣之作用及效果。 就用以於葉片3與覆板2間形成間隙之又另一結構（以 下。己載為第3結構)作說明。如第$圖所示，葉片3在後緣心 於覆板2側具有切口部30，並且於覆板2之外周.緣，緣部2a 構w成形成為相對於覆板2之傾斜面扑擴展空氣之出口的 方向，而形成間隙lle。亦即，為同時具有第丨結構及第2結 構之結構。為此結構時，具有大於第1結構及第2結構之作 用及政果。特別是對噪音之減低具有相當大之效果。關於 此點後述。 201109532 在此，就如上述所構成之送風扇1及使用其之送風機50 之動作作說明。從覆板2之開口流入之空氣於流入設有複數 司 之葉片3間之際，將流動方向做約略直角之改變。在覆板 2與轂4間’在轂4附近流動之空氣改變了流動方向之際的曲 率 、。因此，空氣以約略曲緣狀順暢地流動，風速之減少 ^ ’泉路損失亦較小。如此，由於空氣順暢地流動，故葉 片3之空氣之剝離現象不易產生。 相對於此’在覆板2與轂4間，在覆板2附近流動之空氣 是机動方向之際之曲率大。因此，空氣急遽彎曲’風速 之減》大，流路損失亦大。藉此，空氣之流動紊亂’在葉 。之上部’產生空氣之剝離現象及將空氣以旋渦狀捲入之 區域。結果，易產生噪音。 就此噪音之原因加以說明。當風速之減少大時，向外 風速向篁減小，空氣可往送風扇1之旋轉方向拖矣。因 氣不致被吹出至送風扇1外。由於在送風扇1之外周 ,A速口葉片3之位置而脈動，故此脈動使壓力波產生，而 形成風切頻率噪音。 本實私形態之送風扇1在葉片3，覆板2近處之空氣向外 y風迷向里小。利用此，本實施形態之送風扇1於葉片3之 v緣33與设板2間形成間隙，藉使空氣流至此間隙，可縮小 在送風扇最外周之空氣之風速。 本貫〜形態之間隙lla、nb、Uc之尺寸相對於葉片3 :翼弦方向（第3圖之上下方向）為10%以下，相對於推力方 。（第3圖之左右方向）為50%以下。間隙11a、llb、llc之尺 201109532 寸在翼弦方向及推力方向皆大於此以上時，對風切頻率噪 音有效果，但有作為送風扇1之性能降低之虞。在此狀態， 為維持送風扇1之性能，需增加送風扇之轉速，此時，送風 扇1之效率降低。 第7A圖係顯示本實施形態之風扇殼體5内部之覆板2側 之空氣流動的說明圖。第7B圖係顯示本貫施形態之風扇殼 體5内部之覆板2側之空氣流動的說明圖。此外，第7A圖及 第7B圖所示之送風扇1係第3結構，間隙11c之尺寸相對於翼 弦方向為5%，相對於推力方向為25%。又，送風扇1之直徑 係155mm，轉速係5800rpm。此時，送風扇1之最外周之周 速度約47m/s。 誠如前述，在送風扇1之内部，在外周方向之空氣之風 速向量係覆板2側小於轂4側。因此，在覆板2側，空氣如箭 號A所示，往圓周方向流動。當往此圓周方向之流動成份大 時，產生風切頻率噪音。 在此’不形成間隙11c時之最大風速係47m/s，本實施 形態之送風扇1之最大風速係44m/s。由於壓力脈動音之立 壓與流速之6〜8次方成比例，故最大風速從47〇1/§減少至 44m/s時，對噪音抑制非常具有效果。 另一方面，使用第8圖〜第11圖，就本實施形態之送風 扇1之嗓音特性作說明。第9圖係顯示第2結構之送風扇1之 噪音特性的說明圖。第關係顯示第！結構之送風以之噪 音特性的說明圖。第U圖係顯示第3結構之送風扇丄之噪: 特性的說明圖。此外，第8圖係顯示用以比較之不形成間二 10 201109532 之送風扇的噪音特性之說明圖。此外，不論哪個風扇葉 片數皆為28片，轉速皆為54〇〇rpm。因此，於葉片數28片與 轉速5400rPm之積進一步除以60之2520Hz存在風切頻率。 第8圖、亦即切口部3〇、間隙na、lib、lic、緣部 皆不具有之送風扇中，在風切頻率2520Hz之噪音如圓形記 號所示為28dB。另一方面’在第9圖、亦即為第2結構，於 覆板2構成緣部2a，而形成有間隙lib之送風扇1中，在風切 頻率2520Hz之噪音如圓形記號所示，為26dB。因而 ，Ocy> 減低2dB。在第1 〇圖、亦即為第1結構，構成葉片切口部3〇， 而1成有間隙11a之送風扇1中，在風頻率2520Hz之噪音如 圓形記號所示，為23dB。因而，噪音減低5(jb。在第η圖、 亦即為第3結構，構成葉片切口部30及緣部2a，而形成有間 隙lie之送風扇1中，在風切頻率252〇Hz之噪音如圓形記號 所示，為20dB。因而，噪音減低8dB。如以上，藉於葉片3 之後緣3a與覆板2間設間隙（間隙iia、Ub、Uc任一個），可 減低°喿音。 【圖式簡單說明3 第1圖係本發明第1實施形態之送風扇之立體圖。 第2圖係第1實施形態之送風扇之上面圖。 第3圖係第1實施形態之送風扇之截面圖 第4圖係第1實施形態之另一送風扇之截面圖。 第5圖係第1實施形態之又另一送風扇之截面圖。 第6A圖係搭載有第1實施形態之送風扇之送風機的上 面圖。 201109532 第6B圖係第6A圖之6B-6B線之截面圖。 第7A圖係顯示第1實施形態之風扇殼體内部之覆板側 的空氣流動之說明圖。 第7B圖係顯示第1實施形態之風扇殼體内部之轂側的 空氣流動之說明圖。 第8圖係顯示不形成間隙之送風扇之噪音特性的說明 圖。 第9圖係顯示第2結構之送風扇之嗓音特性的說明圖。 第10圖係顯示第1結構之送風扇之噪音特性的說明圖。 第11圖係顯示第3結構之送風扇之噪音特性的說明圖。 第12圖係習知離心風扇之立體圖。 第13圖係習知離心風扇之部份上面圖。 【主要元件符號說明】 1...送風扇 8."吸入口 2，22...覆板 9...吹出口 2a...緣部 10...舌狀體 2b...傾斜面 11a，lib，lie...間隙 3，23…葉片 20...離心風扇 3a，25...後緣 21...穀板 4…轂 21a...外形部 4a，21b··.孑L 22a...外形部 5...風扇殼體 22b...開口 6...馬達 24...前緣 7...螺絲 24a··.轂板側前緣 12 201109532 24b. ·.覆板側前緣 30.··切口部 25a...轂板侧後緣 50...送風機 25b…覆板側後緣 R...旋轉方向 5. 13201109532 VI. Description of the Invention: [Technical Field of Invention] Field of the Invention The present invention relates to a blower fan that blows air to a centrifugal direction and a blower using the same. I. Prior Art 3 Background of the Invention A blower fan that blows air to a centrifugal direction, that is, a so-called centrifugal fan is described by a centrifugal fan described in Japanese Laid-Open Patent Publication No. 2007-170331. Fig. 12 is a perspective view of a conventional centrifugal fan described in Patent Document 1. Figure 13 is a partial view of a portion of a conventional centrifugal fan. Further, in Fig. 12 and Fig. 13, the direction of rotation of the centrifugal fan is indicated by an arrow R. As shown in Fig. 12, the centrifugal fan includes a hub plate 21, an annular sheathing plate 22 provided opposite to the hub plate 21, and a plurality of blades 23 disposed between the hub plate 21 and the sheathing plate 22. The outer shape portion 21a of the hub plate 21 has a circular shape and has a hole 21b at the center. The rotating shaft of the motor (not shown) can be fixed to the hole 21b. The outer portion 22a of the sheathing plate 22 has a circular shape and has an opening 22b at the center. The surface of the blade 23 has a three-dimensional shape. Further, the blade 23 is disposed such that the front edge 24 of the inner circumferential side end portion is closer to the rotation direction side than the rear edge 25 of the outer circumferential side end portion. The centrifugal fan 20 can be rotated by the driving of the motor. The air is taken in from the opening 22b of the cover panel 22 by the rotation of the centrifugal fan 20. The sucked air is guided from the leading edge 24 of the blade 23 to the trailing edge 25, and is blown toward the outside of the centrifugal fan 20. Part of the above figure is a portion of the centrifugal fan 20 viewed from the side of the cover 2 2 . The center of the C system rotation. Here, the hub plate 201109532 21 side of the trailing edge 25 of the blade 23 serves as the hub side trailing edge 25a, and the side of the covering panel 22 of the trailing edge 25 of the blade 23 serves as the sheathing side trailing edge 25b. The blade 23 has a shape in which the hub-side rear edge 25a is closer to the rotational direction side than the sheath 22 side trailing edge 25b. That is, the trailing edge of the blade 23 is in a shape inclined with respect to the direction of the rotation axis. The centrifugal fan 2 改变 changes the flow of the air taken in from the opening 22b of the sheathing plate 22 at a substantially right angle, and blows it to the outside. Here, when the blade 23 does not have the three-dimensional shape as described above, the air passing through the inside of the centrifugal fan 20 is biased to the side of the hub plate 21. As described above, the blade 23 is configured such that the valley-side trailing edge 2 5 a is closer to the rotational direction side than the sheath-side trailing edge 2 5 b, and the sucked air is guided from the leading edge 24 to the trailing edge 25 during the period. It can be guided from the side of the hub plate 21 to the side of the cover panel 22. Thereby, the air velocity distribution of the trailing edge 25 of the blade 23 which is the blow-out portion of the centrifugal fan 2 can be made uniform. Here, the hub plate 21 side of the leading edge 24 of the blade 23 is the hub side leading edge 24a, and the side of the covering plate 22 of the leading edge 24 of the blade 23 is the covering side leading edge 24b. As shown in Fig. 13, the blade 23 has an entry angle of the front side of the hub plate / 3 h which is larger than the shape of the entrance angle of the front side edge 24b of the cover plate side. That is, the blade 23 has a shape in which the entrance angle of the leading edge 24 gradually decreases from the side of the hub plate 21 toward the side of the sheathing plate 22. Further, as for the trailing edge 25 of the blade 23, as described above, the outlet angle gradually changes from the side of the hub plate 21 toward the side of the cover panel 22. That is, the blade 23 of the conventional centrifugal fan 20 has a three-dimensional shape in which the inlet angle and the outlet angle gradually change from the side of the hub plate 21 toward the side of the sheathing plate 22. Further, the blade 23 has a three-dimensional shape in which the thickness gradually changes. Thereby, the wind speed distribution of the blown air can be made uniform, and the noise can be reduced without deteriorating the performance of the centrifugal fan 20. However, the blades 23 of the centrifugal fan 2 are usually made of a metal plate. Since the blade 23 made of a metal plate is a thin plate, it is difficult to form the three-dimensional shape of the above-mentioned three-dimensional shape 201109532. In particular, it does not change in thickness as a 3_ shape. In order to obtain such a three-dimensional shape, when two sheets of a thin plate made of a metal plate are joined together, it is not only costly to manufacture the blade 23, but the balance of the centrifugal fan 2G is poor when it is rotated. = "No" (four) metal plate production, although the heart can be produced in the main 3D · ^ shape, but the production costs. Therefore, in order to maintain the performance and noise of the centrifugal fan 20 due to the wind speed distribution, when the three-dimensional blade 23 is used, it is difficult to manufacture the centrifugal fan 2 at a low cost. SUMMARY OF THE INVENTION The present invention can provide a blower fan that achieves performance maintenance and noise reduction due to uniformity of wind speed distribution at low cost. The blower fan of the present invention comprises a hub for fixing a rotating shaft of the motor, a cover plate disposed opposite the hub, and a plurality of blades disposed between the hub and the cover plate; and a blade is formed between the trailing edge of the blade and the cover plate gap. By allowing the wind to flow to this gap, the performance can be maintained and the wind speed at the outermost circumference of the fan can be reduced, and the wind cutting frequency noise can be reduced. Moreover, with this simple structure, the fan can be produced at a low price. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a blower fan according to a first embodiment of the present invention. Fig. 2 is a top view of the blower fan of the first embodiment. Fig. 3 is a cross-sectional view showing a fan of the first embodiment. Fig. 4 is a cross-sectional view showing another fan of the first embodiment. Fig. 5 is a cross-sectional view showing still another fan of the first embodiment. Fig. 6A is a plan view showing the upper 201109532 of the air blower equipped with the blower fan of the first embodiment. Fig. 6B is a cross-sectional view taken along line 6B-6B of Fig. 6A. Fig. 7A is an explanatory view showing the flow of air on the side of the cover plate inside the fan casing of the first embodiment. Fig. 7B is an explanatory view showing the flow of air on the hub side inside the fan casing of the first embodiment. Fig. 8 is an explanatory view showing the noise characteristics of the blower fan which does not form a gap. Fig. 9 is an explanatory view showing the noise characteristics of the blower fan of the second structure. Fig. 10 is an explanatory view showing the noise characteristics of the blower fan of the first structure. Fig. 11 is an explanatory view showing the noise characteristics of the blower fan of the third structure. Figure 12 is a perspective view of a conventional centrifugal fan. Figure 13 is a partial view of a portion of a conventional centrifugal fan. I. EMBODIMENT 3 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a perspective view of a blower fan according to a first embodiment of the present invention. Fig. 2 is a top view of the blower fan of the embodiment. In addition, Fig. 2 shows the state in which the fan is removed. Fig. 3 is a cross-sectional view showing the blower fan of the embodiment. Fig. 4 is a cross-sectional view showing another fan of the embodiment. Fig. 5 is a cross-sectional view showing still another fan of the present embodiment. Further, Fig. 3 to Fig. 5 show the state in which the cover plate of the blower fan is mounted. Further, in the third to fifth drawings, the arrangement state of the blades is schematically shown, and the cross-sectional view of the rotating shaft of the blower fan is included. Fig. 6A is a top view of a blower in which the blower fan of the embodiment is mounted. 201109532 The figure is a cross-sectional view of line 6B_6B of Figure 6A. First, the air blower shown in Figs. 6A and 6B will be described. The blower 5 is provided with a fan 1 and a motor 6 for rotating the blower fan 1 in an air flow path formed by the snail-shaped fan case 5. When the blower fan 1 is rotated by the drive of the motor 6, air is sucked from the suction port 8 of the casing 5 and blown out from the blow port 9. The blower 5 is blown out of the air by an air circulation path mounted on a clothes dryer or a clothes dryer (all not shown) to dry the clothes containing moisture. Further, a heating device or a dehumidifying device may be incorporated in the air circulation path as needed. As shown in Figs. 1 and 2, the blower fan 1 includes a hub 4, a cover plate 2 opposed to the hub 4, and a plurality of blades 3 disposed between the hub 4 and the cover plate 2. The hub 4 has a shape of a substantially circular disk that is bulged in a bell shape on the side of the cover panel 2 near the center. The cover panel 2 has a circular ring shape with an opening. Further, the hub 4 has a hole 4a at the center. As shown in Fig. 6B, the hub 4 is fixed to the rotating shaft 6a of the motor 6 by the hole 4a and the screw 7. When the motor 6 is rotated counterclockwise, the valley 4, the sheathing plate 2 and the vanes 3 are integrally formed and rotated counterclockwise. Thereby, air can be drawn into the opening of the cover panel 2 from the suction port 8 of the casing 5. The sucked air is radially blown toward the trailing edge 3a of the end of the blade 3 as the blade 3 rotates. The air blown out in a radial direction is blown out from the air outlet 9. Here, as shown in Fig. 3, the blade 3 has a cut D portion 30 on the side of the cover 2 of the trailing edge 3a. The blade 3 has a cutout portion 30, and a gap 11a is formed between the blade 3 and the cover panel 2. Hereinafter, this structure is described as the first structure. When the blower fan 1 is rotated, the empty fluorine flows into the gap 11a. Thereby, in the fan casing 5', the wind speed in the vicinity of the tongue 1 〇 (see Fig. 6A) which is the fastest wind speed is reduced by 201109532. As a result of the narrowest part of the 1G sash shell 5 and the squirrel, the wind speed distribution of the fan casing 5 can be uniformized _ so that when the blade 3 is made of a metal plate, it can be easily and lowly The price is formed. Further, due to the gap Ua, the maximum wind speed of the fan casing 5 is reduced, and the wind cut frequency „Sanyin is reduced. Further, the gap 11a is formed to have a low rotor performance. Therefore, even if the gap Ua' is blown by the blower 1 The performance is also hardly reduced. Therefore, the performance of the blower 50 can be maintained, and the noise of the air blower can be reduced. Further, even when the blade 3 is made of resin, the formation of the notch portion 30 can be formed without the need for a lower cut shape. 'The fan can be produced at a low cost. Here, the gap between the blade 3 and the cover plate 2 is used to describe the gap between the blade 3 and the cover plate 2. (As shown in Fig. 4, the edge is shown in Fig. 4. 2a structure: forming the cover 2n edge as a direction of expanding the outlet of the air with respect to the inclined surface 2b of the cover 2, and forming a gap lib. Thereby, air flows into the gap 11b between the blade 3 and the cover 2 Therefore, it is possible to have the same action and effect as when the gap 11a of the notch portion 3 is formed. Another structure for forming a gap between the blade 3 and the cover plate 2 (hereinafter, the third structure is described) As shown in Figure $, the blade 3 is at the trailing edge The side of the cover panel 2 has a cutout portion 30, and the outer edge of the cover panel 2 is formed so that the edge portion 2a is formed in a direction to expand the air outlet with respect to the inclined surface of the cover panel 2, thereby forming a gap lle. In order to have both the structure of the second structure and the structure of the second structure, the structure has a larger effect than that of the first structure and the second structure, and particularly has a considerable effect on the reduction of noise. This point will be described later. 201109532 Here, the operation of the blower fan 1 configured as described above and the blower 50 using the same will be described. When the air flowing in from the opening of the cover panel 2 flows between the blades 3 provided with the plurality of divisions, the flow direction is made. A change in the right angle. The air flowing between the sheathing plate 2 and the hub 4 near the hub 4 changes the curvature at the time of the flow direction. Therefore, the air flows smoothly in a roughly curved shape, and the wind speed is reduced. The loss is also small. Thus, since the air flows smoothly, the air stripping phenomenon of the blade 3 is less likely to occur. In contrast, between the sheathing plate 2 and the hub 4, the air flowing in the vicinity of the sheathing plate 2 is a maneuvering direction. Large curvature Therefore, the air is sharply bent and the 'wind speed reduction' is large, and the flow path loss is also large. Thereby, the flow of the air is disturbed 'in the upper part of the leaf', the air peeling phenomenon and the area in which the air is vortexed are generated. As a result, It is easy to generate noise. Explain the reason for this noise. When the wind speed is reduced, the outward wind speed decreases toward the 篁, and the air can be dragged to the direction of rotation of the fan 1. Since the air is not blown out to the fan 1 In the outer periphery of the blower fan 1, the position of the A-speed blade 3 is pulsating, so that the pulsation generates a pressure wave and forms a wind-cut frequency noise. The fan 1 of the present embodiment is in the blade 3, and the air near the cover 2 In this way, the fan 1 of the present embodiment forms a gap between the v-edge 33 of the blade 3 and the plate 2, and the air flows to the gap to reduce the air on the outermost circumference of the fan. The wind speed. The size of the gaps lla, nb, and Uc of the present embodiment is 10% or less with respect to the blade 3: chord direction (upward and downward direction of Fig. 3) with respect to the thrust. (the left and right direction of Fig. 3) is 50% or less. The gaps of the gaps 11a, 11b, and 1111,095,32 inches in the chord direction and the thrust direction are both greater than this, which has an effect on the wind cut frequency noise, but has a performance as a performance of the blower fan 1. In this state, in order to maintain the performance of the blower fan 1, it is necessary to increase the rotational speed of the blower fan, and at this time, the efficiency of the blower fan 1 is lowered. Fig. 7A is an explanatory view showing the flow of air on the side of the cover plate 2 inside the fan casing 5 of the embodiment. Fig. 7B is an explanatory view showing the flow of air on the side of the cover panel 2 inside the fan casing 5 of the present embodiment. Further, the fan 1 shown in Figs. 7A and 7B is a third structure, and the size of the gap 11c is 5% with respect to the chord direction and 25% with respect to the thrust direction. Further, the fan 1 has a diameter of 155 mm and a rotational speed of 5,800 rpm. At this time, the peripheral speed of the outermost circumference of the blower fan 1 is about 47 m/s. As described above, in the inside of the blower fan 1, the air velocity vector in the outer circumferential direction is smaller than the hub 4 side. Therefore, on the side of the cover panel 2, air flows in the circumferential direction as indicated by the arrow A. When the flow component to the circumferential direction is large, the wind cut frequency noise is generated. Here, the maximum wind speed when the gap 11c is not formed is 47 m/s, and the maximum wind speed of the blower fan 1 of the present embodiment is 44 m/s. Since the vertical pressure of the pressure pulsation sound is proportional to the flow rate of 6 to 8 power, the maximum wind speed is reduced from 47〇1/§ to 44m/s, which is very effective for noise suppression. On the other hand, the sound characteristics of the air blowing fan 1 of the present embodiment will be described using Figs. 8 to 11 . Fig. 9 is an explanatory view showing the noise characteristics of the blower fan 1 of the second configuration. The first relationship shows the first! An illustration of the noise characteristics of the structure's air supply. Fig. U is a diagram showing the noise of the fan of the third structure: characteristics. In addition, Fig. 8 is an explanatory view showing the noise characteristics of the blower fan which is not formed to form the second 10 201109532. In addition, no matter which fan blade number is 28 pieces, the rotation speed is 54 rpm. Therefore, the product of the number of blades 28 and the number of revolutions of 5400 rPm is further divided by the 2520 Hz of 60. In Fig. 8, that is, the gap portion 3A, the gaps na, lib, lic, and the edge portion are not provided in the fan, the noise at the wind cut frequency of 2520 Hz is 28 dB as indicated by a circular mark. On the other hand, in the ninth diagram, that is, the second structure, the cover plate 2 constitutes the edge portion 2a, and in the fan 1 in which the gap lib is formed, the noise at the wind cut frequency of 2520 Hz is indicated by a circular mark. It is 26dB. Thus, Ocy> is reduced by 2dB. In the first plan, that is, the first structure, the blade notch portion 3A is formed, and in the fan 1 having the gap 11a, the noise at a wind frequency of 2520 Hz is 23 dB as indicated by a circular mark. Therefore, the noise is reduced by 5 (jb. In the ηth diagram, that is, the third structure, the blade notch portion 30 and the edge portion 2a are formed, and the noise of the wind cut frequency of 252 Hz is formed in the fan 1 in which the gap lie is formed. As indicated by the circular mark, it is 20 dB. Therefore, the noise is reduced by 8 dB. As described above, by providing a gap (any of the gaps iia, Ub, Uc) between the trailing edge 3a of the blade 3 and the cover 2, the click sound can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a blower fan according to a first embodiment of the present invention. Fig. 2 is a top view of a blower fan according to a first embodiment. Fig. 3 is a cross section of a blower fan according to a first embodiment. Fig. 4 is a cross-sectional view showing another fan of the first embodiment. Fig. 5 is a cross-sectional view showing still another fan of the first embodiment. Fig. 6A is a view showing a fan of the first embodiment. Fig. 7A is a cross-sectional view taken along line 6B-6B of Fig. 6A. Fig. 7A is an explanatory view showing the flow of air on the side of the cover plate inside the fan casing of the first embodiment. An explanatory view showing the flow of air on the hub side inside the fan casing of the first embodiment. Fig. 9 is an explanatory view showing the noise characteristics of the fan of the second structure. Fig. 10 is an explanatory view showing the noise characteristics of the fan of the first structure. Fig. 11 is an explanatory view showing the noise characteristics of the fan of the third structure. Fig. 12 is a perspective view of a conventional centrifugal fan. Fig. 13 is a partial view of a part of a conventional centrifugal fan. 1...send fan 8."suction port 2,22...sand plate 9...air outlet 2a...edge 10...tonary body 2b...inclined surface 11a,lib,lie ... gap 3, 23...blade 20...centrifugal fan 3a,25...rear edge 21...valley 4...hub 21a...outer part 4a,21b··.孑L 22a... Outline portion 5... Fan housing 22b... Opening 6... Motor 24... Leading edge 7... Screw 24a··. Hub plate side leading edge 12 201109532 24b. ·. 30.·cut portion 25a... hub plate side trailing edge 50... blower 25b... cover plate side trailing edge R... rotation direction 5.13