200826817 九、發明說明： 【發明所屬之技術領域】 本發明係涉及一種離心風扇，尤係涉及一種對發熱電 子兀件散熱之離心風扇，本發明還涉及一種具有該離心風 扇之散熱裝置及使用該散熱裝置之電子裝置。 【先前技術】 隨著中央處理器（CPU)等電子元件功率之不斷提高， 散熱問題越來越受到人們之重視，在筆記型電腦中更是如 為在有限之空間内高效地帶走系統所產生之熱量，目 前業界主要採用由散熱鰭片組、熱管及離心風扇組合之方 式2行散熱。财紅熱料路徑為：CPU魅之熱量經 熱管傳至散熱則組，再由離心風紐生之氣流將傳至散 :片狀熱里▼走’所_傾扇對纽之散熱性能有 非常大之影響。 2在纽之㈣岐好地提高散_置之散熱性能， /』要針對散熱裝置之離颂扇之葉片參數 Γ故Γ聯峨繼料，顧到合理之組 風扇各變數如何設計亦就顯得尤為重要。 風扇進仃優化設計之難度較高。 X大度地提升t造縣’導致優化設計之轉效益低ζ要 數，而扇之風量係一個报重要之參 2!中風夏之風壓與噪音又係-對矛盾關係，故對 6 200826817 【發明内容】 有鑒於此，有必要提供一種在不增加成本之基礎上即 可增大空氣流量之離心風扇，同時亦有必要提供一種提升 政熱性能之散熱裝置及使用該散熱裝置之電子裝置。 種離心風扇，包括一頂板、一底板、一轉子及設於 頂板與底板之間之一側壁，該侧壁上設有至少一 該頂板上設有-第-進風Π，該底板上設有—第二進風 口，該頂板、底板及側壁合圍形成一容置空間，該轉子設 于該容置空間内，其中該底板在對應轉子之範圍内朝向轉 子所在方向形成一凹陷。 -種散熱裝置，包括—離心風扇及設於雜心風扇之 出風口之至少-鰭片組，其中該離心風扇包括—頂板、一 底板冑子及设於頂板與底板之間之—彳賴，該側壁上 ^至乂 #出風口’該頂板上設有一第一進風口，該底板 上設有-第二進風口，該頂板、底板及側壁合圍形成一容 置空間，該轉子設于該容置空_，該底板树應轉子之 範圍内朝向轉子所在方向形成一凹陷。 種電子裳置’包括—機殼及設於該機殼内之-散軌 裝置，該機殼包括-上蓋及與該上蓋相對之—下蓋，該散 …裝置包括離心風扇及設於該離心風扇之出風口處之至 /.、、、曰片組轉心風扇具有—頂板、與該頂板相對之一 與额之U子，娜㈣扇之頂板 又 $ 口，該離心風扇之底板上設有第二進風 口 ’其中該離心風扇之頂板距該機殼之上蓋之距離大於該 200826817 離心風扇之底板距該機殼之下蓋之距離，該離心風扇之底 板在對應轉子之範圍内朝向轉子所在方向形成一凹陷。- 與習知技術相比，上述離心風扇之底板在對應轉子之 範圍内朝向轉子所在方向形成一凹陷，當該離心風扇組覆 到電子裝置之機殼中時，使得底板之凹陷區域與機殼之^ 蓋之間的距離增加，有利於更多空氣藉由第二進風口進入 離心風扇内，使離心風扇之總流量增加，從而提升散熱性 能。 【實施方式】 為適應可攜式電子裝置如筆記型電腦等朝向輕薄、短 小發展之品求，以及為實現快速散熱之目的，目前對其内 部發熱電子元件所使狀散絲置大多數制配置離心風 扇之主動式散熱設計。 圖5所示為一種可攜式電子裝置5如筆記型電腦等， 該電子裝置5包括一機殼60及設於該機殼6〇内一散熱裝 置50，該散熱裝置5〇用於對電子裝置5内部之發熱電子 凡件（圖未不）如筆記型電腦之中央處理器等進行散熱。 該機殼60包括一上蓋61及一下蓋62。該散熱裝置5〇設 于該上蓋61與下蓋62之間，其包括一離心風扇Μ及一鰭 片、、且52該鰭片組52设於離心風扇51之出風口 511處並 與發熱電子元件熱連接以吸收發熱電子元件所產生之熱 里。該離心風扇51包括一底座512、設於該底座M2上之 一蓋板513及一轉子514,該轉子514設於該底座512内， 其運轉時產生之氣流吹向韓片紕52以將其吸收之熱量散 8 200826817 發。該蓋板513與底座512上分別設有相對之一上進風口 515及一下進風口 516以供外界氣流進入離心風扇51内。 該上、下進風口 515、516均為圓弧形且該上、下進風口 515、516之半徑相等。 當散熱裝置50組裝到電子裝置5之機殼60内時，由 於機殼60之厚度有限，故使得離心風扇51之上進風口 515 與機殼60之上蓋61之間之上間距hl及離心風扇51之下 進風口 516與機殼60之下蓋62之間之下間距腔均較小， 並且通常上間距hi會大於下間距h2。發明人利用cfd (Computational Fluid Dynamics，計算流體力學)軟體對上述 散熱裝置5G置於電子裝置5中之工作情形進行不斷試驗及 流場模擬分析發現’從上進風口 515進入離心風扇&之風 量要遠大於從下進風口 516進入離心風扇51之風量。如在 上間距hi為3.6mm，下間距h2為25mm時，計瞀得出上 進風口之流量為2.59efm，獨風口之流量為132伽，離 心風扇之總流量為3.91efm。發明人研究發現離心風扇& 之進^ 口設計及進風口距電子裝置5之機殼6〇之距離對離 ^ 係。故，發日狀積極對此 以試圖在不需增加生產成本的基礎上 :=行優化設計，來達到良好之散熱效果，乃有 體八其中，實施例之立 體刀解圖，該散熱裝置1G包括—離心風扇12、 片組14a及—第二鰭片組14b。 乂政熟裝置10適合於對筆 9 200826817 記型電腦等可攜式電子裝置中之發熱元件進行散^。 該離心風扇12包括一頂板121、與頂板121相對之 底板122、一轉子124及設於該頂板121與底板122之門 之一渦形之側壁123。其中該側壁123與底板122可藉由 壓鑄或注塑之方式一體製成。可以理解地，該側壁123亦 可與頂板121藉由壓鑄或注塑之方式一體製成。該離心風 扇12之頂板121、底板122及侧壁123合圍形成一容置空 間，該轉子124設于該容置空間内。該轉子124包括_輪 轂125及自輪轂125週邊向外呈輻射狀延伸之複數葉片 126。該頂板121對應轉子124設有一圓形之第一進風口 127，以便外界空氣進入離心風扇12之容置空間内。該側 壁123與底板122相互垂直，該側壁123上開設有第一出 風口 132a及第二出風口 132b，該第一、第二出風口 132a、 132b均呈直線形且兩者相互垂直’如此設置可使離心風扇 12所產生之氣〉瓜從兩相互垂直之方向排出。該第一、第二 出風口 132a、132b處對應設有第一、第二鰭片組14a、14b， 該第一、第二鰭片組14a、14b由複數散熱片堆疊而成，且 該第一、第二鰭片組14a、14b之整體外形與第一、第二出 風132a、132b之形狀相一致。可以理解地，根據散熱需求 不同’該離心風扇12之出風口亦可僅設一個或兩個以上， 出風口之形狀可以為直線形、弧形或兩者之組合，所需鰭 片組之數量及鰭片組之整體外形可根據出風口之數量及形 狀做相應之調整，以便與離心風扇12之出風口相匹配。 請同時參照圖2至圖4，該離心風扇12之底板122具 200826817 有背向轉子124之一底面及面向轉子124之一頂面，其中 該底板122之頂面相對靠近離心風扇12之頂板121，而底 板122之底面相對遠離離心風扇之頂板121。如圖2所示， 該底板122之底面在對應轉子124之範圍内有一下沉尺 寸，從而在底板122之底面上形成一凹陷129a ,且該凹陷 129a區域一直延伸至與離心風扇12之側壁123相接。在靠 近離心風扇12之側壁123處，該凹陷129a區域背向轉子 124方向突設有一凸塊129c，該凸塊12处之高度與底板122 之底面平齊，該凸塊129c之設置可便於離心風扇之定 位及安裝。在底板122之頂面上對應底面之凹陷129a區域 形成一凸起12%，如圖1所示。該底板122對應頂板121 之第一進風口 127設有一圓形之第二進風口 128，以便更 夕之外界空氣進入離心風扇内。在本實施例中，該第二 進風口 128之半徑大於第-進風口 127之半徑，以增加從 第二進風口 128進入之風量。另外’該第二進風口 US之 半徑亦可為與第-進風口 127之半徑相等。該第二進風口 128之中部設有一圓柱形之支樓部13〇，該離心風扇12之 轉子124設於該支撐部130上，由於離心風扇12之底板 122之頂面在轉子124之範圍内形成有—凸起⑽，故離 心風扇U之轉子124與支撐部130均相應上移一定距離， 使得轉子124向離心風扇12之頂板121有所靠近。該支撐 部130藉由複數肋條131與底板122相連接，且這些肋條 131將第二進風口 128分成複數部分。如圖4所示，這些 肋條m呈傾斜設置’使支撐部叫目對於底板您之凹 11 200826817 陷129a更朝向轉子124方向突出，從而該支撐部130之底 面在垂直方向上高於底板122之凹陷129a部分，有利於外 界空氣從第二進風口 128進入離心風扇12内。 圖4為圖1所示散熱裝置10置於一電子裝置1之機殼 2〇内之剖視圖。該機殼2〇可為筆記型電腦等可攜式電子 裝置之外殼，其包括一上蓋21及與該上蓋21相對之一下 蓋22 °該散熱裝置10設于該上蓋21與下蓋22之間，其 中該離心風扇12之頂板121位於該機殼20之上蓋21與該 離心風扇12之底板122之間，且該離心風扇12之底板122 位於該機殼20之下蓋22與離心風扇12之頂板121之間。 該離心風扇12之頂板121與機殼2G之上蓋21之間形成有 上間距（t〇PgaP)H1，該離心風扇12之底板122與機殼 2〇之下蓋22之間形成有一下間距（bottom gap)H2。該上、 下門距HI、H2可分別作為外界空氣進入離心風扇14之第 :、第二進風口 127、128之空氣流道。在本實施例中，離 ^風扇^12之頂板121與機殼2〇之上蓋21之間的上間距 、向度為3.6mm，離心風扇12之底板122之凹陷129a 區域與機殼20之下蓋22之間的下間距H2為3 4mm，而 4立第_,、楚一山 弟二出風口 132a、132b附近該底板122無凹陷 a之區域與機殼2〇之下蓋22之間的間距仍為以醜， =由該凹陷129a之設置，使得該底板m與機殼20之 盍=之_轉得以增加。藉由咖數健擬仿真實 中’計算得出該離心風扇I2之總流量為4.74cfm ,與圖5 丁之離〜風扇51之總流量3 91cfm相比，在離心風扇 12 200826817 12之頂板121與機殼20之上蓋21之間的間距及離心風扇 12之底板122與機忒20之下蓋22之間的間距均保持不變 之情況下，藉由在離心風扇12之底板122上設置該凹陷 129a，增大了該凹陷區域與機殼2〇之間之距離，使得離心 風扇12之總流量增長了 21·2%，可見，離心風扇12之性 能得到有效之提升。每一葉片126包括與輪轂125連接之 第一部分126a及遠離輪轂125之第二部分12仍，該第一部 分126a在從輪轂125往第二部分126b之方向上高度逐漸 增加，這樣可使高度較大之第二部分126b吸入更多之氣 流0 本實施例中，由於離心風扇12之底板122之底面對應 離心風扇12之轉子124範圍内形成一凹陷129a區域。當 該離心風扇12組裝到電子裝置1之機殼2〇内時，使得離 心風扇12之底板122對應轉子124之區域與機殼20之下 蓋22之間的間距增加，有利於更多空氣藉由第二進風口 128進入離心風扇12内，使離心風扇12之總流量增加， 從而達到提升離心風扇12之散熱性能之目的。該底板122 在第一、第二出風口 l32a、132b附近區域未設凹陷129a， 不至於減小第一、第二出風口 132a、132b之大小及減少第 一、第二鰭片組14a、14b設置之面積，這樣可使氣流流經 第一、第二出風口 132a、132b時保持較高之流速，有利於 快速之將第一、第二鰭片組14a、14b所吸收之熱量散發。 另外’該底板122上之凹陷129a部分可在加工底板122時 利用模具一次成型，無需增加製造成本。 13 200826817 綜上所述，本發明符合發明專利要件，爰依法提出專 利申請。惟，以上所述者僅為本發明之較佳實施例，舉凡 熟悉本案技藝之人士’在纽本㈣精神所作之等效修飾 或變化，皆應涵蓋於以下之申請專利範圍内。 【圖式簡單說明】 圖。圖1縣伽散絲置射—健之立體分解 圖2係圖1所示散熱|置之立舰裝圖。 =係圖1所轉熱裝置另-角度之立體組裝圖。 二係圖1所不散熱裝置設於—機殼内之剖視圖。 I。Θ 、土於改進之—散熱裝置置於-機殼内之剖視 【主要元件符 電子裝置 離心風屬 底板 轉子 葉片 第二部分 苐二進風口 凸起 支撐部 f 一出風口 第'讀片組 機毂 下蓋 號說明】 1 12 122 124 126 126b 128 12% 130 132a 14a 20 22 散熱裝置 10 頂板 121 側壁 123 輪轂 125 第一部分 126a 第一進風口 127 凹陷 129a 凸塊 129c 肋條 131 第二出風口 132b 第二·_片組 14b 上蓋 21 上間距 H1 200826817 H2 下間距 15200826817 IX. Description of the Invention: The present invention relates to a centrifugal fan, and more particularly to a centrifugal fan for dissipating heat from a heat generating electronic component, and to a heat sink having the centrifugal fan and using the same Electronic device for the heat sink. [Prior Art] With the continuous improvement of the power of electronic components such as the central processing unit (CPU), the problem of heat dissipation has been paid more and more attention. In the notebook computer, it is more efficient to take away the system in a limited space. The heat generated is currently mainly used in the industry by two types of heat sink fins, heat pipes and centrifugal fans. The path of the rich red hot material is: the heat of the CPU charm is transmitted to the heat dissipation group through the heat pipe, and then the airflow of the centrifugal wind and the new wind will be transmitted to the dispersion: the heat of the sheet is hot and the movement of the fan is very large. The impact. 2 In New Zealand (4), the heat dissipation performance of the _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ especially important. It is more difficult to optimize the design of the fan. X greatly improved t-county's leading to the optimization of the design of the benefits of low-cost, and the fan volume is an important part of the report 2! Wind and summer wind and noise - the contradictory relationship, so on 6 200826817 SUMMARY OF THE INVENTION In view of the above, it is necessary to provide a centrifugal fan that can increase the air flow rate without increasing the cost, and it is also necessary to provide a heat dissipating device for improving the thermal performance and an electronic device using the same. . The centrifugal fan comprises a top plate, a bottom plate, a rotor and a side wall disposed between the top plate and the bottom plate, wherein the side wall is provided with at least one top plate and a first inlet fan, wherein the bottom plate is provided with The second air inlet, the top plate, the bottom plate and the side walls are formed to form an accommodating space, and the rotor is disposed in the accommodating space, wherein the bottom plate forms a recess in a direction of the rotor in a direction corresponding to the rotor. a heat dissipating device comprising: a centrifugal fan and at least a fin set disposed at an air outlet of the hybrid fan, wherein the centrifugal fan comprises a top plate, a bottom plate and a bottom plate and a bottom plate. The top wall is provided with a first air inlet, and the bottom plate is provided with a second air inlet. The top plate, the bottom plate and the side walls are formed to form an accommodation space, and the rotor is disposed in the space. Empty _, the floor tree should form a depression in the direction of the rotor within the range of the rotor. The electronic device includes a casing and a loose-travel device disposed in the casing, the casing including an upper cover and a lower cover opposite to the upper cover, the device comprising a centrifugal fan and being disposed at the centrifugal At the outlet of the fan, the centering fan of the /.,, and cymbal set has a top plate, one of which is opposite to the top plate, and a U-shaped sub-plate, and the top plate of the na (four) fan is further connected to the bottom plate of the centrifugal fan. There is a second air inlet ‘the distance between the top plate of the centrifugal fan and the upper cover of the casing is greater than the distance between the bottom plate of the centrifugal fan of the 200826817 and the lower cover of the casing, and the bottom plate of the centrifugal fan faces the rotor within the range of the corresponding rotor A depression is formed in the direction. - Compared with the prior art, the bottom plate of the centrifugal fan forms a recess in the direction of the rotor in the direction of the corresponding rotor, and when the centrifugal fan set is covered in the casing of the electronic device, the recessed area of the bottom plate and the casing The distance between the covers increases, which facilitates more air entering the centrifugal fan through the second air inlet, increasing the total flow of the centrifugal fan, thereby improving heat dissipation performance. [Embodiment] In order to meet the requirements of portable electronic devices such as notebook computers, which are oriented toward thin and light, short development, and for the purpose of rapid heat dissipation, the current configuration of the internal heat-generating electronic components is mostly configured. The active heat dissipation design of the centrifugal fan. FIG. 5 shows a portable electronic device 5 such as a notebook computer. The electronic device 5 includes a casing 60 and a heat sink 50 disposed in the casing 6. The heat sink 5 is used for electronic The heat-generating electronic components inside the device 5 (not shown) are radiated by a central processing unit such as a notebook computer. The casing 60 includes an upper cover 61 and a lower cover 62. The heat dissipating device 5 is disposed between the upper cover 61 and the lower cover 62, and includes a centrifugal fan and a fin, and 52 is disposed at the air outlet 511 of the centrifugal fan 51 and is connected to the heat generating electrons. The components are thermally connected to absorb heat generated by the heat-generating electronic components. The centrifugal fan 51 includes a base 512, a cover 513 disposed on the base M2, and a rotor 514. The rotor 514 is disposed in the base 512, and the airflow generated during operation is blown to the Korean magazine 52 to The absorbed heat is released 8 200826817. The cover plate 513 and the base 512 are respectively provided with an upper air inlet 515 and a lower air inlet 516 for the outside airflow to enter the centrifugal fan 51. The upper and lower air inlets 515, 516 are all circular arc shapes and the upper and lower air inlets 515, 516 have the same radius. When the heat sink 50 is assembled into the casing 60 of the electronic device 5, since the thickness of the casing 60 is limited, the distance hl between the air inlet 515 above the centrifugal fan 51 and the upper cover 61 of the casing 60 and the centrifugal fan are made. The lower spacing chamber between the lower air inlet 516 and the lower cover 62 of the casing 60 is smaller, and usually the upper spacing hi is greater than the lower spacing h2. The inventor used the cfd (Computational Fluid Dynamics) software to continuously test the operation of the heat sink 5G in the electronic device 5 and the flow field simulation analysis found that the air volume from the upper air inlet 515 into the centrifugal fan & It is much larger than the amount of air entering the centrifugal fan 51 from the lower air inlet 516. For example, when the upper pitch hi is 3.6 mm and the lower spacing h2 is 25 mm, the flow rate of the upper air inlet is 2.59 efm, the flow rate of the single air outlet is 132 gamma, and the total flow of the centrifugal fan is 3.91 efm. The inventors have found that the design of the centrifugal fan & and the distance of the air inlet from the casing 6 of the electronic device 5 are off. Therefore, it is actively attempting to achieve a good heat dissipation effect on the basis of no need to increase the production cost: = line optimization, which is the body of the three-dimensional knife solution of the embodiment, the heat dissipation device 1G The centrifugal fan 12, the sheet set 14a and the second fin set 14b are included. The Qizheng cooked device 10 is suitable for dissipating heat-generating components in a portable electronic device such as a pen 9 200826817. The centrifugal fan 12 includes a top plate 121, a bottom plate 122 opposite to the top plate 121, a rotor 124, and a side wall 123 of a spiral provided on the top plate 121 and the bottom plate 122. The side wall 123 and the bottom plate 122 can be integrally formed by die casting or injection molding. It can be understood that the side wall 123 can also be integrally formed with the top plate 121 by die casting or injection molding. The top plate 121, the bottom plate 122 and the side wall 123 of the centrifugal fan 12 are enclosed to form a receiving space, and the rotor 124 is disposed in the accommodating space. The rotor 124 includes a hub 125 and a plurality of vanes 126 extending radially outward from the periphery of the hub 125. The top plate 121 is provided with a circular first air inlet 127 corresponding to the rotor 124 so that outside air enters the accommodating space of the centrifugal fan 12. The side wall 123 and the bottom plate 122 are perpendicular to each other. The side wall 123 defines a first air outlet 132a and a second air outlet 132b. The first and second air outlets 132a and 132b are linear and perpendicular to each other. The gas produced by the centrifugal fan 12 can be discharged from the two mutually perpendicular directions. First and second fin sets 14a and 14b are respectively disposed at the first and second air outlets 132a and 132b. The first and second fin sets 14a and 14b are stacked by a plurality of heat sinks, and the first 1. The overall shape of the second fin sets 14a, 14b coincides with the shapes of the first and second air outlets 132a, 132b. It can be understood that, depending on the heat dissipation requirement, the air outlet of the centrifugal fan 12 may be only one or two or more. The shape of the air outlet may be linear, curved or a combination of the two, and the number of fin groups required. The overall shape of the fin group can be adjusted according to the number and shape of the air outlet to match the air outlet of the centrifugal fan 12. Referring to FIG. 2 to FIG. 4 , the bottom plate 122 of the centrifugal fan 12 has a bottom surface facing the rotor 124 and a top surface facing the rotor 124 . The top surface of the bottom plate 122 is relatively close to the top plate 121 of the centrifugal fan 12 . The bottom surface of the bottom plate 122 is relatively far from the top plate 121 of the centrifugal fan. As shown in FIG. 2, the bottom surface of the bottom plate 122 has a submerged size in the range corresponding to the rotor 124, so that a recess 129a is formed on the bottom surface of the bottom plate 122, and the recess 129a extends to the side wall 123 of the centrifugal fan 12. Docked. A bump 129c is protruded from the side wall 123 of the centrifugal fan 12 in the direction of the rotor 124. The height of the bump 12 is flush with the bottom surface of the bottom plate 122. The protrusion 129c is arranged to facilitate centrifugation. Positioning and installation of the fan. A projection 12% is formed on the top surface of the bottom plate 122 corresponding to the bottom surface of the recess 129a, as shown in FIG. The bottom plate 122 is provided with a circular second air inlet 128 corresponding to the first air inlet 127 of the top plate 121, so that the outer air of the outer wall enters the centrifugal fan. In this embodiment, the radius of the second air inlet 128 is greater than the radius of the first air inlet 127 to increase the amount of air entering from the second air inlet 128. Further, the radius of the second air inlet US may be equal to the radius of the first air inlet 127. A cylindrical branch portion 13 is disposed in the middle of the second air inlet 128. The rotor 124 of the centrifugal fan 12 is disposed on the support portion 130. The top surface of the bottom plate 122 of the centrifugal fan 12 is within the range of the rotor 124. The protrusion (10) is formed, so that the rotor 124 of the centrifugal fan U and the support portion 130 are respectively moved up by a certain distance, so that the rotor 124 approaches the top plate 121 of the centrifugal fan 12. The support portion 130 is coupled to the bottom plate 122 by a plurality of ribs 131, and the ribs 131 divide the second air inlet 128 into a plurality of portions. As shown in FIG. 4, the ribs m are disposed in an inclined manner so that the support portion is protruded toward the bottom surface of the bottom plate, and the bottom surface of the support portion 130 is vertically higher than the bottom plate 122. The portion of the recess 129a facilitates entry of outside air into the centrifugal fan 12 from the second air inlet 128. 4 is a cross-sectional view showing the heat sink 10 of FIG. 1 placed in a casing 2 of an electronic device 1. The casing 2 can be a casing of a portable electronic device such as a notebook computer, and includes an upper cover 21 and a lower cover 22 opposite to the upper cover 21 . The heat dissipation device 10 is disposed between the upper cover 21 and the lower cover 22 . The top plate 121 of the centrifugal fan 12 is located between the upper cover 21 of the casing 20 and the bottom plate 122 of the centrifugal fan 12, and the bottom plate 122 of the centrifugal fan 12 is located at the lower cover 22 of the casing 20 and the centrifugal fan 12. Between the top plates 121. An upper distance (t〇PgaP) H1 is formed between the top plate 121 of the centrifugal fan 12 and the upper cover 21 of the casing 2G, and a space is formed between the bottom plate 122 of the centrifugal fan 12 and the lower cover 22 of the casing 2 ( Bottom gap) H2. The upper and lower door distances HI and H2 can respectively enter the air flow path of the first and second air inlets 127 and 128 of the centrifugal fan 14 as outside air. In the present embodiment, the upper distance between the top plate 121 of the fan 12 and the upper cover 21 of the casing 2 is 3.6 mm, and the recess 129a of the bottom plate 122 of the centrifugal fan 12 is below the casing 20. The lower spacing H2 between the covers 22 is 34 mm, and the distance between the area of the bottom plate 122 without the recess a and the lower cover 22 of the casing 2 near the tuyere 132a, 132b of the Chuyishan brother The spacing is still ugly, = by the setting of the recess 129a, so that the turn of the bottom plate m and the casing 20 is increased. The total flow rate of the centrifugal fan I2 is calculated to be 4.74 cfm by the number of simulations, which is compared with the total flow of 3 91 cfm of the fan 51 and the fan 51 of the top plate 121 of the centrifugal fan 12 200826817 12 . The distance between the upper cover 21 of the casing 20 and the distance between the bottom plate 122 of the centrifugal fan 12 and the lower cover 22 of the casing 20 are kept constant, by being disposed on the bottom plate 122 of the centrifugal fan 12. The recess 129a increases the distance between the recessed area and the casing 2〇, so that the total flow rate of the centrifugal fan 12 is increased by 21.2%. It can be seen that the performance of the centrifugal fan 12 is effectively improved. Each blade 126 includes a first portion 126a coupled to the hub 125 and a second portion 12 remote from the hub 125. The first portion 126a is gradually increased in height from the hub 125 toward the second portion 126b, such that the height is greater The second portion 126b draws in more airflow. In this embodiment, the bottom surface of the bottom plate 122 of the centrifugal fan 12 forms a recess 129a region corresponding to the rotor 124 of the centrifugal fan 12. When the centrifugal fan 12 is assembled into the casing 2 of the electronic device 1, the spacing between the area of the bottom plate 122 of the centrifugal fan 12 corresponding to the rotor 124 and the lower cover 22 of the casing 20 is increased, which facilitates more air borrowing. The second air inlet 128 enters the centrifugal fan 12 to increase the total flow rate of the centrifugal fan 12, thereby achieving the purpose of improving the heat dissipation performance of the centrifugal fan 12. The bottom plate 122 is not provided with a recess 129a in the vicinity of the first and second air outlets l32a, 132b, so as not to reduce the size of the first and second air outlets 132a, 132b and reduce the first and second fin sets 14a, 14b. The area is set such that the airflow can be maintained at a higher flow rate when flowing through the first and second air outlets 132a, 132b, which facilitates rapid dissipation of heat absorbed by the first and second fin sets 14a, 14b. Further, the portion of the recess 129a on the bottom plate 122 can be molded at one time by the mold when the bottom plate 122 is processed, without increasing the manufacturing cost. 13 200826817 In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. However, the above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by the person skilled in the art of the present invention in the spirit of New Zealand (4) should be included in the following patent application. [Simple diagram of the diagram] Figure. Figure 1 County gamma ray placement - Jian's three-dimensional decomposition Figure 2 is the heat dissipation of the Figure 1 set. = The three-dimensional assembly drawing of the other angle of the heat transfer device of Fig. 1. The second embodiment of Fig. 1 is a cross-sectional view of the non-heat dissipation device disposed in the casing. I. Θ, soil improvement - heat sink placed in the casing - section [main components electronic device centrifugal wind is the bottom plate rotor blade second part 苐 two air inlet convex support part f an air outlet section 'reading group The description of the lower cover of the hub] 1 12 122 124 126 126b 128 12% 130 132a 14a 20 22 Heat sink 10 Top plate 121 Side wall 123 Hub 125 First part 126a First air inlet 127 Depression 129a Bump 129c Rib 131 Second air outlet 132b Second · _ slice 14b upper cover 21 spacing H1 200826817 H2 lower spacing 15