機(jī)械畢業(yè)論文翻譯 間隙傳動機(jī)構(gòu)講解

1、西安工程大學(xué)畢業(yè)設(shè)計(jì)（論文） 晉 中 學(xué) 院 本科畢業(yè)設(shè)計(jì)英文參考資料 題 目 Introduction the design of gear and shaft 院 系 機(jī)械學(xué)院 專 業(yè) 機(jī)械設(shè)計(jì)制造及其自動化 姓 名 劉俊利 學(xué) 號 1114121113 學(xué)習(xí)年限 2011年9 月 至2015年7 月 指導(dǎo)教師 馬維金 職稱 教授 申請學(xué)位 工學(xué)學(xué)士學(xué)位 2015年 2 月 17 日- 1 -齒輪和軸的設(shè)計(jì)介紹摘要：在傳統(tǒng)機(jī)械和現(xiàn)代機(jī)械中齒輪和軸的重要地位是不可動搖的。齒輪和軸主要安裝在主軸箱來傳遞力的方向。通過加工制造它們可以分為許多的型號，分別用于許多的獨(dú)立場合。所以我們對齒輪和軸的了

2、解和認(rèn)識必須是多層次多方位的。關(guān)鍵詞：齒輪；軸；機(jī)械設(shè)計(jì)在直齒圓柱齒輪的受力分析中，是假定各力作用在單一平面的。我們將研究作用力具有三維坐標(biāo)的齒輪。因此，在斜齒輪的情況下，其齒向是不平行于回轉(zhuǎn)軸線的。而在錐齒輪的情況中各回轉(zhuǎn)軸線互相不平行。像我們要討論的那樣，尚有其他道理需要學(xué)習(xí)，掌握。斜齒輪用于傳遞平行軸之間的運(yùn)動。傾斜角度每個(gè)齒輪都一樣，但一個(gè)必須右旋斜齒，而另一個(gè)必須是左旋斜齒。齒的形狀是一漸開線螺旋面。如果一張被剪成平行四邊形（矩形）的紙張包圍在齒輪圓柱體上，紙上印出齒的角刃邊就變成斜線。如果我展開這張紙，在血角刃邊上的每一個(gè)點(diǎn)就發(fā)生一漸開線曲線。直齒圓柱齒輪輪齒的初始接觸處是跨過整個(gè)

3、齒面而伸展開來的線。斜齒輪輪齒的初始接觸是一點(diǎn)，當(dāng)齒進(jìn)入更多的嚙合時(shí)，它就變成線。在直齒圓柱齒輪中，接觸是平行于回轉(zhuǎn)軸線的。在斜齒輪中，該線是跨過齒面的對角線。它是齒輪逐漸進(jìn)行嚙合并平穩(wěn)的從一個(gè)齒到另一個(gè)齒傳遞運(yùn)動，那樣就使斜齒輪具有高速重載下平穩(wěn)傳遞運(yùn)動的能力。斜齒輪使軸的軸承承受徑向和軸向力。當(dāng)軸向推力變的大了或由于別的原因而產(chǎn)生某些影響時(shí)，那就可以使用人字齒輪。雙斜齒輪（人字齒輪）是與反向的并排地裝在同一軸上的兩個(gè)斜齒輪等效。它們產(chǎn)生相反的軸向推力作用，這樣就消除了軸向推力。當(dāng)兩個(gè)或更多個(gè)單向齒斜齒輪被在同一軸上時(shí)，齒輪的齒向應(yīng)作選擇，以便產(chǎn)生最小的軸向推力。交錯(cuò)軸斜齒輪或螺旋齒輪，它們

4、是軸中心線既不相交也不平行。交錯(cuò)軸斜齒輪的齒彼此之間發(fā)生點(diǎn)接觸，它隨著齒輪的磨合而變成線接觸。因此他們只能傳遞小的載荷和主要用于儀器設(shè)備中，而且肯定不能推薦在動力傳動中使用。交錯(cuò)軸斜齒輪與斜齒輪之間在被安裝后互相捏合之前是沒有任何區(qū)別的。它們是以同樣的方法進(jìn)行制造。一對相嚙合的交錯(cuò)軸斜齒輪通常具有同樣的齒向，即左旋主動齒輪跟右旋從動齒輪相嚙合。在交錯(cuò)軸斜齒設(shè)計(jì)中，當(dāng)該齒的斜角相等時(shí)所產(chǎn)生滑移速度最小。然而當(dāng)該齒的斜角不相等時(shí)，如果兩個(gè)齒輪具有相同齒向的話，大斜角齒輪應(yīng)用作主動齒輪。蝸輪與交錯(cuò)軸斜齒輪相似。小齒輪即蝸桿具有較小的齒數(shù)，通常是一到四齒，由于它們完全纏繞在節(jié)圓柱上，因此它們被稱為螺紋

5、齒。與其相配的齒輪叫做蝸輪，蝸輪不是真正的斜齒輪。蝸桿和蝸輪通常是用于向垂直相交軸之間的傳動提供大的角速度減速比。蝸輪不是斜齒輪，因?yàn)槠潺X頂面做成中凹形狀以適配蝸桿曲率，目的是要形成線接觸而不是點(diǎn)接觸。 蝸桿蝸輪機(jī)構(gòu)有單包圍和雙包圍機(jī)構(gòu)。單包圍機(jī)構(gòu)就是蝸輪包裹著蝸桿的一種機(jī)構(gòu)。當(dāng)然，如果每個(gè)構(gòu)件各自局部地包圍著對方的蝸輪機(jī)構(gòu)就是雙包圍蝸輪蝸桿機(jī)構(gòu)。著兩者之間的重要區(qū)別是，在雙包圍蝸輪組的輪齒間有面接觸，而在單包圍的蝸輪組的輪齒間有線接觸。一個(gè)裝置中的蝸桿和蝸輪正像交錯(cuò)軸斜齒輪那樣具有相同的齒向，但是其斜齒齒角的角度是極不相同的。蝸桿上的齒斜角度通常很大，而蝸輪上的則極小，因此習(xí)慣常規(guī)定蝸桿的導(dǎo)

6、角，那就是蝸桿齒斜角的余角；也規(guī)定了蝸輪上的齒斜角，該兩角之和就等于90度的軸線交角。當(dāng)齒輪要用來傳遞相交軸之間的運(yùn)動時(shí)，就需要某種形式的錐齒輪。雖然錐齒輪通常制造成能構(gòu)成90度軸交角，但它們也可產(chǎn)生任何角度的軸交角。輪齒可以鑄出，銑制或滾切加工。僅就滾齒而言就可達(dá)一級精度。在典型的錐齒輪安裝中，其中一個(gè)錐齒輪常常裝于支承的外側(cè)。這意味著軸的撓曲情況更加明顯而使在輪齒接觸上具有更大的影響。另外一個(gè)難題，發(fā)生在難于預(yù)示錐齒輪輪齒上的應(yīng)力，實(shí)際上是由于齒輪被加工成錐狀造成的。直齒錐齒輪易于設(shè)計(jì)且制造簡單，如果他們安裝的精密而確定，在運(yùn)轉(zhuǎn)中會產(chǎn)生良好效果。然而在直齒圓柱齒輪情況下，在節(jié)線速度較高時(shí)，

7、他們將發(fā)出噪音。在這些情況下，螺旋錐齒輪比直齒輪能產(chǎn)生平穩(wěn)的多的嚙合作用，因此碰到高速運(yùn)轉(zhuǎn)的場合那是很有用的。當(dāng)在汽車的各種不同用途中，有一個(gè)帶偏心軸的類似錐齒輪的機(jī)構(gòu)，那是常常所希望的。這樣的齒輪機(jī)構(gòu)叫做準(zhǔn)雙曲面齒輪機(jī)構(gòu)，因?yàn)樗鼈兊墓?jié)面是雙曲回轉(zhuǎn)面。這種齒輪之間的輪齒作用是沿著一根直線上產(chǎn)生滾動與滑動相結(jié)合的運(yùn)動并和蝸輪蝸桿的輪齒作用有著更多的共同之處。軸是一種轉(zhuǎn)動或靜止的桿件。通常有圓形橫截面。在軸上安裝像齒輪，皮帶輪，飛輪，曲柄，鏈輪和其他動力傳遞零件。軸能夠承受彎曲，拉伸，壓縮或扭轉(zhuǎn)載荷，這些力相結(jié)合時(shí)，人們期望找到靜強(qiáng)度和疲勞強(qiáng)度作為設(shè)計(jì)的重要依據(jù)。因?yàn)閱胃S可以承受靜壓力，變應(yīng)力和

8、交變應(yīng)力，所有的應(yīng)力作用都是同時(shí)發(fā)生的。“軸”這個(gè)詞包含著多種含義，例如心軸和主軸。心軸也是軸，既可以旋轉(zhuǎn)也可以靜止的軸，但不承受扭轉(zhuǎn)載荷。短的轉(zhuǎn)動軸常常被稱為主軸。當(dāng)軸的彎曲或扭轉(zhuǎn)變形必需被限制于很小的范圍內(nèi)時(shí)，其尺寸應(yīng)根據(jù)變形來確定，然后進(jìn)行應(yīng)力分析。因此，如若軸要做得有足夠的剛度以致?lián)锨惶螅敲春蠎?yīng)力符合安全要求那是完全可能的。但決不意味著設(shè)計(jì)者要保證；它們是安全的，軸幾乎總是要進(jìn)行計(jì)算的，知道它們是處在可以接受的允許的極限以內(nèi)。因之，設(shè)計(jì)者無論何時(shí)，動力傳遞零件，如齒輪或皮帶輪都應(yīng)該設(shè)置在靠近支持軸承附近。這就減低了彎矩，因而減小變形和彎曲應(yīng)力。雖然來自M.H.G方法在設(shè)計(jì)軸中難于

9、應(yīng)用，但它可能用來準(zhǔn)確預(yù)示實(shí)際失效。這樣，它是一個(gè)檢驗(yàn)已經(jīng)設(shè)計(jì)好了的軸的或者發(fā)現(xiàn)具體軸在運(yùn)轉(zhuǎn)中發(fā)生損壞原因的好方法。進(jìn)而有著大量的關(guān)于設(shè)計(jì)的問題，其中由于別的考慮例如剛度考慮，尺寸已得到較好的限制。設(shè)計(jì)者去查找關(guān)于圓角尺寸、熱處理、表面光潔度和是否要進(jìn)行噴丸處理等資料，那真正的唯一的需要是實(shí)現(xiàn)所要求的壽命和可靠性。由于他們的功能相似，將離合器和制動器一起處理。簡化摩擦離合器或制動器的動力學(xué)表達(dá)式中，各自以角速度w1和w2運(yùn)動的兩個(gè)轉(zhuǎn)動慣量I1和I2，在制動器情況下其中之一可能是零，由于接上離合器或制動器而最終要導(dǎo)致同樣的速度。因?yàn)閮蓚€(gè)構(gòu)件開始以不同速度運(yùn)轉(zhuǎn)而使打滑發(fā)生了，并且在作用過程中能量散

10、失，結(jié)果導(dǎo)致溫升。在分析這些裝置的性能時(shí)，我們應(yīng)注意到作用力，傳遞的扭矩，散失的能量和溫升。所傳遞的扭矩關(guān)系到作用力，摩擦系數(shù)和離合器或制動器的幾何狀況。這是一個(gè)靜力學(xué)問題。這個(gè)問題將必須對每個(gè)幾何機(jī)構(gòu)形狀分別進(jìn)行研究。然而溫升與能量損失有關(guān)，研究溫升可能與制動器或離合器的類型無關(guān)。因?yàn)閹缀涡螤畹闹匾允巧岜砻妗８鞣N各樣的離合器和制動器可作如下分類： 1輪緣式內(nèi)膨脹制凍塊；2輪緣式外接觸制動塊；3條帶式；4盤型或軸向式；5圓錐型；6混合式。分析摩擦離合器和制動器的各種形式都應(yīng)用一般的同樣的程序，下面的步驟是必需的：1假定或確定摩擦表面上壓力分布；2找出最大壓力和任一點(diǎn)處壓力之間的關(guān)系；3應(yīng)用

11、靜平衡條件去找尋（a）作用力；（b）扭矩；(c)支反力?；旌鲜诫x合器包括幾個(gè)類型，例如強(qiáng)制接觸離合器、超載釋放保護(hù)離合器、超越離合器、磁液離合器等等。強(qiáng)制接觸離合器由一個(gè)變位桿和兩個(gè)夾爪組成。各種強(qiáng)制接觸離合器之間最大的區(qū)別與夾爪的設(shè)計(jì)有關(guān)。為了在結(jié)合過程中給變換作用予較長時(shí)間周期，夾爪可以是棘輪式的，螺旋型或齒型的。有時(shí)使用許多齒或夾爪。他們可能在圓周面上加工齒，以便他們以圓柱周向配合來結(jié)合或者在配合元件的端面上加工齒來結(jié)合。雖然強(qiáng)制離合器不像摩擦接觸離合器用的那么廣泛，但它們確實(shí)有很重要的運(yùn)用。離合器需要同步操作。有些裝置例如線性驅(qū)動裝置或電機(jī)操作螺桿驅(qū)動器必須運(yùn)行到一定的限度然后停頓下來

12、。為著這些用途就需要超載釋放保護(hù)離合器。這些離合器通常用彈簧加載，以使得在達(dá)到預(yù)定的力矩時(shí)釋放。當(dāng)?shù)竭_(dá)超載點(diǎn)時(shí)聽到的“喀嚓”聲就被認(rèn)定為是所希望的信號聲。超越離合器或連軸器允許機(jī)器的被動構(gòu)件“空轉(zhuǎn)”或“超越”，因?yàn)橹鲃域?qū)動件停頓了或者因?yàn)榱硪粋€(gè)動力源使被動構(gòu)件增加了速度。這種離合器通常使用裝在外套筒和內(nèi)軸件之間的滾子或滾珠。該內(nèi)軸件，在它的周邊加工了數(shù)個(gè)平面。驅(qū)動作用是靠在套筒和平面之間契入的滾子來獲得。因此該離合器與具有一定數(shù)量齒的棘輪棘爪機(jī)構(gòu)等效。磁液離合器或制動器相對來說是一個(gè)新的發(fā)展，它們具有兩平行的磁極板。這些磁極板之間有磁粉混合物潤滑。電磁線圈被裝入磁路中的某處。借助激勵(lì)該線圈，磁

13、液混合物的剪切強(qiáng)度可被精確的控制。這樣從充分滑移到完全鎖住的任何狀態(tài)都可以獲得。加工基礎(chǔ)作為產(chǎn)生形狀的一種加工方法，機(jī)械加工是所有制造過程中最普遍使用的而且是最重要的方法。機(jī)械加工過程是一個(gè)產(chǎn)生形狀的過程，在這過程中，驅(qū)動裝置使工件上的一些材料以切屑的形式被去除。盡管在某些場合，工件無承受情況下，使用移動式裝備來實(shí)現(xiàn)加工，但大多數(shù)的機(jī)械加工是通過既支承工件又支承刀具的裝備來完成。 機(jī)械加工在知道過程中具備兩方面。小批生產(chǎn)低費(fèi)用。對于鑄造、鍛造和壓力加工，每一個(gè)要生產(chǎn)的具體工件形狀，即使是一個(gè)零件，幾乎都要花費(fèi)高額的加工費(fèi)用?？亢附觼懋a(chǎn)生的結(jié)構(gòu)形狀，在很大程度上取決于有效的原材料的形式。一般來說

14、，通過利用貴重設(shè)備而又無需特種加工條件下，幾乎可以以任何種類原材料開始，借助機(jī)械加工把原材料加工成任意所需要的結(jié)構(gòu)形狀，只要外部尺寸足夠大，那都是可能的。因此對于生產(chǎn)一個(gè)零件，甚至當(dāng)零件結(jié)構(gòu)及要生產(chǎn)的批量大小上按原來都適于用鑄造、鍛造或者壓力加工來生產(chǎn)的，但通常寧可選擇機(jī)械加工。嚴(yán)密的精度和良好的表面光潔度，機(jī)械加工的第二方面用途是建立在高精度和可能的表面光潔度基礎(chǔ)上。許多零件，如果用別的其他方法來生產(chǎn)屬于大批量生產(chǎn)的話，那么在機(jī)械加工中則是屬于低公差且又能滿足要求的小批量生產(chǎn)了。另方面，許多零件靠較粗的生產(chǎn)加工工藝提高其一般表面形狀，而僅僅是在需要高精度的且選擇過的表面才進(jìn)行機(jī)械加工。例如內(nèi)

15、螺紋，除了機(jī)械加工之外，幾乎沒有別的加工方法能進(jìn)行加工。又如已鍛工件上的小孔加工，也是被鍛后緊接著進(jìn)行機(jī)械加工才完成的。機(jī)械設(shè)計(jì)一臺完整機(jī)器的設(shè)計(jì)是一個(gè)復(fù)雜的過程。機(jī)械設(shè)計(jì)是一項(xiàng)創(chuàng)造性的工作。設(shè)計(jì)工程師不僅在工作上要有創(chuàng)造性，還必須在機(jī)械制圖、運(yùn)動學(xué)、工程材料、材料力學(xué)和機(jī)械制造工藝學(xué)等方面具有深厚的基礎(chǔ)知識。任何產(chǎn)品在設(shè)計(jì)時(shí)第一步就是選擇產(chǎn)品每個(gè)部分的構(gòu)成材料。許多的材料被今天的設(shè)計(jì)師所使用。對產(chǎn)品的功能，它的外觀、材料的成本、制造的成本作出必要的選擇是十分重要的。對材料的特性必須事先作出仔細(xì)的評估。仔細(xì)精確的計(jì)算是必要的，以確保設(shè)計(jì)的有效性。在任何失敗的情況下，最好知道在最初設(shè)計(jì)中有有缺陷

16、的部件。計(jì)算（圖紙尺寸）檢查是非常重要的。一個(gè)小數(shù)點(diǎn)的位置放錯(cuò)，就可以導(dǎo)致一個(gè)本可以完成的項(xiàng)目失敗。設(shè)計(jì)工作的各個(gè)方面都應(yīng)該檢查和復(fù)查。計(jì)算機(jī)是一種工具，它能夠幫助機(jī)械設(shè)計(jì)師減輕繁瑣的計(jì)算，并對現(xiàn)有數(shù)據(jù)提供進(jìn)一步的分析?；酉到y(tǒng)基于計(jì)算機(jī)的能力，已經(jīng)使計(jì)算機(jī)輔助設(shè)計(jì)（CAD）和計(jì)算機(jī)輔助制造（CAM）成為了可能。心理學(xué)家經(jīng)常談?wù)撊绾问谷藗冞m應(yīng)他們所操作的機(jī)器。設(shè)計(jì)人員的基本職責(zé)是努力使機(jī)器來適應(yīng)人們。這并不是一項(xiàng)容易的工作，因?yàn)閷?shí)際上并不存在著一個(gè)對所有人來說都是最優(yōu)的操作范圍和操作過程。另一個(gè)重要問題，設(shè)計(jì)工程師必須能夠同其他有關(guān)人員進(jìn)行交流和磋商。在開始階段，設(shè)計(jì)人員必須就初步設(shè)計(jì)同管理人

17、員進(jìn)行交流和磋商，并得到批準(zhǔn)。這一般是通過口頭討論，草圖和文字材料進(jìn)行的。如前所訴，機(jī)械設(shè)計(jì)的目的是生產(chǎn)能夠滿足人類需求的產(chǎn)品。發(fā)明、發(fā)現(xiàn)和科技知識本身并不一定能給人類帶來好處，只有當(dāng)它們被應(yīng)用在產(chǎn)品上才能產(chǎn)生效益。因而，應(yīng)該認(rèn)識到在一個(gè)特定的產(chǎn)品進(jìn)行設(shè)計(jì)之前，必須先確定人們是否需要這種產(chǎn)品。應(yīng)當(dāng)把機(jī)械設(shè)計(jì)看成是機(jī)械設(shè)計(jì)人員運(yùn)用創(chuàng)造性的才能進(jìn)行產(chǎn)品設(shè)計(jì)、系統(tǒng)分析和制定產(chǎn)品的制造工藝學(xué)的一個(gè)良機(jī)。掌握工程基礎(chǔ)知識要比熟記一些數(shù)據(jù)和公式更為重要。僅僅使用數(shù)據(jù)和公式是不足以在一個(gè)好的設(shè)計(jì)中做出所需的全部決定的。另一方面，應(yīng)該認(rèn)真精確的進(jìn)行所有運(yùn)算。例如，即使將一個(gè)小數(shù)點(diǎn)的位置放錯(cuò)，也會使正確的設(shè)計(jì)變

18、成錯(cuò)誤的。一個(gè)好的設(shè)計(jì)人員應(yīng)該勇于提出新的想法，而且愿意承擔(dān)一定的風(fēng)險(xiǎn)，當(dāng)新的方法不適用時(shí)，就使用原來的方法。因此，設(shè)計(jì)人員必須要有耐心，因?yàn)?所花費(fèi)的時(shí)間和努力并不能保證帶來成功。一個(gè)全新的設(shè)計(jì)，要求屏棄許多陳舊的，為人們所熟知的方法。由于許多人墨守成規(guī)，這樣做并不是一件容易的事。一位機(jī)械設(shè)計(jì)師應(yīng)該不斷地探索改進(jìn)現(xiàn)有的產(chǎn)品的方法，在此過程中應(yīng)該認(rèn)真選擇原有的、經(jīng)過驗(yàn)證的設(shè)計(jì)原理，將其與未經(jīng)過驗(yàn)證的新觀念結(jié)合起來。新設(shè)計(jì)本身會有許多缺陷和未能預(yù)料的問題發(fā)生，只有當(dāng)這些缺陷和問題被解決之后，才能體現(xiàn)出新產(chǎn)品的優(yōu)越性。因此，一個(gè)性能優(yōu)越的產(chǎn)品誕生的同時(shí)，也伴隨著較高的風(fēng)險(xiǎn)。應(yīng)該強(qiáng)調(diào)的是，如果設(shè)計(jì)本

19、身不要求采用全新的方法，就沒有必要僅僅為了變革的目的而采用新方法。設(shè)計(jì)流程設(shè)計(jì)開始之前就要想到機(jī)器的實(shí)際性，現(xiàn)存的機(jī)器需要在耐用性、效率、重量、速度，或者成本上得到改善。新的機(jī)器必需具有以前機(jī)器所能執(zhí)行的功能。在設(shè)計(jì)的初始階段，應(yīng)該允許設(shè)計(jì)人員充分發(fā)揮創(chuàng)造性，不要受到任何約束。即使產(chǎn)生了許多不切實(shí)際的想法，也會在設(shè)計(jì)的早期，即在繪制圖紙之前被改正掉。只有這樣，才不致于阻斷創(chuàng)新的思路。通常,還要提出幾套設(shè)計(jì)方案，然后加以比較。很有可能在這個(gè)計(jì)劃最后決定中,使用了某些不在計(jì)劃之內(nèi)的一些設(shè)想。一般的當(dāng)外型特點(diǎn)和組件部分的尺寸特點(diǎn)分析得透徹時(shí)，就可以全面的設(shè)計(jì)和分析。接著還要客觀的分析機(jī)器性能的優(yōu)越性

20、，以及它的安全、重量、耐用性，并且競爭力的成本也要考慮在分析結(jié)果之內(nèi)。每一個(gè)至關(guān)重要的部分要優(yōu)化它的比例和尺寸，同時(shí)也要保持與其它組成部分相協(xié)調(diào)。也要選擇原材料和處理原材料的方法。通過力學(xué)原理來分析和實(shí)現(xiàn)這些重要的特性，如那些靜態(tài)反應(yīng)的能量和摩擦力的最佳利用，像動力慣性、加速動力和能量；包括彈性材料的強(qiáng)度、應(yīng)力和剛度等材料的物理特性，以及流體潤滑和驅(qū)動器的流體力學(xué)。設(shè)計(jì)的過程是重復(fù)和合作的過程，無論是正式或非正式的進(jìn)行，對設(shè)計(jì)者來說每個(gè)階段都很重要。最后，以圖樣為設(shè)計(jì)的標(biāo)準(zhǔn)，并建立將來的模型。如果它的測試是符合事先要求的，則再將對初步設(shè)計(jì)進(jìn)行某些修改，使它能夠在制造成本上有所降低。產(chǎn)品的設(shè)計(jì)需

21、要不斷探索和發(fā)展。許多方案必須被研究、試驗(yàn)、完善，然后決定使用還是放棄。雖然每個(gè)工程學(xué)問題的內(nèi)容是獨(dú)特的，但是設(shè)計(jì)師可以按照類似的步驟來解決問題。產(chǎn)品的責(zé)任訴訟迫使設(shè)計(jì)人員和公司在選擇材料時(shí)，采用最好的程序。在材料過程中，五個(gè)最常見的問題為：（a）不了解或者不會使用關(guān)于材料應(yīng)用方面的最新最好的信息資料；(b)未能預(yù)見和考慮材料的合理用途（如有可能，設(shè)計(jì)人員還應(yīng)進(jìn)一步預(yù)測和考慮由于產(chǎn)品使用方法不當(dāng)造成的后果。在近年來的許多產(chǎn)品責(zé)任訴訟案件中，由于錯(cuò)誤地使用產(chǎn)品而受到傷害的原告控告生產(chǎn)廠家，并且贏得判決）；(c)所使用的材料的數(shù)據(jù)不全或是有些數(shù)據(jù)不確定，尤其是當(dāng)其性能數(shù)據(jù)長期不更新；(d)質(zhì)量控制

22、方法不適當(dāng)和未經(jīng)驗(yàn)證；(e)由一些完全不稱職的人員選擇材料。通過對上述五個(gè)問題的分析，可以得出這些問題是沒有充分理由而存在的結(jié)論。對這些問題的研究分析可以為避免這些問題的出現(xiàn)而指明方向。盡管采用最好的材料選擇方法也不能避免發(fā)生產(chǎn)品責(zé)任訴訟，設(shè)計(jì)人員和工業(yè)界按照適當(dāng)?shù)某绦蜻M(jìn)行材料選擇，可以大大減少訴訟的數(shù)量。從以上的討論可以看出，選擇材料的人們應(yīng)該對材料的性質(zhì)，特點(diǎn)和加工方法有一個(gè)全面而基本的了解。 在隨后生產(chǎn)和售后服務(wù)的幾年中，要接受新觀念的變化，或者由試驗(yàn)和經(jīng)驗(yàn)為基礎(chǔ)，進(jìn)一步分析并改進(jìn)。- 17 - GEAR AND SHAFT INTRODUCTIONAbstract: The impor

23、tant position of the wheel gear and shaft cant falter in traditional machine and modern machines. The wheel gear and shafts mainly install the direction that delivers the dint at the principal axis box. The passing to process to make them can is divided into many model numbers, using for many situat

24、ions respectively. So we must be the multilevel to the understanding of the wheel gear and shaft in many ways.Key words: Wheel gear; Shaft; Machine design In the force analysis of spur gears, the forces are assumed to act in a single plane. We shall study gears in which the forces have three dimensi

25、ons. The reason for this, in the case of helical gears, is that the teeth are not parallel to the axis of rotation. And in the case of bevel gears, the rotational axes are not parallel to each other. There are also other reasons, as we shall learn. Helical gears are used to transmit motion between p

26、arallel shafts. The helix angle is the same on each gear, but one gear must have a right-hand helix and the other a left-hand helix. The shape of the tooth is an in volute helicoids. If a piece of paper cut in the shape of a parallelogram is wrapped around a cylinder, the angular edge of the paper b

27、ecomes a helix. If we unwind this paper, each point on the angular edge generates an in volute curve. The surface obtained when every point on the edge generates an in volute is called an in volute helicoids. The initial contact of spur-gear teeth is a line extending all the way across the face of t

28、he tooth. The initial contact of helical gear teeth is a point, which changes into a line as the teeth come into more engagement. In spur gears the line of contact is parallel to the axis of the rotation; in helical gears, the line is diagonal across the face of the tooth. It is this gradual of the

29、teeth and the smooth transfer of load from one tooth to another, which give helical gears the ability to transmit heavy loads at high speeds. Helical gears subject the shaft bearings to both radial and thrust loads. When the thrust loads become high or are objectionable for other reasons, it may be

30、desirable to use double helical gears. A double helical gear (herringbone) is equivalent to two helical gears of opposite hand, mounted side by side on the same shaft. They develop opposite thrust reactions and thus cancel out the thrust load. When two or more single helical gears are mounted on the

31、 same shaft, the hand of the gears should be selected so as to produce the minimum thrust load. Crossed-helical, or spiral, gears are those in which the shaft center-lines are neither parallel nor intersecting. The teeth of crossed-helical fears have point contact with each other, which changes to l

32、ine contact as the gears wear in. For this reason they will carry out very small loads and are mainly for instrumental applications, and are definitely not recommended for use in the transmission of power. There is on difference between a crossed helical gear and a helical gear until they are mounte

33、d in mesh with each other. They are manufactured in the same way. A pair of meshed crossed helical gears usually have the same hand; that is ,a right-hand driver goes with a right-hand driven. In the design of crossed-helical gears, the minimum sliding velocity is obtained when the helix angle are e

34、qual. However, when the helix angles are not equal, the gear with the larger helix angle should be used as the driver if both gears have the same hand. Worm gears are similar to crossed helical gears. The pinion or worm has a small number of teeth, usually one to four, and since they completely wrap

35、 around the pitch cylinder they are called threads. Its mating gear is called a worm gear, which is not a true helical gear. A worm and worm gear are used to provide a high angular-velocity reduction between non-intersecting shafts which are usually at right angle. The worm gear is not a helical gea

36、r because its face is made concave to fit the curvature of the worm in order to provide line contact instead of point contact. However, a disadvantage of worm gearing is the high sliding velocities across the teeth, the same as with crossed helical gears. Worm gearing are either single or double env

37、eloping. A single-enveloping gearing is one in which the gear wraps around or partially encloses the worm. A gearing in which each element partially encloses the other is, of course, a double-enveloping worm gearing. The important difference between the two is that area contact exists between the te

38、eth of double-enveloping gears while only line contact between those of single-enveloping gears. The worm and worm gear of a set have the same hand of helix as for crossed helical gears, but the helix angles are usually quite different. The helix angle on the worm is generally quite large, and that

39、on the gear very small. Because of this, it is usual to specify the lead angle on the worm, which is the complement of the worm helix angle, and the helix angle on the gear; the two angles are equal for a 90-deg. Shaft angle. When gears are to be used to transmit motion between intersecting shaft, s

40、ome of bevel gear is required. Although bevel gears are usually made for a shaft angle of 90 deg. They may be produced for almost any shaft angle. The teeth may be cast, milled, or generated. Only the generated teeth may be classed as accurate. In a typical bevel gear mounting, one of the gear is of

41、ten mounted outboard of the bearing. This means that shaft deflection can be more pronounced and have a greater effect on the contact of teeth. Another difficulty, which occurs in predicting the stress in bevel-gear teeth, is the fact the teeth are tapered. Straight bevel gears are easy to design an

42、d simple to manufacture and give very good results in service if they are mounted accurately and positively. As in the case of squirt gears, however, they become noisy at higher values of the pitch-line velocity. In these cases it is often good design practice to go to the spiral bevel gear, which i

43、s the bevel counterpart of the helical gear. As in the case of helical gears, spiral bevel gears give a much smoother tooth action than straight bevel gears, and hence are useful where high speed are encountered. It is frequently desirable, as in the case of automotive differential applications, to

44、have gearing similar to bevel gears but with the shaft offset. Such gears are called hypo-id gears because their pitch surfaces are hyperboloids of revolution. The tooth action between such gears is a combination of rolling and sliding along a straight line and has much in common with that of worm g

45、ears.A shaft is a rotating or stationary member, usually of circular cross section, having mounted upon it such elements as gears, pulleys, flywheels, cranks, sprockets, and other power-transmission elements. Shaft may be subjected to bending, tension, compression, or torsion loads, acting singly or

46、 in combination with one another. When they are combined, one may expect to find both static and fatigue strength to be important design considerations, since a single shaft may be subjected to static stresses, completely reversed, and repeated stresses, all acting at the same time.The word “shaft”

47、covers numerous variations, such as axles and spindles. An axle is a shaft, wither stationary or rotating, nor subjected to torsion load. A shirt rotating shaft is often called a spindle.When either the lateral or the torsion deflection of a shaft must be held to close limits, the shaft must be size

48、d on the basis of deflection before analyzing the stresses. The reason for this is that, if the shaft is made stiff enough so that the deflection is not too large, it is probable that the resulting stresses will be safe. But by no means should the designer assume that they are safe; it is almost alw

49、ays necessary to calculate them so that he knows they are within acceptable limits. Whenever possible, the power-transmission elements, such as gears or pullets, should be located close to the supporting bearings, This reduces the bending moment, and hence the deflection and bending stress. Although

50、 the Avon Moises-Hencky-Goodman method is difficult to use in design of shaft, it probably comes closest to predicting actual failure. Thus it is a good way of checking a shaft that has already been designed or of discovering why a particular shaft has failed in service. Furthermore, there are a con

51、siderable number of shaft-design problems in which the dimension are pretty well limited by other considerations, such as rigidity. It is only necessary for the designer to discover something about the fillet sizes, heat-treatment, and surface finish and whether or not shot penning is necessary in o

52、rder to achieve the required life and reliability. Because of the similarity of their functions, clutches and brakes are treated together. In a simplified dynamic representation of a friction clutch, or brake, two inertias I1 and I2 traveling at the respective angular velocities W1 and W2, one of wh

53、ich may be zero in the case of brake, are to be brought to the same speed by engaging the clutch or brake. Slippage occurs because the two elements are running at different speeds and energy is dissipated during actuation, resulting in a temperature rise. In analyzing the performance of these device

54、s we shall be interested in the actuating force, the torque transmitted, the energy loss and the temperature rise. The torque transmitted is related to the actuating force, the coefficient of friction, and the geometry of the clutch or brake. This is problem in static, which will have to be studied

55、separately for earth geometric configuration. However, temperature rise is related to energy loss and can be studied without regard to the type of brake or clutch because the geometry of interest is the heat-dissipating surfaces. The various types of clutches and brakes may be classified as follows:

56、 1. Rim type with internally expanding shoes 2. Rim type with externally contracting shoes 3. Band type 4. Disk or axial type 5. Cone type 6. Miscellaneous type The analysis of all type of friction clutches and brakes use the same general procedure. The following step are necessary: 1. Assume or det

57、ermine the distribution of pressure on the frictional surfaces. 2. Find a relation between the maximum pressure and the pressure at any point 3. Apply the condition of statical equilibrium to find (a) the actuating force, (b) the torque, and (c) the support reactions. Miscellaneous clutches include

58、several types, such as the positive-contact clutches, overload-release clutches, overrunning clutches, magnetic fluid clutches, and others. A positive-contact clutch consists of a shift lever and two jaws. The greatest differences between the various types of positive clutches are concerned with the design of the jaws. To provide a longer period of time for shift action during engagement, the jaws may be ratchet-shaped, or gear-tooth-shaped. Sometimes