【正文】 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)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(dòng)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(huì)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)，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(dòng)與滑動(dòng)相結(jié)合的運(yùn)動(dòng)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(dòng)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(dòng)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)力和交變應(yīng)力，所有的應(yīng)力作用都是同時(shí)發(fā)生的?！拜S”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(dòng)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?，那么?應(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(dòng)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 方法在設(shè)計(jì)軸中難于應(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(dòng)器一起處理。簡化摩擦離合器或制動(dòng)器的 動(dòng)力學(xué)表達(dá)式中，各自以角速度 w1 和 w2 運(yùn)動(dòng)的兩個(gè)轉(zhuǎn)動(dòng)慣量 I1 和 I2，在制動(dòng)器情 況下其中之一可能是零，由于接上離合器或制動(dòng)器而最終要導(dǎo)致同樣的速度。因?yàn)閮?個(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(dòng)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(dòng)器或離合器的類型無關(guān)。因?yàn)閹缀涡螤畹闹匾允巧?熱表面。各種各樣的離合器和制動(dòng)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(dòng)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(dòng)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(dòng)裝置或電機(jī)操作螺桿驅(qū)動(dòng)器必須運(yùn)行到一定的限度然后 停頓下來。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(dòng)構(gòu)件“空轉(zhuǎn)”或“超越”，因?yàn)橹鲃?dòng)驅(qū)動(dòng)件 停頓了或者因?yàn)榱硪粋€(gè)動(dòng)力源使被動(dòng)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(dòng)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(dòng)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 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。GEAR AND SHAFT INTRODUCTIONAbstract: The important position of the wheel gear and shaft can39。t falter intraditional machine and modern wheel gear and shafts mainly install the direction that delivers the dint at the principal axis passing to process to make them can is divided into many model numbers, useding for many situations we must be the multilayers to the understanding of the wheel gear and shaft in many words: Wheel gear。ShaftIn the force analysis of spur gears, the forces are assumed to act in a single shall study gears in which the forces have three reason for this, in the case of helical gears, is that the teeth are not parallel to the axis of in the case of bevel gears, the rotational axes are not parallel to each are also other reasons, as we shall gears are used to transmit motion between parallel helix angle is the same on each gear, but one gear must have a righthand helix and the other a lefthand shape of the tooth is an involute a piece of paper cut in the shape of a parallelogram is wrapped around a cylinder, the angular edge of the paper bees a we unwind this paper, each point on the angular edge generates an involute surface obtained when every point on the edge generates an involute is called an involute initial contact of spurgear teeth is a line extending all the way across the face of the initial contact of helical gear teeth is a point, which changes into a line as the teeth e into more 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 is this gradual of the teeth and the smooth transfer of load from one tooth to another, which give helical gears the ability to transmit heavy loads at high gears subject the shaft bearings to both radial and thrust the thrust loads bee high or are objectionable for other reasons, it may be desirable to use double helical double helical gear(herringbone)is equivalent to two helical gears of opposite hand, mounted side by side on the same develop opposite thrust reactions and thus cancel out the thrust two or more single helical gears are mounted on the same shaft, the hand of the gears should be selected so as to produce the minimum thrust , or spiral, gears are those in which the shaft centerlines are neither parallel nor teeth of crossedhelical fears have point contact with each other, which changes to line contact as the gears wear this reason they will carry out very small loads and are mainly for instrumental applications, and are definitely not remended for use in the transmission of is on difference between a crossed helical gear and a helical gear until they are mounted in mesh with each are manufactured in the same pair of meshed crossed helical gears usually have the same hand。that is ,a righthand driver goes with arighthand the design of crossedhelical gears, the minimum sliding velocity is obtained when the helix angle are , when the helix angle are not equal, the gear with the larger helix angle should be used as the driver if both gears have the same gears are similar to crossed helical pinion or worm has a small number of teeth, usually one to four, and since they pletely wrap around the pitch cylinder they are called mating gear is called a worm gear, which is not a true helical worm and worm gear are used to provide a high angularvelocity reduction between nonintersecting shafts which are usually at right worm gear is not a helical gear because its face is made concave to fit the curvature of the worm in order to provide line contact instead of point , a disadvantage of wo