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黃河科技學(xué)院畢業(yè)設(shè)計（文獻翻譯） 第 21 頁
機械傳動
mechanical drive
機械傳動有多種形式,主要可分為兩類：①靠機件間的摩擦力傳遞動力和運動的摩擦傳動，包括帶傳動、繩傳動和摩擦輪傳動等。摩擦傳動容易實現(xiàn)無級變速,大都能適應(yīng)軸間距較大的傳動場合,過載打滑還能起到緩沖和保護傳動裝置的作用，但這種傳動一般不能用于大功率的場合，也不能保證準(zhǔn)確的傳動比。②靠主動件與從動件嚙合或借助中間件嚙合傳遞動力或運動的嚙合傳動，包括齒輪傳動、鏈傳動、螺旋傳動和諧波傳動等。嚙合傳動能夠用于大功率的場合，傳動比準(zhǔn)確，但一般要求較高的制造精度和安裝精度。
基本產(chǎn)品分類：減速機、制動器、離合器、連軸器、無級變速機、絲杠、滑軌等
發(fā)展歷史
機械傳動機構(gòu)，可以將動力所提供的運動的方式、方向或速度加以改變，被人們有目的地加以利用。中國古代傳動機構(gòu)類型很多，應(yīng)用很廣，除了上面介紹的以外，像地動儀、鼓風(fēng)機等等，都是機械傳動機構(gòu)的產(chǎn)物。中國古代傳動機構(gòu)，主要有齒輪傳動、繩帶傳動和鏈傳動。
1、齒輪傳動。其出現(xiàn)時間不晚于西漢，西漢時的指南車、記里鼓車，東漢張衡發(fā)明的水力天文儀器上，都使用了相當(dāng)復(fù)雜的齒輪傳動系統(tǒng)。這些齒輪只用來傳遞運動，強度要求不高。至于生產(chǎn)上所采用的齒輪，要傳遞較大的動力，受力一般較大，強度要求較高。古代在利用畜力、水力和風(fēng)力進行提水、糧食加工等工作時，都要應(yīng)用此類齒輪。例如在翻車上，須應(yīng)用一級齒輪傳動機構(gòu)，以改變運動的方位和傳遞，適應(yīng)翻車的工作要求。
2、鏈傳動。鏈，在我國古代出現(xiàn)很早，商代的馬具上已有青銅鏈條，其他青銅器和玉器上也有用鏈條作為裝飾的。西安出土的秦代銅車馬上，有十分精美的金屬鏈條。但這都不能算是鏈傳動。作為動力傳動的鏈條，出現(xiàn)在東漢時期。東漢時畢嵐率先發(fā)明翻車，用以引水。根據(jù)其工作原理和運動關(guān)系，可以看作是一種鏈傳動。翻車的上、下鏈輪，一主動，一從動，繞在輪上的翻板就是傳動鏈，這個傳動鏈兼做提水的工作件，因此，翻車是鏈傳動的一種特例。到了宋代，蘇頌制造的水運儀象臺上，出現(xiàn)了一種“天梯”，實際上是一種鐵鏈條，下橫軸通過“天梯”帶動上橫軸，從而形成了真正的鏈傳動。
3、繩帶傳動。這是一種利用摩擦力的傳動方式。在西漢時，四川出產(chǎn)井鹽，在鑿井、提水時，都是用牛帶動大繩輪，收卷繞過滑輪上的繩索，來提升鑿井工具、鹵水等。西漢時出現(xiàn)的手搖紡車，是一種典型的繩帶傳動。在西漢時期的畫像石上，有幾幅手搖紡車圖，可以清楚地看到：大繩輪主動，通過繩索帶動紗錠，用手搖大繩輪旋轉(zhuǎn)一周，紗錠旋轉(zhuǎn)幾十周，效率很高。以后出現(xiàn)的三錠、五錠的紡車，效率就更高了。元代的水運大紡車，也是用繩帶傳動的。東漢時，冶金手工業(yè)有一項重要發(fā)明“水排”，用于鼓風(fēng)。這種繩帶傳動的工作原理是：水力推動臥式水輪旋轉(zhuǎn)，水輪軸上裝有大繩輪，通過繩帶帶動小繩輪，小繩輪軸上端曲柄隨之旋轉(zhuǎn)，通過連桿推動鼓風(fēng)器鼓風(fēng)。這種水排鼓風(fēng)效力很高，可以抵得上幾百匹馬鼓風(fēng)。它的出現(xiàn)，標(biāo)志著東漢時發(fā)達的機械已經(jīng)在我國出現(xiàn)了，因而意義十分重大。
傳動方式分類
機械傳動按傳力方式分，可分為 ：
1 摩擦傳動。
2 鏈條傳動。
3 齒輪傳動。
4 皮帶傳動。
5 渦輪渦桿傳動。
6 棘輪傳動。
7 曲軸連桿傳動
8 氣動傳動。
9 液壓傳動（液壓刨）
10 萬向節(jié)傳動
11 鋼絲索傳動（電梯中應(yīng)用最廣）
12 聯(lián)軸器傳動
13 花鍵傳動。
傳動方式詳解
皮帶傳動
帶傳動是具有中間撓性件的傳動方式，在機械傳動中應(yīng)用較為普遍，特別是帶傳動中的V帶傳動，應(yīng)用極為廣泛。
一、 帶傳動的類型
帶傳動是利用帶作為中間撓性件來傳遞運動或動力的一種傳動方式。
按傳動原理不同，帶傳動分為摩擦型（平帶傳動、V帶傳動等）和嚙合型兩類。
目前機械設(shè)備中應(yīng)用的帶傳動以摩擦型帶傳動居多，下面主要以V帶傳動為例介紹有關(guān)帶傳動的基本知識。
二、帶傳動的基本原理
傳動帶套在主動帶輪1和從動帶輪2上，對帶施加一定的張緊力，帶與帶輪接觸面之間就會產(chǎn)生正壓力；主動輪轉(zhuǎn)動時，依靠帶和帶輪之間的摩擦力來驅(qū)動從動輪轉(zhuǎn)動。
帶傳動的基本原理是依靠帶和帶輪之間的摩擦力來傳遞運動和動力。
三、帶傳動的特點和傳動比
1、帶傳動的特點
由于帶富有彈性，并靠摩擦力進行傳動，因此它具有結(jié)構(gòu)簡單，傳動平穩(wěn)、噪聲小，能緩沖吸振，過載時帶會在帶輪上打滑，對其他零件起過載保護作用，適用于中心距較大的傳動等優(yōu)點。
但帶傳動也有不少缺點，主要有：不能保證準(zhǔn)確的傳動比，傳動效率低(約為0.90～0.94)，帶的使用壽命短，不宜在高溫、易燃以及有油和水的場合使用。
2、帶傳動的傳動比
帶傳動中，主動輪轉(zhuǎn)速 與從動輪轉(zhuǎn)速 之比稱為傳動比，用符號 表示。
四、常用帶傳動
常用的帶傳動有兩種形式，即平帶傳動和V帶傳動。
1、平帶傳動
橫剖面為扁平矩形，工作是環(huán)形內(nèi)表面與帶輪外表面接觸。平帶傳動結(jié)構(gòu)簡單，平帶較薄，撓曲性和扭轉(zhuǎn)性好，因而適用于高速傳動、平行軸間的交叉?zhèn)鲃踊蚪诲e軸間的半交叉?zhèn)鲃?
2、V帶傳動
橫剖面為等腰梯形，工作時置于帶輪槽之中，兩側(cè)面接觸，產(chǎn)生摩擦力較大，傳動能力較強。
五、帶傳動的張緊裝置
帶傳動工作時，為使帶獲得所需的張緊力，兩帶輪的中心距應(yīng)能調(diào)整；帶在傳動中長期受拉力作用，必然會產(chǎn)生塑性變形而出現(xiàn)松弛現(xiàn)象，使其傳動能力下降，因此一般帶傳動應(yīng)有張緊裝置。帶傳動的張緊方法主要有調(diào)整中心距和使用張緊輪兩種，其中它們各自又有定期張緊和自動張緊等不同形式。
六、安裝和維護
為提高V帶傳動的效率，延長V帶的使用壽命和確保帶傳動的正常運轉(zhuǎn)，必須正確做好帶傳動裝置的安裝、維修與保養(yǎng)工作。
1、V帶必須正確地安裝在輪槽之中，一般以帶的外邊緣與輪緣平齊為準(zhǔn)。
2、V帶傳動中兩帶輪的軸線要保持平行，且兩輪相對應(yīng)的V形槽的對稱平面應(yīng)重合。
3、拆、裝V帶時，應(yīng)先調(diào)小兩帶輪中心距，避免硬撬而損壞V帶或設(shè)備。套好帶后，再將中心距調(diào)回到正確位置，帶的松緊要適度。
4、V帶傳動必須安裝防護罩，防止因潤滑油、切削液或其他雜物等飛濺到V帶上而影響傳動，并防止傷人事故的發(fā)生。
5、對一組V帶，損壞時一般要成組更換，新舊帶不能混用。
齒輪傳動
齒輪傳動是由分別安裝在主動軸及從動軸上的兩個齒輪相互嚙合而成。齒輪傳動是應(yīng)用最多的一種傳動形式。
一、齒輪傳動的基本特點
1、齒輪傳遞的功率和速度范圍很大，功率可從很小到數(shù)十萬千瓦，圓周速度可從很小到每秒一百多米以上。齒輪尺寸可從小于1mm到大于10m。
2、齒輪傳動屬于嚙合傳動，齒輪齒廓為特定曲線，瞬時傳動比恒定，且傳動平穩(wěn)、可靠。
3、齒輪傳動效率高，使用壽命長。
4、齒輪種類繁多，可以滿足各種傳動形式的需要。
5、齒輪的制造和安裝的精度要求較高。
二、齒輪傳動的分類
齒輪的種類很多，可以按不同方法進行分類。
按嚙合方式分，齒輪傳動有外嚙合傳動和內(nèi)嚙合傳動。
按齒輪的齒向不同分，齒輪傳動有直齒圓柱齒輪傳動；斜齒圓柱齒輪傳動；人字齒圓柱齒輪傳動和直齒錐齒輪傳動。
三、標(biāo)準(zhǔn)直齒圓柱齒輪傳動
直齒圓柱齒輪傳動是齒輪傳動的最基本形式，它在機械傳動裝置中應(yīng)用極為廣泛。
齒線為分度圓直母線的圓柱齒輪稱為直齒圓柱齒輪，簡稱直齒輪。
直齒圓柱齒輪的主要參數(shù)
?。?）齒數(shù)z 一個齒輪的輪齒總數(shù)稱為齒數(shù)。
?。?）齒形角a
在端平面上，過端面齒廓與分度圓交點處的徑向直線與齒廓在該點處的切線所夾的銳角稱為齒形角。
標(biāo)準(zhǔn)規(guī)定漸開線齒輪的標(biāo)準(zhǔn)齒形角a =20°。
（3）模數(shù)m
齒距p除以圓周率π所得的商稱為模數(shù)，模數(shù)的單位為mm，且已經(jīng)標(biāo)準(zhǔn)化。
四、其他類型齒輪傳動
常用的齒輪傳動除直齒圓柱齒輪傳動外，還有斜齒圓柱齒輪傳動、直齒錐齒輪傳動和蝸桿傳動等。
1、斜齒圓柱齒輪傳動
齒線為螺旋線的圓柱齒輪稱為斜齒圓柱齒輪。
斜齒圓柱齒輪根據(jù)螺旋角的方向不同，分為左旋齒輪和右旋齒輪兩種，其旋向可用右手法則來判斷。伸出右手，手掌朝上，四指指向齒輪軸向方向，若齒向與拇指方向一致則為右旋，反之為左旋。
一對斜齒圓柱齒輪嚙合時，由于輪齒在圓柱面上是螺旋放置的，所以兩嚙合輪齒齒面是逐漸接觸又逐步脫離的，而一對直齒圓柱齒輪嚙合時，兩嚙合齒齒面是同時在齒向全長上接觸，之后又同時脫離。因此，斜齒圓柱齒輪傳動平穩(wěn)性好，沖擊小，特別是在高速重載下更為明顯。
斜齒圓柱齒輪傳動適用于傳動平穩(wěn)性要求高的兩平行軸之間的傳動。
2、直齒錐齒輪傳動
分度曲面為圓錐面的齒輪稱為錐齒輪，它是輪齒分布在圓錐面上的齒輪，當(dāng)其齒向線是分度圓錐面的直母線時稱為直齒錐齒輪。
錐齒輪傳動用于空間兩相交軸之間的傳動，一般多用于兩軸垂直相交成90°的場合。
五、齒輪的失效形式
齒輪在工作過程中由于某種原因而損壞，使其失去正常工作能力的現(xiàn)象稱為失效。齒輪的失效形式有很多種，常見的失效形式有：
1、齒面磨損
齒輪在傳動過程中，輪齒嚙合表面間存在相對滑動。齒輪在受力情況下，齒面間的相對滑動使齒面發(fā)生磨損。磨損會破壞齒面形狀，造成傳動不平穩(wěn)；另外，磨損使輪齒變薄，造成齒側(cè)間隙增大，輪齒強度降低。齒面磨損是潤滑條件差的開式齒輪傳動(外露的齒輪傳動)的主要失效形式，也是開式蝸桿傳動的主要失效形式。
2、輪齒折斷
齒輪在工作中，其輪齒的受力狀況相當(dāng)于懸臂梁，齒根處受到的彎矩最大，所產(chǎn)生的應(yīng)力集中。在嚙合過程中，齒輪根部所受的彎矩是交替變化的，因此，在該處最容易產(chǎn)生疲勞裂紋而使輪齒折斷，輪齒的這種失效形式稱為輪齒的疲勞折斷。齒輪的另一種折斷是長期過載或受到過大沖擊載荷時的突然折斷，稱為過載折斷。
3、輪齒塑性變形
在低速重載的工作條件下，齒輪的齒面承受很大的壓力和摩擦力，由于這些力的作用，材料較軟的齒輪的局部齒面可能產(chǎn)生塑性流動，使齒面出現(xiàn)凹槽或凸起的棱臺，從而破壞齒輪的齒廓形狀，使齒輪喪失工作能力。齒輪的這種失效形式稱為輪齒的塑性變形。
4、齒面點蝕
齒輪工作時，當(dāng)嚙合表面反復(fù)受到接觸擠壓作用，且由此所產(chǎn)生的壓力過大或使用時間過長時，齒面會產(chǎn)生細微的疲勞裂紋。隨著齒輪的連續(xù)工作，裂紋會沿表層不斷擴大，使齒面出現(xiàn)小塊金屬剝落，形成麻點和斑坑。輪齒齒面發(fā)生的這種失效形式稱為齒面點蝕。嚴(yán)重的齒面點蝕會破壞齒輪輪齒的工作表面，造成傳動不平穩(wěn)，產(chǎn)生噪聲，甚至使齒輪失去工作能力。
齒面點蝕這種失效形式多發(fā)生在潤滑條件良好的閉式齒輪傳動中。
5、齒面膠合
在高速重載的閉式齒輪傳動中，齒面潤滑較為困難，嚙合面在重載作用下產(chǎn)生局部高溫使其粘結(jié)在一起，當(dāng)齒輪繼續(xù)運動時，會在較軟的齒面上撕下部分金屬材料而出現(xiàn)撕裂溝痕，這種由于齒面粘結(jié)和撕裂而造成的失效稱為齒面膠合。齒面出現(xiàn)膠合現(xiàn)象后，將嚴(yán)重損壞齒面而導(dǎo)致齒輪失效。閉式蝸桿傳動中極易發(fā)生這種失效。
鏈傳動
鏈傳動是由兩個具有特殊齒形的的齒輪和一條閉合的鏈條所組成，工作時主動連輪的齒與鏈條的鏈節(jié)相嚙合帶動與鏈條相嚙合的從動鏈輪傳動。鏈條傳動主要用于傳動比要求較準(zhǔn)確，且兩軸相距離較遠，而且不宜采用齒輪的地方。這就是我們常見的自行車鏈輪鏈條傳動原理。
一、鏈傳動的特點
1）能保證較精確的傳動比（和皮帶傳動相比較）
2）可以在兩軸中心距較遠的情況下傳遞動力（與齒輪傳動相比）
3）只能用于平行軸間傳動
4）鏈條磨損后，鏈節(jié)變長，容易產(chǎn)生脫鏈現(xiàn)象。
二、滾子鏈
1、滾子鏈的結(jié)構(gòu)
在機械傳動中，常用的傳動鏈?zhǔn)菨L子鏈(也稱套筒滾子鏈)。滾子鏈由內(nèi)鏈板1、外鏈板2、銷軸3、套筒4和滾子5組成。
滾子鏈的內(nèi)鏈板與套筒、外鏈板與銷軸分別采用過盈配合固定，銷軸與套筒、滾子與套筒之間分別為間隙配合；各鏈節(jié)可以自由屈伸，滾子與套筒能相對轉(zhuǎn)動。滾子鏈與鏈輪嚙合時，由于滾子的作用，將套筒與鏈輪齒直接接觸的滑動摩擦轉(zhuǎn)化為滾動摩擦，從而減小了鏈輪齒的磨損。
滾子鏈的長度用節(jié)數(shù)來表示。為了使鏈條的兩端便于連接，鏈節(jié)數(shù)應(yīng)盡量選取偶數(shù)，鏈接頭處可用開口銷或彈簧夾鎖定。當(dāng)鏈節(jié)數(shù)為奇數(shù)時，鏈接頭需采用過渡鏈節(jié)，過渡鏈節(jié)不僅制造復(fù)雜，而且傳遞能力低，因此應(yīng)盡量避免使用。
2、滾子鏈的標(biāo)記
滾子鏈?zhǔn)菢?biāo)準(zhǔn)件，其標(biāo)記為：
鏈號 — 排數(shù) — 整鏈鏈節(jié)數(shù) 標(biāo)準(zhǔn)編號
標(biāo)記示例
08A—1—88GB/T1243—1997表示鏈號為08A(節(jié)距為12.70mm)，單排，88節(jié)的滾子鏈。
3、鏈傳動的使用
(1)為保證鏈傳動的正常工作，兩鏈輪軸線應(yīng)相互平行，且兩鏈輪應(yīng)位于同 一鉛垂平面內(nèi)。
(2)為了提高鏈傳動的質(zhì)量和使用壽命，應(yīng)注意進行潤滑。
(3)鏈傳動可不施加預(yù)緊力，必要時可采用張緊輪裝置。
(4)為了安全和防塵，鏈傳動應(yīng)加裝防護罩。
蝸輪蝸桿傳動
當(dāng)一個齒輪具有一個或幾個螺旋齒，并且與渦輪（類似于螺旋齒輪）嚙合而組成交錯軸傳動時，這種傳動稱為蝸桿傳動。蝸輪蝸桿傳動用于兩軸交叉成90度，但彼此既不平行又不相交的情況下，通常在蝸輪傳動中，蝸桿是主動件，而蝸輪是被動件。
?。?）蝸桿傳動的特點
單級傳動就能獲得很大的傳動比，結(jié)構(gòu)緊湊，傳動平穩(wěn)，無噪聲，但傳動效率低。
?。?）蝸桿傳動中渦輪轉(zhuǎn)向的判定
蝸桿傳動中蝸桿、渦輪轉(zhuǎn)向間的關(guān)系取決于兩者間的相對位置、蝸桿的旋向及其旋轉(zhuǎn)方向。
判斷渦輪相對于蝸桿的轉(zhuǎn)向用左手或右手法則，擋蝸桿為右旋（蝸桿也分左右旋且判斷方法與斜齒輪方向判斷方法相同）時用右手法則，蝸桿為左旋時用左手法則。彎曲四指，是之指向蝸桿的旋向方向（直箭頭表示蝸桿可見側(cè)的圓周運動方向），則拇指的反方向就是渦輪相對于蝸桿的運動方向。
螺旋傳動
螺旋傳動是利用螺桿和螺母組成的螺旋副來實現(xiàn)傳動要求的，主要用于將回轉(zhuǎn)運動變?yōu)橹本€運動，同時傳遞運動和動力。
螺旋傳動的分類：
1）傳力螺旋：以傳遞動力為主，要求以較小的轉(zhuǎn)矩產(chǎn)生較大的軸向推力，用于克服工作阻力。如各種起重或加壓裝置的螺旋。這種傳力螺旋主要是承受很大的軸向力，一般為簡寫工作，每次工作時間較短，工作速度也不高。[email=7@&x]x[/email]
2) 傳導(dǎo)螺旋：以傳遞運動為主，有時也承受較大的軸向載荷。如機床進給機構(gòu)的螺旋等。傳導(dǎo)螺旋主要在較長的時間內(nèi)連續(xù)工作，工作速度較高，因此，要求具有較高的傳動精度。
3）調(diào)整螺旋：以調(diào)整、固定零件的相對位置。如機床、儀器、及測試裝置中的微調(diào)機構(gòu)的螺旋。調(diào)整螺旋不經(jīng)常轉(zhuǎn)動，一般在空載下調(diào)整。
螺旋傳動的特點：傳動精度高、工作平穩(wěn)無噪音，易于自鎖，能傳遞較大的動力等特點。
重要性
工作機一般都要靠原動機供給一定形式的能量，但是，把原動機和工作機直接連接起來的情況很少，往往需要在二者之間加入傳遞動力或改變運動狀態(tài)的傳動裝置：
?。?）工作機所需要的速度一般與原動機的最優(yōu)速度不相符合。。
?。?）很多工作機都需要根據(jù)生產(chǎn)要求進行速度調(diào)整，但是依靠原動機的速度來達到這一目的是不經(jīng)濟的，也不可能。
（3）在有些情況下，需要用一臺原動機帶動若干個工作速度不同的工作機。
?。?）為了安全及維護方便，或因機器的外廓尺寸受到限制等原因，不能將原動機和工作機直接連接在一起。
設(shè)計概要
當(dāng)設(shè)計傳動時，如傳動的功率、傳動比和工作條件已定，則不同的類型傳動各有其優(yōu)缺點。
（1）功率和效率
各類傳動所能傳遞的功率取決于其傳動原理、承載能力、載荷分布、工作速度、制造精度、機械效率、發(fā)熱情況等因素。
效率是評定傳動性能的主要指標(biāo)之一。
?。?）速度
速度是傳動的主要運動特性之一。提高傳動速度是機器的重要發(fā)展方向。
（3）外廓尺寸、質(zhì)量、成本
傳動的外廓尺寸和質(zhì)量與功率和速度的大小密切相關(guān)，也與傳動零件材料的力學(xué)性能有關(guān)。
mechanical drive
Mechanical transmission has a variety of forms, can be divided into two categories:1 on parts of the friction between the transmission power and the movement of the friction transmission, including the belt transmission, transmission and friction wheel transmission. Friction transmission easy to realize stepless speed, can adapt to the larger axial spacing transmission occasions, overload slip but also to cushion and protect the drive device, the drive cannot generally be used to big power situation, also cannot ensure accurate transmission ratio. II by active and follower by middleware meshing gears or transfer of power or motion of the meshing transmission, including gear transmission, chain drive, screw drive and harmonic drive. Gear transmission can be used for large power situation, accurate transmission ratio, but generally require a higher precision and installation accuracy.
Basic product classification: reducer, brake, clutch, shaft coupling, stepless variable speed machine, screw, such as slide
Development history
The mechanical transmission mechanism, which can drive the power provided by the manner of motion, direction or speed change, people have to use. In ancient China, many types of transmission mechanism, application is very wide, in addition to the outside, like it, blower and so on, is a mechanical transmission mechanism. Chinese ancient transmission mechanism, the main gear transmission, belt transmission and chain transmission.
1, gear transmission. The time when the Western Han Dynasty, the car guide, written in drum cart, Zhang Heng of Eastern Han Dynasty invented hydraulic astronomical instruments, using a fairly complex gear transmission system. These gears for transmitting motion, strength requirements is not high. As for the production of the gear, to transfer a larger power, force and generally larger, higher intensity. Ancient in the use of animal power, water and wind power are carrying water, food processing and other work, it can be applied to such gear. For example in a roll-over, requires the use of a gear transmission mechanism, in order to change the moving direction and transfer, to overturn work requirements.
2, chain drive. Chain, in our country ancient times occur very early, the harness has bronze chain, other bronzes and jades is also useful as a decorative chain. Xi'an unearthed Qin copper car right away, have very fine metal chain. But this can not be chain drive. As the power transmission chain, appeared in the Eastern Han dynasty. Bi Lan when the Eastern Han Dynasty the first invention of tipping, for water diversion. According to its working principle and movement relationship, can be regarded as a chain drive. ROPS, sprocket, a driving, a driven, around the wheel of the turning plate is the transmission chain, the transmission chain and make water piece of work, therefore, tipping is a special case of chain drive. The Song Dynasty, Su Song manufacturing waterborne instrument like a table, the emergence of a" ladder", is actually an iron chain, under the horizontal axis through the" ladder" driven on the horizontal axis, thus forming a real chain drive.
3, belt drive. This is a use of force transmission. In the Western Han Dynasty, produced in Sichuan salt, in sinking, water, are cattle drive sheave, winding around a pulley on the ropes, to enhance drilling tools, such as brine. When the Western Han Dynasty the hand spinning wheel, is a kind of typical belt transmission. In the period of the Western Han Dynasty portrait stone, have a few hand spinning wheel graph, can see clearly: large rope pulley rope through active, drive spindles, hand rope wheel rotates a circle, a few weeks spindle rotation, the efficiency is very high. After the three spindles, five spindles of spinning wheels, would be more efficient. The waterborne big wheel, also use the rope transmission. When the Eastern Han Dynasty, the metallurgical industry has an important invention" water", used for blast. The rope drive working principle is: the hydraulic drive horizontal turbine rotation, water wheel shaft is provided with a large rope pulley drive wheel through a string, string, string shaft is a crank to rotate through the connecting rod, drives air blower blower. This water blast effect is very high, can be worth hundreds of horses blast. It appears, marks the Eastern Han Dynasty developed machinery has appeared in our country, so it is of great significance.
Transmission mode classification
Mechanical transmission by way of power transmission points, can be divided into:
1friction drive.
2chain drive.
3gear transmission.
4 belt drive.
5turbine bar transmission.
6wheel drive.
7 crankshaft connecting rod drive
The 8 pneumatic transmission.
9hydraulic ( hydraulic plane )
10universal joint drive
11wire transmission ( elevator in the most widely used )
The 12coupling transmission
13spline drive.
Transmission mode.
Belt drive
Belt drive is a middle flexible part of the transmission mode, in the mechanical transmission is widely used, especially in the belt drive V belt transmission, is widely used.
One, belt type transmission
Belt drive is used as a middle flexible part with to transfer movement and power of a transmission mode.
According to the transmission principle of different, belt drive for friction type ( flat belt, V belt transmission etc.) and meshing type two class.
The mechanical equipment in the application of the belt to the friction belt transmission are, deals with the V belt as an example to introduce the basic knowledge of the belt drive.
Two, the basic principle of belt transmission
The drive belt is sheathed on the driving belt wheel 1and the driven belt wheel 2, on the band exerts certain tension force, belt and belt wheel between the contact surface will produce positive pressure; the driving wheel to rotate, depends on the friction between the belt and belt wheel to drive the driven wheel to rotate.
Belt transmission is the basic principle of relying on the friction between the belt and the belt wheel to transfer movement and power.
Three, belt transmission characteristics and transmission ratio
1, belt transmission characteristics
As with elastic, and rely on friction transmission, so it has the advantages of simple structure, stable transmission, small noise, can buffer the vibration absorption, overload belt on the belt wheel slip, on the other part has the function of overload protection, suitable for center distance larger transmission etc..
But the belt drive also has many disadvantages, mainly include: cannot ensure accurate transmission ratio, transmission efficiency is low ( approximately 0.90to 0.94), with a short service life, not in high temperature, flammable and have the oil and water use.
2, belt drive transmission ratio
Belt drive, the speed of the driving gear and the driven wheel speed is called the gear ratio, represented by the symbol.
Four, commonly used in belt transmission
Commonly used belt transmission has two forms, namely flat belt drive and V belt transmission.
1, flat belt drive
The cross section of a flat rectangular, work is an annular inner surface and the outer surface is in contact with wheel. Flat belt drive belt has the advantages of simple structure, thin, bending and torsion is good, so it is suitable for high speed transmission, parallel to the axis of the drive shaft between the cross or cross half cross drive
In 2, V belt transmission
Cross section is an isosceles trapezoid, work on the belt wheel groove, both sides contact, frictional force is larger, transmission ability.
Five, belt tensioning device
Belt transmission, in order to make access to the tensioning force, two wheel center distance can be adjusted; band in the transmission long are subjected to a tensile force, is bound to produce plastic deformation and relaxation phenomena, so that the transmission capacity decreased, so the general belt proper tensioning device. Belt tensioning method are mainly used for adjusting the center distance and tensioning wheel two, wherein each of them has periodically tensioning and automatic tension in different forms.
In six, the installation and maintenance
In order to improve the V belt transmission efficiency, prolong the service life of the band V and ensure the normal operation of belt drive, must make correct belt drive device installation, repair and maintenance work.
In 1, V must be installed correctly in the round grooves, generally to the outer edge of the belt and the rim flush.
In 2, V in belt transmission wheel axis to maintain two parallel, and two corresponding to the V shaped slot symmetry plane should be coincident.
3, assembly and disassembly, V belt, should adjust two wheel center distance, to avoid a hard prying and damaged V belt or device. A good band, the center distance is adjusted to return to the correct position, the elastic to moderate.
In 4, V belts must be installed protective cover, to prevent lubricating oil, cutting fluid or other debris flying to the V take affect the transmission, and prevent hurt accidents.
In 5, a group of V belt, damage to grouping replacement, new band not mix.
Gear drive
Gear is respectively arranged on the driving shaft and the driven shaft and two gear are engaged with each other. Gear transmission was the most used form of a transmission.
One, the basic characteristic of gear transmission
1, gear transmission power and the speed of a large area, the power can be from small to Shushiwanqian tile, circumferential velocity can be from very small to more than 100meters per second. Gear size from less than 1mm to more than 10m.
In 2, belongs to the meshing transmission gear, gear tooth profile for a specific curve, instantaneous transmission ratio constant, stable transmission, reliable.
In 3, a gear transmission with high efficiency, long service life.
In 4, a gear range, can meet a variety of transmission form need.
In 5, the gear manufacturing and installation of high precision.
In two, the classification of gear transmission
Gear type are many, can be classified according to different method to classify.
According to the meshing points, gear transmission with outer meshing transmission and internal gear transmission.
According to gear tooth to different points, gear with straight tooth cylindrical gears; helical gear; herringbone gear with straight tooth bevel gear drive.
Three, standard spur gear transmission
Straight tooth cylindrical gear drive gear drive are the most basic form of mechanical transmission device, it is widely applied in the.
Tooth line as the pitch circle straight generatrix cylindrical gear called straight tooth cylindrical gear, referred to as the spur gear.
The main parameters of spur gear
(1) the number Z of teeth of a gear tooth number number is called.
(2) the profile angle of a
In the end plane, end surface tooth profile with the pitch circle at the intersection of the radial line and profile in the point of the tangent between acute angle is called the profile angle.
Standard involute gear tooth profile of the standard angle a = 20degrees.
(3) the modulus M
Pitch P divided by PI gains business called modulus, modulus unit is the mm, and have been standardized.
Four, other types of gear transmission
In addition to commonly used gear transmission spur gear transmission, and helical gear, straight bevel gear and worm drive.
1, cylindrical helical gear drive
Dentate line for helical cylindrical gear called helical cylindrical gear.
Cylindrical helical gear with helix angle in different directions, divided into left and right gear two gear, the rotating direction by the right hand rule to judge. Stretched out his right hand, palm up, four fingers are pointing to gear axial direction, if the tooth and the direction is right handed, and vice versa for L.
A pair of helical gears meshing, the tooth in a cylindrical surface is spiral placed, so the two meshing gear tooth surface is gradually exposed gradually disengaged, and a pair of straight tooth cylindrical gear, two gear tooth surface is at the same time in the tooth length of exposure, and then at the same time out. Therefore, helical cylindrical gear drive is of good stability, small impact, especially in high speed and heavy load is more obviously.
Helical cylindrical gear transmission for smooth transmission of high requirements for the two parallel to the axis of the transmission between.
In 2, straight bevel gear drive
Dividing surface is a circular conical surface gear called bevel gear tooth, it is distributed on the cone gear, when the tooth line is a straight line reference cone surface called straight bevel gear.
Bevel gear drive for the space between two intersecting axes drive, more generally used two perpendicular axes intersect at an angle of 90 degrees.
In five, the failure forms of gear
Gear in the work process for some reason and damage, which lost its normal working ability of the phenomenon