汽車(chē)FWD柔性傳動(dòng)軸失效分析

（注：本文是譯文，Original author: Anupam Singhal)

Drive shaft is a mechanical part of transmission system which is used to transfer the power from engine to the wheel. It comprises two constant velocity (CV) joints and the actual shaft is almost universally used in front wheel drive (FWD) vehicles. The usage of drive shaft as a power transmitter in automobile is more convenience because it is less likely to become jammed or broken compared to chain-drives. In operation, drive shaft is generally subjected Torsional and bending stress due to which fatigue and fractural failures may occur. Some common causes of failures are manufacturing, design, maintenance, raw material, and the user originated faults.
傳動(dòng)軸是傳動(dòng)系統(tǒng)的機(jī)械部分，用于將動(dòng)力從發(fā)動(dòng)機(jī)傳遞到車(chē)輪。它包括兩個(gè)等速（CV）接頭，車(chē)輛在實(shí)際應(yīng)用中更多地采用前輪驅(qū)動(dòng)（FWD）。傳動(dòng)軸作為汽車(chē)動(dòng)力傳動(dòng)裝置使用更方便，因?yàn)榕c鏈條傳動(dòng)相比，它不太可能被卡住或斷裂。在操作中，驅(qū)動(dòng)軸通常受到扭轉(zhuǎn)和彎曲應(yīng)力，可能會(huì)發(fā)生疲勞和斷裂故障。一些常見(jiàn)的故障原因是制造、設(shè)計(jì)、維護(hù)、原材料和用戶(hù)引起的故障。

The movement of vehicles can be provided by transferring the torque produced by engines to wheels after some modification. The transfer and modification system of vehicles is called as power transmission system and have different constructive features according to the vehicle’s driving type which can be front wheel drive.
車(chē)輛的運(yùn)動(dòng)可以通過(guò)將發(fā)動(dòng)機(jī)產(chǎn)生的扭矩傳遞到車(chē)輪上進(jìn)行修正。車(chē)輛的傳遞和修正系統(tǒng)被稱(chēng)為動(dòng)力傳動(dòng)系統(tǒng)，根據(jù)車(chē)輛的驅(qū)動(dòng)類(lèi)型具有不同的結(jié)構(gòu)特征。

Most automobiles today use rigid driveshaft to deliver power from a transmission to the wheels. A pair of short flexible driveshaft is commonly used in cars to send power from a differential to the wheels.
現(xiàn)在大多數(shù)汽車(chē)都使用剛性驅(qū)動(dòng)軸將動(dòng)力從變速器傳遞到車(chē)輪。一對(duì)短柔性驅(qū)動(dòng)軸通常用于從差速器向車(chē)輪傳遞動(dòng)力。

There are different types of drive shafts in Automotive Industry:
One-piece driveshaft
Two-piece driveshaft
Slip in Tube driveshaft
汽車(chē)行業(yè)有不同類(lèi)型的驅(qū)動(dòng)軸：
單根驅(qū)動(dòng)軸
雙根驅(qū)動(dòng)軸
滑動(dòng)管傳動(dòng)軸

Drive shafts are carriers of torque. They are subject to torsion and shear stress, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, whilst avoiding too much additional weight as that would in turn increase their inertia.
驅(qū)動(dòng)軸是扭矩的載體。它們受到扭轉(zhuǎn)和剪切應(yīng)力，相當(dāng)于輸入扭矩和負(fù)載之間的差異。因此，它們必須足夠強(qiáng)大以承受壓力，同時(shí)避免過(guò)多的額外重量，因?yàn)檫@反過(guò)來(lái)又增加了它們的慣性。

In front wheel drive operation, two universal joints (CV joints) are used for drive a shaft at constant angular velocity with a large misalignment angle. The inner end of the driveshaft has very little misalignment relative to the transmission housing, while the outer end of the driveshaft is attached to the front wheel and must continue to transmit torque whilst turning through angles up to 40 degrees.
在前輪驅(qū)動(dòng)操作中，兩個(gè)萬(wàn)向節(jié)（CV接頭）用于以恒定的角速度驅(qū)動(dòng)軸，具有較大的未對(duì)準(zhǔn)角度。驅(qū)動(dòng)軸的內(nèi)端相對(duì)于變速器殼體幾乎沒(méi)有錯(cuò)位，而驅(qū)動(dòng)軸的外端連接到前輪，并且必須繼續(xù)傳遞扭矩，使角度達(dá)到40度。

FWD drive shaft can be solid or tubular, equal or unequal length, come with or without damper weight. Equal length shafts are used in some vehicles to help reduce torque steer. The intermediate shaft is used as a link from transaxle to the half shaft. The outer ends have a support bracket and bearing assembly. Looseness in the bearing or bracket can create vibrations. The small damper weight is called torsional damper, that is sometimes attached to one half shaft serves to dampen harmonic vibrations in the drivetrain and to stabilize the shaft as it spins, not to balance the shaft.
FWD驅(qū)動(dòng)軸可以是實(shí)心的或管狀的，長(zhǎng)度相等或不等，有或沒(méi)有阻尼器。等長(zhǎng)軸用于一些車(chē)輛，以幫助減少扭矩轉(zhuǎn)向。中間軸被用作從傳動(dòng)軸到半軸的連桿。外端具有支撐托架和軸承組件。軸承或支架的松動(dòng)會(huì)產(chǎn)生振動(dòng)。小阻尼器稱(chēng)為扭轉(zhuǎn)阻尼器，有時(shí)連接到一個(gè)半軸用于阻尼傳動(dòng)系中的諧波振動(dòng)，并在旋轉(zhuǎn)時(shí)穩(wěn)定軸，而不是平衡軸。

The outer joints generally wear faster than inner joints because of the increased range of operating angles to which they are subjected. Inner joint angles may change only 10 to 20 degrees as outer joint can undergo changes up to 40 degrees in addition to jounce and rebound as the wheels are steered.
外接頭通常比內(nèi)接頭磨損更快，因?yàn)樗鼈兂惺艿墓ぷ鹘嵌确秶黾恿?。?nèi)關(guān)節(jié)角可能只變化10至20度，因?yàn)橥怅P(guān)節(jié)可以發(fā)生變化多達(dá)40度。這就是為什么外部關(guān)節(jié)有更高的故障率。

All CV joints are encased in a protective rubber (neoprene, natural and silicon) or thermoplastic boot. The job of the boot is to retain grease and to keep dirt and water out. The importance of the boot cannot be overemphasized because without its protection the joint does not survive. once CV joint packed with grease and installed, it requires no further maintenance. A loose or missing boot clamp, or a slit, tear, or a small puncture in the boot itself allows grease to leak out and water or dirt to enter. A milky or foamy appearance indicates water contamination. A gritty feeling when rubbed between the fingers indicates dirt. It Results, the joint is destroyed.
所有的CV接頭都用防護(hù)橡膠（氯丁橡膠、天然硅）或熱塑靴包住。靴子的工作是保持油脂和保持污垢和水。靴子的重要性再怎么強(qiáng)調(diào)也不為過(guò)，因?yàn)闆](méi)有它的保護(hù)，關(guān)節(jié)就無(wú)法生存。一旦CV接頭用油脂填充并安裝，則不需要進(jìn)一步維護(hù)。靴子的松動(dòng)或丟失，或縫隙，撕裂，或靴子本身的小穿刺，會(huì)使油脂泄漏，水或污物進(jìn)入。乳白色或泡沫狀的外觀表明水污染。手指間摩擦?xí)r的砂礫感覺(jué)是污垢。結(jié)果是接頭被破壞。

Countries, where the average atmospheric temperature is approximate 40 degree, the failures mainly occur by changing the properties of grease. Grease must change its property on increasing of temperature because of changing in chemical composition. Grease becomes hard and thick on high temperature and does not operates normally. Oil present in grease may leak or vaporized which results failure of joint.
平均氣溫約為40度的國(guó)家，主要是潤(rùn)滑脂性能的改變導(dǎo)致的故障。由于化學(xué)成分的變化，潤(rùn)滑脂必須隨著溫度的升高而改變其性能。油脂在高溫下變硬、變厚，不能正常工作。潤(rùn)滑油中的油可能泄漏或汽化，導(dǎo)致接頭失效。

On the other side, road conditions are firmly effect the drive shaft. Domestic cars are manufactured on the basis of smooth road conditions but some developing countries have very rough road conditions so that premature failure may occur. A rough road condition causes the drive shaft work continuously on bumps and dips. Rough road have more dirt and dust particles, which are accumulated on the boot and in the grease. Which results abrasion of balls or tripods and joint may fail before time.
另一方面，路面狀況對(duì)傳動(dòng)軸產(chǎn)生了很大的影響。國(guó)內(nèi)汽車(chē)是在道路暢通的條件下制造的，但一些發(fā)展中國(guó)家的道路條件很差，所以可能會(huì)發(fā)生過(guò)早的故障。惡劣的路面狀況使驅(qū)動(dòng)軸在凸點(diǎn)和傾角上連續(xù)工作。崎嶇不平的道路上有更多的灰塵和灰塵顆粒，它們堆積在靴子和油脂上。因此，球或三腳架和接頭的磨損可能會(huì)提前失效。

Generally it seems that 80 % of the problems in CV joints are caused by a change in the working distance of the side shaft, 8 % by faults or negligence during installation. 8 % come from cracked axle boots which lead to a loss of lubricant, resulting in soiling of the joint. only the remaining 4 % of all joint failures have been caused by jolts and normal wear and tear of the parts.
一般看來(lái)，CV接頭中的80%的問(wèn)題是由側(cè)軸的工作距離的變化引起的，8%是由于安裝過(guò)程中的故障或疏忽造成的。8%來(lái)自軸靴裂紋，導(dǎo)致潤(rùn)滑劑的損失，接頭的污損。只有其余4%的接頭失效是由零件的顛簸和正常磨損引起的。